JPS62290755A - Ultraviolet-curable silicone composition - Google Patents

Abstract

PURPOSE:To obtain a compsn. which can be uniformly quick-cured by ultraviolet radiation and improves mechanical strengths, by blending a polyorganosiloxane with a surface-treated inorg. filler, a peroxy ester and a phenone photopolymerization initiator. CONSTITUTION:A compsn. consists of 100pts.wt. polyorganosiloxane (A) having the average compositional formula I, 1-50pts.wt. inorg. filler (B) having a surface treated with a silylating agent having a vinyl group, 0.1-5.0pts.wt. peroxy ester (C) of formula II and 0.1-5.0pts.wt. phenone photopolymerization initiator (D) of formula III. In the formulas, R<1> is a monovalent hydrocarbon group excluding a vinyl group; 0<a<=1; 0<b<=3; 1<=a+b<=3; R<2> is a monovalent aliph. hydrocarbon group; R<3> is a monovalent hydrocarbon group; R<4> is H, halogen, a monovalent hydrocarbon group or a 1-10C alkoxy; and R<6> is a 1-10C monovalent hydrocarbon group.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a silicone rubber composition that is cured by ultraviolet irradiation.

[Technical Background of the Invention and Problems Therein] Compositions and methods for curing silicone with ultraviolet rays or electron beams have been previously described in several documents. For example, U.S. Pat. No. 3,726,710 describes that various sensitizers are added to vinyl group-containing polyorganosiloxane, and the resulting polyorganosiloxane is cured by irradiation with high-intensity ultraviolet rays. However, this method has the disadvantage that curing occurs only on the surface and does not uniformly cure the inside.

Further, U.S. Pat. No. 3,816,282 describes a composition in which addition crosslinking is performed using a mercapto group-containing polyorganosiloxane, a polyorganosiloxane, and various organic peroxides; It had serious drawbacks such as poor storage stability at room temperature and accelerated gelation.

Furthermore, the synthesis of mercapto group-containing polyorganosiloxanes requires a multi-step process, and there are also drawbacks such as emitting a bad odor peculiar to mercapto groups. Furthermore, Japanese Patent Publication No. 52-19865 discloses a composition comprising a mercapto group-containing polyorganosiloxane and a dihydric phenol or its alkyl derivative as a gelling inhibitor, but this composition is stable during storage. Although the properties were improved, the drawbacks mentioned above for mercapto group-containing polyorganosiloxanes remained as well. Another drawback was that the curing was limited to the surface and not uniformly to the inside. Furthermore, Japanese Patent Publication No. 52-40334@ discloses a composition in which an addition reaction is avoided using a vinyl group-containing polyorganosiloxane, a polyorganohydrodiene siloxane, and a sensitizer, but this also cures only on the surface. It has serious drawbacks in that it does not harden to the inside and causes foaming.

Furthermore, JP-A-48-19682 proposes a composition comprising an acrylic unsaturated group-containing polyorganosiloxane and a sensitizer, but while this composition has an excellent photosensitizing effect, It has the drawbacks of being easily affected by oxygen and having large changes in photosensitivity over time and dark decay.Furthermore, the synthesis of polyorganosiloxane containing acrylic unsaturated groups requires multiple steps, and the heat resistance of the resulting silicone is poor. The problem was that it was bad. Also, Unexamined Japanese Patent Publication No. 54-
No. 69197 proposes a composition comprising an azide group-containing polyorganosiloxane, a vinyl group-containing polyorganosiloxane, and an organic peroxide. this is,
Water indexing reaction from the hydrocarbon group of polyorganosiloxane by decomposition of azide in polyorganosiloxane containing azide group, insertion reaction into vinyl group of polyorganosiloxane containing vinyl group, crosslinking reaction by coupling reaction of nitrene, and furthermore, organic Water indexing reaction from hydrocarbon groups of polyorganosiloxane by decomposition of peroxide,
It uses crosslinking by insertion reaction of vinyl group-containing polyorganosiloxane into vinyl groups. This composition has the advantage of having excellent photosensitivity, being unaffected by oxygen, and having little change in photosensitivity over time, but has the disadvantage of yellowing. Furthermore, JP-A-55-125123 discloses a method of irradiating a vinyl group-containing polyorganosiloxane or a composition comprising a vinyl group-containing polyorganosiloxane and an organic peroxide with ultraviolet rays with a wavelength of 100 to 300 nm. has been described, but this method has the disadvantage that when only vinyl group-containing polyorganosiloxane is used, the surface is only cured and the deep layer is not cured, and the curing time is too long to be practical. there were. This publication also proposes the use of organic peroxides in combination; however, the peroxide-based, dialkyl-based, and ester-based organic peroxides exemplified here have uncured surfaces and cannot be affected by oxygen. It has the disadvantage that it is easily damaged and requires a long curing time that is impractical.

In order to improve these drawbacks, one of the inventors of the present invention has discovered that by using a peroxyester having a specific structure in vinyl group-containing polyorganosiloxane, the polyorganosiloxane can be cured effectively and uniformly from the inside to the surface. (Japanese Unexamined Patent Publication No. 57-109852)
Publication No.). However, this method has drawbacks such as the fact that it is often pointed out that the mechanical strength of the cured product is insufficient for applications such as potting and coating to cover and protect semiconductor joints and resin sealing of semiconductor parts. There was a thunderstorm.

[Object of the Invention] The object of the present invention is to eliminate such drawbacks and to provide a composition that cures uniformly and rapidly from the inside to the surface by ultraviolet irradiation, and that significantly improves the mechanical strength of the cured silicone rubber. It is to provide.

[Structure 1 of the Invention] As a result of various studies to achieve the above object, the present inventors found that by using an inorganic filler surface-treated with a vinyl group-containing silylating agent, workability A3 and curing of the composition can be improved. The present inventors have discovered that the B]'4 properties of the silicone rubber obtained by the above method are significantly improved, and have completed the present invention.

That is, the present invention provides (A>average compositional formula% formula% (wherein, R1 represents a substituted or unsubstituted monovalent hydrocarbon group excluding a vinyl group, a represents 0<a≦1, and b represents O <
b≦3, and (a+b) satisfies 1≦a+b≦3. ) 100 parts of polyorganosiloxane represented by (B) 1 to 50 parts by weight of an inorganic filler surface-treated with a vinyl group-containing silylating agent, (C) general formula % (wherein R2 is substituted or unsubstituted) 1 of substitution (liT
i is an aliphatic hydrocarbon group, R3 is substituted or unsubstituted 1
0.1 to 5.0m of the peroxyester represented by V) represents the hydrocarbon group of f+Ifi, and (D> general formula (wherein, R4 is a hydrogen atom, a halogen atom, a substituted or unsubstituted monovalent hydrocarbon group and/or carbon number 1
~10 alkoxy group, R5 is 11I having 1 to 10 carbon atoms
The present invention relates to an ultraviolet curable silicone composition comprising 0.1 to 5.0 parts by weight of a phenolic photoinitiator represented by (representing a hydrocarbon group of Ti).

The polyorganosilokinane (A) used in the present invention is represented by the above average compositional formula, in which R1 represents a substituted or unsubstituted monovalent hydrocarbon group other than a vinyl group; Methyl group, ethyl group, propyl group, butyl group, isobutyl group, amyl group, hexyl group, octyl group,
Alkyl groups such as decyl groups; alkenyl groups such as allyl groups and cyclohexenyl groups; cycloalkyl groups such as cyclopentyl groups and cyclohexyl groups; aryl groups such as phenyl groups and naphthyl groups; alkaryl groups such as nitrile groups, xylyl groups, and mesityl groups. Group; β-phenylethyl group.

Aralkyl group such as β-phenylpropyl group; or
Examples include groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms, etc., such as 3.3.3-trifluoropropyl group, chloromethyl group, chlorophenyl group, and cyanoethyl group. From the viewpoints of ease of preparation, strength and heat resistance of the cured film formed, it is preferable that all the groups are methyl groups or methyl groups and phenyl groups. When it is composed of a methyl group and a phenyl group, it is preferable that the phenyl group accounts for 10% or less, and the remainder is a methyl group.

If the phenyl group exceeds 10%, the silicone formed will turn yellow and will also be economically disadvantageous.

The vinyl group of the polyorganosiloxane is involved in the crosslinking reaction of the composition, and also contributes to the adhesion of the cured product to various substrates.

As the amount a of vinyl groups increases, the curing time will be shortened. It is preferably 50% or less of a and b), particularly preferably 10% or less.

Considering the efficient curing time and workability, the viscosity of this polyorganosiloxane at 25°C is 50°C.
It is preferably in the range of ~200.0OOcSt,
It is desirable that it be in the range of roughly 500~ioo, 000C3t. The molecular structure is not particularly limited, and may be linear, branched, or cyclic.

Further, these polyorganosiloxanes may be used alone or in a mixture of two or more without any problem in terms of viscosity and structure.

The surface of the inorganic filler (B) used in the present invention is treated with a vinyl group-containing silylating agent, and the workability of the composition of the present invention and the mechanical properties of the cured silicone rubber are improved. It is intended to improve the Examples of the vinyl group-containing silylating agent include silazane, alkylaminosilane, and alkoxysilane, and it is recommended to use them alone or in combination of two or more. Examples of silazane include 1,1,3.3-tetramethyl-1,3-divinyldisilazane, 2.4.6-dolimethyl-2.4.6-dolivinylcyclosilazane, and alkylaminosilanes include Examples include dimethylvinyl(butylamino)silane, dimethylvinyl(propylamine)silane, and dimethylvinyl(butylamino)silane. Examples of the alkoxysilanes include triorganoalkoxysilanes such as dimethylvinylmethoxysilane, dimethylvinylethoxysilane, and dimethylvinylpropoxysilane, methylvinyldimethoxysilane, vinyl 1-herimethoxysilane, and vinyltriethoxysilane. When treating inorganic fillers with these silylating agents, they may be used alone or
Alternatively, two or more types may be used in combination, or a partially hydrolyzed II/zeta condensate may be used. However, as the vinyl group-containing silylating agent used in the present invention, triorganoalkoxysilanes such as 1.1,3.3-tetramethyl-1,3-divinyldisilazane and dimethylvinylalkoxysilane are used. Best used for mechanical strength purposes,
It was also the most suitable in terms of ease of handling when processing fillers.

The inorganic fillers treated with vinyl group-containing silylating agents may be silica-based fillers known to those skilled in the art, such as fumed silica, precipitated silica, silica aerogel, pyrogenic silica, ground quartz, diatomaceous earth. , glass fine powder, etc., and its specific surface area is 50 to 400T112/
(Things in the range of J are preferable, and moreover 100 to 350 T.
II2/g is desirable.

If the specific surface area is lower than 50Tr12/q, not only will the mechanical strength of the silicone rubber be insufficient, but also the transmission of ultraviolet rays will be hindered, resulting in poor deep curability. If the specific surface area is larger than 400i2/g, it may be used, but it is difficult to obtain industrially and is disadvantageous in terms of cost.

The method for treating the inorganic filler is to adjust the amount of the silylating agent to 30 parts by weight or less per 100 parts by weight of the filler, and (1) mix the silylating agent directly into the filler for treatment.
(2) Dissolving or dispersing the silylating agent in molten ts (organic solvent, water, etc.) and mixing it with the filler for treatment; (3)
) treating the filler with vapors of a silylating agent; or (4)
Generally, examples include a method in which a filler is sufficiently dispersed in a polyorganosiloxane and a silylating agent is added thereto for treatment, but the method is not particularly limited.

The amount of the inorganic filler treated with the vinyl group-containing silylating agent is 1 to 50 parts by weight, more preferably 5 to 2 parts by weight, per 100 parts by weight of (A). If the amount is less than 1 part by weight, the mechanical strength will be insufficient. If the amount exceeds 50 parts by weight, the viscosity of the composition becomes too high, resulting in poor workability and poor deep curability with ultraviolet rays, which is not preferable.

The peroxyester (C) used in the present invention decomposes and generates radicals when irradiated with ultraviolet rays, thereby curing the polyorganosiloxane.

In the formula, R2 is a substituted or unsubstituted monovalent aliphatic hydrocarbon group to avoid imparting compatibility with the above-mentioned polyorganosiloxane, and preferably has a total carbon number of 12 or less. In addition, although there are no particular structural limitations,
From the viewpoint of compatibility, t-butyl group is preferred.

Furthermore, R3 in the formula is not particularly limited as long as it is a substituted or unsubstituted monovalent aromatic hydrocarbon group.

The peroxynisdel of the present invention is compatible with the above-mentioned polyorganosiloxanes and has no coloration, and includes t-butylperoxybenzoate, t-butylperoxy-4-chlorobenzoate, t-butylperoxy-2, t-butylperoxy-2, Examples include 4-dichlorobenzoate and t-butylperoxy-4-toluoate. Among these peroxyesters, t-butyl peroxybenzoate is particularly preferred because it has excellent compatibility, does not require a solvent, and is easy to synthesize.

The amount of peroxyester blended is 0.1 to 5.0 parts by weight with respect to 100ii parts of polyorganosiloxane,
0.1 to 2.0 parts by weight is preferred. If the amount is less than 0.1 part by weight, the curing speed will be slow and a sufficient crosslinking effect will not be obtained. Further, even if it is added in an amount exceeding 5.0 parts by weight, the expected effect cannot be obtained.

The phenone photoinitiator (D) used in the present invention is represented by the above-mentioned general formula. This is necessary because it absorbs ultraviolet rays and generates radicals, but at the same time it has the effect of promoting the decomposition of component (C) and the generation of radicals, and in the composition of the present invention, it has a so-called photosensitizing effect. It is something that you have. That is, in a composition containing a large amount of an inorganic filler for improving strength, the irradiated light is blocked by the filler and difficult to reach deep parts, resulting in insufficient curing. In order to reduce such adverse effects, the (D>component is used.

In the formula, R4 represents a hydrogen atom, a halogen atom, a substituted or unsubstituted monovalent hydrocarbon group, and/or an alkoxy group having 1 to 10 carbon atoms. Therefore, R4 should be selected appropriately when compatibility is concerned.
Its structure is not particularly limited. In the formula, R5 is
It represents a hydrocarbon group having 1 to 10 carbon atoms, and is not particularly restricted structurally for the same reason as R4 above.

Such phenolic photoinitiators include acetophenone, 3 or 4-me]hexyacetophenone, 3 or 4-chloroacetophenone, 3 or 4-bromoacetophenone, 3 or 4-methylacetophenone, 3 or 4-isopropylacetophenone. , propiophenone, benzophenone, 3- or 4-methoxybenzophenone, 4-fluorobenzophenone, 4,4'-dimethoxybenzophenone, etc., and these may be used alone or in combination of two or more. . The back of these (A
Acetophenone is the most preferred because it has good compatibility with the above compounds and requires no solvent during dissolution. The amount of component (D) added is 0.1 to 5.0 parts per 100,000 parts of component (Δ).
0 parts by weight, more preferably 0.2 to 2.0 parts by weight. If the amount added is less than 0.1 part by weight, rapid aggregation cannot be obtained, and if it is added in excess of 5.0 parts by weight, not only will the expected effect not be obtained, but it may remain in the system. This is not practical because it causes a decrease in heat resistance and mechanical strength.

[Effects of the Invention] The ultraviolet curable silicone composition of the present invention having the composition described above is quick-curable when irradiated with ultraviolet rays from a high-pressure mercury lamp, etc., and is cured uniformly from the inside to the surface. This significantly improves the mechanical strength of objects. Therefore, it is suitable for use as a coating/protection material or a sealing material for semiconductors, which requires rationalization of manufacturing and high reliability.

[Examples of the Invention] The present invention will be explained in more detail with reference to Examples and Comparative Examples below. Note that all parts in Examples and Comparative Examples represent parts by weight.

Examples 1 to 7 As a base oil for an ultraviolet curable silicone composition,
Polyorganosiloxanes F-1 to F-4 shown in Table 1 were obtained by polymerization. All of these base oils are end-capped with trimethylsilyl groups. As an inorganic filler, fumed silica TP-1 with a specific surface area of 200iT12/g whose surface was treated with a silylation agent shown in Table 2
~TP-5 was obtained. Among these, TP-4 and TP
-5 does not contain a vinyl group and was used in a comparative example described later.

Using the raw materials obtained above, the compositions shown in Table 3 were uniformly dispersed using a universal kneader to prepare samples.

This sample was poured into a stainless steel container coated with polytetrafluoroethylene to a depth of 31 mm, and after degassing, a 160 W/CIII high pressure mercury lamp for ultraviolet irradiation was used.
When UV-7000 (manufactured by Ushio Inc.) was irradiated for 70 seconds from a distance of 2.0 cm, all were cured well. The properties of the rubber-like cured product were measured and were as shown in Table 3.

Comparative Examples 1 to 3 Samples having the compositions shown in Table 3 were prepared using F-2 as the base oil and P-4 and TP-5 shown in Table 2 as the silyl-treated silica. Apart from this, Example 2
A sample with a composition excluding acetophenone was prepared. These samples were cured in exactly the same manner as in Example 1, and their properties were measured. The results are shown in Table 3.

As can be seen, the properties of hardness and tensile strength are inferior when using fillers treated with silylating agents that do not contain vinyl groups. Furthermore, it has been found that in compositions that do not use acetophenone, even when silica treated with a vinyl group-containing silylating agent is used, the properties are significantly deteriorated.

(Leaving space below) Table 1 Table 2 Table 3 Example 8 100 parts of F-2 as a base oil and 10 parts of untreated fumed silica with a specific surface area of 200TT12/g were added in a universal mixer. 1゜1 for Shun, who has been sufficiently dispersed in advance.
．． 3. 1.5 parts of 3-tetramethyl-1,3-divinyldisilazane are added to treat the dispersed untreated silica. Thereafter, unreacted substances and reaction by-products are removed by heating and kneading. Cool it, add 2.0 parts of 1-butylperoxybenzoate and 2.0 parts of acetate to phenone.
A sample was prepared by adding 100% of the total amount of the sample and dispersing it uniformly. This was cured with ultraviolet light in the same manner as in Example 1, and its properties were investigated. The hardness was 35, the tensile strength was 19k (lf/c), and the elongation was 130%. However, the transparency of the cured product was better in the method of Example 8.

Example 9 A polyorgano having a viscosity of 2000 cSt at 25°C, consisting of 4 mol% of diphenylsiloxane units, 5 mol% of methylvinylsiloxane units, and the remainder dimethylsiloxane units, with both ends of the molecular chain capped with dimethylvinylsilyl groups. To 100 parts of siloxane, 10 parts of rp-i, 2 parts of t-butyl peroxybenzoate, and 1 part of acetophenone were uniformly dispersed using a universal kneader. Place this sample on a glass plate with a thickness of 100 to 200 μm.
When the film was coated to a thickness of 1.5 m and irradiated for 1 second from a distance of 10 cm using an 80 W/cm A-synthesis-generating high-pressure mercury lamp, a transparent elastomer-like film was formed, and no tackiness was observed on the surface. There wasn't.

Examples 10-11 In Example 8, d5 was added, and peroxybenjee-1 was added to 1.
Each was adjusted in the same manner as in Example 8 except that 0<r3 and 3.0 parts. Using this, as in Example 1, ultraviolet! When IQ-cured and examined its properties, it was found to be equivalent to Example 8 in all properties.

Example 12 The same experiment as in Example 9 was carried out except that 4-isopropylacetophenone and 4,4'-1-xybenzophenone were used instead of 70 tophenone, and a good elastomeric coating was obtained. Ta.

Claims (11)

[Claims] (1) (A) Average composition formula (CH_2=CH)_a(R^1)_bSiO_[_4
____(_a_+_b_)]_/_2 (wherein, R
^1 indicates a substituted or unsubstituted monovalent hydrocarbon group excluding a vinyl group, a is 0<a≦1, b is 0<b≦3, (a+
b) is 1≦a+b≦3. ) 100 parts by weight of polyorganosiloxane represented by (B) 1 to 50 parts by weight of an inorganic filler surface-treated with a vinyl group-containing silylating agent, (C) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, In the formula, R^2 represents a substituted or unsubstituted monovalent aliphatic hydrocarbon group, and R^3 represents a substituted or unsubstituted monovalent hydrocarbon group. 0 parts by weight and (D) General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, R^4 is a hydrogen atom, a halogen atom, a substituted or unsubstituted monovalent hydrocarbon group, and/or carbon Alkoxy group having 1 to 10 carbon atoms, R^5 is 1 having 1 to 10 carbon atoms
An ultraviolet curable silicone composition comprising: 0.1 to 5.0 parts by weight of a phenolic photoinitiator represented by the formula (representing a valent hydrocarbon group). (2) The ultraviolet curable silicone composition according to claim 1, wherein the polyorganosiloxane (A) has a viscosity of 500 to 100,000 cSt at 25°C. (3) The ultraviolet curable silicone composition according to claim 1, wherein R^1 is a methyl group or a phenyl group. (4) The ultraviolet curable silicone composition according to claim 1, wherein all R^1's are methyl groups. (5) The ultraviolet curable silicone composition according to claim 1, wherein a is 10% or less of a+b. (6) The vinyl group-containing silylating agent of (B) is 1, 1, 3,
The ultraviolet curable silicone composition according to claim 1, which is 3-tetramethyl-1,3-divinyldisilazane. (7) The ultraviolet curable silicone composition according to claim 1, wherein the vinyl group-containing silylating agent (B) is a dimethylvinyl alkoxysilane. (8) The ultraviolet curable silicone composition according to claim 1, wherein the inorganic filler (B) is a fine silica powder. (9) The specific surface area of the inorganic filler (B) is 100 to 35
The ultraviolet curable silicone composition according to claim 1, which has a radiation density of 0 m^2/g. (10) The ultraviolet curable silicone composition according to claim 1, wherein the peroxyester (C) is t-butyl peroxybenzoate. (11) The ultraviolet curable silicone composition according to claim 1, wherein the phenone photosensitizer (D) is acetophenone.