Organopolysiloxane, room-temperature-curable organopolysiloxane composition containing same, coating agent, and coated article

Abstract

Provided is an organopolysiloxane which is a product of condensation of (a) a silicone oligomer represented by formula (I) with (b) a silicone oil having a silanol group at a molecular chain end and which has a dynamic viscosity at 25°C of 100-2,000 mm2 / s. (In formula (I): R1 represents a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group; R2 represents a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, or an isopropyl group; a, b, c, and d are numbers satisfying 0≤a<1, 0<b≤1, 0≤c<0.5, 0≤d<0.5, and a+b+c+d=1; and e is a number satisfying 0<e≤4.)

Description

Organopolysiloxane, room temperature curable organopolysiloxane composition containing same, coating agent, and coated article

[0001] The present invention relates to an organopolysiloxane, a room-temperature-curable organopolysiloxane composition containing the same, a coating agent, and a coated article.

[0002] Organopolysiloxanes containing alkoxysilyl groups are widely used in paints and coatings. Generally, organopolysiloxanes with terminal alkoxy groups are formulated with a curing catalyst, and when external energy such as heat energy is applied, the terminal alkoxy groups react with each other to form a strong siloxane network. The resulting coating has excellent heat and weather resistance, making it suitable for a wide range of applications, from outdoor structures to automotive and electronic components.

[0003] Organopolysiloxanes containing alkoxysilyl groups are generally produced by hydrolysis and condensation of alkoxysilanes (see Patent Documents 1 and 2). However, many of the highly active alkoxy groups are generally consumed in the hydrolysis and condensation reaction during production, leaving only a few less active alkoxy groups remaining in the resulting organopolysiloxane, and the resulting coatings often have poor curability. The tendency for reduced curability to decrease becomes more pronounced as the molecular weight of the resulting organopolysiloxane increases, and additional steps such as high-temperature heating are required during coating formation to compensate for the poor curability.

[0004] On the other hand, low-molecular-weight organopolysiloxanes with a molecular weight of 5,000 or less have many remaining active alkoxy groups, which gives them excellent reactivity, and some compositions containing low-molecular-weight organopolysiloxanes cure without a heating step. However, the cured coating of low-molecular-weight organopolysiloxanes has problems such as poor mechanical properties due to its thin film, and the application of external heat causes the remaining alkoxy groups in the coating to react sequentially, resulting in cracks over time.

[0005] As mentioned above, in various organopolysiloxanes, if the molecular weight is large, problems such as poor curability due to a small number of polymerizable functional groups occur, while if the molecular weight is small, problems such as low mechanical strength and the occurrence of cracks over time due to heating occur. Furthermore, differences in the molecular weight of the organopolysiloxane affect various physical properties of the coating film, such as the curing temperature, heat resistance, light resistance, solvent resistance, surface hardness, and workability, so a molecular weight appropriate for the application is required.

[0006] For these reasons, molecular weight control is an important factor in the production of organopolysiloxanes, and Patent Document 3 has discovered that organopolysiloxanes having a predetermined peak top and peak area in a specific molecular weight region can solve the above problems, specifically, by combining an organopolysiloxane having a high molecular weight with an organopolysiloxane having a low molecular weight. However, this method requires a solvent to dissolve the high molecular weight organopolysiloxane, which is undesirable from an environmental perspective.

[0007] Patent Document 4 proposes a liquid organopolysiloxane with high molecular weight and high reactivity, which is obtained by reacting a polydimethylsiloxane unit having an alkoxysilyl group with a pre-condensed silicone oligomer. This organopolysiloxane is solvent-free, liquid, and curable at room temperature. However, while it is highly reactive, cracks may occur in the cured film in high-temperature environments.

[0008] Japanese Patent No. 6525573 Japanese Patent No. 4110402 Japanese Patent Publication No. 2021-172707 International Publication No. 2023 / 157603

[0009] The present invention has been made in view of the above circumstances, and has as its object to provide an organopolysiloxane that provides a room-temperature-curable composition that has low viscosity even without the use of a solvent, has excellent curability, and is capable of producing a cured product with good heat resistance, and a room-temperature-curable organopolysiloxane composition containing the same.

[0010] As a result of extensive research into achieving the above-mentioned object, the present inventors discovered that an organopolysiloxane, which is a condensate of a silicone oligomer having alkoxysilyl groups and a silicone oil having silanol groups at the molecular chain terminals, is liquid even in the absence of a solvent, has excellent curing properties, and also provides a cured film of a composition containing this organopolysiloxane that exhibits excellent crack resistance, thereby completing the present invention.

[0011] That is, the present invention provides: 1. A condensation product of (a) a silicone oligomer represented by the following formula (I) and (b) a silicone oil having a silanol group at the molecular chain terminal, which has a kinematic viscosity at 25°C of 100 to 2,000 mm 2 / s, an organopolysiloxane (In the formula, R 1 each independently represents a hydrogen atom, or an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, each of which may be substituted with a halogen atom; R 2represents a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, or an isopropyl group. a, b, c, and d are numbers that satisfy 0≦a<1, 0<b≦1, 0≦c<0.5, 0≦d<0.5, and a+b+c+d=1, and e is a number that satisfies 0<e≦4.) 2. The organopolysiloxane according to 1, wherein in formula (I), a and d are 0. 3. The organopolysiloxane according to 1 or 2, wherein the weight average molecular weight of component (a) measured by gel permeation chromatography is 500 to 3,000 in terms of polystyrene standards. 4. The organopolysiloxane according to any one of 1 to 3, wherein the weight average molecular weight of component (b) measured by gel permeation chromatography is 200 to 2,000 in terms of polystyrene standards. 5. 5. The organopolysiloxane according to any one of 1 to 4, wherein the component (b) is present in an amount of 10 to 80 parts by mass per 100 parts by mass of the component (a); 6. The organopolysiloxane according to any one of 1 to 5, wherein the weight average molecular weight, as measured by gel permeation chromatography in terms of polystyrene, is 5,000 to 100,000; 7. A room-temperature-curable organopolysiloxane composition comprising the organopolysiloxane according to any one of 1 to 6 and a curing catalyst; 8. A coating agent comprising the room-temperature-curable organopolysiloxane composition according to 7; 9. A cured product of the room-temperature-curable organopolysiloxane composition according to 7; 10. A coated article having a substrate and the cured product according to 9, formed on at least one surface of the substrate directly or via one or more other layers.

[0012] The organopolysiloxane of the present invention provides a room-temperature-curable organopolysiloxane composition that exhibits low viscosity and excellent curability even without the use of a solvent. Therefore, a solvent removal step is not required during the formation of a cured coating, and the resulting composition does not adversely affect the working environment due to solvent evaporation, nor does it corrode or deteriorate electrical and electronic components or the circuit boards on which they are mounted. Furthermore, the cured products obtained from the room-temperature-curable composition containing the organopolysiloxane of the present invention exhibit excellent heat resistance, making them suitable for the production of a variety of coated articles.

[0013] The present invention will be described in detail below. [1] Organopolysiloxane The organopolysiloxane of the present invention is a condensation reaction product of (a) a silicone oligomer and (b) a silicone oil having silanol groups at the molecular chain terminals.

[0014] (a) Silicone Oligomer The silicone oligomer of component (a) has an average siloxane unit composition ratio represented by the following formula (I).

[0015]

[0016] In formula (I), R 1 R each independently represents a hydrogen atom, or an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, each of which may be substituted with a halogen atom. 1The alkyl group having 1 to 8 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, neopentyl, n-hexyl, cyclohexyl, n-heptyl, and n-octyl groups, with alkyl groups having 1 to 6 carbon atoms being preferred, and alkyl groups having 1 to 3 carbon atoms being more preferred, with methyl and ethyl being even more preferred. The aryl group having 6 to 18 carbon atoms is preferably one having 6 to 10 carbon atoms, and specific examples thereof include unsubstituted aryl groups such as phenyl and naphthyl groups, and alkylaryl groups such as tolyl, xylyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, and dodecylphenyl groups, with phenyl being preferred. The aralkyl group having 7 to 20 carbon atoms is preferably one having 7 to 10 carbon atoms, and specific examples thereof include a benzyl group and a phenylethyl group. The alkyl group, aryl group and aralkyl group may have some or all of their hydrogen atoms substituted with halogen atoms (fluorine, chlorine, bromine, iodine atoms), and specific examples thereof include a chloromethyl, chloropropyl, bromoethyl, trifluoropropyl, chlorophenyl, and bromophenyl group. Among these, R 1 is preferably a methyl group, an ethyl group or a phenyl group.

[0017] R 2 is a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, or an isopropyl group, among which R 2 is preferably a hydrogen atom, a methyl group, or an ethyl group. 2 Preferably, at least half of the groups are methyl groups, ethyl groups, n-propyl groups or isopropyl groups, and more preferably methyl groups or ethyl groups.

[0018] a, b, c, and d are numbers that satisfy 0≦a<1, 0<b≦1, 0≦c<0.5, 0≦d<0.5, and a+b+c+d=1, respectively. a is a number that satisfies 0≦a<1, but from the viewpoint of crack suppression effect, a number that satisfies 0≦a≦0.3 is preferred, and 0 is more preferred. b is a number that satisfies 0<b≦1, but from the viewpoint of the scratch resistance of the resulting cured product, a number that satisfies 0.2≦b≦1 is preferred. c is a number that satisfies 0≦c<0.5, but from the viewpoint of the curability of the composition and the hardness of the resulting cured product, a number that satisfies 0≦c≦0.4 is preferred. d is a number that satisfies 0≦d<0.5, but from the viewpoint of the curability of the composition and the hardness of the resulting cured product, a number that satisfies 0≦d≦0.2 is preferred, and 0 is more preferred. Although e is a number that satisfies 0<e≦4, it is preferable that e is a number that satisfies 0<e≦3, from the viewpoints of being effective in suppressing the condensation reaction by the condensable functional group and of the crack resistance, water resistance, and weather resistance of the resulting cured product.

[0019] The silicone oligomer may be a compound represented by the formula (I) above, wherein R 1 and R 2 is a methyl group or an ethyl group, and a to d are preferably such that a=0, b is a number that satisfies 0<b≦1, c is a number that satisfies 0≦c<0.5, d=0, and a+b+c+d=1, and e is a number that satisfies 0<e≦3.

[0020] The weight average molecular weight (Mw) of component (a) measured by gel permeation chromatography (GPC) in terms of polystyrene is preferably 500 to 3,000, more preferably 1,000 to 2,000. If Mw is 500 or more, the increase in molecular weight due to condensation proceeds sufficiently, improving heat resistance. Furthermore, if Mw is 3,000 or less, gelation due to an increase in molecular weight can be suppressed, and the occurrence of unevenness and coating irregularities during coating can be prevented. Note that the GPC measurement conditions can be, for example, the methods used in the examples below.

[0021] The component (a) may be used alone or in combination of two or more types.

[0022] There are no particular restrictions on the method for producing component (a), and any conventionally known production method can be used. For example, component (a) can be obtained by hydrolyzing and condensing a silane compound having a hydrolyzable group.

[0023] (b) Silicone oil having silanol groups at the molecular chain terminals Component (b) is a silicone oil having one or more silanol groups at the molecular chain terminals. If component (b) does not have silanol groups, the condensation reaction does not proceed sufficiently, and oil remains in the resulting organopolysiloxane, resulting in poor curing. Groups bonded to silicon atoms other than silanol groups include R 1 Examples of the aryl group include those exemplified below, and a methyl group or a phenyl group is preferred.

[0024] The molecular structure of component (b) can be, for example, linear, branched, or cyclic. A preferred structure for the silicone oil of component (b) is a linear diorganopolysiloxane in which one end, preferably both ends, are blocked with a siloxane unit having a silanol group, such as a hydroxydimethylsiloxane unit, and the main chain is essentially composed of repeating diorganosiloxane units.

[0025] Specific examples of such component (b) include dimethylpolysiloxanes both ends of which are blocked with hydroxydimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers both ends of which are blocked with hydroxydimethylsiloxy groups, dimethylsiloxane-methylphenylsiloxane copolymers both ends of which are blocked with hydroxydimethylsiloxy groups, and dimethylsiloxane-diphenylsiloxane copolymers both ends of which are blocked with hydroxydimethylsiloxy groups.

[0026] The weight average molecular weight (Mw) of component (b) in terms of polystyrene, as determined by gel permeation chromatography, is preferably from 200 to 2,000, more preferably from 300 to 1,500, and even more preferably from 400 to 1,000. An Mw of 200 or more improves the crack resistance of the resulting organopolysiloxane, while an Mw of 2,000 or less can prevent the resulting organopolysiloxane from becoming oily, resulting in poor curing.

[0027] The component (b) may be used alone or in combination of two or more types.

[0028] The amount of component (b) used during the condensation reaction is preferably 10 to 80 parts by mass, more preferably 10 to 70 parts by mass, per 100 parts by mass of component (a). When the amount is 10 parts by mass or more, the increase in molecular weight of the organopolysiloxane due to condensation proceeds sufficiently, improving the heat resistance of the resulting cured product. When the amount is 80 parts by mass or less, gelation due to an increase in molecular weight is suppressed, preventing the occurrence of unevenness and coating irregularities during coating.

[0029] [2] Method for Producing Organopolysiloxane The method for producing the organopolysiloxane of the present invention is not particularly limited. For example, the organopolysiloxane can be obtained by condensing the components (a) and (b) in the presence of a catalyst under heating conditions at 60 to 200°C, followed by a step of distilling off the by-produced alcohol, if necessary.

[0030] Any conventionally known catalyst can be used as the catalyst, and those whose aqueous solutions exhibit an acidic pH of 2 to 7 are preferred, with particularly preferred examples being acidic hydrogen halides, sulfonic acids, carboxylic acids, acidic or weakly acidic inorganic salts, solid acids such as ion exchange resins, etc. Specific examples of acidic catalysts include hydrogen fluoride, hydrochloric acid, nitric acid, sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, formic acid, acetic acid, maleic acid, benzoic acid, lactic acid, phosphoric acid, and cation exchange resins having sulfonic acid or carboxylic acid groups on their surfaces.

[0031] There are no particular restrictions on the amount of catalyst used, but in order to ensure that the reaction proceeds quickly and to facilitate easy removal of the catalyst after the reaction, an amount of 0.02 to 10 parts by mass per 100 parts by mass of component (a) is preferred.

[0032] The conditions for the condensation reaction are not particularly limited, and for example, the temperature for the condensation reaction is preferably 60 to 200° C., and in consideration of improving the reaction rate and preventing decomposition of the organic group, more preferably 60 to 150° C. The time for the condensation reaction is preferably 1 to 10 hours, and more preferably 1 to 8 hours.

[0033] In addition, a solvent may be used in the condensation reaction to the extent that it does not inhibit the reaction, but if used, it is preferable to completely remove it by a treatment such as a stripping step, etc. Specific examples of organic solvents that can be used include methanol, ethanol, propanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, toluene, xylene, etc.

[0034] The organopolysiloxane of the present invention has a kinematic viscosity at 25°C of 100 to 2,000 mm 2 / s, 120 to 1,500 mm 2 / s is preferred, and 140 to 500 mm 2 / s is more preferable. 2 If the curing rate is less than 2,000 mm / s, the heat resistance of the resulting cured product will be insufficient. 2 If the kinematic viscosity exceeds 1 / s, unevenness and coating irregularities will occur during application. The kinematic viscosity is a value measured at 25°C using a Cannon-Fenske viscometer according to the method described in JIS Z 8803:2011 (the same applies hereinafter).

[0035] The organopolysiloxane of the present invention preferably has a weight average molecular weight (Mw) of 5,000 to 100,000, more preferably 5,000 to 50,000, as measured by gel permeation chromatography (GPC) and converted into polystyrene.

[0036] [3] Room-temperature-curable organopolysiloxane composition The room-temperature-curable organopolysiloxane composition of the present invention comprises the following components: (A) a condensation reaction product of the above (a) silicone oligomer represented by formula (I) and the above (b) silicone oil having silanol groups at the molecular chain terminals, which has a kinematic viscosity at 25°C of 100 to 2,000 mm 2 (B) Curing catalyst In the present invention, "room temperature" means an ordinary temperature without any particular heating or cooling, and generally means a temperature range of 0 to 40°C, preferably 5 to 35°C.

[0037] The curing catalyst of component (B) is not particularly limited as long as it is one that is commonly used in organosiloxane-based paints, but organometallic compounds are preferred, such as metal alkoxide compounds of Ti, Al, Zr, Sn, etc., metal chelate compounds, and metal ester compounds, with those containing organotitanium compounds being preferred.

[0038] Specific examples of the metal alkoxide compound include aluminum alkoxides such as aluminum trimethoxide, aluminum triethoxide, aluminum tri-n-propoxide, aluminum triisopropoxide, aluminum tri-n-butoxide, aluminum triisobutoxide, aluminum tri-s-butoxide, and aluminum tri-t-butoxide; tetramethyl titanate, tetraethyl titanate, tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetraisobutyl titanate, tetra-t-butyl titanate, tetra-n-hexyl titanate, and tetraisopropyl titanate. Examples of the alkoxide include titanium alkoxides such as isooctyl titanate and tetra-n-lauryl titanate; zirconium alkoxides such as tetraethyl zirconate, tetra-n-propyl zirconate, tetraisopropyl zirconate, tetra-n-butyl zirconate, tetra-s-butyl zirconate, tetra-t-butyl zirconate, tetra-n-pentyl zirconate, tetra-t-pentyl zirconate, tetra-t-hexyl zirconate, tetra-n-heptyl zirconate, tetra-n-octyl zirconate and tetra-n-stearyl zirconate; and tin alkoxides such as dibutyltin dibutoxide.

[0039] Specific examples of metal chelate compounds include aluminum tris(ethylacetoacetate), aluminum tris(n-propylacetoacetate), aluminum tris(isopropylacetoacetate), aluminum tris(n-butylacetoacetate), aluminum isopropoxybis(ethylacetoacetate), aluminum tris(acetylacetonato), aluminum tris(propionylacetonato), aluminum diisopropoxypropionylacetonato, aluminum acetylacetonato.bis(propionylacetonato), aluminum monoethylacetoacetate.bis(acetylacetonato), aluminum acetylacetonato.di-s-butylate, aluminum methylacetoacetate.di-s-butylate, aluminum di(methylacetoacetate).mono-tert-butylate, aluminum diisopropoxyethylacetoacetate, aluminum monoacetylacetonato, aluminum acetylacetonato.di-s-butylate, aluminum methylacetoacetate.di-s-butylate, aluminum di(methylacetoacetate).mono-tert-butylate, aluminum diisopropoxyethylacetoacetate, aluminum monoacetylacetonato, aluminum monoacetylacetonato. Examples of suitable chelate compounds include aluminum chelate compounds such as diisopropoxy bis(ethylacetoacetate)aluminum; titanium chelate compounds such as diisopropoxy bis(ethylacetoacetate)titanate, diisopropoxy bis(acetylacetonato)titanate, and di-n-butoxy bis(acetylacetonato)titanate; zirconium chelate compounds such as tetrakis(acetylacetonato)zirconium, tetrakis(n-propylacetoacetate)zirconium, and tetrakis(ethylacetoacetate)zirconium; and tin chelate compounds such as tin ester compounds such as dibutyltin diacetate, dibutyltin di(2-ethylhexyl), dibenzyltin di(2-ethylhexyl), dibutyltin dilaurate, dibutyltin diisooctylmaleate, and dibutyltin bis(acetylacetonate). However, the use of titanium chelate compounds is preferred in terms of the reactivity and stability of the composition.

[0040] As the titanium chelate compound, commercially available products can also be used, and examples thereof include D-20, D-25, and D-26 (all manufactured by Shin-Etsu Chemical Co., Ltd.), Orgatix TC-750, and Orgatix TC-401 (manufactured by Matsumoto Fine Chemical Co., Ltd.).

[0041] The amount of the catalyst component blended is preferably 0.1 to 15 parts by mass, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the organopolysiloxane, from the viewpoints of the curability and stability of the composition and the hardness of the resulting cured product. The curing catalyst component may be a single composition or a mixture of multiple compounds with different compositions.

[0042] The room-temperature-curable organopolysiloxane composition of the present invention may contain any additives as appropriate, provided that the effects of the present invention are not impaired. Specific examples of additives include non-reactive silicone oils, reactive silicone oils, silane coupling agents, adhesion promoters, non-reactive polymer resins, fillers, leveling agents, rheology modifiers, reactive diluents, non-reactive diluents, surfactants, dispersants, antifoaming agents, dehydrating agents, antioxidants, antioxidants, antistatic agents, infrared absorbers, ultraviolet absorbers, light stabilizers, fluorescent agents, dyes, pigments, fragrances, abrasives, rust inhibitors, and thixotropy-imparting agents. These may be used alone or in combination of two or more.

[0043] The room-temperature-curable organopolysiloxane composition of the present invention is preferably a solvent-free form substantially free of solvent, but a solvent can be added depending on the intended use and workability. Here, "substantially" means that the solvent content in the composition is 1% by mass or less, particularly 0.1% by mass or less. Within this range, a solvent removal step is not required during the formation of a cured coating, and solvent evaporation does not deteriorate the working environment or cause corrosion or deterioration of electrical and electronic components and the circuit boards on which they are mounted. Specific examples of solvents that can be used include those similar to the reaction solvents used during the production of the organopolysiloxane. Solvents also include those that are not intentionally added to the composition, such as reaction solvents that could not be completely removed by vacuum distillation.

[0044] There are no particular restrictions on the method for producing the composition of the present invention, and it can be obtained by mixing components (A) and (B), and optionally any additives and a solvent, in any order.

[0045] The room-temperature-curable organopolysiloxane composition of the present invention can be used as a so-called one-package room-temperature-curable composition, which is stored as is in a sealed container and cures only upon exposure to moisture in the air at the time of use. Alternatively, the room-temperature-curable organopolysiloxane composition of the present invention can be used as a so-called multi-package room-temperature-curable composition, for example, by storing the organopolysiloxane and the curing catalyst in separate containers and mixing them at the time of use.

[0046] [4] Coating Agents and Coated Articles The room-temperature-curable organopolysiloxane composition of the present invention can be suitably used as a coating agent, particularly as an exterior wall paint, but its application is not limited to coating agents. When used as a coating agent, for example, the composition of the present invention can be applied to at least one surface of a substrate, either directly or via one or more other layers, and then cured to form a film, thereby obtaining a coated article having a cured film of the coating agent laminated, directly or via one or more other layers, on at least one surface of the substrate.

[0047] The substrate may include, but is not limited to, glass, silicon wafers, metals, plastic molded bodies, ceramics, composites thereof, etc. Substrates whose surfaces have been treated with chemical conversion coating, corona discharge treatment, plasma treatment, or acid or alkali solution, as well as decorative plywood whose surface layer is coated with a different type of paint from the substrate itself, can also be used. Examples of other layers include those obtained by polyester resin coating, polyurethane resin coating, aminoalkyd resin coating, lacquer coating, spray coating, and aqueous wax coating.

[0048] The method for applying the coating agent to the substrate may be appropriately selected from known techniques, and various coating methods can be used, for example, roll coating, bar coating, wire bar coating, spray coating, flow coating, spin coating, curtain coating, knife coating, dip coating, brush coating, etc. The amount to be applied is not particularly limited, but usually, an amount that results in a coating thickness of 0.1 to 1,000 μm after drying is preferred, and an amount that results in a coating thickness of 1 to 100 μm is preferable.

[0049] Methods for curing the composition of the present invention include room temperature curing and heat curing. The composition of the present invention can be cured, for example, by leaving it to stand at room temperature for 24 hours or more. When curing by heating, the heating temperature is not particularly limited, but is preferably 100 to 300°C, and more preferably 150 to 250°C. A combination of room temperature curing and heat curing may also be used.

[0050] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0051] In the following examples, the kinematic viscosity was measured at 25°C using a Canon-Fenske viscometer according to the method described in JIS Z 8803:2011. The ratio of the constituent units of the organopolysiloxane was measured using an NMR measurement device manufactured by JEOL Ltd. 1 H-NMR and 29 The molecular weight was calculated from the integrated value of the detected spectrum in Si-NMR. The molecular weight was determined as a weight average molecular weight converted into polystyrene by GPC measurement under the following conditions. [GPC conditions] Apparatus: HLC-8220 (manufactured by Tosoh Corporation) Columns: TSKgel GMHXL-L, TSKgel G4000HXL, TSKgel G2000HXL x 2 Developing solvent: tetrahydrofuran (THF) Flow rate: 1 mL / min Detector: RI Column thermostat temperature: 40°C Standard material: polystyrene

[0052] [1] Production of Organopolysiloxanes Using the following components as raw materials, organopolysiloxanes of Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-9 were produced.

[0053] (a) Component a-1: Mw 1,000, kinematic viscosity 25 mm 2 / s, a = 0, b = 1.0, c = 0, d = 0, e = 1.1 in formula (I), R 1 and R 2 = Methyl group a-2: Mw 1,800, kinematic viscosity 100 mm 2 / s, a = 0, b = 0.66, c = 0.34, d = 0, e = 0.8 in formula (I), R 1 and R 2= Methyl group a-3: Mw 10,000, kinematic viscosity 80 mm 2 / s, a = 0, b = 0.50, c = 0.50, d = 0, e = 0.4 in formula (I), R 1 and R 2 = Methyl group a-4: Mw 200, kinematic viscosity 5 mm 2 / s, a = 0, b = 1.0, c = 0, d = 0, e = 1.9 in formula (I), R 1 and R 2 = methyl group

[0054] Component (b) b-1: Dimethylpolysiloxane having silanol groups at both molecular chain terminals (dimethylpolysiloxane capped at both terminals with hydroxydimethylsiloxy groups, Mw 400, average number of Si atoms 5) b-2: Dimethylpolysiloxane having silanol groups at both molecular chain terminals (dimethylpolysiloxane capped at both terminals with hydroxydimethylsiloxy groups, Mw 1,000, average number of Si atoms 13) b-3: Dimethylpolysiloxane having silanol groups at both molecular chain terminals (dimethylpolysiloxane capped at both terminals with hydroxydimethylsiloxy groups, Mw 3,200, average number of Si atoms 40) b'-4: Dimethylpolysiloxane capped at both terminals with trimethoxysiloxy groups (dimethylpolysiloxane Mw 1,800, average number of Si atoms 22)

[0055] Example 1-1: 100 parts by mass of silicone oligomer a-1, 40 parts by mass of silicone oil b-1, and 2 parts by mass of a strongly acidic cation exchange resin (Lewatit K2629, manufactured by LANXESS) were placed in a 500 mL separable flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer, and the mixture was allowed to react at 100°C for 3 hours with stirring. The reaction solution was then distilled off under normal pressure, and once no more distillate was produced, the mixture was stirred at 105°C for 3 hours. Finally, the distillate was removed under reduced pressure (90°C, 1.3 kPa), and the mixture was filtered to obtain an organopolysiloxane (yield: 120 parts by mass). The physical properties of the resulting organopolysiloxane are listed in Table 1.

[0056] Examples 1-2 to 1-5, Comparative Examples 1-1 to 1-9 Organopolysiloxanes were produced in the same manner as in Example 1-1, except for changing the components and amounts shown in Table 1. The physical properties of the obtained organopolysiloxanes are also shown in Table 1.

[0057] *Measurement is not possible due to increased molecular weight

[0058] [2] Preparation of Room-Temperature-Curable Organopolysiloxane Compositions and Evaluation of Coating Films [Examples 2-1 to 2-5, Comparative Examples 2-1 to 2-9] Room-temperature-curable organopolysiloxane compositions were prepared by adding 2 parts by mass of Orgatix TC-750 (titanium catalyst, manufactured by Matsumoto Fine Chemical Co., Ltd.) to 100 parts by mass of the organopolysiloxanes obtained in Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-9.

[0059] The resulting room-temperature-curable organopolysiloxane compositions were evaluated for coating appearance, tack-free time, and heat resistance using the following methods. The results are shown in Table 2. (1) Coating Appearance: The resulting compositions were applied to a polished steel plate, the surface of which had been wiped clean of oil, to a thickness of 10 μm using a bar coater, and then left to stand for 7 days at 23°C and 50% RH to obtain a cured film. Visually, a coating surface that was uniform, free of irregularities due to gel aggregates or waviness due to cure shrinkage, and not cloudy was rated as ◯; an uneven coating surface, whitening, irregularities due to gel aggregates, or waviness due to cure shrinkage was rated as ×. (2) Tack-Free (TF) Test: Tack-free time was measured in accordance with JIS K6249 at 23°C and 50% RH. The obtained composition was applied to a polished steel plate whose surface had been wiped free of oil to a thickness of 10 μm, and the surface was lightly touched with a fingertip cleaned with ethyl alcohol. If the time it took for the sample to no longer adhere to the fingertip was within 1 hour, it was rated as O, and if it took longer than 1 hour, it was rated as X. (3) Heat Resistance The cured film obtained in the above coating film appearance evaluation was further heated in a dryer at 200°C for 30 minutes, and if the coating film after cooling showed no irregularities or cracks due to cure shrinkage, it was rated as O, and if the coating film showed irregularities or cracks due to cure shrinkage, it was rated as X.

[0060]

[0061] As shown in Table 2, the curable compositions obtained in Examples 2-1 to 2-5 exhibited short tack-free times, excellent curability, and high heat resistance. On the other hand, in Comparative Example 2-1, in which component (a) was changed to the high-molecular-weight silicone oligomer a-3, the molecular weight of the resulting organopolysiloxane increased, causing the entire composition to gel, making it difficult to form a cured film. The composition of Comparative Example 2-2, which consisted only of silicone oligomer a-3 and a curing catalyst, exhibited a long tack-free time and poor curability. Furthermore, in Comparative Example 2-3, in which component (a) was changed to the low-molecular-weight silicone oligomer a-4, the molecular weight of the resulting organopolysiloxane decreased, the kinematic viscosity fell below the lower limit, and the heat resistance of the cured film was insufficient. The cured films of Comparative Example 2-4, which did not use component (b), and Comparative Example 2-5, in which the amount of component (b) was small, the molecular weight of the resulting organopolysiloxane was low, and the kinematic viscosity was below the lower limit, exhibited poor heat resistance. The cured films of Comparative Examples 2-6 and 2-7, in which the amount of component (b) was large, the molecular weight of the resulting organopolysiloxane was high, and the kinematic viscosity exceeded the upper limit, exhibited gel aggregates on the coating surface. In Comparative Example 2-8, in which component (b) was replaced with silicone oil b-3, which has a higher molecular weight, the resulting organopolysiloxane exhibited properties similar to oil, the kinematic viscosity of the composition was low, and the curing properties were insufficient. Furthermore, in Comparative Example 2-9, in which silicone oil b'-4, which does not have silanol groups at the molecular chain terminals, was used, the coating film exhibited whitening due to the presence of unreacted oil on the surface, and the heat resistance was also poor.

Claims

1. A condensate of (a) a silicone oligomer represented by the following formula (I) and (b) a silicone oil having a silanol group at the molecular chain end, wherein the kinematic viscosity at 25 °C is 100 to 2,000 mm 2 / s, an organopolysiloxane. (In the formula, R 1 each independently represents a hydrogen atom, or an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, which may be substituted by a halogen atom, and R 2 represents a hydrogen atom, a methyl group, an ethyl group, an n-propyl group or an isopropyl group. a, b, c and d are numbers satisfying 0 ≦ a < 1, 0 < b ≦ 1, 0 ≦ c < 0.5, 0 ≦ d < 0.5, and a + b + c + d = 1, and e is a number satisfying 0 < e ≦ 4.) 2. The organopolysiloxane according to claim 1, wherein in the formula (I), a and d are 0.

3. The organopolysiloxane according to claim 1 or 2, wherein the weight average molecular weight in terms of polystyrene in the gel permeation chromatography of the component (a) is 500 to 3,000.

4. The organopolysiloxane according to any one of claims 1 to 3, wherein the weight average molecular weight in terms of polystyrene in the gel permeation chromatography of the component (b) is 200 to 2,000.

5. The organopolysiloxane according to any one of claims 1 to 4, wherein the component (b) is 10 to 80 parts by mass with respect to 100 parts by mass of the component (a).

6. The organopolysiloxane according to any one of claims 1 to 5, wherein the weight average molecular weight in terms of polystyrene in the gel permeation chromatography is 5,000 to 100,000.

7. A room temperature curable organopolysiloxane composition comprising the organopolysiloxane according to any one of claims 1 to 6 and a curing catalyst.

8. A coating agent comprising the room temperature curable organopolysiloxane composition according to claim 7.

9. A cured product of the room temperature curable organopolysiloxane composition according to claim 7.

10. A coated article having a substrate and the cured product according to claim 9 formed directly or via one or more other layers on at least one surface of the substrate.

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