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
1999-03-17
2003-09-09
Zalukaeva, Tatyana (Department: 1713)
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...
C524S317000, C524S558000, C524S560000, C526S312000, C526S318300, C526S318400, C526S318440
Reexamination Certificate
active
06617389
ABSTRACT:
The invention pertains to an aqueous polymer dispersion which can be obtained by the emulsion polymerization of &agr;,&bgr;-ethylenically unsaturated monomers comprising a monomer composition A and a monomer composition B, with the reactor being fed the monomer composition A continually being replenished with the monomer composition B, to a process for preparing such dispersions, to aqueous coating compositions incorporating these dispersions, and to high gloss topcoats obtained using these coating compositions.
BACKGROUND OF THE INVENTION
The preparation of polymer dispersions of the aforesaid type is disclosed, int. al., in U.S. Pat. No. 3,804,881. The monomer flow charged to the reactor is continually varying in compositional content through the supply of one or more monomer flows of a different composition to the vessel from which the monomer flow is fed to the reactor. In this way particles continually varying in compositional content are obtained. A key advantage of the process described in this document is indicated to be that the thus obtained polymer dispersions are characterised by a very broad glass transition temperature range. As a result, the topcoats obtained using coating compositions prepared with these dispersions are more flexible at room temperature and have less tendency to exhibit surface tack. The adhesion of the topcoats can be improved still further by a gradual and continuous increase in the concentration of adhesion promoting monomers in monomer composition A prior to the conclusion of the polymerization reaction, which will cause a layer of adhesion promoting functional groups to form on the surface of the disperse particles.
Although coating compositions which contain dispersions prepared in this manner have very good adhesion as compared with coating compositions which do not incorporate adhesion promoting monomers, it was found that the gloss of the topcoats obtained using coating compositions containing these dispersions shows greater similarity to that of topcoats obtained using coating compositions incorporating dispersions of the core/shell type. It was further found that the simultaneous presence of adhesion promoting monomers and carboxylic groups-containing monomers required for the stability of the dispersions is attended with substantial contamination of the reactor.
It should be noted that polymer dispersions with which coating compositions for topcoats having high gloss and good adhesion can be obtained were recently proposed in U.S. Pat. No. 5,021,469. Unlike the presently proposed polymer dispersions, the known polymer dispersions are made up of particles having a core and a shell, the core consisting of a material having a glass transition temperature (Tg) of at least 40° C. and the shell consisting of a material having a Tg of less than 70° C. and at least 20° C. below the Tg of the core material. The shell contains, int. al., ethylenically unsaturated carboxylic acids and nitrogenous, adhesion promoting monomers. Unlike with the preparation of the presently proposed polymer dispersions, there is substantial contamination of the reactor during the preparation. Moreover, when using the presently proposed dispersions topcoats of higher gloss and better adhesion can be obtained.
U.S. Pat. No. 5,326,814 proposes a more specific process for preparing polymer dispersions for the aforesaid use. To improve adhesion, up to 5 wt. % of an ethyleneureido group-containing monomer and 1 to 3 wt. % of an ethylenically unsaturated carboxylic acid are added. The preparative process involves first making a pre-emulsion of all the monomers except for those having an ethyleneureido group. Next, the pre-emulsion is slowly added to the reactor, with an emulsion of the ethyleneureido group-containing monomer also being introduced into the reactor during the first part of the addition process.
The topcoats obtained using these dispersions likewise are in need of improvement when it comes to gloss and tack. Moreover, the process described in this document also has substantial contamination of the reactor. Where the text refers to glass transition temperature, Tg, what is meant is Tg as calculated in accordance with a method described by T. G. Fox in the
Bulletin of the American Physical Society
, Volume 1, Issue 3, p. 123 (1956). This calculation employs the constants as specified by J. Brandup and E. H. Imergut in
Polymer Handbook
, 2
nd
edition, J. Wiley & Sons, New York, pp. 139-192 (1975). (Meth)acrylate in the text stands for acrylate as well as methacrylate. (Hetero)cycloalkyl in the text stands for heterocycloalkyl as well as cycloalkyl.
The invention now provides polymer dispersions with markedly enhanced properties, notably as regards the adhesion and gloss of topcoats obtained using coating compositions containing these dispersions, without any problems being experienced during the preparation of these dispersions as a result of contamination of the reactor.
SUMMARY OF THE INVENTION
The invention consists in that in the preparation of a polymer dispersion of the known type mentioned in the opening paragraph use is made of the monomer compositions A and B, one of which has a Tg in the polymerized state of at least 40° C., as well as at least 60° C. higher than that of the other monomer composition in the polymerized state, and the overall monomer composition is formed by ethylenically unsaturated compounds composed of:
1) at least 80 wt. % of one or more compounds selected from the group of alkenyl aromatic monomer, acrylonitrile, an alkyl, (hetero)cycloalkyl or aralkyl ester of acrylic acid and methacrylic acid having 4-22 C-atoms, acrylamide and methacrylamide, acrylamide and methacrylamide N-substituted with an alkyl, cycloalkyl or aralkyl group having 1 to 18 carbon atoms, vinyl acetate, and vinyl versatate, with up to 25 wt. % of these compounds optionally containing a second functional group capable of reacting with an appropriate curing agent,
2) 0.1 to 5 wt. % of an ethylenically unsaturated carboxylic acid, and
3) 0.1 to 5 wt. % of a nitrogenous, adhesion promoting copolymerizable monomer, with the proviso that at least 60 wt. % of the carboxylic acid is incorporated into the monomer composition holding less than 40 wt. % of the adhesion promoting comonomer, with the mass flow to the reactor of monomers of the composition containing monomer composition A, which is larger by a factor of 1.1 to 11, proceeding simultaneously with the mass flow of monomers of monomer composition B to the composition containing monomer composition A.
The invention also pertains to a process for preparing aqueous polymer dispersions of the aforesaid composition by subjecting a monomer composition A which is continually replenished with a monomer composition B to an emulsion polymerization, with the Tg of one of the monomer compositions in the polymerized state being at least 40° C., as well as at least 60° C. higher than the Tg of the other monomer composition in the polymerized state, with the overall monomer composition being formed by ethylenically unsaturated compounds composed of:
1) at least 80 wt. % of one or more compounds selected from the group of alkenyl aromatic monomer, acrylonitrile, an alkyl, (hetero)cycloalkyl or aralkyl ester of acrylic acid and methacrylic acid having 4 to 22 C-atoms, acrylamide and methacrylamide, acrylamide and methacrylamide N-substituted with an alkyl, cycloalkyl or aralkyl group having 1 to 18 carbon atoms, vinyl acetate, and vinyl versatate, with up to 25 wt. % of these compounds optionally containing a second functional group capable of reacting with an appropriate curing agent,
2) 0.1 to 5 wt. % of an ethylenically unsaturated carboxylic acid, and
3) 0.1 to 5 wt. % of a nitrogenous, adhesion promoting, copolymerisable monomer, with the proviso that at least 60 wt. % of the carboxylic acid is incorporated into the monomer composition holding less than 40 wt. % of the adhesion promoting comonomer, with the mass flow to the reactor of monomers of the composition containing monomer composition A, which is larger by a f
Delaunoit Genevieve
Mestach Dirk Emiel Paula
Akzo Nobel N.V.
Burke Michelle J.
McGillycuddy Joan M.
Vickrey David H.
Zalukaeva Tatyana
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