JPH0873591A - Reparation of organopolysiloxane - Google Patents

Abstract

PURPOSE: To prepare a material for a silicone rubber compd. having a markedly reduced change with the elapse of time by incorporating an amide organosilicon compd. into a polymer of a cyclic organosiloxane and a low-mol.wt. linear organosiloxane. CONSTITUTION: A cyclic organosiloxane and a low-mol.wt. linear organosiloxane are polymerized in the presence of an alkaline catalyst to prepare a high-mol.wt. organosiloxane. After the catalyst is deactivated with an acidic neutralizing agent or by decomposition at a high temp., a silicon compd. of the formula (wherein R<1> to R<3> represent a hydrocarbon residue) is mixed to prepare an organopolysiloxane substantially free from a terminal hydroxyl group. Specific examples of the compd. of the formula include N,O-bis(triethylsilyl)acetamide. When the organopolysiloxane prepd. by this method is kneaded with a reinforcement, such as silica, to prepare a silicone rubber compd., the silicone rubber compd. has a reduction in creep hardening with the elapse of time and a markedly improved storage stability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an organopolysiloxane, and in particular, when used as a raw material for a silicone rubber compound, it has improved creep hardening and gives a compound excellent in storage stability. The present invention relates to a method for producing siloxane gum.

[0002]

As a method for producing an organopolysiloxane polymer, for example,
A method is known in which after cyclic organosiloxane is polymerized in the presence of an alkaline catalyst, the catalyst is neutralized and deactivated if desired, and low volatile components in the product are distilled off. In this case, the degree of polymerization of such a polymer is controlled by the amount of the low molecular weight linear organopolysiloxane which acts as a terminal terminating agent. Further, the structure of the terminal unit of the produced organopolysiloxane depends on the structure of the terminal stopper.

However, in the above-mentioned method for producing an organopolysiloxane, the water contained in the raw material or the catalyst is alkaline, and these can act as a terminal terminating agent. Depending on the structure, the resulting organopolysiloxane may have a hydroxyl group in the terminal unit.

When a high molecular weight organopolysiloxane gum having a hydroxyl group in the terminal unit thus produced is kneaded with a reinforcing agent such as silica to form a silicone rubber compound, the hydroxyl group at the organopolysiloxane end is formed. The bonding reaction between the groups and the silica surface is promoted, and the creep hardening phenomenon of the compound occurs due to aging. The compound having creep hardening as described above has a problem in that before use, a shearing force must be applied again by mastication to bring the compound closer to the initial state.

Therefore, when an organopolysiloxane gum is used as a raw material for a silicone rubber compound, it is usually desirable to design the terminal unit to be a triorganosilyl group. However, as described above, the hydroxyl group is generated due to an unexpected factor, and therefore the treatment is required.

[0006] Conventionally, as a method for reducing hydroxyl groups, Japanese Patent Laid-Open No. 63-120737 discloses a method of using dimethylvinylsilylacetate as a neutralizing agent for alkaline catalysts. It has not been reduced.

Further, a method of neutralizing an alkali metal catalyst by adding triorganohalosilane and hexaorganodisilazane is disclosed in JP-A-60-49033, and this method achieves reduction of hydroxyl groups. However, the use of halosilanes has the disadvantage of corroding metal equipment.

The present invention has been made to solve these problems, and when used as a raw material for a silicone rubber compound, creep hardening is improved,
It is an object of the present invention to provide a method for producing a high molecular weight organopolysiloxane gum that gives a compound having excellent storage stability.

[0009]

Means for Solving the Problems and Actions The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, polymerize a cyclic organosiloxane with a low molecular weight linear organosiloxane in the presence of an alkaline catalyst, In the case of producing a high molecular weight organopolysiloxane, by deactivating the alkaline catalyst after the above-mentioned polymerization and then mixing the organosilicon compound represented by the following general formula (1), the terminal does not contain a hydroxyl group. It was found that an organopolysiloxane can be obtained, and when the thus obtained organopolysiloxane is kneaded with a reinforcing agent such as silica to form a silicone rubber compound, the creep hardening of the silicone rubber compound over time is improved. Can significantly improve the storage stability of the silicone rubber compound And finding the door, the present invention has been accomplished.

[0010]

Embedded image (In the formula, R ¹ , R ² and R ³ represent the same or different unsubstituted or substituted monovalent hydrocarbon groups.)

Therefore, in the present invention, a cyclic organosiloxane is polymerized with a low molecular weight linear organosiloxane in the presence of an alkaline catalyst to deactivate the catalyst, and then the resulting organosiloxane is added to the above-mentioned general formula (1). The present invention provides a method for producing an organopolysiloxane, which comprises mixing an organosilicon compound represented by

The present invention will be described in more detail below. The present invention is to obtain a high molecular weight organopolysiloxane by polymerizing a cyclic organosiloxane with a low molecular weight linear organosiloxane in the presence of an alkaline catalyst. A method for polymerizing an organopolysiloxane using this alkaline polymerization catalyst is known, and, for example, a small amount of an alkaline catalyst is added to a cyclic organosiloxane and a linear organosiloxane having a low molecular weight, and an equilibration reaction is performed under heating at 100 to 180 ° C. It is done by letting.

Examples of the cyclic organosiloxane include those represented by the following formula (2).

[0014]

[Chemical 3]

In the formula, R ⁴ and R ⁵ are the same or different from each other and represent an unsubstituted or substituted monovalent hydrocarbon group, and m is an integer of 3-8. In this case, the hydrocarbon group has 1 to 1 carbon atoms.
0, especially 1 to 6, is preferable, for example, a methyl group,
Alkyl groups such as ethyl and butyl, cycloalkyl groups such as cyclohexyl and cyclopentyl, alkenyl groups such as vinyl and allyl, aryl groups such as phenyl and xylyl, aralkyl groups such as benzyl, etc. Some or all of the hydrogen atoms of the group are halogen atoms,
Examples thereof include groups substituted with a mercapto group, a glycidoxy group, a (meth) acryloxy group, an amino group and the like.

The above cyclic organosiloxanes may be used alone or in combination of two or more.

On the other hand, as the low molecular weight linear organosiloxane which controls the degree of polymerization of the high molecular weight organopolysiloxane, those represented by the following formula (3) can be used.

[0018]

[Chemical 4]

In the formula, R ^{6 to} R ⁹ are the same or different from each other and are unsubstituted or substituted monovalent hydrocarbon groups, R ¹⁰ and R ¹¹ are hydroxyl groups or unsubstituted or substituted monovalent hydrocarbon groups, and n Is 1
It is an integer of 200. In addition, as these monovalent hydrocarbon groups, those having the same carbon number as R ⁴ and R ⁵ are preferable, and the same groups as those mentioned above are exemplified.

It is preferable that a part of the cyclic organosiloxane or the low molecular weight linear organosiloxane as the starting material is previously dried by distillation or by using a desiccant such as silica gel. The low molecular weight linear organosiloxane is a factor that determines the degree of polymerization of the formed organopolysiloxane polymer, and the ratio to the cyclic organosiloxane may be changed according to the desired degree of polymerization.

As the alkaline catalyst, sodium hydroxide is used.
Alkali gold such as aluminum, potassium hydroxide, and cesium hydroxide
Examples include genus compounds and their silanolates. Well
Also, when deactivating these catalysts with an acidic neutralizing agent,
However, it decomposes at a high temperature of 130-150 ° C,
Lose activity ( n-C_FourH₉)_FourQuaternary phospho such as POH
Nium, (CH₃)_FourQuaternary ammonium such as NOH or
Alternatively, those silanolates can be used.

The equilibration reaction using the above raw materials can be carried out under usual conditions, for example, reaction conditions of 100 to 150 ° C. for 30 minutes to 2 hours can be adopted.

After the above reaction, the alkaline catalyst is deactivated by neutralizing it with an acidic neutralizing agent such as hydrochloric acid, ethylene chlorohydrin, acetic acid, carbon dioxide, or by thermally decomposing it. Further, it is preferable to distill off low volatile components thereafter.

The present invention is characterized in that after deactivating the alkaline catalyst in this manner, the organopolysiloxane obtained is mixed with an organosilicon compound represented by the following formula (1).

[0025]

[Chemical 5]

In the formula, R ^{1 to} R ³ represent the same or different unsubstituted or substituted monovalent hydrocarbon groups. In this case, the monovalent hydrocarbon group has 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms,
It is more preferably 1 to 3, and examples of R ^{1 to} R ³ include
Alkyl groups such as methyl group, ethyl group, propyl group or butyl group, cycloalkyl groups such as cyclohexyl group or cyclopentyl group, alkenyl groups such as vinyl group or allyl group, aryl groups such as phenyl group or xylyl group, and the like. Examples thereof include a group in which a hydrogen atom of the group is partially substituted with a halogen atom such as fluorine. Specific examples of the above organic silicon compound include N, O-bis (trimethylsilyl) acetamide and N, O-bis (triethyl). Examples are silyl) acetamide and N, O-bis (trimethylsilyl) trifluoroacetamide.
Since these are all neutral compounds, corrosion of metal equipment does not occur due to their use.

For the addition of the organosilicon compound represented by the above formula (1), a catalytic amount is sufficient, and the addition amount is from 500 to 10
The amount added may be about 00 ppm. Further, the addition may be performed before or after distilling the low volatile component as long as it is after deactivating the alkaline catalyst.

Considering the reaction product residue of the organosilicon compound represented by the above formula (1), it is preferable to add the reaction product residue before distilling off the low volatile content and distill off the reaction product residue together with the low volatile content.

If the organosilicon compound represented by the formula (1) is added in a state where the alkaline catalyst is active, the organosilicon compound acts as a polymer terminal terminating agent to give a product having a desired degree of polymerization. Can't get

After the addition of such an organosilicon compound, in order to complete the reaction, it is preferable to carry out a heat retention at room temperature to 180 ° C. for 10 minutes to 5 hours. In order to allow the production to proceed smoothly, the condition of 100 to 150 ° C. and 30 minutes to 1 hour is more preferable.

The high molecular weight organopolysiloxane obtained in the present invention is not particularly limited, but usually has a number average degree of polymerization of 3,000 to 15,000, and particularly 5,000 to 1.
0000, wherein the hydroxyl group remaining during the production of the high molecular weight organopolysiloxane is replaced by a triorganosilyl group by the addition of the organosilicon compound represented by the above formula (1).

The organopolysiloxane obtained by adding the above-mentioned organosilicon compound is kneaded with a reinforcing agent such as silica to form a silicone rubber compound, and the creep hardening due to the aging of the compound is improved, and the compound is preserved. Significantly improved. This is presumably because, as described above, the hydroxyl group remaining during the production of the organopolysiloxane is replaced with the triorganosilyl group by the organosilicon compound, and the bonding reaction with the silica surface is suppressed. .

[0033]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Example 1 1800 g of octamethylcyclotetrasiloxane, 1,3-divinyl-1,1,3,3
0.5 g of 3-tetramethyldisiloxane and 1,3
To a mixture of 2.6 g of 5,7-tetramethyl-1,3,5,7-tetravinylcyclosiloxane was added 3 g of 10% tetra-n-butylphosphonium hydroxide dimethylpolysiloxanate and 110 ° C. Polymerization reaction was carried out for 1 hour.

After the polymerization reaction, the temperature was kept at 150 ° C. for 2 hours to thermally decompose tetra-n-butylphosphonium hydroxide, 1.3 g of N, O-bis (trimethylsilyl) acetamide was added, and the temperature was kept for 1 hour. Then 140-150
Approximately 5 until 2 mmHg or less under heat retention / decompression at ℃
The low volatiles were distilled off over time. The obtained organopolysiloxane was a colorless and transparent raw rubber product having a number average degree of polymerization of about 8,000.

Then, one of the organopolysiloxanes
100 g of 0% toluene solution was prepared, 0.5 g of tetramethoxysilane and tetrapropyl titanate were added in a catalytic amount, and the initial viscosity and the viscosity of the solution after 4 hours were measured. The relative viscosity ratio (viscosity after 4 hours / viscosity after 4 hours / The initial viscosity) was 1.

This means that the hydroxyl group does not exist in the organopolysiloxane, so that the condensation reaction with the methoxy group of tetramethoxysilane does not occur and the viscosity does not increase.

For comparison, the organopolysiloxane produced by the same method as in the example except that N, O-bis (trimethylsilyl) acetamide in the example was not added had a number average degree of polymerization of about 8,000. It was a colorless and transparent raw rubber product.

When the product thus obtained was subjected to the same viscosity change test as described above, the relative viscosity ratio was 1.23. This is because the hydroxyl group remains in the organopolysiloxane, and thus the condensation reaction between the organopolysiloxane and the methoxy group of tetramethoxysilane is carried out by the intervention of the tetrapropyl titanate catalyst to accelerate the crosslinking.

The specific surface area is 200 m ² / g based on 100 parts by weight of the organopolysiloxane obtained in the example.
Fumed silica (manufactured by Nippon Aerosil Co., Ltd.) 41
3.9 parts by weight of linear dimethylsiloxane having silanol groups at both ends and having an average chain length of 15 to 20 and 3.9 parts by weight of diphenylsilanediol as a dispersion aid for these are added to a kneader mixer to obtain a uniform mixture. 180 after mixing
Heat treatment was carried out at ℃ for 1 hour to obtain a silicone rubber compound.

In order to evaluate the preservability of this base compound, after leaving the base rubber compound at 100 ° C. for 7 days, it was wound around two rolls with an interval of 2 mm until the compound was smoothly wound on the roll. The working time was evaluated. As a result, in spite of the severe storage conditions of 100 ° C and 7 days, it wound around the two rolls very smoothly in an instant (10 seconds), the creep hardening was suppressed, and the compound was excellent in storage stability. It was confirmed that there is.

Incidentally, 0.6 part by weight of 2,4-dichlorobenzoyl peroxide as a vulcanizing agent was uniformly mixed with 100 parts by weight of the base rubber compound to obtain 120 parts by weight.
Vulcanization treatment was performed by press vulcanization at 10 ° C. for 10 minutes, post vulcanization at 200 ° C. for 4 hours, and a physical test was performed on the vulcanized rubber according to JIS-K 6301. The hardness was 55 degrees and the tensile strength was 114 kgf. / Cm ² , tear strength (JIS-A) 1
It had a strength of 6 kgf / cm.

On the other hand, when the same roll workability evaluation was performed on the organopolysiloxanes obtained in Comparative Examples, creep hardening occurred due to a change with time, which made it difficult for two rolls to wind, and the wound rubber compound. Has a hole in it and it took a long time (180 seconds) until it became smooth.

The physical properties of the vulcanized rubber obtained by the same method as in the examples are shown in Table 1 together with the results of the examples.

The silicone rubber compound obtained by using the organopolysiloxane obtained in the example as a raw material is
It was confirmed that the shelf life was superior to that in the comparative example and that the physical properties of the vulcanized rubber were not impaired.

[0046]

[Table 1]

[Example 2] 1800 g of octamethylcyclotetrasiloxane, 1,3-divinyl-1,1,3,3
0.5 g of 3-tetramethyldisiloxane and 1,3
To a mixture consisting of 2.6 g of 5,7-tetramethyl-1,3,5,7-tetravinylcyclosiloxane, 10% K
Add 0.6 g of OH dimethyl polysiloxanate,
A polymerization reaction was carried out at 40 to 150 ° C. for 4 hours.

After the polymerization reaction, 0.5 g of ethylene chlorohydrin, an acidic neutralizing agent, was added, and the mixture was kept warm at 140 to 150 ° C. for 2 hours to sufficiently neutralize the alkaline catalyst.

Subsequently, 1.3 g of N, O-bis (trimethylsilyl) acetamide was added, and the mixture was kept warm for 1 hour and kept at 140 to 150 ° C./low pressure for about 5 hours until the pressure became 2 mmHg or less. Minutes were distilled off. The resulting organopolysiloxane has a number average degree of polymerization of about 90.
00 was a colorless and transparent raw rubber-like product.

The relative viscosity ratio in the viscosity change test with respect to the organopolysiloxane was 1, and in the roll workability evaluation of the silicone rubber compound induced by kneading with the reinforcing silica, the compound was instantaneously (10
(S) And it wrapped around the roll smoothly.

The characteristics of the vulcanized rubber obtained by the same method as in Example 1 are shown in Table 2.

[0052]

[Table 2]

[0053]

According to the present invention, in the production of a high molecular weight organopolysiloxane gum used as a raw material for a silicone rubber compound, the product is obtained by adding and mixing the organosilicon compound represented by the above formula (1). When the silicone rubber compound is formed using the organopolysiloxane obtained by reducing the hydroxyl groups in the compound, the creep hardening over time of the rubber compound, which has been a problem in the past, was improved and the storage stability was improved. However, workability when using the rubber compound is significantly improved.

Claims (1)

[Claims] 1. A cyclic organosiloxane is polymerized with a low molecular weight linear organosiloxane in the presence of an alkaline catalyst to deactivate the catalyst, and then the resulting organosiloxane is added to the following formula (1): ] (Wherein R ¹ , R ² , and R ³ are the same or different from each other and represent an unsubstituted or substituted monovalent hydrocarbon group.) An organopolysiloxane characterized by being mixed. Method.