A high-density polyethylene composition with high environmental stress cracking resistance and preparation method thereof

Abstract

The present invention discloses a high-density polyethylene composition with high environmental stress cracking resistance and a preparation method thereof. The high-density polyethylene composition with high environmental stress cracking resistance comprises the following raw materials in parts by weight: 100 parts of high-density polyethylene (HDPE) resin, 5 to 10 parts of ethylene-acrylate copolymer, 0.1 to 0.5 parts of antioxidant, 0 to 0.5 parts of transesterification catalyst, and 0.5 to 3 parts of multifunctional epoxy compound. The present invention introduces a small amount of dynamic covalent crosslinking ethylene-acrylate copolymer into high-density polyethylene through melt blending, and the resulting composition has excellent environmental stress cracking resistance while maintaining the excellent mechanical properties of high-density polyethylene. The preparation process of the present invention is simple and can be adapted to industrial production, overcoming the problem of poor environmental stress cracking resistance of high-density polyethylene.

Description

Technical Field

[0001] The present invention relates to the technical field of general plastics, and in particular to a dynamic covalently cross-linked high-density polyethylene with high resistance to environmental stress cracking and a preparation method thereof. Background Art

[0002] High-density polyethylene (HDPE) is produced by the Ziegler-Natta coordination polymerization process. Its main macromolecular chain has few branches, resulting in a regular molecular chain arrangement, a crystallinity exceeding 80%, and a high density. HDPE is non-toxic and odorless, possesses excellent mechanical properties, and has a high heat resistance. It is widely used in blow molding, injection molding, extrusion, and rotational molding, particularly in pipes, where it is second only to PVC. However, due to HDPE's high crystallinity and the linear structure of its main macromolecular chain, there are fewer tie molecules connecting HDPE grains or wafers. Under the influence of environmental stress, the wafers are prone to slippage, resulting in macroscopic cracking. This shortcoming significantly limits the application range of HDPE.

[0003] Currently, methods for improving HDPE's environmental stress cracking resistance primarily include blending with elastomers, blending with low-density or linear low-density polyethylene, branching modification, and crosslinking. While simple, the first two methods can easily compromise HDPE's mechanical properties. Branching and crosslinking are more complex and can increase HDPE's viscosity, making molding difficult. Summary of the Invention

[0004] In order to address the deficiencies of the prior art, the present invention provides a high-density polyethylene composition with high environmental stress cracking resistance and a preparation method thereof.

[0005] The present invention provides the following technical solutions:

[0006] A high-density polyethylene composition with high environmental stress cracking resistance, comprising the following raw materials in parts by weight:

[0007] High-density polyethylene (HDPE): 100 parts;

[0008] Ethylene-acrylate copolymer: 5-10 parts;

[0009] Antioxidant: 0.1-0.5 parts;

[0010] Transesterification catalyst: 0-0.5 parts;

[0011] Multifunctional epoxy compound: 1 to 3 parts.

[0012] Furthermore, the high-density polyethylene is polyethylene with a density higher than 0.94.

[0013] Furthermore, the ethylene-acrylate copolymer is an ionomer made by copolymerizing ethylene-acrylic acid or ethylene-methacrylic acid and neutralizing with sodium, potassium, or zinc, such as sarling resin. When the ethylene-acrylate copolymer is ethylene-zinc acrylate or ethylene-methacrylic acid zinc salt, the amount of transesterification catalyst is zero. When the ethylene-acrylate copolymer is ethylene-potassium acrylate, ethylene-potassium methacrylate, ethylene-sodium acrylate, or ethylene-sodium methacrylate, less than 0.5 parts of transesterification catalyst is required.

[0014] Furthermore, the antioxidant is one or a combination of two or more of hindered phenol and phosphite antioxidants.

[0015] Furthermore, the transesterification reaction catalyst is at least one of zinc acetylacetonate, zinc acetate, zinc citrate, stannous octoate, tin isooctanoate, 1,5,7-triazidobicyclo(4.4.0)dec-5-ene, 1,8-diazabicycloundec-7-ene, and 4-dimethylaminopyridine.

[0016] Furthermore, the multifunctional epoxy compound is preferably one or a combination of two or more of epoxy soybean oil, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, 1,4-butanediol diglycidyl ether, bisphenol A diglycidyl ether, epoxy resin E-51, and epoxy resin E-44.

[0017] Furthermore, the method for preparing the high-density polyethylene composition with high stress cracking resistance is characterized by comprising the following steps:

[0018] (1) High-density polyethylene, ethylene-acrylate copolymer, antioxidant, and transesterification catalyst are added in proportion, fully premixed, and then melt-blended.

[0019] (2) Add the multifunctional epoxy compound in proportion and continue melt blending.

[0020] (3) The melt-blended sample is subjected to hot press molding (preferably by a flat plate vulcanizer) to obtain a high-density polyethylene composition with high environmental stress cracking resistance.

[0021] Furthermore, in the step (1), the melt blending temperature is 180-200° C. and the time is 5-10 minutes.

[0022] Furthermore, in the step (2), the melt blending temperature is 180-200° C. and the time is 5-10 minutes.

[0023] Furthermore, in the step (3), the molding temperature is 190-210° C. and the molding time is 3-8 minutes.

[0024] The present invention introduces a small amount of a dynamically covalently crosslinked ethylene-acrylate copolymer network into HDPE. The resulting HDPE material exhibits excellent resistance to environmental stress cracking, overcoming the problem of HDPE's susceptibility to cracking under environmental stress. The network structure also maintains high mechanical properties, while the dynamic covalently crosslinked network exhibits plasticity, minimizing the impact on HDPE's processing properties. This results in an HDPE material with excellent overall performance and resistance to environmental stress cracking.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) The present invention introduces a small amount of dynamic covalently cross-linked ethylene-acrylate copolymer network into HDPE. The dynamic covalently cross-linked ethylene-acrylate copolymer has good compatibility with HDPE and can form an interpenetrating network structure. On the one hand, it can increase the entanglement and interaction force of the lacing molecules, prevent the occurrence of interspherulite slip caused by the presence of environmental media and stress, and improve the resistance to environmental stress cracking. On the other hand, the introduction of the sparse cross-linked network has little damage to the regularity of the macromolecules, and the network structure enables the material to maintain high mechanical properties.

[0027] (2) The dynamic covalently cross-linked ethylene-acrylate copolymer network introduced in the present invention can be thermoplastic by rearranging the network topology under high temperature conditions, which has little effect on the processing properties of HDPE, so that the high-density polyethylene composition with high environmental stress cracking resistance prepared by the present invention has good processing properties.

[0028] (3) When the ethylene-acrylate copolymer is ethylene-acrylic acid or ethylene-zinc methacrylate, the ethylene-acrylate copolymer itself carries an ester exchange catalyst, and there is no need to add an additional ester exchange catalyst, thereby avoiding the migration problem caused by the added catalyst.

[0029] (4) The high-density polyethylene composition with high environmental stress cracking resistance provided by the present invention is prepared by melt blending, which has a simple process and is suitable for industrial production. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to specific test examples. It is necessary to point out that the following test examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0031] Example 1:

[0032] 100 parts of high-density polyethylene (HDPE) resin (Zhenhai Refining and Chemical Company, Sinopec), 8 parts of sarling resin (sodium salt) (DuPont), 0.1 parts of antioxidant 1010 (BASF), 0.1 parts of antioxidant 168 (BASF), 0.2 parts of transesterification catalyst (zinc acetylacetonate) (Sinopharm Chemical Reagent Co., Ltd.), and 1.6 parts of epoxidized soybean oil (Aladdin).

[0033] Preparation method: (1) High-density polyethylene, sarling resin, antioxidant, and transesterification catalyst were weighed in proportion, pre-mixed, and melt-blended at 190° C. for 6 min;

[0034] (2) Add epoxidized soybean oil and continue melt blending at 190°C for 6 minutes.

[0035] (3) The blended sample was hot-pressed at 190°C for 6 minutes using a flat-plate vulcanizer to obtain a high-density polyethylene composition with high resistance to environmental stress cracking.

[0036] Example 2: The specific process is the same as that of Example 1, wherein the amount of sarling resin (sodium salt) is changed to 5 parts (DuPont) and the amount of epoxidized soybean oil is changed to 1 part (Aladdin).

[0037] Example 3: The specific process is the same as Example 1, wherein the amount of sarin resin (sodium salt) is changed to 10 parts (DuPont), the amount of epoxidized soybean oil is changed to 3 parts (Aladdin), and the amount of transesterification catalyst is changed to 0.5 parts (Sinopharm Chemical Reagent Co., Ltd.).

[0038] Example 4: The specific process is the same as that of Example 1, wherein sarling resin (sodium salt) is replaced by sarling resin (lithium salt) (DuPont).

[0039] Example 5: The specific process is the same as that of Example 1, wherein sarling resin (sodium salt) is changed to sarling resin (zinc salt) (DuPont), and the amount of transesterification catalyst is changed to 0.

[0040] Example 6: The specific process is the same as Example 1, wherein the transesterification catalyst is changed to stannous octoate (Aladdin), and the multifunctional epoxy compound is changed to glycerol triglycidyl ether, and the amount used is 1 part (Aladdin).

[0041] Example 7: The specific process is the same as Example 1, wherein the ester exchange catalyst is changed to 1,5,7-triazidobicyclo (4.4.0) dec-5-ene (Sinopharm Chemical Reagent Co., Ltd.), and the multifunctional epoxy compound is changed to E51 (China Petrochemical Corporation Baling Branch), and the amount used is 3 parts.

[0042] Example 8: The specific process is the same as that of Example 1, wherein the melt blending temperature and time in step (1) of the preparation method are changed to 180°C and 10 minutes respectively, and the hot pressing molding time in step (3) is changed to 10 minutes.

[0043] Example 9: The specific process is the same as that of Example 1, wherein the melt blending temperature and time in step (1) of the preparation method are changed to 200°C and 5 minutes respectively. The hot pressing molding temperature in step (3) is changed to 210°C and the time is changed to 3 minutes.

[0044] Comparative Example 1: The specific process is the same as that of Example 1, except that the components do not include sarin resin, transesterification catalyst and multifunctional epoxy compound.

[0045] Comparative Example 2: The specific process is the same as that of Example 1, except that the components do not include an ester exchange catalyst and a multifunctional epoxy compound.

[0046] Table 1

[0047]

[0048] a Refer to GB / T 1040.1-201, tensile rate 100 mm / min; b Refer to GB_T1842-2008

[0049] From the data in Table 1, we can see that the stress cracking resistance of pure HDPE is poor. 50 When ethylene-acrylate copolymer is added, the stress cracking resistance is improved. 50 It can reach 135h, but the mechanical properties also decline significantly. After adding dynamic cross-linked ethylene-acrylate copolymer, the stress cracking resistance of HDPE is further improved. 50 The stress cracking resistance of HDPE can be significantly improved while maintaining good mechanical properties, thus obtaining a HDPE material with excellent comprehensive performance.

Claims

1. A method for preparing a high-density polyethylene composition with high environmental stress cracking resistance, characterized in that: The steps include: (1) adding high-density polyethylene, ethylene-acrylate copolymer, antioxidant, and transesterification catalyst in proportion, fully premixing, and then melt blending; (2) adding the multifunctional epoxy compound in proportion and continuing melt blending; (3) hot pressing the melt-blended sample to obtain a high-density polyethylene composition with high environmental stress cracking resistance; in: High-density polyethylene: 100 parts; Ethylene-acrylate copolymer: 5-10 parts; Antioxidant: 0.1-0.5 parts; Transesterification catalyst: 0-0.5 parts; Multifunctional epoxy compound: 1 to 3 parts.

2. The method for preparing a high-density polyethylene composition with high environmental stress cracking resistance according to claim 1, wherein: The high-density polyethylene is polyethylene with a density higher than 0.

94.

3. The method for preparing a high-density polyethylene composition with high environmental stress cracking resistance according to claim 1, wherein: The ethylene-acrylate copolymer is an ionomer prepared by copolymerizing ethylene-acrylic acid or ethylene-methacrylic acid and neutralizing with sodium, potassium or zinc. When the ethylene-acrylate copolymer is ethylene-acrylic acid zinc salt or ethylene-methacrylic acid zinc salt, the amount of transesterification catalyst is 0. When the ethylene-acrylate copolymer is ethylene-acrylic acid potassium salt, ethylene-methacrylic acid potassium salt, ethylene-acrylic acid sodium salt or ethylene-methacrylic acid sodium salt, less than 0.5 parts of transesterification catalyst needs to be added.

4. The method for preparing a high-density polyethylene composition with high environmental stress cracking resistance according to claim 1, wherein: The antioxidant is one or a combination of two or more of hindered phenol and phosphite antioxidants.

5. The method for preparing a high-density polyethylene composition with high environmental stress cracking resistance according to claim 1, wherein: The transesterification reaction catalyst is at least one of zinc acetylacetonate, zinc acetate, zinc citrate, stannous octoate, tin isooctanoate, 1,5,7-triazidobicyclo(4.4.0)dec-5-ene, 1,8-diazabicycloundec-7-ene, and 4-dimethylaminopyridine.

6. The method for preparing a high-density polyethylene composition with high environmental stress cracking resistance according to claim 1, wherein: The multifunctional epoxy compound is one or a combination of two or more of epoxy soybean oil, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, 1,4-butanediol diglycidyl ether, bisphenol A diglycidyl ether, epoxy resin E-51, and epoxy resin E-44.

7. The method for preparing a high-density polyethylene composition with high environmental stress cracking resistance according to claim 1, wherein: In step (1), the melt blending temperature is 180-200° C. and the time is 5-10 minutes.

8. The method for preparing a high-density polyethylene composition with high environmental stress cracking resistance according to claim 1, wherein: In step (2), the melt blending temperature is 180-200° C. and the time is 5-10 minutes.

9. The method for preparing a high-density polyethylene composition with high environmental stress cracking resistance according to claim 1, wherein: In step (3), the hot pressing molding temperature is 190-210° C. and the time is 3-8 minutes.

10. A high-density polyethylene composition with high environmental stress cracking resistance obtained by the preparation method according to any one of claims 1 to 9.

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