WO1995010633A1

WO1995010633A1 - Process of coating tanned hide with a polyurethane film

Info

Publication number: WO1995010633A1
Application number: PCT/IT1994/000071
Authority: WO
Inventors: Augusto Giovacchini
Original assignee: Nutek Srl
Priority date: 1993-10-15
Filing date: 1994-05-27
Publication date: 1995-04-20
Also published as: ITMI932201A1; ITMI932201A0; IT1272723B

Abstract

Process of integration between the cattle hide tanned, stuffed and dyed, with a film of polyurethane consisting of two chemical components, placed upon a matrix of paper, producing a clearly marked grain corresponding to the desired design of the skin, the film being applied by a spray gun, the purpose being to obtain a two-colour effect between the base and the tip of the skin and to confer upon it the best structural, tactile and aesthetic properties.

Description

PROCESS OF COATING TANNED HIDE WITH A POLYURETHANE FILM

The invention concerns a process for treating cattle hides . In producing material for leather goods generally , foot¬ wear, upholstery and the like, after tanning the split cattle hides are normally given a by-cast treatment to improve their quality. According to the above process this treatment consists of the following stages.

Production of split hides by tanning, stuffing and dyeing skins that have been processed using the best chemicals, passed over plates, dried, perched ,dry-milled, fluffed and nailed. The pattern, following the desired grain, is formed on a matrix consisting of a band of paper in continuous horizontal movement.

A film of polyurethane resin is then applied to said band; this is done by using a gun to spray on a mixture of two chemical products: an adduct and a hardener. The gun is set up on a carriage whose movements are alternatingly horizontal and orthogonal to that of the paper band.

The .adduct. at a temperature of about 60°C, and the hardener, at ambient temperature, are injected simul¬ taneously but separately at a pressure of about 5 atms into the mixing chamber in .the guάi.

A chemical reaction begins inside said chamber and this produces covalent bonds of reticulation inside the po- lyurethan matrix. The reaction of reticulation is ac¬ celerated by passing the band through a linear air fur¬ nace at a temperature of about 100°C.

The split hides are laid by hand on the matrix and the reaction of reticulation proceeds until its completion in approximately 24 hours; this even if only about 100 seconds are actually needed for adhesion of the poly- urethane layer to the hide.

The product thus composed is subjected to dry milling for about 4 hours, followed by compression and stretch- ing in a continuous machine to give a glossy finish at a temperature of 100° and pressure of 20 atms. The hide is then removed by hand from the matrix. The above process produces a two-colour effect between the base and the tip and the chromatic and aesthetic results achieved are both original and attractive.

The grain stands out clearly giving remarkable tactile and visual effects, emphasising the grain itself. The adduct is preferably a viscose liquid of polyure- thane-polyisocyanate dissolved in methylbenzene while the hardener is a liquid of polyetherurethane-isoforon- diamine dissolved in methylethyIketone . Product thickness may vary, according to type, between 1.2 and 1.4 mm, 1.5 and 1.8 mm and 1.2 and 2.2 mm. The purpose of all the means employed - including the stages of the process, its charac eristics especially the pattern to bring out the grain on the hide, colour¬ ing, pressure, stretching, flattening, temperatures used, processing times, chemical products, the two colours be¬ tween base and tip - is to obtain optimum results of softness, body, original colour effects and mechanical strength .

The process offers many advantages, such as:

- original chromatic effects by use of two colours;

- the grain standing out exceptionally well;

- greater mechanical resistance; - increased softness and body, improved tactile quality generally. The above advantages may be summed up as a process en¬ suring exceptional structural, aesthetic and decorative effects . The attached plates emphasise the differences obtainable by the invented process compared with present processes. Plates 1 and 3 show specimens coloured brown and green respectively obtained by processes now in use. Plates 2 and 4 show specimens of substantially similar colours obtained by the invented process.

Though only in picture form these reproductions clearly bring out the improved characteristics of leather obtained by the invented process especially as regards grain pat^¬ tern and general appearance which, considering the type of product concerned , are of fundamental importance.

Claims

C l a i ms

1. Process for integration between a anned cattle hide, and a film of polyurethane comprising the following stages:

- production of split hides by tanning, stuffing and dyeing the skins, passing them on the plates, then drying, perching, dry-milling, fluffing and nailing them;

- formation of the pattern corresponding to the grain of the skin that it is desired to obtain, upon a matrix consisting of a band of paper, - application on said band of a film of polyurethan re¬ sin by spraying it on with a spray gun, the film con¬ sisting of a mixture of two chemicals, one the adduct and the other a hardener, that begin a reaction of reti¬ culation hastened by passing it through a linear air furnace at a temperature of about 100°C.

- laying the split hide by hand on the matrix to complete the reaction of reticulation;

- dry milling;

- compression and stretching; - manual removal of the hide from the matrix; the purpose of all this being to produce an original two-colour effect between the base and the tip of the product and to obtain optimum results of softness, body, mechanical strength and a pleasing appearance.

2. Process as in claim 1, characterized in that the grain has been designed so that it stands out clearly, giving remarkable tactile and vi¬ sual effects emphasising the grain itself.

3. Process as in claim 1, characterized in that dry milling is continued for about four hours .

4. Process as in claim 1, characterized in that compression and stretching are carried out at a temperature of approximately 100°C and at a pressure of 20 atms.

5. Process as in claim 1, characterized in that the adduct is a viscose liquid of polyurethane-polyisocyanate dissolved in methylben- zene .

6. Process as in claim 1, characterised in that the hardener is a liquid of poly- etherurethane-isoforondiamine dissolved in methylethyl- ketone .

7. Process as in claim 1, characterized in that the thickness of the product may vary, according to type, between 1.2 and 1.4 mm, 1.5 and 1.8 mm and 1.2 and 2.2 mm.