JPH04363348A - Coated resin molded product and its production - Google Patents

Abstract

PURPOSE:To provide a coated polypropylene resin molded product maintaining the excellent mechanical properties of the polypropylene resin and improved in the coating adhesivity without requiring a preliminary treatment to the molded product before coated. CONSTITUTION:100 pts.wt. of a resin composition comprising (A) 90-30wt.%, preferably 70-40wt.%, of polypropylene and (B) 10-70wt.%, preferably 30-60wt.%, of an ethylene-alpha-olefin copolymer having a Mooney viscosity of <=50 and a propylene content of >=20wt.% is mixed with (C) >=0.1 pts.wt., of an unsaturated monomer comprising an unsaturated carboxylic acid having one or more hydroxyl groups in the molecule and/or a derivative thereof and (D) an organic radical generator, followed by subjecting the mixture to a thermal treatment. The polypropylene resin composition thus produced is molded and subsequently coated to form a coating film on the surface of the molded product.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated resin molded article made of polypropylene resin with excellent coating film adhesion and a method for producing the same.

0002

[Prior art] Polypropylene resin compositions have good moldability, and molded products thereof have excellent mechanical properties and chemical resistance.
Moreover, it is inexpensive. Therefore, it is widely used as a general-purpose plastic in molded products such as automobile parts and electrical products. On the other hand, since polypropylene resin compositions are non-polar polymers, they generally do not have good adhesion to paints (mainly polar polymers are the paint component) and have poor paint film adhesion. Therefore, before painting the molded product, it is necessary to perform pretreatment such as primer treatment and plasma treatment in advance. However, such pretreatment is troublesome and reduces the productivity of painting operations.

[0003] Conventionally, in order to improve coating adhesion, a polymer mixture of polypropylene and an ethylene-α-olefin copolymer containing an unsaturated carboxylic acid such as maleic anhydride and/or a derivative thereof has been used. A polypropylene resin composition has been proposed which is obtained by adding an organic radical generator, mixing it, and heat-treating it (Japanese Patent Laid-Open No. 62-28
(See Publication No. 0267).

0004

[Problem to be Solved] However, according to the results of the inventors' experimental studies, the resin composition shown in the above publication is
Paint film adhesion is still not sufficient. In addition, in the resin composition of the above publication, even when maleic anhydride, which is considered to be the most preferable unsaturated carboxylic acid, is used, sufficient coating film adhesion cannot be obtained (see comparative examples in the examples below). ). In view of these conventional problems, the present invention has developed a coating using a polypropylene resin that has the excellent mechanical properties of polypropylene, eliminates the need for pre-treatment of molded products prior to coating, and has excellent coating adhesion. The present invention aims to provide a resin molded product and a method for manufacturing the same.

[0005]

[Means for solving the problems] The present invention is a coated resin molded article formed by forming a coating film on the surface of a molded article made of synthetic resin,
The above synthetic resin is a coated resin molded article characterized in that it is the following polypropylene resin composition. (A) 90 to 30% by weight of polypropylene; and (B) 10 to 70% by weight of an ethylene-α-olefin copolymer having a Mooney viscosity of ML1+4 (100°C) 50 or less and a propylene content of 20% by weight or more. (C) 0.1 part by weight or more of an unsaturated monomer consisting of an unsaturated carboxylic acid and/or a derivative thereof having at least one hydroxyl group in the molecule, and (D) an organic A polypropylene resin composition obtained by adding and mixing a radical generator and then heat-treating.

What is most noteworthy about the present invention is that the specific polypropylene resin composition mentioned above is used as the synthetic resin constituting the coated resin molded article. That is, as the polypropylene resin composition, an ethylene-α-olefin copolymer having the specified Mooney viscosity and propylene content is used, and as the unsaturated monomer, the specified unsaturated monomer has at least one hydroxyl group. The method is to use saturated monomers and to add these monomers in specific proportions to the polypropylene. Furthermore, 0.1 part by weight or more of the unsaturated monomer and an organic radical generator are added and mixed to 100 parts by weight of the resin mixture consisting of the polypropylene and ethylene-α-olefin copolymer.

The resin mixture comprises 90 to 30% by weight of polypropylene and 10 to 70% by weight of the ethylene-α-olefin copolymer. If the polypropylene content exceeds 90% by weight, the adhesion of the coating film to the molded article will decrease. On the other hand, when polypropylene is less than 30% by weight,
If the amount of the ethylene-α-olefin copolymer is too large, the rubbery properties of the molded product may become too strong, and the excellent mechanical and chemical resistance inherent to polypropylene resin may be reduced. Furthermore, more preferably polypropylene 70-4
0% by weight, ethylene-α-olefin copolymer 30~
It is 60% by weight. In this case, the coating film adhesion is particularly excellent.

[0008] The polypropylene mentioned above is not particularly limited, but may include polypropylene homopolymer and/or polypropylene.
Alternatively, it is preferable to use a block copolymer containing 25% by weight or less of an ethylene component. In addition, the above ethylene-
The α-olefin copolymer has a Mooney viscosity of ML1+4
(100℃) is 50 or less, and the propylene content is 2
Use 0% by weight or more. Mooney viscosity ML above
1+4 (100°C) refers to the viscosity unit measured with a Mooney shear disk viscometer, that is, the reading on the meter after preheating the large disk to 100°C for 1 minute and 4 minutes after the start of rotation. Here, if Mooney viscosity ML1+4 (100°C) exceeds 50, the effect of improving coating film adhesion is small (Comparative Examples 5 and 6).
), less than 20% by weight of propylene is not practical because the bending fatigue resistance is low (Comparative Example 4).

Further, the ratio (weight fraction) of ethylene:α-olefin:non-conjugated diene in the ethylene-α-olefin copolymer is 0.2 to 0.8:0.8.
-0.2: It is preferable that it is 0-0.1. That is, the ethylene-α-olefin copolymer is an ethylene/propylene copolymer or an ethylene/α-olefin or conjugated diene copolymer. In addition, the α-olefin in the ethylene-α-olefin copolymer includes those having 3 to 12 carbon atoms, such as propylene, 1-butene, 4
-One or two of methyl-1-pentene, 1-hexene, etc.
There are more than species. Among these, the ethylene-α-olefin copolymer is preferably an ethylene-propylene copolymer (EPM), or an ethylene-propylene-nonconjugated diene terpolymer, in which the α-olefin is propylene. . This case is superior in terms of flexibility and low cost.

[0010] Examples of the non-conjugated diene include ethylidene norbornene, cyclopentadiene, 1,4-hexadiene, and methylene norbornene. Among these, ethylidenenorbornene is common and commercially available. Further, the propylene content in the ethylene-α-olefin copolymer is 20% by weight or more. If the amount is less than 20% by weight, the cold impact resistance of the molded article will be low, making it impractical. Note that the propylene content is preferably less than 60% by weight from the viewpoint of flexibility.

Next, 0.1 parts by weight or more of the unsaturated monomer and an organic radical generator are added and mixed with 100 parts by weight of the resin mixture. If the amount of unsaturated monomer is less than 0.1 part by weight, coating film adhesion cannot be improved. In addition, the upper limit of the unsaturated monomer is determined by the rigidity, impact strength, and
Since it adversely affects surface gloss etc., it is preferably 10 parts by weight. The unsaturated monomers include one or both of unsaturated carboxylic acids and derivatives thereof having at least one hydroxyl group (-OH) in the molecule. Such unsaturated monomers include alkyl alcohol N-substituted acid amides (e.g. N-methylol acrylamide);
, polyol esters of acrylic acids (for example, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate), hydroxy acids (for example, hydroacrylic acid), and derivatives thereof.

[0012] Furthermore, the organic radical generator is mainly used for
The unsaturated carboxylic acid is graft-polymerized to the resin mixture, that is, a polymer of polypropylene and ethylene-α-olefin copolymer. The amount added is determined in relation to the type and amount of unsaturated carboxylic acid, but usually the molar ratio of unsaturated carboxylic acid/organic radical generator is 15 to 85. In addition, for 100 parts by weight of the above resin mixture, 0.01 to
The amount is 0.5 part by weight.

[0013] Furthermore, as the organic radical generator,
Commonly used organic peroxides and azo compounds listed below can be used. That is, 2,5-dimethyl-2,5-di(t
-butylperoxy)-3-hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 1
,3-bis(t-butylperoxyisopropyl)benzene,2,2, -bis(t-butylperoxy)-P-
Diisopropylbenzene, dicumyl peroxide, di-
Examples include t-butyl peroxide, t-butyl benzoate, dibenzoyl peroxide, and azobisisobutyronitrile. Among the above, 1,3-bis(t-butylperoxyisopropyl)benzene is most preferred in terms of coating film adhesion. Note that inorganic peroxides such as persulfates can also be used.

Next, in preparing the resin composition, the above-mentioned unsaturated monomer and organic radical generator are added and mixed to the above-mentioned resin mixture, and using a mixer such as an extruder or a Banbury kneader, 170~ Heat treatment is performed at 280°C for 0.2 to 3 minutes. Further, in the resin composition, antioxidants, heat stabilizers, ultraviolet absorbers, colorants, inorganic fillers (calcium carbonate, talc, glass fiber, etc.), etc. can be added as necessary. Further, the material is made into a molding material such as pellets through the heat treatment process described above.

[0015] The coating film to be coated on the surface of the molded product may be, for example, urethane-based, acrylic-based, alkyd-based,
There are general-purpose plastic paints such as epoxy-based paints. Furthermore, among the above paints, urethane paints are superior in terms of film performance and film adhesion. The types of painted resin molded products include automobile parts, electrical products, and various interiors. In addition, the above automobile parts include mudguards, bumpers, spoilers, side moldings, garnishes, instrument panels, console boxes, bodies,
There are grilles, hubcaps, washer nozzles, etc. These automobile parts are used in automobiles that are driven outdoors, and are coated resin molded products that are required to have excellent mechanical strength and particularly excellent paint film adhesion. Therefore, the present invention is particularly useful for application to automobile parts.

[0016] Further, as a method for producing the above-mentioned coated resin molded article, there is a method in which the above-mentioned polypropylene resin composition is molded into the shape of a desired molded article, and then a coating film is formed on the surface of the molded article. . The molded product is molded using a molding machine such as an injection molding machine or an extrusion molding machine using the molding material such as the pellets. Note that before painting, it is preferable to clean the surface of the molded product with a chlorinated organic solvent such as trichloroethane. Additionally, a primer treatment may be applied prior to painting.

[0017]

[Operations and Effects] The polypropylene resin composition used in the coated resin molded article of the present invention is a resin mixture consisting of polypropylene and the above-mentioned specific ethylene-α-olefin copolymer, and the above-mentioned specific unsaturated monomer and It is made by adding and mixing an organic radical generator in a specific ratio and heat-treating it. Therefore, the coated resin molded article of the present invention has better coating film adhesion than the coated resin molded article using the conventional polypropylene resin composition. Furthermore, the coated resin molded product does not significantly reduce the mechanical properties inherent to polypropylene. Therefore, according to the present invention, a coated resin molded product made of polypropylene resin, which has the excellent mechanical properties of polypropylene, does not require pre-treatment of the molded product prior to painting, and has excellent paint film adhesion. can be provided. Moreover, according to the above manufacturing method, a coated resin molded article having excellent coating film adhesion as described above can be manufactured.

[0018]

【Example】

Examples 1 to 8, Comparative Examples 1 to 6 Examples according to the present invention will be described below along with comparative examples. In this example, a polypropylene resin composition is prepared, and then the resin composition is injection molded to form a molded article.
Paint was applied to the surface and the adhesion of the paint film was measured. Furthermore, the breaking strength (%), flexural modulus (MPa), Izod impact strength (-30°C, J/m), and coating peel strength (g/cm) were also measured. These results are shown in Table 1.
, shown in Table 2.

In preparing the above-mentioned polypropylene resin composition, unsaturated A monomer and an organic radical generator were mixed, melt-blended and extruded using a co-directional twin-screw extruder to obtain a pellet-shaped injection molding material. The above mixing ratios are shown in Tables 1 and 2. In addition, the above extrusion conditions are: cylinder inlet temperature 150℃;
The outlet temperature was 200°C and the screw rotation speed was 300 rpm. Further, as the EPR, an ethylene-propylene copolymer (hereinafter referred to as EPM) or an ethylene-propylene-nonconjugated diene terpolymer (hereinafter referred to as EPDM) was used.

Next, the following materials were used as the above raw materials. PP. ．． ．． “Hypol J-300P” Mitsui Petrochemical (
Co., Ltd., MFR (melt flow rate): 1.4g
/10min EPM1. ．． ．． “EP921” manufactured by Japan Synthetic Rubber Co., Ltd.
ML1+4 (100°C): 27, Propylene content: 5
0% EPM2. ．． ．． “EP11” manufactured by Japan Synthetic Rubber Co., Ltd., ML1+4 (100°C): 40, Propylene content:
49% EPM3. ．． ．． “EP01P” manufactured by Japan Synthetic Rubber Co., Ltd., ML1+4 (100°C): 19, Propylene content: 22% EPM4. ．． ．． “EP02P” manufactured by Japan Synthetic Rubber Co., Ltd., ML1+4 (100°C): 24, Propylene content: 26%

[0021]EPM5. ．． ．． “EP91
2P” manufactured by Japan Synthetic Rubber Co., Ltd., ML1+4 (100℃
): 10, Propylene content: 22% EPM6. ．． ．． “EP911P” manufactured by Japan Synthetic Rubber Co., Ltd., ML1+4 (100°C): 15, Propylene content:
15% EPM7. ．． ．． “EP961SP” Japan Synthetic Rubber Co., Ltd.
manufactured by EPDM., ML1+4 (100°C): 63, propylene content: 23%. ．． ．． “EP57P” manufactured by Japan Synthetic Rubber Co., Ltd.
ML1+4 (100℃): 88, Propylene content: 2
8% organic radical generator. ．． ．． “Parkadox 14”
Akzo Co., Ltd., 1,3-bis)t-butylperoxyisopropyl)benzene. Heat stabilizer. ．． ．． “Irganox 1010” manufactured by Ciba Geigy, hindered phenol type.

[0022] The above-mentioned "MFR (melt flow rate)" is the g of the resin material extruded in 10 minutes from an orifice with a diameter of 2.1 mm when the resin material is subjected to a force of 2160 g at 230°C. Shown in numbers. Further, the Mooney viscosity ML1+4 has been described above. Further, a molded article was produced by injection molding the above pellet-like material at an inlet temperature of 150°C and an outlet temperature of 180°C. The size of the molded article was 40 x 110 x 2 mm.

Next, after degreasing the molded product with a chlorinated organic solvent (trichloroethane), a urethane paint was applied to a film thickness of 100 μm, and baked at 85° C. for 40 minutes. did. The above paints are “R278” (main agent) and “R271” (curing agent) manufactured by Nippon B Chemical Co., Ltd.
A two-part type consisting of Further, the above coating film adhesion test was conducted according to JISK-6854 by measuring the coating film peel strength (g/cm) using a 180 degree peeling method.

As can be seen from Tables 1 and 2, Examples 1 to 8 of the present invention all exhibit a coating peel strength of 460 g/cm or more. In particular, EPM1 is 30
Examples 2 to 4 using ~60% by weight of EPM3 and Example 6 using 45% by weight of EPM3 exhibit high coating peel strength of about 1200 (g/cm) or more. Note that "NB" in the Izod impact strength column means that the sample did not break. On the other hand, Comparative Examples 1 to 6 generally had low coating peel strength. In particular, Comparative Example 2, which contained only PP and EPM without adding any unsaturated monomer or organic radical generator, had a coating peel strength of 5 g/cm and extremely poor coating adhesion. Also,
Comparative Example 4 has a high coating peel strength of 870 g/cm, but is inferior to the product of the present invention in terms of cold impact resistance.

Comparative Example 3 is an example in which maleic anhydride (conventional example) which does not have a hydroxyl group is used as the unsaturated carboxylic acid, and the peel strength of the coating film is 605 g/cm, but the elongation at break is extremely high. It has become low. In addition, Comparative Example 5 is EPM
7 has a high Mooney viscosity of 63, and comparative example 6 has a high Mooney viscosity of 63.
has a high Mooney viscosity of 88, so both have low coating peel strength.

[0026]

[Table 1]

[0027]

[Table 2]

Embodiment 9 In this embodiment, the present invention is applied to a mudguard for an automobile, as shown in FIG. As shown in the figure, the mudguard 4 consists of a main body 41, a lower piece 42, and a mounting portion 43. Further, the main body has mounting holes 411 and 412 on the upper left and right sides for mounting the mudguard to the vehicle body, and a similar mounting hole 431 is provided at the upper center of the mounting portion 43. Further, a recess 45 is provided between the main body 41 and the mounting portion 43. Further, a coating film made of the following paint is formed on the surface of the mudguard 4.

The mudguard 4 is injection molded using a synthetic resin made of the polypropylene resin composition shown in Example 3 above. In addition, the above coating film was created by applying urethane paint to the surface of the mudguard using an air atomization coating gun to a coating thickness of 35 μm.
It was baked at 5°C for 40 minutes. The mudguard 4 was subjected to a water-resistant adhesion test to test its paint film adhesion. As a result, even in a test conducted at 40°C for 240 hours, no damage such as cracking or peeling of the coating film was observed, confirming that the coating film had excellent adhesion.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a mudguard in Example 9.

[Explanation of symbols]

4. ．． ．． mudguard, 41. ．． ．． Main body, 42. ．． ．． Lower piece, 43. ．． ．． Mounting part,

Claims (2)

[Claims] Claim 1: A painted resin molded article formed by forming a coating film on the surface of a molded article made of a synthetic resin, wherein the synthetic resin is the following polypropylene resin composition: Goods. (A) 90 to 30% by weight of polypropylene; and (B) 10 to 70% by weight of an ethylene-α-olefin copolymer having a Mooney viscosity of ML1+4 (100°C) 50 or less and a propylene content of 20% by weight or more. (C) 0.1 part by weight or more of an unsaturated monomer consisting of an unsaturated carboxylic acid and/or a derivative thereof having at least one hydroxyl group in the molecule, and (D) an organic A polypropylene resin composition obtained by adding and mixing a radical generator and then heat-treating. Claim 2: (A) 90 to 30% by weight of polypropylene, and (B) 10 to 10% of ethylene-α-olefin copolymer having a Mooney viscosity of ML1+4 (100°C) 50 or less and a propylene content of 20% by weight or more. (C) 0.1 part by weight or more of an unsaturated monomer consisting of an unsaturated carboxylic acid and/or a derivative thereof having at least one hydroxyl group in the molecule; , (D) an organic radical generator, and then heat-treated to form a polypropylene-based resin composition into the shape of a desired molded product, and then the surface of the molded product is A method for producing a coated resin molded product, the method comprising forming a coating film on the coated resin molded product.