Method of preparing carbamate-functional polymers

Details Method of preparing carbamate-functional polymers Method of preparing carbamate-functional polymers

1999-06-28

2001-12-18

Wilson, Donald R. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S360000, C525S370000, C525S374000, C526S100000, C526S135000, C526S192000, C526S221000, C526S320000

Reexamination Certificate

active

06331596

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a method for preparing carbamate-functional polymers, and more particularly to a method of transesterifying a hydroxy-functional polymer with a carbamate compound in the presence of a Bi(III) or Zr(IV) catalyst.
BACKGROUND AND SUMMARY OF THE INVENTION
Polymers and oligomers having carbamate functional groups have been used in a variety of curable coating compositions. Carbamate-functional polymers offer many advantages in these coating compositions, such as resistance to environmental etch and resistance to scratching and marring. One kind of carbamate-functional polymer described in the art is addition-type polymers. One known method for preparing a carbamate-functional polymer is to transesterify a hydroxy-functional acrylic polymer with a carbamate compound. Tin compounds, specifically tin oxides, are typically used for the transesterification or transcarbamation of hydroxy-functional acrylate polymers with carbamate compounds, such as alkyl carbamates. “Transcarbamation” as used in this application is defined as a process where a carbamate group is put on a monomer or polymer at a hydroxyl site.
Tin compounds used as transesterification catalysts, however, are known in the art to cause yellowing and to be deleterious to weathering in humid conditions. Another problem with the use of tin compounds is an undesired increase in the molecular weight of the polymer undergoing transesterification. This is thought to be a result of side reactions that occur as the transesterification reaction continues to run. Additionally, tin catalysts cannot be used for transesterification reactions when there is any acid present in the reaction medium. It would thus be desirable to find other catalysts with improved properties that may be employed for the transesterification or transcarbamation of hydroxy-functional acrylic polymers with carbamate compounds.
The present invention provides a method for preparing carbamate-functional polymers including providing a hydroxy-functional polymer and then reacting a carbamate compound with the hydroxy-functional polymer in the presence of a transcarbamation catalyst. A carbamate-functional polymer is thus formed. The transcarbamation catalyst may be a Bi(III) compound, Zr(IV) compound, or mixtures of these.
The present invention also provides a method for preparing carbamate-functional polymers including polymerizing in a reaction vessel at a temperature below about 150° C. at least one hydroxy-functional monomer in the presence of a transcarbamation catalyst and a carbamate compound having 1 to 4 carbon atoms. An at least partially transcarbamated polymer is formed. The transcarbamation catalyst may be a Bi(III) compound, Zr(IV) compound, or mixtures of these.
The present invention further provides a method for preparing carbamate-functional acrylic polymers including polymerizing in a reaction vessel at a temperature below about 150° C. at least one hydroxy-functional monomer in the presence of a transcarbamation catalyst and a carbamate compound having 1 to 4 carbon atoms. An at least partially transcarbamated polymer is formed. The transcarbamation catalyst may be a Bi(III) compound, Zr(IV) compound, or mixtures of these.
The present invention also provides a carbamate-functional polymer prepared by reacting a hydroxy-functional polymer with a carbamate compound in the presence of a transcarbamation catalyst. The transcarbamation catalyst may be Bi(III) compounds, Zr(IV) compounds or mixtures of these.
DETAILED DESCRIPTION
Hydroxy-containing acrylic monomers useful for preparing hydroxy-functional acrylic polymers of the present invention may be, but are not limited to, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylates, hydroxybutyl methacrylates, and combinations of these. The polymer may be prepared by reacting at least one hydroxy-containing acrylic monomer with one or more other addition-polymerizable monomers. Suitable monomers for copolymerization with acrylic monomers are known in the art. They include, but are not limited to, alkyl esters of acrylic or methacrylic acid, e.g., ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, butyl methacrylate, isodecyl methacrylate, and the like; and vinyl monomers such as styrenic monomers (e.g., styrene, t-butyl styrene), vinyl toluene, and the like. Other examples include methyl acrylate, methyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, isobutyl acrylate, isobutyl methacrylate, pentyl acrylate, pentyl methacrylate, isoamyl acrylate, isoamyl methacrylate, hexyl acrylate, hexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, octyl acrylate, octyl methacrylate, 3,5,5-trimethylhexyl acrylate, 3,5,5-trimethylhexyl methacrylate, decyl acrylate, decyl methacrylate, dodecyl acrylate, dodecyl methacrylate, hexadecyl acrylate, hexadecyl methacrylate, octadecyl acrylate, octadecyl methacrylate, octadecenyl acrylate, octadecenyl methacrylate as well as the esters of maleic, fumaric, crotonic, isocrotonic, vinylacetic and itaconic acids.
Suitable free-radical initiators for the addition polymerization reaction of the present invention include organic peroxides, for example dibenzyl peroxide, dicumyl peroxide, cumene hydroperoxide, di-tert-butyl peroxide, tert butyl hydroperoxide, 2,2-di-tert-butylperoxybutane, tert-amyl perbenzoate, 1,3-bis(tert-butylperoxyisopropyl)benzene, diisopropylbenzene monohydroperoxide and diacyl peroxides, for example diacetyl peroxide, peroxyketals, for example 2,2-di(tert-amylperoxy)propane and ethyl 3,3-di(tert-amylperoxy)butyrate, thermolabile highly substituted ethane derivatives, for example those based on silyl-substituted ethane derivatives, and Azo compounds, for example azo-bis-cyclohexanenitrile and other compounds sold as Vazo® compounds by DuPont.
Carbamate-functional polyester polymers may also be prepared according to the methods of the present invention. The methods of making polyester resins are well-known. For example, the polyester polymer may be prepared from a hydroxyacid, such as citric acid, or from reacting a diacid with a dialcohol.
The carbamate compound employed in the present invention may be any compound having a carbamate group capable of undergoing a transesterification or transcarbamation reaction with a hydroxyl group of a hydroxy-polyacrylate polymer. These may include, for example, methyl carbamate, butyl carbamate, propyl carbamate, ethyl carbamate, 2-ethylhexyl carbamate, cyclohexyl carbamate, phenyl carbamate, hydroxypropyl carbamate, hydroxyethyl carbamate and combinations of these.
The transesterification or transcarbamation catalyst employed in the present invention may be a Bi(III) compound, Zr(IV) compound, or mixtures of these. The transcarbamation reaction occurs between the hydroxy group on the acrylic polymer and the carbamate group. The Bi(III) compound may be, without limitation, bismuth (III) oxide (Bi
2
O
3
) or bismuth (III) tri(2-ethylhexanoate) (Bi(C
7
H
15
COO)
3
). The catalyst employed in the present invention may also be an organo bismuth oxide or the reaction product of a bismuth oxide halide with an alcohol or acid compound. Examples of alcohol compounds may be, but are not limited to, 2-ethylhexanol, neodecanol, and stearyl alcohol, while examples of acid compounds are 2-ethylhexanoic acid, neodecanoic acid, and stearic acid.
The Bi(III) catalyst will catalyze the transesterification reaction even in an acidic environment, such as, for example, with the bismuth (III) tri(2-ethylhexanoate) catalyst, which contains about 30% 2-ethylhexanoic acid. This is in contrast to a tin catalyst, which is poisoned by the presence of any acid group, and therefore cannot catalyze the transesterification reaction.
The zirconium catalyst may be any Zr(IV) compound, including, but not limited to, zirconium alkoxides, zirconium alkanoates, and zirconium dihalide oxides. Examples of these may be zirconium chelate, zirconium dichloride oxide, zirconiu

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