Crocodile leather finishing method

Abstract

The invention relates to the technical field of tanning, in particular to a crocodile leather finishing method which comprises the following steps: step 1, cleaning crocodile leather to be treated; 2, after the crocodile leather is cleaned, the surface of the crocodile leather is coated with a coating; 3, after the coating is sprayed, glazing and polishing are conducted; and 4, finishing the coating. According to the crocodile leather finishing method, micromolecular acrylic filling resin, polyurethane resin and silanized carboxyl modified nanocellulose are compounded, so that a coating is endowed with excellent peel strength, high toughness and high wear resistance, and the acrylic resin is subjected to composite enhanced modification by screening the types and median particle sizes of the nanocellulose, so that the wear resistance of the crocodile leather is improved. The coating is endowed with excellent wear resistance, toughness and color fastness, and the wear resistance of the coating is further improved by using the reinforcing auxiliary agent silanization modified carboxyl nano cellulose and carbonized collagen fiber powder.

Description

Technical Field

[0001] The invention relates to the technical field of leather making, in particular to a crocodile leather finishing method. Background Art

[0002] Crocodile leather is known as the "gold" of leathers for its unique natural gradient checkered pattern, strong texture and its natural luster that becomes more visible the longer it is used. It is known for its top luxury and rarity. Crocodile leather has fine grain and prominent patterns, and a bone structure on the edge, which makes it easy to cause cortical damage during use, which places high demands on the wear resistance, flexibility, and resistance to dry and wet rubbing of the leather coating.

[0003] The present invention uses a modified adhesive, a reinforced acrylic resin and a reinforcing auxiliary agent to simultaneously reinforce the bottom layer, the middle layer and the top layer coatings, thereby improving the adhesion fastness, the wear resistance and the wet rubbing resistance of the coatings, and simultaneously improving the bending resistance of the coatings, which is of great significance for improving the use of crocodile leather products. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the shortcomings of the prior art, the present invention provides a crocodile leather finishing method, which has the advantages of improving the adhesion fastness, wear resistance and wet rubbing resistance of the coating, while improving the bending resistance of the coating, thereby solving the above-mentioned problems.

[0006] (II) Technical solution

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A crocodile leather finishing method comprises the following steps:

[0009] Step 1: Clean the crocodile leather to be treated;

[0010] Step 2: After cleaning, the crocodile leather is coated on its surface;

[0011] Step 3: Polishing and polishing after coating spraying;

[0012] Step 4: Finishing.

[0013] Preferably, the coating in step 2 comprises a reinforced bottom layer, a reinforced middle layer and a reinforced top layer.

[0014] Preferably, the enhanced bottom layer uses the following slurry formulation components:

[0015] Water: 40-55 parts; composite adhesive resin: 10-15 parts; enhanced acrylic resin: 30-35 parts; reinforcing auxiliary agent: 0-4 parts; dye water: 5-15 parts; the sum of the contents of each component is 100 parts.

[0016] The reinforced middle layer uses the following slurry formulation components:

[0017] Water: 40-60 parts; polyurethane resin: 10-15 parts; enhanced acrylic resin: 15-20 parts; reinforcing auxiliary agent: 0-4 parts; wax emulsion: 6-10 parts; dye water: 8-10 parts; the sum of the contents of each component is 100 parts.

[0018] The reinforced top layer uses the following slurry formulation components:

[0019] Water: 50-60 parts; polyurethane brightener: 35-40 parts; hand feeling agent 2-3 parts; cross-linking agent 2-5 parts; reinforcing agent: 0-4 parts; the sum of the contents of each component is 100 parts.

[0020] Preferably, the composite adhesive resin is composed of small molecule acrylic filling resin, polyurethane resin, and silanized carboxyl modified nanocellulose, and the preferred component ratio is small molecule acrylic resin: polyurethane resin is 1:25 to 1:10, and the silanized carboxyl modified nanocellulose accounts for 3% to 6% of the whole slurry.

[0021] Preferably, the enhanced acrylic resin is composited with acrylic resin and silanized carboxyl-modified nanocellulose, and the preferred component ratio is that the silanized carboxyl-modified nanocellulose accounts for 3% to 6% of the entire slurry.

[0022] Preferably, the reinforcing aid is one of silanized carboxyl-modified nanocellulose and carbonized collagen fiber powder.

[0023] Preferably, the silanized carboxyl modified nanocellulose preferably has a median particle size of 30 to 50 μm, and the carbonized collagen fiber powder is obtained by carbonizing and keeping warm at 500° C. for 2 to 6 hours and then grinding, and preferably has a particle size of 20 nm to 3 μm.

[0024] (III) Beneficial effects

[0025] Compared with the prior art, the present invention provides a crocodile leather finishing method, which has the following beneficial effects:

[0026] The present invention gives the coating excellent peel strength, high toughness and high wear resistance by compounding small molecule acrylic filling resin, polyurethane resin and silanized carboxyl modified nanocellulose, and gives the coating excellent wear resistance, toughness and color fastness by screening the types of nanocellulose and the median particle size to carry out composite reinforcement modification on the acrylic resin, and further improves the wear resistance of the coating by using reinforcing agents silanized modified carboxyl nanocellulose and carbonized collagen fiber powder. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The present invention relates to a crocodile leather finishing method, comprising:

[0029] Embodiment 1:

[0030] (1) Preparation of silanized carboxyl-modified nanocellulose:

[0031] Weigh 100g of bleached kraft hardwood pulp with an absolute dry mass and tear it into pieces, then soak it in 500g of 20% sodium hydroxide solution, stir to make the pulp evenly dispersed, then pour 300g of 25% chloroacetic acid solution and 300g of 20% 3-(2,3-epoxypropoxy)propyltrimethoxysilane solution into the above-dispersed suspension, stir evenly and use a pulp bag to concentrate the pulp to a pulp concentration of 20%, and the extruded filtrate can be reused. The concentrated pulp is placed in a high-concentration mixing reactor and reacted at 90°C for 1.5h. After the reaction is completed, the pulp is washed with clean water to neutrality and then diluted with water to a pulp concentration of 3%. The pulp is repeatedly ground at a speed of 1500r / min using a nano-fine grinder until the median particle size of the fiber is 30μm under an optical microscope, thereby obtaining silanized carboxyl-modified nanocellulose.

[0032] (2) Crocodile leather finishing

[0033] The base coating slurry formula components: 40 parts of water; composite adhesive resin (small molecule acrylic filling resin: polyurethane resin = 1:25, silanized carboxyl modified nanocellulose accounts for 3% of the composite adhesive resin slurry): 11 parts; enhanced acrylic resin (silanized carboxyl modified nanocellulose accounts for 6% of the acrylic resin slurry) 30 parts; reinforcing auxiliary agent (silanized carboxyl modified nanocellulose) 4 parts; dye water 15 parts.

[0034] The middle layer coating uses the following slurry formula components: 40 parts of water; 15 parts of polyurethane resin; 20 parts of enhanced acrylic resin (silanized carboxyl-modified nanocellulose accounts for 5% of the acrylic resin slurry); 5 parts of reinforcing additive (silanized carboxyl-modified nanocellulose); 10 parts of wax emulsion; 10 parts of dye water.

[0035] The top coating uses the following slurry formula components: 50 parts of water; 40 parts of polyurethane brightener; 3 parts of feel agent; 5 parts of cross-linking agent; 2 parts of reinforcing agent (silanized carboxyl modified nanocellulose).

[0036] The above different slurry components are sprayed and glazed and polished according to normal processes.

[0037] Embodiment 2:

[0038] (1) The preparation of silanized carboxyl-modified nanocellulose is the same as in Example 1.

[0039] (2) Preparation of carbonized collagen fiber powder: Take the shaved leather produced by the tannery, place it in a carbonization furnace, heat it to 500°C, keep it warm for 4 hours, cool it, grind it, and sieve it to obtain powder of about 20nm.

[0040] (3) Crocodile leather finishing

[0041] The base coating slurry formula components: 45 parts of water; composite adhesive resin (small molecule acrylic filling resin: polyurethane resin = 1:20, silanized carboxyl modified nanocellulose accounts for 4% of the composite adhesive resin slurry): 15 parts; enhanced acrylic resin (silanized carboxyl modified nanocellulose accounts for 6% of the acrylic resin slurry) 28 parts; reinforcing auxiliary agent 0 parts; dye water 12 parts.

[0042] The middle layer coating uses the following slurry formula components: 55 parts of water; 10 parts of polyurethane resin; 15 parts of enhanced acrylic resin (silanized carboxyl-modified nanocellulose accounts for 6% of the acrylic resin slurry); 3 parts of reinforcing additive (silanized carboxyl-modified nanocellulose); 8 parts of wax emulsion; 9 parts of dye water.

[0043] The top coating uses the following slurry formula components: 56 parts of water; 35 parts of polyurethane brightener; 2 parts of feel agent; 3 parts of cross-linking agent; 4 parts of reinforcing agent (silanized carboxyl modified nanocellulose: carbonized collagen fiber powder = 1:1).

[0044] The above different slurry components are sprayed and glazed and polished according to normal processes.

[0045] Embodiment 3:

[0046] (1) Preparation of silanized carboxyl-modified nanocellulose The preparation method was the same as in Example 1, and the median particle size of the fiber was controlled to be about 40 μm.

[0047] (2) The preparation method of carbonized collagen fiber powder is the same as that in Example 2, and the powder is sieved to obtain a powder of about 50 nm.

[0048] (3) Crocodile leather finishing

[0049] The base coating slurry formula components: 43 parts of water; composite adhesive resin (small molecule acrylic filling resin: polyurethane resin = 1:15, silanized carboxyl modified nanocellulose accounts for 5% of the composite adhesive resin slurry): 10 parts; enhanced acrylic resin (silanized carboxyl modified nanocellulose accounts for 6% of the acrylic resin slurry) 35 parts; reinforcing additive (carbonized collagen fiber powder) 2 parts; dye water 10 parts.

[0050] The middle layer coating uses the following slurry formula components: 60 parts of water; 10 parts of polyurethane resin; 16 parts of enhanced acrylic resin (silanized carboxyl-modified nanocellulose accounts for 3% of the acrylic resin slurry); 0 parts of reinforcing additive; 6 parts of wax emulsion; 8 parts of dye water.

[0051] The top coating uses the following slurry formula components: 60 parts of water; 35 parts of polyurethane brightener; 2 parts of hand feeling agent; 2 parts of cross-linking agent; 1 part of reinforcing agent (carbonized collagen fiber powder).

[0052] The above different slurry components are sprayed and glazed and polished according to normal processes.

[0053] Embodiment 4:

[0054] (1) Preparation of silanized carboxyl-modified nanocellulose The preparation method was the same as in Example 1, and the median particle size of the fiber was controlled to be about 50 μm.

[0055] (2) The preparation method of carbonized collagen fiber powder is the same as that in Example 2, and the powder is sieved to obtain powder of about 3 μm.

[0056] (3) Crocodile leather finishing

[0057] The base coating slurry formula components: 55 parts of water; composite adhesive resin (small molecule acrylic filling resin: polyurethane resin = 1:10, silanized carboxyl modified nanocellulose accounts for 3% of the composite adhesive resin slurry): 10 parts; enhanced acrylic resin (silanized carboxyl modified nanocellulose accounts for 3% of the acrylic resin slurry) 30 parts; reinforcing additive 0 parts; dye water 5 parts.

[0058] The middle layer coating uses the following slurry formula components: 49 parts of water; 13 parts of polyurethane resin; 18 parts of enhanced acrylic resin (silanized carboxyl-modified nanocellulose accounts for 4% of the acrylic resin slurry); 2 parts of reinforcing additive (carbonized collagen fiber powder); 8 parts of wax emulsion; 10 parts of dye water.

[0059] The top coating uses the following slurry formula components: 58 parts of water; 37 parts of polyurethane brightener; 2 parts of hand feeling agent; 3 parts of cross-linking agent; 1 part of reinforcing additive.

[0060] The above different slurry components are sprayed and glazed and polished according to normal processes.

[0061] Comparative Example 1:

[0062] The formula components of the bottom coating slurry are: 40 parts of water; 11 parts of adhesive resin (polyurethane resin); 30 parts of acrylic resin; and 15 parts of dye water.

[0063] The middle layer coating uses the following slurry formula components: 40 parts of water; 15 parts of polyurethane resin; 20 parts of acrylic resin; 10 parts of wax emulsion; 10 parts of dye water.

[0064] The top coating uses the following slurry formula components: 50 parts of water; 40 parts of polyurethane brightener; 3 parts of hand feeling agent; 5 parts of cross-linking agent.

[0065] The above different slurry components are sprayed and glazed and polished according to normal processes.

[0066] Comparative Example 2:

[0067] The formula components of the bottom coating slurry are: 45 parts of water; 15 parts of adhesive resin (polyurethane resin); 28 parts of acrylic resin; and 12 parts of dye water.

[0068] The middle layer coating uses the following slurry formula components: 55 parts of water; 10 parts of polyurethane resin; 15 parts of acrylic resin; 8 parts of wax emulsion; 9 parts of dye water.

[0069] The top coating uses the following slurry formula components: 56 parts of water; 35 parts of polyurethane brightener; 2 parts of hand feeling agent; 3 parts of cross-linking agent.

[0070] The above different slurry components are sprayed and glazed and polished according to normal processes.

[0071] Comparative Example 3:

[0072] The formula components of the bottom coating slurry are: 43 parts of water; 10 parts of adhesive resin (polyurethane resin); 35 parts of acrylic resin; and 10 parts of dye water.

[0073] The middle layer coating uses the following slurry formula components: 60 parts of water; 10 parts of polyurethane resin; 16 parts of acrylic resin; 6 parts of wax emulsion; 8 parts of dye water.

[0074] The top coating uses the following slurry formula components: 60 parts of water; 35 parts of polyurethane brightener; 2 parts of hand feeling agent; 2 parts of cross-linking agent.

[0075] Comparative Example 4:

[0076] The formula components of the bottom coating slurry are: 55 parts of water; 10 parts of adhesive resin (polyurethane resin); 30 parts of acrylic resin; and 5 parts of dye water.

[0077] The middle layer coating uses the following slurry formula components: 49 parts of water; 13 parts of polyurethane resin; 18 parts of acrylic resin; 8 parts of wax emulsion; and 10 parts of dye water.

[0078] The top coating uses the following slurry formula components: 58 parts of water; 37 parts of polyurethane brightener; 2 parts of hand feeling agent; 3 parts of crosslinking agent.

[0079] The above different slurry components are sprayed according to the normal process, and the glazing and polishing processes remain unchanged.

[0080] In order to fully understand the performance of the crocodile leather prepared in each embodiment, the abrasion resistance, wet rubbing resistance, bending resistance and adhesion fastness of the coating were tested according to the following methods.

[0081] Wear test: Test according to "Determination of wear resistance of leather in physical and mechanical tests" (QB / T2726-2005), grinding wheel model: CS-10, weight: 1000g. Prepare samples according to the standard, and grind the grinding wheel before each sample test. During the test, the sample condition needs to be constantly observed and the number of times wear begins to occur is recorded.

[0082] Wet rub resistance test: Refer to the standard "Leather color fastness test reciprocating friction color fastness" (QB / T2537-2001) to test the wet rub resistance of the finished product, and use wet felt for testing. According to the standard, select a load of 1000g, test the friction times 300 times, and stop to observe the color loss of the sample and the felt.

[0083] Bending resistance test: Tested in accordance with "Determination of folding fastness of leather in physical and mechanical tests" (GB / T39452-2020)

[0084] Coating adhesion fastness test: in accordance with "Physical and mechanical tests on leather - Determination of adhesion fastness of coatings" (GB / T39452-2020).

[0085]

[0086]

[0087] The table shows the performance indexes of the leather after coating in the embodiments and comparative examples.

[0088] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A crocodile leather finishing method, characterized in that: The following steps are involved: Step 1: Clean the crocodile leather to be treated; Step 2: After cleaning, the crocodile leather is coated on its surface; Step 3: Polishing and polishing after coating spraying; Step 4: Finishing.

2. A crocodile leather finishing method according to claim 1, characterized in that: The coating in step 2 includes a reinforced bottom layer, a reinforced middle layer and a reinforced top layer.

3. A crocodile leather finishing method according to claim 2, characterized in that: The enhanced bottom layer uses the following slurry formulation components: Water: 40-55 parts; composite adhesive resin: 10-15 parts; enhanced acrylic resin: 30-35 parts; reinforcing auxiliary agent: 0-4 parts; dye water: 5-15 parts; the sum of the contents of each component is 100 parts; The reinforced middle layer uses the following slurry formulation components: Water: 40-60 parts; polyurethane resin: 10-15 parts; enhanced acrylic resin: 15-20 parts; reinforcing additive: 0-4 parts; wax emulsion: 6-10 parts; dye water: 8-10 parts; the sum of the contents of each component is 100 parts; The reinforced top layer uses the following slurry formulation components: Water: 50-60 parts; polyurethane brightener: 35-40 parts; hand feeling agent 2-3 parts; cross-linking agent 2-5 parts; reinforcing agent: 0-4 parts; the sum of the contents of each component is 100 parts.

4. A crocodile leather finishing method according to claim 3, characterized in that: The composite adhesive resin is composed of small molecule acrylic resin, polyurethane resin and silanized carboxyl modified nanocellulose, wherein the preferred component ratio is 1:25-1:10, and the silanized carboxyl modified nanocellulose accounts for 3%-6% of the whole slurry.

5. A crocodile leather finishing method according to claim 3, characterized in that: The enhanced acrylic resin is composited with acrylic resin and silanized carboxyl modified nanocellulose, and the preferred component ratio is that the silanized carboxyl modified nanocellulose accounts for 3% to 6% of the whole slurry.

6. A crocodile leather finishing method according to claim 3, characterized in that: The reinforcing auxiliary agent is one of silanized carboxyl modified nanocellulose and carbonized collagen fiber powder.

7. A crocodile leather finishing method according to claim 6, characterized in that: The silanized carboxyl modified nanocellulose preferably has a median particle size of 30 to 50 μm. The carbonized collagen fiber powder is obtained by carbonizing and keeping warm at 500° C. for 2 to 6 hours and then grinding. The preferred particle size is 20 nm to 3 μm.

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