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
1999-05-27
2002-07-16
Wu, David W. (Department: 1713)
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...
C524S507000, C524S517000, C524S531000, C526S317100, C526S318000, C526S318400, C526S346000
Reexamination Certificate
active
06420474
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to water-borne coating compositions and in particular to coating compositions that exhibit good stain resistance properties.
BACKGROUND OF THE INVENTION
Paints are widely used in households for application to both interior and exterior surfaces. For interior surfaces, particularly in kitchens and living areas the resistance of a paint film to domestic stains is an important property. This is especially the case for trim and wall paints that are frequently exposed to domestic stains.
Domestic staining materials include food, oil or grease and beverages such as coffee and red wine. For semi and low gloss interior paints, properties such as mar resistance and wet and dry scrub properties are also important. Good performance for these properties enables the stained surface to be cleaned by scrubbing without causing the treated area to “gloss up” and exhibit a gloss that is different from the surrounding area. However, it is clearly preferable that the paint be not very susceptible to staining materials as well as being able to be effectively cleaned.
Painted surfaces are also susceptible to staining from the substrate, especially in the case of timber substrates containing tannins. The tannin material can “print through” the paint film, discolouring the paint after it has dried. This problem is particularly evident with water-borne latex paints. Various factors can effect this substrate staining and special water-borne latex paints have been developed to overcome this problem. However, in this invention we are not concerned with this type of staining but staining on the outermost surface of the paint. Paints that perform well for substrate staining do not necessarily exhibit good resistance to domestic stains and vice-versa.
Conventional organic solvent based paints that have alkyd resins as binders and which form tightly crosslinked paint films generally exhibit excellent stain resistance properties. It is believed this is due to the low solubility of the staining material in the paint film. However, these paints are losing favour because of the combined adverse effects of volatilised organic solvents on the environment and inconvenience for the applicator from long recoat times and clean up requiring the use of organic solvents. Water-borne versions of alkyds suffer from yellowing problems, particularly in kitchen areas and have not yet met the needs of the market. Conventional water based or latex paints in which the paint film is formed by the coalescence of vinyl or acrylic thermoplastic polymer particles are widely used but hitherto have not exhibited excellent stain resistance together with the required balance of other paint properties, including hardness, film coalescence, pH viscosity stability, and tint strength.
It is essential for adequate mechanical film properties of conventional water based paints that there is good polymer particle coalescence over the range of temperatures encountered in ordinary use. Coalescence is directly related to the hardness or glass transition temperature (Tg) of the polymer particles. Low Tg polymers allow coalescence at lower temperatures than for higher Tg polymers. The hardness of a paint film influences properties such as scuff and abrasion resistance. Maximising film hardness is important especially for paints in kitchens and living areas. Hardness is usually increased by increasing the Tg of the polymer particles. However, enhancing the hardness by increasing the Tg of the polymer in the particle leads to poorer coalescence. In practice the compromise between these properties is overcome by using a volatile temporary organic plasticiser that allows the use of higher Tg polymer particles than otherwise would be able to be used. However, such formulations suffer from the disadvantage of poor early film hardness. This occurs as the volatile plasticiser may take some days before completely volatilising and being removed from the paint film. The use of volatile plasticisers is also not favoured in some applications as it leads to the release into the atmosphere of organic solvents. For trim paints it is desirable that they have film hardness greater than conventional water-borne latex paints intended for broad well application.
Viscosity stability is an important property for commercial paint formulations. Paint products are commercially manufactured within permissible tolerances to predetermined specifications it is important that satisfactory paint characteristics are maintained across the allowable range in the specification. With regard to aqueous latex paints, pH is a manufacturing variable that may be in a range of, for example, 8.5 to 9.5. Viscosity is a paint property that may vary with pH change and for such paints it is important that viscosity at both low and high shear rates is within acceptable limits throughout the pH specification range. Viscosity at low shear rates tends to influence flow and levelling properties. Viscosity at high shear rates affects ease of brushing. A further aspect of viscosity stability is the effect of storage on this property. It is obviously desirable that viscosity does not significantly change with time given the possible long shelf life of commercial products.
The tint strength of a paint is an important property as it indicates whether a paint can be tinted to a particular colour using a standard tinting formula. It is a requirement that paints across a range of product types have similar tint strength so that common tinting formulae may be used across that range. The tint strength is a measure of the amount of coloured tinter that must be added to a white base paint to give a particular colour. If the base paint requires a smaller amount of the tinter it is described as being of low tint strength. Paint with low tint strength may be reformulated with higher levels of titanium dioxide pigment but this can add significantly to formulation costs. Conversely if the tint strength of a base paint is high it would be possible for it to be reformulated with lower levels of titanium dioxide pigment to give the required tint strength at a lower formulation cost. For such a reformulation to be acceptable opacity would be required to be maintained. Accordingly, it is desirable that the tint strength is close to or equal to other produces across the range without having to reformulate the product with high levels of titanium dioxide pigment. In addition, tint strength must be stable over time because of the possible long shelf life of paints.
The binders used for conventional water based paints include a wide range of materials. A recent review article entitled “Polymers for Water-Based Coatings—A Systematic Overview” by J. C. Padget in Journal of Coatings Technology, Vol 66. No. 839, December 1994 at pp 89-101 summarises the various types of materials used. These range from disperse polymers in water such as those used in latex paints to fully water soluble solution polymers. A further class of binders are referred to as water reducible resins which are a hybrid between the water insoluble polymer binders and fully water soluble binders. Such hybrid resin systems usually require significant levels of organic cosolvents to be present and these systems are intended for industrial rather than domestic household applications. An example of such a resin system is disclosed in U.S. Pat. No. 4,230,609 (Burroway et al).
The use of copolymerisable acrylic acid in addition copolymers is summarised in Table 2 of the Padget article and this shows the general effect of increasing the acrylic acid level from 0 to 100%. The viscosity characteristics on neutralisation are set out as the level of acid is increased. At acrylic acid levels of 1% or more the viscosity is described as increasing on neutralisation. At levels of acrylic acid of form 1-2% this viscosity increase is described as being substantially overcome by using a hydrophobic co-monomer such a styrene. This would be as a replacement for a less hydrophobic hard co-monomer such as methyl methacrylate. W
Carey Michelle
Elsbury Karen
George Susan
Houlihan Patrick
Leary Bruce
Bernstein Jason A.
Bernstein & Associates P.C.
Orica Australia Pty Ltd
Wu David W.
Zalukaeva Tanya
LandOfFree
Stain resistant water-borne coating composition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Stain resistant water-borne coating composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stain resistant water-borne coating composition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2899416