Low-temperature-resistant recycled PP plastic product and preparation method thereof

Abstract

The invention relates to a low-temperature-resistant recycled PP plastic product and a preparation method thereof, and belongs to the technical field of high polymer materials. The PP plastic product is prepared from the following components in percentage by weight: 5.8 to 9.2 percent of low-temperature-resistant regenerant, 0.12 to 0.15 percent of nucleating agent, 1.1 to 1.7 percent of lubricant, 0.08 to 0.11 percent of antioxidant, 0.1 to 0.14 percent of light stabilizer and the balance of PP regenerant, adamantane and chain alkane in a molecular main chain of the low-temperature-resistant regenerant form local rigid steps, adamantane units serve as rigid islands to induce uniform crazes in a PP matrix, impact energy can be effectively absorbed in a low-temperature freezing state, short-chain branched alkyl grafted by side chains and PP molecular chains are deeply entangled to form molecular-level topological interlocking, craze convergence is effectively prevented, and the low-temperature-resistant regenerant has the advantages that the low-temperature-resistant regenerant is prepared; particularly in the freezing and thawing cycle stress process, destructive cracks are prevented from being generated, so that the product has stable low-temperature resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and in particular relates to a low-temperature resistant recycled PP plastic product and a preparation method thereof. Background Art

[0002] One of today's greatest environmental challenges is the accumulation of polymer waste on land and in the oceans. Polypropylene (PP), the second-most common plastic, is widely used in automobiles, home appliances, healthcare, construction, logistics, and consumer goods, resulting in a significant amount of waste. In recent years, the PP recycling and regeneration market has grown rapidly, with production capacity continuing to grow rapidly. With waste sorting and recycling becoming a new trend, this has largely addressed the complex composition and post-processing challenges of municipal waste, laying the foundation for the recycling and reuse of waste plastics.

[0003] However, recycled PP undergoes multiple processing, resulting in a decrease in molecular weight, a broadening of molecular weight distribution, and a decrease in melt flow index. In addition, the mechanical properties of PP products deteriorate sharply under ultraviolet exposure and thermal oxidative degradation, and are particularly prone to brittle fracture in low-temperature environments (such as automotive outdoor components and cold chain packaging). Existing improvement measures mainly include: virgin PP blending and secondary toughening modification. Among them, virgin PP blending is to use a certain amount of virgin PP resin to blend with recycled PP, but the proportion of virgin PP is relatively large, generally requiring virgin PP to account for more than 20%, and the low-temperature effect is not significant, which is not in line with sustainable development goals. Secondary toughening modification is to add toughening materials to recycled PP for secondary toughening treatment. Commonly used toughening systems include elastomer toughening such as SEBS and POE. The low-temperature resistance of toughening materials is used to improve the low-temperature performance of recycled PP. The low-temperature toughening effect is relatively good, but the toughening phase and the PP matrix are prone to phase separation, especially under low-temperature freeze-thaw cycles. Phase separation generates large stress, and the mechanical properties deteriorate sharply after a certain cycle. The defects of existing technologies have seriously restricted the development of PP material recycling applications. Summary of the Invention

[0004] In order to solve the technical problems mentioned in the background technology, the purpose of the present invention is to provide a low-temperature resistant recycled PP plastic product and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A low-temperature resistant recycled PP plastic product, specifically comprising: 5.8-9.2wt% of a low-temperature resistant regeneration agent, 0.12-0.15wt% of a nucleating agent, 1.1-1.7wt% of a lubricant, 0.08-0.11wt% of an antioxidant, and 0.1-0.14wt% of a light stabilizer, with the balance being PP recycled material.

[0007] The low temperature resistant regeneration agent is prepared by the following method:

[0008] Step A1: Adamantanediol and anhydrous tetrahydrofuran are mixed and passed through dry nitrogen atmosphere. Methylvinyldichlorosilane is added and stirred for 0.6-0.8 h. Then, n-alkyl glycol and triethylamine are added and the mixture is heated and refluxed for 1.5-2.2 h. After the reaction is complete, methanol is added for washing. The mixture is filtered and then evaporated to remove low-boiling substances, mainly tetrahydrofuran, to obtain an intermediate.

[0009] Preferably, the carbon chain length of the n-alkyl glycol is 8-12. The glycol with this carbon chain length maintains good reactivity and introduces a long carbon chain into the polymer backbone, which is conducive to dispersion in the PP matrix and effectively improves the low-temperature resistance.

[0010] Furthermore, the usage ratio of methylvinyldichlorosilane, adamantanediol, n-alkyl glycol, triethylamine and anhydrous tetrahydrofuran is 0.1 mol: 15-25 mmol: 80-95 mmol: 12-16 mL: 100-150 mL, and adamantanediol and n-alkyl glycol are substituted with methylvinyldichlorosilane to form a chain compound with random blocks.

[0011] Step A2: The intermediate, Karstedt catalyst, and dimethylformamide are mixed, and triisopropylsilane is added and mixed. Nitrogen is introduced for protection, and the temperature is raised to 60-70°C and stirred for reaction for 10-12 hours. After the reaction is completed, water is added to wash, the aqueous phase is removed, and the mixture is dried to obtain a low-temperature resistant regeneration agent;

[0012] Furthermore, the usage ratio of the intermediate, triisopropylsilane, Karstedt catalyst and dimethylformamide is 50g:45-60mmol:15-20mg:180-260mL. Under catalytic activation, triisopropylsilane undergoes hydrosilylation with the double bond of the intermediate side chain, introducing a large number of isopropyl short-branched alkyl structures into the side chain.

[0013] Preferably, the nucleating agent is an amide β-phase nucleating agent, which has stable compatibility and dispersion in the PP matrix, effectively promotes the formation of β-phase crystals, and is beneficial to the improvement of low-temperature performance.

[0014] Preferably, the lubricant is polypropylene wax with a melting point not higher than 150° C., which effectively improves the melt properties and facilitates the full mixing of the PP recycled material with other components.

[0015] Preferably, the antioxidant is compounded by antioxidant 1010 and antioxidant 168, which has good thermal stability and can effectively make up for the loss of antioxidant components in the recycled material.

[0016] Preferably, the light stabilizer is a polymeric hindered amine light stabilizer, which has stable heat resistance and is not prone to migration and failure.

[0017] A preparation method of a low-temperature resistant recycled PP plastic product comprises the following steps: uniformly mixing various raw materials, plasticizing, extruding and compression molding at 200-220°C to obtain the low-temperature resistant recycled PP plastic product.

[0018] Beneficial effects of the present invention:

[0019] The invention discloses a low-temperature-resistant regeneration agent for recycling polypropylene (PP). The low-temperature-resistant regeneration agent is compatible with the regeneration process of PP materials and can effectively improve the low-temperature resistance of the recycled PP through blending and modification. The low-temperature-resistant regeneration agent is formed by replacing adamantanediol, n-alkyl glycol and methylvinyldichlorosilane to form a chain compound with random blocks, which is an intermediate. Triisopropylsilane is then subjected to a hydrosilylation reaction with a double bond on a side chain of the intermediate to introduce short-chain alkyl branches into the side chain in an orderly manner. The molecular main body of the low-temperature-resistant regeneration agent is an alkyl chain structure and has good compatibility with PP. The adamantane and the chain alkane in the main chain form a local rigid ladder. The adamantane unit acts as a "rigid island" to induce uniform silver streaks in the PP matrix and can effectively absorb impact energy in a low-temperature frozen state. The short-chain alkyl branches grafted on the side chain through hydrosilylation have excellent compatibility with PP macromolecular chains and are deeply entangled with the PP molecular chains to form molecular-level topological interlocking, effectively preventing the merging of silver streaks, especially during freeze-thaw cycle stress, avoiding the generation of destructive cracks, and ensuring that the product has stable low-temperature resistance. DETAILED DESCRIPTION

[0020] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] Example 1, preparation of low-temperature resistant recycled PP plastic products, the specific implementation process is as follows:

[0022] (1) Preparation of low-temperature resistant regeneration agent

[0023] Step A1: Adamantanediol and anhydrous tetrahydrofuran were mixed and passed through dry nitrogen for protection. Methylvinyldichlorosilane was added and stirred for reaction for 0.6 h. 1,8-octanediol and triethylamine were then added and the mixture was heated and refluxed for 1.5 h. The ratio of methylvinyldichlorosilane, adamantanediol, 1,8-octanediol, triethylamine, and anhydrous tetrahydrofuran was 0.1 mol: 15 mmol: 95 mmol: 12 mL: 100 mL. After the reaction was completed, methanol was added to wash the mixture. The mixture was filtered and then rotary evaporated to remove low-boiling substances, mainly tetrahydrofuran, to obtain an intermediate.

[0024] Step A2: The intermediate, Karstedt catalyst and dimethylformamide were mixed, and triisopropylsilane was added and mixed. Nitrogen was introduced for protection, and the temperature was raised to 60°C and stirred for reaction for 12 hours. The amount ratio of the intermediate, triisopropylsilane, Karstedt catalyst and dimethylformamide was 50g:45mmol:15mg:180mL. After the reaction was completed, water was added to wash, the aqueous phase was removed and dried to obtain a low-temperature resistant regeneration agent.

[0025] (2) Preparation of low-temperature resistant recycled PP plastic products

[0026] The materials were prepared according to the following components: 5.8 wt % of a low-temperature resistant regeneration agent, which was prepared in this embodiment; 0.15 wt % of a nucleating agent, which was a BT-5 amide β-phase nucleating agent; 1.7 wt % of a lubricant, which was PPW-0921 polypropylene wax with a melting point of 140° C.; 0.11 wt % of an antioxidant, which was a mixture of antioxidant 1010 and antioxidant 168 in a weight ratio of 2:1; 0.14 wt % of a light stabilizer, which was a polymeric hindered amine light stabilizer 622; and the remainder was PP recycled material, which was PP-A01 commercially available recycled material.

[0027] The above raw materials are added to a high-speed mixer and mixed for 15 minutes. The mixture is added to an extruder, and the temperature of the plasticizing zone is controlled to be 200-220°C. In this implementation process, the temperature of plasticizing zone 1 is 200°C, the temperature of plasticizing zone 2 is 210°C, the temperature of plasticizing zone 3 is 220°C, and the temperature of plasticizing zone 4 is 215°C. The plasticized melt is extruded and molded at 20 MPa to obtain a low-temperature resistant recycled PP plastic product.

[0028] Example 2, preparation of low-temperature resistant recycled PP plastic products, the specific implementation process is as follows:

[0029] (1) Preparation of low-temperature resistant regeneration agent

[0030] Step A1: Adamantanediol and anhydrous tetrahydrofuran were mixed and passed through dry nitrogen for protection. Methylvinyldichlorosilane was added and stirred for reaction for 0.7 h. 1,10-decanediol and triethylamine were then added and the mixture was heated and refluxed for 2 h. The ratio of methylvinyldichlorosilane, adamantanediol, 1,10-decanediol, triethylamine, and anhydrous tetrahydrofuran was 0.1 mol: 20 mmol: 90 mmol: 14 mL: 120 mL. After the reaction was completed, methanol was added for washing. The mixture was filtered and then rotary evaporated to remove low-boiling substances, mainly tetrahydrofuran, to obtain an intermediate.

[0031] Step A2: The intermediate, Karstedt catalyst and dimethylformamide were mixed, and triisopropylsilane was added and mixed. Nitrogen was introduced for protection, and the temperature was raised to 70°C and stirred for reaction for 11 hours. The amount ratio of the intermediate, triisopropylsilane, Karstedt catalyst and dimethylformamide was 50g:55mmol:18mg:220mL. After the reaction was completed, water was added to wash, the aqueous phase was removed and dried to obtain a low-temperature resistant regeneration agent.

[0032] (2) Preparation of low-temperature resistant recycled PP plastic products

[0033] The materials were prepared according to the following components: 7.5 wt % of a low-temperature resistant regeneration agent, which was prepared in this embodiment; 0.14 wt % of a nucleating agent, which was a BT-5 amide β-phase nucleating agent; 1.5 wt % of a lubricant, which was PPW-0921 polypropylene wax with a melting point of 140° C.; 0.1 wt % of an antioxidant, which was a mixture of antioxidant 1010 and antioxidant 168 in a weight ratio of 2:1; 0.12 wt % of a light stabilizer, which was a polymeric hindered amine light stabilizer 622; and the remainder was PP recycled material, which was PP-A01 commercially available recycled material.

[0034] The above raw materials are added to a high-speed mixer and mixed for 15 minutes. The mixture is added to an extruder, and the temperature of the plasticizing zone is controlled to be 200-220°C. In this implementation process, the temperature of plasticizing zone 1 is 200°C, the temperature of plasticizing zone 2 is 210°C, the temperature of plasticizing zone 3 is 210°C, and the temperature of plasticizing zone 4 is 220°C. The plasticized melt is extruded and molded at 20 MPa to obtain a low-temperature resistant recycled PP plastic product.

[0035] Example 3, preparation of low-temperature resistant recycled PP plastic products, the specific implementation process is as follows:

[0036] (1) Preparation of low-temperature resistant regeneration agent

[0037] Step A1: Adamantanediol and anhydrous tetrahydrofuran were mixed and passed through dry nitrogen for protection. Methylvinyldichlorosilane was added and stirred for reaction for 0.8 h. 1,12-dodecanediol and triethylamine were then added and the mixture was heated and refluxed for 2.2 h. The ratio of methylvinyldichlorosilane, adamantanediol, 1,12-dodecanediol, triethylamine, and anhydrous tetrahydrofuran was 0.1 mol: 25 mmol: 80 mmol: 16 mL: 150 mL. After the reaction was completed, methanol was added for washing. The mixture was filtered and then rotary evaporated to remove low-boiling substances, mainly tetrahydrofuran, to obtain an intermediate.

[0038] Step A2: The intermediate, Karstedt catalyst and dimethylformamide were mixed, and triisopropylsilane was added and mixed. Nitrogen was introduced for protection, and the temperature was raised to 70°C and stirred for reaction for 10 hours. The amount ratio of the intermediate, triisopropylsilane, Karstedt catalyst and dimethylformamide was 50g:60mmol:20mg:260mL. After the reaction was completed, water was added to wash, the aqueous phase was removed and dried to obtain a low-temperature resistant regeneration agent.

[0039] (2) Preparation of low-temperature resistant recycled PP plastic products

[0040] The materials were prepared according to the following components: 9.2 wt % of a low-temperature resistant regeneration agent, which was prepared in this embodiment; 0.12 wt % of a nucleating agent, which was a BT-5 amide β-phase nucleating agent; 1.1 wt % of a lubricant, which was PPW-0911 polypropylene wax with a melting point of 150° C.; 0.08 wt % of an antioxidant, which was a mixture of antioxidant 1010 and antioxidant 168 in a weight ratio of 2:1; 0.1 wt % of a light stabilizer, which was a polymeric hindered amine light stabilizer 622; and the remainder was PP recycled material, which was PP-A01 commercially available recycled material.

[0041] The above raw materials are added to a high-speed mixer and mixed for 15 minutes. The mixture is added to an extruder, and the temperature of the plasticizing zone is controlled to be 200-220°C. In this implementation process, the temperature of plasticizing zone 1 is 200°C, the temperature of plasticizing zone 2 is 210°C, the temperature of plasticizing zone 3 is 220°C, and the temperature of plasticizing zone 4 is 220°C. The plasticized melt is extruded and molded at 20 MPa to obtain a low-temperature resistant recycled PP plastic product.

[0042] Example 4, preparation of low-temperature resistant recycled PP plastic products, the specific implementation process is as follows:

[0043] (1) Preparation of low-temperature resistant regeneration agent

[0044] Step A1: Adamantanediol and anhydrous tetrahydrofuran were mixed and passed through dry nitrogen for protection. Methylvinyldichlorosilane was added and stirred for reaction for 0.7 h. 1,10-decanediol and triethylamine were then added and the mixture was heated and refluxed for 1.9 h. The ratio of methylvinyldichlorosilane, adamantanediol, 1,10-decanediol, triethylamine, and anhydrous tetrahydrofuran was 0.1 mol: 22 mmol: 90 mmol: 15 mL: 120 mL. After the reaction was completed, methanol was added to wash the mixture. The mixture was filtered and then rotary evaporated to remove low-boiling substances, mainly tetrahydrofuran, to obtain an intermediate.

[0045] Step A2: The intermediate, Karstedt catalyst and dimethylformamide were mixed, and triisopropylsilane was added and mixed. Nitrogen was introduced for protection, and the temperature was raised to 70°C and stirred for reaction for 12 hours. The amount ratio of the intermediate, triisopropylsilane, Karstedt catalyst and dimethylformamide was 50g:50mmol:17mg:240mL. After the reaction was completed, water was added to wash, the aqueous phase was removed and dried to obtain a low-temperature resistant regeneration agent.

[0046] (2) Preparation of low-temperature resistant recycled PP plastic products

[0047] The materials were prepared according to the following components: 8.5 wt % of a low-temperature resistant regeneration agent, which was prepared in this embodiment; 0.13 wt % of a nucleating agent, which was a BT-5 amide β-phase nucleating agent; 1.4 wt % of a lubricant, which was a PPW-0911 polypropylene wax with a melting point of 150° C.; 0.09 wt % of an antioxidant, which was a mixture of antioxidant 1010 and antioxidant 168 in a weight ratio of 2:1; 0.11 wt % of a light stabilizer, which was a polymeric hindered amine light stabilizer 622; and the remainder was PP recycled material, which was a commercially available PP-A01 recycled material.

[0048] The above raw materials are added to a high-speed mixer and mixed for 15 minutes. The mixture is added to an extruder, and the temperature of the plasticizing zone is controlled to be 200-220°C. In this implementation process, the temperature of plasticizing zone 1 is 200°C, the temperature of plasticizing zone 2 is 210°C, the temperature of plasticizing zone 3 is 210°C, and the temperature of plasticizing zone 4 is 220°C. The plasticized melt is extruded and molded at 20 MPa to obtain a low-temperature resistant recycled PP plastic product.

[0049] In Comparative Example 1, referring to Example 4, no low-temperature resistant regeneration agent was added, and the balance was supplemented to 100wt% by compounding PP recycled material and F30G virgin resin in a ratio of 2:1. The rest of the implementation process was exactly the same.

[0050] In Comparative Example 2, referring to Example 4, an equal amount of the low-temperature resistant regeneration agent was replaced with an E1818 type SEBS toughening material, and the rest of the implementation process was exactly the same.

[0051] The above products were sampled and tested, specifically including: impact strength testing at a test temperature of -30°C according to ASTM D256-10; brittle fracture temperature testing using a gradient cooling method according to GB / T 5470-2008; freeze-thaw cycle testing: the sample was frozen at -30°C for 6 hours, thawed at room temperature for 12 hours, and repeated 50 cycles to test impact strength and brittle fracture temperature. The specific test results are shown in Table 1:

[0052] Table 1

[0053] From the test results in Table 1, it can be seen that the impact strength of the samples prepared in the embodiment at -30°C is between 16.9 and 18.7 kJ / m 2 The brittle fracture temperature reaches up to -42°C, which has excellent low-temperature resistance and is stable after freeze-thaw cycles.

[0054] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0055] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A low temperature resistant recycled PP plastic product, characterized in that: The specific components are: low-temperature resistant regeneration agent 5.8-9.2wt%, nucleating agent 0.12-0.15wt%, lubricant 1.1-1.7wt%, antioxidant 0.08-0.11wt% and light stabilizer 0.1-0.14wt%, and the balance is PP recycled material; The low temperature resistant regeneration agent is prepared by the following method: Step A1: Adamantanediol and anhydrous tetrahydrofuran are mixed, and dry nitrogen is introduced. Methylvinyldichlorosilane is added and stirred for 0.6-0.8 h. Then, n-alkyl glycol and triethylamine are added and the mixture is heated and refluxed for 1.5-2.2 h to prepare an intermediate. Step A2: The intermediate, Karstedt catalyst and dimethylformamide are mixed, and triisopropylsilane is added and mixed evenly. Nitrogen is introduced for protection, and the temperature is raised to 60-70° C. and stirred for reaction for 10-12 hours to prepare a low-temperature resistant regeneration agent.

2. A low temperature resistant recycled PP plastic product according to claim 1, characterized in that: The carbon chain length of n-alkyl glycol is 8-12.

3. A low temperature resistant recycled PP plastic product according to claim 2, characterized in that: The usage ratio of methylvinyldichlorosilane, adamantanediol, n-alkyl glycol, triethylamine and anhydrous tetrahydrofuran is 0.1 mol: 15-25 mmol: 80-95 mmol: 12-16 mL: 100-150 mL.

4. The low-temperature resistant recycled PP plastic product according to claim 3, characterized in that: The usage ratio of the intermediate, triisopropylsilane, Karstedt catalyst and dimethylformamide is 50 g: 45-60 mmol: 15-20 mg: 180-260 mL.

5. The low-temperature resistant recycled PP plastic product according to claim 1, characterized in that: The nucleating agent is an amide β-phase nucleating agent.

6. The low-temperature resistant recycled PP plastic product according to claim 1, characterized in that: The lubricant is polypropylene wax with a melting point not higher than 150°C.

7. The low-temperature resistant recycled PP plastic product according to claim 1, characterized in that: The antioxidant is compounded by antioxidant 1010 and antioxidant 168.

8. The low-temperature resistant recycled PP plastic product according to claim 1, characterized in that: The light stabilizer is a polymeric hindered amine light stabilizer.

9. A method for preparing a low-temperature resistant recycled PP plastic product according to any one of claims 1 to 8, characterized in that: Specifically, the raw materials of each component are mixed evenly, plasticized, extruded and molded at 200-220°C to obtain low-temperature resistant recycled PP plastic products.

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