Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Patent
1997-01-02
1998-04-14
Cain, Edward J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
525440, C09D17504
Patent
active
057392161
DESCRIPTION:
BRIEF SUMMARY
This invention relates to binder compositions suitable for the production of coating compositions, which are stoved at elevated temperature and are in particular suitable for the production of multi-layer lacquer coatings, for example in the automotive sector.
DE-A-30 22 996 discloses a storing lacquer in which polymers containing carboxyl groups, such as for example acrylates based on acrylic acid or methacrylic acid and acrylates containing glycidyl groups are combined to yield a curable composition.
WO 84/00771 describes a multi-component system in which four types of binder are mixed together and then applied. The components comprise an acrylate containing hydroxyl groups, acid anhydride, wherein at least 50% are alkylhexahydroxphthalic anhydrides, epoxy resin and melamine resin. The systems have an elevated solids content.
DE-A-23 33 384 describes a binder based on acrylated polyesters, which are obtained by polymerising an acrylate containing hydroxyl groups in a polyester or alkyd resin containing hydroxyl groups. Crosslinking may be performed with melamine resins and epoxy resins simultaneously.
DE-A-38 00 389 describes the modification of copolymers containing hydroxyl groups with lactones, in particular with epsilon-caprolactone.
U.S. Pat. No. 4,501,829 describes polyesters having hydroxyl and carboxyl groups, which are reacted with lactones. The reaction proceeds on the hydroxyl groups. U.S. Pat. No. 4,082,816 describes compositions of (meth)acrylic copolymers containing carboxyl groups and modified with caprolactone and melamine/formaldehyde resins.
The as yet unpublished German patent application P 42 37 658 describes binder compositions which are composed of lactone-modified polyacrylates or polyesters containing carboxyl groups and polymers containing glycidyl groups. Urethanisation of the acidic components is not mentioned.
Some of the stated coating compositions give rise to films having elevated hardness and good weathering resistance. They do not, however, fulfil the constantly rising requirements for elevated resistance to acids and solvents.
The object of the invention is to provide a binder system which may be processed to yield coating compositions which may be stored at elevated temperature to yield coatings having good hardness, good weathering resistance and elevated elasticity and which are additionally resistant to acids and solvents. The coating compositions should additionally exhibit good application characteristics (reduced tendency to sag) even at elevated layer thicknesses.
It has been found that this object may be achieved by a binder composition which is provided by this invention and contains: carboxy-functionalised (meth)acrylic copolymers containing urethane groups and/or of one or more carboxy-functionalised polyesters containing urethane groups, each having an acid value of 30 to 200 mg of KOH/g, with one or more lactones, having at least two epoxy functions per molecule with a number average molecular weight (Mn) of 200 to 10000 g/mol, functions per molecule, wherein the sum of the weight percentages of components A), B), C), D.sub.1) and D.sub.2) amounts to 100 wt. %, together with carboxyl and epoxy groups, relative to the sum of weights of components A) to D.sub.2).
It has been found that the binder compositions according to the invention or the coating compositions produced therefrom give rise to coatings which have elevated solvent resistance, in particular towards xylene, even in the case of the purest possible crosslinking between carboxyl groups and epoxy groups, such that it is possible to work without or only with small quantities of additional crosslinking agents such as polyisocyanates and/or melamine resins.
According to a preferred embodiment of the invention, the carboxy-functionalised (meth)acrylic copolymers containing urethane groups, which may be reacted with lactone according to component A), have a number average molecular weight (Mn) of 1000 to 30000 g/mol. The carboxy-functionalised polyesters containing urethane groups which may correspondin
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E. Vollmert-Verlag-Karlsruhe, 1985, Bruno Vollmert, Grundriss Der Polymer-Reaktionen, pp. 4-20.
Products Finishing, Carl J. Rieger, Metallic-Effect Coatings, Apr. 1976, pp. 54-56.
Duecoffre Volker
Flosbach Carmen
Herrmann Friedrich
Reifferscheidt Heinz-Walter
Schubert Walter
Cain Edward J.
Herberts Gesellschaft mit beschrankter Haftung
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