EP1941094B1

EP1941094B1 - Procedure for the processing of cellulose material to obtain a product similar to leather

Info

Publication number: EP1941094B1
Application number: EP06799880A
Authority: EP
Inventors: Claudio Tomaselli
Original assignee: OKINAWA Srl
Current assignee: OKINAWA Srl
Priority date: 2005-09-09
Filing date: 2006-09-04
Publication date: 2011-03-02
Anticipated expiration: 2026-09-04
Also published as: SM200500021A; EP1941094A1; ATE500379T1; WO2007030084A1; SM200500021B; DE602006020473D1

Abstract

A procedure for the production of material similar to leather in terms of consistency and appearance, in which the raw material is cellulose fibres impregnated with a copolymer dispersion. This raw material is subjected to the following processing stages: Dyeing; Softening; Fixing.

Description

TECHNICAL FIELD

This invention concerns a procedure for processing cellulose material, by means of dyeing and softening, to obtain an unalterable finished material.
More specifically, this invention refers to a dyeing and softening process of cellulose material that makes it possible to obtain a finished product similar in appearance and resistance to leather, and resistant to water, that is to say to washing with detergents and in washing machines, or to dry cleaning professes with ethylene perchlorate.
The procedure according to the invention substantially foresees the use of a method for processing animal skins employed in tanning, using cellulose as the raw material, to obtain a finished skin to be used for manufacturing leather products, with the feature of not altering if subjected to water washing or dry cleaning.
This invention can be applied in the sector for the production of fabrics and products similar to leather used in clothing, furnishing and coverings in general.

BACKGROUND ART

It is known that in the sector of fabrics and materials for coverings, furnishing and clothing there has always been a demand for the production of natural materials derived from artificial products or from other natural but less expensive products.
The typical example is leather, which has been proposed in an artificial form, or reprocessed or recomposed also with natural products in a plurality of solutions, some of which are described below.
The US patent US 4,212,927 proposes a process for the production of artificial leather that foresees the processing of cellulose fibres with aqueous baths following the techniques used for the production of paper. In particular, the process foresees:

placing the support made from fibres in an aqueous dispersion containing at least one bonding agent;
impregnating the fibre support with a water bath containing at least one macromolecule chosen from a group containing acrylic polymers and copolymers;
covering the fibre support with a water bath containing at least one macromolecule chosen from a group containing vinyl and acrylic polymers and copolymers to obtain an intermediate layer;
subjecting the material thus obtained to coating by means of a water bath containing at least one macromolecule chosen from a group containing vinyl and acrylic polymers and copolymers and at least one coalescent agent to obtain a finish layer.

The solution proposed in the Italian patent IT 1.178.956 , on the other hand, foresees implementation of a procedure to obtain synthetic skins similar to natural ones, subjecting porous synthetic materials (synthetic leather), imitating natural skins, to a procedure comparable to tanning.
This patent shows that subjecting a synthetic material to a tanning process produces a product similar to leather even though tanning is not designed to characterize a product but to prevent it from rotting.
The sheet base consists of a vacuolated polyurethane matrix with internal polyester or polyethylene fibres and a coating of polyurethane resin printed with a design similar to natural leather.
According to this patent, the sheet material is subjected to:

a) wetting in drums with water at 50-60°C with surfactants added;
b) the action of an aqueous solution of bi-trivalent metallic salts (tanning-like saline solutions);
c) if necessary, additional processing with an aqueous solution of polyaldehyde;
d) a tanning-like action with caustic soda;
e) a process of greasing with an emulsion of mineral oils and/or fatty acid esters.

The dyeing phase is carried out after greasing with sulphonated esters in a rotating drum for a couple of hours with mixtures of specific metallocomplex dyes for polyester fibres and polyurethane polymers.
These solutions are, however, subject to very obvious practical problems substantially concerning the limits from the point of view of consistency and resistance of the material obtained.
The first solution foresees the use and processing of cellulose and involves the processing of cellulose fibres with aqueous baths following the techniques for the production of paper.
The limits of this type of material essentially concern the fact that the finished product cannot withstand washing processes. In particular, this material undergoes evident alterations if washed in water with detergents either in a washing machine or when dry cleaned using the ethylene perchlorate.
According to the solution proposed in the second document, the Italian patent, the raw material consists of synthetic skins similar to natural ones, which are subjected to a procedure comparable to tanning.
This method, however, is not designed for essentially natural products but for products which are mainly synthetic which primarily consist of polyurethane materials, containing polyester or polyethylene fibres coated with a polyurethane resin printed with a design similar to natural leather.
This material has nothing natural about it, and as a result the finished product will have all the problems typical of artificial products made on a synthetic base.

DESCRIPTION OF THE INVENTION

This invention proposes to provide a procedure for the creation of materials similar to leather and that can eliminate or at least reduce the drawbacks described above.
The invention proposes to provide a procedure for the creation of a material that foresees the features of being similar to leather, both from the point of view of softness and in appearance, and which at the same time guarantees the non-alterability when processed with water or ethylene perchlorate.
The raw material is based on cellulose and is chemically processed in an aqueous solution to dye it and soften it so that it acquires a more leather-like "feel" while maintaining its particular features.
This invention therefore consists of a procedure for the production of a material similar to leather starting from a cellulose base, whose features are described in the main claim.
The dependent claims of the solution in question describe advantageous embodiments of the invention.
The main advantages of this solution, in addition to those based on its production simplicity, concern first of all the fact that the material obtained is resistant and remains unaltered, while having a consistency similar to leather, if subjected to washing in water with detergents, also in a washing machine, or when dry cleaned using ethylene perchlorate.
The procedure according to the invention therefore foresees the use of cellulose as the raw material, in particular a special cellulose material in the form of a white card-like sheet, wound in reels which are then cut into sheets.
One of the features of the cellulose material is that it does not alter when it comes into contact with water or ethylene perchlorate, allowing it to be chemically processed in an aqueous solution to dye it and soften it so that it acquires a leather-like "feel" and maintains its particular features.
According to an essential feature of the invention, the cellulose material is one that is generally used to make labels for jeans and commercially known as TEXON^® 601 produced by Texon International.
This consists of cellulose fibres impregnated with a dispersion of carboxylated styrene-butadiene polymer and containing vulcanizing and ageing agents and non-nitrogenous pigments.
The stages of the procedure according to the invention are as follows:

1) Dyeing of the cellulose-based material;
2) Softening (or greasing) of the material;
3) Fixing of the material.

The procedure is carried out inside rotating cylinders, known as "drums", inserting the sheets of cellulose material and aqueous solutions, and starts with the so-called "wetting" of the material, which consists of soaking it in hot water at 50/60°C and rotating the drum for several hours so that the fibres can react with the chemical products they will subsequently come into contact with.
The first chemical reaction to which the cellulose material is subjected consists of dyeing, carried out with a predetermined quantity of hot water at 40/50°C using either mixtures of metallocomplex dyes alone or adding azodyes and tannin extracts to the solution, this operation lasting from 45 to 60 minutes.
To soften the sheets, so that they acquire a similar "feel" to leather, greasing products are added to the solution in a mixture consisting of sulphonated fish and vegetable oils and synthetic fats, with a further rotation for around 120 minutes.
As is usual when processing leather, the chemical products are then fixed on the material by adding a solution of formic acid to the solution in the drum, and if necessary also a solution of trivalent metal salts, reacting for around 60/90 minutes.
To reinforce the reaction between the chemical products and the cellulose material, a new solution of formic acid is used, after replacing the aqueous solution, with the addition of a resin and left to soak for around 60 minutes.
Processing is now complete and the sheets can be left to dry on heated steel plates.

DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION

A detailed description of the procedure is now given, referring to the following examples.

EXAMPLE I

Six sheets of TEXON^® 601 cellulose material measuring 150 x 150 cm are inserted in a drum of around 0.4 m³ in volume, which rotates at a speed of 12 rpm, with 73.5 1 of hot water at a temperature of around 50°C and rotated for 3 hours and then left to soak overnight.
In the morning, the water is drained off and 19.6 1 of hot water at 40°C are added together with 0.132 kg (from 0.004 kg to 0.224 kg) of a powder mixture of metallocomplex dyes and azodyes and 0.196 kg of tannin extract of quebracho in powder and rotated for 45 minutes.
A 2.058 kg solution is now added, consisting of 60% of sulphonated fish oil, 30% of long-chain phosphoric ester-based synthetic oils and 10% of natural and vegetable oils, and rotated for 120 minutes. The bath is acidified with 0.245 kg of formic acid and rotated for 20 minutes. Another 0.147 kg (up to 0.245 kg) of formic acid is added, rotating the drum for another 30 minutes.
The solution in the drum is now drained off and the material is thoroughly rinsed before adding 29.4 1 of hot water at 40°C with 0.098 kg of formic acid, rotating the drum for 10 minutes and then adding 0.098 kg of a solution of acrylic polymer and rotating for another 30 minutes. The solution is then drained off and the material is rinsed thoroughly again.
The sheets are removed from the drum and left to dry on steel plates.

EXAMPLE II

Proceed as with example I up to the first acidification after the greasing operation with 2.058 kg of oils and add 0.196 kg of chrome sulphate and rotate for 90 minutes. Drain and rinse thoroughly and then proceed as in example I.

EXAMPLE III

As for example I but the 30% solution of synthetic oils is reduced to 25%, adding 5% of modified acrylic polymer.
Following the treatments described above, the finished product is identical to leather both in consistency and in appearance, presenting the fundamental advantage of being resistant to washing and to stress.
The invention is described above with reference to a series of preferred embodiments. It is nevertheless clear that the invention is susceptible to numerous variations that lie within its scope, within the framework of technical equivalents.

Claims

A procedure for the production of material similar to leather in terms of consistency and appearance, characterised in that the raw material is cellulose fibres impregnated with a copolymer dispersion and in that the raw material is subjected to the following processing stages:
• Dyeing;

• Softening;

• Fixing.
A procedure according to claim 1, in which the dyeing phase comprises the insertion of the cellulose material in a drum and processing with hot water with a mixture of powder dyes and tannin extract.
A procedure according to any of the foregoing claims, in which the softening phase comprises the addition of a solution of sulphonated fish oil, synthetic oils and fatty acid esters and acidification of the bath with formic acid.
A procedure according to any of the foregoing claims, in which the fixing phase comprises the draining of the solution in the drum, rinsing and adding of hot water and formic acid with rotation of the drum and adding of a solution of acrylic polymer.
A procedure according to any of the foregoing claims, characterised in that the cellulose fibre is
impregnated with a dispersion of carboxylated styrene-butadiene coplymer.
A procedure according to claim 5, characterised in that the cellulose fibre is impregnated with a dispersion of carboxylated styrene-butadiene copolymer that contains vulcanizing and ageing agents.
A procedure according to claim 5 or 6, characterised in that the cellulose fibre is impregnated with a dispersion containing pigments advantageously non-nitrogenous.
A procedure according to any of the foregoing claims, characterised in that several sheets of cellulose fibre impregnated with a copolymer dispersion are inserted in a drum with a predetermined volume, together with a predetermined quantity of hot water at a predetermined temperature, advantageously 50°C, and in that the drum is rotated for a predetermined time, advantageously three hours, and in that the material is then left to soak for several hours.
A procedure according to claim 8, characterised in that it foresees the subsequent draining of water and the addition of a predetermined quantity of hot water at a predetermined temperature, advantageously 40°C, with a predetermined quantity of a powder mixture of metallocomplex dyes, azodyes and tannin extract of quebracho in powder, followed by rotation of the drum for a predetermined time, advantageously for 45 minutes.
A procedure according to claim 9, characterised in that it foresees the further addition of a solution consisting of 60% of sulphonated fish oil, 30% of long-chain phosphoric ester-based synthetic oils and superior fatty acids and 10% of natural and vegetable oils, and the subsequent rotation for a predetermined time, advantageously 120 minutes, followed by the acidification of the bath with a predetermined quantity of formic acid and rotation for a predetermined time, advantageously 20 minutes, and the subsequent addition of a further quantity of formic acid and rotation for a predetermined time, advantageously 30 minutes.
A procedure according to claim 10, characterised in that it foresees the draining of the solution in the drum and thorough rinsing, followed by the addition of a predetermined quantity of water at a predetermined temperature, advantageously 40°C, with a predetermined quantity of formic acid and rotation of the drum for a predetermined time, for example 10 minutes, and the subsequent addition of a predetermined quantity of an acrylic polymer solution followed by rotation of the drum for a predetermined time, for example 30 minutes, and finally the draining of the solution and thorough rinsing.
A procedure according to any of the claims from 8 to 11, characterised in that it foresees the removal of the sheets and their drying on heated steel plates.