FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
“AQUEOUS EMULSION COMPOSITION OF
ORGANIC PEROXIDE”
ARKEMA FRANCE of 420, Rue d'Estienne
d'Orves, F-92700 Colombes, France;
The following specification particularly describes the invention
and the manner in which it is to be performed.
WO 2014/044949 - 1 - PCT/FR2013/052060
AQUEOUS EMULSION COMPOSITION OF ORGANIC PEROXIDE
Field of the invention
A subject matter of the invention is an aqueous organic 5 peroxide composition
which is liquid at storage temperature and which can be used for the polymerization or
the copolymerization of ethylenically unsaturated monomers and in particular of vinyl
chloride. The invention relates more particularly to an aqueous composition comprising
an emulsifier based on polyvinyl acetate having a high degree of hydrolysis and a low
10 viscosity in solution in water.
Particular precautions in terms of safety have to be taken during the maintenance
and handling of organic peroxides. Organic peroxides are packaged in aqueous
emulsion form. The presence of water, as heat-transfer fluid, makes it possible to absorb
and to dissipate the energy generated in the event of possible decompositions of the
15 peroxides. Furthermore, these emulsions comprise an antifreeze which makes it possible
to keep the emulsion in liquid form at temperatures of less than -10°C, generally of less
than -20°C. These negative temperatures make it possible to prevent the uncontrolled
decomposition of the peroxides during storage and transportation operations.
An organic peroxide emulsion is composed of peroxide droplets stabilized by an
20 emulsifier. Over time, the emulsion destabilizes and the mean size of the peroxide
droplets increases. The increase in the size of the droplets can bring about phase
separation. According to the minimum technical criteria, a peroxide emulsion is
regarded as satisfactory if the mean size of the droplets does not exceed 20 μm
(micrometer). A mean size of the droplets of less than 10 μm, more advantageously of
25 less than 5 μm, is generally required, as well as a maximum size not exceeding 20 μm.
In addition to the safety considerations due to this phenomenon of destabilization,
the use of a nonhomogeneous organic peroxide emulsion as polymerization initiator in a
vinyl monomer emulsion or suspension can bring about a nonhomogeneity in the final
product. This nonhomogeneity is generally characterized by poorly gelled polymer
30 particles during implementation in the molten state (fish eyes, hard grains). In point of
fact, the presence of hard grains opacifies the polymer material. These stability
considerations are thus very important for the applications where the transparency of the
final product is essential, in particular for medical applications.
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Thus, the peroxide droplets (by agglomeration of the peroxide or peroxides
present in the emulsion, in particular after a certain period of time) of an organic
peroxide emulsion have to have a low mean size, to have a homogeneous and
monomodal size distribution and to be stable over time. In particular, the maximum
diameter of these droplets should not exceed 20 μm. This is because 5 phenomena of
agglomeration or of enlargement of peroxide droplets can result in complete or partial
phase separation of the emulsion.
The stages of unloading the emulsion into intermediate storage silos, of pumping
and of introducing a peroxide emulsion into a polymerization reactor are important
10 stages for the quality of the polymer obtained and the reliability of the polymerization
process. These handling stages have to be carried out as rapidly as possible. To do this,
it is crucial for the peroxide emulsion to exhibit a low viscosity so that the flow of the
emulsion is facilitated to the maximum. At a given temperature, the viscosity of this
type of emulsion varies in particular as a function of the shear rate. It decreases when
15 the shear rate increases and becomes stabilized for rate values generally of greater than
100 s-1. Thus, an organic peroxide emulsion must have a maximum dynamic viscosity
of 1000 mPa.s (milliPascal.second) at low temperature, typically of the order of -10°C,
for a shear rate of 100 s-1. The dynamic viscosity measurements are carried out using
coaxial cylinders which create the shearing, for example according to the standard
20 DIN 53019.
In point of fact, a person skilled in the art knows that, for this type of emulsion, to
attempt to reduce the size of the droplets contributes to increasing the viscosity (see
section 1.4 of the paper by J.P. Canselier and M. Poux, “Procédés d’émulsification –
Mécanisme de formation des émulsions” [Emulsification Processes – Mechanism of
25 Formation of the Emulsions], Techniques de l’Ingénieur J2 152, pp. 1-12, publication of
June 10, 2004).
Thus, to achieve these two main objectives simultaneously is a major difficulty
for a person skilled in the art due to the conflicting choices which he is driven to
envisage.
30
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State of the art
The use of partially hydrolyzed polyvinyl acetate (PVA) is widely described in the
literature as colloid agent for the stabilization of organic peroxide emulsion, such as in
the documents EP 5 0 032 757 and US 3 988 261.
A nonhydrolyzed PVA is insoluble in water. The document WO 99/05101
discloses the use of PVA having a degree of hydrolysis of between 45% and 68% for
aqueous peroxyester emulsions. This document specifies that PVAs having a degree of
hydrolysis of greater than 68% produce excessively viscous emulsions which are
10 unstable, the size of the droplets of which varies in excessively great manner after a
certain storage time, which cannot prevent the risks generated during the decomposition
of the peroxides and which are unsuitable for the applications targeted above.
The document WO 03/095500 discloses the use of PVA as protective colloid for
aqueous peroxydicarbonate or diacyl emulsions, having a degree of hydrolysis within a
15 broad range between 45% and 80%, more specifically, as disclosed in the examples,
around a value of the degree of hydrolysis of 65%.
Thus, the state of the art teaches that, on the one hand, in an aqueous organic
peroxide emulsion, the use of polyvinyl acetates having a degree of hydrolysis of less
than a maximum of 70% produces peroxyester, peroxydicarbonate and diacyl peroxide
20 emulsions which satisfy the stringent conditions of viscosity and of stability essential to
the handling of such emulsions and that, on the other hand, above this limit with regard
to the degree of hydrolysis of the PVA, the use of the latter is not under any
circumstances appropriate in such an emulsion.
25 Brief description of the invention
Surprisingly, the applicant company has discovered, contradicting the teachings of
the prior art, that emulsifiers based on polyvinyl acetate having a high degree of
hydrolysis stabilize peroxide emulsions and meet the conditions required relating to the
30 size of the peroxide droplets and the viscosity of the emulsion. These characteristics are
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fulfilled during the highly particular combination of characteristics specific to polyvinyl
acetate, namely a high degree of hydrolysis with a very low intrinsic viscosity.
The present invention thus relates to an aqueous organic peroxide emulsion
composition comprising:
- from 10% to 65% by weight of one or 5 more organic peroxides,
- from 2% to 25% by weight of at least one antifreeze agent,
- from 0.01% to 10% by weight of at least one emulsifying agent,
- optionally at least one additive,
- water, the amount of which is determined so as to form the remainder of the
10 total composition (100%),
characterized in that the emulsifying agent is a colloid agent consisting of a polyvinyl
acetate having a degree of hydrolysis of greater than 80% and a viscosity, measured in
solution in water at 4% by weight at 20°C, of less than or equal to 5 mPa.s, said
viscosity being measured with a Brookfield RVT viscometer, spindle No. 3, 20 rpm
15 (revolutions per minute), according to the standard ISO 2555.
Other characteristics or embodiments of the invention are presented below:
- preferably, the viscosity of the partially hydrolyzed polyvinyl acetate, measured in
solution in water at 4% by weight at 20°C, is less than or equal to 3 mPa.s (always
under the same measurement conditions);
20 - according to one possibility offered by the invention, the partially hydrolyzed
polyvinyl acetate is modified in its acetate groups by metal salts, preferably chosen
from sulfonates and sodium carboxylates;
- advantageously, the composition according to the invention comprises a second
emulsifying agent consisting of a nonionic surfactant of ethoxylated fatty acid type,
25 such as ethoxylated fatty acid mono-, di- or triglycerides or ethoxylated vegetable
oils, ethoxylated fatty alcohol type or a block copolymer comprising at least one
alkylene oxide block type;
- preferably, this second emulsifying agent consists of an ethoxylated castor oil;
- advantageously, the degree of hydrolysis of the polyvinyl acetate is greater than
30 85%, more preferably between 86% and 89%;
- preferably, the organic peroxide or peroxides are chosen from peroxyesters,
peroxydicarbonates and/or diacyl peroxides;
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- according to a distinctive feature specific to the invention, the composition exhibits
a viscosity defined by a flow time of less than 200 seconds, preferably of less than
100 seconds, said flow time being measured at the temperature of 5°C according to
the standard DIN 53211. For further details, the standard DIN 53211 is in this
instance characterized by a diameter of the viscosity cup of 5 4 mm; the dynamic
viscosity is less than 1000 mPa.s and is measured at -10°C for a shear rate of 100 s-1
using a Haake VT550 Viscotester according to the standard DIN 53019;
- likewise, according to a characteristic specific to the invention, the composition
comprises a plurality of droplets formed of peroxide in that the mean size (d50) of
10 said droplets is less than 10 μm (micrometer), preferably less than 5 μm, and the
maximum size (d100) of the droplets is less than 20 μm;
- advantageously, the composition according to the invention comprises more than
30% by weight of one or more organic peroxides, preferably more than 45% by
weight;
15 - advantageously, the polyvinyl acetate is present at between 1% and 5% by weight,
preferably between 0.5% and 3%.
The invention exhibits the following advantages and thus makes it possible to
obtain:
- an emulsion exhibiting a low mean droplet size with a homogeneous and
20 monomodal size distribution,
- an emulsion comprising a mean droplet size (d50) of less than 10 μm after
production or during storage at -20°C for at least 12 weeks. The maximum size (d100)
does not exceed 20 μm,
- an emulsion compatible with the polymerization of ethylenically unsaturated
25 derivatives and in particular of vinyl monomers, such as the vinyl chloride monomer,
- a liquid emulsion having a very low viscosity which allows a very short flow
time.
The present invention also relates to a process for the preparation of the
composition according to any one of the preceding claims, characterized in that it
30 comprises the successive stages of:
- dispersion of the antifreeze agent, optionally at least said additive and also the
colloid agent in water, in order to obtain a homogeneous aqueous phase, then
- the peroxide is added to the aqueous phase, and
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- the mixture thus formed is emulsified during an emulsification stage at a
temperature of less than 5°C, preferably of less than -5°C.
Finally, the invention relates to the use of the composition targeted above in the
polymerization or the copolymerization of ethylenically unsaturated monomers.
Preferably, these ethylenically unsaturated monomers comprise 5 vinyl chloride.
The organic peroxide emulsion according to the present invention can be used in
applications such as the polymerization of acrylic monomers, reactions for modifying
polymers, crosslinking reactions, bulk polymerization reactions and curing processes as
used in unsaturated polyester resins.
10 The description which will follow is given solely by way of illustration and
without implied limitation.
Detailed description of the invention
15 The invention relates to compositions formed of concentrated organic peroxide in
emulsion, said organic peroxide being present at a concentration of 10% to 65%,
preferably of greater than 30% and more preferably of greater than 45% by weight of
the emulsion and being chosen from peroxyesters, peroxydicarbonates and diacyl
peroxides.
20 The preferred peroxides among the peroxyesters are -cumyl
peroxyneodecanoate, -cumyl peroxyneoheptanoate, 2,4,4-trimethylpent-2-yl
peroxyneodecanoate, 3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate, 3-hydroxy-
1,1-dimethylbutyl peroxyneoheptanoate, tert-amyl peroxypivalate, tert-butyl
peroxypivalate, tert-butyl peroxyneoheptanoate, 2,5-dimethyl-2,5-di(2-ethylhexanoyl25
peroxy) hexane, tert-amyl peroxy-2-ethylhexanoate, tert-butyl peroxy-2-ethylhexanoate,
1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, 3-hydroxy-1,1-dimethylbutyl
peroxy-2-ethylhexanoate, tert-butyl peroxyisobutyrate and their mixtures.
The preferred peroxides among the peroxydicarbonates are di(sec-butyl)
peroxydicarbonate, dibutyl peroxydicarbonate, diisopropyl peroxydicarbonate, di(2-
30 ethylhexyl) peroxydicarbonate, bis(3-methoxybutyl) peroxydicarbonate, bis(isobutyl)
peroxydicarbonate, dineopentyl peroxydicarbonate, bis(1-methylheptyl)
peroxydicarbonate, bis[2-(2-methoxyethoxy)ethyl] peroxydicarbonate, bis(3-methoxyWO
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3-methylbutyl) peroxydicarbonate, bis(2-ethoxyethyl) peroxydicarbonate and their
mixtures.
The preferred peroxides among the diacyl peroxides are diisobutyroyl peroxide,
di(3,5,5-trimethylhexanoyl) peroxide, di(2-ethylhexanoyl) peroxide, di(2-ethylbutanoyl)
peroxide and also asymmetric peroxides, such as isobutyroyl 5 octanoyl peroxide,
isobutyroyl decanoyl peroxide, isobutyroyl lauroyl peroxide, 2-ethylbutanoyl decanoyl
peroxide or 2-ethylhexanoyl lauroyl peroxide, and their mixtures.
In order to be able to be stored at temperatures of less than -10°C, preferably of
less than -20°C, the composition according to the invention comprises an antifreeze or
10 more particularly a mixture of antifreeze.
As regards the antifreeze agent, mention may be made, for example, of monools,
diols and triols, such as methanol, ethanol, ethylene glycol, isopropanol, n-propanol,
propane-1,2-diol, propane-1,3-diol, glycerol, butan-1-ol, butan-2-ol, butane-1,3-diol,
butane-1,4-diol and their mixtures, these mixtures comprising at least two of the
15 antifreeze agents listed above, one of light alcohol type and the other of heavy alcohol
type, advantageously a mixture of methanol and propane-1,2-diol.
The emulsifier according to the invention is a polyvinyl acetate having a degree of
hydrolysis of greater than 80% and a viscosity, in solution in water at 4% by weight at
20°C, of less than 10 mPa.s, preferably of less than 5 mPa.s.
20 As regards the partially hydrolyzed polyvinyl acetate, it can consist of Alcotex®
8804, Mowiol® 3-85 or Gohseran® L3266, all well known to a person skilled in the art.
It is not departing from the scope of the invention when a mixture of partially
hydrolyzed polyvinyl acetate according to the present invention is used as emulsifier.
According to one embodiment, the emulsifier according to the invention, namely
25 the partially hydrolyzed polyvinyl acetate, is modified in its acetate groups by metal
salts preferably chosen from sulfonates and sodium carboxylates.
A mixture of unmodified polyvinyl acetate with a modified polyvinyl acetate
according to the present invention can be used as emulsifying mixture for the
stabilization of organic peroxide emulsion.
30 The PVAs modified in their acetate groups are preferably chosen from Gohseran®
L 3266, well known to a person skilled in the art.
A second nonionic emulsifier can be used in combination with the partially
hydrolyzed polyvinyl acetate, modified or unmodified, according to the invention and
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consists of a nonionic surfactant of ethoxylate fatty acid type, which are ethoxylated
mono-, di- or triglyceride derivatives or ethoxylated vegetable oils, ethoxylated fatty
alcohol type or block copolymer comprising at least one alkylene oxide block type. The
ethoxylated vegetable oils are in particular (hydrogenated or nonhydrogenated)
ethoxylated castor oil comprising from 20 to 40 mol of ethylene 5 oxide per mole of
ricinoleic acid; commercial examples are in particular Remcopal® 20, Remcopal® R4097
and Remcopal® RH4090, which are well known to a person skilled in the art.
According to the invention, the second emulsifier, a nonionic surfactant of
ethoxylated castor oil type, is present at a concentration in the invention of between
10 0.01 and 3% by weight, preferably of between 0.5 and 2% by weight.
The emulsion according to the invention can also comprise one or more additives
intended to provide the final thermoplastic composition with specific
properties/characteristics. These additives will ideally be present for the final
polymerization or copolymerization.
15 Thus, as regards the additive, it can be chosen from antioxidants; UV protection
agents; processing aids having the role of improving the final appearance during its use,
such as fatty amides, stearic acid and its salts, ethylenebisstearamide or fluoropolymers;
antifogging agents; antiblocking agents, such as silica or talc; fillers, such as calcium
carbonate and nanofillers, such as, for example, clays; coupling agents, such as silanes;
20 crosslinking agents, such as peroxides; antistatic agents; nucleating agents; pigments;
dyes; plasticizers; viscosity reducers and flame-retardant additives, such as aluminum or
magnesium hydroxides.
The liquid aqueous organic peroxide emulsion of the present invention can
optionally comprise additives including pH-adjusting agents, such as phosphate and
25 citrate buffers, chelating agents, biocides, for example fungicides, antiozonants,
antioxidants, degradation inhibitors, blowing agents and mold-release agents. The
emulsion can also comprise additives normally used to stabilize the organic peroxide or
to delay its decomposition, such as phlegmatizers (isododecane, mineral oil) and
hydroperoxides.
30 These additives can be added in the amounts normally used and known to a
person skilled in the art. These additives are generally used in contents of between
10 ppm and 10 000 ppm by weight, with respect to the weight of final polymer or
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copolymer. The plasticizers, the viscosity reducers and the flame-retardant additives can
reach amounts far above 10 000 ppm.
The invention also relates to a process for the preparation of the emulsion
described above, characterized in that the antifreeze agent, optionally one or more
additives and also at least one emulsifier are dispersed in water, 5 in order to obtain a
homogeneous aqueous phase, and then the peroxide is added to said aqueous phase, the
combined mixture subsequently being emulsified during an emulsification stage at a
temperature of less than 5°C, so as to limit the premature decomposition of the
peroxide, preferably of less than -5°Celsius.
10 Apart from the specific successive stages of the process for the preparation of the
composition according to the invention, the preparation of the emulsion does not differ
in any way from the techniques and devices well known to a person skilled in the art.
The temperature at which emulsion is prepared is not critical but it must be sufficiently
low to prevent a significant degree of decomposition, the result of which would be a
15 loss in the assay. The temperature chosen depends essentially on the organic peroxide or
peroxides. Furthermore, in order to prepare the aqueous emulsions, deionized water or
distilled water is conventionally used.
The preparation process comprises a stage of emulsification with a mixer having a
high shear rate in order to as best as possible divide and/or homogenize the peroxide in
20 the aqueous phase. Mention may be made, by way of example, of mechanically rotating
anchor and paddle stirrers, helical stirrers, that is to say one or more stirrers fitted to a
common shaft, turbine stirrers, that is to say those comprising stationary baffles on the
mixing vessel or in a position adjacent to the stirring members. Use may also be made
of colloid mills and homogenizers. According to one implementational characteristic,
25 the process according to the invention is characterized in that an ultrasonic mixer or a
rotor-stator mixer is used.
Subsequent to the preparation of the emulsion according to the invention, the
stages of pumping and introducing the emulsions into a polymerization reactor had to be
carried out as quickly as possible. The peroxide emulsions must have a low viscosity.
30 Thus, the organic peroxide emulsions according to the invention exhibit a
dynamic viscosity of range at -10°C, 100 s-1, of less than 1000 mPa.s, preferably of less
than 700 mPa.s, immediately after production. The viscosity measurements are carried
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out, for example, according to the standard DIN 53019 with a device of Haake
Viscotester VT550 type at -10°C and for a shear rate of 100 s-1.
Their flowability or flow time, measured by a flow cup technique, is less than 200
seconds, preferably less than 100 seconds (standard DIN 53211, carried out with a
diameter of a cup of 4 mm at a 5 temperature of 5°C).
The subsequent stages of polymerization or copolymerization are not, in the
context of the present invention, different from those of the prior art. The
polymerization of the vinyl chloride monomer is carried out in suspension at an
initiation temperature of between 45 and 70°C.
10 The invention also relates to the use of the emulsion defined above in the
polymerization or copolymerization of ethylenically unsaturated monomers. A
homopolymer is obtained by polymerization when just one ethylenically unsaturated
monomer is polymerized. A copolymer is obtained by polymerization when at least two
ethylenically unsaturated monomers are polymerized. It is understood that the
15 monomers are capable of polymerizing with one another.
Mention may be made, as ethylenically unsaturated monomers of acrylates, vinyl
esters, vinyl halide monomers, vinyl ethers, aromatic vinyl compounds, such as styrene,
or butadiene and preferably vinyl chloride.
20 Preparation of the formulations of the test compositions:
The comparative PVAs, numbered 1, 2, 3, 5, 7 and 8, and the PVAs according to
the invention, numbered 4, 6 and 9, act as emulsifiers in emulsions 1 to 16 (emulsions
11 to 16 use the PVAs previously numbered 4, 6 and 9) and are prepared according to
25 the same procedure.
The aqueous phase containing the PVA, the antifreeze agent and the water is
stirred between 500 and 1000 rpm (revolutions per minute) and maintained at a
temperature of -5°C (Celsius). The organic peroxide is gradually added to the reactor
containing this water/PVA/antifreeze agent mixture. Stirring is maintained at 2000 rpm
30 for three minutes. The combined mixture is subsequently stirred vigorously at 9500 rpm
for two minutes using an UltraTurrax type S-25N 18G device of rotor-stator type and
then at 1000 rpm for one minute while stirring with a paddle. Each emulsion amounts to
200 grams in total.
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Tests carried out:
The dynamic viscosity measurements are carried out using a viscometer of Haake
Viscotester VT550 type. The measurement device is the SV-DIN 5 53019, referring to the
standard DIN 53019. The measurement is carried out using coaxial cylinders which
create the shearing. Between 5 and 10 ml (milliliters) of emulsion is introduced into the
measurement chamber maintained at -10°C. The values given in the examples below
correspond to a shear rate of 100 s-1 and are expressed in mPa.s. The accuracy of the
10 measurement is ±10% of the value shown.
The measurements of flow time are carried out using flow cups of DIN 53211
type (diameter of the viscosity cup: 4 mm). The measurement is carried out on 100 g of
emulsion after conditioning at a temperature of +5°C. The measurements of flow time
are expressed in seconds and the accuracy is ±10% of the value shown.
15 The size of the droplets (d100 and d50) is determined by conventional means using
the light diffraction technique. The term d100 corresponds to the diameter such that
100% of the volume of the sample of organic peroxide droplets in the aqueous emulsion
has a diameter of less than d100 and the term d50 corresponds to the mean diameter such
that 50% of the volume of the droplets of organic peroxide in the aqueous emulsion has
20 a diameter of less than d50. The measurements are carried out using a Malvern Master
Sizer 2000® device at ambient temperature. The droplet sizes d50 or d100 are given to
± 0.5 μm.
Starting materials of the test compositions:
25
Mainly two types/families of emulsions were prepared in order to carry out the
tests which make it possible to characterize the compositions according to the prior art
and according to the invention.
The first emulsion consists of 60% by weight di(2–ethylhexyl) peroxydicarbonate
30 and comprises:
- an antifreeze system which is a mixture of alcohols in a 20/80 ratio by weight of
propylene glycol/methanol, with an overall concentration of 14%;
- a water/antifreeze ratio of 64/36 by weight;
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- a content of di(2–ethylhexyl) peroxydicarbonate of 60% by weight. The di(2–
ethylhexyl) peroxydicarbonate is Luperox® 223 from Arkema with a purity of 97%;
- a content of partially hydrolyzed polyvinyl acetate (PVA) of 1.2% by weight;
- the remainder is distilled water.
The second emulsion consists of 50% by weight tert-5 butyl peroxyneodecanoate
and comprises:
- an antifreeze system which is a mixture of alcohols in a 40/60 ratio by weight of
propylene glycol/methanol, with an overall concentration of 16%;
- a water/antifreeze ratio of 67/33 by weight;
10 - a content of tert-butyl peroxyneodecanoate of 50% by weight. The tert-butyl
peroxyneodecanoate is Luperox® 10 from Arkema with a purity of 97%;
- a content of partially hydrolyzed polyvinyl acetate (PVA) of 1.2% by weight;
- the remainder is distilled water.
15 Characterizations of the PVAs:
The characteristics of the comparative PVAs and of the PVAs according to the
invention are presented in table 1:
TABLE 1
Degree of polymerization Viscosity (mPa.s) Degree of hydrolysis (%)
PVA 1 800 5.6-6.6 72-73
PVA 2 1630 36-42 78.5-81.5
PVA 3 2560 44-52 78.5-81.5
PVA 4 360 3.5-4.5 88
PVA 5 2440 45-49 86.7-88.7
PVA 6 300 3 85-90
PVA 7 Unknown 6-7 86-90
PVA 8 1700 20-26 85-90
PVA 9 Unknown 2.5 87
PVA 10 1100 2.2 42-45
20 The viscosity is measured at 4% in water at 20°C (Brookfield RVT viscosity,
spindle No. 3, 20 rpm).
PVA 9 is a PVA modified by sulfonate functional groups.
It is clearly found that only PVA No. 4, PVA No. 6 and PVA No. 9 correspond to
the criteria (low viscosity and high degree of hydrolysis) defined in the invention. To
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make reading easier, in the table and in the following tables, the PVAs or the emulsions
according to the invention are presented in bold.
A second emulsifier of nonionic surfactant type of ethoxylated castor oil type of
Remcopal® 20 (R20) type is added at 1% by weight to emulsion 10 (with PVA
according to the invention, more specifically PVA No. 4 of the above 5 table), emulsion
11 (with PVA according to the invention, more specifically PVA No. 6 of the above
table) and emulsion 15 (with PVA according to the invention, more specifically PVA
No. 6 of the above table).
10 Emulsions:
Emulsions 1 to 11 and 16 correspond to di(2–ethylhexyl) peroxydicarbonate
peroxide emulsions and emulsions 12 to 15 correspond to tert-butyl
peroxyneodecanoate peroxide emulsions, and are characterized in tables 2 and 3:
15 TABLE 2
Emulsions 1-11, 16 Emulsions 12-15
Di(2–ethylhexyl) peroxydicarbonate, % 60.0
tert-Butyl peroxyneodecanoate, % 50.0
Methanol, % 11.2 9.6
Propylene glycol, % 2.8 6.4
Surfactant, % 1.2 1.2
Water, % 24.8 32.8
TABLE 3
d50 (μm) d100 (μm) Viscosity
(mPa.s)
Flow time (s)
Emulsion 1 (PVA 1) 4 12 1100 145
Emulsion 2 (PVA 2) 7.1 112 2200 > 300
Emulsion 3 (PVA 3) 7.4 141 1650 > 300
Emulsion 4 (PVA 4) 3.9 13.3 790 92
Emulsion 5 (PVA 5) 8.6 100 3090 > 300
Emulsion 6 (PVA 6) 3.4 12.6 670 72
Emulsion 7 (PVA 7) 4.1 19.9 1020 133
Emulsion 8 (PVA 8) 5.2 30.2 3250 >300
Emulsion 9 (PVA 9) 2.7 7.6 580 66
Emulsion 10 (PVA 4/R20) 1.8 4.0 580 83
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Emulsion 11 (PVA 6/R20) 1.8 4.0 530 63
Emulsion 12 (PVA 1) 3.3 8.7 608 64
Emulsion 13 (PVA 9) 3.3 8.7 190 26
Emulsion 14 (PVA 6) 3.8 11.1 363 38
Emulsion 15 (PVA 6/R20) 2.2 5.0 297 37
Emulsion 16 (PVA 10) 4.0 12.6 570 67
It will be noted that, in this instance, only emulsions Nos. 10, 11, 13, 14 and 15
are in accordance with the invention.
PVAs having very high viscosities do not make it possible to obtain fluid
emulsions with short flow times and sufficiently 5 fine droplet sizes.
The more the viscosity of the PVA is low and less than 5 mPa.s, the more the
emulsion meets the performance criteria in terms of fluidity.
The viscosities of the emulsions comprising a nonionic surfactant of ethoxylated
castor oil type (Remcopal® 20 or denoted R20 above) are lower than those comprising
10 only a PVA. This is because addition of a nonionic surfactant, such as an ethoxylated
castor oil of Remcopal® 20 type, to a PVA emulsifier according to the invention
contributes to reducing the viscosity of the corresponding emulsion. Thus, the viscosity
of the emulsion obtained is then close to that achieved with a modified PVA, for
example modified by sulfonate functional groups. Moreover, in addition to reducing the
15 viscosity, the addition of a second emulsifier according to the invention contributes to
reducing the mean size of the organic peroxide droplets.
Generally, a 50% by weight concentrated peroxyester emulsion is slightly more
fluid than a 60% by weight concentrated peroxydicarbonate emulsion. On the other
hand, the emulsions stabilized by the PVAs according to the invention are more fluid
20 than those comprising a comparative PVA (according to the prior art). In the case of the
peresters, the addition of a nonionic surfactant of ethoxylated castor oil type again
contributes to reducing the viscosity of the emulsion while lowering the size of the
droplets. It should be noted that the tests presented here do not include the diacyl
peroxides but the results obtained with regard to the peroxyesters and the
25 peroxydicarbonates allow similar results to be envisaged with the diacyl peroxides. This
is because the diacyl peroxides have formed the subject of preliminary tests as
satisfactory as those obtained with the peroxyesters and the peroxydicarbonates.
WO 2014/044949 - 15 - PCT/FR2013/052060
The emulsions produced with different comparative PVAs and PVAs according to
the invention are stored at a temperature of -20°C for several months. The
characteristics of the different emulsions are measured after different storage times. The
results are presented in table 4:
5
TABLE 4
Emulsion 1
(PVA1)
Emulsion 6
(PVA 6)
Emulsion 11
(PVA 6/R20)
Emulsion 9
(PVA 9)
Emulsion 16
(PVA 10)
d50 (μm)
t = 0
t = 4 weeks
t = 8 weeks
t = 12 weeks
3.3
3.6
3.7
3.8
3.4
/
3.8
4
1.8
/
2.2
2.3
2.7
3.1
3.2
3.3
4.0
4.2
4.2
4.4
d100 (μm)
t = 0
t = 4 weeks
t = 8 weeks
t = 12 weeks
10.0
10.0
10.0
13.2
12.6
/
14.8
15.1
4.0
/
5.8
5.8
7.6
8.7
8.7
8.7
12.6
13.2
15.1
15.1
Viscosity (mPa.s)
t = 0
t = 4 weeks
t = 8 weeks
t = 12 weeks
1100
1180
1170
1170
670
/
730
750
530
/
430
400
580
/
500
/
570
560
630
670
Flow time (s)
t = 0
t = 4 weeks
t = 8 weeks
t = 12 weeks
145
170
171
198
72
/
90
95
63
/
59
57
66
56
52
/
67
70
77
85
The emulsions comprising a PVA according to the invention make it possible to
retain the good properties of the emulsion after a minimum of 12 weeks of storage. The
10 viscosities of the emulsions remain very fluid and less than 1000 mPa.s (measured
according to the standard DIN 53019 with a Haake Viscotester VT550 at -10°C and for
a shear rate of 100 s-1), the flow times remain less than 150 seconds and preferably
100 seconds and the maximum sizes d100 do not exceed 20 μm (micrometers).
WO 2014/044949 - 16 - PCT/FR2013/052060
Generally, only the aqueous peroxide emulsion compositions according to the
invention make it possible to solve the two major technical problems, namely the
enlarging of the peroxide droplets over time, or in other words the stability of the
emulsion, and the viscosity under cold conditions of the emulsion, which is often
excessively high, resulting in particular in unsatisfactory 5 flow times.
WO 2014/044949 - 17 - PCT/FR2013/052060
We Claim:
1. An aqueous organic peroxide emulsion composition comprising:
- from 10% to 65% by weight of one or more organic peroxides,
- from 2% to 25% by weight of at least one 5 antifreeze agent,
- from 0.01% to 10% by weight of at least one emulsifying agent,
- optionally at least one additive,
- water, the amount of which is determined so as to form the remainder of the
total composition (100%),
10 characterized in that the emulsifying agent is a colloid agent consisting of a polyvinyl
acetate having a degree of hydrolysis of greater than 80% and a viscosity, measured in
solution in water at 4% by weight at 20°C, of less than or equal to 5 mPa.s, said
viscosity being measured with a Brookfield RVT viscometer, spindle No. 3, 20 rpm,
according to the standard ISO 2555.
15
2. The composition as claimed in claim 1, characterized in that the viscosity of the
partially hydrolyzed polyvinyl acetate, measured in solution in water at 4% by weight at
20°C, is less than or equal to 3 mPa.s.
20 3. The composition as claimed in claim 1 or 2, characterized in that the partially
hydrolyzed polyvinyl acetate is modified in its acetate groups by metal salts, preferably
chosen from sulfonates and sodium carboxylates.
4. The composition as claimed in any one of the preceding claims, characterized
25 in that it comprises a second emulsifying agent consisting of a nonionic surfactant of
ethoxylated fatty acid type, such as ethoxylated fatty acid mono-, di- or triglycerides or
ethoxylated vegetable oils, ethoxylated fatty alcohol type or a block copolymer
comprising at least one alkylene oxide block type.
30 5. The composition as claimed in claim 4, characterized in that the second
emulsifying agent consists of an ethoxylated castor oil.
WO 2014/044949 - 18 - PCT/FR2013/052060
6. The composition as claimed in any one of the preceding claims, characterized
in that the degree of hydrolysis of the polyvinyl acetate is greater than 85%, more
preferably between 86% and 89%.
7. The composition as claimed in any one of the preceding claims, 5 characterized
in that the organic peroxide or peroxides are chosen from peroxyesters,
peroxydicarbonates and/or diacyl peroxides.
8. The composition as claimed in any one of the preceding claims, characterized
10 in that it exhibits a viscosity defined by a flow time of less than 200 seconds, preferably
of less than 100 seconds, said flow time being measured at the temperature of 5°C
according to the standard DIN 53211.
9. The composition as claimed in any one of the preceding claims, characterized
15 in that it comprises a plurality of droplets formed of peroxide in that the mean size (d50)
of said droplets is less than 10 μm (micrometer), preferably less than 5 μm, and the
maximum size (d100) of the droplets is less than 20 μm.
10. The composition as claimed in any one of the preceding claims, characterized
20 in that it comprises more than 30% by weight of one or more organic peroxides,
preferably more than 45% by weight.
11. The composition as claimed in any one of the preceding claims, characterized
in that the polyvinyl acetate is present at between 1% and 5% by weight, preferably
25 between 0.5% and 3%.
12. A process for the preparation of the composition according to any one of the
preceding claims, characterized in that it comprises the successive stages of:
- dispersion of the antifreeze agent, optionally at least said additive and also the
30 colloid agent in water, in order to obtain a homogeneous aqueous phase, then
- the peroxide is added to the aqueous phase, and
- the mixture thus formed is emulsified during an emulsification stage at a
temperature of less than 5°C, preferably of less than -5°C.
WO 2014/044949 - 19 - PCT/FR2013/052060
13. The use of the composition as claimed in one of claims 1 to 11 in the
polymerization or the copolymerization of ethylenically unsaturated monomers.
14. The use of the composition as claimed in claim 13, characterized 5 in that the
ethylenically unsaturated monomers comprise vinyl chloride.