Note: Descriptions are shown in the official language in which they were submitted.
11~3~Q~
B~ACKGROUND OF THE INVF,NTION f
The present invention relates to electrostatographic
toner compositions adapted for use in an electrophotographic
imaging process, wherein the resinous component of the toner
comprises a block or graft copolymer having crystalline and
amorphous segments.
The formation and development of images on the surface
of photoconductive materials by electrostatic means is well
known. The basic electrostatographic process, as taught by
C.F. Carlson in U.S. patent 2,297,691, involves placing a uni-
form electrostatic charge on a photoconductive insulating layer,
exposing the layer to a light and shadow image to dissipate the
charge on the areas of the layer exposed to the light and dev-
eloping the resulting electrostatic latent image by depositing
on the image a finely divided electroscopic material referred
to in the art as "toner". The toner will normally be attracted
to those areas of the layer which retain a charge, thereby
forming a toner image corresponding to the electrostatic latent
image. This toner image may then be transferred to a copy sub-
strate such as paper. The transferred image may subsequently
be permanently affixed to the copy substrate such as by fusion
wlth heat. Instead of forming the latent image by uniformly
charging the photoconductive layer and then exposing the layer
to a light and shadow image, one may form the latent image by
directly charging an insulating layer, which can be either
photoconductive or non-photoconductive, in image configuration.
The powder may be fixed directly to the insulating layer if
desixed.
One of the important applications of electrostatography
comprises its use in automatic copying machines for general
~ ~J36~
~' office use wherein an electrostatic latent image is developed
using a developer composition comprising a carrier mixed with ~,
fine particles of resinous toner, and the thus formed powder
image is transferred to a copy substrate and then fixed thereon.
Considerable effort has been expended to provide suitable develo-
pers and associated fixing techniques for modern high speed
copying machines. The toner material used must have suitable
electrostatic properties to permit attraction by the carrier
and then selective attraction by the latent images. It must
~lO further be physically strong to permit constant recycling in a
bouncing type of movement. The toner must further be resistant
~o blocking or aggregating at ordinary operating temperatures,
but yet be capable of being readily fixed to the copy sheet.
Fixing techniques employing heat, pressure, solvents
and various combinations thereof have been devised; however,
each of these systems is subject to severe practical limitations
which inhere in the systems themselves and also the toner compo-
sitions heretofore availabIe. Whatever method of fixing is
used, speed, effectiveness, and simplicity in operation are the
principal, desirable characteristics to be obtained. The most
commonly employed fixing techniques employ the use of heat alone
or heat in combination with pressure. The toner materials
employed must melt or block sufficiently above the ordinary
operating temperatures of the machines involved to assure con-
venient storage and handling. However, the materials must also
melt at a practically low temperature to avoid excessively-high
energy consumption and possible heat damage to the copy sub-
strate or delicate machine parts.
It has long been recognized that one of the fastest and
most positive methods of applying heat for fusing the powder
-- 2 --
-` 1.03~ 9
image to paper is to bring the powder image into direct contact
with a hot surface, such as a heated flat plate or roller
However, it was found that as a powder image is tackified by
contact heating, part of the image carried by the copy sheet
would stick to the hot surface so that as the next copy sheet
was contacted with the hot sur~ace, the tackified image par-
tially removed from the first sheet would partially transfer
to the next sheet and, at the same time, part of the tackified
image from said next sheet would adhere to the hot surface.
This p~enomenon is commonly referred to in the printing art as'
"offset". For a given system, this upper temperature limit is
referred to as the "hot offset temperature". Thus, contact
heat fusers are inherently limited to the use of temperatures
and toners which do not cause hot offset of the toner material.
Various types of polymeric materials have been pro-
posed in the prior art for use as the resinous component in
electrostatographic toners. U.S. Patent RE 25,136 teaches toner
material based on polystyrene or copolymers of styrene with
monomers such as alkyl methacrylates. British Patent 1,179,095
teaches toner material based on a combination of two polymeric
materials, one of which polymeric materials has a glass transi-
tion temperature of greater than 20C, and the other a glass
transition temperature of at least 5C lower. These polymeric
materials may be combined by physical admixture, or by forming
block or graft copolymers. Other patents of interest in the
electrostatographic toner area include U.S. Patents 2,788,288;
3,078,342; 3,391,082; 3,502,582; 3,510,338; 3,609,082 and
3,647,~96. As indicated above, these other toner materials
based on amorphous polymers have not proven entirely satisfac-
tory when used with contact heat fusers~
~3~9
While further advances in the art of fixing, includ-
ing the use of offset reducing roller surfaces, have provided
more suitable means to fuse toner images through the use of
heat and pressure with decreased offset, these devices are
still restricted to operate within close temperature toler-
ances due to the narrow fusing latitudes obtainable with
toner materials heretofore available. Exemplary of these
contact fusing devices are those disclosed in U. S. Patents
3,256,002, 3,268,351, 3,291,466, 3,437,032, 3,498,596
and 3,539,161.
SUMMARY OF THE INVENTION
In accordance with one aspect of this invention
there is provided a finely divided, particulate, electro-
statographic toner composition comprising a uniform mixture
of (a) a colorant material and (b) a polymeric material,
said polymeric material comprising a segmented copolymer
consisting of at least one crystalline or crystallizable
polymeric segment chemically linked to at least one amorphous
polymeric segment, said segmented copolymer having a glass
transition temperature of less than about 20C and a melting
point of at least about 45 C, said at least one amorphous
polymeric segment individually having a glass transition
temperature less than the melting point of said crystalline
or crystallizable polymeric segment.
In accordance with another aspect of this invention
there is provided in an electrophotographic imaging process
including the steps wherein a particulate electrostatograph-
ic toner composition is applied in image configuration to
the surface of a recording member, and said recording member
bearing said toner composition in image configuration is
subjected to heat or heat and pressure sufficient to fuse
~ _4_
., . . ,, , ~, ~
~(~36~q~9
said toner composition to the surface of said recording mem-
ber, the improvement which comprises conducting said imaging
process using a finely divided toner composition comprising
a uniform mixture of: (a) a colorant material and (b) a poly-
meric material, said polymeric material comprising a segment-
ed copolymer consisting of at least one crystalline or
crystallizable polymeric segment chemically linked to at
least one amorphous polymeric segment, said segmented copoly-
mer having a glass transition temperature of less than about
20 C and a melting point of at least about 45C, said at
least one amorphous polymeric segment individually having a
glass transition temperature less than the melting point of
said crystalline or crystallizable polymeric segment.
In accordance with another aspect of this inven~ion
there is provided an electrophotographic imaging process
comprising the steps of subjecting the surface of a charged
photoconductive insulating layer to a pattern of light and
shadow such that an electrostatic latent image is formed on
the surface of said layer, developing said latent image by
contact of said surface with a developed composition compris-
ing a mixture of carrier particles and toner material,trans-
ferring the toner material in image configuration from said
. surface to the surface of a recording member, and heating
the surface of said recording member sufficient to fuse said
: toner composition to the surface of said recording member,
said toner material comprising a finely divided composition
~ comprising a uniform mixture of: (a) a colorant material
; and (b) a polymeric material, said polymeric material com-
prising a segmented copolymer consisting of at least one
crystalline or crystallizable polymeric segment chemically
linked to at least one amorphous polymeric segment, said
-4a-
,~
~1~36~Q~
segmented copolymer having a glass transition temperature of
less than about 20C, a melting point of at least about 45C,
and an average molecular weight within the range of about
5,000 to 200,000 grams per moles, said at least one amorphous
polymeric segment individually having a glass transition
temperature less than the melting point of said crystalline
or crystallizable polymeric segment.
By way of supplementary explanation, it has now been
discovered that electrostatographic toner material having
exceptionally desirable mechanical and thermal properties
may be prepared by forming a finely divided mixture compris-
ing a coloring material and a polymeric material which is
block or graft copolymer consisting of at least one cryst-
alline or crystallizable polymeric segment chemically li'nked
to at least one amorphous polymeric segment, sai~d crystalline
or crystallizable segment individually having a glass trans-
ition temperature of less than about 20C and a melting
point of at least about 45C and said amorphous segment
individually having a glass transition temperature less than
the melting point of said crystalline or crystallizable
segment. In the preferred embodiment, the glass transition
temperature of both polymeric segments is less than about
0C and within the range of about 0 to -100C, and the
melting point of the copolymer lies within the range of
about 45 to about 150C. The amount of amorphous polymer
present in the toner copolymers of this invention is prefer-
ably within the range of about 10 to 90% by weight based on
total polymer weight. Toner materials prepared according
to the present invention exhibit thermal and mechan-
-4b-
-'
~ 36~(~9
ical properties which render them extremely useful in xerographi~
processes, particularly high speed processes involving heat con-
tact fusing. The thermal properties of the instant toner ma-
terials are such that they exhibit an extremely low latent heat
of fusion while substantially retaining melting poLnt and melt
crystallization characteristics of toner materials ~ased on
~rystalline or crystallizable homopolymers, thereby allowing
for a broad latitude of fusing temperature without toner off-
set.
DETAILED DESCRIPTIO~ OF THE I~VENTION :
In pressure roll fixing of electrostatographic toners,
three interrelated parametexs of utmost importance in toner
performance are: (1) the minimum fusing temperature, which is
the minimum temperature required for fusing the toner; (2) the
hot offset~ temperature, which is the minimum temperature at
which the hot toner melt begins to adhere to the pressure mem-
ber, i.e., the maximum temperature of operation which avoids
this type of ixing failure; and (3) the fusing latitude, which
is the operating range defined as the difference between the
hot offset temperature and minimum fusing temperature.
Viscosity-temperature relationships for toner materials
have been established, and it is found that a certain viscosity
range is required for the onset of fusing. A second, somewhat
lower, viscosity range has heen found to correspond to off-
setting. The difference between these viscosity ranges is
called the "fusing window". The fusing window depends to a
great extent on specific machine parameters, such as components,
ronfiguration~ speed, etc. For maximum range of fixing opera-
tion, i.e., maximum fusing latitude, one requires a toner
having a minimum temperature dependence on viscosity and
3364~
maximum traverse of the fusing window.
Whereas toner materials o the prior art containing
amorphous polymeric material exhibit a minimum fusing tempera-
ture usually in excess of 150C, and a fusing latitude in many
; 5 cases of less than 20C., it has been found that toner based on
crystalline or crystallizable polymers specifically satisfy the
aforementioned thermal and viscosity criteria. Crystalline
polymers offer the advantages of relatively sharply defined
melting points above which the polymer can be readily induced
to flow and below which at the crystal~ization temperature (Tc)
the polymer can be readily induced to harden. Crystalline or
crystallizable polymers in general also exhibit less tendency
to offset or adhere to fusion rollers even when temperatures of
greater than 100C in the excess of the polymer melting point
(Tm) are encountered during xerographic fusion. In addition,
their mechanical properties are such that these materials are
more resistant to degradation during processing into toner
material.
Although the use of toner material based on crystalline
or crystallizable polymers offers some advantages and flexibili-
ty in terms of thermal and viscosity criteria particularly in
high speed xerographic e~uipment, one disadvantage lies in the
fact that an additional amount of heat energy is required to
transform the polymer from a crystalline state to the state
where the polymer will flow and adhere to the transfer substrate.
This heat energy requirement is known as the "Heat of Fusion"
and may be defined as the amount of energy necessary in trans-
forming a polymer from a crystalline or a partially crystalline
state to a completely disordered amorphous state without a
change in temperature in the crystalline segments of the polymer.
-- 6 --
The heat of fusion is directly relatable to the degree of
crystallinity of a given polymer: the higher the crystallinity, 5
the greater the heat of ~usion, and the greater t~e amount of
heat necessary to melt the polymer.
Thus, whexeas crystalline polymers offer certain
advantages as indicated above, particularly when used as a
toner component in a high speed xerographic prGcess, the addi-
tional heat necessary for toner fusion tends to mitigate these
advantages. In order to overcome the latent heat of fusion and
impart the required flowability characteristics into a crystal-
; line polymer such that good adhesion of the toner to the sub-
strate will occur, it may be necessary to either heat the toner
bearing recording medium to moderate temperature above TM for a
period of time longer than might be desirable in a high speed
operation, or subject the toner bearing substrate for a desir-
ably short period of time to a temperature above TM which is in
excess of that desirable. In the former case, speed is sacri-
ficed; in the latter case, excessive heat and the concomitant
disadvantages associated therewith may be encountered. In either
case, the latent heat of fusion is a factor tending to mitigate
somewhat the previously recited advantages inureing in toner
based on crystalline polymers.
It is thus most advantageous to prepare a toner
material which offers similar advantages of toner based on a
crystalline or crystallizable polymer in terms of mechanical,
physical, chemical and thermal properties, but which also
exhibits a controllably minimal latent heat of fusion. This is
accomplished according to the present invention by providing
toner compositions comprising a block or graft copolymer con-
taining at least one crystalline ur crystallizable polymeric
-- 7 --
segment chemically li~g~o at least one amorphous polymeric
segment. Toner compositions based on such segmented copolymers
have sharp well defined melting points with minimal heats of
fusion, the heat of fusion of a particular copolymer being con-
- 5 trolled as a function of the ratio of amorphous to crystalline
segments present in the copolymer structure~ Of particular
advantage is the fact that low heats of fusion can be achieved
with a minimal effect on the melting point of the copolymer.
The block copolymers can be characterized as materials
represented by any of the following generic schemes: [BA]n, [AB]n,
[ABA]n, or [BAB~n, wherein n is a whole number equal to or greater
than 1, A represents the amorphous polymeric segment and B repres-
ents crystalline or crystallizable polymeric segment. Each seg-
ment need not necessarily be homopolymeric. The individual block
segments A and B may be linked directly to one another in head
to tail fashion such as by covalent bonding resulting from
sequential block copolymerization of the appropriate monomers
or by coupling reaction between terminal functional groups
present on different polymeric molecules. Alternatively, the
block segments may be linked by means of difunctional coupling
agents which remain in the block copolymer molecule, such as,
for example, urethane linkages which would be formed by the
reaction of hydroxyl terminated polymers with an organic diisocy-
anate, or ester linkages formed by the reaction of hydroxy
terminated polymers with dicarboxylic acids or carboxy termin-
ated polymers with glycols, or other linkages formed by reac-
tion of hydroxy terminated polymers with phosgene, dichlorodi-
methyl silane and the like.
Where the block copolymers are formed using difunc-
tional coupling agents, the above recited formula schemes for
-- 8 --
.
1al36~)9
such block copolymers should be considered generic to a speci-
ic scheme wherein the coupling agent moiety is present in the
block copolymer molecule connecting the A segment to the B seg-
ment. In turn, each A or B segment depicted generically above
may comprise a plurality of individual A segments coupled to-
gether or a plurality o B segments coupled together. Thus,
for example, the formula [BA]n should, for the purposes of the
present invention, be considered generic to [Bl]-C-[Al] wherein
each Bl and Al segment may consist of a single polymeric molecule
or a plurality of polymeric molecules of similar structure
coupled together, such as where [Bl] is B or [(B-c-)mB] and[A
is A or [A(-c-A)m], further whereln A and B are as specified
above, m is a positive whole integer e~ual to 1 or greater, and
c is the coupling agent moiety. The same holds true for the
thxee other generic formula schemes recited above. Althou-~h
the coupling techni~ue is preferred because it offers more pre-
cise control over the amounts of each type of polymer lntro-
duced into the polymer chain, it is to be emphasized that any
polymerization techni~ue known to those skilled in the art
affording the capability of preparing the tailor-made block
copolymers of the present invention may be used.
The graft copolymers used as a toner ingredient
according to the present invention can be categorized generic-
ally as branched polymers exemplified by the following schemes:
(I) . . .AAaA~, ., (II) . . . BBBBBBBB. . .
B A
B A
B A
wherein A represents repeating momomeric units contained in
the amorphous polymeric segment and B represents repeating
_ g _
monomeric units cont ~ ~ ~ ~ e crystalline or crystallizable
polymeric segment. As in the case of the block copolymers, the
A and/or B segments may be homopolymeric or copolymeric. The
grafted polymer chain may be present at any position along the
S polymer backbone chain, including at the head or tail of the
backbone polymer. In most instances a plurality of such grafted
polymer chains may be present at various points along the back-
bone. Where the crystalline or crystallizable polymer comprises
the backbone chain, the degree of branching or grafting is pre-
ferably minor in order to preserve the crystalline properties of
the graft copolymer; where the grafted side chains comprise the
crystalline or crystallizable polymer, then a larger number of
side chains are desirable for the same reason. The graft copo-
lymers may be prepared by techniques well known to those skilled
in the ar~. Such techniques include creating a free radical
site or sites along a polymer chain by irradiation or other
technique with subse~uent polymerization of monomer in the pre-
sence of the polymer; introducing active sites along the polymer
chain by o~idation to create peroxide groups which act as free
radical initiators with subsequent polvmerization of monomer;
and by coupling reactions performed by either introducing func-
tional groups along the chain by metallation or other techniaues,
or utilizing functional groups already present, which functional
groups can be made to react either directly with a terminal
functional group present in a second polymer or indirectly by
means of coupling agents. As is the case with the block copoly-
mers, the preferred techniaue for forming graft copolymers
involves reacting preformed polymers because of the more precise
control regarding polymer selection and degree of grafting.
Where the block or graft copolymers are prepared by
-- 10 -- t
-- ~036~
polymerizing a monomer or monomers in the presence of a pre-
formed polymer, the choice of monomer, catalyst and polymeriza-
tion conditions must be such that the polymerizing monomer will
form a polymer having the desired crystalline, amorphous or iso-
mer stFucture. Where the preformed polymer is amorphous, the -
polymerizing monomer and polymerization conditions should be such
as to lead to the formation of a crystalline or crystallizable
polymer; and vice versa. Sequentially polymerized block copoly-
mers are most conveniently prepared by solution polymerization
using organo-metallic catalysts or the active Ziegler or Natta
catalysts which give rise to the so-called "living polymers;"
graft copolymers are most conveniently prepared by solution or
suspension polymerization involving dissolving or dispersing the
backbone polymer in a liquid medium which medium contains graf-
ting monomer, free radical initiator and polymerization catalyst.
The number average molecular weight of the copolymers
employed in the toner compositions of the present invention
should be within the range of about 5,000 to 200,000 g/mole for
best results. At molecular weights of less than about 5,000 it
is found that the copolymer may exhibit hot offsetting due to the
low melt viscosity encountered at this low molecular weight;
above about 200,000 g/mole, the copolymer is more difficult to
fuse or fix in the xerographic process. The preferred range for
optimum hot melt properties is about 15,000 to 150,000 g/mole.
The individual amorphous or crystalline polymer segments forming
the block or graft copolymer preferably have a number average
molecular weight within the range of about 1,000 to 20,000 g~mole,
with a preferred range of about 2,000 to 12,000 g/mole.
As indicated above, segmented copolymers derived from
; 30 monomers polymerized to form crystalline or crystallizable
polymers having a cry~ a~ l~lne TM in the range of about 45 to
`150C and a TG within the range of about 20 to -100C are
particularly suitable for the purposes of this invention. Exam-
ples of suitable genus and species polymers are: Polyesters,
including'polyalkylene polyesters wherein the alkylene group
~ contains at least two carbon atoms such as polydecamethylene
- sebacate, polydecamethylene succinate, polyethylene sebacate,
polyethylene succinate, polyhe~amethylene sebacate, polyhex-
amethylene suberate, polyhexamethylene succinate and the like;
aromatic polyesters such as poly-p-xylene adipate or poly-
diethylene glycol terephthalate; polyvinyl esters and ethers
such as polyvinyl ethyl ether, polyvinyl butyl ether, polyvinyl
2-methoxyethyl ether, polyvinyl stearate and the like, poly- ~
sulfides and sulfones such as polydecamethylene sulfide, poly-
hexamethylene sulfide, polytetramethyléne'sul~one and the ike;
polyethers such as polybutadiene oxide, polyethylene oxide,
polypropylene oxide and the like; polyepihalohydrins such as
polyepifluorohydrin; polyenes including cis and trans polydienes
such as cis 1, 4 polybutadiene and 1,2 trans polybutadiene;
polyolefins such as poly-l-pe'ntene, poly-l-hexadecene, poly-
butene, poly-3-methyl-1-butene and the like; cellulose poly-
mers such as cellulose tricaprate; polyacrylates such as poly-
isobutyl acrylate; polyacids; polyamides; polyurethanes; and
like polymers. Copolymers derived from monomers constituting
two or more of the above polymers may also be used. Particul-
arly preferred as crystalline segments in the block or graft
copolymers are those polymers and copolymers having a TM within
the range of about 55C to'about 120C.
~he amorphous segment of the block or graft copolymers
may similarly be selected from a wide variety of polymeric
- 12 -
~36~
materials having a TG less than the TM f the crystalline polym~r
~egment with which it is to be associated in the block or gra~t
copolymer The TG f the amorphous segment is preferably less
the 0C. Examples of suitable amorphous polymers include
atactic polymers derived from the same or different monomers or
monomer isomers used to form the crystalline or crystallizable
segment of the copolymer recited above, said monomers polymer-
ized under conditions such that atactic rather than isotactic
structure results. Suitable classes of amorphous polymers in-
~10 clude polyvinyl ethers; atactic polyolefins: polyacrylates;
polyoxides such as polypropylene oxide; polysulfides; unsymmet-
rically branched polyesters and polyamides; aliphatic polyurethanes;
and like materials.
It has been further found that electrostatographic or
triboelectric properties of the present toner materials may be
optimized and best controlled by employing isomeric copolymers,
that is, copolymers wherein the crystalline and amorphous seg-
ments have identical chemical compositions but, of course,
different chemical structures. Examples of such copolymers
would be block or graft copolymers wherein the crystalline
segment comprises polybutene-l or -2, and the amorphous segment
comprises polyisobutylene; copolymers wherein the crystalline
segment is polyhexamethylene sebacate and the amorphous segment
is poly-(2-methyl, 2-ethyl, 1,3-propylene sebacate).. Other
combinations include isotactic poly tvinyl n-propyl ether)
and atactic poly (vinyl isopropyl ether; poly (trimethylene
sulfide) and poly (propylene sulfide); poly (hexamethylene
oxide) and atactic poly (vinyl butyl ether); isotactic poly
(isobutyl acrylate) and atactic poly (n-butyl acrylate). Other
isomeric combinations will occur to those skilled in the art.
- 13 -
. .
~64q~ ~
As indicated above, ~or best results the segmented co-
polymers should exhibit a Tm within the range of about 45C to
a~out 150C and a TG within the range of about 20C to -lOO~C.
In order to avoid the possibility of blocking under extreme
conditions, it may be desirable to select crystalline and amor-
phous segments such that the copolymers have a Tm in excess of
about 55C and a TG of less than 0C.
The block or graft copolymers may be ~abricated into
electrostatographic toner using any ~f the known techniques of
the prior art by mixing the copolymers with a colorant material.
Mixing may be accomplished by dispersing the colorant in the
melted copolymer, hardening the polymer and pulverizing the
composition in a device such as a jet or hammermill to form it
into small particles. Alternatively, mixing may be carried out
by combining the colorant with a solution, dispersion or latex
of the copolymer, followed by recovery of the copolymer/colorant
mixture in finely divided form by spray drying techniques.
Suitable methods of mixing are more thoroughly described in
U.S. Patent 3,502,582. The average particle size of the processed
toner should be within the range of about 1 to 30 microns, pre-
ferably between about 3 to 15 microns. A subsequent screening
or slzing operation may be necessary to produce a toner having
this particle size distribution.
The colorant material used in preparing the toner
composition may include any pigment or water or organic solvent
soluble dye. The most common pigments used in electrostato-
graphic toner materials are finely divided carbon black, cyan,
magenta and yellow pigments. The most common dyes are the acid,
basic and dispersed dyes of suitable color as are known in the
art. Typical examples of suitable colorants are discussed in
- 14 -
6~619
U.S. Patent 3,502,582. The pigment or dye should be present in
the amount effective to render the toner highly colored so that
it will form a clearly visible image on a recording member. Pre-
ferably, for sufficient color density, the pigment is employed
in an amount from about 1% to about 20% by weight, based on the
total weight of the colored toner. If the toner colorant employ-
ed is a dye, quantities substantially smaller than about 1% by
weight may be used.
q~e toner composition may be formulated into an elec-
trostatographic developer composition by combining the finely
divided toner with a suitable carrier material such that the
toner forms a coating on the carr}er. The toner and carrier
material may be premixed or mixed inside the developer region
of the xerographic machine. Where the development process in
the well known magnetic brush process, the carrier material will
be a magnetically attractive material such as finely divided
iron particles of about 60 to 120 mesh size. For other than
magnetic brush development , the carrier material may be of any
of the known particulate substances exhibiting appropriate tri-
boelectric effects such that the carrier particles impart a
charge to the finer toner whereby the toner adheres to and coats
each carrier particle. Examples of suitable carriers are inor-
ganic salts, glass, silicon and other materlals such as disclosed
in the aforementioned U.S. Patent 3,502,582. The particle size
of the carrier should be significantly greater than the toner,
preferably within the range of about 50 to 1000 microns. The
toner is most effectively employed at a level from about 0.5 to
10 parts by weight per 100 parts by weight of carrier material.
The toner and developer compositions of the present
in~ention may also contain any of the additives known to be
- 15 -
~1~36~q~9
included in such compositions such as lubrication aids, anti-
oxidants, sensitizing agents, polymeric or non-polymeric plasti-
cizers, and the like.
Description of the Preferred Embodiment
S The following specific embodiment illustrates the
preparation of toner ma-terial wherein the polymeric component
comprises an isomeric block copolyester prepared by coupling
crystalline poly (hexamethylene sebacate) [poly HMS] and
amorphous poly (2-methyl-2-ethyl-1,3,-propylene sebacate) [poly
MEPS] using hexamethylene diisocyanate as the coupling agent
whereby urethane linkages are formed. The block copolyester was
prepared by initially individually synthesizing poly~MS and poly
MEPS, and then subjecting a mixture of these homopolymers to a
coupling reaction as hereinafter described.
ExamPle 1
Crystalline poly (hexamethylene sebacate) was prepared
using a kettle equipped with a stirrer, nitrogen gas inlet tube,
thermometer and condenser by reacting sebacic acid with 1,6
hexamethylene glycol in the presence of a p-toluenesulfonic acid
catalyst as follows: sebacic acid and hexamethylene glycol were
added to the reaction kettle in a respective 1.0 to 1.1 molar
ratio along with 0.5 wt % p-toluenesulfonic acid. The 10 mole
% excess of glycol was used to ensure the predominant presence
of hydroxyl end groups in the reaction product. The mixture was
heated to 165C while stirring. At 165C, an amount of xylene
was added to assist refluxing and this temperature was main-
tained until water evolution ceased (4 hrs.). Afterwards, the
condensers were removed and the excess glycol and catalyst were
removed by sparging with nitrogen for 0.5 hours at 165C. On
cooling to room temperature, the poly (hexamethylene sebacate)
~ 16 -
lQ36~0~
crystallized into an off-white solid. ~ext, the poly ~HMS) from
above was purified by precipitation from a benzene solution into
met~anol using techniques well known in the art. The precipi-
tated poly (HMS) was collected by filtration and dried in vacuo.
Analytical data on this purified material indicate an acid
number of 1.06, an hydroxyl number of 34.4, an ~n of 3165
g/mole, an MWD (MW/M~) of 1.41 by GPC in chloroform, a glass
transition temperature of a~out -62C and a crystalline melting
point of about 65C.
Example 2
Amorphous poly (2-methyl-2-ethyl-1,3-propylene
sebacate) was prepared by reacting sebacic acid and a 10 mole
% excess of 2-methyl-2-ethyl~1,3-propylene glycol in the
presence of 0.5 weight % p-toluenesulfonic acid in the same
manner as in Example 1. On cooling to room temperature after
the polymerization, the poly (MEPS) remained as a clear, tacky
fluid. Analysis indicates it has an acid number of 2.40, an
hydroxyl number of 19.4, an ~n of 5150 g/mole, an MWD of 1,87
by GPC in chloroform, and a glass transition temperature of
about -61C.
Example 3
A block copolyester was prepared by coupling the
hydroxy terminated poly (HMS) prepared in Example 1 and the
hydroxy terminated poly (MEPS) prepared in Example 2 using
hexamethylene diisocyanate as the coupling agent according to
the following procedure: three parts by weight of poly (HMS)
of Example 1 were mixed with one part by weight of poly (MEPS)
of Example 2 in a reaction kettle equipped with a stirrer,
nitrogen gas inlet tube, thermometer and condenser. The mixture
was heated to 135C with stirring, and hexamethylene diisocyanate
- 17 -
1~364~9
was added at a level of 4.5% by weight of the fluid polymeric
mixture. The temperature was maintained at 135C. Within 10
minutes the VisCOslty was such that the polymeric mass began to
envelop and climb the stirrer. The coupling reaction was
terminated after one hour and the copolymer was dissoIved in
benzene and precipitated with stirring into methanol. The
precipitate was collected by filtration, washed thoroughly with
methanol and dried in vacuo. A yield of about 89% was realized
from this coupling reaction. The block copolyester was analyzed
by Nuclear Magnetic Resonance to contain 78.6% poly (HMS) and
21.4% poly (MEPS). It had an intrinsic viscosity in chloroform
of 0.90 dl/g at 25C, a molecular weight believed to be about
45,000 1 15,000 g/mole, crystalline melting point of about 63C,
and a glass transition temperature of about -60C.
Although the structure of the block copolymer molecules
produced according to Example 3 is not precisely known, it is
believed that because of the predominant presence of segments
of polymerized (HMS) in the block copolymer, the copolymer
statistically comprises a plurality of repeating crystalline
poly HMS segments connected by urethane linkages, said repeating
segments in turn connected by urethane linkages with the amor-
phous poly (MEPS) segments at various random points along the
block copolymer chain, such as illustrated in the following
scheme:
.... B-c-B-c-B-c-A-c-B................ wherein
B represents polymerized (HMS)
A represents polymerized (MEPS)
O H H O
and C represents -0-C-N (C H2)6~-C-0-
This segment of structure conforms to the generic structure BAB,
a species of which generic structure for this copolymer is
- 18 -
' [Bll-c-[Al] c-[Bll], wherein 103640~
Bl is [-(B-c-)2B]
Al is A
,and B 1 is B
Example 4 '~
A xerographic toner material was prepared by forming
a mixture of the block copolyester of Exarnple 3 and a finely
divided pigment grade carbon black.
A mixture comprising 95 parts by weight of the block
copolyester of Example 3, and 5 parts by weight of Molocco H
,, 10 carbon black was formed by heating the copolyester to a temper-
ature above its melting point, dispersing therein the carbon
black, and mixing until a uniform dispersion of the carbon black
in the block copolyester was obtained. The mixture was then
guick cooled to a temperature below the melting point of the
block copolyester.
Finely divided toner material having an average
particle size in the order of about 20 microns was prepared by
comminuting the above mixture first in a Fitz mill and subse-
~uently in a jet pulverizer.
The toner was tested by employing it as the toner in
a "Xerox 3600" copy machine embodying a contact heat fusing de-
vice and found to produce very satisfactory copies without toner
offset on the fusing roll.
Exam~les 5 - 11
Several additional samples of isomeric block copoly-
esters having various ratios of poly (HMS) and poly (MEPS) were
prepared ~y coupling the poly (HMS) of Example 1 and the pol,y
(MEPS) of Example 2 using various coupling agents. Synthesis
data for these copolyesters is shown in Table 1.
The block copolyesters of Examples 5, 7, 9~ 10 and 11
-- 19 --
: !~ ~l)3f~9
.
o C~ U C~
U o o o o o o o
o o oo r~ In In ~
_ ~ ~ n
E~
OD ~ ~ ~D a) o
~q ~ ~ ~ o r~ o o~ o~
. ~ o U~ U~
o
~C~ .
~: .
~ o o o o ~ ~
_I ,~ o ~ ~I r- o ~r
.~
c~ ~ N t`l
I
O O V O ~`1 0 ,
~C ~ ~ rl Z O ~ ~
~ u ~--
H
. I ~ ~ ~ ~ ~ ~
I~ ~`l ~ ~ ~ ~ d' ~ '
V U U U C~ ~ U
I -- O ~ ~ ~ U ~
,~ 1 U
m
E~ ..
.,
.,, "., ,,, , u~ a~
. ~ o ~ ~ ~ ~ ~ In
~:
u~ ~D ~ ~ O O
n
O ~
. Q
~ O CO CO OD ~.
o ~ ~ ~ ~ ~ ~
p~ ~ ~
ol :
.
`
l x x x x x x x
u~ ~ ~ ~ ~ ~ F~ ~1
~ ~i
~q~36~ f
were prepared by the method of Example 3; with regard to the
block copolyesters of Examples 6 and 8, the procedure of
Example 3 was modified somewhat in that refluxing was carried
out in chlorobenzene (132C) containing a small amount of
pyridine. General techniques for preparing linear copolyesters
using coupling agents are known in the art as, for example,
disclosed in U.S. Patent 2,691,006.
The copolymers of Examples 5 - 11 were each processed
into toner material by the method of Example ~ and each per-
formed satisfactorily when used in a xerographic machine.
As indicated above, toner materials based on the seg-
mented copolymers of the present invention exhibit minimal
latent heats of fusion and at the same time the sharp, well
defined melting points desirable in a toner material. This
; 15 may be illustrated by a comparison of the latent heats of
fusion PHU - in calories/gm.) and melting points (Tm) for a
plurality of polymer samples containing polymerized hexamethy-
lene sebacate (E~S) and polymerized 2 methyl-2-ethyl-1,3-propylene
sebacate ~MEPS).
Example 12
A series of homopolymer blends having various weight
ratios between about 20-80% oE poly (HMS) and poly (MEPS) were
prepared by forming intimate admixtures of the poly (HMS) pre-
pared according to Example 1 and the poly (MEPS) prepared
according to Example 2.
A series of block copolymer samples having various
weight ratios between about 20-80% of poly (HMS) and poly (MEPS)
were prepared according to the process of Example 3.
A series of random copolymers also having various
weight ratios between about 20-80% of polymerized HMS and poly-
- 21 -
merized MEPS were prepared by a process similar to that described
in Example 1 by reacting simultaneously a mixture of 1, 6
hexamethylene glycol, 2-methyl-2-ethyl-1,3 propylene glycol and
sebacic acidO Various copolymer compositions were achieved by
alterning, systematically, the molar ratio of the two diols in
the condensation reaction with sebacic acid. The copolymers
so prepared exhibited Mn values within the range of about 2200
to 3600 g/mole.
Samples of each type of polymer composition for various
levels of polymerized HMS content were evaluated for latent
heat of fusion and crystalline melting point data, the results
plotted, and the plots interpolated at 80%, 60%, 40%, and 20%
HMS content. Results are shown in Table 2.
TABLE 2
% Random Homopolymer Block
HMS CopolYmer Blend ~polymer
Tm ~ Hu Tm d H T~ ~Hu
100% 65C 30 65C 30 65C 30
80% 57C ~10 64C 25 63C 17
60% 42C - 62C 18 61C 11
40% 22C - 62C 12 56C 7
20% 0C - 61C 6 5~C 6
As can be seen from Table 2, the melting point of the
random copolymers drops off rapidly as the % HMS in the random
copolymer is decreased with a corresponding increase in % MEPS.5
Below about 60% ~S, the copolymers are a viscous fluid unsuit-
able for use in a toner composition. With the homopolymer
blends, the lowering of Tm is much less severe, but~ Hu is
found to drop off in almost direct proportion to the amount of
poly (HMS) in the blend. With the block copolymers, the lower-
-- 22 --
~3~ 9
ing of Tm is somewhat greater than in the blend, but still quite
acceptable for toner use, but most significantly the drop in
u is much higher than in comparable samples of the blend.
Thus, considerably less heat energy is required to melt or fuse
toner based on the block copolymers than is required to melt
toner based on the homopolymer blend.
~lthough the toner ~omposition of the present lnven-
tion may be used in electrophotographic processes embodying any
of the well known techniques of image fixation or fusing such as
radiation, vapor, or liquid fusing, it is employed most advan-
tageously in processes involving contact fusing, as discussed
above, or flash fusing such as for example disclosed in U.S.
Patents 3,465,203, 3,474,223, and 3,529,129. In each of these
processes, exposure of the image recording medium bearing the
powdered toner image, usually paper, to a source of hea~ is for
an extremely llmited tlme duration. In contact fusing, a moving
recording medium is exposed to heat while the medium passes
through a nlp formed by a heated pressure roller and a second
support roller. Wlth radiant flash fusing, the recording medium
is exposed to heat energy in the form of electromagnetic waves
generated usually by a gas lamp, such as a xenon lamp, for a
period of timed measured in milliseconds. With each of these
processes, a maximum amount of heat energy sufficient to properly
fuse the toner without scortching the recording medium is re-
quired over a short period of time. It is thus evident that
the toner compositions of the present invention having sharp
well defined melting points and controllably minimal latent
heats of fusion respond particularly well for use in processes
involving such fusing techniques.
While the invention has been described with reference
- 23 -
1036~
to the embodiments disclosed herein, it is not confined to the
specific embodiment set forth, and this application is lntended
to cover such operative modifications or changes as may come
within the scope of the following claims.
: 10
: 25
- 24 -
