JP2000265109A - Primer composition for polypropylene coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a primer composition not lowering a finish appearance even if a top coating material is subjected to electrostatic coating on the surface of uncured coating film without heating and curing the applied coating film. SOLUTION: This primer composition for polypropylene coating comprises (A) a chlorinated polypropylene, (B) a polyester resin containing >=60 wt.% of the total of a polybasic acid such as adipic acid and a polyhydric alcohol such as ethylene glycol as monomer components, (C) a polyester resin containing >=60 wt.% of the total of a polybasic acid such as orthophthalic acid and a polyhydric alcohol such as propylene glycol as monomer components, (D) an epoxy resin, (E) a polyether resin and (F) a granular electroconductive substance in which the total solid content of the component B and the component C is 20-60 wt.% the total solid content of the component A to the component E and the solid content ratio of the component B to the component C is 1:0.5-1:2.0 by weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a novel primer composition for coating polypropylene.

[0002]

2. Description of the Related Art Polypropylene is widely used for plastic automobile parts such as bumpers and door side moldings, and its surface is usually coated with a top coating to improve aesthetics and durability. I have. Such a polypropylene coated article itself has a low polarity and does not have sufficient adhesion to an overcoat film, so that a primer (undercoat) composition is often applied in advance. Conventionally, as a method of coating a polypropylene object, for example, a process of primer coating-heat curing-top coat coating-heat curing, primer coating-heat curing-coating a top coating base paint-heat curing as required-top coating clear paint A coating-heat curing process and the like are typically performed. In these steps, the top coat is usually applied by electrostatic coating, has excellent finished appearance such as smoothness and sharpness, and has been put to practical use.

However, in recent years, from the viewpoints of productivity improvement and energy saving, in this coating process, it has been desired to realize a process in which a top coat can be electrostatically coated on the uncured coating surface without heating and curing the primer coating film. Have been.

Conventionally, as a primer composition for polypropylene coating, a composition comprising a mixture of urethane-modified chlorinated polypropylene, a hydroxyl- and carboxyl-containing polyester resin, an epoxy resin, a polyether resin, and a conductive substance has been known. Kaihei 6-136316).

However, when the primer coating is electrostatically coated on the uncured surface of the conventional primer composition without heating and curing the primer coating, the top coating is not uniformly applied, and is smooth and clear. It has been found that there is a drawback that it is difficult to finish a coated surface excellent in cinematography.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to achieve good adhesion between a polypropylene coated object and a topcoat film,
In addition, it is an object of the present invention to provide a primer composition which does not deteriorate the finished appearance even if the uncoated coating surface is electrostatically applied to the uncured coating surface without heating and curing the coating film.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned drawbacks of the prior art in coating a polypropylene-coated material, and as a result, a primer composition having a specific composition was found to have a polypropylene-coated material. That the primer coating has good adhesion with the top coat and that the primer coat can be obtained with excellent finish appearance even if the top coat is electrostatically coated without heating and curing the primer coat. The present invention has been completed based on the heading.

That is, the present invention relates to (A) chlorinated polypropylene, (B) as monomer components, adipic acid or its ester-forming derivative, sebacic acid or its ester-forming derivative, terephthalic acid or its ester-forming derivative, and At least one polybasic acid selected from hexahydroterephthalic acid or an ester-forming derivative thereof, ethylene glycol, 1,6-hexanediol and 1,
A polyester resin containing at least one polyhydric alcohol selected from 4-cyclohexanedimethanol in a total amount of 60% by weight or more, and as a (C) monomer component,
Orthophthalic acid, its anhydride or its ester-forming derivative, isophthalic acid or its ester-forming derivative,
At least one polybase selected from hexahydroorthophthalic acid, an acid anhydride or an ester-forming derivative thereof, hexahydroisophthalic acid or an ester-forming derivative thereof, and trimellitic acid, an acid anhydride or an ester-forming derivative thereof Acid and at least one selected from propylene glycol, neopentyl glycol, trimethylolethane, trimethylolpropane and glycerin
A polyhydric alcohol of at least 60% by weight or more, (D) an epoxy resin, (E) a polyether resin, and (F) a particulate conductive material,
In addition, the total solid content of the components (B) and (C) is 20 to 6 based on the total solid content of the components (A) to (E).
0% by weight, and the ratio of the component (B) to the component (C) is from 1: 0.5 to 1: 2.0 in terms of the weight ratio of the solid content.

[0009] The present invention also relates to a coating method characterized by applying the above-mentioned primer composition to an object to be coated with polypropylene, and then applying a top coat without curing the primer coating film.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The primer composition of the present invention will be described in detail.

The present primer composition is to be directly applied to the surface of a polypropylene substrate, and (A) a chlorinated polypropylene, (B) a polyester resin, (C) a polyester resin, and (D) an epoxy resin. , (E)
It is a composition containing a polyether resin and (F) a granular conductive substance.

(A) Chlorinated polypropylene A homopolymer of propylene or a chlorinated copolymer of propylene and another olefin monomer (eg, ethylene, butene, etc.). The chlorine content after chlorination is preferably in the range of 1 to 60% by weight, particularly preferably 10 to 40% by weight. The number average molecular weight is about 5,000 to about 2
00,000, especially about 20,000 to about 100,000
Is suitable. Stereotactically, either isotactic or atactic can be used.

(B) As a polyester resin monomer component, adipic acid or an ester-forming derivative thereof, sebacic acid or an ester-forming derivative thereof,
At least one polybasic acid selected from terephthalic acid or its ester-forming derivative and hexahydroterephthalic acid or its ester-forming derivative, and selected from ethylene glycol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol A polyester resin containing at least one polyhydric alcohol in a total amount of 60% by weight or more. Here, examples of the ester-forming derivative include mono to full C _1-10 alkyl esters of the corresponding acid.

That is, a polyester resin obtained by a polycondensation reaction of a polybasic acid having two or more carboxyl groups in one molecule and a polyhydric alcohol having two or more hydroxyl groups in one molecule, At least 60% by weight of the total solid content of these polybasic acids and polyhydric alcohols is composed of the specific polybasic acids and the specific polyhydric alcohols (hereinafter, these are referred to as monomers A). is necessary.

The polyester resin (B) containing the essential monomer A has a function of aggregating the coexisting particulate conductive substance (F) into a chain state to facilitate conductivity. There is a tendency for the dispersion stability of the substance to decrease. In the polyester resin (B), if the amount of the monomer A is less than 60% by weight, the aggregating ability of the particulate conductive substance (F) decreases, which is not preferable.

As the polybasic acid and polyhydric alcohol used for preparing the polyester resin (B), a monomer A alone or a mixture of the monomer A and a monomer B described later (an essential monomer in the polyester resin (C)) is used. The polyester resin (B) can be prepared by subjecting them to a polycondensation reaction. Particularly, in this polycondensation reaction, in a system in which monomer A and monomer B are used in combination, the amount of monomer A used is at least 60% by weight based on the total solid content of monomer A and monomer B,
Particularly, the range of 70 to 90% by weight is suitable.

The polycondensation reaction using the monomer A alone or a mixture of the monomer A and the monomer B for preparing the polyester resin (B) can be carried out by a method known per se. The obtained polyester resin (B) has a number average molecular weight of about 1,000 to about 5,000, particularly about 1,50.
0-3,000, hydroxyl value is 50-150 mgKOH / g, especially 60-120 mgKOH / g, acid value is 0.5-25 mgKOH / g,
Particularly, the range of 3 to 15 mgKOH / g is suitable.

(C) As the polyester resin monomer component, orthophthalic acid, its acid anhydride or its ester-forming derivative, isophthalic acid or its ester-forming derivative, hexahydroorthophthalic acid, its acid anhydride or its ester-forming Derivatives, hexahydroisophthalic acid or its ester-forming derivative and trimellitic acid, at least one polybasic acid selected from its acid anhydride or its ester-forming derivative, and propylene glycol, neopentyl glycol, trimethylolethane, A polyester resin containing at least 60% by weight or more of at least one polyhydric alcohol selected from methylolpropane and glycerin. Here, examples of the ester-forming derivative include mono to full C _1-10 alkyl esters of the corresponding acid.

That is, a polyester resin obtained by a polycondensation reaction between a polybasic acid having two or more carboxyl groups in one molecule and a polyhydric alcohol having two or more hydroxyl groups in one molecule, At least 60% by weight of the total solid content of these polybasic acids and polyhydric alcohols is composed of the specific polybasic acid and the specific polyhydric alcohol (hereinafter, these are referred to as monomers B). is necessary.

The polyester resin (C) containing the essential monomer B adsorbs the coexisting particulate conductive substance (F) and forms a protective layer on the surface thereof, so that the conductivity is lowered. The tendency to improve the dispersion stability of the particulate conductive material (F) is seen. 60% by weight of monomer B in polyester resin (C)
If the amount is smaller, the dispersion stability of the particulate conductive substance (F) is lowered, which is not preferable.

As the polybasic acid and polyhydric alcohol used for preparing the polyester resin (C), a monomer B alone or a mixture of the monomer B and the monomer A is used, and these are subjected to a polycondensation reaction. Thus, a polyester resin (C) can be prepared. Particularly, in this polycondensation reaction, in a system in which monomer B and monomer A are used in combination, the amount of monomer B used is
60% by weight or more, based on the total weight of the solid content of the monomer and the monomer A, and particularly preferably in the range of 70 to 90% by weight.

The polycondensation reaction using the monomer B alone or a mixture of the monomer B and the monomer A for preparing the polyester resin (C) can be carried out by a method known per se. The obtained polyester resin (C) has a number average molecular weight of about 1,000 to about 8,000, particularly about 2,000.
0 to about 5,000, hydroxyl value is 50 to 150 mgKOH / g,
In particular, 60 to 120 mgKOH / g, acid value is 0.5 to 25 mgKOH / g.
g, especially in the range of 3 to 15 mg KOH / g.

(D) A resin having two or more epoxy groups in one molecule of an epoxy resin . For example, a bisphenol-type glycidyl ether-based epoxy resin, a glycidyl group-containing acrylic epoxy resin, or the like can be preferably used. These have a number average molecular weight of about 1,500 to about 5,000 and an epoxy equivalent of 150 to 3
00 is preferred.

(E) polyether resin, for example, ethylene oxide, propylene oxide,
Polyether polyols based on one or more alkylene oxides selected from butylene oxide, tetramethylene oxide and the like can be suitably used, and these have a number average molecular weight of about 1,000 to about 200,
It is preferably in the range of 000, and may further have a hydroxyl group.

(F) Granular conductive substance The coating composition of the present primer composition is provided with conductivity,
It is for improving the electrostatic coating property of the topcoat paint on the coated surface, specifically, conductive carbon black,
Silver, nickel, copper, graphite and the like can be mentioned. The particle size is suitably in the range of 0.01 to 50 μm.

The primer composition of the present invention comprises (A) chlorinated polypropylene, (B) a polyester resin, (C) a polyester resin, (D) an epoxy resin, (E) a polyether resin, and (F) a particulate conductive material. And usually obtained by mixing them with a coating organic solvent.

The organic solvent may be any known one without particular limitation, and examples thereof include hydrocarbon-based, alcohol-based, ester-based, and ketone-based solvents.

The composition ratio of each of these components can be arbitrarily selected according to the purpose. For example, component (A), component (B),
Based on the total solid content of component (C), component (D) and component (E), component (A) is from 30 to 70% by weight, especially from 45 to 6% by weight.
5% by weight, the total solid content of the components (B) and (C) is 20 to 60% by weight, preferably 25 to 40% by weight,
The component (D) is 3 to 15% by weight, particularly 5 to 10% by weight,
The component (E) is suitably in the range of 3 to 15% by weight, particularly 5 to 10% by weight. The component (B): (C)
The ratio of the components is 1: 0.5 to 1: 2.0 in terms of solid content weight ratio. The component (F) is composed of the component (A), the component (B),
Total solid content of component (C), component (D) and component (E) 1
10 to 40 parts by weight, especially 15 to 25 parts by weight, per 100 parts by weight is suitable. When the total solid content of the component (B) and the component (C) deviates from the above-mentioned 20 to 60% by weight, the adhesion to the article to be coated or the top coat is reduced, and the component (B): C) The ratio of the components is 1: 0.5 to 1: 2.
When the ratio is outside the range of 0, the electrostatic coating property and the storage stability of the coating material are deteriorated.

In the primer composition of the present invention, the components (A), (B), (C), (D),
In addition to the component (E) and the component (F), if necessary, a color pigment such as a solid color pigment, a metallic pigment, and a light interference color pigment, an extender pigment, an anti-settling agent, and an ultraviolet absorber may be added. it can.

The primer composition of the present invention comprises the above (A)
The components, component (B), component (C), component (D), component (E) and component (F) are mixed and dispersed in an ordinary organic solvent for coatings, and the solid content is adjusted to 10 to 60% by weight. Then, it can be painted by air spray, airless spray or the like. The coating film thickness is 5 to 30 μm based on the cured coating film,
In particular, it is preferably from 10 to 20 μm. This coating film can be cured usually by heating at 80 to 160 ° C. for about 10 to 40 minutes.

The primer composition of the present invention has an excellent property that the finished appearance does not deteriorate even when the top coat is electrostatically coated on the uncured coated surface without heating and curing the primer coating film. I have.

Therefore, according to the present invention, there is provided a coating method comprising coating the above-mentioned primer composition on a polypropylene substrate, and then applying a top coat without curing the primer coating film. .

According to the above coating method of the present invention, the primer composition is coated with a top coat without heating and curing, for example, in an uncured state left at room temperature for 1 to 20 minutes after coating. . The method of applying the top coat is not particularly limited, and for example, can be applied by air spray, airless spray, electrostatic method, etc., and even in the case of the electrostatic method, the top coat is uniformly applied. The coated surface can be finished with excellent smoothness and sharpness.

Examples of the above-mentioned polypropylene-coated article include known propylene homopolymers and copolymers of propylene with other polymerizable monomers (eg, ethylene, butene, etc.). In particular, those molded into a shape such as an automobile part such as a bumper or a door side molding can be preferably used. It is preferable that these polypropylene coated articles are molded into a desired shape and size, and the surface is subjected to a chemical conversion treatment by a known method.

As the top coating, an organic solvent-based or water-based thermosetting coating which forms a coating film having excellent weather resistance, smoothness and chemical resistance can be suitably used. Specifically, base resins such as acrylic resin and polyester resin,
A crosslinker such as a melamine resin, a polyisocyanate compound, or a blocked polyisocyanate compound is used as a vehicle component, and a colorless or colored clear paint, a solid color paint, a metallic paint, a light interference color paint, and other top coat paints are exemplified.

The process for coating a polypropylene object using these top coats includes, for example, the following method.

Step a: Primer coating-Uncured-Coating of a top coat such as solid color paint by electrostatic method or the like-Heat curing. In this step, the top coat is one coat.

Step b: Primer coating-Uncured-Top coat base paint such as solid color paint, metallic paint, light interference color paint, etc. is applied by electrostatic method, etc.-Heat curing as required-Clear paint is applied by electrostatic method, etc. Heat curing. In this step, the top coat is two coats.

In these coating steps, the primer coating is preferably left at room temperature to 100 ° C. for about 1 to 10 minutes, for example, and then coated with an overcoat in an uncured state. It is also possible to apply the top coat after heating and curing for about 10 to 40 minutes.
In addition, the method of applying these top coats is not limited to the electrostatic method, and can be applied by any method selected from electrostatic coating, airless spray coating, air spray coating and the like.

The thickness of the top coat applied to the primer coating surface can be arbitrarily selected.
The top coat of step a is 10 to 60 μm, especially 15 to 45 μm.
μm, solid color paint, metallic paint of process b,
Top coat base paint such as light interference color paint is 10-30 μm,
Particularly suitable is 15 to 25 μm, and clear coating is 15 to 50 μm, particularly 25 to 35 μm. These top coats can be cured by heating at 80 to 160 ° C. for about 10 to 40 minutes.

[0041]

The present invention will now be described more specifically with reference to examples and comparative examples. All parts and percentages in each example are based on weight, and the thickness of the coating is based on the cured coating.

The following samples were used in each example.

As the chlorinated polypropylene of the component (A), "Sparklon S-892L" (A-1) (trade name, manufactured by Nippon Paper Industries Co., Ltd., a homopolymer of propylene, and a chlorine content of 22%) , The number average molecular weight was about 50,000).

As the polyester resin of the component (B),
114.6 parts of adipic acid, hexahydroterephthalic acid 1
35.0 parts, 84.2 parts of 1,6-hexanediol,
171.3 parts of 1,4-cyclohexanedimethanol, 79.0 parts of isophthalic acid and trimethylolpropane 6
A polyester resin (B-1) solution having a solid content of 60% obtained by subjecting 5.0 parts to a polycondensation reaction by a conventional method was used. Hydroxyl value 87 mgKOH / g, acid value 12 mgKOH / g, number average molecular weight 2,200.

As the polyester resin of the component (C),
111.5 parts of adipic acid, 1,6-hexanediol 6
0.1 parts, orthophthalic acid 67.8 parts, hexahydroisophthalic acid 180.3 parts, trimethylolpropane 10
A polyester resin (C-1) solution having a solid content of 60% obtained by subjecting 0.8 part and 136.3 parts of neopentyl glycol to a polycondensation reaction by a conventional method was used. Hydroxyl value 1
00 mg KOH / g, acid value 5 mg KOH / g, number average molecular weight 3,30
0.

As the epoxy resin (D), "Epon 1001" (D-1) (trade name, manufactured by Shell Chemical Co., Ltd.)
A bisphenol-type glycidyl ether-based epoxy resin, epoxy equivalent 480) was used.

As the polyether resin of the component (E),
"Exenol S-8500" (E-1) (trade name, number average molecular weight 1,500, manufactured by Asahi Glass Co., Ltd.) was used.

As the particulate conductive substance of the component (F),
“VUCIAN XC-72” (F-1) (trade name, conductive carbon particles having a particle size of 30 μm (0.03 μm) manufactured by Cabot Corporation) was used.

Examples 1 to 3 and Comparative Examples 1 to 6 The above components were mixed at the ratios shown in Table 1 to prepare a conductive primer composition for polypropylene coating. Table 1
Is a solid content.

[0050]

[Table 1]

Next, performance tests of the respective primer compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 6 were performed by the following methods.

Storage stability: 200 cc of the primer composition adjusted to a solid content of 20% was placed in a 200 cc measuring cylinder, allowed to stand at room temperature for 72 hours, and visually observed, and evaluated according to the following criteria. .

○ indicates that the supernatant liquid layer formed by sedimentation of barium sulfate or a conductive substance was 5 cc or less, and that no precipitate was observed in the lower layer (good storage stability). The supernatant layer was 5 to 20 cc, and a little soft precipitate was observed in the lower layer. However, the dispersion state can be easily restored to the original dispersion state by stirring (slightly poor storage stability). When the layer is 20 cc or more, generation of a large amount of precipitate is recognized in the lower layer, and it cannot be restored to the original dispersion state by stirring (poor storage stability).

Conductivity: 2 on the surface of the polypropylene sheet
A piece of conductive tape is stuck at an interval of 35 mm, and then a masking tape is stuck on the entire surface of the other electroconductive tape except for a width of 2 mm from the side at which the tape is spaced. And these masking tape parts,
Apply the primer composition to a film thickness of 10 to 15 μm on the 2 mm width part and the 35 mm space part, peel off the masking tape after 1 minute at room temperature, and heat at 120 ° C. for 20 minutes to cure the primer coating. Was. Next, based on the result of measuring the surface electric resistance between the two exposed conductive tapes with a surface resistivity meter (manufactured by TRECK, Germany), evaluation was made according to the following criteria.

は: 10 ⁸ Ω · cm or less (good electrostatic coating property), Δ: 10 ⁸ -10 ⁹ Ω · cm (electrostatic coating is possible, but coating efficiency is lowered), ×: 10 ¹⁰ Ω · cm or more ( (Electrostatic painting is impossible).

Table 2 shows the test results.

[0057]

[Table 2]

Examples 4 to 6 and Comparative Examples 7 to 12 Each of the primer compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 6 was used to coat a polypropylene object as follows.

After degreased the surface of polypropylene for automobile bumpers with isopropyl alcohol, each primer composition (solid content: 20%) was applied by air spray to a thickness of 10 to 15 μm, and left at room temperature for 1 minute. Thereafter, an organic solvent-based base coat ("SOFLEX 1400", trade name, manufactured by Kansai Paint Co., Ltd., trade name, polyester resin / melamine resin-based metallic paint) is applied to the uncured primer-coated surface to a thickness of 15 to 20 m. And then left at room temperature for 1 minute, then apply an organic solvent-based clear coat (“SOFLEX 1600”, manufactured by Kansai Paint Co., Ltd., trade name, acrylic resin melamine) to the uncured base paint-coated surface. (Resin clear paint)
The coating was electrostatically applied to a thickness of .mu.m and heated at 120.degree. C. for 20 minutes to simultaneously cure these three layers.

Next, the performance tests of the multilayer coating films obtained in Examples 4 to 6 and Comparative Examples 7 to 12 were performed by the following methods.

Adhesion: A cut line was made on the surface of the obtained multilayer coating film with a cutter so as to reach the substrate, and the size was 2 mm.
One hundred x2 mm squares were made, an adhesive cellophane tape was stuck to the surface, and the number of remaining coatings on the squares after abrupt peeling at 20 ° C. was examined to evaluate the adhesion. ○: 100 remaining coatings, Δ: 99 to 95, ×
Indicates 94 or less.

Finished appearance: The finished appearance was evaluated by examining the sharpness of the multilayer coating film. The sharpness was measured with a PGD meter (trade name, manufactured by Japan Color Research Institute).は indicates a PGD value of 0.7 or more, indicating good clarity, and △ indicates a PGD value of 0.4 to
A value of 0.6 indicates normal sharpness, and a symbol X indicates a PGD value of 0.3 or less and poor sharpness.

Table 3 shows the test results.

[0064]

[Table 3]

[0065]

According to the present invention, the following remarkable effects can be obtained.

1. The coating film of the primer composition of the present invention has good adhesion to a polypropylene coated object and a top coat film.

2. Without heating and curing the coating film of the primer composition of the present invention, even if an overcoat is applied by electrostatic method on the uncured coated surface, the overcoat is uniformly applied, and has smoothness and sharpness. Excellent finish can be applied.

3. Specific polyester resin (B) and polyester resin (C) in the primer composition of the present invention
By using together, it is possible to prevent a decrease in dispersion stability while coagulating the particulate conductive material (F) in a chain state, and as a result, the electrostatic coating property of the top coat is improved.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 123/26 C09D 123/26 163/00 163/00 171/02 171/02 (72) Inventor Kazuyuki Kuwano 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Tadahiro Kato 4-171-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Prefecture Kansai Paint Co., Ltd. (72) Inventor Hideyuki Yamada Higashi-Yawata, Hiratsuka-shi, Kanagawa Prefecture 4-17-1 Kansai Paint Co., Ltd. (72) Inventor: Satoshi Tachiki, Aichi Prefecture, Miyoshi-cho, Nishi-kamo-gun, Oaza, 1st place, clear ground, Kansai Paint Co., Ltd. (72) Inventor: Keita Ono, Miyoshi-cho, Nishi-kamo-gun, Aichi Large-sized azure raw flat No. 1 Kansai Paint Co., Ltd. F term (reference) 4D075 AA09 AE06 CA22 EB13 EB33 EB37 EC01 4J038 CB081 CB171 DB002 DD052 DD122 DF002 GA03 GA06 KA20 MA14 NA20 PA07 PC08

Claims (5)

[Claims] 1. A chlorinated polypropylene (A), (B) adipic acid or its ester-forming derivative, sebacic acid or its ester-forming derivative, terephthalic acid or its ester-forming derivative and hexahydroterephthalic acid as monomer components Or at least one polybasic acid selected from ester-forming derivatives thereof and at least one polyhydric alcohol selected from ethylene glycol, 1,6-hexanediol and 1,4-cyclohexanedimethanol in a total of 60 % By weight or more of a polyester resin, (C) as a monomer component, orthophthalic acid, an acid anhydride or an ester-forming derivative thereof, isophthalic acid or an ester-forming derivative thereof, hexahydroorthophthalic acid, an acid anhydride thereof or Ester-forming derivative, hexahydro At least one polybasic acid selected from sophthalic acid or its ester-forming derivative and trimellitic acid, its anhydride or its ester-forming derivative, and propylene glycol, neopentyl glycol, trimethylolethane, trimethylolpropane, and glycerin A polyester resin, (D) an epoxy resin, (E) a polyether resin, and (F) a particulate conductive substance containing at least one polyhydric alcohol selected from the group consisting of at least 60% by weight, and The total solid content of the components (B) and (C) is above (A)
20 to 60% by weight based on the total solid content of the components (E) to (E), and the ratio of the component (B) to the component (C) is 1: 0.5 to 1: 2.0 in terms of solid content weight ratio. A primer composition for polypropylene coating, characterized by comprising: 2. A polyester resin (B) having a number average molecular weight of about 1,000 to about 5,000 and a hydroxyl value of 50 to 150 mg.
The primer composition according to claim 1, which has a KOH / g and an acid value within a range of 0.5 to 25 mgKOH / g. 3. The polyester resin (C) has a number average molecular weight of about 1,000 to about 8,000 and a hydroxyl value of 50 to 150 mg.
The primer composition according to claim 1, which has a KOH / g and an acid value within a range of 0.5 to 25 mgKOH / g. 4. Component (A), component (B), component (C),
The mixing ratio of the component (D) and the component (E) is such that the component (A) is 30 to 70% by weight based on the total solid content thereof,
The components (B) and (C) have a total solid content of 2%.
0 to 60% by weight, the component (D) is 3 to 15% by weight, the component (E) is 3 to 15% by weight, and the component (F) is
The primer composition according to claim 1, wherein the amount is 10 to 40 parts by weight per 100 parts by weight of the total solid content of the components (A) to (E). 5. A coating method comprising applying a primer composition according to claim 1 to a polypropylene substrate, and then applying a top coat without curing the primer coating.