UV curable hardcoat compositions and processes

Details UV curable hardcoat compositions and processes UV curable hardcoat compositions and processes

1995-06-07

2001-11-13

Berman, Susan W. (Department: 1711)

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

Synthetic resins

Compositions to be polymerized by wave energy wherein said...

C522S078000, C522S079000, C522S096000, C522S173000, C428S412000, C428S423100, C428S423700, C428S424200, C428S424400, C428S424600, C428S424700, C428S424800

Reexamination Certificate

active

06316515

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates generally to ultraviolet (UV) cured coatings, and more particularly to UV curable coating compositions, processes of their use, and as well to coated articles resulting therefrom.
Conventionally cured hardcoat finishes have several disadvantages. In general, the coating materials and the curing agent must be applied separately, in a particular sequence and at particular relative levels. Because both the proportions of the ingredients and the timing of their application is critical, conventionally cured hardcoats have been difficult and costly to apply, especially with the consistency and uniformity required in current commercial applications.
UV cured coatings overcome several disadvantages associated with conventional hardcoat finishes. In particular, UV curable coating compositions may be premixed, e.g. the polymerization initiator is added to the active ingredients by the manufacturer when the coating is produced, and not by the coating user when the coating is about to be applied. Thus, mixing and measurement errors can be avoided and a more consistent product can be obtained.
Despite their many advantages, UV curable coating compositions themselves pose problems which must be addressed. For example, typical UV hardcoats are high molecular weight, highly crosslinked films which are formed from the highly reactive acrylate functionality. As such, known UV hardcoats have suffered from limited durability, low solids content and cured resin shrinkage. They have also required high doses of UV light to cure. Other UV hardcoats formulated in an attempt to overcome these problems typically suffer from some combination of loss of abrasion and scratch resistance, poor processibility and unsatisfactory durability. A need therefore exists for a UV curable product which is conveniently processable and which forms cured coatings exhibiting improved physical and chemical properties, e.g. scratch and abrasion resistance, and durability.
SUMMARY OF THE INVENTION
The applicant's invention now addresses these needs and provides in one preferred embodiment a scratch resistant UV curable coating composition. This compositions comprises: (a) 5% to 90% by weight of an acrylated aliphatic urethane having a molecular weight of between about 500 and 2000 and formed by the reaction of (i) a multifunctional acrylate with a molecular weight of between about 190 and 500 and containing at least three polymerizable unsaturated groups per molecule, with (ii) an aliphatic urethane based on a polymer of alkyl carbomonocycle diisocyanate with alkanepolyol polyacrylates; (b) 5% to 30% by weight of a multifunctional acrylate having a molecular weight of between about 170 and 1000 and containing at least two polymerizable unsaturated groups per molecule; and (c) a photopolymerization initiator and/or photopolymerization sensitizer. The composition can also optionally include a solvent. However, unless otherwise specified, percents by weight set forth in this application are calculated exclusive of any solvent present. More preferred compositions can also include suitable light stabilizing agents, e.g. hindered amine and/or benzotriazole derivatives, and also antioxidant materials.
Additional preferred embodiments of the invention relate to coated articles and coating processes resulting from and involving the use of applicant's preferred coating compositions.
One object of the invention is to provide improved ultraviolet curable coating compositions giving coatings and coated articles demonstrating superior chemical and physical properties such as chemical resistance, weather resistance, abrasion resistance, scratch resistance, stain resistance, heat resistance and adhesion.
Another object of the invention is to provide processes for coating articles, e.g. plastic articles, exhibiting improved physical and chemical properties.
Still another object of the present invention is to provide a coated article exhibiting superior physical and chemical properties.
Another object of this invention is to provide coating processes and compositions which enable convenient and consistent, uniform processibility.
Further objects and advantages of the present invention will be apparent from the following description and appended claims.
DESCRIPTION OF PREFERRED EMBODIMENTS
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to certain embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications and applications of the principles of the invention as described herein being contemplated as would normally occur to one skilled in the art to which the invention relates.
As indicated above, one preferred embodiment of this invention relates to a UV curable coating composition. In this regard, Formula I, set forth below, shows starting materials and compositional ranges for preferred coating compositions of the invention. The compositional ranges are given as percent by weight of the composition excluding any solvent which is included.
Formula I:
Acrylated aliphatic urethane
(5-90%)
Multifunctional acrylate
(5-30%)
Photopolymerization initiator/sensitizer
(3-15%)
Hindered amine light stabilizer
(0.1-7.5%)
Benzotriazole
(0.1-7.5%)
Antioxidant
(0.1-3.0)
Flow additive
(0.1-5.0%)
The acrylated aliphatic urethanes according to the invention contain about 5% to about 95% by weight of prereacted multifunctional acrylate and the balance in the aliphatic urethane. More particularly, to obtain the acrylated aliphatic urethanes, a multifunctional acrylate having a molecular weight of about 190 to about 500 and containing at least 3 polymerizable unsaturated groups per molecule (e.g., pentaerythritol triacrylate, diphenyl erythritol tetraacrylate, and trimethylolpropane triacrylate) is prereacted with an aliphatic urethane based on a polymer of alkyl carbomonocycle diisocyanate with alkanepolyol polyacrylates. The acrylate having at least three polymerizable groups provides an acrylated aliphatic urethane giving final coatings demonstrating good surface hardness, for example as evidenced by steel wool scratch resistance.
The preferred acrylated aliphatic urethane has a final number average molecular weight of about 500 to about 2000. More preferably, the acrylated aliphatic urethane has a number average molecular weight of about 800 to about 1000, with those having a number average molecular weight of about 800 being most preferred in work to date. These preferred acrylated aliphatic urethanes provide coatings of good weather and thermal crack resistance. Further, these acrylated aliphatic urethanes provide advantageous application solids, curing rates and material compatibility.
The acrylated aliphatic urethane may be obtained commercially. For example, EBECRYL 8301 (a mixture of greater than 50% polymer of alkylcarbomonocyclic diisocyanate with alkanepolyolpolyacrylates and less than 50% acrylated polyol), available from Radcure Specialties, Inc. of Atlanta, Ga. has been highly preferred in work to date.
Exclusive of any solvent present, as indicated above, the acrylated aliphatic urethane constitutes about 5% to 90% by weight of the coating composition. More preferably, this acrylated aliphatic urethane makes up about 50% to about 90% of the composition, most preferably about 90%. These preferred levels have provided good weather and thermal crack resistance, as well as advantageous viscosity, material capacity and cure rates.
As will be understood, the particular multifunctional acrylate employed will depend upon the desired application viscosity and other properties. The preferred multifunctional acrylates are of the reactive diluent type, have a molecular weight of about 170 to about 1000, and contain at least two polymerizable unsaturated groups per molecule. Representative multifunctional acrylates thus include ethylene glycol di(meth)acrylate, 1, 6-hexanediol

Affiliated with

Also associated with

Rating

UV curable hardcoat compositions and processes does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with UV curable hardcoat compositions and processes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and UV curable hardcoat compositions and processes will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2615393