JP2969205B2 - Primer for polypropylene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene as an object to be coated and a primer for polypropylene having good adhesion to a top coat.

[0002]

2. Description of the Related Art Polypropylene is used for automobile bumpers, door side moldings and the like, and a top coat is applied to this polypropylene to improve aesthetics and durability.

[0003] Since the polypropylene itself has low polarity and does not have sufficient adhesion to the top coat, a primer (undercoat) is applied in advance. As the primer, a primer having a composition similar to that of the polypropylene is used. For example, a primer mainly containing chlorinated polypropylene is widely used. However, although the adhesion of the primer to polypropylene has almost reached a practical level, the adhesion to the top coat and the water resistance are not sufficient, and improvement of this defect is urgently required.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to develop a novel polypropylene primer having good adhesion to polypropylene (substrate) and a top coat, and excellent water adhesion. . As a result, it has been found that a composition comprising a mixture of urethane-modified chlorinated polypropylene, a specific polyester resin, an epoxy resin and a polyether resin can achieve the object and is useful as a primer for polypropylene, and completed the present invention. Was.

That is, the present invention relates to (A) a urethane-modified chlorinated polypropylene, (B) a hydroxyl value of 50 to 150, an acid value of 1 to 40, and a number average molecular weight of 1300 to 8000.
The present invention relates to a primer for polypropylene, characterized by comprising a polyester resin of (C), an epoxy resin and a (D) polyether resin as main components, and optionally further comprising (E) a conductive substance.

[0006] Polypropylene is a substrate to be coated with the primer of the present invention, and may be a homopolymer of propylene or a copolymer with another polymerizable monomer, such as a bumper or a side molding of an automobile. Is already widely used. The polypropylene is molded into a desired shape, and the surface thereof is preferably subjected to a chemical conversion treatment by a known method.

The primer for polypropylene of the present invention comprises:
It is applied directly to the polyurethane (substrate).

The polypropylene primer of the present invention will be described in more detail.

Component (A): urethane-modified chlorinated polypropylene.

The component (A) can be obtained by mixing or adding a chlorinated polypropylene and a polyurethane resin. Among them, chlorinated polypropylene is, for example, chlorinated propylene homopolymer or a copolymer of propylene homopolymer and another olefin monomer, and has a chlorine content of 1 to 60% by weight, particularly 10 to 10% by weight.
40% by weight is preferred. The chlorinated polypropylene has a number average molecular weight of 5,000 to 200,000, particularly 100
100-100,000 is suitable. Stereotactically, either isotactic or atactic can be used.

The polyurethane resin used for preparing the component (A) is a urethanization reaction product of a polyisocyanate compound and a polyol component, and has a free hydroxyl group and / or isocyanate group in the molecule. Is preferred. The polyisocyanate compound is a compound having two or more isocyanate groups in one molecule, and aliphatic, aromatic and alicyclic polyisocyanates known per se can be used. The polyol component has two or more hydroxyl groups in one molecule, and includes, for example, polyester polyol, polyether polyol, low molecular weight polyhydric alcohol and the like.

The component (A) used in the present invention can be obtained by simply mixing the chlorinated polypropylene and the polyurethane resin at ordinary temperature, or by heating to a temperature of about 50 ° C. or higher and hot blending. The two components may be reacted and chemically bonded by hot blending. The ratio of the two components can be arbitrarily selected according to the purpose. However, based on the total solid weight of the two components, chlorinated polypropylene is 5 to 95%, and polyurethane resin is 95%.
~ 5% is suitable.

Component (B): a hydroxyl value of 50 to 150, an acid value of 1 to 40, and a number average molecular weight of 1300 to 800
0 polyester resin.

The component (B) can be obtained, for example, by subjecting a polybasic acid component and a polyhydric alcohol component to an ester reaction. The polybasic acid component is a compound having two or more carboxyl groups in one molecule. One or more polybasic acids selected from aliphatic, alicyclic and aromatic polybasic acids can be used. . Among them, it is particularly preferable to contain an alicyclic polybasic acid. Known polybasic acid components can be used. In particular, when an alicyclic polybasic acid such as hexahydroterephthalic acid having a 1,4-cyclohexylene structure, methylhexahydroterephthalic acid or a lower alkyl ester thereof is used, the finished appearance, solvent resistance and coating film flexibility are obtained. This is preferable because a coating film having excellent properties and the like can be obtained. These anhydrides are also applicable.

The polyhydric alcohol component for preparing the component (B) is a compound having two or more hydroxyl groups in one molecule, and is selected from aliphatic, alicyclic and aromatic polyhydric alcohols. One or more of them can be used, and among them, it is particularly preferable to contain an alicyclic polyhydric alcohol. Known polyhydric alcohol components can be used. Among them, as alicyclic polyhydric alcohols, for example, 1,4-cyclohexanedimethanol having a 1,4-cyclohexylene structure, hydrogenated bisphenol A and hydrogenated The use of bisphenol F or the like is preferred because a coating film excellent in finished appearance, solvent resistance, coating film flexibility and the like can be easily obtained.

In the component (B), the content of the alicyclic polybasic acid and / or polyhydric alcohol component can be arbitrarily selected depending on the purpose.
5% by weight, especially 20-55% by weight, is preferred. Further, the component (B) can be obtained by a known esterification reaction using the above-mentioned polybasic acid component and polyhydric alcohol component together with, if necessary, a monobasic acid or hydroxycarboxylic acid.

The component (B) includes an esterification reaction product of the above-mentioned polybasic acid component and a polyhydric alcohol component (which may further contain a monobasic acid, hydroxycarboxylic acid, or the like), and a polyisocyanate. A urethane-modified polyester resin obtained by reacting a compound is also included. The polyisocyanate compound used here is 2 per molecule.
Examples thereof include aliphatic, alicyclic, and aromatic polyisocyanate compounds having at least two isocyanate groups. Further, addition products of these polyisocyanate compounds with polyhydric alcohols, buret type addition products, isocyanuric ring type addition products, and the like can also be applied as the above polyisocyanate compounds. Particularly, as a polyisocyanate compound, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, 1,3- (or 1,4-)
(Isocyanatomethyl) cyclohexane and addition products containing these are preferred. The ratio of the polyester resin and the polyisocyanate compound for preparing the urethane-modified polyester resin is preferably 0.5 to 20 parts by weight per 100 parts by weight of the polyester resin, and the hydroxyl group in the polyester resin is preferably in the polyisocyanate compound. Preferably, it is in excess of isocyanate groups.

The component (B) has a hydroxyl value of 50 to 150,
It is preferable that the acid value is 1 to 40, particularly 3 to 40, and the number average molecular weight is 1300 to 8000, particularly 1500 to 5000. If the hydroxyl value of the component (B) is less than 50, the adhesion to the top coat is reduced, while if it is more than 150, the water-resistant adhesion is undesirably reduced. Further, when the acid value is less than 1, the adhesion to the top coat decreases, and when the acid value is more than 40, the smoothness of the top coat decreases. When the number average molecular weight is less than 1300, the surface of the coating film becomes tacky, while when it is more than 8000, the compatibility with other components is reduced, and neither is preferred.

Component (C): an epoxy resin having two or more epoxy groups in one molecule, for example, bisphenol-type glycidyl ether, glycidyl group-containing acrylic resin, etc., having a number average molecular weight of 1500
It is preferable that the epoxy equivalent is 150 to 300 and the epoxy equivalent is 150 to 300, respectively.

Component (D): polyether resin.

For example, polyether polyols of one or more alkylene oxides selected from ethylene oxide, propylene oxide, butylene oxide, tetramethylene oxide and the like are preferred. These number average molecular weights are preferably in the range of about 1,000 to 200,000, and may have one or more hydroxyl groups in the molecule.

The primer of the present invention comprises the above (A)
The components (B), (C) and (D) are essential components, but if necessary, a mixture of (E) a conductive substance and (F) cellulose acetate butyrate (CAB) is also included. You.

Component (E): a conductive substance for imparting conductivity to the primer coating film, which is advantageous for improving the electrostatic coating property of the top coat on the primer coated surface.
Specifically, conductive carbon black, silver, nickel,
One or more selected from copper, graphite and the like are mentioned, and these are preferably in the form of powder or particles, and the particle size is suitably from 0.1 to 500 μm.

(F) Cellulose acetate butyrate (CAB) is a cellulose derivative obtained by further butyl etherifying a partially acetylated product of cellulose, and preferably has a degree of acetylation of generally 1 to 34% by weight, preferably 1 to 34% by weight. 7% by weight; butyl group content is generally 16 to
60% by weight, preferably 40-60% by weight; ASTM-
A viscosity of generally from 0.005 to 5 seconds, preferably from 0.005 to 1 second, according to the measurement method described in D-134154;
Are preferably included in the range. Specifically, a product name of a product of Eastman Kodak Company of America, a product name [the butyl group content (% by weight) up to the second digit of the former number, and 3
The digit indicates the hydroxyl group content, and the latter indicates the viscosity (second).]
CAB-171-2, CAB-381-2, CAB
-531-1, CAB-551-0.2 and CAB-5
5-0.01 and the like. Among them, from the viewpoints of solubility, compatibility, viscosity, etc., the butyl group content is high, and low viscosity C
AB-551-0.2 and CAB-55-0.01 are preferred.

The primer of the present invention is the above (A)
Components (B), (C) and (D) are essential components, and if necessary, components (E) and (F) are blended. The mixing ratio of these components can be arbitrarily selected according to the purpose. For example, based on the solid content weight, (A)
3 to 50 parts by weight of component (B) per 100 parts by weight of component,
Particularly preferred is 5 to 35 parts by weight, component (C) is 3 to 20 parts by weight, particularly 5 to 15 parts by weight, and component (D) is 3 to 20 parts by weight, particularly 5 to 15 parts by weight. Further, the component (E) is preferably 100 parts by weight or less, particularly preferably 3 to 50 parts by weight, per 100 parts by weight of the total of the components (A) to (D). Further, the component (F) is used in an amount of 100 parts by weight or less, especially 10 to 5 parts by weight, per 100 parts by weight of the total of the components (A) to (D).
0 parts by weight is preferred.

The primer of the present invention is obtained by mixing and dispersing the above-mentioned components in a usual organic solvent for coating, and obtaining a solid content of 1%.
It is obtained by adjusting to 0 to 60% by weight.

The coating of the polypropylene primer of the present invention is preferably performed mainly by air spray or airless spray. The coating thickness is 5 based on the cured coating.
About 30 μm is preferable, and the coating film is 80 to 15 μm.
It can be cured by heating to about 0 ° C.

An overcoat can be applied to the heat-cured primer-coated surface. As the topcoat paint, any paint that forms a coating film having excellent weather resistance, smoothness and chemical resistance may be used. Specifically, acrylic resin / amino resin or polyisocyanate, alkyd resin or polyester resin /
An overcoating material known per se, such as an amino resin or a polyisocyanate, may be used. These top coats can be used as clear paints containing no or little coloring agents such as color pigments and metallic pigments, solid color paints containing color pigments, and metallic paints containing metallic pigments. These top coats are preferably organic solvent systems using an organic solvent as a solvent or dispersion medium, but may be aqueous paints using water as a solvent or dispersion medium.

The thickness of the top coat is 1 based on the cured coat.
A range of about 0 to 60 μm is preferable. In this case, the top coat may be applied while the primer coating is not cured, and then heated to simultaneously cure the primer coating and the top coating. It is preferable that the top coat is applied by an electrostatic coating method. Examples of the coating method of the top coat include a one-coat method using a solid color paint, a two-coat method using a solid color paint or a metallic paint and a clear paint, and the like.

[0030]

The coating film of the primer of the present invention has excellent adhesion to the polypropylene and the topcoat film. Particularly, even if the coating film is immersed in warm water for a long time, deterioration of the adhesion of the coating film and generation of blisters are recognized. I can't.

Examples and comparative examples according to the present invention will be described. All parts and percentages are in principle based on weight.

I sample 1) Component (A): urethane-modified chlorinated polypropylene

[0033]

[Table 1]

In Table 1, (* 1) Composition ratio: solid content weight ratio.

(* 2) Polyurethane: an adduct of diisocyanate and glycol, having an isocyanate group at the terminal.

2) Component (B): Polyester resin The starting materials shown in Table 2 were reacted in a conventional manner, and then the diisocyanate shown in the same table was subjected to an addition reaction.

[0037]

[Table 2]

Examples 1 to 3 The components shown in Table 3 were mixed and dispersed to prepare a primer of the present invention.

[0039]

[Table 3]

In Table 3, (* 1) Epon 1001: manufactured by Shell Chemical, trade name.

(* 2) Exenol S-8500: trade name, manufactured by Asahi Glass Co., Ltd.

(* 3) Ketchen Black EC: manufactured by Lion Corporation, trade name.

II Performance Test Results The surface of polypropylene for automobile bumpers was treated with trichloroethane and then treated with the primer (solid content 2%).
(Adjusted to 0%) based on the cured coating film by air spraying, and applied to a thickness of 10 to 20 μm, heated and cured under the conditions shown in Table 4 below, and the performance of the formed primer coating film Was tested.

Then, an organic solvent-based solid color topcoat (polyester resin / melamine resin, white) is spray-coated on the primer film thus formed by air spray (the film thickness based on the cured coating film is 25 to 25). 35 μm),
It was cured by heating at 120 ° C. for 20 minutes. The performance of the multilayer coating film thus formed was also evaluated, and the results are shown in Table 4.

[0045]

[Table 4]

Comparative Examples 1 to 7 in Table 4 are as follows.

In Comparative Example 1, the primer of Example 1 was used as a primer.
A primer obtained by removing the polyester resin (B-1) from the composition of the primer was used.

In Comparative Example 2, the primer of Example 1 was used as a primer.
A primer obtained by removing urethane-modified polypropylene (A-1) from the composition of the primer was used.

In Comparative Example 3, the primer of Example 1 was used as a primer.
In the composition of the primer, the polyester resin (B-
The one in which the hydroxyl value of 1) was changed to 45 was used.

Comparative Example 4 uses Example 1 as a primer.
In the composition of the primer, the polyester resin (B-
The thing which changed the hydroxyl value of 1) to 160 was used.

Comparative Example 5 uses Example 1 as a primer.
In the composition of the primer, the polyester resin (B-
The one obtained by changing the acid value of 1) to 50 was used.

Comparative Example 6 uses Example 1 as a primer.
In the composition of the primer, the polyester resin (B-
The one obtained by changing the number average molecular weight of 1) to 1,000 was used.

In Comparative Example 7, the primer of Example 1 was used as a primer.
In the composition of the primer, the polyester resin (B-
The one obtained by changing the number average molecular weight of 1) to 10,000 was used.

Test method Initial adhesion of the primer alone: The above primer was air-sprayed onto polypropylene for automobile bumpers, the surface of which was treated with trichloroethane.
0 μm, dried by heating under the conditions shown in Table 4, and cooled to room temperature.
Cut with a knife to reach the substrate so that 100 mm squares are formed. An adhesive cellophane tape was stuck on the surface, and the cells remaining after sharply peeling off were examined. ○ indicates that no peeling was observed, and x indicates that many peelings occurred.

Initial adhesion after top coating: The above primer was applied to polypropylene for automobile bumpers whose surface was treated with trichloroethane by air spray so that the film thickness based on the cured coating film became 20 μm, and is shown in Table 4. After drying by heating under the conditions described above, and cooling to room temperature, this primer coating is spray-coated with an organic solvent-based solid color top coating (polyester resin / melamine resin) by air spray (a film based on a cured coating). 25-35 μm thick)
It was cured by heating at 120 ° C. for 20 minutes. On this painted surface,
Cut with a blade to reach the substrate so that 100 squares of 2 × 2 mm are formed. An adhesive cellophane tape was stuck on the surface, and the cells remaining after sharply peeling off were examined. ○ indicates that no peeling was observed, and x indicates that many peelings occurred.

Water adhesion: After immersion in warm water of 40 ° C. for 10 days, dried at room temperature, and then cut with a blade to reach the substrate so that 100 squares of 2 × 2 mm are formed on the coating film. . An adhesive cellophane tape was stuck on the surface, and the cells remaining after sharply peeling off were examined. ○ indicates that no peeling was observed, and x indicates that many peelings occurred.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code FI C09D 175/04 C09D 175/04 (72) Inventor Junichi Yamashita 1 Daiji, Hiyoshi, Miyoshi-cho, Nishi-kamo-gun, Aichi Prefecture Kansai Paint Co., Ltd. (72) Inventor: Akihiro Tsuge 1st floor of Azashiji, Miyoshi-cho, Nishikamo-gun, Aichi Prefecture Kansai Paint Co., Ltd. (56) References JP-A-58-76265 (JP, A) JP-A-59-38236 (JP, A JP-A-4-296376 (JP, A) JP-A-4-18474 (JP, A) JP-A-5-279622 (JP, A) JP-A-6-142606 (JP, A) 263038 (JP, A) JP-A-2-120373 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09D 123/26 C09D 5/00 C09D 163/00 C09D 167/00 C09D 171/02 C09D 175/04

Claims (1)

(57) [Claims] (A) a urethane-modified chlorinated polypropylene, (B) a polyester resin having a hydroxyl value of 50 to 150, an acid value of 1 to 40 and a number average molecular weight of 1300 to 8000, (C) an epoxy resin and (D) A) A primer for polypropylene, which comprises a polyether resin as a main component, and further contains (E) a conductive substance as needed.