Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2001-11-01
2003-01-07
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S097000, C264S029300
Reexamination Certificate
active
06503960
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to curable compositions which include a pigment disbursed therein and a dispersion stabilizing additive which maintains the pigment in a disbursed form prior to cure. In particular, the curable compositions of the present invention are radiation curable compositions which have particular application for use in hollow shell molds, such as those employed to make hearing aids.
BACKGROUND OF RELATED TECHNOLOGY
Curable (meth)acryl functionalized compositions have been use for the manufacture of hollow molded articles, and in particular articles such as hearing aids. Such compositions are ordinarily radiation curable due to the manufacturing efficiencies and cost savings as compared to using heat to cure. Additionally, ultraviolet and/or visible light can be employed to concentrate or direct the curing energy at a particular portion of the curable composition and to ensure the proper irradiation.
For example, U.S. Pat. No. 5,763,503 to Cowperthwaite, discloses a method for making hollow shells, i.e. housings for in-ear hearing aids, using a radiation curable composition. This patent discloses the use of a hydroxyalkylmethacrylate-capped component, a difunctional, urethane methacrylate monomer, a minor amount of unreacted hydroxalkyl(C
2-3
) methacrylate monomer and a photoiniator. This composition is described as being pourable and contains a viscosity-increasing amount of viscosity-increasing solid other than a colorant. This patent focuses on controlling and adjusting the viscosity of the composition to achieve formulations which produce better hollow-shelled articles. The presence of viscosity-affecting ingredients, including pigments, is described as being carefully limited.
Other (meth)acrylate-based curable compositions have used a combination of uv curable components to achieve the desired cure properties. For example, Japanese Laid-Open Patent Publication Nos. 10-130601 and 10-130602 reportedly assigned to Nippon Kayakuco, Ltd., disclose uv curing adhesive compositions for use as protective coatings on optical discs which employ a uv curable ethylenically compound, such as a (meth)acrylate compound, a photoinitiator, an organic peroxide and an amino accelerator compound. Among the disclosed curable compounds are 2-hydroxyethyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate and phenyl oxyethyl (meth)acrylate. Another example of a uv curing (meth)acrylate-based composition is disclosed in U.S. Pat. No. 5,908,873, which contains an aliphatic urethane acrylate oligomer, a reactive (meth)acrylate monomer, a release agent and a photoinitiator. This composition is used to affix coated and inked optical fibers in a ribbon configuration.
Using colorants, such as dyes and pigments, in (meth)acryl functionalized curable compositions has been used for visual inspection purposes, as well as providing color to the cured product to meet the demands of the particular application. Many colorants do not stay suspended or uniformly distributed in curable resin compositions for long periods of times, such as when subjected to storage conditions. For this reason, mixing to disburse and/or uniformly distribute the colorants throughout the resin composition is generally required to obtain the desired color upon cure. This additional mixing step is undesirable in production processes because it is costly, can be technician sensitive and may require the use of the mixed composition within a relatively short time period.
Moreover, if mixing of the colorant into the curable composition immediately prior to use is required, uniform dispersion often does not occur due to agglomeration which forms during storage.
One particular commercial area where these problems exist is in the manufacturing and repair of custom hearing aids. In this industry, a variety of different types of flesh tones must be closely matched, typically using low concentrations of pigments which have been chosen to produce a variety of industry standard colors and which allow for tailoring of the curable composition to a particular person's skin. For the most part, these pigments are insoluble particles which tend to fall out of dispersion as sediment, due to their density. Compositions used in molding hollow shell articles, such as hearing aids, generally require relatively low viscosities in order to easily dispense and process the compositions into the final molded article. Low viscosity materials further accelerate the sedimentation of conventional pigments, and in particular the more commonly heavy pigments such as TiO
2
and Fe
2
O
3
.
Efforts to use various filler materials such as silica to provide thixotropic character to pigmented compositions useful in the production of hollow shell articles, such as hearing aids, has been largely unsuccessful due to the resulting surface blemishes and loss of other aesthetic features upon cure. Moreover, these filled compositions were not readily pourable due to the addition of the fillers, causing additional difficulties during manufacturing.
Thus, there is a need for a curable composition which can be effectively used to make cured articles, such as hearing aides and other hollow shell products, which can incorporate a variety of colorants, and in particular solid pigments, and which can be formulated into pourable and relatively low viscosity compositions which do not require substantial mixing prior to use in order to uniformly disburse the colorant therein. Moreover, there is a need for a (meth)acryl functionalized composition, which can cure by a variety of mechanisms, including electromagnetic radiation, and which can be molded into hearing aids and other high quality finished products having precise skin tone matches and coloring.
SUMMARY OF THE INVENTION
The present invention relates to curable compositions which include:
(a) a (meth)acryl functionalized curable component useful as a matrix,
(b) a cure system for said curable component;
(c) a pigment composition comprising of at least one pigment disbursed within said curable component; and
(d) an additive which comprises an alkali metal cation and the reaction product of:
(i) a polyfunctional isocyanate and a member selected from an hydroxy and an amine; or
(ii) a phosgene or phosgene derivative and a compound having 3 to 7 polyethylene glycol ether units terminated at one end with an ether group and the other end with a reactive functional group selected from an amine, an amide, a thiol and an alcohol; or
(iii) a monohydroxy compound, a diisocyanate and a polyamine.
In another aspect of the present invention, there is included a composition useful for the manufacture of hollow shells, such as hearing aids, which includes:
a. a photocurable aliphatic urethane-acrylate oligomer matrix composition having disbursed therein a pigment and a dispersion stabilizer, said stabilizer comprising an alkali metal salt and an additive which is the reaction product of:
(i) a polyfunctional isocyanate and a member selected from an hydroxy and an amine; or
(ii) a phosgene or phosgene derivative and a compound having 3 to 7 polyethylene glycol ether units terminated at one end with an ether group and the other end with a reactive functional group selected from an amine, an amide, a thiol and an alcohol; or
(iii) a monohydroxy compound, a diisocyanate and a polyamine; and
b. a photoiniator.
The curable compositions of the present invention provide the ability to make hollow shell articles, such as hearing aids, having a substantially uniform cross-sectional thickness. Such control is due to the unique curable compositions and the ability to control the radiation exposure used to cure the compositions. Pigments used in the present invention are present in amounts sufficient to produce the desired color of the final article, without interfering with the radiation curing or final properties of the cured polymer. Moreover, the dispersion stabilizing component eliminates the need for mixing just prior to use, and ensures the desired qualities of color, surface finish and overall
Kadziela Vic K.
Litke Alan E.
Gorr Rachel
Hoffmann & Baron , LLP
Loctite Corporation
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