Stock material or miscellaneous articles – Composite – Of polyester
Reexamination Certificate
2000-01-14
2001-08-21
Short, Patricia A. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of polyester
C525S440030, C525S443000, C525S519000, C528S297000, C528S366000, C560S199000, C560S200000
Reexamination Certificate
active
06277497
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to polyester oligomers and polyester polyol-based coating compositions cured with a conventional crosslinker.
Due to legislation in Europe and the United States, coatings industries are under pressure to reduce volatile organic compounds (VOC) in coatings formulations. Therefore, coating compositions are needed which have good physical properties and appearance, but which are inherently low in viscosity and require minimal dilution with solvents. The use of branched hydroxy-functional polyester derivatives prepared by ring-opening with narrow molecular weight distribution and accordingly low viscosity, in coatings, has been described in British Patent 1,528,802. However, application of these polyester oligomers in, say, automotive coatings require the presence of high Tg acrylic polyols to get enough physical drying of the coating film. The present invention allows low-viscosity, low-VOC coatings based on narrow molecular weight distributed polyester polyols containing tertiary acid ester groups, the coatings having sufficiently high Tg for good drying characteristics, physical properties and appearance.
SUMMARY OF THE INVENTION
This invention concerns a low VOC, preferably below about 450 grams per liter, thermoset coating composition comprising a binder which is a branched hydroxy-functional polyester polyol, and a curing agent. The polyester polyol contains this tertiary acid ester group:
wherein R
1
, R
2
and R
3
are independently selected from CH
3
and CH
2
OH; the polyol oligomer having a weight average molecular weight of 400 to 4000 and a hydroxyl number of 100 to 400 (mg KOH/g solid).
Suitably, the curing agent comprises an alkylated melamine formaldehyde compound and/or a blocked (poly)isocyanate compound in a one-package system, or polyisocyanate compound in a two-package system, or other crosslinking agents such as silanes, urea formaldehyde adducts and the like, which react with the functional groups present in the polyester polyol.
The invention is directed to a coating composition comprising:
(a) about 40 to 90 percent by w eight of the composition, of
(i) a hydroxy-functional polyester oligomer having a weight average molecular weight of about 400 to 4000 and a hydroxyl number of 100 to 400, containing at least 20%, by weight of the binder, of a tertiary acid ester end group
(ii) a crosslinking agent; the ratio of (i) to (ii) being about 2:5 to 49:1; and
(b) about 10 to 60 percent by weight of the composition of at least one member selected from the group of solvents, pigments, extenders and additives.
In general, the total of polymeric and oligomeric components of a coating composition are referred to as the “binder” or “binder solids”, and are dissolved, emulsified or otherwise dispersed into a liquid carrier. The binder solids generally include all normally solid polymeric compounds of the composition. Catalysts, pigments and chemical additives such as stabilizers are not considered part of the binder solids. The coating composition of the present invention suitably contains about 30% to 90%, more typically 50% to 85%, by weight of the binder, and about 10% to 70%, more typically 15% to 50% by weight of the composition of an organic solvent carrier, pigments, extenders and other additives.
The process for preparing the binder (a) comprises reacting A (i) and A (ii) or B (i) and B (ii) or combining a mixture thereof as follows:
(A) (i) 10% to 80%, preferably 10% to 65%, more preferably 30% to 60%, by weight of the binder of a polycarboxylic acid or a mixture of polycarboxylic acids, having a weight average molecular weight of 100 to 1500, and an acid value of 100 to 800 (mg KOH/g solid), preferably 250 to 700, and
(ii) 90% to 20%, preferably 90% to 35%, more preferably 70% to 40%, by weight of the binder, of a tertiary acid glycidyl ester, preferably pivalic acid glycidyl ester; and/or
(B) (i) 20% to 80%, preferably 50% to 80%, by weight of the binder of a poly-glycidyl ester derivative reaction product of polycarboxylic acid as described above with epichlorohydrin, having a weight average molecular weight of about 200 to 2000 and an epoxy equivalent weight of 100 to 400, preferably from 140 to 300; and
(ii) 80% to 20% preferably 50% to 20%, based on weight of the binder of a tertiary acid derivative, preferably pivalic acid, dimethylolpropionic acid, hydroxy pivalic acid or a blend of those.
The present composition is useful for finishing the exterior of automobiles and trucks and parts thereof Depending on the presence of pigments and other conventional compounds, the described composition can be used as a colored topcoat and or clearcoat. The invention also includes a process for coating a substrate with the above coating composition. The invention further includes a substrate having adhered thereto a coating composition of the invention.
DETAILED DESCRIPTION
In the synthesis of the polycarboxylic acids, typical mono and polyacids and/or anhydrides are reacted with polyols. Examples of suitable polyacids are: 1,4-cyclohexanedicarboxylic acid (CHDA) hexahydrophtalic acid, methyl-hexahydrophthalic acid, methyl-hexahydrophthalic acid, phthalic acid, isophthalic acid, trimellitic acid, adipic acid, azelaic acid, dodecanedioc acid, and the like, and mixtures thereof Moreover, polycarboxylic acid compounds can be obtained as the reaction product of a polyhydric alcohol and an acid anhydride. Examples of those polyhydric alcohols are: trimethylolpropane (TMP), ditrimethylolpropane, monopentaerythritol (MPE), di-pentaerythritol, ethylene glycol, diethylene glycol, glycerol, trimethyl pentanediol, cyclohexane diol, cyclohexane dimethanol, 1,6,-hexane diol, neopentyglycol, 2,2-butylethylpropane diol, and the like, and mixtures thereof. Examples of suitable acid anhydrides are: hexahydropthtalic anhydride (HHPA), methyl hexahydrophtalic anhydride (MHHPA), phthalic anhydride, trimellitic anhydride, and the like, and mixtures thereof.
A preferred way of preparing a polyacid is the ring-opening polycondensation of a polyol with an anhydride and or acid anhydride. The ring-opening polycondensation of the polyol and the acid anhydride is carried out by techniques known to those skilled in the art. Generally, the reaction can be conducted by combining the polyol and the anhydride, and heating to a temperature of 100° to 170° C., and hold the reaction mixture at that temperature until the theoretical acid number is reached. Preferred compositions are the adducts of TMP and/or MPE with HHPA and/or MHHPA. To obtain the polyester polyol described in the present invention, the described polycarboxylic acid compounds can be reacted with a tertiary acid glycidyl ester, preferably pivalic acid glycidyl ester. The reaction is carried out by combining the reactants and heating at 100° to 170° C., and holding the reaction mixture at that temperature until full conversion of acid and epoxy groups, determined by acid number of epoxy groups using standard titration methods. The hydroxy-functional polyester oligomer can also be obtained using a second synthesis procedure in which a poly-glycidyl ester compound is reacted with a tertiary acid derivative. The epoxy-ester containing compound can be obtained by epoxidation of the above-mentioned polycarboxylic acid derivatives. Examples of epoxy-ester derivatives are hexahydrophthalic acid di-glycidyl ester, trimellitic acid tri-glycidyl ester, polyglycidyl ester of the adducts of TMP and/or MPE with HHPA and/or MHHPA, or mixtures thereof.
In an alternative reaction procedure, the epoxy-ester containing compounds can be reacted with tertiary acid components to yield the described hydroxy-functional polyester derivatives. Examples of the tertiary acid components are pivalic acid, dimethylol propionic acid, hydroxy-pivalic acid.
A catalyst can be used to accelerate ring-opening esterification reactions. Usually employed are: organotin catalysts such as dibutyltindilaurate, dibutyltinoxide, tinoctoate, and the like; tri-substituted amines such as triethylamine, dimethyl benzylamine, dimet
Aerts Armand
DeMarre Anne
Huybrechts Jozef
Palmer G. Todd
Costello James A.
Deshmukh Sudhir G.
E. I. Du Pont de Nemours and Company
Short Patricia A.
LandOfFree
Hydroxy-functional oligomers for high solids coatings does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydroxy-functional oligomers for high solids coatings, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydroxy-functional oligomers for high solids coatings will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2499905