PROCESS FOR PREPARING HALOGENATED POLYMERS
5 [OOUI] The invention relates to a polymerization process, in particular a process for
aqueous suspension or emulsion polymerization, in order to produce halogenated
polymers, in particular halogenated vinyl polymers, such as polyvinyl chloride (PVC) and
PVC copolymers, for example, produced with improved colours, in particular with a high
white index, said process using combinations of shortstoppers such as N-substituted
l o hydroxylamines, for example.
[0002] In the manufacture of such halogenated vinyl polymers, in particular polyvinyl
chloride, it is commercially important to obtain the best yield and the best quality at the
lowest cost. The cost and the performance of both polymerization initiators and
shortstoppers can be significant factors in controlling the yield and quality of the product
rs obtained.
[0003] Ideally, halogenated vinyl polymers and copolymers, in particular PVC, should be
produced with shortstoppers and efficient polymerization initiators, which are cheap and
non-toxic. Currently, a number of shortstoppers exist which can be used in such
polymerization reactions, including those with a hydroxylamine structure. They have been
20 shown to perform well in stopping the radical polymerization of monomers, but there is still
room for improvement as regards obtaining an even whiter resin colour that is less thermally
degraded during the transformation process, in particular for polymerizations using energetic
radicals.
[0004] Occasionally, yellowing of the polymers has been observed, in particular after
2s they have been shaped or transformed by extrusion, injection, moulding or calendering,
and other heat treatments. This is particularly true in the case in which certain
polymerization initiators are used, in particular initiators employing peroxide radicals.
[0005] As an example, di(2-ethylhexyl) peroxydicarbonate and di(sec-butyl)
peroxydicarbonate, sold by Arkema with trade names tuperoxa 225 and iuperoxB 223,
30 are two initiators which are well known to the skilled person, which are cheap and which
have high eficiency, but in some cases produce PVC with undesirable colourations (after
shaping or transformation), in particular when they are used with commercial shortstoppers
which are known and in routine use.
[0006] Examples of shortstoppers which are in routine use for the aqueous suspension
35 polymerization of vinyl chloride are ATSC (acetone-thiosemicarbazone), bisphenol A (4,4'-
isopropylidene-diphenol), sodium nitrite, a-methylstyrene, butylhydroxyanisole,
butylhydroxytoluene, lrganox5 245 (2,4-dimethyl-6-sec-hexadecylphenol), by itself or as a
mixture with lrganox@1076 ~octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].
lrganoxB 1141 (hereinafter IGX 1141) is a commercial mixture of 80 parts by weight of
s lrganox@2 45 and 20 parts by weight of lrganox@1 076.
I00071 Compounds with a hydroxylamine structure are also known in the industry as
shortstoppers for the synthesis of PVC, however most tests have indicated that N,Ndiethylhydroxylamine
(DEHA) by itself, even when used in high concentrations, can
neither improve whitening of the resin nor improve the thermal stability after transforming
ro said resin and thus does not always produce a satisfactory white index.
[0008] Patent US 3 222 334 already discloses that N,N-dialkylhydroxylamines could be
used to stop the emulsion polymerization of vinyl chloride. However, none of the
examples can be used to indicate any particular advantage in using these N,Ndialkylhydroxylamines.
That document suggests that N,N-dialkylhydroxylamines have a
1s non-toxic and non-decolourizing nature, but only with reference to use in various rubbers,
and no distinction can be established between non-discolouration and stabilization of the
colour.
[0009] International application WO 199811 51 71 4 describes the use of ethyl
hydroxylamine as a shortstopper, also having a "surprising non-volatility" as well as low
20 corrosivity and good solubility in water.
[OOIO] However, although it claims the use of such shortstoppers for all radical
polymerizations, that international application only discusses the emulsion polymerization
of rubbers, and all of the examples illustrate the polymerization of such polymers.
[0011] Patent US 4 749 757 describes the use of DEHA (and other polymerization
2s inhibitors) in association with a suspension agent, polyvinyl alcohol (PVA), to
simultaneously increase the density and porosity of the PVC, by keeping a low
concentration (5 ppm to 10 ppm) in the reactor. However, DEHA is not presented as
being a shortstopper for PVC.
[0012] In document JP 02235912, Kanolo et a1 describe a "product of reaction between
30 DEHA, cyctopentadiene and pyrogalloln which, when applied to the walls of the reactor,
prevents the formation of scale. That document concerns a known application which
exploits the properties of hydroxylamines in coatings in order to provide the walls of the
polymerization reactors for the manufacture of PVC with anti-scaling properties.
[0013] Patent US 6 340 729 describes the use of DEHA with certain initiators of the
3s organic peroxide type to improve the colour and thermal stability of PVC. That patent
compares the use of DEHA with other shortstoppers in routine use and discusses the use of
an excess of shortstopper, resulting in yellowing of the polymer,
[0014] The use of DEHA as an agent that can "kill" the polymerization initiator in order to
stop runaway of the vinyl chloride polymerization reaction is also known in the art. Because
5 of its excellent and rapid solubility in water, DEHA is effective in stopping the polymerization
of vinyl chloride when, for example, an unexpected power cut occurs or mechanical
problems arise which cause a breakdown in the agitation system.
[0015] International application W02010/084130 describes systems associating a
hydroxylamine derivative with low concentrations of wholly or partially sterically hindered
10 antioxidant phenolic compounds in order to obtain low colour polyvinyl chloride. However,
such a system has been tested in order to obtain resins with a very high degree of
whiteness using standardized tests which are considered to be stringent; there is still room
for improvement.
[0016] One object of the present invention concerns the preparation of halogenated
is polymers and copolymers; in particular PVC, which have good whiteness properties and an
absence of colouration, or at least a very weak colouration, and which have only a little or no
yellowing after shaping or transformation of said polymers.
[0017] in fact, under certain conditions, in particular for transformation or shaping,
halogenated polymers and copolymers, in particular PVC, prepared using known prior art
20 processes may have colouration, usually yellowing, which may mean that the quality is not
sufficient for the envisaged uses.
[0018] The inventors have now discovered, surprisingly, that it is possibfe to prepare
halogenated vinyl polymers, in particular PVC, with very good whiteness properties, in
particular stability of the white index.
25 [0019] In the present invention, it has been discovered that the use, during the
preparation of halogenated polymers and copolymers, in particular PVC, of an association
of at least one shortstopper with at least one perhalogenate, for example a metal, an alkali
metal or an alkaline-earth metal perhalogenate, means that halogenated polymers and
copolymers, in particular PVC, can be obtained with good whiteness and white index
30 stability properties.
[0020] Thus, in a first aspect, the present invention concerns the use of an association
of at least one shortstopper with at least one perhalogenate, for example a metal, alkali
metal or alkaline-earth metal perhalogenate, in the process for the preparation of
halogenated polymers and copolymers, in particular PVC. This use means that
halogenated polymers and copolymers, in particular PVC, can be obtained with good
whiteness and with stable white index properties.
[0021] In a further aspect, the invention concerns a process for the aqueous
suspension, micro-suspension, emulsion or micro-emulsion polymerization of at least one
halogenated monomer, in particular chlorinated, for example vinyl chloride, by itself or with
one or more other vinyl monomers, preferably less than 50% by weight of one or more other
vinyl monomers, in which at least one shortstopper and at least one perhalogenate, acting as
a whitening agent, are added.
[0022] More precisely, the present invention concerns the process for the preparation of
a halogenated polymer or copolymer, comprising at least the following steps:
a- preparing an aqueous suspension, micro-suspension, emulsion or micro-emulsion of at
least one halogenated monomer, by itself or with one or more other vinyl monomers,
preferably less than 50% by weight of one or more other vinyl monomers;
b- carrying out the polymerization reaction;
c- stopping polymerizatiori by adding at least one shortstopper to the polymerization
medium;
d- adding at least one perhalogenate as a whitening agent before, during or after step c for
stopping polymerization; and
e- draining and drying the polymer or copolymer obtained.
[0023] In the above polymerization or copolymerization process, the polymerization step
is advantageously carried out in the presence of at least one polymerization initiator, said
polymerization reaction preferably being carried out at a temperature above ambient
temperature and below 100°C, preferably at a temperature in the range 45°C to 80°C,
more preferably in the range 50°C to 70°C.
[0024] The polymerization or copolymerization reaction is advantageously carried out
until the degree of conversion of the starting monomer or monomers is in the range 60%
to 90% by weight, preferably in the range 65% to 80%, after which at least one
shortstopper is added.
[0025] The shortstopper which may be used in the process in accordance with the
present invention may be of any type known to the skilled person; in particular, the
shortstopper is advantageously selected from phenolic derivatives such as
butylhydroxyanisole (BHA), butylhydroxytoluene (BHT), 2,4-dimethyl-6-sechexadecylphenol,
octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, by itself or as
a mixture, and mono-alkyl-N- or dialkyl-N,N-substituted hydroxylamines, each alkyl radical
containing 1 to 4 carbon atoms, for example di-ethylhydroxylamine, 4OH-Tempo
(1,4-dihydroxy-2,2,6,6-tetramethylpiperidin) as well as mixtures of two or more thereof in
any proportions, for example mixtures of 2,4-dimethyl-6-sec-hexadecylphenol and
octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.
[0026] Particularly preferably, mono-alkyl-N- or di-alkyl-N,N-substituted hydroxylamines
s are used, each alkyl radical containing 4 to 4 carbon atoms, for example diethylhydroxylamine
(DEHA), 4-OH Tempo (1,4-dihydroxy-2,2,6,6-tetramethylpiperidine),
as well as mixtures of two or more thereof in any proportions, for example mixtures of 2,4-
dimethyl-6-sec-hexadecylphenol, and octadecyl-3-(3,5-di-tert-butyl-4-
hydroxyphenyi)propionate. DEHA is more particularly preferred as a shortstopper in the
lo context of the present invention.
[0027] The perhalogenate csed in the process of the present invention in association with
at least one shortstopper can be used to obtain polymers endowed with a high white index.
The perhalogenates which may be used may be of any type, in particular organic or mineral
perhalogenates, preferably selected from metallic perhalogenates and alkali metal or
is alkaline-earth metal perhalogenates, highly preferably alkali metal or alkaline-earth metal
perchlorates, and highly advantageously sodium perchlorate.
[0028] The process of the present invention may also advantageously comprise a step
for introducing at least one polymerization initiator. These polymerization initiator(s) is(are)
well known to the skilled person and is(are) preferably selected from dialkyl
20 peroxydicarbonates, peroxy-tert-alkanoates, diacyl peroxides and alkyl hydroperoxides,
inter aiia.
[0029] It has also been discovered that using at least one perhalogenate with at least one
shortstopper with a hydroxylamine structure during the synthesis of halogenated polymers or
copolymers offers an action which is rapid and effective in stopping polymerization, resulting
25 in high yields of high quality polymers and copolymers at low cost and with a good white
index, minimal colouration, or even an absence of colouration.
[0030] Hence, the overall cost of PVC production may be substantially reduced by using
at least one association in accordance with the present invention, i.e. at least one
shortstopper and at least one perhalogenate.
30 [0031] In a preferred embodiment, the present invention concerns the process for
synthesizing halogenated vinyl polymers and copolymers using an association of at least
one shortstopper with at least one perhalogenate and using at least one peroxide type
initiator selected, for example, from dialkyl peroxydicarbonates, peroxy-tert-alkanoates,
diacyl peroxides and alkyl hydroperoxides, by themselves or as a mixture of two or more
35 thereof in any proportions.
[0032] In another aspect, the invention concerns improving the colour of extruded
halogenated vinyl polymers and copolymers which have been shaped, transformed or
extruded, for example by injection, moulding, calendering, and others, in particular extruded
PVC, using an association of at least one shortstopper with at least one perhalogenate
during the synthesis of said polymers or copolymers. -
[0033] In yet another aspect, the invention concerns the aqueous suspension, aqueous
micro-suspension or aqueous emulsion polymerization of vinyl chloride, by itself or as a
mixture with one or more other vinyl monomer(s), the polymerization initiator comprising at
least one organic peroxide, preferably selected from dialkyl peroxydicarbonates, peroxytert-
alkanoates, diacyl peroxides and alkyl hydroperoxides and by using, as a
shortstopper, at least one mono- or di-aikyihydroxylamine and at least one perhalogenate.
The polymers or copolymers obtained thereby have excellent whiteness.
[0034] In yet another implementation, the present invention concerns the combination of
an initiator system comprising at least one compound selected from dialkyl
peroxydicarbonates, peroxy-tert-alkanoates, diacyl peroxides and alkyl hydroperoxides
and at least one shortstopper, for example comprising at least one N-monoalkylhydroxylamine
or N,N-dialkylhydroxylamine, and at least one perhalogenate,
preferably at least one perchlorate, said combination not only being used to stop
polymerization in an effective manner, but also to obtain, at the same time, a halogenated
vinyl polymer or copolymer, for example PVC, with good whiteness properties, in particular
good stability of the white index.
[0035] Thus, the invention provides a process for the aqueous suspension, microsuspension,
emulsion or micro-emulsion polymerization of vinyl chloride, by itself or as a
mixture with at least 50% by weight of another vinyl monomer, in the presence of a
polymerization initiator comprising at least one compound selected from dialkyl
peroxydicarbonates, peroxy-tert-alkanoates, diacyl peroxides and alkyl hydroperoxides, in
which process the polymerization formulation contains at least one shortstopper and at
least one perhalogenate.
[0036] In another aspect, the invention also concerns an agent for regulating
polymerization, comprising the combination described above of at least one shortstopper,
for example an N-monosubstituted or N,N-disubstituted hydroxylamine, with at least one
perhalogenate.
100371 The initiator system used in the suspension or micro-suspension process is
advantageously soluble in the monomer or monomers to be polymerized and is generally
composed of one or more compounds which are capable of generating free radicals which
trigger the reaction for the polymerization of said monomer or monomers. The initiator
system used in the emulsion (or micro-emulsion) process is conventionally soluble in the
aqueous phase and triggers the reaction for the polymerization of said monomer or
monomers.
5 [0038] These free radicals generally result from the thermal decomposition of peroxy
compounds; examples of these which may be cited include diacyl peroxides, dialkyl
peroxydicarbonates, peroxy-tert-alkanoates and alkyl hydroperoxides.
[0039] In industrial practice, in order to express the quantity of initiator(s) introduced into
the reaction mixture, the total quantity of active oxygen that can be released by the initiator
ro system is expressed. The total quantity of active oxygen generally used is generally in the
range 0.0005 part by weight to 0.01 part by weight, preferably in the range 0.0015 part by
weight to 0.005 part by weight per 100 parts by weight of the monomer or monomers.
[0040] It is also possible to use a mixture of peroxy compounds, each of them having
different half-lives, at a given temperature, the proportion of one with respect to the other
1s possibly being from 1% to 99% by weight, preferably 10% to 90%. At identical
temperatures, the higher the concentration of initiator(s), the faster the polymerization
kinetics. Similarly, for a given polymerization time, the higher the reaction temperature, the
faster the polymerization kinetics.
[0041] Industrial processes for polymerizing routinely used halogenated vinyl monomers
20 are normally carried out in batch mode, and it is generally desirable to stop polymerization
after reaching a predetermined degree of conversion of said monomer or monomers, in
order to obtain a polymer with well-defined, unchanging characteristics. Typically, the
degree of conversion of the monomer or monomers is in the range from approximately
60% to approximately 90% by weight.
25 [0042] Preferred dialkyl peroxydicarbonates which may be used as polymerization
initiators are those in which each alkyl radical contains 1 to 16 carbon atoms, in a linear,
branched or cyclic chain. Non-limiting examples of such dialkyl peroxydicarbonates are
diethyl, di-isopropyl, di-n-propyl, dibutyl, di-see-butyl, dicetyl, dimyristyl, di-(4-tertbutylcyclohexyl)
and di-(2-ethylhexyl) peroxydicarbonates.
30 [0043] Preference is given to peroxydicarbonates in which each alkyl radical contains 6
to 16 carbon atoms; a more particularly preferred peroxydicarbonate is di-(2-ethylhexyl)
peroxydicarbonate. The dialkyl peroxydicarbonates used in the context of the present
invention are classified into the fast initiator family. They generally have a half-life of 1
hour at approximately 55°C to 70°C and may thus be used for vinyl chloride
35 polymerization temperatures in the range 45°C to 70°C.
[0044] Non-limiting examples of fast initiators which may also be used are peroxy-tertalkanoates,
1 ,I-dimethyl-3-hydroxybutyl peroxy-neodecanoate, cumyl peroxyneodecanoate,
1 ,I ,3,3-tetramethylbutyl peroxy-neodecanoate and I ,3-di-(2-
neodecanoylperoxyisopropyl)benzene, tert-butyl or tert-amyl peroxy-neodecanoate, tert-
5 butyl peroxy-neo-heptanoate, 1- (2-ethy1hexamylperoxy)-1'3-dimethylbutylp eroxypivalate,
1,1,3,3-tetramethylbutyl peroxypivalate, and tert-amyl (or tert-butyl) peroxypivalate.
Peroxy-tert-alkanoates are fast initiators which generally have a half-life of 1 hour at
approximate temperatures in the range 40°C to 75°C.
[0045] It is also possible to use di-iso-butyryl, di-(3,5,5-trimethylhexanoyl), dilauryl,
lo didecanoyl or dibenzyl peroxides as non-limiting examples of fast initiators from the diacyl
peroxide family; they have a half-life of 1 hour at temperatures in the range from
approximately 39°C to 92°C.
[0046] In an industrial aqueous suspension polymerization process carried out
batchwise, it is generally desirable to stop polymerization after obtaining a predetermined
is degree of conversion ' so that a polymer with well-characterized, unchanging
characteristics is obtained. It may also occasionally prove to be necessary to stop or at
least slow down the reaction in the final polymerization phase, i.e. when conversion has
reached values of more than 60% by weight, in order to avoid exothermic reactions at the
end of the reaction which are difficult to control; generally, a shortstopper is used in order
20 to stop the reaction.
[004fl Such shortstoppers are well known to the skilled person. The most frequently
used examples for the polymerization or copolymerization of vinyl chloride which may be
cited are ATSC (acetone-thiosemicarbazone), bisphenol A (4,4'-isopropylidenediphenol),
sodium nitrite, a-methylstyrene, butythydroxytoluene, butylhydroxyanisole, lrganoxa245
25 (2,4-dimethyi-6-sec-hexadecylphenol)b,y itself or as a mixture with irganox@1 076
[octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionatea]n d N,N-di-ethylhydroxylamine
and its derivatives.
[0048] The hydroxylamine derivatives which may be used as shortstoppers
advantageously have the formula HO-NR'R~, where R' and R' may be identical or
30 different and are selected from hydrogen, hydrocarbon chains which may be linear or
branched, saturated or unsaturated, containing 1 to 14 carbon atoms, each hydrocarbon
chain possibly being substituted with one or more functional groups selected from -OH, -
S03, benzyl, amino, mercapto, keto, carboxyl, or R' and R* may together form a cyclic
structure (as in piperidinyloxy compounds), provided that at least one of R' and R~ is other
35 thanH.
[0049] Mixtures of two or more of these shortstoppers may be used, including mixtures
comprising at least one shortstopper as defined hereinabove and one or more other
shortstoppers which are known to the skitled person. Examples which may be cited are
mixtures of N,N-diethylhydroxylamine and bisphenol A.
s [0050] The shortstopper, in particular substituted hydroxylamine, used in the process of
the present invention is introduced in its entirety, preferably so as to obtain between 60%
and 90% conversion of the monomer or monomers, preferably in the range 65% to 80%
from the moment when the pressure starts to drop in the polymerization reactor. Thus,
the quantity of shortstopper, in particular mono- or dialkylhydroxylamine, to be used may
ro vary from 0.0005 to 0.1 parts by weight, preferably in the range 0.001 to 0.05 parts by
weight per 100 parts by weight of the monomer or monomers to be polymerized.
[0051] The shortstopper which may be used in the context of the present invention is
preferably selected from dialkylhydroxylamines, the most particularly preferred
diafkylhydroxylamine being N,N-diethylhydroxylamine because of its solubility in water, the
15 high yield induced by it, and the fact that it is widely commercially available.
[0052] The polymers which may be manufactured by the process of this invention
include but are not limited to polyvinyl chloride. The invention may be applied in a similar
manner to any halogenated polymer or halogenated copolymer, non-limiting examples of
which that may be cited being polyvinylidene fluoride, polyvinyl fluoride, PTFE, and others.
zo [0053] In accordance with the present invention, at least one shortstopper is used in
association with at least one alkali or alkaline-earth metal perhalogenate, the term
"association" denoting a simultaneous, separated or sequenced introduction into the
polymerization reaction medium.
[0054] This "association" may also include any type of additive routinely used by the
2s skilled person, for example additives to improve the thermal stability of halogenated
polymers.
[0055] The perhalogenates which may be used in the context of the present invention
generally and usually have the formula M(X04),, in which X represents a halogen atom, M
represents the counter-ion of the perhalogenate anion and the index n represents the
30 valency of the counter-ion M; in general, n represents 1, 2 or 3.
[0056] The halogen atom X of the perhalogenate used in the present invention is
selected from the fluorine atom (case of perfluorates), the chlorine atom (case of
perchlorates), the bromine atom (case of perbromates) and the iodine atom (case of
periodates). Particularly preferred perhalogenates in the present invention are perchlorates
3s with the formula M(C104),.
[0057] The counter-ion M may be of any type known to the skilled person, for example
selected from metals, alkali metals, alkaline-earth metals, rare earths and others. More
specifically, the counter-ion M is selected from lithium (Li), sodium (Na), potassium (K),
magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), aluminium (Al),
s lanthanum (La) and cerium (Ce). Clearly, mixtures of two or more perhalogenates may be
used in the process of the present invention.
100581 The perhalogenates may be used in the form of solutions or in the form of
complexes with one or more alcohols (polyols, cyclodextrins), ether-alcohols or esteralcohols.
The ester-alcohols also include partial esters of polyols, examples of which that
10 may be cited being mono-ethers of glycerol and mono-thioethers of glycerol. Still others
are described in EP 0 394 547, EP 0 457 471 and WO 1994/24200.
[0059] The alcohols may also be polyhydric alcohols (or polyols), their dimers, trimers,
oligomers and polymers such as, for example di-, tri-, tetra- and poly-glycols, as well as di-
, tri- and tetra-pentaerythritols or vinyl alcohol polymers, irrespective of their degrees of
15 polymerization. Other ~ossibles olvents for the perhalogenates that can be used in the
process of the present invention are phosphates as well as cyclic and acyclic carbonates.
[0060] In this context, the perhalogenates, in particular perchlorates, may be used in a
variety of forms, for example as they are in the form of salts or solutions in water andlor in
one or more organic solvents, or indeed adsorbed onto a support material such as PVC,
20 calcium silicates, zeolites or hydrotalcites, or they may be bonded, after chemical reaction,
to at least one hydrotalcite, or to other compounds with a layered framework.
[0061] Particularly preferred perhalogenates are potassium, sodium and calcium
perchlorates, more particularly preferably sodium perchlorate and/or potassium perchlorate.
By way of example, in the context of the present invention it is possible to use sodium
2s perchlorate, sold by Arkema, in solution at approximately 70% by weight in water.
[0062] The additives which may be used to improve the thermal stability are well known
to the skilled person as thermal stabilizers or thermal co-stabilizers for halogenated
polymers and may be used in association with or independently of the
"shortstopper/perhalogenaten combination as described in the present invention. Such
30 stabilizers or co-stabilizers have been described, for example, in WO 20061058789.
100631 Examples of additives which may be used to improve thermal stability which may
be cited are mercaptocarboxylic acids, for example 2-ethylhexylmercapto-acetic acid and
thioglycolic acid, as well as their esters; alkali metal carbonates, for example sodium
carbonate; P-diketones; epoxidized vegetable oils, for example epoxidized soya oil,
35 epoxidized linseed oil; phosphites; P-ketonic esters; metal salts or soaps, in particular
stearates, for example calcium, barium andlor zinc stearate, adipates, for example
disodium adipate; amino-uracil derivatives andlor thio-uracil derivatives; hydrazides;
mineral compounds such as hydrotalcites or zeolites; alcohols and polyols, in particular
alcohols obtained from saccharides; glycidyl derivatives, a-phenylindole; compounds of
5 the dihydropyridine type such as those described in FR 2 429 806, EP 0 027 439 or
WO 20021092686, and specifically dihydropyridine and poly(dihydropyridine) derivatives,
more particularfy dihydro-I ,4-dimethyl-2,6-dicarbododecyloxy-3,5-pyridine
(stavinorB 0507, Arkema) or thiodi-ethanol-bis-(5-methoxy-carbonyl-2,6-dimethyl-l,4-
dihydropyridine-3-carboxylate (synesalBM, Lagor); enamines, for example those
10 described in patent DE 10 118179; alkanolamine type derivatives; and others, by
themselves or as mixtures of two or more thereof, in any proportions.
[0064] More particular polyol type thermal stabilizers and co-stabilizers which may be
cited are polyols and alcohols obtained from disaccharides selected from penta-erythritol,
dipenta-erythritol, tripenta-erythritol, trimethylolethane, trimethylolpropane, bisis
trimethylolethane, bis-triniethylolpropane, cyclitols (including inositol), polyvinyl alcohols,
hexitols (including sorbitof), maltitol, iso-maltitol, cellobiitol, lactitol, lycasin, mannitol,
lactose, leucrose, tris(hydroxy-ethyl)isocyanurate, tris(hydroxypropyl)isocyanurate,
palatinitol, tetramethylolcyclohexanol, tetramethylolcyclopentanol,
tetramethylolcyclopyranol, xylitol, pentitols (including arabinitol), tetritols, glycerol,
20 diglycerol, polyglycerol, thiodiglycerol and I-0-a-D-glycopyranosyl-D-mannitol dihydrate.
Of these, disaccharide alcohols are particularly preferred.
[0065] The hydrotalcites which may be used as co-stabilizers are well known to the
skilled person and are described, for example, in DE 384 35 81, EP 0 062 813 and
wo 1993/20135.
2s [0066] More specifically, the compounds belonging to the hydrotalcite family may be
represented by the following general formula:
G"I., G ~('0~H) n ( ~ n ~ ) d ~ . d ~ ~ 0
in which
G*' represents one or more metals selected from the group comprising Mg, Ca, Sr, Zn
30 and Sn;
G~' represents the aluminium atom (Al) or the boron atom (B);
An is an anion with valency n;
b is a number in the range 1 to 2, limits included;
0 < x C 0.5; and
35 d is a number in the range 0 to 300, limits included, preferably in the range 0.5 to 30, limits
included;
and preferably, An is selected from OH-. CIOi, HCOB, CH3COO', CsH&OO-, ~ 0 3 ' - ,
(CHOHCOO)?, (CH~COO)~C-H, 3CHOHCOO-,H PO; and HPO~~-.
[0067] Examples which are entirely appropriate to the present invention are
5 AI2O36Mg0 COz 12H20 (ill Mg4,5 A12 (OH)13C02 3.5H20 (ii),
4Mg0 A1203 C02 9H20 (iii), 4Mg0 AI2O3 C02 6H20, ZnO 3Mg0 AI2O3 C02 8-9H20 and
ZnO 3Mg0 C02 5-6H20; of these, the most particularly preferred hydrotalcites are
those with the above references i, ii and iii.
[0068] As indicated above, the anion of the hydrotalcites may be a perchlorate anion,
lo and in this case represents a preferred embodiment of the invention, When the
stabilization or co-stabilization additive is a hydrotalcite with a perhalogenate anion, in
particular a perchlorate anion (CIOi), it may advantageously be partially or totally
substituted for the perhalogenates used as a whitening agent in association with the
shortstopper in the process of the present invention.
i s [0069] The stabilizers or co-stabilizers may also be selected from zeolites which are
known to the skilled person, in particular those with general formula
Td, [(A102X (Si02M wH20, in which
T is an alkali or alkaline-earth metal, preferably selected from Li, Na, K, Mg, Ca, Sr and
Ba;
20 n represents the charge of cation T;
y:x is a number in the range 0.8 to 15, limits included, preferably in the range 0.8 to 1.2,
limits included; and
w is a whole number in the range 0 to 300, limits included, preferably in the range 0.5 to
30, limits included.
2s [0070] Advantageous examples of zeolites include sodium aluminosilicates of the A
zeolite, sodalite, Y zeolite, X zeolite, LSX zeolite type; and zeolites prepared by partial or
complete replacement of the sodium ions by the ions Li, K, Mg, Ca, Sr or Zn, as well as P,
MAP zeolites, and other zeolites obtained after partial or total replacement of sodium ions
by the ions Li, K or H, such as K-F zeolites, D zeolites and others.
30 [0071] Examples of phosphites (phosphorous triesters), thiophosphites and
thiophosphates which may be cited are triphenylphosphite, diphenylalkylphosphites,
phenyldialkylphosphites, tris(nonylphenyl)phosphite, trilaurylphosphite, trioctadecylphosphite,
distearylpentaerythritoldiphosphite, tris(2,4-di-tert-butylpheny1)-
phosphite, di-isodecylpentaerythritoldiphosphite, bis(2,4-di-tert-butyIphenyl)penta-
3s erythritoldiphosphite, bis(2,6-di-tert-butyl-4-methylphenyi)pentaerythritoldiphosphite,
bis(isodecyloxy)penta-erythritoldiphosphite, bis(2,4-di-tert-butyl-6-methy1phenyl)pentaerythritoldiphosphite,
bis(2,4,6-tri-tert-butylphenyl)pentaerythritoldiphosphiie, tristearylsorbitoltriphosphite,
bis(2,4-di-tert-butyI-6-methylphenyl)methylphenyl)methylphosphite
and bis(2,4-di-tert-butyI-6-methylphenyl)ethylphosphite.
5 [0072] Particularly preferred compounds are trioctyl-, tridecyl-, tridodecyl-, tritetradecyl-,
tristearyl, trioleyl, triphenyl, tricresyl, tris-p-nonylphenyl- &d tricylcohexyl-phosphites,
more particularly preferably aryldialkyl- and aikyldiaryl-phosphites, and of these
phenyldidecylphosphiie, 2,4-di-tert-butylphenyldidodecylphosphite, 2,6-di-tertbutylphenyldidodecylphosphite
and dialkyl- and diarylpentaerythritoldiphosphites, such as
lo distearylpentaerythritoldiphosphite, as well as non-stoichiometric triarylphosphites with the
composition, for example, (H19Cg-C6H4)0~-5P(OC~2,~3H25,27)o1r.5 (HBClTC6H4)02P(ic~
H170o)r even (Hl9Cg-C~H4)01.5P(OC9,11H19,23)1,5.
(00731 Preferred organic phosphites are distearylpentaerythritoldiphosphite,
trisnonylphenylphosphite and phenyldidecylphosphite. Other phosphites which may be
is used are phosphorous diesters (with the radicals defined above) and phosphorous monoesters
(with the radicals defined above), optionally in the form of their alkali metal, alkalineearth
metal, zinc or aluminium salts. These phosphorous esters may also be used as an
"alumo-salt" compound as described in DE-A-403 18 18, for example.
[0074] Examples of P-diketones and P-keto-esters which may be used which can be
zo cited are linear or cyclic 1,3-dicarbonyl compounds. It is preferable to use dicarbonyl
compounds with the following formulae: R'1COCHR'2-COR'3 in which R'l represents C1-
Cn2-alkyl, C5-Clo-hydroxyalkyl, C2-C18-alkenyl, phenyl, HO-, C1-C4-alkyl, C1-C4-alkoxy or
phenyl substituted with halogen(s), CrClo-phenylalkyl, C5-C12-cycloalkyl, C5-C12-cycloalkyl
substituted with C1-Cralkyl(s), or a -R'5-S-R'6 or -R(5-0-R(6 group, where RS2re presents
25 the hydrogen atom, C1-CB-alkyl, C2-C12-alkenyl, phenyl, C7-Cj2-atkylphenyl, C7-C10-
phenylalkyl or a -CO-R4, group Rt3 is as defined for R'l or represents CI-C18-alkoxy, RI4 is
a C1-C4-alkyl or phenyl, R5 is a C1-Clo-alkylene and is a C1-Clralkyl, phenyl, C7-C18-
alkylphenyl or CrClo-phenylalkyl.
[0075] Such compounds include the hydroxylated diketones described in EP 0 346 279
30 and the oxa- and thia-diketones described in EP 0 307 358, as well as the isocyanic acid
keto-esters described in US 4 339 383.
[0076] Examples of mercaptocarboxylic esters include the esters of thioglycolic,
thiomalic, mercaptopropionic, mercaptobenzoic and thiolactic acids, mercaptoethyl
stearate and mercaptoethyl oleate, such as those described in FR 2 459 816,
35 EP 0 090 748, FR 2 552 440 and EP 0 365 483. The generic definition of
mercaptocarboxylic esters also comprises esters of polyols and their partial esters, as well
as their thioether derivatives. These molecules may also be latent mercaptides, such as
those described in EP 0 945 485, for example.
[0077] Non-limiting examples of metallic soaps which may be used as stabilizers or co-
5 stabilizers in the context of the present invention include metallic carboxylates of relatively
long-chain carboxylic acids. Typical examples are stearates and laurates, as well as oleates
and salts of shorter chain carboxylic acids. Alkylbenzoic acids are also included as
examples of metallic soaps.
[0078] Examples of metals which may be cited are Li, Na, K, Mg, Ca, Sr, Ba, Zn, Al, La,
10 Ce and the rare earths. It is often also possible to use those which are known to form
synergistic mixtures, such as mixtures of bariumlzinc, magnesiumlzinc, calciumlzinc or
calcium/magnesium/zinc stabilizers. The metallic soaps may be used by themselves or in
mixtures. A list of the most commonly used metallic soaps is provided in "Ullmann's
Encyclopedia of Industrial Chemistry", Eith Ed., Vol. A16 (1985), p. 361 ff. it is
1s advantageous to use organometallic soaps belonging to the family of C2-C22 saturated
aiiphatic carboxylates, unsaturated aliphatic carboxylates, CTCZ aliphatic
carboxylates substituted with at least one OH group, cyclic and bicyclic carboxylates
containing 5 to 22 carbon atoms, benzenecarboxylates, non-substituted or substituted with
at least one -OH group andlor with a C1-C16 alkyl radical, naphthalenecarboxylates, non-
20 substituted or substituted with at least one -OH group andlor with a C1-CI6 alkyl radical,
phenyl-C1-C16-alkylcarboxylates, naphthyl-CI-C16-alkylcarboxylates or phenolates, nonsubstituted
or substituted with a C1-Clz-alkyl radical, tallates and resinates.
[0079] Named examples which may be cited are zinc, calcium, magnesium or barium
salts of monovalent carboxylic acids such as acetic, propionic, butyric, valeric, hexanoic,
2s cenanthic, octanoic, neodecanoic, 2-ethylhexanoic, pelargonic, decanoic, undecanoic,
dodecanoic, tridecanoic, myristic, palmitic, isostearic, stearic, 12-hydroxystearic, behenic,
benzoic, p-tert-butylbenzoic, 3,5-di-tert-butyl-4-hydroxybenzoic, toluic, dimethylbenzoic,
ethylbenzoic, n-propylbenzoic, salicylic, p-tert-octylsa\icyclic and sorbic acids; the calcium,
magnesium or zinc salts of divalent mono-esters of carboxylic acids such as oxalic,
30 malonic, succinic, glutaric, adipic, fumaric, pentane-I ,5dicarboxylic, hexane-1,6-
dicarboxylic, heptane-l,7-dicarboxylic, octane-l,8-dicarboxylic, phthalic, isophthalic,
terephthalic and hydroxyphthalic acids; and the di- or tri-esters of tri- or tetra-valent
carboxylic acids such as hemimellitic, trimellitic, pyromellitic or citric acids.
[0080] Particularly preferably, calcium, magnesium and zinc carboxylates obtained from
3s carboxyllc acids containing 7 to 18 carbon atoms (metallic salts in the narrow sense) are
used such as, for example, benzoates or alkanoates, preferably stearates, oleates,
laurates, palmitates, behenates, hydroxystearates, dihydroxystearates or
2-ethylhexanoates. Stearates, oleates and p-tert-butylbenzoates are particularly preferred.
Overbasic carboxylates such as overbasic zinc octoate are also preferred. Similarly,
5 overbasic calcium soaps are also preferred. If desired, it is also possible to use a mixture
of carboxylates with different structures. In this case, compositions such as those described
above, comprising an organozinc and/or organocalcium compound, are preferred.
[0081] Other mentionable typical examples of metallic soaps or salts which may be cited
are bimetallic salts of dicarboxylic acids such as dilithium, disodium or dipotassium salts of
l o divalent carboxylic acids such as oxalic, malonic, succinic, glutaric, adipic, fumaric,
pentane-1 ,5-dicarboxylic, hexane-I $6-dicarboxylic, heptane-l,7-dicarboxylic, octane-1,8-
dicarboxylic, phthalic, isophthalic or terephthalic acids. Disodium adipate is particularly
preferred.
[0082] Other metallic stabilizers and co-stabilizers which may be cited are
1s organometallic stabilizers', in particular organo-tin stabilizers. These may in particular be
carboxylates, rnaleates, mercaptides and sulphides. Examples of such compounds are
described in US 4 743 640, US 2 567 651, US 2 598 936, US 2 567 652, US 6 174 941,
US 5 925 696, US 6 156 830, US 6 084 013, US 6 194 494, US 4 105 627, US 4 352 903,
and DE 2 427 853.
20 [0083] Particular examples of amino-uracils which may be mentioned are the structures
described in US 4 656 209, US 5 859 100, US 5 925 696 and US 6 084 013.
[0084] The term "aqueous suspension or micro-suspension polymerization" means
polymerization carried out in the presence of at least one initiator which is soluble in oil,
and at least one unsaturated halogenated monomer, for example vinyl chloride by itself or as
2s a mixture with another vinyl monomer, dispersed by any mechanical means in an aqueous
medium comprising at least one suspending agent.
[0085] The proportion of vinyl monomer in the suspension is generally at least 50% by
weight, preferably more than 80% with respect to the total weight of the suspension. A
proportion of vinyl monomer of less than 50% by weight with respect to the total weight of
30 the suspension may also, however, be envisaged in the context of the present invention.
[0086] The vinyl monomers which can be copolymerized in an aqueous suspension with
a vinyl halide, in particular vinyl chloride, are welt known to the skilled person; non-limiting
examples of these which may be cited are vinyl esters such as vinyl acetate, vinylidene
halides such as vinylidene chloride and vinylidene fluoride, acrylic esters such as butyl
35 acrylate, and methacrylic esters such as methyl methacrylate.
[0087] The dispersion or suspension agents generally used in the suspension
polymerization are also well known to the skilled person and are in particular selected
from protective colloids, for example hydrosoluble polymers such as polyvinyl alcohols,
polyethylene oxides, hydrosoluble cellulose derivatives such as methylcellulose,
poly(vinylpyrrolidone), acetate copolymers of gelatine and vinyllmaleic anhydride and
others, as well as mixtures of two or more of these in any proportions.
[0088] These suspension agents may be used by itself or in the form of mixtures in
quantities generally in the range 0.01 to 0.5 part by weight, preferably in the range 0.04 to
0.2 part by weight per 100 parts by weight of monomer component(s).
[0089] The process of the present invention may also be carried out with a buffer system
in order to control the pH of the reaction medium during polymerization. In fact, the pH of
the aqueous medium is, for example, approximately 6 to 7 at the start of the reaction and
may fall to close to about 3.5 due to the production of hydrohalic acid, in particular
hydrochloric acid, in the reaction medium. Thus, in the context of the invention, it is
preferable, but not necessary, to buffer the aqueous suspension.
[0090] Typical buffer systems which may be used may include but are not limited to
those comprising carbonate, bicarbonate, phosphate or citrates. The pH range of the
buffer system is in the range 5 to 8, preferably in the range 5.5 to 7.5. The buffer system is
generally used in a quantity in the range 0.01 to 0.2 part by weight, preferably in the range
0.02 to 0.1 part by weight per 100 parts by weight of monomer(s).
[0091] In another implementation, the process of the present invention may also employ
at least one antioxidant which is added to the reaction medium, either at the start of the
reaction or when the desired conversion has been reached. The at least one antioxidant
may be introduced all at once or in several batches, or continuously into the reactor during
the polymerization reaction.
[0092] Preferred antioxidants which are known to the skilled person which may be used
in the process of the present invention are antioxidants containing phenolic groups,
preferably sterically hindered phenolic groups; non-limiting examples are those selected
from butylhydroxyanisole, butylhydroxytoluene, lrganoxQ 1076 from Ciba, lrganoxB245
from Ciba and Isonox@ 132 (2,6-di-tert-butyi-4-sec-butylphenol) from Schenectady
Chemical. The quantity of antioxidant may vary from 10 ppm to 1000 ppm, more
preferably from 25 ppm to 300 pprn.
[0093] The polymerization reaction of the process of the present invention may be
carried out at any temperature adapted to the suspension, micro-suspension, emulsion or
micro-emulsion polymerization reaction, preferably in the range 45°C to 80°C, more
preferably in the range 50°C to 70°C, which makes the use of a very wide variety of
polymerization initiators possible. When the selected polymerization temperature is not very
high (for example between 30°C and 50°C), it may prove to be useful to employ a
combination of different initiators with half-lives in the selected temperature range
s comprising, for example, a combination of dialkyl peroxydicarbonate and an initiator from
the peroxy-tert-alkanoates family, or a combination of different initiators from the peroxytert-
alkanoate family comprising a peroxy-tert-afkanoate and a peroxy-tert-alkanoate.
[0094] When the selected polymerization temperature is slightly higher (between 55°C
and 65"C), it may be useful to employ a combination of different initiators with half-lives at
lo the selected temperature comprising, for example, a dialkyl peroxydicarbonate and an
initiator from the peroxy-tert-dialkanoates family, or a combination of peroxy-tertalkanoates.
[0095] The peroxy-tert-alkanoates cited above generally have a half-life of 1 hour
between 40°C and 75°C and may thus be used for vinyl chloride polymerization
1s temperatures in the range 50°C to 70°C. Non-limiting examples of these peroxy-tertalkanoates
which may be cited are tert-butyl and tert-amyl peroxy-tert-alkanoates.
[0096] In the case of a relatively high polymerization temperature (between 62°C and
70°C), it may be useful to employ a combination of different initiators with half-lives at the
selected temperature comprising, for example, a dialkyl peroxydicarbonate or a peroxy-
20 tert-alkanoate and a slow initiator (long half-life) from the diacyl peroxide family, such as
dilauroyl peroxide.
[0097] The process of the invention may be carried out using any method which is
known to the skilled person consisting, for example, of dissolving a protective colloid in an
aqueous medium or a monomer, of dispersing the liposoluble polymerization initiator in the
2s aqueous medium or of dissolving it in the monomer component and optionally of dissolving
a buffer system in order to regulate or control the pH of the reaction medium.
[0098] Traces of oxygen are advantageously eliminated in order to result in a residual
quantity of dissolved oxygen in the water in the range 0.0005 to 0.05 part by weight,
preferably in the range 0.001 to 0.02 part by weight, per 100 parts by weight of water.
30 The at least one monomer to be polymerized is then introduced into the reactor, and the
reaction mixture is agitated and brought to a temperature in the range 45°C to 80°C,
preferably in the range 50°C to 70°C.
[0099] During the polymerization, it is not necessary to keep the pressure and the
temperature of the reaction mixture constant. Increasing the programmed temperature
35 either at the start or at the end of the polymerization cycle means that the rate of
decomposition of the initiators and the degree of polymerization can be accelerated. If the
temperature and the pressure are kept constant, the polydispersity of the molecular
masses of the polymer chains is in the range 1.8 to 2.5. In the case of polymerization with
programmed temperature gradients throughout polymerization, a polydispersity in the
5 range 1.8 to 3.5 is observed. These elements are perfectly well known to the skilled
person.
[OIOO] The polymerization reaction is terminated by exhaustion of the liquid monomer
phase, which is characterized by a modification to the liquid monomer/vapour equilibrium
and a drop in the reaction pressure. Just before the drop in reaction pressure, the
lo conversion by weight of monomer is generally in the 65% to 85% range. When the
desired degree of conversion has been reached, the shortstopper is introduced into the
reactor in order to destroy or render inactive any residual traces of initiator.
[0101] Once polymerization is terminated, the polymer formed is separated from the
aqueous medium and then drained and dried. The polymer obtained, in particular in the
15 case of a suspension or micro-suspension process, is generally in the form of particles with a
size which is generally in the range 80 pm to 250 pm.
[0102] In a preferred implementation of the invention, suspension polymerization of the
vinyl chloride is carried out using methods which are well known to the skilled person
employing, in an optimized manner, a quantity of initiator of the peroxydicarbonate type (or
20 a mixture of initiators including peroxydicarbonate and "fast" perester), then polymerization
is stopped by adding, during the pressure drop, a shortstopper of the alkylhydroxylamine
type; the quantity thereof is based on an empirical relationship.
[0103] In the process of the present invention, it has been discovered that adding at
least one perhalogenate with at least one shortstopper to the polymerization reaction
25 medium means that a polymerization product is obtained which has excellent whiteness
properties compared with the same polymerization products obtained without adding
perhalogenate.
[0104] Adding at least one perhalogenate to the polymerization reaction medium may be
carried out at the start, during or at the end of the polymerization reaction, preferably
so during or at the end of the reaction, more preferably at the end of the reaction.
[0105] When the at least one perhalogenate is added at the end of the reaction, it may
be added before, during or after adding the shortstopper. More precisely, the
perhalogenate or perhalogenates and the shortstopper or shortstoppers may be added
simultaneously, sequentially or in a separate manner, preferably simultaneously.
[0106] The quantity of perhalogenate(s) added can vary widely, but in general it is
preferable to add a quantity in the range 0.1 to 10 mol of perhalogenate(s) per I mol of
shortstopper; preferably, this quantity is in the range 0.5 to 5 mol, more preferably in the
range 0.5 to 2 mol. Entirely satisfactory whiteness properties are, for example, obtained
5 using one mole of perhalogenate(s) per mole of shortstopper.
[0107] In a more preferred implementation, the peroxide used is di-2-ethylhexyl
peroxydicarbonate, the shortstopper is a dialkylhydroxylamine, preferably N,Ndiethylhydroxylamine
(DEHA), and the perhalogenate is sodium perchlorate.
[01081 In accordance with yet another aspect, the present invention concerns a
lo composition comprising at least one shortstopper and at least one perhalogenate,
preferably at least one alkali metal or alkaline-earth metal perhalogenate.
[0109] This composition may advantageously be used in the processes for the
polymerization and copolymerization of halogenated vinyl monomers as described above.
This composition advantageously comprises at least one hydroxylamine derivative, for
15 example diethylhydroxylamine, and at least one perhalogenate, for example sodium
perchlorate.
[OIIO] The composition of the present invention may also comprise one or more
additives and/or solvents, for example selected from water, alcohols, stabilizers and costabilizers
(in particular the thermal stabilizers and co-stabilizers described above),
20 colourants and other additives and solvents known to the skilled person.
[0111] A particularly preferred composition comprises, and more preferably consists of,
at least one shortstopper, at least one perhalogenate, at least one thermal stabilizer and/or
co-stabilizer selected from antioxidants, metallic salts, mercaptocarboxylic acids, betadiketones,
epoxidized oils, phosphites, aminouracil derivatives, mineral co-stabilizers,
25 dihydropyridine type compounds, and water; as a non-limiting example, the composition of
the invention comprises and preferably consists of diethylhydroxylamine, sodium
perchlorate and water.
[0112] A composition which can be used to obtain PVC with excellent thermal stability
and excellent whiteness generally comprises:
30 -5% to 40% by weight of diethylhydroxylamine, preferably 10% to 30% by weight, for
example approximately 20% by weight;
-5% to 40% by weight of sodium perchlorate, preferably 10% to 30% by weight, for
example approximately 20% by weight;
- optionally, up to 20% by weight of one or more stabilizers andlor co-stabilizers; and
35 - the complement to 100% by weight of water,
[0113] The following examples serve to illustrate the invention described above and are
not intended to limit this invention to the precise embodiments described herein. Many
other variations and modifications are possible in the light of the above description and
said examples which follow.
5
Example I: Production of S-PVC (suspension process) (comparative)
[0114] 60 kg of demineralized water, 204.5 g of polyvinyl alcohol with a degree of
hydrolysis of 88 mol%, 153.1 g of polyvinyl alcohol with a degree of hydrolysis of 72
mol%, 90.5 g of an aqueous solution (comprising 40% active matter) of polyvinyl alcohol
10 with a degree of hydrolysis of 55 mol% and 549 g of an emulsion of di-(2-ethylhexyl)
peroxydicarbonate comprising 60% active matter ( ~ u p e r o2x2~3~ E N6OH from Arkema)
were introduced into a reactor with a capacity of 1200 litres. The components cited above
were introduced, at ambient temperature and with agitation (100 rpm), into the 1200 L
reactor which was provided with a three-arm turbine type agitator, a heating jacket, a
is baffle and a condenser. '
[0115] After closing the reactor, it was placed under partial vacuum (6.66 kPa absolute)
and the vacuum was maintained for 15 minutes. Agitation was then increased to 265 rpm
and simultaneously, the pumps were switched on in order to inject 362 kg of vinyl chloride
and 286 L of hot water at 95°C. The vinyl chloride injection period was measured at 12
20 min. The hot water injection period was measured at 15 min. The temperature when
charging was complete was approximately 50°C.
[0116] The heating was regulated by circulating a cold waterlhot water mixture with an
adjusted temperature in the heating jacket so that the polymerization temperature of 56.5"C
was reached in 10 minutes. The moment when the polymerization medium reaches 565°C
25 is considered to be the start of polymerization (= time tO) and the pressure at that time (PO) is
then taken as the reference.
[01171 After 5 minutes of polymerization (i.e. time to + 5 min), 200 kg of water was
introduced continuously into the reactor at a constant flow rate of 75 kglh to improve heat
exchange while keeping the exchange surface of the heating jacket constant and to
30 reduce the viscosity of the aqueous suspension.
[01181 After 7 minutes of polymerization (i.e. time tO + 7 min), the condenser was
actuated in order to carry out heat exchange and to keep the temperature in the reactor
constant. Actuation of the condenser was linear in order to reach, in 30 minutes (i.e. time
tO + 37 min), a constant heat exchange rate of 20 000 kcallh.
[0119] Exhaustion of the gas phase (monomer) in the reactor was manifested by a drop
in pressure between 65% and 70% conversion. As soon as the pressure had dropped to
0.3 bar compared with PO, cooling of the polymerization medium by the condenser was
stopped and the polymerization temperature increased. This increase was controlled by
s adjusting the cooling of the heating jacket. This control means that the temperature of the
polymerization medium could be increased in a regular manner.
[0120] As soon as the temperature reached 65"C, polymerization was stopped. This last
polymerization step until the temperature of 65°C is reached is termed HK (heat kick).
The end of HK corresponds to reaching this temperature of 65°C. Polymerization was
15 then stopped by adding an aqueous 85% solution of diethylhydroxylamine (DEHA) which
was injected into the reactior: medium over 1 minute. The quantity added corresponded to
115 ppm by weight of DEHA with respect to the initial monomer weight. The reaction
medium was held at 65°C for 1 minute before being cooled. Rapid cooling of the medium
was carried out using cold water injected into the heating jacket.
15 [0121] The residual monomer was then eliminated from the reaction medium using
conventional techniques, for example by returning to atmospheric pressure (degassing),
and the traces of monomer were then eliminated by degassing under a vacuum of
13.33 kPa at 50°C (stripping).
[0Y22] The PVC slurry thus obtained was then drained using a rotary centrifuge. The
20 moist PVC powder was then dried for 12 hours in a rotary dry air vacuum drier heated to
60°C. The dry PVC powder was then screened through a 500 pm mesh.
[0123] The white index (WI) of this resin was evaluated by measuring the W1 using a
Konica Minolta CM2500D colourimeter, in accordance with IS0 standard 2470. A new
white index WI for this heat treated resin was obtained using the same measurement
25 technique.
[0124] The heat treatment was carried out using a crystallizer produced from
borosilicate glass with an external diameter of 70 mm, a height of 40 mrn and a mass of
45 g, containing 9.5 g to 10.5 g of PVC resin, in a ventilated Heraeus UT6 type forced
convection oven. The oven was heated to a stable temperature of 160°C. The crystallizer
30 was then placed in the centre of the oven and exposed to'this temperature for 10 minutes.
[0125] The resin was then cooled in a dessicator and screened through a 250 pm mesh.
The resin was ready for the post-heat treatment WI measurement.
Example 2: Production of S-PVC (suspension process) (comparative)
[0126] The polymerization was carried out as in Example 1, with the exception that at
the end of HK, an aqueous 50% sodium perchlorate (NaCi04) solution was injected into
the reaction medium for 1 minute. The quantity added corresponded to 115 ppm by
s weight of NaC104 with respect to the initial monomer weight. The reaction medium was
maintained at 65°C for 1 minute before being cooled. Degassing, stripping, emptying,
centrifuging, drying and screening were then carried out in the same manner as in Example
-I and the polymer resins obtained thereby were evaluated in the WI test using the same
criteria.
10
Example 3: Production of S-PVC (suspension process)
[0127] The vinyl chloride polymerization was carried out using the operating procedure
of Example 1, but with the difference that instead of DEHA by itself, a mixture A composed
of DEHA, sodium perchlorate and water was added in respective proportions by weight of
is 20120160. The quantity 'added corresponded to 575 ppm by weight of mixture A with
respect to the initial monomer weight. The reaction medium was maintained at 65°C for 1
minute before being cooled. Degassing, stripping, emptying, centrifuging, drying and
screening were then carried out in the same manner as in Example 1 and the polymer resins
obtained thereby were evaluated in the WI test using the same criteria.
20
Example 4: Production of S-PVC (suspension process)
[0128] The vinyl chloride polymerization was carried out using the operating procedure
of Example 1, but with the difference that after adding the DEHA, an aqueous sodium
perchlorate solution was added. The quantity added corresponded to 115 pprn by weight
25 of DEHA and 115 ppm by weight of NaCIO, with respect to the initial monomer weight.
The reaction medium was maintained at 65°C for 1 minute before being cooled.
Degassing, stripping, emptying, centrifuging, drying and screening were then carried out in
the same manner as in Example 1 and the polymer resins obtained thereby were evaluated
in the W1 test using the same criteria.
30
Example 5: Production of S-PVC (suspension process)
[0129] The vinyl chloride polymerization was carried out using the operating procedure
of Example 4, but with the difference that, instead of DEHA, an aqueous emulsion of
lrgastab@ PVC11 EM was added. lrgastaba PVCI 1 EM is considered to be a PVC
35 polymerization shortstopper. The quantity added corresponded to 485 ppm by weight of
lrgastabe PVCl IEM with respect to the initial monomer weight. The aqueous solution of
sodium perchlorate, corresponding to 115 ppm by weight of NaCI04 with respect to the
initial monomer weight, was still added, following the order of introduction of Example 4.
The reaction medium was maintained at 65°C for 1 minute before being cooled. Degassing,
stripping, emptying, centrifuging, drying and screening were then carried out in the same
manner as in Example 1 and the polymer resins obtained thereby were evaluated in the Wl
test using the same criteria.
Example 6: Production of S-PVC (suspension process)
[0130] The vinyl chloride polymerization was carried out using the operating procedure
of Example 4, but with the difference that, instead of DEHA, a solution of BHA (tbutylhydroxyanisole,
CAS No. 25013-16-5), 20% by weight in ethanol, was added. This
solution is considered to be a PVC polymerization shortstopper. The quantity added
corresponded to 54 ppm by weight of BHA with respect to the initial monomer weight. The
aqueous solution of sodiam perchlorate, corresponding to 115 ppm by weight of NaCI04
with respect to the initial monomer weight, was still added, following the order of
introduction of Example 4. The reaction medium was maintained at 65°C for 1 minute before
being cooled. Degassing, stripping, emptying, centrifuging, drying and screening were then
carried out in the same manner as in Example I and the polymer resins obtained thereby
were evaluated in the WI test using the same criteria.
Example 7: Production of S-PVC (suspension process)
[0131] The vinyl chloride polymerization was carried out using the operating procedure
of Example 4, but with the difference that, instead of DEHA, a solution of lrganoxQ 1076
(octadecyl-3,5-di-tert-butyl-4-hydroxyhydrocinnamae, CAS No. 2082-79-3), 10% by
weight in isododecane (CAS No. 31807-55-3), was added. The quantity added
corresponded to 225 ppm by weight of lrganoxe! 1076 with respect to the initial monomer
weight. The aqueous solution of sodium perchlorate, corresponding to 115 ppm by weight
of NaCIO, with respect to the initial monomer weight, was still added, following the order
of introduction of Example 4. The reaction medium was maintained at 65°C for 1 minute
before being cooled. Degassing, stripping, emptying, centrifuging, drying and screening
were then carried out in the same manner as in Example 1 and the polymer resins obtained
thereby were evaluated in the WI test using the same criteria.
Example 8: Production of S-PVC (suspension process)
101321 A vinyl chloride polymerization was carried out using the operating procedure of
Example 3, but with the difference that before closing the reactor and at the start, the
antioxidant lrganoxa 1076 (octadecyl-3,5-di-tert-butyl-4-hydroxyhydrocinnamate, CAS No.
2082-79-3), 10% by weight in isododecane (GAS No. 31807-55-3), was added. The
quantity added corresponded to 225 ppm by weight of lrganoxm 1076 with respect to the
initial monomer weight. The operating procedure was then identical to that of Example 3.
The polymer resins obtained thereby were evaluated in the WI test using the same
criteria. This example shows that the antioxidant added at the start of polymerization has
no influence on the action of the shortstopper and of the perhalogenate as regards the
white index before and after heat treatment, and thus that conventional known
antioxidants can also be used in the process of the invention.
Example 9: Production of S-PVC (suspension process) (comparative)
[0133] A vinyl chloride polymerization was carried out using the operating procedure of
Example 1, but with the difference that before closing the reactor and at the start, the
antioxidant lrganoxB 1076, 10% by weight in isododecane, was added. The quantity
added corresponded to 225 ppm by weight of lrganox@1 076 with respect to the initial
monomer weight. The operating procedure was then identical to that of Example 1. The
polymer resins obtained thereby were evaluated in the WI test using the same criteria.
Example 10: Production of S-PVC (suspension process) (comparative)
[Ol34] A vinyl chloride polymerization was carried out using the operating procedure of
Example 1, but with the difference that instead of DEHA, a solution of lrganox@ 1076, 10%
by weight in isododecane, was added. The quantity added corresponded to 225 ppm by
weight of irganoxB 1076 with respect to the initial monomer weight. The operating
procedure was then identical to that of Example 1. The polymer resins obtained thereby
were evaluated in the WI test using the same criteria.
Example I 1 : Production of S-PVC (suspension process) (comparative)
101351 A vinyl chloride polymerization was carried out using the operating procedure of
Example 1, but with the difference that instead of DEHA, a solution of BHA, 20% by weight
in ethanol, was added. The quantity added corresponded to 54 pprn by weight of BHA
with respect to the initial monomer weight. The operating procedure was then identical to
that of Example I. The polymer resins obtained thereby were evaluated in the WI test
using the same criteria.
[0136] The WI whiteness index test produced the results shown in Table 1 below:
-- Table 1 --
CLAIMS
5 4. Process for the aqueous suspension, micro-suspension, emulsion or microemulsion
polymerization of at least one halogenated monomer, in particular chlorinated,
for example vinyl chloride, by itself or with one or more other vinyl monomers, preferably less
than 50% by weight of one or more other vinyl monomers, in which at least one shortstopper
and at least one perhalogenate, acting as a whitening agent, are added.
10
2. Process according lo Claim I, in which the polymerization is carried out in the
presence of at least one polymerization initiator.
3. Process according to Claim 1 or Claim 2, in which the shortstopper is selected
15 from phenolic derivative; and mono-alkyl-N- or dialkyl-N,N-substituted hydroxylamines,
each alkyl radical containing 1 to 4 carbon atoms, as well as mixtures of two or more
thereof in any proportions.
4. Process according to any one of Claims 1 to 3, in which the at least one
20 perhalogenate is an organic or mineral perhalogenate selected from metallic
perhalogenates, alkali metal or alkaline-earth metal perhatogenates, preferably from alkali
metal or alkaline-earth metal perchlorates, and advantageously, the at least one
perhalogenate is sodium perchiorate.
2s 5. Process according to any one of the preceding claims, in which the
polymerization is initiated with at least one polymerization initiator selected from dialkyl
peroxydicarbonates, peroxy-tert-alkanoates, diacyl peroxides and alkyl hydroperoxides,
and others.
30 6. Process according to any one of the preceding claims, comprising an initiation
system comprising at least one compound selected from dialkyl peroxydicarbonates, peroxytert-
alkanoates, diacyl peroxides and alkyl hydroperoxides and at least one shortstopper,
comprising at least one N-mono-alkylhydroxylamine or an N,N-dialkylhydroxylamine, and
at least one perhalogenate, preferably at least one perchlorate.
35
7. Process according to any one of the preceding claims, further comprising at least
one thermal stability additive selected from the following thermal stabilizers or thermal costabilizers:
2-ethylhexylmercapto-acetic acid, thioglycolic acid, and esters thereof, alkali
metal carbonates, f3-diketones, epoxidized vegetable oils, phosphites, f3-ketone esters,
s metallic salts or soaps, in particular stearates, adipates, amino-uracil derivatives and/or
thio-uracil derivatives, hydrazides, the mineral compounds hydrotatcites and zeolites,
alcohols and polyols, glycidyl derivatives, a-phenylindoie, compounds of the
dihydropyridine type, enamines, alkanolamine type derivatives, and others, by themselves
or as mixtures of two or more thereof, in any proportions.
10
8. Use of an association of at feast one shortstopper with at least one
perhalogenate, for example a metal, alkali metal or alkaline-earth metal perhalogenate, in
the process for the preparation of halogenated polymers and copolymers, in particular
PVC.
15
9. Use according to Claim 8, in which the shortstopper is selected from phenolic
derivatives and mono-alkyl-N- or dialkyl-N,N-substituted hydroxylamines, each alkyl
radical containing 1 to 4 carbon atoms.
20 10. Use according to Claim 9, in which the shortstopper is selected from diethylhydroxylarnine
and 4-OH-Tempo (1,4-dihydroxy-2,2,6,6-tetramethylpiperidinea)s
well as mixtures of two or more thereof in any proportions.
11. Composition comprising at least one shortstopper and at least one
2s perhalogenate, preferably at least one alkali metal or alkaline-earth metal perhalogenate.
12. Composition according to Claim 1 in which the shortstopper is
diethylhydroxylamine and the perhalogenate is sodium perchlorate.
30 13. Composition according to any one of Claims 11 and 12, comprising:
-5% to 40% by weight of diethylhydroxylamine, preferably 10% to 30% by weight, for
example approximately 20% by weight;
-5% to 40% by weight of sodium perchlorate, preferably 10% to 30% by weight, for
example approximately 20% by weight;
35 - optionally, up to 20% by weight of one or more stabilizers and/or co-stabilizers; and
- 28 -
- the complement to 400% by weight of water.