Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
The invention relates to a triboelectrically chargeable toner powder
for the development of latent electrostatic images, which toner powder can be
fixed by heat in a radiation fusing or contact-fusing device, and which essen-
tially consists of finely divided, coloured toner particles containing an in-
sulating thermoplastic resin and colouring material. The invention relates in
particular to such a toner powder that is triboelectrically positively charge-
able, and of which the insulating thermoplastic resin consists predominantly
of epoxy resin.
The invention also relates to a process for preparing such a toner
powder as well as to developer powders of the so-called one- or two-component
type comprising such toner powder.
Toner powders of the kind referred to above are known and can be used
as such, i.e. as a one-component developer or in the form of two-component de-
velopers to develop latent electrostatic images, for instance such as are ob-
tained electrographically or electrophotographically on a suitable substrate.
The latent electrostatic images may have a positive charge such as, for ex-
ample, in electrophotographic elements based on selenium, or a negative charge
such as, for example, in electrophotographic elements based on zinc oxide.
Examples of thermoplastic resins, which are extensivel~ used in
toner particles, are polystyrene, copolymers of styrene with an acrylate and/or
methacrylate, polyamides, modified phenolformaldehyde resins as well as poly-
ester resins. Carbon black is generally added as colouring material in black
toner powders for use in two-component developers, whereas magnetically at-
tractable pigments, such as for example iron powder, chromium dioxide or
ferrites, frequently are applied in toner powders to be used as one-component
developer. In coloured toner powders employed, for example, in electrographic
multi-colour reproduction processes, organic dyes are added to the thermo-
plastic resin. Powdered materials consisting, for example, of metal, e.g.
iron or nickel, or of metallic oxide, glass, sand or quartz, with or without
a synthetic coating, are applied as carrier particles in two-component de-
velopers.
As most of the thermoplastic resins suitable for toner powders are
charged negatively upon triboelectric contact with conventional carriers,
toner powders for use in admixture with one of such carriers -Eor the develop-
ment of negatively charged electrostatic images must contain a polarity control
agent to ensure a proper charging of the toner powder. Moreover, also in one-
component developers to be used for the development of negatively charged
electrostatic images, the presence of a polarity control agent may be advan-
tageous in order to prevent the toner particles from acquiring a charge of the
wrong polarity upon triboelectric contact with parts of the developing appara-
tus. A polarity control agent is an agent added to the toner to gain the
desirable triboelectric polarity and charging level. In general, the positive
polarity control agents are amino compounds, quaternary ammonium compounds and
organic dyes, in particular basic dyes and their salts. ~xamples of conven-
tional positive polarity control agents are benzyl dimethyl-hexadecyl ammonium
chloride and decyl-trimethyl ammonium chloride, Nigrosine base, Nigrosine
hydrochloride, Safranine T and Crystal Violet. In particular Nigrosine base
and Nigrosine hydrochloride are often used as positive polarity control agents.
Positively chargeable toner powders are used in particular for the
development of electrostatic images having a negative polarity. They are
brought into contact with the surface to be developed by means of one of the
conventional developing methods such as, for example, cascade, magnetic brush
or powder cloud development. In these methods the positively charged toner
powder is deposited on the negatively charged latent image, as a result of
which this becomes visible.
In direct electrophotography the powder image thus formed is fixed
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directly onto the surface on which it has been deposited. In indirect elcctro-
photography it is transferred to a receiving surface and fixed thereon. IJsual-
ly, the powder image is fixed by heating, e.g. by radiant heat in a so-called
radiation or a flash-fusing device by means of electromagnetic radiation or
electromagnetic flash, or by bringing it in a so-called contact-fusing device
into contact with a heated surface, such as a roller and/or belt.
The basic requirements for toner particles in general, and for those
to be used in the development of negative charged electrostatic images in
particular, are pronounced polarity, good charging characteristics such as
sufficient chargeability, uniform charge distribution, charge stability and
low sensitivity to moisture and temperature, good and highly reproducible fus-
ing properties, thermal stability and good permanence dur mg prolonged use.
Moreover, to save energy the initial melting point of the toner powder should
desirably be as close as possible above the glass transition temperature mini- ~;
mally desired for its thermal stability, which temperature generally is between
45 and 60C. Purther, when the toner powder is intended for contact-fusing,
the fusing range should be as wide as possible, preferably some tens of degree
centigrade, in order to preclude the risk of~transferring the image to the
fusing roller and from there back to the paper, which transference is called
offsetting, and to minimi~e the rls~ of contamination of the contact-fuslng
rollers. The lower limit of the fusing range is the lowest temperature at
which the image still has just been sufficiently fixed; the upper limit is the
temperature at which offsetting begins.
Although some known toner powders satisfy a nwnber of the above-
mentioned requirements to a greater or lesser degree, toner powders fulfilling
quite satisfactorily all the aforementioned requirements at the samc time were
practically unknown, hitherto. This applies, in particular, with regard to
positively chargeable toncr powders. One of the major causes for this is that
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most toner po~ders, in order to make them positively chargeable against thccarriers preferred in practice, must be mixed with a polarity control agent.
The most conventional polarity control agents mentioned before, based on basic
dyes, among l~hich are the nigrosines in particular, possess a number of less
favourable properties. As most important may be mentioned, -for example, their
complex, undefined chemical structure and their quality not being constant.
It is often difficult to mix them quite homogeneously l~ith the toner resin,
and even then there is the risk that during the further s~eps in preparing the
toner pol~der and/or during the use itself, the polarity control agent may
migrate to the surface of the toner particles. This may cause the polarity
control agent to deposit, during use of the developer, on the carrier particles>
thereby reducing more and more the chargeability of the toner particles against
them.
Finally, polarity control agents based on basic dyes are more or less
dark-coloured, so that only black or highly dark-coloured toner pol~ders can be
prepared therefrom.
Therefore, nunerous proposals for substitutes for polarity control
agents based on basic dyes have been made. In general, these proposals come
dol~n to a certain positive polarity-controlling group, such as an aminO, an
ammonium, a sulfonium, an oxonium, a phospllonium or a pyridinium group being
coupled to a monomeric or polymeric organic compo~md that is readily miscible
~ith one or more thermoplastic resins chosen for the preparation of the toner
powder, or one of the said groups being coùpled direct to the resin chosen for
the preparation of the toner powder.
Positive polarity control agents of the three types referred to
above are described, for example, in the German Patent Applic~tions, laid open
for public inspection, Nos. 2 226 404, 2 461 643, 2 43S 8~l8 and 2 327 371.
The Japanese Patent Speclf cations Nos. 20096/74 and 29583/74
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describe toner powders, based on epoxy resins, which have been made positively
chargeable by heating 100 parts by weight of an epoxy resin for some hours at
temperatures between 120 and 160C in the presence of 0.5 to 10 parts by weight
of a heterocyclic amine, in particular morpholine or an N-alkyl derivative
thereof. However, the toner powders so obtained prove to give off a very un-
pleasant smell, especially during fixing. Further, when they are used in a
contact-fusing device, their fusing range is rather narrow (about 15C), which
will soon cause offsetting as well as after a short time an objectionable con-
tamination of the contact-fusing rollers, the useful life of their coating thus
being strongly diminished.
Moreover, of epoxy resins it can be said in general that they are
less suitable for use in toner powders, because their strongly reactive epoxy
groups, both during preparation of the toner powder as well as during its stor-
age and use, may easily tend to undesired reactions and from that to instabili-
ty of the toner powder. This is probably the main reason why, up to the pres-
ent, epoxy resins have only been sporadically applied in practice for the pre-
paration of toner powders, although in literature they are occasionally men-
tioned for that purpose.
The object of the present invention is to provide toner powders which
acquire a positive charge upon triboelectric contact with metal carrier partic-
les and which powders are highly stable under normal conditions of s~orage and
use and to a high degree meet the desired properties for toner powders summed
up above. The use of the conventional positive polarity control agents is
avoided. The afore-mentioned drawbacks of epoxy resins in toner powders, re-
sulting from the high reactivity of their epoxy groups, are not only overcome
but that reactivity is even used positively to obtain toner powders which are
adapted to every purpose of application, particularly with respect to the fus-
ing and fixing range, thermal stability and charging level, and which can be
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prepared in a simple and economic way from the kinds of epoxy resin largely
commercially available. The lower limit of the fusing range, as compared to
the toners frequently used hitherto, is particularly close above their glass
transition temperature, and the width of their fusing range may properly
be controlled. Moreover, the toner powders are practically odourless and may
be prepared in any colour.
According to the present invention there is provided a toner powder
acquiring a positive charge upon triboelectric contact with metal carrier
particles, and characterized by stability at temperatures up to 45C and
a melting point of about 60 to 150C, which toner powder comprises
fusible particles containing
a thermoplastic resin constituent, and
colouring materials,
the thermoplastic resin including:
(1) a modified epoxy resin being a derivative of one or more epoxy resins
(A~ of which at least 50~ of the total number of initial epoxy groups have
been blocked partly by chemical reaction with a monofunctional carboxylic acid
and/or phenolic compound and partly by intermolecular reaction with the
hydroxylic groups of the epoxy resin (A) and/or by reaction with a bi-
or polyfunctional epoxy hardener, and
(2) an epoxy amine as positively acting polarity control agent being
the reaction product of an epoxy resin ~B) with a monofunctional secondary
amine having a PKa value higher than 3,
wherein components (1) and (2) may be mutually cross-linked, and wherein
the total mass of the resin components (1) and (2) have an epoxy molar
mass (grams resin/grams equivalent of epoxy) of at least 8000.
By epoxy resins are meant in the context of this invention, condensa-
tion products of a polyphenol, in particular 4,4'-isopropylidene diphenol, with
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a halohydrin, in particular l-chloro-2,3-epoxy propane. Optionally, the
thermoplastic resin may also include, a phenoxy resin, which may be cross-
linked with the modified epoxy resin (1) and the epoxy amine (2).
Both the modified epoxy resin to be used in the toner powders accord-
ing to the invention and the epoxy amine can be prepared by starting from com-
mercially available epoxy resins. As is well known, they generally have an
epoxy molar mass (E.M.M.) below 4,000. By "epoxy molar mass" is meant the mass
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of resin in grams which contains one gram equivalent of epoxy (see pages 4 to
14 of "Handbook of Epoxy Resins" by Lee and Neville, McGraw Hill Book Company,
1967). The choice of the resin or resins to be used as starting products is
mainly determined by the requirements that the toner pwoder should be stable
at temperatures up to 45C and have a melting point between 60 and 150C. The
first requirement is related to the aspect that, before the fusing step, temp-
eratures up to 45C may occur in every stage such as storing, staying and pro-
cessing in the copying apparatus. The second requirement is related, inter
alia, to limiting the energy consumption during the fusing step and to the
maximum temperature the copying paper may be subjected to during fusing, as
otherwise discolouration or even burning could occur.
Suitable as starting material in the preparation of the modified
epoxy resins according to the invention are, for example Epikote 1004 (melting
point 90 - 100 C, E.M.M. 850 - 940, both data according to the specifications
of the supplier, Shell ~ederland Chemie B.V.). Epikote 1006 (melting point
115 - 125 C, E.M.M. 1,55~0 - 1,900), Epikote 1007 (melting point 120 - 130 C,
E.M.M. 1,700 - 2,050), and Epikote 1009 (melting point 140 - 155 C, E.M.M.
2,300 - 3,400). Also mixtures of 2 or more of such resins may be used. How-
ever, as will be explained hereafter in the description, under certain condi-
tions it is possible to use a starting material epoxy resins having lower or
higher melting points than those mentioned above.
In order to meet the requirement that the toner powder according to
the invention is stable under normal conditions of storage and use, at least
50% of the total number of epoxy groups in the starting epoxy resins or epoxy
resins should be blocked as indicated above. What percentage of the total
number of epoxy groups in the starting epoxy resins must be blocked in order
to achieve the d~sired stability depends on the reactivity of the starting
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epoxy resin. The higher the reactiYity of the starting epoxy resin, or resins,
the higher the percentage of blocked epoxy gro~ps must be for obtaining a
stable toner powder. Preferably, the epoxy groups of the starting epoxy resin
or resins are blocked to such a degree, that the E.M.M. value of the total mass
of the components (1), (2) and (3) in the toner powder according to the inven-
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tion is at least 8000. For some of the commercially most readily available
epoxy resins the following table gives a survey of their average E.~.M. and of
the percentage of their epoxy groups which has tbeb]ocked ~ order to increase
its E~M.M~ to a predetermined higher value.
Table
Percentage of blocking Epikote 828 1001 1004 1009
O av . E. M.M. 190 500 900 3200
" 380 1000 1800 6400
" 760 2000 3600 12850
87.5 " 1520 4000 7200 25600
93-75 " 3040 8000 14400>5aO00
96.87 " 6080 1600028800
98.13 " 12160 32000>50000
From the above table it can be seen that from an Epikote 1009 only slightly
more ~han 50% of its epoxy groups need to be blocked in order to obtain a
resin with an E.M.M. of some 8000, whilst of a lower molecular type resin in
general at least some 87.5% of its epoxy groups will have to be blocked for
that purpose.
It should also be remarked that in the case of the lower molecular
weight epoxy resins an increase of the E.M.M. figure of a few thousand in fact
corresponds with only a few percents of increase in blocked epoxy groups. It
will, therefore, be obvious that the requirement that the E .M.M. of the total
mass of components (1), (2) and (3) in the toner powder preferably amounts to
- at least 8000 can be taken in a less stringent sense, the lower the molecular
weight of the starting resin has been.
Although the sensitivity of the E.M.M. figure as a measure for the
reactivity left in the thermoplastic resin constituent apparently decreases
with decreasing molecular weight of the epoxy resin used as starting material,
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37
applicants believe that the E.~.!l. figure still is the best yard stick present-
ly availa~le for that purpose.
Which part of the initial epoxy groups in the starting epoxy resin
or resins must be bloclAed by chemical reaction with a monofunctional carboxylic
acid or phenol and which part by intermolecular reaction and/or by reaction
witll an epoxy hardener, is related to the way in which the toner powder is
intended to be fixed. Applicant has found that if the toner powder according
to the invention is intended for radiation fusing, the viscosity (measured at
1~0 C) of the thermoplastic resin constituent present therein should preferably
be between 10 and 1,000 s.Pa, and its glass transition temperature (Tg) be-
tween 45 and 65 C. For use in an apparatus equipped with a contact-fusing
device the viscosity, measured at 140C, should preferably be between 200 and
200,000 s.Pa, and ths Tg between 45 and S0C.
Blocking by means of a monofunctional phenol or carboxylic acid re-
sults in the desired increase of the E.~ ~l. of the starting epoxy resin without
its molar weight and viscosity substan~ially being increased. Therefore, this
method is advisable for ti~e preparation of the modified epoxy resin fraction
in a toner powder intended for radiation fusing. In certain cases a combina-
tion ~Yith blocking by intermolecular reaction may be useful. The afore-men-
~Q tioned parameters for the viscosity and the Tg, which the epoxy resin mixture
should preferably possess in a toner powder according to the invention intended
for radiation fusing, are met if at least 50% and, preferably, at least 70% of
the epoxy groups of the modified epo~y resin present therein are blocked by
reaction with a monofunctional carboxylic acid or phenol.
Except for the carboxyl and hydroxyl group, respectively, the mono-
functional carboxylic acids and phenols, respectively, to be used for the
bloc~ing process should not contain any further substituent that might react
t~ith the epoxy groups of the epoxy resin under the conditions prevailing during
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the bloc~ing process. Particularly suitable are aliphatic and aromatic car-
boxylic acids and phenols, especially those which have been substituted by one
or more alkyl, aralkyl, cycloalkyl, aryl, alkylaryl, alkoxy or aryloxy groups
and, in addition, are involatile or substantially involatile under the condi-
tions prevailing during the modification process. Examples of such carboxylic
acids are ben~oic acid, 2,4-dimethylbenzoic acid, 4-(~,~-dimethylbenzyl)-ben~oic
acid, 4-phenylben70ic acid and ~I-ethoxybenzoic acid. Further, the saturated
aliphatic carboxylic acids heptanoic acid, nonanoic acid, dodecanoic and iso-
dodecanoic acid, hexadecanoic acid and octadecanoic acid. Examples of above-
meant phenolic compounds are 4-n-butyl phenol, 4-n-pentyl phenol, 2,3,4,6-
tetranethyl phenol, 2,3,5,6-tetramethyl phenol, 4~ dimethylben7yl)phenol,
4-cyclohexyl phenol, 3-methoxy phenol, 4-methoxy phenol and 4-ethoxy phenol.
Of the above compounds substituted or unsubstituted benzoic acid
and 4-~,-dimethylbenzyl)phenol have proved to be most suitable.
To meet the paraneters mentioned above for the E.M.~I., the viscosity
and the Tg, which the thermoplastic resinconstituent should preferably possess in
a toner powder intended for contact-fusing, the thermoplastic resin constituent
must con.ain a low molecular fraction with a mol. weight below 4,000 and a
fraction, which may be cross-linked, with a mol. weight over ~,000, preferably
over 10,000. This condition may have been satisfied by the fact that ~he modi-
fied epoxy resin present in the thermoplastic resin content contains both the
low and the high molecular fraction.
Another possibility, where the modified epoxy resin forms either the
low molecular fraction alone or alrnost completely the high molecular fraction,
and the epoxy amine the missing fraction, will be further explained hereafter
in the description.
A modified epoxy resin with a low and a high molecular fraction can
be obtained, for example, by blocking thc epoxy groups of a commcrcially
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available epoxy resin or mixture of epoxy resins for at least about 5% and,
preferably for about lO - 35%, depending on the star-ting product, by chemical
reaction with a monofunctional carboxylic acid or phenol and the other epoxy
groups up to a total of at least 5Q% by intermolecular reaction with the al-
coholic hydroxyl groups of the resin. Blocking with a monofunctional carboxy-
lic acid or phenol results in the low molecular fraction. The intermolecular
reaction results in an increase of the mol. weight. These reactions can be
carried out simultaneously or one after another. In latter case, at an other-
wise equal Tg, a higher viscosity and a wider fusing range is obtained than in
former case.
However, the desired high molecular fraction can also be obtained by
reacting a part of the epoxy groups of the starting epoxy resin (or resins~
with a polyfunctional epoxy hardener, which reaction may lead to linear or
branched structures. Also in that case the said two reactions can be carried
out simultaneously or after each other. In the present case 4,4'-isopropyli-
dene diphenol is a particularly suitable epoxy hardener. Generally the in-
crease of the molecular weight of the starting epoxy resin to be obtained by
means of an epoxy hardener is higher and faster to attain than the increase
which is obtained by intermolecular reaction. If an epoxy hardener is used
~0 for obtaining the high molecular fraction, preferably 40 to 75% of the epoxy
groups in the ultimately obtained modified epoxy resin must have been blocked
by chemical reaction with a monofunctional carboxylic acid or phenol, and at
most 15 to 60%, preferably 20 to 40%, by reaction with an epoxy hardener.
In the above processes for obtaining a modified epoxy resin with a
low and a high molecular fraction the use of the said blocking reaction with
a monofunctional carboxylic acid or phenol has proved to be necessary for ob-
taining a useful toner. Otherwise too high melting products which cannot be
fused and can hardly be ground are obtained.
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If in the toner powder according to the invention both the modified
epoxy resin and the epoxy amine consist almost completely of low molecular
fractions, the high molecular fraction can be obtained by adding a phenoxy resin
as a third component.
Phenoxy resins are obtained by condensation of a halohydrin, in
particular l-chloro-2,3-epoxypropane with an excess of polyphenol, in parti-
cular 4,4'-isopropylidene diphenol. They have a substantially linear struc-
ture and a molecular weight between 109000 and 80,000. An example of a suitable
C commerically available phenoxy resin is Rrutapox 0717 (mol. weight 30,000), from
Messrs. Bakelite.
However, it is also possible to obtain a thermoplastic resin consti~
tuent with a low and high molecular fraction by using one of the epoxy amines
described hereafter instead of the Eraction blocked with a monofunctional car-
boxylic acid or phenol. In such a mixture the epoxy amine evidently has a
double function: that of polarity control agent and that of low molecular
fraction. In that case the parameters indicated as the preferable ones for
contactfusible toners will be achieved, when the epoxy amine constitutes at
least 5%, and preferably between 10 and 25%, of the ultimate thermoplastic
resin constituent. Although quite useful toner powders can also be obtained
~ in this way, blocking by chemical reaction with a monofu~tional carboxylic
acid or phenol has the additional advantage that the fusing behaviour of the
toner powder can be controlled fully independently of the charging behaviour.
The chemical reaction product of an epoxy resin with an amine, for
the sake of brevity referred to as epoxy amine, present in the epoxy resin
mixture of the toner powder according to the invention, has the primary func-
tion of a polarity control agent. For its preparation one of the kinds of
epoxy resin readily available on the market may be used as starting material. An
epoxy resin having a mol. weight not exceeding 1,500 and an E.M.M. between 150 and
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1,000, in particular with an E.~.M. Of aPPrOXimate1Y 500, is preferably chosen
as starting resin for the preparation of the epoxy ami.nes to be used in the
conte~t of this invention. Examples of con~nercial products that satisfy these
requirements are EpiXote 82S, 1001 and 100~. The starting epoxy resin is re-
acted with a basic amine. The basic starting amine must be a primary or
secondary, mono- or polyfunctional amine having a pK value higher than 3,
preferably with a pK value between 8 and 11. The functionality of an amine
is determined by the number of hydrogen atoms attached to basic nitrogen atoms
in the molecule. As regards the signification of the pK value, reference is
made to the book "Dissociation constants of organic bases in aqueous solution"
of the International Union of Pure and Applied Chemistry, edition ~g~, page 1
and 2.
It is an additional advantage of the epoxy amines according to the
invention that by selecting a starting amine having a certain PKa value the
chargeability of the toner resin prepared therewith can, within certain limits,
properly be controlled. Thus, the freedom in selecting the carrier to be used
in the developer is increased, a possibility which is meeting with increasing
desire.
Preferably used`in the context of this invention are substituted or
unsubstituted aliphatic amines and unsubstituted cyclo-aliphatic and hetero-
cyclic amines. Examples of unsubstituted, monofunctional aliphatic amines that
have been found quite useful are dipropyl-, diisopropyl-, dibutyl-, dipentyl-
and dihexylamine. Particularly good results were obtained with aliphatic
hydroxy-alkylamines, in particular 2-methylaminoethanol and 2,2'-iminodiethanol.
Examples of successfully tested polyfunctional amines are 2-amino-etllanol,
ethylene diamine, diethylene triamine and 2,2'-(etllylene diimino)diethanol.
Since the structure of the epoxy amines according to tlle invention
is closely related to that of the modified epoxy resin they are rcadily miscibler~.
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~ith the tone; resin and show hardly any tendency to mi~rate. As a resui. .ile
toner powder prepared therewith has a good uniform chargeabilit~ and a nigh
charge stability. ~oreover, the present epoxy amines are practically colour-
less, so that positively chargeable toner po~iders in any desired colour can be
prepared therewith.
In general, the quantities of epo~y amine to be used in ~he toner
powder according to the invention range betwcen 0.01 and 1 equivalent base per
kg toner, depending inter alia on the carrier to be used in the developer to-
gether with the toner powder. l~'ith the carriers most often used hithertoJ in
most cases the desired charging level is obtained if.per kg toner powder ac-
cording to the invention between 0.025 and 0.15 equivalent base is present in
the form of an epo~y amine.
Although the function of the epoxy amine in the toner powder accord-
ing to the present invention is primarily that of a polarity control agent, it
can also be used with success for preparing the ~hole higl.l molecular fraction
or part of it in the thermoplastic resin ~onstituant, which is the fraction pre-
ferred in toner powders according to the invention destined for contact fusing.
In that case, the starting epo~y resin must be reacted with an e~cess poly-
functional amine, so that a polyfunctional epoxy amine is obtained. The e~-
cess amine is then removed.
By reacting such a polyfunctional epo~y amine with an epo~y resin
such as, for e~ample, Epi~ote 1001, it is possible, depending on the reaction
conditions chosen and the polyfunctionality of the epo~y amine, to obtain a
higher molecular epoxy resin fraction having the desired mol. ~ei~ht and an
E.r.l.M. e.~ceeding ~,000. By mi.~ing this fraction in ratios between appro~imate-
ly l:S and 1:2 ~ith a low molecular modified epo~y resin of which the epo~y
groups have bcen blocked as above indicated, there is obtaincd a thermoplastic
resin consituent which is at the same time suitable for the preparation of
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positively chargeable toner powders intended for contact-fusing.
The toner powder according to the invention can be prepared by means
of one of the methods generally known for the preparation of toner powder such
as, for example, the kneading, extrusion or hot melt method. According to the
first two methods the resin, the polarity control agent, the colouring material
and, if desired, other ingredients are generally mixed together at approximate-
ly 90 to 160C. In the last-mentioned method the mixing is generally carried
out at about 200C. After cooling, the resulting mass is ground into particles
of the desired degree of fineness, which in general ranges between 2 and 50 ~m.
If desired, it is also possible to divide the mixture in small particles by
spraying of the melt.
Of the three methods mentioned above the hot melt method has proved
to be most suitable for the preparation of the toner powder according to the
invention. The toner powder prepared by that method proves to satisfy even to
a higher degree and to be reproducible, in particular with regard to its most
essential properties such as charge behaviour, stability and fusing behaviour,
than when either of the two other methods are applied. A contributing factor
thereby is that with that method the temperatures and the residence times can
be controlled and maintained most easily as required. Moreover, this method
has proved to be most suitable to effect the conversion of the starting epoxy
resin into the modified epoxy resin to be used in the toner powder according
to the invention during the preparation of the toner powder itself. This has
a number of advantages over a separate preparation of the modified resin.
Accordingly the toner powder according to the invention is preferably
prepared by mixing the starting epoxy resin or mixture of epoxy resins in the
molten state at temperatures between some 150 and 250C with the desired epoxy
amine, colouring material and, if desired~ other ingredients such as, for ex-
ample, plasticizers, flow promoting agents, and the like, and carrying out the
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blocking of the epoxy groups of the starting epoxy resin or mixture of start-
ing epoxy resins with a monofunctional carboxylic acid or phenol, and by inter-
molecular reaction and/or by reaction with a polyfunctional epoxy hardener
during mixing with the ingredients. The blocking reactions described proceed
during the mixing operation of the toner. In that process the basic epoxy
amine functions as the catalyst for these reactions. If desired, tetramethyl
ammonium chloride can be used as an additional catalyst.
The blocking of the epoxy groups of the starting epoxy resin or
resins can be controlled in this method by varying the amount of monofunctional
carboxylic acid or phenol and the reaction temperature and reaction time. If
the blocking of the epoxy groups of the starting epoxy resin or resins is car-
ried out in the presence of the epoxy amine and/or the phenoxy resin, if used,
some cross-linking of the modified resin with the hydroxylic groups of the
epoxy amine and/or phenoxy resin may occur. Such a mutual cross-linking of
the several components is acceptable, provided that the melting point of the
resin constituent obtained is not too high. Mutual cross-linking of the resin
components can be avoided or be diminished by adding the epoxy amine and/or
phenoxy resin after the blocking reactions, carried out for manufacturing the
modified resin, have been completed.
The dyes required for the preparation of other than black-coloured
toner powders often prove not to dissolve readily in the resins frequently
used so far for toner powders. However, a complete solubility of the dye in
the resin is desired for transparent-dyed toner powders applied in multi-colour
processes. Consequently the choice of useful dyes was limited and/or agents
for promoting the solubility had to be used. It is an additional advantage
of the toner powders according to the present invention that numerous dyes
fully dissolve in epoxy resins.
To prepare a powder developer of the two-component type, the toner
- 16 -
powder according to ~he invention is mixed, immediately after its preparation
or in a later stage, with the desired carrier particles. If the developer is
in~ended for magnetic brush development, magnet:i7able iron particles, provided
or not with a surface layer, are used as carrier. The desired particle sizes
of the carriers are known to those skilled in the art. In general, their di-
mensions range between 50 and 150 ~Im. Dependent on the particle size and the
specific mass of the two components the two-component developer generally
contains between 1 and 8 per cent by weight of toner particles.
If the toner powder according to the invention should be used as
such, i.e. as a one-component developer, magnetically attractable material is
preferably incorporated in the resin as the main colouring material in order
to make the toner powder suited for being used in the so called magnetic brush
developing system. The percentage of magnetic material in the toner powder
generally should be between lQ and 50% by weight.
The invention is further illustrated with reference to the following
Examples.
Example 1
This Example relates to a general method for preparing an epoxy amine
illustrated with reference to the preparation of the reaction product of
Epikote 1001 with 2-methylaminoethanol.
While stirring at 120C, a solution of 990 g of Epikote 1001 (E.M.M.
= 495) in 75Q ml of 4-methyl-2-pentanone was gradually added to 300 g of 2-
methylaminoethanol having a PKa f 9.8. After this addition, the whole was
refluxed for two hours. Subsequently, the solvent and the excess amine were
blown off under steam. The base equivalent mass of the dried material was 565.
A comparable reaction product was obtained by gradually adding
Epikote 1001 in the solid state at 120C to the amine, followed by heating for
one hour at 180C. The excess amine was blown off by steam as well. The base
- 17 -
equivalent mass was 580.
Preparation of contact-fusible toners:
_ _ _
Example 2
- In a vessel, provided with a stirrer and oil bath heater, 152 g of
4-~,~-dimethylbenzyl)-phenol and 60 g of the epoxy amine prepared in Example
l from Epikote lO01 and 2-methylaminoethanol were mixed at a temperature of
150 C. Subsequently, 508 g of Epikote lO01 (E.M.M. = 495) were graduallv added,
while the tem~erature was brought up to 200C. Thereupon, 60 g o~ carbon pig-
ment (Printex G; Degussa) were added, after which the temperature was kept at
200C for another hour. The blocking phase of the epoxy resin with the mono-
functional phenol had then been completed and the low molecular fraction was
ready. Subsequently, 220 g of a phenoxy resin (Rutapox 0717, average molecular
weight approx. 30,000) were added; the mixing was then continued for 2 hours
at 200C, after which the melt was drained off and cooled. The resulting mass
was ground and sieved in known manner to give a toner powder having particles
between 8 and 22 ~m, and a specific surface of 0.51 ~m 1.
The residual 4-(~,~-dimethylbenzyl)-phenol in the toner was smaller
than 0.2%. The glass transition temperature (Tg) was 57C. This was deter-
mined from the D.S.C. thermogram recorded by a Du Pont 990 thermal analyser.
Also after prolonged heating at 220 C, a temperature which is well over the
temperatures usually applied in fusing devices, the Tg remained constant at
57C, from which it could be concluded that the toner was thermally stable.
The melt viscosity measured in a cone and plate mechanical spectrometer of
Rheometrics Inc. was 480 s.Pa at a temperature of 140C; the epoxy molar
mass ~E.M.~I.) was 13,000. _
Three parts by weight of the toner powder thus prepared were mixed
with 97 parts of iron powder composed of particles between approximately 50
and 130 um. The toner powder in the developer so obtained had a pronounced
~: ~DY ~C 18 -
t ~
.
:
positive polarity. The triboelectric charge amounted to + 14 ~C/g. The toner
~as very little dusty. By means of this developer combined l~ith a photocon-
ductor based on 7inc o~ide as described in D~ltch Patent Application 7217-'84
hi~h quality copies on plain paper were obtainecl in an automatically oper~ting
copying ap?aratus, permitting very wide tolerances in adiusting its furctions,
such as bias voltage, exposure intensity and the concentration of the toner.
At the end OL an endurance test in a testing apparatus, in the course of which
50,-000 copies were made, no negative influence due to the properties of the
toner powder was noticeable on the image quality. In a contact-fusing device
the toner could be fixed well by heat at temperatures between 76 and 112 C
~idth of the contact-fusing range: 36C). The contact-fusing device used
was fitted l~ith a roller coated with silicone rubber, of which the top layer
had been previously aged. The fusing ranges found were narrower but corres-
ponded more to practical conditions than with a new silicone rubber roller.
The effective contact time of the copy ~ith the heated roller was 1.3 seconds.
Example 3
The preparation according to Example 2 ~as repeated, but nol~ ~ith
the monofunctional carboxylic acid benzoic acid as a blocking agent instead of
the 4-~,a-dimethylbenzyl)-phenol. The ingredients used and their quantities
were: 56.2 g of Epikote 1001, 9.8 g of benzoic acid, 22.0 g of Rutapo~ 0717,
6.0 g of epoxy amine prepared from Epikote 1001 and 2-methylaminoethanol, and
6.0 g of carbon. The residual free benzoic acid was below 0.1%. The toner
gave results which were comparable to those of E.~ample 2. Tg, melt viscosity
(140 C) and E.M '1. were 59 C, 333 s.Pa and above 20,000, respectively.
E~ample 4
The preparation accorcling to Example 2 was repeated, but no~ Wit]l an
increased content of the high ~.olecular fraction. The ingredients used and
their quantities l~ere: 38.0 g of Epikote 1001, 13.5 g of 4-(a,a-dimethylben7yl)-
19 -
`.~
.'''.': ~
~3~37
phenol, 33.6 g oE Rutapox 0717, 8.9 g of epoxy amine prepared from Epikote
1001 and 2-methylaminoethanol, and 6.0 g of carbon. The Tg of the toner was
65 C, the contact-fusing range was 85 to 143C (range 58C). E.M.M. exceeded
20,000, melt viscosity 2,000 s.Pa. The charging and developing behaviour of
the toner corresponded to that of the toner mentioned in Example 2.
Exam~le 5
60 g of phenoxy resin (Rùtapox 0717) were introduced at 200 C in a
Z-blade kneader. Subsequently, a low molecular fraction prepared from 24.2 g
of Epikote 1001, 7.3 g of 4-(~ dimeth~lbenzyl)-phenol, 4.1 g of epoxy amine
according to Example 1 and 4.4 g of carbon, was gradually added and the whole
was then mixed for 2 hours at the equilibrium temperature (approx. 135 C).
The Tg of the toner prepared from that melt was 76C, the E.M.M. exceeded
20,000 and the melt viscosity was 55,000 s.Pa. The contact-fusing range was
100 to more than 160C. The charging and developing behaviour of the toner
corresponded to that of the toner mentioned in Example 2.
Example 6
The preparing method according to Example 2 was repeated, but now
C with 3% each of the anthraquinone dyes Macrolex yellow 3 G~ Macrolex red 5B
and Macrolex blue R (all of Bayer ~.G., Leverkusen) instead of the carbon.
Fully transparent-dyed, positively chargeable toners in the colours yellow,
magenta and blue were obtained. The Tg values were 57C, 61 C and 59C,
respectively.
Example 7
In a powder mixer of a ground mixture of 36 g of epoxy amine prepared
according to Example 1, 60 g of N-cyclohexyl-p-toluenesulphonamide, 9.7 g of
benzoic acid and 9.3 g of succinic acid was premixed with 36 g of carbon and
449 g of Epikote 1006 (E.M.M. 1,700). This mixture was then extruded at 160 C.
Jf ~D~ - 20 -
'.~
.
,
The residence time in the extruder was approximately 5 minutes.
The mixture had a constant Tg value of 58 C. The E.M.M. exceeded 30,000. The
- 20a -
~.~
:
. i .
::: . : : . ::: : : : : :: , :,: , , ;; . :
~L~3~ 37
toner after having been mixed with iron, to give a 4 percent developer, gave
a good image quality; it had a contact-fusing range of 86 - 129C (range 43C).
Example 8
- The preparation according to Example 2 was repeated, but now with
Epikote 828 (E.~Vl.M. 190) as starting resin for the low molecular fraction.
The ingredients used and their 4uantities were: 30.5 g of Epi~ote 828, 27.5 g
of 4-(~,~-dimethylben yl)-phenol, 30 g of Rutapox 0717, 6.0 g of epoxy amine
from Epikote 1001 and 2-methylaminoethanol, and 6.0 g of carbon. The Tg was
48C, the E.)~.M. was 14,000 and the melt viscosity 420 s.Pa. The contact-
fusing range was 66 - 103C (range 37C). The charging and developing be-
haviour of the toner corresponded to that of the toner mentioned in Example 2.
Example 9 (comparative ~xample).
In the same contact-fusing device as mentioned in Example 2, the
contact-fusing ranges of two commercially available toners were determined to
serve as reference for the toners according to the invention. One toner, of
which the chief ingredient was a styrene-butyl methacrylate copolymer, had a
contact-fusing range of 105 to more than 170C, and a Tg of 64C. The other
toner, probably consisting of a terpolymer of styrene, methyl methacrylate and
2-ethylhexyl methacrylate, had a contact-fusing range of 101 to more than
170C, and a Tg of 58C. So, the distance between the Tg and the starting
point of the contact-fusing range with these toners was considerably larger
than with the toners according to the present invention.
Example 10 (comparative Example).
Attemps were made to prepare a toner from an epoxy resin without
blocking with a monofunctional carboxylic acid or phenol. Under the preparing
conditions mentioned in Example 2, 88.0 g of Epikote 1004 ~E.M.M. = 900),
6.0 g of epoxy amine from Epikote 1001 and 2-methylaminoethanol, and 6.0 g of
carbon were mixed. After a short timeJ the mixture hardened and further mixing
- 21 -
r~j
-.;
become impossible. The mixture hardly could be ground and could no longer be
fixed at temperatures below the scorch limit of the paper.
Example 11
This Example relates to toners having various polarity control
agents. The preparation described in Example 4 was repeated, but with the
following epoxy amines.
epoxy aminepK ~starting amine) 25 C
__ a
a. Epikote 1001 / 2-methylaminoethanol 9.8
b. Epikote 828 / 2-methylaminoethanol 9.8
c. Epikote 1001 / dipropylamine11.0
d. Epilote 1001 / di-isopropylamine 11.0
e. Epikote 1001 / 2,2'-iminodiethanol 8.9
f. Epikote 1001 / morpholine 8.4
g- Epikote 1001 / N-methylaniline 4.8
Each toner was prepared with 0.1 base equivalent/kg toner. After
grinding and sieving to give particles between 8 and 35 ~m, two-component
developer~ were prepared with the iron powder mentioned in Example 2 (Carrier
A). The toners with the epoxy amines a. and g. were also mixed with iron
powder, provided with a layer of perfluorodecanoic acid, in the way described
in Research Disclosure, February 1977, under No. 154 39 ~Carrier B).
The measuring results of the toners are given in the following table.
- 22 -
.
,, ~. .,~
¦ melt viscosity chargino level ~C/g
I Tg ~ C) E.M.~ s.Pa 1L~O C) carrier A carrier B
a. 65 exceeding 20,000 2,000 13.1 35.0
b. 6~ ~' 20,000 1,950 12.8
c. 59 ~ 20,000 1,900 12.2
d. 53 ~ 20,000 1,850 11.4
e. 56 ~ 20,000 1,900 9.0
f. 56 " 20,000 1,900 9.6
g 53 " 20,000 1,900 _ 4.0 _ 20.8
The contact-fusing ranges roughly corresponded to those mentioned
in Example ~. From this it appears that by the choice of the amine it is pos-
sible to control the chargeability of the toner without it affecting the fus-
ing properties.
Example 12
This Example relates to a toner of which the high molecular fraction
was prepared by intermolecular reaction. In a heavy derby mi~er a low mole-
cular fraction, blocked with 4-~,u-dimethylbenzyl)-p}lenol, was prepared as in
Example 2 starting from 29.4 g of Epikote 1001 ~E.~L~I. = 495), 8.6 g of 4-(~,
~-dimethylben7yl)-phenol, 6.0 g of epoxy amine from Epikote 1001 and 2-methyl-
aminoethanol, and 6.0 g of carbon. Subsequently, 50 g of Epikote 1009 ~E.~.~l.
= 3,000) were added and the mixture was mixed for 3 hours at 200C. By inter-
molecular reactions between the epoxy groups and the alcoholic hydroxyl groups
of the resin a higher molecular fraction was formed. The toner prepared from
this melt had a Tg of 71 C, an E.M.~. of 11,000 and a melt viscosity of 6,400
s.Pa. The contact-fusing range was 90 to 150C (range 60C). ~lixed with iron
powder the toner powder had good charging properties.
Example 13
The method according to Example 2 was repeated, but now with 24.4 g
of Epikote 828 ~E.~.~. = 190), 19.6 g of 4~ -dimethylben~yl)-phellol ~.0 g
- 23 -
.
~L3~7
of epoYy amine rrom Epikote 1001 and 2-methylaminoethanol, and 6.0 g of carbon
in the iol~ molecular fraction and, to obtain the hlgher molerular fraction,
1~ g of Epi~o.e 1009 (E.M.M. = 3,000). This toner had a Tg of 54 C, an E.~.M.
of 11,000 and a melt viscosity of 175 s.Pa. The contact-fusing range was 68
to 100 C ~range ~2C). The toner powder had good charging properties corres-
ponding to those of the toner mentioned in EYample 2.
To prepare the toner according to this and the other EYamples the
epoYy amine was each time added in he ready-made form to the reaction mi~ture. .
Although this manner is preferred to a certain extent, if so desired the epo~Yy
amine may also be prepared in situ. In that case, the starting epoYy resin
and the starting amine are first added together.~ Subsequently, after compie-
tion of the reaction the other ingredients desired for the preparation of the
toner resin are added.
Preparation of radiation-fusible toners:
E.Yam~le 14
.
A toner specially suitable for fi~Ying by radiant heat ~as prepar~ed
~s follo~s:
At 150C, 16.7 g of 4-(~,~-dimethylbenzyl)-phenol and 5.7 g of epo,Yy
amine from Epikote 1001 and 2-methylaminoethanol were miYed. l`he temperature
~as then increased to 200 C, while a mi,Yture of 35.8 g of Epikote 1001 ~E.M.~I.
= 495) and 35.8 g of Epikote 1004 (E.~.~l. = 900) followed by 6.0 g of carbon
were gradually added. Subsequently, the whole was homogenized for 3 hours at
a temperature of 200 C. The Tg of the toner ~as 59 C, the melt viscosity at
140 C was 20 s.Pa and the E.~l.M. was 10,000. The toner was remarkably well
fusible in an Occ 1700-plain paper copier equipped with a radiant fuser. The
toncr could also be fi.Yed well onto paper at an electromagnetic flash of 4 ms
duratio~ avclcngth 400 - 1,200 nm). The toner mentioned in EYample 4 could
be fi~cd as well in this way. ~lowever, the radlation of ener~y required for
- 24 -
,1 . ,~ " ' `
- ' ' ` ., - '
~3~87
an identical fusing level proved to be approximately three times as high as
that of the present Example.
E.xample 15
In the same manner as described in Example 11, a radiant heat-
; fixable toner was prepared from 24.5 g of 4-~ -dimethylben7yl)-phenol, 6.4 g
of the bifunctional epoxy amine from Epikote 1001 and 2-aminoethanol, 63.1 g
of Epikote 1001 and 6.0 g of carbon. The epo~y amine was built in the epo~y
resin to a further extent. The Tg was 54C, the E.M.hl. 9,000 and the melt
viscosity at 140C was 35 s.Pa.
Example 16
235 g of Epikote 1009 were added to a low molecular phase, prepared
in the same way as described in Example 2, from 126.5 g of Epikote 828, 108.5
g of 4~ -dimethylbenzyl) phenol and 30 g of epoxy amine obtained in ac-
cordance with Example 1.
The resin mass was mixed for 5 hours at 200C. Subsequently 500 g
of magnetite were added and mixed for another hour by kneading. After cooling,
the mass was ground by milling to particles of 10 to 30 microns, whicll partic-
les than were given a spherical shape in a hot air fluidi7ed bed using a known
method. The toner powder so obtained could be used with good results as one-
component developer in a magnetic brush developing system for the development
of latent negative electrostatic images generated on photoconductive zinc
oxide-binder layers or onphotoconductive elements comprising ~n organic photo-
conductor layer overcoatcd with a polyvinylcarbazole layer.
Thè E.M.~I. of the toner po~er was 17,500. The Tg 55 C and the
contact fusing range was 93 to 126C (range 33C).
Exam~le 17
.
In a vessel, provided with a stirrer and oil bath heater, a mixture
of 45 g of epoxy amine, obtained in accordance with example 1, 40 g of carbon
- 25 -
:
,
L87
pigment, 165 g of Epikote 828 and 140 g of 4~ dimethylbenzyl)-phenol, was
heated with stirring to about 185C for 1 hour. Subsequently 350 g of Epikote
1009 were added and the mixture was stirred at about 190C for 3 hours. The
-- melt was drained off and cooled down to room temperature. The solid mass was
ground and sieved in a known manner to give a toner powder having a particle
si~e between 6 and 2S microns. The toner had a Tg of 52 , an E.M~ of 4750
and a melt viscosity of:10 00 s.Pa. The contact fusing range was 77 to 98 C
~range 21C). During manufacture of the toner 83.7% of the initial epoxy
groups were blocked.
The use of an epoxy resin having an E.M.~I. value of less than 500,
and preferably of less than 250, as a starting epoxy resin for manufacturing
the modified resin, as illustrated by this example, has the important advantage
- that a toner powder having a Tg of about 50C and a fusing range starting
slightly above the Tg temperature is obtained, without the necessity of adding
an auxiliary agent such as N-cyclohexyl-p-toluenesulphonamide(compare Example
7.) The auxiliary agent has the disadvantage that it shows a tendency to
migrate out of the toner powder and to deposit on the carrier particles and/or
the fusing rollers of the fixing device. It thus unfavourably influences the
charging characteristics of the toner powder and the durability of the fusing
rollers.
- 26 -
LSA
- :
