Sprayable polypropylene composition, preparation method thereof and sprayed part

Abstract

The invention provides a sprayable polypropylene composition, a preparation method thereof and a spraying piece. The sprayable polypropylene composition comprises the following components in percentage by weight: 23-81.6% of linear homo-polypropylene or co-polypropylene, 8-15% of atactic polypropylene, 10-30% of polyolefin elastomer, 0-30% of talcum powder, 0.2-1% of heat stabilizer mixture and 0.2-1% of black master batch. The polypropylene composite material obtained by adopting the technical scheme has the characteristics of being easy to spray, free of flame treatment and excellent in sprayed paint adhesive force. According to the polypropylene composite material disclosed by the invention, linear homo-polypropylene or co-polypropylene and atactic polypropylene are used as base materials, and meanwhile, the talcum powder and the heat stabilizer are cooperated to interact, so that the polypropylene composite material is endowed with high strength and high heat resistance, and the production requirements of automobile part spraying paint are met.

Description

Technical Field

[0001] The invention relates to a sprayable polypropylene composition and a preparation method thereof and a spray-coated part. Background Art

[0002] PP (polypropylene) can obtain materials with different properties through modification methods such as toughening, filling, strengthening, and blending. Because of its low cost and excellent comprehensive performance, modified PP has been widely used in automobile interior decoration, especially the raw materials used for injection molding of automobile interior decoration parts are mainly modified polypropylene materials. With polypropylene as the interior material, the polypropylene decorative parts after paint spraying have good appearance and can produce beautiful visual effects and touch. Since polypropylene material is a non-polar material with low surface energy, it has poor compatibility with most polymers, is not easy to infiltrate, bond and print, has poor coating performance, and has low bonding strength with paint. In order to improve the paint adhesion of polypropylene, it is usually surface treated before painting, and the surface polar groups are increased by surface oxidation treatment with flame, corona discharge or gas plasma, etc., to enhance the adhesion of the coating, but this method has complicated process, high production cost, and potential safety hazards. Therefore, it is necessary to develop a sprayable polypropylene composition and sprayed parts thereof with simple spraying process and low manufacturing cost. Summary of the invention

[0003] The problem to be solved by the present invention is to provide a polypropylene material that can be used for spraying interior paint, the polypropylene material has excellent mechanical properties, and can avoid the flame treatment or corona treatment required in the spraying process, so as to produce low-cost parts with high paint adhesion.

[0004] The purpose of the present invention can be achieved through the following technical solutions.

[0005] A sprayable polypropylene composition comprises the following raw materials in percentage by weight:

[0006] Linear homopolypropylene or copolymer polypropylene 23-81.6%;

[0007] Atactic polypropylene 8-15%;

[0008] Polyolefin elastomer 10-30%;

[0009] Talc 0-30%;

[0010] Heat stabilizer mixture 0.2-1%;

[0011] Black masterbatch 0.2-1%.

[0012] In the above-mentioned sprayable polypropylene composition,

[0013] The linear homopolypropylene or copolymer polypropylene has a weight average molecular weight of 10^4 to 10^6, a molecular weight distribution width of 1 to 20, and a melt flow rate of 0.1-100 g / 10min (230°C, 2.16 kg); preferably, the weight average molecular weight of the polypropylene is 2×10^5 to 5×10^5, the molecular weight distribution width is 4 to 10, and the melt flow rate is 20-60 g / 10min (230°C, 2.16 kg).

[0014] The atactic polypropylene has a weight average molecular weight of 10^2 to 10^5 and a viscosity of 1000 to 9000 mPa·s (177°C); preferably, the atactic polypropylene has a weight average molecular weight of 4×10^3 to 9×10^3 and a viscosity of 2000 to 4000 mPa·s (177°C).

[0015] The polyolefin elastomer includes but is not limited to one or a combination of two or more of ethylene-butene copolymer, ethylene-octene copolymer, etc., and has a melt flow rate (190°C×2.16kg) of 0.5-60g / 10min, preferably a melt flow rate (190°C×2.16kg) of 1-30g / 10min.

[0016] The talcum powder has an average particle size of 1-20 μm, preferably talcum powder with an average particle size of 1-10 μm.

[0017] The heat stabilizer mixture includes a primary antioxidant and an auxiliary antioxidant, wherein the primary antioxidant is a hindered phenol or thioester antioxidant, including but not limited to a combination of one or more of 3114 (chemical name: 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6[1H,3H,5H]trione), 1010 (chemical name: tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol), and DSTP (chemical name: stearyl thiodipropionate); the auxiliary antioxidant is a phosphite or ester antioxidant, including but not limited to a combination of one or more of 618 (chemical name: dioctadecyl pentaerythritol diphosphite) and 168 (chemical name: tris(2,4-di-tert-butylphenyl) phosphite).

[0018] The black masterbatch is a carbon black masterbatch with polyethylene or polypropylene as a carrier.

[0019] The preparation method of the above-mentioned sprayable polypropylene composition comprises the following steps: putting the above-mentioned linear homopolypropylene or copolymer polypropylene resin, atactic polypropylene, polyolefin elastomer, talcum powder, heat stabilizer mixture and black masterbatch into a twin-screw extruder for melt mixing and dispersion, and extruding and granulating through the twin-screw extruder to obtain the polypropylene composition.

[0020] Then the polypropylene composition is injection molded on an injection molding machine to form the required mechanical property test sample and sample 1 for painting. Sample 1 is sprayed under a certain spraying process to form sample 2. The paint used is commercially available TYPE C paint, the manufacturer is Pet Chemical (Shanghai) Co., Ltd. Sample 2 is baked and cured at a certain temperature to obtain the final sample 3.

[0021] As an embodiment, during the extrusion granulation process, the temperature of each section of the twin-screw extruder is set to 190-240° C. Further, during the extrusion granulation process, the temperature of each section of the twin-screw extruder is set to 200-220° C.

[0022] As an embodiment, during the injection molding process, the temperature of each section of the injection molding machine is set to 190-240° C. Further, during the injection molding process, the temperature of each section of the injection molding machine is set to 200-220° C.

[0023] As an embodiment, in the spraying process, the sprayed paint is adjusted to an umbrella shape with an angle of 30 to 90° through the spray gun air outlet valve and the atomizing valve, and is further selected to be adjusted to an umbrella shape with an angle of 60 to 70°. The paint is sprayed on the surface of sample 1 in four directions once each, and two rounds of spraying are performed for a total of eight times to obtain sample 2, whose paint film thickness is 20 to 50 μm, and the paint film thickness is further selected to be 30 to 40 μm.

[0024] As an embodiment, the baking curing process is to heat treat the sprayed sample 2 at 60-100° C. for 10-60 minutes. Further, the baking curing process is to heat treat the sprayed sample 2 at 70-90° C. for 30-40 minutes to obtain the final sample 3.

[0025] The invention provides a sprayable polypropylene material prepared by the above method and composed of a mixture of linear homopolypropylene or copolymerized polypropylene, atactic polypropylene, polyolefin elastomer, talcum powder, black masterbatch and a heat stabilizer.

[0026] The parameters reflecting the performance of polypropylene materials are: elastic modulus ≥ 1600MPa, tensile strength ≥ 18MPa, notched impact strength ≥ 30KJ / m2. The parameters reflecting the paint adhesion of sprayed parts are: adhesion ≤ level 1, adhesion ≤ level 1 after heat aging at 100℃ for 500h.

[0027] The key point of the present invention is: by adding a specific proportion of atactic polypropylene to linear homopolypropylene or copolymer polypropylene, the fluidity of each component in the system is improved, the dispersibility of polyolefin elastomer in the resin is improved, so that during the injection molding process of the polypropylene composite material, the polyolefin elastomer is more enriched in the surface layer of the injection molded sample, which is conducive to the improvement of the spray adhesion performance of the polypropylene composite material injection molded part. At the same time, due to the presence of atactic polypropylene, the movement ability of the polypropylene molecular chain segment can be enhanced, so that polypropylene has a more complete crystallization behavior during the injection molding process, thereby maintaining excellent mechanical properties. In addition, the present invention, while using linear homopolypropylene or copolymer polypropylene, atactic polypropylene, as a matrix material, also cooperates with talcum powder and a heat stabilizer to interact, thereby giving the polypropylene material high strength and high heat resistance, meeting the production needs of spraying paint on automotive parts. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. It should also be understood that after reading the content described in the present invention, those skilled in the art may make changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0029] The various measurements shown in the detailed description of the present invention and in the examples are determined as follows.

[0030] Elastic modulus / tensile strength: According to ISO 527 method.

[0031] Notched impact strength: according to ISO 180 method.

[0032] Adhesion: According to GB / T 9286 method, 0-5 levels, the lower the level, the better the adhesion.

[0033] Crystallinity: Use a differential scanning calorimeter (DSC) to measure the DSC crystallization melting curve of the cast base film. The test conditions are: N2 atmosphere, sample mass of about 5 mg, the sample is heated from room temperature to 210°C at 10°C / min, the DSC crystallization melting curve is recorded, and the melting enthalpy (△H) of the sample is obtained from the curve. The crystallinity (Xc) of the sample is calculated according to the following formula:

[0034]

[0035] Wherein, ΔH is the melting enthalpy of the sample, J / g; ΔH0 is the melting enthalpy of polypropylene when it is 100% crystallized, which is 207 J / g.

[0036] Embodiment 1:

[0037] Copolymer polypropylene (weight average molecular weight of 2.8×10^5, molecular weight distribution width of 4.7, melt flow rate of 50g / 10min), atactic polypropylene (weight average molecular weight of 6.3×10^3, viscosity of 3200mPa·s), polyolefin elastomer (ethylene-butene copolymer, melt flow rate of 1.2g / 10min), talcum powder (average particle size of 6μm), heat stabilizer mixture (heat stabilizer 1010, heat stabilizer 168 and heat stabilizer DSTP, mass ratio of 1:1:1), and black masterbatch are mixed in a mass ratio of 52.4:8:18:20:0.6:1, melt-blended and granulated on a twin-screw extruder, and then injection-molded on an injection molding machine into corresponding mechanical samples and sample 1 for painting, sample 1 is sprayed under a certain spraying process to form sample 2, and sample 2 is baked and cured at a certain temperature to obtain the final sample 3. The process conditions are: extrusion temperature 210℃, injection temperature 215℃, the sprayed paint is adjusted to an umbrella shape with an angle of 65°, the paint is sprayed in four directions once each, two rounds of spraying for a total of 8 times, the paint film thickness is 35μm, and it is baked at 80℃ for 35 minutes after spraying.

[0038] Embodiment 2:

[0039] The steps of Example 2 are basically the same as those of Example 1, except that the mass ratio of copolymerized polypropylene, atactic polypropylene, polyolefin elastomer, talcum powder, thermal stabilizer, and black masterbatch in Sample 1 is 49.4:11:18:20:0.6:1.

[0040] Embodiment 3:

[0041] The steps of Example 3 are basically the same as those of Example 1, except that the mass ratio of copolymerized polypropylene, atactic polypropylene, polyolefin elastomer, talcum powder, thermal stabilizer, and black masterbatch in Sample 1 is 45.4:15:18:20:0.6:1.

[0042] Embodiment 4:

[0043] The steps of Example 4 are basically the same as those of Example 1, except that the copolymerized polypropylene resin in Sample 1 is replaced with linear homopolypropylene, and the mass ratio of linear homopolypropylene, atactic polypropylene, polyolefin elastomer, talcum powder, thermal stabilizer, and black masterbatch is 52.4:8:18:20:0.6:1.

[0044] Comparative Example 1:

[0045] The steps of Comparative Example 1 are basically the same as those of Example 1, except that Sample 1 does not contain atactic polypropylene, and the mass ratio of copolymerized polypropylene, polyolefin elastomer, talcum powder, heat stabilizer, and black masterbatch is 60.4:18:20:0.6:1.

[0046] Comparative Example 2:

[0047] The steps of Comparative Example 2 are basically the same as those of Example 1, except that the mass ratio of copolymerized polypropylene, atactic polypropylene, polyolefin elastomer, talcum powder, thermal stabilizer and black masterbatch in Sample 1 is 55.4:5:18:20:0.6:1.

[0048] Comparative Example 3:

[0049] The steps of Comparative Example 3 are basically the same as those of Example 1, except that the mass ratio of copolymerized polypropylene, atactic polypropylene, polyolefin elastomer, talcum powder, thermal stabilizer and black masterbatch in Sample 1 is 40.4:20:18:20:0.6:1.

[0050] Comparative Example 4:

[0051] The steps of Comparative Example 4 are basically the same as those of Example 1, except that Sample 1 does not contain atactic polypropylene, the copolymer polypropylene resin is replaced by linear homopolypropylene, and the mass ratio of linear homopolypropylene, polyolefin elastomer, talcum powder, heat stabilizer, and black masterbatch is 60.4:18:20:0.6:1.

[0052] Table 1, performance parameters of polypropylene materials and sample 3 after spraying in Examples 1-4 and Comparative Examples 1-4

[0053]

[0054] It can be seen from the comparison between Examples 1, 2, 3, and 4 and Comparative Examples 1 and 4 that after adding atactic polypropylene to the linear homopolypropylene or copolymer polypropylene resin for modification, the fluidity of each component in the system is improved, the dispersibility of the polyolefin elastomer in the resin is improved, and the polyolefin elastomer is more enriched in the surface of the injection molded sample during the injection molding of the polypropylene composite material. After spraying, Sample 3 and Sample 3 are aged at 100°C for 500h, and their paint adhesion is both level 0, which is significantly better than Comparative Examples 1 and 4. At the same time, due to the presence of atactic polypropylene in the resin system, the mobility of the polypropylene molecular chain segments can be enhanced, so that the polypropylene has a relatively complete crystallization behavior during the injection molding process, and its mechanical properties and crystallinity are well improved or maintained, the mechanical properties elastic modulus is maintained above 1600MPa, the tensile yield strength is not less than 18MPa, and the toughness notched impact strength is ≥30KJ / m2, which meets the rigidity and toughness requirements of the modified PP material for automotive interior.

[0055] By comparing Examples 1, 2, and 3 with Comparative Examples 2 and 3, it can be seen that when the amount of atactic polypropylene added to Comparative Example 2 is relatively low, the crystallinity of the modified polypropylene is further improved, and the elastic modulus and tensile yield strength mechanical properties are higher, but the dispersion ability of each component in the system is not further improved, so the paint adhesion of Sample 3 is only Level 2, and the paint adhesion of Sample 3 is Level 5 after aging at 100°C for 500h, which does not meet the adhesion requirements; when the amount of atactic polypropylene added to Comparative Example 3 is relatively high, the crystallinity of the modified polypropylene is significantly reduced, and the elastic modulus and tensile strength mechanical properties are lower than the mechanical property requirements of the modified PP material for interior decoration, and the application of conventional modified PP materials for interior decoration is not met.

Claims

1. A sprayable polypropylene composition, characterized in that: It includes the following raw materials in percentage by weight: Linear homopolypropylene or copolymer polypropylene 23-81.6%; Atactic polypropylene 8-15%; Polyolefin elastomer 10-30%; Talc 0-30%; Heat stabilizer mixture 0.2-1%; Black masterbatch 0.2-1%.

2. A sprayable polypropylene composition according to claim 1, characterized in that: The linear homopolypropylene or copolymer polypropylene has a weight average molecular weight of 10^4 to 10^6, a molecular weight distribution width of 1 to 20, and a melt flow rate of 0.1-100 g / 10 min.

3. A sprayable polypropylene composition according to claim 2, characterized in that: The weight average molecular weight of polypropylene is 2×10^5~5×10^5, the molecular weight distribution width is 4~10, and the melt flow rate is 20-60g / 10min.

4. A sprayable polypropylene composition according to claim 1, characterized in that: The atactic polypropylene has a weight average molecular weight of 10^2 to 10^5 and a viscosity of 1000 to 9000 mPa·s.

5. A sprayable polypropylene composition according to claim 4, characterized in that: The weight average molecular weight of atactic polypropylene is 4×10^3~9×10^3, and the viscosity is 2000~4000mPa·s.

6. A sprayable polypropylene composition according to claim 1, characterized in that: The polyolefin elastomer includes but is not limited to one or a combination of two or more of ethylene-butene copolymer, ethylene-octene copolymer, etc., and its melt flow rate (190°C×2.16kg) is 0.5-60g / 10min.

7. A sprayable polypropylene composition according to claim 6, characterized in that: The polyolefin elastomer has a melt flow rate of 1-30 g / 10 min.

8. A sprayable polypropylene composition according to claim 1, characterized in that: The average particle size of the talcum powder is 1-20 μm.

9. A sprayable polypropylene composition according to claim 8, characterized in that: The average particle size of the talcum powder is 1-10 μm.

10. A sprayable polypropylene composition according to claim 1, characterized in that: The heat stabilizer mixture includes a primary antioxidant and an auxiliary antioxidant, wherein the primary antioxidant is a hindered phenol or thioester antioxidant, including but not limited to a combination of one or more of 3114 (chemical name: 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6[1H,3H,5H]trione), 1010 (chemical name: tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol), and DSTP (chemical name: stearyl thiodipropionate); the auxiliary antioxidant is a phosphite or ester antioxidant, including but not limited to a combination of one or more of 618 (chemical name: dioctadecyl pentaerythritol diphosphite) and 168 (chemical name: tris(2,4-di-tert-butylphenyl) phosphite).

11. A sprayable polypropylene composition according to claim 1, characterized in that: The black masterbatch is a carbon black masterbatch with polyethylene or polypropylene as a carrier.

12. The method for preparing the sprayable polypropylene composition according to any one of claims 1 to 11, characterized in that: The method comprises the following steps: putting the linear homopolypropylene or copolymer polypropylene resin, atactic polypropylene, polyolefin elastomer, talcum powder, a heat stabilizer mixture and black masterbatch into a twin-screw extruder for melt mixing and dispersion, and extruding and granulating through the twin-screw extruder to obtain the polypropylene composition.

13. The method for preparing a sprayable polypropylene composition according to claim 12, characterized in that: In the extrusion granulation process, the temperature of each section of the twin-screw extruder is set to 190-240°C; in the injection molding process, the temperature of each section of the injection molding machine is set to 190-240°C.

14. The method for preparing a sprayable polypropylene composition according to claim 13, characterized in that: During the extrusion granulation process, the temperature of each section of the twin-screw extruder is set to 200-220°C; during the injection molding process, the temperature of each section of the injection molding machine is set to 200-220°C.

15. A spray-coated part, characterized in that: The polypropylene composition prepared according to any one of claims 1-14 is injection molded on an injection molding machine to form the required mechanical property test sample and sample 1 for painting, and the sample 1 is sprayed under a certain spraying process to form sample 2. The paint used is commercially available TYPE C paint, manufactured by Pet Chemical (Shanghai) Co., Ltd., and sample 2 is baked and cured at a certain temperature to obtain the final sample 3.

16. A spray-coated part according to claim 15, characterized in that: During the spraying process, the sprayed paint is adjusted into an umbrella shape with an angle of 30 to 90° through the spray gun air outlet valve and the atomizing valve. The paint is sprayed on the surface of sample 1 in four directions once each, and two rounds of spraying are performed for a total of 8 times to obtain sample 2, whose paint film thickness is 20 to 50 μm, and the paint film thickness is further selected to be 30 to 40 μm.

17. A spray-coated part according to claim 16, characterized in that: The paint spraying is adjusted to form an umbrella shape with an angle of 60 to 70 degrees.

18. The spray-coated part according to claim 15, characterized in that: The baking and curing process is to heat treat the sprayed sample 2 at 60-100° C. for 10-60 minutes. The final sample 3 was obtained.

19. A spray-coated part according to claim 18, characterized in that: The baking and curing process is to heat treat the sprayed sample 2 at 70 to 90° C. for 30 to 40 minutes.

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