Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
2002-03-20
2004-11-09
Tarazano, D. Lawrence (Department: 1773)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C428S516000, C428S520000, C428S522000, C428S523000, C525S064000, C525S273000, C525S391000, C427S407100, C427S409000
Reexamination Certificate
active
06815081
ABSTRACT:
The present invention relates to a novel multicoat color and/or effect coating system for a primed or an unprimed substrate. The present invention further relates to a novel process for producing a multicoat color and/or effect coating system on a primed or unprimed substrate. The present invention relates not least to the use of the novel multicoat and/or effect coating system, and of the novel process for producing it, in automotive OEM finishing and refinishing, in industrial coating, including container coating and coil coating, and in furniture coating.
Multicoat color and/or effect coating systems for primed or unprimed substrates are known. Normally, they comprise a surfacer coat, which absorbs mechanical energy, and a solid-color and/or effect topcoat. In another variant, they comprise a surfacer coat, a color and/or effect basecoat, and a clearcoat. For the coating of plastics, it is also common to employ a multicoat system which comprises a color and/or effect basecoat and a clearcoat. In many cases, such multicoat systems are produced by the wet-on-wet technique, in which in particular the basecoat film is merely dried but not cured before the application of the clearcoat film, and the basecoat film and clearcoat film are cured together.
In the coating materials used to produce known multicoat color and/or effect coating systems, constituents are frequently used that are prepared by free-radical polymerization of olefinically unsaturated monomers. These constituents are also referred to as binders. In the majority of cases, the binders of said type comprise acrylate copolymers.
Acrylate copolymers and coating materials comprising them are described, for example, in the patents EP-B-0 447 428, EP-B-0 593 454, EP-B-0 052 776, or DE-A-42 04 518.
Acrylate copolymers may be prepared by well-known polymerization processes in bulk, solution or emulsion. Polymerization techniques for preparing acrylate copolymers, especially polyacrylate resins, are general knowledge and are widely described (cf., e.g., Houben-Weyl, Methoden der organischen Chemie, 4th Edition, Volume 14/1, pages 24 to 255 (1961)).
Further examples of suitable copolymerization processes for preparing acrylate copolymers are described in patents DE-A-197 09 465, DE-C-197 09 476, DE-A-28 48 906, DE-A-195 24 182, EP-A-0 554 783, EP-B-0 650 979, WO 95/27742, DE-A-38 41 540, and WO 82/02387.
Suitable reactors for the copolymerization processes are the customary and known stirred vessels, cascades of stirred vessels, tube reactors, loop reactors, and Taylor reactors, as described for example in patents DE-B- 1071 241 and EP-A-0 498 583 or in the article by K. Kataoka in Chemical Engineering Science, Volume 50, No. 9, 1995, pages 1409 to 1416.
The free-radical polymerization used to prepare the acrylate copolymers is often very exothermic and difficult to control. The implications of this fact for the reaction regime are that it is necessary to avoid high monomer concentrations and/or the batch mode, where the entirety of the monomers is introduced as an initial charge in an aqueous medium, emulsified and subsequently polymerized to completion. Even the tailoring of defined molecular weights, molecular weight distributions, and other properties frequently causes difficulties. The tailoring of a certain profile of properties in the acrylate copolymers, however, is of great importance for their use as binders in coating materials, since by this means it is possible to influence the profile of performance properties of the coating materials in a direct way.
There has therefore been no lack of attempts to control the free-radical copolymerization of olefinically unsaturated monomers in a targeted manner.
For instance, International Patent Application WO 98/01478 describes a process in which the copolymerization is conducted in the presence of a free-radical initiator and of a thiocarbonylthio compound as chain transfer agent.
International Patent Application WO 92/13903 describes a process for preparing copolymers having a low molecular weight by means of free-radical chain polymerization in the presence of a group transfer agent containing a carbon-sulfur double bond. These compounds act not only as chain transfer agents but also as growth regulators, so that only low molecular weight copolymers result.
International Patent Application WO 96/15157 discloses a process for preparing copolymers having a comparatively narrow molecular weight distribution, in which a monomer is reacted with a vinyl-terminated macromonomer in the presence of a free-radical initiator.
Furthermore, International Patent Application WO 98/37104 discloses the preparation of acrylate copolymers having defined molecular weights by means of free-radical polymerization in the presence of a chain transfer agent containing a C—C double bond and containing radicals which activate this double bond in terms of the free-radical addition reaction of monomers.
Despite the significant progress in this area, there is still a lack of a universally applicable process of controlled free-radical polymerization which in a simple manner provides chemically structured polymers, especially acrylate copolymers, and by means of which it is possible to tailor the profile of properties of the polymers in respect of their use in coating materials, which are used to produce multicoat color and/or effect coating systems.
As a result, it continues to be necessary to take other measures, in some cases more complex ones, to harmonize the profiles of properties and material compositions of the surfacers, basecoat materials and clearcoat materials in such a way that the multicoat color and/or effect coating systems have the high optical quality and intercoat adhesion required by the market and no longer give rise to problems such as deficient condensation resistance of the surfacer coats, cracking (mud cracking) in the basecoats, or leveling defects or surface structures in the clearcoats.
It is an object of the present invention to provide new multicoat color and/or effect coating systems and also new processes for producing them, in which at least one coat of the multicoat color and/or effect coating system is produced from a coating material which may be adapted in a simple manner to its respective use as surfacer, basecoat and/or clearcoat material. The aim is to realize this object in a simple manner by tailoring the profile of properties of the coating materials, in particular through the use of chemically structured polymers obtainable by means of controlled free-radical polymerization. The new multicoat color and/or effect coating systems which result should no longer have the disadvantages of the prior art but instead should exhibit outstanding optical quality, intercoat adhesion and condensation resistance and should not exhibit any cracking (mud cracking), leveling defects or surface structures. Moreover, it should be possible to use these chemically structured polymers as grinding resins which make it possible in an advantageous manner to provide pigment pastes having a particularly good capacity for incorporation by mixing for the surfacers, basecoat and clearcoat materials used to produce the new multicoat color and/or effect coating systems.
Accordingly, we have found the novel multicoat color and/or effect coating system ML for a primed or unprimed substrate, which comprises, lying above one another in the stated sequence
(1) a surfacer coat FL which absorbs mechanical energy, and
(2) a color and/or effect topcoat DL or
(1) a surfacer coat FL which absorbs mechanical energy,
(2) a color and/or effect basecoat BL, and
(3) a clearcoat KL or
(1) a color and/or effect basecoat BL and
(2) a clearcoat KL,
wherein at least one coat FL and/or DL or BL and/or KL or FL, BL and/or KL, preferably at least two coats FL, BL and/or KL or all coats FL and DL or BL and KL or FL, BL and KL of the multicoat system ML has or have been produced from a coating material comprising at least one constituent (A) preparable by free-radical polymerization of
a) at least one olefinically u
BASF Coatings AG
Tarazano D. Lawrence
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