Polyethylene resin capable of improving environmental stress cracking resistance as well as preparation method and application of polyethylene resin

Abstract

The invention discloses polyethylene resin with improved environmental stress cracking resistance as well as a preparation method and application thereof. The polyethylene resin with improved environmental stress cracking resistance comprises the following components in parts by weight: 98-100 parts of high density polyethylene (HDPE) resin, more than 0.5 part and less than 2 parts of amino silicon oil and 0-0.04 part of stearate. According to the invention, the defects of high cost, complex process and the like caused by improving the ESCR performance of the HDPE through a polymerization process in the prior art can be overcome, and the environmental stress cracking resistance of the HDPE can be remarkably improved through formula modification.

Description

Technical Field

[0001] This invention relates to the field of polymer material modification technology, specifically to a polyethylene resin with improved environmental stress cracking resistance, its preparation method, and its application. Background Technology

[0002] High-density polyethylene (HDPE) hollow containers are widely used for packaging high-risk contents such as pesticides, strong chemicals, and surfactants due to their excellent chemical stability and mechanical properties. However, in these harsh chemical environments, container materials have long faced a technical bottleneck due to insufficient resistance to environmental stress cracking (ESCR). ESCR refers to the premature brittle cracking of materials under the combined action of stress and specific chemical media, directly threatening the sealing integrity and safety of the packaging. Especially in applications involving pesticides, high-end chemicals, and concentrated surfactants, this is not simply a matter of choosing packaging materials, but a critical component directly related to production, transportation safety, environmental safety, and public safety. If containers rupture and leak due to material failure, it poses risks to transportation, storage safety, and environmental protection. Therefore, improving the reliability of HDPE containers, particularly their resistance to environmental stress cracking (ESCR) against the erosion of their contents, is a key technical requirement for ensuring the safety of chemical packaging and has significant industrial application value.

[0003] Currently, the industry mainly improves the intrinsic ESCR performance of HDPE resin by optimizing polymerization processes, such as controlling molecular weight and its distribution, and introducing comonomers. However, this often involves complex catalyst systems and process adjustments, resulting in high costs and limited flexibility. The fundamental technical challenge facing the industry is that the traditional performance optimization path for HDPE materials has reached its limit. While controlling the molecular chain structure through polymerization processes, such as increasing molecular weight, broadening molecular weight distribution, and introducing comonomers to improve intrinsic ESCR, is effective, its marginal benefits are diminishing, and it is often accompanied by new problems such as deterioration in processing performance and a sharp increase in production costs. More importantly, in the face of increasingly complex and harsh chemical media, relying solely on the resistance of the resin itself is no longer sufficient. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a polyethylene resin with improved environmental stress cracking resistance that can overcome the defects of high cost and complex process in improving the ESCR performance of HDPE through polymerization process, and significantly improve the ESCR performance of HDPE through formulation modification, as well as the preparation method and application.

[0005] This invention is achieved through the following technical solution: a polyethylene resin for improving resistance to environmental stress cracking, comprising the following components in parts by weight: High-density polyethylene (HDPE) resin: 98-100 parts; Amino silicone oil: greater than 0.5 parts and less than 2 parts; Stearates: 0 to 0.04 parts.

[0006] Furthermore, it also includes antioxidant B215, wherein the antioxidant B215 is present in parts by weight of 0.1 to 0.2 parts.

[0007] Further, the amino silicone oil is in the form of 0.55 to 1.95 parts by weight, more preferably, the amino silicone oil can be in the form of 0.55 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, or 1.95 parts.

[0008] Furthermore, the viscosity of the amino silicone oil is 1000–10000 mPa·s.

[0009] Furthermore, the viscosity of the amino silicone oil is 5000–10000 mPa·s.

[0010] Further: the stearate is zinc stearate.

[0011] Furthermore, the antioxidant B215 includes phenolic antioxidants and phosphite antioxidants.

[0012] Further: the phenolic antioxidant is A01010, and the phosphite antioxidant is A0168.

[0013] A method for preparing a polyethylene resin with improved environmental stress cracking resistance as described above includes the following steps: S1. Ingredients: Accurately weigh high-density polyethylene (HDPE) resin, amino silicone oil, stearate, and antioxidant B215; S2. Premixing: Weigh out the high-density polyethylene (HDPE) resin, amino silicone oil, stearate and antioxidant B215 into a small blade mixer and mix them at room temperature until uniform to obtain a premix. S3. Melt blending and granulation: The premixed material is fed into a twin-screw extruder for melt blending, extrusion granulation; S4. Cooling and pelletizing: After the extruded molten strip is cooled in a water bath, it is pelletized into uniform resin particles by a pelletizer.

[0014] An application of a polyethylene resin as described above to improve resistance to environmental stress cracking, wherein the polyethylene resin is used in the manufacture of hollow containers.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention utilizes a specific blend of amino silicone oil and stearate to create a synergistic effect with the HDPE matrix, significantly improving the environmental stress cracking resistance of HDPE resin. This makes it suitable for more demanding chemical packaging environments, breaking through the traditional polymerization strategy that relies on expensive and complex polymerization processes to improve ESCR. The invention achieves performance upgrades for general-purpose HDPE resins through simple and efficient formulation modification, with a simple process, low cost, and easy industrialization.

[0016] 2. By using amino silicone oil within a specific viscosity range in synergy with stearate, a stress dissipation network can be formed more effectively in the HDPE matrix, hindering the propagation of streaks. Stearate can interact with the amino functional groups of amino silicone oil, promoting the dispersion and stability of amino silicone oil in the matrix and preventing excessive silicone oil precipitation.

[0017] 3. While significantly improving resistance to environmental stress cracking, this invention optimizes the amount of high-viscosity amino silicone oil added, thereby controlling the influence of the resin on other key mechanical properties, such as tensile breaking strength, yield elongation, and whether silicone oil is precipitated, within an acceptable range, thus maintaining the overall practicality of the material. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below. The described embodiments are some, but not all, of the embodiments of the present invention. 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.

[0019] The raw material information of this invention is shown in Table 1: Table 1

[0020] Example 1 The components and their weights used in the product of this embodiment are as follows: 990g of HDPE resin; Amino silicone oil 1 (viscosity: 1000 mPa·s) 10g; Stearate 300mg; Antioxidant (A0168) 1000mg; Antioxidant (A01010) 500mg.

[0021] S1. Ingredients: Accurately weigh HDPE resin, amino silicone oil, zinc stearate, A0168, and A01010.

[0022] S2. Premixing: Weigh the HDPE resin, amino silicone oil, zinc stearate, A0168 and A01010 into a small blade mixer and mix them at room temperature until uniform to obtain a premix.

[0023] S3. Melt blending and granulation: The premixed material is fed into a twin-screw extruder for melt blending, extrusion granulation; S4. Cooling and pelletizing: After the extruded molten strip is cooled in a water bath, it is pelletized into uniform resin particles by a pelletizer.

[0024] The total mixing time for the small blade mixer is 2 minutes, the speed is 800 rpm, and the rotation direction is as follows: clockwise for 21 seconds, stop for 5 seconds, counterclockwise for 21 seconds, stop for 5 seconds, clockwise for 21 seconds, stop for 5 seconds, counterclockwise for 21 seconds, and so on, until the total mixing time reaches 2 minutes. The extruder temperature is set from 180℃ to 230℃, the die head temperature is 230℃, and the screw speed is 25 rpm. For some samples with high oil content, the extrusion efficiency decreases, and the screw speed is gradually increased, up to a maximum of 40 rpm.

[0025] Example 2 990g of HDPE resin; 10g of amino silicone oil 2 (viscosity: 5000-10000 mPa·s); Stearate 300mg; Antioxidant (A0168) 1000mg; Antioxidant (A01010) 500mg.

[0026] The preparation method in this embodiment is the same as that in Example 1.

[0027] Example 3 990g of HDPE resin; Amino silicone oil 2 (viscosity: 5000-10000 mPa·s) 10g; Antioxidant (A0168) 1000mg; Antioxidant (A01010) 500mg.

[0028] The preparation method in this embodiment is the same as that in Example 1.

[0029] Comparative Example 1 980g of HDPE resin; Amino silicone oil 2 (viscosity: 5000-10000 mPa·s) 20g; Stearate 300mg; Antioxidant (A0168) 1000mg; Antioxidant (A01010) 500mg.

[0030] The preparation method of this comparative example is the same as that of Example 1.

[0031] Comparative Example 2 1000g of HDPE resin; Stearate 300mg; Antioxidant (A0168) 1000mg; Antioxidant (A01010) 500mg.

[0032] The preparation method of this comparative example is the same as that of Example 1.

[0033] Comparative Example 3 990g of HDPE resin; 10g of amino-free dimethyl silicone oil (viscosity: 1000 mPa·s); Stearate 300mg; Antioxidant (A0168) 1000mg; Antioxidant (A01010) 500mg.

[0034] The difference between the preparation method of this comparative example and the preparation method of Example 1 is that the amino silicone oil in step S1 is replaced with amino-free dimethyl silicone oil.

[0035] Comparative Example 4 1000g of HDPE resin; 1g of amino silicone oil 2 (viscosity: 5000-10000 mPa·s); Stearate 300mg; Antioxidant (A0168) 1000mg; Antioxidant (A01010) 500mg.

[0036] The preparation method of this comparative example is the same as that of Example 1.

[0037] Comparative Example 5 995g of HDPE resin; 5g of amino silicone oil 2 (viscosity: 5000-10000 mPa·s); Stearate 300mg; Antioxidant (A0168) 1000mg; Antioxidant (A01010) 500mg.

[0038] The preparation method of this comparative example is the same as that of Example 1.

[0039] In Preparation Examples 1 to 3 and Comparative Examples 1 to 5, the pelletized samples were prepared and their performance was tested according to the following standards: Environmental stress cracking resistance: tested according to ASTM D1693 standard, with TX-10 as the test reagent.

[0040] Tensile breaking strength: tested according to ISO 527-2 standard.

[0041] Elongation at yield: Tested according to ISO 527-2 standard.

[0042] The test results are shown in Table 2: Table 2

[0043] Results analysis and discussion: 1. Analysis of the synergistic effect between zinc stearate and amino functional groups: Example 1 added 1 part of low-viscosity amino silicone oil and 0.03 parts of zinc stearate. According to the experimental results, no silicone oil precipitation occurred. In contrast, Comparative Example 3 added 1 part of amino-free dimethyl silicone oil and 0.03 parts of zinc stearate. According to the experimental results, although its ESCR was high, silicone oil precipitation was obvious. Comparing the two, it can be seen that when zinc stearate is added, the amino-containing silicone oil can avoid precipitation. This indicates that there is a key synergistic effect between zinc stearate and amino functional groups, rather than zinc stearate acting alone.

[0044] Further analysis of Comparative Example 2, which added only 0.03 parts of zinc stearate without silicone oil, shows that using zinc stearate alone significantly reduces ESCR. Comparative Example 3 indicates that while the absence of amino silicone oil can substantially improve ESCR, it also causes silicone oil precipitation. Therefore, the role of amino silicone oil is that its polar amino functional groups can interact with the HDPE matrix, while the siloxane backbone provides slip and stress buffering capabilities. Zinc stearate, as a processing aid, regulates the dispersion and distribution of silicone oil in the matrix through its interaction with amino groups. Together, they optimize the microstructure and stress distribution of the material, thereby achieving high ESCR without silicone oil precipitation.

[0045] Furthermore, in Example 3, 1 part of high-viscosity amino silicone oil was added without the addition of zinc stearate, and no silicone oil precipitation occurred. This indicates that when high-viscosity amino silicone oil is used, it is not necessary to rely on zinc stearate to prevent silicone oil precipitation. This suggests that the viscosity of silicone oil itself is also an important factor affecting its compatibility and precipitation behavior.

[0046] 2. Dosage-effect analysis of high-viscosity amino silicone oil addition: The experimental results of Example 2, which added 1 part of high-viscosity amino silicone oil, show that its ESCR is high and no silicone oil precipitation occurs. The experimental results of Comparative Example 1, which added 2 parts of high-viscosity amino silicone oil, show that its ESCR is even higher, but silicone oil precipitation occurs. Therefore, it can be concluded that the amount of amino silicone oil added, between 1 and 2 parts, is the key window for balancing ESCR improvement and preventing precipitation. Meanwhile, the experimental results of Comparative Example 4, which added 0.1 parts of high-viscosity amino silicone oil, and Comparative Example 5, which added 0.5 parts of high-viscosity amino silicone oil, show that the ESCR of both is lower than that of the blank control, Comparative Example 2. Therefore, it indicates that at low addition amounts (≤0.5 parts), ESCR not only does not increase but actually decreases.

[0047] Therefore, the effective addition range of high-viscosity amino silicone oil should be between 0.5 parts and less than 2 parts. Adding less than this range may introduce defects due to the inability to form an effective stress-dissipating phase, while adding more than this range can easily lead to silicone oil precipitation. At an addition of 1 part, a significant improvement in ESCR can be achieved without noticeable silicone oil precipitation.

[0048] 3. Analysis of the synergistic effect of amino silicone oil viscosity: By comparing Example 1 (low-viscosity amino silicone oil with a viscosity of 1000 mPa·s) and Example 2 (high-viscosity amino silicone oil with a viscosity of 5000-10000 mPa·s), with no silicone oil precipitation in either case (1 part added), the high-viscosity amino silicone oil showed a more significant improvement in ESCR. This indicates that, at the same addition amount, higher viscosity amino silicone oil can more effectively improve ESCR. The mechanism is that the high-viscosity amino silicone oil phase can form a stronger and more stable stress dissipation network in the matrix, thereby more effectively hindering the expansion and convergence of crazing. Therefore, high-viscosity amino silicone oil in the viscosity range of 5000-10000 mPa·s is a better choice.

[0049] In summary, this invention significantly improves the environmental stress cracking resistance of HDPE by combining amino silicone oil and zinc stearate in a melt-blending process without excessively sacrificing processing performance and economy. Through systematic research on factors such as silicone oil type, viscosity, and addition amount, an optimized formulation window was established where high-viscosity amino silicone oil, in an addition range of greater than 0.5 parts to less than 2 parts, can simultaneously achieve high ESCR and silicone oil-free precipitation in synergy with zinc stearate. This method breaks through the limitations of traditional methods that rely on polymerization processes to adjust molecular chain structure, providing a feasible approach for rapidly and economically customizing HDPE materials with high environmental stress cracking resistance.

[0050] The above detailed description is a specific description of feasible embodiments of the present invention. These embodiments are not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included in the patent scope of this case.

Claims

1. A polyethylene resin with improved resistance to environmental stress cracking, characterized in that, Includes the following components in parts by weight: High-density polyethylene (HDPE) resin: 98-100 parts; Amino silicone oil: greater than 0.5 parts and less than 2 parts; Stearates: 0 to 0.04 parts.

2. The polyethylene resin for improving environmental stress cracking resistance according to claim 1, characterized in that: It also includes antioxidant B215, wherein the antioxidant B215 is present in parts by weight of 0.1 to 0.2 parts.

3. The polyethylene resin for improving environmental stress cracking resistance according to claim 1, characterized in that: The amino silicone oil is present in parts by weight of 0.55 to 1.

95.

4. The polyethylene resin for improving environmental stress cracking resistance according to claim 1, characterized in that: The viscosity of the amino silicone oil is 1000–10000 mPa·s.

5. The polyethylene resin for improving environmental stress cracking resistance according to claim 1, characterized in that: The viscosity of the amino silicone oil is 5000-10000 mPa·s.

6. The polyethylene resin for improving environmental stress cracking resistance according to claim 1, characterized in that: The stearate is zinc stearate.

7. The polyethylene resin for improving environmental stress cracking resistance according to claim 2, characterized in that: The antioxidant B215 includes phenolic antioxidants and phosphite antioxidants.

8. The polyethylene resin for improving environmental stress cracking resistance according to claim 7, characterized in that: The phenolic antioxidant is A01010, and the phosphite antioxidant is A0168.

9. A method for preparing a polyethylene resin with improved environmental stress cracking resistance as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Ingredients: Accurately weigh high-density polyethylene (HDPE) resin, amino silicone oil, stearate, and antioxidant B215; S2. Premixing: Weigh out the high-density polyethylene (HDPE) resin, amino silicone oil, stearate and antioxidant B215 into a small blade mixer and mix them at room temperature until uniform to obtain a premix. S3. Melt blending and granulation: The premixed material is fed into a twin-screw extruder for melt blending, extrusion granulation; S4. Cooling and pelletizing: After the extruded molten strip is cooled in a water bath, it is pelletized into uniform resin particles by a pelletizer.

10. The application of a polyethylene resin with improved environmental stress cracking resistance as described in any one of claims 1-8, characterized in that: The polyethylene resin is used to prepare hollow containers.

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