Heat-resisting package for hot-melt adhesive

Details Heat-resisting package for hot-melt adhesive Heat-resisting package for hot-melt adhesive

1999-12-01

2001-09-25

Pelham, Joseph (Department: 3742)

Electric heating

Heating devices

Combined with container, enclosure, or support for material...

C219S201000, C220S001600, C222S105000, C222S146500, C383S906000

Reexamination Certificate

active

06294761

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the packaging of hot substances including hot-melt adhesives, and in particular to packages including a flexible liner capable of withstanding such substances, without compromising package integrity.
BACKGROUND OF THE INVENTION
This invention relates to hot melt adhesives which are used in industry in a wide variety of applications, and in particular to their packaging for shipment to the user and their utilization in the user's manufacturing operations.
In prior art hot melt adhesive packages, considerable secondary processing of the adhesive is required. Molten adhesive at the point of production is commonly poured onto a moving chilled belt, which rapidly solidifies in the form of a ribbon. The solid ribbon is then cut into sticks and typically packed into cartons of about 50 lb (25 kg) and shipped to the customer. Other shapes such as pillows, chicklets or pellets may also be formed for shipment to the customer. At the customer's facility, the solid pieces are transferred with a worm feed or directly by hand to a vat in which the adhesive is remelted, and therefrom dispensed for use. Since in some cases the contents of a single carton may be used up quickly, constant attention is needed to ensure that the vat is replenished. In some cases the vat may be open topped, thus putting the operator at risk of being burned by hot adhesive. The use of relatively small packages results in the consumption of large amounts of packaging material which has to be disposed of by the customer. Also, in facilities which use more than one type of adhesive, the presence of large numbers of small packages increases the possibility of error.
SUMMARY OF THE INVENTION
It is an object of this invention to allow the packaging and shipping of adhesive which originates in a molten flowable state so as to minimize secondary processing, thus reducing shipping, manufacturing and handling costs. The invention comprises a package having a flexible envelope of heat resisting material, a rigid holder for the envelope, and ports sealed to the envelope to permit the filling and draining of hot melt. It further comprises an electrical heater with a temperature measuring device and a control system. Finally, the invention comprises a method for forming a durably impervious seal between the flexible envelope material and the ports. The package is filled with hot melt adhesive and allowed to cool. It is shipped to the user and the contents are reheated by activation of the heater. The use of the shipping container as the reheating vessel allows the aforementioned vat to be eliminated. Furthermore, the package, including the envelope and/or the heat, can be re-used, possibly resulting in a significant economic benefit. Optionally, instead of being allowed to cool, the adhesive can be kept in its molten state by applying the necessary heat at all stages of its handling including transportation. This allows the end user to avoid losing time in reheating the adhesive. The invention allows the shipping of adhesive in quantities of up to about 330 gallons (1245 l), with a mass of about 3300 lb (1500 kg). When such quantities are dispensed in a controlled manner, considerably less labor is required than heretofore. Furthermore, the handling of relatively few large packages reduces the risk of dispensing the wrong adhesive in error.
Flexible containers for liquids obviously must be formed from a flexible material. For liquids at and near room temperature, a variety of materials are available to choose from, such as polyethylene, polypropylene, paper, foil and metallized laminates. Materials for use under relatively benign thermal conditions are easily processed with regard to their ability to be shaped and to be sealed to themselves or other fitments by the use of heat-sealing or adhesive techniques. With increasing temperatures, the problem becomes more challenging. While various polymeric sheet materials which are capable of retaining their integrity at temperatures of up to about 800° F. (425° C.) are known in general, and layers of such sheets may be heat-sealed together, it has not been disclosed to form reliably impervious heat-seals between such materials and fitments which must be attached thereto.
Therefore, it is a purpose of this invention to provide an impervious heat-seal between a sheet of heat-resisting polymer and a rigid fitment block which selectively allows or impedes the passage of a molten substance through the sheet.
It is further a purpose of the invention to provide a system comprising a flexible envelope for molten substances, the envelope having impervious heat seals with inlet and outlet fixtures and retaining its structural integrity at temperatures of up to 150° C., and preferably up to at least 200° C. The formation of such impervious seal between the envelope and the fixtures is critical for practical applications of this invention.
According to a first embodiment, this invention provides a receptacle for containing a molten material, comprising: a flexible envelope impervious to the molten material and including an inlet and an outlet; an inlet port imperviously sealed to the envelope at the inlet and extending outward from the inlet; and an outlet port imperviously sealed to the envelope at the outlet and extending outward from the outlet; wherein the receptacle retains its structural integrity up to a temperature of at least 150° C., and preferably up to at least 200° C.
According to other embodiments, the invention relates to a method for containing, transporting and dispensing a material. The method comprises: providing a receptacle that comprises a flexible envelope impervious to the material when molten and including an inlet and an outlet, a rigid holder into which the flexible inlet is disposed, and a heating element disposed between the rigid holder and the envelope, and in thermal contact with an exterior of the envelope; introducing the molten material into the envelope through an inlet port extending from the envelope inlet and an exterior of the container; closing the inlet port, and transporting the container to a desired location; activating the heating element to heat the material to a desired temperate in its molten state; and dispensing the material in its molten state from an outlet port extending from the envelope outlet and the exterior of the container; wherein the receptacle retains its structural integrity up to a temperature of at least 150° C.
This invention also relates to a method of forming a seal between a flexible sheet and a contact surface of a rigid block, comprising: providing a flexible sheet of a material having an aperture therethrough; providing a rigid block of material including a lower flange; inserting the rigid block through the aperture such that an upper surface of the lower flange contacts an inner surface of the flexible sheet surrounding the aperture; placing the rigid block flange surface and the flexible sheet inner surface in contact with a preheated support surface, and applying pressure for a predetermined time to form a seal between the flange and flexible sheet that is impervious to molten substances at a temperature of at least 150° C.
In particular, the present invention discloses regimes of temperature, pressure and time in which heat seals can be made between a sheet of heat-resisting polymer and a rigid fitment. The capability of making such heat seals enables the fabrication of flexible envelopes for receiving, containing and dispensing hot fluids at temperatures up to about 200° C., which in turn enables the fabrication of packaging systems which enable bulk quantities of such fluids to be admitted, contained, transported and dispensed.


REFERENCES:
patent: 4574986 (1986-03-01), Baris et al.
patent: 4629094 (1986-12-01), Vogel et al.
patent: 5145083 (1992-09-01), Takahashi
patent: 5181625 (1993-01-01), Podd et al.
patent: 5206309 (1993-04-01), Altman
patent: 5335820 (1994-08-01), Christianson
patent: 5356029 (1994-10-01), Hogan
patent: 5655679 (1997-08-01), Sch

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