A chrome-free tanning process of an ecological leather is characterized by a TWS+sodium lignosulfonate+TWLZ ternary tanning process system. The sodium lignosulfonate added can not only have a fixation effect on a TWS tanning agent to make the TWS tanning not undergo detanning at a low pH, but also significantly improve the uniformity of distribution of a TWLZ tanning agent in a hide/skin and promote the formation of a stable cross-linked network structure by the TWLZ tanning agent in a collagen fiber, which effectively overcomes the defects of tanning performance of the existing tanning systems to obtain a leather with uniform and sufficient tanning, a high isoelectric point, a strong electropositivity, excellent absorption for post-tanning chemicals, and a prominent softness, and gives a leather a wide use range and a high quality.

A chrome-free tanning process of an ecological leather is characterized by a TWS+sodium lignosulfonate+TWLZ ternary tanning process system. The sodium lignosulfonate added can not only have a fixation effect on a TWS tanning agent to make the TWS tanning not undergo detanning at a low pH, but also significantly improve the uniformity of distribution of a TWLZ tanning agent in a hide/skin and promote the formation of a stable cross-linked network structure by the TWLZ tanning agent in a collagen fiber, which effectively overcomes the defects of tanning performance of the existing tanning systems to obtain a leather with uniform and sufficient tanning, a high isoelectric point, a strong electropositivity, excellent absorption for post-tanning chemicals, and a prominent softness, and gives a leather a wide use range and a high quality.

The present invention is directed to a process for retanning leather comprising the steps of: a) providing tanned or pre-tanned leather b) treating the tanned leather of step a) with a composition comprising hollow microspheres, preferably as an aqueous composition, the hollow microspheres have a true density of from 0.01 to 0.10 g/cm.sup.3 (25? C.) and/or a bulk density of the dry powder of 0.005 to 0.06 g/cm.sup.3 (25? C.), c) drying, whereby the temperature of the leather during drying does not exceed 75? C. as well as to leather obtained by said process.

The present invention is directed to a process for retanning leather comprising the steps of: a) providing tanned or pre-tanned leather b) treating the tanned leather of step a) with a composition comprising hollow microspheres, preferably as an aqueous composition, the hollow microspheres have a true density of from 0.01 to 0.10 g/cm.sup.3 (25? C.) and/or a bulk density of the dry powder of 0.005 to 0.06 g/cm.sup.3 (25? C.), c) drying, whereby the temperature of the leather during drying does not exceed 75? C. as well as to leather obtained by said process.

A chrome-free tanning process of an ecological leather is characterized by a TWS+sodium lignosulfonate+TWLZ ternary tanning process system. The sodium lignosulfonate added can not only have a fixation effect on a TWS tanning agent to make the TWS tanning not undergo detanning at a low pH, but also significantly improve the uniformity of distribution of a TWLZ tanning agent in a hide/skin and promote the formation of a stable cross-linked network structure by the TWLZ tanning agent in a collagen fiber, which effectively overcomes the defects of tanning performance of the existing tanning systems to obtain a leather with uniform and sufficient tanning, a high isoelectric point, a strong electropositivity, excellent absorption for post-tanning chemicals, and a prominent softness, and gives a leather a wide use range and a high quality.

A chrome-free tanning process of an ecological leather is characterized by a TWS+sodium lignosulfonate+TWLZ ternary tanning process system. The sodium lignosulfonate added can not only have a fixation effect on a TWS tanning agent to make the TWS tanning not undergo detanning at a low pH, but also significantly improve the uniformity of distribution of a TWLZ tanning agent in a hide/skin and promote the formation of a stable cross-linked network structure by the TWLZ tanning agent in a collagen fiber, which effectively overcomes the defects of tanning performance of the existing tanning systems to obtain a leather with uniform and sufficient tanning, a high isoelectric point, a strong electropositivity, excellent absorption for post-tanning chemicals, and a prominent softness, and gives a leather a wide use range and a high quality.

A method for forming chrome-free retanned leather including: (a) contacting wet white with from 1% to 8%, by solids weight, based on the wet weight of wet white, retanning agent selected from the group consisting of: i) an aqueous emulsion polymer including, as copolymerized units, from 2% to 35%, by weight, based on the weight of the emulsion polymer, ethylenically-unsaturated monomer bearing at least one epoxy group, the emulsion polymer having a weight average molecular weight of from 2,000 to 100,000; ii) a compound selected from the group comprising piperazine, piperazine hydrates, salts of piperazine, and combinations thereof; and iii) combinations of i) and ii); (b) heating the contacted wet white; and (c) drying the contacted, heated wet white is provided. The present application also relates to chrome-free retanned leather formed by the method of the invention.

A method for forming chrome-free retanned leather including: (a) contacting wet white with from 1% to 8%, by solids weight, based on the wet weight of wet white, retanning agent selected from the group consisting of: i) an aqueous emulsion polymer including, as copolymerized units, from 2% to 35%, by weight, based on the weight of the emulsion polymer, ethylenically-unsaturated monomer bearing at least one epoxy group, the emulsion polymer having a weight average molecular weight of from 2,000 to 100,000; ii) a compound selected from the group comprising piperazine, piperazine hydrates, salts of piperazine, and combinations thereof; and iii) combinations of i) and ii); (b) heating the contacted wet white; and (c) drying the contacted, heated wet white is provided. The present application also relates to chrome-free retanned leather formed by the method of the invention.

A recycling process for achieving near-zero emissions of tannery effluent is characterized in that effluent recycling is carried out independently in soaking, liming, re-liming, de-liming bating, pickling chrome tanning, re-tanning, neutralizing, and dyeing procedures. The effluents in the above procedures can be recycled in each step. This process greatly reduces effluent discharge and helps solve the problem of tanning pollution. The process also improves the quality of the finished leather, effectively decreases loose grain rate and increases compactness and fullness of the finished product. The project can reduce chemical material consumption by 15%-55%. For example, the consumption of chromium powder can be reduced up to 65%. Consumption of other chemical materials can be reduced by more than 90%, while certain chemical materials can be essentially completely conserved.

A recycling process for achieving near-zero emissions of tannery effluent is characterized in that effluent recycling is carried out independently in soaking, liming, re-liming, de-liming bating, pickling chrome tanning, re-tanning, neutralizing, and dyeing procedures. The effluents in the above procedures can be recycled in each step. This process greatly reduces effluent discharge and helps solve the problem of tanning pollution. The process also improves the quality of the finished leather, effectively decreases loose grain rate and increases compactness and fullness of the finished product. The project can reduce chemical material consumption by 15%-55%. For example, the consumption of chromium powder can be reduced up to 65%. Consumption of other chemical materials can be reduced by more than 90%, while certain chemical materials can be essentially completely conserved.