JPH0753743A - Surface preparation agent for resin molding - Google Patents

Abstract

PURPOSE:To suppress the bleeding to the surface of a resin molding to thereby make possible the formation of a coating film reduced in a long-term change in the coated surface and improved in performances and stability by surface- treating a resin molding with an aqueous solution of a specified organic acid. CONSTITUTION:The objective agent is prepared by adding a surfactant used for removing dirt adchered after molding such as dust or oil and being of a type and in an amount selected according to the kind of the resin and the state of adhesion of dust, oil or the like and optionally a builder to an aqueous solution of at least one organic acid selected between an alkyl-free carboxylic acid such as oxalic, malonic, succinic, gultaric, or adipic acid and an alkyl-free hydroxycarboxylic acid such as glycolic, malic, tartaric or citric acid. A resin molding is sprayed with this agent or is immersed in it at a suitable temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based pretreatment agent for resin moldings such as polypropylene and polyurethane used in automobiles, for example, bumper bumpers.

[0002]

2. Description of the Related Art Conventionally, resin molded products used for automobile bumpers and the like are manufactured by injection molding. For resins such as polyurethane that easily adhere to the mold, a wax-based external mold release agent is applied to the mold surface during molding, and metal soap such as zinc stearate is pre-filled as an internal mold release agent inside the resin. In many cases. In addition, various additives other than the internal mold release agent are blended in the resin for the purpose of improving strength, coating adhesion, weather resistance and the like. As a result, the internal release agent and other highly hydrophobic internal additives bleed to the surface during molding. The presence of an external release agent or a bleeding internal additive on the surface deteriorates the adhesion of the coating film after coating, and also causes repelling of the coating, which deteriorates the appearance of the coating film. Therefore, as the pre-coating treatment, not only removal of dirt such as dust and oil attached after molding but also removal of the external release agent and the internal additive bleeding on the surface is important.

Conventionally, as a pretreatment for coating resin molded products,
Solvent washing with 1,1,1-trichloroethane, freon and the like has been mainly used. These treatments were able to dissolve and remove the release agent, were easy to dry, and were excellent in workability. However, as is well known, the development of alternative pretreatment methods is urgently required due to environmental problems. As an alternative pretreatment method, cleaning with acid-based and alkaline-based water-based cleaning agents and solvent emulsion-type cleaning agents has been studied. However, these methods require a rinsing step, which is different from the solvent washing, and thus a drying step is necessary (Japanese Patent Laid-Open No. 27472.5-3949).
9). However, even if the release agent on the surface is dropped by washing,
In the drying process, the internal mold release agent and the highly hydrophobic internal additive bleed to the surface, so that the drying temperature must be kept low and it takes a long time to dry and the equipment becomes large. In addition, if the time between cleaning and coating is long, internal mold release agents and highly hydrophobic internal additives will gradually bleed to the surface even at room temperature, affecting the coating properties. I won't. As described above, conventionally, removal of the internal additive when the internal additive contained in the resin molded product bleeds on the surface has been studied, but about suppressing the internal additive from bleeding on the surface itself. Had not been considered.

[0004]

DISCLOSURE OF THE INVENTION The present invention is intended to suppress the surface bleeding of an internal resin additive during a drying step or a lapse of time after a water-based pretreatment of a resin molded article. That is, the purpose is to make the equipment compact by increasing the drying temperature, improve the coating performance of coating repellency and coating adhesion, and especially to stabilize the coating performance by suppressing the aging of the coating surface. To do.

[0005]

The inventors of the present invention suppress the surface bleeding of an internal resin additive by surface-treating a resin molded product with an aqueous solution containing a specified organic acid, thereby suppressing the change with time of the coating surface. The present invention has been completed by finding that it is possible to suppress and stabilize the coating performance.

That is, the present invention is a resin characterized by comprising an aqueous solution containing 0.05% by weight or more of at least one selected from carboxylic acids and oxycarboxylic acids having no alkyl group in the molecular structure as an essential component. Provided is a water-based pretreatment agent for molded articles.

The structure of the present invention will be described in detail below. The water-based coating pretreatment agent for resin molded products of the present invention (hereinafter abbreviated as coating pretreatment agent) contains at least one selected from carboxylic acids and oxycarboxylic acids having no alkyl group in the molecular structure as an essential component. The most important feature is that it is an aqueous solution. Here, the alkyl group does not contain in its molecular structure, C _n H _{2n + 1} - is that the end groups such as do not exist in the molecule.

Specific examples of the carboxylic acid containing no alkyl group include oxalic acid, malonic acid, succinic acid, glutaric acid and adipic acid. Specific examples of the oxycarboxylic acid containing no alkyl group include glycolic acid, malic acid, tartaric acid, and citric acid.

The content in at least one aqueous solution selected from carboxylic acids not containing an alkyl group and oxycarboxylic acids is preferably 0.05% by weight or more. More preferably, it is 0.1% by weight or more. If it is 0.05% by weight or less, the effect of suppressing the surface bleeding of the internal additive contained in the resin molded product is not obtained.

As described above, in the present invention, an aqueous solution containing at least one selected from carboxylic acids and oxycarboxylic acids having no alkyl group is effective in suppressing the internal additive contained in the resin molded article. A surfactant is used to remove dirt such as dust and oil attached after molding. The surfactant to be used may be contained in the pretreatment for coating of the present invention together with the organic acid specified in the present invention, or dirt such as dust and oil may be contained in advance only as the surfactant. It may be removed with a liquid and then with a pretreatment agent for coating which does not contain the surfactant of the present invention.

The type and amount of the surfactant used are selected according to the purpose of the type of resin, the state of adhesion of dust, oil, etc., and are not particularly limited.

Further, the pretreatment agent for coating of the present invention may contain other builders, if necessary, in addition to the surfactant.
The present invention is an aqueous solution containing the above-mentioned specific organic acid.

The pretreatment agent for coating of the present invention can be either sprayed or dipped. Further, the liquid temperature is not specified for the effect of the present invention, that is, for suppressing the bleeding of the internal additive. However, when the surfactant is contained in the pretreatment agent for coating of the present invention, for the purpose of removing oil, dust, etc. with the surfactant, an appropriate temperature is determined according to the adhesion state thereof. .

[0014]

When treated with the aqueous pretreatment agent of the present invention, the surface free energy of the resin surface increases. This effect is not lost even if it is washed with water after the treatment, and does not deteriorate even after drying or after drying. The surface bleeding suppression effect of internal additives is
It seems that this is due to the increase in the surface free energy of the resin surface. The organic acid specified by the present invention does not contain an alkyl group in the molecule, but those containing an alkyl group increase the surface free energy immediately after the treatment, but tend to deteriorate with drying or aging. Therefore, if an organic acid containing an alkyl group is used, the coatability will not be improved. Further, since the surface free energy to be subjected to the coating pretreatment of the present invention is increased, the wettability of water liquid is improved and the drying property is improved.

[0015]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples. 1) Test agent-Amine-cured polyurethane material (bumper material) External release agent: Oxidized wax type Internal release agent: Zinc stearate-Hard polypropylene material (bumper material)

2) Pretreatment Agent Composition (Pretreatment Agent 1) (corresponding to the coating pretreatment agent of the present invention) Sulfuric acid 3% by weight Polyoxyethylene nonylphenyl ether 0.5% by weight (EO added mole) Organic acid Table 1 Reference water balance

(Pretreatment agent 2) (not equivalent to the coating pretreatment agent of the present invention) Sulfuric acid 3% by weight Polyoxyethylene nonylphenyl ether 0.5% by weight (HLB: 12) Water balance

(Pretreatment agent 3) (corresponding to the coating pretreatment agent of the present invention) Organic acid See Table 1 Water balance

(Pretreatment agent 4) (corresponding to the coating pretreatment agent of the present invention) Polyoxyethylene nonylphenyl ether 0.5% by weight (HLB: 12) Organic acid See Table 1 Water balance

3) Treatment method Method A: Treatment with pretreatment agent 180 seconds 80 ° C. ↓ water washing 30 seconds normal temperature ↓ pure water washing 30 seconds normal temperature ↓ draining drying 10 minutes 80 and 120 ° C.

Method B: Treatment with pretreatment agent 2 180 seconds 80 ° C. ↓ Washing with water 30 seconds at room temperature ↓ Treatment with pretreatment agent 3 10 seconds at room temperature ↓ Washing with pure water 30 seconds at room temperature ↓ Draining 10 minutes 80 and 120 ° C.

Method C: Treatment with Pretreatment Agent 4 180 seconds 80 ° C. ↓ Draining and drying 10 minutes 80 and 120 ° C. (Pretreatment agent treatment and water washing were performed by spray treatment.)

4) Coating The pretreated material was left standing under the following standing conditions and then painted. Leaving condition 1; painting within 12 hours after pretreatment Leaving condition 2; painting 5 days after pretreatment

(Primer) Amine-cured polyurethane material; Soflex 1000 (manufactured by Kansai Paint Co., Ltd.) Baking condition -110 ° C., 15 minutes Film thickness-15-20 μm Hard polypropylene material; Soflex 2500 (manufactured by Kansai Paint Co., Ltd.) Baking Conditions-100 ° C, 10 minutes Film thickness-15-20 μm

(Topcoating) Both materials; SOFEX 1200 (manufactured by Kansai Paint Co., Ltd.) Baking conditions-120 ° C., 20 minutes Film thickness-35 to 40 μm

5) Evaluation Test Method (Contact Angle) After pretreatment, draining, drying, and leaving, a drop of distilled water was dropped on the surface of the test material, and the contact angle was measured by a goniometer contact angle meter. The smaller the contact angle, the lower the surface energy and the better the coatability.

(Water-resistant secondary adhesion) After being left for 24 hours after coating, cut a 2 mm square goggles on the surface of each coating material with a 100-mass sharp cutter, dip it in deionized water at a temperature of 40 ° C. for 240 hours, and then sell tape. Was adhered to the cut portion of the bag and was rapidly peeled off. The larger the remaining number, the better the adhesion.

(Coating Repelling Test) The appearance after the primer coating was visually evaluated. The evaluation was carried out in the following three grades of ◯, Δ and ×. O: Primer repelling is not recognized. Δ: A flesh-like cissing is observed. ×: Repellent where the substrate is visible is also recognized.

The results of performance evaluation are shown in Table 1. The following can be said from the results of Table 1. In Examples 1 to 6 of the present invention, compared with Comparative Examples 1 to 7, even under the high temperature coating baking conditions, the contact angle is low and changes little even after the pretreatment of coating and the passage of time. Also, the water-resistant secondary adhesion is good, and no coating cissing is observed. Such good characteristics indicate that the bleeding of the internal additive in the resin molded product is suppressed. In addition, in Examples 1 to 6 of the present invention, there is no difference in initial contact angle, change in contact angle over time, water-resistant secondary adhesion, and coating cissing property due to differences in the processing methods of method A, method B, and method C. That is, the surfactant may be contained in the coating pretreatment agent of the present invention, or may be contained in the pretreatment agent of the present invention containing no surfactant after being treated with a liquid containing only the surfactant in advance. It indicates that it may be treated with a pretreatment agent for painting. In the case of adding no organic acid shown in Comparative Examples 1 and 2,
Compared with No. 6, the initial contact angle, the change in contact angle over time, the water-resistant secondary adhesion, and the coating repellency are all inferior. In Comparative Examples 3 to 4, the concentration of the organic acid having no alkyl group is 0.01 to 0.03% by weight, and the organic acid concentration of Examples 1 to 6 is 0.05 to 0.03.
When the content is lower than 2.0% by weight, the initial contact angle, the change in contact angle over time, the water-resistant secondary adhesion, and the coating repellency are all inferior. That is, it is shown that there is a critical value regarding whether or not the effect of the present invention is exhibited at an organic acid concentration of 0.05% by weight. In the case of the organic acid having an alkyl group shown in Comparative Examples 5 to 7, the initial contact angle is so different as compared with Examples 1 to 6 even though the organic acid concentration is 0.5 to 2.0% by weight. However, it is inferior in the change in contact angle over time, the water-resistant secondary adhesion, and the coating repellency.

[0030]

When the resin molded product is treated with the water-based pretreatment agent for coating of the present invention, the surface bleeding of the internal additive contained in the resin molded product can be suppressed. As a result, high temperature drying is possible and drying time can be shortened, making it possible to make equipment compact, and at the same time, because it suppresses surface aging, stable coating performance and improved workability are obtained. To be

[0031]

[Table 1]

Claims (2)

[Claims] 1. At least one selected from a carboxylic acid and an oxycarboxylic acid having no alkyl group in the molecular structure.
An aqueous coating pretreatment agent for resin molded products, which comprises an aqueous solution containing 0.05% by weight or more of seed as an essential component. 2. The carboxylic acid containing no alkyl group is oxalic acid, malonic acid, succinic acid, glutaric acid or adipic acid, and the oxycarboxylic acid containing no alkyl group is glycolic acid, malic acid, tartaric acid or citric acid. The water-based coating pretreatment agent for resin molded products according to claim 1, which is an acid.