JP2011147910A - Method of forming multi-layer coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a multi-layer coating film having excellent surface smoothness of a natural fiber reinforced polypropylene based resin molding in which fiber mesh is concealed and having excellent coating performance such as adhesiveness. <P>SOLUTION: The method of forming the multi-layer coating film includes forming a primer coating film and a top coating film in this order on the surface of a resin molding. The resin molding mainly comprises a natural fiber reinforced polyolefin based resin wherein the content of the natural fiber in the resin molding is 10-40 mass% and the primer coating film contain one of chlorinated polypropylene, (meth)acrylic modified chlorinated polypropylene and acid anhydride modified chlorinated polypropylene having 5-40 mass% chlorine content. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is intended to provide a method for forming a multilayer coating film that facilitates the coating of a polyolefin molded body reinforced with natural fibers that are low in cost, lightweight, rigid, and excellent in surface smoothness.

  Paint is applied to the surface of molded products for the purpose of adding added value such as decorativeness to resin molded products used in automobiles, home appliances, building materials, etc., or increasing the weather resistance and extending the product life. This has been done widely. As these resin molded products, low-cost, lightweight and rigid fiber-reinforced plastics in the recent flow of oil-removal resources, as an alternative to conventional glass fiber, it is natural fiber plant fiber Reinforced plastics have been proposed.

  For example, regarding a natural fiber-containing molding material based on an unsaturated polyester resin and a molding obtained therefrom, a molding having a low residual monomer content and no styrene odor is produced (see Patent Document 1).

  Alternatively, for molding pellets that contain a core of natural fibers coated with a sheath of thermoplastic material, the resulting pellets retain a high level of fiber length and impart a high level of mechanical performance during the molding process. (See Patent Document 2).

  Alternatively, a plant fiber reinforced plastic that is superior in strength performance to a conventional fiber reinforced plastic using a plant fiber as a reinforcing material is provided (see Patent Document 3).

  Alternatively, the present invention relates to a method for producing a biodegradable resin composite material and a method for molding a biodegradable resin composite material, and in particular, a method for producing a biodegradable resin composite material containing plant fibers and excellent in strength and productivity, and the biodegradable resin The present invention relates to a method for molding a composite material (see Patent Document 4).

  Or more specifically, it relates to a plant fiber reinforced plastic molding, and more specifically, a fiber reinforced plastic molding material mainly composed of a fiber obtained by spinning wood pulp using an amine oxide as a solvent and a thermosetting resin, and the molding material. The present invention relates to a fiber-reinforced plastic molded product (see Patent Document 5).

  Alternatively, a plant fiber-containing resin composition in which a plant fiber is impregnated with a resin, the resin is filled in the conduit of the plant fiber, and the specific gravity is 90 of the weighted average value of the true specific gravity of the plant fiber and the true specific gravity of the resin. % Or more (see Patent Document 6).

  Or it is related with the manufacturing method of a high intensity | strength vegetable fiber containing resin composition. In the production of a plant fiber-containing resin composition, the moisture in the plant fiber is removed while kneading the plant fiber containing moisture and the resin, and the kneaded product is molded to obtain a resin composition (see Patent Document 7).

  Alternatively, the present invention relates to a natural fiber reinforced thermoplastic resin injection-molded article having excellent neutralizing performance that uses natural fibers as reinforcing fibers and releases charged static electricity (see Patent Document 8).

  In particular, a molding composition in which plant fibers such as linen and ramie are kneaded into a polyolefin resin typified by polypropylene resin is low-cost and lightweight, so future use expansion is expected. ing. Polyolefin resins are inexpensive and have excellent mechanical properties, heat resistance, chemical resistance, water resistance, and the like, and thus are used in a wide range of fields.

  However, such a polyolefin-based resin generally has a low polarity because it does not have a polar group in the molecule, and has a drawback that it is difficult to paint or bond. In order to remedy this drawback, the surface of the molded body made of the polyolefin resin is chemically treated with a chemical or the like, or the surface of the molded body is oxidized by a technique such as corona discharge treatment, plasma treatment or flame treatment. Various approaches have been attempted. However, these methods require not only a special apparatus, but also cannot be said to have a sufficient effect of improving paintability and adhesiveness. Therefore, in recent years, in order to improve the adhesion to paint, a rubber component or a hydroxyl group-containing polyolefin resin is included as a modifier in the polyolefin resin to ensure adhesion with the paint (patent document). 9-11).

  Further, as a device for imparting good adhesion to these polyolefin resins, acid-modified polyolefin resins obtained by graft-modifying polyolefin resins such as chlorinated polypropylene and ethylene-propylene copolymer with maleic anhydride, ( An acrylic modified polyolefin resin graft-modified with a (meth) acrylic monomer has been developed as a coating resin material for a primer (see Patent Documents 12 to 25).

  However, when plant fiber such as flax (linen) or ramie (ramie) is used as a reinforcing material for polyolefin resin, the uniformity of fiber thickness is not as good as that of glass fiber used in the past. Because it is uniform, the fiber texture appears prominently on the surface of the molded product, and the fiber texture does not disappear during top coating, resulting in surface defects. When metallic coating is applied, the metallic pigment is oriented along the fiber texture, resulting in commercial value. It is the current situation that has been significantly impaired.

Japanese Patent Laid-Open No. 6-16753 Special Table 2003-53936 JP 2005-67064 A Japanese Patent Laying-Open No. 2005-307078 JP 2006-316285 A JP 2007-197539 A JP 2007-224126 A JP 2009-131204 A JP-A-5-239276 JP-A-8-109293 Japanese Patent Laid-Open No. 10-147688 JP-A-5-97937 Japanese Patent Laid-Open No. 5-132531 JP-A-10-158447 Japanese Patent Laid-Open No. 11-181193 JP 2001-114843 A JP 2000-143928 A JP 2001-11365 A JP 2001-114960 A JP 2001-152078 A JP 2002-188042 A Japanese Patent Laid-Open No. 2002-212241 JP 2005-126483 A JP 2008-19320 A JP 2008-56913 A

  As described above, a molded article made of a polyolefin resin reinforced with vegetable fibers is low in cost, light weight, and excellent in rigidity, but the fiber eyes of the plant fibers are raised on the surface of the molded article, and the surface smoothness is poor. Even if the top coat is applied, the fiber texture does not disappear, but on the contrary, the surface texture is enhanced by the top coat and the fiber texture is more emphasized, resulting in a significant loss of commercial value.

  In the present invention in which plant fibers that are natural fibers are used as reinforcing materials, if the plant fibers are exposed to a high temperature in a melt-plasticized cylinder during injection molding, the plant fibers may be thermally deteriorated and the desired performance may not be obtained. Therefore, the plasticization temperature is preferably as low as 220 ° C. or less, and in this respect, a polyolefin resin is preferable.

  Further, when polypropylene homopolymer is used as the polyolefin-based resin in order to further reduce the cost, there is a problem that the adhesion of the primer coating for a polypropylene resin molded article is not always satisfactory.

  In view of such problems, the object of the present invention is to provide a method for forming a multi-layer coating film that is excellent in coating film performance such as surface smoothness and adhesion, etc., in which the fiber mesh is concealed in a polypropylene resin molded product reinforced with natural fibers. Is to provide.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be achieved with the following configuration, and have reached the present invention.

According to the present invention, on the surface of the resin molded body, a primer coating film, a method for forming a multi-layer coating film that sequentially forms a top coating film,
The resin molding is mainly composed of a polyolefin-based resin reinforced with natural fibers, and the content of natural fibers is 10 to 40% by mass with respect to the resin molding,
The primer coating film contains any one of chlorinated polypropylene, (meth) acryl-modified chlorinated polypropylene, or acid anhydride-modified chlorinated polypropylene having a chlorine content of 5 to 40% by mass. A method of forming a coating is provided.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the method of forming a multilayer coating film in the natural fiber reinforced polyolefin molded object excellent in surface smoothness and coating-film adhesiveness.

  Hereinafter, the formation method of the multilayer coating film to the polyolefin molded object reinforced with the natural fiber of this invention is demonstrated concretely.

  The method for forming a multilayer coating film according to the present invention comprises a resin molded body mainly composed of polyolefin resin reinforced with natural fibers, a primer coating film formed on the surface thereof, and a top coating film. It consists of a layer coating.

  As the polyolefin-based resin reinforced with natural fibers, conventionally known various molding materials can be used. As long as it is a polypropylene-based resin, a propylene homopolymer may be used, and a structural unit derived from propylene A block copolymer containing a structural unit derived from an α-olefin having 2 to 12 carbon atoms excluding propylene may be used.

  As the α-olefin having 2 to 12 carbon atoms excluding propylene, known ones can be used. For example, ethylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, nonene- Examples thereof include chain α-olefins such as 1, decene-1, 4-methylpentene-1, and 4-methylhexene-1, and cyclic α-olefins such as cyclopentene and cyclohexene. These α-olefins can be used alone or in combination of two or more.

  The comonomer content in the propylene random copolymer is preferably 0.5 to 20 mol%, more preferably 1 to 15 mol%. The comonomer content in the propylene block copolymer is preferably 0.5 to 50 mol%, more preferably 1 to 40 mol%.

  Furthermore, such a molding material is a natural fiber such as hemp fiber (flax, hemp, cannabis, manila hemp, burlap, sisal, kenaf, etc.) for the purpose of increasing impact resistance and rigidity or increasing adhesion to the primer. It is essential to contain 10 to 40% by mass of one or more plant fibers such as bamboo fibers (such as true bamboo and bamboo mulberry), cotton, coconut fibers and pineapple fibers with respect to the resin molding. Preferably it is 12-30 mass%, More preferably, it is 15-25 mass%. It is considered that the cellulose component improves the adhesion to the primer in the plant fiber. If the plant fiber is less than 10% by mass, the adhesion of the primer is remarkably inferior, and the impact resistance and rigidity are also inferior. On the other hand, when it exceeds 40 mass%, the fluidity | liquidity in a metal mold | die will be inferior, and a satisfactory molded object cannot be obtained. The average fiber length and average fiber diameter of the plant fiber differ depending on the type of plant fiber and the method of fiberization thereof, but the average fiber length of the plant fiber is preferably 1 to 40 mm, more preferably 1.5 to 5 mm. . Moreover, 5-300 micrometers is preferable and, as for an average fiber diameter, More preferably, it is 10-150 micrometers. If the average fiber length of the plant fiber is less than 1 mm, it is difficult to sufficiently reflect the original strength and rigidity of the fiber. If the average fiber length exceeds 40 mm, the plant fiber and the polyolefin resin are melted and kneaded. The fibers are entangled with each other, resulting in poor dispersion and poor appearance due to variations in strength and irregularities on the surface of the molded product. In addition, when the average fiber diameter is less than 5 μm, the original fiber shape of the plant fiber is not maintained, and the strength of the molded body tends to decrease. When the average fiber diameter exceeds 300 μm, the surface smoothness of the molded body is inferior due to the fiber mesh, and the appearance It tends to be defective and is not preferable.

  These polyolefin fibers reinforced with natural fibers can contain a crystal nucleating agent, an ultraviolet absorber, an antioxidant, a release agent, a silane coupling agent, a flame retardant, or a coloring pigment, if necessary. .

  Next, a known method can be used as a method for producing polyolefin resin pellets reinforced with natural fibers according to the present invention. That is, as a method for producing polyolefin resin pellets reinforced with natural fibers, a drawing method for obtaining long fiber reinforced pellets is particularly preferable in terms of productivity and production cost. Alternatively, plant fibers cut to a predetermined length and polyolefin resin pellets are put into a biaxial kneading extruder, the polyolefin resin is melted and kneaded with plant fibers, and this is extruded and cooled and solidified. The method of cutting to predetermined length is mentioned.

  Next, the primer composition used in the present invention will be described.

  The primer composition used in the present invention contains, as a main component, any of chlorinated polypropylene, (meth) acryl-modified chlorinated polypropylene, or acid anhydride-modified chlorinated polypropylene having a chlorine content of 5 to 40% by mass. In addition, if necessary, inorganic particles such as calcium carbonate, talc, clay, colored pigments, conductive pigments such as carbon black, (meth) acrylic modified polypropylene resin or acid anhydride modified polypropylene resin, acrylic resin, alkyd resin, Various resins such as polyester resins, melamine resins, epoxy resins, blocked isocyanate resins, organic solvents such as toluene, xylene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, ultraviolet absorbers, antioxidants, antifoaming agents, or It contains optional components such as antistatic agents . Furthermore, for the purpose of improving the adhesiveness with a molded product mainly composed of polyolefin resin reinforced with natural fibers, cellulose such as nitrocellulose, cellulose propionate, ethyl cellulose, acetyl cellulose or cellulose acetate butyrate. A fibrous resin that is a derivative can be used.

  The chlorine content of the chlorinated polypropylene used in the present invention is essential to be 5 to 40% by mass, preferably 10 to 30% by mass. When the chlorine content is 5% by mass or more, the compatibility with the vehicle component is not lowered and the storage stability is good. On the other hand, if the chlorine content is 40% by mass or less, good adhesion to a polyolefin substrate can be obtained.

  The weight average molecular weight of the chlorinated polypropylene used in the present invention is preferably 30,000 to 200,000. When the weight average molecular weight is less than 30,000, the strength of the coating film obtained from the primer composition is low, and when high-pressure water washing or the like is performed, the coating film is easily peeled off from the surface of the polypropylene substrate at a high water pressure. On the other hand, if the weight average molecular weight exceeds 200,000, the wettability with respect to the polypropylene base material is lowered, the adhesion is lowered, the viscosity is increased, and the coating workability tends to be lowered.

  The chlorinated polypropylene used in the present invention can be easily obtained by subjecting polypropylene to a chlorination reaction by a known method. For example, raw material polypropylene is dispersed or dissolved in water or a medium such as carbon tetrachloride or chloroform, and chlorine gas is blown in a temperature range of 60 to 120 ° C. under pressure or normal pressure in the presence of a catalyst or under irradiation with ultraviolet rays. Is done.

  Examples of the raw material polypropylene include crystalline polypropylene, propylene-α-olefin copolymer, ternary copolymer composed of unsaturated carboxylic acid monomer, unsaturated vinyl ester monomer and ethylene, and ethylene-vinyl acetate copolymer. Can be mentioned.

  The crystalline polypropylene is isotactic polypropylene and can have a weight average molecular weight of 10,000 to 300,000.

  The propylene-α-olefin copolymer is a copolymer of propylene as a main component and an α-olefin copolymerized therewith, and either a block copolymer or a random copolymer can be used. Examples of the α-olefin component include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 4-methyl-1-pentene. The propylene component content is suitably 55 to 98 mol%, and if it is less than 55 mol%, the adhesion to polypropylene decreases. Moreover, when it exceeds 98 mol%, the softness | flexibility of a coating film will be impaired.

  The ternary copolymer is obtained by copolymerizing an unsaturated carboxylic acid monomer, an unsaturated vinyl ester monomer, and ethylene by a known method such as a high-pressure radical polymerization method, a solution polymerization method, or an emulsion polymerization method.

  The acid anhydride-modified chlorinated polypropylene used in the present invention is a polypropylene derivative containing a chlorinated polypropylene portion and an acid anhydride portion bonded to the chlorinated polypropylene portion. It is essential that the chlorine content is 5 to 40% by mass. The acid anhydride partial content is preferably 0.8 to 5% by mass, and the weight average molecular weight is preferably 10,000 to 100,000. The acid anhydride portion is a modified portion obtained by grafting, for example, a group derived from an acid such as maleic anhydride or itaconic anhydride. The reason why the weight average molecular weight is set as low as 10,000 to 100,000 here is that if the chlorine content is low, the crystallinity increases and the storage stability in the primer composition is prevented from being lowered. is there.

  The acid anhydride-modified chlorinated polypropylene is obtained by modifying polypropylene by reacting with an acid anhydride and chlorine. For example, the reaction with chlorine is performed by introducing chlorine gas into a solution containing polypropylene. Moreover, reaction with an acid anhydride is performed by making an acid anhydride react with a polypropylene (or chlorinated polypropylene), for example in presence of a peroxide.

  The acid anhydride-modified chlorinated polypropylene is not particularly limited as long as its chlorine content is in the range of 5 to 40% by mass. When the chlorine content is less than 5% by mass, the acid anhydride-modified chlorinated polypropylene is crystallized, and the storage stability of the primer composition tends to decrease. On the other hand, when the chlorine content exceeds 40% by mass, the polarity of the acid anhydride-modified chlorinated polypropylene increases, and the solvent resistance tends to decrease.

  The acid anhydride partial content of the acid anhydride-modified chlorinated polypropylene is not particularly limited as long as it is in the range of 0.8 to 5% by mass. Solvent resistance falls that acid anhydride part content is less than 0.8 mass%. On the other hand, when the content of the acid anhydride exceeds 5% by mass, the acid anhydride group increases and the water resistance decreases.

  The acid anhydride-modified chlorinated polypropylene is not particularly limited as long as its weight average molecular weight is in the range of 10,000 to 100,000. When the weight average molecular weight is less than 10,000, the strength of the primer coating film is lowered, and the coating film surface is easily damaged. On the other hand, when the weight average molecular weight exceeds 100,000, the wettability with respect to the polyolefin substrate decreases, and the adhesion with the substrate decreases.

  The (meth) acryl-modified chlorinated polypropylene used in the present invention is a polypropylene containing a chlorinated polypropylene portion and a (meth) acrylic polymer chain portion grafted on the chlorinated polypropylene portion.

  The (meth) acryl-modified chlorinated polypropylene used in the present invention is obtained, for example, by graft polymerization of (meth) acrylic monomer to chlorinated polypropylene in the presence of a peroxide. Specific examples of (meth) acrylic monomers include (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Etc.

  The (meth) acryl-modified chlorinated polypropylene is a hydroxyl group-containing (meth) acryl-modified chlorinated polypropylene obtained by graft polymerization of a hydroxyl group-containing (meth) acrylic monomer to chlorinated polypropylene in the presence of a peroxide. There may be. Examples of the hydroxyl group-containing (meth) acrylic monomer used here include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) acrylate.

  Such (meth) acryl-modified chlorinated polypropylene can be used singly or in combination of two or more.

  The chlorine content of the (meth) acryl-modified chlorinated polypropylene used in the present invention is essential to be 5 to 40% by mass, and preferably 10 to 30% by mass. When the chlorine content is 5% by mass or more, the compatibility with the vehicle component is not lowered and the storage stability is good. On the other hand, if the chlorine content is 40% by mass or less, good adhesion to a polyolefin substrate can be obtained.

  The weight average molecular weight of the (meth) acryl-modified chlorinated polypropylene used in the present invention is preferably 30,000 to 200,000. When the weight average molecular weight is less than 30,000, the strength of the coating film obtained from the primer composition is low, and when high-pressure water washing or the like is performed, the coating film is peeled off from the surface of the polypropylene substrate with high water pressure. On the other hand, if the weight average molecular weight exceeds 200,000, the wettability with respect to the polypropylene substrate is lowered, the adhesion is lowered, the viscosity is increased, and the coating workability is lowered.

  The primer composition according to the present invention includes, as appropriate, (meth) acryl-modified polypropylene resin, acid anhydride-modified polypropylene resin, acrylic resin, alkyd resin, polyester resin, melamine resin, epoxy resin, and blocked isocyanate resin and the like, toluene Organic solvents such as xylene, ethyl acetate, butyl acetate, methyl ethyl ketone, and methyl isobutyl ketone may be blended. When the resin is blended, it is blended so that the resin becomes 0 to 100 parts by mass with respect to 100 parts by mass in total of chlorinated polypropylene, (meth) acryl-modified chlorinated polypropylene, or acid anhydride-modified chlorinated polypropylene. .

  The primer composition according to the present invention may be formulated with an inorganic pigment such as titanium dioxide or carbon black, an organic pigment such as phthalocyanine blue, or an extender pigment such as calcium carbonate, talc, or precipitated barium sulfate.

  The method for applying the primer composition to the polypropylene substrate is not particularly limited, but spray coating is preferred.

  The formation method of the multilayer coating film of this invention may perform a preheating process as needed after each process. In addition, preheating means heating-drying to such an extent that the formed coating film is not hardened, and the normally formed coating film is heated at 40-60 degreeC for 3 to 10 minutes.

  Moreover, after each process, you may dry a coating film by a baking drying process, for example for 5 to 30 minutes at 80-120 degreeC, respectively.

  The film thickness after curing is preferably in the range of 5 to 50 μm, and more preferably 25 to 45 μm, for example, in the primer coating. If it is less than 5 μm, it may be too thin to obtain a continuous coating film. On the other hand, when it exceeds 50 μm, it becomes difficult to obtain a uniform coating film.

  In the surfacer coating film, the film thickness after curing is preferably 20 to 50 μm, in the metallic base coating film is preferably 10 to 20 μm, and in the clear coating film, 20 to 60 μm is preferable.

  The surfacer coating, top coating, metallic base coating, and clear coating are not particularly limited, and examples thereof include two-component urethane coating, one-component melamine baking coating, one-component acrylic baking coating, and one-pack lacquer coating.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example and a comparative example, the scope of the present invention is not limited at all by these Examples and comparative examples.

<Preparation example>
"Production of polypropylene resin molded plate reinforced with natural fibers"
A polypropylene resin molded plate reinforced with natural fibers having the composition shown in Table 1 was produced by the following method. The unit is part by mass.

  As a method for producing a resin pellet reinforced with natural fibers, a known method can be used. For example, a pellet having a pellet diameter of 3 mm and a pellet length of 8 mm was produced by a drawing method. A natural fiber reinforced resin injection-molded plate was produced by using an injection molding machine having a clamping force of 100 tons and pellets shown in Table 1 as molding raw materials, and a flat plate having a length of 150 mm, a width of 150 mm, and a thickness of 2.5 mm.

  Two types of polypropylene-based resins were used: (A) Prime Polypro J707G (block polymer, manufactured by Prime Polymer Co., Ltd.) and (B) Prime Polypro J106MG (Homopolymer, manufactured by Prime Polymer Co., Ltd.). In Preparation Example 3, maleic acid-modified polypropylene (Yumex 1001, manufactured by Sanyo Chemical Industries, Ltd.) was used in order to improve the interfacial adhesion and impregnation between (C) polypropylene resin and plant fiber.

  As plant fibers for reinforcement, (D) jute, (E) ramie (ramie), (F) bamboo (Moso bamboo) were used. (D) has an average fiber length of 5 mm and an average fiber diameter of 20 μm, (E) has an average fiber length of 30 mm and an average fiber diameter of 25 μm, and (F) has an average fiber length of 5 mm and an average fiber diameter of 90 μm.

"Preparation of primer paint"
Primer paints were prepared according to the formulation shown in Table 2. The unit is part by mass. A known method can be used to prepare the coating material. For example, the components shown in Table 2 were blended and the pigment was dispersed using a sand mill.

(A) Chlorinated polypropylene: Chlorine content 9 mass%, weight average molecular weight 80,000, toluene 80 mass% contained chlorinated polypropylene solution (B) Chlorinated polypropylene: Chlorine content 15 mass%, weight average molecular weight 100,000 Chlorinated polypropylene solution containing 65% by mass of toluene (C) Chlorinated polypropylene: Chlorine content 35% by mass, weight average molecular weight 150,000, chlorinated polypropylene solution containing 45% by mass of toluene (D) Acid anhydride-modified chlorinated polypropylene : Maleic anhydride-modified chlorinated polypropylene containing 70% by mass of toluene obtained by grafting 3.5% by mass of maleic anhydride onto a chlorinated polypropylene resin having a chlorine content of 12.5% by mass and a weight average molecular weight of 30,000. E) Acid anhydride modified chlorinated polypropylene: chlorine content 20% by mass, 65% by weight toluene-containing maleic anhydride-modified chlorinated polypropylene (F) (meth) acryl-modified chlorinated polypropylene obtained by grafting 1% by weight of maleic anhydride onto a chlorinated polypropylene resin having a weight average molecular weight of 33,000: chlorine 65% by mass toluene-containing methacrylic acid-modified chlorinated polypropylene (G) (meth) acryl-modified chlorinated product obtained by grafting methacrylic acid to a chlorinated polypropylene resin having a content of 12.5% by mass and a weight average molecular weight of 55,000 Polypropylene: 65% by mass of toluene containing methacrylic acid obtained by grafting methacrylic acid to a chlorinated polypropylene resin having a chlorine content of 20% by mass and a weight average molecular weight of 80,000. Chlorinated polypropylene: containing chlorine 3 mass%, weight average molecular weight 50 000, chlorinated polypropylene solution containing 80% by mass of toluene (I) Chlorinated polypropylene: Chlorine content: 45% by mass, weight average molecular weight 100,000, chlorinated polypropylene solution containing 65% by mass of toluene (J) Acid anhydride modified chlorination Polypropylene: Maleic anhydride-modified chlorinated polypropylene (K) acid containing 80% by mass of toluene obtained by grafting 1% by mass of maleic anhydride to a chlorinated polypropylene resin having a chlorine content of 3% by mass and a weight average molecular weight of 50,000 Anhydrous-modified chlorinated polypropylene: Maleic anhydride-modified chlorination containing 60% by mass of toluene obtained by grafting 3% by mass of maleic anhydride onto a chlorinated polypropylene resin having a chlorine content of 50% by mass and a weight average molecular weight of 33,000. Polypropylene (L) acrylic modified chlorinated polypropylene: Chlorine Methacrylic acid modified chlorinated polypropylene (M) acrylic modified chlorinated polypropylene containing 75% by weight of toluene obtained by grafting methacrylic acid to a chlorinated polypropylene resin having a content of 4.5% by weight and a weight average molecular weight of 55,000: Chlorine Methacrylic acid-modified chlorinated polypropylene containing 65% by mass of toluene obtained by grafting methacrylic acid to a chlorinated polypropylene resin having a content of 45% by mass and a weight average molecular weight of 80,000 CAB381-2: cellulose acetate butyrate (Eastman Kodak (Made by company)
Etocel 100: Ethylcellulose (manufactured by Nisshinsei)

"Formation of multi-layer coating film"
(Examples 1-15 and Comparative Examples 1-9)
The natural fiber reinforced polypropylene resin molded plate prepared in the above preparation example is first washed with water-based power wash and air-dried, and then the primer composition prepared in the above preparation example is spray-coated so as to have a dry film thickness of 15 μm. And dried at 80 ° C. for 10 minutes. After cooling, the solvent-based two-component urethane silver metallic base paint (Planit # 732: manufactured by Dainippon Paint Co., Ltd.) is further spray-coated on the coating film so as to have a dry film thickness of 15 μm. Clear paint (Planit # 750: manufactured by Dainippon Paint Co., Ltd.) is spray-coated to a dry film thickness of 35 μm, dried at 100 ° C. for 30 minutes, left in a room at 23 ° C. and 50% RH for 24 hours, and then applied. The film appearance, coating film adhesion (initial adhesion), and liquid resistance (warm water immersion) were evaluated by the following test methods. The results are shown in Table 3.

[Appearance of coating film]
The coating film appearance of the obtained coating test piece was visually observed. Evaluation was performed according to the following criteria.
A: Uneven color, blemish, or irregularity is not observed, and fiber eyes are hardly observed.
○: Color irregularities, flares, and irregularities are not observed, but a slight fiber texture is observed.
Δ: Slight unevenness of color, blemish, unevenness, and fiber texture are observed.
X: Color unevenness, armpits, bumps, and fiber texture are observed.

[Adhesion between substrate and coating film]
According to JIS K 5600-5-6: Adhesion (cross-cut method), an initial coating adhesion test was performed. The adhesion of the coating film was evaluated on the basis of the following 0 to 5 based on the classification of the test results described in JIS K 5600-5-6.
<6-level evaluation>
0: The edges of the cut are completely smooth, and there is no peeling in any lattice eye.
1 ... Small peeling of the coating film at the intersection of cuts. It is clearly not more than 5% that the crosscut is affected.
2 ... The coating is peeled along the edge of the cut and / or at the intersection. The cross-cut part is clearly affected by more than 5% but not more than 15%.
3 ... The coating film is partially or completely peeled along the edge of the cut, and / or various parts of the eye are partially or completely peeled off. The cross-cut portion is clearly affected by more than 15% but not more than 35%.
4: The coating film has been partially or completely peeled along the edges of the cut, and / or some eyes have been partially or completely peeled off. The cross-cut portion is clearly affected by more than 35% but not more than 65%.
5: When the degree of peeling exceeds Category 4.

(Liquid resistance)
JIS K 5600-6-2: Durability against water action by immersion was measured according to liquid resistance (water immersion method). In this case, adjust the water temperature to 40 ± 1 ° C, soak for 30 hours, take out the test piece, remove moisture with water-absorbing paper, and immediately bulge the whole surface or other damage state according to JIS K 5600-8-2 Inspected. Thereafter, the test piece was placed at room temperature for 24 hours, and a decrease in the adhesion of the test piece was examined according to JIS K 5600-5-6: Adhesion (cross-cut method).

(Examples 16 to 20 and Comparative Example 10)
The plant fiber reinforced polypropylene resin molded plate produced in the above preparation example is first washed with aqueous power wash and air-dried, and then the primer composition produced in the above preparation example is dried to 30 μm and 45 μm. Spray painted and dried at 80 ° C. for 20 minutes. After cooling, the solvent-based two-component urethane silver metallic base paint (Planit # 732: manufactured by Dainippon Paint Co., Ltd.) is further spray-coated on the coating film so as to have a dry film thickness of 15 μm. Clear paint (Planit # 750: manufactured by Dainippon Paint Co., Ltd.) is spray-coated to a dry film thickness of 35 μm, dried at 100 ° C. for 30 minutes, left in a room at 23 ° C. and 50% RH for 24 hours, and then applied. The film appearance, coating film adhesion (initial adhesion), and liquid resistance (warm water immersion) were evaluated in the same manner as the above test method. The results are shown in Table 4.

(Examples 21 to 23)
The plant fiber reinforced polypropylene resin molded plate prepared in the above preparation example is first washed with aqueous power wash and air-dried, and then the primer composition prepared in the above preparation example has a dry film thickness of 15 μm, 30 μm and 45 μm. And then dried at 80 ° C. for 20 minutes. After cooling, the solvent-based two-component urethane topcoat paint (Planit # 800 White: manufactured by Dainippon Paint Co., Ltd.) was spray-coated to a dry film thickness of 35 μm and dried at 100 ° C. for 30 minutes. After being left in a room at 23 ° C. and 50% RH for 24 hours, the appearance of the coating film, coating film adhesion (initial adhesion), and liquid resistance (warm water immersion) were evaluated in the same manner as described above. The results are shown in Table 5.

(Examples 24 to 25)
The plant fiber reinforced polypropylene resin molded plate produced in the above preparation example is first washed with water-based power wash and air-dried, and then the primer composition produced in the above preparation example is spray-coated so as to have a dry film thickness of 10 μm. Subsequently, a solvent-based two-component urethane surfacer paint (Autoplasf Multi HBECO: manufactured by Dainippon Paint Co., Ltd.) was spray-coated to a dry film thickness of 20 μm and 35 μm, and dried at 80 ° C. for 30 minutes. After cooling, the solvent-based two-component urethane silver metallic base paint (Planit # 732: manufactured by Dainippon Paint Co., Ltd.) is further spray-coated on the coating film so as to have a dry film thickness of 15 μm. Clear paint (Planit # 750: manufactured by Dainippon Paint Co., Ltd.) is spray-coated to a dry film thickness of 35 μm, dried at 100 ° C. for 30 minutes, left in a room at 23 ° C. and 50% RH for 24 hours, and then applied. The film appearance, coating film adhesion (initial adhesion), and liquid resistance (warm water immersion) were evaluated in the same manner as described above. The results are shown in Table 6.

Claims (9)

It is a method of forming a multilayer coating film in which a primer coating film and a top coating film are sequentially formed on the surface of the resin molded body,
The resin molding is mainly composed of a polyolefin resin reinforced with natural fibers,
And content of natural fiber is 10-40 mass% with respect to a resin molding,
The primer coating film contains any one of chlorinated polypropylene, (meth) acryl-modified chlorinated polypropylene, or acid anhydride-modified chlorinated polypropylene having a chlorine content of 5 to 40% by mass. Method for forming a coating film.   The natural fibers are flax, hemp, cannabis, manila hemp, burlap, sisal hemp fiber, kenaf hemp fiber, true bamboo and buddha bamboo bamboo fiber, cotton, palm fiber, or pineapple fiber plant fiber alone or in combination. The method for forming a multilayer coating film according to claim 1.   The method for forming a multilayer coating film according to claim 1 or 2, wherein the average fiber length of the plant fibers is 1 to 40 mm, and the average fiber diameter of the plant fibers is 5 to 300 µm.   The method for forming a multilayer coating film according to claim 1, wherein the polyolefin resin is a polypropylene resin.   The method for forming a multilayer coating film according to any one of claims 1 to 4, wherein the primer coating film further contains a fiber-based resin.   The method for forming a multilayer coating film according to claim 5, wherein the fiber-based resin comprises at least one of nitrocellulose, cellulose propionate, ethyl cellulose, acetyl cellulose, or a cellulose derivative of cellulose acetate butyrate.   The method for forming a multilayer coating film according to claim 1, wherein the primer coating film has a thickness of 25 to 45 μm.   The method for forming a multilayer coating film according to any one of claims 1 to 7, wherein the top coating film comprises a metallic base coating film and a clear coating film.   The method for forming a multilayer coating film according to any one of claims 1 to 8, wherein a primer coating film, a surfacer coating film, and a top coating film are sequentially formed on the surface of the resin molded body.