JPS61218639A - Primer composition for plastic - Google Patents

Abstract

PURPOSE:To provide a primer composition containing a maleic acid-modified propylene-ethylene copolymer, a specific carbamic acid ester and an electrically conductive substance, applicable by electrostatic coating, and giving a coating film having excellent adhesivity to plastic material and shock-absorbing property. CONSTITUTION:The objective primer for plastic contains (A) 100pts.wt. of a modified propylene-ethylene copolymer obtained by grafting maleic acid or its anhydride to the copolymer, (B) 5-30pts.wt. of a carbamic acid ester of formula (n is integer of <=340) and (C) <=100pts.wt. of an electrically conductive substance (e.g. electrically conductive carbon; metals such as silver, nickel, aluminum, etc.; semiconductor substance such as zinc oxide, tin oxide, tungsten oxide, nickel-coated mica, etc.).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a primer composition for plastics, and particularly to a primer composition for plastics suitable for electrostatic coating and removal of top coats for car bodies.

(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 meliamide resin, polybutylene terephthalate resin, and polycarbonate resin. Polyester resin modified with fatty acids, oil-free polyester resin,
Intermediate paint for car bodies whose main composition is epoxy-modified polyester resin, melamine resin, etc. (for example, JP-A-57-98
575) was frowned upon. Under these circumstances, the following methods are used to paint plastic parts, especially plastic parts for automobiles. For example, after the primer made of the polyurethane resin paint is applied and dried,
It is applied to the car body after the intermediate coating, and the top coat paint is applied to the car body as an integral part or at the same time as the car body.
Baking is performed at 50°C for 15 to 40 minutes. Or, after molding and demolition, it is put into the car body that has undergone electrodeposition baking treatment, and has adhesion to meliamide resin, melibutylene tele-7 tallate resin, polycarbonate resin, etc., and is suitable for steel plates that make up the car body. The above-mentioned intermediate coating for car bodies is applied as a substitute for a primer when the car body is assembled or applied simultaneously with the car body, and after the intermediate coating is baked at 80 to 120°C for 5 to 20 minutes, it is further made to have the following composition. A top coat containing amino alkyd resin and amino acrylic resin as main components is applied, and then heated at 130 to 150°C for 1 hour after application.
Baking is performed for 5 to 40 minutes to form a coating film.

Top coat composition: a) Amino alkyd resin 1 coat 1 bake type solid color 2) Amino acrylic resin 2 coats 1 base mv solid color 1 amino acrylic resin 1 coat) 1 bake type metallic color 2) Amino acrylic resin 2-coat, 1-bake type metallic color (problems to be solved by the invention) However, with such conventional primer compositions, after the primer composition is applied, a hard coating film is formed thereon. When the top coat for the car body is electrostatically coated 1 (a) When subjected to impact at low temperatures, the impact resistance of the coated resin is significantly lower than that of the uncoated resin material.

(→ There is a problem that when a conductive substance that improves electrostatic coating properties is mixed into a primer composition, the above characteristics are further promoted.

(Means for Solving the Problems) This invention uses a modified polyolefin resin and a specific carnocumic acid ester as a binder component of a primer composition, and the modified polyolefin resin improves adhesion to plastic materials and shock absorption. by dispersing a conductive substance with a carbamate ester and preferably reducing the volume resistivity of the coating film to 107 Ω-am or less.
This solves the above problems.

In the plastic brimer composition of the present invention, a modified polyolefin resin is used as the first essential component. Ethylene copolymer (4) with a grafting amount of 0.1 to 50 PHR (parts by weight/10 parts by weight)
0 parts by weight), preferably from 0.8 to 20 PER.

The propylene-ethylene copolymer that is the raw material for the modified copolymer (g) is a random copolymer of propylene and ethylene, and the propylene content is in the range of 50 to 75 molti, preferably 60 to 70 molti. .

The amount of lehnic acid or its anhydride used in the modified copolymer ① is 0. If it is less than IPHR, the adhesion of the primer composition to the plastic material and the 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 moles, the solvent resistance of the coating film will be poor, and if it exceeds 75 moles, the solubility in organic solvents will decrease and the coating film material will be and adhesion to top coat paints is reduced.

The grafting method of leicic acid or its anhydride to the propylene-ethylene copolymer is carried out using a conventionally well-known method, for example, the method described in JP-A-55-48260. .

Next, the specific carbamate ester used as the second essential component in this invention is a carbamate ester represented by the following general formula (n in the formula is a number of 340 or less), and is a modified copolymer. ■A function that complements the pigment dispersibility of the modified copolymer (4), which has excellent toner compatibility and is extremely difficult to disperse pigments and conductive substances (0) described later, without impairing the physical properties of the primer composition. It is used in a range of 5 to so PHR%, preferably 10 to 20 PEH, based on the modified copolymer (1). That is, the primer composition of the present invention can be easily prepared by dispersing the pigment or conductive substance (0) in advance with the carbamate ester (B) and then mixing it with the modified copolymer (1).

If the monthly usage amount of carbamate ester (B) is less than 5 PHR, it will be difficult to disperse pigments and conductive substances;
If it exceeds 0 PHR, there is a drawback that the physical properties of the primer composition deteriorate. Also, carbamate ester (B)
A number average molecular weight in the range of 500 to 1,500 is suitable for dispersing pigments without impairing the physical properties of the primer.

Next, the conductive substance (0) used as the eighth 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 paint.
100 PER or less with respect to the modified copolymer (4),
Preferably, it is used in the range of 20 to 50 PHR. If the amount of the conductive substance (C) exceeds 100 P, the physical properties of the primer coating, especially the viscosity, will deteriorate and the impact resistance will deteriorate. Use of conductive material (C) is below 100 PHR,
The volume resistivity value of the dry primer coating film is 1079-C or less, preferably 105-C from the viewpoint of electrostatic coating properties of the top coat.
The composition is adjusted so that the resistance is Ω-C or less.

Typical examples of conductive materials include conductive carbon such as 7 Arnes black and channel black; gold such as silver, nickel, and aluminum; semiconductor materials such as zinc oxide, tin oxide, tungsten oxide, and nickel-coated mica. These conductive substances can be used alone or in combination with 2s or more.

The composition of this invention contains the above-mentioned components (1) to (C).
Besides, organic solvents are used. The organic solvent is one that can dissolve the modified copolymer (I) and the carbamate ester (B), which are binder components, and a conventionally well-known organic solvent is used. Examples of the organic solvent include aromatic solvents such as benzene, toluene and xylene; aliphatic solvents such as hexane and heptane; alcohols such as methanol, ethanol and butanol; 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, desilver, etc. that are commonly used in the production of paints. However, since it is relatively difficult to disperse the conductive substance, it is advantageous to disperse this substance in the carbamate ester (B) in advance and add it to the carbamate ester (B) 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 in the range of 8 to 50 μm.

(Function) As mentioned above, the composition of the present invention contains the modified copolymer (4), the carbamate ester @), and the conductive substance (G). Conductive substances such as the modified copolymer (1) have excellent compatibility with the polymer (1), and it is extremely difficult to disperse pigments and conductive substances (C) without impairing the physical properties of the primer composition. By supplementing the dispersibility, homogenization is promoted, and since the modified copolymer (4) is given a polar component of lehnic acid, it improves the adhesion of the primer composition to the plastic material and the ability to coat it on it. The adhesion with the top coat paint is greatly improved, and the solubility in the organic solvent used is also improved. Furthermore, since the modified copolymer (1) 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.

Butylcarbamate was preliminarily dispersed in a solution of the anhydrous acid-modified propylene-ethylene copolymer (modified acrylic resin in Comparative Example 5) shown in Table 1 dissolved in a mixed solvent of equal amounts of toluene and xylene. A primer composition was prepared by adding a conductive substance (in Comparative Example 4, only the conductive substance was added) and sufficiently mixing and dispersing with a paint conditioner.

Test Examples 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 onto the following plastic materials to a thickness of 5 μm at room temperature, and cured at room temperature. Next, a coconut oil-modified alkyd/melamine resin paint (manufactured by Kansai Heint Co., Ltd., trade name: Amirac) was electrostatically coated onto the primer coating film to a thickness of 40 μm and cured by heating to prepare a coated plate for testing. 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, O indicates good, Δ indicates no problem in practical use, and × indicates poor.

(a) Low-temperature impact resistance (b) Paint film performance (a) Coverage performance (b) Adhesion (c) Heat resistance) Moisture resistance (e) Gasoline resistance (c) Electrostatic paintability/plastic material : (4) Polyamide (P) resin based on 6 nylon or 6-6 nylon, with glass fiber, talc, and other inorganic materials alone or in combination. ')
411 Modified PBT resin blended with 5 to 20 elastomers such as polybutadiene and ethylene propylene rubber (KPR) as a means of improving impact resistance (Table 8).

(0 Polycarbonate (pa) resin A blend of 5 to 40% PBT resin etc. based on PO resin as a base to improve heat resistance and chemical resistance (Table 4).

Evaluation method: (a) Low temperature impact resistance high rate impact test (HjJh mate Im
parttest) Measure the impact energy when the center of impact punches out the sample using the R Engineering T testing machine manufactured by IJ Tsuku (Rheome, USA) (The moving speed of the center of impact is always maintained at a constant speed without changing before and after punching. drip). The test (impact velocity 11.1 at -40℃
m/sea condition), the yield energy is IQ
The condition is that it is Jou1 or higher.

(b) Coating film performance (a) Coating film appearance The appearance is inspected indoors under a daylight color fluorescent lamp with a brightness of 50 lux or more, from a position approximately 5 Qcm away from the surface to be inspected, with normal visual acuity.

However, paint defects such as blisters and pinholes can be detected at close range a!
)" You can do it from the diagonal direction〇 (→Use a multi-cutting cutter on the coating surface of the adhesion test and draw parallel lines at equal intervals IIIm that touch the substrate orthogonally to each other. Make 100 squares.In this state, stick a cellophane adhesive tape with enough width and peel it upwards at once.The number of squares without peeling of the painted surface is counted and evaluated as a percentage of the total number (100).

(c) The heat resistance test piece was placed in a constant temperature bath at 90° C. for 500 hours, and after being left at room temperature for 24 hours, the appearance of the coating film, discoloration, and changes in the coating surface due to heat, etc. were examined.

) Humidity resistance for both temperature and humidity! ! Using an adjustable sealed box, 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 the occurrence of blistering and its changes every 24 hours for 24 hours. I will do it until (e) Drop about 0.8 to 0.5 m of Ganlin onto the surface of the gasoline resistance test piece, leave it in a test chamber for 4 hours, wipe it off with a cloth, and immediately remove any stains, discoloration, or stains on the paint film. Inspect for softening, peeling, cracking, etc.

(0) Electrostatic coating properties H) 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 painting (baking diameter measurement), and measure the weight of the discharged paint (solid content). Efficiency is measured from

(b) Coating quality confirmation (exterior measurement) Visually compare the exterior finish with a standard plate (air spray) and measure the film thickness from the cut section.

(Efficiency of the Invention) As explained above, the primer composition of the present invention contains a conductive substance in addition to the modified copolymer (2) and the specific carbamate ester (2). ) Electrostatic top coat coating is now possible, (→ Low temperature impact resistance does not deteriorate, (c) Intermediate coat coating can be substituted, reducing painting man-hours and costs, (2) Polypropylene resin material Moreover, the effect can be obtained that it can be put to practical use as a primer for a polyurethane resin material layer.

Claims (1)

[Claims] 1(A) A modified propylene-ethylene copolymer grafted with lenic acid or its anhydride, and this copolymer 100
To parts by weight, (B) 5 to 30 parts by weight of a carbamate ester represented by the following general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (n in the formula indicates a number of 340 or less) and conductivity. substance 10
A primer composition for plastics, characterized in that it contains 0 parts by weight or less.