Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-11-13
2002-04-30
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S064000, C525S068000, C525S075000, C525S084000, C428S423100, C427S385500, C528S073000
Reexamination Certificate
active
06380308
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to new binder compositions of polyacrylate polyols and crosslinking agents, a process for their preparation and their use for the production of coatings.
2. Description of the Prior Art
The advantage of high-solids polyacrylate resins is to be seen in the reduction in the emission of organic compounds, preferably solvents, during the application of the coating. To obtain these high-solids coating formulations, corresponding polyacrylate resins with low viscosities, i.e. low molecular weights, should be used.
It is known that free-radical solvent polymerization can be used for the preparation of low-viscosity polymers (e.g. EP-A 408 858, EP-A 398 387 and U.S. Pat. No. 4,145,513). The properties of these polymers are impaired by the use of considerable amounts of polymerization regulators and secondary products thereof. In particular, the thiols employed as polymerization regulators may smell nauseous or may even be toxic. In EP-A 225 808, EP-A 225 809 and EP-A 778 298, &agr;-olefins, such as e.g. 1-octene or 1-decene, which have no unpleasant smell, are therefore used as regulators. However, two-component polyurethane (2C PU) lacquers based on the polyacrylate resins according to EP-A 225 809 and aliphatic polyisocyanates have too slow a physical drying to be employed e.g. for use in car repair and large vehicle lacquering. The drying of 2C PU lacquers according to EP-A 778 298 also no longer completely meets current application requirements in this respect and is therefore in need of improvement.
EP-A 635 523 and EP-A 638 591 describe high-solids polyacrylate resins which are prepared by bulk polymerization and are then diluted with a suitable solvent.
EP-A 635 523 describes the effect, known from solvent polymerization, of the preparation of high-solids polyacrylate resins with a unimodal narrow distribution using peroxides containing tert-amyl groups, but applied to bulk polymerization. As expected, it was demonstrated that lower-viscosity polyacrylate resins are obtained with peroxides containing tert-amyl groups than with peroxides containing tert-butyl groups. However, bulk polymerization has disadvantages compared with solvent polymerization, in particular with respect to the removal of the heat of reaction. The polyacrylate resins prepared in the examples of the above mentioned application have viscosities at 23° C. of between 2,790 and 9,130 mPa.s at a solids content of 70 wt. %, and are therefore in the medium-solids than in the high-solids range. They do not meet the current requirements of high-solids lacquers.
EP-A 171 847 and EP-A 638 591 describe high-solids copolymers which have a relatively low viscosity at a high solids content due to the use of (meth)acrylate monomers with sterically bulky (cyclo)alkyl radicals. However, the resistance of such copolymers to solvents and chemicals no longer completely meets the current requirements of highly resistant car repair lacquers. In the preparation of the copolymers according to EP-A 638 591 by bulk polymerization, a monoepoxide (Cardura E 10) is initially introduced into the reaction vessel as the reaction medium in all the examples described. During the polymerization this monoepoxide reacts with the (meth)acrylic acid metered in and is thus incorporated into the polyacrylate. Predominantly secondarily bonded hydroxyl groups are formed by this reaction, and, in addition to the primary hydroxyl groups or secondary hydroxyl groups introduced by hydroxy-functional monomers (hydroxyethyl methacrylate and hydroxypropyl methacrylate respectively), are available for the reaction with the polyisocyanate used as a crosslinking agent.
However, secondary hydroxyl groups have a significantly lower reactivity towards polyisocyanates than primary hydroxyl groups. 2C PU lacquers which are cured at low temperatures (car repair and large vehicle lacquering, wood lacquering) and are based on polyacrylate resins with predominantly secondarily bonded hydroxyl groups therefore achieve an adequate crosslinking density and a satisfactory resistance to solvents only after several days. Precisely in car repair and large vehicle lacquering, however, a rapid chemical crosslinking is also urgently necessary, in addition to a rapid physical drying, in order thus to allow the vehicle to be further used as quickly as possible.
It is therefore the object of the invention to provide new binder compositions based on hydroxy-functional copolymers and (cyclo)aliphatic lacquer polyisocyanates which give high-solids lacquers which, in addition to a rapid physical drying, also show a rapid chemical crosslinking at room temperature (23° C.) and an excellent resistance to solvents after a short curing time of 1 to 2 days.
New high-solids binder compositions, which can be cured to give high-quality coatings are obtained by combination of the OH-functional binder components essential to the invention with polyisocyanates. In addition to outstanding optical properties of the films and a high resistance to solvents and chemicals, these coatings show a very rapid physical drying and chemical crosslinking at room temperature and a good surface hardness.
The very good overall profile of properties of the resulting coating films, such as hardness, elasticity and resistance to chemicals, solvents and weathering, allows use in vehicle lacquering, preferably in car repair and large vehicle lacquering. Other fields of use lie in the sectors of general industrial lacquering, corrosion protection and wood and furniture lacquering, it also being possible for other crosslinking resins to be used as the polyisocyanates.
SUMMARY OF THE INVENTION
The invention relates to a binder composition containing
A) 50 to 90 parts by wt., preferably 90 to 60 parts by wt. of OH-functional graft copolymer resins prepared by copolymerization of
a) 0.1 to 10 parts by wt. of at least one optionally functional polybutadiene with a number-average molecular weight of 500 to 10,000 and a structure which is at least 20% 1,2-vinyl,
b) 5 to 60 parts by wt. of at least one unsaturated aromatic monomer,
c) 10 to 50 parts by wt. of at least one hydroxyalkyl ester of acrylic and/or methacrylic acid having 2 to 4 C atoms in the hydroxyalkyl radical and a primary hydroxyl group,
d) 5 to 70 parts by wt. of at least one cycloaliphatic ester of acrylic and/or methacrylic acid having 1 to 12 C atoms in the alcohol component,
e) 5 to 50 parts by wt. of at least one aliphatic ester of acrylic and/or methacrylic acid having 1 to 8 C atoms in the alcohol component,
f) 0.1 to 5 parts by wt. of at least one &agr;,&bgr;-mono-olefinically unsaturated mono- or dicarboxylic acid having 3 to 7 C atoms and/or at least one maleic acid or fumaric acid half-ester having 1 to 14 C atoms in the alcohol radical and
g) 0 to 40 parts by wt. of further copolymerizable olefinically unsaturated compounds and
B) 10 to 50 parts by wt. of a polyfunctional crosslinking agent or crosslinking agent mixture,
the sum of the parts by wt. of components A) and B), based on the weight of A) and B), and the sum of the parts by wt. of components a) to g) in each case being 100.
The invention also relates to a process for the preparation of the binder compositions according to the invention characterized in that the graft copolymers A) described above are prepared by free-radical polymerization in organic solvents at temperatures between 150 and 240° C. and are combined with suitable crosslinking resins B).
The invention also provides the use of the binder compositions according to the invention to produce lacquers for vehicle lacquering, in particular for car repair and large vehicle lacquering, for general industrial, wood and furniture lacquering and in the corrosion protection sector.
DETAILED DESCRIPTION OF THE INVENTION
A large number of polyfunctional crosslinking agents are suitable according to the invention, including aminoplast resins, such as alkoxylate melamine resins, melamine-formaldehyde condensation products, urea resins, guanidine resins, phen
Mundstock Holger
Sonntag Michael
Wamprecht Christian
Bayer Aktiengesellschaft
Gil Joseph C.
Gorr Rachel
Roy Thomas W.
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