CA1111182A - Process for improving the properties of pulverulent polyvinyl chloride - Google Patents

Abstract

Abstract of the disclosure:
A dry powder of a vinyl chloride homo-, co- or graft-poly-mer is heated up to 75 - 120° C during from 10 to about 360 minu-tes in the presence of an organic, aliphatic compound having two hydroxyl groups and from 2 to 24 carbon atoms.

Description

The invention relates to a process for improvin~ the properties o~ pulverulent vinyl chloride polymer~, in which the polymer is sub~ected to heat treatment at 75 to 120a for 10 to approximately 360 minutes in the presence of an organic aliphatic compound having 2 OH groups and 2 to 24 carbon atoms.
As a re~ult of recent investigations lnto damaging physiolo-gical actions o~ monomeric vinyl chloride that may possibly occur, it l~ desirable to obtain from this monomer polymers that have a substantially lower content oi monomeric ~inyl chloride (VC) than was customary h:Ltherto.
In the known indu~trial ma~ufacturing proces~es o~ polyvinyl chloride and of it~ oopolymers and graft polymers with other mono-mers or polymers, which contain a predominant proportion of poly-merlsed vinyl chloride, at the end o~ the polymerisation process and arter releasing the reaction mixture pressure a product is obtained which contains up to 3 ~ by weight oi unreacted vinyl ~ ~ ohl~ride.
:~' ~ ' ' ' ' ' : ' . , 2 -.- .- . - - : , ~ 8 2 If the reaction products of the emulsion or the suspension polymerisation are in the form of a dispersion o~ the polymer in water, the residual monomer content can be reduced by treating with steam or heated inert gases. Various processes are known f,or this~ In some processes the aqueous dispersion is intimately mixed with the steam simply be conveying the two together in a tube or by spraying the dispersion in a steam atmosphere and after a relatively short or long contact time, this mixture, optionally with additional heating through the container walls, is separated again into the gaseous phase containing monomer and into an aqueous polymer dispersion having a reduced monomer contentO It is also known to remove the monomer content b~ pa~sing water vapor in countercurrent to the aqueous polymer dispersion in a column or to treat the dispersion with inert gas in a pipe evaporator.
It is ~urthermore known to remove residual monomer ~rom aqueous dispersions o~ vinyl chloride polymers by vaporising certain quantities o~ water for at least 15 minutes at 150 to 650 torr, In a ~urther known process slurrie~ or latices of ~inyl chlorlde polymers are either heated to temperature~ o~ 70 to 125~ or brought into contact with at least one organic liquid at bmperatures o~ 25 to 125C and the monomer removed ~rom the slurrie~.
It i8 also known to remove residual monomers by treating with steam moist vinyl chloride polymerisation product from emulsion or suspension polymerisation.

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All these processes are concerned with mixtures of polymer and water either in the form of aqueous dispersions, in which the proportion of water is greater than the proportion of polymer, or in the form of moist products, as produced by decanting aqueous polymerisation products of suspension polymerisation a~d possessing, - generally, a water content of 15 to 35 /~ by weight.
Some of the processes mentioned require considerable expen-diture on apparatus. In the case of t~e short process (duration of treatment a few seconds to a few minutes) the monomer removal effect is generally inadequate. In so far as it concerns the degassing of aqueous disparsions, difficulties may arise as a result of foaming, either neces~itating additional expenditure on apparatus or the addition of special agents which increase the co~ts and may also influence the end product in an unde`sirable manner. All of the processes mentioned require a relatively large amount of energy since, in some cases, apart from the polymer, considerable quantities o~ water must be heated or evaporated.
They are furthermore not very well suited to polymers that are - produced without water, for example according to the buIk or gas phase polymerisation proces~
To remove re~idual monomers ~rom dry vinyl chloride polymers, namely those that have been obtained according to the bulk or gas phase polymerisation prooess, a process is known in which water vapor is ¢ondensed onto the dry polymers and, after this conden~ed water has acted for some time, it is evaporated again by the action o~ heat. As a result of the addition of water by means of condensa-tion an important advantage of the so-called "dry" polymerisation pro-cess, that is,-being able to dispense with ~eparating the water by ~iltration and/or drying, i~ lost. In addition, i~ is clear that onl~

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polymers havin~ a residual monomer content of above 0.01 % by weight of vinyl chloride can be produced according to this pro-cess and these do not meet the recent ideas put forward for a physiologically tolerable polyvinyl chloride (at most 0~001 by weight of residual vinyl chloride or less~.
A process has now been ~ound for reducing to a very low level the residual contents of monomeric vinyl chloride in æubstan-tially dry vinyl chloride polymers with~ut the above mentioned disadvantages.
This is a process for improving the properties of homo-, co- or gra~t polymers that contain at least 50 ~0 by weight of polymerised vinyl chloride units, in which after removing the main quantity o~ unreacted monomer or monomers and, if present, water, the polymers, in a pulverulent ~tate and at atmospheric pressure or reduced pressure, are subjected to a heat treatment,characterized in that the heat treatment is carried out for 10 to approximately 360 minute~ at 75 to 120C in the pre~ence o~ 0.01 to 5 ~ by weight (calculated on the polymer) of at least one aliphatic, ~aturated or unsaturated, branched or unbranched aompound t~t contains 2 iree hydroxyl groups and 2 to approx~mately 24 carbon atoms and that, in the oase o~ 4 or more carbon atoms, may also contain at least one C-0-C groupO
~ he removal of the main quantity of the unreacted monomer or monomers is darried out according to known processes by relieving the pressure o~ the polymeri~ation mixture. If the polymer has been pr~oduced by bulk or gas phase polymerisation and is already dry, it is generally subsequently evacuated. The vacuum is then removed with inert gas. I~ the polymer has been produced in aqueo~s ~ 5 ~
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~u~pension, after relieving the pressure of the polymerisation mix-ture the sepa~ation of the water i~ carried out, ~or eY.ample, by decanting and drying in an air current. In all case~ a pulverulent polymer is obtained which generally still contain~ 1 to 0.1 ~ by weight of residual monomer(s).
The subsequent heattreatment can be carried out under atmos-pheric pressure or reduced pressure. It is advantageously carried out at 50 to 760 torr, especially at atmospheric pressure. The heat treatment is carried out for 10 to approximately 360 minutes at temperatures o~ 75 to 120C. During the course of this one or more inert gases such as air, nitrogen and steam ~or mixtures of at least two of the gases air, nitroxen and steam are advanta-geouslg passed through the ~essel in which the treatment ls carried out. ~ir, especially i8 u~ed.
The concentration o~ the monomeric vinyl chloride in the polymer decreases as the temperature and the duration of the treatment increase.
If the duration of the treatment is less than 10 minutes then the re~idual monomer content achieved is generally not ~ufficiently low.
With higher temperatures and longer treatment time~ unde~irable dis-colouring o~ the polymer increa~e~. Thi~ make~ polymer~ o~ this type strlkingly unattractive, particularly in thermopla~tic processing, because only moulded articles with discoloration~ can be produced.
In the ab~ence of compounds having 2 iree OH groups and 2 to appro-ximately 24 carbon atoms, used in accordance with the in~ention, such d1scolouration8 occur prematurely and, as a result, extensive removal of the reeidual monomer is possible either only im~erfectly or only by accepting undesired discoloration. If the heat treatment i~ carried out in the pre~se~ce o~ the above mentioned compound~ it is possible to increase the treatment time and temperature.

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Above 120C temperature and above ~60 minutes treatment time theprocess according to the invention offers no further advantages in practice, since beyond these conditions the particle varia-tions are too pronounced and discoloration occurs. Particularly good results are obtained if the treatment is carried out at 80 to 100~ .
Advantageously the heat treatment is carried out in such a manner that the product of treatment temperature (C) and treatment time (hours) is 25 to 350 (a . h) and especially 50 to 260 (C 0 h)~
~he heat treatment is carried out in the presence of 0.01 -to 5 ~ by weight (calculat~d on dry polymer) of at least one aliphatic saturated or unsaturated, branched or unbranched compound having 2 free hydroxyl ~roups and 2 to 24 carbon atoms, which in the case of 4 or more carbon atoms may also contain at least one C-0-C group.
Below 0.01 % by weight the aetion of the compounds i~ no longer observed; above 5 ~o by weight addition, the disadv~ntages of such 'Sadaitions as a result of a deterioration in the pourability of the polym~r ~Fxx~ler, reduction m the thermal stability under load and transparency of the moulded articles produced ~rom the polymer, as well as adhesion to the part~ oi the pro¢e~sing machine, outwei~h the advantagesO
Advantageously, 0.2 to 2 ~ by weight and especially 0.5 to 1.5 ,' by weight (calculated on dry polymer) are used.
~he sAid compounds may be added to the reaction mixture before or during the polymerisation of the vinyl chloride or may be added, after polymerisation, to the finished polymer before the heat treat-mentO ~or the purpose of better distribution in the finished polymer the compound~ may be added diluted with, or dissolved in, readily ....
volatile solvents, for example water.

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Too ~re~t a dilution with water should be avoided, since in the presence of relatively large amounts of water, commencing at approximately 5 ~ by weight o~ water calculated on the dry pol~ymer, the effect according to the invention decreases and discoloration occurs increasingly the higher the quanti~y of water.
The compounds to be used in accordance with -the invention may contain C-0-C bonds, that is ether-oxygen bridges. Good results are obtained with compounds of the formula X
H0 (CH2 - CH ~ )n H

in which X = H and/or CH~-n = 1 to 12.

Diglycol or triglycol or a mixture o~ diglycol and triglycol are especially suitable for the heat treatment according to the invention.
Apart from these aliphatic saturated compounds with ether-oxygen bridges good results are also obtained if the heat treatment ~s carried out in the ~resence of aliphatic, saturated or unsatursted, branched or unbranched compounds having 2 free hydroxyl groups and 3 to 12 carbon atoms that do not contain ether-oxygen bridges.

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There may be mentioned as examples of such compounds: l,3-pro-panediol; 1,4-butanediol; l,6-hexanediol; 1,5-pentanediol;

2,5-hexanediol; 1,10-decanediol. Particularly good results are obtained with 2-butene-1,4-diol.
Of the subst~nces to be used in accordance with the invention it is possible to employ one individually or mi~tures of several of these substances.
The addition of these substances before or during polymerisa-tion does not noticeably alter the quality or the rlatt~e of the particles of the polymer produced; al~ substances that are advant-ageously used and are cu~tomary in polymerisation may be used together with the sub~tances to be used in accordance with the invention, Dry vinyl chloride homo-, co- or graft polymers that contain at least 50 % by weight of polymerised vinyl chloride units and have been produced according to the emulsion or suspension polymeri-sation process, are suitable for the treætment according to the inven-tion, The polymers preferably used are those that have been produced in the gas phase and especially those produced by bulk polymerisation at temperatures of 30 to 85C. All the polymerisation processe~
mentioned may be carried out continuously or in batches Vinyl chloride homo- or copolymers with a content of at least 80 ~ by weight (calculated on total polymer) of polymerised vinyl chloride, especially homopolymers with a content of at least 98 70 by weight (calculated on total polymer) o~ polymerised vinyl chloride, ~re especiall~ suitable.
One or more of the following monomers are suitable for copoly-merisation wit~ vinyl chloride, for example: olefins such as ethylene or propylene; vinyl esters of s-traight-chained or branched carboxylic :.
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" -' . ~ ~ ' , acids having 2 to 20, preferably 2 to 4 carbon atoms, such as vinylacetate, vinylpropionate, vinylbutyrate, vinyl-2-ethylhexoate, vinylisotridecanoic acid esters; vinyl halide~, such as vinyl fluoride, vinylidene fluoride, virylidene chloride, vinyl ether, vinyl pyridine; unsaturated acids, such as maleic, fumaric, acrylic, and methacrylic acids and their mono or diesters with mono or dialco-hols having 1 to 10 carbon atoms; maleic acid anhydride; maleic acid imide and its N-substitution products with aromatic, cycloaliphatic and optionally branched, aliphatic substituents; acrylonitrile and styrene.
There may be used ~or gra~t polymerisation, for example, elastomeric polymers that have been obtained by the polymerisation of one or more o~ the ~ollowing monomers: dienes, such as butadiene and cy¢lopentadiene; olefins, such as ethylene and propylene;
unsaturated acids, ~uch as acrylic or methacrylic acid and the esters of such acids with mono or dialcohols having 1 to 10 carbon atoms; styrene; acrylonitrile; vinyl compounds, such as vinyl esters of straight-chained or branched carboxylic acids having 2 to 20, pre~erably 2 to 4, carbon atoms; vinyl halides, such as vinyl ¢hloride and vinylidene ohloride.
~ he polymeri~ation can be carried out with or without a seed polymer in the presence of 0.001 to ~ ~o by weight, preferably 0.01 to 0.3 % by weight, calculated on the monomers, of radical-forming catalysts, such as, ~or example, diargl and diacyl peroxides, such as diacetyl, acetylbenzoyl, dilauroyl, dibenzoyl, bis-2,4-dichloro-benzoyl and bis-2-methylbenzoyl peroxides; dialkyl peroxides, such 88 di-tert.-butyl peroxidR; peresters, such as tert.-butyl percar-bonate; tert.-butyl peracetate, tert.-butyl peroctanoate, tert.-butyl perpivalate; dialkyl peroxidicarbonatesS such as diisopropyl, : :

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diethylhexyl, dicyclohex~l and ~iethylcyclohexyl peroxidicarbonates;
mixed anhydrides of organic sulfo peracids and organic acids, such as acetylcyclohexylsulfonyl peroxide; azo compounds known as poly-merisation catalysts, such as a~oisobutyric acid nitrile; for the polymerisation using aqueous phases it is furthermore possible to use in addition to the above mentioned catalysts, peroxydisulfates, peroxydiphosphates, or perborates of potassiumJ sodium or ammonium, hydrogen peroxide, tert.-butyl hydroperoxide or other water-soluble peroxidesS as well as mixtures of various catalysts, wherein peroxlde catalysts may be used also in the presence o~ 0.01 to 1 ~ by weight, calculated on the monomers, of one or more reducing sub~tances that are suitable for making up a redox catalyst system, such as, ~or example, sulfites, bisulfites, dithionites, thiosulfates, al~ehyde sulfoxylate such as, for example, sodium formaldehyde sulfoxy-late. Optionally, the polymerisation may be carried out in the presence of 0.05 to 10 parts of metal per million parts of monomer, of readily 3eluble or sparingly soluble metal salts, for example, of copper, silver, iron or chromium.
Molecular weight regulators may be added be~ore or durinæ
polymer;isation: such a~, ~or example, aliphatic aldehydes having 2 to 4 carbon atoms, chlorohydrocarbons or bromohydrocarbons such a~, for example, dichloroethylene and trichloroethylene, chlorofcr~t bromoform, methylene chloride and mercaptans; also other polymerisa-tion au2iliarie~Q, such as anitoxidants, for example, 2,6-di-tert.-butyl-4-methylphenol , trisnonylphenyl phosphite, other additives, such as epoxidised oils, for example, soya bean oil; fatty alcohols or fatty acid esters or au2iliaries for further processing of the polymer, such as, for example, known lubricants, waxes, heat and light stabilizers, plasticizers and pigments. The last-mentioned ' , .' ',, . ~ .:
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auxiliaries for further processing may alternatively be added at the end of the polymerisation process, optionally in a dissolved, molten or dispersed state.
If polymerisation is carried out using an aqueous liquor, this may contain 0.01 to 1 5~ by weight, preferably 0.05 to 0.3 5 by weight, calculated on the monomers, of one or more protective -colloids such as, for example, polyvinyl alcohol optionally containing - --_ _ .. . . . .. . . . . . . .. .. . .. . . . . . . . . . . . . . . . .. . . .. . . .
up to 70 mole % of acetyl groups; cellulose derivatives, such as water-soluble methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, mixed cellulose ~hers, for example methylhydroxypropyl cellulose; as well as gelatin, and also co-polymers of maleic acid or the semi-esters thereof and styrenes.
Polymerisation in a(lueous liquor can furthermore be carried out in the presence of 0.01 to 5 ~o by weight, calculated on the monomers, of one or more emulsifiers, wherein the emulsifiers are - introduced in admixture with the above-mentioned protective colloid.s.
It is possible to use anionic, amphoteric, cationic and non-ionic emulsifiers. Suitahle anionic emul~ifiers are, for example, alkali.metal salts, a~kaline ea~th metal salts and amm~nium salts of fatty ZO acids, such as lauric acid, palrnitic acid or steario aoid, of acid fatty alcohol sulfuric acid esters, of paraffinsu.lfo acids, of alkylarylsulfo acids, such as dodecylbenzenes~fo acid or dibutyl-naphthalenesulfo acid, of sulfosuccinic acid dialkyl ester~, and the alkali r~tal and amnoniurnsalts of epoxy group-containLng fatty acids, such as epoxystearic acid, of reaction products of peracids, for example, peracetic acid with unsaturated fatty acids, such as oleic acid or linoleic acid, or unsaturated hydroxy fatty acids, such as ricinoleic acid. Suitable amphoteric or cation-active emulsifiers are, for example: alkyl betaines, such as dodecyl betaine and ' ' .

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alkylpyridinium salts, such as hydroxyethyldodecylammonium chloride.
Suitable non-ionic emulsifiers are, for example: partial fatty acid esters of polyhydric alcohols, such as glycerylmonostearate, sorbitol monolaurate, oleate or palmitate, polyoxyethylene ethers of fatty alcohols or aro~atic hydro~y compounds; polyoxyethylene esters o~
fatty acids as well as polypropylene oxide-, polyethylene oxide condensation products.
After polymerisation there ~y be added to the polymers produced other substances, such as, for example, the processing auxiliaries mentioned above for stabilising and improvi~g the properties of the polymers for further proce~sing, optionally before or after separa~
ting the aqueous liquor.
For the treatment according to the invention the vinyl chloride polgmers may contai.n up to 20 % by weight, calculated on the total substance, of compounds that do not consist o~ polymerised vinyl chloride. Such compounds may, ~or exa~ple, be monomeric vinyl .
ch~oride as well as other monomers used for polymerisation, poly-merisation auxiliaries as well as, optionally, further processing auxiliaries; for example, those mentioned above; poly~er~ not containin~ vinyl chloride, such a~ impact stren~th modifier~, polymeric additives ~or improving the flow properties and processing properties and/or thermal stability under load and pigments.
~ he heat treatment is carried out in the presence o~ one or more inert gases such as, ~or example, a1r, nitrogen or steam.
During this heat treatment it is advantageous to move the polymer powder and/or the gas phase in order to achieve intensive .
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contact o~ the two phase3 with one another. Mechanical ~r pneumatic means are suitable for this, for example, stirring, causing turbulence in ~he po~der, allowing the powder totrickle down or spraying the powder in the gas chamber, wherein an additional relative speed with respect to the solid particles may optionally be given to the gas, for example in such a manner that the gas flows through a more or less loosened-up layer of po~tder, preferably upwards from below.
The treatment according to the invention may advantageously be carried out in the polymerisation ve~sel after removing the main quantity of liquid or gaseous reactants, or in one or more devices, connected in series, for example, a down pipe or flow pipe, a high-speed mixer, a revolving tube advantageously provided on the inaide with scoops, or a cyclone, it being possible for both the gas and the polymer to be circu~ated. Advantageously a device is used in which the polymer is guided, in a rotationaily ~~
symmetric container in several flow rings arranged one above the other, by means of-the tangential introduction of gas using ; appropriate fittings, or a fluidised bed or vortex bed is used.
The process according to the invention makes it possible to subject vinyl chloride polymers, and especially those that have been produced at ~0 to 85C according to the bulk polymerisation pro¢ess, to an intensive temperature treatment as is necessary to remove harm~ul re~sidual monomers, for example, vinyl chloride, without havir~ to euffer marked discoloration of the material impairing its further use, The tre~ted polymers, contrary to thosenot treated, do not exhibit any impairment of the properties important for processing and use. The process may be carried out continuously and is not very liable to failure.
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The temperature can optionally be adjusted to the desired treatment ef~ect, thereby guaranteeing an intensive but careful treatment. The necessary devices are relatively simply built, sturdy and require little space for construction. In particular, the treatment of the polymer in thePlYmeriZatin vessel necessitates only very low investment costs.
The ~ollowing examples are intended to illustrate the invention in detail. The results of measurements listed therein were determined as ~ollows:
K value:

According to DIN 53 726, solvent: cyclohexanone.
VC r~esidual monomer content:

Determined by gas chromatography according to the "head-space"
method (Zeitschrift f~r Analytische Chemie, 255 (1971) pages 345 to 350).

Discoloration test-. .
Polymer 100 part~
Di-n-octyltin-bis-thioacetic acid ethylhexyl ester 1.5 parts 2 ~ ~ubricant mixture, consistin~ of hyclro~enated D ca3tor oil, triglyceride and monoglyceride, (obtainable under the name ~oxiol~G~ 4) 007 parts Montanic acid ester of 1,3-butanediol 0~3 parts Deno ~ /rade ~k ~ 15-, . .
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The components are thoroughly Mixed mechanically without heating and 300 grams of the mixture are plasticized for three minutes on a laboratory rolling mill with two rollers, whilst applying heat, to form a 3 mm thick rolled sheet.
, Technical data:

~oller diameter 150 mm ~peed of rollers 11 revs~min Roller temperature ~75C

A~ter coolin~ the rolled sheet, rectangular portions o~
10 10 x 12 cm are cut out of the sheet, 12 of these portions are : placed into a compression mould with internal dimensions of 11 x 12.5 cm, which is arranged in a plate press heated to 175C.
The rolled sheet portions are pre-heated under slight pressure ~or

3.5 minutes then, ~or a period of ~ minute, the full pressure of 40 ~ cm2 is applied, after a further 4 minutes cooling is effected with water under pressure to room temperature, the pressure is relaxed, the pressed plate i8 removed from the rnould and obs~r~i.ng the edge o~ the plate against a uniforr~y light, neutral white background, the color number i8 visuallg determined in accordance with a 5 part notation scale:
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Not~tion 1:
Color as standard (usually faintly yellowish) .
. Slightly discolored (yellowish) ~ ~ .
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Notation 3:
Clearly discolored (strong yellow color or reddish yellow) . Notation 4:
Strongly discolored ( brown-yellow to orange-yellow) Notation 5~
Very strongly discolored (light brown or orange red).

The standard used was a vinyl chloride homopolymer produced according to the bulk process havin~ a K-value of ~7, as yielded by polymerisation without subseauent heat treatment o~ the polymer and having a residual vinyl chloride content o~ 1 /0 by weight (calculated on the polymer).

BxamPle 1,~.
100 grams of diglycol and 500 grams of water are mixed in a I high-speed mixer for ~ minutes with 10 kg of a vinyl chloride ; 15 homopolymer, produced by bulk polymerisation at 69C, having a ~-value of 57 and a residual vinyl chloride content of l % by weight (calculated on the polymer), and then the mixture i~ treated ior 3 hours at 85C in a circulating air dryin~ chamber and sub-sequently cooled. At the end of the heat treatment 10C93 gram~
of polymer are obtained.
A flample of the powder yielded by the heat treatment was dissolved in tetrah,ydro~uran, ~ubJected to a silylation reaction with bis-trimeth,ylsilyl-trifluoroacetamide analogously to the method described in the book by Allan E. Pierce l'Silylation o~
organic compounds'!, Publisher~: Pierce Chemical Comp~, Rockford/Ill, .
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~1118;2 U.S.A., 1968, pa~e 72 et sea.; the polymer was then precipitated from the solution with methanol and the tetrah,ydrofuran-methanol mixture examined by gas chromatography, A silylation product of the diglycol could not be detected.
The determination o~ the residual vinyl chloride (V~)-content is carried out by gas chromat`ography according to the "head-space"
method (see above) at 7 parts per 1 million parts (=PPM) of dry polymer. The discoloration test resulted in the notation 1.5.
For the purpose of better comparison the values determined are listed in the following table.

ComPa~rison exPeriment A~
The procedure is as in Example 1, using the same bulk polymer but with the difference that the diglycol-water mixture is not added. The values determined are listed in the following ~5 table.

a~ c,~ _ ent B:

The prooedure is as in Bxample 1, u~ing the same bulk polymer, but with the difference that only 500 grams o~ water, without digly¢ol, are added to lO kg of polymer.
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~20 Compari30n ex~eriment ~: , The procedure is as in Example 1, usin~ the same bulk polymer, but with the difference that instead of the mixture of diglycol and water, a mixture of 100 grams of phenol and 500 grams of water is added to lO kg of polymer. The values determined are listed in the following tableO

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Example 2:
., A bulk polymer of vinyl chloride is produced according to the 2-stage seed technique, wherein before the main polymerisation (second stage) 1 % by weight (calculated on the total amount of vinyl chloride used in both stages) o~ diglycol is added to the reaction mixture and polymerisation is then ef~ected at 6ZC.
The main quantity of the excess, unreacted vinyl chlori.de is removed from the polymer produced by evacuating three time~ to approximately 50 torr. A~ter this treatment the po~y~er still contains 0.2 ~ by weight of monome,ric vinyl chloride and has a K-value of 60. 10 kg of the polymer thus produ.ced are then treated for 300 minutes at 85C under normal pressure in a circulati~g air drying chamber, and subsequently cboled. ~he vall1es measured .
are listed in the followine table.

. 15 Exam~ples~-5 .are carried out as in Example 1, but varying quantities of diglycol-: water mixture are added to the polymer.
in Example 3:400 grc~m~ o~ dielycol and 1000 gra~s of water in ~x~mple 4:10 grams o~ diglycol and 100 grams of water in ~xample 5:5 grams of diglycol and 100 ~rams of ~ater.

'i x~m~, , 100 grams of 1,6-hexanediol c~nd 500 grams of water are mixed for 3 minutes in a high-speed mixer with 10 kg of a vinyl chloride homopolymer produced by bulk polymerisation at 55C having a E-value .

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1~ 8;2 of 67 and a residual vin~l chloride content of 0.3 5D by weight (calculated on the dry polymer), and the mixture is then treated for 50 minutes at 92C in a circulating air drying chamber and subsequently cooled. The values measured are listed in the following table.

Example 7:

A mixture of 100 grams 2-butene-1,4-diol and 500 grams of water is added to 10 kg of a vinyl chloride homopolymer produced by bulk pol,ymerisation at 62~ having a K-v~lue o~ 60 and a residual vinyl chloride content o~ 0.2 ~o by weight (calculated on ; the dry polymer).
In a pressure-tight cylindrical vessel of 40 liters capacity having an oil-heated dol~ble jacket and an anchor mixer scraping along the wall, of which the mixer blades, curved ~15 in the shape of screws, are approximately 5 cm wide, brush the entire base and approximately 80 % of the side walls of the vessel and rotate at 60 rev/min, the polymer to which the above-described mixture has been added is treated for 90 minutes at a pressure of 250 torr. The temperature of the heating oil is 92 C, the tempera-,,20 ture of the polymer is measured at 85 C. During the treatment a , weak air current is passed through the vessel.
; After 90 minutes, the reduced pressure is removed and coolin~
' i8 ef~ected. The values measured are listed in the following table.
, Exa,mPle 8:
~25 In the same apparatus as i8 described in Example 7, a mixture o~ 200 grams of 1~1o-decanediDl and 500 grams of ethanol is added to 10 kg of a vinyl chlorlde homopolymer produced by bulk polymerisation ' .,~ . . , . . . .......... , , . . ................. - ~

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at 69a, and the mixture is treated for 120 minutes at a product temperature of 97C, a pressure of 100 torr and a stirrer speed of 60 rev/min whilst passing through a wealc air current, then the reduced pressure is removed and cooling is carried out. The values measured are listed in the following table.

~xample 9:

A mixture of 200 grams of a polyglyool of the average formula HO(CH2CH20)11H and 500 grams of water is added to 10 kg of a vinyl chloride homopolymer produced by bu~k polymerisation at 62C, having a K-value of 60 and a residual vinyl chloride content of 0.2 5o by weight (calculated on dry polymer), the mixture is mixed for 3 minutes in a high-speed mixer, then treated for 280 minutes at 75C
in a circulating air drying chamber and subsequently cooled. The values measured are listed in the following table.

~E~am~le lO:
:; . .
The procedure is as in Example 1, using the same polymer, but instead o~ diglycol-water, a mixture of 50 grams o~ 1,3-propanediol and 500 grams of water is added. The heat treatment at 85C is only 120 minutes long. The value~ measured are listed in the ~ollowin~ table.

Exam le ~11i :~ .
The prooedure is as in ~xample 8, using the same polymer, but j~ instead o~ decanediol-ethanol, a mixture of lO0 grams of 1,4-butanediol and 500 grams of water ls addedO The heat treatment is ef~ected at a product temperature of 90C. The values measured are iisted in the following table. ~-,',i ~ ' ' ~ -21-. . . ... .. . . . , ~ , . , ~ .:

- ~1111;!3Z
`
, : .
Exam~le 12:

The procedure 1s as in Example 1, using the same polymer, except that instead of diglycol-water, a mixture of.200 grams o~ neopentylglycol and 500 grams of water is added. ~he values measured are listed in the following table.
':

In the table:

. .
VC. - vinyl chloride min - minutes PPM = parts per 1 million parts of dry pol~Ymer.

' , ' .
.

,, :
~ - 22- . .
,; ' : ..
', '~', ' . . ~,.

~ h ~1111182 r ~ ~ ~ d ~ ~ If ~ L~ L~ ~ Ll~ _ ~I L~ t~J 1~ ~
___ . _. _ _ _ _ _ __ rl O O CQ _ t-- _ Ir~~D 0 _ t~l ~ ~D N O ~
~C~ ~
_ _ _ _ .' ~V ~ 01 N 1:~1 N ~111~ u~ r-- C~J ~ O O O (~J
-_ -.-- -.. - . - -- - - .-~ 3 o o o oo 8 ~ o o o o N 0 O O O

Z _ __ _ ~ ~ _ h æ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 0O ~ ~ O ~
. ~ _ _ __ __ _ _ _ _ ~1~ ~V 0 0 0 0 a:~ 0 0 0 N 0 1~ ~ 0 O 0 ~.~ ~ _ . _ _ _ _ _ 1.

IS~ _ _ _ ~ O O _ ~J N O _ ~J

h ~:t ~ ~ 151 V _ ~1 1~ ~ U~ ~D t-- 0 O~ O _ C`J
.. ,. .1 . . _ _ . ~.

~: ~ d ~ o o o F~ F~l F~ ~ 1~ F~ F~ ~1 F~ 1 i3 F~ li~ ~` ~
, .. ..... . . . . .. . .

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for improving the properties of homo-, co-or graft polymers that contain at least 50% by weight of polymerised vinyl chloride units, in which the main quantity of unreacted monomers and any water present are removed, the polymer in a pulverulent state is subjected to a heat treatment at atmospheric or reduced pressure, the heat treatment being carried out for 10 to approximately 360 minutes at 75 to 120°C in the presence of 0.01 to 5 % by weight, calculated on the polymer, of at least one aliphatic, saturated or unsaturated, branched or unbranched compound that contains 2 free hydroxyl groups and 2 to approximately 24 carbon atoms and that, in the case of a compound having 4 or more carbon atoms may also contain at least one C-O-C group.

2. A process as claimed in claim 1 in which the heat treatment is carried out at a pressure of 50 to 760 torr.

3. A process as claimed in claim 1 in which the heat treatment is carried out in a vessel and during the heat treatment, air, nitrogen or steam, or a mixture of at least two of said gases is passed through the vessel.

4. A process as claimed in claim 1, claim 2 or claim 3 in which the heat treatment is carried out at 80-100°C.

5. A process as claimed in claim 1, claim 2 or claim 3 in which the heat treatment is carried out in such a manner that the product of treatment temperature in °C and treatment time in hours is in the range of from 25 to 350 (°C. h).

6. A process as claimed in claim l, claim 2 or claim 3 in which the treatment is carried out in the presence of 0.2 -2% by weight, calculated on the polymer, of at least one of said components as described in claim l.

7. A process as claimed in claim l, claim 2, or claim 3 in which the heat treatment is carried out in the presence of at least one compound of the formula wherein X represents H or -CH3 and n represents an integer of from l - 12.

8. A process as claimed in claim 1, claim 2 or claim 3 in which the heat treatment is carried out in the presence of diglycol or triglycol or a mixture of diglycol and triglycol.

9. A process as claimed in claim 1, claim 2, or claim 3 in which the heat treatment is carried out in the presence of 2-butene-1,4-diol.

10. A process as claimed in claim l, claim 2 or claim 3 in which the polymer is a product produced by bulk polymerisation at 30 to 85°C and which contains at least 80 % by weight of polymerised vinyl chloride units.