JPH0726088A - Aqueous primer composition - Google Patents

Abstract

PURPOSE:To provide an aqueous primer compsn. being a stable emulsion, with excellent appearance and water resistance and giving a primer coating film with good adhesion to the substrate. CONSTITUTION:This primer compsn. is prepd. by neutralizing a modified chlorinated polypropylene resin prepd. by graft-polymerizing a chlorinated polypropylene resin, an unsatd. carboxylic acid and at least one emulsifier selected from a polymerizable nonionic emulsifier and an ammonium salt type polymerizable anionic emusifier, with an amine and emulsifying it into water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous primer composition used for coating plastic molded products such as polypropylene resin molded products for automobile bumpers.

[0002]

2. Description of the Related Art Bumpers for automobiles have been changed to plastic moldings in order to reduce their weight and diversify their designs. Among the plastic molded products, thermoplastic resin molded products such as polypropylene resin can be recycled, and their future use will further increase. Since a polypropylene resin easily repels an organic solvent or water, a primer composition that forms a primer coating film that is easy to apply and has excellent adhesiveness is required.

In the field of coating, in order to reduce environmental pollution by organic solvents as much as possible and further improve safety and health for workers, organic solvent type paints have been changed to water-based paints, and primer is also the same. Is changing. Compared with the organic solvent type primer, the aqueous emulsion type primer has a content of the organic solvent reduced to about 1/10 or less, contains a resin as a coating film forming element in a higher concentration, and has a lower content. Viscosity. That is, the organic solvent type primer cannot contain the resin, which is a coating film forming element, in a high concentration when the viscosity is low enough to be applied.

The aqueous primer composition proposed in Japanese Patent Laid-Open No. 4-72337 is a carboxyl group-containing modified chlorinated polyolefin obtained by graft-polymerizing an unsaturated carboxylic acid such as maleic acid or acrylic acid onto a chlorinated polyolefin, and a urethane resin. Also, the epoxy resin is used as an essential component, the main component resin is neutralized with a tertiary amine, and dispersed in water with a surfactant. Neutralization with a tertiary amine makes it possible to simultaneously perform aqueous conversion and chain extension.

[0005]

When the acid group contained in the modified chlorinated polyolefin is neutralized with an amine, the amine is dissolved in the organic solvent in which the modified polyolefin is dissolved, and the chlorinated polyolefin part is decomposed. I can not make an emulsion. An aqueous primer composition obtained by emulsifying the modified chlorinated polyolefin with an emulsifier without neutralizing it with an amine forms a coating film having low water resistance because the emulsifier remains in the primer coating film. Further, the conventional aqueous primer composition has insufficient adhesion to the base.

An object of the present invention is to provide a water-based primer composition which is a stable emulsion, has excellent appearance and water resistance, and has good adhesion to a substrate.

[0007]

In order to solve the above problems, the present invention is selected from a chlorinated polypropylene resin, an unsaturated carboxylic acid, a polymerizable nonionic emulsifier and an ammonium salt type polymerizable anionic emulsifier. Provided is an aqueous primer composition in which a modified chlorinated polypropylene resin obtained by graft polymerization with at least one emulsifier is neutralized with an amine and emulsified in water.

The chlorinated polypropylene resin used in the present invention has only to be chlorinated to the extent that the polypropylene resin, which is a homopolymer of propylene, becomes soluble in an organic solvent. For example, the degree of chlorination is 20 to 30% by weight. . Here, the degree of chlorination is the amount of chlorine (percentage by weight) in the solid content of the chlorinated polypropylene resin. If the degree of chlorination is less than 20% by weight, the chlorinated polypropylene resin may not be soluble, and if it exceeds 30% by weight, the adhesion of the chlorinated polypropylene resin may deteriorate.

Unsaturated carboxylic acids are graft polymerized to modify the chlorinated polypropylene resin so that it has acid groups. The unsaturated carboxylic acid may be a monomer having an acid group such as a carboxyl group and a polymerizable double bond group, and examples thereof include acrylic acid, methacrylic acid, maleic acid and maleic anhydride. A polymerizable emulsifier is graft-polymerized to modify the chlorinated polypropylene resin so that it has a hydrophilic group. The polymerizable emulsifier used here is at least one selected from a polymerizable nonionic emulsifier and an ammonium salt type polymerizable anionic emulsifier. The polymerizable nonionic emulsifier is a compound having a polymerizable double bond group and a nonionic hydrophilic group. Nonionic hydrophilic group, for _{example, - (CH 2 CH 2 O} ) n - [n
Represents an integer of 5 to 40] or an OH group of alcohol. A suitable polymerizable nonionic emulsifier is polyoxyethylene nonylphenyl ether acrylate. Even if the nonionic hydrophilic group remains in the primer coating, it does not adversely affect the water resistance of the primer coating. The ammonium salt-type polymerizable anionic emulsifier is a compound having a polymerizable double bond group and an anionic hydrophilic group which has become an ammonium salt. The anionic hydrophilic group is, for example, a sulfonic acid group. The preferred anionic emulsifier is ammonium 2-sulfoethyl methacrylate. When the anionic hydrophilic group of the anionic emulsifier is a metal salt, the metal ion remains in the primer coating film and reduces the water resistance of the primer coating film, but in the present invention, the anionic hydrophilic group is an ammonium salt. Therefore, when baking for forming a primer coating film, ammonium ions become ammonia and volatilize, which does not adversely affect the water resistance of the primer coating film.

Graft polymerization of the chlorinated polypropylene resin, unsaturated carboxylic acid and the above polymerizable emulsifier is carried out by solution polymerization in an organic solvent. Other polymerizable monomers for graft polymerization are also graft-polymerized, if necessary. The organic solvent is an aromatic organic solvent such as toluene, xylene, and a liquid aromatic vinyl compound described later. The polymerization initiator used for the graft polymerization is an oil-soluble polymerization initiator such as benzoyl peroxide.
The graft polymerization can be carried out by a usual solution polymerization technique.

The above-mentioned other polymerizable monomers are used for the purpose of improving film-forming properties that contribute to the appearance, low-temperature flexibility, and weather resistance. The other monomers include, for example, aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene; methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth). It is at least one selected from acrylic acid esters and methacrylic acid esters such as acrylate, 2-ethylhexyl (meth) acrylate, and 2-hydroxyethyl (meth) acrylate.

The reaction product for the graft polymerization is 30 to 80% by weight, preferably 40 to 40% by weight, based on the solid content of the modified chlorinated polypropylene resin produced.
-70 wt%, unsaturated carboxylic acid 1-3 wt%, preferably 1.5-2.5 wt%, the above-mentioned polymerizable emulsifier 2-10
%, Preferably 3-8% by weight and the balance of other polymerizable monomers. If the content of the chlorinated polypropylene resin is less than 30% by weight, the primer coating film becomes inferior in initial adhesion, and if it exceeds 80% by weight, the film-forming property is deteriorated, the appearance is deteriorated, and the weather resistance is insufficient. There is a problem. When the unsaturated carboxylic acid is out of the above range, the primer coating film has poor water resistance. If the amount of the polymerizable emulsifier is less than 2% by weight, the emulsion of the resin produced will be unstable, and if it exceeds 10% by weight, the primer coating film will have poor water resistance.

By the above graft polymerization, an acid group derived from an unsaturated carboxylic acid is added to the chlorinated polypropylene resin,
A hydrophilic group derived from the polymerizable emulsifier is introduced to produce a modified chlorinated polypropylene resin (hereinafter referred to as "modified resin"). The modified resin has a number average molecular weight of 10,000 to 80,000, preferably 20,000 to 50,000,
And has an acid value of 5 to 25, preferably 10 to 20. The reaction solution containing the modified resin can be used as it is, or
If necessary, unreacted substances and organic solvent are removed, and a modified resin is made into an organic solvent solution having a desired concentration and emulsified in water. The organic solvent used here is, for example, the one described above. The modified resin can be emulsified by the action of the hydrophilic group without using an ordinary emulsifier, but by neutralizing the acid group with an amine, a more stable emulsion is formed. The amount of amine added is p in the modified resin emulsion.
The ratio is such that the H value (or hydrogen ion concentration) is 7.5 to 9.5, and preferably 8.0 to 9.0.

The amine used for neutralization is at least one selected from primary, secondary and tertiary amines, preferably tertiary amines such as trialkylamine, N-alkylpyrrolidone and monoethanolamine. is there. The emulsification can be carried out according to a usual method except that an emulsifier is not used.For example, water is added to an organic solvent solution of a modified resin with stirring, followed by addition of an amine to perform primary emulsification, and further under high pressure. Secondary emulsification is performed. After emulsification, an amine is added as needed to adjust the pH of the emulsion to the above pH range. This pH adjustment is performed for stabilizing the emulsion and stabilizing the paint after it is made into paint. The finally obtained emulsion contains the modified resin in an amount of 20 to 40% by weight, preferably 25 to 35% by weight.

In addition to the modified resin and the amine used for neutralization, the primer composition of the present invention may optionally contain various components, for example, resins for improving coating film performance such as urethane resin and epoxy resin, and coloring. Pigments, extender pigments, paint control agents,
It may contain an anti-armpit agent, a fluidity modifier, an anti-cissing agent, and a plasticizer. The urethane resin or the epoxy resin is added in an emulsified or water-soluble form in order to improve the weather resistance of the primer coating film. The emulsification is preferably carried out by neutralizing with an amine, rather than using an ordinary emulsifier, in terms of water resistance. Although various pigments are used, it is preferable to use talc in an amount of 1 to 5% by weight based on the resin solid content because the adhesion of the primer coating film is further improved.

The aqueous primer composition of the present invention can be applied by a conventional method for applying an aqueous primer.
Drying and baking can be performed in the same manner as in a normal aqueous primer. Drying and baking are, for example, 60 to 120.
C., preferably 70 to 100.degree. C., for 5 to 60 minutes, preferably 10 to 40 minutes. This gives the appearance (especially 5
(At low humidity of 0 to 60%), a primer coating film having excellent adhesion to a substrate and excellent water resistance is formed. As in the usual case, the primer coating film has a dry film thickness of 5 to 50 μm, preferably 10 to 20 μm. The objects to be coated are plastics such as polyolefins such as polypropylene. On the coating film of the primer composition of the present invention, ordinary intermediate coating and top coating are applied by a conventional method to complete the final coating.

[0017]

In this invention, a carboxyl group and a hydrophilic group are introduced by graft-polymerizing a chlorinated polypropylene resin, an unsaturated carboxylic acid and a polymerizable emulsifier. The modified resin thus produced has a carboxyl group and a hydrophilic group on the surface of droplets of an organic solvent containing the same. Therefore, by neutralizing the carboxyl group with an amine, the amine does not dissolve in the solvent and the chlorinated polypropylene is dissolved. The resin does not decompose and forms a stable aqueous emulsion. A primer coating film is formed by applying this emulsion, drying and baking. The amine used for neutralization volatilizes by drying and baking and does not remain in the coating film. Since the emulsifier is a nonionic type or an ammonium salt type anionic type, the coating film does not contain metal ions or cationic groups that reduce water resistance.

[0018]

EXAMPLES Examples of the present invention and comparative examples outside the scope of the present invention will be shown below, but the present invention is not limited to the following examples. (Example 1) Toluene 100g, styrene 36g, butyl acrylate 36g, methacrylic acid 4 in a reaction vessel.
g, the following formula:

[0019]

[Chemical 1]

Polyoxyethylene nonyl phenyl ether acrylate represented by
MA-564, the average number of repetitions of oxyethylene is 5
40) and 14 g of chlorinated polypropylene resin (chlorine amount 25% by weight, number average molecular weight 30,000) are charged, and the mixture is stirred while heating to 100 ° C. in about 1 hour,
A homogeneous solution was obtained. When the liquid temperature reached 100 ° C., benzoyl peroxide (hereinafter, referred to as “BP.
O. 1.0 g) and added at 100-105 ° C for 2
After reacting for a time, B. P. O. 1.0 g was added and the mixture was reacted for 2 hours. P. O. Add 1.0 g of 2
The reaction was carried out for a time to obtain a modified resin solution. After the completion of this reaction, 675 g of deionized water was added with stirring, and then 3.6 g of triethylamine was further added, followed by stirring for 1 hour,
Primary emulsification was performed to obtain a mixture with water. This mixture was emulsified three times using a high-pressure emulsifier under a pressure of 700 kg / cm ² to complete the secondary emulsification. Triethylamine was added to the obtained emulsion to adjust the pH to 8.5 to obtain an olefin emulsion as the aqueous primer composition of the present invention. In this emulsion, the number average molecular weight and acid value of the modified resin were 40,000 and 15, the average particle diameter was 1.7 μm, and the heating residue (resin solid content) was 30% by weight.

(Examples 2 and 3) The raw material formulations are shown in Table 1.
In the same manner as in Example 1 except that the change is made as shown in
An olefin-based emulsion, which is the aqueous primer composition of the present invention, was obtained. (Comparative Examples 1 to 5) Olefin-based emulsions as comparative aqueous primer compositions were obtained in the same manner as in Example 1 except that the raw material formulations were changed as shown in Table 1.

(Conventional Example 1) A resin solution was obtained in the same manner as in Example 1 except that the polymerizable emulsifier was not used. 700 g of this resin solution was charged into a reaction vessel, the inside of the system was kept at 50 ° C., 10.6 g of triethylamine, and Neugen EA-140 (polyethylene glycol nonyl phenyl ether, average repetition number of ethylene glycol: 12,
5 g of a nonionic surfactant having an HLB value of 14 manufactured by Dai-ichi Kogyo Yakuhin Co., Ltd. was charged and stirred for 1 hour, followed by deionized water 20.
00 g was gradually charged, and stirring was continued for another hour. Next, the solvent was removed under reduced pressure at 70 ° C. to distill off toluene and water until the amount of the distillate amounted to 600 g to obtain an olefin-based emulsion which was a conventional aqueous primer composition.

(Conventional Example 2) A resin solution was obtained in the same manner as in Example 1 except that the polymerizable emulsifier was not used. 1700 g of this resin solution was charged into a reaction vessel, dimethylethanolamine was added to the carboxyl group of the resin solution so as to have a neutralization equivalent of 1.0 with stirring well, and 2075 g of deionized water was further added. As a result, an olefin-based emulsifier, which is the aqueous primer composition of

Table 1 shows the average particle size of the modified resin and the heating residue in the emulsions of the above Examples, Comparative Examples and Conventional Examples. RMA-653 has the following formula:

[0025]

[Chemical 2]

It is a product of Nippon Emulsifier Co., Ltd. of ammonium 2-sulfoethyl methacrylate represented by:

[0027]

[Table 1]

The emulsion stability of the aqueous primer compositions of the above Examples, Comparative Examples and Conventional Examples was examined. Further, each aqueous primer composition was directly spray-coated on a polypropylene resin molding plate so as to have a dry film thickness of 20 μm, dried at 80 ° C. for 40 minutes and baked to form a primer coating film. The appearance, initial adhesion, and moisture resistance of the primer coating film were examined. The results are shown in Table 2.

The appearance was visually evaluated for surface irregularities and evaluated according to the following criteria. ○: It has a smooth surface. C: Unevenness is seen on the surface, resulting in orange peel. The initial adhesion was examined by a 2 mm goggles test (sticking / peeling of a cellophane adhesive tape) and evaluated according to the following criteria. ○: There is no peeling at all. ×: Peeling was observed even if slightly.

Moisture resistance adhesion was evaluated by the following criteria after being left to stand for 10 days at 50 ° C. and 98% relative humidity by a 2 mm cross stitch test. ○: There is no peeling at all. ×: Peeling was observed even if slightly.

[0031]

[Table 2]

As seen in Table 2, the primer compositions of the examples are stable emulsions and give primer coatings excellent in appearance, adhesion and moisture resistance. In Comparative Example 1, the chlorinated polypropylene resin has a chlorine content of 38% by weight.
Since the above-mentioned one was used, a coating film having poor initial adhesion was formed. In Comparative Example 2, since a chlorinated polypropylene resin having a chlorine content of 17% by weight was used, a coating film having poor appearance and poor moisture resistance was formed. In Comparative Example 3, the proportion of the chlorinated polypropylene resin was reduced to 25% by weight and the proportion of the polymerizable emulsifier was increased to 10.5% by weight, so that a coating film having poor initial adhesion was formed. In Comparative Example 4, the unsaturated carboxylic acid was not used at all and the proportion of the polymerizable emulsifier was increased to 11.2% by weight, so that a coating film having poor water resistance was formed. In Comparative Example 5, since the proportion of unsaturated carboxylic acid was increased to 4% by weight, butyl methacrylate, which was more excellent in water resistance than butyl acrylate, was used, but a coating film having poor water resistance was formed. In Conventional Example 1, since the polymerizable emulsifying agent was not used and the ordinary emulsifying agent was used, the initial adhesiveness passed, but the moisture resistance adhesiveness was poor. In Conventional Example 2, neither a polymerizable emulsifier nor an ordinary emulsifier was used, so that the moisture-resistant adhesion was poor, and the particle size was coarse, 3 μm or more, and resin precipitation was observed.

[0033]

EFFECT OF THE INVENTION The aqueous primer composition of the present invention is a stable emulsion because the aromatic organic solvent solution of the above modified resin is emulsified in water, and is excellent in appearance and water resistance and adheres well to the substrate. Gives a primer coating with good properties.

Front Page Continuation (72) Inventor Takahide Maeda 1-4-1 Chuo, Wako-shi, Saitama Stock Research Institute Honda Technical Research Institute (72) Inventor Takeshi Ogawa 1-1-4 Chuo, Wako-shi, Saitama Stock Company Honda R & D Laboratories (72) Inventor Shinnosuke Kono Invitation to Hirakata City, Osaka Prefecture 2-14-1 Otani Nippon Bee Chemical Co., Ltd.

Claims (5)

[Claims] 1. A modified chlorinated polypropylene obtained by graft-polymerizing a chlorinated polypropylene resin, an unsaturated carboxylic acid, and at least one emulsifier selected from a polymerizable nonionic emulsifier and an ammonium salt-type polymerizable anionic emulsifier. An aqueous primer composition in which a resin is neutralized with an amine and emulsified in water. 2. A modified chlorinated polypropylene resin comprising 30 to 80% by weight of a chlorinated polypropylene resin, 1 to 3% by weight of an unsaturated carboxylic acid, 2 to 10% by weight of an emulsifying agent, and other polymerizable monomer residues for graft polymerization. The composition according to claim 1, wherein the composition is copolymerized at a ratio of. 3. The pH value is 7.5 to 9.5.
Or the composition according to 2. 4. The chlorinated polypropylene resin has a chlorination degree of 2.
The composition according to any one of claims 1 to 3, which is 0 to 30% by weight. 5. The modified chlorinated polypropylene resin is 20 to
The composition according to any one of claims 1 to 4, comprising 40% by weight.