JP2002212426A - Conductive silicone rubber composition and conductive part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive silicone rubber composition less vulnerable time-dependent coagulation because it uses spherical silver particles and achieving stable volume resistivity when added to a silicone rubber composition because it is excellent in dispersability and to provide conductive parts particularly excellent in resistance stability when subjected to repeated deformation because the silver particles are high in dispersability and therefore less prone to fall away. SOLUTION: The conductive silicone rubber composition is characterized in that it contains 100 pts.wt. of (A) organopolysiloxane described by average composition formula (1), R1nSiO(4-n)/2, (wherein R1 denotes identical or different optionally substituted monohydric hydrocarbon groups, with n is a positive number of 1.98-2.02) and provided with at least two unsaturated aliphatic groups, (B) 500-2,000 pts.wt. of spherical silver particles, and (C) a hardener enough in quantity to harden component (A).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a conductive silicone rubber composition and a conductive component using the same.

[0002]

2. Description of the Related Art Since silver powder has a high electric conductivity, an addition-curable silicone rubber composition, a condensation-curable silicone rubber composition, a peroxide-cured silicone rubber composition and the like are used. As a conductive filler of the silicone rubber composition. A silicone rubber composition containing silver powder is cured to form a low-resistance silicone rubber, and is therefore used in fields requiring heat resistance and conductivity. In general, silver powder used in a silicone rubber composition has a higher-order structure such as a flake shape or a grape shape in order to obtain a low electric resistance value with a small amount of addition.

[0003] However, these silver powders have a strong agglomeration and cannot be added to the silicone rubber composition when stored for a long time, or when the obtained conductive parts are repeatedly deformed, There was a problem that the higher-order structure of the silver powder was broken and the resistance value was increased.

[0004] The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a conductive silicone rubber composition that provides a cured product having a stable electric resistance even after repeated deformation, and a conductive component using the same.

[0005]

Means for Solving the Problems and Embodiments of the Invention The present inventors have conducted intensive studies in order to achieve the above object, and as a result, it has been found that spherical silver powder can be blended into a silicone rubber composition as silver powder. Effective, spherical silver powder is less agglomerated with time, and when blended into a silicone rubber composition, has excellent dispersibility, so that a stable volume resistivity can be obtained, especially conventional flake silver powder, grape-like The present inventors have found that a stable and low electric resistance value can be obtained even after repeated deformation as compared with the case where silver powder is added, and have accomplished the present invention. That is, conventionally, as a technique for obtaining a low resistance by adding silver powder, the shape of the silver powder is dendritic, flake, irregular,
Grapes are considered to be good, and a mixture of silver powders having these shapes may be used.However, in order to form a low-resistance silicone rubber, dispersion is not completely independent, and silver powder is partially dispersed. It is desirable to be connected. However, when using silver powders having these higher-order structures, deformation of the conductive parts breaks the structure of the silver powder inside, and thus increases the resistance value. By using this, such a problem was solved, and a silicone conductive component having stable conductivity could be obtained.

Accordingly, the present invention relates to (A) the following average composition formula (1): R ¹ _n SiO _{(4-n) / 2} (1) (wherein, R ¹ is the same or different unsubstituted or substituted 1 And n is a positive number from 1.98 to 2.02), and an organopolysiloxane having at least two aliphatic unsaturated groups: 100 parts by weight, (B) spherical silver Powder: 500 to 2,000 parts by weight, (C) curing agent:
(A) Provided is a conductive silicone rubber composition containing an amount capable of curing the component.

The present invention also provides a conductive part made of a cured product of the conductive silicone rubber composition.

Hereinafter, the present invention will be described in more detail.

The organopolysiloxane as the component (A) of the silicone rubber composition according to the present invention is represented by the following average composition formula (1). R ¹ _n SiO _{(4-n) / 2} (1) (wherein, R ¹ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and n is a positive number of 1.98 to 2.02) Is.)

In the above formula, R ¹ is an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a cycloalkyl group such as a cyclohexyl group, a vinyl group, an allyl group, a propenyl group. Group, butenyl group,
Alkenyl groups such as hexenyl groups, phenyl groups, aryl groups such as tolyl groups, benzyl groups, aralkyl groups such as phenylethyl groups, and the like, and some or all of the hydrogen atoms bonded to carbon atoms of these groups are halogen atoms, The same or different, preferably unsubstituted or substituted monovalent carbon having 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms selected from a chloromethyl group, a trifluoropropyl group, a cyanoethyl group and the like substituted with a cyano group and the like. It is a hydrogen group. Particularly preferred are a methyl group, a vinyl group, a phenyl group and a trifluoropropyl group. In this case, R ¹ needs to have at least two aliphatic unsaturated groups (alkenyl groups), and the content of the aliphatic unsaturated group in R ¹ is 0.001 to 2
It is preferably 0 mol%, particularly preferably 0.025 to 5 mol%. N is a positive number between 1.98 and 2.02. The organopolysiloxane of the above formula (1) is preferably basically linear, but may be one or a mixture of two or more compounds having different molecular structures. Further, the organopolysiloxane has an average degree of polymerization of 100 to 20,000.
It is preferably 0. In particular, when a liquid composition is used, the average degree of polymerization is 100 to 3,000, preferably 50 to 3,000.
When the composition is a millable composition, the average degree of polymerization is 3,000 to 20,000, preferably 4,000.
0 to 10,000.

Next, the spherical silver powder of the component (B) may be spherical as long as the primary particles are spherical, but the higher order structure (aggregation) obtained by aggregating the primary particles is spherical. There may be. It is to be noted that there is no problem even if several spherical silver powders are collected and some of them are in a ball shape. In this case, the spherical silver powder has an aspect ratio of 2 or less, more preferably 1.
It is preferably 5 or less, more preferably 1.3 or less. Furthermore, the specific surface area of the silver powder is preferably 1.0 m ² / g or less, particularly preferably 0.8 m ² / g or less, in order to obtain resistance stability particularly during repeated deformation. Also,
The average particle size is not particularly limited, and may be in the range of 0.05 to 100 μm.
m, particularly preferably 0.2 to 5 μm.

The amount of the spherical silver powder is 100 parts by weight of the organopolysiloxane (A) (parts by weight, the same applies hereinafter).
500 to 2,000 parts, preferably 700 to 1,
500 parts, especially 800 to 1,000 parts. If the amount of the spherical silver powder is too small, sufficient conductivity may not be obtained. If the amount is too large, the compounding may be difficult or the mechanical strength may be reduced.

The method for producing a spherical silver powder of the present invention comprises:
There is no particular limitation, and any spherical powder produced by, for example, an electrolytic method, a pulverizing method, a heat treatment method, an atomizing method, or a chemical manufacturing method may be used.

When the silver powder is agglomerated, it is preferable to pulverize the agglomerated silver powder. The apparatus for pulverizing the agglomerated silver powder is not particularly limited. For example, a stamp mill, a ball mill, a vibration mill, a hammer mill, Known devices such as a rolling roller and a mortar can be used. Alternatively, silver powder composed of reduced silver, atomized silver, electrolytic silver or a mixture of two or more of these may be ground.

The curing agent of the component (C) is vulcanized and cured by utilizing a radical reaction, an addition reaction, a condensation reaction or the like with an organic peroxide usually used for vulcanizing a conductive silicone rubber composition. The curing mechanism is not limited as long as it is one, and various conventionally known curing agents can be used, but crosslinking by an organic peroxide and an addition reaction is preferable.

For example, in the case of organic peroxide crosslinking, examples of the organic peroxide catalyst include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-
Methylbenzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dicumyl peroxide,
Examples thereof include 2,5-dimethyl-bis (2,5-t-butylperoxy) hexane, di-t-butyl peroxide, and t-butyl perbenzoate. The amount of the organic peroxide catalyst to be added may be 0.1 to 5 parts based on 100 parts of the organopolysiloxane (A).

In addition, in the case of addition reaction crosslinking, a known organohydrogenpolysiloxane / platinum-based catalyst can be used. In this case, a known catalyst can be used as the platinum-based catalyst. Specifically, a platinum element simple substance, a platinum compound, a platinum complex, chloroplatinic acid, an alcohol compound of chloroplatinic acid,
Examples thereof include aldehyde compounds, ether compounds, and complexes with various olefins. The amount of the platinum-based catalyst to be added is desirably in the range of 1 to 2,000 ppm as platinum atoms with respect to the organopolysiloxane of the first component.

On the other hand, the organohydrogenpolysiloxane has at least two hydrogen atoms directly bonded to silicon atoms.
It not particularly limited as long as it has more than five, linear, branched, may or cyclic, R ² _a H _b Si
O _{(4-ab) / 2} (R ² is the same unsubstituted or substituted monovalent hydrocarbon group as R ¹ and preferably does not have an aliphatic unsaturated bond. A and b are 0 ≦ a <3, 0 <b <3, 0 <a
+ B <3. ) Are preferable, and those having a polymerization degree of 300 or less are particularly preferable. In particular,
Diorganopolysiloxane having a terminal blocked by a dimethylhydrogensilyl group, a copolymer of a dimethylsiloxane unit, a methylhydrogensiloxane unit and a terminal trimethylsiloxy unit, a dimethylhydrogensiloxane unit (H (CH ₃ ) ₂ SiO _0.5 Unit) and SiO ₂
Low-viscosity fluid consisting of units, 1,3,5,7-tetrahydrogen-1,3,5,7-tetramethylcyclotetrasiloxane, 1-propyl-3,5,7-trihydrogen-1, Examples thereof include 3,5,7-tetramethylcyclotetrasiloxane and 1,5-dihydrogen-3,7-dihexyl-1,3,5,7-tetramethylcyclotetrasiloxane.

The amount of the organohydrogenpolysiloxane as the curing agent is such that the hydrogen atoms directly bonded to silicon atoms are 50 to 500 with respect to the aliphatic unsaturated groups (alkenyl groups) of the organopolysiloxane of the first component. It is desirable to use the compound in a ratio of mol%.

When the organopolysiloxane contains a hydroxyl group, a polyfunctional alkoxysilane or siloxane and a tin or titanium organic metal salt can be used as the condensation curing agent. Note that the amount of the curing agent added may be the same as that of a normal conductive silicone rubber composition.

The silicone rubber composition may contain, if necessary, a filler such as silica, clay, calcium carbonate, diatomaceous earth, or titanium dioxide, a low-molecular siloxane ester, diphenylsilanediol, α, ω-
Silanol group-containing low molecular weight organosilicon compounds such as dimethylsiloxane diol, etc., dispersants, heat resistance improvers such as iron oxide, cerium oxide, iron octylate, etc., and various carbon functional silanes for improving adhesion and moldability. Alternatively, a platinum compound or the like for imparting flame retardancy may be added and mixed.

Further, an inorganic material for forming a sponge;
An organic foaming agent may be added. As this blowing agent,
Examples thereof include azobisisobutyronitrile, dinitropentamethylenetetramine, benzenesulfone hydrazide, and azodicarbonamide, and the amount of addition is preferably in the range of 1 to 10 parts with respect to 100 parts of the organopolysiloxane (A). . Thus, when a foaming agent is added to the composition of the present invention, a sponge-like conductive silicone rubber can be obtained.

The conductive silicone rubber composition of the present invention comprises:
The volume resistivity of the cured product is 1 × 10 ^-FiveΩcm or less,
Volume resistivity of initial and restored after 50% elongation
Is 100 or less, especially 10 or less, especially 5 or less.
Is preferred.

The cured product can be suitably used as an electric contact material such as an electric switch and a connector, and a conductive component such as an electromagnetic wave shielding material.

[0025]

EFFECT OF THE INVENTION The conductive silicone rubber composition of the present invention uses a spherical silver powder, so that there is little agglomeration over time, and when it is blended into a silicone rubber composition, it has excellent dispersibility, so that it has a stable volume. The resistivity can be obtained.
In addition, since the silver powder is well dispersed, it is possible to obtain a conductive component in which the silver powder is less likely to fall off, which has particularly excellent resistance stability during repeated deformation.

[0026]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following examples, all parts are parts by weight.

Examples 1 and 2, Comparative Examples 1 to 3 The average degree of polymerization of 99.85 mol% of dimethylsiloxane units and 0.15 mol% of methylvinylsiloxane units is about 8.0.
00, 100 parts of methylvinylpolysiloxane, average particle size 2 μm, aspect ratio 1.1, specific surface area 0.3 m ² /
g of spherical silver powder (FIG. 1) was added as shown in Table 1, and 0.5 part of dicumyl peroxide was added.
Heating and pressurizing treatment was performed for 0 minutes to obtain a 1 mm sheet.

The electrical characteristics of this sheet were measured using SRIS-230.
After measuring according to No. 1 and then elongating by 50%, the resistance value of the restored sheet was confirmed.

Further, as Comparative Examples 2 and 3, those using AgC-BO (Fukuda metal product name, specific surface area 1.8 m ² / g) silver powder having a higher-order structure (grape shape) were used in Example 1. The characteristics when 400 and 800 parts were added to the same polymer as in Example 1 were examined. Table 1 shows the above results.

[0030]

[Table 1]

[0031]

[Brief description of the drawings]

FIG. 1 is an electron micrograph of a spherical silver powder used in Examples.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F071 AA67 AB07 AD02 AE15 AF37 AF39 AF40 AH12 BA01 BB03 BC01 BC03 4J002 CP131 CP141 DA076 EK037 EK047 FA086 FD010 FD116 FD147 GQ02 5G301 DA03 DA42 DD06 DD10

Claims (5)

[Claims] (A) The following average composition formula (1): R ¹ _n SiO _{(4-n) / 2} (1) (wherein, R ¹ is the same or different, unsubstituted or substituted monovalent hydrocarbon group) Wherein n is a positive number from 1.98 to 2.02), an organopolysiloxane having at least two aliphatic unsaturated groups: 100 parts by weight, (B) a spherical silver powder: 500 to 2,000 parts by weight, (C) curing agent:
(A) A conductive silicone rubber composition comprising an amount capable of curing the component. 2. The spherical silver powder has a specific surface area of 1.0 m ² / g.
The composition of claim 1 wherein: 3. The cured product has a volume resistivity of 1 × 10 ⁻⁵ Ω · c.
m or less, and the ratio of the volume resistivity of the initial one and the one restored after elongation by 50% is 100 or less.
A composition as described. 4. The composition according to claim 1, which is used for an electric contact material or an electromagnetic wave shielding material. 5. A conductive component comprising a cured product of the composition according to claim 1.