JPH082532B2 - Method for continuously producing heat-vulcanizable silicone rubber compound - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a continuous method for producing a heat-vulcanizable silicone rubber compound, and more specifically, a method for mechanically shearing the basic constituents of the silicone rubber compound in advance in advance. To form a fluid powder-granular mixture, and introduce the fluid powder into the feed port of a co-rotating twin-screw continuous kneading extruder (hereinafter, abbreviated twin-screw extruder) to obtain a homogeneous mixture. Continuous production method for efficiently obtaining a novel silicone rubber compound.

[Technical background of the invention and its problems]

A heat-vulcanizable silicone rubber compound is a base compound that contains high-viscosity polydiorganosiloxane (raw rubber) as the main raw material, and a silica-based reinforcing filler and various additives to impart various properties. That is. This compound is usually compounded with a vulcanizing agent by a rubber processor and then heat-cured to finally obtain a silicone rubber molded product. As the vulcanizing agent, a well-known one such as an addition reaction type crosslinking agent composed of a combination of an organic peroxide or polyorganohydrogensiloxane and a platinum compound can be used.

Conventionally, such a heat vulcanizing type silicone rubber compound has been manufactured by a double-arm kneader (dough mixer),
A general method is to uniformly knead the high-viscosity polydiorganosiloxane raw rubber, the inorganic filler and various additives using an internal mixer (Banbury mixer), a two-roll mill or the like. The kneader is most often used among these devices, but this dough mixer consists of a large tank with two large mixing blades inside, and the mixing blades mix the raw rubber and the filler to obtain a homogeneous mixture. A mixture is formed. In this case, heating and kneading may be performed in order to reduce crepe hardening (reversion to plasticization) of the generated compound over time. Therefore,
For example, a kneader with a capacity of 2 tons requires a minimum of 6 hours to a maximum of 48 hours. Further, the agglomerate thus obtained is subjected to an extrusion filter in order to remove the mixed foreign matter, and becomes the final compound.

As described above, since a conventional method for producing a heat-vulcanizable silicone rubber compound requires a large-scale production apparatus and a great deal of time, a rational continuous production method has been studied for some time.

As such a manufacturing method, for example, JP-A-61-40327
Japanese patent publication is disclosed. This relates to a method for producing a liquid silicone rubber base containing a polyorganosiloxane and an inorganic filler as main components using a twin-screw continuous extruder. The polyorganosiloxane used here has a preferable viscosity range limited to 300 to 30,000 cP at 25 ° C., and has a good fluidity, so that it is very compatible with the inorganic filler. Therefore, the liquid silicone rubber base mixed with the filler and other additives can be easily manufactured by one twin-screw extruder. However, the viscosity of polyorganosiloxane at 25 ° C is 1x.
In the case of exceeding 10 ⁵ cP, in order to uniformly mix the polyorganosiloxane with an inorganic filler, particularly a reinforcing silica filler having a specific surface area of 50 m ² / g or more by a twin-screw extruder alone,
Often, it takes a long time, and the composition ratio of the obtained rubber base is partially different. Therefore, the fact is that the production method with a twin-screw extruder using high-viscosity polyorganosiloxane has not yet reached the stage of practical application.

On the other hand, as a method for producing a heat-vulcanizable silicone rubber mixture containing high viscosity polyorganosiloxane as a main raw material
No. 50-25650 is disclosed. This manufacturing method is 25 ℃
Mechanical shearing with a high-speed rotor using a polyorganosiloxane having a viscosity in the range of 1 × 10 ^{5 to} 2 × 10 ⁸ cP and a filler selected from a reinforcing filler, an extendable filler and a mixture thereof. It is intended to obtain a free-flowing silicone rubber powder mixture by a means in a short time. However, when the granular mixture prepared by this method is left to stand at room temperature for a long time, the granular compositions adhere to each other to impair the fluidity, or conversely, the granular composition forms a structure (crepe curing). It has a great defect in stability over time (storage stability), such as being in a state close to rubber and being unable to be plasticized by rolls anymore. Therefore, there is a drawback that the range of application as a heat-vulcanizable silicone rubber composition is extremely limited.

Further, when the vulcanizing agent is already contained and the vulcanizing agent is already contained, this silicone rubber powder has an advantage that it can be directly molded into a silicone rubber by an injection molding machine or an extruder. However, when the vulcanizing agent is not contained, the powdery material is once formed into an agglomerate by a roll or the like, and the composition is obtained by adding a vulcanizing agent to the agglomerate, and is molded into a silicone rubber, At this time, there are drawbacks such that the step of making the powdery material into a lump is not easy and it takes a long time, so that it cannot always be said that the manufacturing method is rational.

[Object of the Invention]

The object of the present invention is to solve the above-mentioned drawbacks of the prior art and establish a system capable of continuously producing a heat-vulcanizable silicone rubber compound, whereby a system that is reasonably stable in a short time and stable over time is established. Another object of the present invention is to provide a method for continuously producing a heat-vulcanizable silicone rubber compound.

[Structure of Invention]

The present inventors have conducted extensive studies to achieve such an object, and as a result, obtained a substantially uniform composition containing the basic constituent components of the heat-vulcanizable silicone rubber in advance as a granular material. By continuously supplying the powdery or granular material to a twin-screw extruder in the same direction, it is possible to obtain a silicone rubber compound excellent in dispersibility of filler equal to or more than that obtained by the conventional manufacturing method. Heading out, the present invention has been accomplished.

That is, the present invention provides (A) a polydiorganosiloxane having a viscosity at 25 ° C. of at least 1 × 10 ⁵ cP, and (B)
First, an inorganic filler and (C) a processing aid are used as basic constituent components, and these components are substantially uniformly dispersed and fragmented by a high-speed mechanical shearing method to obtain a fluid granule. And a second step of obtaining a uniform rubber compound from the discharge port of the extruder by continuously quantitatively supplying the powder or granular material from the supply port of the co-rotating twin-screw continuous kneading extruder. A method for continuously producing a heat-vulcanizable silicone rubber compound, which is characterized in that

The component (A) polydiorganosiloxane used in the present invention is generally used for this type of heat-vulcanizable silicone rubber and has a viscosity at 25 ° C. of at least 1 × 10 ⁵ c.
It is P or more, and preferably has a range of 1 × 10 ⁶ to 2 × 10 ⁸ cP. When the viscosity is less than 1 × 10 ⁵ cP, the processability of the obtained heat-vulcanizable silicone rubber compound and the mechanical strength of the vulcanized product are unsatisfactory, which is not preferable. On the other hand, when the viscosity exceeds 2 × 10 ⁸ cP, it is not preferable because it is difficult to mix the inorganic filler and the stability of the obtained compound with time (storage stability) becomes a problem. .

Such a polydiorganosiloxane may be one already known in the art, and has the general formula R ² (▲ R ^{1 2} ▼ SiO) _n SiR ¹ ₂ R ² (wherein R ¹ is a monovalent substituted or unsubstituted carbon atom). Hydrogen group, 0 to 1.0 of the hydrocarbon group
% Is a vinyl group, R ² is a monovalent group selected from the group consisting of a methyl group, a vinyl group, a phenyl group and a hydroxyl group, and n represents a number of 1,000 to 10,000), and It is a linear polymer. As R ¹ other than vinyl group,
Alkyl groups such as methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, decyl group and dodecyl group; cycloalkyl groups such as cyclopentyl group and cyclohexyl group; 2-phenylethyl group, 2-phenylpropyi group An aralkyl group such as a group; an aryl group such as a phenyl group and a tolyl group; an allyl group, a cyclopentenyl group,
Examples thereof include an alkenyl group such as a cyclohexenyl group; and a substituted hydrocarbon group such as a chloromethyl group, a chlorophenyl group, and a 3,3,3-trifluoropropyl group. Considering heat resistance and the like, R ¹ It is preferable that 50% or more is a methyl group. Further, when the vinyl group in R ¹ is 0%, R ² is a vinyl group, and when R ² is other than a vinyl group, it is necessary that at least two vinyl groups are present in one molecule. . When the amount of vinyl groups is less than 2 in one molecule, the obtained rubber composition is not sufficiently vulcanized, which is not preferable. Further, the vinyl group in R ¹ may be more than 1.0%, but in that case, there is a decrease in heat resistance of the vulcanized silicone rubber and a decrease in mechanical strength due to an increase in crosslink density, which is preferable. Absent. It is also possible to blend the polydiorganosiloxanes having different vinyl group contents to each other so as to obtain the above vinyl group content.

Next, in the present invention, favorable results are obtained when n is in the range of 1,000 to 10,000, that is, when the polydiorganosiloxane having the above viscosity range is used. Then, the substantially linear polymer may contain a branched polysiloxane in which a part is branched within a possible range.

As the inorganic filler as the component (B) used in the present invention, any one can be used as long as it is used for compounding a silicone rubber. Examples of such an inorganic filler include fumed silica, reinforcing silica having a specific surface area of, for example, precipitated silica of more than 50 m ² / g, the surface having polyorganosiloxane, organoalkoxysilane, organochlorosilane, triorganodisilazane, etc. Surface-treated silica, diatomaceous earth, fine quartz powder, aluminum oxide, titanium oxide, iron oxide, cerium oxide, cerium hydroxide, magnesium oxide, zinc oxide, calcium carbonate, zirconium silicate, carbon Examples include black and ultramarine. These inorganic fillers may be used alone or in combination of two or more.
The blending amount is 100 g of polydiorganosiloxane (A).
It is selected from the range of 10 to 200 parts by weight with respect to parts by weight,
It is preferably 10 to 100 parts by weight. If it is less than 10 parts by weight, the reinforcing effect is not sufficient, and if it exceeds 200 parts by weight, it is difficult to mix.

In the present invention, among the above-mentioned inorganic fillers, one kind selected from the reinforcing silica and the surface-treated silica or a mixture thereof is used in an amount of 10 to 100 per 100 parts by weight of the component (A).
It is preferable that the composition is blended in parts by weight, preferably 10 to 80 parts by weight. If it is less than 10 parts by weight, sufficient mechanical strength cannot be obtained,
This is because if it exceeds 100 parts by weight, it will be difficult in manufacturing.

The processing aid of the component (C) used in the present invention is to improve the dispersibility of the inorganic filler during kneading, shorten the aging period of the obtained silicone rubber composition, prevent crepe hardening, adjust the plasticity of the compound, etc. The organosilanes having a silanol group or an alkoxy group selected from an alkyl group having 1 to 6 carbon atoms in the molecule, a low viscosity polysiloxane, or a resinous material. Examples of the organosilanes include diphenylsilanediol, dimethylsilanediol, methylvinylsilanediol,
Examples include diphenyldimethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane, and phenyltrimethoxysilane. Low-viscosity polysiloxane is a methyl group, phenyl group, vinyl group, 3,3,3-
It may contain one or more trifluoropropyl groups. Its viscosity at 25 ° C. is in the range of 1 to 300 cP, preferably in the range of 5 to 100 cP. Examples of such a low-viscosity polysiloxane include α, ω-dihydroxypolydimethylsiloxane, α, ω-dimethoxypolydimethylsiloxane, α, ω-dimethoxypolymethylphenylsiloxane, α, ω-diethoxypolymethylvinylsiloxane, α , Ω-dimethoxypolymethylvinylphenylsiloxane and the like are exemplified. If the viscosity is less than 1 cP, volatilization is likely to occur and the added amount varies, which makes it difficult to obtain a stable composition, which is not preferable. Further, it is possible to use those having a viscosity of more than 300 cP, but in that case, the active group content of the silanol group or the alkoxy group is small, and it is not possible to sufficiently exert the effect of improving the above-mentioned various properties, which is preferable. Absent. The silicone resinous material contains an organic group similar to the above-mentioned low-viscosity polysiloxane or the above R ¹ group,
It has a terminal terminated with a silanol group and / or an alkoxy group and has a softening point of 150 ° C. or lower.
When the softening point exceeds 150 ° C., the effect on the dispersibility of the filler is small, which is not preferable.

The addition amount of these processing aids is 0.1 to 30 parts by weight, preferably 0.5 to 15 parts by weight, relative to 100 parts by weight of the component (A).
If the addition amount is less than 0.1 parts by weight, the effect of addition will not be exhibited, and if the addition amount exceeds 30 parts by weight, mechanical strength and plasticity will decrease, which is not preferable.

The thermally vulcanizable silicone rubber composition of the present invention contains various additives well known in the art, such as oxides of various metals, hydroxides thereof, and / or the like, in addition to the above-mentioned basic components. Alternatively, heat resistance improvers selected from fatty acid salts thereof, vulcanization reversion inhibitors, flame retardants (platinum compounds), coloring inhibitors for vulcanized products such as polyorganohydrogensiloxane, silicone oils, etc. Plasticizer, metallic soap as internal release agent, pigment, dye, etc.
Additives known in the art can be added.

In carrying out the present invention, the above (A) to (C)
The order of adding the components and other optional components is not particularly limited, but it is usually performed according to the following steps.

That is, as shown in FIG. 1, (A) to (C)
Ingredients are weighed by respective feed pumps P1 to P3
Sent to T1. In this case, measure the component (B) beforehand in the measuring tank.
It is better to charge T1 first and then component (A) and component (C) in the high-speed mixer in the next step (A) to (C).
When the components are transferred, the components (A) and (C) can be advantageously prevented from adhering to the wall of T1. For the component (A), it is more advantageous to the continuous operation of the production that the tip portion of the pump P1 is reformed as described below and is molded into pellets and then supplied to T1. That is, this pump
A perforated plate having a large number of holes with a diameter of 1 to 10 mm is installed at the tip of the outlet of P1, and the tip (A) of the columnar extruded from the perforated plate can be cut into pellets. It is preferable to provide a rotary blade (rotary chopper). Then, using this P1, the component (A) is pelletized, and when it is fed into the inorganic filler that has been weighed in advance as described above, the filler adheres to the surface of the pellet and its shape is well preserved. The advantage is that the transfer to the next high-speed rotary mixer becomes easy. Since the component (C) is a liquid or solid particulate material, it is added as it is.

The main components thus measured are supplied to the mixer M1. This mixer M1 has a blade with a blade radius of about 10 to 65 cm, the rotation speed is 200 to 6,000 rpm, and the peripheral speed of the blade tip is 15 to 4
A device adjusted to be 5 m / sec is generally used.
The high speed rotating blades impart a strong mechanical shearing action to the feedstock to effect premixing. In this mixing process, in order to impart fluidity to the preliminary mixture, the mixing is stopped when the preset current value is reached. The current value is almost constant at the start of mixing, but the current value rises as the uniform dispersibility of the polydiorganosiloxane and the filler increases. This current value eventually reaches a maximum value, and when the current value is exceeded, the mixture becomes a lump and the current value decreases. If this mixture becomes lumpy and loses its fluidity, it becomes difficult to transfer it to the next step. Therefore, the current value before the maximum value is experimentally determined, and when the current value is reached, the mixer is stopped. In this way, the granular material is obtained and discharged to the supply hopper T2. This powder has an average particle size of 1 to 15,000 μm.
The range is from 10 to 10 for continuous automatic operation in the next process.
The range of 4,000 μm is particularly preferable. The rotation speed of M1 and the processing time (current value) are determined in order to obtain powder particles in such a range.

Preferred examples of the high speed mixer M1 used in the present invention include Henschel mixers, micro speed mixers and other commercially available products. When such a device is used, only the above-mentioned components (A) and (B) are introduced into a measuring tank, which is made into powder or granules in advance by a mixer M1, and then separately measured (C) component is added. It is also possible to introduce from the supply port attached to M1. In addition, (A) ~
Optional components (property improving additives) other than component (C) can also be used as M1
Can be mixed in. However, when a coloring pigment or the like is used, contamination of the device poses a problem, so it is preferable to add it from the supply port of the same-direction twin-screw extruder M2 in the next step.

In the present invention, heating or cooling is not particularly required in the M1 mixing step, but it is preferable to keep the temperature within a certain range in order to obtain a uniform mixed powder or granule. Its temperature is 10 to 10
The temperature is selected from the range of 0 ° C., but it is preferably around room temperature for the next step, and usually cooling by passing water is often performed.

Since the first step of the present invention is a batch system,
It is also possible to increase all or part of the process equipment to two or more stations. By the rational implementation of the first step, it is possible to continuously supply the powdery particles to the next step, and as a result, it is possible to smoothly operate the continuous production system of the heat-vulcanizable silicone rubber compound.

The free-flowing silicone rubber powder obtained in the first step is discharged to the mixture supply hopper T2 for the co-direction twin-screw extruder M2. The T2 is equipped with a wall scraping blade of 5 to 10 rpm, which allows continuous discharge to the constant amount belt feeder F1. this
From F1, the silicone rubber powder is continuously supplied to the same-direction twin-screw extruder M2 in a fixed amount.

The same-direction twin-screw extruder M2 has two rotating screws arranged in parallel in the barrel and rotating in synchronization with each other in the same direction. There is a different-direction twin-screw extruder as an extruder similar to this, but this type is not used in the present invention because the compound at the tip of the screw undergoes local shearing action to cause uneven kneading. Better.

The extruder M2 used in the present invention has a screw rotation speed of 0.
It has a capacity of ~ 1000 rpm. The screw of this extruder is not particularly limited to its L / D,
L / D = 25 to 50 considering the compounding efficiency of the compound
It is preferable to select from the range. The screw configuration and screw shape can be appropriately selected from commercially available ones, but a screw configured with a double or triple thread screw is preferable. This same direction 2
As the axial extruder, Werner Freidler (Wern
er & Pfleiderer KG), Toshiba Machine TEM mixer, Ikegai PCM mixer, etc.

These extruders are preferably those capable of both cooling and heating the entire barrel or divided parts, and those capable of temperature control in a wide range of 0 to 300 ° C. are various heat vulcanizing silicone rubbers. It is convenient because it can be applied to compounds. This temperature control is usually performed using a jacket or an electric heater. In the present invention, cooling is not always necessary, but it is generally performed at the rear part of the barrel and is rapidly cooled using a refrigerant to remove sensible heat due to heating at the front part or shear heat generation. This rapid cooling not only facilitates packing of the silicone rubber compound discharged from the extruder, but also has the effect of alleviating the plasticization return (crepe hardening) phenomenon of the compound after heating and kneading, which is a great advantage. Become.

Providing one or more vents (decompression zones) at appropriate locations in the middle or end of the extruder barrel,
A device capable of removing volatile components and degassing, a device provided with a second supply port capable of adding other components that could not be added in the previous step, and the like can also be advantageously used. The extrusion capacity of this extruder is preferably a capacity balanced with the first step. The selection can be easily made by the inner diameter of the barrel and the rotation speed of the screw.

The silicone rubber powder granules introduced into the above-mentioned twin-screw extruder M2 are kneaded inside, and the silicone rubber compound equivalent to that obtained by the conventional kneader formulation is discharged from the end discharge port in an extremely short time. can get. This second
In the process, heat kneading and / or deaeration are usually carried out, especially when untreated reinforcing silica is used as the inorganic filler. Also, during the first step or from the supply port to the extruder M2, an organosilicon compound reactive with silanol on the silica surface such as trimethylalkoxysilane, hexamethyldisilazane, and 1,3-divinyltetramethyldisilazane is added. Then, the surface treatment of the inorganic filler can be performed while heating and kneading in the extruder M2. Thus, by kneading by heating with the extruder M2 in the second step, it is possible to prevent the crepe hardening of the silicone rubber compound over time and to treat the surface of the inorganic filler. Here, the heating temperature is not particularly limited and may be appropriately selected usually from the range of 100 to 300 ° C.

As described above, in the present invention, this second step is highly likely to be the rate-determining step for producing the heat-vulcanizable silicone rubber compound, and therefore the improvement of the extruder capacity is a key point. Therefore, in order to increase the efficiency of the system, the time required for this second step (the time from the supply port to the discharge port of the granular material) should be adjusted to 1 to 60 minutes, preferably 1 to 30 minutes. Should be implemented in.

〔The invention's effect〕

By adopting the above-mentioned manufacturing method, a thermal vulcanization type silicone rubber compound equivalent to the conventional one can be obtained continuously and in a short time by a combination of relatively small-sized equipment, and the labor saving and energy saving of the process can be significantly achieved. be able to. Therefore, the method of the present invention has a great effect on the rationalization of the industrial production method of the heat-vulcanizable silicone rubber compound.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the examples and comparative examples, all parts are parts by weight.

Example 1 21,000 parts of fumed silica (Silica I) having a specific surface area of 300 m ² / g was charged into a measuring tank T1 from an inorganic filler supply pump P2. From the tip of the polydiorganosiloxane supply pump P1 with the plate and rotary blade attached to it, from the tip of the polydiorganosiloxane supply pump, the diameter is 3 mm and the length is 5 mm.
9 dimethylsiloxane units molded into mm pellets
9.8 mol% and methylvinylsiloxane units 0.2 mol%
Trimethylsilyl group end-capped polymethylvinylsiloxane with a viscosity of 15,000,000 cP at 25 ℃
Part (raw rubber I) and from P3 as a processing aid, 3,000 parts of α, ω-dimethoxypolydimethylsiloxane (processing aid I) having a viscosity of 15 cP at 25 ° C and a viscosity of 3 at 25 ° C.
0 cP, α, ω-dimethoxypolymethylphenylsiloxane (processing aid II) consisting of 67 mol% of dimethylsiloxane units and 33 mol% of diphenylsiloxane units 3,
The mixture with 000 parts was metered into T1. The whole amount was transferred to a Henschel mixer (high speed mixer M1) with a processing capacity of 500 and a mixing blade radius of about 48 cm. It was started immediately and ran at 800 rpm to provide strong mechanical shear. Read the steady-state current value at the beginning of operation, and check the 1.
When the number reached 5 times, the operation was stopped and powder was obtained. The composition of this powder is shown in Table 1. The powder and granules thus obtained were supplied to the following mixture supply hopper T2. The time from the start to the discharge was 7 minutes. Meanwhile, the mixer was cooled by passing water. The temperature of the obtained granules is 39 ° C.
The particles were fluid spherical particles having an average particle diameter of 60 μm. The powder and granules were quantitatively supplied to the twin-screw extruder M2 in the same direction by the quantitative belt feeder F1. This extruder M2 has a screw diameter (D) of 50 mm, a shaft length of 2,400 mm (screw L / D = 48),
Made by TOSHIBA MACHINE, which can change the screw rotation speed from 0 to 1,000 rpm
TEM-50 (trade name) was used. The barrel of this device has an L
/ D = 1-5, powder supply port, L / D = 20-22 and L
The first and second open vent ports are provided at the positions of / D = 36 to 38, respectively, and the kneaded product is discharged from the discharge port of L / D = 48. A vacuum pump can be attached to the vent port for degassing under reduced pressure, and the vent port in the front part also serves as a supply port for other additives such as pigments. Also L /
D = 0 to 10 can be water-cooled, and the range of 10 to 38 is 3 with an electric heater
It was set so that it could be heated up to 00 ° C and could be rapidly cooled with a refrigerant of -10 ° C between 38 and 48.

Using this device, the silicone rubber powder is
The screw rotation speed was adjusted so that it could be fed at a speed of 000 parts. During operation, the compound temperature of L / D = 36-38 was heated so that the compound temperature was maintained at 270 ° C, and low fraction was removed and deaerated under reduced pressure by the second vent port. The section of L / D = 38 to 48 was cooled by a refrigerant at -10 ° C. The compound temperature during discharge was about 90 ° C. The time required for this second step was 75 minutes.

The heat-vulcanizable silicone rubber compound thus obtained was masticated with a roll, and a part of it was subjected to the Williams plasticity sample method specified in JIS C 2123, immediately after sample preparation and after standing for 3 days. The other balance was press vulcanized by adding 0.3 part of 2,5-dimethyl-2,5-di-t-butylperoxyhexane per 100 parts of the compound, and press-vulcanized to a thickness of 2 mm. The above silicone rubber sheet was subjected to post-vulcanization at 200 ° C. for 1 hour. For this sheet, general physical properties were measured by the method specified in JIS K 6301. The results are shown in Table 1.

Comparative Example 1 The same composition as in Example 1 was trial-produced using a 100 kneader. After the composition became uniform, the mixture was heated and kneaded at 150 ° C. for 4 hours. After cooling, filtration was performed with a single-screw extruder to obtain a final compound. The total process time from preparation by this method required 8 hours.

For the rubber compound thus obtained, the plasticity and physical properties were measured in the same manner as in Example 1. The results are shown in Table 1. Further, when the dispersibility of the filler was observed with a microscope and compared with Example 1, no difference was observed.

From the above results, the kneader prototype and the silicone rubber compound of Example 1 are completely equivalent in characteristics,
It can be seen that there is a large difference in the manufacturing time.

Comparative Example 2 500 parts of the powder and granules obtained in the first step of Example 1 were taken out from T2 and made into a lump (compound) with a roll. 10 of these
About 0 part, a sample was prepared for measuring the plasticity in the same manner as in Example 1, 300 parts were stored to investigate the change over time, and left at room temperature for testing every month. When the compound left to stand was attempted to be plasticized with a roll after 1 month, pseudo-crosslinking (crepe hardening) was progressing to generate a microgel, and it was difficult to plasticize after 3 months. Further, with respect to the remaining 100 parts, a rubber sheet similar to that of Example 1 was prepared and its physical properties were measured. The results are shown in Table 1.

From the above results, it is clear that the powder and granules that do not go through the mixing process by the same-direction twin-screw extruder have poor storage stability and have a great quality problem.

Example 2 50,000 parts of raw rubber I used in Example 1 and a specific surface area of 210 m
25,000 parts of precipitated silica of ² / g, 2,500 parts of α, ω-dihydroxypolydimethylsiloxane (processing aid III) having a viscosity of 50 cP at 25 ° C. and 40 parts of zinc stearate as an internal mold release agent were prepared in the same manner as in Example 1. I put it in a Henschel mixer. It was operated at 800 rpm for 6 minutes to obtain a granular material. The powder and granules were fed to the extruder M2 at a rate of 1,200 parts per minute by a quantitative belt feeder F1. This compound was heated and kneaded so that the final temperature would be 280 ° C., and the vent portion was used for degassing under reduced pressure in both the first and second portions. The cooling of the rear part was performed in the same manner as in Example 1.

The compound thus obtained was tested exactly as in Example 1. The results are shown in Table 1. Further, when the roll workability of this compound was examined, it was found to be equal to or higher than that obtained by the conventional manufacturing method, and it was possible to dispense 0.3 mm when an 8-inch roll was used.

Comparative Example 3 The same test as in Comparative Example 2 was performed using the powder and granules obtained in Example 2. The compound obtained from this granular material could be sufficiently plasticized even after standing at room temperature for 3 months. However, the compound immediately after production had a very high degree of plasticity and poor fluidity. The plasticity and physical properties of this compound were measured, and the results are shown in Table 1. Further, when the plasticity and physical properties were measured every one month and the aging effect of the compound was examined, it was found that about 3 months were required to obtain the same properties as in Example 2. The physical properties at that time were hardness 54 and tensile strength.
The properties were 63 kgf / cm ² and elongation 320%, which were almost the same as the properties of Example 1. Further, when the roll workability of the compound was investigated, it was confirmed that the compound had an adhesive property on the roll surface, and it was difficult to dispense 1 mm with an 8-inch roll. Therefore, it was found that the effect of adding the internal release agent was not obtained at all by simply leaving the compound at room temperature.

Comparative Example 4 The same raw material as in Example 1 was used, and an attempt was made to produce a heat-vulcanizable silicone rubber compound using a linear co-directional twin-screw extruder without the first step. As a simple method, half of the raw material of Example 1 was charged into a Henschel mixer, operated for 30 seconds to produce an inhomogeneous crude mixture, and this was taken out in 10 divided petroleum cans so as to have a homogeneous component as much as possible. did. Using this, the crude mixture was fed to the extruder M2 under the same operating conditions as in Example 1. According to this method, the kneading was still insufficient until the first vent port, and the powder remained in a powder state. The discharged compound also had no viscosity, and the roll workability was very poor. Moreover, when a sample was partially taken from the discharged compound and the specific gravity thereof was measured, the variation from the average value exceeded ± 100%. Thus, the method of obtaining the heat-vulcanizing type silicone rubber compound only by the twin-screw extruder cannot be adopted at the present technical level.

Example 3 Consists of 94.8 mol% of dimethylsiloxane units, 0.2 mol% of methylvinylsiloxane units and 5 mol% of diphenylsiloxane units and has a viscosity at 25 ° C. of 18,000,000 cP.
Of dimethylvinylsilyl end-blocked polyorganosiloxane (raw rubber II), 50,000 parts of fumed silica (silica II) having a specific surface area of 200 m ² / g, 500 parts of diatomaceous earth, Example 1
A silicone rubber compound was produced in the same manner as in Example 1 except that 4,000 parts of the processing aid I of Example 1 and 50 parts of heat-resistant additive iron dioctanoate were used as raw materials. The various properties were measured and the results are shown in Table 1. This compound was immediately wound around the roll even after 6 months, and the roll workability was not different from the initial stage.

Example 4 3,3,3-Trifluoropropylmethylsiloxane unit 9
Consisting of 9.7 mol% and methyl vinyl siloxane unit 0.3%, viscosity at 25 ℃ 30,000,000cP trimethylsilyl group end-blocked polyorganosiloxane (raw rubber) 50,000
A composition comprising, by weight, 17,500 parts of fumed silica (silica III) surface-treated with 1,3-divinyltetramethyldisilazane, 10,000 parts of fine quartz powder and 3,000 parts of Processing Aid II of Example 1 was used. It was manufactured in the same manner as in No. 1 and its characteristics were measured. The results are shown in Table 1.

The heat-vulcanizable silicone rubber compound obtained here was also stable over time.

Example 5 A granular material was obtained in the same manner as in Example 1 from 50,000 parts of raw rubber I used in Example 1, 25,000 parts of silica II of Example 3 and 5,000 parts of processing aid III. Large machine TEM-10 with the same direction twin-screw extruder with the same structure and screw diameter of 100 mm
A thermal vulcanization type silicone rubber compound was obtained in the same manner as in Example 1 using 0 (manufactured by Toshiba Machine). At this time, the supply rate of the powder and granules was 3,000 parts per minute. The same test as in Example 1 was performed on this compound, and the results are shown in Table 1. From this example, it is apparent that even if the extruder is made large in size, it is possible to obtain a product which is sufficiently satisfactory in terms of characteristics and the productivity is remarkably improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a system configuration of an apparatus used in the manufacturing method of the present invention. P1 …… Polydiorganosiloxane supply pump P2 …… Inorganic filler supply pump P3 …… Processing aid supply pump T1 …… Measuring tank M1 …… High speed mixer T2 …… Mixture supply hopper F1 …… Belt feeder M2 …… Same direction Twin screw extruder

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location C08L 83:04 (72) Inventor Junichiro Watanabe 133 Nishishinmachi, Ota-shi Gunma Toshiba Toshiba Silicon Co., Ltd. (56) References JP-A-50-25650 (JP, A) JP-A-54-60358 (JP, A) JP-A-61-40327 (JP, A)

Claims (4)

[Claims] 1. A) The viscosity at 25 ° C. is at least 1 ×.
The basic constituents were 10 ⁵ cP polydiorganosiloxane, (B) inorganic filler and (C) processing aid, which were substantially uniformly dispersed and comminuted by a high speed mechanical shearing method. First to obtain a fluid granular material
And a second step of obtaining a uniform rubber compound from the discharge port of the extruder by continuously quantitatively supplying the powder or granular material from the supply port of the co-rotating twin-screw continuous kneading extruder. A method for continuously producing a heat-vulcanizable silicone rubber compound, which comprises: 2. The component (A) polydiorganosiloxane is subdivided into pellets by a rotary chopper provided at the outlet of the supply pump, and the components (B) and (C) are obtained.
The manufacturing method according to claim 1, which is dispersed together with the components. 3. The manufacturing method according to claim 1, wherein the screw of the co-rotating twin-screw continuous extruder is constituted by a two-thread or three-thread screw. 4. The kneading step in the same-direction twin-screw extruder is 100 to 300.
The manufacturing method according to claim 1, which is carried out under heating at ℃.