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
1999-12-08
2003-03-04
Nutter, Nathan M. (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...
C528S048000, C524S366000, C524S591000, C524S800000, C524S839000, C428S423100
Reexamination Certificate
active
06528610
ABSTRACT:
The present invention relates to an industrial floorcovering or exterior coating, to a composition which is useful for such coatings and to a process for obtaining these coatings.
The invention relates more particularly to the combination of certain polyols with certain isocyanate formulations.
The coatings described in the invention are particularly advantageous for application to metallic supports, but it especially solves a problem for nonmetallic supports, among which mention may be made of plant supports such as wood and mainly mineral supports, of variable porosity, such as concrete, plaster, stone or phosphomagnesium support.
It is thus possible to obtain coatings of controlled permeability (waterproof [impermeability to liquids] while at the same time allowing the support to breathe [permeability to gases]) whose depth of penetration into the support and flexibility may be adjusted by modifying, in particular, the size and Tg of the polyol as well as the nature of the surfactant used.
These coatings may be applied without problem to wet supports.
These coatings may be used for interiors or exteriors, on horizontal or vertical walls with particular success:
as a topcoat for industrial floors (in general mineral or wood support): the abrasion strength is improved and the permeability to water is reduced, thus giving hard-wearing floors which are easy to maintain;
as a leakproofing coating: a flexible leaktight coating can be formed by impregnation, and can be applied to exteriors at low temperature in the presence of moisture, without any problems of cracking arising.
The term “coating” means, in particular:
1) Impregnation “Resins”
These products are intended to penetrate into and fill pores, to a depth ranging from 0.1 to 3 mm and more depending on the porosity of the support, generally from 0.5 to 3 mm.
They are generally applied by spraying or by brush in order to help the penetration into the support. Their function is to reduce the porosity, reduce soiling, facilitate cleaning and improve the hard-wearing nature and reinforce the mechanical properties.
The impregnation resins known in the art are based on epoxides, polyurethanes, polymethyl methacrylate or polyester.
2) Paints, Coatings (stricto sensu)
These are thin films of at least about 10
−2
mm, generally from 0.1 to 1 mm, based on synthetic epoxy, polyurethane or methacrylate resins, used alone or combined, and which generally contain fine fillers and pigments.
They are applied to horizontal or vertical supports, by brush, by roller, by scraper or by spraying.
In the case of application to a horizontal support, semi-thick coatings may be obtained by dusting fillers onto a fresh coat.
These floorcoverings are intended, as with the impregnation resins, to reduce the porosity of the support, thereby reducing the formation of dust, facilitating cleaning, improving the abrasion resistance, the resistance to corrosive chemical agents: acids, bases, solvents, oils, etc.
3) Synthetic Resin Screeds (Including Selfsmoothing Coatings)
Selflevelling floors can consist of mixtures of resins and fillers applied to thicknesses of from 1 to 3 mm and floated, which give the floor a smooth appearance (suppression of the macroscopic coarseness) and/or which can be made skid-proof by dusting with fillers (silica, corundum, etc.).
Synthetic resin screeds are applied more thickly (4 mm to 1.5 cm).
A coating should be obtained which has very good mechanical and chemical characteristics and a beautiful esthetic appearance.
In particular, high compressive and flexural strengths should be obtained (R
compression
:60 to 120 MPa−R
flexure
:28 to 45 MPa)
The screeds should be particularly abrasion-resistant and recommended for use in areas sustaining heavy traffic, and should also have good chemical resistance to attack.
One of the aims of the present invention is to provide polyurethane resins which give, in particular, flexible coatings which mask the existing cracks in the support and which can resist cracking induced by the support.
Such compositions are useful in particular for varnishes (to the constraints of which they lend themselves particularly well), but also for paints. More generally, they can be useful for any application using the properties of isocyanate condensation.
In the rest of the present description, the term “dispersion” will be used for polymers containing hydroxyl functions and in particular polyols, while the expression “emulsions” will be used for blocked or unblocked isocyanates.
The use of organic solvents is increasingly being criticized by the authorities in charge of safety at work, since these solvents, or at least some of them, are reputed to be toxic or chronotoxic. For this reason, efforts are being made to develop more and more techniques which replace the solvent-medium techniques or which reduce the amount of solvent in order to overcome the drawbacks associated with solvents.
One of the solutions most frequently used lies in the use of emulsions or dispersions in water.
In order to prepare films of paints or varnishes, two dispersions are mixed together, an emulsion containing the isocyanate, which may be blocked, and a polyol dispersion.
The mixture of the dispersions, which can also contain pigments and fillers, is then applied to a support in the form of a film with the aid of standard techniques for using industrial paints or resins. When the preparation contains blocked isocyanates, the film+support assembly is cured at a temperature which is sufficient to release the isocyanate functions and to condense them with hydroxyl groups of the polyol particles. However, such techniques are virtually impossible to perform successfully externally.
In the present description, the particle size characteristics often refer to notations of the type d
n
in which n is a number from 1 to 99; this notation is well known in many technical fields, but is slightly less common in chemistry, and it may thus be useful to recall its meaning. This notation represents the particle size such that n% (by weight, or more exactly by mass, since weight is not an amount of matter but rather a force) of the particles is less than or equal to said size.
In the description hereinbelow, the polydispersity index will be used, which is defined as
I
=(
d
90
−d
10
)/
d
50
Typically, the average size ratios, or the d
50
when it can be determined, between the isocyanate emulsion and the polyol dispersion are between 2 and 200. Thus, the average sizes of the isocyanate emulsions manufactured according to the technique described in the French patent application filed on 31.03.1993 under No. 93/03795 and published under No. 2,703,358 on 07.10.94, have average sizes of between 0.1 and 10 micrometers and more generally between 0.3 and 2 micrometers. The polyol dispersions used in combination with these emulsions have average sizes, measured by quasielastic light scattering, of between 20 and 200 nanometers and more generally between 50 and 150 nanometers.
When, as is generally the case, dispersions of different sizes are mixed together so as to obtain molar ratios between the NCO and OH groups of between 0.3 to 10 and more preferably between 0.8 and 1.5, instability of the mixtures of the two dispersions is observed.
By way of example, this instability is reflected by a macroscopic separation which takes place rapidly, generally within a few minutes, to give a fluid phase, on the one hand, and a very viscous phase, on the other hand.
The result is that not only are these mixtures impossible to store, but also it is extremely difficult to apply this mixture to the surface which it is desired to cover or impregnate by the usual techniques for applying paints and varnishes. If these unstable mixtures are applied to a support, such as a glass or metal plate, the resulting film is not transparent but, rather, appears opaque and heterogeneous and is thus unsuitable.
These problems are particularly acute in the case of masked or unmasked isocyanates, when they are mixed with insoluble polyols
Frouin Laurent
Jeannette Thierry
Nabavi Minou
Prat Evelyne
Bissett Melanie
Nutter Nathan M.
Rhodia Chimie
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