JPH0579390B2 - - Google Patents

Description

[Detailed description of the invention]

[Background of the Invention] <Industrial Application Field> The present invention relates to a method for coating a resin molded body for coating a propylene resin material. More specifically, the present invention relates to a method for coating a resin molded body formed by molding a resin composition comprising a specific propylene resin and a diene polymer having a terminal hydroxyl group or a hydrogenated product thereof. <Prior Art> Conventionally, it has been known that polypropylene resin has no polar groups in its structure and has high crystallinity, so that paints adhere to it extremely poorly. Therefore, in order to improve this poor adhesion, the surface of polypropylene is modified by applying a primer or plasma treatment in advance to improve paintability before applying the paint. I was letting it happen. <Problems to be Solved by the Invention> However, such coating methods have conventionally had the following problems. In other words, the primer application method requires the use of expensive primers,
In addition to the disadvantages of higher painting costs due to the increased number of painting steps, it also creates a poor work environment due to the need to volatilize the solvent in the primer, and is not safe due to the risk of fire. There was a problem. On the other hand, in the plasma processing method, since a high degree of vacuum is required, expensive equipment must be installed, and furthermore, since the method is a batch method, an increase in cost cannot be avoided. Furthermore, the surface after plasma treatment is unstable, and the adhesion of the paint decreases when it comes into contact with foreign matter, which can lead to variations in coating film performance, making handling extremely inconvenient. Therefore, if such primer application and plasma treatment processes could be omitted, it would be possible to simplify the painting process, improve the working environment, and reduce costs. Many studies have also been conducted to try to improve these problems. However, in the end, this objective has not yet been achieved, and polypropylene resin materials are painted without being able to omit such primer application, plasma treatment, etc. [Summary of the Invention] <Summary> As a result of extensive research in view of the above problems, the present inventors have found that the above problems can be solved by using a specific resin composition. As a result, the present invention was completed. That is, the coating method for the resin molded article of the present invention uses a propylene-ethylene block copolymer with an ethylene content of 3 to 45 weight % and/or an ethylene content of 0.5 to 10 weight %, which may contain an elastomer of 70 weight % or less. % propylene/ethylene random copolymer to 100 parts by weight, diene polymer having a hydroxyl group at the end or its hydrogenated product 0.01
This method is characterized in that a paint is directly applied to a molded article made of a resin composition to which ~10 parts by weight is added. <Effects> By using a specific resin composition, the coating method for resin molded bodies of the present invention overturns the conventional wisdom that it is impossible to directly coat propylene resins, and enables the coating of molded bodies to It is difficult to predict and surprising that a coated molded object with good paint adhesion can be obtained by directly applying paint without prior surface modification treatment such as primer application or plasma treatment. It is. [Specific Description of the Invention] [] Resin Molded Body The resin molded body used in the coating method for a resin molded body of the present invention is obtained by molding a resin composition consisting of the following components into various shapes. It is something. (1) Resin composition (a) Component propylene resin The propylene resin constituting the resin composition of the present invention is a crystalline resin having an ethylene unit content of 3 to 45% by weight, preferably 5 to 40% by weight. The content of propylene/ethylene block copolymer and/or ethylene units is 0.5 to 10% by weight, preferably 1 to 10% by weight.
It is composed of 5% by weight of a crystalline propylene/ethylene random copolymer, and any copolymerizable monomer components other than these ethylene components and propylene components are within the range that does not significantly impair the effects of the invention. (e.g. 30% by weight or less, preferably 15% by weight or less) and other α- Olefin,
The copolymer may be a copolymer of divinylbenzene, vinylsilane, unsaturated carboxylic acid, or the like. Such random or block copolymers are
Flexural modulus measured in accordance with JIS-K7203
3000~20000Kg/ ^cm2 , preferably 4000~18000Kg/
cm ² , particularly preferably 5000 to 15000 Kg/cm ² of the resin. The melt flow rate (MFR) of this copolymer resin is not particularly limited, but the value measured in accordance with ASTM-D1238 is usually 0.01 to 200 g/10 min, preferably 0.1 to 100 g/10 min.
10 min, particularly preferably within the range of 0.5 to 50 g/10 min. Among these propylene resins, it is preferable to use propylene/ethylene block copolymers. These resins can be appropriately selected from commercially available resins. Diene polymer having a hydroxyl group at the end or its hydrogenated product Among the diene polymer having a hydroxyl group at the other end or its hydrogenated product constituting the resin composition of the present invention, examples of the diene polymer having a hydroxyl group at the end include, for example. There is polyhydroxy polybutadiene. Specifically, it has at least one hydroxyl group at the end and has a molecular weight of 200 to 100,000, preferably 500 to 100,000.
50,000, particularly preferably 800 to 10,000 polymers which are liquid, semi-solid or solid at room temperature. The average number of hydroxyl groups per molecule is generally 1 to 10, especially 1.5.
~5 is preferable, and the hydroxyl value is generally 15~5.
250, preferably 25 to 125 (KOHmg/g) is particularly preferred. The diene polymer having a hydroxyl group at the end is 1,
It can be produced using 3-diene as a raw material by well-known methods such as radical polymerization and anionic polymerization. Specifically, for example,
Examples include the method described in Japanese Patent No. 51-71391. When produced by the above-mentioned radical polymerization, it can be easily obtained by polymerizing a diene monomer using hydrogen peroxide as a polymerization initiator. In addition, in the case of producing by the above-mentioned anionic polymerization, at least one of both terminals is obtained by polymerizing a conjugated diene using an anionic polymerization catalyst, such as an alkali metal or an organic alkali metal compound, according to a well-known method. For example, a living polymer having a structure in which an alkali metal is bonded to a monoepoxy compound, formaldehyde, acetaldehyde, acetone, halogen alkylene oxide, or polyepoxide may be reacted. At least one type of conjugated diene monomer is used as a raw material monomer for these polymers.
Examples of the conjugated diene monomer include 1,3-butadiene, 1,3-pentadiene, isoprene, chloroprene, 2,3-dimethyl-1,3-butadiene, and 1-phenyl-1,3-butadiene. In addition, as a hydrogenated product of a diene polymer having a hydroxyl group at the end, the above-mentioned diene polymer having a hydroxyl group at the end can be prepared by a conventional method, for example, as described in JP-A-Sho.
It can be obtained by hydrogenation using the method described in Japanese Patent No. 51-71391. Regarding the degree of hydrogenation, the double bonds contained in the polymer may be completely or partially hydrogenated, but in particular, the iodine value is usually 0 to 0.
20, particularly preferably 0 to 5 (g/100g). These diene polymers having hydroxyl groups at their terminals and hydrogenated products thereof can be used alone or as a mixture of a plurality of them. Additional Components In addition to the above-mentioned essential components, the resin composition of the present invention may contain additional components as shown below, within a range that does not significantly impair the effects of the present invention. Such additional components include, for example, polyolefins other than the above-mentioned propylene resins, specifically low-pressure polyethylene, medium-pressure polyethylene,
Polyethylene resins such as high-pressure polyethylene, linear low-density polyethylene, stereoregular polypropylene, stereoregular poly-1-butene, stereoregular poly-4-methyl-1-pentene, etc., or
Olefin-based, styrene-based, acrylic-based elastomers, inorganic fillers, specifically natural silica such as quartz, synthetic silica produced by wet or dry methods, natural silicates such as kaolin, mica, talc, asbestos, and silicic acid. Synthetic silicates such as calcium and aluminum silicate, metal hydroxides such as magnesium hydroxide and aluminum hydroxide, metal oxides such as alumina and titania, metal powders such as calcium carbonate, aluminum and bronze, carbon black, glass fiber, carbon fiber, potassium titanate,
There are whiskers such as calcium sulfate, zinc oxide, silicon titanide, sapphire, beryllia, boron carbide, and silicon carbide. In addition, other additives,
Specific examples include colorants, stabilizers, dispersion aids, molecular weight regulators, crosslinking agents, and nucleating agents. Among these additional components, the above-mentioned olefin elastomer is advantageous because rigidity, impact resistance, etc. can be adjusted. Such olefin-based elastomers include copolymers of α-olefins such as ethylene, propylene, 1-butene, 1-pentene, and 1-hexene, or copolymers of these and nonconjugated dienes. The copolymer has an initial elastic modulus of 400 Kg/cm ² or less, preferably 200 Kg/cm ² or less, particularly preferably 100 Kg/cm 2 as measured in accordance with JIS-K 6301.
It is preferably an amorphous or low crystalline copolymer with a particle size of 2 cm ² or less. Specific examples of the non-conjugated diene include dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, dicyclooctadiene, methylenebornene, 5-ethylidene-2-norbornene, and 5-vinyl-2-norbornene. , 5-methylene-2-norbornene, 5-methyl-1,4-hexadiene, 7-methyl-1,6-octadiene, and the like. These olefin elastomers are
Mooney viscosity ML ₁₊₄ measured at is usually 1 to 200,
It is preferably in the range of 5 to 150, particularly preferably 7 to 100. Among these olefin elastomers, ethylene elastomers are preferred in terms of quality and stability. Specifically, ethylene/propylene copolymer rubber (EPM), ethylene/1-butene copolymer rubber, ethylene/propylene/1-butene copolymer rubber, ethylene/propylene/non-conjugated diene copolymer rubber (EPDM), ethylene/ Examples include 1-butene-nonconjugated diene copolymer rubber, ethylene/propylene/1-butene/nonconjugated diene copolymer rubber, and the like. Among these ethylene-based elastomers, EPM is particularly preferred because it is less likely to cause surface roughness of the molded product, resulting in a beautiful painted surface. However, it is generally known that elastomer formulations tend to improve paint adhesion, but in the present invention, even without elastomer formulations, direct coating has good paint adhesion, and the predicted This is a surprising and difficult thing to do. (b) Quantitative ratio The quantitative ratio of the above-mentioned components constituting the resin composition used in the present invention is usually 100 parts by weight of the propylene resin including additional components: diene having a hydroxyl group at the end; The polymer or its hydrogenated product is blended in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 7 parts by weight, particularly preferably 0.1 to 5 parts by weight. When the blending amount of a diene polymer having a hydroxyl group at the end or its hydrogenated substance is less than the above range,
The reproducibility of paint adhesion is poor and the adhesion strength of paint is weak. On the other hand, if the amount exceeds the above range, the amount of the expensive polymer added will increase, resulting in an increase in the cost of the resin composition, and the polymer will bleed, resulting in a decrease in paint adhesion. In addition, when blending an elastomer as an additional component, 1 to 70% by weight, especially 5 to 60% by weight, especially 5 to 60% by weight, based on 100% by weight of the total amount with the propylene resin.
It is preferable to use 10 to 50% by weight since mechanical strength is excellent. (c) Blending By mixing the above constituent components, a resin composition that is a raw material for the resin molded article of the present invention is produced. There is no particular restriction on the mixing order of these components, and there are methods such as mixing the above components at the same time, mixing any two components in advance, and then mixing the remaining components. It's okay. As a mixing method, any conventionally known kneading machine such as a Brabender Plastograph, single or twin screw extruder, high-power screw kneader, Banbury mixer kneader, roll, etc. can be used. (2) Molding The resin molded article used in the present invention can be obtained by molding the above resin composition by various molding methods. Molding can be performed by a conventional method. That is, any molding method such as injection molding, compression molding, extrusion molding (sheet molding, blow molding), etc. may be used. In particular, the coating method of the present invention is effective even for injection-molded objects with complex shapes. [] Painting The method of painting the resin molded article in the present invention is as follows:
It is possible to adopt a process that excludes surface modification processes such as primer application and plasma treatment from the conventional painting process. That is, a paint is applied to a molded article made of the above-mentioned resin composition either directly or after degreasing if necessary. In the method of the present invention, "direct coating" means coating without applying the conventional primer coating or plasma treatment, and unless it deviates from the technical idea of the present invention, some kind of coating must be applied before applying the paint. This does not exclude surface treatment. One example of such surface treatment is degreasing treatment. This type of degreasing treatment is a normal operation that is generally performed just before applying paint, and it removes hand dirt and grime that inevitably adhere to the surface of the molded product during the process from molding the resin composition to painting. Machine oil, etc. can be washed and removed. Specifically, there are cleaning methods using organic solvents or their vapors, water, steam, acids, alkaline water, surfactant aqueous solutions, etc.
Among these, a cleaning method using organic solvent vapor is preferred. Furthermore, the means for applying the paint include spraying, brushing, and roller application, and any of these methods can be employed in the method of the present invention. Examples of paints that can be used in the method of the present invention include commonly used paints, such as acrylic paints, epoxy paints, urethane paints, alkyd paints, and melamine paints. Among these, acrylic paints and urethane paints are preferred, and acrylic paints are particularly preferred. [] Coated resin molded body The molded body coated by the coating method for resin molded bodies of the present invention has a coating thickness of generally 10 to 100 μm, preferably
It is applied at a thickness of 20 to 70 μm, and the coating is usually 400 μm thick.
Since it is strongly adhered with a peel strength of more than g/cm, especially 700 to 2000 g/cm, it can be used for various industrial parts, such as automobile exterior parts such as automobile bumpers, mudguards, side moldings, wheel caps, and spoilers. instrument panel, lever,
It can be used as automotive interior parts such as knobs and linings, electric appliances such as pots, vacuum cleaners, washing machines, refrigerators, identification devices, audio equipment, and daily goods such as color boxes and storage cases. [Experimental Examples] The present invention will be described in more detail with reference to Examples below. The molding conditions and test methods for obtaining test samples from the resin compositions produced in each Example are as shown below. be. In addition, "part" in an example is a weight ratio. Molding conditions Molding machine: Meiki Seisakusho injection molding machine M40A-SJ Molding temperature: 230℃ Molded product: Flat plate (65mm x 65mm x 2mm) Three-point bending modulus test piece (90mm x 10mm x 4mm) Flexural modulus JIS Measured according to K-7203. Measured in accordance with MFR ASTM-D 1238. Painting Paint: Painting was performed using a one-component acrylic paint and a two-component urethane paint. Coating method: Each paint was prepared and sprayed using an air spray gun so that the film thickness was approximately 40 μm. Thereafter, acrylic paints were baked at 100°C for 60 minutes, and urethane paints were baked at 120°C for 60 minutes. Checkerboard test for evaluating paint adhesion: Using a single-edged razor, draw 11 vertical and horizontal parallel lines perpendicular to the surface of the test piece at 2mm intervals to create 100 checkerboards. On top of that, apply cellophane adhesive tape (JIS-Z1522) with sufficient pressure, hold it at about 30 degrees to the coating surface, and peel it off at once toward you. Observe the condition of the area surrounded by the grid. Check the number of grid marks that did not peel off. was recorded. Examples 1 to 19 and Comparative Examples 1 to 5 Synthesis of diene polymers having hydroxyl groups at the terminals In an autoclave with a capacity of 500 ml, 100 g of 1,3-butadiene, 70 g of isopropyl alcohol, and 10 g of 60% hydrogen peroxide were used in an argon atmosphere. Polymerization was carried out at 90°C for 5 hours. After the reaction is complete,
Unreacted monomers were removed and the resulting diene polymer was dried. The obtained polymer had a molecular weight of about 2900 and a hydroxyl value of about 88 (KOHmg/g). Synthesis of hydrogenated product of diene polymer having a hydroxyl group at the end 50g of the diene polymer obtained in the above synthesis of the diene polymer having a hydroxyl group at the end, 50g of cyclohexane, 5g of ruthenium catalyst supported on 5% carbon
was placed in an autoclave with a capacity of 200 ml, and after replacing the system with an argon gun, hydrogen gas was added at 50 kg/cm ²
I sent it until it became. The temperature of this was raised to 100°C, and the reaction was carried out for 10 hours while supplying hydrogen gas so that the total pressure was maintained at 50 Kg/cm ² . After the reaction was completed, hydrogen was removed and the catalyst was removed by filtration, and the resulting hydrogenated product was precipitated in methanol, separated by filtration, and dried to obtain the desired product. The iodine value of the obtained diene polymer hydrogenate was 1.5 (g/100g), and the hydroxyl value was
It was 87.8 (KOHmg/g). Molding of resin moldings The ingredients shown in Table 1 are mixed using a twin-screw extruder.
The mixture was melted and kneaded at 200°C to form pellets. The pellets were used to injection mold a flat plate and a three-point flexural modulus test piece. The ingredients in Table 1 are as follows. Propylene resin/block copolymer (1): Ethylene content 8.2% by weight, flexural modulus 10000Kg/cm ² and MFR 33g/
Propylene/ethylene block copolymer with 10 min.・ Block copolymer (2): Ethylene content 13% by weight, flexural modulus 6000Kg/cm ² and MFR 30g/
Propylene/ethylene block copolymer with 10 min.・ Block copolymer (3): Ethylene content 7.5% by weight, flexural modulus 11500Kg/cm ² and MFR 10g/
Propylene/ethylene block copolymer with 10 min.・Random copolymer: ethylene content 3.4% by weight,
Flexural modulus is 10500Kg/ ^cm2 and MFR15g/
Propylene/ethylene random copolymer with 10 min.・Homopolymer: Flexural modulus is 13000Kg/ ^cm2 and
Polypropylene with MFR25g/10min. Olefin elastomer/EPM(1): Mooney viscosity ML ₁₊₄ (100℃) is 70,
Ethylene-propylene copolymer rubber/EPDM with specific gravity 0.86: Mooney viscosity ML ₁₊₄ (100℃) is 47,
Ethylene-propylene-ethylidene-norbornene copolymer rubber with a specific gravity of 0.86 Hydroxyl group-containing diene polymer or its hydrogenated product/Diene polymer (1): Diene polymer/diene polymer hydrogenated product obtained by synthesizing the diene polymer having a hydroxyl group at the end ( 1): Diene polymer hydrogenated product obtained by the synthesis of the hydrogenated diene polymer having a hydroxyl group at the terminal. Diene polymer hydrogenated product (2): Iodine value 0.5
(g/100g), coating of butadiene polymer hydrogenated resin molding with hydroxyl value 46.9 (KOHmg/g) After degreasing the flat plate formed by the above resin molding process with trichloroethane vapor for 30 seconds, The paint was applied using an air gun. After baking and drying, the pieces were left at room temperature for 48 hours and a grid test was conducted. Table 1 shows the results of the elastic modulus and paint adhesion of the resin composition obtained. The composition of Comparative Example 5 was too soft to measure its flexural modulus. Furthermore, during painting, the flat plate of the test piece was severely deformed during degreasing treatment with trichloroethane vapor and baking drying after coating, and the surface of the flat plate also became uneven, making it impossible to evaluate.

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Claims (1)

[Claims] 1 100 parts by weight of a propylene-ethylene block copolymer with an ethylene content of 3-45% by weight and/or a propylene-ethylene random copolymer with an ethylene content of 0.5-10% by weight, which may contain 70% by weight or less of an elastomer. In contrast, diene polymers with hydroxyl groups at the ends or their hydrogenated products
1. A method for coating a resin molded body, which comprises directly applying a paint to a molded body made of a resin composition to which 0.01 to 10 parts by weight has been added.