US3682692A - Flame retardant nylon-containing material - Google Patents

Abstract

THERE IS DISCLOSED NYLON-CONTAINING FABRICS RENDERED FLAME RETARDANT BY THE TREATMENT THEREOF WITH A COATING COMPOSITON CONSISTING ESSENTIALLY OF AN AQUEOUS EMULSION CONTAINING ONE OR MORE FLAME RETARDING AGENTS SUCH AS NH4BR, A LATEX MATERIAL SUCH AS VINYL CHLORIDE POLYMER AS THE DISPERSED PHASE OF SAID EMULSION AND A SUITABLE THICKENING AGENT. OTHER ADDITIVES MAY ALSO BE INCLUDED, ESPECIALLY THOSE WHICH FUNCTION AS PLASTICIZERS AND FLAME RETARDANTS SUCH AS TRI(2,3-DIBROMOPROPYL) PHOSPATE.

Description

United States Patent Oflice 3,682,692 Patented Aug. 8, 1972 3,682,692 FLAME RETARDANT NYLON-CONTAINING MATERIAL James E. Lamson and Richard C. Nametz, St. Louis, Mich., assignors to Michigan Chemical Corporation, St. Louis, Mich.

No Drawing. Continuation-impart of abandoned application Ser. No. 767,462, Oct. 14, 1968. This application Dec. 4, 1970, Ser. No. 97,417

Int. Cl. C09k 3/28; C09d /18; 133% 27/34 U.S. Cl. 117-137 11 Claims ABSTRACT OF THE DISCLOSURE There is disclosed nylon-containing fabrics rendered flame retardant by the treatment thereof with a coating composition consisting essentially of an aqueous emulsion containing one or more flame retarding agents such as NH Br, a latex material such as vinyl chloride polymer as the dispersed phase of said emulsion and a suitable thickening agent. Other additives may also be included, especially those which function as plasticizers and flame re'- tardants such as tris(2,3-dibromopropyl) phosphate.

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a continuation-in-part of U.S. patent application Ser. No. 767,462, filed Oct. 14, 1968, now abandoned.

BACKGROUND OF THE INVENTION Field of the invention The field to which the present invention pertains is the field of flame retardants. Specifically the invention is concerned with nylon-containing material to render it flame retardant by surface treatment with a suitable flame retardant coating composition.

Description of the prior art It is well known that various fabrics made from nylon or containing nylon together with other materials, are rather flammable. Even if the material from which the fabric was made is in itself not especially flammable, the fabric is often prone to ignition due to its relatively open structure. In addition, the presence of dyes and finishing coatings or the use of other and more flammable materials in association with the nylon tend to make the finished fabric still more flammable.

The problem of flammability may of course, be overcome in part by certain treatments of the nylon and other materials from which the fabric is made. Some may be modified chemically or may be mechanically blended with various fillers or flame retardant additives prior to being spun into a fiber or formed into non-woven sheet material if the later is utilized. However, these methods of overcoming the difliculty caused by flammability are open to objection. In the first place, relatively large amounts of the flame retardant materials must be used, thus increasing the expense and rendering the fabric resulting from this treatment impracticable from the economic point of view. Such methods, can and often do, alter characteristics or properties of the fabrics undesirably, such for instance as color, color stability, tear strength, wear life and the like. For instance nylon fabrics used for upholstery in automobiles are required to be strong to withstand sewing and handling without fraying, ripping or pulling apart at the seams. To help achieve this required structural strength in these nylon fabrics, they are generally provided with backing layers, usually of the condensation or latex type. These' backing layers, however, are quite flammable themselves and consequently serve to enhance the flammability of the fabric. For example melamine-formaldehyde or ureaformaldehyde condensation products are converted to the insoluble state on the nylon fabric to help it attain desirable physical and structural characteristics. Similarly latex formulations of the vinyl chloride type are also used.

SUMMARY OF THE INVENTION It is therefore often desirable to treat a finished fabric made from nylon or containing it, such for example as upholstery material, drapery material, pile fabric and the like in order to render it highly resistant tonburning, and retarding the propagation of flame if ignition should occur. The treatment should be relatively inexpensive, easily applied, and should be relatively permanent to laundering, dry cleaning and the like to which the treated materials are often subjected; that is, it should be durable.

These objectives may be accomplished by treating the desired surface of the nylon-containing fabric with certain compositions contemplated for use in practicing the invention. These compositions are essentially aqueous emulsions containing one or more fire retarding agents in combination with a latex material to serve as the dispersed phase of said emulsions. Other additives including surfactants or emulsifying agents may also be employed depending on the fabric to be treated and its intended use.

The fire retarding agents utilized by the present invention cannot be classified generally. However, halogen-containing compounds, alone or in combination, with phosphorus-containing compounds have been found quite effective. For example, ammonium bromide, ammonium chloride, dibasic ammonium phosphate, tris(2,3-dibromopropyl) phosphate, tetrabromophthalic anhydride, hexabromocyclododecane, tris(l-bromo 3 chloroisopropyl) phosphate and tris(1,3-dichloropropyl) phosphate have been utilized with success. Of course, if desired, compounds having synergistic values may be added to enhance the effectiveness of these fire retarding agents such as antimony trioxide or arsenic trioxide.

Many organic phosphates function as plasticizers when mixed or incorporated in resins and polymers. In the compositions of the present invention these phosphates, especially when they contain bromine, operate as both fire retarding agents and plasticizers. It is for this reason that use of tris(2,3-dibromopropyl) phosphate is preferred. As to the latex material it can be selected from the group consisting of polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, mixtures thereof and urethane-base latex materials. These latex compositions are available commercially under various trade names and trademarks. In ad dition, the emulsion contains a thickening agent and a solubilizer therefor to provide the desired viscosity; a typical agent is hydroxyethyl cellulose. Wetting agents are somtimcs used to assist in the penetration of the material to be treated. Some fabrics tend to shed the aqueous treating compositions, especially if they had been pre-treated with a water or oil repellant.

Compositions containing latex and inorganic oxides have also shown effective fire retardation on nylon-containing fabrics. Of significance is the composition utilizing ferric oxide, Fe O with a polyvinylidene chloride latex, ethylhydroxy cellulose as a thickener and water at a pH range of 7-9.

These treating compositions may be applied to the surface of the fabric in any appropriate and convenient manner, such as by brushing or dipping the fabric in a bath of the composition. Also, suitable applying equipment may be utilized. For example, the composition may be applied to the fabric by a roller and the quantity which is added may be controlled by a doctor blade.

The fire retardant coating is formed by drying the composition after its application. Depending upon the particular formulation and especially the type of latex which it contains, the drying operation may or may not take place 4 As to the use of hydroxides other than ammonium hydroxide, it should be understood that alkali metal hydroxides such as sodium or potassium hydroxide would work as well as ammonium hydroxide insofar as the flame at ambient temperatures. If a polyvinyl chloride or a poly- 5 retardancy characteristics of the compositions of the presvinyl acetate latex is utilized, it is necessary to dry the cut invention. It has been observed, however, that the treated surface at somewhat elevated temperatures to cure above-mentioned bases tend to leave a residue in or on them. Normally such drying operations are conducted in the treated fabric. This is not desirable and may require an ordinary oven so that the drying results from air confurther treatment. Of course, the purpose of the hydroxide vection. Under most circumstances the fabric should be addition is to maintain the compositions at a pH range of dried for 10-20 minutes at 1l0-l30 C. If the drying 79, said range being optimum for both the consistency operation is conducted at ambient temperatures, there is of the compositions and consequent application on the -also danger of strike thru; that is, the water penetrates a ri s to be treated.

too deeply in the fabric causing problems, An emulsifying agent may also be utilized if desired.

If the drying operation, for the coating composition In addition to certain advantages in formulating the cornutilized, is conducted at the proper temperature the coatpositions, as explained hereinafter, an emulsifying agent ing will be clear and colorless and consequently will not increases the shelf life of the composition. The use of an alter the appearance of the fabric. This is, of course, most m l ifying agent has some advantages in treating some desirable since the right texture and color are of considerfabrics, although in y instances, it y be used Withbl importance for almost ll f b i out difiiculty. If an emulsifying agent is used, an inorganic Th present i ti i illu t t d by th following type is preferred. For example a blend of oil soluble calamples which are intended to be illustrative and not Cillm sulfonates with polyoxyethylene ethers may be utilimiting. Instead of setting forth a detailed description of lized to advantage. An emulsifying agent of this type is several embodiments of the invention under headings en- Emcol H14l-see Table I. titled Example 1, Example 2 etc., the data and infor mation providing such examples of the invention are ar- Formulation composltlons ranged herein as follows: While there exists a number of methods to formulate (a) Compositions useful in connection with the invencompositions similar to thOSC 0f the present invention it i (T bl I), is recommended that the following procedures be fol- (b) Techniques for formulating such compositions and lowed: also for treating the fabric (Procedure hereinafter), and TO an aqueous Solution f the flame retarding (c) Test methods for determining fire retardation or agent such as ammonium bromide is added a solution of fire resistance of the fabric (Test Methods hereinammonium hydroxide the l ke to provide a pH of after). about 8. A thickening agent such as hydroxyethyl cellu- TABLE I Composition l Hydroxyethyl cellulose.

1 Tris(2,3-dibromopropyl) phosphate.

' 'Iris(1-bromo-3-chloroisopropyl) phosphate. 4 'Ictrabromophthalio anhydride.

5 Hcxsbromocyclododecane.

Emulsifying agent 7 I "Geon is a trademark of B. F. Goodrich Chemical 00., Akron, Ohio. Geon 450 Latex is a vinyl chloride acrylic copolymer; Geon" 652 Latex is a vinylidene chloride-vinyl chloride copolymer and Geon 576 Latex 1s a polyvmylidene chloride polymer.

7 Typical emulsifying agents which are commercially available such as Emcol H-l ll (a trademark of Witco Chemical 00., Inc., 277 Park Avenue,

New York, N.Y.) are satisfactory. These emulsifiers are blends of oil soluble calcium sulfonates with polyhydroxyethylene others.

As is evident from Table I, the effective amount of the flame retarding agent can have a relatively wide range with respect to the weight of the composition. It has been found that the flame retarding agents should fall within the range of 525% by weight of the composition.

Use of halogen-containing organo-phosphates as fire retarding agents and plasticizers in the compositions of the present invention should not exceed 12% by weight. The reason for this limitation is due to the fact that at levels higher than 12% by weight substantially more ammonium hydroxide, or any other hydroxide, would be needed which in turn would affect both the solid contents and the viscosity of the composition. Since the hydroxide is added in the form of an aqueous solution, any addition would tend to dilute the composition and consequently decrease the viscosity. From this, however, it should not be construed that the viscosity is of a critical nature; it is only preferable that it be about 3.6)(10 cps.

lose is then added and kept in suspension by agitation at high shear. At this point some adjustment such as further addition of the hydroxide may be indicated. To the thickened solution a fire retardant plasticizer such as tris (2,3-dibromopropyl) phosphate is added and finally the latex is added at which time only mild agitation of the aqueous mixture can be used since the latex cannot stand high shear. It would coagulate.

(B) When an emulsifier is used the procedure is changed as follows: The emulsifier is added to the aqueous solution or suspension of the flame retarding agent. At this stage the addition of a phosphate plasticizer is quite helpful as it assists in obtaining a suspension without utilizing high agitation and shear. The latex resin is then added followed by the hydroxide and finally the thickening agent.

Procedure B has been found more convenient for formulation purposes when the composition contains emulsifiers. Occasionally it may be preferred to avoid the use of emulsifying agents, especially those of the organic type since they have a tendency to wet the fabric excessively and thus interfere with the effectiveness of the flame retardant compositions.

(C) When an inorganic oxide such as Fe O is used, it is added to water and with the aid of a thickening agent such as hydroxyethyl cellulose it is suspended in solution to which is added the latex resin. Of course the pH is always adjusted with the aid of a base such as ammonium hydroxide.

Fabric treatment The compositions of this invention may be applied to the fabric by any suitable means. A thin film spreader having a doctor blade which rested directly on the fabric was used to provide the specimen of Table I. The composition was applied to the fabric by a roller and then subjected to the spreader, although it could be applied by dipping the fabric into a bath. The doctor blade was so adjusted that a film approximately 3 mils in thickness was applied. Other equipment may be used if desired such as knife coating means or suitable pad or spraying equipment. The fabric was then placed in an oven and heated at 230 F. for -20 minutes.

The add-on, that is, the increase in weight of the fully treated fabric as compared with the untreated fabric, was approximately 1.25 oz. per square yard. The fabrics used throughout the experiments were 100 percent nylon made by 'various manufacturers. Nylon fabrics suitable for upholstery, and especially automobile upholstery, were of particular interest. Usually these fabrics weigh about 6 oz. per square yard. Thus a typical add-on as taught by the invention increases the weight by about If thicker films or coatings are desired the spreader or other applying device may be adjusted to do so. Add-ons of the order of 1.60 oz. per square yard have been used.

In treating the nylon-containing fabrics, the type of water repellant used in their production was found to be quite influential. A fluorocarbon type of water repellant was found to be satisfactory; that is, it could be used, if desired, without adversely affecting the fire retardation of the fabric. However, some other water repellants do have an adverse effect. For example, it is not recommended that a wax extended fluorocarbon, or a silicone material be employed. However, it will be understood that such wax extended or silicone repellants could be used, if they are considered absolutely necesary, although the fire retardation of the treated fabric would not be very satisfactory.

Test methods Before discussing the particular tests utilized in connection with the present invention, some general comments seem indicated. In the first place, considerable confusion prevails as to what could be called a fire retardant fabric, a self-extinguishing fabric and a fire resistant fabric. Usually fire retardation is measured by means of some type of match test. In such tests a cold fabric is exposed to a match or a luminous flame under a carefully specified set of conditions and the extent to which the fabric chars is measured. Usually a fabric is considered self-extinguishing if the flame goes out a short time after the match flame is removed or the match is consumed. According to some of these tests, a fabric cannot be considered self-extinguishing if it continues to smolder or glow for more than a short time, even if the flame does go out quickly. Some investigators consider the fabric to be fire resistant if it is self-extinguishing according to some version of the match test. However, this expression has also been used for fabrics which maintain some of their original properties and characteristics after relatively long exposure to very high temperatures, such for instance as 2500 F. It is suggested that the last-mentioned fabrics should be termed fire protective rather than fire resistant; but, as noted, there is confusion in the art in defining these terms.

The principal test utilized for purposes of this invention was a recently revised version of the match test. According to this test, a specimen of the fabric, 1" x 12", was cut. A mark was made in the middle of the 12" length for each specimen and the specimen was suspended vertically lengthwise from a clamp. A wooden match was lit and used to ignite the bottom of the 1" edge of the specimen. The specimen was exposed to the flame of the match until the match was consumed (about 15 seconds). If the flame was extinguished within 5 seconds after the match was consumed and the specimen was not burned past the center mark, the fabric is considered to be self-extinguishing or fire resistant if that term does not mean fire protective. If any of the specimen is burned beyond the center mark or if they produce afterglow for more than one minute after the fabric flame has gone out, the specimen may be considered as fire-retardant; but not as fire-resistant or self-extinguishing. By comparing each specimen with the others, one can obtain a measure of the fire retardation of various treated fabrics as compared to each other, or as compared to untreated fabric.

In order to obtain results which can be duplicated or to obtain meaningful results if comparative data are sought, it is necessary to precondition the specimen prior to the actual test procedure mentioned above. There are various accepted ways of preconditioning. Usually they involve preheating the specimen for a number of hours and sometimes at a specified relative humidity. One accepted method of preconditioning is ASTM test 1692- 59T see R. C. Nametz, Ind. and Eng. Chemistry, vol. 59, 5,19 7).

Some results of utilizing the match test referred to above in connection with the present invention appear in Table II.

The fabric mentioned above if untreated and tested provides a burn time of about 41 sec. To be considered as flame resistant, the burn time, according to this test, should be less than 5 sec. This is empirical however. Longer times still indicate apreciable fire retardation. At what point such retardation is slight enough to say it is insignificant depends on the use to which the fabric is to be put, and on the investigators judgment. It is suggested that a 30 second burn time would be poor indeed; but that a time of 10 to 12 seconds would indicate at least fair flame retardant properties.

Tests other than the match test have been suggested and, of course, could be used in connection with the present invention if desired. For example, in the Ellipse Flammability test the shape of the specimen is a quarter ellipse, the major axis of which is 3.5 inches and the minor axis 2 inches. The specimen is clamped with the major axis in a vertical position. The ignition is on the vertical edge A; inch below the top. The specimens shape is said to be such that the curved edge will not burn for selfextinguishing fabrics, and that the length of the edge which is burned is a measure of flame retardation (see American Dyest-utf Reporter, vol. 53, No. 19, pg. 23-26).

Another test, the Federal Aviation Agency test, involves a specimen 2 inches in width and 12" in length. The specimen is clamped in a horizontal frame with the coated side up. One and one-half inches is allowed to drop vertically into a Bunsen burner flame which is 3 inches high with a 1 /2 inch blue cone, and is kept there for 15 seconds. The flame is removed and the burn rate is measured. If the flame goes out during the first minute after removal of the :Bunsen burner and the specimen does not burn more than four inches, the fabric is considered self-extinguishing.

Clean nylon, even if in the form of a dense fabric, is sometimes considered to be fire retardant without special treatment. However, this is questionable; and surely if various dyes, finishes and blends with other fabrics are involved, the resulting fabric will not be fire retardant and certainly will not be fire resistant. It is believed that no fabric containing an appreciable amount of nylon can be made truly fire. protective by a coating treatment, since the nylon when exposed to very high temperatures will melt. This is an inherent characteristic of mylon and consequently under these conditions it will continue to burn. However, nylon-containing fabrics when subjected to the protective procedure of the present invention will be rendered fire retardant, and in many instances fire resistant or self-extinguishing.

'What is claimed is:

1. A flame retardant nylon-containing material having deposited on a surface thereof a thin coating cured from an aqueous composition comprising water, a fire retarding agent selected from ammonium halides and ferric oxide, a latex resin selected from the group of vinyl chloride, vinylidene chloride, their copolymers and mixtures thereof, and a thickening agent, said composition having a pH range of from 7-9.

2. A flame retardant nylon-containing material according to claim 1 wherein said ammonium halide is ammonium bromide.

3. A flame retardant nylon-containing material according to claim 1 wherein said ammonium halide is ammonium chloride.

4. A flame retardant nylon-containing material according to claim 1 wherein said aqueous composition further contains a halogen-containing phosphate ester.

5. A flame retardant nylon-containing material according to claim 1 wherein said thickening agent is hydroxyethyl cellulose.

6. A flame retardant nylon-containing material according to claim 4 wherein said halogen-containing phosphate ester is one selected from the group consisting of tris(2,3- dibromopropyl) phosphate, tris( 1,3 -dichloroisopropyl) phosphate and tris( 1 bromo 3 chloroisopropyl) phoshate. I

P 7. A flame retardant nylon material having a flame retardant backing comprising the cured product of an aqueous composition containing (a) a fire retarding agent selected from ammonium bromide, ammonium chloride and mixtures thereof, and ferric oxide;

(b) a latex resin selected from vinyl chloride, vinylidene chloride, their copolymers and mixtures thereof;

(c) a halogen-containing phosphate ester;

(d) a thickening agent; and

'(e) a base providing a pH range of from 7-9.

8. A flame retardant nylon material according to claim 7 wherein said halogen-containing phosphate is selected from tris(2,3-dibromopropyl) phosphate, tris(1,3-dichloroisopropyl) phosphate and tris(.1-bromo-3-chloroisopropyl) phosphate.

9. A flame retardant nylon material according to claim 7 wherein said base is ammonium hydroxide.

10. A flame retardant nylon material according to claim 7 wherein fire retarding agent constitutes from 5 to 25% by weight of said aqueous composition.

11. A flame retardant nylon material according to claim 7 wherein said thickening agent is hydroxyethyl cellulose.

References Cited UNITED STATES PATENTS 2,917,476 12/1959 Peterson et al. 117-137 X 2,953,480 9/1960 Burnell 117138.8 X 2,286,744 6/1942 Leatherman 117-1137 3,100,154 8/1963 Oshima 117-137 X 2,933,455 5/1960 Doying 252428 2,574,515 11/1951 Walter et al. 117-136 X 2,922,726 1/1960 Moretti et al. 117136 X 3,279,929 10/1966 Peters 117-137 X FOREIGN PATENTS 805,499 112/1958 Great Britain 117-137 653,360 12/1962 Canada 117-137 863,738 3/1961 Great Britain 117137 973,355 10/1964 Great Britain 11713'6 WILLIAM D. MARTIN, Primary Examiner H. .I. GWINN'ELL, Assistant Examiner US. Cl. X.R. 1 1l7--138.8 N