Organopolysiloxane, its production method, adhesion promoter, aqueous coating composition, and primer composition

Abstract

Provided is a water-soluble organopolysiloxane which is represented by formula (1) and is excellent in preservation stability. (In the formula: R1 is a monovalent hydrocarbon group having 1-10 carbon atoms; each R2 is independently a monovalent hydrocarbon group which has 1-10 carbon atoms and which may be substituted with a glycidyloxy group; R3 is a monovalent saturated hydrocarbon group having 1-6 carbon atoms, and at least some of R3s are a monovalent saturated hydrocarbon group having 3-6 carbon atoms; a, b, c, and d are numbers satisfying a ≥ 0.5, b ≥ 0, c ≥ 0, d ≥ 0, and a + b + c + d = 1; and x and y are numbers satisfying x ≥ 1 and 0 < y ≤ 0.5.)

Description

[Technical Field]

[0001] The present invention relates to an organopolysiloxane, a method for producing the same, an adhesion promoter, an aqueous coating composition, and a primer composition; more specifically, the present invention relates to an organopolysiloxane that contains 3-glycidyloxypropyl group-containing siloxane units as constituent units and has silanol groups, a method for producing the organopolysiloxane, 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 Laid-Open No. 2017-114852

Summary of the Invention

Problems to be Solved by the Invention

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a water-soluble organopolysiloxane having an organic functional group and excellent storage stability.

Means for Solving the Problems

[0009] As a result of intensive studies to solve the above problems, the present inventors have found that an organopolysiloxane having a specific amount of a siloxane unit having a 3-glycidyloxypropyl group and having a silanol group has excellent storage stability, and an aqueous composition containing the organopolysiloxane was found to have excellent adhesion and be suitable as a primer, leading to the completion of the present invention.

[0010] That is, the present invention provides: 1. An organopolysiloxane represented by the following formula (1):

Chemical Formula

[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 1 is 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 3is a monovalent saturated hydrocarbon group having 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, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, and n-hexyl; and cycloalkyl groups such as cyclohexyl. From the viewpoint of stability, the organopolysiloxane of the present invention is 3 At least a part of, preferably all of R 3 is a monovalent saturated hydrocarbon group having 3 to 6 carbon atoms, preferably a monovalent saturated hydrocarbon group having 3 or 4 carbon atoms, more preferably a branched alkyl group having 3 or 4 carbon atoms, and further preferably an isopropyl group or an isobutyl 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. a is a number equal to or greater than 0.5, and preferably a number from 0.5 to 1. 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, preferably a number of 0 to 0.5, and is preferably 0 from the viewpoint of the amount of epoxy groups contained in the organopolysiloxane of the present invention. c is a number of 0 or more, preferably a number of 0 to 0.5, and is preferably 0 from the viewpoint of the reactivity of the epoxy group. d is a number of 0 or more, preferably a number of 0 to 0.5, and is preferably 0 from the viewpoint of storage stability.

[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 satisfying 0 < y ≤ 0.5, and from the point of reducing the alcohol generated by hydrolysis, a number of 0 < y ≤ 0.3 is preferred, and a number of 0.01 ≤ y ≤ 0.1 is more preferred. When y is 0, although the organopolysiloxane of the present invention is a material with little environmental load substantially without alcohol generation, due to the high reactivity of the silanol group, problems such as insufficient storage stability and inapplicability to practical use occur. The above R 3 contains a monovalent saturated hydrocarbon group having 3 to 6 carbon atoms, so that the reactivity of the active silanol group can be controlled, and an improvement in the desired storage stability can be expected.

[0020] As the organopolysiloxane of the present invention, those represented by the following formula (1a) are preferred.

[0021]

Chemical formula

[0022] In formula (1a), R 3 is the same as above, a1 = 1, and x1, y1 are numbers satisfying x1 ≥ 1, 0.01 ≤ y 1 ≤ 0.1.

[0023] From the viewpoints of water solubility and handling properties, the weight average molecular weight of the organopolysiloxane of the present invention is preferably 500 to 10,000, and more preferably 500 to 1,000. The weight average molecular weight in the present invention is a standard polystyrene conversion value by gel permeation chromatography (GPC). Also, the kinematic viscosity of the organopolysiloxane of the present invention is preferably 100 to 500 mm 2 / s, and more preferably 200 to 450 mm 2 / s. The kinematic viscosity is the value at 25°C measured with 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 can be produced, for example, by (co)hydrolytic condensation under acidic conditions of a silane monomer containing a 3-glycidyloxypropyl group-containing silane compound, such as 3-glycidyloxypropyltrimethoxysilane or 3-glycidyloxypropyltriethoxysilane, represented by the following formula (i), and, if necessary, one or more of a silane compound represented by the following formula (ii), a silane compound represented by the following formula (iii), and a silane compound represented by the following formula (iv), in the presence of an alcohol having 3 to 6 carbon atoms, represented by the following formula (v):

[0026] [ka]

[0027] In the above formula, R 1 and R 2 is the same as above. Each R is independently a monovalent saturated hydrocarbon group having 1 to 6 carbon atoms, which may be linear, branched, or cyclic. Specific examples thereof include R 3 Among these, a methyl group and an ethyl group are preferred. R 0 R is a monovalent saturated hydrocarbon group having 3 to 6 carbon atoms, preferably 3 or 4 carbon atoms. 0 The monovalent saturated hydrocarbon group may be linear, branched, or cyclic, and specific examples thereof include R 3Among the groups exemplified above, the same groups having 3 to 6 carbon atoms can be mentioned, but among them, branched monovalent saturated hydrocarbon groups having 3 or 4 carbon atoms are preferred, branched alkyl groups having 3 or 4 carbon atoms are more preferred, and an isopropyl group and an isobutyl group are even more preferred.

[0028] Specific examples of the 3-glycidyloxypropyl group-containing silane compound represented by the above formula (i) include 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyltripropoxysilane, 3-glycidyloxypropyltributoxysilane, etc. Specific examples of the silane compound 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 and trialkoxysilanes such as decyltrimethoxysilane, decyltriethoxysilane, and decyltriethoxysilane. Specific examples of the silane compound represented by the above formula (iii) include dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, methylethyldimethoxysilane, methylethyldiethoxysilane, methylpropyldimethoxysilane, methylpropyldiethoxysilane, 3-glycidyloxypropylmethyldimethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, cyclopentylmethyldimethoxysilane, cyclohexylmethyldimethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, diphenyldimethoxysilane, and diphenyldiethoxysilane. 、 Examples include dialkoxysilanes such as methyloctyldimethoxysilane. Specific examples of the silane compound represented by the formula (iv) include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. Furthermore, hydrolysis condensation products of these 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] Examples of the alcohol represented by the above formula (v) include n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, pentyl alcohol, neopentyl alcohol, hexyl alcohol, and cyclohexyl alcohol. Preferred are alcohols having 3 or 4 carbon atoms, and more preferred are isopropanol and isobutanol.

[0031] The amount of alcohol added is preferably 0.1 to 5 mol, more preferably 0.5 to 2 mol, per 1 mol of the silane monomer.

[0032] The amount of water used in the hydrolysis of the silane monomer is 0.8 to 1.1 times by mole, and preferably 1 to 1.1 times by mole, per mole of Si(OR) groups such as alkoxysilyl groups, from the viewpoint of suppressing the reaction with the epoxy groups and reducing the number of remaining Si(OR) groups such as alkoxysilyl groups (R is the same as above, the same applies hereinafter).

[0033] 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.

[0034] In the hydrolysis reaction, organic solvents other than alcohols may be used as needed to the extent that they do not inhibit the reaction. Usable organic solvents are preferably those that are compatible with water, which is the starting material for the reaction, and preferred are esters, ketones, ethers, etc. Furthermore, taking into consideration the distillation conditions for removing the generated alcohol, it is preferable that the organic solvent has a low boiling point, and it is desirable that the organic solvent has a boiling point of 150°C or less under atmospheric pressure. 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.

[0035] 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.

[0036] 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.

[0037] (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 %.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] (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.

[0042] 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.

[0043] 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]

[0044] 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 ( 1The H-NMR measurement conditions are as follows. The kinematic viscosity is the value measured at 25°C using a Cannon-Fenske viscometer.

[0045] (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)

[0046] [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 472 g (2.0 mol) of 3-glycidyloxypropyltrimethoxysilane and 60 g of isopropanol. 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 (Ep1). The kinematic viscosity of the resulting organopolysiloxane at 25°C was 395 mm 2The functional group amount of the epoxy group contained was 198 g / mol, and the weight average molecular weight was 608. 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.

[0047] [ka]

[0048] [Example 1-2] The same procedure as in Example 1-1 was carried out, except that the isopropanol in Example 1-1 was changed to 74 g of isobutanol, to obtain a colorless, transparent liquid organopolysiloxane (Ep2). The kinematic viscosity of the resulting organopolysiloxane at 25°C was 432 mm 2 The functional group amount of the epoxy group contained was 202 g / mol, and the weight average molecular weight was 668. 1 As a result of analysis by H-NMR and GPC measurement, the organopolysiloxane (Ep2) had a structure represented by the following formula (3).

[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 (Ep3). The kinematic viscosity of the resulting organopolysiloxane at 25°C was 726 mm2 The functional group amount of the epoxy group contained was 189 g / mol, and the weight average molecular weight was 830. 1 As a result of analysis by H-NMR and GPC measurement, the organopolysiloxane (Ep3) had a structure represented by the following formula (4).

[0051] [ka]

[0052] [Comparative Example 1-2] A 1-L three-neck flask equipped with a stirrer, condenser, dropping funnel, and thermometer was charged with 141.6 g (0.6 mol) of 3-glycidyloxypropyltrimethoxysilane and 168 g (1.4 mol) of dimethyldimethoxysilane. 82.8 g of 0.2% hydrochloric acid (4.6 mol as water) 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 (Ep4). 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, it was found that the organopolysiloxane (Ep4) had a structure represented by the following formula (5). When mixed with ion-exchanged water, organopolysiloxane (Ep4) was incompatible, turned cloudy, and had poor water solubility.

[0053] [ka]

[0054] [2] Storage stability evaluation [Examples 2-1, 2-2, Comparative Example 2-1] The organopolysiloxanes (Ep1 to Ep3) synthesized in Examples 1-1 and 1-2 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 of storage at room temperature 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 Ep3 that does not contain bulky alkoxysilyl groups, showed a significant increase in viscosity and a significant decrease in water solubility over time due to the progress of the condensation reaction. Such a material can only be handled immediately after production and is of such poor quality that it is not suitable for practical use. In contrast, the organopolysiloxanes Ep1 and Ep2 obtained in Examples 1-1 and 1-2 exhibited similar behavior over time at 25°C, but the extent of the change was small, and it was clear that almost no change was observed when stored at 5°C.

[0057] [3] Preparation and evaluation of primer compositions [Examples 3-1 and 3-2, 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 △: Colored ×: Foreign matter, unevenness, whitening, 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 and 3-2, in which the organopolysiloxanes Ep1 and Ep2 obtained in Examples 1-1 and 1-2 were used as primer components, the urethane paints exhibited excellent coating film appearance, adhesion, and hardness. These results demonstrate that the organopolysiloxanes of the present invention are useful as adhesion-contributing components for environmentally friendly water-based paints, and indicate the possibility of application not only in primers but also as adhesion improvers 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, resulting in a significant deterioration in the coatability of the urethane paint and a loss in the appearance of the paint 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 monovalent saturated hydrocarbon group having 1 to 6 carbon atoms, while R 3 at least a portion of which are monovalent saturated hydrocarbon groups having 3 to 6 carbon atoms, 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 and 0<y≦0.

5.

2. R 3 2. The organopolysiloxane of claim 1, wherein is a monovalent saturated hydrocarbon group having 3 or 4 carbon atoms.

3. 2. The organopolysiloxane of claim 1, wherein b, c, d, and y are numbers satisfying b=0, c=0, d=0, and 0.01≦y≦0.

1.

4. A method for producing the organopolysiloxane according to any one of claims 1 to 3, comprising: A method for producing an organopolysiloxane, comprising (co)hydrolyzing and condensing a silane monomer containing a 3-glycidyloxypropyl group-containing silane compound represented by formula (i) below, and optionally one or more of a silane compound represented by formula (ii) below, a silane compound represented by formula (iii) below, and a silane compound represented by formula (iv) below, in the presence of an alcohol represented by formula (v) below, with the addition of 0.8 to 1.1 times the molar amount of water per mole of Si(OR) groups (R is a monovalent saturated hydrocarbon group having 1 to 6 carbon atoms) of the silane monomer under acidic conditions: 【Chemistry 2】 (In the formula, R 1 , R 2 and R is the same as above, R 0 is a monovalent saturated hydrocarbon group having 3 to 6 carbon atoms.

5. An adhesion promoter comprising the organopolysiloxane according to any one of claims 1 to 3.

6. An aqueous coating composition comprising the organopolysiloxane of any one of claims 1 to 3.

7. A primer composition comprising the organopolysiloxane according to any one of claims 1 to 3.

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