JP2603386B2 - Method for producing silicone rubber foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a silicone rubber foam.
It relates to a method of manufacturing, in particular, to a method of manufacturing a foam and uniform cell structure fine.

[0002]

2. Description of the Related Art Conventionally, silicone rubber foams have been widely produced by a method in which a silicone rubber material containing a finely divided inorganic filler, a foaming agent and a vulcanizing agent are simultaneously added, mixed, heated and foamed and cured. Have been. As a foaming agent used therefor, usually, azbisisobutyronitrile (AIB)
N) is used. It is known that AIBN is easily chemically decomposed by heating to generate a gas, and the generated gas is used to mold a silicone rubber compound into a foam (Japanese Patent Publication No. 44-461). .

[0003]

However, the silicone rubber foam produced by such a method is AIBN.
Since the state of the cells changes due to the influence of the particle size of the above, it was difficult to obtain a foam having a uniform cell structure with good reproducibility.

Accordingly, it is an object of the present invention to provide a method for obtaining a silicone rubber foam having a uniform cell structure with good reproducibility. Another object of the present invention is to provide a silicone rubber foam having very fine cells and desirable practically.

[0005]

Means for Solving the Problems The present inventors have conducted a number of experimental studies on the method for solving the above-mentioned problems, particularly focusing on the particle size of the foaming agent AIBN, and have set the particle size within a specific range. It has been found that the above-mentioned problems can be effectively achieved when adjusting , preparing and adding and blending the master batch . That is, the present invention proposes a method for producing a silicone rubber foam comprising the constituent elements described in the claims.

The silicone rubber compound based on diorganopolysiloxane used in the present invention is usually prepared by mixing a finely divided inorganic filler with a silicone rubber.
It is a molding material containing about 20 to 60% by weight, preferably 30 to 50% by weight, and the inorganic filler is preferably fumed silica.

[0007] In the compound comprising such a diorganopolysiloxane and an inorganic filler, generally known means can be used to improve the dispersibility of the filler in the polysiloxane. For example, a method using a dispersing aid is practical, and silane treatment of the surface of the inorganic filler is also an effective means, and does not hinder the molding of the foam.

A method for preparing a silicone rubber compound by mixing a desired amount of an inorganic filler with a diorganopolysiloxane can employ any conventionally known mixing method. Blenders such as Banbury mixers and mixing ginsules are preferably used.

The AIBN used in the present invention is a pulverizing and foaming agent component having an average particle diameter adjusted to 5 to 75 μm, and 0.5 to 10 parts by weight based on 100 parts by weight of the silicone rubber compound is used. Can be Average particle size is 5μ
Below m, the presence of such fines has been found to be undesirable, as many large bubbles exceeding 200 μm are formed, contrary to the expectation that fine bubbles would be formed.

[0010] Although the reason is not clear, AIBN ultrafine particles are liable to cause agglomeration between particles, and the contacting particles partially break down with each other during thermal decomposition to become interconnected, making the cell structure large and nonuniform. It is presumed that. Also 75
When the diameter exceeds μm, the formed bubbles become large and the diameter becomes
It is not preferable because a silicone rubber foam having a fine cell structure exceeding 200 μm is formed and has a fine uniform cell structure.

Furthermore, the addition amount is the silicone - is less than 0.5 parts by weight with respect to emissions rubber compound 100 parts by weight, the degree of foaming is low silicone - Ngomu obtained only unsatisfactory as a foam. If it exceeds 10 parts by weight, the obtained foam tends to crack or deform, which is not preferable.

The organic peroxide used as the third component in the present invention is a polymerization curing catalyst for diorganopolysiloxane. Examples of such an organic peroxide include:
Benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxide
Oxy) hexane and dicumyl peroxide. These can be used in combination of two or more.

The amount used is in the range of 0.05 to 5 parts by weight based on 100 parts by weight of the silicone rubber compound. If the amount is less than 0.05 parts by weight, the crosslinking and curing reaction at the time of heating and foaming becomes insufficient, and if it exceeds 5 parts by weight, foaming is inhibited, and a foam of a fine uniform cell having a desired degree of foaming cannot be obtained. Not preferred.

In the present invention , since AIBN usually has a risk of causing a decomposition reaction due to heat, simultaneous mixing of the three components with heat generation is not preferable , and AIBN is added to silicone raw rubber such as diorganopolysiloxane. In addition,
For example, a master batch is prepared in advance by mixing uniformly using a mixin grease. This is the AIBN component
Silicone rubber mainly composed of diorganopolysiloxane
Method for adding to a mixture of a compound and an organic peroxide
Is adopted. The mixed composition thus prepared is
AIBN 0.5 to 10 weight per 100 parts by weight of the compound
Parts and 0.05 to 5 parts by weight of organic peroxide
Is done. In that case, it will be understood that the raw silicone rubber component supplied from the masterbatch is comprised as part of the above silicone rubber compound.

The AIBN-containing master thus prepared
The batch consists of a silicone rubber compound and an organic peroxide.
To the mixture without decomposing AIBN.
The mixture can be constantly mixed , and for example, can be kneaded with a mixture of mixin to prepare a uniform composition. This kneading is particularly preferably performed with two rolls, and can be carried out safely and extremely efficiently without decomposing AIBN.

[0016]

According to the present invention , diorganopolysiloxane is
Silicon rubber compounds and organic peroxides as main components
And a homogeneous composition of AIBN can be efficiently prepared , and a predetermined amount thereof is put into a predetermined mold in consideration of the degree of foaming.
After foaming by heating to an appropriate temperature, for example, about 100 to 200 ° C, by heating to a higher temperature and curing,
A desirable foam having a fine and uniform cell configuration can be obtained with good reproducibility.

[0017]

Next, the present invention will be described.the method ofMore detailed examples
This will be described in detail. Example 1 and Comparative Examples 1-2  5 kg of commercially available AIBN is pulverized with a pulverizer and averaged.
Three types of powder with particle size of 3μm, 35μm and 200μm
Made. Each of the powders is made of an equal weight of silicon
Rubber (Shin-Etsu Chemical Co., Ltd .: Trade name: KE76VBS)
Mix, knead for 5 minutes with planetary mixer,Three kinds
Uniform master-batch, ie average grain of AIBN
The diameters are 3 μm (Comparative Example 1), 35 μm (Example 1) and 200 μm.
μm (Comparative Example 2)Making a master-batch composition
Was.

Next, methylvinyl silicone (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name: KE-151U), the above master batch composition, and benzoyl peroxide (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: C-1) Dicumyl peroxide (trade name: C-3, manufactured by Shin-Etsu Chemical Co., Ltd.) having a weight ratio of 100:
The mixture was mixed at a ratio of 3.5: 0.4: 2, and kneaded with a mixture of mixin to prepare a uniform composition.

[0019]Comparative Examples 3 to 5 AIBN was pulverized in the same manner as in Example 1 to obtain an average particle diameter of 3 μm.
m, 35μm and 200μm powders are prepared and
Mix and knead each with silicone rubber in advance and mix
For preparation of powdery composition without making batch
Using. Each composition has an AI for ease of comparison.
Along with the BN powder, add the same weight of silicone raw rubber
In addition, the following weight ratios, ie, methyl vinyl silicone:
Benzoyl peroxide: dicumyl peroxide:
AIBN powder: 100% silicone silicone rubber.
A 4: 2: 1.75: 1.75 homogeneous composition was prepared. .

[0020] Each composition prepared as described above, the following
Thus, a foam was produced . Each composition was first formed into a shape having a length of 300 mm, a width of 300 mm, and a thickness of 5 mm, and this was placed in a box shape having a length of 300 mm, a width of 300 mm, and a height of 16 mm and covered with a flat plate. After heating for 30 minutes to a temperature of 175 ° C and firing, a further 10 minutes in a hot air circulator at a temperature of 200 ° C.
It was cured by heating for a period of time to obtain a silicone rubber vulcanized foam having a thickness of 15 mm. The cell size of each of the obtained foams was measured, and the results are summarized in Table 1 below.

Table 1 AIBN Flat Example 1 Comparative Example 1 〃2 〃3 〃4 〃5 Equivalent particle size (μm) 35 3 200 3 35 200 Average cell diameter (μm) 150 400 300 450 200 350 Maximum cell diameter (〃) 200 800 450 900 350 600 Minimum cell diameter (〃) 100 50 200 50 150 200 Maximum / minimum cell diameter difference (〃) 100 750 250 850 200 400

According to Table 1, the average particle size was 3 μm (comparative example).
1), 35 μm (Example 1) or 200 μm (Comparative Example 2)
The average cell diameter of the foam of each composition prepared using the AIBN master batch was about 400 μm and 150 μm, respectively.
m, 300 μm, and AIBN particles having a particle size of 3 μm or 200 μm form coarser cells as compared with the fine cells of the foam obtained by the method of the present invention , and have a variation in cell diameter.
It can be understood that the luck is great . In addition, AIBN powder
Add directly to the composition without kneading with silicone raw rubber
When kneading is used, compared to using kneaded material,
In general, it is found that the cell diameter becomes coarse and the variation also increases.
You. In short, a fine and uniform silicone rubber foam
In order to obtain, the average diameter of the AIBN powder whose particle size is to be adjusted is small.
It is inappropriate to be too large or too large to meet the requirements of the present invention.
It is understood that adding is extremely important.

The AIBN particle size adjusted to 35 μm is
Compositions corresponding to Example 1 and Comparative Example 4 using powder
Make 5 samples each and repeat each
After foaming, the reproducibility of cell formation of each foam was examined. So
As a result, the AIBN powder was mixed and kneaded with the raw silicone rubber.
In Example 1, the average cell diameter was 14%.
Reproduced with uniform fine bubbles within a narrow range of 0 to 160 μm
AIBN powder and silicone raw material
A composition that is added and compounded without mixing with rubber
The cell diameter is about 180 ~ 220μm
And the variability is slightly larger
Admitted.

[0024]

Industrial Applicability The silicone rubber foam obtained by the present invention has a fine and uniform cell structure, and has an extremely excellent feeling, moderate hardness and good cushioning properties, and is therefore suitable as a cosmetic puff. Also, taking advantage of the fact that a stable roller resistance value is obtained, so that uneven charging of the toner conveyance and the photosensitive drum (OPC) is less likely to occur. Beam printer
(LBP) development roller, toner transport roller or transfer roller used for developing and transferring toner
It is extremely useful as a semi-conductive roller for the above-mentioned method. Furthermore,
The foam can be widely applied to other uses such as packing, seals and tubes.

Continuation of the front page (56) References JP-A-49-53956 (JP, A) JP-A-63-260934 (JP, A) JP-A-63-72734 (JP, A) JP-A-63-39932 (JP, A) , A) Tokubo Sho 62-49895 (JP, B2)

Claims (1)

(57) [Claims] 1. A powdery azobisisobutyronitrile having an average particle diameter of 5 to 75 μm is added to a diorganopolysiloxane.
Mix to make a master batch of blowing agent,
-Adding the batch to a mixture of a silicone rubber compound based on diorganopolysiloxane and an organic peroxide;
In addition, 0.5 to 10 parts by weight of azobisisobutyronitrile and 0.05 parts of organic peroxide per 100 parts by weight of the compound
Heat foaming and curing the mixed composition containing up to 5 parts by weight
A method for producing a silicone rubber foam.