JP2015057763A - Electroconductive liquid silicone rubber composition, and normal-temperature shrinkable rubber member for high-voltage cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroconductive liquid silicone rubber composition which has low viscosity and is such an addition cure type that a cured product excellent in productivity, workability, electric characteristics and rubber strength is obtained, and to provide a normal-temperature shrinkable rubber member for high-voltage cables, which member comprises a cured/molded product of the electroconductive liquid silicone rubber composition.SOLUTION: The electroconductive liquid silicone rubber composition is a composition for the normal-temperature shrinkable rubber member for high-voltage cables, which member is attached to a juncture or terminal of the high-voltage cable to hold the juncture or terminal. The electroconductive liquid silicone rubber composition contains: (A) an organopolysiloxane having two or more silicon atom-bonded alkenyl groups in one molecule thereof; (B) an organohydrogenpolysiloxane having three or more silicon atom-bonded hydrogen atoms in one molecule thereof; (C) fumed silica having 50-400 m/g BED method specific surface area; (D) furnace black having 0.1 mass% or lower sulfur content; and (E) an addition reaction catalyst, and has 200-2,000 Pa-s viscosity at a shear rate of 0.9 sat 23°C.

Description

  TECHNICAL FIELD The present invention relates to a conductive liquid silicone rubber composition that provides a silicone rubber molded product for a cold-shrinkable rubber member used for a high voltage cable, and in particular, a silicone rubber molded product having excellent conductivity and workability (low viscosity). The present invention relates to a conductive liquid silicone rubber composition that provides (cold-shrinkable rubber member) and a cold-shrinkable rubber member for a high-voltage cable comprising a cured molded product thereof.

  Usually, the connection part of the high voltage cable of 6,600V or more and the terminal part of the high voltage cable are usually in a cylindrical shape (or bamboo ring shape) with an opening at one or both ends. Is used.

  At this time, when the silicone rubber molded product having a substantially cylindrical shape is inserted into a high-voltage cable at room temperature (20 ° C. ± 15 ° C.), the rubber molded product is expanded in diameter with an expanded diameter holding member and the cable is inserted. After removing the expanded diameter holding member, it can be substantially shrunk to the original dimensions before the expanded diameter, that is, it has excellent permanent elongation resistance. As a method of mounting a normal temperature shrinkable rubber member, a method in which a silicone rubber molded product is expanded in diameter with a diameter expansion holding member in advance, a cable is inserted, the diameter expansion holding member is removed, and a method of mounting is put into practical use. ing.

The silicone rubber molded product as a normal temperature shrinkable rubber member is usually composed of two layers, the inner layer is made of conductive silicone rubber for the purpose of dielectric relaxation, and the outer layer is made of insulating silicone rubber having tracking resistance. Yes. However, in the production of the conductive silicone rubber, when the conductive liquid addition curable silicone rubber composition is cured and molded, a composition containing a large amount of a conductive filler such as carbon black in order to ensure conductivity is Usually, since the viscosity becomes very high, it takes a lot of time for the injection process at the time of molding, and thus there are problems in terms of productivity and workability.
In addition, the following literature is mentioned as a prior art relevant to this invention.

JP 2002-315171 A JP 2006-320197 A

  The present invention has been made in view of the above circumstances, and in a conductive liquid silicone rubber composition used for a normal temperature shrinkable rubber member for a high voltage cable, because of its low viscosity, it is excellent in productivity and workability, and further has electrical characteristics, An object of the present invention is to provide an addition-curable conductive liquid silicone rubber composition that gives a conductive silicone rubber molded article having excellent rubber strength, and a cold-shrinkable rubber member for a high-voltage cable comprising the cured molded article of the composition. .

  As a result of intensive studies to achieve the above object, the present inventors have found that an appropriate amount of a specific furnace black is used as a conductive filler in a conductive liquid silicone rubber composition used for a normal temperature shrinkable rubber member for a high voltage cable. By adding in this range, it was found that an addition-curing type conductive liquid silicone rubber composition giving a silicone rubber molded article having low viscosity and excellent conductivity was obtained, and the present invention was made.

Accordingly, the present invention provides a conductive liquid silicone rubber composition used for the following cold-shrinkable rubber member for high-voltage cables, and a cold-shrinkable rubber member for high-voltage cables comprising a cured molded product of the composition. In the present invention, “cold shrinkage” means excellent shrinkage (permanent elongation resistance) after elongation or diameter expansion at room temperature (25 ° C. ± 15 ° C.).
[1]
A conductive liquid silicone rubber composition for a normal temperature shrinkable rubber member for a high voltage cable, which is attached to a connecting portion of the high voltage cable or a terminal portion thereof and holds the connecting portion of the high voltage cable or the terminal portion thereof,
(A) Organopolysiloxane containing an average of at least two alkenyl groups bonded to silicon atoms in one molecule: 100 parts by mass
(B) Organohydrogenpolysiloxane containing at least three hydrogen atoms bonded to silicon atoms in one molecule: 0.5 to 20 parts by mass,
(C) Fumed silica having a specific surface area of 50 to 400 m ² / g by BET method: 10 to 40 parts by mass,
(D) Furnace black having a sulfur content of 0.1% by mass or less as a conductive filler: 1 to 25 parts by mass,
(E) Addition reaction catalyst: A conductive liquid silicone rubber composition comprising a catalyst amount and having a viscosity at 23 ° C. at a shear rate of 0.9 s ⁻¹ of 200 to 2,000 Pa · s.
[2]
Component (A) is an organopolysiloxane having the following average composition formula (1)
R ¹ _a SiO _{(4-a) / 2} (1)
(Wherein R ¹ is the same or different, unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and a is a positive number in the range of 1.5 to 2.8.)
[1] The conductive silicone rubber composition according to [1].
[3]
Furthermore, (F) the following average composition formula (2)
R ² _b SiO _{(4-b) / 2} (2)
(In the formula, R ² is the same or different, unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and b is a positive number in the range of 1.5 to 2.8.)
Or an organopolysiloxane containing an average of one alkenyl group bonded to a silicon atom in one molecule at a ratio of 20/80 to 80/20 with respect to the mass of the component (A) [1] or [2] The conductive silicone rubber composition according to [2].
[4]
A cold shrink rubber member for a high voltage cable that is attached to a connecting portion of the high voltage cable or a terminal portion thereof and holds the connecting portion of the high voltage cable or the terminal portion thereof, [1], [2] or [3 ] The normal temperature shrinkable rubber member for high voltage cables containing the hardened | cured material of the electroconductive liquid silicone rubber composition of description.
[5]
A cold shrink rubber member for a high voltage cable that is attached to a connecting portion of the high voltage cable or a terminal portion thereof and holds the connecting portion of the high voltage cable or the terminal portion thereof, [1], [2] or [3 A room-temperature-shrinkable rubber member for high-voltage cables having an inner layer of the cured molded product of the conductive liquid silicone rubber composition as described above and an insulating silicone rubber layer containing no conductive component on the outer peripheral surface of the inner layer as an outer layer.
[6]
The room temperature shrinkable rubber member for high-voltage cables according to [4] or [5], wherein the volume resistivity of the cured molded product of the conductive liquid silicone rubber composition is 0.8 Ωm or less.

  Since the conductive liquid silicone rubber composition of the present invention has a low viscosity, the material injection time can be shortened and the molding process time can be greatly shortened. Therefore, the conductive liquid silicone rubber composition is excellent in productivity and workability. A silicone rubber molded product obtained by curing and molding is useful as a normal temperature shrinkable rubber member for a high voltage cable since it has excellent electrical characteristics and rubber strength.

The present invention will be described in detail below.
The conductive liquid silicone rubber composition used for the cold-shrinkable rubber member for high-voltage cables of the present invention is
(A) an organopolysiloxane containing an average of at least two alkenyl groups bonded to silicon atoms in one molecule;
(B) an organohydrogenpolysiloxane containing at least three hydrogen atoms bonded to silicon atoms in one molecule;
(C) fumed silica having a specific surface area of 50 to 400 m ² / g according to the BET method,
(D) Furnace black having a sulfur content of 0.1% by mass or less,
(E) An addition reaction catalyst is contained.

In this case, in addition to the above components, if necessary, as an optional component,
(F) An organopolysiloxane containing an average of one alkenyl group bonded to a silicon atom in one molecule can be blended.

The organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms in one molecule of the component (A) acts as a main agent (base polymer) of the composition of the present invention. In general, those represented by the following average composition formula (1) can be used.
R ¹ _a SiO _{(4-a) / 2} (1)
Wherein R ¹ is an unsubstituted or substituted monovalent hydrocarbon group having the same or different carbon number of 1 to 10, preferably 1 to 8, and a is 1.5 to 2.8, preferably 1 .8 to 2.5, more preferably a positive number in the range of 1.95 to 2.05.)

Here, as the unsubstituted or substituted monovalent hydrocarbon group bonded to the silicon atom represented by R ¹ , a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, Pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, alkyl group such as decyl group, aryl group such as phenyl group, tolyl group, xylyl group, naphthyl group, benzyl group, phenylethyl group, phenylpropyl Aralkyl groups such as groups, vinyl groups, allyl groups, propenyl groups, isopropenyl groups, butenyl groups, hexenyl groups, cyclohexenyl groups, octenyl groups and other alkenyl groups, and some or all of the hydrogen atoms of these groups are fluorine. Substituted with halogen atoms such as bromine, chlorine, cyano groups, etc., such as chloromethyl group, chloropro Group, bromoethyl group, trifluoropropyl group, but cyanoethyl group and the like, that more than 90 mole% of the total R ¹ is a methyl group, in particular, all of R ¹ other than the alkenyl group is a methyl group It is preferable.

Of R ¹ , at least 2 (usually 2 to 50), particularly about 2 to 20 are alkenyl groups (preferably those having 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, It is preferably a vinyl group. In addition, this alkenyl group can be 0.05-20 mol% with respect to all R < ¹ > groups, Preferably it is 0.1-10 mol%, More preferably, it can be about 0.1-5 mol%.

The alkenyl group content is preferably 5 × 10 ^{−6 to} 5 × 10 ⁻³ mol / g, particularly 1 × 10 ⁻⁵ to 1 × 10 ⁻³ mol / g in the organopolysiloxane. If the amount of the alkenyl group is less than 5 × 10 ⁻⁶ mol / g, the resulting cured product has low rubber hardness, and there is a risk that sufficient sealing performance may not be obtained, and more than 5 × 10 ⁻³ mol / g. If the amount is too large, the resulting cured product has too high a crosslinking density, which may result in brittle rubber.
This alkenyl group may be bonded to a silicon atom at the end of the molecular chain, may be bonded to a silicon atom in the middle of the molecular chain (non-terminal), or may be bonded to both.

The structure of this organopolysiloxane is usually composed of repeating main chain of diorganosiloxane units (R ¹ ₂ SiO _2/2 ) (R ¹ is the same as above), and both ends of the molecular chain are blocked with triorganosiloxy groups. Is basically a linear diorganopolysiloxane, but partially contains a small amount of branching units (R ¹ SiO _3/2 ) (R ¹ is the same as above) A branched chain structure or a cyclic structure may also be used.

In the present invention, in addition to the organopolysiloxane having an average of 2 or more alkenyl groups in one molecule of the component (A), as an optional component as required, (F) an average of 1 alkenyl groups in one molecule One organopolysiloxane can be used in combination. Examples of the organopolysiloxane of component (F) include those represented by the following average composition formula (2).
R ² _b SiO _{(4-b) / 2} (2)
Wherein R ² is an unsubstituted or substituted monovalent hydrocarbon group having the same or different carbon number of 1 to 10, preferably 1 to 8, and b is 1.5 to 2.8, preferably 1 .8 to 2.5, more preferably a positive number in the range of 1.95 to 2.05.)
In this case, R ² may be the same as R ¹ , but an average of one alkenyl group such as a vinyl group contained in one molecule. Although b is as above-mentioned, since a linear thing is preferable, b = 1.95-2.05 are especially preferable.

As such an organopolysiloxane having an average of one alkenyl group in one molecule of component (F), for example, one end of the molecular chain is blocked with a diorganoalkenylsiloxy group and the other end is a triorganosiloxy group. A linear organopolysiloxane whose main chain is a diorganosiloxane unit (the organo group in this case means an unsubstituted or substituted one-price hydrocarbon group other than an alkenyl group in the above R ² ), etc. Can be mentioned. Such an organopolysiloxane containing only one alkenyl group in one molecule is used in combination with the component (A) from the viewpoints of room temperature shrinkage and carbon drop resistance of the cured silicone rubber. desirable. The blending ratio (mass ratio) when the components (A) and (F) are used in combination is such that the component (A): component (F) is 80:20 to 20:80, particularly about 75:25 to 50:50. Preferably there is.

  In any of (A) component organopolysiloxane and (F) component organopolysiloxane, the molecular weight is preferably 1,500 or less, usually 100 to 1,500, more preferably, Preferably it is 150-1,000. If it is less than 100, sufficient rubber feeling may not be obtained, and if it is higher than 1,500, the viscosity becomes high and molding may be difficult. In the present invention, the degree of polymerization (or molecular weight) can be usually determined as the weight average degree of polymerization (or weight average molecular weight) in terms of polystyrene in gel permeation chromatography (GPC) analysis using toluene or the like as a developing solvent. .

Component (B) is an organohydrogenpolysiloxane having at least three hydrogen atoms (SiH groups) bonded to silicon atoms in one molecule. The SiH group in the molecule crosslinks with the alkenyl group bonded to the silicon atom in the component (A) by a hydrosilylation addition reaction, and acts as a curing agent (crosslinking agent) for curing the composition. This (B) component organohydrogenpolysiloxane has the following average composition formula (3)
R ³ _c H _d SiO _{(4-cd) / 2} (3)
Wherein R ³ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, which are the same or different from each other. C is 0.7 to 2.1, d Is a positive number satisfying 0.001 to 1.0 and c + d = 0.8 to 3.0.)
And having at least 3 (usually 3 to 300), preferably 3 to 100, more preferably 3 to 50 silicon atoms bonded to silicon atoms in one molecule. Preferably used.

Here, in the above formula (3), examples of the unsubstituted or substituted monovalent hydrocarbon group represented by R ³ include the same groups as those exemplified for R ¹ described above. Those having no group unsaturated bond are preferred. C is preferably 0.8 to 2.0, d is preferably 0.01 to 1.0, and c + d is preferably 1.0 to 2.5.

  The molecular structure of the organohydrogenpolysiloxane may be any of linear, cyclic, branched, or three-dimensional network structures, and the number of silicon atoms in one molecule or the degree of polymerization is 2 to 2. 300 (pieces), particularly 4 to 150 (pieces) room temperature (25 ° C.) and liquid (usually 1,000 mPa · s or less, preferably about 0.1 to 500 mPa · s at 25 ° C.) are suitable. Used. Here, this viscosity value is a value measured by a rotational viscometer (for example, BL type, BH type, BS type, cone plate type, etc.).

  In addition, the hydrogen atom couple | bonded with a silicon atom may be located in any of the molecular chain terminal and the middle of a molecular chain, and may be located in both.

Examples of the organohydrogenpolysiloxane of the component (B) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris (hydrogendimethylsiloxy) methylsilane, Tris (hydrogendimethylsiloxy) phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane / dimethylsiloxane cyclic copolymer, trimethylsiloxy group-blocked methylhydrogenpolysiloxane at both ends, trimethylsiloxy group-blocked dimethylsiloxane at both ends Methyl hydrogen siloxane copolymer, both ends dimethyl hydrogen siloxy group-capped dimethyl polysiloxane, both ends dimethyl hydrogen siloxy group capped dimethyl siloxane methyl high Rogen siloxane copolymer, trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane copolymer, trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane copolymer, both-end trimethylsiloxy group-blocked Methylhydrogensiloxane / methylphenylsiloxane / dimethylsiloxane copolymer, both ends dimethylhydrogensiloxy-blocked methylhydrogensiloxane / dimethylsiloxane / diphenylsiloxane copolymer, both ends dimethylhydrogensiloxy-blocked methylhydrogensiloxane / dimethylsiloxane-methylphenylsiloxane copolymer, (CH _{3) 2} HSiO _1/2 units and (CH _{3) 3} SiO _1/2 units and SiO _4/2 Position and a copolymer, (CH ₃₎ a copolymer consisting of ₂ HSiO _1/2 units and SiO _4/2 units, and (CH _{3) 2} HSiO _1/2 units and SiO _4/2 units (C Examples thereof include copolymers composed of ₆ H ₅ ) ₃ SiO _1/2 units, and compounds obtained by substituting part or all of the methyl groups with other alkyl groups or phenyl groups in the above exemplified compounds.

  (B) The compounding quantity of organohydrogenpolysiloxane of a component is 0.5-20 mass parts with respect to 100 mass parts of (A) component, Preferably it is 0.6-15 mass parts. Further, the molar ratio of silicon atom-bonded hydrogen atoms (SiH groups) in component (B) to the sum of silicon-bonded alkenyl groups contained in the entire composition, particularly alkenyl in components (A) and (F) The molar ratio of the hydrogen atom (SiH group) bonded to the silicon atom in the component (B) to the group is hydrogen atom (SiH group) / alkenyl group bonded to the silicon atom = 0.8 to 3.0, particularly 1. It is preferable to blend the organohydrogenpolysiloxane of component (B) so as to be 0 to 2.5. When the blending amount (mass) of the component (B) is too small, or when this ratio is less than 0.8, sufficient rubber hardness cannot be obtained in the resulting cured product, and the blending amount of the component (B) ( If the mass) is too large, or if this ratio is greater than 3.0, the resulting rubber has poor permanent elongation resistance (permanent elongation increases), and the rubber molded product after removal of the expanded diameter holding member Will be deformed.

Component (C), fumed silica (fumed silica), is essential to give sufficient strength to the resulting silicone rubber. BET specific surface area of the fumed silica, 50 to 400 m ² / g, preferably at 150~350m ² / g, rubber strength of the cured product obtained and 50 m ² / g less is poor, also 400 meters ² / If it is larger than g, the permanent elongation of the resulting rubber increases (that is, the permanent elongation resistance deteriorates).

  The component (C) fumed silica may be used as it is, but it may be used as it has been pretreated with a surface hydrophobizing agent, or it may be treated by adding a surface treating agent during kneading with silicone oil. It is preferable to use it. As these surface treatment agents, known surface treatment agents such as alkylalkoxysilanes, alkylchlorosilanes, alkylsilazanes, silane coupling agents, titanate treatment agents and fatty acid esters may be used alone, or two or more of them may be used simultaneously. Or you may use at a different timing.

  Moreover, the compounding quantity of a fumed silica is 10-40 mass parts with respect to 100 mass parts of (A) component, and it is preferable that it is 15-35 mass parts. When the blending amount is less than 10 parts by mass, sufficient rubber strength cannot be obtained in the obtained cured product, and when it exceeds 40 parts by mass, the resulting rubber has a large permanent elongation (that is, poor permanent elongation resistance). The shape of the rubber molded product after the removal of the expanded diameter holding member is changed.

  (D) Furnace black of a component is a component used as the characteristic of this invention, and is furnace black in which sulfur content was reduced to 0.1 mass% or less. Carbon black as a conductive filler is classified into furnace black, channel black, acetylene black, thermal black, etc. depending on its production method, but it is usually a poisoning problem for platinum catalysts that are catalysts for hydrosilylation addition reactions. From the viewpoint of (impurities such as sulfur contained in carbon black), acetylene black is commonly used. However, in the case of acetylene black, since it is inferior in the conductivity imparting effect, the target conductivity (low volume resistivity) cannot be obtained unless a large amount is added. Therefore, in order to obtain the desired conductivity (low volume resistivity) of about 0.8 Ωm or less, which is normally required in the conductive liquid silicone rubber composition used for the normal temperature shrinkable rubber member for high voltage cables, acetylene black is used. The composition blended in a large amount results in a very high viscosity, resulting in poor productivity, workability, etc., because it takes a lot of time for the material injection process at the time of molding. The goal cannot be achieved. In addition, channel black and thermal black cannot be used because there are many poisoning components (sulfur impurities) of the catalyst.

  Therefore, in the conductive liquid silicone rubber composition used for the normal temperature shrinkable rubber member for high voltage cables of the present invention, the poisoning component represented by sulfur is 0.1% by mass or less (0 to 0.1% by mass). Preferably, furnace black reduced to about 0.05% by mass or less (0.001 to 0.05% by mass), more preferably 0.03% by mass or less (0.001 to 0.03% by mass) is selective. Applies to When the sulfur content exceeds 0.1% by mass, the curability (hydrosilylation addition reaction) of the composition is impaired when the furnace black is blended in such a blending amount that the desired conductivity is obtained.

  In general furnace black, a sulfur content of about 0.5% by mass is usually contained as an impurity. However, as furnace black having a high graphitization degree and reduced sulfur content, for example, TIMCAL ( Ensaco 150G, 210G, 250G, 260G, 350G, etc. manufactured by Switzerland, and Toka Black # 3800, # 3845, # 3855, etc. manufactured by Tokai Carbon Co., can be suitably used for the conductive liquid silicone rubber composition of the present invention. In addition, about sulfur content in this furnace black, it can measure by the method etc. based on ASTMD1619 etc., for example.

  (D) The addition amount of furnace black of a component is 1-25 mass parts with respect to 100 mass parts of (A) component, Preferably it is 5-22 mass parts. If the amount is less than 1 part by mass, there is no effect on imparting electrical conductivity for the purpose of dielectric relaxation by a high voltage cable (ie, low volume resistivity). If the amount exceeds 25 parts by mass, the viscosity of the composition increases, Sexuality is impaired.

  The (E) component addition reaction catalyst comprises a silicon atom-bonded alkenyl group in component (A) or (A), (F) and a hydrogen atom (SiH group) bonded to a silicon atom in component (B). This is a catalyst for hydrosilylation addition reaction. Examples of the addition reaction catalyst include platinum black, platinum chloride, chloroplatinic acid, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and olefins, and a platinum-based catalyst such as platinum bisacetoacetate. Platinum group metal catalysts such as palladium-based catalysts and rhodium-based catalysts, and the like, and platinum-based catalysts are particularly preferable.

  The addition amount of the addition reaction catalyst can be a catalyst amount, and is usually 0.5 to 500 ppm in terms of the mass of the platinum group metal with respect to the total of the component (A) or (A) and (F). In particular, it can be about 1 to 100 ppm.

  In the conductive liquid silicone rubber composition of the present invention comprising the components (A) to (E) or the components (A) to (F), the curing time (pot life) is used to put the composition into practical use. In the case where it is necessary to adjust the hydrosilylation addition reaction, a low molecular (cyclic) siloxane oligomer having a high vinyl group content such as tetramethyltetravinylcyclotetrasiloxane, as a reaction control agent (reaction inhibitor) for the hydrosilylation addition reaction, Uses nitrogen-containing compounds such as triallyl isocyanurate, tetramethylethylenediamine, benzotriazole, alkyl maleates, acetylene alcohols and their silane or siloxane modified products, hydroperoxides, and mixtures thereof. It doesn't matter.

  Furthermore, if necessary, inorganic pigments such as cobalt blue and ultramarine blue, colorants such as organic dyes, heat resistance and flame retardancy improvers such as cerium oxide, zinc carbonate, manganese carbonate, titanium oxide, and iron oxide. In addition, for the purpose of adjusting the viscosity of the silicone rubber composition or adjusting the hardness of the cured silicone rubber, it is also possible to add an organopolysiloxane containing an average of less than 2 (usually 1) alkenyl groups in the molecule. .

The viscosity of the conductive liquid silicone rubber composition used for the cold-shrinkable rubber member for high-voltage cables of the present invention is 200 to 2,000 Pa · s at 23 ° C. and a shear rate of 0.9 s ⁻¹ . Preferably it is 500-2,000 Pa.s, More preferably, it is 500-1,500 Pa.s. When this viscosity exceeds 2,000 Pa · s, it takes time to inject the material, and when it is lower than 200 Pa · s, many burrs of the molded product are generated, and the molding process takes time. The viscosity is one of rotational viscometers, in particular, a rotational precision viscometer, such as HAAKE Rheostress 6000 (manufactured by Thermo scientific) or a precision rotational viscometer Rotovisco RV1 (HAAKE). One may be used.

  The conductive liquid silicone rubber composition of the present invention has a thickness cured at 120 ° C. for 10 minutes after press curing (primary curing) and then in an oven at 200 ° C. for 4 hours under post curing (secondary curing) conditions. The volume resistivity of a 1 mm cured product (silicone rubber) is preferably 0.8 Ωm or less (0.01 to 0.8 Ωm), particularly preferably 0.1 to 0.8 Ωm. The volume resistivity can be measured by the parallel terminal electrode method of JIS K 6249. In addition, in order to make volume resistivity into the said range, by adjusting (controlling) suitably the compounding quantity of each component of the electroconductive liquid silicone rubber composition of this invention, especially the compounding quantity of (D) component furnace black. It becomes possible.

In the present invention, the conductive liquid silicone rubber composition of the present invention is heat-cured (molded) by a molding method such as compression molding, injection molding, injection molding, transfer molding, etc. It is possible to obtain a cured conductive silicone rubber used as a normal temperature shrinkable rubber member for a high voltage cable that is attached to the portion and holds the connecting portion of the high voltage cable or the terminal portion thereof. In addition, as a curing condition (primary curing) of the conductive liquid silicone rubber composition, a temperature of 100 to 200 ° C., particularly 120 to 180 ° C., for 30 seconds to 30 minutes, particularly 1 to 15 minutes is preferable.
In addition, the obtained conductive silicone rubber is post-cured (secondarily cured), for example, at 150 to 220 ° C., particularly at 180 to 200 ° C. for 30 minutes to 6 hours, particularly for about 1 to 4 hours, as necessary. May be.

In addition, as a normal temperature shrinkable rubber member for high voltage cables, a member having a cured molded product of the conductive liquid silicone rubber composition as an inner layer and an insulating silicone rubber layer as an outer layer on the outer peripheral surface of the inner layer is preferable.
Here, as the insulating silicone rubber layer having the outer layer, a conventionally known insulating addition-curable silicone rubber composition containing no conductive component is used.
An example of a method for molding a conductive liquid silicone rubber composition according to the present invention and a method for attaching a high voltage cable to a normal temperature shrinkable rubber member for a high voltage cable according to the present invention is as follows. The core is set, the mold is closed, and the conductive liquid silicone rubber composition of the present invention is injected. After heat curing, an integral rubber molded product of the core and the cured conductive silicone rubber is taken out. Furthermore, the above-mentioned integral rubber molded product is set in another mold, the mold is closed, and an insulating addition-curable silicone rubber composition containing no conductive component outside the conductive silicone rubber of the integral rubber molded product inject. A heat-cured product is taken out, and an integral rubber molded product in which insulating silicone rubber is formed on the outer layer of the core and conductive silicone rubber is taken out. Pull out the core, expand the diameter of the integral rubber molded product, insert the resin spiral core, store the rubber molded product, and insert the wire into the resin spiral core when installing the wire. Take out and attach the rubber molding to the wire.

  Moreover, as thickness of the normal temperature shrinkable rubber member for high voltage cables, it is preferable that it is 2-40 mm, especially 4-35 mm. Specifically, the thickness of the inner layer is preferably about 0.1 to 10 mm, particularly about 2 to 8 mm, and the thickness of the outer layer is about 2 to 30 mm, particularly about 2 to 25 mm. preferable.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. In the following examples,% is mass%. The degree of polymerization is a weight average degree of polymerization in terms of polystyrene in gel permeation chromatography (GPC) analysis using toluene as a developing solvent.

[Example 1]
75 parts by mass of dimethylpolysiloxane (vinyl group content = 0.000053 mol / g) having an average degree of polymerization of 500 with both ends of the molecular chain blocked with dimethylvinylsiloxy groups and a specific surface area by BET method of 300 m ² / g 25 parts by mass of certain fumed silica (Aerosil 300, manufactured by Nippon Aerosil Co., Ltd.), 5 parts by mass of hexamethyldisilazane, 0.2 parts by mass of 1,3-divinyl-1,1,3,3-tetramethyldisilazane, water After mixing 2.0 parts by mass at room temperature (25 ° C.) for 30 minutes, the temperature was raised to 150 ° C., and stirring was continued for 3 hours, followed by cooling to obtain a silicone rubber base. In this silicone rubber base 100 parts by weight, on average, one end of a molecular chain is blocked with a dimethylvinylsiloxy group and the other end is blocked with a trimethylsiloxy group, and the average polymerization degree is 220 in a molecule. Put 22 parts by weight of dimethylpolysiloxane (vinyl group content = 0.000063 mol / g), 15 parts by weight of furnace black Ensaco 260G (manufactured by TIMCAL, 0.020% sulfur content by ASTM D1619), and stir for 30 minutes Then, on average, one end of the molecular chain is blocked with a dimethylvinylsiloxy group and the other end is blocked with a trimethylsiloxy group, and the average degree of polymerization is 220. 3 parts by mass of siloxane, and a compound having SiH groups at both molecular chain ends and side chains as a crosslinking agent. 1.9 parts by weight of both molecular chains of chilled hydrogen polysiloxane (polymerization degree 16; dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer having both ends of a molecular chain having a SiH group amount of 0.0031 mol / g) Methyl hydrogen polysiloxane having a SiH group at the terminal and side chain (molecular chain both ends dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer having a degree of polymerization of 18 and a SiH group amount of 0.0053 mol / g) 0.7 parts by mass [SiH group / alkenyl group = 1.5], 0.1 part by mass of ethynylcyclohexanol as a reaction control agent, 0.2 parts by mass of platinum catalyst (Pt concentration 1%) are added and stirred for 15 minutes. Then, a conductive liquid silicone rubber composition was prepared. The viscosity of this conductive liquid silicone rubber composition was measured using a cone and plate measuring jig of a precision rotary viscometer HAAKE Rheostress 6000 (Thermo Scientific) at a shear rate of 0.9 s ^-1 at 23 ° C. As measured. The obtained results are shown in Table 1.
In addition, this conductive liquid silicone rubber composition was press-cured at 120 ° C. for 10 minutes and then post-cured in an oven at 200 ° C. for 4 hours to obtain a cured conductive silicone rubber having a thickness of 2 mm and a thickness of 1 mm. Each was produced. Using this conductive silicone rubber cured product having a thickness of 2 mm, hardness, tensile strength, elongation at break, and tear strength (crescent) were measured based on JIS K 6249. Moreover, volume resistivity was measured by the JISK6249 parallel terminal electrode method about the conductive silicone rubber hardened | cured material of thickness 1mm. These results are shown in Table 1.

[Comparative Example 1]
In Example 1, Furnace Black Ensaco260G (manufactured by TIMCAL) 15 parts by mass was changed to 23 parts by mass of acetylene black HS-100 (sulfur content 0.000%, manufactured by Denki Kagaku Kogyo Co., Ltd.). Thus, a conductive silicone rubber composition was prepared. The viscosity of this conductive silicone rubber composition was measured as a viscosity at a shear rate of 0.9 s ⁻¹ at 23 ° C. using a cone and plate measuring jig of a precision rotary viscometer HAAKE Rheostress 6000 (manufactured by Thermo scientific). It was measured. The obtained results are shown in Table 1.
The conductive silicone rubber composition was press-cured at 120 ° C. for 10 minutes and then post-cured in an oven at 200 ° C. for 4 hours to obtain a cured conductive silicone rubber having a thickness of 2 mm and a thickness of 1 mm, respectively. Produced. Using this conductive silicone rubber cured product having a thickness of 2 mm, hardness, tensile strength, elongation at break, and tear strength (crescent) were measured based on JIS K 6249. Moreover, volume resistivity was measured by the JISK6249 parallel terminal electrode method about the conductive silicone rubber hardened | cured material of thickness 1mm. These results are shown in Table 1.

Claims (6)

A conductive liquid silicone rubber composition for a normal temperature shrinkable rubber member for a high voltage cable, which is attached to a connecting portion of the high voltage cable or a terminal portion thereof and holds the connecting portion of the high voltage cable or the terminal portion thereof,
(A) Organopolysiloxane containing an average of at least two alkenyl groups bonded to silicon atoms in one molecule: 100 parts by mass
(B) Organohydrogenpolysiloxane containing at least three hydrogen atoms bonded to silicon atoms in one molecule: 0.5 to 20 parts by mass,
(C) Fumed silica having a specific surface area of 50 to 400 m ² / g by BET method: 10 to 40 parts by mass,
(D) Furnace black having a sulfur content of 0.1% by mass or less as a conductive filler: 1 to 25 parts by mass,
(E) Addition reaction catalyst: A conductive liquid silicone rubber composition comprising a catalyst amount and having a viscosity at 23 ° C. at a shear rate of 0.9 s ⁻¹ of 200 to 2,000 Pa · s. Component (A) is an organopolysiloxane having the following average composition formula (1)
R ¹ _a SiO _{(4-a) / 2} (1)
(Wherein R ¹ is the same or different, unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and a is a positive number in the range of 1.5 to 2.8.)
The conductive silicone rubber composition according to claim 1, which is represented by: Furthermore, (F) the following average composition formula (2)
R ² _b SiO _{(4-b) / 2} (2)
(In the formula, R ² is the same or different, unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and b is a positive number in the range of 1.5 to 2.8.)
Or an organopolysiloxane containing an average of one alkenyl group bonded to a silicon atom in one molecule in a ratio of 20/80 to 80/20 with respect to the mass of the component (A). 3. The conductive silicone rubber composition according to 2.   4. A normal temperature shrinkable rubber member for a high voltage cable, which is attached to a connecting portion of the high voltage cable or a terminal portion thereof and holds the connecting portion of the high voltage cable or the terminal portion thereof, and the conductive material according to claim 1, 2, or 3. Room temperature shrinkable rubber member for high-voltage cables, comprising a cured molded product of a conductive liquid silicone rubber composition.   4. A normal temperature shrinkable rubber member for a high voltage cable, which is attached to a connecting portion of the high voltage cable or a terminal portion thereof and holds the connecting portion of the high voltage cable or the terminal portion thereof, and the conductive material according to claim 1, 2, or 3. Room temperature shrinkable rubber member for high-voltage cables having a cured molded product of the conductive liquid silicone rubber composition as an inner layer and an insulating silicone rubber layer containing no conductive component on the outer peripheral surface of the inner layer as an outer layer.   The room temperature shrinkable rubber member for a high voltage cable according to claim 4 or 5, wherein the volume resistivity of the cured molded product of the conductive liquid silicone rubber composition is 0.8 Ωm or less.