Combination for storing and applying heat softenable moisture curable materials

Abstract

A combination for use in storing and applying moisture curable materials which includes (1) a container assembly with a tubular wall of moisture vapor transmissive polymeric material having an inner surface defining a chamber and a plunger within the tubular wall adapted to move along the wall toward an outlet end in sealing engagement with an inner surface of the wall; (2) a moisture curable material within the chamber which is solid at normal room temperature, is softenable to a suitable viscosity for application of less than 30,000 centipoise when heated to a temperature in the range of about 140 to 230 degrees Fahrenheit or 60 to 110 degrees Centigrade, and has little adhesion to the wall, even when said adhesive is moisture cured; and (3) an envelope of moisture impermeable material around the container assembly.

Description

FIELD OF THE INVENTION[0001] 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[0002] 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 t...

AI Technical Summary

Benefits of technology

[0004] 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.

[0009] The tubular wall of moisture vapor transmissive polymeric material can be of a polyolefin material such as polyethylene or polypropylene which are readily available, relatively inexpensive, and have low surface energy or critical surface tension (i.e., it appears that the critical surface tension should be lower than about 35 dynes / centimeter which is the critical surface tension of ABS to which the moisture curable materials listed above will adhere quite strongly when moisture cured, but can be about 31 dynes / centimeter which is the critical surface tension of polyethylene, or about 29 dynes / centimeter which is the critical surface tension of polypropylene, to either of which those moisture curable materials have little adhesion when moisture cured). Polyethylene or polypropylene have relatively low Heat Deflection Temperatures under pressure which are reported in the Materials Selection chapter of Machine Design magazine's "Basics of Design Engineering", June, 1994, the content whereof is hereby incorporated herein by reference. (e.g., under 64 pounds per square inch or 4.5 kilograms per square centimeter pressure the Heat Deflection Temperature (HDT) for medium density polyethylene is about 120 to 165 degrees Fahrenheit or 49 to 74 degrees Centigrade, the Heat Deflection Temperature for high density polyethylene is about 140 to 190 degrees Fahrenheit or 60 to 88 degrees Centigrade, and the Heat Deflection Temperature for unmodified polypropylene is about 200 to 250 degrees Fahrenheit or 93 to 121 degrees Centigrade). Such materials, however, can be suitable for use with the type of moisture curable material described above which softens 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, and preferably in the range of about 180 to 190 degrees Fahrenheit or 82 to 88 degrees Centigrade. Syringes molded of these materials having various capacities (e.g., 32 cubic centimeters) and which have at the outlet ends of their walls a transverse end wall from the center of which projects a outlet nozzle are readily commercially available (e.g., from Plas-Pak Industries, Inc., Norwich, Conn.). Such a syringe filled with the moisture curable material that is sealed within the removable envelope of moisture impermeable material can be stored for a long period of time (e.g., over 6 months at 90 degrees Fahrenheit or 32 degrees Centigrade and 90 percent relative humidity).

[0010] The means for receiving the container assembly after it is removed from the envelope of moisture impermeable material and for heating the moisture curable material in it to a suitable viscosity for application can be an electrically heated cylindrical chamber adapted to closely receive the tubular wall of the container assembly. The container assembly can either be inserted into that chamber for a time sufficient to soften the moisture curable material and then removed from the chamber while the heated moisture curable material is applied, which facilitates manipulation of the container assembly or syringe during application of the moisture curable material; or the container assembly can remain in the heated chamber during application of the moisture curable material from an end portion of container assembly projecting from the chamber which insures that the moisture curable material will remain at the temperature needed for application over an extended period of time. If the container assembly remains in the heated chamber during application of the moisture curable material, that chamber can either be mounted at a fixed location, or can be moved with the container to a location at which the moisture curable material is to be applied. As an alternative to use of such a heated chamber, the container assembly can be heated by other means, such as by immersing the container assembly in boiling water, by the use of an oven, or otherwise.

Problems solved by technology

With longer exposure to atmospheric moisture (e.g., over 4 days) the bladder of moisture cured material can have thickened sufficiently that it will be very difficult to rupture, however, the bladder becomes self sealing against further moisture penetration when it reaches a thickness of about 1 / 8 inch (0.32 cm), thereby for a long time protecting a central core of the uncured moisture curable material that still can be heated and removed with significant difficulty such as the use of an awl or punch to rupture the bladder through the outlet end of the container assembly or syringe, after which the bladder when heated will still be soft, collapsible and separable from the tubular wall so that the uncured moisture curable material in the container assembly or syringe can be expelled.

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