JP2006054244A - Electromagnetic steel sheet with heat-resistance adhesive insulating film and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic steel sheet with a heat-resistance adhesive insulating film which can be adhered by pressing and heating after it is punched or sheared and be annealed for relieving stress, and to provide its manufacturing method. <P>SOLUTION: The electromagnetic steel sheet with a heat-resistance adhesive insulating film is provided with a film made mainly of a thermoplastic siloxane polymer on at least one side of the steel sheet. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface-coated electrical steel sheet that can be bonded by pressurization and heating after punching or shearing and can be subjected to strain relief, and a method for producing the same.

  Non-oriented electrical steel sheets are mainly used as iron cores for motors and transformers. Usually, the surface of a non-oriented electrical steel sheet has an insulating film formed, and after punching continuously into a predetermined shape, it is generally laminated and integrated by a method such as welding or caulking. . Depending on the required magnetic properties, the iron core is subjected to strain relief after being integrated.

  In the method of integrating the magnetic steel sheets laminated by welding or caulking, there are problems that the iron core edge portion is short-circuited and insulation is lowered, and that magnetic characteristics are deteriorated due to processing strain. As a method for avoiding defects due to welding or caulking, a technique has been proposed in which an insulating film exhibiting adhesiveness is formed on a magnetic steel sheet in advance by thermocompression bonding and, after punching or shearing, laminated and thermocompression bonded. For example, a method for producing a surface-coated electrical steel sheet for adhesion (Patent Document 1), characterized in that a liquid mixture mainly composed of an acrylic modified epoxy resin emulsion blended with a latent curing agent is applied and incompletely baked (Patent Document 1), An electromagnetic steel sheet with an insulating film coated with an adhesive resin containing a foaming agent (Patent Document 2) has been proposed. These so-called adhesive coating techniques can alleviate the problems caused by caulking and welding, but since the steel sheet surface is coated with an organic resin, the adhesive strength cannot be maintained when strain relief annealing is performed. For this reason, although it is possible to use the electrical steel sheet which gave the adhesive coating about the core which does not perform distortion removal annealing, it cannot be used about the core which carries out distortion suppression for iron loss reduction.

  On the other hand, a method of fixing the magnetic steel sheet processed by punching or the like into a predetermined shape after strain relief is also conceivable, but it is necessary to apply an adhesive to each small punched piece, Workability is poor.

  In addition, as a method for producing a laminated sheet of amorphous alloy ribbon (Patent Document 3), if a heat resistant adhesive is applied to the amorphous alloy ribbon and laminated, it is annealed at a high temperature of 350 ° C. or higher. However, this heat-resistant adhesive is mainly composed of borosiloxane resin containing Si-O bond and BO bond as the main chain. is there.

Japanese Patent No. 2613725 JP 2002-260910 A International Publication WO 86/05314

  The present invention improves the heat resistance of the adhesive insulating film of the electromagnetic steel sheet with an adhesive insulating film that can be integrated with the iron core without welding and caulking, and even if the strain relief is performed, the adhesion state and the insulating property An object is to provide a magnetic steel sheet with a heat-resistant adhesive insulating film and a method for producing the same.

In order to solve the above problems, the following means are used.
(1) An electrical steel sheet with a heat-resistant adhesive insulating film, characterized by having a film mainly composed of a thermoplastic siloxane polymer on at least one surface of the steel sheet.
(2) The heat-resistant adhesive insulating film contains 50% or more of T nuclei bonded with methyl groups as Si nuclei with respect to all Si nuclei, and T ₃ nuclei out of T nuclei are 80% or more. (1) The electrical steel sheet with a heat-resistant adhesive insulating film.
(3) The electrical steel sheet with a heat-resistant adhesive insulating coating according to (2), wherein the heat-resistant adhesive insulating coating contains 0.5% or more and less than 20% of Si nuclei bonded with epoxy groups with respect to all Si nuclei. .
(4) A coating solution containing a thermoplastic siloxane polymer having a weight average molecular weight of 5000 or more and 100000 or less prepared by hydrolyzing one or both of organotrialkoxysilane or organotrichlorosilane in the presence of a hydrochloric acid catalyst is applied to at least one surface of a steel plate. A method for producing a magnetic steel sheet with a heat-resistant adhesive insulating film, characterized by baking.

  According to the present invention, it is possible to provide an electrical steel sheet with a heat-resistant adhesive insulating film that can be bonded by pressurization and heating after punching or shearing and can be subjected to strain relief annealing. Iron core can be integrated without welding and caulking, and iron loss deterioration due to welding and caulking can be avoided. Adhesive state and insulation are maintained even after strain relief annealing, so the iron core has excellent magnetic properties. Can be produced.

  In the present invention, a thermoplastic siloxane polymer layer is formed on at least one surface of the electrical steel sheet. Here, the siloxane polymer means that the inorganic component consists only of Si and O.

The inorganic polymer is a polymer in which a main skeleton is constituted by inorganic bonds of M (metal or semimetal) -O (oxygen) -M. When M is Si, the Si—O bond is called a siloxane bond. Si, like C, can be directly chemically bonded to an organic group or H like Si-CH ₃ , Si-C ₆ H ₅ , or Si-H. A modified inorganic polymer can be obtained. A siloxane polymer film in which M is Si may exhibit thermoplasticity or thermosetting properties depending on the structure of molecules constituting the film. When the siloxane skeleton is configured in a three-dimensional network, it is thermosetting. When a single-chain linear siloxane polymer is crosslinked, it often exhibits thermosetting properties. On the other hand, in the case of a film in which a linear siloxane polymer made of a triple chain or a ladder polymer described later is a main constituent, thermoplasticity is exhibited.

  When magnetic steel sheets having thermoplastic siloxane polymer layers on both sides are laminated, the upper and lower films softened by heating at the time of hot pressing are integrated, so that the magnetic steel sheets can be bonded during cooling. In addition, when magnetic steel sheets having a thermoplastic siloxane polymer layer only on one side are laminated in the same direction, the film component softened by heating spreads uniformly on the surface of the electromagnetic steel sheet without the thermoplastic siloxane polymer layer. Can be glued.

  The electrical steel sheet and the thermoplastic siloxane polymer layer are in close contact with the oxide film on the surface of the electrical steel sheet mainly through hydrogen bonds represented by Fe—O... HO—Si. This hydrogen bond shifts to a chemical bond represented by Fe—O—Si in a heat treatment process such as baking of the thermoplastic siloxane polymer layer, adhesion between the magnetic steel sheets, and strain relief. The surface of the electrical steel sheet is coated and baked with an inorganic-organic mixed treatment liquid mainly composed of magnesium chromate and an acrylic resin, or an inorganic treatment liquid composed of a mixed liquid of magnesium chromate, magnesium phosphate and boric acid. It may be covered with an insulating film generated in this way. When the surface of the electrical steel sheet is covered with an insulating film, the thermoplastic siloxane polymer layer adheres through hydrogen bonds such as Cr—O... HO—Si. This hydrogen bond is considered to shift to a chemical bond such as Cr—O—Si in the subsequent heat treatment process. The thermoplastic siloxane polymer is bonded to the surface of the electrical steel sheet through the inorganic component as described above, and the main skeleton is formed of an inorganic bond, so heat treatment such as adhesion by heat press, strain relief annealing, etc. Even if the organic component may be thermally decomposed in the process, the main skeleton remains as it is, so that the adhesiveness can be maintained.

  Even after the strain relief, the thermoplastic siloxane polymer layer functions as an oxide film composed of an Si—O—Si inorganic skeleton as described above, so that sufficient insulation can be maintained. In particular, when the surface of the electrical steel sheet is treated with an inorganic-organic mixed treatment liquid, an inorganic treatment liquid, or the like to form an insulating film such as a chromic acid, high insulation is exhibited.

  The temperature at which the thermoplastic siloxane polymer exhibits thermoplasticity for exhibiting adhesiveness needs to be 100 ° C. or higher. If thermoplasticity appears below 100 ° C., blocking resistance is reduced, which is not suitable. The upper limit of the hot press temperature may be equal to or lower than the strain relief temperature, but it is usually desirable to be 300 ° C. or lower because a high temperature hot press is expensive. The pressure of the hot press is preferably 0.1 MPa or more and 50 MPa or less, and particularly preferably 1 MPa or more and 20 MPa or less. When the pressure of the hot press is low, sufficient adhesiveness cannot be obtained, so that it is difficult to integrate as an iron core. When the pressure of hot pressing is high, the adhesive layer may flow and protrude from the interlayer.

  The temperature for strain relief is usually 650 ° C. or higher and 850 ° C. or lower.

Of the four bonds of Si, one of which forms a Si-R bond (R is an organic group or H) and the remaining three are Si-O bonds is called a T nucleus. Among the T nuclei, the number of those bonded to Si through O, that is, Si bonded to R of R-Si (-O-Si≡) ₃ is called T ₃ nucleus . Si nuclides can be examined by NMR. In general, examples of Si nuclei forming a siloxane polymer include D nuclei and Q nuclei in addition to T nuclei. In the D nucleus, two of Si's four bonds form Si-R (R is an organic group or H) bond, and the remaining two are Si-O bonds. The Q nucleus is a Si-O bond in four of the four Si bonds.

When the T ₃ nucleus Si repeats bonding according to a certain rule, a ladder molecule as shown in FIG. 1 is formed.

  When R is a methyl group, the degree of carbonization during the strain relief and the amount of gas generation are small, so that the adhesive strength after strain relief is particularly high.

A polymer composed of ladder-like molecules is entangled with ladder-like molecular chains by coating and baking, and a hardened surface state without stickiness or blocking is obtained. Molecular chains that have been entangled at 100 ° C. or higher are broken and become fluid, that is, thermoplastic. The thermoplastic siloxane polymer exhibiting the properties of a polymer composed of such ladder-shaped molecules includes 50% or more of T nuclei bonded with methyl groups as Si nuclei with respect to all Si, and T ₃ It is desirable that the nucleus is 80% or more, particularly preferably 95% or more. When the number of T nuclei bonded with methyl groups as Si nuclei is less than 50% of the total Si, carbonization during strain relief annealing becomes intense, or the adhesive layer expands due to gas generation, resulting in a decrease in adhesive strength. Therefore it is not suitable. If the number of T ₃ nuclei in the T nuclei is less than 80%, the formation of ladder molecules becomes difficult, which is not suitable. The ladder molecule shown in Fig. 1 is composed of 100% T ₃ nuclei. T ₃ nuclei are not necessarily ladder-like molecules, but a high proportion of T ₃ nuclei is a necessary condition for forming ladder-like molecules.

  In addition to the Si nucleus bonded to the methyl group, when the Si bonded to the epoxy group is contained in an amount of 0.5% or more and less than 20% with respect to the total Si, the adhesion between the heat-resistant adhesive insulating film and the electrical steel sheet is particularly high. When it is less than 0.5%, the effect of improving the adhesion is small. If it exceeds 20%, carbonization becomes violent, or the adhesive layer expands due to gas generation, resulting in a decrease in adhesive strength.

  The electrical steel sheet with a heat-resistant adhesive insulating film of the present invention is a thermoplastic siloxane having a mass average molecular weight of 5000 or more and 100000 or less obtained by hydrolysis under a hydrochloric acid catalyst using one or both of organotrialkoxysilane or organotrichlorosilane as a starting material. It can be produced using a polymer. Examples of organotrialkoxysilane include triethoxysilane, trimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, isobutyltrimethoxysilane, Isobutyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, glycidoxypropyltrimethoxysilane, glycidoxypropyltriethoxysilane, aminopropyltrimethoxysilane And aminopropyltriethoxysilane. Examples of the organotrichlorosilane include methyltrichlorosilane, ethyltrichlorosilane, and phenyltrichlorosilane.

  One or both of organotrialkoxysilane and organotrichlorosilane may be hydrolyzed after being dispersed in an organic solvent. As the solvent, various alcohols such as methanol, ethanol, propanol and butanol, acetone, toluene, xylene and the like can be used. The mass ratio of the organic solvent to the organoalkoxysilane at the time of hydrolysis is desirably 1: 0.5 to 1: 2.

  Hydrolysis is performed by adding 0.1 to 1 times as much water as the number of moles of all alkoxy groups in the starting material. Hydrochloric acid is added as a hydrolysis catalyst. When organotrichlorosilane is used as a raw material, hydrochloric acid is produced as a by-product by adding water, and hydrolysis is carried out under a hydrochloric acid catalyst without any special treatment. Sometimes it is good.

  The hydrolyzed sol is usually converted into a thermoplastic siloxane polymer by promoting the polycondensation reaction by a process such as concentration. Concentration is preferably carried out so that the organic solvent, by-product alcohol and the like are removed by a rotary evaporator or the like, and the mass of the concentrate is about 15 to 60% of the mass of the solution before the concentration. Concentration promotes the polycondensation reaction of organoalkoxysilane and increases the molecular weight. When the weight average molecular weight of the organoalkoxysilane is 5000 or more and 100,000 or less, a film exhibiting good thermoplasticity can be obtained. A molecular weight of less than 5000 is not suitable because it does not exhibit thermoplasticity after baking of the film. When the molecular weight exceeds 100,000, stickiness remains even after the film is baked, which is not suitable. As a method other than the concentration, a thermoplastic siloxane polymer can be obtained by adding an alkali such as KOH and refluxing in a nitrogen atmosphere to accelerate the polycondensation reaction.

  The thermoplastic siloxane polymer is usually diluted about 1.5 to 10 times with an organic solvent or water before coating to form a coating solution for forming a heat-resistant adhesive insulating film. Examples of the organic solvent for dilution include various alcohols such as methanol, ethanol, propanol and butanol, acetone, toluene, xylene and the like.

  The coating solution for forming a heat-resistant adhesive insulating film may contain diorganodialkoxysilane such as dimethoxydimethylsilane and diethoxydimethylsilane as a solute in addition to the thermoplastic siloxane polymer. The molar ratio of the diorganodialkoxysilane to the organotrialkoxysilane constituting the thermoplastic siloxane polymer is preferably 0.1 or less. When this ratio exceeds 0.1, the film becomes sticky after baking.

  One or more metal alkoxides selected from B, Si, Al, Ti, Zr, Nb, Ta, and W may be hydrolyzed simultaneously with the organoalkoxysilane to prepare a sol. By adding metal alkoxides of B, Al, Ti, Zr, Nb, Ta, and W, hydrolysis / polycondensation reaction of organoalkoxysilane is promoted. Since the metal alkoxides of Al, Ti, Zr, Nb, Ta, and W are all more reactive than alkoxysilane, some alkoxy groups are β-diketone, β-ketoester, alkanolamine, alkylalkanolamine, An alkoxide derivative substituted with an organic acid or the like may be used. The molar ratio of one or both of the metal alkoxide or alkoxide derivative other than Si to the total Si is preferably 0.1 or less. When this ratio exceeds 0.1, it is not preferable because the development of thermoplasticity becomes insufficient or the coating solution gels. Further, when a tetraalkoxide of Si such as tetraethoxysilane or tetramethoxysilane is added as a metal alkoxide, the film becomes hard and is not easily damaged. The molar ratio of Si tetraalkoxide to the organotrialkoxysilane constituting the thermoplastic siloxane polymer is preferably 0.3 or less. When this ratio exceeds 0.3, it becomes difficult to develop thermoplasticity as a whole film.

The prepared sol is applied to a magnetic steel sheet by a roll coater, bar coater, flow coater, dip coater, spray or the like. The coating amount is preferably 1 g / m ² or more and 30 g / m ² or less, particularly preferably 2 g / m ² or more and 10 g / m ² or less. After application, an electrical steel sheet with a heat-resistant adhesive insulating film can be produced by baking at 50 to 200 ° C.

  First, three types of thermoplastic siloxane polymer precursors were prepared.

Thermoplastic precursor A
Hydrolysis was performed by adding dropwise a mixed aqueous solution of 35.3 g of water and 1.04 g of 35% hydrochloric acid to a liquid for mixing 178 g of methyltriethoxysilane and 138 g of ethanol. The hydrolyzed liquid was concentrated using a rotary evaporator until no solvent was produced at 58 ° C. The mass of the concentrate was 30% of the solution mass before concentration. The mass average molecular weight of this concentrate was 10,000. Since this concentrate showed spinnability, it is considered that methyltriethoxysilane was polymerized in the form of a chain polymer. When this concentrate was heat-treated at 70 ° C for 15 minutes, it solidified, but softened from around 180 ° C and showed thermoplasticity. This concentrate is called thermoplastic precursor A.

Thermoplastic precursor B
Hydrolysis was performed by adding dropwise a mixed aqueous solution of 35.3 g of water and 1.04 g of 35% hydrochloric acid to a liquid for mixing 178 g of methyltriethoxysilane and 138 g of ethanol. The hydrolyzed liquid was concentrated using a rotary evaporator until no solvent was produced at 85 ° C. The mass of the concentrate was 21% of the solution mass before concentration. This concentrate had a weight average molecular weight of 27000. This concentrate also exhibited spinnability and thermoplasticity. This concentrate is called thermoplastic precursor B.

Thermoplastic precursor C
Hydrolysis was performed by adding dropwise a mixed aqueous solution of 35.3 g of water and 1.04 g of 35% hydrochloric acid into a mixture for mixing 240 g of phenyltriethoxysilane and 138 g of ethanol. The hydrolyzed liquid was concentrated using a rotary evaporator until no solvent was produced at 58 ° C. The mass of the concentrate was 40% of the solution mass before concentration. The concentrate had a mass average molecular weight of 20000. This concentrate also exhibited spinnability and thermoplasticity. This concentrate is called thermoplastic precursor C.

  Next, a siloxane-based sol containing a glycidoxypropyl group was synthesized.

Ep-1
Acetic acid (1.8 g), tetraethoxytitanium (2.3 g), and glycidoxypropyltriethoxysilane (278.4 g) were stirred for 24 hours.

Ep-2
12.6 g of acetic acid, 16.0 g of tetraethoxytitanium, 62.5 g of tetraethoxysilane, and 194.9 g of glycidoxypropyltriethoxysilane were stirred for 24 hours.

Ep-3
Acetic acid 5.4 g, tetraethoxytitanium 6.8 g, tetraethoxysilane 145.8 g, and glycidoxypropyltriethoxysilane 278.4 g were stirred for 24 hours.

  Each of these precursors was mixed with a dilute solution and a siloxane-based sol containing a glycidoxypropyl group in the proportions shown in Table 1 to obtain a coating solution.

  The sol shown in the comparative example was synthesized as follows.

Non-thermoplastic sol A
178 g of methyltriethoxysilane and 152 g of tetramethoxysilane are dispersed in 270.3 g of 2-ethoxyethanol. Sol A was prepared by hydrolyzing by adding 36 g of water using 4.8 g of acetic acid as a catalyst.

Non-thermoplastic sol B
260.28 g of ethyl acetoacetate and 227.9 g of tetraethoxytitanium were dispersed in 92 g of ethanol, and 1500 g of polydimethylsiloxane having an average molecular weight of 3000 modified by carbinol at both ends was added and stirred. Sol B was prepared by adding dropwise a mixed solution of 92 g of ethanol and 36 g of water.

In Examples and Comparative Examples, each coating solution was applied on both sides of a non-oriented electrical steel sheet having a thickness of 0.5 mm shown in Table 1 with a roll coater, and baked in an oven set at 70 ° C. for 15 minutes. The coating amount was 7 g / m ² . In any case, there was no stickiness of the film surface after baking.

Two pieces of a test piece having a width of 3 cm and a length of 10 cm were used, and a part of the test piece was overlapped so that the area of the bonded portion was 6 cm ² , followed by hot pressing. Prior to hot pressing, the applied film other than the bonded part was scraped off. Two test pieces were bonded by a hot press at 200 ° C. for 1 minute and 10 MPa. The strain relief was performed in nitrogen at 750 ° C. for 2 hours. The adhesive strength before and after strain relief annealing was evaluated using the shear tensile strength, which is the horizontal strength of the bonded surface. The results were as shown in Table 1.

  Since Comparative Examples 1 to 3 used a siloxane-based polymer that did not exhibit thermoplasticity, they could not be bonded by hot pressing. Comparative Examples 4 and 5 are conventionally used as an adhesive coat. Since the coating liquid is organic and the organic is thermally decomposed during strain relief annealing, the adhesive strength after strain relief annealing cannot be obtained. On the other hand, in Examples 1 to 10 of the present invention, the adhesive strength after strain relief annealing is obtained, and the electrical steel sheet with an adhesive insulating film that can be integrated with the iron core without performing welding or caulking. It was confirmed that it could be provided.

The figure which shows the structure of a ladder-like siloxane polymer.

Claims (4)

  An electrical steel sheet with a heat-resistant adhesive insulating coating, comprising a coating composed mainly of a thermoplastic siloxane polymer on at least one surface of the steel plate. The heat-resistant adhesive insulating film contains 50% or more of T nuclei bonded with methyl groups as Si nuclei with respect to all Si nuclei, and T ₃ nuclei out of T nuclei is 80% or more. Item 2. An electrical steel sheet with a heat-resistant adhesive insulating film according to Item 1.   3. The electrical steel sheet with a heat-resistant adhesive insulating coating according to claim 2, wherein the heat-resistant adhesive insulating coating contains 0.5% or more and less than 20% of Si nuclei bonded with epoxy groups with respect to all Si nuclei.   A coating solution for forming a heat-resistant adhesive insulating film containing a thermoplastic siloxane polymer having a mass average molecular weight of 5000 or more and 100,000 or less prepared by hydrolyzing one or both of organotrialkoxysilane and organotrichlorosilane in a hydrochloric acid catalyst A method for producing a magnetic steel sheet with a heat-resistant adhesive insulating film, characterized by being applied to one side and baked.

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