US3219513A - Crock-resistant fabric - Google Patents

Description

United States Patent 3,219,513 CRUCK-RESKSTANT FABREC John Wharton, Mobile, Ala., assignor to Courtaulds (North America) Inc., a corporation of Alabama No Drawing. Filed Dec. 6, 1061, Ser. No. 157,588 1 Claim. (Cl. 161-87) This invention relates to colored rayon staple fiber, and in particular to colored rayon staple fiber having high resistance to crocking, both wet and dry, and to yarn and fabric made therefrom.

Rayon, i.e., regenerated cellulose, fiber is the least expensive of all synthetic fibers. It is possessed of numerous attractive properties which permit its employment in a wide range of applications. However, there remain some uses for which rayon is not as well suited as might be desired. Thus, for example, the use of rayon in upholstery fabrics has been somewhat limited because of its tendency to exhibit crocking, particularly when wet. Crocking is a term used to described the rubbing off of dye or color from a fabric.

Thus, the tendency of colored rayon to crock is par ticularly objectionable in upholstery fabrics from which the color may rub off onto white or light colored clothing. It is also objectionable in garment fabrics, e.g. in linings and in colored undergarments.

Resistance to crocking is rated according to a standard technique identified as AATCC Test Procedure 8-1957. In general this measures the degree to which color is transferred when the colored fabric in question is rubbed against a piece of white cloth in a particular way. Many fabric purchasers specify a minimum crock resistance and fabrics having less than this cannot be sold. For automobile seat fabrics, for example, a minimum wet crock rating of three is specified and fabrics having less than this cannot be sold for automobile upholstery. Considering the size of the automobile market a wet crock rating of 3 is therefore in an economic sense, a critical rating.

Rayon fiber can, of course, be dyed after it is spun or after it is made into cloth. For many reasons, however, it is desirable to mix the coloring agent with the viscose solution and form the fibers with the color already deposited within them. This technique is referred to in the art as spin dyeing or solution dyeing. It is Widely practiced with azo dyestuffs, vat dyestuffs, carbon black, inorganic oxides and other stable coloring materials. Generally fiber made in this way is superior to fiber colored in other ways in its resistance to crocking; however, the crocking resistance of spun-dyed rayon textile fiber has still left much to be desired.

In present day use there are three general types of rayon fiber. The first, which may be referred to as normal textile fiber, is characterized in having a low degree of crystallinity, say 30 to 40% as determined by the X-ray method. It has an elongation of say 16 to 21% dry and 18 to 25% wet. The individual fibers have crenulated surfaces and a very pronounced skin-core structure. For most textile purposes this fiber is used in the staple form.

Recently there has been introduced a relatively new type of rayon, also specifically for textile purposes. This material has a high degree of crystallinity, generally over 50%, and normally on the order of 65%. It has a generally circular cross-section and an even surface. It has an elongation of not more than say 10% dry and 12% wet. It, too, is usually employed as staple fiber.

3,2l9,5l3 Patented Nov. 23, 1065 ice A third type of rayon currently being made in large volume is the type usually employed in tire yarn. It is characterized by a relatively low degree of crystallinity, i.e., less than say 45%, a high extensibility (say 22 to 35% dry and 28 to 45% wet), a smooth non-crenulated skin and substantially no skin-core structure. Such rayon has not customarily been used for textile purposes. It is made and used as continuous filament yarn rather than staple and it is of course not colored.

It has now been discovered that when filaments of a type somewhat similar to this third type are spun dyed, cut up into staple and then converted into fabric, the fabric so obtained has remarkably high resistance to wet crocking.

The invention thus comprises a rayon staple fiber having a degree of crystallinity below about 45% (as determined by X-ray methods), a dry extensibility of above about 20%, a wet extensibility of above about 28%, a substantially all-skin structure and containing at least about 2% by weight coloring matter evenly distributed across its cross section.

The invention further comprises yarns and fabrics made from such staple fiber.

In manufacturing fiber of this type, viscose containing less than about 8.5% cellulose, normally 6 to 7.5% cellulose, and more than say 5% NaOI-I, preferably 6 to 7.5% NaOH and having a '7 number of at least 35, usually between about 37 and about 65, is spun into an acid spinning bath. The bath contains not more than about 10% H 50 usually between about 5.5 and about 8.5% H 80 not less than about 3.0% ZnSO usually between about 3 and about 7% ZnSO, and between about 12 and about 23% Na SO The proportion of Na SO will in general depend on the zinc content, i.e., 3% ZnSO will call for about 23% Na SO and 7% ZnSo, will require about 12% Na SO The temperature of the bath will be above about 45 C., usually between about 55 C. and about C. As noted above the viscose will also contain at least 2% coloring material based on cellulose. The precise amount will of course depend on the material and on the shade desired, but usually it will be between about 2.5 and about 4.5% on the weight of cellulose.

The spinning is further conducted in the presence of a viscose modifier. The modifier is preferably added to the viscose, where it is normally present in a proportion between about 0.008 and about 4.0%, on the weight of viscose and preferably between about 0.03 and about 1% on the weight of viscose. In certain cases, the modifier may be added to the spinning bath where it will usually constitute between about 0.1 and about 1.0% by weight of the bath.

The use of viscose modifiers has been known in the rayon industry for several years. These substances vary greatly in chemical composition and appear to differ among one another in the mechanism through which they operate. However, the effect in every case is to produce filaments which have thick skins or are all skin. The filaments may be oval, round or bean-shaped in cross section and have a smooth skin, free from the crcnulations normally found in textile grade rayon,

Among the substances which have been found useful as modifiers are quaternary ammonium compounds as disclosed in United States Patent 2,536,014, aliphatic monoamines as disclosed in United States Patent 2,535,044, aliphatic diamines as disclosed in British Patent 762,772, salts of N-substituted dithiocarbamic acids, ethers of the formula RO(CH CH O),,R where R is alkyl or aryl, n

is an integer from 1 to 4 and R is hydrogen, alkyl, or aryl, as disclosed in British Patent 741,728 and polyethylene glycols of formula HO(CH CH O), H where n is at least 4, as disclosed in United States Patent 2,696,423. Generally it is preferred to use polyethylene glycol modifiers having a molecular weight from about 1500 to about 10,000.

Preferably the pigment or coloring matter is introduced into the viscose by means of a non-aging viscose-compatible carrier, such, for example, as sodium carboxymethyl cellulose or the salts of polyacrylic or polymeth' acrylic acid as disclosed in United States Patents 2,783,- 8 and 2,993,018. Alternatively, in accordance with another conventional technique, a portion of the viscose can be withdrawn from the main stream just before extrusion, mixed with the coloring matter and reunited with the main stream. It is, of course, also possible to mix the color with batches of viscose in spinning concentrations initially. Difliculties are experienced here, however, in maintaining constant shades.

After spinning, the viscose filaments may be withdrawn from the spinning bath, stretched between about 40 and about 100% either in air or in a dilute (say 1 to 4% H 80 acid bath at say 60 to 100 C., and cut up into staple. The staple may then be washed in accordance with conventional practice, and dried.

Alternatively the filaments after stretching may be washed and dried in the form of tow and subsequently cut into staple after they have been dried.

Colored staple fiber made as indicated will have a thick skin or be all-skin; have a smooth non-crenulated surface and a circular, oval or bean-shaped cross-section, It will have a crystallinity of less than 45%, usually between about 35 to about 40%, as determined 'by X-ray techniques, an extensibility (wet) of more than 28% (usually from 30 to about 45%) and an extensibility (dry) of more than (usually from 20 to 35%). It will have the coloring material distributed uniformly throughout its cross-section. It is of interest that fibers made in this way show little or no fibrillation when agitated at high velocity in pure water.

Staple fiber having the characteristics described can be made into yarns by any convenient technique, using the cotton system, for example, and then woven or knitted into fabrics. They may also be used to make the so-called non woven fabrics. Such fabrics are of excellent hand and appearance and have in general a crock rating at least greater than comparable fabrics made out of conventional textile grade rayon. They will have in general a wet crock rating above 3 and in many instances above 4. As such they are of particular utility in upholstery and garment fabrics.

It will be understood that viscose rayon fibers made in accordance with the invention may be used by themselves or blended with other types of fibers, to make combination yarns or non-woven fabrics. Similarly yarns made wholly from the novel staple fiber may be used alone in the manufacture of woven or knitted fabrics, or in combination with yarns made of other fibers. The benefits of the invention become increasingly important as the proportion of the novel rayon fibers in the yarn or fabric increases, However, they begin to have a noticeable effect when the proportion of the new fibers reaches about 25% by weight of the blend.

Among the fibers which may be blended with the novel staple fiber are fibers of cellulose esters, for example, cellulose acetate (acetone soluble cellulose acetate or cellulose triacetate), and fibers of synthetic linear polymers, for example, of polyamides such as nylon 6 or nylon 66, of polyesters, for example, polyethylene terephthalate, of polyolefins such as polyethylene or polypropylene and of addition polymers derived from acrylonitrile.

The invention will be further described with reference to the following examples which are given for purposes 4;. of illustration only and are not to be taken as in any way limiting the scope of the claims.

Example 1 Spun dyed staple fiber A was produced by premixing 10 parts by weight of phthalocyanine blue containing 15% of an anionic dispersing agent (a sodium salt of a naphthalene sulfonic acid) into 90 parts of a viscose containing 7.5% cellulose and 6% sodium hydroxide and having a gamma number of 60. After mixing and deaeration the pigmented viscose was injected at constant rate through pumps into a cylindrical enclosed high speed mixer together with a larger quantity of filtered non-pigmented viscose of similar composition but containing 4% of a polyethylene glycol having a molecular weight of about 2000. The proportions of pigmented and non-pigmented viscose were such as to give a final blend containing 3% phthalocyanine blue on cellulose. This mixture was then deaerated and spun through 5000 hole 3 mil jets into a spinning bath containing 7.0% H 18.0% sodium sulfate and 5.0% ZnSO and having a temperature of 55 C. After a 70% stretch, fixation, cutting, washing and drying the 1 /2 denier pigmented staple fiber had tenacities of 3.8 g./den. dry and 2.5 g./-den. wet, and extensibilities of 24% dry and 34% wet. It had a smooth surface and a bean-shaped cross-section. Skin-core differentiation was not present. It had a crystallinity of about 38% and did not fibrillate after 2 hours beating in water at 400 strokes/ min.

The fiber was made into a 30s count yarn which in turn was used to make a knitted stocking fabric,

A similar fabric was made from spun dyed conventional textile grade rayon fiber (Fiber B) 1 /2 denier having a dry elongation of 17%, a wet elongation of 21%, a crystallinity of about 43% and containing 3% phthalocyanine blue. The two fabrics were then tested for crock rating. The results are shown below:

Example 2 To a viscose containing 6.5% cellulose and 5.5% NaOH and having a gamma number of 65 was added 3.5% on cellulose of a finely dispersed carbon black having an average ultimate particle size of 400- A. together with 15% on the weight of carbon black of a nonionic dispersing agent and 0.5% on the weight of viscose of a mixed coagulation modifier containing principally polyethylene glycol and an ethylene oxide lauryl amine condensation product. The viscose was spun into a bath con taining 6.5% H 80 14% Na SO and 6.5% ZnSO at 60 C. The tow was stretched 83%, fixed in an acid bath at C. and cut into staple.

The black staple had tenacities of 4.1 g./den. dry, and 3.0 g./den. wet. Its extensibilities were 22% dry and 36% wet. It had a homogeneous, oval, non-crenulated cross-section and a crystallinity of about 40%. It did not fibrillate under the conditions described in Example 1.

The staple fiber was spun into 20s yarn and then woven into a plain weave cloth. The cloth showed a wet crocking index of 4.0.

A similar fabric made from the same denier conventional textile grade yarn having a wet extension of 20%, a dry extensibility of 17% and a crystallinity of 42% showed a wet crock rating below 3.

I claim:

A colored fabric characterized by its high resistance to wet crocking and composed of at least 25 by weight of viscose staple fiber having a crystallinity below about 40%, a dry extensibility of greater than 20% and a wet extensibility of greater than 28%, having a substantially least 3.

References Cited by the Examiner UNITED STATES PATENTS Helm et a1 106-164 Lutgerhorst 1854 Wegrnann et a1 106165 Thurnm 106165 Howsmon 106-165 Vosters 106165 Cox et a1 2882 Matray et al 2882 Mix 106168 DONALD W. PARKER, Primary Examiner. Schlack 1 10 MERVIN STEIN, Examiner.