Ultraviolet-curable polysiloxane composition and damping material

Abstract

To provide an ultraviolet-curable polysiloxane composition capable of forming a silicone gel which is uniformly cured at a surface part and an inner part with a small amount of ultraviolet irradiation and is effective for vibration isolation and damping of a small drive device.SOLUTION: There is provided an ultraviolet-curable polysiloxane composition which comprises: 100 pts.mass of an organosiloxane (A) having at least one or more vinyl groups; a mercaptoalkyl group-containing organopolysiloxane (B) in an amount so that the number of moles of mercaptoalkyl groups is 0.1 to 1.0 mole based on 1 mol of vinyl groups of the organopolysiloxane (A); 0.1 to 5 pts.mass of a photopolymerization initiator (C) based on 100 pts.mass of the organopolysiloxane (A); and 0.5 to 5 pts.mass of a piperidone derivative (D) based on 100 pts.mass of the organopolysiloxane (A).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a damping material made of an ultraviolet-curable polysiloxane composition and a cured product thereof, and more particularly to a damping material made of an ultraviolet-curable polysiloxane composition having excellent uniformity of curing between the surface and the interior and excellent ultraviolet curing properties, and a cured product thereof. [Background technology]

[0002] Silicone gel is a viscoelastic material obtained by crosslinking organopolysiloxane having alkenyl groups such as vinyl groups bonded to silicon atoms with a crosslinking agent in the presence of an addition reaction catalyst, and since it has a small complex elastic modulus and a large loss factor (tan δ), it is flexible and has excellent shock and vibration absorption properties, and also has excellent mechanical strength, heat resistance, and cold resistance, and is therefore used in a wide range of fields, for example, as an adhesive, a sealant, a potting material, a coating material, and a damping material used in driving devices that require precise control, such as optical pickup devices. In particular, for vibration isolation and damping of driving parts of optical pickup devices, etc., ultraviolet-curable polysiloxane compositions are used, which can be supplied in an uncured state (liquid) to the location where vibration isolation and damping are required and cured with ultraviolet light to form a silicone gel, from the viewpoint of the ease of assembly of the silicone gel.

[0003] In order to avoid inhibition of curing by oxygen, this type of ultraviolet-curable polysiloxane composition uses an ene-thiol reaction system composition that contains a crosslinking agent made of an organopolysiloxane containing at least two mercaptoalkyl groups in one molecule and a base material made of an organopolysiloxane containing at least two alkenyl groups in one molecule.

[0004] In recent years, with the miniaturization of electric and electronic devices, the drive devices used therein have also become smaller, and the volume and thickness of the silicone gel used as a damping material have become smaller. Therefore, if the silicone gel used is a UV-curable polysiloxane composition that has been cured in a non-uniform state between the surface and the inside, the non-uniform curing state affects the damping performance, so it is important to make the curing state of the silicone gel uniform in order to control the drive device with high precision. However, a film-like surface layer that is more cured than the inside may be formed near the surface of the silicone gel to which UV rays are incident, and when the volume of the silicone gel is small, the non-uniform curing state associated with the formation of this surface layer may affect the damping performance. As a means of eliminating this effect, Patent Document 1 discloses that when a UV-curable silicone composition is irradiated with specific UV rays to cure it, the surface becomes harder than the inside and a silicone gel with less adhesion is formed on the surface, and it has been reported that depending on the UV irradiation conditions, the surface does not harden and the surface and the inside become uniform. Thus, methods for suppressing the formation of a silicone gel surface layer due to UV irradiation conditions have been investigated. However, in production processes in which damping materials are used, adjustments to irradiation conditions or changes to the UV light source affect productivity, and so there has been a demand for the application of UV-curable polysiloxane compositions that provide excellent curing uniformity.

[0005] Therefore, the present applicant has proposed an ultraviolet-curable silicone gel composition in which a specific hindered amine compound is added to a silicone gel consisting of an organopolysiloxane having at least one vinyl group, an organopolysiloxane containing a mercaptoalkyl group, and a photopolymerization initiator (Patent Document 2). The ultraviolet-curable silicone gel composition described in Patent Document 2 has excellent curing uniformity between the surface and the inside without requiring special ultraviolet irradiation conditions as in the curing method of Patent Document 1. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-231732 [Patent Document 2] JP 2020-172581 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, the ultraviolet-curable silicone gel composition described in Patent Document 2 requires a greater ultraviolet ray irradiation dose (accumulated light amount) than conventional ones, specifically 3000 mJ / cm2, in order to cure the composition. 2 The problem was that an integrated light amount of 10 ...

[0008] A second object of the present invention is to provide a damping material having a uniform hardened structure on the surface and inside and excellent damping performance. [Means for solving the problem]

[0009] The ultraviolet-curable polysiloxane composition of the present invention contains: 100 parts by mass of an organopolysiloxane (A) having at least one vinyl group; a mercaptoalkyl group-containing organopolysiloxane (B): parts by mass such that the number of moles of the mercaptoalkyl group is 0.1 to 1.0 mole per mole of the vinyl group in the organopolysiloxane (A); a photopolymerization initiator (C): 0.1 to 5 parts by mass per 100 parts by mass of the organopolysiloxane (A); and a piperidone derivative (D): 0.5 to 5 parts by mass per 100 parts by mass of the organopolysiloxane (A).

[0010] The ultraviolet-curable polysiloxane composition of the present invention contains 0.5 to 5 parts by mass of the piperidone derivative (D) per 100 parts by mass of the organopolysiloxane (A), thereby suppressing the formation of a film-like surface layer on the surface irradiated with ultraviolet light, thereby uniformly curing the surface and the interior, and also enabling rapid curing under conditions of low ultraviolet irradiation dose, and thus enabling the formation of a cured product (silicone gel) with a small integrated light dose.

[0011] In addition, in the ultraviolet-curable polysiloxane composition of the present invention, the piperidone derivative (D) is preferably a 4-piperidone derivative. By selecting a 4-piperidone derivative as the piperidone derivative (D), an ultraviolet-curable polysiloxane composition can be obtained that can be rapidly cured under conditions of low ultraviolet irradiation dose to form a silicone gel with a small integrated light dose, and that has an improved effect of uniformly curing the surface and the inside.

[0012] In addition, in the ultraviolet-curable polysiloxane composition of the present invention, it is also preferable that the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring in the above-mentioned 4-piperidone derivative is a linear or branched alkyl group. By selecting a 4-piperidone derivative in which a linear or branched alkyl group is bonded to the nitrogen atom in the nitrogen-containing six-membered ring as the piperidone derivative (D), an ultraviolet-curable polysiloxane composition can be obtained that can be rapidly cured under conditions of low ultraviolet irradiation dose to form a silicone gel with a small integrated light dose, and that has an improved effect of uniformly curing the surface and the inside.

[0013] In addition, in the ultraviolet-curable polysiloxane composition of the present invention, the 4-piperidone derivative of the piperidone derivative (D) is preferably 1-methyl-4-piperidone. By selecting 1-methyl-4-piperidone as the piperidone derivative (D), it is possible to obtain an ultraviolet-curable polysiloxane composition that can be rapidly cured under conditions of a lower ultraviolet irradiation dose to form a silicone gel with a small accumulated light dose and that has an excellent effect of uniformly curing the surface and the inside.

[0014] In addition, in the ultraviolet-curable polysiloxane composition of the present invention, the piperidone derivative (D) is preferably a 2-piperidone derivative. By selecting a 2-piperidone derivative as the piperidone derivative (D), it is possible to obtain an ultraviolet-curable polysiloxane composition that can be rapidly cured under conditions of low ultraviolet irradiation dose to form a silicone gel with a small integrated light dose, and that has an improved effect of uniformly curing the surface and the inside.

[0015] In addition, in the ultraviolet-curable polysiloxane composition of the present invention, it is also preferable that the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring in the above-mentioned 2-piperidone derivative is a linear or branched alkyl group. By selecting a 2-piperidone derivative in which a linear or branched alkyl group is bonded to the nitrogen atom in the nitrogen-containing six-membered ring as the piperidone derivative (D), it is possible to obtain an ultraviolet-curable polysiloxane composition that can be rapidly cured under conditions of low ultraviolet irradiation dose to form a silicone gel with a small integrated light dose, and that has an improved effect of uniformly curing the surface and the inside.

[0016] In addition, in the ultraviolet-curable polysiloxane composition of the present invention, the 2-piperidone derivative of the piperidone derivative (D) is preferably 1,5-dimethyl-2-piperidone. By selecting 1,5-dimethyl-2-piperidone as the piperidone derivative (D), an ultraviolet-curable polysiloxane composition can be obtained that is rapidly cured under conditions of a lower ultraviolet irradiation dose, can form a silicone gel with a small accumulated light dose, and has an excellent effect of curing the surface and the inside uniformly.

[0017] It is also preferred that the ultraviolet-curable polysiloxane composition of the present invention further contains a hindered phenol compound (E): 0.5 to 5 parts by mass per 100 parts by mass of the organopolysiloxane (A). By using the hindered phenol compound (E) in combination with the piperidone derivative (D), it is possible to obtain an ultraviolet-curable polysiloxane composition that can form a silicone gel with the surface and interior uniformly cured, even under conditions of a lower ultraviolet irradiation dose.

[0018] The damping material of the present invention is made of the cured product of the above-mentioned UV-curable polysiloxane composition. The cured product of the above-mentioned UV-curable polysiloxane composition, i.e., silicone gel, has a structure in which the surface and the inside are uniformly cured, so that the damping performance is uniform and the vibration-proofing and vibration-damping properties are excellent. Effect of the Invention

[0019] According to the present invention, the ultraviolet-curable polysiloxane composition is based on an organopolysiloxane (A) having at least one vinyl group, an organopolysiloxane containing a mercaptoalkyl group (B), and a photopolymerization initiator (C), and further contains a piperidone derivative (D), which allows the composition to be rapidly cured under conditions of low ultraviolet irradiation to form a cured product (silicone gel) with a small cumulative amount of light, and the surface and interior are cured uniformly, so that even when a damping material made of this cured product is applied in a small volume in vibration prevention and damping of a driving device that requires precise drive control, stable damping performance can be obtained. Furthermore, by using the piperidone derivative (D) in cooperation with the hindered phenol compound (E), uniform curing can be achieved between the surface and interior, while curing can be further accelerated under conditions of low ultraviolet irradiation, and a cured product (silicone gel) can be obtained with low energy. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The ultraviolet-curable polysiloxane composition according to the present invention and the damping material made of the cured product thereof will be described in detail below.

[0021] 1. UV-curable polysiloxane composition The ultraviolet-curable polysiloxane composition of the present invention comprises an organopolysiloxane (A) having at least one vinyl group, an organopolysiloxane (B) containing a mercaptoalkyl group, a photopolymerization initiator (C), and a piperidone derivative (D). In this specification, the organopolysiloxane (A) is also referred to as vinyl group-containing organopolysiloxane (A), and the organopolysiloxane (B) is also referred to as mercaptoalkyl group-containing organopolysiloxane (B).

[0022] (Vinyl-containing organopolysiloxane (A)) The vinyl group-containing organopolysiloxane (A) constituting the ultraviolet-curable polysiloxane composition of the present invention is an organopolysiloxane (A) having at least one vinyl group in one molecule, and is the main component of the ultraviolet-curable polysiloxane composition. The bonding position of the vinyl group in the component (A) is not limited, and it may be bonded to the molecular chain terminal or the molecular chain side chain, or it may be bonded to both. In addition, the silicon-bonded organic group other than the vinyl group in the vinyl group-containing organopolysiloxane (A) is substituted with a methyl group or a phenyl group. In addition, the molecular structure of the vinyl group-containing organopolysiloxane (A) is preferably substantially linear (straight-chain), but may have a branched structure in part. Specific examples of the vinyl group-containing organopolysiloxane (A) include dimethylsiloxane terminally blocked with dimethylvinylsiloxy groups, dimethylsiloxane-diphenylsiloxane copolymer terminally blocked with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymer terminally blocked with dimethylvinylsiloxy groups, dimethylsiloxane one molecular end blocked with dimethylvinylsiloxy groups and the other molecular end blocked with trimethylsiloxy groups, dimethylsiloxane one molecular end blocked with dimethylvinylsiloxy groups and the other molecular end blocked with trimethylsiloxy groups, methylvinylsiloxane-diphenylsiloxane, dimethylsiloxane-methylvinylsiloxane copolymer terminally blocked with trimethylsiloxy groups at both molecular ends, and dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymer terminally blocked with trimethylsiloxy groups at both molecular ends. These can be applied alone or in combination of two or more kinds.

[0023] (Mercaptoalkyl Group-Containing Organopolysiloxane (B)) The mercaptoalkyl group-containing organopolysiloxane (B) constituting the ultraviolet-curable polysiloxane composition of the present invention is a crosslinking agent component for crosslinking the vinyl group-containing organopolysiloxane (A) by an ene-thiol reaction between the vinyl group of the vinyl group-containing organopolysiloxane (A) and the mercaptoalkyl group possessed by component (B), and is, for example, an organopolysiloxane in which a mercaptoalkyl group is substituted at the molecular chain end or side chain. More specifically, it is an organopolysiloxane such as (CH 3 ) 3 SiO 1 / 2 Units, (CH 3 )(HS(CH 2 ) n )SiO 2 / 2 Units (n is an integer from 2 to 20) and (CH 3 ) 2 SiO 2 / 2 It is preferable that the organopolysiloxane is a mercaptoalkyl group-containing organopolysiloxane consisting of HS(CH 2 ) n (n is an integer of 2 to 20) groups are more preferably present in one molecule in an average number of more than 3. The mercaptoalkyl group is not particularly limited, but examples thereof include a mercaptoethyl group, a mercaptopropyl group, and a mercaptohexyl group.

[0024] The amount of the mercaptoalkyl group-containing organopolysiloxane (B) is, from the viewpoint of the curability of the ultraviolet-curable polysiloxane composition, such that the number of moles of the mercaptoalkyl group in the mercaptoalkyl group-containing organopolysiloxane (B) is 0.1 to 1.0 mole per mole of the vinyl group in the vinyl group-containing organopolysiloxane (A). If the amount of the mercaptoalkyl group-containing organopolysiloxane (B) is less than 0.1 mole, the curability of the ultraviolet-curable polysiloxane composition decreases, and if it is more than 1.0 mole, there are too many crosslinking points, and the hardness of the cured product (silicone gel) after curing of the ultraviolet-curable polysiloxane composition becomes too high, and the vibration-proofing and vibration-damping effects advantageous as a damping material cannot be obtained.

[0025] (Photopolymerization initiator (C)) The photopolymerization initiator (C) constituting the ultraviolet-curable polysiloxane composition of the present invention is for promoting the crosslinking reaction between the vinyl group in the vinyl group-containing organopolysiloxane (A) and the mercaptoalkyl group in the mercaptoalkyl group-containing organopolysiloxane (B) under ultraviolet irradiation, and known ones can be used. Specifically, 1-hydroxy-cyclohexyl-phenyl-ketone, 2,2-dimethoxy-2-phenylacetophenone, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, Michler's ketone, benzoin propyl ether, benzoin ethyl ether, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2- Methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, thioxanthone, diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide; Omnirad 184, 369, 651, 500, 907, 1173, TPO H (all manufactured by BASF), etc. are listed, and acetophenone-based compounds are preferred from the viewpoint of promoting the crosslinking reaction. The photopolymerization initiator (C) can be applied alone or in combination of two or more kinds. The amount of the photopolymerization initiator (C) to be blended is an amount effective for initiating an ultraviolet reaction, that is, 0.1 to 5 parts by mass per 100 parts by mass of the vinyl group-containing organopolysiloxane (A).

[0026] (Piperidone derivatives (D)) The piperidone derivative (D) constituting the ultraviolet-curable polysiloxane composition of the present invention is a component for suppressing the formation of a film-like surface layer on the surface of the cured product (silicone gel) of the ultraviolet-curable polysiloxane composition, forming a cured product with a small cumulative light amount, and uniformly curing the surface and the inside. The piperidone derivative (D) may be a 2-piperidone derivative, a 3-piperidone derivative, or a 4-piperidone derivative, but is preferably a liquid at room temperature (1 to 30°C) from the viewpoint of dispersibility in the ultraviolet-curable polysiloxane composition. The piperidone derivative (D) may be a known liquid derivative, but is preferably selected from a 4-piperidone derivative or a 2-piperidone derivative from the viewpoint of the ability to cure under conditions of a lower ultraviolet irradiation amount to form a silicone gel with a small cumulative light amount and to uniformly cure the surface and the inside. As the piperidone derivative (D), a 2-piperidone derivative, a 3-piperidone derivative or a 4-piperidone derivative may be used alone or two or more of them may be selected and used in combination.

[0027] The degree of the action of the 4-piperidone derivative to uniformly cure the surface and the inside under the condition of a lower UV irradiation dose varies depending on the type of functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring. Specific examples of the 4-piperidone derivative include 4-piperidone in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a hydrogen atom, as well as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, Examples of linear or branched alkyl groups include n-hexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 1-ethylbutyl, 2-ethylbutyl, n-heptyl, 1-methylhexyl, and 1-ethylpentyl groups, and 4-piperidone derivatives such as 1-methyl-4-piperidone, 1-ethyl-4-piperidone, 1-propionyl-4-piperidone, 1-isopropyl-4-piperidone, and 1,2,2,6,6-pentamethyl-4-piperidone. Further examples include 4-piperidone derivatives in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a benzyl group, such as 1-benzyl-4-piperidone, 1-(2-phenylethyl)-4-piperidone, or 1-benzyl-3-carbomethoxy-4-piperidone; 4-piperidone derivatives in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a furylmethyl group, such as 1-(2-furylmethyl)-4-piperidone; 4-piperidone derivatives in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a formyl group, such as 1-formyl-4-piperidone; and 4-piperidone derivatives in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a trityl group. In addition, as the 4-piperidone derivative, 2,2,6,6-tetramethyl-4-piperidone, 3,5-bis[(4-methylphenyl)methylene]-4-piperidone, 3-methoxycarbonyl-4-piperidone, 3,5-bromo-2,2,6,6-tetramethyl-4-piperidone, and the like, which have a functional group bonded to a carbon atom in a nitrogen-containing six-membered ring, can also be used.Among these, from the viewpoints of dispersibility in the vinyl group-containing organopolysiloxane (A) and the mercaptoalkyl group-containing organopolysiloxane (B) and uniform curing at a low cumulative light dose, 4-piperidone derivatives in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a hydrogen atom, a linear or branched alkyl group, a benzyl group, a furylmethyl group, or a trityl group, and 4-piperidone derivatives having a functional group bonded to a carbon atom in the nitrogen-containing six-membered ring are preferred, 4-piperidone derivatives in which the functional group is a linear or branched alkyl group are more preferred, and 1-methyl-4-piperidone is even more preferred. The 4-piperidone derivatives may be used alone or in combination of two or more kinds.

[0028] 2-piperidone derivatives have different degrees of action of uniformly curing the surface and the inside under conditions of lower UV irradiation dose, depending on the type of functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring. Specific examples of 2-piperidone derivatives include 2-piperidone in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a hydrogen atom, as well as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl, 1-ethyl ... and 2-piperidone derivatives such as N-methyl-2-piperidone, 1-ethyl-2-piperidone, 1-propionyl-2-piperidone, 1-isopropyl-2-piperidone, and 1,5-dimethyl-2-piperidone, which are linear or branched alkyl groups exemplified by n-hexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 1-ethylbutyl, 2-ethylbutyl, n-heptyl, 1-methylhexyl, and 1-ethylpentyl groups. Other examples of the 2-piperidone derivative include 1-benzyl-2-piperidone or 1-(2-phenylethyl)-2-piperidone, in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a benzyl group, N-cyclohexyl-2-piperidone, in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a cyclohexyl group, 1-formyl-2-piperidone or 1-(benzoylformyl)-2-piperidone, in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a formyl group, and 1-trityl-2-piperidone, in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a trityl group. As the 2-piperidone derivative, those having a functional group bonded to a carbon atom of the nitrogen-containing six-membered ring, such as 1,5-dimethyl-2-piperidone, 3-amino-2-piperidone, or N-chloro-2-piperidone, can also be used.Among these, from the viewpoints of dispersibility in the vinyl group-containing organopolysiloxane (A) and the mercaptoalkyl group-containing organopolysiloxane (B) and uniform curing at a low cumulative light dose, 2-piperidone derivatives in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a hydrogen atom, a linear or branched alkyl group, a benzyl group, a cyclohexyl group, or a trityl group, and 2-piperidone derivatives having a functional group bonded to a carbon atom in the nitrogen-containing six-membered ring are preferred, 2-piperidone derivatives in which the functional group is a linear or branched alkyl group are more preferred, and 1,5-dimethyl-2-piperidone is particularly preferred. The 2-piperidone derivatives may be used alone or in combination of two or more kinds.

[0029] 3-piperidone derivatives have different degrees of action of uniformly curing the surface and the inside under conditions of lower UV irradiation dose, depending on the type of functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring. Specific examples of 3-piperidone derivatives include 3-piperidone in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a hydrogen atom, as well as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, and 2,2-dimethylpropyl groups. , a straight-chain or branched alkyl group exemplified by 1-ethylpropyl group, n-hexyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 1-ethylbutyl group, 2-ethylbutyl group, n-heptyl group, 1-methylhexyl group, and 1-ethylpentyl group; and 3-piperidone derivatives such as 1-methyl-3-piperidone, 1-ethyl-3-piperidone, 1-propionyl-3-piperidone, and 1-isopropyl-3-piperidone. Other examples include 3-piperidone derivatives such as 1-benzyl-3-piperidone or 1-(2-phenylethyl)-3-piperidone in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a benzyl group, 1-(2-furylmethyl)-3-piperidone in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a furylmethyl group, 1-formyl-3-piperidone in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a formyl group, and 1-trityl-3-piperidone in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a trityl group. As the 3-piperidone derivative, those having a functional group bonded to a carbon atom of the nitrogen-containing six-membered ring, such as 1,5-dimethyl-3-piperidone and N-chloro-3-piperidone, can also be used.Among these, from the viewpoints of dispersibility in the vinyl group-containing organopolysiloxane (A) and the mercaptoalkyl group-containing organopolysiloxane (B) and uniform curing at a low cumulative light dose, 3-piperidone derivatives in which the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring is a hydrogen atom, a linear or branched alkyl group, a benzyl group, a furylmethyl group, a formyl group, or a trityl group, and 3-piperidone derivatives having a functional group bonded to a carbon atom in the nitrogen-containing six-membered ring are preferred. The 3-piperidone derivatives may be used alone or in combination of two or more kinds.

[0030] It is important that the amount of the piperidone derivative (D) is more than 0.1 part by mass and less than 10 parts by mass, preferably 0.5 to 5 parts by mass, more preferably 1 to 3 parts by mass, and particularly preferably 1.5 to 2.5 parts by mass, relative to 100 parts by mass of the vinyl group-containing organopolysiloxane (A). If it is less than 0.1 part by mass, the effect of uniformly curing the ultraviolet-curable polysiloxane composition is insufficient, and if it is more than 10 parts by mass, bleeding out from the cured product of the ultraviolet-curable polysiloxane composition becomes significant, so it is blended within the above range.

[0031] (Hindered phenol compounds (E)) The ultraviolet-curable polysiloxane composition of the present invention preferably further contains a hindered phenol compound (E), which cooperates with the piperidone derivative (D) to cause a crosslinking reaction between the vinyl group-containing organopolysiloxane (A) and the mercaptoalkyl group-containing organopolysiloxane (B) under conditions of a low accumulated light intensity, thereby functioning as a component that improves the curability of the ultraviolet-curable polysiloxane composition. Examples of the hindered phenolic compound (E) include benzenepropanoic acid, 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7-C9 branched alkyl ester, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,4-dimethyl-6-(1-methylpentadecyl)phenol, di Examples of such esters include ethyl [{3,5-bis(1,1-di-tert-butyl-4-hydroxyphenyl)methyl}phosphonate, 3,3′,3″,5,5′,5″-hexane-tert-butyl-4-a,a′,a″-(mesitylene-2,4,6-tolyl)tri-p-cresol, 4,6-bis(octylthiomethyl)-o-cresol, ethylene bis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], and hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. Among these, benzenepropanoic acid, 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7-C9 branched alkyl ester (e.g., BASF, trade name: Irganox1135) is particularly preferred. The hindered phenol compound (E) may be used alone or in combination of two or more kinds.

[0032] The content of component (E) is 0.5 to 5 parts by mass, and preferably 1 to 2.5 parts by mass, based on 100 parts by mass of the vinyl group-containing organopolysiloxane (A). If it is less than 0.5 parts by mass, the curability is insufficient, and if it is more than 5 parts by mass, bleeding out from the cured product of the ultraviolet-curable polysiloxane composition becomes significant, so it is blended in the above range.

[0033] (Filler) The ultraviolet-curable polysiloxane composition of the present invention may further contain a filler for imparting viscoelastic properties and further functionality to the cured product. The filler is not particularly limited as long as it is a powder that can impart functionality and adjust the viscoelastic properties of the cured product and does not inhibit the thiol-ene reaction, and can be appropriately selected and applied according to the purpose, such as fumed silica represented by AEROSIL (registered trademark) of Nippon Aerosil Co., Ltd., REOLOSIL (registered trademark) of Tokuyama Corporation, WACKER HDK (registered trademark) of Asahi Kasei Wacker Co., Ltd., silica and silicone resins such as TOKUSIL (registered trademark) of Tokuyama Corporation, metal oxides such as alumina, and fibrous compounds such as cellulose nanofibers.

[0034] (Other Ingredients) The ultraviolet-curable polysiloxane composition of the present invention may contain other components as necessary within the range that does not impair the effects of the present invention. Examples of other components include thixotropy-imparting agents, heat resistance-imparting agents, flame retardant agents, pigments, dyes, tackiness / adhesiveness-imparting agents, polymerization inhibitors, and additives for improving weather resistance, such as antioxidants, ultraviolet absorbers, and light stabilizers, and known ones can be used for these.

[0035] As the tackiness / adhesion imparting agent, for example, one or more silicone resin-based adhesion improvers (not containing an aliphatic unsaturated group or a mercapto group) selected from the group consisting of MQ resin, MDQ resin, MT resin, MDT resin, MDTQ resin, DQ resin, DTQ resin and TQ resin are preferred, one or more silicone resin-based adhesion improvers selected from the group consisting of MQ resin, MDQ resin, MDT resin and MDTQ resin are more preferred from the viewpoint of flowability and dispersibility in the ultraviolet-curable polysiloxane composition, and MQ resin is even more preferred from the viewpoint of tackiness imparting effect and easy structure control. A silane coupling agent may also be added to improve adhesion to the adherend. Examples of the silane coupling agent include triethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 1,3-bis(3-methacryloxypropyl)tetramethyldisiloxane, trimethoxysilylpropyl diallyl isocyanurate, bis(trimethoxysilylpropyl)allyl isocyanurate, tris(trimethoxysilylpropyl)isocyanurate, triethoxysilylpropyl diallyl isocyanurate, bis(triethoxysilylpropyl)allyl isocyanurate, tris(triethoxysilylpropyl)isocyanurate, etc. In addition, as other examples of the silane coupling agent, disiloxane compounds having functional groups such as (meth)acryloxy groups, alkoxy groups (e.g., methoxy, ethoxy, propoxy), and amino groups, such as 1,3-bis(3-methacryloxypropyl)tetramethyldisiloxane, can also be used. Of these, from the viewpoint of improving adhesion and bonding properties, it is preferable that the agent contains an aliphatic unsaturated group, and 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 1,3-bis(3-methacryloxypropyl)tetramethyldisiloxane are more preferable. The tackiness and adhesion imparting agent may be one type or two or more types.

[0036] As the antioxidant, any antioxidant that can prevent oxidation of the cured product of the composition according to the present invention and can add a function of improving weather resistance can be used. The hindered phenol-based compound (E) also functions as an antioxidant, but other examples include hindered amine-based antioxidants.The hindered amine antioxidant can be appropriately selected from known antioxidants. For example, N,N',N'',N''-tetrakis-(4,6-bis(butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino)-triazin-2-yl)-4,7-diazadecane-1,10-diamine, dibutylamine·1,3,5-triazine·N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine·N-(2,2,6,6-tetramethyl-4 poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}], polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, and bis[2,2,6,6-tetramethyl-1(octyloxy)-4-piperidine decanedioate]. lysyl) ester, reaction products of 1,1-dimethylethyl hydroperoxide with octane (70%)]-polypropylene (30%), bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) tert-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione, and the like.

[0037] As the light stabilizer, one that can add a function of preventing photo-oxidative deterioration of the composition according to the present invention or its cured product can be used. The piperidone derivative (D) also functions as a light stabilizer, but other examples include benzotriazole-based, hindered amine-based, and benzoate-based compounds. Among these, hindered amine-based light stabilizers are preferred as light stabilizers. Among them, it is preferred to use a tertiary amine-containing hindered amine-based light stabilizer in order to improve the storage stability of the composition. As the tertiary amine-containing hindered amine-based light stabilizer, light stabilizers such as Tinuvin 622LD, Tinuvin 144, and CHIMASSORC119FL (all manufactured by BASF); MARK LA-57, LA-62, LA-67, and LA-63 (all manufactured by Asahi Denka Kogyo Co., Ltd.); and Sanol LS-765, LS-292, LS-2626, LS-1114, and LS-744 (all manufactured by Sankyo Co., Ltd.) can be mentioned. Examples of ultraviolet absorbers that function as light resistance stabilizers include ultraviolet absorbers such as benzotriazole-based, triazine-based, benzophenone-based, and benzoate-based compounds. Known ultraviolet absorbers can be appropriately selected, and examples of such ultraviolet absorbers include 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate / polyethylene glycol 3-(1,1,3,3-tetramethylbutyl)phenol, and methyl 3-(1,1,3,3-tetramethylbutyl)-4-hydroxyphenyl)propionate / polyethylene glycol 3-(1,1,3,3-tetramethylbutyl)phenol. 00 reaction product, benzotriazole-based ultraviolet absorbers such as 2-(2H-benzotriazol-2-yl)-6-(linear and side chain dodecyl)-4-methylphenol, triazine-based ultraviolet absorbers such as 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol, benzophenone-based ultraviolet absorbers such as octabenzone, benzoate-based ultraviolet absorbers such as 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate, etc. The above light stabilizers and ultraviolet absorbers may be one type or two or more types.

[0038] (Method for producing ultraviolet-curable polysiloxane composition) The ultraviolet-curable polysiloxane composition of the present invention is produced by mixing the above-mentioned components (A) to (D) or (A) to (E) with fillers and other various components added as necessary at a predetermined mixing ratio. The order in which the above-mentioned components (A) to (C) or (A) to (D) are mixed is not particularly limited. The mixing means is not particularly limited, and examples thereof include a single-screw extruder, a twin-screw extruder, a kneader, a Banbury mixer, and a roll mill.

[0039] (Cured product of ultraviolet-curable polysiloxane composition) The ultraviolet-curable polysiloxane composition of the present invention is cured by irradiation with ultraviolet light to form a cured product (silicone gel). The ultraviolet-curable polysiloxane composition of the present invention can form a cured product (silicone gel) in which the surface and the inside are uniformly cured quickly with a small amount of ultraviolet light irradiation. Specifically, the ultraviolet-curable polysiloxane composition described in the above-mentioned Patent Document 2 (JP Patent Publication No. 2020-172581) can be cured with an ultraviolet light irradiation dose of 3000 mJ / cm. 2 Whereas the ultraviolet-curable polysiloxane composition of the present invention required an integrated light dose of 2000 mJ / cm 2 With the following cumulative light amount, a cured product (silicone gel) can be formed in which the surface and the inside are uniformly cured, and the composition has excellent low-energy curing properties. More specifically, the cumulative light amount of ultraviolet light should be sufficient to cure the ultraviolet-curable polysiloxane composition, but the cumulative light amount should be 500 to 2000 mJ / cm. 2 For example, the integrated light amount can be selected from 500 to 2000 mJ / cm 2 It is preferable to set the integrated light amount to 500 to 1500 mJ / cm 2 It is more preferable to set the integrated light amount to 500 to 1000 mJ / cm 2It is more preferable that the amount of light is set to 100%. With such a low cumulative light amount, a cured product can be obtained in which the surface and the inside are uniformly cured. The light source of the irradiated ultraviolet light and the wavelength range of the ultraviolet light are not particularly limited, and for example, known sources such as a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a black light lamp, a microwave excited mercury lamp, a metal halide lamp, a sodium lamp, a halogen lamp, a xenon lamp, an LED, a fluorescent lamp, sunlight, and an electron beam irradiation device can be used.

[0040] 2. Damping material The damping material of the present invention is made of the cured product (silicone gel) of the above-mentioned ultraviolet-curable polysiloxane composition, and has a structure in which the surface and the inside are uniformly cured, so that it has excellent damping properties and can obtain stable damping performance even when applied in a small volume. The damping material can be formed, for example, by supplying the ultraviolet-curable polysiloxane composition to a location where vibration prevention or vibration control is desired, and curing it by irradiating it with ultraviolet light at the same time as or after supplying it. In addition, the damping properties of the damping material can be adjusted by changing the compounding ratio of each component of the above-mentioned ultraviolet-curable polysiloxane composition within the above range. EXAMPLES

[0041] EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not particularly limited to these examples.

[0042] The compounds related to the respective components used in the examples and comparative examples are as follows. <Vinyl-containing organopolysiloxane (A)> : Dimethylsiloxane terminated with dimethylvinylsiloxy groups at the molecular chain ends (Gelest, DMS-V33) <Mercaptoalkyl Group-Containing Organopolysiloxane (B)> : Dimethylsiloxane-mercaptopropylmethylsiloxane copolymer with the molecular chain ends blocked with trimethylsiloxane (Gelest, SMS-042) <Photopolymerization initiator (C)> : 2-Hydroxy-2-methyl-1-phenyl-propan-1-one (BASF, Omnirad1173) <Piperidone derivatives (D)> (d1) 1-Methyl-4-piperidone (Tokyo Chemical Industry Co., Ltd.) (d2) 1-isopropyl-4-piperidone (Tokyo Chemical Industry Co., Ltd.) (d3) 1,5-Dimethyl-2-piperidone (Tokyo Chemical Industry Co., Ltd.) <Hindered phenol compounds (E)> (e1) Benzenepropanoic acid, 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7-C9 branched alkyl ester (BASF, Irganox 1135)

[0043] The ultraviolet-curable polysiloxane compositions in the following Examples and Comparative Examples were evaluated according to the following methods (1) and (2).

[0044] (1) Low energy curing The ultraviolet-curable polysiloxane composition was poured into a glass container (inner diameter 45 mm) to a height of 2 mm, and then ultraviolet light was irradiated from a high-pressure mercury lamp (manufactured by Ushio Inc., model UVL-1500M2-N1) to measure the minimum cumulative light quantity required to cure the composition to the inside. The cumulative light quantity was determined to be 1000 mJ / cm. 2 The following cases are rated as "◎" (excellent), and the cumulative light amount is 1000mJ / cm 2 Exceeding 2000mJ / cm 2 The following cases are marked as "○" (good), and the cumulative light amount is 2000mJ / cm 2 Here, the state of curing to the inside was confirmed by irradiating an uncured sample with the above-mentioned high-pressure mercury lamp with an integrated light quantity of 6000 mJ / cm2. 2 The complex modulus of elasticity of the hardened material after it has been hardened to the inside by irradiating it with ultraviolet light is Gr * (Reference value when cured to the inside) and the complex modulus G of the cured material after irradiating an uncured sample with UV light at the integrated light dose of the above test * and the complex modulus G * is the complex elastic modulus Gr *If the hardening rate is 90% or more, it is deemed to have hardened to the inside. * and G * The specimens were those that had become disc-shaped and could retain their shape after UV irradiation, and measurements were made in torsional shear mode (25°C, 10Hz frequency) using a dynamic viscoelasticity measuring device (TA Instruments, ARES-G2) in accordance with JIS K7244-10. Those that were liquid or flowed after UV irradiation and could not retain their shape were judged to be in an uncured state without even needing to be measured.

[0045] (2) Curing uniformity The ultraviolet-curable polysiloxane composition was poured into a glass container (inner diameter 45 mm) to a height of 2 mm, and then irradiated with ultraviolet light from a high-pressure mercury lamp (Ushio Inc., model UVL-1500M2-N1) to produce a cured product with a thickness of 2 mm. When the surface of the cured product was pressed with a spatula (Shimizu Akira Co., Ltd., Sundia Micro Spatula), the accumulated light intensity was 3000 mJ / cm. 2 If wrinkles were observed on the surface and a hardened film was confirmed, the result was rated as "×" (failed), and the cumulative light dose was 3000 mJ / cm 2 When no hardened film was observed and there was no change in the surface (no wrinkles), it was rated as "○" (good). 2 When no hardened film was observed and there was no change in the surface (no wrinkles), the test was rated as "Excellent".

[0046] [Example 1] A plastic container with a lid was charged with 100 parts by mass of the vinyl group-containing organopolysiloxane (A), 6.5 parts by mass of the mercaptopropyl group-containing organopolysiloxane (B), 1 part by mass of the photopolymerization initiator (C), and 0.5 parts by mass of the piperidone derivative (D) (d1): 1-methyl-4-piperidone, and this mixture was then mixed at 2000 rpm for 2 minutes using a centrifugal mixer (product name: Awatori Rentaro (registered trademark) ARE-250, product of Thinky Corporation) and degassed at 2200 rpm for 1 minute, to obtain an ultraviolet-curable polysiloxane composition of Example 1. The amount of mercaptoalkyl group-containing organopolysiloxane (B) in the ultraviolet-curable polysiloxane composition of this Example 1 was such that the number of moles of mercaptoalkyl groups in the mercaptoalkyl group-containing organopolysiloxane (B) was 0.90 moles per mole of vinyl groups in the vinyl-containing organopolysiloxane (A). The obtained ultraviolet-curable polysiloxane composition was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0047] [Examples 2 to 4] The ultraviolet-curable polysiloxane compositions of Examples 2 to 4 were obtained in the same manner as in Example 1, except that the amount of piperidone derivative (D), (d1): 1-methyl-4-piperidone, was changed as shown in Table 1. Each of the obtained ultraviolet-curable polysiloxane compositions was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0048] The evaluation results of Examples 1 to 4 are shown in Table 1.

[0049] [Table 1]

[0050] [Example 5] An ultraviolet-curable polysiloxane composition of Example 5 was obtained in the same manner as in Example 1, except that as the piperidone derivative (D), (d2): 1-isopropyl-4-piperidone was used instead of (d1): 1-methyl-4-piperidone in Example 1. The obtained ultraviolet-curable polysiloxane composition was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0051] [Examples 6 to 8] The ultraviolet-curable polysiloxane compositions of Examples 6 to 8 were obtained in the same manner as in Example 5, except that the amount of piperidone derivative (D), (d2): 1-isopropyl-4-piperidone, was changed as shown in Table 2. Each of the obtained ultraviolet-curable polysiloxane compositions was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0052] The evaluation results of Examples 5 to 8 are shown in Table 2.

[0053] [Table 2]

[0054] [Example 9] The ultraviolet-curable polysiloxane composition of Example 9 was obtained in the same manner as in Example 1, except that the piperidone derivative (D) was (d3): 1,5-dimethyl-2-piperidone instead of (d1): 1-methyl-4-piperidone in Example 1. The obtained ultraviolet-curable polysiloxane composition was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0055] [Examples 10 to 12] The ultraviolet-curable polysiloxane compositions of Examples 10 to 12 were obtained in the same manner as in Example 9, except that the amount of piperidone derivative (D), (d3): 1,5-dimethyl-2-piperidone, was changed as shown in Table 3. Each of the obtained ultraviolet-curable polysiloxane compositions was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0056] The evaluation results of Examples 9 to 12 are shown in Table 3.

[0057] [Table 3]

[0058] [Example 13] The ultraviolet-curable polysiloxane composition of Example 13 was obtained in the same manner as in Example 2, except that 0.5 parts by mass of (e1) benzenepropanoic acid, 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7-C9 branched alkyl ester was further added as the hindered phenol compound (E). The obtained ultraviolet-curable polysiloxane composition was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0059] [Examples 14 and 15] The ultraviolet-curable polysiloxane compositions of Examples 14 and 15 were obtained in the same manner as in Example 13, except that the amount of (e1) benzenepropanoic acid, 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7-C9 branched alkyl ester of the hindered phenol compound (E) was changed as shown in Table 4. Each of the obtained ultraviolet-curable polysiloxane compositions was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0060] [Example 16] The ultraviolet-curable polysiloxane composition of Example 16 was obtained in the same manner as in Example 6, except that 0.5 parts by mass of (e1) benzenepropanoic acid, 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7-C9 branched alkyl ester was further added as the hindered phenol compound (E). The obtained ultraviolet-curable polysiloxane composition was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0061] [Example 17] The ultraviolet-curable polysiloxane composition of Example 17 was obtained in the same manner as in Example 10, except that 1.0 part by mass of (e1) benzenepropanoic acid, 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7-C9 branched alkyl ester was further added as the hindered phenol compound (E). The obtained ultraviolet-curable polysiloxane composition was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0062] The evaluation results of Examples 13 to 17 are shown in Table 4.

[0063] [Table 4]

[0064] [Comparative Example 1] An ultraviolet-curable polysiloxane composition of Comparative Example 1 was obtained in the same manner as in Example 1, except that the piperidone derivative (D) was not added. The obtained ultraviolet-curable polysiloxane composition was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0065] [Comparative Example 2 and Comparative Example 3] The ultraviolet-curable polysiloxane compositions of Comparative Example 2 and Comparative Example 3 were obtained in the same manner as in Example 1, except that the amount of piperidone derivative (D), (d1): 1-methyl-4-piperidone, was changed as shown in Table 5. Each of the obtained ultraviolet-curable polysiloxane compositions was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0066] [Comparative Example 4 and Comparative Example 5] The ultraviolet-curable polysiloxane compositions of Comparative Examples 4 and 5 were obtained in the same manner as in Example 5, except that the amount of piperidone derivative (D), (d2): 1-isopropyl-4-piperidone, was changed as shown in Table 5. Each of the obtained ultraviolet-curable polysiloxane compositions was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0067] The evaluation results of Comparative Examples 1 to 5 are shown in Table 5.

[0068] [Table 5]

[0069] [Comparative Examples 6 and 7] The ultraviolet-curable polysiloxane compositions of Comparative Examples 6 and 7 were obtained in the same manner as in Example 9, except that the amount of piperidone derivative (D), (d3): 1,5-dimethyl-2-piperidone, was changed as shown in Table 6. Each of the obtained ultraviolet-curable polysiloxane compositions was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0070] [Comparative Example 8] An ultraviolet-curable polysiloxane composition of Comparative Example 8 was obtained in the same manner as in Example 3, except that 2.0 parts by mass of (f1) 1-phenylpiperidine was blended as the hindered amine compound (F) used in the above-mentioned Patent Document 2, instead of the piperidone derivative (D) in Example 3. The obtained ultraviolet-curable polysiloxane composition was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0071] [Comparative Example 9] An ultraviolet-curable polysiloxane composition of Comparative Example 9 was obtained in the same manner as in Example 3, except that 2.0 parts by mass of (f2) ethyl 1-methylpipecolate was blended as the hindered amine compound (F) used in the above-mentioned Patent Document 2, instead of the piperidone derivative (D) in Example 3. The obtained ultraviolet-curable polysiloxane composition was cured by ultraviolet irradiation, and the above-mentioned (1) low-energy curability and (2) curing uniformity were evaluated.

[0072] Table 6 shows the evaluation results of Comparative Examples 6 to 9.

[0073] [Table 6]

[0074] (Evaluation Results) From the evaluation results of Examples 1 to 17 shown in Tables 1 to 4, the ultraviolet-curable polysiloxane composition of the present invention, which contains 0.5 to 5 parts by mass of piperidone derivative (D) per 100 parts by mass of vinyl-containing organopolysiloxane (A), cures sufficiently to the inside even under ultraviolet irradiation conditions with a small integrated light amount, and cures uniformly on the surface and inside without forming a cured film on the surface of the cured product. These findings demonstrate that the composition has excellent low-energy curability and cure uniformity.

[0075] Furthermore, from the evaluation results of the group of Examples 1 to 4 and Examples 13 to 15 shown in Tables 1 to 5, the group of Examples 5 to 8 and Example 16, and the group of Examples 9 to 12 and Example 17, it was found that an ultraviolet-curable polysiloxane composition having excellent low-energy curability and curing uniformity can be obtained with either a 4-piperidone derivative or a 2-piperidone derivative as the piperidone derivative (D).

[0076] Furthermore, from the evaluation results of Examples 1 to 12 shown in Tables 1 to 3 and the evaluation results of Examples 13 to 17 shown in Table 4, it was found that the low-energy curing property was further improved by using the piperidone derivative (D) in combination with the hindered phenol compound (E). The results of Examples 13 to 15 showed that the amount of the hindered phenol compound that can obtain the effect of improving the low-energy curing property by using the piperidone derivative (D) in combination with the hindered phenol compound (E) is preferably in the range of at least 0.5 to 5 parts by mass per 100 parts by mass of the vinyl group-containing organopolysiloxane (A).

[0077] On the other hand, from the evaluation results of Comparative Example 1 shown in Table 5 and Comparative Examples 8 and 9 shown in Table 6, the ultraviolet-curable polysiloxane composition of Comparative Example 1, which did not contain the piperidone derivative (D), had a poor cure uniformity because a film-like surface layer was formed near the surface during cure, in which the cure was more advanced than in the interior. Also, the ultraviolet-curable polysiloxane compositions of Comparative Examples 8 and 9, in which the hindered amine compound (F) was used instead of the piperidone derivative (D), had good cure uniformity, but required a large cumulative amount of ultraviolet light for cure, and had poor low-energy curability.

[0078] Furthermore, the evaluation results of Comparative Examples 2, 4, and 6 shown in Tables 5 and 6 showed that when the blending ratio of piperidone derivative (D) was 0.1 part by mass per 100 parts by mass of vinyl group-containing organopolysiloxane (A), the cure uniformity was poor. The evaluation results of Comparative Examples 3, 5, and 7 showed that when the blending ratio of piperidone derivative (D) was 10 parts by mass per 100 parts by mass of vinyl group-containing organopolysiloxane (A), both the low-energy curability and the cure uniformity were poor. Therefore, it was found that it is important to keep the blending ratio of piperidone derivative (D) more than 0.1 part by mass and less than 10 parts by mass, and that a blending ratio of 0.5 to 5 parts by mass is preferable. [Industrial Applicability]

[0079] The ultraviolet-curable polysiloxane composition of the present invention is cured by ultraviolet light and exhibits excellent uniformity of curing between the surface and interior even under ultraviolet light irradiation conditions with a low integrated light dose, and is therefore useful as a damping material used for vibration prevention and vibration control in driving devices for small electric / electronic devices and precision machinery.

Claims

1. 100 parts by mass of an organopolysiloxane (A) having at least one vinyl group; a mercaptoalkyl group-containing organopolysiloxane (B): a part by mass in which the number of moles of the mercaptoalkyl group is 0.1 to 1.0 moles per mole of the vinyl group in the organopolysiloxane (A); Photopolymerization initiator (C): 0.1 to 5 parts by mass per 100 parts by mass of the organopolysiloxane (A); a piperidone derivative (D): 0.5 to 5 parts by mass per 100 parts by mass of the organopolysiloxane (A), The piperidone derivative (D) is any one of the following (i) to (iii): (i) a 2-piperidone derivative in which a functional group is bonded to a nitrogen atom in the nitrogen-containing six-membered ring of 2-piperidone (excluding 1,5-dimethyl-2-piperidone), or 3-amino-2-piperidone, a 2-piperidone derivative in which a functional group is bonded to a carbon atom in the nitrogen-containing six-membered ring of 2-piperidone (ii) a 3-piperidone derivative in which a functional group is bonded to a nitrogen atom in the nitrogen-containing six-membered ring of 3-piperidone, or 1,5-dimethyl-3-piperidone, a 3-piperidone derivative in which a functional group is bonded to a carbon atom in the nitrogen-containing six-membered ring of 3-piperidone (iii) a 4-piperidone derivative in which a functional group is bonded to a nitrogen atom in the nitrogen-containing six-membered ring of 4-piperidone (excluding 1-methyl-4-piperidone), or 2,2,6,6-tetramethyl-4-piperidone, 3,5-bis[(4-methylphenyl)methylene]-4-piperidone, 3-methoxycarbonyl-4-piperidone, or 3,5-bromo-2,2,6,6-tetramethyl-4-piperidone, which are 4-piperidone derivatives in which a functional group is bonded to a carbon atom in the nitrogen-containing six-membered ring of 4-piperidone.

1. An ultraviolet-curable polysiloxane composition comprising:

2. The piperidone derivative (D) is 2. The ultraviolet-curable polysiloxane composition according to claim 1, which is a 4-piperidone derivative (excluding 1-methyl-4-piperidone) in which a functional group is bonded to a nitrogen atom in a nitrogen-containing six-membered ring of 4-piperidone.

3. 3. The ultraviolet-curable polysiloxane composition according to claim 2, wherein the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring in the 4-piperidone derivative is a linear or branched alkyl group.

4. 3. The ultraviolet-curable polysiloxane composition according to claim 2, wherein the 4-piperidone derivative is 1-ethyl-4-piperidone, 1-propionyl-4-piperidone, 1-isopropyl-4-piperidone, 1,2,2,6,6-pentamethyl-4-piperidone, 1-benzyl-4-piperidone, 1-(2-phenylethyl)-4-piperidone, 1-benzyl-3-carbomethoxy-4-piperidone, 1-(2-furylmethyl)-4-piperidone, 1-formyl-4-piperidone, or 1-trityl-4-piperidone.

5. The piperidone derivative (D) is 2. The ultraviolet-curable polysiloxane composition according to claim 1, which is a 2-piperidone derivative (excluding 1,5-dimethyl-2-piperidone) in which a functional group is bonded to a nitrogen atom in a nitrogen-containing six-membered ring of 2-piperidone.

6. 6. The ultraviolet-curable polysiloxane composition according to claim 5, wherein the functional group bonded to the nitrogen atom in the nitrogen-containing six-membered ring in the 2-piperidone derivative is a linear or branched alkyl group.

7. 6. The ultraviolet-curable polysiloxane composition according to claim 5, wherein the 2-piperidone derivative is N-methyl-2-piperidone, 1-ethyl-2-piperidone, 1-propionyl-2-piperidone, 1-isopropyl-2-piperidone, N-chloro-2-piperidone, 1-benzyl-2-piperidone, 1-(2-phenylethyl)-2-piperidone, N-cyclohexyl-2-piperidone, 1-formyl-2-piperidone, 1-(benzoylformyl)-2-piperidone, or 1-trityl-2-piperidone.

8. The ultraviolet-curable polysiloxane composition according to any one of claims 1 to 7, further comprising a hindered phenol compound (E) in an amount of 0.5 to 5 parts by mass per 100 parts by mass of the organopolysiloxane (A).

9. A damping material comprising a cured product of the ultraviolet-curable polysiloxane composition according to any one of claims 1 to 7.