JP2002363294A - High filling kneading method of filler in silicone rubber - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a high filling method of silicone rubber with a filler which does not require a large amount of energy consumption, a lower degree of freedom in compounding design, or a new capital investment. SOLUTION: In a kneading process of a silicone rubber, a filler having a negative triboelectric potential is mixed with a cationic antistatic agent or deionized water to be kneaded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a kneading method capable of highly filling a silicone rubber with a filler.

[0002]

2. Description of the Related Art In order to respond to the demand for higher functionality of rubber, not only silicone rubber, unless a large amount of filler is blended,
Increasingly, it is difficult to meet those demands. In other words, as in the design of conductive and heat conductive rubber that enables high energy transfer, or the design of sound insulation and insulating rubber that hinder energy transfer, the amount of filler and the expression of those characteristics are In closely related fields, there has been a strong demand for the development and establishment of high-filling technology for fillers.

Hitherto, as a technique for highly filling a filler in the field of silicone rubber, improvement and devising of a stirring and kneading apparatus and improvement in efficiency of a required power for stirring have been the main approaches to these problems, and there are many patents. It has been published. It is well known that the development of the kneading method has been advanced, and the research on the multistage mixing, the surface modification of the filler, and the efficient softener (plasticizer) has been widely conducted.

[0004] However, they have a large economical burden, such as a large consumption of energy, a great reduction in the degree of freedom in the design of blending, and a large capital investment, and each has a great disadvantage.

[0005] In particular, among rubbers, silicone rubber, which exhibits a strong negative charge during kneading, uses silica powder and alumina powder, which also show a tendency to be negatively charged during kneading, as main general-purpose fillers. Has a large electrostatic repulsion force at the time of kneading, which is the most important factor that makes it difficult to mix a large amount of filler.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems of the prior art and is directed to a silicone rubber which does not require a large amount of energy consumption, a lower degree of freedom in compounding design, or a new capital investment. An object of the present invention is to provide a method for highly filling a filler.

[0007]

Means for Solving the Problems The inventors of the present invention have intensively studied means for achieving the above object by a relatively simple method. As a result, when silicone rubber is filled with a filler having a negative triboelectric potential, The present inventors have found that high filling can be achieved by coexistence of a system antistatic agent or deionized water, and have completed the present invention.

That is, the present invention provides a silicone rubber characterized in that in the kneading step of the silicone rubber, a cationic antistatic agent or deionized water is mixed and kneaded with a filler exhibiting a negative triboelectric potential. This is a high filling kneading method of the filler.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
It is known that silicone rubber exhibits a large negative frictional charge potential. Therefore, kneading of a filler having a positive frictional charge potential, such as magnesia (MgO), requires less power and requires a short time and a high filling compound. Can be prepared.

However, silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) powders, like silicone rubber, are negatively charged, so that an electrostatic repulsion between the rubber and the filler is generated during kneading, so that the compound It took a long time to get together. In particular, this tendency is large in a dry season such as winter (humidity is about 40% or less).

The present invention solves the above-mentioned problem, and uses a cationic antistatic agent or deionized water with respect to silica or alumina having a negative triboelectric potential, or other filler having a negative triboelectric potential. It is characterized in that it can be highly filled by relatively simple means of coexisting and kneading.

The cationic antistatic agent used here is a group of chemicals which when dissolved in water or isopropyl alcohol exhibit strong cation properties. The main ones include monoalkylammonium chloride, dialkylammonium chloride and ethylene oxide-added ammonium chloride.

The deionized water is water from which ionic components have been removed, and can be easily obtained by passing it through an ion exchange resin. Tap water is not preferred because it contains legal chlorine ion components.

The term "highly filled filler" as defined in the present invention does not specify exactly how much the compounding amount should be, but generally the above filling amount is based on 100 parts by weight of the polyorganosiloxane base polymer. Means 100 parts by weight or more of the agent.
It refers to the case of compounding that takes a long time to form a compound. In particular, the effect of the present invention is remarkable when 400 or more parts by weight of the above filler is blended with respect to 100 parts by weight of the polyorganosiloxane base polymer.

[0015] The amount of the cationic antistatic agent or deionized water to be added is difficult to determine unambiguously because the preferable amount of addition varies depending on the relative humidity of the kneading work environment and the properties of the compounding materials. . As a rough guide, it is desirable to try adding 0.5 to 5% by weight of a negatively chargeable filler, measure the charge amount in that case, and adjust it.

It is effective to add the cationic antistatic agent or deionized water in the form of a mist using a spray or the like. There is no problem to add it as it is.
However, if kneading after preliminarily mixing with the filler in advance, care must be taken because the charged potential often does not decrease.

The silicone rubber used in the present invention comprises:
It is obtained by blending (a) a polyorganosiloxane base polymer, (b) a curing agent, and, if necessary, various additives, and dispersing them uniformly. Among the various components used in such a polyorganosiloxane composition, (a) a silicone base polymer and (b) a curing agent are appropriately selected depending on a reaction mechanism for obtaining a rubber-like elastic body. is there. As the reaction mechanism, (1) a crosslinking method using an organic peroxide vulcanizing agent, (2) a method using a condensation reaction, (3) a method using an addition reaction, and the like are known. It is well known that the preferred combination of component and component (b), ie a curing catalyst or crosslinking agent, is determined.

That is, when the crosslinking method of the above (1) is applied, as the base polymer of the component (a), at least two of the organic groups bonded to silicon atoms in one molecule are usually vinyl groups. Is used. As the curing agent of the component (b), an acyl peroxide such as benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, or p-chlorobenzoyl peroxide is used. In addition, these organic peroxide vulcanizing agents are used as one kind or as a mixture of two or more kinds. The compounding amount of the organic peroxide as the curing agent of the component (b) is preferably in the range of 0.05 to 15 parts by weight based on 100 parts by weight of the silicone base polymer of the component (a). If the compounding amount of the organic peroxide is less than 0.05 parts by weight, the vulcanization is not sufficiently performed, and if the compounding amount exceeds 15 parts by weight, not only there is no further special effect, but also the physical properties of the obtained silicone rubber are reduced. This is because it may have an adverse effect.

When the condensation reaction of the above (2) is applied, a polydiorganosiloxane having hydroxyl groups at both ends is used as the base polymer of the component (a). As the curing agent (b), first, as a crosslinking agent, ethyl silicate, propyl silicate, methyltrimethoxysilane, vinyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, methyltris (methoxyethoxy) silane, vinyltris ( Methoxyethoxy) silane, alkoxy type such as methyltripropenoxysilane; acetoxy type such as methyltriacetoxysilane and vinyltriacetoxysilane; methyltri (acetone oxime) silane, vinyltri (acetone oxime) silane, methyltri (methylethylketoxime) silane, Examples thereof include vinyltri (methylethylketoxime) silane and the like and a partial hydrolyzate thereof. Further, hexamethyl-bis (diethylaminoxy) cyclotetrasiloxane, tetramethyldibutyl-bis (diethylaminoxy) cyclotetrasiloxane, heptamethyl (diethylaminoxy) cyclotetrasiloxane, pentamethyl-tris (diethylaminoxy) cyclotetrasiloxane, hexamethyl-bis ( Cyclic siloxanes such as methylethylaminoxy) cyclotetrasiloxane and tetramethyl-bis (diethylaminoxy) -mono (methylethylaminoxy) cyclotetrasiloxane are also exemplified. As described above, the cross-linking agent may be any of a silane or siloxane structure, and the siloxane structure may be any of linear, branched and cyclic structures. Furthermore, when using these, it is not necessary to be limited to one type, and two or more types can be used in combination. Among the curing agents (b), curing catalysts include iron octoate, cobalt octoate, manganese octoate, tin carboxylate such as tin naphthenate, tin caprylate, and tin oleate: dimethyltin oleate, dimethyl Organic tin compounds such as tin laurate, dibutyltin diacetate, dibutyltin octoate, dibutyltin dilaurate, dibutyltin oleate, diphenyltin diacetate, dibutyltin oxide, dibutyltin methoxide, dibutylbis (triethoxysiloxy) tin, and dioctyltin dilaurate are used. . Among the curing agents of the component (b), the amount of the crosslinking agent is preferably 0.1 to 20 parts by weight based on 100 parts by weight of the base polymer of the component (a). If the amount of the cross-linking agent is less than 0.1 part by weight, sufficient strength cannot be obtained in the cured rubber, and if it exceeds 20 parts by weight, the obtained rubber becomes brittle, and all are hardly practical. In addition, the compounding amount of the curing catalyst is as follows.
It is preferably 0.01 to 5 parts by weight based on 00 parts by weight. If the amount is smaller than the above range, the curing catalyst is insufficient, and it takes a long time to cure, and the curing in the interior far from the contact surface with air becomes poor. On the other hand, if it is more than this, the storage stability will decrease. A more preferred range for the amount is 0.1 to 3 parts by weight.

(A) when the addition reaction of the above (3) is applied
As the base polymer of the component, those similar to the base polymer in the above (1) are used. In addition, as a curing agent of the component (b), a platinum catalyst such as chloroplatinic acid, a platinum olefin complex, a platinum vinyl siloxane complex, platinum black, and a platinum triphenylphosphine complex is used as a curing catalyst. A polydiorganosiloxane having an average of at least two hydrogen atoms bonded to silicon atoms in one molecule is used. Among the curing agents of the component (b), the amount of the curing catalyst is preferably in the range of 1 to 1000 ppm in terms of platinum element based on the base polymer of the component (a). If the amount of the curing catalyst is less than 1 ppm in terms of platinum element, curing will not proceed sufficiently, and 1000 ppm
Even if the ratio exceeds the above, improvement of the curing speed and the like cannot be expected. The amount of the crosslinking agent is such that the hydrogen atom bonded to the silicon atom in the crosslinking agent per one alkenyl group in the component (a) is
The amount is preferably 0.5 to 4.0, more preferably 1.0 to 3.0. When the amount of hydrogen atoms is less than 0.5, curing of the composition does not proceed sufficiently, and the hardness of the composition after curing becomes low. The physical properties and heat resistance of the composition are reduced. The organic group in the polyorganosiloxane as the base polymer of the component (a) used in the various reaction mechanisms as described above is a monovalent substituted or unsubstituted hydrocarbon group, such as a methyl group, an ethyl group, Propyl group, butyl group, hexyl group, alkyl group such as dodecyl group, aryl group such as phenyl group, β-phenylethyl group, unsubstituted hydrocarbon group such as aralkyl group such as β-phenylpropyl group, , Chloromethyl group, 3,
A substituted hydrocarbon group such as a 3,3-trifluoropropyl group is exemplified. In general, a methyl group is frequently used because of ease of synthesis and the like.

The silicone rubber of the present invention may optionally further contain a pigment, a heat resistance improver, a flame retardant, and the like, and may be used in combination with another polyorganosiloxane as long as the effects of the present invention are not impaired. Is also good.

[0022]

EXAMPLES The present invention will be described more specifically with reference to the following examples. In the examples, parts mean parts by weight. Example 1 A 3-liter capacity kneader was charged with 1.5 kg of a vinyl group-containing polydimethylorganosiloxane having a polymerization degree of 6000 as a silicone base polymer, and "Aerosil 200" (trade name: manufactured by Nippon Aerosil Co., Ltd.) as silica powder. ) Was charged 50 g at a time.

After visually confirming that 50 g of the silica powder was completely integrated with the base polymer, the next silica powder was charged. After the addition of the silica powder, 1 g of a monoalkylammonium chloride “Agard T-28” (trade name, manufactured by Lion Corporation) (existing chemical substance No. 2-184) was added as a cationic antistatic agent.

The antistatic agent is prepared as an aqueous solution, and the active ingredient is 28%.

The measurement was carried out for the time from the injection of Aerosil in batches to the integration with the base polymer, the electrostatic potential at 1 minute and 3 minutes after the charging of the antistatic agent, and the electrostatic potential in a series of kneading operations. The maximum and minimum values were read from the recorder.

The point at which the silica powder fed in batches was not integrated with the base polymer even after kneading for 2 hours was defined as the end point of kneading.

The measurement of the electrostatic potential was carried out by a widely used vibrating electrode type surface electrometer (used by Kasuga Electric Co., Ltd.). This was placed in a compound of a kneader stirring tank at a predetermined distance determined by an instrument and measured.

Since the measured value changes continuously from time to time, the maximum value and the minimum value were read from the recorder, and the other values were compared at a fixed time such as an interval of 10 minutes from the start of kneading. Comparative Examples 1 and 2 As Comparative Example 1, the same operation as in Example 1 was carried out except that no cationic antistatic agent was used. As Comparative Example 2, glycerin monostearate “Likemar P-100” was used as a nonionic antistatic agent. (Product name: manufactured by Riken Vitamin Co., Ltd.)
Was performed in the same manner as in Example 1 except that was added in place of "Agard T-28". However, since the melting point was around 65 ° C., it was preheated and charged in a liquid state.

Table 1 shows the results.

[0030]

[Table 1]

Example 2 In a kneader having a capacity of 3 liters, 1.2 kg of a vinyl group-containing polydimethylorganosiloxane having a polymerization degree of about 5200 was charged as a silicone base polymer, and "AS-40" (trade name: Showa) was used as alumina powder. Denko Corporation
Was prepared at a time, 200 g each.

After visually confirming that 200 g of alumina powder was completely integrated with the base polymer, the next alumina powder was charged. After charging the alumina powder, 8 g of deionized water was added.

The measurement was performed in the same manner as in Example 1 above. Comparative Examples 3 and 4 As Comparative Example 3, the same operation as in Example 2 was performed except that deionized water was not used, and as Comparative Example 4, an operation was performed except that tap water in Ota City, Gunma Prefecture was added instead of deionized water. The same operation as in Example 2 was performed.

Table 2 shows the results.

[0035]

[Table 2]

Claims (1)

[Claims] In a silicone rubber kneading step, a filler having a negative triboelectric potential is kneaded in the presence of a cationic antistatic agent or deionized water. High filling kneading method.