A polypropylene material with a low linear expansion coefficient and its preparation method

Abstract

This invention discloses a polypropylene material with a low linear expansion coefficient, prepared from the following components in parts by weight: 74-80 parts polypropylene resin, 5 parts compatibilizer, 10-15 parts mineral filler, 0.2-0.4 parts composite antioxidant, and 0.2-0.3 parts nucleating agent; wherein the compatibilizer is a compound of polypropylene grafted with maleic anhydride and ethylene-methyl acrylate copolymer. This invention selects polypropylene grafted with maleic anhydride (PP-MAH) and ethylene-methyl acrylate copolymer (EMA) as compatibilizers and controls their ratio to obtain a polypropylene material with a low linear expansion coefficient. This material has both a low linear expansion coefficient and a low density, with a density of 1.02 g / cm³. 3 At that time, the linear expansion coefficient can reach 60*10. ‑6 M / (M*K).

Description

Technical Field

[0001] This invention relates to the field of polymer materials, specifically to a polypropylene material with a low linear expansion coefficient and its preparation method. Background Technology

[0002] Polypropylene resin possesses excellent flexural strength and electrical insulation properties. In automotive applications, modified polypropylene composites are widely used in both passenger and commercial vehicles. However, due to the high dimensional shrinkage rate (1.4-1.6%) of polypropylene resin, polypropylene products are often unsuitable for precision assembly during production and use. Furthermore, under high and low temperature operating environments, the assembly gap dimensions change significantly, indicating an excessively large coefficient of linear expansion. Therefore, modifying polypropylene to have a low coefficient of linear expansion is of practical significance.

[0003] Currently, some research has been conducted on existing polypropylene materials with low linear expansion coefficients. For example, Chinese patent CN113024953A discloses a modified polypropylene material with low shrinkage and low linear expansion coefficient and its preparation method. The raw materials mainly include polypropylene, carboxylated multi-walled carbon nanotubes, furfuryl-amino monomers, catalysts, toughening agents, antioxidants, and fillers. This invention first uses furfuryl-amino monomers and carboxylated multi-walled carbon nanotubes to prepare modified carboxylated multi-walled carbon nanotubes under the action of a catalyst. Then, the modified carboxylated multi-walled carbon nanotubes are added to polypropylene to obtain a modified polypropylene material with low shrinkage and low linear expansion coefficient. The composition of this invention does not affect processing and molding, can prevent the aggregation of carbon nanotubes, improves mechanical properties, and has permanent antistatic properties. It can be applied to parts for automobiles, home appliances, and electronic products with high requirements for dimensional stability. Chinese Patent CN 102924806 A discloses a low linear expansion coefficient polypropylene composite for automobile bumpers and its preparation method. The low shrinkage rate polypropylene composite for automobile bumpers is characterized by being composed of 40-65% polypropylene, 0-2% heat stabilizer, 0-2% processing aid, 20-25% toughening agent, 0-6% compatibilizer, 5-10% ultrafine talc powder, and 10-15% chopped flat glass fiber by weight. However, currently published literature reports that the filler content is generally not less than 25%, resulting in high density of polypropylene composite materials and heavy molded products. Summary of the Invention

[0004] In view of this, the present invention provides a polypropylene material with a low linear expansion coefficient and a method for preparing the same, in order to solve the problems mentioned in the background art. The material provided by the present invention has high rigidity, high heat resistance, high dimensional stability, high impact resistance, and a low linear expansion coefficient, which meets the requirements of automotive material development.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention discloses a polypropylene material with a low linear expansion coefficient, prepared from the following components in parts by weight:

[0007]

[0008] The compatibilizer is composed of polypropylene grafted with maleic anhydride and ethylene-methyl acrylate copolymer.

[0009] As a further aspect of the present invention, the melt index of the polypropylene resin is 25-30 g / 10 min.

[0010] As a further aspect of the present invention: the filling mineral is basic magnesium sulfate whiskers with a diameter of 0.7 to 1.2 μm and an aspect ratio of 60 to 84.

[0011] As a further aspect of the present invention, the mass ratio of the polypropylene grafted with maleic anhydride and the ethylene-methyl acrylate copolymer is 0.25 to 4.

[0012] As a further aspect of the present invention: the composite antioxidant is composed of antioxidant 1010 and antioxidant 168 mixed in a weight ratio of (0.8 to 1.2):1.

[0013] As a further aspect of the present invention: the nucleating agent is an α-crystal nucleating agent.

[0014] Another aspect of the present invention discloses a method for preparing a polypropylene material with a low linear expansion coefficient as described in any of the preceding claims, comprising the following steps:

[0015] Weigh each component according to the weight and mix them. Then add the mixture to the side feed port of the twin-screw extruder. After melting, extrusion and granulation, a polypropylene material with a low linear expansion coefficient is obtained.

[0016] The twin-screw extruder has a temperature range of 150℃ to 210℃ in each zone, a die temperature range of 190℃ to 215℃, a screw speed range of 200rpm to 400rpm, three sets of ZME-type kneading blocks on the shearing end of the screw, and a set of reverse kneading blocks on the homogenizing end.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. This invention selects polypropylene grafted with maleic anhydride (PP-MAH) and ethylene-methyl acrylate copolymer (EMA) as compatibilizers, and controls their ratio to obtain a polypropylene material with a low linear expansion coefficient. This material has both a low linear expansion coefficient and a low density, with a density of 1.02 g / cm³. 3 At that time, the linear expansion coefficient can reach 60*10. -6M / (M*K).

[0019] 2. This invention discloses a method for preparing polypropylene material with a low linear expansion coefficient. The screw assembly is specialized, the process is relatively simple, and the equipment used, except for the specialized screw components, are all commonly used polymer processing equipment, without increasing additional costs and facilitating industrial production. This invention employs a side-feeding port, combined with a special screw design, to prevent whiskers from being crushed by the screw shearing process and to avoid disrupting the overall length-to-diameter ratio of the whiskers, thereby improving good mechanical properties and the linear expansion coefficient. Detailed Implementation

[0020] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0022] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0023] The polypropylene resin, with a molecular weight of 28 g / min, was selected from SK Corporation.

[0024] Polypropylene grafted with maleic anhydride PP-MAH, KT-1, with a grafting rate of approximately 2-3%, is sourced from Shenyang Ketong Plastics Co., Ltd.

[0025] Ethylene-methyl acrylate copolymer EMA, 2022, from DuPont.

[0026] The compound antioxidant is composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1. Antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]) and tris(2,4-di-tert-butylphenyl) phosphite (168) are both selected from BASF.

[0027] Nucleating agent, α-crystal nucleating agent, brand name NA-11, selected from ADK Company.

[0028] Filler mineral, basic magnesium sulfate whiskers, grade WS-3D, manufactured by Yingkou Kangru Technology Co., Ltd.

[0029] All materials are commercially available, commonly used products.

[0030] It is understood that the above-mentioned raw materials and reagents are merely examples of some specific embodiments of the present invention, making the technical solution of the present invention clearer, and do not mean that the present invention can only use the above-mentioned reagents. The specific scope shall be determined by the claims. In addition, unless otherwise specified, "parts" in the examples and comparative examples refer to parts by weight.

[0031] Any range described in this invention includes the endpoint, any value between the endpoints, and any subrange consisting of the endpoint or any value between the endpoints.

[0032] Examples 1-8 and Comparative Examples 1-4 were carried out according to the following steps:

[0033] Weigh each component according to the proportions in Table 1. After mixing all components, to ensure stable feeding of the mixture containing whiskers, feed is not made through the main feed port of the horizontal twin-screw extruder, but through the side feed port for melt extrusion granulation. The process parameters of the horizontal twin-screw extruder are as follows: Zone 1 temperature 170℃, Zone 2 temperature 175℃, Zone 3 temperature 180℃, Zone 4 temperature 185℃, Zone 5 temperature 200℃, Zone 6 temperature 200℃, Zone 7 temperature 205℃, Zone 8 temperature 210℃, Die temperature 210℃, and Screw speed 250 rpm. The screw shape of the parallel twin-screw extruder is a single-threaded screw; the ratio of screw length L to diameter D, L / D, is 40; the shearing end of the screw is equipped with three sets of ZME-type kneading blocks, and the homogenizing end is equipped with one set of reverse kneading blocks.

[0034] Comparative Example 5 was carried out according to the following steps:

[0035] Weigh each component according to the proportions in Table 1. After mixing all components, feed them through the side feed port, not the main feed port, of the horizontal twin-screw extruder for melt extrusion granulation. The process parameters of the horizontal twin-screw extruder are as follows: Zone 1 temperature 170℃, Zone 2 temperature 175℃, Zone 3 temperature 180℃, Zone 4 temperature 185℃, Zone 5 temperature 200℃, Zone 6 temperature 200℃, Zone 7 temperature 205℃, Zone 8 temperature 210℃, Die temperature 210℃, and Screw speed 250 rpm. The screw of the parallel twin-screw extruder has a single-threaded shape; the ratio of screw length L to diameter D, L / D, is 40; the shearing end of the screw is equipped with two sets of kneading blocks, and the homogenizing end is equipped with one set of reverse kneading blocks.

[0036] Table 1

[0037]

[0038]

[0039] The polypropylene materials prepared in the above examples and comparative examples were subjected to the following performance tests:

[0040] Linear expansion coefficient: tested according to ISO 11359-2 standard, temperature range -30℃~80℃, test direction is longitudinal;

[0041] Impact performance: -30℃, tested according to GB / T1843 standard;

[0042] Density: 23℃, tested according to GB / T1033.1 standard;

[0043] The performance test results are shown in Table 2.

[0044] Table 2

[0045]

[0046] Examples 1-4 describe polypropylene materials prepared by adjusting the compatibilizer ratio with a fixed mineral filler content of 15 parts. Table 2 shows that the compatibilizer formulation significantly improves the linear expansion coefficient of the polypropylene material, while also enhancing its low-temperature impact resistance. Furthermore, when the compatibilizer ratio of EMA / PP-MAH is (2-3):(3-2), both the linear expansion coefficient and low-temperature impact resistance of the polypropylene material are significantly improved. This is because the methyl acrylate in EMA is highly compatible with basic magnesium sulfate whiskers, and its elasticity is not affected even with the addition of more than 50% filler. It also contains vinyl groups that are compatible with all polyolefin resins. PP-MAH contains maleic anhydride, a polar group, which increases the polarity of the polypropylene resin, further enhancing its compatibilizing effect. Examples 5-8 describe polypropylene materials with a low linear expansion coefficient prepared by adjusting the compatibilizer ratio with a fixed mineral filler content of 10 parts. Table 2 shows that the compatibilizer formulation significantly improves the linear expansion coefficient of the polypropylene material, while also enhancing its low-temperature impact resistance.

[0047] Compared to Example 2, the ratio range of the two compatibilizers in Comparative Examples 1-4 was either larger or smaller. The linear expansion coefficient of the material was greater than that of Example 2, and the low-temperature impact strength was lower than that of Example 2. This is because the compounding of the two compatibilizers requires a certain ratio range to be effective. The thread design of Comparative Example 5 is different from that of Example 2. The linear expansion coefficient of Comparative Example 5 is significantly higher than that of Example 2, and its low-temperature impact performance is also significantly lower than that of Example 2. This is because Comparative Example 5 has a conventional thread structure design, in which the whiskers are crushed by the screw shearing, and the overall aspect ratio of the whiskers is destroyed. In contrast, the three sets of ZME-type kneading blocks at the shearing end of Example 2 can better maintain the overall aspect ratio of the whiskers.

[0048] In summary, this invention, by employing specific compatibilizers and a dedicated thread design, and by controlling the appropriate ratio between the compatibilizers, prepares a polypropylene material with a low linear expansion coefficient. This material exhibits both low density and a good low linear expansion coefficient, as well as excellent low-temperature impact performance.

[0049] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0050] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A polypropylene material with a low linear expansion coefficient, characterized in that, It is prepared from the following components in parts by weight: 74-80 parts of polypropylene resin 5 parts compatibilizer 10-15 parts of filling minerals Compound antioxidant 0.2~0.4 parts, Nucleating agent 0.2~0.3 parts; The compatibilizer is composed of polypropylene grafted with maleic anhydride and ethylene-methyl acrylate copolymer in a mass ratio of 0.25 to 4. The filling mineral is basic magnesium sulfate whiskers; The preparation method of the polypropylene material with low linear expansion coefficient is as follows: Weigh each component according to the weight and mix them. Then add the mixture to the side feed port of the twin-screw extruder. After melting, extrusion and granulation, a polypropylene material with a low linear expansion coefficient is obtained. The twin-screw extruder has a zone temperature of 150℃~210℃, a die temperature of 190℃~215℃, a screw speed of 200rpm~400rpm, three sets of ZME-type kneading blocks on the screw shearing end, and a set of reverse kneading blocks on the homogenizing end.

2. The polypropylene material with a low linear expansion coefficient according to claim 1, characterized in that, The melt flow index of the polypropylene resin is 25-30 g / 10 min.

3. The polypropylene material with a low linear expansion coefficient according to claim 1, characterized in that, The basic magnesium sulfate whiskers have a diameter of 0.7–1.2 μm and an aspect ratio of 60–84.

4. The polypropylene material with a low linear expansion coefficient according to claim 1, characterized in that, The composite antioxidant is composed of antioxidant 1010 and antioxidant 168 mixed in a weight ratio of (0.8~1.2):

1.

5. The polypropylene material with a low linear expansion coefficient according to claim 1, characterized in that, The nucleating agent is an α-crystal nucleating agent.

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