GB2338712A

GB2338712A - Anti-fouling compositions, and their use in polymerisation processes

Info

Publication number: GB2338712A
Application number: GB9914593A
Authority: GB
Inventors: Giuseppe Raspanti
Original assignee: 3V Sigma SpA
Current assignee: 3V Sigma SpA
Priority date: 1998-06-23
Filing date: 1999-06-22
Publication date: 1999-12-29
Anticipated expiration: 2019-06-22
Also published as: GB2338712B; IT1301786B1; GB9914593D0; ITMI981435A1

Abstract

Compositions endowed with high activity against the formation of build-up on the internal surfaces of the polymerisation reactions of vinyl chloride and vinyl acetate, comprising a) at least one product deriving from the condensation between an aldehyde or a precursor thereof, a phenol compound and a carboxylic aromatic acid hydroxylated on the aromatic nucleus; b) at least one product deriving from the condensation between formaldehyde, or a precursor thereof, and an α-naphthol compound, c) optionally, at least one polycarboxylic acid, in which said acid can bear onto the non-carboxylic carbon atoms from 1 to 3 radicals independently selected from halogen atoms and the groups O-R 4 and NH-R 5 , wherein R 4 and R 5 independently represent hydrogen, (C 1-6 ) alkyl or (C 1-6 )acyl, or their salts with alkali metals.

Description

2338712 ANTI-FOULING COMPOSITIONS, POLYIERISATION PROCESSES AND THEIR USE

IN THE The present invention refers to anti fou l ing L compositions capable of suppressing he formation of scales in the polymerisation processes of vinyl acetate or vinyl chloride, or in the polymerisation processes using mixtures thereof, with or without other monomers or polymers polymerisable with them, said processes beinc:

io carried out in aqueous suspension, aqueous emulsion or J= bu l k - It is known that the formation of fouling C'scale", "build-up") represents one of the greatest problems which are encountered in all of the above mentioned polymerisation processes. In fact, part of the formed polymer tenaciously adheres to the internal walls of the reaction system, in particular to those of the reactor, thus forming scales with deleterious effects towards both the fLinal product itself, due to small fragments of scale which, by detaching from the reactor walls, can be included into the polymerised product. thus worsening its quality, and the safety of the reaction, because the build-up reduces the thermal exchange of the wall, thus giving raise to safety problems because of the worsened thermal exchange.

This build-up hinders the polymerisa::ion operations in such a way that it becomes necessary to clean the reactor thoroughly after each reaction.

This cleaning is burdensome, in tha:: it decreases the outnut of the plants, and is dangerous for the operators due to the toxicity 0 f the monomers, particularly of vinyl chloride.

Several products and techniques were developed for reducing:hese drawbacks, all based on the coating of the 2 interna- wall of the reactor with products which sha-uld inhibit the ad- liesicn of scales or even their formation, as an example by prevent-ing the polymerisation of the monomers o- said walls. Phenoj--.,0c---, naidebyde condensation z)--zduc's (GB 1439339; j? 54-1C7991; C-1k 1191899; E? 0 052 421), or x.-x-ures cf dyes (alizarin, xant:hcnes, natural. lavcno-4ds, nai3.',.,-hcaui.,icnes, hydroxyant.racuinones and eters) with agents such as polysaccnarides, pc-'yv-r.vl polyvinylpyrrclidc-ie were proposed as 10 the coatings. See 54834; J-1- 04154801; 59302 and JP 04031402.

710 0 614 913 suggests the use of condensation products between quinones and heterccyclic c=pounds -avng a'!oast two a-mir-o groups, whereas J.n E:P 0 606 013 here are described, among others, condensation products between quinones and -jarticular dia-T-'...no-d-Jcher.yls s,,:.bs-,-Jtutued with carboxylic or sulphonic gi-oups. In EP 0 695 761, t-he use o nroducts is described, obtained by cordensatlon of a "Phe.no-"' compound such as, for i,-stance, oher.cl er 1-naphthol, in the zresence ef a b--car-'-cxy-'-c allphatic acid. Finally, in, WO 98/24820, there are described comiDounds deriving c fram the condensation between aldehydes, hyd--cxvlazed aromatic 2i carboxyllic acids and phencl compounds, which seem to be endowed with remazkab-'e ar--i-fc,-,1iJng properties.

The -ost widely used r=ducts seem to be those -.'e3cr-be,4 in 7-- B1 0 052 421. However, though. they g,-je satIsfactory results ir. terms of suppression of the b u _ 1 d -,-, m formatior, they do not a-'-'^-W the ach-'eve.me,-i:: of repeated polymerisations without seeing to it that t h e ier:ia.4a--.s o' the teactlon system have to be coated eac'- tme.

go- instance, JP 04342701; JP 041 JP 04154805; JP 04108805; J-P 041 1 3 All of these anti-fouling agents can be applied in the most different manners, which depend on the nature of the Droduct and their capability of adhering to the reactor walls. The most common methods contemplate the coat-in-- bv painting or spraying, in which case lt sha111 be necessary to prepare suitable solutions of the same products, for example, aqueous solutions. In case of spraying, nitrogen or, better, water vapour, at a 51-7 bar pressure, can be used as the propellants.

As said above, the performances of these products can be enhanced through the use of film-forming agents such as, for instance, oo'Lvsacchar-des or hi g, 1 v hydroxylated polyvinyl.alcohols.

It has now surprisingly been found that compositions particular anti-fouling agents are ca-.:)able of suppressing at a surprisingly high extent the formatIon OL scales in the polymerisation processes of vinv-' chloride, or vinyl acetate, or mixtures thereof, in the presence or in the absence of other monomers or pollymers polymerisable therewith.

Therefore, an objec't of the present invention is represented by antifouling compositions comprising:

a) at least one product deriving from th.e condensation between an aldehyde or a precursor thereof (A), a phenol compound (B) and a carboxylic- aromatic acid hydrexylated on the aromatic nucleus (C); b) at least one product deriving from the condensaiic)n between formaldehyde, or a precursor --hereof, and a compound of formula I 1 4 OH (R1) m R I where-'n m is 1, 2 or 3, and R and R1 are independently selected fr--,-r. hydrogen, halogen, (Cl-5)alky-l, hydroxy and carbo (C1-5) alkoxv; c) ontionallv, at least one polycarboxyllic acid, in which sa-d acid can bear onto the non-carboxylic carbon atoms from 1 io 3 radicals 'Mdependently selected from halogen atoms and the groups 0---R4and NH-RS, where:'_n R4 and RS independently represent hydrogen, (Cl-6)alkyl or an acy- group from 1 to 6 carbon atoms, or --heir salts w--'th alkali metals.

Th e activity of the compositions a g a i ns t the formation cf, scales is parti--u':arlv high; it was observed that, o f t e n, it is of synera-- 'c type; in fact, ?--heir application allows to obtain results which are better than those ach-eved with the application of the single components a) or b), or, converseiv, the same effects can be achieved if, on the other hand, lower amounts of -he composItions according to the Invention are appl-led. In any case, it was noted that the comoositions of the present invention are capable of suppressing in an almost complete manner the formation of scales on. -the internal walls of e -reactor and, i r_ gene--a!, of 1he pol,,rip.e--isation system, as well as to allow the c a r a Out 0- repeated pclymerlsations wlihout applying- tn e co.mpcsi---, ons from t-'me to t-,,-,te before of each run, thus obtaining the desired effect, namely the complete, or almost complete absence of formation of scales.

Another favourable characteristic the compositions of the invention is to possess a reduced sensitivity towards the pH variations during the polymerisation processes.

In addition, the obtained polymers display better physical characteristics.

Another object of the present invention is the use o the above mentioned compositions as anti-foullng agents in the polymerisation processes of viny! c-.lor-'de or vinyl acetate, or mixtures thereof, in the Presence or in the absence of other monomers or polymers polymerisable therewith.

An additional object of the presen: invention is a method for suppressing the formation of scales in the polymerisation processes of vinyl chloride or vinyl acetate, or mixtures thereof, in the presence or in the absence of other monomers or polymers polvir.erisable therewith, which comprises the coating of the internal walls of a polymerisation reactor with at least one of the comz)ositions according to the present invention.

Still an additional object of the preseni invention a process of polymerisation of vinyl chloride or vi.--i-v'L acetate, or mixtures thereof, in the presence or in the absence of other monomers or polymers polymerisable therewith, carried out in a reactor, the internal walls of which are coated with at least one of the compositlons of the invention, and the polymers obtained through such, a process.

Finally, a further object of the present invention _s a polyrierJLsation reactor, the internal walls of which are coated with at least one of said compositions.

In the components a), compound (A) can be any a'dehvde canable of condensing at the orthe- and/or para z)ositions with respect to a hydroxyl present on -the arow.at---- nucleus.

_'_15 purpose such aldehvdes precursors. a 1 i a t i c benzaldehvde or instance, furfurol, 6 Several aldehvdes proved to be suitable Preferabiv, formaldehyde, or ts as paraldehyde or paraforma-'ldehyde, from 2 to 5 carbon atoms, heterocvclic aldehydes such as, for are employed. The phenol compound (B) can be any mono- or po' vhyd-oxylated phenol in which at least -WO of the ortho- and/or para-positions with respect to the hydroxy group or groups are free such as, 10 for instance, phenol, cresol, ethylphencl, resorcinol, pyrocaz'necol, hydroquinone,:)v-t-ogal-'ol or bisphenol A, or, again, a compound of formula i. Preferably, phenol, rescrc-,7..--1 er compounds of formula I wherein m is 1 or 2, R and R, are as above de.-'::- Jned and R,, when it is different 15 from '".,;drogen, is at the 7- or 8- position are employed. F-inalIv, compound (C) is a hvdroxy-'ated carboxvlic aromatIc acId of formula C'00H R 2 I _.

-L wherein R2 is selected from hydrogen, hydroxy, (1-1-5)a-kyl, hyciroxv(C,-:)alkvl, halo, phenyl and hydrox.,,7:)'.-ien,l; R3 has the same meanings of R2, with the excluslon of hvdrogen; x and the dotted lines, taken together, can represent either the divalent radical ortho-2onde-sed with the benzene ring of formula III (OH 11 p 7 i 11 wherein P is an integer selected from 1 and 2, or they represent nothing; with the -following provisos:

-4) when x and the dotted lines, 'Caken together, represenz the radical of formula III, at: least two of the orthoand/or para-positions with respect to the hydroxy group or groups must be free; ii) when x and the dotted lines, taken t_ o g e t h er, 10 represent nothing, at least one of R2 or R3 represents hyd-roxy, and at least two of rhe ortho- and/or paraposit--'cns with respect to the hydroxy group or grouPs must be free.

Preferably, monohydzoxybenzoic acids such as, for instance, salicylic acid and 4-.hydroxy-benzc-i-- acid, d-hydroxybenzoic acids such as, for instance, cc-, P- and yresorcylic acids, 2,3-dihydroxy- ber-zcic acid, 2,5dihydroxv-benzoic acid, monohydroxylated alkoxy'zeizoic acids such as, for example, 2-hydroxy-S-.,nethoxy-benzoic:

acid, hydroxynapb.'..,ioic acids such as, for instance, 6hydroxy-2naphthoic acid. are employed.

Components a) and their preparation are described in, WO 98/24820. Preferably, components a) are products der.iving from the condensation between formaldehyde, or a p--ec,arsor thereof, a re5orcilic acid and Inaphthol.

Components b), namely the compounds of formula 1, and their nrenaration, are described in E? 31 0 052 421. ?referably, components b) aze products deriving from the condensation between formaldehyde, or a precursor t,ereof, and 1-riaphthol or 1,3-dihyd--oxynaphr-b.alene.

8 Preferably, components c) are the oxalic, malon-lc, succinic, maleic, malic, citric, tartaric, alutaric, glutamic, aspartic, acetylaspartic, adipic, phthalic, isophthalic, tereDhthalic and 2-bromosuccinic acids, or their corresponding salts with alkali metals.

The ratios between the components comprised in the compositions of --'-e present invention may vary withIn very wide limits, expressed by weight. In the:)racz-,ce, it is preferred to use components a) in amounts varyIng from about 20 to about 8010, components b) i- amounts varying from about 80 to about 20%, and comoonents c) in amounts varying from about 0 to about 20%, said values being calculated on the total weight of the components a), b) and c).

Generally, the compositions according to the present invention are used in the form of solutions. They can be prepared by mixing components a) and b) and, if desired, components c) to homogeneity, irrespective of the o_rder in which --hev car, be admixed. For mere illustrative purposes. one can prepare separate aqueous alkaline solutions of components a) and b), mix them together and, if desired, add components c), seeing to it that the pH of the resulting final composition is comprised between about 8 and about 13.5. Alternatively, one can mix --he solutions of components a) and b) as directly obtained from the processes of their preparation (said solutions be.ing alkaline solutions as well) and optionally add components c), always seeing to it that the of the resu17-ing f-inai composition is comprIsed betweer about 8 and about 73.5. Or, even, a solid mixture of the ccmQonents a) and b) and, optionally c) prepared, in the desired weight ratios, and alkaline solution is prepared therefrom, co=rised between about 8 and about 13.5. The -5 f i r S -- anaqueous a a o H Is 9 conferred by bases such as, for instance, s a d..JL un. o r Potassi= hydroxide, ammoni a, lower aliphatic a_mines, Mono-, di-, or triethanolamine, and the like, Other,nethods for preparing solutions of the compositions of the -nvent-4on w-J11 altpear obvious for the art skilled technician.!-- is also possible to ucilize solutions of the cempositions of the jinvention in organic solvents.

!-- order to favour the adhesion of the conposit-lcns to those parts of the reactor, cr the react..J.op. system, where it I's suitable that this adhesion occurs, one can utilize surfactants or film-formimg agents such as, for 4nsta, L rice, polyvinyl alcohols with a h-'gh number of hydroxyls. Prelferred are polyvinyl alcohols having a hydrolysis degree not lower than 96% and a 4% vIscosity water of 20 mPa. s, measured with a e viscosimeter, cr, preferably, 40 mPa.s or more.!'L used, these surfactants or film-forming agents are added to the compositions _In amounts comprised between about C.5% and 2C%, calculated on the weight of the composition.

The concentration of the solutions of th. e compositions of the invention to be utilized f 0 r t h e application onto the walls of the reactor or, more in general, of the reaction system, can vary within very wide limits. As an example, it can be comprised between 23 about 1 and about 15% and, pre'ferably, between about 1 and 9%; in any case, concentrations even lower tha.n 1% Drcved to be effective as well. These concentrations can be achieved -4, absolutely conventional manners.

The amount of composition according to the present inventien which has to be applIed onto:he walls of the reactor, cr onto of those parts of the reaction systen, whe.re 17- IS desirable that this occurs, 11s ca-.r-ticu-larly low. Generally, nor- more than 3 and not less than O.CI grams of composition per m' of surface and, preferably, not more than 2 and not less surface are sufficient. In any between about 0,01 and about 0.01 and 0.04 grams per m 2 effective as well.

2 -,ian O.Cl grams per m 0case, also amounts ranging 1 or, even, between about of surface proved to be The comiDositions of the invention can be applied to the walls of the nolvmer-isa--icn reactor, or the reaction svs-.e.m, in the most different methods. As an example, when said compositions are used in the form of aqueous alkaline solutions, thev are usually applied by means of IC h e known water-steam or nitrogen spraving IC-echni-ue under::)ressure, but they can also be applied by brushing [5 or, as in:he case of viny"L' chloride, by utilising the monomer i::self as the carrier. The aDplicat-Jon can be carried out both on hot and cold walls, by employing preheated solutions, or at room temperature, though 'the temperature is not critical.

The polymerisations of vinyl acetate chloride which are referred to in the present are h or-nopo 1 ymerisat ions or copolymer-isations them, In the presence or in the absence c-." monomers or polymers polymerisable -herewith such as, instance, other vinyl esters or aryl, alkyl, cycloal)<,,71 esters of 'unsaturated mono- and polycarboxylic acids with 3-1 carbon a'oms 11ke methyl acrylate, butv! methacrviate, acrylonitr-ile, methacrylonitrile, unsal.--u--p-ied diesters such as diethvl maleate, a 1 lvI esters like allyl acetate, cc-olefins like e--hvlene and propy'lene, vinyl ethers and styrene compounds. the copolymerisat- ions also compr-, se the Doly-ne---sat--'lon of vinyl chloride in the presence of preformed polymers, optionally In the presence of graftIng ager--s, to form grafted vinyl chloride ool-,,mes. Examples of t e s e --re-formed polymers to form grafted vnyl and vinyl invention between one or more 1 11 chlor ide polymers comprise jolv-2-etPylhexyl-acryla'.e, pc-!y-n-butyl- acryla'.e and clef -.-1s/v-,nyl esz:ers copolymers, 3uCh as the e thy 1 erle /V --.iy acetaze copolymers.

The composizio.ns of the present inventJon proved zc be carticularl, effective in --he case of jclymer-,sa'--or.s y J,-i aqueous suspension or e.mulson, but also in:he case of bulk polymerisations the practical absence of scales aclhering to the walls was ob5erved as well.

In the suspension homo- and copol.vmerisat-,'cns cf acetate and/or vinyl chloride, suspending agents having col lcido-protective properties can allso be em.cloved such as, for instance, partially hydrolysed acetates, cellulose ethers, gelatine, sorbitel esters of tatty acids.

Generally, the emoloyed ai-,ant-,"uies vary fr=. 0.05 and 2% by weight, calculated on the total weight of the used moncmers. n the enrulsion polymerisations, surfactants such as Polyglycoll esters of nonylphenol or sodium or salts Of C12-18 fatty acids, of alkylphosphates, of alkylsulphosuccinates, of sulphonated alkylbenzenes, of sulphanated olef ins, of sulphuric esters of fatty alcchols are employed as the emulsifying agents.

Generally, the employed quantities vary frc-,i 0.05 and 0.5% by weight, calculated an the total weight of the used monomers.

k-iy suitable polymerisation init-lator can be used, provided th a t 1 t is soluble in the empi cved vinyl c t Monorriers. Examples c, t h e s e catalysts, in pc-:ymerisations, are peroxides like lauroyl wercxide, acety! cyclahexyl sulphony! peroxide, azo compounds like azobis(dimethylvalero,iitrile) and 'Dezoxydica--bonates like dcetylperoxydicarbor.ate, d--so-croc)ylperoxydicarbcna--e, 12 and analogues. These -Jr-it.latcrs, as well as any other conventional agent, can be employed in the usual amounts of 0.01 - 1% w/w on the total weight of the employed monomers. in the eir.uls..en polyrr.erisation6, oil-soluble initlators can be used like diacyl or dialkyl peroxides such as lauroyl or benzoyl perexide, per-esters such as t-butyl peroxyji-.valate or t- bultyl per- 2 -ethylhexanca te, peroxydi-i-carbonate hydrosoluble to persul.,'ates, with sodium metabisulphite, sodium formaldehyde sulfaxilate and the like.

The operating conditions for the polymerisations are those well known and usually employed for the emulsion and suspension polymer-isations of vinyl acetate and vi-ny! chloride, or Mixtures thereof, in the presence 'or in the absence of one or more menomers or polymers polymerisable therewith.

The temperatures are in the range between 40 and 20 80'C and the pressure is generally comprised between 5 and 14 bar for vinyl chloride, and between 65 and 95'C and atmospheric pressure for vinyl acetate.

The failowing examples further illustrate the invention.

is dicetylperoxydicarbonate, or redox Ln-itiator systems based 0 r.

hydrogen peroxide, hydroperoxides combined 1 Preparation Of tho compositions according to thEI invention EY-AMPLE 1 250 Grams of the solution of the anti-fouling agent as obtained in Example 1 cf WO 9e/24820 are added with 250 g of the sclution. cf the anti-fouling agent as obtained in Example 1 of EP BI 0 052 421. The resulting m-xtu--e is stirred at room temiDeratUre till homogeneity.

13 ELE 2 250 Gram of the solution of the anti-fouling agent as obtained in Example 8 of WO 98/24820 are added with 250 g of the solution of the anti-fouling agent as obtained in Example 1 of EP B1 0 052 421 and 20 g of polyvinyl alcohol having a hydrolysis degree of 96%. The resulting mixture is stirred at room temperature till complete solution, thus obtairling.a viscous solution.

500 Gram of the solution of the anti-fouling agent as obtained in Example 8 of WO 98/24820 are added with 500 g of the solution of the anti-fouling agent as obtained in Example 11 of EP BI 0 052 421 and 100 g of sodium citrate. The resulting mixture is stirred to hamogeneity at room temperatu_re.

EXAMPLE 4

350 Grams of the solution of the anti-fouling agent as obtained in Example 24 of WO 98/24820 are added with 15C g of the solution of the anti-fouling agent as obtained in Example 1 of EP 31 0 052 421 and 10 g c-' polyvinyl alcohol having a hydrolysis degree of 96%. The resulting mixture is stirred till homogeneous solution, thus obtaining a viscous solution.

EXAMPLE 5

200 Grams cf the solution of the anti-fouling agent as obtained in Example 25 of WO 98/24820 are added with 300 g of the solution of the anti-fouling agent as obtained in Example 11 of EP 31 0 052 421, 10 g of scd-luin tartrate and 10 g of polyvinyl alcohol having a hydrolysis degree jo of 96%. The resulting mixture is stirred till complete solution at room temperature, thus obtaining a viscous solution. EXAMPLE 6 14 A com,,)os-tion was Drepared following the procedure of Example 5, by emplov-"n-- --',-e compound of Example 1 of E-P B1 0 052 4211 instead ef tha- of Example 11.

EXAMPLE 7 500 Grams of the solution of theanti- fouling obtained in Example 27 of 1P70 98/24820 are added g of the solution of: the antiagent as in Example 1 of EP Bl 0 052 421 and 10 g of alcohol having a hydrolysis degree of 962--z. The stirred till so"uti mixture is homogeneous obtaining a viscous solut-ion.

agent as with 500 obta-L'ned polyvinyl resul'L--nc on, th U S By operating substantially as described in Examples 3 and 5 and 6, sollutions c-OL the compositiors of the _nvention containing the sodium salts of succinic, mal e i c, tartaric, g lu t a r i c, glutamic, aspart-ic, acetylaspartic, were prepared.

EXAMPLES 8-16

Pelymerisation-of vinyl a.cetate monome.r- iVAM) in a-,ueol-,s suspension In a 25 litre stainless steel reactor, ejuipped with reflux condenser and anchor stirrer, the --ol-owina ir.g-ed'en±s were loaded -n parts by weJght:

a d i pi c, -,)h tha l i c and 2-bromo-suc---,n'lc 2) 5 VAM Water PVOH (26/88) Acetaldehyde Benzoylperoxide -PVOH: polyvinyl alcohol 50 0.05 0.4 0.03 The mixture was refluxed at atmospheric pressure and the polymerisation was carried out for four hours until conversion not lower than 99--z was reached.

AccordIng to this procedure, single pol yme,-i sat ions in the absence and in the presence of the coTnos-iiions of the Present invention, and in the presence cf the art known anti-fouling agents were effected. The composi.::-ions and -he art known anti-fouling agents were applied In ihe amount of 0. 3 g per m 2 of surface reactor, usIng the spraying method. The amount of build-up was determined after the emptying and washing of the reactor, bv collecting and weighing it.

The obtained results are reported '= the followinc Table 1, and are expressed in parts per million (ppml with reference to the loaded monomers.

TABLE 1

Example Composition of Example Build-up (ppm) 8 -24'00 9 1:races 2 absent 11 4 absent 12 6 absent 13 Ex.1 of WO 98/24820 325C 14 Ex. 8 of WO 98/24820 __100 is Ex. 24 of WO 98/24820 180 16 Ex. 1 of EP 0 052 421 220 -- 1 -- -- - - EXAMPLES 17-26 Polymerisation of vinyl chloride monomer Ln a,,ljeo suspension a 100 litre, internally glass -"-ed, stainless steel reactor, equipped with a Pfaudler stirrer, and 16 after eliminating the oxygen, the following ingredients were loaded _in parts by weight:

VC-M Water POLIVIL CT11 S 404 (3V SIGMA, ltaly) POLIVIC'M SP 808 (3V SIGMA, Italy) Me --hyll.-,,ydroxypropylcellulose Sodium hydra gencarbonate Bis (4-t- butylcyclohexyl) peroxydicarbonate 150 0. 0 4 0.04 0.04 0.03 0.04 as active substance The system, was heated to 54 OC, corresponding to a K-value oZE the PVC polymer of about 70, while the polymerisation was pressure -rose to 7/8 ate, and. the carried on for about 7 hours. When the pressure decreased by 2-3 ate, the reaction was stopped exhausting the unreacted monomer and isolating it.

According to this procedure, single polymerisa'---Jo.-ls were carried out, In the absence and in the presence of the compcsitions of the present invention, and in the presence of the art known anti-fouling agents. The compositions and the art known anti-fouling agents wee applied in the amount of 0.5 g per m 2 of reactor surface using the spraying method. The amount of build-up was determined after the emptying and washing of the reactor, by collecting and weighing it.

The obtained results are reported in the follewing Table 2, and are expressed in parts per million (ppr.1) with reference to the loaded monomer.

17 TABLE 2

Example Composition of Example Build-up (ppm) 1/ --------- 7330 18 1 absent 19 2 absent 5 absent 21 6 absent 22 Ex. 1 of WO 98/24820 55 23 Ex. 8 of WO 98/24820 40 24 Ex. 24 of WO 98/24820 so Ex. 1 of EP 0 052 421 70 26 Ex. 11 of EP 0 052 421 60 EXAMPLES 27-33 The same polymerisation of the foregoing carried out for four consecutive times, in and -1-r. the presence of the compositions of invention, and in the presence of the art fouling agents. The compositions and the art example was the absence the present known anti- known Louling agents were applied in the amount of 0.5 g per ir, 2 of reactor surface, using the spraying method, only one time before the first Polymerisation. The amount of build-up was determined after the emptying and washing of the reactor at the end of the fourth run, by c-c)llec7:i,,, ig and 'weighing it.

The obtained results are reported in Table 3, aPi are expressed in parts per million (ppm) wit., reference to the loaded monomers.

18 TABLE 3

Example Composition of Example Build-up (ppm) 2-1 --------- -7330 28 2 traces 29 absent 6 absenr 1 Ex. 8 of WO 98/24820 60 32 Ex. 27 of WO 98/24820 75 33 Ex. 1 of E? 0 052 421 9 0 The s ame results, namely the absence o r t.ri e practical- absence of formation of build-up were obtained 5 Iby applying the --omposii-icns of tne -invent-on -i- the a-nounts of 0.03 and 0.02 grams per -r. 2 of reactor sj--,:ace, with the compositions of Examples 1, 2, 3, in iDert--icu-a-- and 6.

19

Claims

1. An anti-fouling composition comprising:

a) at least one product deriving from the condensation between an aldehyde or a precursor thereof, a phenol compound and a carboxylic aromatic acid h-vdrox.vla-Led on the aromatic nucleus; b) at least one product deriving from the condensation between formaldehyde, or a precursor thereof, a nd a compound of formula I 0 H (R,) m I R wherein m is 1, 2 or 3, and R and R, are indeDenden-Liv 15 selected from hydrogen, halogen, (Cl-5)alkyl, 'hydroxy and carbo (Cl-5) alkoxy; c) optionally, at least one polycarboxylic acid, in which said acid can bear onto the non-carboxylic carbon atoms from 1 to 3 radicals independently selected from halogen atoms and the groups 0---R4and NH-R5, wherein R, and R5 independently represent hydrogen, (Cl-6)alkyl or an acyl group from 1 to 6 carbon atoms, or their sa---s with alkali metals.

2. A composition as claimed in claim 1, wherein, Ln the components a), the aldehyde, or a precursor lEhereof, Is an aldehyde capable of condensing at the ort-ho- and/or para- positions with respect to a hydroxyl on an aromatic nucleus.

3. A composition as claimed in claim 1 or 2 wherein, in components a) the phenal compound is a mono- or pelyhydroxylated phenol in which at least two of the ortho- and/or para-positions with respect to the hydroxy group or groups are free, or it is a compound of formula

4. A composition as claimed in any preceding claim, wherein, in components a), the aromatic carboxylic ac.-Ld hydroxylated on the arciratic nucleus is a co=ound of formula 7-1 COOH R2 X T I 3 wherein R2 is selected from hydrogen, hydroxy, (C 1-5)alkoxy, 1 ( c 1-5) alkyl, hydroxy (C 1-5) alkyl, halo, phenyl and hydroxyphenyl; R3 has the same meaning as R2, with the exclusion of hydrogen; x and the dotted lines, takern together, can represent either the divalent radical orthccandensed with the benzene ring of formula 1II -I.

-(CH) p i i --I wherein p is an integer selected from 1 and 2, or they represent ncthing; with the following provisos:

21 i) when x and the dotted lines, taken together, represent the radical of formula III, at least two of the cr-hoand/or para-positions with respect to the hydrcxy group or groups must be free; ii) when x and the dotted lines, taken together, represent nothing, at least one of R2 or R3 represents hydroxy, and at least two of the ortho- and/or pa-a3:)ositions with respect to the hyd-roxy group cr groups must be free.

5. A composition as claimed in any one of claims 1 to 4, wherein components a) are products deriving fzom the condensation between formaldehyde, or a precursor t-'miereo,jo, a resorcylic acid and Inaphthol.

6. A composition as claimed in any preceding claim, wherein components b) are products derivIng from the condensation between formaldehyde, or a precursor thereof, and l-naphthol or 1,3-dihydroxy- naphthalene.

7. A composition as claimed in any preceding claim, wherein components c) are the oxalic, malonic, succinic, maleic, malic, citric, tartaric, glutaric, glutamic, aspartic, acetylaspartic, adipic, phthalic, lsophthallc, terephthalic and 2- bromosuccinic acids, and their corresponding salts with alkali metals.

8. A composition as claimed in any one of claims 1 to 7, wherein components a) are present in amounts varying from about 20 to about 80%, components b) in amounts varying f.-orr. about 80 to about 20%, and components c) in amounts varying from about 0 to about 20%, said values being calculated on the total weight of the componenns a), b) and c).

9. A composition as claimed in any one of claims 1 to 8, in the form of a liquid solution.

10. A composition as claimed in claim 9, in the form of aqueous alkaline solution.

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11. Use of a composition as claimed in any one of claims 1 L0 10 as an anti-fouling agent in a polvmerisation :)rocess of vnvl chloride or vinyl acetate, or mixtures thereof, in the presence or in the absence of ot.-ier monomers or polymers polymerisable therewith.

2. A method for suppressing the formation of scales in a polymer i sat ion process of vinyl chloride or v_nyl acetate, or mixtures thereof, in the oresence or in t-he absence of other monomers or polymers polymerisable therewith, which comprises coating the internal walls of a polymerisation reactor with at least one composition as defined in any one of claims 1 to 10.

13. A process of polymer isat ion of v-invl chloride or vinyl acetate, or mixtures thereof, in the presence or -n r-',-ie absence of other monomers or polymers polymerisable therewith, carried out in a reactor, theinternal walls of which are coated with at least one composition as defined in any one of claims 1 to 10.

14. 2 polymerisation reactor, the internal walls of which are coated with at least one composition as defined in any one of claims 1 to 10.

15. An anti-fouling composition as claimed In any one of claims 1 to 10 substantially as herein described.

16. An anti-fouling composition as claimed in any one of claims 1 to 10 substantially as herein exemplified in any example.

17. Use as claimed in claim 11, or a method as claimed in claim 12, or a process as claimed in claim 13 substantially as herein described or exemplified.