JP2013104020A - Silicone rubber composition, method for producing the same, and masterbatch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a silicone rubber composition, wherein crosslinked product obtained therefrom is excellent in heat-aging resistance; a method for producing the silicone rubber composition; and a masterbatch.SOLUTION: This silicone rubber composition comprises: a silicone rubber to be crosslinked by an organic peroxide; and the organic peroxide. The silicone rubber composition further comprises 0.1 to 10 pts.mass of basic zinc carbonate as an auxiliary crosslinking agent based on 100 pts.mass of the silicone rubber.

Description

  The present invention relates to a silicone rubber composition that is crosslinked with an organic peroxide, a method for producing the same, and a masterbatch.

  In recent years, with an increase in the ambient temperature around the engine room of an automobile and an increase in the information processing speed of a computer, a demand for a polymer having excellent heat resistance is increasing.

  In order to increase heat resistance, organic peroxides are increasingly used as cross-linking agents instead of sulfur in cross-linked polymers (Patent Document 1).

  In silicone rubber that is crosslinked with an organic peroxide, it is desired to improve heat aging resistance.

  In patent document 2, mechanical strength is high by blending 50 to 200 parts by weight of zinc carbonate powder or basic zinc carbonate powder with 100 parts by mass of silicone rubber. It is described that an excellent silicone rubber can be obtained.

  In Patent Document 3, organic peroxide is added by blending 0.5 wt% to 10 wt% active zinc white and 2 wt% to 3 wt% basic magnesium carbonate with 100 wt% of millable silicone rubber. It is disclosed that a foamed molded product of silicone rubber is produced without using a product and an organic thermal decomposition generator.

JP 2003-103528 A JP-A-10-77413 JP 2008-189798 A

  An object of the present invention is to provide a silicone rubber composition in which a crosslinked product is excellent in heat aging resistance, a method for producing the same, and a masterbatch.

  The silicone rubber composition of the present invention is a silicone rubber composition containing a silicone rubber that is crosslinked with an organic peroxide and an organic peroxide. The silicone rubber composition contains 0.1 parts as a crosslinking aid with respect to 100 parts by mass of the silicone rubber. It is characterized by containing 10 to 10 parts by mass of basic zinc carbonate.

  In the present invention, the silicone rubber is preferably a millable silicone rubber.

  In the present invention, basic zinc carbonate used as a crosslinking aid may be contained as a composite with other zinc compounds such as zinc oxide.

  The masterbatch of the present invention is a masterbatch for preparing the above-mentioned silicone rubber composition of the present invention, characterized in that it contains 20 to 120 parts by mass of basic zinc carbonate with respect to 100 parts by mass of the silicone polymer. Yes.

  The method for producing the silicone rubber composition of the present invention is a method for producing the silicone rubber composition of the present invention, comprising the step of preparing the masterbatch of the present invention, the silicone rubber with the masterbatch and the organic peroxide. And a step of blending the product.

  By using the silicone rubber composition of the present invention, a crosslinked product having excellent heat aging resistance can be obtained.

  By using the master batch of the present invention, handling at the time of kneading and the like is facilitated, and the crosslinking aid can be uniformly dispersed in the silicone rubber.

  According to the production method of the present invention, handling at the time of kneading and the like becomes easy, and the crosslinking aid can be uniformly dispersed in the silicone rubber.

  Hereinafter, the present invention will be described in more detail.

<Crosslinking aid>
In the present invention, 0.1 to 10 parts by mass of basic zinc carbonate is contained as a crosslinking aid with respect to 100 parts by mass of silicone rubber. The content of basic zinc carbonate is more preferably 0.2 to 7 parts by mass, and further preferably 0.5 to 5 parts by mass.

  If the content of basic zinc carbonate is small, the heat aging resistance may not be sufficiently improved. When there is too much content of basic zinc carbonate, a crosslinked material may foam, and heat aging resistance may not fully be improved.

  As basic zinc carbonate, what is marketed as basic zinc carbonate and zinc carbonate, activated zinc white, transparent zinc white, etc. are mentioned. Active zinc white is generally a composite containing 53 to 77% by mass of zinc oxide and 22 to 45% by mass of basic zinc carbonate. Moreover, almost 100% of the transparent zinc white is basic zinc carbonate.

  In the present invention, a crosslinking aid other than basic zinc carbonate may be further added to the silicone rubber.

  In the present invention, the crosslinking aid is selected from organic acids, fatty acids, fatty acid metal salts, fatty acid esters, resin acids, resin acid metal salts, resin acid esters, silicic acid, silicates (Na salts, etc.), and silane coupling agents. The surface treatment may be performed with at least one kind. Any structure that covers all or part of the surface may be used, and it is not always necessary to continuously cover the entire surface.

  As the surface treatment method, when the crosslinking aid is an aqueous slurry, the surface treatment agent can be treated in a wet state by dissolving the surface treatment agent as it is or in an appropriate temperature and solvent. Further, if the crosslinking aid is in a powder form, the surface treatment agent can be treated in a dry state by dissolving the surface treatment agent as it is or with an appropriate temperature and solvent.

<Silicone rubber>
The silicone rubber used in the present invention is not particularly limited as long as it can be crosslinked by an organic peroxide. For example, high temperature vulcanization type HTV and room temperature vulcanization type RTV are mentioned. Among these, HTV can be particularly preferably used. Accordingly, millable silicone rubber is preferably used.

<Organic peroxide>
Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2, 5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne- 3, or 1,3-bis (t-butylperoxypropyl) benzene, di-t-butylperoxy-diisopropylbenzene, t-butylperoxybenzene, 2,4-dichlorobenzoyl peroxide, 1,1-di -T-butylperoxy-3,3,5-trimethylsiloxane, n-butyl-4,4 Di -t- butyl peroxy valerate, and the like.

  The mixing ratio of the basic zinc carbonate to the organic peroxide is preferably in the range of 5 to 2000 parts by mass, more preferably in the range of 20 to 1333 parts by mass with respect to 100 parts by mass of the organic peroxide. If the blending amount of basic zinc carbonate with respect to the organic peroxide is too small, the heat aging resistance may not be sufficiently improved. Moreover, when there are too many mixing ratios of the basic zinc carbonate with respect to an organic peroxide, heat aging resistance cannot be improved in proportion to a compounding quantity, and it may become economically disadvantageous. In addition, the mechanical characteristics and the like may be deteriorated.

<Other additives>
In the present invention, as described above, in addition to basic zinc carbonate, other crosslinking aids may be used in combination as the crosslinking aid. For example, zinc oxide, fine particle zinc oxide, cerium oxide, sulfur, p, p'-dibenzoylquinone oxime (BQO), triallyl isocyanurate, trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, N, N'-m -Phenylene dimaleimide and the like.

  Moreover, you may contain a well-known additive as needed. As such, for example, wet silica, dry silica, alkali silica, highly dispersible silica (HDS), clay, talc, aluminum hydroxide, magnesium hydroxide, feldspar, calcium carbonate, basic magnesium carbonate, carbon black, etc. Can be used in combination as appropriate. Furthermore, process oils, antioxidants, anti-aging agents, activators, additives such as stearic acid, zinc oxide, wax, and vulcanizing agents such as sulfur and vulcanization accelerators may be added as desired. it can.

<Silicone rubber composition>
The method of blending the basic zinc carbonate and the organic peroxide with the silicone rubber is not particularly limited. For example, a conventionally known kneading apparatus, specifically, a Banbury mixer (registered trademark), an intermix ( (Registered trademark), kneader, roll and the like.

  In addition, a master batch in which basic zinc carbonate is blended at a high concentration with silicone rubber, which will be described below, is prepared, and this master batch and organic peroxide are blended with silicone rubber to produce a silicone rubber composition. May be.

<Master batch>
The masterbatch of the present invention is characterized by containing 20 to 120 parts by mass of basic zinc carbonate with respect to 100 parts by mass of the silicone polymer. Furthermore, content of basic zinc carbonate is 40-120 mass parts, More preferably, it is 60-100 mass parts.

  When there is too little content of basic zinc carbonate, the viscosity at the time of masterbatch preparation may be too low, and dispersion | distribution may become inadequate. Moreover, when there is too much content of basic zinc carbonate, the viscosity of a masterbatch will increase and workability may fall.

  When basic zinc carbonate or a composite containing the same is directly blended into the silicone rubber, there is a problem that the blended silicone rubber tends to adhere to a roll or the like and is difficult to handle. Such a problem can be solved by using the master batch of the present invention.

  Examples of the silicone polymer include silicone oil, organopolysiloxane, diorganopolysorboxane, triorganosiloxane, tetraorganosiloxane, and silicone rubber.

<Crosslinked product>
By heating the silicone rubber composition of the present invention, the silicone rubber can be crosslinked to form a crosslinked product. Although heating temperature is suitably adjusted with the organic peroxide etc. to be used, generally it is preferable that it is the range of 120-200 degreeC, More preferably, it is the range of 150-180 degreeC. The heating time is determined with reference to tc (90) measured with a curast meter at each temperature.

  A crosslinked product obtained by crosslinking the silicone rubber composition of the present invention is excellent in heat aging resistance. Therefore, in the fields of E & E, OA equipment, heavy electricity, electric wires, packing, gaskets, tapes, tubes, sheets, heater heating element, defroster wire, TV parts, sensors, connectors, keyboard switches, rolls, heating sheets, Cable, Anode cap, Defroster, Hot air brush, Turn belt, O-ring, Valve, Harness end insulation, Jarpot packing, Automotive, Transportation field, Diaphragm, Rolling, Plug boot, Waterproof connector, Radiator hose, Turbo charge hose , Intercooler hose, oil seal, ignition hood, packing, gacket, heat shrink tube, joint hose, cable joint connector, plug cover, terminal plate, high voltage molded product, EGR ho Oil seals for rear flange shafts, hoses, rolls, anti-vibration rubber, valves, packings, tubes, jigs, heat-resistant mechanical parts in the industrial machinery field, packings, lumicars, nipples, various catheters in the medical and food fields , Transfusion tubes, shunts, storage containers, cardiopulmonary, artificial skin, gaskets, stoppers, O-rings, milking machine tubes, plugs for household cooking utensils, food production equipment parts, conveyor belts, pipettor spots, etc. , Underwater glasses, snorkels, mouthpieces, goggles bands, architectural gaskets and the like.

  Moreover, since improvement in water vapor resistance can also be expected, it can be suitably used for food packing (jars, rice cookers, pots), gaskets, sealing materials used for O-rings, and packing.

  Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to the following examples.

(Examples 1-7 and Comparative Examples 1-5)
0.75 parts by mass of a crosslinking agent (organic peroxide) is blended with 100 parts by mass of silicone rubber, and the crosslinking aids shown in Tables 1 and 2 are blended in the proportions shown in Tables 1 and 2. It was blended as follows.

  The silicone rubber, the crosslinking agent and the crosslinking aid are as follows.

Silicone rubber: trade name SH831U, millable silicone rubber, manufactured by Toray Dow Corning, hardness 30
・ Crosslinking agent: Trade name RC-4 (50P), manufactured by Toray Dow Corning Co., Ltd. ・ Crosslinking aid A: Active zinc white (basic zinc carbonate content 33% by mass), trade name: Active zinc white AZO Made by Chemical Co., Ltd. ・ Crosslinking aid B: Basic zinc carbonate, trade name: Zinc carbonate, manufactured by Shodo Chemical Co., Ltd. Agent D: Calcium carbonate, trade name: Whiten P-30, manufactured by Shiraishi Kogyo Co., Ltd. ・ Crosslinking aid E: 50% by mass of active zinc white-containing silicone masterbatch, 50% by mass of active zinc white (Oil: SH200 (10CT)).

  After kneading using an 8-inch roll, and after kneading, the silicone rubber composition was crosslinked by setting the heating conditions for primary crosslinking to 170 ° C. for 15 minutes and the heating conditions for secondary crosslinking to 200 ° C. for 4 hours.

  The obtained silicone rubber cross-linked product was subjected to the following thermal aging test to measure compression set, tensile strength change rate, and elongation change rate. Tables 1 and 2 show the measurement results.

(Examples 8 to 9 and Comparative Example 6)
0.6 parts by mass of a crosslinking agent (organic peroxide) was blended with 100 parts by mass of silicone rubber, and the crosslinking aids shown in Table 3 were blended so as to have the blending ratios shown in Table 3.

  The silicone rubber, the crosslinking agent and the crosslinking aid are as follows.

Silicone rubber: trade name SH851U, millable silicone rubber, manufactured by Toray Dow Corning, hardness 50
・ Crosslinking agent: Trade name RC-4 (50P), manufactured by Toray Dow Corning Co., Ltd. ・ Crosslinking aid A: Activated zinc flower (basic zinc carbonate content 33% by mass), Trade name: Activated zinc flower AZO, exactly the same Made by Chemical Co., Ltd. ・ Crosslinking aid B: Basic zinc carbonate, Trade name: Zinc carbonate, manufactured by Shodo Chemical Co., Ltd.

  After kneading using an 8-inch roll, and after kneading, the silicone rubber composition was crosslinked by setting the heating conditions for primary crosslinking to 170 ° C. for 15 minutes and the heating conditions for secondary crosslinking to 200 ° C. for 4 hours.

  The obtained silicone rubber cross-linked product was subjected to the following thermal aging test to measure the compression set, tensile strength change rate, and elongation change rate. Table 3 shows the measurement results.

[Thermal aging test]
A test piece was placed in a thermostat at 230 ° C. for 72 hours, and a heat aging test was conducted.

[Measurement of compression set]
According to the method specified in JIS K 6262, it was tested using a compression apparatus. After the thermal aging test, the test piece was taken out and allowed to stand at room temperature for 30 minutes, and then the compression set was measured at a compression ratio of 25%. The measurement results are shown in Tables 1 and 2.

[Measurement of change rate of tensile strength and elongation]
Before and after the above heat aging test, the tensile strength and elongation were measured to determine the tensile strength change rate and the elongation change rate.

  As shown in Table 1, in the crosslinked products of the silicone rubber compositions of Examples 1 to 7 according to the present invention, the compression set after the heat aging test is smaller than those of Comparative Examples 1 to 5 shown in Table 2. . Moreover, the tensile strength change rate and the elongation change rate are also smaller than those of Comparative Examples 1 to 5, indicating that the heat aging resistance is excellent.

  In Comparative Example 5 in which a large amount of basic zinc carbonate was blended, the cross-linked product was foamed, and the mechanical properties were reduced.

  From the above, the compounding amount of basic zinc carbonate is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 7 parts by mass, and still more preferably 0.00 to 100 parts by mass of silicone rubber. It turns out that it is 5-5 mass parts.

  As shown in Table 3, in the crosslinked products of the silicone rubber compositions of Examples 8 to 9 according to the present invention, the compression set after the heat aging test is smaller than that of Comparative Example 6. Moreover, the tensile strength change rate and the elongation change rate are also smaller than those of Comparative Example 6, indicating that the heat aging resistance is excellent.

Claims (5)

A silicone rubber composition comprising a silicone rubber crosslinked with an organic peroxide and an organic peroxide,
A silicone rubber composition comprising 0.1 to 10 parts by mass of basic zinc carbonate as a crosslinking aid with respect to 100 parts by mass of silicone rubber.   The silicone rubber composition according to claim 1, wherein the silicone rubber is a millable silicone rubber.   The silicone rubber composition according to claim 1 or 2, wherein basic zinc carbonate is contained as a composite with zinc oxide. A masterbatch for preparing the silicone rubber composition according to any one of claims 1 to 3,
A masterbatch comprising 20 to 120 parts by mass of basic zinc carbonate with respect to 100 parts by mass of the silicone polymer. A method for producing the silicone rubber composition of claims 1-3,
Preparing a masterbatch according to claim 4;
A method for producing a silicone rubber composition, comprising: adding a master batch and an organic peroxide to silicone rubber.