KR20120125032A - A processing method for natural leather - Google Patents

Abstract

PURPOSE: A manufacturing method of natural leather is provided to provide a natural leather remarkably reducing residues of Cr6+ while satisfying tensile strength, UV discoloration, thermal discoloration, etc required for environment-friendly natural leather. CONSTITUTION: A manufacturing method of a natural leather comprises: a fabric-preparation step comprising a depilation, decalcification, precipitation into acid of pH 2-3 of wet-salted hide; a tanning step Cr-tanning the fabric; a neutralization step increasing pH of the fabric to 5-7; a dyeing and fatliquoring step fatliquoring the fabric by a synthetic oil fatliquor; a reduction step reducing 6-valent chrome(Cr^6+) to trivalent chrome(Cr^3+) of the fabric by using a reducing agent selected from sodium thiosulfate and sodium bisulfate; and a step of drying the reduced fabric.

Description

Manufacturing method of natural leather {A processing method for natural leather}

The present invention relates to a method for producing natural leather, and after a dyeing branch step using synthetic oil (Synthetic oil) as a fatliquor with a leather fabric subjected to an oily step using a chromium (Cr) tanning agent Toxic hexavalent chromium (Cr ⁶⁺ ) is converted to non-toxic trivalent chromium (Cr ³ ) by sequentially performing a reduction step of treatment with a reducing agent selected from (Na ₂ S ₂ O ₃ ) and sodium bisulfite (NaHSO ₃ ). ^{The present} invention relates to a method for producing a non-toxic natural leather converted to ⁺ ) or significantly reduced the residual amount of hexavalent chromium (Cr ⁶⁺ ).

Generally, leather refers to a product made by applying a suitable treatment from hides or skins of mammals, and leather products have been used for various materials such as clothing, footwear, and bags. Recently, artificial leather or synthetic leather using various synthetic resins replaces natural leather to some extent, but the demand for natural leather with excellent thermal insulation, hygroscopicity, moisture resistance, breathability, sound absorption, and sound insulation continues. have.

Raw materials, which are raw materials for making leather, have animal tissues and decay after long-term storage. Therefore, the process of converting the animal components present in raw hides to vegetation is required during processing the final leather product. . Tanning agents are used during the oil process to prevent animal skin from becoming stiff.

Tanning agents include vegetable tanning agents using components obtained by extracting the leaves and fruits of plants with brine, and oil tanning agents using oils extracted from plants or animals.However, in order to change the animal components of raw hides to vegetable components, Chromium (Cr) and zirconium (Zr) are used as tanning agents. In fact, chromium is the most widely used tanning agent for raw hide processing. However, the chromium used as the tanning agent is trivalent chromium (Cr ³⁺ ), but is oxidized during the leather processing to be converted into hexavalent chromium (Cr ⁶⁺ ). Hexavalent chromium (Cr ⁶⁺ ) is prone to vaporization and possesses strong oxidative and toxic toxicity, so when in contact with the human body, there is a risk of difficulty in breathing, nasal mucosa, inflammation, hemorrhagic kidney disorders, acute intoxication of hematuria and bronchial cancer, lung cancer. have. As a result, many countries around the world are tightening regulations by setting environmental standards and usage limits for hexavalent chromium (Cr ⁶⁺ ). Therefore, in the tanning industry, it is necessary to develop treatment process technology that does not generate hexavalent chromium (Cr ⁶⁺ ).

In order to solve the above problems, the present inventors exclude natural oil branching using animal and fish oil and apply synthetic oil branching using hexavalent chromium (Cr) when applying eggplant in the dyeing process using salted bark. ⁶⁺ ) was inhibited, and after the dyeing process, hexavalent chromium (Cr ⁶⁺ ) was trivalent chromium by using sodium thiosulfate (Na ₂ S ₂ O ₃ ) and sodium bisulfite (NaHSO ₃ ) as reducing agents. The present invention was completed by ^recognizing that reduction of (Cr ³⁺ ) to the hexavalent chromium (Cr ⁶⁺ ) content in the leather fabric can be significantly reduced.

The present invention satisfies the properties of tensile strength, UV discoloration, thermal discoloration, etc. required for environment-friendly natural leather, while providing a method for producing natural leather that significantly reduces the residual amount of hexavalent chromium (Cr ⁶⁺ ). There is this.

In order to solve the above problems, the present invention

Fabric preparation step comprising the process of immersing the salt skin in hair loss, deliming, and acid solution of pH 2-3;

A planetary step comprising a process of chrome tanning the prepared fabric;

A neutralization step of raising the pH of the tanned fabric to 5 to 7;

Dyeing branch step comprising the step of having the neutralized fabric as a synthetic oil branch agent;

The dyed fabric is reduced to hexavalent chromium (Cr ⁶⁺ ) to trivalent chromium (Cr ³⁺ ) using a reducing agent selected from sodium thiosulfate (Na ₂ S ₂ O ₃ ) and sodium bisulfite (NaHSO ₃ ). Reducing step to make; And

Drying the reduced fabric; Characterized in that the manufacturing method of natural leather comprising a.

The manufacturing method of the present invention is capable of producing non-toxic natural leather having a very small amount of hexavalent chromium (Cr ⁶⁺ ) despite chromium tanning.

The production method of the present invention is capable of producing a natural leather that satisfies all properties such as tensile strength, UV discoloration, thermal discoloration required for environmentally friendly natural leather.

Natural leather manufacturing method according to the present invention, the fabric preparation step, chromium tanning oil phase step, neutralizing step of increasing the pH of the fabric to facilitate the penetration of chemicals, such as dyes and new charcoal, dyeing step step, hexavalent chromium (Cr ⁶⁺ ) Is reduced to trivalent chromium (Cr ³⁺ ), and a coating step to conceal the scratch marks of the leather fabric.

In the above-described method for producing natural leather, the present invention selects Synthetic oil Fatliquor as a branching agent (Fatliquor) in the dyed eggplant stage. Natural oil fatty acids such as fish and animal oils consist of unsaturated fatty acids, and double bonds in these unsaturated fatty acids easily generate radicals under conditions such as heat, light and pH to oxidize chromium to hexavalent chromium. It is a major cause of increasing the content of (Cr ⁶⁺ ). Thus, in the present invention, by selecting and using the synthetic oil-based agent in the dyeing step, the cause of increasing the content of hexavalent chromium (Cr ⁶⁺ ) by the oxidation reaction of chromium was completely solved. The synthetic oil branching agent used in the present invention is a conventional branching agent used in the art, and specifically, paraffin oil, spindle oil, silicone oil, etc., which do not include a double bond, may be used. As a result, the natural leather fabric of the present invention is excellent in daylight fastness, and has the advantage of preventing discoloration of leather such as heat discoloration.

In addition, in the present invention, as a part of efforts to reduce the residual amount of hexavalent chromium (Cr ⁶⁺ ) in the natural leather fabric, the reduction step is further performed after the dyeing branch step. That is, in the reduction step, hexavalent chromium (Cr ⁶⁺ ), which may remain in the leather fabric, was reduced to non-toxic trivalent chromium (Cr ³⁺ ). In the reduction step of the present invention, a conventional one can be used as a reducing agent, but particularly preferably one or more selected from sodium thiosulfate (Na ₂ S ₂ O ₃ ) and sodium bisulfite (NaHSO ₃ ). Sodium thiosulfate (Na ₂ S ₂ O ₃ ) or sodium bisulfite (NaHSO ₃ ) as the reducing agent selected and used in the reduction step of the present invention is another reducing agent, for example, ferrous sulfate (FeSO ₄ ), sodium sulfate ( Na ₂ SO ₄ ), sulfur dioxide (SO ₂ ) has a superior effect of less affecting leather color and excellent reducing effect.

Referring to the manufacturing method of the natural leather fabric of the present invention having the characteristics as described above in more detail for each manufacturing step as follows.

The first step is the fabric preparation step. The fabric preparation step consists of hair loss, deliming, and acid deposition of salt skin.

In the present invention, salted skin is used, which is obtained by separating the leather and the flesh from the slaughterhouse and salting the leather using salt. Salted bark can inhibit the growth of perishable microorganisms in leather by dehydration by osmotic action, and has the effect of inhibiting the growth of aerobic bacteria by the sterilization of chlorine and the decrease of oxygen solubility of high concentration salt solution. It also prevents oxidation by preventing air contact as much as possible.

Hair loss is the process of removing the hairs remaining on the napkins, using strong alkaline chemicals such as lime (sodium bicarbonate), sodium sulfite, sodium carbonate, sodium hydroxide, etc. Elutes. Deliming is a process of removing the strong alkaline chemicals used in the hair loss process, and neutralizing by adding acid, acid salt, and ammonium salts to restore the nap swelled by the strong alkaline chemicals to its original state. The deliming agent is selected from a nitrogen based deliming agent and a non-nitrogen based deliming agent. Nitrogen based deliming agents include ammonium, such as ammonium chloride (salt), ammonium sulfate (urethane), and the like. Non-nitrogen based deliming agents include carboxyl ester-based "Decaltal ES (BASF)" and polyvalent aromatics. Products such as "Decaltal N (BASF)", "Delime 500 (KORIN)" based on salts of multivalent aromatic acids, and "Demarscal RBB (TFL)", a mixture of inorganic and organic acids, can be used. have. The pH of the raw hides after the deliming process is about 10-12. Pickling is the process of dipping raw hides in acid to obtain a pH suitable for tanning. The acid used for pickling may be an organic acid such as lactic acid, formic acid, acetic acid, butyric acid, propionic acid, or an inorganic acid such as sodium bisulfite (Na ₂ S ₂ O ₅ ) converted to sodium bisulfite (NaHSO ₃ ). In addition, salt is additionally used in the pickling process to prevent swelling and destruction of the fiber tissue by the acid. The pH control range by pickling may vary depending on the type of tanning agent used in the next oily step. When chromium tanning agent is used, the pH during pickling is preferably about 2.0 to 3.0.

The second step is a planetary step of chrome tanning the prepared fabric.

In the planetary phase, collagen protein of unstable structure is combined with chromium, a tanning material, to change into stable protein. This tanning process results in the improvement of other physical properties such as heat resistance, corrosion resistance, chemical resistance and flexibility. The chromium tanning agent is specifically chromium sulfate (Cr ₂ (SO ₄ ) ₃ ), chromium potassium alum, chromium chloride (CrCl ₃ ), chromium fluoride (CrF ₃ ), chromium hydroxide (Cr (OH) ₃ ) And the like, and based on 100 parts by weight of the fabric, chromium tanning agent may be used within the range of 1 to 5 parts by weight.

The third step is a neutralization step of increasing the pH of the fabric to facilitate penetration of dyes, xanthan and oil components. The pH of the fabric passed through the oil phase is low to about 2 to 4, and the pH of the fabric is increased to 5 to 7, preferably 6 to 6.5, through the neutralization step. Allow dyes and briquettes to easily penetrate. The neutralizer used in the neutralization step may include sodium hydrogen carbonate (heavy bath), sodium formate (sodium phosphate), sodium acetate (sodium oxate) and the like.

The fourth step is a dyeing branch step for imparting color to the fabric.

The fabric is dyed by immersing it in a dyeing drum maintained at a temperature of 50 ℃ to 60 ℃, and is carried out together with a fatliquoring process to maximize the emulsification effect on the dyed leather. That is, the emulsion solution in which the synthetic oil-branched agent is mixed with water at a concentration of 5 to 15% by weight is added to the dyeing drum and left to stand. By going through the branching process, the leather becomes flexible even after it is dried.It reduces the friction between fibers when it is externally applied, and provides washing resistance, water resistance, waterproofing, etc. in addition to adjusting heat, chemicals, texture, color, etc. It protects leather from physical and chemical external effects. Synthetic oil branching agent in the present invention can be used within the range of 5 to 15 parts by weight (based on the solid content) based on 100 parts by weight of the fabric. If the amount of synthetic oil used is too low, the flexibility of the leather may be inferior and the quality of the leather may be in general. If the amount of synthetic oil used is excessive, the oil may rise on the surface of the leather, resulting in white crystals. Spew) is undesirable and undesirable.

In the fifth step, since a small amount of hexavalent chromium (Cr ⁶⁺ ) may remain in the raw hide after the dyeing branch step, a reduction step of converting hexavalent chromium (Cr ⁶⁺ ) into trivalent chromium (Cr ³⁺ ) to be.

The present invention uses at least one selected from sodium thiosulfate (Na ₂ S ₂ O ₃ ) and sodium bisulfite (NaHSO ₃ ) as the reducing agent. The reduction step is carried out by dipping the fabric in an aqueous reducing agent. The concentration of the reducing agent in the aqueous solution is preferably 0.1 to 5.0% by weight. If the concentration of the reducing agent is less than 0.1% by weight, the reduction effect is not sufficient. There is a problem, and it is better to select the above range.

The sixth step is a drying step of removing moisture by drying the wet leather fabric. The drying step is a process that removes moisture in the leather to make the leather fabric in a practical state, as well as fully reacts and fixes unbound materials, and improves physical properties and yields by applying appropriate physical and mechanical forces. The drying step is a conventional process and the present invention does not place any particular limitation on its selection. For example, it can be generally classified into a water removal process using a hot plate, a milling process for releasing the strength by rotating the leather in a drum, and a toggle process for preventing the shrinkage of the leather generated during drying.

In the series of manufacturing methods for the production of natural leather described above, except for the dyeing branch step and the reduction step of using a synthetic oil branching agent, the remaining production steps are generally manufactured in the art and are specifically limited in the present invention. I do not. In addition, in addition to the above-described manufacturing step, it is also included in the scope of the present invention to additionally perform a process that is usually performed to improve the physical properties of the leather fabric.

Such a present invention will be described in more detail based on the following examples, but the present invention is not limited thereto.

EXAMPLES Production of Natural Leather Fabric

Example 1.

Natural leather fabric was prepared by performing the following manufacturing process using salted pork skin.

Step 1: After filling the drum with 300 g of water, 7 g of lime (sodium bicarbonate), 3.5 g of sodium sulfite (Na ₂ SO ₃ ), and 0.2 g of dodecylbenzenesulfonic acid to prepare an alkaline solution, the salted pork skin The drum was spun for 20 hours at 25 ° C. by dipping 100 g. The pig skin was taken out from the alkaline solution, rinsed with water (200 g ㅧ once), and left for one day. Then, in a drum 100 g of water, 1.2 g of ammonium sulfate. 1.7 g of ammonium chloride, 1.0 g of lipase (Pancron SBM-1, Samgyeop), and 0.2 g of dodecylbenzenesulfonic acid were prepared to prepare a deliming solution. Rotated. The pig skin was removed from the deliming solution and rinsed with water (200 g ㅧ once) for 2 hours. Then, fill the drum with 100 g of water and 8.1 g of salt, mix for 10 minutes, deposit the pork skin, add 0.6 g of formic acid, leave for 10 minutes, and add 1.3 g of sulfuric acid three times at 20 minute intervals. Was added to adjust the pH of the solution to 3. And the drum was rotated for 1 hour at 25 ℃ temperature.

Step 2: After adding 6.5 g of chromium sulfate ((Cr ₂ (SO ₄ ) ₃ ) to the acid solution immersed in the donpi blood and rotating the drum for 2 hours, Tanbase (BASF, MgO) 0.6 g, preservative ( 0.16 g of SC-F30, Shinchon Co., Ltd.) and 0.1 g of dodecylbenzenesulfonic acid were added and the drum was rotated at a temperature of 30 ° C. for 8 hours.

Step 3: The pig skin was taken out of the tanning solution and rinsed with water (200 g ㅧ once). Porcine fabrics were dehydrated and then rearranged (0.6? 09 mm) through a split and shaving process. Then, the pig skin was immersed in a neutralization solution (pH 6.5) in which 200 g of water, 3.0 g of sodium acetate, 3.0 g of sodium bicarbonate, and 1.0 g of dodecylbenzenesulfonic acid were mixed and left at 40 ° C. for one day.

Step 4: The donpi was removed from the neutralization solution and rinsed with water (200 g ㅧ once). The drum was filled with 100 g of water, 1 g of 20% ammonia water, 1.0 g of homogenized charcoal (Tanigan R7, manufactured by Bayer), 10 g of synthetic oil liquor (INGRASSANTE VFM, manufactured by ALPA), and 2 g of sulfuric acid. After preparing (pH 3.5), the pig skin was soaked and the drum was rotated for 3 hours at a temperature of 60 ° C.

Step 5: The donpi was removed from the eggplant solution and rinsed with water (200 g ㅧ once). Then, the drum was filled with 100 g of water and 3 g of sodium thiosulfate (Na ₂ S ₂ O ₃ ) to prepare a reducing solution, and then the drum was immersed for 30 minutes at 25 ° C. temperature.

Step 6: The donpi was taken out from the reducing solution and rinsed with water (200 g ㅧ once). The milling step of releasing the hot plate dried pork skin in a drum to release the strength, and the Toggle step of drying the pork skin with the edges fixed to prevent shrinkage of the pork skin during drying. Leather was manufactured.

Example 2.

To prepare a natural leather by the method of Example 1, 3 g of sodium bisulfite (NaHSO ₃ ) was used in place of sodium thiosulfate (Na ₂ S ₂ O ₃ ) as a reducing agent.

Comparative Example 1

A natural leather fabric was manufactured by the method of Example 1, but the reduction process of the fifth step was not performed.

Comparative Example 2

To prepare a natural leather fabric by the method of Example 1, in the fourth step of the dyeing eggplant process instead of synthetic oil eggplant (INGRASSANTE VFM, manufactured by ALPA company) natural oil eggplant agent (suboxidized eggplant oil based on soybean oil ) Was used.

Comparative Example 3

To prepare a natural leather fabric by the method of Example 1, in the fourth step of the dyeing eggplant process instead of synthetic oil eggplant (INGRASSANTE VFM, manufactured by ALPA company) natural oil eggplant agent (suboxidized eggplant oil based on soybean oil ), And the reduction process of the fifth step was not performed.

[Experimental Example]

For the natural leather prepared in Examples 1, 2 and Comparative Examples 1 to 3, the tensile strength, washing dyeing fastness, UV discoloration, thermochromic, and hexavalent chromium content were measured. The results are shown in Table 1 below.

1) Tensile strength: According to the KS M 6882 test method, the maximum load when the test piece is cut by pulling at a tensile speed of 100 ± 20 mm / min by a tensile tester was read, and obtained according to the following equation (1). The test value was the average of the measured values of two test pieces.

[Equation 1]

In Equation 1, T represents tensile strength, W represents the maximum load during cutting, and S represents the cross-sectional area of the test piece.

2) Washing color fastness: Put 0.5 g of detergent, 100 mL of water and 10 stainless steel beads in the test bottle of the laundry tester according to the KS K 0430 test method, and put the composite specimen sealed with the test specimen and the attached bag at the temperature of 40 ℃. Sealed and then run for 30 minutes. Excess water was removed from the filter paper and dried at 40 ° C. to 45 ° C. and then evaluated on a gray scale.

3) UV discoloration: A method of measuring the discoloration of leather by UV according to ASTM D 1148 test method. After disposing the specimen in a chamber and exposing it to a sun lamp for 24 hours, the discoloration degree is gray scale. Evaluated as.

4) Thermal discoloration: A method of measuring the discoloration of leather by heat. The specimen was placed in a dryer and exposed to 110 ° C. for 1 hour, and then the degree of discoloration was evaluated by gray scale.

5) Hexavalent chromium content: A method of measuring the hexavalent chromium content in a leather fabricated according to EN ISO 17075 test method, eluting soluble hexavalent chromium in a sample using a phosphate buffer solution of pH 8.0, If necessary, the material subject to detection was removed by solid phase extraction. The eluted chromium was oxidized from 1,5-diphenylcarbazide to 1,5-diphenylcarbazone to spectroscopically quantify at 540 nm.

Item Suitable range
(Spec) Example Comparative example One 2 One 2 3 Tensile Strength (Kgf / ㎡) 1.5 or more 1.7 1.6 1.7 1.7 1.8 Wash fastness 3 or more 4 4 4 4 4 UV discoloration 3 or more 4 4 4 2 2 Heat discoloration 3 or more 4 4 4 2 2 Cr ⁶⁺ content (ppm) 3 or less 0 0 40 20 60

As can be seen from the results of Table 1, the leather produced by the method of Examples 1 and 2 according to the present invention satisfies all the properties required for natural leather, such as tensile strength, color fastness to washing, UV discoloration, thermochromic Hexavalent chromium is not detected at all.

On the contrary, Comparative Example 1 in which the reduction step was omitted showed the result that 40 ppm or more of hexavalent chromium was detected. In Comparative Example 2 using a natural oil branching agent rather than a synthetic oil as a branching agent, hexavalent chromium was detected at 20 ppm or more and showed a low UV discoloration degree. In addition, Comparative Example 3, which carries out the coating step immediately after the dyeing eggplant process using natural oil eggplant without a reduction step, has a high hexavalent chromium content, which is difficult to apply as an environmentally friendly leather and does not satisfy all the properties required as natural leather. I can't.

Therefore, the manufacturing method of the natural leather of the present invention is useful as an environmentally friendly leather manufacturing method.

Claims (3)

Fabric preparation step comprising the process of immersing the salt skin in hair loss, deliming, and acid solution of pH 2-3;
An oiliness step comprising a process of tanning the prepared fabric with chromium (Cr);
A neutralization step of raising the pH of the tanned fabric to 5 to 7;
Dyeing branch step comprising the step of having the neutralized fabric as a synthetic oil branch agent;
The dyed fabric is reduced to hexavalent chromium (Cr ⁶⁺ ) to trivalent chromium (Cr ³⁺ ) using a reducing agent selected from sodium thiosulfate (Na ₂ S ₂ O ₃ ) and sodium bisulfite (NaHSO ₃ ). Reducing step to make; And
Drying the reduced fabric;
Natural leather manufacturing method comprising a.
The method according to claim 1,
The synthetic oil branching agent is a method of producing natural leather, characterized in that the synthetic oil selected from paraffin oil, spindle oil, and silicone oil mixed with water at a concentration of 5 to 15% by weight.
The method according to claim 1,
The reducing agent is a method of producing natural leather, characterized in that used by mixing in water at a concentration of 0.1 to 5.0% by weight.