JP3198835B2 - Silicone rubber composition for extrusion molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone rubber for extrusion molding which has a high hardness, a high modulus and a high strength and gives a silicone rubber useful as a gasket for construction, a wiper blade for automobiles, various tubes, hoses and the like. Composition.

[0002]

2. Description of the Related Art In general, silicone rubber is excellent in weather resistance, durability, heat resistance, physiological inertness, coloring property, and the like. Widely used in the field of parts, automobile parts, medical instruments, etc., especially in the case of silicone rubber for extrusion used for ultra-fine tubes and wiper blades for automobiles, hardness (JIS-A) 60 degrees Above
It is desired to provide a high hardness and high modulus of 0% modulus of 40 kgf / cm ² or more.

[0003] Conventionally, silicone rubber which gives high hardness has been
Production is carried out by adding a relatively large amount of a silica filler to a siloxane polymer. However, this method causes a problem in terms of economy because the dischargeability of the silicone rubber composition is reduced.

It is generally known that a silicone rubber composition having excellent physical properties can be obtained by blending finely divided silica with a siloxane polymer. However, when a large amount of this is added, a silicone rubber having high hardness and high modulus can be obtained. On the other hand, other physical properties are reduced on the contrary, especially the tear strength,
The compression set characteristic is significantly reduced.

[0005] JP-A-2-124977 and JP-A-63-130663 disclose an extrudable silicone rubber composition comprising components (A), (B) and (D) of the present invention which will be described later. However, the characteristic (C) component of the present invention is not disclosed, and a sufficiently high hardness,
High modulus was not obtained and the field of use was limited.

The present invention has been made in view of the above circumstances, and provides a silicone rubber having high hardness, high modulus, and excellent tear strength and compression set characteristics, and having excellent moldability for extrusion molding. It is intended to provide a silicone rubber composition.

[0007]

The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that an organopolysiloxane represented by the following average composition formula (1) has a specific surface area of 100 m ² / g. to silicone rubber compositions containing the above fine silica powder, R ² ₃ of the following general formula (2)
A specific amount of an organosiloxane copolymer having a specific molar ratio of SiO _1/2 units and SiO ₂ units and containing a specific amount of a vinyl group is blended, and an organic polymer represented by the following general formula (3) is used as a crosslinking agent. By using oxide,
The present invention has been found to provide a silicone rubber extruded product having excellent moldability for extrusion molding, high hardness, high modulus, and excellent tear strength and compression set. It is a thing.

That is, the present invention provides: (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; , Wherein n is a positive number from 1.98 to 2.02.) 100 parts by weight of an organopolysiloxane having an average degree of polymerization of 2,000 or more, and (B) a specific surface area of 100 m ² / g or more of fine powder silica 10
100 parts by weight, (C) the following general formula _{^{(2) R 2 3 SiO 1/2}} ... (2) ( wherein, R ² is a vinyl group, a phenyl group, an alkyl group or a C 3 1 to 8 carbon atoms indicates 10 fluoroalkyl group, each R is a triorganosiloxy units and SiO ₂ units and a main structural unit represented by may also be.) to be the same or different, R ² ₃ SiO _1/2 units and SiO Organopolysiloxane copolymer 5 whose molar ratio to ₂ units is in the range of 0.6: 1 to 1.2: 1 and 0.003 to 0.4 mol% of all R ² is a vinyl group (D) 0.1 parts by weight of an organic peroxide represented by the following general formula (3).
And (E) a degree of polymerization of 1,000 or less and a vinyl group of 0.01 to
Organopolysiloxane oil containing 30 mol%
An extrusion-molded silicone rubber containing 50 parts by weight and having a 100% modulus of 40 kgf / cm ² or more and a hardness (JIS-A) of 60 degrees or more for an extrusion-cured silicone rubber. A silicone rubber composition is provided.

[0009]

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Now, the present invention will be described in more detail. The silicone rubber composition of the present invention comprises (A) an organopolysiloxane, (B) finely divided silica, (C) an organosiloxane copolymer, and (D) an organic polymer. It is mainly composed of an oxide.

Here, the organopolysiloxane of the component (A) has the following average composition formula (1) R ¹ _n SiO _{(4-n) / 2} (1) (wherein R ¹ is the same or different. An unsubstituted or substituted monovalent hydrocarbon group, n is a positive number from 1.98 to 2.02).

Here, R ¹ is an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, a cycloalkyl group such as a cyclohexyl group, an alkenyl group such as a vinyl group, an allyl group, a butenyl group or a hexenyl group; Group, aryl group such as tolyl group, or selected from chloromethyl group, trifluoropropyl group, cyanoethyl group, etc. in which part or all of the hydrogen atoms bonded to carbon atoms of these groups are substituted with halogen atoms, cyano groups, etc. It is preferable that they are the same or different unsubstituted or substituted monovalent hydrocarbons having 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms. Also,
0.001 mol% of the total R ^1, in particular 0.025
Preferably, 0.5 mol% is alkenyl groups.

N is a positive number from 1.98 to 2.02, and this organopolysiloxane has a molecular chain end blocked with a trimethylsilyl group, a dimethylvinyl group, a dimethylhydroxysilyl group, a trivinylsilyl group or the like. It is preferred that

The organopolysiloxane is basically a linear diorganopolysiloxane, but may be a mixture of two or more kinds having different molecular structures. The viscosity of this organopolysiloxane at 25 ° C. is 1
00,000 cs or more, preferably 100,000 to 1
0,000,000 cs. The average degree of polymerization is 2,000 or more, preferably 2,000 to 10
0000, more preferably 5,000 to 10,000
It is.

The organopolysiloxane of this type can be obtained by cohydrolyzing and condensing one or more of the selected organohalogenosilanes, or a cyclic polysiloxane (trimer or tetramer of siloxane, etc.). ) Is subjected to ring-opening polymerization using an alkaline or acidic catalyst.

The finely divided silica as the component (B) is essential for obtaining a silicone rubber having excellent mechanical strength, and for this purpose, it is necessary to have a specific surface area of 100 m ² / g or more. There is. As this fine powder silica,
Typical examples thereof include fumed silica, sedimentable (wet) silica, and silica obtained by hydrophobizing the silica surface.

The amount of the fine silica powder added is as follows:
(A) 10 to 100 parts by weight with respect to 100 parts by weight of the component;
More preferably, it is 30 to 80 parts by weight. If the amount is less than 10 parts by weight based on 100 parts by weight of the diorganopolysiloxane of the component (A), a sufficient reinforcing effect cannot be obtained, and if the amount is more than 100 parts by weight, processability deteriorates. This is because the physical strength of the resulting silicone rubber decreases.

The organopolysiloxane copolymer of the component (C) is indispensable for imparting a high modulus to the silicone rubber. The copolymer has the following general formula (2): R ² ₃ SiO _1/2 . (2) (In the formula, R ² represents a vinyl group, a phenyl group, an alkyl group having 1 to 8 carbon atoms or a fluoroalkyl group having 3 to 10 carbon atoms, and each R may be the same or different.) Triorganosiloxy units (M units) represented by
And ₂ units (Q units) as a main constitutional unit, the molar ratio of R ² ₃ SiO _1/2 units and SiO ₂ units 0.6: 1 to 1.2: 1
By weight, and from 0.003 to 0.4 mol% of the total R ² is an organopolysiloxane copolymer is a vinyl group.

The alkyl group is a methyl group,
Examples of the group include an ethyl group and a propyl group. Examples of the fluoroalkyl group include a 3,3,3-trifluoropropyl group. Preferred groups for R ² are a vinyl group and a methyl group.

In the copolymer, M to Q unit
The unit molar ratio (M / Q) is 0.6 to 1.
2, more preferably 0.7 to 1.1. When there are more triorganosiloxy units than this range, workability such as an increase in the tackiness of the composition before curing is remarkably poor. The viscosity of the polysiloxane copolymer becomes too high, and the amount of the remaining silanol becomes too large, so that stable synthesis becomes difficult.

The present organopolysiloxane copolymer may be used as long as the purpose of the composition of the present invention is not impaired.
SiO ₂ units, other units other than triorganosiloxy units, for example, ^{_{R 2 SiO 3/2, R 2 2}} SiO 2/2 , etc. units (R ²
Has the same meaning as described above. ) Can also be included.

The content of the vinyl group directly bonded to the silicon atom (the content of the vinyl group in all R ² ) is 0.003 to 0.4 mol%, more preferably 0.05 to 0.25 mol%.
If the content of the vinyl group directly bonded to silicon atoms is less than 0.003 mol%, a sufficient modulus cannot be exhibited, while if it is more than 0.4 mol%, the physical properties of the vulcanized molded product are remarkably deteriorated, and Disappears.

Such an organopolysiloxane copolymer can be produced by a method known per se. For example, blended and R ² ₃ SiCl and SiCl ₄ to be in the range of molar ratio described above, it is readily synthesized by performing co-hydrolytic condensation.

The amount of component (C) is 5 to 50 parts by weight, preferably 7 to 40 parts by weight, per 100 parts by weight of component (A). If the amount is less than 5 parts by weight, the effect of improving the modulus and the effect of improving the tear strength is small, and if it is more than 50 parts by weight, the elongation of the cured silicone rubber decreases.

In the present invention, it is recommended that an organopolysiloxane oil be blended as the component (E). The organopolysiloxane oil (E) has a degree of polymerization of 1,000 or less and a vinyl group of 0.01 or less.
It must be contained in an amount of from 30 to 30 mol%, preferably from 0.1 to 10 mol%, and it is preferable that both ends represented by the following formulas are blocked with vinyl groups.

[0026]

Embedded image (Wherein, R is a monovalent hydrocarbon group similar to R ^1, can be exemplified the same as R ^1, the .Vi methyl group is particularly preferable as .R excluding alkenyl groups vinyl M is an integer of 3 ≦ m ≦ 1,000, and n is 0 ≦ n
Is an integer of ≦ 500, and 0 <m + n ≦ 1,000. )

This organopolysiloxane oil (E)
Is used in an amount of 5 to 50 parts by weight per 100 parts by weight of component (A).
Parts by weight, more preferably 7 to 40 parts by weight. If the amount is less than 5 parts by weight, the effect is not recognized.

Next, the component (D) of the present invention is an organic peroxide represented by the following general formula (3).

[0029]

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Here, R ³ and R ⁴ are n-propyl group, i-propyl group, t-butyl group, n-butyl group and n-propyl group.
-Amyl group, t-amyl group, hexyl group, heptyl group,
Examples thereof include an octyl group, a 2-ethylpropyl group, a 2-ethylbutyl group, a 2-ethylhexyl group, a cumyl group, a trimethylsilyl group, a triethylsilyl group, a triphenylsilyl group, and the like, even if R ³ and R ⁴ are the same. May be different.

The component (D) may be added in an amount necessary for vulcanization and curing of a normal silicone rubber. Generally, it is added to 100 parts by weight of the diorganopolysiloxane (A). 0.1 to 10 parts by weight, more preferably 0.5
-5 parts by weight.

In the present invention, in addition to the peroxide represented by the above general formula (3), conventionally known compounds can be used in combination according to the mechanism or speed of the crosslinking reaction. For example, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, 2,4-dicumyl peroxide,
2,5-dimethyl-bis (2,5-t-butylperoxy) hexane, di-t-butyl peroxide, t-butyl perbenzoate, and the like.

The silicone rubber composition of the present invention may contain, if necessary, a filler such as crushed quartz or calcium carbonate as an extender, and an inorganic or organic foaming agent for forming a sponge, for example, azobis. Isobutyronitrile, dinitropentamethylenetetramine, benzenesulfonylhydrazide, azodicarbonamide and the like can be blended.

Further, various additives such as a colorant and a heat resistance improver, a releasing agent and a dispersant for a filler can be optionally added as required. Here, diphenylsilanediol, various alkoxysilanes, carbon functional silane, silanol group-containing low molecular weight siloxane, etc. used as a filler dispersant can be used to the extent that the effects of the present invention are not impaired. Further, in order to prevent surface tackiness and discoloration of the obtained silicone rubber, 0.05 to 5 parts by weight of an organohydrogenpolysiloxane having a hydrogen atom bonded to a silicon atom is added to 100 parts by weight of the component (A). Parts may be added.

In the silicone rubber composition of the present invention, the above-mentioned components are uniformly mixed using a general-purpose rubber kneading machine such as a two-roll mill, a Banbury mixer or a dough mixer (kneader), and if necessary, heated. It can be manufactured by processing.

The silicone rubber composition thus prepared is extruded by an extruder equipped with a die having a desired shape, and then cured by heating in a vulcanizing furnace. A high modulus extruded silicone rubber cured product can be obtained intermittently or continuously. Here, as the vulcanizing furnace, a hot blast furnace, a UHF furnace, a steam furnace, an IR furnace, or the like is used, and the type thereof is not particularly limited as long as sufficient heat can be applied to vulcanization molding of silicone rubber. The vulcanization conditions are 80-500 ° C., especially 2
The temperature can be 1 second to 1 hour, particularly 5 seconds to 15 minutes at 00 to 350 ° C.

The silicone rubber thus obtained has a 100% modulus of 40 kgf / cm ² or more, preferably 45 to 60 kgf / cm ² . If it is less than 40 kgf / cm ^2, it cannot be used for applications requiring high strength, and the object of the present invention cannot be achieved. This silicone rubber has such excellent physical properties as hardness and high modulus, and is suitable for applications such as ultrafine tubes, wiper blades for automobiles, various tubes and hoses.

[0038]

According to the silicone rubber composition for extrusion molding of the present invention, an extruded silicone rubber having high hardness and high modulus can be obtained without impairing tensile strength and compression set characteristics.

[0039]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Examples 1 to 6 and Comparative Examples 1 to 4 The following polymers, oils, resins, dispersants, and fillers are shown in Table 1.
And kneaded with a kneader, and heat-treated at 180 ° C. for 2 hours to prepare a compound. Furthermore,
A silicone rubber composition was prepared by adding the following curing agent at a ratio shown in Table 1 with respect to 100 parts by weight of the compound.

Next, the cylinder diameter is 40 mmφ, the ratio of the cylinder length L to the diameter D is L / D = 12, and the outer diameter is 2 mm.
The mixture was extruded with an extruder equipped with a 5 mm × 2 mm die, and then vulcanized and cured in a hot air oven at 350 ° C. for 3 minutes, and then post-cured at 200 ° C. for 4 hours using a dryer. Various rubber properties of the obtained silicone rubber were measured. Table 1 shows the results.

[0042] Polymer dimethylsiloxane units 99.95 mol%, methylvinylsiloxane units 0.025 mol%, dimethylvinyl siloxane units consist 0.025 mol%, rubbery organopolysiloxane average degree of polymerization of about 8,000 (Hereinafter referred to as polymer 1).

Dimethylsiloxane unit 99.825 mol%, methylvinylsiloxane unit 0.15 mol%, dimethylvinylsiloxane unit 0.025 mol%,
A rubbery organopolysiloxane having an average degree of polymerization of about 8,000 (hereinafter referred to as polymer 2).

An oily organopolysiloxane composed of oil dimethylsiloxane units and having an average degree of polymerization of about 500 and having a viscosity of 5,000 cs at 25 ° C., terminated by a vinyl group [vinyl content: 0.20 mol%] (Hereinafter referred to as oil 1).

An average degree of polymerization of about 180, consisting of dimethylsiloxane units and having a terminal blocked by a vinyl group,
Oily organopolysiloxane having a viscosity of 600 cs [vinyl content: 0.55 mol%] (hereinafter referred to as oil 2).

The resin is composed of SiO ₂ units, dimethylvinylsiloxy units and trimethylsiloxy units. The molar ratio of dimethylvinylsiloxy units and trimethylsiloxy units to SiO ₂ units is 1: 0.12: 0.94, and M / Q Ratio = 1.1,
An organopolysiloxane copolymer having a vinyl content of 0.085 mol% and a 50% toluene solution having a viscosity at 25 ° C. of 3.5 cs (hereinafter referred to as Resin 1).

It is composed of SiO ₂ units, dimethylvinylsiloxy units and trimethylsiloxy units, and the molar ratio of dimethylvinylsiloxy units and trimethylsiloxy units to SiO ₂ units is 1: 0.06: 0.9, and the M / Q ratio is = 1.1, an organopolysiloxane copolymer having a vinyl content of 0.098 mol% and a 50% toluene solution having a viscosity of 5 cs at 25 ° C. (hereinafter referred to as Resin 2).

The dispersant has silanol groups at both ends and has an average polymerization degree of 13
A dimethylpolysiloxane having a viscosity at 5 ° C. of 15 cs.

Fumed silica having a filler specific surface area of 300 m ² / g [manufactured by Nippon Aerosil Co., Ltd.]

Curing agent 2,4-dichlorobenzoyl peroxide represented by the following formula (i) (hereinafter referred to as curing agent 1): 1,6-hexanediolbis- represented by the following formula (ii)
t-butyl peroxycarbonate (hereinafter, referred to as curing agent 2) 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane (hereinafter, referred to as curing agent 3) represented by the following formula (iii)
The peroxide represented by the following formula (iv) (hereinafter referred to as curing agent 4)
That)

[0051]

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[0052]

[Table 1]

From the results in Table 1, it can be seen that the examples (1 to 1) of the present invention
6) In each case, the 100% modulus is 40 kgf / cm.
^{It has been found that} a high-hardness, high-modulus silicone rubber for extrusion having a hardness of ² or more, a hardness (JIS-A) of 60 degrees or more, and a tensile strength of 90 kgf / cm ² or more is provided.

The compositions of Example 1 and Comparative Example 2 were extruded and cured to obtain an outer diameter of 4 mm and a wall thickness of 0.5 m.
m silicone rubber tube was manufactured. When this tube was pulled by hand, the tube of Example 1 did not break, but the tube of Comparative Example 2 did.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C08L 83:07) B29K 83:00 (56) References JP-A-6-306296 (JP, A) JP-A-2-124977 ( JP, A) JP-A-64-24858 (JP, A) JP-A-6-157908 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 83/04 C08L 83/07 C08K 3/36 C08K 5/14

Claims (1)

(57) [Claims] (A) The following average composition formula (1): R ¹ _n SiO _{(4-n) / 2} (1) (wherein, R ¹ is the same or different and is unsubstituted or substituted monovalent carbonized) A hydrogen group, n is a positive number of 1.98 to 2.02), 100 parts by weight of an organopolysiloxane having an average degree of polymerization of 2,000 or more, and (B) a fine particle having a specific surface area of 100 m ² / g or more. Powdered silica 10
100 parts by weight, (C) the following general formula _{^{(2) R 2 3 SiO 1/2}} ... (2) ( wherein, R ² is a vinyl group, a phenyl group, an alkyl group or a C 3 1 to 8 carbon atoms indicates 10 fluoroalkyl group, each R is a triorganosiloxy units and SiO ₂ units and a main structural unit represented by may also be.) to be the same or different, R ² ₃ SiO _1/2 units and SiO Organopolysiloxane copolymer 5 whose molar ratio to ₂ units is in the range of 0.6: 1 to 1.2: 1 and 0.003 to 0.4 mol% of all R ² is a vinyl group ５０50 parts by weight, (D) the following general formula (3) 0.1 to 10 parts by weight of an organic peroxide represented by: and (E) a polymerization degree of 1,000 or less and a vinyl group of 0.01 to
Organopolysiloxane oil containing 30 mol%
An extrusion-molded silicone rubber containing 50 parts by weight and having a 100% modulus of 40 kgf / cm ² or more and a hardness (JIS-A) of 60 degrees or more for an extrusion-cured silicone rubber. Silicone rubber composition.