Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2001-02-02
2003-07-22
Seidleck, James J. (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, C522S109000, C522S110000, C522S071000, C522S077000, C522S083000, C522S181000, C522S180000, C522S113000, C522S120000, C522S121000, C522S092000, C522S134000, C522S137000, C522S141000, C522S142000, C522S143000
Reexamination Certificate
active
06596787
ABSTRACT:
BACKGROUND OF THE INVENTION
Light curable liquid acrylic ester adhesives for glass bonding using low intensity ultraviolet (“UV”) light are known. Such adhesives are useful for glass assembly and repair applications in which high intensity UV light is unavailable or impractical. Using such adhesives, broken glassware and decorative glass items can be rapidly bonded and fabricated using low intensity light sources which give output in the UV/visible wavelength region.
One problem associated with such known UV glass bonding adhesives is yellowing on storage and exposure to light during use. Another problem common with such adhesives is surface cure inhibition when cured under atmospheric conditions.
A number of fast curing low-yellowing acrylate functional oligomer products are known for use in UV/electron beam (“EB”) curable printing inks and the like. However, such products typically have poor adhesive strength to glass.
It would be desirable to provide an improved low intensity UV/visible curable adhesive suitable for glass bonding which provides good adhesive strength, fast tack-free time and reduced yellowing than commercially available adhesives. Desirably such adhesives should also display good humidity resistance.
SUMMARY OF THE INVENTION
The present invention is directed to low intensity UV/visible curable adhesives which provide improved low-yellowing properties with fast fixture time at low UV intensity over current glass bonding adhesives. These adhesives maintain good bond strength and durability at least comparable to known UV acrylic glass bonding adhesives. The composition of the present invention includes:
a) an aliphatic polyether urethane acrylate oligomer having an average of least 2.5 acrylate groups per molecule, suitably in an amount of 50% 75% by weight of the total composition;
b) at least one of
i) a combination of at least one aliphatic (poly)ester urethane diacrylate and at least one alkoxylated bisphenol A di(meth)acrylate; or
ii) a urethane di(meth)acrylate of alkoxylated hydrogenated bisphenol A, suitably in an amount of 5%-70% by weight of the total composition;
c) a diluent (meth)acrylate ester having an ambient viscosity of about 100-5,000 cps, suitably in an amount of 5%-60% by weight of the total composition;
d) optionally an adhesion promoter, suitably in an amount of 0.2%-30% by weight of the total composition; and
e) a photoinitiator component, suitably in an amount of 0.2%-10% by weight of the total composition.
A further aspect of the invention provides a method of glass bonding in which an adhesive composition is applied to at least one of a pair of glass substrates, and then the substrates are joined and subjected to low intensity UV radiation for sufficient time to fixture the adhesive.
DETAILED DESCRIPTION OF THE INVENTION
For purposes of the present invention low intensity UV radiation is radiation from a broad spectrum UV or a UV/visible source, having an intensity at 365 nm of about 6 milliwatts or less per square centimeter, at the substrate surface.
Component a)
The aliphatic polyether urethane acrylate compounds useful in the invention are suitably prepared by reacting an aliphatic diisocyanate with an aliphatic polyether polyol, at a ratio of about 2 or more isocyanate groups of the diisocyanate per hydroxyl group of the polyether polyol compound. The remaining isocyanate groups are then reacted with a suitable hydroxyalkyl acrylate compound to produce the acrylated oligomer. The reaction can also be run in reverse sequence, preparing acrylate functional isocyanate intermediates which are then used as capping agents for the polyether polyols. The polyether polyol has an average of at least 2.5 hydroxyl groups per molecule, typically 2.5-3.5 hydroxyl groups per molecule and preferably about 3 hydroxyl groups per molecule. The polyether repeat units may suitably be ethylene oxide (—C
2
H
4
O—), propylene oxide (—C
3
H
6
O—) or butylene oxide (—C
4
H
8
O—) repeat units, or mixtures thereof. In the foregoing, propylene includes n-propylene and isopropylene, and butylene includes 1,2-butylene, 1,3-buctylene, 2-methyl-1,3-propylene and 1,4-butylene. Preferred polyols may be propoxylated glycerol or propoxylated trimethylolpropane. Examples of suitable aliphatic diisocyanate include isophorone diisocyanate, methylene-bis-cyclohexane diisocyanate and 1,6-hexane diisocyanate. Examples of suitable hydroxy functional acrylate compounds include hydroxyethyl acrylate, hydroxypropyl acrylate and other diol monoacrylate esters. A desirable commercial acrylated aliphatic polyether urethane oligomer is PHOTOMER® 6019, sold by Henkel Corp., Ambler, Pa, reported in U.S. Pat. Nos. 5,908,873 and 6,014,488 to be an aliphatic urethane acrylate oligomer from polyether polyol, isophorone diisocyanate and hydroxyethyl acrylate. Mixtures of aliphatic polyether urethane acrylate compounds may be used as this component of the inventive formulation. This aliphatic polyether urethane acrylate component is employed at an amount of about 5% to about 70%, preferably 10-40%, by weight of the composition.
Component b)
The second component of the inventive compositions is a di(meth)acrylate oligomer component. The second component may be either a combination of an aliphatic polyester urethane diacrylate and an alkoxylated bisphenol A di(meth)acrylate, or a block (meth)acrylate terminated poly,ether urethane based on hydrogenated bisphenol A. This second component is suitably present in an amount from about 5% to about 70% by weight of the composition.
The aliphatic polyester urethane diacrylate suitably may, be an oligomeric compound having a viscosity at 160° F. (71° C.) of about 700 to 5,000 cps 1,000-5,000 mPa·s), preferably about 1,000 to about 2,500 cps (1,000-2,500 mPa·s). An example such compound is PHOTOMER® 6210 sold by Henkel Corp. The aliphatic polyester urethane diacrylate is suitably employed at an amount of about 15% to about 50%, such as 20-40%, by weight of the composition. Mixtures of aliphatic polyester urethane diacrylates may be employed.
The alkoxylated bisphenol A di(meth)acrylate compound is used in combination with the aliphatic polyester urethane diacrylate to enhance the adhesive strength of the cured formulation. Ethoxylated bisphenol A dimethacrylate compounds having 2-6 ethoxylate groups per molecule are preferred. The alkoxylated bisphenol A di(meth)acrylate compound is employed at an amount of about 5% to about 50%, preferably about 10% to about 15%, by weight of the composition.
The urethane di(meth)acrylate of hydrogenated bisphenol A may be prepared by reacting 2 moles of a diisocyanate with 1 mole of hydrogenated bisphenol A. The intermediate of this reaction is then reacted with 2 moles of 2-hydroxyethyl methacrylate to produce the desired methacrylate terminated polyurethane block resin. The diisocyanate is suitably an aromatic diisocyanate, desirably toluene diisocyanate. The block polyurethane diacrylate should be used in an amount of from about 5% to about 50% by weight of the composition.
Desirably the components a) and b), respectively are present in a relative weight ratio of from about 1:3 to about 3:1, such as about 1:1.
Component c)
Liquid diluent monomers which are liquid esters, preferably acrylate and methacrylate esters having a viscosity of 100-5,000 cps (100-5,000 mPa·s), preferably 100-4,000 cps (100-4,000 mPa·s), more preferably 100-2,000 cps 200-2,000 mPa·s), are desirable to provide a satisfactory viscosity to the inventive compositions. Suitably, such (meth)acrylate monomers include mono, di, or poly(meth)acrylate compounds, examples of which are &bgr;-carboxyethyl acrylate, isobornyl acrylate, n-octyl acrylate, n-decyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, ethoxyethoxyethyl acrylate, ethoxylated phenyl monoacrylate hydroxyethyl acrylate, isooctyl acrylate, n-butyl acrylate, dipropylene glycol diacrylate, tetraethylene glycol diacrylate, 1,6-hexane diol diacrylate, tripropylene glycol diacrylate, glycerol triacrylate, trimethylol propane diacrylate, trimethylol propane triacrylate, pentaeryt
DeMarco JoAnn
Levandoski Susan
Bauman Steven C.
Henkel Loctite Corporation
McClendon Sanza L.
Seidleck James J.
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