JP3323211B2 - Continuous production method of siloxane polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously producing a siloxane polymer, and more particularly to a method for continuously producing a siloxane polymer using a pyrolytic base catalyst.

[0002]

2. Description of the Related Art Hitherto, siloxane polymers and copolymers have generally been produced by a batch polymerization method using an acid or a base as a catalyst.

That is, in this batch polymerization method, a siloxane monomer, for example, dimethyltetramer (octamethylcyclotetrapolysiloxane) is inserted into a polymerization vessel and dried by distillation or reflux of siloxane vapor in a molecular sieve column. Next, after heating the dried siloxane monomer to about 155 ° C., potassium hydroxide, for example, as a polymerization catalyst is added in the form of a pulverized slurry of methyl tetramer, and the polymerization is allowed to proceed under stirring. As the polymerization reaction proceeds, monomers add to the ends of the polymer chains, forming progressively longer polymers. When the polymerization proceeds and a siloxane polymer having a desired viscosity is obtained, water is added as a chain terminator, for example, to terminate the polymerization reaction. Thereafter, the potassium hydroxide added as a polymerization catalyst is neutralized with a neutralizing agent such as phosphoric acid,
Finally, unreacted monomers are separated and removed by distillation to obtain a silanol-terminated siloxane polymer.

However, in the above batch polymerization method,
There was a problem that the characteristics of the product varied from batch to batch. For this reason, the following continuous production method has been proposed as a new method replacing this batch polymerization method.

For example, JP-A-56-11927 discloses that an alkali metal hydroxide of cyclopolysiloxane or a silanolated product thereof is mixed as a polymerization catalyst, and the mixture is subjected to extrusion flow using a static mixer. A method of continuously producing a siloxane polymer by neutralizing a polymerization catalyst after a sufficient residence time in which polymerization is completed by introducing a chain terminator such as water into the polymerization reaction zone while passing through a polymerization apparatus of the system. It has been disclosed.

[0006]

With the recent spread of applications of siloxane polymers to the field of electric and electronic materials, alkali metals contained in siloxane polymers cause electrical troubles, which has become a problem. This is because the alkali metal salt, which is a neutralization product of the polymerization catalyst used in the above method, cannot be completely separated and removed from the siloxane polymer, but remains partially.

To solve this problem, a method using a pyrolytic base catalyst as a polymerization catalyst, which is known as one of batch polymerization methods, is effective.

However, in this method, since the viscosity of the reactant rapidly rises due to the addition of the pyrolytic base catalyst, a helical ribbon type stirrer having a strong stirring power must be used. In addition to the need for power energy, there is a problem that a very long time is required for a series of steps from polymerization to decomposition of the catalyst and removal of unreacted monomers, resulting in low productivity. In addition, there is a disadvantage that the characteristics of the product vary because of the batch method as described above.

The present invention has been made in view of the above-mentioned problems, and uses a pyrolysis-type base catalyst as a polymerization catalyst and a siloxane having good characteristics by a continuous production method without causing variations in characteristics. An object of the present invention is to provide a method for continuously producing a siloxane polymer, which can produce a polymer stably, economically and with good productivity.

[0010]

DISCLOSURE OF THE INVENTION The continuous process for producing a siloxane polymer of the present invention comprises the steps of (a) preheating and heating a cyclopolysiloxane, a pyrolytic base catalyst, and a part of a total amount of a chain terminating agent. And (b) passing the premix through a static mixer which is maintained under pressure to provide a sufficient residence time to complete the polymerization of the cyclopolysiloxane, and to the beginning of the reaction zone of the static mixer. (C) heating the reaction mixture to a temperature equal to or higher than the decomposition temperature of the pyrolytic base catalyst and sufficiently decomposing the pyrolytic base catalyst. It is characterized by passing through a static mixer giving a long residence time.

[0011] As the monomer used as the starting material in the present invention can be any cyclo polysiloxanes, usually 3-6 mer dimethylcyclopropane polysiloxysilane <br/> hexane is used, inter alia tetramer The dimethyl cyclopo
The use of polysiloxane is preferable. It is desirable to use a sufficiently dried monomer (having a water content of 20 ppm or less) as the monomer. If necessary, the monomer may be subjected to a degassing treatment and dried before preheating. The preheating of the monomer is performed in order to quickly start the ring-opening polymerization of the monomer in the next step, and the polymerization temperature is raised to a polymerization temperature, usually 80 to 100 ° C, preferably 85 to 95 ° C using a heat exchanger or the like. Let warm. The amount of the monomer to be supplied is appropriately determined depending on the polymerization temperature and the amount of the catalyst to be used for determining the polymerization reaction rate, the degree of polymerization of the polymer to be obtained, the volume of a static mixer as a polymerization vessel, and the like.

The pyrolytic base catalyst used in the present invention includes tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and tetraalkylammonium silanolates obtained by silanolating these. Among them, tetramethylammonium silanolate having good compatibility with cyclopolysiloxane is preferably used. The tetramethylammonium silanolate is thermally decomposed by heating at 130 to 160 ° C. for about 3 hours as shown in the following formula (I).

(CH ₃ ) ₄ NO-[(CH ₃ ) ₂ SiO] _m -N (CH ₃ ) ₄ → 2 (CH ₃ ) ₃ N + CH ₃ -[(CH ₃ ) ₂ SiO] _m -CH ₃ … (I) The amount of the pyrolytic base catalyst to be introduced is suitably in the range of 50 to 300 ppm based on the cyclopolysiloxane monomer.

Examples of the chain terminator used in the present invention include water, a low-molecular-weight triorganosilyldiorganopolysiloxane having 2 to 20 silicon atoms and a monovalent hydrocarbon group as an organic group. The silyl diorganopolysiloxane whose organic group contains an aliphatic unsaturated group may be mentioned, and these are selected according to the final use of the product siloxane polymer. That is, the characteristics of the obtained siloxane polymer differ depending on the chain terminator used. For example, when water is used, a silanol-terminated diorganosiloxane represented by the formula (II) is obtained as a polymerization product. When the organic group is a monovalent hydrocarbon group and a low molecular weight triorganosilyldiorganopolysiloxane having 2 to 20 silicon atoms is used, the triorganosilyl-terminated diorganopolysiloxane represented by the formula (III) is used. can get. Further, when a low molecular weight triorganosilyldiorganopolysiloxane having an organic group containing an aliphatic unsaturated group is used, an aliphatically unsaturated group-containing triorganosilyl-terminated diamine represented by the formula (IV) is used. An organopolysiloxane is obtained.

[0015]

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[0016]

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[0017]

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(In each formula, R represents a lower saturated or unsaturated alkyl or aryl group such as methyl, ethyl, propyl, vinyl, phenyl, etc., and n is about 50 to 20.
00. Specifically, examples of the low molecular weight triorganosilyldiorganopolysiloxane in which the organic group is a monovalent hydrocarbon group having 2 to 20 silicon atoms include trimethylsilyldimethylpolysiloxane and the like. Examples of the molecular weight triorganosilyldimethylpolysiloxane whose organic group contains an aliphatic unsaturated group include vinyldimethylsilyldimethylpolysiloxane.

The total amount of the chain terminator determines the average molecular weight of the obtained siloxane polymer. Therefore, the amount of the chain terminator to be introduced is determined according to the average molecular weight of the target siloxane polymer. In the present invention,
This chain terminator is introduced separately during the premixing and during the polymerization reaction. The chain terminator introduced at the time of pre-mixing has both the function as the original chain terminator and the function of adjusting the viscosity of the starting component when introduced into the static mixer of the next step. The introduction of a part of the total amount of the chain terminator is an essential condition for achieving the continuous production of the siloxane polymer aimed at by the present invention. The amount introduced during pre-mixing is therefore such that it is necessary to adjust the viscosity, and finally the amount required for chain termination together with the amount introduced into the static mixer for the subsequent polymerization. Will be introduced. In particular,
When water is used as the chain terminator, silanol-terminated diorganosiloxane having a viscosity of 100 to 1,000,000 centipoise at 25 ° C. is polymerized by introducing a total amount of 100 to 4,000 ppm based on the monomer cyclopolysiloxane,
Among them, it is preferable to introduce 50 to 300 ppm during the premixing. When a low molecular weight triorganosilyldiorganopolysiloxane having 2 to 20 silicon atoms in which the organic group is a monovalent hydrocarbon group is used as the chain terminator, the terminal triorganosilyl group may be added to the monomer cyclopolysiloxane. It is necessary to adjust the concentration, but the total amount is 300-20,000ppm
, A triorganosilyl-terminated diorganosiloxane having a viscosity of 100 to 1,000,000 centipoise at 25 ° C. is polymerized, of which 50 to 500 p
The introduction in the pm range is preferred. Furthermore, when using a low molecular weight triorganosilyl diorganopolysiloxane whose organic group contains an aliphatic unsaturated group as the chain terminator, it is necessary to adjust the terminal triorganosilyl group concentration as described above. , By introducing a total amount of 750 to 50,000 ppm based on the monomer cyclopolysiloxane,
A triorganosilyl-terminated diorganosiloxane having a viscosity at 100 DEG C. of 100 to 1,000,000 centipoise is polymerized, of which 300 to 20,000 ppm is preferably introduced during premixing.

Next, the method of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an example of an apparatus for continuously producing a siloxane polymer used in the practice of the present invention.

In the present invention, firstly, cyclo polysiloxane starting material, octamethylcyclotetrasiloxane polysiloxanolate <br/> San monomer is dimethyl cyclic siloxane example tetramer, ejectable supplied at a constant flow rate pump,
For example, by a diaphragm type constant volume pump P _1, line mixer for premixing via monomer feed line A, is introduced continuously and quantitatively for example a static mixer 1. The diaphragm type constant displacement pump has a high discharge pressure and has no sealing surface between the pump and the driving unit, so that it is preferably used in this case. In the monomer supply line A,
A monomer preheater 2 is interposed, and the cyclopolysiloxane is polymerized at the monomer preheater 2 at a polymerization temperature of, for example, 80 to
It is preheated to about 100 ° C. and introduced into the static mixer 1. For the monomer preheating group 2, for example, a heat exchanger is used.

On the other hand, a supply pump capable of discharging a pyrolytic base catalyst, for example, tetramethylammonium silanolate, and a chain terminator, for example, water as a part of the total introduction amount, at a constant flow rate, similarly to the monomer. For example, they are continuously and quantitatively introduced into the static mixer 1 through the catalyst supply line B and the chain stopper supply line C by the plunger type constant volume pumps P ₂ and P ₃ , and mixed with the preheated monomer. . The plunger type constant displacement pump is preferably used in this case because it can supply with high accuracy at a small flow rate. In addition, a gear type constant displacement pump or the like is preferably used.

The static mixer 1 mixes these monomers, the pyrolytic base catalyst, and the chain terminator so as to have a uniform composition, and adjusts the viscosity to an appropriate level to form a static mixer 3 for the subsequent polymerization. It is for sending out to. Although a dynamic mixer can be used in place of the static mixer 1, use of a static mixer is more preferable from the viewpoint of handleability and the like. As a dynamic mixer, for example, 2
Has a 3-stage paddle type stirrer and a rotation speed of 800 to 2,000
r. p. An inline mixer capable of high-speed dispersion at m is used. In these mixers, the introduction of the pyrolytic base catalyst and the chain terminator is performed on the mixer so that the chain terminator does not reduce the activity of the pyrolytic base catalyst or cause clogging of the introduction nozzle. It is desirable to introduce them so that they do not come into contact with each other from the addition ports provided at non-identical positions. In the case of the static mixer 1,
Furthermore, it is desirable that the tip of the nozzle be located at the center of the tube constituting the static mixer 1, thereby preventing the mixture from remaining on the tube wall.

Thus, for example, the static mixer 1
The premix of the monomer, the pyrolytic base catalyst, and the chain terminator mixed in the above is subjected to a residence time of, for example, 4 to 5 minutes and then to a static mixer 3 for performing main polymerization, for example, L / D 50 to 50%. A static mixer is arranged in about 100 pipes and introduced into a mixer having a jacket having a jacket through which a heat medium for temperature control circulates. This static mixer 3
Is maintained under a pressure of, for example, 10 to 20 kg / cm ² to suppress the decomposition of the pyrolysis-type base catalyst, while maintaining a polymerization temperature, for example, an almost constant internal temperature of 80 to 100 ° C., to the premix. On the other hand, it uniformly provides a sufficient residence time to complete the polymerization of the monomer. In the static mixer, the preliminary mixture introduced into the static mixer 3 is subjected to the polymerization of the monomer by the catalytic action of the uniformly dispersed pyrolysis type base catalyst, and the viscosity increases. It is desirable to use one having a high number of divided layers, for example, an SMX type or SMV type static mixer manufactured by Sulzer is suitably used. Then, at the beginning of the reaction zone of the static mixer, a chain terminator is introduced which determines the degree of polymerization of the monomers. The introduction may be performed only once, but to prevent pressure loss, 2-3
It is desirable to introduce them separately. In the example shown,
A supply pump capable of discharging at a constant flow rate, for example, a plunger type constant volume pump P ₄ , P ₅ through a chain stopper supply line D and a chain stopper supply line E downstream thereof.
Is introduced in two separate installments. The introduction point of the chain stopper is preferably at the center of the tube constituting the static mixer 3 as in the case of the pre-mixing, whereby the stagnation of the mixture on the tube wall can be prevented. .

While passing through the static mixer 3 in this manner, the polymer of the cyclopolysiloxane monomer polymerized to a desired degree of polymerization is mixed with the unreacted monomer and the pyrolytic base catalyst, etc. After the pressure is returned to normal pressure by the pressure regulating valve 4, the decomposition temperature of the pyrolytic base catalyst is, for example, decomposed by a heating device 5 such as a heat exchanger for the purpose of deactivating the activity of the pyrolytic base catalyst. After heating at 130-160 ° C., it is then introduced into a temperature-controllable static mixer 6 which provides a sufficient residence time for the pyrolytic base catalyst to completely decompose. As the static mixer 6 used here, the same type as used for the polymerization can be used. While passing through the static mixer 6, the introduced reaction mixture is heated to a temperature equal to or higher than the decomposition temperature of the pyrolytic base catalyst, for example, 160 ° C.
By heating at ~ 200 ° C, the pyrolytic base catalyst is completely decomposed and discharged.

The reaction mixture leaving the static mixer 6 is subsequently heated by a heating device 7 such as a heat exchanger to a temperature higher than the boiling point of the unreacted monomer, for example, 200 to 220 ° C. Is introduced into the gas-liquid separator 8 maintained at 2 to 10 mmHg to separate unreacted monomers and desired polymer products. The unreacted monomer and polymer product separated here are supplied from a monomer discharge line F and a polymer discharge line G, respectively, to a cooling device 9, 1 such as a heat exchanger inserted between these two lines.
It is cooled by 0 and discharged to the outside.

[0028]

According to the method for continuously producing a siloxane polymer of the present invention, the premixing of a monomer and a pyrolytic base catalyst is
Since a part of the chain terminator was also added and mixed at the same time, it was possible to create a near-ideal continuous mixed flow in a static mixer for subsequent polymerization, and to use a pyrolytic base catalyst and The polysiloxane can be favorably polymerized to continuously produce a siloxane polymer having a desired degree of uniform polymerization.

And, depending on the chain terminator used, silanol-terminated diorganosiloxane, triorganosilyl-terminated diorganopolysiloxane, triorganosilyl-terminated diorganopolysiloxane containing an aliphatic unsaturated group,
Siloxane polymers that can be used in a wide range of applications can be produced.

[0030]

Next, examples will be described.

Example 1 An octamethylcyclotetrasiloxane monomer was polymerized under the conditions shown in Table 1 to obtain a silanol-terminated polymer.

That is, an octamethylcyclotetrasiloxane monomer having a water content of 20 ppm, which was preheated to about 90 ° C. by a monomer preheater, together with tetramethylammonium silanolate (KOH equivalent: 100 ppm) and 90 ppm of water, was prepared as shown in Table 1.
Under the conditions shown in the figure, a small static mixer (inner diameter of 6 inches, length of 4.7m, L / D = 1.0, SMX type static mixer inserted, jacket around which heat transfer oil for temperature control circulates around the outer circumference) ) Was continuously and quantitatively introduced and mixed.

Next, the mixture was heated at a temperature of 100 ° C. and a pressure of 1
A static mixer for polymerization controlled at 3.0 kg / cm ² (8 inch inside diameter, 4.7 m long, L / D = 1.0, SMX type static mixer inserted inside, heat transfer oil for temperature control on the outer periphery (With a circulating jacket), and near the inlet of the static mixer for polymerization, water of 220 ppm relative to the monomer was introduced by a plunger type constant volume pump.

Subsequently, the reaction mixture discharged from the static mixer for polymerization was returned to normal pressure by a pressure control valve, heated to about 140 ° C. by a heat exchanger, and then controlled to a temperature of 180 ° C. to reduce the size of the catalyst for thermal decomposition. Static mixer (inner diameter 10 inches, length 4.7m,
(With an SMX static mixer manufactured by Sulzer, L / D = 1.0, having a jacket around which a heat transfer oil for temperature control circulates).

Further, the reaction mixture discharged from the small static mixer for catalytic pyrolysis is heated at a temperature of 2 ° C. by a heat exchanger.
After heating to 10 ° C, the system was introduced into a gas-liquid separation tank with the system pressure maintained at 5 mmHg, and unreacted monomers were removed from the upper part to obtain a silanol-terminated diorganopolysiloxane having a viscosity of 110,000 centipoise at 25 ° C. Was. The residual monomer content in the obtained silanol-terminated diorganosiloxane was 2.3%, and the polymerization rate was 86%.

Example 2 Except that the production conditions were changed as shown in Table 1, the introduction of the chain terminator was performed twice during the premixing and at the inlet of the static mixer for polymerization. The octamethylcrotetrasiloxane monomer was polymerized with the same apparatus and the same material as in Example 1 to obtain a silanol-terminated diorganopolysiloxane having a viscosity of 8,500 centipoise at 25 ° C. The residual monomer content in the obtained silanol-terminated diorganosiloxane was 5.2%, and the conversion was 80%.

Example 3 The same apparatus and the same materials as in Example 2 except that trimethylsilyldimethylpolysiloxane having 4 silicon atoms was used as a chain terminator and the production conditions were changed as shown in Table 1. The octamethylcrotetrasiloxane monomer is polymerized at 25 ° C. to have a viscosity of 11,00 at 25 ° C.
0 centipoise of trimethylsilyl terminated dimethylpolysiloxane was obtained. The residual monomer amount in the obtained trimethylsilyl-terminated diorganosiloxane was 1.8%, and the conversion was 87%.

Example 4 The same equipment as in Example 2 except that vinyldimethylsilyldimethylpolysiloxane having 20 silicon atoms was used as a chain terminator and the production conditions were changed as shown in Table 1. By polymerizing octamethylcrotetrasiloxane monomer with the same material, the viscosity at 25 ° C. becomes 3,
050 centipoise of vinyldimethylsilyl-terminated dimethylpolysiloxane was obtained. The amount of residual monomer in the obtained vinyldimethylsilyl-terminated dimethylpolysiloxane was 2.0%, and the conversion was 83%.

[0039]

[Table 1]

[0040]

As described above, according to the present invention,
Since a thermal decomposition type base catalyst is used as the polymerization catalyst and can be completely decomposed and removed, the problem of deterioration in characteristics due to the remaining neutralization reactant such as a conventional acid or base catalyst is solved.

Since a siloxane polymer having a desired uniform degree of polymerization can be continuously produced using such a pyrolytic base catalyst, a conventional batch type catalyst using a pyrolytic base catalyst can be used. Compared with the polymerization method, the characteristics of the product do not vary, and a siloxane polymer having good characteristics can be produced stably, economically and with high productivity.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an apparatus used for carrying out the method of the present invention.

[Explanation of symbols]

1, 3, 6 Static mixer 2 Monomer preheater 3 Degassing gas tank for polymerization 4 Pressure regulating valve 5, 7 Heating device 8 Gas-liquid separation vessel 9,10 ......... cooling device _{P 1, 2, 3, 4} , 5 ......... constant volume pump

Claims (4)

(57) [Claims] 1. Preliminarily mixing (a) a preheated cyclopolysiloxane, a pyrolytic base catalyst, and a part of the total amount of a chain terminator, and (b) the premix under pressure. Passing through a static mixer which is maintained and provides a sufficient residence time to complete the polymerization of the cyclopolysiloxane, and introducing the remaining chain stopper to the first portion of the reaction zone of the static mixer;
Next, (c) the reaction mixture is heated to a temperature equal to or higher than the decomposition temperature of the pyrolytic base catalyst, and passed through a static mixer that provides a sufficient residence time to completely decompose the pyrolytic base catalyst. A continuous process for producing a siloxane polymer. 2. The continuous process for producing a siloxane polymer according to claim 1, wherein the chain stopper is water. 3. The siloxane polymer according to claim 1, wherein the chain terminator is a low molecular weight triorganosilyldiorganopolysiloxane in which the organic group is a monovalent hydrocarbon group and has 2 to 20 silicon atoms. Continuous production method. 4. The continuous process for producing a siloxane polymer according to claim 3, wherein the organic group of the low molecular weight triorganosilyldiorganopolysiloxane of the chain terminator contains an aliphatic unsaturated group.