Stock material or miscellaneous articles – Composite – Of polycarbonate
Reexamination Certificate
1999-03-18
2001-01-30
Hoke, Veronica P. (Department: 1714)
Stock material or miscellaneous articles
Composite
Of polycarbonate
Reexamination Certificate
active
06180240
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to acrylic ultraviolet light absorber and hindered amine light stabilizer compounds, method therefore and coating compositions containing the same, wherein the compounds include a carbamate functionality.
2. Discussion of the Prior Art
Curable coating compositions such as thermoset coatings are widely used in the coatings art. They are often used for topcoats in the automotive and industrial coatings industry. Color-plus-clear composite coatings are particularly useful as topcoats where exceptional gloss, depth of color, distinctness of image, or special metallic effects are desired. The automotive industry has made extensive use of these coatings for automotive body panels. Color-plus-clear composite coatings, however, require an extremely high degree of clarity in the clearcoat to achieve the desired visual effect. High-gloss coatings also require a low degree of visual aberrations at the surface of the coating in order to achieve the desired visual effect such as high distinctness of image (DOI).
In the field of automotive coatings, it has become an objective to obtain a clearcoat (i.e., the outermost automotive coating) that is resistant to being etched by environmental fallout. Environmental etching is manifested by pitting, water spotting or chemical spotting of the coating or any combination of these. Environmental etch resistance is desirable because it improves the appearance and useful life of the coating.
Environmental etch resistance can be measured by visual examination of the coating, or by a profilometer or by subjecting a coating on a test panel to a saline solution in a temperature gradient oven test. Environmental etch resistance is generally measured by visual examination by individuals skilled at examining finishes for the degree of environmental etch therein. Environmental etch resistance has become more important as the amount of acid rain, and other industrial fallout has increased. Currently, environmental etching of automotive finishes is generally greatest in the areas most greatly affected by industrial fallout.
The incorporation of the HALS or UVAs as free additions or as polymer or oligomer bound UVA or HALS into a coating composition generally improves resistance of the coating composition to degradation caused by ultraviolet light exposure. Binding the HALS or UVA to an oligomer or polymer stabilizes the HALS or UVA in a coating composition, prevents migration of the UVA or HALS into other coating layers and retains the UVA or HALS in the clearcoat, where it is needed.
A coating composition containing a carbamate functional resin has shown to be effective against environmental etch even without the addition of HALS and UVAs. The addition of free HALS and UvAs, (i.e. not polymer- or oligomer-bound), has effected little or no improvement in environmental etch resistance in the coatings containing carbamate functional resins. Unexpectedly, it has been shown that addition of the polymer- or oligomer-bound HALS or UVA to a carbamate containing coating provides improved environmental etch resistance of the cured film.
SUMMARY OF THE INVENTION
According to the present invention, durability enhancing agents comprising oligomer-bound and polymer-bound ultraviolet light absorber (UVA) or hindered amine light stabilizer (HALS) compounds comprise a UVA and/or HALS bonded to an oligomeric or polymeric component, and the agents include more than one carbamate functional group, or group convertible to a carbamate functional group. The oligomer or polymer may comprise more than one UVA or HALS bound thereto, or a mixture of UVA(s) and HALS bound thereto. The oligomer-bound or polymer-bound UVA or HALS may also include additional reactive functionality that is crosslinkable into a cured coating film.
The oligomer- or polymer-bound HALS or UVA may comprise the principal resin or a separate component of the coating composition. The invention is also directed to the cured coating composition, and a method for incorporating ultraviolet light absorbing compounds and hindered amine light stabilizers into a cured coating composition comprising reacting the ultraviolet light absorbing and/or hindered amine light stabilizing compound into a crosslinked matrix which is formed upon curing the coating composition.
Generally, the incorporation of the polymer- or oligomer- bound UVA or HALS into a coating composition stabilizes the HALS or UVA in a coating composition, prevents migration of the UVA or HALS into other coating layers and retains the UVA or HALS in the where it is needed. The polymer- or oligomer-bound HALS or UVA according to the present invention, including carbamate functionality, provides the unexpected result of improved environmental etch resistance of the cured film.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a durability enhancing agent which is an acrylic oligomer-bound or acrylic polymer-bound ultraviolet light absorber or hindered amine light stabilizer, comprising a UVA or HALS, or mixture of UVA and HALS, bonded to an acrylic oligomer or polymer, wherein the agent includes more than one carbamate functional group, or group convertible to a carbamate functional group and may include other reactive functionality that is crosslinkable into a coating film. The oligomer- or polymer-bound HALS or UVA may comprise the principal resin or a separate component of a coating composition.
The ultraviolet light absorber or hindered amine light stabilizer compounds are reacted onto the oligomer or polymer by addition or grafting reactions. The UVA or HALS may be copolymerized with monomers used to form the oligomer or polymer.
Examples of ultraviolet light absorbers useful in the present invention include benzotriazoles, 2-hydroxybenzophenones, oxanilide, and 2-hydroxyphenyltriazines. In a preferred embodiment, the ultraviolet absorber is a polymer-bound benzotriazole.
One example of benzotriazole useful in the present invention is shown in formula (Ia):
wherein, in the compounds of the formula (Ia), R
1
, R
2
and R
3
can be hydrogen, but at least one of the radicals R
1
and R
2
must be other than hydrogen. Additionally, R
1
, R
2
and R
3
can be halogen, hydroxyl halogen methyl, alkyl having 1 to 18 carbons, phenyl alkyl having 1 to 4 carbons in the alkyl moiety, hydroxy alkyl having 1 to 24 carbon atoms in the alkyl chain, such as methyl, ethyl, propyl, butyl, hexyl, octyl, nonyl, dodecyl, tetradecyl, hexadecyl, octadecyl, nonadecyl and eicosyl and also corresponding branched isomers, alkyl substituted by —COOH, —COOY
8
, —CONH
2
, —CONHY
9
, —CONY
9
Y
10
, —NH
2
, —NHY
9
, —NY
9
Y
10
, —NHCOY
11
, —CN, and/or —OCOY
11
, which has 4 to 20 carbon atoms, is interrupted by one or more oxygen atoms and is unsubstituted or substituted by hydroxyl or alkoxy having 1 to 12 carbon atoms, alkenyl having 3 to 6 carbon atoms, glycidyl, cyclohexyl which is unsubstituted or substituted by hydroxyl, alkyl having 1 to 4 carbon atoms and/or —OCOY
11
, phenylalkyl which has 1 to 5 carbon atoms in the alkyl moiety and is unsubstituted or substituted by hydroxyl, chlorine and/or methyl, —COY
12
or —SO
2
Y
13
, or, if u is 2, Y
2
is alkylene having 2 to 16 carbon atoms, alkylene having 4 to 12 carbon atoms, xylene, alkylene which has 3 to 20 carbon atoms, is interrupted by one or more —O— atoms and/or substituted by hydroxyl, —CH
2
CH(OH)CH
2
—O—Y
15
, —OCH
2
CH(OH)CH
2
,—CO—Y
16
—CO—, —CO—NH—Y
17
—NH—CO—, or —(CH
2
)
m
—CO
2
—Y
18
—OCO—(CH
2
)
m
, in which m is 1,2 or 3, Y
8
is amine, alkylamine or cycloalkylamine wherein the alkyl or cyclosalkyl group is between 1 and 6 carbon atoms and may be substituted or unsubstituted, alkyl having 1 to 18 carbon atoms, alkenyl having 3 to 18 carbon atoms, alkyl which has 3 to 20 carbon atoms, is interrupted by one or more oxygen or sulfur atoms or -NT
6
— and/or is substituted by hydroxyl, alkyl which has 1 to 4 carbon atoms and is substituted by —P(O) (OY
14
)
2
, —NY
9
Y
10
or —OCOY
11
and/or hydroxyl, alkenyl having 3 to 18 c
Boisseau John E.
Oberg Patricia K.
Rehfuss John W.
St. Aubin Donald L.
BASF Corporation
Hoke Veronica P.
Sabourin Anne Gerry
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