US2998294A

US2998294A - Process for improving chrome tanned leather

Info

Publication number: US2998294A
Application number: US832181A
Authority: US
Inventors: Locke Charles Thomas
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1959-08-07
Filing date: 1959-08-07
Publication date: 1961-08-29
Anticipated expiration: 1978-08-29

Description

United States Patent 2,998,294. PROCESS FOR IMPROVING CHROMETANNED. LEATHER Charles Thomas Locke, Plymouth, Wis., assignor to E. I.

du Pont de Nemours and Company, Wilmington, Del.,

a corporation of Delaware NoDrawing. Filed Aug. 7, 1959, Ser. No. 832,181

12 Claims. (Cl. 8-9.4;21)

The invention relates to a novel process for improving chrome tanned leather. andvparticularly to a process for filling and lumping fully chrome tannedleather.

It is an objectof this invention to=provide a new and improved process for improving the quality of fully chrome tanned leather. Another object is, to provide a process for filling and plumping chrome tanned leather, particularly to provide a leather which is full, dense, smooth, tight-grained and has improved. body. Other objects are to advance the art. Still other objects will appear hereinafter.

The above and other objects may be accomplished inv accord with this invention which involves the process which comprises impregnating fully chrome tanned leather at a temperature of from about 80 F. to about 120 F. with anaqueous solution ofa water-soluble inorganic acidic salt of a metalof the group consisting of aluminum, zirconium and zinc in an amountto provide from about 0.5% to about 2.5% by weight of said salt based on the leather, then impregnating the leather at a temperatureof from about 75 F. to about 135 F. with an aqueous solution of di(methoxymethyl)dimethylolurea in an amount to provide from about 1.5% to about 30% by weight of said urea based on the leather, and then impregnating the leather at a temperature of from about 80 F. to about 135 F. with an aqueous solution of a water-soluble inorganic acidic salt of a metal of the, group consisting of aluminum, zirconium and zinc in an amount to provide from about 0.5 to about 10% by weight of the acidic salt based on the leather.

Such process is essentially a filling and plumping process and is not atanning or retanning process. By means of the process of this invention, the finished leather. is rendered noticeably full and dense. leather is rendered very smooth and tight whereby it providesan excellent surface for snufiing or butfingtoobtain a nap or--a buck finish. The solidity of the, leather, is. so: greatly improved that cowhide; can be made to approach, the leather qualities of high grade calfskin.

p The process of this; invention may be applied advantageously to. any type of chrome; tanned leather including split and shaved side leather, grain and suede and the like. The leather may be obtained from goatskin, cowhide, sheepskin, etc., and the product may be used for shoe, case, glove, and garment leathers. The leather to be treated by this process should be properly fully chrome tannedl. If the original chrome tan did not penetrate sufficiently, leaving untanned spots on the flesh side after splitting, the leather should be retanned in the usual manner with basic chromic sulfate.

The salts which may be employed in accord with this invention are the: water-soluble, inorganic acidic salts of used because they discolor the leather, but can be used if;

the leather is. to be dyed dark shades. Preferred salts are those of aluminum and zirconium, particularly aluminum sulfate and zirconium sulfate.

The grain ofthe "ice Di(methoxymethyl)dimethylolurea is. a known composition which hasbeen employedfor imparting creaseresis'tant properties totextiles. .Its properties and preparation are described by Etzel: in Patent 2,825,710.

Theprocessof this invention comprises the three steps of. treating the chrome tannedleather with the acidic salt,

subsequently treating -i-t, with. the di(methoxymethyl)dithe salt based on the leather, preferably from about 0.5% to about 2.0%. The aqueous solution should containthe salt in a concentration of from about 0.5 to about 20% by weight, preferably from about 0.75% to about 10%. The quantity of the acidic salt based on the leather employed in this step is dependent upon the degree of penetration of the di(methoxymethyl)dimethylolurea desired and the amount of filling desired in the leather. The lower amount of the acidic, salt will be used where it is desired that the final leather will have the maximum amount of filling and thickness. The higher amount of acidic salt will be employed when it is desired to impart a minimum advantageous amount of filling in the final leather. This first step of the process of thisinvention and theamount of acidic salt employed therein are essential to control the degree of penetration and of retention of the di(methoxymethyl)dimethylolurea in the leather. The di(methoxymethyl)dimethylolurea is insolubilized by the acidic salts. If the leather is not first impregnated with the acidic salt or if materially less than 0.5% thereof is employed, the di(methoxymethyl)dimethylolurea will completely penetrate the leather but, when the final treatment with the acidic salt is carried out, only surface fixa tion of the di(methoxymethyl)dimethylolurea occurs and that remaining in the interior ofthe leather is washed out during subsequent drumming procedures, whereby the desired filling and plumping effects will not be accomplished throughout the leather. On the. other hand, if materially more than about 2.5% of the acidic salt is employed in this first step, the di(methoxymethyl)dimethylolurea will become fixed at the surface of the leather before it is able to penetrate into the interior of the leather, whereby the desired filling and plumping effect throughout the leather will not be obtained.

The chrome tanned leather, containing the acidic salt from the first step, is impregnated withfrom about 1.5% to about 30% by weight of the di(methoxymethyl)dimethylolurea by drumming the leather with an aqueous solution thereof. The amount of the di(methoxymethyl) dirnethylolurea employed will be directly proportional to the amount of plumping and filling obtained. Materially less than about 1.5% based on the leather gives inadequate filling and plumping, and materially more than 30% is unnecessary for obtaining maximum filling and plumping. The preferred amount of di(methoxymethyl)dimethylolurea is from about 5% to about 6% by weight based on the weight of the leather taken. The aqueous solution employed in this step usually will contain the di(methoxyrnethyl)dimethylolurea in a concentration of from about 10% to about by weight, preferably from about 20% to about 70%. The leather is impregnated with such solution by the usual drumming procedure which may be carried out at a temperature at from about 75 F. to about 135 F., preferably from about F. to about F. The usual drumming time will vary from about one hour at the lower temperatures to about 10 to 40 minutes at the higher temperatures. The most preferred time and temperature will be about 30 minutes at about 130 F.

The leather, impregnated with the di(methoXymethyD- dimethylolurea, must be again impregnated with an aqueous solution of an acidic salt of the character employed in the first step, which acidic salt may be the same or different from that employed in the first step. In this third step, the acidic salt employed will be from about 0.5% to about 10% by weight based on the weight of the leather taken, preferably from about 1.5% to about 2.0%. The aqueous solution employed will contain the acidic salt in a concentration of from about 0.5% to about 20% by weight, preferably from about 10% to about 15%. Again, the impregnation is carried out by drumming, usually at a temperature of from about 80 F. to about 135 F., preferably from about 100 F. to about 110 F. The time of drumming may vary from about 10 minutes to about 30 minutes. This third step is required for complete insolubilization of the di(methoxymethyl)dimethylolurea and optimum plumping and filling of the leather. When a large amount of the acidic salt is used in the first step and a small amount of di(methoxymethyDdimethylolurea is employed in the second step, only a small amount of acidic salt is necessary in the third step. However, excessive amounts of the acidic salt in the third step is not objectionable and, to the extent that it penetrates the leather, it provides additional filling effects.

After the final impregnation with the acidic salt, the leather that results is finished off by rinsing and it may be treated with softening agents and/ or fat liquor in the normal manner. If white leather is desired, it may be treated with a white pigment, such as titanium dioxide,

and this may be done during the fat liquor procedure. If desired, acid or direct dyes may be used either prior to the process of this invention or at any step of the process. When dyes are used, it is desirable to treat the chrome tanned leather with a neutral syntan after the first step of this process, as this prevents undesired precipitation of dye by the acidic salt and ensures that a level dyeing is obtained. The neutral syntans are well known surface active agents employed for leveling dyes in leathers and are represented by neutral naphthalene syntan which is a sulfonated naphthalene condensate synthetic retanning agent.

It is particularly advantageous to treat the leather, obtained by the process of this invention, with a mixture of a softener and a sulfonyl chloride tanning agent. This treatment imparts a very desirable softening effect to the leather fibers. The preferred softeners are paraffin wax and petrolatum, and these agents are preferably employed as a dispersion in an aqueous solution of the alkali-metal sulfonates of parafiin wax and petrolatum. These and other softener compositions, such as fatty acid amides and alkyl biguanidines, are well known in the art. The sulfonyl chloride tanning agents are well known (I. Am. Leather Chemists Assoc. 44, pages 222, (1949)), and consist essentially of incompletely chlorosulfonated hydrocarbon oils such as No. 40 white oil. These agents are commonly used as aqueous dispersions in the leather art to produce chamois type leathers. In softening the full, tight-grained leather obtained by the novel process of this invention, the softener and sulfonyl chloride tanning agents are mixed and used to drum the leather at from about 80 F. to about 130 F. for from about 30 minutes to about 60 minutes. If desired, subsequent treatments with fat liquoring agents, such as neatsfoot oil, may be given to the leather to add a desired greasy feel.

In order to more clearly illustrate this invention, preferred modes of carrying it into elfect and advantageous results obtained thereby, the following examples are 4 given in which the proportions are by weight except where specifically indicated otherwise.

Example 1 Chrome tanned cowhide leather from the splitting and shaving machine is placed in a drum and retanned with basic chromium sulfate in the usual manner to cover untanned spots on the fleshside after splitting.

The sides are rinsed and then treated with 2.0 percent aluminum sulfate and 75 percent water, based on the weight of the leather. The sides are drummed 20 minutes at F. Then, 20 percent of the leather weight of a 10 percent solution of neutral naphthalene syntan water is added and the sides are drummed for 20 minutes at 110 F. 27.5 percent of the leather weight of a 20 percent solution of di(methoxylmethyl)dimethylolurea in water is added and the sides are drummed 30 minutes at 110 F. Then, 20 percent of a 10 percent solution of aluminum sulfate in water is added and the sides are drummed for 20 minutes at 110 F. The sides are rinsed and fat liquored in the usual manner. A white pigment, titanium dioxide, is added with the fat liquor to produce a White leather. A cowhide shoe upper leather is produced which has an unusually smooth and tight grain. The leather is full and dense.

When the process is applied to chrome tanned goatskin and to chrome tanned sheepskin for shoe and garment leathers, a full, dense leather is obtained.

When zinc sulfate is used in the above example, essentially the same results are obtained.

Example 2 Chrome tanned cowhide leather is placed in a drum and rinsed at F. Based on the weight of the leather, 1.5 percent of a dye, Resorcin Brown C. I. 234, 1.0 percent neutral naphthalene syntan, 1.0 percent aqueous ammonia (37.0%), and 75 percent water are added at 120 F. and the sides are drummed for 30 minutes. Then, 5.0 percent of a 10-percent solution of aluminum sulfate in water is added at 110 F. and the sides are drummed 20 minutes. 27.5 percent of a 20-percent solution of di(methoxymethyl)dimethylolurea in water is added at 110 F. and the sides are drummed 30 minutes. Then 20 percent of a 10-percent solution of aluminum sulfate in water is added at 110 F. and the sides are drummed for 20 minutes. The sides are rinsed and fatliquored in the usual manner.

The leather is dried and staked in the usual manner and the grain is bufi'ed to obtain a. nap for a buck finish. The resultant leather has an unusually full and dense body with a fine nap.

In lieu of aluminum sulfate in the above example, aluminum chloride is used with essentially the same results.

Example 3 Rinse chrome tanned side leather in a drum, drain and add on the weight of the leather 2 percent sodium chloride, 1.5 percent zirconium sulfate and 200 percent water. Drum 20 minutes at 100 F. Add 8.6 percent on the Weight of the leather of a 68% by weight aqueous solution of di(methoxymethyl) dimethylolurea and 20 percent water. Drum 30 minutes at 100 F. Add 1.5 percent zirconium sulfate and 10 percent water and drum 20 minutes at 100 F. Rinse for 20 nlinutes at F. and drain. Then, add 3 percent of a sulfonyl chloride tanm'ng agent (incompletely chlorosulfonated No. 40 white oil dispersed with aLlpha-pinene and a polyethylene oxide adduct of a fatty alcohol) and 3 percent of a softener (a dispersion of parafiin wax and petrolatum in an aqueous solution of the sodium sulfonates of paraffin and petrolatum) and percent water and drum for 30 minutes at 130 F. Drain and add 1 percent neatsfoot oil and 1 percent of sulfated neatsfoot oil at 130 F. with 150 percent water and drum 30 minutes.

After drying, this leather is very light in color and i8 a good quality white leather. It is dense and has avery fine break.

It will be understood that the preceding examples have been given for illustrative purposes solely and that this invention is not limited to the specific embodiments described therein. On the other hand, it will be apparent to those skilled in the art, subject to the limitations set forth in the general description, that many variations and modifications can be made in the materials, proportions, conditions and techniques employed without departing from the spirit or scope of this invention.

From the preceding description, it will be apparent that this invention provides a novel process for greatly improving the quality of chrome tanned leather. Particularly, it provides a finished leather which is noticeably more full and dense and has a grain which is very smooth and tight, whereby the treated leather is useful for a wide variety of purposes for which the original chrome tanned leather is not adapted. Accordingly, it is believed that this-invention constitutes a very valuable advance in and contribution to the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The process for improving chrome tanned leather which comprises impregnating fully chrome tanned leather at a temperature of from about 80 F. to about 120 F. with an aqueous solution of a water-soluble inorganic acidic salt of a metal of the group consisting ofaluminum, zirconium andzinc in an amount to provide from about 0.5% to about 2.5% by weight of said salt based on the leather, then impregnating the leather at a temperature of from about 75 F. to about 135 F. with an aqueous solution of di(methoxymethyl) dimethylolurea in an amount to provide from about 1.5% to about 30% by weight of said urea based on the leather, and then impregnating the leather at a temperature of from about 80 F. to about 135 F. with an aqueous solution of a water-soluble inorganic acidic salt of a metal of the group consisting of aluminum, zirconium and-zinc in an amount to provide from about 0.5% to about 10% by.

weight of the acidic salt based on the leather.

2. The process for improving chrome tanned leather which comprises impregnating fully chrome tanned leather at a temperature of from about 80 F. to about 120 F. with an aqueous solution of a water-soluble inorganic acidic salt of a metal of the group consisting of aluminum, zirconium and zinc in an amount to provide from. about 0.5 to about 2.5% by weight of said salt based on the leather, then impregnating the leather at a temperature of from about 75 F. to about 135 F. with an aqueous solution of di(methoxymethyl) dimethylolurea in an amount to provide from about to about 6% by weight of said urea based on the leather, and then impregnating the leather at a temperature of from about 80 F. to about 135 F. with an aqueous solution of a water-soluble inorganic acidic salt of a metal of the group consisting of aluminum, zirconium and zinc in an amount to provide from about 0.5 to about 10% by weight of the acidic salt based on the leather.

3. The process for improving chrome tanned leather which comprises impregnating fully chrome tanned leather at a temperature of from about 100 F. to about 110 F. with an aqueous solution of a water-soluble inorganic acidic salt of a metal of the group consisting of aluminum, zirconium and zinc in an amount to provide from about 0.5 to about 2.5% by weight of said salt based on the leather, then impregnating the leather at a temperature of from about 100 F. to about 130 F. with an aqueous solution of di(methoxymethyl)dimethylolurea in an amount to provide from about 5% to about 6% by weight of said urea based on the leather, and then impregnating the leather at a temperature of from about 100 F. to about 110 F. with an aqueous solution of a water-soluble inorganic acidic salt of a metal of the group consist- 6 ing of aluminum, zirconium and zinc in an amount to provide from about 1.5% to about 2.0% byweight of the acidic salt based on the leather;

4. Theprocess forimproving chrome tanned leather which comprises impregnating fully chrome tanned leather at a temperature of from about F. to about 120 F. with an aqueous solution of awater-soluble inorganic acidic salt of aluminum in an amount to provide from about 0.5% to about 2.5% by weight of said salt based on the leather, then impregnating the leather at a temperature of from about 75 -F. to about 135 F. with an aqueous solution of di(rnethoxymethyl) dimethylolurea in an amount to provide from about 1.5% to about 30% by weight of said urea based on the leather, and then impregnatingthe leather at a temperature of from about 80 F. to about 135 F. with an aqueous solution of a water-soluble inorganic acidic salt of aluminum in anamount to provide from about 0.5 to about 10% by weight of the acidic salt based on the leather.

5. The process for improving chrome tanned leather which comprises impregnating fully chrome tanned leather at a temperature of from about 80 F. to about 120 F. with an aqueous solution of a water-soluble inorganic acidic salt of aluminum in an amount to provide from about 0.5% to about 2.5 by weight of said salt based on the leather, then impregnating the leather at a temperature of from about 75 F. to'about 135 F. with an aqueous solution of di(methoxymethyl)dimethylolurea in an amount to provide fromabout 5% to about 6% by weight of said urea based on the leather, and then impregnating the leather at a temperature of from about 80 F. to aboutL135 F. with an aqueous solution of a Water-soluble inorganic acidic salt of aluminum in an' amount to provide from about, 0.5 to about 10% by weight of the acidic salt based on the leather.

6. The process for improving chrome tanned leather which comprises impregnating fully chrome tanned leather at a temperature of from about 80 F. to about 120 F. with an aqueous solution of aluminum sulfate in an amount to provide from about 0.5 to about 2.5 byweight of said aluminum sulfate based on the leather, then impregnating the leather at a temperature of from about 75 F. to about 135 with an aqueous solution of d-i(methoxymethyl)dimethylolurea in an amount to provide from about 1.5 to about 30% by weight of said urea based on the leather, and then impregnating the leather at a temperature of from about 80 F. to about 135 F. with an aqueous solution of aluminum sulfate in an amount to provide from about 0.5% to about 10% by weight of the aluminum sulfate based on the leather.

7. The process for improving chrome tanned leather which comprises impregnating fully chrome tanned leathor at a temperature of from about F. to about F. with an aqueous solution of aluminum sulfate in an amount to provide from about 0.5 to about 2.5 by Weight of said aluminum sulfate based on the leather, then impregnating the leather at -a temperature of from about 100 F. to about F. with an aqueous solution of di(methoxymethyl)dimethylolurea in an amount to provide from about 5% to about 6% by weight of said urea based on the leather, and then impregnating the leather at a temperature of from about 100 F. to about 110 -F. with an aqueous solution of aluminum sulfate in an amount to provide from about 1.5% to about 2.0% by weight of the aluminum sulfate based on the leather.

8. The process for improving chrome tanned leather which comprises impregnating fully chrome tanned leather at a temperature of from about 100 F. to about 110 F. with an aqueous solution of aluminum chloride in an amount to provide from about 0.5% to about 2.5 by weight of said aluminum chloride based on the leather, then impregnating the leather at a temperature of from about 100 F. to about 130 F. with an aqueous solution of di(methoxymethyl)dimethylolurea in an amount to provide from about to about 6% by weight of said urea based on the leather, and then impregnating the leather at a temperature of from about 100 F. to about 110 F. with an aqueous solution of aluminum chloride in an amount to provide from about 1.5% to about 2.0% by weight of the aluminum chloride based on the leather. 7 9. The process for improving chrome tanned leather which com-prises impregnating fully chrome tanned leather at a temperature of from about 80 F. to about 120 F. with an aqueous solution of a water-soluble inorganic acidic salt of zirconium in an amount to provide from about 0.5% to about 2.5% by weight of said salt based on the leather, then impregnating the leather at a temperature of from about 75 F. to about 135 F. with an aqueous solution of di(methoxyrnethyl)dimethylolurea in an amount to provide from about 1.5% to about 30% by weight of said urea based on the leather, and then impregnating the leather at a temperature of from about 80 F. to about 135 F. with an aqueous solution of a Water-soluble inorganic acidic salt of zirconium in an amount to provide from about 0.5% to about 10% by weight of the acidic salt based on the leather.

10. The process for improving chrome tanned leather Which comprises impregnating fully chrome tanned leather at a temperature of from about 100 F. to about 110 F. with an aqueous solution of a water-soluble inorganic acidic salt of zirconium in an amount to provide from about 0.5 to about 2.5% by weight of said salt based on the leather, then impregnating the leather at a temperature of from about 100 F. to about 130 F. with an aqueous solution of di(methoxymethyl)dimethylolurea in an amount to provide from about 5% to about 6% by Weight of said urea based on the leather, and then impregnating the leather at a temperature of from about 100 F. to about 110 F. with an aqueous solution of a water-soluble inorganic acidic salt of zirconium in an amount to provide from about 1.5 to about 2.0% by weight of the acidic salt based on the leather.

11. The process for improving chrome tanned leather which comprises impregnating fully chrome tanned leather at a temperature of from about 80 F; to about 120 F. with an aqueous solution of zirconiumsulfate in an amount to provide from about 0.5% to about 2.5% by weight of said zirconium sulfate based on the leather, then impregnating the leather at a temperature of from about F. to about 135 F. with an aqueous solution of di(methoxymethyl) dimethylolurea in an amount to provide from about 1.5% to about 30% by weight of said urea based on the leather, and then impregnating the leather at a temperature of from about F. to about 135 F. with an aqueous solution of zirconium sulfate in an amount to provide from about 0.5 to about 10% by weight of the zirconium sulfate based on the leather.

12. The process for improving chrome tanned leather which comprises impregnating fully chrome tanned leather at a temperature of from about F. to about F. with an aqueous solution of zirconium sulfate in an amnount to provide from about 0.5% to about 2.5% by weight of said zirconium sulfate based on the leather, then impregnating the leather at a temperature of from about 100 F. to about F. with an aqueous solution of di( methoxyrnethyl)dimethylolurea in an amount to provide from about 5% to about 6% by Weight of said urea based on the leather, and then impregnating the leather at a temperature of from about 100 F. to about 110 F. with an aqueous solution of zirconium sulfate in an amount to provide from about 1.5% to about 2.0% by weight of the zirconium sulfate based on the leather.

OFlaherty et al.: Chemistry and Technology of Leather, vol. 2, Reinhold Pub. Corp., N.Y., 1958, p. 476.

Claims

1. THE PROCESS FOR IMPROVING CHROME TANNED LEATHER WHICH COMPRISES IMPREGNATING FULLY CHROME TANNED LEATHER AT A TEMPERATURE OF FROM ABOUT 80*F. TO ABOUT 120*F. WITH AN AQUEOUS SOLUTION OF A WATER-SOLUBLE INORGANIC ACIDIC SALT OF A METAL OF THE GROUP CONSISTING OF ALUMINUM, ZIRCONIUM AND ZINC IN AN AMOUNT TO PROVIDE FROM ABOUT 0.5% TO ABOUT 2.5% BY WEIGHT OF SAID SALT BASED ON THE LEATHER, THEN IMPREGNATING THE LEATHER AT A TEMPERATURE OF FROM ABOUT 75*F. TO ABOUT 135*F. WITH AN AQUEOUS SOLUTION OF DI(METHOXYMETHYL) DIMETHYLOLUREA IN AN AMOUNT TO PROVIDE FROM ABOUT 1.5% TO ABOUT 30% BY WEIGHT OF SAID UREA BASED ON THE LEATHER, AND THEN IMPREGNATING THE LEATHER AT A TEMPERATURE OF FROM ABOUT 80*F. TO ABOUT 135*F. WITH AN AQUEOUS SOLUTION OF A WATER-SOLUBLE INORGANIC ACIDIC SALT OF A METAL OF THE GROUP CONSISTING OF ALUMINUM, ZIRCONIUM AND ZINC IN AN AMOUNT TO PROVIDE FROM ABOUT 0.5% TO ABOUT 10% BY WEIGHT OF THE ACIDIC SALT BASED ON THE LEATHER.