CA1095343A - Internally coated reaction vessel for use in olefinic polymerization - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

This invention relates to a polymerization reac-tion vessel having an approximate monolayer coating on the inner surfaces thereof resulting from applying thereto an aqueous alkali metal hydroxide coating solution containing a straight chain or branched polyaromatic amine and a dis-persant operable in aqueous media, such as, for example, polyvinyl alcohol. When polymerizing olefinic monomers.
such as vinyl halides, vinylidene halides, and vinylidene monomers having at least one terminal

Description

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BACKG~OUND OE` THF INVENTION
~arious kype chemical processes are commonl.y carried out i.n large, stir.red vessels which are frequently pxovided with au~iliary equipment, such as ba.Efles, heat transfer coils which enable heat to be supplied or ex~
tracted :Erom the contents oE the vessels, a.nd the like.
In many cases, however, such processes eventually produce undesirable deposits on the surfaces of the equipment with which the reaction mixtures come into contact. Such 13 deposits interere with the efficient transfer of heat to ~:
and ~rom the interior of the vessels. Further, these deposits have a tendency to deteriorate and to partially fragment resulting in contamination of the reaction mixture and the products produced therefromO This prohlem is particularly prevalent in polymeri~ation type redc~ions, ~:
since the deposits, or "build up", of solid polymer on reactor surfaces, not only interferes with heat transfer, ~ut decreases productivity and adversely affects polymer quality.
This problem is particularly bad in the commer-cial production o~ polymers and copolymers o~ v.inyl and vinylidene halides, when polymerized alone or with other vinylidene monomers ha~in~ a termlnal CH~=C~ group, or with pol~merizable monoolefinic monomers. For example~
in the commercial production of vinyl chloride polymers, the same are usually produced in the form of discrete particles by pol~merization in aqueous suspension systems~
When employing such a polymer.ization system, the vinyl chloride, and other comonomers when used, are maintained in the form of small discrete droplets by the use of

- 2 -

3~3 suspending agents and agitation. When the reaction is complete, the resul~ant polymer is washed and dried.
These aqueous suspens.ion system polymerl~atiorl reaGtiOnS
are usually conduc~ed under pressure in me~al reactors equippe~ ~ith baffles and high speed agitators. However, tnese suspeIlsion systems are inherently uns~able and during the polymerization reaction~ vinyl chloride pol~mer builds up on the inte.rior suxfaces of the polymerization xeactor, including ~he surfaces of the baffle~ and agitator4 Ob-viousIy, this polymex buildup must be removed since i~
results in further formation of polymer buildup which in turn results in a crust that adversely affects heat trans-fer and contaminates the polymer being produced.
The nature of the polymer buildup, or insoluble deposit on the walls of the reactor, is such that in the commercial production vf polymers, as described above~
it has in the past been standard practice, after each polymeri2ation reactiQn is completed, ~to have an operator enter the reactor and scrape the polymer buildup off the walls and of the baffles and agitator. An operation such as this is not only costly, both in labor and down-time of the reactor, but presents potentîal health hazards as well. While various methods have heretofore been proposed to recluce the amount and natur~ oE polymer buildup on polymerization reactor surfaces~ such as solvent cleaning, ~arious hydraulic and mechanical reactor cleaners, ancl the like, none has proved to be the ultimate in polymer buildup removal. That is to say~ thesQ various methocls and apparatus have done an acceptable job, but there is still room for impxovement in this area, particularly, i3~3 from an economic point of view.
In Canadian Patent 1,065,207, issued October 30, 1979, of Donald E. Witenhafer, James B Haehn and Louis Cohen, there is disclosed and claimed a process or coating the inner surfaces of a polymerization ves~sel or reactor with an aqueous alkali metal hydroxide coating solution containing a straight chain or branched polyaroma-tic amine.
This claimed process has proved to be more than satis-factory in achieving the intended results and multiple reactions can be run in the polymerization vessel so coated without opening the same between each reaction.
However, experience with such process, on a commercial scale, has shown that more dilute coating solutions would be desirable in order to reduce costs and more importantly, to reduce the color of said solutions. Since the poly-aromatic amines are coloxed condensation polymers, there is a tendency, on occasion, for some of the polymer particles being formed during the polymerization reaction in the presence of the coating on the inner surfaces of the poly merizer to become discolored which, of course, is undesir-able and to be avoided, if possible. It should be pointed out, however, that the effectiveness of such coating solutions in reducing, and substantially eliminating, polymer buildu~ is not affected by such discoloration problem. Therefore, it would be desirable to have an improved coating solution which substantially eliminates the potential discoloration problem.
It has been found that if a polymerizatian ~.~

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reactiOn vessel, particularly one having inner surfaces of stainless steel, has been previously coated on said inner surfaces with the propex coating, undesirable polymer buildup on said surfaces can be substantially decreased, and in many cases entirely eliminated, when polymerizing olefinic monomers therein. I have no~ found that when the interior surfaces of a polymerization reactor are coated with an aqueous alkali metal hydro~ide coating solution containing, in certain necessary predescribed concentra-tions, a straight chain or branched polyaromatic amine con-densation product and an aqueous media dispersant, polymer buil~up on said interior surfaces of the reaction is essentially eliminated. Due to the nature of the coating solution or composition, it can be applied to the inner surfaces of the reactor without opening the same thus providing a closed polymerization system. By use of the particular com~ination of components in the coating solu-tion, the necessary critical surface tension (~c) for wetting of a solid surface is obtained which results in greatly reduced concentration o~ the polyaromatic amine in the coating composition and application thereof tothe sur~aces in a monolayer, or multilayer when more than one application is made, producing a water-wettable surface resistant to polymer formation thereon. In polymerizing the monomers in such a coated reaction vessel or reactor, the same is done in an aqueous polymerization medium which is kept in constant contact with said coated surfaces throughout the polymerization reaction.
In accordance with the present invention, a , .
, - 5 -.' .-~L~g53~l3 fllm or coating o~ a polyaromatic amine and an aqueousmedia dispersant is applied to the interior surfaces of a polymeriæation reactor or vessel by merely contacting said surfaces with an aqueous alkali metal hydroxide solution of said polyaromatlc amine and dispersant. Likewise, all exposed surfaces in the interior of the reactor, besides the interior walls, such as the baffles, agitator, and the like, are also treated in like manner. After the aqueous alkali metal hydroxide solution has been applied to the suraces, the polymeriæation medium can be intro--duced to the reactor and the reaction started without the necessity of drying said surfaces prior to the intro-duction of the polymerization medium. Although it is not necessary, the coated interior surfaces of the reactor can be washed with water prior to introduction of the poly-merization medium in order to remove excess coating solu-tion therefrom. This can bè accomplished by spraying the surfaces with water, or filling the reactor with water and draining. Surprisingly, there is thereby left, in either case, a tightly adhering coating or film on said surfaces which is not affected by the polymerization medium, even when agitated, in the sense of preventing the coating from achieving its assigned function, namely, the prevention of polymer buildup on said surfaces.
The polyaromatic amines useful in the practice of the present invention are made by means of a condensa-tion reaction of two or more of the compounds listed below or by the self~condensation reaction of any of the com-pounds listed below containing at least one -OH group and 3~3 at least one -NH2 ~roup. Generally, such reactions are carried out with heat .in the presence oE an aci.dic catalyst. Th~ polyaromatic amines thus ~ormed have the following general structures:

1 ~ ~x wherein A, B and C are either ~5 ~ or wher~in R3 and R4 are the same as defined below~ and ~5 is -N-/ or a straight chain or branched alkylene or alkyli~
d~ne group containing from l to 5 carbon atoms, and wherein A, B and C may be the same or different and each r~peating unit may be the same or different; Rl and R~ are eith~r -~, ~~ H2 or ~3 4 and may be the same or different; R3 is -H, halogen, or .
an alkyl group containing from l to 8 carbon atoms and may be the same or different; R4 is -H, --OH, -N~2, or an alkyl group containing from l to 8 carbon atoms and may be : the same or different; x is an inteyer from 1 to 20; and ~o y is an integer from 0 to 20, When a trifunctional com~

psund is employed, such as the trihydroxy benzenes, for example, then branched chains will result thus producing a branched polyaromatic amine; and x Y
wherei.n ~ and B are either R5 - ~ - or

4 R~ R~
wherein R3, ~4 and R5 are the same as in formula (A3, and wherein A and ~ may be the same or different and each repeating unit may be the same or ~iffererlt; Rl is -H
-OH, -N~2 or ''~';~-, ~2 is -~, or ~R

x is an inte~er rom 1 to 4; and y is an integer from l :
to 15.
The compounds generally useul in making the polyaromatic amines employed in the pre~ent invention are (a3 the polyamino benzenes having the formula:
NH
t 2 ~ }l2 wherein Rl is H, -NH2, -OH or an alkyl group containing from l to 8 carbon atoms, and R2 is ~H, halogen, or an ;;

.: .

3~13 alkyl group as defined for Rl, such as/ ~or example, ortho, meta and paxaphenylene diamines; diami.no toluenes, diamino xylenes~ diamino phenols, triam.ino ben~enes~ tolu~
enes an~ xylenes; ethyl, propyl~ butyl and. pentyl di- and tri-aminc) benzenes; and the like; the most: pre-Eerred compounds being those in which Rl is -H a~ld R~ is -H t me~hyl, or ethyl; (b) the polyhydric phenols having the :ormula OH

R ~

wherein R3 is ~H, -NH2, -OH, or an alkyl group contain~
i.ng from 1 to 8 carbon atoms, and R4 i5 H~ -OH, halogen, or an alkyl group as de~ined for R3/ such as, for example, catechol, resorcinol~ chloro-resorcinol, hydroquinone ~
phloroglucinol, pyrGgallol ~ etc.; dihydroxy toluenes and xylenes; trihydroxy toluenes and xylenes; ethyl, propyl t butyl and pentyl di- and txi-hydroxy benzenes; and the like, the most preerred compounds being those in which R3 is -H and R~ is -H or -OH; (c~ the aminophenols and alkyl-substituted aminophenols having the formula pH

1(~ N~2 wherein R5 is -H, -NH~, -OH or an alkyl group containing from 1 to 8 carbon atoms, and R6 is -H, -NH2, halogen or an alkyl group as de~ined ~or R5/ such as, for example0 ~ ~53~3 ortho, meta, and para-aminophenols; diamino- alld triamino-phenols; methyl, ethyl, prop~l~ butyl and pentyl antino and diami.nophenols; and the li~e t the mo5.t praferred com-pounds being those in which R5 is H and R6 is -H or -N~2; and (d) d.iphenylamines, alkyl subst.ituted diphenyl-amines and other compounds having the formula R ~

wherein R is -N~ or a straiyht chain or branched alkyl group containing from 1 to 5 carbon atoms, and R1, R~, R3 and R4 may each be H, -NE~, -0~, halogen or an allcyl group containing from 1 to 8 carbon atom~ and at least two are -N~I2, ~OH or one of each, such as r for example, bis-phenol A, and the like, the most pre~erred compounds : bPing those in which R1 and Rg are -OH or -NE12 and R2 and R3 are -~. ;
The halogen in the above formula~ may be chlorine, hromine, iodine, or fluorine.
The molecular weight or degree o condensation of th~ polyaromatic ~mlne depends upon the ratio in which the reac.tants ar~ combined~ the time and temperature of heatlng, and the ~ind and concentrat.ion of the catalyst.
When reacting two or more of any of the above compounds together, they are usually employed in equal molar p.ropor-tions. EIowever, in order ~or the resultant condensation polymer or product to be soluble in aqueous a].kali metal hydroxide solutions, there must be a suffi.ciency oE
hydroxyl groups present on -the aromatic nucleii. In view ~19~;3~3 of this, it is preferable to employ the starting materials in such amounts and use reaction conditions such that a polyaromatic amine condensation product is obtained which has a maximum number of molecules terminated at both ends by hydroxyl groups. Qn the other hand, referring to the above formulas, iE Rl and R2 are -~-I2 groups, then suffi-cient of the R3 and R4 groups must be hydroxyl in order to achieve the necessary solubility. It has been found that about 2 or more hydroxyl groups per 1000 molecular weight are required for the above-mentioned solubility.
It is the acidity of such hydroxyl groups that enhances the solubility of the polyaromatic amines in aqueous alkali metal hydroxide solutions, such as sodium hydroxide, for example.
It is also possible to regulate the molecular weight of the polyaromatic amines by the use of small amounts of monofunctional compounds. For example, one can use small amounts of an aromatic monoamine or a phenol to cap the polymerization and thereby control the molecular weight. Those polyaromatic amines having a molecular weight greatar than about 250 are satisfactory~ The upper limit of molecular weight will vary depending upon the particular cornpound or compounds employed in making the polyaromatic amine. Suffice it to say that the particular polyaromatic amine should have a molecular weight such that it is workable and soluble in an aqueous alkali metal hydroxide solution so that it can be readily applied to the inner surfaces of the reactor when in a coating solu- -tion containing appropriate amounts of dispersant, as described hereinafter. I have found that for purposes J

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3~3 of the instant invention, polyaromatic am:ines having a molecular weiyht in the range o~ about 250 to about 1000 are preferred.
Particularly useful polyaromatic amines for the present invention are those obtained when an aromatic diamine and a polyhydric phenol are reacted together in approximately equal molar ratio. However, it is possible to use an excess of either the diamine or the phenol. he only difference is that when an excess of the polyhydric phenol is employed, polyaromatic amines are obtained which have a somewhat higher softening point than those made in the presence of an excess of the aromatic diamine. While some of the polyaromatic amines useful in the practice of the present invention do not have a definite softening point, it has been found that among the solid polyaromatic amines, those having a softening point in the range of about 65Co to about 150C. are most satisfactory. The softening point of the polyaromatic amine is determined by a procedure which is adequately described in the afore-mentioned Canadian Patent 1, 065 1 207 When making the polyaromatic amines an acid catalyst is employed. ~Cl is the most effective catalyst.
However, other useful catalysts may be employed, such as, for example, methane sulfonic acid, benzene sulfonic acid, sulfanilic acid, phosphoric acid, iodine, benzene disul-fonic acid, hydrogen bromide ( B r), hydrogen iodide (HI), aluminum chloride, and the like~ The concentration of catalyst will vary but it has been found that a catalyst - 12 _ , , .

:
. ~

;343 concen-tration of ~rom ab~ut 0~005 mole t.o clbOUt O . 20 rnole per mole of the compound being sel~-condensed, or per mole of the amlno compound when one or more compourlds a:re being recacted, is satisfactory. At any rate, the amount of catalyst employed i5 not eritical.
The tempexature of the reactioxl of the compounds, eikhex alone or with others~ will vary depending upon the tim~ of the reaction and the molecular weight desired in the final produc~ ~or sxample, one can heat the reac-tion in~redients rapidly to 315C. ancl then hold at that temperature for various periods o time. Also, the reac-tion ingredients can be hea~e~ to various ~emperatures above 300C. and immediately cooled. When this latter procedure is employed/ the reaction time is defined as 0 lS ho~.lrs. Accordingly, the temperature of the reaction will ~axy from abou~ 150C. to about 360C. and ~h~ time of reaction will vary ~rom abou~ 0 hour to abouk 3 hours.
The preferred range of reaction te~perature is from 175~C.
to 330C. and the time of reaction from 0 hour to 1 hourO
It is unders~oodJ of course, ~hat ~he particular time and temperature selected is dependent upon the cataly~t em-p:l.oyed and the final molecular weiyh~ of the polyaroma~ic amine de~ixed.
The important part of the instant invP~tion, and th~ significan~ improvement in khe use of polyaromatic amine reactor coa~ing compositions~ is the combination of an aqlleolls media dispersant or suspending agent, with the polyaromatic amine i.n the coa~.ing composition~ The aqueous media dispersants or su~pending agents useful in the present invention are polyvinyl alcohol, polyvinyl pyrxoli-`

3~L3 done, gelat:in (Ca.l:E ski~ starch, and hydroxy propyl ~lethyl cellulose (Me~.hocel). The amount of disp~rsant or sus-pendinCJ agent employed in -~he coatiny composition or solutioll i.s set ou-t. here:inaEt~r.
Th~ most pre~erred dispersants or su~pending agents are the polyvinyl alcohols ~here.inafter "PVA") which are produced by hydrolyzing po.l.yvinyl ace~ate ~o an amount in the range o abou~ 75% to about 100%. ~ince most of th~ commercial PVA'~ are hydrolyzed pol~y~inyl acetates of about 88~ is preerred, or prac~ical reasons, to employ a PVA which is in the range of about 85% to about 30~
hydrolyzed poly~inyl acetate. It should be noted that when employing a PVA which contains about 25~ vinyl acetate groups ~hyd.roly~îs = 75%~ in water, turbid.i~y occur~ indi-cating incomple-~e solution, particul~rly upon heating~ How-ever, when th~ same PVA is employe~ in the aqueous ~lkali metal hy~roxide coating solution of the present invention, such turbidity disappears since ~urther hydrolysis occurs At the hi~h p~l of th~ hydroxide coating solution. The most preferred PVA is one which is an 88~ hy~rolyzed poly-vinyl asetate.
As has been previously pointed out, an alkali metal hy~roxid~ solution of a polyaromatic amine, as de-fined abo~e~ wh~n applied to the interior surace~ of a polymeri.2at.ion react~r~ will reduce the buildup o pol~mar thereon~ Howe~er, the polyaromatic am.ines are colored matexial~ and solutions ~hereof will di~color ~he polymer particles that do form on the inner surfaces of the reactor~
Xf these p~lymer particles are inadvertently removed from saîd surfaces, during the course of mak:in~ the pol~meriza-tion product, such as polyvinyl chloride (PVC~, the , . .

;3~3 entire batch oE pol~ner can be rejec~ed for .inerio.r ~uality due to the occurrence of said of-white particles of pol~ner. The di.scoloration problem is primarily due to the necessaril~ high concentrations of polyaromatic amines khat mus~ be employe~ in order to get the proper amount ther~of adsorhed on the interior surfaces o the reackor. It should be poin~ed out, however, t.hat the polyaromatic ~nines do substantially eliminate buildup on said surfaces when the concen~ration thereof is suffl-ciently high in the coating composition.
The reason for the necessity to use such a large amount of polyaromatic amine is tha~ you need a water-wettable surface in ordex ~o pxevent buildup. An ordinary solid sur~ace, such as stainless steel for example, is not water~wettable due to the normal contamination of said surface with organic materials through contact with the atmo~phere. The ~urface can be cl~aned, such as with chromic acid, for example, and it will become water~
wettable~ However~ this is not the full answer, since the surface will not remain in that condi~io~ for a sufficient length of time r ~ha~ is, fox more than the duration of a single polymeri2ation reaction. That is to say, the surface must be recleaned after each polymerization cycle. There-fore, appl.~ing a coating to the suxface which w.ill be water wettable and resist polymer buildup thereon and rema:in on said suxf.lce throughout mul-tiple reaction c~cles is more desirable.
When a metal or solid surface is non-wettable r a liquid, such as waterJ thereon will foxm dropletc; and not flow out into a smooth uniform film. The angle formed : .

between the tclngent of the side of the drople-t and t:he mPtal or glass surface :is called the "contact angl~3" and is xeferred to as "khe~a ~! ~o~. ~ ~r~her measurement of ~he wettability of a solid ~u.rface is ~he cri.~ical surface S ~ension fox wet.t.ing a soli~ surface ancl i.s expr~s~ed as "yc~ he ~c is measured in dynes per centimeter~ Using water as the standard, in order for a solid surface to be wettable, ~ m~ls~ ~qual zero or be ~ery close to it, and ~ mus~ be 72 dynes/cm. or greater.
Mo.re importantly, the material being applied to the surface should not only ~orm a wettable surface, bu-t ~-also form a layer or film thereon which is not readily removable. This film adhere~ to the solid or metal sur- ~
face by a~sorption and in many case~, the film is a mono- :
layer of the ma~erial applied which is of the order o a molecule in thickness~ The films o the coating compo5i-tions o~ the instant inven~ion have a thickness of about 20~ or les~ indicating a film approximately one mo.lecule in thickness~ These ilms of such thickness are invisible to the naked eye thus solving the color problem heretofore referred ~oO The film or layer formed by the coating composition applied to th~ surface is not re~ova~le by washin~ with water. Tha~ .is ~o say~ the coating or .-Eilm is resistant ~o r~noval rom ~he surfaces when a tur-~5 bulQnt aqueous reaG~ion medium is in contac~ therewith, caused by the agita~ion o:E ~he polymeriza~ion mixture in the reactor.
The coat.ing solutions of the instant .invention are made by conventional methods, using heat and agitation where necessaryO The polyaromatic amine and the di.spersant 1~ ~

s~

or suspending acJent are c1issolved in t.he appropriate aqueous alkali metal hyd:tox:ide so~ ion to arl exterlt such that the solids contellt of ~he coating solu~iorl does not p~e~ent it roil~ bein~ easil~r applied Oxl the~ inner sur-Faces o ~he reactor. Usuall~ a coat.ing solutiorl ha~:ing a solids conte~llt o:~ polyaromatic amlne in the range o:~ abollt 0.01% ~:o about 0 ~1.05~ ~y weigh-~ and of di~persant .in the range of about O.U02% to about 0.02% ~y weicJht is satis-~ac~ory~ rrhe total ~olids ~ontent of the po.lyaromatic ~nine and d:ispersan~ of the ~oating solution will be in the range of abou~. 0 ~ ol 25~ to abou~t 0~12% by weigh~t~ How~
ever, since the solids contexl~ depends upon the molecular weigh~ of the inc3redien~s in the coat.ing solution, the total solids cont~n~ could~ iIl c~r~ain .instances/ be greater than 0.12% or less than 0.012~ ~y weightO Irrespective o~ the ~otal soLids conten-t chosen, within the limits de~ined ab~ve, it is im~ortan~ that ~he ratio of poly-aromatic amine ~o dispersant be kep~ within cer-tain pre-scribed limits. I have founc1 chat a ratio of polyaromatic amine to dispersan~ in the range between about 10 to 1 to about 2 to 1 is sa~ actory. Th~ pre~erred or optimum ratio is one in the xange of 7:1 to 2:1~ For example, I
have ~ound tha~. a ra~io o~ pQlyaromatlc amin~ to polyvinyl alcohol of 5:1 comes clos~ to the conceptual model wherein each polyaromatic anion pres~nt associates with each ~CH~-CHO~ repeatirlg unit of the polyvinyl alcohGl~ ei-ther by hydroge:rl bonding or hydrophohic bond ing. Xn the coa~ing solution a polyelectrolyte co~plex is believed to be ox~!ed between the polyaromatic amine and dispersant with the latter acting as a carrier ~or the .. ., . -, : : :

polyarol~cl~.i.c .mline ~o the reactor sllrf~cec;. When the dispersan~ is p:resent as a p~r~ of ~he reclpe i.n the poly merizatioll mecliwn, rather ~.h~n in the co.~t.i.nc3 so:l.ution/
it CanX10~ act ,.lS a ca:rr:ier :Eor ~:he polyaromatic arnine after the fac~t:) si.nce the amine i.s a.Lready on ~he wall and o necess.i ~y r i.n higher concen~ra-tion due ~:o ~he absence of the dispersant in ~he coating solution. ~lso, with such hi~her concen~.:ra~ion o:E polyaromatic a~i.ne, a ~i~ible colored surfac2 co~t:ing .results, which r as previousl~
po:inted out~ is to be aYoided. It is only when e~ploying the coatin~ composition of the instant invention that the -.
~esired result is ob~ained~ namely, ~he use of a more dilute ~olution o:E polyaromatic am;ne and elimination of the color problem.
The important aspect of the present invention is that the use of ~ dispersant or suspe:nding agent in the coating solution allows the use of ~ower concentrations of polyaromatic amin~ re~ulting in a ligh~ly colored coating solutioll. In ~act r at pxeferred so:Lids conc~ntrations, the color or tha coating solution i5 slightly amber~colored :.
thus eliminating ~he off-white par~icle problem previousiy referred to~ ~t has been ~ound ~ha~ by the use o~ dis-persant~ in the coating solution, the necessary concentra--tion of polyaromatic amine therein can be reduced by a faetor in the range of bet~een abou~ 10 to about 100 with khe aforesa.id ac~o~panying benefi~s o:~ eliminatinc~ any possible problem~ of o~-white particles being produced by color~d particl~s of polyar~matic amine react~r surface coat.ing and al~o, a considerable econom.ic bene~it by use of l~s polyaromatic amine. For example, when employing ~39~3~3 0.02~ po].yaromat.:i~^ amine an~ 0.004% po~yvinyL alcohoL
in a COatillg SolU~iOn ver5us 1 . 5% polyaromatic amine with-out poly~inyl alcollo.l r the c~oncen~ratioll:recll:~cti.orl factor is 75~
T:he a~ueous alkali me-tal hydroxi.de solutions used in mak:Lng the coati.ng solutions o:~ the lnstant inven~
tion are thosP made from a metal in Group lA of the periodic syst~m~ ~'or example, such hydroxides as sodium hyd~oxidel lithium h~droxide~ potassium hydroxide r rubidium hydroxide/ ce~ium hydroxi.de, and francium hydroxide.
~queous SOlUtiOIl~ of other compounds may also be used.
For example, aqu~ou~ solution of quaternary amines, such ::
as the tetraalkyl arnmonium hydroxides, and the like J OX
other alkali me~al salts, such as phosphates, for example~
tr.isodium phosphate, and the like. I have found that it is most important that the compound chosen must, in aqueous solution, have a su~fici~ntly high basicity or pH, usually about 12 o.r higher. Pre~exably, sodium hydroxide is em~
pL~yed and in a pH range of 12 to 13.5 in the final coating solution, However, i~ is be:Lie~ed that some com-pounds having a p~ lower ~han 12 woul~ be operable in the present invention. It has ~een found, fox e~ample, that the mo~t .~uccess~ul use of ~he coating solutions o the pre~ent inverltion occur~ most e~Eiciently in solutions having a pH of about 12.5O
The temperatuxe of the aqueous alkali metal : hydroxide $olution when the polyaromatic amine and di~
persant axe dissolvecl ~herein i5 not cx.iti.cal. Usually a temperatwre in the range of about oac. to about 100C~
is satisfactory. The ord~r or dissolution of the .ingre-- 19 - `

, . ~

3~3 dients is not c:ritic~al, bu~ slnce ~-.he ~.isper~3ant: usual.ly d.isso:Lves more slow:L~r -than the polya:romat;ic amine, i t :Ls put into sQluth~n irs ~ ation dur.iny dissolution o~
th~ coatlrly .so:L~:Ltioll ing:redients is desirable and in some S instanc~s nec~ssary~ particular:l.y when the polyaromatic a~nine is o:F a h.i gll molecular weight ~ In order to obtain the desired .results~ ~he concen~ration o the alkali metal hydroxide in the a~ueolls coa~in~ ss:~lution should be :between abou~ 0 ~ 04% by weight and about 0 ~ 50% by weight~ Prefer-ably the con~entra~ion of a3 kali metal hydroxide i5 from 0 ~10% to 0 ~ ~5~ by ~eight.
A~ ~previ ously pointed out, the coating solution is usually applied ~o the inner reactor surEaces by spray~
ing. However, .it is also possi~le to apply the coating solution ~y f 7 ooding the reactor and then draining r paint-incJ or brushing on, but sp.raying is ~he most practical and economical me l:hod o~ application . A~ ~ex spraying the coating solult.ion on the inner suraces and drainillg the reactc)r, the polymerization reaction can be started . 20 ~ nediately without furt:her treatment of sa~.d sur~aces. :~
~lowever, i~ has been found that e:~cell~n~ results are obtained wherl after applying ~he coating so:Lu tion ~o the inner surfaces of the reactQr, the coated surface~ axe ~prayed with water and ~he reac~ox dxained prior to charg-ing the reactor with th2 polymerization mixture or recipe.
It ~hould al50 be poin~ed vut that ~he pre~enk coating w3rk~i equally well Oll glass or metal surfaces, such as stainless steel, and the likeO
While the exa~t adhesion mechani.sm of the coat-ing to the surface~ of the reactor is not known for cer~

53~3 tain, it is be1ieved to invol.ve some type~ o~ e1ectrica1 force ox adsorpt:ioll between the reactor suriaces and the po1yaroma~ic amine ~ clispersant comp1ex, At any rate, the ~oating compos1tivn oE the present invention does suhstantia1:Ly eliminate po1yTner buildup on the reactor surEaces and what 1i~1e pol~er ~uildup, if any, that may occur, is o -~he sancly type which is of such a nature that it is readi1y removab1e from the reactor surfaces without the nec~ssity of manucl1 scraping procedures. The polymer bui1dup to be avoided is what is referred to as "paper buildup" since this type of buildup is very di~fi~
cu1t to remove and usua11y re~uires hand scraping or the use of a high pressure jet stream of water or oth2r liquid. In ei.ther event, the reactor must be opened in order to clean the same, which, of course/ allows the escape of unreac~ed vinyl chloride into the atmosphere.
In accordance with the present invant.ion~ multi-ple pol~meri~ation~ may be run without opening the reactor between chaxges. In one experiment, mor~ than 100 charges of vinyl chloride were polymeri7.ed to polyvlnyl chl oride using the ~uspension polymeriza~ion procass, in a reactor haviny thP coatiny of the instant lnvention on the inner suraces thereof, and r~coat1ng said surfaces without opening the reaetor between charges. This i~ accomplished by applyin~ the coa~ing through spray nozæles mounted on the reactor~ 'rhe rinse water is li3cewi~e ~ntered thxouyh said nozæles. When the reactox was op~ned at the compl~-tion of the experiment and the inner ~urfaces examined, it was ~ound that they were ~:Lean wi~h only small isolated spots of sandy bu:Lldup~ ~.ith ~he reactor being classified ~ 21 -3~

as cleall/ or in factory parlance, would be clas~,ifiec1 a~
a "clean poly'~r Al~hough seYeral charqes may be run wi~h-out recoatillg the surfaces, it has be~rl ~ound to be expeditlous, an~ preferred, ~o recoat ~;he internal surfaces of the reac~or after each charge ~o insure uniorm and efficient production~ ~5 pre~riously pointed out, with the spray noz~les pe~manently mounted at strategic points on the reac~or, i~ i.s possible ~o reach all inner surfaces thereof~ When it is decided to recoat the react~r, the reactor is drained, and the inner surfaces of the reactor are flushed with water. The coating solu~ion is sprayed on the surfaces by means of the spray no~zles and the reactor is drained oE t~e excess ~olution in such a way that the same can be s~nt. to a xecovery syst~m, if desired.
Then, optionally t the sur~aces are sprayed with water and effluent is discarded~ or recovered~ if de~ired. There-after, the reactor is charged with ~he polyme.rization medium and i~gred.ients in the usual manner and the poly-merization reaction commenced~ I~ is understood, of cours~ at one can recoat the reactor as often as de~
sir~d without openîng -the same, even aft~r evexy ch~rge is pol~meriæed.
After the application of the ~oating compo~ition on the interior ~uxfaces Q~ th2 reaction vessel, and when elected, spraying the~eo~ with water, the reaction to be carried out in the equipment may be comm2nced i~ne~
diately, no particular modiica~ion of proce~sing techniques being required due to the pxesence of the coating. Further~
util.i~a~ion 5f ~he intexnally coated reaction ve~sel of the pxesent invention doe~ not adversely affect the heat ~5~3~3 ~tabil.ity or oth~ar phy~ical. and chemical properties of the pol~mexs produc!ed there.inO
Whi1.e the present invention i.s sp~cif.ically illustra-~ed with regard to the suspen~ion polymeriæation of vinyl chloride, i~ is to be unde.rstood ~hat the ap-para~us and p.rocess may likewise be applied in the disper-sion, emu:Lsion, or suspension polymeri.æation of any poly-meriza~le e~hyl~nically unsatura~ed monomer or monomers where undesirable polymer buildup oceurs. Examples o~
suc~ monomers are other vi~yl hali.des aIld vinyl.idene halides, ~uch as vinyl br~mide, v.inylidene chloride t etcO;
v.iny~idene monomexs having at least onP terminal CH~-C~
grouping, such as esters of acrylic acid, for example, methyl acrylate~ ethyl acrylate, butyl acxylate, octyl acrylate, cyanoethyl acrylate, and the like; vinyl acetate, esters oE methacrylic acid such as methyl methacrylate, butyl methacrylate, and th2 lik~; Styï ene and styre~e derivativ~s including ~methyl styrene, vin~l toluene r chlorost~re~e; vinyl naphthalene; diolefin~ includin~ :
butadiene~ i~oprene, chloroprene, and the like; and mix-tures of any of these types of monomers and other vinyli-dene mono~ers copolymeriza~le th~rewith; and other vinyli~
dene monomers of the ty es known to those ~killed in the art.
The presen~ invention, however, is particularly applicable to the suspension polymerizati.on O-e vi.tly~
chlorid~, either alo~e or in admixture with one or more other vinylidene monomers having at least one terminal C~2=C~ grouping, copol~merizable therewith in ~mount~ as ~reat as about 80g or more by weight~ based on the weight - 23 ~

.

3~

of the monomer mixture, since polymer buildup in the reaction vessal is a particularly had problem here.
In the presen~ invent.ion~ the pol~nerizat.ion process is usually conclucted at a ~emperature in the range of abou~ 0C. to abou~ 100C. depe3nding upon the particular monomer or mon~mers being polr~erized. ~owever it is preEerred to employ ~e~peratures in the range o~
about 40C. to abou~ 70C., since, at these temperatures polymers having the mos~ benefic.ial properties are pro-la duced. Th~ time of the polymerization reac~ion will vary from about ~ to about 15 hours.
Th~ polymerization process may be carried out at autogenous pressures although superatmospheric pressures of up to 10 atmosphere~ or more may be employed wi.th some advantage with the mor~ volatile monomers. Supera~mos~
pheric p~essures may al~o be employed with those monomers having th~ requisite volatilities at reaction temperatures permitting reflux cooling of the reaction mixture.
Further~ the polymerization process may be carried out utilizing a full reactor technique. That i5 the reaction vessel is completely illed with the polymeri-zation mediwm and kept that way throughout the .reaction by constan~ addition there~o of water or addit.ional ma~e-up liquid containing the monomer or moncmers in the same proportion a~ at star~--up. Upon the addition o~ a certain predetexmined amou.nt of liquid, the polymeri~at.ion reaction is termin~ted~ usually by the addition thereto of a short-stopping agent. The necessity or the addition of liquid i~ due ~o ~he shrinkage in volume o~ ~he reac~ion medi~m produced by the conversion o the monomer or monomers to ~ . .

;3~3 the polymeric state.
It is again emphasized that the ratio of poly-aromatic amine (PAM) to dispersant in the coa-ting solution is most important. By way of illustration, for example, where PVA is adsorbed preferentially nearly exclusively, a surface results showiny a significant contact angle (4) with water and characterized by a Yc of about 55 d/cm.
(dynes/centimeter). Where the polyaromatic amine is pre-ferentially adsorbed, a surface results showing a contact angle with water of 0 and a y ~72 d/cm~ If too low a ratio of PAM/PVA is employed, there is competition between adsorption of free P~A and PAM-PVA complex which results in a Yc less than 72 d/cm. If too high a ratio is em-ployed, both PAM and PAM-PVA complex adsorb giving a Yc ~72 d/cm. However, since at low concentrations, the P~M adsorption is not as efficient as the complex, a greater total concentration of PAM in the coating solution is required.
I have found that the best single criterion for determining the proper PAM/dispersant ratio is the "minimum concentration of PAM required to adsorb `~
to form an irreversible water~wettable layer having a Yc of >72 d/cm. in 5 seconds". This correlates well with ., good performance as a reactor coating to eliminate polymer buildup. Concentrations in the coating solution of PAM
below this minimum concentration require a longer time for adsorption and if appreciably below this concen-tration~ will not parform well as a buildup preventing coating. Concentrations appreciably above this minimum value, while adsorbing and working, cause increase in ._ .

.. . . . . . .

~a~9r-~3~ ~

color o F the coating solution and the .r~sultant "off-white" problems above-referred to.
In order to illustrate the above, a series of coating solutions were made up, using polyv.inyl alcohol and varying ~he P~M/PVA ratio in ].ight of the parameters outlined above. The polyaromati~ amine employed was made by the reaction of m-phenylenediamine (m-PDA) with resorcinol ~Re.s~) in equimolar par~s. HCl was used as the catalyst in the following recipe:
Mole Grams m-PDA 1.0 lQ3 Res. 1.0 110 HCl 0.1 3.65 The m PDA and Res. were premixed and charged to a three-necked round bottom flask. The HC1 catalyst was added and heating started with the temperature taken from room temperature up to 3159C. as rapidly as possible. Melting .
of the char~e occurred at about ~0-70C. When most o the solid had melted, a stream of nitrogen gas was intro-duced into the melt by mean~ of a dip tube which provided agita-tio~ of the mixture. The reaction mixture was held at 315C. for a period of 1/2 hour~ Thereafter the heat was removed and a stream of air was ~irected over the 1ask. When the temp~rature had dropped to 250C., the batch was quenched by pouring into a mixture of ice and water with agitation. The pvlyaromatic amine was then filtered off and air-dried at room temperature. The softening point of the polyaxomatic amine or xesin was 111C. This resin is designated as PAM-I for purposes o~ simpliGity w.ith respect to ~he speciEic examples, which ~ollow hereinaE-ter, The polyaromatic amine thus produced and the polyvinyl alcohol were dissolved in aqueous NaOH in vary-ing ratios, as indicated in the table that follows, and S the resul~ing solu~ions were adjusted to ,a p~ of about 120 The minimum concentration o the PAM in each case was then determined. The results are tabulated in the fol-lowing table:
TABLE I
.
Minimum Concentra-Yc in d/cm tion of PAM to give Ratio Adsorbed Yc >72 d/cm in S
PAM~PVA Laver seconds 1. IPAM only) ~72 0.35%
2. 10/1 >7~ 0.14%
3. ~/1 >72 0.09 4. 6/1 >72 0.04% :

5~ 5/1 ?72 0.02% ~ ~:

6. 3/1 ~7~ 0.04%

7~ 2/1 ~55 0.~2 ~o ~.20% :
(Does not give Yc >7~

8. (PV~ only) ~55 - ,~ :
The above results show that the optimum ratio of PAM/P~A
i5 5: 1 . Further, the concentration of polyaromatic amine is greatly reduced when employing polyvinyl alcohol in conjunction therewith. ~hen employing polyvinyl alcohol it i5 possible to use 1/30th less polyarvmatic ~mine and achie~e the desired results.
The same procedure as above was followed using other disp~rsants in place of PVA and the optimum ratio of polyaro~atic amine/dispersant and the minim~ concen-tration to give Yc >72 d~cm. in 5 seconds. The results were as follvws.

~0~53~3 TABLE II
Optimum Minimum Concentration Ratio. of PAM -to give Yc >72 Dis~ersant PAM/Dispersant d/cm in 5 seconds _ Hydxoxy propy].
methyl cellulose 6/1 0.03%
Polyvinyl 10 pyrrolidone 2J1 0.075%
Gelatin 2/1 0.04%
It is .noted that in each case the concentration of poly-aromatic amine was greatly reduced.
. The polyaromatic amines used in the present in-vention will oxidize on normal exposure to oxygen. This oxidation is not detrimental if the PAM is used within a short time after being made. However, oxidation of the PAM causes darkening in color of the same, with its at-tendant difficulties~ as previously pointed out, and further, the adherence to the reactor surfaces is adversely affected by such oxidation. However, by employing a dis-persant in the coating solu-tion, adherence to the wall of the polyaromatic amine is enhanced in spite of any oxidation thereof that might occur. This i5 SO because the dispersant acts as a carrier for the PAM and binds it to the surfaces, so to speak. This avoids the necessity of employing high concentrations of PAM and prolonged application times.
PAM solutions on oxidation show an increase in.
the minimum concentration to give Yc >72 d/cm in 5 seconds adsorption. For example, referring to Table I above,.a fresh P~M solution shows such a minimum concentration of 0.35~. When this solution was aged one hour exposed to . - 28 -~'Y

the a~mosphere the adsorption time, becau~e of oxidation, increased to greater than 120 seconds. After aging for 2 days the minimum concentration had increased to 0.80%.
~ence, the mechanism of transport to the surface was sig-nificantly altered by the oxidation of th~e PAM. On the other hand, in the case of the PAM/P~A complex, even though the PAM oxidation occurs on aging, the mechanism of transport ~o the surface is not affected by aging for 2 days since the PVA polymer chain acts as the carrier and is not noticeably affected by the oxidation. This was shown by the following experimental data given in Table III. . ~:
TAE~E III

% Light Time to a lS Trans- Yc 72 Formulation A~e mission Layer 1, 1. 0.05% P~M Fresh 77.6% 15 ~econds :
0.0067~ PVA
0O033~ NaOH
20 2. Same 2 days 60.0% <20 seconds 3. Same 13 days 36.0% ~30 seconds From the above, it can readily be seen that the adsorption time of the PAM/P~ complex is far superior to PAM alone, I
that is, >30 seconds after 13 days versus ~120 se~onds -:
after l hour.
Although oxidation of high pH solutions of poly-aromatic amine~di~persant is orders of magnitude less critical than solutions of polyaromatic amine alone, in terms of adsorption efects, the very low concentrations of polyaromatic amine possible in the instant invention make the ratio of available oxyg~n to polyaromatic amine much greater for a given aging condition so that eventually ~ 29 -.

53~

aging ef~ects will be noticeable, ~hat is, in 13 days and above. For this reason, and to less~n the chance of col~r problems, even further than that produced by the abil.ity to use very low concentrat.ions of polyaromatic S amine in the present coating solutions, it: is o~ten desir-able to incOrpQrate antioxidants in the coating solution.
Such addition does not adversely af fect the properties or performance of the coating solutions. I have found that when sodium ascorbate is incoxporated in the coating solu-tion, in amounts in the range o about 0.0S~ to about 0~10%
by weight, such addition slgnificantly retards both dark - ening of the solutio~ and increase in ad~orption time, when compared to controls containing no antioxidant, for periods up to 14 days. It was found that sodium dithionite and sodium "phenolic acid" were also of value as antioxi-dants in the coating solukions of the instant invention.
I~ order to rate the various coatings, as particularly set forth in the specific examples which follow hereina~ter, we have devised a rating scale with respect to paper and sandy buildup. An uncoated reactor, referred to as the control, where normal amvunts o~ both types of buil~up occux, is given a rating of 1O5. Any rating below 1.0 is good or a definite improvement. In other words, 0.0 rating is perfect, and so on.
In order to ~urther illustrate the present invention, the following specific examples are given.
It is to be understood, however, that this is merely intended in an illustrative and not limitative sense. In .the examples, all parts and percents are by weight unless okhexwise indicated.

EX~NPLE I
In this example ~he polyaromatic amine was made by the reaction o~ m~phenylenediamine (m-PDA) wi~h xesor-cinol (Res.) in e~uimolar part~, as described abo~e, and the product designated P~M-I. The coating solution wa~ l;
made up as fo?lows, with the ingredients being ~ixed with agitation in the order listed:
1. Demineralized H2O 731.5 part~
2. 50~ NaOH 3.0 part~
3. 10% Na Ascorbate in H o 3.0 parts 4. 2~ Polyvinyl alcohol ~PVA~ 1.5 paxt~ ~ , (88% hydrolyzed polyvinyl . .:
acetate~
5. 15% PAM-I, 10% NaOH 1.0 part The resultant coati~g solution contained the ollowing ,.
percentages:
1. O.0200~ PAM-I
2. 0O0040% PVA
3. 0.20~ added NaOH
4. 0.05% Na Ascorbate .
~he pH of the coating solution was 12.45 and the time of adsorptiQn on the reactor surfaces was les~ than 5 seconds~ ;
The inner surfaces of the reactor were coated by spraying j: ;
the coati~g ~olution thereon and then rinsed wi h w~ter.
The following recipe was then charyed to the reactor in u~ual fa~hion:
Vinyl ch~oriae1000 ~rams W~tex ~deminexalized)2055 grams 88~ hydroly~ed polyvinyl acetate 0,5 gram ~p~ cataly~t) 0.5 cc (1~ di-secondary butyl peroxydicarbonate The reaction was ~arried out with a full reactor, that is~ sufi~ient water was added to fill the reactor and at a temperature of 57~C. with agitation. The reaction was continued with addition of water as the ~ixture shrank ~ 31 -.... .
.;: .
. .

3~3 becau~ of the ~orma tion o:f ?olymisr in order to keep the reac~or ull. The r~ac~ion wa~ di~;cont~ ed UpOXl the addl-tion of 400 grams of wa~er. ~h~ conten~; o the re;actor wer~ kherl r~ov~d in wsual ~ashion~ ~rh~ ~ame pro~edllre of coating and polymterizat:ion was repe~t~d ~wo mc3xe time~
making a total o~ three cyc:le~ or charges, q'hereaft r ~ !
~h~ internal surface~ wer~s ~xamined and ~la~ Eied in accordalllc~ with the afor~m2ntioned procedure for rating said surfaces. The :rating was as ~ollows: paper buildup -0 . O and salldy buildup 0.1. I* can readily be seen that the coated reactor was far superior to the control, or ;~
uncoated r~actor, which had a rating of 1.5. It should also be p~intéd out that there were no changes in the properties of the polymers proauced in ~he pre~ence o~
lS the coating, particularly, no change in color of the poly-mer and no of-white particles were present.
EXAMPLE II
~ .
In this example, ~he same coating solution as in Example I was employed. Also, the same polymerization recipe and conditions were used as in Exa~ple I. However, in this experiment thP inner surfaces o the reactor were coated by spraying the coating ~olution thereon but the coating wa~ not rinsed with water. The recipe was added i~mediately ater coating and draining th~ excess. When the pol~meri2atiorl was complete, the contents were removed and the inner surfaces coated as before. When th~ second cycle or charge was complete, the suraces were examined and xated as in Example I. The rating was a~ foll~wso paper buildup 0.0 and sandy buildup 0.1. Again it can be seen that the coated reactor was ~ar superior to the con-~ 3~ -.

~ gr;343 trol. Further, this ex~llpls shows tha~ it is ~ot necessary to rinse the coating with watar after app:Lication to the inner surfaces and prior to polymeriza~ion. The properties of the pol~mer were unal-~er~d and no off-whi~e particles o~ pol~m~r were observed.
EXAMPLE III
In this Example, the same polym~erization rec.ipe and conditions were usad as in Example I. The coating solution wa~ made up as follows, with ~he ingr~dients being mixed with agitation in the order listed:
1. Demineralized H~O78.3 parts 2. 1% NaO~ 19.7 parts 3. 0.05% Ascorbic acid0.1 part 4, 0.5% hydrox~propyl methyl cellulose1.7 par~s 5. 15~ P ~M-I, 10% NaOH0.34 part The resultant coating solution contai~ed the following percentages:
1~ O.05% PAM-I
2~ 2~ 0.008~ Hydroxypropyl methyl c~llulose 3. 0.23% Added NaOH
4. 0.05~ Ascorbic acid The same procedure for coating the reactor was followed as in Example I. Three pol~meri~ation charges or cycles were run as in Ex~mple Io Thereafter, the internal surfaces were examined and classified in accordanc~
with the aforementioned procedure for rating said su.r-faces. The rating wa~ a~ follows: paper buildup 0.3 and sandy buildup 0.O. The coated reactor was far superior to the control or uncoated reactor~ which had a rating of 1.5.
EX~MPL~ IV
The same procedures, as outlined in Exa~ples ' ~53~3 I and III, w~re followed in th.is Example using the fol~
lowing coating sol~ltion:
1. Demineralized H2O 64.~ parts ~ MaO~ 1~.7 parts 3. 0~2% polyvinyl pyrroli~
done (PVP) in ~I20~0.0 parts 4. 15~ PAM-I, 10% NaOH 0.53 part The resultant coating solution contained the following perc~.ntages:
1. 0.08% PAM~
2. 0.04~ PVP
3. 0.~0% Added NaOH
The ~ame procedures were then followed as in Example :tII
and the rating of the reactor after 3 charges was as follows: paper buildup 0.3 and sandy buildup 0.3. Again the reactor was far superior to the control or uncoated reactox.
Coating of the internal surfaces of the poly-merization reactor, in accordance ~ith the present in vention, substantlally reduces, and in many cases, practically ~liminates polymer buildup on said surfaces during the pol~merization reaction and thus results in increased production over a unit period of time. In those in$tan~es where a little polymer ~uildup does ac-cumulate on the interior surfaces, it is not of the hard~
rough~ difficult-to-rem~ve type and is easily removed with . :
out employing the difficult and tedious ~craping metho~s that are presently necessary in the art. More importantly, the present invention ~nables one to operate a clo~d :
polymerlzation ~y~tem, which, in the case o vinyl chloride polymexi~ation, has the advan~age of reducing drastically the parts p~x million of vinyl chloride in the abmosphere of the plant. Such reduction in viny~ chloride in the :

.

.

atmosphexe meets the requirements recently promulgated by OSE~ ~Occupa~i~nal Safety and Health ~d~inistration) and EPA ~Environmental Protection Agency). NuDnexous other advantages o the present invention will be apparent to those skilled in the art.
While the present invention has been de~cribed in terms of its specific embodiments, certain modifications and equivale~ts will be apparent to those skilled in the art and are intended to be included within the scope of the present inventio~, which is to be limited only by the scope of the appended claims.

Claims (51)

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

1. A process for substantially eliminating the buildup of polymers on the internal surfaces of a poly-merization reaction vessel which comprises applying to said surfaces a coating solution comprised of an aqueous alkali metal hydroxide solution containing from about 0.01% to about 0.10% by weight of a straight chain or branched polyaromatic amine having a molecular weight greater than about 250 and having at least 2 -OH groups per 1000 mole-cular weight and from about 0.002% to about 0.02% by weight of an aqueous media dispersant, the ratio of said poly-aromatic amine to said dispersant being in the range of about 10:1 to about 2:1, said polyaromatic amine having the structure selected from the group consisting of I. wherein (1) A, B, and C are selected from the group con-sisting of (a) wherein R3 is -H, halogen, or an alkyl group containing from 1 to 8 carbon atoms and may be the same or different; R4 is -H, -OH, -NH2 or an alkyl group containing from 1 to 8 carbon atoms and may be the same or different; and R5 is or a straight chain or branched alkylene or alkylidene group containing from 1 to 5 carbon atoms; and (b) wherein R3 and R3 are the same as for (a); and wherein A, B, and C may be the same or different and each repeating unit may be the same or different; (2) R1 and R2 are either -H, -OH, -NH2, or and may be the same or different and wherein R3 and R4 are the same as for (a); and (3) x is an integer from 1 to 20 and y is an integer from 0 to 20; and II. wherein (4) A, B, R1, R3, R4 and R5 are the same as in I and R2 is -H, or as defined in (2); and (5) x is an integer from 1 to 4 and y is an integer from 1 to 15.

2. A process as defined in Claim 1 wherein the polyaromatic amine has the structure I.

3. A process as defined in Claim 1 wherein the polyaromatic amine has the structure II.

4. A process as defined in claim 1, wherein the dis-persant is polyvinyl alcohol and the ratio of polyaromatic amine to polyvinyl alcohol is in the range of 7:1 to 4:1.

5. A process as defined in claim 1, wherein the pH
of the coating solution is 12 or greater.

6. A process as defined in claim 1, wherein the total solids in said coating solution is from about 0.012% to about 0.12% by weight.

7. A process as defined in claim 1, wherein the poly-aromatic amine is the reaction product of a polyamino benzene having the formula wherein R1 is -H, -NH2, -OH or an alkyl group containing from 1 to 8 carbon atoms; and R2 is -H, halogen or an alkyl group as defined for R1, and a polyhydric phenol having the formula wherein R3 is -H, -NH2, -OH or an alkyl group containing from 1 to 8 carbon atoms; and R4 is -H, halogen or an alkyl group as defined for R3.

8. A process as defined in claim 1, wherein the polyaromatic amine is the reaction product of a polyamino benzene having the formula wherein R1 is -H, -NH2, -OH or an alkyl group containing from 1 to 8 carbon atoms; and R2 is -H, halogen, or an alkyl group as defined for R1, and a compound selected from the group consisting of diphenylamines, alkyl-substituted diphenylamines and other compounds all having the formula wherein R is or a straight chain or branched alkylene or alkylidene group containing from 1 to 5 carbon atoms; and R1, R2, R3 and R4 may each be -H, -NH2, OH, halogen or an alkyl group containing from 1 to 8 carbon atoms and at least 1 of which is -OH.

9. A process as defined in Claim 1 wherein the polyaromatic amine is the reaction product of a polyamino benzene having the formula wherein R1 is -H, -NH2, -OH or an alkyl group containing from 1 to 8 carbon atoms; and R2 is -H, halogen or an alkyl group as defined for R1, and an aminophenol or an alkyl-substituted aminophenol having the formula wherein R5 is -H, -NH2, -OH or an alkyl group containing from 1 to 8 carbon atoms; and R6 is -H, -NH2, halogen or an alkyl group as defined for R5.

10. A process as defined in Claim 1 wherein the polyaromatic amine is the reaction product of an aminophenol or an alkyl-substituted aminophenol having the formula wherein R5 is -H, -NH2, -OH or an alkyl group containing from 1 to 8 carbon atoms; and R6 is -H, -NH2, halogen or an alkyl group as defined for R5, and a compound selected from the group consisting of diphenylamines, alkyl-substituted diphenylamines and other compounds all having the formula wherein R is or a straight chain or branched alkylene or alkylidene group containing from 1 to 5 carbon atoms; and R1, R2, R3 and R4 may each be -H, -NH2, -OH, halogen or an alkyl group containing from 1 to 8 carbon atoms and at least one of which is -OH or -NH2.

11. A process as defined in Claim 1 wherein the polyaromatic amine is the reaction product of a polyhydric phenol having the formula wherein R3 is -H, -NH2, -OH or an alkyl group containing from 1 to 8 carbon atoms; and R4 is -H, halogen or an alkyl group as defined for R3, and a compound selected from the group consisting of diphenylamines and alkyl-substituted diphenylamines and other compounds all having the formula wherein R is or a straight chain or branched alkylene or alkylidene group containing from 1 to 5 carbon atoms; and R1, R2, R3 and R4 may each be -H, -NH2, -OH, halogen or an alkyl group containing from 1 to 8 carbon atoms and at least 1 of which is -NH2.

12. A process as defined in Claim 1 wherein the alkali metal hydroxide is sodium hydroxide.

13. A process as defined in Claim 1 wherein the alkali metal hydroxide is potassium hydroxide.

14. A process as defined in Claim 1 wherein the alkali metal hydroxide is lithium hydroxide.

15. A process as defined in Claim 1 wherein the polyaromatic amine is the reaction product of m-phenylene-diamine and resorcinol.

16. A process as defined in Claim 1 wherein the polyaromatic amine has a molecular weight in the range of about 250 to about 1000.

17. A process as defined in Claim 1 wherein the polyaromatic amine has a softening point in the range of about 65°C. to about 150°C.

18. A process as defined in Claim 1 wherein the dispersant is polyvinyl alcohol.

19. A process as defined in Claim 2 wherein the dispersant is an 88% hydrolyzed polyvinyl acetate, the alkali metal hydroxide is sodium hydroxide, the pH of the coating solution is 12 or greater and the ratio of polyaromatic amine to polyvinyl alcohol is in the range of 7:1 to 2:1.

20. A process as defined in Claim 3 wherein the dispersant is an 88% hydrolyzed polyvinyl acetate, the alkali metal hydroxide is sodium hydroxide, the pH of the coating solution is 12 or greater and the ratio of poly-aromatic amine to polyvinyl alcohol is in the range of 7:1 to 4.1.

21. A process as defined in Claim 15 wherein the dispersant is polyvinyl alcohol.

22. A process as defined in Claim 21 wherein the alkali metal hydroxide is sodium hydroxide.

23. A process as defined in Claim 22 wherein the pH of the coating solution is 12 or greater.

24. A process as defined in Claim 23 wherein the ratio of polyaromatic amine to polyvinyl alcohol is 5:1.

25. A process as defined in Claim 4 wherein the alkali metal hydroxide is sodium hydroxide.

26. A process as defined in Claim 1 wherein the coating solution contains from about 0.05% to about 0.10% by weight of an antioxidant selected from the group consisting of sodium ascorbate, sodium dithionite and sodium phenolic acid.

27. A process as defined in Claim 26 wherein the polyaromatic amine is the reaction product of m-phenylene-diamine and resorcinol.

28. A process as defined in Claim 27 wherein the alkali metal hydroxide is sodium hydroxide.

29. A process as defined in Claim 28 wherein the dispersant is polyvinyl alcohol.

30. A process as defined in Claim 29 wherein the ratio of polyaromatic amine to polyvinyl alcohol is 5:1.

31. A process as defined in Claim 30 wherein the pH of the coating solution is 12 or greater.

32. A process as defined in Claim 1 wherein the dispersant is selected from the group consisting of poly-vinyl alcohol, polyvinyl pyrrolidone, gelatin (calf skin), starch, and hydroxy propyl methyl cellulose.

33. A process as defined in Claim 1 wherein the dispersant is hydroxy propyl methyl cellulose.

34. A process as defined in Claim 1 wherein the dispersant is polyvinyl pyrrolidone.

35. A process as defined in Claim 1 wherein the dispersant is gelatin (calf skin).

36. A process as defined in Claim 33 wherein the ratio of polyaromatic amine to hydroxypropyl methyl cellu-lose is 6:1.

37. A process as defined in Claim 34 wherein the ratio of polyaromatic amine to polyvinyl pyrrolidone is 2:1.

38. A polymerization reaction vessel having on all the internal surfaces thereof a coating comprised of a straight chain or branched polyaromatic amine having a molecular weight greater than about 250 and having at least 2 -OH groups per 1000 molecular weight and an aqueous media dispersant, the ratio of said polyaromatic amine to disper-sant being in the range of about 10:1 to about 2:1, said polyaromatic amine having the structure selected from the group consisting of I. wherein (1) A, B, and C are selected from the group con-sisting of (a) wherein R3 is -H, halogen, or an alkyl group containing from 1 to 8 carbon atoms and may be the same or different;

R4 is -H, -OH, -NH2 or an alkyl group containing from 1 to 8 carbon atoms and may be the same or different; and R5 is or a straight chain or branched alkylene or alkylidene group containing from 1 to 5 carbon atoms; and (b) wherein R3 and R4 are the same as for (a); and wherein A, B, and C may be the same or different and each repeating unit may be the same or different; (2) R1 and R2 are either -H, -OH, -NH2, or and may be the same or different and wherein R3 and R4 are the same as for (a); and (3) x is an integer from 1 to 20 and y is an integer from 0 to 20; and II.

wherein (4) A, B, R1, R3, R4 and R5 are the same as in I and R2 is -H, or as defined in (2); and (5) x is an integer from 1 to 4 and y is an integer from 1 to 15.

39. A polymerization reaction vessel as defined in Claim 38 wherein the polyaromatic amine has the structure I.

40. A polymerization reaction vessel as defined in Claim 38 wherein the polyaromatic amine has the structure II.

41. A polymerization reaction vessel as defined in Claim 38 wherein the polyaromatic amine is the reaction product of m-phenylenediamine and resorcinol.

42. A polymerization reaction vessel as defined in Claim 38 wherein the coated surfaces are characterized by having a critical surface tension of at least 72 dynes/
centimeter and a contact angle of about zero.

43. A polymerization reaction vessel as defined in Claim 38 wherein the dispersant is polyvinyl alcohol.

44. A polymerization reaction vessel as defined in Claim 42 wherein the polyaromatic amine is the reaction product of m-phenylenediamine and resorcinol.

45. A polymerization reaction vessel as defined in Claim 44 wherein the dispersant is polyvinyl alcohol which is an 88% hydrolyzed polyvinyl acetate.

46. A polymerization reaction vessel as defined in Claim 39 wherein the coated surfaces are characterized by having a critical surface tension of at least 72 dynes/
centimeter and a contact angle of about zero.

47. A polymerization reaction vessel as defined in Claim 40 wherein the coated surfaces are characterized by having a critical surface tension of at least 72 dynes/
centimeter and a contact angle of about zero.

48. A polymerization reaction vessel as defined in claim 38, 39 or 40, wherein the dispersant is hydroxy propyl methyl cellulose.

49. A polymerization reaction vessel as defined in calim 38, 39 or 40, wherein the dispersant is polyvinyl pyrrolidone.

50. A polymerization reaction vessel as defined in claim 38, 39 or 40, wherein the dispersant is gelatin (calf skin).

51. A polymerization reaction vessel as defined in claim 38, 39 or 40, wherein the dispersant is starch.