JPS61108661A - Electrically conductive silicone rubber composition - Google Patents

Abstract

PURPOSE:To provide the titled compsn. having less variability in resistance, by blending crushed vulcanized silicone rubber with a silicone rubber substrate contg. carbon black. CONSTITUTION:30-200pts.wt. crushed vulcanized silicone rubber having a particle size of 0.1-1.0mm is blended with 100pts.wt. silicon rubber substrate having the formula [wherein R is an (un)substituted monovalent hydrocarbon group; n is 1.9-2.05] and contg. 5-50wt% carbon black. EFFECT:The hardness of moldings can be widely controlled. USE:A material for contacts of switches, antistatic material, electromagnetic wave-shielding material, etc.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a conductive silicone rubber composition, in particular, a conductive silicone rubber composition with the addition of carbon black made by blending a vulcanized silicone rubber pulverized product as a filler. This invention relates to a binding π silicone rubber composition.

(Prior art) Caustic silicone rubber compounded with carbon black as a conductivity imparting agent is widely used as a contact material for various switches, an antistatic material, a magnetic wave shielding material, etc. However, conventionally known In the conductive silicone rubber composition, the specific resistance value of the molded article obtained from it is adjusted by the addition ratio of carbon black blended into the silicone rubber base material.

This amount of addition is uniquely determined, and along with this, the hardness of the molded product obtained from this composition is also uniquely determined, so the range of variation in hardness is unclear. This has the disadvantage that a conductive silicone rubber composition with a relatively high specific resistance value has a small addition ratio of carbon black, so the molded products obtained from this composition have a large variation in resistance value. Tona flea),
This variation had the disadvantage that it increased as the resistivity value increased.

(Structure of the Invention) The present invention has solved this disadvantage. Conductivity that allows the hardness of a conductive silicone rubber molded product having a certain resistance value to be adjusted over a wide range, and also allows for reducing variations in the resistance value of a conductive silicone rubber molded product that has a relatively high resistance value. The present invention relates to a silicone rubber composition, which is characterized in that a pulverized silicone rubber product of 71r1ε: is added and blended into a silicone rubber base material containing carbon black.

To explain this, the present inventors have investigated various methods for adjusting the hardness of conductive silicone rubber compositions containing carbon black, and found that this conductive silicone rubber composition contains vulcanized fillers. By adding a crushed silicone rubber product having a hardness of There was no increase in the resistance value, and the resistance value only increased slightly [1], and the variation in resistance value was the same or only slightly different from the variation in resistance value of the molded product obtained from the composition before adding the vulcanized silicone rubber pulverized product. Furthermore, the hardness of a molded article obtained from a conductive silicone rubber composition to which this pulverized product is added is comparable to that of a molded article obtained from an EV composition of silicone rubber containing W sulfur, which has an equivalent resistance value. In addition to discovering that the pulverized vulcanized silicone rubber can be added to a conductive silicone with practical physical properties without causing an extreme deterioration of the physical properties of the molded product, it has been found that Confirm that a rubber molded product can be obtained.

The present invention was completed by conducting research on the type and amount of pulverized vulcanized silicone rubber.

The silicone rubber base material which is the main material of the composition of the present invention is a conventionally known one. Aryl groups such as alkenyl groups and phenyl groups,
Or a chloro(M-3,3,3-)lifluoropropyl group in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with a halogen atom, a cyan group, etc.

Same or different unsubstituted or substituted monovalent hydrocarbon groups such as cyanmethyl group, n is a positive number of 1.9 to 2.05. It is preferable to use an organopolysiloxane in which 50 mol% or more of the methyl groups are present, and the viscosity of this organopolysiloxane is 500 to 1,000,000 c.
S, preferably 1.000 to 500.0 OOcS.

This silicone rubber based on organopolysiloxane itself has excellent insulating properties, so in order to make it conductive, it is necessary to add a conductivity imparting agent to it. In products, it is essential to select and add carbon black as a conductivity imparting agent. This carbon black may be a commercially available carbon black, such as acetylene black, touch black, harness plaque thermal black, etc., but the amount added depends on the conductivity required for the composition of the present invention. Just set it.

Regarding this, since the electrical resistance of the conductive silicone rubber composite acid of the present invention is 3 to IKΩ, the amount of carbon black to be blended may be within the range of 5 to 50% by weight.

The crushed vulcanized silicone rubber added to the compositions of the invention can be of any type, especially if it is ground vulcanized silicone rubber - it is heated with radiation in the presence of a peroxide catalyst. Sulfurized.

Vulcanization may be obtained by heating addition reaction in the presence of a platinum-based catalyst or by curing with moisture in the air at room temperature, but it is preferably vulcanized with a peroxide catalyst. It is best to use pulverized products. Since this vulcanized silicone rubber is usually made into a molded product, it may be a cut piece during the backing of the molded product, and it is advantageous industrially to use recovered products such as this cut piece. However, this particle has a particle size of 0.1 to 1.0 mm.
It is recommended that the

In the conductive silicone rubber composition of the present invention, the amount of carbon platter added in order to obtain the target specific resistance value can be made smaller than in a composition without the addition of pulverized vulcanized silicone rubber. The hardness of a molded article obtained from the conductive silicone rubber composition of the present invention to which a vulcanized pulverized silicone product is added can be adjusted to a large extent by the hardness of the pulverized silicone rubber product and the amount added. This gives the effect of being able to. The amount of this vulcanized silicone rubber pulverized product may be determined depending on the hardness expected of the molded product obtained from the conductive silicone rubber of the present invention, but it is usually 1 for 100 parts by weight of the silicone rubber base material. The amount may be in the range of 30 to 200 parts by weight, and within this range, the physical properties of the silicone rubber base material will not be significantly impaired.

Next, examples of the present invention will be given, and parts in each example indicate parts by weight.

Example 1 4.0 parts of vulcanizing agent C-8 (trade name manufactured by Shin-Etsu Chemical Co., Ltd.) and 60 parts of acetylene/black were added to 100 parts of 7-gum rubber compacted @KFi951U (part name manufactured by Shin-Etsu Chemical Co., Ltd.). When the conductive silicone rubber base material A was prepared by heating and vulcanizing it at 180° C. for 10 minutes, the rubber elastic molded product obtained from this composition had a specific resistance value of 4. It exhibited physical properties of 0Ω-1 and hardness (JIS A) of 67°H.

Next, the silicone rubber compound mentioned above - KE95
Vulcanized silicone rubber pulverized with an average particle size of 0.35 m obtained by blending 2 parts of vulcanizing agent ○-8 with 1 U 100 parts and pulverizing the molded product obtained by vulcanization using a new roll mill. The product was added to the above silicone rubber base material A [in the amount r shown in Table 1, and the amount of acetylene black added to this as the additive 21119 of this pulverized product increased as shown in Table 1. A conductive silicone rubber composition was prepared in which the conductive silicone rubber composition was successively reduced in temperature, and the resistivity, hardness, and general physical properties of the rubber elastic body obtained by pressurizing and heating vulcanization at 180°C for 10 minutes were measured. The results shown in the table were obtained.

Incidentally, the relationship between the acetylene black content and the specific resistance value is as shown in the human curve in FIG.

The correlation between the specific resistance value and the hardness of this material was as shown in the curve B in FIG.

Comparative Example The silicone rubber base material AjC in Example 1 was prepared without adding the vulcanized silicone rubber base material AjC in Example 1.
, silicone rubber compound KK9 as degree adjuster
A silicone rubber material B containing 100 parts of 51t7 (mentioned above) and 2 parts of vulcanizing agent 0-8 (mentioned above) was mixed at the compounding ratio shown in Table 2, and the acetylene black content of this material was varied. These were heated under pressure at 180°C for 10 minutes to make a rubber elastic body1), and when the physical properties of this body were measured, the results shown in Table 2 (6) were obtained, and in this case, the silicone rubber material Although the hardness decreased with the addition of B, the specific resistivity increased significantly, and the variation in the resistivity value also increased significantly.

The relationship between the acetylene black content and the specific resistance value of this product is as shown in the line C1II in Figure 1.
The correlation between specific resistance value and hardness was shown in the second plot curve.

Actual tumor example 2 The silicone rubber material in Example 1, the silicone rubber material B used in the comparative example, and the pulverized silicone rubber product used in Example 1 were mixed at the compounding ratio shown in Table 3. After preparing conductive silicone rubber compositions and examining the acetylene black content, specific resistance value, variation, and physical properties of molded products, the third
The results shown in the table were obtained, and the resistivity value of the product to which vulcanized pulverized silicone rubber was added was only slightly increased, and the variation in resistivity was the same as that of the product without the addition, or only slightly increased. It was confirmed that a large change in hardness could be achieved.

Note that the correlation between these carbon black contents and resistivity is shown in Curve 8-F [! 1] line, and the correlation between the specific resistance value and hardness was as shown in the 0 curve and H curve in FIG.

[Brief explanation of the drawing]

Figures 1 and 3 are graphs of the relationship between carbon black content and specific resistance of a rubber elastic body obtained from a conductive silicone rubber composition, and Figure 2 is a graph of the relationship between the specific resistance value and hardness of this rubber elastic body. This shows a relationship graph.

Claims (1)

[Scope of Claims] 1. A conductive silicone rubber composition comprising a silicone rubber base material containing carbon black and a vulcanized silicone rubber pulverized product blended therein. 2. Vulcanized silicone rubber pulverized product has a particle size of 0.1 to 1
．． The conductive silicone rubber composition according to claim 1, which has a thickness of 0 mm. 3. Add the vulcanized silicone rubber pulverized product to 100 parts by weight of the silicone rubber base material containing carbon black.
The conductive silicone rubber composition according to claim 1 or 2, which contains 30 to 200 parts by weight. 4. Silicone rubber base material contains 5 to 50 carbon black
Claims 1 and 2 contain % by weight.
The conductive silicone rubber composition according to item 1 or 3.