CN114789128B - Coating method for forming special pattern coating film - Google Patents

Coating method for forming special pattern coating film Download PDF

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Publication number
CN114789128B
CN114789128B CN202210026477.1A CN202210026477A CN114789128B CN 114789128 B CN114789128 B CN 114789128B CN 202210026477 A CN202210026477 A CN 202210026477A CN 114789128 B CN114789128 B CN 114789128B
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China
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acrylic resin
weight
coating
average molecular
molecular weight
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CN114789128A (en
Inventor
金哲圭
安真佑
孙畅庸
朱庸畯
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KCC Corp
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KCC Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/24—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials for applying particular liquids or other fluent materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/24—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas with means, e.g. a container, for supplying liquid or other fluent material to a discharge device
    • B05B7/2402—Apparatus to be carried on or by a person, e.g. by hand; Apparatus comprising containers fixed to the discharge device
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B9/00—Spraying apparatus for discharge of liquids or other fluent material, without essentially mixing with gas or vapour
    • B05B9/03—Spraying apparatus for discharge of liquids or other fluent material, without essentially mixing with gas or vapour characterised by means for supplying liquid or other fluent material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/50—Multilayers
    • B05D7/56—Three layers or more
    • B05D7/58—No clear coat specified
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/62—Polymers of compounds having carbon-to-carbon double bonds
    • C08G18/6216—Polymers of alpha-beta ethylenically unsaturated carboxylic acids or of derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
    • C09D175/04—Polyurethanes
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
    • C09D175/04—Polyurethanes
    • C09D175/06—Polyurethanes from polyesters
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/60—Additives non-macromolecular
    • C09D7/61—Additives non-macromolecular inorganic

Abstract

The present invention relates to a coating method which is excellent in workability and productivity and which can form a special pattern with a degree of inertia.

Description

Coating method for forming special pattern coating film
Technical Field
The present invention relates to a coating method for forming a special pattern coating film, and more particularly, to a coating method which is excellent in workability and productivity and consistently forms a special pattern.
Background
In the case of coating a surface of an object to be coated, such as a crack or a groove, a method of performing putty work before coating to compensate for an appearance defect has been performed. As an example, korean patent No. 2124756 discloses a recoating method of a sheet metal part of a vehicle part, which includes a polishing process of finishing a surface by polishing a heated construction site after applying putty to the construction site and heating. However, in the case of performing the putty work as described above, the polishing work is performed manually after the putty work, and the above-described process is often repeated many times depending on the degree of the appearance defect, and thus there is a problem in that the work time and the labor cost are increased.
In particular, there are many cases where defects are generated in the appearance of the raw material such as castings due to its characteristics, and there is a problem that workability and productivity are lowered when the conventional method is adopted. Therefore, as a coating method capable of compensating for the appearance defect of the object to be coated, a coating method excellent in workability and productivity, which can replace the conventional putty work, is demanded.
Disclosure of Invention
(problem to be solved by the invention)
The present invention provides a coating method, which forms a special pattern coating film to give a three-dimensional effect to the surface of the coating film, thereby compensating the appearance defect of a coated object.
(measures taken to solve the problems)
The present invention provides a coating method comprising a step of coating a polyurethane coating composition using an Airless Gun (Airless Gun) or a top-coat Gun (Bon Tile Gun), wherein the polyurethane coating composition comprises: a main agent comprising a thermosetting acrylic resin, a thermoplastic acrylic resin, and an extender pigment; and a curing agent comprising an isocyanate resin.
(effects of the invention)
According to the coating method of the present invention, a special pattern coating film is formed to give a three-dimensional effect to the surface of the coating film, whereby the appearance defect of the coated object can be compensated. The coating method of the present invention can replace the existing putty operation, and can provide a coating method with excellent operability and productivity.
Drawings
FIG. 1 is a schematic illustration of an airless gun.
Fig. 2 is a photograph showing the surface of the coating film according to example 1.
Fig. 3 is a photograph showing the surface of the coating film according to example 2.
Fig. 4 is a photograph showing the surface of the coating film according to comparative example 4.
Fig. 5 is a photograph showing the surface of the coating film according to comparative example 5.
Fig. 6 is a photograph showing the surface of the coating film according to comparative example 6.
(description of the reference numerals)
100: an airless spray gun; 101: an air cap; 102: an air delivery nozzle;
103: a paint delivery nozzle; 104: an air supply hose; 105: and a paint supply hose.
Detailed Description
The present invention will be described in detail below. However, the present invention is not limited to the following, and each component may be variously modified or selectively mixed and used as necessary. Thus, it should be understood to cover all modifications, equivalents, or alternatives falling within the spirit and technical scope of the present invention.
The functional group values such as "acid value", "hydroxyl value (hydroxyl value)" used in the present specification are measured by a usual method known in the art, and for example, may represent values measured by a titration method. The "glass transition temperature" is determined by usual methods known in the art, for example, it can be determined by differential scanning calorimetry (differential scanning calorimetry, DSC). The "number average molecular weight" and "weight average molecular weight" are determined by usual methods known in the art, and may be determined, for example, by GPC (gel permeation chromatograph, gel permeation chromatography). In addition, "viscosity" is determined by a usual method known in the art, and may be determined using, for example, a brookfield viscometer (brookfield viscometer).
The coating method according to the present invention includes a step of coating a polyurethane coating composition using an Airless gun (Airless gun), the polyurethane coating composition including: a main agent comprising a thermosetting acrylic resin (acrylic resin), a thermoplastic acrylic resin, and an extender pigment; and a curing agent comprising an isocyanate resin.
< polyurethane coating composition >
The coating method according to the present invention includes a step of coating the polyurethane coating composition using an Airless Gun (Airless Gun) or a top-coat Gun (Bon Tile Gun). In the present invention, the above polyurethane coating composition includes: a main agent comprising a thermosetting acrylic resin, a thermoplastic acrylic resin, and an extender pigment; and a curing agent comprising an isocyanate resin.
The viscosity of the above polyurethane coating composition may be 50 to 150KU (25 ℃ C.), for example, 100 to 120KU (25 ℃ C.). In the case where the polyurethane coating composition has a viscosity in the aforementioned range, a special pattern (relief pattern) can be imparted to the coating film with a maintained inertia. Specifically, in the case where the viscosity of the polyurethane coating composition is less than the above-described range, in the case where the surface of the object to be coated is a vertical surface perpendicular to the floor, the viscosity and thixotropic properties (shape-retaining properties) are poor, and therefore the coating material flows down before the pattern formation, and there is a possibility that a sufficient relief (emboss) effect is not imparted. In addition, when the thickness of the coating film becomes thick, the overlapped coating material may flow downward. On the other hand, when the viscosity of the polyurethane coating composition exceeds the above-mentioned range, the thixotropic property and viscosity excessively increase to possibly cause erroneous operation of the coating gun, and thus workability may be lowered.
The thixotropic value (thixotropic index) (ASTM D2196) of the above polyurethane coating composition may be 5,000 to 10,000, for example, may be 7,000 to 9,000, and as another example, may be 7,000 to 8,000. In the case where the polyurethane coating composition has thixotropic properties in the aforementioned range, a special pattern (relief pattern) can be imparted to the coating film with inertia. Specifically, in the case where the thixotropy of the polyurethane coating material is smaller than the above-described range, the coating material may flow downward before patterning, and in the case where it exceeds the above-described range, the thixotropy and viscosity excessively increase to possibly cause the failure of the coating gun, and thus, workability may be lowered.
Main agent
The polyurethane coating composition includes a thermosetting acrylic resin, a thermoplastic acrylic resin, and an extender pigment as a main agent. The above-mentioned main agent can further include a solvent and additives commonly used in the art.
Acrylic resin
The main agent of the coating composition contains a thermosetting acrylic resin and a thermoplastic acrylic resin. The thermosetting acrylic resin and the thermoplastic acrylic resin may be prepared by polymerizing a (meth) acrylate monomer and a vinyl monomer.
The type of the (meth) acrylic acid ester monomer is not particularly limited, but for example, one or more selected from N-methylolacrylamide, 2-hydroxypropyl methacrylate, propyl methacrylate, t-butylaminoethyl methacrylate, dicyclopentenyloxyethyl methacrylate, acrylic acid dimer, hexanediol diacrylate, t-butyl acrylate, triisopropylsilyl acrylate, benzyl methacrylate, hydroxyethyl methacrylate phthalate, 2-hydroxyethyl methacrylate, trimethylolpropane triacrylate, tripropylene glycol diacrylate, ethyl methacrylate, diacetone acrylamide, isobutyl methacrylate, hydroxyisopropyl methacrylate, isopropyl methacrylate, cyclohexyl methacrylate, triisopropylsilyl methacrylate, isobornyl acrylate, t-butylcyclohexyl methacrylate, trimethylcyclohexyl methacrylate, acrylonitrile, methyl methacrylate, acrylic acid, t-butyl methacrylate, isobornyl methacrylate, methacrylonitrile, methacrylic acid, acrylamide, methacrylamide, vinyl chloride, and cyclohexyl vinyl ether can be used.
The kind of the vinyl monomer is not particularly limited, but for example, one or more selected from styrene, methyl styrene, dimethyl styrene, fluoro styrene, ethoxy styrene, methoxy styrene, phenylene vinyl ketone, tert-butyl vinyl benzoate, vinyl cyclohexanoate, vinyl acetate, vinyl pyrrolidone, vinyl chloride, vinyl alcohol, acetoxystyrene, tert-butyl styrene and vinyl toluene can be used.
The solid content of the above thermosetting acrylic resin may be 45 to 65%, for example, 49 to 55%. When the solid content of the thermosetting acrylic resin is less than the above-mentioned range, the OH group bonded to isocyanate is insufficient, and the physical properties of the whole coating film are lowered. In contrast, when the solid content of the thermosetting acrylic resin exceeds the above-mentioned range, OH groups remain in the coating material after bonding with isocyanate, and other bonds are formed in addition to the urethane bonds, as a result of which the chemical and mechanical properties of the coating film are lowered.
The acid value of the above thermosetting acrylic resin may be 1 to 15mgKOH/g, for example, 3 to 9mgKOH/g. When the acid value of the thermosetting acrylic resin is smaller than the above-described range, the chemical resistance and weather resistance are lowered, and when the acid value exceeds the above-described range, the chemical resistance and corrosion resistance are lowered.
The glass transition temperature of the above thermosetting acrylic resin may be 50 to 100 ℃, for example, 60 to 90 ℃. When the glass transition temperature of the thermosetting acrylic resin is less than the above-described range, hot water resistance and hardness are lowered, and when the glass transition temperature exceeds the above-described range, chemical resistance and corrosion resistance are lowered.
The hydroxyl value of the above thermosetting acrylic resin may be 60 to 90mgKOH/g, for example, 80 to 89mgKOH/g. When the hydroxyl value of the thermosetting acrylic resin is smaller than the above-mentioned range, the OH group bonded to isocyanate is insufficient, and the viscosity of the paint is lowered, whereby there is a possibility that the paint may flow down from the paint surface or the stereoscopic effect may not be sufficiently achieved during the painting, and the physical properties of the whole coating film may be lowered. In contrast, when the hydroxyl value of the thermosetting acrylic resin exceeds the above-mentioned range, OH groups remain in the coating material after bonding with isocyanate, and other bonds are formed in addition to the urethane bonds, as a result, the viscosity and thixotropic properties of the coating material become high, leading to a decrease in appearance, and workability at the time of coating is lowered, and the chemical and mechanical properties of the coating film are lowered.
The number average molecular weight of the thermosetting acrylic resin may be 8,000 to 14,000 g/mol, for example, 10,000 to 13,000 g/mol, and the weight average molecular weight may be 12,000 to 30,000 g/mol, for example, 18,000 to 29,000 g/mol. When the number average molecular weight and the weight average molecular weight of the thermosetting acrylic resin are smaller than the above-mentioned ranges, the appearance effect and the hardness are reduced, and when the number average molecular weight and the weight average molecular weight are larger than the above-mentioned ranges, the chemical resistance and the corrosion resistance are reduced.
The content of the above thermosetting acrylic resin may be 5 to 35% by weight, for example, 10 to 30% by weight, based on the total weight of the main agent. When the content of the thermosetting acrylic resin is less than the above-described range, the processability and chemical resistance of the coating film are lowered, and when the content exceeds the above-described range, the brightness value is lowered.
The solid content of the above thermoplastic acrylic resin may be 40 to 65%, for example, 45 to 60%. When the solid content of the thermoplastic acrylic resin is less than the above-mentioned range, the OH group bonded to isocyanate is insufficient, and the physical properties of the whole coating film are lowered. In contrast, when the solid content of the thermoplastic acrylic resin exceeds the above-mentioned range, OH groups remain in the coating material after bonding with isocyanate, and other bonds are formed in addition to the urethane bonds, as a result of which the chemical and mechanical properties of the coating film are lowered.
The acid value of the above thermoplastic acrylic resin may be 1 to 20, for example, 4 to 10mgKOH/g. When the acid value of the thermoplastic acrylic resin is smaller than the above-described range, the chemical resistance and weather resistance are lowered, and when the acid value exceeds the above-described range, the chemical resistance and corrosion resistance are lowered.
The glass transition temperature of the above thermoplastic acrylic resin may be 0 to 40 ℃, for example, may be 10 to 30 ℃. When the glass transition temperature of the thermoplastic acrylic resin is less than the above-mentioned range, hot water resistance and hardness are lowered, and when the glass transition temperature exceeds the above-mentioned range, chemical resistance and corrosion resistance are lowered.
The hydroxyl value of the above thermoplastic acrylic resin may be 50 to 100mgKOH/g, for example, 60 to 90mgKOH/g. When the hydroxyl value of the thermoplastic acrylic resin is smaller than the above-mentioned range, the OH group bonded to isocyanate is insufficient, and the physical properties of the whole coating film are lowered. In contrast, when the hydroxyl value of the thermoplastic acrylic resin exceeds the above-mentioned range, OH groups remain in the coating material after bonding with isocyanate, and other bonds are formed in addition to the urethane bonds, as a result of which the chemical and mechanical properties of the coating film are lowered.
The number average molecular weight of the thermoplastic acrylic resin may be 3,000 to 9,000 g/mol, for example, 5,000 to 8,000 g/mol, and the weight average molecular weight may be 15,000 to 30,000 g/mol, for example, 17,000 to 25,000 g/mol. When the number average molecular weight and the weight average molecular weight of the thermoplastic acrylic resin are smaller than the above-mentioned ranges, the appearance effect and the hardness are reduced, and when the number average molecular weight and the weight average molecular weight are larger than the above-mentioned ranges, the chemical resistance and the corrosion resistance are reduced.
The content of the above thermoplastic acrylic resin may be 1 to 30% by weight, for example, 5 to 20% by weight, based on the total weight of the main agent. When the content of the thermoplastic acrylic resin is less than the above-described range, the processability and chemical resistance of the coating film are lowered, and when the content exceeds the above-described range, the brightness value is lowered.
Pigment
The main agent of the coating composition contains extender pigment. The extender pigment plays a role of filling the pores in the coating film and compensating for the formation of the coating film and imparting thickening property or mechanical property to the coating film. Therefore, when the extender pigment is contained, a good appearance of the coating film can be obtained, and hardness, impact resistance, rust resistance, and the like can be improved. In particular, extender pigments improve the thixotropic properties of the paint, and thus, exert a stereoscopic effect imparting a special pattern and also maintain the relief pattern after drying.
As the extender pigment, extender pigments commonly used in coating compositions can be used without limitation, and as non-limiting examples, there are calcium carbonate, clay, talc, magnesium silicate, kaolin, mica, silica, aluminum silicate, aluminum hydroxide, barium sulfate, and the like. The aforementioned components may be used singly or in combination of two or more.
The above extender pigment may be contained in an amount of 20 to 40% by weight, for example, 25 to 35% by weight, based on the total weight of the main agent. When the content of the extender pigment is less than the above-described range, it is difficult to form a special pattern due to low viscosity and thixotropic properties, and when it exceeds the above-described range, dispersibility is deteriorated, so that not only mechanical properties are lowered, but also equipment is erroneously operated due to high viscosity, thereby lowering coating workability.
In the coating composition of the present invention, the compounding ratio (weight ratio) of the above extender pigment to the above acrylic resin (thermosetting acrylic resin and thermoplastic acrylic resin) may be 0.5 to 0.9:1, for example, may be 0.7 to 0.9:1. when the blending ratio of the extender pigment to the acrylic resin is smaller than the above-described range, it is difficult to form a pattern due to a decrease in viscosity and thixotropic properties, and when it exceeds the above-described range, the coating gun is clogged due to a high viscosity and thixotropic properties, and flexibility (flexibility) in the coating material is insufficient, thereby lowering the mechanical properties of the coating film.
The main agent of the above coating composition can further contain a color pigment in addition to the extender pigment. Colored pigments can be used in order to make the paint appear a desired color (color) or to increase the strength or gloss of the coating film. As such a pigment, an organic pigment, an inorganic pigment, a metallic pigment, an aluminum paste (Al-paste), a pearl (pearl) or the like which is generally used in a paint can be used without limitation, and they can be used singly or in combination of two or more. Examples of the color pigments that can be used include azo-based, phthalocyanine-based, iron oxide-based, cobalt-based, carbonate-based, sulfate-based, silicate-based, chromate-based pigments, and the like, and examples thereof include titanium dioxide, zinc oxide, bismuth vanadate, azure green, carbon black, iron oxide red, iron oxide yellow, navy blue, cyanine blue, and mixtures of two or more thereof.
The content of the above pigment may be 30 to 50% by weight based on the total weight of the main agent. When the content of the pigment satisfies the above-described range, the degree of curing of the coating film becomes high, and the physical properties of the coating film can be improved.
Solvent(s)
The main agent of the above coating composition can contain a solvent. The solvent adjusts the viscosity of the paint to improve workability and also plays a role in improving the appearance brightness of the coating film.
As the above-mentioned solvent, a usual organic solvent known in the art can be used without limitation. As the organic solvent, aromatic hydrocarbons, ester solvents, ether solvents, alcohol solvents, or a mixture thereof can be used. As non-limiting examples of the organic solvent which can be used, there are cyclohexanone, xylene, toluene, cellosolve acetate, methyl ethyl ketone, dibasic ester, propylene glycol methyl ether acetate, butyl acetate, ethyl acetate, propylene glycol monomethyl ether acetate, 3-methoxybutyl acetate, ethylene glycol butyl ether, diglyme, diethylene glycol diethyl ether, diethylene glycol butyl ether, methanol, ethanol, isopropanol, n-butanol, amyl alcohol, butyl carbitol, isophorone or a mixed solvent thereof, and the like.
In the present invention, the content of the above-mentioned solvent may be a residual amount satisfying the total weight (100 wt%) of the main agent, for example, may be 5 to 15 wt% based on the total weight of the main agent. When the content of the solvent is within the above-described range, workability can be improved and excellent physical properties of the coating film can be exhibited.
Additive agent
The main agent of the above-mentioned coating composition may optionally further contain additives commonly used in the coating field within a range not impairing the inherent properties of the above-mentioned composition. As non-limiting examples of the additive that can be used in the present invention, there are dispersants, defoamers, leveling agents, plasticizers, toners, ultraviolet absorbers, surface regulators, softeners, adhesion enhancers, wetting agents, or mixtures thereof, and the like.
The above additives may be appropriately added in a content range well known in the art, and for example, the above additives can be contained in an amount of 0.01 to 15% by weight, respectively, with respect to the total weight of the main agent. In the case where the content of the above-mentioned additives is within the aforementioned range, the appearance effect and hardness of the coating film can be improved.
Curing agent
The polyurethane coating composition contains an isocyanate resin as a curing agent. The isocyanate resin is capable of reacting an isocyanate group (-NCO) contained in a molecule with the acrylic resin described above to form a polyurethane resin.
As the isocyanate resin, a usual isocyanate compound used in polyurethane synthesis in the art can be used without limitation. Examples of the diisocyanate include diphenylmethylene diisocyanate (Methylene Diphenyl Diisocyanate, MDI), toluene diisocyanate (Toluene diisocyanate, TDI), hexamethylene diisocyanate (Hexa Methylene Diisocyanate, HMDI), isophorone diisocyanate (Isophorone Diisocyanate, IPDI), metaxylene diisocyanate (MXDI), tetramethylxylene diisocyanate (TMXDI), an alicyclic diisocyanate (H12 MDI) obtained by hydrogenation on the benzene ring of MDI, and an alicyclic diisocyanate (hydrogenated XDI) obtained by hydrogenation on the benzene ring of Xylene Diisocyanate (XDI). The aforementioned components can be used singly or in combination of two or more.
The solid content of the above isocyanate resin may be 50 to 70%, for example, 55 to 65%. When the solid content of the isocyanate resin is less than the above-described range, the polyurethane bond is less formed, resulting in a decrease in the physical properties of the whole coating film. In contrast, when the solid content of the isocyanate resin exceeds the above-mentioned range, NCO groups remain in the coating material after bonding with the acrylic resin, and other bonds are formed in addition to the urethane bonds, as a result of which the chemical and mechanical properties of the coating film are lowered.
The isocyanate group content (NCO%) of the above isocyanate resin may be 5 to 20%, for example, 7 to 15%. When the isocyanate group content of the isocyanate resin is less than the above-described range, the polyurethane bond formation is small, and the physical properties of the entire coating film are lowered. In contrast, when the isocyanate group content of the isocyanate resin exceeds the above-described range, NCO groups remain in the coating material after bonding with the acrylic resin, and other bonds are formed in addition to the urethane bonds, as a result of which the chemical and mechanical properties of the coating film are reduced.
The number average molecular weight of the above isocyanate resin may be 1,500 to 3,500 g/mol, for example, 1,800 to 2,500 g/mol. When the number average molecular weight of the isocyanate resin is less than the above-mentioned range, the polyurethane bond is less formed, and the physical properties of the whole coating film are lowered. In contrast, when the number average molecular weight of the isocyanate resin exceeds the above-mentioned range, NCO groups remain in the coating material after bonding with the acrylic resin, and other bonds are formed in addition to the urethane bonds, as a result, the chemical and mechanical properties of the coating film are lowered.
The above isocyanate resin may be contained in an amount of 90% or more, for example, 95 to 100% by weight, with respect to the total weight of the curing agent portion. When the content of the isocyanate resin is less than the above-described range, the polyurethane bond is less formed, resulting in a decrease in the physical properties of the whole coating film.
As an example, the above main agent and the above curing agent may be mixed in an amount of 7 to 10: a mixing ratio (volume ratio) of 1 can be used, for example, as 9:1 (volume ratio).
< coating method >
The coating method of the structure according to the present invention includes a step of coating the polyurethane coating composition using an Airless Gun (Airless Gun) or a top-coat Gun (Bon Tile Gun). As the above polyurethane coating composition, the above polyurethane coating composition can be used.
The coated article may include surfaces of metal raw materials such as concrete, plywood, solid wood, particle board, fiberboard, gypsum board, acrylic (acrylic) board, glass, steel pipe, steel plate, and the like.
The polyurethane coating composition of the present invention can be applied using an airless gun or a top-coat gun, whereby a concave-convex structure can be formed on the surface of the coating film with one inertia. As an example, in the present invention, the spraying can be performed in a manner similar to the air-assisted airless spraying (Air Assisted Airless Spray) using an airless gun. In this case, a paint having high viscosity and thixotropic properties can be sprayed, and an excellent uneven structure can be obtained, and also excellent workability can be ensured.
Fig. 1 illustrates an example of an airless gun that can be used in the present invention. Airless gun 100 includes an air cap 101, an air delivery nozzle 102, a paint delivery nozzle 103, an air supply hose 104, and a paint supply hose 105. Paint is transferred to the air cap 101 through the paint delivery nozzle 103 and the paint supply hose 105, air is transferred to the air cap 101 through the air delivery nozzle 102 and the air supply hose 104, and then paint is sprayed together with air. The air cap 101 and the injection pressure of the airless gun 100 can be selected according to the size and the degree of concavity and convexity of the pattern to be embodied. For example, as the air cap, an internal mix (internal mix), an external mix 8-hole (external mix-8 hole), an external mix 4-hole (external mix-4 hole), or the like can be used.
The paint spray pressure and the air spray pressure can be adjusted in situ according to the size of the desired special pattern (relief), for example in the range of 2 to 5 bar (bar).
As an example, the airless gun 100 having an external mix 8-hole (external mix-8 hole) air cap 101 can be used, and the coating material spray pressure is adjusted to 2 to 4 bar, and the air spray pressure is adjusted to 3 to 5 bar for coating. When the coating is performed under the above conditions, a circular pattern having a constant size is easily formed. Specifically, when the paint spraying pressure is less than the above-described range, the amount of paint supplied is small, and thus the size of the formed pattern becomes small, and when it exceeds the above-described range, the amount of paint supplied is large, and thus the pattern is formed too much or the paint flows down, and thus it becomes difficult to form the pattern. In the case where the air ejection pressure is smaller than the above-described range, the pattern is formed large so as to flow downward, and in the case where the air ejection pressure exceeds the above-described range, the size of the formed pattern is too small.
As the above polyurethane coating composition, it can be coated 1 to 5 times by the method described previously, and the dry coating film thickness can be formed to 150 to 700 μm, for example, can be formed to 200 to 600 μm. In the case where the thickness of the dried coating film of the above polyurethane coating composition is less than the above-mentioned range, the hiding property of the coating film may be lowered or the stereoscopic effect may not be sufficiently embodied, and in the case where it exceeds the above-mentioned range, it may be difficult to form a pattern due to the coating film flowing down.
The polyurethane coating composition can be used as a mid-coat, and as an example, can be applied intermediate a polyurethane primer and a polyurethane topcoat.
The present invention will be described in more detail with reference to examples. However, the following examples are merely for aiding in understanding the present invention, and the scope of the present invention is not limited in any way to the examples.
Examples 1 to 12
The coatings of examples 1-12 were carried out according to the polyurethane coating compositions (main agent: curing agent=9:1 volume ratio) and coating methods of tables 1-2 below.
Comparative examples 1 to 6
The coatings of comparative examples 1 to 6 were carried out according to the polyurethane coating compositions (main agent: curing agent=9:1 volume ratio) and coating methods of table 3 below.
TABLE 1
TABLE 2
TABLE 3
Thermosetting acrylic resin 1: the solid content was 50%, the acid value was 3mgKOH/g, the glass transition temperature was 89 ℃, the hydroxyl value was 88mgKOH/g, the number-average molecular weight (Mn) was 11,000, and the weight-average molecular weight (Mw) was 20,000.
Thermosetting acrylic resin 2: the solid content was 54%, the acid value was 8mgKOH/g, the glass transition temperature (Tg) was 82 ℃, the hydroxyl value was 83mgKOH/g, the number-average molecular weight was 12,500, and the weight-average molecular weight was 28,000.
Thermosetting acrylic resin 3: the solid content was 55%, the acid value was 20mgKOH/g, the glass transition temperature was 110 ℃, the hydroxyl value was 85mgKOH/g, the number-average molecular weight was 12,000, and the weight-average molecular weight was 25,000.
Thermoplastic acrylic resin 1: the solid content was 53%, the acid value was 10mgKOH/g, the glass transition temperature was 20 ℃, the hydroxyl value was 84mgKOH/g, the number-average molecular weight was 7,500, and the weight-average molecular weight was 22,000.
Thermoplastic acrylic resin 2: the solid content was 50%, the acid value was 4mgKOH/g, the glass transition temperature was 26 ℃, the hydroxyl value was 68mgKOH/g, the number-average molecular weight was 6,000, and the weight-average molecular weight was 17,500.
Thermoplastic acrylic resin 3: the solid content was 55%, the acid value was 22mgKOH/g, the glass transition temperature was 0 ℃, the hydroxyl value was 110mgKOH/g, the number-average molecular weight was 8,000, and the weight-average molecular weight was 15,000.
Colored pigments: is a mixture, wherein TiO 2 (CR 826) 25%, iron oxide Yellow (iron oxide Yellow) 52 19%, geolor Yellow 958F 28%, geolor Yellow 954F 28%.
Extender pigment: is a mixture, wherein NA-400 is 61%, china Clay (China Clay) is 26%, and super mica is 13%.
Anti-settling agent 1: silica-based additives (AEROSIL R-972, winning Industrial group (ENOVIK INDUSTRIES)).
Anti-settling agent 2: wax additives (Monora 3300M, HS CHEM Co.).
Thixotropic improver: bentonite-based additives (viscidel B8, LAVIOSA CHEMICAMINERARIA SPA).
Adhesion enhancing agent: silane-based additives (CG-O187, mong photochemical Co., ltd.).
Flow inhibitor: garamite 1958 (BYK).
Dispersing agent: disper BYK104 (BYK).
And (3) a thickening agent: RHEYBYK-7410 ET (BYK).
Defoaming agent: RHEFLOW AF-770 (KS chemical Co.).
Isocyanate resin: the solids content was 60%, the isocyanate group content was 12%, and the number average molecular weight was 2,000.
Experimental example-evaluation of physical Properties
For the polyurethane coating compositions prepared according to the respective examples and comparative examples, physical properties were evaluated in the following manner. In addition, patterns of the coating film surfaces were observed after forming the coating films according to the respective examples and comparative examples. The evaluation results are shown in the following tables 4 to 6 and FIGS. 2 to 6.
Adhesion property
Evaluation was performed according to ASTM D3359 (1 mm cross cut). The evaluation criteria are as follows.
And (3) the following materials: the non-peeled part is more than 95%
O: the non-peeled part is more than 90% and less than 95%
Delta: the non-peeled part is more than 85% and less than 90%
X: the non-peeled portions were less than 85%.
Workability of work
Workability was evaluated by measuring viscosity according to ASTM D562.
Drying property
The dry film (200 μm) was measured for touch dryness and the dryness was evaluated.
Storage stability
Whether precipitation occurred or not was observed after 7 days of standing at 60℃according to ASTM 2471.
Hardness of
Pencil hardness was measured according to ASTM D2794. The evaluation criteria are as follows.
And (3) the following materials: 3H or more
O: 2H or more and less than 3H
Delta: 1H or more and less than 2H
X: less than 1H.
Fluidity of the product
Fluidity was measured by a fluidity tester (Sag meter) according to ASTM D4400. The evaluation criteria are as follows. And (3) the following materials: 20 milli inches (Mills) or more
O: 18 mils or more and less than 20 mils
Delta: 15 mils or more and less than 18 mils
X: less than 15 mils.
TABLE 4
Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
Adhesion property ◎ ◎ ◎ ◎ △ ○
Workability of work ◎ ◎ ◎ ◎ ○ △
Drying property ○ ○ ○ ○ △ △
Storage stability ◎ ○ ○ ◎ ○ ○
Hardness of ◎ ◎ ○ ○ △ △
Fluidity of the product ◎ ◎ ◎ ○ ○ ○
And (3) the following materials: very good, o: excellent, delta: good, X: failure of
TABLE 5
Example 7 Example 8 Example 9 Example 10 Example 11 Example 12
Adhesion property ○ ○ ○ △ △ ○
Workability of work ○ ○ △ △ △ △
Drying property △ △ ○ ○ △ △
Storage stability ○ ○ ○ △ ○ ○
Hardness of △ △ △ ○ △ ○
Fluidity of the product ○ ○ ○ △ △ △
TABLE 6
Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Comparative example 6
Adhesion property △ △ ○ ○ △ △
Workability of work △ X X X X X
Drying property △ X X X X X
Storage stability △ △ ○ ○ ○ ○
Hardness of X △ X △ △ △
Fluidity of the product △ △ X X X X
From the results of tables 4 to 6 above, it was confirmed that coating films formed according to the coating compositions and coating methods of examples 1 to 12 according to the present invention showed excellent physical properties on all the physical property items measured. As shown in fig. 2 and 3, a special pattern (irregularities) was formed on the surface of the coating film formed by the methods according to examples 1 and 2 of the present invention, and as a result, a three-dimensional effect was imparted to the surface of the coating film, and the appearance defect of the coated object could be compensated for.
In contrast, the coating films formed from the coating compositions of comparative examples 1 to 3, which were drawn out of the compositions according to the present invention, showed poor physical properties as compared with examples. Specifically, in the case of comparative example 1 using only a thermosetting acrylic resin and comparative example 2 using only a thermoplastic acrylic resin, poor physical properties were exhibited in all measurement items. On the other hand, in the case of comparative example 3 containing no extender pigment, workability, drying property, hardness and fluidity were all poor.
The coating films formed according to the coating methods of comparative examples 4 to 6, from which the conditions according to the present invention were removed, showed poor physical properties as compared with examples. Specifically, comparative example 4, comparative example 5, and comparative example 6, in which the paint spray pressure was out of the range of the present invention, and the air spray pressure was out of the range of the present invention, all showed poor workability, drying property, and fluidity. As shown in fig. 4 and 5, in the case of comparative example 4 in which the paint spray pressure was too low, a pattern of a small size was formed due to the small amount of paint supplied, and in the case of comparative example 5 in which the paint spray pressure was too high, a pattern was formed too large due to the large amount of paint, and in both cases, it was difficult to sufficiently compensate for the appearance defect of the object to be painted. In addition, as shown in fig. 6, in the case of comparative example 6 in which the air ejection pressure was too weak, the pattern was formed to be large and drool downward.
On the other hand, in the case of using the coating compositions according to examples 1 to 12 of the present invention without using an airless gun or a top-coat gun in the coating method, it was impossible to achieve spraying itself due to high viscosity.

Claims (5)

1. A coating method is characterized in that,
comprising the step of applying a polyurethane coating composition using an airless gun fitted with an air cap,
the polyurethane coating composition comprises: a main agent comprising a thermosetting acrylic resin, a thermoplastic acrylic resin, and an extender pigment; and a curing agent comprising an isocyanate resin,
the above thermosetting acrylic resin has a solid content of 45 to 65%, an acid value of 1 to 15mgKOH/g, a glass transition temperature of 50 to 100 ℃, a hydroxyl value of 60 to 90mgKOH/g, a number average molecular weight of 8,000 to 14,000 g/mol, a weight average molecular weight of 12,000 to 30,000 g/mol,
the above thermoplastic acrylic resin has a solid content of 40 to 65%, an acid value of 1 to 20mgKOH/g, a glass transition temperature of 0 to 40 ℃, a hydroxyl value of 50 to 100mgKOH/g, a number average molecular weight of 3,000 to 9,000 g/mol, a weight average molecular weight of 15,000 to 30,000 g/mol,
the polyurethane coating composition has a viscosity of 50 to 150KU at 25 ℃ and a thixotropic value of 5,000 to 10,000 as determined according to ASTM D2196,
when the airless gun is used for coating, the applicable coating spray pressure is 2 to 4 bar, and the applicable air spray pressure is 3 to 5 bar.
2. The coating method according to claim 1, wherein,
the above isocyanate resin has a solid content of 50 to 70%, an isocyanate group content of 5 to 20% and a number average molecular weight of 1,500 to 3,500 g/mol.
3. The coating method according to claim 1, wherein,
the polyurethane coating composition comprises: a main agent comprising 5 to 35% by weight of the above thermosetting acrylic resin, 1 to 30% by weight of the above thermoplastic acrylic resin, and 20 to 40% by weight of the above extender pigment, based on the total weight of the main agent; and a curing agent comprising 90 to 100% by weight of an isocyanate resin.
4. The coating method according to claim 1, wherein,
the air cap mounted on the airless gun is an external mixing 8-hole air cap.
5. The coating method according to claim 1, wherein,
the above polyurethane coating composition is applied in a thickness of 150 to 700 μm in dry film thickness.
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