US3494977A - Treatment for leather - Google Patents

Description

United States Patent 3,494,977 TREATMENT FOR LEATHER Roger J. Heit, Midland, Mich, gssignor t0 Dow Corning Corporation, Midland, Mich, a corporation of Michigan No Drawing. Filed Mar. 28, 1968, Ser. No. 716,994 Int. Cl. C08g 47/10, 31/24 US. Cl. 260825 8 Claims ABSTRACT OF THE DISCLOSURE ltlle NHECHZCHZNHCHZOHCHzSiOg/g and 16 g. of

c llleaslo SiO :4 SiD/leO SiMe in which R is an alkyl radical of 16 to 24 carbon atoms.

This invention relates primarily to treatment of suede leather and other types of unfinished 1 leather employed in the manufacture of shoes and garments. One of the problems with leather garments occurs when they are dry cleaned. The dry cleaning solvent extracts much of the fat liquor from the leather, thereby rendering it hard and undesirable by way of feel. In present operation in the dry cleaning shop the leather garment is immersed in the dry cleaning solvent which generally contains neatsfoot oil and thereafter removed from the solvent and dried and then sprayed with an emulsion or solution of wax or some other material to enhance softness. After such treatment the water or solvent is evaporatediand it is necessary to brush the leather several times in order to obtain the original nap and softness. In general, at least two brushings is required and these are usually hand operations. If water repellency is desired, the garment is sprayed with a suitable product. Consequently, the dry cleaning of leather garments is quite expensive.

Also, dry cleaning of present leather garments often removes large quantities of dye from the leather, particularly in those cases where the less expensive non-acidic dyes are employed. Consequently, it is often necessary for the dry cleaner to add a dye to the leather after dry cleaning. All of this adds additional expense to the dry cleaning of the garment.

It would be highly desirable to have a material which could be added to the dry cleaning solution or which could be applied to the leather immediately after dry cleaning which would obviate most of the brushing step and which would impart to the leather a high degree of water repellency and would maintain the original softness and high nap of the suede leather. In addition, it would be highly desirable to have a material which Unfinished leather refers to leather which is not finished with a coating of polymeric materials such as acrylates.

3,494,977 Patented Feb. 10, 1970 "ice would prevent or retard the extraction of dye from the leather during dry cleaning.

In adition to dry cleaning there are instances in which a suitable material could be added at the tannery in order to enhance the water repellency and the softness and luster of suede leather. This is particularly true with respect to pigskin which is at present being employed to make shoes called Hush-Puppies.

One of the difiiculties with such shoes is that although they are quite comfortable they tend to absorb large quantities of water and to harden on use and to become quite dirty. Consequently, such shoes are worn primarily in warmer or drier climates, such as California or Florida. However, they also have extensive markets in the colder and/or wetter regions of the country. If properly treated the market for such shoes in the colder and wetter regions could be greatly enhanced because of their resistance to deterioration by water.

This invention relates to a method of treating leather which comprises impregnating the leather with 1) a copolymer of units of the formula and (B) Me SiO units in amount of at least 3 moles 2 of (B) per mole of (A), and (2) a polysiloxane of the unit formula hie RSi O which can contain up to 96 mol percent copolymerized Me SiO units in which siloxanes (l) and Y is an acid anion,

R is an alkylene radical of 2 to 6 inclusive carbon atoms,

R is a lower alkyl radical,

a has a value from 0 to l,

b has a value from 0 to 2, and

R" is an alkyl or an aralkyl radical of at least 9 carbon atoms, and the weight ratio of (l) to (2) is from 4:1 to 0.75:1.

This invention also relates to compositions of matter consisting essentially of mixtures of (l) and (2). The term consisting essentially of means that the compositions can contain other ingredients normally employed in the treatment of leather which do not materially change the effects of the combination l) and (2).

(1) and (2) can be applied to the leather either as a mixture (i.e., simultaneously) or they can be applied separately. In either case the application can be from solvent solutions or aqueous solutions or emulsions. The solvent solutions are generally preferred when employing (1) and (2) during dry cleaning of a leather garment. Aqueous emulsions are generally preferred when the (1) and (2) are applied to leather at the tannery during processing of the leather. The amount of (l) and (2) used on the leather is not critical, but can vary from 0.5 to 25% total (1) and (2) by weight based on the 2 Based on unit weight (i.e., 74 for MeaSiO).

dry weight of the leather depending upon the particular type of leather and the desired eflect.

The term leather employed herein includes animal hide in general, including cowhide, pigskin, sheepskin, horsehide, etc. As mentioned above, the treatment of this invention is particularly suitable to suede leather, that is leather having a nap, and such leather, as is well known is primarily employed in the manufacture of coats, jackets, and special types of shoes.

Copolymer (1) employed in this invention is a copolymer of an aminoalkylsiloxane of the type shown and dimethylsiloxane. For the purpose of this invention R can be any alkylene radical of from 2 to 6 carbon atoms, such as CH CH CH CH CH and R can be any lower alkyl radical such a methyl, ethyl, propyl, isopropyl or butyl and a can be or 1. Therefore the amine can be substituted on a silicon with no other substituents or on a silicon with one other substituent.

As can be seen the amine can be employed per Se or in the form of an amine salt. Thus, Y can be any acid anion either from a carboxylic acid or other organic acids such as sulfonic acid, or phosphinic acid or acid alkyl sulphonate; or it can be derived from inorganic acids such as hydrochloric, hydrobromic, sulfuric, nitric, phosphoric, etc. Preferably, Y is an anion of a monocarboxylic acid, such as acetic, formic, propionic, hexoic, etc. In general, it is preferred to employ the amine salt when the composition is to be used in the form of an aqueous dispersion. When the composition is to be employed in the form of solvent solutions, it is preferred that the amine per se be used.

As is noted, the ratio of aminosiloxane units and dimethylsiloxane units must be such that there is at least 3 mols of dimethylsiloxane units per mol of aminosiloxane unit. The upper limit of this ratio is not critical, however, it is preferred that there be no more than 1000 dimethylsiloxane units per amine siloxane units with optimum results often being obtained with no more than 100 Me SiO units per amine siloxane unit.

Ingredient (2) of this invention can be an alkylmethylsiloxane or an aralkylmethylsiloxane of the formula RMeSiO in which R" can be a hydrocarbon radical having at least 9 carbon atoms such as alkyl radicals, such as decyl, dodecyl, tetradecyl, octadecyl, C H and myricyl; or any aralkyl radical such as beta-phenylpropyl If desired, composition (2) can have dimethylsiloxane copolymerized with the R"MeSiO and the dimethyl can be present in amounts up to 96 mol percent of the total composition (2).

Both components (1) and (2) can have silicon-bonded hydroxyls on the ends of the chain or they can be endblocked with triorgano-substituted siloxanes or with any other of the endblocking units normally employed in commercial siloxanes such as alkoxy groups, acetoxy groups, etc.

Also the structure of (l) and (2) is not critical since these materials can be in the form of linear, branched or cyclic molecules or mixtures thereof.

In addition to (l) and (2), the leather can also be treated with other materials normally employed in leather to perform specific functions therein, such as, for example, glutaraldehyde, or other materials used in the tanning or fixing processes. The additional materials can be used in admixture with or in Separate steps with respect to (1) and (2).

The following examples are illustrative only and should not be construed as limiting the invention which is properly delineated in the appended claims. Me is employed herein as an abbreviation of the methyl radical.

EXAMPLE 1 375 g. of

Mes HO S iO H having a viscosity of about 250 cs. at 25 C. was mixed with 125 g. of

Me (MeO) SiCH JHCHZNHCHZCIENH:

and heated at about C. for 1.5 hours to copolymerize the ingredients. 34 g. of the above product [designated (1)] was mixed with (2) 16 g. of

we a MeSiO SiO 24 SiMeO) -,SiMe

in which R represents radicals of the formula C H to (lliez) Bile MBgSiO SiO 4(Si0 SiMes C20H41; and 50 g. of perchloroethylene.

Three sheepskin suede leather amples having a dry weight of 700 g. were washed with isopropanol and then covered with 5 gallons of perchloroethylene. To the leather was added the above solution of 1) and (2) in amount such that there was a total of 6% by weight (1) and (2) in the treating bath based on the dry weight of the leather. The leather was tumbled for one hour then removed from the vessel and dried for 48 hours at roomtemperature and then 15 minute at 70 C. The spray rating of the resulting leather was 70 based on Federal Test Method 5526 (US. Government publication). It did not water spot when a drop of water was applied and allowed to evaporate. The gloss and feel of this leather was excellent and the nap was very prominent.

EXAMPLE 2 53.4 g. of (1) of Example 1 and 26.6 g. of (2) of Example 1 was dissolved in 15 g. of an aliphatic hydrocarbon solvent and 5 g. of isopropanol. The above solution was added to an aliphatic hydrocarbon solvent in a commercial dry cleaning establishment during the dry cleaning of a suede leather coat in the amount of 4% by weight of (A) and (B) based on the dry weight of the leather. The garment was tumbled for 25 minutes, then centrifuged to remove the solvent and dried at roomtemperature for 48 hours and then 10 minutes at 65 C. After light brushing the coat had excellent sheen, nap and softness. It did not water spot and had a spray rating of 65.

EXAMPLE 3 53.4 g. of (1) of Example 1 was mixed with 70 g. of xylene and 26.6 g. of

Me CruHzr 0141120 Me SiO (S iO)2o(Si0 (SlO)4osiMea H CHMe Suede leather was covered with 5 gallons of xylene and the above composition was added in amount of 4% by weight of (l) and (2) based upon the dry weight of the leather. The mixture was agitated for 30 minutes and then removed from the solution, dried 48 hours at Made by the addition of a mi t of olefinh. ranging from CIQHS: t0 zoHio to cu r 5 room-temperature and then 15 minutes at 70 C. The resulting leather was soft and had excellent lustre and a spray rating of 70. It did not water spot.

EXAMPLE 4 This example is given by way of comparison to show that dimethylsiloxane cannot be substituted for (2) in the compositions of this invention. The process of Example 1 was repeated except that three-fourths of composition (2) was replaced by lYlea Me si (Si 0 SiMe3 having a viscosity of 350 cs. The resulting suede leather had a poor appearance and the spray rating was less than 50.

EXAMPLE This example illustrates the step-wise addition of (l) and (2). Four samples of pigskin suede leather were washed with water for 15 minutes at 130 F. then drained and covered with water in a Najort washer. A 40% aqueous emulsion of (2) of Example 1 was added in amount to give 5% by weight (2) based on the dry weight of the leather. The leather was then agitated for 30 minutes at 130 F. 2.5% glutaraldehyde was added based on the dry weight of the leather and agitation was continued 45 minutes at 130 F. 2.4 g. of a 0.2% by weight solution of sodium bicarbonate was added to the leather in three portions at intervals of 5 minutes. This was for the purpose of adjusting the pH of the leather. The leather was washed 15 minutes, drained and refloated in water at 130 F.

A composition 1) was prepared by reacting 37.5%

MeC O OH Me (MeCOOH-HaN CHzCHzNHCHzJIHCHzSi 02/2) 1 2 0) by weight of a hydroxyl-endblocked dimethylpolysiloxane fluid having 1.63% by weight silicon-bonded hydroxyl, 12.5% by weight hide (N180) SlCHzCH2CHNHCH2CH2NH2 and 6.8% by Weight acetic acid in 43.2% by weight isopropanol. This solution was added to the leather bath in amount to give 5% by weight (1) based on the dry weight of the leather. The bath was then agitated 30 minutes at 130 F. The leather was then removed and washed with water at 90 F. It was dried, staked, buffed and dry milled in the usual manner employed in tanneries. The resulting leather had good tracking, good temper and good water resistance, as shown by the fact that it absorbed only 21.2% by weight water after 4000 flexes on leather flex tester No. 1002, sold by Dow Corning Corporation, Midland, Mich.

EXAMPLE 6 Equivalent results were obtained when the following silanes are substituted for the silane in composition (1) of Example 1. H NCH CH NH(CH Si(OMe) H NCH CH NH(CH Si (OMe 3 and EXAMPLE 7 Equivalent results are obtained when the following amine salts are substituted for the acetate salt (1) of Example 5.

4 The product was a copolymer of the average formula 6 That which is claimed is: 1. A method of treating leather which comprises impregnating the leather with (1) a copolymer of the unit formula and (B) units of the formula Me SiO in amount of at least 3 mols of (B) per mole of (A), and

( 2) a polysiloxane of the unit formula Me RS iO which can contain up to 96 mol percent copolymerized Me SiO units in which siloxanes 1) and (2) Y is an acid anion, R is an alkylene radical of 2 to 6 inclusive carbon atoms, R is a lower alkyl radical, a has a value from 0 to 1, b has value from 0 to 2, and R" is an alkyl or an aralkyl radical of at least 9 carbon atoms, the weight ratio of (1) to (2) being from 4:1 to 0.75:1.

2. The method in accordance with claim 1 in which the leather is impregnated with an organic solvent solution of (1) and (2).

3. The method in accordance with claim 2 in which (1) is a copolymer of I HaNCHeCHgNHCHzCHOHzSiO z and Me SiO and (2) is a copolymer of and Me SiO in which R" is an alkyl radical of at least 9 carbon atoms.

4. The method of claim 1 in which (B) is present in amount from 3 to 100 mols per mol of (A).

5. The method of claim 3 in which (B) is present in amount of from 3 to 100 mols per mol of (A).

6. A composition of matter consisting essentially of a mixture of 1) a copolymer of the unit formula (Y-)bH; NCH2CHzNHRSiO '2 and (B) units of the formula Me SiO in amount of at least 3 mols of (B) per mole of (A), and (2) a polysiloxane of the unit formula which can contain up to 96 mol percent copolymerized Me SiO units in which siloxanes (1) and (2) Y is an acid anion, R is an alkylene radical of 2 to 6 inclusive carbon atoms, R is a lower alkyl radical, a has a value from 0 to 1, b has a value from 0 to 2, and R" is an alkyl or an aralkyl radical of at least 9 carbon atoms, the weight ratio of (1) to (2) being from 4:1 to 0.75:1.

7. The composition of claim 6 in which (1) is a copolymer of NHzCHzCHzNHCHzCHCHgSiOa/z and Me SiO and ,(2) is a copolymer of 1 and Me SiO in which R" is an alkyl radical of at least 9 carbon atoms.

8. The composition of claim 6 in which (B) is present in amount of from 3 to 100 mols per mol of (A).

SAMUEL H. BLECH, Primary Examiner US. Cl. X.R.