Case 00269(2)
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VINYL ACETATE POLYMERS METHODS OF MAKING THEM
AND USES THEREOF
This invention relates to vinyl acetate polymers, methods of making them and uses of
them. More especially but not exclusively the invention relates to partially hydrolysed
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vinyl acetate polymers for use as primary granulating agents in the production of polyvinyl
chloride (PVC) by the polymerization of vinyl chloride (VCM).
PVC is a commercially very important polymer. Much PVC is prepared by free radical
addition polymerization of VCM suspensions. The VCM suspensions are stabilised by
primary granulating agents which stabilize the VCM droplets and allow the droplet size to
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be regulated.
Typical primary protective agents are partially hydrolysed polyvinyl acetate polymers and
copolymers which have been prepared by polymerizing vinyl acetate monomer (VAM) in
the presence of an aldehyde as a chain transfer agent and then partially hydrolysing the
resulting product. For example GB 2 002 789 describes a primary granulating agent. Vinyl
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acetate monomer (VAM), methanol, acetaldehyde and azobisisobutyronitrile (AIBN) are
heated together until about 75% of the VAM has been polymerized. The principal role of
the methanol is as a solvent. The principal role of the acetaldehyde is as a chain transfer
agent (CTA) and the principal role of the AIBN is as a radical initiator. The acetaldehyde
and unreacted VAM are removed using methanol vapour to give a solution of polyvinyl
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acetate (PVAc) in methanol. The PVAc is partially hydrolysed to give a polymer having a
degree of hydrolysis of 70.1% and a degree of polymerization of 350. The resulting
polymer has a strong absorbance at 280nm demonstrating the presence of unsaturated
carbonyl functionality in the polymer (Lloyd, D. G., J. Applied Polymer Sci., 1959, 1, 7072) introduced from the acetaldehyde.
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It has now been unexpectedly found that it is not essential to use aldehydes as chain
transfer agents to introduce unsaturation when making partially hydrolysed polyvinyl
acetate (co)polymers for use as primary granulating agents for VCM polymerization.
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In accordance with an aspect of the invention it has been found that partially hydrolysed
polyvinyl acetate polymers having a relatively high ethylenic unsaturation are useful as
primary granulating agents.
Furthermore it has been unexpectedly found that using selected organic halides such as
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organic chlorides and bromides as chain transfer agents during the polymerization of VAM
leads to relatively high ethylenic unsaturation in the eventual partially hydrolysed polymer,
even if the selected chloride or bromide does not contain ethylenic unsaturation itself. This
is demonstrated by trichloroethylene which inherently having ethylenic unsaturation
introduces little ethylenic unsaturation into the polymer in view of its low chain transfer
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constant for vinyl acetate.
According to the invention therefore there is provided a partially hydrolysed polyvinyl
acetate polymer or copolymer having a degree of hydrolysis in the range 65 to 95% and at
least 53µmoles preferably at least 54µmoles of ethylenic unsaturation per gram of
polymer. The molecular mass Mn of the polymer or copolymer can be in the range 10 000
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to 100 000 such as 15 000 to 50 000, preferably 17 000 to 40 000. In some embodiments
the copolymer comprises no more than 5wt% preferably no more than 2wt% of the comonomer. A co-monomer can have allyl functionality preferably wherein the allyl group
containing co-monomer is of structural formula I
R2R3C=CR1CR4R5X
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I
where X is selected from Cl, Br, OR6 and CO2R7
R1, R2, R3, R6 and R7 are independently selected from H and C1-6 straight chain or
branched alkyl, and CO2R8 where R8 is selected from H and C1-6 straight chain or
branched alkyl and
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R4 and R5 are independently selected from H, C1-6 straight chain or branched alkyl, OC16 straight chain or branched alkyl or where R4 and R5 taken together are =O or
Case 00269(2)
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or where X is H or C1 to C6 straight chain or branched alkyl, R1, R2 and R3 are as
hereinbefore defined and R4 and R5 are independently -OR9 or –OOCR10 where R9 and
R10 are independently selected from C1-6 straight chain or branched alkyl.
In embodiments R1, R2 and R3 are independently selected from H, methyl and ethyl and X
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is Cl or OR7 where R7 is H or methyl. In these embodiments R4 and R5 are preferably H.
In embodiments R1 and R3 are independently selected from H and CO2R8 where R8 is H,
methyl or ethyl, R2 is H, methyl or ethyl, X is CO2R7 where R7 is H, methyl or ethyl. In
these embodiments R4 and R5 can be H.
In embodiments R2 and R3 are independently selected from H and CO2R8 where R8 is H,
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methyl or ethyl, R1 is H, methyl or ethyl, X is CO2R7 where R7 is H, methyl or ethyl. In
these embodiments R4 and R5 can be H.
A co-monomer can have di-olefin functionality and may be selected from vinyl
norbornene, ethylidene norbornene, norbornadiene, dicyclopentadiene, 1,5 cyclooctadiene,
tetrahydroindenes, 1,4 hexadiene and 1,4 pentadiene.
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A co-monomer can have acryl functionality preferably selected from monomers of
structural formula II
R11R12C=CR13COZ
II
where R11, R12 and R13 are independently selected from H, C1-6 straight chain or
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branched alkyl OC1-6 straight chain or branched alkyl and
Z is OH, OR14 or NR14R15 where R14 and R15 are independently selected from H and
C1-8 straight chain or branched alkyl or aromatic groups such as phenyl.
In embodiments R11, R12 and R13 are independently selected from H, methyl and ethyl
and Z is OR14 where R14 is H, methyl, ethyl or 2-ethylhexyl.
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Embodiments of the invention further provide a partially hydrolysed polyvinyl acetate
polymer or copolymer having a molecular mass Mn in the range 10 000 to 100 000, a
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degree of hydrolysis in the range 65 to 95%, at least 40 µmoles of ethylenic unsaturation
per gram of polymer and a polydispersity index less than 2.3.
Polymer or copolymers of the invention can be used as a primary granulating agent in the
polymerization or copolymerization of VCM.
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The invention further provides a method of preparing PVC comprising polymerizing VCM
optionally in the presence of a co-monomer in the presence of a polymer or copolymer of
the invention.
The invention further provides PVC obtainable by a process of the invention.
The invention still further provides a method of preparing a polymer or copolymer of the
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invention by reacting VAM and optionally a co-monomer in the presence of a chlorine or
bromine containing chain transfer agent having a polyvinyl acetate polymerization chain
transfer value in the range 0.01 to 5, preferably 0.2 to 3 more preferably 0.25 to 1.2, and
subjecting the resulting material to partial hydrolysis. In embodiments of the invention the
chlorine or bromine containing chain transfer agent is at least one of carbon tetrachloride,
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chloral, ethylidene bromide, hexachloroethane, trichloroacetaldehyde, E-1-chloro-butene,
Z-1-chloro butene, E-1-chlorobut-2ene, Z-1-chlorobut-2-ene, 2-chlorobut-1-ene, 3chlorobut-1-ene, E-3-chlorobut-2-ene, Z-3-chlorobut-2-ene, 1-chloro-2-methylpropene, 3chloro-2-methylpropene-, vinyl bromide, allyl chloride and ethyl dichloroacetate. The
VAM may be polymerized in the presence of an allyl group containing co-monomer. The
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allyl group containing co-monomer can be of structural formula I
where X is selected from Cl, Br, OR6 and CO2R7
R1, R2, R3, R6 and R7 are independently selected from H and C1-6 straight chain or
branched alkyl, and CO2R8 where R8 is selected from H and C1-6 straight chain or
branched alkyl and
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R4 and R5 are independently selected from H, C1-6 straight chain or branched alkyl or
where R4 and R5 taken together are =O or
or where X is OH or C1 to C6 straight chain or branched alkyl, R1, R2 and R3 are as
hereinbefore defined and R4 and R5 are independently -OR9 or –OOCR10 where R9 and
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R10 are independently selected from C1 to C6 straight chain or branched alkyl or aromatic
groups. In embodiments of the invention the allyl group containing monomer is selected
from one or more of allyl acetate, allyl chloride, allylidene diacetate,
The invention yet further provides the use of a partially hydrolysed polyvinyl acetate
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polymer or copolymer as a dispersion stabilizer in suspension polymerization of a vinyl
compound, the polymer or copolymer being characterised by the ratio of absorbance at
280nm of a 0.2wt% aqueous solution of the vinyl alcohol polymer to the absorbance at
320nm of a 0.2wt% aqueous solution of the vinyl alcohol polymer is more than 0.7 at 30°C
and a Yellow Index of 40 or lower according to JIS K 7105 (1981) as measured on a dry
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powder, the absorbance being measured with an optical path length of 1cm.
The invention still further provides the use of a partially hydrolysed polyvinyl acetate
polymer or copolymer as a dispersion stabilizer in suspension polymerization of a vinyl
compound, the polymer or copolymer being characterised by the absorbance at 280nm
being no more than 0.36 and the absorbance at 320nm being no more than 0.36 the
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absorbance being measured of a 0.2wt% aqueous solution at 30C with an optical path
length of 1cm. In embodiments the absorbance at 280nm is no more than 0.2 preferably no
more than 0.1. In embodiments the absorbance at 320nm is no more than 0.15 preferably
no more than 0.1.
Throughout this disclosure where values are mentioned it is intended that they may form
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the upper or lower limit of a range of values especially in combination with another
mentioned value.
The invention is not especially limited as to the nature of the organic halide provided that it
has a chain transfer constant for vinyl acetate of at least 0.01, more preferably at least 0.02,
yet more preferably in the range 0.02 to 5 and still more preferably in the range 0.02 to 2
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such as 0.25 to 1.2. Throughout this disclosure where values are mentioned it is intended
that they may form the upper or lower limit of a range of values especially in combination
with another mentioned value. Chain transfer constants can be determined by performing a
series of low conversion, bulk vinyl acetate polymerisations at a constant initiator/
monomer ratio but varying transfer agent / monomer molar ratios at constant temperature.
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Typically polymerisation is performed at 60°C to less than 15% conversion using AIBN as
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the initiator. Molecular weights of the isolated polymer are obtained by either GPC or
viscometry. Plotting 1/Pn (the degree of polymerisation) against the transfer/monomer
ratio gives the chain transfer constant as the gradient for minimally rate retarding agents
asThe chain transfer constant can be determined by methods described by Clarke, Howard
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and Stockmayer, Macromol. Chem, 1961, 44, 427-447.
By way of non-limiting example suitable organic chlorine or bromine compounds include
carbon tetrachloride, hexachloroethane, chloral, vinyl bromide, ethylidene bromide, allyl
chloride, methallyl chloride, 1-chloro-but-2-ene (ie crotyl chloride) and ethyl
dichloroacetate. The invention need not be restricted to a single chain transfer agent and
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optionally more than one could be used. It is also possible to use other chain transfer
agents which need not have a chain transfer constant within the preferred range nor indeed
to be organic halides provided that at least some organic halide chain transfer agent,
preferably having a chain transfer constant in the above ranges is present such that the
resulting PVA has sufficient unsaturation. The chain transfer agents could also be added all
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at once at the beginning of the polymerization or discontinuously or continuously during
part or all of VAM polymerization. Consequently, the concentration of agent can be varied
during the polymerization arbitrarily in order to make a specific molecular weight or
molecular weight distribution or polymer blend.
Those skilled in the art will have no difficulty in devising methods of polymerizing the
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VAM. In general VAM is stirred with the organic halide and an initiator in the substantial
absence of oxygen.
A solvent can be present. The solvent should be a solvent for both the VAM and the
produced polyvinyl acetate and compatible with the other materials present. Examples of
suitable solvents include methanol, ethanol, toluene, methyl acetate and diethyl ether.
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Methanol is generally preferred. The purpose of the solvent is to allow polymerization to
proceed further before the mixture becomes too viscous to stir effectively than would
otherwise be the case. The precise amount of solvent present is not of the essence of the
invention. In general since the solvent may participate in chain termination it is desirable,
but not essential, to keep the amount of solvent at a low level.
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Conventional free radical initiators such as AIBN, di-benzoyl peroxide and lauroyl
peroxide may be used. Conveniently the free radical initiator is added in solution form for
example in a toluene or xylene solution of concentration of about 0.2M. The amount of
free radical initiator used depends on the desired rate of reaction.
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If desired a co-monomer can be present. Those skilled in the art will have no difficulty in
devising suitable co-monomers nor in devising methods of co-polymerization. Particularly
preferred co-monomers are those with allyl functionality such as allyl acetate, allylidene
diacetate and allyl chloride or substitution variants thereof. It will be apparent to the skilled
worker that allyl chloride can function both as a chain transfer agent and a co-monomer.
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Suitable co-monomers can be added in varying quantities according to the levels of
incorporation desired and can be added continuously or discontinuously. Other suitable comonomers include olefins such as propylene and butenes, di-olefins particularly those
having at least one allylic hydrogen such as vinyl norbornene, ethylidene norbornene,
norbornadiene, dicyclopentadiene, 1,5 cyclooctadiene, 1,6 octadiene, tetrahydroindenes 1,4
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hexadiene and 1,4 pentadiene which are typically used in the production of EPDM rubbers,
acrylic acid and its salts, acrylates such as methyl acrylate and ethyl acrylate; methacrylic
acid and its salts, methacrylates such as methyl methacrylate and ethyl methacrylate;
acrylamide and its derivatives such as N-methyl acrylamide, or N-ethyl acrylamide or N,N
dimethyl acrylamide; vinyl ethers such as methyl vinyl ether or ethyl vinyl ether, nitriles
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such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride, vinylidene
chloride and vinyl fluoride; allyl compounds such as (meth)allyl chloride, crotyl chloride
and their derivatives, allyl acetate, allyl ethers, (meth)allyl ethers, (meth)allyl esters such as
1-methallyl acetate or ethers or crotonic esters and crotonic ethers such as 3-methallyl
acetate; allylidene compounds such as allylidene diacetate or allylidene diethers such as
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dimethoxyacrolein or diethoxyacrolein; or unsaturated carboxylic acids such as crotonic
acid, fumaric acid, maleic acid or itaconic acid and their salts and esters such as dimethyl
fumarate or diethyl itaconate.
The precise temperature at which polymerization is performed is not of the essence of the
invention. If the temperature is too low then the reaction time will be too long. If the
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temperature is too high then the initiator will decompose at too high a rate. In general
terms the temperature should not exceed 75°C and preferably is in the range 60 to 70°C but
Case 00269(2)
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the skilled worker can by routine experimentation devise ways of operating outside this
range and above 75°C. The initiator is chosen to have a suitable half-life in the temperature
range and solvent mix selected. Those skilled in the art will have no difficulty in selecting
appropriate initiators and reaction temperatures. Initiators can be added at the start of the
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polymerization, intermittently or continuously, depending upon the choice of initiator used.
Suitable examples include benzoyl peroxide, lauryl peroxide, hydrogen peroxide and
AIBN.
The reaction is allowed to proceed until the desired proportion of the VAM has been
polymerized. Typically this will be of the order of 50 to 80% such as 60 to 70%. At this
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point the polymer may have Mw of about 10 000 to 500 000 preferably about 15 000 to
100 000 such as 20 000 to 70 000.The polymer may have a polydispersity of about 1.5, 1.7,
1.9, 2.1, 2.3, 2.5, 2.7, 2.9, 3.1, 3.2, 3.5, 3.7, 3.9, 4.1,4.3,4.5, 4.7, 4.9 or 5.1.
The polymer is then separated from unreacted VAM. Those skilled will have no difficulty
in devising suitable ways of doing this. One way of achieving this is to add methanol as
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either liquid or vapour and distil off the VAM/methanol azeotrope leaving a solution of the
polymer in methanol. At least some methanol can be removed from the polyvinyl acetate
polymer solution. Optionally additives can be added in small quantities such as mild bases
(for example pyridine or di-isopropylamine or sodium bicarbonate) as well as
polymerization inhibitors.
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The polyvinyl acetate polymer is then subjected to partial hydrolysis. Those skilled in the
art will have no difficulty in devising suitable ways of hydrolysing the polymer. Acid
catalysed hydrolysis can be used but base catalysed hydrolysis is preferred. A way of
hydrolysing the polyvinyl acetate is to add a small amount of base for example a solution
of sodium methoxide in methanol to a solution of the polyvinyl acetate in methanol with
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vigorous mixing. Other bases which could be used include hydroxides or alkoxides such as
ethoxides of sodium, potassium, lithium, magnesium, calcium or ammonium and any
combination thereof. Other solvents can be used such as THF, toluene, methyl acetate
provided adequate solubility is achieved. By changing the types of solvent (and thus the
dielectric constants of the mixture) changes to the block factor (η, or “blockiness”) can be
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made (Moritani and Fujiwara, Macromol. Chem, 1977, 10, 532-535). A wet solid gel
Case 00269(2)
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rapidly forms which can be aged and/or kneaded and/or extruded until the desired degree
of hydrolysis is obtained. The hydrolysis reaction is then stopped for example by addition
of water or acetic acid, optionally in the presence of an active amine material such as
hydroxylamine, semicarbazide or hydrazine and in the presence of a suitable diluent such
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as methyl acetate, water, methanol, ethanol or mixtures thereof. In an embodiment of the
invention the gel is finely chopped and mixed with a dilute solution of acetic acid for
example in water or methyl acetate optionally in the presence of hydroxylamine.
Hydrolysis is allowed to continue until the desired degree of hydrolysis is achieved.
Typically degrees of hydrolysis are in the range 65% to 90%, preferably between 69 and
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75% more preferably in the range of 68-73% such as about 70%. 70% hydrolysis means
that 70% of the acetate groups have been hydrolysed from the polyvinyl acetate.
After hydrolysis and “termination” of the hydrolysis reaction, the mixture should be freed
of the supernatant liquid. Various methods can be used such as filtration or centrifuging to
leave a swollen polymer gel. The hydrolysed polymer can then be dried for use. Those
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skilled in the art will have no difficulty in devising suitable drying techniques. Examples
include heating under reduced pressure, or heating with hot inert gas such as nitrogen or
carbon dioxide or heating in air. Drying with hot gas with less oxygen than is present in air
such as less than 5% oxygen could be used. Where oxygen is present it is preferred that the
flammability limit of the polymer, or indeed any volatiles given off during drying, should
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not be exceeded. Optionally some water or steam can be present in the gas stream.
In general the polymer will not be dried to absolute dryness but rather volatiles are
generally removed down to a low level such as below 5wt% such as 3wt%. Drying is
typically performed on a polymer which has been ground or chopped with a graded particle
size, or it has been produced in a small particle size during hydrolysis and is typically
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performed over a period of 0.5 hours to 20 hours. Typically drying is performed at
temperatures between 100°C and 150°C, such as 110-140°C more preferably 125-135°C
for example at 130°C. During drying additional dehydration of the polymer backbone can
occur leading to increased levels of conjugated and unconjugated unsaturation being
developed as measured by a variety of means. This procedure is described in US3220992.
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The resulting polymer may have a polydispersity of about 1.5, 1.7, 1.9, 2.1, 2.3, 2.5, 2.7,
2.9, 3.1, 3.2, 3.5, 3.7, 3.9, 4.1, 4.3, 4.5, 4.7, 4.9 or 5.1. In preferred embodiments of the
invention the polydispersity is less than 2.3. Using such low polydispersity values can
allow low amounts of unsaturation to be used such as 40µmoles, 42µmoles, 44µmoles,
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48µmoles, 50µmoles, 52µmoles of ethylenic unsaturation per gram of polymer as well as
the higher values hereinbefore mentioned.
The ratio of absorbance at 280nm to the absorbance at 320nm may be in the range of 0.7 to
2 or greater, for example 0.7 to1.8 such as 0.85 to 1.5 for example 1.3 to 1.8.
The invention can provide high levels of unconjugated unsaturation in the PVA polymer
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leading to good performance in the production of PVC. The invention can avoid the
formation of conjugated unsaturation which can result in the PVC being coloured.
Furthermore the invention can prevent excessive cross-linking in the PVA polymer which
has a beneficial result as cross-linking can decrease PVA solubility.
Finished hydrolysed polymers may be blended together at this stage to provide certain
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properties. For example, two different molecular weight polymers may be hydrolysed
separately but blended to give a wider polydispersity, but with more uniform hydrolysis
characteristics or alternatively different levels of hydrolysis can be blended to achieve a
required specification.
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Measurement of the degree of hydrolysis and blockiness.
The partially hydrolysed PVA is fully dried to remove all water by drying in a vacuum
oven at 60°C overnight. The weighed PVA (typically 0.5 g) is then dissolved in distilled
water as a 1-2wt% solution and once fully dissolved, is titrated to neutrality using
phenolphthalein indicator and a few drops of 0.1M caustic solution. To this solution is
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added an excess of 0.1M caustic solution, such as 50 ml and this is allowed to stir and react
for 2 hours. The excess quantity of caustic can then be back titrated against 0.1M dilute
acid until clear.
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The hydrolysis is performed under conditions such that the block character of the partially
hydrolysed polymer is in the range 0.3 to 0.8 such as 0.35 to 0.45 preferably in the range
0.37 to 0.41. US 7193012 describes how block character can be varied and Moritani and
Fujiwara, Macromol. Chem, 1977, 10, 532-535 explains how block character can be
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measured.
Determination of unsaturation level.
The resulting partially hydrolysed polyvinyl alcohol should have significant ethylenic
unsaturation in it. The unsaturation level is generally at least 53µmoles per gram of
polymer however where the polydispersity is 2.3 or less the unsaturation level can be 40 or
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greater such as 42, 44, 46, 48, 50 or 52µmoles per gram of polymer. Ethylenic unsaturation
can be quantified by iodine number which is a measure of the mass of iodine which 100g
of material react with. Iodine number can be measured by the methods described in ASTM
D1959-97 save that water rather than chloroform is used as a solvent and that results are
reported as the number of micro moles of iodine per gram of polymer as described below.
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Unsaturation can be formed anywhere within the polymer molecules at any stage of the
synthesis such as at the chain ends, or within the backbone of the polymer or as pendant
groups from the addition of specific co-monomers.
A sample of PVA is fully dried by heating overnight in a vacuum oven at 60°C.
Approximately 0.5g is weighed accurately into a small bottle and dissolved fully in a 3:1
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by weight water/methanol solution. To this solution is added 0.5ml of Hanus solution, CAS
number 9012-63-9, which must be measured accurately. The solutions should then be
mixed thoroughly and stored in the dark for 1 hour. After this period an excess of
potassium iodide is added (1 gram) and the excess iodine liberated is back titrated against
0.01M thiosulphate solution using starch indicator.
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In preferred embodiments of the invention there are more than 53µmoles for example more
than 54 or more than 55, such as more than 60 such as more than 70 for example 72µmoles
or more of ethylenic unsaturation per gram of dry polymer.
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Molecular Weight
The resulting polymer or copolymer generally has a Mn in the range 10 000 to 100 000
such as 15 000 to 40 000, preferably 17 000 to 30 000. In view of the values of
polydispersity disclosed herein it will be trivial for the skilled worker to deduce Mw values
5
which for example can be in the range. 15 000 to 250 000 such as 20 000 to 50 000.
Molecular weight can be determined by the procedure set forth in Dawkins et al Polymer
40 (1999) 7331-9 specifically: Molar mass characterisation of the as-supplied PVOH
samples was performed following reacetylation to PVAc. The reacetylation procedure
involved dissolution of PVOH (0.2 g) in N,N-dimethylformamide (10 ml) followed by
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additions of N-methyl imidazole (0.25 ml) as catalyst and acetic anhydride (0.3 ml) . After
thorough agitation this mixture was allowed to stand at ambient temperature for 30 min.
THF (90 ml) was then added and a suitable aliquot of solution was filtered through a
0.45µm PTFE membrane filter. Characterisation by SEC was performed on solutions of
PVAc with two “mixed-B” PL gel columns in series (10 μm x 300mm x 7.5 mm, Polymer
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Laboratories Ltd., UK) and 10 cm guard column at 35°C, with tetrahydrofuran as solvent
at a flow rate of 1 ml min. The instrumentation consisted of pump, degasser, auto-sampler,
column oven, refractive index detector, and PL-Cirus GPC/SEC workstation, all supplied
by Agilent formerly Polymer Laboratories Ltd., UK. Molar mass calibration was obtained
with Agilent EASICAL A and B polystyrene standards
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Preparation of PVC
The finally obtained polymer can be used as a primary protective agent in the
polymerization of VCM for example in conventional ways. The polymer can be used alone
or in conjunction with other primary protective agents which may be, but need not be, in
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accordance with the invention. Thus for example the polymer can be made up into a water
solution for example at about 4wt% for example in the range 2 to 6wt% and then added to
demineralised water. Optionally other primary protective agents can be added. A
secondary suspending agent can also be added. The mixture can be stirred and subjected to
reduced pressure to reduce the dissolved gas content. VCM can be added and the mixture
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stirred. An initiator can be added and the warm solution allowed to react. After some time
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unreacted VCM can be removed for example under reduced pressure and the produced
polymer removed from the suspension for example by using a centrifuge. The skilled
worker will well understand how to use the material as a primary protective agent.
The following non-limiting examples exemplify the invention:
5
All samples were prepared from materials which were used as received directly from
suppliers, such as Sigma Aldrich unless otherwise stated. All materials were of 99+%
purity or better. Vinyl acetate typically contained 3-20ppm of hydroquinone inhibitor,
which was not removed. All solutions used in polymerization were rigorously freeze-thaw
degassed using standard Schlenk-line techniques. Polymerizations were performed under a
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nitrogen atmosphere, with a stirring speed around 250rpm and the temperature being
maintained using a water bath. Precipitation was achieved by pouring a methanolic
solution, containing approximately 20wt% polymer, into an excess of distilled water. For
the hydrolysis, the THF was HPLC grade and was dried (and de-inhibited) by passing
through a column containing a 40cm bed of dried alumina powder. All samples of
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polyvinyl acetate were dried for a minimum of 16 hours in a vacuum oven at below 1
mbar, as were all samples of polyvinyl alcohol for analytical tests. For PVC
polymerization tests, however, the PVA samples were, unless otherwise stated, dried for
only 4 hours at 60°C under vacuum in order to prevent overdrying. Hydrolysis was
performed as hereinbefore described
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Production of polyvinyl acetate 1 (comparative)
VAM
280ml
Methanol
320ml
AIBN solution
9 ml (as a 0.2M solution in toluene)
The ingredients were heated at 60°C under nitrogen with continuous stirring in a 1 litre
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flask for 7.5 hours. At the end of this period the mixture was heated under reduced pressure
(8mbar.) Methanol/VAM azeotrope followed by methanol was distilled from the mixture
to leave 175g of a white polymer after isolation by precipitation into water and drying
under vacuum at 60°C.
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Production of polyvinyl acetate 2 (comparative)
5
VAM
440ml
Propanal
8.0ml
Methanol
160ml
AIBN solution
6 ml (as a 0.2M solution in toluene)
The ingredients were heated at 60°C under nitrogen with continuous stirring in a 1 litre
flask for 7 hours. At the end of this period, methanol (300ml) was added and the mixture
heated under reduced pressure (8mbar.) Methanol/VAM azeotrope followed by methanol
was distilled from the mixture to leave 275g of a white polymer after isolation by
10
precipitation into water and drying under vacuum at 60°C.
Polyvinyl acetate 3 (comparative)
This was purchased from Aldrich Chemical Co as product # 189480 and used as supplied.
Production of polyvinyl acetate 4 (comparative)
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VAM
280ml
Methanol
320ml
Allyl acetate
10 ml
AIBN solution
12ml (as a 0.2M solution in toluene)
The ingredients were heated at 60°C under nitrogen with continuous stirring in a 1 litre
flask for 10 hours. At the end of this period the mixture was heated under reduced pressure
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(8mbar) to remove methanol/VAM azeotrope followed by methanol to leave 144g of a
white polymer after isolation by precipitation into water and drying under vacuum at 60°C.
Production of polyvinyl acetate 5 (invention)
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VAM
580ml
Allyl chloride
5.0ml
Methanol
20ml
AIBN solution
24 ml (as a 0.2M solution in toluene)
The ingredients were heated at 60°C under nitrogen with continuous stirring in a 1 litre
flask for 5 hours. At the end of this period methanol (300ml) was added and the mixture
Case 00269(2)
15
heated under reduced pressure (8mbar.) Methanol/VAM azeotrope followed by methanol
was distilled from the mixture to leave 329g of a white polymer after isolation by
precipitation into water and drying under vacuum at 60°C.
Production of polyvinyl acetate 6 (invention)
5
10
Initial solution
VAM
725ml
Allyl chloride
6.0ml
Methanol
25ml
AIBN solution
30 ml (as a 0.2M solution in toluene)
The ingredients were heated at 60°C under nitrogen with continuous stirring in a 1 litre
flask for 6.5 hours. After 2 hours (2ml) and 4 hours (2ml) additional aliquots of allyl
chloride were added. At the end of the 6.5 hour period methanol (300ml) was added and
the mixture heated under reduced pressure (8mbar.) Methanol/VAM azeotrope followed by
methanol was distilled from the mixture to leave 303g of a white polymer after isolation by
15
precipitation into water and drying under vacuum at 60°C.
Production of polyvinyl acetate 7 (invention)
Initial solution
20
VAM
580ml
Allyl chloride
5.0ml
Methanol
20ml
AIBN solution
24 ml (as a 0.2M solution in toluene)
The ingredients were heated at 60°C under nitrogen with continuous stirring in a 1 litre
flask for 5 hours. After 1.5 hours (2ml) and 3 hours (2ml) additional aliquots of allyl
chloride were added. At the end of the 5 hour period methanol (300ml) was added and the
25
mixture heated under reduced pressure (8mbar.) Methanol/VAM azeotrope followed by
methanol was distilled from the mixture to leave 253g of a white polymer after isolation by
precipitation into water and drying under vacuum at 60°C.
Case 00269(2)
16
Production of polyvinyl acetate 8 (invention)
Initial solution
5
VAM
725ml
Allyl chloride)
4.6ml
Methanol
25ml
Propanal
2.5ml
AIBN solution
13 ml (as a 0.2M solution in toluene)
The ingredients were heated at 60°C, under nitrogen with continuous stirring in a 1 litre
flask for 7.8 hours. After 2 hours (1.6ml), 4 hours (1.3ml), 5.5 hours (1.0ml) and 7 hours
10
(1.0ml) additional doses of allyl chloride were added. At the end of the 7.8 hour period
methanol (400ml) was added and the mixture heated under reduced pressure (8mbar.)
Methanol/VAM azeotrope followed by methanol was distilled from the mixture to leave
387g of a white polymer, after isolation by precipitation into water and drying under
vacuum at 60°C.
15
20
Production of polyvinyl acetate 9 (invention)
VAM
1160ml
CCl4
4.0ml
Methanol
36ml
AIBN solution
12 ml (as a 0.2M solution in toluene)
The ingredients were heated at 60°C under nitrogen with continuous stirring in a 1 litre
flask for 5.7 hours. At the end of this period methanol (600ml) was added and the mixture
heated under reduced pressure (8mbar.) Methanol/VAM azeotrope followed by methanol
was distilled from the mixture to leave 489g of a white polymer after isolation by
precipitation into water and drying under vacuum at 60°C. After hydrolysis and initial
25
drying to remove the bulk of the solvent (>95%,) the sample was dried at 130°C for 5
hours under air.
Case 00269(2)
17
Production of polyvinyl acetate 10 (invention)
5
VAM
1160ml
CCl4
4.0ml
Methanol
36ml
AIBN solution
12 ml (as a 0.2M solution in toluene)
The ingredients were heated at 60°C under nitrogen with continuous stirring in a 1 litre
flask for 8 hours. After 3 hours (1ml) and 5 hours (1ml), additional doses of CCl4 were
added. At the end of this period methanol (600ml) was added and the mixture heated under
reduced pressure (8mbar.) Methanol/VAM azeotrope followed by methanol was distilled
10
from the mixture to leave 422g of a white polymer after isolation by precipitation into
water and drying under vacuum at 60°C. After hydrolysis and initial drying to remove the
bulk of the solvent (>95%,) the sample was dried at 130°C for 3 hours under an
atmosphere of 20vol% steam in nitrogen.
15
Production of polyvinyl acetate 11 (invention)
Initial solution
20
VAM
580ml
C2Cl6
5.0g
Methanol
20ml
AIBN solution
6 ml (as a 0.2M solution in toluene)
The ingredients were heated at 60°C under nitrogen with continuous stirring in a 1 litre
flask for 8 hours. After 4 hours, an additional 1g of C2Cl6 was added, dissolved in 8ml of
VAM. At the end of the 8 hour period methanol (300ml) was added and the mixture
heated under reduced pressure (8mbar.) Methanol/VAM azeotrope followed by methanol
25
was distilled from the mixture to leave 262g of a white polymer after isolation by
precipitation into water and drying under vacuum at 60°C.
Case 00269(2)
18
Production of polyvinyl acetate 12 (comparative)
5
VAM
580ml
HCCl3
84ml
Methanol
20ml
AIBN solution
6 ml (as a 0.2M solution in toluene)
The ingredients were heated at 60°C under nitrogen with continuous stirring in a 1 litre
flask for 7 hours. At the end of this period methanol (300ml) was added and the mixture
heated under reduced pressure (8mbar.) Methanol/VAM azeotrope followed by methanol
was distilled from the mixture to leave 295g of a white polymer after isolation by
10
precipitation into water and drying under vacuum at 60°C.
Production of polyvinyl acetate 13 (comparative)
Stirred solution
15
Pumped solution
VAM
173ml
240ml
Methanol
347ml
---
Allylidene diacetate 4.2ml
AIBN solution
11.7ml
12ml (as a 0.2M solution in toluene)
The ingredients in the stirred solution were heated at 60°C under nitrogen with continuous
stirring in a 1 litre flask for 7.8 hours. During that period, some of the pumped solution
(containing VAM and allylidene diacetate) was added continuously at a rate of 22 ml/hr
20
using an HPLC pump. Not all of the solution was added. At the end of this period the
mixture was heated under reduced pressure (8mbar) to remove methanol/VAM azeotrope
followed by methanol to leave 147g of a white polymer after isolation by precipitation into
water and drying under vacuum at 60°C.
25
Case 00269(2)
19
Production of polyvinyl acetates 14 (invention)
Stirred solution
5
Pumped solution
VAM
880ml
480ml
Methanol
36ml
---
Allylidene diacetate 8ml
8ml
Carbon tetrachloride 4ml
0.5ml
AIBN solution
12ml (as a 0.2M solution in toluene)
The ingredients in the stirred solution were heated at 60°C under nitrogen with continuous
stirring in a 2 litre flask for 6.2 hours. During that period, the pumped solution (containing
10
VAM, allylidene diacetate and carbon tetrachloride) was added continuously at a rate of 90
ml/hr using an HPLC pump until all the feed had been added (5.5 hours) and the reaction
was then allowed to continue. At the end of this period the mixture heated under reduced
pressure (8mbar) to remove much of the VAM. After this, methanol 300ml was added and
methanol/VAM azeotrope followed by methanol was distilled from the mixture to leave
15
483g of a white polymer after isolation by precipitation into water and drying under
vacuum at 60°C.
Production of polyvinyl acetate 15 (invention)
VAM
20
145ml
1-Chloro-but-2-ene* 3.0ml
Methanol
5ml
AIBN solution
3ml (as a 0.2M solution in toluene)
* This material was used as received from Sigma Aldrich as was stated as being
25
“predominately” the E isomer.
The ingredients were heated at 60°C under nitrogen with continuous stirring in a 250 ml
flask for 7.5 hours. After 4 hours an additional 0.5ml of 1-chloro-but-2-ene was added. At
the end of the 7.5 hour period methanol (100ml) was added and the mixture heated under
Case 00269(2)
20
reduced pressure (8mbar). Methanol/VAM azeotrope followed by methanol was distilled
from the mixture to leave 34g of a white polymer, after isolation by precipitation into water
and drying under vacuum at 60°C.
Production of polyvinyl acetate 16 (invention)
5
VAM
580ml
Allyl chloride
5.0ml
Methanol
20ml
AIBN solution
24 ml (as a 0.2M solution in toluene)
The ingredients were heated at 60°C under nitrogen with continuous stirring in a 1 litre
10
flask for 5 hours. After 1.5 hours (2ml) and 3 hours (2ml) additional aliquots of allyl
chloride were added. At the end of the 5 hour period methanol (300ml) was added and the
mixture heated under reduced pressure (8mbar.) Methanol/VAM azeotrope followed by
methanol was distilled from the mixture to leave 253g of a white polymer, after isolation
by precipitation into water and drying under vacuum at 60°C.
15
Preparation of polyvinyl acetate 17 (invention)
Initial solution
20
Pumped solution
VAM
725ml
150ml
Dicyclopentadiene
2.5g
7.5g
Methanol
25ml
Propanal
16ml
AIBN solution
15 ml (as a 0.2M solution in toluene)
The ingredients in the stirred solution were heated at 60°C under nitrogen with continuous
stirring in a 1 litre flask for 4 hours. During that period, the pumped solution (containing
5wt% dicyclopentadiene dissolved in VAM) was added continuously at a rate of 33 ml/hr
25
using an HPLC pump for the duration of the polymerisation. Not all of the solution was
added. At the end of this period the mixture heated under reduced pressure (8mbar) to
remove much of the VAM. After this, methanol (300ml) was added and methanol/VAM
azeotrope followed by methanol was distilled from the mixture to leave 362g of a white
polymer after isolation by precipitation into water and drying under vacuum at 60°C.
Case 00269(2)
21
Preparation of polyvinyl acetate 18 (invention)
Initial solution
5
Pumped solution
VAM
725ml
143ml
Ethylidene norbornene
2.5ml
7.5ml
Methanol
25ml
Propanal
16ml
AIBN solution
15 ml (as a 0.2M solution in toluene)
The ingredients in the stirred solution were heated at 60°C under nitrogen with continuous
10
stirring in a 1 litre flask for 4 hours. During that period, the pumped solution (containing
5wt% ethylidene norbornene mixed in VAM) was added continuously at a rate of 30 ml/hr
using an HPLC pump for the duration of the polymerisation. . Not all of the solution was
added. At the end of this period the mixture was heated under reduced pressure (8mbar) to
remove much of the VAM. After this, methanol 300ml was added and methanol/VAM
15
azeotrope followed by methanol was distilled from the mixture to leave 386g of a white
polymer after isolation by precipitation into water and drying under vacuum at 60°C.
Hydrolysis of polyvinyl acetate
To 144g of the white polymer, (polyvinyl acetate) dissolved in 580g of anhydrous THF
was added a 16.5ml aliquot of methanol. This solution was allowed to warm to 30°C with
20
stirring for at least 2 hours until the polymer had fully dissolved. The temperature was
maintained at 30°C (using a water bath) whilst adding a solution of 4g of sodium
methoxide in 36g of methanol and this was stirred rapidly for 3 minutes to mix the
solutions thoroughly. Stirring was allowed to continue for a further 2 hours, whereupon the
solid gel was chopped with a hand-held blender (whilst in the solution) and a solution of
25
acetic acid in methyl acetate was added in excess (relative to the sodium methoxide) to
stop the reaction. After 30 minutes, the hardened gel was filtered from the supernatant
liquid. The product was then dried at 60°C under vacuum.
The produced partially hydrolysed polyvinyl acetate was characterized by measuring the
UV absorbance at 215, 280 and 320nm of a 0.2wt% aqueous solution. The content of
Case 00269(2)
22
ethylenic unsaturation was calculated by determining the unsaturation level of the polymer
using the revised procedure of ASTM D1959-97 hereinbefore described. Yellow Index was
determined for all samples using a Data Colour Microflash instrument with a powder
loaded cell according to Japanese Standard JIS K 7105 (1981). All samples were below 40,
5
except samples 9, 10, 11 and 14 which were typically around 50. The results obtained and
the corresponding values determined for synthesised polymers are shown in Table 1.
Preparation of PVC
A solution of polyvinyl acetate primary granulating agent was made up as a 4wt% PVA
solution in water. Similarly a solution of another primary agent of 88% degree of
10
hydrolysis (PVA 88%) was also made up as a 4wt% solution in water.
To a 160 litre autoclave containing 70 litres of demineralised water at 20°C was added
550g of 4wt% primary granulating agent solution. To this was added 165g of a 4wt% of a
known PVA 88% solution (PA7) and 83g of a commercially available secondary
suspending agent with a degree of hydrolysis between 45 and 66% (PVA55% Mw=113k.)
15
This was stirred, evacuated to remove air and heated, before charging with 44kg of vinyl
chloride monomer and 40g of di-2-ethylhexylperoxy-dicarbonate suspension (60% in
water.) The reaction mixture was heated at 58°C for 6 hours to allow the reaction to
complete. After cooling and evacuation to remove the remaining vinyl chloride monomer,
the polymer suspension was centrifuged and dried to give a white polymer which was then
20
tested for mean grain size on a Beckman Coulter LS230 Particle size analyzer instrument.
The results obtained with a range of primary granulating agents are shown in Table 1. In
the Table pDi is the ratio of Mw/Mn, DOH is degree of hydrolysis in mol%, unsaturation is
in µmoles of ethylenic unsaturation per gram and MGS is mean grain size in µm.
Case 00269(2)
23
Table 1
Poly
CTA (constant)
Co-monomer
pDi
Mn
280nm
320nm
Blockiness DOH
Unsaturation
MGS
1†
Methanol (0.0006)
---
2.1
45k
0.08
0.04
0.37
72.7
25
>500
2†
Propionaldehyde
---
2.0
47k
0.2
0.08
0.38
70.6
15
276
mer
(0.1)
3†
Ex Aldrich
---
2.5
32k
0.54
0.22
0.38
70.5
25
192
4†
Methanol (0.0006)
Allyl acetate
1.9
43k
0.1
0.06
0.38
73.8
15
>500
5
Allyl chloride (0.31)
Allyl chloride
2.3
39k
0.09
0.05
0.38
72.7
56
164
6
Allyl chloride (0.31)
Allyl chloride
2.1
27k
0.08
0.06
0.38
70.3
78
158
7
Allyl chloride (0.31)
Allyl chloride
2.0
22k
0.05
0.03
0.38
71.8
110
133
8
Allyl chloride (0.31)
Allyl chloride
1.8
38k
0.11
0.04
0.38
75.6
66
174
Propionaldehyde
(0.1)
9
CCl4 (0.96)
---
4.5
38k
0.94
0.64
0.38
70.9
77
146
10
CCl4 (0.96)
---
2
29k
1.0
1.40
0.38
69.6
104
155
11
C2Cl6 (1.0)
---
1.9
34k
0.78
0.88
0.37
71.2
79
---
12†
CCl3H (0.015)
---
1.9
23k
0.18
0.16
0.37
75.7
18
>500
13†
Methanol (0.0006)
Allylidenediaceta 2.1
40k
0.2
0.14
0.38
72.3
35
212
Case 00269(2)
24
te
14
CCl4 (0.96)
Allylidenediaceta 3.9
34k
0.94
0.7
0.38
70.4
74
151
te
15
1-Cl-2-butene (0.3)
1-Cl-2-butene
1.8
33k
0.17
0.12
0.38
80.7
68
---
16
3-Cl-2-
3-Cl-2-
1.9
50k
0.07
0.04
0.38
71.4
97
148
methylpropene (0.3)
methylpropene
Propionaldehyde
Dicyclopentadien 1.9
65k
0.19
0.08
0.38
76.0
112
---
(0.1)
e
Propionaldehyde
Ethylidene
57k
0.2
0.07
0.38
69.1
100
---
(0.1)
norbornene
17
18
† Indicates comparative example.
2.0
Case 00269(2)
25
From the table there is a range of different polymers presented with varying properties.
Provided that the polymers have a consistent degree of hydrolysis and also a consistent
block factor in the range of 0.3 to 0.8 especially 0.30-0.45, the dispersion efficiency of
polymers can be compared according to the mean grain size. The lower the value of the
5
mean grain size, the better the material performs. As can be seen, the unsaturation level is
substantially in agreement with this MGS value, with high values of unsaturation being a
good predictor of the ultimate performance and with values over 53 such as 54 or more
being found for polymers which provide, for this recipe, a mean grain size below 160
micron. It will further be apparent to the skilled worker for example by review of examples
10
9 and 10 that there may be an inverse relation between the molecular weight of a polymer
of the invention and its degree of unsaturation. It will still further be apparent to the skilled
worker for example by comparison of examples 5, 6 and 7 that using unsaturated organic
halides with a chain transfer constant in the claimed range as both a chain transfer agent
and as a co-monomer can give rise to enhanced performance compared to using the
15
material as a chain transfer agent alone. The results further demonstrate that chain transfer
agents and co-monomers can be combined in any combination. The effects of comonomers and unsaturation are believed to operate independently. Such combinations
could include ethylene co-monomer with carbon tetrachloride, or itaconic acid and allyl
chloride or methallyl chloride. Other combinations such as maleic or fumaric acids as co-
20
monomers with allyl chloride or methallyl chloride or allylidene diacetate with allyl
chloride could also be used. Alternatively, halide containing chain transfer agents such as
(meth)allyl chloride and carbon tetrachloride can be substituted where conventionally an
aldehyde such as acetaldehyde or butraldehyde, or a mercaptan may have been used.
25
Case 00269(2)
26
Claims
1.
A partially hydrolysed polyvinyl acetate polymer or copolymer having a degree of
hydrolysis in the range 65 to 95% and at least 53µmoles preferably at least 54µmoles of
5
ethylenic unsaturation per gram of polymer.
2.
A partially hydrolysed polymer or copolymer as claimed in claim 1 wherein the
molecular mass Mn of the polymer or copolymer is in the range 10 000 to 100 000 such as
15 000 to 50 000, preferably 17 000 to 40 000.
10
3.
A partially hydrolysed copolymer as claimed in claim 1 or claim 2 wherein the co-
polymer comprises no more than 5wt% preferably no more than 2wt% of the comonomer.
4.
15
A partially hydrolysed polyvinyl acetate copolymer as claimed in claim 1 wherein a
co-monomer has allyl functionality preferably wherein the allyl group containing comonomer is of structural formula I
R2R3C=CR1CR4R5X
20
I
where X is selected from Cl, Br, OR6 and CO2R7
R1, R2, R3, R6 and R7 are independently selected from H and C1-6 straight chain or
25
branched alkyl, and CO2R8 where R8 is selected from H and C1-6 straight chain or
branched alkyl and
R4 and R5 are independently selected from H, C1-6 straight chain or branched alkyl, OC16 straight chain or branched alkyl or where R4 and R5 taken together are =O or
30
Case 00269(2)
27
where X is H or C1-6 straight chain or branched alkyl, R1, R2 and R3 are as hereinbefore
defined and R4 and R5 are independently -OR9 or –OOCR10 where R9 and R10 are
independently selected from C1-6 straight chain or branched alkyl.
5
5.
A partially hydrolysed polyvinyl acetate copolymer as claimed in claim 1 wherein a
co-monomer has olefin functionality preferably selected from vinyl norbornene, ethylidene
norbornene, norbornadiene, dicyclopentadiene, 1,5 cyclooctadiene, tetrahydroindenes, 1,4
hexadiene and 1,4 pentadiene.
10
6.
A partially hydrolysed polyvinyl acetate copolymer as claimed in claim 1 wherein a
co-monomer has acryl functionality preferably selected from monomers of structural
formula II
R11R12C=CR13COZ
15
II
where R11, R12 and R13 are independently selected from H, C1-6 straight chain or
branched alkyl OC1-6 straight chain or branched alkyl and
20
Z is OH, OR14 or NR14R15 where R14 and R15 are independently selected from H and
C18 straight chain or branched alkyl or aromatic groups.
7.
A partially hydrolysed polyvinyl acetate polymer or copolymer having a molecular
mass Mn in the range 10 000 to 100 000, a degree of hydrolysis in the range 65 to 95%, at
25
least 40 µmoles of ethylenic unsaturation per gram of polymer and a polydispersity index
less than 2.3.
8.
The use of a polymer or copolymer as claimed in any one of the preceding claims
as a primary granulating agent in the polymerization of VCM.
30
9.
A method of preparing PVC comprising polymerizing VCM in the presence of a
polymer or copolymer as claimed in any one of claims 1 to 7.
Case 00269(2)
5
28
10.
PVC obtainable by a process as claimed in claim 8.
11.
A method of preparing a polymer as claimed in any one of claims 1 to 7 comprising
reacting VAM and optionally a co-monomer in the presence of a chlorine or bromine
containing chain transfer agent having a polyvinyl acetate polymerization chain transfer
value in the range 0.01 to 5, preferably 0.2 to 3 more preferably 0.25 to 1.2, and subjecting
the resulting material to partial hydrolysis.
10
12.
A method as claimed in claim 11 wherein the chlorine or bromine containing chain
transfer agent is at least one of carbon tetrachloride, chloral, ethylidene bromide,
hexachloroethane, trichloroacetaldehyde, E-1-chloro-butene, Z-1-chloro-butene, E-1chloro-but-2ene, Z-1-chlorobut-2-ene, 2-chlorobut-1-ene, 3-chlorobut-1-ene, E-3chlorobut-2-ene, Z-3-chlorobut-2-ene, 1-chloro-2-methylpropene, 3-chloro-215
methylpropene-, vinyl bromide, allyl chloride and ethyl dichloroacetate.
13.
A method of preparing a polymer as claimed in any one of claims 10 to 12
comprising polymerizing VAM in the presence of an allyl group containing co-monomer.
20
14.
A method as claimed in claim 13 wherein the allyl group containing co-monomer is
of structural formula I
where X is selected from Cl, Br, OR6 and CO2R7
25
R1, R2, R3, R6 and R7 are independently selected from H and C1-6 straight chain or
branched alkyl, and CO2R8 where R8 is selected from H and C1-6 straight chain or
branched alkyl and
R4 and R5 are independently selected from H, C1-6 straight chain or branched alkyl or
30
where R4 and R5 taken together are =O or
Case 00269(2)
29
where X is OH or C1 to C6 straight chain or branched alkyl, R1, R2 and R3 are as
hereinbefore defined and R4 and R5 are independently -OR9 or –OOCR10 where R9 and
R10 are independently selected from C1 to C6 straight chain or branched alkyl or are
aromatic groups.
5
15.
A method as claimed in claim 14 wherein the allyl group containing monomer is
selected from one or more of allyl acetate, allyl chloride and allylidene diacetate.
16.
10
The use of a partially hydrolysed polyvinyl acetate polymer or copolymer as a
dispersion stabilizer in suspension polymerization of a vinyl compound, the polymer or
copolymer being characterised by the ratio of absorbance at 280nm of a 0.2wt% aqueous
solution of the vinyl alcohol polymer to the absorbance at 320nm of a 0.2wt% aqueous
solution of the vinyl alcohol polymer is more than 0.7 at 30°C and a Yellow Index of 40 or
lower according to JIS K 7105 (1981) as measured on a dry powder, the absorbance being
15
measured with an optical path length of 1cm.
17.
The use of a partially hydrolysed polyvinyl acetate polymer or copolymer as a
dispersion stabilizer in suspension polymerization of a vinyl compound, the polymer or
copolymer being characterised by the absorbance at 280nm being no more than 0.36 and
20
the absorbance at 320nm being no more than 0.36 the absorbance being measured of a
0.2wt% aqueous solution at 30C with an optical path length of 1cm.
18.
A use as claimed in claim 17 wherein the absorbance at 280nm is no more than 0.2
preferably no more than 0.1.
25
19.
A use as claimed in claim 17 or claim 18 wherein the absorbance at 320nm is no
more than 0.15 preferably no more than 0.1.
Case 00269(2)
30
ABSTRACT
VINYL ACETATE POLYMERS METHODS OF MAKING THEM
AND USES THEREOF
5
The invention provides partially hydrolysed vinyl acetate polymers with a high degree of
ethylenic unsaturation which can be introduced by polymerizing VAM in the presence of
chlorine or bromine containing chain transfer agents and then partially hydrolysing the
resulting material. The product is especially useful as a primary suspension agent in the
10
15
production of PVC.