WO1997002994A1

WO1997002994A1 - Venting system for high-viscosity-liquid containers

Info

Publication number: WO1997002994A1
Application number: PCT/US1996/007536
Authority: WO
Inventors: Neville Kersey Vakharia
Original assignee: W.L. Gore & Associates, Inc.
Priority date: 1995-07-11
Filing date: 1996-05-23
Publication date: 1997-01-30
Also published as: AU5803296A

Abstract

An apparatus is provided for venting liquid containers (10), and particularly for venting liquid containers of highly viscous liquids. The apparatus includes a vessel having a threaded neck (14). A cap (12) is suitably dimensioned for screwthreadably engaging the threaded neck. The cap defines an interior cap surface (18). The cap has formed therethrough at least one aperture (20). A mounting member (22) mounts a gas permeable membrane (24). The mounting member is disposed on the interior cap surface in communication with the aperture. A gas permeable membrane is mounted to the mounting member in an angled relation with respect to the interior cap surface and in liquid sealing relation with respect to the at least one aperture.

Description

TITLE OF THE INVENTION

VENTING SYSTEM FOR HIGH-VISCOSITY-LIQUID CONTAINERS

FIELD OF THE INVENTION

The invention generally relates to liquid containers, and more particularly to a venting system for containers of highly viscous fluids.

BACKGROUND OF THE INVENTION

It has become increasingly useful to enclose liquids in plastic containers. Many liquids which are enclosed within such plastic containers require venting to an atmosphere external to the container, to relieve any pressure differential between the intemal volume of the container and an external atmosphere.

Such venting may be required due to temperature fluctuations, altitude changes, and vapor pressures of the liquid. Liquids which may require such venting include, but are not limited to, aqueous caustic alkali solutions, concentrated salt solutions, aqueous acids, peroxide solutions, hypochlorite solutions, and concentrated surfactant solutions.

In the past, hydrophobic vents have been used in combination with these plastic containers. One such hydrophobic vent is defined by a perforated plastic container which incorporates a porous, gas permeable membrane. More particularly, it is known to perforate a top portion of a liquid container cap, and to bond to the cap a porous, gas permeable membrane. In this type of vent, the gas permeable membrane is disposed in liquid sealing relation with the perforation, while permitting gases from within the container to pass through the membrane and through the perforations in the cap to the atmosphere. In the same manner, air from the atmosphere can travel into the container as needed.

In another type of vent for a liquid container, a suitably dimensioned grooved polyethylene liner is positioned within a threaded liquid container cap. In this type of vent, the polyethylene liner is disposed within the liquid container cap in a fashion that orients the grooved surface of the polyethylene liner downward, toward the interior of the liquid container. This type of vent is torque sensitive, and provides venting by way of a vent path through the grooves of the polyethylene liner, between the cap and the neck of the container, and between the threads of the cap and the threads of the container neck. As may be appreciated, if a cap is torqued too tightly on the container, the grooves in the polyethylene liner collapse. The collapsed grooves block the vent paths. Accordingly, because this type of vent is torque sensitive, liquid may leak from a container in certain circumstances, such as when the liquid- filled container is place on its side, for example.

Although these vents for liquid containers may have operated with varying degrees of success, in particular applications, they are not particularly suitable for use with containers of highly viscous fluids. More particularly, in a container of a highly viscous fluid having a vent of the type described hereinabove, typically, the highly viscous fluid adheres to flat interior surfaces of these vent systems. The adhering viscous fluid blocks the vents and the vent paths, thereby preventing gas flow between the internal volume of the container and an external atmosphere.

The foregoing illustrates limitations known to exist in present containers incorporating hydrophobic vents and vented liners. Thus, it is apparent that it would be advantageous to have a venting system or configuration, for a liquid container of a highly viscous fluid, that permits the efficient and effective venting of the container, thereby overcoming the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereafter.

SUMMARY OF THE INVENTION

The present invention advances the art of vents for liquid containers beyond which is known to date. In one aspect of the present invention, an apparatus is provided for venting liquid containers, and particularly for venting liquid containers of highly viscous liquids. The apparatus includes a vessel having a threaded neck. A cap is suitably dimensioned for screwthreadably engaging the threaded neck. The cap defines an interior cap surface. The cap has formed therethrough at least one aperture. A mounting member mounts a gas permeable membrane. The mounting member is disposed on the interior cap surface in communication with the aperture. The gas permeable membrane is mounted to the mounting member in an angled relation with respect to the interior cap surface and in liquid sealing relation with respect to the at least one aperture.

In one embodiment of the present invention, at least a portion of the mounting means mounts the gas permeable membrane at an angle greater than about 60 degrees with respect to the interior cap surface. The mounting means may comprise a cylindrical sleeve, a vent cage, or other suitably dimensioned shaped member. The gas permeable membrane may comprise a planar sheet, or may be shaped in the form of a sleeve or tube. In another embodiment of the present invention, the gas permeable membrane is an oleophobic membrane. Alternatively, the gas permeable membrane may be both oleophobic and hydrophobic. Preferably, the gas permeable membrane has predetermined surface properties which resist low surface tension liquids. The gas permeable membrane may also comprise a laminate of an oleophobic membrane which is bonded to a support material.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of a preferred embodiment of the invention, will be better understood when read in conjunction with the appended drawings. For purposes of illustrating the invention, there is shown in the drawings an embodiment which is presently preferred. It should be understood, however, that the invention is not limited to the precise arrangement and instrumentality shown. In the drawings: Figure 1 is a partial sectional view of a liquid container incorporating an embodiment of the venting system of the present invention;

Figure 2 is a partial sectional view of a liquid container incorporating an alternate embodiment of the present invention;

Figure 3 is a partial sectional view of a liquid container incorporating an alternate embodiment of the present invention; and

Figure 4 is a partial sectional view of a liquid container incorporating an alternate embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, wherein similar reference characters designate corresponding parts throughout the several views, a top portion of a liquid container is illustrated generally at 10 in Figures 1 , 2, 3 and 4. The liquid container has a vessel portion (not shown) which may contain a variety of liquids. The present invention is intended for use with containers for high viscous liquids or high viscous liquids having a low surface tension. Such liquids may require venting to an atmosphere external to an interior volume of the liquid container.

A threaded removable cap 12 is provided for selectably sealing the liquid container. The cap 12 is suitably dimensioned for screwthreadably engaging a threaded neck portion 14 of the liquid container. The cap 12 defines an interior portion 16 and an interior cap surface 18. An aperture 20 is formed through the cap for permitting gas flow between the interior volume of the liquid container and an external atmosphere.

A mounting means 22, for mounting a gas permeable membrane 24, is disposed on the interior cap surface 18, in communication with the aperture 20. The mounting means 22 may comprise a cylindrical sleeve member, as illustrated in Figure 1 , which is either made integral with, or otherwise attached to, the interior cap surface 18. As illustrated in Figure 2, the mounting means 22 may altematively comprise a curved mounting member disposed on the interior cap surface 18. As best illustrated in Figure 3, the mounting means 22 may comprise a vent cage which is attached to, or otherwise made integral with, the interior cap surface 18. Also, and as illustrated in Figure 4, the mounting means 22 may comprise an extended cylindrical sleeve member. As best seen by a comparison of Figures 1 , 2, 3 and 4 the mounting means 22 should locate the gas permeable membrane 24 in a non-parallel manner with respect to the interior cap surface 18, and in liquid sealing relation with respect to the aperture 20. Any suitable altemative mounting means may be employed provided that the gas permeable membrane 24 is mounted in a non-parallel, or angled, manner with respect to the interior cap surface 18, and in liquid sealing relation with respect to the aperture 20. It has been discovered that in order to achieve a proper clearing of the high viscosity liquid from a venting surface of the gas permeable membrane 24, at least one portion of the mounting means 22 should mount the gas permeable membrane 24 at an angle greater than about 60 degrees with respect to the interior cap surface 18. In this regard, when a high viscosity liquid contacts the gas permeable membrane 24 mounted in such a fashion, the angled positioning of the membrane 24 causes the liquid to roll off the membrane surface instead of remaining fixed to the membrane surface, as has occurred with known venting systems.

The mounting means 22 may be made as a modification to the cap 12 during its manufacture, such as a modification to a threaded cap mold. Alternatively, the mounting means may comprise a separate part which is made integral with the cap by any suitable method, such as by ultrasonic welding, heat welding, or solvent bonding, for example.

The gas permeable membrane 24 may be a comprised of a generally planar sheet of membrane, as shown in Figures 1 and 2, which is fixedly attached to the mounting means 22 by any suitable method. Alternatively, the gas permeable membrane may be comprised of a sleeve or tube of membrane, as shown in Figures 3 and 4, which is positioned about the mounting means 22. Whatever shape employed, the gas permeable membrane is preferably one which provides unique surface properties that resist low surface tension liquids. For example, one such gas permeable membrane which is particularly well suited for use in accordance with the teachings herein is an oleophobic membrane which is described in detail in United States patent 5,116,650, incorporated herein by reference.

This gas permeable oleophobic membrane is provided with passageways, or continuous pores, throughout the membrane. The membrane is coated with an amorphous copolymer of 10-40 mole percent tetrafluoroethylene and complementary 60-90 mole percent of perfluoro-2,2- dimethyl-1 ,3-dioxole. Thus, it may also contain minor amounts of other comonomer units. The copolymer is available from the DuPont Company as Teflon® AF 1600 in which the mole percent of the dioxole units present is about 65%, and as Teflon AF 2400 in which the mole percent dioxole units present are about 85 mole percent. The coating coats at least a portion of the interior of the pores but does not fully block the pores. Thus, the gas permeability property of the gas permeable membrane remains intact. The presence of the amorphous copolymer coating renders the membrane more oleophobic than the membrane without the coating.

Preferred as a gas permeable membrane is porous polytetrafluoroethylene (PTFE), especially microporous expanded polytetrafluoroethylene membrane sheet made as described in U.S. Patent

3,953,566, incorporated herein by reference, which has a microstructure of nodes interconnected with fibrils. The resulting micropores or voids permit effective gas or air flow while providing liquid water resistance. These porous PTFE membranes preferably have a Gurley number of 600 or less. The amorphous dioxole copolymer is conveniently applied from solution in which the solvent is perfluoro- (2-butyltetrahydrofuran). The solution should be dilute because the ultimate coating should not cover and seal the passageways, in order to preserve the gas permeable nature of the material. The solution preferably contains 0.01 to 5.0 percent wt./wt. dissolved solids. The coating solution is applied by any convenient means to the material and spread uniformly over the surface of the material. Dip coating can be used so as to impregnate the pores. The solvent is then evaporated by any convenient means.

The materials used to form the gas permeable membrane may contain various other additive ingredients to impart specific properties to the product or as a process aid.

The resulting coated membrane exhibits unusually good hydrophobic and oleophobic properties while having effective gas or air flow through the material. The resulting coated membrane can be used in applications involving gas flow where the membrane should be resistant to penetration by water, oil, or lipid emulsions.

Porous PTFE alone, normally has little oleophobicity, yet with the coating of the amorphous dioxole copolymer described herein, the coated material is rendered oleophobic. The gas permeable membrane may also be employed in a laminate form.

The laminate comprises the coated, oleophobic membrane which is bonded to a support material. The support material is preferably polyethylene, polypropylene, or polyester, and preferably in non-woven form. The support material allows for easier handling of the gas permeable membrane and functions as a bonding layer when attaching the gas permeable membrane 24 to the mounting means 22.

The laminate may be formed by any suitable process such as by a thermal bonding process, wherein the gas permeable membrane and the support material are fed into a roller system comprised of a stainless steel heated roll in contact with a silicone rubber nip roll. The stainless steel roll is heated to a temperature that will sufficiently soften the support material so that the support material will bond to the gas permeable membrane. For a polyester support material, temperatures in excess of 150°C are typically used. The nip roll cylinder pressure is typically 25-35 pounds per square inch. The line speed for this continuous process is typically 10-20 feet per minute. As the material cools down after the hot roll - nip system, it is taken up as the completely bonded construction. The bonded gas permeable membrane and support construction are suitably dimensioned for mounting on a suitable mounting means 22.

Preferably, the threaded cap 12 is injection molded of polypropylene, which is the most common material used for plastic closures.

The gas permeable membrane 24 or the laminate comprising the bonded gas permeable membrane and support material may be attached to mounting means 22 by one of several common methods known to those skilled in the art.

In one preferred method, the laminate of bonded gas permeable membrane and support material is bonded to the mounting means 22 by the use of heat and pressure. A heat-sealing head is made of similar dimensions to the cap 12. To bond the laminate of gas permeable membrane and support material to the mounting means 22, temperatures must be used that are high enough to soften the material of the mounting means and to allow the material of the mounting means to flow into the structure of the polyester support material of the laminate. These temperatures are typically in excess of 160°C. The pressure required to create the heat seal is typically in the range of 50 pounds per square inch. The time of contact between the laminate and cap under heat and pressure is typically 0.5 - 3 seconds. Once the laminate comprising the gas permeable membrane and support has been heat sealed to the mounting means 22, the cap 12 can then be used in a container for high viscosity or high viscosity and low surface tension liquids. In the embodiment of the present invention illustrated in Figures 3 and 4, the sleeve or tube shaped gas permeable membrane 24, or the laminate comprising the bonded gas permeable membrane and support material, may be sized to be snug fittingly or close fittingly attached to the mounting means 22, without the need for any additional adhesive or heat sealing techniques.

In order to test the functionality of the apparatus of the present invention, a high viscosity liquid is added to the container. This liquid may also contain a component that is known to release gases into the closed container. The liquid container is sealed with a cap 12. The container is then inverted and then placed upright. This causes the high viscosity liquid to completely contact the vent. While the container is upright, the container is observed for any pressure build up due to the component in the liquid that generates gases into the container. If no pressure buildup occurs, then the venting system is functioning and has not been blocked by the high viscosity liquid. When the container is inverted to its proper upright position, the venting system functions in reverse, i.e. air flows from the atmosphere into the container. This is useful when the container undergoes temperature or altitude changes, or when the liquid contains gas scavenging components. Thus, the vent is bi-directional and permits gas exchange into and out of the container functioning in all conditions of use.

Although a few exemplary embodiments of the present invention have been described in detail above, those skilled in the art readily appreciate that many modifications are possible without materially departing from the novel teachings and advantages which are described herein. Accordingly, all such modifications are intended to be included within the scope of the present invention, as defined by the following claims.

Claims

CLAIMS:

1. An apparatus for venting liquid containers comprising: a vessel having a threaded neck; a cap suitably dimensioned for screwthreadably engaging the threaded neck, the cap defining an interior cap surface, the cap having at least one aperture formed therethrough; a mounting means for mounting a gas permeable membrane, the mounting means being disposed on the interior cap surface in communication with the aperture; and a gas permeable membrane; wherein the mounting means mounts the gas permeable membrane in an angled relation with respect to the interior cap surface and in liquid sealing relation with respect to the aperture.

2. An apparatus as claimed in claim 1 , wherein at least a portion of the mounting means mounts the gas permeable membrane at an angle greater than about 60 degrees with respect to the interior cap surface.

3. An apparatus as claimed in claim 1 , wherein the mounting means comprises a cylindrical sleeve.

4. An apparatus as claimed in claim 1 , wherein the mounting means comprises a vent cage.

5. An apparatus as claimed in claim 1 , wherein the gas permeable membrane is a planar sheet.

6. An apparatus as claimed in claim 1 , wherein the gas permeable membrane is shaped in the form of a sleeve.

7. An apparatus as claimed in claim 1 , wherein the gas permeable membrane is an oleophobic membrane.

8. An apparatus as claimed in claim 1 , wherein the gas permeable membrane has predetermined surface properties which resist low surface tension liquids.

9. An apparatus as claimed in claim 1 , wherein the gas permeable membrane is oleophobic and hydrophobic.

10. An apparatus as claimed in claim 1 , wherein the gas permeable membrane is a laminate.

11. An apparatus as claimed in claim 10, wherein the laminate comprises an oleophobic membrane which is bonded to a support material.

12. An apparatus as claimed in claim 11 , wherein the support material is selected from a group consisting essentially of polyethylene, polypropylene, and polyester.

13. An apparatus as claimed in claim 1 , wherein the gas permeable membrane is shaped in the form of a tube.