JPH0657757B2 - Coating composition for direct coating of polyolefin molded products - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coating composition for direct coating of polyolefin-based molded products, and its object is to directly coat the polyolefin-based molded products such as motorcycle parts and automobile parts (usually A polyolefin-based molded product that can form a coating film that has excellent properties such as adhesion, weather resistance, hardness, chemical resistance, solvent resistance, gasoline resistance, and feeling of flesh by simply applying a coating finish. It is intended to provide a coating composition for direct coating.

(Prior Art and Problems Thereof) In recent years, coated polyolefin-based molded products have been used in the fields of motorcycle parts such as mudguards and automobile parts such as bumpers.

However, it is generally difficult to obtain a coated polyolefin-based molded article by directly painting and finishing the polyolefin-based molded article.

Therefore, when applying a paint finish to a polyolefin-based molded product, it is necessary to pre-treat the polyolefin-based molded product by flame treatment, corona discharge, chrome-sulfuric acid treatment, etc., or to apply an undercoat coating. After performing a pretreatment to improve the adhesion of the coating, it was necessary to finish the coating with a topcoat paint.

That is, conventionally, it is impossible to directly apply a coating process to a polyolefin-based molded article without performing a pretreatment, and there is a drawback that a special pretreatment facility or a pretreatment process is required. .

Moreover, even after such pretreatment, various properties such as adhesion, weather resistance, hardness, chemical resistance, solvent resistance, and feeling of flesh are still obtained.
There was a problem that I couldn't get something satisfactory.

In fact, among the difficult-to-paint plastics, especially polyolefin resins such as polyethylene or polypropylene generally have high crystallinity and low polarity, and therefore have very weak surface activity, such as paints, printing inks and adhesives. Adhesion is extremely poor, and such a polyolefin-based resin having poor adhesion must always be pretreated.

As such pretreatment, for example, "Painting and Paint" magazine 19
On pages 35 to 50 of the August 81 issue, the surface is treated by physical treatment such as surface polishing, chromic acid mixture treatment, solvent treatment, plasma treatment, corona discharge treatment, ultraviolet irradiation treatment, gas smoke treatment, etc. As a general technique, a technique of causing small unevenness on the surface and then applying a paint, an ink, an adhesive or the like has been proposed as a general technique.

However, it is difficult to make a coating film with good adhesion even by such surface treatment by pretreatment, and even if it is a coating film after pretreatment, its coating properties such as weather resistance etc. I had a problem with.

As described above, it is said that the coating film formed of the resin such as the chlorinated polyolefin which has been subjected to such pretreatment also has relatively good adhesion as described above in the coating using the internal chlorinated polyolefin resin as the vehicle. However, over time, there was a big problem in coating film characteristics.

As described above, as a coating method of the surface coating film of the polyolefin resin or the polyolefin resin molded article, first, the surface treatment as the pretreatment and the physical and chemical surface treatment,
Further, it is necessary to perform at least two steps of coating the coating material thereafter, and even in the resin constituting the coating film, if the coating material is made of only chlorinated polyolefin resin having excellent adhesiveness, the chlorinated polyolefin resin is used. Although the adhesiveness of is improved satisfactorily, the weather resistance is not desirable. Therefore, by applying a secondary coating of auryl resin or urethane resin on this coating film, the poor adhesion to polyolefin resin can be obtained. In addition, attempts have been made to improve the coating film characteristics of the resin having good adhesion.

Therefore, as disclosed in JP-A-52-98062, "Coating Method for Polypropylene Molded Article", a propylene or ethylene polymer or a copolymer having good adhesion to a difficult-to-paint plastic such as polypropylene is used as a base treatment. Primarily contains a chlorinated polymer and uses a paint consisting of chlorinated rubber, fatty acid-modified, acrylated or styrenated alkyd resin, etc. as a primary undercoating treatment, and then has excellent weather resistance on this substrate. Acrylic or styrenated alkyd resin or acrylic resin containing 10% or more of acrylic component, mainly melamine resin, acrylic component
A very complicated process of overcoating with an acrylated or styrenated alkyd resin containing 10% or more or an acrylic resin, polyisocyanate, a topcoat paint mixed with a thermoplastic acrylic resin, and in some cases overcoating again was necessary. .

As the disclosed technology of such a base coating treatment agent for polyolefin-based molded articles, JP-A-59-140269, "Paint resin composition", JP-A-59-27968, "Paint resin composition", JP-A-48-40828 discloses a "coating composition" and the like.

All of these were paint compositions for the undercoating treatment except the last paint, and were paints in which a chlorinated polyolefin resin and a general-purpose acrylic resin were mixed.

However, the compatibility between the chlorinated polyolefin resin and the general-purpose acrylic resin is extremely poor, and it is easy to separate during storage, gelate, or particles grow and precipitate,
There was a problem in terms of long-term stability.

Therefore, the present inventors have already disclosed in JP-B-62-49302 that the main component is a chlorinated polyolefin and the active hydrogen compound for urethane resin, which have solved the above-mentioned drawbacks, and the diisocyanate compound is a main component. We have already clarified the coating composition for direct coating of polyolefin moldings, which is characterized by comprising a curing agent.

Indeed, the present invention is an excellent one in which the conventional drawbacks have been solved, but there is a drawback that the storage stability after the production is accompanied by the complication during the production of the main ingredient preparation, and the baking time is required at the time of coating. there were.

(Means for Solving the Problem) The present invention is based on a main component composed mainly of a graft polymer resin obtained by graft-polymerizing a pretreated chlorinated polyolefin and an active hydride for urethane resin, and a diisocyanate compound as a main component. The graft polymer resin has an active hydrogen content of 20 to 120 relative to the solid content of the polymer resin, a chlorine content of 25 to 50% by weight, and an average molecular weight of 5,000 to 50,000. By providing a coating composition for direct coating of a polyolefin-based molded article, which is a graft polymer resin and can be directly coated on a polyolefin-based molded article, the above-mentioned conventional problems are solved.

(Structure of the Invention) In the present invention, a main agent containing a polymer resin obtained by graft-polymerizing a chlorinated polyolefin and a hydride for a urethane resin as a main component, and a curing agent containing a diisocyanate compound as a main component.

As the chlorinated polyolefin used for preparing the main component graft polymer resin, conventionally known chlorinated polyolefins such as chlorinated polyethylene and chlorinated polypropylene are preferably used.

Among such chlorinated polyolefins, particularly in the present invention, a chlorinated polyolefin having a chlorine content after graft polymerization of 25 to 50% by weight and an average molecular weight of 5,000 to 50,000 can be preferably used.

The reason for this is that when the chlorine content of the chlorinated polyolefin-based graft polymer resin is less than 25% by weight, it is difficult to dissolve in a solvent and it is difficult to form a complete solution. Dechlorination at high temperature is easy to cause thickening at low temperature, and there is a problem in terms of long-term stability. On the other hand, when the chlorine content exceeds 50% by weight, a thread is drawn from the injection nozzle during coating, The so-called stringing phenomenon easily occurs, and
During long-term use, the coating film tends to change over time,
Since there is a slight problem in terms of weather resistance, a material having the above chlorine content is suitable.

Further, when the average molecular weight of the chlorinated polyolefin-based graft polymer resin is a low molecular weight of less than 5,000, the coating does not cure smoothly and does not dry, and even when cured, the coating film causes blocking etc. There is a problem in that it is difficult to obtain a coating film that can be used for, on the other hand, when the average molecular weight exceeds 50,000, the coating workability becomes poor and the compatibility with other resins also becomes poor. Since there are some problems, those having the above average molecular weight are preferable.

That is, the chlorine content after graft polymerization is 25 to 50% by weight,
The object of the present invention is achieved only by using a combination of chlorinated polyolefin resins having an average molecular weight of 5,000 to 50,000.

In the present invention, when the chlorinated polyolefin resin is graft-polymerized, the chlorinated polyolefin resin to be used is subjected to a pretreatment such as oil modification or petroleum resin modification in advance.

As the active hydride for urethane resin used in the present invention, acrylic polyol, polyester polyol, polyether polyol, alkyd polyol,
Examples thereof include 2-hydroxyethyl acrylate monomer or oligomer.

In the present invention, the main component is a graft polymer resin of the active hydrogen compound for urethane resin and the chlorinated polyolefin.

The active hydrogen content of the graft polymer resin as the main component, that is,
The OH value is 20 to the solid content of the graft polymer resin.
About 150 is desirable.

This polymerization ratio is a weight ratio and is 100% of chlorinated polyolefin resin.
On the other hand, it is desirable that the active hydrogen compound for urethane resin is 100 to 1000.

As the curing agent used in the present invention, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate and the like, and prepolymer diisocyanate compounds thereof are used. The main component.

In this invention, a graft polymer resin having an active hydrogen compound for urethane resin as a main component is blended, and a diisocyanate compound is blended in a curing agent to form a two-component system. This is because the active hydrogen compound for urethane resin and the diisocyanate compound are polymerized by the urethane reaction to form a urethane resin when applied at least and baked.

Further, in the present invention, the reason why the graft polymer resin made of chlorinated polyolefin is blended as the main component and used in combination with the above urethane resin is as follows.

That is, the chlorinated polyolefin resin has excellent adhesion to the polyolefin molded article, but has poor various properties such as weather resistance, hardness, chemical resistance, solvent resistance, and feeling of thickness of the coating film, while urethane Resin has poor adhesion to polyolefin molded products, but the weather resistance, hardness, chemical resistance, and
While it has excellent properties such as solvent resistance and feeling of flesh,
In the case of a resin obtained by graft-polymerizing a urethane resin and a chlorinated polyolefin resin, the disadvantages of both resins are eliminated and only the advantages are exhibited, adhesion, weather resistance, hardness, chemical resistance, solvent resistance. A coating film in which all of the various properties such as property and feeling of fleshness are good is obtained, and in particular, it is a combined use of a chlorinated polyolefin resin and a urethane resin, which is superior to the inventions disclosed by the present inventors. Is.

The polyolefin-based molded article to which the coating composition for direct coating of the polyolefin-based molded article according to the present invention is applied is a vehicle such as a mudguard or a vehicle such as a bumper molded from a polyolefin-based resin such as polyethylene or polypropylene. Refers to parts or other molded products.

When the coating composition for direct coating of a polyolefin-based molded article according to the present invention as described above is applied to a polyolefin-based molded article, for example, a graft polymer of the chlorinated polyolefin-based resin and an active hydrogen compound for urethane resin is used. resin
300 to 1200 parts by weight is added, and if necessary, a pigment such as titanium oxide, carbon black, red iron oxide, etc. and a solvent such as toluene are added to the main component, and the above curing agent is not added to the polyolefin-based pretreatment. It is advisable to apply a single coating directly to the molded product, and bake and dry at 70 to 100 ° C for 20 to 40 minutes to finish the coating.

(Effect) As described in detail above, the present invention is based on a main component of a graft polymer resin obtained by graft-polymerizing a pretreated chlorinated polyolefin and an active hydride for urethane resin,
And a curing agent containing a diisocyanate compound as a main component, the graft polymer resin has an active hydrogen content of 20 to 120 relative to the solid content of the polymer resin, and a chlorine content of 25 to 50% by weight, on average. Since it is a coating composition for direct coating of polyolefin-based molded products, which can be directly coated on polyolefin-based molded products, which is a graft polymer resin having a molecular weight of 5,000 to 50,000, it is a polyolefin-based resin for automobiles, motorcycle parts, etc. When applying a paint finish on a molded product, directly use a urethane resin paint polymerized with a chlorinated polyolefin resin on the polyolefin-based molded product without performing a pretreatment to improve the adhesion of the paint as in the past. It has a coating film that can be applied with a single coating and has various properties such as adhesion, weather resistance, hardness, chemical resistance, solvent resistance, and feeling of flesh. A coated polyolefin-based molded article can be obtained, which has an excellent effect that it is suitable for use as a motorcycle component, an automobile component, or the like.

(Example) Hereinafter, the present invention will be described based on examples.

Example 1 (main ingredient) (Curing agent) Dismodur N75 100 parts by weight (Bayer Co. product name) Chlorine obtained by previously degreasing a polypropylene molded article for motorcycle parts with benzine, and then mixing the above-mentioned main agent and curing agent on the polypropylene molded article. Polypropylene resin polymerized urethane resin paint is applied directly in one coat to finish the coating.
A coated polypropylene molded product having coating film characteristics as shown in Table 1 was obtained.

Comparative Example 1 (main ingredient) (Curing agent) 100 parts by weight of Dice Module N75 A chlorinated polypropylene resin-containing urethane resin coating obtained by mixing the above-mentioned main component and curing agent is finished in accordance with Example 1 and has coating film characteristics as shown in Table 1. A coated polypropylene molded product was obtained.

Comparative Example 2 (main ingredient) (Hardening agent) 100 parts by weight of Dice Module N75 A chlorinated polypropylene resin-containing urethane resin coating obtained by mixing the above-mentioned main component and curing agent was directly applied once by a single coating in the same manner as in Example 1 to give the results shown in Table 1. A coated polypropylene molded product having such coating film characteristics was obtained.

Comparative Example 3 In the composition of Example 1, a coating finish was applied according to Example 1 except that a chlorinated polypropylene resin was not used to obtain a coated polypropylene molded article having coating film characteristics as shown in Table 1.

In the above-mentioned Example 1, various properties such as adhesion, weather resistance, hardness, chemical resistance, and feeling of flesh of the coating film are excellent, but in Comparative Example 1 and Comparative Examples 2 and 3, workability and There is a problem in any of the various characteristics, and Comparative Example 2 has an average molecular weight of 50,000.
The spray workability was extremely poor due to the use of chlorinated polypropylene.

Continuation of the front page (56) Reference JP 59-140269 (JP, A) JP 59-27968 (JP, A) JP 58-17174 (JP, A) JP 48-40828 (JP , A)

Claims (1)

[Claims] 1. A main agent containing a graft polymer resin obtained by graft-polymerizing a pretreated chlorinated polyolefin and an active hydride for urethane resin as a main component, and a curing agent containing a diisocyanate compound as a main component. The graft polymer resin is a graft polymer resin having an active hydrogen content of 20 to 120 relative to the solid content of the polymer resin, a chlorine content of 25 to 50% by weight, and an average molecular weight of 5,000 to 50,000. A coating composition for direct coating of a polyolefin-based molded product, which can be directly coated on a characteristic polyolefin-based molded product.