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
1999-12-23
2002-04-02
Gorr, Rachel (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...
C528S027000, C528S032000, C525S101000, C525S124000, C428S423100, C427S407100
Reexamination Certificate
active
06365699
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to curable compositions and composite coatings on substrates containing tricarbamoyl triazines and process for applying the composition for mar and abrasion resistance.
Of increasing concern in many geographic areas is the encounter with acidic precipitation. Coatings, particularly automotive original equipment coatings, that are resistant to such environmental conditions like those that are resistant to etching by atmospheric acid precipitation (“acid etch resistance”) are becoming increasingly desirable. Original equipment manufacturers are requiring that coating systems demonstrate acid etch resistance.
In addition to the requirement of acid etch resistance, original equipment coatings must also demonstrate mar and abrasion resistance; i.e., the appearance of the coating must not be detrimentally affected when the coating is contacted with an abrasive material. Mar and abrasion resistance is a desirable property particularly due to the popularity of commercial car washes where brushes are often used to wash car bodies.
A number of commercial coating systems which demonstrate acid etch resistance do not provide adequate mar and abrasion resistance. Microparticulate materials such as silica, metal sulfides, and crosslinked styrene-butadiene have been added to these coating systems to improve mar resistance, but gloss and distinctness of image of the systems are adversely affected due to light scattering at the particle surfaces.
Recently, curing agents for coatings with active hydrogen-containing materials have been developed that are triisocyanato or tricarbamoyl triazines as shown in U.S. Pat. Nos. 4,930,213 and 5,084,541. The U.S. Pat. No. 4,939,213 ('213) patent shows the use of these curing agents in a coating composition to improve environmental resistance for powder coatings, coil coatings and can coatings. As noted on page 1 of the '213 patent, when the active hydrogen-containing compounds are hydroxylated polymers, environmentally-resistant coatings are provided.
It would be desirable to provide a curable composition for use as a coating which avoids the marring problems of the prior art coating systems while maintaining excellent acid etch resistance and appearance properties.
SUMMARY OF THE INVENTION
In accordance with the present invention, a curable composition, which is capable of exhibiting improved mar and acid etch resistance, is provided which comprises (a) about 30 to 90 percent by weight, based on total weight of resin solids, of a film-forming composition comprising:
(i) an acrylosilane polymer, an acrylic polyol polymer, and optionally an alkylated melamine-formaldehyde crosslinking agent; and (b) about 10 to 70 percent by weight, based on total weight of resin solids, of a tricarbamoyl triazine compound of the formula: C
3
N
3
(NHCOXR)
3
, wherein X is nitrogen, oxygen, sulfur, phosphorus, or carbon, and R is a lower alkyl group having 1 to 12 carbon atoms, or mixtures of lower alkyl groups.
The process of the present invention and the composite coating involve applying a first coating as a primer surfacer coating layer to a substrate, curing the primer surfacer layer, and applying a second or an additional coating layer which is the aforedescribed tricarbamoyl triazine compound containing curable coating composition, and curing this coating.
The invention also provides a process for applying a color-plus-clear composite coating to a substrate comprising applying to the substrate a pigmented or colored first curable coating composition to form a base coat and applying to the base coat a second curable coating composition which is transparent to form a clear coat over the base coat. The clear coat can be the curable composition of the present invention.
DETAILED DESCRIPTION
In the following description, reference to number average and weight average molecular weights refers to measurements determined by gel permeation chromatography using a polystyrene standard as is well known to those skilled in the art. Where ranges of amounts are stated in percentages for components that are combined to yield a composition, the amount of each of those various components yielding the composition are generally selected from each range for that component so that the total amount of the components in the composition equals around 100 percent.
In the curable composition of the present invention, the aforedescribed film-forming compositions each is capable of film formation with crosslinking. Crosslinking can be through the one or more designated polymeric materials with the crosslinking material. For the film-forming compositions with the additional polymeric material or with two polymeric materials that are reactive with each other, the additional polymeric material and/or the inter-reactivity of both polymers results in crosslinking. The polyepoxide and a polyacid film-forming composition has the polyacid that is used as the crosslinking agent since the polyepoxide is the major component of the film. For the film-forming composition of the acrylosilane polymer and the acrylic polyol polymer, these polymeric materials have functionality so that one reacts to form crosslinks with the other along with any alkylated melamine-formaldehyde crosslinking agent. This occurs in a similar manner in the film-forming composition of polyisocyanate and a polymer having at least one group that is reactive with isocyanate. It is believed without limiting the present invention that the tricarbamoyl triazine compound is a crosslinking agent that also provides crosslinking in addition or further to that of the aforementioned film-forming compositions.
The film-forming composition in the curable composition of the present invention preferably comprises a mixture of a polyepoxide and a polyacid crosslinking agent. Preferably, the polyepoxide is present in the film-forming composition (i) in amounts of about 10 to 90, more preferably from about 25 to 50 percent by weight based on total weight of resin solids in the film-forming composition (i). Preferably, the polyepoxides have a glass transition temperature (Tg) less than 50° C., more preferably less than 30° C. The Tg is described in
PRINCIPLES OF POLYMER CHEMISTRY
, Flory, Cornell University Press, Ithaca, N.Y., 1953, pages 52-57. The Tg can be calculated as described by Fox in
Bull. Amer. Physic. Society
, 1,3, page 123 (1956). The Tg can be measured experimentally by using a penetrometer such as a DuPont 940 Thermomedian Analyzer. The Tg of the polymers as used herein refers to the calculated values unless otherwise indicated.
Among the polyepoxides which can be used are epoxy-containing acrylic polymers which are preferred, epoxy condensation polymers such as polyglycidyl ethers of alcohols and certain polyepoxide monomers and oligomers. Epoxy-containing acrylic polymers are preferred because they yield products which have the optimum combination of coating properties; i.e., smoothness, gloss, durability, and solvent resistance. The epoxy-containing acrylic polymer is a copolymer of an ethylenically unsaturated monomer having at least one epoxy group and at least one polymerizable ethylenically unsaturated monomer which is free of epoxy groups. The preparation of the epoxy-containing acrylic polymer may be conducted as disclosed in U.S. Pat. No. 4,650,718, incorporated herein by reference. The epoxy-containing acrylic polymer typically has a number average molecular weight between about 1000 and 20,000, preferably about 1000 to 10,000, and more preferably about 1000 to 5000.
The ethylenically unsaturated monomers useful in preparing the epoxy-containing acrylic polymer can be selected from numerous art-recognized monomers such as the below-described nonexclusive examples. Examples of ethylenically unsaturated monomers containing epoxy groups are those containing 1,2-epoxy groups and include glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether. Examples of ethylenically unsaturated monomers which do not contain epoxy groups are vinyl monomers and alkyl e
Mauer George W.
Meier James A.
Stahl Lynne R.
Gorr Rachel
PPG Industries Ohio Inc.
Uhl William J.
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