US 3524760 A
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United States Patent US. Cl. 117-63 9 Claims ABSTRACT OF THE DISCLOSURE Process for rendering leather oil and water resistant which comprises subjecting leather, which has been impregnated with a fluoropolymer, to a hot solvent which is a hydrocarbon, a halogenated hydrocarbon, a ketone or an ester, which boils between 35 C. and 210 C. and which dissolves the fluoropolymer in amounts of at least 0.1% by weight at 25 C. Preferably the fluoropolymer is a copolymer of a methacrylate or acrylate ester which contains pendent perfluoroalkyl groups of 4-14 carbons and a nonfiuorinated vinylidene monomer; while the solvent is trichloroethylene. Preferably, also, the leather is treated in an atmosphere of the solvent vapor.
BACKGROUND OF THE INVENTION Field of the invention This invention relates to a process for the treatment of leather to render it oil and water resistant. More specifically, the process of this invention is directed to the substantial saturation of leather, which has previously been impregnated with a fluorinated polymer composition, with a selected hot solvent, followed by drying.
Description of the prior art Leather has long been used in applications Where long wear and shape retention are important. Its unique porous structure, which provides insulating properties while permitting the passage of water vapor, has made it especially useful for shoes, gloves and coats. However, leather has poor water resistance, and much effort has been, and is being, expended to overcome this deficiency. For example, a discussion of methods for water-proofing leather is found in US. Pat. 2,693,996.
Oil repellency is also lacking in leather as usually processed. This shortcoming is particularly noticeable in brushed suede shoes where the napped surface and the oil receptivity of the leather makes for unsightly stains whenever such shoes come into contact with oily materials. In order to be aesthetically acceptable, treatments for improving the water and oil repellency of leather must preserve the appearance as well as the other desirable properties of the leather. This invention confers improved water and oil repellency upon the leather while preserving the appearance and other desirable qualities.
The treatment of leather to obtain water repellency has been practiced for many years. A review of useful methods is given in US. Dept. of Commerce publication OT 5, Dept. of Commerce, 23, 85, No. 3 (1955). Many types of polymers and methods for their application to leather are discussed therein, but oil repellency is not considered. In the usual procedure, leather is treated with an aqueous "ice dispersion of a water repellent and a fat liquor oil. The dispersion also contains the usual dispersing agents, durability agents and the like. This treatment is usually called the fat liquoring step. It is preferably carried out in a tanning drum. The treated leather is then dried, staked (softened by repeated flexing) and, optionally, buffed or sueded (nap raised by rubbing with an abrasive).
However, in order to confer satisfactory oil and water repellency on leather, particularly suede, a successful process must leave the repellent agent both on the sur face and in the body of the leather. Surface treatment are quickly dissipated by wear and lose their effectiveness. On the other hand, many organic solvent treatments designed to penetrate and carry repellent agents within the body of the leather fail because the leather strains out the active ingredient, leaving it near the surface only. Dispersions of oil and water repellent fiuoropolymers can be wet drummed into leather from aqueous media; however, the maximum oil and water repellency is not normally developed without a heat cure. Unfortunately, complete cure of such fiuoropolymers usually requires temperatures above 150 C., which is destructive to leather and cannot be tolerated.
The process of this invention overcomes the deficiencies of the art and provides for effective penetration of the water and oil repellent into the leather by treating it, after staking and, optionally, sueding, with a selected hot solvent followed by drying. The action of the solvent is not completely understood; however, it seems to distribute the water and oil repellent finoropolymer through out the body of the leather while concentrating the largest portion near the surface. The results of this treatment are striking in that both water and oil repellency are significantly better than attained by other known treatments.
SUMMARY OF THE INVENTION This invention is directed to a process for imparting oil and water repellency to leather which comprises intimately contacting leather pre-treated with an aqueous dispersion of a water and oil repellent fiuoropolymer composition with a hot solvent which has a boiling point of from 35 C. to 210 C., which dissolves the fiuoropolymer in an amount of at least 0.1% by weight based on the weight of solvent, as measured at 25 C., and which is selected from hydrocarbons, halogenated hydrocarbons, ketones or esters, for a time sufiicient for the leather to uniformly absorb about 40% to by weight of the solvent based on the Weight of the leather and at a temperature of between 35 C. and C; followed by drying the treated leather.
DESCRIPTION OF THE INVENTION (1) The water and oil repellent fluoropolymer.-Any water and oil repellent organic fiuoropolymer having a pendant prefluoroalkyl group of 4-14 carbon atoms can be employed. Among the most useful are copolymers of fiuorinated vinylidene monomers and non-fluorinated vinylidene monomers.
The fluorinated monomer may also be substituted with or contain amine, amide, thionyl or sulfonyl groups, and the like. Any monomer of the above described nature may be employed so long as the resulting polymer exhibits the required solubility in the solvents used in the invention.
The most useful fluoromonomers have the formula CF3 :CH2
wherein n is a cardinal number of 3 to 13, inclusive. These monomers may be prepared as described in Example II of U.S. Pat. 3,282,905. The preferred fiuoromonomer component described in this paragraph is a mixture wherein n is 6, 8 and 10 in the weight ratio of 3/2/1 with less than 10% 12 and 14.
Other fluoromonomers useful in preparing the fluoropolymers used in this invention have the formulae R SO N(R)R'OCOCR=CH (prepared as described in U.S. Pat. 2,803,615)
R;CH OCOCR"=CH (prepared as described in U.S. Pat. 2,642,416)
R;CON(R)R'OCOCR"=CH (prepared as described in U.S. Pat. 3,304,278), and R (CH OCOCR":CH
(prepared as described in U.S. Pat. 3,102,103). In the above formulas R represents a perfiuoroalkyl group of 6 to 14 carbons, R represents an alkyl group of 1 to 18 carbons, R represents an alkylene group of 2 to 6 carbons, R" represents hydrogen or methyl, and m represents a cardinal number of 3-12.
The nonfluorinated vinylidene monomer is preferably an ester of acrylic or methacrylic acid. They impart water repellency to the resulting copolymer and also afifect the solubility in the selected solvents used in the invention. Preferred esters are the alkyl methacrylates or alkyl acrylates wherein the alkyl groups contain from 4 to 18 carbon atoms, although best results are obtained with alkyl groups of 8 to 12 carbon atoms. Representative alkyl methacrylates and acrylates include 2-ethylhexyl methacrylate, n-octyl methacrylate, n-dodecyl methacrylate, octadecyl methacrylate, butyl methacrylate, lauryl methacrylate (a commercial product containing about 60% n-dodecyl methacrylate, 27% n-tetradecyl methacrylate, 7% lower methacrylates and 6% higher methacrylates), and the corresponding acrylates.
The weight proportion of fiuoromonomer in the copolymer may vary from about 3% to about 92%, with 50% to 75% being preferred.
Most preferably, the copolymer will also contain a small amount of n-methylolacrylamide and/ or 2-hydroxyethyl methacrylate to assist the stability of the copolymer.
The copolymerization of the fiuoromonomer and the vinylidene monomer is carried out in aqueous media in the absence of air. The monomers are mixed in water in the presence of a surface-active agent, such as sodium lauryl alcohol sulfate or the dimethyloctadecyl amine salt of acetic acid. A molecular weight controller, such as dodecyl mercaptan, may be used if desired. Then a catalyst-initiator, such as 2,2'-azobisisobutyramidine dihydrochloride or ones listed in U.S. Pat. 3,282,905, is added and the procedure carried out at preferably 60-80 C. for 2 to 6 hours. The reaction is complete when the inherent viscosity of the mixture reaches about 0.5.
(2) The application of the copolymer to leather.-The application of the copolymer to leather is usually carried out at a pH of 2.5 to 7 (preferably 3 to in a mixture of about 200% to 300% by weight of water based on the weight of the leather present, about 4% to 8% weight of a fat-liquoring agent (used as a 10% aqueous solution) based on the weight of the leather, and about 1% to 4% weight of the copolymer dispersion copolymer) based on the weight of the leather. The leather is agitated in this mixture for about 0.5 to 1 hour at 20 C. to 60 C. (preferably 40 C. to 60 C.), after which time the aqueous solution is clear, the polymer having been absorbed by the leather. The leather is then dried at about 60 C. to 100 C., staked, and bufied if desired. The leather is then ready for the solvent treatment.
The application of the copolymer to the leather is normally carried out by wet end drumming in the fat-liquoring step of the leather-making process. Penetration of the leather when water wet is more satisfactory than when solvents are used to introduce the copolymer. The fatliquoring agents are usually sulfonated oils having a pH slightly below 7.0. Any known commercial fat-liquoring agent is operable in this process, and normal fat-liquoring conditions and equipment therefor may be employed.
Drying, staking and, optionally, sueding may be carried out in the usual manner without any alteration because of process treatment.
(3) The solvent treatment step.-It has been found that the mere presence in leather of a water and oil repellent polymer is not sufficient to impart satisfactory repellent properties to the leather. As seen in Example 6 hereinbelow, water and oil repellency of leather samples which contain the polymer but which have not been given the solvent treatment of this invention are unsatisfactory. It has been found necessary to orient the polymeric agent so that its unique properties can be brought to bear where needed at the surface of the leather. This is the function of the solvent treatment of the invention.
The solvents used in this step must be capable of dissolving the fluorinated Water and oil repellent polymer in the previously described minimum amounts, and should not be flammable or toxic. Preferably they should have a boiling point between 40 C. and 130 C. Many hydrocarbons, halogenated hydrocarbons, ketones and esters fall within the foregoing qualifications. Representative solvents include trichloroethylene, methyl chloroform, perchloroethylene, 1,1,2,2-tetrachloro-2-fiuoroethane, 1,1,2- trichloro-1,2,2-trifluoroethane, ethyl butanate, dipropyl ketone, naphtha (Stoddard solvent), benzene, xylene, ethyl bromide, n-benzyl bromide, tetrachloroethylene and 1,1,2,2-tetrachloro-1,Z-difiuoroethane. A preferred class of solvent comprises halogenated hydrocarbons of up to 5 carbon atoms, especially trichloroethylene.
Preferably the leather is exposed to an atmosphere of the hot solvent vapor, preferably a 100% atmosphere, for several, e.g., 1-2, minutes; and then removed to a dryer to be dried between 25 C. and 100 C. Solvent pick-up by the leather may range from 40% to of leather Weight depending on the density of the leather. The solvent can also be applied by dipping the leather into it, by spraying or by curtain coating, so long as a uniform absorption of the above-mentioned solvent is attained.
Leather treated by the process of this invention has excellent oil and water repellent qualities. In the A.A.T.'C.C. 21-1964 Standard Test for Water Repellency, Static Absorption Test, values of only 30% to 40% water absorption are regularly obtained with pigskin suede treated according to this invention, as compared with 75% to for such pigskin without the solvent treatment and over for pigskin without the solvent treatment and the polymer impregnation. With the A.A.T.C.C.- l18-1966-T test for surface oil repellency, ratings of 6 are attained with pigskin suede treated in accordance with this invention, as compared with ratings of zero for the pigskin when the solvent treatment is omitted.
As evidenced by Example 11, the solvent-treating step of this invention transports the polymeric composition to all surfaces and throughout the leather, providing a continuous barrier to the penetration of water and oil. Transmission of water vapor (breathing) through leather treated by the process of this invention is satisfactory. When tested according to Test Method F-32 of the American Leather Chemists Association (1957), values of 7 to 9.5 mg. of water vapor per sq. cm. per hour are obtained. Values above 5.0 are usually considered satisfactory.
Another advantage of the process of this invention is the uniform reproducible quality of the treated leather. Many treatments in which polymers are caused to penetrate the leather must include a spray step or other surface treatment to insure repellency, but such treatments are unnecessary in the process of this invention.
(4) Examples-The process of this invention is described in greater detail in the following examples which are merely representative and are not intended to be limiting:
Example 1--Polymer preparation.ne hundred thirty milliliters of deionized water is placed in a 500 ml. flask equipped with a thermometer, nitrogen inlet, condenser, stirrer and rubber septum for catalyst injection. The water is refluxed and purged for one hour with nitrogen.
A mixture of 2 g. of the sodium salt of lauryl alcohol sulfate, 60 ml. deionized water, 65 g. of
F(CF CH CH OCOC CH CH where n is 6, 8 or 10 in the weight ratio of 3/2/1 with less than 10% being components where n is 12 and 14, and 35 g. of lauryl methacrylate (a commercial product containing about 60% n-dodecyl methacrylate, 27% n-tetradecyl methacrylate, 7% lower methacrylate esters, and 6% higher methacrylate esters) is mixed in a highspeed kitchen blender for 10 minutes. This dispersion is then thinned with 83 ml. deionized water and purged one hour with nitrogen.
The temperature of the water in the flask is lowered to 80 C. and the monomer dispersion added down through the condenser. The temperature is adjusted to 65 C., and 0.38 ml. of a 60% solution of n-methylol acrylamide in water and 0.15 ml. of dodecyl mercaptan is injected through the septum. After /2 hour stirring at 65 C., 40 mg. of 2,2-azobisisobutyramidine dihydrochloride in 2 ml. of water is added. A slight heat rise after 10-15 minutes is observed.
The polymerization is stirred at 70 C. for 4 hours. Inherent viscosity of the product is about 0.5. The dispersion is stored in a polyethylene bottle to prevent skin formation which occurs on glass surfaces. The pH is about 4.0.
The copolymer of this example provides excellent water and oil repellency when applied by the process of this invention.
Example 2Polymer preparation.-Another copolymer was prepared in the same manner as in Example 1 except for the following diiferences:
1) An equal weight (2 g.) of the dimethyloctadecyl amine salt of acetic acid is substituted for the sodium salt of lauryl alcohol sulfate of Example 1 as a dispersing a cut.
(2) About 0.4 ml. of 2-hydroxyethyl methacrylate is added with the n-methylolacrylamide of Example 1.
The dispersing agent of (1) in this example provides a cationic dispersion in contrast to the anionic dispersion of Example 1.
The water and oil repellency provided by this co- The pH of the last rinse water was above 4.0. Three hundred parts of water at about 49 C. was added to the wet pigskins, then a mixture containing parts (based on leather weight) of a 6% aqueous solution of an anionic fat liquor oil and 20 parts (based on leather weight) of a 0.5% aqueous suspension of the copolymer containing parts where n is 6, 8, and 10 in weight ratio 3/2/1 with less than 10% 12 and 14; 35 parts lauryl methacrylate and 0.25 part n-methylol acrylamide was added through the gudgeon and the drum rotated for 45 minutes. This treatment time is sufficient to deposit the polymer within the body of the leather. The spent liquor was drained and the pigskins rinsed for 3 to 5 minutes with 300 parts of water at 45 -50 C. They were then removed from the drum and horsed up to drain overnight. The skins were stapled to boards and dried for 3 hours at 65 75 C. When dry they were staked, then bufied on a sanding wheel, the latter process conferring the unique quality of suede leather.
Example 4-The solvent step.Pieces of pigskin, /5 sq. ft. in area and weighing about 25 g. each, were each treated in a quart jar with a mixture of 250 cc. of water, 1.5 g. of a 10% solution in water of the fat liquoring agent used in Example 3, and 0.5 g. of the polymer used in Example 3 as a 25% dispersion in water. The jar was shaken for 45 minutes at 35 -45 C., after which time the mixture appeared clear. The leather piece was then drained, dried for one hour at C., staked and buffed.
Each leather piece was then treated with one of the solvents listed in the following Table I by suspending the piece over a bath of boiling solvent for several minutes. Each piece was then subjected to tests for surface oil, static oil and static water.
The static Water test is the American Association of Textile Chemists and Colorists Test-21-64, execpt that test pieces were 4.1 cm.-in-diameter discs instead of 2- inch squares.
The surface oil test is A.A.T.C.C. test-118-1966T.
Static oil test was performed by weighing the 4.1 cm.- in-diameter leather discs, immersing them in Nujol for 10 minutes, then lightly blotting off the surface oil and reweighing. The percent weight gain is recorded.
An additional test for solvent applicability was made by drying treated samples of solvent wet leather on a paper towel, then observing the subsequent oil and water repellent qualities of the spot on the towel. When oil and water repellency Was conferred on the paper towel, indicating solution and transport of the copolymer in the leather, the solvent was also found to be successful in the leather treatment.
The data are recorded in Table I.
TABLE I.PERFO RMANCE OF VARIOUS SOLVENTS Percent Static Static polymer Polymer Surface oil test water test Boiling solubility takeup on oil test percent wt. percent wt; Solvent point, C. at 25 0. paper towel grade gain gain Ethyl butanate 121 1 6 5 30 Dipropylketoue 143. 5 1 6 7 36 Stoddard solvent (naphtha) 176-210 1 6 5 36 Benzene 1 4 9 44 Xylene 1 6 3 36 Ethyl bromide. 38 1 4 8 39 n-Beuzyl bromide 156 1 6 4 39 Methyl chloroform 74 1 5 5 38 Tetrachloroethylene 121 1 6 5 36 Trichloroethylene 88 1 6 6 34 CFClz-CFrCLn. 47. 5 .1 5 29 35 CChF'COlZF. 93 1 7 8 35 polymer is efiective but is inferior to the dispersion of 7 Example 1.
Example 3Treatment of leather with the fluorinated copolymer.-One hundred parts of chrome tanned, dyed pigskin leather was placed in a tanning drum and rinsed In the above table, the grades in the surface oil test indicate improving oil repellency from 0 to 9. In the other two tests, the percent gain in Weight of water or oil are reported, thus the best repellency is indicated by a low number. If there is no take-up of the polymer several times with 200 part batches of water at 45-50 C. 75 on the paper towel, the solvent is unsatisfatcory for use in the process. It will be seen that halogenated aliphatic hydrocarbons provide the most satisfactory combination of qualities for use in the leather-treating process of this invention.
Example 5-Comparison of vegetable and chrometanned leather with and without various treating components-Tests were made to compare the results obtained on vegetable tanned leather and chrome-tanned leather by omitting various components in the fluoropolymer treatment step. In all tests, trichloroethylene was used in the solvent step, as described in Example 4, and the tests carried out Were the same as those described in Example 4.
The following Table II shows the results of tests carried on six experiments (denoted by the numbers in parentheses). The active components present during the fluoropolymer treatment step are listed vertically for each experiment. A dash means that that component was omitted. The percent figures are the amount of that particular component employed, and are based on the weight of leather employed.
TABLE II.-VEGETABLE TANNED CALFSKIN Experiment Component of fluoropolymer treatment step (1) (2) (3) (4) (5) (6) 930 Oil (anionic tat liquor), percent. 6 6 l2 Anionic fluorop olymer (the polymer of example 1), percent 1 1 Catalix T (Sandoz Chem. Co.)
(cationic iat liquor), percent 4 4 8 Cationic fluoropolymer (the polymer of Example 2), percent 1 1 Surface oil test grade 5 0 5 5 Percent wt. gain static oil..- 71 23 75 25 Percent wt. gain static water 71 44 53 100 58 47 The results of varied process treatments on chrome tanned leather are shown in the following Table III which is set up as was Table II.
TABLE III.CHROME TANNED PIGSKIN Cationic fluoropolymer (The polymer of The process of the invention gives improved oil and water repellency on both vegetable tanned and chrome tanned leather. Best results were obtained with anionic fat liquor and the anionic copolymer dispersion in Example 1.
Example 6Comparison of leathers treated with varying amounts of fluoropolymer and with and without the solvent step-Samples of a number of different kinds of leather were tested after application of several levels of polymer according to the procedure of Example 3 and with and without the solvent treatment of Example 4. The polymer used was that whose preparation is described in Example 1. Trichloroethylene was used for the solvent treatments. Percent polymer refers to the percent of polymer present in the leather based on the weight of leather used. The tests run were the same as described in Example 4. Data are recorded in Tables 1V, V and VI.
TABLE IV.SHEEPSKIN SUEDE Experiment Percent polymer present TABLE V.GOATSKIN SUEDE Experiment Percent polymer present 0 0 6 6 1.25 1. 25 Solvent treatment N 0 Yes No Yes N 0 Yes Surface oil test, grade 0 0 0 7 0 7 Static oil, percent gain in wt.-. 121 116 90 65 76 33 Static water, percent gain in wt... 87 80 54 22 36 5 TABLE VI.SPLIT COWHIDE Experiment Percent polymer present 0 0 0. 6 0. 6 1. 25 1. 25 Solvent treatment. No Yes N 0 Yes No Yes Surface oil test, grade. 0 0 0 6+ 0 6+ Static oil, percent gain in wt. 76 70 77 15 68 8 Static water, percent gain in wt..... 103 103 102 87 100 83 The superiority of samples employing the solvent step and the fluoropolymer treatment step is self-evident.
Example 7.-Methods of applying the so1vent.This example indicates the relative performance of treating leather in the solvent step of this invention where (1) the solvent is applied by dipping leather samples into it and (2) by exposing the leather to hot solvent vapor. Representative samples of pigskin suede were treated with the polymer of Example 1, as described in Example 3. The solvent used was methyl chloroform. Both methods of solvent treatment provide great improvement, but the Vapor treatment is significantly better both for oil repellency and water repellency. The treatment, whether by, dipping into solvent or exposing to solvent vapor, is reproducible in its effects in a number of applications to diiferent samples of skin representing a cross section of skins. The tests carried out were the same as these decribed in Example 4. The results are shown in the following Tables VII and VIII.
TABLE VII.WATER ABSORPTION OF TREATED LEATHER, PERCENT STATIC WATER ABSORPTION I I No solvent Dipped into Exposed to Pigskin skin No. treatment solvent solvent vapor TABLE VIII.OIL ABSORPTION OF TREATED LEATHER,
PERCENT STATIC OIL ABSORPTION N o solvent Dipped into Exposed to PlgSkll'l skin No. treatment solvent solvent vapor Example 8Method of applying the s0lvent.--A comparison was made of the effect upon oil and water repellency of treating leather in the solvent step of the invention by exposing a number of samples of pigskin suede to hot solvent vapor, by spraying, and by curtain coating-direct application of a thin stream of liquid. Trichloroethylene is the solvent used in these tests. The leather was treted with the copolymer of Example 1 by the method of Example 3. The tests made are those described in Example 4. Data are shown in Table IX. The vapor exposure method again gives the most satisfactory results overall.
TABLE IX.GOMPARISON OF SOLVENT APPLICATION METHODS Curtain coating Spraying Vapor exposure Solvent pickup, percent gain in wt 59 87 112 120 140 67 70 125 60 to 70 Surface oil test, grade 5+ 6 5 6 4 3 2 4 4 5 7 6 7 6 6 Static oil test, percent gain in wt 4 5 19 6 9 11 9 17 4 5 3 3 1 2 3 4 Static water test, percent gain in wt 33 34 44 33 40 37 34 39 37 40 31 36 31 31 32 34 Example 9The effect of various fluoropolymers.- A number of different copolymers were made according to the method of Example 1. The same fluoromonomer was used, but a number of different hydrocarbon ester monomers were used, all other materials being the same as in Example 1. Results of Static Oil and Water Tests and Surface Oil Tests are recorded for each copolymer applied to pigskin suede as described in Example 4, following solvent treatment as described in Example 4. The data are shown in Table X.
These data show that the copolymer is effectively distributed through the cross sectional area of the leather, providing oil and water repellency over the life of the leather article.
The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described, for obvious modifications will occur to those skilled in the art.
TABLE X Static Static Percent oil test, water test, used in percent percent Surface oil Comonomer copolymer wt. gain wt. gain test, grade 2-ethylhexylmethacrylate- 2. 5 43 6 N-Octyl methaerylate 35 l. 3 37 6 n-Dodecyl methacrylate 35 4. 4 51 6 Cir-methacrylate 35 7. 4 69 6 n-Butyl methacrylate 35 11. 3 66 5 Homopolymcr of I*(CF2) nOHZCHZOCOC (OH3)=CH2 63 91 1 Control, no treatment 75 0 While all of the copolymers tested showed good improvement in water and oil repellency eifects, the most eifective are those where the hydrocarbon chain length is in the C to C range.
Example 10--Eifect of a sulfonamide fluoropolymer.-- A copolymer of chloroprene and prepared as in Example 3 part D of US. Pat. 3,068,187 was applied to pigskin suede by wet drumming after fat liquoring. The amount used, 0.6% based on dyed leather weight, was completely taken up by the leather. The sample was then dried, staked, buffed and vapor treated with trichloroethylene as in Ex. 4, then tested as in Ex. 5. Surface oil test grade improved from 0 before treatment to 5 after treatment. Static oil pick-up improved from 75% before treatment to 12% after treatment. Static water pick-up improved from 100% before treatment to 55% after treatment.
Example 1lDistribution of fluoropolymer within the leather. In order to determine the quantitative effect of the solvent treatment of the invention in distributing the fluorocopolymer of Example 1 in the leather, samples were carefully sectioned into a bottom (hair) side, a center section and a top (buffed) side. After treatment with 0.5% of the copolymer (based on weight of leather), as described in Example 3 and the solvent treatment of Example 4, whole pieces of unsectioned leather had a fluorine content of from 0.25% to 0.45% depending on the weight and density of the skin and on the degree of bufling used. Generally the bottom or grain side contained the most fluorine because it is most porous and is not buffed. The flesh or top side contained less fluorine because of the bufling, while the denser center section contained the least fluorine. The results of a number of such tests are shown in Table XI.
The embodiments of the invention in which an exclusive property or privilege is claimed are as follows:
1. Process for imparting oil and water repellency to leather which comprises intimately contacting, at a temperature of between 35 C. and 140 C., leather pretreated with an aqueous dispersion of an oil and water repellent organic fluoropolymer having a pendant perfluoroalkyl group of 4-14 carbon atoms until the leather contains about 0.25% to about 1.0% of the fluoropolymer based on the weight of the leather, with a solvent which has a boiling point between 35 C. and 210 C., which dissolves the fluoropolymer in an amount of at least 0.1 percent by weight based on the weight of solvent as measured at 25 C, and which is selected from hydrocarbons, halogenated hydrocarbons, ketones or esters, for a time sufiicient for the pretreated leather to uniformly absorb about 40 percent to about percent by weight solvent based on the weight of the leaher; followed by drying the leather.
2. The process of claim 1 wherein the solvent has a boiling point of between 40 C. and C.
3. The process of claim 2 wherein the solvent is a halogenated hydrocarbon.
4. The process of claim 3 wherein the solvent is a halogenerated hydrocarbon of up to five carbon atoms and wherein the halogen substituents are selected from the class consisting of fluorine, chlorine, and mixtures of both.
5. The process of claim 4 wherein the halogenated hydrocarbon is selected from trichloroethylene, methyl chloroform, tetrachloroethylcne, perchloroethylene, 1,1, 2,Z-tetrachloro-2-fluoroethane and 1,1,2 trichloro-1,2,2- trifluoroethane.
6. The process of claim 1 wherein the leather is intimately contacted with the solvent by subjecting the leather to an atmosphere of the solvent vapor.
7. The process of claim 6 wherein the atmosphere is substantially a one hundred percent atmosphere of the solvent vapor.
8. The process of claim 6 wherein the solvent is a halogenated hydrocarbon of up to five carbon atoms and wherein the halogen substituents are selected from the class consisting of fluorine, chlorine and mixtures of both.
9. The process of claim 1 wherein the fluoropolymer is a copolymer of an acrylate or methacrylate ester which 11 12 contains pendant perfluoroalkyl groups of 4 to 14 car- 3,081,274 3/ 1963 Heine et a1. 117142 bon atoms, and a nonfiuorinated acrylate or methacrylate 3,236,672 2/1966 Shane et a1. 117-1355 ester WILLIAM D. MARTIN, Primary Examiner References Cited UNITED STATES PATENTS' 2,766,134 10/1956 Davis 117-63 US. Cl. X.R. 3,034,925 5/1962 De Marco et a1. 117135.5 117 135 5 142; 94 2 9433 5 W. R. TRENOR, Assistant Examiner