JPH0527652B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a primer composition for plastics,
In particular, the present invention relates to a primer composition for plastics that is suitable for use in electrostatically applying a top coat for a car body. (Prior Art) Conventional primer compositions for plastics include, for example, polyurethane resin-based primer compositions that are commonly used for all plastic materials, and plastic materials such as polyamide resins, polybutylene terephthalate resins, and polycarbonate resins. Intermediate coatings for car bodies whose main composition is fatty acid-modified polyester resin, oil-free polyester resin, epoxy-modified polyester resin, melamine resin, etc.
No. 98575) was used. Under these circumstances, the following methods are used for painting plastic parts, especially plastic parts for automobiles.
For example, after a primer made of the above-mentioned polyurethane resin paint is applied and dried, it is applied to the car body that has been coated with an intermediate coat, and the top coat is applied either as an integral part of the car body or at the same time as the car body.
Separate printing is being performed. Or after molding and degreasing,
The intermediate coating for the car body, which has adhesive properties to polyamide resin, polybutylene terephthalate resin, polycarbonate resin, etc. and is suitable for the steel plates that make up the car body, is applied to the car body that has undergone the electrodeposition baking process, and is used as a primer. As an alternative, it can be painted integrally with the car body or painted at the same time as the car body, and after painting the intermediate coat, it can be applied for 80~
Baking is carried out at 120℃ for 5 to 20 minutes, and a top coat containing amino alkyd resin and amino acrylic resin as main components having the following composition is applied.
Then, after application, baking is performed at 130 to 150°C for 15 to 40 minutes to form a coating film. Top coat composition: (a) Amino alkyd resin-based 1-coat, 1-bake solid color (b) Aminoacrylic resin-based 2-coat, 1-bake solid color (c) Aminoacrylic resin-based 1-coat, 1-bake metallic color (d) Aminoacrylic resin 2-coat, 1-bake type metallic color (problem to be solved by the invention) However, in the case of such conventional primer compositions, after the primer composition is applied, a hard coating film is formed thereon. When topcoat paint for car bodies is applied electrostatically, (a) When subjected to impact at low temperatures, the impact resistance of the coated resin is significantly lower than that of uncoated resin materials. (b) When a conductive substance that improves electrostatic coating properties is mixed into a primer composition, there is a problem in that the above characteristics are further enhanced. (Means for Solving the Problems) This invention uses a modified polyolefin resin and a specific carbamate ester as binder components of a primer composition, and the modified polyolefin resin improves adhesion to plastic materials and shock absorption ability. The conductive substance is dispersed in the carbamate ester, preferably to increase the volume resistivity of the coating film.
The above-mentioned problem is solved by reducing the resistance to 10 ⁷ Ω-cm or less. In the plastic primer composition of the present invention, a modified polyolefin resin is used as the first essential component. Ethylene copolymer (A), the amount of grafting is
0.1 to 50 PHR (parts by weight/100 parts by weight of resin), preferably 0.3 to 20 PHR. The propylene-ethylene copolymer that is the raw material for the modified copolymer (A) is a random copolymer of propylene and ethylene, and the propylene content is 50 to 75 mol%, preferably 60 to 75% by mole.
It is in the range of 70 mol%. If the amount of maleic acid or its anhydride used in the modified copolymer (A) is less than 0.1 PHR, the adhesion of the primer composition to the plastic material and top coat will be insufficient, and the solubility in organic solvents will also decrease. . On the other hand, if it exceeds 50 PHR, the water resistance of the coating film will deteriorate. In addition, if the propylene content in the propylene-ethylene copolymer is less than 50 mol%, the solvent resistance of the coating film will be poor, and if it exceeds 75 mol%, the solubility in organic solvents will decrease, and the coating film material and top coat. adhesion to the surface is reduced. The method of grafting maleic acid or its anhydride onto the propylene-ethylene copolymer is a conventionally well-known method, for example, as described in JP-A-55-1989.
This is carried out using the method described in Publication No. 48260. Next, the specific carbamate ester used as the second essential component in this invention has the following general formula: It is a carbamic acid tester represented by (n in the formula is a number of 340 or less), and has excellent compatibility with the modified copolymer (A), without impairing the physical properties of the primer composition. It has the function of complementing the pigment dispersibility of the modified copolymer (A) in which it is extremely difficult to disperse the conductive substance (C), and has a function of complementing the pigment dispersibility of the modified copolymer (A), and preferably has a content of 5 to 30 PHR, preferably 10 to Used in the range of 20PHR. That is, the primer composition of the present invention can be easily prepared by dispersing the pigment or conductive substance (C) in advance with the carbamate ester (B) and then mixing it with the modified copolymer (A). If the amount of carbamate (B) used is less than 5 PHR, it will be difficult to disperse pigments and conductive substances;
If it exceeds 30 PHR, there is a drawback that the physical properties of the primer composition deteriorate. Further, the number average molecular weight of the carbamate ester (B) in the range of 500 to 1500 is suitable for dispersing the pigment without impairing the physical properties of the primer. Next, the conductive substance (C) used as the third component in the primer composition of the present invention is used as an essential component to improve the electrostatic coating properties of the top coat. For A)
It is used in a range of 100 PHR or less, preferably 20 to 50 PHR. If the amount of the conductive substance (C) exceeds 100 PHR, the physical properties of the primer coating film, particularly the viscosity, will decrease and the impact resistance will deteriorate. The use of conductive substances (C)
At 100 PHR or less, the volume resistivity of the dry primer film is 10 ⁷ Ω due to the electrostatic coating properties of the top coat.
-cm or less, preferably 10 ⁵ Ω-cm or less. Typical examples of conductive materials (C) include conductive carbon such as furnace black and channel black; metals such as silver, nickel, and aluminum; and semiconductor materials such as zinc oxide, tin oxide, tungsten oxide, and nickel-coated mica. can be mentioned,
These conductive substances may be used alone or in combination of two or more. In addition to the components (A) to (C) described above, an organic solvent is used in the composition of the present invention. The organic solvent used is one that can dissolve the modified copolymer (A) and the carbamate ester (B), which are binder components, and is a well-known organic solvent. Examples of the organic solvent include aromatic solvents such as benzene, toluene and xylene; aliphatic solvents such as hexane and heptane; alcohol solvents such as methanol, ethanol and butanol; and ketone solvents such as acetone and methyl ethyl ketone. , these can be used alone or in combination of two or more. The primer composition is prepared by mixing and dispersing the above-mentioned components using a ball mill, roll, attritor, dissolver, etc. that are commonly used in the production of paints. However, dispersing conductive substances is relatively difficult, so
It is advantageous to disperse this substance in the carbamate ester (B) in advance and add it when preparing the primer composition. The primer composition is applied to the plastic material by a commonly known method such as spray coating, dip coating, or roll coating. The primer composition may be dried by either natural drying or heat drying. The thickness of the coating film thus formed is usually 3
It is in the range of ~50 μm. (Function) The composition of the present invention is a modified copolymer as described above.
(A), a carbamate ester (B), and a conductive substance (C).As mentioned above, the carbamate ester has excellent compatibility with the modified copolymer (A), and is used as a primer composition. By supplementing the dispersibility of conductive substances in the modified copolymer (A), in which it is extremely difficult to disperse pigments and conductive substances (C) without impairing their physical properties, homogenization is promoted and the modified copolymer is Because the polymer (A) is given a polar component of maleic acid, the adhesion between the primer composition and the plastic material as well as the adhesion with the top coat applied thereon are greatly improved, making it easier to use. Improved solubility in organic solvents. Furthermore, since the modified copolymer (A) has viscosity, the coating film formed from the primer composition using it has extremely excellent impact absorption ability, and is superior to the coating film formed from the conventional primer composition. It has excellent impact resistance that is not found in other types of paint, and because it contains conductive substances, it can be applied electrostatically as a top coat. (Examples) The present invention will be described below with reference to Examples, Comparative Examples, and Test Examples. Examples 1 to 5 and Comparative Examples 1 to 6 Maleic anhydride modified propylene shown in Table 1
A conductive substance previously dispersed using butyl carbamate was added to a solution of an ethylene copolymer (modified acrylic resin in Comparative Example 5) dissolved in a mixed solvent of equal amounts of toluene and xylene (in Comparative Example 4). A primer composition was prepared by thoroughly mixing and dispersing with a paint conditioner.

[Table] Test Example The primer compositions of Examples 1 to 5 and Comparative Examples 1 to 6 were adjusted to a coating viscosity using the above-mentioned solvent, and spray-coated to a thickness of 5 μm on the following plastic materials at room temperature, and cured at room temperature. Next, apply 40μ of coconut oil-modified alkyd/melamine resin paint (manufactured by Kansai Paint Co., Ltd., trade name: Amirakku) on the primer coating.
A coated plate for testing was created by applying a thick electrostatic coating and curing with heat. The following experiments were conducted on these coated plates and the results are shown in Tables 2 to 4. In the coating film performance test results, ◎ indicates excellent, ◯ indicates good, △ indicates no problem in practical use, and × indicates poor. (a) Low temperature impact resistance (b) Paint film performance (a) Paint film appearance (b) Adhesion (c) Heat resistance (d) Moisture resistance (e) Gasoline resistance (c) Electrostatically coatable plastic material: (A) Polyamide (PA) resin 6-6 nylon or 6-6 nylon base filled with 5 to 40% of inorganic materials such as glass fiber and talc alone or in combination (Table 2). (B) Polybutylene terephthalate (PBT) resin Modified PBT blended with 5 to 20% elastomer such as polybutadiene and ethylene propylene rubber (EPR) as a means of improving impact resistance.
Resin (Table 3). (C) Polycarbonate (PC) resin Polycarbonate (PC) resin A blend of 5 to 40% PBT resin, etc. based on PC resin to improve heat resistance and chemical resistance (Table 4).

[Table] *4 Tested only on materials

[Table] *4 Tested only on materials

【table】

[Table] *4 Test evaluation method for materials only: (a) Low temperature impact resistance High rate impact test
Impact test) Using a RIT tester manufactured by Rheometrics Inc. in the United States,
Measure the impact energy when the center of impact punches out the sample (the moving speed of the center of impact remains constant before and after punching). In this test (-40°C and impact velocity of 11.1 m/sec), the yield energy must be 10 Joul or more. (b) Paint film performance (a) Paint film appearance Carry out the visual inspection with normal visual acuity from a position approximately 50 cm away from the surface to be inspected indoors under conditions of 500 Lux or higher using a daylight fluorescent lamp. However, painting defects such as blisters and pinholes may be treated from close range or diagonally. (b) Adhesion Using a multi-cross cutter, draw parallel lines of 1 mm at equal intervals that touch the substrate orthogonally to each other, using a multi-cross cutter to cut a 1 mm square on the coated surface of the test piece.
Make 100 pieces. In this state, adhere a cellophane adhesive tape with enough width and peel it upward at once.The number of squares where the painted surface does not peel off is counted and evaluated as a percentage of the total number (100 pieces). (c) Heat resistance The test piece was placed in a constant temperature bath at 90℃ for 500 hours.
After leaving it at room temperature for 24 hours, examine the appearance of the paint film and any changes to the paint surface caused by heat, such as discoloration or gloss shrinkage. (d) Moisture resistance Use a sealed box where both temperature and humidity can be adjusted. Place the test piece horizontally in a sealed box adjusted to a temperature of 50 ± 1°C and a relative humidity of 98% or higher, and check for blistering and humidity every 24 hours. Check the state of change and continue for up to 240 hours. (e) Gasoline resistance Approximately 0.3 to 0.5 ml of gasoline was dropped onto the surface of the test piece, and after leaving it in the test chamber for 4 hours, it was wiped off with a cloth and immediately removed, the coating film would become glossy, stained, or
Inspect for discoloration, softening, peeling, cracking, etc. (C) Electrostatic coating properties (a) Transfer efficiency measurement (TE) Wrap Saran wrap around the surface of the test piece, calculate the weight of the adhered paint from the difference in weight before and after electrostatic coating (measured after baking), and calculate the weight of the ejected paint (solid). Efficiency is measured from (calculated from minutes). (b) Coating quality confirmation (appearance measurement) Visually compare the appearance finish with a standard plate (air spray) and measure the film thickness from the cut cross section. (Effects of the Invention) As explained above, since the primer composition of the present invention contains a conductive substance in addition to the modified copolymer (A) and the specific carbamate ester (B), ( (b) Electrostatic topcoating is possible, (b) Low-temperature impact resistance does not deteriorate, (c) Intermediate coating can be substituted, reducing painting man-hours and costs, and (d) Polypropylene The effect can be obtained that it can be put to practical use as a primer for resin-based materials and polyurethane resin-based materials.

Claims (1)

[Scope of Claims] 1 (A) a modified propylene-ethylene copolymer grafted with maleic acid or its anhydride, and (B) the following general formula based on 100 parts by weight of this copolymer. A primer composition for plastics, characterized in that it contains 5 to 30 parts by weight of a carbamate ester represented by the formula (n represents a number of 340 or less) and 100 parts by weight or less of a conductive substance.