Polypropylene hydrocarbon negative pressure thermoforming material and preparation method thereof

Abstract

The invention relates to the technical field of polypropylene sheet processing, in particular to a polypropylene hydrocarbon negative-pressure thermoforming material and a preparation method thereof, and the polypropylene hydrocarbon negative-pressure thermoforming material is prepared from the following raw materials in parts by weight: 15-20 parts of polypropylene, 10-15 parts of low-density polyethylene, 5-10 parts of linear low-density polyethylene and 4-8 parts of high-density polyethylene. The melt index of the low-density polyethylene under the test conditions of 230 DEG C and 2.16 kg is 2-2.5 g / 10 min; the melt index of the linear low density polyethylene under the test conditions of 190 DEG C and 2.16 kg is 1-3 g / 10 min; the melt index of the high density polyethylene under the test conditions of 230 DEG C and 2.16 kg is 0.2-0.5 g / 10 min; the polymerization degree of polypropylene is 500-15000, the problems of post-shrinkage phenomenon and low melt strength existing in the process of preparing the heterogeneous multi-cavity electronic tray from polypropylene can be effectively solved by changing the formula, the dimensional accuracy and the forming quality of the tray are improved, the mechanical property and the chemical corrosion resistance of the tray are enhanced, and the service life of the tray is prolonged. Therefore, the packaging box has a wider application prospect in the field of packaging and transportation of electronic components.

Description

Technical Field

[0001] This application relates to the technical field of polypropylene sheet processing, and more specifically, to a polypropylene hydrocarbon negative pressure thermoforming material and a preparation method thereof. Background Art

[0002] Heterogeneous multi-cavity electronic trays are mainly prepared by thermoforming a sheet under negative pressure. During the manufacturing, transportation, and storage of electronic components, heterogeneous multi-cavity electronic trays can effectively protect the components from electrostatic, collision, and moisture effects. Among them, polypropylene has good corrosion resistance to chemicals such as acids, alkalis, and salts and can work stably under high temperature, high pressure, and harsh environments. This enables it to effectively resist the erosion of various chemicals during the packaging and transportation of electronic components, protecting the electronic components from damage. At the same time, polypropylene has a hard texture, good strength and rigidity, can withstand a certain amount of mechanical stress, and is not easily deformed. Electronic components may be subject to collision and extrusion during transportation and storage, and the strength of polypropylene can effectively protect the safety of electronic components.

[0003] However, during use, it is found that polypropylene has a post-shrinkage phenomenon, and it is prone to dimensional changes after demolding, resulting in low dimensional accuracy, which will affect the fitting accuracy between the tray and the electronic components. At the same time, the melt strength of polypropylene is relatively low, and it is prone to sag during thermoforming, resulting in uneven thickness, and even cracking and piercing the mold. This problem is more obvious especially for large-scale heterogeneous multi-cavity electronic trays. The main reason is that the forming cycle of large trays is longer, and the temperature gradient is larger during the cooling process, which is prone to cause uneven shrinkage. Summary of the Invention

[0004] In order to solve the problems of post-shrinkage phenomenon and low melt strength of polypropylene when preparing heterogeneous multi-cavity electronic trays, this application provides a polypropylene hydrocarbon negative pressure thermoforming material and a preparation method thereof.

[0005] In the first aspect, this application provides a polypropylene hydrocarbon negative pressure thermoforming material, adopting the following technical scheme: A polypropylene hydrocarbon negative pressure thermoforming material is prepared from the following raw materials in parts by weight: 15 - 20 parts of polypropylene 10 - 15 parts of low-density polyethylene 5 - 10 parts of linear low-density polyethylene 4 - 8 parts of high-density polyethylene The melt index of the low-density polyethylene under the test conditions of 230°C and 2.16 kg is 2 - 2.5 g / 10 min; The melt index of the linear low-density polyethylene under the test conditions of 190°C and 2.16 kg is 1 - 3 g / 10 min; The melt index of the high-density polyethylene under the test conditions of 230 °C and 2.16 kg is 0.2 - 0.5 g / 10 min; The degree of polymerization of the polypropylene is 500 - 10,000.

[0006] By adopting the above technical solution, reasonably selecting and proportioning polypropylene, low-density polyethylene, linear low-density polyethylene and high-density polyethylene can effectively solve the problems of post-shrinkage and low melt strength existing in the preparation of the isomeric multi-cavity electronic tray with polypropylene. It not only improves the dimensional accuracy and molding quality of the tray, but also enhances the mechanical properties and chemical corrosion resistance of the tray, making it have a wider application prospect in the packaging and transportation fields of electronic components.

[0007] By optimizing the parameters of polypropylene, low-density polyethylene, linear low-density polyethylene and high-density polyethylene and using them synergistically, the fluidity of the polypropylene hydrocarbon negative pressure thermoforming material is improved, making it easier to fill the mold during thermoforming, reducing the sagging phenomenon, and thus improving the dimensional accuracy. At the same time, the melt strength of the polypropylene hydrocarbon negative pressure thermoforming material is increased, the sagging phenomenon during thermoforming is reduced, the thickness uniformity of the product is ensured, and the molding quality is improved.

[0008] Using polypropylene, low-density polyethylene, linear low-density polyethylene and high-density polyethylene with specific parameters in combination can further improve the flexibility, strength and impact resistance of the polypropylene hydrocarbon negative pressure thermoforming material, and improve the comprehensive mechanical properties of the polypropylene hydrocarbon negative pressure thermoforming material.

[0009] Preferably, the polypropylene is syndiotactic polypropylene, and the degree of polymerization of the syndiotactic polypropylene is 1,000 - 5,000.

[0010] By adopting the above technical solution, when the polypropylene is selected as syndiotactic polypropylene and the degree of polymerization is controlled within the range of 1,000 - 5,000, the post-shrinkage phenomenon of the polypropylene can be effectively improved, thereby improving the dimensional accuracy of the isomeric multi-cavity electronic tray and ensuring its good fit with the electronic components. At the same time, the mechanical properties of the syndiotactic polypropylene within this range of the degree of polymerization are optimized, further enhancing the strength and rigidity of the material, so that the electronic tray can better protect the electronic components from collision and extrusion damage during transportation and storage.

[0011] Preferably, the weight ratio of the polypropylene to the low-density polyethylene is 1:(0.5 - 1).

[0012] By adopting the above technical solution and optimizing the weight ratio of polypropylene and low-density polyethylene, the post-shrinkage phenomenon of polypropylene materials can be effectively improved, and the dimensional stability of the molded materials can be enhanced. The addition of low-density polyethylene can reduce the brittleness of polypropylene and increase the toughness of the material, thereby reducing the sagging phenomenon during thermoforming, making the thickness of the molded electronic tray more uniform and avoiding problems such as cracking or die penetration. At the same time, this ratio optimizes the overall performance of the material, further improving the fitting accuracy between the electronic tray and electronic components on the basis of ensuring strength and rigidity.

[0013] Preferably, the weight ratio of the polypropylene and the high-density polyethylene is (3 - 2):1.

[0014] By adopting the above technical solution and optimizing the weight ratio of polypropylene and high-density polyethylene, the sagging phenomenon of polypropylene materials during negative-pressure thermoforming can be effectively improved. The addition of high-density polyethylene increases the melt strength of the material, reducing problems such as uneven thickness and cracking caused by the relatively low melt strength of polypropylene itself during the molding process, and is particularly suitable for the preparation of large-sized heterogeneous multi-cavity electronic trays. In addition, this ratio can also reduce the post-shrinkage phenomenon and improve the dimensional accuracy of the tray while ensuring good mechanical properties of the material, thereby enhancing its fitting stability with electronic components.

[0015] Preferably, the polypropylene is homopolypropylene, and the polymerization degree of the homopolypropylene is 5000 - 15000.

[0016] By adopting the above technical solution, the use of homopolypropylene endows the material with more stable chemical properties and higher heat resistance, enabling it to maintain good mechanical strength and dimensional stability in high-temperature environments. At the same time, the polymerization degree range of homopolypropylene is 5000 - 15000, and this specific range effectively balances the processing performance and physical properties of the material, ensuring both the fluidity of the material during thermoforming and avoiding the problem of too low melt strength caused by too high polymerization degree, thereby significantly improving the dimensional accuracy and molding quality of the heterogeneous multi-cavity electronic tray.

[0017] Preferably, the melt index of the low-density polyethylene under the test conditions of 230°C and 2.16 kg is 2.5 g / 10 min, the melt index of the linear low-density polyethylene under the test conditions of 190°C and 2.16 kg is 2 g / 10 min; the melt index of the high-density polyethylene under the test conditions of 230°C and 2.16 kg is 0.4 g / 10 min.

[0018] The melt index of low-density polyethylene is optimized to 2.5 g / 10 min, which can effectively improve the fluidity of the material, making it easier to fill the mold cavity during negative-pressure thermoforming, improving the forming efficiency, and reducing the probability of sagging at the same time. The melt index of linear low-density polyethylene is optimized to 2 g / 10 min, further enhancing the tear resistance and flexibility of the material, which helps to reduce the risk of cracking when forming complex structures. The melt index of high-density polyethylene is optimized to 0.4 g / 10 min, significantly improving the rigidity and heat resistance of the material, ensuring that large-scale heterogeneous multi-cavity electronic trays have reduced uneven shrinkage during the cooling process, and improving the dimensional accuracy and stability.

[0019] Secondly, the present application provides a method for preparing a polypropylene hydrocarbon negative-pressure thermoforming material, adopting the following technical solution: A method for preparing a polypropylene hydrocarbon negative-pressure thermoforming material, comprising the following preparation steps: S1. Mix polypropylene, low-density polyethylene, linear low-density polyethylene, and high-density polyethylene to obtain a mixture; S2. Extrude the mixture through a screw machine and press it into sheets to obtain a polypropylene hydrocarbon negative-pressure thermoforming material.

[0020] By adopting the above technical solution, after mixing polypropylene, low-density polyethylene, linear low-density polyethylene, and high-density polyethylene and extruding them through a screw machine, the melt strength of the material can be effectively improved, the sagging phenomenon during thermoforming can be reduced, thereby improving the thickness uniformity of the product and avoiding problems such as cracking or die penetration. At the same time, this preparation method has a simple process and is convenient to operate, which helps to improve production efficiency. And by precisely controlling the ratio and melt index of each component, a negative-pressure thermoforming material with more stable performance can be obtained, which is especially suitable for the preparation of large-scale heterogeneous multi-cavity electronic trays, ensuring that their dimensional accuracy and mechanical properties meet the usage requirements.

[0021] Preferably, the extrusion temperature is 205 - 225 °C.

[0022] By adopting the above technical solution, optimizing the extrusion temperature can effectively improve the post-shrinkage phenomenon of the polypropylene material, reduce the dimensional change after demolding, thereby improving the dimensional accuracy of the heterogeneous multi-cavity electronic tray and ensuring its good fit with electronic components. At the same time, this temperature range helps to improve the melt strength of the material, avoid sagging problems during thermoforming, ensure uniform tray thickness, and reduce the risks of cracking and die penetration.

[0023] To sum up, the present application has the following beneficial effects: 1. By compounding polypropylene with low-density polyethylene, linear low-density polyethylene, and high-density polyethylene, the melt strength of the material is significantly improved, effectively solving the problems of uneven thickness and cracking caused by insufficient melt strength of traditional polypropylene during thermoforming; 2. The reasonable combination of each component in the composite material can improve the post-shrinkage phenomenon of polypropylene, reduce the uneven shrinkage during the cooling process, thereby improving the dimensional accuracy of the prepared isomeric multi-cavity electronic tray and ensuring its good fit with electronic components; 3. The polyolefin negative pressure thermoforming material retains the excellent chemical corrosion resistance and high strength characteristics of polypropylene. At the same time, the mechanical properties are further enhanced by optimizing the formula, enabling the prepared tray to better resist the influence of external environmental factors and protect the safety of electronic components. Specific Embodiments Examples

[0024] Example 1 A polyolefin negative pressure thermoforming material is prepared by the following method: S1. Mix 150 g of polypropylene, 100 g of low-density polyethylene, 50 g of linear low-density polyethylene, and 40 g of high-density polyethylene to obtain a mixture; S2. Extrude the mixture through a screw extruder at an extrusion temperature of 205 °C and press it into sheets to obtain the polyolefin negative pressure thermoforming material.

[0025] The melt index of the low-density polyethylene under the test conditions of 230 °C and 2.16 kg is 2 g / 10 min; The melt index of the linear low-density polyethylene under the test conditions of 190 °C and 2.16 kg is 1 g / 10 min; The melt index of the high-density polyethylene under the test conditions of 230 °C and 2.16 kg is 0.2 g / 10 min; The polypropylene is irregular polypropylene with a degree of polymerization of 500.

[0026] Examples 2-3 are different from Example 1 in that the types, amounts, and parameters of the raw materials for preparing the polyolefin negative pressure thermoforming material are different. The specific differences are shown in Table 1: Table 1 Types, amounts, and parameters of raw materials for preparing the polyolefin negative pressure thermoforming material in Examples 1-3 Example 4 A polyolefin negative pressure thermoforming material. The difference between this example and Example 1 is that the polypropylene is syndiotactic polypropylene with a degree of polymerization of 1000.

[0027] Example 5 A polyolefin negative pressure thermoforming material. The difference between this example and Example 1 is that the polypropylene is syndiotactic polypropylene with a degree of polymerization of 5000.

[0028] Example 6 A negative pressure thermoforming material for polypropylene hydrocarbons. The difference between this example and Example 4 is that the amount of syndiotactic polypropylene used is 200 g, and the amount of low-density polyethylene used is 100 g.

[0029] Example 7 A negative pressure thermoforming material for polypropylene hydrocarbons. The difference between this example and Example 4 is that the amount of syndiotactic polypropylene used is 150 g, and the amount of low-density polyethylene used is 150 g.

[0030] Example 8 A negative pressure thermoforming material for polypropylene hydrocarbons. The difference between this example and Example 4 is that the amount of syndiotactic polypropylene used is 180 g, and the amount of high-density polyethylene used is 60 g.

[0031] Example 9 A negative pressure thermoforming material for polypropylene hydrocarbons. The difference between this example and Example 4 is that the amount of syndiotactic polypropylene used is 160 g, and the amount of high-density polyethylene used is 80 g.

[0032] Example 10 A negative pressure thermoforming material for polypropylene hydrocarbons. The difference between this example and Example 1 is that the polypropylene is homopolypropylene, and the melt flow rate of the homopolypropylene is 5000.

[0033] Example 11 A negative pressure thermoforming material for polypropylene hydrocarbons. The difference between this example and Example 1 is that the polypropylene is homopolypropylene, and the melt flow rate of the homopolypropylene is 15000.

[0034] Example 12 A negative pressure thermoforming material for polypropylene hydrocarbons. The difference between this example and Example 1 is that the amounts are 180 g of polypropylene, 10 g of low-density polyethylene, 80 g of linear low-density polyethylene, and 80 g of high-density polyethylene; The melt index of the low-density polyethylene under the test conditions of 230 °C and 2.16 kg is 2 g / 10 min; The melt index of the linear low-density polyethylene under the test conditions of 190 °C and 2.16 kg is 3 g / 10 min; The melt index of the high-density polyethylene under the test conditions of 230 °C and 2.16 kg is 0.3 g / 10 min; The polypropylene is syndiotactic polypropylene, and the degree of polymerization of the syndiotactic polypropylene is 35000.

[0035] Example 13 A polypropylene hydrocarbon negative pressure thermoforming material. The difference between this embodiment and Embodiment 1 is that the melt index of low-density polyethylene under the test conditions of 230 °C and 2.16 kg is 2.5 g / 10 min, and the melt index of linear low-density polyethylene under the test conditions of 190 °C and 2.16 kg is 2 g / 10 min; the melt index of high-density polyethylene under the test conditions of 230 °C and 2.16 kg is 0.4 g / 10 min.

[0036] Comparative example Comparative example 1 A polypropylene hydrocarbon negative pressure thermoforming material. The difference between this comparative example and Embodiment 1 is that the addition amount of low-density polyethylene is 0, and the amount of linear low-density polyethylene used is 150 g.

[0037] Comparative example 2 A polypropylene hydrocarbon negative pressure thermoforming material. The difference between this comparative example and Embodiment 1 is that the addition amount of linear low-density polyethylene is 0, and the amount of high-density polyethylene used is 90 g.

[0038] Comparative example 3 A polypropylene hydrocarbon negative pressure thermoforming material. The difference between this comparative example and Embodiment 1 is that the amount of low-density polyethylene used is 140 g, and the amount of high-density polyethylene used is 0 g.

[0039] Comparative example 4 A polypropylene hydrocarbon negative pressure thermoforming material. The difference between this comparative example and Embodiment 1 is that the melt index of low-density polyethylene under the test conditions of 230 °C and 2.16 kg is 3 g / 10 min.

[0040] Comparative example 5 A polypropylene hydrocarbon negative pressure thermoforming material. The difference between this comparative example and Embodiment 1 is that the melt index of high-density polyethylene under the test conditions of 230 °C and 2.16 kg is 0.1 g / 10 min.

[0041] Comparative example 6 A polypropylene hydrocarbon negative pressure thermoforming material. The difference between this comparative example and Embodiment 1 is that the amount of low-density polyethylene used is 40 g, the amount of linear low-density polyethylene used is 80 g, and the amount of high-density polyethylene used is 70 g.

[0042] Detection method / Test method Melt strength: The prepared polypropylene composite material was extruded through a die head with a diameter of 3 mm at 200 °C and 30 r / min using a PolyLab OS type torque rheometer, and its melt strength was tested with a Gottfert Rheotens.

[0043] Impact strength: Tested with reference to standard ISO 180 2000.

[0044] Tensile strength: Tested with reference to GB / T 1040.2 - 2006. The experimental data are shown in Table 2 as follows: Table 2 Experimental data of Examples 1 - 13 and Comparative Examples 1 - 6 From the experimental data of Example 1 and Comparative Examples 1 - 6, it can be seen that in this application, by jointly using specific polypropylene, low - density polyethylene, linear low - density polyethylene, and high - density polyethylene, the melt strength of the polypropylene hydrocarbon negative - pressure thermoforming material can be greatly improved, and problems such as uneven thickness and cracking caused by insufficient melt strength during the thermoforming process of polypropylene can be effectively solved. At the same time, the impact strength and tensile strength of the polypropylene hydrocarbon negative - pressure thermoforming material can also be improved, which is beneficial to enhancing the protective performance of the polypropylene hydrocarbon negative - pressure thermoforming material.

[0045] From the experimental data of Example 1 and Examples 4 - 5, it can be seen that by using specific syndiotactic polypropylene, it is beneficial to improve the melt strength, impact strength, and tensile strength of the polypropylene hydrocarbon negative - pressure thermoforming material, making it easier to prepare large - scale trays from the polypropylene hydrocarbon negative - pressure thermoforming material.

[0046] From the experimental data of Example 4 and Examples 6 - 7, it can be seen that by optimizing the dosages of syndiotactic polypropylene and low - density polyethylene, the melt strength, impact strength, and tensile strength of the polypropylene hydrocarbon negative - pressure thermoforming material are further improved.

[0047] From the experimental data of Example 4 and Examples 8 - 9, it can be seen that by optimizing the dosages of syndiotactic polypropylene and high - density polyethylene, the melt strength, impact strength, and tensile strength of the polypropylene hydrocarbon negative - pressure thermoforming material are further improved.

[0048] From the experimental data of Example 4 and Examples 10 - 11, it can be seen that by optimizing the use of homopolypropylene, the melt strength, impact strength, and tensile strength of the polypropylene hydrocarbon negative - pressure thermoforming material are further improved.

[0049] From the experimental data of Example 4 and Examples 12 - 13, it can be seen that optimizing the parameters of polypropylene, low - density polyethylene, linear low - density polyethylene, and high - density polyethylene is beneficial to further improving the melt strength, impact strength, and tensile strength of the polypropylene hydrocarbon negative - pressure thermoforming material.

[0050] The polypropylene hydrocarbon negative - pressure thermoforming materials of Example 1 and Comparative Examples 1 - 6 were made into sheets with a thickness of 1 mm, and then large - scale structurally - isomeric multi - cavity electronic trays were obtained through negative - pressure thermoforming. After processing, the structurally - isomeric multi - cavity electronic trays were visually observed. The experimental data are shown in Table 3 as follows: Table 3 Example 1 and Comparative Examples 1-6 From the experimental data of Example 1 and Comparative Examples 1-6, it can be seen that the polyolefin negative-pressure thermoforming material prepared in this application can well prepare a complete and good structurally isomeric multi-cavity electronic tray through the negative-pressure thermoplastic forming method.

[0051] This specific embodiment is only an explanation of this application, and it is not a limitation of this application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions according to needs, but as long as it is within the scope of the claims of this application, it is protected by the patent law.

Claims

1. A negative pressure thermoforming material for polypropylene hydrocarbons, characterized in that, Prepared from the following raw materials in parts by weight: 15 - 20 parts of polypropylene 10 - 15 parts of low - density polyethylene 5 - 10 parts of linear low - density polyethylene 4 - 8 parts of high - density polyethylene The melt index of the low - density polyethylene under the test conditions of 230°C and 2.16 kg is 2 - 2.5 g / 10min; The melt index of the linear low - density polyethylene under the test conditions of 190°C and 2.16 kg is 1 - 3 g / 10min; The melt index of the high - density polyethylene under the test conditions of 230°C and 2.16 kg is 0.2 - 0.5 g / 10min; The degree of polymerization of the polypropylene is 500 - 15000.

2. The polypropylene hydrocarbon negative pressure thermoforming material according to claim 1, characterized in that: The polypropylene is syndiotactic polypropylene, and the degree of polymerization of the syndiotactic polypropylene is 1000 - 5000.

3. The polypropylene hydrocarbon negative pressure thermoforming material according to claim 2, characterized in that: The weight ratio of the polypropylene to the low - density polyethylene is 1:(0.5 - 1).

4. The polypropylene hydrocarbon negative pressure thermoforming material according to claim 2, characterized in that: The weight ratio of the polypropylene to the high - density polyethylene is (3 - 2):

1.

5. The polypropylene hydrocarbon negative pressure thermoforming material according to claim 1, wherein: The polypropylene is homopolypropylene, and the degree of polymerization of the homopolypropylene is 5000 - 15000.

6. The polypropylene hydrocarbon negative pressure thermoforming material according to claim 1, characterized in that: Prepared from the following raw materials in parts by weight: 18 parts of polypropylene 10 parts of low - density polyethylene 8 parts of linear low - density polyethylene 8 parts of high - density polyethylene The melt index of the low - density polyethylene under the test conditions of 230°C and 2.16 kg is 2 g / 10min; The melt index of the linear low - density polyethylene under the test conditions of 190°C and 2.16 kg is 3 g / 10min; The melt index of the high - density polyethylene under the test conditions of 230°C and 2.16 kg is 0.3 g / 10min; The polypropylene is syndiotactic polypropylene, and the degree of polymerization of the syndiotactic polypropylene is 35000.

7. The polypropylene hydrocarbon negative-pressure thermoforming material according to claim 1, characterized in that: The melt index of the low - density polyethylene under the test conditions of 230°C and 2.16 kg is 2.5 g / 10min, the melt index of the linear low - density polyethylene under the test conditions of 190°C and 2.16 kg is 2 g / 10min; the melt index of the high - density polyethylene under the test conditions of 230°C and 2.16 kg is 0.4 g / 10min.

8. A preparation method of the polypropylene hydrocarbon negative-pressure thermoforming material according to any one of claims 1-7, characterized in that, Including the following preparation steps: S1. Mix the polypropylene, low - density polyethylene, linear low - density polyethylene and high - density polyethylene to obtain a mixture; S2. Extrude the mixture through a screw machine and press it into sheets to obtain a polypropylene hydrocarbon negative - pressure thermoforming material.

9. The preparation method of a polypropylene hydrocarbon negative-pressure thermoforming material according to claim 8, wherein: The extrusion temperature is 205 - 225°C.

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