A degradable high-density polyethylene-bio-based polyester blend material for garbage cans and a preparation method thereof

Abstract

The application relates to the technical field of polyethylene, and discloses a degradable high-density polyethylene-bio-based polyester blended material for a garbage can and a preparation method thereof; the high-density polyethylene, bio-based polyester, styrene-based citric ester grafted POE, antioxidant and filler are blended, and extruded in a double-screw extruder to obtain the high-density polyethylene-bio-based polyester blended material. The styrene-based citric ester grafted POE improves the compatibility between polyethylene and polylactic acid and the like, and improves the mechanical properties of the blended material. The polylactic acid and polylactide have excellent biodegradability, and the citric ester grafted on the side of the POE also has good biodegradability; when added into the polyethylene material, the biodegradation rate of the blended material can be improved.

Description

Technical Field

[0001] This invention relates to the field of polyethylene technology, specifically to a biodegradable high-density polyethylene-bio-based polyester blend material for trash cans and its preparation method. Background Technology

[0002] High-density polyethylene (HDPE) is inexpensive, highly corrosion-resistant, rigid, and has excellent weather resistance, making it widely used in packaging bags, garbage cans, agricultural films, and electrical wires and cables. Ethylene-octene copolymer (POE) elastomers exhibit high elasticity and toughness, as well as excellent abrasion resistance, and are important in applications among polyethylene, PBT polyester, nylon, and other polymer materials. However, the extensive use of polyethylene and other plastics can cause serious environmental problems such as white pollution.

[0003] In recent years, the development of biodegradable materials such as polylactic acid (PLA) and polycaprolactone (PVC) has been a research hotspot. Blending polyesters like PLA with materials such as polyethylene can impart good biodegradability to the materials. However, polyethylene has poor compatibility with polyesters like PLA, and blending them can affect the mechanical and other properties of the materials, usually requiring the addition of compatibilizers and other additives. Summary of the Invention

[0004] This invention provides a high-density polyethylene-bio-based polyester blend material and its preparation method, which solves the problems of low strength and poor biodegradability of polyethylene materials.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this invention is: a high-density polyethylene-bio-based polyester blend material and its preparation method; the blend material comprises 60-75 parts by weight of high-density polyethylene, 25-40 parts by weight of bio-based polyester, 15-30 parts by weight of styrene-citric acid ester grafted POE, 0.2-0.4 parts by weight of antioxidant, and 10-25 parts by weight of filler. The preparation method of the blend material is as follows:

[0006] (1) Toluene, ethylene-octene copolymer, styrene citrate, and benzoyl peroxide were added to the reaction vessel. Nitrogen gas was introduced and the reaction was carried out. Methanol was added to the solution to precipitate the precipitate. The precipitate was collected after filtration and then purified by extraction with acetone in a Soxhlet extractor to obtain styrene citrate grafted POE.

[0007] (2) High-density polyethylene, bio-based polyester, styrene-based citrate grafted POE, antioxidant, and filler are blended and extruded in a twin-screw extruder at 150-200℃ in zones one to five of the extruder; pelletized and injection molded in an injection molding machine at 170-200℃ in zones one to three to obtain a high-density polyethylene-bio-based polyester blend material.

[0008] Preferably, the filler includes calcium carbonate or talc.

[0009] Preferably, the antioxidant includes antioxidant 1010 or antioxidant 168.

[0010] Preferably, the bio-based polyester includes polylactic acid or polycaprolactone.

[0011] Preferably, the mass ratio of ethylene-octene copolymer, styrene citrate, and benzoyl peroxide is 100:(6-18):(0.3-0.8).

[0012] Preferably, the reaction temperature is 70-80℃ and the reaction time is 12-24h.

[0013] Preferably, the preparation method of styrene-based citrate ester includes: adding toluene, citrate ester, triethylamine, and 4-dimethylaminepyridine to a reaction vessel; adding 4-vinylbenzoyl chloride dropwise in an ice-water bath; reacting at 25-45°C for 18-24 h; filtering; distilling the filtrate under reduced pressure; washing with n-hexane; dissolving the product in ethyl acetate; evaporating by heating in a fume hood; and crystallizing by cooling in an ice-water bath to obtain styrene-based citrate ester. The reaction formula is as follows:

[0014]

[0015] Preferably, the molar ratio of citrate, triethylamine, 4-dimethylaminepyridine, and 4-vinylbenzoyl chloride is 1:(1-1.2):(0.03-0.05):(1.4-1.8).

[0016] Preferably, the citrate is trimethyl citrate, triethyl citrate, tripropyl citrate, or tributyl citrate.

[0017] Preferably, high-density polyethylene-bio-based polyester blends are used in biodegradable trash cans.

[0018] The beneficial technical effects of this invention are as follows: Styrene citrate is used to solution graft POE, introducing polystyrene molecular chains containing citrate structures into the side chains of POE. This is then melt-blended with high-density polyethylene, polylactic acid (PLA) and other bio-based polyesters, and fillers such as calcium carbonate to obtain a blended material. POE, as an olefin copolymer, has excellent compatibility with polyethylene. Simultaneously, the citrate structure grafted onto POE contains multiple ester groups, which also exhibit good compatibility with polyester materials such as PLA. Therefore, styrene citrate grafting onto POE improves the compatibility between polyethylene and PLA, thereby enhancing the mechanical properties of the blended material.

[0019] In this invention, POE is used as a high-performance elastomer material, and its side chains are also grafted with rigid styrene polymer molecular chains, which can further improve the mechanical strength of polyethylene blends, giving the blends higher tensile strength and impact strength.

[0020] The polylactic acid and polylactide of this invention exhibit excellent biodegradability, and the citrate esters branched onto the POE side also possess good biodegradability. When added to polyethylene materials, they can improve the biodegradability of the blend. The blend prepared by this invention has good mechanical properties, is biodegradable, and environmentally friendly, making it suitable for applications such as plastic trash cans, packaging bags, and agricultural films. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The following high-density polyethylene grades are listed below: HDPE LP552-01 (Guangzhou Hongcheng Plastics Co., Ltd.); ethylene-octene copolymer DF640 (Huizhou Yishengyuan Trading Co., Ltd.); polylactic acid REVODE213T (Dongguan Xinrui New Materials Co., Ltd.); and polycaprolactone N-500CESU (Dongguan Xinrui New Materials Co., Ltd.).

[0023] Example 1

[0024] (1) Add 1.5 L toluene, 0.4 mol trimethyl citrate, 0.4 mol triethylamine, and 20 mmol 4-dimethylaminepyridine to the reaction vessel. Add 0.66 mol 4-vinylbenzoyl chloride dropwise in an ice-water bath. Then react at 30 °C for 24 h. Filter, distill the filtrate under reduced pressure, wash with n-hexane, dissolve the product in ethyl acetate, heat in a fume hood to volatilize, and cool in an ice-water bath to crystallize, to obtain styrene carbamate citrate.

[0025] (2) Add 20L toluene, 2kg ethylene-octene copolymer, 120g styrene citrate, and 6g benzoyl peroxide to the reaction vessel, purge with nitrogen, and react at 75℃ for 12h. Add methanol to the solution to precipitate, filter and collect the precipitate, and then extract and purify with acetone in a Soxhlet extractor to obtain styrene citrate grafted POE.

[0026] (3) 15 kg of high-density polyethylene, 5 kg of polylactic acid, 3 kg of styrene-based citrate grafted POE, 80 g of antioxidant 1010 and 4 kg of calcium carbonate were blended and extruded in a twin-screw extruder. The temperatures of the first to fifth zones of the extruder were 150°C, 175°C, 190°C, 200°C and 200°C respectively. The mixture was then pelletized and injection molded in an injection molding machine. The temperatures of the first to third zones were 170°C, 200°C and 190°C respectively to obtain a high-density polyethylene-bio-based polyester blend material.

[0027] Example 2

[0028] (1) Add 1.5 L of toluene, 0.4 mol of tributyl citrate, 0.48 mol of triethylamine, and 12 mmol of 4-dimethylaminepyridine to the reaction vessel. Add 0.72 mol of 4-vinylbenzoyl chloride dropwise in an ice-water bath. Then react at 45 °C for 18 h. Filter, distill the filtrate under reduced pressure, wash with n-hexane, dissolve the product in ethyl acetate, heat in a fume hood to volatilize, and cool in an ice-water bath to crystallize, to obtain styrene citrate.

[0029] (2) Add 30L toluene, 2kg ethylene-octene copolymer, 240g styrene citrate, and 12g benzoyl peroxide to the reaction vessel, purge with nitrogen, and react at 70℃ for 24h. Add methanol to the solution to precipitate, filter and collect the precipitate, and then extract and purify with acetone in a Soxhlet extractor to obtain styrene citrate grafted POE.

[0030] (3) 13.5 kg of high-density polyethylene, 6.5 kg of polylactic acid, 4.5 kg of styrene-based citrate grafted POE, 40 g of antioxidant 168 and 5 kg of calcium carbonate were blended and extruded in a twin-screw extruder. The temperatures of the first to fifth zones of the extruder were 150°C, 175°C, 190°C, 200°C and 200°C respectively. The mixture was then pelletized and injection molded in an injection molding machine. The temperatures of the first to third zones were 170°C, 200°C and 190°C respectively to obtain a high-density polyethylene-bio-based polyester blend material.

[0031] Example 3

[0032] (1) Add 1.2 L of toluene, 0.4 mol of triethyl citrate, 0.48 mol of triethylamine, and 18 mmol of 4-dimethylaminepyridine to the reaction vessel. Add 0.56 mol of 4-vinylbenzoyl chloride dropwise in an ice-water bath. Then react at 25 °C for 24 h. Filter, distill the filtrate under reduced pressure, wash with n-hexane, dissolve the product in ethyl acetate, heat in a fume hood to volatilize, and cool in an ice-water bath to crystallize, to obtain styrene citrate.

[0033] (2) Add 30L toluene, 2kg ethylene-octene copolymer, 360g styrene citrate, and 16g benzoyl peroxide to the reaction vessel, purge with nitrogen, and react at 80℃ for 18h. Add methanol to the solution to precipitate, filter and collect the precipitate, and then extract and purify with acetone in a Soxhlet extractor to obtain styrene citrate grafted POE.

[0034] (3) 12 kg of high-density polyethylene, 8 kg of polycaprolactone, 6 kg of styrene-based citrate grafted POE, 70 g of antioxidant 1010 and 2 kg of talc were blended and extruded in a twin-screw extruder. The temperatures of the first to fifth zones of the extruder were 150°C, 175°C, 190°C, 200°C and 200°C respectively. The mixture was then pelletized and injection molded in an injection molding machine. The temperatures of the first to third zones were 170°C, 200°C and 190°C respectively to obtain a high-density polyethylene-bio-based polyester blend material.

[0035] Comparative Example 1 differs from Example 1 in that ethylene-octene copolymer is used instead of styrene-citrate grafted POE.

[0036] (1) 15 kg of high-density polyethylene, 5 kg of polylactic acid, 3 kg of ethylene-octene copolymer, 80 g of antioxidant 1010 and 4 kg of calcium carbonate were blended and extruded in a twin-screw extruder. The temperatures of the first to fifth zones of the extruder were 150°C, 175°C, 190°C, 200°C and 200°C respectively. The mixture was then pelletized and injection molded in an injection molding machine. The temperatures of the first to third zones were 170°C, 200°C and 190°C respectively. This yielded a high-density polyethylene-bio-based polyester blend material.

[0037] Comparative Example 2 differs from Example 1 in that methyl acrylate is used instead of styrene citrate.

[0038] (1) Add 20L toluene, 2kg ethylene-octene copolymer, 120g methyl acrylate and 6g benzoyl peroxide to the reaction vessel, purge with nitrogen, react at 75℃ for 12h, add methanol to the solution to precipitate, filter and collect the precipitate, then extract and purify with acetone in a Soxhlet extractor to obtain methyl acrylate grafted POE.

[0039] (2) 15 kg of high-density polyethylene, 5 kg of polylactic acid, 3 kg of methyl acrylate grafted POE, 80 g of antioxidant 1010 and 4 kg of calcium carbonate were blended and extruded in a twin-screw extruder. The temperatures of the first to fifth zones of the extruder were 150°C, 175°C, 190°C, 200°C and 200°C respectively. The mixture was then pelletized and injection molded in an injection molding machine. The temperatures of the first to third zones were 170°C, 200°C and 190°C respectively to obtain a high-density polyethylene-bio-based polyester blend material.

[0040] Comparative Example 3 differs from Example 1 in that styrene is used instead of styrene citrate.

[0041] (1) Add 20L toluene, 2kg ethylene-octene copolymer, 120g styrene and 6g benzoyl peroxide to the reaction vessel, introduce nitrogen gas, react at 75℃ for 12h, add methanol to the solution to precipitate, filter and collect the precipitate, and then extract and purify it with acetone in a Soxhlet extractor to obtain styrene-grafted POE.

[0042] (2) 15 kg of high-density polyethylene, 5 kg of polylactic acid, 3 kg of styrene-grafted POE, 80 g of antioxidant 1010 and 4 kg of calcium carbonate were blended and extruded in a twin-screw extruder. The temperatures of the first to fifth zones of the extruder were 150°C, 175°C, 190°C, 200°C and 200°C respectively. The mixture was then pelletized and injection molded in an injection molding machine. The temperatures of the first to third zones were 170°C, 200°C and 190°C respectively to obtain a high-density polyethylene-bio-based polyester blend material.

[0043] Comparative Example 4 differs from Example 1 in that methyl 4-vinylbenzoate (CAS No. 1076-96-6) is used instead of styrene citrate.

[0044] (1) Add 20L toluene, 2kg ethylene-octene copolymer, 120g methyl 4-vinylbenzoate, and 6g benzoyl peroxide to the reaction vessel, purge with nitrogen, and react at 75℃ for 12h. Add methanol to the solution to precipitate the precipitate, filter and collect the precipitate, and then extract and purify it with acetone in a Soxhlet extractor to obtain methyl 4-vinylbenzoate grafted POE.

[0045] (2) 15 kg of high-density polyethylene, 5 kg of polylactic acid, 3 kg of methyl vinyl benzoate grafted with POE, 80 g of antioxidant 1010 and 4 kg of calcium carbonate were blended and extruded in a twin-screw extruder. The temperatures of the first to fifth zones of the extruder were 150°C, 175°C, 190°C, 200°C and 200°C respectively. The mixture was then pelletized and injection molded in an injection molding machine. The temperatures of the first to third zones were 170°C, 200°C and 190°C respectively to obtain a high-density polyethylene-bio-based polyester blend material.

[0046] Table 1: Performance Tests

[0047]

[0048] As shown in Table 1, compared with Comparative Examples 1-4, Examples 1-3 exhibit higher tensile strength, impact strength, and biodegradability, demonstrating higher mechanical strength and better biodegradability. This is mainly due to the addition of styrene-based citrate-grafted POE to high-density polyethylene and bio-based polyester. POE has excellent compatibility with polyethylene, and the POE-grafted citrate structure contains multiple ester groups, also showing good compatibility with polyester materials such as polylactic acid. This styrene-based citrate-grafted POE improves the compatibility between polyethylene and polylactic acid, enhancing the mechanical properties of the blend. Furthermore, POE, as a high-performance elastomer, also has rigid styrene polymer molecular chains grafted onto its side chains, further improving the mechanical strength of the polyethylene blend, resulting in higher tensile and impact strength. Simultaneously, the POE-grafted citrate exhibits good biodegradability, contributing to a higher biodegradability rate of the blend.

Claims

1. A high-density polyethylene-bio-based polyester blend material, characterized in that, The blend material comprises 60-75 parts by weight of high-density polyethylene, 25-40 parts by weight of bio-based polyester, 15-30 parts by weight of styrene-based citrate-grafted POE, 0.2-0.4 parts by weight of antioxidant, and 10-25 parts by weight of filler. The preparation method of styrene citrate-grafted POE includes: adding toluene, ethylene-octene copolymer, styrene citrate, and benzoyl peroxide to a reaction vessel, introducing nitrogen gas and reacting, adding methanol to the solution for precipitation, collecting the precipitate after filtration, and then purifying it with acetone in a Soxhlet extractor to obtain styrene citrate-grafted POE. The preparation method of the styrene carbamate citrate includes: adding toluene, citrate, triethylamine, and 4-dimethylaminepyridine to a reaction vessel, adding 4-vinylbenzoyl chloride dropwise in an ice-water bath, reacting at 25-45°C for 18-24 h, filtering, distilling the filtrate under reduced pressure, washing with n-hexane, dissolving the product in ethyl acetate, heating to volatilize, and cooling in an ice-water bath to crystallize, thereby obtaining styrene carbamate citrate; The molar ratio of citrate, triethylamine, 4-dimethylaminepyridine, and 4-vinylbenzoyl chloride is 1:(1-1.2):(0.03-0.05):(1.4-1.8). The citrate ester is trimethyl citrate, triethyl citrate, tripropyl citrate, or tributyl citrate.

2. The high-density polyethylene-bio-based polyester blend material according to claim 1, characterized in that, The filler includes calcium carbonate or talc; the antioxidant includes antioxidant 1010 or antioxidant 168.

3. The high-density polyethylene-bio-based polyester blend material according to claim 1, characterized in that, The bio-based polyester includes polylactic acid or polycaprolactone.

4. The high-density polyethylene-bio-based polyester blend material according to claim 1, characterized in that, The mass ratio of the ethylene-octene copolymer, styrene citrate, and benzoyl peroxide is 100:(6-18):(0.3-0.8).

5. The high-density polyethylene-bio-based polyester blend material according to claim 1, characterized in that, In the preparation method of POE grafted with styrene-based citrate, the reaction temperature is 70-80℃ and the reaction time is 12-24h.

6. A method for preparing a high-density polyethylene-bio-based polyester blend material as described in any one of claims 1-5, characterized in that, The preparation method includes: blending high-density polyethylene, bio-based polyester, styrene-based citrate grafted POE, antioxidants, and fillers, extruding in a twin-screw extruder, with the extruder's first to fifth zones at 150-200℃; pelletizing, and injection molding in an injection molding machine, with the first to third zones at 170-200℃, to obtain a high-density polyethylene-bio-based polyester blend material.

7. The application of a high-density polyethylene-bio-based polyester blend material obtained by the preparation method as described in claim 6 in a biodegradable trash can.

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