Organopolysiloxane, adhesion promoter, aqueous coating composition, and primer composition

Abstract

Provided is a water-soluble organopolysiloxane which is represented by formula (1) and exhibits excellent storage stability. (In the formula, R1 is a monovalent hydrocarbon group having 1-10 carbon atoms, R2 moieties are each independently a monovalent hydrocarbon group having 1-10 carbon atoms which may be substituted with a glycidyloxy group, R3 is a methyl group or an ethyl group, a, b, c and d are numbers that satisfy the relationships a ≥ 0.5, b ≥ 0, c > 0, d ≥ 0, and a+b+c+d=1, and x and y are numbers that satisfy the relationships x ≥ 1 and y ≤ 0.5.)

Description

[Technical Field]

[0001] The present invention relates to an organopolysiloxane, an adhesion promoter, an aqueous coating composition, and a primer composition; more specifically, the present invention relates to an organopolysiloxane that contains, as constituent units, 3-glycidyloxypropyl group-containing siloxane units and diorganosiloxane units and that has silanol groups; an adhesion promoter comprising the organopolysiloxane; and an aqueous coating composition and a primer composition that contain the organopolysiloxane. [Background technology]

[0002] Compounds having two or more different reactive functional groups in one molecule are known as coupling agents that bond different materials together. Among these, silane coupling agents that have a hydrolyzable silyl group such as an alkoxysilyl group as one of the reactive groups and further have various organic reactive groups such as a primary amino group, a secondary amino group, a glycidyl ether group, a methacryl group, a ureido group, a vinyl group, a mercapto group, or an isocyanate group are known as primers that improve the adhesion of paints and as adhesion promoters that are added to paint compositions.

[0003] Furthermore, compositions have been reported that use a silane coupling agent as a monomer and add a reactive organopolysiloxane obtained by hydrolyzing and condensing a hydrolyzable silyl group. For example, Patent Document 1 proposes a coating material and adhesive sheet containing an organosilsesquioxane having an epoxy group, and Patent Documents 2 to 4 propose the use of a relatively low molecular weight oligomer obtained by partially hydrolyzing and condensing a silane coupling agent having an epoxy group as an adhesion improver.

[0004] The advantages of using oligomers and / or polymers obtained by hydrolysis and condensation of silane coupling agents compared to silane coupling agents include, firstly, that they have a high molecular weight and low volatility, which eliminates concerns about the reduction of active ingredients during processes such as drying. Another advantage is that it generates less volatile organic compounds (VOCs). Compared to silane coupling agents, which generate alcohol through hydrolysis, oligomers that have been partially hydrolyzed in advance generate less alcohol per unit mass of active ingredient, making them a suitable material for such needs, given the recent trend toward reducing environmental impact through the conversion of solvent-based paints to water-based and solvent-free paints.

[0005] Aiming to further reduce VOCs, aqueous solutions containing hydrolysis condensates obtained by completely hydrolyzing a silane coupling agent and removing the generated alcohol have also been proposed. Patent Documents 5 to 7 propose aqueous silane compositions containing hydrolysis condensates containing functional groups such as amino groups, mercapto groups, and carboxy groups, while Patent Document 8 proposes an aqueous silane composition containing a hydrolysis condensate having an ethylene glycol group.

[0006] In all of these aqueous silane compositions, the hydrolysis condensation product of the silane coupling agent is highly active, and from the viewpoint of handling and stability, it is essential to prepare them as aqueous solutions, but their storage stability is insufficient. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2019-143161 [Patent Document 2] International Publication No. 2018 / 34232 [Patent Document 3] Japanese Patent Application Publication No. 2018-127507 [Patent Document 4] Japanese Patent Publication No. 2022-27097 [Patent Document 5] European Patent No. 0675128 [Patent Document 6] Japanese Patent Application Laid-Open No. 2016-44278 [Patent Document 7] Japanese Patent Application Laid-Open No. 2015-34097 [Patent Document 8] Japanese Patent Application Publication No. 2017-114852 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a water-soluble organopolysiloxane that has organic functional groups and exhibits excellent storage stability. [Means for solving the problem]

[0009] As a result of extensive research aimed at solving the above problems, the present inventors have found that an organopolysiloxane having specific amounts of siloxane units having 3-glycidyloxypropyl groups and diorganosiloxy units, and having silanol groups, has excellent storage stability, and that an aqueous composition containing this organopolysiloxane has excellent adhesion and is suitable as a primer, which led to the completion of the present invention.

[0010] That is, the present invention is 1. An organopolysiloxane represented by the following formula (1): [ka] (In the formula, R 1 is a monovalent hydrocarbon group having 1 to 10 carbon atoms, and R 2 are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted with a glycidyloxy group, and R 3 is a methyl group or an ethyl group, a, b, c, and d are numbers that satisfy a≧0.5, b≧0, c>0, d≧0, and a+b+c+d=1, and x and y are numbers that satisfy x≧1, y≦0.5. 2. The organopolysiloxane according to 1, wherein a, b, c, and d are numbers satisfying the following conditions: 0.5≦a≦0.9, b=0, 0.1≦c≦0.5, and d=0. 3. An adhesion promoter comprising the organopolysiloxane according to 1 or 2. 4. An aqueous coating composition containing the organopolysiloxane according to 1 or 2. 5. A primer composition containing the organopolysiloxane according to 1 or 2. to provide. [Effects of the Invention]

[0011] The organopolysiloxane of the present invention contains highly reactive epoxy groups, which are effective in modifying organic resins and improving adhesion to resin substrates, and also has excellent stability, thereby achieving a long usable period. Furthermore, the organopolysiloxane of the present invention contains silanol groups, which not only provide excellent reactivity with inorganic substrates but also exhibit high water solubility, making it useful as an additive for aqueous coating compositions. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a 1H-NMR spectrum of organopolysiloxane Ep1 obtained in Example 1-1. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be specifically described below. (1) Organopolysiloxane The organopolysiloxane according to the present invention is represented by the following general formula (1).

[0014] [ka]

[0015] In the above formula, R 1is a monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, which may be linear, branched, or cyclic, and specific examples thereof include alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, and n-decyl groups; cycloalkyl groups such as cyclopentyl and cyclohexyl groups; alkenyl groups such as vinyl, allyl, butenyl, hexenyl, and octenyl groups; and aryl groups such as phenyl and naphthyl groups. Among these, methyl, ethyl, n-propyl, and phenyl groups are preferred, methyl and ethyl groups are more preferred, and methyl groups are even more preferred.

[0016] R 2 are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, which may be substituted with a glycidyloxy group, and specific examples thereof include the above-mentioned R 1 and glycidyloxy-substituted alkyl groups such as a glycidyloxypropyl group. Among these, methyl, ethyl, n-propyl, glycidyloxypropyl, and phenyl groups are preferred, methyl and ethyl groups are more preferred, and methyl groups are even more preferred.

[0017] R 3 is a methyl group or an ethyl group.

[0018] a, b, c, and d represent the molar ratio of each siloxane unit and are numbers that satisfy the relationship a+b+c+d=1. The character a is a number equal to or greater than 0.5, and is preferably a number from 0.5 to 0.9. If a is less than 0.5, the amount of available epoxy groups will be small, and the effect of improving adhesion will not be expected. In addition, the organopolysiloxane represented by formula (1) will become highly viscous, gummy, or solid, resulting in poor handleability and reduced water solubility. b is a number of 0 or more, but is preferably 0 in terms of the amount of epoxy groups contained in the organopolysiloxane of the present invention. c is a number exceeding 0 and preferably a number of 0.1 to 0.5. When c is 0, the organopolysiloxane has a structure composed only of trisiloxane units and tetrasiloxane units, and the silanol groups contained therein have high reactivity, resulting in insufficient storage stability and making the product unsuitable for practical use. d is a number of 0 or more, but is preferably 0 in terms of the reactivity of the silanol group.

[0019] x and y respectively represent the number of moles of hydroxyl groups and alkoxy groups bonded to one mole of Si atoms. x is a number of 1 or more, and from the viewpoint of storage stability, is preferably a number of 1 to 2. If it is less than 1, the organopolysiloxane will be poor in water solubility and reactivity with inorganic substrates. y is a number of 0.5 or less, and is preferably a number of 0.4 or less from the viewpoint of reducing alcohol produced by hydrolysis.

[0020] The organopolysiloxane of the present invention is preferably one represented by the following formula (1a).

[0021] [ka]

[0022] In formula (1a), R 2 and R 3 is the same as above, a1 and c1 are numbers that satisfy 0.5≦a1≦0.9, 0.1≦c1≦0.5, and a1+c1=1, and x1 and y1 are numbers that satisfy x1≧1, y1≦0.5.

[0023] From the viewpoints of water solubility and handleability, the weight average molecular weight of the organopolysiloxane of the present invention is preferably 500 to 10,000, more preferably 500 to 1,000. The weight average molecular weight in the present invention is a value calculated as a standard polystyrene by gel permeation chromatography (GPC). The kinematic viscosity of the organopolysiloxane of the present invention is 100 to 500 mm 2 / s is preferable, 200 to 450 mm 2 The kinematic viscosity is a value measured at 25°C using a Cannon-Fenske viscometer.

[0024] The organopolysiloxane of the present invention preferably contains 1% by mass or less of water and free alcohol as impurities. Although water does not fall under the category of VOCs, if present in excess it can react with epoxy groups, and therefore it is desirable to minimize its content when storing the organopolysiloxane of the present invention for long periods of time.

[0025] (2) Method for producing organopolysiloxane The method for producing the organopolysiloxane of the present invention is not particularly limited, but it can be produced, for example, by co-hydrolytic condensation under acidic conditions of alkoxysilanes containing one or more of 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, or a mixture thereof, represented by the following formula (i); diorganodimethoxysilane, diorganodiethoxysilane, or a mixture thereof, represented by the following formula (iii); and, if necessary, organotrimethoxysilane, organotriethoxysilane, or a mixture thereof, represented by the following formula (ii); and tetramethoxysilane, tetraethoxysilane, or a mixture thereof, represented by the following formula (iv).

[0026] [ka] (In the formula, R 1 ~R 3 is the same as above.)

[0027] Specific examples of the diorganodimethoxysilane and diorganodiethoxysilane represented by the above formula (iii) include dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, methylethyldimethoxysilane, methylethyldiethoxysilane, methylpropyldimethoxysilane, methylpropyldiethoxysilane, 3-glycidyloxypropylmethyldimethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, cyclopentylmethyldimethoxysilane, cyclopentylmethyldiethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexylmethyldiethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, methyloctyldimethoxysilane, and methyloctyldiethoxysilane.

[0028] Specific examples of the organotrimethoxysilane and organotriethoxysilane represented by the above formula (ii) include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, octyltrimethoxysilane, and octyltriethoxysilane. workman Examples of the silane include trialkoxysilanes such as decyltrimethoxysilane, decyltriethoxysilane, and decyltriethoxysilane. Furthermore, hydrolysis condensation products of the above silane compounds may also be used. These may be used alone or in combination of two or more.

[0029] The amount of these silane monomers used is preferably adjusted according to the molar ratio of each siloxane unit constituting the desired organopolysiloxane (the values ​​of a to d in formula (1)).

[0030] The amount of water used for hydrolysis of the alkoxysilane monomer is preferably 0.8 to 1.1 times, more preferably 1 to 1.1 times, by mole per mole of alkoxysilyl group, from the viewpoint of suppressing the reaction with the epoxy group and reducing the amount of residual alkoxysilyl groups.

[0031] The acid component used to adjust the acidic conditions during the hydrolysis reaction is not particularly limited as long as it is a commercially available Brønsted acid, but from the viewpoint of ease of availability, formic acid, acetic acid, citric acid, hydrochloric acid, and nitric acid are preferred. The amount of acid used is preferably 0.0001 to 0.01 moles per mole of silane monomer, from the viewpoint of suppressing an increase in the molecular weight of the organopolysiloxane obtained by an excessive dehydration condensation reaction between silanols and a decrease in water solubility due to a decrease in the number of silanol groups.

[0032] In the hydrolysis reaction, an organic solvent may be used as needed to the extent that it does not inhibit the reaction. The organic solvent used is preferably one that is compatible with water, which is the reaction raw material, and alcohols, esters, ketones, ethers, etc. are preferred. In addition, taking into consideration the distillation conditions for removing the generated alcohol, the organic solvent preferably has a low boiling point, and a solvent having a boiling point of 150°C or less under atmospheric pressure is desirable. Specific examples of alcohols include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentyl alcohol, neopentyl alcohol, hexyl alcohol, and cyclohexyl alcohol. Specific examples of esters include ethyl acetate and butyl acetate. Specific examples of ketones include acetone, methyl ethyl ketone, and cyclohexanone. Specific examples of ethers include tetrahydrofuran, tetrahydropyran, and dioxane.

[0033] The temperature for the hydrolysis reaction is preferably 55 to 70°C, and the reaction time is preferably 1 to 5 hours. After the hydrolysis reaction of the silane monomer, it is preferable to carry out a step of distilling off water, alcohol produced by hydrolysis of the alkoxysilyl group, and the organic solvent under reduced pressure at a temperature in the range of 30 to 80°C.

[0034] The organopolysiloxane of the present invention can be used as an adhesion promoter in curable compositions such as paints, and because of its excellent water solubility, it can also be used in aqueous paint compositions.

[0035] (3) Water-based paint composition The aqueous coating composition of the present invention contains the organopolysiloxane described above. The organopolysiloxane may be used alone or in combination of two or more. The aqueous coating composition of the present invention preferably contains water as a solvent, and is particularly preferably an aqueous solution containing only water as a solvent. The amount of the organopolysiloxane in the composition is preferably 5 to 50 mass %, more preferably 10 to 40 mass %.

[0036] Specific examples of aqueous coating compositions include compositions containing aqueous resins such as aqueous epoxy resin compositions and aqueous urethane resin compositions, and the organopolysiloxane of the present invention can be used as one component of these aqueous resin compositions. Specific examples of the aqueous resin include aqueous epoxy resin, aqueous polyurethane resin, aqueous polyester resin, aqueous acrylic resin, and the like. The aqueous coating composition of the present invention may also contain any additives such as organic solvents, antioxidants, ultraviolet absorbers, light stabilizers, thickeners, dispersants, and adhesion promoters, as long as the effects of the present invention are not impaired.

[0037] There are no particular restrictions on the method for producing the aqueous coating composition of the present invention, and examples include a method in which the organopolysiloxane, solvent, and optionally an aqueous resin and other additives are mixed in a conventional manner.

[0038] The resulting aqueous coating composition can be applied to a predetermined substrate directly or via another layer such as a primer layer, and then dried for 1 to 60 minutes in an environment of 20 to 50°C and 30 to 60% RH to form a coating film. The substrate is not particularly limited, but examples thereof include plastic molded bodies, wood products, ceramics, glass, metals, and composites thereof. The method for applying the aqueous coating composition is not particularly limited and can be appropriately selected from conventionally known methods, such as brush coating, wiping, spraying, immersion, bar coating, flow coating, roll coating, curtain coating, spin coating, and knife coating.

[0039] (4) Primer composition The organopolysiloxane of the present invention can be suitably used as a coupling component in an aqueous primer composition (paint) or as an aqueous reactive binder. The primer composition of the present invention contains the organopolysiloxane described above, and the organopolysiloxane may be used alone or in combination of two or more different types. The primer composition of the present invention preferably contains water as a solvent, and is particularly preferably an aqueous solution containing only water as a solvent. The amount of the organopolysiloxane in the composition is preferably 5 to 50 mass %, more preferably 10 to 40 mass %. Furthermore, the primer composition of the present invention may contain any additives within the range that does not impair the effects of the present invention, and specific examples thereof include the same additives as those exemplified for the aqueous coating composition.

[0040] There are no particular limitations on the method for producing the primer composition of the present invention or the method for forming the primer layer, and examples thereof include the same methods as those for the aqueous coating composition.

[0041] Further, other layers may be formed on the surface of the primer layer, and examples of such other layers include a coating layer made of a cured coating of an aqueous resin composition containing an aqueous acrylic resin, an aqueous polyester resin, an aqueous epoxy resin, an aqueous urethane resin, etc. Among these, a coating layer made of a cured coating of an aqueous urethane resin composition is preferred. The coating layer can also be formed by the same method as for the aqueous paint composition. [Example]

[0042] The present invention will be specifically explained below using examples and comparative examples, but the present invention is not limited to these. In the following examples, unless otherwise specified, "parts" and "%" mean "parts by mass" and "% by mass", respectively. In addition, GPC measurement and proton nuclear magnetic resonance spectrum ( 1 The H-NMR measurement conditions are as follows. The kinematic viscosity is the value measured at 25°C using a Cannon-Fenske viscometer.

[0043] (1) GPC measurement conditions Apparatus: Tosoh Corporation HLC-8320GPC Developing solvent: tetrahydrofuran (THF) Flow rate: 0.6mL / min Detector: Refractive index detector (RI) Column: TSK Guardcolumn SuperH-H TSKgel SuperHM-N(6.0mmI.D.×15cm×1) TSKgel SuperH2500(6.0mmI.D.×15cm×1) (All manufactured by Tosoh Corporation) Column temperature: 40℃ Sample injection volume: 50 μL (2.0% THF solution) Standard: Monodisperse polystyrene (2) 1 H-NMR measurement conditions Equipment: BURKER AVANCE III 400 Solvent: CDCl3 Internal standard: tetramethylsilane (TMS)

[0044] [1] Synthesis of organopolysiloxane [Example 1-1] A 1-L three-neck flask equipped with a stirrer, condenser, dropping funnel, and thermometer was charged with 425 g (1.8 mol) of 3-glycidyloxypropyltrimethoxysilane and 24 g (0.2 mol) of dimethyldimethoxysilane. 104.4 g (5.8 mol as water) of 0.2% hydrochloric acid was added dropwise to the flask (the internal temperature was controlled between 20 and 40°C during the addition). After the addition was complete, the mixture was stirred at 70°C for 1 hour, and then distilled under reduced pressure at 70°C to remove the alcohol generated by the hydrolysis reaction and excess water, yielding a colorless, transparent liquid organopolysiloxane (Ep1). The kinematic viscosity of the resulting organopolysiloxane at 25°C was 429 mm 2 The functional group amount of the epoxy group contained was 202 g / mol, and the weight average molecular weight was 610. 1 As a result of analysis by H-NMR and GPC measurement, the organopolysiloxane (Ep1) had a structure represented by the following formula (2). 1 The H-NMR spectrum is shown in Figure 1.

[0045] [ka]

[0046] [Example 1-2] A colorless, transparent liquid organopolysiloxane (Ep2) was obtained by the same procedure as in Example 1-1, except that the amounts of 3-glycidyloxypropyltrimethoxysilane, dimethyldimethoxysilane, and 0.2% hydrochloric acid were changed to 236 g (1.0 mol), 120 g (1.0 mol), and 90 g (5.0 mol as water), respectively. The kinematic viscosity of the resulting organopolysiloxane at 25°C was 218 mm 2 The functional group amount of the epoxy group contained was 258 g / mol, and the weight average molecular weight was 700. 1As a result of analysis by H-NMR and GPC measurement, the organopolysiloxane (Ep2) had a structure represented by the following formula (3).

[0047] [ka]

[0048] [Examples 1-3] A 1-L three-neck flask equipped with a stirrer, condenser, dropping funnel, and thermometer was charged with 425 g (1.8 mol) of 3-glycidyloxypropyltrimethoxysilane and 44 g (0.2 mol) of 3-glycidyloxypropylmethyldimethoxysilane. 104.4 g (5.8 mol as water) of 0.2% hydrochloric acid was added dropwise to the flask (the internal temperature was controlled between 20 and 40°C during the addition). After the addition was complete, the mixture was stirred at 70°C for 1 hour, and then distilled under reduced pressure at 70°C to remove the alcohol generated by the hydrolysis reaction and excess water, yielding a colorless, transparent liquid organopolysiloxane (Ep3). The kinematic viscosity of the resulting organopolysiloxane at 25°C was 361 mm 2 The functional group amount of the epoxy group contained was 200 g / mol, and the weight average molecular weight was 510. 1 As a result of analysis by H-NMR and GPC measurement, the organopolysiloxane (Ep3) had a structure represented by the following formula (4).

[0049] [ka]

[0050] [Comparative Example 1-1] 472 g (2.0 mol) of 3-glycidyloxypropyltrimethoxysilane was placed in a 1 L three-neck flask equipped with a stirrer, condenser, dropping funnel, and thermometer. 108 g of 0.2% hydrochloric acid (6.0 mol as water) was added dropwise to the flask (the internal temperature was controlled between 20 and 40°C during the dropwise addition). After the dropwise addition, the mixture was stirred at 70°C for 1 hour, and then distilled under reduced pressure at 70°C to remove the alcohol generated by the hydrolysis reaction and excess water, yielding a colorless, transparent liquid organopolysiloxane (Ep4). The kinematic viscosity of the resulting organopolysiloxane at 25°C was 726 mm 2 The functional group amount of the epoxy group contained was 189 g / mol, and the weight average molecular weight was 830. 1 Analysis by H-NMR and GPC measurements revealed that the organopolysiloxane (Ep4) had a structure represented by the following formula (5).

[0051] [ka]

[0052] [Comparative Example 1-2] A colorless, transparent liquid organopolysiloxane (Ep5) was obtained by the same procedure as in Example 1-1, except that the amounts of 3-glycidyloxypropyltrimethoxysilane, dimethyldimethoxysilane, and 0.2% hydrochloric acid were changed to 141.6 g (0.6 mol), 168 g (1.4 mol), and 82.8 g (4.6 mol as water) of the 3-glycidyloxypropyltrimethoxysilane, dimethyldimethoxysilane, and 0.2% hydrochloric acid, respectively. The kinematic viscosity of the resulting organopolysiloxane at 25°C was 181 mm 2 The functional group amount of the epoxy group contained was 288 g / mol, and the weight average molecular weight was 930. 1 As a result of analysis by H-NMR and GPC measurement, the organopolysiloxane (Ep5) had a structure represented by the following formula (6). When mixed with ion-exchanged water, organopolysiloxane (Ep5) was incompatible, turned cloudy, and had poor water solubility.

[0053] [ka]

[0054] [2] Storage stability evaluation [Examples 2-1 to 2-3, Comparative Example 2-1] The organopolysiloxanes (Ep1 to Ep4) synthesized in Examples 1-1 to 1-3 and Comparative Example 1-1 were evaluated for kinematic viscosity and water solubility immediately after production, and after 1 month, 2 months, and 3 months when stored at room temperature (25°C) and 5°C. The results are shown in Table 1. The water solubility was evaluated as follows: when each organopolysiloxane was mixed with ion-exchanged water at 25°C to a concentration of 10%, if it dissolved uniformly it was marked "Good" and if it became cloudy it was marked "Poor."

[0055] [Table 1]

[0056] As shown in Table 1, Comparative Example 2-1, which used organopolysiloxane Ep4, which contains no disiloxane units and is composed only of trisiloxane units, showed high silanol activity and a significant increase in viscosity and decrease in water solubility over time due to the progression of the condensation reaction. Such materials can only be handled immediately after production and are of such poor quality that they are not suitable for practical use. In contrast, the organopolysiloxanes Ep1 to Ep3 obtained in Examples 1-1 to 1-3 exhibited similar behavior over time at 25°C, but the extent of the change was small, and it is clear that almost no change was observed when stored at 5°C.

[0057] [3] Preparation and evaluation of primer compositions [Examples 3-1 to 3-3, Comparative Examples 3-1 to 3-5] The primer components shown in Table 2 below were diluted with ion-exchanged water to a solid content of 30%, and the resulting composition was wiped onto a polished steel plate, followed by drying for 30 minutes in an environment of 25°C and 50% RH. Next, 100 parts of water-based paint resin BURNOCK WD-551 (manufactured by DIC Corporation) and 30 parts of isocyanate-based curing agent BURNOCK DNW-5500 (manufactured by DIC Corporation) were mixed, and the water-based urethane paint diluted with water was applied using a No. 14 bar coater, left to stand in an environment of 25°C and 50% RH for 3 days, and then cured at 80°C for 4 hours.

[0058] The coating film obtained above was subjected to the following evaluations, and the results are shown in Table 2. (1) Coating appearance The coating film was visually inspected to determine whether or not there was any abnormality. ○: No abnormalities ×: Foreign matter, unevenness, cloudiness, etc. (2) Initial adhesion According to JIS K5600, six lines are made on the coating film at 2mm intervals using a razor blade. Each cut is made into 25 grids, and cellophane tape (registered trademark, Nichiban After thoroughly adhering the coating, when it was quickly peeled off in a 90° direction, the coating The number of squares (X) that remained without peeling was expressed as X / 25. (3) Boiling adhesion The adhesion of the evaluation sample after immersion in boiling water for 10 hours was measured in the same manner as the initial adhesion. was evaluated by the following. (4) Pencil hardness A 750g load was applied using a method conforming to the pencil scratch test described in JIS K5600-5-4. The weight was applied and measured.

[0059] [Table 2] KBM403: 3-glycidyloxypropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd.) KBE903: 3-aminopropyltriethoxysilane (Shin-Etsu Chemical Co., Ltd.) MP200: Hydrolysis condensate of 3-glycidyloxypropyltrimethoxysilane (Momentive Performance Materials, CoatOSil MP200 silane) Eg-Pr: a [3-(2,3-dihydroxyprop-1-oxy)propyl]silanol oligomer-containing composition described in Example 4 of JP 2017-114852 A

[0060] As shown in Table 2, in Examples 3-1 to 3-3, in which organopolysiloxanes Ep1 to Ep3 obtained in Examples 1-1 to 1-3 were used as primer components, the urethane paints exhibited excellent coating film appearance, adhesion, and hardness. These results indicate that the organopolysiloxane of the present invention is useful as an adhesion-contributing component for environmentally friendly water-based paints, and that it may be used not only as a primer but also as an adhesion improver added to paints. On the other hand, in Comparative Examples 3-1 and 3-3, in which 3-glycidyloxypropyltrimethoxysilane and its hydrolysis condensate were used as the primer component, the adhesion was insufficient. Comparative Example 3-2 was a primer component having an amino group that is highly reactive with urethane paint, and as a result showed good improvement in adhesion, but the reactivity tended to be too high, which significantly deteriorated the coatability of the urethane paint and resulted in a loss of appearance of the coating film. Comparative Example 3-4 showed poor adhesion, possibly due to insufficient reactivity between the ethylene glycol structural group and the urethane coating material.

Claims

1. An organopolysiloxane represented by the following formula (1): 【Chemistry 1】 (In the formula, R 1 is a monovalent hydrocarbon group having 1 to 10 carbon atoms, and R 2 are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted with a glycidyloxy group, and R 3 is a methyl group or an ethyl group, a, b, c, and d are numbers that satisfy a≧0.5, b≧0, c>0, d≧0, and a+b+c+d=1, and x and y are numbers that satisfy x≧1, y≦0.

5.

2. 2. The organopolysiloxane of claim 1, wherein a, b, c, and d are numbers that satisfy the following conditions: 0.5≦a≦0.9, b=0, 0.1≦c≦0.5, and d=0.

3. An adhesion promoter comprising the organopolysiloxane of claim 1 or 2.

4. 3. An aqueous coating composition comprising the organopolysiloxane of claim 1 or 2.

5. A primer composition comprising the organopolysiloxane of claim 1 or 2.

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