JP2002296940A - Silicone rubber composition for heat fixing roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicone rubber composition which has a low thermal conductivity and a small variation in hardness, and is suitably used as a coating material for a fixing roll. SOLUTION: 100 parts by weight of a thermosetting silicone rubber composition is surface-treated with alkoxysilane or alkoxysiloxane, and the true density is 0.05 to 0.2 g /
A silicone rubber composition for a heat fixing roll, comprising 0.1 to 100 parts by weight of glass hollow microspheres having a cm ³ and a 90% residual pressure resistance of 1.5 × 10 ⁶ N / m ² or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone rubber composition used for forming a heat fixing roll of a heat fixing device in an electrostatic recording device such as an electrophotographic copying machine and a printer.

[0002]

Technical Background of the Invention and Problems Thereof Heat-curable liquid silicone rubber compositions have been used in various fields because of their excellent moldability, heat resistance and electrical insulation after molding. PP with excellent heat resistance and mold release properties
Widely used for fixing rolls such as C, LBP, and FAX. In such an apparatus utilizing an electrophotographic process, there is a method of fixing a toner image transferred from a photoreceptor surface to a copy paper to a copying machine. As a method of fixing the toner image, there is widely used a method in which a copy sheet is passed between a heated heater roll and a pressure roll which are rotating in pressure contact with each other, and the toner image on the copy sheet is thermally fused and fixed. Has been adopted. In this heat fusion method, generally, by increasing the thermal conductivity of the roll material, a copying machine or a printer having a high response can be obtained. With the trend toward cost reduction and cost reduction, on the contrary, there is a need for a material having low thermal conductivity, that is, good heat storage and leading to energy saving.

As such a material, there is a silicone rubber foam utilizing the low thermal conductivity of gas. However, be careful of the toxicity and odor of the decomposed gas, the explosiveness of hydrogen gas, and the handling during storage of the uncured material. In addition, there is a problem that it is difficult to obtain a silicone rubber foam having fine and uniform cells in the molding such as injection molding in which the foam is formed in a mold.

In order to solve this problem, Japanese Patent Laid-Open Publication No. 2000-2000
According to Japanese Patent Application Publication No. -143986, the thermal conductivity is 5 × 10 ⁻⁴ cal.
In order to attain a temperature of / cm · sec · ° C. or lower, a method has been proposed in which various hollow fillers are independently used, regardless of whether they are organic or inorganic. However, with the organic hollow filler, there is a problem that the thermal conductivity and hardness of the molded product greatly vary depending on the molding conditions, and with the inorganic hollow filler, a sufficient thermal conductivity may not be achieved.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has a low thermal conductivity and a small variation in its hardness, and is preferably used as a coating material for a fixing roll. It is intended to provide a rubber composition.

[0006]

The present inventors have made intensive studies to achieve the above object, and as a result, as a filler to be blended, a glass having a specific true density and a 90% residual compressive strength subjected to surface treatment with alkoxysilane or alkoxysiloxane. It has been found that the use of hollow microspheres made of aluminum is extremely effective, and the present invention has been completed.

That is, according to the present invention, 100 parts by weight of a thermosetting silicone rubber composition is subjected to a surface treatment with an alkoxysilane or an alkoxysiloxane to have a true density of 0.0
5-0.2 g / cm ³ , 90% residual pressure resistance 1.5 ×
Glass hollow microspheres of 10 ⁶ N / m ² or more 0.1-100
A silicone rubber composition for a heat-fixing roll, characterized in that it is blended in parts by weight.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The hollow filler used in the present invention is a true density of 0.05 to 0.2 g / cm ³ , a 90% residual pressure resistance of 1.5 × 10 ⁶ N / m, which has been surface-treated with alkoxysilane or alkoxysiloxane. ^Two or more glass hollow microspheres. True density of 0.05 g / cm ³ less than the readily easily separated, also can not achieve the 0.2 g / cm ³ greater than the sufficient thermal conductivity. On the other hand, if the 90% residual pressure resistance is smaller than 1.5 × 10 ⁶ N / m ² , the outer shell is broken by the pressure during molding, and a sufficient thermal conductivity cannot be achieved.

Further, the average particle size of the glass hollow microspheres is 200 μm or less, preferably 150 μm or less, more preferably 120 μm or less. If the average particle size is too large, the hollow filler is broken by injection pressure during molding. This causes problems such as an increase in thermal conductivity and an increase in surface roughness after roll forming. Although the lower limit of the average particle diameter of the hollow filler is not particularly limited, it is usually 10 μm, particularly 20 μm. Here, the average particle diameter can be usually determined as a weight average value (or median diameter) by a laser light diffraction method.

Further, by treating the surface of the hollow microspheres with alkoxysilane or alkoxysiloxane, the separation of the filler can be suppressed, and the workability and compression set characteristics of the composite material can be improved. Examples of such alkoxysilanes include trimethylsilanol, trimethylmethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, tetramethoxysilane, triethylsilanol, trimethylethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane, tetraethoxysilane, phenyl Dimethylsilanol, phenyldimethylmethoxysilane, phenylmethyldimethoxysilane, phenyltrimethoxysilane, phenyldimethylethoxysilane, phenylmethyldiethoxysilane, phenyltriethoxysilane, diphenylmethylsilanol, diphenylmethylethoxysilane, triphenylsilanol, triphenylmethoxy Silane, triphenylethoxysilane, vinyldimethylsilanol, (α-na Chill) Although dimethyl silanol, and the like, from the compatibility with the silicone polymer, methyltrimethoxysilane, methyltriethoxysilane, tetramethoxysilane, tetraethoxysilane is preferred. Alkoxysiloxane is a polymer of alkoxysilane.

As a method of this surface treatment, a method in which 0.1 to 20 parts by weight of a treating agent is sprayed on 100 parts by weight of hollow microspheres in advance and then treated at a temperature of 100 ° C. to 200 ° C. Any method may be used, such as a method in which hollow microspheres and a treating agent are added, and the mixture is heated and kneaded at a temperature of 100 ° C to 200 ° C.

The amount of the hollow microspheres made of glass is 0.1 to 100 parts by weight, preferably 0.1 to 30 parts by weight, per 100 parts by weight of the thermosetting organopolysiloxane composition.
Parts by weight, more preferably 0.1 to 20 parts by weight. If the amount is too small, the thermal conductivity is 4 × 10 ⁻⁴ cal / cm.
If the amount is not less than sec · ° C. and the amount is too large, there is a disadvantage that the rubber strength of the cured product is weakened and the durability as a roll molded product is deteriorated.

In the present invention, more preferably, the glass hollow microspheres (0.1 to 1) obtained by subjecting the above composition (100 parts by weight of a thermosetting silicone rubber composition to surface treatment with alkoxysilane or alkoxysiloxane) are used.
(A composition containing 100 parts by weight) and a true density of 0.3.
It is a composition containing 0.01 to 0.1 parts by weight of hollow microspheres made of thermoplastic resin of 01 to 0.1 g / cm ³ . By adding a small amount of hollow microspheres made of a thermoplastic resin in this manner, the pressure applied during molding can be suppressed, and stable thermal conductivity and hardness can be obtained. When the true density of the organic hollow microspheres made of a thermoplastic resin is 0.01 g / cm ³ or less, the organic hollow microspheres are easily separated like the hollow microspheres made of glass. 0.1 g / cm
^{If it is} larger than ³ , the thermal conductivity and hardness of the molded product will vary. The blending amount of the hollow microspheres made of a thermoplastic resin is 0.01 to 10 parts by weight based on 100 parts by weight of the thermosetting silicone rubber composition. If the amount is too small, the above effects cannot be obtained. If the amount is too large, the hardness may vary.

The silicone rubber composition for a heat fixing roll of the present invention has a cured product (silicone rubber) having a thermal conductivity of 4
× 10 ⁻⁴ cal / cm · sec · ° C. or less, usually 0.5
× 10 ⁻⁴ cal / cm · sec · ° C. to 4.0 × 10 ⁻⁴ c
al / cm · sec · ° C., especially 1.5 × 10 ⁻⁴ cal
/ Cm · sec · ° C to 3.5 × 10 ^-4 cal / cm · s
It is preferably ec · ° C. Thermal conductivity 4.0 × 1
If it is higher than 0 ^-4 cal / cm · sec · ° C., the object of the present invention cannot be achieved.

Next, the thermosetting silicone rubber composition according to the present invention has a viscosity before curing of 1 to 1,000,000.
liquid thermosetting silicone which is cP, preferably 500-500,000 cP. The curing mechanism may be either an addition reaction curing type or an organic peroxide curing type.

More specifically, it is not particularly limited as long as it is a generally used heat-curable silicone rubber, and comprises a polyorganosiloxane as a base polymer, silica powder, additives, a curing agent, and the like. Silica powder and additives need not be contained.

The polyorganosiloxane of the base polymer is an average unit formula: R1aSiO (4-a) / 2 (wherein R1 is a substituted or unsubstituted monovalent hydrocarbon group, and a is in the range of 1.98 to 2.02) , Which are mainly linear, but may be partially branched or form a three-dimensional structure, and may be a homopolymer, a copolymer or a homopolymer or a copolymer thereof. May be used.

The substituted or unsubstituted monovalent hydrocarbon group bonded to the silicon atom of the polyorganosiloxane includes, for example, an alkyl group such as a methyl group, an ethyl group and a propyl group; a vinyl group, an allyl group and a butadienyl group. An unsubstituted hydrocarbon group such as an alkenyl group such as phenyl group; a cycloalkenyl group such as phenyl group, xenyl group and naphthyl group; an arylaryl group such as benzyl group; an alkylaryl group such as tolyl group and xylyl group. And substituted hydrocarbon groups such as chloromethyl group and 3,3,3-trifluoropropyl group.

As the monovalent hydrocarbon group bonded to the silicon atom, a methyl group is mainly used, and from the viewpoint of heat resistance and workability, it is preferable that 93 mol% or more is a methyl group. Further, as a cross-linking group, it is preferable to have a vinyl group, and from the viewpoint of mechanical strength and cross-linking property, it may be contained in an amount of 0.001 to 5% with respect to the total number of organic groups, particularly preferably 0.1 to 5%.
The range of 02 to 2% is preferred.

The molecular chain terminal of the polyorganosiloxane is exemplified by a hydroxyl group, an alkoxy group or a triorganosilyl group, and a triorganosilyl group is more preferable. Examples of the triorganosilyl group include a trimethylsilyl group, a dimethylvinylsilyl group, a methylphenylvinylsilyl group, and a methyldiphenylsilyl group.

The average degree of polymerization of the polyorganosiloxane ranges from 1,000 to 20,000, preferably from 3,000 to 1,500.
0, particularly preferably 5000 to 10,000. If the degree of polymerization is too small, it is difficult to obtain a sufficient mechanical strength, while if it is too large, it is difficult to mix the compound into the system.

The silica powder should not be blended when it is desired to obtain a rubber cured product having a low hardness, but may be used when high strength is required. In the present invention, known materials such as fumed silica, wet silica, and calcined silica generally used for compounding silicone rubber and the like are used, but are not particularly limited. These finely divided silica-based fillers may be used as they are,
Those surface-treated with silane, polyorganosiloxane, hexaorganodisilazane or the like may be used, or they may be reacted with these treating agents in-process.

The amount of the silica powder is not particularly limited, but in order to improve the strength and processability, about 1 to 200 parts by weight, preferably about 1 to 200 parts by weight, per 100 parts by weight of the polyorganosiloxane. About 5 to 60 parts by weight is preferable.

The curing agent is appropriately selected according to the reaction mechanism for obtaining the rubber elastic body. As the reaction mechanism, a crosslinking method with an organic peroxide vulcanizing agent and a method by an addition reaction are known, and it is well known that a preferable combination with a curing catalyst or a crosslinking agent is determined by the reaction mechanism. is there. In the case of a crosslinking method using an organic peroxide, the curing catalyst may be benzoyl peroxide, dicumyl peroxide, cumyl-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, di- Various organic peroxide vulcanizing agents such as t-butyl peroxide and the like are used. In particular, dicumyl peroxide, cumyl-t-butyl peroxide, 2,5-dimethyl-2,5- Di-t-butylperoxyhexane and di-t-butyl peroxide are preferred. In addition, these organic peroxide vulcanizing agents are used as one kind or as a mixture of two or more kinds.

The amount of the organic peroxide is 0.05 to 15 parts by weight based on 100 parts by weight of the polyorganosiloxane base polymer.
A range of parts by weight is preferred. The amount of the organic peroxide is 0.
If the amount is less than 05 parts by weight, the vulcanization is not sufficiently performed, and if the amount exceeds 15 parts by weight, not only there is no special effect but also the physical properties of the obtained silicone rubber molded article may be adversely affected. Because there is.

When the addition reaction is applied, a platinum catalyst such as chloroplatinic acid for curing, a platinum olefin complex, a platinum vinyl siloxane complex, platinum carbon, a platinum triphenylphosphine complex or the like is used as a curing agent. As the agent, an organopolysiloxane having at least two hydrogen atoms bonded to silicon atoms per molecule on average is used. Among the curing agents, the compounding amount of the curing catalyst is preferably in the range of 1 to 1000 ppm in terms of platinum atomic weight based on 100 parts by weight of the polyorganosiloxane base polymer. The amount of the curing catalyst is 1 ppm as platinum atom.
If it is less than 10%, curing will not proceed sufficiently, and if it exceeds 1000 ppm, particularly improvement of the curing speed cannot be expected.

The amount of the crosslinking agent is such that the hydrogen atom bonded to the silicon atom in the crosslinking agent is 0.5 to 4.0 with respect to the alkenyl group in the polyorganosiloxane base polymer.
Is preferable, and more preferably 1.0 to
The quantity is 3.0. If the amount of hydrogen atoms is less than 0.5, curing in the composition does not proceed sufficiently,
The hardness of the cured composition decreases, and the amount of hydrogen atoms decreases.
If it exceeds 4.0, the physical properties and heat resistance of the composition after curing are reduced.

The composition of the present invention contains, in addition to the above components, ground quartz,
Silica-based filler such as diatomaceous earth, dimethyl silicone oil for low hardness, processing aid for improving workability, various additives such as titanium oxide, iron oxide, cerium oxide, vanadium oxide, chromium oxide, etc. Metal oxides,
A pigment, a heat-resistant agent, a flame-retardant-imparting agent and the like can be added as long as the properties of the composition of the present invention are not impaired.

[0029]

EXAMPLES The present invention will be described more specifically with reference to the following examples. In the following examples, parts show parts by weight. Example 1 25 ° C., both ends closed with a dimethylvinylsilyl group
100 parts of polydimethylsiloxane having a viscosity of 5,000 cP in 100 parts by weight, glass hollow microspheres (glass bubbles K15: true density: 0.15 g / cm ³ , 90% residual pressure resistance: 2.1 × 10 ⁶ N / m ² , average) Particle size 100 μm: 11 parts by Sumitomo 3M), 1 part of methyltriethoxysilane,
Iron oxide (SR550: Tone Sangyo Co., Ltd.) as a heat-resistant additive
Was placed in a two-part planetary mixer and stirred at 130 ° C. Thereafter, stirring was continued while cooling to room temperature, and then 6.9 methyl hydrogen polysiloxane having Si-H groups at both terminals and side chains was further used as a crosslinking agent.
Part, ethynylcyclohexanol 0.1 as a reaction inhibitor.
1 part was added, and stirring was continued for 15 minutes, and 0.1 part of a platinum solution (Pt concentration: 1%) was mixed with the completed silicone rubber composition, and pressurized at 120 ° C. for 10 minutes to obtain a 2 mm or 6 mm thick film. A sheet was obtained, the specific gravity and hardness (JIS E) were measured from a 2 mm sheet, and the thermal conductivity and compression set were measured from a 6 mm sheet. Further, the viscosity of the silicone rubber composition before curing was measured. Further, the degree of separation of the filler was examined.

Regarding the hardness (JIS E),
The measurement was carried out three times at each end, and the respective average values were determined. The thermal conductivity was determined using a rapid thermal conductivity meter (QTM-500, manufactured by Kyoto Electronics Industry Co., Ltd.). For the compression set, see JIS K 6249.
Was determined based on Example 2 0.5 parts of a thermoplastic resin hollow microsphere (Matsumoto Microsphere F-80ED: manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) having a true density of 0.02 g / cm ³ was further added to the composition of Example 1. A sheet was obtained and evaluated in the same manner as in Example 1 except that the blended composition was used. Comparative Example 1 A sheet was obtained and evaluated in the same manner as in Example 1 except that one part of the treatment agent methyltriethoxysilane was not added and mixing was performed at room temperature. Comparative Example 2 Example 1 was repeated except that glass hollow microspheres of Cellstar Z-36 (true density: 0.35 g / cm ³ , average particle diameter: 56 μm: manufactured by Tokai Kogyo KK) were used as glass hollow microspheres. A sheet was obtained and evaluated in the same manner as described above. Comparative Example 3 Instead of the glass hollow microspheres, the thermoplastic resin hollow microspheres having a true density of 0.02 g / cm ³ used in Example 2 were used.
A sheet was obtained and evaluated in the same manner as in Example 1 except that one part of the composition was used. Comparative Example 4 A sheet was obtained and evaluated in the same manner as in Example 1 except that the mixture was not mixed with glass hollow microspheres but mixed at room temperature.

The results are shown in Table 1.

[0032]

[Table 1]

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat (reference) C08L 101: 00) F term (reference) 2H033 BB02 BB06 BB08 3J103 AA02 AA12 AA85 FA18 GA57 GA58 HA03 HA47 HA60 4J002 AA012 CP031 CP081 CP131 CP141 DL006 FA102 FA106 FB096 FB106 FB266 FD010 FD140 FD150 GM00

Claims (2)

[Claims] 1. A 100% by weight of a thermosetting silicone rubber composition is surface-treated with an alkoxysilane or an alkoxysiloxane, and has a true density of 0.05 to 0.2 g /
A silicone rubber composition for a heat fixing roll, comprising 0.1 to 100 parts by weight of glass hollow microspheres having a cm ³ and a 90% residual pressure resistance of 1.5 × 10 ⁶ N / m ² or more. object. 2. A true density obtained by subjecting 100 parts by weight of a thermosetting silicone rubber composition to surface treatment with alkoxysilane or alkoxysiloxane, and having a true density of 0.05 to 0.2 g /
cm ^3, 90% residual pressure resistance true density and 0.1 parts by weight 1.5 × 10 ⁶ N / m ² or more glass hollow microspheres thermoplastic 0.01 to 0.1 g / cm ³ A silicone rubber composition for a heat fixing roll, comprising 0.01 to 10 parts by weight of resin hollow microspheres.