JPH04363371A - Impact resistant primer and coating film forming method - Google Patents

Abstract

PURPOSE:To obtain an impact resistant primer containing specific amounts of a polyolefin resin in which its acid component is grafted and a butylated melamine resin, and useful for the formation of lamination coating film for car, etc. CONSTITUTION:The objective impact resistant primer containing (A) polyolefin resin being an ethylene-propylene copolymer in which the acid component of maleic (anhydride), etc., is grafted and (B) butylated melamine resin obtained by subjecting melamine resin to addition (condensation) reaction with an aldehyde and further subjecting the reactional product to etherification, at a weight ratio of the components (A):(B) of (90-50):(10-50).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a primer for forming impact-resistant laminated coatings, and more particularly to an impact-resistant primer useful for forming coatings on automobiles, etc., and a method for forming coatings.

0002

[Prior Art] Japanese Patent Publication No. 62-21027 discloses that a modified polyolefin primer, which is a conventional ethylene-propylene copolymer modified with an acid such as maleic acid, can be used as an adhesion improver when coating on plastics. It is publicly known.

[0003] Has the same composition as above, and has a Tg point of -30
JP-A-61-114779 discloses that a polyolefin substantially grafted with maleic acid is applied after electrodeposition at ~-60°C, and then various intermediate coats and top coats are applied to impart chipping resistance. It is disclosed in the No. 1 publication and elsewhere.

[0004] In addition, after the two parts are assembled, the Tg point is -30 to -60°C by applying the coating directly on the plastic member and after applying the electrodeposition coating on the iron member.
JP-A-61-11478 discloses that a polyolefin substantially grafted with maleic acid is coated, and then various intermediate coats and top coats are applied to impart chipping resistance.
It is disclosed in Publication No. 0.

[0005]

[Problems to be Solved by the Invention] The problem to be solved by the present invention is to provide an impact-resistant primer (hereinafter referred to as the present primer) suitable for applications requiring impact resistance in laminated coating films of two or more layers such as automobiles. The object of the present invention is to alleviate the difference in impact energy of delamination that tends to occur particularly when there is a large hardness difference between the base coat/intermediate coat and between the intermediate coat/top coat.

From this point of view, although using only polyolefin grafted with an acid component as the primer is flexible and effective in absorbing impact energy, the coating film strength and cohesive force are weak, and further improvements are desired. ing.

That is, an object of the present invention is to improve the impact resistance of laminated coating films for automobiles and other coating films that require impact resistance.

[0008]

[Means for Solving the Problems] According to the present invention, the above problems can be solved by a polyolefin resin (A
) (hereinafter sometimes referred to as grafted polyolefin resin) and butylated melamine resin (B) is 90.
~50:10-50 (parts by weight) of impact-resistant primers.

The grafted polyolefin resin used in the present invention is based on a copolymer with ethylene in which propylene accounts for 50 mol% or more, as shown in Japanese Patent Publication No. 62-21027, for example. Approximately 0.1 to 50% by weight of components such as maleic acid and maleic anhydride
, preferably 0.3 to 20% by weight, more preferably 5
~20% by weight grafted.

[0010] Butylated melamine resin is usually obtained by subjecting a melamine resin to an addition reaction or addition condensation reaction with an aldehyde such as formaldehyde or paraformaldehyde, and then etherifying it with butanol, isobutanol or the like. The preferred etherification rate is 20-90
%. Depending on the degree of reaction, methylol groups other than the alkylated methylol group, imino groups, etc. may be present.

[0011] In addition to the above, methyl and butyl mixed etherified melamine resins, methylated melamine resins, etc. can be used as the melamine resin, and when these ordinary melamine resins are applied to the present invention, the butylated melamine resin of the present invention can be used. Compared to the selected case, it is necessary to increase the baking temperature or to accelerate curing using an acid catalyst, which is not preferable.

[0012] The ratio of the grafted polyolefin resin and the butylated melamine resin is 90 to 50:10 to 50 (parts by weight), and if the ratio of the butylated melamine resin is less than 10%, interlayer formation may occur due to repeated thermal tests etc. The releasability decreases, and if it exceeds 50%, the flexibility becomes poor and the effect of absorbing impact energy is low, making it impossible to achieve the object of the present invention. A preferred range is 40 to 20 parts by weight of the butylated melamine resin to 60 to 80 parts by weight of the grafted polyolefin resin.

[0013] This primer has a high hardness (pencil hardness of about H to 2H) cationic electrodeposition coating and a relatively soft (pencil hardness of about F to H) polyester resin intermediate coating to be described later. Although it has a composition suitable for absorbing energy,
The undercoat film is softer than the cationic type (pencil hardness approximately HB-F)
) can be applied to the absorption of impact energy between the anionic electrodeposited coating and the hard polyester resin intermediate coating.
It can be used not only between the undercoat film and the intermediate coat film, but also between the intermediate coat film and the top coat film. The dry film thickness of this primer is 1 to 50 μm.

Pigments such as talc, zinc white, and barium sulfate are added to this primer in order to improve adhesion by adjusting the pigment weight concentration (
PWC) is preferably blended in a range of 5 to 20%. If the PWC is less than 5%, it is too soft and cracks occur when the laminated coating is subjected to a thermal cycle test, and if the PWC is more than 20%, the flexibility becomes poor and the impact energy absorption effect decreases, which is not preferable.

[0015] Preferred embodiments of this primer are as follows. (1) An impact-resistant primer whose acid component is maleic acid or maleic anhydride. (2) An impact-resistant primer in which the polyolefin resin is an ethylene-propylene copolymer. (3) An impact-resistant primer in which the propylene content of the ethylene-propylene copolymer is 50 mol% or more. (4) Pigment weight concentration (PWC) of impact-resistant primer
An impact-resistant primer having a content of 5 to 20%. (5) The ratio of (A) polyolefin resin grafted with an acid component to (B) butylated melamine resin is 80.
~60: Impact resistant primer having a content of 20 to 40 (parts by weight).

Examples of the electrodeposition paint used in the present invention include the cationic electrodeposition paint disclosed in Japanese Patent Publication No. 59-15929 and the anionic electrodeposition paint widely used heretofore.

[0017] As the intermediate coating paint used in the present invention, there are various types of paints that mainly have the anticorrosive properties of the undercoat paint and the function of helping the finish of the top coat paint.
An alkyd resin-based (polyester resin-based) intercoating paint containing fine-particle talc and having excellent chipping resistance as disclosed in Japanese Patent No. 951 is preferably used.

The top coating used in the present invention may be solid or metallic, and the type of coating may be water-based, powder-based, or solvent-based. For example, in the case of solid colors, chromatic paints such as white, red, and black are applied in one step on a polyester resin intermediate coating, and in the case of metallic colors, foil-like pigments such as aluminum are mixed. For example, the Tokko Kokko 1986-11, which is a wet-on-wet finish of clear paint on top of metallic paint.
907, or after applying a normal intermediate coating, apply a color intermediate coating of an appropriate hue range,
JP-A No. 63-53033, which was then coated with a glittering paint containing mica and a clear paint in a foil-like shape.
A typical example is the coating system disclosed in the above publication.

Further, as a typical example of a clear paint used as a top coat, there is a melamine resin curing type disclosed in JP-A-2-142867 whose acid value and hydroxyl value are specified.

Preferred embodiments of the coating film forming method of the present invention are as follows. (1) A coating film forming method in which the electrodeposition coating film is formed using a cationic electrodeposition paint. (2) A coating film forming method in which the electrodeposition coating film is formed using an anionic electrodeposition paint. (3) A coating film forming method in which an impact-resistant primer coating film and an intermediate coating coating film are formed by two coats and one bake using a wet-on-wet method. (4) A coating film forming method in which the coating film forming resin of the intermediate coating film is a polyester resin. (5) A coating film forming method in which the intermediate coating film is formed from a color intermediate coating paint. (6) A method for forming a coating film in which the intermediate coating film is formed of a chipping-resistant intermediate coating material. (7) A coating film forming method in which the top coat is derived from a solvent-based, powder-based, or water-based paint. (8) A coating film forming method in which a clear paint is applied over a solid color topcoat or a glittering pigment-containing topcoat to form a topcoat film. (9) A method for forming a paint film, in which a clear paint is overcoated on a metallic or metallic-like paint film to form a top coat.

[0021]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but these descriptions are merely illustrative and do not limit the scope of the present invention.

[0022]

[Table 1]

[0023]

[Table 2]

Formation of laminated coating film (i) Apply an undercoat [cationic electrocoating paint Power Top U-50 (hardness 2H) manufactured by Nippon Paint Co., Ltd.] to a dry film thickness of 20 μm. Baked at ℃ for 30 minutes. (ii) Apply this primer to a dry film thickness of 2 to 4 μm and apply it wet-on-wet to the next step (iii)
) I do.

(iii) Intermediate paint [Nippon Paint Co., Ltd.]
Co., Ltd.'s Olga P-2 (hardness F) (polyester resin paint)] was applied to a dry film thickness of 35 μm.
Baking was performed at ℃ for 25 minutes (the primer coating and intermediate coating were 2C/1B).

(iv) Top coat 1 [Superlac M-80 Silver (acrylic resin paint) manufactured by Nippon Paint Co., Ltd.] was applied to a dry film thickness of 18 μm, and the next step (v )I do.

(v) Top coat 2 [Nippon Paint Co., Ltd.]
Co., Ltd.'s Superlac O-100 Clear (acrylic resin paint)] was applied to a dry film thickness of 30 μm.
Baking was performed at 140°C for 25 minutes (top coat 1 and 2).
is 2C/1B).

[0028] A coating film obtained by the above process was used as a test piece for chipping resistance. A test piece for the thermal test was prepared by laminating top coats 1 and 2 of 2C/1B on top of the coating film obtained in the above process under the same coating conditions as above.

Evaluation method (i) Cold heat test The following test was performed on the test piece obtained in the above process by making scratches that reached the base material. The steps from ■ to ■ below were considered as one cycle: ■ -30
The steps of ±2°C x 1 hour, room temperature x 80 minutes, 80±2°C x 1 hour, room temperature x 80 minutes were repeated, and evaluation was made based on the number of cycles until cracking occurred. Note that an evaluation value of 5+ indicates that 5 cycles or more were performed.

(ii) Chipping resistance A test was conducted using a Gravelo tester under the following conditions. Stone: JIS A 5001 road crushed stone (size 10-15mmφ, amount 500g x 5 times) Test temperature -20°C Angle 90° Air pressure 5kg/cm2 Distance
35cm

Evaluation Chipping resistance A five-grade visual evaluation was conducted based on the following criteria, with the evaluation of the coating system without using a primer as the standard. ◎ Very good ○ Excellent △ Standard × Poor × × Very poor

(iii) Hardness (Primer) This primer was applied to a polished steel plate to a dry film thickness of 10 μm, baked at 140°C for 25 minutes, left for 24 hours, and then tested in accordance with JIS K 5400 8.4. (Pencil hardness) was measured at 2. In addition, the evaluation value 6B- is displayed as 6B.
Indicates that:

[0033]

[Table 3]

The following primers B1 to B5 were used in comparative examples. B1 This primer A1 to Yuban U-20N
-60 Excluding 1.9 parts, total 126.2 parts by weight B
2 Euban U-20N-6 of this primer A1
0 is 1.45 parts, total 126.65 parts by weight B3
19.5 parts of Euban U-20N-60 of this primer A1, total 145.7 parts by weight B4
Super Beckamine 13-53 for comparison primer B1
Added 2.3 parts by weight of 5J (total 128.3
Parts by weight) B5 20 parts by weight of Super Beckamine 13-535J added to comparative primer B1 (total 146.2 parts by weight)

[0035]

Effects of the Invention The present invention is capable of preventing delamination between two layers with different hardness, especially between an electrodeposition coating and an intermediate coating with different hardness, by using the present primer containing a specific melamine resin. This is an excellent invention that achieved its purpose.

Claims (2)

[Claims] 1. An impact-resistant primer characterized in that the ratio of polyolefin resin (A) grafted with an acid component to butylated melamine resin (B) is 90-50:10-50 (parts by weight). . Claim 2: (A) (i) An electrodeposition coating film is formed on a substrate, and (ii) the ratio of polyolefin resin (A) grafted with an acid component to butylated melamine resin (B) is 90. ~50: form an impact-resistant primer coating film of 10 to 50 (parts by weight), (iii) form an intermediate coat film, and (iv) form a top coat film, or (B) (
i) forming an electrodeposited coating film on the substrate, (ii) forming an intermediate coating film, and (iii) determining the ratio of the acid component-grafted polyolefin resin (A) and butylated melamine resin (B). 90-50: A method for forming a coating film, comprising forming an impact-resistant primer coating film of 10-50 (parts by weight), and (iv) forming a topcoat coating film.