TW202405098A - Coating composition - Google Patents

Abstract

Object: Provided is a coating composition with excellent scratch resistance and processability. Resolution: The coating composition contains: a polyester resin (A) having a weight average molecular weight from 2000 to 40000 and a glass transition temperature of -70 to 40 DEG C; an amino resin (B); a blocked polyisocyanate compound (C); and a polyolefin resin particle (D), wherein a coating film obtained by curing the coating composition at 220 DEG C for 60 seconds has an increase rate of a friction coefficient of 50% or less during scratching in a scratch test under continuously increasing load.

Description

Coating composition

The present invention relates to a coating composition excellent in scratch resistance and workability.

In the past, precoated metal sheets such as precoated steel sheets coated by coil coating have been widely used as roofs, walls, shutters, garage and other building materials, various home appliances, switchboards, refrigerated display cabinets, and steel furniture. and kitchen appliances and other residential-related products.

For pre-coated steel sheets, in terms of durability, it is very important that the coating film has good processability when processed by pressing processing, etc., and that the coating film does not easily peel off from the base material when the surface of the coating film is impacted, that is, scratch resistance. Good sex.

However, those with good workability generally tend to have poor scratch resistance, and those with good scratch resistance tend to have poor processability.

Regarding the paint used for coating metal plates, if the paint is set to a harder resin composition in order to improve the scratch resistance, the scratch resistance will be good, but the workability will be reduced. On the contrary, if it is set to a soft resin composition, the scratch resistance will be good, but the workability will be reduced. Although the processability is improved, it is easily scratched.

In addition, scratch resistance can be improved by applying hard particles, but there are cases where equipment such as molds and the back side coating are damaged, or particles that fall off and coating films that are scraped off remain in the mold, resulting in a decrease in molding processability.

In addition, when applying wax, if a large amount is used, it may become too slippery, which may lead to a decrease in the storage properties of the steel and workability at the production site, or if a small amount is used, the scratch resistance may decrease.

Patent Document 1 discloses a coated steel plate, which includes a steel plate, a plating layer covering the steel plate and containing aluminum and zinc, a base coating layer covering the plating layer, and a top coating layer covering the base coating layer. , the aforementioned base coating includes a first polyester resin with crosslinking and a first soft resin as a polyester polyol, and the glass transition temperature is above 50°C, and the aforementioned top coating includes a second polyester resin with crosslinking , as the second soft resin and particulate wax of polyester polyol.

However, the coated plated steel sheet described in Patent Document 1 sometimes has insufficient balance between the storage properties of the steel material, the scratch resistance, and the workability. Advanced technical documents patent documents

Patent Document 1: Japanese Patent Application Publication No. 2019-167563

The problem to be solved by the invention The problem to be solved by the present invention is to provide a coating composition excellent in scratch resistance and workability. Technical means to solve problems

The present inventors conducted diligent research and found that the above-mentioned problems can be solved by a coating composition containing a polyester resin and an amine resin having a specific weight average molecular weight and a glass transition temperature range, and completed the present invention. , blocked polyisocyanate compounds and polyolefin resin particles, The increase rate of the friction coefficient during the scraping process of the coating film obtained by the scratch test using the continuous load increase method is less than 50%. That is, the present invention relates to the following: 1. A coating composition containing a polyester resin (A) with a weight average molecular weight of 2,000 to 40,000 and a glass transition temperature of -70 to 40°C, an amine resin (B), and a blocked polyisocyanate compound (C ) and polyolefin resin particles (D) coating composition, The coating film obtained by hardening the coating composition at 220°C for 60 seconds is subjected to a scratch test using the continuous load increase method. The increase rate of the friction coefficient during the scraping process of the coating film is less than 50%; 2. The coating composition as described in the above item 1, which contains at least one selected from the group consisting of phthalic anhydride and isophthalic acid as the acid component of the polyester resin (A); 3. The coating composition as described in the above item 1 or 2, which contains at least one alcohol selected from the group consisting of neopentyl glycol and 1,6-hexanediol as the polyester resin (A) Element; 4. The coating composition as described in any one of the above items 1 to 3, wherein the blocking agent of the blocked polyisocyanate compound (C) contains an oxime compound; 5. The coating composition as described in any one of the above items 1 to 4, wherein the polyolefin resin particles (D) contain structural units derived from ethylene; 6. The coating composition as described in item 5 above, wherein the polyolefin resin particles (D) are polyethylene resin particles; 7. A coating composition, which is a coating film obtained by curing the coating composition as described in any one of the above items 1 to 6 at 220°C for 60 seconds and passing the scratch test by the continuous load increase method. The scratch distance during the film scraping process is more than 10 mm; 8. A coated metal plate coated with the coating composition described in any one of the above items 1 to 6. Invention effect

The coating composition of the present invention contains polyester resin, amine resin and blocked polyisocyanate compound with a specific weight average molecular weight and glass transition temperature range. Since the polyester resin has a lower glass transition temperature and further generates The urethane bond with excellent physical properties serves as a cross-linked structure, so it has excellent processability. In addition, since it also contains polyolefin resin particles, the stress caused by the load exerted on the coating film when scratches are formed is dispersed throughout the coating film, which has a relaxing effect, and it is speculated that the coating film is less likely to produce scratches.

In addition, the increase rate of the friction coefficient during the scraping process measured by the continuous load increase method of the coating film is controlled to less than 50%, so the scratch resistance is also excellent.

Therefore, according to the coating composition of the present invention, it is possible to obtain a coating composition capable of forming a coating film with excellent scratch resistance and workability.

The coating composition of the present invention (hereinafter, sometimes simply referred to as the coating) contains polyester resin (A), amine resin (B), blocked polyisocyanate compound (C) and polyolefin resin particles (D) its composition. Detailed description below. ＜Polyester resin (A)＞

Polyester resin (A) is a polyester resin containing hydroxyl groups. Examples include oil-free polyester resin, oil-modified alkyd resin, and modified products of these resins, such as urethane-modified polyester resin, amine-modified polyester resin, etc. Formate modified alkyd resin, epoxy modified polyester resin, etc.

The oil-free polyester resin contains an esterified product of a polybasic acid component and a polyhydric alcohol component. As the polybasic acid component, for example, those selected from the group consisting of phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, succinic acid, and trabutylene are mainly used. One or more dibasic acids in the group consisting of diacid, adipic acid, sebacic acid, maleic anhydride, etc. and lower alkyl esters of these acids, together with benzoic acid, crotonic acid, Monobasic acids such as tertiary butyl benzoic acid, trimellitic anhydride, methylcyclohexene tricarboxylic acid, pyromellitic dianhydride and other polybasic acids of three or more species, etc.

As the polyol component, for example, ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 3-methylpentanediol, 1,4-hexanediol, 1, Dihydric alcohols such as 6-hexanediol may be used in combination with trivalent or higher polyhydric alcohols such as glycerin, trimethylolethane, trimethylolpropane, and neopentylerythritol as needed. These polyhydric alcohols can be used individually or in mixture of 2 or more types.

In addition, part of the above-mentioned acid components and alcohol components can also be replaced with dimethylol propionic acid, hydroxypivalic acid, p-hydroxybenzoic acid, etc.; lower alkyl esters of these acids; lactones such as ε-caprolactone. Oxygen-containing acid components.

The esterification or transesterification reaction of these components can be carried out by methods known per se.

As the acid component, from the viewpoint of weather resistance, phthalic anhydride and isophthalic acid are particularly preferred.

When using phthalic anhydride and/or isophthalic acid, the total amount is preferably 40 mol% or more, and more preferably 50 mol% or more based on the total acid component.

As the alcohol component, neopentyl glycol and 1,6-hexanediol are particularly preferred from the viewpoint of crystallization suppression and processability.

When neopentyl glycol and/or 1,6-hexanediol are used, the total amount of the total amount of the alcohol component is preferably 10 mol% or more, more preferably 50 mol% or more, and particularly preferably 60 mol%. %above.

Alkyd resin is obtained by reacting the acid component and alcohol component of the above-mentioned oil-free polyester resin with oil fatty acid using a method known per se. Examples of the oil fatty acid include coconut oil fatty acid, soybean oil fatty acid, and linseed oil. Fatty acids, safflower oil fatty acids, pine oil fatty acids, dehydrated castor oil fatty acids, tung oil fatty acids, etc. The oil length of alkyd resin is preferably less than 30%, especially about 5 to 20%.

Examples of the urethane-modified polyester resin include a low molecular weight oil-free polyester resin obtained by reacting the above-mentioned oil-free polyester resin or an acid component and an alcohol component used in producing the above-mentioned oil-free polyester resin. The isocyanate compound is reacted by a method known per se.

In addition, the urethane-modified alkyd resin includes a low molecular weight alkyd resin obtained by reacting the above-mentioned alkyd resin or each component used in producing the above-mentioned alkyd resin, and a polyisocyanate compound reacted by a method known per se. The one who becomes.

Examples of polyisocyanate compounds that can be used when producing urethane-modified polyester resins and urethane-modified alkyd resins include hexamethylene diisocyanate, isophorone diisocyanate, and phenylene diisocyanate. Methyl diisocyanate, toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-methylene bis(cyclohexyl isocyanate), 2,4,6-triisocyanatotoluene, etc.

The above-mentioned urethane-modified resin is generally preferably modified in an amount in which the amount of the polyisocyanate compound forming the urethane-modified resin is 30 mass % or less relative to the urethane-modified resin. The one who saves.

Examples of the epoxy-modified polyester resin include products obtained by reacting a polyester resin produced from each component used to produce the above-mentioned polyester resin and reacting a carboxyl group of the resin with an epoxy group-containing resin; Products in which the hydroxyl groups in the ester resin and the hydroxyl groups in the epoxy resin are bonded through polyisocyanate compounds are reaction products obtained through the addition, condensation, grafting, etc. reactions of polyester resin and epoxy resin.

Regarding the degree of modification in the epoxy-modified polyester resin, it is generally preferable to use one in which the amount of the epoxy resin is 0.1 to 30% by mass relative to the epoxy-modified polyester resin.

From the viewpoint of scratch resistance and processability, the weight average molecular weight of the polyester resin (A) is preferably in the range of 2,000 to 40,000, more preferably in the range of 2,000 to 30,000, and further more preferably in the range of 3,000 to 20,000.

The "weight average molecular weight" in this specification is a value calculated based on the molecular weight of standard polystyrene based on the chromatogram measured using a gel permeation chromatograph according to the method described in JIS K 0124-2011.

The gel permeation chromatography system used "HLC-8120 GPC" (manufactured by Tosoh Corporation). As the columns, four columns were used: "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL" and "TSKgel G-2000HXL" (all manufactured by Tosoh Co., Ltd., trade names). : Tetrahydrofuran, measurement temperature: 40°C, flow rate: 1 ml/min, detector: RI.

From the viewpoint of scratch resistance and processability, the glass transition temperature (hereinafter, sometimes referred to as "Tg point") of the polyester resin (A) is preferably -70 to 40°C, particularly preferably -60 to 30°C, more preferably within the range of -60°C to 10°C.

In this specification, the measurement of the Tg point of the polyester resin is based on differential scanning calorimetry (DSC) using a differential scanning calorimeter.

From the viewpoint of hardening and processability, the hydroxyl value of the polyester resin (A) is preferably 10 to 300 mgKOH/g, more preferably 10 to 250 mgKOH/g, and further more preferably 10 to 200 mgKOH/g. within the range.

In addition, from the viewpoint of reactivity with the amino resin (B) and the blocked polyisocyanate compound (C), the polyester resin (A) preferably has 20 mgKOH/g or less, especially 1 to 15 mgKOH. Acid value within the range of /g.

Polyester resin (A) can be used individually or in combination of 2 or more types. ＜Amine resin (B)＞

Examples of the amino resin (B) include hydroxymethyl obtained by the reaction of melamine, urea, phenylguanidine, acetylguanidine, stereoguanidine, spiroguanidine, dicyandiamide and other amine components with aldehydes. Aminated resin.

Examples of aldehydes used in the above reaction include formaldehyde, parformaldehyde, acetaldehyde, and benzaldehyde.

In addition, those obtained by etherifying the above-mentioned methylolated amino resin with alcohol can also be used as the amino resin.

Examples of the alcohol used for etherification include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 2-ethylbutanol, 2-ethylhexanol, and the like.

Among the above-mentioned amino resins, melamine resin is preferably used from the viewpoint of curability, and among these, methyl etherified melamine resin and a mixed etherified melamine resin of methyl ether and butyl ether are particularly preferably used.

Specific examples of the above-mentioned melamine resin include: CYMEL 300, CYMEL 303, CYMEL 325, CYMEL 327, CYMEL 350, CYMEL 730, CYMEL 736, CYMEL 738 [the above are all manufactured by Mitsui-Cytec Co., Ltd.], Melan 522 , Melan 523 [the above are all manufactured by Hitachi Chemical Co., Ltd.], NIKALAC MS001, NIKALAC MX430, NIKALAC MX650 [the above are all manufactured by Sanwa Chemical Co., Ltd.], Sumimal M-55, Sumimal M-100, Sumimal M-40S [ The above are all methyl etherified melamine resins such as Sumitomo Chemical Co., Ltd.], Resimene 740, Resimene 747 [the above are all made by Monsanto Co., Ltd.]; U-VAN 20SE, U-VAN 225 [the above are all Mitsui Toyaku Co., Ltd. [Made in Dainippon Ink and Chemicals Co., Ltd.] butyl etherified melamine resin; CYMEL 232, CYMEL 266, CYMEL XV-514, CYMEL 1130 [the above are all manufactured by Mitsui-Cytec Co., Ltd.], NIKALAC MX500, NIKALAC MX600, NIKALAC MS35 , NIKALAC MS95 [all made by Sanwa Chemical Co., Ltd.], Resimene 753, Resimene 755 [all made by Monsanto Co., Ltd.], Sumimal M-66B [made by Sumitomo Chemical Co., Ltd.], etc. Mixed ethers of methyl ether and butyl ether Chemical melamine resin, etc.

The amino resin can be used alone or in combination of two or more types. <Blocked polyisocyanate compound (C)>

The blocked polyisocyanate compound (C) is a compound obtained by blocking the free isocyanate group of the polyisocyanate compound with a blocking agent.

Examples of the polyisocyanate compound include aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, aromatic aliphatic polyisocyanate compounds, aromatic polyisocyanate compounds and crude products thereof, modified products of these polyisocyanate compounds, and the like.

Specific examples of the aliphatic polyisocyanate compound include: ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), dodecyldiisocyanate, 1,6,11- Undecane triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethyl hexanoate, fumarate bis(2-isocyanate) ethyl) ester, bis(2-isocyanatoethyl) carbonate, 2-isocyanatoethyl 2,6-diisocyanatohexanoate, etc.

Specific examples of the alicyclic polyisocyanate compound include: isophorone diisocyanate (IPDI), dicyclohexylmethane-4,4'-diisocyanate (hydrogenated MDI), cyclohexane diisocyanate, methylcyclohexane diisocyanate Hexane diisocyanate (hydrogenated TDI), 4-cyclohexene-1,2-dicarboxylic acid bis(2-isocyanatoethyl) ester, 2,5-and/or 2,6-norbornane diisocyanate, etc. .

Specific examples of the aromatic aliphatic polyisocyanate compound include m- and/or tere-xylylene diisocyanate (XDI), α,α,α',α'-tetramethylxylylene diisocyanate ( TMXDI) etc.

Specific examples of the aromatic polyisocyanate compound include: 1,3-and/or 1,4-phenylene diisocyanate, 2,4-and/or 2,6-toluene diisocyanate (TDI), crude TDI, 2 ,4'-and/or 4,4'-biphenyl methane diisocyanate (MDI), 4,4'-diisocyanate biphenyl, 3,3'-dimethyl-4,4'-diisocyanate base Benzene, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, crude MDI, 1,5-naphthalene diisocyanate, 4,4',4"-triphenylmethane triisocyanate, Meta- and p-isocyanato-phenylsulfonyl isocyanate, etc.

Examples of modified materials include biuret modified materials, isocyanurate modified materials, and mixtures of two or more of these.

As the polyisocyanate compound, from the viewpoint of processability and scratch resistance, hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI) can be preferably used.

Examples of the blocking agent for blocking the isocyanate group include: phenols such as phenol, cresol, and xylenol; ε-caprolactam, δ-valerolactam, γ-butyrolactamine, β- Propyrolactam and other lactams; methanol, ethanol, n- or isopropyl alcohol, n-, iso- or tertiary butanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, dibutanol Ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, benzyl alcohol and other alcohols; formamide oxime, acetaldehyde oxime, acetone oxime, methyl ethyl ketoxime, diethyl oxime, Oximes such as benzophenone oxime and cyclohexane oxime; active methylenes such as dimethyl malonate, diethyl malonate, ethyl acetyl acetate, methyl acetate acetate, acetyl acetone, etc. Capping agent.

Among the above-mentioned blocking agents, from the viewpoint of curability, an oxime-based blocking agent, especially methyl ethyl ketoxime, is preferably used.

The free isocyanate groups of the polyisocyanate compound can be easily blocked by mixing the polyisocyanate compound with the blocking agent.

From the viewpoint of curability, the number average molecular weight of the blocked polyisocyanate compound (C) is preferably in the range of 100 to 10,000, particularly preferably in the range of 100 to 5,000.

The blocked polyisocyanate compound (C) can be used alone or in combination of two or more types.

From the viewpoint of hardening and processability, based on the total solid content of polyester resin (A), amino resin (B) and blocked polyisocyanate compound (C), the polyester resin (A) The total solid content is preferably 50 to 95 mass %, more preferably 60 to 90 mass %, further more preferably 65 to 85 mass %, the solid content of the amino resin (B) and the blocked polyisocyanate compound (C) The total amount of substances is preferably 5 to 50 mass %, more preferably 10 to 40 mass %, and more preferably 15 to 35 mass %.

In addition, from the viewpoint of curability and processability, based on the total solid content of the amino resin (B) and the blocked polyisocyanate compound (C), the total solid content of the amino resin (B) is relatively Preferably, it is 1 to 83% by mass, more preferably 5 to 75% by mass, further preferably 5 to 70% by mass, and the total solid content of the blocked polyisocyanate compound (C) is preferably 1 to 50% by mass. Preferably, it is 1 to 40 mass %, and further more preferably, it is in the range of 1 to 35 mass %. <Polyolefin resin particles (D)>

The polyolefin resin particle (D) is preferably a polymer containing one or a combination of two or more structural units derived from ethylene, propylene, butylene, or longer chain olefins, and more preferably contains a polymer derived from ethylene, propylene Or the structural unit of butene.

From the viewpoint of scratch resistance, it is particularly preferable that the polyolefin resin particles (D) contain a structural unit derived from ethylene, and further more preferably, they are polyethylene resin particles.

When the aforementioned polymer has two or more structural units, it may be a random copolymer or a block copolymer. In addition, its stereoregularity and branching amount are not limited.

Examples of such polyolefin resin particles (D) include VISCOL 330-P (polypropylene wax, manufactured by Sanyo Chemical), FLO-THENE UF4 (low-density polyethylene fine powder, manufactured by Sumitomo Seiki), and FLO-BEADS HE-3040N (high-density polyethylene particles, manufactured by Sumitomo Seiko), FLO-BEADS CL-2080 (low-density polyethylene particles, manufactured by Sumitomo Seika), FLO-BEADS LE-1080 (low-density polyethylene particles, manufactured by Sumitomo Seika) Chemical Co., Ltd.) and MIPELON XM-220 (high-density polyethylene powder, produced by Mitsui Chemical Co., Ltd.), etc.

From the viewpoint of scratch resistance, the average particle diameter of the polyolefin resin particles (D) is preferably 5 to 30 µm, more preferably 5 to 25 µm, and further more preferably 5 to 20 µm.

From the viewpoint of scratch resistance, it is preferable to use powder as the polyolefin resin particles (D).

Polyolefin resin powder can be obtained by pulverizing polyolefin resin by mechanical pulverization, chemical pulverization (solvent method), or the like. Alternatively, a resin other than an olefin resin may be used as the core of the powder, and a protective colloid layer containing an olefin resin may be present on the surface of the core to obtain a polyolefin resin powder.

The above-mentioned average particle diameter is the value of the volume-based particle size distribution median diameter (d50) measured by the laser diffraction scattering method using a Microtrac particle size distribution measuring device (trade name "MT3300", manufactured by Nikkiso Co., Ltd.).

In addition, from the viewpoint of scratch resistance and processability, the polyolefin resin of the polyolefin resin particles (D) is preferably low-density, and particularly preferably low-density polyethylene.

As the range of the above-mentioned density, from the viewpoint of scratch resistance and workability, 0.905 to 0.960 g/cm ³ is preferred, 0.910 to 0.945 g/cm ³ is particularly preferred, and 0.915 to 0.945 g/cm 3 is even more preferred. cm ³ range.

From the viewpoint of scratch resistance and processability, the solid content of polyolefin resin particles (D) is determined by the solid content of polyester resin (A), amine resin (B) and blocked polyisocyanate compound (C). Based on the total amount of substances, it is preferably 0.1 to 40% by mass, more preferably 1 to 30% by mass, and further preferably 1 to 20% by mass.

The coating composition of the present invention may optionally contain pigments, hardening catalysts, pigment dispersants, ultraviolet absorbers, ultraviolet stabilizers, defoaming agents, surface conditioners, resin particles other than polyolefin resin particles (D), and silicone-containing particles. Additives such as acrylic resin, matting agents such as silica powder, and organic solvents are well-known materials used in conventional coatings.

Specific examples of pigments include: white pigments such as titanium white and zinc white; blue pigments such as cyanine blue and indanthrene blue; green pigments such as cyanine green and verdigris; organic red pigments such as azo and quinacridone pigments Inorganic red pigments such as , Iron Dan; Organic yellow pigments such as benzimidazolones, isoindolinones, isoindolines and quinoline yellows; yellow pigments such as titanium yellow, chromium yellow and yellow iron oxide; carbon Black pigments such as black, graphite, pine smoke and other black pigments; clay, talc, barium oxide, calcium carbonate and other extender pigments; anti-rust pigments such as aluminum tripolyphosphate, zinc molybdate, vanadium pentoxide, etc.

The curing catalyst is prepared as necessary in order to promote the reaction between the polyester resin (A), the amino resin (B) and the blocked polyisocyanate compound (C).

As the amino resin (B), a sulfonic acid compound or an amine neutralized product of a sulfonic acid compound can preferably be used.

Representative examples of sulfonic acid compounds include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, and the like.

The amine in the amine neutralization product of the sulfonic acid compound may be any one of primary amine, secondary amine and tertiary amine. Among these, in terms of coating stability, reaction acceleration effect, and physical properties of the coating film obtained, the amine neutralized product of p-toluenesulfonic acid and/or the amine of dodecylbenzenesulfonic acid can be preferably used. Neutralizer.

Examples of the blocked polyisocyanate compound (C) include: tin octoate, dibutyltin di(2-ethylhexanoate), dioctyltin di(2-ethylhexanoate), dioctyltin diacetate, Organometallic compounds such as dibutyltin dilaurate, dibutyltin oxide, monobutyltin trioctanoate, lead 2-ethylhexanoate, and zinc octoate.

From the viewpoint of curability, the curing catalyst is preferably 0.1 to 5.0 mass based on the total solid content of the polyester resin (A), the amino resin (B) and the blocked polyisocyanate compound (C). %, preferably within the range of 0.1 to 2.0 mass%.

The coating composition of the present invention can be prepared by combining the polyester resin (A), the amino resin (B), the blocked polyisocyanate compound (C) and the polyolefin resin particles (D), as well as the curing catalyst if necessary, etc. Obtained by uniformly mixing other ingredients.

Mixing can be performed using a mixing device such as a disperser or a homogenizer.

The coating composition is preferably applied in such a manner that a viscosity in the range of 10 to 100 seconds is obtained using Ford Cup No. 4 (20° C.) and the solid concentration is usually adjusted to a range of 20 to 60% by mass.

In this specification, the solid content (non-volatile content) concentration of the coating during coating can be determined by the following method: weigh 1.0g on the tinplate and adjust it to a viscosity suitable for coating under the conditions of a temperature of 20°C and a humidity of 60%. For the sample before coating, the volatile components are removed at a heating temperature of 105°C for 3 hours, and the remaining amount is calculated as a mass percentage. ＜Rise rate of friction coefficient during scraping＞

The coating composition of the present invention is characterized in that the coating film hardened at 220° C. for 60 seconds has an increase rate of friction coefficient of less than 50% during the scraping process of the coating film obtained by the scratch test using the continuous load increase method.

In the present invention, the increase rate of the friction coefficient in the scraping process refers to a value measured in the following manner.

In the scratch test using the steel needle load increase method, there are ASTM D7027-05 and ISO 19252 standards. The increase rate of the friction coefficient in the present invention is based on these standards using a biaxial load cell type scratch testing machine Scoot (Scot PF-SCT-01, a scratch testing machine of Profid Co., Ltd.) for scratch testing. According to the measurement The value calculated as a result.

After degreasing with isopropyl alcohol, the surface of a 70 mm × 150 mm × 0.35 mm tin plate was coated using a bar coater so that the hardened film thickness became 15 µm. The measurement was performed using Ford Cup No. 4 at 20°C. A coating composition with a coating viscosity of 130 seconds was dried at 220° C. for 60 seconds, and the result was used as a test plate.

As a steel needle, press a tungsten carbide coin-shaped indenter with a diameter of 23.5 mm and a thickness of 1.5 mm against the coating film at an angle of 45°. Use the continuous load increase method from the initial load of 1N to the maximum of 20N (the increase speed is about 4N). / second), scrape off the coin-shaped indenter at a speed of 20 mm/second. In addition, the test was conducted in an environment of 20°C.

The increase rate of the friction coefficient (horizontal stress/vertical load) in the coating film scraping process (from the start of scraping to before peeling off) when scraping off under the above test conditions is defined as the friction coefficient of the coating film scraping process. Rise rate.

The friction coefficients at the start of scraping and before peeling off are determined by visual reading from the curve of Scoot's scratch test. The reading values are calculated according to the following formula 1, from which the scraping of the coating film can be derived. The rate of increase of the friction coefficient of the process. Rise rate of friction coefficient during scraping process (%) = [(b-a)/a]×100 (Formula 1) (a and b in (Formula 1) are as follows, a: friction coefficient at the beginning of scraping, b: friction coefficient before peeling off)

For example, if the friction coefficient at the start of scraping is 0.60 and the friction coefficient before peeling off is 0.90, the amount of increase is 0.30. Therefore, based on (0.30/0.60)×100, the increase rate becomes 50%.

In the present invention, the reason why the increase rate of the friction coefficient in the scraping process of the coating film in the scratch resistance (scratch resistance) is a useful indicator is that a coating film with good scratch resistance is resistant to the scraping load, so the scraping Slowly progress, the friction coefficient of the coating film scraping process rises slowly. The better the coating, the smaller the increase rate of the friction coefficient. However, the coating film with poor scratch resistance has weak resistance to the scraping load, so scraping takes a short time. As time progresses, peeling occurs (the indenter reaches the substrate), so the friction coefficient during the coating film scraping process rises sharply. The worse the coating, the greater the increase in friction coefficient.

If the increase rate of the friction coefficient in the coating film scraping process exceeds 50%, the scratch resistance (scratch resistance) of the obtained coating film may decrease.

The increase rate of the friction coefficient is 50% or less, preferably 45% or less, further preferably 40% or less. The lower limit of the increase rate of the friction coefficient is not limited, and examples thereof include 1% or more, 5% or more, 10% or more, 15% or more, etc.

In addition, in the above-mentioned scratch test, from the viewpoint of scratch resistance (scratch resistance), the scratch distance in the coating film scraping process is preferably 10 mm or more, more preferably 15 mm or more, and further more preferably 20 mm or more. The upper limit of the scratch distance in the coating film scraping process is not limited. For example, it can be 60 mm or less, preferably 50 mm or less, more preferably 40 mm or less.

In the present invention, the increase rate of the friction coefficient during the coating film scraping process mainly depends on the types of polyester resin (A), amine resin (B), blocked polyisocyanate compound (C) and polyolefin resin particles (D) Change according to quantity.

By adjusting the increase rate of the friction coefficient to 50% or less, a coating film excellent in both scratch resistance and workability can be obtained. In addition, as long as the coating composition of the present invention is used and the coating film formed under the above conditions has an increase rate of friction coefficient in the scraping process, it is within the above range. Therefore, it goes without saying that the coating composition of the present invention is not limited to the state in which a coating film is formed under the above conditions. Similarly, for embodiments in which the scratch distance in the scraping process of the coating film is within the aforementioned range, the coating composition of the present invention is of course not limited to the state in which the coating film is formed under the aforementioned conditions.

Examples of coating methods for the coating composition of the present invention include curtain coating, roller coater coating, dip coating, spray coating, etc. The dry film thickness is usually 5 to 50 µm, preferably Coating in the range of 8 to 30 µm.

When applying the coating composition of the present invention to coil coating, the coating method is not limited. In terms of the economy of coil coating, curtain coating and roller coater coating are recommended. When applying a roller coater, it is practically suitable to use the bottom feeding method that usually uses two rollers (so-called reverse coating, natural coating). In order to optimize the uniformity of the coating surface, it is also possible to use three rollers. Top loading or bottom loading mode.

Examples of the object to be coated include cold-rolled steel sheets, hot-dip galvanized steel sheets, electro-galvanized steel sheets, galvanized alloy steel sheets (zinc alloy steel sheets such as iron-zinc, aluminum-zinc, and nickel-zinc), aluminum sheets, stainless steel sheets, Copper plate, copper-plated steel plate, tin-plated steel plate, etc.

They can also perform sandblasting, surface conditioning, surface treatment, etc., as well as primer coating as needed.

The surface of the object to be coated can be directly coated with primer as long as it is not contaminated by contaminants such as oil. However, in order to improve the adhesion and corrosion resistance of the coating film, it is ideal to perform well-known metal surface treatment. Well-known metal surface treatment methods include phosphate surface treatment, chromate surface treatment, chromium-free zirconium surface treatment, and the like.

As the primer for forming a primer film on the object to be coated, well-known primers used in the fields of colored steel plate coating, industrial machine coating, metal parts coating, etc. can be applied. From the perspective of environmental protection, it is better to use chromium-free primer paint that does not contain chromium-based anti-rust ingredients.

The coating film of the coating composition of the present invention can be hardened for about 15 seconds to 30 minutes when the material reaches the maximum temperature of 120 to 260°C. In pre-coating by coil coating, etc., the firing time is usually in the range of 15 to 90 seconds when the material reaches the maximum temperature of 160 to 260°C.

The coating composition of the present invention is excellent in scratch resistance and workability, and therefore can be particularly preferably used as a coating for pre-coated steel plates as a coating for the above-mentioned substrate. Example

Hereinafter, the present invention will be described in more detail using production examples, working examples and comparative examples, but the present invention is not limited thereto. Unless otherwise stated, "parts" in each example means parts by mass, and "%" means mass %. Manufacturing example Manufacturing of polyester resin (A) Manufacturing example 1

Add the following ingredients to the flask equipped with a thermometer, stirrer, distillation tower and water separator in the following order. 1,6-Hexanediol: 46.02 parts (0.39 mole parts) Neopentyl glycol: 46.20 parts (0.44 mole parts) Glycerin: 15.04 parts (0.17 mole parts) Adipic acid: 32.12 parts (0.22 mole parts) Phthalic anhydride: 39.96 parts (0.27 mole parts) Isophthalic acid: 64.74 parts (0.39 mole parts) Defoaming agent: trace amount

The temperature was raised while flowing nitrogen gas through the system, and stirring was started from that point when stirring was possible. After making the system uniform by stirring, add the polymerization catalyst below 100°C.

Then, the temperature was raised while stirring, and it took 3 to 10 hours to raise the temperature from 140°C to 230°C. After confirming the generation of condensation water midway, the flow of nitrogen gas was stopped. When the generation of condensation water is confirmed below 140°C, it takes 3 to 10 hours to raise the temperature to 230°C from the time (temperature) when the generation of condensation water is confirmed. Through the azeotrope of condensed water and ethylene glycol, when the temperature at the top of the distillation tower rises, the heating is weakened and the temperature rise rate is slowed down.

When it reaches 230°C, check the acid value, viscosity, etc. after 60 minutes. After another 30 minutes, add 8.87 parts (4% by mass relative to the product) of xylene (reflux solvent), and promote polymerization at 220°C until the acid value becomes 5.0. mgKOH/g or less.

When the acid value of the product becomes 5.0 mgKOH/g or less, heating is stopped and cooling is performed. When the temperature of the product becomes lower than the boiling point of the diluting solvent, the diluting solvent is added to obtain a solution of the polyester resin (A1) (solid content: 65 mass %). Production Examples 2 to 9

The solution of each polyester resin (A1) to (A9) was obtained by manufacturing in the same manner as in Production Example 1 except that the types and amounts of the acid component and alcohol component were set as shown in Table 1. Polyester resins (A6) to (A9) are for comparative examples.

Table 1 also shows the weight average molecular weight (Mw), glass transition temperature (Tg (°C)), and hydroxyl value.

In addition, the composition ratio of the acid component and the alcohol component in Table 1 is a molar ratio. Table 1 Manufacturing example No. 1 2 3 4 5 6 7 8 9 Polyester resin(A) A1 A2 A3 A4 A5 A6 A7 A8 A9 Adipic acid 0.22 0.21 0.22 0.5 0.15 0.2 0.15 0.62 0.15 Phthalic anhydride 0.27 0.63 0.3 0.2 0.35 0.58 0.1 isophthalic acid 0.39 0.462 0.15 0.45 0.44 0.12 0.44 terephthalic acid 0.4 0.4 neopentyl glycol 0.44 0.61 0.1 0.2 0.1 0.7 0.2 0.05 1,6-Hexanediol 0.39 0.39 0.7 0.8 0.3 0.1 0.8 Ethylene glycol 0.7 0.2 1,4-cyclohexanedimethanol 0.7 0.7 glycerin 0.17 0.2 0.2 0.15 0.1 Weight average molecular weight (Mw) 5200 2200 35000 2200 15500 1800 45000 3000 30000 Tg(℃) -11 -twenty three -25 -62 37 -twenty three 15 -71 41 Hydroxyl value (mgKOH/g) 106 84 56 78 65 120 6 125 32 Manufacturing Example 1 of Paint Composition

The coating composition is obtained by the following process.

Use 3 parts (solid content) of a pigment dispersant (Note 1), 15 parts solid content of the polyester resin (A1) shown in Production Example 1, 80 parts of titanium dioxide (Note 2) as a white pigment, and 80 parts of titanium dioxide (Note 2) as a black pigment. Disperse 10 parts of pigment carbon black (Note 3) to make a pigment dispersion slurry, add 55 parts of polyester resin (A1) (solid matter), and 20 parts of amino resin (B1) (solid matter), and seal it 10 parts of polyisocyanate compound (C1) (solid matter), 5 parts of polyolefin resin particles (D1) (solid matter), 0.5 parts of curing catalyst A (solid matter), 0.2 parts of curing catalyst B (solid matter), surface conditioner (Note 4) 1 part (solid matter) and stirred to obtain coating composition No. 1.

The above notes are described below. (Note 1) Pigment dispersant: DISPER BYK-111, manufactured by BYK Co., Ltd., wet pigment dispersant (Note 2) Titanium dioxide: TIPAQUE CR-95, manufactured by Ishihara Industrial Co., Ltd. (Note 3) Carbon black: Carbon MA-100, manufactured by Mitsubishi Chemical Co., Ltd. (Note 4) Surface conditioner: DISPARLON LF-1982, manufactured by Kusumoto Chemical Co., Ltd., acrylic polymer

In addition, the raw materials in Table 2 are as follows, and the preparation amounts are solid matter amounts.

Amine resin (B1): CYMEL 303LF, manufactured by Allnex Japan Co., Ltd., low molecular weight methyl etherified melamine resin. The content of hexa(methoxymethyl)melamine is 60% by mass or more.

Blocked polyisocyanate compound (C1): Sumidur BL3175, manufactured by Sumika Bayer Urethane Co., Ltd., is a methyl ethyl ketoxime blocked compound of HDI isocyanurate. Polyolefin resin particles (D1): FLO-BEADS CL-2080, manufactured by Sumitomo Seika Co., Ltd., low-density polyethylene particles, average particle diameter 11 µm, 0.92 g/cm ³ Polyolefin resin particles (D2): FLO- BEADS LE-1080, manufactured by Sumitomo Seika Co., Ltd., low-density polyethylene particles, average particle diameter 6.0 µm, 0.92 g/cm ³ Polyolefin resin particles (D3): MIPELON XM-220, manufactured by Mitsui Chemicals Co., Ltd. Ultra-high molecular weight polyethylene particles, average particle diameter 30 µm, 0.94 g/cm ³ Polyolefin resin particles (D4): FLO-BEADS HE-3040, manufactured by Sumitomo Seika Co., Ltd., high-density polyethylene particles, average particle diameter 11 µm, 0.96 g/cm ³ Polyolefin resin particles (D5): FLO-BEADS RP, manufactured by Sumitomo Seika Co., Ltd., polypropylene particles, average particle diameter 5 to 15 µm, 0.91 g/cm ³

Hardening catalyst A: Nacure 5225, manufactured by King Industries, a secondary amine neutralized product of dodecylbenzene sulfonic acid in an isopropyl alcohol solution.

Hardening catalyst B: Fourmate TK-1, manufactured by Takeda Pharmaceutical Co., Ltd., is used as a hardening catalyst for organotin solutions and a dissociation catalyst for blocked polyisocyanate compounds. Examples 2 to 13 and Comparative Examples 1 to 5

Except that the raw materials and amounts used are set as shown in Table 2, the coating compositions No. 1 to 18 were obtained in the same manner as in Example 1. In each coating composition, the pigment dispersion slurry was prepared using 15 parts of the polyester resins listed in Table 2 for each coating composition.

In addition, coating composition Nos. 14 to 18 are coating compositions for comparative examples.

For each of the obtained coating compositions, a test plate was prepared as described above for the increase rate of the friction coefficient during the scraping process, and the increase rate of the friction coefficient during the scraping process of the coating film and the scratch distance during the scraping process of the coating film were evaluated. Production of test plates (primer-coated plated steel plate specifications)

KP color 8625 primer (Kansai Paint Co., Ltd.) was applied to the front and back sides of a chemically treated 0.35 mm thick molten 55% aluminum-zinc coated steel plate (Galvalume steel plate) so that the dry film thickness became 5 µm. (Pre-coated steel plate with polyester primer), heat and bake for 40 seconds in such a way that the material reaches the maximum temperature of 220°C to obtain a primer-coated steel plate. Using a bar coater, apply each coating composition obtained in the above manner on the surface of the primer-coated steel plate so that the dry film thickness becomes about 15 µm, and heat and bake until the material reaches a temperature of 220°C. for 60 seconds to obtain each coated steel plate. The following performance tests were performed on each of the obtained coated steel sheets. Performance evaluation Scratch resistance: Using Scoot (Profid Co., Ltd.'s scratch testing machine Scoot PF-SCT-01), press a coin with a sharp corner of tungsten carbide against the test plate at an angle of 45°. At a speed of 20 mm/s, scrape 100 mm while increasing the load with an initial load of 1N and a maximum load of 20N. Evaluation is based on the following criteria. (The rate of increase in the friction coefficient during the scraping process is calculated based on the aforementioned record of the rate of increase in the friction coefficient during the scraping process.) In addition, the test was conducted in an environment of 20°C. The graphs of the Scoot test in Example 1 and Comparative Example 1 are shown in Figure 1 and Figure 2 respectively. ◎: The increase rate of friction coefficient during the coating film scraping process is less than 30% ○: The increase rate of friction coefficient in the coating film scraping process is greater than 30% and less than 50% ×: The increase rate of friction coefficient during the coating film scraping process is greater than 50%

Processability: Indicates the T number that will not cause cracking in the bent part when the test panel is bent 180 degrees with the coated surface facing out in a room at 20°C. The T number is set as 0T when nothing is clamped inside the bent part and is bent 180 degrees. When the test plate is bent by sandwiching one plate of the same thickness, it is set as 1T. When two plates are clamped, the T number is set as 0T. It is 2T. When 3 pieces are clamped, it is set to 3T. When 4 pieces are clamped, it is set to 4T. When 5 pieces are clamped, it is set to 5T. When 6 pieces are clamped, it is set to 6T. Based on the following judgment results. ◎: Almost no cracking during 4T bending processing ○: Visible cracks were seen during the 4T bending process, but almost no cracks were seen during the 6T bending process. ×: Obvious cracks can be seen during 6T bending processing

The evaluation results of each of the above-mentioned tests are shown together in Table 2. Table 2 Example 1 2 3 4 5 6 7 8 9 10 11 12 13 Coating composition No. 1 2 3 4 5 6 7 8 9 10 11 12 13 Polyester resin(A) A1 70 70 70 70 70 70 70 85 50 A2 70 A3 70 A4 70 A5 70 A6 A7 A8 A9 Amine resin(B) B1 20 20 20 20 20 20 20 20 20 20 20 5 40 Blocked polyisocyanate compound (C) C1 10 10 10 10 10 10 10 10 10 10 10 10 10 Polyolefin particles (D) D1 5 40 0.1 5 5 5 5 5 5 D2 5 D3 5 D4 5 D5 5 hardening catalyst A 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 B 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Rise rate of friction coefficient during coating film scraping process Below 50%(%) 27 35 29 33 30 20 48 twenty three 46 43 twenty one 45 18 More than 51%(%) Scratch distance during coating film scraping process 10 mm or more 20 17 twenty one 18 20 25 12 25 13 13 25 13 27 less than 10 mm scratch resistance ◎ ◎ ◎ ◎ ◎ ◎ ○ ◎ ○ ○ ◎ ○ ◎ Processability ◎ ◎ ◎ ◎ ◎ ○ ◎ ○ ◎ ◎ ○ ◎ ○ table 3 Continued table 2 Comparative example 1 2 3 4 5 Coating composition No. 14 15 16 17 18 Polyester resin(A) A1 70 A2 A3 A4 A5 A6 70 A7 70 A8 70 A9 70 Amine resin(B) B1 20 20 20 20 20 Blocked polyisocyanate compound (C) C1 10 10 10 10 10 Polyolefin particles (D) D1 5 5 5 5 D2 D3 D4 D5 hardening catalyst A 0.4 0.4 0.4 0.4 0.4 B 0.01 0.01 0.01 0.01 0.01 Rise rate of friction coefficient during coating film scraping process Below 50%(%) twenty two 20 More than 51%(%) 127 59 63 Scratch distance during coating film scraping process 10 mm or more 25 25 less than 10 mm 7 9 9 scratch resistance × ◎ × × ◎ Processability ◎ × ◎ ◎ × Industrial applicability

We can provide coating compositions that can form coating films with excellent scratch resistance and processability.

1: Friction coefficient reading value at the beginning of scraping off the coating film (Example 1) 2: Friction coefficient reading value before the coating film is peeled off (Example 1) 3: Friction coefficient reading value at the beginning of coating film scraping (Comparative Example 1) 4: Friction coefficient reading value before the coating film is peeled off (Comparative Example 1) 5: Vertical load diagram of Scoot test results 6: Horizontal stress diagram of Scoot test results 7: Friction coefficient diagram of Scoot test results

Figure 1 is a graph of the scratch resistance test of the coating film of the coating composition of the present invention and the Scoot test of Example 1. (When scratch resistance is good) Figure 2 is a graph of the scratch resistance test of the coating film and the Scoot test of Comparative Example 1. (In case of poor scratch resistance)

1: Friction coefficient reading value at the beginning of scraping off the coating film (Example 1)

2: Friction coefficient reading value before the coating film is peeled off (Example 1)

5: Vertical load diagram of Scoot test results

6: Horizontal stress diagram of Scoot test results

7: Friction coefficient diagram of Scoot test results

Claims (8)

A coating composition containing a polyester resin (A) with a weight average molecular weight of 2,000 to 40,000 and a glass transition temperature of -70 to 40°C, an amine resin (B), a blocked polyisocyanate compound (C) and Coating composition of polyolefin resin particles (D), The coating film obtained by hardening the coating composition at 220°C for 60 seconds was subjected to a scratch test using the continuous load increase method. The increase rate of the friction coefficient during the scraping process of the coating film was less than 50%. The coating composition of Claim 1, which contains at least one selected from the group consisting of phthalic anhydride and isophthalic acid as the acid component of the polyester resin (A). The coating composition of Claim 1, which contains at least one selected from the group consisting of neopentyl glycol and 1,6-hexanediol as the alcohol component of the polyester resin (A). The coating composition of claim 1, wherein the blocking agent of the blocked polyisocyanate compound (C) contains an oxime compound. The coating composition of claim 1, wherein the polyolefin resin particles (D) contain structural units derived from ethylene. The coating composition of claim 5, wherein the polyolefin resin particles (D) are polyethylene resin particles. A coating composition in which the coating film obtained by curing the coating composition according to any one of claims 1 to 6 at 220°C for 60 seconds is subjected to a scratch test using the continuous load increase method and the coating film is scraped off. The scratch distance is more than 10 mm. A coated metal plate coated with the coating composition according to any one of claims 1 to 6.