Bleaching and dyeing; fluid treatment and chemical modification – Treatment of hides – skins – feathers and animal tissues – Leather dehydration
Reexamination Certificate
2000-10-19
2003-12-16
Gupta, Yogendra N. (Department: 1751)
Bleaching and dyeing; fluid treatment and chemical modification
Treatment of hides, skins, feathers and animal tissues
Leather dehydration
C008S094150, C008S09419C
Reexamination Certificate
active
06663676
ABSTRACT:
This invention is concerned with a process for the preparation of an aqueous composition for treating leather. In particular, this invention concerns a process involving the use of hygroscopic particles.
Leather processors involved with the wet end treatment of leathers tend to prefer the chemicals used in their tanneries, particularly the more hazardous chemicals, to be supplied from the manufacturers in a liquid format, such as a solution, suspension, dispersion or emulsion, rather than in a solid format, such as a powder. The reason for this is derived from the problems associated with handling hazardous chemicals in confined environments: liquids do not suffer the dusting problems associated with powders. Indeed, it is the dusting issue which is of increasing concern to the leather processors and formulators, as the presence of even a low quantity of dust in the atmosphere of a factory may provide a health risk to workers or pose a combustion risk.
Although supplying chemicals in a liquid format overcomes the dusting problem, liquids can be more expensive to transport than chemicals in a solid format.
Though many powdered products currently supplied to the leather processors are dusting, such as phenolic retanning agents, it is expected that health and safety legislation in many countries may soon force leather processors to reduce worker exposures to dusting materials.
Some powdered products, such as dyes, include an anti-dusting aid/agent, such as a mineral oil, to render the powders non-dusting. However, because the anti-dusting oil is included into the tanning mill with the powdered dye, the resultant leathers become impregnated with the anti-dusting oil. Anti-dusting oil in dyestuffs and other solid additives is a major contributor to fogging, a particularly detrimental characteristic in an automotive or aircraft leather.
South African patent application 9711432 discloses compositions for the simultaneous retanning and fatliquoring of pretanned leather pelts. The compositions are presented in such a form that they give a homogeneous mixture when added to at least 8 times the amount of water at from 10 to 60° C. The compositions are preferably in the form of a solid, but may also be in the form of a solution, dispersion or emulsion. The compositions are disclosed to be non-dusting. This non-dusting property is believed to derive from the presence in the composition of the fatliquoring agent. Fatliquoring agents are fatty, oily or waxy in nature, so have inherently a dust-suppressing effect on the disclosed solid retanning agents. Since the compositions are manufactured by the supplier prior to delivery to the tannery, the supplier has in effect fixed the relative concentrations of retanning and fatliquoring components of the solid composition, thereby limiting the leather processor from varying the concentrations of these components at the tannery. Whilst this may be acceptable to some leather processors, leather processors generally prefer to retain their freedom to vary the retanning and fatliquoring component concentrations themselves, thereby to give them opportunity to change processing conditions, for example when different reaction conditions are required to produce a different effect on the finished leather, or when the quality or type of leather to be treated is changed and different reaction conditions are required to produce the same effect on the finished leather. There is no disclosure or suggestion in the South African patent application that a retanning agent may be supplied in a solid format optionally in the absence of a fatliquoring agent.
Homopolymers of acrylic acid (polyacrylic acid), copolymers comprising more than 50 wt % polymerised acrylic acid, and basic salts thereof, herein individually and jointly referred to as polymers of acrylic acid, have been used for many years in the wet end treatment of leathers as retanning agents. Such retanning agents have always been supplied to leather processors in a liquid format: polyacrylic acid is soluble in water, so retanning agents based on polyacrylic acid are supplied to leather processors as aqueous solutions; copolymers comprising more than 50 wt % polymerised acrylic acid may be soluble or insoluble in water so, depending upon the hydrophobicity of the polymerised co-monomer(s) and/or the extent of neutralization, have always been supplied to leather processors as aqueous solutions or aqueous suspensions, dispersions or emulsions.
It is an object of the present invention to provide a process for rendering solid leather processing chemicals less dusting. Preferably, the process can be used on a broad range of solid leather treatment chemicals, such as on powdered enzymes to reduce dusting during handling in the bating step of the leather making process, and on powdered tanning chemicals such as chromium sulphate or vegetable extracts to reduce dusting during handling in the tanning step of leather making.
In another aspect, it is an object of the present invention to provide a solid, non-dusting composition intended to be dissolved or dispersed directly into a predetermined amount of water and then used as a retanning agent in the wet end treatment of leather, which composition does not essentially require the presence of a fatliquoring agent or other ingredient to render the composition substantially non-dusting.
In another aspect, it is an object of the present invention to provide a substitute for an anti-dusting oil, which substitute does not contribute to fogging in a leather.
In accordance with the present invention there is provided a method of preparing a composition for treating leather, which method comprises adding a predetermined amount of a solid particulate leather treatment composition into a predetermined amount of aqueous diluent or carrier in a vessel at a tannery which solid particulate composition comprises 0.1 wt % or more based on the total weight of said particulate composition of a particulate hygroscopic material; and dissolving or dispersing said solid particulate composition in said aqueous diluent or carrier.
In accordance with another aspect of the present invention, there is provided an article of commerce comprising i) a solid particulate leather treatment composition comprising 0.1 wt % or more based on the total weight of said particulate composition of a particulate hygroscopic material; ii) packaging suitable for receiving, transporting and storing said solid particulate composition without exposing said solid particulate composition to moisture and; and iii) instructions for the handling of said solid particulate composition at the tannery, including instructions for dissolving or dispersing a predetermined amount of said particulate composition directly into a predetermined amount of aqueous diluent or carrier in a vessel. In one embodiment, where the packaging is soluble in aqueous environments or readily destroyed by the mechanical action of the tanning mill, the article of commerce is added directly to the water or other aqueous diluent or carrier in the tanning mill.
In accordance with another aspect of the present invention, there is provided the use in the preparation at a tannery of an aqueous composition for treating leather, such as a bating, tanning, retanning or dying composition, of a solid particulate leather treatment composition comprising 0.1 wt % or more based on the total weight of said particulate composition of a particulate hygroscopic material.
In accordance with another aspect of the present invention, there is provided a process of rendering a solid, dusting leather treatment composition non-dusting, which method comprises admixing a particulate solid, dusting leather treatment composition with a particulate solid hygroscopic material to form an admix, which hygroscopic material is present in said admix in an amount of at least 0.1 wt % based on the total weight of said admix.
In accordance with another aspect of the present invention, there is provided the use of a hygroscopic material as an anti-dusting agent in a solid particulate leat
El A'mma Anton Georges
Fritsche Monika Ulrike
Hodder James John
Greenblatt Gary D.
Gupta Yogendra N.
Kumar Preeti
Rohm and Haas Company
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