USE OF METHYL MERCAPTO-ESTERS AS CHAIN TRANSFER AGENTS
[0001] The subject of the invention is mercapto-methyl esters of carboxylic
acids, and the process for preparing same. The invention also relates to the use
of said mercapto-ester derivatives as a chain transfer agent in free-radical
emulsion (co)polymerization reactions, and to the free-radical emulsion
(co)polymerization processes using said mercapto-methyl esters of carboxylic
10 acids as chain transfer agents.
[0002] The intrinsic characteristics of polymers, such as the average size of the
chains and their distributions have strong influences on the macroscopic
properties of the resulting materials. Indeed, the properties of a polymer, in
particular in solution or in the molten state, such as the viscosity, are greatly
15 dependent on its molar mass and on its polydispersity index. As a general rule,
the lower the molar mass of a polymer and the narrower its distribution, the
lower the viscosity of said polymer. A low viscosity is generally sought in
forming applications, for example by injection-molding or extrusion of polymer.
[0003] When in the form of an emulsion, latex and the like, for example in
20 coating and adhesive applications, polymers having a narrow molar mass
distribution are preferred. Such polymers with a narrow molar mass distribution
are generally prepared in the presence of a chain transfer agent (or more simply
"transfer agent", or else "CTA").
[0004] The use of a transfer agent makes it possible to obtain a more
25 homogeneous polymer particle size and also increased stability, in comparison
with a polymer prepared without transfer agent. This increased stability allows
better resistance during the various storage, pumping and transporting
operations, and also improved compatibility of polymer emulsions, during
formulation processes, with the constituents which are, for example, part of the
30 composition of paint.
[0005] Molecules of mercaptan type have been widely used for many decades
in the polymer industry as chain transfer agents in free-radical polymerization.
The use of a transfer agent of mercaptan type in free-radical polymerization
makes it possible to reduce the average size of the polymer chains, and also, in
!
WO 2014/125223 - 2 - PCT/FR2014/050296
certain cases, to reduce their polydispersity index. These transfer agents can be
used in bulk polymerizations, in homogeneous or dispersed solvent-based
media.
[0006] However, mercaptans, which are sulfur-containing molecules, can have
5 the disadvantage of being odorous and, in certain cases, toxic. The handling
and use thereof are thus made difficult, requiring specific measures for
protection of the personnel and equipment using these sulfur-containing
compounds, not to mention the always increasing numerous legislation and
regulations which prohibit the use of molecules that are toxic and harmful to
10 humans and to the environment.
[0007] Many molecules comprising a mercaptan group have been widely
described in the literature. For example, patent US 2 281 613 discloses the use
of isohexylmercaptan, of octadecylmercaptan and of dodecylmercaptan as
transfer agents in the emulsion (co)polymerization of 1,3-butadiene and of
15 1,3-butadiene derivatives.
[0008] Document US 2 497 107 discloses the use of mercapto-ethyl esters of
carboxylic acid in the emulsion copoiymerization of isoprene or of butadiene in
the presence of a-methylstyrene, of styrene and of acrylonitrile.
[0009] Patent US 4 593 081 discloses the use of alkyl 3-mercaptopropionates
20 in the emulsion copoiymerization of acrylic monomers.
[0010] However, these known chain transfer agents all have one or more
drawbacks, such as toxicity, noxiousness, unpleasant odor, lack of
effectiveness, in terms of polymerization quality and yield, to mention only the
main ones.
25 [0011] There therefore remains a need for chain transfer agents which do not
have the drawbacks described above.
[0012] Surprisingly, the inventors have discovered, after various experiments
and manipulations, that mercapto-methyl esters of certain specific carboxylic
acids, used as chain transfer agents in free-radical emulsion polymerization
30 processes, make it possible to prepare polymers and copolymers with improved
properties, in particular with a lower molar mass and a narrower distribution
than the polymers obtained with the mercapto-ethyl esters of homologous
carboxylic acids.
WO 2014/125223 - 3 - PCT/FR2014/050296
[0013] Another advantage associated with the use of the mercapto-methyl
esters of carboxyiic acids according to the present invention lies in the fact that
these mercapto-esters can be obtained from renewable raw materials and in
particular from raw materials of vegetable origin.
5 [0014] In addition, these mercapto-esters, which will be defined later, also
have the advantage of not being odorous, or being weakly odorous, and do not
require particular precautions during uses thereof.
[0015] According to a first aspect, the present invention thus relates to the use,
as a chain transfer agent in a free-radical emulsion polymerization process of at
10 least one mercapto-methyl ester of a carboxyiic acid, represented by formula (1)
below:
RN R2 9
HSr ^ T O (1)
in which:
- Ri and R2, which may be identical or different, are chosen, independently of
15 one another, from a hydrogen atom and a linear, branched or cyclic, saturated
or unsaturated hydrocarbon-based radical comprising from 1 to 20 carbon
atoms, and optionally substituted with one or more radicals chosen from
carboxy, alkylcarbonyl and alkoxycarbonyl (where alkyl and alkoxy comprise
from 1 to 10 carbon atoms); and
20 -A represents a linear, branched or cyclic, saturated or unsaturated,
hydrocarbon-based divalent chain comprising from 2 to 30 carbon atoms, limits
included, optionally interrupted with one or more heteroatoms chosen from
oxygen, sulfur and nitrogen.
[0016] According to a first embodiment of the invention, the compounds of
25 formula (1) for which Ri and R2 are identical and each represent a hydrogen
atom (primary mercaptans) are preferred.
[0017] According to another embodiment, the use according to the invention
uses at least one compound of formula (1) in which Ri represents a hydrogen
atom and R2 represents a linear, branched or cyclic, saturated or unsaturated
30 hydrocarbon-based radical comprising from 1 to 20 carbon atoms, and
optionally substituted as defined previously (secondary mercaptans).
WO 2014/125223 - 4 - PCT/FR2014/050296
[0018] According to yet another embodiment, in the compound of formula (1),
Ri and R2, which may be identical or different, each represent a linear,
branched or cyclic, saturated or unsaturated hydrocarbon-based radical,
comprising from 1 to 20 carbon atoms, and optionally substituted as defined
5 previously (tertiary mercaptans).
[0019] In the context of the present invention, preference is given to the
mercapto-methyl esters of carboxylic acids comprising a primary mercaptan
chain, and then those comprising a secondary mercaptan chain and, finally,
those comprising a tertiary mercaptan chain.
10 [0020] In the case of the compounds of formula (1) comprising a secondary or
tertiary mercaptan chain, preference is given to those for which the
hydrocarbon-based radicals (forming R2 or Ri and R2 respectively) are
hydrocarbon-based radicals comprising from 1 to 20 carbon atoms, preferably
from 1 to 10 carbon atoms, and more preferably from 1 to 6 carbon atoms. The
15 hydrocarbon-based radicals are chosen from radicals which are linear,
branched or cyclic, preferably linear, and saturated or unsaturated, preferably
saturated.
[0021] Among the preferred substituents of these hydrocarbon-based radicals,
mention may be made of substituents of alkoxycarbonyl type, where alkoxy
20 comprises from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms, and
more preferably from 1 to 4 carbon atoms, and for example alkoxy represents
methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl or t-butyl. The compounds of
formula (1) for which at least one of the radicals Ri or R2 is substituted with a
methoxycarbonyl group are particularly preferred.
25 [0022] According to another preferred embodiment, the divalent chain A
comprises from 3 to 30 carbon atoms, more preferably from 4 to 30 carbon
atoms, and more particularly from 5 to 30 carbon atoms, limits included. The
divalent chain A of the compounds of formula (1) may be saturated or totally or
partially unsaturated, linear, branched or cyclic, and interrupted with one or
30 more heteroatoms chosen from O, S and N, or even be interrupted with one or
more cycles or heterocycles, themselves saturated or totally or partially
unsaturated. The divalent chains A which do not comprise heteroatoms, i.e. the
divalent chains A which are hydrocarbon-based divalent radicals, optionally
WO 2014/125223 - 5 - PCT/FR2014/050296
comprising one or more unsaturations in the form of double and/or triple
bond(s), are preferred.
[0023] Nonlimiting examples of divalent chain A which may be mentioned
include -(CH2)n- chains, or -(CH2)ni-C=C-(CH2)n2- chains, where n represents
5 an integer between 2 and 30 carbon atoms, preferably between 3 and 30
carbon atoms, more preferably between 4 and 30 carbon atoms, and typically
between 5 and 30 carbon atoms, limits included, and ni + n2 is equal to n-2.
[0024] Among the compounds of formula (1), those in which Ri and R2 are
identical or different and each represent a hydrogen atom or a hydrocarbon-
10 based group and A is as defined previously, are preferred.
[0025] According to one particularly preferred embodiment, the compounds of
formula (1) are those for which A represents a linear hydrocarbon-based
divalent radical comprising from 3 to 18 carbon atoms, more preferably from 4
to 18 carbon atoms, and more preferentially from 6 to 18 carbon atoms, limits
15 included. Particularly preferred representatives are thus methyl
mercaptoundecanoate, methyl mercaptodecanoate and dimethyl
9-mercaptooctadecyl-1,18-dioate, preferably methyl mercaptoundecanoate and
methyl mercaptodecanoate, and more preferably methyl mercaptodecanoate.
[0026] The compounds of formula (1) described above can easily be prepared
20 from the corresponding unsaturated precursor methyl ester which is used in a
sulfhydration reaction according to techniques known to those skilled in the art.
The term "sulfhydration reaction" is intended to mean the Markovnikov reaction
of free-radical addition of H-S-H to a C=C double bond, according to the
following scheme:
[0027] The term "unsaturated precursor methy! ester" is intended to mean a
methyl ester comprising at least one double bond capable of being sulfhydrated
in one or two steps according to a conventional free-radical addition reaction via
the action of hydrogen sulfide (as described, for example, in FR 2 424 907) or of
30 a precursor of hydrogen sulfide, for example thioacetic acid (as described, for
example, in US 4 701 492), a tertiary mercaptan, for example tedWO
2014/125223 - 6 - PCT/FR2014/050296
butylmercaptan (as described, for example, in FR 2 603 889), or via a catalytic
addition of hydrogen sulfide (as described, for example in US 4 102 931).
[0028] Thus, the sulfhydration agent used for the sulfhydration of the
unsaturated methyl ester to give a compound of formula (1) may be of any type
5 known to those skilled in the art and, for example, chosen from hydrogen
sulfide, thioacetic acid (TAA), and other compounds known to those skilled in
the art and normally used in organicrcompound sulfhydration reactions.
[0029] This sulfhydration reaction is advantageously carried out in the
presence of homogeneous or heterogeneous acid catalyst and/or under
10 ultraviolet (UV) light irradiation (either by direct photolysis at wavelengths of
between 180 nm and 300 nm, or in the presence of photoinitiators). According
to one preferred embodiment, the sulfhydration reaction is carried out without
catalyst, and under UV irradiation.
[0030] This sulfhydration reaction can be carried out in the presence or in the
15 absence of solvent, preferably in the presence of one or more solvents which
can be advantageously chosen for their transparency to UV light according to
the wavelength used and the ease with which they are separated from the
reaction medium. Such solvents can, for example, be chosen from light alkanes
(1 to 6 carbon atoms), ethylene glycol ethers, aromatic hydrocarbons, aliphatic
20 hydrocarbons, and the like, and also mixtures of two or more of them in any
proportions.
[0031] As a variant, the sulfhydration reaction can be carried out in the
presence of one or more, preferably one, compound(s) capable of forming free
radicals. Such compounds are known to those skilled in the art and can be
25 chosen, for example, from peroxides, and by way of nonlimiting indication, from
hydrogen peroxide, sodium peroxide or potassium peroxide, te/f-alkyl (for
example terf-butyl) hydroperoxides, terf-alkyl peroxides, terf-alkyl peresters,
cumene hydroperoxide, azobisisobutyronitrile, and the like, and mixtures of two
or more of them in any proportions.
30 [0032] When the sulfhydration reaction described above is carried out via the
action of thioacetic acid in the presence of a free-radical initiator and/or by
irradiation with UV light, as described previously, this reaction is followed by a
methanolysis reaction in acid medium, making it possible to free the desired
WO 2014/125223 - 7 - PCT/FR2014/050296
mercaptan of formula (1). This methanolysis reaction is well known and can be
carried out according to any conventional techniques.
[0033] At the end of the sulfhydration step, the mercapto-esters can be
obtained in the form of mixtures of isomers (primary, secondary and/or tertiary
5 mercaptans) which can be subsequently separated and optionally purified
according to conventional separation and/or purification techniques, for example
by distillation, under atmospheric pressure or under reduced pressure
depending on the nature of the mercaptan of interest to be recovered.
[0034] The precursor methyl esters comprising at least one double bond
10 capable of being sulfhydrated using a sulfhydration reagent are known and
commercially available or else can be prepared according to any methods and
procedures known to those skilled in the art and available in the patent
literature, the scientific literature or Chemical Abstracts or else on the Internet.
[0035] According to one embodiment, the precursor methyl esters comprising
15 at least one double bond capable of being sulfhydrated can be obtained by
transesterification of glycerides (mono-, di- or triglycerides, preferably
triglycerides) with methanol, according to conventional methods known to those
skilled in the art and, for example, according to the process described in
EP-B-0 658 183. The unsaturated glycerides which can be used originate
20 essentially from animal or vegetable, preferably vegetable, oils or fats, among
which mention may be made, by way of nonlimiting indication, of soybean oil,
sunflower oil, linseed oil, rapeseed oil, castor oil, palm oil, palm kernel oil,
coconut oil, jatropha oil, cottonseed oil, peanut oil, olive oil, Vernonia oil,
Cuphea oil, Hevea oil, Honesty oil, safflower oil, camelina oil, Calophyllum
25 inophyllum oil, Pongamia pinnata oil, beef tallow, cooking oil or fat, but can also
be hydraulic or lubricating oils.
[0036] According to another embodiment, the precursor methyl esters of the
compounds of formula (1) can also be obtained by cross-metathesis from other
methyl esters, or even from glycerides (the latter will subsequently be subjected
30 to a transesterification step with methanol), for instance those defined
previously. The metathesis reactions are well known to those skilled in the art
and most commonly call for an intermolecular reaction between two compounds
each bearing at least one double bond, as described, for example, in
international application WO 2009/047444.
WO 2014/125223 - 8 - PCT/FR2014/050296
[0037] In particular, the compounds of formula (1) in which R1t or Ri and R2l
represent(s) a hydrocarbon-based radical substituted with an alkoxycarbonyl
radical (di- and triesters, respectively) can advantageously be obtained by
metathesis from unsaturated monoesters, according to metathesis techniques
5 known to those skilled in the art. Examples of unsaturated methyl esters which
can be used in a metathesis reaction in order to produce di- and triesters
include methyl oleate, methyl palmitoleate and methyl arachidonate, alone or as
mixtures of two or more of them in any proportions. According to this
embodiment, dimethyl 9-octadecene-1,18-dioate can, for example, be readily
10 obtained by metathesis of methyl oleate and/or of methyl palmitoleate.
[0038] The sources of methyl esters of formula (1) are thus very numerous and
varied, and examples, given by way of nonfimiting indication, of methyl esters
bearing an unsaturation capable of being sulfhydrated include, in an indicative
and nonfimiting manner, methyl hexenoates, methyl decenoates, methyl
15 undecenoates, methyl dodecenoates, methyl oleate, methyl linoleate, methyl
myristoleate, methyl palmitoleate, methyl linoleate, methyl linolenate, methyl
arachidonate, methyl ricinoleate and dimethyl 9-octadecene-1,18-dioate, and
also mixtures of two or more of them in any proportions.
[0039] Preferably, the unsaturated methyl esters are chosen from methyl
20 decenoates and methyl undecenoates, more preferably from methyl decen-9-
oate and methyl undecen-10-oate.
[0040] As a variant, the precursor methyl esters of the compounds of formula
(1) can also be obtained from the corresponding acids, which are subjected to
an esterification reaction with methanol according to conventional esterification
25 techniques well known to those skilled in the art.
[0041] Examples, given by way of nonlimiting indication, of methyl ester
precursor acids include, in a nonlimiting manner, hexenoic acids, decenoic
acids, undecenoic acids, dodecenoic acids, oleic acid, iinoleic acid, myristic
acid, palmitic acid, iinoleic acid, linolenic acid, arachidonic acid, ricinoleic acid,
30 diacids and triacids which can be obtained by cross-metathesis according to
conventional methods of synthesis by metathesis, as indicated above, and for
example 9-octadecene-1,18-dioic acid. Preferably, said acids are chosen from
decenoic acids and undecenoic acids and mixtures of two or more of them in
^
WO 20T4/125223 - 9 - PCT/FR2014/050296
any proportions, more preferably from decen-9-oic acid and undecen-10-oic
acid.
[0042] Among the compounds of formula (1), preference is given to those for
which Ri represents a linear, branched or cyclic, saturated or unsaturated
5 hydrocarbon-based radical comprising from 1 to 20 carbon atoms, substituted
with one or more alkoxycarbonyl radicals, where alkoxy comprises from 1 to
10 carbon atoms, and R2 represents hydrogen, on the one hand, and Ri and
R2, which may be identical or different, each represent a linear, branched or
cyclic, saturated or unsaturated hydrocarbon-based radical comprising from 1 to
10 20 carbon atoms, substituted with one or more aikoxycarbonyl radicals, where
alkoxy comprises from 1 to 10 carbon atoms.
[0043] Thus and according to another aspect, the present invention relates to
the compounds of formula (1') below:
15 in which:
- R't represents a linear, branched or cyclic, saturated or unsaturated
hydrocarbon-based radical comprising from 1 to 20 carbon atoms, substituted
with one or more alkoxycarbonyl radicals, where alkoxy comprises from 1 to 10
carbon atoms;
20 - R'2 is chosen from a hydrogen atom and a linear, branched or cyclic, saturated
or unsaturated hydrocarbon-based radical comprising from 1 to 20 carbon
atoms, substituted with one or more alkoxycarbonyl radicals, where alkoxy
comprises from 1 to 10 carbon atoms; and
-A represents a linear, branched or cyclic, saturated or unsaturated,
25 hydrocarbon-based divalent chain comprising from 2 to 30 carbon atoms, limits
included, optionally interrupted with one or more heteroatoms chosen from
oxygen, sulfur and nitrogen.
, [0044] The compounds of formula (1') form a subset of the compounds of
formula (1), all of the compounds of formula (11) being included in general
30 formula (1). The compounds of formula (1') for which R'i represents a linear,
branched or cyclic, saturated or unsaturated hydrocarbon-based radical
comprising from 1 to 20 carbon atoms, substituted with a methoxycarbonyl
WO 2014/125223 - 10 - PCT/FR2014/050296
radical, R'2 represents a hydrogen atom, and A is as defined previously, are
preferred.
[0045] An example of an unsaturated mercapto diester of formula (1') is
represented by dimethyl 9-mercaptooctadecyl-1,18-dioate.
5 [0046] According to the present invention, the mercapto-esters of formula (1)
have entirely advantageous applications in the field of polymer synthesis as
chain transfer agents.
[0047] Thus, the invention also relates to an emulsion (co)polymerization
process comprising the formation of an emulsion in water of at least one
10 monomer with at least one mercapto-ester of formula (1) as chain transfer
agent.
[0048] More specifically, the invention relates to an emulsion
(co)polymerization process, comprising at least the following steps:
a) forming an emulsion, in an aqueous medium, of at least one monomer
15 containing vinyl unsaturation,
b) adding to said emulsion at least one chain transfer agent of formula (1)
as defined previously,
c) carrying out the (co)polymerization reaction, optionally in the presence of
a (co)polymerization initiator,
20 d) optionally purifying and recovering the desired (co)polymer.
[0049] In the (co)polymerization process according to the invention, the
amount of chain transfer agent(s) of formula (1) is generally between 0.01% and
5% by weight, preferably between 0.03% and 3% by weight, relative to the total
weight of the emulsion.
25 [0050] As regards the amount of monomer(s), it is most commonly between
10% and 60% by weight, preferably between 20% and 50% by weight, relative
to the total weight of the emulsion.
[0051] The monomers which can be used in the (co)polymerization process
according to the invention are the monomers commonly and normally used in
30 free-radical emulsion polymerization reaction, and advantageously the
monomers referred to as containing vinyl unsaturation(s), and more particularly
vinyl monomers, conjugated diene monomers, acrylic monomers, methacrylic
monomers, and mixtures of two or more of them in any proportions, to mention
only the most common of them.
WO 2014/125223 - 11 - PCT/FR2014/050296
[0052] In one embodiment of the process according to the invention,
nonlimiting examples of monomers comprise acrylic acid, alkyl acrylates,
methacryiic acid, alkyl methacrylates, conjugated dienes, styrene and styrene
derivatives, acrylamide, acryionitrile, and also mixtures of two or more of them
5 in any proportions.
[0053] According to one preferred embodiment, the monomers are chosen
from:
• acrylic acid,
• methyl acrylate, ethyl acrylate, n-propyi acrylate, /so-propyl acrylate,
10 n-b'utyl acrylate, /so-butyl acrylate, terf-butyl acrylate, n-pentyl acrylate,
neo-pentyl acrylate, /so-amyl acrylate, n-hexyl acrylate, /so-hexyl acrylate,
cyclohexyl acrylate, /so-octyl acrylate, 2-ethyihexyl acrylate, decyl acrylate,
/so-decy! acrylate, lauryl acrylate, stearyl acrylate and /so-bornyl acrylate,
and mixtures thereof,
15 • methacryiic acid,
• methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, /so-propyl
methacrylate, n-butyl methacrylate, /so-butyl methacrylate, ferf-butyl
methacrylate, n-pentyl methacrylate, neo-pentyl methacrylate, /so-amyl
methacrylate, n-hexyl methacrylate, /so-hexyl methacrylate, cyclohexyl
20 methacrylate, /so-octyl methacrylate, 2-ethylhexyl methacrylate, decyl
methacrylate, /so-decyl methacrylate, lauryl methacrylate, stearyl
methacrylate, hydroxyethyl methacrylate, hydroxypropy! methacrylate,
acetoxyethyl methacrylate, acetoxypropyl methacrylate, tertbutylaminoethyl
methacrylate, 2-(3-oxazolidinyl)ethyl methacrylate,
25 /so-bornyl methacrylate, and the like, and mixtures thereof,
• acryionitrile, methacrylonitrile, acrylamide and methacrylamide, and
mixtures thereof,
• allylacetoacetates, ethylene, propylene, styrene and substituted styrenes,
butadiene, vinyl acetate, vinyl versatate, vinyl butyrates and other vinyl
30 esters, halogenated vinyl monomers, such as vinyl chloride, vinylidene
chloride, and the like, and mixtures thereof.
[0054] The monomeric compounds listed above can of course be used alone
or as mixtures, for example as mixtures of two or more of them in any
WO 2014/125223 - 12 - PCT/FR2014/050296
proportions. When two or more monomers are used in the process of the
present invention, this results in a copolymer; when a single monomer is used in
the process of the present invention, this results in a homopolymer. The
copolymers and homopolymers are grouped together under the generic term
5 (co)polymers in the description of the present invention.
[0055] The copolymers can be obtained in the form of random, block or
alternating copolymers, depending on the operating conditions of the
copolymerization process, which conditions are well known to those skilled in
the art.
10 [0056] The (co)poiymerization reaction medium can also comprise at least one
surfactant and/or at least one polymerization initiator and/or at least one chainterminating
agent.
[0057] In one embodiment of the present invention, the surfactant(s) used can
be chosen from anionic surfactant(s) and/or non-ionic surfactant(s), such as
15 alkyl, aryl or alkylaryl sulfates, sulfonates or phosphates of alkali metals or the
corresponding ammonium salts. Surfactants such as alkylsulfonic acids,
sulfosuccinate salts, fatty acid salts, ethoxylated alcohols, amphiphilic
copolymers, and also mixtures of two or more of them, can also be used.
[0058] In general, the amount of surfactant(s) depends on the concentration of
20 monomer(s) in the emulsion, and on the nature of the monomer(s), and most
commonly is between 0.05% and 10% by weight, relative to the total weight of
the emulsion.
[0059] The emulsion (co)polymerization of monomers according to the
invention can be initiated by free-radical initiators of any type, generally of
25 oxidizing type, known to those skilled in the art, such as, in a nonlimiting
manner, hydrogen peroxide, sodium peroxide, potassium peroxide, te/Y-butyl
hydroperoxide and feAf-alkyi hydroperoxides in general, fe/f-alkyl peroxides, tertalky!
peresters, cumene hydroperoxide, ammonium or alkali metal persulfates,
alkali metal perborates (for example sodium perborate), perphosphoric acid and
30 associated salts thereof, potassium permanganate, ammonium or alkali metal
salts of peroxydisulfuric acids, and also mixtures of two or more of them.
[0060] For initiation of the reaction by oxidation-reduction, at least one
oxidizing agent chosen from those listed above can be used in combination with
a reducing agent such as ascorbic acid, /so-ascorbic acid, sodium formaldehyde
WO 2014/125223 - 13 - PCT7FR2014/050296
sulfoxylate, sodium sulfite, sodium bisulfite, sodium thiosulfate, sodium
hydrosulfite, sodium sulfide, sodium hydrosulfide or dithiosulfate,
formamidinesuifonic acid, hydroxymethanesulfonic acid, sodium 2-hydroxy-2-
sulfinatoacetate, acetone bisulfite, ethanolamine, glycoiic acid, lactic acid,
5 glyceric acid, malic acid and tartaric acid, and also mixtures of two or more of
them.
[0061] The oxidation-reduction reactions can themselves be catalyzed by
metal salts such as iron, copper, manganese, silver, platinum, vanadium, nickel,
chromium, palladium or cobalt salts. These catalysts can be added in contents
10 of between 0.01 ppm and 25 ppm by weight, relative to the total weight of the
emulsion.
[0062] The amount of (co)polymerization initiator(s) is generally between
0.001% and 1% by weight, relative to the total weight of the emulsion.
[0063] The emulsifying phase is generally water or a water/organic solvent(s)
15 mixture, the quantity of which is that which is sufficient (qs) to reach 100% by
weight, relative to the total weight of the emulsion.
[0064] In one embodiment of the process, the emulsion of monomer(s)
comprises between 0.1% and 1% by weight of at least one compound of
formula (1), between 20% and 60% by weight of at least one monomer
20 containing vinyl unsaturation(s) defined previously, between 0.1% and 5% by
weight of at least one surfactant, between 0.005% and 1% by weight of at least
one polymerization initiator, and water in sufficient quantity to reach 100% by
weight, relative to the total weight of the emulsion.
[0065] According to one embodiment of the process of the invention, the
25 compound of formula (1) can be added continuously or batchwise, either at the
beginning of the reaction, or several times during the process, or else
continuously throughout the process or throughout a part of the process.
[0066] The inventors have discovered, surprisingly, that the free-radical
(co)polymerization reaction is controlled all the better, in terms of molar mass
30 and polydispersity, when it is carried out in the presence of at least one transfer
agent of formula (1), i.e. of at least one mercapto-methyl ester, where the
mercaptan function is tertiary, secondary or primary, preferably secondary or
primary, more preferably primary.
WO 2014/125223 - 14 - PCT/FR2014/OS0296
[0067] The emulsion according to the invention can be prepared according to
the usual techniques well known to those skilled in the art in the field of
monomer emulsions. The emulsion process according to the invention can be
carried out either batchwise or continuously, and either with a single addition of
5 monomer(s) at the beginning of the reaction, or with one or more continuous or
batchwise addition(s) of monomer(s) over time, according to the techniques
commonly used in the emulsion field.
[0068] Likewise, the polymerization initiator(s) can be added all at once at the
beginning of the process, several times during the process, or else continuously
10 throughout the process.
[0069] The free-radical (co)polymerization reaction initiation phase can be
carried out thermally, photochemically, electrochemically or by oxidationreduction
reaction, or else by any method known to those skilled in the art
specializing in this type of reaction.
15 [0070] The reaction for thermally initiating the polymerization is preferentially
carried out at a temperature of between 50°C and 100°C.
[0071] The (co)polymerization reaction according to the present invention can
itself be carried out at any temperature and any pressure that those skilled in
the art will be able to adjust according to the nature and the
20 amount/concentration of the monomers present in the emulsion.
Advantageously, the (co)polymerization process of the invention is carried out
at atmospheric pressure at a temperature of between 0°C and 100°C,
preferably between 10°C and 90°C.
25 [0072] The following nonlimiting examples make it possible to illustrate the
invention and understand it more clearly.
Example 1: Preparation of methyl 10-mercaptodecanoate
30 [0073] 9-Decenoic acid (100 g; 0.588 mol) is added to 237 g (300 ml;
7.406 mol) of methanol and the mixture is brought to reflux, with stirring in the
presence of 10 g of wet Amberlyst® 15 cation exchange resin. The assembly
uses continuous drying of the methanol by passing over a Soxhlet apparatus
loaded with molecular sieve (30 g). After 24 hours at reflux and elimination of
WO 2014/125223 - 15 - PCT/FR2014/050296
the solvent under vacuum, the degree of conversion of the acid to ester is close
to 99%.
[0074] The resulting methyl 9-decenoate (156 g) is placed in a photochemical
reactor comprising a reaction loop, with 100 g of pentane and 60 molar
5 equivalents of liquefied hydrogen sulfide (1806 g condensed at 20°C under a
pressure of 17.5 bar).
[0075] The mixture is recirculated (60 l/h) in the reaction loop within which it is
subjected to UV radiation (wavelength: 254 nm, power: 12 watts) for 3 hours at
a temperature of 38°C and a pressure of 23 bar.
10 [0076] The excess hydrogen sulfide is then flushed to a thermal oxidizer by
decompression of the medium, and then by stripping with nitrogen. The mixture
is then distilled in order to eliminate the solvent and the sulfides formed
(T: 130°C, pressure: 5 mbar).
[0077] The resulting mercaptan has a purity greater than 98.5% (measured by
15 chromatography). The amount of primary mercaptan obtained is 97.7%, and the
amount of secondary mercaptan obtained is 2.3%, these percentages being
percentages by weight relative to the total weight of mercaptans obtained.
Example 2: Preparation of methyl 11-mercaptoundecanoate
20
[0078] Methyl 11-mercaptoundecanoate is prepared according to a procedure
similar to that described in Example 1 above, using methyl 10-undecenoate.
Examples 3 to 8: Emulsion polymerization
25
[0079] 40 g of butyl acrylate (Aldrich), 40 g of methyl methacrylate (Arkema),
0.04 g of potassium persulfate (Aldrich), 2.4 g of Dowfax2A1 surfactant (Dow),
0.04 g of sodium hydrogen carbonate (buffer, Aldrich), 332 g of demineralized
water and 0.4 g of chain transfer agent according to the present invention are
30 added to a refrigerated jacketed reactor equipped with a stirrer motor and a
reflux condenser.
[0080] The monomer emulsion is heated at a temperature of between 70°C
and 75°C for 5 hours.
3
WO 2014/125223 - 16 - PCT/FR2014/050296
[0081] The polymerization reaction is stopped when the solids content reaches
20% by weight. The solids content is measured by means of a Mettler
thermobalance at a temperature of 105°C.
[0082] The analysis of the polymers by size exclusion chromatography is
5 carried out in tetrahydrofuran (THF) at 40°C at 0.3 g/l with a flow rate of
1 ml/min, on a set of MIXED A gel permeation columns (Plgel) (30 cm) with a
refractometric detector. The columns are calibrated with a poly(methyl
methacrylate) standard.
[0083] This analysis by size exclusion chromatography makes it possible to
10 determine the weight-average molecular weight (Mw) and also the numberaverage
molecular weight (Mn). The poiydispersity index is obtained by
calculating the Mw/Mn ratio. The results are given in the following Table 1:
15
[0084] Examples 3 to 8 above are examples of preparation of butyl
acrylate/methyl methacrylate copolymer with identical operating conditions,
except for the transfer agents used.
[0085] The copolymerizations of Examples 3 and 4 are carried out with the
20 chain transfer agents according to the invention. In Examples 5 and 6
(comparative), the chain transfer agents are linear-chain and branched-chain
mercaptans, respectively, and are available from Arkema. In Example 7
(comparative), the chain transfer agent was prepared according to a procedure
similar to that used to prepare the chain transfer agents according to the
25 invention from 10-decenoic acid subjected to an esterification reaction with
ethanol. Finally, in Example 8 (comparative), the transfer agent used is a
mercapto-acid available from Aldrich.
17- PCT/FR2014/050296
[0086] The results in Table 1 above show that the chain transfer agents
according to the present invention are particularly suitable for emulsion
preparation of (co)polymers. Indeed, the (co)polymers obtained not only have
sizes (Mw) which are entirely in accordance with those of the copolymers
5 obtained with chain transfer agents conventionally used in the prior art, or even
smaller sizes, but also and especially have polydispersity indices which are very
low and significantly lower than those obtained with the chain transfer agents of
mercapto-ethyl ester type, which are nevertheless structurally close.
[0087] The use of chain transfer agents according to the invention thus makes
10 it possible to prepare (co)polymers of which the properties in terms of molecular
weight and of polydispersity are entirely unexpected from the viewpoint of the
prior art. This makes it possible to envisage the use of these (co)polymers in
specific applications requiring polymers with a low polydispersity index, for
example in the fields of paints and coatings in general, adhesives, coating of
15 paper, lubrication additives, and the like.

CLAIMS
5 1. Use, as a chain transfer agent in a free-radical emulsion polymerization
process, of at least one mercapto-methyl ester of a carboxylic acid, of formula
(1):
in which:
10 - R-i and R2, which may be identical or different, are chosen, independently of
one another, from a hydrogen atom and a linear, branched or cyclic, saturated
or unsaturated hydrocarbon-based radical comprising from 1 to 20 carbon
atoms, and optionally substituted with one or more radicals chosen from
carboxy, alkylcarbonyl and alkoxycarbonyl (where alkyl and aikoxy comprise
15 from 1 to 10 carbon atoms); and
- A represents a linear, branched or cyclic, saturated or unsaturated,
hydrocarbon-based divalent chain comprising from 2 to 30 carbon atoms, limits
included, optionally interrupted with one or more heteroatoms chosen from
oxygen, sulfur and nitrogen.
20
2. Use of a compound according to Claim 1, in which R-i and R2 each
represent a hydrogen atom.
3. Use of a compound according to Claim 1 or Claim 2, in which A is a
25 -(CH2)n- chain, or a -(CH2)ni-C=C-(CH2)n2- chain, where n represents an integer
between 2 and 30 carbon atoms, preferably between 3 and 30 carbon atoms,
more preferably between 4 and 30 carbon atoms, and typically between 5 and
30 carbon atoms, limits included, and ni + n2 is equal to n-2.
30 4. Use according to any one of the preceding claims, in which the
compound of formula (1) is methyl mercaptoundecanoate or methyl
mercaptodecanoate, preferably methyl mercaptodecanoate.
WO 2014/125223 - 19 - PCT/FR2014/050296
5. Compound of formula (1'):
in which:
5 - R'i represents a linear, branched or cyclic, saturated or unsaturated
hydrocarbon-based radical comprising from 1 to 20 carbon atoms, substituted
with one or more alkoxycarbonyl radicals, where alkoxy comprises from 1 to 10
carbon atoms;
- R'2 is chosen from a hydrogen atom and a linear, branched or cyclic, saturated
10 or unsaturated hydrocarbon-based radical comprising from 1 to 20 carbon
atoms, substituted with one or more alkoxycarbonyl radicals, where alkoxy
comprises from 1 to 10 carbon atoms; and
- A represents a linear, branched or cyclic, saturated or unsaturated,
hydrocarbon-based divalent chain comprising from 2 to 30 carbon atoms, limits
15 included, optionally interrupted with one or more heteroatoms chosen from
oxygen, sulfur and nitrogen.
6. Compound according to Claim 5, in which R'i represents a linear,
branched or cyclic, saturated or unsaturated hydrocarbon-based radical
20 comprising from 1 to 20 carbon atoms, substituted with a methoxycarbonyl
radical, R'2 represents a hydrogen atom, and A is as defined in Claim 5.
7. Compound according to Claim 5 or Claim 6, which is dimethyl
9-mercaptooctadecyl-1,18-dioate.
25
8. Emulsion (co)polymerization process comprising at least the following
steps:
a) forming an emulsion, in an aqueous medium, of at least one monomer
containing vinyl unsaturation,
30 b) adding to said emulsion at least one chain transfer agent of formula (1)
according to any one of Claims 5 to 7,
WO 2014/125223 - 20 - PCT/FR2014/050296
c) carrying out the (co)poiymerization reaction, optionally in the presence of
a (co)polymerization initiator,
d) optionally purifying and recovering the desired (co)polymer.
5 9, Process according to Claim 8, In which the amount of chain transfer
agent(s) of formula (1) is between 0.01% and 5% by weight, preferably between
0.03% and 3% by weight, relative to the total weight of the emulsion.
10. Process according to Claim 8 or Claim 9, in which the monomers
10 containing vinyl unsaturation are vinyl monomers, conjugated diene monomers,
acrylic monomers, methacrylic monomers, and mixtures of two or more of them
in any proportions.
11. Process according to any one of Claims 8 to 10, in which the reaction
15 medium also comprises at least one surfactant and/or at least one
polymerization initiator and/or at least one chain-terminating agent.