Coating agent for forming etching resist film

Abstract

The present invention provides a coating agent for forming an etching resist film, which is capable of forming an etching resist film having excellent resist properties and removability. The coating agent for forming an etching resist film according to the present invention contains, in terms of solid content, 100 parts by mass of an aqueous alkyd resin, 0.10 to 30 parts by mass of a melamine resin, and 5.0 to 100 parts by mass of an extender pigment in a solvent, the total amount of the solid content of the aqueous alkyd resin, the melamine resin, and the extender pigment accounting for 80% by mass or more of the total solid content.

Description

[Technical Field]

[0001] The present invention relates to a coating agent for forming an etching resist film, which is used to form an etching resist film on the surface of a grain-oriented electrical steel sheet. [Background technology]

[0002] Grain-oriented electrical steel sheets have excellent magnetic properties and are primarily used as materials for the iron cores of transformers. To improve the energy efficiency of transformers, it is necessary to reduce the iron loss of grain-oriented electrical steel sheets. One known method for reducing the iron loss of grain-oriented electrical steel sheets is to introduce linear grooves into the surface of the sheet. In this method, non-uniform strain is introduced by forming linear grooves on the surface of the steel sheet. This subdivides the width of the magnetic domains and reduces iron loss.

[0003] One known method for forming linear grooves on the surface of a steel sheet is an etching process using an etching resist film. For example, Patent Document 1 describes a method for forming linear grooves on the surface of a steel sheet by applying a coating agent for forming an etching resist film to the surface of the steel sheet while leaving continuous or discontinuous linear regions as non-coated regions in a direction intersecting the rolling direction, baking the coating agent, and then etching the steel sheet. Patent Document 2 describes a method for forming linear grooves on the surface of a steel sheet, in which a cold-rolled sheet that is not necessarily flat is wound around a roll surface and the coating agent for forming an etching resist film is applied while correcting the shape of the cold-rolled sheet, thereby leaving the non-coated regions correctly and reducing the variation in the shape of the linear grooves formed by the etching process. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-88121 [Patent Document 2] Japanese Patent Application Publication No. 6-108300 Summary of the Invention [Problem to be solved by the invention]

[0005] As a result of independent investigations, the inventors have found that there is room for improvement in the properties of the etching resist film formed on the surface of grain-oriented electrical steel sheets in the above-mentioned conventional techniques. Specifically, when electrolytic etching is performed using an etching resist film according to the conventional technique, there are cases in which a part of the surface of the etching resist film is discolored, causing a change in appearance. The change in color tone of the etching resist film suggests a decrease in the resistance of the etching resist film to the electrolytic etching solution (hereinafter sometimes referred to as "resist properties").

[0006] Furthermore, in the prior art, when an etching resist film that is no longer needed after etching is stripped and removed using a strong alkaline aqueous solution, there have been cases where part of the etching resist film remains on the surface of the grain-oriented electrical steel sheet without being stripped.

[0007] The present invention has been made in view of the above-mentioned problems of the conventional art, and an object of the present invention is to provide a coating agent for forming an etching resist film, which is capable of forming an etching resist film having excellent resist properties and removability. [Means for solving the problem]

[0008] The gist and configuration of the present invention are as follows. [1] In the solvent, in terms of solids, 100 parts by weight of a water-based alkyd resin, 0.10 parts by weight or more and 30 parts by weight or less of a melamine resin, and 5.0 parts by mass or more and 100 parts by mass or less of extender pigment Contains the total amount of solid contents of the aqueous alkyd resin, the melamine resin, and the extender pigment accounts for 80 mass% or more of the total solid contents; Coating agent for forming etching resist film. [2] The aqueous alkyd resin is an aqueous alkyd resin obtained by reacting an alkyd resin with a polymerizable vinyl monomer. [1] The coating agent for forming an etching resist film according to [1]. [3] The proportion of the total solid content in the coating agent for forming an etching resist is 10% by mass or more and 80% by mass or less. The coating agent for forming an etching resist film according to [1] or [2]. [4] The solvent includes ethylene glycol mono-n-butyl ether. [1] The coating agent for forming an etching resist film according to any one of [1] to [3]. [Effects of the Invention]

[0009] The etching resist film formed by applying the coating agent for forming an etching resist film according to the present invention to the surface of a grain-oriented electrical steel sheet and baking it has superior resist properties and removability compared to conventional techniques. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below.

[0011] <Coating agent for forming etching resist film> In one embodiment, the present invention provides a method for producing a medicament for the treatment of a pulmonary arthritis. In the solvent, in solids equivalent, 100 parts by weight of a water-based alkyd resin, 0.10 parts by weight or more and 30 parts by weight or less of a melamine resin, and 5.0 parts by mass or more and 100 parts by mass or less of extender pigment Contains the total amount of solid contents of the aqueous alkyd resin, the melamine resin, and the extender pigment accounts for 80 mass% or more of the total solid contents; This invention relates to a coating agent for forming an etching resist film.

[0012] The coating agent for forming an etching resist film according to the present invention is composed primarily of an aqueous alkyd resin, to which a melamine resin crosslinker and an extender pigment are added, and the resulting mixture is dissolved or mixed in a solvent. The coating agent for forming an etching resist film according to the present invention is applied to the surface of a grain-oriented electrical steel sheet and baked at a predetermined temperature for a predetermined time, resulting in evaporation of the solvent and a crosslinking reaction, forming an etching resist film on the surface of the grain-oriented electrical steel sheet. In this specification, the term "coating agent for forming an etching resist film" refers to a liquid coating agent primarily composed of a resin, which is used to form an etching resist film. In this specification, the term "etching resist film" refers to a solid film formed on the surface of a substrate after the above-described process using the coating agent for forming an etching resist film. The commonly used term "etching resist" can sometimes refer to a coating agent for forming an etching resist film and sometimes to an etching resist film. In this specification, the terms "coating agent for forming an etching resist film" and "etching resist film" are used strictly separately.

[0013] As described above, the coating agent for forming an etching resist film is applied so as to leave continuous or discontinuous linear regions in a direction intersecting the rolling direction as non-coated regions. During the etching treatment, the coated regions protected by the etching resist film prevent contact between the surface of the grain-oriented electrical steel sheet and the etching solution, and corrosion of the grain-oriented electrical steel sheet does not occur. In the non-coated regions, corrosion occurs due to contact of the surface of the grain-oriented electrical steel sheet with the etching solution, forming linear grooves. After the etching treatment is completed, the etching resist film is removed as necessary.

[0014] <Solid content and solid content equivalent> Before describing each component contained in the coating agent for forming an etching resist film according to the present invention, we will explain how the components are labeled. In this specification, "solid content" refers to the remaining solid components contained in the coating agent for forming an etching resist film, excluding substances that are lost by evaporation, such as solvents and water. When the coating agent for forming an etching resist film is applied to the surface of a grain-oriented electrical steel sheet and baked, substances such as solvents and water evaporate, and an etching resist film is formed by the remaining solid content.

[0015] As used herein, the term "solids content equivalent" refers to the content of each component in a coating agent for forming an etching resist film being expressed based on the solid content of the component. As described below, the coating agent for forming an etching resist film according to the present invention is prepared by mixing an aqueous alkyd resin, a melamine resin, and an extender pigment in a solvent. The aqueous alkyd resin and melamine resin used in the preparation may themselves contain a solvent. Furthermore, the volume pigment may adsorb moisture from the air. Therefore, when expressing the content of each component, it is appropriate to express the content in terms of solids content, rather than the content of the components actually mixed. Specifically, the solid content of the aqueous alkyd resin contained in the coating agent for forming an etching resist film is defined as 100 parts by mass, and the content is expressed in parts by mass of the solid content of the other components converted based on this.

[0016] The content of each component expressed in terms of solid content remains unchanged before and after application and baking of the coating agent for forming an etching resist film. Therefore, by quantitatively analyzing the components of the etching resist film after baking, the content of each component, calculated as solid content, contained in the coating agent for forming an etching resist film before baking can be determined.

[0017] <Ingredients of coating agent for forming etching resist film> Hereinafter, each component contained in the coating agent for forming an etching resist film according to the present invention will be described. (1) Water-based alkyd resin The coating agent for forming an etching resist film according to the present invention contains 100 parts by mass of an aqueous alkyd resin, calculated as solids, in a solvent. As described above, the aqueous alkyd resin is the main component of the coating agent for forming an etching resist film according to the present invention, and also serves as the main component of the etching resist film after application and baking. The term "aqueous resin" refers collectively to both water-dispersible resins, in which the resin is uniformly dispersed in water, and water-soluble resins, which are easily soluble in water.

[0018] As the aqueous alkyd resin, any conventionally known resin can be used without any particular limitation. The alkyd resin, which is the raw material for the aqueous alkyd resin, can be obtained by a dehydration condensation reaction between a polybasic acid, a polyhydric alcohol, and a fat or oil or a processed fat or oil product, and optionally further reacting with a monobasic acid. In a preferred embodiment, the coating agent for forming an etching resist film according to the present invention is an aqueous alkyd resin obtained by reacting an alkyd resin with a polymerizable vinyl monomer. In this preferred embodiment, by using an aqueous alkyd resin obtained by reacting an alkyd resin with a polymerizable vinyl monomer, a coating agent for forming an etching resist film can be obtained that can form an etching resist film with excellent resist properties and removability.

[0019] ·Polybasic acid Examples of polybasic acids used in the synthesis of alkyd resins include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, tetrahydrophthalic acid, succinic acid, maleic acid, adipic acid, sebacic acid, azelaic acid, himic acid, itaconic acid, methylhexahydrophthalic acid, 1,4-cyclohexanedicarboxylic acid, methylcyclohexenetricarboxylic acid, pyromellitic acid, and anhydrides thereof. These polybasic acids can be used alone or in combination of two or more.

[0020] Polyhydric alcohol Examples of polyhydric alcohols used in the synthesis of alkyd resins include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, butanediol, decanediol, diethylene glycol, pentanediol, neopentyl glycol, butylethylpropanediol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, etc. These polyhydric alcohols can be used alone or in combination of two or more.

[0021] Oils and fats and processed oil products Examples of fats and oils used in the synthesis of alkyd resins include tung oil, linseed oil, dehydrated castor oil, safflower oil, soybean oil, castor oil, tall oil, rice bran oil, and their fatty acids, as well as hygienic fatty acids. Furthermore, processed fats and oils obtained using the above-mentioned fats and oils as the main raw material can be used. Examples of such processed fats and oils include modified oils, isomerized oils, polymerized oils, maleated oils, and boiled oils, all of which are obtained using the above-mentioned fats and oils as the main raw material. These fats and oils and processed fats can be used alone or in combination of two or more.

[0022] ·Monobasic acid Examples of monobasic acids that may be optionally used in the synthesis of alkyd resins include benzoic acid, pt-butylbenzoic acid, methylbenzoic acid, versatic acid, isodecanoic acid, isotridecanoic acid, crotonic acid, non-drying oil fatty acids, etc. These monobasic acids may be used alone or in combination of two or more.

[0023] Polymerizable vinyl monomers In a preferred embodiment of the present invention, conventionally known polymerizable vinyl monomers can be used without particular limitation as the polymerizable vinyl monomer to be reacted with the alkyd resin to obtain the aqueous alkyd resin. Examples of the polymerizable vinyl monomer to be used in the reaction with the alkyd resin include (meth)acrylic acid ester monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, ethylcyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, toluyl (meth)acrylate, and glycidyl (meth)acrylate; aromatic polymerizable unsaturated monomers such as styrene, α-methylstyrene, chlorostyrene, vinyltoluene, vinylnaphthalene, phenyl (meth)acrylate, benzyl (meth)acrylate, and vinyl benzoate; vinyl monomers such as vinyl acetate and vinyl propionate; N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, and N-butoxymethyl (meth)acrylate. N-alkoxy-substituted amide monomers such as di(meth)acrylamide; fluorine-containing vinyl monomers such as perfluoroethylene, perfluoropropylene, and vinylidene fluoride; silicon-containing vinyl monomers such as vinyltrimethoxysilane and vinyltriethoxysilane; dialkyl esters of maleic acid and fumaric acid; alkenes such as ethylene and propylene; conjugated dienes such as butadiene and isoprene; monomers such as vinyl chloride and allyl chloride; (meth)acrylic acid, itaconic acid, maleic acid monomethyl ester, maleic acid monobutyl ester, itaconic acid monobutyl ester, sulfonic acid group-containing (meth)acrylates, phosphoric acid group-containing (meth)acrylates, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate;Lactone adducts of 2-hydroxyethyl (meth)acrylate, ring-opening adducts of ethylene oxide to 2-hydroxyethyl (meth)acrylate or 2-hydroxypropyl (meth)acrylate, ring-opening adducts of propylene oxide to 2-hydroxyethyl (meth)acrylate or 2-hydroxypropyl (meth)acrylate, dimers and trimers of 2-hydroxyethyl (meth)acrylate or 2-hydroxypropyl (meth)acrylate, N,N-dimethylaminoethyl ... Examples of polymerizable vinyl monomers include N,N-methylethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dipropylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-methylpropylaminopropyl (meth)acrylate, N,N-diethylaminopropyl (meth)acrylate, N,N-dipropylaminopropyl (meth)acrylate, N,N-dimethylaminopropyl acrylamide, and N,N-diethylaminopropyl acrylamide. These polymerizable vinyl monomers can be used alone or in combination of two or more.

[0024] The aqueous alkyd resin may be commercially available or synthesized from raw materials. When using a commercially available product, it is preferable to use one synthesized using one of the compounds listed above as raw materials. When synthesizing an aqueous alkyd resin from raw materials, the following procedure is preferably used. First, a predetermined amount of polybasic acid, polyhydric alcohol, oil or fat or processed oil product, and optionally a monobasic acid are charged into a reaction vessel, and the contents are heated while stirring to cause a dehydration condensation reaction. When the acid value of the solids reaches 3 to 30 mgKOH / g, heating is stopped and the mixture is cooled. The acid value of the solids is preferably measured in accordance with Japanese Industrial Standard JIS K 0070. Next, a solvent is added to the resulting reaction mixture to prepare an alkyd resin solution. The alkyd resin solution is heated with stirring, and a previously prepared mixture of polymerizable vinyl monomer and polymerization initiator is added dropwise. After the dropwise addition, the polymerization initiator is further added dropwise to the reaction mixture and stirred to allow the reaction. A neutralizer and a solvent are then added to the reaction mixture and mixed to obtain a solution containing an aqueous alkyd resin.

[0025] The aqueous alkyd resin synthesized by the above procedure preferably has an acid value of 30 mgKOH / g or more and 80 mgKOH / g or less, a hydroxyl value of 50 mgKOH / g or more and 150 mgKOH / g or less, a number average molecular weight of 2,000 or more and 10,000 or less, and a weight average molecular weight of 10,000 or more and 50,000 or less.

[0026] The solvent used in synthesizing the water-based alkyd resin is not particularly limited. Preferred solvents include glycol ethers such as ethylene glycol mono-n-butyl ether, diethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-t-butyl ether, dipropylene glycol monomethyl ether, methyl cellosolve, ethyl cellosolve, and t-butyl cellosolve; and alcohols such as isopropyl alcohol and butyl alcohol.

[0027] The polymerization initiator used in synthesizing the water-based alkyd resin is not particularly limited, but preferred examples of the polymerization initiator include dibenzoyl peroxide and 2,2'-azobisbutyronitrile.

[0028] The neutralizing agent used in synthesizing the water-based alkyd resin is not particularly limited, but preferred neutralizing agents include, for example, triethylamine and diethylethanolamine.

[0029] (2) Melamine resin The coating agent for forming an etching resist according to the present invention contains a melamine resin in a solvent in an amount of 0.10 parts by mass or more and 30 parts by mass or less, calculated as solid content. The melamine resin is contained in the coating agent for forming an etching resist as a crosslinking agent that crosslinks the aqueous alkyd resin. The inclusion of the melamine resin improves adhesion between the etching resist film and the grain-oriented electrical steel sheet. Examples of the melamine resin that can be used include methylated melamine and butylated melamine.

[0030] When the solvent contains 0.10 parts by mass or more of melamine resin per 100 parts by mass of the aqueous alkyd resin, calculated as solid content, the adhesion between the formed etching resist film and the grain-oriented electrical steel sheet is enhanced, and the resist properties are improved. On the other hand, when the melamine resin is contained in an amount of 30 parts by mass or less, the crosslink density does not increase excessively. As a result, the etching resist film maintains appropriate hardness and adhesion, and the removability of the etching resist film does not deteriorate. Therefore, the content of melamine resin is set to 0.10 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the aqueous alkyd resin, calculated as solid content. The content of melamine resin is preferably 1.0 part by mass or more, and more preferably 2.0 parts by mass or more. The content of melamine resin is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less.

[0031] (3) Extender pigment The coating agent for forming an etching resist film according to the present invention contains 5.0 parts by mass or more and 100 parts by mass or less of an extender pigment, calculated as solids, in a solvent. The extender pigment is contained in the coating agent for forming an etching resist film as a coating extender. Extender pigments are generally inexpensive and chemically stable, making them suitable for use as extenders for etching resist films. The type of extender pigment is not particularly limited, and various known extender pigments can be used. Examples of preferred extender pigments include calcium carbonate, barium sulfate, and aluminum hydroxide. These extender pigments can be used alone or in combination.

[0032] When the solvent contains 5.0 parts by mass or more of the extender pigment per 100 parts by mass of the aqueous alkyd resin solids, the thickness of the etching resist film is easily ensured and the resist properties are improved. On the other hand, when the extender pigment is contained in an amount of 100 parts by mass or less, the extender pigment concentration is not excessive, and adhesion and resist properties are not deteriorated. Therefore, the content of the extender pigment is set to 5.0 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the aqueous alkyd resin, calculated as solids. The content of the extender pigment is preferably 6.0 parts by mass or more, and more preferably 10 parts by mass or more. The content of the extender pigment is preferably 80 parts by mass or less, and more preferably 50 parts by mass or less.

[0033] In the coating agent for forming an etching resist film according to the present invention, the total solid content of the aqueous alkyd resin, the melamine resin, and the extender pigment accounts for 80% by mass or more of the total solid content. In this specification, "total solid content" refers to the total solid content of all components contained in the coating agent for forming an etching resist film. When the total solid content of the aqueous alkyd resin, the melamine resin, and the extender pigment accounts for 80% by mass or more, the components of the etching resist film formed by the coating agent for forming an etching resist film are not significantly diluted by the other components described below. Therefore, the effects of the present invention exhibited by the etching resist film are not impaired. There is no particular upper limit to the total solid content of the aqueous alkyd resin, the melamine resin, and the extender pigment, and the total solid content may be 100% by mass or less.

[0034] (4) Solvent The coating agent for forming an etching resist film according to the present invention contains a water-based alkyd resin, a melamine resin, and an extender pigment in a solvent. The solvent functions to uniformly dissolve the resin and uniformly mix the pigment, and also facilitates application of the coating agent for forming an etching resist film. In addition, from the viewpoint of affinity with the water-based alkyd resin, the solvent preferably contains ethylene glycol mono-n-butyl ether.

[0035] The solvent can be used by mixing with a hydrophilic solvent. Specific examples of hydrophilic solvents include glycol ethers such as diethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-t-butyl ether, dipropylene glycol monomethyl ether, methyl cellosolve, ethyl cellosolve, and t-butyl cellosolve, as well as alcohols such as isopropyl alcohol and butyl alcohol. These solvents can be used alone or in combination of two or more.

[0036] The solvent may be mixed with a hydrophobic solvent such as toluene, xylene, etc. These hydrophobic solvents may be used alone or in combination of two or more.

[0037] The proportion of the solvent in the coating agent for forming an etching resist film is not particularly limited, but is preferably 20% by mass or more and 90% by mass or less. In other words, the proportion of the total solids in the coating agent for forming an etching resist film is preferably 10% by mass or more and 80% by mass or less. When the amounts of the solvent and total solids in the coating agent for forming an etching resist film are within the above ranges, the storage stability of the coating agent for forming an etching resist film and the workability when applying it to a grain-oriented electrical steel sheet are good.

[0038] (5) Other ingredients In a preferred embodiment, the coating agent for forming an etching resist film according to the present invention further contains, in a solvent, one or more components selected from surfactants, rust inhibitors, lubricants, leveling agents, neutralizing agents, antifoaming agents, antioxidants, and coloring pigments. These components are added to further improve the performance and uniform application of the etching resist film. These other components can be used alone or in combination of two or more. When the total amount of the solid content of these other components is 20 mass% or less of the total solid content, the performance of the etching resist film can be sufficiently maintained.

[0039] <Method of manufacturing a coating agent for forming an etching resist film> Next, a method for producing a coating agent for forming an etching resist film according to the present invention will be described. The method for producing a coating agent for forming an etching resist film is not particularly limited, but preferably follows the procedure below. First, a portion of a solution containing an aqueous alkyd resin is placed in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, etc., and an extender pigment and, if necessary, a hydrophilic solvent are added to uniformly disperse the resulting material. Next, the remainder of the solution containing the aqueous alkyd resin and a melamine resin are added and dispersed to obtain a dispersion. If necessary, a leveling agent, a neutralizing agent, an antifoaming agent, and a solvent or water are added to the resulting dispersion to obtain a coating agent for forming an etching resist film.

[0040] <Method of manufacturing steel sheet with etching resist coating> Next, a preferred method for producing an etching resist coated steel sheet using the coating agent for forming an etching resist film according to the present invention will be described, although the method for producing an etching resist coated steel sheet using the coating agent for forming an etching resist film according to the present invention is not limited to the method described here.

[0041] (1) Steel plate First, a steel sheet to which a coating agent for forming an etching resist film is applied is prepared. The steel sheet to which the coating agent for forming an etching resist film is applied is any steel sheet that will ultimately become a grain-oriented electrical steel sheet and has been hot-rolled. Grain-oriented electrical steel sheets are generally manufactured by the following process: a steel slab is hot-rolled to form a hot-rolled steel sheet; the hot-rolled steel sheet or the hot-rolled annealed steel sheet obtained by hot-rolling the hot-rolled steel sheet is then cold-rolled once or twice or more times with intermediate annealing between them to form a cold-rolled steel sheet; the cold-rolled steel sheet is then subjected to primary recrystallization annealing to form a primary recrystallized sheet; and the primary recrystallized sheet is then subjected to secondary recrystallization annealing to obtain a secondary recrystallized sheet.

[0042] When a grain-oriented electrical steel sheet is manufactured using a steel sheet with an etching resist coating, the components and composition of the final grain-oriented electrical steel sheet are not particularly limited. The thickness of the grain-oriented electrical steel sheet is also not particularly limited. Thinning the steel sheet reduces iron loss, but if it is too thin, shape stability deteriorates and the manufacturing cost of the steel sheet increases. Therefore, the thickness of the grain-oriented electrical steel sheet is preferably 50 μm or more. Furthermore, as the sheet thickness increases, iron loss increases accordingly. Therefore, the thickness of the grain-oriented electrical steel sheet is preferably 0.50 mm or less, and more preferably 0.30 mm or less.

[0043] In the present invention, there are two types of steel sheets to which the coating agent for forming an etching resist film is applied. One is a grain-oriented electrical steel sheet as a finished product obtained by completing all processes up to the secondary recrystallization annealing described above. The other is a steel sheet as an intermediate product during the manufacturing process of a grain-oriented electrical steel sheet. Specific examples of the latter include a hot-rolled steel sheet after hot rolling, a hot-rolled annealed sheet obtained by hot-rolling a hot-rolled steel sheet, a cold-rolled steel sheet after cold rolling in a single cold rolling process, a cold-rolled steel sheet before or after intermediate annealing or a cold-rolled steel sheet after intermediate annealing in a case where cold rolling is performed in two or more processes with an intermediate annealing in between, and a primary recrystallized sheet after primary recrystallization annealing. In the present invention, the steel sheet to which the coating agent for forming an etching resist film is applied is collectively referred to as a "steel sheet" regardless of whether it is a finished product or an intermediate product.

[0044] In the present invention, the target to be subjected to the etching treatment by applying the coating agent for forming an etching resist film may be either the above-mentioned finished steel sheet or an intermediate steel sheet. However, if the intermediate steel sheet is subjected to the etching treatment to form grooves on the surface thereof and then further rolled, the grooves formed by the etching treatment may disappear. Therefore, when an intermediate steel sheet is used, it is preferable to use a cold-rolled steel sheet or a primary recrystallized steel sheet after all cold rolling has been completed.

[0045] In the present invention, the etching resist film formed on the surface of the grain-oriented electrical steel sheet may be burned away or deteriorated at the high temperatures encountered when the steel sheet is subjected to heat treatment. Therefore, when the intermediate product described above is used as the steel sheet to which the coating agent for forming an etching resist film is applied, it is preferable to apply the coating agent for forming an etching resist film, followed by baking and etching treatments in succession, and then carry out the subsequent heat treatment steps. Note that the series of steps for forming grooves on the surface of the grain-oriented electrical steel sheet may be carried out once or twice or more times.

[0046] (2) Coating of etching resist coating Next, the coating agent for forming an etching resist film is applied to at least one surface of the hot-rolled steel sheet, leaving a plurality of non-coated regions where the coating agent for forming an etching resist film is not applied, which are linearly arranged along a direction intersecting the rolling direction of the steel sheet. The surface to which the coating agent for forming an etching resist film is applied may be one surface of the steel material or both surfaces of the steel material.

[0047] The method for applying the coating agent for forming an etching resist film is not particularly limited. When gravure printing is used as the method for applying the coating agent for forming an etching resist film, a coated region where an etching resist film is formed and a non-coated region where no etching resist film is applied can be formed simultaneously.

[0048] In the present invention, the direction in which the linear non-coated regions are provided is a direction that intersects with the rolling direction, and the angle between the rolling direction and the direction in which the linear non-coated regions are provided is preferably 50° or more, more preferably 60° or more, and most preferably 90°. The non-coated regions may be provided in a continuous line or discontinuous line. The non-coated regions may be provided at equal intervals or may not be at equal intervals. The width of the non-coated regions may be, for example, 0.20 mm.

[0049] (3) Baking treatment of coating agent for forming etching resist film Next, the steel sheet coated with the coating agent for forming an etching resist film is baked. The method for performing the baking treatment is not particularly limited, and baking treatments using commonly used methods such as hot air, infrared heating, and induction heating can be applied.

[0050] The baking temperature can be a temperature that is generally used. The baking temperature is preferably 120°C or higher and 350°C or lower in terms of the maximum steel sheet temperature. In this specification, the "maximum steel sheet temperature" refers to the temperature measured on the surface of the steel sheet and the maximum temperature reached in the heat treatment process. If the maximum steel sheet temperature is 120°C or higher, the curing of the coating agent for forming an etching resist film proceeds sufficiently. If the maximum steel sheet temperature is 350°C or lower, thermal decomposition of the etching resist film can be prevented. The maximum steel sheet temperature is more preferably 300°C or lower. The baking time in the baking treatment, i.e., the time from the start of heating until the maximum steel sheet temperature is reached, is not particularly limited, but is preferably about 10 to 60 seconds.

[0051] In the manufacturing method of grain-oriented electrical steel sheet, the amount of etching resist film attached per side is 0.50 g / m 2 The adhesion weight of the etching resist film is preferably 0.50 g / m or more. 2 By setting the thickness to the above, it is possible to provide a grain-oriented electrical steel sheet with an etching resist film having particularly excellent resist properties. 2 It is more preferable that the amount of the etching resist film deposited on one side is 20 g / m or more. 2 The coating weight of the etching resist film is preferably 20 g / m or less. 2 The amount of the etching resist film deposited on one side can be determined by dissolving and removing only the etching resist film from the grain-oriented electrical steel sheet with the etching resist film after baking treatment using a hot alkali or the like, and measuring the change in weight of the grain-oriented electrical steel sheet before and after removal.

[0052] (4) Etching process Next, the steel sheet on which the etching resist film has been formed is subjected to an etching treatment to form grooves on the surface of the steel sheet in the non-coated areas. The etching method is not particularly limited, but can be, for example, electrolytic etching. When electrolytic etching is performed, it is preferable to use an electrolyte such as NaCl, KCl, CaCl2, or NaNO3, and the current density is 5 to 20 A / dm 2 The electrolysis time is preferably about 5 to 20 seconds. The conditions for the etching process are preferably adjusted so that, in a cross section perpendicular to the extension direction of the grooves formed by the etching process, the angle between the sidewalls of the grooves and the plate thickness direction is 60 degrees or less, and the height of the convex portions formed at the bottom of the grooves is 1 / 2 or less of the maximum depth of the grooves. By adjusting the shape of the grooves in this way, non-uniform strain is introduced, thereby increasing the effect of reducing iron loss. The depth of the grooves can be, for example, 20 μm.

[0053] In the method for producing grain-oriented electrical steel sheet, after the etching treatment, the remaining treatments required to convert the steel sheet into a grain-oriented electrical steel sheet are appropriately carried out depending on the treatment stage of the steel sheet in the above-mentioned manufacturing process of the grain-oriented electrical steel sheet, thereby making it possible to produce a grain-oriented electrical steel sheet with reduced iron loss.

[0054] In the method for producing grain-oriented electrical steel sheet, an etching resist film remains after forming grooves by etching. This etching resist film may or may not be peeled off after etching. If the etching resist film is not peeled off, it can also function as an insulating tension film. When the etching resist film is removed, the removal method is not particularly limited and any well-known method can be used. For example, a method for removing the etching resist film can be used in which the grain-oriented electrical steel sheet is immersed in an alkaline solution such as an NaOH aqueous solution to soften the etching resist film, and then the etching resist film is washed off and removed using a brush. [Example]

[0055] The effects of the present invention will be specifically explained below based on examples, but the present invention is not limited to these examples.

[0056] (1) Manufacturing of coating agents for forming etching resist films The starting materials were prepared as shown in Table 1: resin, melamine resin, extender pigment, and other ingredients. Of the starting materials shown in Table 1, the water-based alkyd resin indicated by symbol a1 was produced by the method described below. The other starting materials used were those manufactured by the manufacturers and trade names shown in Table 1.

[0057] [Table 1]

[0058] The waterborne alkyd resin designated by symbol a1 in Table 1 was produced by the following method. First, 75 parts by mass of linseed oil, 16 parts by mass of glycerin, 40 parts by mass of phthalic anhydride, 1 part by mass of maleic anhydride, 20 parts by mass of pentaerythritol, and 5 parts by mass of xylene were placed in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dehydrator, and nitrogen gas inlet tube. The mixture was heated and stirred under a nitrogen atmosphere until the temperature reached 220°C. The reaction was continued until the acid value of the solid content of the mixture reached 8 mgKOH / g, after which the mixture was cooled. The acid value of the solid content was measured in accordance with Japanese Industrial Standard JIS K 0070. Next, 72 parts by mass of ethylene glycol mono-n-butyl ether was added as a solvent to the resulting reaction mixture and mixed to obtain an alkyd resin solution having an oil length of 55%, an acid value of 8 mgKOH / g, a hydroxyl value of 120 mgKOH / g, a heating residue of 65%, a number average molecular weight of 3,200, and a weight average molecular weight of 19,500.

[0059] Next, 150 parts by mass of the resulting alkyd resin solution was placed in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, etc., and stirred while heating. Once the solution temperature reached 110°C, a premixed mixture of 16 parts by mass of styrene, 16 parts by mass of methyl methacrylate, 4 parts by mass of acrylic acid, and 1 part by mass of dibenzoyl peroxide as a polymerization initiator was added dropwise over 4 hours to carry out a dehydration condensation reaction. After completion of the dropwise addition, while maintaining the reaction mixture at 110°C, a mixture of 0.5 parts by mass of dibenzoyl peroxide and 5 parts by mass of ethylene glycol mono-n-butyl ether as a polymerization initiator was added dropwise over 3 hours, and the mixture was subsequently stirred at 110°C for 2 hours to carry out the reaction, followed by cooling. Next, 14 parts by mass of triethylamine was added to the resulting reaction mixture and stirred, and then 5 parts by mass of ethylene glycol mono-n-butyl ether was added and mixed to obtain a solution (symbol a1 in Table 1) containing an aqueous alkyd resin having an oil length of 38, an acid value of 56 mgKOH / g, a hydroxyl value of 84 mgKOH / g, a heating residue of 65%, a number average molecular weight of 3,200, and a weight average molecular weight of 25,700.

[0060] Next, the starting materials listed in Table 1 were mixed according to the following procedure to prepare a coating agent for forming an etching resist film having the components and solids content listed in Table 2. First, a portion of the resin-containing solution was placed in a disperser, and the extender pigment, the organic pigment (d1 or d2) among the other components, and ethylene glycol mono-n-butyl ether (5% by mass of the total) as a solvent were added and uniformly dispersed. A particle gauge was used to confirm that the particle size of the extender pigment was 10 μm or less. Next, the remaining resin and melamine resin were added and dispersed to obtain a dispersion. Furthermore, to improve film-forming properties, 0.5% by mass of the surfactant (d3 or d4) among the other components was added to the resulting dispersion. Furthermore, triethylamine was added as a neutralizing agent and ethylene glycol mono-n-butyl ether was added as a solvent to adjust the pH of the coating agent for forming an etching resist film to 9.0 and the solids content to 60% by mass.

[0061] The components and solid content of the 23 different coating materials for forming etching resist films, each with different components and compositions, are shown in Table 2. The mass % content of each component shown in Table 2 represents the proportion of the solid content of each component relative to the total solid content. The mass parts of other components represent the mass parts of other components based on 100 mass parts of resin (symbol a1, a2, or a3). It should be noted that, among the coating agents for forming etching resist films shown in Table 2, comparative example No. 23 uses a water-based epoxy resin (symbol a3) as the resin, rather than a water-based alkyd resin.

[0062] [Table 2]

[0063] (2) Manufacturing of steel sheets with etching resist coating A steel sheet measuring 150 mm wide and 300 mm long was cut out from a 0.23 mm thick grain-oriented electrical steel sheet and used as a test material. The coating agent for forming an etching resist film produced by the above method was uniformly applied to the entire surface of one side of this test material using a roll coater. Next, the test material coated with the coating agent for forming an etching resist film was baked in a hot air baking oven at the maximum steel sheet temperature and drying time shown in Table 3, and then allowed to cool to room temperature to obtain a steel sheet with an etching resist film.

[0064] Next, the properties of the 23 types of steel sheets with etching resist films produced by the above method were evaluated by the following methods. The evaluation results are shown in Table 3.

[0065] [Table 3]

[0066] <Adhesion amount> The amount of the etching resist film deposited after baking was measured by a gravimetric method. Specifically, the etching resist film alone was dissolved and removed from the test material using a heated potassium hydroxide solution, and the change in weight of the steel sheet before and after dissolution and removal was measured. The amount of deposition was calculated by dividing the measured weight change by the area of one side of the test material.

[0067] <Adhesion> The test material was cut to a width of 30 mm and a length of 50 mm, and a 24 mm wide and 50 mm long piece of cellophane tape was applied to the surface of the cut test material on which the etching resist film was formed (the test surface). Next, the test material was bent 180° using a 5 mm diameter round rod with the test surface as the compression side, and the cellophane tape was then peeled off. The area ratio of the etching resist film that had adhered to the cellophane tape and peeled off was calculated, and the adhesion was evaluated according to the following criteria. A rating of A or B was considered a pass, and an F was considered a fail. (Evaluation criteria) A: Area ratio is 5.0% or less B: Area ratio is greater than 5.0% and less than or equal to 10% F: Area ratio is greater than 10%

[0068] <Scratch resistance> Two test pieces of each type were prepared by cutting the test material into pieces 100 mm wide and 200 mm long. For each of the two test pieces, the test surfaces on which the etching resist film was formed were placed together, and a pressure of 196 kPa (2 kgf / cm) was applied in the normal direction of the test surfaces. 2 ) and sliding in the longitudinal direction at a relative speed of 2 cm / s for 10 seconds. Next, scratches on the surface of the test surface were visually observed to calculate the scratch occurrence area ratio, and scratch resistance was evaluated according to the following criteria. A rating of A, B, or C was considered a pass, and F was considered a fail. (Evaluation criteria) A: Almost no defects are observed B: Slight scratches are visible C: Scratches are clearly visible F: Defects that expose the steel substrate are observed

[0069] <Resist characteristics> The test material was cut into pieces 30 mm wide and 250 mm long and then subjected to electrolytic etching. The appearance of the surface of the etching resist film after electrolytic etching was visually observed, and the resist characteristics were evaluated by calculating the area ratio of the area where discoloration was observed. A 20% aqueous NaCl solution was used as the electrolyte for electrolytic etching. The conditions for electrolytic etching were an electrolyte temperature of 25°C and a current density of 8 A / dm 2 The current application time was 3 minutes. The resist characteristics were evaluated according to the following criteria: A or B was considered to be pass, and F was considered to be fail. (Evaluation criteria) A: The area ratio of discolored areas is 0.0% or less B: The area ratio of discolored areas is greater than 0.0% and less than 5.0% F: The area ratio of discolored areas is greater than 5.0%

[0070] <Removability> The test material for which the resist properties were evaluated was immersed in a 25% aqueous sodium hydroxide solution at 50°C for 10 seconds, then removed and washed with water to remove the etching resist film. The test surface of the test material after the etching resist film had been removed was visually observed, and the area ratio of the area where the etching resist film had peeled off was calculated to evaluate the removability. The removability was evaluated according to the following criteria. A rating of A or B was considered a pass, and an F was considered a fail. (Evaluation criteria) A: The area ratio of the peeled part is 100% B: The area ratio of peeled parts is 90% or more but less than 100% F: The area ratio of peeled parts is less than 90%

[0071] According to the evaluation results shown in Table 3, the etching resist films formed using the coating agent for forming an etching resist film according to the present invention passed the property evaluation results for all evaluation items. On the other hand, the test materials No. 18 to 22, in which the content of the coating agent for forming an etching resist film in terms of solid content did not satisfy the range of the content specified in the present invention, and the test material No. 23, in which a water-based epoxy resin was used as the resin, failed the property evaluation results for one of the evaluation items.

Claims

1. In the solvent, in terms of solid content, 100 parts by mass of aqueous alkyd resin, A melamine resin in an amount of 0.10 parts by mass or more and 30 parts by mass or less, and 5.0 parts by mass or more and 100 parts by mass or less of extender pigment It contains, The total amount of solids of the aqueous alkyd resin, the melamine resin, and the extender pigment accounts for 80% by mass or more of the total solids. A coating agent for forming etching resist films.

2. The aqueous alkyd resin is an aqueous alkyd resin obtained by reacting an alkyd resin with a polymerizable vinyl monomer. The coating agent for forming an etching resist film according to claim 1.

3. The proportion of the total solid content in the etching resist film forming coating agent is 10% by mass or more and 80% by mass or less. The coating agent for forming an etching resist film according to claim 1.

4. The proportion of the total solid content in the etching resist film forming coating agent is 10% by mass or more and 80% by mass or less. The coating agent for forming an etching resist film according to claim 2.

5. The solvent comprises ethylene glycol mono-n-butyl ether. A coating agent for forming an etching resist film according to any one of claims 1 to 4.