KR20110114911A - Method of preparing linear and brnched polysiloxane mixtures having silanol end groups - Google Patents

Abstract

The present invention relates to a process for preparing low molecular weight linear and branched polysiloxane mixtures, all of which are terminated with silanol groups, and more particularly, to equilibrating a cyclosiloxane and a mixture of dialkoxysilane and trialkoxysilane using an acidic catalyst. To prepare a low molecular weight linear and branched polysiloxane mixture, all of which terminate at the end with an alkoxy group, and then add water to the hydrolysis reaction to substitute the alkoxy group with a silanol group, where both ends have a low molecular weight linear and branched form. A method for producing a polysiloxane mixture and a method of using the polysiloxane mixture as a plasticizer in preparing a silicone rubber compound.

Description

METHODS OF PREPARING LINEAR AND BRNCHED POLYSILOXANE MIXTURES HAVING SILANOL END GROUPS}

The present invention relates to a process for preparing low molecular weight linear and branched polysiloxane mixtures, all of which are terminated with silanol groups, and more particularly, to equilibrating a cyclosiloxane and a mixture of dialkoxysilane and trialkoxysilane using an acidic catalyst. To prepare a low molecular weight linear and branched polysiloxane mixture, all of which are terminated with an alkoxy group, to which hydrolysis is carried out by addition of water, to which the alkoxy group is substituted with a silanol group. A method of preparing a type polysiloxane mixture and a method of using the polysiloxane mixture as a plasticizer in preparing a silicone rubber compound.

In general, low molecular weight polysiloxanes in which the sock ends are finished with silanol groups are used as plasticizers useful in the production of silicone rubber (HTV), and low molecular weight polysiloxanes in which the sock ends are finished with silanol groups have been synthesized in various ways.

First, there is a method for producing dimethyldichlorosilane by hydrolysis under neutrality. Dimethyldichlorosilane is hydrolyzed to produce a hydrochloric acid solution, which is a strong acid. Such strong acid causes condensation reaction of silanol and chloro groups, making synthesis of polymers having a relatively low molecular weight difficult. In addition, there is a need for an additional neutralization step to remove the generated hydrochloric acid, and because a large amount of solvent is used, a by-product is generated.

U. S. Patent No. 3,309, 390 discloses a method for synthesizing low molecular weight polysiloxanes in which the sock ends are silanol groups using acidic clay under cyclotrisiloxane and acetone solvents. When the sock end is prepared with silanol-based low molecular weight polysiloxane, there are disadvantages in that it uses cyclotrisiloxane, which is not widely used commercially, and a large amount of solvent.

In US Pat. No. 4,066,680, a cyclosiloxane mixture is reacted with acetic anhydride and acetic acid to synthesize a low molecular weight polysiloxane in which the socks are terminated with acyloxy, and then hydrolyze with a sodium carbonate solution to reduce the molecular weight of the socks to finish with Disclosed is a method of making polysiloxanes. However, this method also has a disadvantage in that a lot of by-products are generated, and acyloxy groups are not completely removed, and an acetic acid odor remains in the final composite.

US Pat. No. 4,395,563 discloses a process in which dialkoxysilanes are hydrolyzed under various catalysts to synthesize low molecular weight polysiloxanes in which the sock ends are silanol groups. This method also has a disadvantage in that a large amount of by-products are generated and oligomers (n = 2-3) having a very small molecular weight are synthesized. When the molecular weight is very small, since it volatilizes due to the high temperature during the compounding process by using it as a plasticizer of the silicone rubber, it can no longer serve as a plasticizer.

Recently, a technique for producing a low molecular weight polysiloxane in which a sock end is a silanol group by reacting cyclosiloxane and dialkoxysilane has been proposed. However, this technique also has a disadvantage in that it is not satisfactory in silanol content and plasticizer properties.

U.S. Patent 3,309,390 U.S. Patent 4,066,680 U.S. Patent 4,395,563

The present invention is to solve the problems of the prior art as described above, to provide a method for producing a linear and branched polysiloxane mixture, both ends of the silanol group, the generation of by-products and excellent performance when applied as a plasticizer It is technical problem to do.

The present invention to solve the above technical problem, 1) equilibrating the cyclosiloxane and the mixture of dialkoxysilane and trialkoxysilane in the presence of an acidic catalyst to produce a linear and branched polysiloxane mixture, both ends of which are alkoxy groups And 2) hydrolyzing the polysiloxane mixture obtained as a result of step 1 to change all of its ends into silanol groups, thereby providing a process for producing a linear and branched polysiloxane mixture terminated at all ends with silanol groups. do.

According to another aspect of the present invention, there is provided a plasticizer composition for a silicone rubber compound comprising a polysiloxane mixture prepared according to the present invention.

According to another aspect of the invention, there is provided a silicone rubber compound comprising as a plasticizer component a polysiloxane mixture prepared according to the invention.

Hereinafter, the present invention will be described in more detail.

In the first step of the method for preparing a polysiloxane mixture of the present invention, an equilibrium reaction of the cyclosiloxane and dialkoxysilane / trialkoxysilane mixture in the presence of an acidic catalyst (ie, a reaction in which the content of the linear polymer and the cyclic polymer is constant after a certain reaction time has elapsed) ) To prepare low molecular weight linear and branched polysiloxane mixtures, all of which are terminated by alkoxy groups.

As the cyclosiloxane, a cyclosiloxane compound substituted with alkyl of 1 to 4 carbon atoms, alkenyl of 2 to 4 carbon atoms or aryl of 6 to 10 carbon atoms, and having 3 to 12 [Si-O] units in the ring structure It is possible to use, preferably those represented by the following formula (1):

Formula 1

[SiR ₁ R ₂ O] _n

(Wherein R ₁ and R ₂ are independently methyl, vinyl or phenyl and n is an integer from 3 to 12.)

Examples of the cyclosiloxane include cyclodimethylsiloxane, cyclomethylvinylsiloxane, cyclomethylphenylsiloxane, and the like, which may be used alone or in combination.

As said dialkoxysilane, the silane compound which has two C1-C4 alkyls, C2-C4 alkenyl, or C6-C10 aryl substituents, and two C1-C10 alkyl-oxy substituents It is possible to use, preferably those represented by the following formula (2):

Formula 2

R ₃ R ₄ Si (OR ₅ ) ₂

(Wherein R ₃ and R ₄ are independently methyl, vinyl or phenyl, and R ₅ is independently an alkyl group having 1 to 10 carbon atoms.)

Examples of the dialkoxysilanes include dimethyldimethoxysilane, dimethyldiethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, and the like. Can be used.

As said trialkoxysilane, the silane compound which has C1-C4 alkyl, C2-C4 alkenyl, or C6-C10 aryl substituent, and three C1-C10 alkyl-oxy substituents It is possible to use, preferably those represented by the following general formula (3):

Formula 3

R ₆ Si (OR ₇ ) ₃

(Wherein R ₆ is methyl, vinyl or phenyl, and R ₇ is independently an alkyl group having 1 to 10 carbon atoms.

Examples of the trialkoxysilane include methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and the like. May be used or mixed.

There is no particular limitation on the usage ratio between the reactants in the first step, preferably 20 to 80 parts by weight, more preferably 30 to 70 parts by weight of a dialkoxysilane / trialkoxysilane mixture with respect to 100 parts by weight of cyclosiloxane. If the amount of dialkoxysilane / trialkoxysilane mixture to 100 parts by weight of cyclosiloxane is less than 20 parts by weight, the molecular weight of the final polysiloxane mixture may be high, which may cause difficulty in expressing proper plastic performance when applied as a plasticizer of silicone rubber compound. When the content exceeds 80 parts by weight, the molecular weight of the final polysiloxane mixture is too low to increase the likelihood of volatilization during the production of the silicone rubber compound, and the content of silanol groups is too high, which may cause problems in the storage stability of the polysiloxane mixture itself.

 The trialkoxysilane content in 100% by weight of the dialkoxysilane / trialkoxysilane mixture is preferably 10 to 90% by weight, more preferably 20 to 80% by weight. When the trialkoxysilane content in the alkoxysilane mixture is less than 10% by weight, the silanol group content of the final polysiloxane mixture may not be significantly different from the general plasticizer, and thus, there may be a problem in that excellent plasticization performance is difficult, and more than 90% by weight. If the silanol group content of the final polysiloxane mixture is too high, there may be a problem in the storage stability of the polysiloxane mixture itself.

As the acidic catalyst, a general acid catalyst used in synthesizing a silicone polymer may be used, and examples thereof include sulfuric acid, hydrochloric acid, acidic clay, and acidic ion exchange resin. Among them, acidic clay treated with sulfuric acid, acidic ion exchange resin, and the like are more preferable in terms of eliminating the neutralization process, and it is particularly preferable to use acidic clay treated with sulfuric acid. When acidic clay is used as a catalyst, since the catalyst is solid, there is no need for neutralization by use of a neutralizing agent or washing after the equilibration reaction, and there is an advantage that the filter can be easily removed. The amount of the catalyst generally used is 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight based on 100 parts by weight of cyclosiloxane.

The equilibration reaction temperature is preferably 50 to 130 ° C, more preferably 70 to 100 ° C. The equilibrium attainment time at the reaction temperature is about 3-7 hours. Equilibration reaction time can be adjusted according to reaction temperature and catalyst amount. However, when the amount of catalyst is large, it is difficult to filter, so it is preferable to use a small amount of catalyst as much as possible. The lower the amount of catalyst, the higher the reaction temperature is, the higher the reaction time is, but the higher the temperature, the higher the unconditional boiling point of the alkoxysilane to be used, it is preferable not to exceed the boiling point of the alkoxysilane. If the reaction proceeds above the boiling point, it becomes difficult to react the correct equivalent of raw material.

The molecular weight of the low molecular weight linear and branched polysiloxane mixture terminated at the end of the alkoxy group in step 1 is determined by the amount of dialkoxysilane and trialkoxysilane used, and the equilibration reaction is carried out by controlling the amount of alkoxysilane used. It is possible to control the alkoxy group content of the polysiloxane mixture produced by, it is possible to control the silanol group content of the polysiloxane mixture synthesized by hydrolysis in two steps to be described later.

In the above two steps of the method for producing a polysiloxane mixture of the present invention, water is added to the low molecular weight linear and branched polysiloxane mixtures obtained at the end of the first step, all of which are terminated with an alkoxy group, to hydrolyze and alkoxy groups. Will be replaced by. By then removing the solid catalyst and reaction by-products, a low molecular weight linear and branched polysiloxane mixture can be obtained with both ends terminated with silanol groups.

In order to lower the temperature of the resultant mixture prepared in step 1 and promote the hydrolysis reaction, it is preferable to proceed with the hydrolysis reaction by adding water without removing the acidic clay catalyst remaining after the equilibration reaction. If the water to be used contains ions, acids, bases, and the like, the storage stability of the low molecular weight linear and branched polysiloxane mixtures, all of which are terminated with silanol groups, becomes poor, so that neutral ion-exchanged water is preferably used. The amount of water used for the hydrolysis reaction is theoretically 2 to 10 times, more preferably 2 to 5 times the amount of water capable of substituting all of the terminal alkoxy groups. The reaction temperature of the hydrolysis reaction is preferably 25 to 80 ° C, more preferably 60 to 80 ° C, and the reaction time is preferably about 1 hour.

In order to lower the temperature of the reactants after the hydrolysis reaction and to remove the catalyst and byproduct alcohol, unreacted water and cyclosiloxane used in the reaction, the solid catalyst is first filtered out, and alcohol, water and cyclosiloxane are distilled under reduced pressure. Can be removed. Removal of the catalyst, side reactions, and unreactants results in a mixture of low molecular weight linear and branched polysiloxanes, all of which end terminated with silanol groups.

The average molecular weight of the low molecular weight linear and branched polysiloxane mixtures produced by the above-mentioned methods, all of which are terminated with silanol groups, is preferably 500 to 3,000, more preferably 500 to 2,000. In addition, the OH content is preferably 4 to 10% by weight. If the OH content is within the above range, it can be usefully used as a plasticizer in the production of silicone rubber, and can also be used as an intermediate in the production of other siloxane polymers. On the other hand, when the OH content is less than 4% by weight, the plasticizing effect may be lowered. When the OH content is more than 10% by weight, the plasticizer may have a disadvantage of volatilizing during the production of the silicone rubber compound at a high temperature.

Plasticizers in silicone rubber (HTV) are additives used to facilitate the dispersion of hydrophilic silica and hydrophobic siloxane gums and mainly use low molecular weight silanol terminated polysiloxanes. These plasticizers improve the compatibility of silica and siloxane gums to increase the dispersing effect, increase the storage stability of the silicone rubber compound, and improve the flowability during roll work and extrusion / molding molding. It plays a role of strengthening physical properties.

Therefore, the higher the plasticizer having a higher silanol content, the higher the surface treatment efficiency with silica, which has the advantage of reducing the plasticizer content used in the production of the silicone rubber compound. In the case of the linear polysiloxane having silanol groups at the sock end, the molecular weight should be lowered in order to increase the silanol content, but when the molecular weight is low, there is a problem of volatilization during the production of the silicone rubber compound. The polysiloxane mixture prepared according to the present invention has an excellent plasticizing effect by increasing the silanol content at the same molecular weight.

Accordingly, according to another aspect of the present invention, there is provided a plasticizer composition for a silicone rubber compound, comprising a polysiloxane mixture prepared according to the present invention.

According to another aspect of the invention, there is also provided a silicone rubber compound comprising as a plasticizer component a polysiloxane mixture prepared according to the invention. The silicone rubber compound of the present invention generally contains 0.1 to 10% by weight of the polysiloxane mixture.

According to the present invention, it is possible to prepare linear and branched polysiloxane mixtures, all of which are terminated with silanol groups, which have low by-products and excellent performance when applied as a plasticizer. You can get it.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are illustrative of the present invention, and the contents of the present invention are not limited by the following examples.

Example  One

 370.75 g of cyclodimethylsiloxane (5 mol D), 60.11 g (0.5 mol) dimethyldimethoxysilane, 68.11 g (0.5 mol) methyltrimethoxysilane, acidic clay (DC-A3) , Donghae Chemical) 5 g was added. The temperature was raised while stirring to react for 4 hours at 70 degreeC. After the catalyst was added and sampled every hour and analyzed by gas chromatography, it was confirmed that the composition of the mixture was constant after 3 hours. The temperature was lowered to room temperature and 54.03 g of water was added thereto. The temperature increased slightly (about 3 ~ 5 ℃) by the initial exotherm of water. The temperature was then raised to 70 ° C. with stirring to hydrolyze for 1 hour. After hydrolysis was completed, the mixture was lowered to room temperature, and the acidic clay was filtered using a paper filter. After removing the acidic clay, methanol, water, and cyclosiloxane produced by unreacted and side reactions were removed in a new 1 L flask connected with a vacuum gauge and a thermometer under a vacuum of 120 ° C. and 10 torr.

Finally, a low molecular weight linear and branched polysiloxane mixture (plasticizer A) with a viscosity of 42.5 cP, a molecular weight of 850, and an OH content of 5.01%, all terminated with silanol groups was obtained. No oxy peak was observed. This confirmed that the ends were all silanol groups.

Example  2

Under the same conditions as in Example 1, 370.75 g of cyclodimethylsiloxane (4 mol of D units), 24.04 g (0.2 mol) of dimethyldimethoxysilane, and 108.98 g (0.8 mol) of methyltrimethoxysilane were reacted to obtain a final viscosity. A low molecular weight linear and branched polysiloxane mixture (plasticizer B) having a terminal end of all silanol groups having 39.8 cP, a molecular weight of 730 and an OH content of 6.52%. In the same manner as in Example 1, it was confirmed that both ends were silanol groups.

Comparative example  One

Under the same conditions as in Example 1, 370.75 g of cyclodimethylsiloxane (5 mol of D units) and 120.22 g (1 mol) of dimethyldimethoxysilane were reacted to finally have a viscosity of 41.3 cP, a molecular weight of 830, and an OH content. A low molecular weight linear polysiloxane mixture (plasticizer C) with 4.1% terminal all terminated with silanol groups was obtained. In the same manner as in Example 1, it was confirmed that both ends were silanol groups.

Example  3 ~ 5, Comparative example  2 ~ 3

100 g of siloxane gum having a vinyl group (SF3901C, KCC Co., Ltd.), 30 g of silica, and plasticizers A, B, and C prepared in Examples 1 and 2 and Comparative Example 1 were added by weight as shown in Table 1 below. A silicone rubber compound was prepared.

The visual observation results of the silica dispersibility in preparing the silicone rubber compound, the hardness and the plasticity of the prepared compound are shown in Table 1 below.

TABLE 1

¹ Hardness: KS M 6518

² Plasticity: KS M 6605 (William's plasticity)

From the experimental results in Table 1, it can be seen that the polysiloxane mixture prepared according to the present invention gives good plasticizing performance even when a small amount of the silicone rubber compound is prepared. The plasticity value indicates the hardness and softness of the silicone rubber, and the lower the plasticity, the softer it is. When the plasticizer of the plasticizer is excellent in the same formulation, the dispersion of silica is made well, and thus the plasticity is lowered. In this case, the present Example shows a low plasticity in comparison with the comparative example. It can be seen that the silica dispersion was better than that of the comparative example.

Claims (11)

1) equilibrating a cyclosiloxane and a mixture of dialkoxysilane with a trialkoxysilane in the presence of an acidic catalyst to prepare a linear and branched polysiloxane mixture, all of which terminate at an alkoxy group, and
2) hydrolyzing the polysiloxane mixture obtained as a result of step 1 and replacing all of its ends with silanol groups;
A process for preparing linear and branched polysiloxane mixtures, all of which terminate at ends with silanol groups. The cyclosiloxane of claim 1, wherein the cyclosiloxane is substituted with alkyl having 1 to 4 carbon atoms, alkenyl having 2 to 4 carbon atoms or aryl having 6 to 10 carbon atoms, and having 3 to 12 [Si-O] units in the ring structure. Siloxane. The method of claim 1, wherein the cyclosiloxane is represented by the following formula (1):
Formula 1
[SiR ₁ R ₂ O] _n
(Wherein R ₁ and R ₂ are independently methyl, vinyl or phenyl and n is an integer from 3 to 12.) 2. The dialkoxysilane according to claim 1, wherein the dialkoxysilane has 2 alkyl of 1 to 4 carbon atoms, alkenyl of 2 to 4 carbon atoms or aryl substituents of 6 to 10 carbon atoms, and 2 alkyl-oxy substituents of 1 to 10 carbon atoms. It is a silane compound. The method of claim 1, wherein the dialkoxysilane is represented by the following formula (2):
Formula 2
R ₃ R ₄ Si (OR ₅ ) ₂
(Wherein R ₃ and R ₄ are independently methyl, vinyl or phenyl, and R ₅ is independently an alkyl group having 1 to 10 carbon atoms.) 3. The trialkoxysilane according to claim 1, wherein the trialkoxysilane has one alkyl of 1 to 4 carbon atoms, alkenyl of 2 to 4 carbon atoms or an aryl substituent of 6 to 10 carbon atoms, and three alkyl-oxy substituents of 1 to 10 carbon atoms. It is a silane compound. The method of claim 1, wherein the trialkoxysilane is represented by the following formula (3):
Formula 3
R ₆ Si (OR ₇ ) ₃
(Wherein R ₆ is methyl, vinyl or phenyl, and R ₇ is independently an alkyl group having 1 to 10 carbon atoms.) The method according to claim 1, wherein the trialkoxysilane content in 100% by weight of the mixture of dialkoxysilane and trialkoxysilane is 10 to 90% by weight. 2. The method of claim 1, wherein the average molecular weight of the low molecular weight linear and branched polysiloxane mixtures, all of which are terminated with silanol groups, is 500-3,000, and their OH content is 4-10 wt%. A plasticizer composition for a silicone rubber compound, comprising a polysiloxane mixture prepared by the method of any one of claims 1 to 9. A silicone rubber compound comprising as a plasticizer component a polysiloxane mixture prepared by the method of claim 1.