THPC


Tetrakis(hydroxymethyl)phosphonium chloride (THPC) is an organophosphorus compound with the chemical formula [P(CH2OH)4]Cl. 
The cation P(CH2OH)4+ is four-coordinate, as is typical for phosphonium salts. 
THPC has applications as a precursor to fire-retardant materials, as well as a microbiocide in commercial and industrial water systems.

THPC is a water-soluble tetrakis(hydroxymethyl) phosphonium salt that is a common ingredient in commercial flame-retardant (FR) formulations.

THPC is produced by the reaction of formaldehyde, phosphine, and hydrochloric acid. 
THPC and its sulfur salt THPS are the predominant FR chemicals used for cotton apparel, especially children's sleepwear

Usage:

THPC is Flame retardant ingredient for the finishing of cotton and polyester fabrics.
Formulations including THPC are applied to pure cotton or polyester cotton as well as other fabrics.
Treated textiles show excellent flame-retarding, handling, wash resistance, and low tear strength effects as opposed to untreated fabrics.

Preferred IUPAC name: Tetrakis(hydroxymethyl)phosphanium chloride
Other names
Tetrahydroxymethylphosphonium chloride, THPC
Identifiers
CAS Number: 124-64-1 
ChemSpider: 29038 
ECHA InfoCard: 100.004.280 


Tetrakis(hydroxymethyl)phosphonium chloride


CAS names
Phosphonium, tetrakis(hydroxymethyl)-, chloride (1:1)

IUPAC names
Tetrakis(hydroxymethyl) phosphonium chloride

tetrakis(hydroxymethyl)phosphanium chloride
tetrakis(hydroxymethyl)phosphanium;chloride
Tetrakis(hydroxymethyl)phosphonium chloride
tetrakis(hydroxymethyl)phosphonium chloride
tetrakis(hydroxymethyl)phosphonium chloride
THPC

Trade names
Tetrakis Hydroxymethyl Phosphonium Chloride
THPC

Application
Tetrakis(hydroxymethyl)phosphonium chloride solution (80% in H2O) has been used as a reducing agent and stabilizing ligand for the synthesis of gold nanoparticles (AuNPs) from gold(III) chloride trihydrate (HAuCl4.3H2O).
It is a tetra-functional, amine-reactive, aqueous crosslinker that can be used for tuning the properties of protein-based hydrogels for 3D cell encapsulation applications.[10]

We are a leading supplier of Tetrakis (hydroxymethyl) phosphonium chloride (THPC), ca. 80% solution in water, a good durable flame retardant in textiles, as well as a microbiocide in commercial and industrial water systems.

Linear Formula (HOCH2)4PCl 
Molecular Weight 190.56 


PubChem CID: 31298

Properties
Chemical formula: (HOCH2)4PCl
Molar mass: 190.56 g·mol−1
Appearance: crystalline
Density: 1.341 g/cm3
Melting point: 150 °C (302 °F; 423 K)

Hazards
R-phrases (outdated)    R21 R25 R38 R41 R42/43 R51/53
S-phrases (outdated)    S22 S26 S36/37/39 S45 S60 S61

CAS Registry #    124–64–1    
Synonyms: THPC    
Molecular weight    190.58    
Physical state: Crystalline solid; sold as 80% aqueous solution    
Color: 80% aqueous solution is straw-colored or clear and colorless    
Solubility: Soluble in water, methanol, ethanol; less than 1 mg/mL in DMSO, insoluble in ether, reaction with acetone    
Vapor pressure: 80% aqueous solution: 1.0 mm Hg at 25 °C    
PH: 1 for aqueous solution of unspecified concentration;
2 for 80% aqueous solution    
Melting point: 154°C    
Boiling point: 80% aqueous solution: 118°C    
Density (water=1) 80% aqueous solution: 1.322 g/cm3 at 17.8°C; 1.34 g/cm3 at 20°C    

Tetrakis(hydroxymethyl)phosphonium chloride (THPC) and sulfate (THPS) are of importance in the textile industry as flame retardants, in the oil industry as scale-removers, as biocides for water systems, in the leather industry as tanning agents, in nanochemistry as reductants and stabilizers of nanoparticles, and as oxygen-scavengers in medical uses. 
In the majority of cases, THPC and THPS themselves are not chemically active and solely play a role of reservoirs for the more reactive species tris(hydroxymethyl)phosphine (THP) and/or formaldehyde. 
The contents of THPC/THPS solutions greatly depend on pH, which is now recognized as a key factor, for example, in metal hydrosol preparations, biocidal activity, and ecotoxicity.

THPC is a new class anti-microbial agent, with minimum effects on the environment. THPC's benefits include low toxicity, low dosage and rapid breakdown in the environment.
      
Chemical Name:    Tetrakis (hydroxymethyl) phosphonium chloride
Chemical Structure: [(CH2OH)4P] Cl
ABBREVIATION: THPC
CAS No: 124-64-1

Tetrakis(hydroxymethyl) phosphonium chloride (THPC) is a water soluble organophosphorus compound that has low toxicity, rapid breakdown in the environment, and no or little bioaccumulation.

CAS #: 124-64-1
EINECS #: 204-707-7
Synonyms:tetrakis hydroxymethyl phosphonium chloride; THPC; Pyroset TKC; Retardol C; Proban CC

Flame Retardants & Textile Auxiliaries
THPC, as well as THPS, are used in the flame-resistant fabric industry to improve the tear strength of cotton and other cellulosic fabrics.
Please see Tetrakis-Hydroxymethyl Phosphonium Cloride-Urea Pre-condensate Polymer (THPC-UPC)

THPC can be also used as tanning agents in the leather industry.


Oilfield Operations
THPC is an anti-microbial agent against SRB (Sulfate Reducing Bacteria) with minimum effects on the environment used in oilfield drilling and production applications. 
THPC 80% can be also used as an iron control chemistry to prevent iron sulfide scale common in the oil and gas industry.

Industrial and Commercial Water Treatment
Tetrakis Hydroxymethyl Phosphonium chloride (THPC) can be also used for the control of bacteria, algae, and fungi in industrial/commercial recirculating cooling water systems, in heat transfer water systems, and in industrial process water systems.


APPLICATIONS
· Industrial / Commercial Water Treatment - control of bacterial growth
· Oilfield - control of bacterial growth
· Textiles
· Disinfectants
· Chemical Intermediate

Synthesis and reactions
THPC can be synthesized with high yield by treating phosphine with formaldehyde in the presence of hydrochloric acid.

PH3 + 4 H2C=O + HCl → [P(CH2OH)4]Cl
THPC converts to tris(hydroxymethyl)phosphine upon treatment with aqueous sodium hydroxide:

[P(CH2OH)4]Cl + NaOH → P(CH2OH)3 + H2O + H2C=O + NaCl
Application in textiles
THPC has industrial importance in the production of crease-resistant and flame-retardant finishes on cotton textiles and other cellulosic fabrics.
A flame-retardant finish can be prepared from THPC by the Proban Process, in which THPC is treated with urea. 
The urea condenses with the hydroxymethyl groups on THPC. 
The phosphonium structure is converted to phosphine oxide as the result of this reaction.

[P(CH2OH)4]Cl + NH2CONH2 → (HOCH2)2POCH2NHCONH2 + HCl + HCHO + H2 + H2O
This reaction proceeds rapidly, forming insoluble high molecular weight polymers. 
The resulting product is applied to the fabrics in a "pad-dry process." 
This treated material is then treated with ammonia and ammonia hydroxide to produce fibers that are flame-retardant.

THPC can condense with many other types of monomers in addition to urea. 
These monomers include amines, phenols, and polybasic acids and anhydrides.

Tris(hydroxymethyl)phosphine and its uses
Tris(hydroxymethyl)phosphine, which is derived from tetrakis(hydroxymethyl)phosphonium chloride, is an intermediate in the preparation of the water-soluble ligand 1,3,5-triaza-7-phosphaadamantane (PTA). 
This conversion is achieved by treating hexamethylenetetramine with formaldehyde and tris(hydroxymethyl)phosphine.

Tris(hydroxymethyl)phosphine can also be used to synthesize the heterocycle, N-boc-3-pyrroline by ring-closing metathesis using Grubbs' catalyst (bis(tricyclohexylphosphine)benzylidineruthenium dichloride). 
N-Boc-diallylamine is treated with Grubbs' catalyst, followed by tris(hydroxymethyl)phosphine. 
The carbon-carbon double bonds undergo ring closure, releasing ethene gas, resulting in N-boc-3-pyrroline.
The hydroxymethyl groups on THPC undergo replacement reactions when THPC is treated with α,β-unsaturated nitrile, acid, amide, and epoxides. 
For example, base induces condensation between THPC and acrylamide with displacement of the hydroxymethyl groups. (Z = CONH2)

[P(CH2OH)4]Cl + NaOH + 3CH2=CHZ → P(CH2CH2Z)3 + 4CH2O + H2O + NaCl
Similar reactions occur when THPC is treated with acrylic acid; only one hydroxymethyl group is displaced, however.

Tetra-hydroxymethyl phosphonium chloride (THPC) is widely used in flame retardant finishing, industrial water treatment and leather manufacture industry

Tetrakis(hydroxymethyl)phosphonium chloride
124-64-1
THPC
Pyroset TKC
TETRAMETHYLOLPHOSPHONIUM CHLORIDE
Phosphonium, tetrakis(hydroxymethyl)-, chloride
NCI-C55061
Tetra(hydroxymethyl)phosphonium chloride
UNII-58WB2XCF8I
Tetrakis(hydroxymethyl)phosphochloride
58WB2XCF8I
tetrakis(hydroxymethyl)phosphanium;chloride
Retardol C
Phosphonium, tetrakis(hydroxymethyl)-, chloride (1:1)
Proban CC
CCRIS 317
HSDB 2923
tetrakis(hydroxymethyl)phosphanium chloride
EINECS 204-707-7
Tetrahydroxymethylphosphonium chloride
NSC 30698
Tetrakis(hydroxymethyl)phosphonium Chloride (ca. 80% in Water)
AI3-22268
Tetrakis(hydroxymethyl)phosphonium chloride, ca. 80% solution in water
Tetrakis-(hydroxymethyl)fosfoniumchlorid [Czech]
Tetrakis-(hydroxymethyl)fosfoniumchlorid
ACMC-1BPFQ
DSSTox_CID_1330
EC 204-707-7
DSSTox_RID_76085
DSSTox_GSID_21330
SCHEMBL196471
CHEMBL2131547
DTXSID5021330
WLN: Q1P1Q1Q1Q & G
NSC30698
Tox21_302070
ANW-43807
MFCD00031687
NSC-30698
AKOS015918384
Tetra(hydroxymethyl)phosphoniumchloride
NE10887
NCGC00164162-01
NCGC00255382-01
CAS-124-64-1
DB-007909
tetrakis-(hydroxymethyl)phosphonium chloride
FT-0631726
Phosphonium, chloro-tetrakis(hydroxymethyl)-
EN300-19000
Q7706566
359406-89-6


Chemical Name:Tetrakis(hydroxymethyl)phosphonium chloride
Synonyms: THPC;THPS-UPC;meso-THPC;pyrosettkc;nci-c55061;AURORA KA-1157;HISHICOLIN THPC;tetramethylolphosphonium chloride;tetrakis(hydroxymethyl)phosphonium;tetrakis(hydroxymethyl)phosphochloride

Tetrakis(hydroxymethyl)phosphonium chloride Chemical Properties,Uses,Production
Chemical Properties
Clear light pink or yellow-green solution

Uses
Flame-retarding agent for cotton fabrics. May be used in combination with triethylolamine and urea (Roxel process) or with triethanolamine and tris(1-aziridinyl) phosphine oxide.

Definition
A crystalline compound made by the reaction of phosphine, formaldehyde, and hydrochloric acid.

General Description
Clear slightly viscous,colorless to yellow liquid (20% H2O solution).

Air & Water Reactions
Hygroscopic. Water soluble.

Reactivity Profile
Tetrakis(hydroxymethyl)phosphonium chloride reacts vigorously with oxidizers and alkalis. Reacts with cellulose.

Health Hazard
ACUTE/CHRONIC HAZARDS: Tetrakis(hydroxymethyl)phosphonium chloride may be corrosive. When heated to decomposition, it may emit very toxic fumes of POx, hydrogen chloride and bis(chloromethyl)ether. Decomposition of Tetrakis(hydroxymethyl)phosphonium chloride in an aqueous environment may produce phosphine, formaldehyde and hydrogen chloride.

Fire Hazard
Tetrakis(hydroxymethyl)phosphonium chloride is probably combustible.

Purification Methods
Crystallise it from AcOH and dry it at 100o in a vacuum. An 80% w/v aqueous solution has d4 1.33 [Reeves J Am Chem Soc 77 3923 1955]. [Beilstein 1 IV 3062.]

•    THPS-UPC
•    THPC
•    TETRA(HYDROXYMETHYL)PHOSPHONIUM CHLORIDE
•    TETRAKIS(HYDROXYMETHYL)PHOSPHONIUM CHLORIDE
•    tetramethylolphosphonium chloride
•    nci-c55061
•    Phosphonium,tetrakis(hydroxymethyl)-,chloride
•    pyrosettkc
•    tetrakis-(hydroxymethyl)fosfoniumchlorid
•    tetrakis(hydroxymethyl)phosphochloride
•    tetrakis(hydroxymethyl)-phosphoniuchloride
•    tetrakis(hydroxymethyl)phosphonium
•    TETRAKIS(HYDROXYMETHYL)PHOSPHONIUM CHLOR IDE, 80% SOLUTION IN WATER
•    TETRAKIS(HYDROXYMETHYL)PHOSPHONIUM CHLOR IDE, 80% IN H2O
•    Tetrakis(Hydroxymethyl)Phosphorium Chloride
•    TetrakisHydroxymethylPhosphoniumChloride(Thpc)
•    AURORA KA-1157
•    tetrakis(hydroxymethyl)phosphonium chloride solution
•    HISHICOLIN THPC
•    Tetrakis(hydroxymethyl)phosphonium Chloride (ca. 80% in Water)
•    TETRAKIS(HYDROXYMETHYL)PHOSPHONIUM CHLORIDE, CA. 80% SOLUTION IN WATER
•    meso-THPC
•    TETRAKIS(HYDROXYMETHYL)PHOSPHONIUM CHLORIDE: 80% IN WATER
•    Tetrakis(HydroxyMethyl) PosphoniuM Chloride
•    Tetrakis(hydroxyMethyl)phosphoniuM chloride solution,~80% in H2O
•    PhosphoniuM,tetrakis(hydroxyMethyl)-, chloride (1:1)
•    Tetrakis(hydroxymethyl)phosphonium chloride, 80% solution in H2O
•    Tetrakis(hydroxymethyl) phosphonium chloride (70-80 % in water)
•    Tetrakis(hydroxymethyl)phosphonium chloride fandachem
•    124-64-1
•    HOCH24PCl
•    C4H12O4PClC4H12ClO4P
•    CH2OH4PCl
•    C4H12O4PCl
•    C4H12ClO4P
•    C10H24O12P2
•    Phosphonium Compounds
•    Synthetic Reagents
•    Phosphonium Salts
•    Phase Transfer Catalysts
•    texitile auxiliary agents
•    Phosphonium Compounds
•    Greener Alternatives: Catalysis
•    Phase Transfer Catalysts
•    Phosphonium Salts
•    Phosphonium Salts


Application in textiles
THPC has industrial importance in the production of crease-resistant and flame-retardant finishes on cotton textiles and other cellulosic fabrics. A flame-retardant finish can be prepared from THPC by the Proban Process, in which THPC is treated with urea. The urea condenses with the hydroxymethyl groups on THPC. The phosphonium structure is converted to phosphine oxide as the result of this reaction.

[P(CH2OH)4]Cl + NH2CONH2 → (HOCH2)2POCH2NHCONH2 + HCl + HCHO + H2 + H2O
This reaction proceeds rapidly, forming insoluble high molecular weight polymers. The resulting product is applied to the fabrics in a "pad-dry process." This treated material is then treated with ammonia and ammonia hydroxide to produce fibers that are flame-retardant.

THPC can condense with many other types of monomers in addition to urea. These monomers include amines, phenols, and polybasic acids and anhydrides.

Tris(hydroxymethyl)phosphine and its uses
Tris(hydroxymethyl)phosphine, which is derived from tetrakis(hydroxymethyl)phosphonium chloride, is an intermediate in the preparation of the water-soluble ligand 1,3,5-triaza-7-phosphaadamantane (PTA). This conversion is achieved by treating hexamethylenetetramine with formaldehyde and tris(hydroxymethyl)phosphine.

Tris(hydroxymethyl)phosphine can also be used to synthesize the heterocycle, N-boc-3-pyrroline by ring-closing metathesis using Grubbs' catalyst (bis(tricyclohexylphosphine)benzylidineruthenium dichloride). N-Boc-diallylamine is treated with Grubbs' catalyst, followed by tris(hydroxymethyl)phosphine. The carbon-carbon double bonds undergo ring closure, releasing ethene gas, resulting in N-boc-3-pyrroline. The hydroxymethyl groups on THPC undergo replacement reactions when THPC is treated with α,β-unsaturated nitrile, acid, amide, and epoxides. For example, base induces condensation between THPC and acrylamide with displacement of the hydroxymethyl groups. (Z = CONH2)

[P(CH2OH)4]Cl + NaOH + 3CH2=CHZ → P(CH2CH2Z)3 + 4CH2O + H2O + NaCl
Similar reactions occur when THPC is treated with acrylic acid; only one hydroxymethyl group is displaced, however.

Uses:
1.Flame retardant for textile finishing, applicable to pure cotton or polyester cotton and other textile. The treated textile has very good flame-retarding effect, good handle, strong washing resistance, and small tear strength loss with the original performances of fabrics not affected.
2.As flame retardant of plastic, paper etc.


TOXICOKINETICS
Absorption
Dermal
No studies were identified that investigated the dermal absorption of THPC or other tetrakis(hydroxymethyl) phosphonium salts by humans. Dermal application of THPC to rats resulted in body weight loss and death (Aoyama 1975), indicating that THPC is absorbed by this route. Ulsamer et al. (1980), citing a 1953 report by the Wisconsin Alumni Research Foundation, stated that THPC can be absorbed through the skin in large amounts (1.5 gm/kg). It is not clear whether this is a derived amount or one based on animal data. The subcommittee could not locate a copy of the 1953 report.

Inhalation
No studies were identified that investigated the absorption of THPC following inhalation exposures.

Oral
Acute, subchronic, and chronic toxicity studies in rats and mice provide indirect evidence that THPC is absorbed through the gastrointestinal tract and becomes systemically bioavailable (see Hazard Identification section).

Distribution
No studies were identified that investigated the distribution of THPC or of other tetrakis(hydroxymethyl) phosphonium salts in humans or laboratory animals following dermal, inhalation, or oral exposure. Since the liver has been shown to be a target organ for THPC toxicity (see NTP 1987), it can be inferred that THPC is distributed systemically.

Metabolism
No studies were identified that investigated the metabolism of THPC or of other tetrakis(hydroxymethyl) phosphonium salts.

Excretion
No studies were identified that investigated the excretion of THPC or of other tetrakis(hydroxymethyl) phosphonium salts.

Go to:
HAZARD IDENTIFICATION2
Dermal Exposure
Irritation
No skin reactions were observed in 100 volunteers (23 males, 77 females) aged 9–63 yr who were exposed to THPC-treated fabric for 72 hr (Osbourn 1971). Volunteers were treated topically (location not specified) with THPC-treated fabric patches, some of which were moistened with distilled water.

THPC was found to be non-irritating to the skin in 38 male volunteers who were dermally exposed to fabric patches containing Proban® 210, a THPC-based FR (Albright and Wilson 1982, as cited in IPCS 2000). The THPC content of the fabric patches was not reported. The fabric patches were applied to the forearms of the volunteers and covered for 48 hr. The test sites were then uncovered and examined for skin reactions 50 hr, 90 hr, 1 wk, and 2 wk after exposure.

Moderate to severe skin reactions were observed in male white rats and rabbits treated topically for 8 d with 0.75 mL of 15%, 20%, or 30% aqueous THPC (Aoyama 1975). In rats, skin redness was observed starting on d 4 for rats treated with 15% and 20% THPC, while redness was observed beginning on d 2 in rats treated with 30% THPC. Skin redness in the 30% dose group became very intense on d 6 followed by partial hair loss on d 7 and death on d 9. Rabbits treated topically for 6 d with 1 mL of 15% or 30% aqueous THPC developed skin redness on d 2–3, which became severe by no later than d 6. Skin necrosis developed on d 3–12. Total hair loss occurred in both dose groups by d 11–13, but hair began to regrow in both dose groups by d 18–19. Toxicity was comparatively more severe in rabbits treated with 30% THPC.

Ulsamer et al. (1980), citing the 1953 report by the Wisconsin Alumni Research Foundation, state that THPC is a mild skin irritant in the female rat and caused lethality, skin sloughing, and hyperemia after dermal application of >1.5 g/kg (species not given). The 1953 report was not located by the subcommittee.

Systemic Effects
Moderate to severe skin effects characterized by tissue changes were observed in male white rats and rabbits treated topically for 8 d with 0.75 mL of 15%, 20%, or 30% aqueous THPC (Aoyama 1975). Treatment was intended to be for 20 d in both species but was discontinued after 8 d in rats because of severe weight loss and after 6 d in rabbits due to severe skin reactions. Rabbits continued to be observed until d 20. In rats, histological examination of the skin showed atrophy, enhanced keratinization of the epidermis, and degeneration of the hair roots in all treated animals. In rabbits, histological examination of the skin showed severe subepidermal fibrosis without regeneration of epidermis papillae.

A high rate of deaths occurred in white mice treated repeatedly on their tails with aqueous extracts from fabric treated with a THPC-based FR (Afanas'eva and Evseenko 1971). Mice were treated with the extracts daily for 21 d. The extracts reportedly contained formaldehyde, hydrogen chloride, and organophosphorus compounds (not identified). 
The authors did not describe how the extracts were prepared, the sex of the animals used, or the number of animals tested. The authors reported that 50–70% of the treated animals died over the course of the experiment and exhibited weight loss and changes in the appearance of their fur. Tail-skin irritation was evident after 10–12 d of treatment and many of the tails fell off.

Immunological Effects
Afanas'eva and Evseenko (1971) reported that many (number not reported) of the mice treated with aqueous extracts from fabrics treated with a THPC-based FR developed leukopenia. The authors note that in addition to exposure to THPC, the extracts also contained formaldehyde, hydrogen chloride, and organophosphorus compounds and the exact composition of the extracts was not reported. Therefore, it is not possible to determine whether dermal exposure to THPC itself was the cause for the increased incidence of leukopenia in this study.

Neurological Effects
Mice treated with aqueous extracts from fabrics treated with a THPC-based FR became sluggish, had “reduced working capacity” for static work, and 20–40% lower cholinesterase activity levels (Afanas'eva and Evseenko 1971).

Developmental Effects
No studies were identified that investigated the toxic effects of THPC on reproduction or development following dermal exposure.


Beyond gold: rediscovering tetrakis-(hydroxymethyl)-phosphonium chloride (THPC) as an effective agent for the synthesis of ultra-small noble metal nanoparticles and Pt-containing nanoalloys†
José L. Hueso,*ab   Víctor Sebastián,a   Álvaro Mayoral,ac   Laura Usón,a   Manuel Arrueboab  and  Jesús Santamaría*ab  
Author affiliations
Abstract
The use of tetrakis-(hydroxymethyl)-phosphonium chloride (THPC) as simultaneous reducing agent and stabilizing ligand has been extended to the single-step synthesis at room temperature of a wide variety of monometallic nanoparticles and bi-/tri- metallic nanoalloys containing noble metals with potential application in catalysis. 
The colloidal suspensions exhibit mean diameters below 4 nm with narrow size distributions and high stability in aqueous solution for long periods of time.


Flame Retardant Finish of Cotton Fabrics by Ammonia Curing/THPC-Urea
December 2016 Textile Science and Engineering 53(6):434-441
DOI:10.12772/TSE.2016.53.434
Abstract
Cotton fabrics were treated with tetrakis(hydroxymethyl)phosphonium chloride-urea precondensate via pad-dry-ammonia curing to reduce the flammability of the fabrics. 
Optimum finishing conditions were investigated for durable flame retardancy including the physical properties such as tensile strength and color fastness to washing. 
The fabrics treated by this technique showed excellent durable flame resistance, higher tensile strength, and a slightly lower tearing strength in comparison with the untreated fabric.


Title:     THPC - Thiourea Flame-Retardant Finish for Cotton Textiles
Authors:     Sharma, J. K.
Lal, Krishan
Bhatnagar, Hari L.
Issue Date:     Dec-1977
Publisher:     NISCAIR-CSIR, India
Abstract:     A new formulation based on tetrakis (hydroxymethyl)-phosphonium chloride (THPC), thiourea and small amounts of ammonium dihydrogen orthophosphate has been tried as an agent for imparting flame retardancy to cotton textiles. 
The effect of laundering on the tensile strength tear strength char length crease recovery, flex abrasion, air permeability and oxygen index of the treated sample has been studied. 
The treated fabrics exhibit flame-retardant properties even after 30 launderings. 
The performance of the formulation les within the limits specified in ASTM standards.


Tetrakis(hydroxymethyl)phosphonium chloride, oligomeric reaction products with urea
EC number: 500-057-6 | CAS number: 27104-30-9
The technical product "Tetrakis(hydroxymethyl)phosphonium chloride, oligomeric reaction products with urea" (THPC-urea) is a condensate of THPC and urea. The functional group of the THPC is the OH group. The functional group of the urea is the amino group NH2. The condensation of THPC and urea does not change both functional groups.

The first read across approach between THPC and THPS is considered applicable, as the organic phosphonium cation, which is the responsible part for the toxicological effects, is the same for both salts. The different anions (chlorid and sulfat) have no great influence on the solubility (both very high), the vapour pressure (both extrem low), and the log Kow (both extrem low and negativ).

The second read-across approach between THPC and THPC-urea is based on the fact, that THPC is an impurity of the technical product THPC-urea. THPC is more reactive and more toxic than THPC-urea. A worst case scenario is created assuming that THPC-urea is completely reactive like THPC.

Furthermore, the oxidative degradation of THPC-urea, THPS and THPC results in the same main metabolite THPO, which is far less toxic than THPC-urea, THPS and THPC.


Journal of Polymer Science: Polymer Chemistry Edition
Article
The chemistry of THPC–urea polymers and relationship to flame retardance on wool and wool–polyester blends. II. Relative flame‐retardant efficiency on wool, polyester, and wool‐polyester blends
Avraham Basch  Benjamin Nachamowitz  Sarah Hasenfratz  Menachem Lewin
Abstract
Optimum flame retardance in THPC‐urea‐type formulations was achieved by approximately 1—0.9 THPC‐urea mole ratio and slow urea addition. 
A phosphonium salt structure is more efficient in flame retarding 100% wool and wool‐polyester blends than a phosphine oxide structure. 
Both structures are equivalent in flame retarding 100% polyester. 
It is considered probable that a vapor‐phase mechanism is predominant in the phosphorus‐based flame retardancy of wool, whereas a mixed solid‐vapor phase mechanism operates for 100% polyester.


Tetrakis Hydroxymethyl Phosphonium Chloride-Urea (THPC-U)
Chemical formula:C9O7H24P2Cl2N2
Molecular weight:405.15
Standard executed:
Q/XFH 10-2014
Properties:Transparent or light yellow liquid.
Usage:
Flame retardant for the finishing of cotton and polyester fabrics. 
Applied to pure cotton or polyester cotton as well as other fabrics. 
Treated textiles show excellent flame-retarding, handling, wash resistance, and low tear strength effects as opposed to untreated fabrics.

At present, tetra-hydroxymethyl phosphonium chloride (THPC) is widely used in flame retardant finishing, industrial water treatment and leather manufacture industry etc., and its decomposition will affect the actual application. 
So the thermal decomposition and acid-alkali decomposition of THPC were studied by 31P nuclear magnetism resomance (31P NMR), thermo-grav imetric analysis (TGA) and differential scanning calorimetry (DSC) respectively. 
The results showed that THPC solution was stable when pH<5.0, containing THPC, tri-hydroxy methyl phosphine (TrHP), and tri-hydroxy methyl phosphine oxide (TrHPO ). 
THPC began to decompose at pH5.0 and yielded an unstable substance tetra-hydroxy methyl phosphonium hydroxide (THPH ), whose chemical shifts was 36ppm. 
At pH8.0, THPC converted to TrHP and TrHPO completely. When pH>9.0, all of the phosphorus compounds converted to TrHPO. 
Consequently, THPC content decreased when pH of the THPC solution rose. Thermal decomposition experiment was also carried out. 
The structure of THPC began to change when heated to 152.4°C and lose weight at 184.41°C. 
Therefore, application temperature should be below 152°C, which could give a favorable guide in THPC application.


The Action of Tetrakis(hydroxymethyl)phosphonium Chloride on Wool and Hair
L. S. Bajpai  C. S. Whewell  J. M. Woodhouse
First published: May 1961 https://doi.org/10.1111/j.1478-4408.1961.tb02435.xCitations: 14
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Abstract
Wool treated with THPC absorbs acid and premetallised dyes more readily than does untreated wool, and addition of THPC to solutions of premetallised dyes increases the rate at which the dye is taken up by the wool. 
Because of their ability to reduce the ·S·S· linkages in wool, solutions of THPC are effective setting agents, even at pH 1·3. 
Although oxidised, iodinated, and deaminated wools cannot be set in boiling water, they take a set in THPC solutions. 
Wool treated with potassium cyanide, however, cannot be set either in water or in THPC solutions.

Some Properties of Viscose Rayon Fabrics Treated with Tetrakishydroxy Phosphonium Chloride (THPC) Resins
R.S. GandhiFirst Published May 1, 1970 Research Article
https://doi.org/10.1177/004051757004000507
Article information 
 No Access
Abstract
Data are reported on the moisture regain, water of imbibition, tear strength, elastic properties, and flame resistance of chemically modified viscose rayon fabrics.

The data reveal that THPC behaves as if it were a derivative of formaldehyde. 
Under moderate curing conditions, substitution of hydroyxy groups in cellulose occurs, but when curing conditions are more severe, cross-linking takes place. 
Both triethanolamine and urea inhibit the reaction of THPC with cellulose and reduce acid degradation. 
Treatment of fabric with THPC-urea or THPC-melamine resins also leads to polymer deposition, especially at high curing temperatures. 
Both in the presence and absence of urea, when substantial quantities of triethanolamine are added, THPC decomposes, and the amount of phosphorus fixed is reduced. 
Triethanolamine appears to act in a complex manner; its effect is due not solely to its alkalinity. 
Only in the presence of urea does the fabric acquire flame resistance, although phosphorus is fixed even in the absence of urea. 
Fabric aminized with 2-amino ethyl sulfuric acid is on subsequent treatment with THPC, also flameproofed. 
Due to the presence of amino groups in the fabric, however, THPC reacts with fewer hydroxyl groups, and the losses in tear strength are less.


Production and use
(a) Production
Tetrakis(hydroxymethyl) phosphonium salts have been produced for commercial use since the 1950s. The first, THPC, was introduced in 1953. The salts are produced by the reaction of formaldehyde with phosphine in the appropriate aqueous acid (Weil, 1980; Hawley, 1981).

Two US companies supply THPS and THPC. Combined annual use of each compound in the USA is 900–4500 tonnes (National Toxicology Program, 1987).

(b) Use
Tetrakis(hydroxymethyl) phosphonium salts are used to produce crease-resistant flame-retardant finishes on cotton textiles and cellulosic fabrics (Hooper, 1973; Hooper et al., 1976a, b). THPC, THPS and THPA/P can be cured on the fabric with amine compounds (e.g., ammonia, urea, melamine-formaldehyde resins) to form durable, cross-linked flame-retardant resin finishes (Weil, 1980). Recently, THPS has largely replaced THPC in commercial use (Duffy, 1983); THPA/P has never been a major commercial product. Many co-reactants have been used to form flame-retardant finishes with these compounds. One of the most popular processes has been the tetrakis(hydroxymethyl) phosphonium hydroxide-ammonia finish, in which THPS is converted to a free organic base and then cured on the fabric by reaction with ammonia gas (Weil, 1980).

In 1974, over 14 million metres of cotton flannel for children's nightwear were estimated to have been treated with tetrakis(hydroxymethyl) phosphonium salts in the USA

A method of chemical aftertreatment for the reduction of free formaldehyde release of a durable flame retardant finished cotton fabric
Saleem, Saima
University of Borås, Faculty of Textiles, Engineering and Business.
2015 (English)
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
Student thesis
Abstract [en]
This thesis aims at developing a method of chemical aftertreatment for reduction of free formaldehyde release of a tetrakis (hydroxymethyl) phosphonium chloride (THPC) urea precondensate, ammonia cured durable flame retardant finished cotton fabric, by preventing the formation of free formaldehyde. 
Formaldehyde is toxic and carcinogenic. According to the worldwide standards, acceptable limit of free formaldehyde release, for the fabrics that have skin contact, is only 75 ppm (measured by water extraction method). In this research, a cotton fabric flame retardant finished in an industrial plant in Pakistan is used. Fabric is finished by the application of THPC urea precondensate and ammonia cured, oxidized and washed. After finishing, it is not aftertreated with sodium metabisulfite that is a commonly used aftertreatment method for the reduction of free formaldehyde release. Aftertreatment with sodium metabisulfite has various problems that include large number of hot washings and there is an increase in the formaldehyde release during fabric storage. 
If the fabric has 75 ppm of free formaldehyde, there is often an increase in free formaldehyde release during fabric storage. 
There is a very limited research on the aftertreatment methods and few reports of application of these aftertreatments on flame retardant fabrics have been published. 
In this research, two methods of aftertreatments are developed to reduce the free formaldehyde contents to 75 ppm or less. 
One is the aftertreatment with a combination of resorcinol 1% and diethylene glycol 4%. 
The other is the combination of resorcinol 1% and boric acid 6%. 
For both these aftertreatments, ammonium acetate 0.5% is used as a catalyst. 
Fabric is padded with the solution and then dried at 130̊ C for 8 minutes. 
After drying, fabric is rinsed with water at 40̊ C. 
The aftertreatment methods developed in this research have shown a long term effect in keeping the formaldehyde release below 75 ppm during fabric storage that is not available with other conventional aftertreatment methods. 
These aftertreatment methods have no adverse effect on the flame retardancy of the THPC ammonia cured finished fabric and the fabric is soft as compared to the original flame retardant finished fabric and to the fabric after treated with existing methods. 
These new developed methods have industrial application because there is no use of any solvent and there is no use of any special equipment for the aftertreatment.

Place, publisher, year, edition, pages
2015.
Keywords [en]
Aftertreatment, flame retardant, free formaldehyde, tetrakis (hydroxymethyl) phosphonium chloride (THPC) urea pre-condensate, ammonia curing, sodium metabisulfite, resorcinol, diethylene glycol, boric acid, curing, oxidation

The Effect of Tetrakis(hydrogymethyl)phosphonium Chloride (THPC) on Selected Properties of Fibers
Anne Tai, Howard L. Needlfs
First Published January 1, 1979 Research Article
https://doi.org/10.1177/004051757904900108
Article information 
 No Access
Abstract
The effect of tetrakis(hydroxymethyl)phosphonium chloride (THPC) on the physical and chemical properties of wool. cotton, rayon, nylon, and polyester was examined. 
THPC had the greatest effect on wool, reducing its flammability and decomposition temperature and increasing the extensibility and dyeability of the fiber. 
The effect of THPC on cotton and rayon differed, primarily due to the greater extent of reaction of THPC with rayon than with cotton. 
Both cellulosics became slightly more flame retardant, their decomposition temperatures decreased, and both became more weak and brittle. 
In addition, THPC-treated rayon showed improved wet wrinkle recovery and dyeabitrty with d rect dyes. 
THPC reacted with nylon to give a more flame retardant fiber of lower decomposition temperature and greater dyeability, but the treated nylon also exhibited inferior tensile properties. 
Polyester did not react significantly with THPC and showed only slight changes in properties. 
THPC treatment had a marked effect on the fibers, and this effect should be considered when preparing finishes containing this reagent.

Flameproofing of textiles
Dec 11, 1975 - Albright & Wilson Ltd.
A process for flameproofing cellulosic textile fibres which comprises impregnating the fabric with an aqueous solution containing a pre-condensate of urea and a THP salt together with any excess of the THP salt necessary to make up a ratio of urea to THP lying between 0.05:1 and 0.25:1 molar, the solution being neutralized by the addition of an alkali or base to a pH in the range 5 to 8, and treating the impregnated fibres with ammonia to form a cross-linked polymer.

Latest Albright & Wilson Ltd. Patents:
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Skip to: Description  ·  Claims  ·  References Cited  · Patent History  ·  Patent History
Description
This invention relates to a treatment of cellulosic textile fibres to render them flame-resistant. Such treatments are referred to herein for convenience as `flameproofing` treatments notwithstanding that they may not completely inhibit all flame formation. The treatment to which the invention relates is that in which fibres are impregnated with a precondensate of a tetrakis hydroxymethyl phosphonium salt such as the chloride (hereinafter called a THP salt or THPC in the case of the chloride) and a nitrogen-containing compound and are then treated with ammonia. In this way a cross-linked polymer is formed on the fibres and renders them flame-resistant.

An early disclosure of a flameproofing treatment involving the use of THPC and a nitrogen compound was U.K. patent specification No. 740,269, in which the cross-linking or curing of the polymer was effected by heat. In U.S. Pat. No. 2,772,188 it was proposed to cure the polymer by the use of ammonia, while U.K. patent specification No. 906,314 which corresponds to U.S. Pat. No. 2,983,623 describes the process, which eventually achieved commercial success, of applying the ammonia in two stages, first as gaseous NH.sub.3 and second as aqueous ammonia. The result aimed at in this evolution was so to control the degree of cross-linking that the add-on of resin required for flameproofing did not unduly impair the handle of the textile. In addition it was desired to reach an acceptable degree of wash-fastness and this was substantially achieved by the two stage gaseous/aqueous method.

The best results in terms of a compromise between maximum flameproofing and softest handle have been obtained by using urea as the nitrogen compound and curing with ammonia. Heat curing of urea polymers is unsatisfactory and it would be necessary to use a compound of higher functionality such as melamine, or a mixture of melamine and urea, if heat curing were to be used, but in fact this method is not used since it results in fabric with a poor handle.

It has been assumed hitherto that if an ammonia cured urea/THPC resin is to be used, the correct proportions of urea to THPC are those in which these reactants appear in the pre-polymer which is to be cross-linked with the aid of ammonia, namely 0.5:1 molar. However two recent developments have led to difficulties in the use of this composition. The first is the desire to flameproof lighter fabrics than hitherto, the second the imposition of stricter flameproofing tests for certain goods. As regards the first, while the composition is satisfactory for fabrics of greater weight than say 4 oz per sq yd, if applied to lighter fabrics it may impair the handle to such an extent as to make the fabric unacceptable.

In order to deal with this problem attempts have been made to use ammonia-cured THPC alone, without the addition of a nitrogen compound such as urea. To make this possible, the THPC is first neutralised from its normal pH of about 3 to 7 by the addition of a suitable alkali or base. Such a process is the subject of U K patent specification No. 938,990, but some confusion has since arisen owing to the description of similar processes as having been carried out with `THPOH`. In fact the existence of this specific compound in neutralised solutions of THPC is somewhat hypothetical, and we prefer to use simply the expression `neutralised THPC`.

The flameproofing of textiles is governed in many countries by specifications issued from time to time by governmental bodies. Originally specifications generally in force were based on vertical strip tests such as British Standard (BS) 3119:1959. At the present time children's nightwear is governed by the following specifications: BS 2963:1958 in the U K and United States Specification FF3-71 in the USA. We have established that these latter tests are more severe than those previously used and that higher add-ons of THP-based flameproofing resins are required to meet these standards. This results in a firmer fabric handle, which may be unacceptable even for fabrics which could be satisfactorily treated under the original specifications.

The object of the present invention is to provide a flameproofing treatment which will meet all the above specifications without rendering the resulting fabric unacceptably stiff. It will be appreciated that these two requirements are opposed to each other and we have discovered that by varying the ratio of urea to THPC in the impregnating solution we can shift the result towards greater flame resistance or better handle, and that by selecting the ratio within certain limits a fabric acceptable on both counts can be obtained.

The invention consists in a process for flameproofing cellulosic textile fibers which comprises impregnating the fabric with an aqueous solution containing a pre-condensate of urea and a THPC salt together with any excess of the THPC salt necessary to make up a ratio of urea to THP lying between 0.05:1 and 0.25:1 molar, the solution being neutralised by the addition of an alkali or base to a pH in the range 5 to 8, and treating the impregnated fibres with ammonia to form a cross-linked polymer.

The impregnating solution for use in the invention may be made up by mixing the requisite quantities of urea and THPC in water and refluxing to cause them to react to form the pre-condensate. Alternatively a solution with a molar ratio of urea to THP salt of 0.5:1 may be refluxed and the necessary quantity of THPC to obtain the correct ratio of urea to THP added afterwards. However it is made, the solution is neutralised to a pH of 5 to 8, preferably 5.8 to 7. This is conveniently effected by adding caustic soda, but other alkalis such as sodium carbonate can be used. It will be understood that too high a pH may lead to instability of the solution, in which case a lower pH within the stated range is used.

The THP salt is normally the chloride, but other halides such as the bromide, or other salts such as the acetate the sulphate or phosphate, may be used.

The concentration of the solution of pre-condensate is preferably 20 to 40% by weight. Preferred values are 25 to 30%. It is convenient to make initially a solution of about 50% concentration, which is then diluted shortly before use. Preferably the neutralisation is effected at this stage rather than at the manufacturing stage.

The treatment with ammonia may be carried out by the two-stage gaseous/aqueous process referred to above. Alternatively the rapid gas cure method which is the subject of British Pat. Nos. 1,439,608 and 1,439,609 may be used.

A better understanding of the invention will be given by the following experimental results:

Five sets of solutions were made up, each set having a different value for the molar ratio of urea:THPC as follows:

(a) 0, (b) 0.05, (c) 0.125, (d) 0.25, (e) 0.5.

The solutions within each set had successively decreasing total contents of THPC in order to vary appropriately the add-on of THPC on the treated fabric. The most concentrated solution of each set was made by preparing a solution of a urea THPC pre-condensate (molar proportions 0.5:1) with excess THPC (except in the case of (e)) in such quantities that the total THPC content was 48% and the molar ratio of urea:THPC was that required for the set. Five parts of caustic soda per 100 parts of THPC was added to give a pH of 5.9. This solution as such, and diluted solutions obtained by adding successive quantities of about 10% of water made up the set.

Samples of a cotton winceyette fabric weighing 150 g per sq meter were padded in each solution of each set to approximately 80% wet pick-up and the THPC add-on as referred to below was calculated from the percentage of THPC in the solution and the wet pick-up. Each sample was dried at 85.degree. C and then cured continuously by passing ammonia gas through the fabric at the rate of 251/minute. The samples were then washed for 30 minutes at 50.degree. C in a solution of 4.5g/1 of synthetic detergent containing approximately 20% of sodium perborate, rinsed well and dried.

The samples were then tested according to the following flammability tests.

British Standard 3119:1959 A general test for flameproof fabrics using a conditioned specimen 121/2 inches .times. 2 inches ignited by applying a standard 11/2 inches high luminous flame for 12 seconds.

Department of Commerce FF3-71 Specified in the USA for children's sleepwear. A predried specimen held in a clamp which covers the vertical edges ignited by standard 11/2 inches high luminous flame applied for 3 seconds.

British Standard 2963:1958 Method A Specified for Children's Nightwear in the U K. A free hanging strip of conditioned fabric 6 feet by 11/2 inches is ignited by applying the standard 11/2 inches high luminous flame for 12 seconds. This method gives erratic results with flame retardant treated in fabrics because the specimen is free to move in and out of the flame. The test was modified by using a shorter (15 inches) sample and by applying the igniting flame continuously to the lower edge of the specimen until it was ignited across the full width and immediately withdrawing the igniting flame (approximately 3 seconds).

The acceptance limits for the three tests were maximum char lengths on any specimen of 41/2 inches on BS 3119, 7 inches on FF3-71 and 10 inches on BS 2963. Although it might appear that the severity of a particular test would be related to the permitted char length the reverse proved to be the case, since the use of a shorter ignition time favours the maintenance of the burning once the specimen has been ignited, whilst the provision of vertical edges as in BS 2963 permits the more rapid spread of flame. It is possible to class the treated fabric samples into 4 groups as follows:

Fr class 1 -- Fail all three tests

Fr class 2 -- Pass BS 3119 but fail FF3-71 and BS 2963

Fr class 3 -- Pass BS 3119 and FF3-71 but fail BS 2963

Fr class 4 -- Pass all three tests.

In addition the samples were graded for handle and were divided into two groups:

Group A -- Fabric handle acceptable

Group B -- Fabric handle excessively stiff.

Table I shows the results of the above in terms of THPC add-ons for the various gradings. (See over).

Table 1 ______________________________________ % THPC add-ons giving different Flame Resistance and Handle Gradings Set urea/ molar (a) (b) (c) (d) (e) THPC 0 0.05 0.125 0.25 0.5 ______________________________________ FR Class 4 Handle B -- 39.0, 32.2 38.9, 32.3 32.1 26.2, 23.1 Handle A -- 28.1 27.0 26.3 FR Class 3 Handle B 39.0, 35.0 -- -- -- 21.5 Handle A 32.2 25.1, 22.8 21.9 22.6 19.2 FR Class 2 Handle A 28.8, 26.4 20.6, 17.0 18.6, 15.3 18.5, 15.7 17.6, 15.9 24.1, 19.6 14.2 16.3 FR Class 1 Handle A -- 13.6 12.6 12.6 12.2 ______________________________________

In a further set of experiments solutions with various urea:THPC mole ratios and a concentration of total THPC of 32% were made up as described above and used to test samples of the same fabric in the same way. The samples were assessed for flame resistance and handle again in the same way as described above. The results in terms of THPC add-on, flame resistance and handle are shown in Table II. The whole was repeated using a series of solutions with a total THPC concentration of 24% and the results are shown in Table III. (See over).

Table Table II ______________________________________ Urea/THPC % THPC Flame Resistance Handle Molar Ratio Add-on Class Group ______________________________________ 0 26.5 2 A 0.05 25.7 3 A 0.1 25.1 3 A 0.15 25.1 3 A 0.2 26.1 3 A 0.25 25.6 4 A 0.3 25.9 4 B 0.35 25.9 4 B 0.4 27.0 4 B 0.45 26.5 4 B 0.5 25.2 4 B ______________________________________

Table III ______________________________________ Urea/THPC Flame Resistance Ratio % THPC Class Handle ______________________________________ 0 19.8 2 A 0.05 19.0 2 A 0.1 19.4 2 A 0.15 19.4 2 A 0.2 19.6 2 A 0.25 19.0 2 A 0.3 19.4 2 A 0.35 19.6 2 A 0.4 19.2 3 A 0.45 19.2 3 A 0.5 18.6 3 A ______________________________________

The results of Tables I, II, and III are shown graphically in the accompanying drawing, in which the abscissae represent molar ratios of urea:THPC and the ordinates the percentage THPC add-ons. The prints represent the figures in the Table and each is marked with its FR class number. The distribution of the points is such that the field can be divided into four areas as shown each corresponding with one of the FR classes. Curve H divided the field according to the handle of the respective samples, Group A (acceptable) lying below curve H and Group B (unacceptable) above the curve.

It will be seen that fabrics which pass all the flame resistance tests and have an acceptable handle are those treated with solutions in sets (b), (c) and (d), ie with molar ratios of urea to THPC of 0.05:1 to 0.25:1.

Claims
1. A process for flameproofing cellulosic textile fabric which comprises impregnating the fabric with an aqueous solution containing a pre-condensate of urea and a tetrakis hydroxymethyl phosphonium salt together with any excess of the tetrakis hydroxymethyl phosphonium salt necessary to make up a ratio of urea to tetrakis hydroxymethyl phosphonium lying between 0.05:1 and 0.25:1 molar, the solution being neutralised by the addition of an alkali or base to a pH in the range 5 to 8, and treating the impregnated fibres with ammonia to form a cross-linked polymer.

2. A process as claimed in claim 1 in which the tetrakis hydroxymethyl phosphonium salt is the chloride.

3. A process as claimed in clain 2 in which the pH of the solution lies between 5.8 and 7.

4. A process as claimed in claim 1 in which the pH of the solution lies between 5.8 and 7.

Tetrakis(hydroxymethyl)phosphonium chloride (THPC) and sulfate (THPS) are of importance in the textile industry as flame retardants, in the oil industry as scale-removers, as biocides for water systems, in the leather industry as tanning agents, in nanochemistry as reductants and stabilizers of nanoparticles, and as oxygen-scavengers in medical uses. 
In the majority of cases, THPC and THPS themselves are not chemically active and solely play a role of reservoirs for the more reactive species tris(hydroxymethyl)phosphine (THP) and/or formaldehyde. The contents of THPC/THPS solutions greatly depend on pH, which is now recognized as a key factor, for example, in metal hydrosol preparations, biocidal activity, and ecotoxicity.

1. Tetrakis(hydroxymethyl)Phosphonium Derivatives

The bulk of today's durable flame retardant for cellulose centers around the use of derivatives of tetrakis(hydroxymethyl)- phosphonium salts (THP). 
These derivatives can be applied by padding, drying, curing and oxidizing to yield serviceable flame retardant fabrics. 
Add-ons are high and the handle of the fabric is stiffer so the finish is normally used for protective clothing applications.

a. Tetrakis (hydroxymethyl) phosphonium Chloride (THPC)

THPC is the most important commercial derivative and is prepared from phosphine, formaldehyde and hydrochloric acid at room temperature. 
It contains 11.5 % phosphorous and is applied by a pad-dry-cure -> oxidize -> scour process.

The compound is highly reducing in character and the methylol groups condense with amines to form insoluble polymers. 
It is applied with urea, dried and cured. 
Control of pH and the oxidation state of the phosphorus is important in determining the flame retardant properties and the durability of the finish. 
The release of HC1 may cause the fabric to tender during curing unless pH is controlled. 
The final step in finishing requires oxidation of P+3 to P+5 with hydrogen peroxide. 
This step too must be controlled to prevent excessive tendering of the fabric. 
An alternative to the THPC is THPS. Sulfuric acid is used instead of HC1 and the corresponding phosphine sulfate is formed in place of the phosphine chloride.

b. THPC-Urea Precondensate
The Proban process (Albright and Wilson) replaces heat curing with an ammonia gas curing at ambient temperature. 
This minimizes fabric tendering associated with heat and acids. 
A Precondensate of THPC with urea (1: 1 mole ratio) is applied, dried and the fabric passed through an ammonia gas reactor. 
An exothermic reaction creates a polymeric structure within the voids of the cotton fiber. 
The ammonia cure gives a P:N ratio of 12. 
Weight percentages of the respective elements should be P,N > 2%. 
To enhance durability and light fastness of dyes, P+3 is oxidized to P+5 with hydrogen peroxide.

c. Tetrakis (hydroxymethyl) phosphonium Hydroxide (THPOH)
From the forgoing discussion, THPC is usually partly neutralized with amines, amides and/or alkali. 
Complete neutralization of THPC with sodium hydroxide yields a compound referred to as THPOH. 
The distinction between THPC used in a partially neutralized condition and THPOH is difficult to define. 
If the curing agent is basic as is ammonia, the distinction become meaningless.


THPOH-ammonia has received a great deal of commercial attention. 
The major advantage over THPC is reduced fabric tendering and reduced stiffness. 
Fabrics padded with THPOH give off formaldehyde during drying.


Flame retardant finish on textiles
by webmaster | Jun 20, 2019 | Challenges

Flame retardant finish on textiles
Introduction
 
Textiles are subject to growing requirements for fire resistance. 
It’s a very broad field: the risks of exposure to fire are very different for a firefighter, a bath towel, a bed sheet or a curtain. 
Similarly, the consequences of a fire on a boat, on a train or a building are very different.

It is therefore not surprising that a wide variety of solutions exists to make a textile flame-retardant, nor that a large number of standards have emerged to respond to this wide variety of situations.

In order to obtain a fabric meeting one or more of these standards, following options are possible:

To use an intrinsically fireproof material: asbestos, fiberglass or, more recently, basalt.
To add a flame-retardant product to the mass of the fiber. This obviously only works with artificial fibers (viscose type) or synthetic fibers (such as polyester or polyamide).
To perform a treatment on the fabric itself.
The first solution has the advantage of being radical but not necessarily comfortable nor cheap. 
Furthermore, the resources used are often non-renewable.

The second solution has the advantage to give the certainty of acquisition of the permanent character of the property. 
However, this involves greater logistic constraints because it is necessary to have at the desired time the necessary wire, in good fineness and good twist. 
Beside that the fibers tend to be more expensive, the synthetic fibers are inclined to melt in case of fire. 
The resultant droplets can cause deep and painful burns. 
This feature makes the pure synthetic fibers poorly suited for protective clothing.

The rest of this article will be devoted to flame-retardant treatments on fabrics, which offer the overall advantage of being able to be applied late in the manufacturing process, which eases logistic constraints. 
In addition, the treatment can often be modulated by varying the amount of product. 
This enables to optimize the result, taking into account multiple constraints: fire resistance, mechanical and coloristic characteristics, handle, price, …

Textile treatments
 

Multiple axes can serve as a classification here: the nature of the fibers (cellulose, polyester, wool,…), the wash resistance  of the treatment (from not washable to permanent), the application process (padding or coating, mainly) and finally fire/smoke requirements characterized by national or international  standards, the latter particularly for maritime, air or rail transport.

In the framework of the FARBioTY project, we are focusing on flax fibers, composed mainly of cellulose, for use in the railway sector. 
In this context, the only interesting point is the durability of the treatment.

From non-permanent to permanent
 

Non-permanent and semi-permanent treatment

In this category, the principle consists of dissolving a salt in water, impregnating the fabric with this solution and drying the fabric. 
The salt remains on the fabric and helps to delay the appearance or spread of fire. Impregnation is often performed by padding; in the textile field, this operation refers to dipping the fabric in a bath, followed by a passage between two superimposed rollers on which applies a high pressure. This device called ‘mangle’ makes it possible to standardize the impregnation, to get the product deeply into the fabric and to recover the excess, thus facilitating the drying that follows.


This is a very simple technique to implement, relatively cheap and applicable to many fibers. 
However, there is no question of putting this cloth in machine to wash it because the salt would disappear immediately. 
It is therefore suitable for applications where the fabric is not exposed to water. 
Note also that some products in this class are based on halogens (especially bromine). 
Environmental and / or health issues have led to the ban of some of them such as decaBDE.

Semi-permanent treatments are used for substrates that may be exposed to water without being soaked. 
This concerns, for example, furniture fabrics, which can be rubbed and moistened to remove a stain. By cons, we rarely put a chair or an armchair in a washing machine! The biggest difference lies in the type of chemical used.

Permanent treatment
 

 

In this case, two types of treatment exist for cellulose: the first is to chemically bind a molecule to the cellulose, using one of its OH groups. 
The other is based on a polymerization of a product with itself, forming a network in and around the fiber, without creating any chemical bonding. In both cases, the product used is a phosphorus derivative.

In the first case, it is necessary to work in an acid conditions, which causes a loss of fiber strength, typically 15 to 30%. 
This solution was obviously not chosen for reinforcing fabric.

The other solution makes it possible to maintain almost unchanged mechanical strengths, it can also be used on cellulose / synthetic fiber mixtures and it gives a better resistance to fire. On the other hand, the fabric contains remnants of residual formaldehyde and the handle is more rigid.

It is applied as follows:

Padding in a bath containing the flame-retardant product. 
It is a pre-condensate of THPC (Tetrakis Hydroxymethyl phosphonium chloride).
Drying according to well-defined criteria.
Passage into a machine filled with gaseous ammonia allowing a polycondensation chemical reaction to take place. 
The ammonia group serves as a link between the different molecules.


Washing and oxidation to remove unbound products and to stabilize phosphorus at a five-fold bond
Finally drying

This technique allows obtaining excellent fireproof results, up to M1 and B1classifications, while maintaining the mechanical characteristics of the products. 
For now, it is mainly used for the production of protective clothing for trades exposed to fire risks: firefighters, military, metallurgists, electricians, …

Conclusion
 

This article proposes a brief overview of techniques for obtaining fire retardant fabrics. 
All the points discussed deserve further development, in particular the question of the physicochemical mechanisms used.
We hope, however, that this little text has clarified some ideas.


3,698,854 
PROCESS FOR PRODUCING FLAME RESISTANT ORGANIC
TEXT LES Darrel J. Donaldson, Floyd L. Normand, and George L. Drake, Jr., Metairie, La., assignors to the United States of America as represented by the Secretary of Agri culture No Drawing. Filed June 24, 1970, Ser. No. 49,556 Int. C. D06m 13/32, 13/38 U.S. C. 8-116 P 6 Claims 

ABSTRACT OF THE DISCLOSURE 
Cellulosic and other textiles are rendered flame resistant upon treatment with single-bath aqueous solutions con taining tetrakis(hydroxymethyl)phosphonium chloride or the related tetrakis (hydroxymethyl)phosphonium hy droxide, tris(hydroxymethyl)phosphine, and tris(hydroxy methyl)phosphine oxide-and cyanamide, in mole ratios of about from 1:0.5 to 1:4, respectively, and catalyzed preferably by a phosphorus-containing compound, such as phosphoric acid, ammonium phosphate, chloromethyl phosphonic acid, and sodium phosphate. 
The solutions are applied to various fabrics by the pad-dry-cure technique, and the treatments are found to be durable to innumerable laundering cycles. 
The finish contained the added quality of wrinkle resistance.

A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America. This invention relates to a process for rendering textiles flame resistant. 
More specifically, this invention relates to a process for rendering cellulosic and other organic textiles flame resistant upon treatment with one of several solu tions containing a phosphorus compound and cyan amide-the phosphorus compound being tetrakis(hydrox ymethyl)phosphonium chloride (THPC) or a derivative related thereto-and a catalyst of the phosphoric acid type. 
Textile products treated by the process of the instant invention are durable to repeated launderings and con tinue to be flame resistant. 
The treated products are obviously useful in the home, office, dormitory, etc. in the form of drapes, sheets, upholstery, garments, etc. 
The main object of the instant invention is to provide a new method of rendering textiles flame resistant. 
Another object of the instant invention is to cause cyan amide to react with phosphorus compounds of the type THPC by utilizing an acidic catalyst, such as phosphoric acid, to produce a flame resistant finish which is durable to innumerable launderings, and has the added property of wrinkle resistance without yellowing the textile material. 
Tetrakis(hydroxymethyl)phosphonium chloride is known to react with nitrogen compounds such as amines to form polymeric materials which, when applied to organic textiles, renders them flame resistant (see U.S. Patents 2,809,941 and 2,812,311). 
However, when THPC was reacted with cyanamide a slightly soluble material was formed and the fabric, treated with this material did not pass the vertical flame test.

O'Brien reported on a cyanamide-phosphoric acid flame retardant finsh for cotton. 
In the treating bath it was necessary to use at least 20% phosphoric acid to achieve any degree of flame resistance. 
The finish was not durable to laundering, and failed the standard vertical flame test after about 10 laundering cycles see Textile Research J., 38, page 256 (1968). 
We discovered that by incorporating THPC in the above formulation and an acid in catalytic concentration an insoluble polymeric material is formed and the fabric passes the standard vertical flame test (U.S. Federal Supply Service “Textile Test Methods,' Federal Specification CCC-T-1916, Method 5902, U.S. Government Printing Office, 1951). 
For example, a cotton fabric padded with a solution containing about 20.8% THPC and 9.2% cyanamide failed to pass the standard vertical flame test.
 However, when 1% of an acidic sub stance, such as phosphoric acid was added to the above Solution, the fabric passed the test. 
In general terms, the invention is this. 
A solution is prepared containing THPC and cyanamide in about 1:0.5 to about 1:4 mole ratio . . . the preferred ratio range being from 1:2 to 1:3 . . . 
THPC to cyanamide. To this solution an acidic substance such as phosphoric acid is added to give about from 0.5% to about 4% concentration, the preferred concentration being in the range of 1.5% to 2.5%. 
The organic fibrous material is immersed in this solution and the excess liquid removed by conven tional textile methods. 
The material is then dried and cured by any conventional manner such as an oven. 
It is of advantage to dry the textile at a temperature of about from 50 to 110° C. for about from 1 to 10 minutes, before it is cured at a temperature of about from 110° C. to 180 C. for about from 1 to 10 minutes. 
The fabric can also be dried and cured in a single step at the temperature range of about from 110° to 180° C.; however, the strength of the fabric is decreased as com pared to the conventionally dry-cured samples. 
The degree of flameprofing imparted to a textile by these compounds can be varied from a low degree to a very high degree by varying the amount of polymer de posited on the fabric surface. 
Surface active agents, water repellents, resin and other textile treating agents may be incorporated in the treating bath. 
Other advantages in accordance with the spirit of the instant invention are that textiles treated by this process are shrink resistant, wrinkle resistant, glow resistant, and rot resistant, and these effects are permanent and resistant to laundering and dry cleaning. 
In this process the term organic fibrous material in cludes any hydrophilic fibrous material that is a material which absorbs or adsorbs water, such as cotton, rayon, ramie, jute, wool, paper, cardboard, and the like materials and combinations of these as well as any chemical and physical modifications of these. 
In reference to the chemical reagents, the phosphorus containing compounds related to the preferred THPC, such as products formed from its decomposition and derivatives thereof can be used. 
For example, the intermedi ate THPOH can be used, as well as the oxide and other phosphonium salts. 
The THPOH is generally not a com pound which is retrieved from the top of the counter and poured. 
In fact, THPOH can be obtained by adding an aqueous solution of NaOH to THPC, enough to give a pH of about from 7 to 8. 
Illustrative examples of suitable nitrogen compounds include amides, and particularly cyanamide. 
Acidic materials compatible with this invention are phosphoric acid, ammonium and metal salts of persulfate, sulfamate, phosphate, chloride, nitrate, sulfate, and the like organic acids, such as acetic, citric and substituted phosphoric acids. 
The treated samples of the instant invention were tested in various manners, among which was the standard verti cal flame test (AATCC Test Method 34-1966), the angle flame test use by Guthrie et al. (see Textile Research J. 23, pages 527-32, 1953), wrinkle resistance (AATCC Test Method 66-1968), and rot resistance (AATCC Test Method 30-1957T).


The following examples are provided to illustrate the significant details of the invention and should not be con strued as limiting the invention in any manner whatever. 
The percent figures cited throughout the examples are based on weights. 
Example 1 
Scoured, desized, and bleached cotton sateen was im pregnated with an aqueous solution containing 10.2 g of cyanamide, 23.3 g of THPC (a THPC to cyanamide mole ratio of 1:2), 2.5 g. of phosphoric acid catalyst (HPO4), and 64 g. of water, to a 70% wet pickup. 
This sample was dried 5 minutes at 85 C. and cured 5 minutes at 50 C. in an electric oven. 
The sample was rinsed with hot water for about 15 minutes and then allowed to dry. 
The finished sample had a 17% add-on, and was submitted to and passed the 180° angle match test. 
The sample was further submitted to 30 laundering cycles, using a commercial detergent, then tested again, and found to pass the 180 angle match test as before, thereby illustrating the dura bility of the treatment to laundering.

Example 2 
A fabric sample of the type employed in Example 1 was impregnated with an aqueous solution containing 10.7 g. of cyanamide, 24.4 g. of THPC (a THPC to cyanamide mole ratio of 1:2), 1.0 g. of HPO and 63.9 g, of water to a wet pickup of 70%. 
The fabric was dried 5 minutes at 85 C. and cured 5 minutes at 150° C. in an electric oven. 
The finished sample had a 12% add-on, and had ex cellent flame resistance, as measured by standard vertical flame test. 
This flame resistance was equally effective after the sample had been submitted to 30 laundering cycles. 
Therefore, add-ons as low as 12% imparted durable flame resistance to the textile. 

Example 3 
A fabric sample of the type employed in Example 1 was impregnated with an aqueous solution containing 16.3 g. 
THPC, 7.2 g. cyanamide (a THPC to cyanamide mole ratio of 1:2), 1.6 g. of HPO, and 74.9 g of water to a wet pickup of 70%. 
The fabric was dried 5 minutes at 85 C. and cured 10 minutes at 140° C. in an electric oven. 
The sample was rinsed with hot water for 15 minutes and then allowed to dry. 
The finished sample had an 8.4% add-on, 1.73% phosphorus, and the flame test gave a 4.0 in. char length. The sample was submitted to 30 laundering cycles, and had a 1.38% phosphorus con tent with 3.75 in. char length.

Example 4 
A fabric sample of the type employed in Example 1 was impregnated with an aqueous solution containing 20 g. 
THPC, 13.8 g. cyanamide (a THPC to cyanamide mole ratio of 1:3), 2.5 g. HPO, and 63.7 g of water to a Wet pickup of 70%. 
The sample was dried 5 minutes at 85 C. and cured 3 minutes at 160° C. in an electric oven, then hot-water-washed and dried. 
The add-on was 16.3%, and the sample passed the standard vertical flame test after 30 laundering cycles with a 2.5 inch char length. 
Therefore, a ratio of 1:3 of THPC-cyanamide im parted durable flame resistance to the cotton textile.

Example 5 
A fabric sample of the type employed in Example 1 was impregnated with an aqueous solution containing 27 g. 
THPC, 5.9 g, cyanamide (a THPC to cyanamide mole ratio of 1:1), 2.5 g. of HPO catalyst, and 64.6 g. of water to a 70% wet pickup. 
The fabric was dried at 85 C. for 5 minutes and cured at 160° C. for 3 minutes. 
After washing and drying, the fabric sample had a 14.7% add on, and after 30 laundering cycles the flame test yielded a 3.0 in. char length. 
Therefore, a THPC to cyanamide mole ratio of 1:1 also provided flame resistance to the cotton textile, 4.

Example 6
The fabric sample and treatment was as in Example 5 except that the THPC to cyanamide mole ratio was 1:2. The finished fabric sample had a 9% add-on and after submitting the sample to 30 laundering cycles the flame test yielded a 3.0 inch char length. 

Example 7 
A fabric sample of the type employed in Example 1 was impregnated with an aqueous solution containing 22.2% THPC, 9.8% cyanamide, 4.0% dibasic sodium phosphate (Na2HPO4), and 64% water to a wet pickup of about 80%. 
The fabric sample was dried 4 minutes at 85 C. and cured 3 minutes at 160° C., then washed and dried as the other fabric samples. 
The add-on was 18.4%, and after 30 launderings passed the standard vertical flame test with a 4.0 char length. 
Therefore dibasic sodium phosphate was an effective catalyst in the THPC-cyan amide reaction. 

Example 8 
A desized, scoured, and bleached cotton printcloth was impregnated with a solution containing 19.5 g. 
THPC, 8.6 g. of cyanamide (a THPC to cyanamide mole ratio of 1:2), 2.0 g. HPO4, and 69.9 g, of water to give about 100% wet pickup. 
The wet impregnated fabric was dried 5 minutes at 85° C. and cured 5 minutes at 150° C., then washed in hot water and allowed to dry. 
The sample thus treated had a 19.9% add-on and a 2.6% phosphorus content. 
The flame test showed an initial char length of 3.75 inches after 30 laundering cycles. 
After laundering the phosphorus content was 2.22%. 
A portion of the treated fabric was placed in a soil burial bed. 
The treated sample retained 70% of its original breaking strength after 6 weeks in the burial bed while the untreated control had degraded completely within the first week of burial. 
Therefore, the THPC-cyanamide-HPO, system not only im parts durable flame retardancy to the textile but also pro tects the material from attack by microorganisms. 

EXAMPLE 9 
A fabric sample of the type employed in Example 8 was impregnated with an aqueous solution containing 19.5 g. THPC, 8.6 g. cyanamide (a THPC to cyanamide mole ratio of 1:2), 2.0 g. of HPO, and 69.9 g of water to a wet pickup of 85%. 
The sample was dried 2 minutes at 85 C. and cured 2% minutes at 150° C. on a tenter frame. The fabric was washed and dried as in the other examples, and had a 15.4% add-on. 
After the sample was Submitted to 30 laundering cycles the flame test gave a 5.0 inch char length. This fabric was submitted to wrinkle recovery evaluation tests and gave a dry, conditioned value of 253. 
The wet crease recovery angle was 226°. Therefore, the data shows that the finish imparts wrinkle recovery properties to the textile. 

EXAMPLE 10 
A fabric sample of the type employed in Example 8 was impregnated with an aqueous solution containing 17.3g. 
THPC, 7.7 g. of cyanamide (a THPC to cyanamide mole ratio of 1:2), 5 g. of ammonium phosphate (NH4)2HPO4 and 70 g. water to a wet pickup of 70%. 
The fabric was dried 5 minutes at 85° C. and cured 5 minutes at 140 C., then given a hot water wash and dried as in the other examples. 
The add-on was 17.5%. After 10 launderings the char length was 3.5 inches. 
The THPC-cyanamide finished is applicable to light weight fabrics such as printcloth. 

EXAMPLE 11
Desized, scoured, and bleached twill was impregnated with an aqueous solution containing 19.5 g. THPC, 8.6 g. of cyanamide (a THPC to cyanamide mole ratio of 1:2), 2.0 g. of chloromethyl phosphonic acid catalyst, and 69.9 g, of Water to a wet pickup of about 60%, Thefabric sample was dried at 85 C. for 3 minutes and cured 3 minutes at 160° C., then hot water washed and dried as in the other examples. The add-on was 12%. 
The sample was submitted to 30 laundering cycles, then flame tested as the others. The char length was 3.75 inches.
Therefore, chloromethylphosphonic acid was also an effective catalyst for the THPC-cyanamide system.

EXAMPLE 12 
A wool fabric sample was impregnated with an aqueous solution containing 15.7 g. of THPC, 10.3 of cyanamide (a THPC to cyanamide ratio of 1:3), 4.0 g. of HPO. catalyst, and 70 g. of water to about 80% wet pickup. The fabric sample was dried at 85° C. for 5 minutes and cured at 150° C. for 5 minutes, then washed in hot water for 15 minutes. 
The add-on was 15%, and the fabric passed the 180° angle match test. 

EXAMPLE 13 
Cellulosic cardboard was impregnated with an aqueous solution containing 15.7 g. THPC, 10.3 g. cyanamide (a THPC to cyanamide mole ratio of 1:3), 4.0 g. of HPO, catalyst, and 70 g. water to a wet pickup of about 110%. 
The sample was dried 10 minutes at 85° C. and cured 5 minutes at 150° C. 
The sample was washed in hot water for 15 minutes and allowed to dry. 
The add-on was 28%. The sample was submitted to a 180° angle match test and passed.

 EXAMPLE 14 
A broadcloth sample, a blend of 50% cotton and 50% avril, was impregnated with an aqueous solution contain ing 19.5%g. of THPC, 8.6 g. of cyanamide (a THPC to cyanamide mole ratio of 1:2), 2.0 g. of H3PO4 catalyst, and 69.9 g, of water to a wet pickup of 62%. 
After drying the sample 5 minutes at 85° C and curing 5 minutes at 150 C the sample was washed and dried as the other fabric samples. 
The add-on was 10%. The sample was then submitted to a 180° angle flame test and passed. 
We claim: 1. 
A process for imparting flame resistance to a cel lulosic material, comprising: 
(a) impregnating the cellulosic material with an aqueous solution containing 
(I) a phosphorus compound selected from the group consisting of tetrakis (hydroxymethyl) phosphonium chloride, tetrakis(hy droxymethyl) phosphonium hydroxide, tris (hydroxy methyl)phosphine oxide, and tris (hydroxymethyl) phosphine,
 (II) cyanamide, said phosphorus com pound and cyanamide being present in a phosphorus compound to cyanamide molar ratio of about from 1:0.5 to 1:4, and (III) about from 0.5% to 4.0% of chloromethylphosphonic acid; 
(b) drying the wet-impregnated material at a tem perature of about from 50° C. to 110° C. for about from 1 to 10 minutes; 
(c) curing the dry, impregnated material at a tem perature of about from 110° C. to 180° C. for about from 1 to 10 minutes; and ... 
(d) water-washing the cured material to remove all unreacted reagents. 
2. The process of claim 1 wherein the phosphorus compound is tetrakis (hydroxymethyl)phosphonium chloride.
 3. The process of claim 1 wherein the phosphorus compound is tetrakis (hydroxymethyl)phosphonium hydroxide. 
4. The process of claim 1 wherein the phosphorus compound is tris (hydroxymethyl) phosphine oxide. 
5. The process of claim wherein the phosphorus com pound is tris (hydroxymethyl)phosphine. 
6. The product produced by the process of claim 1.

Tetrakis(hydroxymethyl) phosphonium salts represent the major class of chemicals used as a flame retardant for cotton, cellulose and cellulose-blend fabrics. 
There is low migration from fabrics treated with tetrakis(hydroxymethyl) phosphonium chloride (THPC)-urea. 
The sulfate salt (THPS) is mainly used as a biocide. 

The acute oral toxicity of THPC and THPS is moderate; dermal toxicity is low.

         
IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, AND ANALYTICAL METHODS
Identity

Tetrakis(hydroxymethyl) phosphonium salts (THP salts) have the following general chemical structure :

     

The commercially relevant salts of THP are the sulfate (THPS) and the chloride (THPC). In addition, tetrakis(hydroxymethyl) phosphonium chloride-urea condensate is the major commercially available flame retardant product.

In the past other salts and salt-urea condensates have been used;their names and CAS numbers are listed in IARC (1990).

    Tetrakis(hydroxymethyl) phosphonium chloride (THPC)

    Chemical formula:         C4H12O4PCl

    Chemical structure:

     

    Chemical name:            Phosphonium, tetrakis(hydroxymethyl)
                              chloride

    Relative molecular mass:  190.56

    CAS registry number:      124-64-1

    CAS name:                 Phosphonium tetrakis(hydroxymethyl)
                              chloride

    IUPAC name:               Tetrakis(hydroxymethyl) phosphonium
                              chloride

    Trade names:              Tolcide PC800; Tolcide THPC; Retardol C

    Synonyms:                 Tetrahydroxymethyl phosphonium chloride
                              Tetramethylol phosphonium chloride

    C2.1.2  Tetrakis(hydroxymethyl) phosphonium sulfate (THPS)

    Chemical formula:         C8H24O8P204S

    Chemical structure:

    Chemical name:            Phosphonium, tetrakis(hydroxymethyl)
                              sulfate

    Relative molecular mass:  406.28

    CAS registry number:      55566-30-8

    CAS name:                 Phosphonium, tetrakis(hydroxymethyl)sulfate (2:1)

    IUPAC name:               bis[tetrakis(hydroxymethyl) phosphonium]sulfate (salt)

    Trade names:              Tolcide PS75; Tolcide THPS, Retardol S

    Synonyms:                 Octakis(hydroxymethyl) phosphonium sulfate

    C2.1.3  Tetrakis(hydroxymethyl) phosphonium chloride-urea condensate
            (THPC-urea)

    Chemical formula:         [C4H12O4P.CH4N2O.Cl]x

    Chemical name:            Tetrakis(hydroxymethyl) phosphonium
                              chloride-urea copolymer

    Chemical structure:

     

    Relative molecular mass:  300 for the repeat unit shown above

    CAS registry number:      27104-30-9

    CAS name:                 Phosphonium, tetrakis(hydroxymethyl)-chloride, polymer with urea

    Trade names:              Proban CC; Retardol AC
                              Proban 210 is no longer produced.

  

Technical products

THPC and THPS are marketed in concentrated aqueous solutions at approximately 80 and 75% (by weight), respectively 


    C2.3  Conversion factors

    THPC      1 ppm = 7.76 mg/m3
              1 mg/m3 = 0.128 ppm

    THPS      1 ppm = 16.61 mg/m3
              1 mg/m3 = 0.0602 ppm

Analytical methods

A standard method for THPS and THPC determination is by iodine titration. 
However, this not substance specific and is therefore subject to interference by many other chemicals that may be present in the sample to be analysed. 
The method involves dilution in water containing an aliquot of a saturated solution of disodium hydrogen orthophosphate. 
A solution of polystyrene sulfonic acid is then added followed by a few drops of a starch indicator. 
Titration against a previously standardized iodine solution is then carried out 

      

        Table 8.  Physical and chemical properties of THP salts
                                                                                                                           
       Parameter                           THPS                                     THPC                  THPC-urea copolymer

                                 100%                     75%                      80-85%
                                                                                                                            

    Appearance             Soft waxy solid         Colourless liquid            Clear straw-coloured     Straw-coloured liquid
                                                                                liquid

    Odour                  Resembles               Resembles aldehyde           Pungent                  Pungent
                           aldehyde

    Boiling point (°C)                             108.5                        115

    Melting point (°C)     54.2-81.5                                                                     -21

    Flash point                                                                 >100

    Vapour pressure        <2.6 × 10-4 Pascal      26.7 mmHg at 25°C
                           at 20°C

    Viscosity                                      38 cStp at 25°C                                       0.27 Pa.s at 29°C

    pH                                             3.19 (0.01 M solution)       < 2                      5

    Stability              21°C -- stable for      21°C -- stable for 14 days   Stable under normal      Stable under normal
                           14 days                                              conditions               conditions
                           54°C -- stable for      54°C -- stable for 14 days
                           14 days

    Table 8.  (continued)
                                                                                                                           
       Parameter                           THPS                                     THPC                  THPC-urea copolymer

                                 100%                     75%                      80-85%
                                                                                                                            
    Decomposition                                  Oxides of sulfur, phosphorus Oxides of phosphorus;    Oxides of phosphorus;
    products                                       and carbon;  phosphine       chlorine, ammonia        chlorine, ammonia

    Relative density       1.53                    1.39                         1.34                     1.31

    Solubility             Infinitely soluble in   Completely soluble           Completely soluble       Miscible with water
                           water

    Log n-octanol/water                            -9.8 (calculated)
    partition coefficient
                                                                                                                            

Production levels and processes

THP salts have been produced for commercial use since the 1950s.
The first of these, THPC, was introduced in 1953.

THP salts are synthesized in high yields through the reaction of formaldehyde with phosphine and the corresponding acid in an enclosed process (Weil, 1980; Hawley, 1981).

PH3 + HCl + 4CH2O --> [(HOCH2)4P]Cl
The resulting products exist in an equilibrium with THP+, which is highly pH dependent. Increasing the pH shifts this equilibrium to the right with the resultant production of formaldehyde, i.e., one of the methylol groups from the THP salt becomes hydrolysed.

  

    C3.2.2  Uses

THPC-based products represent the major class of chemicals used as flame retardants for cotton, cellulose and cellulose-blend fabrics.
Until 1976, THPC was the major THP salt used as a flame retardant. In addition, THPS and some mixed salts were commercially available.

THPC-based flame retardants have been found to be more reactive and efficient as flame retardants when compared with similar THPS-based products (Albright & Wilson, personal communication to  IPCS). 
Nowadays, the THPC-urea condensates dominant the market for flame retardant treatment of cellulose and cellulose-blend fabrics  where durability to laundering and dry cleaning is required.

       

The major application of THPS now is as a biocide in a variety of preservative applications which include leather, textile, paper and photographic films, as well as industrial water treatment and offshore oil production processes.
    

    

What are the characteristics of pullene flame retardant fabrics
Pullulene is a kind of flame-retardant auxiliary agent and also a kind of flame-retardant process. 
The flame-retardant pullulene fabric produced by this process has many advantages and is widely used.
 
The flame retardant process of pullulene method originated from Aowei Company in the United Kingdom, and its main ingredients are low-molecular-weight pre-condensed products of tetramethylolphosphorus chloride (THPC) and amide. 
After the fabric is impregnated with flame retardant, the pre-condensed body formed by THPC and amide penetrates into the amorphous area and gap of the fiber, and then the ammonia gas cross-links the hydroxymethyl in the pre-condensed body during the ammonia fumigation, and is inside the fiber After forming a flame-retardant polymer, it is oxidized to stabilize it. 
Therefore, the fabric treated by the Proben method has a soft hand feel and little loss of strength, and basically maintains the comfort and durability of the fabric.
 
The water-soluble flame retardant of pullulan easily penetrates into the fiber and becomes a high molecular polymer after the ammonia fumigation chemical reaction, forming inherent crosslinks, making it have durable flame retardant properties, and this flame retardant 
The performance does not decrease with the increase of washing times. 
At the same time, this flame-retardant finishing does not change the original characteristics of the fabric fibers, thereby maintaining the original properties of the fabric. This kind of pullulene flame-retardant cloth has the characteristics of charring in case of fire, self-extinguishing from the fire, and effective prevention of flame spread. 
The flame-retardant protective clothing made of it can effectively prevent the flame from harming the human body and provide effective Security protection.
 
The development of flame-retardant fabrics made of pullulan makes fabrics made of natural fibers have reliable flame-retardant properties and good durability, which can be used in modern daily life and professional working environments.


 

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