JPH01203433A - Molded article of polyester resin for coating - Google Patents

Abstract

PURPOSE:To obtain the present molded article having excellent adhesivity to various coating compounds without carrying out surface treatment by primer coating, by blending a thermoplastic resin with a specific phenoxy compound and an inorganic filler in a specific ratio and molding. CONSTITUTION:100pts.wt. polymer mixture comprising 99.5-70wt.%, preferably 98-85wt.% thermoplastic resin (preferably polyester consisting essentially of polybutylene terephthalate) and 0.5-30wt.%, preferably 2-15wt.% phenoxy compound which comprises a main chain having a repeating unit shown by the formula and has 2,000-100,000, preferably 8,000-75,000 average molecular weight is blended with 0-125pts.wt., preferably 10-100pts.wt. inorganic filler (e.g., glass fibers) and molded to give the aimed molded article having excellent mechanical strength and capable of being coated by one application.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a thermoplastic polyester resin molded article suitable for painting. More specifically, the present invention relates to a polyester resin molded article that can be coated with excellent adhesion to various paints by a simple coating method.

[Conventional technology and its issues]

Thermoplastic polyester resin is easy to process, has excellent mechanical strength, and other physical and chemical properties, so it is widely used in fields such as automobiles, electrical and electronic equipment, other precision machinery, building materials, and miscellaneous goods. Ru.

On the other hand, such thermoplastic polyester resin molded products are often painted for the purpose of beautifying the appearance of the molded product. However, there are problems with paintability, such as poor adhesion between the paint and resin when coating with various paints, and even when a good paint film is formed, it does not maintain a stable paint film for a long time. However, cracking and peeling tend to occur, making it difficult to obtain a coated product that can be used for practical purposes. For this reason,
When painting a polyester resin molded product, there are two methods: first forming a layer of a so-called primer, a substance that has good affinity for both the resin and the paint film, on the resin surface, and then applying a top coat; A commonly used method is chemically etching and then painting.

This method improves the adhesion of the paint film and makes it possible to obtain a coated product that can be used for practical purposes, but the two-step coating process makes the process complicated and is economically disadvantageous. .

Under these circumstances, there has been a desire for a method for obtaining polyester resin molded articles with strong coating film adhesion that can withstand practical use by applying a coating directly to the molded article, that is, so-called one-coat painting.

[Means to solve the problem]

The inventors of the present invention have conducted intensive research to obtain polyester molded products with practically sufficient coating adhesion through simple one-coat painting. It was discovered that a molded article made of a resin composition blended with a polyester resin has excellent paintability, and the present invention was achieved.

That is, the present invention provides (A) a thermoplastic polyester resin of 99.5 to 70% by weight (B) a main chain having a repeating unit having a structure substantially represented by the following formula (1) and an average molecular weight of about 2.000 to 100, 0
00 phenoxy compound and 0 to 125 parts by weight of an inorganic filler based on 100 parts by weight of the polymer mixture of (C) (A) and (B). This invention relates to polyester resin molded products with excellent paintability.

When a molded product made from such a composition is painted, the adhesion of the paint film is significantly improved, and one-coat painting is possible without any special surface treatment, and even with such a simple painting method, it has excellent properties. It is completely unexpected and surprising that such an adhesion force is produced.

Hereinafter, the constituent components of the molded article of the present invention will be explained in detail.

First, the thermoplastic polyester (A) used in the present invention is a polyester obtained by polycondensation of a dicarboxylic acid compound and a dihydroxy compound, polycondensation of an oxycarboxylic acid compound, or polycondensation of a mixture of these three components. The present invention is effective for both polyester and copolyester.

Examples of dicarboxylic acid compounds used here include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid,
These include known dicarboxylic acid compounds such as diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenylethanedicarboxylic acid, cyclohexane dicarboxylic acid, adipic acid, and sebacic acid, and alkinohair alkoxy or halogen substituted products thereof. These dicarboxylic acid compounds can also be used in the form of derivatives capable of forming esters, for example lower alcohol esters such as dimethyl ester. In the thermoplastic polyester of the present invention, one or more of the above compounds are used as constituent monomers.

Next, examples of dihydroxy compounds constituting the thermoplastic polyester (A) include ethylene glycol, propylene glyconopebutanediol, neopentyl glycol, hydroquinone, resorcinol, dihydroxyphenyl, naphthalene diol, dihydroxydiphenyl ether, and cyclohexanediol. Nobe 2.2-bis (4
-Hydroxyhydroxy compounds such as (hydroxyphenyl)propane, polyoxyalkylene glycols, and alkyl, alkoxy, or halogen-substituted products thereof, and they can be used alone or in a mixture of two or more.

Further, examples of oxycarboxylic acids that can be used as the structural unit of (A) include oxybenzoic acid, oxynaphthoic acid, diphenyleneoxycarboxylic acid, and alkyl, alkoxy, or halogen substituted products thereof. can be given. Furthermore, derivatives of these compounds capable of forming esters can also be used. In the present invention, one or more of these compounds may be used.

In the present invention, the above compounds are used as monomer components,
Any thermoplastic polyester produced by polycondensation can be used, and may be used alone or in a mixture of two or more, but preferably polyalkylene terephthalate,
More preferably, the effects of the present invention are particularly remarkable when thermoplastic polyester mainly composed of polybutylene terephthalate is used.

Furthermore, in the present invention, thermoplastic polyesters may be modified by known methods such as crosslinking and graft polymerization.

Next, in the present invention, the component (B) blended into the thermoplastic polyester resin (8) as described above has a repeating unit of the structure represented by the formula (1) and has an average molecular weight of at least 2.000 and 100.000. Hereinafter, preferably g,
It is a high molecular weight phenoxy compound having a molecular weight of not less than ooo and not more than 75,000.

This polymer compound may have other structural units mixed in its main chain as long as it has the structure of formula (1) as its main chain, and
The terminal structure is not particularly limited and is arbitrary, but for boat fishing, it is a phenol, alcohol, or alkyl group.

In order to improve the paintability that is the objective of the present invention, it is essential to blend component (B) with a specific molecular weight as described above, and this does not preclude the addition of other general thermoplastic resins. If other thermoplastic resins are blended in place of component (B) of the present invention, the effect on paintability as achieved in the present invention cannot be obtained.

In addition, if the molecular weight of component (B) is too low, the effect on paintability will not be sufficiently obtained, while if the molecular weight is too high, the melt viscosity will become extremely high, and the dispersibility in polyester resin will deteriorate, resulting in excellent properties. Molded products with paintability cannot be obtained.

In addition, the blending amount of component (B) is the thermoplastic polyester (A
) 0.5-30% by weight for 99.5-70% by weight
It is. If the blending amount is less than 0.5% by weight, the adhesion of the molded product to the paint will not be significantly improved compared to the case of thermoplastic polyester resin alone, which is not preferable.
If the amount exceeds % by weight, the inherent physical and chemical properties of the thermoplastic polyester resin, especially chemical resistance, will deteriorate, which is not preferable.

The preferred blending ratio is (A) 98 to 85% by weight of the thermoplastic polyester resin and 2% by weight of the phenoxy compound (B).
~15% by weight.

Next, the inorganic filler (C) used in the present invention is preferably blended in order to obtain a molded product with excellent performance such as mechanical strength, heat resistance, and dimensional stability (deformation resistance, warpage resistance, etc.).
In particular, in order to perform post-coating baking at high temperatures, it is necessary to increase the heat distortion temperature, and for this purpose it is effective to add an inorganic filler. Depending on the purpose, fibrous, powder-like, or plate-like fillers are used for this purpose.

Fibrous fillers include glass fiber, asbestos fiber,
Inorganic materials such as carbon fiber, silica fiber, silica/alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, and fibrous materials of metals such as stainless steel, aluminum, titanium, copper, and brass. Examples include fibrous substances. Particularly typical fibrous fillers are
Glass fiber or carbon fiber.

On the other hand, examples of powdery fillers include carbon black, silica, quartz powder, glass peas, glass powder, calcium silicate, aluminum silicate, kaolin, talc, clay, diatomaceous earth, silicates such as wollastonite, and iron oxide. , metal oxides such as titanium oxide, zinc oxide, and alumina, metal carbonates such as calcium carbonate and magnesium carbonate, metal sulfates such as calcium sulfate and barium sulfate, silicon carbide, silicon nitride, boron nitride, and various others. Examples include metal powder.

In addition, as plate-shaped fillers, mica, glass flakes,
Examples include various metal foils.

These inorganic fillers can be used alone or in combination of two or more. The combined use of a fibrous filler, particularly glass fiber or carbon fiber, and a granular and/or plate-like filler is a preferable combination, especially in terms of achieving both mechanical strength, dimensional accuracy, electrical properties, and the like.

When using these fillers, it is desirable to use a sizing agent or a surface treatment agent if necessary. Examples of this include functional compounds such as epoxy compounds, isocyanate compounds, silane compounds, and titanate compounds. These compounds may be used after surface treatment or convergence treatment, or may be added at the same time when preparing the material.

These inorganic fillers are added in an amount of 0 to 125 parts by weight per 100 parts by weight of the polymer mixture (A) and (B). If the amount of filler added exceeds 125 parts by weight, the moldability of the polyester mixture will deteriorate significantly, which is not preferred. Particularly preferably 10 to 100 parts by weight.

Further, in addition to the above-mentioned components, small amounts of other thermoplastic polymer substances may be used in combination with the molded article of the present invention depending on the purpose. The thermoplastic polymer materials used here include, for example, polyolefins such as polyethylene and polypropylene and their copolymers, polyamides,
BS, polyphenylene oxide, polyalkyl acrylate, polyacetal, polysulfone, polyether sulfone, polyetherimide, polyether ketone,
Examples include fluororesin. Furthermore, two or more of these thermoplastic polymer substances can also be used in combination.

Furthermore, the molded article of the present invention may contain known substances that are generally added to thermoplastic resins and thermosetting resins, such as stabilizers such as antioxidants and ultraviolet absorbers, antistatic agents, flame retardants, dyes, etc. Coloring agents such as pigments, lubricants, crystallization promoters, crystal nucleating agents, etc. can also be added as appropriate depending on the required performance.

The polyester molded article of the present invention can be prepared using equipment and methods generally used for preparing and molding synthetic resin compositions. In other words, the necessary ingredients can be mixed, kneaded using a single-screw or twin-screw extruder, extruded to form pellets for molding, and then molded. Some of the necessary components can be mixed and molded as a masterbatch. In order to improve the dispersion and mixing of each component, some or all of the resin components are pulverized, mixed and melt-extruded to form pellets, etc.
Both are possible.

Furthermore, the resin composition according to the present invention can be molded by any of extrusion molding, injection molding, compression molding, vacuum molding, blow molding, and foam molding, and any of the molded products molded in this way can be coated easily. You can obtain products with excellent properties.

In the present invention, the molded article can be painted with any of the known paints commonly used for plastic materials, but alkyd resin paints or modified versions thereof, melamine or melamine alkyds can be used. Resin-based paints, urethane resin-based paints, or their modified products,
Acrylic resin paints and the like are preferably used.

Conventionally, when painting a polyester resin molded product, it generally required surface roughening by etching or undercoating with a primer, and it was extremely difficult to achieve a practical coating without such pretreatment. According to the method, sufficient practical adhesion of the coating film can be obtained without such pre-treatment, and it is extremely economical. However, the present invention does not preclude these pretreatments. Furthermore, it goes without saying that it is generally desirable to perform preliminary cleaning and drying such as removal and degreasing of the surface of the molded article prior to painting.

For painting molded products, we use heka-coating, dip-coating, roller-coating,
Spray painting, flow painting, airless spray, electrostatic painting, etc.
Any known method can be used, and baking can also be performed depending on the purpose.

〔Example〕

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

In addition, in the present invention, the tensile strength is determined according to ASTM 0638.
, flexural strength and flexural modulus meet ASTM D 790, and Izod impact strength meets AST! , (measured by D 256.

The adhesion strength of the coating film was evaluated by a base peel test.

That is, cuts were made on the painted surface in the shape of a substrate at 1 mm intervals with a cutter knife, cellophane tape was applied and instantly peeled off, and the number of remaining pieces per 100 1 mm squares was evaluated. Furthermore, in order to examine changes in the adhesion of the coating film over time, a peel test was performed on a coated plate immersed in water at 40° C. for 240 hours, and the results are also listed.

Examples 1 to 6 and Comparative Examples 1 to 5 Polybutylene terephthalate resin, phenoxy resin (B) as shown in Table 1, and optionally an inorganic filler (C)
After adding and mixing glass fiber as
A pellet-like composition was prepared by melt-kneading using a twin-screw extruder.

Next, test pieces for measuring mechanical properties and flat plates (thickness: 3 mm) for coating tests were made from the pellets using an injection molding machine.

After cleaning the surface of this test piece with trichloroethane, it was sprayed with a melamine alkyd paint [Amirac, manufactured by Kansai Paint ■] using a spray gun and painted.
It was baked at ℃ for 30 minutes and dried. The thickness of the resulting coating film was approximately 30 μm. The mechanical properties of the test piece and the adhesion evaluation results of the coating film were as shown in Table 1.

Example 7.8 and Comparative Example 6.7 Pellets having the compositions shown in Table 2 were prepared in the same manner as above, and test pieces were molded. After cleaning the surface of this test piece with trichloroethane, it was spray-painted with a urethane paint (Rethane PG-60J E manufactured by Kansai Paint Co., Ltd., baked at 80° C. for 30 minutes, and dried.

The thickness of the resulting coating film was approximately 30 μm. The mechanical properties of the test piece and the adhesion evaluation results of the coating film were as shown in Table 2.

Example 9 and Comparative Example 8 Pellets having the composition shown in Table 3 were prepared in the same manner as described above, and test pieces were molded. After cleaning the surface with trichloroethane,
Acrylic paint [Kansai Paint Preparation “Soflex NO”
, lOJ:] was spray-painted, baked at 60° C. for 20 minutes, and dried. The thickness of the resulting coating film was approximately 30 μm. The mechanical properties of the test piece and the adhesion evaluation results of the coating film were as shown in Table 3.

〔Effect of the invention〕

As is clear from the above description and examples, the resin molded product of the present invention has an extremely excellent effect on improving the adhesion of the coating film, and has been applied to conventional two-coat coating methods using primers and chemical coating methods. For thermoplastic polyester, for which practical paint film adhesion could not be obtained without surface etching treatment, it is possible to create a paint film with sufficient adhesion for practical use even with so-called one-coat painting without these special treatments. This makes it possible to simplify the painting process and reduce painting costs.

Furthermore, the molded product of the present invention has improved tensile strength, bending strength, and flexural modulus compared to a molded product made of polyester resin alone.
It has extremely excellent mechanical properties with almost no loss in impact strength, and combined with the above-mentioned excellent paintability, it has extremely high practicality.

Applicant's agent Kaoru Furutani

Claims (1)

[Scope of Claims] 1 (A) Thermoplastic polyester resin 99.5 to 70% by weight (B) A main chain having a repeating unit having a structure substantially represented by the following formula (1) and having an average molecular weight of about 2, 000~100,0
00 phenoxy compound 0.5-30% by weight ▲Mathematical formulas, chemical formulas, tables, etc. are available▼(1) and (C) 0-125 parts by weight per 100 parts by weight of the polymer mixture of (A) and (B) A polyester resin molded product for painting made by molding a resin composition containing an inorganic filler. 2. The polyester resin molded article for painting according to claim 1, wherein the thermoplastic polyester resin of component (A) is a polyester mainly containing polybutylene terephthalate. 3 The molecular weight of the phenoxy compound of component (B) is 8,00
The polyester resin molded article for painting according to claim 1 or 2, which has a molecular weight of 0 to 75,000. 4. The polyester resin molded article for painting according to claim 1, 2 or 3, wherein the amount of the inorganic filler as component (C) is 10 to 100 parts by weight. 5. The polyester resin molded article according to claim 1, 2, 3, or 4 is coated with one type selected from alkyd resin paint, melamine resin paint, melamine/alkyd resin paint, urethane resin paint, and acrylic resin paint. A painted molded product that is coated with two or more types of paint without surface treatment by applying a primer.