CS275887B6 - Method for the production of leather for shoe uppers for summer and spring time - Google Patents

Description

(57)

A method of making leather for the uppers of footwear for spring and summer, wherein after a traditional wet bath treatment and during a dry treatment after punching or punching the skin, two separate acrylic resin treatments are provided, which after polymerization imparts better compactness and firmness to the skin, increased surface strength due to the coating of the inner surface at the locations corresponding to the apertures or holes so that the risk of enlarging the apertures and holes and tearing the skin while wearing the shoe is avoided. Made leather is specially designed for production of shoes for spring and summer.

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WHAT

CS 275807

CS 275887 Β 5

The invention relates to a process for the production of leathers for the uppers of shoes as well as for these made leathers. In particular, the invention relates to a method of processing sheepskin with wool to obtain punched or perforated hides having the compactness and strength characteristics necessary for their use in the manufacture of leather for shoe uppers having wool on their inner side, said uppers for the manufacture of footwear for spring and summer.

The process according to the invention differs from the traditional processing of sheepskin with wool in that the skin is treated with acrylic resins of different composition after tanned and perforated.

At present, footwear suitable for the hot months and especially summer is known which has perforated or pierced calf upper and is without lining, the upper having the characteristics of compactness and strength required for this specific use.

However, the disadvantages of these leather products are the inadequate hygienic properties of the openings present, as well as the difficulties of inevitable friction between the inner surface of the shoe and the skin of the foot; another drawback is the lack of heat exchange between the exterior and the interior, which heat exchange is necessary as a reliable way to maintain the optimum temperature inside the shoe.

To date, these prior art problems have been solved by generally designing materials such as textile fabrics for summer footwear that are capable of guaranteeing non-sweating; however, such materials may not be used for long-term worn footwear which should not be subject to rapid wear due to factors such as weather, shock or other external stress.

Accordingly, there is a clear need for leathers for the manufacture of hot shoe uppers, wherein these uppers having holes or holes would not have the above-mentioned drawbacks and have the desired strength and durability characteristics while guaranteeing a comfortable fit.

The above-mentioned requirements meet the method of the invention and the leather produced by the method of the invention. The method according to the invention provides a raw material for the production of summer shoe uppers in the form of punched or perforated sheepskin leather with wool, which is able to form a coating on its inner side which provides a constant internal temperature while circulating air, foot overheating, and thus foot sweating, while internal antistatic properties reduce clogging of dust particles into footwear. Furthermore, the leather according to the invention is characterized in that there is nowhere to be pressed against the foot so as to ensure a comfortable fit, and the leather according to the invention is even advantageously used as a blood circulation stimulator and as a means suitable for absorbing electrostatic energy generated by the human body.

It should be recalled that sheepskin with wool as such for its characteristic properties, such as a very open fibrous texture for the large amount of hair covering the skin and also the presence of very short fibers, is not as such suitable for the production of shoe uppers.

Therefore, in order to be able to use the pierced or perforated leather for the manufacture of footwear during the spring and summer seasons, the method according to the invention uses wool-treated sheepskin at the end of the re-treading and after punching or punching.

In this way, two effects are achieved:

a) the leather has a higher compactness and strength so that it can be punctured or perforated without the risk of the leather tearing and the upper can be made by adapting it to the desired model,

(b) the strength of the leather at the points corresponding to the inner surface of the holes or holes shall be increased, so as to prevent their enlargement and expansion, and at the same time tearing the leather at the holes or holes as much as possible when wearing the footwear

CS 275887 B 7

As mentioned above, the main characteristics of the process of the invention are the deposition and subsequent polymerization of acrylic resins in two successive stages within the fiber skin texture and at points corresponding to the inner surface of the holes or holes during tanning and finishing of the traditional type.

Essentially, the operations of the invention are carried out in the final stage of the tread and after punching or punching. The traditional sequence of normal leather processing operations distinguishes bath operations from dry operations.

The treatment in the bath consists of the following phases:

(a) a soak in which the skin free of organic residues and blood is softened to avoid fitting, using a bath consisting of cold water and a surfactant such as FORYL B8 (a mixture of anionic and nonionic type surfactants market by Henkel Company), then the skin will restore its natural moisture content during exposure to enzymatic products (an enzyme product derived from pancreatic bacteria), such as REVERDASA 120 (Rohn Poulenc);

(b) scouring, in which the pieces of meat and fat remaining after skinning are removed, the subcutaneous layer also being removed, so that the tanning agents can penetrate the skin much more quickly and evenly;

(c) washing to remove residual dirt and some natural fat from the skin; after this operation, the natural fats in the skin are more evenly distributed; this step is preferably carried out using emulsified perchlorethylene, thereby speeding up the washing;

(d) picking, which is the transition from biological to anabiological stages; in this operation, the skin is prepared for chroming to be suitable for treatment with chromium salts;

(e) tanning as a traditional treatment of chromium salts (basic chromium sulphate at pH 2.8) to obtain leather which is both soft, sufficiently compact and poorly elastic to allow sweat to pass through;

(f) an acid removal step after which the frame is aged for 48 hours, neutralizing the hydrolysable acid bound to the protein substance (since such acid causes uneven coloring) with a composition consisting of a mixture of buffer salts having a neutralizing effect (eg CORATIL ND from Henkel) ;

(g) tanning in which the strength and consistency of the leather is improved as well as properties such as suitability for grinding.

Dry processing of the traditional type includes finishing, punching or punching and subsequent finishing.

According to the invention, these traditional processing steps are complemented by the above-mentioned acrylic resin processing steps.

In the final stage of re-screening, the fiber structure of the leather is strengthened by using an acrylic resin, especially acrylic acid esters, which are polymerized when introduced into the skin, thereby densifying the fiber structure and obtaining a leather which exhibits high compactness and strength. and punching.

The second operation of the invention is carried out during the dry treatment of the leather after punching or punching and is based on treating the surface of the leather inside the punched holes or holes with an acrylic type resin prepared from a mixture of acrylic acid and acrylic ester. the inner walls of the holes or holes, so as to avoid, as far as possible, the risk of enlarging the holes and tearing the leather during use.

CS 275887 B 7

The invention therefore relates to a method for producing leather for shoe uppers of shoes for spring and summer, wherein after treatment of sheep skin in a bath comprising soaking, scouring, washing, picking, tanning, acid removal and tanning, the acrylic ester resin in % of the aqueous solution, then the resin is polymerized to become denser and, after punching or punching, the skin is treated with the methacrylic resin in the aqueous solution, and then the resin is polymerized at places corresponding to the inner surface of the holes or holes.

British Patent Specification No. 2,074,173 A discloses a process for treating leather with hydrophilic acrylic resins in the form of an aqueous dispersion to form a fine film on the surface of the leather.

British Patent Specification No. 2 074173 discloses a solution or aqueous dispersion of a polymer suitable for the treatment of fur and leather, which polymer is based on monomeric units of nitrogen-containing acrylic and / or methacrylic esters, acrylic and / or methacrylic acid esters acrylic and / or methacrylic. This polymer solution or dispersion is considered to be suitable for tanning and re-tanning.

In contrast to this known prior art, the invention relates to a method of treating leather to be punched, wherein the skins are treated in a neutralizing bath consisting of water and de-acidifying after conventional processing steps such as soaking, scouring, washing, pickling, tanning and tanning. an agent to which the acrylic ester compound is added and polymerized to thicken the original fiber web and after punching, the skins are treated with methacrylic resin in aqueous solution, allowing the resin to be polymerized to consolidate the inner surface (s) of the holes or holes.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a method for producing leather for shoe uppers, intended for spring and summer, by bathing sheepskin with wool by a process comprising soaking, scouring, washing, picking, tanning, neutralizing, retagging and punching in a dry state. by neutralizing the skin in a bath of 45 to 50 ° C containing 7 g / l of soluble acrylic resin, formic acid is added to the bath after a residence time of 30 minutes to two hours and the polymerization is terminated in a dry state at a pressure of 2.0 MPa at 100 to 120 ° C for 4 to 8 minutes and after punching, the skin is soaked again in a water bath at a temperature of 50 to 60 ° C containing 4 to 6 g / l of soluble acrylic resin, then at Formic acid is added at 60 ° C and the resin is allowed to polymerize for 30 to 45 minutes.

The use of the acrylic resins according to the invention in the form of aqueous solutions and not in the form of aqueous dispersions allows better and better penetration into the leather as opposed to obtaining only a surface deposit which can cause excessive hardening of the product and further improves the dyeability of the leather with anionic dyes.

In the process of the invention, the polymeric acrylic ester compound is added to a neutralization bath consisting of water at 50 ° C and an acid removal agent (for example CORATIL ND above); leather is introduced into this bath and the pH is adjusted to 6.

By using the neutralizing bath according to the invention, it is achieved that the chromium salts are fixed and the polymeric acrylic ester ester compound, for example ICATAN 38 from Icap Company, used in the form of an aqueous solution, effectively penetrates into the leather.

The acrylic ester-based resin is preferably added to the neutralization bath after approximately one hour after the neutralization is complete, at a concentration of 7 g / l to achieve penetration into the leather fibers as much as possible in places where the leather itself is less strong and especially in marginal parts where the structure is less loose and the fibers are long.

CS 275887 8 7

In the process according to the invention, the acrylic ester resin is allowed to polymerize for 30 minutes to two hours, after complete penetration into the leather, by first slightly adding formic acid, whereby the resin is bound to the leather fiber and then directly to the leather in a dry state. which is already completely dry, at a pressure of 2.0 MPa and at a temperature of 100 to 120 ° C for 4 to 8 seconds.

After the holes or holes in the wool leather have been formed, the punching being carried out by a press having a plate having small spines, the treatment with acrylic acid and acrylic acid ester is carried out as described above. Preferably, this treatment is carried out by soaking the punctured leather in a water bath at 50-60 ° C to which a prepolymerized acrylic acid-acrylic ester resin (e.g., ORASIL-ANG from Henkel Company) is added at a concentration of about 4 to 60 ° C. 6 g / l, wherein the resin is polymerized by adding formic acid over a period of 30 to 45 minutes at a temperature of about 60 ° C.

Thus, the resin is deposited on the surface of the perforated leather at locations corresponding to the inner walls of the apertures and holes, the resin itself being absorbed by fibers not covered by the perforation, so that the above-mentioned advantage is achieved by increasing the surface strength of the leather thus obtained.

The invention also relates to leather obtained by the process according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated, but not limited, by the accompanying drawings, in which Fig. 1 is a diagram of the method of the invention and Fig. 2 is a schematic sketch of a shoe made of leather according to the invention.

Referring to Fig. 1, the various steps of processing sheepskin with wool are shown, which are divided into group A comprising bath treatment steps and group 8 comprising dry treatment steps. The steps characteristic of the invention are two operations in which acrylic resin treatment is carried out, which are classified as processing steps A and after the punching step in sequence B.

Group A distinguishes between biological treatment steps, including soaking, scouring and washing, a transient stepping step, and anabiological steps including tanning, acid removal and tanning.

The dry treatment stage 8 comprises finishing, embossing or punching, processing with the polymeric acrylic compound of the invention and subsequent finishing.

The process according to the invention is as follows:

(a) Raw sheepskin with wool is soaked in a cold water bath (one skin per 20 liters of water), the water bath containing FORYLL ΒΘ, a Henkel Company surfactant, in an amount of 1 g / l and left overnight, then wash with tap water in the morning until clear water is drained, FORYLL BB (1 g / l) and REVERDASA 120 (0,2 g / l) are added and the skin is left in the bath for 48 hours (soak degree) .

(b) After blending, a bath containing water at 35-38 ° C and 1.5 g / l perchlorethylene (as solvent) and 3 g / l FORYLLU BB (surfactant) is prepared and the skin is soaked in the bath, one skin counts 20 liters of bath; then the skin is washed in running water.

(c) A cold water bath containing 40 g / l of salt (approximately 4 ° C) is prepared and the skin is left in such a bath for 30 minutes, counting 20 liters of bath per skin; then add 2.5 g / l organic acid (for example BASCAF F from BASF Company) and leave the bath to stand for two hours, then add 3 g / l formic acid and leave the skin in the bath for 2 to 3 hours at pH 2.8 (pinning). The task of picking is to prepare the skin for chroming; Picking accelerates the uptake of chromium salts through the skin, making the chromium salts less reactive due to the acidic character of the bath, and therefore their penetration is more even. The addition of salt is necessary to prevent swelling of the skin due to the contained acid.

CS 275887 B 7

d) The skin is then treated as follows (tanning): Leave in a cold water bath (20 liters bath per skin) for two hours, containing the chromium salt, GRASSAN OHS, a commercially available product of Henkel Company in the amount of 1, 6 g / l, leave the bath to stand for one hour, then add IMPLENAL AP, a commercially available product from BASF Company, and leave the skin in the bath for another hour, and finally add 10 g / l of salt and the skin leave in this bath for two or three hours; finally, 1 g / l of sodium carbonate and 1 g / l of sodium bicarbonate are added and the skin is left in this bath for 3-4 hours; eventually the skin spreads on the frame.

In this way, the leather is treated to fit the shoe uppers, since the leather obtained is well tanned, has a Tg of approximately 90 ° C and is soft, rubbery to the touch, sufficiently compact and poorly elastic and well breathable.

It can be observed that the addition of basic chromium sulfate at a pH of approximately

2.8 facilitates evenness of penetration, adding also electrolyte-resistant synthetic sulphite grease (Grassan DHS) and masking agent (IMPLENAL AP), which have a filling and stabilizing effect on chromium tanning. The final addition of the alkaline compound in the final stage serves to enlarge the chromium compound molecule and fix it in the fiber-to-fiber deposit, thereby obtaining a well-tanned leather that is strong and durable.

e) Acid removal is carried out after maturing of tanned leather for about 48 hours on the frame using water at 45 ° C, whereby the leather is soaked (counting 20 liters of water per leather), then 2 g / 1 CORATILU NO, processed for one hour, then 3 g / l of GRASAN DHS is added and the leather is processed for another one hour.

f) The retreading is carried out in a manner known per se and, when finished, is carried out with an acrylic resin treatment, which is a characteristic step of the treatment according to the invention. In this process, the leather is treated in a water bath at a temperature of 45-50 ° C (8 l bath counts per leather) containing 7.8 g / l CORATIL NO and 7 g / l ICATAN 38.

After grinding the meat side of the leather and after dyeing the previously dried leather, the dry treatment is carried out:

(g) a punching or punching operation is carried out after the traditional finishing operation by applying to the leather of an aqueous dispersion of aliphatic polyurethane (ASTACIN Finish PUD) in an amount of 80-100 g / leather at a temperature of 110 ° C and a pressure of 15 MPa followed by polymerization. A second characteristic operation of the invention is then carried out, wherein the leather is soaked in a water bath at a temperature of 50 to 60 ° C containing DRASIL-ANG from Henkel Company, a pre-synthetic methacrylic resin in an aqueous solution at a concentration of 4 to 6 g / l. Formic acid is then added at 60 ° C over 45 minutes and the polymerization is terminated to form a coating on the surface of the punctured or perforated leather at points corresponding to the inner surface of the holes (h) and a further finishing (i) is performed.

Giant. 2 illustrates the use of leather obtained by the method of the invention for the manufacture of shoe upper.

On the inside of the shoe a layer of wool is visible, while on the outside a suede leather or napa 2 with holes 3 is visible.

In addition, the results of standard tests to determine the properties that are desirable in leather for uppers are given.

Testing of the rind skin treated according to the invention (sample A) and untreated rind skin (sample B) is carried out: the tensile strength and ductility are determined, the structural strength is determined, the tension and the tensile strength of the split-faced split-ball method are determined , the wear resistance is determined by repeatedly continually folding the light skin and wiping its surface.

CS 275887 Β 5

Sample A (processed according to the method of the invention)

Standard method: UNI ISO 3376 - determination of tensile strength and tension strength. A suitably conditioned sample is subjected to tensile stress upon rupture on a strength tester.

The tensile strength is obtained by dividing the tear load by the cross-section of the sample and is given in MPa. The ductility is calculated as the difference between the initial length of the sample and its final length. This difference is expressed as a percentage of the initial sample length.

Conditioning and testing: normal Al-type atmosphere (20 - 2 ° C, 65-5 relative humidity). -UNI ISO 2589 - leather - mechanical tests - thickness determination

Sample Tensile strength MPA The biggest extension 1 11.4 39.4 2 12.35 42.2 3 12.52 44.0

Mean tensile strength = 12.1 MPa

Mean maximum elongation = 41.87%

Standard method UNI ISO 3377 IUP 8 - determination of structural strength

The rectangular specimen in which the prescribed shape is cut is suspended from the protruding ends of the pair of specimen holders between the clamps of the tester. The stress at the maximum elongation required to move the holders apart is considered to be the value of the structural strength.

Conditions and testing: normal atomosphere type A2 (23 - 2 ° C, relative humidity 50-5%). Stroke speed: 100 and 10 mm / minute

Sample Structural strength (N / nini) 1 51.6 2 44.5 3 42.3

Mean structural strength = 46.12 N / µm

Standard method UNI ISO 3379 - Determination of deepness and tensile strength of split-face split-ball method.

The steel ball is pressed into the central portion of the meat side of the skin of the sample cut in the form of a disc, which is firmly clamped around the circumference.

The pressure on the ball and the subsequent elongation of the sample is recorded when the split split leather cracks and eventually the skin ruptures.

Conditions and testing: normal atmosphere type Al (20 - 2 ° C, 65-5 relative humidity)

Sample 1 2 3 crack load (N) 137.2 303.8 250.8 tear strength (mm) 5.4 6.1 6.0 breaking strength (N) 470.4 678.1 527.2 elongation at rupture (mm) 7.2 9.3 8.6

CS 2758-7 B 6

Medium

Medium

Medium

Medium crack load: Tear strength: 5.8 mm Burst load: 558.6 N Burst elongation: 8.3 mm

230.6

Standard Method Wear 8433 / TUP 20 - Determination of resistance to repeated use (ie continuous bending) of light leather and surface skin rubbing.

This determination is made by clamping each sample into two test piece terminals.

One terminal terminal is left to stand while the other is oscillating with an amplitude of 22.5 ° at a frequency of 100 - 5 cycles per minute to carry the bent sample.

Testing conditions: normal atmosphere type AI (20 - 2 ° C, relative humidity 65 - 5%)

- six rectangular samples measuring 70 x 45 mm are obtained by cutting.

The number of test cycles is 50 000 cycles.

The samples at the end of the test shall show no cracks or any other sign of deterioration.

Sample B (untreated according to the invention)

and

Standard method: UNI ISO 3376 - determination of tensile strength and tension strength. The suitably conditioned sample is subjected to tensile stress after rupture on a strength tester.

The tensile strength is obtained by dividing the tear load by the cross-section of the sample and is given in MPa. The ductility is calculated as the difference between the initial length of the sample and its final length. This difference is expressed as a percentage of the initial sample length.

Conditioning and testing: normal atmosphere type AI (20 - 2 ° C, 65 - 5% relative humidity)

- (INI ISO 2589 - Leather - Mechanical tests - Determination of thickness

Sample Limit tensile strength Biggest extension - · - MPa ductility 2 1 21.28 60.6 2 19.70 46.8 : 3 15.96 45.6 7 '·: in Medium tensile strength 18,97 MPa in. ·: Medium the largest extension - elongation = 51,0%

ř | Standard method UNI ISO 3377 IUP 8 - determination of structural strength? The rectangular specimen in which the prescribed shape is cut is suspended from the protruding ends of the pair of specimen holders between the clamps of the tester. The stress at ^{: the} maximum elongation required to move the holders apart is considered to be a structural strength value.

j Conditions and testing: normal atmosphere type A2 (23 - 2 ° C, relative humidity 50 - 5%).

ΐ Tensile speed 100 - 10 mm / minute

AND

I *

I í

CS 2758S7 Β 6

Sample Structural strength H / ntm 1 73.1 2 68.6 3 64.1

Mean structural strength = 68.6 N / µm

Standard method UNI ISO 3379 - Determination of deepness and tensile strength of split-face split-ball method.

The steel ball is pressed into the central portion of the meat side of the skin of the sample cut in the form of a disc, which is firmly clamped around the circumference.

The pressure on the ball and the subsequent elongation of the sample is recorded when the split leather begins to crack and the skin eventually breaks.

Conditions and testing: normal atmosphere type AI (20 - 2 ° C, relative humidity 65-5%).

Sample 1 2 3 crack load (N) - - - tear strength (mm) - - - - breaking strength (N) 510.0 589.0 478.0 elongation at rupture (mm) 10.5 9.2 9.0

Mean breaking strength: 528.6 N

Medium elongation at break: 9.5 mm

Standard method UNI 8433 / IUP 20 - Determination of resistance · Repeated use (continuous bending) of light leather and superficial rubbing

This determination is made by clamping each sample into two test piece terminals.

- one terminal terminal is left at rest while the other is oscillating with an amplitude of 22.5 ° at a frequency of 100 - 5 cycles per minute, thereby carrying the bent sample.

Conditions and testing: normal atmosphere type AI (20 - 2 ° C, relative humidity 65-5%). - six rectangular samples measuring 70 x 45 mm are obtained by cutting.

Number of test cycles: 50 000.

The samples at the end of the test shall show no cracks or any other sign of deterioration.

Table 1 below summarizes the results of the above technological tests

CS 2758-7 B 6

Table 1

Property Sample A modified Sample B untidy Aries skin Sheep (sheep) skin Medium strength tensile, MPa 12.1 18.97 10 8 Ductility, 41.87 51 40 40 Structural strength, N / mm 46.13 68.6 40 40 Medium load at rupture, N 558.6 528.6 120 120 Elongation at break, mm 8.3 9.5 7, 5 8 Mean crack load, N 230.6 120 120 Mean tear strength, mm 5.8 - 7, 5 8 Ball test, number of test cycles 50 000 good good

The table above shows that the values obtained for Sample A are not only better than those obtained for sheepskin for shoemaking uppers, but are better than those obtained for ram leather.

The invention is described with reference to some specific embodiments, but variations and modifications of the process are, of course, possible while maintaining the spirit of the invention.

PATENT CLAIMS

Claims (2)

A method for producing leather for uppers of shoes for spring and summer, wherein the bath is treated with wool skin by a process comprising soaking, disappearing, washing, picking, tanning, neutralizing, retagging and punching in a dry state, characterized in that the leather is neutralized in a bath of 45 to 50 ° C containing 7 g / l of soluble acrylic resin, after a residence time of 30 minutes to two hours, formic acid is added to the bath and the polymerization is terminated in a dry state at a pressure of 20 bar at 100 to 120 ° C for 4 to 8 minutes and after punching, the skin is soaked again in a water bath at 50 to 60 ° C containing 4 to 6 g / l of soluble acrylic resin, then at 60 ° C formic acid is added and the resin is added. and allowed to polymerize for 30 to 45 minutes. 2 drawings CS 275887 Β 5