JPH04117457A - Silicone rubber composition and cured product - Google Patents

Abstract

PURPOSE:To prepare the title compsn. having excellent processability and workability and giving a cured article having a low hardness by compounding an organopolysiloxane, a specific organosilicon compd., and a fine silica powder as the main components. CONSTITUTION:The title compsn. is prepd. by compounding, as the main components, an organopolysiloxane of formula I [wherein R is a (substd.) monovalent hydrocarbon group and 0.0001-0.5mol% of all the R groups are alkenyl; and (a) is 1.95-2.05] having a degree of polymn. of 3000 or higher, an organosilicon compd. obtd. by reacting an organosilicon compd. of formula II [wherein R<1> is a (substd.) monovalent hydrocarbon group; X is H, alkyl, or alkoxyalkyl; 0<=b<0.2; 0<=c<0.2; and 1<d<=4] with an organopolysiloxane of formula III [wherein R<2> is a (substd.) monovalent hydrocarbon group contg. no aliph. unsatd. group; R<3> is alkenyl or (meth)acryl; Y is H, alkyl, or alkoxyalkyl; 1.8<e<2.2; 0.004<f<0.2; and 0<=g<0.2] having a degree of polymn. of 20-300 in a wt. ratio of the organosilicon compd. to the organopolysiloxane of 0.005-0.5, and a fine silica powder having a specific surface area of 50m<2>/g or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a silicone rubber composition that has excellent processability and workability and provides a cured product with low hardness, and a cured product thereof.

Silicone rubber compositions that are intended to spread are processed and molded into various shapes because the cured product has excellent heat resistance, weather resistance, durability, mold releasability, and electrical properties.・Used in various fields such as electronic parts, automobile parts, and OA equipment parts.

In recent years, silicone rubber compositions have been used in large quantities in copiers, printers, etc., especially in OA equipment that has become rapidly popular.In this field, silicone rubber compositions have excellent heat resistance, mold releasability, compression set, etc. It has become indispensable as a roll material because it gives a hardened product.

However, silicone roll materials have hardness (JI
S-A) A material with a low hardness of 40 or less is required, but a silicone rubber composition that provides a cured product with such a low hardness is
Since the silicone polymer (crude rubber) is manufactured by adding a relatively small amount of filler, there are problems in that the workability during processing and molding of the silicone rubber composition is poor and the economics of manufacturing parts is poor.

Furthermore, it is known that a silicone rubber composition with excellent physical properties can be obtained by blending a silica filler into a silicone polymer (raw rubber), but in order to blend a silica filler, it is usually necessary to Since a low-molecular organopolysiloxane having silanol groups is used as a wetter, silicone rubber compositions containing silica fillers have low plasticity and a sticky surface, making it difficult to roll and extrude. It had drawbacks such as poor performance.

Therefore, it has been desired to improve the processability and workability of low-hardness silicone rubber compositions.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a silicone rubber composition that has excellent processability and workability and provides a cured product with low hardness, and a cured product thereof.

As a result of intensive studies to achieve the above object, the inventor of the present invention found the following general formula (1) % formula % (1) (wherein R is a substituted or unsubstituted Represents a monovalent hydrocarbon group, and 0.0001 to 0.5 mol% of the entire R group is an alkenyl group. Also, a is a number in the range of 1.95 to 2.05.) For a silicone rubber composition containing an organopolysiloxane having a degree of polymerization of 3000 or more and fine powder silica having a specific surface area of 50 rrr/g or more, as a wetter, the following general formula (2) % formula % (2) (However, in the formula R1 is a substituted or unsubstituted monovalent hydrocarbon group, X is a group selected from a hydrogen atom, an alkyl group, and an alkoxyalkyl group, and bee.

d is 0≦bo0.2. O≦c<0.2゜1<d
The number is in the range of ≦4. ) and an organosilicon compound represented by the following general formula (3) % formula % (3) (wherein R2 is a substituted or unsubstituted monovalent hydrocarbon group containing no aliphatic unsaturated group, and R3 is an alkenyl group,
It is an acrylic group or a methacrylic group, Y is a group selected from a hydrogen atom, an alkyl group, and an alkoxyalkyl group, and e+f+g are 1.8<e<2.2, 0.0, respectively.
The number is in the range of 04<f<0.2°0≦g<0.2.

) and the organopolysiloxane having a polymerization degree of 20 to 500, and the compound of general formula (2)/-organopolysiloxane of general formula 3) in a weight ratio of 0.005 to 0.5.
By blending with an organosilicon compound obtained by reacting in a ratio such that
The present inventors have discovered that a silicone rubber composition can be obtained that has a small compression set and provides a cured product with low hardness, and has accomplished the present invention.

Therefore, the present invention comprises (1) an organopolysiloxane of the above formula (1) with a degree of polymerization of 3000 or more, (II) an organosilicon compound of the above formula (2), and the above (3).
An organopolysiloxane having a polymerization degree of 20 to 500 and a compound of formula (2)/compound of formula (3) in a weight ratio of 0.
A silicone rubber composition containing as main components an organosilicon compound obtained by reacting at a ratio of 0.005 to 0.5, and (m) finely powdered silica having a specific surface area of 50 rrr/g or more, and curing the same. A cured product obtained by this method is provided.

The present invention will be explained in more detail below.

The first essential component of the present invention is represented by the following general formula (1)% formula% (1
) is an organopolysiloxane represented by

Here, the R group is a substituted or unsubstituted monovalent hydrocarbon group, preferably one having 1 to 10 carbon atoms, and 0.0
It is necessary that 01 to 0.5 mol%, particularly 0.01 to 0.3 mol%, be alkenyl groups such as vinyl groups and allyl groups. If the content of this alkenyl group is less than the above range, the curability of the organopolysiloxane will be insufficient, and if it is more than the above range, the cured product obtained from the composition will not only become hard. properties (especially heat resistance) deteriorate. In addition, R groups other than the above alkenyl groups include, for example, alkyl groups such as methyl, ethyl, propyl, and butyl; cycloalkyl groups such as cyclohexyl; aryl groups such as phenyl and tolyl; benzyl, Aralkyl groups such as β-phenylethyl groups, and groups in which some or all of the hydrogen atoms bonded to the carbon atoms of these hydrocarbon groups are substituted with halogen atoms such as fluorine and chlorine, or cyano groups (for example, 3, 3.3-trifluoropropyl group, chloromethyl group, cyanoethyl group), etc.

Note that R groups other than alkenyl groups are generally methyl groups, but if cold resistance, radiation resistance, and transparency are required, up to 20 mol% of phenyl groups may be included as R groups. It is preferable that

Furthermore, when oil resistance and gasoline resistance are required, it is preferable that the R group contains a cyanoethyl group or a 3,3.3-trifluoropropyl group.

Further, in the composition formula (1), a is 1.95 to 2.
05, preferably 1.98 to 2.01. Organopolysiloxanes with a of less than 1.95 are difficult to synthesize with a degree of polymerization of 3,000 or more, and
It is not easy to stably synthesize organopolysiloxanes with a polymerization degree of 3,000 or more with good reproducibility for organopolysiloxanes having a polymerization degree of more than 2.05.

In order to provide sufficient mechanical strength, this organopolysiloxane has a degree of polymerization of 3,000 or more, preferably 5.0.
00 to 10,000.

The organopolysiloxane used in the present invention is substantially composed of diorganopolysiloxane units, but may also contain small amounts of triorganosiloxy units, monoorganosiloxane units, and Sin units, and may also contain molecular chains. The terminal may be blocked with a hydroxyl group or a triorganosiloxy unit.

In the present invention, the following general formula % formula % (2
) (However, in the formula, R1 is a substituted or unsubstituted monovalent hydrocarbon group, X is a group selected from a hydrogen atom, an alkyl group, and an alkoxyalkyl group, and b, a.

d is 0≦bo0.2. O≦c<0.2゜1<d
The number is in the range of ≦4. ) and an organosilicon compound represented by the following general formula (3)% formula (3) (wherein R2 is a substituted or unsubstituted monovalent hydrocarbon group containing no aliphatic unsaturated group, and R1 is an alkenyl group,
It is an acrylic group or a methacrylic group, Y is a group selected from a hydrogen atom, an alkyl group, and an alkoxyalkyl group, and e+ f9g is 1.8<e<2.2, 0.
The number is in the range of 004<f<0.2°0≦g<0.2. ) An organosilicon compound obtained by reacting with an organopolysiloxane having a polymerization degree of 20 to 500 is blended. This organosilicon compound is effective as a wetter component when compounding the first essential component described above and the third essential component described later, and in the present invention, as described above, the compound of formula (2) and the third essential component (3 By blending an organosilicon compound which is reactively bonded with a compound of the formula ), a composition having good extrusion moldability and low compression set can be obtained. In this case, if the compound of formula (2) and the compound of formula (3) are simply mixed but not reacted together, good extrusion moldability and low compression set will not be obtained, thus defeating the object of the present invention. It cannot be achieved.

Here, R1 in formula (2) preferably has 1 to 10 carbon atoms, and includes, for example, an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a vinyl group, an allyl group, a butenyl group, etc. Aryl groups such as alkenyl groups, phenyl groups and tolyl groups, cycloalkyl groups such as cyclohexyl groups, aralkyl groups such as benzyl groups and β-phenylethyl groups, or part or all of the hydrogen atoms bonded to carbon atoms of these groups. is the same or different unsubstituted or substituted monovalent hydrocarbon group selected from chloromethyl group, γ-trifluoropropyl group, cyanoethyl group, etc. substituted with a halogen atom, cyano group, etc., and X is a hydrogen atom, methyl group,
An alkyl group having preferably 1 to 6 carbon atoms, such as an ethyl group or a propyl group, and an alkoxy group, preferably having 1 to 6 carbon atoms, such as a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, or an ethoxyethyl group. Carbon number is 1~
It is a group selected from 6 alkoxyalkyl groups. Also, b is O≦b<0.2, preferably 0≦b<0.1, C
is O≦c<0.2, preferably O≦c<0.1, d is 1
<d≦4, preferably 2<d<3.

Furthermore, R2 in formula (3) is a substituted or unsubstituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated group, preferably having 1 to 1 carbon atoms.
For example, alkyl groups such as methyl group, ethyl group, propyl group, butyl group; cycloalkyl groups such as cyclohexyl group; aryl groups such as phenyl group and tolyl group; benzyl group, β-phenylethyl group, etc. aralkyl groups, and groups in which some or all of the hydrogen atoms bonded to the carbon atoms of these hydrocarbon groups are substituted with halogen atoms such as fluorine and chlorine, or cyano groups (for example, 3,3゜3-trifluoro propyl group, chloromethyl group, cyanoethyl group)
Preferably, 50% or more of R2 is a methyl group. Further, R3 is preferably an alkenyl group having 2 to 4 carbon atoms such as a vinyl group, an allyl group, a butenyl group,
It is an acrylic group or a methacrylic group, and Y is the same hydrogen atom as X, an alkyl group such as a methyl group, an ethyl group, or a propyl group, or a methoxymethyl group or a methoxyethyl group.

It is a group selected from alkoxyalkyl groups such as ethoxymethyl group and ethoxyethyl group. Note that X and Y may be the same or different.

Furthermore, e is 1.8<e<2.2, preferably 1.95<
e<2.05, f is a number in the range of 0.004<f<0.2, preferably 0.005<f<0.1, g is a number in the range of 05g<0.2, preferably 05g<0.1. be.

Note that the organopolysiloxane of formula (3) may substantially contain diorganopolysiloxane units, monoorganosiloxane units, and 5i02 units, but this may include 0.02 to 502 units of the total organic groups. Preferably, the 20 mole percent contains alkenyl groups such as vinyl groups. If the alkenyl group content is less than 0.02 mol%, the desired low compression set properties may not be obtained, and if it exceeds 20 mol%, the resulting silicone rubber will have high hardness. , heat resistance may decrease.

Furthermore, the degree of polymerization of this organopolysiloxane is 20 to 5.
00, preferably 40 to 200, but good extrudability cannot be obtained outside this range.

The organosilicon compound of the formula (2) and the organopolysiloxane of the formula (3) have a weight ratio of compound of the formula (2)/(3).
0.005 to 0.5, preferably 0.05
They are mixed and reacted at a ratio of ~0.3.

Furthermore, as a method for reacting the compound of formula (2) with the compound of formula (3), for example, a siloxane unit having a hydrosilyl group is introduced into the organosilicon compound of formula (2) under acid equilibrium, and then the compound of formula (3) is reacted with the compound of formula (3). ) A method of addition-reacting an alkenyl group of an organopolysiloxane of the formula in the presence of platinum, (2)
The hydroxyl group or alkoxy group of the organosilicon compound of the formula and (3
Examples include a method of dehydrating or dealcoholizing the terminal alkoxy group or hydroxyl group of the organopolysiloxane of the formula (2), but the method is not limited to these methods.

The amount of the organosilicon compound, which is the second essential component, is preferably 0.1 to 20 parts by weight, particularly 1 to 10 parts by weight, based on 100 parts by weight of the organopolysiloxane, which is the first essential component. If the blending amount is less than 0.1 part by weight, fine powder silica, which is the third essential component, may not be properly blended, and if it exceeds 20 parts by weight, the physical properties of the silicone rubber composition after curing may deteriorate. It may be stored away.

Next, finely powdered silica, which is the third essential component of the present invention, is blended as a filler.This finely powdered silica is used to impart appropriate hardness to the cured product of the silicone rubber composition, and also to provide tensile strength. In order to improve mechanical strength such as strength, BET specific surface area is 50 resistance/g or more, preferably 1
00 to 400rd/g is used.

Furthermore, fine powder silica has an average particle size of its primary particles of 0.0.
05-10-1, particularly preferably 0.01-14.

Specific examples of such fine powder silica include fumed silica, calcined silica, precipitated silica, etc., and one type of these may be used alone or two or more types may be used in combination.

Further, these finely powdered silicas may be surface-treated with, for example, linear organopolysiloxane, cyclic organopolysiloxane, hexamethyldisilazane, dichlorodimethylsilane, or the like. Incidentally, the surface treatment can be performed by a normal method.

The amount of finely powdered silica blended is preferably 5 to 100 parts by weight, particularly 10 to 50 parts by weight, per 100 parts by weight of the organopolysiloxane, which is the first essential component. , even if a small amount is added,
The processability of the silicone rubber composition may deteriorate, or a cured product with sufficient mechanical strength may not be obtained.

The method of compounding the silicone rubber composition of the present invention is not particularly limited, but usually, the above-mentioned essential components are charged into a mixer such as a kneader, blended at room temperature, and then mixed at room temperature.
It can be obtained by heat treatment at a temperature of 00 to 200°C for 1 to 5 hours.

Further, the silicone rubber composition of the present invention can be cured by a conventionally known method utilizing a hydrosilylation reaction, a method of vulcanization using an organic peroxide as a catalyst, or the like.

When the composition of the present invention is cured using a hydrosilylation reaction, it is preferable to use a combination of an organohydrodiene polysiloxane and a platinum group metal catalyst as a curing agent. In this case, the organohydrodiene polysiloxane may be any organopolysiloxane having two or more SiH groups in the molecule, linear,
It may be either cyclic or branched. Moreover, such a SiH group may be located at the end of the polysiloxane chain or may be located in the middle. Such organohydrodiene polysiloxane is preferably used in an amount such that the proportion of SiH groups is 0.5 to 3 mol, particularly 1 to 2 mol, per mol of alkenyl group of the organopolysiloxane of formula (1). .

Furthermore, the platinum group metal catalyst used at the same time acts as a catalyst for the hydrosilylation reaction between the alkenyl group in the organopolysiloxane of formula (1) and the SiH group in the organohydrodiene polysiloxane, ( 1) Usually 0°1 to 11000 relative to the total amount of organopolysiloxane and organohydrodiene polysiloxane of formula
pp, especially 1 to 10100 pp as platinum metal). Such platinum group metal catalysts include, for example, the finely powdered metal platinum catalyst described in U.S. Pat. No. 2,970,150, the chloroplatinic acid catalyst described in U.S. Pat. No. 2,823,218, and the Patent No. 3.159
, 601 and 3,159,662, U.S. Pat. No. 3,516,9
46, U.S. Pat. No. 3,775,452 and U.S. Pat. No. 3,814
The platinum-vinylsiloxane complex described in No. 780, etc., can be used.

When the composition of the present invention is cured by a hydrosilylation reaction, a reaction control agent such as methylvinylcyclotetrasiloxane or acetylene alcohol is added to ensure good storage stability at room temperature and maintain an appropriate pot life. It is desirable to carry out the hydrosilylation reaction at 60
It is preferable to carry out heating at a temperature of ~400°C for about 1 minute to 5 hours.

In addition, when an organic peroxide is used as a catalyst, the organic peroxide is usually 0.01 to 3 parts by weight, particularly 0.05 to 1 part by weight, per 100 parts by weight of organopolysiloxane.
It can be cured by heating at a temperature of 100 to 400°C for about 1 minute to 5 hours. As the organic peroxide, any organic peroxide that is commonly used for curing peroxide-curable silicone rubber can be used without particular limitation, such as benzoyl peroxide, bis(2,
4-dichlorobenzoyl) peroxide, di-t-butyl peroxide, 2,5-dimethyl-di-t-butyl peroxyhexane, t-butyl perbenzoate,
Examples include t-butylperoxyisopropyl carbonate and dicumyl peroxide, and these may be used alone or in combination of two or more.

The composition of the present invention may contain a known rubber compounding agent which is appropriately blended into a silicone rubber composition. Examples of rubber compounding agents include crushed silica, diatomaceous earth, iron oxide, zinc oxide, titanium oxide, carbon black, barium oxide, magnesium oxide, cerium hydroxide, lucium carbonate, magnesium carbonate, zinc carbonate, asbestos, and glass wool. , fine mica powder, fused silica powder, etc. Furthermore, if necessary, pigments, dyes, anti-aging agents, antioxidants, antistatic agents, flame retardants such as antimony oxide and chlorinated paraffin, and thermal conductivity improvers such as boron nitride and aluminum oxide may be added. There is no problem.

The silicone rubber composition of the present invention has good extrudability,
It has excellent processability and workability, and provides a cured product with low compression set and low hardness, and is useful as a roll material for office automation equipment such as copying machines and printers. Furthermore, since the silicone rubber composition of the present invention has a high Williams plasticity, it is suitable as a material for extrusion molding of construction gaskets, fax rolls, medical tubes, etc., as well as rubber contacts, nipples, constant velocity joint boots, etc. , plug boots,
It is also suitable as a material for anode caps, electric wires, etc.

<Examples, Comparative 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 addition, in the following examples, all parts are parts by weight.

[Example 1] 1 to 10 parts of ethyl silicate 40 (manufactured by Colcoat ■)
3.5,7-titramethylcyclotetrasiloxane 0.
6 parts of trifluoromethanesulfonic acid and an additional 110 parts of trifluoromethanesulfonic acid.
00 pp was added and stirred for 4 hours under a nitrogen stream. Next, the mixture was neutralized with sodium hydrogen carbonate, filtered through magnesium sulfate, and then diluted with toluene.

This is (CHa) a S 1 part unit 96.92 rin O1%
and block both ends (CH□)2 (CHz = C
H) Dropped into a mixed solution heated to 100°C of 50 parts of organopolysiloxane (degree of polymerization 65) consisting of 3.08 mo1% of 0.7 parts of Sx and chloroplatinic acid octyl alcohol solution (containing 1100 ppp of platinum). did.

Then, toluene was stripped off at 100° C. under a reduced pressure of 10 Torr to obtain a product. Two parts of the obtained product (
CH3) 25iO units 9'9, 825 mo1%.

(CH3)(CH2=CH)SiO unit 0.15mol1
%.

(CH3)Z(CH2=CH)SiO,, 2 units 0.0
25 mo1% of organopolysiloxane raw rubber with an average degree of polymerization of 8000, and further added to this is dimethylpolysiloxane with terminal silanol group (degree of polymerization 10).
) and 320 parts of Aerosil 200 (trade name: Fuumedo Shiriyoku, manufactured by Nippon Aerosil ■) were added, kneaded in a kneader, and heat-treated at 150° C. for 2 hours to prepare base compound 1.

[Example 2] 1.0 parts to 10 parts of ethyl silicate 40 (manufactured by Colcoat ■).
3,5.7-titramethylcyclotetrasiloxane 0.
Add 6 parts of trifluoromethanesulfonic acid and add 11 parts of trifluoromethanesulfonic acid.
000pp was added and stirred for 4 hours under a nitrogen stream6.
Next, the mixture was neutralized with sodium hydrogen carbonate, filtered through magnesium sulfate, and then diluted with toluene.

This is (CH3), 98.57 mo1% of Si○ units and both ends are blocked (CH3)2 (CH2=CH)Si○
It was dropped into a mixed solution heated to 100° C. of 105 parts of organopolysiloxane (polymerization degree 140) consisting of 1.43 mo1% of □/2 units and chloroplatinic acid octyl alcohol solution (containing 1100 ppp of platinum). and 1
Toluene was stripped off at 00° C. under reduced pressure of 10 Torr to obtain a product. Two parts of the obtained product were dissolved in (CH,)
, 99.825 mo1% of SiO units.

(CHi) (CH2=CH)Si○ unit 0.15mol1
%.

(0M3), (CH,=CH)sio, 1 part unit 0.0
25 mo1% of organopolysiloxane raw rubber with an average degree of polymerization of 8000, and further added to this is dimethylpolysiloxane with terminal silanol group (degree of polymerization 10).
) and 320 parts of Aerosil 2oO (trade name: Fuumedo Shiriyoku, manufactured by Nippon Aerosil ■) were added, kneaded in a kneader, and heat-treated at 150° C. for 2 hours to prepare base compound 2.

[Example 3] 1.5 parts of trimethoxysilane was diluted with 5 parts of toluene,
This was combined with 96.92 mo1% of (CH3)25iO units and (CH3)2(CH,=CH)SiO to block both ends.
1 of 50 parts of organopolysiloxane (degree of polymerization 65) consisting of 1/2 unit 3.08 mo1% and chloroplatinic acid octyl alcohol solution (containing 1100 ppp of platinum)
It was dropped into the mixed solution heated to 00°C.

Then, toluene was stripped off under reduced pressure of 100'C and 10 Torr to obtain a product. Two parts of the product obtained was 99.8250101% of (CH,)2Sio units.

(CH3) (CHz = CH) S i O unit 0
．． 15mo1%.

(CH3)2(CH2=CH)S10t/2 unit 0.0
It is added to 100 parts of organopolysiloxane raw rubber with an average degree of polymerization of 8000, consisting of 25 mo1%, and further added with terminal silanol group dimethylpolysiloxane (degree of polymerization 1000).
) and 20 parts of Aerosil 200 (trade name of Fuumedo Shiriyoku manufactured by Nippon Aerosil ■) were added, kneaded in a kneader, and heat-treated at 150° C. for 2 hours to prepare base compound 3.

[Comparative example 1] (CHa)z　S　io unit 99,825mol1%.

(CH,)(CH,=CH)SiO unit 0.15mol1
%.

(CHl), (CH2=CH)SiOilz unit 0.0
4 parts of terminal silanol group dimethylpolysiloxane (polymerization degree 10) and 320 parts of Aerosil 200 (trade name of fumed silica manufactured by Nippon Aerosil ■) were added to 100 parts of organopolysiloxane raw rubber consisting of 25 mo1% and having an average degree of polymerization of 8000, and kneaded. - and heat-treated at 150° C. for 2 hours to prepare base compound 4.

[Comparative example 2] (CHa)z　S　1 part unit 99.825mo1%.

(CH,)(CH2=CH)SiO unit 0.15 O1
%.

(CHa)z(CH2=CH)SxO172 unit 0.0
100 parts of organopolysiloxane raw rubber with an average degree of polymerization of 8000 consisting of 25 mo1%, 2 parts of ethyl polysilicate 40, 2 parts of terminal silanol group dimethylpolysiloxane (degree of polymerization 10) and Aerosil 200 [Nippon Aerosil ■ manufactured by Fumed Silica] Add 320 parts of the product name,
The mixture was kneaded in a kneader and heat-treated at 15 parts C for 2 hours to prepare Base Compound 5.

[Comparative example 3] (CH,)2SiO unit 99.825 mo1%.

(CH3) (CH2=CH)SiO unit 0.15no1
%.

(CH3)z (CH2” CH) S log 12
Average degree of polymerization consisting of 0.025 mo1% unit is 8000
To 100 parts of organopolysiloxane raw rubber, (CH,
) 2 parts of organopolysiloxane (degree of polymerization 65) consisting of 96.92 x 01% of 2SiO units and 3 x 08 mo1% of (CHa)z(CH2=CH)S101/z units blocking both ends, dimethylpolymer with terminal silanol groups 2 parts of siloxane (degree of polymerization 10) and 320 parts of Aerosil 200 (trade name of Fumed Siliki, manufactured by Nippon Aerosil ■) were added, kneaded in a kneader, and heat treated at 150'C for 2 hours to prepare base compound 6. .

Next, the plasticity of the compounds 1 to 6 was determined according to JISC21.
It was measured according to No. 37. That is, after kneading the compound again, a load was applied 10 minutes later, and the height after 3 minutes was measured using a dial gauge. The results are shown in Table 1.

In addition, for each 100 parts of Compounds 1 and 3 to 5, 0.03 part of an octyl alcohol modified solution of chloroplatinic acid (platinum content: 1% by weight), 1,3°5.7-tetramethyl-1,3 , 5, add 0.25 parts of fuchitravinylcyclotrisiloxane and 11.20 parts of crosslinking agent *), 17
After press vulcanization at 0°C for 10 minutes, post-vulcanization was performed at 200°C for 4 hours. The physical properties of the obtained cured product were measured by the following method. The results are shown in Table 2.

*) 1 average structural formula : Measured based on JIS K 6301 Type A.

stretch: Measured according to JIS K 6301.

Tensile strength: Measured according to JIS K 6301.

Compression set: Measured after being left in a hot air dryer at 100°C for 22 hours in accordance with JIS K 6301.

Table 2 Also, for each 100 parts of Compounds 3 and 4, 2
, 0.6 part of 4-dichlorobenzoyl peroxide was added, press vulcanization was performed at 120°C for 10 minutes, and then post-vulcanization was performed at 200°C for 4 hours, and the physical properties of the product were measured. The results are shown in Table 3.

Table 3 Next, the compound to which these vulcanizing agents were added was extruded using a die with a cylinder diameter of 40 m/φ10 mm and a cylinder length to diameter ratio of L/D=12,20 mmφ/10 Iφ. It is supplied to the machine and then heated to room temperature (1
A round rod-shaped silicone rubber molded body with an external diameter of 5 mm was continuously extruded at a rate of 1 m/min at a temperature of 300
The molding was carried out by passing through a heating furnace having a total length of 2 m in which hot air of .degree. The results are shown in Table 4.

Table 4 × The shape could not be maintained and a round rod shaped molded product was obtained.The shape could not be maintained and a molded product could not be obtained.From the results in Tables 1 to 4, the silicone rubber composition of the present invention has good processability and workability. It has been confirmed that it provides a cured product with excellent properties and low compression set and low hardness.

Distributor: Shin-Etsu Chemical Co., Ltd. Agent: Patent Attorney Takashi Kojima

Claims (1)

[Claims] 1. (I) The following general formula (1) RaSiO_(_4_-_a_)_/_2...(1) (However, in the formula, R represents a substituted or unsubstituted monovalent hydrocarbon group. and 0.0001 to 0.5 mol% of the entire R group is an alkenyl group.Also, a is a number in the range of 1.95 to 2.05. organopolysiloxane, (II) (a) the following general formula (2) H_b(R^1)_c(XO)_dSiO_(_4_-
_b_-_c_-_d_)_/_2...(2) (However, in the formula, R^1 is a substituted or unsubstituted monovalent hydrocarbon group, and X is selected from a hydrogen atom, an alkyl group, and an alkoxyalkyl group. b, c, d are each 0
The numbers are in the range of ≦b<0.2, 0≦c<0.2, 1<d≦4. ) and (b) the following general formula (3) (R^2)_e(R^3)_f(YO)_gSiO_(
＿４＿−＿e＿−＿f＿−＿g＿）＿／＿２・・・(３
) (However, in the formula, R^2 is a substituted or unsubstituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated group, R^3 is an alkenyl group, an acrylic group, or a methacryl group, and Y is a hydrogen atom. , a group selected from an alkyl group and an alkoxyalkyl group, and e, f, and g are each 1.8<e<2.2,
0.004<f<0.2, 0≦g<0.2, ) is a number in the range of Organopolysiloxane of formula (3) has a weight ratio of 0.005 to 0.5
A silicone rubber composition containing as main components an organosilicon compound obtained by reacting in a proportion such that: and (III) finely powdered silica having a specific surface area of 50 m^2/g or more. 2. A cured product obtained by curing the silicone rubber composition according to claim 1.