JP2002234947A - Conductive material compounded rubber composition and its preparation process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a preparation process for a conductive material compounded rubber composition in which an inorganic conductive material is finely blended to a base rubber and the rubber composition has high whiteness and can be colored. SOLUTION: The conductive material compounded rubber composition that can be colored is prepared by adding a solvent to a base rubber to swell the base rubber. Then, an inorganic conductive material and rubber chemicals are mixed and kneaded with the swollen rubber, and preferably the solvent is removed from the obtained compound rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive compounded rubber composition containing an inorganic conductive material and capable of being colored by compounding a pigment, and a method for producing the same. The present invention relates to a conductive compounded rubber composition compounded with good dispersibility and a method for producing the same.

[0002]

2. Description of the Related Art A conductive rubber is obtained by compounding and dispersing a material for imparting conductivity to rubber and imparting conductivity to rubber which is originally an insulator.
Fax electrode plates, electrostatic wiring paper, photosensitive paper, IC storage cases, rolls for copiers, conductive adhesives, conductive tires, medical rubber products, connector elements, etc., also in industrial fields such as OA equipment and high-tech equipment It has become an indispensable material.

Heretofore, carbon-based materials such as carbon black have been most often studied and used as conductivity-imparting materials. However, since carbon-based materials themselves are dark black, conductive The rubber is inevitably black-colored rubber, and the molded body of the rubber is inevitably completely black in design such as a black case, a black housing, a black roll, etc.

[0004] For example, in recent marketing of OA equipment, design (design) is an important element rather than simply appealing for the high functionality of hardware on a catalog, and personal computers, mobile equipment, mobile phones, and the like. , Copiers and other devices are designed in a smart form (form) to appeal to the tastes of users, and of course, the body is white, red, blue, green,
Purple, yellow, pearl, gray, etc.
It is common to see that OA devices with colorful bodies fill the sales floors of stores. Similarly, parts of industrial products such as belts, switches, trays, sheets, cables, rolls, and the like and their materials have been increasingly colored.

[0005] As described above, in view of the recent market needs, colorization is becoming an important factor in the development of materials. Instead, there is a demand for a conductive rubber capable of imparting various desired colors by adding a pigment. Such a conductive rubber can be basically realized by using an inorganic conductive material such as conductive zinc oxide, which is not itself black, as the conductivity imparting material.

[0006]

The conductive rubber which can be made into a bright color is obtained by mixing the above-mentioned inorganic conductive material and rubber chemicals with a base rubber and kneading with a kneading machine to form a conductive compounded rubber composition. After being processed into an appropriate form, it is vulcanized (cured).

The kneading operation is performed by a Banbury mixer, a kneader, a roll machine or the like. When the kneading operation is used for the above-mentioned purpose, an inorganic conductive material such as fine or powdery conductive zinc oxide is usually used. It is necessary to ensure a desired conductivity by blending in a higher mass part.

According to studies by the present inventors, when these powdery inorganic conductive materials are kneaded into a base rubber together with other rubber chemicals, as the amount of the inorganic conductive materials added increases, The hardness of the object increases, the mechanical load increases sharply, and a large shear strain is applied.
It was found that heat was generated even at 0 ° C. or higher. Specifically, at the stage where about 100 parts by mass of the inorganic conductive material is blended with 100 parts by mass of the base rubber, kneading becomes rapidly difficult, and usually about 200 parts by mass is considered to be the limit for kneading and mixing ( Hereinafter, parts by mass may be simply referred to as parts.)

The conductive compounded rubber composition (usually referred to as compounded rubber or kneaded rubber material) containing the inorganic conductive material in such a high number of parts as described above is subjected to calendering and extrusion in the following steps. After being processed into a desired shape by processing, sheet processing with a roll, etc., it is vulcanized and cured, but the compounded rubber composition has a very high viscosity, so its flowability is very poor. . Therefore, it is extremely difficult to process, for example, it is difficult to form a desired shape, for example, a thin sheet by a commonly used calendering process or extrusion process. Also, even when vulcanizing in a mold,
There is a problem that molding cannot be performed sufficiently due to poor fluidity.

[0010]

Means for Solving the Problems The present inventors have conducted intensive studies on a method for producing a conductive compounded rubber composition containing a large number of inorganic conductive materials, and as a result, the base rubber has been swollen in advance. It has been found that kneading is easily performed, and the present invention has been completed.

That is, according to the present invention, the following inventions are provided. (1) A method for producing a conductive compounded rubber composition,
(I) a swelling step of swelling the base rubber by adding a solvent to the base rubber, and (ii) a kneading step of mixing and kneading an inorganic conductive material and a rubber chemical with the swelled swelled rubber. A method for producing a colorable conductive compounded rubber composition, comprising:

(2) A method for producing a conductive compounded rubber composition, comprising: (i) a swelling step of swelling the base rubber by adding a solvent to the base rubber; and (ii) adding a solvent to the swelled rubber. A kneading step of mixing and kneading an inorganic conductive material and a rubber chemical, and (iii) a solvent removing step of removing a solvent from the obtained compounded rubber composition, a colorable conductive compounded rubber composition comprising: Method of manufacturing a product.

(3) The method according to (2), wherein the solvent is removed after molding the compounded rubber composition into a molded article.

(4) The method according to (3), wherein the molded body from which the solvent has been removed is vulcanized.

(5) The solvent according to any one of (1) to (4), wherein the solvent is a mineral oil selected from the group consisting of paraffinic oil, naphthenic oil and aromatic oil, or industrial gasoline for rubber. The method described in.

(6) The method according to any one of (1) to (5), wherein the solvent is used in an amount of 50 to 800 parts by mass based on 100 parts by mass of the base rubber.

(7) 200 to 500 parts by mass of an inorganic conductive material is mixed with 100 parts by mass of the base rubber.
The method according to any one of (4).

(8) When the inorganic conductive material is conductive zinc oxide,
The method according to any one of (1) to (4), which is conductive potassium titanate or conductive titanium oxide.

(9) The hardness of the cured conductive rubber obtained from the conductive compounded rubber composition is 95 or less, the volume resistivity is 1 × 10 ¹¹ Ω · cm or less, and the Hunter whiteness is 20 or less.
The method according to any one of (1) to (4) above.

(10) In the conductive compounded rubber composition, the inorganic conductive material is used in an amount of 200 to 100 parts by mass of the base rubber.
500 parts by mass, the hardness of the obtained cured conductive rubber is 95 or less, and the volume resistivity is 1 × 10 ¹¹ Ω · cm.
A colorable conductive compound rubber composition having a Hunter whiteness of 20 or more.

(11) The conductive compounded rubber composition according to (10), wherein the inorganic conductive material is conductive zinc oxide, conductive potassium titanate or conductive titanium oxide.

(12) The compounded rubber composition according to (10) or (11) is molded and vulcanized, and has a hardness of 95 or less, a volume resistivity of 1 × 10 ¹¹ Ω · cm or less, and a hunter. A conductive rubber molded product having a whiteness of 20 or more.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a flow sheet showing an example of a method for producing a conductive compounded rubber composition and a conductive rubber molded product of the present invention.

First, a swelling step (a) is performed in which a solvent 13 is added to the base rubber 10 to swell the base rubber. The base rubber, which has no fluidity by itself, swells and fluidizes with a solvent to have an appropriate viscosity.Even when a high mass part of an inorganic conductive material is blended, it is easy to apply without excessive shear strain to the machine. Can be kneaded into rubber.

The base rubber is a natural rubber or a synthetic rubber having no fluidity, and has a ML _{1 + 4} (100 ° C.) of about 25 to 160 in terms of Mooney viscosity.

Examples of usable base rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), and 1,2-polybutadiene rubber (1,2-
BR), chloroprene rubber (CR), styrene-butadiene rubber (SBR), butyl rubber (IIR), nitrile rubber (acrylonitrile-butadiene rubber) (NB
R), hydrogenated nitrile rubber (HNBR), ethylene-propylene rubber (EPM, EPR, EPDB, EPT),
Acrylic rubber (ACM, ANM), epichlorohydrin rubber (CO, ECO), ethylene-vinyl acetate rubber (E
VA), silicone rubber (Q), methyl silicone rubber (MQ), vinyl-methyl silicone rubber (VMQ),
Phenyl-methylsilicone rubber (PMQ), polysulfide rubber (T), urethane rubber (U), polyether urethane rubber (EU), polyester urethane rubber (AU), fluoro rubber (FKM), and the like are preferred. These can be used alone or as a blend rubber of two or more.

The solvent added to the base rubber is not particularly limited as long as it has a certain degree of compatibility with the rubber and can swell the rubber.
Mineral oils, vegetable oils, plasticizers and organic solvents can be used.

The mineral oils include paraffinic oils, naphthenic oils, aromatic oils and the like, and the vegetable oils include tall oil, castor oil, palm oil, peanut oil, rapeseed oil, cottonseed oil, factice and the like. No. Examples of the plasticizer include phthalic acid diesters such as dibutyl phthalate and phthalic acid (2-ethylhexyl);
Fatty acid dibasic acid esters such as -ethylhexyl) and sebacic acid (2-ethylhexyl); phosphoric acid triesters such as tricresyl phosphate and tri (2-ethylhexyl) phosphate; glycol esters such as polyethylene glycol esters; epoxy fatty acid esters and the like Epoxy compounds. Examples of the organic solvent system include alcohols such as methanol, ethanol, and isopropanol; aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane and cyclohexane;
Ketones such as methyl ethyl ketone and cyclohexane; esters such as ethyl acetate; ethers such as ethyl ether and tetrahydrofuran; halogen-substituted hydrocarbons such as trichloroethylene and carbon tetrachloride; In particular, industrial gasoline No. 2 for rubber known as so-called rubber volatilization is preferable.

In the present invention, it is desirable that the above-mentioned solvent is used in an amount of preferably 50 to 800 parts by mass, more preferably 100 to 500 parts by mass, based on 100 parts by mass of the base rubber. If the amount of the solvent is too small, the base rubber does not swell sufficiently, and in the next kneading step, it is difficult to knead the inorganic conductive material such as a powder into the base rubber with good dispersibility, and If it is added in an excessively large amount, the rubber becomes a paste and the load of the solvent removing step in the subsequent steps increases, which is not preferable. If the state of the base rubber after swelling is represented by viscosity, the rheometer characteristic (100 ° C.) F
It is preferably about 0.1 to 5 in min. If the viscosity is higher than this, it is difficult to mix and knead the inorganic conductive material in the kneading step. If the viscosity is lower than this, the rubber may be in a liquid state and flow out of the gap of the kneading machine, which is not preferable.

The swelling step is basically performed by adding a solvent to the base rubber and allowing it to stand, and does not require particularly strong mechanical stirring. The apparatus for performing the swelling treatment is not particularly limited as long as the container accommodates the base rubber and the solvent and can be hermetically closed for a required time while keeping both well in contact. In addition, the said container may be provided with a stirring apparatus, and if desired, in order to shorten the time of a swelling process, gentle stirring can also be added. In addition, the temperature for performing the swelling treatment is not particularly required to be about 10 to 40 ° C. without heating, and the swelling time (resting time) is 10 to 200 hours, preferably 15 to 100 hours, and more preferably. Is 2
It is about 0 to 50 hours.

As described above, the kneading step (b) in which the inorganic conductive material 15 and the rubber chemical 17 are added to and kneaded with the sufficiently swollen and fluidized rubber is performed.

The inorganic conductive material 15 is a material other than a carbon-based material such as carbon black. The rubber composition containing the same does not have a dark color such as black and can be colored in a bright color by adding a pigment. If so, any conventionally known ones can be used. For example, zinc oxide doped with one or more of aluminum, indium, titanium, tin, strontium, boron and silicon, or a solid solution of zinc oxide and one or more of these oxides, or indium oxide doped with tin Or a solid solution of indium oxide and tin oxide; a tin oxide doped with antimony or a solid solution of tin oxide and antimony oxide; a solid solution of indium oxide and tin oxide (ITO); a solid solution of tin oxide and antimony oxide; Particles mainly composed of metal oxides such as solid solutions of titanium oxide, solid solutions of aluminum oxide and magnesium oxide, potassium titanate, tin oxide doped with antimony and coated on the titanium oxide surface, and gold, silver and copper , Nickel and other metal particles are preferred, and In terms of stability, is preferably a metal oxide, are preferred, especially zinc oxide based. Specifically, conductive zinc oxide, conductive potassium titanate, conductive titanium oxide and the like are used.

The inorganic conductive material is preferably a base rubber 100
It is blended in an amount of 200 to 500 parts by mass with respect to parts by mass. The inorganic conductive material is preferably particles having a size of preferably about 0.01 to 300 μm, more preferably about 0.1 to 100 μm. The particle size is obtained by converting the specific surface area determined by the BET method into a particle size.

The reason why the object of the present invention is an inorganic conductive material is that most of organic conductive materials are liquid,
This is because it is not necessary to swell the base rubber in the first place during kneading, and if a large amount of the base rubber is blended, bleeding is likely to occur, and in any case, the benefits of applying the present invention are poor.

The volume resistivity (electrical resistivity) of the inorganic conductive material is preferably 1 × 10 ⁻² Ω · cm to 1 × 10 ^11.
Ω · cm, more preferably 1 × 10 ⁻² Ω · cm to 1 × 1
0 ⁷ Ω · cm, more preferably, 1 × 10Ω · cm~
It is about 1 × 10 ⁴ Ω · cm. These volume resistivities are
10 g of a sample was placed in a cylinder having an inner surface with an inner diameter of 25 mm, which was processed with a fluororesin, pressurized at 100 kg / cm ² (10 MPa), and measured with a tester (Ω · cm).

As the rubber chemicals 17 to be compounded into the base rubber together with the inorganic conductive material, ordinary rubber compounding agents are preferably used. For example, vulcanizing agents (curing agents), vulcanization accelerators, vulcanization accelerators, antioxidants (antioxidants), fillers (reinforcing agents and bulking agents), coloring agents, lubricants, ultraviolet absorbers, light stability Agents, antibacterial agents, flame retardants and the like.

As the vulcanizing agent, conventionally known sulfur, for example, sulfur,
Inorganic sulfur compounds, organic sulfur compounds, organic peroxides,
A metal oxide is used, and in particular, when sulfur or a sulfur compound is used, the volume resistivity can be further reduced, which is preferable. The amount of these additives is about 0.1 to 5 parts by mass based on 100 parts of the base rubber.

For kneading, a Banbury mixer, a kneader,
In a conventionally known device such as an intermix or a roll machine, swelling rubber, an inorganic conductive material, and a desired rubber chemical are charged to carry out the process.

It should be noted that in the present invention,
Since the base rubber which has been swollen in advance in the swelling step (a) is used, kneading can be performed extremely easily even when a high mass part of an inorganic conductive material is blended.

That is, the swollen base rubber has a sufficiently low viscosity, does not impose a burden on the kneading machine, and the inorganic conductive material and the like can be mixed even when a considerably high mass thereof is blended.
Kneading can be performed without excessive heat generation. In practice, the kneading operation is usually performed at 5 to 50 ° C. without heating.
For 1 to 60 minutes, preferably 2 to 4 minutes.
Sufficient dispersion in rubber is completed in a short time of about 0 minutes, more preferably about 5 to 20 minutes. Therefore, a vulcanizing agent and a vulcanization accelerator can be added and kneaded at the initial kneading stage. On the other hand, in the conventional kneading method,
Since the viscosity is lowered while kneading, it is necessary to heat the apparatus to about 100 ° C. in advance (so-called warming work) in order to reduce the kneading load. In some cases, the viscosity of the rubber is lowered by adding a softening agent and kneading is performed. However, as the amount of the inorganic conductive material increases, the shear strain increases, and as described above, considerable heat is generated up to about 140 ° C., Excessive load was applied and kneading became difficult.

Thus, according to the present invention, a conductive compounded rubber composition 20 in which an inorganic conductive material or the like is compounded in a high amount by mass and sufficiently dispersed is obtained. After the kneading was completed, the composition 20 in which the inorganic conductive material and the rubber chemicals were blended in the base rubber was mixed with the solvent 1
3, but the solvent basically has a high insulating property in many cases, and the content changes the volume resistivity of the conductive compounded rubber composition. That is, since the volume resistivity increases as the residual amount of the solvent increases, it is preferable to appropriately select the content according to the intended use of the rubber composition. For example, when the compound rubber composition is used for antistatic purposes, a volume resistivity of about 1 × 10 ¹¹ Ω · cm is sufficient, and the solvent is not substantially removed or a relatively large amount is used. May be left. For applications requiring a lower volume resistivity, the solvent is preferably removed to some extent or sufficiently.

When removing the solvent, it is preferable to remove the solvent from the conductive compounded rubber composition at least before vulcanization. This is the solvent removal step (d).

The solvent removal step may be performed from the compounded rubber composition 20 after the direct kneading, as shown by the dotted line l ″ in the figure. However, in order to improve the moldability in the molding process of the composition, The compounded rubber composition is first molded into a desired shape (c) in a state where the solvent remains and the fluidity is maintained,
It is preferable to remove the solvent from the obtained molded body 23 according to line l '.

The molding step is a step of processing the compounded rubber composition of the present invention after kneading into a product suitable for the purpose, such as a sheet, a belt or a roll. Normally, sheet-shaped (especially thin sheet) processed products are processed by calendering or roll sheet processing, and include flat plates, sheets, tubes (single-layer or multilayer), round bars (rolls), and packing products with complicated cross-sectional shapes. Is performed by extrusion molding. Although the compounded rubber composition of the present invention contains a high mass part of an inorganic conductive material, the base rubber is sufficiently swollen and has fluidity. Molding is easily performed under the processing conditions employed in extrusion molding.

The solvent removing step (d) for removing the solvent from the obtained molded body 23 is basically performed by a usual drying operation. However, unlike the drying of water, the solvent removed by drying cannot be released to the atmosphere and must be collected. It is desirable that the solvent be reused, and the solvent vapor may ignite (explosion in some cases). And appropriate drying equipment (and drying conditions) in consideration of the boiling point of the solvent, etc.
It is preferable to select

For example, a method of setting a compounded rubber molded article containing a solvent in this dryer using a box dryer or the like and drying it under reduced pressure, An inert gas circulation drying method in which an inert gas such as a gas is circulated and dried under atmospheric pressure can be employed. It is preferable that the solvent vapor generated in this way is brought into contact with a condenser to be condensed, and then reused in the base rubber swelling step again. That is, the recovered solvent 13 ′ (or 1
3 '') is used as or as part of the swelling solvent 13 according to the recycling loop 1. The solvent may be recovered by a known means such as an activated carbon adsorption method, a gas absorption method, and a pressurized liquefaction method. As a heat source for heating, any heating such as steam heating, hot air heating, infrared heating, electric heating, and microwave heating can be used.

The compact 25 from which the solvent has been removed is finally subjected to a vulcanization step (e). Vulcanization is performed by heating the compounded rubber molded body obtained by calendering or extrusion as described above in the presence of a cross-linking agent such as sulfur to cause cross-linking. This is the process of making a product.

The apparatus for vulcanization may be any apparatus which can accommodate and heat the compounded rubber molded product 25 from which the solvent has been removed. For example, a typical vulcanizing can is used. Set, steam heating, hot air heating, infrared heating,
It may be heated by any means such as electric heating and microwave heating. Further, vulcanization can be performed while pressing the molded body with a vulcanizing press. Further, when the molded article is in the form of a sheet or a belt, it is possible to heat and vulcanize the sheet while continuously moving the sheet or the like. The vulcanization temperature can vary depending on the type of the base rubber and the vulcanizing agent, but is usually 120 to
It is about 200 ° C. The vulcanization time can be determined in advance by continuously measuring the changes in the tensile stress and torque of the test piece of the rubber molded body under constant temperature conditions and graphing it. , 2-60
Minutes, preferably about 5 to 60 minutes. Thus, a vulcanized conductive rubber molded body 29 is obtained.

In the case of forming a molded article having a more complicated shape, a mold can be used. In this case, preferably, the compounded rubber composition containing the solvent is directly poured into the hollow portion (cavity) of the mold, and is heated and vulcanized while the mold is being formed. However, in the present invention, a vent is formed by passing through a mold, and this is connected to a vacuum pump. After molding, the inside of the mold is vacuum-evacuated and degassed from the vent to remove the solvent. Is preferred. In this case, as the solvent is removed, it is desirable that the mold is further press-pressed so that the molding is strengthened so that the compounded rubber composition is pressed against the inner surface of the mold. When the solvent is sufficiently removed while maintaining the mold, the mold is heated to the vulcanization temperature to perform vulcanization. Alternatively, it is also possible to form a molded body after removing the solvent to a few percent in advance, put the molded body in a mold, and perform vulcanization while pressing the molded body. Finally, the vulcanized conductive rubber molded body 29 is removed from the mold.

The conductive compounded rubber composition 20 of the present invention is obtained by mixing an inorganic conductive material and a rubber chemical with a base rubber swollen and fluidized by treating with a specific solvent during the compounding process as described above. It is obtained by kneading with good dispersibility,
As a basic composition, at least 200 to 500 parts by mass of the inorganic conductive material is mixed with the rubber chemicals with good dispersibility with respect to 100 parts by mass of the base rubber. And since the composition contains a high mass part of an inorganic conductive material such as white zinc oxide instead of black carbon black, it is a composition that can be colored by adding a pigment. The cured product (cured conductive rubber, that is, the conductive rubber molded body 29) obtained by curing (vulcanizing) the compound has the following characteristics.

That is, the hardness of the cured product is 95 or less, preferably 40 or more, and more preferably 95 or less.
That is all. This hardness is determined according to JIS K6253 (ISO
According to 48), a spring hardness (Hs) is measured using a type A durometer.

The cured product has a volume resistivity of at least 1 × 10 ¹¹ Ω · cm, preferably 1 × 10 ¹⁰ Ω · c.
m or less, more preferably 1 × 10 ⁹ Ω · cm or less, most preferably 1 × 10 ⁸ Ω · cm or less, and 1 × 10 ⁹ Ω · cm or less.
Ω · cm or more. The volume resistivity of this cured product is JI
It is a value measured by an insulation resistance meter according to SK6911.

Further, the color of the cured product is white or light gray, gray or dark gray, preferably white, or gray or light gray. The hunter whiteness (Wb) is at least 20 or more, preferably 30 or more, more preferably 40 or more, more preferably 50 or more and 95 or less. Generally, dark gray corresponds to Wb of about 20 to 30, gray corresponds to about 30 to 40, light gray corresponds to about 40 to 50, and white corresponds to 50 or more. In particular, if the hunter whiteness is 30 to 40 or more, a small amount (2 to 2)
By adding a pigment of about 3 PHR), a light-colored compounded rubber composition can be easily obtained, which is preferable. Hunter whiteness is a value measured by a Hunter spectral colorimeter.

As described above, when the conductive compounded rubber composition of the present invention is compounded with an inorganic conductive material, at least a volume resistivity of 1 × 10 ¹¹ Ω · cm, preferably 1 × 10 ¹¹ Ω · cm or less, which could not be realized conventionally. ¹⁰ Ω · cm or less, and the hunter whiteness is at least 20 or more, preferably 30 or more.
The above is a colorable conductive compounded rubber composition that can be made into rubber products of various colors by compounding a pigment.

[0055]

The present invention will be described below with reference to examples. However, these are merely examples of the embodiments, and the technical scope of the present invention is not limited thereto.

In the following Examples and Comparative Examples, parts indicate parts by mass, and the hardness, volume resistivity, Hunter whiteness and color tone of the cured product were measured as follows.

The hardness is measured in accordance with JIS K6 as described above.
According to H.253, a spring hardness (Hs) was measured using an A type durometer.

The volume resistivity was measured with a super insulation resistance meter (SM-10E type) manufactured by Toa Denpa Kogyo Co., Ltd. or a four-terminal electrode type resistance meter (Loresta type) manufactured by Mitsubishi Yuka Corporation.

Hunter whiteness (W) and hunter whiteness (W
b) is a Hunter-type spectrocolorimeter (S
E2000), and the color tone was visually determined based on the hunter whiteness.

Further, the color tone of the compounded rubber composition when a pigment was added was measured by the above color difference meter. The measurement items were expressed as follows using L, a, b, W, and Wb. L = lightness [color brightness (0 to 100)] a = chromaticity [hue and saturation: red (+), green (-
B) chromaticity [hue and saturation: yellow direction (+), blue direction (-
Display)] W = whiteness [(0-100)] Wb = whiteness [(0-100)]

Example 1 (1) Natural Rubber (NR) (RSS # 3) as Base Rubber
It was used. To 100 parts of the base rubber, 200 parts of industrial gasoline No. 2 (hereinafter, simply referred to as industrial gasoline or rubber volatiles) was added as a solvent, and the mixture was allowed to stand in a closed container for 25 hours to be sufficiently swollen.

(2) 100 parts of the swollen base rubber (in terms of mass before swelling) and conductive zinc oxide (2
3-K, manufactured by Hakusuitek Co., Ltd., aluminum-doped conductive zinc oxide (volume resistivity 250 Ω · cm, particle size 0.1 to 0.
25 μm)) 250 parts and 1.75 sulfur as vulcanizing agent
Parts, 1.0 part of a vulcanization accelerator (Noxeller NS-G, manufactured by Ouchi Shinko Chemical Co., Ltd.),
(Type 0, manufactured by Toyo Seiki Co., Ltd., internal volume: 600 mL), but kneading was completed in 13 minutes without any particular heat generation and little increase in mechanical load. The kneaded compound rubber composition was observed by SEM, and it was observed that the swollen rubber particles and the conductive zinc oxide particles were uniformly mixed.

(3) The compounded rubber composition containing a solvent was processed by a roll machine to form a sheet having a thickness of 2 mm. The sheet is set in a box dryer capable of reducing the pressure, and
The solvent was removed by drying at 0 mmHg (0.0133 MPa) and 30 ° C. for 5 hours.

(4) A sheet-like molded product of the compounded rubber composition is put into a mold, set in a vulcanizer, and set at a pressure of 9.8 MPa, 1
Vulcanized at 60 ° C. for 10 minutes. In addition, this vulcanization time,
At this temperature, the time is 1.5 times the T90 value (the time to reach the value of 90 when the maximum torque and the minimum torque are measured by a rheometer and divided by 100). Table 1 shows the measurement results of the hardness, volume resistivity, color tone, and Hunter whiteness (Wb) of the cured product (conductive rubber cured product) obtained as described above. (Note that "PHR" in the table indicates the amount (part) of conductive zinc oxide per 100 parts of the base rubber. The same applies hereinafter.)

[0065]

[Table 1]

Comparative Example 1 The same experiment as in Example 1 was conducted except that the amount of conductive zinc oxide to be added to 100 parts of the base rubber was changed to 100 parts. Table 1 shows the results.

In addition, Labo Plastomill (BR600 type,
In the kneading by Toyo Seiki Co., Ltd., internal volume: 600 mL), there was no particular heat generation, and almost no increase in mechanical load was observed, and the kneading was completed in 10 minutes. The kneaded compound rubber composition was observed by SEM, and it was observed that the swollen rubber particles and the conductive zinc oxide particles were uniformly mixed.

Example 2 The same experiment as in Example 1 was conducted except that the amount of zinc oxide to be mixed with 100 parts of the base rubber was changed to 350 parts. Table 1 shows the results.

In addition, Labo Plastomill (BR600 type,
In the kneading by Toyo Seiki Co., Ltd., internal volume: 600 mL), there was no particular heat generation, and almost no increase in mechanical load was recognized, and the kneading was completed in 14 minutes. The kneaded compound rubber composition was observed by SEM, and it was observed that the swollen rubber particles and the conductive zinc oxide particles were uniformly mixed.

Example 3 The same experiment as in Example 1 was conducted except that the amount of conductive zinc oxide to be mixed with 100 parts of the base rubber was changed to 450 parts. Table 1 shows the results.

In addition, Labo Plastomill (BR600 type,
In the kneading by Toyo Seiki Co., Ltd., internal volume: 600 mL), the kneading was completed in 15 minutes without generating any heat and hardly increasing the mechanical load. The kneaded compound rubber composition was observed by SEM, and it was observed that the swollen rubber particles and the conductive zinc oxide particles were uniformly mixed.

Example 4 As a base rubber, nitrile-
The same experiment as in Example 1 was performed except that butyl rubber (NBR-N232S) was used. Table 2 shows the results.

In addition, Labo Plastomill (BR600 type,
In the kneading by Toyo Seiki Co., Ltd., internal volume: 600 mL), there was no particular heat generation, and almost no increase in mechanical load was recognized, and the kneading was completed in 14 minutes. The kneaded compound rubber composition was observed by SEM, and it was observed that the swollen rubber particles and the conductive zinc oxide particles were uniformly mixed.

[0074]

[Table 2]

Comparative Example 2 The same experiment as in Example 4 was performed except that the amount of conductive zinc oxide to be added to 100 parts of the base rubber was changed to 100 parts. Table 2 shows the results.

In addition, Labo Plastomill (BR600 type,
In the kneading by Toyo Seiki Co., Ltd., internal volume: 600 mL), no particular heat was generated, and almost no increase in mechanical load was observed, and the kneading was completed in 12 minutes. The kneaded compound rubber composition was observed by SEM, and it was observed that the swollen rubber particles and the conductive zinc oxide particles were uniformly mixed.

Example 5 The same experiment as in Example 4 was performed except that the amount of conductive zinc oxide to be mixed with 100 parts of the base rubber was changed to 350 parts. Table 2 shows the results.

In addition, Labo Plastomill (BR600 type,
In the kneading by Toyo Seiki Co., Ltd., internal volume: 600 mL), the kneading was completed in 28 minutes without generating any particular heat and hardly increasing the mechanical load. The kneaded compound rubber composition was observed by SEM, and it was observed that the swollen rubber particles and the conductive zinc oxide particles were uniformly mixed.

Example 6 The same experiment as in Example 4 was performed except that the amount of conductive zinc oxide to be mixed with 100 parts of the base rubber was changed to 450 parts. Table 2 shows the results.

A lab plast mill (BR600 type,
In the kneading by Toyo Seiki Co., Ltd., internal volume: 600 mL), there was no particular heat generation and almost no increase in the mechanical load was recognized, and the kneading was completed in 16 minutes. The kneaded compound rubber composition was observed by SEM, and it was observed that the swollen rubber particles and the conductive zinc oxide particles were uniformly mixed.

Example 7 The same experiment as in Example 1 was conducted except that the number of parts of the inorganic conductive material was changed to 300 parts per 100 parts of the base rubber. Table 3 shows the results.

Example 8 The same experiment as in Example 4 was conducted except that the number of parts of the inorganic conductive material was changed to 300 parts with respect to 100 parts of the base rubber. Table 3 shows the results.

Example 9 The same experiment as in Example 7 was performed except that the inorganic conductive material was changed to conductive titanium. Table 3 shows the results.

Example 10 The same experiment as in Example 8 was conducted except that the inorganic conductive material was changed to conductive titanium. Table 3 shows the results.

Example 11 The same experiment as in Example 7 was conducted except that the inorganic conductive material was changed to conductive potassium titanate. Table 3 shows the results.

Example 12 The same experiment as in Example 8 was performed except that the inorganic conductive material was changed to conductive potassium titanate. Table 3 shows the results.

[0087]

[Table 3]

Example 13 The same experiment as in Example 1 was performed except that the solvent was changed to toluene. The results are shown in Table 4 together with Example 1.

Example 14 The same experiment as in Example 4 was performed except that the solvent was changed to toluene. The results are shown in Table 4 together with Example 4.

[0090]

[Table 4]

Examples 15 to 17 The pigments shown in Table 5
The same experiment as in Example 1 was carried out except that a portion was added. Table 5 shows the results.

[Comparative Example 3] Raw material rubber was used in place of the pigment.
Parts, except that no solvent and conductive zinc oxide are used,
Table 5 shows the results of the same experiment as in Example 1.

[0093]

[Table 5]

Example 18 The same experiment as in Example 1 was performed except that the base rubber was changed to SBR. Table 6 shows the results.

Examples 19 to 21 The pigments shown in Table 6
The same experiment as in Example 18 was performed, except for adding a part. Table 6 shows the results.

Comparative Example 4 Raw rubber was used instead of pigments
Parts, except that no solvent and conductive zinc oxide are used,
Table 6 shows the results of the same experiment as in Example 18.

[0097]

[Table 6]

Comparative Example 5 The same experiment as in Example 2 was performed except that no solvent was used. Table 7 shows the results. When no solvent is used, Labo Plastomill is basically kept at 90 ° C.
Work is not possible unless heated to 30 ° C.
An exotherm resulted in an overall temperature of 90 + 30 = 120 ° C., so the addition of the vulcanizing agent had to be performed in a very short time. In addition, the base rubber and the conductive zinc oxide particles are not uniformly mixed, and the rubber is covered with the conductive zinc oxide, that is, it is in a so-called ragged state, and it is necessary to collect the rubber by a roll operation. In addition, there was a concern that the torque of the Labo Plastomill was high and the shaft was damaged.

[0099]

[Table 7]

[0100]

According to the conductive compounded rubber composition produced by the method of the present invention, the inorganic conductive material is compounded in a high mass part with good dispersibility and the whiteness is high. Light colored rubber can be formed.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an example of a method for producing a conductive compounded rubber composition and a conductive rubber molded product of the present invention.

[Explanation of symbols]

 Reference Signs List 10 base rubber 13 solvent 13 'recovery solvent 13' 'recovery solvent 15 inorganic conductive material 17 rubber chemicals 20 compounded rubber composition 23 molded body 25 desolvated molded body 29 conductive rubber molded body (a) swelling step (b) ) Kneading step (c) Forming step (d) Desolvation step (e) Vulcanization step

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 21/00 C08L 21/00 (72) Inventor Ken Takagi 669 Yokota, Oaza, Iizuka-shi, Fukuoka Hakusui Tech Co., Ltd. (72) Inventor Takao Tanaka 669, Yokota, Iizuka City, Fukuoka Prefecture F-term (reference) 4F070 AA04 AA05 AC14 AC18 AC32 AC94 AE05 AE06 AE08 AE28 FA09 FA13 FB06 FC02 GB02 GB07 GC02 4F071 AA10 AA18 AB03 AE15 AE19 AF34Y AF37 AF37Y AG05 AG12 AH05 AH12 BA09 BB01 BB03 BC01 4J002 AC011 AC031 AC041 AC061 AC081 AC091 AC111 AE042 AE052 BB061 BB151 BB181 BD121 BG041 CH041 CK021 CK031 FD031 DE030 CK041

Claims (12)

[Claims] 1. A method for producing a conductive compounded rubber composition, comprising: (1) a swelling step in which a solvent is added to a base rubber to swell the base rubber; and (2) a swelling step in which the swollen rubber is swollen. A method for producing a colorable conductive compounded rubber composition, comprising at least a kneading step of mixing and kneading an inorganic conductive material and a rubber chemical. 2. A method for producing a conductive compounded rubber composition, comprising: (1) a swelling step in which a solvent is added to a base rubber to swell the base rubber; and (2) an inorganic compound is added to the swelled rubber. A kneading step of compounding and kneading a conductive material and a rubber chemical, and (3) a solvent-removable step of removing a solvent from the obtained compounded rubber composition, a colorable conductive compounded rubber composition, characterized by comprising: Manufacturing method. 3. The method according to claim 2, wherein the solvent is removed after molding the compounded rubber composition into a molded article. 4. The method according to claim 3, wherein the molded body from which the solvent has been removed is vulcanized. 5. The method according to claim 1, wherein the solvent is a mineral oil selected from the group consisting of paraffin oils, naphthenic oils and aromatic oils, or industrial gasoline for rubber. Method. 6. A solvent is added in an amount of 5 parts by weight based on 100 parts by weight of the base rubber.
The method according to any one of claims 1 to 5, wherein 0 to 800 parts by mass is used. 7. The method according to claim 1, wherein the inorganic conductive material is blended in an amount of 200 to 500 parts by mass based on 100 parts by mass of the base rubber. 8. The method according to claim 1, wherein the inorganic conductive material is conductive zinc oxide, conductive potassium titanate, or conductive titanium oxide. 9. The cured conductive rubber obtained from the conductive compounded rubber composition has a hardness of 95 or less and a volume resistivity of 1 ×.
The method according to any one of claims 1 to 4, wherein the Hunter whiteness is 20 or more and 10 ¹¹ Ω · cm or less. 10. The conductive compounded rubber composition contains 200 to 500 parts by mass of an inorganic conductive material with respect to 100 parts by mass of a base rubber, and the cured conductive rubber obtained has a hardness of 95 or less and a volume resistance of not more than 95. A colorable conductive compounded rubber composition having a ratio of 1 × 10 ¹¹ Ω · cm or less and a Hunter whiteness of 20 or more. 11. The conductive compounded rubber composition according to claim 10, wherein the inorganic conductive material is conductive zinc oxide, conductive potassium titanate, or conductive titanium oxide. 12. The compounded rubber composition according to claim 10 or 11, which is formed and vulcanized, has a hardness of 95 or less, a volume resistivity of 1 × 10 ¹¹ Ω · cm or less, and a Hunter whiteness of not more than 1 × 10 ¹¹ Ω · cm. A conductive rubber molded product having a particle size of 20 or more.