A kind of easy-to-spray polypropylene composite material and preparation method thereof

Abstract

The present invention belongs to the technical field of polymer modified materials, and relates to a polypropylene composite material that is easy to spray and a preparation method thereof. By weight, the polypropylene composite material that is easy to spray contains 59-84 parts of polypropylene, 1-3 parts of compatibilizer and 5-8 parts of polyvinyl pyrrolidone, the compatibilizer is PP-g-MAH or PP-g-GMA, and the K value of polyvinyl pyrrolidone is 12-17. Preparation method: After mixing each component in a high-speed rotating mixer according to a ratio, granulating by a twin-screw extruder, and obtaining a polypropylene composite material that is easy to spray by dry drawing. The polypropylene composite material of the present invention effectively improves the adhesion of the paint surface, is easy to spray, and also realizes the versatility of solvent-based paint or water-based paint. The preparation method of the present invention is simple, the raw material stability is good, and the cost is low.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer modified materials and relates to an easily sprayable polypropylene composite material and a preparation method thereof. Background Art

[0002] Polypropylene resin is widely used in automobiles, home appliances and many other industries due to its low price, excellent mechanical properties, simple molding process and other advantages. For example, in the automotive field, the entire interior and exterior decoration such as bumpers, door panels, pillars and other parts all involve polypropylene resin materials, especially automotive exterior parts such as bumpers, which usually require the use of surface spraying technology. Because polypropylene is a non-polar material with low surface energy and low bonding strength with paint, common automotive polypropylene spray parts usually need flame treatment and three layers of primer, color paint and topcoat spraying to meet the requirements of the parts, which is very costly. In order to reduce the cost of automotive polypropylene spray parts, optimize the parts spraying process, and improve the adhesion of polypropylene paint, a lot of research has been done in the prior art.

[0003] For example, patent application CN103627262A provides a primer-free, directly sprayable bumper composite material and a preparation method thereof. By adding a loaded nickel ion talcum powder, the adhesion of the material to the paint is increased, so that the primer is omitted in the material spraying, and the primer spraying process is simplified; patent application CN109181118A discloses a primer-free sprayable automotive exterior material and a preparation method thereof. By adding a highly active synergist and an interface promoter, the adhesion between the PP substrate and the paint is improved, and the color paint or topcoat is directly sprayed.

[0004] In addition, the oily paint currently used contains a large amount of organic solvents. During the production process, the organic solvents evaporate and have a serious impact on the life and health of workers and the environment. Therefore, with the improvement of environmental protection requirements, more and more companies are promoting the use of water-based paints, which use water as a solvent and are environmentally friendly. There are also related studies on polypropylene materials for water-based paint spraying. For example, patent application CN117777603A discloses a polypropylene composite material that can be used for efficient spraying of water-based paint and a preparation method thereof, which adds porous polypropylene and dopamine-modified nanocellulose fibers, improves the surface adhesion of water-based paint on polypropylene, and is conducive to the efficient spraying of water-based paint of polypropylene; for example, patent application CN117757184A discloses a reactive high-polarity polypropylene composite material and a preparation method and application thereof, wherein the acrylate grafted polypropylene added has good compatibility with the acrylate component in the water-based paint, improves the adhesion of the paint surface, and can be sprayed without flame treatment.

[0005] Although the polypropylene composite materials prepared by these prior arts have been optimized in terms of paint adhesion and spraying process and can be sprayed, they still have the following shortcomings: (1) the stability of inorganic fillers loaded with metal ions is poor, or the activity of highly active substances is too high, the preparation process is difficult to control, and the stability of polypropylene composite materials needs to be improved; (2) they are only suitable for organic solvent-based paints (solvent paints) or water-based paints, and their versatility also needs to be improved.

[0006] Therefore, it is necessary to develop a polypropylene composite material that is easy to spray and has better stability and versatility. Summary of the invention

[0007] The purpose of the present invention is to solve the above problems existing in the prior art and to provide a polypropylene composite material that is easy to spray and a preparation method thereof.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A polypropylene composite material that is easy to spray contains, by weight, 59-84 parts of polypropylene, 1-3 parts of a compatibilizer and 5-8 parts of polyvinyl pyrrolidone. The compatibilizer is PP-g-MAH (maleic anhydride grafted polypropylene) or PP-g-GMA. The K value of the polyvinyl pyrrolidone is 12-17, and the corresponding molecular weight is relatively small, 3000-16000.

[0010] The present invention utilizes the property that polyvinyl pyrrolidone is both soluble in water and soluble in various organic solvents, and utilizes the migration effect of small molecules to make polyvinyl pyrrolidone relatively enriched on the surface of polypropylene composite material, so that when solvent-based paint or water-based paint is sprayed, organic solvent or water dissolves and swells polyvinyl pyrrolidone to form a deeper physical binding layer, and polyvinyl pyrrolidone has a higher polarity and good compatibility with film-forming resin, which effectively improves the adhesion of the paint surface and achieves the effect of easy spraying. In addition, since the compatibility of polyvinyl pyrrolidone with polypropylene is not good and the bonding force is weak, it is easy to peel off from the polypropylene matrix when used alone as the bonding layer between the paint surface and polypropylene. Therefore, the present invention strengthens the compatibility of polyvinyl pyrrolidone with the polypropylene matrix through a compatibilizer.

[0011] As the priority technical solution:

[0012] The above-mentioned easy-to-spray polypropylene composite material further contains 5-20 parts by weight of an inorganic filler, wherein the inorganic filler is talcum powder, calcium carbonate and the like.

[0013] The above-mentioned easy-to-spray polypropylene composite material further contains 5-10 parts by weight of a toughening agent, wherein the toughening agent is POE (ethylene-octene polymer), SEBS, etc.

[0014] The easy-to-spray polypropylene composite material as described above further contains 0.2-0.6 parts by weight of an antioxidant, wherein the antioxidant is antioxidant 1010, antioxidant 168, etc.

[0015] The above-mentioned easy-to-spray polypropylene composite material further contains 0.1-0.3 parts by weight of a lubricant, and the lubricant is a commercially available dispersed lubricant EBS (ethylene bisstearamide) or the like.

[0016] The polypropylene composite material that is easy to spray as described in any of the above items, the polypropylene is at least one of copolymer polypropylene or homopolymer polypropylene, and its melt flow rate at 230° C. and 2.16 kg is 5-100 g / 10 min.

[0017] A sprayable polypropylene composite material as described in any one of the above items, having a tensile strength of 18-21 MPa, a flexural modulus of 930-1260 MPa, and a Charpy notched impact strength of 18-26 kJ / m 2 , the melt flow rate at 230°C and 2.16kg is 26-28g / 10min.

[0018] The present invention also provides a method for preparing a polypropylene composite material that is easy to spray as described in any of the above items, wherein the components are mixed in a high-speed rotating mixer for 3-5 minutes according to a ratio, granulated by a twin-screw extruder, and the polypropylene composite material that is easy to spray is obtained by dry-stranding, wherein the processing temperature of the twin-screw extruder is 180-190°C.

[0019] Beneficial effects:

[0020] (1) The polyvinyl pyrrolidone of the present invention is relatively enriched on the surface of the polypropylene composite material, so that when the solvent paint or water-based paint is sprayed, the organic solvent or water dissolves and swells the polyvinyl pyrrolidone to form a physical bonding layer. In addition, the polyvinyl pyrrolidone has a high polarity and good compatibility with the film-forming resin, which effectively improves the adhesion of the paint surface and achieves the versatility and easy spraying effect of the solvent paint or water-based paint spraying.

[0021] (2) The polyvinyl pyrrolidone used in the preparation method of the present invention has good compatibility and stability, the preparation process is easy to control, the raw materials are easily available, and the cost is low. DETAILED DESCRIPTION

[0022] 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. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0023] The following are the test methods for the relevant performance indicators in each embodiment and comparative example:

[0024] (1) Tensile strength: After baking in an oven at 110°C for 3 h, the samples were injection molded and tested in accordance with ISO 527-2:2012.

[0025] (2) Flexural modulus: After baking in an oven at 110°C for 3 h, the samples were injection molded and tested in accordance with ISO 178:2019.

[0026] (3) Charpy notched impact strength: After baking in an oven at 110°C for 3 h, the samples were injection molded and tested in accordance with ISO 179-1:2010.

[0027] (4) Melt flow rate at 230° C. and 2.16 kg: tested in accordance with ISO 1133-1:2011.

[0028] (5) Adhesion grade of water-based paint or solvent paint: After baking in an oven at 110°C for 3 hours, injection mold the sample, let it stand at room temperature for 48 hours, and then test it in accordance with GB / T 9286-2021 "Scratch test for paints and varnishes".

[0029] All raw materials in the embodiments and comparative examples of the present invention are conventional and commonly used products on the market. The products with indicated manufacturers and brands are only used in the embodiments, and such products from other manufacturers and other brands are also feasible.

[0030] Polypropylene: Copolymer polypropylene is used, the manufacturer is China SABIC (Tianjin) Petrochemical Co., Ltd., brand 511MK40T;

[0031] Polyvinylpyrrolidone K15 and polyvinylpyrrolidone K25: the manufacturer is Guangdong Yuemei Chemical Co., Ltd.;

[0032] Inorganic filler: The type of inorganic filler does not affect the effect. The embodiments and comparative examples of the present invention use talcum powder, the manufacturer of talcum powder is Liaoning Aihai Talc Co., Ltd., and the brand of talcum powder is 51205;

[0033] Compatibilizer: PP-g-MAH, manufactured by Jiayirong Polymer (Shanghai) Co., Ltd., brand name CMG5001;

[0034] Toughening agent: The type of toughening agent does not affect the effect. POE is selected from SK of South Korea and the grade is 875L in each embodiment and comparative example of the present invention.

[0035] Antioxidant: The manufacturer of antioxidant 1010 is BASF, and the manufacturer of antioxidant 168 is BASF;

[0036] Water-based paint: the brand is Sanhe;

[0037] Solvent paint: the brand is Qianjin.

[0038] Example 1

[0039] A method for preparing a polypropylene composite material that is easy to spray, the specific steps are as follows:

[0040] (1) Preparation of raw materials;

[0041] Polypropylene: 59 parts by weight, manufactured by China SABIC (Tianjin) Petrochemical Co., Ltd., brand 511MK40T;

[0042] Polyvinyl pyrrolidone: 8 parts by weight, K value is 15;

[0043] Compatibilizer: 3 parts by weight, PP-g-MAH;

[0044] Inorganic filler: 20 parts by weight of talc;

[0045] Toughening agent: 10 parts by weight of POE;

[0046] Antioxidants: 0.3 parts by weight of antioxidant 1010 and 0.3 parts by weight of antioxidant 168;

[0047] Lubricant: 0.2 parts by weight of EBS;

[0048] (2) Mixing and granulation;

[0049] After mixing the components in a high-speed rotary mixer for 3 minutes according to the above ratio, the components are granulated by a twin-screw extruder with a processing temperature of 190° C. After dry-stranding, a polypropylene composite material that is easy to spray is obtained.

[0050] The test results of tensile strength, flexural modulus, Charpy notched impact strength and melt flow rate at 230°C and 2.16 kg of the finally prepared polypropylene composite material are shown in Table 1.

[0051] The spraying method of the above-mentioned easy-to-spray polypropylene composite material has the following process flow: water washing and degreasing → water blowing → drying → cooling → spraying color paint → standing for leveling → spraying varnish → standing for leveling → baking → cooling, the drying temperature is 60°C, the drying time is 30 minutes, the baking temperature is 85°C, and the baking time is 30 minutes.

[0052] The paint film thickness of the polypropylene composite material after spraying is 0.1 mm. When the color paint and the varnish are both water-based paints, the measured water-based paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1. When the color paint and the varnish are both solvent paints, the measured solvent paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1.

[0053] Example 2

[0054] A method for preparing a polypropylene composite material that is easy to spray, the specific steps are as follows:

[0055] (1) Preparation of raw materials;

[0056] Polypropylene: 62 parts by weight, manufactured by China SABIC (Tianjin) Petrochemical Co., Ltd., brand 511MK40T;

[0057] Polyvinyl pyrrolidone: 5 parts by weight, K value is 15;

[0058] Compatibilizer: 3 parts by weight of PP-g-MAH;

[0059] Inorganic filler: 20 parts by weight of talc;

[0060] Toughening agent: 10 parts by weight of POE;

[0061] Antioxidants: 0.3 parts by weight of antioxidant 1010 and 0.3 parts by weight of antioxidant 168;

[0062] Lubricant: 0.2 parts by weight of EBS;

[0063] (2) Mixing and granulation;

[0064] After mixing the components in a high-speed rotary mixer for 3 minutes according to the above ratio, the components are granulated by a twin-screw extruder with a processing temperature of 190° C. After dry-stranding, a polypropylene composite material that is easy to spray is obtained.

[0065] The test results of tensile strength, flexural modulus, Charpy notched impact strength and melt flow rate at 230°C and 2.16 kg of the finally prepared polypropylene composite material are shown in Table 1.

[0066] The spraying method of the above-mentioned easy-to-spray polypropylene composite material has the following process flow: water washing and degreasing → water blowing → drying → cooling → spraying color paint → standing for leveling → spraying varnish → standing for leveling → baking → cooling, the drying temperature is 60°C, the drying time is 30 minutes, the baking temperature is 85°C, and the baking time is 30 minutes.

[0067] The paint film thickness of the polypropylene composite material after spraying is 0.1 mm. When the color paint and the varnish are both water-based paints, the measured water-based paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1. When the color paint and the varnish are both solvent paints, the measured solvent paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1.

[0068] Example 3

[0069] A method for preparing a polypropylene composite material that is easy to spray, the specific steps are as follows:

[0070] (1) Preparation of raw materials;

[0071] Polypropylene: 69 parts by weight, manufactured by China SABIC (Tianjin) Petrochemical Co., Ltd., brand 511MK40T;

[0072] Polyvinyl pyrrolidone: 5 parts by weight, K value is 15;

[0073] Compatibilizer: 3 parts by weight of PP-g-MAH;

[0074] Inorganic filler: 15 parts by weight of talc;

[0075] Toughening agent: 8 parts by weight of POE;

[0076] Antioxidants: 0.3 parts by weight of antioxidant 1010 and 0.3 parts by weight of antioxidant 168;

[0077] Lubricant: 0.2 parts by weight of EBS;

[0078] (2) Mixing and granulation;

[0079] After mixing the components in a high-speed rotary mixer for 3 minutes according to the above ratio, the components are granulated by a twin-screw extruder with a processing temperature of 190° C. After dry-stranding, a polypropylene composite material that is easy to spray is obtained.

[0080] The test results of tensile strength, flexural modulus, Charpy notched impact strength and melt flow rate at 230°C and 2.16 kg of the finally prepared polypropylene composite material are shown in Table 1.

[0081] The spraying method of the above-mentioned easy-to-spray polypropylene composite material has the following process flow: water washing and degreasing → water blowing → drying → cooling → spraying color paint → standing for leveling → spraying varnish → standing for leveling → baking → cooling, the drying temperature is 60°C, the drying time is 30 minutes, the baking temperature is 85°C, and the baking time is 30 minutes.

[0082] The paint film thickness of the polypropylene composite material after spraying is 0.1 mm. When the color paint and the varnish are both water-based paints, the measured water-based paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1. When the color paint and the varnish are both solvent paints, the measured solvent paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1.

[0083] Example 4

[0084] A method for preparing a polypropylene composite material that is easy to spray, the specific steps are as follows:

[0085] (1) Preparation of raw materials;

[0086] Polypropylene: 84 parts by weight, manufactured by China SABIC (Tianjin) Petrochemical Co., Ltd., brand 511MK40T;

[0087] Polyvinyl pyrrolidone: 5 parts by weight, K value is 15;

[0088] Compatibilizer: 1 part by weight of PP-g-MAH;

[0089] Inorganic filler: 5 parts by weight of talc;

[0090] Toughening agent: 5 parts by weight of POE;

[0091] Antioxidants: 0.3 parts by weight of antioxidant 1010 and 0.3 parts by weight of antioxidant 168;

[0092] Lubricant: 0.2 parts by weight of EBS;

[0093] (2) Mixing and granulation;

[0094] After mixing the components in a high-speed rotary mixer for 3 minutes according to the above ratio, the components are granulated by a twin-screw extruder with a processing temperature of 190° C. After dry-stranding, a polypropylene composite material that is easy to spray is obtained.

[0095] The test results of tensile strength, flexural modulus, Charpy notched impact strength and melt flow rate at 230°C and 2.16 kg of the finally prepared polypropylene composite material are shown in Table 1.

[0096] The spraying method of the above-mentioned easy-to-spray polypropylene composite material has the following process flow: water washing and degreasing → water blowing → drying → cooling → spraying color paint → standing for leveling → spraying varnish → standing for leveling → baking → cooling, the drying temperature is 60°C, the drying time is 30 minutes, the baking temperature is 85°C, and the baking time is 30 minutes.

[0097] The paint film thickness of the polypropylene composite material after spraying is 0.1 mm. When the color paint and the varnish are both water-based paints, the measured water-based paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1. When the color paint and the varnish are both solvent paints, the measured solvent paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1.

[0098] Comparative Example 1

[0099] A method for preparing a polypropylene composite material, the specific steps are as follows:

[0100] (1) Preparation of raw materials;

[0101] Polypropylene: 57 parts by weight, manufactured by China SABIC (Tianjin) Petrochemical Co., Ltd., brand 511MK40T;

[0102] Polyvinyl pyrrolidone: 10 parts by weight, K value is 15;

[0103] Compatibilizer: 3 parts by weight of PP-g-MAH;

[0104] Inorganic filler: 20 parts by weight of talc;

[0105] Toughening agent: 10 parts by weight of POE;

[0106] Antioxidants: 0.3 parts by weight of antioxidant 1010 and 0.3 parts by weight of antioxidant 168;

[0107] Lubricant: 0.2 parts by weight of EBS;

[0108] (2) Mixing and granulation;

[0109] The components were mixed in a high-speed rotary mixer for 3 minutes according to the above ratio, and then granulated by a twin-screw extruder with a processing temperature of 190° C. The polypropylene composite material was obtained by dry-stranding.

[0110] The test results of tensile strength, flexural modulus, Charpy notched impact strength and melt flow rate at 230°C and 2.16 kg of the finally prepared polypropylene composite material are shown in Table 1.

[0111] The spraying method of the above-mentioned polypropylene composite material has the following process flow: water washing and degreasing → water blowing → drying → cooling → spraying color paint → standing for leveling → spraying varnish → standing for leveling → baking → cooling, the drying temperature is 60°C, the drying time is 30 minutes, the baking temperature is 85°C, and the baking time is 30 minutes.

[0112] The paint film thickness of the polypropylene composite material after spraying is 0.1 mm. When the color paint and the varnish are both water-based paints, the measured water-based paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1. When the color paint and the varnish are both solvent paints, the measured solvent paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1.

[0113] Comparative Example 2

[0114] A method for preparing a polypropylene composite material, the specific steps are as follows:

[0115] (1) Preparation of raw materials;

[0116] Polypropylene: 64 parts by weight, manufactured by China SABIC (Tianjin) Petrochemical Co., Ltd., brand 511MK40T;

[0117] Polyvinyl pyrrolidone: 3 parts by weight, K value is 15;

[0118] Compatibilizer: 3 parts by weight of PP-g-MAH;

[0119] Inorganic filler: 20 parts by weight of talc;

[0120] Toughening agent: 10 parts by weight of POE;

[0121] Antioxidants: 0.3 parts by weight of antioxidant 1010 and 0.3 parts by weight of antioxidant 168;

[0122] Lubricant: 0.2 parts by weight of EBS;

[0123] (2) Mixing and granulation;

[0124] The components were mixed in a high-speed rotary mixer for 3 minutes according to the above ratio, and then granulated by a twin-screw extruder with a processing temperature of 190° C. The polypropylene composite material was obtained by dry-stranding.

[0125] The test results of tensile strength, flexural modulus, Charpy notched impact strength and melt flow rate at 230°C and 2.16 kg of the finally prepared polypropylene composite material are shown in Table 1.

[0126] The spraying method of the above-mentioned polypropylene composite material has the following process flow: water washing and degreasing → water blowing → drying → cooling → spraying color paint → standing for leveling → spraying varnish → standing for leveling → baking → cooling, the drying temperature is 60°C, the drying time is 30 minutes, the baking temperature is 85°C, and the baking time is 30 minutes.

[0127] The paint film thickness of the polypropylene composite material after spraying is 0.1 mm. When the color paint and the varnish are both water-based paints, the measured water-based paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1. When the color paint and the varnish are both solvent paints, the measured solvent paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1.

[0128] Comparative Example 3

[0129] A method for preparing a polypropylene composite material, the specific steps are as follows:

[0130] (1) Preparation of raw materials;

[0131] Polypropylene: 59 parts by weight, manufactured by China SABIC (Tianjin) Petrochemical Co., Ltd., brand 511MK40T;

[0132] Polyvinyl pyrrolidone: 8 parts by weight, K value is 25;

[0133] Compatibilizer: 3 parts by weight of PP-g-MAH;

[0134] Inorganic filler: 20 parts by weight of talc;

[0135] Toughening agent: 10 parts by weight of POE;

[0136] Antioxidants: 0.3 parts by weight of antioxidant 1010 and 0.3 parts by weight of antioxidant 168;

[0137] Lubricant: 0.2 parts by weight of EBS;

[0138] (2) Mixing and granulation;

[0139] The components were mixed in a high-speed rotary mixer for 3 minutes according to the above ratio, and then granulated by a twin-screw extruder with a processing temperature of 190° C. The polypropylene composite material was obtained by dry-stranding.

[0140] The test results of tensile strength, flexural modulus, Charpy notched impact strength and melt flow rate at 230°C and 2.16 kg of the finally prepared polypropylene composite material are shown in Table 1.

[0141] The spraying method of the above-mentioned polypropylene composite material has the following process flow: water washing and degreasing → water blowing → drying → cooling → spraying color paint → standing for leveling → spraying varnish → standing for leveling → baking → cooling, the drying temperature is 60°C, the drying time is 30 minutes, the baking temperature is 85°C, and the baking time is 30 minutes.

[0142] The paint film thickness of the polypropylene composite material after spraying is 0.1 mm. When the color paint and the varnish are both water-based paints, the measured water-based paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1. When the color paint and the varnish are both solvent paints, the measured solvent paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1.

[0143] Comparative Example 4

[0144] A method for preparing a polypropylene composite material, the specific steps are as follows:

[0145] (1) Preparation of raw materials;

[0146] Polypropylene: 62 parts by weight, manufactured by China SABIC (Tianjin) Petrochemical Co., Ltd., brand 511MK40T;

[0147] Polyvinyl pyrrolidone: 8 parts by weight, K value is 15;

[0148] Compatibilizer: 0 parts by weight of PP-g-MAH;

[0149] Inorganic filler: 20 parts by weight of talc;

[0150] Toughening agent: 10 parts by weight of POE;

[0151] Antioxidants: 0.3 parts by weight of Antioxidant 1010 and 0.3 parts by weight of Antioxidant 168

[0152] Lubricant: 0.2 parts by weight of EBS;

[0153] (2) Mixing and granulation;

[0154] The components were mixed in a high-speed rotary mixer for 3 minutes according to the above ratio, and then granulated by a twin-screw extruder with a processing temperature of 190° C. The polypropylene composite material was obtained by dry-stranding.

[0155] The test results of tensile strength, flexural modulus, Charpy notched impact strength and melt flow rate at 230°C and 2.16 kg of the finally prepared polypropylene composite material are shown in Table 1.

[0156] The spraying method of the above-mentioned polypropylene composite material has the following process flow: water washing and degreasing → water blowing → drying → cooling → spraying color paint → standing for leveling → spraying varnish → standing for leveling → baking → cooling, the drying temperature is 60°C, the drying time is 30 minutes, the baking temperature is 85°C, and the baking time is 30 minutes.

[0157] The paint film thickness of the polypropylene composite material after spraying is 0.1 mm. When the color paint and the varnish are both water-based paints, the measured water-based paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1. When the color paint and the varnish are both solvent paints, the measured solvent paint adhesion grade of the polypropylene composite material after spraying is shown in Table 1.

[0158] Table 1 Composition ratio and performance test results of various embodiments and comparative examples

[0159]

[0160] Note: Adhesion levels are divided into six levels from 0 to 5, with 0 indicating the best adhesion and 5 indicating the worst adhesion.

[0161] By comparing Comparative Example 1 with Example 1, it can be seen that the proportion of polyvinyl pyrrolidone K15 in the total weight of the raw material ratio in Comparative Example 1 increases, and the three mechanical properties of tensile strength, flexural modulus, and Charpy notched impact strength are significantly reduced. This is because too much small molecule polyvinyl pyrrolidone is dispersed in the material, which destroys the crystallization properties of polypropylene and thus affects the mechanical properties.

[0162] By comparing Comparative Example 2 with Example 1, it can be seen that the proportion of polyvinyl pyrrolidone K15 in the total weight of the raw material ratio in Comparative Example 2 is reduced, and the paint adhesion is significantly reduced. This is because the amount of polyvinyl pyrrolidone K15 used is too small, and the concentration on the material surface is too low to form an effective bonding surface, resulting in low paint adhesion.

[0163] By comparing Comparative Example 3 with Example 1, it can be seen that the K value of the polyvinyl pyrrolidone of Example 1 is 15, and the K value of the polyvinyl pyrrolidone of Comparative Example 3 is 25. The paint adhesion of Comparative Example 3 is significantly reduced. This is because K15 is the smallest molecular weight label of polyvinyl pyrrolidone. The larger the K value, the larger the molecular weight. When the molecular weight of polyvinyl pyrrolidone is too large, on the one hand, the migration ability of polyvinyl pyrrolidone is weak and it cannot be enriched to the surface. On the other hand, polyvinyl pyrrolidone is easy to agglomerate inside the material, and the surface concentration is significantly reduced, resulting in a decrease in paint adhesion.

[0164] By comparing Comparative Example 4 with Example 1, it can be seen that Example 1 adds the compatibilizer PP-g-MAH, while Comparative Example 4 omits the compatibilizer PP-g-MAH. The paint adhesion of Comparative Example 4 is significantly reduced. This is because the addition of the compatibilizer improves the compatibility of polyvinyl pyrrolidone and polypropylene, so that the surface-enriched polyvinyl pyrrolidone is evenly dispersed to form a staggered structure on the one hand, and on the other hand, the binding force between polyvinyl pyrrolidone and polypropylene is improved, thereby improving the paint adhesion.

Claims

1. A polypropylene composite material that is easy to spray, characterized in that: Calculated by weight, it contains 59-84 parts of polypropylene, 1-3 parts of compatibilizer and 5-8 parts of polyvinyl pyrrolidone, the compatibilizer is PP-g-MAH or PP-g-GMA, and the K value of polyvinyl pyrrolidone is 12-17.

2. The easily sprayable polypropylene composite material according to claim 1, characterized in that: Calculated by weight, it also contains 5-20 parts of inorganic fillers.

3. The easily sprayable polypropylene composite material according to claim 1, characterized in that: By weight, it also contains 5-10 parts of toughening agent.

4. The easily sprayable polypropylene composite material according to claim 1, characterized in that: By weight, it also contains 0.2-0.6 parts of antioxidant.

5. The easily sprayable polypropylene composite material according to claim 1, characterized in that: Calculated by weight, it also contains 0.1-0.3 parts of lubricant.

6. The easily sprayable polypropylene composite material according to claim 1, characterized in that: The polypropylene is at least one of copolymer polypropylene and homopolypropylene, and has a melt flow rate of 5-100 g / 10 min at 230° C. and 2.16 kg.

7. A method for preparing an easily sprayable polypropylene composite material as claimed in any one of claims 1 to 6, characterized in that: After mixing the components in a high-speed rotary mixer for 3-5 minutes according to the proportion, the components are granulated by a twin-screw extruder, and the polypropylene composite material which is easy to spray is obtained by dry-stranding. The processing temperature of the twin-screw extruder is 180-190°C.

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