JPH0813927B2 - Method for producing silicone anti-vibration rubber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a silicone anti-vibration rubber.

[Prior Art] In recent years, as computer peripherals, audio products, and automobile parts have become more and more precise and measures against heat and vibration are becoming more important, we would like you to add vibration-proof effect to thermally stable silicone rubber. The demand is increasing.

The anti-vibration transmissibility T of the system is given by the following equation in the case of a system with one degree of freedom: Where X _in : Excitation force to the system (external force) X _out : Transfer force from the system ω: Angular frequency of external force ω _o : Natural frequency Is known to be represented by. As can be seen from this equation, T becomes maximum at the resonance point (ω / ω _o = 1) and decreases as (ω / ω _o ) increases. T also decreases as ω _o is small if the angular frequency ω of the external force is the same. As a method of reducing the natural frequency ω _o , it is conceivable to reduce the spring constant k (that is, reduce the rubber hardness), and add mass to the system to increase m.

Heretofore, it has been proposed to reduce the rubber hardness of the silicone rubber as an attempt to enhance the vibration damping effect by reducing the natural frequency ω _o of the silicone rubber. However, this reduces the loss coefficient tan δ. T near the resonance point
Is almost inversely proportional to tan δ, so T is large near the resonance point, which is not appropriate.

As another silicone anti-vibration system, it has been proposed to mold a container made of synthetic rubber or silicone rubber into the required shape and put silicone oil or silicone gel inside (Yasuo Yoshifuku, Department of Industrial Physics, Chubu University, “Impact”). Test result report of cushioning material "1984).

[Problems to be Solved by the Invention] The above system can obtain a good vibration damping property because the spring constant k can be made small and tan δ can be made large, but a container made of synthetic rubber or silicone rubber can be molded into a desired shape. There is a problem that it is not easy to do and lacks practicality. Further, when a container is made of silicone rubber, there is a drawback that silicone oil or the like in the container oozes out.

[Means for Solving the Problems] Therefore, an object of the present invention is to provide a production method capable of easily obtaining a silicone rubber molded article having excellent vibration damping properties by a single molding step. .

That is, the present invention provides (A) an average composition formula: [Wherein R is a substituted or unsubstituted monovalent hydrocarbon group; a is a number from 1.99 to 2.02], and (B) a fine silica powder having a specific surface area of 50 m ² / g or more. A silicone comprising a composition containing (C) a boron-containing polysiloxane and (D) a curing agent, followed by secondary vulcanization at a temperature of 180 to 250 ° C. for 1 to 6 hours after primary vulcanization. The present invention provides a method for manufacturing a vibration proof rubber.

Average compositional formula (I) representing the organopolysiloxane of component (A) which constitutes the composition used in the method of the present invention.
In the above, examples of the substituted or unsubstituted monovalent hydrocarbon group represented by R include alkyl groups such as methyl group, ethyl group and propyl group, alkenyl groups such as vinyl group and allyl group, phenyl group and tolyl group. Aryl group, and part or all of hydrogen atoms bonded to carbon atoms of these groups are one or more kinds such as halogen atom (eg, chlorine atom, fluorine atom, bromine atom), cyano group, mercapto group and the like. Examples include a substituted 3,3,3-trifluoropropyl group, a cyanopropyl group, a mercaptopropyl group and the like. Among these substituted or unsubstituted monovalent hydrocarbon groups, a methyl group, a vinyl group, a phenyl group and the like are preferable.

In the organopolysiloxane of component (A), at least 50% of all R's contained in the molecule must be methyl groups, and more preferably 75% or more are methyl groups. When the methyl group content of all R is less than 50%, the anti-vibration effect at low temperatures is significantly reduced, the temperature dependence of the physical properties of the polymer is increased, and the heat resistance is reduced.

Further, in the average composition formula (I), a is 1.99 to 2.02, and the organopolysiloxane as the component (A) is a substantially linear polymer. The average degree of polymerization of the organopolysiloxane is preferably 3000 to 15000, and particularly preferably 5000 to 10000. If it is less than 3000, sufficient mechanical strength cannot be obtained.
If it exceeds 0, roll processability is remarkably deteriorated.

The organopolysiloxane can be prepared by a method well known to those skilled in the art, which is a ring-opening polymerization of a cyclic organopolysiloxane, which is well known as an oligomer, in the presence of an acid or alkali catalyst.

As the silica fine powder of the component (B) constituting the composition, for example, fine powders of fumed silica, precipitated silica and the like are typical. These fine powders need to have a specific surface area of 50 m ² / g or more, and preferably 100 m ² / g or more, in order to obtain a sufficient vibration damping effect.

The blending amount of the silica powder of the component (B) is 100 parts of the component (A).
The amount is preferably 10 to 100 parts by weight, more preferably 30 to 60 parts by weight. If the amount of component (B) is too small, the anti-vibration property will be sufficient, and if it is too large, physical properties such as tensile strength and tear strength of the obtained rubber molded product will deteriorate. If necessary, the silica fine powder may be used in combination with, for example, quartz powder, diatomaceous earth, or the like, which gives better vibration damping properties. These quartz powders are the above silica fine powders.
It is desirable to use less than 200 parts by weight per 100 parts by weight.

The component (C) is an additive for accelerating the decomposition of the internal polymer by the secondary vulcanization of the silicone rubber made into a rubber elastic body by the primary vulcanization, which will be described later, and causing it to gel. The boron-containing polysiloxane as the component (C) contains at least one boron in the main chain or side chain of the siloxane bond. These may be used alone or in combination of two or more. However, if added in excess, the physical properties of the rubber will be significantly impaired due to excessive gelation, so it is preferably in the range of 0.1 to 20 parts by weight, more preferably 0.5 to 5 parts by weight.

The component (D) is a cross-linking agent necessary for obtaining a rubber elastic body, and is exemplified by peroxide. The types of peroxide include dicumyl peroxide and di-t.
-Butyl peroxide, t-methylcumyl peroxide, 2,5-dimethyl-2,5-di (t-methylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) Hexine, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide and the like. The amount added is usually 0.05 to 5 parts by weight, preferably 0.1 to 2 parts by weight.

In addition to the components (A) to (D) described above, the composition may be used as a conventionally known additive, for example, as a heat resistance improver, as long as it does not impair the required physical properties of the anti-vibration rubber. Titanium oxide, red iron oxide, cerium oxide, barium zirconate; halogen compounds as flame retardants,
Antimony oxide; various carbon functional silanes may be added.

In the above composition to be vulcanized in the method of the present invention, a predetermined amount of the above-mentioned components (A) to (D) and other components optionally added may be used, for example, a two-roll roll, a kneader. It can be obtained by kneading with a Banbury mixer or the like.

Primary vulcanization of the composition according to the method of the present invention is, for example, two rolls, a calender, after being formed into a desired shape by a method such as an extruder, under a pressure of about 50 to 100 kg / cm ² , about 120 ° C. An elastic body is obtained by heating at ~ 200 ° C.

Furthermore, to obtain a silicone anti-vibration rubber molded product, 80 to 250
Secondary vulcanization is required at a temperature of ℃, preferably 190-250 ℃. By this secondary treatment, the polymer inside the silicone rubber is decomposed into a gel state. Secondary vulcanization temperature is 180 ℃
When it is less than the above range, the internal polymer is not sufficiently decomposed, and it is difficult to form a proper gel state. The time for this secondary vulcanization is 1
~ 6 hours, usually 3-6 hours. For example, treatment at 200 ° C. for 4 hours is preferable.

[Examples] Next, the present invention will be described with reference to Examples. In the following, "part" means "part by weight".

Examples 1 and 2 and Comparative Example 1 Organopolysiloxane raw rubber (polymerization degree 8000) consisting of 99.975 mol% of dimethylsiloxane unit and 0.025 mol% of trivinylsiloxane unit at the end (to be referred to as organopolysiloxy raw rubber 1) and Dimethyl siloxane unit 99.85 mol%, methyl vinyl siloxane unit 0.1
Organopolysiloxane raw rubber consisting of 5 mol% and terminated with trimethylsiloxy groups (polymerization degree 8000)
(It will be referred to as organopolysiloxane raw rubber 2)
100 parts, 0 parts or a combination of 80 parts and 20 parts, respectively, and 55 parts of Silexo Pharmaceutical Co. Carplex CS-5 (specific surface area of about 150 m ² / g) as silica fine powder and dimethyldimethoxy as a dispersant. 8 parts silane, formula [Here, Me represents a methyl group. ] 4 parts of dimethylpolysiloxane represented by the following formula, 1 part of a boron-containing polysiloxane having a structure represented by the following formula (HO) ₂ BO-Si (-OSiMe ₂ ) _n- (OB (OH) ₂ [where n 35-45] was added and kneaded with a two-roll mill, and then heat-treated in an oven at 180 ° C. for 2 hours.

About the compound thus obtained, 0.65 parts of 2,4-dichlorobenzoyl peroxide was added with a two-roll mill, and pressure-molded at 120 ° C for 10 minutes to form a silicone rubber sheet with a thickness of 2 mm, and at 120 ° C for 15 minutes. Molded and about 12 mm thick,
A silicone rubber sample having a diameter of about 28 mm for measuring anti-elasticity and anti-vibration properties was prepared. Samples obtained by heat treating these at 200 ° C for 4 hours in a hot air circulation oven are JIS K 6
Mechanical properties and tan δ were measured according to 301. First result
Shown in the table.

A comparative example not containing the boron-containing polysiloxane is also shown. Samples containing boron-containing polysiloxane
It has a large tan δ and shows good vibration damping characteristics.

Examples 3 and 4 and Comparative Examples 2 to 4 The organopolysiloxane raw rubber 1 used in Example 1 was made of Erosil 200 (specific surface area 200 m ² / g, trade name of Japan Airsil Co., Ltd.), and silyl group having an OH group at the end. 12 parts, boron-containing polysiloxane 2 used in Example 1
The composition is as shown in Table 2 and the temperature is 160 ° C using a kneader.
For 2 hours.

Next, 0.65 parts of 2,4-dichlorobenzoyl peroxide was added to this compound by using a roll, and 120 ° C.
After pressure molding for 10 minutes, and after-curing at 200 ° C. for 4 hours, a cylindrical sample having a thickness of 12 mm and a diameter of 28 mm was obtained.

When the spring constant and tan δ of this sample were measured, the results shown in Table 2 were obtained. Those containing boron-containing polysiloxane have small spring constant and large ta
Since it has nδ, it can be seen that it is effective as a vibration isolation system.

Further, when this sample was cut, the inside had a gel structure in a semi-solid state with no fluidity.

[Effects of the Invention] The silicone vibration-insulating rubber molded product obtained by the method of the present invention has a small spring constant and a large loss coefficient tan δ, and therefore exhibits excellent vibration-damping properties. Moreover, according to the method of the present invention, it can be manufactured extremely easily as compared with the conventional method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Nakamura 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory (56) Reference Japanese Patent Publication No. 38-635 (JP, B1)

Claims (1)

[Claims] 1. An average composition formula (A): An organopolysiloxane represented by the formula [wherein R is a substituted or unsubstituted monovalent hydrocarbon group; a is a number from 1.99 to 2.02], and (B) a fine silica powder having a specific surface area of 50 m ² / g or more. A silicone comprising a composition containing (C) a boron-containing polysiloxane and (D) a curing agent, followed by secondary vulcanization at a temperature of 180 to 250 ° C. for 1 to 6 hours after primary vulcanization. Method for manufacturing anti-vibration rubber.