Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-12-14
2003-01-28
Lovering, Richard D. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C106S002000, C252S180000, C422S241000
Reexamination Certificate
active
06512045
ABSTRACT:
The present invention relates to build-up suppressing compositions, which are capable of preventing the formation of build-up in vinyl acetate or vinyl chloride polymerization processes, or in polymerization processes utilizing a mixture thereof, with or without other monomers or polymers polymerizable therewith, which processes are effected in aqueous suspension, aqueous emulsion or in bulk.
Build-up formation (“scale”) is known to be one of the major problems with all of the polymerization processes cited above. In fact, part of the formed polymer tenaciously adheres to the reaction system inner walls, particularly the reactor walls, thus forming build-up with deleterious effects toward both the final product itself, due to small fragments of build-up which, when detached from the reactor walls, can be included in the polymerized product thus worsening its quality, and the safety of the reaction as the build-up slows the thermal exchange of the wall giving rise to safety problems due to overheating.
This build-up adversely affects the polymerization operations making it necessary to clean the walls after each run.
This cleaning is costly as it decreases the plant output and is dangerous for the operators due to the toxicity of the monomers, particularly vinyl chloride.
A number of products and techniques have been developed to mitigate this problem, all of which are based on coating the reactor walls with products which should inhibit adhesion of the build-up or even its formation, for example by preventing the polymerization of the monomers on the reactor walls. Phenol-formaldehyde condensation products (GB 1439339; JP 54-107991; CA 1181899; EP 0052421) or dye mixtures (alizarin, xanthones, natural flavonoids, naphthoquinones, hydroxyanthraquinones and others) with film-forming elements such as polysaccharides, polyvinyl alcohols, polyvinylpyrrolidone were proposed as reactor wall coating. See for example JP 04342701; JP 04154804; JP 04154801; JP 04154805; JP 04108805; JP 04159302 and JP 04031402.
EP 0 614 915 suggests the use of condensation products between quinones and heterocyclic compounds having at least two amino groups, whereas in EP 0 606 013 there are described, inter alia, condensation products between quinones and particular diamino-diphenyls substituted with carboxylic or sulfonic groups. EP 0 695 761 discloses the use of products obtained by condensing a “phenol” compound, such as phenol or 1-naphthol, in the presence of an aliphatic bicarboxylic acid. Finally, WO 98/24820 discloses compounds obtained by condensation of aldehydes, hydroxylated aromatic carboxylic acids and phenol compounds, which apparently have remarkable anti build-up characteristics.
The products more widely used seem to be those described in EP B1 0 052 421. However, although remarkable results as to suppression of build-up formation are achieved, those agents do not allow carrying out an appreciable number of repeated polymerizations if not by applying them to the reaction system inner walls before each run.
All these build-up suppressing agents can be applied in a number of manners, which depend on the nature of the product and on its capacity of adhering to the reactor walls.
The more common methods comprise coating by painting or spraying, in which case it shall be necessary to prepare suitable solutions of the same products, for example aqueous solutions. In case of spraying, nitrogen or water vapour at 5-15 bar pressures can be used as propellant.
As stated above, the performances of these products can be enhanced with the use of film-forming agents, such as polysaccharides or highly hydroxylated polyvinyl alcohols.
It has now been found that compositions based on particular build-up suppressing agents are surprisingly effective in remarkably suppressing the formation of build-up in the polymerization processes of vinyl chloride or vinyl acetate, or mixtures thereof, in the presence or in absence of other monomers or polymers polymerizable therewith.
Therefore, an object of the present invention comprises build-up suppressing compositions containing:
a) at least one product deriving from the condensation of an aldehyde (A), a phenol compound (B) and an aromatic carboxylic acid hydroxylated on the aromatic nucleus (C);
or
at least one product deriving from the condensation between formaldehyde, or a precursor thereof, and a compound of formula (I)
in which m is 1, 2 or 3, and R and R
1
are independently selected from hydrogen, halogen, (C
1-5
)alkyl, hydroxyl and carbo(C
1-5
)alkoxyl; and
b) at least one polycarboxylic acid, optionally having on the non carboxylic carbon atoms 1 to 3 radicals independently selected from halogen atoms and the groups OR—R
4
and NH—R
5
, in which R
4
and R
5
are independently hydrogen, (C
1-6
)alkyl or a C
1
-C
6
acyl group, or the alkali metal salts thereof.
The build-up suppressing activity of these compositions is particularly high, often even synergistic. In fact, the use thereof provides better results than those attained upon application of the single components a) or, conversely, the same effects can be obtained by using lower amounts of the compositions of the invention. It has been observed that the compositions of the present invention are capable of suppressing almost completely the formation of build-up on the inner walls of the reactor and, in general, of the polymerization system, thus allowing to carry out repeated polymerizations without need for the compositions to be applied before each single run, always providing the desired effect, namely a substantial absence of build-up.
A further favorable characteristic of the compositions of the invention is that they have reduced sensitivity to pH changes in the polymerization processes.
Furthermore, the obtained polymers have better physical characteristics.
A further object of the present invention is the use of one or more of the above build-up suppressing compositions in the polymerization processes of vinyl chloride or vinyl acetate, or mixtures thereof, in the presence or in the absence of other monomers or polymers polymerizable with them.
Still another object of the present invention is a method for suppressing build-up formation in the polymerization processes of vinyl chloride or vinyl acetate, or mixtures thereof, in presence or in absence of other monomers or polymers polymerizable with them, which comprises coating the inner walls of a polymerization reactor with at least one of the build-up suppressing compositions of the invention.
The present invention further comprises a polymerization process of vinyl chloride or vinyl acetate, or mixtures thereof, in the presence or in the absence of other monomers or polymers polymerizable with them, effected in a reactor whose inner walls are coated with one or more of the compositions of the invention, and the polymers obtained by means of said process.
Finally, a further object of the present invention is a polymerization reactor whose inner walls are coated with one or more of the above build-up suppressing agents.
In components a), compound (A) can be any aldehyde capable of condensing at the ortho- and/or para-positions with respect to a hydroxyl present on an aromatic nucleus. Many aldehydes proved suitable to this purpose. Preferably, formaldehyde, or its precursors, such as paraldehyde or paraformaldehyde, aliphatic aldehydes having from 2 to 5 carbon atoms, benzaldehyde or heterocyclic aldehydes, such as, furfural are used. The phenol compound (B) can be any mono- or polyhydroxylated phenol in which at least two of the ortho- and/or para-positions to the hydroxy group(s) are free, for example, phenol, cresol, ethylphenol, resorcinol, pyrocathecol, hydroquinone, pyrogallol or bisphenol A, or a compound of formula (I). Phenol, resorcinol or compounds of formula (I) wherein m is 1 or 2, R and R
1
are as defined above and R
1
, when it is different from hydrogen, is at the 7- or 8-positions are preferably used. Finally, compound (C) is a hydroxylated aromatic carboxylic acid of formula (II):
wherein R
2
is selected from the g
3V Sigma S.p.A.
Lovering Richard D.
LandOfFree
Build-up suppressing compositions and the use thereof in... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Build-up suppressing compositions and the use thereof in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Build-up suppressing compositions and the use thereof in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3016523