Dispensing – With discharge assistant – Insertable cartridge or removable container
Reexamination Certificate
2001-03-19
2002-08-27
Jacyna, J. Casimer (Department: 3751)
Dispensing
With discharge assistant
Insertable cartridge or removable container
C222S001000, C222S391000
Reexamination Certificate
active
06439438
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to combinations, structures, devices, and methods for use in storing and applying heat softenable moisture curable materials such as adhesives, coatings or sealers.
BACKGROUND
Moisture curable adhesive materials (e.g., moisture curable urethane adhesives) are well known that are solid at room temperature, that can be heated to a flowable state for application, that after being applied between objects in their heated flowable state will adhere those objects together upon cooling, and that subsequent to solidifying will cure and build adhesive strength (i.e., adhesion to those objects and internal strength) by the absorption of atmospheric moisture. Such adhesive materials after being moisture cured can develop shear adhesion strength generally in the range of about 1000 pounds per square inch or about 690 newtons per square centimeter which is significantly greater than the range of shear adhesion strength of about 250 to 700 pounds per square inch or about 172 to 483 newtons per square centimeter that can be developed by conventional hot melt adhesives (i.e., hot melt adhesives are solid at room temperature, can be heated to a flowable state for application, after being applied between objects in their heated flowable state will adhere those objects together upon cooling, but have no means for developing significant further adhesive strength after cooling). While the adhesive strength of the moisture curable adhesive materials is not as high as that which can be developed using epoxy resins (i.e., epoxy resins can develop shear adhesion strengths in the range of about 2000 to 45000 pounds per square inch or 1379 to 3103 newtons per square centimeter), such moisture curable adhesive materials are more easily applied, require less clamping time before the material will solidify sufficiently to hold objects together, provide sufficient adhesive strength for use in many structural applications, and are less expensive than epoxy resins. Thus, there is significant commercial use of such moisture curable adhesive materials, particularly to join moisture vapor permeable materials (e.g., wood or plastic objects) together or to join one moisture vapor permeable material to another material that is not moisture vapor permeable (i.e., the moisture vapor permeable material or materials allow atmospheric moisture to enter and cure the adhesive material).
One problem with using moisture curable adhesive materials to join such objects is that they are typically applied using complex systems that are sealed against moisture, and the adhesive materials they apply must be heated to relatively high temperatures (e.g., 240 to 300 degrees Fahrenheit or 116 to 149 degrees Centigrade) before they will melt and can be applied. It takes a fairly long time (e.g., about 45 minutes) to initially bring the adhesive material in the system to the required application temperature, and maintaining the system at that temperature can normally only be justified if a fairly large amount of the adhesive material is to be applied over an extended period of time, such as to a series of objects moving along an assembly line. Thus, such moisture curable adhesive material application systems are impractical if only occasional applications of the adhesive material are required over an extended period of time.
DISCLOSURE OF THE INVENTION
The present invention provides a combination and method for storing and applying moisture curable materials (e.g., adhesives, coatings or sealers) that is inexpensive and practical for use even if only occasional applications of the moisture curable materials are required over an extended period of time.
This invention results from the recognition that moisture curable materials which, at about 140 to 230 degrees Fahrenheit or 60 to 110 degrees Centigrade, soften to a suitable flowable viscosity for application, can be stored in and applied from inexpensive container assemblies or syringes of polymeric materials that can withstand temperatures in that range and have sufficiently low surface energy that the moisture cured materials will not adhere well to them, even though, undesirably, those polymeric materials allow the passage of moisture vapor from the atmosphere. Even if moisture vapor transmission through the container assembly or syringe cures the material within it when the container assembly is exposed to the atmosphere, that cured material forms a bladder around uncured moisture curable material within the container assembly; and when the container assembly and material are heated into that range of about 140 to 230 degrees Fahrenheit or 60 to 110 degrees Centigrade that bladder will soften with the uncured material, will easily separate from the wall of the container assembly and collapse when pressure is applied to it because of the low surface energy of that wall, and will rupture under that pressure (or can be ruptured with an implement) so that the uncured material can be discharged from the container assembly.
The combination according to the present invention for use in storing and applying moisture curable materials comprises the container assembly or syringe including a tubular wall of moisture vapor transmissive polymeric material (e.g., material with a moisture vapor transmission (MVT) coefficient (cc-mil/100 square inch—24 hour—atm) of over 0.254 and up to at least 36), and a plunger or seal within the polymeric wall adjacent an inlet end of the wall that is adapted to move along the wall toward an outlet end of the wall in sealing engagement with an inner surface of the wall (e.g., a polypropylene or polyethylene syringe); and the moisture curable material within the chamber, which material is a solid at normal room temperature, will, when heated to a temperature in the range of about 140 to 230 degrees Fahrenheit or 60 to 110 degrees Centigrade, soften to a suitable flowable viscosity for application (e.g., a viscosity of less than 30,000 centipoise, preferably of less than 15,000 centipoise, and most preferably in the range of about 8,000 to 12,000 centipoise), and has little or no adhesion to the polymeric material in the tubular wall even when the material is moisture cured (e.g., the polymeric material in the tubular wall has a critical surface tension lower than about 35 dynes/centimeter). A removable layer or envelope of moisture impermeable material is provided entirely around the container assembly prior to its use. After (or possibly before) the container assembly is removed from the layer or envelope of moisture impermeable material it can be heated by various means to heat the moisture curable material within it to a suitable viscosity for application, after which various means can be used to drive the plunger along the wall toward its outlet end to discharge and apply the moisture curable material.
After the container assembly or syringe is removed from the layer or envelope of moisture impermeable material the moisture curable material within it will typically be useful for 3 to 4 days or more (i.e., that time may be extended if the moisture curable material is being used in a low humidity environment or if the container assembly or syringe is again sealed within the layer or envelope of moisture impermeable material between its uses to apply the moisture curable material). During the time that the container assembly or syringe is outside of the envelope and exposed to the atmosphere, atmospheric moisture vapor can pass through the walls of the container assembly or syringe, causing the moisture curable material to cure inwardly from its outer surface to form the bladder of the cured moisture curable material that will soften but will not melt upon heating. That bladder extends around a central core of uncured moisture curable material within the syringe that will still soften to a suitable viscosity for application when heated to a temperature in the range of about 140 to 230 degrees Fahrenheit or 60 to 110 degrees Centigrade. If the moisture curable material within the container assembly or syringe
Pearson Walter C.
Schouten Gerald P.
3M Innovative Properties Company
Huebsch William L.
Jacyna J. Casimer
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