U.S. patent application number 09/995916 was filed with the patent office on 2002-06-13 for method of emulsion polymerization.
Invention is credited to Aert, Huub Van, Huybrechts, Jos, Thillo, Etienne Van, Vermeersch, Joan.
Application Number | 20020072580 09/995916 |
Document ID | / |
Family ID | 27222881 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020072580 |
Kind Code |
A1 |
Aert, Huub Van ; et
al. |
June 13, 2002 |
Method of emulsion polymerization
Abstract
A method has been disclosed of preparing ultrafine hydrophobic
latex particles of polymers and copolymers by free radical emulsion
polymerization in a water-based system, making use therefor, in
order to polymerize or copolymerize monomers or monomer mixtures
respectively, of at least one compound selected from the group
consisting of dimers and cobalt complexes, acting as a chain
transfer agent (CTA), wherein said latex particles have an average
particle size of less than 100 nm, being more than 10% lower than
if prepared in the absence of said CTA, characterized in that said
polymerization is conducted in a water-based reaction in the
presence of a chain transfer agent and of a surfactant, wherein
said surfactant is present in a concentration versus said monomer
or monomer mixture of from 5 up to 25% by weight for a non-ionic
surfactant or from 0.05 up to 10% by weight for an ionic
surfactant, more particularly a surfactant in a concentration below
twice its critical micelle concentration.
Inventors: |
Aert, Huub Van; (Pulderbos,
BE) ; Vermeersch, Joan; (Deinze, BE) ; Thillo,
Etienne Van; (Essen, BE) ; Huybrechts, Jos;
(Turnhout, BE) |
Correspondence
Address: |
Joseph T. Guy Ph.D
Nexsen Pruet Jacobs & Pollard LLP
201 W. McBee Avenue
Greenville
SC
29603
US
|
Family ID: |
27222881 |
Appl. No.: |
09/995916 |
Filed: |
November 28, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60264567 |
Jan 26, 2001 |
|
|
|
Current U.S.
Class: |
526/319 ;
524/832; 526/171 |
Current CPC
Class: |
C08F 2/24 20130101; C08F
2/22 20130101; C08F 2/38 20130101 |
Class at
Publication: |
526/319 ;
526/171; 524/832 |
International
Class: |
C08L 033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 26, 2000 |
EP |
00000002.6 |
Claims
1. Method of preparing, by free radical emulsion polymerization, of
ultrafine hydrophobic latex polymer or copolymer particles, making
use therefor, in order to polymerize or copolymerize monomers or
monomer mixtures respectively, of at least one compound selected
from the group consisting of dimers and cobalt complexes, acting as
a chain transfer agent (CTA), wherein said latex particles have an
average particle size of less than 100 nm, being more than 10%
lower than if prepared in the absence of said CTA, characterized in
that said polymerization is conducted in a water-based reaction in
the presence of a chain transfer agent and of a surfactant, wherein
said surfactant is present in a concentration versus said monomer
or monomer mixture of from 5 up to 25% by weight for a non-ionic
surfactant or from 0.05 up to 10% by weight for an ionic
surfactant.
2. Method according to claim 1, wherein said surfactant is present
in a concentration below twice its critical micelle
concentration.
3. Method according to claim 1, wherein said dimers are selected
from the group consisting of .alpha.-methyl vinyl compounds or
.alpha.-ethyl vinyl compounds.
4. Method according to claim 2, wherein said dimers are selected
from the group consisting of .alpha.-methyl vinyl compounds or
.alpha.-ethyl vinyl compounds.
5. Method according to claim 1, wherein said dimer is selected from
the group consisting of dimers or cross-dimers of
.alpha.-methylstyrene, methyl methacrylate, hydroxy ethylacrylate,
benzyl methacrylate, allyl methacrylate, methacrylonitrile,
glycidyl methacrylate, methacrylic acid, tert.-butyl methacrylate,
isocyanatoethyl methacrylate,
meta-isopropenyl-.alpha.,.alpha.-dimethyl isocyanate (TMI),
.omega.-sulfoxyalkyl methacrylates and alkali salts thereof.
6. Method according to claim 1, wherein said cobalt complex is
selected from the group consisting of cobalt(II) and cobalt(III)
complexes.
7. Method according to claim 6, wherein said cobalt(II) complex is
bis(boron difluorodiphenyl-glyoximate)cobaltate(II) or its di-aqua
adduct.
8. Method according to claim 1, wherein said dimer is a
water-soluble oligomer having surface-active graft copolymers with
a hydrophilic graft and a hydrophobic main chain.
9. Method according to claim 1, wherein said surfactant is an
anionic surfactant, present in an amount of from 0.1 up to 5% by
weight versus said monomer or monomer mixture.
10. Method according to claim 1, wherein said latex particles have
an average particle size of less than 100 nm, being more than 20%
less than if prepared in the absence of said CTA.
11. Method according to claim 1, wherein said latex particles have
an average particle size of from 10 to 90 nm.
12. Use of ultrafine hydrophobic latex particles of polymers and
copolymers, prepared according to the method of claim 1, in
printing plates for computer-to-plate or computer-to-press
applications, in silver halide based graphic, medical,
cinematographic and micrographic film materials, in photoresist
applications and in ink-jet media.
Description
[0001] The application claims the benefit of U.S. Provisional
Application No. 60/264,567 filed Jan. 26, 2001.
FIELD OF THE INVENTION
[0002] The present invention relates to a method of emulsion
polymerization making use therefor of a group of selected pure
dimers acting as addition fragmentation chain transfer agents and
of cobalt complexes as catalytic chain transfer agents (CTA's).
BACKGROUND OF THE INVENTION
[0003] Dimers which are often used in order to control the
molecular weight in solution polymerizations are e.g. the
.alpha.-methyl styrene dimer (CAS 6144-04-3 or 6362-80-7) and MMA
(methyl methacrylate) dimer (CAS No. 71674-93-6 or 28261-32-7). For
control of molecular weight in emulsion polymerizations only the
.alpha.-methylstyrene dimer has been used by Japan Synthetic Rubber
Co U.S. Pat. Nos. 5,637,644 and 5,444,118) until now.
[0004] In JP-A 11-292907 e.g. Sekisui was using the
.alpha.-methylstyrene dimer in a surfactant free emulsion
polymerization of styrene which was resulting in the synthesis of a
polymer latex having large particle sizes.
[0005] Similar to the use of these dimers in emulsion
polymerization, macromers can be used. A useful macromer is first
prepared by making use of a solution polymerization step. After
isolation of this macromer, it is further used in an emulsion
polymerization step. This technique has e.g. been applied by Du
Pont (in WO 99/42505) and by Rodia Chimie (see WO 99/57167). That
polymerization method however implies that two steps are required:
a first solution polymerization step and, subsequently, an emulsion
polymerization step wherein use is made of the macromer prepared in
the first solution polymerization step mentioned hereinbefore.
[0006] Control on particle sizes in emulsion polymerization can be
done by controlling preparation parameters as amount, type and mode
of addition of initiator and surfactant. Addition of traditional
chain transfer agents like mercaptans may also have an influence on
particle size, but in this case only small changes in particle size
are obtained. When making use of lauryl mercaptan it has often been
found that the particle size slightly increases because of the
presence of more droplet nucleation as the lauryl mercaptan
dissolves in the monomer phase and as it allows a higher degree of
droplet nucleation, as in mini-emulsion polymerizations, wherein
cetylalcohol is used as co-surfactant. In case of the novel chain
transfer agents, such as dimers and cobalt complexes, particle size
can decrease drastically. A higher number of particles is obtained,
presumably due to a higher radical flux. Exit of radicals may occur
more frequently, which gives re-entry in another micelle (micelle
nucleation) or extra initiation of monomers in the aqueous phase
(homogeneous nucleation). In case of the use of dimers, radical
addition fragmentation gives a more water soluble radical which can
enter in the aqueous phase. The employed dimer can be designed in
order to have good copolymerization parameters with the monomers
used and in order to obtain radicals with enough water solubility
after fragmentation. Also the water solubility of the cobalt
complexes can be adjusted.
[0007] Introducing dimeric compounds by addition fragmentation
transfer is expected to give macromers with unsaturated endgroups.
Said macromers might be used for further polymerization, resulting
in the synthesis of graft- or block copolymers. Besides the
.alpha.-methylstyrene dimer and the MMA dimer also functional
dimers could be used, resulting in end-functional telechelics. So
in U.S. Pat. No. 5,264,530 an improved method of free radical
polymerization in an aqueous system, wherein the method employs a
macromonomer mixture, having terminal ethylenic unsaturatation, as
a chain transfer agent under aqueous conditions. Such macromonomers
are advantageous for controlling the molecular weight of polymers
or copolymers produced therewith but molecular weight reduction has
little or no effect on mean particle size as has been established
therein. Although the lowest particle size obtained is about 80 nm,
a reduction percentage of only 7% versus the comparative example
can be reached. The limited effect upon particle size in U.S. Pat.
No. 5,264,530 can be explained as follows.
[0008] 1) The influence of dimers on particle size will be much
more pronounced at low surfactant concentrations. If a surfactant
concentration is used far above its CMC (critical micelle
concentration: micellar nucleation will be more decisive than
homogeneous nucleation for the result obtained. Employed dimers
will be more effective in reducing the particle size in case that
particle nucleation occurs via homogeneous nucleation. In U.S. Pat.
No. 5,264,530 a combination of two anionic surfactants is used
[Trem LF 40 (allyl dodecyl sulfosuccinate sodium salt) and Dupanol
WAOI (sodium lauryl sulfate)]. The initial surfactant concentration
is about 4.6 gram/liter TREM LF40+3,9 gram/liter Dupanol WAOI which
result in a total amount of 8.5 gram/liter of anionic surfactant.
The CMC of Dupanol WAOI is about 2.05 gram/liter. So in case of the
emulsion copolymerisation, described in the U.S. Patent reference,
the surfactant concentration is much higher than the CMC, and so
micellar nucleation will influence particle size more
pronounced.
[0009] 2)If a mixture of oligomers is used, larger particle sizes
might be obtained due to a lower solubility of the longer oligomers
in water. When longer oligomeric radicals are present in a latex
particle, re-entry in the aqueous phase is difficult due to the
limited water solubility. As a comparison when pure dimeric
compounds are used the addition-fragmentation reaction yields a
monomer radical, which easily can give a re-entry in the aqueous
phase. Furthermore, the presence of longer oligomers gives rise to
the formation of block- or graft-copolymers, which may act as
in-situ formed surfactants and consequently alter the particle
nucleation mechanism.
[0010] 3) As described by Caterine L. Moad in Macromolecules, 1996,
volume 29, page 7717-7726 a pure dimer behaves much more different
than the trimer or higher macromonomers, with respect to chain
transfer activity, kinetics and mechanism of chain transfer. The
rate determining step, i.e. the addition of the double bond and
formation of the radical intermediate is mainly controlled by
steric effects. In case of an adduct of the dimer the steric
repulsion is much less. Differences in kinetics, chain transfer
mechanism and steric hinderance of pure dimers in comparison with a
mixture of oligomers might influence particle nucleation, and
consequently also particle size.
[0011] Cobalt complexes are well-know as chain-transfer agent used
in order to control polymer molecular weights, but use of cobalt
complexes, even in combination with unpurified monomers (containing
still some inhibitor), thereby causing a significant particle size
decrease, hardly affects molecular weights of polymers thus
formed.
[0012] Control of molecular weight and particle size now is
particularly important in applications, where e.g. sharp-transition
melting or latex coalescence is used. Also in applications where
transparency and where the specific surface area is important,
research to provide control of particle size is crucial.
Furthermore smaller particle sizes can facilitate film formation.
In some cases this might lead to the situation that less
plasticizer is required to give sufficient film formation using
dispersions or latices with a high glass transition temperature
(Tg) or a high minimal film forming temperature (MFT).
[0013] So it is e.g. well-known that is difficult to obtain small
particle sizes in emulsion polymerization, without making use of
high surfactant or initiator concentrations.
[0014] High concentrations of surfactant or initiator can provide
undesired polymer mixtures, e.g. when polymer latex particles are
used in ink-jet applications or as surface sizing agents. In that
case said high concentration of surfactant may lead to bleeding of
ink and to an inferior image quality.
OBJECTS OF THE INVENTION
[0015] It is an object of the present invention to provide a method
for preparing a (co)polymer latex, wherein small (ultrafine)
particle sizes are obtained.
[0016] It is a further object of the invention to moreover provide
a (co)polymer latex, wherein said small (ultrafine) particles show
a decreased degree of polydispersity (low polydispersity
index).
[0017] It is still a further object of the invention to provide a
method wherein no solution polymerization is required prior to
emulsion polymerization.
[0018] Moreover the object of the present invention is to provide
useful applications in materials for the polymer latex prepared by
the method of the present invention.
SUMMARY OF THE INVENTION
[0019] In order to reach the objects of the present invention a
method has been described of preparing, by free radical emulsion
polymerization in a water-based system, of ultrafine hydrophobic
latex polymer and latex copolymer particles optionally having low
polydispersity, making use therefor, in order to polymerize or
copolymerize monomers or monomer mixtures respectively, of at least
one compound selected from the group consisting of dimers and
cobalt complexes, acting as a chain transfer agent (CTA), wherein
said latex particles have an average particle size of less than 100
nm, being more than 10% lower than if prepared in the absence of
said CTA, characterized in that said polymerization is conducted in
a water-based reaction in the presence of a chain transfer agent
and of a surfactant, wherein said surfactant is present in a
concentration versus said versus said monomer or monomer mixture of
from 5 up to 25% by weight for a non-ionic surfactant or from 0.05
up to 10% by weight for an ionic surfactant. Particularly preferred
is a surfactant concentration below twice its critical micelle
concentration.
[0020] Further advantages and embodiments of the present invention
will become apparent from the following description.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The present invention thus offers a method for preparing a
polymer latex having ultrafine monodisperse latex particles making
use therefor, in an emulsion polymerization step, of (purified)
dimeric compounds, also called dimers, wherein the said dimers are
selected from the group consisting of .alpha.-methyl vinyl
compounds or .alpha.-ethyl vinyl compounds. Said dimeric compounds
acting as chain transfer agents have a chemical structure according
to the general formulae (I) or (II) 1
[0022] wherein each of R1-R4 independently represents hydrogen, a
substituted or unsubstituted alkyl group; or wherein each of R1,
R2, R3 and R4 independently represents an oligomeric or a polymeric
group.
[0023] In one embodiment according to the method of the present
invention, said (purified) dimer is selected from the group
consisting of dimers or cross-dimers of .alpha.-methylstyrene,
methyl methacrylate, hydroxy ethylacryla-te, benzyl methacrylate,
allyl methacrylate, methacrylonitrile, glycidyl methacrylate,
methacrylic acid, tert.-butyl methacrylate, isocyanatoethyl
methacrylate, meta-isopropenyl-.alpha.,.alp- ha.-dimethyl
isocyanate (TMI), .omega.-sulfoxyalkyl methacrylates and alkali
salts thereof.
[0024] In a preferred embodiment said (purified) dimeric compound,
if present as a hydrophobic, apolar dimer, has a low molecular
weight, i.a. a molecular weight of not more than 300, and more
preferably a molecular weight of not more than 200 in order to
provide a sufficiently high water-solubility in order to perform an
emulsion polymerization reaction. Opposite thereto hydrophilic
dimers may have higher molecular weights.
[0025] In the particular case wherein each of R1 and R2 in general
formula (I) represents hydrogen the structure corresponds with the
dimer of .alpha.-methyl styrene, which is commerially available
from Mitsui Chemical (Japan), Herdillia Chemicals (India) en Goi
Chemical (Japan). In another particular case wherein each of R3 and
R4 in formula (II) represents methyl the structure corresponds with
the dimer of methyl methacrylate, which can be prepared by the
method described by DuPont, wherein cobalt(II) complexes are used
as chain transfer agents as has been described in WO 99/42505.
[0026] According to the method of the present invention said cobalt
complex(es) is(are) selected from the group consisting of
cobalt(II) and cobalt(III)-carbon complexes.
[0027] With respect to the said cobalt(II) complexes a preferably
used cobalt (II)comples is the diphenyl complex, simply called
"cobalt II diphenyl complex" given hereinafter (see formula (III))
2
[0028] This complex is also applicable as the same structure
without the water molecules present: from the thus applied
bis(boron difluorodiphenylglyoximate) cobaltate II complex, the
chemical stucture has been given below (see formula(IV))
[0029] The CAS-number (number in CHEMICAL ABSTRACTS) has been added
thereto. 3
[0030] Besides the cobalt II diphenyl complex also the dimethyl
derivative can be used or other cobalt II complexes. Under CASRN
26220-72-4, said bis(boron difluorodimethyl-glyoximate) cobaltate
(II) complex or its di-aqua adduct is known and its structure is
given hereinafter as formula (V): 4
[0031] Besides cobalt II complexes also cobalt III complexes can be
used. Suitable cobalt III complexes have e.g. been described by
Alexei Alexeyevich Gridnev in PCT-Application WO 9941218(1999) or
given by Bunichiro Yamada in J. Polym. Sci., Chem. Ed., volume 32,
page 2745 - 2754 (1994). Examples of such cobalt III complexes are
[bis[m-(2,3-butanedione
dioximato)(2-)O,O'tetraflorodiborato(2-propyl)N,N-
',N",N'"](2-propyl)Co(III)]] or
benzylbis(dimethylglyximato)(pyridine)coba- lt III.
[0032] When the cobalt complexes are used as chain transfer agent
in order to control the latex particle size in emulsion
polymerizations, as described in the preferred embodiments of the
current invention, usually the molecular weight of the formed
polymer decreases drastically. Surprisingly, when the monomers were
used without further purification, the molecular weight decrease
was much less. Due to the presence of the inhibitor MEHQ
(hydroquinone monomethyl ether) the molecular weight remains high,
which is important, in particular in order to obtain the required
mechanical strength. In case of the scratch resistant backing layer
of a graphic film, as described in one of the embodiments of the
present invention, a high molecular weight PMMA is preferred in
order to obtain the desired mechanical properties. Therefore in
most experiments MMA was not destilled. When cobalt complexes are
then used in emulsion polymerization, no significant molecular
weight decrease occurs. Its influence on particle size however
remains the same.
[0033] Irrespective of the preparation method of the dimeric
compounds, whether performed by making use of clay or ion exchange
resins, catalysis by cobalt(II) complexes or other synthetic
procedures, it is a stringent demand in the present invention to
start from (purified) dimeric compounds, in order to reach the
benifits as described hereinbefore.
[0034] In another embodiment according to the method of the present
invention, said (purified) dimer is selected from the group
consisting of .alpha.-methylstyrene-dimer, a methyl methacrylate
dimeric compound.
[0035] More particularly said (purified) dimeric compounds used in
the method of the present invention have a chemical structure
selected from the group consisting of (numbers in CHEMICAL
ABSTRACTS -CAS-added between brackets):
[0036] 4-methyl-2,4-diphenyl-1-pentene (CASRN 6144-04-3 or
6362-80-7)
[0037] 2,2-dimethyl-4-methylene-pentanedioic acid, dimethyl ester
(CASRN 71674-93-6 or 28261-32-7)
[0038] 2,2-dimethyl-4-methylene pentanedioic acid dibutyl ester
(CASRN 100639-40-5)
[0039] 2,2-dimethyl-4-methylene entanedioic acid
bis(2-isocyanatoethyl) ester(CASRN 100639-43-8)
[0040] 2,2-dimethyl-4-methylene pentanedioic acid dicyclohexyl
ester (CASRN 100639-44-9)
[0041] 2,2-dimethyl-4-methylene pentanefioic acid
bis(2-hydroxypropyl) ester(CASRN 100639-45-0)
[0042] 2,2-dimethyl-4-methylene pentanefioic acid
bis(oxiranylmethyl) ester(CASRN 199542-57-9)
[0043] 2,2-dimethyl-4-methylene- glutaric acid (CASRN
10297-25-3)
[0044] 2,2-dimethyl-4-methylene pentanedioic acid
bis(2-hydroxyethyl) ester (CASRN 100639-42-9)
[0045] 2,4-bis-(4-(hexadecyloxy)-phenyl)-4-methyl-1-pentene (CASRN
3902-46-3)
[0046]
1,1'-[(,1,-dimethyl-3-methylene-1,3propanediyl)di-3,1-phenylene]bis-
-ethanone (or 2,4-bis(4-acetoxyphenyl)-4-methyl-1-pentene)
(CASRN160185-22-8)
[0047] In the general formulae (I) and (II) each of R1-R4, besides
the already mentioned hydrogen and alkyl substituents in the dimer
formulae, independently represents hydroxyl, carboxylic acid,
amino, sulphonate, phosphonate and salts thereof; isocyanato or
oligomeric groups.
[0048] Similar compounds which have not been prepared by
dimerization of a .alpha.-methyl containing monomer, e.g. with two
methyl groups next to the CH.sub.2-group in the formulae (I) and
(II), may be replaced by other substituents.
[0049] Besides the dimers of methacrylates or alpha-methylstyrene
derivatives also cross-dimers can be used as described in the
following references:
[0050] Yamada, Bunichiro; Konosu, Osamu. Kobunshi Ronbunshu (1997),
54(10), 723-730;
[0051] Kobatake, Seiya; Yamada, Bunichiro. J. Polym. Sci., Part A:
Polym. Chem. (1996), 34(1), 95-108;
[0052] Yamada, Bunichiro; Tagashira, Shinji; Aoki, Shuzo. J. Polym.
Sci., Part A: Polym. Chem. (1994), 32(14), 2745-2754;
[0053] Yamada, Bunichiro; Kobatake, Seiya; Aoki, Shuzo. Macromol.
Chem. Phys. (1994), 195(2), 581-90
[0054] Akutsu, Fumihiko; Aoyagi, Kaoru; Nishimura, Nozomu; Kudoh,
Masaaki; Kasashima, Yoshio; Inoki, Mari; Naruchi, Kiyoshi. J. Chem.
Soc., Perkin Trans. 2 (1996), (5), 889-892;
[0055] Kudoh, Masaaki; Akutsu, Fumihiko; Odagawa, Yoshiyuki;
Naruchi, Kiyoshi; Miura, Masatoshi. Macromol. Chem. Phys. (1994),
195(1), 385-90.
[0056] Examples of such cross-dimers are:
[0057] CASRN 139623-17-9: pentanedioic acid, 2-ethyl-4-methylene-,
dimethyl ester: cross-coupled dimer obtained by thermal reaction of
sodium crotonate/methacrylate in solid state followed by
esterification with diazomethane. 5
[0058] Otherwise making use of functional dimers
.alpha.,.omega.-functiona- l polymers can be prepared by emulsion
polymerization. Besides the formation of ultra-fine latex
particles, the resulting polymer chains have a functional
end-group. When the dimer of e.g. hydroxyethylmethacrylate (HEMA)
is used as chain transfer agent a bis-hydroxy terminated polymer is
obtained. This phenomenon has already been described by Haddleton
(Polymer (1998), 39(14), 3119-3128) in a solution polymerization
reaction. Hydroxyethyl methacrylate dimer macromonomer prepared
from catalytic chain transfer polymerization and isolated as a pure
compound is an efficient chain transfer agent. The mode of chain
transfer proceeds via .beta.-scission, thus resulting in breaking
the bond in the dimeric molecule in order to get two identical
parts when adding to a propagating poly(methyl methacrylate)
radical, terminating the polymerization and providing a
hydroxyethyl methacrylate radical which reinitiates polymerization.
A combination of these two reaction phenomena leads to di-hydroxy
telechelic products, demonstrated to have a functionality of 2.05
by a combination of NMR and size exclusion chromatographt. The
dimer used has the structure as given below:
[0059] CASRN 100639-42-7: HEMA dimer:
2,2-dimethyl-4-methylene-pentanedioi- c acid, bis(2-hydroxyethyl)
ester 6
[0060] In order to obtain .alpha.,.omega.-functional polymers,
methacrylate dimers are very suitable agents while they being quite
easily prepared by making use of the cobalt complexes.
[0061] Another example makes use of the benzyl methacrylate dimer
macromonomer as a radical addition fragmentation chain transfer
agent in a polymerization of MMA. This results in poly(methyl
methacrylate) with both .alpha.- and .omega.- terminal benzyl
methacrylate units. Catalytic hydrogenation of
.alpha.,.omega.-benzyl methacrylate terminal poly(methyl
methacrylate) results in evolution of toluene and formation of
.alpha.,.omega.-dicarboxyl functional telechelic poly(methyl
methacrylate).
[0062] A preferred dimer used in our experiments has been given
hereinafter:
[0063] CASRN 208192-24-9: 2,2-dimethyl-4-methylene-, pentanedioic
acid bis(phenylmethyl) ester 7
[0064] In the experiments hereinafter an investigation reaction of
such funtional dimers in an emulsion (co)polymerization reaction
has been performed. The prepared end-functional polymers can be
used as building blocks for blockcopolymers and networks: e.g. the
hydroxy-terminated polymers prepared from the HEMA-dimer can be
used in order to prepare polyester- or polyurethane-
blockcopolymers. Cross-linked networks can be formed e.g. by
casting films of the latices with .alpha.,.omega.-dicarbox- ylic
functional polymer latices in combination with water-based epoxy
resins, as e.g. those available from SHELL (The Netherlands) or
CIBA-GEIGY (Switzerland). The polymers prepared from the dimer of
allyl-methacrylate, thus having allylic end-groups can be used in
reaction with hydride-functional polysiloxanes in a hydrosilation
reaction. This type of reaction gives opportunities to prepare
numerous novel siloxane block- and graft- copolymers.
[0065] Mixed dimers can lead to functional telechelics with
reactive end-groups having complementary reactivity. One also could
mix latices with different functional groups, e.g. hydroxy
end-terminated polymer latices with isocyanato functional
latices.
[0066] Upon casting of such latices cross-linking occurs after film
formation. The use of reactive polymer latex blends is described by
John Geurts in his PhD thesis (Technical University of Eindhoven)
or in Van Es,S. et al. NATO ASI Ser., Ser. E, (1999), volume 335,
page 451-462.
[0067] It is clear that the functional polymers prepared in an
emulsion polymerization reaction are particularly useful for
further interesting reactions in water-based systems. The dried
polymer can be isolated by freeze-drying or vacuum-drying and can
be used in further reactions performed in organic solvents or in
melt reactions.
[0068] Different types of oligomeric macromonomers are suitable for
use as chain transfer agents in emulsion polymerization reactions,
such as e.g. those containing oligo(hydroxyethyl methacrylate)
macromers as mentioned in DuPont's WO 99/42505, clearly give rise
to a lower particle size, if compared e.g. with the water-insoluble
macromonomers with 2-ethyl-hexyl-methacrylate mentioned in WO
99/57167 (Rhodia Chemie). So according to the method of the present
invention water-soluble (purified) oligomers are preferred, as e.g.
the water-soluble macromonomers having surface-active graft
copolymers with a hydrophilic graft and a hydrophobic main chain,
generated by in-situ polymerization as disclosed by DuPont.
Although besides dimers also trimers, and even tetramers might be
useful in order to reach the objects of the present invention, it
can be expected that dimers are superior with respect thereto, due
to a better solubility in water and to the fact that pure dimers
(A--A) lead to well-defined polymeric compounds, opposite to the
less-defined polymeric compounds generated after reactions when use
has been made from timers (A--A--A) or tetramers as becomes clear
from a simple representation of the reaction scheme made
hereinafter:
A--A+nB.fwdarw.A(B).sub.nA (XVI)
A--A--A+nB.fwdarw.AA(B).sub.nA (XVII)
A--A--A+nB.fwdarw.AAA(B).sub.nA (XVIII)
A--A--A+nB.fwdarw.AAAA(B).sub.nA (XIX)
[0069] The well-defined character of the prepared polymers is
particularly important for the functional dimers.
[0070] A survey of such chain transfer agents and a comparison of
their activities in bulk polymerizations of methyl methacrylate has
e.g. been reviewed in Macromolecules, 29, 7717 (1996).
[0071] In another embodiment of the method according to the present
invention said (purified) dimer is thus a water-soluble oligomer
having surface-active graft copolymers with a hydrophilic graft and
a hydrophobic main chain. An example of a preferred structure of an
oligomeric dimer, e.g dimer of methacryl oxy (polyethylene oxide)
has been given hereinafter in the formula (XX) 8
[0072] In this formula (XX) R represents a member selected from the
group consisting of hydrogen, alkyl, sulphonic acid, carboxylic
acid and phosphonic acid or salts thereof.
[0073] The (preferably water-soluble) dimeric compound having a low
molecular weight can thus, apart from being dissolved in its
monomer, be dissolved in an aqueous phase. Emulsion polymerization
may further be performed semi-continuous or batch-wise, but
essentially the reaction proceeds in a one step water-based
procedure, implying no solution polymerization in advance.
[0074] It has clearly been pointed out that making use of the
method of the present invention by addition of dimeric compounds
according to the general formulae (I) or (II), makes particle size
to decrease with a factor of more than 10% on the average, if
compared with a method wherein dimeric compounds are absent during
emulsion polymerization. In a preferred embodiment said latex
particles have an average particle size being at least 20% lower
than if prepared in the absence of said chain transfer agents
(CTA's).
[0075] More particularly use of modified dimers, e.g.
hydroxyethyl-methacrylate dimers as e.g. hydroxyethyl methacrylate
dimer, results in bis-hydroxyl terminated polymers. As by these
polymerization reactions end-group functional polymers become
available this opens new perspectives in order to fully reach the
advantages, mentioned in the objects of the present invention, more
particularly with respect to the preparation of latex polymer
particles having smaller particle sizes, without the need to apply
a solution polymerization step prior to the said emulsion
polymerization.
[0076] A preferred embodiment of the present invention consists in
the presence in the polymerization reaction step of a low
concentration of surfactant versus the functional dimer in order to
provide well-defined .alpha.,.omega.-terminated telechelics. So
according to the method of the present invention presence of low
ionic, and even more preferred anionic surfactant or initiator
concentrations of from 0.05 wt % up to 10 wt % versus monomer or
monomer mixture concentations is preferred, more preferably from
0.05 up to 5% by weight versus said monomer or monomer mixture
concentrations and even most preferably in an amount of from 0.05
up to 1 wt %. As already set forth hereinbefore said surfactant is
present in a much higher concentration, i.a. of from 5 up to 25% by
weight for a non-ionic latex. According to the present invention
the surfactant itself is present in a concentration below twice its
critical micelle concentration.
[0077] Monomers which may be used in the emulsion
(co)polymerization reactions according to the method of the present
invention are selected form the group of styrenes derivatives,
methacrylates, acrylates, methacrylamides, acrylamides, maleimides,
vinyl ethers, vinyl esters. More specifically the monomers used in
the emulsion polymerisation consist of the group of styrene,
para-methylstyrene, tert.-butylstyrene, methylmethacrylate,
ethylmethacrylate, butylmethacrylate, glycidylmethacrylate,
hydroxyethylmethacrylate, .alpha.-methylstyrene, ethylacrylate,
butylacrylate, vinylacetate, vinyl versatate, butadiene, isoprene,
acrylonitrile, methacrylonitrile, sulfoethyl methacrylate and its
alkali salts, acrylic acid, methacrylic acid, tert-butyl
acrylamide, AMPS, N-isopropylacryl-amide, itaconic acid, maleic
acid, maleic anhydride, vinylidene chloride, isopropylmethacrylate,
dialkyl itaconate, acrylonitrile, methacrylonitrile and vinyl
chloride.
[0078] According to the method of the present invention useful
surfactants are compounds selected from the group consisting of
anionic surfactants, non-ionic surfactants or cationic surfactants,
or mixtures thereof. Particular examples of anionic surfactants are
fatty alcohol sulphates, alkylphenol sulphates, fatty alcohol ether
sulphates, fatty alcohol ether sulphates, alkylphenol ether
sulphates, alkylbenzene sulphonic acid, alkyl ether carboxylic acid
and salts thereof, alkyl sulphosuccinates, alkyl
sulphosuccinamates, phosphate esters, .alpha.-olefin sulphonates,
etc. . . Particular examples of non-ionic surfactants are alcohol
ethoxylates, alkylphenol ethoxylates, polyethylene
oxide/polyethylene oxide block copolymers, polyvinyl alcohol,
polyvinyl pyrrolidone,sorbitan fatty acid esters, sorbitan ester
ethoxylates, etc. . . Particular examples of cationic surfactants
are alkyl dimethylamines, quaternary ammonium compounds, etc. . .
In some cases the presence of ionic groups at the surface of, or
buried in the polymer latex particle should be avoided by using low
concentrations of anionic surfactant and low persulphate initiator
concentrations in order to obtain pure hydrophobic latex
particles.
[0079] According to the present invention said ultrafine
hydrophobic latex particles of polymers and, prepared according to
the method as disclosed herein, are suitable for use in printing
plates for computer-to-plate or computer-to-press applications,
including lithography and flexography, in silver halide based
graphic, cinematographic and micrographic film materials, in
medical diagnostic or recording photographic film materials, in
photoresist applications and in ink-jet media. Use of said
hydrophobic (co)polymer latex particles in coated layers as e.g. in
materials for ink-jet applications moreover leads to the desired
advantage of lower load of the layers with said surfactants and to
reduction of disadvantageous "bleeding" effects, resulting
therefrom. The fine polymer particles can be used as organic
pigments in ink-jet media, instead of the usually employed
inorganic pigments, such as silica and aluminum oxide. Using such
ultrafine latices the desired gloss can be obtained with good
drying characteristics. Otherwise a sharp polarity switch occurs
between hydrophobic and hydrophilic states in applications where it
is desired, as e.g. in printing plates, computer-to-plate and
computer-to-press applications. In graphic or medical silver halide
film materials transparency is very important. In order to obtain
an hard scratch resistant films, such as in backing layers,
polymers with a high glass transition temperature are used. In
order to obtain sufficient film formation NMP (N-methyl
pyrrolidone) was added. In order to improve film formation with
addition of less NMP, the ultrafine latex polymers prepared
according to the method of the present invention are useful. As an
additional advantage use of lower amounts of NMP is environmentally
more attractive and acceptable.
[0080] According to the present invention ultrafine hydrophobic
latex particles of polymers and copolymers prepared according to
the method as described hereinbefore, are used in printing plates
for computer-to-plate or computer-to-press applications or are used
in silver halide based graphic, medical, cinematographic and
micrographic film materials, in photoresist applications and in
ink-jet media, without however being limited thereto. Illustrations
thereof can be found hereinafter in the examples.
[0081] Application of the method of the present invention clearly
illustrates that the (purified) chain transfer agent used in the
water-based emulsion polymerization reaction without a prior
solution polymeriza-tion reaction step is not only influencing
molecular weight of the polymer, but also has a remarkable
influence on the size of the latex particles thus obtained in that,
according to the method of the present invention particle sizes of
less than 100 nm, more preferably in the range from 10 to 90 nm and
even more preferably in the range from 20 to 70 nm are easily
available, wherein a reduction in particle size of at least 10%,
and more preferably of more than 20% less than if prepared in the
absence of said CTA has been attained. Particle sizes were always
measured with a Brookhaven BI90 particle sizer.
[0082] Making use of the method of the present invention thus
clearly makes decrease particle size of polymer latex particles and
polydispersity thereof as becomes clear from the reactions wherein
dimers (dimeric compounds) in emulsion polymerization have been
used. This will be illustrated, without being exhaustive, in the
Examples hereinafter.
EXAMPLES
[0083] While the present invention will hereinafter be described in
connection with preferred embodiments thereof, it will be
understood that it is not intended to limit the invention to those
embodiments. The molecular weights as mentioned in the examples are
measured by means of Size Exclusion Chromatography using THF as
solvent. Prior to this analysis the samples are freeze dried. The
solids content are obtained by drying in a oven during 12 hours at
105.degree. C. Particle size of the latices are measured by means
of light scattering using a Brookhaven BI90 particle sizer.
[0084] 1. Semi-continuous Emulsion Polymerization of MMA (Methyl
Methacrylate) Making Use of the MMA Dimer as Chain Transfer Agent
(MMA=Methyl Methacrylate)
[0085] 20.0 g of a 10 wt % aqueous solution of an anionic
surfactant as Empicol ESB 70 (lauryl ethoxy (2EO) sulfate) and 353
g of water were added into a 1 l jacketed reactor with nitrogen
flow and stirred at 250 rpm. Subsequently the reactor was heated to
85.degree. C. 20 gram of MMA and 0.40 g of the MMA-dimer were added
into the reactor. The emulsion was stirred for 5 minutes.
Subsequently the reaction was initiated by addition of 25 g of a 2
wt % aqueous solution of K.sub.2S.sub.2O.sub.8 into the reactor.
80.0 g of MMA combined with 1.60 g of MMA-dimer were pumped into
the reactor within a time interval of 30 minutes.
[0086] When all ingredients were added the reaction was allowed to
continue for two additional hours, after which the residual monomer
was stripped by vacuum destillation. The reactor was cooled to room
temperature and subsequently the latex was filtered over coarse
filtration paper.
[0087] 2.Semi-continuous Emulsion Polymerization of Styrene Using
.alpha.-methylstyrene Dimer as Chain Transfer Agent
[0088] 54.0 gram of a 10 wt % aqueous solution of Empicol ESB 70
(lauryl ethoxy (2EO) sulfate) and 1258.8 g of water were added into
a 2 l jacketed reactor with nitrogen flow and stirred at 250 rpm.
The reactor content was heated up to 80.degree. C. Subsequently 30
gram of a 2 wt % aqueous K.sub.2S.sub.2O.sub.8 solution were added.
After 10 minutes the monomer phase and initiator solution are added
simultaneously during 2 hours. The monomer phase contained 360
grams of stryrene and 7.2 grams of .alpha.-methylstyrene dimer. The
initator solution was containing 60 grams of a 2 wt % aqueous
K.sub.2S.sub.2O.sub.8 solution. The reactor contents was post
heated during 1 hour at 80.degree. C. Residual monomer was removed
afterwards by vacuum destillation for 1 hour at 80.degree. C. The
latex was cooled to room temperature, filtered over a coarse
filtration paper and a biocide was added.
[0089] Employed Dimers
[0090] Whereas the MMA-dimer was not commercially available, the
.alpha.-methyl-styrene dimer was available from many differing
companies, like Mitsui Chemicals (Japan), GOI Chemical (Japan) and
Herdillia Chemicals (India). AMSD-GRH (V61706), from GOI Chemical
Co., having a purity of 97.18%, was used. The MMA dimer was
prepared by means of a cobalt (II) complex supplied by DuPont. The
MMA dimer was prepared by means of a cobalt (II) complex, i.e. a
(bis(boron difluorodimethyl-glyoxi- mate) cobaltate (II)
complex).
[0091] 3. MMA Emulsion Polymerization Making Use of MMA Dimer(Table
1)
1TABLE 1 Melt Reaction .phi. visco Pas Reaction No. Parameters Conc
% (nm) Mn Mw MWD 200.degree. C. 1 No CTA, 20.53 64 104846 320120
3.053 (comp.) 0.5% K.sub.2S.sub.2O.sub.8, 2% Empicol ESB,
85.degree. C. 2 2% MMA Dimer 20.4 49 12757 31997 2.508 1823 (inv.)
0.5% K.sub.2S.sub.2O.sub.8, 2% Empicol ESB, 85.degree. C.
[0092] Making use of low amounts of surfactants (0.5 wt % only) and
pure MMA dimer thus leads to a reduction of the weight average
molecular weight (Mw) and the number average molecular (Mn). The
molecular weight distribution (MWD) or polydispersity index (D) is
calculated by dividing the Mw by the Mn. Besides the lower
molecular weights and lower MWD, the average particle size of the
polymer latex particles is reduced with at least 25% if compared
with the comparative method, performed without making use of said
MMA Dimer as CTA.
[0093] 4. Styrene Emulsion Polymerization with
.alpha.-Methylstyrene-Dimer (see Following Table 2)
[0094] Dimers were used herein as addition-fragmentation CTA in
styrene emulsion polymerizations. Since the cobalt II diphenyl
complex is not active for styrene polymerizations. Some reactions
were performed using either the .alpha.-methylstyrene dimer or MMA
dimer as addition-fragmentation CTA.
[0095] Opposite to the MMA-dimer the .alpha.-methylstyrene dimer is
commercially available from companies, like Mitsui Chemicals
(Japan), GOI Chemical (Japan) and Herdillia Chemicals (India). In
these experiments AMSD-GRH, from GOI Chemical Co., with a purity of
97.18%, was used. The MMA dimer was prepared by means of a cobalt
(II) complex, called "cobalt II diphenyl complex", given
hereinbefore as formula (III).
[0096] The MMA dimer was synthesized in the following way.
Destilled methylmethacrylate (500 ml) dissolved in acetone (500 ml)
was put into a two liter three necked round bottom flask, and
fittes with a gas inlet and reflux condenser. After purging with
argon for two hours at 72.degree. C. the bis(boron
difluorodimethyl-glyoximate) cobaltate (II) complex (170 mg) and
AIBN (500 mg) were added. Conversions were kept low in order to
avoid higher molecular weight oligomers to be formed. This was
achieved by taking two hours as the reaction time, after which the
unreacted MMA was removed by a rotary evaporator. Pure MMA dimer
(150 gram) was obtained by destination under reduced pressure
(53.degree. C., 4.times.10.sup.-3 bar). 9
[0097] As can be concluded from the results in Table 2 hereinafter,
besides molecular weight reduction and decreased polydispersity,
presence of 2% of .alpha.-Methylstyrene dimer leads to a remarkable
reduction of about 30% in particle size!
[0098] It is further clear that the results obtained with MMA dimer
are less convincing with styrene: besides a particle size reduction
of not more than 10%, the molecular weight decrease is less
significant! Therefore one should be aware of selecting the best
dimer which has good copolymerization parameters (reactivity
ratios) with the reading monomers. E.g. the MMA dimer will work
sufficient in copolymerization with acrylates and methacrylates,
whereas the alpha-methyl styrene dimer is suitable for use in
styrene copolymerization.
2TABLE 2 Melt Reaction .phi. visco Pas Exp. No. parameters Conc %
(nm) Mn Mw MWD 200.degree. C. 3 No CTA, 0.5% 20.4 78 119563 312764
2.616 (comp.) K.sub.2S.sub.2O.sub.8, 1.5% Empicol ESB, 80.degree.
C. 4 0.5% .alpha.-Methyl- 20.36 58 22522 70206 3.117 (inv.) styrene
dimer, 0.5% K.sub.2S.sub.2O.sub.8, 1.5% Empicol ESB, 80.degree. C.
5 2% .alpha.-Methylstyrene 20.11 54 9706 28870 2.974 84.2 (inv.)
dimer, 0.5% K.sub.2S.sub.2O.sub.8, 1.5% Empicol ESB, 80.degree. C.
6 2% MMA dimer, 20.65 70 40000 121318 3.033 3075 0.5%
K.sub.2S.sub.2O.sub.8, 1.5% Empicol ESB, 80.degree. C.
[0099] 5. Example of a Methyl Methacrylate (MMA) Emulsion
Polymerization Using the Cobalt II Diphenyl Complex (formula (III)
Hereinbefore) as Chain Transfer Agent, Making Use of a Persulfate
Initator
[0100] 36.0 grams of a 10% aqueous solution of Empicol ESB 70 and
1303 g water were added to a 2 l jacketed reactor with nitrogen
flow, stirred at a rate of 250 rpm. The cobalt complex, set forth
hereinbefore as formula (III) (0.02 gram=60 ppm) was dissolved
separately in the methyl methacrylate (MMA) monomer (360 gram). The
monomer-cobalt complex mixture was kept under nitrogen.
Subsequently 20% of the MMA containing 20% of the cobalt complex
was added to the reactor. Then the reactor was heated to 85.degree.
C. and flushed with nitrogen. 100.8 grams of a 2% aqueous solution
of Na.sub.2S.sub.2O.sub.8 was prepared (corresponding with 0.56%
towards monomer amount). 25% of the initiator solution was added to
the heated reactor. After 18 minutes initial latex particles were
formed. Then 50% of the initiator solution and 80% of the
monomer/cobalt II diphenyl complex mixuture was pumped
simultaneously in the reactor during 30 minutes. When all
ingredients were added, the reaction was allowed to continue for an
additional 15 minutes.
[0101] A post initiation was performed consequently, making use of
25% of the initator solution. After 40 minutes the residual monomer
was stripped by vacuum destillation. The resulting polymer latex
had a particle size of 62 nm, measured by making use of a
Brookhaven BI 90 particle sizer.
[0102] 6. Example of a MMA Emulsion Polymerization Using the Cobalt
II Diphenyl Complex (Formula (III) Hereinbefore) as Chain Transfer
Agent and Making Use of an Azo Initiator
[0103] 360 g of MMA and 0.02 gram (=60 ppm) of cobalt II diphenyl
complex were combined in a flask and stirred magnetically. 72.0 g
of an aqueous solution (10 wt %) of the surfactant Empical ESB 70
were added to a 2 liter jacketed reactor and combined with 1278 g
of water. The reactor was pursed with nitrogen. Then 20% of the
monomer/cobalt complex mixture were added to the reactor. The
reactor was heated to 85.degree. C. After 5 minutes the initiator
(4,4'-azobis(4-cyanopentanoic acid) potassium salt) was added (90 g
of a 2% aqueous solution=0.5% towards monomer amount). During 30
minutes 80% left of the monomer/cobalt mixture were added during 30
minutes. When all monomer was added the reaction was continued for
2 hours at 85.degree. C. Residual monomer was removed by vacuum
destillation. The resulting polymer latex had a particle size of 52
nm, as measured by means of a Brookhaven BI 90 particle sizer.
Other similar emulsion polymerizations of MMA have been summarized
in the Table 3 below. The same conclusions with respect to the
advantageous use of CTA's can be drawn as in the previous examples.
Further in Table 4 hereinafter, following the experiments according
to the point 7 were set out, wherein styrene copolymer latex
particles have been prepared with .alpha.-methyl styrene dimer as
CTA (and compared with laurylmercaptan--LSH).
3TABLE 3 MMA Polymeri- Reaction .phi. zation No. parameters (nm) Mn
Mw MWD 7 No CTA, 0.56% Na.sub.2S.sub.2O.sub.8, 78 167953 569367
3.39 (comp.) 1% Empicol ESB, 85.degree. C., 21 employed MMA >
99.9% pure + 10-25 ppm inhibitor MEHQ 8 60 ppm Cobalt II 63 154947
350494 2.26 (inv.) diphenyl, 0.56% Na.sub.2S.sub.2O.sub.8, 1%
Empicol ESB, 85.degree. C., 21 employed MMA > 99.9% pure + 10-25
ppm inhibitor MEHQ 9 0.5% AIBN(COOK).sub.2, No 71 205167 603924
2.94 (comp.) CTA 2% Empicol ESB, 85.degree. C., 21 Destilled MMA 10
30 ppm Cobalt II 54 25703 48090 1.87 (inv.) diphenyl, 0.5%
AIBN(COOK).sub.2, 2% Empicol ESB, 85.degree. C., 21 Destilled MMA
11 60 ppm Cobalt II 52 5782 10028 1.73 (inv.) diphenyl, 0.5%
AIBN(COOK).sub.2, 2% Empicol ESB, 85.degree. C., 21 Destilled MMA
used 12 60 ppm Cobalt II 51 48945 84549 1.73 (inv.) diphenyl, 0.5%
AIBN(COONa).sub.2, 2% Empicol ESB, 85.degree. C., 21 employed MMA
99% + 100 ppm inhibitor MEHQ 13 60 ppm Cobalt II 46 64773 103871
1.82 (inv.) diphenyl, 1.25% AIBN(COONa).sub.2, 2% Empicol ESB,
85.degree. C., 21 employed MMA 99% + 100 ppm inhibitor MEHQ 14 No
CTA, 0.50% 47 127794 478574 3.75 Comp. AIBN(COONa).sub.2, 6%
Empicol ESB, 85.degree. C., 21 employed MMA 99% + 10- 25 ppm
inhibitor MEHQ 15 60 ppm Cobalt II 26 133767 502936 3.76 Inv.
diphenyl, 0.50% AIBN(COONa).sub.2, 6% Empicol ESB, 85.degree. C.,
21 employed MMA 99% + 10- 25 ppm inhibitor MEHQ 16 60 ppm Cobalt II
36 116659 306216 2.62 diphenyl, 0.50% AIBN(COONa).sub.2, 2% Empicol
ESB, 85.degree. C., 21 employed MMA 99% + 10- 25 ppm inhibitor
MEHQ, all MMA + initiator added semi-continously
[0104] Styrene Copolymer Latex Particles Prepared with
.alpha.-methyl Styrene Dimer as CTA (and Comparison with
Laurylmercaptan--LSH)
[0105] LSH=laurylmercaptan; AMSD=.alpha.-methylstyreen dimer;
NIPA=N-isopropyl acrylamide
4TABLE 4 Chain Exp. Monomers Transfer .phi. Mn Mw No. Weight ratio
Agent (wt %) (nm) g/mol g/mol D 17 Styrene/NIPA LSH 0.025% 67 56316
193518 3.4 comp. 85/15 18 Styrene/NIPA AMSD 1.0% 57 32769 101140
3.09 inv. 85/15 19 Styrene/ No CTA 55 71907 191538 2.66 comp.
Acrylonitrile 66.3/33.7 20 Styrene/ AMSD 0.5% 47 81889 478978 5.80
inv. Acrylonitrile 66.3/33.7 21 Styrene/ No CTA 62 79369 208977
2.63 comp. Methacrylo- nitrile 60.8/39.2 22 Styrene/ AMSD 0.5% 55
42052 98703 2.35 comp. Methacrylo- nitrile 60.8/39.2 23
Styrene/Methacrylo- AMSD 1.0% 55 31237 68286 2.19 inv. nitrile
60.8/39.2 24 Styrene/ AMSD 2.0% 50 19582 43487 2.22 inv.
Methacrylo- nitrile 60.8/39.2
[0106] 8. Other Latices Prepared Using AMSD (see illustration in
Table 5)
5TABLE 5 Exp. Monomers .phi. Mn Mw No. Weight ratio CTA(wt %) (nm)
g/mol g/mol D 25 t-butylstyrene/ No CTA 47 159250 988401 6.2* Comp.
acrylonitrile 75.15/24.85 26 t-butylstyrene/ AMSD 0.5% 41 155958
972945 6.2* Inv. acrylonitrile 75.15/24.85 *= bimodal
distribution
[0107] It can easily be deduced from the Tables 4 and 5 that AMSD
(=.alpha.-ethylstyrene dimer) acts in a superior way with respect
to LSH (=-laurylmercaptan) in order to provide latex polymer
particles having extremely fine sizes (at least 10% smaller than
prepared without CTA) and a low polydispersity, according to the
objects of the present invention.
[0108] 9. Examples with Respect to Use in CtP Thermal Printing
Plate
[0109] a. Use of polystyrene homopolymer latices (see Table 6)
6 TABLE 6 Sensitivity Latex no. CTA mJ/cm.sup.2 3 (comp.) 0.015%
LSH 245 6 (inv.) 2.0% MMA-dimer 225 4 (inv.) 0.5% ANSD 200 5 (inv.)
2.0% ANSD 185
[0110] LSH: laurylmercaptan, AMSD: alpha-methylstyrene dimer
[0111] b. Use of styrene copolymer latices (see Table 7)
7 TABLE 7 Monomers Sensitivity Latex No. Used CTA mJ/cm.sup.2 17
(comp.) Styrene/NIPA 0.015% LSH 310 18 (inv.) Styrene/NIPA 1.0%
ANSD 275 21 (comp.) Styrene/ No CTA 250 methacrylonitrile 22 (inv.)
Styrene/ 0.5% AMSD 230 methacrylonitrile 23 (inv.) Styrene/ 1.0%
AMSD 225 methacrylonitrile 24 (inv.) Styrene/ 2.0% AMSD 215
methacrylonitrile AMSD: alpha-methylstyrene dimer; NIPA=
N-isopropyl acrylamide
[0112] Results as illustrated in the Tables 6 and 7 are
self-explaining in that a higher sensitivity is attained for
materials wherein use has been made of ultrafine hydrophobic latex
particles of polymers and copolymers, prepared according to the
method of this invention.
[0113] 10. Examples Illustrating Application in the Backing Layer
of Graphic Silver Halide Film Materials (See Table 8)
[0114] As a particular advantage of making use of ultrafine polymer
latex parameters prepared according to the method of the present
invention improvement of "haze", resulting in a remarkably better
clarity of the film material, has been proved in the Table 8
hereinafter.
8TABLE 8 Haze Visual film Latex no. Monomers used/CTA NMP % 560 nm
clarity 7 (comp.) MMA/no CTA 0 60.91 Extremely Mat 7 (comp.) MMA/no
CTA 2.5 1.31 Slightly mat 7 (comp.) MMA/no CTA 5 0.49 Slightly mat
8 (inv.) MMA/60 ppm 0 39.09 Mat Cobalt II diphenyl 8 (inv.) MMA/60
ppm 2.5 0.83 Slightly mat Cobalt II diphenyl 8 (inv.) MMA/60 ppm 5
0.4 Clear Cobalt II diphenyl
[0115] Having described in detail preferred embodiments of the
current invention, it will now be apparent to those skilled in the
art that numerous modifications can be made therein without
departing from the scope of the invention as defined in the
appending claims.
* * * * *