JPH09169907A - Semiconductive heat-shrinkable silicone rubber composition and rubber tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductive heat-shrinkable silicone rubber tube small in variation in the volume resistivity over semiconductive area without impairing the characteristics such as heat resistance, cold resistance, weatherability, etc., inherent in silicone rubber. SOLUTION: This silicone rubber composition essentially comprises (A) 100 pts.wt. of an organopolysiloxane of the formula R<1> n SiO(4-n)/2 (R<1> is a same or different kind of (substituted) monovalent hydrocarbon group; (n) is 1.9-2.1 on average), (B) 5-80 pts.wt. of an organopolysiloxane 50-200 deg.C in softening temperature, (C) 10-150 pts.wt. of spherical silicone elastomer particles 0.1-100μm in average diameter, (D) such an amount of an electroconductive material as to provide the composition with a volume resistivity of 10<3> -10<10> Ω.cm, and (E) such an amount of a curing agent as to be effective for the composition to be cured. The other objective tube is obtained by use of the composition. Various kinds of rolls for conventional copiers have been shaped normally by pressure molding, etc.; the rubber tube of the present invention is made of a heat- shrinkable rubber and therefore can be directly covered on a core metal, leading to roll molding process simplification and being hopeful of roll manufacturing cost reduction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various rolls such as toner transport rolls, developing rolls, charging rolls, transfer rolls, fixing rolls and various electric and electronic devices used in printers such as office automation equipment and copying machines. The present invention relates to a semiconductive heat-shrinkable silicone rubber composition and a semiconductive silicone heat-shrinkable rubber tube suitable for obtaining a semiconductive silicone heat-shrinkable rubber tube used as a coating for antistatic measures.

[0002]

2. Description of the Related Art Silicone rubber is widely used as various electrical insulating parts because of its excellent heat resistance and electrical insulation. In addition, a conductive substance such as carbon black, graphite, various metal powders such as silver, nickel, and copper is added to these to reduce the volume resistivity to about 10 ¹⁰ to 10 ⁻³ Ω · cm, and the conductive silicone It has been put to practical use as rubber.

However, a conductive silicone rubber is obtained.
If Ketjen Black and acetyl
Highly filled with conductive carbon black such as Renblack
Several Ω · cm to several tens With volume resistivity in the range of Ω · cm
The ones made are relatively stable in such a resistivity range,
10^Three-10^TenIn the semi-conductive region of Ω · cm,
The variation is extremely large and it is difficult to stabilize the resistivity.
It was difficult. This is the dispersion of carbon depending on the molding conditions.
It is considered that this is due to a significant change in.

In particular, when a heat-shrinking agent having a predetermined softening point is added to such a semi-conductive silicone rubber composition to impart heat-shrinkability, it becomes more difficult to control the semi-conductive region.

[0005] The present invention has been made in view of the above circumstances,
A semi-conductive silicone heat-shrinkable rubber tube capable of forming a stable volume resistivity in a semi-conductive region (10 ³ to 10 ¹⁰ Ω · cm) without deteriorating the inherent properties of silicone rubber such as heat resistance. An object of the present invention is to provide a conductive heat-shrinkable silicone rubber composition and a semi-conductive silicone heat-shrinkable rubber tube obtained from this silicone rubber composition.

[0006]

Means for Solving the Problems and Modes for Carrying Out the Invention As a result of intensive studies for achieving the above-mentioned object, the present inventor has found that the semiconductive materials containing the following components (A) to (E) as essential components. Mold the heat-shrinkable silicone rubber composition into a tube shape,
By stretching, it is possible to obtain a semi-conductive silicone heat-shrinkable rubber tube with little variation in the resistivity in the semi-conductive region without deteriorating the inherent heat resistance, cold resistance, weather resistance, etc. of the silicone rubber. , This rubber tube can be directly coated by heating the roll core of charging rolls, developing rolls, transfer rolls, etc. of dry copiers, etc., and various conventional rolls can be pressure-molded with non-heat-shrinkable compounds. As a result, they have found that the process of manufacturing various rolls can be simplified as compared with a shaped product, and have completed the present invention.

Accordingly, the present invention provides (A) the following average composition formula (1) R ¹ _n SiO _{(4-n) / 2} (1) (wherein R ¹ is the same or different, unsubstituted or substituted) Which is a monovalent hydrocarbon group, and n is an average number of 1.9 to 2.1): 100 parts by weight (B) Organopolysiloxane having a softening temperature of 50 to 200 ° C. Siloxane resin: 5 to 80 parts by weight (C) Spherical silicone elastomer particles having an average particle diameter of 0.1 to 100 μm: 10 to 150 parts by weight (D) Conductive material: 10 ³ to 10 ¹⁰ Ω · cm volume resistivity (E) Curing agent: A semi-conductive heat-shrinkable silicone rubber composition, which comprises a curing effective amount as an essential component, and a semi-conductive layer obtained by tube-forming and stretching the silicone rubber composition. Heat resistant silicone heat shrinkable rubber tube Offer.

The present invention will be described in more detail below. The organopolysiloxane (A) constituting the semiconductive heat-shrinkable silicone rubber composition of the present invention is represented by the following average composition formula (1). Is.

R ¹ _n SiO _{(4-n) / 2} (1) (wherein R ¹ is the same or different and is unsubstituted or substituted 1
A valent hydrocarbon group is shown, and n is an average number of 1.9 to 2.1. )

In the above formula, R ¹ is the same or different and is unsubstituted or substituted, preferably 1 to 10 carbon atoms, more preferably 1 carbon atom.
To 8 monovalent hydrocarbon groups, for example, alkyl groups such as methyl group, ethyl group, propyl group and butyl group, cycloalkyl groups such as cyclohexyl group, alkenyl groups such as vinyl group, allyl group, butenyl group and hexenyl group. Groups, phenyl groups, aryl groups such as tolyl groups, or 3,3,3-trifluoropropyl groups in which some or all of the hydrogen atoms bonded to carbon atoms of these groups are substituted with halogen atoms, cyano groups, etc. , 2-cyanoethyl group and the like. It is preferable that 0.001 to 15 mol%, more preferably 0.01 to 5 mol% of R ¹ is an alkenyl group, particularly a vinyl group. Also, n is a positive number of 1.9 to 2.1.

The organopolysiloxane represented by the above formula (1) is preferably one in which the molecular chain terminal is blocked with a trimethylsilyl group, a dimethylvinyl group, a dimethylhydroxysilyl group, a trivinylsilyl group or the like.
Further, it is basically preferable to be linear, but it may be one kind or a mixture of two or more kinds having different molecular structures.

When the addition reaction cross-linking is carried out by the combination of the organohydrogenpolysiloxane of the component (E) and the platinum catalyst, which will be described later, the organopolysiloxane of the above formula (1) has at least two alkenyl groups. There is a need.

The organopolysiloxane represented by the above formula (1) has an average degree of polymerization of 100 to 30,000, preferably 3,000 to 10,000, and a viscosity at 25 ° C. of 100 cs (centistokes) or more, particularly 100,000 to. It is preferably 10,000,000 cs.

The organopolysiloxane resin having a softening temperature of the component (B) in the range of 50 to 200 ° C. is a component which imparts heat shrinkability, and when the softening temperature is lower than 50 ° C., it is stretched (expanded) and then shaped over time. However, a dimensional change occurs, while a temperature higher than 200 ° C. requires a high temperature to shrink and is not practical. The preferred softening temperature range is 60 to 1
80 ° C.

The structure of such an organopolysiloxane is not particularly limited as long as the softening temperature is within the above range, but those having a main structure of R ¹ SiO _1.5 units are preferable, and further R ¹ ₂ SiO units, R ¹ ₃ SiO _0.5 unit, S
iO ₂ units may be contained (provided that R ¹ has the same meaning as above), and specifically, C ₆ H ₅ SiO _1.5 units, CH ₃ S
iO _1.5 unit, (CH ₃ ) ₂ SiO unit, (CH ₃ ) (CH
₂ = CH) SiO units are preferable,
It can be obtained by co-hydrolyzing and condensing various silanol monomers and chlorosilane at a desired mixing ratio.

The blending amount of the component (B) is 5 to 80 parts with respect to 100 parts of the component (A) (parts by weight, the same applies hereinafter).
It should preferably be in the range of 10 to 60 parts. If the blending amount is less than this range, heat shrinkability cannot be imparted, while if it is too large, the physical properties of the molded article as a rubber elastic body deteriorate. In addition, when the component (B) is mixed with the component (A), it is preferably performed at a temperature equal to or higher than the softening point of the component (B).

The spherical silicone elastomer particles as the component (C) are added for the purpose of improving the moldability of the heat-shrinkable silicone rubber composition, improving the elasticity after molding and curing, and stabilizing the resistivity. .

As the spherical silicone elastomer particles, those having an average particle diameter of 0.1 to 100 μm, preferably 0.5 to 40 μm are used. Particles having an average particle size of less than 0.1 μm are difficult to manufacture, and it is difficult to sufficiently obtain the effect of addition, and if it exceeds 100 μm, the mechanical strength of the rubber cured product may be impaired.

In this case, the spherical silicone elastomer particles are not particularly limited in kind, grade, production method and the like as long as they are a cured product of an organopolysiloxane having the above-mentioned average particle diameter, and suitable ones can be used. In particular,
As the spherical silicone elastomer particles, although not particularly limited, a method of curing a curable organosiloxane composition in a spray dryer at 230 to 300 ° C to obtain a granular silicone elastomer (Japanese Patent Laid-Open No. 59-96122) Or a curable organopolysiloxane composition, for example, an addition-reaction-type organopolysiloxane composition comprising a vinyl-containing organopolysiloxane and an organohydrogenpolysiloxane, wherein the emulsion particles are dispersed in water using a surfactant. Diameter 20
μm or less, adding a platinum-based catalyst for an addition reaction, and curing the organopolysiloxane contained in the emulsion particles before spray drying or by the end of spray drying (Japanese Patent Application Laid-Open No. Sho 62).
No. 257939) and the like can be used. In particular, vinyl group-containing organopolysiloxane and organohydrogenpolysiloxane are made into an emulsion by using a surfactant, and an addition reaction is carried out with a platinum-based catalyst. Those cured and manufactured are preferable. As the elastomer particles, those whose surface is treated with silane, siloxane or the like in advance or during the production thereof can be used.

The amount of the spherical silicone elastomer particles of the component (C) used is 10 to 1 with respect to 100 parts of the component (A).
It is preferably 50 parts, especially 20 to 120 parts.
If the blending amount of the component (C) is less than the above proportion, the effect of addition cannot be obtained, and if it exceeds the above proportion, the mechanical strength of the cured product decreases.

As the conductive material of the component (D), it is preferable to use one of conductive carbon black, conductive zinc white, and conductive titanium oxide, either alone or in combination of two or more. The addition amount of the component (D) varies depending on the conductive material, but the volume resistivity after curing of the composition of the present invention is 10 ³ to.
It is selected to be 10 ¹⁰ Ω · cm.

As the conductive carbon black, those commonly used in conductive rubber compositions can be used. For example, acetylene black, conductive furnace black (CF), super conductive furnace black (SCF), extra. Conductive furnace black (XCF), conductive channel black (CC), furnace black and channel black heat-treated at a high temperature of about 1500 ° C. can be mentioned.

Specific examples of acetylene black include electrified acetylene black (manufactured by Denki Kagaku), Shaunigan acetylene black (manufactured by Shawnigan Chemical), and the like.
Conductive furnace blacks include Continex CF (manufactured by Continental Carbon Co., Ltd.) and Vulcan C (manufactured by Cabot Co.), and super conductive furnace blacks include Continex SCF (manufactured by Continental Carbon Co.) and Vulcan SC (manufactured by Cabot Co.). Examples of the extra conductive furnace black include Asahi HS-500 (manufactured by Asahi Carbon Co., Ltd.) and Vulcan XC-72 (manufactured by Cabot Co.), and examples of the conductive channel black include Kolux L (manufactured by Degussa). , Furnace Black 1
It is also possible to use Ketjen Black EC and Ketjen Black EC-600JD (Ketjen Black International) as seeds. Among these, acetylene black is excellent in conductivity because it has a low content of impurities and has a developed secondary structure structure, and is particularly preferably used in the present invention. In addition, Ketjen Black EC, Ketjen Black EC-600JD, and the like, which exhibit excellent conductivity even at a low filling amount due to their excellent specific surface area, can be preferably used.

The amount of the conductive carbon black as the component (D) added is such that the organopolysiloxane 10 as the component (A) is added.
It is preferably 1 to 50 parts, especially 5 to 20 parts, relative to 0 parts. If the addition amount is less than 1 part, desired conductivity may not be obtained, and if it exceeds 50 parts, the volume resistivity of the obtained member may be 1 × 10 ² Ω · cm or less. May not be a semi-conductive region.

Further, as the conductive zinc white, specifically, a conductive zinc white manufactured by Honjo Chemical Co., Ltd. is preferably used, and by adding 50 to 300 parts, especially 80 to 250 parts thereof, 1 A volume resistivity of × 10 ⁵ to 1 × 10 ¹⁰ Ω · cm can be obtained. If the amount added is less than 50 parts, the electrical conductivity cannot be obtained, while if it exceeds 300 parts, the mechanical properties may be significantly deteriorated. Therefore, the amount added is more preferably 100 to 250 parts.

Further, examples of the white conductive titanium oxide include ET-500W (manufactured by Ishihara Sangyo Co., Ltd.). In this case, the basic composition is TiO ₂ · SnO ₂
Preferably, b is doped. In addition, the addition amount is the same as the addition amount of the above-described conductive zinc white.

The curing agent as the component (E) is not particularly limited in its curing mechanism as long as it can be vulcanized and cured by utilizing an addition reaction or a radical reaction which is usually used for vulcanization of conductive silicone rubber. However, in the case of the semi-conductive silicone heat-shrinkable rubber tube of the present invention, the fully-blended heat-shrinkable silicone rubber composition is extrusion-molded and usually HAV vulcanized (Ho.
t Air Vulcanization: hot air vulcanization), that is, vulcanization and curing with normal pressure hot air. From such a point, when carbon black or the like is used as the conductive material, a usual silicone rubber composition is used. Since the acyl-based organic peroxide used in 1) accompanies the phenomena of foaming and unvulcanization, a non-acyl-based organic peroxide or an addition reaction curing agent is preferable, and an addition reaction curing agent is particularly preferable. Examples of the addition reaction curing agent include an organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to silicon atoms in one molecule, and a platinum catalyst. In this case, the amount of the organohydrogenpolysiloxane used is such that the molar ratio of the alkenyl group bonded to the silicon atom of the organopolysiloxane (A) and the SiH group (SiH
/ Si-alkenyl group) is 0.5 to 5, and the amount of the platinum-based catalyst used is 0.1 to 2000 pp with respect to the component (A).
m is preferable. Also 2,5-dimethyl-2,
It is also possible to add an alkyl peroxide such as 5-di (t-butylperoxy) hexane and an organic peroxide such as aralkyl peroxide such as dicumyl peroxide to the addition reaction curing system to accelerate vulcanization. . Further, when the organic peroxide is used alone, the organopolysiloxane 10 as the component (A) is used.
0.1 to 10 parts is preferable to 0 part. As the organohydrogenpolysiloxane and the platinum-based catalyst, known ones can be used.

The heat-shrinkable silicone rubber composition contains
Reinforcing silica fillers such as silica hydrogel (hydrous silicic acid), silica aerogel (silicic anhydride-fumed silica), clay, calcium carbonate, diatomaceous earth, titanium dioxide, and other fillers, low-molecular-weight siloxane ester, if necessary. A silanol, a dispersant such as diphenylsilanediol,
A heat resistance improver such as iron oxide, cerium oxide or iron octylate, various carbon functional silanes for improving adhesiveness and molding processability, a platinum compound for imparting flame retardancy and the like may be added and mixed.

The semiconductive heat-shrinkable silicone rubber composition of the present invention can be obtained by mixing these components, and the mixing method is generally roll, kneader, Banbury mixer (internal mixer) or the like. The mixer used may be used. When mixing,
In order to disperse the component (B) uniformly, it is preferable to knead at a temperature not lower than the softening temperature of the component (B).

The semiconductive heat-shrinkable silicone rubber composition thus obtained is extruded, for example, into a tube shape by an extruder, vulcanized through a hot air oven (vulcanization tower) at a temperature of 100 ° C. or higher, and formed into a tube shape. A vulcanized product molding can be obtained.
Further, as the molding method, not only the extrusion-HAV vulcanization described above but also a tube-shaped vulcanization molded article may be formed by compression molding, injection molding or the like.

By heating these tubular vulcanized molded products to a temperature not lower than the softening temperature of the component (B) in the composition, stretching (expanding) with air or a jig, and cooling in that state. A semi-conductive silicone heat-shrinkable rubber tube can be obtained. When this is coated on a roll core metal or the like, the rubber tube shrinks by heating and the coating can be easily performed. Moreover, you may make it adhere | attach using a conductive adhesive as needed.

When the semi-conductive silicone heat-shrinkable rubber tube thus obtained is coated on a roll core,
The volume resistivity between the surface and the core metal is 1 × 10 ³ to 1 × 10.
^It can be in the range of ¹⁰ Ω · cm, and the variation in volume resistivity within the roll is within one digit, so it is suitable for various rolls (copier rolls, developing rolls, charging rolls, transfer rolls) of copying machines. is there.

[0033]

EXAMPLES The present invention will be described below in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. All parts in each example are parts by weight.

[Examples 1 and 2] 99.85 mol% of dimethylsiloxane units and 0.1 of methylvinylsiloxane units.
100 parts of 5 mol% of methylvinylpolysiloxane having an average degree of polymerization of about 8000 blocked with dimethylvinylsilyl groups, 20 parts of treated silica R-972 (manufactured by Nippon Aerosil Co., Ltd.), organopolysiloxane resin [composition: C ₆ H ₅ SiO _1.5 unit 30 mol%, CH ₃ SiO _1.5
65 mol% unit, (CH ₃ ) ₂ SiO unit 4 mol%, (C
_{H 3) (CH 2 = CH} ) SiO units 1 mol%, the softening temperature 1
20 to 20 parts by heating with a kneader, and after cooling, spherical silicone elastomer particles KMP-594
(Particle size: 3 to 10 μm, manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed in an amount shown in Table 1, and acetylene black was further added and kneaded.

Further, 2.0 parts of methyl hydrogen polysiloxane represented by the following formula (A) (wherein Me represents a methyl group) as a curing agent and an isopropanol solution of chloroplatinic acid (platinum concentration 1%): Mix 1 part, about 1.0
A sheet having a thickness of mm was taken out and heated in a hot air dryer at 200 ° C. for 15 minutes to obtain a vulcanized sheet.

With respect to the obtained vulcanized sheet, hardness, elongation,
The tensile strength and volume resistivity were measured, and the stretch retention and heat shrinkage were measured according to the following methods. Table 1 shows the results.

[0037]

Embedded image

[Examples 3 and 4] Instead of acetylene black, conductive zinc white (manufactured by Honjo Chemical Co., Ltd.) or white conductive titanium oxide ET-500W (manufactured by Ishihara Sangyo Co., Ltd.)
Was added at the ratio shown in Table 1, and otherwise the vulcanized sheet was obtained in the same manner as in Example 1 and its properties were evaluated. Table 1 shows the results.

<Measurement Method of Stretch Retention and Heat Shrinkage>
The test pieces were separated by punching with JIS No. 2 dumbbells. A straight line (marked line) with a length of 2 cm at the center of each test piece
Was heated in an oven at 200 ° C. for 30 minutes, stretched so that the marked line was about 5 cm, fixed on a jig, and cooled in the atmosphere at room temperature. The length of the marked line when fixed to the jig is L ₁ , and the length of the marked line when removed from the jig after cooling and left at room temperature for 24 hours is L
₂ , after removing from the jig, heated to 200 ° C for 5 minutes and cooled, the length of the marked line is L ₃ , and the original length of the marked line is L ₀ (= 2
cm), the stretching retention rate and the heat shrinkage rate were calculated by the following formulas.

[0040]

[Equation 1]

[0041]

[Table 1]

Example 5, Comparative Example 1 The uncured composition of Example 2 was extruded into a tube by an extruder and passed through a heating vulcanization tower (250 ° C.) to give an outer diameter of 13.4 mm. A vulcanized tube having an inner diameter of 6.8 mm was obtained. Next, this tube was put into a stainless steel pipe having an inner diameter of 16 mm and a length of 5 m, heated to 150 ° C., and a pressure of 4 kgf was applied to the tube.
/ Cm ² of air was sent to draw the tube, and the tube was cooled to room temperature under pressure.

The obtained heat-shrinkable rubber tube had an inner diameter of 9.2 mm after stretching and an inner diameter of 6.8 mm after heat-shrinking at 200 ° C., and showed sufficient heat-shrinkability.

Next, the heat-shrinkable rubber tube obtained was applied to a core metal (outer diameter 8 mm) and a conductive adhesive X-32-1280-6.
(Shin-Etsu Chemical Co., Ltd.) coated thinly, 1
Heat shrinkage was performed at 50 ° C. for 30 minutes. The obtained roll outer diameter was 14 mm.

As Comparative Example 1, a roll having a composition of Example 2 in which spherical silicone elastomer particles were not added was made into a heat-shrinkable rubber tube, which was similarly coated with a core metal to prepare a roll.

Next, the electrical characteristics of the obtained roll were measured. The electrical characteristics are shown in Fig. 1 and the electrode 3 with a width of 7 mm
The roll was brought into contact with and the resistance between the electrode 3 and the roll core 2 was measured. The variation was evaluated at 20 measurement points in the axial direction. In this case, the measured voltage is 1000
V, measuring instrument 4 was Advantest Digital Ultra High Resistance Meter R8340. Table 2 shows the results.

[0047]

[Table 2]

From the results shown in Tables 1 and 2, it was confirmed that a semiconductive silicone heat-shrinkable rubber tube having a stable electric resistance value in the semiconductive region was obtained.

[0049]

EFFECTS OF THE INVENTION According to the present invention, the semiconducting silicone heat-shrinkability has little variation in the volume resistivity in the semiconducting region without deteriorating the inherent heat resistance, cold resistance, weather resistance and the like of the silicone rubber. A rubber tube can be obtained, and various rolls for conventional copying machines are usually shaped by pressure molding or the like.
Since the present invention is made into a heat-shrinkable rubber tube, it can be directly coated on the cored bar, the process is simplified for roll forming, and the effect of cost reduction can be expected.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of measuring electric characteristics of a roll.

[Explanation of symbols]

 1 roll 2 core metal 3 electrode 4 measuring instrument

Claims (3)

[Claims] 1. (A) The following average composition formula (1) R ¹ _n SiO _{(4-n) / 2} (1) (wherein R ¹ is the same or different and is unsubstituted or substituted monovalent carbon) A hydrogen group and n is an average number of 1.9 to 2.1): 100 parts by weight (B) Organopolysiloxane resin having a softening temperature in the range of 50 to 200 ° C .: 5 -80 parts by weight (C) Spherical silicone elastomer particles having an average particle diameter of 0.1 to 100 µm: 10 to 150 parts by weight (D) Conductive material: an amount giving a volume resistivity of 10 ³ to 10 ¹⁰ Ω · cm ( E) Curing agent: A semiconductive heat-shrinkable silicone rubber composition, characterized in that a curing effective amount is an essential component. 2. The semiconductive heat shrinkage according to claim 1, wherein the conductive material of the component (D) is one kind or two or more kinds selected from conductive carbon black, conductive zinc white and conductive titanium oxide. Silicone rubber composition. 3. A semiconductive silicone heat-shrinkable rubber tube obtained by tube-forming and stretching the silicone rubber composition according to claim 1.