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
2000-04-28
2002-09-17
Cain, Edward J. (Department: 1714)
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...
C524S440000, C524S441000, C524S501000, C524S589000, C524S591000, C523S171000
Reexamination Certificate
active
06451896
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an aqueous coating system containing at least two components, and its use for the preparation of aqueous coating compositions, in particular for the preparation of waterborne basecoats. The aqueous coating system can be used for coating vehicles and vehicle parts, in particular in vehicle repair coating.
BACKGROUND OF THE INVENTION
In the field of vehicle coating, in particular of vehicle repair coating, there are different ways of preparing water-based coatings. In order to respond to an increasing number and variety of colour shades and to obtain a perfect repair coating with exactly matching colour shades, mixing systems are conventionally used in vehicle repair coating, whereby different base colours are kept in the form of mixing colours or pigment pastes and a defined number of base colours are mixed together shortly before application according to a given mixing formula, depending on the desired colour shade. Meanwhile, apart from solvent-based mixing systems, there are also systems based on aqueous coatings. The waterborne basecoats to be used can be modified with rheology-influencing compounds, for example layered silicates or thickeners based on polyacrylate or polyurethane/urea in order to obtain an optimal rheological behaviour. The rheology-influencing compounds can thereby be added to the waterborne basecoats directly while they are being prepared or as an additional component in a mixing system.
In EP-A-578 645 a mixing system for vehicle repair coating is described with base colours A, which contain less than 5 wt-% water, pigments, water-dilutable polyurethane, aminoplast, polyacrylate and/or polyester resins and organic solvents, and with pigment-free components B, which contain water, water-dilutable polyurethane, aminoplast and/or polyester resins, whereby rheology additives can also be contained in component B.
A disadvantage of this mixing system is the unfavourable flowing behaviour of the components A as well as the unfavourable metering capacity of these components and their problematic miscibility with the components B. Furthermore, the coating compositions prepared according to these mixing systems show a poor sagging resistance, in particular at critical places such as flanges, edges or corners, as well as unsatisfactory special effect properties.
EP-A-730 626 describes an aqueous coating system of 2 components, with a component I, which contains water, water-dispersable binders, pigments and additives and a component II, consisting of water and a rheology additive, preferably a layered silicate. This coating system has been shown to be unfavourable in particular in the preparation of special effect coatings. The special effect coatings prepared with this coating system show poor special effect properties and poor sagging resistance as well as insufficient covering of irregularities in the substrate, deriving for example from sanding marks of an applied and sanded primer surfacer. The coating compositions are moreover difficult to filter.
EP-A-608 773 describes a modular system for the preparation of aqueous coating compositions, which contains special effect modules with at least 20 wt-% water, pigments and water-dilutable binders, and binder modules with water-dilutable binders, water and optionally organic solvents and/or additives. Mention is generally made of a rheology module that can be optionally co-used, which contains rheology additives and water as well as optional water-dilutable binders. Nothing is said, however, about the precise composition and handling of such a rheology module. The aqueous coating compositions prepared with this modular system also still show disadvantages with respect to special effect properties, covering capacity and sagging resistance.
There is a need for aqueous coating compositions useful as waterborne basecoats, which contain special effect pigments, have suitable rheology, improved covering capacity as well as an improved sagging resistance. In addition, the coating compositions should be stable during storage for a long period of time, for example 12 months, and should be easily filtered before their use. Further, coatings which cover the substrate in an excellent manner should be obtained.
SUMMARY OF THE INVENTION
This need is satisfied by the coating system for the preparation of aqueous coating compositions to be described hereinafter. The coating system comprises in combination the following separate components:
A) 55-95 wt-% of at least one special effect pigment composition comprising, water, at least one special effect pigment, and at least one water-dilutable resin selected from the group consisting of at least one water-dilutable resin selected from polyurethane, polyester and poly(meth)acrylate resin, the amount of water constituting at least 15 wt % of the total weight of said component A and
B) 5-45 wt-% of a pigment-free composition comprising
B1) 0.3-5.0 wt-% of at least one inorganic layered silicate,
B2) 1.0-20.0 wt-% of at least one water-dilutable polyurethane resin,
B3) 75.0-98.7, wt-% water.
The special effect pigment present in component A have a plate-like structure which in the coating on the substrate provides a change in colour and/or brightness depending on the light angle of incidence or angle of observation. The wt %s of components A and B total 100 wt %, and the wt %s of B1, B2, and B3 total 100 wt % of component B. In component B, the preferred amount of B1 is 0.5-3.0 wt %, the preferred amount of B2 is 2.0-10.0 wt %, and the preferred amount of water is 87.0-97.5 wt %. Preferred coating systems according to the invention contain 70-95 wt-% of component A and 5-30 wt-% of component B.
The aqueous coating composition is prepared by mixing together components A and B and the resultant aqueous coating composition produces surprising results as a water-borne basecoat for such substrates as vehicles and vehicle parts. The components by themselves are storage stable, as are the aqueous coating compositions prepared therefrom. Such compositions exhibit excellent rheology. Such compositions also exhibit very good special effect properties and a good sagging resistance, in particular at critical places, and a very good covering of the substrate, including the masking of surface irregularities such as sanding marks.
The coating system according to the invention can contain additional components as part of the combination of separate components, for example at least one of the components C, D and E, as follows:
C) at least one colour composition comprising water, at least one colour pigment, and at least one water-dilutable resin selected from the group consisting of polyurethane, polyester, and poly(meth)acrylate resins,
D) at least one cross-linking composition comprising at least at least one cross-linking agent, and
E) at least one binder composition comprising at least one water-dilutable binder resin. These additional components extend the utility of the aqueous coating composition prepared from components A and B, without detracting from the advantageous coating characteristics of the composition.
DETAILED DESCRIPTION OF THE INVENTION
One or more of each component can be present in the coating system according to the invention. For simplification, the singular shall be used in the description of each component hereinafter.
Component A contains one or more water-dilutable binders. The water-dilutable binders are conventional water-dilutable polyurethane, polyester and/or poly(meth)acrylate resins and include the modified resins thereof, known to the skilled person.
The water-dilutable binders mentioned can be ionically and/or nonionically modified in order to obtain sufficient water dilutability, i.e. dispersibility in water. An anionic and/or a non-ionic modification is preferred. An anionic modification can be obtained, for example, by way of at least partially neutralized carboxyl groups. A non-ionic modification can be obtained, for example, by incorporating polyethylene oxide units.
Examples of water-dilutable polyurethane resins
Wandelmaier Klaus
Wiggershaus Stefan
Benjamin Steven C.
Cain Edward J.
E. I. du Pont de Nemours and Company
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