US2522666A - Reacting a chrome-tanned hide first with a sulfonic acid syntan and then with methylol-melamine - Google Patents

Reacting a chrome-tanned hide first with a sulfonic acid syntan and then with methylol-melamine Download PDF

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US2522666A
US2522666A US710949A US71094946A US2522666A US 2522666 A US2522666 A US 2522666A US 710949 A US710949 A US 710949A US 71094946 A US71094946 A US 71094946A US 2522666 A US2522666 A US 2522666A
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chrome
leather
melamine
methylol
tanned
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US710949A
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William O Dawson
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Wyeth Holdings LLC
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American Cyanamid Co
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    • C—CHEMISTRY; METALLURGY
    • C14—SKINS; HIDES; PELTS; LEATHER
    • C14C—CHEMICAL TREATMENT OF HIDES, SKINS OR LEATHER, e.g. TANNING, IMPREGNATING, FINISHING; APPARATUS THEREFOR; COMPOSITIONS FOR TANNING
    • C14C3/00—Tanning; Compositions for tanning
    • C14C3/02—Chemical tanning
    • C14C3/28—Multi-step processes

Definitions

  • This invention relates to the production of I white leather by retanning chrome tanned leather with a Water-soluble methylol melamine.
  • the principal object of the invention is to obtain leather having greatly improved whiteness and light-resistance imparted by the methylol melamine while maintaining the strength and other desirable properties of chrome tanned leather.
  • a further object is the provision of a process that is capable of making a high-grade white leather from skinny, spready hides that are unsuitable for making chrome white leather by other processes. Still further objects will appear from the fol owing descriptions of preferred embodiments of the invention.
  • My present invention like my earlier patent above referred to, is directed to a combined tannage of hides or skins with a basic chromium sulfate taming agent and with methylol melamine, but constitutes an improvement thereover.
  • a white leather comparable in feel and texture to the white leather produced by tanning skins with melamine-formaldehyde resins alone, as described in my Patent No. 2,316,741
  • This leather in addition to its excellent white appearance and texture, has all of the strength and other desirable characteristics of chrome tanned leather, and therefore constitutes a chrome leather of greatly improved surface appearance.
  • the melamine resin-treated chrome leather of my present invention has a substantially increased plumpness and weight as compared with chrome leather prepared from the same stock but containing no methylol melamine, and is therefore greatly enhanced in value.
  • Mv present invention in its broadest aspects, consists in the application to chrome tanned leather ofan aromatic sulfonate tanning agent and awater-soluble melamine-formaldehyde condensation product. or methylol melamine, in suitable amounts.
  • chrome tanned leather In the manufacture of chrome tanned leather by either the one-bath or the two-bath process the substance of the hide or skin is caused to combine with a basic chromium sulfate which converts it into leather.
  • the chrome leather from this treatment is described in the tannery Application November 19, 1946, Serial No. 710,949
  • . 2 a as "blue'stock, since it is light blue in color.
  • an aromatic sulfo nate tanning agent such as disulfodinaphthyl methane, obtained by condensing about two mols of naphthalene-sulfonic acid with one mol of formaldehyde; or with the corresponding formaldehyde condensation products of sulfonated phenols or sulfonated cresols.
  • bleaching agents are believed to form 'a colorless complex with the chrome present-in the leather and thus lighten its color; however, the bleached leather still retains a bluish cast and is somewhat gray in col'or'rather than White.
  • r -I have found that wateresoluble melamineformaldehyde condensation products, or meth: ylol melamines, will combine with the bleached, chrome tanned leather to form leather which is both permanent and truly white in color. More-. over, the leather which -I obtain by impregnating the bleached chrome leatherwith methylol melamine is light-resistant; i.
  • the discolora-z tion upon continued exposure of the leather to ultra-violet light is much less than with ordi-e' nary chrome leather bleached with aromatic sulfonate tanning agents.
  • Impregnation of the bleached chrome leather with methylol mela; mine also causes an additional plumpingand increase inweight, but without any of the difficulties' "caused by drawn grain that are fre--- quently encountered in plumping,and the white leather so obtained canbe lubricated and softened by ordinary fat-liquoring treatments with vegetable or animal oils which may be unsulfonated but are preferably sulfonated in character. .1'
  • the chrome tanned sides were-placed in a tanning drum and washed 30 minutes in water at temperatures up to l25-135 F.
  • the water was changed and 3% of a disulfodinaphthylmethane tanning agent having a pH .of 6-8 was added to the drum, based on the shaved weight of the sides, and the drum was rotated 45 minutes, drained and washed 15 minutes at 130 F., and again drained.
  • Approximately 75-100% of water at 130 F. was then introduced into the drum and 3.5% of trimethylol melamine was added, based on the weight of the sides.
  • the drum was then rotated for 30 minutes, allowed to stand for one hour, rotated an additional 30 minutes, and then stopped overnight.
  • the leather prepared by this process was found to have gained /2 to 1 ounce in weight, as compared with white chrome tanned leather from the same stock to which no methylol melamine was added.
  • the leather was very white, had a deep white cut showing good impregnation of the methylol melamine, was full and tight, and had an unusually uniform break.
  • the water-soluble methylol melamines used in practicing my invention should remain water soluble in the presence of salt, and should therefore be substantially unpolymerized. They may be prepared as described in my issued patents referred to above, or by any other suitable process.
  • the trimethylol melamine used in the above example was a spray-dried methylol melamine which was substantially unpolymerized and not salt-sensitive. This product was prepared as follows:
  • a quantity of formaldehyde in the form of a 37% aqueous solution was weighed, charged to a mixing vessel maintained at a temperature below 60 'F., and adjusted with sodium hydroxide to a pH of 8.0.
  • Micropulverized melamine was added to the formaldehyde solution, with agitation, in an amount sufficient to bring the molecular ratio of formaldehyde to melamine to 3.611, care being taken to maintain the temperature sufficiently low to prevent reaction.
  • This unreacted slurry was immediately pumped under pressure through a heat exchanger at a temperature of 220 F., at such a rate that it took approximately 2 minutes for a given quantity of the slurry to pass therethrough.
  • the material was then pumped through a cooling heat exchanger, which rapidly cooled the syrupy product to approximately 120 F. From the cooling heat exchanger the product was introduced into a spray drier and spraydried at a gas temperature of 450 F. The process was continuous from one step into the other, as all the individual units were interconnected for continuous flow.
  • the product had the following analysis:
  • the amount of synthetic tanning agent may vary from about 1% to about 5%, based on the weight of the leather. Usually hides of better grade than those described in the above example will require smaller quantities than the 3.5% that was actually used, about 12.5% being sufficient in most cases.
  • a neutralized synthetic tanning agent is preferred, the aromatic sulfonate may be alkaline or acid.
  • the water-soluble methylol melamine may be used in amounts of about 1% to about 5%, based on the weight of the chrome tanned leather, the exact amount depending on the degree of whiteness and fullness desired.
  • the methylol melamine is usually applied after the aromatic sulfonate tanning agent, it may be applied simultaneously therewith if desired; in fact the aromatic sulflonate may be applied after the methylol melamine in some cases.
  • a method of obtaining a light-resistant white chrome tanned leather which comprises re acting fully tanned chrome tanned blue stock with about 1-5% of its weight of an aromatic sul- Ionate tanning agent and subsequently reacting the aromatic sulfonate treated stock with about 2-5% of its weight of a water-soluble methylol melamine.
  • a method of obtaining a light-resistant white chrome tanned leather which comprises reacting fully tanned chrome tanned blue stock with about 1-5% of its weight of a disulfodinaphthylmethane tanning agent and subsee quentl reacting the di-sulfodinaphthylmethane treated stock with about 2-5'% of its weight of water-soluble methylol melamine.
  • a method of producing chrome-tanned leather lof improved whitenes and light-resistance from skins so inferior in quality as to be normally unsuitable for making chrometanned leather which comprises first subjecting said skins to a full chrome tannage, then reacting the resulting chrome-tanned leather of in.- ferior grade with about 1-5% of its weight of .a formaldehyde condensation product of an arcmatic sulfonic acid, and then reacting it with about 1-5% of its weight of a water-soluble methylol melamine.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Treatment And Processing Of Natural Fur Or Leather (AREA)

Description

Patented Sept. 19, 1950 REACTING A CHROME-TANNED HIDE FIRST WITH A SULFONI-C ACID. SYNTAN AND THEN WITH METHYLOL -MELAMINE William '0. Dawson, Stamford, Conn., assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing.
This invention relates to the production of I white leather by retanning chrome tanned leather with a Water-soluble methylol melamine. The principal object of the invention is to obtain leather having greatly improved whiteness and light-resistance imparted by the methylol melamine while maintaining the strength and other desirable properties of chrome tanned leather. A further object is the provision of a process that is capable of making a high-grade white leather from skinny, spready hides that are unsuitable for making chrome white leather by other processes. Still further objects will appear from the fol owing descriptions of preferred embodiments of the invention.
In my Patent No. 2,316,740 dated April 13, 1943, I have shown that hides or skins that have been tanned or partially tanned with methylol melamines may be treated with other tanning agents such as vegetable tans, chrome tannages, and iron tannages. The process of that patent is based on the preliminary tannage of hides or skins with water-soluble methylol melamines, followed by applying the chrome, vegetable or iron tannage on top of the methylol melamine.
My present invention, like my earlier patent above referred to, is directed to a combined tannage of hides or skins with a basic chromium sulfate taming agent and with methylol melamine, but constitutes an improvement thereover. I have now discovered that a white leather comparable in feel and texture to the white leather produced by tanning skins with melamine-formaldehyde resins alone, as described in my Patent No. 2,316,741, can be obtained by the procedures hereinafter described. This leather, in addition to its excellent white appearance and texture, has all of the strength and other desirable characteristics of chrome tanned leather, and therefore constitutes a chrome leather of greatly improved surface appearance. Moreover, the melamine resin-treated chrome leather of my present invention has a substantially increased plumpness and weight as compared with chrome leather prepared from the same stock but containing no methylol melamine, and is therefore greatly enhanced in value.
Mv present invention, in its broadest aspects, consists in the application to chrome tanned leather ofan aromatic sulfonate tanning agent and awater-soluble melamine-formaldehyde condensation product. or methylol melamine, in suitable amounts. The advantages which I obtain by this treatment will be clear from the following discussion:
In the manufacture of chrome tanned leather by either the one-bath or the two-bath process the substance of the hide or skin is caused to combine with a basic chromium sulfate which converts it into leather. The chrome leather from this treatment is described in the tannery Application November 19, 1946, Serial No. 710,949
4 Claims. (01. 8-94.33)
. 2 a as "blue'stock, since it is light blue in color. When'whiteleather is desired it is customary to bleach this blue stock with an aromatic sulfo nate tanning agent such as disulfodinaphthyl methane, obtained by condensing about two mols of naphthalene-sulfonic acid with one mol of formaldehyde; or with the corresponding formaldehyde condensation products of sulfonated phenols or sulfonated cresols. These bleaching agents are believed to form 'a colorless complex with the chrome present-in the leather and thus lighten its color; however, the bleached leather still retains a bluish cast and is somewhat gray in col'or'rather than White. r -I have found that wateresoluble melamineformaldehyde condensation products, or meth: ylol melamines, will combine with the bleached, chrome tanned leather to form leather which is both permanent and truly white in color. More-. over, the leather which -I obtain by impregnating the bleached chrome leatherwith methylol melamine is light-resistant; i. e., the discolora-z tion upon continued exposure of the leather to ultra-violet light is much less than with ordi-e' nary chrome leather bleached with aromatic sulfonate tanning agents. Impregnation of the bleached chrome leather with methylol mela; mine also causes an additional plumpingand increase inweight, but without any of the difficulties' "caused by drawn grain that are fre--- quently encountered in plumping,and the white leather so obtained canbe lubricated and softened by ordinary fat-liquoring treatments with vegetable or animal oils which may be unsulfonated but are preferably sulfonated in character. .1'
One of the most remarkablefeatures of the process of my invention. is the fact that it can be ..used to make a high-grade white leather from skinny, spready sides that are normally unsuitable for making chromewhite leather and haveheretofore required heavy vegetable retannage. The following is a'specific example of the application of the process of my invention to this type of skins; however, it will be understood that'the process isalso app icable without material :change. to skins of better quality, and the invention is not limited tothe treatment of skins of low r ade.
, 1,000 pounds of pickled sides of the above grade were placed in a tanning drum together with gallons of water containing 50 pounds of salt (NaCl) and 15 gallons of 33.5% basic chrome liquor were added containing an amount of basic chromium sulfate equivalent to 2-2.5 pounds of sodium bichromate per gallon. The chrome liquor was added in three feeds about 20 minutes apart while rotating the drum, and the drumming was continued for a total of 3 hours. The liquor was then neutralized with sufficient sodium bicarbonate solution-until;theleather showed a heat resistance of 200 F.
The chrome tanned sides were-placed in a tanning drum and washed 30 minutes in water at temperatures up to l25-135 F. The water was changed and 3% of a disulfodinaphthylmethane tanning agent having a pH .of 6-8 was added to the drum, based on the shaved weight of the sides, and the drum was rotated 45 minutes, drained and washed 15 minutes at 130 F., and again drained. Approximately 75-100% of water at 130 F. was then introduced into the drum and 3.5% of trimethylol melamine was added, based on the weight of the sides. The drum was then rotated for 30 minutes, allowed to stand for one hour, rotated an additional 30 minutes, and then stopped overnight. The following morning the drum was rotated 15 minutes and the .leather was washed with water and fatliquored. of sulfonated vegetable oil and-1% of neats-foot oil were used for the fat liquoring along with 4% of titanium dioxide, and the drum was rotated 30 minutes. The leather was then horsed up and dried.
The leather prepared by this process was found to have gained /2 to 1 ounce in weight, as compared with white chrome tanned leather from the same stock to which no methylol melamine was added. The leather was very white, had a deep white cut showing good impregnation of the methylol melamine, was full and tight, and had an unusually uniform break.
The water-soluble methylol melamines used in practicing my invention should remain water soluble in the presence of salt, and should therefore be substantially unpolymerized. They may be prepared as described in my issued patents referred to above, or by any other suitable process. The trimethylol melamine used in the above example was a spray-dried methylol melamine which was substantially unpolymerized and not salt-sensitive. This product was prepared as follows:
A quantity of formaldehyde in the form of a 37% aqueous solution was weighed, charged to a mixing vessel maintained at a temperature below 60 'F., and adjusted with sodium hydroxide to a pH of 8.0. Micropulverized melamine was added to the formaldehyde solution, with agitation, in an amount sufficient to bring the molecular ratio of formaldehyde to melamine to 3.611, care being taken to maintain the temperature sufficiently low to prevent reaction. This unreacted slurry was immediately pumped under pressure through a heat exchanger at a temperature of 220 F., at such a rate that it took approximately 2 minutes for a given quantity of the slurry to pass therethrough. The material was then pumped through a cooling heat exchanger, which rapidly cooled the syrupy product to approximately 120 F. From the cooling heat exchanger the product was introduced into a spray drier and spraydried at a gas temperature of 450 F. The process was continuous from one step into the other, as all the individual units were interconnected for continuous flow. The product had the following analysis:
1.4% moisture 36.5% nitrogen 42.2 total formaldehyde 2.9% free formaldehyde 3.0-3.2 molecular ratio of formaldehyde to melamine pH of 7.8
A fusion temperature of 81.5 C.
A solubility in water at 25 C of 25 parts per 100 parts of water, and 50 parts per 100 at 75 Q.
Infinitely -water dilutable without producing hydrophobidity The amount of synthetic tanning agent may vary from about 1% to about 5%, based on the weight of the leather. Usually hides of better grade than those described in the above example will require smaller quantities than the 3.5% that was actually used, about 12.5% being sufficient in most cases. Although a neutralized synthetic tanning agent is preferred, the aromatic sulfonate may be alkaline or acid.
The water-soluble methylol melamine may be used in amounts of about 1% to about 5%, based on the weight of the chrome tanned leather, the exact amount depending on the degree of whiteness and fullness desired. Although the methylol melamine is usually applied after the aromatic sulfonate tanning agent, it may be applied simultaneously therewith if desired; in fact the aromatic sulflonate may be applied after the methylol melamine in some cases.
From the foregoing description it is apparent that the process of my invention can be applied either to hides such as cowhide or to so-called skins such as calfskins, gloat skins, etc. In the appended claims the term skins is used to designate either hides or skins, both of which may be treated with equal facility by the process of my invention.
What I claim is:
l. A method of obtaining a light-resistant white chrome tanned leather which comprises re acting fully tanned chrome tanned blue stock with about 1-5% of its weight of an aromatic sul- Ionate tanning agent and subsequently reacting the aromatic sulfonate treated stock with about 2-5% of its weight of a water-soluble methylol melamine.
2. A method of obtaining a light-resistant white chrome tanned leather which comprises reacting fully tanned chrome tanned blue stock with about 1-5% of its weight of a disulfodinaphthylmethane tanning agent and subsee quentl reacting the di-sulfodinaphthylmethane treated stock with about 2-5'% of its weight of water-soluble methylol melamine.
3. A method of producing chrome-tanned leather lof improved whitenes and light-resistance from skins so inferior in quality as to be normally unsuitable for making chrometanned leather which comprises first subjecting said skins to a full chrome tannage, then reacting the resulting chrome-tanned leather of in.- ferior grade with about 1-5% of its weight of .a formaldehyde condensation product of an arcmatic sulfonic acid, and then reacting it with about 1-5% of its weight of a water-soluble methylol melamine.
4. A method according to claim 3 in which the aromatic sulfonic acid-formaldehyde condensation product is a .disulfodinaphthyl methane,
WILLIAM O. DAWSON,
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS

Claims (1)

1. A METHOD OF OBTAINING A LIGHT-RESISTANT WHITE CHROME TANNED LEATHER WHICH COMPRISES REACTING FULLY TANNED CHROME TANNED BLUE STOCK WITH ABOUT 1-5% OF ITS WEIGHT OF AN AROMATIC SULFONATE TANNING AGENT AND SUBSEQUENTLY REACTING THE AROMATIC SULFONATE TREATED STOCK WITH ABOUT 2-5% OF ITS WEIGHT OF A WATER-SOLUBLE METHYLOL MELAMINE.
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE968753C (en) * 1951-08-10 1958-03-27 Jacques Wolf & Co Process for the production of water-soluble dicyandiamide-formaldehyde condensation products which can be precipitated by acidification
DE1034810B (en) * 1955-04-16 1958-07-24 Bayer Ag Process for improving the material properties of leather
DE976615C (en) * 1954-05-26 1964-01-09 Bayer Ag Process for the preparation of products from dicyandiamide-formaldehyde condensation products and metal salts of formaldehyde-condensed arylsulfonic acids

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2017863A (en) * 1934-03-12 1935-10-22 American Cyanamid & Chem Corp Synthetic tanning material
US2204512A (en) * 1937-10-06 1940-06-11 Rohm & Haas Tanning material
US2303209A (en) * 1941-03-05 1942-11-24 American Cyanamid Co Leather tanning and finishing
US2316740A (en) * 1942-07-25 1943-04-13 American Cyanamid Co Leather manufacture
US2322959A (en) * 1941-10-25 1943-06-29 American Cyanamid Co Tanning

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2017863A (en) * 1934-03-12 1935-10-22 American Cyanamid & Chem Corp Synthetic tanning material
US2204512A (en) * 1937-10-06 1940-06-11 Rohm & Haas Tanning material
US2303209A (en) * 1941-03-05 1942-11-24 American Cyanamid Co Leather tanning and finishing
US2322959A (en) * 1941-10-25 1943-06-29 American Cyanamid Co Tanning
US2316740A (en) * 1942-07-25 1943-04-13 American Cyanamid Co Leather manufacture

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE968753C (en) * 1951-08-10 1958-03-27 Jacques Wolf & Co Process for the production of water-soluble dicyandiamide-formaldehyde condensation products which can be precipitated by acidification
DE976615C (en) * 1954-05-26 1964-01-09 Bayer Ag Process for the preparation of products from dicyandiamide-formaldehyde condensation products and metal salts of formaldehyde-condensed arylsulfonic acids
DE1034810B (en) * 1955-04-16 1958-07-24 Bayer Ag Process for improving the material properties of leather

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