Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-03-14
2002-09-17
Nakarani, D S (Department: 1773)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S453000, C525S456000, C525S474000
Reexamination Certificate
active
06451930
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to an additive for a film-forming composition to be applied to a substrate, typically as a topcoat, having improved adhesive properties.
Typically, when a windshield is affixed to the body of a vehicle, an adhesive is used to attach the windshield to the body. The adhesives commonly used for attachment of a windshield to the body of the vehicle are moisture-cured adhesives containing isocyanate (NCO) groups. These adhesives are commercially available from Essex Specialty Products, Inc. of Auburn Hills, Michigan, among other sources. The above described adhesives adhere well to many of the curable film-forming compositions used as vehicle topcoats. However, many of the commonly available adhesives do not adhere well to topcoats that contain carbamate and/or urea groups.
One solution to the problem of the failure of moisture-curable adhesives to adhere to carbamate and/or urea-containing topcoats is to prime the topcoat with a moisture curable urethane primer wherever the adhesive is to be applied. Although effective, this method adds an additional step to the process of adhering a windshield or other items to the vehicle body.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a carbamate and/or urea group-containing topcoat composition to which NCO group-containing moisture curable adhesives will bond, forming a strong linkage between the adhesive and the topcoat.
The present invention provides a film-forming composition having improved adhesion to certain commercially available adhesives. This composition is typically applied to a substrate as a topcoat. The composition includes a resin component that includes a curable film-forming polymer with carbamate and/or urea groups. The curable film-forming polymer is typically an acrylic and/or polyester polymer. The composition also includes a material containing a hydrolyzable silyl group. The hydrolyzable silyl group is typically a group having the structure:
where R is a hydrogen or a monovalent hydrocarbon group, X is alkoxy, acyloxy, aminooxy, phenoxy, thioalkoxy or amino and (a) is an integer number from 0 to 2, wherein if (a) is 2, the two R groups can be the same or different and when (a) is 0 or 1, the two or three X groups can be the same or different.
Typically, (a) is 0 and X is methoxy or ethoxy. The silyl group-containing material can be monomeric, oligomeric or polymeric and can have more than one silyl group.
The present invention is also directed to a method for preparing a coated substrate which includes the step of applying to an exposed surface of a substrate, typically having one or more undercoating layers, a topcoat as described above. Lastly, the present invention is directed to a substrate, such as, without limitation, an automobile body, which is coated with the above-described film-forming composition.
DETAILED DESCRIPTION OF THE INVENTION
The use of numerical values in the various ranges specified in this application, unless expressly indicated otherwise, are stated as approximations as though the minimum and maximum values within the stated ranges were both preceded by the word “about.” In this manner slight variations above and below the stated ranges can be used to achieve substantially the same results as values within the ranges.
Also, the disclosure of these ranges is intended as a continuous range including every value between the minimum and maximum values.
As used herein, except when otherwise noted, the term “polymer,” and the like, shall refer to both polymeric and oligomeric materials.
The curable film-forming composition of the present invention is typically used to form a topcoat on a substrate. The composition is applied to the substrate and is subsequently cured. The composition includes a resin component, which includes at least two materials. The first material in the resin component is a film-forming polymer which is the primary curable constituent of the topcoat. The second material in the resin component is a material having one or more silyl groups where the silyl groups include one or more hydrolyzable groups. The hydrolyzable silyl group-containing material should be present in the composition in additive quantities so that the hydrolyzable silyl groups do not participate to any substantial extent in the curing of the resin component.
The film-forming polymer can be any polymer having active groups which are substantially carbamate and/or urea. A typical film-forming polymer having carbamate groups is a polymer or copolymer as described in U.S. Pat. Nos. 25 5,593,785 and 5,814,410, which are incorporated herein by reference. The polymer is typically an acrylic or a polyester-containing material. The typical film-forming polymer includes pendant and/or terminal groups, which are substantially carbamate and/or urea groups. By “substantially,” it is understood that there can be other pendant or terminal groups in the polymer chain, such as hydroxyl groups, so long as a cured film, prepared from a composition including the polymer as a primary resin component, demonstrates about 100% adhesive failure and about 0% cohesive failure when a given adhesive is placed on the film and is cured, due, at lease in part, to the presence of carbamate and/or urea groups on the polymer chain. A typical carbamate and/or urea group-containing polymer is a polymer having pendant and/or terminal groups that are about 10% up to about 100% carbamate and/or urea. In other words, the polymer typically has a carbamate + urea equivalent weight of about 150-2000.
As aforementioned, the film-forming compositions of the invention preferably comprise one or more polymer materials having carbamate and/or urea functional groups. Carbamate and/or urea functional groups can be incorporated into the polymer prepared from polymerizable ethylenically unsaturated monomers by copolymerizing, for example, ethylenically unsaturated monomers with a carbamate functional vinyl monomer, such as a carbamate functional alkyl ester of acrylic or methacrylic acid. The polymerizable ethylenically unsaturated monomers can include, for example and without limitation, alkyl esters of (meth)acrylic acid including methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethyl hexyl(meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxybutyl (meth)acrylate, trifluoroethyl (meth)acrylate, pentafluoropropyl (meth)acrylate, perfluorocyclohexyl (meth)acrylate, (meth)acrylonitrile, glycidyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, (meth)acrylamide, alpha-ethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N,N-dimethyl acrylamide, N-methyl acrylamide, acryloyl morpholine and N-methylol (meth)acrylamide, and vinyl aromatic compounds such as styrene, alpha-methyl styrene, and vinyl toluene. As used herein, “(meth)acrylate” and like terms is intended to include both acrylates and methacrylates. Useful carbamate functional alkyl esters can be prepared by reacting, for example, a hydroxyalkyl carbamate, such as the reaction product of ammonia and ethylene carbonate or propylene carbonate, with methacrylic anhydride. Other useful carbamate functional vinyl monomers include, for instance, the reaction product of hydroxyethyl methacrylate, isophorone diisocyanate, and hydroxypropyl carbamate; or the reaction product of hydroxypropyl methacrylate, isophorone diisocyanate, and methanol. Still other carbamate functional vinyl monomers may be used, such as the reaction product of isocyanic acid (HNCO) with a hydroxyl functional acrylic or methacrylic monomer such as hydroxyethyl acrylate, and those described in U.S. Pat. No. 3,479,328, incorporated herein by reference. Carbamate functional groups can also be incorporated into the acrylic polymer by reacting a hydroxyl functional acrylic polymer with a low molecular weight alkyl carbamate such as
Burgman John W.
Kilic Soner
Martin David C.
Valenta Jane N.
Altman Deborah M.
Nakarani D S
PPG Industries Ohio Inc.
Uhl William J.
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