Field of the Invention
5 The invention relates to an aqueous emulsion of dialkyl peroxide, stored at room
10
temperature, comprising a specific emulsifier, namely a polyethoxylated nonionic
emulsifier, and more particularly at least one sorbitan ester.
The present invention also relates to the process for preparing such an emulsion
and also to the use of this emulsion in applications for which it is particularly intended.
Prior Art
Organic peroxides are species that are highly unstable when they are heated. In
the event of an uncontrolled increase in temperature, certain organic peroxides risk
igniting or exploding violently. This behaviour is therefore incompatible especially with
15 the rules in force for the transportation and storage ofhazardous material.
Organic peroxides must therefore be placed in a solvent (phlegmatizer) or in a
suspension/emulsion in water in order to be able to be transported (oil-in-water
emulsion). The presence of a phlegmatizer (solvent, water) greatly attenuates the
violence of the decomposition.
20 Moreover, the major advantage of emulsions/suspensions of organic peroxides
in water lies in the fact that in the event of decomposition, this will take place without a
major risk of fire since water constitutes a powerful reserve for absorbing calories,
whereas a phlegmatizer (solely solvent, without the presence of water) may catch fire.
Emulsions of liquid organic peroxides in water have been developed essentially
25 for peroxides that must be stored at low temperature. Peroxydicarbonates, certain
peroxyesters and diacyl peroxides will be included in particular.
The main application of these highly reactive peroxides with respect to the
temperature criterion, conventionally in emulsion form, is the polymerization or
copolymerization of ethylenically unsaturated monomers, especially of vinyl chloride.
30 When organic peroxides have a self-accelerated decomposition temperature
(SADT) that is well above room temperature, the advantage of the phlegmatized form
(of solvent or water type) may also lie in the saving in storage in tem1s of the amount of
organic peroxide by change of storage category according to the national regulations in
- 2-
force. This may make it possible to conserve in the production unit a larger amount of
organic peroxide than when the peroxide is phlegmatized.
Thus, for example, 2,5-dimethyl-2,5-di(tert-butylperoxyhexane) peroxide in pure
5 form is classified UN3103, i.e. of type C, whereas, when diluted to 50% by mass in a
mineral oil, it becomes classified UN3109, i.e. of type F (UN classification "Transport
of dangerous goods" relating to peroxides). In the Dutch regulation for the storage of
organic peroxides, known as VROM, it is possible to store in metering equipment
5000 litres of a type F peroxide or 100 litres of a type C peroxide.
10 This logistic advantage is thus associated with the improvement in the safety of
the organic peroxide by the presence of the phlegmatizer (solvent or water).
Now, in certain applications, the presence of a solvent (in the case of an oil-type
phlegmatizer) may present certain drawbacks during use, such as exudation, in
particular when the peroxide is used in extrusion at high temperature or potential
15 exudation (fogging) during the use of the polymer into which the organic peroxide is
added.
This emulsion must remain stable without phase separation for at least two
months of storage at room temperature.
At the present time, there is not available on the market an aqueous emulsion
20 based on dialkyl peroxide which affords optimum safety for peroxides of this type and
which is capable of industrial storage, i.e. without phase separation over a relatively
long period (minimum interval of two months).
In the prior art, US 3988261 discloses gelled aqueous emulsions of peroxides
25 that must be stored in the cold, such as peresters or peroxydicarbonates, but the teaching
of said patent does not concern dialkyl peroxides, which are peroxides of different
nature.
Emulsions of dialkyl peroxides are envisaged in US 4440885, but the physical
state of the peroxide is solid, and this solid is then dissolved in a suitable solvent before
30 being emulsified in water. Said document describes the use of three emulsifiers with an
overall HLB ("hydrophilic-lipophilic balance") (HLB of the emulsion and not of the
various components) of between 9 and 20, but these compositions are not stable beyond
- 3 -
one week (phase separation of the emulsion). Moreover, this solvent br:tves rise to
exudation problems over the extruders, as mentioned previously.
US 7943685 describes a quite specific application in which a latex of elastomer
and of an organic peroxide of dialkyl type is produced, an emulsifier of ionic type
5 (sodium Iaury! sulfate) and additives for crosslinking elastomers, methyl oleate sulfate
and two zinc mercaptoluimidazoles are used. In said document, the latex is prepared just
before use, and the notion of stability without phase separation for several months is
therefore not a criterion considered here.
WO 00/42078 discloses compositions of orgamc peroxide emulsions thus
10 including dialkyl peroxides in the presence of a copolymer of an a, P-unsaturated
dicarboxylic acid partially cthoxylated on the carboxylic acid function and of a CR to
C24 a-olefin and ethoxylated fatty alcohol. The examples cited in said document
illustrate compositions based on peroxydicarbonates or peresters. Now, since the
structure of dialkyl peroxides is intrinsically less polar than that of peresters or
15 percarbonates, it is not possible for a person skilled in the art to extrapolate these results
to dialkyl peroxides.
WO 01132613 for its part claims the preparation of an emulsion of various
organic peroxides by direct synthesis in emulsion of the peroxide concerned. The
corresponding halides are emulsified. The examples given do not concern dialkyl
20 peroxides, but peroxides typically used for the manufacture of PVC (peresters,
peroxydicarbonates, diacyl peroxides). The emulsifiers used in this case are based on
partially hydrolysed PV A, alkylcellulose ethers (such as methylcellulose or
hydroxypropylcellulose), gelatin, polyvinylpyrrolidone, polyethoxylated sorbitan
monolaurate and polyacrylic acid.
25 WO 20111015567 discloses the composition of an aqueous emulsion of a
peroxide with an active oxygen content of greater than or equal to 7% by weight. The
examples in said document describe only the case of a particular diacyl peroxide,
diisobutyryl peroxide, which is the only peroxide present in the examples. The object of
said document consists in rendering safe and secure the transportation of organic
30 peroxides that decompose rapidly, which is not an identical problem to the long-term
(several months) stabilization of an aqueous emulsion that is ab initio transportable, i.e.
non-hazardous. The object of said document consists in developing an emulsion for an
organic peroxide that is intrinsically highly unstable and that could not be transpmied in
-4-
pure form but only diluted (solvent or aqueous emulsion), which is not the case for all
the peroxides described in said document since, in particular, it is known that a good
number of dialkyl peroxides, although having a high content of active oxygen greater
than 7% by weight, may ·be transported in pure form. As has been mentioned
5 previously, the advantage of an emulsion of such dialkyl peroxides lies in more
favourable conditions of use and/or storage than a product that is pure and/or diluted
with solvent.
The problem thus lies here in searching for a dialkyl peroxide composition that
is stable on storage at room-temperature (no phase separation for at least two months).
1 0 Diisobutyryl peroxide is imperatively emulsified at low temperature according to
the examples cited in WO 2011/015567 and is also stored at low temperature
(below 0°C, more precisely at -25°C/-30°C in the two examples). Now, a person skilled
in the art knows perfectly . that the temperature is . a key parameter in the
stabilization/destabilization of an emulsion. As indicated in the document "Techniques
15 de l'Ingenieur - Procedes d'emulsification - Mecanisme de formation des emulsions"
[Engineering techniques - Emulsification processes - Mechanism of formation of
emulsions] by J.P. Canselier and M. Poux, document J2-152, published on 10 June
2014, more precisely in paragraph 1.3.3, and also in example 1 of WO 20111015567 in
which a temperature increase to 35°C destabilizes the emulsion, a temperature rise will
20 have an influence on the solubility of the emulsifier in water, and thus on its residual
concentration in the continuous phase, and will consequently have an influence on the
surface tension of the interfacial zone.
Moreover, thermal agitation and Brownian motion are higher at positive than at
negative temperature and encounter between droplets is thus facilitated, such that the
25 stability of the emulsion will be decreased. It is also important to note the influence of
the viscosity of the phases present and of the emulsion itself on the quality of the
emulsion and on its stability, but an increase in temperature will tend to decrease its
viscosity and therefore the creaming and flocculation phenomena may potentially be
accelerated. As a result, the existing teaching for non-gelled organic peroxide emulsions
30 stored at negative temperature is difficult to extrapolate to emulsions of organic
peroxide, and especially of dialkyl peroxide, stored at room temperature.
In addition, it will be noted that diisobutyryl peroxide is a significantly more
polar compound than dialkyl peroxides since it contains, in addition to the peroxide
- 5 -
bond (oxygen-oxygen bond), polar groups of carbonyl type (acyl). Now, a person
skilled in the art knows that the preparation of an oil-in-water emulsion of a less polar
organic compound (in this case the dialkyl peroxide) will require a larger amount of
energy or particularly efficient surfactants to sufficiently reduce the interfacial tension
5 between the aqueous medium and the organic phase to obtain droplet sizes that are
sufficiently fine and stable over the storage time.
Finally, the special feature of this emulsion is that the organic peroxide, which is
too hazardous in pure form, is phlegmatized beforehand in a solvent and then
emulsified. The composition of this emulsion is itself very close to that which is
l 0 described in WO 03/095500.
JP 2001064312 is also known, which also discloses an emulsion of polar
peroxides that are stable under cold temperature conditions ( -I5°C). The five emulsions
presented in the examples of .said document all systematically comprise an .antifreeze, a
protective colloid (more precisely a polyvinyl acetate PV A) and an emulsifier.
15 Moreover, the three peroxides of the examples- !crt-butyl peroxyisobutyrate (Kayaester
0), bis(3,5,5-trimethylhexanoyl) peroxide (Trigonox 36) and bis(2-ethylhexyl)
peroxydicarbonate (Kayacarbon EH) - all have polar groups of carbonyl type (acyl,
ester and/or carbonate) in addition to the oxygen-oxygen peroxide bond.
20 Brief description of the invention
25
lt has been found that suspension agents such as partially hydrolysed polyvinyl
acetate or cellulose derivatives do not allow, when they are used alone, the storage of
dialkyl peroxides in aqueous emulsion in industrial storage (no phase demixing for at
least two months).
Such suspension agents are, however, often used, on the other hand, for the
emulsion stability of peroxydicarbonates, diacyl peroxides or peresters stored in the
cold.
The Applicant has thus discovered, after various experiments and manipulations,
that it is necessary to use a polyethoxylated nonionic surfactant, but that the nature of
30 this nonionic emulsifier is important such that the objectives of the invention are not
achieved with all types of nonionic emulsifiers. Thus, when used alone (a single
emulsifier is used), nonionic emulsifiers such as partially hydrolysed polyvinyl acetate
' .
- 6-
and/or cellulose derivative (pure celluloses cannot be used as emulsifier, in particular
for this type of peroxide) do not fall within the context of the present invention.
To define what should be understood by the term "nonionic surfactant", the
Applicant refers to the 1995 article entitled "Tensioactifs" [Surfactants] by Chantal
5 Lat-pent, published by "Les Techniques de l'Ingenieur".
10
15
Thus, the present invention relates to an aqueous emulsion of dialkyl peroxide
consisting of:
- at least one dialkyl peroxide in liquid form at room temperature, representing
between 10% and 75% by weight of the emulsion,
- at least one emulsifier representing from 0.01 % to 10% by weight of the
emulsion,
- optionally, at least one antifreeze,
-optionally, at least one functional additive,
- water, the amount of which is determined so as to form the rest of said
emulsion (1 00%),
characterized in that the emulsifier is a polyethoxylated nonionic surfactant.
It is understood here that the dialkyl peroxide is in liquid form at "room
temperature", i.e. a temperature between 10°C and 30°C (Celsius), preferentially
20 between 15°C and 25°C.
By the term "ethoxylated nonionic surfactant", the aqueous emulsion according
to the invention intends to exclude partially hydrolysed polyvinyl acetates (PV A),
conventionally used at the present time for certain aqueous emulsions (based on
25 peroxydicarbonates, peroxyesters and/or diacyl peroxide), and cellulose derivatives of
the nonionic surfactant that may be used to satisfy the criteria of the invention since the
Applicant has shown that, for these surfactants, used alone, the emulsions do not satisfy
the essential criterion of industrial storage, in other words the emulsion containing such
components undergoes phase separation within an interval of less than two months. On
30 the other hand, their use as additive for the emulsion is not excluded from the limits of
- 7 -
this invention, especially for adjusting the viscosity of the emulsion and in particular
when it is desired to make it less fluid.
The term partially hydrolysed "polyvinyl acetates" means any derivative or
component comprising at least one polyvinyl acetate function or being included in the
5 family of polyvinyl acetates, and having a degree of hydrolysis of greater than or equal
to 10 mol% and a viscosity at 20-23°C, as conventionally measured by a person skilled
in the art (i.e. as a 4% aqueous solution in water or in a Brookfield RVT 3/20
viscometer), of greater than or equal to 1 mPas. These partially hydrolysed polyvinyl
acetates may be chosen from block or random copolymers.
l 0 The term "cellulose derivatives" means components derived from cellulose
known to those skilled in the art. Thus, cellulose derivatives are classified as a function
of the type of chemical treatment as cellulose acetate, the main families of cellulose
derivatives being cellulose ethers and ~ellulose esters.
As examples of such cellulose derivatives, mention will be made of
15 methylcellulose (MC), hydroxyethylcellulose (HEC), carboxymethylcellulose (CMC)
and methyl hydroxypropylcellulose (MHPC).
According to a particularlarly advantageous aspect, the aqueous emulsion
according to the invention has an SADT (self-accelerating decomposition temperature)
20 of greater than or equal to 50°C, preferably greater than or equal to 60°C.
It has been shown that the overall HLB (hydrophilic-lipophilic balance) of the
emulsifier must be between 5 and 14, preferentially between 7 and 12 and even more
preferentially between 9 and 10.
It will be noted that the antifreeze will be used when the aqueuous emulsion is
25 intended to be stored in the cold, conventionally in an environment in which the
temperatures are below 0°C. The antifreeze then conventionally serves to prevent the
formation of ice.
It is important to note that, from an industrial viewpoint, there is very great
30 advantage in developing an emulsion of dialkyl peroxides that is stable for at least two
months during storage at room temperature. The term "stability of the emulsion" means
1-
- 8 -
herein the presence of a single phase of milky appearance without the presence of a pure
organic phase (degree of purity of greater than 60%), which would destroy the
advantage of the emulsion especially with regard to its safety on storage.
5 Other characteristics and features of the primary mixture of the invention are
presented below:
-preferably, the emulsifier consists of at least one sorbitan ester;
- advantageously, the emulsifier consists of a mixture of at least two sorbitan
esters, preferably with an ethoxylated sorbitan ester;
l 0 - according to a possibility offered by the invention, the emulsifier consists of an
ethoxylated plant oil, preferably a castor oil comprising from 1 0 to 20 mol of ethylene
oxide, or a mixture of such an ethoxylated oil with a sorbitan ester, which itself is
optionally ethoxylated;
- the dialkyl peroxide represents more than 40% by weight of the emulsion,
15 preferably between 55% and 65% by weight of said emulsion;
20
25
30
-advantageously, the emulsifier represents between 1% and 3% by weight of the
emulsion;
- preferably, the dialkyl peroxide consists of 2,5-dimethyl-2,5-di(tertbutylperoxy)
hexane ;
- in the case where the emulsifier consists of at least one sorbitan ester, said
sorbitan ester consists of a monolaurate, monooleate or trioleate, monosteareate or
tristearate of sorbitan and the ethoxylated structures thereof;
- also in this last case, the ethoxylated sorbitan ester has a degree of ethoxylation
of less than or equal to 20 mol of ethylene oxide.
The invention also relates to a process for preparing the aqueous emulsion
according to any one of the preceding claims, characterized in that it comprises the steps
of:
-dispersing and homogenizing the emulsifier in water, and then
- adding the dialkyl peroxide to the aqueous emulsion, and then
- emulsifying the mixture thus made during an emulsification step at a
temperature below 30°C, preferentially at a temperature of between l8°C and 25°C.
5
- 9 -
The term "emulsified" means stirring or m1xmg, preferably using a stirrer
rotating at at least 2000 rpm (revolutions per minute) or even more than 5000 rpm, the
reaction medium or the medium into which the various components forming the
emulsion according to the invention are introduced.
The invention also relates to a use ofthe aqueous emulsion as mentioned above,
for:
- the crosslinking of elastomers, or
- the polymerization of ethylene derivatives or acrylic monomer derivatives
l 0 alone or with other monomers.
15
20
25
Specifically, it is not .excluded to use the dialkyl peroxide as described in the
present invention in applications for the polymerization of ethylene derivatives or
acrylic monomer derivatives alone or with other monomers, when the presence of water
does not prohibit polymerization.
The description that follows IS given solely for non-limiting illustrative
purposes.
Detailed description of the invention
As regards the dialkyl peroxide, it is in the following conventional crude forms:
R-0-0-R or R-0-0-R-R'-0-0-R'
Thus, the branches R orR' may consist of aliphatic components (as is the case in
the examples presented below), but also optionally of branches bearing aromatic or
cyclic functions.
As examples of components belonging to the family of dialkyl peroxides,
mention may be made especially of 2,5-dimethyl-·2,5-di(tertbutylperoxy)-
3-hexyne (Luperox® 130), di-tert-butyl peroxide (Luperox® DI), di-tertamyl
peroxide (Luperox(ll) DTA), tert-butyl cumyl peroxide (Luperox® 801 ), di(tertbutylperoxy
isopropyl)benzene (Luperox@ F and Luperox® 802), 2,5-dimethyl5
10
- 10-
2,5-di(tert-butylperoxy)hexane (Luperox® 101), dicumyl peroxide (Luperox® DCP),
3,6,9-triethyl-3,6,9-trimethyl-] ,4,7-triperoxonane (Trigonox® 301) and 3,3,5,7,7-
pentamethyl-1 ,2,4-trioxepane (Trigonox® 311 ). A mixture of these peroxides obviously
also forms part of the invention.
Hereinbelow, the examples of preparation of an aqueous emulsion in accordance
with the invention all comprise 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, but it is
clearly understood that other peroxides of the dialkyl peroxide family have been tested
and show substantially similar results to those presented here with this peroxide.
As regards the emulsifier, it consists of a polyethoxylated nomomc agent.
Partially hydrolysed PV As and cellulose derivatives cannot be used alone in the context
of this invention (as emulsifier), but their use as additives may optionally be envisaged.
Hereinbelow,. the invention is presented with mainly at least one sorbitan ester,
and also a composition with castor oil, but it is clearly understood that other
15 polyethoxylated nonionic emulsifiers have been tested and show identical or
substantially similar characteristics and properties to those presented herein.
It should moreover be noted that, in the examples of compositions according to
the invention, two nonionic emulsifiers are present, but the Applicant has discovered
that the objectives of the invention - namely, in particular, preparing an emulsion of
20 dialkyl peroxide that is stable over time at room temperature - are achieved, or virtually
achieved, when a single nonionic surfactant (excluding PYA or cellulose derivative) is
used in the emulsion.
It has been found by the Applicant that examples of surfactants satisfying the
criteria of the invention are chosen from ethoxylated alkylphenols, ethoxylated fatty
25 alcohols, ethoxylated carboxylic acid esters, ethoxylated amides, ethoxylated fatty
amines, copolymers bearing ethoxyl propoxyl blocks, ethoxylated (hydrogenated or
non-hydrogenated) plant or animal oils, sorbitan esters and/or ethoxylated sorbitan
esters, and ethoxylated glycerol esters.
30 The present invention has the additional advantage of affording the intended
application the same level of perfonnance as the dialkyl peroxide used in pure form.
- 11 -
As regards the antifreeze, optionally present in the emulsion, examples that may
be mentioned include monoalcohols, diols and triols, such as methanol, ethanol,
ethylene glycol, isopropanol, n-propanol, 1,2-propanediol, 1,3, propanediol, glycerol,
5 !-butanol, 2-butanol, 1,3-butanediol and 1,4-butancdiol and mixtures thereof, these
mixtures comprising at least two of the antifreezes listed previously, conventionally one
of light alcohol type and the other of heavy alcohol type, advantageously a mixture of
methanol and 1 ,2-propanediol.
10 The emulsion according to the invention may also compnse one or more
functional additives intended to afford particular properties/characteristics to the
polymer to which the peroxide is added.
Thus, as regards the additive, it may be chosen from antioxidants;. UV -protecting
agents; processing agents, whose function is to improve the final appearance during its
15 use, such as fatty amides, stearic acid and salts thereof, ethylene bis-stearamide or
fluorinated polymers; antifogging agents; antiblocking agents such as silica or talc;
fillers such as calcium carbonate and nanofillers, for instance clays; coupling agents
such as silanes; crosslinking agents such as peroxides; antistatic agents; nucleating
agents; pigments; colourants; plasticizers; fluidizers and flame-retardant additives such
20 as aluminium hydroxide or magnesium hydroxide.
The liquid aqueous emulsion of organic peroxide of the present invention may
optionally also contain additives including pH modifiers such as phosphate and citrate
buffers, chelating agents, biocides, for example fungicides, antiozonizers, antioxidants,
anti degrading agents, swelling agents and mould-release agents.
25 The aqueous emulsion according to the invention may also comprise viscosity
modifiers, such as PYAs (partially hydrolysed polyvinyl acetate) or cellulose
derivatives.
Finally, the liquid aqueous emulsion of organic peroxide of the present invention
may also contain additives usually used for stabilizing the organic peroxide or for
30 delaying its decomposition, such as phlegmatizers (isododecane, mineral oil, etc.) or
hydroperoxides.
These additives may be added in the amounts usually used and known to those
skilled in the art. These additives are generally used in contents of between 10 ppm and
5
10
- 12 -
10 000 ppm by weight relative to the weight of the final polymer. The plasticizers,
fluidizers and flame-retardant additives may reach amounts much higher than 10 000
ppm.
The object of the invention is not to specifically define the use of the emulsion,
except for the uses specifically mentioned which are those more particularly targeted in
the context of the present invention.
Example of preparation of an emulsion according to the invention :
The preparation example presented below is in accordance with that which made
it possible to prepare the, test emulsions, but it is quite clear- that a person. skilled in the
art manages to prepare the desired formulations by modifying the amounts given below.
The aqueous phase containing the emulsifier (also referred to as "surfactant") or
15 the mixture of emulsifiers and water is stirred at between 500 and 1 000 rpm
(revolutions per minute) and maintained at 20-22°C (Celsius). The dialkyl peroxide is
added gradually to the reactor containing this water/surfactant mixture. Stirring is
maintained for three minutes at 2000 rpm. The assembly is then stirred vigorously using
an "Ultra Turrax type S-25N 1 8G" dispersion machine for two minutes at 9500 rpm
20 (revolutions per minute), and then stirred using a paddle at 1000 rpm for one minute.
25
Each emulsion is prepared on 200 grams in total. The emulsion is stored in a
closed polyethylene flask.
Starting materials used :
The dialkyl peroxide consists of Luperox® 101 from the company ARKEMA,
which is 95% pure and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.
The water used is conventionally distilled laboratory water.
The surfactants (emulsifiers) used will be specified in each example.
~~~~~~~--------~----~--------- -
- 13 -
Tests performed :
The droplet size ( d50) is determined via conventional means, which are well
known to those skilled in the art, using the light scattering technique. The term d50
corresponds to the mean diameter such that 50% of the volume of the droplets of
5 organic peroxide in the aqueous emulsion has a diameter less than dso. The
measurements are taken using a Malvern Master Sizer 2000® machine at room
temperature. The droplet size d50 is given with an accuracy of ± 0.5 IJ.m (micrometre).
The flow time measurements are taken using consistometric cups according to
standard DIN 53211 (viscosity cup diameter : 4 mm), which are well known to those
1 0 skilled in the art. The measurement is taken on 100 grams of emulsion after
conditioning at + 5°C. The flow time measurements are expressed in seconds and the
accuracy is ± I 0 % of the indicated value. A value of less than 50 seconds reflects a
fluid emulsion.
As regards the measurement of the phase separation (presence oft wo phases) or
15 otherwise, the dialkyl peroxide emulsions are stored at a controlled temperature of 20 ±
2°C. The visual phase separation mentioned in the examples is observed when an
organic phase 0.2mm thick is visible to the eye or when it is possible to observe a large
drop of liquid at the bottom of the flask (reflecting non-unifom1ity and instability of the
organic peroxide emulsion) or alternatively when two separate phases appear by phase
20 separation. The emulsions are observed every day for the first week after preparation,
and then every week for the first month after preparation, and then once a fortnight.
Results of the tests on the samples :
Table 1 below presents the test results for emulsions not in accordance with the
25 definition of the invention.
All these emulsions compnse Luperox ® 101 (2,5-dimethyl-2,5-di(tertbutylperoxy)
hexane which represents 60% by weight of the emulsion, i.e. a molar
concentration ofLuperox® 101 at about 63% for all these compositions.
Each of these compositions is defined more precisely below:
30 - Composition lA : 1.2% by weight of polyvinyl acetate partially hydrolysed to
71-73%, Alcotex® 72.5 from Synthomer; HLB (hydrophilic-lipophilic balance) =11.5
- Composition lB : 2% by weight of polyvinyl acetate partially hydrolysed to
88%, Alcotex® 8804 from Synthomer ; HLB = 1 5.8
- 14-
- Composition lC : 2% by weight of polyvinyl acetate partially hydrolysed to
54-57%, Alcotex® 552P from Synthomer; HLB = 7.8
-Composition lD: 1.2% by weight of carboxymethylcellulose, Blanose 7M1C
from Ashland Aqualon ;
5 - Composition lE : 1.2% by weight of polyvinyl acetate partially hydrolysed to
10
71-73%, Alcotex® 72.5 and 1% by weight of sodium lauryl sulfate (SLS, Aldrich)
- Composition IF : 1.2% of sodium dodecylbenzene sulfate (Aldrich)
Table 1
lA JB lC lD lE lF
dso (~m) 14 8.5 19.6 Emulsion not 3.8 17
Storage time 2 days ,3 days 3 days homogeneous 1 day 1 day
at which at t=O
phase
separation is
observed
It will thus be noted in particular that the emulsifiers tested here and cited in
US 4440885 and WO 01/32613 do not make it possible to obtain an emulsion that is
stable during the storage time.
Table lB below presents test results for organic peroxide emulsions prepared
15 and stored at room temperature comprising surfactants typically used in the context of
polar organic peroxides (those used in WO 2011/015567) for which the preparation and
storage temperature of the emulsion is negative.
All these emulsions comprise Luperox® 101 (2,5-dimethyl-2,5-di(tertbutylperoxyhexane)
which represents 60% by weight of the emulsion, i.e. a molar
20 concentration of Luperox® 1 0 1 at about 63% for all these compositions.
Each ofthese compositions is more precisely defined below:
- Composition J BA: 0.8% by weight of polyvinyl acetate partially hydrolysed to
71-73%, Alcotex® 72.5 from the company Synthomer and 0.8% by weight ofBrij® L23
from Aldrich (lauryl alcohol ethoxylated with 23 EO, HLB = 16.9)
'. ·.·
- 15 -
-Composition lBB: 1.2% by weight of polyvinyl acetate partially hydrolysed to
71-73%, Alcotex® 72.5 from the company Synthomer and 0.4% by weight ofBrij® L23
from Aldrich (lauryl alcohol ethoxylated with 23 EO, HLB = 16.9)
- Composition lBC: 0.8% by weight of polyvinyl acetate partially hydrolysed to
5 71-73%, Alcotex® 72.5 from the company Synthomcr and 0.8% by weight of Brij®
S1 00 from Aldrich (stearyl alcohol ethoxylated with 100 EO, HLB = 18)
10
- Composition lBD: 1.2% by weight of polyvinyl acetate partially hydrolysed to
71 -73%, Alcotex® 72.5 from the company Synthomer and 0.4% by weight of Brij®
SlOO from Aldrich (stearyl alcohol ethoxylated with 100 EO, HLB = 18)
Table JB
lBA lBB lBC lBD
d50 (J.lm) 9.7 8.1 13.9 11.5
Storage time in which phase 3 days 3 days 3 days 7 days
separation is observed
It will be noted that the emulsifiers tested (PYA+ ethoxylated fatty alcohol) here
and included in the composition of the emulsion of example 1 of patent WO
201 11015567 do not make it possible to obtain a dialkyl peroxide emulsion whose
15 stability exceeds one week.
Table 2 below presents the test results for emulsions in accordance with the
definition of the invention.
All these emulsions compnse Luperox® 101 (2,5-dimethyl-2,5-di(tert-
20 butylperoxy)hexane which represents 60% by weight of the emulsion, i.e. a molar
concentration of Luperox® 101 at about 63% for all these compositions, except for
composition 2G which contains 70% by weight ofLuperox® 101.
Each of these compositions is defined more precisely below:
- Composition 2A: 0.8% by weight of sorbitan trioleate containing 20 mol of
25 ethylene oxide (Tween 85, HLB= 10.5) and 0.8% by weight of sorbitan monooleate
(Span 80, HLB = 4.3); overall HLB = 7.4
- Composition 2B: 0.8% by weight of sorbitan monooleate containing 20 mol of
ethylene oxide (Tween 80, HLB = 1 5) and 0.8% by weight of sorbitan monooleate
(Span 80, HLB = 4.3); overall HLB = 9.65
:· . ;, . - ·
- 16-
- Composition 2C : 0.2% by weight of sorbitan monolaurate containing 20 mol
of ethylene oxide (Tween 20, HLB = 16.7) and 1.4% by weight of sorbitan monolaurate
(Span 20, HLB = 8.6) ; overall HLB = 9.6
- Composition 2D : 1.4% by weight of sorbitan trioleate containing 20 mol of
5 ethylene oxide (Tween 85, HLB = 1 0.5) and 0.2% by weight of sorbitan monolaurate
(Span 80, HLB = 4.3); overall HLB = 9.7
10
- Composition 2E : 0.9% by weight of sorbitan trioleate 'containing 20 mol of
ethylene oxide (Tween 85, HLB = 10.5) and 0.7% of sorbitan monolaurate (Span 20,
HLB = 8.6) ; overall HLB = 9.7
- Composition 2F : 1.2% by weight of ethoxylated castor oil containing 20 mol
of ethylene oxide (Surfaline® R20, HLB = 9.5) and 1% by weight of ethoxylatcd castor
oil containing 12 mol of ethylene oxide (Decohfix® C070, HLB = 8.2);
:-Composition 2G :. emlllsion containing 70%.by_weight of Luperox~ 101 and
0.8% by weight of sorbitan monooleate containing 20 mol of ethylene oxide (Tween 80,
15 HLB = 15) and 0.8% by weight of sorbitan monooleate (Span 80, HLB = 4.3) ; overall
HLB = 9.65
20
Table 2
2A 2B 2C 2D 2E 2F 2G
Flow time (s) 17 17 15 17 14 19 24
dso ().lm) at t = 0 12.0 10.4 9.1 9.8 10.0 10.0 10.2

CLAIMS
1. Aqueous emulsion of dialkyl peroxide consisting of:
- at least one dialkyl peroxide in liquid form at room temperature, representing
5 between 10% and 75% by weight of the emulsion,
- at least one emulsifier representing from 0.01 % to 10% by weight of the
emulsion,
- optionally, at least one antifreeze,
- optionally at least one functional additive,
10 - water, the amount of which is determined so as to form the rest of said
emulsion (100%),
characterized in that the emulsifier is a polyethoxylated nonionic surfactant.
2. Emulsion according to Claim 1, characterized m that the emulsifier
15 consists of at least one sorbitan ester.
20
25
30
3. Emulsion according to Claim 2, characterized in that the emulsifier
consists of a mixture of at least two sorbitan esters, preferably with an ethoxylated
sorbitan ester.
4. Emulsion according to any one of Claims 1 to 3, characterized in that the
emulsifier consists of an ethoxylated plant oil, preferably a castor oil comprising from
10 to 20 mol of ethylene oxide, or a mixture of such an ethoxylated oil with a sorbitan
ester, whjch is itself optionally ethoxylated.
5. Emulsion according to any one of the preceding claims, characterized in
that the dialkyl peroxide represents more than 40% by weight of the emulsion,
preferably between 55% and 65% by weight of said emulsion.
6. Emulsion according to any one of the preceding claims, characterized in
that the emulsifier represents between 1% and 3% by weight of the emulsion.
- 19 -
7. Emulsion according to any one of the preceding claims, characterized in
that the dialkyl peroxide consists of 2,5-dimethyl-2,5-di(tert-bntylperoxy)hexane.
8. Emnlsion according to either of Claims 2 and 3, characterized in that the
5 abovementioned sorbitan ester consists of a monolaurate, monooleate or trioleate,
monostearate or tristearate of sorbitan, and the ethoxylated structures thereof
9. Emulsion according to any one of Claims 2, 3 or 7, characterized in that
10 the ethoxylated sorbitan ester has a degree of ethoxylation of less than or equal to 20
mol of ethylene oxide.
15
20
10. Process for preparing the aqueous emulsion according to any one of the
preceding claims, characterized in that it comprises the steps of:
dispersing and homogenizing the emulsifier in water, and then
adding the dialkyl peroxide to the aqueous emulsion, and then
emulsifying the mixture thus made during an emulsification step at a
temperature below 30°C, preferentially at a temperature of between \8°C and 25°C.
11. Use of the aqueous emulsion according to any one of Claims l to 9, for:
the crosslinking of elastomers, or
the polymerization of ethylene derivatives or acrylic monomer
derivatives alone or with other monomers.