Conductive composition with excellent high-temperature...

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...

Reexamination Certificate

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C524S506000, C525S333700, C525S342000

Reexamination Certificate

active

06555620

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an electrically-conductive composition having an excellent storage stability at high temperatures and an electrically-conductive roller prepared therefrom. More particularly, the electrically-conductive composition of the invention comprises a compound having at least one alkenyl group which can undergo hydrosilylation reaction per molecule and an isobutylene skeleton, a compound having at least two hydrosilyl groups per molecule, a hydrosilylation catalyst, a compound having aliphatically unsaturated bond, and an electrical conductivity-providing material. The composition of the invention exhibits a good storage stability at a temperature as high as 30° C. to 80° C.
BACKGROUND ART
An addition type hardenable composition comprising a compound having an alkenyl group and an isobutylene skeleton, a compound having a hydrosilyl group and a hydrosilylating catalyst or an electrically-conductive composition obtained by adding an electrical conductivity-providing material to such an addition type hardenable composition is known.
However, these compositions are mainly composed of polymer and thus have a relatively high viscosity. The components in these compositions may undergo thickening. Thus, these compositions are disadvantageous in that their workability and processability are very poor.
In order to lower the viscosity of the foregoing composition and hence eliminate the foregoing disadvantage, it has heretofore been practiced to add a plasticizer having a lower viscosity than that of main components or the like. However, it is disadvantageous in that when a large amount of plasticizer is added, the hardened product obtained by hardening the composition exhibits deteriorated physical properties and there is a great risk of bleed, etc.
On the other hand, as the temperature rises, these polymers show a viscosity drop. Thus, it is thought that if the composition can be handled at temperatures higher than ordinary temperature, a good workability can be given and no adverse effects can be given to the physical properties thereof. However, these compositions are disadvantageous in that they are not always excellent in storage stability at temperatures higher than room temperature and thus can readily be gelled, that is, they exhibit an extremely poor storage stability at high temperatures (e.g., higher than room temperature) (as described in JP-A-3-188166 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”), U.S. Pat. No. 3,445,420).
Further, according to U.S. Pat. No. 5,629,387, the use of a long-chain &agr;-acetylene alcohol makes it possible to improve storage stability. However, this approach is disadvantageous in that the resulting composition exhibits a deteriorated hardenability.
Various techniques are known for composition for addition type hardenable electrically-conductive roller comprising a liquid polymer (as described in JP-A-7-300564, JP-A-11-80669). However, it is the status of quo that no compositions having an excellent storage stability and hardenability have been obtained yet.
In general, an electrically-conductive roller is made of a resin such as urethane and NBR. However, a roller prepared from these resins is disadvantageous in that it is subject to change of electrical properties due to environmental change because these resins are somewhat hygroscopic themselves.
The present invention has been worked out in the light of these circumstances. The present invention provides an electrically-conductive composition having an excellent storage stability at high temperatures which can be handled at temperatures higher than room temperature and an electrically-conductive roller having an excellent productivity.
DISCLOSURE OF THE INVENTION
The inventors made extensive studies of solution to the foregoing problems. As a result, it was found that the addition of a compound containing an aliphatically unsaturated bond as a storage stability improver to the foregoing electrically-conductive composition which can undergo hydrosilylation reaction makes it possible to obtain a composition having an excellent storage stability at temperatures higher than room temperature and the use of such a composition makes it possible to obtain an electrically-conductive roller having an excellent productivity and processability because the viscosity thereof can be lowered by heating. The present invention has thus been worked out.
Further, the electrically-conductive roller of the invention is characterized in that since the isobutylene polymer as a main component has a low hygroscopicity, the roller exhibits an excellent stability of electrical properties against environmental change.
The electrically-conductive composition of the invention comprises the following components (A) to (E):
(A) An isobutylene polymer having at least one alkenyl group which can undergo hydrosilylation reaction per molecule;
(B) A compound having at least two hydrosilyl groups per molecule;
(C) A hydrosilylation catalyst;
(D) An acetylene alcohol having the following structure:
 wherein R
14
and R
15
each independently represent a hydrogen atom, alkyl group or aryl group, with the proviso that R
14
and R
15
may be connected to each other to form a ringp; and
(E) An electrical conductivity-providing material.
In an embodiment, the component (D) is an acetylene alcohol having a molecular weight of not smaller than 110.
In an embodiment, the component (D) is an acetylene alcohol having a boiling point of not lower than 140° C. at ordinary pressure.
In an embodiment, the sum of the number of carbon atoms in R
14
and R
15
in the general formula of acetylene alcohol is from 4 to 8.
In an embodiment, the component (D) is an ester compound having an aliphatically unsaturated bond.
In an embodiment, the component (D) is at least one compound selected from the group consisting of 2-phenyl-3-butyne-2-ol, 1-ethynyl-1-cyclohexanol and 3,5-dimethyl-1-hexyne-3-ol.
In an embodiment, the component (E) is carbon black.
In another aspect of the invention, an electrically-conductive roller obtained by hardening any of the foregoing compositions around a metallic shaft is provided.
In an embodiment, the electrically-conductive roller is obtained by heating the composition to a temperature of from 30° C. to 80° C., injecting the composition into a mold, and then hardening the mold at a temperature of not lower than 100° C.
In an embodiment, the electrically-conductive roller is obtained by treating the foregoing composition as a two-part liquid composition consisting of a composition (I) comprising components (A), (B), (C), (D) and (E) and a composition (II) comprising components (A), (B), (D) and (E), heating the various compositions to a temperature of from 30° C. to 80° C., measuring the weight of the various compositions, injecting the various compositions into a mold while being mixed, and then hardening the mixture at a temperature of not lower than 100° C.
In an embodiment, the ratio (I)/(II) of viscosity of the composition (I) to the composition (II) is from 0.5 to 2.0.
In an embodiment, the roller resistivity is from 10
7
to 10
11
&OHgr;.
In an embodiment, the roller resistivity is from 10
3
to 10
10
&OHgr;.
In an embodiment, the roller resistivity is from 10
5
to 10
10
&OHgr;.
In an embodiment, the roller hardness is of not greater than 30°.
BEST MODE FOR CARRYING OUT THE INVENTION
The component (A) to be used in the invention is an isobutylene polymer having at least one alkenyl group which can undergo hydrosilylation reaction per molecule. The term “isobutylene polymer” as used herein is meant to indicate one having a skeleton mainly composed of isobutylene units as monomer units. In this case, all the monomers may be formed by isobutylene units. Monomer units copolymerizable with isobutylene may be contained in an amount of not greater than 50% (by weight hereinafter), more preferably not greater than 30%, particularly not greater than 20% based on the weight of the isobutylene polymer. In the polymer skeleton, ho

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