A method for manufacturing high-quality regenerated leather from leather waste

Abstract

The application provides a preparation method of high-quality regenerated leather from leather waste, comprising the following steps: (1) dispersing leather waste in an aqueous solution to prepare a leather fiber solution, wherein the concentration of the leather fiber solution is 0.05%-0.5%; (2) adding a chemical reagent PAM or CPAM into the leather fiber solution and stirring uniformly, wherein the amount of the chemical reagent is 0.1-5 wt%; (3) dehydrating and forming the leather fiber solution to prepare a wet-state regenerated leather; and (4) performing heat pressing and drying treatment on the wet-state regenerated leather to prepare a high-strength regenerated leather. The preparation method has simple preparation process and less process flow, and can prepare the high-performance regenerated leather with high strength and good uniformity, fully utilizes a large amount of leather waste, effectively reduces the waste of resources, and has wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of leather production, and particularly relates to a preparation method for preparing regenerated leather by using hot-pressing process and wet papermaking. BACKGROUND

[0002] With the increasing demand for leather products, the development market of the leather industry is rapidly increasing. The development of the leather industry is not limited to traditional leather products such as leather shoes, leather clothes, and bags. It is also rapidly developing in emerging fields such as automotive interiors, providing a new growth point for the leather industry. According to statistics, in 2022, the operating income of the leather industry and shoe industry in China reached 11339.9 billion yuan. Although in 2023, the production and sales of the leather industry in China have decreased slightly, since the beginning of 2024, the sales revenue and profit of key enterprises in the industry have shown a significant rebound, and the industry has shown a preliminary upward trend. However, such a large demand has also brought great pressure to the leather industry. According to incomplete statistics from relevant departments, about 1.6 million tons of leather waste are generated in the leather processing industry in China every year, which not only pollutes the environment but also causes a huge waste of biomass resources. In response to the "double carbon" policy and green development, how to reasonably utilize these leather waste to produce regenerated leather is one of the key research directions in the industry.

[0003] The treatment of leather waste in industry is mostly landfill or incineration, which not only causes serious pollution to the environment, but also causes a lot of resource waste. How to recycle leather waste has become one of the key research topics of researchers. At present, according to the characteristics of various types of leather waste, the utilization methods of leather waste mainly include the following three types: the first type is the edge of rawhide before tanning and the second and third layers of naked skin. This type of waste is mainly recycled for food, medicine, and daily use; the second type is the second and third layers of base leather after tanning and dyeing, which is mainly recycled for preparing regenerated leather and fillers; the third type of waste leather is mainly recycled for extracting collagen or fillers, which is mainly base leather scraps after tanning or shaved leather waste.

[0004] The leather waste used in the present application belongs to the second type of the above-mentioned waste shavings. In application, the method for manufacturing regenerated leather can be divided into wet method and dry method according to the amount of water. Although the dry method can solve the problems of large water consumption and large sewage discharge in the process of manufacturing regenerated leather, the manufacturing process is more complex than the wet method, the yield is low, and it is difficult to realize industrialized production. The present research uses the wet method to manufacture regenerated leather. Guo Peipei et al. once used the wet method to beat the leather waste into slurry, used urea-formaldehyde resin as adhesive, and manufactured regenerated leather according to the papermaking process, but the urea-formaldehyde resin has the problem of formaldehyde release in use, and its storage stability is poor. Therefore, it is still a challenging work to select a suitable auxiliary agent for manufacturing regenerated leather by wet method.

[0005] In order to expand the treatment method of leather waste, reduce resource waste, and implement the concept of "green economy" and sustainable development, the present application makes full use of leather waste, adopts hot pressing process and wet papermaking technology, uses acrylamide as an auxiliary agent, and develops a method for manufacturing high-strength regenerated leather from leather waste. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a preparation method for manufacturing high-quality regenerated leather from leather waste, which has simple preparation process, less process flow, can prepare high-performance regenerated leather with high strength and good uniformity, fully utilizes a large amount of leather waste, effectively reduces resource waste, and has wide application prospect.

[0007] The present application is implemented as follows:

[0008] A preparation method for manufacturing high-quality regenerated leather from leather waste, comprising the following steps:

[0009] (1) dispersing leather waste in an aqueous solution to prepare a leather fiber solution, wherein the concentration of the leather fiber solution is 0.05% to 0.5%;

[0010] (2) adding a chemical reagent PAM or CPAM to the leather fiber solution and stirring uniformly, wherein the amount of the chemical reagent is 0.1 to 5 wt%;

[0011] (3) dehydrating and forming the leather fiber solution to prepare a wet-state regenerated leather;

[0012] (4) hot-pressing and drying the wet-state regenerated leather to prepare a high-strength regenerated leather.

[0013] Further, the length of the leather fiber in step (1) is 1 to 3 mm.

[0014] Further, the mesh number of the dehydrating and forming screen in step (3) is 60 to 200.

[0015] Further, the wet-state regenerated leather in step (3) has a water content of 30% to 60%.

[0016] Further, the hot-pressing time in step (4) is 5 to 30 min, the temperature is 80 to 110 DEG C, and the pressure is 0.5 to 2.5 MPa.

[0017] The present application has the following advantages:

[0018] (1) The present application makes full use of leather waste generated in leather factories, effectively reduces the waste of shavings, collagen and other resources, and has great significance for promoting the high-value application of leather waste and the new development of the leather industry.

[0019] (2) The present application uses wet papermaking technology to make the leather waste papermaking process simpler and more cost-effective.

[0020] (3) The present application simultaneously uses wet forming, chemical strengthening and hot pressing technology to prepare high-performance regenerated leather with high strength and good uniformity.

[0021] That is, the present application uses combined wet forming, chemical strengthening and hot pressing technology to manufacture regenerated leather. Wet forming can achieve good dispersion and full contact of leather waste fibers. Chemical reagent PAM or CPAM can build multiple action bonds between leather waste fibers, and hot pressing process can further improve the action strength of leather waste fibers, ultimately building a high-performance regenerated leather with high strength and good uniformity. DETAILED DESCRIPTION

[0022] The technical solutions of the present application will be described clearly and completely in combination with specific embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments are not specified by the manufacturer, they are all conventional products that can be purchased on the market. Example 1

[0023] (1) The leather waste with a fiber length of 3 mm was dispersed in an aqueous solution to prepare a leather fiber solution with a concentration of 0.08%; 0.5% PAM was added to the leather fiber solution and stirred uniformly; the above leather fiber solution was dehydrated to form a wet-state regenerated leather (the dehydrated forming mesh number was 200); and the wet-state regenerated leather was hot-pressed at 2.5 MPa, 100 DEG C for 30 min to prepare a high-strength regenerated leather. The tensile strength of the obtained sample was 4.2 N / mm 2 , the tear strength was 11.9 N / mm, the sample uniformity was good, and the deviation of the tensile strength of 5 points was less than 3%.

[0024] Comparative Example 1

[0025] (1) Leather waste with a fiber length of 1 mm was dispersed in an aqueous solution to prepare a 0.08% leather fiber solution; 0.5% PAM was added to the leather fiber solution and stirred uniformly; the above leather fiber solution was dehydrated and formed (dehydration forming mesh number was 200) to prepare a wet-state regenerated leather; and then air drying treatment was performed, and the tensile strength of the obtained sample was 0.05 N / mm 2 , the tear strength was 0.89 N / mm, the sample uniformity was good, and the deviation of the tensile strength of 5 points was less than 5%.

[0026] Comparative Example 2

[0027] (2) Leather waste with a fiber length of 3 mm was dispersed in an aqueous solution to prepare a 0.08% leather fiber solution; no chemical reagent was added, and direct stirring was performed uniformly; the above leather fiber solution was dehydrated and formed (dehydration forming mesh number was 200) to prepare a wet-state regenerated leather; and the wet-state regenerated leather was subjected to hot pressing treatment at 2.5 MPa, 100°C for 30 min to prepare a regenerated leather. The tensile strength of the obtained sample was 1.0 N / mm 2 , the tear strength was 4.2 N / mm, the sample uniformity was good, and the deviation of the tensile strength of 5 points was less than 5%.

[0028] Comparative Example 3

[0029] (3) Leather waste with a fiber length of 3 mm was dry-formed to prepare a regenerated leather; then the sample was soaked in a 0.5% PAM solution; and the soaked sample was subjected to hot pressing treatment at 2.5 MPa, 100°C for 30 min to prepare a regenerated leather. The tensile strength of the obtained sample was 0.5 N / mm 2 , the tear strength was 2.2 N / mm, and the sample uniformity was poor, and the deviation of the tensile strength of 5 points was greater than 10%. Example 2

[0030] (1) Leather waste with a fiber length of 1 mm was dispersed in an aqueous solution to prepare a 0.05% leather fiber solution; 0.1% PAM was added to the leather fiber solution and stirred uniformly; the above leather fiber solution was dehydrated and formed (dehydration forming mesh number was 60) to prepare a wet-state regenerated leather; and the wet-state regenerated leather was subjected to hot pressing treatment at 0.5 MPa, 80°C for 5 min to prepare a high-strength regenerated leather. The tensile strength of the obtained sample was 2.9 N / mm 2 , the tear strength was 9.8 N / mm, the sample uniformity was good, and the deviation of the tensile strength of 5 points was less than 4%. Example 3

[0031] (1) Take the leather waste with fiber length of 2 mm and disperse it in aqueous solution to prepare a 0.2% leather fiber solution; add 1% PAM to the leather fiber solution and stir uniformly; dehydrate and form the above leather fiber solution (dehydrating forming mesh number is 100) to prepare a wet-state regenerated leather; and perform hot pressing treatment on the wet-state regenerated leather at 1.5 MPa, 90°C and for 10 min to prepare a high-strength regenerated leather. The tensile strength of the obtained sample is 3.0 N / mm 2 , the tear strength is 10.9 N / mm, the sample uniformity is good, and the deviation of the tensile strength of 5 points is less than 3%. Example 4

[0032] (1) Take the leather waste with fiber length of 3 mm and disperse it in aqueous solution to prepare a 0.3% leather fiber solution; add 1% PAM to the leather fiber solution and stir uniformly; dehydrate and form the above leather fiber solution (dehydrating forming mesh number is 150) to prepare a wet-state regenerated leather; and perform hot pressing treatment on the wet-state regenerated leather at 2 MPa, 110°C and for 20 min to prepare a high-strength regenerated leather. The tensile strength of the obtained sample is 5.7 N / mm 2 , the tear strength is 15.3 N / mm, the sample uniformity is good, and the deviation of the tensile strength of 5 points is less than 2%. Example 5

[0033] (1) Take the leather waste with fiber length of 2 mm and disperse it in aqueous solution to prepare a 0.4% leather fiber solution; add 2.5% PAM to the leather fiber solution and stir uniformly; dehydrate and form the above leather fiber solution (dehydrating forming mesh number is 200) to prepare a wet-state regenerated leather; and perform hot pressing treatment on the wet-state regenerated leather at 2.5 MPa, 100°C and for 30 min to prepare a high-strength regenerated leather. The tensile strength of the obtained sample is 4.9 N / mm 2 , the tear strength is 13.1 N / mm, the sample uniformity is good, and the deviation of the tensile strength of 5 points is less than 5%. Example 6

[0034] (1) Take the leather waste with fiber length of 3 mm and disperse it in aqueous solution to prepare a 0.5% leather fiber solution; add 5% PAM to the leather fiber solution and stir uniformly; dehydrate and form the above leather fiber solution (dehydrating forming mesh number is 200) to prepare a wet-state regenerated leather; and perform hot pressing treatment on the wet-state regenerated leather at 2.5 MPa, 100°C and for 30 min to prepare a high-strength regenerated leather. The tensile strength of the obtained sample is 5.2 N / mm 2 , the tear strength is 13.7 N / mm, the sample uniformity is good, and the deviation of the tensile strength of 5 points is less than 4%. Example 7

[0035] (1) Take the leather waste with fiber length of 1mm to be dispersed in aqueous solution to prepare a 0.25% leather fiber solution; add 0.1% CPAM to the leather fiber solution and stir uniformly; perform dewatering forming (dewatering forming mesh number is 150) on the above leather fiber solution to prepare a wet-state regenerated leather; perform hot pressing on the wet-state regenerated leather at 2MPa, 100℃ and for 20min to prepare a high-strength regenerated leather. The tensile strength of the obtained sample is 3.2N / mm 2 , the tear strength is 11.1N / mm, the sample uniformity is good, and the deviation of the tensile strength of 5 points is less than 5%. Example 8

[0036] (1) Take the leather waste with fiber length of 3mm to be dispersed in aqueous solution to prepare a 0.08% leather fiber solution; add 0.5% CPAM to the leather fiber solution and stir uniformly; perform dewatering forming (dewatering forming mesh number is 150) on the above leather fiber solution to prepare a wet-state regenerated leather; perform hot pressing on the wet-state regenerated leather at 2.5MPa, 80℃ and for 20min to prepare a high-strength regenerated leather. The tensile strength of the obtained sample is 4.2N / mm 2 , the tear strength is 12.6N / mm, the sample uniformity is good, and the deviation of the tensile strength of 5 points is less than 3%. Example 9

[0037] (1) Take the leather waste with fiber length of 3mm to be dispersed in aqueous solution to prepare a 0.20% leather fiber solution; add 1% CPAM to the leather fiber solution and stir uniformly; perform dewatering forming (dewatering forming mesh number is 200) on the above leather fiber solution to prepare a wet-state regenerated leather; perform hot pressing on the wet-state regenerated leather at 2.5MPa, 90℃ and for 30min to prepare a high-strength regenerated leather. The tensile strength of the obtained sample is 4.8N / mm 2 , the tear strength is 13.8N / mm, the sample uniformity is good, and the deviation of the tensile strength of 5 points is less than 4%.

[0038] In summary, the present application uses the method of wet papermaking to make the regenerated leather sample, that is, through the addition of acrylamide additives in the papermaking process, the preliminary leather waste slurry is obtained; the leather waste fiber slurry is made by using the kathariner paper former, and the sample is hot pressed at a certain temperature, pressure and time to obtain the regenerated leather sample. The regenerated leather prepared by the method of the present application is improved in strength performance, and the leather also has relatively good uniformity. At the same time, the preparation method of the present application has simple process steps, less process flow and low manufacturing cost, which can promote the sustainable development of resources.

[0039] While the foregoing description has described specific embodiments of the application, one ordinary skill in the art will appreciate that various modifications and changes can be made thereto without departing from the spirit and scope of the application, as set forth in the appended claims.

Claims

1. A method for preparing high-quality recycled leather from leather waste, characterized in that: Includes the following steps: (1) Disperse leather waste in an aqueous solution to prepare a leather fiber solution, wherein the concentration of the leather fiber solution is 0.05%~0.5%; (2) Add the chemical reagent PAM to the leather fiber solution and stir until homogeneous; the amount of the chemical reagent is 0.1~5 wt%; (3) The above-mentioned leather fiber solution is dehydrated and molded to prepare wet recycled leather; the mesh number of the dehydration molding is 60~200, and the water content of the wet recycled leather is 30%~60%; (4) High-strength recycled leather is prepared by hot pressing and drying of wet recycled leather; the hot pressing time is 5~30min, the temperature is 80~110℃, and the pressure is 0.5~2.5 MPa.

2. The method for preparing high-quality recycled leather from leather waste according to claim 1, characterized in that: The leather fiber length in step (1) is 1~3 mm.

3. The method for preparing high-quality recycled leather from leather waste according to claim 1, characterized in that: The chemical reagent PAM is CPAM.