JPH11228836A - Production of liquid silicone rubber base - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a liquid silicone rubber base having excellent fluidity, satisfying the physical properties of a final product and capable of sufficiently coping with the tendency variety of kinds of the final products by a batch process. SOLUTION: In producing a liquid silicone rubber base mainly composed of an organopolysiloxane having >=2 alkenyl groups bonding to are silicon atom in the molecule and a reinforcing silica filler having >=50 m<2> /g specific surface area (by BET method), a batch-type pressurizing high shear blender in which opened port parts at both ends of a cylindrical mixing container 1 are closed and at least one of the opened port parts is transferably provided and two side boards 2 and 3 capable of increasing or decreasing the volume of a mixing chamber in the mixing container by their transferring and one shafted stirring wing transferably provided so as a position in the mixing chamber to be changeable together with the transferring of the side boards 2 and 3 and/or to be independent to the transferring is used, and the inner pressure of the mixing chamber and the position of the stirring wing are varied by the side boards to perform kneading.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention makes it possible to produce a liquid silicone rubber base useful as a raw material of a liquid silicone rubber composition used for electrics, automobiles, office machines and the like by a batch method in a simple and short time. The present invention relates to a method for producing a liquid silicone rubber base.

[0002]

2. Description of the Related Art In the recent silicone rubber market, liquid silicone rubber compositions having high fluidity, easy to apply to injection molding machines, etc., and excellent in automatic processability. Is getting attention. Among them, a production process with high productivity is demanded especially for a general-purpose addition-curable liquid silicone rubber composition mainly composed of an alkenyl group-containing organopolysiloxane, whose demand has been increasing in recent years.

That is, these liquid silicone rubber compositions are usually produced by blending a curing agent or the like with a common liquid silicone rubber base in consideration of processes corresponding to diversification of products. It is manufactured by various methods regardless of the method or the continuous method.

However, in such a method for producing a liquid silicone rubber base, the reinforcing silica used as a filler has a fine particle size, a low bulk density, and many active sites on its surface. In addition, in the uniform kneading with the organopolysiloxane, there is a problem that the batch method requires a long time for mixing of powder and heat treatment at elevated temperature.

[0005] For this reason, generally, in a batch method, for example, hexamethyldisilazane,
The use of a wetter such as diphenylsilanediol is indispensable, but as a result, there are drawbacks in that the composition and the process are complicated and the production cost is high.

On the other hand, in the continuous method, for example, Japanese Patent Application Laid-Open No. 61-40327 proposes to use a twin-screw continuous extrusion kneader as a measure for solving the above problem. There was a drawback that it was difficult to cope with diversification of the base itself.

Further, in order to increase the kneading capacity of the filler in a continuous kneader, for example, a pre-blend method of oil and powder is disclosed in JP-A-1-56736, and a vacuum roll is disclosed in JP-A-7-41562. There have been proposed methods of increasing the bulk density of powders, but all of these methods have drawbacks such as complicated processes and high investment costs.

Therefore, there is a need for the development of a technique for efficiently producing a liquid silicone rubber base without the above-mentioned problems.

The present invention has been made in view of the above circumstances, and provides a liquid silicone rubber base which has good fluidity, provides a high quality product, and can sufficiently cope with diversification of products by a batch method. It is an object of the present invention to provide a method for producing a liquid silicone rubber base which can be efficiently produced in a short time.

[0010]

In order to achieve the above object, the present invention provides an organopolysiloxane having two or more alkenyl groups bonded to a silicon atom in one molecule, and a specific surface area ( (BET method) is 50 m ² / g
In producing a liquid silicone rubber base containing the above-mentioned reinforcing silica filler as a main component, a cylindrical mixing container,
Two side plates that close both end openings of the mixing container and at least one of the side plates is movably disposed, and the movement allows the volume of the mixing chamber in the mixing container to be increased or decreased,
Batch-type pressurized high-shear kneader provided with a single-shaft stirring blade movably disposed so as to be able to change its position in the mixing chamber together with and / or independently of the movement of the side plate. Is used to supply the liquid silicone rubber base material into the mixing chamber of the mixing vessel, and either or both of an operation of changing the internal pressure of the mixing chamber by moving the side plate and an operation of changing the position of the stirring blade. And a method for producing a liquid silicone rubber base, which comprises kneading the raw materials while performing the above.

According to the production method of the present invention, the liquid silicone rubber-based raw material is kneaded using the above-mentioned batch-type pressurized high-shear kneader, so that a conventional batch-type kneader such as a kneader is used. Can be kneaded uniformly and in a short time even with a high filling ratio of a filler that was very difficult to mix in the organopolysiloxane component, and therefore has good fluidity and can finally satisfy the physical properties of the product In addition, a liquid silicone rubber base that can sufficiently cope with the diversification of products can be efficiently manufactured in a very short time with a simple process at a low cost.

Hereinafter, the present invention will be described in more detail.
An organopolysiloxane having two or more alkenyl groups bonded to a silicon atom in one molecule, and a specific surface area (BET)
Method) is to produce a liquid silicone rubber base containing a reinforcing silica filler of 50 m ² / g or more as a main component.

As the organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in one molecule, those represented by the following average composition formula (1) are preferably used.

R _a SiO _{(4-a) / 2} (1) (wherein R is a substituted or unsubstituted monovalent hydrocarbon group bonded to a silicon atom, and a is 1.8 to 2.2) Is a positive number.)

In the above formula (1), R is a substituted or unsubstituted monovalent hydrocarbon group, and is a substituted or unsubstituted alkyl group, cycloalkyl group, alkenyl group, aryl group, aralkyl group having 12 or less carbon atoms. And the like, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, tert-butyl group, pentyl group,
Alkyl groups such as hexyl group, cycloalkyl groups such as cyclohexyl group and cycloheptyl group, alkenyl groups such as vinyl group and allyl group, aryl groups such as phenyl group and naphthyl group, aralkyl groups such as benzyl group and phenylethyl group, And a trifluoropropyl group in which part or all of the hydrogen atoms in these hydrocarbon groups have been substituted with halogen atoms such as fluorine atoms and chlorine atoms, cyano groups and the like. Particularly preferred are a methyl group, a phenyl group and a trifluoropropyl group, and a preferred alkenyl group is a vinyl group. a is a positive number from 1.8 to 2.2.

The organopolysiloxane needs to have at least two alkenyl groups in one molecule from the viewpoint of obtaining an addition reaction type liquid silicone rubber composition.

The structure of the organopolysiloxane is preferably basically linear, but may have a branched structure in part. Preferably, it is an organopolysiloxane in which both terminals are blocked with an alkenyl group.

Further, the viscosity of the above-mentioned organopolysiloxane is 50 to 5,000,000 cps at 25 ° C.
(Centipoise), especially 100-1,000,000 c
It is preferably ps.

As the organopolysiloxane, two or more kinds having different viscosities and molecular structures may be used.

As the filler, specific surface area (BET)
Law) 50m ² / g or more, preferably 100~400m ² /
g of reinforcing silica filler is used. Such fillers include, for example, fumed silica, precipitated silica, and hydrophobicized silica obtained by treating the surface of these silicas with silazane, reactive silane, siloxane, or the like. These fillers may be used alone or in combination of two or more. These can be used in combination.

The amount of the filler can be appropriately determined depending on the kind of the filler and the size of the specific surface area.
0 parts by weight, especially 20 to 100 parts by weight, is suitable. For example, the blending amount of the fumed silica having a specific surface area of 300 m ² / g is preferably 20 to 70 parts by weight, particularly preferably 30 to 60 parts by weight. For example, in the case of precipitated silica having a specific surface area of 230 m ² / g,
The amount is preferably 30 to 100 parts by weight, particularly preferably 35 to 70 parts by weight.
Note that the minimum amount of these fillers can be a value corresponding to the filler ratio of the base compound composition to be produced, and the maximum amount of addition depends on the type of filler and the specific surface area. It can be a limit value that can be compounded by a kneader.

In the production method of the present invention, a dispersant for facilitating the mixing of the filler can be added together with the above raw materials, if necessary. In this case, as the dispersing agent, a compound which generates a nitrogen compound which inhibits the curing of the addition reaction after the reaction represented by hexamethyldisilazane is not preferable, and a compound containing a silanol group and containing no nitrogen atom is preferable. Are preferred, and 1,1,1,3,
Α, ω-diorganosiloxanediols having a degree of polymerization of 100 or less, such as 5,7,7,7-octamethyl-3,5-dihydroxytetrasiloxane, and trimethylsilanol are preferred.

The dispersant is added in an amount of not more than 10 parts by weight, especially 0 to 100 parts by weight of the organopolysiloxane.
5 parts by weight is desirable. If the amount of the dispersant exceeds 10 parts by weight, the cost may be increased and the physical properties of the obtained rubber may be adversely affected.

If necessary, other known additives that can be compounded in the liquid silicone rubber base may be compounded.

In the present invention, the above-mentioned raw materials are kneaded by using a single-shaft batch-type pressurized high-shear kneader. This kneader has a cylindrical mixing vessel and an opening at both ends of the mixing vessel. Two side plates which are closed and at least one of which is movably arranged, whereby this movement can increase or decrease the volume of the mixing chamber in the mixing vessel, and together with and / or independent of the movement of the side plates And a uniaxial stirring blade movably disposed so that the position in the mixing chamber can be changed.

More specifically, the batch-type high-shear kneader used in the present invention has a structure as shown in FIG. 1, for example.

That is, in FIG. 1, reference numeral 1 denotes a cylindrical mixing container, and both ends of the mixing container 1 are closed by two side plates (side shells) 2 and 3, respectively. 1 has a mixing chamber 1a formed therein. In this case, the outer peripheral surface of one side plate 2 is slidably in contact with the inner peripheral surface of the container 1 and is disposed so as to be able to reciprocate in the horizontal direction in the figure by hydraulic cylinders 4 and 4. As a result, the volume of the mixing chamber 1a fluctuates, and the mixing chamber 1a is adjusted to a pressurized state or a depressurized state. Further, the other side plate 3 is detachably fixed to the container 1. Reference numeral 5 denotes a main shaft rotatably provided by a suitable driving device (not shown), and a tip of the main shaft 5 penetrates the one side plate 2 and protrudes into the container 1. A stirrer 6 in the shape of a letter or the like is attached so that it can rotate integrally with the main shaft 5. Reference numeral 7 denotes a shaft seal portion of the main shaft 5. The main shaft 5 is provided so as to be capable of reciprocating in the left-right direction in the figure by a hydraulic cylinder 8, and the stirring blade 6 reciprocates integrally with the reciprocating motion.
In the mixing chamber 1a can be changed. The other side plate 3 is connected with a raw material supply pipe 9, a product discharge pipe 10, and an exhaust pipe 11 each having a valve interposed therebetween. Although not shown, a heating means such as an electric heater or a jacket structure is attached to the container 1 so that the temperature at the time of kneading can be maintained at a set value.

A specific example of such a batch-type pressurized high-shear kneader is "Press Mixer" (trade name of VOITH). This kneading machine supplies raw materials to one side of a horizontal cylindrical mixing vessel, deaerates the inside of the mixing vessel,
It has a semi-fixed side plate (side body) with a product outlet, and the other side plate (side body) is equipped with a uniaxial stirring blade bearing that can reciprocate left and right, and is installed in a movable state. Movable side plate. This mixing vessel creates a pressurized or depressurized state by the reciprocating motion of the movable side plate, and at the same time, enables effective kneading by the rotation and reciprocating motion of the stirring blade.

In the present invention, the liquid silicone rubber-based raw material is charged into the mixing vessel of the batch-type pressurized high-shear kneader, and the operation of changing the pressure in the vessel by moving a side plate installed in a movable state is carried out. The kneading is performed while performing at least one of the operation of rotating and the operation of moving the main shaft having the wing to obtain a liquid silicone rubber base.

Specifically, a liquid silicone rubber base can be manufactured by the following method. That is, first, raw materials such as an organopolysiloxane and a filler-reinforcing silica are charged into a mixing vessel of the batch-type pressurized high-shear kneader through an inlet. In this case, the organopolysiloxane as the raw material may be charged all at once, or may be partially charged in advance and kneaded with the filler, and then the remaining organopolysiloxane may be added. The initial charge is 100% of the total amount.
To 30% by weight.

The filler may be added simultaneously with the organopolysiloxane, or may be charged after the addition of the organopolysiloxane. Further, the entire amount of the filler can be charged at one time, but depending on the type of the filler, the filler may be divided and added two or more times.

In the present invention, the liquid silicone rubber-based raw material charged into the mixing container is moved by moving a side plate installed in a movable state to change the internal pressure of the container, and the main shaft having a stirring blade is rotated by itself. The kneading is performed by performing at least one of the operation of rotating the stirring blade and the operation of moving the main shaft having the stirring blade. In the present invention, by performing this kneading operation, it is possible to knead the filler, which was very difficult to mix in the organopolysiloxane in kneading using a normal batch-type kneader, in a short time, and at a high filling ratio. it can.

For example, after the filler is added to the organopolysiloxane in the mixing vessel, the charging port is closed, and the movable side plate is moved so that the maximum internal pressure of the mixing vessel is 1 to 20 barr, especially 1.5 to 12 barr. And the peripheral speed at the tip of the stirring blade is 1 to 15 m / sec.
c, in particular, rotating the stirring blade in the mixing vessel by rotating at a rotational speed of 4 to 13 m / sec, and reciprocating left and right at 1 to 300 seconds / cycle, particularly 4 to 60 seconds / cycle. Thereby, the filler can be effectively kneaded into the organopolysiloxane in a short time. In this case, the movable side plate can be reciprocated within a range where the maximum internal pressure can be maintained, and the reciprocating movement of the movable side plate can be 1 to 300 seconds / cycle, particularly 4 to 60 seconds / cycle.

When the organopolysiloxane and the filler are charged, it is preferable that the inside of the mixing vessel be at atmospheric pressure or reduced pressure. When the filler is dividedly charged, stirring need not be stopped, but it is preferable that at least the internal pressure of the mixing vessel is set to atmospheric pressure or reduced pressure.

Further, the liquid temperature at this time is raised to a set temperature by heating the mixing container with a heating device such as an electric heater or a jacket in parallel with the mixing of the filler, together with the self-heating effect by stirring. It is desirable to raise the temperature, and the set temperature is preferably 200 to 300 ° C. Set temperature is 200
If the temperature is lower than 0 ° C, it may take a long time to improve the flowability of the liquid silicone rubber base. If the temperature is higher than 300 ° C, there is a possibility that a part of the raw material is deteriorated.

In order to raise the temperature to the above-mentioned temperature in a short time, a heating device such as a jacket is heated to a high temperature.
It is preferable to increase the ratio of the filler as much as possible or to achieve a higher rotation speed. It is also possible to move the movable side plate during the temperature rise to bring the inside of the mixing vessel into a pressurized state, or to bring the inside of the mixing vessel into a reduced pressure state using a vacuum pump.

When the temperature reaches the set temperature, it is desirable to take a certain heat treatment time, and this heat treatment time can be adjusted according to the set temperature.
Preferably, it is 60 minutes. Further, during this heat treatment, the maximum internal pressure of the mixing vessel is set to 1 to 20 barr, particularly 1.5 to 12 barr for maintaining the set temperature and uniform kneading.
And the main shaft is set at a peripheral speed of 1 to 1 at the tip of the stirring blade.
While rotating at a rotational speed of 5 m / sec, especially 4 to 13 m / sec, reciprocating motion is performed at right and left at 1 to 300 sec / cycle, particularly 4 to 60 sec / cycle. In order to remove the gas, the movable side plate may be pulled from time to time to open the exhaust valve and perform a decompression operation.

After the predetermined heat treatment, heating of the jacket is stopped, the cooling is switched to appropriate cooling, and the remaining 0 to 70 parts by weight of the organopolysiloxane can be charged all at once or divided into two or more portions. In this charging step, the maximum internal pressure is set to a pressurized state of 1 to 20 barr, and the main shaft is rotated at a rotational speed such that the peripheral speed of the tip of the stirring blade is 1 to 10 m / sec. More preferably, it is reciprocated in a cycle and uniformly dispersed.

When the dilution kneading is completed, the rotation of the main shaft is stopped.
Retract the stirring blade and the movable side plate, open the exhaust valve to release the pressure in the mixing vessel, open the discharge valve, and discharge the base compound in the stirring vessel while moving the stirring blade and the movable side plate forward. Can be. After the discharge is completed, the stirring blade and the movable side plate are retracted, and the process for charging the next batch can be started.

The liquid silicone rubber base obtained by the method of the present invention is mixed with an addition reaction catalyst (curing agent) such as an organohydrogenpolysiloxane and a platinum-based catalyst, and, if necessary, with components such as a pigment and a heat resistance improver. An addition-curable liquid silicone rubber composition can be obtained.

[0041]

According to the method for producing a liquid silicone rubber base of the present invention, a liquid which has good fluidity, can finally satisfy the physical properties of a product, and can sufficiently cope with diversification of products. The silicone rubber base can be efficiently manufactured in a simple process by a batch method in a very short time, and the productivity can be greatly improved as compared with a batch method using a conventional batch kneader.

[0042]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In addition, in the following examples, all parts show a weight part and the viscosity shows the measured value at 25 degreeC. The used batch-type pressurized high-shear kneader has a mixing vessel diameter of 250 mm, a total volume of about 9 L, and is hydraulically driven and has a hydraulic pump of 15 KW.

Example 1 Using a batch-type pressurized high-shear kneader shown in FIG. 1, a linear dimethylpolysiloxane in which both terminal groups of a molecular chain were blocked with a dimethylvinylsilyl group (viscosity of 10, After charging 70 parts of 000 cSt) and 47 parts of silica powder (Nipsil LP, manufactured by Nippon Silica Co., Ltd.) in a stirring vessel, the stirring shaft was set to 800 to 90 under sealing.
The rotation was performed at 0 rpm, the pressure plate was moved so that the internal pressure was about 10 barr at the maximum, and the stirring blade was reciprocated right and left at a cycle of 5 seconds. After 2 minutes, the operation was stopped, the internal pressure was purged, and the inside was confirmed. As a result, it was found that the silica powder was completely kneaded with siloxane and had a block shape. The compound temperature at this time was 82 ° C.

Subsequently, after steam of 4 kg / cm ² gauge was passed through the jacket, kneading was continued under the same pressure and rotation as described above. As a result, the temperature reached 154 ° C. after 5 minutes and 210 ° C. after 10 minutes. did. After the inside was once purged and decompressed, and generated moisture and volatile matter were exhausted, kneading was continued for 30 minutes under the same kneading conditions. At this time, the temperature was 212 ° C., and the base was a uniform translucent grease having no filler agglomerate or gel.

Next, the steam of the jacket was switched to cooling water, 30 parts of the same linear dimethylpolysiloxane for dilution as described above was charged, and the stirring shaft was rotated at about 400 rpm under sealing to move the pressure plate. , Internal pressure up to 1
0 barr and stirring blades 4
It was reciprocated in a second cycle, kneaded for 3 minutes and stopped.

The liquid silicone rubber base thus obtained was uniform and flowable at a temperature of 114 ° C. without appearance dispersion of filler agglomerates or gels. The time required from the initial raw material preparation to the tap was a very short total of 62 minutes including the heat treatment time of 30 minutes.

Example 2 In Example 1, 1,1,1,3,5,7,7,7- was used as a dispersant together with linear dimethylpolysiloxane and silica powder at the time of the first charge.
A liquid silicone rubber base was obtained in the same manner as in Example 1 except that 3 parts of octamethyl-3,5-dihydroxytetrasiloxane was added.

The obtained liquid silicone rubber base was uniform and flowable at a temperature of 121 ° C. without appearance defects such as filler agglomerates and gel-like substances. The time required from the initial raw material preparation to the tap was 55 minutes in total including the heat treatment time of 30 minutes.

Example 3 A liquid silicone rubber was prepared in the same manner as in Example 1 except that 3 parts of trimethylsilanol was added as a dispersant together with the linear dimethylpolysiloxane and silica powder at the time of the initial preparation. Got the base.

The obtained liquid silicone rubber base was uniform and flowable at a temperature of 110 ° C. without appearance defects such as filler agglomerates and gel-like substances. The time required from the initial raw material preparation to the tap was 59 minutes in total including the heat treatment time of 30 minutes.

[Comparative Example 1] A kneader (12 L in total volume) which is a general batch type apparatus for producing a liquid silicone rubber base
The kneading of the same composition as in Example 1 was carried out by using a double blade type kneader of (1), and the jacket was heated by an electric heater.

First, 70 parts of a linear dimethylpolysiloxane (viscosity: 10,000 cSt) in which both terminal groups of a molecular chain, which is a main agent, are blocked with a dimethylvinylsilyl group is charged into a mixing vessel, and then silica powder (Nipsil LP) is added. When 47 parts of Nippon Silica Co., Ltd.) were charged at once and the stirring was started, the oil was still covered with the silica powder even at the maximum number of revolutions, and it stopped without forming a lump even after 1 hour.

Comparative Example 2 Using the same apparatus and components as in Comparative Example 1, kneading was carried out by the following method. First, 5.0 parts of hexamethyldisilazane as a wetter was charged into 70 parts of linear dimethylpolysiloxane, and the mixture was stirred for 5 minutes. Then, the silica powder was gradually charged while observing the state. As a result, 47 parts of the silica powder was completely contained and formed into a lump. The temperature at this time was 75 ° C.
Subsequently, the temperature was raised and kneading was performed at the maximum rotation, but it took about 70 minutes to exceed 200 ° C.

Subsequently, after the heat treatment was continued for 30 minutes, the heater was turned off, and the above polysiloxane 30 for dilution was removed.
Parts are divided into 3 parts, 7 parts, and 20 parts.
After kneading at the maximum rotation for 20 minutes, the operation became almost uniform and the operation was stopped.

The liquid silicone rubber base thus obtained has a temperature of 97 ° C., and has small filler agglomerates in appearance and gel-like substances having a difference in viscosity in part, and the like.
There was almost no flowability. The time required from the initial raw material preparation to the tap was a total of 3 hours including the heat treatment time of 30 minutes.

Each of the liquid silicone rubber bases obtained in the above Examples and Comparative Examples was redispersed by a three-roll mill, and then a two-liquid type was prepared by adding a compounding composition as shown in Table 1 using a 5-L universal mixer. (A type product, B type product) were prepared respectively. The organopolysiloxane added here is the same diorganopolysiloxane used in Examples and Comparative Examples.

The viscosities of the A type product and the B type product of each of the obtained Examples and Comparative Examples, the curability when the A type product / B type product were mixed in equal amounts, and various physical properties after curing were measured by the following methods. did. Table 2 shows the results. Curability: The curing start time (T ₁₀ ) and curing end time (T ₉₀ ) of the composition were calculated using a rheometer measured by Toyo Seiki Seisaku-sho, Ltd. Tensile strength, elongation, and tear strength: A type and B type products obtained using a silicone rubber base are mixed in equal amounts, and a dumbbell No. 2 type test piece is punched from a heat-cured rubber sheet, and Kamishima Seisakusho Co., Ltd. It was measured using a tensile tester.

[0058]

[Table 1]

[0059]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a batch-type pressurized high-shear kneader used in the production method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mixing container 2,3 Side plate (side body) 4,4 Hydraulic cylinder 5 Main shaft 6 S-shaped stirring blade 7 Shaft seal part 8 Hydraulic cylinder 9 Raw material supply pipe 10 Product discharge pipe 11 Exhaust pipe

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kenichi Kimura 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Kagaku Kogyo Co., Ltd. Gunma Office (72) Inventor Takayuki Matsuzawa 2-chome Isobe, Annaka-shi, Gunma 13-1 Shin-Etsu Chemical Industry Co., Ltd. Gunma Office

Claims (4)

[Claims] 1. An organopolysiloxane having two or more alkenyl groups bonded to a silicon atom in one molecule, and a reinforcing silica filler having a specific surface area (BET method) of 50 m ² / g or more. In producing the liquid silicone rubber base, a cylindrical mixing container, and both ends of the mixing container are closed, and at least one of the mixing containers is movably disposed, and this movement reduces the volume of the mixing chamber in the mixing container. Two side plates that can be increased or decreased, and a single-shaft agitator movably arranged to be able to change its position in the mixing chamber with and / or independently of the movement of the side plates. Using a batch-type pressurized high-shear kneader equipped with wings, supplying the liquid silicone rubber-based raw material into the mixing chamber of the mixing vessel, and changing the internal pressure of the mixing chamber by moving the side plate; and A method for producing a liquid silicone rubber base, wherein the raw material is kneaded while performing one or both of the operations of changing the position of the stirring blade. 2. The method according to claim 1, further comprising a step of performing a heat treatment at 200 to 300 ° C. 3. The method according to claim 1, wherein a dispersant is added to the liquid silicone rubber-based raw material. 4. The method according to claim 1, wherein the dispersant is 1,1,1,3,5,7,7,
The method according to claim 3, which is 7-octamethyl-3,5-dihydroxytetrasiloxane or trimethylsilanol.