Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2002-06-27
2003-11-11
Wilson, D. R. (Department: 1713)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C427S386000, C427S387000, C427S487000, C427S496000, C427S508000, C427S517000, C525S274000, C525S286000, C525S292000, C525S301000, C525S303000, C525S309000, C525S310000, C525S326500, C525S327700, C525S328800, C525S328900, C525S329400, C525S329500, C525S330100, C525S330200, C525S330600, C525S330700, C525S333100, C525S333200, C525S333300, C525S333500
Reexamination Certificate
active
06645562
ABSTRACT:
The present invention relates to a process for preparing a curable coating and for curing thereof.
Oligomers, polymers with low Dp (degree of polymerization), of acrylate or methacrylate unit-containing backbones are of commercial interest and have industrial uses for many different applications, such as adhesives, inks, coatings, films, and others. A suitable low Dp value will provide a material with a molecular weight high enough for reduced toxicity, yet low enough for low viscosity. However, production of such oligomers has proven to be difficult and is frequently carried out by cumbersome and/or not very selective processes. It becomes even more difficult if a crosslinkable or curable oligomer composition is desired for the applications. This is because crosslinking or curing property typically requires the presence of additional reactive pendant groups in the oligomers. Such reactive pendant groups may be partially or substantially eliminated or reacted away by unintended side reactions or premature crosslinking reactions during the oligomerization reaction.
Several approaches have been tried and used to effect production of such oligomers. For example, one approach uses chain transfer agents to control Dp. As a result of the chain transfer chemistry involved, one chain transfer agent is incorporated into each backbone structure of the oligomers. This makes the oligomer property much less uniform and harder to control. In addition, the most commonly used chain transfer agents are mercaptans. Due to their odors and chemical properties, it becomes increasingly more difficult socially and less acceptable environmentally to use such sulfur-based materials. Other common chain transfer agents such as hypophosphites, bisulfites and alcohols would also impart additional functionalities into the oligomers. Such additional functionalities may not be compatible with other ingredients in a formulated product or suitable for the intended applications. Removal of the additional functionality from the resultant oligomers may be difficult and/or expensive.
Another approach calls for the use of large amounts of initiators or catalysts. This approach adds raw material cost to oligomer production. It also may result in undesirable oligomer chain degradations, branching, and unintended or premature crosslinking of the product prior to use. In addition, any residual initiators or catalysts in the product may have to be removed before the product can be used for many applications to avoid compatibility or contamination problems.
U.S. Pat. No. 4,356,288, discloses the preparation of terminally-unsaturated oligomers with a Dp in the range of from about 6 to about 30 from esters of acrylic acid by an anionic polymerization reaction carried out in the presence of a catalytic amount of an alkoxide anion. Alkoxide anions are known to be sensitive to water. Accordingly, the method is often adversely affected by the presence of moisture, resulting in lower yield and/or lower uniformity of the oligomer product.
Another patent, U.S. Pat. No. 5,710,227, discloses a high temperature, continuous polymerization process for preparing terminally unsaturated oligomers which are formed from acrylic acid and its salts, and acrylic acid and its salts with other ethylenically unsaturated monomers. The high temperature, continuous polymerization process solves many of the problems associated with previously known methods for preparing terminally-unsaturated oligomers formed from acrylic acid. However, the neat form of many of the acrylic acid products are solid at room temperature and, thus, requiring either heating and/or the addition of a solvent to handle and use the products.
U.S. Pat. No. 5,484,850 discloses copolymer compositions which are crosslinkable by a free radical method and have a Mn from 1500 to 6000 and a polydispersity of 1 to 4. Copolymer A is composed of from 50 to 85 mol % of a monomer (al) containing methacryloyl group; from 15 mol % to 50 mol % of another monomer (a
2
) capable of undergoing free-radical polymerization; and from 5 mol % to 50 mol % of the total amount of the monomers (a
1
) and (a
2
) being monomers (a
3
) which carry functional groups selected from the group consisting of hydroxy, carboxyamido, amino, carbonyl, isocyanate, carboxyl and epoxy, the functional groups being capable of undergoing a condensation or addition reaction. The polymerization is carried out at a temperature from 140 to 210° C. and with an average residence time of from 2 minutes to 90 minutes. Copolymer A reacts with an olefinically unsaturated monomer B which carries a functional group which is complementary to the functional groups of monomers (a
3
). The products are solids which tend to limit their uses and processing options.
The present invention seeks to overcome the problems associated with the previously disclosed methods for preparing oligomers, particularly curable or crosslinkable liquid oligomers, by providing an oligomerization process that produces curable oligomers with a low Dp, in the range of from 3 to 100, without the need of excessive amounts of initiators. The curable oligomer products are in liquid form and may be terminally unsaturated. The crosslinkable or curable functionality is incorporated into the oligomer by a reaction after the oligomerization—a post-oligomerization reaction—between the oligomer or altered oligomer with a modifier which contains a crosslinkable/curable functional group. The present invention also provides curable oligomer compositions prepared according to the disclosed process. Furthermore, the invention provides curable oligomer compositions which are substantially free of metals, salts and/or surfactant contaminants. The product from the present invention is useful for a number of applications, such as films, markings, coatings, paints, adhesives, binders, inks and others.
One aspect of the present invention relates to a method for producing a curable coating on a substrate surface comprising:
(A) applying to said substrate surface a layer of a curable composition; and
(B) drying, or allowing to dry, said layer,
wherein said curable composition is a composition prepared by a process comprising the steps of:
(a) forming an oligomer having a Dp in the range of from 3 to 100 by either:
(i) oligomerizing a mixture comprising a monomer A and a monomer B, wherein said monomer A has at least one functional group which remains substantially unreacted during said oligomerizing; or
(ii) oligomerizing a mixture comprising a monomer A equivalent and a monomer B and generating said at least one functional group during or after said oligomerizing;
wherein said oligomer has a first number of monomer units incorporated into its backbone; and
wherein said oligomerizing is conducted at a temperature in the range of from 150° C. to 650° C., a pressure in the range of from 3 MPa to 35 MPa which is sufficient to maintain said mixture in a fluid state, and a residence time in the range of from 0.1 second to 1 minute; and
(b) reacting a modifier having at least one reactive moiety with said oligomer through a reaction under a second condition between said reactive moiety of said modifier and said functional group incorporated into said oligomer to produce said curable composition, wherein said modifier further comprises a curable group selected from the group consisting of a carbon—carbon double bond, an oxygen-containing heterocyclic group and mixtures thereof, and said curable group remains pendant in said curable composition and crosslinkable after said reaction.
A second aspect of the present invention relates to a method for producing a curable coating on a substrate surface comprising:
(A) applying to said substrate surface a layer of a curable composition; and
(B) drying, or allowing to dry, said layer,
wherein said curable composition is a composition prepared by a process comprising the steps of:
(a) forming an oligomer having a Dp in the range of from 3 to 100 by either:
(i) oligomerizing a mixture comprising a monomer A and a monomer B, wherein said monomer A has
Beckley Ronald Scott
Bowe Michael Damian
Brown Ward Thomas
Greenblatt Gary David
Lange Barry Clifford
Clikeman Richard R.
Falk Stephen T.
Wilson D. R.
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