John V. Beninate

Conventional Pad-Dry-Cure Process for Durable- Flame and Wrinkle Resistance With Tetrakis (Hydroxymethyl) Phosphonium Hydroxide (THPOH)

A durable-flame retardant based on tetrakis (hydroxymethyl ) phosphonium hydroxide (THPOH), urea, and trimethylolmelamine has been developed and applied to cotton fabric. The process is accomplished by padding fabric through a water solution of the three components to a wet pickup of about 75%, drying at moderate temperature, and curing at an elevated temperature. Solutions of 25-34% total solids containing the three components in a molar ratio of 2 : 4 : 1 (THPOH: urea : methylolmelamine), when applied to cotton fabrics of 8-9-oz weight, imparted flame resistance, and only minimal losses in breaking and tearing strength. The treated fabrics retained 91-95% break strength and 73-80% tear strength. Wrinkle recovery angles (W + F) of treated fabrics ranged from 280° to 306°. Wash- wear and durable-press properties are discussed. Little or no yellowing of treated fab rics was observed when bleached with sodium hypochlorite solution and scorched between heated plates. Resin add-ons of fabrics treated in this manner ranged from 15 to 19%. Flame resistance of fabrics treated by this process is retained after boiling the treated fabrics in a soap-sodium carbonate solution for 3 hr or after 15 laundering cycles.

Durable Flame-Retardant Treatments for Blends of Cotton, Wool, and Polyester:

Durable flame-retardant treatments based on a vinyl phosphonate oligomer or Thps were applied to cotton, cotton/polyester, cotton/wool, and cotton/polyester/wool medium-weight twill fabrics. The treatments were applied by either a pad, dry, cure process or a two-step procedure consisting of a pad, dry, cure application of DMDHEU followed by a Thps-NH3 cure process. Flammability of the treated fabrics was evaluated by a number of tests, including burning rate, vertical char length, oxygen index, and a flame-extinguishment test. Physical properties were determined by standard tests to measure breaking strength, wrinkle recovery, stiffness, durable- press rating and shrinkage due to laundering. Cotton/wool blend fabrics treated with Thps-urea-TM M had the best flame-retardant properties.

An Economical Durable Flame-Retardant Finish for Cotton1

Selected low-cost N-methylol compounds have been incorporated with tetrakis(hydroxymethyl)phosphonium hydroxide (THPOH formulations and applied to cotton fabric by a number of different processing techniques. N-methylol compounds evaluated in this study were trimethylolmelamine, dimethylolethyleneurea, and dimethylolmethoxyethyl carbamate. THPOH reacts with ammonia at room temperature and with methylolamides at elevated temperatures. The flame-retardant finish produced by reacting the phosphonium hydroxide with ammonia is very durable and effective at modest add-ons. Even with modest add-ons (12–20% depending on fabric construction and weight), the phosphorus content is rather high (up to 6%). This study has shown that the amount of phosphorus needed in the flame retardant can be reduced to a fraction of that originally required by increasing the nitrogen content. Use of trimethylolmelamine and THPOH with an ammonia cure, followed by a heat cure, produced the most effective flame resistance. Treated fabrics had 100% tensile strength retention and a good hand. This treatment has resulted in the use of lesser quantities of THPOH to produce a lower-cost durable flame-retardant finish for cotton.

The Effect of Hypochlorite Bleach on Flame-Retardant Finishes Based upon THPC

THPC-based flame retardants containing melamine or APO tend to yellow the fabric after high-temperature cure or after exposure to XaOCI bleach. The yellowing can be removed with Ka2S20.; however, it returns with repeated washes in hypochlorite solution D, 2]. The yellowing is thought to result from a reaction of chlorine with a nitrogen atom in the flame-retardant polymer [1]. If this is so the bleaching may also cause a loss in strength of treated fabric, which would also be related to the stability of the chlorine-nitrogen bond. THPC-amine and THPC-amide polymers, when first produced, exist partially as the phosphine (CH2hP and partially as the oxide (-CH=)3P-O [3]. It is known that an RZ02 or sodium perborate aftenvash of fabric treated with THPC-based flame retirdants oxidizes the phosphine structure and eliminates odors [4J It is conceivable that the oxidation state of the flame retardant also affects durability of the, finish to laundering with hypochlorite bleach. Seven THPC-based flame-retardant fabrics were given repeated hypochlorite washes and tested for flame retardancy, color, and breaking strength, and then these properties of nonoxidized and oxidized fabrics, after repeated hypochlorite washings, were compared. .

Wool -- Its Effect on Flame-Retardant Properties of Blend Fabrics

Durable phosphorus-based flame retardants were applied to twill fabrics con taining cotton and wool to study the effect of wool on the flame retardancy and physical properties of the blend fabrics. The presence of wool in untreated blend fabrics caused burning rates to decrease and oxygen index values to increase as wool content increased in the blends. These effects were also observed in cotton/ wool blends treated with low levels of the Thps-urea-TMM flame retardant, but were less pronounced in fabrics treated at high levels. Thermogravimetric analyses were conducted to study the thermal degradation of the treated and untreated fabrics. The presence of wool in treated blend fabrics did not sig nificantly change strength retention, area shrinkage and wrinkle recovery values in comparison to similarly treated 100% cotton fabrics.

Polyacrylates in flame retardant treatments of textile fabrics

Durable phosphorus-based flame retardants containing polyacrylate emul sions were applied to cotton, cotton-polyester, and cotton-wool twill fabrics to study the effect of the added polyacrylates on the physical properties and flame retardancy. The Thps-urea-TMM flame retardant with added polyacrylate im parted better overall physical properties to 100% cotton fabric than to cotton blend fabrics. Treatments containing polyacrylates with low glass transition temperatures produced fabrics with the highest abrasion resistance, tearing strength and wrinkle recovery. The flame retardancy of treated fabrics was not adversely affected by the addition of polyacrylates to the flame retardant treatments.

Technique for Measuring the Oxygen Index of Fibrous and Powdered Cellulose Derivatives

A technique to assess the flame resistance of small quantities of fibrous or powdered derivatives of cotton cellulose was developed. The procedure is an adaptation of the oxygen index (OI) fabric flammability test. Cellulose fibers or powders were pressed into 0.5-g discs, 1 1/4 in. in diameter which were used to measure the OIs in the instrument employed for fabric OI determinations. Comparison of OIs of discs and fabrics representing untreated and conven tionally treated FR cottons resulted in a linear relationship; disc OI values were higher due to higher fiber density and lower accessibility of oxygen to the substrate. Among the experimental treatments of cotton cellulose, OI values of fibrous and powdered celluloses were uniformly low with increasing tritylation, peaked and dropped with increasing tosyl concentration and rose with increas ing mesylation. Some derivatives would be considered flame resistant.