WO2006074084A1

WO2006074084A1 - Container assembly

Info

Publication number: WO2006074084A1
Application number: PCT/US2005/047453
Authority: WO
Inventors: Kevin D. Foust; Daniel T. Scott; Rodolfo M. Cordova
Original assignee: 3M Innovative Properties Company
Priority date: 2004-12-30
Filing date: 2005-12-22
Publication date: 2006-07-13
Also published as: EP1838597B1; EP1838597A1; ATE497917T1; JP2008526627A; US20060144726A1; DE602005026330D1; US20070228072A1

Abstract

A container assembly for retaining a moisture-sensitive material has a selectively resealable outer container (12) defining a chamber, where a bond portion (16) of an inner surface of the outer container is formed of ultrasonically weldable material. The container assembly also has an inner container (14) having a humidity-control substance, where the inner container is disposed within the chamber. The humidity-control substance is in humidity transferable communication with the chamber. A bond portion (16) of an outer surface of the inner container is formed of ultrasonically weldable material. The bond portions of the outer and inner containers are ultrasonically welded to each other to fix the position of the inner container within the chamber of the outer container.

Description

CONTAINER ASSEMBLY

BACKGROUND OF THE INVENTION

The present invention relates to a container assembly for retaining a moisture- sensitive material. More specifically, the present invention relates to a container assembly having an outer container and an inner container, where the inner container has a humidity- control substance and is ultrasonically welded to the outer container.

Moisture-sensitive materials, such as pharmaceuticals, are often stored in hermetically and waterproof resealable containers. When opened for access to those materials, however, there may be an exchange of moisture between the air inside the container and the air outside the container. This may affect the properties of the moisture-sensitive material stored in the container. The quality of moisture-sensitive material may be affected if the moisture level (which may be measured in terms of "relative humidity") of the air inside the container falls below or rises above a desired level. For this and other reasons, many containers for moisture-sensitive materials contain a humidity-control substance to control the moisture in the container. The humidity-control substance may be any material that adsorbs moisture from the air and/or any hygroscopic ("water-pulling") material that promotes retention of moisture, such as, but not limited to, bentonite clay, silica gel, montmorillonite clay, molecular sieve, calcium oxide, calcium sulfate, glycerol, sorbitol, sodium PCA, or propylene glycol. The humidity-control substance may be used to help the moisture-sensitive material maintain its moisture content by either adding or subtracting moisture to the air inside the container. When the humidity-control substance subtracts moisture from the air inside the container, it acts as a desiccant; when the humidity-control substance adds moisture to the air inside the container, it acts as a humectant. The humidity-control substance may help keep the moisture-sensitive material fresher, and may also extend a shelf-life of the moisture-sensitive material, even if the container is opened and closed numerous times.

The humidity-control substance is often packaged in a container ("inner container" or "canister") that has holes in it or a membrane designed to allow moisture into or out of the inner container and keep the humidity-control substance (often in particle form) from leaking out of the inner container. The inner container may also contain a material aimed at controlling odors, such as, but not limited to, activated carbon. The inner container may be formed of a rigid or non-rigid material. The inner container is usually placed inside a chamber of the outer container, in order for the humidity-control substance to be in humidity transferable communication with the chamber (and hence, the moisture-sensitive materials stored therein). Typically, the inner container is not secured inside the moisture-sensitive material container ("outer container"). This may cause problems because a consumer may be able to easily, deliberately, or unintentionally remove the inner container from the outer container, which may then affect the quality of the moisture-sensitive material remaining in the chamber of the outer container. The inner container may also interfere with dispensing of the moisture-sensitive material from the outer container, such as by blocking an opening of the outer container.

Some existing container assemblies fix the position of the inner container within the chamber of the outer container to address the aforementioned problems. However, other problems may arise with the existing methods of securing the inner container inside of the outer container. For example, the securing method may create additional steps and concerns during the assembly process, such as managing the purchasing and stocking of additional materials on a regular basis. If a conventional glue or adhesive is used to fix the position of the inner container within the outer container, it has been known that new problems may be introduced into the assembling process, such as adding to the total assembling time due to additional set-times and clean up requirements, as well as new process control and robustness issues. It has also been known that using a glue or adhesive may release material or fumes into the chamber of the outer container (known as "out- gassing"), which may adversely affect the quality of the moisture-sensitive material contained in the chamber of the outer container. Another problem with existing methods of fixing the position of the inner container within the chamber of the outer container is that some container materials, such as high density polypropylene, may resist glue or adhesive application. This may be troublesome if an inner container manufacturer only manufactures its containers from a material that resists adhesives or glues.

SUMMARY OF THE INVENTION In one aspect, the present invention is a container assembly for retaining a moisture-sensitive material, the container assembly including a selectively resealable outer container defining a chamber therein and an inner container including a humidity-control substance. The inner container is disposed within the chamber of the outer container and has the humidity-control substance in humidity transferable communication with the chamber. A bond portion of an inner surface of the outer container is formed of ultrasonically weldable material and a bond portion of an outer surface of the inner container is formed of ultrasonically weldable material. The bond portions of the outer and inner containers are ultrasonically welded to each other to fix the position of the inner container within the chamber of the outer container.

In another aspect, the present invention is a method of forming a container assembly for retaining a moisture-sensitive material therein. The method includes providing a selectively resealable outer container which has a chamber therein, wherein a bond portion of an inner surface of the outer container is formed of ultrasonically weldable material, providing an inner container comprising a humidity-control substance, wherein a bond portion of an outer surface of the inner container is formed of ultrasonically weldable material, disposing the inner container within the chamber of the outer container, wherein the humidity-control substance is in humidity-transferable communication with the chamber, and ultrasonically welding the bond portions of the outer and inner containers to each other to fix the position of the inner container within the chamber of the outer container.

The present invention will be further explained with reference to the drawing figures listed below, where like structure is referenced by like numerals throughout the several views.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. IA is a perspective view of a first exemplary embodiment of a container assembly in accordance with the present invention.

FIG. IB is a side view of the container assembly of FIG. IA, where the chamber of the outer container contains a plurality of dental material composition capsules. FIG. 2A is a perspective view of a second exemplary embodiment of a container assembly in accordance with the present invention. FIG. 2B is a side view of the container assembly of FIG. 2A, where the chamber of the outer container is partially filled with a powder material, and the cap of FIG. 2A has been replaced with a cap having a flip top.

FIG.3 illustrates a method of forming a container assembly in accordance with 5 the present invention, with the outer container shown in section.

DETAILED DESCRIPTION o The present invention is a container assembly having an outer container and an inner container, where the inner container has a humidity-control substance and is fixed within a chamber of the outer container by an ultrasonic bond. As discussed above, if an inner container is not secured inside a chamber of an outer container, a consumer may be able to easily, deliberately, or unintentionally remove the inner container from the outer container, 5 which may than affect the quality of a moisture-sensitive material contained in the chamber of the outer container. The inner container may also interfere with dispensing of the moisture- sensitive material from the outer container. The present invention recognizes the need for fixing a position of an inner container within a chamber of an outer container that does not require the use of glues or adhesives. 0 The present invention utilizes ultrasonic welding (also known as ultrasonic bonding) to fix a position of an inner container having a humidity-control substance (e.g., canister 14 of FIG. IA) within a chamber (e.g. chamber 13 of FIG. IA) of an outer container (e.g., outer container 12 of FIG. IA). Ultrasonic welding utilizes high frequency vibrations to bond two materials together. Unlike the use of glues and adhesives, the ultrasonic welding 5 process produces little or no waste or hazardous out-gassing. That is, the welded components (e.g., outer container 12 and canister 14) are not hazardous and the welding process will not affect the quality of the moisture-sensitive material stored in the container assembly. The present invention allows an outer container and an inner container that are formed of materials that may resist adhesives and glues to be readily welded together. o Ultrasonic welding times are also shorter than the set-times necessary for most glues and adhesives. Current ultrasonic welding times are in a range of 0.250 milliseconds. That is, a foil weld strength is realized after about 0.250 milliseconds using current ultrasonic welding methods. As a result of a shorter ultrasonic welding time, the additional step of fixing an inner container within a chamber of an outer container does not introduce an overly burdensome amount of additional time to a container assembly assembling process.

FIG. IA is a perspective view of a first exemplary embodiment of a container assembly in accordance with the present invention. Container assembly 10 is formed of outer container 12, canister 14, and cap 15. Container assembly 10 may be used for storing a moisture-sensitive material, such as a pharmaceutical product or one or more capsules containing a dental material composition. More particularly, the moisture-sensitive material may be stored in chamber 13, which is defined by cap 15 and the bottom and side walls of outer container 12. Outer container 12 and canister 14 may be formed of any material that can be ultrasonically welded, such as, but not limited to, a polypropylene, high density polypropylene, low density polypropylene, or polyethylene terephthalate. The material forming outer container 12 and/or canister 14 may also be transparent (as shown for outer container 12 in FIGS. IA and IB). Outer container 12 and canister 14 do not necessarily have to be formed of the same material, so long as they can be welded together ultrasonically. Furthermore, only the portions of outer container 12 and canister 14 that are to be welded together need to be formed of a material that can be ultrasonically welded (although the entire outer container 12 and canister 14 may be formed of the ultrasonically weldable material). The portions of outer container 12 and canister 14 that are to be welded together may be called the "bond portions", where the bond portions may constitute a portion of an inner surface of outer container 12 and a portion of an outer surface of canister 14.

A humidity-control substance may be stored in canister 14. Canister 14 may also be known as an "inner container". Canister 14 may contain any humidity-control substance, including, but not limited to bentonite clay, silica gel, montmorillonite clay, molecular sieve, calcium oxide, calcium sulfate, glycerol, sorbitol, sodium PCA, or propylene glycol. Canister 14 may also contain a material aimed at controlling odors, such as, but not limited to, activated carbon. As discussed above, the humidity-control substance may be used to control the humidity inside chamber 13 by adsorbing excess moisture from the air in the container when the moisture level inside chamber 13 exceeds a desired level and/or promoting the retention of moisture inside chamber 13 by adding moisture to the air inside chamber 13 as the moisture level inside chamber 13 falls below a desired level. The air inside chamber 13 may be set at a desired moisture level at the time the moisture-sensitive material is deposited inside chamber 13. As container assembly 10 is used, the moisture level inside chamber 13 may change, depending upon many factors, including how many times outer container 12 is opened and closed, the amount of moisture that leaks through a joint defined by cap 15 and outer container 12, and the humidity level of the air outside of outer container 12. Even before container assembly 10 is opened by a consumer, moisture may affect the moisture-sensitive material. For example, if a seal is formed under cap 15 (such as a foil layer) or over cap 15 after moisture-sensitive material is "bottled" inside outer container 12 (where the seal is to be broken or removed by the consumer when container assembly 10 reaches the consumer), some moisture may still leak through the seal.

In general, if the humidity level of the air surrounding outer container 12 is not the same as the humidity level inside chamber 13, moisture may transfer between chamber 13 and the surrounding air. Not only may moisture transfer through possible leaks in the joint between cap 15 and outer container 12, but moisture may also transfer when cap 15 is opened (through self-sealing flip-top 18 or otherwise), which may cause the moisture level inside chamber 13 to exceed a desired level. An increased moisture level may compromise the quality of the moisture-sensitive material contained in chamber 13. The humidity-control substance inside canister 14 may be used to address an excess moisture problem by acting as a desiccant and adsorbing some or all of the excess moisture. That is, if the moisture level in chamber 13 of outer container 12 exceeds a certain level, the humidity-control substance will adsorb at least some of the excess moisture.

The amount of moisture the humidity-control substance may adsorb depends upon many factors, including the type of humidity-control substance selected, the quantity of humidity-control substance used, the adsorption rate of the humidity-control substance, and the moisture content of the humidity-control substance. The type and quantity of the humidity-control substance used may be modified to modify the amount of moisture the humidity-control substance adsorbs in order to maintain the desired moisture level inside chamber 13. Those skilled in the art can modify such variables to maintain the desired moisture level. If the moisture level inside chamber 13 falls below a desired level, the quality of the moisture-sensitive material contained in chamber 13 maybe compromised. By acting as a humectant, the humidity-control substance may release moisture into chamber 13 to address the lower-than-desired moisture level. That is, if the moisture level in chamber 13 drops below a certain level, the humidity-control substance will release moisture into chamber 13 of outer container 12 until the desired level is reached, or until at least a moisture level closer to the desired level is reached. The amount of moisture the humidity-control substance may release depends upon many factors, including the type of humidity-control substance selected, the quantity of humidity-control substance used, and the moisture content of the humidity-control substance. Those skilled in the art can modify such variables to maintain the desired moisture level. As discussed above, the moisture level inside chamber 13 may change as container assembly 10 is used. If the air outside outer container 12 is more humid than the moisture level inside chamber 13, the moisture level inside chamber 13 may increase when cap 15 is opened (through flip-top 18 or otherwise) or through any leakage in the joint formed by cap 15 and outer container 12, which may cause the moisture level inside chamber 13 to exceed a desired level. If the moisture level of the air outside outer container 12 is lower than the moisture level of the air inside chamber 13, the moisture level inside chamber 13 may fall below a desired level. An increased or decreased moisture level may compromise the quality of the moisture-sensitive material contained in chamber 13. The humidity-control substance may be used to address an excess or insufficient moisture problem by giving up moisture to a drier atmosphere and absorbing moisture from a humid atmosphere. In this way, the humidity-control substance may be used to help the moisture-sensitive material retain its moisture as well as help maintain a desired moisture level in chamber 13.

A plurality of openings 17 in canister 14 provides a channel for humidity transferable communication between the humidity-control substance and chamber 13. That is, openings 17 allow the humidity-control substance to either extract or input moisture into chamber 13 of outer container 12, depending upon the type of humidity-control substance being used and depending upon the difference between the actual and desired moisture level of chamber 13 of outer container 12. Openings 17 may be shaped such that the humidity- control substance does not leak from canister 14, or another mechanism may be provided to prevent such leakage, such as a permeable membrane. It may be important to keep substantially all of the humidity-control substance sealed in canister 14, because if the substance contacts the moisture-sensitive material, such contact may adversely affect the quality of the moisture-sensitive material. The humidity-control substance contained in canister 14 helps to keep the moisture-sensitive material fresher and may also extend a shelf- life of the moisture-sensitive material, even if outer container 12 is opened and closed numerous times. The humidity-control substance should be designed to maintain the atmosphere inside chamber 13 of outer container 12 at the desired moisture level for as long as container assembly 10 is reasonably expected to be used to store the moisture-sensitive material.

Although canister 14 is shown to be a cylindrical shape, canister 14 may be any shape and/or size that minimizes interference with the transfer of the moisture-sensitive material into or out of chamber 13 of outer container 12. Furthermore, canister 14 may be formed of any rigid or non-rigid material that may be ultrasonically welded. For example, canister 14 may be formed in a pillow-shaped pouch, where the pouch is formed of a flexible material that may be ultrasonically welded. Canister 14 is ultrasonically welded to outer container 12 at weld joint 16, such that aposition of canister 14 is fixed within chamber 13 of outer container 12. In the embodiment shown in FIG. IA, weld joint 16 is where an interior, bottom wall of outer container 12 and an outer, bottom surface of canister 14 contact one another. Although FIG. IA shows canister 14 fixed at a center of the bottom wall of outer container 12, canister 14 may be fixed anywhere along the inner, bottom wall of outer container 12. Canister 14 may also be fixed to a side wall of outer container 12. The entire bottom surface of canister 14 does not necessarily have to be welded to outer container 12. Weld joint 16 only needs to be strong enough to hold canister 14 in place and strong enough to withstand the force exerted on canister 14 during use of container assembly 10. For example, if container assembly 10 is used for holding pharmaceutical pills for use by a consumer, the weld joint should be strong enough to withstand the force of a consumer handling outer container 12 to extract a pill. That is, canister 14 should not become unsecured if a consumer aggressively shakes outer container 12. Weld joint 16 should also be strong enough to hold canister 14 in its fixed position during shipping and other handling of container assembly 10. Any method of ultrasonic welding known in the art may be used to weld canister 14 to outer container 12. If canister 14 is formed of more than one part (e.g., a top portion and a bottom portion that fit together), canister 14 may be ultrasonically welded shut in addition to being ultrasonically welded to outer container 12. If canister 14 is ultrasonically welded shut, it will decrease the likelihood of canister 14 breaking open and releasing the humidity-control substance into chamber 13 of outer container 12. As discussed earlier, it may be important to keep substantially all of the humidity-control substance sealed in canister 14 because if the humidity-control substance contacts the moisture-sensitive material, the quality of the moisture-sensitive material may be affected.

Cap 15 provides a selectively resealable opening for access to chamber 13. Cap 15 may be foπned of any material that does not react with the moisture-sensitive contents of chamber 13, such as, but not limited to, a plastic material or a glass material. Cap 15 does not necessarily have to be foπned of the same material as outer container 12, nor does cap 15 need to be formed of a material that can be ultrasonically welded. In one embodiment, cap 15 has a flip top 18 that is connected to main body 20 of cap 15 by flexible connection 19. Flexible connection 19 may be any connection that allows flip-top 18 to be opened and closed a plurality of times without breaking, such as, but not limited to, a living hinge. Flip top 18 allows outer container 12 to be selectively resealed once it has been opened. When flip top 18 is lifted (as shown in FIG. IA), opening 21 is exposed, and a consumer may extract the moisture-sensitive material contained in chamber 13 of outer container 12 through opening 21. Flip-top 18 allows a user to easily access the contents of outer container 12 without removing cap 15. Cap 15 may be attached to outer container 12 by any method known in the art. For example, cap 15 may be "popped" onto outer container 12 by an interference friction fit, or cap 15 may be a twist-on cap. Although FIG. IA shows container assembly 10 having cap 15 with flip top 18, cap 15 may be any resealable mechanism. For example, cap 15 may just twist on without having a flip-top. However, a flip-top arrangement reduces the possibility of a consumer losing cap 15 because cap 15 does not have to be removed iri order to access the contents of outer container 12. Cap 15 may also be shaped to cover opening 21 by an interference friction fit with portions of outer container 12 adjacent opening 21, rather than by opening via a friction fitting within cap 15 itself, as shown in FIG. IA.

FIG. IB is a side view of container assembly 10 of FIG. IA, where chamber 13 of outer container 12 contains a plurality of dental material composition capsules 22. FIG. IB is used to illustrate how container assembly 10 may be used to store dental material composition capsules 22. An example of a dental material composition capsule that may be stored in outer container 12 is a 3M ESPE Z 100 Restorative, available from 3M Company, St. Paul, Minnesota.

FIG. 2A is a perspective view of a second exemplary embodiment of a container assembly in accordance with the present invention. Container assembly 30 is formed of outer container 32, inner container 34, and cap 36 (shown closed). Outer container 32 defines chamber 33, which may be used to store a moisture-sensitive material. Inner container 34 may be used to store a humidity-control substance. Inner container 34 serves a similar function as canister 14 in FIG. IA, but is shown in FIG. 2A to have a different shape. Inner container 34 is also fixed in a different position than canister 14 of FIG. IA. Once again, inner container 34 may be formed in any shape and/or size that minimizes interference with the transfer of the moisture-sensitive material into or out of chamber 33 of outer container 32, such as a cylindrical or pillow shape. Furthermore, inner container 34 may be formed of any rigid or non-rigid material that may be ultrasonically welded. Outer container 32 and inner container 34 may be formed of any material that can be ultrasonically welded, such as, but not limited to, a polypropylene, high density polypropylene, low density polypropylene, or polyethylene terephthalate. The material forming outer container 32 and/or inner container 34 may also be transparent (as shown for outer container 32 in FIGS. 2 A and 2B). Outer container 32 and inner container 34 do not necessarily have to be formed of the same material, so long as they can be welded together ultrasonically. Furthermore, only the bond portions of outer container 32 and inner container 34 that are to be welded together need to be formed of a material that can be ultrasonically welded (although the entire outer container 32 and inner container 34 may be formed of the ultrasonically weldable material). Inner container 34 is ultrasonically welded to outer container 32 at weld joint

38. Weld joint 38 is where an interior, side wall of outer container 32 and an exterior, side surface of inner container 34 contact one another. However, the entire side surface of inner container 34 does not need to contact outer container 32. A sufficiently strong weld joint 38 may be achieved by welding less than the full contact area. As discussed above in reference to weld joint 16 of FIG. IA, weld joint 38 should be strong enough to hold inner container 34 in place during use of container assembly 30, as well as during shipping and related handling of container assembly 30. Once again, inner container 34 maybe ultrasonically welded closed in order to help prevent the humidity-control substance contained therein from leaking into chamber 33 of outer container 32.

A plurality of openings 39 in inner container 34 provides a channel for humidity transferable communication between the humidity-control substance contained in inner container 34 and chamber 33. Openings 39 may be shaped such that the humidity- control substance does not leak from inner container 34, or another mechanism may be provided to prevent such leakage, such as, but not limited to, a permeable membrane. Just as in FIG. IA, the humidity-control substance contained in inner container 34 helps the moisture- sensitive material maintain its quality and freshness, and may also extend a shelf-life of the moisture-sensitive material, even if cap 36 is opened and closed numerous times. The humidity-control substance should be designed to maintain the air inside chamber 33 of outer container 32 at the desired moisture level for as long as container assembly 30 is reasonably expected to be used to store the moisture-sensitive material. Inner container 34 may also contain a material aimed at controlling odors, such as, but not limited to, activated carbon.

The configuration of container assembly 30 shown in FIG. 2A may be used to store a moisture-sensitive material in powder form, such as a dental material composition, in addition to the pharmaceuticals or dental material composition capsules discussed in reference to FIG. IA. Inner container 34 may have to be fixed in a location other than the bottom surface of outer container 32 when a powder is being stored in chamber 33 in order for the humidity-control substance to work properly. When a powder is stored in chamber 33 of outer container 32, the powder may contain little or no air pockets and so, if inner container 34 were located at the bottom of chamber 33 of outer container 32 (e.g., in the configuration shown in FIG. IA), inner container 34 may not be in humidity transferable communication with the powder because openings 39 may be blocked. In that situation, regulating the moisture level of the air inside chamber 33 would be difficult. The configuration of FIG. 2A allows the humidity-control substance contained in inner container 34 to remain in humidity-transferable communication with a powder because, as long as the powder does not fill outer container 32 to its brim, at least some of openings 39 should be exposed above the powder. Cap 36 may be formed of any material that does not react with the contents of chamber 33, such as, but not limited to, a plastic or a glass material. Cap 36 does not necessarily have to be formed of the same material as outer container 32, nor does cap 36 need to be formed of a material that can be ultrasonically welded. Although FIG.2A shows cap 36 without a flip top (such as flip top 18 shown in FIG. IA), cap 36 may have a flip top or any other type of top known in the art. FIG.2B is a side view of container assembly 30 of FIG.2A, where chamber 33 of outer container 32 is partially filled with powder material 40, and cap 36 has been replaced with cap 42 having flip top 44 connected to a main body 43 of cap 42 by flexible connection 46. Flexible connection 46 may be any connection that allows flip top 44 to be opened and closed a plurality of times without breaking, such as, but not limited to, a living hinge. Flip top 44 defines opening 48 into chamber 33 of outer container 32, thereby allowing extraction of powder material 40 from chamber 33. As FIG. 2B shows, inner container 34 is exposed both above and below powder material 40. This positioning of inner container 34 allows the humidity-control substance contained in inner container 34 to be in humidity transferable communication with the air inside chamber 33. If inner container 34 were fixed in outer container 32 such that inner container 34 was completely immersed by powder 40, the humidity-control substance contained in inner container 34 may not be able to maintained the desired moisture level of the air in chamber 33 because all openings 39 (not shown) would be blocked and the humidity-control substance would not be in humidity transferable communication with the air inside chamber 33. Although all openings 39 of inner container 34 do not necessarily have to be completely uncovered, some openings 39 should be exposed to chamber 33 in order for the humidity-control substance in inner container 34 to be in humidity transferable communication with the air in chamber 33.

FIG. 3 illustrates a method of forming a container assembly in accordance with the present invention. FIG. 3 is a side view of the container assembly, where outer container 52 is shown in section. FIG. 3 shows fixture 50, outer container 52, chamber 53, inner container 54, and ultrasonic horn 56. Inner container 54 is aligned on fixture 50 such that a bond portion of inner container 54 is exposed. A bond portion of outer container 52 is then placed into contact with the exposed bond portion of inner container 54, such that a portion of fixture 50 and inner container 54 are disposed inside chamber 53. The bond portions of inner container 54 and outer container 52 contact one another at weld joint 58, where weld joint 58 is the location that inner container 54 is to be fixed within chamber 53 of outer container 52. Inner container 54 contains a humidity-control substance, which is in humidity-transferable communication with chamber 53.

During ultrasonic welding, a strong frictional heat is generated at the portions of the objects that are to be welded together by simultaneously applying pressure and ultrasonic vibration to melt and weld these portions. Thus, ultrasonic welding requires pressure to be applied to the objects being welded together. Fixture 50 and opposed ultrasonic horn 56 are urged together to apply pressure to outer container 52 and inner container 54, such that outer container 52 and inner container 54 are pressed together at weld joint 58. As the desired amount of pressure is applied, ultrasonic horn 56 is then activated to vibrate at a high frequency to melt and weld the bond portions of inner container 54 and outer container 52 that are in contact with one another at weld joint 58. The area of ultrasonic horn 56 that is contacting outer container 52 should be substantially the same as the area of inner container 54 contacting outer container 52.

Outer container 52 and inner container 54 should be ultrasonically welded in a controlled environment to maintain a desired moisture equilibrium level within chamber 53 of outer container 52. The desired moisture equilibrium level of chamber 53 should be selected as a function of the moisture-sensitive material to be stored in chamber 53 of outer container 52. If the humidity-control substance contained in inner container 54 is moisturized (either before or after the ultrasonic welding process), the welding environment should be sufficiently humidified so that the humidity-control substance does not lose some or all of its moisture to the welding environment. If the humidity-control substance is dried (either before or after the ultrasonic welding process), the welding environment should be sufficiently dry so that the humidity-control substance does not saturate with the moisture from the welding environment before the moisture-sensitive material that is to be stored in the container assembly is inserted into chamber 53 of outer container 52.

After inner container 54 is fixed within outer container 52 using a ultrasonic welding method, the moisture-sensitive material may be inserted in outer container 52, and then a cap may be placed on outer container 52. The cap should also be placed on the outer container 52 in a controlled environment and sealed thereon to preserve the desired environmental conditions within chamber 53.

Claims

CLAIMS:

1. A container assembly for retaining a moisture-sensitive material therein, the container assembly comprising: a selectively resealable outer container defining a chamber therein, wherein a bond portion of an inner surface of the outer container is formed of ultrasonically weldable material; and an inner container comprising a humidity-control substance, wherein the inner container is disposed within the chamber of the outer container and has the humidity-control substance in humidity transferable communication with the chamber, wherein a bond portion of an outer surface of the inner container is formed of ultrasonically weldable material, and wherein the bond portions of the outer and inner containers are ultrasonically welded to each other to fix the position of the inner container within the chamber of the outer container.

2. The container assembly of claim 1 wherein the bond portion of the inner surface of the outer container is disposed on a bottom wall of the outer container.

3. The container assembly of claim 1 wherein the bond portion of the inner surface of the outer container is disposed on a side wall of the outer container.

4. The container assembly of claim 1 wherein the inner container is shaped to minimize interference with the transfer of moisture-sensitive material into or out of the chamber.

5. The container assembly of claim 1 wherein the outer container has a single opening for access to the chamber therein, and wherein the outer container has a cap for resealably covering the opening.

6. The container assembly of claim 5 wherein the cap is flexibly attached to the outer container.

7. The container assembly of claim 5 wherein the cap is shaped to sealably cover the opening by an interference friction fit with portions of outer container adjacent the opening.

8. The container assembly of claim 1 wherein the ultrasonically weldable materials of the outer and inner containers comprise polymers.

9. A method of forming a container assembly for retaining a moisture-sensitive material therein, the method comprising: providing a selectively resealable outer container which has a chamber therein, wherein a bond portion of an inner surface of the outer container is formed of ultrasonically weldable material; providing an inner container comprising a humidity-control substance, wherein a bond portion of an outer surface of the inner container is formed of ultrasonically weldable material; disposing the inner container within the chamber of the outer container, wherein the humidity-control substance is in humidity-transferable communication with the chamber; and ultrasonically welding the bond portions of the outer and inner containers to each other to fix the position of the inner container within the chamber of the outer container.

10. The method of claim 9, and further comprising: selecting a desired moisture equilibrium level for the humidity-control substance, as a function of the moisture-sensitive material to be stored in the chamber of the outer container; and placing the humidity-control substance at the desired moisture equilibrium level.

11. The method of claim 10, and further comprising: introducing the moisture-sensitive material into the chamber of the outer container while the humidity-control substance is at the desired moisture equilibrium level; and sealing the outer container to retain the moisture-sensitive material therein.

12. The method of claim 9 wherein the moisture-sensitive material comprises a plurality of capsules containing dental material compositions.

13. The method of claim 9 wherein the moisture-sensitive material comprises a dental material composition in powdered form.

14. The method of claim 9 wherein the ultrasonically welding step further comprises: aligning the inner container on a fixture to expose the bond portion thereof; placing the bond portion of the outer container into contact with the exposed bond portion of the inner container; and exposing the aligned and contacting bond portions of the inner and outer containers to ultrasonic emissions from an ultrasonic horn.