JP5191977B2 - Conductive liquid silicone rubber composition - Google Patents

Description

  The present invention relates to a conductive liquid silicone composition.

  A liquid silicone composition in which a polyorganosiloxane is used as a base polymer and diluted with a solvent is used for paints and markings by taking advantage of its properties as a liquid material in addition to the characteristics of the silicone base polymer and its excellent workability and handleability. It is widely used in various applications including agents. In particular, a conductive liquid silicone composition to which a conductive material such as carbon black is added is used in various electric circuits and electronic parts including a switching mechanism, taking advantage of the property of conductivity.

  As a conductive material that imparts conductivity to the liquid silicone composition, carbon black is frequently used as described above from the viewpoints of conductivity and cost that can be imparted to the silicone material. However, the silicone base polymer and carbon black have no inherent affinity, and the dispersibility or solubility of carbon black in a solvent is extremely poor, so that there is a problem that it is difficult to obtain a uniform dispersion or dissolution state as a liquid. .

  On the other hand, for example, in Patent Document 1, in addition to a silicone base polymer, carbon black, and a solvent, a conductive material in which a polyorganosiloxane having an alkenyl group at both ends and a viscosity of 3000 to 500000 cps (25 ° C.) is blended. Liquid silicone compositions are described. Although the above-mentioned polyorganosiloxane has an effect on the stabilization of the conductive performance and the like, a sufficient effect is not necessarily obtained with respect to the performance of maintaining the uniformly dispersed or dissolved state of the liquid. For this reason, even if the carbon black can be uniformly dispersed or dissolved, a separation phenomenon occurs during subsequent steps or storage, and it is difficult to maintain a uniform dispersion or solution state over a long period of time. There's a problem.

  Patent Document 2 describes a conductive silicone rubber composition containing a phenyl group-containing organosilicon compound in addition to a silicone base polymer and carbon black. The conductive silicone rubber composition described in Patent Document 2 has a uniform mixing property and uniform dispersibility of carbon black when preparing a silicone rubber composition (kneaded material) for obtaining a rubber-like elastic body. In order to enhance, the above-mentioned phenyl group-containing organosilicon compound is blended, and no consideration is given to maintaining a uniform dispersed state or dissolved state of the liquid silicone composition.

Japanese Patent No. 2563003 Japanese Patent Publication No. 3-47663

  As described above, the conventional conductive liquid silicone composition can disperse or dissolve carbon black once evenly due to the extremely poor dispersibility or solubility of carbon black in a solvent. However, there has been a problem that a separation phenomenon occurs during subsequent processes and storage. Such a problem is not sufficiently improved even when a conventional polyorganosiloxane-based treatment agent is used. Accordingly, there is a need for a conductive liquid silicone composition that can maintain a uniform dispersion or solution state for a long period of time.

  The present invention has been made in order to cope with such problems. By further increasing the affinity between the silicone base polymer or solvent and carbon black, a uniform dispersion or solution can be maintained over a long period of time. An object of the present invention is to provide a conductive liquid silicone composition that makes it possible.

（式中、Ｒ^１はメチル基を、Ｒ^２ はα−メチルスチリル基を示し、ｎおよびｍはｎ＋ｍが５〜１０００の範囲の数である）
で表され、かつ前記Ｒ^２基を有するＳｉＯ単位を少なくとも５ｍｏｌ％含有するシリコーンオイル０．５〜３０質量部と、（Ｃ）導電性カーボンブラック５〜１００質量部と、（Ｄ）必要量の硬化剤と、（Ｅ）溶剤を（Ａ）成分のポリオルガノシロキサン１００質量部に対して１０〜２０００質量部とを含有することを特徴としている。
また、本発明の塗料用導電性液状シリコーンゴム組成物において、硬化剤としては、好ましくはメチルトリス（メチルエチルケトオキシム）シラン又はトリメトキシシランと、錫化合物又は有機チタネートとの組み合わせである。 The conductive liquid silicone composition for paints of the present invention is
(A) 100 parts by mass of a condensation reaction type polyorganosiloxane having a degree of polymerization of 100 to 2000,
(B)

(Wherein R ¹ represents a methyl group, R ² represents an α -methylstyryl group, and n and m are numbers in the range of n + m from 5 to 1000)
And 0.5 to 30 parts by mass of a silicone oil containing at least 5 mol% of the SiO unit having the R ² group, (C) 5 to 100 parts by mass of conductive carbon black, and (D) a necessary amount of It is characterized by containing 10 to 2000 parts by mass of the curing agent and (E) solvent with respect to 100 parts by mass of the polyorganosiloxane of component (A).
In the conductive liquid silicone rubber composition for paints of the present invention, the curing agent is preferably a combination of methyltris (methylethylketoxime) silane or trimethoxysilane and a tin compound or organic titanate.

In the conductive liquid silicone composition of the present invention, in addition to (A) component polyorganosiloxane, (C) component carbon black, (D) component curing agent, and (E) component solvent, ) As a component, silicone oil containing at least 5 mol% of SiO units represented by the above formula (1) and containing R ² groups is blended. The component (B) silicone oil improves the affinity between the silicone base polymer or solvent and the carbon black, and further maintains the ability to improve this affinity, so the conductive liquid silicone composition is uniformly dispersed. It can be maintained as a liquid or a solution.

  As described above, according to the present invention, a conductive liquid silicone composition capable of maintaining a uniform dispersion or solution state for a long period of time while providing good conductivity with carbon black is stably provided. It becomes possible to do. This greatly contributes to the improvement in post-curing properties, reliability, storage stability, handleability, practicality and the like of the conductive liquid silicone composition.

Hereinafter, modes for carrying out the present invention will be described.
The conductive liquid silicone composition of the present invention comprises (A) component polyorganosiloxane (silicone base polymer), (B) component silicone oil (silicone treatment agent), (C) component conductive carbon black, ( It contains a curing agent as component D) and a solvent as component (E) as essential components.

  The (A) component polyorganosiloxane serves as the base polymer of the conductive liquid silicone composition of the present invention, and has a degree of polymerization in the range of 100 to 2,000. When the polymerization degree of the silicone base polymer exceeds 2000, the viscosity increases, and the fluidity required for the liquid silicone composition, that is, the low viscosity cannot be obtained. On the other hand, when the degree of polymerization of the silicone base polymer is less than 100, the characteristics when the conductive liquid silicone composition is cured deteriorates, and the original physical characteristics of the cured silicone cannot be obtained. The degree of polymerization of the silicone base polymer (A) is more preferably in the range of 200 to 1,000.

  In the polyorganosiloxane of the above component (A), the side chain group bonded to the silicon atom constituting the main skeleton is an alkyl group such as a methyl group, an ethyl group or a propyl group, a cyclopentyl group or a cyclohexyl group. Unsubstituted monovalent hydrocarbon groups such as cycloalkyl groups, vinyl groups, alkenyl groups such as allyl groups, and some or all of hydrogen atoms bonded to carbon atoms of these groups are substituted with halogen atoms or cyano groups. Examples thereof include substituted monovalent hydrocarbon groups such as a chloromethyl group, a chloropropyl group, a 3,3,3-trifluoropropyl group, and a 2-cyanoethyl group. These side chain groups may be the same or different.

Among the monovalent hydrocarbon groups described above, in particular, 90 mol% or more of the side chain groups are preferably methyl groups from the viewpoint of the properties and handling properties of the cured silicone.
The end of the molecular chain of polyorganosiloxane is blocked with a hydrolyzable group or a hydroxyl group, as with a general silicone base polymer, or a structure blocked with an alkenyl group such as a vinyl group depending on the curing reaction applied. Applies. The alkenyl group may be used as part of the side chain group.

（式中、Ｒ^１はメチル基を、Ｒ^２ はα−メチルスチリル基を示し、ｎおよびｍはｎ＋ｍが５〜１０００の範囲の数である）
で実質的に表される組成を有し、かつ側鎖基としてＲ^２基を有するＳｉＯ単位を５ｍｏｌ％以上含有するものである。 The component (B) silicone oil is a treatment agent that increases the affinity between the conductive carbon black and the silicone-based polymer or solvent,

(Wherein R ¹ represents a methyl group, R ² represents an α -methylstyryl group, and n and m are numbers in the range of n + m from 5 to 1000)
And containing 5 mol% or more of SiO units having an R ² group as a side chain group.

As the R ¹ group in the formula (1), it is particularly preferable to apply a methyl group from the viewpoint of handleability. The R ² group characterizes the component (B) and is a monovalent group selected from α -methylstyryl groups. Among these, it is more preferable to apply an α-methylstyryl group from the viewpoint of the above-described affinity improvement effect and its sustainability.

  For the silicone oil as component (B), an organosiloxane having n + m in the range of 5 to 1000 in the above formula (1) is applied. When the value of n + m indicating the degree of polymerization of the silicone oil is less than 5, the molecule is too small to sufficiently increase the affinity of carbon black for the silicone base polymer and solvent. On the other hand, when the value of n + m exceeds 1000, the molecule becomes too large, and the properties of the carbon black as a treating agent deteriorate. The value of n + m is more preferably in the range of 10 to 500.

Then, (B) a silicone oil as component shall contain at least 5 mol% or more ranges of SiO units having the R ² groups as described above. When the content of the R ² group-containing SiO unit is less than 5 mol%, the affinity between the (A) component silicone base polymer and the (E) component solvent and the (C) conductive carbon black is sufficient. The conductive liquid silicone composition cannot be maintained as a uniform dispersion or solution. The SiO unit having an R ² group is more preferably contained in the range of 10 mol% or more in the silicone oil as the component (B) from the viewpoint of improving affinity and its sustainability. However, if the content is too large, not only the effect is not obtained, but also the synthesis becomes difficult industrially and the cost is increased. Therefore, the content of the SiO unit having R ² group is 80 mol%. It is preferable to make it less than.

  As described above, the silicone oil of component (B) is a component that increases the affinity between the conductive carbon black of component (C) and the silicone base polymer of component (A) and the solvent of component (E). By blending such a component (B) silicone oil into a conductive liquid silicone composition containing conductive carbon black, it becomes possible to stably obtain a uniform dispersed or dissolved state as a liquid. Furthermore, since the silicone oil as the component (B) has a high surface modification effect on the conductive carbon black and is excellent in its sustainability, the conductive liquid silicone composition can be maintained as a uniform dispersion or solution. . That is, the separation phenomenon of the conductive liquid silicone composition during storage or the like is greatly suppressed.

  The blending amount of the silicone oil as the component (B) is in the range of 0.5 to 30 parts by mass with respect to 100 parts by mass of the silicone base polymer as the component (A). When the blending amount of the silicone oil as the component (B) is less than 0.5 parts by mass, the above-described affinity improvement effect cannot be sufficiently obtained. On the other hand, when the blending amount of the component (B) exceeds 30 parts by mass, the properties (eg, mechanical properties) of the cured product obtained by curing the conductive liquid silicone composition may be deteriorated. (B) The compounding quantity of a component is more preferable to set it as the range of 1-10 mass parts with respect to 100 mass parts of (A) component.

  Component (C), conductive carbon black, is a component that imparts conductivity to the conductive liquid silicone composition and its cured product. As the conductive carbon black as the component (C), acetylene black, furnace black, channel black, ketjen black and the like, which are usually used for conductive rubber compositions and the like, are applied. Specifically, acetylene black, conductive furnace black, super conductive furnace black, extra conductive furnace black, conductive channel black, ketjen black, furnace black heat-treated at high temperature, and the like can be used. Among these conductive carbon blacks, acetylene black, in particular, has a low impurity content and has a developed secondary structure structure, so that it has excellent conductivity imparting characteristics and is preferably used in the present invention. .

  The blending amount of the conductive carbon black as the component (C) is in the range of 5 to 100 parts by mass with respect to 100 parts by mass of the polyorganosiloxane as the component (A). If the blending amount of conductive carbon black is less than 5 parts by mass, sufficient conductivity may not be obtained. On the other hand, when it exceeds 100 parts by mass, even when the silicone oil of the component (B) is blended, there is a possibility that the separation phenomenon is likely to occur, and the mechanical properties of the obtained silicone cured product are deteriorated. The blending amount of the conductive carbon black is more preferably in the range of 10 to 80 parts by mass, particularly in view of the balance between conductivity and mechanical properties.

  The component (D) curing agent is a variety of known curing agents capable of vulcanizing and curing the component (A) by utilizing a radical reaction or addition reaction usually applied to the curing of the silicone composition. It can be appropriately selected and used, and is not particularly limited to the curing mechanism. Examples of such a curing agent include organic peroxides such as di-t-butyl peroxide and 2,5-dimethyl-2,5-di-t-butylperoxyhexane. Examples of the addition reaction type curing agent include a combination of an organohydrogenpolysiloxane (crosslinking agent) containing at least two hydrogen atoms bonded to silicon atoms in one molecule and a platinum catalyst. . Further, examples of the condensation reaction type curing agent include a combination of a crosslinking agent such as methyltris (methylethylketoxime) silane or trimethoxysilane and a catalyst such as a tin compound or organic titanate.

What is necessary is just to mix | blend a required quantity with the hardening | curing agent mentioned above similarly to the case of a normal silicone composition. Specifically, for example, in the case of an organic peroxide, it is preferable to blend about 0.05 to 15 parts by mass with respect to 100 parts by mass of the (A) component polyorganosiloxane.
In the case of an addition reaction type curing agent, the platinum catalyst is used in an amount of 1 to 1000 ppm in terms of platinum element with respect to 100 parts by mass of the polyorganosiloxane of component (A), and the crosslinking agent is contained in component (A). It is preferable to blend such an amount that 0.5 to 4.0 hydrogen atoms bonded to silicic group atoms in the crosslinking agent are added to one alkenyl group. In the case of a condensation reaction type curing agent, 0.5 to 20 parts by mass of a crosslinking agent and about 0.01 to 5 parts by mass of a catalyst may be blended with 100 parts by mass of the polyorganosiloxane of component (A). preferable.

  (E) The solvent of a component is mix | blended as an essential component, when obtaining the electroconductive liquid silicone composition of desired viscosity. The solvent to be used is appropriately selected according to the use of the conductive liquid silicone composition, for example, hydrocarbons such as toluene, xylene, cyclohexane, n-hexane, n-heptane, n-octane, and naphtha. Solvents, halogenated hydrocarbon solvents such as chloroform, carbon tetrachloride, trichloroethylene, perfluoropropane, ether solvents such as propyl ether, n-butyl ether and tetrahydrofuran, ester solvents such as ethyl acetate and butyl acetate, Ketone solvents such as acetone, methyl ethyl ketone, acetophenone, alcohol solvents such as methanol, ethanol, isopropanol, butanol, ethylene glycol, hexamethyldisiloxane, octamethyltrisiloxane, hexamethylcyclotrisi Hexane, siloxane solvents such as octamethylcyclotetrasiloxane, or a mixture of these solvents, it is possible to use various solvents.

  The amount of the component (E) solvent described above is appropriately set according to the viscosity of the intended conductive liquid silicone composition. The viscosity of the conductive liquid silicone composition is set according to the intended use, etc., but considering the handleability and practicality as a liquid conductive silicone composition, the viscosity is 1000 P or less. Is preferred. In consideration of characteristics after curing the conductive liquid silicone composition, the viscosity of the conductive liquid silicone composition is preferably 10 P or more. The viscosity of the conductive liquid silicone composition is not determined only by the amount of the solvent, but when obtaining the conductive liquid silicone composition having the above-described viscosity, for example, 100 parts by weight of the polyorganosiloxane of component (A) It is preferable to add about 10 to 2000 parts by mass of solvent with respect to parts.

  The conductive liquid silicone composition of the present invention includes components other than the components (A) to (E) as necessary, that is, silica-based filler, quartz powder, and fused quartz powder that are usually used in silicone compositions. Further, diatomaceous earth, talc, calcium carbonate, titanium oxide, iron oxide, aluminum oxide and the like may be added. Further, a plasticizer, a heat resistance improver, a flame retardant, a processing aid, a dispersant, a colorant, and the like may be blended.

  The conductive liquid silicone composition of the present invention can be obtained by uniformly dispersing and mixing the components (A) to (E) and additional components blended as necessary. For example, (A) component silicone base polymer and (B) component silicone oil are charged into a universal kneader or kneader, and then (C) component conductive carbon black is added and mixed to uniformly disperse and mix Let At this time, the conductive carbon black may be added and mixed several times. In addition, it is allowed to pass these mixtures through three rolls or to heat knead. The conductive liquid silicone composition of this invention is obtained by adding the solvent of (E) component and the hardening | curing agent of (D) component to the uniform mixture obtained in this way, and making it disperse | distribute or dissolve uniformly.

  In addition, the usage of the conductive liquid silicone composition of the present invention is not particularly limited, but it is possible to utilize various properties inherent to the silicone composition and properties as a liquid, using conductive paints, ink materials, and electric fields. It is suitably used for a relaxation paint or the like. The conductive liquid silicone composition used for such applications preferably has a viscosity of about 10 to 1000 P, but the specific viscosity can be appropriately set according to the purpose of use.

  Next, specific examples of the present invention and evaluation results thereof will be described.

Example 1
First, the end of the molecular chain is blocked with a hydroxyl group, the polydimethylsiloxane base polymer B having a polymerization degree of 780 and a viscosity of 87 P, 50 mol% of α-methylstyryl groups (others are methyl groups), and a polymerization degree of 60 Silicone oil A and acetylene black (DENKA BLACK HS-100 (trade name, manufactured by Denki Kagaku Kogyo Co., Ltd.)) were prepared as conductive carbon black.

After adding 5 parts by mass of silicone oil A to 100 parts by mass of the siloxane base polymer B described above and mixing it uniformly for 10 minutes at room temperature, 20 parts by mass of acetylene black is charged into a kneader and uniformly added for 1 hour at room temperature. Kneaded. Thereafter, naphtha no. 200 parts by mass of No. 5 was added, and the resulting mixture was mixed and stirred to obtain a uniformly dispersed silicone dispersion. To this silicone dispersion, 15 parts by mass of methyltris (methylethylketoxime) silane and 0.05 parts by mass of dibutyltin dilaurate were added as a curing agent and mixed uniformly to obtain a conductive liquid silicone composition. This electroconductive liquid silicone composition was used for the characteristic evaluation mentioned later.

Reference example 1
Among the components prepared in Example 1 described above, silicone oil A was prepared in place of silicone oil B containing 30 mol% of phenyl groups (others were methyl groups) and having a polymerization degree of 35.

A conductive liquid silicone composition was prepared in the same manner as in Example 1 except that the components described above were mixed at the blending ratio shown in Table 1. This electroconductive liquid silicone composition was used for the characteristic evaluation mentioned later.

Comparative Examples 1 to 4
A conductive liquid silicone rubber composition was prepared in the same manner as in Example 1 except that the components and compounding ratios shown in the comparative example column of Table 1 were used . This conductive liquid silicone rubber composition was subjected to the characteristic evaluation described later.
In addition, each component in the table is as follows.
Polydimethylsiloxane base polymer A: Polydimethylsiloxane base polymer whose molecular chain ends are blocked with vinyl groups, the degree of polymerization is 810, and the viscosity is 100P.
Silicone oil C: Silicone oil having an α-methylstyryl group content of 3 mol% (others are methyl groups) and a polymerization degree of 60 (silicone oil not corresponding to the component (B) of the present invention)
Comparative Examples 1 to 3 are obtained by applying polydimethylsiloxane base polymer A, blending methylhydrogenpolysiloxane as a curing agent and chloroplatinic acid as a curing catalyst, and adding toluene as a solvent. No. 4 applies polydimethylsiloxane base polymer B, methyltris (methylethylketoxime) silane and dibutyltin dilaurate as a curing agent, and naphtha No. 4 as a solvent. 5 is added.

The characteristics of the conductive liquid silicone compositions of Example 1, Reference Example 1 and Comparative Examples 1 to 4 described above were evaluated as follows. First, the viscosity of each conductive liquid silicone composition was measured, and each composition was put in a test tube having a length of 300 mm, and the thickness of the oil separated after standing for 2 weeks was measured. Also, each conductive liquid silicone composition was cured under the conditions of 150 ° C. × 1 hour for the addition curable composition and 23 ° C. and 50% RH × 7 days for the condensation curable composition. Volume resistivity was measured. These measurement results are also shown in Table 1.

As is clear from Table 1, the conductive liquid silicone compositions according to Example 1 and Reference Example 1 both have a low viscosity, and the state of a uniform dispersion even after standing for a long period of time. You can see that it is kept. As described above, the conductive liquid silicone composition of the present invention has both good conductivity and storage stability as a uniform liquid.

Claims (2)

(A) 100 parts by mass of a condensation reaction type polyorganosiloxane having a degree of polymerization of 100 to 2000,
(B)

(Wherein R ¹ represents a methyl group, R ² represents an α -methylstyryl group, and n and m are numbers in the range of n + m from 5 to 1000)
Represented by
And 0.5-30 parts by mass of silicone oil containing at least 5 mol% of SiO units having the R ² group,
(C) 5 to 100 parts by mass of conductive carbon black;
(D) a required amount of curing agent;
(E) A conductive liquid silicone composition for paints, which contains 10 to 2000 parts by mass of the solvent with respect to 100 parts by mass of the polyorganosiloxane as the component (A). The conductive liquid silicone rubber composition for paint according to claim 1, wherein the curing agent is a combination of methyltris (methylethylketoxime) silane or trimethoxysilane and a tin compound or an organic titanate.