Coating processes – With post-treatment of coating or coating material – Plural film forming coatings wherein one coating contains a...
Reexamination Certificate
1999-07-22
2001-04-10
Cameron, Erma (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Plural film forming coatings wherein one coating contains a...
C427S407200, C427S386000, C427S389700, C427S393600
Reexamination Certificate
active
06214414
ABSTRACT:
BACKGROUND OF THE INVENTION
Ceramic substrates, especially those of glass, are often coated, either locally or completely, with one or more coating compositions. Local application is usually practiced to apply lettering, designs, or other indicia to the ceramic substrates; when used in this manner the coating compositions are generally referred to as “inks” . Application of indicia to glass bottles is a commercially important example.
The coatings applied to bottles must be tough and resistant to marring by abrasion or impact and they should be resistant to degredation by caustic solutions commonly is employed for cleaning bottles.
Many of the bottle coatings now used are “applied ceramic labels” , that is, they are applied as inorganic frits which are then exposed to high temperatures. Applied ceramic labels, however, suffer from one or more disadvantages, such as the presence of heavy metals, low gloss, low color brilliance, the necessity of using high temperatures to melt the frits after application, and often a requirement to subsequently reanneal the labeled bottles.
Organic coatings have been used for bottle coatings, but resistances to abrasion and impact of many of these coatings are typically low, and resistances to degredation by caustic bottle-cleaning solutions have often also been low.
Organic coatings based primarily on epoxy resins, dicyandiamide curing agent, and reactive siloxane, and usually containing various additional components, are known. See, for example, the following United States patents: U.S. Pat. No. 3,468,835, U.S. Pat. No. 3,471,312, U.S. Pat. No. 3,607,349, U.S. Pat. No. 5,346,933, and U.S. Pat. No. 5,411,768.
Unfortunately, due primarily to the presence of the dicyandiamide curing agent, some crosslinking of the coating composition does occur at application temperatures and such crosslinking eventually causes the coating composition to thicken to the point it cannot be applied. Accordingly, a major problem with the prior coatings has been short pot life, where “pot life” is the length of time the coating will remain fluid enough to apply to substrates at application temperatures.
THE INVENTION
It has now been found that heating to elevated temperature a ceramic substrate having thereon a sequence of coatings of pigmented coating compositions wherein the is pigmented coating composition of at least one coating of the sequence is substantially free of amino-functional curing agent, and the pigmented coating composition of at least one other coating of the sequence comprises amino-functional curing agent, serves to crosslink all of the pigmented coating compositions of the coatings of the sequence.
Accordingly, the invention is a method comprising heating to elevated temperature a ceramic substrate having thereon a sequence of coatings of pigmented coating compositions wherein each of said pigmented coating compositions comprises: (a) reactive organic resin which is polyhydroxy-functional, polyepoxy-functional, or both epoxy-functional and hydroxy-functional; (b) reactive wax; (c) color-imparting pigment; and (d) blocked polyisocyanate; wherein: (e) the pigmented coating composition of at least one coating of the sequence is substantially free of amino-functional curing agent; and (f) the pigmented coating composition of at least one other coating of the sequence further comprises amino-functional curing agent; to crosslink all of the pigmented coating compositions of the coatings of the sequence and to adhere the sequence to the ceramic substrate.
Because one or more of the pigmented coating compositions are substantially free of amino-functional curing agent, they exhibit much longer pot lives than those which contain amino-functional curing agent. Frequently the pot lives of the pigmented coating compositions which are substantially free of amino-functional curing agent are longer than many of the coating compositions of the prior art. Although it is not desired to be bound by any theory or mechanism, it is believed that the effect of the amino-functional curing agent during crosslinking is able to diffuse to the coating or coatings which did not originally contain a significant amount of amino-functional curing agent.
For purposes of the present invention, inks are considered to be coating compositions.
The reactive organic resin which is polyhydroxy-functional and which is used in the invention, may be widely varied. A class of polyhydroxy-functional reactive organic resin which is frequently employed comprises the polyhydroxy-functional polyester resins. As used herein and in the claims, the term “polyhydroxy-functional” means that on a number average molecular weight basis, the polyester contains on average, more than one hydroxyl group per molecule. Preferably the polyester contains, on average, at least two hydroxyl groups per molecule.
The polyhydroxy-functional polyester resins which can be used in the present invention are numerous and widely varied. Such polyhydroxy-functional polyesters are preferably polyhydroxy-functional substantially saturated polyester resins, as that term is customarily understood in the industry. As used herein and in the claims, the term “saturated polyester” is intended to include polyesters containing aromatic unsaturation since aromatic unsaturation is generally unreactive in polyesters. Nevertheless, some ethylenic unsaturation may be present when circumstances warrant. Ethylenic unsaturation, when present, is often introduced by employing a small amount of ethylenically unsaturated acid such as maleic acid or fumaric acid, during preparation of the polyester. Usually less than 10 mole percent of the acids used to prepare the hydroxy-functional polyesters employed in the present invention are ethylenically unsaturated acids. Often less than 5 mole percent of the acids used to prepare the hydroxy-functional polyesters are ethylenically unsaturated acids. Preferably the ethylenically unsaturated acids are substantially absent.
The polyhydroxy-functional polyesters may be produced from one or more polyols and one or more polycarboxylic acids using well-known polycondensation procedures employing an excess of polyol to obtain a polymer having the desired proportion of hydroxyl groups. Examples of such procedures include, but are not limited to, direct esterification of polycarboxylic acid (or its anhydride if such anhydride exists) with polyol, transesteresterification, and reaction between polycarboxylic acid halide and the polyol. Notwithstanding the method of preparation used, it is convenient to classify polyhydroxy-functional polyesters according to the polyols and polycarboxylic acids which were used in direct esterification, or which would be used in a theoretical direct esterification.
The polyols which can be used are numerous and widely varied. They are often aliphatic, alicyclic, aromatic, aliphatic-alicyclic, aliphatic-aromatic, alicyclic-aromatic, or aliphatic-alicyclic-aromatic in nature. Usually the polyols contain from 2 to 20 carbon atoms. Frequently the polyols contain from 2 to 12 carbon atoms. The polyols are usually predominately diols. In most instances diols constitute at least 90 mole percent of the polyols. Often diols constitute at least 95 mole percent of the polyols. At least 98 mole percent is preferred. Frequently diols constitute all of the polyols.
Examples of suitable diols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, 1,3-propanediol, dipropylene glycol, trimethylene glycol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2,2-dimethylpropane-1,3-diol, 2-ethyl-2-butylpropane-1,3-diol, 2-ethyl-2-isobutylpropane-1,3-diol, 1,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 1,6-hexanediol, thiodiethanol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol-1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethylcyclobutane-1,3-diol, 1,4-xylylenediol, 3-hydroxy-2,2-dimethylpropyl 3-hydroxy-2,2-dimethylpropanoate, 4,4′1-(1-methylethylidene)bis[cyclohexanol],and 4,4&prim
Montague Robert A.
Morris George D.
Nehmsmann Louis J.
Tang Robert H.
Wang Alan E.
Cameron Erma
Morris George D.
PPG Industries Ohio Inc.
LandOfFree
Method for forming a sequence of crosslinked pigmented... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for forming a sequence of crosslinked pigmented..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for forming a sequence of crosslinked pigmented... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2440219