Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2000-02-03
2004-07-13
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
active
06762272
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel family of compositions containing masked isocyanates and polyols. The invention relates more particularly to powders, including mixtures of powders, and to their use as powders in coatings such as paints, particularly to high gloss coatings and paints.
2. Description of the Related Art
For reasons associated with protection of the environment and safety at work, it is increasingly sought to eliminate the use of solvents in coating techniques and particularly in paints. More particularly, reducing VOCs (Volatile Organic Compounds) is an increasingly current preoccupation in the paint and varnish industry. With this aim, the development of products with higher solids content makes it possible to decrease the amounts of solvents required to achieve the application viscosity, and thus to reduce the solvents evaporated during drying of paint film.
Another alternative is to use products in aqueous phase in which the water has replaced the organic solvents as the agent carrying the organic binder. However, a small amount of organic solvent is required to use and form the film of paint. Furthermore, they give rise to water-soluble residues which may be tricky and expensive to process.
In this context, coating techniques using powders are increasingly being developed. A few details of this technique should be given herein in order to gain a better understanding of the present invention. The technique uses a very finely powdered material for which air acts as a vector.
In general, an electrostatic charge of several kilovolts applied between a gun and the article to be painted allows the coating precursor powder, which is to be sprayed by the applicator gun, to be attracted and retained.
Firing of the article between 150 and 200° C. allows melting, spreading and then crosslinking of the paint powder (paint being considered the ultimate example for coatings) in order to obtain a uniform and homogeneous layer of the coating.
This technique is non-polluting and has an application yield of close to 100% by virtue of the possibility of recycling the unused powder.
Among the families of products which may be used in this field, mention should be made of the following. The majority of the market is occupied by so-called “epoxy-polyester hybrid” powder paints, followed by polyesters and polyurethanes, and then so called “epoxy” powders.
In order to obtain good quality strength on exteriors (in particular with respect to UV radiation and moisture), it is essential to use coatings based on TGIC (triglycidyl isocyanurate)- polyester or polyurethane which, alone, makes it possible to achieve the required levels of performance.
The coating powders may be in several finishes (surface, aspect, color, sheen, etc.). For example, copending application Ser. No. 09/240,598, filed Feb. 1, 1999, now U.S. Pat. No. 6,291,624, the entire contents of which are herein incorporated by reference, describes compositions for obtaining matt or satin coatings. Such coatings are defined therein as having a coefficient of reflection which is at most equal to about 50% at a 60° angle of incidence.
The compositions of interest in the present case can advantageously provide high gloss coatings. As used herein, a high gloss coating is one which, when applied to a metal support and after crosslinkling, has a coefficient of reflection which is greater than 80%, preferably greater than 85%, more preferably greater than 90% and most preferably greater than 95%, for a 60° angle of incidence.
For further details regarding the techniques of powder painting, reference may be made to the following books: P. Grandou and P. Pastour,
Peintures et Vernis
[Paints and Varnishes], I les constituents, II techniques et industries [techniques and industries]; pub. Hermann; R. Lambourne,
Paints and Surface Coatings, theory and practice
, pub. Halsted Press;
Powder Coating, The Complete Finisher Hand Book
, the Powder Coating Institute; and Myers and Long,
Treatise on Coatings,
5 volumes, pub. Marcel Dekker.
U.S. Patent No. 3,991,034, to Takeo et al, discloses a polyester resin composition suitable for preparing a powder paint, which comprises a polyester and a polyisocyanate blocked with an alkyl p-hydroxybenzoate. The composition is characterized as being a thermosetting polyester resin composition. The alcohol functionality and the extent of crosslinking of the disclosed compositions are relatively low. The mechanical properties of the coatings formed are therefore lacking.
To overcome or conspicuously ameliorate the problems associated with the related art, it is an object of the invention is to provide compositions which make it possible to obtain high gloss coatings with superior mechanical properties. The compositions are easy to use, and the coatings which can be obtained therefrom advantageously have a high gloss finish and good weather resistance.
It is a further object of the invention to provide a process for preparing the compositions.
It is a further object of the invention to provide paint compositions wherein the paint is a high gloss paint. The paint compositions can be prepared by the so-called powder technique using the inventive compositions.
Other objects and aspects of the present invention will become apparent to one of ordinary skill in the art on a review of the specification and claims appended hereto.
SUMMARY OF THE INVENTION
These aims and others which will appear hereinbelow are achieved by provision of a composition useful for obtaining a high gloss coating. The composition features an isocyanate which is at least partially masked by one or more masking agent, and having a degree of liberation with respect to the masking agent at 120° C. of 5% or less. A polyol has a glass transition temperature of about 40° C. or more, a hydroxyl number of about 10 mg/g or more and an average molecular mass Mn of about 500 g/mol or more.
In accordance with a further aspect of the invention, a composition useful for obtaining a high gloss coating is provided. The composition features an isocyanate which is at least partially masked by one or more masking agent, having a glass transition temperature of about 20° C. or more. A polyol has a glass transition temperature of about 40° C. or more, a hydroxyl number of about 10 mg/g or more and an average molecular mass Mn of about 500 g/mol or more. At least one of the following conditions apply:
the composition further comprises a carboxylic function, with the proviso that, when the carboxylic acid function which is free or in the form of a salt, is greater than 30 mg KOH/g, the amine content is lower than 0.6% (equivalent) of the isocyanate (masked and free);
the composition is essentially free of an esterification, catalyst, especially a carbamatation catalyst, which is solid and/or non-liposoluble;
the composition is essentially free of a matt-effect wax; and
the composition further comprises a liposoluble catalyst.
According to a further aspect of the invention, a process for preparing the compositions is provided. The process involves the steps of preblending the isocyanate, the polyol and any other components in a blender, and melting, homogenizing and dispersing the polyol and other meltable components of the blend in an extruder having one or more screws.
In accordance with a further aspect of the invention, high gloss paint compositions comprising the composition are provided.
As used herein, the term “about” is used to emphasize the fact that the value is rounded up and that, when the figure(s) furthest to the right of a number are zeros, these zeros are positional zeros and not significant figures unless, of course, otherwise stated.
Also as used herein, the term “essentially free” means that the component in question is absent from the composition, or is present in such an insignificant amount that a high gloss coating can be obtained from the composition.
A carboxylic function is advantageously in intimate mixture with the a isocyanate component of the comp
Ardaud Pierre
Bernard Jean-Marie
Vogin Bernard
Williams Francis John
Burns Doane Swecker & Mathis L.L.P.
Chimie Rhodia
Sergent Rabon
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