Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2003-03-13
2004-10-12
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S127000, C525S128000, C525S131000
Reexamination Certificate
active
06803412
ABSTRACT:
BACKGROUND
The invention relates to moisture curable hot melt sealants.
Insulating glass assemblies such as insulating glass units and insulating sash assemblies often include a pair of glass sheets maintained in a fixed spaced relation to each other by a spacing and sealing structure that extends around the periphery of the inner facing surfaces of the glass sheets to define a sealed and insulating space between the glass sheets. In the case of insulating sash assemblies, the glass panes are adhered to a frame. The glass sheets are usually attached to the structure by a sealant or adhesive composition. The sealant or adhesive composition is also used to seal the edges of the insulating sash assembly so as to establish a barrier that prevents moisture from penetrating into the interior of the assembly. Insulating sash assemblies are described, e.g., in U.S. Pat. No. 6,286,288.
Sealant compositions are also used to bond an insulating glass assembly, e.g., an insulating glass unit, to a frame. This process is often referred to as “back bedding.” Back bedding is discussed in, e.g., U.S. Pat. Nos. 6,286,288 and 5,856,404 and incorporated herein. In the fabrication of door and window units back bedding sealants are often used to seal and bond panes of glass and insulating glass units to retain the pane or the unit in position within a frame, to provide a weather proof seal, to reinforce the structural strength of the assembly, or a combination thereof.
Variables that arise in bonding two substrates of different materials, such as bonding a glass substrate to a polymer substrate, include the different coefficients of thermal expansion and contraction associated with the two materials. The differences in these coefficients can cause stresses to be exerted on one or more of the substrates when the assembly experiences a change in temperature, which can torque polymer substrates and cause fractures in glass substrates.
Two common classes of sealants used in the insulating glass industry include chemically curing, thermoset compositions, and thermoplastic, one-part hot melt butyl-type compositions. Chemically curing systems often include liquid polysulphides, polyurethanes, mercaptan-modified polyether polyurethanes and silicones. Thermoplastic compositions, which are also referred to as “non-curing systems,” are often polyisobutylene-polyisoprene copolymer rubber-based hot melt compositions.
Chemical curing thermoset sealants are usually two-component systems in which the components are combined, at room temperature, just prior to application. The sealants have low initial green strength and require cure time prior to handling. The slow cure can increase manufacturing time and costs.
Non-curing hot melt systems generally set faster and can overcome the disadvantage of having a slow cure time, but hot melts are more susceptible to fluctuations in ambient temperature and may soften with high temperatures or stiffen with cold and do not develop as high ultimate bond strengths in comparison to curing systems. When insulating glass assemblies constructed with thermoplastic sealants are placed under load and temperature, the thermoplastic sealant may flow or deform to relieve the load. In addition, thermoplastic sealants are often applied at very high temperatures, e.g., in excess of 300° F.
Other sealant compositions that have been developed include a one part sealant that includes thermoplastic hot melt resin and an atmosphere curing resin capable of polymerizing upon exposure to ambient atmosphere.
SUMMARY
In one aspect, the invention features a moisture curable hot melt sealant composition that includes a polyurethane prepolymer having isocyanate functional groups, silane functional groups, or a combination thereof, a reactive plasticizer capable of reacting with at least one of the polyurethane prepolymer and itself, and thermoplastic polymer.
In one embodiment, the polyurethane prepolymer includes silane functional groups. In other embodiments the polyurethane prepolymer includes isocyanate functional groups.
In some embodiments, the composition includes from about 5% by weight to about 50% by weight the polyurethane prepolymer, from no greater than 20% by weight the reactive plasticizer, and from about 5% by weight to about 80% by weight the thermoplastic polymer. In other embodiments, the composition includes from about 10% by weight to about 40% by weight the polyurethane prepolymer, from about 2% by weight to about 15% by weight the reactive plasticizer, and from about 10% by weight to about 70% by weight the thermoplastic polymer. In another embodiment, the sealant includes from about 15% by weight to about 35% by weight the polyurethane prepolymer, from about 3% by weight to about 10% by weight the reactive plasticizer, and from about 15% by weight to about 60% by weight the thermoplastic polymer.
In one embodiment, the reactive plasticizer has a molecular weight of from about 300 g/mole to about 10,000 g/mole. In other embodiments, the reactive plasticizer has a molecular weight of from about 500 g/mole to about 6,000 g/mole.
In some embodiments, the polyurethane prepolymer includes the reaction product of polyester polyol, polyisocyanate; and monofunctional alcohol.
In one embodiment, the polyurethane prepolymer includes the reaction product of polyester polyol, polyisocyanate, monofunctional alcohol and hydrogen active organofunctional silane.
In some embodiments, the hydrogen active organofunctional silane includes amino-alkoxysilane, mercapto-alkoxysilane, or a combination thereof.
In another embodiment, the hydrogen active organofunctional silane includes N-methyl-3-amino-2-methylpropyltrimethoxysilane, N-ethyl-3-amino-2-methylpropyltrimethoxysilane, N-ethyl-3-amino-2-methylpropyldiethoxysilane, N-ethyl-3-amino-2-methylpropyltriethoxysilane, N-ethyl-3-amino-2-methylpropylmethyldimethoxysilane, N-butyl-3-amino-2-methylpropyltrimethoxysilane, 3-(N-methyl-3-amino-1-methyl-1-ethoxy)propyltrimethoxysilane, N-ethyl-4-amino-3,3-dimethylbutyidimethoxymethylsilane, N-ethyl-4-amino-3,3-dimethylbutyltrimethoxysilane, bis-(3-trimethoxysilyl-2-methylpropyl)amine, N-(3′-trimethoxysilylpropyl)-3-amino-2-methylpropyltrimethoxysilane, N-(n-butyl)aminopropyltrimethoxysilane, or a combination thereof.
In one embodiment, the monofunctional alcohol has from 12 to 20 carbon atoms.
In some embodiments, the reactive plasticizer includes silyl-terminated polyether. In other embodiments, the reactive plasticizer includes alkoxysilyl reactive groups. In another embodiment, the reactive plasticizer is selected from the group consisting of aldimines, ketimines, oxazolidines, dioxolanes, and combinations thereof.
In another embodiment, the composition exhibits an initial lap shear of at least 10 psi. In some embodiments, the composition exhibits an open time of at least 60 seconds. In other embodiments, the composition exhibits a softening temperature of no greater than 50° C.
In another embodiment, the sealant composition has a glass transition temperature of less than −5° C. In one embodiment, the sealant composition has a glass transition temperature of less than −25° C. In some embodiments, the composition exhibits a viscosity of from about 150,000 centipoise to about 400,000 centipoise at 230° F. In other embodiments, the composition exhibits a lap shear of at least 80 psi after three weeks at 23° C. and 50% relative humidity.
In other embodiments, the composition, after cure, exhibits an elongation of at least 200%.
In one embodiment, the composition, after cure, exhibits a tensile strength of at least 100 psi. In some embodiments, the composition, after cure, exhibits a modulus at 100% elongation of no greater than 300 psi. In another embodiment, the composition, when in the form of a cured 60 mil film, exhibits a moisture vapor transmission rate no greater than 10 g/m
2
/day.
In other embodiments, the composition further includes at least one of tackifying agent, non-reactive plasticizer and silane adhesion promoter.
In some embodiments, the thermoplastic polymer includes ethy
Acevedo Margarita
Nguyen-Misra Mai T.
Gorr Rachel
H.B. Fuller Licensing & Financing Inc.
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