Composite material based on plant fiber and biomass adhesive and application of composite material

Abstract

The invention discloses a composite material based on plant fibers and a biomass adhesive and application of the composite material. The composite material is prepared from the following raw materials: the plant fibers and the adhesive, the adhesive comprises a plant adhesive and a modified adhesive; the modified adhesive is prepared from the following raw materials: inorganic nanoparticles modified with carboxyl, polyvinyl alcohol modified with sulfydryl and bean flour. According to the composite material based on the plant fibers and the biomass adhesive, the technical contradictions that a traditional biological material is low in strength, difficult to process and not environmentally friendly are solved, and meanwhile high-value utilization of waste resources is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to a composite material based on plant fiber and biomass adhesive and applications thereof. Background Art

[0002] In recent years, with growing environmental awareness, the environmental problems posed by traditional petroleum-based plastics have become increasingly prominent. Synthetic polymers, such as polyethylene (PE) and polypropylene (PP), are difficult to degrade in the natural environment due to their stable chemical structures. Studies have shown that it takes 200-400 years for a typical plastic bag to completely decompose in soil. These non-degradable plastic wastes not only cause serious "white pollution" but also accumulate in the food chain, forming microplastic particles that pose a potential threat to marine ecosystems and health. Against this backdrop, the research and development of biodegradable materials has become a key focus in materials science.

[0003] Currently, the mainstream biodegradable materials on the market primarily include polylactic acid (PLA) and starch-based plastics, but these materials still face significant technical bottlenecks in practical application. First, their mechanical properties lag significantly behind those of traditional petroleum-based plastics. Conventional PLA typically has a tensile strength of less than 15 MPa and an elongation at break of less than 10%, making it difficult to meet the basic strength requirements for packaging materials and consumer products. Second, processing requirements are demanding. For example, PLA requires processing temperatures between 160 and 180°C, which not only consumes a lot of energy but also easily leads to thermal oxidative degradation. More critically, to improve the interfacial bonding properties of plant fiber composites, existing technologies often require the addition of synthetic adhesives such as epoxy resins and polyurethanes. The introduction of these non-biodegradable components degrades the material's fully biodegradable properties. Furthermore, billions of tons of agricultural waste, such as rice husks, coffee grounds, and sugarcane bagasse, are generated globally each year. Most of these natural plant fiber resources, rich in cellulose and hemicellulose, are simply incinerated or landfilled, resulting in significant resource waste and an additional environmental burden. Therefore, it is urgent to develop a new composite material with excellent mechanical properties, good processing properties and complete biodegradability. Summary of the Invention

[0004] The present invention aims to address the aforementioned technical problems existing in the prior art. To this end, it proposes a composite material based on plant fibers and a biomass adhesive. This overcomes the technical limitations of traditional biomaterials, which include low strength, difficulty in processing, and environmental concerns, while also achieving high-value utilization of waste resources.

[0005] The present invention also provides a method for preparing the composite material based on plant fiber and biomass adhesive.

[0006] The present invention also proposes the application of a composite material based on plant fiber and biomass adhesive in beauty tools, packaging boards, building boards and flexible daily necessities.

[0007] According to one aspect of the present invention, a composite material based on plant fiber and biomass adhesive is proposed, wherein the raw materials for preparing the composite material include: plant fiber and adhesive;

[0008] The adhesive includes plant adhesive and modified adhesive;

[0009] The raw materials for preparing the modified adhesive include: inorganic nanoparticles modified with carboxyl groups, polyvinyl alcohol modified with thiol groups, and soybean powder.

[0010] Epoxy groups can undergo ring-opening reactions with active groups (amino, carboxyl) in soy flour, synergistically constructing a stable three-dimensional network structure. On the one hand, they lock the molecular chains through covalent bonds to reduce free volume, and on the other hand, they effectively neutralize the water absorption of hydrophilic groups (such as hydroxyl groups), resulting in a synergistic enhancement of water resistance and bonding strength. Compared to single-component systems, the hybrid network of epoxy-modified PVA and soy glue achieves significant breakthroughs in interfacial bonding and hydrophobicity through the dual effects of covalent crosslinking and physical entanglement. Carboxylated inorganic nanoparticles act as rigid nodes, and thiol-modified PVA acts as flexible segments, forming a "rigid and flexible" IPN structure. When subjected to external force: the carboxylated inorganic nanoparticles can share the tensile stress, while the thioether-crosslinked PVA network absorbs the remaining energy through segment slip.

[0011] In some embodiments of the present invention, the raw materials for preparing the inorganic nanoparticles modified with carboxyl groups include: inorganic nanoparticles, mercaptopropionic acid, ethylenediaminetetraacetic acid and adipic acid.

[0012] In some embodiments of the present invention, the raw materials for preparing the polyvinyl alcohol modified with thiol groups include: polyvinyl alcohol, sulfuric acid and thioglycolic acid.

[0013] In some embodiments of the present invention, the plant fiber includes at least one of wood powder, bamboo powder, straw, rice husk powder, rice bran, coffee grounds, and tea leaves.

[0014] In some embodiments of the present invention, the plant adhesive includes at least one of starch glue, lignin glue and plant protein glue.

[0015] According to the second aspect of the present invention, a method for preparing a composite material based on plant fiber and biomass adhesive is proposed, comprising the following steps: mixing the plant fiber and the modified adhesive, then mixing with the plant adhesive, plasticizing, and hot pressing.

[0016] In some embodiments of the present invention, the step of mixing the plant fiber and the modified adhesive comprises: alkali washing and removing impurities from the plant fiber, and then reacting the plant fiber at 0.5-1 MPa and 70-80° C. for 40-50 minutes.

[0017] In some embodiments of the present invention, the alkali washing step of the plant fiber comprises: crushing the plant fiber raw material to 120-180 mesh and then treating it with sodium hydroxide solution at 60-70° C. for 2 hours.

[0018] In some embodiments of the present invention, the impurity removal step includes washing the alkali-washed plant fiber with water and then drying it.

[0019] In some embodiments of the present invention, the mass ratio of the plant fiber to the modified adhesive is 1:0.2-0.5.

[0020] In some embodiments of the present invention, the plasticizing temperature is 80-100°C.

[0021] In some embodiments of the present invention, the conditions for the hot pressing molding are: 120-150° C., 10-20 MPa, and hot pressing for 10-30 minutes.

[0022] In some embodiments of the present invention, the modified fiber is obtained by mixing the plant fiber and the modified adhesive, and the mass ratio of the plant fiber to the modified adhesive is 0.8 to 3.5:1.

[0023] In some embodiments of the present invention, the plasticizing step further comprises adding a plasticizing aid, wherein the plasticizing aid comprises at least one of glycerin, sorbitol, citrate and epoxidized soybean oil.

[0024] In some embodiments of the present invention, the hot pressing further comprises crushing the material in a crusher to obtain a granular degradable composite material.

[0025] In the present invention, lignin is selectively removed through alkali treatment, exposing the cellulose microfibril network. Vacuum impregnation then allows the modified adhesive to fully penetrate the cell lumen and interstices between microfibrils. During the pre-curing stage, the carboxylated inorganic nanoparticles in the modified adhesive form Zn-OC coordination bonds with the cellulose hydroxyl groups. Simultaneously, the thiolated PVA cross-links via thioether bonds, creating a "rigid-flexible" dual network within the cell wall and increasing its elastic modulus. After cross-linking and curing, the adhesive fills the interstices between the microfibrils, increasing the compressive yield strength of the cell wall. After a secondary vacuum treatment to remove free adhesive, directional porosity is retained, endowing the material with adaptive deformation capabilities. This pre-curing treatment imparts both high-pressure tolerance and low-pressure permeability.

[0026] According to the third aspect of the present invention, the application of the composite material based on plant fiber and biomass adhesive in beauty tools, packaging boards, building boards and flexible daily necessities is proposed. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0028] Example 1

[0029] This embodiment provides a composite material based on plant fiber and biomass adhesive, specifically:

[0030] S1. Bamboo powder was ground to 120-180 mesh (preferably 150 mesh), stirred in 5% sodium hydroxide solution at 60°C for 2 hours to remove lignin, washed with water to pH 7.0, and dried at 60°C to a moisture content of ≤5%. The fiber was then placed in a vacuum tank and evacuated to -0.09 MPa for 30 minutes. A modified adhesive (mass ratio 1:2) was then injected and pressurized to 0.8 MPa for 30 minutes. The fiber was then pre-cured at 80°C for 40 minutes (crosslinking degree controlled at 60 ± 5%). Finally, a second vacuum treatment (-0.05 MPa) was performed to remove the free adhesive.

[0031] The preparation method of the modified adhesive is as follows: 5 parts of nano ZnO (particle size ≤ 50nm) and 3 parts of mercaptopropionic acid are reacted at pH 6 (acetic acid-sodium acetate buffer) and 50-60°C for 4 hours, and 0.1 parts of EDTA are added to inhibit the ZnO from absorbing the ZnO. 2+ Dissolved to obtain carboxylated ZnO (modification degree ≥ 85%), 10 parts of adipic acid and modified ZnO were mixed in a 1:0.3 molar ratio, pre-condensed at 130 ° C / 1 h, and then vacuum polycondensed at 150 ° C / 1 h, and 0.5 parts of p-toluenesulfonic acid catalyst was added to obtain a hybrid with an intrinsic viscosity of 0.6 dL / g (component A), 15 parts of PVA and 4 parts of 2-iminothiolane hydrochloride were mixed at pH 7. React at 65°C for 45 minutes to generate thiolated PVA, crosslink the thiolated PVA with 20 parts of urea-denatured soy flour at 25-30°C in the presence of 0.05 parts of vitamin C for 4 hours to form a three-dimensional network (component B). Mix components A and B at a mass ratio of 1:1.2 at 60°C for 1 hour to form an interpenetrating network structure adhesive A through condensation reaction of residual carboxyl groups with hydroxyl / thiol groups; then react the adhesive A with soy flour at a mass ratio of 3:1 at 80°C for 1 hour, add 0.5 parts of genipin and 5% of plasticizer to obtain a modified adhesive with excellent bonding properties and biodegradability;

[0032] S2. The precured fiber was mixed with a plant adhesive (starch glue) in a mass ratio of 6:4, 1% silane coupling agent (KH550) and 5% glycerol were added, and stirred at 600 rpm at 0.8 MPa and 85 ° C for 10 minutes to form a homogeneous premix;

[0033] S3. Preheat the premix at 90°C and 2MPa for 5 minutes to heat the material evenly; then raise the temperature to 110°C and pressurize it to 10MPa for 10 minutes to promote the cross-linking reaction; finally, raise the temperature to 120°C and increase the pressure to 15MPa, and cure for 5 minutes to ensure that the material is fully formed. After hot pressing, cool it down to below 40°C at a rate of no more than 5°C per minute, demould it, and crush it in a crusher to obtain a granular biodegradable composite material.

[0034] Example 2

[0035] This embodiment provides a composite material based on plant fiber and biomass adhesive, specifically:

[0036] S1. Bamboo powder was ground to 150 mesh, stirred in a 5% sodium hydroxide solution at 60°C for 2 hours to remove lignin, and then washed with water to a pH of 7.0. The fibers were then dried at 60°C to a moisture content of 5%. The fibers were then placed in a vacuum jar and evacuated to -0.09 MPa for 30 minutes. A modified adhesive (liquid-to-solid ratio of 1:2) was then injected and pressurized to 0.8 MPa for 30 minutes. The fibers were then pre-cured at 80°C for 40 minutes (crosslinking degree controlled at 60%). Finally, a second vacuum jar (-0.05 MPa) was applied to remove the free adhesive.

[0037] The preparation method of the modified adhesive is as follows: 5 parts of nano ZnO (particle size 50nm) and 3 parts of mercaptopropionic acid are reacted at pH 6.3 (acetic acid-sodium acetate buffer) and 55°C for 4 hours, and 0.1 parts of EDTA are added to inhibit the ZnO from absorbing the ZnO. 2+Dissolved to obtain carboxylated ZnO (modification degree 85%), 10 parts of adipic acid and modified ZnO were mixed in a molar ratio of 1:0.3, pre-condensed at 130 ° C for 1 hour, and then vacuum polycondensed at 150 ° C for 1 hour, and 0.5 parts of p-toluenesulfonic acid catalyst was added to obtain a hybrid (component A) with an intrinsic viscosity of 0.7 dL / g. 15 parts of PVA and 4 parts of 2-iminothiolane hydrochloride were mixed at pH 7.3, react at 65°C for 45 minutes to produce thiolated PVA. The thiolated PVA was cross-linked with 20 parts of urea-denatured soy flour at 28°C in the presence of 0.05 parts of vitamin C for 4 hours to form a three-dimensional network (component B). Components A and B were mixed at a mass ratio of 1:1.35 at 70°C for 1.5 hours to form an interpenetrating network adhesive A through condensation reaction of residual carboxyl groups with hydroxyl / thiol groups. Adhesive A was then reacted with soy flour at a mass ratio of 3:1 at 80°C for 1 hour. 0.5 parts of genipin and 5% of a plasticizer were added to produce a modified adhesive.

[0038] S2. The precured fiber and the plant adhesive were mixed in a mass ratio of 6:4, 1% silane coupling agent (KH550) and 5% glycerol were added, and stirred at 600 rpm at 0.8 MPa and 85°C for 10 minutes to form a homogeneous premix;

[0039] S3. Preheat the premix at 90°C and 2MPa for 5 minutes to ensure uniform heating of the material; then raise the temperature to 110°C and pressurize to 10MPa for 10 minutes to promote the full cross-linking reaction; finally, raise the temperature to 120°C and increase the pressure to 15MPa, and cure for 5 minutes to ensure that the material is fully formed. After hot pressing, cool the premix at a rate of 5°C per minute to below 40°C, demold it, and crush it in a crusher to obtain a granular biodegradable composite material.

[0040] Example 3

[0041] This embodiment provides a composite material based on plant fiber and biomass adhesive, specifically:

[0042] S1. Ground straw (moisture content ≤ 8%) to 120-180 mesh (preferably 150 mesh), stirred in 5% sodium hydroxide solution at 60°C for 2 hours to remove residual oil, washed with water to a pH of 7.0, and dried at 60°C to a moisture content ≤ 5%. The fibers were then placed in a vacuum tank, evacuated to -0.09 MPa for 30 minutes, and then injected with a modified adhesive (liquid-to-solid ratio 1:2). The pressure was then increased to 0.8 MPa for 30 minutes, followed by pre-curing at 80±2°C for 40 minutes (crosslinking degree controlled at 60±5%). Finally, a second vacuum treatment (-0.05 MPa) was performed to remove the free adhesive.

[0043] The preparation method of the modified adhesive is as follows: 3 parts of nano ZnO (particle size ≤ 50 nm) and 3 parts of mercaptopropionic acid are reacted at pH 6 (acetic acid-sodium acetate buffer) and 50°C for 4 hours, and 0.1 parts of EDTA are added to inhibit the ZnO from absorbing the ZnO. 2+ Dissolved to obtain carboxylated ZnO (modification degree ≥ 85%), 10 parts of adipic acid and modified ZnO were mixed in a 1:0.3 molar ratio, pre-condensed at 130 ° C / 1 h, and then vacuum polycondensed at 150 ° C / 1 h, and 0.5 parts of p-toluenesulfonic acid catalyst was added to obtain a hybrid (component A) with an intrinsic viscosity of 0.5-0.7 dL / g, 15 parts of PVA and 4 parts of 2-iminothiolane hydrochloride were mixed at pH 7-7.5, 65 ° C for 45 minutes to generate thiolated PVA, the thiolated PVA and 20 parts of urea-denatured soy flour are cross-linked at 25-30 ° C in the presence of 0.05 parts of vitamin C for 4 hours to form a three-dimensional network (component B); components A and B are mixed at a mass ratio of 1:1.2 at 60 ° C for 1 hour, and an interpenetrating network structure of adhesive A is formed through a condensation reaction between residual carboxyl groups and hydroxyl groups / thiol groups; the adhesive A is then reacted with soy flour at a mass ratio of 3:1 at 80 ° C for 1 hour, and 0.5 parts of genipin and 5% of a plasticizer are added to prepare a modified adhesive with excellent bonding properties and degradability;

[0044] S2. The precured fiber and the plant adhesive were mixed in a mass ratio of 6:4, 1% silane coupling agent (KH550) and 5% glycerol were added, and the mixture was stirred at 0.8 MPa and 85°C at 600 ± 50 rpm for 10 minutes to form a homogeneous premix;

[0045] S3. Preheat the premix at 90°C and 2MPa for 5 minutes to heat the material evenly; then raise the temperature to 110°C and pressurize it to 10MPa for 10 minutes to promote the cross-linking reaction; finally, raise the temperature to 120°C and increase the pressure to 15MPa, and cure for 5 minutes to ensure that the material is fully formed. After hot pressing, cool it down to below 40°C at a rate of no more than 5°C per minute, demould it, and crush it in a crusher to obtain a granular biodegradable composite material.

[0046] Example 4

[0047] This embodiment provides a composite material based on plant fiber and biomass adhesive, specifically:

[0048] S1. Bamboo powder was ground to 150 mesh, stirred in a 5% sodium hydroxide solution at 60°C for 2 hours to remove lignin, and then washed with water to a pH of 7.0. The fibers were then dried at 60°C to a moisture content of 5%. The fibers were then placed in a vacuum jar and evacuated to -0.09 MPa for 30 minutes. A modified adhesive (liquid-to-solid ratio of 1:2) was then injected and pressurized to 0.8 MPa for 30 minutes. The fibers were then pre-cured at 80°C for 40 minutes (crosslinking degree controlled at 60%). Finally, a second vacuum jar (-0.05 MPa) was applied to remove the free adhesive.

[0049] The preparation method of the modified adhesive is as follows: 5 parts of nano ZnO (particle size 50nm) and 3 parts of mercaptopropionic acid are reacted at pH 6.3 (acetic acid-sodium acetate buffer) and 55°C for 4 hours, and 0.1 parts of EDTA are added to inhibit the ZnO from absorbing the ZnO. 2+ Dissolved to obtain carboxylated ZnO (modification degree 85%), 10 parts of adipic acid and modified ZnO were mixed in a molar ratio of 1:0.3, pre-condensed at 130 ° C for 1 hour, and then vacuum polycondensed at 150 ° C for 1 hour, and 0.5 parts of p-toluenesulfonic acid catalyst was added to obtain a hybrid (component A) with an intrinsic viscosity of 0.7 dL / g. 15 parts of PVA and 4 parts of 2-iminothiolane hydrochloride were mixed at pH 7.3, react at 65°C for 45 minutes to produce thiolated PVA. The thiolated PVA was cross-linked with 20 parts of urea-denatured soy flour at 28°C in the presence of 0.05 parts of vitamin C for 4 hours to form a three-dimensional network (component B). Components A and B were mixed at a mass ratio of 1:1.35 at 70°C for 1.5 hours to form an interpenetrating network adhesive A through condensation reaction of residual carboxyl groups with hydroxyl / thiol groups. Adhesive A was then reacted with soy flour at a mass ratio of 3:1 at 80°C for 1 hour. 0.5 parts of genipin and 5% of a plasticizer were added to produce a modified adhesive.

[0050] S2. The precured fiber and the plant adhesive were mixed in a mass ratio of 6:4, 1% silane coupling agent (KH550) and 5% glycerol were added, and stirred at 600 rpm at 0.8 MPa and 85°C for 10 minutes to form a homogeneous premix;

[0051] S3. The premix is ​​first preheated at 100°C and 3 MPa for 5 minutes; then the temperature is raised to 125°C and the pressure is increased to 12 MPa, and maintained for 15 minutes; finally, the temperature is raised to 140°C, the pressure is increased to 18 MPa, and cured for 8 minutes; after completion of hot pressing, the temperature is gradually lowered to below 40°C at a rate of 3°C per minute, and then demolded and crushed in a crusher to obtain a granular biodegradable composite material.

[0052] Comparative Example 1

[0053] This comparative example provides a composite material based on plant fiber and biomass adhesive. The difference between this comparative example and Example 1 is that the fiber is not pre-cured, and the fiber is mixed with the plant adhesive and the modified adhesive for reaction, and the other conditions are the same.

[0054] Comparative Example 2

[0055] This comparative example provides a composite material based on plant fiber and biomass adhesive. The difference between this comparative example and Example 1 is that the inorganic nanoparticles are modified with amino groups, and the other conditions are the same.

[0056] The amino groups can only form hydrogen bonds with the cellulose hydroxyl groups, while the carboxyl groups can form Zn-OC coordination bonds with the cellulose, resulting in a decrease in the interfacial bonding strength. 2+ The metal ion bridging effect of ZnO cannot establish a stable three-dimensional cross-linked network between the fiber and the adhesive like carboxylated ZnO.

[0057] Test example:

[0058] Table 1 Performance results

[0059]

[0060] The bonding strength and tensile strength of Comparative Example 1 decreased because: first, the fibers that have not been pre-cured cannot achieve deep penetration of the adhesive, the carboxylated inorganic nanoparticles cannot fully enter the gaps between the cellulose microfibers to form Zn-OC coordination bonds, and the thiolated polyvinyl alcohol (PVA-SH) is also difficult to construct a sulfide bond cross-linking network with cellulose, resulting in a reduction of about 40-50% in the interfacial chemical bonding strength; secondly, direct mixing causes the adhesive to be enriched on the fiber surface but insufficiently filled inside, forming stress concentration points, which easily cause interfacial debonding and microcrack expansion when subjected to stress; finally, the one-step curing process causes the cross-linking network to be unevenly distributed, with both over-crosslinked brittle areas and under-crosslinked weak links, which significantly weakens the overall mechanical properties of the material.

[0061] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A composite material based on plant fiber and biomass adhesive, characterized in that: The raw materials for preparing the composite material include: plant fibers and adhesives; The adhesive includes plant adhesive and modified adhesive; The raw materials for preparing the modified adhesive include: inorganic nanoparticles modified with carboxyl groups, polyvinyl alcohol modified with thiol groups, and soybean powder.

2. The composite material based on plant fiber and biomass adhesive according to claim 1, characterized in that: The raw materials for preparing the inorganic nanoparticles modified with carboxyl groups include inorganic nanoparticles, mercaptopropionic acid, ethylenediaminetetraacetic acid and adipic acid.

3. The composite material based on plant fiber and biomass adhesive according to claim 1, characterized in that: The raw materials for preparing the polyvinyl alcohol modified with thiol groups include polyvinyl alcohol, sulfuric acid and thioglycolic acid.

4. The composite material based on plant fiber and biomass adhesive according to claim 1, characterized in that: The plant fiber comprises at least one of wood powder, bamboo powder, straw, rice husk powder, rice bran, coffee grounds and tea leaves.

5. The composite material based on plant fiber and biomass adhesive according to claim 1, characterized in that: The plant adhesive comprises at least one of starch glue, lignin glue and plant protein glue.

6. A method for preparing a composite material based on plant fiber and biomass adhesive according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: mixing the plant fiber and the modified adhesive, reacting the mixture, and then mixing the mixture with the plant adhesive, plasticizing the mixture, and hot pressing the mixture.

7. The preparation method according to claim 6, characterized in that The step of mixing the plant fiber and the modified adhesive comprises: alkali washing the plant fiber, removing impurities, and then reacting the plant fiber at 0.5-1 MPa and 70-80° C. for 40-50 minutes.

8. The preparation method according to claim 6, characterized in that The plasticizing temperature is 80-100°C.

9. The preparation method according to claim 6, characterized in that The conditions for the hot pressing molding are: 120-150° C., 10-20 MPa, and hot pressing for 10-30 minutes.

10. Use of the composite material based on plant fiber and biomass adhesive according to any one of claims 1 to 5 in cosmetic tools, packaging boards, building boards and flexible daily necessities.

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