JP2014097607A - Internal mixer, kneading method and rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition which has improved dispersibility of silica by efficiently removing water and alcohol produced as a by-product in the coupling reaction between the silica and a silane coupling agent and also has improved reactivity of the silica, and thereby providing a vulcanized rubber having improved dynamic viscoelasticity property.SOLUTION: An internal mixer includes: a kneading part 4 which has a casing 2 and a rotor 3, and which kneads a rubber composition containing at least raw rubber, silica and a silane coupling agent; a neck part 5 positioned in the upper portion of the kneading part 4, and having a cylindrical space inside thereof; a charging port 6 provided at the upper portion on the side surface side, of the neck part 5; a ram 7 vertically movable in the cylindrical space of the neck part 5, and capable of pressing the rubber composition in the kneading part from above in the kneading of the rubber composition; and a drop door 9 positioned in the lower surface of the kneading part, and discharging downward the kneaded rubber composition. By using the internal mixer, the rubber composition is kneaded while the temperature of the ram is conditioned to 50-120°C.

Description

  The present invention relates to a closed mixer, a kneading method, and a rubber composition for kneading a rubber composition containing at least raw rubber and silica.

  Silica is used as a filler for reinforcing rubber. Silica tends to aggregate particles due to hydrogen bonding of silanol groups which are surface functional groups. Therefore, when silica is blended in the rubber composition, it is preferable to add a silane coupling agent in order to improve the dispersion of silica. As a result, the silica and the coupling agent are subjected to a coupling reaction to improve dispersibility and suppress re-aggregation, thereby improving the fuel efficiency and wettability of the tire.

  A coupling reaction between silica and a silane coupling agent will be described below. In such a coupling reaction, after the silica and the silane coupling agent are bonded through a dehydration reaction, the adjacent coupling agents take in water and hydrolyze to form siloxane bonds with each other on the silica surface. Cover the group. At that time, alcohol is generated as a reaction byproduct. Thus, the dispersibility of the silica in the rubber can be improved by covering the hydrophilic group on the silica surface with the silane coupling agent, thereby increasing the affinity between the silica and the rubber and preventing self-aggregation. However, if the water and alcohol by-produced during the coupling reaction are not efficiently removed, the coupling reaction does not proceed sufficiently and the dynamic viscoelastic properties of the final vulcanized rubber are reduced, or the silica is dispersed. The effect of improving the performance may be reduced.

  In order to solve the above problem, in Patent Document 1 below, water and alcohol released during kneading of the rubber material by connecting an exhaust duct to a hopper that receives the rubber material discharged from the kneading part of the hermetic mixer Is described.

  In Patent Document 2 below, the temperature of the kneading part of the hermetic mixer is adjusted, and the kneading temperature of the rubber material is set to 130 to 170 ° C., so that water and alcohol released during the kneading of the rubber material are effective. Describes the technology to exhaust.

JP 2005-231057 A JP 2006-123272 A

  However, each of the above prior arts has the following problems. That is, in the technique described in Patent Document 1, when exhaust treatment is performed at the initial stage of rubber material kneading, solid content such as a filler containing silica may be clogged in the duct pipe, and exhaust treatment is performed later in the rubber material kneading. Even if it does, since the water and alcohol have already been taken in the rubber, their removal efficiency is significantly reduced.

  In the technique described in Patent Document 2 below, the kneading temperature of the rubber material is merely devised, and there is room for improvement in terms of water and alcohol removal efficiency.

  The present invention has been made in view of the above circumstances, and the problem is that the dispersibility of silica is improved by efficiently removing water and alcohol by-produced during the coupling reaction between silica and a silane coupling agent. And it is providing the rubber composition which the dynamic viscoelastic property of vulcanized rubber improved by raising the reactivity of silica.

  As a result of intensive studies to solve the above problems, the present inventor does not stay in the casing of the kneading part but water and alcohol by-produced during kneading of the rubber composition, and dew condensation occurs on the lower surface of the ram, which is mixed into the casing again. As a result, it has been found that water and alcohol cannot be efficiently removed from the rubber composition. In order to solve this problem, the ram of the closed mixer was redesigned so that the temperature could be controlled. By setting the ram temperature to an appropriate temperature, condensation of water and alcohol on the lower surface of the ram was prevented and silica was dispersed. The point which can improve the property was also found. The present invention has been made based on such discovery and has the following configuration.

  That is, the closed mixer according to the present invention is a closed mixer for kneading a rubber composition containing at least raw rubber, silica and a silane coupling agent, and has a casing and a rotor, and the rubber composition A kneading part for kneading, a neck part located above the kneading part and having a cylindrical space inside, an inlet provided in the upper part on the side surface of the neck part, and a cylindrical part of the neck part The rubber composition after kneading is located on the lower surface of the kneading part and a ram that can move up and down in the space and can press the rubber composition in the kneading part from above when kneading the rubber composition And a drop door for discharging an object downward, wherein the ram is a ram that can be temperature-controlled at 50 to 120 ° C.

  As far as the present inventor can know, up to now, as a closed mixer, the ram does not have a temperature control function, or not only the temperature of the ram can be controlled independently, but the temperature can be controlled in the same system as the rotor or casing. The reality is that only what has been made exist. In the hermetic mixer according to the present invention, the temperature can be set independently by the ram independently of the rotor and / or casing, specifically 50 to 120 ° C. When the rubber composition is kneaded using water, it is possible to prevent water and alcohol from condensing on the lower surface of the ram, and to prevent them from entering the casing again. As a result, the moisture content of the rubber composition after kneading can be reduced. Furthermore, when the ram is set to 50 to 120 ° C., the dispersibility of silica during rubber kneading is enhanced. On the other hand, if the temperature of the ram is less than 50 ° C., it is impossible to prevent water and alcohol from condensing on the lower surface of the ram, and these will be mixed again in the casing, and if the temperature of the ram exceeds 120 ° C., Dispersibility worsens.

  In the above-described closed mixer, the neck portion is preferably a neck portion that can be temperature-controlled at 50 to 120 ° C. Water and alcohol by-produced during rubber kneading may condense not only on the lower surface of the ram but also on the inner wall surface of the neck portion. Therefore, when using a closed mixer whose neck can be set to 50 to 120 ° C., it is possible to prevent condensation of water and alcohol on the inner wall surface of the neck when rubber is kneaded, and these are mixed into the casing again. Can be prevented. As a result, the moisture content of the rubber composition after kneading can be further reduced.

  In the above-mentioned closed mixer, it is preferable to have an air blow that can allow external air to flow in from an air inlet formed in a side surface of the casing. According to such a configuration, it is possible to more efficiently prevent water and alcohol that have condensed on the lower surface of the ram and / or the inner wall surface of the neck portion from entering the casing.

  The rubber composition kneading method according to the present invention is a rubber composition kneading method containing at least raw rubber, silica and a silane coupling agent, and has a casing and a rotor, and kneads the rubber composition. A kneading part, a neck part located above the kneading part and having a cylindrical space inside, a charging port provided in an upper part on the side of the neck part, and a cylindrical space in the neck part The rubber composition is positioned on the lower surface of the kneading part, and the rubber composition after kneading is placed on the lower surface of the kneading part when the rubber composition is kneaded. The rubber composition is kneaded in a state where the temperature of the ram is adjusted to 50 to 120 ° C. using a closed mixer provided with a drop door that is discharged downward. According to this production method, a rubber composition having a low moisture content and excellent silica dispersibility can be produced. In order to further reduce the moisture content of the rubber composition, it is preferable to knead the rubber composition in a state in which the neck portion is temperature-controlled at 50 to 120 ° C., and the closed mixer serves as a side surface of the casing. It is preferable to have an air blow through which the external air can flow from an air inlet formed in the air inlet, and knead the rubber composition while flowing the external air from the air blow into the casing.

  The rubber composition produced by any one of the above rubber composition production methods has a low moisture content and is excellent in silica dispersibility. When the rubber composition contains a styrene butadiene rubber modified with an amine and an alkoxysilane, silica, and a silane coupling agent composed of at least one of Si75 and protected mercaptosilane, the moisture content is low and the silica is highly dispersed. In addition to the properties, various rubber properties are also excellent.

The conceptual diagram which shows the structure of the closed type mixer which concerns on this invention

  In the present invention, a closed mixer is used for kneading the rubber composition. As such a closed mixer, a meshing intermix type mixer, a tangential Banbury type mixer, a pressure kneader, or the like can be used. In particular, a meshing intermix type mixer can be suitably used.

  A preferred embodiment of a hermetic mixer according to the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing a configuration of a closed mixer according to the present invention.

  The hermetic mixer 1 is provided at a kneading part 4 having a casing 2 and a rotor 3, a neck part 5 having a cylindrical space inside the kneading part 4, and an upper part on the side surface side of the neck part. The inlet 6, a ram 7 that can move up and down in the cylindrical space of the neck portion 5, and a drop door 9 positioned on the lower surface of the kneading portion 4 are provided.

  In the present embodiment, a pair of rotors 3 are arranged in the width direction of the kneading unit 4 in the casing 2 of the kneading unit 4 and rotate in predetermined directions using a motor as a power source. At that time, when the rubber composition receives a shearing force in the gap between the rotor 3 and the casing 2 and the ram 7, the coupling reaction between the silica and the silane coupling agent proceeds while the rubber composition is kneaded. . The temperature of the rubber composition at the time of kneading is set to 130 to 180 ° C., for example, and the kneading time is exemplified to be 1 to 15 minutes.

  An opening 2a is provided at the center of the upper surface of the casing 3 of the kneading part 4, and a neck part 5 having a cylindrical space inside is provided above the opening 2a. At the upper part on the side surface side of the neck portion 5, there is provided an inlet 6 through which raw materials rubber, compounding agents such as silica and a silane coupling agent can be charged. Two or more input ports 6 may be provided in order to input the raw rubber and the compounding agent from separate input ports. The raw rubber and the compounding agent charged from the charging port 6 pass through the cylindrical space of the neck portion 5 and are charged into the casing 2 from the opening 2a of the casing 2.

  The ram 7 is formed in a shape capable of closing the opening 2 a of the casing 2, and is provided so as to be movable in the vertical direction in the cylindrical space of the neck portion 5 by a shaft 8 connected to the upper end thereof. The ram 7 can press and press the rubber composition existing in the casing 2 of the kneading part 4 by its own weight or a pressing force from the shaft.

  The drop door 9 located on the lower surface of the casing 2 of the kneading part 4 is closed when the rubber composition is kneaded in the kneading part 4, and is opened after the kneading is finished to discharge the rubber composition downward. Can do.

  The hermetic mixer according to the present invention is characterized in that the ram 7 is a ram whose temperature can be adjusted to 50 to 120 ° C. By controlling the temperature of the ram 7 within such a temperature range, it is possible to prevent the volatilized water and alcohol from condensing on the lower surface of the ram 7. In order to prevent dew condensation of water and alcohol on the lower surface of the ram 7 and efficiently increase the dispersibility of silica, the temperature controllable range of the ram 7 is preferably 60 to 100 ° C., and 70 to 90 ° C. More preferably.

  In the closed mixer according to the present invention, the neck portion 5 is preferably the neck portion 5 that can be temperature-controlled at 50 to 120 ° C. By adjusting the temperature of the neck portion 5 to such a temperature range, it is possible to prevent the volatilized water and alcohol from condensing on the inner wall surface of the neck portion 5. In order to more effectively achieve the effects of preventing condensation of water and alcohol on the inner wall surface of the neck portion 5 and improving the dispersibility of silica, the temperature controllable range of the neck portion 5 is 60 to 100 ° C. It is preferable that it is 70-90 degreeC.

  However, when the casing 2 and the rotor 3 are heated similarly to the ram 7, when the rubber composition is kneaded in the kneading part 4, the rubber abnormally generates heat and the kneadability is remarkably deteriorated. Therefore, in order to promote the reaction of silica and improve the dispersibility, it is preferable that the temperature control range of the casing 2 and the rotor 3 is lower than the temperature control range of the ram 7, and further, the casing 2 and the rotor 3 are 30 to 60 ° C. It is more preferable that the temperature can be adjusted.

  The hermetic mixer according to the present invention may have an air blow (not shown in FIG. 1) through which external air can flow from an intake port formed in the side surface of the casing 2. By letting external air flow into the casing 2, water and alcohol can be forcibly discharged from the casing 2, and the water content of the rubber composition after kneading can be reduced. On the other hand, when an exhaust port is formed in the side surface of the casing 2 and water and alcohol in the casing 2 are sucked and discharged, the duct pipe may be clogged with a filler such as silica or water and alcohol.

  The method for producing a rubber composition according to the present invention is characterized in that the rubber composition is kneaded in a state where the temperature of the ram 7 is adjusted to 50 to 120 ° C. by using the above-mentioned closed mixer. According to this production method, a rubber composition having a low moisture content and excellent silica dispersibility can be produced. In order to further reduce the moisture content of the rubber composition, it is preferable to knead the rubber composition in a state in which the neck portion 5 is adjusted to a temperature of 50 to 120 ° C., and from the intake port formed in the side surface of the casing 2. It is preferable that the rubber composition has an air blow into which external air can flow, and the rubber composition is kneaded while the external air flows into the casing from the air blow.

  The rubber composition produced by the above production method has a low moisture content and excellent silica dispersibility. Below, the raw material of the rubber composition which can be used by this invention is demonstrated.

  As the raw material rubber to be charged, diene rubber can be preferably used. Examples of the diene rubber include natural rubber (NR), polyisoprene rubber (IR), styrene butadiene rubber (SBR), polybutadiene rubber (BR), butadiene rubber (SPB) containing syndiotactic-1,2-polybutadiene, A chloroprene rubber (CR), a nitrile rubber (NBR), etc. are mentioned, These can each be used individually or as a 2 or more types of blend. These exemplified diene rubbers are those having terminal modified as required (for example, terminal modified BR, terminal modified SBR, etc.), or modified to give desired characteristics (for example, modified). NR) can also be used. As this terminal-modified diene rubber, diene rubber whose polymer terminal is modified with various modifiers can be used, and various known modification methods can be used. Specifically, as the modifier, tin compound, aminobenzophenone compound, isocyanate compound, diglycidylamine compound, cyclic imine compound, halogenated alkoxysilane compound, glycidoxypropylmethoxysilane compound, neodymium compound, alkoxysilane compound, amine Examples thereof include a combination of a compound and an alkoxysilane compound. In the case of synthetic rubber, the polymerization method, molecular weight, etc. are not particularly limited, and the combination of the rubber type and the blend ratio can be appropriately selected depending on the site and use of the rubber composition. Regarding polybutadiene rubber (BR), in addition to those synthesized using a cobalt (Co) catalyst, a neodymium (Nd) catalyst, a nickel (Ni) catalyst, a titanium (Ti) catalyst, and a lithium (Li) catalyst, WO2007 What was synthesize | combined using the polymerization catalyst composition containing the metallocene complex as described in -129670 can also be used. Among these diene rubbers, use of BR and / or SBR is preferable, use of SBR is more preferable, and use of modified SBR modified with amine and alkoxysilane is particularly preferable.

  As the silica, wet silica, dry silica, sol-gel silica, surface-treated silica, etc. used for usual rubber reinforcement are used. Of these, wet silica is preferable. It is preferable that the compounding quantity of a silica is 20-120 mass parts with respect to 100 mass parts of raw rubber, and it is more preferable that it is 40-100 mass parts.

  The silane coupling agent is not particularly limited as long as it contains sulfur in the molecule, and various silane coupling agents blended with silica in the rubber composition can be used. For example, bis (3-triethoxysilylpropyl) tetrasulfide (for example, “Si69” manufactured by Degussa), bis (3-triethoxysilylpropyl) disulfide (for example, “Si75” manufactured by Degussa), bis (2-tri Sulfide silanes such as ethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) disulfide, γ-mercaptopropyltri Mercaptosilanes such as methoxysilane, γ-mercaptopropyltriethoxysilane, mercaptopropylmethyldimethoxysilane, mercaptopropyldimethylmethoxysilane, mercaptoethyltriethoxysilane, 3-octanoylthio-1- Examples thereof include protected mercaptosilanes such as propyltriethoxysilane and 3-propionylthiopropyltrimethoxysilane. It is preferable that the compounding quantity of a silane coupling agent is 2-25 mass parts with respect to 100 mass parts of silica, More preferably, it is 5-15 mass parts.

  A typical example of the vulcanizing agent is sulfur. Sulfur should just be normal sulfur for rubber | gum, For example, powder sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur etc. can be used.

  In the present invention, the rubber composition contains at least a compounding agent other than raw rubber, silica, silane coupling agent and vulcanizing agent, such as filler, zinc oxide, stearic acid, vulcanization accelerator, vulcanization accelerator, Compounding agents usually used in the rubber industry such as vulcanization retarders, anti-aging agents, reversion inhibitors, softeners such as waxes and oils, processing aids, etc. are appropriately blended within a range not impairing the effects of the present invention Can be used.

  The filler means an inorganic filler usually used in the rubber industry, such as carbon black, clay, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide. Among the inorganic fillers, carbon black can be particularly preferably used.

  As carbon black, for example, conductive carbon black such as acetylene black and ketjen black can be used in addition to carbon black used in ordinary rubber industry such as SAF, ISAF, HAF, FEF, and GPF. The carbon black may be a granulated carbon black or a non-granulated carbon black granulated in the normal rubber industry in consideration of its handleability.

  As the vulcanization accelerator, sulfenamide vulcanization accelerator, thiuram vulcanization accelerator, thiazole vulcanization accelerator, thiourea vulcanization accelerator, guanidine vulcanization, which are usually used for rubber vulcanization. Vulcanization accelerators such as accelerators and dithiocarbamate vulcanization accelerators may be used alone or in admixture as appropriate.

  As an anti-aging agent, an aromatic amine-based anti-aging agent, an amine-ketone-based anti-aging agent, a dithiocarbamate-based anti-aging agent, a thiourea-based anti-aging agent, etc., which are usually used for rubber other than a phenol-based anti-aging agent May be used as needed.

(Raw material)
a) Rubber component (the total amount is 100 parts by mass)
Modified styrene butadiene rubber (modified SBR) 100 parts by mass: HPR340 manufactured by JSR Corporation (modified S-SBR, amount of bound styrene: 10% by mass, modified with amine and alkoxyl silane)
b) 20 parts by mass of carbon black (HAF-HS (N339)): Seast KH manufactured by Tokai Carbon Co., Ltd.
c) Silica 70 parts by mass: Tosoh Silica Industry Co., Ltd. “Nipseal AQ”
d) a silane coupling agent 7 parts: protected _{mercaptosilane: (C n H 2n + 1} O) 3 Si-C m H 2m -S-CO-C k H 2k + 1 with a coupling agent represented by (n = 2, m = 3, k = 7), “NXT” made by Momentive Performance Materials
e) Oil 40 parts by mass: Japan Energy Corporation “Process X-140”
f) 2 parts by mass of stearic acid: “stearic acid” manufactured by NOF Corporation
g) 3 parts by mass of zinc oxide: “Zinc oxide 2 types” manufactured by Mitsui Mining & Smelting Co., Ltd.
h) Anti-aging agent 2 parts by mass: “Antigen 6C” manufactured by Sumitomo Chemical Co., Ltd.
i) 2 parts by weight of wax: “paraffin wax 135” manufactured by Nippon Seiwa Co., Ltd.
j) 2.1 parts by mass of sulfur: “oil-treated 150 mesh powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
k) 1.5 parts by mass of vulcanization accelerator: “Noxeller CZ-G” manufactured by Ouchi Shinsei Chemical Co., Ltd.

Examples 1-2 and Comparative Examples 1-4
1 is used, the temperature of the ram 7, the neck portion 5, the casing 2, the rotor 3, the rotor 3 and the drop door 9 is set to the temperatures shown in Table 1, and the rubber composition in the kneading portion 4 is used. Kneaded. In Example 1 and Comparative Examples 2 to 4, a hermetic mixer having an air blow capable of flowing external air from an air inlet formed in the side surface of the casing 2 was used. The rubber composition after kneading was vulcanized under the following vulcanization conditions and evaluated.

[Dynamic viscoelasticity]
Vulcanized at 160 ° C. for 30 minutes, and tan δ at a temperature of 70 ° C./frequency of 10 Hz, initial strain of 10%, and dynamic strain of 2% using a Toyo Seiki viscoelasticity tester according to JIS K6394. An index evaluation was performed with the measurement result of Comparative Example 1 taken as 100. The smaller the value, the better the dynamic viscoelasticity. The results are shown in Table 1.

[Pain effect]
From the maximum shear force when the strain is changed from 0.5 to 45% using RPA2000 manufactured by Alpha Technologies and vulcanized rubber vulcanized at 160 ° C for 30 minutes at a temperature of 60 ° C and a frequency of 1.667 Hz. The value obtained by subtracting the minimum shear force was measured, and index evaluation was performed with the measurement result of Comparative Example 1 as 100. The smaller the value, the better the dispersibility of the filler. The results are shown in Table 1.

DESCRIPTION OF SYMBOLS 1 Sealing mixer 2 Casing 3 Rotor 4 Kneading part 5 Sheet-like rubber molding apparatus 6 Neck part 7 Ram 8 Shaft 9 Drop door

Claims (8)

A closed mixer for kneading a rubber composition containing at least raw rubber, silica and a silane coupling agent,
A kneading part having a casing and a rotor, kneading the rubber composition; a neck part located above the kneading part and having a cylindrical space inside; and provided on an upper side of the neck part. An inlet, a ram that can move up and down in the cylindrical space of the neck part, and can knead the rubber composition in the kneading part from above when kneading the rubber composition, and the kneading part A drop door located on the lower surface and discharging the rubber composition after kneading downward,
The closed mixer is characterized in that the ram is a ram whose temperature can be adjusted to 50 to 120 ° C.   The hermetic mixer according to claim 1, wherein the neck portion is a neck portion that can be temperature-controlled at 50 to 120 ° C.   3. The hermetic mixer according to claim 1, further comprising an air blow capable of flowing in external air from an air inlet formed in a side surface of the casing. A method for kneading a rubber composition containing at least raw rubber, silica and a silane coupling agent,
A kneading part having a casing and a rotor, kneading the rubber composition; a neck part located above the kneading part and having a cylindrical space inside; and provided on an upper side of the neck part. An inlet, a ram that can move up and down in the cylindrical space of the neck part, and can knead the rubber composition in the kneading part from above when kneading the rubber composition, and the kneading part Using a closed mixer provided with a drop door located on the lower surface and discharging the rubber composition after kneading downward,
A rubber composition kneading method, wherein the rubber composition is kneaded in a state where the temperature of the ram is adjusted to 50 to 120 ° C.   The method for kneading a rubber composition according to claim 4, wherein the rubber composition is kneaded in a state where the neck portion is temperature-controlled at 50 to 120 ° C. 6.   The closed mixer has an air blow capable of flowing external air from an air inlet formed in a side surface of the casing, and the rubber composition while allowing external air to flow into the casing from the air blow The method for kneading a rubber composition according to claim 4 or 5, wherein kneading is carried out.   The rubber composition manufactured by the kneading | mixing method of the rubber composition in any one of Claims 4-6.   The rubber composition according to claim 7, comprising a styrene butadiene rubber modified with an amine and an alkoxysilane, silica, and a silane coupling agent comprising at least one of Si75 and a protected mercaptosilane.

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