Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2000-06-27
2002-02-26
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...
C522S079000, C522S083000, C522S071000, C522S100000, C522S102000, C522S103000, C522S101000, C522S170000, C522S181000, C522S182000
Reexamination Certificate
active
06350791
ABSTRACT:
FIELD OF THE INVENTION
The present invention refers to a thermosettable adhesive comprising a thermosettable polymer component, a thermoformable polymer component and an effective amount of a heat-activatable and/or photoactivatable curing system for curing the thermosettable polymer component. The present invention furthermore refers to thermosettable adhesive tapes comprising at least one layer of the thermosettable adhesive with at least one exposed surface.
BACKGROUND OF THE INVENTION
A thermosettable adhesive which is the photopolymerzation product of a precursor consisting essentially of:
(a) from about 30% to about 80% by weight of a photopolymerizable monomeric or prepolymeric syrup containing an acrylic ester of a nontertiary alcohol, and a moderately polar copolymerizable monomer;
(b) from about 20% to about 60% by weight of an epoxy resin or a mixture of epoxy resins containing no photo-polymerizable groups;
(c) from about 0.5% to about 10% by weight of a heat-activatable hardener for the epoxy resin;
(d) from about 0.01% to about 5% of a photoinitiator; and
(e) from 0% to about 5% of a photocrosslinking agent, is described in U.S. Pat. No. 5,086,088. Thermosettable pressure-sensitive adhesive tapes can be obtained, for example, by coating the precursor of U.S. Pat. No. 5,086,088 onto a flexible carrier web such as a silicone release liner with a subsequent exposure to UV-irradiation. The thermosettable adhesive tapes thus obtained, can be crosslinked upon exposure to temperatures of, for example, 170° C.
European Patent Application EP 0,620,259 discloses an optionally tacky thermosettable hot-melt composition and hot-melt tapes comprising, for example, a thermosettable epoxy component, a thermoplastic polyester component, a photoinitiator for cationically curing the epoxy component and optionally a hydroxyl-containing material.
Depending on their melt flow behavior, thermosettable adhesive tapes are typically mainly used for bonding or for melt-sealing applications, respectively. Thermosettable bonding adhesive tapes allow for the preparation of assemblies by sandwiching, for example, such tapes between two substrates such as, for example, glass or optionally coated metal substrates with subsequent thermosetting of the thermosettable adhesive tape. Thermosettable melt-sealing adhesive tapes are frequently used for sealing of metal seams or for providing protective and/or topographical features, for example, to primed or unprimed, optionally coated metal parts or joints to seal joints formed by such metal parts. Thermosettable melt-flowable adhesive tapes are used, for example, in the automotive industry where they are applied to metal joints in automobiles and then thermoset and painted, for example, during a subsequent painting cycle. Thermosettable melt-flowable adhesive materials are described, for example, in WO 94/21,741.
Assemblies adhered by thermoset bonding tapes and joints sealed and covered by thermoset melt-sealing tapes are often characterized by desirable mechanical properties such as high values of overlap shear strength or high impact strength. It was, however, found that the 90° peel adhesion of thermoset bonding or melt-sealing tapes, respectively, of the prior art to various surfaces and, in particular, to primed or unprimed, optionally coated metal surfaces often is too low to meet all practical requirements. It was furthermore observed that painted, cured sealer tapes obtained, for example, when applying thermosettable melt-sealing tapes of the prior art to joints formed by primed or unprimed metal parts of automobile bodies with subsequent thermosetting and painting, often tend to exhibit an insufficient durability resulting in the formation of cracks in the painting layer of the melt-sealed area and, in particular, at the edges of the thermoset melt-sealing tape.
Therefore there was a need for improving the 90° peel adhesion of thermoset bonding or melt-sealing adhesive materials without adversely affecting other properties of the thermoset or of the corresponding thermosettable, respectively, adhesive material such as, for example, the 90° peel adhesion, the tensile strength or the overlap shear strength of the corresponding thermosettable adhesive material and the overlap shear strength or the thermal expansion coefficient of the thermoset adhesive to a degree which is unacceptable for various applications. There was furthermore a need for providing a thermosettable melt-sealing adhesive material which when applied to metal seams or joints of metal parts with subsequent thermosetting and painting, forms durable sealings which, in particular, do not exhibit cracks in the paint layer or at the edges of the melt sealing layer or exhibits such cracks only to a minor, practically acceptable degree. Other needs addressed and solved by the present invention, are evident from the detailed description of the invention below.
BRIEF DESCRIPTION OF THE INVENTION
The present invention refers to a thermosettable adhesive and, in particular, to a thermosettable pressure-sensitive adhesive comprising each a thermosettable polymer component, a thermoformable polymer component, an effective amount of a heat-activatable and/or photoactivatable curing system for curing the thermosettable polymer component, and from 0.5-20 wt. % with respect to the mass of the thermosettable adhesive of one or more hydroxides and/or hydroxyoxides of Al, Mg and/or Zr. Thermosettable adhesives comprising one or more hydroxides and/or hydroxyoxides of Al are especially preferred. The present invention also refers to thermosettable adhesive tapes comprising at least one layer of a thermosettable adhesive according to the invention wherein such layer exhibits at least one exposed surface and optionally comprises a backing, and to the use of the thermosettable adhesive and the thermosettable adhesive tapes for melt sealing or bonding applications.
More specifically, the present invention refers to a thermosettable adhesive and, in particular, to a thermosettable pressure-sensitive adhesive which each are obtainable by photopolymerization of a precursor comprising
(i) from about 25 to 60 wt. % of a photopolymerizable, optionally partly prepolymerized mixture comprising at least one acrylic acid ester of a non-tertiary alcohol, and at least one reinforcing, copolymerizable monomer,
(ii) from about 8 to 60 wt. % of one or more epoxy resins and/or epoxy monomers or oligomers containing no photopolymerizable groups,
(iii) from 0 to about 15 wt. % of one or more additional thermoformable polymers selected from the group comprising polyvinylacetate, poly(ethylene vinyl acetate), polyacetals, polyesters and/or poly(caprolactones),
(iv) from about 0.1 to 10 wt. % of a heat-activatable curing system for the epoxy component (ii),
(v) from about 0.005 to 3 wt. % of a photoinitiator for the acrylate component (i), and
(vi) from about 0.1 to 20 wt. % of one or more hydroxides and/or hydroxyoxides of Al, Mg and/or Zr
wherein all weight percentages refer to the mass of the thermosettable adhesive.
The present invention furthermore refers to a thermosettable adhesive and, in particular, to a thermosettable pressure-sensitive adhesive which are each obtainable by extrusion of a mixture comprising
(i) from about 2 to 80 wt. % of one or more polyesters,
(ii) from about 5 to 80 wt. % of one or more epoxy resins and/or epoxy monomers or oligomers,
(iii) from 0 to 15 wt. % of one or more additional thermoformable polymers selected from the group comprising polyacrylate, polyvinylacetate, poly(ethylene vinyl acetate), polyacetals and/or poly(caprolactones),
(iv) an effective amount of one or more heat-activatable and/or photoactivatable curing systems for the epoxy component (ii),
v) from about 0.1 to 20 wt. % of one or more hydroxides and/or hydroxyoxides of Al, Mg and/or Zr
wherein the onset temperature of the curing reaction of the epoxy component (ii) is higher than the extrusion temperature and wherein all weight percentages refer to the mass of the thermosettable adhesive layer.
DETAILED DESCRIPTION
Feichtmeier Georg
Willett Peggy S.
3M Innovative Properties Company
Knecht III Harold C.
McClendon Sanza L
Seidleck James J.
Szymanski Brian E.
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