A process for the simultaneous tanning and dyeing of collagen containing fibrous material, wherein the said material is treated with a liquor containing at least one reactive dyestuff selected from the group of formula (1) and (2)

##STR00001## wherein A.sub.1, A.sub.2 and A.sub.3 are each independently of the others the radical of a monoazo, polyazo, metal-complexed azo, anthraquinone, phthalocyanine, formazan or dioxazine chromophore having at least one sulfo group, B is an organic bridge member, Q.sub.1, Q.sub.2, Q.sub.3 and Q.sub.4 are each independently of the others hydrogen or unsubstituted or substituted C.sub.1-C.sub.4alkyl, G.sub.1 and G.sub.2 are halogen, 3-carboxypyridin-1-yl or 3-carbamoylpyridin-1-yl, (Z.sub.1).sub.2-3 is 2 to 3 identical or different fiber reactive radicals, Z.sub.2 and Z.sub.3 are each independently of the other identical or different fiber reactive radicals, and b is the number 0 or 1, by combining two steps of leather production, tanning and dyeing, into a single step, thus, preserving resources and reducing the environmental impact.

A process for the simultaneous tanning and dyeing of collagen containing fibrous material, wherein the said material is treated with a liquor containing at least one reactive dyestuff selected from the group of formula (1) and (2)

##STR00001## wherein A.sub.1, A.sub.2 and A.sub.3 are each independently of the others the radical of a monoazo, polyazo, metal-complexed azo, anthraquinone, phthalocyanine, formazan or dioxazine chromophore having at least one sulfo group, B is an organic bridge member, Q.sub.1, Q.sub.2, Q.sub.3 and Q.sub.4 are each independently of the others hydrogen or unsubstituted or substituted C.sub.1-C.sub.4alkyl, G.sub.1 and G.sub.2 are halogen, 3-carboxypyridin-1-yl or 3-carbamoylpyridin-1-yl, (Z.sub.1).sub.2-3 is 2 to 3 identical or different fiber reactive radicals, Z.sub.2 and Z.sub.3 are each independently of the other identical or different fiber reactive radicals, and b is the number 0 or 1, by combining two steps of leather production, tanning and dyeing, into a single step, thus, preserving resources and reducing the environmental impact.

Provided is a hexavalent chromium treatment agent capable of penetrating inside of a leather and capable of reducing not only hexavalent chromium present in the vicinity of the surface of the leather but also hexavalent chromium present inside the leather into trivalent chromium. The hexavalent chromium treatment agent of the present invention comprises a hexavalent chromium-reducing compound capable of reducing hexavalent chromium into trivalent chromium, a nonionic surfactant, and an aqueous solvent. The hexavalent chromium-reducing compound preferably comprises an organic compound (A) that has a specific structure capable of acting to reduce hexavalent chromium into trivalent chromium, that has a hydroxyphenyl group, and that has no aldehyde groups and no carboxyl groups.

Provided is a hexavalent chromium treatment agent capable of penetrating inside of a leather and capable of reducing not only hexavalent chromium present in the vicinity of the surface of the leather but also hexavalent chromium present inside the leather into trivalent chromium. The hexavalent chromium treatment agent of the present invention comprises a hexavalent chromium-reducing compound capable of reducing hexavalent chromium into trivalent chromium, a nonionic surfactant, and an aqueous solvent. The hexavalent chromium-reducing compound preferably comprises an organic compound (A) that has a specific structure capable of acting to reduce hexavalent chromium into trivalent chromium, that has a hydroxyphenyl group, and that has no aldehyde groups and no carboxyl groups.

A process is provided for obtaining a tannin extract isolated from grapes using grape seeds. The process comprises: preparing the grape seeds as the source of tannins; preparing an aqueous solution of a polyphenol-solubilising agent selected from urea, a compound containing the SO.sub.3 group and sodium hydroxide at concentration ranging between 1% and 15% by weight; performing a single extraction in an autoclave reactor; separation and direct concentration in order to produce the isolated extract. The invention also relates to the tannin extract obtained. The new tannin extract isolated from grape seeds comprises a mixture of tannins and non-tannins, the composition whereof provides the extract with improved antioxidant and light fastness properties. The tannin extract isolated from grape seeds further comprises a colouring agent.

The present invention relates to the use of reactive colourless and metal-free protein cross-linking agents for the cross-linking (tanning) of protein-containing substrates, said agents are environmentally friendly and give an improved fixation yield, a long-term cross-linking (tanning) stability and good washing off properties. The present invention further relates to processes for the cross-linking (tanning) of protein-containing substrates thereby creating an environmentally friendly process which minimizes the use of chemicals and further improves the quality and efficiency of the tanning and dyeing process.

##STR00001##

A process for obtaining a tannin extract isolated from whole grape seeds is provided. The process is performed in as a one-pot reaction and in a single extraction step, wherein the seeds are processed without grinding or milling. Also provided is a tannin extract with improved antioxidant and light fastness properties obtained from whole grape seeds that includes a mixture of tannins and non-tannins, in which the content of tannins or polyphenols is higher than 50%. Ise, the tannin extract isolated from whole grape seeds can include a coloring agent.

A process for obtaining a tannin extract isolated from whole grape seeds is provided. The process is performed in as a one-pot reaction and in a single extraction step, wherein the seeds are processed without grinding or milling. Also provided is a tannin extract with improved antioxidant and light fastness properties obtained from whole grape seeds that includes a mixture of tannins and non-tannins, in which the content of tannins or polyphenols is higher than 50%. Ise, the tannin extract isolated from whole grape seeds can include a coloring agent.

A method for tanning an animal substrate comprising the steps: i) agitating the animal substrate with a chromium-free tanning agent; and ii) agitating the animal substrate with a tanning agent having an oxazolidine group; wherein at least some of the agitation is performed in the presence of a solid particulate material having an average particle size of from 1 to 500 mm.

A method for tanning an animal substrate comprising the steps: i) agitating the animal substrate with a chromium-free tanning agent; and ii) agitating the animal substrate with a tanning agent having an oxazolidine group; wherein at least some of the agitation is performed in the presence of a solid particulate material having an average particle size of from 1 to 500 mm.