Method for producing polysiloxane resin and use thereof

Abstract

To provide a production method that can yield a polysiloxane resin applicable to a coating film exhibiting superior durability when subjected to repeated thermal and cold shocks.SOLUTION: A production method according to the present disclosure comprises a step of subjecting silane compounds (A) and (B) to dehydration condensation in the presence of water and a dehydration condensation catalyst to obtain a dehydration-condensed product, and a step of adding a monomer (C) to the dehydration-condensed product and obtaining a polysiloxane resin by performing radical polymerization, wherein an amount of water used relative to a total number of hydrolyzable groups in the silane compounds (A) and (B), a glass transition temperature of a graft chain derived from the monomer (C) in the polysiloxane resin, and a proportion of structural units derived from the silane compounds (A) and (B) in the polysiloxane resin are within specific ranges.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a polysiloxane resin and its use. [Background technology]

[0002] Polysiloxanes, which are inorganic polysiloxanes grafted with acrylics, which have organic properties (hereinafter referred to as "polysiloxane-based resins"), have attracted industrial attention due to their interesting properties as inorganic-organic hybrid resins.

[0003] In particular, in the field of paints, water-based paints containing polysiloxane resins are becoming increasingly popular in the market due to their minimal adverse effects on the human body and the environment, and there is a growing demand for them in a variety of applications.

[0004] For example, Patent Document 1 discloses a polysiloxane resin having a polymer containing, as a structural unit, a structural unit derived from a monomer having a radical polymerizable group, the monomer including (i) a monomer that is soluble in water and does not form micelles in water, and (ii) a monomer that can form micelles in water.

[0005] Patent Document 2 also discloses a photocatalyst-supported structure having a photocatalyst layer on a substrate via an adhesive layer containing an aqueous silicone-modified resin. Patent Document 2 also discloses that the aqueous silicone-modified resin is a resin obtained by a method including a step of preparing a polymer having a hydrolyzable silyl group and an acid group by polymerizing a polymerizable monomer in a mixture containing specific components. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2022 / 202269 [Patent Document 2] International Publication No. 2016 / 157841 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the above-mentioned conventional techniques have room for improvement in terms of durability of coating films obtained from polysiloxane-based resins when subjected to repeated thermal and cold stimuli. One aspect of the present invention aims to realize a production method for obtaining polysiloxane-based resins that can be used for coating films that have excellent durability when subjected to repeated thermal and cold stimuli. [Means for solving the problem]

[0008] In order to solve the above problems, a method for producing a polysiloxane resin according to one aspect of the present invention includes mixing a silane compound (A) having a radically polymerizable unsaturated group and a hydrolyzable silyl group, and a silane compound other than the silane compound (A) represented by the following general formula (I): R 1 n -Si-(OR 2 ) 4-n (I) (In the formula, R 1 are each independently an alkyl group having 1 to 10 carbon atoms or an unsubstituted or substituted aryl group, and R 2 are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n is an integer of 0 to 3. The method includes a first step of dehydrating and condensing a silane compound (A) represented by the formula (I) in the presence of water and a dehydration condensation catalyst to obtain a dehydration condensate, and a second step of adding a monomer (C) having a radically polymerizable unsaturated group to the dehydration condensate obtained in the first step and conducting radical polymerization to obtain a polysiloxane resin, wherein in the first step, 0.9 equivalents or more of the water is used relative to the total number of hydrolyzable groups in the silane compound (A) and the silane compound (B), the polysiloxane resin obtained in the second step has a glass transition temperature of -10°C to 9°C, and the proportion of structural units derived from the silane compound (A) and the silane compound (B) in 100% by weight of the polysiloxane resin is 25 to 45% by weight. [Effects of the Invention]

[0009] According to one aspect of the present invention, a production method can be provided that can obtain a polysiloxane-based resin that can be used for a coating film that has excellent durability when subjected to repeated thermal stimulation. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described in detail below. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more and B or less."

[0011] 1. Method for producing polysiloxane resin A method for producing a polysiloxane resin according to one embodiment of the present invention includes the following steps: a first step of dehydrating and condensing a silane compound (A) having a radically polymerizable unsaturated group and a hydrolyzable silyl group with a silane compound (B) other than the silane compound (A) and represented by general formula (I) in the presence of water and a dehydration condensation catalyst to obtain a dehydration condensate; and a second step of adding a monomer (C) having a radically polymerizable unsaturated group to the dehydration condensate obtained in the first step and conducting radical polymerization to obtain a polysiloxane resin. In the first step, the water is used in an amount of 0.9 equivalents or more relative to the total number of hydrolyzable groups in the silane compound (A) and the silane compound (B). The glass transition temperature (Tg) of the graft chain derived from the monomer (C) in the polysiloxane resin obtained in the second step is −10°C to 9°C. The proportion of the structural units derived from the silane compound (A) and the silane compound (B) in 100% by weight of the polysiloxane resin is 25 to 45% by weight.

[0012] Polysiloxane resins have siloxane bonds with high bond energy in their main chains, and therefore are expected to have high weather resistance when used as coating resins. However, conventional polysiloxane resins are brittle and prone to cracking, so there is room for improvement in terms of durability of coating films obtained from polysiloxane resins when subjected to repeated thermal and thermal stimuli.

[0013] In the first step of the production method, the amount of water used relative to the total number of hydrolyzable groups in the silane compound (A) and the silane compound (B) is 0.9 equivalents or more, thereby increasing the degree of condensation of the resulting polysiloxane resin, i.e., promoting the conversion of the hydrolyzable groups to siloxane bonds. By achieving a high degree of condensation in the polysiloxane resin before curing, cracking due to shrinkage after curing of the polysiloxane resin can be reduced.

[0014] In addition, in the above-described production method, a polysiloxane resin having graft chains can be obtained through the first and second steps. By controlling the Tg of the graft chains to a relatively low range, flexibility can be imparted to the graft chains. Furthermore, by controlling the ratio of structural units derived from the silane compound (A) and the silane compound (B), a balance can be achieved between the hardness due to the main chain of the polysiloxane resin and the softness due to the graft chains.

[0015] As a result, a polysiloxane-based resin usable for coating films having excellent durability when subjected to repeated thermal stimulation can be obtained. In this specification, durability when subjected to repeated thermal stimulation in a humid environment is also referred to as "humid thermal resistance." The obtained polysiloxane-based resin also has excellent water resistance.

[0016] Patent Documents 1 and 2 do not disclose a production method for controlling three factors: the amount of water used relative to the hydrolyzable groups in the silane compound (A), the glass transition temperature of the graft chain derived from the monomer (C) in the polysiloxane resin, and the proportion of structural units derived from the silane compounds (A) and (B) in the polysiloxane resin. Therefore, it has not been easy to obtain the above-mentioned polysiloxane resin using conventional techniques.

[0017] The polysiloxane resin obtained by this production method can be used in a dissolved or dispersed state in an aqueous medium that has minimal adverse effects on the human body and the environment, and can therefore contribute to the achievement of Sustainable Development Goals (SDGs), such as Goal 12, "Ensure sustainable consumption and production patterns."

[0018] <1st process> The first step is a step of obtaining a dehydration condensation product by dehydration condensation of a silane compound (A) having a radically polymerizable unsaturated group and a hydrolyzable silyl group with a silane compound (B) represented by general formula (I) other than the silane compound (A) in the presence of water and a dehydration condensation catalyst. In the first step, hydrolysis is also carried out in addition to the dehydration condensation.

[0019] The dehydration condensate is a dehydration condensate of silane compound (A) and silane compound (B). The dehydration condensate can also be considered a co-condensate of silane compound (A) and silane compound (B). The dehydration condensate can serve as the main chain of the polysiloxane resin obtained in the second step. The dehydration condensate is also called a polysiloxane macromer.

[0020] The silane compound (A) has a radically polymerizable unsaturated group and a hydrolyzable silyl group. In the first step, the silane compound (A) undergoes dehydration condensation with itself and / or with the silane compound (B) to form a polysiloxane macromer. In the second step described below, the radically polymerizable unsaturated group in the silane compound (A) undergoes radical polymerization with the radically polymerizable unsaturated group derived from the monomer (C). This forms a graft chain derived from the monomer (C). In the first step, since a certain amount of structural units derived from the silane compound (A) are contained in the polysiloxane macromer, the radical polymerization in the second step proceeds smoothly.

[0021] In one embodiment of the present invention, the silane compound (A) is represented by the following general formula (II): R 3 a R 4b -Si-(OR 5 ) 4-a―b (II) (In the formula, R 3 is a substituted alkyl group or alkenyl group having 1 to 10 carbon atoms and having a radically polymerizable unsaturated group, or an aryl group having a radically polymerizable unsaturated group and optionally having other substituents, and R 4 are each independently an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, or an unsubstituted or substituted aryl group, and R 5 are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, and a+b is an integer of 1 to 3.

[0022] In general formula (II), it is particularly preferable that a is 1 and b is 0 or 1. The radically polymerizable unsaturated group is not particularly limited, but examples thereof include a (meth)acryloyl group and a (meth)acrylamide group.

[0023] R 3is a substituted alkyl group having a radical polymerizable unsaturated group, examples of the silane compound include (meth)acryloxymethyltrimethoxysilane, (meth)acryloxymethylmethyldimethoxysilane, (meth)acryloxymethyldimethylmethoxysilane, (meth)acryloxymethyltriethoxysilane, (meth)acryloxymethylmethyldiethoxysilane, (meth)acryloxymethyldimethylethoxysilane, 2-(meth)acryloxyethyltrimethoxysilane, 2-(meth)acryloxyethylmethyldimethoxysilane, 2- (Meth)acryloxyethyl dimethyl methoxy silane, 2-(meth)acryloxyethyl triethoxy silane, 2-(meth)acryloxyethyl methyl diethoxy silane, 2-(meth)acryloxyethyl dimethyl ethoxy silane, γ-(meth)acryloxypropyl trimethoxy silane, γ-(meth)acryloxypropyl methyl dimethoxy silane, γ-(meth)acryloxypropyl dimethyl methoxy silane, γ-(meth)acryloxypropyl triethoxy silane, γ-(meth)acryloxypropyl methyl diethoxy silane, γ- (Meth)acryloxypropyldimethylethoxysilane, 4-(meth)acryloxybutyltrimethoxysilane, 4-(meth)acryloxybutylmethyldimethoxysilane, 4-(meth)acryloxybutyldimethylmethoxysilane, 4-(meth)acryloxybutyltriethoxysilane, 4-(meth)acryloxybutylmethyldiethoxysilane, 4-(meth)acryloxybutyldimethylethoxysilane, 5-(meth)acryloxypentyltrimethoxysilane, 5-(meth)acryloxypentylmethyldimethoxysilane, 5-(meth)acryloxypentylmethyldimethoxysilane p) acryloxypentyldimethylmethoxysilane, 5-(meth)acryloxypentyltriethoxysilane, 5-(meth)acryloxypentylmethyldiethoxysilane, 5-(meth)acryloxypentyldimethylethoxysilane, 6-(meth)acryloxyhexyltrimethoxysilane, 6-(meth)acryloxyhexylmethyldimethoxysilane, 6-(meth)acryloxyhexyldimethylmethoxysilane, 6-(meth)acryloxyhexyltriethoxysilane, 6-(meth)acryloxyhexylmethyldiethoxysilane,6-(meth)acryloxyhexyldimethylethoxysilane, etc.

[0024] R 3 Examples of the silane compound in which is an alkenyl group include vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, etc. The alkenyl group is also included in the radical polymerizable unsaturated group.

[0025] R 3 is an aryl group having a radically polymerizable unsaturated group and optionally having other substituents, examples of the silane compound include p-styryltrimethoxysilane, p-styrylmethyldimethoxysilane, p-styryldimethylmethoxysilane, p-styryltriethoxysilane, p-styrylmethyldiethoxysilane, and p-styryldimethylethoxysilane.

[0026] Among these, R is the most popular from the viewpoint of versatility. 3 As the alkyl group, a (meth)acryloyl group-substituted alkyl group or alkenyl group is preferred.

[0027] R 4 Examples of the alkyl group in R include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, an amyl group, an isoamyl group, a hexyl group, a cyclohexyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a heptyl group, an isoheptyl group, an n-octyl group, an isooctyl group, and a 2-ethylhexyl group. 4 Examples of the aryl group in R include a phenyl group, a naphthyl group, and a benzyl group. When a is 1 and b is 1, R 4 is preferably a methyl group.

[0028] R 5Examples of the alkyl group in R include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a nonyl group, and a decyl group. From the viewpoint of facilitating condensation of the silane compound (A) with the silane compound (B), R 5 The alkyl group preferably has 1 to 3 carbon atoms, and is most preferably a methyl group having 1 carbon atom.

[0029] The amount of silane compound (A) is preferably 1% by weight or more, more preferably 2% by weight or more, based on 100% by weight of the total amount of the polysiloxane resin. When the amount of silane compound (A) is 1% by weight or more, based on 100% by weight of the total amount of the polysiloxane resin, sufficient graft polymerization can be achieved directly or indirectly with the monomer (C). As a result, a polysiloxane resin with excellent storage stability can be obtained. Furthermore, the upper limit of the amount of silane compound (A) is not particularly limited as long as the effects of the present invention are achieved, but it is preferably 10% by weight or less, more preferably 8% by weight or less.

[0030] The silane compound (B) is a silane compound represented by the general formula (I): R 1 n -Si-(OR 2 ) 4-n (I) (In the formula, R 1 are each independently a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or an unsubstituted or substituted aryl group, and R 2 are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n is an integer of 0 to 3. The silane compound (B) is a compound having a hydrolyzable silyl group represented by the following formula: The silane compound (B) does not have a radically polymerizable unsaturated group.

[0031] In the first step, the silane compound (B) undergoes dehydration condensation with the silane compound (A) and / or with itself to form a polysiloxane macromer. The silane compound (B) is a main component constituting the polysiloxane chain, which is the main chain.

[0032] R 1 Examples of the alkyl group in R include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, an amyl group, an isoamyl group, a hexyl group, a cyclohexyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a heptyl group, an isoheptyl group, an n-octyl group, an isooctyl group, and a 2-ethylhexyl group. 1 Examples of the aryl group in the formula (I) include a phenyl group, a naphthyl group, and a benzyl group.

[0033] R 2 Examples of the alkyl group in include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a nonyl group, and a decyl group.

[0034] Specific compounds represented by general formula (I) include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane, propyltrimethoxysilane, propyltriethoxysilane, propyltriisopropoxysilane, butyltrimethoxysilane, butyltriethoxysilane, butyltriisopropoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, hexyltriisopropoxysilane, octyltrimethoxysilane, and octyltriethoxysilane. , octyltriisopropoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriisopropoxysilane, dimethyldimethoxysilane, diphenyldimethoxysilane, trimethylmonomethoxysilane, triphenylmonomethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and the like.

[0035] The silane compound (B) preferably has a trialkoxysilyl group. That is, the silane compound (B) is preferably a trialkoxysilane compound in which n is 1. When n is 1, there are three crosslinkable hydrolyzable groups, and a polymer with a network structure can be formed. Specific examples of compounds in which n is 1 are suitable from the viewpoint of availability, such as methyltrimethoxysilane and phenyltrimethoxysilane.

[0036] From the viewpoint of facilitating condensation of the silane compound (B) with the silane compound (A), R 2 The alkyl group preferably has 1 to 3 carbon atoms, and most preferably 1 carbon atom.

[0037] The amount of silane compound (B) is preferably 10% by weight or more, more preferably 20% by weight or more, and even more preferably 40% by weight or more, based on 100% by weight of the total amount of polysiloxane resin. When the amount of silane compound (B) is 10% by weight or more, based on 100% by weight of the total amount of polysiloxane resin, the polysiloxane resin exhibits effects such as excellent weather resistance, toughness, tackiness, etc. Furthermore, the upper limit of the amount of silane compound (B) is not particularly limited as long as the effects of the present invention are exhibited, but is, for example, 90% by weight or less.

[0038] The dehydration condensation catalyst is a catalyst that promotes the dehydration condensation in the first step. Examples of the dehydration condensation catalyst include neutral catalysts, acidic catalysts, and basic catalysts. From the viewpoint of ease of use, neutral catalysts or acidic catalysts are preferred.

[0039] The neutral catalyst may be a neutral salt. The use of a neutral salt as a catalyst makes it possible to obtain a polysiloxane macromer with an appropriate degree of condensation, and as a result, to obtain a solution or dispersion containing a polysiloxane resin in water with excellent storage stability.

[0040] Furthermore, the use of a neutral salt as a catalyst in the first step has the following advantages. Polysiloxane resins can be obtained without deactivating the organic substituents before, after, or during storage after hydrolysis and dehydration condensation. · The neutral salt itself does not corrode manufacturing or storage containers, so it can be used without restrictions on the materials of manufacturing or storage equipment. The complicated steps of removing the acid or base and neutralizing the catalyst, which are required when an acidic or basic catalyst is used, can be omitted.

[0041] As used herein, the term "neutral salt" refers to a positive salt composed of an acid and a base. There are no particular limitations on the neutral salt, but salts composed of a combination of a cation selected from the group consisting of Group 1 element ions, Group 2 element ions, tetraalkylammonium ions, and guanidium (guanidinium) ions, and an anion selected from the group consisting of Group 17 element ions excluding fluoride ions, sulfate ions, nitrate ions, and perchlorate ions are preferred.

[0042] The neutral salt is not particularly limited, but examples thereof include lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, francium chloride, beryllium chloride, magnesium chloride, calcium chloride, strontium chloride, barium chloride, radium chloride, tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetrabutylammonium chloride, tetrapentylammonium chloride, tetrahexylammonium chloride, and guanidium chloride; lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, francium bromide, beryllium bromide, magnesium bromide, calcium bromide, strontium bromide, barium bromide, radium bromide, tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide, tetrapentylammonium bromide, tetrahexylammonium bromide, and guanidium bromide. Lithium iodide, sodium iodide, potassium iodide, rubidium iodide, cesium iodide, francium iodide, beryllium iodide, magnesium iodide, calcium iodide, strontium iodide, barium iodide, radium iodide, tetramethylammonium iodide, tetraethylammonium iodide, tetrapropylammonium iodide, tetrabutylammonium iodide, tetrapentylammonium iodide, tetrahexylammonium iodide, guanidium iodide; Lithium sulfate, sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate, francium sulfate, beryllium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, barium sulfate, radium sulfate, tetramethylammonium sulfate, tetraethylammonium sulfate, tetrapropylammonium sulfate, tetrabutylammonium sulfate, tetrapentylammonium sulfate, tetrahexylammonium sulfate, guanidium sulfate;Lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate, francium nitrate, beryllium nitrate, magnesium nitrate, calcium nitrate, strontium nitrate, barium nitrate, radium nitrate, tetramethylammonium nitrate, tetraethylammonium nitrate, tetrapropylammonium nitrate, tetrabutylammonium nitrate, tetrapentylammonium nitrate, tetrahexylammonium nitrate, guanidium nitrate; lithium perchlorate, sodium perchlorate, potassium perchlorate, rubidium perchlorate, cesium perchlorate, francium perchlorate, beryllium perchlorate, magnesium perchlorate, calcium perchlorate, strontium perchlorate, barium perchlorate, radium perchlorate, tetramethylammonium perchlorate, tetraethylammonium perchlorate, tetrapropylammonium perchlorate, tetrabutylammonium perchlorate, tetrapentylammonium perchlorate, tetrahexylammonium perchlorate, guanidium perchlorate, etc.;

[0043] Among these neutral salts, from the viewpoint of use as a catalyst, compounds that generate a highly nucleophilic Group 17 element ion as an anion are more preferred, and compounds that generate a chloride ion, a bromide ion, or an iodide ion are even more preferred.

[0044] Furthermore, in consideration of availability and safety during handling, the following neutral salts are particularly preferred: lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, magnesium chloride, calcium chloride, strontium chloride, lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, magnesium bromide, calcium bromide, strontium bromide, lithium iodide, sodium iodide, potassium iodide, rubidium iodide, cesium iodide, magnesium iodide, calcium iodide, strontium iodide, tetrabutylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium iodide.

[0045] As the acidic catalyst, an organic acid is preferred in view of compatibility with the silane compound, and a phosphoric acid ester or a carboxylic acid can be suitably used. Examples of the organic acid include ethyl acid phosphate, butyl acid phosphate, dibutyl pyrophosphate, butoxyethyl acid phosphate, 2-ethylhexyl acid phosphate, isotridecyl acid phosphate, dibutyl phosphate, bis(2-ethylhexyl)phosphate, formic acid, acetic acid, butyric acid, and isobutyric acid.

[0046] As the basic catalyst, an organic base is preferred due to its compatibility with the silane compound and the dilution solvent, and an amine compound can be suitably used. Examples of the organic base include triethylamine, diazabicycloundecene, and 1,4-diazabicyclo[2.2.2]octane.

[0047] These dehydration condensation catalysts may be used alone or in combination of two or more.

[0048] The amount of the dehydration condensation catalyst is preferably 0.1 ppm to 50,000 ppm, more preferably 1 ppm to 10,000 ppm, even more preferably 5 ppm to 1,000 ppm, and particularly preferably 10 ppm to 500 ppm, relative to the total amount of the silane compound (A) and the silane compound (B). When the amount of the dehydration condensation catalyst is 0.1 ppm or more, the catalyst functions appropriately. When the amount of the dehydration condensation catalyst is 50,000 ppm or less, the effects of suppressing the rapid progress of the reaction and suppressing a decrease in water resistance due to residual salts are achieved.

[0049] In the first step, water is also used. This water is also referred to as "condensation water." The amount of condensation water in the first step is 0.9 equivalents or more, and may be 1.0 equivalents or more, or even 1.1 equivalents or more, relative to the total number of hydrolyzable groups in the silane compound (A) and the silane compound (B). The amount of condensation water in the first step is preferably 3.0 equivalents or less, more preferably 2.5 equivalents or less, even more preferably 2.0 equivalents or less, and particularly preferably 1.5 equivalents or less, relative to the total number of hydrolyzable groups in the silane compound (A). The hydrolyzable group in the silane compound (A) is, for example, OR in the general formula (II). 5 The hydrolyzable group in the silane compound (B) refers to, for example, OR in the general formula (I). 2 Refers to...

[0050] If the amount of condensation water is 0.9 equivalents or more, the hydrolysis and dehydration condensation of the silane compound can be promoted, increasing the degree of condensation and improving the resistance to wet, cold, and water. If the amount of condensation water is 3.0 equivalents or less, the degree of condensation can be prevented from becoming too high, and the progression of gelation during synthesis can be suppressed.

[0051] In the first step, an organic solvent is generated as a result of dehydration condensation and hydrolysis. Examples of the organic solvent generated in the first step include methanol, ethanol, and 2-propanol.

[0052] <Second process> The second step is a step of adding a monomer (C) having a radically polymerizable unsaturated group to the dehydration condensate obtained in the first step and carrying out radical polymerization to obtain a polysiloxane resin. The monomer (C) is a monomer having a radically polymerizable unsaturated group but not a hydrolyzable silyl group. In the second step, the radically polymerizable unsaturated group in the monomer (C) undergoes radical polymerization with the radically polymerizable unsaturated group derived from the silane compound (A), forming a graft chain derived from the monomer (C) on the polysiloxane main chain.

[0053] The radically polymerizable unsaturated group in the monomer (C) is not particularly limited as long as it can contribute to radical polymerization with the silane compound (A), etc. Examples of the radically polymerizable unsaturated group in the monomer (C) include a (meth)acryloyl group, a (meth)acrylamide group, and a vinyl group.

[0054] The Tg of the graft chain derived from the monomer (C) in the polysiloxane resin obtained in the second step is −10° C. or higher, and may be −7° C. or higher, or may be −5° C. or higher. From the viewpoint of resistance to wet heat and cold, the Tg of the graft chain is 9° C. or lower, preferably 7° C. or lower, and more preferably 5° C. or lower. In this specification, the Tg of the graft chain means the value calculated by Fox's formula (T.G. Fox, Bull. Am. Phys. Soc. 1, 123 (1956)).

[0055] The proportion of the structural units derived from the silane compound (A) and the silane compound (B) in 100% by weight of the polysiloxane resin is 25% by weight or more, preferably 30% by weight or more, from the viewpoint of water resistance, and 45% by weight or less, preferably 40% by weight or less, from the viewpoint of humidity resistance.

[0056] The proportion of the structural units derived from the monomer (C) in 100% by weight of the polysiloxane resin is preferably 55% by weight or more, more preferably 60% by weight or more, from the viewpoint of humidity resistance, cold resistance, and weather resistance, and the proportion of the structural units derived from the monomer (C) is preferably 75% by weight or less, more preferably 70% by weight or less.

[0057] The monomer (C) preferably contains a monomer (C1) having a salt structure consisting of an acid and a base and having a radically polymerizable unsaturated group, and a monomer (C2) not having the salt structure and having a radically polymerizable unsaturated group. By using the monomer (C1), a polysiloxane resin that is easily soluble or dispersible in water can be obtained. Furthermore, by using the monomer (C2) in combination, a polysiloxane resin with superior water resistance can be obtained.

[0058] Examples of the monomer (C1) include sodium sulfoethyl methacrylate, sodium 2-(methacryloyloxy)ethanesulfonate, sodium 2-(methacryloyloxy)polyalkyleneoxide sulfonate, sodium acrylamido-t-butylsulfonate, potassium 2-(methacryloyloxy)ethanesulfonate, potassium 2-(methacryloyloxy)polyalkyleneoxide sulfonate, potassium acrylamido-t-butylsulfonate, calcium 2-(methacryloyloxy)ethanesulfonate, 2-(methacryloyloxy)polya Examples of the alkylene oxide sulfonate include calcium alkylene oxide sulfonate, calcium acrylamido-t-butyl sulfonate, ammonium sulfoethyl methacrylate, ammonium 2-(methacryloyloxy)ethanesulfonate, ammonium 2-(methacryloyloxy)polyalkylene oxide sulfonate, ammonium acrylamido-t-butyl sulfonate, sodium acrylate, potassium acrylate, calcium acrylate, ammonium acrylate, sodium methacrylate, potassium methacrylate, calcium methacrylate, and ammonium methacrylate.

[0059] The monomer (C1) can be obtained as a commercially available product. Examples of such commercially available products include "Antox MS-2N-D" manufactured by Nippon Nyukazai Co., Ltd., "ATBS-Na" manufactured by Toagosei Co., Ltd., "Eleminol RS-3000" manufactured by Sanyo Chemical Industries, Ltd., "sodium acrylate" and "potassium acrylate" manufactured by Asada Chemical Industry Co., Ltd., and Adeka Reasop SR-05, SR-10, SR-20, SR-1025, SR-2025, SR-3025, SR-10S, NE-10, NE-20, NE-30, NE-40, SE-10, SE-20, ER-10, ER-20, ER-30, and the like manufactured by ADEKA Corporation. ER-40, Nippon Nyukazai Co., Ltd.'s Antox-MS-60, RMA-1120, RMA-564, RMA-568, RMA-506, MA-30, MA-50, MA-100, MA-150, MPG130-MA, MPG-130MA, RMA-150M, RMA-300M, RMA-450M, RA-1020, RA-1820, Daiichi Kogyo Seiyaku Co., Ltd.'s Aqualon KH-05, KH-10, RN-20, RN-30, RN-50, RN-2025, HS-10, HS-20, HS-1025, BC05, BC10, BC0515, BC10 25, Sanyo Chemical Industries, Ltd. Eleminol JS-2, JS-20, RS-30, Kao Corporation Latemul S-180, S-180A, PD-104, PD-420, PD-430, NOF Corporation Blenmar PE-90, PE-200, PE-350, AE-90, AE-200, AE-350, PP-500, PP-800, PP-1000, AP-400, AP-550, AP-800, 700PEP-350B, 10PEP-550B, 55PET-400, 30PET-800, 55PET-800, 30PPT-800, 50P PT-800, 70PPT-800, PME-100, PME-200, PME-400, PME-1000, PME-4000, AME-400, 50POEP-800B, 50AOEP-800B, AEP, AET, APT, PLE, ALE, PSE, ASE, PKE, AKE, PNE, ANE, PNP, ANP, PNEP-600, Kyoeisha Chemical Co., Ltd. Light Ester 130MA, 041MA, MTG, Light Acrylate EC-A, MTG-A, 130A, DPM-A, P-200A, NP-4EA, NP-8EA, EHDG-A,Examples include NK-ESTER M-20G, M-40G, M-90G, M-230G, AMP-10G, AMP-20G, AMP-60G, AM-90G, and LA manufactured by Shin-Nakamura Chemical Co., Ltd.

[0060] The amount of monomer (C1) is preferably 1% by weight or more, more preferably 5% by weight or more, based on 100% by weight of the total amount of polysiloxane resin. When the amount of monomer (C1) is 1% by weight or more, the polysiloxane resin can be easily uniformly dispersed or solubilized in water. There is no particular upper limit to the amount of monomer (C1) based on 100% by weight of the total amount of polysiloxane resin as long as the effects of the present invention are achieved, but it is preferably 30% by weight or less, more preferably 20% by weight or less.

[0061] These monomers (C1) can be used alone or in combination of two or more.

[0062] The monomer (C2) is not particularly limited as long as it is a monomer that does not have a salt structure, unlike the monomer (C1), has a radically polymerizable unsaturated group, and does not have a hydrolyzable silyl group. Examples of the monomer (C2) include (meth)acrylic acid alkyl esters and monomers other than (meth)acrylic acid alkyl esters, as shown below.

[0063] In one embodiment of the present invention, the (meth)acrylic acid alkyl ester may be a (meth)acrylic acid ester having an alkyl group having 1 to 18 carbon atoms and not containing functional groups such as a hydroxyl group or an epoxy group. The alkyl group in the (meth)acrylic acid alkyl ester may be linear or branched, or may be a cyclic cycloalkyl group. Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, and isobornyl (meth)acrylate.

[0064] Examples of monomers other than (meth)acrylic acid alkyl esters include nitrile group-containing radical polymerizable monomers such as (meth)acrylonitrile; epoxy group-containing radical polymerizable monomers such as glycidyl (meth)acrylate; hydrophilic radical polymerizable monomers such as 2-hydroxypropyl (meth)acrylate; radical polymerizable monomers having a polyoxyalkylene chain; monomers having two or more polymerizable unsaturated bonds such as polyethylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, and allyl (meth)acrylate; and fluorine-containing radical polymerizable monomers such as trifluoro(meth)acrylate, pentafluoro(meth)acrylate, perfluorocyclohexyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl methacrylate, and β-(perfluorooctyl)ethyl (meth)acrylate.

[0065] In the second step, the amount of monomer (C1) in 100% by weight of the total amount of monomer (C1) and monomer (C2) is preferably 5% by weight or more, more preferably 10% by weight or more. When the amount of monomer (C1) is 5% by weight or more, the polysiloxane resin is easily dispersed or solubilized uniformly in water. From the viewpoint of obtaining a coating film with better water resistance and weather resistance, the upper limit of the amount of monomer (C1) in 100% by weight of the total amount of monomer (C1) and monomer (C2) is preferably 50% by weight or less, more preferably 30% by weight or less, and even more preferably 25% by weight or less.

[0066] The radical polymerization is preferably carried out in the presence of an initiator and a water-soluble organic solvent. The use of a water-soluble organic solvent allows the radical polymerization of the highly hydrophobic polysiloxane macromer obtained in the first step with the monomer (C) to proceed smoothly.

[0067] The initiator is a radical polymerization initiator, and is not particularly limited as long as it is a substance capable of initiating a radical polymerization reaction between the radically polymerizable unsaturated group derived from the silane compound (A) and the monomer (C).

[0068] Examples of the initiator include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), tert-butyl peroxypivalate, tert-butyl peroxybenzoate, tert-butylperoxy-2-ethylhexanoate, di-tert-butyl peroxide, cumene hydroperoxide, and diisopropyl peroxycarbonate.

[0069] The amount of initiator is preferably 0.01 to 10 wt %, more preferably 0.05 to 7 wt %, and even more preferably 0.1 to 5 wt %, based on 100 wt % of the total amount of the polysiloxane resin. When the amount of initiator is 0.01 wt % or more, polymerization tends to proceed appropriately. Furthermore, when the amount of initiator is 10 wt % or less, a polymer with an appropriate molecular weight tends to be obtained.

[0070] Examples of water-soluble organic solvents include methanol, ethanol, 2-propanol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, polyethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol monoisobutyl ether, propylene glycol monomethyl ether, propylene glycol dimethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, ethylene glycol diethyl ether, etc. Among these, considering the possibility of volatilization during coating film formation, alcoholic solvents such as methanol, ethanol, and 2-propanol are particularly preferred.

[0071] In the second step, in addition to the monomer (C), the initiator, water, and the water-soluble organic solvent, any additives may be added within the range in which the effects of the present invention are achieved. Such additives can be appropriately selected by those skilled in the art.

[0072] The polysiloxane resin obtained in the second step is a product in which graft chains have been formed on the dehydration condensate (co-condensate) obtained in the first step, and can also be called a graft co-condensate. It can also be said that the polysiloxane resin has the polysiloxane macromer obtained in the first step as the main chain, and side chains derived from the monomer (C) formed thereon.

[0073] The weight-average molecular weight of the polysiloxane resin obtained in the second step is preferably 5,000 to 500,000, more preferably 8,000 to 100,000, and even more preferably 10,000 to 80,000. When the weight-average molecular weight of the polysiloxane resin is 40,000 or more, a coating film with excellent water resistance and weather resistance can be obtained. In this specification, the weight-average molecular weight is a value measured by gel permeation chromatography (GPC). The weight-average molecular weight of the polysiloxane resin can be controlled by adjusting the amount of initiator.

[0074] The second step preferably includes a step of intermittently adding the monomer (C1), the monomer (C2), an initiator, and a water-soluble organic solvent to the dehydrated condensate to carry out radical polymerization. Water may also be added optionally in this step. By intermittently adding the reaction materials in this manner, the radical polymerization reaction can be carried out stably.

[0075] <Other processes> The production method may include a third step of removing the organic solvent generated in the first step and the organic solvent used in the second step by devolatilization. The devolatilization temperature is preferably 60°C or lower, more preferably 50°C or lower, from the viewpoint of preventing gelation of the polysiloxane resin. Furthermore, the devolatilization temperature is preferably 30°C or higher, more preferably 40°C or higher, from the viewpoint of devolatilization efficiency.

[0076] The production method may also include a fourth step of dispersing or dissolving the resulting polysiloxane resin in water. For example, the second step may be followed by the third step and then the fourth step, or the second step may be followed by the fourth step and then the third step.

[0077] [2. Polysiloxane Resin] A polysiloxane resin according to one embodiment of the present invention is obtained by the above-described method for producing a polysiloxane resin. Since the amount of water used relative to the hydrolyzable groups in the silane compound (A) is controlled in the production method, the polysiloxane resin has a high degree of condensation. However, since hydrolyzable silyl groups and siloxane bonds are mixed, the structure of the polysiloxane resin is complex, making it difficult to identify the number or positions of crosslinking points and impossible to express by a general formula. Furthermore, identifying the properties associated with such a complex structure requires an unrealistic number of experiments under various conditions. Therefore, it can be said that there are circumstances in which it is impossible or almost impractical to directly identify the polysiloxane resin by its structure or properties.

[0078] 3. Top Coat Composition A top coat composition according to one embodiment of the present invention includes the polysiloxane resin described above. A cured film obtained from the top coat composition has excellent wet heat and cold resistance and water resistance. The top coat composition may be an aqueous solution or aqueous dispersion containing the polysiloxane resin. Alternatively, the top coat composition may be an aqueous paint.

[0079] The top coat composition may contain additives commonly used in the art. Examples of such additives include pigments, fillers, plasticizers, film-forming aids, wetting / dispersing agents, thickeners, antifoaming agents, preservatives, antioxidants, antisettling agents, leveling agents, UV absorbers, antistatic agents, antifreeze agents, antibacterial agents, antifungal agents, tackifiers, and rust inhibitors. The top coat composition may contain one or more additives. The amount of these additives can be appropriately determined by one skilled in the art depending on the intended use.

[0080] 4. Laminate A laminate according to one embodiment of the present invention includes an undercoat layer and a topcoat layer containing the polysiloxane resin. The topcoat layer may be a cured film obtained by curing the topcoat composition. The laminate can also be said to be a laminate in which the undercoat layer and the topcoat layer are laminated in this order on a substrate.

[0081] Examples of the undercoat that forms the undercoat layer include a primer, a sealer, and a filler.

[0082] The primer is not particularly limited, and various primers commonly used in the coating field can be used. For example, any of oil-based, water-based, and anti-rust primers can be used. Specific examples of primers include epoxy-based primers, urethane-based primers, silicone-based primers, and zinc-rich primers.

[0083] The sealer is not particularly limited, and various sealers commonly used in the coating field can be used. For example, any of oil-based, water-based, and anti-rust sealers can be used. Specific examples of sealers include epoxy-based sealers, urethane-based sealers, silicone-based sealers, and zinc-rich sealers.

[0084] The filler is not particularly limited, and various fillers commonly used in the coating field can be used. Specific examples of fillers include elastic fillers. Conventional water-based coatings have been prone to cracking, especially when applied to an elastic filler and subjected to repeated cold and heat stimuli. In contrast, the top coat layer containing a polysiloxane resin according to one embodiment of the present invention has excellent resistance to humidity, cold, and heat, even when laminated on an elastic filler.

[0085] The substrate may be either an organic substrate or an inorganic substrate, and examples of the substrate include interior and exterior building materials, automobile parts, metals such as aluminum, stainless steel, and silver, ceramic substrates such as slate, concrete, roofing tiles, mortar, gypsum board, asbestos slate, asbestos board, precast concrete, lightweight aerated concrete, calcium silicate board, tile, and brick, glass, and stone materials such as natural marble and granite.

[0086] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0087] An embodiment of the present invention may include the following features. <1> A silane compound (A) having a radical polymerizable unsaturated group and a hydrolyzable silyl group, and a compound other than the silane compound (A) represented by the following general formula (I): R 1 n -Si-(OR 2 ) 4-n (I) (In the formula, R 1 are each independently an alkyl group having 1 to 10 carbon atoms or an unsubstituted or substituted aryl group, and R 2are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n is an integer of 0 to 3. A method for producing a polysiloxane resin, comprising: a first step of dehydrating and condensing a silane compound (A) represented by the formula (I) in the presence of water and a dehydration condensation catalyst to obtain a dehydration condensate; and a second step of adding a monomer (C) having a radically polymerizable unsaturated group to the dehydration condensate obtained in the first step and conducting radical polymerization to obtain a polysiloxane resin, wherein in the first step, 0.9 equivalents or more of the water is used relative to the total number of hydrolyzable groups in the silane compound (A) and the silane compound (B), the polysiloxane resin obtained in the second step has a glass transition temperature of -10°C to 9°C, and the proportion of structural units derived from the silane compound (A) and the silane compound (B) in 100% by weight of the polysiloxane resin is 25 to 45% by weight. <2> The monomer (C) includes a monomer (C1) having a salt structure composed of an acid and a base and having a radically polymerizable unsaturated group, and a monomer (C2) not having the salt structure and having a radically polymerizable unsaturated group. <1> 1. A method for producing the polysiloxane resin according to claim 1. <3> The radical polymerization is carried out in the presence of an initiator and a water-soluble organic solvent. <1> or <2> 1. A method for producing the polysiloxane resin according to claim 1. <4> The silane compound (B) has a trialkoxysilyl group. <1> ~ <3> 1. A method for producing the polysiloxane resin according to any one of the above. <5> The water-soluble organic solvent is an alcohol solvent. <3> 1. A method for producing the polysiloxane resin according to claim 1. <6> <1> ~ <5> 1. A polysiloxane resin obtained by the method for producing a polysiloxane resin according to any one of the above items 1 to 8. <7> <6> A top coat composition comprising the polysiloxane resin described in 1. <8> A primer layer; <6> A laminate comprising a top coat layer containing the polysiloxane resin according to claim 1. [Example]

[0088] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0089] 〔material〕 The following materials were used in the examples and comparative examples.

[0090] (Silane compound (A)) Vinyltrimethoxysilane (abbreviated as "Vi-TMS"): "A-171" manufactured by Momentive Performance Materials Japan, LLC (Silane Compound (B)) Methyltrimethoxysilane (abbreviated as "M-TMS"): "Z-6033" manufactured by Dow Toray Industries, Inc. Phenyltrimethoxysilane (abbreviated as "Ph-TMS"): "Z-6124" manufactured by Dow Toray Industries, Inc. (Monomer (C1)) Sodium acrylamido-t-butyl sulfonate (abbreviated as "ATBS-Na"): "ATBS-Na" manufactured by Toagosei Co., Ltd. Ether sulfate type ammonium salt (abbreviated as "SR-10"): "ADEKA REASOAP SR-10" manufactured by ADEKA Corporation (Monomer (C2)) Methyl methacrylate (abbreviated as "MMA"): manufactured by Mitsubishi Gas Chemical Company, Inc. Butyl acrylate (abbreviated as "BA"): manufactured by Nippon Shokubai Co., Ltd. (Dehydration condensation catalyst) Dibutyl phosphate (DBP): manufactured by Johoku Chemical Industry Co., Ltd., acid catalyst Lithium chloride (abbreviated as "LiCl"): Kanto Chemical Co., Ltd., neutral salt Tetrabutylammonium bromide (TBAB): Tokyo Chemical Industry Co., Ltd., neutral salt (initiator) Radical polymerization initiator: 2,2'-azobis(2,4-dimethylvaleronitrile): "V-65" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. [Measurement and evaluation methods] Measurements and evaluations in the examples and comparative examples were carried out by the following methods.

[0091] <Tg of graft chain> The Tg of the grafted chains was calculated using the Fox equation.

[0092] <Water resistance> (Creation of coating film) An aqueous solution or dispersion containing a polysiloxane resin was applied to glass using a 6-mil wide applicator, and the applied solution was cured at 50°C for 18 hours to prepare a test specimen having a coating film (cured film).

[0093] (Evaluation method) The test specimens were immersed in pure water at 50°C for 24 hours, and the appearance was visually evaluated immediately after removal. A specimen without whitening, cracking, wrinkles, or blisters was rated as "good," while a specimen with whitening, cracking, wrinkles, or blisters was rated as "poor."

[0094] <Wet and cold resistance> (Preparation of test specimen) Cured films were prepared using the polysiloxane resins of the Examples and Comparative Examples as aqueous paints (white base paints) containing the components formulated according to the formulations shown in Table 2. Briefly, the mill base obtained by blending the components listed in the "Mill Base" column in Table 2 was added to the components listed in the "Cutback" column in Table 2 to obtain the aqueous paints. A water-based cationic sealer (Nippon Paint) was applied as a primer to a slate board (50 mm x 150 mm) whose back and sides had been sealed with Arethrethan (Kansai Paint). An underfiller, Elastic Excel (Nippon Paint), was applied as an elastic filler layer to the resulting primer layer using a sandblasting roller, and the aqueous paint was then applied to the elastic filler layer. The aqueous paint was applied using an air spray to a dry film thickness (the film thickness of the cured film after drying) of approximately 40 μm. The resulting coating was dried for 4 hours at 23°C and 50% RH (first application). Furthermore, the water-based paint was again applied to the dried film obtained in the first application using an air spray so that the dried film thickness was approximately 40 μm (i.e., so that the film thickness of the cured film on the elastic filler layer after drying was a total of 80 μm). The resulting coating film was dried at 23°C and 50% RH for one week (second application). These operations resulted in a laminate consisting of a primer layer, an elastic filler layer, and a cured film laminated in this order on a slate board substrate. The resulting laminate was used as a test piece to measure the wet / cold heat resistance of the cured film.

[0095] (Evaluation method) The test specimens were evaluated for wet heat and cold resistance using a freeze-thaw tester (Marui Co., Ltd., Model MIT-682-3-11). One cycle consisted of cooling in air at -20°C for two hours and then submerging in water at 10°C for two hours. The appearance was visually evaluated after 30 cycles. A sample was rated "good" if there were no cracks, peeling, wrinkles, or blisters, and "poor" if there were cracks, peeling, wrinkles, or blisters.

[0096] Example 1 (Preparation of dehydrated condensate (first step)) A reactor equipped with a stirrer, thermometer, and reflux condenser was charged with 23.9 parts by weight of M-TMS, 20.3 parts by weight of Ph-TMS, 2.9 parts by weight of Vi-TMS, 14.5 parts by weight of pure water, and 0.014 parts by weight of DBP, and the mixture was reacted at a reaction temperature of 65°C for 3 hours with stirring, thereby obtaining a dehydrated condensate.

[0097] (Preparation of polysiloxane resin (second step)) A reactor equipped with a stirrer, thermometer, reflux condenser, nitrogen gas inlet tube, and dropping funnel was charged with 10 parts by weight of 2-propanol, and the temperature was raised to 70°C while introducing nitrogen gas. Then, a mixed solution of the dehydrated condensate, 2.5 parts by weight of ATBS-Na, 6.0 parts by weight of SR-10, 23.5 parts by weight of MMA, 38.0 parts by weight of BA, 1.4 parts by weight of 2,2-azobis(2,4-dimethylvaleronitrile), and 8.0 parts by weight of 2-propanol was added dropwise from the dropping funnel at a constant rate over 3 hours. Next, a mixed solution of 0.14 parts by weight of 2,2-azobis(2,4-dimethylvaleronitrile) and 4.0 parts by weight of 2-propanol was added to the reactor. The mixture was then stirred at 70°C for 1 hour. Thereafter, 100 parts by weight of water was added, and the mixture was subjected to devolatilization using a rotary evaporator until the nonvolatile components reached 50%.The mixture was then cooled to room temperature, yielding a polysiloxane resin.

[0098] [Examples 2 to 6, Comparative Examples 1 to 5] A polysiloxane resin was obtained in the same manner as in Example 1, except that the amounts of each component were changed as shown in Table 1.

[0099] [Evaluation results] The amounts charged and the evaluation results of the examples and comparative examples are shown in Table 1. In Table 1, "polysiloxane units" refers to the proportion of structural units derived from silane compound (A) and silane compound (B) in 100% by weight of the polysiloxane resin. "Acrylic polymer units" refers to the proportion of structural units derived from monomer (C1) and monomer (C2) in 100% by weight of the polysiloxane resin.

[0100] Here, "100% by weight of polysiloxane resin" corresponds to the sum of "the total weight of silane compound (A) and silane compound (B) minus the weight of volatile components generated by hydrolysis" and "the total weight of monomer (C1) and monomer (C2)." In other words, "polysiloxane units" and "acrylic polymer units" can be calculated using the following formula.

[0101] Polysiloxane unit [%] = 100 × total weight of silane compound (A) and silane compound (B) minus the weight of volatile components generated by hydrolysis / (total weight of silane compound (A) and silane compound (B) minus the weight of volatile components generated by hydrolysis + total weight of monomer (C1) and monomer (C2)) Acrylic polymer unit [%] = 100 × total weight of monomer (C1) and monomer (C2) / (total weight of silane compound (A) and silane compound (B) excluding the weight of volatile components generated by hydrolysis + total weight of monomer (C1) and monomer (C2))

[0102] [Table 1]

[0103] [Table 2]

[0104] In Examples 1 to 6, in which the amount of water used in the first step was 0.9 equivalents or more relative to the total number of hydrolyzable groups in the silane compound (A) and the silane compound (B), the Tg of the graft chain was −10 to 9°C, and the proportion of polysiloxane units was 25 to 45% by weight, the water resistance and wet, cold, and heat resistance were good. In Comparative Example 1, in which the amount of water used in the first step was less than 0.9 equivalents relative to the total number of hydrolyzable groups in the silane compound (A) and the silane compound (B), cracks due to shrinkage were observed after curing, resulting in poor wet, cold, and heat resistance. In Comparative Example 2, in which the Tg of the graft chain exceeded 9°C, poor flexibility and cracks were observed. In Comparative Example 3, in which the proportion of polysiloxane units exceeded 45% by weight, similarly poor flexibility and cracks were observed. Comparative Example 4, in which the amount of water used in the first step was less than 0.9 equivalents relative to the total number of hydrolyzable groups in silane compound (A) and silane compound (B), and the proportion of polysiloxane units was less than 25% by weight, showed poor water resistance and wet, cold, and heat resistance. Comparative Example 5, in which the Tg of the graft chain exceeded 9°C and the proportion of polysiloxane units was less than 25% by weight, also showed poor water resistance and wet, cold, and heat resistance. This indicates that a low proportion of polysiloxane units makes the product more susceptible to the effects of water. [Industrial Applicability]

[0105] One aspect of the present invention can be utilized in the fields of various water-based paints and coating agents.

Claims

1. A silane compound (A) having a radical polymerizable unsaturated group and a hydrolyzable silyl group, and a silane compound other than the silane compound (A) represented by the following general formula (I): R １ ｎ -Si-(OR ２ ) ４－ｎ ・・・(I) (In the formula, R １ are each independently an alkyl group having 1 to 10 carbon atoms or an unsubstituted or substituted aryl group, and R ２ each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n represents an integer of 0 to 3. In a first step, a silane compound (B) represented by the formula (I) is subjected to dehydration condensation in the presence of water and a dehydration condensation catalyst to obtain a dehydration condensate; a second step of adding a monomer (C) having a radically polymerizable unsaturated group to the dehydration condensate obtained in the first step and conducting radical polymerization to obtain a polysiloxane-based resin; In the first step, the amount of water used is 0.9 equivalents or more based on the total number of hydrolyzable groups in the silane compound (A) and the silane compound (B), the glass transition temperature of the graft chain derived from the monomer (C) in the polysiloxane resin obtained in the second step is −10° C. to 9° C., a ratio of structural units derived from the silane compound (A) and the silane compound (B) to 100% by weight of the polysiloxane resin is 25 to 45% by weight.

2. 2. The method for producing a polysiloxane resin according to claim 1, wherein the monomer (C) comprises a monomer (C1) having a salt structure consisting of an acid and a base and having a radically polymerizable unsaturated group, and a monomer (C2) not having the salt structure and having a radically polymerizable unsaturated group.

3. 2. The method for producing a polysiloxane resin according to claim 1, wherein the radical polymerization is carried out in the presence of an initiator and a water-soluble organic solvent.

4. The method for producing a polysiloxane resin according to claim 1 , wherein the silane compound (B) has a trialkoxysilyl group.

5. 4. The method for producing a polysiloxane resin according to claim 3, wherein the water-soluble organic solvent is an alcohol-based solvent.

6. A polysiloxane resin obtained by the method for producing a polysiloxane resin according to any one of claims 1 to 5.

7. A top coat composition comprising the polysiloxane resin according to claim 6.

8. A laminate comprising an undercoat layer and a topcoat layer containing the polysiloxane resin according to claim 6.

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