Bleaching and dyeing; fluid treatment and chemical modification – Treatment of hides – skins – feathers and animal tissues – Tanning
Patent
1993-06-30
1994-11-29
Willis, Jr., Prince
Bleaching and dyeing; fluid treatment and chemical modification
Treatment of hides, skins, feathers and animal tissues
Tanning
8 942, 8 9421, 8 9423, 252 857, 427389, C14C 900
Patent
active
053686098
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a softening filler for leather.
DESCRIPTION OF THE PRIOR ART
Animal hides or skins, for example of cattle, sheep, goats, pigs, deer, kangaroos, reptiles, are tanned with tanning agents, such as for example chromium, tannin, aldehyde, aluminium, zirconium, to produce tanned leather. The leather is then pared to a suitable thickness and subsequently treated with retanning agents, fillers, levelling agents or fat liquors to produce leathers with different properties for various applications. In other words, so many different properties and qualities are required that the leather cannot be processed in a single tanning process to meet the various requirements. Accordingly, the leather is treated in a second tanning process known as retanning. Various retanning agents are available according to the intended application. For example, retanning with chromium improves dyeing and softening properties while retanning with aldehyde provides soft and voluminous properties and is used for white leather as colorless tanning in the same way as aluminium or zirconium. The tanning agents also fill the leather and thus make it compact and inelastic; on the other hand, the resin-like tanning materials make the leather voluminous. Accordingly, retanning agents include fillers in the broader sense, polyurethane and polyacrylic acid resins in particular being used as fillers. These fillers have the disadvantage that they fix the leather fibers closely to one another, resulting in a reduction in flexibility. Accordingly, so-called fat liquor is often used for softening, exerting a softening effect on the leather fibers by impregnation of the leather with oil and fat. However, large quantities of fat liquor are required to make the leather sufficiently molt so that the leather becomes heavy and oily on its surface. Accordingly, softening with fat liquor is of limited practical value.
The problem addressed by the present invention was to provide a softening filler for leather which would provide the leather with considerable softness and with a light and highly voluminous feel without causing the leather fibers to adhere to one another or forming a greasy surface.
BRIEF DESCRIPTION OF THE INVENTION
The invention relates to a softening filler for leather comprising thermoexpansible microcapsules (TEMCs). The TEMCs used in accordance with the invention are microcapsules of a thermoplastic resin, in which a volatile liquid described, for example, in Japanese patent publication 42-26526 (1967) is enclosed.
Suitable TEMCs according to the invention expand at temperatures in the range from 60.degree. to 180.degree. C. and preferably at temperatures in the range from 80.degree. to 150.degree. C. and consist of a thermoplastic resin having a softening point of 70.degree. to 100.degree. C. and preferably 80.degree. to 85.degree. C. as the shell of the capsules. Suitable resins are polyvinyl chloride, polyvinylidene chloride, polyolefin, polyester, polyurethane, polyacrylate, polyvinyl acetate, polystyrene or copolymers thereof. The diameter of the microcapsules is preferably 1 to 200 .mu.m, more preferably 3 to 100 .mu.m and most preferably 5 to 50 .mu.m. The increase in the expansion volume of the capsules should be of the order of 5 to 70-fold and As preferably 10 to 60-fold.
DETAILED DESCRIPTION OF THE INVENTION
It is assumed that the TEMCs used as softening filler in accordance with the invention function by a mechanism whereby the microcapsules enter the space between the leather fibers, are subsequently expanded by heat and the space thus expanded makes the leather soft and voluminous. Accordingly, the quantity of fat liquor used can be reduced so that the weight of the final leather is reduced.
The TEMCs are dispersed in a suitable medium, preferably an aqueous medium, and the leather isimmersed in this dispersion in a rotating vat. Impregnation need not only be carried out in this way, but may also be carried out, for example, by allowing the TEMC dispersion to flow onto a
REFERENCES:
patent: 3914360 (1975-10-01), Gunderman et al.
patent: 4016326 (1977-04-01), Schaefer
patent: 4044176 (1977-07-01), Wolinski et al.
patent: 4837200 (1989-06-01), Kondo et al.
Chemical Abstracts, vol. 80, No. 10, Mar. 11, 1974, Columbus, Ohio; Abstract No.: 49291, Kedlaya, K. J., "Leather Lubricants", p. 71; col. 1.
Diamond Alan D.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Ortiz Daniel S.
Szoke Ernest G.
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