Polypropylene composite material as well as preparation method and application thereof

Abstract

The invention discloses a polypropylene composite material as well as a preparation method and application thereof. The polypropylene composite material comprises the following components in parts by weight: 20-60 parts of polypropylene resin; 10 to 30 parts of polystyrene resin; 10 to 30 parts of a polypropylene-polystyrene grafted copolymer; and 1 to 10 parts of a maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer. The polypropylene composite material disclosed by the invention is based on a polypropylene and polystyrene composite system, and the polypropylene-polystyrene grafted copolymer and the maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer are introduced, so that the surface polarity of the material is remarkably improved while excellent light transmission is maintained; therefore, the characteristics of high light transmittance and high paint binding force are obtained. And an injection molded part made of the composite material can be directly sprayed or coated with mucilage glue only by a simple cleaning process, so that a complicated surface polarity pretreatment process is thoroughly omitted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a polypropylene composite material and a preparation method and application thereof. BACKGROUND

[0002] As a high cost-effective general-purpose plastic, polypropylene (PP) can significantly improve its mechanical and optical properties through modification, obtaining a material with high strength, high toughness and excellent transparency, which makes it have broad application prospects in the fields of automotive interior and exterior parts, electronic product housings, household appliance panels and other fields with high requirements for transparency and comprehensive performance. However, polypropylene is essentially a non-polar polymer, and the surface energy of high crystallinity transparent polypropylene designed for high light transmission is usually lower. This characteristic leads to poor compatibility of polypropylene with most polar polymers. In the application end, in order to meet the diversified modeling design and functional requirements (such as coloring, improving texture, and increasing functionality), the surface of the polypropylene parts for vehicles usually needs to be sprayed. The problem is that the paint used for spraying (whether it is a polar solvent type or a water-based system) is difficult to effectively wet and spread on the low surface energy polypropylene surface, and direct spraying is prone to the problem of insufficient adhesion, which manifests as paint peeling, paint film peeling and other defects.

[0003] Currently, in order to improve the paint adhesion of polypropylene, the industry generally relies on a surface treatment process before coating: first, use a solvent to clean and remove surface oil and dust, and then perform surface oxidation treatment through flame treatment, corona discharge or gas plasma, etc. to increase the surface polarity group, thereby increasing the surface energy of the material and enhancing the bonding force with the paint. Although these surface treatment technologies are effective to some extent, they have a complicated process flow, a long processing time, and high equipment investment and operating costs. For parts that need to maintain high light transmittance, additional processing may also introduce the risk of surface defects or optical inhomogeneity.

[0004] Therefore, how to break through the limitations of the prior art and develop a polypropylene composite material that itself has high light transmittance and excellent paint adhesion, fundamentally avoiding the complicated surface treatment process before coating, has become a key technical problem to be solved in the industry. SUMMARY

[0005] In order to overcome the deficiencies of the prior art, the purpose of the present application is to provide a polypropylene composite material with high light transmittance and high paint adhesion.

[0006] The present application is realized by the following technical solutions: A polypropylene composite material, by weight, comprising the following components: 20-60 parts of polypropylene resin; 10-30 parts of polystyrene resin; polypropylene-polyphenylstyrene graft copolymer 10-30 parts; maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer 1-10 parts.

[0007] The weight fraction of the polypropylene resin can be 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts or 60 parts, and specific point values between the above point values.

[0008] Preferably, the polypropylene resin is selected from homopolymer polypropylene.

[0009] Preferably, the polypropylene resin has a melt index of 1-120 g / 10 min (which can be 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110 or 120 g / 10 min, and specific point values between the above point values) at 230℃, 2.16 kg, more preferably 10-80 g / 10 min.

[0010] The mass content of the polypropylene resin in the polypropylene composite material of the present application is not less than 35%.

[0011] The weight fraction of the polystyrene resin can be 10 parts, 15 parts, 20 parts, 25 parts or 30 parts, and specific point values between the above point values.

[0012] Preferably, the polystyrene resin is selected from general-purpose polystyrene.

[0013] The weight fraction of the polypropylene-polyphenylstyrene graft copolymer can be 10 parts, 15 parts, 20 parts, 25 parts or 30 parts, and specific point values between the above point values.

[0014] The polypropylene-polyphenylstyrene graft copolymer of the present application is a polypropylene graft polystyrene copolymer with polypropylene as the main chain and polystyrene as the side chain.

[0015] The polypropylene-polyphenylstyrene graft copolymer of the present application can be obtained commercially or by self-preparation. The polypropylene-polyphenylstyrene graft copolymer of the present application can be prepared by free radical reaction of polypropylene resin and styrene monomer.

[0016] The application provides a method for preparing a polypropylene-polystyrene graft copolymer by a free radical reaction method, comprising the following steps: dissolving a free radical initiator into styrene monomers (the amount of the free radical initiator is 0.1%-0.5% of the mass of the styrene monomers) to obtain a styrene monomer solution containing the free radical initiator; injecting the styrene monomer solution and polypropylene into a full-sealing reaction type double-screw extruder through a metering pump at a mass ratio of 3:7-7:3; and generating a graft copolymer with a polypropylene backbone and polystyrene side chains through graft copolymerization of the styrene monomers and the polypropylene matrix under the action of the free radical initiator; the length-diameter ratio of the screw of the extruder is 40:1-56:1; the barrel temperature of the extruder is set to be between 50-230 DEG C from the feeding port to the end of the port; the free radical initiator is preferably at least one of azo compound type free radical initiators and peroxide type free radical initiators; the azo compound type free radical initiators include azobisisobutyronitrile, azobisisoheptyl nitrile and the like; and the peroxide type free radical initiators include benzoyl peroxide (BPO), methyl ethyl ketone peroxide (MEKP), di-tert-butyl peroxide (DTBP) and the like.

[0017] The weight fraction of the maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer can be 1 part, 2 parts, 4 parts, 6 parts, 8 parts or 10 parts, and specific point values between the above point values.

[0018] Preferably, the styrene mass content of the maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer is 20%-50% (can be 20%, 25%, 30%, 35%, 40%, 45% or 50%, and specific point values between the above point values), preferably 35%-45%. The styrene content is tested by a thermogravimetric analysis method, and the content is calculated by the mass loss of the corresponding styrene decomposition stage in the weight loss curve.

[0019] Preferably, the maleic anhydride grafting rate of the maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer is 1.0%-2.0%. The maleic anhydride grafting rate is tested by a chemical titration method, and the grafting rate is calculated by titration through the chemical reaction of the characteristic groups of grafting.

[0020] Preferably, the mass ratio of the polypropylene-polystyrene graft copolymer to the maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer is (1.5-10):1, preferably (2.5-6):1.

[0021] As a preferred scheme, the polypropylene composite material of the present application further comprises 0-1 parts of a nucleating agent (which can be 0.01 parts, 0.05 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts or 1 part, and specific point values between the above point values) by weight; preferably 0.05-1 parts of the nucleating agent; more preferably 0.2-0.8 parts of the nucleating agent; the nucleating agent is selected from at least one of sorbitol nucleating agent and aromatic carboxylate nucleating agent.

[0022] Preferably, the sorbitol nucleating agent is selected from sorbitol acetal nucleating agent; and the aromatic carboxylate nucleating agent is selected from at least one of aluminum benzoate, aluminum p-t-butylbenzoate and sodium bicycloheptane dicarboxylate.

[0023] The present application has found that, in the polypropylene composite material system of the present application, by adding a specific nucleating agent, the light transmittance of the material can be improved, and the surface tension of the material can be further increased, and the adhesion between the material surface and paint can be improved.

[0024] According to the performance requirements of the material, the polypropylene composite material of the present application further comprises 0.1-2 parts of an auxiliary agent (which can be 0.1 parts, 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1 parts, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts or 2 parts, and specific point values between the above point values) by weight; the auxiliary agent comprises at least one of a heat stabilizer and a lubricant; the heat stabilizer is selected from at least one of a phenolic heat stabilizer, an amine heat stabilizer, a phosphite heat stabilizer, a semi-hindered phenolic heat stabilizer, a complex of acryloyl functional group and thioester heat stabilizer, and a calixarene heat stabilizer; and the lubricant is selected from at least one of a low molecular ester lubricant, a metal soap lubricant, a stearic acid complex ester lubricant and an amide lubricant. The present application does not have special requirements for the types and sources of the heat stabilizer and the lubricant, and the skilled person can select the types of the heat stabilizer and the lubricant according to the actual situation.

[0025] The present application also provides a preparation method of the above-mentioned polypropylene composite material, which comprises the following steps: uniformly mixing the components according to the ratio, and then performing melt blending extrusion granulation on a double-screw extruder to prepare the polypropylene composite material, wherein the length-diameter ratio of the double-screw extruder is 40:1-56:1, the processing temperature is 120-220℃, and the screw rotation speed is 400-600 rpm.

[0026] The present application also provides the application of the above-mentioned polypropylene composite material in automobile interior and exterior decoration parts. Specifically, the polypropylene composite material is suitable for paint spraying parts and adhesive coating parts.

[0027] The present application has the following beneficial effects: The polypropylene composite material of the present application is based on a polypropylene-polystyrene composite system, by introducing a polypropylene-polystyrene graft copolymer and a maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer, the material surface polarity is significantly improved while maintaining excellent light transmittance, thereby obtaining the characteristics of high light transmittance and high paint adhesion. The injection molded parts made therefrom only need to be subjected to a simple cleaning process to directly perform spraying or adhesive coating, completely eliminating the complex surface polarity pretreatment process. The polypropylene composite material of the present application not only greatly saves the preparation time and economic cost of the sprayed / packaged parts, but also expands the degree of freedom of design, especially suitable for large-scale production of automotive light-transmitting polypropylene parts, and has a wide application prospect in the field of automotive interior and exterior decoration. DETAILED DESCRIPTION

[0028] The present application will be described in detail below in conjunction with specific examples. The following examples will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be pointed out that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made. These all belong to the protection scope of the present application. If the reagents or instruments used are not specified by the manufacturer, they are considered to be conventional products that can be purchased on the market.

[0029] The raw materials used in the examples and comparative examples of the present application are described as follows, but are not limited to these materials: Polypropylene resin 1: homopolymer polypropylene, melt index under the condition of 230℃, 2.16kg is 10g / 10min, PPKF-BM301C, Ningbo Jinfa; Polypropylene resin 2: homopolymer polypropylene, melt index under the condition of 230℃, 2.16kg is 30g / 10min, PPH-Y26, Zhenhai Refinery; Polystyrene resin: general-purpose polystyrene, GPPS-QG7535, Qilu Chemical; Polypropylene-polystyrene graft copolymer 1: self-made; the preparation method is as follows: dissolve the free radical initiator dibenzoyl peroxide BPO in styrene monomer (the amount of free radical initiator is 0.5% of the mass of styrene monomer) to obtain a styrene monomer solution containing a free radical initiator, inject the styrene monomer solution and polypropylene into a full-sealing reaction type double-screw extruder through a metering pump at a mass ratio of 1:1, the styrene monomer and the polypropylene matrix undergo graft copolymerization under the action of the free radical initiator to generate a polypropylene-polystyrene graft copolymer with polypropylene as the main chain and polystyrene as the side chain; wherein the length-diameter ratio of the extruder screw is 48:1, and the screw temperature of the extruder is set from the feeding port to the end of the port as follows: mixed section temperature 60℃, initiation polymerization section 80℃, melting section temperature 180℃, and extrusion section temperature 200℃.

[0030] Polypropylene-polystyrene graft copolymer 2: self-made; the preparation method is as follows: the free radical initiator dibenzoyl peroxide BPO is dissolved in styrene monomer (the amount of the free radical initiator is 0.5% of the mass of the styrene monomer) to obtain a styrene monomer solution containing a free radical initiator, the styrene monomer solution and polypropylene are injected into a full-sealing reaction type double-screw extruder through a metering pump at a mass ratio of 3:7, and the styrene monomer and the polypropylene matrix undergo graft copolymerization under the action of the free radical initiator to generate a polypropylene-polystyrene graft copolymer with polypropylene as the main chain and polystyrene as the side chain; wherein the length-diameter ratio of the extruder screw is 48:1, and the screw cylinder temperature of the extruder is set to be 60°C for the mixing section, 80°C for the initiation polymerization section, 180°C for the melting section, and 200°C for the extrusion section from the feeding port to the end of the port.

[0031] Maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer 1: styrene content 40%, maleic anhydride grafting rate 1.1%, RP6670, USA Kraton; Maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer 2: styrene content 30%, maleic anhydride grafting rate 1.7%, FG1901GT, USA Kraton; Maleic anhydride grafted polypropylene: ADMER AT3494T, Mitsui Chemical; Nucleating agent 1: sorbitol acetal nucleating agent, MILLAD NX8000K, Milliken; Nucleating agent 2: aluminum benzoate, A1-PTBBA, Japan Diayu; Nucleating agent 3: substituted aryl phosphate salt nucleating agent, TMP-6, Shanxi Chemical; Auxiliary 1: heat stabilizer, antioxidant 1010 and antioxidant 168 compounded at a mass ratio of 1:2, commercially available; the same heat stabilizer is used in each parallel experiment; Auxiliary 2: lubricant, zinc stearate, commercially available; the same lubricant is used in each parallel experiment.

[0032] Preparation method of the polypropylene composite material of the examples and comparative examples: According to the proportion, the components are uniformly mixed, and then melt blending extrusion granulation is carried out on a double-screw extruder, wherein the length-diameter ratio of the double-screw extruder is 48:1, the processing temperature is set to be 120°C for the mixing section, 180°C for the melting section, and 200°C for the extrusion section, and the screw rotation speed is 500 rpm, so as to prepare the polypropylene composite material.

[0033] Related performance test methods: (1) Light transmittance: The polypropylene composite was injection molded into a 100 mm*100 mm*3 mm sample, and the light transmittance of the sample was measured according to the standard method of GB 2410-2008.

[0034] (2) Surface polarity: The polarity of the material was characterized by the dyne value according to the standard method of GB / T 14216-2008. The greater the dyne value, the better the polarity. In order to meet the crosshatch test, the dyne value was required to be above 38.

[0035] (3) Crosshatch test: After the surface of the sample was cleaned with deionized water, primer was sprayed, then color paint and varnish were sprayed, and finally the paint was cured by baking at 85°C for 45 min; the adhesion of the material to the paint was determined according to the standard method of ISO 2409-2007. Ten horizontal and ten vertical straight lines were drawn on the coating using a crosshatch knife, forming 100 small squares (about 1 mm*1 mm each); the standard adhesive tape (3M 600 adhesive tape) was tightly attached to the gridded area, and pressure was applied with a rubber eraser to enhance adhesion, then the tape was quickly torn off in the vertical direction (90°), and this operation was repeated twice. According to the area and distribution of the coating peeling off the gridded area, the adhesion grade was determined according to the standard.

[0036] Adhesion grade evaluation standard: no peeling off is rated as 0, peeling off area <5% is rated as 1, 5%≤peeling off area <15% is rated as 2, 15%≤peeling off area <35% is rated as 3, 35%≤peeling off area <65% is rated as 4, and peeling off area ≥65% is rated as 5.

[0037] Table 1: Component allocation ratio (by weight) and related performance test results of Examples 1-11 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Polypropylene resin 1 55 30 55 55 55 55 55 55 55 Polypropylene resin 2 45 60 Polystyrene resin 15 25 20 10 15 15 15 15 15 15 15 Polypropylene-polystyrene graft copolymer 1 25 15 20 30 25 25 25 25 20 27 Polypropylene-polystyrene graft copolymer 2 25 Maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer 1 5 10 8 3 5 5 5 10 3 5 Maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer 2 5 Nucleating agent 1 0.5 0.2 0.5 1 0.5 0.5 0.5 0.5 Nucleating agent 2 0.8 Nucleating agent 3 0.5 Auxiliary 1 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Auxiliary 2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Transmittance / % 82 84 81 75 82 79 75 76 80 78 78 Dyne value / dyn / cm 40 42 38 38 38 39 38 38 40 38 38 Haze test rating 0 rank 0 rank 0 rank 0 rank 0 rank 0 rank 0 rank 0 rank 0 rank 0 rank 0 rank Table 2: Component allocation ratio (by weight) and related performance test results of Comparative Examples 1-5 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Polypropylene resin 1 55 55 55 55 55 Polystyrene resin 15 15 15 15 Polypropylene-polystyrene graft copolymer 1 5 25 25 25 Maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer 1 5 5 5 Maleic anhydride grafted polypropylene 5 Nucleating agent 1 0.5 0.5 0.5 0.5 0.5 Auxiliary 1 0.2 0.2 0.2 0.2 0.2 Auxiliary 2 0.2 0.2 0.2 0.2 0.2 Transmittance / % 68 70 67 67 69 Dyne value / dyn / cm 33 34 30 32 29 Haze test rating 2 rank 3 rank 3 rank 2 rank 3 rank 3 rank From the above example and comparative example results, it can be seen that based on the polypropylene and polystyrene composite system, by introducing polypropylene-polystyrene graft copolymer and maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer synergistic effect, the material surface polarity is significantly improved while maintaining excellent light transmittance, thereby obtaining a polypropylene composite material with a light transmittance ≥75% and a dyne value ≥38, and a high paint adhesion property.

[0038] From the comparison of Example 1 and Examples 7 / 8, it can be seen that the preferred addition of a specific nucleating agent in the present application is beneficial to improving the light transmittance of the material, and can further increase the dyne value and further improve the adhesion of the material surface to the paint.

[0039] The amount of polypropylene-poly-styrene graft copolymer of Comparative Example 1 is too small or not added, the light transmittance of the material is reduced, the dynes value is decreased, and the binding force with paint is reduced.

[0040] Comparative Example 3 does not add polystyrene resin, the light transmittance of the material is reduced, the dynes value is decreased, and the binding force with paint is reduced.

[0041] Comparative Example 4, compared with Example 1, uses maleic anhydride grafted polypropylene instead of maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer, and there is no obvious improvement in the light transmittance and polarity of the material.

[0042] Comparative Example 5 does not add maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer, the light transmittance of the material is reduced, the dynes value is decreased, and the binding force with paint is reduced.

[0043] It should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A polypropylene composite, characterized in that, By weight parts, including the following components: Polypropylene resin 20-60 parts; Polystyrene resin 10-30 parts; Polypropylene-polystyrene graft copolymer 10-30 parts; Maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer 1-10 parts.

2. The polypropylene composite of claim 1, wherein, The polypropylene resin is selected from homopolymer polypropylene; the melt index of the polypropylene resin under the condition of 230℃, 2.16kg is 1-120g / 10min, preferably 10-80g / 10min.

3. The polypropylene composite of claim 1, wherein, The polystyrene resin is selected from general-purpose polystyrene.

4. The polypropylene composite of claim 1, wherein, The polypropylene-polystyrene graft copolymer is a polypropylene graft polystyrene copolymer with polypropylene as the main chain and polystyrene as the side chain.

5. The polypropylene composite of claim 1, wherein, The mass content of styrene of the maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer is 20%-50%, preferably 35%-45%.

6. The polypropylene composite of claim 1, wherein, The mass ratio of the polypropylene-polystyrene graft copolymer to the maleic anhydride grafted styrene-ethylene / butylene-styrene block copolymer is (1.5-10):1, preferably (2.5-6):

1.

7. The polypropylene composite of claim 1, wherein, By weight parts, it also includes 0-1 parts of a nucleating agent; preferably 0.05-1 parts of a nucleating agent, more preferably 0.2-0.8 parts of a nucleating agent; the nucleating agent is selected from at least one of sorbitol nucleating agent, aromatic carboxylate nucleating agent; the sorbitol nucleating agent is selected from sorbitol acetal nucleating agent; the aromatic carboxylate nucleating agent is selected from at least one of aluminum benzoate, aluminum p-tert-butyl benzoate, sodium bicycloheptane dicarboxylate.

8. The polypropylene composite of claim 1, wherein, By weight parts, it also includes 0.1-2 parts of an auxiliary agent; the auxiliary agent includes at least one of a heat stabilizer, a lubricant; the heat stabilizer is selected from at least one of phenolic heat stabilizer, amine heat stabilizer, phosphite heat stabilizer, semi-hindered phenolic heat stabilizer, acryloyl functional group and thioester complex heat stabilizer, calixarene heat stabilizer; the lubricant is selected from at least one of stearate lubricant, low molecular ester lubricant, metal soap lubricant, stearic acid complex ester lubricant, amide lubricant.

9. Process for the production of a polypropylene composite material according to any one of claims 1 to 8, characterized in that, The following steps are included: according to the ratio, uniformly mix each component, then melt blend extrusion granulation on a twin-screw extruder to prepare a polypropylene composite material, wherein the length-diameter ratio of the twin-screw extruder is 40:1-56:1, and the processing temperature is 180℃-220℃.

10. The polypropylene composite material of any one of claims 1-8 for use in automotive interior and exterior trim parts.