US3480582A - Fire-resistant fiber blends - Google Patents

Description

Nov. 25, 1969 R. B. BROOKS 3,480,582

FIRE-RES I STANT FIBER BLENDS Filed Oct. 51, 1966 I00 L USTEI? (BRIGHT) TREATED UNBLE/VDED F/BFER (SEW-8M6 T) h 50 TREATED 50% UNTREATED} H55? ELF/V05 t 3 is 50% LUSTER a (BRIGHT-BULL) q 8Q (saw-00a) 0%L1/5TER' 1I\ll|.|.|l|.:.. (F DULL) 0 2 4 6 8 l0 l2 /4 l6 I8 20 ADD! 77 V5 IN VEN TOR. ROBE/P T BRUC E BROOKS A 7' TOR/VE Y United States Patent 3,480,582 FIRE-RESISTANT FIBER BLENDS Robert Bruce Brooks, Darien, Conn., assignor to American Cyanamid Company, Stamford, Conn., a corporation of Maine Continuation-impart of application Ser. No. 528,090, Feb. 17, 1966. This application Oct. 31, 1966, Ser. No. 591,015

Int. Cl. C08f 45/56, 47/12, 45/58 U.S. Cl. 26045.75 10 Claims ABSTRACT OF THE DISCLOSURE Fire-retardant fiber blends of improved luster comprising, in combination, (a) about to 90% treated synthetic fibers having solid fire-retardant additive in finely divided particulate form dispersed therein and (b) to 95% untreated synthetic fibers; the amount of said fire-retardant additive in said treated fibers being sufficient to render fabrics of the fiber blend fire-retardant.

This application is a continuation-in part of application Ser. No. 528,090, filed Feb. 17, 1966.

This invention relates generally to improved synthetic fibers and more particularly to fiber blends which are useful for making fabrics which are fire resistant, lustrous to an acceptable degree and of good dyeability. More particularly, it relates to the provision of blends of synthetic fibers in which a portion of the fiber is treated with solid fire-retardant in a sufficient quantity to protect the entire fiber blend, whereby fabrics made from the resulting fiber blends are fire-retardant, lustrous, dyeable and light-fast.

Synthetic fibers in the form of continuous filaments or staple are extensively used in the production of knitted fabrics, woven fabrics, non-woven felts, pile fabrics, carpets, etc. as is well-known in the textile industry. For many uses, it is important that fabrics be fire-resistant, or self-extinguishing, when exposed to flame. It has been known that this result could be obtained by the use of certain additives such as haloalkylphosphates. The problem of obtaining fire-resistance in textile materials is complicated by the need for avoiding numerous deleterious effects which may be occasioned by the addition of fire-retardant materials. Among these bad effects which may be necessary to avoid may be mentioned (a) the necessity for using a sutficiently high concentration of the fire-retardant material within the fibers as to adversely affect the textile properties, such as strength and elongation of the fibers, (b) imparting a firm feel or hand to the fabric, (c) discoloration of the fabric, (d) increased susceptibility of dyed textile fabric containing fire-retardant to fading of the dye when the fabric is ex posed to light, heat, laundering, etc. (e) leaching out of the fire-retardant material from the fabric during laundering, dyeing, etc. and (f) increase in soiling tendency of the fabric as may be caused when a fire-retardant is used which tends to form a sticky or liquid surface on the fibers.

It has been observed that solid fire-retardant additives, dispersed in concentrations exceeding 1% by weight of the fiber, give rise to marked delustering effects which also influence the shade of the dyed fabric. Thus, a severely delustered treated fiber may well appear to be only half as deeply dyed as a dyed, untreated fiber even though the two fibers contain identical amounts of dye.

An extremely effective class of solid fire-retardants is disclosed in the application of which the present application is a continuation-in-part. These additives are capable of providing fire protection without many of the 3,480,582 Patented Nov. 25, 1969 ICC disadvantages normally associated with fire-retardant agents. While they are able to perform their fire-retardant function without detracting from the textile properties of the fiber as was the case with the previous fire-retardants, nevertheless even these improved solid fire-re- ;iabrdants tend to significantly dull or deluster the treated Liquid halogenated organic fire retardants are commonly used, but a problem encountered with these is their adverse effect on the light-fastness of the dyed fiber containing them as well as the adverse effect they have on the soiling resistance of the fiber.

In many applications, synthetic fibers are required to have a certain degree of brightness in addition to being self-extinguishing. For example, a carpet lacking luster presents a dull and lifeless appearance and is commercially unattractive. Since it is desirable that a carpet be fire-resistant as well as have controllable luster, the inclusion of solid additives which tend to diminish luster is undesirable. Similarly, it is commercially important to obtain the greatest color intensity which a given dyestufi is capable of producing and it, of course, follows that the fire-retardant should not adversely affect the light-fas ness of the dyestuff.

Accordingly, it is the main object of the present invention to provide fiber blends from which fabrics can. be made which not only possess suitable fire-retardant characteristics but which also have acceptable luster, dyeability and light-fastness, whereby fabrics such as carpets and draperies produced from such fiber blends satisfy all commercial requirements with respect to performance characteristics and appearance.

More specifically, it is an object of the present invention to provide blends of treated fibers and untreated fibers, the treated fibers having solid fire-retardant additives dispersed therein in an amount which is sufficient to render fabrics made from the entire fiber blend selfextinguishing without at the same time totally delustering the fabrics.

Briefly stated, the objects of this invention are obtained by blending synthehtic fibers, treated with an effective amount of solid fire-retardant, with untreated and relatively lustrous synthetic fibers, whereby the amount of fire-retardant additive introduced in the treated fibers is sufficient to make fabrics prepared from the blend fireretardant, and the proportion of untreated fiber is sufficient to produce a composite having a desired degree of luster. A significant and surprising feature of the invention resides in the fact that by blending treated and untreated fibers, the additives in the treated fibers serve also to benefit the untreated fibers in respect to fire-retardancy, whereas dullness, loss of dyeability and lightfastness introduced by the additive are minimized by the presence of the untreated fibers.

In the present application, the term untreated fiber is intended to mean a fiber which has not been sig, nificantly delustered. Thus, the untreated fiber may contain a very small amount of a solid fire-retardant or other solid additive provided such a low concentration would be without significant effect upon the luster of the fiber. Likewise, a fiber is considered to be untreated for the purposes of the present invention it it contains a liquid fire-retardant or any other additive which has no significant effect on the luster of the fiber. By treated fiber is meant a fiber wherein at least 1% solid additive is dispersed and the fiber is delustered. Similarly, the term blend as used in fiber blend encompasses mixtures of treated and untreated fibers such as can be obtained by combining treated and untreated fibers into a yarn.

For a better understanding of the present invention as well as other objects and further features thereof, reference is made to the following detailed description as read in conjunction with the accompanying drawing whose single figure graphically illustrates the variation of luster with concentration and distribution of solid fire-retardant additive. In the discussion to follow, luster will be expressed on a scale ranging from full-dull to full-bright. Untreated fibers will be regarded as fullbright. The luster of fibers to which large quantities of the solid fire-retardant are added will be taken as fulldull. Actually, the full-dull condition is approached by a fiber which has more than about 1% of solid fireretardant dispersed evenly throughout since the brightness is reduced exponentially if the solid fire-retardant is evenly dispersed throughout all of the fiber as the concentration of the retardant goes from to 1%.

In accordance with the present invention, however, when 50 parts of full-dull fiber having as much fire retardant therein as is required to impart fire retardant properties to twice the fiber, is blended with 50 parts of untreated full-bright fiber, the resultant blend becomes dull-bright, that is, it has a luster which is about midway between full-dull and full-bright. Advantageously, it also has about 1.5 times the apparent dyeability of a fiber blend having the same amount of additive uniformly dispersed throughout all fibers. Significantly, the presence of excess fire retardant additive in the' treated portion of the fiber blend also protects the untreated fibers in the blend. As a consequence, carpets and other fabrics produced from such fiber blends, exhibit fire retardant characteristics and yet have a desired degree of brightness and dyeability.

As another example of the advantageous effects obtained by the methods of this invention, a blend composed of 25 parts of treated fiber having 4 times the required amount of the fire-retardant additive and 75 parts of untreated fiber will produce a fiber blend which gives 2 a fire retardant fabric, even though only one out of four fibers contains a fire-retardant. The fabric prepared from the fiber blend suffers only a 25% reduction from fullbright and thus, the luster in said fabric varies in a linear manner with the proportion of treated to untreated fibers, regardless of the concentration of fire retardant additives in the treated fibers.

The concept underlying the present invention is illustrated in the graph shown in the drawing wherein the percentage of delustration or dullness is plotted against the percentage of fire-retardant additive. The solid line in the graph represents a fiber treated with an additive and it will be seen in this curve that the luster is reduced sharply as the percentage of additive is increased, such that a fiber with additive (point 1 on the curve in the drawing) is about 99% delustered and is virtually full-dull. When the percentage of fire-retardant additive is (at point 2 of the curve), fabrics from the fiber are full-dull. It will also be seen that a much smaller concentration of finely divided solid fire-retardant dulls fabrics from the fiber to a high degree, for as the percentage of the fire retardant additive goes from 0 to 1%, the luster exponentially drops, reaching 90% of fulldull at 1%.

The dash line in the graph represents a 5050 blend of fibers treated with 20% fire-retardant and untreated fibers, the blend of fibers having 10% fire-retardant additive at point 3 on the dash line. It will be seen that the luster of this fiber blend is mid-way between full-dull and full-bright notwithstanding the high percentage of fire-retardant present in the fiber blend. Fabrics prepared from this fiber blend will appear to dye to a deeper shade than fabrics prepared from fibers which are 100% treated, though both fabrics have the same total amount of fire-retardant additive. Likewise, the fabrics prepared from the fiber blend will have improved light-fastness if the fireretardant is a halogenated organic compound as compared with a fabric prepared from fibers which are 100% treated.

The present invention is applicable to all synthetic fibers which are spun by melt, solvent and solution processes and in which a solid, finely ground fire-retardant compound or combination of compounds can be dispersed. Thus, the present invention is applicable to the preparation of fire-retardant fabrics of blends of nylon fibers, cellulosic fibers, polyester fibers, polyolefin fibers, and especially fibers of acrylonitrile polymers and interblends thereof. As used herein, the term acrylonitrile polymer means a composition of matter which contains an average of at least about 70% acrylonitrile in the polymer molecule. The remainder of the polymer molecule may contain an average of up to about 30% of other ethylenically unsaturated materials as is wellknown in the art. Illustrative of other compounds which may be copolymerized with acrylonitrile to form polymers useful in the practice of this invention, are those which may be found, for example, in US. Patent 3,104,- 938, issued Sept. 24, 1963, and US. Patent 3,040,008, issued June 19, 1962, and in various other US. patents mentioned therein.

The method of the present invention whereby synthetic fibers can be made into fire retardant fabrics which retain much of the oroginal luster of the synthetic fiber, can be finely divided fire-retardant compound. Particularly useful compounds are brominated aromatic compounds and chlorinated aromatic compounds, with an organic phosphine or antimony oxide as a synergist; or an organic phosphine compound alone. These compounds and their use as fire-retardant agents are fully described in the application of which the instant application is a continuationin-part. Each of the useful compounds should be a highmelting solid having a melting point above about C. and preferably above about C. and should be substantially insoluble in water and capable of being subdivided to form a uniform dispersion in the polymer solution or spin dope.

Uniform dispersions should have particles of less than about 10 microns in diameter and preferably less than about 5 microns in diameter, in order to allow the polymer to be spun into fibers. Such uniform dispersions may be produced by dissolving the compound in the spin dope or polymer solution if such additive compound is soluble therein or may be produced by any of the technical means for comminuting solid materials when the additive is insoluble in the polymer solution or spin dope. The technology of producing the uniform dispersion will not be described in detail herein since such techniques are wellknown in the art and are used for dispersing materials such as titanium dioxide delustering, dyes, pigments, etc., in polymer Solutions and spin dopes. These same techniques are generally applicable to dispersing in the polymer solution or spin dope the flame-retardant additives used in the present invention.

As an example of a fire-retardant agent which can be used in the present invention, there can be named solid high-melting, water-insoluble, :brominated and/ or chlorinated aromatic compounds in combination with a synergist such as antimony oxide or a solid high-melting, waterinsoluble organic phosphine; or such phosphine alone.

In the practice of the present invention, it is possible to have blends of between 90: 10 and 5:95 treated and untreated fibers. In general, it is preferred to have the fiber blend contain about 10 to 50% of treated fibers. In conjunction with the range of treated and untreated fibers, there must be considered the amount of fire-retardant present in the treated fibers. The additive fire-retardant may be present in a weight concentration of 150% based on treated fiber. Within this range it is found that a desirable balance of properties is obtained if the fireretardant usage is above about 2% and below about 30% of the weight of treated fiber.

In the following examples, the burning propensity of fibers was determined by the following test procedure. Nominal 16.5 denier per filament, 4 inch, crimped staple was processed into 2 ply 50s (Philadelphia count) car pet yarn. The yarn was then tufted into carpets having a inch pile height. Such carpets were provided with one-inch wide strips of fibers to be tested separated by one-third inch wide strips of wool. A secondary jute backing was secured in place to each sample by synthetic latex, after which the sample was cured in a 250 F. oven for 20 minutes. After cooling, the test sample was placed in a draft-free area in a horizontal position on a wooden base to minimize heat transfer. Two drops of benzene were placed on the carpet face at least 1% inches from any edge of the carpet. The benzene was immediately ignited with a match and allowed to burn freely. The benzene ignited the carpet pile and then quickly burned olf while the carpet continued to burn. A self-extinguishing sample will usually go out within one minute while a burning sample will continue to burn unchecked until the whole carpet is consumed. To determine the burning propensity for this carpet construction, at least twenty identical carpets were tested in the foregoing manner and the percent classified as burning was reported as the carpet burning propensity. To determine the burning prohence the fiber was given an arbitrary rating of 100% luster.

Example 3 To 98.33 parts of a 10% polymer solution as described in Example 1, was added 1.38 parts of finely ground perchloropentacyclodecane, and 0.29 parts Sb O Fiber was produced in an identical manner as in Example 1, but it contained 16.7% combined additive. This fiber was examined by the same panel, which agreed that it could not distinguish a luster difference betwen this sample and that of Example 1 and, therefore, it was given a rating of luster.

Example 4 Fiber from Example 3 was blended with untreated fiber of Example 2 in various proportions. These fiber blends were submitted to the same panel, which was asked to rate the luster values of these fibers on a scale of 0 to 100 relative to the luster of fiber from Examples 1 and 2, and an average of the ten ratings was obtained as representative of each fiber blend. The results of these tests are found in Table I.

TABLE I.ACRYLIC FIBER pensity of the fiber, the carpet burning propensities were determined for at least four different carpet weights and stitches per inch (all having the same /8 inch pile height, however) and were plotted as a function of carpet weight. The value on the smooth curve fitted to these points for a standard carpet of 37 ounces per square yard or 5.6 stitches per inch was reported as fiber burning propensity or burning propensity.

By fire-retardant is meant having a lower burning propensity than corresponding fabrics made entirely of untreated fibers.

The following examples are presented to further illustrate the present invention.

Example 1 To 99.0 parts of a solution containing 10% copolymer Additive in Treated From Table I, it can be seen that (1) burning propensity decreases with increase of additive in blend (same behavior as in fibers) and (2) burning propensities'of blends and of unblended fibers are about equal with equal percents of additives.

Example 5 TABLE II Fiber (Wt. Percent Additive in Fiber Blend Treated] of Treated Fiber) (P Fadeometer" Untreated Burnrng N0. in Fiber CaBIu (C H5CHmPO CGBIfl (CsHaCHmPo Total Luster Hrs. Rating Propensity Example 2 By comparison, a fiber was produced in the same manner but without the additives and examined by the panel From Table II it can be seen that (l) fire-retardant fiber blends of this invention are superior in light fastness and luster compared to fibers uniformly treated with the same quantity of fire retardant. It can also be seen that the fire retardancy of such fiber blends is significantly improved over that of untreated fibers.

Example 6 To further illustrate the advantages of this invention with respect to improvements in depth of dye shade, a fiber was prepared as in Example 1 containing 17.0% C Br and 2.9% Sb O Respective 40/60, 30/70 and 20/80 blends of treated fiber and untreated fiber of Example 2 were dyed. A control sample composed of 100% untreated fiber was also dyed. The actual dye pickup was measured which declared this fiber to be very bright or lustrous; by dissolving in DMF (or NaSCN) and measuring reflectance and found to be identical in each case. Apparent dyeability of the fiber, as measured by GE. spectrophotometer reflectance, showed the 100% treated fiber to be only half as deep in shade as the untreated fiber. The blended fibers varied in dyeability between these extremes and were substantially deeper in shade than would be expected from non-blended fibers containing the indicated levels of additive.

TABLE III Additive Treated/ (percent of Fade- Dyenbility Untreated total ometer GE. in Fiber fiber) Luster (Hours) Reflectance) From Table III it will be apparent that blends of treated and untreated fire-retardant fibers, though less lustrous than fibers having no fire retardant, are much better with respect to luster, light fastness and apparent dyeability than fibers which were uniformly treated with fire-retardant.

While there have been described several examples of composite flame-retardant acrylic fibers in accordance with the invention, it will be appreciated that many changes and modifications may be made therein without, however, departing from the essential spirit of the invention as defined in the annexed claims.

I claim:

1. A fire-resistant fiber blend, said fiber blend comprising (a) about 5% to treated synthetic fibers treated with a solid fire-retardant additive in finely divided particulate form dispersed therein, and (b) 10% to of untreated synthetic fiber substantially free of said solid fire-retardant additive having significant delustering effect on the fiber; the amount of said fire-retardant additive in said treated fibers being sufficient to render fabrics of the fiber blend fire-retardant.

2. The fiber blend of claim 1 wherein the synthetic fiber is a fiber composed of an acrylonitrile polymer.

3. A fiber blend as set forth in claim 2, wherein the blend is composed of 10%-50% treated fibers and 90 50% untreated fibers.

4. A fiber blend as set forth in claim 3, wherein said treated fiber contains solid, high-melting, finely dispersed organic bromine to chlorine compound and a synergist to augment the effect of the flame retardant.

5. A fiber blend as set forth in claim 4, wherein the concentration of bromine in the treated fiber is in the range of 1.0% to 25% in conjunction with 0.2% to 5.0% antimony trioxide.

6. A fiber blend as set forth in claim 4, wherein said synergist is a solid organo-phosphorous compound.

7. A fiber blend as set forth in claim 5, wherein the treated fibers contain 1.5% to 25% of hexabrornobenzene and 0.2% to 3.5% antimony trioxide as a synergist.

8. A fiber blend as set forth in claim 6, wherein said synergist is tri-benzyl phosphine oxide.

9. A fabric produced from the synthetic fiber blends of claim 1.

10. A carpet fabric produced from the fiber blend of claim 2.

References Cited UNITED STATES PATENTS 3,076,034 1/1963 Gordon 26045.7 3,269,963 8/1966 Ilgemann et a1 26045.7 3,341,625 9/1967 Gillham et al 26045.7 3,361,847 1/1968 Zimmermann et al. 26045.7

DONALD E. CZAIA, Primary Examiner V. P. HOKE, Assistant Examiner US. Cl. X.R.

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