PROCEDE DE POLYMERISATION PAR OXYDO-REDUCTION

REDOX POLYMERIZATION PROCESS

Abrégé français

La présente invention concerne une polymérisation en émulsion consistant à faire réagir ensemble un initiateur de polymérisation, un réducteur et une espèce polymérisable, sous réserve que l'initiateur de polymérisation ne soit pas un hydroperoxyde. Cette polymérisation en émulsion se caractérise en ce que l'initiateur de polymérisation et le réducteur réagissent ensemble pour fournir une fraction moitié à radicaux libres de l'initiateur, à la suite de quoi cette fraction à radicaux libres déclenche la polymérisation de l'espèce polymérisable. Cette opération est exécutée à une température de départ initialement basse qui augmente ensuite selon une courbe déterminée jusqu'à une température finale présélectionnée de polymérisation.

Abrégé anglais

A process for emulsion polymerization comprising the steps of reacting
together a polymerization initiator, a reductor, and a polymerizable species,
with the proviso that the polymerization initiator is not a hydroperoxide,
characterized in that the polymerization initiator and the reductor are
reacted together to provide a free radical moiety of the initiator, whereupon
this free radical moiety initiates polymerization of the polymerizable
species, this step being carried out at an initial cold start temperature,
whereafter the temperature is increased to follow a temperature profile to a
final preselected polymerization temperature.

Revendications

NEW CLAIM
1. A Process for emulsion polymerization
comprising the steps:
- of reacting together a polymerization
initiator, a reductor, and a polymerizable species, with
the proviso that the polymerization initiator is not a
hydroperoxide, wherein the polymerization initiator and
the reductor are reacted together to provide a free
radical moiety of the initiator,
characterized in that the free radical moiety
initiates polymerization of the polymerizable species,
this step being carried out at an initial cold start
temperature, whereafter the temperature is actively
increased by means of an external heat supply source so
that the polymerization follows an increasing temperature
profile to a final preselected polymerization
temperature, this final temperature being higher than the
cold start temperature,
wherein the polymerization initiators are
selected from the group consisting essentially of
aliphatic and aromatic peroxy esters and peroxy
carbonates.


12a
CLAIMS
2. Process according to claim 1 carried out at an initial temperature of up to
70°C, for example carried out at an initial temperature of up to
50°C and
preferably of up to 35°C.
3. Process according to claim 1 or 2 carried out at an initial temperature
lying
in the range of +10° to 35°C, preferably in the range of
15° to 25°C.
4. Process according to any one of the preceding claims wherein the initial
temperature is maintained for a predetermined length of time, for example
up to 2 hours, preferably up to 1 hour, most preferably up to half an hour.
5. Process according to any one of the preceding claims wherein the
temperature is increased subsequent to the initial temperature
maintenance period to follow a temperature profile to a final
polymerization temperature, preferably up to a final polymerization
temperature of at the most 90°C, and wherein the final polymerization
temperature preferably lies in the range of 50-80°C and most preferably
is


13
70°C or less.
6. Process according to claim 5 wherein the initial temperature is increased
incrementally per pre-selected time period, preferably by about 20°C
per
hour.
7. Process according to claim 6 wherein the initiator is selected from the
group consisting essentially of: diisobutanoyl peroxide, cumyl
peroxyneodecanoate, 2,4,4-trimethylpentyl-2-peroxyneodecanoate, tert-
amyl peroxyneodecanoate, bis(4-tert-butylcyclohexyl)peroxydicarbonate,
bis(-ethylhexyl)peroxydicarbonate, tert-butyl peroxyneodecanoate, dibutyl
peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxy-
dicarbonate, tert-amyl peroxypivalate, tert-butyl peroxypivalate, bis(3,5,5-
trimethylhexanoyl) peroxide, dilauroyl peroxide, didecanoyl peroxide, 2,5"-
bis(2-ethylhexanoylperoxy)-2,5-dimethylhexane, tert-amyl peroxy-2-
ethylhexanoate, dibenzoyl peroxide, tert-butyl peroxy-2-ethylhexanoate,
tert-butyl peroxydiethylacetate, 1,4-bis(tert-butylperoxycarbo)cyclohexane,
tert-butyl peroxyisobutanoate, 1,1-bis(tert-butylperoxy)-3,3,5-
trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, tert-butyl
peroxy-3,5-trimethylhexanoate, 2,2-bis(tert-butylperoxy)butane, tert-
butylperoxy isopropyl carbonate, tert-butylperoxy 2-ethylhexyl carbonate,
tert-butyl peroxyacetate, tert-butyl peroxybenzoate, di-tert-amyl peroxide,
dicumyl peroxide, bis(tert-butylperoxyisopropyl)benzene, 2,5-bis(tert-
butylperoxy)-2,5-dimethylhexane, tert-butyl cumyl peroxide, 2,5-bis(tert-
butylperoxy)-2,5-dimethyl-3-hexyne, and di-tert-butyl peroxide.
8. Process according to claim 7 wherein the initiator is substantially non
water-soluble and is selected from the group consisting essentially of:
- alifatic and aramatic peroxyesters, preferably tert-butyl peroxy-2-


14
ethylhexanoate (Trigonox 21), tert-amyl peroxy-2-ethylhexanoate, tert-
butyl peroxybenzoate (Trigonox C), tert-amyl peroxybenzoate, tert-butyl
peroxyacetate, tert-butyl peroxy-3,5-trimethylhexanoate, tert-butyl
peroxyisobutanoate, tert-butyl peroxydiethylacetate, tert-butyl
peroxypivalate;
- peroxycarbonates, preferably tert-butyl peroxyisopropyl carbonate
(Trigonox BPIC), and tert-butyl peroxy-2-ethyl hexyl carbonate Trigonox
117).
9. Process according to any one of the preceding claims wherein the reductor
is chosen from the group consisting essentially of: sodium formaldehyde
sulfoxylate (SFS), sodium bisulfate, Ascorbic acid (vitamin C), aldehydes, for
example glutaraldehyde, sodium metabisulfite, sodium dithionate, and
sugars.
10. Process according to any one of the preceding claims wherein the
polymerizable species is selected from the group consisting essentially of:
acrylonitrile, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate,
2-
ethylhexyl acrylate, methoxyethyl acrylate, dimethyl aminoacrylate,
methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl
methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, lauryl
methacrylate, stearic methacrylate, dimethyl aminomethacrylate, allyl
methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-
hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, acrylamide,
methacrylamide, glycidyl acrylate, vinyl ester of versatic acid, styrene, para-

methyl styrene, vinyl acetate, alpha-methyl styrene.
11. Process according to any one of the preceding claims carried out in the
presence of a catalyst, said catalyst preferably being a water soluble salt


15

derived from a transition metal, and most preferably being selected from the
group consisting essentially of Fe2+, Co3+, Cu+, and Ce3+.
12. Process according to any one of the preceding claims wherein the initiator
and the reductor are provided in the following ratios 10:1 to 1:5, preferably
4:1 to 1:2.
13. Process according to any one of the preceding claims wherein the ratio of
catalyst: oxidator is about 0-0.1 on a molar basis.
14. A polymer obtainable according to the process of any one of the preceding
claims.
15. Polymer according to claim 14 having one or more of the following
characteristics:
- a conductivity lower than about 5,
- a low residual monomer level,
- a particle size of less than about 220 nm, preferably less than 200 nm.
16. Use of a polymer according to claims 14 and/or 15 in coatings and/or
adhesives.

Description

CA 02346993 2001-04-11
WO 00/22003 PCT/EP99/07769
REDOX POLYMERIZATION PROCESS
The present invention relates to a process for emulsion polymerization, to the
polymers obtainable by such a process, and to their uses.
The production of water based resins, for example by means of emulsion
polymerization techniques, is carried out thermally with inorganic
persulfates. A
problem with thermal polymerization is the process time, which leads to a less
than desirable reactor output.
io
An object of the present invention is to provide an alternative polymerization
process which aims to improve the process time.
The first aspect of the present invention provides a process according to
claim 1.
I5
Since the polymerizatian process according to the present invention provides a
free radical initiator moiety by means of a redox reaction instead of by
thermal
decomposition, the polymerization can be carried out with a so-called "cold
start",
which involves the process time being reduced and the reactor output per unit
2 o time being increased.
A redox polymerization is known for tertiary butyl hydroperoxide "Trigonox A-
W70". The inventors have shown, however, that a redox polymerization utilizing
other organic peroxides provides unexpectedly good results.
The inventors have shown that polymerization can start at a lower initial
temperature, which means that because of the longer "heating-up" time
necessary in thermal polymerization, the polymerization time can be reduced
utilizing the process of the current invention.
The inventors have furthermore demonstrated that the process according to the
present invention enables a polymer with a very low residual monomer level to
be
GONFiRMATION COPY


CA 02346993 2001-04-11
WO 00/22003 PCT/EP99/07769
2
obtained, whilst, with respect to thermal polymerization, the amount of
initiator
used can be reduced.
Good results have been achieved under the conditions as defined in claims 2-6.
The polymerization initiator is most preferably a substantially non-water
soluble
initiator, such as defined in claim 7 or 8, since these non-water soluble
initiators
yield an unexpectedly high efficiency in polymerization.
to This higher efficiency results in shorter polymerization times and in
polymer
resins with improved properties. The higher efficiency of the organic
peroxides is
expressed by the low level of residual monomers and by the low molecular
weights (Mw/Mn) of the polymers formed.
i5 Furthermore, the conductivity of the resins initiated with the organic
peroxide/redox system is lower than for corresponding resins that were
initiated
by persulfates.
The reductor of the redox system preferably is chosen from the following
group:
Zo sodium formaldehyde sulfoxyiate (SFS), sodium bisulfate, Ascorbic acid
(vitamin
C), aldehydes, for example glutaraldehyde, sodium metabisulfite, sodium
dithionate, and sugars, wherein the reductor most preferably is sodium
formaldehyde sulfoxide.
a5 The polymerizable species preferably is chosen from the following group:
acrylonitrile, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate,
2-
ethylhexyl acrylate, methoxyethyl acrylate, dimethyl aminoacrylate,
methacrylic
acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl
methacryfate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearic
3o methacrylate, dimethyl aminomethacrylate, aliyl methacrylate, 2-
hydroxyethyl


CA 02346993 2001-04-11
WO 00/Z2003 PCT/EP99/07769
3
acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-
hydroxypropyl
methacrylate, acrylamide, methacrylamide, glycidyl acrylate, vinyl ester of
versatic acid, styrene, para-methyl styrene, vinyl acetate, alpha-methyl
styrene,
wherein the polymerizable species most preferably comprises vinyl acetate
s and/or the vinyl ester of versatic acid.
Further preferred process conditions are detailed in claims 11-15.
The polymerization is carried out in a conventional emulsion, for example in a
to mixture of anionic and non-ionic surfactants such as Witconate (sodium
alpha-
olefin sulfonate) and Syntopon (ethoxylated nonylphenol); however, other
emulsifiers or mixtures are also possible.
This emulsifier solution preferably is a mixture of nonionic and anionic
emulsifiers
15 and most preferably is selected from the group consisting essentially of:
long-chain aliphatic carboxylates (ionic)
- alkylbenzene sulfonates (ionic)
- alkyl sulphates (ionic)
- dialkylsulphosuccinate (ionic)
so - ethoxylated alcohols (nonionic)
- ethoxylated alkyl phenols (nonionic)
- ethoxylated amine or amides (nonionic).
A second aspect of the present invention provides a polymer obtainable
as according to this process.
The invention will now be further elucidated by way of the following examples.
Examples 1-6 are comparative examples and Examples 7-12 are examples
according to the present invention using a redox system. Examples 3, 4, 6, 8-
12
3o were subjected to a temperature profile increasing from an initial
temperature to a


CA 02346993 2001-04-11
WO 00/22003 PCT/EP99/07769
4
final temperature, i.e. subjected to a so-called "cold-start", and Example 7
was
carried out at constant temperature.
ProcedurP,sf~r~naration
s The polymerization in all the examples was carried out in a 0.25 L glass
reactor
with a stirrer under nitrogen. A seed was prepared first by adding 10% of the
reactive components at polymerization temperature.
The preparation of the seed was carried out as follows;
io The reactor was filled with buffered (NaAc/HAc) emulsifier solution
(Witconate/Syntopon), prepared with oxygen-free deionized water. At the
polymerization temperature 10% of the pre-emulsion containing soaps (Witconate
and Syntopon), monomers, and, in the case of the redox system according to the
present invention, also reductor and catalyst, were added. In addition the
solution
i5 or pre-emulsion of the initiator was added to achieve control over the
accurate
dosing of the initiator.
After a polymerization time of 30 minutes the remaining monomers, pre-
emulsion,
and initiator solution were dosed in 2.5 hours. In Examples 3, 4, 6, 8-12 the
ao temperature was increased to the final temperature in the same period,
following
a temperature profile. The final temperature was maintained for 1 hour.
The composition of the buffered soap solution used was as follows:
NaAC.3aq 0.25 g (sodium acetate)
as HAc 0.11 g (acetic acid)
H20 30.3 g
Witconate 0.38 g (soap)
Syntopon 0.38 g (soap)


CA 02346993 2001-04-11
WO 00/22003 PCT/EP99/07769
Thermal system
The temperature was kept at 70°C during the polymerization. The
composition of
the used pre-emulsion was:
Witconate 1.28 g
Syntopon 1.28 g
H20 34.43 g
Vac (vinyl acetate) 52.5 g (monomer)
VEOVA (vinyl ester of versatic acid) 22.5 g (monomer)
5
The initiator solution was composed of 4.18 mmoles ammoniumlsodium or
potassium persulfate in 25 g H20. The total process time including the time
needed for heating up the reactor contents to 70°C before
polymerization
amounted to 5.5 hours.
to
Exam I~es 2, 5, 7
The temperature was kept at 70°C (Examples 2, 5) and 20°C
(Example 7),
respectively. The composition of the used pre-emulsions was as follows:
Witconate 1.28 g
Syntopon 1.28 g
H20 34.43 g
Peroxide 1.04-4.18 mmoles as mentioned in the examples
Vac (vinyl acetate) 52.5 g (monomer)
VEOVA (vinyl ester of 22.5 g (monomer)
versatic acid)
i5 The reductor SFS (sodium formaldehyde sulfoxyde: 0.65 g) and the catalyst
(FeS04 16.7 mg) were dissolved in 25 g H20.
The total process time was 4 hours.


CA 02346993 2001-04-11
WO 00/22003 PCT/EP99/07769
6
Exam leo s 3. 44 6, 8-12
The polymerization temperature was kept at 20°C for the first 30
minutes to
prepare a seed. The temperature was then increased by 20°C/hour to
70°C
following a temperature profile.
It is noted that other starting temperatures and temperature programmes can be
used, either for initiating polymerization or for initiating and completing
polymerization.
io In all the examples the residual monomers were determined by gas
chromatography (GC). The molecular weight of the prepared polymers was
determined by gel permeation chromatography (GPC) with polystyrene for
calibration. The conversion/solids content was determined by standard
procedure. The viscosity was determined using a Brookfield digital viscometer.
is
The results are shown in Table 1.
F_xamples 13-24
ao Procedure of pre ap ration
The polymerization in all examples was carried out in a 0.25 L glass reactor
with
a stirrer under nitrogen. A seed was prepared first by adding 10% of the
reactive
components at polymerization temperature.
is The preparation of the seed was carried out as follows:
The reactor was filled with the emulsifier solution (sodium lauryl sulfate in
water)
prepared with oxygen-free deionized water. ~ At the starting polymerization
temperature 10% of the pre-emulsion containing soap, monomers, and in the
case of the redox system, also reductor and catalyst, were added. In addition
the
3 o solution or pre-emulsion of the initiator was added to achieve control
over the


CA 02346993 2001-04-11
WO 00/22003 PCT/EP99107769
7
accurate dosing of the initiator.
After a polymerization time of 30 minutes the remaining monomers, pre-
emulsion,
and initiator solution were dosed in 2.5 hours. The temperature was increased
to
s the final temperature in the same period, following a temperature profile.
The final
temperature was maintained for 1 hour.
The composition of the soap solution was as follows:
0.10 g sodium lauryl sulfate (emulsifier)
l0 25.0 ml deionized water
Pre-emulsion:
1.60 g sodium lauryl sulfate
30 ml deionized water
is 70 g monomer mixture (butylacrylate I styrene I methacrylic acid = 6/4/0.1)
including the initiator (1.04 meq), if not water-soluble.
The reductor SFS (sodium formaldehyde sulfoxylate 0.16 g) and the catalyst
(Fe"S04 2.8 mg) were dissolved in 10 ml water.
ao The molar ratio oxidator: reductor: Fe = 1: 1: 0.01
The results are shown in Tables 2 and 3.


CA 02346993 2001-04-11
WO 00/22003 PCT/EP99/07769
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CA 02346993 2001-04-11
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CA 02346993 2001-04-11
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CA 02346993 2001-04-11
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11
Results
As reference the emulsion copolymerization of vinylacetate and VeoVa with
potassium persulfate at 70°C was used (thermal conditions).
The results show low residual monomer levels for the non-water soluble
organic peroxides (peroxyesters) under redox conditions. As the efficiency of
the non-water-soluble peroxyesters such as Trigonox C was much higher than
that of the water-soluble persulfates and hydroperoxides, the levels of
addition
to could be lowered to 20-40% of the original milli-equivalents of initiator
used.
Due to lower amounts of initiator and reductor, a higher value for pH and
lower
values for the conductivity were obtained. The prepared polymer had molecular
weights (Mw/Mn) comparable with those of the reference copolymer of
VeoVaNAc.
The peroxyesters such as Trigonox 21 gave a high conversion of monomers at
ambient temperature.
The invention is not limited to the above description; rather, the requested
ao rights are determined by the following claims.