JP2006328420A - Coating composition and coat finishing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating composition capable of forming a coating excellent in a finishing characteristic, a drying characteristic, a hardness and the like; and useful as a base coat. <P>SOLUTION: The coating composition contains a coating forming constituent comprising: (A) a modified vinyl copolymer obtained by copolymerizing (i) a vinyl monomer mixture of 5 to 95 wt.%, and (ii) a cellulose acetate butyrate of 5 to 95 wt.%; (B) a polyester resin having a glass transition temperature of -70 to 0°C; and (C) an acrylic resin having a glass transition temperature of 0 to 80°C. A solid component of the coating composition contains the constituent (A) of 5 to 75 wt.%, the constituent (B) of 5 to 40 wt.%, and the constituent (C) of 5 to 90 wt.%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coating composition that can form a coating film excellent in finish, drying, hardness, etc., and particularly useful as a base coat.

  Conventionally, acrylic lacquers, acrylic urethane paints and aminoacrylic resin paints have been used for repairing automobiles and painting and repairing industrial machines, buildings, structures, furniture (including steel), especially automobile repairs. In the field of paints, acrylic lacquer and acrylic urethane paint are mainly used from the viewpoint of room temperature drying. In this field, in recent years, metallic finishes that include bright pigments and metallic finishes that are repeatedly applied with clear paints have become the mainstream, and when a lacquer type paint is used as the base coat, the dryness of the base coat is important. Paints based on a vehicle based on a blend of polyester resin and cellulose acetate butyrate (CAB) or acrylic resin blended with polyester resin and CAB have been used, but the compatibility of each component is insufficient Therefore, there are problems such as having an adverse effect on the finishing performance, and also causing unevenness in the metallic base, resulting in a reduction in finishing performance due to the occurrence of unevenness and modulation.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have improved the compatibility of each component with a composition comprising a CAB graft copolymer, a polyester resin, and an acrylic resin in a specific ratio. Further, the present inventors have found that a coating film having a good finish can be formed without causing unevenness and unevenness even in a metallic base.

  That is, the present invention provides (A) (i) a modified vinyl copolymer obtained by copolymerizing 5 to 95% by weight of a vinyl monomer mixture and (ii) 5 to 95% by weight of cellulose acetate butyrate, (B) A polyester resin having a glass transition temperature of −80 to 0 ° C., and (C) an acrylic resin having a glass transition temperature of 0 to 80 ° C. as a coating film forming component, the component (A) being 5 to 75% by weight in the total solid content, (B) 5 to 40% by weight of component and (C) component in a proportion of 5 to 90% by weight, and a base coat paint applied to the surface of the substrate, and then top The present invention provides a paint finishing method used as the base coat paint in a paint finish method for painting a clear paint.

  According to the present invention, a composition obtained by blending a CAB graft copolymer, a polyester resin, and an acrylic resin in a specific ratio improves the compatibility of each component, and even in a metallic base, there is no unevenness or unevenness. Without being generated, a coating film having good finish can be formed.

  In the present invention, the modified vinyl copolymer (A) is obtained by copolymerizing a vinyl monomer mixture (i) and cellulose acetate butyrate (ii). The vinyl monomer mixture (i) is one or more selected from conventionally known vinyl monomers. For example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2- Alkyl esters of acrylic acid or methacrylic acid such as ethylhexyl (meth) acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate; hydroxyl group-containing vinyl monomers such as 2-hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; (Meth) acrylic acid, styrene, vinyl toluene, vinyl acetate, (meth) acrylonitrile, (meth) acrylamide, glycidyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, (meth) acryloylio Phenoxyethyl chloride, t- butyl acrylamide sulfonic acid, Na salt of sulfoethyl methacrylate, K salt or ammonium salt, Na salt of styrene sulfonic acid, such as K salts and ammonium salts. Among these, vinyl comprising 50% by weight or more, preferably 60 to 99% by weight of methyl methacrylate and / or ethyl methacrylate, and 50% by weight or less, preferably 1 to 40% by weight of other copolymerizable vinyl monomers. The monomer mixture can be preferably used from the viewpoint of compatibility with cellulose acetate butyrate (ii) and the hardness of the coating film. If the ratio of methyl methacrylate and / or ethyl methacrylate used is less than 50% by weight, the compatibility with the cellulose acetate butyrate (ii) is lowered, and the varnish may become cloudy, which is not desirable.

  Cellulose acetate butyrate (ii) is a cellulose derivative obtained by further butyl esterifying a partially acetylated product of cellulose, preferably having an acetyl group content of generally 1 to 30% by weight and a butyl group content of generally 16 to 60% by weight. Specifically, for example, “EAB-381-0.5”, “EAB-551-0.2”, “EAB-551-0.01” (both manufactured by Eastman Kodak, Inc., trade name), etc. Can be illustrated.

  The copolymerization of the vinyl monomer mixture (i) and cellulose acetate butyrate (ii) can be carried out by a solution polymerization method in the presence of a radical polymerization initiator such as an organic peroxide. The copolymerization ratio of the vinyl monomer mixture (i) and cellulose acetate butyrate (ii) is 5 to 95% by weight, preferably 10 to 90% by weight of the vinyl monomer mixture (i), and cellulose acetate butyrate (ii). ) 5 to 95% by weight, preferably 10 to 90% by weight. When the (i) is less than 5% by weight ((ii) exceeds 95% by weight), the adhesion is lowered, while (i) exceeds 95% by weight ((ii) is less than 5% by weight). In other words, the drying property and hardness are lowered, and further, metal unevenness is caused, which is not preferable.

  The modified vinyl copolymer thus formed is remarkably excellent in solubility in organic solvents and compatibility with other resins. In the present invention, it is desirable that substantially all of the blended cellulose acetate butyrate is copolymerized with the vinyl monomer mixture, but a small amount of cellulose acetate butyrate and vinyl monomer mixture remain unreacted, Even if it remains in the copolymer, there is no problem.

  In the present invention, the polyester resin (B) is a resin having a glass transition temperature of −70 to 0 ° C., preferably −65 to −10 ° C., and a conventionally known polybasic acid and a polyhydric alcohol as main components according to a conventional method. It can be obtained by copolymerization. Examples of the polybasic acid include adipic acid, succinic acid, isophthalic acid, terephthalic acid, phthalic anhydride, maleic anhydride, trimellitic acid, hexahydrophthalic anhydride, sodium 5-sulfoisophthalate, and the like. Examples thereof include ethylene glycol, propylene glycol, glycerin, trimethylolpropane, neopentyl glycol, 1,6-hexanediol, pentaerythritol, and sorbitol. Further, if necessary, fatty acids such as dehydrated castor oil fatty acid, linseed oil fatty acid, soybean oil fatty acid, tall oil fatty acid, monobasic acids such as benzoic acid, and fats and oils can be used as copolymerization components.

  When the polyester resin (B) has a glass transition temperature of less than −70 ° C., the drying property and the hardness are remarkably lowered. Because there is a fear, it is not preferable.

  In the present invention, the acrylic resin (C) is a resin having a glass transition temperature of 0 to 80 ° C., preferably 5 to 75 ° C., and solution polymerization of a conventionally known monomer mixture mainly composed of acrylic acid or methacrylic acid ester is used. Can be obtained by copolymerization according to the conventional method. Examples of the acrylic acid or methacrylic acid ester include alkyl esters of acrylic acid or methacrylic acid listed in the above-mentioned vinyl monomer mixture (i), and one or more of these exemplified vinyl monomers. A copolymerization component can be selected as appropriate.

  When the glass transition temperature of the acrylic resin (C) is less than 0 ° C., the drying property and hardness are lowered. On the other hand, when it exceeds 80 ° C., the drying is too fast and the smoothness of the coating film is impaired. Since it falls, it is not preferable.

  In the present invention, the above components (A) to (C) are used as coating film forming components, and in these total solids, the component (A) is 5 to 75% by weight, preferably 10 to 70% by weight, and the component (B). Is contained in an amount of 5 to 40% by weight, preferably 10 to 35% by weight, and the component (C) is contained in an amount of 5 to 90% by weight, preferably 10 to 80% by weight. When the content of the component (A) is less than 5% by weight, the drying property and hardness are reduced, and metal mottling unevenness is observed. When the content exceeds 75% by weight, the adhesion is decreased, and the component (B) If the content is less than 5% by weight, the adhesion is lowered, and if it exceeds 40% by weight, the drying property and hardness are lowered.

  The composition of the present invention can further contain bright pigments such as aluminum paste, pearl powder, graphite, and MIO, colored pigments such as titanium white, phthalocyanine blue, and carbon black, extender pigments, and the like. Additives for coating materials such as ultraviolet absorbers, light stabilizers, antioxidants, surface conditioners, pigment dispersants, and curing catalysts can be blended.

  The composition of the present invention may be used as a one-pack type or as a two-pack type paint composition using a crosslinking agent such as a polyisocyanate compound.

  The present invention also provides a paint finishing method using the coating composition of the present invention obtained as described above as the base coat paint in a paint finishing method in which a base coat paint is applied to the substrate surface and then a top clear paint is applied. A method is provided.

  Examples of the base material surface include those in which a normal primer coating is mainly applied to a metal or plastic material, for example, an automobile body that has been subjected to electrodeposition coating or intermediate coating, or a repair coating surface of an automobile body. Can be mentioned.

  The coating composition of the present invention is usually applied to the substrate surface so that the dry film thickness is in the range of 10 to 30 μm, and a base coat film is obtained. The base coat coating may be cured before the top clear coating is applied, or the top clear coating may be applied wet-on-wet on the base coat coating.

  As the top clear coating used in the method of the present invention, conventionally known top clear coatings can be used without particular limitation, and mainly include organic solvent type coatings (including non-aqueous dispersion type) and powder coatings. There are curable paints based on acrylic resins and fluororesins with functional groups and cross-linking agents such as (block) polyisocyanates and melamine resins, or lacquer paints based on cellulose acetate butyrate-modified acrylic resins. It can be used suitably. In particular, when a urethane curable coating is used as the top clear coating, the isocyanate component partially penetrates from the top clear coating into the base coat coating, so the modified vinyl copolymer (A) and polyester used in the base coat In the case where the resin (B) and the acrylic resin (C) contain a hydroxyl group, it is preferable because a crosslinking agent component does not have to be used in the base coat paint.

  In addition, the top clear paint may contain paint additives such as polymer fine particles, a curing catalyst, an ultraviolet absorber, an antioxidant, a surface conditioner, and an antifoaming agent, if necessary. The coating film with the top clear coating is suitably in the range of 20 to 100 μm in terms of dry film thickness.

  As the coating method, normal spray coating, electrostatic coating, etc. are adopted for the base coat paint and the top clear paint, but there are no particular restrictions on other coating methods.

  Hereinafter, the present invention will be described in more detail with reference to examples. Here, “parts” and “%” mean “parts by weight” and “% by weight”, respectively.

Production of modified vinyl copolymer (A) A reactor equipped with a thermometer, a stirrer, a reflux condenser and a dropping funnel was charged with the following components, heated in a nitrogen gas atmosphere, and raised to 100 ° C. over about 1 hour. Warm up.

Toluene 120 parts Butyl cellosolve acetate 80 parts “EAB-381-0.5” 200 parts (manufactured by Eastman Kodak Company, cellulose acetate butyrate)
After confirming that the cellulose acetate butyrate was completely dissolved at 100 ° C., the following mixture of vinyl monomer mixture and polymerization initiator was dropped into the cellulose acetate butyrate solution over 3 hours.

2-hydroxyethyl methacrylate 3 parts methyl methacrylate 97 parts benzoyl peroxide 2 parts 30 minutes after completion of dropping, 0.5 part of azobisisobutyronitrile is added, and further maintained at 100 ° C. for 2 hours under a nitrogen atmosphere, and then xylene Was added to obtain a colorless and transparent modified vinyl copolymer solution having a nonvolatile content of 50%.

Production of polyester resin (B) A reactor equipped with a reflux condenser with a heating device, thermometer, stirrer, rectifying tower and water separator was charged with the following components and heated, and 160 ° C to 230 ° C over 3 hours. The temperature was raised to.

Hexahydrophthalic anhydride 26.7 parts Adipic acid 28 parts Neopentyl glycol 5.3 parts 1,6-hexanediol 40 parts This is maintained at 230 ° C. for 1 hour, and the produced condensed water (7.4 parts) is rectified. Was distilled off. Subsequently, 5 parts of xylene was added, xylene and condensed water were refluxed, and water was removed using a water separator. Two hours after the addition of xylene, the acid value starts to be measured. When the acid value becomes 2 or less, the mixture is cooled to 120 ° C., and then the mixed solvent of xylene / butyl acetate = 1/1 has a nonvolatile content of 70%. Dilution was performed to obtain a polyester resin solution. The resin solution had a Gardner viscosity of T, a resin weight average molecular weight of 20,000, a hydroxyl value of 55, a glass transition temperature of −60 ° C., and a DBR (dibasic acid ratio) of 0.95.

Preparation of acrylic resin (C) Thermometer, stirrer, reflux condenser and reactor equipped with a dropping pump were charged with 25 parts of toluene and 43 parts of xylene, heated to 110 ° C. while stirring, and the following monomer mixture: A mixture of polymerization initiators was added dropwise at a constant rate at 110 ° C. over about 3 hours.

Styrene 10 parts Methyl methacrylate 20 parts N-butyl acrylate 50 parts 2-Hydroxyethyl methacrylate 19 parts Acrylic acid 1 part t-Butyl peroxyethyl hexanate 1.2 parts After completion of dropping, keep at 110 ° C. for 1 hour and stir Continued. Thereafter, a solution prepared by dissolving 0.5 part of azobisdimethylvaleronitrile in 10 parts of xylene as an additional catalyst was added dropwise at a constant rate over 1 hour. And after completion | finish of dripping, it maintained at 110 degreeC for 1 hour, and complete | finished reaction. The resulting acrylic copolymer solution, a non-volatile content 50.2%, a clear solution with a uniform Gardener viscosity Z _2, the copolymer weight average molecular weight 50,000, hydroxyl number is 82, the glass The transition temperature was 60 ° C.

Example 1 of making metallic base paint
The modified vinyl copolymer solution, the polyester resin solution, and the acrylic resin solution obtained in the above production examples were blended in the blending amounts shown in Table 1, respectively, and “Aluminum paste K-9800” (Asahi Kasei Metals, aluminum paste). Then, xylene and butyl acetate were added in the formulation shown in the same table, and the mixture was stirred with a disper for about 20 minutes to prepare a metallic base paint. Note that (Note) in the table is prepared by adjusting “EAB-381-0.5” to a 30% solid content solution with a mixed solvent of xylene / butyl acetate = 50/50.

  About the said coating material, the resin mixed solution before adding an aluminum paste was apply | coated to the glass plate with the doctor blade so that the coating film thickness might be set to 100 micrometers, and the compatibility of the resin mixed solution was visually evaluated from the transparency ((circle): Good) , Δ: Somewhat bad, ×: Bad). In addition, each paint is applied to a glass plate with a doctor blade in a constant temperature and humidity chamber at a temperature of 20 ° C. and a humidity of 75% so that the coating film thickness is 100 μm. The time until (touch drying time) was measured.

Painting example 2
11 to 12 seconds (Ford Cup # 4/25 ° C.) with a thinner composition of toluene / xylene / ethyl acetate / butyl acetate = 50/20/10/20 with respect to 100 parts by weight of the metallic base paint obtained in Example 1 above. ) And diluted with 50 parts by weight of “Letane PG2K curing agent” (Kansai Paint Co., Ltd.) to 100 parts by weight of “Letane PG2K Clear” (Kansai Paint Co., Ltd.). Was diluted with a thinner of the above composition for 13 to 14 seconds (Ford Cup # 4/25 ° C.), adjusted to viscosity and used for coating.

  A commercial lacquer primer surfacer was coated on a tin plate with a thickness of 40 μm, dried at room temperature for 30 minutes, and then polished with # 400 water-resistant abrasive paper. On top of this, the metallic base paint having the above-mentioned viscosity was spray-coated so as to have a dry film thickness of 30 μm, and the unevenness was investigated. Furthermore, after the metallic base was dry to the touch, the clear coating having the above viscosity was spray-coated so that the dry film thickness was 40 μm and 80 μm, and both coatings were compared to evaluate the modulation unevenness (O: no unevenness, (Triangle | delta): There exists slight unevenness and x: Unevenness is remarkable). The results were Fukimura: ○, Modimura: ○.

  Further, the following performance test was performed on the coated plate obtained by coating the clear paint with a dry film thickness of 40 μm. The results were pencil hardness: B and water resistance: Δ.

  (* 1) Pencil hardness: After the coated plate was left at a temperature of 20 ° C. for 24 hours, a pencil scratch test was conducted at the same temperature to examine the hardness of the pencil at which the coating film was torn.

(* 2) Water resistance: The above-mentioned coated plate was left in a constant temperature and humidity room at a temperature of 20 ° C. and a humidity of 75% for 7 days, and then the coated surface state after being immersed in tap water at 20 ° C. for 7 days was examined : No abnormality, Δ: glossy, ×: blistering).

Claims (4)

(A) (i) a modified vinyl copolymer obtained by copolymerizing 5 to 95% by weight of a vinyl monomer mixture and (ii) 5 to 95% by weight of cellulose acetate butyrate, and (B) a glass transition temperature of -70. A polyester resin at ˜0 ° C. and (C) an acrylic resin having a glass transition temperature of 0 to 80 ° C. as a film-forming component, the component (A) in the total solid content of 5 to 75% by weight, and the component (B) A coating composition comprising 5 to 40% by weight and component (C) in a proportion of 5 to 90% by weight. The coating composition according to claim 1, wherein the vinyl monomer mixture (i) comprises 60 to 99% by weight of methyl methacrylate and / or ethyl methacrylate and 1 to 40% by weight of other copolymerizable vinyl monomers. In a paint finishing method in which a base coat paint is applied to a substrate surface and then a top clear paint is applied, (A) (i) 5 to 95% by weight of a vinyl monomer mixture and (ii) cellulose acetate butyrate A modified vinyl copolymer obtained by copolymerizing 5 to 95% by weight, (B) a polyester resin having a glass transition temperature of −70 to 0 ° C., and (C) an acrylic resin having a glass transition temperature of 0 to 80 ° C. As a film-forming component, the total solid content of the component (A) is 5 to 75% by weight, the component (B) is 5 to 40% by weight, and the component (C) is 5 to 90% by weight. A paint finishing method characterized by painting a paint composition. 4. The paint finishing method according to claim 3, wherein the top clear paint is a urethane curable paint.