A multilayer flexible natural latex leather and a method for preparing the same

Abstract

This disclosure provides a multilayer flexible natural latex leather, comprising a base fabric layer and at least two natural latex composition layers. The natural latex composition layers are made from a preform containing the following components in parts by weight: 100 parts natural latex and 3-10 parts crosslinking agent. At least one natural latex composition layer serves as an adhesive layer, bonding the other natural latex composition layers to the base fabric layer. This multilayer flexible natural latex leather uses natural latex as the base material, making it a pure natural raw material with good sustainability and renewability. The bio-based crosslinking agent and plant-derived filler effectively overcome the high carbon footprint disadvantage of traditional petroleum-based or mineral raw materials. The plant-derived filler has good renewability, eliminating the high dependence on non-renewable mineral resources. Using modified natural latex instead of traditional synthetic glue can give the final leather product a softer feel and lower hardness.

Description

Technical Field

[0001] This invention relates to the field of synthetic leather, specifically to a multi-layer flexible natural latex leather and its preparation method. Background Technology

[0002] As a composite material that can replace animal leather, synthetic leather has superior durability and cost-effectiveness compared to animal leather, making it popular in the consumer market and widely used in the production of footwear, clothing, bags, and sports products. However, traditional synthetic leather production processes cannot avoid the use of organic solvents or plasticizers, and the finished products pose potential chemical hazards to users.

[0003] Polyurethane, polyvinyl chloride, and plasticizers are the main raw materials for the production of synthetic leather. In the current synthetic leather manufacturing field, whether it is soft polyvinyl chloride, solvent-based polyurethane resin, waterborne polyurethane resin, silicone resin, or solvent-free polyurethane resin, the original source of its basic raw materials comes from multiple processing steps after oil extraction, and oil is a non-renewable resource. In conventional technologies, the raw materials for traditional synthetic leather are highly dependent on various fossil energy and mineral resources, which are non-renewable and have low sustainability. Furthermore, the bonding process between the plastic layer and the base fabric layer of traditional synthetic leather requires the use of synthetic adhesives as an bonding layer, and the amount of adhesive used and the bonding process both affect the feel and softness / hardness of the final leather product. Summary of the Invention

[0004] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a multilayer flexible natural latex leather and its preparation method to solve the aforementioned problems.

[0005] (II) Technical Solution To achieve the above objectives, at least one embodiment of this disclosure provides a multilayer flexible natural latex leather, comprising a base fabric layer and at least two natural latex composition layers, wherein the natural latex composition layers are made of a preform containing the following components in parts by weight: 100 parts of natural latex and 3 to 10 parts of crosslinking agent; In this process, at least one layer of natural latex composition serves as an adhesive layer, bonding other layers of natural latex composition to the base fabric layer.

[0006] For example, in a multilayer flexible natural latex leather provided in at least one embodiment of this disclosure, the natural latex composition layer includes a dense layer, an intermediate layer and an adhesive layer, the dense layer and the intermediate layer are stacked, and the adhesive layer is disposed between the intermediate layer and the base fabric layer as the adhesive layer.

[0007] For example, in a multilayer flexible natural latex leather provided in at least one embodiment of this disclosure, the natural latex composition further comprises 0 to 20 parts by weight of filler.

[0008] For example, in a multilayer flexible natural latex leather provided in at least one embodiment of this disclosure, the filler is a plant-derived filler.

[0009] For example, in a multilayer flexible natural latex leather provided in at least one embodiment of this disclosure, the natural latex composition further includes one or more additives selected from colorants, stabilizers, leveling agents, and tackifiers.

[0010] For example, in a multilayer flexible natural latex leather provided in at least one embodiment of this disclosure, the stabilizer is one or more of hindered phenolic antioxidants or hindered amine light stabilizers; the leveling agent is one or more of organosilicon leveling agents or acetylenic diol leveling agents; and the tackifier is one or more of polyurethane associative tackifiers, acrylate alkali-swelling tackifiers, or cellulose tackifiers.

[0011] For example, in a multilayer flexible natural latex leather provided in at least one embodiment of this disclosure, the crosslinking agent is one or more of a bio-based isocyanate crosslinking agent or a bio-based blocked isocyanate crosslinking agent.

[0012] For example, in at least one embodiment of this disclosure, a multilayer flexible natural latex leather is provided, wherein the base fabric layer is a polyester fabric, an acrylic fabric, a spandex fabric, or a natural fiber fabric.

[0013] According to another aspect of the present invention, a method for preparing multilayer flexible natural latex leather is also provided, comprising the following steps: S1. Prepare a preform of at least two natural latex compositions; S2. The pre-formed natural latex composition is applied layer by layer onto the release paper. After each layer is applied, it is heated at 80-120°C to form a film, thereby forming a multi-layered natural latex composition. S3. After the last layer of natural latex composition preform is applied, a base fabric layer is laminated on it, and then heated at 80-160°C to cure the natural latex composition preform and use it as an adhesive layer to bond the adjacent natural latex composition layers to the base fabric layer. S4. Remove the release paper to obtain a multi-layered flexible natural latex leather base.

[0014] For example, in the method for preparing multilayer flexible natural latex leather provided in at least one embodiment of this disclosure, in step S2, a dense layer is first coated to form a dense layer, and then an intermediate layer is coated to form a dense layer; in step S3, an adhesive layer is coated to form the final layer.

[0015] (III) Beneficial Effects Compared with the prior art, the present invention provides a multilayer flexible natural latex leather and its preparation method, which has the following beneficial effects: This invention uses natural latex as the base material for leather making, which is a pure natural raw material with good sustainability and renewability. The bio-based crosslinking agent and plant-derived filler used in this invention effectively overcome the high carbon footprint disadvantage of traditional petroleum-based or mineral raw materials. The plant-derived filler used in this invention has good renewability, freeing it from high dependence on non-renewable mineral resources. The multi-layer flexible natural latex leather of this invention uses modified natural latex to replace traditional synthetic glue, which can give the final leather product a softer feel and lower hardness. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] It should be understood that in the various embodiments of the present invention, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0018] It should be understood that in this invention, "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0019] The inventors discovered through research that polyurethane, polyvinyl chloride, and plasticizers are the main raw materials for synthetic leather production. In the current synthetic leather manufacturing field, whether it is soft polyvinyl chloride, solvent-based polyurethane resin, water-based polyurethane resin, silicone resin, or solvent-free polyurethane resin, the initial source of their basic raw materials all comes from multiple processing steps after oil extraction, and oil is a non-renewable resource. In conventional technologies, the source of raw materials for traditional synthetic leather is highly dependent on various fossil energy and mineral resources, which are non-renewable and have low sustainability. Moreover, in the process of bonding the plastic layer and the base fabric layer of traditional synthetic leather, synthetic adhesives are required as an adhesive layer. The amount of adhesive used and the bonding process both affect the feel and softness / hardness of the final leather product, and there is room for improvement.

[0020] Based on the above ideas, at least one embodiment of this disclosure provides a multilayer flexible natural latex leather, including a base fabric layer and at least two natural latex composition layers, wherein the natural latex composition layers are made of a preform containing the following components in parts by weight: 100 parts of natural latex and 3 to 10 parts of crosslinking agent; The composition comprises at least one layer of natural latex composition as an adhesive layer, bonding other natural latex composition layers to the base fabric layer; the natural latex composition layer includes a dense layer, an intermediate layer, and an adhesive layer, with the dense layer and intermediate layer stacked, and the adhesive layer disposed between the intermediate layer and the base fabric layer as an adhesive layer; the natural latex composition further comprises 0-20 parts by weight of filler; the filler is plant-derived filler; the natural latex composition further comprises one or more additives selected from colorants, stabilizers, leveling agents, and tackifiers; the stabilizer is one or more of hindered phenolic antioxidants or hindered amine light stabilizers; the leveling agent is one or more of organosilicon leveling agents or acetylenic diol leveling agents; the tackifier is one or more of polyurethane associative tackifiers, acrylate alkali-swelling tackifiers, or cellulose tackifiers; the crosslinking agent is one or more of bio-based isocyanate crosslinking agents or bio-based blocked isocyanate crosslinking agents; the base fabric layer is polyester fabric, acrylic fabric, spandex fabric, or natural fiber fabric.

[0021] The cross-linking agent can be bio-based pentamethylene diisocyanate, prepared by the fermentation route of plant-based starch sugar.

[0022] Among them, plant-derived fillers can be wood flour, bamboo flour, cork flour, starch, or cellulose micron.

[0023] The method for preparing multi-layer flexible natural latex leather was also disclosed, including the following steps: Natural latex, crosslinking agent, filler, colorant, stabilizer, leveling agent, and tackifier are weighed according to different weight ratios and mixed evenly in a mixer to obtain a dense layer preform, an intermediate layer preform, and an adhesive layer preform. The dense layer preform is evenly coated onto release paper and heated to form a film at a temperature of 80–120°C. The intermediate layer preform is evenly coated onto the dense layer and heated to form a film at a temperature of 80–120°C. The adhesive layer preform is evenly coated onto the intermediate layer and laminated with a textile fabric, i.e., the base fabric layer, and then heated to form a film at a temperature of 80–160°C. The release paper is removed to obtain a multi-layer flexible natural latex leather base. Surface treatment is performed by roller coating, where a leather surface treatment agent is evenly printed onto the multi-layer flexible natural latex leather base and dried to obtain the finished multi-layer flexible natural latex leather.

[0024] It should be noted that, in this invention, the natural latex composition refers to a homogeneous mixture formed by adding a crosslinking agent and optional other additives through physical blending, with the aforementioned natural latex as the main continuous phase. This composition can be cured and shaped under heating conditions by the action of the crosslinking agent. The modified natural latex mentioned in this article refers to such a natural latex composition with added necessary and optional additives.

[0025] It should be noted that the leather surface treatment agent can be a water-based polyurethane surface treatment agent, a water-based acrylic surface treatment agent, or an organosilicon hand feel agent, depending on the gloss, touch, and physical properties required for the final product. The drying temperature is 100-130℃, and the time is 1-3 minutes.

[0026] The following describes a multi-layer flexible natural latex leather and its preparation method provided by the present disclosure through several specific embodiments.

[0027] Example 1: Preparation of multi-layer flexible natural latex leather: Prepare the dense layer preform: Weigh 100 parts of natural latex, 3 parts of crosslinking agent, 10 parts of filler, 4 parts of colorant, 1 part of stabilizer, 0.5 parts of leveling agent, and 2 parts of tackifier according to the following weight ratio, and mix them evenly with a mixer to obtain the dense layer preform. Preparation of intermediate layer preform: Weigh 100 parts of natural latex, 3 parts of crosslinking agent, 10 parts of filler, 1 part of stabilizer, 0.5 parts of leveling agent, and 2 parts of tackifier according to the following weight ratio, and mix them evenly with a mixer to obtain the intermediate layer preform. Prepare the adhesive layer preform: Weigh 100 parts of natural latex, 5 parts of crosslinking agent, 20 parts of filler, 0.5 parts of leveling agent, and 2 parts of tackifier according to the following weight ratio, and mix them evenly with a mixer to obtain the adhesive layer preform. The dense layer preform is evenly coated onto the release paper and heated to form a film material at a temperature of 100℃. The intermediate layer prefabricated material is evenly coated onto the dense layer and heated to form a film material at a temperature of 100℃. The adhesive layer pre-prepared material is evenly coated onto the intermediate layer and then laminated with the textile fabric, i.e. the base fabric layer, and then heated to form a film material at a temperature of 150℃. Remove the release paper to obtain a multi-layered flexible natural latex leather base; The surface treatment is carried out by roller coating, which involves uniformly printing the leather surface treatment agent onto a multi-layer flexible natural latex leather base and then drying it to obtain the finished multi-layer flexible natural latex leather.

[0028] Example 2: Preparation of multi-layer flexible natural latex leather: Preparation of dense layer preform: Weigh 100 parts of natural latex, 4 parts of crosslinking agent, 20 parts of filler, 8 parts of colorant, 1.5 parts of stabilizer, 1 part of leveling agent, and 1 part of tackifier according to the following weight ratio, and mix them evenly with a mixer to obtain dense layer preform. Preparation of intermediate layer preform: Weigh 100 parts of natural latex, 4 parts of crosslinking agent, 20 parts of filler, 1.5 parts of stabilizer, 1 part of leveling agent, and 1 part of tackifier according to the following weight ratio, and mix them evenly with a mixer to obtain the intermediate layer preform. Prepare the adhesive layer preform: Weigh 100 parts of natural latex, 6 parts of crosslinking agent, 20 parts of filler, 1 part of leveling agent, and 1 part of tackifier according to the following weight ratio, and mix them evenly with a mixer to obtain the adhesive layer preform. The dense layer preform is evenly coated onto the release paper and heated to form a film material at a temperature of 110℃. The intermediate layer prefabricated material is evenly coated onto the dense layer and heated to form a film material at a heating temperature of 110℃. The adhesive layer pre-prepared material is evenly coated onto the intermediate layer and then laminated with the textile fabric, i.e. the base fabric layer, and then heated to form a film material at a temperature of 160℃. Remove the release paper to obtain a multi-layered flexible natural latex leather base; The surface treatment is carried out by roller coating, which involves uniformly printing the leather surface treatment agent onto a multi-layer flexible natural latex leather base and then drying it to obtain the finished multi-layer flexible natural latex leather.

[0029] Comparative Example 1: Preparation of traditional multilayer polyurethane leather: Preparation of dense layer preform: Weigh 100 parts of water-based polyurethane dispersion, 3 parts of crosslinking agent, 4 parts of colorant, 1 part of stabilizer, 0.5 parts of leveling agent, and 2 parts of tackifier according to the following weight ratio, and mix them evenly with a mixer to obtain dense layer preform. Preparation of intermediate layer preform: Weigh 100 parts of solvent-based polyurethane solution, 3 parts of crosslinking agent, and 1 part of colorant according to the following weight ratio, and mix them evenly with a mixer to obtain the intermediate layer preform; Prepare the adhesive layer preform: Weigh 100 parts of solvent-based polyurethane solution and 3 parts of crosslinking agent according to the following weight ratio, and mix them evenly with a mixer to obtain the adhesive layer preform. The dense layer preform is evenly coated onto the release paper and heated to form a film material at a temperature of 100℃. The intermediate layer prefabricated material is evenly coated onto the dense layer and heated to form a film material at a temperature of 150℃. The adhesive layer pre-prepared material is evenly coated onto the intermediate layer and then laminated with the textile fabric, i.e. the base fabric layer, and then heated to form a film material at a temperature of 150℃. Remove the release paper to obtain a traditional multi-layer polyurethane leather base; The surface treatment is performed by roller coating, which involves uniformly printing the leather surface treatment agent onto the traditional multi-layer polyurethane leather base and then drying it to obtain the finished traditional multi-layer polyurethane leather.

[0030] The finished products obtained from the two sets of embodiments and one set of comparative examples were tested under the same conditions, and the results are shown in Table 1: Table 1: Main Technical Specifications Based on the performance test data of the above-mentioned traditional multilayer polyurethane leather products and the multilayer flexible natural latex leather of the present invention under the same conditions, it can be seen that the multilayer flexible natural latex leather of the present invention has lower stiffness and softness and higher softness while achieving the same level of strength and elongation as the traditional multilayer polyurethane leather products, which means that a softer hand feel can be obtained. Furthermore, this invention uses natural latex to replace traditional petroleum-based solvent-based polyurethane resin, water-based polyurethane resin, silicone resin, or solvent-free polyurethane resin in proportion, uses biological fillers to replace mineral-based fillers, and uses biological crosslinking agents to replace traditional petroleum-based crosslinking agents, thereby reducing the dependence on fossil energy and mineral resources of raw materials and improving the sustainability of multilayer flexible natural latex leather.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A multi-layer flexible natural latex leather, characterized in that, It includes a base fabric layer and at least two layers of natural latex composition, wherein the natural latex composition layer is made of a preform containing the following components in parts by weight: 100 parts of natural latex and 3 to 10 parts of crosslinking agent; In this process, at least one layer of natural latex composition serves as an adhesive layer, bonding other layers of natural latex composition to the base fabric layer.

2. The multi-layer flexible natural latex leather according to claim 1, characterized in that, The natural latex composition layer includes a dense layer, an intermediate layer, and an adhesive layer, wherein the dense layer and the intermediate layer are stacked, and the adhesive layer is disposed between the intermediate layer and the base fabric layer as the bonding layer.

3. The multi-layer flexible natural latex leather according to claim 1 or 2, characterized in that, The natural latex composition also contains 0 to 20 parts by weight of filler.

4. The multi-layer flexible natural latex leather according to claim 3, characterized in that, The packing material is plant-derived.

5. The multi-layer flexible natural latex leather according to claim 1 or 2, characterized in that, The natural latex composition also includes one or more additives selected from colorants, stabilizers, leveling agents, and tackifiers.

6. The multi-layer flexible natural latex leather according to claim 5, characterized in that, The stabilizer is one or more of hindered phenolic antioxidants or hindered amine light stabilizers; the leveling agent is one or more of organosilicon leveling agents or acetylenic diol leveling agents; the tackifier is one or more of polyurethane associative tackifiers, acrylate alkali-swelling tackifiers or cellulose tackifiers.

7. The multi-layer flexible natural latex leather according to claim 1 or 2, characterized in that, The crosslinking agent is one or more of a bio-based isocyanate crosslinking agent or a bio-based blocked isocyanate crosslinking agent.

8. The multi-layer flexible natural latex leather according to claim 1 or 2, characterized in that, The base fabric layer is made of polyester, acrylic, spandex, or natural fiber.

9. A method for preparing multilayer flexible natural latex leather as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Prepare a preform of at least two natural latex compositions; S2. The pre-formed natural latex composition is applied layer by layer onto the release paper. After each layer is applied, it is heated at 80-120°C to form a film, thereby forming a multi-layered natural latex composition. S3. After the last layer of natural latex composition preform is applied, a base fabric layer is laminated on it, and then heated at 80-160°C to cure the natural latex composition preform and use it as an adhesive layer to bond the adjacent natural latex composition layers to the base fabric layer. S4. Remove the release paper to obtain a multi-layered flexible natural latex leather base.

10. The method for preparing multilayer flexible natural latex leather according to claim 9, characterized in that, In step S2, a dense layer is first coated to form a dense layer, and then an intermediate layer is coated to form a dense layer; in step S3, an adhesive layer is coated to form the final layer.

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