Stock material or miscellaneous articles – Composite – Of polyamidoester
Patent
1993-09-03
1994-11-29
Lusignan, Michael
Stock material or miscellaneous articles
Composite
Of polyamidoester
4274071, 427409, 4274121, 4284258, 528 49, 528 69, 528 73, B32B 2700, B32B 2740
Patent
active
053689445
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the production of a multicoat protective and/or decorative finish in which resin is applied to the substrate surface as basecoat, and subsequently
This process represents the well known basecoat-clearcoat process, used above all for the preparation of high-quality finishes, especially of metallic finishes for automobile bodies. In the "wet-on-wet" process, the pigmented basecoat first applied is coated, after a brief flash-off period, with a transparent topcoat (clearcoat) without a baking stage. Both paint coats are then baked together in a single operation.
The paint industry has made great efforts to reduce the amounts of organic solvents used especially in basecoats. Aqueous basecoats have been developed which are increasingly displacing conventional basecoats comprising exclusively organic solvents.
From EP-A-89,497, German Offenlegungsschrift 3,545,618, EP-A-355,433, U.S. Pat. No. 4,719,132 and German Offenlegungsschrift 3,903,804 it is known that especially aqueous basecoats containing a water-thinnable polyurethane resin are particularly well suited for the process under discussion.
The aim of the present invention is to produce aqueous, polyurethane resin-containing basecoats which furnish improved multicoat finishes of the basecoat-clearcoat type when the process described above is used. The aim of the present invention is in particular to produce aqueous, polyurethane resin-containing basecoats which furnish refinishes with improved adhesion.
Surprisingly, it has been found that when aqueous basecoats comprising a water-thinnable polyurethane resin which contains structural units of the formula ##STR2## are employed, improved multicoat finishes of the basecoat-clearcoat type are obtained, X representing a divalent aromatic hydrocarbon radical, preferably a naphthylene, biphenylene, 1,2-phenylene, 1,3-phenylene or 1,4-phenylene radical, particularly preferably a 1,3-phenylene radical, each optionally substituted by halogen, methyl or methoxy, and R.sup.1 and R.sup.2 representing an alkyl radical having 1 to 4 carbon atoms, particularly preferably a methyl radical. The multicoat finishes obtained with these basecoats possess improved adhesion properties when used for refinishing.
EP-A-369,389 describes water-thinnable polyurethane resins which are prepared using tetramethylxylylene diisocyanate (TMXDI, 1,3- or 1,4-bis(2-iso-cyanatoprop-2-yl)benzene) and are said to be usable also in coating compositions. However, EP-A-369,389 makes no reference to the basecoat-clearcoat process.
Polyurethane resins containing the structural units (I) can be prepared by using diisocyanates of the general formula ##STR3## for the preparation of the polyurethane resins, R.sup.1, R.sup.2 and X having the same meaning as in the formula (I).
Diisocyanates of the formula (II) are known (their preparation is described, for example, in EP-A-101,832, and US Patents 3,290,350, 4,130,577 and 4,439,616) and some are commercially available (for example, 1,3-bis(2-isocyanatoprop-2-yl)benzene is marketed by American Cyanamid Company under the trade name TMXD I (META).RTM.).
The polyurethane resins are used in the form of aqueous dispersions. The preparation of aqueous polyurethane resin dispersions is known to a person skilled in the art and is also described, for example, in EP-A-89,497, German Offenlegungsschrift 3,545,618, EP-A-355,433, U.S. Pat. No. 4,719,132 and German Offenlegungsschrift 3,903,804.
The polyurethane resins used according to the invention are usually prepared by reacting molecular weight of 400 to 5000 or a mixture of such polyester polyols and/or polyether polyols, the component (B) consisting of a diisocyanate of the formula (II) or a mixture of such diisocyanates, a molecular weight of 60 to 400 (number average) or a mixture of such compounds and, optionally, isocyanate groups.
The polyurethane resins usually have a number average molecular weight of at least 1000. The number average molecular weight of the polyurethane resins should preferably be at least 4000, parti
REFERENCES:
patent: 4652494 (1987-03-01), Bravet et al.
patent: 4719132 (1988-01-01), Porter
patent: 4879365 (1989-11-01), Petschke et al.
patent: 5204379 (1993-04-01), Kabota et al.
Arendt, Volker D et al, "m and p--TMXOI: Two New Isocyanotes For The Polyarethane Industry," Journal of Cellular Plastics, Nov., Dec., 1982, pp. 376-383.
Hartung Michael
Lassmann Walter
Poth Ulrich
Wegner Egon
BASF Lacke & Farben Aktiengesellschaft
Lusignan Michael
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