Modified bamboo fiber, PBAT composite material and plastic object

Abstract

The invention relates to the technical field of plastic material preparation, and discloses a modified bamboo fiber, a PBAT composite material and a plastic object. The modified bamboo fiber comprises bamboo fiber subjected to hot pressing treatment in water and a closed aziridine cross-linking agent loaded on the bamboo fiber, and the mass ratio of the bamboo fiber subjected to hot pressing treatment in water to the closed aziridine cross-linking agent is 100: (1-10). The PBAT composite material comprises the following components in parts by weight: PBAT and modified bamboo fibers, and the mass ratio of the PBAT to the modified bamboo fibers is 100: (20-40). The modified bamboo fiber is subjected to hot pressing treatment in water, so that the generation of volatile gas caused by high-temperature processing can be avoided when the modified bamboo fiber is applied to the plastic material, and the interface interaction with the plastic material can be improved; the closed aziridine cross-linking agent can release active groups at high temperature, and can react with active functional groups such as hydroxyl and carboxyl on the surfaces of the bamboo fibers and the surfaces of the plastic materials, so that the interface interaction between the bamboo fibers and the plastic matrix is improved, and the tensile strength of the composite material is improved.

Description

Technical Field

[0001] This invention relates to the field of plastic material preparation technology, and more specifically, to modified bamboo fiber, PBAT composite material and plastic objects. Background Technology

[0002] Polybutylene adipate (PBAT) is considered one of the most promising alternative materials due to its biodegradability and mechanical properties close to those of traditional plastics. However, it suffers from drawbacks such as high cost and slow degradation. Bamboo fiber is renewable, inexpensive, and fully biodegradable. Adding it to PBAT to prepare PBAT / bamboo fiber composites can reduce costs, regulate degradation rates, and expand its application range. However, the significant difference between the hydrophobicity of PBAT and the hydrophilicity of bamboo fiber leads to uneven dispersion of bamboo fiber and poor interfacial compatibility. Simple mixing can increase the brittleness and decrease the strength of the composite material. Furthermore, bamboo fiber contains a large amount of hemicellulose, pectin, sugars, and other substances that are easily decomposed at the molding and processing temperatures of the composite material. The resulting low-molecular-weight compounds cause porosity in the composite material, severely affecting its mechanical properties.

[0003] Current technologies mostly focus on the preparation of composite materials of PBAT and starch, with very little research on the preparation of composite materials of PBAT and bamboo powder. Starch is divided into amylose and amylopectin. Amylose is a linear molecule composed of α-glucose linked by α-1,4-glycosidic bonds, while amylopectin, in addition to α-1,4-glycosidic bonds, also has α-1,6-glycosidic bonds, forming a branched structure. The bamboo fiber involved in this invention is a fibrous material with a large aspect ratio obtained from bamboo as raw material through crushing and grinding. The two have significant differences in properties. Starch can achieve a certain degree of fluidity through plasticization with low-molecular-weight substances, thereby enabling it to entangle with PBAT molecular chains and fuse well together to obtain a composite material with good comprehensive performance. Bamboo fiber does not have this characteristic and is mostly filled in PBAT matrix in solid form. Therefore, the technical challenge of achieving good processing and mechanical properties is what this invention addresses.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide modified bamboo fiber, PBAT composite materials and plastic articles, which aim to improve at least one of the problems mentioned in the background art.

[0006] This invention is implemented as follows: In a first aspect, the present invention provides a modified bamboo fiber, comprising bamboo fiber hot-pressed in water and a blocked aziridine crosslinking agent loaded on the bamboo fiber hot-pressed in water, wherein the mass ratio of the bamboo fiber hot-pressed in water to the blocked aziridine crosslinking agent is 100:1~10.

[0007] Secondly, the present invention provides a method for preparing modified bamboo fiber as described in the foregoing embodiments, comprising: The modified bamboo fiber is obtained by mixing and stirring the hot-pressed bamboo fiber in water with an aqueous solution of a blocked aziridine crosslinking agent until the water is removed.

[0008] In an optional embodiment, before mixing and stirring the bamboo fiber after hot-pressing in water with an aqueous solution of a blocked aziridine crosslinking agent, the process further includes: Bamboo fiber is mixed with water and reacted in a closed environment at 100~200℃ for at least 5 hours. After cooling, solid-liquid separation and drying are performed to obtain bamboo fiber that has undergone hot-pressing treatment in water. Optionally, the reaction time is 5.5 to 6.5 hours in a closed environment at 100 to 200 degrees Celsius.

[0009] In an optional embodiment, the mass concentration of the blocked aziridine crosslinking agent in the aqueous solution is 1-10%.

[0010] In an optional implementation, the water is removed by drying at 80~100°C.

[0011] Thirdly, the present invention provides a PBAT composite material, comprising, by weight, 100 parts of PBAT and 20-40 parts of modified bamboo fiber as described in the foregoing embodiments.

[0012] In an optional embodiment, 15 to 50 parts of a reinforcing agent, wherein the reinforcing agent is calcium lignosulfonate, are also included.

[0013] In an optional embodiment, 0.8 to 8.4 parts of dispersant are also included; Optionally, the dispersant is selected from at least one of fatty acid amides.

[0014] Fourthly, the present invention provides a method for preparing a PBAT composite material as described in any of the foregoing embodiments, comprising mixing the various components evenly and then melt-extruding and granulating. Optionally, the melting temperature is 140~155℃; Optionally, methods for uniformly mixing the components include: Mix all materials except PBAT thoroughly, and then mix the thoroughly mixed material with PBAT.

[0015] Fifthly, the present invention provides a plastic article made of PBAT composite material as described in any of the foregoing embodiments.

[0016] The present invention has the following beneficial effects: The modified bamboo fiber provided by this invention is bamboo fiber that has undergone hot-pressing treatment in water and is loaded with a blocked aziridine crosslinking agent. The hot-pressing treatment of bamboo fiber increases its mechanical properties and removes some of the original hemicellulose, sugars, pectin, etc., from the bamboo fiber by dissolving them in water. This eliminates the generation of volatile gases caused by high-temperature processing when the modified bamboo fiber is subsequently applied to plastic materials, reducing the probability of defects in the plastic composite material. The hot-pressing treatment also causes partial carbonization of the bamboo fiber, increasing its surface roughness and reducing its hydrophilicity, thus improving the interfacial interaction with the plastic material. Furthermore, the blocked aziridine crosslinking agent loaded on the fiber is stable at low temperatures, but releases active groups upon reaching its deblocking temperature. These groups react with hydroxyl and carboxyl groups on the surface of the bamboo fiber and the plastic material, enhancing the interfacial interaction between the bamboo fiber and the plastic matrix and improving the tensile strength of the composite material.

[0017] The PBAT composite material provided by this invention has better mechanical properties because it includes the modified bamboo fiber provided in the embodiments of this invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0019] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0020] This invention provides a modified bamboo fiber, comprising bamboo fiber hot-pressed in water and a blocked aziridine crosslinking agent loaded on the bamboo fiber hot-pressed in water, wherein the mass ratio of the bamboo fiber hot-pressed in water to the blocked aziridine crosslinking agent is 100:1~10.

[0021] The modified bamboo fiber provided by this invention is bamboo fiber that has undergone hot-pressing in water and is loaded with a blocked aziridine crosslinking agent. The hot-pressing process increases the mechanical properties of the bamboo fiber and removes some of the original hemicellulose, sugars, and pectin in the bamboo fiber, eliminating the generation of volatile gases caused by high-temperature processing when the modified bamboo fiber is subsequently applied to plastic materials, thus reducing the probability of defects in the plastic composite material. The hot-pressing process also causes partial carbonization of the bamboo fiber, increasing surface roughness and reducing hydrophilicity, thereby improving the interfacial interaction with the plastic material. The blocked aziridine crosslinking agent loaded on the fiber is stable at low temperatures, but releases active groups upon reaching its deblocking temperature. These groups react with hydroxyl and carboxyl groups on the surface of the bamboo fiber and the plastic material, enhancing the interfacial interaction between the bamboo fiber and the plastic matrix and increasing the tensile strength of the composite material. Therefore, the modified bamboo fiber improved by this invention, when used as a plastic modifier filler, can improve the mechanical properties of plastics.

[0022] The method for preparing modified bamboo fiber provided in this embodiment of the invention includes: The modified bamboo fiber is obtained by mixing and stirring the hot-pressed bamboo fiber in water with an aqueous solution of a blocked aziridine crosslinking agent until the water is removed.

[0023] The preparation method provided in this embodiment of the invention can produce modified bamboo fiber that can be applied to plastics to improve the mechanical properties of plastics.

[0024] Specifically, the preparation method is as follows: (1) Add bamboo fiber and water to a hydrothermal reactor. The amount of water added should be enough to completely submerge the bamboo fiber. Seal the reactor and raise the temperature of the reactor to 100~200℃, and react for at least 5 hours (preferably 5.5~6.5 hours). After the reaction is complete, the bamboo fiber is cooled, removed, washed with deionized water, and then dried to obtain bamboo fiber that has undergone hot pressing in water.

[0025] (2) Mix the bamboo fiber that has been hot-pressed in water with an aqueous solution of a blocked aziridine crosslinking agent (unblocked at a temperature above 120°C) until it is homogeneous, and then remove the water to obtain the modified bamboo fiber.

[0026] Optionally, the dehydration method involves drying a mixture of bamboo fiber and an aqueous solution of a blocked aziridine crosslinking agent at 80-100°C to obtain modified bamboo fiber.

[0027] Optionally, the mass concentration of the blocked aziridine crosslinking agent in the aqueous solution is 1-10%.

[0028] Optionally, the unblocking temperature of the blocked aziridine crosslinking agent is greater than 120°C.

[0029] The PBAT composite material provided in this embodiment of the invention comprises, by weight, 100 parts PBAT and 20-40 parts modified bamboo fiber provided in this embodiment of the invention.

[0030] The PBAT composite material has better mechanical properties because it includes the modified bamboo fiber provided in the embodiments of the present invention.

[0031] Optionally, the PBAT composite material also includes 15-50 parts of a reinforcing agent, namely calcium lignosulfonate. The addition of an appropriate amount of calcium lignosulfonate can significantly improve the tensile strength of the PBAT composite material, thus providing reinforcement.

[0032] Optionally, the PBAT composite material further includes 0.8 to 8.4 parts of a dispersant, the dispersant being selected from at least one of fatty acid amides. The addition of an appropriate amount of dispersant can improve the tensile strength of the composite material.

[0033] Specifically, fatty acid amides include stearamide, palmitamide, laurylamide, oleamide, erucamide, ethylene bis-stearamide, or ethylene bis-oleamide.

[0034] The method for preparing PBAT composite material provided in this embodiment of the invention includes mixing the various components evenly and then melt-extruding and granulating.

[0035] The melting temperature is usually high, exceeding the unblocking temperature of the blocked aziridine crosslinking agent. The active groups released during the unblocking process can react with the hydroxyl and carboxyl groups on the surface of bamboo fiber and the terminal carboxyl and terminal hydroxyl groups in PBAT, thereby improving the interfacial interaction between the PBAT matrix and bamboo fiber and thus improving the tensile strength of the composite material.

[0036] It should be noted that the modified bamboo fiber provided in this embodiment of the invention can be applied not only to PBAT composite materials, but also to other plastic materials. When applied to other plastic materials, it can also improve the mechanical properties of the plastic materials.

[0037] Optionally, methods for uniformly mixing the components include: Modified bamboo fiber, dispersant, and reinforcing agent are placed in a high-speed mixer and mixed at high speed to obtain the first mixture; Add PBAT to the mixture from the previous step and continue to mix at high speed until homogeneous to obtain the second mixture; The second mixture obtained in the previous step is added to a parallel twin-screw extruder and melt-extruded and blended at 140~155℃ to obtain PBAT composite material.

[0038] An embodiment of the present invention provides a plastic object made of PBAT composite material provided in the embodiment of the present invention.

[0039] Example 1 Bamboo fiber and water were added to a hydrothermal reactor, the reactor was sealed, and the temperature of the reactor was raised to 180°C and reacted for 6 hours. After the reaction was completed, the bamboo fiber was cooled, removed, washed with deionized water, and then dried to obtain bamboo fiber that had been hot-pressed in water.

[0040] Bamboo fibers that have undergone hot-pressing in water are mixed with an aqueous solution of a 6% (w / w) blocked aziridine crosslinking agent to obtain a slurry. The mass ratio of bamboo fibers to blocked aziridine crosslinking agent is 100:6. The slurry is then dried at 90°C to obtain modified bamboo fibers.

[0041] By weight, 34 parts of the modified bamboo fiber obtained in the above steps, 0.8 parts of dispersant and 25 parts of reinforcing agent (calcium lignosulfonate) are mixed in a high-speed mixer and mixed evenly at high speed to obtain the first mixture; Add 100 parts of PBAT to the mixture from the previous step and continue to mix at high speed until homogeneous to obtain the second mixture; The second mixture was added to a parallel twin-screw extruder and melt-extruded at 150°C to obtain PBAT composite material.

[0042] Examples 2-4 Examples 2-4 are basically the same as Example 1, except that the hot pressing temperatures in the hydrothermal reactor are 100℃, 140℃ and 200℃, respectively.

[0043] Comparative Example 1 This comparative example is basically the same as Example 1, except that the bamboo fiber was not subjected to hydrothermal pressing.

[0044] Examples 5-7 Examples 5-7 are basically the same as Example 1, except that the mass ratio of bamboo fiber to blocked aziridine crosslinking agent is 100:1, 100:2 and 100:10, respectively.

[0045] Comparative Example 2 This comparative example is basically the same as Example 1, except that the bamboo fiber after hot pressing in water was not loaded with a blocked aziridine crosslinking agent.

[0046] Examples 8-10 Examples 8-10 are basically the same as Example 1, except that the amount of modified bamboo fiber used is 10 parts, 20 parts and 40 parts respectively.

[0047] Comparative Example 3 This comparative example is basically the same as Example 1, except that modified bamboo fiber was not used when manufacturing the PBAT composite material.

[0048] Examples 11-14 Examples 11-14 are basically the same as Example 1, except that the amount of dispersant used is 0 parts, 1.6 parts, 5 parts and 8.4 parts respectively.

[0049] Examples 15-18 Examples 15-18 are basically the same as Example 1, except that the amount of reinforcing agent used is 0 parts, 10 parts, 40 parts and 50 parts respectively.

[0050] Experimental Example 1 The tensile strength and elongation at break of the PBAT composite materials prepared in the examples and comparative examples were tested using the method of GB / T 1040.1-2018 (Determination of tensile properties of plastics), and the test results are recorded in Table 1.

[0051] Table 1 Mechanical properties of composite materials under different hot-pressing conditions

[0052] As shown in Table 1, the PBAT composite material prepared directly from bamboo fiber without hot pressing exhibits the lowest mechanical properties. These properties increase with increasing hot pressing temperature, reaching their optimal level at 180℃. Using water as a solvent for hot pressing allows for the dissolution and removal of some water-soluble substances such as hemicellulose, sugars, and pectin, eliminating the generation of volatile gases during hot-melt processing and reducing porosity in the composite material, thus minimizing defects. Simultaneously, it induces partial carbonization of the bamboo fiber, increasing surface roughness, reducing hydrophilicity, and enhancing the interfacial interaction with PBAT.

[0053] Table 2 Mechanical properties of composite materials with different amounts of sealing agent

[0054] Aziridine crosslinking agents are blocked and stable at low temperatures, but they release active groups at the unblocking temperature, reacting with active functional groups such as hydroxyl and carboxyl groups. The active groups released in this application can react with the hydroxyl and carboxyl groups on the surface of bamboo fibers, as well as the terminal carboxyl and terminal hydroxyl groups in PBAT, improving the interfacial interaction between the PBAT matrix and bamboo fibers, thereby increasing the tensile strength of the composite material. As shown in Table 2, the tensile strength increases with increasing crosslinking agent dosage, reaching its maximum at a 100:6 ratio, an increase of 18.1% compared to the unblocked composite.

[0055] Table 3 Mechanical properties of composite materials with different amounts of modified bamboo fiber

[0056] As can be seen from Table 3, the tensile strength of the composite material with modified bamboo fiber is significantly improved compared with that without modified bamboo fiber, and the optimal ratio of modified bamboo fiber is 100:34.

[0057] Table 4 Mechanical properties of composite materials with different amounts of dispersant

[0058] Bamboo fiber is a solid with a large aspect ratio and a powdery appearance. The uniformity of its dispersion in the PBAT matrix affects the mechanical properties of the composite material. Data from Table 4 shows that a PBAT to dispersant ratio of 100:0.8 increases the tensile strength of the composite material, while excessive amounts decrease its mechanical properties. The elongation at break increases with increasing dispersant dosage, but excessive amounts decrease it.

[0059] Table 5 Mechanical properties of composite materials with different amounts of reinforcing agents

[0060] As can be seen from the data in Table 5, the addition of calcium lignosulfonate can increase the tensile strength of the composite material.

[0061] In summary, the modified bamboo fiber provided in this invention, due to its hot-pressing treatment in water, avoids the generation of volatile gases caused by high-temperature processing when applied to plastic materials, thus improving the interfacial interaction with the plastic material. Furthermore, the loading of a blocked aziridine crosslinking agent on the fiber releases active groups at high temperatures, which react with hydroxyl and carboxyl groups on the surface of the bamboo fiber and the plastic material, further enhancing the interfacial interaction between the bamboo fiber and the plastic matrix and improving the tensile strength of the composite material. Therefore, the modified bamboo fiber improved by this invention, when used as a plastic modifier filler, can improve the mechanical properties of plastics.

[0062] In a preferred embodiment, adding calcium lignosulfonate as a reinforcing agent to PBAT can further enhance the tensile strength of the PBAT material. Furthermore, using industrial waste calcium lignosulfonate as a filler and reinforcing agent achieves comprehensive utilization of waste materials.

[0063] The PBAT composite material provided by this invention has better mechanical properties because its components include the modified bamboo fiber provided by this invention.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A modified bamboo fiber, characterized in that, The product includes bamboo fiber that has undergone hot-pressing in water and a blocked aziridine crosslinking agent loaded on the bamboo fiber after hot-pressing in water, wherein the mass ratio of the bamboo fiber after hot-pressing in water to the blocked aziridine crosslinking agent is 100:1~10.

2. The method for preparing modified bamboo fiber as described in claim 1, characterized in that, include: The modified bamboo fiber is obtained by mixing and stirring the hot-pressed bamboo fiber in water with an aqueous solution of a blocked aziridine crosslinking agent until the water is removed.

3. The preparation method according to claim 2, characterized in that, Before mixing and stirring the bamboo fiber after hot-pressing in water with an aqueous solution of a blocked aziridine crosslinking agent, the following steps are also included: Bamboo fiber is mixed with water and reacted in a closed environment at 100~200℃ for at least 5 hours. After cooling, solid-liquid separation and drying are performed to obtain the bamboo fiber after hot-pressing in water. Optionally, the reaction time is 5.5 to 6.5 hours in a closed environment at 100 to 200 degrees Celsius.

4. The preparation method according to claim 2, characterized in that, The mass concentration of the blocked aziridine crosslinking agent in the aqueous solution is 1~10%.

5. The preparation method according to claim 2, characterized in that, The method of removing water is drying at 80~100℃.

6. A PBAT composite material, characterized in that, By weight, it comprises: 100 parts PBAT and 20-40 parts modified bamboo fiber as described in claim 1.

7. The composite material according to claim 6, characterized in that, It also includes 15 to 50 parts of a reinforcing agent, wherein the reinforcing agent is calcium lignosulfonate.

8. The composite material according to claim 6, characterized in that, It also includes 0.8 to 8.4 parts of dispersant; Optionally, the dispersant is selected from at least one of fatty acid amides.

9. The method for preparing the PBAT composite material according to any one of claims 6 to 8, characterized in that, This includes mixing all the components evenly, followed by melt extrusion granulation; Optionally, the melting temperature is 140~155℃; Optionally, methods for uniformly mixing the components include: Mix all materials except PBAT until homogeneous, and then mix the homogeneous mixture with PBAT until homogeneous.

10. A plastic object, characterized in that, It is made from the PBAT composite material as described in any one of claims 6 to 8.

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