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

Abstract

To provide an organopolysiloxane that enables a room-temperature-curable composition to have low viscosity without employing a solvent, to have superior curability, and to form a cured product with excellent heat resistance.SOLUTION: 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).SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Organopolysiloxanes containing an alkoxysilyl group are widely used in paints and coating agents. Generally, an organopolysiloxane having an alkoxy group at the terminal is blended with a curing catalyst, and by applying external energy such as thermal energy, the terminal alkoxy groups react with each other to form a strong siloxane network. The resulting coating is excellent in heat resistance and weather resistance, and thus the construction targets range from outdoor buildings to automobile parts and electronic parts.

[0003] Organopolysiloxanes containing an alkoxysilyl group are generally produced by hydrolytic condensation of alkoxysilane (Patent Documents 1 and 2). However, generally, many of the highly active alkoxy groups are consumed by the hydrolytic condensation reaction during production, and only a small number of low-active alkoxy groups remain in the resulting organopolysiloxane, and many of the coatings are inferior in curability. The tendency of the curability to decrease becomes more prominent as the molecular weight of the resulting organopolysiloxane is higher, and in order to compensate for the low curability, additional processes such as heating at a high temperature during film formation are required.

[0004] On the other hand, in a low molecular weight organopolysiloxane having a molecular weight of 5,000 or less, since many active alkoxy groups remain and thus the reactivity is excellent, there are compositions containing a low molecular weight organopolysiloxane that cure without going through a heating process. However, the cured film of the low molecular weight organopolysiloxane has problems such as low mechanical properties because it is a thin film, and the residual alkoxy groups in the film react sequentially when heat is applied from the outside, resulting in cracks over time.

[0005] As described above, in various organopolysiloxanes, when the molecular weight is large, there are problems such as deterioration of curability due to a small number of polymerizable functional groups. When the molecular weight is small, there are problems such as low mechanical strength and generation of cracks over time due to heating. In addition, due to differences in the molecular weight of organopolysiloxanes, various physical properties such as the curing temperature, heat resistance, light resistance, solvent resistance, surface hardness, and workability of the coating film also vary. Therefore, a molecular weight suitable for the application is required.

[0006] For these reasons, molecular weight control is an important factor in the production of organopolysiloxanes. In Patent Document 3, it has been found that an organopolysiloxane having a predetermined peak top and peak area in a specific molecular weight range can solve the above problems. Specifically, by combining an organopolysiloxane with a high molecular weight and an organopolysiloxane with a low molecular weight, the above problems have been solved. However, this method requires a solvent to dissolve the organopolysiloxane with a high molecular weight, which is not preferable from the perspective of environmental considerations.

[0007] In Patent Document 4, a liquid organopolysiloxane having a high molecular weight and high reactivity, which is obtained by reacting a polydimethylsiloxane unit having an alkoxysilyl group with a pre-condensed silicone oligomer, has been proposed. This organopolysiloxane can achieve both being solvent-free and liquid and room temperature curability. However, while it has high reactivity, cracks may occur in the cured film in a high-temperature environment.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention has been made in view of the above circumstances, and provides an organopolysiloxane that gives a room-temperature curable composition that is low-viscosity even when no solvent is used, has excellent curability, and can produce a cured product with good heat resistance, and a room-temperature curable organopolysiloxane composition containing the same.

Means for Solving the Problems

[0010] As a result of intensive studies to achieve the above object, the present inventor has found that an organopolysiloxane, which is a condensate obtained by condensing a silicone oligomer having an alkoxysilyl group and a silicone oil having a silanol group at the molecular chain end, is liquid even without a solvent, has excellent curability, and the cured film of the composition containing the organopolysiloxane has excellent crack resistance, and has completed the present invention.

[0011] That is, the present invention is 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, having a kinematic viscosity at 25°C of 100 to 2,000 mm 2 / s of an organopolysiloxane,

Chemical formula

Advantages of the Invention

[0012] The organopolysiloxane of the present invention provides a room temperature curable organopolysiloxane composition that has a low viscosity even when no solvent is used and excellent curability. Therefore, a solvent removal step is not required during the formation of the cured film, and it does not cause deterioration of the working environment due to the volatilization of the solvent, or corrosion and deterioration of electrical and electronic components and the circuit boards on which they are mounted. In addition, the cured product obtained from the room temperature curable composition containing the organopolysiloxane of the present invention is excellent in heat resistance and thus suitable for the production of various coated articles.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, the present invention will be specifically described. [1] Organopolysiloxane The organopolysiloxane of the present invention is a condensation reaction product of (a) a silicone oligomer and (b) a silicone oil having a silanol group at the molecular chain terminal.

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

[0015]

Chemical formula

[0016] In formula (I), 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 with a halogen atom. R 1Examples of the alkyl group having 1 to 8 carbon atoms include linear, branched, and cyclic ones. Specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, neopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl groups, etc. Among them, an alkyl group having 1 to 6 carbon atoms is preferable, and an alkyl group having 1 to 3 carbon atoms is more preferable. A methyl group and an ethyl group are even more preferable. Examples of the aryl group having 6 to 18 carbon atoms preferably have 6 to 10 carbon atoms. Specific examples thereof include unsubstituted aryl groups such as phenyl and naphthyl groups; alkylaryl groups such as tolyl, xylyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, dodecylphenyl groups, etc. Among them, a phenyl group is preferable. Examples of the aralkyl group having 7 to 20 carbon atoms preferably have 7 to 10 carbon atoms. Specific examples thereof include benzyl group, phenylethyl group, etc. In addition, in the above alkyl group, aryl group, and aralkyl group, some or all of the hydrogen atoms may be substituted with halogen atoms (fluorine, chlorine, bromine, iodine atoms). Specific examples thereof include chloromethyl, chloropropyl, bromoethyl, trifluoropropyl, chlorophenyl, bromophenyl groups, etc. 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 them, R 2 is preferably a hydrogen atom, a methyl group, or an ethyl group. Also, more than half of R 2 is preferably a methyl group, an ethyl group, an n-propyl group, or an isopropyl group, and a methyl group or an ethyl group is more preferable.

[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 the crack suppression effect, a number that satisfies 0 ≦ a ≦ 0.3 is preferable, and 0 is more preferable. 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 preferable. c is a number that satisfies 0 ≦ c < 0.5, but from the viewpoints of the curability of the composition and the hardness of the resulting cured product, a number that satisfies 0 ≦ c ≦ 0.4 is preferable. d is a number that satisfies 0 ≦ d < 0.5, but from the viewpoints of the curability of the composition and the hardness of the resulting cured product, a number that satisfies 0 ≦ d ≦ 0.2 is preferable, and 0 is more preferable. e is a number that satisfies 0 < e ≦ 4, but from the viewpoints of being effective in suppressing the condensation reaction by the condensable functional group, and the crack resistance, water resistance, and weather resistance of the resulting cured product, e is preferably a number that satisfies 0 < e ≦ 3.

[0019] As the above silicone oligomer, in the above formula (I), R 1 and R 2 are a methyl group or an ethyl group, a to d are 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, which is preferable.

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

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

[0022] The production method of the component (a) is not particularly limited, and a conventionally known production method can be adopted. For example, it can be obtained by hydrolytic condensation of a silane compound having a hydrolyzable group.

[0023] (b) Silicone oil having a silanol group at the molecular chain end (b) The component is a silicone oil having one or more silanol groups at the molecular chain ends. When the component (b) does not have a silanol group, the reaction does not proceed sufficiently during the condensation reaction, the oil remains in the obtained organopolysiloxane, and poor curing occurs. Examples of the group bonded to the silicon atom other than the silanol group include those exemplified as R in the component (a) 1 and a methyl group or a phenyl group is preferred.

[0024] Examples of the molecular structure of the component (b) include linear, branched, cyclic, etc. The preferred structure of the silicone oil of the 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 basically composed of a repetition of diorganosiloxane units.

[0025] Specific examples of such a component (b) include dimethylpolysiloxane blocked with hydroxydimethylsiloxy groups at both ends, dimethylsiloxane-methylhydrogensiloxane copolymer blocked with hydroxydimethylsiloxy groups at both ends, dimethylsiloxane-methylphenylsiloxane copolymer blocked with hydroxydimethylsiloxy groups at both ends, dimethylsiloxane-diphenylsiloxane copolymer blocked with hydroxydimethylsiloxy groups at both ends, and the like.

[0026] (b) component, in terms of polystyrene equivalent weight average molecular weight (Mw) in gel permeation chromatography, is preferably 200 to 2,000, more preferably 300 to 1,500, and even more preferably 400 to 1,000. If Mw is 200 or more, the crack resistance of the obtained organopolysiloxane is improved. If it is 2,000 or less, the occurrence of curing defects due to the obtained organopolysiloxane becoming oil-like can be suppressed.

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

[0028] The amount of the (b) component used in the condensation reaction is preferably 10 to 80 parts by mass, more preferably 10 to 70 parts by mass, based on 100 parts by mass of the (a) component. If it is 10 parts by mass or more, the molecular weight increase of the organopolysiloxane by condensation proceeds sufficiently, and the heat resistance of the obtained cured product is improved. Also, if it is 80 parts by mass or less, gelation due to the increase in molecular weight can be suppressed, and the occurrence of unevenness or coating irregularities during coating can be prevented.

[0029] [2] Method for producing organopolysiloxane The method for producing the organopolysiloxane of the present invention is not particularly limited. For example, in the presence of a catalyst, the (a) component and the (b) component are condensed under heating conditions of 60 to 200 °C, and then, if necessary, it can be obtained by passing through a step of distilling off the by-produced alcohol.

[0030] As the catalyst, conventionally known ones can be used. Those whose aqueous solution shows acidity with pH 2 to 7 are preferred, and in particular, acidic hydrogen halides, sulfonic acids, carboxylic acids, acidic or weakly acidic inorganic salts, solid acids such as ion exchange resins, etc. are preferred. Specific examples of the acidic catalyst 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, cation exchange resins having a sulfonic acid or carboxylic acid group on the surface, etc.

[0031] The amount of the catalyst used is not particularly limited, but considering that the reaction proceeds rapidly and the ease of removing the catalyst after the reaction, 0.02 to 10 parts by mass is preferable with respect to 100 parts by mass of the component (a).

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

[0033] In addition, during the condensation reaction, a solvent may be used as long as it does not inhibit the reaction. If used, it is preferable to completely remove them by treatment such as a stripping process. Specific examples of the organic solvent that can be used include methanol, ethanol, propanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, toluene, xylene, and the like.

[0034] The kinematic viscosity of the organopolysiloxane of the present invention at 25°C is 100 to 2,000 mm 2 / s, preferably 120 to 1,500 mm 2 / s, and more preferably 140 to 500 mm 2 / s. If it is less than 100 mm 2 / s, the heat resistance of the obtained cured product is insufficient, and if it exceeds 2,000 mm 2 / s, unevenness or coating irregularities during coating will occur. The kinematic viscosity is the measured value at 25°C by a Cannon-Fenske viscometer measured by the method described in JIS Z 8803:2011 (hereinafter the same).

[0035] Also, the weight average molecular weight (Mw) in terms of polystyrene in the gel permeation chromatography (GPC) of the organopolysiloxane of the present invention is preferably 5,000 to 100,000, and more preferably 5,000 to 50,000.

[0036] [3] Room temperature curable organopolysiloxane composition The room-temperature curable organopolysiloxane composition of the present invention contains the following components. (A) A condensation reaction product of the silicone oligomer represented by the above formula (I) and the silicone oil having a silanol group at the molecular chain end, and the kinematic viscosity at 25°C is 100 to 2,000 mm 2 / s of organopolysiloxane (B) A curing catalyst [[ID=⑨]]In the present invention, "room temperature" means the normal temperature without particularly heating or cooling, and generally means a temperature range of 0 to 40°C, preferably 5 to 35°C.

[0037] (B) As the curing catalyst of the component, as long as it is generally used in organosiloxane-based paints, it is not particularly limited, but an organometallic compound is preferred. For example, metal alkoxide compounds such as Ti, Al, Zr, Sn, metal chelate compounds, metal ester compounds, etc. can be mentioned, and those containing an organic titanium compound are 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; titanium alkoxides such as tetramethyl titanate, tetraethyl titanate, tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetraisobutyl titanate, tetra-t-butyl titanate, tetra-n-hexyl titanate, tetraisooctyl 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, etc.

[0039] Specific examples of the metal chelate compound include aluminum chelate compounds such as tris(ethylacetoacetate)aluminum, tris(n-propylacetoacetate)aluminum, tris(isopropylacetoacetate)aluminum, tris(n-butylacetoacetate)aluminum, isopropoxybis(ethylacetoacetate)aluminum, tris(acetylacetonato)aluminum, tris(propionylacetonato)aluminum, diisopropoxypropionylacetonatoaluminum, acetylacetonato·bis(propionylacetonato)aluminum, monoethylacetoacetate·bis(acetylacetonato)aluminum, acetylacetonatoaluminum·di-s-butyrate, methylacetoacetatealuminum·di-s-butyrate, di(methylacetoacetate)aluminum·mono-tert-butyrate, diisopropoxyethylacetoacetatealuminum, monoacetylacetonato·bis(ethylacetoacetate)aluminum, etc.; titanium chelate compounds such as diisopropoxy·bis(ethylacetoacetate)titanate, diisopropoxy·bis(acetylacetonato)titanate, di-n-butoxy·bis(acetylacetonato)titanate, etc.; zirconium chelate compounds such as tetrakis(acetylacetonato)zirconium, tetrakis(n-propylacetoacetate)zirconium, tetrakis(ethylacetoacetate)zirconium, etc.; tin chelate compounds such as tin ester compounds such as dibutyltin diacetate, dibutyltin di(2-ethylhexylate), dibenzyltin di(2-ethylhexylate), dibutyltin dilaurate, dibutyltin diisooctyl maleate, dibutyltin bis(acetylacetonate), etc. Among them, using a titanium chelate compound is suitable from the viewpoints of the reaction activity and stability of the composition.

[0040] As the above titanium chelate compound, commercially available products can also be used. For example, D-20, D-25, D-26 (all manufactured by Shin-Etsu Chemical Co., Ltd.), Organicx TC-750, Organicx TC-401 (manufactured by Matsumoto Fine Chemical Co., Ltd.), etc. can be mentioned.

[0041] From the viewpoints of the curability and stability of the composition and the hardness of the resulting cured product, the blending amount of the above catalyst component is preferably 0.1 to 15 parts by mass, more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the above organopolysiloxane. The curing catalyst component may be a single composition or a mixture of a plurality of compounds having different compositions.

[0042] The room-temperature curable organopolysiloxane composition of the present invention may appropriately contain any additive as long as the effects of the present invention are not inhibited. Specific examples of the additive include non-reactive silicone oil, reactive silicone oil, silane coupling agent, adhesion-imparting agent, non-reactive polymer resin, filler, leveling agent, rheology modifier, reactive diluent, non-reactive diluent, surfactant, dispersant, defoaming agent, dehydrating agent, anti-aging agent, antioxidant, antistatic agent, infrared absorber, ultraviolet absorber, light stabilizer, fluorescent agent, dye, pigment, fragrance, abrasive, rust inhibitor, thixotropy-imparting agent, and the like. These may be used individually or in combination of two or more.

[0043] The room-temperature curable organopolysiloxane composition of the present invention preferably has a solvent-free form that substantially does not contain a solvent, but a solvent can also be added and used from the viewpoints of its use and workability. Here, "substantially" means that the solvent contained in the composition is 1% by mass or less, particularly 0.1% by mass or less. Within such a range, a solvent removal step is not required during the formation of the cured film, and the volatilization of the solvent does not cause deterioration of the working environment or corrosion or deterioration of electrical and electronic components and circuit boards on which they are mounted. Specific examples of the usable solvent include the same ones as the reaction solvent used during the production of the organopolysiloxane. The solvent also includes those that are not intentionally added components in the composition, such as reaction solvents that could not be completely removed by distillation under reduced pressure.

[0044] The production method of the composition of the present invention is not particularly limited, and it can be obtained by mixing the components (A) and (B), and optionally any additives and solvents in any order.

[0045] The room-temperature curable organopolysiloxane composition of the present invention can be used as a so-called one-pack type room-temperature curable composition that is stored as it is in a sealed container and starts to cure only when exposed to moisture in the air during use. Also, the room-temperature curable organopolysiloxane composition of the present invention can be used as a so-called multi-pack type room-temperature curable composition in which, for example, the organopolysiloxane and the curing catalyst are stored separately in different containers and mixed at the time of use.

[0046] [4] Coating agent and coated article The room-temperature curable organopolysiloxane composition of the present invention can be suitably used as a coating agent, and is particularly suitably used for exterior wall paint applications, but its applicable uses are not limited to coating agents. When used as a coating agent, for example, the composition of the present invention is applied to at least one surface of a substrate, directly or through one or more other layers, and cured to form a film, whereby a coated article having a cured film of the coating agent laminated on at least one surface of the substrate, directly or through one or more other layers, can be obtained.

[0047] The above-mentioned substrate is not particularly limited, and examples include glass, silicon wafers, metals, plastic moldings, ceramics, and composites thereof. In addition, substrates whose surfaces have been subjected to chemical conversion treatment, corona discharge treatment, plasma treatment, treatment with an acid or an alkali solution, or decorative plywood coated with a paint of a different type from the substrate body can also be used. Examples of the other layer include those obtained by polyester resin coating, polyurethane resin coating, aminoalkyd resin coating, lacquer coating, spray coating, and aqueous wax coating.

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

[0049] Examples of the method 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 standing at room temperature for 24 hours or more. When curing by heating, the heating temperature is not particularly limited, but 100 to 300 °C is preferred, and 150 to 250 °C is more preferred. It is also possible to apply a combination of room temperature curing and heat curing.

Examples

[0050] Hereinafter, examples and comparative examples will be shown to more specifically explain the present invention, 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 Cannon-Fenske viscometer by the method described in JIS Z 8803:2011. The constitutional unit ratio of the organopolysiloxane was calculated from the integrated values of the detection spectra in 1 H-NMR and 29 Si-NMR using an NMR measuring device manufactured by JEOL Ltd. The molecular weight was determined as the weight average molecular weight in terms of 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 × 2 Developing solvent: Tetrahydrofuran (THF) Flow rate: 1 mL / min Detector: RI Column thermostat temperature: 40 °C Standard substance: Polystyrene

[0052] [1] Production of organopolysiloxane 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, in formula (I), a = 0, b = 1.0, c = 0, d = 0, e = 1.1, R 1 and R 2 = methyl group a-2: Mw 1,800, kinematic viscosity 100 mm 2 / s, in formula (I), a = 0, b = 0.66, c = 0.34, d = 0, e = 0.8, R 1 and R 2 = methyl group a-3: Mw 10,000, kinematic viscosity 80 mm 2 / s, in formula (I), a = 0, b = 0.50, c = 0.50, d = 0, e = 0.4, R 1 and R 2 = methyl group a-4: Mw 200, kinematic viscosity 5 mm 2 / s, in formula (I), a = 0, b = 1.0, c = 0, d = 0, e = 1.9, R 1 and R 2 = methyl group

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

[0055] [Example 1-1] Into a 500 mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer, 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 added, and the reaction was carried out at 100 °C for 3 hours while stirring. Then, the reaction solution was distilled off under normal pressure, and stirring was carried out at 105 °C for 3 hours after no more distillate came out. Finally, after removing the distillate by distillation under reduced pressure (90 °C, 1.3 kPa), filtration was carried out to obtain an organopolysiloxane (yield 120 parts by mass). The physical properties of the obtained organopolysiloxane are shown in Table 1.

[0056] [Examples 1-2 to 1-5, Comparative Examples 1-1 to 1-9] The components and compounding amounts shown in Table 1 were changed, and an organopolysiloxane was produced in the same procedure as in Example 1-1. The physical properties of the obtained organopolysiloxane are also shown in Table 1.

[0057]

Table 1

[0058] [2] Production of room temperature curable organopolysiloxane composition and evaluation of coating film [Examples 2-1 to 2-5, Comparative Examples 2-1 to 2-9] To 100 parts by mass of the organopolysiloxanes obtained in Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-9, 2 parts by mass of Orgatix TC-750 (titanium catalyst manufactured by Matsumoto Fine Chemical Co., Ltd.) was added to produce a room temperature curable organopolysiloxane composition.

[0059] Regarding the obtained room-temperature curable organopolysiloxane composition, the appearance of the coating film, the tack-free time, and the heat resistance were evaluated by the following methods. The results are shown in Table 2. (1) Appearance of the coating film The obtained composition was applied to a polished steel plate wiped with surface oil to a thickness of 10 μm using a bar coater, and allowed to stand for 7 days under the conditions of 23 °C and 50% RH to obtain a cured film. Visually, those with a uniform coating film surface, no unevenness due to gel aggregates or undulations on the film surface due to curing shrinkage, and no cloudiness were marked as ○, and those with a non-uniform coating film surface, whitening, unevenness due to gel aggregates, or undulations on the film surface due to curing shrinkage were marked as ×. (2) Tack-free (TF) test The tack-free time was measured at 23 °C and 50% RH according to JIS K6249. After applying the obtained composition to a polished steel plate wiped with surface oil to a thickness of 10 μm, the surface was gently touched with a fingertip washed with ethyl alcohol, and those with a time of less than 1 hour until the sample no longer adhered to the fingertip were marked as ○, and those with a time longer than 1 hour were marked as ×. (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 those with no cracks due to unevenness or curing shrinkage in the cooled coating film were marked as 〇, and those with cracks due to unevenness or curing shrinkage in the coating film were marked as ×.

[0060]

Table 2

[0061] As shown in Table 2, it can be seen that the curable compositions obtained in Examples 2-1 to 2-5 have a short tack-free time, excellent curability, and high heat resistance. On the other hand, in Comparative Example 2-1 where the (a) component was changed to the silicone oligomer a-3 with a large molecular weight, the entire composition gelled due to the increase in the molecular weight of the obtained organopolysiloxane, making it difficult to form a cured film. In addition, the composition of Comparative Example 2-2 consisting only of the silicone oligomer a-3 and the curing catalyst had a long tack-free time and poor curability. Also, in Comparative Example 2-3 in which the component (a) was changed to a silicone oligomer a-4 having a low molecular weight, the molecular weight of the obtained organopolysiloxane decreased, the kinematic viscosity was less than the lower limit, and the heat resistance of the cured film was insufficient. The cured films of Comparative Example 2-4 in which the component (b) was not used and Comparative Example 2-5 in which the addition amount of the component (b) was small, the molecular weight of the obtained organopolysiloxane decreased, and the kinematic viscosity was less than the lower limit were inferior in heat resistance. The cured films of Comparative Examples 2-6 and 2-7 in which the addition amount of the component (b) was large, the molecular weight of the obtained organopolysiloxane increased, and the kinematic viscosity exceeded the upper limit had gel aggregates generated on the coating film surface. In Comparative Example 2-8 in which the component (b) was changed to a silicone oil b-3 having a high molecular weight, the obtained organopolysiloxane exhibited properties close to those of an oil, the kinematic viscosity of the composition decreased, and the curability was insufficient. Furthermore, in Comparative Example 2-9 using a silicone oil b'-4 having no silanol group at the molecular chain end, whitening of the appearance occurred due to the remaining unreacted oil on the coating film, and the heat resistance was also inferior.

Claims

1. (a) A condensate of a silicone oligomer represented by the following formula (I) and (b) a silicone oil having a silanol group at the molecular chain end, having a kinematic viscosity at 25 °C of 100 to 2,000 mm 2 / s, an organopolysiloxane. 【Chemical 1】 (wherein 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 with 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, 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 claim 1, 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 claim 1, 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 claim 1, 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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