SUBSCRIPTS A B
= cyclohexane-benzene equilibrium
cyclohexane-methylcyclopentane equilibrium or component benzene C = cyclohexane Hz = hydrogen i = arbitrary component or reaction JP = methylcyclopentane 0 = total hydrocarbon partial pressure 1 = dehydrogenation of cyclohexane to benzene 2 = isomerization of cyclohexane to methylcyclopentane T = total =
literature Cited
Bertolancini, R. J., Brennan, H. RI. (to Standard Oil Co.), U.S. Patent 3,376,214 (April 2, 1968). Breck, D. W., J . Chem. Educ., 41 (12), 678 (1964). Bridges, J. hl., Houghten, G., J . Amer. Chem. Soc., 81, 1334 (1959). Ciapetta, F. G., PetrolChem Eng., 33 (j),C-19 (1961). Haensel, V., Donaldson, G. R., Riedl, F. J., Proc. of the Third Int. Congr. of Catalysis, 294 (1964).
Hooke, R., Jeeves, T. A., J . Ass. Comput. Much., 8 (2), 212 (1961). Hopper, J. R., PhD dissertation, Louisiana State University, Baton Rouge, LA, 1969. Hougen, 0. A., Watson, K. M.,“Chemical Process Principles, Part 111,Kinetics and Chtalysis,” Wiley, New York, NY, 1947. Jungers, J. C., Balaceanu, J. C., Coussemant, F., Eschard, F., Giraud, A., Hellin, M., Leprince, P., Limido, G. E., “Cin4teque Chimique AppliquB,” Technip, Paris, France, 1958. Levenspiel, O., “Chemical Reaction Engineering, ” Wiley, New York, NY, 1962. Miller, R., Chem. Week, 95 (20), 77 (1964). Mills, G. A., Heinemann, H., Rlilliken, T. H., Oblad, A. G., Ind. Eng. Chem., 45 (I), 134 (1953). Pickert, P. E., Bolton, A. P., Lanewala, 11.A., Chem. Eng., 75 (16), 133 (1968). Popescu, A., Negotia, N., Baiulescu, E., Bucuresti, Ser. Stiint Xat. (Romania), 12, 137 (1963); CA, 64, 12571 (1966). Ritchie, A. W., Yixon, A. C., Amer. Chem. SOC.,Dzv. Petrol. Chem. P r e p . , 11 (3), 93 (1966). Weller, S., AIChE J., 2 (I), 59 (1956). RECEIVED for review October 29, 1971 ACCEPTEDFebruary 7, 1972 Presented at the 68th National AIChE Meeting, February 28March 4, 1971, Houston, TX.
Flame-Retardant Finishing of Polyester-Cellulose Blends Giuliana C. Tesoro, Joseph Rivlin, and Donald R. Moore’ Research and Development Center, Burlington Industries, Inc., P.O. Box 21327, Greensboro, N C 27420
Experimental data reported confirm that organophosphorus flame retardants which are suitable for finishing of 100% cellulosics are not adequate for polyester-cotton blends. One approach to imparting durable flame-retardant properties to the blends is to include bromine in the insolubilized finish. Experimental routes available for this purpose are discussed. Results are presented for the modification of the cotton component in blends with a reactive unsaturated phosphonate, followed by bromination of pendant allyl groups introduced. This new approach offers a potentially promising method for obtaining flame-retardant polyestercotton blend fabrics without impairment of aesthetics.
T h e difficult problem of obtaining durable flame-retardant properties in polyester-cellulose fabrics and particularly polyester-cotton has been discussed extensively during recent years. Approaches that have been found satisfactory for 100% cellulosics have limited value for the finishing of blends, and few, if any, promising leads are available from published literature. The purpose of the m-ork reported is to provide a n experimental basis for a better definition of the problem and for meaningful generalizations regarding possible solutions. For 100% cellulose the insolubilization of compounds containing phosphorus and nitrogen has proved to be an effective way to impart durable flame-retardant properties. Although 1
To whom correspondence should be addressed.
164 Ind. Eng. Chem. Prod.
Res. Develop., Vol. 1 1, No. 2, 1972
the efficiency of insolubilization and effects on fabric properties vary significantly for different chemical systems, i t has been repeatedly shown that cotton (or rayon) fabrics containing a sufficient amount of nonionic phosphorus (preferably in conjunction with nitrogen) are in fact self-extinguishing. Such fabrics pass a vertical flammability test (e.g., AATCC 34-1966) and exhibit reduced flammability when tested in a normal environment by whatever procedure one may use (match test, oxygen index, rate of burning). Without dwelling on the parameters which determine “sufficiencyJ1for the amount of phosphorus present, we can state that self-extinguishing 100% cellulose fabrics can be obtained. With proper selection of fabric, chemical system, and conditions of application, the effect of the flame-retardant
finish on performance properties can be controlled, and flame retardancy can be retained through a large number of launderings, dry cleanings, or use exposures. The assumption that polyester-cotton fabrics could be finished similarly proved to be only partially correct and not fruitful, even in those instances where the presence of a relatively high percentage of cotton suggested a predictable response to the treatment's. An analysis of the reasons for the failure of polyester-cotton to respond t'o flame-retardant treatments based on insolubilizat'ion of organophosphorusnitorgen systems is revealing. The primary factors to be considered in comparing analogous systems on 100% cellulose and polyester-cellulose blends are: Efficiency of insolubilization (fixation of the finish) Effectiveness of fixed phosphorus (and nitrogen) in the presence of polyester Durability (and aesthetics) The efficiency of insolubilization is obviously dependent on t'he substrate. For hydroxyl reactive finishes, reaction efficiency can be expected to decrease as the amount of polyester in the fabric increases, and the tot'al number of available reactive sites (hydroxyls) decreases, even though factors other than stoichiometry may play a role. From an aqueous solution, t'he reagent's in the finish penetrate the cellulosic component preferentially, and for a given concentration of reagents in the treating solut'ion, the concentration present in the cellulose increases as the amount of cellulose present in the blend decreases. The effectiveness of fixed phosphorus and nitrogen in suppressing combustion is different for lOOyo cellulose and polyester-cellulose combinations. Since the postulat,ed mechanism of flame retardation by phosphorus in cellulose involves enhanced dehydrat'ion at' the expense of organic volatiles, it' is reasonable to assume that the presence of fuel originating from the pyrolytic degradat'ion of polyester would require additional and probably different combustionsuppressing species. Some evidence in support of this assumption can be found in the work of Hofman and Raschdorf (1970) who reported the results of preliminary work on the pyrolytic degradation of cotton and polyester. Ahalysisof the pyrolysis products obtained from 100% cotton and from 100% polyester, untreated and treated with K-methylol-3(dimethyl phosphono)propionamide (Pyrovatex CP) indicated, for example, that far greater amounts of benzene are formed in bhe pyrolysis of the polyester fabrics as compared to cotton. I n conjunction with concern for efficiency and effectiveness, consideration must also be given to problems of distribution and durability of the added finish on polyester-cellulose fabrics. The use of polymer-forming finishes (as dist,inct from the use of hydroxyl-reactive compounds) can minimize the problem of efficiency, since insolubilization in this case is not primarily dependent on reaction of the compounds with cellulose hydroxyls. However, this approach inherently leads to formatioil of polymer on fiber surfaces and to increased stiffness in treated fabric. Furthermore, for a t least one such treatment (Linden et al., 19iO), polymer present on the surface of polyester fibers tends to "peel off" in fibrillation and would presumably be lost in laundering and in use. Quantitative statements of these difficulties are not available from the literature. T o illustrate some problems of efficiency and effectiveness with precision, we will report data obtained on fabrics of varying polyester content with two systems known to be satisfactory for flame-ret,ardant finishing of 1007, cellulosics and considered to be illustrative
of a hydroxyl-reactive finish (phospkonate) and of a polymerfmming system. The fabrics had the characteristics given as foliows:
wt,
Count, W X F
021
s q yd
100% Cotton (sheeting) 65/35 Polyester-cotton (shirting) 50/50 Polyester-cotton (sheeting) 35/65 Polyester-cotton (sheeting)
3.86 2.97 3.54 3.85
104 135 99 76
X X X X
94 71 85 70
The finishing treatments were as follows: N-hlethylol3-(dimethyl phosphono) propionamide Pyrovatex CP: Technical Bulletin 081-4B (2iOM), T A P Division, Ciba Dye and Chemical Co. Bath Formulation: 4Oy0 (or lower) Pyrovatex C P (active solids); 0.35y0 2-Methyl-2-amino-1-propanol hydrochloride; 0.1% Xonionic surfactant Fabric samples (20-40 grams) were padded a t a roll pressure of 30 psi (about 70% wet pick-up), dried 4 min a t 93"C, cured 3 min a t 175OC, washed with nonionic surfactant, and dried. The use of melamine resin as coreactant, as recommended in the technical bulletin, was omitted to avoid the presence of extra nitrogen in the treated samples. Tetrakis(hydroxymethy1)phosphonium chloride-hydroxide-ammonia (THPOH) THPOH-NH3-02: Procedure essentially as described b y Beninate et al. (1968), modified to include oxidation of residual phosphine on the treated fabric Bath Preparation: A T H P O H solution was prepared by adding 25y0 S a O H to 80% tetrakis (hydroxy-methyl) phosphonium chloride dropwise with stirring until the p H reached 7.5. The concentration of the solution was then adjusted to the desired T H P O H content by adding the required amount of water. Fabric samples (20-40 grams) were padded a t a roll pressure of 30 psi (about 70% wet pick-up), partially dried (90 see a t 93OC), and immediately exposed to ammonia gas in a vented vessel for 5 min. The samples were washed with nonionic surfactant, then padded through a 10% solution of hydrogen peroxide, rewashed, and dried. Flammability evaluations were : Oxygen Index: See Fenimore and Alartin (1966) and Isaacs (1970) Vertical Test: AATCC 34-1966 For a system in which reaction of the flame retardant with hydroxyl groups is the predominant insolubilization mechanism, results are shown in Figure 1. This shows the relation-
o 65/35
COTTON/POLYESTER & 5 0 / 5 0 COTTON/POLYESTER
5
10
15
20
25
30
X Phosphonate (Pyrovatex CP) OWF
Figure 1.
Phosphonate treatment of cotton and blends
Ind. Eng. Chem. Prod. Res. Develop., Vol. 1 1 , No. 2, 1972
165
't
30t I
25t 2o 20 X Weight Gain
l5 15
100% COTTON o 6 5 / 3 5 COTTON/POLYESTER
I
5 0 / 5 0 COTTON/POLYESTER I 3 5 / 6 5 COTTON/POLYESTER
A
26
/loo%
t
COTTON
/
OXYGEN
-
t
5
POLYESTER /COTTON
O S;
3%) phosphorus content, corresponding to a 157, weight gain, is reached by applying the polymer-forming THPOH-"3-02 finish. Blends containing 35, 50, and 65% polyester give similar results with respect to this correlation. -4summary of data is shown in Table I. Some observations were made concerning the appearance of these treated fabrics: there was no discoloration; phosphonate-treated fabrics were relatively soft whereas THPOH-XH3-Oa-treated fabrics were stiffened significantly; measurements of flex stiffness showed a more pronounced trend of increasing stiff ness with increasing weight gain for the blends than for 10070 cotton. I n conclusion, the results show that these known systems (phosphonate and THPOH-KH3-O2) are not satisfactory for the flame-retardant finishing of polyester-cotton blends. For the phosphonate, reaction with cellulose in the blend gives low yields and insufficient phosphorus cont'ent. The effectiveness of the phosphorus introduced appears to be limited, since the slope of the oxygen index-phosphorus content curve indicates incipient leveling off of the oxygen index a t about 1% phosphorus. For the THPOH system, insolubilization proceeds in good yields on the blends, and high phosphorus content (>3%) can be obtained. However, the oxygen index increases slowly as the phosphorus content increases above l%, and the maximum oxygen index obtained is about 24.0. The effect of polymer-forming systems (such as THPOH-"1-02) on the hand of polyester blends is generally objectionable. Some indications of loss of finish in washing have also been obtained for the THPOH-NH3-02 system on 50150 polyester-cotton fabrics.
These results support the hypothesis that successful finishes for polyester-cotton should include components which can effectively suppress combustion of the polyester, in concert with the flame-retardant action of phosphorus in cotton. Halogen, and more specifically bromine, is a good candidate. The remainder of this report is concerned with the role of bromine in enhancing flame-retardant effectiveness of phosphorus-nitrogen finishes in polyester-cotton fabrics. Role of Bromine
There are, in principle, four general approaches for obtaining polyester-cotton blends in which the flame-retardant treatment includes bromine. These may be defined as follows: Use of modified (bromine-containing) polyester fiber in the blend and treatment of the cotton with a phosphorus-nitrogen system Application (to fabric by finishing) of a bromine-containing system for the polyester and a phosphorusnitrogen system for the cotton Application (to fabric by finishing) of a single reactive system in which bromine, phosphorus, and nitrogen are present Application (to fabric by finishing) of a reactive system in which phosphorus-nitrogen is present and bromine is added in a subsequent reaction of the modified fabric The first approach requires bromine-containing polyester fiber which is not currently available. A blend containing such a fiber, subsequently finished with flame retardants designed for the cellulose and applied from a n aqueous system, would consist essentially of two separately treated fibers. I t s behavior might be similar to that of fabric obtained b y the second approach, in which two flame-retardant systems designed for the polyester and cotton component, respectively, are introduced simultaneously or in sequence. Specific combinations of this type have been examined in a n AATCC Intersectional Contest (1968) and by Tesoro and Meiser (1970), and one has been covered in a recent patent to Ciba (1970). The third approach seemingly offers a practical route to the desired result (insolubilizing phosphorus, nitrogen, and bromine on the blend fabric). Several examples of flame-retardant polymers containing these elements and recommended for fabric finishing are documented in the literature (Hamalainen et al., 1956; Toy and Rattenbury, 1956). I n the case of reactive monomeric compounds, however, the solubility, distribution, and reactivity of organophosphorus reagents containing high percentages of bromine are different from those of halogen-free analogs, and generalizations concerning efficiency, effects, and durability are not possible. As a n example of problems encountered b y using reactive compounds of high bromine content, we report a comparison of reactions of two N-methylol 3-(dialkyl phosphono)propionamides on 50/50 polyester-cotton b y a catalyzed pad/dry/cure procedure. T h e compounds are: (R0)zPCHzCHzCONHCHzOH
/I 0 R=CHa (Pyrovatex CP) R=BrCH&HBrCHzThe fabric was treated with a solution of the reagent (from water for the methyl compound; from a water-dioxane mixture for the dibromopropyl compound), with 0.35% 2-methyl2-amino-1 propanol hydrochloride catalyst in a conventional
Table II. Application of Phosphonates to SO/SO Polyester-Cotton
(RO)J’OCHZCH,CONHCHzOH R=CHs-
Reagent (OWF), % ’ Weight gain, % Phosphorus found, yo Bromine found, yo,initial After 25 launderings After dioxane rinse Oxygen index, initial After 25 launderings After solvent rinse
R=CHzBrCHBrCHz-
34 8.4 1.25
34 16.0 1.0
...
7.8
... ... 22.5 22.0 22.6
4.8
1.5 25.6 23.1 20.0
pad/dry/cure/wash sequence. From the data summarized in Table 11, what appears to be high-reaction efficiency for the dibromopropyl compound is more probably deposition of the water insoluble reagent; a rinse with dioxane readily removes most of the added compound. Although these results are specific for the compound used {N-methylol-3- [bis(2,3dibromopropyl)phosphono]propionamide], they reflect some inherent difficulties in approaches involving reaction of cellulose with reactive organophosphorus compounds of high bromine content, and similar results have been obtained with other reagents i n this class. We have found that the difficulty can be avoided by employing phosphorus-nitrogen reagents containing unsaturation for modification of the cellulose and by introducing covalently bound bromine in a subsequent step as outlined in the fourth approach. I n the remainder of this paper, results obtained on 50/50 polyester-cotton by applying this “postbromination” concept are compared with the results of a two-component treatment corresponding to the second approach. The latter consisted of diffusion and heat fixation of a brominated compound into the polyester, followed b y finishing of the bromine containing fabric with a phosphorusnitrogen reagent. I n fabric treated in this manner, the bromine compound is present primarily in the polyester component, whereas phosphorus and nitrogen are part of the substituent group on cellulose. I n fabric treated by the postbromination sequence, bhe bromine, phosphorus, and nitrogen are covalently bound to the cellulose substituent, and the polyester component is essentially unchanged. This comparison was designed to provide answers to the following questions: Is the effectiveness of a given bromine content dependent on whether the bromine compound is present i n the polyester or in the cotton component? I s it possible to obtain flame-retardant polyester-cotton fabric by modifying the cellulose component only? Which combination of phosphorus, nitrogen, and bromine contents can provide adequate flame-retardant properties on polyester-cotton blends? Flame-Retardant Polyester-Cotton Blends (50/50)
The experimental procedures used for the preparation of the samples are outlined in Table 111, which also lists the compounds used for the treatments. The introduction of bromine was carried out as follows. Two-Component Sequence. Fabric samples were padded with the desired concentration of bromine compound [tris(2,3-dibromopropyl)phosphate or hexabromobiphenyl] in Ind. Eng. Chem. Prod. Res. Develop., Vol. 11, No. 2, 1972
167
28t
0
26 e . " -
Oxygen Index
---
Oxygen Index
1.0- I . I X P
22
2ot T
I 1.0
I
20
I
I
3.0 4.0
I 5.0
I 6.0
I
70
% Br
Figure 4. 50/50 Polyester-cotton, two-component treatment
1 .0-1.1%
P (total),
1
1
I
1.0
20
I
I
3.0 4.0 X Br
I 5.0
I
I
6.0
710
Figure 5. 50/50 Polyester-cotton reacted with allylNMPA, postbraminoted
Even within these limitations, a comparison of the results obtained is of interest. Figure 4 shows the relationship of Two-component sequence Postbrominotion sequence oxygen index to bromine content for fabric treated b y the Pad with perchloroethylene Pad with aqueous solution of two-component sequence. Varying amounts of the bromine solution of brominated unsaturated P / N comcompounds were introduced in the first treatment, and the compounde.b, dry poundd and catalyst. subsequent reaction with the phosphonate (Pyrovatex CP) Dry was designed to give l.O-l.lyototal phosphorus in all treated Heat 3 rnin at 2OOOC Cure 3 min at 175°C samples. (A reference curve of oxygen index vs. bromine Wash, then dry clean 30 Wash and squeeze (pad) min in perchloroethylene content is shown for fabric treated by padding with varying (room temp) concentrations of T B P P from perchloroethylene and drying Pad with aqueous solution Immerse wet fabric in only). For samples treated according to the two-component of P / N compoundc and bromine solution at room sequence to 1-1.1% phosphorus, bromine from T B P P is catalyste, dry temp indicated to be somewhat more effective than bromine from Cure 3 rnin at 175°C H B B P in increasing the oxygen index. For both compounds, Wash Wash the first 1% bromine yields a proportionally greater increase a Tris(2,3-dibromopropyl)phosphate (TBPP). Hexabromoin the oxygen index value than do additional amounts. At a biphenyl (HBBP). (CH~O)ZP(O)CHZCHZCONHCH~OH (Pyrovatex CP). (CHz=CH-CHzO)ZP(0)CHzCHzCONHCHzOH total phosphorus content of 1-1.1%, an oxygen index of 25.5 (allyl-NMPA). e 2-Methyl-2-amino-1-propanol hydrochloride. is reached a t about 3y0bromine with T B P P . The results obtained in the postbromination of fabric treated with the diallyl phosphonamide(ally1-NMPA) are perchloroethylene, dried, and heated 3 min a t 200OC. The shown in Figure 5 for samples containing 0.7-0.75y0 phossamples were washed in nonionic detergent, dry cleaned in phorus and 1.0-1.170phosphorus. The oxygen index appears perchloroethylene a t room temperature for 30 min, and dried. to increase linearly with bromine content, and 6 4 % bromine The samples were then treated with Pyrovatex C P as dewould be required to approach self-extinguishing behavior scribed earlier. (assumed to correspond to an oxygen index > 26). Postbromination. Fabric samples reacted with the desired The data available are not sufficient to warrant firm conconcentration of AT-methylol-3-(diallylphosphono)propionclusions or generalizations. However, a comparison of the amide (by the procedure described earlier for Pyrovatex CP) data shown in Figures 4 and 5 suggests some tentative answers were padded through water, then soaked for 30 min in a to the questions posed earlier. When the polyester component sufficient amount of a 2% solution of bromine in chloroform of a 50/50 polyester-cotton fabric is modified with a bromineto provide 300y0 excess of bromine (calculated from the containing compound and the cotton with phosphorusamount' required to saturate the allyl groups). The brominated nitrogen according to the two-component sequence, the samples were washed in nonionic detergent and dried. presence of a small amount of bromine in the polyester (about A limited range of fixed bromine and phosphorus contents 1% on total fabric weight), in conjunction with about 1% in treated fabrics is available experimentally a t this time. phosphorus and O.5y0 nitrogen, increases the oxygen index I n the two-component procedure the maximum amount of significantly and more than a comparable amount in the fixed bromine (not removed in washing or d r y cleaning) cotton. The bromine content required to reach a given obtained on the 50/50 blend is about 3%. Low efficiency of oxygen index in conjunction with about 1% phosphorus the subsequent reaction of cellulose with the phosphonate and 0.570 nitrogen is indicated to be somewhat lower for (Figure 3) leads to fixed phosphorus of about 1-1.1%. For fabric modified in this manner than for fabric in which t'he postbromination the low efficiency of the initial cellulose bromine, as well as the phosphorus and nitrogen, is present reaction with the unsaturated phosphonate is the limiting in the cotton component. factor, and relatively high bromine contents can be reached It is feasible, however, to obtain flame-retardant polyesterin the modified fabric through bromination of pendent' allyl cotton (at least a t the 50/50 blend level) by modifying the groups. cotton component only, when the cotton modification inTable Ill. Procedures for Finishes Confaining Bromine
168 Ind. Eng. Chem. Prod. Res. Develop., Vol. 1 1 , No. 2, 1972
Table IV. 50/50 Polyester-Cotton Treated with Allyl N M P A and Brominated Treated
Weight gain after allylNMPA reaction, yo 8.9-10.5 Efficiency (fixation) in allylNMPA reaction, % 30-40 Total weight gain after bromination, % 14-16 Typical % phosphorusnitrogen-bromine in finished sample Process washed 1.1/0.5/5,2 After 5 launderings 0.9/-/5.2 After 25 launderings 0.85/0.4/3.9 Oxygen index of finished sample Process washed 25.8 After 5 launderings 25.4 After 25 launderings 25.0 After solvent extraction 25.4 Crease recovery (W x F), degrees 113 X 114 Tensile strength (W X F), lbs 81 X 81 Tear strength (W X F), grams 1025 X 925 Stoll-flex (1/2’ X 2)(W X F), cycles 3300 X 50003-
Table V. 100% Cotton Treated with Allyl-NMPA and Brominated Treated
Untreated
I
.
.
.
I
.
...
... ... ... 16.9 ... .
.
t
... 111 X 116
89 X 79
Weight gain after allyl-NMPA reaction, yo Efficiency (fixation) in allylNMPA reaction, % Total weight gain after bromination, % Typical yo phosphorus-nitrogenbromine in finished sample Process washed After 5 launderings After 25 launderings Oxygen index of finished sample Process washed After 5 launderings After 25 launderings After solvent extraction Crease recovery (W X F), degrees Tensile strength (W X F), lbs Tear strength (W X F), grams Stoll-flex (1/2’ X 2)(W X F), cycles
Untreated
12.0-13.6
...
45-50
...
17-19
...
1.4/0.7/5.8 1.1/0.6 1.1/0.6/5.4
... ... ...
27.8 27.8 26.8 27.8
18.2 ... ... ...
94 x 93 59 X 51 865 X 800
73 x 77 75 X 63 1063 X 813
558 X 388
498 X 690
1413 X 1100
5000+
corporates phosphorus, nitrogen, and bromine in the treated fabrics according to the postbromination sequence. I n this case, a n oxygen index of 25.5 is reached a t about 1-1.1% phosphorus, 0.5% nit’rogen, and 5.5y0 bromine (Figure 5 ) . It is estimated that self-extinguishing 50/50 polyester-cotton could be obtained, for example, by modification of the cotton with reagents yielding l.070 phosphorus, 0.5% nitrogen, and 6 4 % bromine, or 1.5% phosphorus, 0.75% nitrogen, and 4-570 bromine in the treated fabric. Since it is difficult to int,roduce these elements by simple react’ion of cellulose with brominated reagents, reaction with unsaturated compounds followed by bromination in situ offers a viable route to the desired products. White 50/50 polyester-cotton fabric treated with the N methylol diallyl phosphonamide (allyl-SMPA) and brominated in situ is essentially unchanged in appearance and physical properties. Results obtained in the evaluation of treated samples are summarized in Table IV. The interpretation of these results may be facilitated by reference to the results of comparable experiments on 100% cotton fabric which are summarized in Table V. Utilization of the reagent is low, particularly for the blend. However, good flameretardant properties are obtained a t reasonable weight gains without impairment of aesthetics or physical properties. The treated cotton easily passes the vertical test with a char lengt’h of 3.7-4.2 in. initially and after 25 launderings. The treated blend just fails a t t,he level of modification shown in Table IV. Summary and Conclusions
Phosphonate and T H P O H systems are not generally adequate for flame-retardant finishing of polyester-cotton blends. The low efficiency of insolubilization, the low effectiveness of the phosphorus (and nitrogen) introduced, and, in some instances. both factors lead to the conclusion that
successful finishes for polyester-cotton must include other contributory elements or structures. One approach is to include bromine. Several methods are available in principle to include bromine in flame-retardant systems for polyester-cotton. Among those examined, reaction of the cotton with unsaturated organophosphorus compounds and bromination in situ offers considerable promise. The results show that the contribution of bromine to flame retardancy in polyestercotton containing phosphorus and nitrogen is not entirely independent of its location within the substrate. The feasibility of obtaining flame-retardant polyestercotton (50/50 by modifying the cotton component only) has been demonstrated. Excellent aesthetics, durability, and retention of physical properties have been obtained for fabric treated in accordance x i t h a new approach involving modification of the cotton with a reactive organophosphorus compound containing unsaturation and subsequent bromination of the alkenyl groups introduced. literature Cited
AATCC Intersectional Contest (Piedmont Section), Amer. Dyest. Rep., 57,373-7 (1968). Beninate, J. V., Boylston, E. K., Drake, G. L., Reeves, W. A., Anier. Dyest. Rep., 57, 981-5 (1968). Ciba, A.G., German Offenlegungsschrift No. 2,013,665 (1970). Fenimore, C. P., Martin, F. J., Combust. Flume, 10 (2), 136-9 (1966). Hamalainen, C., Reeves, W. A., Guthrie, J. D., Tezt. Res. J., 26. 145-9 (1956). ---, \
Hofman, P., Raschdorf, F., Textilveredlufig,5 (6), 486-97 (1970). Isaacs, J. L., Fire Flammability, 1, 36-47 (1970). Linden, P., Sello, S. B., Skovronek, H., Proceedings of the Fourth Annual Conference of the Information Council on Fabric Flammability, pp 173-88, December 1970. Tesoro, G. C., RIeiser, C. H., Text. Res. J.,-40,430-6 (1970). Tesoro, G. C., Sello, S. B., Willard, J. J., ibid., 39, 180-90 (1969). Toy, A. D. F., Rattenbury, K. H. (to Victor Chemical Works), U.S. Patent 2,735,789 (February 21, 1956). RECEIVED for review December 7, 1971 ACCEPTED February 7, 1972 Presented at the Division of Cellulose, Wood, and Fiber Chemistry, 162nd Meeting, ACS, Washington, DC, September 1971. Ind. Eng. Chem. Prod. Res. Develop., Vol. 1 1 , No. 2, 1972
169
