U.S. patent application number 09/728249 was filed with the patent office on 2002-08-15 for copolymerization of reactive silicone and urethane precursors for use in conductive, soft urethane rollers.
Invention is credited to Chiang, Albert C., Roderick, John A..
Application Number | 20020111419 09/728249 |
Document ID | / |
Family ID | 24926045 |
Filed Date | 2002-08-15 |
United States Patent
Application |
20020111419 |
Kind Code |
A1 |
Chiang, Albert C. ; et
al. |
August 15, 2002 |
Copolymerization of reactive silicone and urethane precursors for
use in conductive, soft urethane rollers
Abstract
The invention relates to a low tacky, conductive, soft urethane
roller for use in a printer. The roller includes a metal salt
evenly or homogeneously distributed in a copolymer formed of a
diisocyanate, a reactive silicone containing an amine group; and a
polyol or a polyamine. The roller can also have a volume
resistivity of between about 1E5 ohm-cm and about 5E10 ohm-cm, and
includes a metal salt solution in a copolymer formed of a
diisocyanate, a reactive silicone containing a hydroxyl group
and/or an amine group; and a polyol and/or a polyamine.
Inventors: |
Chiang, Albert C.; (Mystic,
CT) ; Roderick, John A.; (Scituate, RI) |
Correspondence
Address: |
ROBERT C. NABINGER
FISH & RICHARDSON P.C.
225 Franklin Street
Boston
MA
02110-2804
US
|
Family ID: |
24926045 |
Appl. No.: |
09/728249 |
Filed: |
November 30, 2000 |
Current U.S.
Class: |
524/588 |
Current CPC
Class: |
C08K 3/16 20130101; Y10T
428/31663 20150401; C08K 3/16 20130101; C08L 75/04 20130101 |
Class at
Publication: |
524/588 |
International
Class: |
C08K 003/10 |
Claims
What is claimed is:
1. A conductive roller for use in a printer, the roller comprising
a metal salt evenly distributed in a copolymer formed of the
following precursors: (i) a diisocyanate; (ii) a reactive silicone
containing an amine group; and (iii) a polyol or a polyamine.
2. The conductive roller of claim 1, wherein the roller is suitable
for use in a laser printer.
3. The conductive roller of claim 1, wherein the roller includes a
solid solution of metal salt evenly distributed in the
copolymer.
4. The conductive roller of claim 1, the roller being substantially
free of plasticizer and free of non-reactive silicone oil.
5. The conductive roller of claim 1, wherein the copolymer includes
between about 0.001% and about 5% of the metal salt by weight.
6. The conductive roller of claim 1, wherein the metal salt is a
transition metal salt or a lithium salt.
7. The conductive roller of claim 1, wherein the metal salt is
selected from the group consisting of iron chloride, copper
chloride, lithium perchlorate, lithium chloride, lithium bromide,
lithium iodide, iron bromide, iron iodide, copper bromide, and
copper iodide.
8. The conductive roller of claim 1, wherein the diisocyanate has
an NCO of no less than 2.0.
9. The conductive roller of claim 1, wherein the amount of reactive
silicone is about 0.5 wt % to about 20 wt % based on the total
weight of the copolymer.
10. The conductive roller of claim 1, wherein the molecular weight
of the reactive silicone ranges from about 500 to about 30,000.
11. The conductive roller of claim 1, wherein the molecular weight
of the reactive silicone ranges from about 1,000 to about
15,000.
12. The conductive roller of claim 1, wherein the reactive silicone
further contains a hydroxyl group.
13. The conductive roller of claim 12, wherein the reactive
silicone contains an end-capping amino group or an end-capping
hydroxyl group.
14. The conductive roller of claim 13, wherein the amount of
diisocyanate is about 10 wt % to about 50 wt %; the amount of
reactive silicone is about 1 wt % to about 20 wt %; and the amount
of polyol/polyamine is about 50 wt % to about 85 wt %.
15. The conductive roller of claim 13, the roller having a volume
resistivity of between about 1E5 ohm-cm and about 5E10 ohm-cm.
16. The conductive roller of claim 1, wherein the reactive silicone
has the following formula: 2wherein each of R.sub.1, R.sub.5, and
R.sub.8, independently, is hydrogen, alkyl, aryl, aralkyl, alkoxy,
aryloxy, aralkoxy, hydroxyalkyl, aminoalkyl, hydroxyalkoxy,
aminoalkoxy, hydroxyl, or amino; each of R.sub.2, R.sub.3, R.sub.4,
R.sub.6, and R.sub.7, independently, is hydrogen, alkyl, aryl,
aralkyl, alkoxy, aryloxy, or aralkoxy; and x is 10-2,000; provided
that at least one of R.sub.1, R.sub.5, and R.sub.8 contains a
hydroxyl group or an amino group.
17. The conductive roller of claim 16, wherein each of R.sub.1,
R.sub.5, and R.sub.8, independently, is hydrogen, methyl, ethyl,
amino-substituted phenyl, hydroxyl-substituted phenyl, methoxy,
ethoxy, hydroxyl, or amino; each of R.sub.2, R.sub.3, R.sub.4,
R.sub.6, and R.sub.7, independently, is hydrogen, methyl, ethyl,
phenyl, naphthyl or alkylphenyl; and x is 20-500.
18. The conductive roller of claim 1, wherein the amount of polyol
and/or polyamine is about 50 wt % to about 85 wt % based on the
total weight of the copolymer.
19. The conductive roller of claim 1, wherein the polyol and/or
polyamine has a molecular weight ranges from about 44 to about
15,000.
20. The conductive roller of claim 1, the roller having a hardness
of between 25 shore A and 50 shore A.
21. The conductive roller of claim 1, wherein the copolymer
exhibits a stable volume resistivity even when the humidity changes
from about 10% to about 90% and the temperature changes from about
10.degree. C. to about 40.degree. C.
22. The conductive roller of claim 1, wherein the copolymer
exhibits low tackiness even when the humidity changes from about
10% to about 90% and the temperature changes from about 10.degree.
C. to about 40.degree. C.
23. A conductive roller for use in a printer, the roller having a
volume resistivity of between about 1E5 ohm-cm and about 5E10
ohm-cm and comprising a metal salt evenly distributed in a
copolymer formed of the following precursors: (i) a diisocyanate;
(ii) a reactive silicone containing a hydroxyl group or an amine
group; and (iii) a polyol or a polyamine.
24. The conductive roller of claim 23, the roller having a volume
resistivity of between about 5E5 ohm-cm and about 5E8 ohm-cm.
25. The conductive roller of claim 23, wherein the roller is
suitable for use in a laser printer.
26. The conductive roller of claim 23, wherein the roller includes
a solid solution of metal salt evenly distributed in the
copolymer.
27. The conductive roller of claim 23, the roller being
substantially free of plasticizer and free of non-reactive silicone
oil.
28. The conductive roller of claim 23, wherein the copolymer
includes between about 0.001% and about 5% of the metal salt by
weight.
29. The conductive roller of claim 23, wherein the metal salt is a
transition metal salt or a lithium salt.
30. The conductive roller of claim 23, wherein the metal salt is
selected from the group consisting of iron chloride, copper
chloride, lithium perchlorate, lithium chloride, lithium bromide,
lithium iodide, iron bromide, iron iodide, copper bromide, and
copper iodide.
31. The conductive roller of claim 23, wherein the diisocyanate has
an NCO of no less than 2.0.
32. The conductive roller of claim 23, wherein the amount of
reactive silicone is about 1 wt % to about 20 wt % based on the
total weight of the copolymer.
33. The conductive roller of claim 23, wherein the molecular weight
of the reactive silicone ranges from about 500 to about 30,000.
34. The conductive roller of claim 23, wherein the molecular weight
of the reactive silicone ranges from about 1,000 to about
15,000.
35. The conductive roller of claim 23, wherein the reactive
silicone contains an end-capping amino group or an end-capping
hydroxyl group.
36. The conductive roller of claim 35, wherein the amount of
diisocyanate is about 10 wt % to about 50 wt %; the amount of
reactive silicone is about 1 wt % to about 20 wt %; and the amount
of polyol/polyamine is about 50 wt % to about 85 wt %.
37. The conductive roller of claim 23, wherein the reactive
silicone has the following formula: 3wherein each of R.sub.1,
R.sub.5, and R.sub.8, independently, is hydrogen, alkyl, aryl,
aralkyl, alkoxy, aryloxy, aralkoxy, hydroxyalkyl, aminoalkyl,
hydroxyalkoxy, aminoalkoxy, hydroxyl, or amino; each of R.sub.2,
R.sub.3, R.sub.4, R.sub.6, and R.sub.7, independently, is hydrogen,
alkyl, aryl, aralkyl, alkoxy, aryloxy, or aralkoxy; and x is
10-2,000; provided that at least one of R.sub.1, R.sub.5, and
R.sub.8 contains a hydroxyl group or an amino group.
38. The conductive roller of claim 37, wherein each of R.sub.1,
R.sub.5, and R.sub.8, independently, is hydrogen, methyl, ethyl,
amino-substituted phenyl, hydroxyl-substituted phenyl, methoxy,
ethoxy, hydroxyl, or amino; each of R.sub.2, R.sub.3, R.sub.4,
R.sub.6, and R.sub.7, independently, is hydrogen, methyl, ethyl,
phenyl, naphthyl or alkylphenyl; and x is 20-500.
39. The conductive roller of claim 23, wherein the amount of polyol
and/or polyamine is about 50 wt % to about 85 wt % based on the
total weight of the copolymer.
40. The conductive roller of claim 23, wherein the polyol and/or
polyamine has a molecular weight ranges from about 44 to about
15,000.
41. The conductive roller of claim 23, the roller having a hardness
of between 25 shore A and 50 shore A.
42. The conductive roller of claim 23, wherein the copolymer
exhibits a stable volume resistivity even when the humidity changes
from about 10% to about 90% and the temperature changes from about
10.degree. C. to about 40.degree. C.
43. The conductive roller of claim 23, wherein the copolymer
exhibits low tackiness even when the humidity changes from about
10% to about 90% and the temperature changes from about 10.degree.
C. to about 40.degree. C.
44. A laser printer comprising a conductive roller, the roller
having metal salt evenly distributed in a copolymer formed of the
following precursors: (i) a diisocyanate; (ii) a reactive silicone
containing a hydroxyl group or an amine group; and (iii) a polyol
or a polyamine.
45. The laser printer of claim 44, wherein the roller includes a
solid solution of metal salt evenly distributed in the
copolymer.
46. The laser printer of claim 44, the roller being substantially
free of plasticizer and free of non-reactive silicone oil.
47. The laser printer of claim 44, wherein the copolymer includes
between about 0.001% and about 5% of the metal salt by weight.
48. The laser printer of claim 44, wherein the metal salt is a
transition metal salt or a lithium salt.
49. The laser printer of claim 44, wherein the amount of reactive
silicone is about 1 wt % to about 20 wt % based on the total weight
of the copolymer.
50. The laser printer of claim 44, wherein the molecular weight of
the reactive silicone ranges from about 500 to about 30,000.
51. The laser printer of claim 44, wherein the reactive silicone
contains an end-capping amino group or an end-capping hydroxyl
group.
52. The laser printer of claim 51, wherein the amount of
diisocyanate is about 10 wt % to about 50 wt %; the amount of
reactive silicone is about 1 wt % to about 10 wt %; and the amount
of polyol/polyarmine is about 50 wt % to about 85 wt %.
53. The laser printer of claim 44, wherein the reactive silicone
has the following formula: 4wherein each of R.sub.1, R.sub.5, and
R.sub.8, independently, is hydrogen, alkyl, aryl, aralkyl, alkoxy,
aryloxy, aralkoxy, hydroxyalkyl, aminoalkyl, hydroxyalkoxy,
aminoalkoxy, hydroxyl, or amino; each of R.sub.2, R.sub.3, R.sub.4,
R.sub.6, and R.sub.7, independently, is hydrogen, alkyl, aryl,
aralkyl, alkoxy, aryloxy, or aralkoxy; and x is 10-2,000; provided
that at least one of R.sub.1, R.sub.5, and R.sub.8 contains a
hydroxyl group or an amino group.
54. The laser printer of claim 44, wherein the amount of polyol
and/or polyamine is about 50 wt % to about 85 wt % based on the
total weight of the copolymer.
55. The laser printer of claim 44, wherein the polyol or polyamine
has a molecular weight ranges from about 44 to about 15,000.
56. The laser printer of claim 44, the roller having a hardness of
between 25 shore A and 50 shore A.
57. The laser printer of claim 44, wherein the copolymer exhibits a
stable volume resistivity and low tackiness even when the humidity
changes from about 10% to about 90% and the temperature changes
from about 10.degree. C. to about 40.degree. C.
58. A method of preparing a conductive roller for use in a laser
printer, the roller comprising a metal salt evenly distributed in a
copolymer formed of precursors including a diisocyanate; a reactive
silicone containing a hydroxyl group or an amine group; and a
polyol or a polyamine, the method comprising: supplying three
streams of precursors to a roller mold, the first stream containing
diisocyanate with an amount ranging from about 10 wt % to about 50
wt %; the second stream containing a silicone-polyol/polyamine
mixture wherein the amount of the silicone precursor ranges from
about 1 wt % to about 20 wt % and the amount of polyol/polyamine
ranges from about 10 wt % to about 45 wt %; and the third stream
containing about 10 wt % to about 45 wt % of the polyol/polyamine
and about 0.001 wt % to about 5 wt % of the metal salt; and curing
the precursors in the roller mold to form the conductive roller;
the wt % recited herein being based on the total weight of the
copolymer.
Description
TECHNICAL FIELD
[0001] This invention relates to conductive, soft urethane rollers,
e.g., developer rollers, charge rollers, or toner transfer rollers,
for use in an electrophotographic printer, e.g., a laser printer.
The invention also relates to an electrophotographic printer
containing such a roller.
BACKGROUND
[0002] A laser printer often includes a digital light emitter
photoconductor drum, a charge roller, a developer roller, a
developer blade, a transfer roller, and a toner storage unit.
During printing, the transfer roller supplies toner to the
developer roller, and the developer blade forms the toner into a
thin, even layer on the surface of the developer roller. The charge
roller, which is in contact with the surface of the photoconductive
drum, receives a high voltage from a power supply, and charges the
photoconductive drum with a positive or negative charge. After the
photoconductive drum has been exposed a light emitter, the surface
of the photoconductor drum forms an electrostatic latent image. The
voltage difference between the developer roll and the
photoconductive drum allows the former to transfer toner to the
drum surface. Areas of the drum surface that are discharged by the
laser attract the toner, whereas areas that are more highly charged
repel the toner. The discharged and charged areas thus form toner
images. The laser printer may also include a toner-removal wiper
that removes excess toner from the surface of the developer roller
after the developer roller has contacted the photoconductor drum.
The toner on the drum subsequently is transferred to paper, and
then fuses to form the print.
[0003] Many different designs of laser printers are known. They
include Shiraki et al., U.S. Pat. No. 5,768,668; Sato, U.S. Pat.
No. 5,752,146; Park, U.S. Pat. No. 5,727,022; Okada et al., U.S.
Pat. Nos. 5,669,047 and 5,655,197; Sakaguchi, U.S. Pat. No.
5,602,631; Iguchi et al., U.S. Pat. No. 5,600,417; Ikeda et al.,
U.S. Pat. No. 5,367,367; Kogo et al., U.S. Pat. Nos. 5,324,885 and
5,214,239; Kinoshita et al., U.S. Pat. Nos. 5,311,264 and
5,287,150; Nishio, U.S. Pat. Nos. 5,241,343, 5,076,201, and
5,062,385; and Goyert et al., U.S. Pat. No. 4,521,582; all of which
are incorporated herein by reference.
[0004] The charge roller and developer roller are usually
cylindrical in shape and typically include a central shaft
surrounded by a synthetic rubber or urethane elastomer portion.
Many charge rollers for use in electrophotographic printing contain
multiple layers of rubber coating or foam coating with carbon black
filler inside. Due to the need to coat the surface with multiple
layers, low production and high cost result.
[0005] Coating a charge roller of high conductivity and soft
durometer with one layer of rubber/foam (specifically, urethane)
has been a challenging task. Most soft charge rollers having high
conductivity (typically, 5E5-5E7) need to contain plasticizer to
maintain the right hardness (typically, 25 Shore A-50 Shore A). The
use of plasticizer, however, may lead to tackiness on the surface
of the roller, which can result in poor print quality.
[0006] Having the right hardness is also important for proper
functioning of a developer roller. Typically, a developer roller
has a durometer ranging from about 50 Shore A to 65 Shore A. For
use in a high speed, high resolution printer, rollers are typically
required to have lower durometer (e.g., 30-50 Shore A). When the
hardness drops to below 50 Shore A, the surface of the roller can
become too tacky for the toner powder to be properly transferred
from the developer roller to the drum, resulting in poor print
quality. On the other hand, a hardness of more than 50 Shore A may
lead to partial melting of the toner for high speed, high
resolution printers.
SUMMARY OF INVENTION
[0007] In general, the invention features a conductive roller
(e.g., a developer roller or charge roller) for use in laser
printers or other electrophotography printers such as photocopier
or thermal printer. The roller includes an inner shaft surrounded
by a single layer of conductive solid or foam thermoset copolymer
formed of reactive silicone and urethane precursors. A roller
containing solid thermoset copolymer means that the thermoset
urethane portion contains no void. In contrast, a roller containing
foam thermoset copolymer contains void, e.g., a microcellular
roller. The rollers generally have a uniform volume resistivity
ranging from about 1E5 to about 5E10 ohm-cm; preferably, from about
5E5 to about 5E9 ohm-cm, and a hardness of between about 25 Shore A
and about 50 Shore A; preferably, between about 30 Shore A and
about 45 Shore A.
[0008] The thermoset copolymer exhibits a stable volume resistivity
even when the humidity changes from about 10% to about 90% and the
temperature changes from about 10.degree. C. to about 40.degree. C.
By "stable volume resistivity" is meant that the ratio of volume
resistivity at 10.degree. C., 20% relative humidity (LL) to the
volume resistivity at 40.degree. C., 90% relative humidity (HH) is
less than 50. The thermoset copolymer also exhibits low tackiness
under the same conditions (i.e., from LL to HH). The entire
copolymer displays uniform conductivity. A roller has low tackiness
if it does not adhere to another identical roller during storage,
i.e., no pressure is applied to the rollers, and the coefficient of
friction is less than 2.0.
[0009] In one aspect, the conductive roller contains a metal salt
evenly or homogeneously distributed in a copolymer formed of the
precursors: (i) a diisocyanate, (ii) a reactive silicone containing
an amine group, and (iii) a polyol or a polyamine. The
incorporation of silicone into the backbone of the copolymer
generally allows the resulting copolymer to have low tackiness
property and better resistance to change in humidity and
temperature. The roller preferably is substantially free of
plasticizer and non-reactive silicone oil. As used herein, a
copolymer that is "substantially free" of a material means that the
amount of the material is negligible in the composition, i.e., less
than about 0.001 wt % of the total weight of the copolymer. By
"non-reactive" is meant the silicone oil does not incorporate into
the backbone of the copolymer.
[0010] In another aspect, the conductive roller has a volume
resisitivity of between about 1E5 ohm-cm and about 5E10 ohm-cm and
contains a metal salt completely dissolved and evenly or
homogeneously distributed in a copolymer formed of the precursors:
(i) a diisocyanate, (ii) a reactive silicone containing a hydroxyl
group or an amine group, and (iii) a polyol or a polyamine.
[0011] The invention also features methods of preparing the roller
including the thermoset copolymer, as well as laser printers
including the roller.
[0012] Other features and advantages will be apparent from the
description of the preferred embodiments thereof, and also from the
claims.
DETAILED DESCRIPTION
[0013] A preferred conductive roller contains a shaft surrounded by
a single layer of solid conductive silicone-containing thermoset
copolymer. The outer surface of the roller may be uncoated, or may
be coated with, e.g., a rubber such as a urethane rubber, nitrile
rubber or silicone rubber. The thickness of the coating may be,
e.g., between 1.5 and 10 mil. The shaft can be made of steel,
aluminum, a conductive plastic, pultrusion conductive rod, or any
other material commonly used for the shaft of a conductive
roller.
[0014] The conductive roller can be used in photographic printing
or electrophotographic printing; preferably, the roller is used in
electrophotographic printers, e.g., laser printers, thermal
printers, and photocopiers.
[0015] In one embodiment, the preferred silicone-containing
thermoset copolymer is formed of precursors such as a diisocyanate,
a polyol or a polyamine, and a reactive silicone containing an
amine group. In another embodiment, the preferred
silicone-containing thermoset copolymer, which has a volume
resistivity of between about 5E5 ohm-cm and about 5E9 ohm-cm, is
formed of precursors such as a diisocyanate, a polyol or a
polyamine, and a reactive silicone containing a hydroxyl group
and/or an amine group.
[0016] The silicone-containing thermoset copolymer also includes a
solid solution of metal salt evenly or homogeneously distributed
therein, and may further include a catalyst, a light stabilizer, or
antioxidant. The copolymer is substantially free of a non-reactive
silicone oil or a plasticizer that can migrate to the surface of
roller after cure.
[0017] The preferred isocyanate is a one-shot or prepolymer
materials that have an NCO no less than 2, preferably, about 6-32.
NCO is defined as the combined % wt of N, C, and O in 100 g of
isocyanate. Specific examples of such an isocyanate include
methylene diisocyanate (MDI) (e.g., Isonate 2143L, Isonate 180,
Isonate 181, Isonate 191, Isonate 226, Isonate 240, and Isonate 125
M, all available from Dow Chemical, Midland, Mich.; Mondur PF,
Mondur M, Mondur XP-744, Mondur CD, and Mondur E-501, all available
from Bayer, Pittsburgh, Pa.; Lupranate M10, Lupranate M20S,
Lupranate M70L, Lupranate M200, Lupranate No. 78 Iso, Lupranate M,
Lupranate MS, Lupranate MP-102, Lupranate 103, and Lupranate 218
Iso, all available from BASF, Parsippany, N.J.); hydrogenated
methylene diisocyanate (HMDI) (Uniroyal Chemical, Middlebury,
Conn.); toluene diisocyanate (TDI) (Uniroyal Chemical, Middlebury,
Conn.); p-phenylene diisocyanate (PPDI), (Uniroyal Chemical,
Middlebury, Conn.); hexamethylene diisocyanate (HDI), (Bayer,
Pittsburgh, Pa.); and naphthyl diisocyanate (NDI), (Bayer,
Pittsburgh, Pa.). The preferred isocyanate also includes
prepolymers cured with esters such as adipate or caprolactone or
prepolymers cured with polyether such as polypropylene glycol
(PPG), polytetramethylene ethylene glycol (PTMEG), or other types
of glycol (Du Pont, Wilmington, Del.). The preferred copolymer can
include more than one type of isocyanate, e.g., a combination of
MDI and PPDI. The preferred weight percent of the isocyanate ranges
from 5 wt % to about 85 wt %, and more preferably, from about 10 wt
% to about 84 wt %, based on the total weight of the copolymer.
[0018] Examples of the preferred polyol or polyamine include
butanediol (XB) (available from GAF Chemicals, Wayne N.J.);
tremethanol propane (TMP) (available from Hoechst Celanese, Dallas,
Tex.); trisopropylamine (TIPA) (available from Dow Chemical,
Midland, Mich.); Isonol 93 (available from Upjohn Co., Kalamazo,
Mich.); hydroquinone ethyl ether (HQEE) (available from Eastman
Chemical Co., Kingsport, Tenn.); hexanediol (available from Aldrich
Chemical, Milwaukee, Wis.); Pluracol Polyol 994LV, Pluracol Polyol
816, Pluracol Polyol 945, Pluracol Polyol 1117, Pluracol Polyol
380, Pluracol Polyol HP-6500T, Pluracol Polyol 538, Pluracol Polyol
220, Pluracol Polyol 628, and Pluracol Polyol TPE 4542 (all
available from BASF, Parsippany, N.J.); Acclaim Polyol 4220 and
Acclaim Polyol 3000 (available from Arco Chemicals, New Square
Pa.); and Polamine 3000 and Polamine 4000 (available from Air
Products, Allentown, PA). The preferred weight percent of polyol or
polyamine ranges from 50 wt % to about 85 wt %, and more
preferably, from about 55 wt % to about 84 wt %, based on the total
weight of the copolymer. The preferred polyol or polyamine has a
molecular weight ranging from about 44 to 15,000; preferably, from
about 90 to 10,000.
[0019] The reactive silicone precursor contains at least one,
preferably, two or more, reactive hydrogen atom. A reactive
hydrogen atom refers to a hydrogen atom that is displaced in a
coupling reaction, for example, a hydrogen atom of a hydroxyl group
or an amine group. The hydroxyl group or the amine group can be
present at any position of the reactive silicone precursor. The
copolymer can be formed of more than one type of reactive silicone
precursor, for example, a combination of a reactive silicone
precursor having end-capping hydroxyl groups and a reactive
silicone precursor having end-capping amino groups.
[0020] A urethane linkage (--NH--C(.dbd.O)--O--) results when a
hydroxyl group of the reactive silicone precursor reacts with the
diisocyanate; whereas a urea linkage (--NH--C(.dbd.O)--NH--)
results when an amine group of the reactive silicone precursor
reacts with the diisocyanate. In general, copolymers containing
polyurea displays higher rigidity than those containing
polyurethane. The rigidity of the copolymer can be adjusted by the
ratio of the number of hydroxyl groups to the number of amino
groups present in the silicone precursor. Moreover, as mentioned
above, the preferred silicone-containing copolymers have better
resistance towards changes in humidity.
[0021] Preferably, the reactive hydrogen atom forms part of an
end-capping group of the precursor. An end-capping group, e.g., a
hydroxyl or an amine group, is a group attaching to the silicon
atom at the ends of the precursor. The preferred reactive silicone
precursor can contain an end-capping amino group, an end-capping
hydroxyl group, or a mixture of both, thus resulting in a linear
copolymer when polymerizes with the diisocyanate. See the general
formula below: 1
[0022] Each of R.sub.1, R.sub.5, and R.sub.8, independently, is
hydrogen, alkyl, aryl, aralkyl, alkoxy, aryloxy, aralkoxy,
hydroxyalkyl, aminoalkyl, hydroxyalkoxy, aminoalkoxy, hydroxyl, or
amino. Preferably, each of R.sub.1, R.sub.5, and R.sub.8,
independently, is hydrogen, methyl, ethyl, amino-substituted
phenyl, hydroxyl-substituted phenyl, methoxy, ethoxy, hydroxyl, or
amino. Each of R.sub.2, R.sub.3, R.sub.4, R.sub.6, and R.sub.7,
independently, is hydrogen, alkyl, aryl, aralkyl, alkoxy, aryloxy,
or aralkoxy. Preferably, each of R.sub.2, R.sub.3, R.sub.4,
R.sub.6, and R.sub.7, independently, is hydrogen, methyl, ethyl,
phenyl, naphthyl, or alkylphenyl. x is 10-2,000, preferably,
20-500. At least one of R.sub.1, R.sub.5, and R.sub.8 has to
contain a hydroxyl group or an amino group. Note that R.sub.1,
R.sub.2, R.sub.3, R.sub.6, R.sub.7, and R.sub.8 are end-capping
groups of the above-depicted reactive silicone precursor.
[0023] Alkyl, as used herein, is a straight or branched hydrocarbon
chain containing 1 to 8 carbon atoms. Examples of alkyl include,
but are not limited to, methyl, ethyl, propyl, isopropyl, butyl,
isobutyl, sec-butyl, tert-butyl, n-pentyl, and 2-methylhexyl. As
used herein, aryl is an aromatic group containing 6-12 ring atoms
and can contain fused rings, which may be saturated, unsaturated,
or aromatic. Examples of an aryl group include phenyl, naphthyl,
biphenyl, phenanthryl, and anthracyl.
[0024] Examples of the preferred reactive silicone precursor
include GP-145, GP-6, and GP7100 (available from Genesee Polymer
Corp., Mich.). The preferred weight percent of reactive silicone
precursor ranges from 0.5 wt % to about 20 wt %, and more
preferably, from about 2 wt % to about 10 wt %, based on the total
weight of the copolymer. The preferred reactive silicone precursor
has a molecular weight ranging from about 500 to 30,000;
preferably, from about 1,000 to 15,000.
[0025] The metal salt provides the silicone-containing thermoset
copolymer with the appropriate conductivity, for example, a volume
resistivity ranges from about 1E5 to about 5E 10 ohm-cm,
preferably, from about 1E6 to about 5E8 ohm-cm. The metal salt is
fully dissolved and evenly or homogeneously complexed with the
thermoset copolymer, resulting in a uniform, three-dimensional
charge distribution. Examples of metal salts that can be used
include transition metal halide salts such as iron chloride, copper
chloride, iron bromide, iron iodide, copper iodide, and copper
bromide; and lithium salts such as lithium chloride, lithium
bromide, and lithium perchlorate. All of these are available from
Aldrich Chemical, Milwaukee, Wis. The thermoset copolymer typically
includes between about 0.001% and about 5%, preferably, between
about 0.002% and 2%, of the metal salt by weight.
[0026] In one embodiment, the preferred copolymer, which is formed
of a reactive silicone precursor having an amino group, contains
one or more of a transition metal salt (e.g., iron chloride or
copper chloride). This copolymer can be used in forming a roller in
a xerographic printer. In another embodiment, the preferred
copolymer, which is formed of a reactive silicone precursor having
a hydroxyl group, contains one or more of a lithium salt (e.g.,
lithium perchlorate). This copolymer can be used in forming a
roller in a laser printer.
[0027] Examples of catalysts that can be used in forming the
copolymer include Fomrez UL-32 and Fomrez 29 (available from Witco,
Taft, La.); and Dabco T-12, Dabco T-9, and Dabco 331v (available
from Air Products, Allentown, Pa.). The copolymers may include, for
example, between about 0.005% and about 1% of the catalyst by
weight.
[0028] Examples of UV light stabilizers that can be used include
Tinuvin P, Tinuvin C 353 FF, Tinuvin 111 FB, Tinuvin 111 FDL,
Tinuvin 123, Tinuvin 144, Tinuvin 213, Tinuvin 234, Tinuvin 326,
Tinuvin 327, Tinuvin 328, Tinuvin 622LD, Tinuvin 765, Tinuvin 770
DF, Tinuvin 783FB, Tinuvin 783FD, Tinuvin 783FDL, Uvitex OB,
Chimassorb 81, Chimassorb 119FL, and Chimassorb 944 LD/FL (all
available from Ciba, Tarrytown, N.Y.). Typically, the thermoset
copolymer includes between about 0.1% and about 5%; preferably,
between about 1% and about 3%, of the stabilizer by weight.
[0029] Examples of antioxidants include Irganox 245, Irganox 1010,
Irganox 1076, Irganox 1098, Irganox 1135, Irganox 5057, and Naugard
(2,6-di-tert-butyl-p-cresol, BHT) (all available from Ciba,
Torryton, N.Y.). The thermoset copolymer generally includes between
about 0.1% and about 5%; preferably, about 0.1% and about 3%, of
the antioxidant by weight.
[0030] Both the UV light stabilizer and the antioxidant inhibit the
addition reaction and oxidation reaction of the roller surface.
[0031] The roller can be prepared by combining the appropriate
urethane precursors and other ingredients in a tube or shaft mold
that includes a pre-baked shaft with an adhesive coating. The shaft
can be, for example, in a rod-shaped or a circular tube, while the
mold can be in U-shaped, rectangular, square, or circular. The
molding procedure can be, for example, vertical or horizontal
casting, spin casting, a centrifugal method, or an extrusion or
protrusion process. The mixture is cured for 15-30 minutes at
160-180.degree. F., and the resulting roller is demolded and
post-cured for 12-16 hours at 180.degree. F. in the oven. The
desired top coating (if any) is applied to the roller by an
extrusion or spray-coating process, and then may undergo finish
grinding to provide a final roller with specified dimensioning,
resistivity, and surface roughness for use in a laser printer.
[0032] In a preferred procedure, the metal salt is at least
partially dissolved in polyol/polyamine before being combined with
the additional polyol/polyamine, reactive silicone precursor, and
isocyanate to form a solution in which the salt is completely
dissolved. This typically is accomplished, for example, by heating
a mixture including the salt and polyol/polyamine at an elevated
temperature (e.g., 80.degree. F.-130.degree. F.) for one or two
hours under vacuum. For purposes of this application, the resultant
solution will be referred to as the "conductive curative." The
conductive curative also may include, for example, the UV light
stabilizer and/or antioxidant and/or coloration.
[0033] Conductivity measurement is obtained using the method ASTM
D257-78 (Keithley 487 picoammeter/voltage source). Hardness
measurement is determined by using Shore instrument.
EXAMPLE 1
[0034] An example of a charge roller including a thermoset urethane
portion was made according to the following procedure, using a Max
machine, an automated metering machine.
[0035] The Max machine was set up to meter three streams of
materials including isocyanate, a mixture of reactive silicone
precursor and polyol, and conductive curative (which includes
polyol, metal salt, and other ingredients such as antioxidant, UV
stabilizer, or coloration) into a steel mold with eight cavities,
according to the following process parameters (total flow rate 650
g/min):
[0036] Stream Temperature Material Flow rate (g/min)
1 Stream Temperature Material Flow rate (g/min) B1 90.degree. F.
Isocyanate 2143L 73.3 (I-2143) B2 150.degree. F. Reactive silicone
348.2 precursor (GP145)/ polyol (HP-6500T) A 90.degree. F.
Conductive curative 228.6
[0037] The B1 stream was continuously feeding from a 55-gallon drum
under high vacuum. The NCO of the isocyanate was 28.91.
[0038] To obtain the B2 stream, 9 kg of HP-6500T was placed in a
5-gallon container and heated to 150.degree. F. This was followed
by slowly adding 1 kg of GP-145 to the 5-gallon container under
mechanical stirring.
[0039] The following ingredients were mixed to form stream A:
2 Composition Amount (parts) Amount (kg) Pluracol polyol (HP-6500T)
325.87 68.04 Poly BD (20LM) 24.00 5.01 TIPA 1.50 0.31 XB 11.50 2.4
Anhydrous lithium 8.50 1.8 perchlorate UV light stabilizer (T-328)
12.00 2.5 Antioxidant (BHT) 3.50 0.73 Catalyst (UL-29) 0.15 0.03
Black coloration 1.20 0.25
[0040] The ingredients listed above were mixed in a 55-gallon
container at 120.degree. F. for two hours under vacuum. The mixture
was then cooled to about 90.degree. F. with stirring before it was
charged (as stream A) into the Max machine.
[0041] To prepare the shaft (which has an OD of 10 mm and a length
of 27.5 mm), it was first coated with a conductive adhesive (e.g.,
MPC Conadh 1000, available from Mearthane Products of Cranston,
R.I.) using a brush while the shaft was rotating. The conductive
adhesive-coated shaft was dried under venting oven for at least
three hours, which was then prebaked at 220.degree. F. for at least
two hours. The shaft was then assembled in a cavity having an OD of
21.8 mm and a length of 241 nm.
[0042] The materials of streams A, B 1, and B2 (prepared according
to the protocol set forth above) were then poured from the Max
machine then poured into a mold of eight cavities. The mold was
maintained at 160.degree. F. on rotatory round table equipped with
heating hood for about 10-15 minutes (while the materials of
streams A, B 1, and B2 are being cured). The cured copolymer was
then taken out of the cavity and postcured at 180.degree. F. for
8-16 hours.
[0043] A cube for hardness testing was also prepared by pouring the
materials (streams A, B1, and B2) into a separate cube mold,
1.2".times.1.3".times.0.5", which stays next to the mold at the
same temperature (i.e., the mold temperature) during molding and
postcuring.
[0044] After rough grinding and finish grinding, the properties of
the thermoset copolymer portion of the roller were tested. The
thermoset copolymer had a hardness (on cube) of 42 Shore A and a
hardness (on roller) of 50-53 Shore A. Volume resistivity of the
cube and the roller were also measured. The cube and the roller
were placed in a humidity chamber at 72.degree. F., 50% relative
humidity before measurements. Both displayed a volume resistivity
of about 2E6 after two weeks in the chamber.
[0045] The roller was finish grinded to a size of 18.7 mm OD and
230 mm length (for the urethane portion). The final roller had a
surface roughness of less than 0.6 um, preferably about 0.4 um.
Examples 2-8
[0046] Charge rollers described in the following examples were
prepared using the same general procedure used in Example 1. The
following tables provide the amount (in parts) of each ingredient
in the thermoset copolymer:
3 Stream Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 B1 100.0 100.0
100.0 100.0 100.0 100.0 100.0 (I-2143L) A 437.3 396.7 548.6 419.2
480.5 477.1 475.3 Conductive curative B2 400.0 -- -- 503.5 312.0
312.0 312.0 (GP- 145/HP- 6500T) B2 -- 334.3 322.4 -- -- -- --
(GP-145/P- 380)
[0047] Listed below is the composition of conductive curative
(stream A) in each of Examples 2-8:
4 Composition Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 HP-6500T
325.9 -- -- 350.0 325.9 325.9 325.9 P-380 -- 250.0 450.0 -- -- --
-- Poly BD 24.0 24.0 24.0 24.0 24.0 24.0 24.0 (20LM) TIPA 1.5 1.5
1.5 1.5 1.5 1.5 1.5 XB 11.5 11.5 11.5 11.5 11.5 11.5 11.5 Lithium
1.0 5.4 7.4 8.5 10.0 13.0 14.0 perchlorate (anhy.) Iron (III) -- --
-- -- -- -- 9 chloride T-328 12.0 12.0 12.0 12.0 12.0 12.0 12.0 BHT
3.5 3.5 3.5 3.5 3.5 3.5 3.5 Carbon black -- -- -- -- 4.0 4.0 4.0
UL-29 0.15 0.03 0.04 0.15 0.15 0.15 0.15 Black 1.2 1.2 1.2 1.2 1.2
1.2 1.2 coloration
[0048] Listed below is the composition of reactive silicone/polyol
(stream B2) in each of Examples 2-8:
5 Composition Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 GP-145 10.0
20.0 20.0 10.0 10.0 10.0 10.0 HP-6500T 90.0 -- -- 90.0 90.0 90.0
90.0 P-380 -- 80.0 80.0 -- -- -- --
[0049] Physical properties of the roller prepared in each of
Examples 2-8 are provided below:
6 Properties Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Hardness 36
A 35 A 32 A 34 A 41 A 40 A 40 A Vol. 1.8E7 2.2E7 1.3E7 1.2E7 1.0E7
1.5E7 1.6E7 Resistivity (ohm-cm)
Examples 9-14
[0050] Developer rollers described in the following examples were
prepared using the same general procedure used in Example 1. The
following tables provide the amount (in parts) of each ingredient
in the thermo set copolymer:
7 Stream Temp. Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 B1
180.degree. F. 100.0 100.0 100.0 100.0 100.0 100.0 (V-6020; NCO =
6.85) A 150.degree. F. 24.7 21.7 21.8 21.8 21.8 21.8 Conductive
curative B2 90.degree. F. 165.6 172.2 173.0 173.0 173.0 173.0 (GP-
145/HP- 6500T)
[0051] Listed below is the composition of conductive curative
(stream A) in each of Examples 9-14:
8 Composition Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 HP-6500T
250.0 200.0 200.0 200.0 200.0 200.0 T-1000 20.0 20.0 20.0 20.0 20.0
20.0 TIPA 20.0 20.0 20.0 20.0 20.0 20.0 I-93 80.0 80.0 80.0 80.0
80.0 80.0 Iron (III) 0.56 0.08 0.14 0.20 -- -- chloride Copper (II)
0.07 0.01 0.02 -- 0.25 -- chloride Lithium 0.07 0.01 0.02 -- --
0.22 perchlorate (anhy.) T-328 6.0 6.0 6.0 6.0 6.0 6.0 BHT 3.0 3.0
3.0 3.0 3.0 3.0 T-12 0.19 0.19 0.19 0.19 0.19 0.19 Black 1.2 1.2
1.2 1.2 1.2 1.2 coloration
[0052] Listed below is the composition of reactive silicone/polyol
(stream B2) in each of Examples 9-14:
9 Composition Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 GP-145 5.0
10.0 10.0 10.0 10.0 10.0 HP-6500T 95.0 90.0 90.0 90.0 90.0 90.0
[0053] Properties of the roller prepared in each of Examples 9-14
are provided below:
10 Properties Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Hardness 40
A 43 A 43 A 43 A 43 A 43 A Vol. 1.4E8 2.0E9 1.0E9 1.1E9 1.3E9 1.0E9
Resistivity (ohm-cm)
[0054] Other embodiments are within the claims.
* * * * *