UV and air curable liquid silicone composition and cured product

Abstract

This curable liquid silicone composition contains specified proportions of: (A) a diorganopolysiloxane having at least one alkenyl group per molecule; (B) an organohydrogenpolysiloxane having at least two silicon atom-bonded hydrogen atoms per molecule; (C) a platinum-based catalyst mixture that is activated by moisture and / or oxygen; (D) a dehydrating agent; and (E) an organic zirconium compound. The curable liquid silicone composition: exhibits one-pack storage stability for a long period of time in a sealed container in the dark at a temperature between cold storage and room temperature; and, when brought into contact with moisture and / or oxygen, and especially moisture (humidity) and / or oxygen in air without being heated, can yield a silicone rubber cured product or silicone gel cured product which is cured to the inner part thereof and exhibits excellent transparency, low coloration and interior visibility.

Description

[Technical Field]

[0001] The present invention is activated by moisture and / or oxygen. It also possesses the ability to be activated by ultraviolet light. A platinum-based catalyst mixture can be used to cure a silicone rubber cured product (silicone elastomer elastic body) or a silicone gel cured product that exhibits excellent transparency, low coloration, and internal visibility. Ultraviolet rays and atmosphere This invention relates to curable liquid silicone compositions (curable liquid silicone rubber compositions or curable liquid silicone gel compositions) and their cured products. [Background technology]

[0002] In light of the demands for energy conservation and the Sustainable Development Goals (SDGs), there has been a growing need for curable liquid silicone compositions that can be cured without heating. Furthermore, one-component curable liquid silicone compositions are preferred for ease of use, as well as to improve workability and prevent mixing errors during application.

[0003] In curable liquid silicone compositions, crosslinking reactions that are one-component and can be cured without heating include condensation reactions, ultraviolet radical reactions, and hydrosilylation addition reactions, some of which have significantly shortened shelf life or can activate catalysts with certain types of ultraviolet light. However, all of these methods suffer from insufficient deep curing or curing in areas shaded by ultraviolet light, limiting their applicable uses.

[0004] The following are examples of prior art related to the present invention. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] U.S. Patent No. 4510094 [Patent Document 2] U.S. Patent No. 4530879 [Patent Document 3] Patent No. 6020740 [Patent Document 4] International Publication No. 2022 / 270366 [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention has been made in view of the above circumstances, and has the ability to be stored in a sealed container under light shielding for a long period of time in a single liquid state at refrigeration to room temperature (-5 to 38°C), and does not come into contact with moisture and / or oxygen, particularly moisture (humidity) and / or oxygen in the atmosphere, at room temperature (23°C ± 15°C) without heating (i.e., at room temperature (23°C ± 15°C)). or UV irradiation This makes it possible to provide a cured silicone rubber or silicone gel product that is fully cured, transparent, low-coloring, and has excellent internal visibility. Ultraviolet rays and atmosphere This is a curable liquid silicone composition that provides a colorless, transparent cured product that is particularly effective for inspecting defects in sealing components, as it allows for easy observation of the inside of the component. Ultraviolet rays and atmosphere The objective is to provide a curable liquid silicone composition and its cured product. [Means for solving the problem]

[0007] The inventors of the present invention have conducted extensive research to solve the above-mentioned problems and have found that a curable liquid silicone composition comprising an aerobic platinum-based catalyst mixture that is activated by contact with moisture and / or oxygen, particularly moisture (humidity) and / or oxygen in the atmosphere, and acts as a catalyst for hydrosilylation addition reactions, a dehydrating agent such as at least one compound selected from silyl ketenes and α-silyl esters, and an organozirconium compound as a dehydration accelerator, provides a curable liquid silicone rubber composition or a curable liquid silicone gel composition that has long-term storage stability as a one-component composition, exhibits good curability including internally after exposure to the atmosphere for a predetermined time, and provides a transparent cured product with excellent transparency, low coloration, and internal visibility, thereby completing the present invention.

[0008] The present invention cures a liquid silicone composition into a silicone rubber or silicone gel by means of a curing (crosslinking) reaction system that applies a hydrosilylation addition reaction using a (aerobic) platinum-based catalyst mixture activated by moisture and / or oxygen. Notably, the curable liquid silicone composition of the present invention has "one-part storage stability in a sealed container under light shielding" at refrigeration to room temperature (temperature range of -5 to 38°C), and under non-heating conditions (that is, room temperature (23°C±15°C)), the catalyst function is activated by "contacting with air (moisture (humidity) and / or oxygen in the atmosphere)" to allow the hydrosilylation addition reaction to proceed, so that not only the air-contacting surface, but also the interior (deep portion) and shaded portions of the composition are cured.

[0009] Accordingly, the present invention provides the following Ultraviolet rays and atmosphere curable liquid silicone composition and a cured product of the Ultraviolet rays and atmosphere curable liquid silicone composition. [1] (A) a diorganopolysiloxane having at least one alkenyl group per molecule, (B) an organohydrogenpolysiloxane having hydrogen atoms bonded to at least two silicon atoms per molecule: in an amount such that the amount of silicon-bonded hydrogen atoms in component (B) is 0.5 to 4 moles per mole of alkenyl groups in component (A), (C) a platinum-based catalyst mixture activated by moisture and / or oxygen: It also possesses the ability to be activated by ultraviolet light. in an amount of 0.1 to 1,000 ppm in terms of mass of platinum atoms in component (C) relative to the total mass of components (A) and (B), (D) a dehydrating agent: 0.01 to 5 parts by mass relative to 100 parts by mass in total of components (A) and (B), and (E) an organic zirconium compound: 0.001 to 5 parts by mass relative to 100 parts by mass in total of components (A) and (B) comprising Ultraviolet radiation accelerates hardening, and hardens upon contact with moisture (humidity) and / or oxygen in the atmosphere. A curable liquid silicone composition. [2] The curable liquid silicone composition according to [1], wherein the dehydrating agent as component (D) is at least one compound selected from silyl ketenes and α-silyl esters. Ultraviolet rays and atmosphere A curable liquid silicone composition. [3] The (C) component is an aerobic platinum-based catalyst mixture comprising a reaction mixture of a platinum-alkenyl group-containing organosiloxane complex and an organosilicon compound having at least one hydrogen atom bonded to a silicon atom per molecule in an amount such that there is an excess molar of hydrogen atoms bonded to a silicon atom relative to the alkenyl group in the platinum-alkenyl group-containing organosiloxane complex [1] or [2]. Ultraviolet rays and atmosphere A curable liquid silicone composition. [4] A UV and air-curable liquid silicone composition according to the dehydration accelerator [1], wherein component (E) is one selected from tetraethoxyzirconium, tetran-propoxyzirconium, tetraisopropoxyzirconium, tetran-butoxyzirconium, tetra(2-ethylhexyloxy)zirconium, zirconium diisopropoxybis(ethylacetoacetate), and zirconium tetraacetylacetonate. [5] Furthermore, the ultraviolet and air-curable liquid silicone composition according to [1] contains (G) a platinum-based catalyst activated by ultraviolet light: in an amount such that the mass of platinum atoms contained in component (G) is 0.1 to 1,000 ppm relative to the total mass of components (A) and (B). [ 6 ] [1]~[ 5 [as described in any of the following] Ultraviolet rays and atmosphere A cured product of a curable liquid silicone composition. [Effects of the Invention]

[0010] The curable liquid silicone composition of the present invention undergoes a curing reaction by an aerobic platinum-based catalyst mixture that is activated upon contact with moisture and / or oxygen, particularly moisture (humidity) and / or oxygen in the atmosphere, and acts as a catalyst for hydrosilylation addition. The curable liquid silicone composition of the present invention, which contains the above platinum-based catalyst mixture, a dehydrating agent such as at least one compound selected from, for example, silyl ketenes and α-silyl esters, and an organozirconium compound as a dehydration accelerator, has sufficient long-term one-component storage properties when stored at refrigeration to room temperature and transported in a sealed container protected from light. When used, upon contact with moisture and / or oxygen, particularly moisture (humidity) and / or oxygen in the atmosphere, without heating (i.e., at room temperature), the platinum-based catalyst mixture contained in the composition is activated, the hydrosilylation addition reaction proceeds, and it is possible to obtain a cured product with little discoloration (excellent transparency, low coloration, and internal visibility) that is cured not only at the air interface but also internally / in shadowed areas. Therefore, the curable liquid silicone compositions of the present invention (curable liquid silicone rubber composition and curable liquid silicone gel composition) can contribute to energy conservation and the production of various parts and products in accordance with the SDGs. [Modes for carrying out the invention]

[0011] The present invention will be described in detail below.

[0012] [Curable liquid silicone composition] The curable liquid silicone composition of the present invention (curable liquid silicone rubber composition or curable liquid silicone gel composition) is a composition comprising the components (A) to (E) described below, and other components as necessary.

[0013] [(A) Alkenyl group-containing diorganopolysiloxane] The alkenyl group-containing diorganopolysiloxane of component (A) is a linear or branched diorganopolysiloxane having at least one, preferably 1 to 20, alkenyl groups in one molecule, and acts as the main component (base polymer) of the curable liquid silicone composition of the present invention (hereinafter also referred to as the composition of the present invention). Typically, the main chain portion consists of repeating diorganosiloxane units, and both ends of the molecular chain are sealed with triorganosiloxy groups, resulting in a linear diorganopolysiloxane. However, it may also be a branched chain containing a branched structure in part of the siloxane structure that constitutes the molecular chain.

[0014] The alkenyl group-containing diorganopolysiloxane of component (A) contains at least one (usually 1 to 50), preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 or 2 alkenyl groups per molecule. Examples of alkenyl groups include vinyl groups, allyl groups, propenyl groups, isopropenyl groups, butenyl groups, hexenyl groups, cyclohexenyl groups, etc., which typically have about 2 to 8 carbon atoms. The alkenyl group may be bonded to a silicon atom at the end of the molecular chain, or to a silicon atom at the non-terminus (middle of the molecular chain), and it is preferable that the product contains at least an alkenyl group bonded to a silicon atom at both ends of the molecular chain. In this case, the alkenyl group may be present only at both ends of the molecular chain, or at both ends and at the non-terminus (middle of the molecular chain).

[0015] Examples of such alkenyl group-containing diorganopolysiloxanes include linear diorganopolysiloxanes represented by the following general formula (1). [ka] (In the formula, R 1X is an unsubstituted or substituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond. X is an alkenyl group, and at least one is present in each molecule. n is a non-negative integer, m is a non-negative integer, and a is an integer between 0 and 3 for each bonded silicon atom, but at least one of the a and m at both ends is an integer of 1 or greater.

[0016] In the formula, R 1 Examples of unsubstituted or substituted monovalent hydrocarbon groups that do not contain aliphatic unsaturated bonds include those having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, and more preferably 1 to 6 carbon atoms. Specifically, these include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl groups; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl groups; aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenylyl groups; and aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl groups. Furthermore, some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with halogen atoms such as fluorine, chlorine, or bromine, or with cyano groups, for example, chloromethyl group, 2-bromoethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group, chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5,6,6,6-nonafluorohexyl group, and preferably unsubstituted or substituted alkyl groups having 1 to 3 carbon atoms, such as methyl group, ethyl group, propyl group, chloromethyl group, bromoethyl group, 3,3,3-trifluoropropyl group, and cyanoethyl group, and unsubstituted or substituted phenyl groups, such as phenyl group, chlorophenyl group, and fluorophenyl group. 1 A methyl group or a phenyl group is preferred as the element.

[0017] In the formula, examples of the alkenyl group for X include those having about 2 to 8 carbon atoms, such as a vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, and cyclohexenyl group; among these, lower alkenyl groups such as vinyl group and allyl group are preferred.

[0018] In the formula, n is an integer of 0 or greater, preferably an integer of 10 to 2,000, more preferably an integer of 50 to 1,200; m is an integer of 0 or greater, preferably an integer of 0 to 40, more preferably an integer of 0 to 20. Further, n and m are preferably integers satisfying 10 ≦ n+m ≦ 2,000, more preferably integers satisfying 50 ≦ n+m ≦ 1,200 and 0 ≦ m / (n+m) ≦ 0.2. In this case, each unit in the parentheses respectively enclosed by n and m may be arranged randomly. In the formula, a is an integer of 0 to 3 for each bonded silicon atom, preferably an integer of 1 to 3.

[0019] Further, examples of the alkenyl group-containing diorganopolysiloxane include, in the above general formula (1), monofunctional siloxy units constituting the molecule (X a R 1 (3-a) SiO 1 / 2 unit) and difunctional siloxane units ((X)(R 1 )SiO 2 / 2 unit, (R 1 )2SiO 2 / 2 unit), in addition, trifunctional siloxane units constituting branch points (that is, (R 1 )SiO 3 / 2 or (X)SiO 3 / 2 silsesquioxane units represented by the above formula), which have a small amount of said units in the molecule, and branched diorganopolysiloxanes that may contain a cyclic structure, ladder structure and / or cage structure in the molecule can be mentioned.

[0020] Further, such an alkenyl group-containing diorganopolysiloxane preferably has a viscosity at 23°C of 10 to 1,000,000 mPa·s, particularly about 100 to 500,000 mPa·s.

[0021] In the present invention, the number of repeating diorganosiloxane units (or degree of polymerization) in the molecule can usually be determined as the number-average molecular weight (or number-average degree of polymerization) in polystyrene terms in gel permeation chromatography (GPC) analysis using toluene or the like as the developing solvent. Viscosity can usually be measured using a rotational viscometer (e.g., BL type, BH type, BS type, cone plate type, rheometer, etc.) at 23°C.

[0022] The alkenyl group-containing diorganopolysiloxane of component (A) may be used alone or in combination of two or more types. Furthermore, in order to avoid impairing the function of the platinum-based catalyst mixture of component (C) described later, it is advisable to reduce the amount of oxygen and water contained in the alkenyl group-containing diorganopolysiloxane of component (A) before incorporating it into the composition. This can be done, for example, by substitution with an inert gas such as nitrogen gas, heating, depressurization, or a combination thereof.

[0023] [(B) Organohydrogenpolysiloxane] The organohydrogenpolysiloxane of component (B) is an organohydrogenpolysiloxane having a linear, cyclic, branched, or three-dimensional network structure (resin structure) with at least two (usually 2 to 200), preferably about 2 to 100, hydrogen atoms (SiH groups) bonded to silicon atoms in one molecule, and functions as a curing agent (crosslinking agent) for the curable liquid silicone composition of the present invention.

[0024] Examples of such organohydrogenpolysiloxanes include the organohydrogenpolysiloxane represented by the following average composition formula (2). H b R 2 c SiO (4-b-c) / 2 (2) (In the formula, R 2each independently represents an unsubstituted or substituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond, b and c are numbers satisfying 0.001≦b≦1.2, 0.8≦c≦2 and 0.8<b+c≦3, preferably numbers satisfying 0.05≦b≦1, 1.5≦c≦2 and 1.8≦b+c≦2.7.)

[0025] In the formula, R 2 examples of the unsubstituted or substituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond include the same ones exemplified as R 1 in the above general formula (1); for example, those having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 7 carbon atoms can be mentioned, and particularly preferred are lower alkyl groups having 1 to 3 carbon atoms such as a methyl group, a phenyl group, and a 3,3,3-trifluoropropyl group.

[0026] As component (B), those that are liquid at room temperature (23°C±15°C, the same applies hereinafter) with 2 to 300 silicon atoms per molecule, particularly 3 to 150 silicon atoms, especially about 3 to 100 silicon atoms, are suitably used. The hydrogen atoms bonded to silicon atoms may be located either at the molecular chain terminals or in the middle (non-terminal positions) of the molecular chain, or may be located at both positions.

[0027] Examples of such organohydrogenpolysiloxanes include, for example, methylhydrogencyclosiloxane oligomers such as 1,1,3,3-tetramethyldisiloxane, 1,1,3,3,5,5-hexamethyltrisiloxane, 1,3,5,7-tetramethyltetracyclosiloxane, and 1,3,5,7,9-pentamethylpentacyclosiloxane, tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, methylhydrogenpolysiloxane with trimethylsiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane-methylhydrogensiloxane copolymer with trimethylsiloxy groups sealed at both ends of the molecular chain, diphenylsiloxane-methylhydrogensiloxane copolymer with trimethylsiloxy groups sealed at both ends of the molecular chain, and methylphenylsiloxane-methylhydrogensiloxane with trimethylsiloxy groups sealed at both ends of the molecular chain. Copolymer, dimethylsiloxane / diphenylsiloxane / methylhydrogensiloxane copolymer with trimethylsiloxy groups sealed at both ends of the molecular chain, dimethylpolysiloxane with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, methylhydrogenpolysiloxane with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane / methylhydrogensiloxane copolymer with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, diphenylsiloxane / methylhydrogensiloxane copolymer with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, methylphenylsiloxane / methylhydrogensiloxane copolymer with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane / diphenylsiloxane / methylhydrogensiloxane copolymer with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, dimethylhydrogensiloxy units and SiO 4 / 2Examples include a three-dimensional network structure silicone resin consisting of units, which may optionally include trimethylsiloxy units, dimethylsiloxane units, methylhydrogensiloxane units, hydrogensilsesquioxane units, and / or methylsilsesquioxane units, and compounds in which some or all of the methyl groups in each of the above-mentioned exemplary compounds are substituted with other alkyl groups or phenyl groups. Note that component (B) and the organosilicon compound in component (C) described later may be the same.

[0028] The organohydrogenpolysiloxane used in the composition of the present invention can be obtained by known methods, for example, the following general formula: R 2 SiHCl2 and R 2 2SiHCl (where R 2 The same applies as described above.) At least one chlorosilane selected from the above is (co)hydrolyzed and condensed, or the chlorosilane is mixed with the following general formula: R 2 3SiCl and R 2 2SiCl2 (wherein, R 2 The same applies as described above. It can be obtained by co-hydrolysis condensation with at least one chlorosilane selected from the above. Alternatively, the organohydrogenpolysiloxane may be obtained by equilibrating the polysiloxane obtained by this (co)hydrolysis condensation.

[0029] The amount of organohydrogenpolysiloxane in component (B) is such that, from the viewpoint of curing to give a good silicone rubber or gel, there are 0.5 to 4 moles of hydrogen atoms (i.e., SiH groups) bonded to silicon atoms in the organohydrogenpolysiloxane of component (B) for every 1 mole of alkenyl groups in the alkenyl group-containing diorganopolysiloxane of component (A), and preferably 0.8 to 2.5 moles.

[0030] The organohydrogenpolysiloxane of component (B) may be used alone or in combination of two or more types. Furthermore, in order to avoid impairing the function of the aerobic platinum-based catalyst mixture of component (C) described later, it is advisable to reduce the amount of oxygen and water contained in the organohydrogenpolysiloxane of component (B) before incorporating it into the composition. This can be done, for example, by replacing it with an inert gas such as nitrogen gas, heating, reducing pressure, or a combination thereof.

[0031] [(C) Platinum-based catalyst mixture activated by moisture and / or oxygen] The platinum-based catalyst mixture of component (C), which is activated by moisture and / or oxygen, is activated by contact with moisture and / or oxygen, particularly moisture (humidity) and / or oxygen in the atmosphere, and acts as a catalyst for hydrosilylation addition reactions. It is an aerobic platinum-based catalyst mixture consisting of a reaction mixture of a platinum-alkenyl group-containing organosiloxane complex and an organosilicon compound having at least one hydrogen atom (SiH group) bonded to a silicon atom in one molecule, in an amount such that the amount of hydrogen atoms (SiH groups) bonded to a silicon atom is in excess moles (more than 1 in molar ratio) relative to the alkenyl group in the platinum-alkenyl group-containing organosiloxane complex. Furthermore, this platinum-based catalyst mixture has been confirmed to be activatable by ultraviolet light, and irradiating the composition with ultraviolet light can accelerate the curing of the composition. In this invention, "aerobic" refers to the property (aerobic reaction type) in which a catalyst has low catalytic activity as a hydrosilylation addition reaction catalyst in an oxygen-free, low-moisture sealed state where contact with moisture (humidity) and oxygen is blocked, but is activated as a hydrosilylation addition reaction catalyst by contact with moisture (humidity) and / or oxygen in the atmosphere. Furthermore, "sealed state (or under sealed conditions)" refers to a state in which contact with the atmosphere is blocked (i.e., contact with moisture (humidity) and oxygen is blocked), and a sealed container refers to a container that achieves this sealed state.

[0032] Here, in the platinum-based catalyst mixture of component (C), the platinum-alkenyl group-containing organosiloxane complex is preferably a complex of platinum, platinum chloride, chloroplatinic acid, or chloroplatinate with a vinyl group-containing siloxane (for example, an organodisiloxane compound having two alkenyl groups in one molecule, such as 1,3-divinyl-1,1,3,3-tetramethyldisiloxane). For example, in the case of a complex of chloroplatinic acid (H2PtCl6) and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, three molecules of the bidentate ligand 1,3-divinyl-1,1,3,3-tetramethyldisiloxane coordinate to one molecule of chloroplatinic acid.

[0033] Platinum-alkenyl group-containing organosiloxane complexes are preferably used dissolved in solvents such as toluene, lower alcohols, higher alcohols, and silicones. The platinum atom content (concentration) in the solution is preferably 0.05 to 5% by mass.

[0034] In the platinum-based catalyst mixture of component (C), suitable organosilicon compounds having at least one hydrogen atom (SiH group) bonded to a silicon atom in one molecule include organohydrogensilanes and organohydrogensiloxane oligomers having at least one SiH group (for example, 1 to 10, preferably 1 to 5) in one molecule. However, organohydrogensiloxane oligomers are more preferred in terms of handling and safety. The molecular structure of this organohydrogensiloxane oligomer may be linear or cyclic, and the number of silicon atoms in one molecule is preferably 2 to 40, more preferably 2 to 10, and even more preferably 2 to 5.

[0035] Examples of organohydrogensilanes and organohydrogensiloxane oligomers used in the present invention include trialkoxy(hydrogen)silane, alkyldialkoxy(hydrogen)silane, dialkylalkoxy(hydrogen)silane, 1,1,1,3,3-pentamethyldisiloxane, 1,1,3,3-tetramethyldisiloxane, 1,1,1,3,5,5,5-heptamethyltrisiloxane, 1,1,3,3,5,5-hexamethyltrisiloxane, 1,1,1,3,5,7,7,7-octamethyltetrasiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, and 1,3,5,7,9-pentamethylcyclopentasiloxane. These compounds may be used individually or in combination of two or more.

[0036] The platinum-based catalyst mixture of component (C) is a reaction mixture in which the alkenyl groups in the platinum-alkenyl group-containing organosiloxane complex react with SiH groups derived from the organosilicon compound, which are added in excess molar amount relative to the alkenyl groups during the preparation of the mixture (i.e., more than 1 mole per mole of alkenyl groups, preferably 1.1 to 30 moles, more preferably 1.5 to 25 moles, and even more preferably about 5 to 25 moles), in a moisture and oxygen-free atmosphere (for example, under sealed conditions with no contact with moisture (humidity) and oxygen), so that all of the alkenyl groups are converted to alkylene groups by hydrosilylation addition (substantially eliminating the alkenyl groups), and excess SiH groups derived from the organosilicon compound remain in the mixture.

[0037] The method for preparing the platinum-based catalyst mixture of component (C) involves mixing the above-mentioned platinum-alkenyl group-containing organosiloxane complex and an organosilicon compound having at least one hydrogen atom (SiH group) bonded to a silicon atom in one molecule, in a moisture- and oxygen-free atmosphere, in a blending ratio such that the SiH groups of the organosilicon compound are in excess molar relative to the alkenyl groups in the platinum-alkenyl group-containing organosiloxane complex.

[0038] Here, the blending ratio in which the SiH groups of an organosilicon compound having at least one hydrogen atom (SiH group) bonded to a silicon atom in one molecule are in excess moles relative to the alkenyl groups in the platinum-alkenyl group-containing organosiloxane complex means that the blending ratio of the platinum-alkenyl group-containing organosiloxane complex and the organosilicon compound is such that for every mole of alkenyl groups in the complex, there is more than 1 mole of SiH groups in the organosilicon compound, preferably 1.1 to 30 moles, more preferably 1.5 to 25 moles, and even more preferably about 5 to 25 moles.

[0039] Furthermore, the mixing method is not particularly limited as long as it is a method in which the platinum-alkenyl group-containing organosiloxane complex and the organosilicon compound having at least one hydrogen atom (SiH group) bonded to a silicon atom in one molecule are uniformly mixed, but it is preferable to carry out the mixing using a glass reactor such as a glass flask or a stainless steel reactor.

[0040] The atmosphere during mixing should be free of moisture and oxygen, preferably an inert gas atmosphere such as nitrogen or under reduced pressure (vacuum). The temperature does not need to be heated and can be room temperature. The mixing time (i.e., reaction time) should be sufficient for the platinum-alkenyl group-containing organosiloxane complex and the organosilicon compound having at least one hydrogen atom (SiH group) bonded to a silicon atom in each molecule to be uniformly mixed, preferably 0.5 to 100 hours, and particularly preferably 1 to 24 hours.

[0041] Furthermore, in the platinum-based catalyst mixture of component (C), if the organosilicon compound having at least one hydrogen atom (SiH group) bonded to a silicon atom in one molecule is an organohydrogensiloxane oligomer having at least two hydrogen atoms (hereinafter sometimes referred to as adjacent silicon atoms) bonded to each of adjacent silicon atoms (hereinafter sometimes referred to as adjacent silicon atoms) via ether oxygen atoms forming a siloxane bond (Si-O-Si) (for example, if the organosilicon compound is 1,1,3,3-tetramethyldisiloxane, 1,1,1,3,5,7,7,7-octamethyltetrasiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, 1,3,5,7,9-pentamethylcyclopentasiloxane, etc.) In this case, it is preferable to obtain the reaction mixture obtained by uniformly mixing an organohydrogensiloxane oligomer having at least two adjacent SiH groups and a platinum-alkenyl group-containing organosiloxane complex in a moisture- and oxygen-free atmosphere, and then further bringing the reaction mixture into contact with moisture and / or oxygen by means of mixing in air, or by mixing the organohydrogensiloxane oligomer having at least two adjacent SiH groups and the platinum-alkenyl group-containing organosiloxane complex in a blending ratio in which the SiH groups in the organohydrogensiloxane oligomer having at least two adjacent SiH groups are in excess molars relative to the alkenyl groups in the platinum-alkenyl group-containing organosiloxane complex, while in contact with moisture and / or oxygen. As a result, a curable liquid silicone composition containing the mixture as a hydrosilylation addition reaction catalyst can have its long-term one-component storage properties improved under sealed conditions, without impairing its curability when in contact with moisture (humidity) and / or oxygen in the atmosphere, provided that moisture and oxygen are substantially absent from the storage system (composition).

[0042] When the organosilicon compound having at least one hydrogen atom (SiH group) bonded to a silicon atom in one molecule is an organohydrogensiloxane oligomer having at least two hydrogen atoms (adjacent SiH groups) bonded to each of adjacent silicon atoms via ether oxygen atoms forming a siloxane bond (Si-O-Si), the preparation method preferably includes a step of further mixing the reaction mixture obtained by mixing in a moisture- and oxygen-free atmosphere, while in contact with moisture and / or oxygen. This step involves contacting the reaction mixture with moisture and / or oxygen by means such as mixing in air, and for example, the mixing time in air is preferably 0.5 to 100 hours, particularly 1 to 12 hours. After that, this platinum-based catalyst mixture is stored in a sealed container.

[0043] Furthermore, as an alternative preparation method for an organosilicon compound having at least one hydrogen atom (SiH group) bonded to a silicon atom in one molecule, which is an organohydrogensiloxane oligomer having at least two hydrogen atoms (adjacent SiH groups) bonded to adjacent silicon atoms via ether oxygen atoms forming siloxane bonds (Si-O-Si) in one molecule, a platinum-alkenyl group-containing organosiloxane complex and the organohydrogensiloxane oligomer are mixed in the above-mentioned blending ratio in which the SiH groups of the organohydrogensiloxane oligomer are in excess molar relative to the alkenyl groups in the platinum-alkenyl group-containing organosiloxane complex, while in contact with water and / or oxygen. This preparation method brings the above components into contact with water and / or oxygen by means such as mixing them in the air, and for example, the mixing time in the air is preferably 0.5 to 100 hours, particularly 1 to 12 hours. Subsequently, this platinum-based catalyst mixture is placed in a sealed container.

[0044] (C) Component may be used alone or in combination of two or more types. The amount of the platinum-based catalyst mixture in component (C) is such that, based on the mass of platinum atoms contained in component (C), it is 0.1 to 1,000 ppm relative to the total mass of components (A) and (B), and preferably 0.5 to 200 ppm. If the amount of component (C) is less than the above range, the curing of the curable liquid silicone composition will be insufficient due to the influence of catalyst inhibiting factors, and if it is more than the above range, the shelf life will be poor. Furthermore, since the amount of component (C) is a so-called catalytic amount, the excess molar amount of SiH groups remaining in component (C) is negligibly small and does not substantially affect the molar ratio of SiH groups in component (B) to alkenyl groups in component (A) mentioned above.

[0045] [(D) Dehydrating agent] The dehydrating agent in component (D) is added to remove moisture from the curable liquid silicone composition of the present invention, and by adding the dehydrating agent in component (D), it is possible to obtain better shelf life.

[0046] As described above, the platinum-based catalyst mixture of component (C), which is one of the core technologies of the present invention, exhibits low catalytic activity in an oxygen-free, low-moisture environment where contact with moisture (humidity) and oxygen is blocked. Its catalytic function as a hydrosilylation addition reaction catalyst is activated upon contact with moisture and / or oxygen from the outside air (atmosphere) (aerobic reaction type). For this reason, it has been confirmed that reducing the amount of moisture in each component and the amount of moisture in the mixed composition improves the one-component storage properties of the curable liquid silicone composition. Therefore, introducing a mechanism that consumes moisture originating from each component in the composition, as well as trace amounts of moisture entering from outside the container, within the composition when stored in a sealed container (by dehydrating with a dehydrating agent (D)) is useful in ensuring one-component storage properties.

[0047] As a dehydrating agent for component (D), both inorganic and organic compounds can function as long as they do not impair the functions of components (A), (B), and (C) above. However, some dehydrating agents may cause foaming due to compounds produced as by-products in the dehydration reaction. Furthermore, many dehydrating agents can cause decomposition of organohydrogenpolysiloxanes in component (B) or organosilicon compounds containing at least one hydrogen atom (SiH group) bonded to a silicon atom in each molecule contained in component (C), as well as a decrease in the catalytic activity of the platinum-based catalyst mixture in component (C).

[0048] Therefore, as the dehydrating agent for component (D), silyl ketenes (including silyl ketene acetals), silyl enol esters, and α-silyl esters are preferred as they enable efficient dehydration in system. These compounds have a structure in which the by-products produced during dehydration do not impair the functions of components (A), (B), and (C), and they dissolve in the curable liquid silicone composition, thus enabling a stable curable liquid silicone composition. In particular, silyl ketenes (including silyl ketene acetals) and α-silyl esters undergo dehydration under non-basic conditions, so they do not cause decomposition of organohydrogenpolysiloxane (component (B)) or organosilicon compounds containing at least one hydrogen atom (SiH group) bonded to a silicon atom in one molecule contained in component (C), nor do they cause a decrease in the catalytic activity of the platinum-based catalyst mixture (component (C)).

[0049] Examples of silyl ketenes (including silyl keten acetals) include 1-methoxy-2-methyl-1-(trimethylsiloxy)propene, dimethylketentrimethylsilyl acetal, and tert-butoxy-1-(trimethylsiloxy)propene.

[0050] Examples of α-silyl esters include ethyl 2-(trimethoxysilyl)propionate (ECMS) and octyl 2-(methyldimethoxysilyl)propionate (OCMS-2).

[0051] The dehydrating agent of component (D) may be added to each component beforehand, added during the preparation of the composition, or added to the prepared composition afterward. The amount added is preferably 0.01 to 5 parts by mass per 100 parts by mass of the total of components (A) and (B), and is preferably 0.01 to 5% by mass of the total composition, particularly 0.1 to 2% by mass. If the amount of component (D) added is too small, the dehydrating effect may be insufficient, and if the amount of component (D) added is too large, it may adversely affect the change in physical properties of the cured product when it is heated.

[0052] [(E) Organozirconium compounds] Component (E) is an organozirconium compound and functions as a catalyst (i.e., a dehydration accelerator) to promote the reaction between the dehydrating agent of component (D) and water. Specific examples of the organozirconium compound of component (E) include zirconium alkoxy ester compounds such as tetraethoxyzirconium, tetran-propoxyzirconium, tetraisopropoxyzirconium (also known as tetra(isopropyl)zirconate), tetran-butoxyzirconium (also known as tetra(n-butyl)zirconate), and tetra(2-ethylhexyloxy)zirconium, as well as zirconium chelate compounds such as zirconium diisopropoxybis(ethylacetoacetate) and zirconium tetraacetylacetonate.

[0053] The amount of component (E) added is preferably 0.001 to 5 parts by mass per 100 parts by mass of the total of components (A) and (B), and is preferably 0.001 to 5% by mass of the entire composition, particularly 0.01 to 1% by mass. If the amount of component (E) added is too small, the removal of water (dehydration) from the composition may be insufficient, and if the amount of component (E) added is too large, it may cause deterioration of the organohydrogenpolysiloxane (crosslinking agent) of component (B).

[0054] The organozirconium compound may be used as is, or, if necessary for ease of use, may be diluted with a solvent. In this case, examples of solvents include lower alcohols such as toluene, isopropanol (IPA), and n-butanol, higher alcohols, and silicone-based solvents. The content of the organozirconium compound in the solution is preferably 1% by mass or more.

[0055] In addition, other catalysts with similar functions as dehydration accelerators include titanate esters (tetra(isopropyl) titanate (TPT), tetrabutyl titanate (TBT), tetra(2-ethylhexyl) titanate (TOT), etc.) and titanium chelate compounds (titanium diisopropoxybis(ethyl acetate), titanium tetraacetylacetonate, etc.). However, these cause discoloration and yellowing of the cured product, and are therefore not applicable to the objective of the present invention, which is to obtain a colorless and transparent cured product that allows for easy observation of the inside of the cured product and is effective for verifying defects in sealing parts. Furthermore, tin compounds (dibutyldimethoxytin, dibutyltin dilaurate, etc.) can also be used as dehydration accelerators, but their use is undesirable due to environmental impact issues.

[0056] [Other ingredients] In addition to components (A) to (E) above, the curable liquid silicone composition of the present invention may contain, as necessary, various optional components, provided that the objectives of the present invention are not impaired.

[0057] [(F) Hydrosilylation addition reaction regulator] The curable liquid silicone composition of the present invention may further contain, as an optional component, a hydrosilylation addition reaction control agent of component (F) for the purpose of improving one-liquid storage properties.

[0058] As described above, the platinum-based catalyst mixture of component (C) of the present invention has the property of being activated by contact with moisture and / or oxygen. For this reason, moisture in each component, moisture introduced during the composition preparation and container filling processes, and oxygen and moisture entering from outside the sealed container may cause a portion of the platinum-based catalyst mixture of component (C) to be activated as a hydrosilylation addition reaction catalyst. This partially activated catalyst may significantly reduce the one-liquid shelf life of the composition, but such a reduction in one-liquid shelf life can be suppressed by supplementally incorporating the hydrosilylation addition reaction control agent of component (F).

[0059] Examples of hydrosilylation reaction control agents include acetylene alcohols such as 1-ethynylcyclohexanol and 3-methyltrideca-1-in-3-ol (EMDC), silanes and siloxane modified versions of acetylene alcohols such as dimethylbis(1,1-dimethyl-2-propynyloxy)silane (PLR-22) and 3-(trimethylsilyloxy)-3-methyl-1-butyne (PLR-31), tri(isopropyl) phosphite, tris(di-tert-butylphenyl) phosphite, triphenyl phosphite, and tris(2-ethylhexyl) Examples include compounds selected from the group consisting of phosphorous acid compounds such as phosphites (especially phosphorous acid esters), ethylenediamines such as tetramethylethylenediamine, benzotriazoles such as benzotriazole and 5-methyl-1H-benzotriazole, and mixtures thereof. In particular, phosphorous acid compounds, especially the phosphorous acid esters tri(isopropyl)phosphite and tris(di-tert-butylphenyl)phosphite, are preferred because they yield a curable liquid silicone composition with good one-component storage properties under light-shielding and sealed conditions.

[0060] The amount of hydrosilylation addition reaction regulator component (F) added may be any amount that does not affect the curability of the composition of the present invention, depending on the performance of each hydrosilylation addition reaction regulator. Preferably, the amount added is within a range that does not impair the curability due to the hydrosilylation addition reaction carried out by the platinum-based catalyst mixture component (C), which is activated by exposure to air (moisture and / or oxygen). In the case of phosphorous compounds such as phosphite esters, the amount added may be trace, less than 1 mole per mole of platinum atoms contained in the composition, and particularly around 0 to 0.75 moles. When blending, it is preferable that the amount be 0.1 mole or more per mole of platinum atoms contained in the composition. If the amount of component (F) added is too large, it may deactivate the platinum-based catalyst mixture component (C), which is activated by moisture and / or oxygen at the time of use, and, if component (G) described later is blended, the platinum-based catalyst component (G), which is activated by ultraviolet light at the time of use, so that the curability when exposed to air may decrease.

[0061] [(G) Platinum-based catalysts activated by ultraviolet light] As mentioned above, the platinum-based catalyst mixture of component (C) is activated not only by oxygen / air but also by ultraviolet irradiation. If it is necessary to impart an even more pronounced curing acceleration function by ultraviolet irradiation, it is possible to add an ultraviolet-activated platinum-based catalyst. A platinum-based catalyst that is activated by light with a wavelength of 200 to 500 nm, preferably ultraviolet light with a wavelength of 200 to 410 nm, is a catalyst that is inert under light shielding and, when irradiated with light with a wavelength of 200 to 500 nm, preferably ultraviolet light with a wavelength of 200 to 410 nm, transforms into an active platinum-based catalyst (hydrosilylation addition reaction catalyst) at room temperature, and can promote the hydrosilylation addition reaction between the alkenyl group in component (A) and the silicon atom-bonded hydrogen atom in component (B).

[0062] (G) As a platinum-based catalyst activated by ultraviolet light, platinum acetylacetonate complexes and platinum cyclopentadienyl complexes, as described in U.S. Patent No. 4510094 and U.S. Patent No. 4530879, are used. Specific examples of such (G) components include complexes of (η5-cyclopentadienyl)trialiphatic platinum compounds. Among these, cyclopentadienyltrimethylplatinum complexes and methylcyclopentadienyltrimethylplatinum complexes are preferred. Other examples include bis(β-diketonato)platinum compound complexes. Among these, bis(acetylacetonato)platinum complexes are preferred.

[0063] The platinum-based catalyst activated by ultraviolet light is preferably used dissolved in a solvent such as toluene, lower alcohol, higher alcohol, or silicone-based solvent. The amount (concentration) of the ultraviolet-activated platinum-based catalyst in the solution is preferably 0.05 to 5% by mass.

[0064] The amount of platinum-based catalyst in component (G) is preferably 0.1 to 1,000 ppm, more preferably 0.1 to 500 ppm, and even more preferably 0.1 to 50 ppm, relative to the total mass of components (A) and (B). In particular, with the low-coloration composition according to the present invention, ultraviolet irradiation light penetrates easily to deeper layers, resulting in good UV curing properties.

[0065] In addition to the above-mentioned (F) hydrosilylation addition reaction control agent and (G) platinum-based catalyst activated by ultraviolet light, the curable liquid silicone composition of the present invention may further contain, as necessary, additives such as inorganic fillers, adhesion promoters, pigment pastes, and reinforcing silicone resins as other optional components.

[0066] The curable liquid silicone composition of the present invention can be prepared by mixing the above components (A) to (E), and optionally other components, in accordance with conventional methods. Preferably, the components are added in the following order while mixing: (A) alkenyl group-containing diorganopolysiloxane, (B) organohydrogenpolysiloxane, (D) dehydrating agent, (E) organozirconium compound, and (C) platinum-based catalyst mixture activated by water and / or oxygen. If (F) hydrosilylation reaction control agent is added, it is preferable to add it after adding (E) the organozirconium compound. If (G) ultraviolet-activated platinum-based catalyst is added, it is preferable to add it after adding (C) the platinum-based catalyst mixture activated by water and / or oxygen.

[0067] According to the curable liquid silicone composition of the present invention, by using a highly airtight container that can block or reduce the intrusion of oxygen and moisture, particularly moisture (humidity) and oxygen from the atmosphere, and storing it in a sealed container under light shielding, superior one-component storage properties can be obtained. This makes it possible to distribute and sell the composition as a one-component curable liquid silicone composition. Furthermore, the curable liquid silicone composition of the present invention can be rapidly cured not only on the air-contacting surface but also in the interior / shadowed areas by opening the sealed container and exposing it to the atmosphere at room temperature, thereby contacting it with moisture (humidity) and / or oxygen in the atmosphere, and providing a cured silicone rubber or silicone gel product with minimal discoloration.

[0068] [Method for curing a curable liquid silicone composition] The curing method for the curable liquid silicone composition of the present invention is usually performed by a step of exposure to air at room temperature for a predetermined time. However, it is also possible to cure the curable liquid silicone composition by a step of irradiating it with ultraviolet light at room temperature, followed by an exposure to air at room temperature for a predetermined time.

[0069] [Ultraviolet irradiation process] The above ultraviolet irradiation step can be performed to accelerate the curing of the composition, and involves irradiating the curable liquid silicone composition of the present invention with ultraviolet light at room temperature (23°C ± 15°C), preferably with light of 200 to 500 nm at room temperature. By irradiating with ultraviolet light, the platinum-based catalyst mixture of component (C) and the platinum-based catalyst of component (G) in the ultraviolet-irradiated area are activated and act as catalysts for the hydrosilylation addition reaction, thereby accelerating the hydrosilylation addition reaction and curing the ultraviolet-irradiated area. The lamps used to emit ultraviolet light are not particularly limited as long as they can supply ultraviolet light with a wavelength of 200 to 500 nm. Examples include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, xenon lamps, metal halide lamps, and ultraviolet LED lamps. The amount of ultraviolet irradiation varies depending on the type and amount of the photoactive platinum complex used (a platinum-based catalyst mixture of component (C) and a platinum-based catalyst of component (G)), but it is sufficient to activate the photoactive platinum complex, and can range from 10 to 1,000 mW / cm². 2 Especially 20-400 mW / cm² 2 It is preferable to irradiate with ultraviolet light for 0.1 seconds to 5 minutes, and particularly for about 0.5 seconds to 1 minute.

[0070] [Exposure process to the atmosphere] The above-mentioned exposure step to the atmosphere involves exposing the material to the atmosphere at room temperature for a predetermined time. By exposing the curable liquid silicone composition of the present invention described above to the atmosphere at room temperature (23°C ± 15°C) for a predetermined time (usually 0.5 hours or more, preferably 1 to 48 hours, more preferably 2 to 24 hours), the platinum-based catalyst mixture of component (C) is activated and acts as a catalyst for the hydrosilylation addition reaction. This further promotes the hydrosilylation addition reaction, thereby curing areas that are shaded or not reached by ultraviolet light, particularly those exposed to ultraviolet light.

[0071] The cured silicone rubber and silicone gel products of the curable liquid silicone composition of the present invention obtained in this manner exhibit excellent low coloration (transparency), heat resistance, and electrical insulation properties, making them applicable to automotive components, aircraft, home appliances, and the like. [Examples]

[0072] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Viscosity is measured using a rotational viscometer at 23°C, and the degree of polymerization is the number-average degree of polymerization in polystyrene terms obtained from GPC analysis using toluene as the developing solvent. Me represents a methyl group, and Vi represents a vinyl group. "Room temperature" means 23°C.

[0073] [Examples 1-4, Comparative Examples 1-5] A curable liquid silicone composition was prepared according to the following procedure. (Preparation of curable liquid silicone composition) Each composition was prepared by uniformly mixing the components in the amounts shown in Table 2 below in a brown glass bottle under a nitrogen atmosphere at room temperature (23°C), and then sealing the brown glass bottle in a light-shielded container. The molar ratio of SiH groups in component (B) to vinyl groups in component (A) is approximately 1.0. The additions at this time were mixed and added in the following order: (A) alkenyl group-containing diorganopolysiloxane, (B) organohydrogenpolysiloxane, (D) dehydrating agent, (E) dehydration accelerator, (F) hydrosilylation addition reaction regulator, (C) platinum-based catalyst mixture activated by water and / or oxygen, and (G) platinum-based catalyst activated by ultraviolet light. If there was a component that was not added, that component was skipped and the addition of the subsequent components continued. Furthermore, in order to prepare the compositions with good reproducibility, (A) alkenyl group-containing diorganopolysiloxane and (B) organohydrogenpolysiloxane were pre-dehydrated by degassing under reduced pressure in glass flasks at 120°C. The mixing and container filling processes of the compositions were carried out under a nitrogen atmosphere.

[0074] The components are as follows: (A) Alkenyl group-containing diorganopolysiloxane: A branched diorganopolysiloxane containing vinyl groups, having a viscosity of 800 mPa·s at 23°C as shown by the following average formula. [ka]

[0075] (B) Organohydrogenpolysiloxane: Linear organohydrogenpolysiloxanes represented by the following average formula [ka]

[0076] (C) Aerobic platinum-based catalyst mixture: An aerobic platinum-based catalyst mixture prepared as described below was used. A toluene solution of a platinum-alkenyl group-containing organosiloxane complex (platinum atom content 0.5% by mass) and 2.0 g of 1,1,3,3-tetramethyldisiloxane were uniformly mixed and reacted in a 25 g glass bottle over 12 hours under a nitrogen atmosphere at room temperature (23°C). The mixture was then uniformly mixed in air at room temperature (23°C) while in contact with air for 2 hours, and then sealed to prepare an aerobic platinum-based catalyst mixture.

[0077] [Table 1]

[0078] (D) Dehydrating agent: 2-(trimethoxysilyl)propionate ethyl (ECMS)

[0079] (E) Dehydration accelerator: (E-1) Tetra(isopropyl) zirconate (75% by mass IPA solution) (E-2) Tetra(n-butyl) zirconate (87% by mass n-butanol solution) (E-3) Tetra(isopropyl) titanate (TPT / 100% by mass) (E-4) Tetra(2-ethylhexyl) titanate (TOT / 100% by mass)

[0080] (F) Hydrosilylation addition reaction regulator: Tris(di-tert-butylphenyl) phosphite (0.31% by mass in toluene solution) represented by the following formula [ka]

[0081] (G) Platinum-based catalysts activated by ultraviolet light: Toluene solution of methylcyclopentadienyltrimethylplatinum complex (platinum content 0.5% by mass)

[0082] The curable liquid silicone compositions prepared were evaluated as follows: cured product appearance (colorability, internal visibility), one-component storage under light-shielding and sealed conditions, curability after UV irradiation after storage, and aerobic curability after storage.

[0083] [Appearance of cured product] The appearance of the cured product is evaluated visually, and includes colorability and internal visibility. The coloration was determined by visually inspecting the shade, including the degree of transparency (transparent, translucent) of the cured product. Internal visibility was assessed by placing a printed material beneath a 20mm thick gel-cured material that had hardened in a glass petri dish, and visually inspecting the text (8pt Mincho font) on the printed material. If the text was legible, it was considered good; if it was visible but not legible, it was considered acceptable; and if the text was not visible, it was considered poor.

[0084] [One-liquid storage stability (light-shielded / sealed)] For one-component storage, a curable liquid silicone composition was filled into a brown glass bottle under a nitrogen atmosphere, sealed, and then left in the brown glass bottle in the open air at room temperature. The viscosity and gelation behavior of the curable liquid silicone composition was observed. The viscosity and gelation behavior was observed by tilting the brown glass bottle and observing the degree to which the composition in the bottle flowed (fluidity). A decrease in fluidity compared to immediately after sealing was judged to indicate that the curable liquid silicone composition had viscoused or gelled. In addition, the brown glass bottle containing the sealed curable liquid silicone composition was first observed for 5 minutes after being left in the open air at room temperature, and then observed daily thereafter to confirm the time (minutes, days) until the curable liquid silicone composition viscoused or gelled.

[0085] For evaluating curability after UV irradiation and aerobic curability, a curable liquid silicone composition stored in a sealed brown glass bottle for one day was used, as described above.

[0086] [Cureability after UV irradiation] The curing properties after UV irradiation were tested by pouring 50g of each composition prepared in the examples and comparative examples into a black plastic petri dish with a diameter of 60mm and a depth of 30mm, and irradiating it at 23°C using a UV-LED lamp with a wavelength of 365nm at an irradiation intensity of 100mW / cm². 2 and dose of 3,000 mJ / cm² 2 After irradiating with ultraviolet light, the composition was allowed to harden in air at 23°C, and the hardened state (deep hardening properties) of the hardened material removed from the plastic petri dish was checked. Observations were taken at 10 minutes, 30 minutes, 1 hour, 6 hours, and 24 hours after UV irradiation. Samples without hardened or gelled areas on the surface or inside were classified as unhardened, those with hardened or gelled areas only on the surface were classified as surface-hardened, those that did not deform under their own weight when the petri dish was tilted were classified as stopped flowing, and those that hardened uniformly throughout were classified as gel-hardened.

[0087] [Aerobic curing] For aerobic curing (curing in the shade (without UV irradiation)), multiple samples were prepared by placing 25g of each composition prepared in the examples and comparative examples into an aluminum petri dish with a diameter of 60mm and a depth of 1mm, after placing an aluminum plate (25mm x 50mm) with 1mm spacers at both ends, and allowing the compositions to cure in air at 23°C. The curing state on the back of the aluminum plate was visually confirmed at 10 minutes, 30 minutes, 1 hour, 6 hours, and 24 hours after UV irradiation. Uncured was defined as having no hardened or gelled areas on the surface or inside, flow stopped when the petri dish did not deform under its own weight when tilted, and gel-cured when the entire surface was uniformly hardened.

[0088] [Table 2]

[0089] As a result of the above findings, it was confirmed that the curable liquid silicone composition of the present invention has excellent one-component storage properties in a light-shielded and sealed container, and that after standing in the atmosphere, the platinum-based catalyst mixture is activated, the hydrosilylation addition reaction proceeds even in shaded areas, and a rubbery or gel-like cured product with good transparency, low coloration, and internal visibility is obtained. Furthermore, due to its high transparency, it was confirmed that it also exhibits excellent deep curing properties when cured with ultraviolet light, which may shorten the process time when sealing parts.

Claims

1. (A) Diorganopolysiloxane having at least one alkenyl group in one molecule, (B) Organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule: an amount such that 0.5 to 4 moles of hydrogen atoms bonded to silicon atoms in component (B) are per mole of alkenyl groups in component (A), (C) A platinum-based catalyst mixture that is activated by moisture and / or oxygen and also has the ability to be activated by ultraviolet light: an amount such that the mass of platinum atoms in component (C) is 0.1 to 1,000 ppm relative to the total mass of components (A) and (B). (D) Dehydrating agent: 0.01 to 5 parts by mass per 100 parts by mass of the total of components (A) and (B), and (E) Organic zirconium compound: 0.001 to 5 parts by mass per 100 parts by mass of the total of components (A) and (B) A liquid silicone composition that contains a substance whose curing is accelerated by ultraviolet irradiation and which also hardens upon contact with moisture (humidity) and / or oxygen in the atmosphere.

2. The UV and air-curable liquid silicone composition according to claim 1, wherein the dehydrating agent of component (D) is at least one compound selected from silyl ketenes and α-silyl esters.

3. The ultraviolet and air-curable liquid silicone composition according to claim 1, wherein component (C) is an aerobic platinum-based catalyst mixture comprising a reaction mixture of a platinum-alkenyl group-containing organosiloxane complex and an organosilicon compound having at least one hydrogen atom bonded to a silicon atom in one molecule in an amount such that there is an excess mole of hydrogen atoms bonded to silicon atoms relative to the alkenyl groups in the platinum-alkenyl group-containing organosiloxane complex.

4. The UV and air-curable liquid silicone composition according to Claim 1, wherein component (E) is a dehydration accelerator consisting of one selected from tetraethoxyzirconium, tetran-propoxyzirconium, tetraisopropoxyzirconium, tetran-butoxyzirconium, tetra(2-ethylhexyloxy)zirconium, zirconium diisopropoxybis(ethylacetoacetate), and zirconium tetraacetylacetonate.

5. The ultraviolet and air-curable liquid silicone composition according to Claim 1, further comprising (G) a platinum-based catalyst activated by ultraviolet light: an amount such that the mass of platinum atoms contained in component (G) is 0.1 to 1,000 ppm relative to the total mass of components (A) and (B).

6. A cured product of an ultraviolet and air-curable liquid silicone composition according to any one of claims 1 to 5.

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