US3460896A - Polyester fibers having improved hydrophilicity as a result of modification with phosphoric acid,phosphorous acid or perchloric acid - Google Patents

Description

United States Patent O 3,460,896 POLYESTER FIBERS HAVING IMPROVED HYDRO- PHKLICITY AS A RESULT OF MODIFICATION WITH PHOSPHORIC ACID, PHOSPHOROUS ACID R PERCHLORIC ACID John R. Caldwell, Kingsport, Tenn., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Oct. 14, 1964, Ser. No. 403,907 Int. Cl. D06p 3/52, 3/00 U.S. Cl. 8-1155 4 Claims As is well known, various polymeric materials such as high molecular weight linear polyesters which are generally useful in the production of products such as fibers, filaments, yarns, fabrics, and the like have certain draw- 3,460,896 Patented Aug. 712, 1969 insoluble particles are formed in the product mass'which tend to clog the minute orifices of spinnerettes when the filaments are produced by the melt spinning process.

'In addition to the above mentioned expedients, Canadian Patent No. 620,001 describes a process for treating polyester fibers in which an organic acid is applied and ice : the treated fiber is then heated at a temperature of 2.00

to 220. All of the acids disclosed in this patent contain organic radicals and hence are not inorganic acids nor do they or can they produce the effects on polyester fiber materials which are produced by inorganic acids in accordance with the present invention to be set forthhereinafter. A somewhat related disclosure is that of US. 2,893,896 which describes the treatment of ,polyester sub strates with halogenated fatty acids but makes-no men tion of the application of inorganic acids as employed in the present invention. In another disclosure, namely, Ca-

backs 0r deficiencies whichlimit their usefulness in such products. For example, it is known that many types of polymeric materials when extruded in the form of filaments and converted into yarns do not" have the desired resistance to soiling by a variety of substances, especially oily or greasy-substances, which'such yarn materials .2

of fibers and filaments for textile uses. As to wettability,

this is an especially important property when such polyester fibers are employed in apparelfabrics because the transmission of moisture from the skin is facilitated if the fiber material employed has good wettability. Such readily wettable fibers possess the property of wicking away water from the body for more efficient evaporation and thus greater comfort to the wearer. In other applications such as the sizing'of fibers and yarns, wettability is an important property in the application of various coatings such as gelatin, polyvinyl alcohol and other substances which are normally deposited from aqueous or alcohol or other solutions. It is also apparent that 'dyeability is an important property in polyester textile fibers in order to obtain uniform and permanent coloration of the fiber material by the dyes generally employed for this purpose as well as to enable the material to receive and permanently retain printing inksand other coloring materials.

Various expedients have been employed in the prior art to overcome the above mentioned drawbacks and deficiencies inherent in the use of linear polyesters for the manufacturers of fibers and filaments. Among these may be mentioned the application of various sizing or coating compositions which form an adherent surface layer which tends to provide the desired properties in the finished material. Another is the employment in the reaction mixture from which the polyester is formed of a substance which will react chemically with the polyester to add on chemical groups which will provide the desired properties. In this case it has been found that under certain circumstances unstable products result and in some "cases undesirable nadian 652,277, which is an extension of the invention described in Canadian 620,001, there is described the application-to polyester fibers of salts of organic acids together with'a volatile base. This patent, like 620,001, does not disclose any salts of inorganic acids such as are used in the instant invention as will be avident from the detailed description which-follows. U.S. 2,805,173 discloses'jthe treatment of 'a-polyseter film base, not 'a fiber, with chlorosulfonic aciddissolved in trichloroethylene or other organic solvent. Chlorosul: fonic acid is an acid chloride which decomposes in water. Hence, it cannot be applied to a fiber material from aqueous solutions. This disclosure is therefore in no way pertinent to the present specific invention.

It is thus apparent from the above discussion that it was in no way recognized or suggested inthe prior art that the valuable fiber properties described in the present application could be obtained by treating polyester fibers with inorganic acids under the mild conditions employed in the instant invention.

' The present invention has as an object to provide polyester fibers having improved surface characteristics which give the fiber material good wettability, excellent adhesive properties with respect to-deposited coatings, dyes and printing iriks and especially good resistance to soiling, particularly by oily soils.

Another object is to provide a convenient and readily applied and controlled process for the treatment of polyester fibers, whether in the form of cut staple, spun yarn, continuous filaments or continuous filament tow, yarns or knitted or woven fabrics and whether used alone or in admixture or associated with another synthetic fiber material or with natural fibers, whereby the polyester material is given a special surface which gives it the properties referred to in the preceding paragraph;

Other objects will appear hereinafter.

These objects are accomplished by the following invention which comprises applying from aqueous solution to polyester fiberseither alone or in association with other synthetic or natural fibers and in the form of fibers as such, or in the form of spun yarn, continuous filaments or continuous filaments tow, or fabrics an inorganic acid having a dissociation constant of at least 10- such as phosphoric acid, phosphorous acid, perchloric acid and sulfuric acid, or a salt ofsuch acids with ammonia or volatile amines in an amount corresponding to from 0.1 percent to 5.0 percent and preferably from 0.3 percent to 1.0 percent based on the weight of the polyester material, heating the so treated polyester material to a temperature within the range of 200 C. for a period of 0.1 to 30 minutes'and thereafter removing the acid by washing with water. Surprisingly, it was found that this relatively mild treatment with inorganic acids produces a profound change in the surface of the polyester fiber material, convetting it from a highly hydrophobic surface which has poor wettability, poor adhesion with respect to deposited coatings, especially those deposited from aqueous media, and poor resistance to soiling, to a material which has, not only excellent wettability and adhesion properties but also excellent resistance to soiling, particularly by oily soils.

Although reference has been made above to the use as a treating agent for the polyester fiber material of a single acid or salt, in accordance with the invention a mixture of such acids or salts may be employed and applied in the range of concentrations stated.

It will be seen from the above that the present process is essentially a three step process, namely, (1) treating the fiber surface with an aqueous solution of an inorganic acid or a salt thereof, (2) heating the treated fiber to a mild temperature for a brief period and (3) thereafter removing the acid or salt solution from the fiber. While it is not known exactly what type of chemical transformation takes place in the superficial surface layers of the polyester fibers and no specific theory is relied upon for an explanation, it is to be assumed that some sort of hydrolytic transformation or rearrangement of the polyester material takes place whereby polar groups (presumably both hydroxyl and carboxyl) are formed thereon, thus changing the polyester surface, which is normally extremely hydrophobic and repellent to aqueous media, to one which is readily wettable by water or aqueous solutions or suspensions of various substances such as gelatin, polyvinyl alcohol, dyes, printing inks and other materials. Such polar groups remain permanently attached to the fiber material during conditions of use. Another surprising and unexpected result of the treatment of the polyester fiber material by inorganic acids or their salts in accordance with the invention is that the material is thereby rendered highly resistant to soiling, particularly by oily soils of various kinds.

One phase of the present process which should be emphasized is the fact that no chemical groups or layers of another material are added to the surface of the polyester material during treatment and the acid (or salt) merely acts to effect some sort of hydrolytic chemical transformation of the superficial surface layers under the influence of mild heat but is subsequently removed as such and does not remain in the finished product. This, among others, is one of the features of the present invention which sets it off from and distinguishes it from the prior art as discussed above. Another distinguishing feature is the fact that inorganic acids are employed to effect the hydrolytic transformation and they are permitted to remain on the fiber material under the influence of mild heating for a sufiicient length of time to produce the desired effect.

As indicated above and in the examples to follow, the polyester fiber material can be treated while in any desired physical form as, for example, cut staple, spun yarn, single filaments, continuous filament tow, as such, either alone or in blends with other man made fibers or filaments such as cellulose acetate, viscose rayon, nylon and the like or with various kinds of natural fibers such as cotton, wool and others, or in the form of knitted, Woven or other types of fabrics. For example, a fabric made from 60 percent polyester fiber and 40 percent cotton can be treated as described above and in accordance with the procedure illustrated in the examples forming a part of this specification. In a similar fashion, the process may be applied to a blend of 50 percent polyester fibers and 50 percent wool or viscose.

Reference has been made to applying to the polyester fiber material an aqueous solution of the inorganic acid or a salt thereof so as to apply to the polyester material from 0.5 to 5.0 percent and preferably 0.3 to 1.0 percent of the acid or salt, based on the weight of the polyester. In some cases the solvent media may be a mixture of water with an organic solvent having afiinity for or a solvating action on the polyester material such as a lower alcohol. The concentration of the acid or salt in such media will be determined by the amount of the salt or acid desired to be deposited within the weight percentage limits just indicated. When the acid is applied from aqueous solutions surfactants may be used to facilitate uniform wetting of the hydrophobic polyester surface. The surfactants may be of the anionic, cationic or nonionic types. Examples of typical surfactants falling in these categories are sodium dodecyl sulfate, octadecyl amine The acid or salt solutions may be applied by either continuous or bath operations using conventional dip, spray, roll or other suitable equipment known to those skilled in the art to which the invention relates.

Reference has also been made to that step of the process of the invention in which, after application of the acid or salt treating solution, the treated polyester fiber material is heated under conditions that evaporate substantially all of the solvent as, for example, Within a temperature of -200" C. and preferably -160 C. for a period of 0.1 to 30 minutes. The time and temperature required will depend upon a number of variables such as the physical form and chemical composition of the polyester, the specific acid used, the amount of acid to be deposited and the like. In a typical case, a fabric is passed through a 0.2 percent solution of phosphoric acid, then into a hot air oven having a temperature of C. The water is evaporated Within a few seconds by a hot air blast and the polyester fiber material in either fiber, continuous filaments, tow, or fabric form is then subjected to the same temperature for one minute or more as may be required.

Fibers treated by the process have improved adhesion for coatings of gelatin, rubber, various vinyl polymers such as polyvinyl butyral and many others. As indicated above, a particularly valuable aspect of the process of the invention is the treatment of polyester fibers in any of the forms mentioned above to improve their resistance to soiling. The discoloration in fabrics may be caused, for example, by the absorption of oily materials in perspiration or by contact with lubricating oils, foods, etc. It also has been demonstrated that polyester fibers have a tendency to pick up oils and greasy materials from drycleaning fiuids and laundry water in which other oil soiled fabrics have been treated. It has been found, quite surprisingly, that the hydrophilic surface produced by the process of the invention enables the treated polyester fiber material to resist Wetting by oils and greasy materials and to retain their original white color under severe conditions of use.

The polyesters which are susceptible to improvement in accordance with the objects of the invention as stated above, are those commonly employed for the manufacture of textile fibers. Thus, the polyesters treated in accordance with this invention can be most advantageously derived from terephthalic acid, 4,4-sulfonyldibenzoic acid, 4,4'-diphenic acid, 1,2-di(p-carboxyphenyl)-ethane, l,2-di(p-carboxyphenoxy)-ethane, 4,4-dicarboxy-diphenyl ether, and the various esters of these acids such as the lower alkyl diesters. These compounds can be generically grouped as hexacarbocyclic nuclear dicarboxylic bifunctional compounds wherein the carboxyl radicals are nuclearly situated in a para relationship. Such compounds can be reacted in accordance with the well-known techniques illustrated in numerous issued patents with bifunctional glycols containing from about 2 to about 10 carbon atoms. Examples of such glycols include ethylene glycol, tetramethylene glycol, 2,2,4,4-tetraalkyl-1,3-cyclobutanediol, pentamethylene glycol, neopentylene glycol, 1,4 cyclohexanedimethanol, quinitol, 1,4 bis(hydroxyethyl)benzene, etc. Illustrative of the more advantageous polyesters are poly(ethylene terephthalate), the polyester from pentamethylene glycol and 4,4-sulfonyldibenzoic acid, the polyester from 1,4-cyclohexanedimethanol and terephthalic acid and various modified polyesters related thereto, e.g., those wherein up to 30 mole percent of another aromatic dicarboxylic acid or an aliphatic dicarboxylic acid is employed as a modifier.

The test for soiling and to determine the improved resistance to soiling of fibers treated in accordance with our invention is as follows:

SOILING PROCEDURE A soiling solution was prepared by the following composition:

The lard and stearic acid were melted together in a beaker and the mineral oil, premixed with the carbon black, was added and stirred into the melt and the carbon tetrachloride then added to form the solution. 2 /2 by 2 /2" swatches of a bleached cotton print cloth (such as standard bleached cotton print supplied commercially for this purpose) were immersed in the soiling solution contained in a screw-cap bottle equipped with means for continuous shaking or agitation. Agitation of the swatches in the soiling solution was continued for two minutes. The samples were then taken from the bottle and dried in air at room temperature.

SOIL TEST PROCEDURE The antisoiling properties of polyester fibers treated in accordance with the present invention was determined by washing a clean swatch of a fabric woven from such fibers together with two swatches of cotton fabric which had been presoiled by treatment with the soiling solution described above. A clean 2 /2 x 2 /2" swatch of the polyester fabric was immersed, together with the two soiled cotton swatches, in 100 cc. of a wash solution made up by dissolving 2 grams of a detergent sold under the trade mark Tide in 1000 cc. of demineralized water contained in a l-pint Launder-Ometer jar provided with suitable heating means. Fifteen stainless steel balls were added, the jar closed by its glass cap and rotated at about 30 r.p.m. for 30 minutes at 160 F. This constitutes one soiling cycle. The swatches were then removed from the jar and the polyester swatch washed with demineralized water and dried in a forced air oven at 250 F. Swatches of untreated polyester fabrics, when washed with soiled cotton swatches in this manner, picked up soil therefrom and came out of the wash solution colored gray to dark gray. However, the same fabrics, but treated in accordance with the instant invention, picked up little, if any, color when washed several separate and consecutive times with fresh pieces of the soiled cotton fabric.

In the following examples and description I have set forth several of the preferred embodiments of my invention but they are included merely for purposes of illustration and not as a limitation thereof.

Example I A solution of 4 g. H PO and 0.5 g. Pluronic L-44 was prepared in 200 cc. of water. Pluronic L-44 is a nonionic polyalkylene oxide wetting agent made by Wyandotte Company.

A fabric made from poly(ethylene terephthalate) fibers was soaked in the solution, pressed to twice its original weight, and heated at 150 C. for 5 minutes. A fabric made from poly(1,4-cyclohexanedimethylene terephthalate) was treated in a similar way. After washing and drying, the fabrics had greatly improved resistance to soiling when subjected to the above described soiling test.

Example H An add-on of 0.3 percent phosphorus acid was applied from aqueous solution to a fabric made from poly(ethyl ene terephthalate). The water was evaporated and the fabric was heated at 120 for 5 minutes. After washing, the fabric had excellent resistance to soiling. Similar results were obtained on fabrics made from poly(1,4-cyclohexanedimethylene terephthalate), poly(ethylene 2,6- naphthalenedicarboxylate) and poly(pentamethylene 4,4- sulfonyldibenzoate Example III An add-on of 0.4 percent phosphoric acid was used, as described in Example II. The treated fabrics had excellent resistance to soiling.

Example IV An add-on of 0.3 percent phosphoric acid and 0.2 percent sulfuric acid was used as described in Example II, with similar results.

Example V An add-on of 0.1 percent sulfuric acid was applied from aqueous solution to a fabric made from poly(ethylene terephthalate). The water was evaporated at -100 7 with a hot air blast and the fabric was then subjected to a temperature of approximately for 1.0-1.5 minutes. Alternatively, a temperature of and reaction time of 20-30 seconds can be used. The fabric was then passed through a water bath to remove the residual acid. The treated fabric had improved adhesion for rubber latex coatings. It had greatly improved resistance toward soiling by oily soils when tested as above described.

For comparison, a fabric was treated with an add-on of 0.1 percent hydrochloric acid and then subjected to the same heating conditions as described above. It did not show any improvement with respect to soil resistance or adhesion of latex coatings.

Example VI A tow of poly(ethylene terephthalate) fibers was passed through a bath to give an add-on of 0.6 percent phosphoric acid, based on the fiber weight. Butyl alcohol or isopropylalcohol-water was used as the solvent for the phosphoric acid. The bath also contained 0.1 percent nonionic wetting agent to give uniform wetting of the fibers. The tow was then passed through a hot air blast at 100-110 to evaporate most of the water. The tow was then run through a crimper at a temperature of -150". The fibers had excellent resistance to soiling 'by oily soils.

Example VII Fibers of poly (ethylene terephthalate) were passed through a bath to give an add-on of 0.4 percent perchloric acid, based on the fiber weight. After the water was evaporated, the fibers were heated at 80-90 for 20 minutes. They had improved resistance to soiling by oily soil.

An amine salt of perchloric acid can be used such as the pyridine, ethylamine or trimethylamine salt. When a salt is used, it may be advantageous to employ a higher reaction temperature such as 120-140.

Example VIII A fabric made from poly(ethylene terephthalate) was padded with a water solution of the monopyridine salt of sulfuric acid, to give an add-on of 0.5 percent. The water was evaporated at 100 and the fabric was then heated at 120130 for one minute. The fabric was washed in water to remove the acid. The treated fabric had improved resistance to soiling.

Example IX A fabric made from poly(etl1ylene terephthalate) was boiled for 5 minutes in a 2 percent solution of sodium hydroxide. Although some loss in weight occurred, the fabric did not show any improvement in soil resistance.

The same type of fabric was padded with 1.0 percent sodium hydroxide from water solution. The water was evaporated and the fabric was heated at 120 for minutes. After washing in water, the fabric did not show any improvement in soil resistance.

It is thus apparent that the treatment of polyester fibers with the strong inorganic acids of the present invention produces a result that is entirely different and unpredictable from the results obtained by treatment with alkalies.

Example X A fabric made from poly(ethylene terephthalate) was boiled for periods of 1 minute to 30 minutes in a 10 percent aqueous solution of phosphoric acid. None of the fabrics showed any improvement with respect to adhesion of coatings or resistance to soiling. It is believed that any hydrolysis products formed under these conditions are dissolved away from the fiber surface during the reaction. Hence, there is no change in the surface properties of the fiber.

In contrast, when the acid treatment is carried out under the special conditions disclosed in the present invention, an entirely difierent type of reaction takes place. Polar groups, probably carboxyl and hydroxyl, are generated by hydrolytic cleavage of polymer chains. These groups remain attached to the polymer surface, thereby imparting new and valuable properties. This is an entirely unpredictable discovery.

It will be seen from the above description of my invention that a means is thereby provided for bringing about a profound change in a normally hydrophobic, difiicultly wettable polyester fiber material which renders the surface of the material hydrophilic and readily wetta- =ble. In addition the invention completely changes the soiling characteristics of the polyester fiber material, from one which is readily soilable, particularly by oily soils in laundering with other fibers or fabrics which have been soiled by such materials, to a material which is highly resistant to soiling of various kinds including such oily soils. It is to be particularly noted that quite unexpectedly the polyester fiber material is given excellent wattability, good adhesive properties with respect to deposited layers such as gelatin, poly(vinyl alcohol), dyes, printing inks and the like and high soiling resistance characteristics by an extremely simple procedure which does not involve the addition of any material to the poly ester itself, as by the deposition of coatings or the addition of any chemical groups thereto. As will be obvious from the above description the acid or salt applied to the polyester fiber material remains on it, in accordance with the invention, only long enough to accomplish the development of the permanently attached polar groups in the polyester surface but is subsequently completely removed and does not remain in the treated fiber. Thus it can be said that an entirely unexpected and highly valuable improvement in the treatment of polyester fibers results from the present invention.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, variations and modifications can be effected within the spirit and scope of the invention as described hereinabove, and as defined in the appended claims.

I claim:

1. A high melting crystalline linear polyester fiber material made by the process which comprises (1) coating said fibers with an essentially aqueous solution containing an inorganic acid having a dissociating constant of at least 10*, of ammonium salts of such acids, or volatile amine salts of such acids, wherein said inorganic acid is phosphoric acid, phosphorous acid, or perchloric acid, (2) heating said coated fibers to form substantially dry acid coated fibers having on the surface from about 0.05 to about 5% by weight of said acid, (3) heating at to 200 C. said substantially dry acid coated fibers to form polar groups on the fiber surfaces without significant alternation of the physical surface structure, and (4) washing said fibers to remove substantially all of said acid.

2. A high melting, crystalline linear polyester fiber material as defined by claim 1 produced by the use of phosphoric acid.

3. A high melting, crystalline linear poleyster fiber material as defined by claim 1 produced by the use of phosphorous acid.

4. A high melting, crystalline linear polyester fiber material as defined by claim 1 produced by the use of perchloric acid.

References Cited UNITED STATES PATENTS 3,107,968 10/1963 Pascal 8-55 FOREIGN PATENTS 683,218 11/ 1952 Great Britain. 749,456 5/1956 Great Britain.

NORMAN G. TORCHIN, Primary Examiner J. CANNON, Assistant Examiner US. Cl. X.R. 855

Claims (1)

1. A HIGH MELTING CRYSTALLINE LINEAR POLYESTER FIBER MATERIAL MADE BY THE PROCESS WHICH COMPRISES (1) COATING SAID FIBERS WITH AN ESSENTIALLY AQUEOUS SOLUTION CONTAINING AN INORGANIC ACID HAVING A DISSOCIATING CONSTANT OF AT LEAST 10**-3, OF AMMONIUM SALTS OF SUCH ACIDS, OR VOLATILE AMINE SALTS OF SUCH ACIDS, WHEREIN SAID INORGANIC ACID IS PHOSPHORIC ACID, PHOSPHOROUS ACID, OR PERCHLORIC ACID, (2) HEATING SAID COATED FIBERS TO FORM SUBSTANTIALLY DRY ACID COATED FIBERS HAVING ON THE SURFACE FROM ABOUT 0.05 TO ABOUT 5% BY WEIGHT OF SAID ACID, (3) HEATING AT 80 TO 200*C. SAID SUBSTANTIALLY DRY ACID COATED FIBERS TO FORM POLAR GROUPS ON THE FIBER SURFACES WITHOUT SIGNIFICANT ALTERNATION OF THE PHYSICAL SURFACE STRUCTURE, AND (4) WASHING SAID FIBERS TO REMOVE SUBSTANTIALLY ALL OF SAID ACID.