US2746837A

US2746837A - Manufacture of leather using a modified vinyl ether-maleic anhydride copolymer, and resulting product

Info

Publication number: US2746837A
Application number: US263985A
Authority: US
Inventors: Joseph S Kirk
Original assignee: General Aniline and Film Corp
Current assignee: GAF Chemicals Corp
Priority date: 1951-12-28
Filing date: 1951-12-28
Publication date: 1956-05-22
Anticipated expiration: 1973-05-22

Description

Unite MANUFACTURE 3F LEATHER USKNG A MBDH FED VTNYL ETHER-MALEHC ANHYDRIDE C33- PULYlt ER, AND REULTENG PRUDUCE Joseph S. Kirk, Newtown, Pa, assignor to Generai 85 Film Corporation, a corporation of Deiaware No Drawing. Application December 255, N51, Serial No. 263,985

12 Claims. (Si. 8-94.33)

the ammonium salt-half amide, the converted copolymers employed in such treatment and the products produced thereby.

There is a demand on the part of tanners of lightweight skins such as calfskins and goatskins for a product or a method which will permit the use of chromium salts as tanning agents but which will avoid the empty unfilled character of chrome tannage and yet not detract from the clear neutral color of chrome leather and its normal afiinity for acidic type dyestuffs. It is recognized by the tanning art that salts of chromium have many virtues which are desired both by the tanners and the users of leather. Chief among these are the high degree of stability of the leather, the simplicity of the tanning operation and high degree of substantivity to all acidic type dyestuffs. Chrome leather has the disadvantage, however, in being empty and unfilled, lacking the roundness and body which is generally desired of leather. This is of particular disadvantage to tanners of lightweight skins.

Vegetable-tanned leather, or the leather produced by subjecting skins to the action of the natural plant tanning extracts, has most of the attributes of fullness and body required of leather. It lacks the extreme resistance to deterioration of chrome tanned leather, and in addition is frequently dark colored and has generally poor afiinity for the direct or cotton type dyestuffs. In addition, vegetable-tanned leather is less resistant to reversal by alkalis and hot water than is chrome tanned leather. For these reasons special precautions must be observed in the manufacture of leather by vegetabletanning processes.

In order to improve the body and fullness of chrome tanned leather many materials have been tried. Among these are the sulfonated aromatic condensates, various organic acids (masking agents) and other agents. The sulfonated aromatic condensates as a rule are sensitive to light, becoming discolored upon exposure to light, and in addition have a strong retarding action on the absorption of acidic dyestuifs, causing weak and washed out shades. The organic acids such as formic, acetic and phthalic acids etc. have a modifying action on the deposition of the chrome in the skin but do not materially contribute to the filling and bodying action. They have no pronounced effect on the dyeing characteristics of the leather.

it is an object of this invention to provide a method for fulling, Plumping, stuffing and improving the dye receptivity and other properties of hides, skins and leather before, during or after tanning. Another object of this invention is the provision of a composition useful in the aforementioned method. A further object is the provision of improved hides, skins and leather. Other objects will appear as the description proceeds.

States Patent These objects are attained by the instant invention which comprises treatment of hides, skins and leather with a vinyl ether-maleic anhydride copolymer in which from about 5 to 15% of the anhydride groups have been converted to the salt-half amide with a member of the group consisting of ammonia and lower aliphatic primary and secondary amines. The use of the aforementioned converted copolymers result in the following unique properties and advantages which are of great value to the leather trade:

When used in conjunction with chrome tannage they impart body and fullness to the leather. They may be applied either prior to chrome tanning, during, or subsequent to it. When applied to hides, skins and leather as above they cause no appreciable alteration in their receptivity to dyestuffs, in contrast to previously employed expedients. Full uniform shades and blacks are easily obtained on susequent dyeing operations. They are insensitive to any concentration of salt or acid used in tanning and they are not precipitated from solution by 10% salt or 2% sulfuric acid. They may accordingly be used on bated stock prior to pickling and the salt and acid added to the skins as in normal pickling operations. They require no special alteration of procedure from customary methods of chrome tanning. They may be applied to pickled skins at pH 2.5-4.0, and after absorption by the skin, chorme tanning solutions may be applied directly to it. They are only mildly astringent and do not cause case hardening of the surface of the leather. Their use has been found to improve the body, feel and fullness of suede leather producing a fine uniform nap to the suede. This latter characteristic is of extreme importance to suede manufacturers.

The converted copolymers of the instant invention may be produced in a manner well known in the art. Suitable methods for producing the initial copolymer by condensation between the maleic anhydride and the vinyl ether are described in U. 3. Patent No. 2,047,398 and others. The production of the full ammonium salt (substantially complete conversion of anhydride groups) of a vinyl ether-maleic anhydride half amide copolymer is disclosed in U. S. Patent No. 2,313,565, but it is emphasized that no claim is made to the methods and compositions described therein since it has been found that copolymers in which more than about 15% of the anhydride groups have been converted to the salt-half amide with a member of the group consisting of ammonia and lower aliphatic primary and secondary amines are undesirable for the treatment of hides, skins and leather in accordance with the instant invention. They are taken up much more slowly by the hides, skins and leather, and produce decreased plumping, fulling and stufiing effects. On the other hand, at least about 5% of the anhydride groups should be converted to the salt-half amide since otherwise the solubility in aqueous media, speed of take-up, and plumping, fulling and stufling eifects are insufiicient. Within the range of about 5 to 15% conversion the copolymers of the invention have been found to possess, as compared for example with the unconverted or initial copolymers, the highly desirable properties of increased solubility in aqueous media, faster take-up by the hides, skins and leather, increased plumping, stufiing, fulling and bodying action, and the like. The preferred range is from 8 to 12% conversion, and within this range a copolymer with about an 11% conversion has been found to give optimum results.

While the preferred copolymer for use in the instant invention is the vinyl methyl ether-maleic anhydride copolymer, other vinyl ether-maleic anhydride copolymers may be used which are sufficiently water soluble and resistant to the action of salts and acids, as for example, those derived from n-butyl, isobutyl, Z-methoxyethyl (from vinylation of methyl Cellos-olve), 2- ethoxyethyl (from vinylation of Cellosolve) and especially vinyl ethyl ethers. Dry ammonia is preferred for conversion of the requisite number of anyhydride groups in the copolyrner to ammonium salt, half amide groups, but other amines may be employed which produce converted copolymers with the desired solubility, non-sensitivity and other properties. Such other amines are for the most part in the lower aliphatic group, such as dimethyl amine, ethanolamine and the like. It will be understood that use of amines other than ammonia for the conversion will result in production of the corresponding amine salts of the corresponding half-substituted amides of the initial vinyl ether-maleic anhydride copolymers.

The converted copolymers of the invention possess the additional advantageous properties of dissolving in aqueous media to produce a pH within the operative range for producing the desired results, which is from about 2.5 to 4.0. Accordingly, unless influenced by other factors, no pH adjustment of the resulting solution with its attendant disadvantages is necessary. Thus, for example, by merely dissolving a copolymer with about an 11% anhydride conversion in water a solution is obtained with a pH of about 3.8, whereby no adjustment of pH by addition of acids or bases need be made before treatment of hides, skins and leather therewith. The preferred pH range is from 3.0 to 3.8.

In general, the converted copolymers of the invention may be incorporated in amounts of about 0.5 to 6% based on the weight of the hides, skins or leather, Impregnation is generally accomplished from aqueous media at any suitable temperature and for a period of time suf ficient to allow impregnation in the desired amount. Since the process proceeds by way of exhaustion, the amount incorporated into the hides, skins and leather will depend essentially on the total amount of converted copolymer in the treating bath and the duration of treatment, and not on the concentration of the treating bath. The concentration of the treating bath may accordingly range from the saturation point down to that suflicient to supply the total amount of copolymer desired to be incorporated. The temperature, duration, concentration, and other conditions of treatment will of course be some what dependent on the character of the skin or leather being treated and the results desired. In general, operating temperatures on raw skins are usually held below about 85 F. On chrome leather, after-treatment temperatures as high as 140 F. may be used. Too large an amount of copolymer, when applied to blue chromed skins, is diflicult to exhaust from solution and gives too much fullness, yielding a bloated, over-plump character to the skin. Likewise, too large an amount when used on drained, pickled skins, although readily exhausted, imparts more than the desired plumpness to the leather with resultant loss of footage. Obviously, the lowest amounts effective for producing the desired results are economically desirable. The aqueous medium containing the converted copolymers of the invention may also contain other common leather and skin treating additives, buffering agents and the like, which do not detract from the desired result.

While the copolymers of the invention may be employed in conjunction with any tanning agents such as alum, natural tanning agents and the like, it is especially advantageous in the production of chromed leather. In such production the converted copolymer may be used either prior to tanning with chrome or may be applied on the shaved blue stock. Excellent filling and plumping have been obtained by either method. The use on blue shaved stock permits selection for weight at the end of the tannage and is definitely advantageous in building up light-weight stock. Use after tanning has the further advantage of not requiring any changes in the complex tanning formulations and procedures already being em ployed by the tanners. However, since at a pH of about 3.0 to 3.3 chrome solutions cause a rapid rise in the viscosity of solutions of the converted copolymers employed in this invention, with resultant decrease in the amount and speed of take-up by the skins and leather, care should be taken in applying such solutions to chromed, tanned to avoid the presence of appreciable quantities of uncombined or unneutralized chrome. This may be accomplished by washing.

The hides, skins and leather which may be treated in accordance with the instant invention may be from any of the common sources. The leather produced is plumped, fulled, bodied, stuifed, and has a soft and mellow feel. Because of the mild, non-astringent character of the treatment it may be used in the production of grain leathers in order to increase the body. In the production of suede kid the leather has a more uniform nap with much better bufiing qualities than obtainable by other plumping agents or chrome alone. The color is not reduced as with other products, thus yielding full bloomy blacks on subsequent. dyeing. In most cases the color is definitely superior to straight chromed leather. Lightweight goatskins are definitely plumped. Calf suedes and splits are likewise improved. Of course in the treatment of any of the hides, skins and leather their pH should be taken into consideration in order that optimum results may be obtained. Slight adjustment of the pH of the treating solution may be necessary to compensate therefor. The leather produced in accordance with this invention may be subjected to any of the various kinds of finishing treatments customarily used.

The following examples are illustrative of the instant invention and are not to be regarded as limitative:

Example 1 1330 grams of vinyl methyl ether-maleic anhydride copolymer (NsP250.76) were suspended in 6500 cc. of benzene. 35 grams of anhydrous ammonia were bubbled through the slurry over a period of 4 hours at 50-55 C. After all the ammonia had been added, the slurry was warmed for 30 minutes, filtered and the filtrate washed with benzene and dried in vacuum to yield 1355 grams of dry powder. Nitrogen analysis indicated that about 11% of the initial anhydride groups in the copolymer had been converted to the ammonium salt of its half amide.

Example 2 375 grams of chrome tanned calf leather were thoroughly washed for 15 minutes, drained, and then immersed in 2000 cc. of water. The product of Example 1 was easily dissolved in warm water in an amount to produce a 10% aqueous solution, of which 112 cc. were added to the leather treating bath. The addition amounted to about 3 of the said product on the weight of the leather. After 15 minutes of working, the bath had a pH of 3.1. The leather was worked in the bath for 40 more minutes, after which 11.2 grams of Tanolin R (commercial chromium sulfate containing 25% CrzOz) were added. The leather was then worked in the bath for one hour longer, at which time the measured pH of the bath was 3.0. 4 grams sodium bicarbonate were added to the bath and the leather worked therein for an hour longer, removed, washed and horsed up. The treated leather had a highly desirable plumpness and fullness of feel, somewhat like a vegetable-tanned product, and was readily dyed to any shade. The converted copolymer was taken up by the leather from the bath in a comparatively rapid and complete manner.

Example 3 1000 grams of Nigerian skins, drained pickle weight, were worked for 15 minutes in a bath containing 20 grams of salt and 7.5 grams of anhydrous sodium acetate in 1000 cc. of water. There was then added a solution of 30 grams of the product of Example 1 (3% on the weight of the skin) in 400 cc. of water. Said solution was previously made by dissolving the said product in hot water and had a pH of 3.8 without any adjustment with alkali being necessary. After running for 1% hours, the pH was measured at 3.5 and 50 grams of iron free aluminum sulfate were added to the bath. After running for another 5 minutes, 7.5 grams of soda ash were added. After working the skins in the bath for 30 minutes longer, there was added a solution of 100 grams of Tanolin R (commercial chromium sulfate containing 25% CrzOs) in 500 cc. of water. The skins were worked in the bath for 1%. hours longer, the pH measured at 3.2, and 15 grams sodium bicarbonate added. After working for 30 minutes longer, the pH was 3.6 and grams of sodium bicarbonate added. The skins were worked in the bath for 30 minutes, at which time the pH was 3.95. The skins were then removed, washed and horscd up. The treated skins were plump and solid, and were readily dyed in light or dark shades. The converted copolymer was taken up by the skins from the bath comparatively rapidly and completely.

Example 4 The process of Example 3 was repeated except that an 11% converted vinyl ethyl ether-maleic anhydride copolymer was employed. Improvements similar to those obtained in Example 3 were obtained.

Example 5 Skins treated in accordance with Example 3, were pearled, crusted and bufled in accordance with the normal practice of the art. They were wet back with 1% ammonia (28%) and /2% wetting agent in 7 times their weight of water at 135 F. The skins thus prepared for dyeing were divided into two parts.

One part of the skins were dyed in known manner in the regular developed black process using:

18% Diazo Black BHN conc. (C. I. 401) 3% sodium nitrite 4% metatoluylene diamine After coloring the skins were fatliquored, crusted, staked, buffed and dry milled in the customary suede procedure. The finished skins were then compared with regular chrome suede leather dyed and treated by identical procedure and were found to have a shorter silkier nap and a fuller bloomier color.

Example 6 The other part of the skins prepared for dyeing in the previous example were, in known manner, colored black by dyeing in a drum at 140 F. with 18% of a dyestuft mixture composed as follows:

40% Chrome Leather Fast Black 86 conc., Pr 371 Sulphon Cyanine 5RA Extra conc., C. I. 284 15% Resorcine Brown G, C. I. 234

20% Benzo Dark Green BA-CF, C. I. 583

10% Ethyl Acid Violet 4B conc., C. I. 53

The dyestuif was applied in two additions using 10% and 8% respectively followed by two additions of formic acid of 3% each. The skins were processed after coloring as in Example 5. The finished skins were found to be of excellent suede having a deeper bloomier color than regular chrome leather dyed in a similar manner.

Example 7 The product of Example 4 was prepared and colored by the procedure of Example 5, producing an improved colored leather as compared with leather which had not been treated with the converted copolymer.

Various modifications and variations of this invention will be obvious to a worker skilled in the art and it is understood that such modifications and variations are to be included within the purview of this application and the spirit and scope of the appended claims.

Unless otherwise indicated, the proportions recited above are based on the weight of the hides, skins and leather being treated.

What is claimed is:

1. A process comprising treating hides, skins and leather with a lower alkyl vinyl ether-maleic anhydride copolymer in which at least about 5 and no more than 15 of the anhydride groups have been converted to the salt-half amide with a member of the group consisting of ammonia and lower aliphatic primary and secondary amines.

2. The process of claim 1, in which the vinyl ether is vinyl methyl ether.

3. The process of claim 2, in which about 11% of the anhydride groups have been converted to the ammonium salt-half amide.

4. The process of claim 1, in which the vinyl ether is vinyl ethyl ether.

5. The process of claim 4, in which about 11% of the anhydride groups have been converted to the ammonium salt-half amide.

6. A process comprising treating hides, skins and leather in an aqueous medium with a lower alkyl vinyl ether-maleic anhydride copolymer in which at least about 5 and no more than 15 of the anhydride groups have been converted to the salt-half amide with a member of the group consisting of ammonia and lower aliphatic primary and secondary amines.

7. A process comprising treating hides, skins and leather in an aqueous medium at a pH of about 2.5 to 4.0 with a lower alkyl vinyl ether-maleic anhydride copolymer in which at least about 5 and no more than 15 of the anhydride groups have been converted to the salt-half amide with a member of the group consisting of ammonia and lower aliphatic primary and secondary amines.

8. Hides, skins and leather treated by the process of claim 1.

9. A process comprising treating hides, skins and leather with a lower alkyl vinyl ether-maleic anhydride copolymer in which at least about 5 and no more than 15 of the anhydride groups have been converted to the salt-half amide with a member of the group consisting of ammonia and lower aliphatic primary and secondary amines and then dyeing the treated hides, skins and leather.

10. The process of claim 1, in which the vinyl ether is vinyl methyl ether.

11. The process of claim 9 in which the vinyl ether is vinyl ethyl ether.

12. The products of the process of claim 9.

References Cited in the file of this patent UNITED STATES PATENTS 1,976,679 Fikentscher Oct. 9, 1934 2,047,398 Voss et al. July 14, 1936 2,156,069 Schlack Apr. 25, 1939 2,160,375 Voss et al. May 30, 1939 2,205,882 Graves June 25, 1940 2,205,883 Graves June 25, 1940 2,220,867 Kirk Nov. 5, 1940 2,313,565 McDowell et al Mar. 9, 1943 2,456,177 Cuprey Dec. 14, 1948 2,469,428 Beachell May 10, 1949 2,469,437 Kirk May 10, 1949 2,543,602 Rowland Feb. 27, 1951 2,577,041 Seymour Dec. 4, 1951 2,609,350 Spatt Sept. 2, 1952

Claims

1. A PROCESS COMPRISING TREATING HIDES, SKINS AND LEATHER WITH A LOWER ALKYL VINYL ETHER-MALEIC ANHYDRIDE COPOLYMER IN WHICH AT LEAST ABOUT 5 AND NO MORE THAN 15% OF THE ANHYDRIDE GROUPS HAVE BEEN CONVERTED TO THE SALT-HALF AMIDE WITH A MEMBER OF THE GROUP CONSISTING OF AMMONIA AND LOWER ALIPHATIC PRIMARY AND SECONDARY AMINES.