JP2005199503A - Rubber kneading method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber kneading method capable of obtaining a rubber kneaded material having a constant stable viscosity always stable even if the viscosity of a charging rubber raw material varies. <P>SOLUTION: In a process for kneading compounding chemicals (B) with the rubber raw material (A) using a hermetically closed mixer, the compounding amount of at least one of the compounding chemicals (B) is controlled on the basis of the actually measured or estimated value of the viscosity of the rubber raw material (A) before and/or during kneading. Especially, the rubber kneading method is preferably used in the rough kneading of a raw material rubber, the compounding amount of a peptizer is controlled on the basis of a viscosity value obtained by measuring Mooney viscosity prescribed in JIS K6300 under a condition that a temperature is 60°C and the (L-type) number of rotations of a rotor is 6 rmp before rough kneading. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber kneading method, and more particularly to a kneading method capable of always obtaining a rubber kneaded material having a stable viscosity even when the viscosity of a rubber raw material varies.

  In the rubber processing industry, kneading compounded chemicals with rubber raw materials is basically an essential essential process. In this kneading step, obtaining a rubber kneaded product having a stable viscosity is necessary in order to ensure dimensional accuracy and quality uniformity in the subsequent steps such as extrusion and rolling operations, and eventually the final rubber addition. The quality of sulfur products is also greatly affected.

  Conventionally, when a rubber composition is kneaded using an internal mixer, a method in which a certain amount of compounded chemicals are added and kneaded with respect to the input mass of the rubber raw material is generally used. It was. In this method, when the viscosity of the rubber raw material to be charged is stable, a rubber kneaded material having a stable viscosity can be obtained by adding kneading under predetermined kneading conditions thereafter.

  However, in the above kneading method, when the viscosity of the rubber raw material to be fed is fluctuated and is not constant, the viscosity variation is the same as the viscosity variation as it is or just slightly reduced. In the subsequent post-process, there were significant problems in production control and quality control.

  As a countermeasure against such a viscosity fluctuation of the raw rubber, a method of adjusting by extending or shortening the kneading time can be considered. However, this method causes a problem of generation of gel or insufficient mixing, and physical properties of the vulcanized rubber. In the present situation, it is very difficult to adopt as a practical kneading method in order to adversely affect performance.

  In extrusion kneading, (1) a method of stabilizing the viscosity of a kneaded material by detecting the melting position of the material in the kneading chamber and controlling the opening / closing degree of the gate according to the melting position (see, for example, Patent Document 1) ), And (2) The operation of charging the required amount of the compounding chemical or compound is incorporated from the compounding chemical input port provided in the middle of the extruder, which is controlled based on the number of revolutions of the extruder or the discharge amount. However, it is difficult to apply these methods to the process of kneading compounded chemicals into rubber raw materials using a closed mixer. .

When a compounding agent having a plasticizer is kneaded with an elastomer raw material using a closed mixer, the supply of the plasticizer is interrupted when the amount of power of the power section that rotates the rotor falls to the set lower threshold. In addition, a kneading apparatus and a kneading method for kneading a set amount of plasticizer by resuming the supply of the plasticizer when it rises to the upper limit threshold are disclosed (for example, see Patent Document 3). . However, this technique has a problem that it is necessary to attach a feeding device to the mixer and it can be applied only to a compounding agent having fluidity.
JP 07-186138 A Japanese Patent Laid-Open No. 08-230015 JP-A-11-333830

  As described above, in order to obtain a rubber kneaded material with a stable viscosity, it has been dealt with by adjusting the discharge conditions and the like so far, but from the viewpoint of productivity improvement and quality control, there is a big change in the discharge conditions. Due to restrictions, it was difficult to sufficiently absorb the viscosity variation of the raw rubber.

  The present invention has been made in view of the above problems, and its technical problem is always constant even when the viscosity of the raw rubber fluctuates without impairing the level of productivity and quality control. It is to provide a rubber kneading method so that a rubber kneaded product having a viscosity can be obtained.

In order to solve the above problems, the present invention provides the following kneading method. That is,
<1> The viscosity of the rubber raw material (A) before and / or during the kneading in the step of kneading the compounded chemicals (B) with the rubber raw material (A) using a closed mixer. A rubber kneading method characterized by controlling at least one compounding amount in the compounding chemicals (B) based on a value obtained by actually measuring or estimating the above.
<2> Before kneading, the Mooney viscosity defined in JIS K6300 of the rubber raw material (A) is measured, and at least one compounding amount in the compounding chemicals (B) is controlled based on the viscosity value. The rubber kneading method as described in <1> above, wherein
<3> A master that correlates the viscosity created based on the viscosity data by measuring or estimating the Mooney viscosity defined in JIS K6300 of the rubber raw material (A) before or during kneading. The rubber kneading method according to <1>, wherein the compounding amount of the compounding chemicals (B) is controlled based on the curve.
<4> The material according to any one of <1> to <3>, which is applied to at least one kneading step among kneading raw material rubber, masterbatch kneading, and final kneading. Rubber kneading method.
<5> The above-mentioned <1> to <1>, wherein the compounded chemicals whose compounding amount is controlled are at least one compounded chemical that affects plasticization of the rubber raw material (A) in the kneading step. 4. The rubber kneading method according to any one of 4>.
<6> The rubber kneading method according to <5>, wherein the compounding chemical affecting plasticization of the rubber raw material (A) is a demulcent (peptizer).
<7> In the kneading of the raw material rubber, based on the viscosity value obtained by actually measuring the Mooney viscosity specified in JIS K6300 under the conditions of a temperature of 60 ° C. and a rotor (L-type) rotational speed of 6 rpm before the kneading, The rubber kneading method according to the above <6>, wherein the blending amount of the peptizer) is controlled.
<8> In the above item <7>, based on the difference between the Mooney viscosity measured value and the standard Mooney viscosity value (KPa · sec), the blending amount of the peptizer (peptizer) is substantially changed every ± 1 KPa · sec. A rubber kneading method characterized by controlling by increasing / decreasing only ± 0.001 part by mass.

  The rubber kneading method of the present invention is a kneading method capable of always obtaining a rubber kneaded material having a stable and constant viscosity even when the viscosity of the rubber raw material fluctuates by finding a rubber kneading method including control of optimum blending. Can be provided. The present rubber kneading method is particularly effective in stabilizing the viscosity of a rubber kneaded product by applying it to a natural rubber mastication process in which the viscosity and impurity content vary greatly depending on the origin and season.

The rubber kneading method of the present invention is the above-mentioned rubber before and / or during the kneading in the step of kneading the compounded chemicals (B) into the rubber raw material (A) using a closed mixer. Based on a value obtained by actually measuring or estimating the viscosity of the raw material (A), at least one blending amount in the blended chemicals (B) is controlled.
Hereinafter, embodiments of the present invention will be described in detail.

(Closed mixer)
Examples of the internal mixer used in the present invention include a closed biaxial mixer represented by a so-called “Banbury mixer”, and a cross-sectional view of one embodiment thereof is shown in FIG.
The hermetic mixer (2) is composed of a combination of a mixing body (3) and a floating weight (10). The mixing body (3) forms a mixing chamber (4) in which two cylindrical surfaces formed in a semicircular cross section are combined. Above the mixing chamber (4), a closing part (5) formed in a cylindrical surface is provided.

  The central axis of the semicircular cylindrical surface of the mixing chamber (4) is provided with first and second rotating shafts (6a, 6b), respectively. The rotary shafts (6a, 6b) are respectively provided with first and second blades (7a, 7b) to form a pair of rotors (8). In the rotor (8), the first and second rotating shafts (6a, 6b) are rotated toward each other by the power unit (9), and the first blade (7a) and the second rotating shaft are mutually rotated. By the blade (7b), the rubber raw material (A) and the compounding chemicals (B) are mixed while being sheared.

  The floating weight (10) is provided with an outer peripheral surface (11) that fits inside the opening (5) of the mixing body (3) and is pressed into the tip so that the rubber raw material (A) can be easily mixed. A pressure contact surface (12) is formed. The floating weight (10) is configured to be fitted inside the opening (5) by the hydraulic cylinder (13) and to be detached. At both ends of the hydraulic cylinder (13), guide rods (16) for guiding the floating weight (10) are provided. When mixing in the state of FIG. 1 or when moving to the state of FIG. Furthermore, when moving from the state of FIG. 2 to the state of FIG. 1, it also has a function of guiding and holding the floating weight (10).

FIG. 2 is a state diagram in which the floating weight (10) is moved upward from the mixing body (3). In the state of FIG. 2, the rubber raw material (A) and the compounding chemicals (B) are put into the mixing body (3). Further, when kneading is completed in the mixing body (3) and the kneaded material is taken out, it is taken out in the state shown in FIG.
In the mixing apparatus (1) configured as described above, the raw material rubber (A) and various compounding chemicals (B) are charged into the mixing chamber (4) and kneaded.

(Rubber raw materials and chemicals)
Examples of the rubber raw material (A) used in the kneading method of the present invention include natural rubber (NR) and various synthetic rubbers. The natural rubber may be a sheet rubber or a block rubber, such as RSS # 1 to # 5. All NRs can be used.
As the synthetic rubber, various diene synthetic rubbers, diene copolymer rubbers, special rubbers, modified rubbers, and the like can be used. Specifically, butadiene-based polymers such as polybutadiene (BR), copolymers of butadiene and aromatic vinyl compounds (for example, SBR, NBR, etc.), copolymers of butadiene and other diene compounds, etc .; polyisoprene (IR), copolymers of isoprene and aromatic vinyl compounds, isoprene polymers such as copolymers of isoprene and other diene compounds; chloroprene rubber (CR), butyl rubber (IIR), halogenated butyl rubber ( X-IIR); ethylene-propylene copolymer rubber (EPM), ethylene-propylene-diene copolymer rubber (EPDM), and an arbitrary blend thereof.

The compounding chemicals (B) used in the kneading method of the present invention are appropriately selected from known rubber compounding chemicals used in the rubber industry depending on the required performance of the intended rubber product and the necessity of the production method. Selected. For example,
(1) As reinforcing agent or filler, carbon black such as SAF, ISAF, HAF, FEF, GPF, silica, silane coupling agent, powdered inorganic substance, resin reinforcing agent, etc .;
(2) Sulfur, vulcanizing agent, vulcanization accelerator, organic peroxide, resin vulcanizing agent, zinc white, metal oxide, stearic acid, etc. necessary for rubber crosslinking;

(3) Process oil, extender oil, softener, plasticizer, tackifier, petroleum resins;
(4) Anti-aging agents, antioxidants, UV absorbers, paraffin waxes, ozone deterioration inhibitors, etc .;
(5) A peptizer for peptizers (peptizers, etc.);
(6) Pigments and colorants, scorch inhibitors, retarders, etc.

The rubber kneading method of the present invention is preferable for a natural rubber kneading process in which differences in viscosity, impurity content, etc. are relatively large depending on the country of production and the season of collection. It is suitably applied to the so-called “kneading process” in which a plasticizer (peptizer) is added to adjust the plasticity to a level at which it can be easily processed, and the effect of stabilizing the viscosity of the kneaded substance to a certain level is remarkably exhibited. .
Typical examples of the peptizer include BASS (2,2′-dibenzamide diphenyl disulfide) and BASZ (zinc salt of 2-benzamidothiophenol), and rubber components to be used as natural rubber and the like. About 0.01 to 1.0 part is preferably blended with respect to 100 parts by weight, and more preferably within the range of 0.05 to 0.5 part.

(Measurement method of rubber viscosity)
The method for measuring the viscosity of the rubber raw material (A) of the present invention is not particularly limited, but a Mooney viscosity measuring method that is commonly used in the rubber processing industry and widely recognized for reliability and convenience is desirable.
The Mooney viscosity is measured according to JIS K6300 (1994 edition). In this specification, after setting a rubber sample at a predetermined temperature and preheating for 1 minute, the L-type rotor is used to determine the Mooney viscosity. The torque value (ML _{1 + 4} ) after 4 minutes from the start of rotation at a rotational speed (for example, 6 rpm) is taken as the Mooney viscosity of the sample, and the unit is expressed in Pa · sec to KPa · sec.

(Rubber kneading method of the present invention)
The rubber kneading method of the first aspect of the present invention is based on a value obtained by actually measuring or estimating the viscosity of the rubber raw material (A) before and / or during the kneading. It is characterized by controlling the amount of at least one of them.

The rubber kneading method of the first aspect of the present invention will be specifically described based on the control flowchart shown in FIG.
First, before kneading, the viscosity of the raw material rubber to be added is actually measured according to, for example, the Mooney viscosity measuring method described above. In addition, the viscosity of the raw material rubber during kneading is generally very difficult to measure directly, so as a substitute value, for example, the power value and torque value of the drive motor of the hermetic mixer, This is estimated based on the temperature of the kneaded rubber or the gradient thereof.

The viscosity value actually measured or estimated in this manner is compared with a preset standard value to calculate at least one compounding amount of the required compounding chemicals, and the compounding chemicals are measured based on the calculated values. Then, the mixture is put into a closed mixer and kneaded.
Here, based on the actually measured or estimated viscosity value, it is only necessary to calculate the blending amount of the blended chemicals and change the input amount for the necessary chemicals in the blended chemicals (B). For other chemicals, the standard blending amount may be used as it is.
In addition, each of the compounding chemicals calculated as described above may be added all at once at the start of kneading, or divided into two or more times. You may throw it in. In particular, when the viscosity of the raw material rubber being kneaded is estimated and the blending amount is changed based on the estimated value, it is necessary to divide it into two or more times including the variable amount.

  The rubber kneading method of the second aspect of the present invention is the above-described first kneading method, in which the Mooney viscosity defined in JIS K6300 of the rubber raw material (A) is measured before kneading, and based on the viscosity value. It is characterized by controlling at least one compounding amount in the compounding chemicals (B).

  In the kneading method of the second aspect of the present invention, the Mooney viscosity defined in JIS K6300 of the rubber raw material (A) is measured as an external setup operation before kneading, and the viscosity value is set to a preset standard value. Compared with the necessary chemicals in the compounded chemicals (B), the amount of the compound is increased or decreased, and can be controlled easily and accurately without impairing the productivity. Easy to get.

  The rubber kneading method of the third aspect of the present invention is the first kneading method in which the Mooney viscosity defined in JIS K6300 of the rubber raw material (A) is measured or estimated before or during kneading, It is characterized in that at least one compounding amount in the compounding chemicals (B) is controlled based on a master curve that relates the viscosity and the compounding amount created based on the viscosity data.

  In the rubber kneading method of the third aspect of the present invention, an example of a master curve that relates the viscosity and the blending amount is shown in FIG. This master curve takes the measured value or estimated value of Mooney viscosity specified in JIS K6300 before or during kneading of the rubber component to be added on the horizontal axis, and the required compounding of the compounding chemical corresponding to each viscosity value. A composite curve indicating the number of copies, which is created based on data actually measured or estimated in advance.

  Once the master curve that relates the above-mentioned viscosity and blending amount is prepared according to the blending prescription to which the rubber kneading method of the present invention is applied and the closed mixing model (for example, Banbury mixer model and capacity), Thereafter, the compounding amount of the necessary chemicals can be controlled easily and accurately, and a rubber kneaded material having a stable and constant viscosity can be obtained more easily.

  The rubber kneading method of the fourth aspect of the present invention is applied to at least one kneading step among the raw rubber kneading, masterbatch kneading, and final kneading in the first to third kneading methods. Features.

  The rubber kneading method of the present invention is not particularly limited and can be applied to all rubber kneading methods. Among them, raw rubber kneading, masterbatch kneading, and final kneading can be used. , Preferably applied to at least one kneading step, more preferably applied to raw rubber kneading and masterbatch kneading, and most preferably applied to raw rubber kneading. preferable.

  In the rubber kneading method of the fifth aspect of the present invention, in the first to fourth kneading methods, the compounding chemicals whose compounding amount is controlled affects the plasticization of the rubber raw material (A) in the kneading step. It is characterized by being at least one kind of compounding chemicals.

  A rubber kneading method according to a sixth aspect of the present invention is characterized in that, in the fifth kneading method, the compounding chemical that affects the plasticization of the rubber raw material (A) is a peptizer. .

  In the rubber kneading method according to the sixth aspect of the present invention, BASS (2,2′-dibenzamide diphenyl disulfide) and BASZ (2-benzamide) are used as a peptizer used as a peptizer. Preferred examples include zinc salt of thiophenol.

  The rubber kneading method of the seventh aspect of the present invention is such that, when the sixth kneading method is applied to the kneading of the raw rubber, the Mooney viscosity specified in JIS K6300 is set to a temperature of 60 ° C. ) Based on the viscosity value measured under the condition of 6 rpm, the blending amount of the above demulcent (peptizer) is controlled.

  As described above, the Mooney viscosity specified in JIS K6300 of the raw rubber before mastication is based on the viscosity measured at the temperature of 60 ° C. and the rotation speed of the L-shaped rotor of 6 rpm. By controlling the blending amount of the agent (peptizer), the kneaded product of NR rubber with a more stable and constant viscosity can be easily obtained in the kneading of natural rubber (NR), etc., whose viscosities and impurity contents vary greatly depending on the origin. And it is surely obtained.

The rubber kneading method according to an eighth aspect of the present invention is the seventh kneading method, wherein the difference is ± 1 KPa · sec based on the difference between the measured value of Mooney viscosity and the standard Mooney viscosity value (KPa · sec). It is characterized in that it is controlled by increasing or decreasing the blending amount of the peptizer (peptizer) by substantially ± 0.001 part by mass.
Here, “substantially” ± 0.001 part by mass means to increase or decrease the Mooney viscosity by measuring or weighing using the usual means in the industry in the measurement of the Mooney viscosity and the weighing of the compounding chemical (dissolving agent). It means the number of parts by mass including the error in the process and the omission in the normal charging or kneading.

As described above, the Mooney viscosity specified in JIS K6300 of the raw rubber before mastication was measured with the viscosity value (M ₁ ) measured under the conditions of a temperature of 60 ° C. and the rotation speed of the L-shaped rotor of 6 rpm, and the standard Mooney viscosity value ( This is referred to as M ₀ based on a difference _{(M 1 -M 0) KPa ·} sec with.), ± the amount of嚼解agent per difference ± 1 KPa · sec (peptizers) relative to the standard amount 0 By controlling by increasing / decreasing only 0.001 parts by mass, the most stable kneaded product of NR rubber with constant viscosity, especially in the kneading of natural rubber (NR), etc., whose viscosities and impurity contents vary greatly depending on the origin. It is definitely obtained.

  Examples of the present invention will be specifically described below, but the present invention is not limited to these examples. In the following, “parts (PHR)” represents “parts by mass”.

[Example 1]
(1) Prepare three types of natural rubber NR (α), NR (β), NR (γ) with different origins, and set the Mooney viscosity (ML _{1 + 4} ) before kneading at a temperature of 60 ° C. As a result of measurement using an L-shaped rotor at a rotation speed of 6 rpm, they were 120, 110, and 100 KPa · sec, respectively.

(2) The base viscosity of the raw material NR rubber is set to 110 KPa · sec, and the base compounding amount of the peptizer BASS (2,2′-dibenzamide diphenyl disulfide) for the base rubber of the base viscosity is 0.1 PHR. And Further, the required thermal history value of kneading of the reference viscosity rubber (that is, the integrated value of temperature x time from the start of kneading to discharging) is set to 24000 ° C. · sec.

(3) 100 parts of the above NR (β) is mixed with 0.1 PHR of the kneading accelerator BASS, put into a Banbury mixer, and the heat history value after starting the kneading is 24000 ° C. · sec. When it reached, the rubber kneaded material was discharged. The Mooney viscosity (ML _{1 + 4} ) of this rubber kneaded product was 80 KPa · sec as a result of measurement under the same conditions as described above.

(4) As a rubber kneading method according to the present invention, for the natural rubber NR (α) and NR (γ), the difference between the reference viscosity 110 KPa · sec and the Mooney viscosity before each kneading (120, 100 KPa · sec) According to (+10, −10 KPa · sec), the blending amount of the kneading accelerator increased / decreased by +0.01 and −0.01 PHR, that is, ASS (α) is BASS0.11PHR, NR (γ) is BASS0.09PHR was blended and kneaded with the same heat history value as in the case of NR (β). The Mooney viscosity (ML _{1 + 4} ) of this rubber kneaded product was 82 KPa · sec for NR (α) and 78 KPa · sec for NR (γ).

(5) On the other hand, as a conventional rubber kneading method, for natural rubber NR (α) and NR (γ), as with NR (β), 0.1 PHR of a peptizer BASS is blended with NR100 parts. , Kneading was performed at the same heat history value as in the case of NR (β). The Mooney viscosity (ML _{1 + 4} ) of this rubber kneaded product was 84 KPa · sec for NR (α) and 76 KPa · sec for NR (γ).

(6) As apparent from the above, in the rubber kneading method according to the present invention, the viscosity of the rubber kneaded product is different from the viscosity variation (maximum-minimum) of the rubber kneaded product according to the conventional method of 8 KPa · sec. The variation was 4 KPa · sec, and a variation reduction effect of 50% was obtained.

It is sectional drawing of the closed mixer used for this invention. It is the state figure which opened the opening part of FIG. It is a flowchart of the rubber kneading method of the present invention. It is a master curve that correlates viscosity and blending amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ......... Kneading apparatus 2 ......... Kneading machine 3 ......... Kneading main body 4 ......... Kneading chamber 5 ......... Opening part 6a ......... First rotating shaft 6b ......... Second rotating shaft 7a ... …… First blade 7b ………… Second blade 8 ………… Rotor 9 ……… Power section 10 ……… Floating weight 11 ……… Outer peripheral surface 12 ……… Pressure contact surface 13 ……… Hydraulic cylinder 16 ……… Guide lot

Claims (8)

  In the step of kneading the compounded chemicals (B) into the rubber raw material (A) using a closed mixer, the viscosity of the rubber raw material (A) is measured or measured before and / or during the kneading. A rubber kneading method comprising controlling at least one compounding amount in the compounding chemicals (B) based on an estimated value.   Before kneading, the Mooney viscosity defined in JIS K6300 of the rubber raw material (A) is actually measured, and the blending amount of at least one of the blended chemicals (B) is controlled based on the viscosity value. The rubber kneading method according to claim 1.   Before or during kneading, the Mooney viscosity defined in JIS K6300 of the rubber raw material (A) is measured or estimated, and based on a master curve that relates the viscosity created based on the viscosity data and the blending amount. The method for kneading rubber according to claim 1, wherein the compounding amount of at least one compound in the compounding chemicals (B) is controlled.   The rubber kneading method according to any one of claims 1 to 3, wherein the rubber kneading method is applied to at least one kneading step among raw rubber kneading, masterbatch kneading, and final kneading.   The compounding chemicals whose compounding amount is controlled are at least one compounding chemical that affects the plasticization of the rubber raw material (A) in the kneading step. The method for kneading rubber described in the item.   6. The rubber kneading method according to claim 5, wherein the compounding chemical affecting plasticization of the rubber raw material (A) is a demulcent (peptizer).   In the mastication of the raw rubber, before the mastication, the Mooney viscosity defined in JIS K6300 was measured based on the viscosity value measured under the conditions of a temperature of 60 ° C. and a rotor (L-type) rotation speed of 6 rpm. 7. The rubber kneading method according to claim 6, wherein the blending amount is controlled.   In Claim 7, based on the difference (KPa · sec) between the measured value of the Mooney viscosity and the standard Mooney viscosity value, the blending amount of the peptizer (peptizer) is substantially ± 0 for each ± 1 KPa · sec difference. A rubber kneading method characterized by controlling by increasing / decreasing only 001 parts by mass.

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