Method for preparing wood-plastic composite material from camellia oleifera shell powder and regenerated polypropylene

Abstract

The invention provides a method for preparing a wood-plastic composite material from camellia oleifera shell powder and regenerated polypropylene, and relates to the technical field of waste utilization. The method comprises the following steps: pretreating camellia oleifera shells, namely drying the camellia oleifera shells at 55-85 DEG C, performing heat treatment at 115-155 DEG C, and crushing to obtain pretreated camellia oleifera shell powder; mixing the pretreated camellia oleifera shell powder, the modified regenerated polypropylene, a defoaming agent and an auxiliary agent, and extruding; the mass of the pretreated camellia oleifera shell powder is 5-35% of the total mass. Different pretreatment technologies are designed for specific components of the camellia oleifera shells, volatile substances and residual grease are reduced, the compatibility with a polypropylene matrix is enhanced, and therefore the low-bubble and high-performance wood-plastic composite material is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of waste utilization, and particularly relates to a method for preparing a wood-plastic composite material from camellia shell powder and recycled polypropylene. Background Art

[0002] Wood-plastic composite materials (WPC) are mainly composed of thermoplastic resins (such as polypropylene PP) and wood fiber powder or other biomass fillers, and are prepared by methods such as melt extrusion and injection molding. Although traditional wood powder can improve the flexural strength and rigidity in wood-plastic materials, there are still the following deficiencies: 1. Unstable raw material quality: The sources of wood powder are diverse, and the particle size, composition, and moisture content fluctuate greatly, affecting the stability of product performance. 2. Problems of bubbles and pores: Residual moisture and volatile substances in wood powder are prone to form bubbles at high temperatures, resulting in internal defects and performance degradation of products. 3. Insufficient toughness: Wood powder reinforcement often leads to a significant decrease in the impact strength and elongation at break of the material, making it difficult to balance toughness and rigidity. 4. Challenges in resource sustainability: There is still a large dependence on forest resources, and it is urgent to expand more extensive and renewable biomass sources.

[0003] In this context, agricultural by-products have attracted much attention as alternative raw materials to wood powder. Camellia fruit shell is all parts of the camellia fruit except the camellia seeds. As a biomass raw material, camellia husk has a complex composition, containing a large amount of lignin, cellulose, and hemicellulose that cannot be directly utilized by microorganisms. Among them, lignin accounts for about 30%, cellulose accounts for about 17%, and hemicellulose accounts for about 22%. As a by-product resource after camellia seeds are shelled, camellia shell is rich in resources and low in price, providing an abundant and stable raw material source for wood-plastic composite materials.

[0004] Chinese Patent CN115433409A discloses a method for preparing a camellia fruit shell-based biomass composite material and a polyethylene wood-plastic decorative board. The camellia fruit shell-based biomass composite material includes the following components: modified camellia fruit shell powder and polypropylene, wherein the modified camellia fruit shell powder is obtained by treating camellia fruit shell with an alkali solution and accounts for 45%-55% by mass.

[0005] Chinese Patent CN114290454A relates to a modified camellia fruit shell powder and its preparation method, a camellia fruit shell powder filler and its application. The preparation method includes the following steps: (1) Mix camellia fruit shell powder, N antioxidant H solution, and polypropylene, react to obtain a reaction solution, adjust the pH of the reaction solution, centrifuge to obtain a first precipitate, and dry the first precipitate to obtain pre-modified camellia fruit shell powder; (2) Soak the pre-modified camellia fruit shell powder in boric acid solution to obtain an acidic camellia fruit shell powder solution, adjust the pH of the acidic camellia fruit shell powder solution, centrifuge to obtain a second precipitate, and dry the second precipitate to obtain modified camellia fruit shell powder.

[0006] Camellia oleifera shell contains components similar to wood powder such as cellulose, hemicellulose, and lignin, but also contains saponins, a small amount of oil, and other volatile organic components. These components are prone to produce gases or chemical changes at high temperatures, causing bubbles and performance degradation. Therefore, directly using untreated Camellia oleifera shell powder (OTH) cannot fully utilize its advantages. Existing technologies mostly use alkali treatment to process Camellia oleifera shell powder, which is prone to cause pollution and does not pay attention to the bubble problem during the forming process.

[0007] In summary, designing a new pretreatment technology for the specific components of Camellia oleifera shell and preparing a wood-plastic composite material with low bubbles and high performance are the research focuses of researchers in this field. Summary of the Invention

[0008] In view of the above problems, the present invention provides a method for preparing a wood-plastic composite material from Camellia oleifera shell powder and recycled polypropylene. A differential pretreatment technology is designed for the specific components of Camellia oleifera shell to reduce volatile substances and residual oil, enhance the compatibility with the polypropylene matrix, and thus prepare a wood-plastic composite material with low bubbles and high performance.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] On the one hand, the present invention provides a method for preparing a wood-plastic composite material from Camellia oleifera shell powder and recycled polypropylene, comprising the following steps:

[0011] S1: Pretreatment of Camellia oleifera shell: After drying the Camellia oleifera shell at 55 - 85°C, heat-treat it at 115 - 155°C, and then crush it to obtain pretreated Camellia oleifera shell powder;

[0012] S2: Mix and extrude the pretreated Camellia oleifera shell powder, modified recycled polypropylene, defoaming agent, and additives; the mass of the pretreated Camellia oleifera shell powder is 5% - 35% of the total mass.

[0013] Preferably, in S1, the Camellia oleifera shell needs to be cleaned and decontaminated before drying;

[0014] Preferably, in S1, the drying time is 2 - 6 h.

[0015] Preferably, in S1, the drying temperature is 60 - 80°C.

[0016] Preferably, in S1, the heat-treatment time is 30 - 120 min.

[0017] Preferably, in S1, the heat-treatment temperature is 120 - 150°C.

[0018] Preferably, S1 further includes sieving. More preferably, the mesh number of the sieving is 40 - 100 meshes. Even more preferably, the sieving is multi-stage sieving.

[0019] Preferably, in S2, the modified recycled polypropylene refers to maleic anhydride grafted polypropylene.

[0020] Preferably, in S2, the mass of the modified recycled polypropylene is 1%-5% of the total mass. Further preferably, in S2, the mass of the modified recycled polypropylene is 2%-4% of the total mass.

[0021] Preferably, in S2, the defoaming agent is WT-25.

[0022] Further preferably, the grafting rate of the maleic anhydride grafted polypropylene is 0.8%-1.2%.

[0023] Preferably, in S2, the mass ratio of the pretreated camellia shell powder, modified recycled polypropylene, defoaming agent and additive is 5-35:1-5:70-95:0.1-2.

[0024] Further preferably, in S2, the mass ratio of the pretreated camellia shell powder, modified recycled polypropylene, defoaming agent and additive is 10-25:2-4:70-90:0.5-2.

[0025] Preferably, in S2, the additive is selected from at least one of antioxidant, ultraviolet stabilizer, lubricant and silane coupling agent.

[0026] Preferably, the antioxidant is selected from at least one of Irganox1010, BHT, Irganox 1076 and Irganox1035;

[0027] Preferably, the ultraviolet stabilizer is UV-770;

[0028] Preferably, the lubricant is stearic acid;

[0029] Preferably, the silane coupling agent is 3-(methacryloyloxy)propyltrimethoxysilane;

[0030] Preferably, in S2, the extrusion temperature is 150-200 °C; further preferably, in S2, the extrusion temperature is 170-200 °C.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention designs a heat treatment step for the unique components of saponins, residual oils and volatile organic compounds in camellia shells, which is different from the simple drying and pulverization of traditional wood powder, and significantly reduces the generation of bubbles during the molding process.

[0033] 2. The present invention utilizes the synergistic effect of maleic anhydride grafted polypropylene and silane coupling agent to endow the oil-tea shell powder with more stable interfacial compatibility in the R-PP matrix, and balance the tensile, flexural and impact properties.

[0034] 3. The present invention introduces various auxiliary agents such as antioxidants, ultraviolet stabilizers and lubricants, and flexibly proportions them according to application requirements to improve the aging resistance, processing performance and surface quality of the material, and meet diversified applications such as outdoor landscapes and weather-resistant structural components. Detailed implementation manners

[0035] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the following combines specific embodiments to further clarify the present invention. However, the following embodiments are only the preferred embodiments of the present invention, not all of them. Based on the embodiments in the implementation manners, other embodiments obtained by those skilled in the art without creative efforts all belong to the protection scope of the present invention. It is worth noting that the raw materials used in the present invention are all ordinary commercially available products, and their sources are not specifically limited. The technical and scientific terms used in the embodiments have the meanings commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0036] Term explanation:

[0037] OTH: Oil-tea shell powder after pretreatment

[0038] R-PP: Recycled polypropylene

[0039] Raw materials: The oil-tea shells in the southern Jiangxi region are selected as raw materials. The industrial chain in this region is complete, the output is rich, and the quality is controllable, providing guarantee for large-scale and stable supply of oil-tea shell by-products.

[0040] Antioxidant lrganox1010, purchased from Dongguan Xingyuan Chemical Co., Ltd.

[0041] Ultraviolet stabilizer UV-770, purchased from Dongguan Kangjin New Materials Technology Co., Ltd.

[0042] Lubricant stearic acid, purchased from Guangzhou Tongjie Chemical Co., Ltd.

[0043] Silane coupling agent, 3-(methacryloyloxy)propyltrimethoxysilane, purchased from Dongguan Kangjin New Materials Technology Co., Ltd.

[0044] Example 1

[0045] A method for preparing a wood-plastic composite material from oil-tea shell powder and recycled polypropylene, the raw material composition is shown in Table 1, and it includes the following steps:

[0046] S1: Pretreatment of oil-tea camellia shell: After the oil-tea camellia shell is cleaned and impurities are removed, it is dried at 70 °C for 4 h, then heat-treated at 130 °C for 1 h, pulverized, and passed through 40-mesh, 60-mesh, and 80-mesh sieves in multiple stages to obtain the final fine powder of oil-tea camellia shell below 80 mesh, and the pretreated oil-tea camellia shell powder is obtained.

[0047] S2: The pretreated oil-tea camellia shell powder, maleic anhydride grafted polypropylene, WT-25, antioxidant lrganox1010, and stearic acid are mixed and extruded at 180 °C.

[0048] Example 2

[0049] A method for preparing a wood-plastic composite from oil-tea camellia shell powder and recycled polypropylene, the raw material composition is shown in Table 1, and it includes the following steps:

[0050] S1: Pretreatment of oil-tea camellia shell: After the oil-tea camellia shell is cleaned and impurities are removed, it is dried at 55 °C for 6 h, then heat-treated at 155 °C for 30 min, pulverized, and passed through 40-mesh, 60-mesh, and 100-mesh sieves to obtain the final fine powder of oil-tea camellia shell below 100 mesh, and the pretreated oil-tea camellia shell powder is obtained.

[0051] S2: The pretreated oil-tea camellia shell powder, maleic anhydride grafted polypropylene, WT-25, and antioxidant lrganox1010 are mixed and extruded at 150 °C.

[0052] Example 3

[0053] A method for preparing a wood-plastic composite from oil-tea camellia shell powder and recycled polypropylene, the raw material composition is shown in Table 1, and it includes the following steps:

[0054] S1: Pretreatment of oil-tea camellia shell: After the oil-tea camellia shell is cleaned and impurities are removed, it is dried at 85 °C for 2 h, then heat-treated at 115 °C for 120 min, pulverized, and passed through 40-mesh, 60-mesh, and 80-mesh sieves in multiple stages to obtain the final fine powder of oil-tea camellia shell below 80 mesh, and the pretreated oil-tea camellia shell powder is obtained.

[0055] S2: The pretreated oil-tea camellia shell powder, maleic anhydride grafted polypropylene, WT-25, and ultraviolet stabilizer UV-770 are mixed and extruded at 200 °C.

[0056] Example 4

[0057] A method for preparing a wood-plastic composite from oil-tea camellia shell powder and recycled polypropylene, the raw material composition is shown in Table 1, and it includes the following steps:

[0058] S1: Pretreatment of oil-tea camellia shell: After the oil-tea camellia shell is cleaned and impurities are removed, it is dried at 70 °C for 4 h, then heat-treated at 130 °C for 1 h, pulverized, and passed through 40-mesh, 60-mesh, and 80-mesh sieves in multiple stages to obtain the final fine powder of oil-tea camellia shell below 80 mesh, and the pretreated oil-tea camellia shell powder is obtained.

[0059] S2: Mix the pretreated camellia shell powder, maleic anhydride grafted polypropylene, WT-25 and 3-(methacryloyloxy)propyltrimethoxysilane, and extrude at 180 °C.

[0060] Example 5

[0061] A method for preparing a wood-plastic composite from camellia shell powder and recycled polypropylene, the raw material composition is shown in Table 1, and it comprises the following steps:

[0062] S1: Pretreatment of camellia shell: After cleaning and removing impurities from the camellia shell, dry it at 70 °C for 4 h, then heat-treat it at 130 °C for 1 h, pulverize it, and pass through 40-mesh, 60-mesh, and 80-mesh sieves in multiple stages to obtain the final camellia shell fine powder with a particle size below 80 mesh, thus obtaining the pretreated camellia shell powder;

[0063] S2: Mix the pretreated camellia shell powder, maleic anhydride grafted polypropylene, WT-25, antioxidant, and ultraviolet stabilizer UV-770, and extrude at 180 °C.

[0064] Example 6

[0065] A method for preparing a wood-plastic composite from camellia shell powder and recycled polypropylene, the raw material composition is shown in Table 1, and it comprises the following steps:

[0066] S1: Pretreatment of camellia shell: After cleaning and removing impurities from the camellia shell, dry it at 70 °C for 4 h, then heat-treat it at 130 °C for 1 h, pulverize it, and pass through 40-mesh, 60-mesh, and 80-mesh sieves in multiple stages to obtain the final camellia shell fine powder with a particle size below 80 mesh, thus obtaining the pretreated camellia shell powder;

[0067] S2: Mix the pretreated camellia shell powder, maleic anhydride grafted polypropylene, WT-25, antioxidant lrganox1010, ultraviolet stabilizer UV-770, and stearic acid, and extrude at 180 °C.

[0068] Comparative Example 1

[0069] A method for preparing a wood-plastic composite from recycled polypropylene, the raw material composition is shown in Table 1, and it comprises the following steps: Extrude recycled polypropylene (R-PP) at 180 °C.

[0070] Comparative Example 2

[0071] A method for preparing a wood-plastic composite from recycled polypropylene, the raw material composition is shown in Table 1, and it comprises the following steps:

[0072] Mix WT-25, wood powder, and maleic anhydride grafted polypropylene, and extrude at 180 °C.

[0073] Comparative Example 3

[0074] A method for preparing a wood-plastic composite from oil-tea camellia shell powder and recycled polypropylene, the raw material composition is shown in Table 1, and the method comprises the following steps:

[0075] S1: Pretreatment of oil-tea camellia shells: After cleaning and removing impurities from the oil-tea camellia shells, they are dried at 70 °C for 4 h, then heat-treated at 130 °C for 1 h, pulverized, and passed through 40-mesh, 60-mesh, and 80-mesh sieves in multiple stages to obtain the finally obtained oil-tea camellia shell fine powder with a particle size below 80 mesh, thus obtaining the pretreated oil-tea camellia shell powder;

[0076] S2: Mix the pretreated oil-tea camellia shell powder, WT-25, and maleic anhydride grafted polypropylene, and extrude at 180 °C.

[0077] Comparative Example 4

[0078] A method for preparing a wood-plastic composite from oil-tea camellia shell powder and recycled polypropylene, the raw material composition is shown in Table 1, and the method comprises the following steps:

[0079] S1: Pretreatment of oil-tea camellia shells: After cleaning and removing impurities from the oil-tea camellia shells, they are dried at 90 °C for 1 h, then heat-treated at 100 °C for 150 min, pulverized, and passed through a 40-mesh sieve to obtain the finally obtained oil-tea camellia shell fine powder with a particle size of 40 mesh, thus obtaining the pretreated oil-tea camellia shell powder;

[0080] S2: Mix the pretreated oil-tea camellia shell powder, maleic anhydride grafted polypropylene, WT-25, antioxidant lrganox1010, and stearic acid, and extrude at 100 °C.

[0081] Table 1. Formulation composition (mass percentage %) of Examples 1-6 and Comparative Examples 1-4

[0082]

[0083]

[0084] Test Example 1

[0085] Test methods and standards:

[0086] 1. Melt index: The sample is tested with a melt flow rate instrument according to GB / T3682.1.

[0087] Put the prepared sample into the sample cylinder of the test equipment, set 230 °C and 2.16 kg on the test instrument, and then start the test process. Heat the sample to the preset temperature and keep it for 10 minutes. During this period, the test equipment will monitor the mass change during the melting process and calculate the melt flow index value accordingly.

[0088] 2. Specific gravity: Measure according to GB / T 1033.3

[0089] 3. Impact strength: Make the sample into a rectangular specimen with a length of 100 mm ± 2 mm and a width of 50 mm ± 1 mm, and the thickness is the original thickness of the profile. Then test it with an instrument according to GB / T 29418.

[0090] Install the sample on the fixture, adjust the position of the specimen so that the impact point of the falling weight is at the center of the specimen. Start the falling weight impact testing machine and let the falling weight freely fall from the specified height to impact the specimen. Observe the damage of the specimen and record whether the specimen cracks, the crack propagation situation, etc.

[0091] 4. Tensile strength and elongation at break: Obtain the sample from the wood-plastic composite material products by injection molding or cutting. The shape is dumbbell-shaped. Then test it with an electronic universal tensile testing machine according to GB / T 1040.1.

[0092] Install the sample on the fixture of the tensile testing machine, ensure that the specimen is clamped and evenly stressed. Set the test speed of the testing machine to 50 mm / min, start the testing machine, start the tensile test, and monitor and record the force and displacement data during the tensile process in real time until the specimen breaks or reaches the predetermined elongation at break.

[0093] Install the sample on the fixture of the tensile testing machine, ensure that the specimen is clamped and evenly stressed. Set the test speed of the testing machine to 50 mm / min, start the testing machine, start the tensile test, and monitor and record the force and displacement data during the tensile process in real time until the specimen breaks or reaches the predetermined elongation at break.

[0094] 5. Flexural strength and flexural modulus: Obtain the sample from the wood-plastic composite material products by cutting. The shape is rectangular. Then test it with an electronic universal testing machine according to the standard of GB / T 29418.

[0095] Install the specimen on the bending fixture, ensure that the specimen is in close contact with the fixture and does not slide or shift during the test. Set the test speed of the testing machine to 2 mm / min, start the testing machine, start the bending test, and monitor and record the force and displacement data during the bending process in real time until the specimen breaks or reaches the predetermined bending deformation.

[0096] The results are shown in Table 2:

[0097] Table 2. Test results

[0098]

[0099] As can be seen from Table 2, when comparing Examples 1-6 with Comparative Examples 1-5, the impact strength is increased to 4.2 kJ / m 2 The elongation at break is up to 30% at most, and the flexural modulus can be increased to 1500 MPa, achieving a balance between rigidity and toughness and enhanced weather resistance.

[0100] This is because the pretreatment step of the present invention can directionally remove saponins, residual oils and low-molecular-weight volatile substances. Most traditional wood powder treatments do not involve such directional chemical component removal. Heat treatment can reduce gas release during subsequent molding and inhibit bubble formation. At the same time, different ratios and combinations of additives have also achieved a balance between rigidity and toughness and enhanced weather resistance. The materials prepared by the present invention can meet diverse application scenarios such as indoor and outdoor decoration, landscape architecture, and building components.

[0101] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than a limitation on the protection scope of the present invention. Any simple modification or equivalent replacement made by those of ordinary skill in the art to the technical solution of the present invention shall not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a wood-plastic composite material from camellia oleifera shell powder and recycled polypropylene, characterized in that: The following steps are involved: S1: Camellia oleifera shell pretreatment: After the camellia oleifera shell is dried at 55-85°C, it is heat treated at 115-155°C and crushed to obtain the pretreated camellia oleifera shell powder; S2: pretreated camellia oleifera shell powder, modified recycled polypropylene, defoaming agent and auxiliary agent are mixed and extruded; the mass of the pretreated camellia oleifera shell powder is 5%-35% of the total mass.

2. The method according to claim 1, characterized in that In S1, the drying time is 2-6 hours and the temperature is 60-80°C.

3. The method according to claim 1, characterized in that In S1, the heat treatment time is 30-120 minutes and the temperature is 120-150°C.

4. The method according to claim 1, characterized in that: The S1 further comprises sieving, wherein the mesh number of the sieving is 40-100 meshes.

5. The method according to claim 1, characterized in that In S2, the modified recycled polypropylene refers to maleic anhydride grafted polypropylene.

6. The method according to claim 7, characterized in that: In S2, the mass of the modified recycled polypropylene is 1%-5% of the total mass.

7. The method according to claim 1, characterized in that In S2, the defoaming agent is WT-25.

8. The method according to claim 1, characterized in that In S2, the mass ratio of the pretreated camellia oleifera shell powder, modified recycled polypropylene, defoaming agent and auxiliary agent is 5-35:1-5:70-95:0.1-2.

9. The method according to claim 8, characterized in that In S2, the mass ratio of the pretreated camellia oleifera shell powder, modified recycled polypropylene, defoaming agent and auxiliary agent is 10-25:2-4:70-90:0.5-2.

10. The method according to claim 1, characterized in that In S2, the auxiliary agent is selected from at least one of an antioxidant, a UV stabilizer, a lubricant, and a silane coupling agent.

11. The method according to claim 1, characterized in that: In S2, the extrusion temperature is 150-200°C.

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