Composite coating composition for plastic base material as well as preparation method and application of composite coating composition

Abstract

The invention discloses a composite coating composition for a plastic substrate as well as a preparation method and application of the composite coating composition. The composition comprises the following raw materials in parts by weight: 20-80 parts of waterborne epoxy emulsion; 5 to 20 parts of a glycidyl methacrylate grafted polyisobutylene copolymer emulsion; 3-20 parts of a curing agent emulsion; 0.5 to 1 part of a silane coupling agent; and 2-10 parts of a filler. Compared with the prior art, the adhesive property of the coating and a plastic base material is improved by introducing the glycidyl methacrylate grafted polyisobutylene copolymer, the problem of insufficient adhesive force of a traditional water-based coating is solved, and meanwhile, the environment-friendly advantage of a water-based system is kept.

Description

Technical Field

[0001] The invention relates to a composite coating composition for a plastic substrate, a preparation method and application thereof, and belongs to the technical field of waterborne epoxy materials. Background Art

[0002] Plastic substrates (such as polypropylene and TPO) are widely used in automotive, home appliance, and other fields due to their lightweight, chemical resistance, and low cost. However, their low surface polarity and high crystallinity make it difficult for traditional coatings to form effective adhesion, requiring reliance on solvent-based primers or surface pretreatments (such as corona treatment and flame treatment). These methods pose environmental risks and complex processes.

[0003] Among existing water-based coating systems, epoxy resin coatings offer excellent chemical resistance and mechanical properties, but their adhesion to non-polar plastic substrates is insufficient. Therefore, developing an environmentally friendly water-based coating that can directly bond to plastic substrates without pretreatment is of great significance. Summary of the Invention

[0004] Purpose of the Invention: To address the aforementioned technical problems, the present invention provides a composite coating composition for plastic substrates, its preparation method, and its application. By introducing a glycidyl methacrylate-grafted polyisobutylene copolymer, the present invention improves the adhesion of the coating to the plastic substrate, addressing the insufficient adhesion of traditional water-based coatings while maintaining the environmental advantages of water-based systems.

[0005] Technical solution: In order to achieve the above purpose, the present invention adopts the following technical solution:

[0006] A composite coating composition for a plastic substrate, comprising the following raw materials in parts by weight:

[0007] 20-80 parts of water-based epoxy emulsion;

[0008] 5-20 parts of glycidyl methacrylate grafted polyisobutylene copolymer emulsion;

[0009] 3-20 parts of curing agent emulsion;

[0010] Silane coupling agent 0.5-1 part;

[0011] 2-10 parts of filler.

[0012] As a specific embodiment, the water-based epoxy emulsion is selected from liquid bisphenol A / F epoxy emulsion or solid bisphenol A / F epoxy emulsion; the solid content of the water-based epoxy emulsion is 45-80%.

[0013] As a specific embodiment, the glycidyl methacrylate grafted polyisobutylene copolymer emulsion is mainly prepared from polyisobutylene, glycidyl methacrylate, a comonomer, an initiator and a stabilizer.

[0014] As a specific embodiment, the solid content of the glycidyl methacrylate grafted polyisobutylene copolymer emulsion is 30-60 wt %.

[0015] As a specific embodiment, the curing agent in the curing agent emulsion is selected from one or more of a water-based polyamide curing agent and a water-based imidazoline curing agent; and the solid content of the curing agent emulsion is 40-60%.

[0016] As a specific embodiment, the silane coupling agent is selected from one or a combination of epoxy silane coupling agents, amino silane coupling agents, phenylamino silane coupling agents, vinyl silane coupling agents, isocyanate silane coupling agents, acrylic silane coupling agents, isobutylene silane coupling agents, styrene silane coupling agents, urea silane coupling agents, chloropropyl silane coupling agents, sulfide silane coupling agents.

[0017] As a specific embodiment, the filler is selected from one or a combination of silicon micropowder, talc powder, and mica powder.

[0018] The present invention also provides a method for preparing the composite coating composition for a plastic substrate, comprising the following steps:

[0019] First, water-based epoxy emulsion and glycidyl methacrylate grafted polyisobutylene copolymer emulsion are stirred and mixed at high speed, curing agent emulsion, silane coupling agent and filler are added, dispersed at high speed, and viscosity is adjusted with deionized water to prepare the composite coating composition.

[0020] As a specific implementation scheme, the speed of the high-speed stirring is 4000-6000 rpm, and the stirring time is 5-15 minutes; the speed of the high-speed dispersion is 1000-2000 rpm, and the dispersion time is 15-25 minutes.

[0021] Finally, the present invention provides application of the composite coating composition in coating the surface of a plastic substrate.

[0022] Technical Effect: Compared with the prior art, the composite coating composition of the present invention has the following advantages:

[0023] 1. High adhesion: Through the interaction between the polar groups of glycidyl methacrylate grafted polyisobutylene copolymer and the surface of the plastic substrate, the adhesion of the coating on substrates such as polypropylene and TPO reaches level 0 (tested by the 100-grid method).

[0024] 2. Environmental protection: All water-based system, low VOC content, in line with environmental protection requirements.

[0025] 3. Simplified process: no substrate pretreatment is required, and it can be directly coated, reducing production costs. DETAILED DESCRIPTION

[0026] The present invention will be further illustrated below with reference to specific examples.

[0027] Unless otherwise defined herein, scientific and technical terms used in this application shall have the meanings commonly understood by one of ordinary skill in the art.

[0028] 1) The raw materials of the following examples and comparative examples are as follows:

[0029] Water-based epoxy emulsion: Handai Chemical bisphenol A solid epoxy emulsion HDE-8370, solid content 55%.

[0030] Glycidyl methacrylate grafted polyisobutylene copolymer: Shanghai Yuyu New Material Technology Co., Ltd., reagent grade, active ingredient 99%, solid content 45wt%.

[0031] Polyamide curing agent emulsion: Handai Chemical water-based polyamide curing agent emulsion HDH-6350, solid content 50%.

[0032] The filler is talcum powder: Qingdao Haishengyuan, 500 mesh.

[0033] The silane coupling agent was KH550, purchased from Nanjing Shuguang.

[0034] 2) The product performance testing methods of the following examples and comparative examples are as follows:

[0035] Test method: Refer to ISO2409 for the cross-cut test. As a simple, fast and intuitive adhesion test method, the cross-cut test is widely used to evaluate the bonding strength between the coating and the substrate. Its core principle is to simulate the peeling of the coating under mechanical stress by cutting regular grid scratches on the coating surface, thereby evaluating its adhesion level. During the test, a special tool is used to draw perpendicular parallel lines on the surface of the sample, with 6 to 11 cuts horizontally and vertically to form 25 to 100 squares. The depth must penetrate the coating to the substrate to form several small squares (usually 1mm×1mm or 2mm×2mm). The coating in the square is then peeled off with tape (press the tape against the grid area, press to remove bubbles, and then quickly tear it off at a 60° angle. Repeat 2 to 3 times). Observe the proportion of the coating peeling area under the light source and score it against the standard grade chart to determine the strength of the adhesion:

[0036] Grade 0 - no peeling, that is, the edge of the cut is completely smooth and there is no peeling on the edge of the grid;

[0037] Grade 1: There is small flaking at the intersection of the cuts, and the actual damage in the cross-cut area does not exceed 5%;

[0038] Grade 2 - The edges and / or intersections of the cuts are peeled, with the area exceeding 5% but less than 15%;

[0039] Level 3 - There is partial or complete flaking along the edge of the cut, and / or some grids are completely flaked. The flaked area is more than 15% but less than 35%;

[0040] Level 4 - Large pieces of the cut edge are peeled off / or some squares are partially or completely peeled off, the area of ​​which is greater than 35% of the cross-cut area but not more than 65%;

[0041] Level 5: Shedding area > 65%.

[0042] Example 1

[0043] (1) 60 parts of aqueous epoxy emulsion and 10 parts of glycidyl methacrylate grafted polyisobutylene copolymer emulsion were stirred at 5000 rpm for 10 minutes;

[0044] (2) Add 18 parts of curing agent emulsion, 5 parts of talc powder and 1 part of silane coupling agent, and disperse at high speed (1500 rpm) for 20 minutes;

[0045] (3) 6 parts of deionized water were used to adjust the viscosity to the construction requirements to prepare coating A.

[0046] Example 2

[0047] Similar to Example 1, except that the amount of glycidyl methacrylate grafted polyisobutylene copolymer emulsion added was adjusted to 5 parts, the amount of waterborne epoxy emulsion added was adjusted to 62 parts, and the amount of curing agent emulsion added was adjusted to 21 parts.

[0048] Example 3

[0049] Similar to Example 1, except that the amount of glycidyl methacrylate grafted polyisobutylene copolymer emulsion added was adjusted to 15 parts, the amount of waterborne epoxy emulsion added was adjusted to 57 parts, and the amount of curing agent emulsion added was adjusted to 16 parts.

[0050] Comparative Example 1

[0051] Similar to Example 1, except that the amount of glycidyl methacrylate grafted polyisobutylene copolymer emulsion added was adjusted to 0 parts, the amount of waterborne epoxy emulsion added was adjusted to 65 parts, and the amount of curing agent emulsion added was adjusted to 23 parts.

[0052] Comparative Example 2

[0053] Similar to Example 1, except that the amount of glycidyl methacrylate grafted polyisobutylene copolymer emulsion added was adjusted to 25 parts, the amount of waterborne epoxy emulsion added was adjusted to 50 parts, and the amount of curing agent emulsion added was adjusted to 13 parts.

[0054] Comparative Example 3

[0055] Similar to Example 1, except that the addition amount of the polyamide curing agent emulsion is adjusted to 30 parts, the addition amount of the water-based epoxy emulsion is adjusted to 50 parts, and the addition amount of the glycidyl methacrylate grafted polyisobutylene copolymer emulsion is adjusted to 8 parts.

[0056] Application testing:

[0057] The coatings in Examples 1-3 were applied to polypropylene and TPO boards (without pretreatment), and then dried and cured before being subjected to a cross-grid test.

[0058] The test results are shown in the following table:

[0059]

[0060]

[0061] The test results show that, while the coatings of Examples 1-3 remain VOC-free, their adhesion on PP and TPO is better than that of the system without glycidyl methacrylate grafted polyisobutylene copolymer (Comparative Example 1) or with an excess of glycidyl methacrylate grafted polyisobutylene copolymer (Comparative Example 2), fully verifying the excellent performance of the composition of the present invention.

[0062] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A composite coating composition for a plastic substrate, characterized in that: The composition comprises the following raw materials in parts by weight: 20-80 parts of water-based epoxy emulsion; 5-20 parts of glycidyl methacrylate grafted polyisobutylene copolymer emulsion; 3-20 parts of curing agent emulsion; Silane coupling agent 0.5-1 part; 2-10 parts of filler.

2. The composite coating composition for a plastic substrate according to claim 1, characterized in that: The waterborne epoxy emulsion is selected from liquid bisphenol A / F epoxy emulsion or solid bisphenol A / F epoxy emulsion; the solid content of the waterborne epoxy emulsion is 45-80%.

3. The composite coating composition for a plastic substrate according to claim 1, characterized in that: The glycidyl methacrylate grafted polyisobutylene copolymer emulsion is mainly prepared from polyisobutylene, glycidyl methacrylate, comonomer, initiator and stabilizer.

4. The composite coating composition for a plastic substrate according to claim 1, characterized in that: The solid content of the glycidyl methacrylate grafted polyisobutylene copolymer emulsion is 30-60 wt %.

5. The composite coating composition for a plastic substrate according to claim 1, characterized in that: The curing agent in the curing agent emulsion is selected from one or more of a water-based polyamide curing agent and a water-based imidazoline curing agent; and the solid content of the curing agent emulsion is 40-60%.

6. The composite coating composition for a plastic substrate according to claim 1, characterized in that: The silane coupling agent is selected from one or a combination of epoxy silane coupling agents, amino silane coupling agents, phenylamino silane coupling agents, vinyl silane coupling agents, isocyanate silane coupling agents, acrylic silane coupling agents, isobutylene silane coupling agents, styrene silane coupling agents, urea silane coupling agents, chloropropyl silane coupling agents, sulfide silane coupling agents.

7. The composite coating composition for a plastic substrate according to claim 1, characterized in that: The filler is selected from one or a combination of silicon micropowder, talc powder, and mica powder.

8. The method for preparing a composite coating composition for a plastic substrate according to any one of claims 1 to 7, characterized in that: The following steps are involved: First, water-based epoxy emulsion and glycidyl methacrylate grafted polyisobutylene copolymer emulsion are stirred and mixed at high speed, and then curing agent emulsion, silane coupling agent and filler are added and dispersed at high speed. Deionized water is used to adjust the viscosity to prepare the composite coating composition.

9. The method for preparing a composite coating composition for a plastic substrate according to claim 8, wherein: The speed of the high-speed stirring is 4000-6000 rpm, and the stirring time is 5-15 minutes; the speed of the high-speed dispersing is 1000-2000 rpm, and the dispersing time is 15-25 minutes.

10. Use of the composite coating composition according to any one of claims 1 to 7 in coating the surface of a plastic substrate.

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