Degradable composite foaming material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of materials, and discloses a degradable composite foaming material as well as a preparation method and application thereof. The degradable composite foaming material comprises the following raw material components: polylactic acid, modified wood flour, a foaming agent and an auxiliary agent, the preparation process of the modified wood flour comprises the following steps: (1) mixing wood flour with a silane coupling agent and a solvent, then adjusting the pH value to be acidic, carrying out a first reaction, and drying to obtain silane coupling agent modified wood flour; (2) mixing the silane coupling agent modified wood flour, pentaerythritol triacrylate and isocyanate acrylate, adding an initiator, and carrying out a second reaction to obtain an intermediate product; and (3) mixing the intermediate product with polylactic acid, adding a catalyst, and carrying out a third reaction to obtain the modified wood flour. The degradable composite foaming material not only has good degradability, but also has good mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of materials, and in particular relates to a degradable composite foam material and a preparation method and application thereof. Background Art

[0002] For a long time, plastics have been widely used in many fields such as packaging, building materials, and electronics due to their low cost, easy processing, and diverse performance, which has profoundly changed people's lives and production methods. However, the non-degradability of traditional petroleum-based plastics has gradually exposed serious drawbacks. A large amount of plastic waste is difficult to decompose in the natural environment. Over time, it not only occupies a large amount of land resources, but also causes immeasurable damage to soil structure and water ecology, thus triggering the "white pollution" problem, which is becoming increasingly serious and has become a global environmental problem. Against this background, degradable plastics came into being. They can gradually decompose into small molecules under natural environmental conditions through the action of microorganisms, light, heat, etc., effectively alleviating the environmental pressure of plastic waste, bringing hope to solving the "white pollution" crisis, and becoming a research hotspot in the field of materials.

[0003] Wood flour in nature, as a natural cellulose material, is environmentally friendly. However, due to its strong polarity, while most biodegradable plastics are non-polar or weakly polar polymers, the significant difference in polarity between the two leads to poor compatibility between wood flour and biodegradable plastics during the compounding process, making it difficult for wood flour to be evenly dispersed in the plastic matrix. This problem greatly limits the improvement of composite material performance. To overcome this obstacle, the current mainstream methods are mostly centered around chemical modification: functionalizing the surface of wood flour to promote a closer bond with the plastic matrix; and changing the structure of wood flour or its surface properties through physical treatment to enhance interfacial compatibility.

[0004] However, despite the above-mentioned modification methods adopted in the existing technology, the compatibility problem between wood powder and biodegradable plastics remains prominent. In the actual production process, even after chemical or physical treatment, the agglomeration of wood powder in the plastic matrix still occurs from time to time, making it difficult to achieve truly uniform dispersion, resulting in a large number of weak interface areas within the composite material. When the material is subjected to external forces, these weak areas are very likely to cause stress concentration, causing the material to crack and break prematurely, seriously affecting the mechanical properties of the composite material. Key indicators such as tensile strength, flexural strength, and compressive strength are far lower than expected, resulting in restrictions on the use of the material.

[0005] In addition, biodegradable composite materials are prepared using a foaming process, which can significantly reduce density, achieve lightweighting, enhance thermal insulation and cushioning properties, improve melt fluidity and reduce material usage. However, the existing process faces problems such as mismatch between the thermal stability of the foaming agent and the matrix, poor filler dispersion leading to uneven foaming (such as combined bubbles and broken holes), residual chemical foaming agents affecting degradability, high cost and energy consumption of physical foaming, and sensitive and difficult-to-control process parameters, which greatly restrict its application scope.

[0006] Therefore, a new composite foam material is needed, which not only has good degradability but also good mechanical properties and an easily controllable foaming process. Summary of the Invention

[0007] The present invention aims to address at least one of the technical problems existing in the aforementioned prior art. To this end, the present invention provides a degradable composite foam material, a preparation method, and applications thereof. The degradable composite foam material of the present invention not only exhibits excellent degradability but also exhibits excellent mechanical properties. Furthermore, the preparation process of the degradable composite foam material is controllable, resulting in a degradable composite foam material with stable mechanical properties.

[0008] A first aspect of the present invention provides a degradable composite foam material.

[0009] A degradable composite foam material, the raw material components of which include polylactic acid, modified wood powder, foaming agent and additives;

[0010] The preparation process of the modified wood flour comprises the following steps:

[0011] (1) Mixing wood powder with a silane coupling agent and a solvent, then adjusting the pH to acidic, reacting for the first time, and drying to obtain wood powder modified with a silane coupling agent;

[0012] (2) mixing the wood flour modified with the silane coupling agent, pentaerythritol triacrylate and isocyanate acrylate, adding an initiator, and reacting for a second time to obtain an intermediate product;

[0013] (3) The intermediate product is mixed with polylactic acid, a catalyst is added, and the reaction is carried out for the third time to obtain modified wood powder.

[0014] The isocyanate groups (-NCO) react chemically with the hydroxyl groups (-OH) on the surface of the wood powder to form stable carbamate bonds (-NHCOO-), which reduces the interfacial tension between the wood powder and the polymer matrix (such as PLA) and improves the interfacial bonding strength25.

[0015] Preferably, in step (1), the wood powder is derived from various plants, such as pine, oak, poplar, bamboo, straw powder, rice husk powder, and coconut shell powder. For example, the wood powder can be obtained by crushing, grinding, and screening the scraps from solid wood furniture factories, density board factories, and multi-layer board factories.

[0016] Preferably, in step (1), the mesh size of the wood flour is 100-300 mesh, more preferably 200-250 mesh.

[0017] Preferably, the wood powder is dried before use, for example, at 60-100° C. for 6-12 hours.

[0018] Preferably, in step (1), the solvent comprises water or a mixture of water and alcohol. The amount of solvent can be added as needed, for example, the mass of the solvent is 30-100% of the mass of the wood flour.

[0019] Preferably, in step (1), the mass ratio of the wood powder to the silane coupling agent is 100:(1-10), more preferably 100:(3-8).

[0020] Preferably, in step (1), the silane coupling agent is selected from at least one of KH550, KH560 or KH570.

[0021] Preferably, in step (1), while adding the silane coupling agent, hydroxyl-terminated silicone oil is also added.

[0022] Preferably, in step (1), the pH is adjusted to 4-6.

[0023] Preferably, in step (1), the temperature of the first reaction is 60-80° C., and the reaction time is 2-6 hours.

[0024] Preferably, in step (2), the mass ratio of the silane coupling agent-modified wood flour, pentaerythritol triacrylate and isocyanate acrylate is 100:(10-25):(8-15), and more preferably 100:(15-25):(10-12).

[0025] Preferably, in step (1), the drying temperature is 60-100° C. and the drying time is 2-8 hours.

[0026] Preferably, in step (2), the silane coupling agent-modified wood flour, pentaerythritol triacrylate, and isocyanate acrylate are mixed in toluene or acetone. Mixing in a toluene or acetone solvent allows for more uniform mixing and a more uniform reaction. The amount of toluene or acetone used can be adjusted as needed.

[0027] Preferably, in step (2), the temperature of the second reaction is 60-80° C., and the reaction time is 2-4 hours.

[0028] Preferably, in step (2), the initiator comprises benzoyl peroxide.

[0029] Preferably, in step (2), the mass of the initiator is 1-3% of the mass of the wood powder modified with the silane coupling agent.

[0030] Preferably, in step (2), the isocyanate acrylate includes isocyanate ethyl acrylate or isocyanatoethyl methacrylate.

[0031] Preferably, in step (3), the mass ratio of the intermediate product to polylactic acid is 20-25:(75-80).

[0032] Preferably, in step (3), the catalyst is an organic tin catalyst, such as stannous octoate.

[0033] Preferably, in step (3), the mass of the catalyst is 0.1-1% of the total mass of the intermediate product and polylactic acid.

[0034] Preferably, in step (3), the temperature of the third reaction is 160-180° C., and the reaction time is 1-2 hours.

[0035] Preferably, the preparation process of the modified wood flour comprises the following steps:

[0036] S1. Mix wood flour and KH570 (1-5% of the mass of the wood flour), adjust the pH to 4-6, stir and react at a temperature of 110-135°C for 4-6 hours, and dry to obtain KH570 modified wood flour;

[0037] S2, mixing the KH570 modified wood flour, pentaerythritol triacrylate (accounting for 15-25% of the weight of the KH570 modified wood flour, as a cross-linking agent, which needs to provide sufficient double bonds to participate in the free radical polymerization reaction and increase the cross-linking density of the material) and isocyanate acrylate (accounting for 10% of the weight of the modified wood flour), adding an initiator (benzoyl peroxide, 1-2 wt%), heating to react at a temperature of 60-80° C. for a reaction time of 2-4 hours, and drying to obtain an intermediate product;

[0038] S3. Mix the intermediate product and polylactic acid in a mass ratio of 20-25:75-80, add a catalyst (stannous octoate, accounting for 0.5-1% of the total mass of the intermediate product and polylactic acid), and heat to react at a temperature of 160-180° C. for 1-2 hours to obtain the modified wood flour.

[0039] The acrylate groups (e.g., C=C double bonds) in isocyanate acrylates can synergize with crosslinkers like pentaerythritol triacrylate in free radical polymerization reactions to form a three-dimensional crosslinked network, increasing the material's crosslink density and mechanical stability. Furthermore, when initiated by benzoyl peroxide, the acrylate double bonds break and bind to the crosslinker, enhancing the mechanical properties of the composite.

[0040] Preferably, in step (2), when adding pentaerythritol triacrylate, a complex alcohol is also added, and the complex alcohol includes 2,2-dihydroxymethylpropane-1,3-diol, ethylene glycol and trimethylolpropane.

[0041] The specific types of complex alcohols mentioned above (the specific polyhydroxyl groups and molecular backbone structure of 2,2-dimethylolpropane-1,3-diol, ethylene glycol, and trimethylolpropane facilitate the formation of a stable spatial network structure after the reaction) can improve the fluidity of the polylactic acid chain segments, increase melt strength, and inhibit cell collapse during the foaming process, thereby enhancing cell uniformity and the mechanical strength of the biodegradable composite foam material. The complex alcohols react with isocyanate acrylates (containing -NCO groups) to form urethane bonds, building a multi-crosslinked network and enhancing the overall crosslink density of the material. The complex alcohols can also form hydrogen bonds with the surface hydroxyl groups of wood flour, strengthening the interfacial bonding strength with the polylactic acid matrix.

[0042] Preferably, the composite alcohol comprises 2,2-dimethylolpropane-1,3-diol, ethylene glycol, and trimethylolpropane in a mass ratio of 1:(0.1-0.8):(0.5-1.5), more preferably 1:(0.3-0.6):(0.6-1.2). A composite alcohol composition in this specific ratio is more conducive to obtaining a biodegradable composite foam material with improved mechanical strength.

[0043] Preferably, the foaming agent comprises sodium bicarbonate.

[0044] Preferably, the auxiliary agent includes at least one of a lubricant or a toughening agent.

[0045] Preferably, the lubricant comprises at least one of magnesium stearate or zinc stearate.

[0046] Preferably, the toughening agent includes at least one of polybutylene succinate and ethylene vinyl acetate.

[0047] Preferably, the raw material components, calculated by mass ratio, include 60 parts of polylactic acid, 20-40 parts of modified wood flour, 0.5-2.5 parts of foaming agent, and 0.1-10 parts of auxiliary agent; further preferably, the raw material components, calculated by mass ratio, include 60 parts of polylactic acid, 25-35 parts of modified wood flour, 1-2 parts of foaming agent, and 0.1-5 parts of auxiliary agent.

[0048] A second aspect of the present invention provides a method for preparing a degradable composite foam material.

[0049] A method for preparing a degradable composite foam material comprises the following steps:

[0050] (1) Mixing the raw material components and melting them to obtain a blend;

[0051] (2) granulating the blend and then pre-pressing the mixture to obtain a pre-pressed product;

[0052] (3) placing the pre-pressed material into a mold, performing foaming treatment, cooling, and demoulding to obtain the degradable composite foam material.

[0053] Preferably, the melting temperature is 170-180° C., for example, 179° C. or 180° C. The temperature is maintained at the melting temperature for 3-5 minutes.

[0054] Preferably, the pre-pressing temperature is 160-170° C. and the pressure is 3-8 MPa, for example, 5-6 MPa.

[0055] Preferably, the foaming process is: at a foaming temperature of 160-185°C and a pressure of 3-8 MPa, maintaining heat and pressure for 5-10 minutes, then cooling to 110-125°C and a pressure of 3-6 MPa, maintaining heat and pressure for 10-15 minutes.

[0056] More preferably, the foaming process is as follows: maintaining the foaming temperature at 160°C-185°C and the pressure at 3-8 MPa for 5-10 minutes, then cooling the temperature to 110-125°C and the pressure at 3-6 MPa for 10-15 minutes, and then further cooling the temperature to 80-110°C and the pressure at 4-6 MPa for 20-30 minutes. This three-stage temperature gradient treatment is beneficial for obtaining a biodegradable composite foam material with better foaming effect and better mechanical properties.

[0057] A third aspect of the present invention provides an application of a degradable composite foam material.

[0058] A plastic product comprises the above-mentioned degradable composite foam material.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] (1) The biodegradable composite foam material of the present invention comprises raw material components including polylactic acid, modified wood powder, foaming agent and auxiliary agent, wherein the preparation process of the modified wood powder includes modification with a silane coupling agent, cross-linking modification with pentaerythritol triacrylate and isocyanate acrylate, and further reaction with polylactic acid to obtain modified wood powder, which greatly improves the interfacial compatibility between the wood powder and polylactic acid. After foaming, a biodegradable composite foam material having not only good biodegradability but also good mechanical properties can be obtained.

[0061] (2) During the preparation of the modified wood powder, when pentaerythritol triacrylate is added, a complex alcohol is also added, and the complex alcohol includes 2,2-dimethylolpropane-1,3-diol, ethylene glycol and trimethylolpropane. The above-mentioned specific type of complex alcohol (the specific polyhydroxyl groups and molecular skeleton structure of 2,2-dimethylolpropane-1,3-diol, ethylene glycol and trimethylolpropane are conducive to the construction of a stable spatial network structure after the reaction) can improve the fluidity of the polylactic acid chain segment, increase the melt strength, and inhibit the collapse of the foam cells during the foaming process, thereby improving the uniformity of the foam cells and the mechanical strength of the degradable composite foam material, and also improving the mechanical stability. The complex alcohol can react with isocyanate acrylate (containing -NCO groups) to form urethane bonds, construct a multiple cross-linked network, and enhance the overall cross-linking density of the material. The complex alcohol can also form hydrogen bonds with the hydroxyl groups on the surface of the wood powder, thereby enhancing the interfacial bonding strength with the polylactic acid matrix. DETAILED DESCRIPTION

[0062] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0063] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0064] Example 1

[0065] A biodegradable composite foam material, the raw material components include 60 parts of polylactic acid, 20 parts of modified wood flour, 1 part of foaming agent (sodium bicarbonate), and 6 parts of auxiliary agents (1 part of magnesium stearate and 5 parts of polybutylene succinate);

[0066] The preparation process of modified wood flour includes the following steps:

[0067] S1. Mix wood powder (the wood powder is poplar wood powder with a mesh size of 200-250 mesh, and the wood powder is dried at 80°C for 7 hours before use) with KH570 (4% of the weight of the wood powder) and water (the weight of the water is 60% of the weight of the wood powder), adjust the pH to 6, stir and react at a temperature of 70°C for 5 hours, and dry at a temperature of 90°C for 8 hours to obtain KH570 modified wood powder;

[0068] S2. Mix KH570 modified wood flour, pentaerythritol triacrylate (accounting for 20% of the mass of KH570 modified wood flour), ethyl isoisocyanate acrylate (accounting for 10% of the mass of KH570 modified wood flour), and acetone (the mass of acetone is 30% of the mass of KH570 modified wood flour), add an initiator (benzoyl peroxide, accounting for 1 wt% of the mass of KH570 modified wood flour), heat to react, the reaction temperature is 70°C, the reaction time is 3 hours, and dry at 60°C for 3 hours to obtain an intermediate product;

[0069] S3. The intermediate product and polylactic acid are mixed in a mass ratio of 25:75, a catalyst (stannous octoate, accounting for 0.8% of the total mass of the intermediate product and polylactic acid) is added, and the mixture is heated to react at a temperature of 170° C. for 1.5 hours to obtain modified wood powder.

[0070] A method for preparing a degradable composite foam material comprises the following steps:

[0071] (1) The raw material components were mixed and melt-treated at 175°C for 5 minutes to obtain a blend;

[0072] (2) The blend is placed in a pulverizer for pulverization and granulation, and then pre-pressed at a temperature of 170°C and a pressure of 6 MPa to obtain a pre-pressed product;

[0073] (3) The pre-pressed material is placed in a mold for foaming treatment. The foaming process is as follows: the foaming temperature is 175°C, the pressure is 5 MPa, and the heat and pressure are maintained for 6 minutes, then the temperature is lowered to 120°C, the pressure is 4 MPa, and the heat and pressure are maintained for 15 minutes, and then the material is cooled to room temperature and demolded to obtain a biodegradable composite foam material.

[0074] Example 2

[0075] A biodegradable composite foam material, the raw material components include 60 parts of polylactic acid, 22 parts of modified wood flour, 1.2 parts of a foaming agent (sodium bicarbonate), and 6 parts of an auxiliary agent (1 part of zinc stearate and 5 parts of polybutylene succinate);

[0076] The preparation process of modified wood flour includes the following steps:

[0077] S1. Mix wood powder (the wood powder is poplar wood powder with a mesh size of 200-250 mesh, and the wood powder is dried at 80°C for 7 hours before use) with KH570 (3% of the weight of the wood powder) and water (the weight of the water is 50% of the weight of the wood powder), adjust the pH to 5, stir and react at a temperature of 80°C for 5 hours, and dry at a drying temperature of 90°C for 8 hours to obtain KH570 modified wood powder;

[0078] S2, mixing KH570 modified wood flour, pentaerythritol triacrylate (accounting for 22% of the mass of KH570 modified wood flour), ethyl isoisocyanate acrylate (accounting for 12% of the mass of KH570 modified wood flour), and acetone (the mass of acetone is 30% of the mass of KH570 modified wood flour), adding an initiator (benzoyl peroxide, accounting for 2 wt% of the mass of KH570 modified wood flour), heating to react at a temperature of 80°C for a reaction time of 4 hours, and drying at 60°C for 3 hours to obtain an intermediate product;

[0079] S3. The intermediate product and polylactic acid are mixed in a mass ratio of 20:80, a catalyst (stannous octoate, accounting for 1% of the total mass of the intermediate product and polylactic acid) is added, and the mixture is heated to react at a temperature of 175° C. for 1.5 hours to obtain modified wood powder.

[0080] A method for preparing a degradable composite foam material comprises the following steps:

[0081] (1) The raw material components were mixed and melt-treated at 175°C for 5 minutes to obtain a blend;

[0082] (2) The blend is placed in a pulverizer for pulverization and granulation, and then pre-pressed at a temperature of 170°C and a pressure of 6 MPa to obtain a pre-pressed product;

[0083] (3) The pre-pressed material is placed in a mold for foaming treatment. The foaming process is as follows: the foaming temperature is 175°C, the pressure is 5 MPa, and the heat and pressure are maintained for 6 minutes, then the temperature is lowered to 120°C, the pressure is 4 MPa, and the heat and pressure are maintained for 15 minutes, and then the material is cooled to room temperature and demolded to obtain a biodegradable composite foam material.

[0084] Example 3

[0085] A biodegradable composite foam material, the raw material components include 60 parts of polylactic acid, 20 parts of modified wood flour, 1 part of foaming agent (sodium bicarbonate), and 6 parts of auxiliary agents (1 part of magnesium stearate and 5 parts of polybutylene succinate);

[0086] The preparation process of modified wood flour includes the following steps:

[0087] S1. Mix wood powder (the wood powder is poplar wood powder with a mesh size of 200-250 mesh, and the wood powder is dried at 80°C for 7 hours before use) with KH570 (4% of the weight of the wood powder) and water (the weight of the water is 60% of the weight of the wood powder), adjust the pH to 6, stir and react at a temperature of 70°C for 5 hours, and dry at a temperature of 90°C for 8 hours to obtain KH570 modified wood powder;

[0088] S2. KH570 modified wood flour, pentaerythritol triacrylate (accounting for 20% of the mass of KH570 modified wood flour), complex alcohol (the complex alcohol is composed of 2,2-dihydroxymethylpropane-1,3-diol, ethylene glycol and trimethylolpropane in a mass ratio of 1:0.5:1, and the complex alcohol accounts for 3% of the mass of KH570 modified wood flour), ethyl isoisocyanate acrylate (accounting for 10% of the mass of KH570 modified wood flour), and acetone (the mass of acetone is 30% of the mass of KH570 modified wood flour) are mixed, and an initiator (benzoyl peroxide, accounting for 1 wt% of the mass of KH570 modified wood flour) is added. The mixture is heated to react at a temperature of 70°C for 3 hours, and dried at 60°C for 3 hours to obtain an intermediate product.

[0089] S3. The intermediate product and polylactic acid are mixed in a mass ratio of 25:75, a catalyst (stannous octoate, accounting for 0.8% of the total mass of the intermediate product and polylactic acid) is added, and the mixture is heated to react at a temperature of 170° C. for 1.5 hours to obtain modified wood powder.

[0090] A method for preparing a degradable composite foam material comprises the following steps:

[0091] (1) The raw material components were mixed and melt-treated at 175°C for 5 minutes to obtain a blend;

[0092] (2) The blend is placed in a pulverizer for pulverization and granulation, and then pre-pressed at a temperature of 170°C and a pressure of 6 MPa to obtain a pre-pressed product;

[0093] (3) The pre-pressed material is placed in a mold for foaming treatment. The foaming process is as follows: the foaming temperature is 175°C, the pressure is 5 MPa, and the heat and pressure are maintained for 6 minutes, then the temperature is lowered to 120°C, the pressure is 4 MPa, and the heat and pressure are maintained for 15 minutes, and then the material is cooled to room temperature and demolded to obtain a biodegradable composite foam material.

[0094] Example 4

[0095] Compared with Example 1, the only difference in Example 4 is that the foaming process is as follows: the foaming temperature is 178°C, the pressure is 5 MPa, the heat preservation and pressure maintenance are 6 minutes, then the temperature is lowered to 120°C, the pressure is 4 MPa, the heat preservation and pressure maintenance are 15 minutes, and then the temperature is further lowered to 90°C, the pressure is 4 MPa, the heat preservation and pressure maintenance are 25 minutes, and the mixture is cooled to room temperature and demolded to obtain a degradable composite foam material.

[0096] Example 5

[0097] Compared with Example 3, the only difference of Example 5 is that an equal amount of polyethylene glycol is used instead of 2,2-dihydroxymethylpropane-1,3-diol, and the other processes are the same as those of Example 3.

[0098] Comparative Example 1

[0099] Compared with Example 1, the only difference of Comparative Example 1 is that an equal amount of ethyl acetate is used to replace the pentaerythritol triacrylate in Example 1, and the other processes are the same as those in Example 1.

[0100] Comparative Example 2

[0101] Compared with Example 1, the only difference of Comparative Example 2 is that Comparative Example 2 does not have the process of modifying the wood powder with KH570, that is, in the preparation process of the modified wood powder in Comparative Example 2, there is no step S1, and Comparative Example 2 uses an equal amount of wood powder instead of KH570 modified wood powder to prepare the modified wood powder.

[0102] Product effect testing

[0103] 1. Mechanical strength test

[0104] The degradable composite foam materials prepared in the above embodiments and comparative examples were taken as samples. The sample shape was a rectangular parallelepiped with dimensions of 20 mm in length × 20 mm in width × 10 mm in height. Referring to the GB / T8813-2008 standard, the compression performance of the degradable composite foam material samples was tested using a universal mechanical testing machine. The compression rate was 2 mm / min, and the maximum value of deformation less than 10% was taken as the compressive strength of the sample (the greater the compressive strength, the better the mechanical properties of the degradable composite foam material). In addition, the apparent density of each sample was measured, and the results are shown in Table 1.

[0105] Table 1

[0106] As can be seen from Table 1, the compressive strength of the degradable composite foam material prepared in the embodiment of the present invention is significantly better than that of the comparative example, being stable at 5.98-6.58 MPa. The apparent density of the degradable composite foam material prepared in the embodiment of the present invention is stable at 0.35-0.37 MPa.

[0107] From the results of Example 3 and Example 1, it can be seen that the addition of the complex alcohol significantly improves the compressive strength of the degradable composite foam material. From the results of Example 3 and Example 5, it can also be seen that the type of complex alcohol has a significant effect on the compressive strength of the prepared degradable composite foam material.

[0108] 2. Stability test

[0109] The degradable composite foam materials prepared in Example 1, Example 3, Example 5, and Comparative Example 1 were soaked in 100°C water for 8 hours, and then the compressive strength was tested according to the method of "1. Mechanical Strength Test" above. The results are shown in Table 2.

[0110] Table 2

[0111] Where, compressive strength retention rate = compressive strength after immersion in 100℃ water for 8 hours / compressive strength before immersion in 100℃ water for 8 hours 100%.

[0112] As can be seen from Table 2, the degradable composite foam material prepared in the present invention can still maintain good mechanical properties even after being subjected to boiling water treatment. In particular, the degradable composite foam material prepared by using a specific complex alcohol in Example 3 of the present invention has the best mechanical stability.

Claims

1. A degradable composite foam material, characterized in that: The raw material components include polylactic acid, modified wood flour, foaming agent and additives; The preparation process of the modified wood flour comprises the following steps: (1) Mixing wood powder with a silane coupling agent and a solvent, then adjusting the pH to acidic, reacting for the first time, and drying to obtain wood powder modified with a silane coupling agent; (2) mixing the wood flour modified with the silane coupling agent, pentaerythritol triacrylate and isocyanate acrylate, adding an initiator, and reacting for a second time to obtain an intermediate product; (3) The intermediate product is mixed with polylactic acid, a catalyst is added, and the reaction is carried out for the third time to obtain the modified wood powder.

2. The degradable composite foam material according to claim 1, characterized in that: In step (1), the mass ratio of the wood powder to the silane coupling agent is 100:(1-10).

3. The degradable composite foam material according to claim 1, characterized in that: In step (1), the silane coupling agent is selected from at least one of KH550, KH560 or KH570; and / or, in step (1), the pH is adjusted to 4-6.

4. The degradable composite foam material according to claim 1, characterized in that: In step (1), the temperature of the first reaction is 60-80° C., and the reaction time is 2-6 hours; and / or, in step (2), the mass ratio of the silane coupling agent-modified wood flour, pentaerythritol triacrylate, and isocyanate acrylate is 100:(10-25):(8-15).

5. The degradable composite foam material according to claim 1, characterized in that: In step (2), the temperature of the second reaction is 60-80° C., and the reaction time is 2-4 hours; and / or, in step (2), the initiator includes benzoyl peroxide.

6. The degradable composite foam material according to claim 1, characterized in that: In step (3), the mass ratio of the intermediate product to the polylactic acid is 20-25:(75-80); and / or, in step (3), the temperature of the third reaction is 160-180° C., and the reaction time is 1-2 hours.

7. The degradable composite foam material according to claim 1, characterized in that: In step (2), when pentaerythritol triacrylate is added, a complex alcohol is also added, wherein the complex alcohol includes 2,2-dihydroxymethylpropane-1,3-diol, ethylene glycol and trimethylolpropane.

8. The degradable composite foam material according to claim 1, characterized in that: The foaming agent includes sodium bicarbonate; and / or the auxiliary agent includes at least one of a lubricant or a toughening agent.

9. The degradable composite foam material according to claim 1, characterized in that: The raw material components, calculated by mass ratio, include 60 parts of polylactic acid, 20-40 parts of modified wood flour, 0.5-2.5 parts of foaming agent, and 0.1-10 parts of auxiliary agent.

10. The method for preparing the degradable composite foam material according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) Mixing the raw material components and melting them to obtain a blend; (2) granulating the blend and then pre-pressing the mixture to obtain a pre-pressed product; (3) placing the pre-pressed material into a mold, performing foaming treatment, cooling, and demoulding to obtain the degradable composite foam material.

11. A plastic product, characterized in that: The invention comprises the degradable composite foam material according to any one of claims 1 to 9.

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