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

Abstract

The invention provides a method for preparing high-quality regenerated leather from leather waste, which comprises the following steps: (1) dispersing the leather waste in an aqueous solution to prepare a leather fiber solution with the concentration of 0.05-0.5%; (2) adding a chemical reagent PAM or CPAM into the leather fiber solution, and uniformly stirring; the dosage of the chemical reagent is 0.1-5 wt%; (3) dehydrating and forming the leather fiber solution to prepare wet regenerated leather; and (4) carrying out hot-pressing drying treatment on the wet regenerated leather to prepare the high-strength regenerated leather. The method is simple in preparation process and few in flow, the high-performance regenerated leather with high strength and good uniformity can be prepared, a large amount of leather waste is fully utilized, resource waste is effectively reduced, and the application prospect is wide.

Description

[Technical field]

[0001] The invention relates to the technical field of leather production, and in particular to a method for preparing regenerated leather by utilizing a hot pressing process and wet papermaking. [Background technology]

[0002] As people's demand for leather products increases, the market for the development of the leather industry is rapidly expanding. The development of the leather industry is not limited to traditional leather products such as leather shoes, leather clothes, and bags. It is also developing rapidly in emerging fields such as automotive interiors, providing new growth points for the leather industry. According to statistics, in 2022, the operating income of the national leather industry and footwear industry reached 1,133.99 billion yuan. Although in 2023, my country's leather industry saw a slight decline in production and sales, since the beginning of 2024, the sales revenue and profits of key enterprises in the industry have rebounded significantly, initially showing a positive trend of recovery. However, such a large demand has also brought tremendous pressure to the leather industry. According to incomplete statistics from relevant departments, about 1.6 million tons of leather waste is generated in my country's leather processing industry each year, which not only pollutes the environment, but also causes a huge waste of biomass resources. On the basis of responding to the "dual carbon" policy and green development, how to make rational use of these leather wastes to produce recycled leather is one of the current research focuses of the industry.

[0003] Most of the industrial methods of dealing with leather waste are landfill or incineration, which not only causes serious pollution to the environment, but also causes a lot of waste of resources. How to recycle leather waste has become one of the key topics for researchers. At present, according to the characteristics of various types of leather waste, there are mainly three ways to utilize leather waste: the first type is the edges and corners of raw hides before tanning and the second and third layers of bare leather. This type of waste is mainly recycled for food, medicine, and daily use; the second type is the second and third layers of crust leather after tanning and dyeing, which is mainly recycled for the preparation of regenerated leather and fillers; the third type of waste leather is mainly recycled for the extraction of collagen or fillers, which is mainly the fragments of crust leather after tanning or the shaved leather waste.

[0004] The leather waste used in this application belongs to the second category of the above-mentioned waste leather scraps. In terms of application, the method of making regenerated leather can be divided into a wet method and a dry method according to the amount of water used. Although the dry method can solve the problems of high water consumption and large sewage discharge in the process of manufacturing regenerated leather, its manufacturing process is more complicated than the wet method, the yield is low, and it is difficult to achieve industrial production. Solid research uses a wet method to manufacture regenerated leather. Guo Peipei and others used a wet method to beat waste leather waste into a slurry, used urea-formaldehyde resin as an adhesive, and manufactured regenerated leather according to the papermaking process, but urea-formaldehyde resin will have formaldehyde release problems during use, and its storage stability is poor. Therefore, selecting a suitable auxiliary agent as a wet method for manufacturing regenerated leather is still a challenging task.

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

[0006] The technical problem to be solved by the present invention is to provide a preparation method for manufacturing high-quality regenerated leather from leather waste. The preparation process is simple and has few processes. High-performance regenerated leather with high strength and good uniformity can be prepared, which makes full use of a large amount of leather waste, effectively reduces the waste of resources, and has broad application prospects.

[0007] The present invention is achieved in that:

[0008] A method for preparing high-quality regenerated leather from leather waste comprises 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 chemical reagent PAM or CPAM to the leather fiber solution and stirring evenly; the amount of the chemical reagent is 0.1 to 5%wt;

[0011] (3) dehydrating and molding the leather fiber solution to prepare wet regenerated leather;

[0012] (4) The wet regenerated leather is subjected to a hot press drying process to prepare high-strength regenerated leather.

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

[0014] Furthermore, the mesh number of the dehydration forming in step (3) is 60 to 200.

[0015] Furthermore, the moisture content of the wet regenerated leather in step (3) is 30% to 60%.

[0016] Furthermore, the hot pressing time in step (4) is 5 to 30 minutes, the temperature is 80 to 110° C., and the pressure is 0.5 to 2.5 MPa.

[0017] The present invention has the following advantages:

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

[0019] (2) The present invention utilizes wet papermaking technology to make the process of making recycled leather from leather waste simpler and at a lower cost.

[0020] (3) The present invention simultaneously utilizes the combined technology of wet molding, chemical strengthening, and hot pressing to prepare high-performance regenerated leather with high strength and good uniformity.

[0021] That is, the present invention adopts the combined wet forming, chemical strengthening and hot pressing technology to manufacture the regenerated leather. The wet forming can achieve good dispersion and sufficient contact and winding of leather waste fibers, the chemical reagent PAM or CPAM can construct multiple action bonds between leather waste fibers, and the hot pressing process can further enhance the action strength of leather waste fibers, and finally construct a high-performance regenerated leather with high strength and good uniformity. [Specific implementation method]

[0022] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0023] Embodiment 1:

[0024] (1) 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 evenly; the leather fiber solution was dehydrated and formed (the mesh number of the dehydration forming process was 200) to prepare wet regenerated leather; the wet regenerated leather was subjected to a hot pressing treatment at 2.5 MPa, 100°C, and 30 min to prepare high-strength regenerated leather. The tensile strength of the obtained sample was 4.2 N / mm 2The tear strength is 11.9N / mm, the sample uniformity is good, and the deviation of tensile strength at 5 points is less than 3%.

[0025] Comparative Example 1:

[0026] (1) Leather waste with a fiber length of 1 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 evenly; the leather fiber solution was dehydrated and formed (the mesh number of the dehydration forming process was 200) to prepare wet regenerated leather; and then air-dried. The tensile strength of the obtained sample was 0.05 N / mm 2 The tear strength is 0.89N / mm, the sample uniformity is good, and the deviation of tensile strength at 5 points is less than 5%.

[0027] Comparative Example 2:

[0028] (2) Dispersing leather waste with a fiber length of 3 mm in an aqueous solution to prepare a leather fiber solution with a concentration of 0.08%; directly stirring without adding chemical reagents; dehydrating and molding the leather fiber solution (the mesh number of the dehydration molding is 200) to prepare wet regenerated leather; subjecting the wet regenerated leather to a hot press treatment at 2.5 MPa, 100°C, and 30 minutes to prepare regenerated leather. The tensile strength of the obtained sample is 1.0 N / mm 2 The tear strength is 4.2N / mm, the sample uniformity is good, and the deviation of tensile strength at 5 points is less than 5%.

[0029] Comparative Example 3:

[0030] (3) Take leather waste with a fiber length of 3 mm and dry-form regenerated leather; then soak it in a 0.5% PAM solution; and perform a hot press treatment on the soaked sample at 2.5 MPa, 100°C, and 30 min to prepare regenerated leather. The tensile strength of the obtained sample is 0.5 N / mm 2 The tear strength is 2.2N / mm, and the sample uniformity is poor. Taking 5 points, the deviation of tensile strength is greater than 10%.

[0031] Embodiment 2:

[0032] (1) Leather waste with a fiber length of 1 mm was dispersed in an aqueous solution to prepare a leather fiber solution with a concentration of 0.05%; 0.1% PAM was added to the leather fiber solution and stirred evenly; the leather fiber solution was dehydrated and formed (the mesh number of the dehydration forming was 60) to prepare wet regenerated leather; the wet regenerated leather was subjected to a hot pressing treatment at 0.5 MPa, 80°C, and 5 min to prepare high-strength regenerated leather. The tensile strength of the obtained sample was 2.9 N / mm 2The tear strength is 9.8N / mm, the sample has good uniformity, and the deviation of the tensile strength at 5 points is less than 4%.

[0033] Embodiment 3:

[0034] (1) Leather waste with a fiber length of 2 mm was dispersed in an aqueous solution to prepare a leather fiber solution with a concentration of 0.2%; 1% PAM was added to the leather fiber solution and stirred evenly; the leather fiber solution was dehydrated and formed (the mesh number of the dehydration forming process was 100) to prepare wet regenerated leather; the wet regenerated leather was subjected to a hot pressing treatment at 1.5 MPa, 90°C, and 10 min to prepare high-strength regenerated leather. The tensile strength of the obtained sample was 3.0 N / mm 2 The tear strength is 10.9N / mm, the sample has good uniformity, and the deviation of the tensile strength at 5 points is less than 3%.

[0035] Embodiment 4:

[0036] (1) 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 0.3%; 1% PAM was added to the leather fiber solution and stirred evenly; the leather fiber solution was dehydrated and formed (the mesh number of the dehydration forming was 150) to prepare wet regenerated leather; the wet regenerated leather was subjected to a hot pressing treatment at 2MPa, 110°C, and 20min to prepare high-strength regenerated leather. The tensile strength of the obtained sample was 5.7N / mm 2 The tear strength is 15.3N / mm, the sample has good uniformity, and the deviation of the tensile strength at 5 points is less than 2%.

[0037] Embodiment 5:

[0038] (1) Leather waste with a fiber length of 2 mm was dispersed in an aqueous solution to prepare a leather fiber solution with a concentration of 0.4%; 2.5% PAM was added to the leather fiber solution and stirred evenly; the leather fiber solution was dehydrated and formed (the mesh number of the dehydration forming process was 200) to prepare wet regenerated leather; the wet regenerated leather was subjected to a hot pressing treatment at 2.5 MPa, 100°C, and 30 minutes to prepare high-strength regenerated leather. The tensile strength of the obtained sample was 4.9 N / mm 2 The tear strength is 13.1N / mm, the sample has good uniformity, and the deviation of the tensile strength at 5 points is less than 5%.

[0039] Embodiment 6:

[0040] (1) 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 0.5%; 5% PAM was added to the leather fiber solution and stirred evenly; the leather fiber solution was dehydrated and formed (the mesh number of the dehydration forming process was 200) to prepare wet regenerated leather; the wet regenerated leather was subjected to a hot pressing treatment at 2.5 MPa, 100°C, and 30 minutes to prepare high-strength regenerated leather. The tensile strength of the obtained sample was 5.2 N / mm 2 The tear strength is 13.7N / mm, the sample has good uniformity, and the deviation of the tensile strength at 5 points is less than 4%.

[0041] Embodiment 7:

[0042] (1) Leather waste with a fiber length of 1 mm was dispersed in an aqueous solution to prepare a leather fiber solution with a concentration of 0.25%; 0.1% CPAM was added to the leather fiber solution and stirred evenly; the leather fiber solution was dehydrated and formed (the mesh number of the dehydration forming was 150) to prepare wet regenerated leather; the wet regenerated leather was subjected to a hot pressing treatment at 2MPa, 100°C, and 20min to prepare high-strength regenerated leather. The tensile strength of the obtained sample was 3.2N / mm 2 The tear strength is 11.1N / mm, the sample has good uniformity, and the deviation of the tensile strength at 5 points is less than 5%.

[0043] Embodiment 8:

[0044] (1) 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% CPAM was added to the leather fiber solution and stirred evenly; the leather fiber solution was dehydrated and formed (the mesh number of the dehydration forming was 150) to prepare wet regenerated leather; the wet regenerated leather was subjected to a hot pressing treatment at 2.5 MPa, 80°C, and 20 min to prepare high-strength regenerated leather. The tensile strength of the obtained sample was 4.2 N / mm 2 The tear strength is 12.6N / mm, the sample has good uniformity, and the deviation of the tensile strength is less than 3% at 5 points.

[0045] Embodiment 9:

[0046] (1) 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 0.20%; 1% CPAM was added to the leather fiber solution and stirred evenly; the leather fiber solution was dehydrated and formed (the mesh number of the dehydration forming process was 200) to prepare wet regenerated leather; the wet regenerated leather was subjected to a hot pressing treatment at 2.5 MPa, 90°C, and 30 min to prepare high-strength regenerated leather. The tensile strength of the obtained sample was 4.8 N / mm 2The tear strength is 13.8N / mm, the sample has good uniformity, and the deviation of the tensile strength at 5 points is less than 4%.

[0047] In summary, the present invention adopts a wet papermaking method to paper regenerated leather samples, that is, by adding acrylamide additives during the papermaking process, a preliminary leather waste slurry is obtained; then the leather waste fiber slurry is papered using a Kaiser paper sheet former, and the sample is hot-pressed under a certain temperature, pressure and time to obtain a regenerated leather sample. The regenerated leather prepared by the method of the present invention is well improved in strength performance, and the leather also has a relatively good uniformity. At the same time, the preparation method of the present invention has simple process steps, fewer processes, and low production costs, which can promote the sustainable development of resources.

[0048] Although the specific implementation modes of the present invention are described above, those skilled in the art should understand that the specific implementation modes described are only illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for producing high-quality regenerated leather from leather waste, characterized in that: The steps include: (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%; (2) adding chemical reagent PAM or CPAM to the leather fiber solution and stirring evenly; the amount of the chemical reagent is 0.1 to 5%wt; (3) dehydrating and molding the leather fiber solution to prepare wet regenerated leather; (4) The wet regenerated leather is subjected to a hot press drying process to prepare high-strength regenerated leather.

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

3. The method for producing high-quality regenerated leather from leather waste according to claim 1, characterized in that: The mesh number of the dehydration molding in step (3) is 60 to 200.

4. The method for producing high-quality regenerated leather from leather waste according to claim 1, characterized in that: The moisture content of the wet regenerated leather in step (3) is 30% to 60%.

5. The method for producing high-quality regenerated leather from leather waste according to claim 1, characterized in that: The hot pressing time in step (4) is 5 to 30 minutes, the temperature is 80 to 110° C., and the pressure is 0.5 to 2.5 MPa.