JP5248013B2 - Conductive silicone rubber compound package and method for storing conductive silicone rubber compound - Google Patents

Description

  The present invention relates to a package and a storage method for a conductive silicone rubber compound containing conductive carbon black.

  Various conductive rubbers in which a conductive material is blended with a rubber-like substance exhibiting electrical insulation properties are known, and are applied in various fields by utilizing characteristics and conductivity as a rubber-like substance. On the other hand, silicone rubber, one of the electrically insulating rubbery substances, is excellent in heat resistance, cold resistance, weather resistance, etc., and is widely used as an electrically insulating rubber. By adding a conductive material, it has been put into practical use as a conductive silicone rubber.

  Examples of the conductive material to be added to the conductive silicone rubber include conductive carbon black, conductive metal oxide, metal powder, etc. Among them, conductive carbon black is easily available, and depending on the purpose. It is often used because the electrical resistance can be adjusted arbitrarily.

  However, a silicone rubber composition containing conductive carbon black as a conductive material is highly conductive, with its volume resistivity easily changing due to the affinity and dispersibility of conductive carbon black particles to silicone rubber. However, when the blending amount of carbon black is increased, the plasticity is increased and the moldability is lowered. Accordingly, various methods have been proposed to deal with such problems, for example, by blending a phenyl group-containing organosilicon compound or applying a special vulcanization system, and each has a certain effect (for example, (See Patent Documents 1 and 2.)

  Under such circumstances, recently, when a silicone rubber composition containing conductive carbon black is stored for a long period (several months) (usually stored in a bag such as polyethylene), it is expected. On the other hand, it has been found that the degree of plasticity is lowered and it becomes difficult to mold, or even if it can be molded, the initial hardness and volume resistivity may not be obtained.

That is, until now, silicone rubber compositions containing conductive carbon black were thought to increase in plasticity or viscosity over time. However, silicone rubber compositions containing conductive carbon black were used for a long time. In particular, it has been found that when stored in a hot and humid environment, the plasticity is lowered and molding may be difficult. For this reason, measures against such a decrease in plasticity over time associated with long-term storage have been demanded.
Japanese Patent Publication No. 3-47663 Japanese Patent Laid-Open No. 5-25393

  The present invention has been made in response to such problems of the prior art, and suppresses a decrease in plasticity and changes in physical properties over time of a silicone rubber composition containing a conductive carbon black. Another object of the present invention is to provide a conductive silicone rubber compound package and storage method that can maintain good moldability and physical properties.

  As a result of intensive studies to solve the above-mentioned problems of the prior art, the present inventors have surprisingly found that the deterioration in plasticity and the change in physical properties over time due to long-term storage are caused by moisture in the atmosphere. There was a cause (this time-dependent change has been observed to increase as the humidity of the atmosphere increases. This fact has not been reported so far. It is thought that it is adsorbed on the surface of the conductive carbon black in the compound and changes the dispersion state of the conductive carbon black, etc. The most surprising point is that the hygroscopicity like acetylene black is generally very low. In the case of the known conductive carbon black, a decrease in plasticity and a change in physical properties were observed under the influence of moisture in the atmosphere.) By storing and storing conductive silicone rubber compound containing N-black in an airtight container, it is possible to suppress a decrease in plasticity with time and a change in physical properties. The inventors have found that physical properties can be maintained, and have completed the present invention.

That is, the conductive silicone rubber compound package according to one embodiment of the present invention has a lower plasticity after being left in an unwrapped state in an atmosphere of a temperature of 40 ° C. and a humidity of 80% RH for 120 days. The uncured millable conductive silicone rubber compound containing acetylene black or ketjen black is housed in an airtight container having a moisture permeability of 10 g / m ² · 24 hours or less, and the inside of the airtight container is evacuated, or It is characterized by being in a state filled with dry gas.

In addition, the method for storing the conductive silicone rubber compound according to one aspect of the present invention is such that the plasticity after leaving for 120 days in an unwrapped atmosphere at a temperature of 40 ° C. and a humidity of 80% RH is greater than the initial plasticity. An uncured millable conductive silicone rubber compound containing low acetylene black or ketjen black is contained in an airtight container having a moisture permeability of 10 g / m ² · 24 hours or less, and the inside of the airtight container is evacuated. Or it is stored as a state filled with dry gas.

  According to the present invention, it is possible to suppress a decrease in plasticity and change in physical properties of a conductive silicone rubber compound containing conductive carbon black over time, and to maintain good moldability and physical properties over a long period of time. .

  Hereinafter, embodiments of the present invention will be described.

  In the present invention, the conductive silicone rubber compound containing conductive carbon black is obtained by adding conductive carbon black and various additives (excluding curing agents) blended as necessary to polyorganosiloxane, A kneaded product.

The polyorganosiloxane has an average composition formula R _a SiO _{(4-a) / 2}
R in the formula is an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group or a dodecyl group; a cycloalkyl group such as a cyclohexyl group; a vinyl group, an allyl group or a butaniel group An aryl group such as an alkenyl group, a phenyl group, a tolyl group, or a part or all of hydrogen atoms bonded to carbon atoms of these groups is substituted with a halogen atom, an amino group, an epoxy group, a carboxyl group, a cyano group, or the like. The same or different unsubstituted or substituted monovalent hydrocarbon group selected from chloromethyl group, trifluoropropyl group, cyanoethyl group, etc., a is 1.8 to 2.1, and its average degree of polymerization is 1000 As described above, it is preferable to be in the category of so-called millable type. The average degree of polymerization is more preferably 4000 or more. The polyorganosiloxane preferably has a linear molecular structure, but may have a partially branched chain in the molecule.

  The conductive carbon black is not particularly limited, and may be arbitrarily selected from those commonly used in this type of composition such as acetylene black, conductive furnace black, and conductive channel black. Examples of acetylene black include Denka Black (trade name, manufactured by Denki Kagaku Kogyo Co., Ltd.) and Shaunigan Acetylene Black (trade name, manufactured by Shaunigan Chemical Co., Ltd.). As conductive furnace black, Continex CF, Continex SCF (the product name made by Continental Carbon), Vulcan C, Vulcan SC, Vulcan P, Vulcan XC-72 (the product name made by Cabot), Asahi HS- 500 (trade name, manufactured by Asahi Carbon Co., Ltd.). An example of the conductive channel black is Kourax L (trade name, manufactured by Degussa). Further, Ketjen Black EC and Ketjen Black EC-600JD (trade name, manufactured by Ketjen Black International Co., Ltd.), which are a kind of furnace black, can also be used. Among these, acetylene black and ketjen black are preferable because the effects of the present invention are particularly remarkable.

  The amount of the conductive carbon black is usually in the range of 3 to 150 parts by mass with respect to 100 parts by mass of the base polymer polyorganosiloxane.

  Examples of additives that are blended as necessary include fillers, pigments, heat resistance improvers, flame retardants, and the like. Specific examples of the filler include, for example, silica hydrogel (hydrous silicic acid), silica airgel (silicic anhydride), reinforcing silica such as fumed silica, ground quartz powder, clay, calcium carbonate, diatomaceous earth, titanium dioxide. Etc. Specific examples of the heat resistance improver include iron oxide, cerium oxide, cerium hydroxide, and iron octylate. In addition, a saturated aliphatic hydrocarbon such as isoparaffin, a release agent such as a fatty acid metal salt and a fatty acid amide, a blowing agent such as azodicarbonamide and azobisisobutyronitrile, and the like can also be blended.

  In addition, a phenyl group-containing organosilicon compound, a surfactant, a processing aid, and the like blended for the purpose of improving the dispersibility of the conductive carbon black can also be used.

  Next, the material and structure of the airtight container for accommodating the conductive silicone rubber compound as described above is not particularly limited as long as the conductive silicone rubber compound can be airtightly accommodated. . Specifically, for example, a sealable sheet or film made of metal or resin, a bag-like container made of a composite sheet or film based on them, a semi-rigid or hard container made of metal, resin, glass or the like Etc.

For the purposes of the present invention, these hermetic containers preferably have a water vapor transmission rate of 10 g / m ² · 24 hours or less, 0 g / m ² · 24 hours or as close as possible (ie moisture). It is more preferable that the light is not transmitted at all or hardly transmitted. Here, the moisture permeability of the airtight container can be measured in accordance with JIS Z 0222, JIS K 7129, and JIS Z 0208.

  Specific examples of the composite sheet / film include a multi-layered sheet / film made of resin such as polyethylene, polypropylene, and polyester, a sheet / film made of resin such as polyethylene, polypropylene, and polyester, and a metal foil such as aluminum. And the like laminated. These sheets and films may be further laminated with a nonwoven fabric or paper for reinforcement. A bag-like container made of an aluminum laminate sheet obtained by laminating aluminum on a resin sheet / film is commercially available as an aluminum laminated bag, and can be preferably used as an airtight container of the present invention.

  Further, in the present invention, when the conductive silicone rubber compound is accommodated in such an airtight container, after the conductive silicone rubber compound is accommodated, the container is depressurized to be evacuated or dried in the container. It is preferable to fill with gas. As the dry gas, in addition to dry air, an inert gas such as nitrogen gas can be used. This makes it possible to almost completely block contact of the conductive silicone rubber compound with moisture, and to almost completely prevent a decrease in plasticity and change in physical properties of the conductive silicone rubber compound over time. .

  From this point of view, the above-described aluminum laminated bag is preferably used as an airtight container. That is, for example, a conductive silicone rubber compound is put into an aluminum laminate bag, a nozzle is inserted into the mouth portion of the aluminum laminate bag, and then the mouth portion is sandwiched between pads to close the gap between the aluminum laminate bag and the nozzle. In this state, suction is performed from the nozzle, the inside is evacuated, and the mouth is sealed with a heat-sealing seal or the like. Alternatively, an inert gas is filled into the aluminum laminated bag through the nozzle, and then the mouth is sealed and sealed. Thereby, the package excellent in the long-term storage property of the conductive silicone rubber compound can be obtained.

  In the present invention, a desiccant may be stored in the hermetic container for the purpose of reducing moisture in the hermetic container and maintaining the low humidity environment for a long period of time. As the desiccant, known ones can be used, for example, calcium oxide, magnesium oxide, calcium chloride, magnesium chloride, magnesium sulfate, sodium sulfate, diphosphorus pentoxide, aluminum oxide, barium oxide, silica gel and the like. It is done. In order to prevent the conductive silicone rubber compound containing conductive carbon black from being contaminated, the desiccant is preferably used by filling it into a bag-like container made of a moisture-permeable sheet or film.

  The conductive silicone rubber compound package of the present invention is obtained by opening an airtight container in use, taking out the conductive silicone rubber compound inside, and obtaining vulcanized and cured by a conventional method to obtain conductive silicone rubber. Can do. In this case, the curing agent is not limited in its curing mechanism as long as it is vulcanized and cured using radical reaction, addition reaction, condensation reaction and the like used for vulcanization of conductive silicone rubber, Various conventionally known curing agents can be used. For example, organic such as di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, dicumyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide In addition to peroxides, as addition reaction curing agents, organohydrogenpolysiloxanes containing at least two hydrogen atoms bonded to silicon atoms in one molecule and platinum-based catalysts, and condensation curing agents, Polyfunctional alkoxysilanes or siloxanes and organometallic acid salts can be used.

  In the present invention, since the decrease in plasticity of the conductive silicone rubber compound during storage is suppressed, it can be satisfactorily molded by ordinary methods such as pressure molding, extrusion molding, injection molding and calendar molding. A product having the desired physical properties can be obtained stably.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, these examples do not limit the scope of the present invention. In the following description, “parts” means “parts by mass” unless otherwise specified.

Examples 1-3
As a polyorganosiloxane, both ends are blocked with dimethylvinylsilyl groups, the average degree of polymerization is 7000, a linear methylvinylpolysiloxane containing 0.25 mol% of methylvinylsiloxane units, and a specific surface area of 69 m as a conductive carbon black. ² / g of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd .; expressed as acetylene black A), specific surface area of 39 m ² / g of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd .; written as acetylene black B) and specific surface area of 1270 m ² / g ketjen black (made by Lion Co., Ltd .; expressed as ketjen black), and pulverized quartz powder (average particle size 1.2 μm) as a filler, and conductive silicone rubber compound at a compounding ratio shown in Table 1. Prepared.

  That is, each component was charged into a kneader and kneaded at room temperature for 1 hour to combine the compounds, and then heat treated at 150 ° C. for 1 hour to obtain a conductive silicone rubber compound.

Next, each conductive silicone rubber compound obtained is placed in an aluminum laminate bag (moisture permeability of 0.03 g / m ² · 24 hours: measured according to JIS Z 0222), sealed under reduced pressure, and conductive silicone rubber compound packaging. After making it into a body, it was left in an environment of temperature 40 ° C. and humidity 80% RH.

  120 days later, the conductive silicone rubber compound was taken out of each conductive silicone rubber compound package, and the plasticity at 23 ° C. was measured. Also, 2 parts of platinum catalyst TC-25A (trade name, manufactured by GE Toshiba Silicone) and 2 parts of curing agent TC-25C (trade name, manufactured by GE Toshiba Silicone) are added to 100 parts of each conductive silicone rubber compound. After adding and kneading sufficiently with two rolls, this kneaded product is put into a mold, pressed at 170 ° C. for 10 minutes, and then post-cured at 200 ° C. for 4 hours to obtain silicone rubber having a thickness of 6 mm and 2 mm, respectively. Sheets were prepared and the hardness and volume resistivity were measured. These measurement results are shown in Table 1 together with the measurement results of the plasticity, hardness and volume resistivity measured in the same manner for the conductive silicone rubber compound immediately after preparation, that is, the silicone rubber sheet produced using the same. Also shown.

The plasticity of the conductive silicone rubber compound and the methods for measuring the hardness and volume resistivity of the silicone rubber sheet are as follows.
<Plasticity>
After winding 100 times with two rolls (8 inches, 3 mm between rolls), the measurement was performed according to JIS K 6249, and the value after 5 minutes was set as the plasticity under a prescribed load.
<Hardness>
Measurement was performed according to JIS K 6249.
<Volume resistivity>
Measured with a multimeter manufactured by Advantest.

  For comparison with the present invention, Table 1 shows an example in which the conductive silicone rubber compound prepared in the same manner as in Examples 1 to 3 was placed in a polyethylene bag and stored as it was without sealing the mouth. The results of similar evaluation tests were also shown (Comparative Examples 1 to 3).

  As is clear from Table 1, in all the conductive silicone rubber compounds stored by the method of the Examples, the plasticity, hardness and volume resistivity were hardly changed from the initial values even after 120 days. On the other hand, in the comparative example, the plasticity, hardness, and volume resistivity all changed with storage for 120 days, and in particular, a significant decrease in plasticity and volume resistivity was observed.

Claims (3)

Uncured millable conductive material containing acetylene black or ketjen black, in which the plasticity after standing for 120 days in an unwrapped atmosphere at a temperature of 40 ° C. and humidity of 80% RH is lower than the initial plasticity The silicone rubber compound is housed in an airtight container having a water vapor transmission rate of 10 g / m ² · 24 hours or less, and the inside of the airtight container is filled with a vacuum or a dry gas. Compound packaging.   2. The conductive silicone rubber compound package according to claim 1, wherein the airtight container is formed of a laminated film including a metal layer and a resin layer. Uncured millable conductive material containing acetylene black or ketjen black, in which the plasticity after standing for 120 days in an unwrapped atmosphere at a temperature of 40 ° C. and humidity of 80% RH is lower than the initial plasticity The silicone rubber compound is stored in an airtight container having a moisture permeability of 10 g / m ² · 24 hours or less, and the inside of the airtight container is stored in a vacuum or a state filled with a dry gas. How to store rubber compounds.