JPS6156257B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a curable organopolysiloxane composition, and particularly to a curable organopolysiloxane composition that provides a rubber elastic film with no surface tack upon short-term irradiation with ultraviolet rays, radiation, or electron beams. For a silicone composition that can form a rubber elastic film, a hydrolyzable polyfunctional silane or siloxane and a catalyst such as a heavy metal carboxylate are added to an organopolysiloxane whose ends are capped with hydroxyl groups, and these are condensed. something that reacts,
It is generally said that vinyl methyl polysiloxane and organohydrodiene siloxane are subjected to an addition reaction in the presence of a platinum-based catalyst, but products based on this condensation reaction take a long time to cure and shrink due to volatilization of the condensate during curing. Addition reaction products have poor curing properties at low temperatures below 60°C, and fast-curing products have a short pot life of less than a few minutes after mixing with these siloxanes. I was at a disadvantage. Therefore, a composition consisting of a mercapto group-containing organopolysiloxane and a vinyl group-containing organopolysiloxane, which can be cured at room temperature by ultraviolet irradiation and has excellent curing properties, has also been proposed (Japanese Patent Publication No.
(see Publication No. 6512, Special Publication No. 57-34318),
This composition has the disadvantage that the cured product obtained from it has limited surface tackiness and rubber strength, does not have desirable physical properties as a rubber elastic body, and therefore does not provide an excellent rubber elastic film. A method in which a composition consisting of a functional vinyl group-containing organopolysiloxane and an organic peroxide is cured by ultraviolet irradiation (Japanese Patent Application Laid-Open No. 125123-1983)
(see Japanese Patent Application Publication No. 2003-100002) has the disadvantage of slow curing speed. The present invention relates to a curable organopolysiloxane composition which solves these disadvantages, and which is composed of formula (A). (R ¹ , R ² , R ³ are monovalent hydrocarbon groups that do not contain the same or different unsaturated bonds, a is 2 or 3,
100 parts by weight of an organopolysiloxane whose molecular chain terminals are blocked with multi-vinyl groups (n is a positive number);
(B) General formula (Here, R ⁴ is an alkylene group, R ⁵ is a monovalent organic group,
b consists of 0.1 to 50 parts by weight of a mercaptoalkyl group-containing organopolysiloxane having at least two siloxane units represented by 0, 1 or 2) in the molecule, and (C) 0 to 10 parts by weight of a sensitizer. It is characterized by: To explain this, the present inventors have conducted various studies on the modification of ultraviolet, radiation, and electron beam-curable organopolysiloxanes. As the vinyl group-containing organopolysiloxane, an organopolysiloxane terminal-capped with a multi-vinyl group represented by the above formula is particularly selected, and as the mercapto group-containing organopolysiloxane, a siloxane group represented by the above formula is selected. If a mercaptoalkyl group-containing organopolysiloxane having at least two mercaptoalkyl groups is selected, this composition can be easily and quickly hardened to a deep layer by UV irradiation for 1 second or less or electron beam irradiation for several Mrad or less, resulting in surface tackiness. In addition to discovering that the rubber elastic body obtained in this way can have an elongation rate of as much as 500%, and that the volume increase/decrease upon curing is extremely The present invention was completed after confirming that the material has excellent weather resistance and durability, and that its physical properties do not deteriorate due to aging even when exposed outdoors. The vinyl group-containing organopolysiloxane as component (A) constituting the organopolysiloxane composition of the present invention has the formula R ¹ , R ² , and R ³ are alkyl groups such as methyl, ethyl, and propyl;
Examples include aryl groups such as phenyl groups, aralkyl groups such as benzyl groups, and alkaryl groups such as xylene groups, preferably having 1 to 19 carbon atoms.
They are considered to be the same or different monovalent hydrocarbon groups that do not contain unsaturated bonds, but the a value is 2 or 3 because the molecular chain terminals are required to be blocked with a multi-vinyl group. And this n value is determined by the viscosity of this organopolysiloxane at 25℃.
The value may be set to 300,000 to 100,000 cS, preferably in the range of 500 to 20,000 cS for convenience in solvent-free coating. In addition, the mercaptoalkyl group-containing organopolysiloxane as component (B) constituting this organopolysiloxane composition has the general formula

It contains a siloxane unit represented by [Formula] in its molecule, where R ⁴ is an alkylene group such as a methylene group, ethylene group, propylene group, butylene group, etc., and R ⁵ is a methyl group, ethyl group, propyl group, etc. Alkyl groups, aryl groups such as phenyl groups, alkenyl groups such as vinyl groups and allyl groups, aralkyl groups such as benzyl groups, alkaryl groups such as xylene groups, and monovalent monovalent groups such as triorganosiloxy groups. Organic group, b value
It is considered to be 0.1 or 2. The siloxane unit of this general formula is

[Formula] HS C ₃ H ₆ SiO _{1.5 ,}

【formula】

[Formula] is exemplified. Since this (B) component is to be reacted with the multi-vinyl group-blocked organopolysiloxane as the (A) component, it must have at least two of the above-mentioned siloxane groups in its molecule. , the viscosity is about 5 to 500 cS (25°C). The organopolysiloxane composition of the present invention can be obtained by uniformly mixing the vinyl group-containing organopolysiloxane as the component (A) and the mercaptoalkyl group-containing organopolysiloxane as the component (B). However, if the blending ratio of component (B) is less than 0.1 part by weight to 100 parts by weight of component (A), it will not be possible to obtain a cured film with the desired elasticity; As a result, the physical properties of the rubber deteriorate significantly due to aging, and the initial rubber elasticity is no longer obtained, and only the hardness increases.
The disadvantage is that the physical properties of the rubber are extremely poor, so
The amount of component (B) needs to be in the range of 0.1 to 50 parts by weight per 100 parts by weight of component (A). However, if the curing of this composition is slow within this blending range, (C)
A known sensitizer may be added as a component, and examples of the sensitizer include acetophenone, propionphenone, benzophenone, xantone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole,
- Methylacetophenone, 4-chlorobenzophenone, 4-ethylbenzophenone, 4-hydroxybenzophenone, benzoin, benzoin ethyl ether, Michler's ketone, etc. are exemplified, and the amount added depends on the type and required amount. The amount may be determined as appropriate depending on the curing rate, etc., but it may be approximately 10 parts by weight or less per 100 parts by weight of component (A).
The organopolysiloxane composition may also contain an antioxidant such as hydroquinone, which acts as a pot life extender, if necessary.
It may be added in a range of 1000 ppm, and may be used for diorganopolysiloxane, various colorants, fillers, fine powder silica as a thixotropic agent, titanium oxide, carbon black, lithopone, fine powder metal powder, etc. Plasticizers, extenders, stabilizers, adhesion promoters, adhesives, etc. may be added. This organopolysiloxane composition is usually used without a solvent, but in some cases it may be added with a solvent. Examples of the solvent include aliphatic hydrocarbons such as hexane and heptane, Examples include aromatic hydrocarbons such as benzene, toluene, and xylene, chlorinated hydrocarbons such as methylene chloride and trichloroethylene, esters such as ethyl acetate and butyl acetate, and ketones such as methyl ethyl ketone and acetone. The organopolysiloxane composition of the present invention can be easily and quickly cured by light (ultraviolet) or electron beam irradiation, such as ultraviolet irradiation for 1.0 seconds or less or electron beam irradiation for 5 Mrad or less, to form a cured film with rubber elasticity. The light sources used include xenon lamps rich in ultraviolet wavelengths, low-pressure, medium-pressure, and high-pressure mercury lamps, and the electron beam sources include Van de Graaff type, resonant transformer type, wired type, Dynamicron type, and high-frequency type. 50 ~ emitted from an electron beam accelerator
It is preferable to use an electron beam with an energy of 1000 KeV, preferably in the range of 100 to 300 KeV. More specifically, regarding ultraviolet rays, the output per unit length is
The main wavelength is 365nm at 80 to 160W/cm.
An irradiation time that has a wavelength range of 230 to 450 nm may be used, and the irradiation time is generally several seconds or less, but a short time is preferable to avoid being affected by heat, so the irradiation time is 1.0 seconds or less. is preferred. For electron beams, it is sufficient to irradiate a spot beam at high speed or to irradiate a continuous curtain-like beam from a linear filament, and for ultraviolet rays, the irradiation time should be within 1 second per lamp with an electrical input of 160 W/cm. Bye. Note that the electron beam irradiation dose may be in the range of 0.1 to 10 Mrad. Since the organopolysiloxane composition of the present invention has the above-mentioned properties, it can be widely used in various fields, and it can be used in conventionally known room-temperature curable silicone rubber applications, such as electrically insulating potting materials, printed circuit boards, etc. In addition to being useful as a coating material for industrial applications, a coating material for glass sleeves, a sealing material for construction, etc., it can also be used as a coating material for plastic substrates, an impregnating agent for electrical insulation, a water repellent, and even as a release agent. In either case, it has the advantage of providing a cured film with rubber elasticity and excellent mechanical properties, heat resistance, weather resistance, water resistance, etc. on the surface to be treated. Next, examples of the present invention will be given, in which parts are parts by weight and viscosity is a value measured at 25°C. Example 1 95 parts of dimethylpolysiloxane with a viscosity of 10,000 cS, which was capped with trivinylsilyl groups at both ends,
Mercaptopropyl group-containing methylpolysiloxane 5 with a viscosity of 25 cS, containing 10 siloxane groups represented by (HSCH ₂ CH ₂ CH ₂ ) (CH ₃ )SiO in the molecule, and capped at both ends with trimethylsilyl groups.
15 parts of finely powdered silica, 2 parts of 4-ethylbenzophenone and 500 ppm of hydroquinone,
These were passed twice through a triple roll to form an organosiloxane composition. Next, this composition was formed into a sheet with a thickness of 2 mm, and this was irradiated with ultraviolet rays from a high-pressure mercury lamp (160 W/cm) from a distance of 80 mm for 1.0 seconds.
After curing, it became an elastic sheet with the physical properties shown in Table 1. In addition, when a 2 mm thick sheet made from the composition obtained without adding 4-ethylbenzophenone in the above was irradiated with a 2 Mrad electron beam from a low energy electron accelerator (manufactured by Energy Science), This sheet also had excellent elasticity and exhibited the physical properties shown in Table 1. For comparison, in place of the dimethylpolysiloxane in the above, 99.5 mol% of dimethylsiloxane units with both ends capped with vinyldimethylsilyl groups and 0.5 mol% of vinyldimethylsiloxane units were used.
dimethylpolysiloxane with a viscosity of 10,000 cS (Comparative Example 1), 99.5 mol% of dimethylsiloxane units with both ends capped with vinyldimethylsilyl groups,
Methylvinylpolysiloxane (Comparative Example 2) containing 0.5 mol% of vinylmethylsiloxane units and a viscosity of 10000cS, and dimethylsiloxane units with both ends capped with vinyldimethylsilyl groups having a viscosity of 95.0cS.
An organopolysiloxane composition was prepared in the same manner as above using methylvinylpolysiloxane (Comparative Example 3) with a vinyl methylsiloxane unit content of 5.0 mol % and a viscosity of 10000 cS, and this was made into a 2 mm thick methylvinyl polysiloxane composition.
When this sheet was irradiated with ultraviolet rays and electron beams in the same manner as above, the physical properties of the obtained cured product were as listed in Table 1.

[Table] Example 2 A viscosity of 5000 cS consisting of 97 mol% dimethylsiloxane units and 3 mol% diphenylsiloxane units with both ends capped with divinylmethylsilyl groups.
95 parts of methylphenylvinylsiloxane oil containing a mercaptoalkyl group with a viscosity of 50 cS, with both ends capped with trimethylsilyl groups, consisting of 50 mol% of mercaptopropyl(methyl)siloxane units and 50 mol% of dimethylsiloxane units. 8 parts organopolysiloxane, 15 parts finely powdered silica
50 ppm of hydroquinone and 2 parts of benzoin ethyl ether as a sensitizer were added to prepare an organosiloxane composition, which was formed into a 2 mm thick sheet and then irradiated with ultraviolet rays in the same manner as in Example 1. However, a rubber elastic body with physical properties as shown in Table 2 was obtained. In addition, a sheet made from a composition obtained in the same manner as above except that no sensitizer was added,
When electron beam irradiation was performed in the same manner as in Example 1, a rubber elastic body was obtained in this case as well, and exhibited physical properties as shown in Table 2.

[Table] Example 3 To 95 parts of dimethylpolysiloxane with a viscosity of 3000 cS, both ends of which are capped with trivinylsilyl groups,

It has five siloxane groups represented by the formula in its molecule. An organopolysiloxane composition was prepared by uniformly mixing 5 parts of mercaptopropyl group-containing methylpolysiloxane with a viscosity of 15 cS, both ends of which are capped with trimethylsilyl groups, 500 ppm of hydroquinone, and 2 parts of 4-methoxybenzophenone as a sensitizer. A silicone rubber composition (Sample 3) was prepared by adding 12 parts of finely powdered silica to 100 parts of this composition and passing it through a triple roll twice to prepare a silicone rubber composition (Sample 4). Next, these samples 3 and 4 were filled in a metal tube with air excluded and stored at room temperature for one month, but neither of them increased in viscosity and did not gel. When the material was taken out of the tube, exposed to air, and irradiated with ultraviolet rays for 1.0 seconds in the same manner as in Example 1, it became a rubber elastic material with no surface tack. Even when irradiated, a rubber elastic body with no surface tack was formed, and when the physical properties of this rubber elastic body were measured, the results were shown in Table 3.

[Table] Example 4 100 parts of a methylphenylpolysiloxane oil having a viscosity of 3000 cS, which is capped at both ends with trivinylsilyl groups and consists of 97 mol% of dimethylsiloxane units and 3 mol% of diphenylsiloxane units, was mixed with the formula

10 parts of mercaptopropyl group-containing methylpolysiloxane having 10 siloxane units represented by the formula in the molecule, a methoxy group content of 24% by weight, and a viscosity of 17cS, hydroquinone
500 ppm and 2 parts of benzoin ethyl ether as a sensitizer were added and mixed uniformly to form an organosiloxane composition. Next, this composition was uniformly applied to a polyethylene laminate paper so that the film thickness was 0.8 μm, and the coated surface was irradiated with ultraviolet rays for 1.0 seconds in the same manner as in Example 1. The cured film had rubber elasticity, and when we examined the peeling performance of this cured film, it showed excellent peelability, and the alkoxy groups it contained also had good adhesion to polyethylene laminate paper, and the film surface was friction-resistant. However, it did not fall off. In addition, when the composition without adding a sensitizer was applied to polyethylene laminate paper in the same manner as above and irradiated with electron beam in the same manner as in Example 1, the applied surface also showed no surface tack. The resulting cured film had no rubbery elasticity and exhibited physical properties similar to those described above.

Claims (1)

[Claims] 1 Formula (A) (Here, R ¹ , R ² , and R ³ are monovalent hydrocarbon groups that do not contain the same or different unsaturated bonds, a is 2 or 3, and n is a positive number.) The terminal of the molecular chain is a polyvinyl group. organopolysiloxane capped with
100 parts by weight (B) General formula (here, R ⁴ is an alkylene group, R ⁵ is a monovalent organic group, and b is 0, 1 or 2) A mercaptoalkyl group-containing organopolysiloxane having at least two siloxane units in the molecule
A curable organopolysiloxane composition comprising 0.1 to 50 parts by weight (C) of a sensitizer and 0 to 10 parts by weight.