Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-07-16
2002-02-05
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S201000
Reexamination Certificate
active
06344502
ABSTRACT:
BACKGROUND OF THE INVENTION
The automotive industry has been trying for years to develop lower volatile organic content (VOC) coatings without sacrificing performance in areas such as durability, gloss retention, solvent and humidity resistance and the like.
The present invention produces a low VOC coating composition which is particularly well-suited for use as an automotive enamel coating or as a coating for industrial applications. This invention relates to lower VOC, non-aqueous dispersions (NAD's) comprising an acrylic polymer stabilized in an alkyd steric stabilizer. The NAD's of this invention are particularly useful in automotive applications as one and two component primers, sealers and topcoat enamels and in industrial applications as coatings for equipment, parts and the like.
For purposes of this invention, NAD's are polymeric particles having a core-shell type morphology dispersed in a non-polar solvent such as a hydrocarbon. The “core” is comprised of a polar copolymer produced by a free-radical addition reaction and the “shell” comprises an alkyd resin or an acrylic/alkyd copolymer. A large portion of the shell resin is soluble in the hydrocarbon solvent and thus forms the continuous phase. However, a small portion of the shell resin is adsorbed onto the surface of the core polymer particles and acts as a steric stabilizer for those dispersed particles.
SUMMARY OF THE INVENTION
The present invention relates to a non-aqueous dispersion which is especially suited for use as an automotive enamel coating. The non-aqueous dispersion of this invention comprises polymeric particles having a core-shell type morphology dispersed in a non-polar solvent such as a hydrocarbon. The “core” is comprised of a polar copolymer produced by a free-radical addition reaction and the “shell” comprises an alkyd resin or an acrylic/alkyd copolymer. A large portion of the shell resin is soluble in the hydrocarbon solvent and thus forms the continuous phase. However, a small portion of the shell resin is adsorbed onto the surface of the core polymer particles and acts as a steric stabilizer for those particles.
The polymer portion of the NAD produced by the free-radical addition reaction can be comprised of either hard monomers like methyl methacrylate or soft monomers like ethyl acrylate. However, it is essential that two type of monomers, (i) a polar monomer such as hydroxyethyl acrylate, and (ii) an amine-functional monomer, are included. The alkyd is preferably a long oil alkyd having some hydroxy-functionality. The total solids content of the NAD is preferably greater than about 70% by weight.
A preferred non-aqueous dispersion comprises a ratio of about 90:10 to about 10:90 core resin:alkyd resin, more preferably a ratio of about 60:40 core resin:alkyd resin in non-polar hydrocarbon solvent. Preferably from between about 2% to about 10% by weight of the resin produced by the free-radical addition reaction is comprised of an amine-functional acrylic monomer selected from the group consisting of dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylamide, diethylaminoethyl methacrylamide, n-t-butylaminoethyl acrylate, n-t-butylaminoethyl methacrylate, monomers resulting from the reaction of dialkyl amines with glycidyl methacrylate, and mixtures thereof. Also, preferably, from between about 5% to about 40% by weight, more preferably from between about 10% to about 30% by weight of the resin produced by the free-radical addition reaction is comprised of a polar monomer selected from the group consisting of acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, 4hydroxy butyl acrylate, 4-hydroxy butyl methacrylate, polyethyleneoxide hydroxyethyl acrylate, adducts of hydroxyethyl acrylate and caprolactone, mixtures thereof, and the like. The glass transition temperature (Tg) of the acrylic resin should be between about −22 degrees C. and about 105 degrees C., preferably between about 10 degrees C. and about 70 degrees C. Chain transfer agents and free-radical initiators common to the acrylic polymerization industry can be useful and will be described in more detail below.
The alkyd portion of the NAD is preferably relatively high in hydroxy value, generally having a hydroxy number between about 10 and about 150, preferably between about 30 and about 50. The alkyd is also preferably relatively low in molecular weight, preferably having an Mn of between about 2000 and about 4000, with a polydispersity generally less than 10, preferably between about 3 and about 10. The acid value of the alkyd should be in the range of about 5 to about 20, oil length should be greater than about 30% but generally less than about 70% and viscosity of the alkyd measured at 25 degrees C., 70% solids by weight in 50-flash naphtha should be less than about 50 poise, preferably less than about 10 poise.
As one-component coatings, the NAD's of this invention can be cured autooxidatively with the assistance of typical transition metal driers such as those based on cobalt and manganese. As two-component coatings, the NAD's of this invention, in addition to autooxidative cure, can be crosslinked with isocyanate-functional materials by reacting the hydroxy groups of the alkyd with the NCO groups of the isocyanate and the surface hydroxy groups of the acrylic core.
Accordingly, it is an object of this invention to teach lower VOC non-aqueous dispersions having particular suitability for use as automotive and industrial coatings.
It is a further object of this invention to teach one and two component coating compositions containing the non-aqueous dispersions of this invention.
These and other objects and benefits will become more apparent from the detailed description and examples which follow below.
DETAILED DESCRIPTION OF THE INVENTION
General Considerations
As stated above, the present invention relates to a non-aqueous dispersion which is especially suited for use as an automotive enamel coating. The non-aqueous dispersion of this invention comprises polymeric particles having a core-shell type morphology dispersed in a non-polar solvent such as a hydrocarbon. The “core” is comprised of a polar copolymer produced by a free-radical addition reaction and the “shell” comprises an alkyd resin or an acrylic/alkyd copolymer. A large portion of the shell resin is soluble in the hydrocarbon solvent and thus forms the continuous phase. However, a small portion of the shell resin is adsorbed onto the surface of the core polymer particles and acts as a steric stabilizer for those particles.
The portion of the NAD produced by the free-radical addition reaction can be comprised of either hard monomers like methyl methacrylate or soft monomers like ethyl acrylate. However, it is essential that two monomers, (i) a polar monomer such as hydroxyethyl acrylate, and (ii) an amine-functional monomer, are included. The alkyd is preferably a long oil alkyd having some hydroxy-functionality. The total solids content of the NAD is preferably greater tan about 70% by weight.
A preferred non-aqueous dispersion comprises a ratio of about 90:10 to about 10:90 core resin:alkyd resin, more preferably a ratio of about 60:40 core resin:alkyd resin in non-polar hydrocarbon solvent. Preferably from between about 2% to about 10% by weight of the core resin is comprised of an amine-functional monomer, preferably a tertiary amine or a hindered secondary amine, selected from the group consisting of dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylamide, dimethylaminoethyl metacrylamide, n-t-butylaminoethyl acrylate, n-t-butyldimethyl methacrylate, monomers resulting from the reaction of dialkyl amines with glycidyl methacrylate, and mixtures thereof. Also, preferably, from between about 5% to about 40%, more preferably from between about 10% to about 30% by weight of the core resin is comprised of a polar monomer selected from the group consistin
Babjak John R.
Capino Liza A.
Kraan John D.
Shalati Mohamad D.
Smith Susan L.
Katterle Paul R.
McDonald Robert E.
Michl Paul R.
The Sherwin-Williams Company
Tsang Vivien Y.
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