US2599142A

US2599142A - Tanning and bleaching leather with a sulfoaromaticmelamine-formaldehyde resin

Info

Publication number: US2599142A
Application number: US110022A
Authority: US
Inventors: Jack T Thurston; Adams Pierrepont
Original assignee: American Cyanamid Co
Current assignee: Wyeth Holdings LLC
Priority date: 1949-08-12
Filing date: 1949-08-12
Publication date: 1952-06-03
Anticipated expiration: 1969-06-03

Description

Patented June 3, 195?;

TANNING AND BLEAOHING LEATHER WITH A SULFOAROMATICMELAMINE-FORMAL- DEHYDE RESIN Jack T. Thurston, Riverside, and Pierrepont Adams, Glenbrook, Conn., assignors to American Cyanamid Company, New York, N. Y., a

corporation of Maine No Drawing. Application August 12, 1949,

, Serial No. 110,022

' Claims.

This invention relates to the treatment of skins and/or hides and more particularly, to processes for bleaching or whitening chrome tanned leather and to the leather products obtained by such processes.

It is an object of the present invention to produce white leather.

It is another object of the present invention to provide a process for bleaching chrome tanned leather. I

Another object of the present invention is the provision of new and improved bleaching agents for chrome tanned leather.

A further object of the present invention is the provision of new and improved agents for tanning hides and. skins to produce white leather.

The above and other objects may be attained by treating skins and/or hides or leather with a water-soluble aldehyde condensation product of a .sulfonated aromatic hydrocarbon-substituted melamine or an alkali metal or ammonium salt thereof.

The invention will be described in greater detail in conjunction with the following examples in which proportions are given in parts by weight. The examples are merely illustrative, and it is not intended that the scope of the invention should be limited to the details therein set forth.

Example 1 254 parts (0.9 mol) of p-sulfophenylmelamine 360 parts (0.9 mol) of sodium hydroxide,

aqueous 219 parts (2.7 mols) of formaldehyde, 37%

aqueous The above ingredients are placed together in a suitable vessel equipped with means for reflux. The reaction mixture is heated and refluxed for l-3 hours. The product is cooled and filtered.

Example 2 A 30.4 parts (0.1 mol) of sodium salt of p-sulfophenylmelamine 16.2 parts (0.2 mol) of formaldehyde, 37%

aqueous 150 parts of water Example 3 37.4 parts (0.12 mol) of sodium salt of p-sulfophenylmelamine 2 10.0 parts (0.12 mol) of formaldehyde, 37%

aqueous 181 parts of water The procedure of Example 2 is followedexcept that the reaction mixture is refluxed for only one hour.

Example 4 The procedure of Example 215 followed except that the reaction mixture is refluxed for only one hour and the product is clarified by passing it through a centrifuge. I

Example 5 1350 parts (3.8 mols) of sodium salt of p-sulfophenylmelamine, 85 purity 452.0 parts (5.6 mols) of formaldehyde, 37%

aqueous 5198 parts of water The above ingredients are mixed together in a suitable vessel and heated at reflux for one hour.

After cooling for one hour, the reaction product is clarified by passing it through a centrifuge.

Example 6 10.9 parts (0.025 mol) of the mono-sodium salt of 4,8-disulfo-alpha-naphthylmelamine 6.1 parts (0.075 mol) of formaldehyde, 37%

aqueous 73.6 parts of water An aqueous solution of the sulfon'aphthyl melamine is heated with excess alkali, the'excess alkali is neutralized with hydrochloric acid and the solution, with triethanolamine.

Ea'ample 7 10.9 parts (0.025 mol) ofthe mono-sodium salt of 6,8-disulfo-beta-naphthylmelamine 6.1 parts (0.075 mol) of formaldehyde, 37%

aqueous 73.6 parts of water The procedure of Example 6 is followed, and the slightly hazy solution obtained is filtered Formalde hyde is then introduced and the ingredients are mixed together in a suitable vessel and heated at Y warm. The filtered solution, which is precipitated by m t re o alt end is Pis -d a a tanning and r bleaching agent for leather.

Example 8 13.1 parts (0.025 mol based on average molecular weight) of a mixture of the mono;- and cliammonium salts of 3,6,8-trisulfoialp flflfll ph thylmelamine 6.1 parts (0.075 mol) of formaldehyde. 37%

aqueous r 1 71.5 parts of water The above ingredients are placed in a suitable vessel and heated. At the boiling .point, the

reaction mixture clears to a yellowbran'g'solu tion which is refluxed for 1 hour and then cooled. The solution obtained has good bleaching propi ss l ihs "Example 9 100 parts of pickled kidskin are drummed with 100 parts of water containing lo'parts of sodium lqr dg- .23 par s o the r s n of Exam le e addedthe sk nis tumbled o an :hour. nd

are added- After f rther tumbl n 1. rom 12-15 hours, the tanned skin has a pH of 2.4.

12.8 parts of borax are then added to the skin hich i d ummed $9. a h ur nt 9 he skin is' now'. 4.85.

kierlashed and arts?! ut Emir tes wet, it is white and well tanned. 7

Example 11 Pieces of chrome tanned side leather are by wight, based onthe shaved weight of the stock, "or Water containing-10%"of' the resinof Example 2, 10%. of the resin of Example 3, and of the resin of Example 1, respectively.

low by sulfonation .of phenylmelamine or it may in 00% I drumming in a medium float of water containing 3% sodium acetate for 20 rninutesat 85 F. The drum is drained to a shortfioat, 20% of the resin of Example 5 is added, and the leather is drummed for 45 minutes at 120 F. The leather is then fat liquored and dried. A bright white l ath r su ts- The prsulfophenylmelamine used in Example 1 and :for .the prep'aration of its sodium salt for Examples 2 5 maybe prepared as described be- .be repared directly by condensation of sulfanilic acid and arnmonia with cyanuric chloride. We have found thatsulfanilic acid Will not condense with melamine in the same manner as it does with urea to form the corresponding sulionated phenyl .deriyative.

Hawa an f ,v-wlfwhe y e a ms .41 ha t? 09. 119 9 9? ahecr mslan-im pa i-361 9 9i9, a&isi 9 Pa ts 9: wate A mixture of the first two ingredients is heated with stirring at about 100 C. After 1 5 minutes the solution is pink in color and contains 0.33 mol ofsulfuric acid. The sulfonation is'completed by stirring for an additional minutes "at about 100 C. The reaction product is then cooled with ice, and the water is added dropwise' to the' cooled sul-fonation mixture. 13.5 parts of a white insoluble material is obtained after filtration, washing with water and drying at 106 C. The sulfonation thus yields 69% p-suliophenylmelamine. V

The naphthylmelamines of Examples 6-8 may be prepared by" reaction of cyanu-rio chloride with the corresponding naphth ylamine sulfonic acid. The procedure is illustrated by the follow- Theyare then washed, tacked out and dridl 1n 1 each case :wel-l bleached leather results"? Example 12 I Pieces of chrome tanned side leather are shed i911}?! 11 3143 a .ahqyt 2%.??

c.2 12 s i'lilea h d $9 .0 m n tes t HQ G- 1. 9% ath ist! base 9a th shared us aht a e k f wa c nt n n 9% nd 29% r e e am le tad. 19% as .9%. nin ay i am e 1, re pectivel Thsy are hen s ed t i i q but at; area bleached.

aaaa- Eatamplem V Pieces of chrome tanned leather are washed in tap water for 1% hours and then drummed for 1 i=9. 1:597? 1 2 Weight ased. th shar d Weiht th ste s 9f Wat r cgntaia n 29 s tes ease o res cm a. They are then washed, tacked out and dr ed, The skins obtained are well bleached. I

chrome tanned side leather isineutrailz'ea by mg detailed preparation.

A solution of {(4 parts (0.4 'mol) of cyanuric chloride in 127 parts of hot acetoneis'poured into a mixtureo'f 400 parts of ice and 400 parts of water. To this are added 12-2 parts (0.4 mol) of 1-naphthy1amine-4,8 disulfonic acid as a slurin an Part 9 wa er n 60 Part or 19 dium h naiq .s l ti a The mi ture s stirred at 15 -20" 0. for 1.5 hours. parts of a eais ammpni ar hen dde and t e reaction is allowed to continue for another 1.? hours, the temperature rising to 33 C. 50 parts r Of the ammonia are then added, and the reaction mixture is heated under reflux for 1. urs an fi ter d hot. r

292 parts of 10% hydrochloric acid are added to the filtrate and the mixture is allowed to cool. The solution is reduced toabout one fifth its um y ev p at o an t en c oled and n1; tered. The solid is recrystallized iron a small amoun o We??? aml is at 10 aromatic hydrocarbon-substituted melamines described in the aforegoing examples and the accompanying description have the formula where R is an aromatic hydrocarbon radical and X is selected from the group consisting of hydrogen, alkali metal and' ammonium, and 1 1., is an integer from 1 to 3.

Similarly, formaldehyde-yielding materials such as paraformaldehyde and hexamethylenetetramine may be substituted for the formaldehyde of the examples as may other 'aldehydes including acetaldehyde, paraldehyde, furfural, and the like. I a I We have found that the melamine derivative or salt thereof and formaldehyde should be-condensed in molar ratios of from about 1:1 to about 1:5, respectively. p 1

' The condensation of formaldehyde with the melamine derivative maybe carried out' at pI-Is varying from about 3.5 to 9.5 without effecting the bleaching ability of the product. We prefer carrying out the reaction at pHs of from about 6 to 9.

The formaldehyde and melamine derivative are preferably condensed for periods of time up to about an hour at reflux. Beyond that time little additional formaldehyde combines with the melamine derivative. At the boiling point of an aqueous solution of melamine derivative and formaldehyde the quantity of formaldehyde combining with the melamine derivative becomes constant after about one hour and even dropping the pH of the solution after this time, for example, from about 8.5 to about 4.5, does not effect the amount of combined formaldehyde.

While we have set up certain limitations on the ratio of reactants, the reaction time and the l pH of reaction, the bleaching efiect of the new resinous bleaching agents appears to be independent of these variables.

The water-soluble condensation products here described are acid-sensitive. In aqueous solution they may be converted to the insoluble or hydrophobe state by the addition of acid, with consequent precipitation of a solid white resin. Since the chrome salts in leather tanned therewith will generate sulfuric acid when brought into contact with water, it is possible by the process of the present invention to capitalize on the acid-sensitivity of the condensation products on the one hand and the capacity of the chrometanned leather to generate sulfuric acid in the presence of water on the other for the bleaching or whitening of green chrome-tanned leather.

The bleaching process of the present invention may be carried out simply by drumming chromed leather in a watersolution of one of the described melamine derivative condensation products. Varying concentrations, e. g., from about 1% to about by weight of solid resin based on the shaved weight of the stock, may be used in the process and our invention is in no sense limited to the use of any particular concentration. We prefer to use from about 5% to about 25% resin. on the same basis.

The formaldehyde-melamine derivative con- 6f densation products of the present invention may be employed alone for the whitening of chrome tanned leather, or they may be employed in combination with other bleaching agents. In such instances the leather may be first treated with a secondary bleaching agent and a condensation product of the present invention applied thereafter, the two bleaching agents may be used in conjunction with each other, or the secondary bleaching agent may be used for after-treatingleather which has been bleached with the products described in the present case.

Moreover, the condensation products of the present invention may be used as tanning agents, see Example 7, either alone or in conjunction with other tanning agents, i. e'., vegetable, mineral or synthetic. Ifthelatter, our new agents may be used for the initial tannage or for the after-tannage.

The leather products obtained by'the process of the present invention and having incorporated therein a formaldehyde condensation product of a sulfonated aromatic-substituted melamine offer the advantage in the manufacture of white leathers of a reduced requirement of white pigment such as titanium dioxide for covering the leather surface. Such bleached leathers may also be of advantage in obtaining brighter colors in dyeing.

We claim:

1. A process of tanning and bleaching which comprises treating hides and skins with an aqueous solution of a water-soluble acid-sensitive condensation product of 1 mol of a sulfonated aromatic hydrocarbon substituted melamine having the formula wherein R, is an aromatic hydrocarbon radical, X is selected from the group consisting of hydrogen, alkali metal and ammonium, and n is an integer from 1 to 3 with about 1 to about 5 mols of formaldehyde.

2. A process of bleaching leather which comprises treating tanned leather with an aqueous solution of a water-soluble acid-sensitive condensation product of 1 mol of a sulfonated aromatic hydrocarbon substituted melamine having the formula wherein R. is an aromatic hydrocarbon radical. X} is selected from the group consisting of hydrogen, alkali metal and ammonium, and n is an integer from 1 to 3 with about 1 to about 5 mols of formaldehyde.

3. A process according to claim 2 in which the substituted melamine is p-sulfophenylmelamine.

4. A process of bleaching chrome tanned leather which comprises treating chrome tanned leather with an aqueous solution of a water-soluble acid-sensitive condensation product of 1 .7 mol of at annotated aromatic hym'ombon sub stmxtefl momma having the formula wherem "R is an arozr ratic hydrocarbon X ,is selected from the sroup consisting of v drogen, alkali metal and ammonimmm'nd mis 1 emmmemm 8 wherein 2B. is an hydrocarbon raekcezl. X ,is selected the group consisting of hydrogen, alkali meta-1 and :ammomum, and in is an integer from 1 to 3 with about 1 to about 5 7 mols of formaldehyde, and then with a different tanning agent.

JACK T. THURSTON. PIERREPONT ADAMS.

REFERENCES CITED The following references are of record in the file of this patent:

STATES PATENTS Number Name 7 Date 1 949 513 Bergmmm Feb. 20, 1934 2,122,133, Dohse June 28, 1-938 2.303.399 Grim New. 24, 1942 2316,3210 ,r Apr. 13 19413 2,328,424 .D'Jflerio Aug. 31,1943 2,353,556 Grim Jul 111;, 1944 2,411,679 DiAleHe Mar. &8, 194' 2,493,495 Keller t 911. June 15. 949

om REFEBEN'GES Journal 5: the American Leather Chemists Association. 1944. mac 9-

Claims

1. A PROCESS OF TANNING AND BLEACHING WHICH COMPRISES TREATING HIDES AND SKINS WITH AN AQUEOUS SOLUTION OF A WATER-SOLUBLE ACID-SENSITIVE CONDENSATION PRODUCT OF 1 MOL OF A SULFONATED AROMATIC HYDROCARBON SUBSTITUTED MELAMINE HAVING THE FORMULA