JP2008150505A - Silicone rubber composition and fixing member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicone rubber composition which simultaneously possesses excellent high thermal conductivity and environmental stability and high durability. <P>SOLUTION: The silicone rubber composition comprises (A) 100 pts.wt. specific organopolysiloxane, (B) 50 to 1,000 pts wt. zinc oxide prepared by firing zinc hydroxide granulated by the wet method or zinc carbonate at 600-1,800°C or by firing zinc oxide prepared by the American method or the French method at 800-1,800°C and thereafter surface-treating the fired zinc oxide with a surface treating agent, and (C) a catalytic amount of a curing agent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a highly durable silicone rubber composition having high thermal conductivity and excellent environmental stability, and a fixing member using such a silicone rubber composition.

  Conventionally, silicone rubber compositions that cure to become silicone rubbers are well known, and potting of electrical and electronic parts is made possible by utilizing their excellent properties such as weather resistance, heat resistance, cold resistance, and electrical insulation. Widely used in molding materials, rolls, etc. for materials, coating materials and mold making.

  In addition, it is known that various substances are blended in silicone rubber in order to improve thermal conductivity. As a conventional technique related to zinc oxide, Patent Document 1 discloses a silicone rubber blended with a surface-treated conductive metal oxide. There is a description of a composition and a roll, zinc oxide is exemplified as a conductive metal oxide, and Patent Document 2 exemplifies zinc white as a filler. However, although the example about using for a heater roll is given, the example implemented concretely is not seen and the material actually used is not found. This is because zinc oxide, which is conventionally used as a filler for rubber, is zinc oxide manufactured by the American method or French method, or fine-particle zinc oxide manufactured by a wet method. The decrease and increase in hardness were observed, and although the intrinsic thermal conductivity was high, it was thought that it was not actually usable.

  In recent years, a fixing belt having a silicone rubber elastic layer on a belt base material has become widespread. With the increase in color-type copying machines and printers, it is considered that an elastic layer is necessary to obtain clearer image characteristics. Further, from the viewpoint of energy saving, the elastic layer is required to have a high thermal conductivity characteristic and a technique for reducing the hardness. Furthermore, as the demand for copiers and printers expands, these types of components are manufactured in various countries, so there are problems with storage stability at high temperatures and high humidity in terms of storage stability before and after production. It was. Therefore, the applicant of the present application has a high durability silicone rubber composition having high thermal conductivity and excellent environmental stability by blending a specific zinc oxide, and a fixing member using such a silicone rubber composition. A silicone rubber composition was proposed.

Such a silicone rubber composition eliminates the above-mentioned drawbacks of the prior art, and by adding zinc oxide, a silicone rubber having high thermal conductivity can be obtained and is a very suitable material as a fixing member. As a result of high filling, a change in weight is observed in a high-temperature and high-humidity environment, and problems remain in environmental stability.
JP-A-8-12889 JP-A-8-134356 JP 2000-302971 A

  That is, the present invention can provide a fixing member using a silicone rubber having high thermal conductivity and excellent environmental stability, and also provides a silicone rubber composition having high durability and a fixing member using the silicone rubber. It is what.

  As a result of intensive studies to achieve the above object, the present inventors have found that it is extremely effective to add a specific zinc oxide to an organopolysiloxane, and have completed the present invention.

That is, the present invention
(A) 100 parts by weight of an organopolysiloxane represented by the following general formula (1)
R ¹ _a SiO _{(4-a) / 2} (1)
(In the formula, R ¹ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and a is a positive number of 1.90 to 2.05.)
(B) Zinc hydroxide or zinc carbonate granulated by a wet process is calcined at a temperature of 600 to 1800 ° C. 50 to 1000 parts by weight of zinc oxide calcined at a temperature and previously surface-treated with a surface treatment agent
(C) A silicone rubber composition comprising a catalytic amount of a curing agent, and a fixing member obtained by uniformly coating and curing the silicone rubber composition on a roll core.

  The silicone rubber composition of the present invention is a silicone rubber excellent in high thermal conductivity and environmental stability. By using such a silicone rubber composition, a fixing member excellent in durability can be provided.

  The present invention will be described in detail below. The component (A) constituting the composition of the present invention is an organopolysiloxane represented by the general formula (1), wherein R1 is an alkyl group such as a methyl group, ethyl group, propyl group or butyl group, vinyl Group, allyl group, butenyl group and other alkenyl groups, phenyl group, tolyl group and other aryl groups or hydrogen atoms bonded to carbon atoms of these groups partially or entirely substituted with halogen atoms, cyano groups, etc. Group, chloropropyl group, 3,3,3-trifluoropropyl group, 2-cyanoethyl group, the same or different unsubstituted or substituted monovalent hydrocarbon group, preferably having 1 to 10 carbon atoms, More preferably, it is 1-8. A is a positive number from 1.90 to 2.05.

  This preferably has a linear molecular structure, but there is no problem if the molecule contains a partially branched one. In addition, it is sufficient that the end of the molecular chain is blocked with a triorganosilyl group or a hydroxyl group. As the triorganosilyl group, a trimethylsilyl group, a dimethylvinylsilyl group, a methylphenylvinylsilyl group, a methyldiphenyl group can be used. Examples include a silyl group, a methyldivinylsilyl group, and a trivinylsilyl group.

  Although there is no limitation on the degree of polymerization of this, the degree of polymerization is preferably 100 to 2000 when it is a liquid silicone rubber, and the degree of polymerization is preferably 2000 to 10,000 when it is a millable silicone rubber. It may be individual or a mixture of them, and the blending ratio is not particularly limited.

  Zinc oxide used for the component (B) of the present invention is zinc oxide having specific physical properties obtained by a specific production method, and is a characteristic component for achieving the intended effect of the present invention.

  That is, as zinc oxide used for the component (B) of the present invention, among zinc oxides, calcined zinc oxide obtained by calcining zinc hydroxide or zinc carbonate granulated by a wet method at a temperature of 600 to 1800 ° C. Or zinc oxide prepared by calcining zinc oxide prepared by the American method or the French method at a temperature of 800 to 1800 ° C., and having an average particle size in the range of 1 to 50 μm is preferable. The average particle diameter of zinc oxide is preferably 1 to 50 μm, more preferably 3 to 20 μm. If the average particle size is less than 1 μm, the hardness of the silicone rubber increases and high filling cannot be performed, and a silicone rubber with high thermal conductivity cannot be obtained. If it exceeds 50 μm, the strength of the silicone rubber is significantly reduced.

  When zinc hydroxide or zinc carbonate granulated by a wet method is fired, the firing temperature is 600 to 1800 ° C, preferably 700 to 1800 ° C, more preferably 800 to 1800 ° C. When the firing temperature is lower than 600 ° C., the heat resistance of the silicone rubber is lowered, and when it exceeds 1800 ° C., the particles are fixed and aggregates are generated.

  Moreover, when baking the zinc oxide prepared by the American method or the French method, a calcination temperature is 800-1800 degreeC, Preferably it is 900-1800 degreeC, More preferably, it is 1000-1800 degreeC. When the firing temperature is lower than 800 ° C., the heat resistance of the silicone rubber is lowered, and when it exceeds 1800 ° C., the particles are fixed and aggregates are generated.

Although not particularly limited, the zinc oxide used preferably has a BET specific surface area of 0.01 to ⁵ m ² / g. When the BET specific surface area is smaller than 0.01 m ² / g, the particle diameter becomes too large, and when the BET specific surface area exceeds 5 m ² / g, the hardness of the rubber is high and the heat resistance is also lowered.

  In the present invention, as the component (B), the above zinc oxide that has been previously surface-treated with a surface treatment agent is used. Such surface-treated zinc oxide is effective in improving the stability of the rubber cured product, that is, increasing the weight under high temperature and high humidity, and improving the stability of the rubber cured product and the durability of the fixing member. is there. Examples of the surface treatment agent include silane compounds, silazanes, polyorganosiloxanes, and the like, but silane compounds are particularly preferable in consideration of the surface treatment effect on zinc oxide used as the component (B). Examples of silane compounds include vinyltrichlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropylmethyldichlorosilane, 3-chloropropylmethyldiethoxysilane, and 3-chloropropylmethyldimethoxy. Silane, 3-chloropropyltriethoxysilane, 3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxy Silane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-mercap Propyltrimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, diphenylsilanediol, dimethyldichlorosilane And methyltrichlorosilane.

  Examples of silazane include hexamethyldisilazane and divinyltetramethyldisilazane.

  Moreover, as polyorganosiloxane, what is shown by the following general formula is illustrated, The polymerization degree is 100 or less, Preferably it is 50 or less.

RaSiO _{(4-a) / 2}
In the formula, R represents hydrogen and / or a monovalent substituted or unsubstituted hydrocarbon group. Examples of the monovalent substituted or unsubstituted hydrocarbon group include an alkenyl group such as a vinyl group, a methyl group, and an ethyl group. An unsubstituted hydrocarbon group such as an alkyl group such as a propyl group, a butyl group, a hexyl group or a dodecyl group, an aryl group such as a phenyl group, an aralkyl group such as a β-phenylethyl group or a β-phenylpropyl group, And substituted hydrocarbon groups such as chloromethyl group and 3,3,3-trifluoropropyl group. In general, a methyl group, a vinyl group, a phenyl group, and a 3,3,3-trifluoropropyl group are preferable. Moreover, a is a number from 0 to 3.0.

  These surface treatment agents may be used alone or in combination of two or more, depending on the required properties of the present composition, and are not particularly limited. Further, the addition amount of the surface treatment agent is preferably 0.1 to 10% by weight, more preferably 0.2 to 5% by weight, and most preferably 0. 5 to 3% by weight. When the amount is less than 0.1% by weight, the treatment is not sufficiently performed and the effect of the present invention is not seen. On the other hand, if it exceeds 10% by weight, other characteristics such as compression set are affected.

  As a method of treating zinc oxide used as component (B) with these surface treatment agents, (i) a method of mixing the surface treatment agents together when preparing the composition, or (ii) surface treatment in advance. There is a method of blending the applied component (B). (Ii) The surface treatment method is not particularly limited, but a surface treatment agent is added to zinc oxide prepared so as to satisfy the conditions of the present invention, and a normal stirring device such as a Henschel mixer is used. A method of processing is used. In any treatment method, treatment at normal temperature or treatment under heating may be used, but it is preferable to carry out the treatment at about 100 to 300 ° C. (Ii) is preferable from the viewpoint of effect, but can be selected as appropriate.

  In the present invention, the amount of the surface treatment as component (B) is 50 to 1000 parts by weight with respect to 100 parts by weight of (A) organopolysiloxane. If it is less than 50 parts by weight, the thermal conductivity is poor, and if it exceeds 1000 parts by weight, the strength decreases.

  The curing agent of component (C) is appropriately selected according to the reaction mechanism for obtaining a rubber elastic body. As the reaction mechanism, (1) a crosslinking method using an organic peroxide vulcanizing agent, (2) a method using an addition reaction, etc. are known, and depending on the reaction mechanism, (A) component and (C) component, that is, curing It is well known that the preferred combination with the catalyst or cross-linking agent as well as the amount of component (C) is determined.

  Hereinafter, (A) the organopolysiloxane and (C) the curing agent in each of the reaction mechanisms (1) to (2) will be described.

  First, in the case of applying the crosslinking method of (1), usually, as the organopolysiloxane of component (A), at least two of the organic groups bonded to silicon atoms in one molecule are vinyl, propenyl, Organopolysiloxanes that are alkenyl groups such as butenyl and hexenyl are used. Of these groups, a vinyl group is particularly preferred because of ease of synthesis and availability of raw materials. The curing agent for component (C) includes benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, cumyl-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxy. Various organic peroxide vulcanizing agents such as hexane and di-t-butyl peroxide are used and give particularly low compression set. Therefore, dicumyl peroxide, cumyl-t-butyl peroxide, 2,5-dimethyl- 2,5-Di-t-butylperoxyhexane and di-t-butylperoxide are preferred. These organic peroxide vulcanizing agents are used as one kind or a mixture of two or more kinds.

  The blending amount of the organic peroxide as the curing agent of the component (C) is preferably in the range of 0.05 to 15 parts by weight with respect to 100 parts by weight of the organopolysiloxane of the component (A). When the amount of the organic peroxide is less than 0.05 parts by weight, the vulcanization is not sufficiently performed, and when it exceeds 15 parts by weight, there is no particular effect, and the obtained conductive silicone rubber This is because physical properties may be adversely affected.

  As the organopolysiloxane of the component (A) when the addition reaction of (2) is applied, the same organopolysiloxane as used in the above (1) can be used. As the curing agent for component (C), platinum catalysts such as chloroplatinic acid, platinum olefin complexes, platinum vinylsiloxane complexes (including cyclic vinylsiloxanes), platinum black, and platinum triphenylphosphine complexes are used as curing catalysts. As the cross-linking agent, an organopolysiloxane having an average of at least two hydrogen atoms bonded to silicon atoms per molecule is used.

  Of the curing agent of component (C), the amount of the curing catalyst is preferably in the range of 1 to 1000 ppm in terms of platinum element with respect to 100 parts by weight of organopolysiloxane of component (A). If the amount of the curing catalyst is less than 1 ppm as the amount of platinum element, curing will not proceed sufficiently, and if it exceeds 1000 ppm, no improvement in the curing rate can be expected. The amount of the crosslinking agent is preferably such that the amount of hydrogen atoms bonded to silicon atoms in the crosslinking agent is 0.2 to 4.0 with respect to one alkenyl group in component (A), more preferably 0.5. It is the amount that becomes ~ 3.0 pieces. It is possible to adjust the hardness of the composition after curing with the amount of hydrogen atoms, and it is effective to reduce the amount of hydrogen atoms to less than 1.0 to reduce the hardness. When the number is less than 0.2, curing of the composition does not proceed sufficiently, and when the amount of hydrogen atoms exceeds 4.0, the physical properties and heat resistance of the cured composition are lowered.

  In addition, the composition of the present invention includes a heat resistance improver such as low molecular weight siloxane having a degree of polymerization of 100 or less, iron oxide, cerium oxide, iron octylate, platinum compound, iron oxide, azo compound, titanium oxide as necessary. Polyorganosilsesquioxane such as flame retardants, pigments, etc. may be blended, and saturated aliphatic hydrocarbons such as isoparaffin solvents for the purpose of imparting processability and moldability to the composition, and other ordinary silicone rubbers Other additives added to the composition can also be added.

  In recent years, a member called a fixing belt with a thin rubber elastic layer has become widespread, and in view of workability, a low-viscosity one tends to be preferred in order to make it thin. Is preferred, but is not particularly restricted.

  As a method for producing the composition of the present invention, blending and kneading may be performed by a conventionally used apparatus such as a kneader, a Banbury mixer, a mixing roll or the like.

  In addition, the silicone rubber composition of the present invention can be molded and cured by a usual method such as pressure molding, extrusion molding, injection molding, calendar molding, and the like to obtain a product.

  In particular, the silicone rubber composition of the present invention is useful as a silicone rubber roll material or a fixing member. The silicone rubber composition of the present invention is coated with a uniform on a roll core metal and cured as usual. Excellent fixing member can be obtained. Thick roll materials and thin fixing belts are examples of this.

  The silicone rubber composition of the present invention preferably has a viscosity of 5 to 1,000 Pas (23 ° C.), more preferably 10 to 700 Pas (23 ° C.), and most preferably 20 to 300 Pas (23 ° C.). It is. In addition, the silicone rubber composition of the present invention desirably has a cured product having a thermal conductivity of 0.6 W / m.K or more, preferably 0.8 W / m.K or more, and more preferably 1.0 W / m.K or more.

The silicone rubber composition of the present invention will be described in detail with reference to examples. In addition, the viscosity in an Example is the value measured in 23 degreeC, and a part is a weight part. In the examples, the silicone rubber composition was evaluated as follows.
Rubber sheet ・ Hardness JIS K 6249 Type A durometer ・ Heat dissipation (thermal conductivity) Rapid thermal conductivity meter made by Kyoto Electronics ・ Specific gravity JIS K 6249
・ Compression set JIS K 6249 180 ℃, 22 hours

Example 1
One part of vinyltriethoxysilane was added as a surface treatment agent to 100 parts of zinc oxide (1) obtained by calcining zinc hydroxide granulated by a wet method at 850 ° C. and uniformly dispersed using a Henschel mixer. Then, it heat-processed at 150 degreeC for 1 hour, and obtained the zinc oxide (processed powder) A. Next, 60 parts of dimethylpolyorganosiloxane (vinyl group content = 0.08 mmol / g) blocked with dimethylvinylsiloxy group blocked at both ends of a molecular chain having a viscosity of 3000 centipoise was blended in a kneading apparatus, and zinc oxide A was added thereto. 300 parts and 1 part of Fe3O4 are blended, heated and kneaded at 150 ° C for 2 hours, diluted with the remaining 40 parts of polyorganosiloxane, and further blocked with trimethylsiloxy groups at both ends of the molecular chain with a viscosity of 5 centipoise. 5 parts of dimethylsiloxane / methylhydrogensiloxane copolymer (silicon-bonded hydrogen atom content 3 mmol / g), 0.1 part of complex of chloroplatinic acid and divinyltetramethyldisiloxane and 0.1 part of 1-ethynyl-1-cyclohexanol Were uniformly mixed to prepare a silicone rubber composition of the present invention. The silicone rubber composition was cured in a mold at 150 ° C. for 10 minutes, and then heat treated in air at 200 ° C. for 4 hours to obtain a silicone rubber sheet. And evaluation of hardness, compression set, thermal conductivity, and specific gravity was performed. As an environmental stability test, the cured rubber was immersed in warm water at 50 ° C., and the weight increase rate from the initial stage was measured after aging (after 1 day and after 7 days).

  The results are as shown in Table 1.

Example 2
To 100 parts of zinc oxide (1), 1 part of dimethyldiethoxysilane is added as a surface treatment agent and dispersed uniformly using a Henschel mixer, followed by heat treatment at 150 ° C. for 1 hour. B) B was obtained.

  A silicone rubber composition was prepared and evaluated in the same manner as in Example 1 except that 300 parts of zinc oxide B was used instead of zinc oxide A.

Example 3
To 100 parts of zinc oxide (1), 1 part of hexamethyldisilazane is added as a surface treatment agent and dispersed uniformly using a Henschel mixer, followed by heat treatment at 150 ° C. for 1 hour. I got C).

  In Example 1, a silicone rubber composition was similarly prepared and evaluated except that 300 parts of zinc oxide C was used instead of zinc oxide A.

Comparative Example 1
In Example 1, a silicone rubber composition was similarly prepared and evaluated except that the surface treatment was not performed and zinc oxide (1) was blended.

Comparative Example 2
In Example 1, a silicone rubber composition was similarly prepared and evaluated except that 50 parts of pulverized quartz (CRYSTALITE VX-S manufactured by Tatsumori Industry Co., Ltd.) was used instead of zinc oxide (1).

Example 4
An addition type liquid silicone rubber primer was applied to the surface of an aluminum shaft having a diameter of 10 mm and a length of 300 mm. The silicone rubber composition of Example 1 was filled between a 40 μm fluorine PFA tube with an inner surface treated with a primer and an aluminum shaft, cured by heating at 120 ° C. for 30 minutes, and further post-cured at 200 ° C. for 4 hours. A PFA resin-coated silicone rubber roll having an outer shape of 16 mm and a length of 250 mm was obtained.

  When this fixing member was mounted on an electrophotographic copying machine and a continuous paper passing test was performed in an environment of 50 ° C. × RH 90%, 50,000 sheets could be continuously passed.

Comparative Example 3
In Example 4, when a sheet passing test of the fixing member was performed in the same manner except that the silicone rubber of Comparative Example 1 was used instead of the silicone rubber of Example 1, abnormal noise started to be generated at 8000 sheets and 10,000 sheets. The evaluation was stopped because it was difficult to pass through the sheets.

Claims (4)

(A) 100 parts by weight of an organopolysiloxane represented by the following general formula (1)
R ¹ _a SiO _{(4-a) / 2} (1)
(In the formula, R ¹ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and a is a positive number of 1.90 to 2.05.)
(B) Zinc hydroxide or zinc carbonate granulated by a wet process is calcined at a temperature of 600 to 1800 ° C. 50 to 1000 parts by weight of zinc oxide calcined at a temperature and previously surface-treated with a surface treatment agent
(C) A silicone rubber composition comprising a catalytic amount of a curing agent.   The silicone rubber composition according to claim 1, which has a viscosity of 5 to 1,000 Pas (23 ° C).   The silicone rubber composition according to claim 1 or 2, wherein the average particle diameter of zinc oxide is 1 to 50 µm.   A fixing member obtained by uniformly coating and curing the silicone rubber composition according to claim 1 on a roll mandrel.