Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing silicon
Reexamination Certificate
2000-04-27
2001-10-09
Moore, Margaret G. (Department: 1712)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic compound containing silicon
C528S038000, C556S425000, C252S182290, C252S182300
Reexamination Certificate
active
06300287
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a parting agent for a toner used in a copier. More particularly, this invention relates to a copier toner parting agent which does not lose any of its parting properties or turn into a gel under high-temperature conditions near 200° C., and which does not cause any problems with paper feed or the like.
BACKGROUND OF THE INVENTION
Because of their excellent heat resistance and parting properties, organopolysiloxanes are commonly used as parting agents for copier toners. However, when dimethylpolysiloxane, a typical organopolysiloxane, is used as a toner parting agent, the methyl groups in the dimethylpolysiloxane gradually begin to be pyrolyzed in the vicinity of 150° C. Pyrolysis becomes quite sudden at high temperatures over 200° C., which leads to diminished parting properties and generation of gel, which causes problems with paper feed, for example.
A toner parting agent composed of a mercapto group-containing organopolysiloxane or a carboxyl group-containing organopolysiloxane has been proposed in an effort to solve these problems (Japanese Patent Publication 58-52589). A toner parting agent composed of a mixture of an amino group-containing organopolysiloxane and dimethylpolysiloxane has also been proposed (Japanese Patent Publication 59-4699). There has also been a proposal for enhancing the heat resistance of a toner parting agent by adding iron, copper, or another redox type metal or metal compound to dimethylpolysiloxane (see Japanese Laid-Open Patent Application 1-204085). These toner parting agents, however, are not entirely satisfactory, and there is a need for a parting agent for a copier toner without these problems.
One object of this invention is to provide a parting agent for a copier toner, which has no loss of parting properties or generation of gel under high-temperature conditions near 200° C., and which causes no problems with paper feed or the like. These objects can be met by keeping the amount of formaldehyde generated during exposure to high temperatures within a specific range with an organopolysiloxane used as a toner parting agent.
SUMMARY OF THE INVENTION
This invention relates to a parting agent for a copier toner. The parting agent comprises a diorganopolysiloxane having the average unit formula: R
a
SiO
4−a/2
, where the R groups are substituted or unsubstituted monovalent hydrocarbon groups that are the same or different, and where at least 50 mol % of the R groups are methyl groups, and 1.95≦a≦2.20. The diorganopolysiloxane has a viscosity of 10 to 100,000 centistokes at 25° C. and generates no more than 5 ppm by weight of formaldehyde per hour when kept at 200° C. in an air atmosphere.
DETAILED DESCRIPTION OF THE INVENTION
The diorganopolysiloxane used in this invention has the average unit formula: R
a
SiO
4−a/2
, where the R groups are substituted or unsubstituted monovalent hydrocarbon groups that are the same or different, and 1.95≦a≦2.20. Examples of R include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, decyl, dodecyl, tetradecyl, or other saturated aliphatic hydrocarbon groups; cyclopentyl, cyclohexyl, or other saturated alicyclic hydrocarbon groups; phenyl, tolyl, naphthyl, or other aromatic hydrocarbon groups; or a group in which the hydrogen atoms bonded to the carbon atoms in these groups have been partially substituted with an organic group including an epoxy group, carboxyl group, mercapto group, or the like; or a halogen atom. Preferably, R to has between 1 and 20 carbon atoms. At least 50 mol % of these R groups are methyl groups, and preferably, at least 95 mol % are methyl groups.
This diorganopolysiloxane must have a viscosity of 10 to 100,000 centistokes at 25° C., and preferably 10 to 60,000 centistokes. When the diorganopolysiloxane is kept at 200° C. in an air atmosphere, the amount of formaldehyde generated per hour must be no more than 5 ppm by weight. It is also preferable for the content of siloxane oligomer having 20 silicon atoms or less to be 3000 ppm or less.
Preferably, 0.0001 to 1 mol % of the R groups in the average unit formula are organic groups of General Formula (1) to suppress the generation of formaldehyde.
—R
1
—C
6
H
X
R
2
(4−x)
OH General Formula (1):
where R is a divalent hydrocarbon group. Examples of suitable divalent hydrocarbon groups include ethylene, propylene, butylene, methylpropylene, or other such alkylene group, and alkylene-arylene groups expressed by the formula —(CH
2
)
2
C
6
H
4
. Ethylene and propylene groups are preferred. Examples of R
2
include the same substituted and unsubstituted monovalent hydrocarbon groups as given for R above, hydroxyl groups, methoxy groups, ethoxy groups, or other alkoxy group. The subscript x is an integer from 0 to 4.
Specific examples of the organic groups of General Formula (1) include the following.
Preferably, 0.0001 to 1 mol % of the R groups in the above average unit formula are organic groups of General Formula (2) to suppress the generation of formaldehyde
—R—NHCH
2
CH
2
)
b
NHR
3
, General Formula (2):
where R is a divalent hydrocarbon group as described above. R
3
is a hydrogen atom or a monovalent hydrocarbon group, examples of which include methyl, ethyl, phenyl, and cyclohexyl groups. The subscript b is an integer from 0 to 10.
Specific examples of organic groups of General Formula (2) include the following organic groups.
—CH
2
CH
2
CH
2
NHCH
2
CH
2
NH
2
—CH
2
CH
2
CH
2
NH
2
—CH
2
CH(CH
3
)CH
2
NHCH
2
CH
2
NH
2
—CH
2
CH
2
CH
2
NHC(CH
3
)
3
The content of organic groups having General Formula (1) or (2) should be such that the molecular weight (equivalents) of the diorganopolysiloxane per phenolic hydroxyl group or per amino group (—NH
2
or —NH—)is between 10,000 and 5,000,000, and preferably between 50,000 and 500,000. If there are fewer than 10,000 equivalents, intermolecular crosslinking will tend to occur between the phenol groups or amino groups and the material will be more prone to gelling, which is disadvantageous from a cost standpoint. If 5,000,000 is exceeded, the amount of formaldehyde that is generated will not be suppressed sufficiently.
A diorganopolysiloxane containing organic groups expressed by General Formula (1) or (2) can be manufactured by a known method. To manufacture the targeted diorganopolysiloxane, a diorganopolysiloxane containing groups expressed by General Formula (1) or (2) and a diorganopolysiloxane not containing groups expressed by General Formula (1) or (2) may each be manufactured separately, and then these two types of diorganopolysiloxane may be blended in suitable amounts.
When a diorganopolysiloxane not containing organic groups of General Formula (1) or (2) is used for the copier toner parting agent, it is preferable to add an organic antioxidant to the diorganopolysiloxane to suppress formaldehyde generation.
It is most effective for the antioxidant to be a phenol-based antioxidant or an amine-based antioxidant classified as a radical chain inhibitor, or a diorganopolysiloxane containing aromatic amino groups selected from the following formulas.
Examples of these antioxidants include phenyl-&agr;-naphthylamine, &agr;-naphthylamine, N,N′-diphenyl-p-phenylenediamine, N,N′-di-t-butyl-p-phenylenediamine, phenothiazine, and other such amino-based antioxidants, and 2,6-di-t-butyl-p-cresol, 2,6-di-t-butylphenol, 2,4-di-methyl-6-t-butylphenol, 2,2′-methylenebis(4-methyl-6-t-butylphenol), 4,4′-thiobis(3-methyl-6-t-butylphenol), and other such phenol-based antioxidants. Examples of diorganopolysiloxanes containing groups of the above formulas include the following compounds.
These antioxidants are added in amounts of 0.001 to 5.0 wt %, preferably 0.01 to 1.0 wt %, per 100 weight parts of diorganopolysiloxane.
The diorganopolysiloxane in this invention must generate no more than 5 ppm of formaldehyde by weight per hour. The amount of formaldehyde generation can be quantified by the following method, for example.
1.0 g of diorganopolysiloxane is weighed out in a
Ishikawa Hiroki
Naganawa Tsutomu
Ona Isao
Cesare James L. De
Dow Corning Toray Silicone Company, Ltd.
McKellar Robert L.
Moore Margaret G.
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