US3304194A - Non-woven fabrics of resin-bonded regenerated cellulose - Google Patents

Description

United States Patent C) 3,304,194 NON-WGVEN FABRICS 8F RESlN-BQNDED REGENERATED CELLULGSE Jan Dabrowski, North Augusta, S.C., assignor to United Merchants and Manufacturers, Inc., New York, N.Y.,

a corporation of Delaware No Drawing. Filed Dec. 4, 1962, Ser. No. 242,088

7 Claims. (Cl. 117-10) This invention relates to the production of non-woven fabrics and more particularly to a process of producing such fabrics involving the bonding of the fabrics to form fabrics of light weight, having draping qualities and hand closely approximating woven and knit fabrics, good wash properties and durability. The invention comprehends the resultant novel non-woven fabric as well as the process of making same.

Non-woven fabrics are composed of fibers which are mechanically and/or chemically bonded together and which fabrics are not made by weaving or knitting or similar textile techniques but are commonly produced by sheeting an aqueous slurry of the fibers in paper-making or Fourdrinier equipment, although they can also be produced as air-laid or carded non-woven Webs. One important class of such fabrics is produced from regenerated cellulose fibers, such, for example, as viscose rayon or cuprammonium rayon employing the so-called highteacity rayon staple fiber of from about 50% to 90% extensibility. The expression rayon is used herein in its broad conventional sense to include all forms of regenerated cellulose fibers employed in making non-woven fabrics, including but not limited to viscose rayon and cuprammonium rayon. The rayon staple fiber is dispersed in water, binder, desirably phosphated starch, say in amount of from 2% to 8% based on the weight of the slurry, and resin, usually a solution of butylated melamine formaldehyde resin in amount of about 1% based on the weight of the rayon staple fiber, is added to the slurry of fiber to improve the wet tensile strength of the resultant web with consequent improved handling properties of the web, the resultant slurry sheeted out to produce a web on the so-called wire which usually is a perforated nylon endless belt. Water is extracted from the wet web thus produced usually by subjecting the web to high vacuum, the dewatered web dried by passage over heated stainless steel drying cylinders, and the dried web wound into rolls of unsaturated non-woven fabric. The unsaturated fabric customarily is unwound, cut to remove uneven edges and rewound.

Conventional practice is to saturate the non-woven web thus produced by passage through a bath containing a resinous impregnant in a concentration of about 10% to 20% or more based on the weight of the bath, the amount of resin used depending on the particular resin, the properties, density, thickness, etc. of the non-woven fabric subjected to impregnation and the desired properties of the final product. The impregnating procedure invariably involved passing the non-woven fabric through a bath, immersed therein, and then through a pair of squeeze rolls which remove the excess saturant and produce an impregnated web containing approximately 100% of saturant by weight based on the dry weight of the non-woven fabric. The thus saturated web is dried by passage over a series of steam-heated stainless steel cylinders.

Saturants heretofore used are the reactive acrylic emulsions, acrylonitrile-butadiene copolymers, polyvinyl chlorides and polyvinyl acetates, invariably in amounts to deposit on the non-woven fabric from 10% to 20% solids by weight or more based on the dry weight of the fabric. Saturation of non-woven fabrics with these saturants involves a number of problems in the production of the fabrics having the desired properties including, among others: 1) the tensile strength of the fabric in the dry state and even more so in the wet state is poor and in many cases in the wet state below acceptable standards for washable fabrics; (2) frequently these thermoplastic latices in emulsion form are not compatible with the commonly used fire retarding agents, pigments or dyestuffs or water repellents, and hence the use of these resins renders it difficult and at times impossible to incorporate in the fabric, preferably during the saturation, a fire retardant, a water repellant and/ or pigment or dyestuff to produce the desired color; (3) the resins are relatively expensive, particularly in the amounts required to obtain fabrics having the desired properties which prompted the use of the resins; (4) fabrics impregnated with these saturants cannot be embossed readily to obtain a desired pattern effect because the resin saturant tends to stick to the surface of the fabric under the temperature and pressure conditions of the embossing with the fabric adhering to the embossing rollers with consequent damage to the fabric; and (5) the amount of saturant required to obtain necessary tensile strength is so great as to add appreciably to the weight of the fabric and in some cases result in a fabric which no longer has the advantageous light weight properties per unit area.

It is a principal object of the present invention to provide a process for producing saturated non-woven fabrics, which process overcomes the objections and problems inherent in the heretofore known procedures of producing saturated non-woven fabrices and results in a light weight, saturated non-woven fabric having improved tensile properties.

Another object of this invention is to provide such process in which the saturant is used in relatively small quantities and yet imparts not only an improvement in the tensile properties of the saturated non-woven fabrics but results in the fabric having good washing properties and durability.

Another object of this invention is to provide a novel saturated non-woven fabric containing a relatively small amount of saturant per unit weight of non-woven base, thus producing a saturated fabric of light weight having good draping properties similar to those of knitted and woven textiles, good washing properties and durability.

Other objects and advantages of this invention will be apparent from the following detailed description thereof.

In accordance with this invention an unsaturated nonwoven fabric composed or rayon fibers as hereinabove described and available commercially under the trademark Strytex (St. Regis Paper Co.) is saturated to contain from 0.5% to about 4% by weight of water-soluble salt of deacetylated chitin and approximately the same amount of a thermosetting resin, preferably an aldehyde precondensate, with or without pigments or dyestuffs, Water repellent agent, or fire retardant agent, depending on the desired properties of the final product, and the saturated web subjected to heat at a temperature of from 280 F. to 350 F. to effect curing of the resin and reaction between the resin and the deacetylated chitin to produce a reaction product which is uniformly distributed throughout the web.

Surprisingly, the saturated web having this reaction product uniformly distributed therethroughout has high tensile strength in the dry state and reasonably good tensile strength in the wet state, both appreciably higher than the tensile strength of saturated non-woven fabrics produced employing much greater amounts of the heretofore known saturants for non-woven fabrics, such as the acrylic resins heretofore commonly employed, and this both in the lengthwise and crosswise directions of the web. Moreover, the water-soluble deacetylated chitin and the aldehyde precondensates as Well as their reaction products are compatible with basis dyestuffs suitable and used for coloring the fabric, with phosphorus type fire retardants, such as diammoniurn hydrogen phosphate and phosphoric acid, and also with commonly used water repellents, such, for example, as wax emulsions, aluminum stearate and other metal salts of the higher fatty acids employed as water repellents. Furthermore, the nonwoven saturated web containing the reaction product of deacetylated chitin and the aldehyde precondensate in the amounts herein disclosed can be embossed, i.e., the saturant does not stick to the surface of the fabric under the temperature and pressure conditions employed in the embossing and the saturated fabric does not adhere to the embossing rolls. Accordingly, non-woven fabrics can be produced having a pleasing soft hand and desired embossed appearance, of relatively high tensile strength, good durability, fire retardant, if desired, and any desired color, and this without involving added processing steps because the fire retardant, water repellent and the dye or pigment can be incorporated in one and the same bath as that containing the deacetylated chitin and the aldehyde precondensate.

The deacetylated chitin can be obtained by heating crude chitin successively with soda ash and hydrochloric acid to remove the lime salts and adherent protein followed by digesting with the sodium hydroxide or other alkali at an elevated temperature under conditions excluding oxidation, to produce deacetylated chitin. The deacetylated chitin thus produced is reacted with the aqueous acetic acid, producing the water-soluble acetic acid salt. While it is preferred to use the acetic acid salt, other acid salts may be used, such, for example, as those formed by treating the purified deacetylated chitin with itaconic, formic, pyruvic or lactic acid. For a. more detailed description of the production of such acid salts of deacetylated chitin, reference may be had to United States Patents 2,040,879 and 2,040,880, granted May 19, 1936.

The deacetylated chitin may be added as such to the aqueous bath and the acid, such as acetic acid, also added to the bath to form the water-soluble salt in situ or, alternatively, the water-soluble salt can be added to the bath. When the salt is added the amount used is from 0.5% to about 4% based on the total weight of the bath. When adding the acid and deacetylated chitin separately, from 0.5 to 2% of the deacetylated chitin is added and approximately the same amount by weight of acid as the deacetylated chitin.

The thermosetting resin, as noted, is preferably an aldehyde precondensate and is added to the bath in amount approximately equal to the amount of water-soluble salt of deacetylated chitin, namely, from about .5 to 4% based on the total weight of the bath. Preferred thermosetting resins are the melamine formaldehyde resins containing from 2 to 6 mols of formaldehyde per mol of melamine, such as the melamine formaldehyde resin sold under the trade-name Aerotex Resin M.W.; the ethylene urea formaldehyde resins, e.g., Valrez EU; the urea formaldehyde resins, e.'g., Valrez P.R.; the methylated urea formaldehyde resins, e.g., Wicaset 55; and the triazone resins, e.g., Permafresh 197 having the formula:

Wherfiill or An acid catalyst is employed in the bath. The preferred catalyst is 2 amino-2 methyl-1 propanol hydrochloride (Valcat AH), although other acid catalysts, such as NH Cl or tartaric acid employed with aldehyde precondensates to catalyze the curing thereof can be used. The amount of catalyst used is usually less than 1%, preferably about 0.5 based on the weight of the bath.

In addition to the water-soluble salt of deacetylated chitin, thermosetting resin and catalyst, the bath can contain a fire retardant, such as phosphoric acid in amount of from 12% to 15%, and diamrnonium hydrogen phosphate in amount of from 6% to 8%; pigment or dyestuif, preferably a basic dyestuif, usually in amount of from 0.1% to 0.5 and a water repellent, such as wax emulsion, aluminum salts of higher fatty acids, etc., preferably in amount of from 8% to 12%, the rest of the bath being water.

impregnation of the unsaturated non-woven fabric is desirably effected by passing the fabric through the bath, immersed therein, and then through a pair of press rolls which effect removal of the excess saturant so that the fabric leaves the press rolls with a wet pick-up of from to 110%, usually about based on the dry weight of the unsaturated fabric. The thus impregnated fabric is then passed through a heating oven or curing zone maintained at a temperature of from 275 F. to 350 F. for a residence time of from 1 to 5 minutes. The residence time and curing temperature are inversely related. At the higher temperatures, shorter residence times are used and at the lower temperatures longer residence times are used, both within the stated ranges.

Unsaturated non-woven fabrics of regenerated cellulose fibers take up the saturant readily so that the aqueous solution of the deacetylated chitin and the aldehyde procondensate, which is also water-soluble, is substantially uniformly distributed throughout the non-woven fabric, in effect forming films on the fibers. Upon subsequent curing, i.e., during the heating, reaction takes place between the thermosetting resin and the deacetylated chitin, producing a reaction product in the form of a matrix or skeleton structure surrounding the fibers, which matrix or skeleton is relatively light in weight. In general it adds to the weight of the fibers not more than about 4% and surprisingly imparts to the non-woven fabric improved tensile strength both in the lengthwise and crosswise direction and when the fabric is dry as Well as when it is wet; good washing properties (the reaction product is water-insoluble), durability, and enables the impregnated fabric to be calendered to produce compacting or desired surface effects without the saturant bleeding and without the sticking of the saturated fabric to the calendering rollers. Preferably the calendering is effected immediately after impregnation and drying of the fabric and before passage of the impregnated fabric through the heating or curing zone where the reaction between the deacetylated chitin and the aldehyde precondensate takes place. The calendered fabric, it has been found, has an unusually supple hand.

The following examples are given for illustrative purposes with the understanding that the present invention is not to be limited to these examples.

In the examples all percentages are given on a weight basis. Where the percentages refer to the content of the bath, they are based on the total weight of the bath.

In the test data which follows the dry strength is determined by conventional textile tensile strength determination procedures involving the well known Scott tester, Model .T. The wet strength is determined by the same procedure except that the test specimen of the fabric was wetted out and then squeezed by the nip of a laboratory padder before testing so that in all cases the test samples had approximately the same water content when the determination of tensile strength was made. In all cases the same test procedure was used so that the results are truly comparative.

Example I In this example a non-woven fabric made from viscose staple fiber of about 50% extensibility, inch staple length and 1.5 denier weight, to produce an unsaturated web having a weight of 2.8 ounces per square yard, was saturated by passage through a bath containing 1% deacetylated chitin, 1% acetic acid, 3% ethylene urea formaldehyde (Valrez EU) and 0.5% acid catalyst (Valcat AH). The residence time in the bath was about 2-3 seconds, and the web upon leaving the bath passed through a pair of press rolls; the saturated web leaving the press rolls had a wet pick-up of 100%. Thus the saturated web contained the same relative percentages of the constituents as in the bath except that because of the reaction between the deacetylated chitin and the acetic acid the saurated web contained approximately 2% by weight of the acetic acid salt of the deacetylated chitin. The saturated web was cured by passage through an oven maintained at 310 F.; the residence time within the oven was two minutes.

Example II This example differs from Example I in that the bath also contained 12% of a water repellent, namely, a wax emulsion sold under the trade-name Atco-dri T.S.N. The impregnation and curing times were the same as in Example I.

For comparative purposes the same non-woven fabric was treated in four different baths containing, respectively, 5% (Run A); (Run B); (Run C); and (Run D) acrylic resin (Rhoplex PIA-8). The baths containing 5% and 10% Rhoplex HA-8 contained 0.5% of an acid catalyst (Valcat AH), and the baths containing 15% and 20% Rhoplex HA-S contained .75% of this acid catalyst. Treatment was otherwise the same, namely, the impregnation was carried out to give 100% wet pick-up and the curing was effected at 310 F. for two minutes.

Tensile strength determinations were made for both the dry strength and wet strength, lengthwise and crosswise, of the resultant non-woven saturated fabrics and also of the unsaturated non-woven fabric (control, without treatment) the same as that employed in the examples and in the comparative runs. In Table I which follows the data thus obtained is given.

tensile strength procedures as disclosed herein. The data thus obtained is given in Table II which follows:

TABLE II Dry Strength Wet Strength Length Width Length Width Example I 26. 0 16. 0 6. 0 2. 5 R A 12. 0 3. 0 21. 0 5. 5 22. 0 6. 0

1 Unable to emboss. 2 Cut.

Example III In this example a non-woven fabric also made from viscose staple fiber having a weight of 2.8 ounces per square yard was saturated by passage through a bath having the following composition:

(1) 25 pints of 4% acetic acid salt of deacetylated chitin; (2) 3 pints of ethylene urea formaldehyde (Valrez EU); (3) /2 pint of aminehydrochloride catalyst (Valcat AH); (4) 12 pints of water repellent (Atco-dri) (5) .05 pint of a basic dye; and

(6) 59 /2 pints of water.

The non-woven fabric was passed through this solution and then through a pair of press rolls leaving the latter with a wet pick-up of 110% to 130%. The saturated fabric was dried, embossed in a hot calender at 300 F. to 340 F. under a pressure of from tons to 6 0 tons per roller face, and the embossed fabric heated to 320 F. for two minutes, thus curing the resin and resulting in a water-insoluble reaction product between the resin and the deacetylated chitin. The colored non-woven fabric thus produced was strong and water repellent.

Example IV In this example the non-woven fabric employed as the base had a weight of 2.8 ounces per square yard. A saturating bath was prepared containing 55.99% water, 12% phosphoric acid, 8% diammonium hydrogen phosphate, 2% acid buffer (D.C.Y.), 20% acetic acid salt of deacetylated chitin as a 4% solution of the salt, 2% ethylene urea formaldehyde, 0.1% basic dyestuff (Rhodamine B concentrate). The saturation of the unsaturated The saturated non-woven fabrics of Example I and of the comparative runs were passed through embossing rollers at a temperature of 340 P. which exerted a pressure of 60 tons per 53 inches of the face of the roll. The embossed products, with the exception of that from Run A which could not be embossed because of sticking to hot roller and web separation, were tested to determine the tensile strength both in the dry and wet state by the same non-woven fabric was carried out by passing the fabric through the bath and then through a pair of press rolls; the wet pick-up was The thus saturated fabric was cured at 320 F. for two minutes.

The resultant saturated non-woven fabric showed exceptionally good fire retarding properties. Its dry tensile strength in the lengthwise direction was 13, and in the widthwise direction was 12. This fabric is particularly useful in the field of relatively inexpensive draperies having fire retardant properties. The tensile strength is more than adequate for this purpose and the fire retarding properties are exceptionally good. \Vhen subjected to a match test, there was no flame propagation or after-glow.

It will be noted that the present invention provides a process of producing saturated non-woven fabrics of light weight, improved tensile properties, both in the dry and wet states, good Washing properties and durability and Which can be embossed Without the fabric adhering to the embossing rollers and without bleeding of the saturant taking place during the embossing operation. The embossing preferably precedes the heating of the saturated fabric to form the water-insoluble reaction product of the deacetylated chitin and aldehyde precondensate. Thus this reaction product serves to maintain the embossed effects, whether they be glazed effects produced by smooth calender rolls, schreinered effects or raised and depressed design areas produoed by cooperating embossing rollers having raised and mating depressed areas. The resultant embossed fabrics are relatively wash-fast. The reaction product imparts strength and body to the fabrics, including the embossed fabrics, which will not Wash out in normal handling, including washing in laundries or home washing machines.

,Since certain changes in carrying out the process of producing the saturated non-woven fabrics and in the resultant saturated non-woven fabrics which embody this invention can be made without departing from the scope of this invention, it is intended that all matter contained in this specification shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. The process of producing non-woven fabrics of regenerated cellulose which comprises saturating the unsaturated non-woven fabric with an aqueous solution containing a water-soluble salt of deacetylated chitin, an amino-formaldehyde resin precondensate in water-soluble form and a small amount of acid catalyst to uniformly distribute throughout the non-woven fabric, from about .5 to 4% of the water-soluble salt of deacetylated chitin, approximately the same Weight of aldehyde precondensate, and a small amount of acid catalyst, and thereafter heating the saturated fabric to a temperature of from 275 F. to 350 F. for from 1 to 5 minutes, and

thus reacting the deacetylated chitin and aldehyde precondensate to form a water-insoluble reaction product uniformly distributed throughout the non-woven fabric.

2. The process as defined in claim 1., in which the fabric prior to the heat treatment is embossed and thereafter is heated to cure the resin.

3. A non-woven fabric consisting essentially of regenerated cellulose filbers bonded together by a matrix constituted of the reaction product of deacetylated chitin and an amino-formaldehyde resin precondensate, the amount of said reaction product present being from about 1% to 4% based on the weight of the fibers.

4. An embossed non-Woven fabric consisting essentially of regenerated cellulose fibers bonded together by a waterinsoluble matrix consisting of the reaction product of an amino-formaldehyde resin precondensate and deacetylated chitin, which reaction product is formed after the embossing of the fabric impregnated with a solution containing deacetylated chitin and aldehyde precondensate whereby the reaction product serves to maintain the raised and depressed surfaces formed by the embossing substantially wash-proof.

5. The process of claim 1 in which the amino is urea.

6. The process of claim 1 in which the acid catalyst is selected from the group consisting of 2-amino-2-met-hyllpropanol hydrochloride, NH Cl and tartaric acid.

7. The fabric of claim 4 in which the amino is urea.

References Cited by the Examiner UNITED STATES PATENTS 2,047,225 7/1936 Rigby 117164 2,961,344 11/1960 Hurd et al. ll7--l26 3,137,589 6/1964 Manneheim et al. 161-170 3,228,790 1/1966 Sexsmith et al. 117-140 OTHER REFERENCES Robinette, Hillary: Dyeing and Finishing, Modern Textiles Magazine, Vol. 38, No. 6, pp. 46, 48 (1957), TS 168 8 Al R 21.

ALFRED L. LEAVITT, Primary Examiner.

RICHARD D. NEVIUS, Examiner.

A. H. ROSENSTEIN, Assistant Examiner.

Claims (1)

1. THE PROCESS OF PRODUCING NON-WOVEN FABRICS OF REGENERATED CELLULOSE WHICH COMPRISES STARUATING THE UNSATURATED NON-WOVEN FABRIC WITH AN AQUEOUS SOLUTION CONTAINING A WATER-SOLUBLE SALT OF DEACETYLATED CHITIN, AN AMINO-FORMALDEHYDE RESIN PRECONDENSATE IN WATER-SOLUBLE FORM AND A SMALL AMOUNT OF ACID CATALYST TO UNIFORMLY DISTRIBUTE THROUGHOUT THE NON-WOVEN FABRIC, FROM ABOUT .5% TO 4% OF THE WATER-SOLUBLE SALT OF DEACETYLATED CHITIN, APPROXIMATELY THE SAME WEIGHT OF ALDEHYDE PRECONDENSATE, AND A SMALL AMOUNT OF ACID CATALYST, AND THEREAFTER HEATING THE SATURATED FABRIC TO A TEMPERATURE OF FROM 275*F. TO 350*F. FOR FROM 1 TO 5 MINUTES, AND THUS REACTING THE DEACETYLATED CHITIN AND ALDEHYDE PRECONDENSATE TO FORM A WATER-INSOLUBLE REACTION PRODUCT UNIFORMLY DISTRIBUTED THROUGHOUT THE NON-WOVEN FABRIC.