US2273973A - Artificial leather - Google Patents

Description

Patented Feb. 24, 1942 I OFFICE ARTIFICIAL LEATHER Robert C. Medl, Jr., Newark, Del, assignoi-- to Hercules Powder Company, Wilmington, Del., a corporation of Delaware No Drawing.

2 Claims.

This invention relates to improved artificial leather and more particularly to artificial leather capable of retaining its flexibility at extremely low temperatures.

Artificial leather has heretofore been manufactured by coating 9. flexible composition of nitrocellulose, softeners, and pigment upon a fiexible base such as a moderately heavy cotton cloth or fibrous felt. It has not heretofore been wholly satisfactory for automobile upholstery in cold weather because of the coating becoming brittle at low temperatures. This has been true even when the best nitrocellulose softener for low temperature flexibility used by the art, namely raw castor oil, has been the sole softener of the coating. Actually, raw castor oil as the sole softener is not satisfactory for automobile artificial leather, as it is exuded when the coating is exposed to the sun in very hot weather. This is prevented by using polymerized oils, in part at least, or-adding other softeners. Usually such modification increases the brittleness of the coating at low temperatures.

It is an object of this invention to provide artificial leather which is flexible at very low temperatures and which is free from the defect of exuding softener when heated:

Artificial leather in accordance with this invention comprises a moderately heavy web-like flexible base and thereon a flexible coating comprising nitrocellulose and a softener selected from the group consisting of the lower aliphatic esters of ricinoleic acid, the lower aliphatic esters of polymerized ricinoleic acid, the lower aliphatic esters of ricinoleic acid which has its hydroxyl group esterified-with a lower fatty acid, and the lower aliphatic esters of polymerized ricinoleic acid which has its hydroxyl esterified with a lower fatty acid. Pigments, fillers, and other softeners may be included in the coating.

Artificial leather in accordance with this invention retains its flexibility at very low temperatures. If desired, an artificial leather in accordance with this invention may be made which retains its flexibility at a temperature as low as 35 F.; that is, its coating is not cracked at -3S F. by the cold crack. test hereinafter described. By this same test, the nitrocellulose artificial leather heretofore best in flexibility at low temperatures, namely one with its coatirg softened by raw castor oil, fails at about ,1. Furthermore, the improved artificial leather does not exude softener when heated as by the sun in very hot weather.

The lower aliphatic esters which are utilized as Application November 23, 1938, Serial No. 241,989

softeners in this improved artificial leather may be, for example, the methyl, ethyl, or butyl esters, and so forth. The esters of polymerized ricinoleic acid and of polymerized ricinoleic acid which has its hydroxyl esterified with a lower fatty acid may be derivatives of ricinoleic acid polymerized by heating, oxidizing. or both. The esters of ricinoleic acid and polymerized ricinoleic acid which have their hydroxyls esterified with a lower fatty acid may be, for example, the esters of acetylated ricinoleic acid or esters of acetylated polymerized ricinoleic acid, or the same propionylated instead of, acetylated, etc. In general, the butyl ester of acetylated ricinoleic acid is preferably utilized.

The nitrocellulose utilized in the coating is one soluble in the usual artificial leather coating dope solvents. Preferably, it has a nitrogen content of about 11 to about 12.6.% Its viscosity is preferably above that of the type known as RS 100 second nitrocellulose but a useful artificial leather can be made with 15 second nitrocellulose or lower viscosity nitrocellulose, although toughness decreases as viscosity is lowered.

The moderately heavy web-like flexible base which is utilized in the improved artificial leather may be any one of the usual bases of artificial leather such as a cotton or other cloth of sheeting, sateen, broken twill, etc. construction, or such as a fibrous felt of similar thickness, or a latex impregnated felt, and so forth. Such bases vary in weight from about 3 to about 12 ounces per square yard.

The improved artificial leather in accordance with this invention may have, for example, from about 3 to about 14 ounces, say about 8 ounces, dry weight of the coating composition deposited per square yard of the flexible base. This coating will desirably comprise an amount of one of the ricinoleic ester softeners hereinbefore mentioned within the range of about to about 200%, and preferably within the range of about to about by weight. of the nitrocellulose contained therein. It will be appreciated that where softer coatings are desired, more softener may be used and that where harder coatings are desired, less softener may be used. It will also be appreciated that there is variation .in the degree of softness imparted by the various said softeners.

When the improved artificial leather contains as its only softener one of the hereinbefore mentioned ricinoleate esters, it may retain its flexibility at a temperature as low as 35 F., as does, for example, the artificial leather later described in Example 1. Usually, flexibility at so extremely low a temperature is not necessary, allowing modification with other softeners to improve resistance to sunlight or to lower the cost. One or more additional softeners, such as vegetable oil softeners, for example, raw castor oil, polymerized eastor oil, polymerized cottonseed oil, the mixture of pohlmerized rapeseed oil and castor oil known as Baker's blended oil," and so forth; or such as resinous softeners, for example, the condensation product of an omega-omega dicarboxylic acid and a polyhydric alcohol or alcohols known as Paraplex RG 2 and so forth, or such solvent softeners as. for example tricresyl phosphate, may be used to replace part of the hereinbefore described ester. However, the additional softener used is limited to those softeners compatible with a mixture of nitrocellulose and one of the ricinoleic ester softeners hereinbefore described. Thus it has now become possible to include in the coating softeners such as "Baker's blended oil and "Paraplex RG 2" which impart resistance to sunlight and at the same time to obtain an artificial leather flexible at low temperatures. In general, the greater the portion of the total softener consisting of one of the ricinoleic ester softeners hereinbefore described, the lower will be the temperature at which the coating becomes brittle. In general also, .the greater the portion of the total softener consisting of a highly polymerized softener, the higher will be the temperature at which the coating becomes brittle. v When a second softener is used, the ratio of total softener to nitrocellulose varies with the particular material used as the second softener,

- In general, the coating will comprise about the The coatings of the improved artificial leather are preferably pigmented. Desirably, the pigments utilized will comprise materials high in covering power, such as for example, titanium dioxide, and especially materials which are also highly opaque to ultraviolet light such as, for example, lead titanate and carbon black. Howby the pressure of heated engraved plates or rollers to impart grain or other designs.

The cold crack test herein used to measure the temperature at which an artificial leather coating becomes brittle and is cracked by very rough handling, will now be described. A strip of artiflcial leather by 4" is hung in a closed chamber for 30 minutes in circulating air at a controlled temperature. The strip is then picked up by the ends with gloved hands and quickly and vigorously bent 180 over a 1 s" mandril rigidly mounted'in the chamber, at the same time pulling the length of the strip over the mandril, the coated side being away from the mandril. The highest temperature at which the coating cracks is the temperature of failure.

Following are examples to illustrate the artificial leather according to this invention. Proportions are in parts by weight.

Example I A coating dope according to composition 1 of Table l was prepared by dispersing 75 parts of ever, any of the usual pigments of the artificial leather art may be used.

The artificial leather in accordance with this invention may be prepared by any of the common methods of the art. Conveniently, a coating dope is prepared by mixing alcohol-wet nitrocellulose, softener or softeners, pigment paste made by dispersing pigment in a portion'of the softener, and solvents in a vessel equipped with suitable means of agitation until a smooth dope is obtained. The solvents may be any of the usual nitrocellulose coating solvents such as, for example, a mixture of 30% ethyl acetate, 20% alcohol, and 50% toluene. The dope may then be spread on the hereinbefore described flexible base, smoothed by a doctor blade, and the coat dried, preferably at an elevated temperature.

= Additional coats may be applied until the desired thickness is obtained. The softness of the various coats may be varied. The quantity of pigment may also be varied in the different coats.

The smooth artificial leather may be embossed Paraplex RG 2 the pigment in 25 parts of the softener on a three roll mill and then mixing a portion of the resulting paste with the proper quantities of the other ingredients.

Table 1 I Composition No.

Buty ester of acetylated ricinoleic ac Ethyl ester of aoet lated l mcrized ricinoleic aeidflnfyj Methyl ricinoleate "Baker's blended oil". Raw castor oil Nitrocellulose,

2% nitrogen 150 slty Red iron oxide p gment. Carbon black pigment. Solvent Solvent composition was:

207 butyl acetate by weight. g ethyl acetate by Weight. alcohol by weight. 45% toluene by weight.

The mixture was worked to a smooth dope in a closed vessel equipped with a slow-moving agitator. The dope was then applied to cotton sateen cloth weighing '1 ounces per square yard with a knife coater in approximately twenty coats, drying after each coat,,to obtain a coating weighing 10 ounces per square yard when dry. The coated cloth was then embossed at 160 F.

and 1500 lbs. per square inch pressure for one were used instead of 55 parts of the butyl ester of acetylated ricinoleic acid, was found to fail at 0 F. in the same cold crack test. Furthermore," it exuded oil when heated one hour at to F. The usual requirement of the automobile industry is that no exudation of sofigiaerpoccur upon heating one hour at to smears 3 Example I! A coating dope according to composition No. 2

of Table 1 was prepared in the manner of Example 1 except that the pigment paste was made by dispersing 70 parts or the pigment in 30 parts "Baker's blended oil. The dope was coated upon cotton broken twill cloth weighing 9 ounces per square yard in the manner of Example 1 until 9 ounces per square yard of dry coating had. been applied. It was embossed in the manner of Example I.

This artificial leather required cooling to at least as low a temperature as -15 F. to crack the coating by the hereinbefore described cold crack test. It did not exude oil when heated one hour at 200 F. It required 40% longer exposure to artificial sunlight furnished by a glassenclosed cored-carbon arc to be rendered brittle so that the coating cracked wherever it was bent 180' over a inch mandrilthan did artificial leather with a coating of nitrocellulose softened with raw castor oil similarly pigmented and similarly prepared upon a similar base, and similar in softness at 70 F.

Example I III A coating dope according to composition No. 3 of Table l was prepared in a manner similar to that of Example 1 except that the pigment paste was made by dispersing 72 parts of the pigment in 28 parts of raw castor oil. The dope was coated upon cotton broken twill cloth weighing 9 ounces per square yard in the manner of Example 1 until a coating weighing when dry about 8 to 9 ounces per square yard was obtained. The coated cloth was embossed in the manner of Example '1.

This artificial leather required cooling to at least as low a temperature as -15 F. to crack the coating by the hereinbeiore described cold crack test. It did not exude oil when heated one hour at 175 F.

Example IV A coating dope according to composition No. 4 of Table l was prepared in a manner similar to that of Example 1 except that the pigment paste was made by dispersing 75 parts or the pigment in 25 parts of a mixture of half butyl acetyl ricinoleate and half raw castor oil. The dope' to artificial sunlight to a condition oi brittleness such that any 180' bend over a 3," mandril caused cracking of the coating, was better than that of an artificial leather differing only in that the softener of this example was replaced by raw castor 011.

Example V A coating dope according to composition No. 5 of Table 1 was prepared in the manner of Example 1 except that the pigment paste was made by dispersing 6 parts of the pigment in a mixture of 30 parts of the ethyl ester of acetylated polymerized ricinoleic acid and 30 parts Baker's blended voil. The dope was coated in the manner of Example 1 on cotton sheeting weighing 4.5

' ounces'per square yard until about 6 ounces per square yard of dry coating had been applied.

This artificial leather required cooling to as low a temperature as 15 F. to fail by the cold crack test hereinbefore described. It did not exude oil on heating one-hour at 200 F.

Example VI A coating dope according to composition No. 6 of Table 1 was prepared in the manner of Example 1 except that the pigment paste was made by dispersing 8 parts of the pigment in a mixture of 30 parts methyl ricinoleate and 30 parts Baker's blended oil. .The dope was coated in the manner of Example 1 on cotton sheeting weighing 4.5

ounces per square yard until about 6 ounces per square yard of dry coating had been applied.

This artificial leather required cooling to as low a temperature as 15 F. to fail by the cold crack test hereinbeiore described. It did not exude oil on heating one hour at 190 F.

It will be understood that the details and examples given hereinbeiore are illustrative only, and in no way limiting on my invention as broadly described hereinbeioreand in the appended claims.

What I claim and desire to protect by Letters Patent is: v

1. An artificial leather which is resistant to spewing at high temperatures and retains its flexibility at low tempeartures which consists of a fiexible base web and a coating oi a pigmented composition consisting of about 40 parts 0! nitrocellulom, about parts of butyl acetyl ricinoleate and about 30 parts of a mixture of castor oil and polymerized rapeseed oil.

2. An artificial leather which is resistant to spewing at high temperatures and retains its flexibility at low temperatures which consists of a base oi a broken twill cotton cloth and a coating of a pigmented composition consisting oi about 40 parts 01 nitrocellulose. about 30 parts 0! butyl acetyl ricinoleate and about 30 parts of a mixture oi castor oil and polymerized rapeseed oil.

ROBERT c. MEDL, Jn.