JPS63260954A - Conductive silicone rubber composition - Google Patents

Abstract

PURPOSE:To provide the title compsn. having excellent moldability, electrical conductivity, etc., by mixing an organopolysiloxane having a high average degree of polymn. with a specific organosilicon compd. having a phenyl group, electrically conductive carbon black and a curing agent in a predetermined weight ratio. CONSTITUTION:100pts.wt. organopolysiloxane (A) having an average degree of polymn. not lower than 100 is mixed with 0.5-40pts.wt. organosilicon compd. (B) having a phenyl group, represented by formula I (wherein R is an unsubstituted or substd. monovalent hydrocarbon group; X is H, hydroxyl or a hydrolyzable group; 0<=a<=3; 0<b<=3; 0<=c<=3; 0<a+b+c<=4) (e.g., a compd. of formula II or III), 3-150pts.wt. electrically conductive carbon black (C) (e.g., ketjen black) and 0.1-10pts.wt. curing agent (D) (e.g., di-t-butyl peroxide) to obtain the desired electrically conductive silicone rubber. The compsn. is suitable for use as a packing material for shielding electromagnetic waves.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a conductive silicone rubber composition, in particular a conductive silicone rubber composition that has good molding processability and that can be cured to a volume resistivity of 1Ω·1 without problems such as vulcanization failure. The present invention relates to a conductive silicone rubber composition that is useful as keyboards, connectors, packing materials for electromagnetic shielding, etc., since it provides silicone rubber exhibiting high conductivity as described below.

(Prior art) Silicone rubber has excellent electrical insulation, weather resistance, heat resistance, and cold resistance because the organopolysiloxane that constitutes it has a unique skeleton, and is used for various purposes. However, the volume resistivity of carbon black, graphite, metal powder such as silver, copper, nickel, metal fiber, etc. is 10r''~10-4Ω・
Because it exhibits conductivity of 1, it is also used in keyboards, connectors, and backing materials for electromagnetic shielding in desktop calculators, personal computers, watches, etc.

However, in conductive silicone rubber compositions containing conventionally known carbon black, such as acetylene black and Ketjen Black EC (trade name manufactured by Lion Akzo), the volume resistivity remains low even when the amount of carbon black is increased. It is possible to reduce the resistance to only about 2Ω·1, and addition of a large amount of carbon black increases the plasticity of the composition and impairs its fluidity, resulting in poor formability in roll processing, extrusion molding, molding, etc. This has the disadvantage of making molding difficult.

Furthermore, the sulfur contained in carbon black.

The drawbacks are that curing is impaired by impurities such as oil, resulting in poor curing, and that the resulting silicone rubber has poor mechanical strength.

On the other hand, conductive silicone rubber blended with metal powder such as silver or nickel exhibits high conductivity with a volume resistivity of about 10-4 Ω·1, but adding a large amount of this metal powder increases the specific gravity of the silicone rubber composition. Let me.

The disadvantage is that the silicone rubber is expensive, and the general physical properties of the silicone rubber obtained by curing it deteriorate, and the resistance increases due to the oxidation of the metal powder in a high-temperature atmosphere. 10 by adjusting the amount added
Although a conductive rubber having a resistance of about -1 Ω·l can be obtained, there is a drawback that the resistance value varies slightly and a stable product cannot be obtained.

(Structure of the Invention) The present invention relates to a conductive silicone rubber composition that solves the above-mentioned problems.
100 parts by weight of an organopolysiloxane having a molecular weight of 00 or more,
2) Formula R(CGH5) a≦3, b is o<b≦3, C is O≦C≦3
0.5 to 40 parts by weight of a phenyl group-containing organosilicon compound represented by O < a + b + c ≤ 4), 3) 3 to 150 parts by weight of conductive carbon black, 4) 0.1 part by weight of a curing agent.
~10 parts by weight.

That is, as a result of various studies by the present inventors in order to develop a conductive silicone rubber that does not have the above-mentioned disadvantages,
Even if carbon black is used as a conductivity imparting agent in a known organopolysiloxane composition consisting of an organopolysiloxane and a curing agent, when a phenyl group-containing organosilicon compound represented by the above formula is added to the known organopolysiloxane composition, the phenyl group has affinity with carbon black,
This organosilicon compound gathers at the carbon black interface and covers the carbon black surface, protecting the carbon black chains from the stress caused by kneading and blending, making it easy to add a large amount of carbon black. The moldability of objects is no longer impaired,
Furthermore, it was discovered that since impurities such as sulfur and oil contained in carbon black do not transfer to the organopolysiloxane, this composition does not cause curing problems, and this results in good moldability. It was confirmed that cured silicone rubber is easy to heat cure, and by adding a large amount of carbon black, it is possible to easily obtain a cured silicone rubber product with a volume resistivity of 1 Ω·1 or less.

The present invention was completed by conducting research on the amount of compounding and other factors.

The organopolysiloxane as the first component constituting the composition of the present invention has an average composition of 1SiO d 4-d 2 , where R1 is an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, A cycloalkyl group such as a cyclohexyl group, an alkenyl group such as a vinyl group or an allyl group, an aryl group such as a phenyl group or a tolyl group, or some or all of the hydrogen atoms bonded to the carbon atoms of these groups can be replaced with a halogen atom or a cyano group. The same or different unsubstituted or substituted monovalent hydrocarbons selected from chloromethyl group, trifluoropropyl group, cyanoethyl group, etc., d is 1.8 to 2.10, and generally the main It is said that the chain consists of dimethylsiloxane units, and vinyl groups, phenyl groups, trifluoropropyl groups, etc. are introduced into the main chain, but this product has a degree of polymerization of 1.
If the degree of polymerization is less than 00, the mechanical strength after curing will be poor and it will become very brittle, so it is necessary to have a degree of polymerization of 100 or more.

Next, the phenyl group-containing organosilicon compound as the second component in the composition of the present invention is represented by the formula %, where R is the same or different unsubstituted or Substituted monovalent hydrocarbon, X
is a hydrogen atom, a hydroxyl group, or an alkoxy group such as a methoxy group, an ethoxy group, or a propoxy group, an acetoxy group, an amino group, an aminoxy group, a ketoxime group, an amide group, or a hydrolyzable group such as an alkenyloxy group; b
, c is 0≦a≦3, o<b≦3, O≦C≦3 and 0<
It is assumed that a + b + C ≦ 4, but if the viscosity is too high, it will be difficult to obtain the effects described later, so it is preferable that the kinematic viscosity is 1.0 OOcS or less, and the following Examples include organosilanes and organopolysiloxanes.

(CHi) (C-Hs)z 5iH1 (aH3) (csHs)z 5xOH1 (CH3) (C
,H,)Si(OCCH,), .

(C,Hs)Si(N(CHa)Ji,CH.

(CH,)(C6H5), 5L-0-8L-0-Si(
C, R5)2(CHI), CH.

(CH,)□SL (0-8i(CH3)(C,H,)
)40 Si (CHa)200-8i (CH3
),, (cH3)3Sx(o 5t(CsHs)zsuzenHtsu-5i(CH3),+-0-8i(CH,)3,(
C,H,)Si-EO-3L(CH,),Hte, ,(
C,H,)Si(OC2H5)3,(CH,)(C
,H,), 5i-0-8i(C,H,), (CH,).

Note that if the amount of this phenyl group-containing silicon compound is 0.5 parts by weight or less based on 100 parts by weight of the organopolysiloxane as the first component, it is too small and the carbon black as a conductive material to be described later. If the amount exceeds 40 parts by weight, the composition will have poor workability and the mechanical strength of the cured product obtained by curing it will decrease. .

- Since surface blooming also occurs, a range of 0.5 to 40 parts by weight is required, with a preferred range of 1 to 10 parts by weight.

Furthermore, the conductive carbon black as the third component in this composition is added to impart conductivity to the cured silicone rubber product made from this composition, and it is used for this purpose. These include Palcan C, Palcan SC, Palcan P, Palcan XC-72 (trade name manufactured by Cabot Corporation in the United States), Continex CF, Continex 5CF (trade name manufactured by Continental Carbon Corporation in the United States). ], Asahi H3-50
0 [Asahi Carbon Co., Ltd. product name], Ketjen Black EC
, Ketjen Black EC-DJ600 (manufactured by Lion Akzo Co., Ltd.), Denka Black (Denka Kagaku Kogyo product name), etc. Among these, it has a large specific surface area, so it has excellent conductivity with a small amount of filling. Preferably, Ketjenblack EC-DJ600, which exhibits high conductivity, is preferred.If the amount of the third component added is 3 parts by weight or less based on 100 parts by weight of the organopolysiloxane as the first component, the desired conductivity cannot be achieved. is not obtained, and if the amount exceeds 150 parts by weight, it becomes difficult to blend and the moldability of the composition decreases.
Since the mechanical strength of the cured product obtained after curing also becomes poor, the amount needs to be in the range of 3 to 150 parts by weight.

The curing agent as the fourth component in this composition is added to harden this composition, and it is a hardening agent that is added in order to harden this composition. -2,5-di(t-butylperoxy)hexane, dicumyl peroxide, etc. may be used, but in this case, the organopolysiloxane as the first component is converted into a vinyl group-containing organopolysiloxane, and then the vinyl group is added to the organopolysiloxane containing vinyl groups. It may be made of an organohydrodienepolysiloxane having a hydrogen atom bonded to a silicon atom (=iSiH bond) that undergoes an addition reaction with a platinum-based catalyst. Contains an alkoxy group, an acetoxy group, which undergoes a condensation reaction with this silanol group,
An organic silicon compound containing a hydrolyzable group such as a ketoxime group may be added. Furthermore, this fourth
The amount of the curing agent added as a component may be such as to harden this composition, but this range is from 0.1 to 10 parts by weight based on 100 parts by weight of the organopolysiloxane as the first component. Bye.

The conductive silicone rubber composition of the present invention includes the above-described first to
It can be obtained by uniformly mixing the fourth component, which is optionally filled with reinforcing silica such as silica hydrogel (hydrated silicic acid), silica aerogel (anhydrous silicic acid), M, L-type silica, etc. It is optional to add and mix fillers such as clay, calcium carbonate, diatomaceous earth, and titanium dioxide, and heat resistance improvers such as iron oxide and cerium oxide.

The composition of the present invention obtained as described above is characterized by the addition of a phenyl group-containing organosilicon compound as a second component. This substance is said to contain a group, and this substance covers the surface of the carbon black particles, which makes it possible to add a large amount of carbon black, even up to 1f50 parts by weight. The volume resistivity of the cured silicone rubber product can be lowered to 1Ω·1 or less, and the processability of this product does not deteriorate even when a large amount of carbon black is added, and furthermore, Since sulfur, oil, etc. contained in the composition do not migrate into the organopolysiloxane as the first component, the composition has the advantage that these impurities do not cause problems such as poor curing of the composition. As mentioned above, by adding a large amount of carbon black, the volume resistivity of the cured product can be lowered to 1Ω・1 or less, so this cured product can be used in various electrical and electronic parts such as keyboards, connectors, and even electromagnetic waves. It has industrial advantages in that it can be used as a backing material for a shield, a one-sided heating element, an electrode roll for a copying machine, an elastic electrode, etc.

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

Examples 1-3. Comparative Example 1 Methylvinylpolysiloxane 100 consisting of 99.7 mol% dimethylsiloxane units and 0.3 mol% methylvinylsiloxane units and having an average degree of polymerization of about s, ooo
Phenyl group-containing organosilicon compounds (A) [kinematic viscosity 170 cS), (B) [kinematic viscosity 30 cS), (C
) [kinematic viscosity 100 cS] and carbon black Ketjenblack EC-DJ600 (mentioned above) were added in the amounts shown in Table 1 and kneaded with two rolls.
0.8 part of dimethyl-2,5-di(t-butylperoxy)hexane was added and homogenized to form siloxane compositions 1 to 1.
For comparison, a siloxane composition (2) was prepared in the same manner as above except that the above-mentioned phenyl group-containing organosilicon compound was not added.

Next, these siloxane compositions I~■ were heated to □170°C.
X30kg/c! A sheet with a thickness of 1 m was made by compression molding for 10 minutes under the conditions of J, and then heated at 200°C in a dryer.
When the volume resistivity of the sample obtained by heat treatment for 4 hours was measured, the results shown in Table 1 were obtained, and the results show that the addition of the phenyl group-containing organosilicon compound increases the volume resistivity of the cured product. It was confirmed that it was effective in reducing the rate.

Table 1 Note that in Examples 1 and 2 above, the amount of the phenyl group-containing organosilicon compounds (A) and (B) varied from 5 parts to 2 parts.
When treated in the same manner as in Example 1 and Example 2 except that the volume resistivity of the cured product was changed to 9.1Ω,
・Bi, 9.40・Bi, but the average of 100 parts of the above methylvinylpolysiloxane was combined with 70 parts of this methylvinylpolysiloxane (average degree of polymerization 8,000) and the molecular chain terminals were blocked with dimethylvinylsilyl groups. The degree of polymerization is about 5
A mixture with 30 parts of dimethylpolysiloxane 00,
Add to this the phenyl group-containing organosilicon compound (A) described above.
Part 5 and Carbon Black Ketjen Black EC-D
After adding 08 parts of J600 and kneading with two rolls, 8 parts of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane was added thereto to homogenize the resulting siloxane composition. When the volume resistivity of the sample obtained by heat treatment at ℃ for 4 hours was measured, it was 9.3Ω・
It showed a value of 1.

Examples 4-5, Comparative Examples 2-3 Methyl vinyl polysiloxane 100 consisting of 99.85 mol% dimethylsiloxane units and 0.15 mol% methylvinylsiloxane units and having an average degree of polymerization of about s, o o o 5 parts of the phenyl group-containing organosilicon compound (A) used in Example 1 and carbon black Palkan P
After adding 50 parts or 70 parts (as mentioned above) and kneading with two rolls, 1.0 part of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane was added and mixed uniformly. Siloxane compositions (1) and (2) were prepared, and for comparison, siloxane compositions (1) and (2) were also prepared in the same manner as above except that the above-mentioned phenyl group-containing organosilicon compound was not added.

Next, these compositions (1) and (2) were treated in the same manner as in Examples 1 to 3 to prepare samples, and the volume resistivity was measured.
The results shown in Table 2 were obtained, and these results confirmed that the addition of a phenyl group-containing organosilicon compound can lower the volume resistivity of the cured product and suppress curing failure. It was done.

Table 2 Examples 6 to 7, Comparative Example 4 Methylvinyl poly, consisting of 99.7 mol% dimethylsiloxane units and 0.3 mol% methylvinylsiloxane units, with an average degree of polymerization of about s, o o o. 100 parts of siloxane, phenyl group-containing organosilicon compound (A) or (B) used in Examples 1 and 2, and carbon black.
Ketjen Black EC-DJ600 (mentioned above) was added in the amount shown in Table 3 and kneaded with two rolls to make Compounds 1 and 2, and no phenyl group-containing organosilicon compound was added. is processed in the same manner as above to make Compound 3, and then the lever compounds 1 to 3 are processed using a Koka-type flow tester (manufactured by Shimadzu Corporation) to form a compound with a diameter of 1.
rIn, flowing out from a nozzle with a length of 1 rrn under a load, and its apparent viscosity was measured.

The results shown in Table 3 were obtained.

Next, an isopropyl alcohol solution of chloroplatinic acid (platinum amount: 2% by weight) is added to 1 to 3,100 parts of these compounds.
0.1 part of acetylene alcohol and 0.05 part of acetylene alcohol and 1.0 part of methylhydrodiene polysiloxane of the formula
% and mixed uniformly to make siloxane compositions ① to M. These were compression molded for 10 minutes at 150°C xaokg/aJ to create a sheet with a thickness of lll11. When we measured the volume resistivity of the sample obtained by heat treatment for a period of time, we obtained the results as listed in Table 3. From these results, it was found that the addition of a phenyl group-containing organosilicon compound lowers the apparent viscosity. It was confirmed that the processability was improved and that the volume resistivity could be lowered to 1Ω·1 or less.

Table 3 Comparative Example 5 100 parts of silicone rubber compound KE-520U (Shin-Etsu Chemical Co., Ltd., product name) was mixed with silver glass beads-8-3,000-83 [glass beads coated with silver].
250 parts of Toshiba Baroty 2 Co., Ltd. product name] was added as a conductivity imparting agent, and after kneading with two rolls, 2,5-
Add 0.8 parts of dimethyl-2゜5-di(t-butylperoxy)hexane and mix uniformly to prepare a siloxane composition, which was compressed for 10 minutes at 170°C and 30 kg/aJ. Form into a sheet with a thickness of 15 in.
The initial resistance of the sample obtained by heat treatment at 0°C for 2 hours and the sample in Example 6 described above and the initial resistance of the sample obtained by heat treatment at 200°C for 2 hours
When the resistance value after 0 hours of heat treatment was opened, the fourth
The results shown in the table were obtained, and the results showed that carbon-based conductive rubber to which a phenyl group-containing organosilicon compound was added had a higher initial resistance than metal-based conductive rubber; It was confirmed that there was no change in resistance over time with almost no damage.

Table 4

Claims (1)

[Claims] 1. 1) 100 parts by weight of an organopolysiloxane having an average degree of polymerization of 100 or more; 2) Formulas ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (where R is the same or different unsubstituted or a substituted monovalent hydrocarbon group; X is a hydrogen atom, a hydroxyl group, or a hydrolyzable group; a is 0≦a≦3; b is 0<b≦3;
0.5 to 40 parts by weight of a phenyl group-containing organosilicon compound represented by 0<a+b+c≦4). 3) 3 to 150 parts by weight of conductive carbon black. 4) A conductive silicone rubber composition comprising 0.1 to 10 parts by weight of a curing agent.