CA1170400A - Peroxyester-monosaccharide redox catalyst system for vinyl chloride polymerization - Google Patents

Abstract

ABSTRACT
A process for the bulk or suspension polymerization of vinyl chloride in the presence of a redox catalyst system consisting of a peroxyester and a monosaccharide or a carboxylic acid ester of a monosaccharide.

Description

~ ~ ~7()~

PEROXYESTER-MONOSACCHARIDE REDOX CATALYST SYSTEM
FOR VINYL CHLORIDE POLYMERIZATION
FIELD OF THE INVENTION

This invention relates to a process for the polymerization of vinyl chloride, in bulk or suspension systems, using a redox catalyst system consisting of a peroxyester and a monosaccharide or monosaccharide carboxylic acid ester.
BACKGROUND OF THE INVENTION
The suspension polymerization of vinyl chloride is generally carried out at temperatures below 70~C using organic soluble initiators. Although lauroyl peroxide was earlier the most ~idely used catalyst, in recent years other low temperature catalysts including azobisisobutyronitrile, dlisopropyl peroxydicarbonate, t-butyl peroxypivalate and mixtures thereof f ha~e been adopted. These and other catalysts are described in Pennwalt Corporation, Lucidol Division, Technical Bulletin 30.90, "Free Radical Initiators for the Suspension Polymeri-zation of Vinyl Chloride" (1977).
The choice of initiator is dictated by its half-life and by its influence on the polymexization process and the properties of the poly(vinyl chloride) produced thereby.
The polymerization of vinyl chloride is characterized by a short induction period, followed by a gradually increasing ,. ~

7~

rate of polymerization~ Luring the earlier ~tages of th~ polym~r-ization, the reaction rate i8 lower than the maximum ~o that the capacity of the reactor i~ not fUlly utilized. Peroxye~ter~
reduce the induction period and, due to a more constarlt rate o~
polymerization, increase reactor productivity. ~uxther, peroxy-ester~ can generally be used at levels below tha~ needed for per-oxides and give much less chain bra.nch.ing ~uring polymerization.
Although peroxyester~ ~uch as dii~opropyl peroxydicar-bonate and t-butyl peroxypivalate offer num~rou~ advantage3 in vinyl chloride polymerization, ~heir di~advantages include the necessi~y for low temperature ~hipping and ~orage and decrea~ed efficiency at elevated temperatures.
The use of peroxyesters having higher deco~po~ition temperature~ i8 not feasible in present poly(vlnyl chloride) production facilities due to the higher mcnomer pxe~ures involved and the low molecular weight and poorer stabil~ty of th~ re~ulta~t resins. Neverthele~s, the handling ad~antage~ of ~u~h peroxy-esters makes ~heir use extremely attractive.
The use of higher temperature cataly~t~ at lower temper-atureR i~ a common practice in polymer technology. Thu~, redox ~y~tems ~uch a~ anunonium per~ulfate - ~odium metabisulfite and hydrogen peroxide - ferrous ~ulfate are used in emulsion polymer-ization while benzoyl peroxide - dimethylaniline and methyl ethyl ketone peroxide - cobalt naphthenate are used in ~tyrene - un~at-urated polye~ter polymerization.
Reducing agent~ use~ in conjunctlon with monomer-~oluble peroxye~ters in the polymerization o vinyl chloride include potas~ium me~abisulfite (N. ~ischer and C. La~bling, French Pa~0nt

2,086,635 (1972), ~odium bi~ulfi~e ~H. Minato, K~ ~ashimotG, and T. Yasui, JapanD Patent 68 20,300 (l968), ~odium bisulfite -cupric chloride (B. K~ Shen, U. S. Patent 3,668,l94 (l972), ~odium dithionite - ferrou~ aulfate ~H. Mi~atoO Japan. Pa ent 70 04, ~g4 ~l970~ a~d trialkyl boron (R. Kato and I. Soemat~u, Jap~n. Patent 5498('65~ (19651t A. V. Rya~ov, V. A. Dodonov, and YO A. Iv~nova, Tr~ Xhim. Xhim. Tekknol., l970, 238~ Stockho~ upe~fo~Pat Fabrik~ A/B, Brit. Patent 961,254 (lg64).
- Variou~ sugars including ~luco~e, dsxtrose, fructo~e and sorbose have been used as activator~ in ~! activated recipes"
for the emulsion polymerization of butadieno and ~tyrene. The~e so-called "sugar-iron-peroxide" recipes con~n benzoyl peroxide, cumene hydroperoxide or other hydroperoxides as oxidant, ferric or ferrouc ~alt~ a3 reducing agent, a sugar a~ "activator" and, generally, sodium pyropho~phate as complexing agent 1F. A. Bovey, I. M. Kolthoff, A. I. Medalia, and ~. J~ Meehan, "Emulsion Polymer-ization", Interscience Publishers, New York, 1955, pp. ~5-89 and 374-390). Dextrose ha~ al~o been used in a cumene-hydroperoxide-ferrous sulfate-sodium pyropho~phate catalyst ~ystem for the graft copolymerization oE ~tyrene and acrylonitrile onto a polybutadiene latex ~W. C. Calvert, U. S. Patent 3,238,275 (l9661 To Sakuma and I. Maka~ura, Japan. Patent 13,635 ~'66) (l966).

SUMM~RY OF T~E I~VENTION
~ n object of the pre~ent invention i~ to provide a process for th~ polymerization of vinyl chlorid*, in the pre~o~c~

~ ~7~

of peroxygen compounds at temperatures at which thé latter are stable and readily handled. Another object of the present inven-tion is to provide a process for the bulk and suspension polymer-ization of vinyl chloride at temperatures below 70C using per-oxygen compounds which, at ~hese temperatures, do not generate free radicals at a sufficient rate to initiate polymeri~ation at a practical rate, if at all.
It has now been found that this improvement in vinyl chloride polymerization can be achieved by utilizing a redox cata-lyst system consisting of a peroxyester and a monosaccharide ormonosaccharide carboxylic acid ester.
Thus the present invention provides in a broad aspect a process for the preparation of polymers and copolymers of vinyl chloride, which consists in polymerization in bulk or suspension, in the presence of a redox catalyst system consisting of a peroxy-ester and a reducing agent seIected from the class consisting of a monosaccharide, a carboxylic acid ester of a monosaccharide, a disaccharide, and a carboxylic acid ester of a disaccharide.
In another aspect the invention provides a process for the preparation of polymers and copolymers of vinyl chloridP, which consists in polymerization in bulk or suspension, in the presence of a redox catalyst system consisting of a peroxyester, a reducing agent selected from the class consisting of a monosaccharide and a carboxylic acid ester of a monosaccharide, and a stannous or antimony (III) car~oxylate.

:~ ~ 7(~4~

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, the polymerization of vinyl chloride is carried out in bulk or suspension, under the conditions applicable thereto and well known to those skilled in the art, using a catalyst system consisting of a monomer-soluble peroxyester and a reducing agent which is a monosaccharide or a carboxylic acid ester of a monosaccharide.
The half-life of a free radical catalyst is the time required for 50% decomposition at a particular temperature. The half-life is only relevant as regards the temperature at which it is desired to conduct a polymerization, e.g. the polymerization of vinyl chloride below 70C to produce poly(vinyl chloride) with greater thermal stability than polymer produced above 70C.
The ha~f-life of a peroxyester refers to thermal decomposition and,consequently, if a polymerization is to be conduoted ~t 50C, a ~, \
i `~:
, -4a-j 7(.)~

catalyst with a half-life of 20 hours or less at 50C, can be used for the polymerization, e.g. t-butyl peroxypivalate or t-butyl peroxyneodecanoate, as is well known to those skilled in the art.
However, if it is desired to conduct the polymeri-zation with a catalyst which does not require refrigerated shipment and/or storage, which are required by t-butyl peroxypivalate and t-butyl peroxyneodecanoate, than in accordance with the present invention, a catalyst with a half-life of more than S0 hours at 50C can be used in the presence of a suitable reducing agent, e.g. t-butyl peroxyoctoate which has a half-life of 133 hours at 50C in the absence of the reducing agent may be used.
Alternatively, if it is desired to conduct poly~.erization at or below 25C, in oxder to maintain better control of the reaction exotherm or to obtain a higher molecular weight, less branched polymer, the aforementioned peresters, despite the requirement for refrigerated shipping and storage, having half-lives of more than 150 hours at 25C, may be used in the presence of a suitable reducing agent.
The process of the present invention utilizes a peroxy-ester, in the presence of a suitable reducing agent, at a tempera-ture ~here the peroxyester has a half-life of more than 50 hours in the absence of the reducing agent.
The peroxyesters which may be used in the process of the present invention are the alkyl and aralkyl peroxyesters of aliphatic or aromatic carboxylic acids or carbonic acid and may be represented by the structural formula ~ ~ ~7(~

R-O-O-C-R' where R is an alkyl, aralkyl or alkoxycarbonyl group, R' is an alkyl, aralkyl, aryl or alkoxy group, and Rand R' are the same or different. When R and/or R' contain alkyl or aralkyl moieties, the latter may contain 1-20 carbon atoms and may be primary, secondary or tertiary~ linear or branched, acyclic or cyclic, saturated or unsaturated and may contain non-hydrocar~on substitu-ents includ~ halogen and hydroxyl groups. When R' is an aromatic moiety, it may be uns~bstituted or may contain hydrocarbon, halogen and/or other substituents.
The peroxyesters may be monoperoxyesters or the diperoxyesters of dicarboxylic acids or diols.
Representati~e peroxyesters include t-butyl peroxy-acetate, t-butyl peroxyisobutyrate, t-butyl peroxypivalate, t-butyl peroxyneodecanoate, t-butyl peroxybenzoate, t-butyl peroxyoctoate, t-butyl peroxyl2-ethylhexanoate?, t-amyl peroxy-neodecanoate, cumyl neodecanoate, isobutyl peroxypivalate, sec-butyl peroxybenzoate, n-butyl peroxyoctoate, t-butyl peroxy-

3,3,5-trimethylhexanoate, t-butyl peroxy-2-methylbenzoate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, 2,5-dimethyl~2,5--bis(benzoylperoxy)hexane/ 2,5-dimethyl-2,5-bis(octanoylperoxy)-~`hexane, di-t-butyl diperoxyphthalate, t-butyl peroxymaleic acid, t-butyl peroxyisopropylcarbonate, di(sec-butyl) peroxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate, diisopropyl peroxydi-carbonate, di(n-propyl)peroxydicarbonate, di(2-ethylhexyl)peroxy-~icarbonate, dicyclohexyl perocydicarbonate, diaetyl peroxydi-carbonate and the like.
'.~

The process of the present invention i~ carried ou~
with a redox catalyst ~y~t~m consisting of a monomer~~olubl~
peroxygen compound, i.e. a peroxye~ter, and a reductan~ bulk polymerization, a monomer-soluble reductant i~ required, while su~pension polymerization permits the u~e of either a monomer-~oluble or a monomer-insoluble reductant.
The monosaccharides which may be u~ed a~ reduct~nt~ in the practice of the pr~ent invention include pentose~ a~d hexoaes wherein the carbonyl group i~ either an aldehyde or a ketone, i.e.
polyhydroxyaldehydes commonly referred to a3 aldose~ and poly-hydroxyketone3 commonly referred to as ksto~es~
Representative monosaccharides or reducing sugar~ include arabinose, xylo~e, lyxose, ribo~e, gluco~e, gulo~e, manno~e, allose, galactose, tallo3e, altrose, ido~e, fructose and sorbo~e.
The carboxylic acid esters of the monosaccharides which may he u~ed a~ reductants in the present invention include the ester~ of aliphatic and aromatic carboxylic acids. Th~ aliphatic carboxylic acid~ contain 1-26 carbon atoms and may be linear or branched, cyclic or acyclic, saturated or u~saturat~d. The aromatic carboxylic acids may be sub~tituted or unaubstituted.
~ epre~entative carboxylic acid e~ter~ include the e~t~rs of acetic acid, propionic acid, butyric acid, octanoic acid, ~tearic acid, benzoic acid and the like.
The concentration of peroxyester i8 generally 0001~5%
b~ weight of the vinyl chloride, with a preferred concentration o~
0.05-1% by weight. The peroxyester/reduc~ant mole ratio is generally 1/0.01-2, with a preferred mole ratio of 1/0.1-1.

:~31 7(~J'I~

The redox catalyst s~stem consisting of a peroxyester - and a monosaccharide or a carboxylic acid ester of a mono-saccharide may also contain the stannous or antimony (III) salt of an aromatic or aliphatic carboxylic acid. The presence of the metal carboxylate permits the use of lower concentrations of the peroxyester. The monosaccharide/metal carboxylate mole ratio is generally 1/9.01-1. Representative carboxylates are derived from aromatic carboxylic acids or aliphatic carboxylic acids which contain 1-26 carbon atoms and may be linear or branched, cyclic or acyclic, saturated or unsaturated, inc~uding the stannous and antimony (III) salts of acetic acid,propionic acid, butanoic acid, caproic acid, lauric acid, stearic acid and the like.
The procedures normally used in the suspension polymerization of vinyl chloride are applicable to the process of the present invention. Typical procedures are described in Encyclopedia of Polymer Science and Technology, 14, 339-343(1971)~
The polymerization may be conducted at or above atmos-pheric pressure. In the usual procedure, the reactor is charged ?O at atmospheric pressure and the pressure rises when the contents of the reactor are brought to reaction temperature. The pressure may increase further due to the reaction exotherm andthen re~ain constant until the conversion reaches about 70~, after which it decreases rapidly as the reaction continues.
The polymerization temperature may range from -50 to ; +70C for bulk polymerization, although temperatures of 40 to 60C are preferred. Suspension polym0rization may be carried out at temperatures of +5 to +70C, although preferred temperatures , ~ ~7()~

are in the 20-60C range.
The concentrations of monomer and water, e.g. about 2/1 weight ratio, and the types and concentrations of suspending agents are those normally used in suspension polymerization and are well known to those skilled in the art. Typical suspending agents include poly(vinyl alcohol?, partially saponified polytvinyl acetate?, gelatin, methylcellulose, vinyl acetate-maleic anhydride copolymer and the like. Various emulsifiers such as sulfonated oils and ethylene oxide condensation products may be added to control surface tension and particle shape. Buffers may be used, where necessary, e.g. when gelatin is used as suspending agent. Chain transfer agents su h as chlorinated hydrocarbons and iso-butylene may be used in the preparation of low molecular weight polymer.
Although the pero~yester-~onosaccharide or -~onosaccharide carboxylic acid ester catalyst system of the present invention is particularly usefuI in the bulk and suspension polymerization of vinyl chloride, the redox system may also be used in the copolymer-ization of vinyl chloride with vinylidene chloride, vinyl acetate, ` 20 and other monomers which undergo copolymerization with ~inyl chloride.
The ~ollowing examples are illustrative embodiments of the practice of the present invention and are not -to be construed as limitations on the invention or the claims. Numerous modifica-tions will be obvious to those skilled in the art.

~9_ ~ ~r 7~3~

EXAMPL~ I
Ao A 4 oz gla~s bottle was charged with the following ~u~pension recipe: .
21 ml dis~illed water (boiled) 1 ml lX aqueouR 801utio~ of Tween 60 (polyoxyethylene sorbitan monostearate,. P~tlas CneT~ical Ind-u~tries Inc. ) 1 ml lX aqueous solution of Span*60 (sorbitan ~no-~tearate, Atla~ Chemical Indu~trie~ Inc.. ) 2 ml lX aqueou~ solution o~ Methocel*A-15 (methyl cellulo~e with vi~co~ity of 15 cp0 as ~ 2%
aqueou~ solution, Dow Chemical Ot). ) Nitrogen wa~ bubbled through the aqueou~ ~olution ~or 15 a~inute~.
Ga~eoua vinyl chloride waEI purlied by pa~sage through two SX aqueous sodium hydroxide 801ution~ dri~d by pa~salge through a 8i~ I gel column and then condensed with tlle ~ld of a dry ic~
bath. After 0.041 g (0.23 mmole) glucoss zlnd 10 g liquid v~nyl chloride were added to the E~u~pen~ion recipe, the bottle wa~ clo~ed with a s~crew cap containing a center hol;~ and a eelf-~aling ga~Xet.
The addition o~ 0.055 ml (0.23 mmole) t-butyl peroxyoctoate (0.5~
by wsight of vinyl chloride) was made by injection through the ga~ket using a hypodennic syringe. The bot~le wa~ placed in a 50C con~ta~t temperature bath and shaken for 7 hour~. The botkle was removed from the bath and the residual monomer was released by insertir~g a needle in~o the gasket. Th~ yield of poly (vinyl chloride) was 4~,1 g (41%
conver~ ion 3 ~
B. P, l~o~tle was charged in the same manner and with the * Trade Marks.

..

1.~ 7(~

same reactants as in A, except for the omission o glucose. No polymer was isolated after 7 hours at 50gC.
EXAMPLE II
The procedure of Example I was repeated, using the same suspension recipe, with 10 g vinyl chloride,0.055 ml ~0.23 mmole) t-butyl peroxyoctoate (0.5~ by weight of vinyl chloride) and 0.02 g (0.115 mmole) glucose. After 7 hours at 50C, the yield of polymer was 3.9 g (39% conversion).
~ EXAMPLE III
The procedure of Example I was repeated, using the same suspension recipe, wlth 10 g vinyl chloride, 0.022 ml (0.092 mmole) t-butyl peroxyoctoate (0.2% by weight of vinyl chloride) and 0.017 g (0.092 mmole) glucose. After 7 hours at 50C, the yield of polymer was 2.0 g (20% conversion).
EXAMPLE I~
The procedure of Example I was repeated, using the same suspension recipe, with 10 g vinyl chloride, 0.055 ml (0.23 mmole) t-butyl peroxyoctoate (0.5~ by weight of vinyl chloride) and 0.041 g (0.23 mmole) sorbose. The conversion was 31% after 20 7 hours at 50C.
EXA~PLE V
The procedure of Example I was repeated, using the - same suspension recipe, with 10 g vinyl chloride, 0.055 ml (0.23 mmole) t-butyl peroxyoctoate and 0.041 g (0.23 mmole) fructose. The conversion was 30~ after 7 hours at 50C.

.
~r .
.

EX~MPI~ VI

The proc~dure of Example I was repeated, u~ing the sam~
suspension reclpe, with 10 g vinyl chloride, 0.055 ml (0.~3 mmole) t-butyl peroxyoctoate and 0.09 g (0.23 mmole) ~-glucose pentaacetate.
The bottle was shaken a~ 50C for 7 hours to yield 4.5 g (45~ con-version~ polymer.

EXAMPLE VII
The procedure of Example I was repeate~ with 10 g vinyl chloride, 0.055 ml (0.23 mmole) t-butyl peroxyoctoate and 0.045 g (0.115 mmola)oc-glucose pentaacetate. After 16 hour~ at 50C the yield o~ polymer was 7.2 g (72% conver~ion).

~XAMPLE VIII
The procedure o~ Example I wa~r#peated wlth 10 g vinyl chloride, 0.055 ml (0.23 mmole) t-butyl paroxyoctoato and 0.018 g ~0.092 mmole) ~-glucos2 pentaacetate. The yield of polymer wa~

4.0 g ~40% conversion) after 7 hour~ at 50C~

~XAMPLE IX
The procedure of Example I was ~? peated with 10 g vinyl chloride, 0.055 ml (0.23 mmole) t-butyl peroxyoctoate and 0.156 g (0.23 mmola) sucrose octaacetate. The yield of polymer was 3~1 g (31~h conver~ion) after 7 hours at 50 C.

L 7~ J!I~

EXAMPLE X
A 6 oz glass bottle was charged wi~h th~ following suspension recipe;
~2 ml distilled water 2 ml 1% aqu~ous solution of Tween 60 2 ml 1,~ aqueous solution of Span 60 4 ml 1% agueous solution of Methocel A-15 Nitrogen was bu~bled through the aqueou8 8~ution Po~ 15 minukea.
The bottle was charged with 20 g liqui vi~yl c~loride, 0.044 ml (0.184 mmole) t-butyl peroxyoc~-oate ~0.2~ by waight o~
vinyl chloride) and 0.0165 g ~0~092 mmole3 c~-Dt~-glucose (dextro~e), as described in Example I. A~ter 16 hours at 50C, the yteld of poly(vinyl chloride) was 9.2 g (46~ conversiQn).

EX~PLE XI
The procedure of Example X was repeat~d u~ing the same suspension recipe and reactants. In addition, 0.005 g (0.0092 mmole) stannous laurate (glucose/stannous laurate mole ratio = 10/1) was c arged to the reaction mixture. The yield of polymer wa~ 15.g g (79.5% conversion) after 16 hours at S0 C.

- In addition to the monosaccharides which function a~
reductants in the practice of the present invention, the disaccharides which are reducing sugar~ pex se, e.g. malto~e, lactose, cellobio~a an~ gentiobiose, a~ well a~ disaccharides which rea~ily undexgo hydrolysis to reducing monosaccharides in ~he aqueou~ environm~nt used in suspension polymerization, e.g. sucro~e, may be u~ed in th~

pra~tice of this invention~ although they are generally les~
ef~ective reductants than the mono~accharides. The carboxylic acid esters o~ the disaccharides may also be used as reductants, as illustrated by the use of sucrose octaacetate in Example IX.
While particular embodiments of this inv0ntion have been disclosed above, i~ will be understood that the invention is obviously subject to variation and modi~ication without departing from its broader aspects.

Claims (18)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the preparation of polymers and co-polymers of vinyl chloride, which consists in polymerization in bulk or suspension, in the presence of a redox catalyst system consisting of a peroxyester and a reducing agent selected from the class consisting of a monosaccharide, a carboxylic acid ester of a monosaccharide, a disaccharide, and a carboxylic acid ester of a disaccharide.

2. A process for the preparation of polymers and co-polymers of vinyl chloride, which consists in polymerization in bulk or suspension, in the presence of a redox catalyst system consisting of a peroxyester and a reducing agent selected from the class consisting of a monosaccharide and a carboxylic acid ester of a monosaccharide.

3. The process of claim 2 wherein the polymerization is carried out at a temperature where the peroxyester has a half-life of more than 50 hours in the absence of the reducing agent.

4. The process of claim 3 wherein said polymerization temperature is in the range from -50° to +70°C.

5. The process of claim 3 wherein said polymerization temperature is between 20° and 60°C.

6. The process of claim 2 wherein said peroxyester is selected from the class consisting of alkyl peroxyesters of ali-phatic carboxylic acids, aromatic carboxylic acids and carbonic acid.

7. The process of claim 2 wherein said monosaccharide is selected from the class consisting of aldoses and ketoses.

8. The process of claim 7 wherein said aldose is glucose.

9. The process of claim 7 wherein said ketose is fructose.

10. The process of claim 2 wherein said carboxylic acid ester of a monosaccharide is an ester of an aliphatic acid.

11. The process of claim 10 wherein said carboxylic acid ester of a monosaccharide is an ester of acetic acid.

12. The process of claim 2 wherein said carboxylic acid ester of a monosaccharide is glucose pentaacetate.

13. The process of claim 6 wherein said peroxyester is t-butyl peroxyoctoate.

14. A process for the preparation of polymers and copolymers of vinyl chloride, which consists in polymerizati on in suspension, in the presence of a redox catalyst system consisting of a peroxyester and a reducing agent selected from the class consisting of a disaccharide and a carboxylic acid ester of a disaccharide.

15. The process of claim 14 wherein said carboxylic acid ester of a disaccharide is sucrose octaacetate.

16. A process for the preparation of polymers and copolymers of vinyl chloride, which consists in polymerization in bulk, in the presence of a redox catalyst system consisting of a peroxyester and a carboxylic acid ester of a disaccharide.

17. A process for the preparation of polymers and copolymers of vinyl chloride, which consists in polymerization in bulk or suspension, in the presence of a redox catalyst system con-sisting of a peroxyester, a reducing agent selected from the class consisting of a monosaccharide and a carboxylic acid ester of a monosaccharide, and a stannous or antimony (III) carboxylate.

18. The process of claim 17 wherein said stannous carboxyl-ate is selected from the class consisting of stannous laurate and stannous octoate.