Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
1999-10-12
2001-06-12
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...
C522S015000, C522S024000, C522S025000, C522S120000, C522S129000, C522S141000, C522S146000, C522S170000, C522S181000, C526S332000, C526S333000, C528S393000, C528S405000, C528S406000, C528S408000, C528S418000, C528S421000
Reexamination Certificate
active
06245827
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed toward improved liquid ultraviolet (UV) resin compositions that comprise resin compounds blended with several defined additional chemicals. The inventive compositions have the property that when the composition is subject to ultra violet light the composition cures to a solid throughout the volume of the entire composition. This property permits the composition to be useful in applications where the possibility of exposing all of the area (and the volume beneath) of the composition to ultraviolet radiation is not present. This cure process, which continues the cure by using a trigger mechanism provided by the ultraviolet light, has been termed shadow cure. The present invention cures into areas which have no exposure to light by use of novel and surprising chemistry.
These resin compositions have enhanced properties that make them desirable materials for an ever-growing number of commercial uses. These uses include:
(a) Industrial uses such as sealing material for coils and printed circuit boards, potting compounds and sealing compounds generally and as adhesives,
(b) Surgical and medical uses such as sealing of medical equipment containing electronic components,
(c) A variety of automotive manufacture uses including industry potting and sealing of various automotive components, and
(d) Electronic uses where tight and reliable sealing are required including encapsulation of electronic components and parts.
Advantages of the Instant Invention Include:
(a) Ease of use as a one component product not requiring on-site mixing of two or more components,
(b) Reduced volatile organic compounds (VOC) released into the atmosphere,
(c) Rapid, deep and complete cure throughout the entire volume of the resin composition upon application of ultraviolet light and without the necessity of on-site heating.
2. Background of the Invention
Resin compositions which cure by exposure to ultraviolet radiation are known in the art. Such compositions found in actual commercial usage today, however, in the fields discussed above are very few. An even smaller number of such compositions are known to the art which completely cure by brief exposure to ultraviolet radiation in areas not reached by such light.
3. Description of the Prior Art
Some prior art of interest is discussed below for background.
Reactions between epoxides and compounds having aliphatic hydroxyl groups have been known. Such reactions have been generally carried out at elevated temperatures by heating the reactants in the presence of basic or acid catalysts. For example, U.S. Pat. No. 2,914,490 describes the thermal reactions of a variety of epoxides with different types of polyols including copolymers containing reactive hydroxyl groups. Such reactions proceed very slowly in the presence of a catalyst at room temperature with elevated temperatures necessary to get reasonable reaction rates and useful properties.
U.S. Pat. No. 3,450,613 disclosed photopolymerizable epoxy compositions comprising the reaction product of an epoxy resin prepolymer and an ethylenically unsaturated organic acid, a photosensitizer, and optionally polyfunctional acids or bases. On exposure to ultraviolet light there is a photoinduced polymerization of the ethylenically unsaturated portion of the reaction product. The cure of the composition is completed by outside heating to bring about reaction of the epoxy resin portion of the composition. Compositions such as this, and commercial products using their type of mechanism, have very poor usefulness because of the requirement of both light and heat to effect a complete polymerization cure of the entire composition. Such compositions are often oxygen sensitive and usually have very poor thermal stability.
U.S. Pat. No. 4,256,828 describes photocopolymerizable compositions which contain epoxides, organic material with hydroxyl functionality and a photosensitive aromatic sulfonoic or iodonium salt of a halogen containing complex ion. U.S. Pat. No. 5,837,398 refers to U.S. Pat. No. 4,256,828 and describes a battery sealant composition which does not require an organic solvent.
U.S. Pat. No. 4,699,802 shows a dual curing coating method using liquid silicones curable by ultraviolet light on a substrate having no readily accessible areas to direct UV light using a process of first, irradiation, and then exposing the radiated composition to a moisture cure. See also U.S. Pat. No. 5,008,301 which shows a three mechanism curing system using separate light, heat and moisture outside mechanisms.
U.S. Pat. No. 5,017,406 describes an UV curable composition cured with polysilane with a peroxide photoinitiator. Peroxides used include dibenzoyl peroxide and hydrogen peroxide.
U.S. Pat. No. 5,712,231, in a description of the prior art, states that heat-activated peroxides may have been added to acrylic, exoxy, silicone and polyurethane systems but could not be used where heat sensitive electronic components are involved.
There has long been a need for a thermally stable, one-part, photocurable resin compositions, such as epoxy compositions, which provides a flexible or solid coating and an assured complete cure and seal. Such composition has not heretofore been provided by the many artisans working in the field.
OBJECT AND SUMMARY OF THE INVENTION
Object of the Invention:
It is an object of the invention to provide a liquid resin product which upon activation by ultra violet light will cure into a solid or a flexible solid throughout its entire volume including that volume not reached by the ultra-violet light.
It is a specific object of the invention to provide commercial curable one component resin compositions useful for sealing structures where a substantial portion of the resin composition is shielded behind structures and components, and not therefore reachable by light.
SUMMARY OF THE INVENTION
The present invention is a resin composition which possesses an enhanced shadow cure chemistry mechanism, i.e., the composition cures by exposure to ultraviolet radiation throughout its entire volume without the need for any other outside stimuli.
The invention concerns an ultraviolet radiation curable composition having enhanced cure properties activated from an initial ultraviolet radiation by internally generated heat into areas shadowed. The composition is a stable, storable liquid at room temperatures and, upon activation by ultraviolet light, turns into a hard or flexible solid material throughout its entire volume.
In a preferred embodiment, this invention is of a resin composition including an additive of one or more organic peroxide thermal initiators to dialkyl iodonium salt cationic photoinitiators, that are sensitized with one or more alpha-hydroxy-ketones. The composition provides a self-propagating thermal curing reaction first activated by a short duration of ultraviolet radiation at its surface. The thermal reaction is non-directional, thus eliminating the line of sight limitation of current ultraviolet radiation curing processes. Complete curing of the composition can be achieved in a very short time; often after only a few minutes or less. The activation period can be provided by only a few seconds of ultraviolet light using a wide variety of commercial ultraviolet light sources.
The ultraviolet radiation polymerization and cross linking of epoxy and vinyl ether resins, for example, by current cationic photoinitiator chemistry has, up to now, been limited to thin coatings of usually less than 0.06 in. thick, and even less if the composition is pigmented. These current product and processes suffers from line of sight limitations, in that the resin composition not directly illuminated with ultra violet light does not cure.
The inventive product, in comparison with the known commercial art, uses activation by ultraviolet light and by use of a chemistry process available in situ results in the surface UV irradiation step activating a chemical curing process.
This curing process produces an ongoing exothermic reaction that propagates
Berman Susan W.
Cronin Michael J.
Elementis Specialties, Inc.
LandOfFree
Ultraviolet curable resin compositions having enhanced... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ultraviolet curable resin compositions having enhanced..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ultraviolet curable resin compositions having enhanced... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2442688