JP2009067847A - Re-tanning agent and leather product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a re-tanning agent for achieving production of "light leather" products compared to leather products produced by using a conventional re-tanning agent. <P>SOLUTION: The re-tanning agent using a collagen powder comprising crosslinked regenerated collagen is provided, and the agent is used for carrying out a re-tanning process on leather tanned by using a chromium tanning agent or formalin usually used as a tanning agent. Thus, leather products achieving further light-weight can be produced while maintaining sufficient whiteness, physical strength and weather resistance such as fastness against sun rays as characteristics of normal leather products. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to retanning leather tanned with chromium tanning agents or formalin.

  Leather tanned products are made from raw hides of various animals such as cattle and pigs through a processing process called “tanning”, which usually consists of two processes called “tanning” and “re-tanning”. It is carried out using a suitable tanning agent.

For example, a leather tanning method is disclosed in which a tanned leather or formalin is used as the tanning agent, and the tanned leather is retanned with titanyl sulfate or ammonium sulfate as the retanning agent (Patent Document 1). However, leather tanned products produced by such a method have a high specific gravity, and the needs for “light leather” products are increasing in recent years as the tastes for leather products are diversified.
JP-A-63-118400

    The object of the present invention is to provide a retanning method for producing a "lighter leather" compared to conventional retanning techniques.

That is, the present invention
[1] A retanning agent characterized by containing a collagen powder comprising crosslinked regenerated collagen.

  [2] The retanning agent according to claim 1, wherein the regenerated crosslinked collagen is crosslinked with a treatment liquid containing an organic compound and / or a metal salt.

  [3] The organic compound is a monofunctional epoxy compound, and the following general formula (1):

(In the formula, R represents a substituent represented by R ₁ —, R ₂ —O—CH ₂ — or R ₂ —COO—CH ₂ —, and R ₁ represents a hydrocarbon group having 2 or more carbon atoms or CH. _{3. The} retanning agent according to claim 1, wherein the retanning agent is ₂ Cl, and R ₂ represents a hydrocarbon group having 4 or more carbon atoms.

  [4] The retanning agent according to any one of claims 1 to 3, wherein the metal salt is basic aluminum chloride or basic aluminum sulfate represented by the following formula.

Al (OH) _n Cl _3-n or Al ₂ (OH) _2n (SO ₄ ) _3-n
(Where n is 0.5 to 2.5)
[5] The retanning agent according to any one of claims 1 to 5, wherein the average particle size of the collagen powder is 0.01 to 80 µm.

  [6] A leather tanned product comprising 1 to 10% by weight of the leather of the retanning agent according to any one of claims 1 to 5.

  [7] A leather tanned product obtained by retanning a leather tanned with a chrome tanning agent or formalin with the retanning agent according to claims 1, 2, 3, 4 and 5.

  [8] A leather characterized by adding a retanning agent according to claims 1, 2, 3, 4 and 5 to a leather tanned with a chrome tanning agent or formalin, and retanning with a rotating drum. A method of manufacturing tanned products.

  The retanning agent of the present invention can produce a leather tanned product having a light specific gravity and a reduced weight.

  Embodiments of the present invention will be described below.

  The retanning agent of the present invention is a collagen powder composed of crosslinked regenerated collagen.

  The average particle size of the collagen powder of the present invention is preferably about 0.1 to several mm since it shows a tanning effect. More preferably, the effect is improved with a powder having an average particle size of 0.01 to 80 μm. Particularly preferably, the effect is remarkable with a powder having an average particle diameter of 0.01 to 20 μm. A powder having an average particle size of 0.01 to 20 μm can be prepared by classifying a crushed regenerated collagen powder. In addition, it is called chromium, formaldehyde, glutaraldehyde, aluminum, iron, zirconium salts used in the present tanning, or synthin commonly used in retanning, as long as the effect of the present retanning agent is not impaired during retanning. Retanning agents such as synthetic tannins and synthetic tannins synthesized by imitating plant tannins can be used as necessary. As used herein, synthane includes, for example, phenols and / or aryl sulfonates and various polymers and copolymers such as those obtained by condensing formaldehyde with acrylate, methacrylate, acrylamide and / or acrylonitonyl homopolymers and copolymers. It is.

  The collagen powder of the present invention is composed of crosslinked regenerated collagen. Cross-linked regenerated collagen can be obtained by producing a solubilized collagen solution from the skin, bones, tendons, etc. of animals such as cattle, pigs, horses, deer, rabbits, birds, fish, etc., and crosslinking the collagen. Thus, it is possible to provide a novel collagen powder that can solve the quality problems of the conventional collagen powder. Furthermore, by spinning a solubilized collagen aqueous solution into regenerated collagen fibers, a completely new collagen powder can be provided by thoroughly purifying the collagen and carrying out precise crosslinking in the fiberizing process by spinning.

  As a method for producing the regenerated collagen, for example, as disclosed in Japanese Patent Application Laid-Open No. 2002-249882, it is preferable to use a portion of the floor skin as a raw material. The floor skin is obtained from, for example, fresh floor skin obtained from animals such as cows, pigs, horses, deer, sea breams, birds, fish, and salted raw skin. Most of these skins are composed of insoluble collagen fibers, but are usually used after removing the meaty portion adhering to the net and removing the salt used to prevent spoilage and alteration. In addition, other materials such as bones and tendons of the animals can be used in the same manner.

  The insoluble collagen fibers contain impurities such as lipids such as glyceride, phospholipids and free fatty acids, proteins other than collagen such as glycoproteins and albumin. These impurities have a great influence on quality such as gloss and strength, odor and the like when powdered. Therefore, for example, lime pickled to hydrolyze the fat in insoluble collagen fibers, unraveling the collagen fibers, and then subjected to leather treatments such as acid / alkali treatment, enzyme treatment, solvent treatment, etc. It is preferable to remove these impurities in advance.

  The insoluble collagen that has been treated as described above is subjected to a solubilization treatment in order to cleave the cross-linked peptide portion. As the solubilization method, a publicly-known publicly known alkali solubilization method or enzyme solubilization method can be applied. When applying the alkali solubilization method, it is preferable to neutralize with an acid such as hydrochloric acid. In addition, you may use the method described in Japanese Patent Publication No.46-15033 as an improved method of the conventionally known alkali solubilization method.

  The enzyme solubilization method has an advantage that regenerated collagen having a uniform molecular weight can be obtained, and can be suitably employed in the present invention. As such an enzyme solubilization method, methods described in, for example, Japanese Patent Publication No. 43-25829 and Japanese Patent Publication No. 43-27513 can be employed. Further, the alkali solubilization method and the enzyme solubilization method may be used in combination.

  When the solubilized collagen is further subjected to operations such as pH adjustment, salting out, washing with water and solvent treatment, it is possible to obtain regenerated collagen with excellent quality and so on. It is preferable to apply a treatment. The solubilized collagen obtained has an acidity adjusted to pH 2 to 4.5 with an acid such as hydrochloric acid, acetic acid, lactic acid or the like so as to be a stock solution having a predetermined concentration of, for example, 1 to 15% by weight, preferably about 2 to 10% by weight. Dissolved using solution. The obtained aqueous collagen solution may be defoamed with stirring under reduced pressure as necessary, and may be filtered to remove fine dust that is a water-insoluble matter. In the solubilized collagen aqueous solution obtained, if necessary, for example, a stabilizer for the purpose of improving mechanical strength, improving water resistance / heat resistance, improving gloss, improving spinnability, preventing coloring, preserving, etc. An appropriate amount of an additive such as a water-soluble polymer compound may be blended.

  Regenerated collagen is formed by discharging the solubilized collagen aqueous solution into the inorganic salt aqueous solution through, for example, a spinning nozzle or a slit. As the inorganic salt aqueous solution, for example, an aqueous solution of a water-soluble inorganic salt such as sodium sulfate, sodium chloride, or ammonium sulfate is used, and the concentration of these inorganic salts is usually adjusted to 10 to 40% by weight. The pH of the inorganic salt aqueous solution is usually 2 to 13, preferably 4 to 12, by adding a metal salt such as sodium borate or sodium acetate, hydrochloric acid, boric acid, acetic acid, sodium hydroxide, or the like. It is preferable to adjust. When the pH is less than 2 or exceeds 13, the peptide bond of collagen tends to be subject to hydrolysis, and the target collagen powder tends to be difficult to obtain. Further, the temperature of the inorganic salt aqueous solution is not particularly limited, but it is usually preferably 35 ° C. or lower. When the temperature is higher than 35 ° C., the soluble collagen is denatured, so that the strength is lowered and stable production becomes difficult. In addition, although the minimum of temperature is not specifically limited, Usually, it can adjust suitably according to the solubility of inorganic salt.

  The free amino group of the collagen is modified with an alkyl group having 2 to 20 carbon atoms and having a hydroxyl group or an alkoxy group at the β-position or γ-position. The carbon number main chain indicates a continuous carbon chain of an alkyl group bonded to an amino group, and the number of carbons existing through other atoms is not considered. As a reaction for modifying a free amino group, a conventionally known alkylation reaction of an amino group can be used. In view of reactivity, ease of treatment after the reaction, etc., the alkyl group having 2 to 20 carbon atoms having a hydroxyl group or an alkoxy group at the β-position is preferably a compound represented by the following general formula (2).

—CH ₂ —CH (OX) —R (2)
(In the formula, R represents a substituent represented by R ¹ —, R ² —O—CH ₂ — or R ² —COO—CH ₂ —, and R ¹ in the substituent has 2 or more carbon atoms. A hydrocarbon group or CH ₂ Cl, R ² represents a hydrocarbon group having 4 or more carbon atoms, and X represents hydrogen or a hydrocarbon group.)
Preferable examples of the general formula (2) include a glycidyl group, a 1-chloro-2-hydroxypropyl group, and a 1,2-dihydroxypropyl group. In addition, a structure in which a glycidyl group is added to a free amino group in collagen can be mentioned. Furthermore, a structure in which the epoxy compound used is subjected to ring-opening addition and / or ring-opening polymerization starting from the hydroxyl group contained in the alkyl group described in the above-mentioned preferred group can be mentioned. Examples of the terminal structure include those having the aforementioned alkyl group structure.

  Examples of amino acids constituting the free amino group of the regenerated collagen include lysine and hydroxylysine. Furthermore, although the amino acid that originally constitutes collagen is arginine, the amino group of ornithine, which is produced by partial hydrolysis during hydrolysis under alkaline conditions to obtain the regenerated collagen, is also present. Alkylation reaction is performed. In addition, in the present invention, the reaction proceeds also in the secondary amine contained in histidine.

  The modification rate of the free amino group can be measured by amino acid analysis, and calculated based on the amino acid analysis value of the regenerated collagen fiber before the alkylation reaction or the known composition of the free amino acid constituting the collagen used as the raw material Is done. In the modification of the amino group in the present invention, the structure modified with an alkyl group having 2 or more carbon atoms having a hydroxyl group or an alkoxy group at the β-position or γ-position may be 50% or more of the free amino group. The other moiety may be a free amino group or a structure modified with another substituent. The modification rate of the free amino acid in the regenerated collagen needs to be 50% or more, more preferably 65% or more, and still more preferably 80% or more. When the reaction rate is low, good characteristics cannot be obtained due to heat resistance.

  Here, in the modification of a free amino group, one molecule of an alkylating agent usually reacts per one free amino group, but two or more molecules may react. Furthermore, a cross-linking reaction may be present in the molecule or between the molecules via a hydroxyl group, an alkoxy group or other functional group present in the β-position or γ-position of the alkyl group bonded to the free amino group. . Specific examples of the alkylation reaction include an addition reaction of an epoxy compound, an addition reaction of a hydroxyl group at the α-position or β-position or an aldehyde compound having this derivative, and a subsequent reduction reaction, a hydroxyl group at the β-position or γ-position. Alternatively, a substitution reaction such as a halogenated compound having 2 or more carbon atoms having an alkoxy group, an alcohol, and an amine is exemplified, but the invention is not limited thereto.

  Treatment liquids containing organic compounds include aldehydes, epoxies, phenol derivatives, etc., which are used for crosslinking and are alkylation reagents. The modification reaction by is preferable because it exhibits excellent characteristics, and a monofunctional epoxy compound is particularly preferable.

  Specific examples of the monofunctional epoxy compound include, for example, olefin oxides such as ethylene oxide, propylene oxide, butylene oxide, isobutylene oxide, octene oxide, styrene oxide, methyl styrene oxide, epichlorohydrin, epibromohydrin, and glycidol. Glycidyl methyl ether, butyl glycidyl ether, octyl glycidyl ether, nonyl glycidyl ether, undecyl glycidyl ether, tridecyl glycidyl ether, pentadecyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl Ether, t-butylphenyl glycidyl ether, dibromophenyl glycidyl ether, benzyl glycidyl ether, polyethylene Examples include glycidyl ethers such as xidoglycidyl ether, glycidyl formate, glycidyl acetate, glycidyl acrylate, glycidyl methacrylate, glycidyl benzoate and the like, glycidyl amides, etc. Absent.

  Among monofunctional epoxy compounds, since the water absorption rate of regenerated collagen decreases, it is preferable to treat with a monofunctional epoxy compound represented by the following general formula (1). In the formula, R is the same as described above.

The regenerated collagen thus obtained is swollen with water or an aqueous solution of an inorganic salt. This swelling is preferably in a state containing water or an aqueous solution of an inorganic salt 4 to 15 times the weight of regenerated collagen. If it is in this range, the aluminum salt content in the regenerated collagen is moderate, and the water resistance and strength are balanced, so that it is easy to handle.

The treatment solution containing a metal salt is used for crosslinking the swollen regenerated collagen, and here, it is immersed in an aqueous solution of an aluminum salt. As the aluminum salt aqueous aluminum salt solution, the following _{formula, Al (OH) n Cl 3} -n, or _{Al 2 (OH) 2n (SO} 4) in _3-n (wherein, n is 0.5 to 2. 5). Basic aluminum chloride or basic aluminum sulfate represented by formula (5) is preferred. Specifically, for example, aluminum sulfate, aluminum chloride, alum or the like is used. These aluminum can be used individually or in mixture of 2 or more types. The aluminum salt concentration of the aluminum salt aqueous solution is preferably 0.3 to 5% by weight in terms of aluminum oxide. If the concentration of the aluminum salt is within this range, the content of the aluminum salt in the regenerated collagen fiber is moderate, and the balance of water resistance, softness after treatment, and texture can be achieved.

  The pH of the aluminum salt aqueous solution is usually adjusted to 2.5 to 5 using, for example, hydrochloric acid, sulfuric acid, acetic acid, sodium hydroxide, sodium carbonate or the like. If the pH is less than 2.5, the collagen structure tends to be broken and denatured. If the pH exceeds 5, the aluminum salt precipitates and is difficult to penetrate. This pH is first adjusted to 2.2 to 3.5, and the aluminum salt aqueous solution is sufficiently infiltrated into the regenerated collagen. Thereafter, for example, sodium hydroxide, sodium carbonate or the like is added to 3.5 to 5 It is preferable to complete the treatment by adjusting to pH 1, but when a highly basic aluminum salt is used, only the first pH adjustment of 2.5 to 5 may be used. Moreover, the liquid temperature of this aluminum salt aqueous solution is although it does not specifically limit, 50 degrees C or less is preferable. When the liquid temperature exceeds 50 ° C., the regenerated collagen tends to be denatured.

  The time for immersing the regenerated collagen in this aluminum salt aqueous solution is 3 hours or more, preferably 6 to 25 hours. If the immersion time is less than 3 hours, the reaction of the aluminum salt is difficult to proceed, and the water resistance of the regenerated collagen becomes insufficient. Moreover, although there is no restriction | limiting in particular in the upper limit of immersion time, reaction of aluminum salt will fully advance within 25 hours, and water resistance will also become favorable. It should be noted that an inorganic salt such as sodium chloride, sodium sulfate, potassium chloride or the like may be appropriately added to the aqueous solution of the aluminum salt so that the aluminum salt is not rapidly absorbed into the regenerated collagen and uneven concentration occurs.

  The crosslinked regenerated collagen thus treated with the aluminum salt is then washed, oiled and dried. The regenerated collagen fiber obtained in this way has almost no coloration treated with a conventional chromium salt and is excellent in water resistance, so it is clear that the advantages of the present invention are great. In order to prevent collagen denaturation (gelatinization), attention should be paid to the temperature history during processing. In order to prevent denaturation even after crosslinking, it is essential to maintain the moisture and temperature control during production, powdering and product storage at or below the denaturation conditions of regenerated collagen. Since most of the gelatinized materials have changed characteristics, it is difficult to express the characteristics of the target collagen. It is advantageous to use the regenerated collagen in terms of preventing denaturation.

  Here, an aluminum salt is used as the metal salt, but metal salts such as zirconium and iron can also be used.

  In the case of spinning from a collagen solution, it is easy to mix and color a pigment or dye in the solution or immediately before spinning by a known method. The pigments and dyes to be used can be selected according to the purpose, without any elution separation in the spinning process or powdering process, and according to the required quality of the product used. Moreover, a filler, an anti-aging agent, a flame retardant, an antioxidant, etc. can also be added as needed. In such a collagen fiber manufacturing process, a film can be manufactured by the same method using a slit nozzle, and this can be pulverized.

  In the present invention, the regenerated collagen obtained by the above method can be made into a collagen powder (regenerated collagen powder) composed of regenerated collagen crosslinked by pulverization. However, when the regenerated collagen is a fiber or film, Can be made into a regenerated collagen powder by cutting to a fiber length or size suitable for pulverization, further pulverizing the cut, or directly pulverizing the fiber or film. The cutter that can be used in the production of the regenerated collagen powder in the present invention is not particularly limited, but is cut to about 0.1 mm to several mm with a rotary blade cutter, belt cutter, shearing machine, cutter mill, etc., which are usually used for cutting fibers. To do. In addition, this cut cotton can be crushed in roller mills, rod mills, ball mills (dry, wet), jet mills, pin mills, vibration mills, centrifugal (CF) mills, planetary ball mills, shearing mills such as grinder mills, etc. And then finely pulverized using a medium stirring type ultrafine pulverizer or the like. By using a hard ball such as a zirconia ball, it can be preferably used from the viewpoint of preventing the ball material from being mixed into the powder and from the viewpoint of grinding efficiency, but it is also possible to use a ball of another material such as an alumina ball. it can.

  The leather tanned product of the present invention is produced from raw hides of various animals such as cattle and pigs through a processing step called “real tanning” and “retanning”. For example, it can be produced by tanning leather tanned with a chrome tanning agent or formalin as the present tanning agent using a retanning agent containing collagen powder composed of crosslinked regenerated collagen.

  The leather tanned product of the present invention can be produced using the following method. For example, leather tanned with chrome tanning agent or formalin is whitened by hot water washing with 0.3% oxalic acid, and then neutralized with sodium formate / bicarbonate (PH 4.2-4.5). It is put in a drum, collagen powder made of crosslinked regenerated collagen according to the present invention is added at a ratio of 1 to 10% by weight of leather weight, and the drum is rotated for 1 to 7 hours to perform retanning. Thereafter, the liquid is drained, water is added, a greasing agent is added and the treatment is performed for 1 hour, and then the pH is adjusted to 3.2. Then, the process is completed by washing with water. The addition amount of the retanning agent of the present invention to be used is preferably 5 to 10% by weight. If the amount of collagen powder is in the range of 1 to 10% by weight of the leather weight, a balance between surface properties and weight reduction can be achieved.

  In addition, the said addition amount (weight%) of the retanning agent of this invention is the weight with respect to the weight of the leather after removing the extra water | moisture content from the tanning process by chromium or formalin, and then the whitening process, and also neutralized. %.

  Examples and comparative examples will be described below.

  Example 1 showed the production method of the leather sample which used CF mill powder, and Example 2 used R1 fine powder. In addition, Comparative Example 1 shows a method for producing a leather sample using a mixture of Sintan, namely, Retan 540, which is one of Sintan, and Comparative Example 2, which is Retan 540, Retigan ZF, and Tanigan 3LN. Note that “%” simply means “% by weight”.

Example 1
A commercially available chrome-shaved leather was whitened by washing with hot water added with 0.3% oxalic acid, and then neutralized with sodium formate / sodium bicarbonate (PH 4.2-4.5). The retanning agent is added at a rate of 5% of the leather weight, and the drum is rotated for 1 to 7 hours to perform retanning. Here, when the retanning agent of the present invention is added, all the water in the drum after neutralization is removed, and the water contained in the leather is used as the main moisture, thereby enabling efficient treatment. Thereafter, the liquid is drained, water is added, a greasing agent is added and the treatment is performed for 1 hour, and then the pH is adjusted to 3.2. Then, the process is completed by washing with water. The retanning agent of the present invention used here is obtained by pulverizing crosslinked regenerated collagen with a CF (centrifugel) mill (referred to as CF mill).

(Example 2)
A commercially available chrome-shaved leather was whitened by washing with hot water added with 0.3% oxalic acid, and then neutralized with sodium formate / sodium bicarbonate (PH 4.2-4.5). The retanning agent is added at a rate of 5% of the leather weight, and the drum is rotated for 1 to 7 hours to perform retanning. Here, when the retanning agent of the present invention is added, all the water in the drum after neutralization is removed, and the water contained in the leather is used as the main moisture, thereby enabling efficient treatment. Thereafter, the liquid is drained, water is added, a greasing agent is added and the treatment is performed for 1 hour, and then the pH is adjusted to 3.2. Then, the process is completed by washing with water. The retanning agent of the present invention used here is a fine powder (referred to as R1 fine powder) obtained by classifying a crosslinked regenerated collagen obtained by pulverizing with a CF (centrifugel) mill (CF mill).

(Comparative Example 1)
Commercially available chrome-shaved leather was whitened by washing with 0.3% oxalic acid and then neutralized with sodium formate / bicarbonate (PH 4.2-4.5). The tanning agent is added at a rate of 5% of the leather weight and the drum is retanned for 1-7 hours. Thereafter, the liquid is drained, water is added, a greasing agent is added and the treatment is performed for 1 hour, and then the pH is adjusted to 3.2. Then, the process is completed by washing with water. The commercially available retanning agent used here is Retan 540 (manufactured by Rohm and Haas) which is one of the syntans.

(Comparative Example 2)
Commercially available chrome-shaved leather was whitened by washing with 0.3% oxalic acid and then neutralized with sodium formate / bicarbonate (PH 4.2-4.5). The tanning agent is added at a rate of 5% of the leather weight and the drum is retanned for 1-7 hours. Thereafter, the liquid is drained, water is added, a greasing agent is added and the treatment is performed for 1 hour, and then the pH is adjusted to 3.2. Then, the process is completed by washing with water. The commercial retanning agent used here is a mixture of Retan 540 belonging to Sintan, Retigan ZF (manufactured by LANXESS), and Tanigan 3LN (manufactured by LANXESS).

  The following evaluation was performed on the samples produced in this example and the comparative example.

(Visual, tactile evaluation and thickness measurement)
About the sample produced in Example (1,2) and Comparative example (1,2), the whiteness evaluation by visual evaluation, the elasticity of the silver surface part by tactile sensation, the flesh of the flesh surface (opposite side of the silver surface) In order to evaluate the length of the leather and light leather, 5 points were randomly measured for each sample with a thickness gauge to evaluate the swelling, and the average was taken as the thickness of the leather sample (shown in Table 1).

  As a result, both CF mill and R1 fine powder treated with the Shintan of the comparative example have higher whiteness, better elasticity, and moreover, the state of the fluff is kept at an appropriate length. there were. Although the thickness was within the range of five-point measurement, the result was that the sample treated with the CF mill powder and R1 fine powder of the example was thicker than the comparative sample.

(Physical strength evaluation)
The samples prepared in Examples (1, 2) and Comparative Examples (1, 2) were subjected to a tensile test and a tear test by a method according to JIS K 6550 as physical strength evaluation (shown in Table 2). The evaluation was performed by measuring two points in each of two directions of parallel and vertical directions, and the average values were listed in the table.

  As a result, in both the tensile and tear tests, the samples treated with CF mill and R1 fine powder showed almost the same strength as the samples treated with Shintan and Retan 540. In actual product use, the strength of the sample satisfies the required strength.

(Evaluation of fastness to sunlight)
For the samples prepared in Examples (1, 2) and Comparative Examples (1, 2), as a sunlight fastness test, an irradiation test using a carbo arc lamp (compares color difference with an unirradiated one in an irradiation time of 20 hours). (Shown in Table 3). The larger the ΔE * ab value in Table 3, the more yellow the sample is.

  As a result, the sample treated with the CF mill of Example and R1 fine powder showed higher whiteness and higher fastness to sunlight than the Shintan and Retan 540 treated samples of Comparative Example.

(Aluminum content measurement)
About the sample produced in Example 1, after dividing | segmenting into three layers, a silver surface, a center, and a meat surface, after carrying out wet oxidative decomposition (nitric acid-sulfuric acid-perchloric acid) about each layer, aluminum determination is performed by atomic absorption analysis. went. The aluminum content% in the table is shown as a value relative to the weight of the whole leather dried indoors for 3 days.

  As a result, the presence of aluminum was confirmed on any of the silver surface, the center, and the meat surface, and the silver surface and the meat surface on the surface side had higher values.

Claims (8)

  A retanning agent comprising a collagen powder comprising crosslinked regenerated collagen.   The retanning agent according to claim 1, wherein the regenerated crosslinked collagen is subjected to a crosslinking treatment with a treatment liquid containing an organic compound and / or a metal salt. The organic compound is a monofunctional epoxy compound, and the following general formula (1):
(In the formula, R represents a substituent represented by R ₁ —, R ₂ —O—CH ₂ — or R ₂ —COO—CH ₂ —, and R ₁ represents a hydrocarbon group having 2 or more carbon atoms or CH. _{3. The} retanning agent according to claim 1, wherein the retanning agent is ₂ Cl, and R ₂ represents a hydrocarbon group having 4 or more carbon atoms. The retanning agent according to any one of claims 1 to 3, wherein the metal salt is basic aluminum chloride or basic aluminum sulfate represented by the following formula.
Al (OH) _n Cl _3-n or Al ₂ (OH) _2n (SO ₄ ) _3-n
(Where n is 0.5 to 2.5)   6. The retanning agent according to claim 1, wherein the collagen powder has an average particle size of 0.01 to 80 [mu] m.   A leather tanned product comprising 1 to 10% by weight of the leather weight of the retanning agent according to any one of claims 1 to 5.   A leather tanned product obtained by retanning leather tanned with a chrome tanning agent or formalin with the retanning agent according to claim 1, 2, 3, 4 and 5.   A leather tanned product characterized by adding a retanning agent according to claims 1, 2, 3, 4 and 5 to a leather tanned using a chrome tanning agent or formalin, and retanning using a rotating drum. Production method.