Ultraviolet-curable silicone gel composition, and silicone gel cured product obtained by curing said composition

Abstract

The present invention pertains to an ultraviolet-curable silicone gel composition containing components (A)-(D): (A) 5-95 parts by mass of an organopolysiloxane compound having two or more alkenyl groups per molecule; (B) 5-95 parts by mass of an organopolysiloxane compound represented by average formula (1) (R1 1R2 2SiO1 / 2)a(R2 3SiO1 / 2)2-a(R2 2SiO)b; (C) an organohydrogen polysiloxane having three or more hydrosilyl groups per molecule; and (D) a hydrosilylation reaction catalyst in a catalytic amount. Thus, the present invention provides: an ultraviolet-curable silicone gel composition which, after being cured, has excellent heat resistance, etc., exhibits a stable loss coefficient tanδ in a wide frequency range, and can be suitably used for improving the reliability of vibration-damping performance; a silicone gel cured product obtained by curing the composition; and a vibration-damping material using the cured product.

Description

UV-curable silicone gel composition and cured silicone gel obtained by curing said composition

[0001] The present invention relates to an organopolysiloxane gel composition useful as a vibration damping material that forms a gel upon exposure to ultraviolet light, a cured product thereof, and a vibration damping material using the same.

[0002] Silicone gel is obtained by curing organopolysiloxanes with reactive functional groups to a low crosslink density, and after curing, it exhibits excellent heat resistance, cold resistance, adhesion, etc. Furthermore, because it is in gel form and has a low elastic modulus, low stress, and excellent stress buffering properties, it is widely used as a damping material for optical applications, and for protecting automotive electronic components and electronic materials.

[0003] Among these, thermosetting addition reaction type silicone gel compositions have the advantage that it is possible to freely adjust the amount of aliphatic unsaturated groups bonded to silicon atoms and the amount of hydrogen atoms bonded to silicon atoms (Si-H groups) in one organopolysiloxane molecule, and that the hardness of the gel can be freely designed by changing the ratio of the amount of Si-H to the amount of aliphatic unsaturated groups bonded to silicon atoms. However, because this thermosetting addition reaction type silicone gel composition requires heating to cure, it is difficult to apply it to substrates or members that have low heat resistance.

[0004] As a solution to this problem, a UV-curable silicone gel using a radical reaction has been reported (Patent Document 1). It uses an enethiol reaction to avoid damage from oxygen, and has the advantage of being able to cure instantaneously with UV irradiation for a few seconds to a few minutes. On the other hand, this reaction has the disadvantage that it does not cure in dark areas, so if a light-shielding area is present in the component, poor curing can occur below the light-shielding area, or additional UV irradiation from the side is required, which increases the number of processes.

[0005] Meanwhile, as a solution to this problem, an ultraviolet-curable silicone gel produced by a hydrosilylation reaction has been reported (Patent Document 2). This gel is evaluated by penetration, but the loss factor tan δ obtained by dynamic viscoelasticity measurement is used as an indicator of vibration-damping performance. A high loss factor tan δ allows the material to dissipate and attenuate the mechanical energy imparted to it as heat or other energy. In other words, the desired vibration-damping performance cannot be achieved unless this parameter is controlled. Furthermore, if the loss factor tan δ changes significantly over a wide frequency range, variations in vibration-damping performance will occur.

[0006] International Publication No. 2011 / 136170 JP 2003-213132 A

[0007] The present invention has been made in view of the above circumstances, and has as its object the provision of an ultraviolet-curable silicone gel composition that, after curing, has excellent heat resistance and the like, exhibits a stable loss factor tan δ over a wide frequency range, and is suitable for use in improving the reliability of vibration-damping performance; a silicone gel cured product obtained by curing the composition; and a vibration-damping material using the cured product.

[0008] In order to solve the above problems, the present invention provides a composition comprising the following components (A) to (D): (A) an organopolysiloxane containing at least two alkenyl groups per molecule: 5 to 95 parts by mass; (B) an organopolysiloxane represented by the following average formula (1): (R １ １ R ２ ２ SiO １／２ ) a (R ２ ３ SiO １／２ ) ２－a (R ２ ２ SiO) ｂ (1) (In formula (1), R １ represents an alkenyl group, R ２(a) is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms and not containing an alkenyl group, and a is 0.2 or more and less than 2, and b is a positive number.) 5 to 95 parts by mass (provided that the total of components (A) and (B) is 100 parts by mass); (C) an organohydrogenpolysiloxane having at least three hydrogen atoms bonded to silicon atoms per molecule, in an amount such that the hydrosilyl groups (Si—H) in component (C) are 0.1 to 2.0 moles per mole of alkenyl groups in components (A) and (B); and (D) a catalytic amount of a photoactivatable hydrosilylation reaction catalyst, wherein the cured product of the silicone gel composition has a loss factor tan δ in the range of 0.2 to 1.0 at 25°C and a frequency of 0.1 to 50 Hz.

[0009] The ultraviolet-curable silicone gel composition of the present invention, which contains components (A) to (D), exhibits excellent heat resistance and other properties after curing, and exhibits a stable loss factor tan δ over a wide frequency range, making it suitable for use in improving the reliability of vibration-damping performance.

[0010] The present invention also provides a cured silicone gel product obtained by curing the above ultraviolet-curable silicone gel composition.

[0011] Such a cured silicone gel has excellent heat resistance and exhibits a stable loss factor tan δ over a wide frequency range, making it useful as a vibration-damping material that can be suitably used to improve the reliability of vibration-damping performance.

[0012] The present invention provides a silicone gel composition, characterized in that the cured product has a loss factor tan δ in the range of 0.2 to 1.0 at 25°C and a frequency of 0.1 to 50 Hz.

[0013] Such a silicone gel composition will have excellent heat resistance and other properties after curing, and will exhibit a stable loss factor tan δ over a wide frequency range, making it suitable for use in improving the reliability of vibration damping performance.

[0014] The silicone gel composition is preferably UV-curable.

[0015] Such an ultraviolet-curable silicone gel composition has excellent heat resistance and other properties after curing, and exhibits a stable loss factor tan δ over a wide frequency range, making it an ultraviolet-curable silicone gel composition that can be suitably used to improve the reliability of vibration damping performance.

[0016] The silicone gel composition further comprises the following components (A) to (D): (A) an organopolysiloxane containing at least two alkenyl groups per molecule; (B) a siloxane represented by the following average formula (1): (R １ １ R ２ ２ SiO １／２ ) a (R ２ ３ SiO １／２ ) ２－a (R ２ ２ SiO) ｂ (1) (In formula (1), R １ represents an alkenyl group, R ２ (wherein a and b may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups having 1 to 10 carbon atoms and not containing alkenyl groups, a is 0.2 or more and less than 2, and b is a positive number), (C) an organohydrogenpolysiloxane having at least three hydrogen atoms bonded to silicon atoms per molecule, and (D) a photoactivatable hydrosilylation reaction catalyst.

[0017] A silicone gel composition containing components (A) to (D) like this will have excellent heat resistance and other properties after curing, and will exhibit a stable loss factor tan δ over a wide frequency range, making it suitable for use in improving the reliability of vibration damping performance.

[0018] The present invention provides a cured silicone gel product obtained by curing a silicone gel composition characterized in that the cured product has a loss factor tan δ in the range of 0.2 to 1.0 at 25°C and a frequency of 0.1 to 50 Hz.

[0019] Such a cured silicone gel has excellent heat resistance and exhibits a stable loss factor tan δ over a wide frequency range, making it useful as a vibration-damping material that can be suitably used to improve the reliability of vibration-damping performance.

[0020] In the present invention, the ultraviolet-curable silicone gel composition or the cured product of the silicone gel composition (cured silicone gel product) is used as a vibration damping material.

[0021] By using such a silicone gel cured product as a vibration-damping material, it is possible to provide a vibration-damping material that has excellent heat resistance, etc., exhibits a stable loss factor tan δ over a wide frequency range, and can be used to preferably improve the reliability of vibration-damping performance.

[0022] As described above, the ultraviolet-curable silicone gel composition of the present invention can provide an ultraviolet-curable silicone gel composition that has excellent heat resistance and exhibits a stable loss factor tan δ over a wide frequency range after curing and is suitable for improving the reliability of vibration-damping performance, as well as a silicone gel cured product obtained by curing the composition, and a vibration-damping material using the cured product.

[0023] Thus, there has been a need for the development of an ultraviolet-curable silicone gel composition that, after curing, has excellent heat resistance and the like, exhibits a stable loss factor tan δ over a wide temperature range, and can be used favorably to improve the reliability of vibration-damping performance; a silicone gel cured product obtained by curing such a composition; and a vibration-damping material using such a cured product.

[0024] As a result of extensive research into achieving the above-mentioned objects, the present inventors discovered that a specific ultraviolet-curable silicone gel composition according to the present invention can provide an ultraviolet-curable silicone gel composition that exhibits a stable loss factor tan δ over a wider frequency range than conventional silicone gel compositions, leading to improved reliability, and thus completed the present invention.

[0025] That is, the present invention provides a composition comprising the following components (A) to (D): (A) 5 to 95 parts by mass of an organopolysiloxane containing at least two alkenyl groups per molecule; (B) an organopolysiloxane represented by the following average formula (1): (R １ １ R ２ ２ SiO １／２) a (R ２ ３ SiO １／２ ) ２－a (R ２ ２ SiO) ｂ (1) (In formula (1), R １ represents an alkenyl group, R ２ a is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms and not containing an alkenyl group, a is 0.2 or more and less than 2, and b is a positive number.), which may be the same or different; 5 to 95 parts by mass (provided that the total of components (A) and (B) is 100 parts by mass); (C) an organohydrogenpolysiloxane having at least three hydrogen atoms bonded to silicon atoms per molecule, in an amount such that the number of hydrosilyl groups (Si—H) in component (C) is 0.1 to 2.0 moles per mole of alkenyl groups in components (A) and (B); and (D) a catalytic amount of a photoactivatable hydrosilylation reaction catalyst, wherein the cured product of the silicone gel composition has a loss factor tan δ in the range of 0.2 to 1.0 at 25°C and a frequency of 0.1 to 50 Hz.

[0026] The present invention will be described in detail below, but the present invention is not limited thereto.

[0027] [Component (A)] The organopolysiloxane of component (A) contains at least two, and preferably from 2 to 6, alkenyl groups bonded to silicon atoms per molecule. The alkenyl groups preferably contain from 2 to 8 carbon atoms, and specific examples include vinyl, allyl, butenyl, pentenyl, hexenyl, and heptenyl groups, with vinyl being particularly preferred.

[0028] Examples of the organic group bonded to a silicon atom other than the above-mentioned alkenyl group include unsubstituted or substituted monovalent hydrocarbon groups having 1 to 10 carbon atoms and no aliphatic unsaturated bonds. Specific examples include linear alkyl groups, branched alkyl groups, cyclic alkyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups. Preferred examples of linear alkyl groups include those having 1 to 10 carbon atoms, such as methyl, ethyl, propyl, hexyl, octyl, and decyl groups, more preferably those having 1 to 6 carbon atoms. Preferred examples of branched alkyl groups include those having 1 to 10 carbon atoms, such as isopropyl, isobutyl, tert-butyl, and 2-ethylhexyl groups, more preferably those having 1 to 6 carbon atoms. Preferred examples of cyclic alkyl groups include those having 3 to 10 carbon atoms, such as cyclopentyl and cyclohexyl groups. Preferred examples of aryl groups include those having 6 to 10 carbon atoms, such as phenyl and tolyl groups. Preferred examples of the aralkyl group include those having 7 to 10 carbon atoms, such as a 2-phenylethyl group and a 2-methyl-2-phenylethyl group. Preferred examples of the halogenated alkyl group include those having 1 to 10 carbon atoms, more preferably those having 1 to 6 carbon atoms, such as a 3,3,3-trifluoropropyl group, a 2-(nonafluorobutyl)ethyl group and a 2-(heptadecafluorooctyl)ethyl group.

[0029] Of these, preferred are linear alkyl groups and aryl groups, more preferred are linear alkyl groups and aryl groups having 1 to 6 carbon atoms, and particularly preferred are methyl and phenyl groups.

[0030] The viscosity of component (A) at 23°C is preferably in the range of 50 to 100,000 mPa·s, and more preferably in the range of 500 to 100,000 mPa·s. A viscosity within this range ensures easy handling of the composition and favorable physical properties for the cured product of the composition. The viscosity is measured using a rotational viscometer (TVB-10M, manufactured by Toki Sangyo Co., Ltd.).

[0031] The number of repeating units of siloxane bonds in one molecule of component (A) is 50 to 3,000, preferably 50 to 2,000, more preferably 100 to 1,500, and even more preferably 120 to 1,000. If the number of repeating units is 50 or more, the resulting cured product will have excellent flexibility and a sufficient tan δ. If the number of repeating units is 3,000 or less, the viscosity of the resulting cured product will not be too high, resulting in excellent workability. The number of repeating units of siloxane bonds in a molecule is ２９ It can be measured by Si-NMR (the same applies to the examples).

[0032] The molecular structure of component (A) is not particularly limited and may be, for example, linear, branched, partially branched linear, or dendritic (dendrimer-like), with linear and partially branched linear being preferred. Component (A) may be a single polymer having any of these molecular structures, a copolymer having any of these molecular structures, or a mixture of two or more of these polymers.

[0033] Examples of component (A) include dimethylpolysiloxanes terminally blocked with dimethylvinylsiloxy groups, dimethylpolysiloxanes terminally blocked with methylphenylvinylsiloxy groups, dimethylsiloxane-methylphenylsiloxane copolymers terminally blocked with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers terminally blocked with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers terminally blocked with silanol groups, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers terminally blocked with silanol groups, and dimethylsiloxane-methylvinylsiloxane copolymers terminally blocked with trimethylsiloxy groups.

[0034] The organopolysiloxane of component (A) may use either a single compound, or a combination of two or more different compounds.

[0035] [Component (B)] In the present invention, component (B) is an organopolysiloxane represented by the average formula (1). This organopolysiloxane is a straight-chain linear polysiloxane, and is a mixture of molecules having vinyl groups at both ends, molecules having a vinyl group at one end, and molecules having no vinyl groups. The ratio of these molecules is set so that a in formula (1) is a number between 0.2 and 2. If a is less than 0.2, the amount of vinyl groups in the organopolysiloxane is small, resulting in a decrease in the curability of the composition. If a is 2, component (B) becomes an organopolysiloxane contained in component (A), which increases the amount of vinyl groups in the organopolysiloxane and results in a hard cured product, which is undesirable.

[0036] In the average formula (1), R １ is an alkenyl group, and R ２ is preferably a linear alkyl group or an aryl group, more preferably a linear alkyl group or an aryl group having 1 to 6 carbon atoms, and particularly preferably selected from a methyl group and a phenyl group.

[0037] In order to ensure effective dispensing of the composition, the viscosity of the organopolysiloxane of component (B) is preferably in the range of 50 to 100,000 mPa s at 23°C. It is preferable that b in the above average formula (1) be a value that ensures the viscosity falls within the above range; specifically, it is 30 to 1,200, preferably 40 to 1,100, more preferably 50 to 1,000, and even more preferably 60 to 900.

[0038] The organopolysiloxane of component (B) can be easily produced by a method known per se, for example, ２ ３ SiCl,R ２ ２ SiCl ２ , R １ R ２ ２ It is produced by subjecting a hydrolyzate of a chlorosilane such as SiCl to an equilibration reaction in the presence of an alkali or acid catalyst at room temperature or under heat.

[0039] The proportion of component (A) out of a total of 100 parts by mass of components (A) and (B) is 5 to 95 parts by mass, preferably 10 to 90 parts by mass, and by appropriately selecting this blending ratio, the softness of the silicone gel after curing, i.e., the loss factor tan δ, can be changed as needed. If the blending amount is less than 5 parts by mass, the loss factor tan δ of the resulting composition will be extremely high, and there is a risk of fluidity developing, whereas if it exceeds 95 parts by mass, the loss factor tan δ will be extremely low, and the gel will become hard, which may reduce its function as a vibration-damping material.

[0040] [Component (C)] Component (C) acts as a crosslinking agent for components (A) and (B). It is essential that component (C) contains an organohydrogenpolysiloxane having at least three hydrogen atoms bonded to silicon atoms (Si—H groups) per molecule. In other words, as long as this organohydrogenpolysiloxane having at least three Si—H groups is used, it is also possible to use an organohydrogenpolysiloxane having only two Si—H groups in combination for adjusting the loss factor tan δ. Examples of component (C) include known organosilicon compounds, but are not particularly limited. In the present invention, the amount of SiH groups is １ It can be measured by H-NMR (the same applies to the examples).

[0041] The component (C) can be exemplified by the following average composition formula (2): ｃ R ２ ３－ｃ SiO-(HR ２ SiO) ｄ - (R ２ ２ SiO) ｅ -SiR ２ ３－ｃ H ｃ (2) (wherein, R ２may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups having 1 to 10 carbon atoms and not containing alkenyl groups, c is 0 or 1, d and e are integers, 2c+d≧3, and d+e is a number such that the viscosity of the organohydrogenpolysiloxane of formula (2) at 25°C is 1 to 5,000 mPa s, preferably d+e≧4, and more preferably 200≧d+e≧4.

[0042] The viscosity of the organohydrogenpolysiloxane of component (C) at 25°C as measured with a rotational viscometer (TVB-10M, manufactured by Toki Sangyo Co., Ltd.) is preferably 1 to 5,000 mPa s, more preferably 1 to 2,000 mPa s, and even more preferably 5 to 500 mPa s. This organohydrogenpolysiloxane may be a mixture of two or more types.

[0043] R ２ Specific examples of the monovalent hydrocarbon group include the group R ２ Although the same groups as those shown in the above can be mentioned, a methyl group and a phenyl group are preferred.

[0044] Component (C) can be used singly or in combination of two or more. When an organohydrogenpolysiloxane having two Si—H groups is used in combination, for example, one in which d=0 in the above formula (2) can be used.

[0045] The amount of component (C) to be blended is an amount that results in a molar ratio of Si—H groups in component (C) per combined mole of alkenyl groups in components (A) and (B) of 0.1 to 2.0, preferably 0.1 to 1.8, and more preferably 0.1 to 1.5. If the amount of Si—H groups is less than 0.1 mole, the composition will not cure sufficiently and the loss factor tan δ may exceed 1. If the amount of Si—H groups exceeds 2.0 moles, the resulting cured silicone gel may be prone to yellowing when heated and may also exhibit reduced mechanical properties.

[0046] [Component (D)] Component (D) is a photoactivated hydrosilylation catalyst. Photoactivated hydrosilylation catalysts are activated by irradiation with light, particularly ultraviolet light of 300 to 400 nm, and promote the addition reaction between alkenyl groups in components (A) and (B) and hydrosilyl groups in component (C). Examples of photoactivated hydrosilylation catalysts include platinum-group metal catalysts and nickel-based metal catalysts. Platinum-group metal catalysts include platinum-, palladium-, and rhodium-based metal complex compounds, while nickel-based metal catalysts include nickel-, iron-, and cobalt-based metal complex compounds. Platinum-based metal complex compounds are particularly preferred because they are relatively readily available and exhibit good catalytic activity.

[0047] The photoactivated hydrosilylation catalyst is activated by irradiation with ultraviolet light, particularly of 300 to 400 nm, and reacts with, for example, (η ５ -cyclopentadienyl)tri(σ-alkyl)platinum complex compounds and β-diketonatoplatinum complex compounds, specifically (methylcyclopentadienyl)trimethylplatinum(IV), (cyclopentadienyl)trimethylplatinum(IV), (1,2,3,4,5-pentamethylcyclopentadienyl)trimethylplatinum(IV), (cyclopentadienyl)dimethylethylplatinum(IV), (cyclopentadienyl)dimethylacetylplatinum(IV), (trimethylsilylcyclopentadienyl)trimethylplatinum(IV), (methoxycarbonylcyclopentadienyl)trimethylplatinum(IV), (dimethylphenylsilylcyclopentadienyl ) trimethylcyclopentadienyl platinum (IV), trimethyl (acetylacetonato) platinum (IV), trimethyl (3,5-heptanedionato) platinum (IV), trimethyl (methylacetoacetate) platinum (IV), bis (2,4-pentanedionato) platinum (II), bis (2,4-hexanedionato) platinum (II), bis (2,4-heptanedionato) platinum (II), bis (3,5-heptanedionato) platinum (II), bis (1-phenyl-1,3-butanedionato) platinum (II), bis (1,3-diphenyl-1,3-propanedionato) platinum (II), bis (hexafluoroacetylacetonato) platinum (II), and the like.

[0048] When using these catalysts, if they are solid catalysts they can be used in solid form, but in order to obtain a more uniform cured product it is preferable to use a solution of the catalyst in an appropriate solvent and then dissolve it in the silicone compound of component (A) or component (B).

[0049] The type of solvent to be used is not particularly limited as long as the catalyst is soluble in it. In addition to common hydrocarbon solvents, the catalyst may also be dissolved in silicone oil to eliminate concerns about residual solvent in the composition.

[0050] Examples of hydrocarbon solvents include toluene, xylene, methyl ethyl ketone, and cyclopentanone.

[0051] The silicone oil can be dissolved in the alkenyl group-containing organopolysiloxane exemplified as component (A) or component (B).

[0052] When the catalyst is used as a solution, the preferred mixing ratio of component (A) or component (B) to the catalyst solution is in the range of 100:0.01 to 2.00 (mass ratio). If the amount of catalyst solution added is within this range, it will have a favorable effect on the physical properties of the cured product and will disperse throughout the composition. Therefore, the concentration of the catalyst solution can be adjusted appropriately so that it falls within this mixing ratio range.

[0053] The amount of hydrosilylation catalyst used can be a catalytic amount, but is typically preferably 1 to 1,000 ppm (calculated as the mass of platinum group metal) relative to the total mass of components (A) and (B), and more preferably 3 to 500 ppm. If the amount of hydrosilylation catalyst used is in the range of 1 ppm to 1,000 ppm, the addition reaction will be accelerated, curing the silicone composition, and the resulting silicone gel will have sufficient heat resistance.

[0054] The hydrosilylation reaction catalyst of component (D) may use either a single compound or a combination of two or more different compounds.

[0055] [Other Components] In addition to the above components (A) to (D), the present composition may optionally contain the following various compounding ingredients, including component (E) (control agent).

[0056] [Component (E)] Component (E) is an optional component that acts as a hydrosilylation reaction catalyst inhibitor (cure inhibitor). It can be added before photocuring, for example, during preparation of the silicone gel composition of the present invention or during use, to prevent the composition from thickening or gelling. Examples of such components include acetylene alcohols such as 1-ethynyl-1-hydroxycyclohexane, 3-methyl-1-butyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 3-methyl-1-penten-3-ol, and phenylbutynol; 3-methyl-3-penten-1-yne, 3,5-dimethyl-3-hexen-1-yne, dimethylbis(1,1-dimethyl-2-propynyloxy)silane; polymethylvinylsiloxane cyclic compounds; and organophosphorus compounds. The addition of these compounds can maintain appropriate curing reactivity and storage stability. Component (E) may be used alone or in combination of two or more.

[0057] The amount of component (E) blended is in the range of 0 to 5 parts by mass, preferably 0.0002 to 5 parts by mass, and more preferably 0.0004 to 4 parts by mass, per 100 parts by mass of the total of components (A), (B), and (C). When blended, the amount is 5 parts by mass or less, so that the resulting composition has sufficient curability.

[0058] (Fillers) Other examples of inorganic fillers include silica-based fillers such as surface-untreated or surface-hydrophobized fumed silica (fumed silica, dry silica), precipitated silica (wet silica), colloidal silica, sol-gel silica, crystalline silica (fine quartz powder), fused silica, and crushed silica, as well as iron oxide, zinc oxide, titanium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, and carbon black. The addition of these fillers can adjust the hardness and mechanical strength of the gel-like cured product obtained from the composition. Hollow inorganic fillers or rubbery spherical fillers can also be added.

[0059] (Adhesion Imparting Agent) In order to impart adhesion, a known adhesion imparting agent containing an epoxy group, an alkoxy group, or the like may also be added.

[0060] (Hardness Adjusting Agent) Furthermore, a non-crosslinkable organopolysiloxane that does not contain hydrogen atoms or alkenyl groups bonded to silicon atoms can also be added to the UV-curable silicone gel composition of the present invention, for example, for the purpose of adjusting the hardness of the cured silicone gel.

[0061] The amounts of the above other components used are arbitrary and depend on the characteristics of the resulting UV-curable silicone gel composition and the physical properties of the cured product.

[0062] [Cured Product] The UV-curable silicone gel composition of the present invention, which contains the above-mentioned components, can be cured to form a cured product that has excellent heat resistance, etc., and exhibits a stable loss factor tan δ over a wide frequency range, and is suitable for improving the reliability of vibration damping performance. Because the UV-curable silicone gel composition of the present invention uses a photoactivated hydrosilylation reaction catalyst, the composition can be poured into a suitable mold, or coated or potted on a suitable substrate, and then cured by irradiating it with light.

[0063] Here, the light irradiated during curing is preferably near-ultraviolet light (hereinafter sometimes simply referred to as ultraviolet light). There are no particular restrictions on the type of actinic ray used to cure the ultraviolet-curable silicone gel composition of the present invention to obtain a cured silicone gel product, and the ultraviolet radiation may be light having multiple emission spectra or light having a single emission spectrum.

[0064] Examples of light having multiple emission spectra include lamps such as metal halide lamps, xenon lamps, carbon arc lamps, chemical lamps, sodium lamps, low-pressure mercury lamps, high-pressure mercury lamps, and ultra-high-pressure mercury lamps; gas lasers such as nitrogen lasers; liquid lasers using organic dye solutions; and solid-state lasers using inorganic single crystals containing rare earth ions.

[0065] Light having a single emission spectrum is light having a peak (i.e., maximum peak wavelength) in the range of 300 to 400 nm, preferably 350 to 380 nm. Examples of light sources that irradiate such light include ultraviolet light-emitting diodes (ultraviolet LEDs) and ultraviolet light-emitting semiconductor element light sources such as ultraviolet light-emitting semiconductor lasers.

[0066] A useful ultraviolet wavelength range is 220 to 400 nm, more preferably 320 to 380 nm. When using light having multiple emission spectra, a bandpass filter capable of cutting wavelengths other than 365 nm can be used to irradiate only a desired wavelength.

[0067] The amount of ultraviolet light irradiation (illuminance) is not particularly limited as long as it is an amount of irradiation sufficient for curing, but the cumulative amount of light is preferably 1,000 to 20,000 mJ / cm 2 , more preferably 2,000 to 15,000 mJ / cm 2 When the amount of ultraviolet light irradiation (illuminance) is within the above range, sufficient energy can be obtained to activate the photoactivatable hydrosilylation reaction catalyst in the composition, and a cured product with sufficient physical properties can be obtained.

[0068] The light irradiation device is not particularly limited, and for example, a spot type irradiation device, a surface type irradiation device, a line type irradiation device, a conveyor type irradiation device, or the like can be used.

[0069] When curing the ultraviolet-curable silicone gel composition of the present invention, the light irradiation time depends on the illuminance of the light used, but is, for example, 1 to 300 seconds, preferably 10 to 200 seconds, and more preferably 30 to 150 seconds. After 1 to 60 minutes, and particularly 5 to 40 minutes, of light irradiation, the composition loses its fluidity and a cured silicone gel product can be obtained.

[0070] Furthermore, the ambient temperature during photocuring affects the curing time. In other words, the time required for complete curing is longer at lower temperatures and shorter at higher temperatures. To take advantage of the advantages of photocuring, the ambient temperature during curing is preferably 10 to 120°C. If the ambient temperature during curing is within this range, curing will not take a long time and the substrate will not suffer from thermal degradation (thermal deformation or thermal discoloration).

[0071] The cured silicone gel obtained by curing the UV-curable silicone gel composition of the present invention can be used as a vibration-damping material due to its excellent dynamic viscoelastic properties. In other words, this cured gel exhibits high vibration-damping properties and stable frequency dependency, such as a loss factor tan δ of 0.2 to 1.0 over a wide frequency range (0.1 Hz to 50 Hz).

[0072] Furthermore, depending on the package design, the area where vibration isolation or damping is desired may have a complex part shape, and even when irradiated with light, the silicone gel composition may not be sufficiently distributed. To address such concerns, a hydrosilylation reaction with dark curing properties is useful because it can sufficiently cure dark areas over time after light irradiation. Furthermore, a UV-curable silicone gel composition can be supplied to a substrate with dark areas that cannot be directly irradiated with UV light, and then irradiated with UV light to cure the silicone composition, thereby forming a cured product.

[0073] The vibration-damping properties of the vibration-damping material can be adjusted by varying the blending ratio of each component of the ultraviolet-curable silicone gel composition within the above ranges.

[0074] The present invention will be specifically explained below using examples and comparative examples, but the present invention is not limited to these. The components (raw materials) used in the examples and comparative examples are listed below. The molecular structure of each compound is １ H and ２９ This was confirmed by Si-NMR.

[0075] Components (raw materials) used in the examples and comparative examples: (A) Component (A-1): Dimethylpolysiloxane (CH ２ =CH(CH ３ ) ２ SiO １／２ ) ２ ((CH ３ ) ２ SiO) ４６０(A-2): Dimethylpolysiloxane (CH) having a viscosity of 30,000 mPa·s and terminated at both molecular chain ends with dimethylvinylsiloxy groups ２ =CH(CH ３ ) ２ SiO １／２ ) ２ ((CH ３ ) ２ SiO) ７４０

[0076] Component (B): Polysiloxane containing dimethylpolysiloxane, one molecular chain end of which is capped with dimethylvinylsiloxy groups and one molecular chain end of which is capped with trimethylsiloxy groups, having a viscosity of 800 mPa·s, prepared by the method described in the examples of Japanese Patent No. 2849027 (CH ２ =CH(CH ３ ) ２ SiO １／２ ) １．９ ((CH ３ ) ３ SiO １／２ ) ０．１ ((CH ３ ) ２ SiO) ８５ (a=1.9)

[0077] Component (C) (C-1): Organohydrogenpolysiloxane 1 (H(CH ３ ) ２ SiO １／２ ) ２ (H(CH ３ ) SiO) ２ ((CH ３ ) ２ SiO) １４ (C-2): Organohydrogenpolysiloxane 2 ((CH ３ ) ３ SiO １／２ ) ２ (H(CH ３ ) SiO) ３ ((CH ３ ) ２ SiO) ２７ (C-3): Organohydrogenpolysiloxane 3 ((CH ３ ) ３ SiO １／２ ) ２ (H(CH ３) SiO) １６ ((CH ３ ) ２ SiO) ２８ (C-4): Organohydrogenpolysiloxane 4 (H(CH ３ ) ２ SiO １／２ ) ２ ((CH ３ ) ２ SiO) １８

[0078] Component (D): Photoactivatable hydrosilylation catalyst (methylcyclopentadienyl)trimethylplatinum(IV) / [dimethylpolysiloxane terminated at both molecular chain ends with dimethylvinylsiloxy groups (viscosity 600 mPa·s)]=0.5% / 99.5%

[0079] Component (E): Cure inhibitor dimethylbis(1,1-dimethyl-2-propynyloxy)silane

[0080] Examples 1 to 4, Comparative Examples 1 to 4 Using the above components (raw materials), the ultraviolet-curable silicone gel compositions shown in Table 1 were prepared. The blend amounts in Table 1 indicate mass amounts.

[0081] Dynamic Viscoelasticity Measurement (Sample Preparation) For Examples 1 to 4 and Comparative Examples 1 to 4, dynamic viscoelasticity was measured using a dynamic viscoelasticity measuring device (manufactured by TA Instruments, product name: ARES-G2). Each composition was placed on a 20 mm diameter stainless steel parallel disk (GEOM DISP DISC 316 SST) in the lower measuring section of the device, and sandwiched between 20 mm diameter quartz disks (Upper UV Geometry assembly) equipped with a reflective mirror assembly in the upper measuring section, with the jig distance between the upper and lower parallel disks set to 1.0 mm. At this time, excess composition on the outer periphery of the parallel disks was removed. The hydrosilylation catalyst was activated by irradiating the specimen with a 365 nm wavelength UV-LED irradiator (BlueWave MX-150 - RediCure 365 nm, manufactured by Dymax) at an illuminance of 100 mW / cm for 90 seconds at 25°C, followed by standing at 40°C for 2 hours to fully promote the addition curing reaction. (Measurement) The loss factor tan δ of the cured specimen prepared using the above equipment was then measured at 25°C, a strain value of 10%, and frequencies of 0.1, 1, 10, and 50 Hz. This measurement was performed in shear mode. The results are shown in Table 1.

[0082] High-Temperature, High-Humidity Test: For Examples 1 to 4, cured silicone gels were prepared in the same manner as in the dynamic viscoelasticity measurement described above. The cured products were left to stand at a temperature of 85°C and a humidity of 85% RH (relative humidity) for 1,000 hours, after which the loss factor tan δ at 25°C and a frequency of 10 Hz was measured using a dynamic viscoelasticity measuring device (TA Instruments, ARES-G2). The results are shown in Table 1.

[0083]

[0084] As shown in Table 1, the cured silicone gel products using the UV-curable silicone gel composition of the present invention in Examples 1 to 4 exhibited stable and appropriate loss factor tan δ over a wide frequency range from 0.1 Hz to 50 Hz. Furthermore, in the high-temperature, high-humidity test, the loss factor tan δ at 10 Hz showed almost no change from the loss factor tan δ at 10 Hz before the test. These results confirm that the cured products using the UV-curable silicone gel composition of the present invention have excellent vibration-damping properties and heat resistance.

[0085] On the other hand, in Comparative Examples 1 and 2, which did not contain the essential component (B) of the present invention, and Comparative Example 3, which did not contain the essential component (A), the loss factor tan δ changed significantly from 0.1 Hz to 50 Hz in the dynamic viscoelasticity measurement test. Furthermore, in Comparative Example 4, in which the essential component (C) of the present invention consisted solely of an organohydrogenpolysiloxane ((C-4)) having no three Si—H groups, curing was insufficient. These results confirmed that compositions lacking the essential components of the present invention have inferior vibration-damping properties.

[0086] From the above, it is clear that the present invention can provide an ultraviolet-curable silicone gel composition that has excellent heat resistance and other properties after curing, exhibits a stable loss factor tan δ over a wide frequency range, and can be used favorably to improve the reliability of vibration damping performance.

[0087] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. The following components (A) to (D): (A) an organopolysiloxane containing at least two alkenyl groups in one molecule: 5 to 95 parts by mass, (B) a compound represented by the following average formula (1): (R １ １ R ２ ２ SiO １／２ ) a (R ２ ３ SiO １／２ ) ２－a (R ２ ２ SiO) ｂ (1) (In formula (1), R １ represents an alkenyl group, R ２ a is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms and not containing an alkenyl group, a is 0.2 or more and less than 2, and b is a positive number); (C) an organohydrogenpolysiloxane having at least 3 hydrogen atoms bonded to silicon atoms per molecule; and (D) a catalytic amount of a photoactivatable hydrosilylation reaction catalyst, wherein the cured product of the silicone gel composition has a loss factor tan δ in the range of 0.2 to 1.0 at 25° C. and a frequency of 0.1 to 50 Hz.

2. A silicone gel cured product obtained by curing the ultraviolet-curable silicone gel composition according to claim 1.

3. A silicone gel composition, the cured product of which has a loss factor tan δ in the range of 0.2 to 1.0 at 25°C and a frequency of 0.1 to 50 Hz.

4. The silicone gel composition according to claim 3, characterized in that the silicone gel composition is UV-curable.

5. The silicone gel composition comprises the following components (A) to (D): (A) an organopolysiloxane containing at least two alkenyl groups in one molecule, (B) a silyl group represented by the following average formula (1): (R １ １ R ２ ２ SiO １／２ ) a (R ２ ３ SiO １／２ ) ２－a (R ２ ２ SiO) ｂ (1) (In formula (1), R １ represents an alkenyl group, R ２ where may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups having 1 to 10 carbon atoms containing no alkenyl groups, a is 0.2 or greater but less than 2, and b is a positive number), (C) an organohydrogenpolysiloxane having at least 3 hydrogen atoms bonded to silicon atoms per molecule, and (D) a photoactivatable hydrosilylation reaction catalyst.

6. A silicone gel cured product obtained by curing the silicone gel composition according to claim 3.

7. A silicone gel cured product according to claim 2 or 6, which is used as a vibration damping material.