Receptacles – Sidewall structure – Collapsible wall feature
Utility Patent
1998-11-04
2001-01-02
Moy, Joseph M. (Department: 3727)
Receptacles
Sidewall structure
Collapsible wall feature
C220S667000, C215S382000
Utility Patent
active
06168041
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the injection stretch blow molded tubular containers. In addition this invention relates to the injection stretch blow molding of thin wall tubular containers having a high strength and good barrier properties.
BACKGROUND OF THE INVENTION
Tubular containers are used for dispensing a number of different products. Tubular containers are containers that are designed not to stand on their bottom surface, are semi-rigid, and have a limited elastic deformation. These containers are designed to dispense the contained product by squeezing and are preferably collapsible. By collapsible, it is meant that the tubular container remains deformed after the application and removal of a deforming force. There is no regaining of the original shape with the resulting suckback of significant amounts of air into the tubular container to replace the dispensed product.
The uses for these containers include food products, oral care products and personal care products. They are particularly useful in dispensing oral care and personal care products. These products are viscous materials such as lotions, pastes or gels. The tubular containers that are presently used encompass a range of materials and a number of manufacturing techniques. These tubes comprise metallic tubes, multilayer laminate tubes, extruded tubes and extrusion blow molded tubes. Metallic tubes usually are collapsible aluminum tubes. Multilayer laminate tubes can be comprised solely of polymer layers or can contain paper and/or metal foil layers. A paper layer would be a print layer and a foil layer would be a barrier layer as well as a layer that produces a collapsible tube. Extruded tubes are made from a continuously extruded tube that is cut to the desired lengths. This can be of a single layer or multilayer plastic construction.
In most laminate tubes or extruded tubes the tube body is produced separate from the tube shoulder and nozzle. The tube shoulder and nozzle is injection molded and in many instances then bonded onto the tube body. If not bonded onto the tube body it will be compression molded to the tube body. In this technique the nozzle and shoulder are formed at the same time that they are bonded onto the tube body.
Blow molded tubes presently are produced by an extrusion blow molding technique. In this technique, a material is extruded into a tubular form, placed in a mold that is the shape of the desired tube and a gas, such as air, is blown into the extrusion to form the extrusion to the shape of the mold. The tube then as taken from the mold has a fully formed shoulder and nozzle as well as sidewall. The bottom end also will be closed. The tubular container can be filled from the top opening if the opening is of a sufficient diameter. If not, the bottom end can then be severed so that the tube can be bottom filled with product. When filled from the bottom the bottom is crimp sealed and a closure attached to the other end. However, it is preferred to have a sufficiently large opening for top filing and to top fill.
In contrast to the multilayer laminate tubes and the extruded tubes, but similar to extrusion blow molded tubes, the injection stretch blow molded tubes are manufactured in a finished form. No additional forming such as connection to a shoulder and nozzle is required. However, the blow molded tubes of this invention also are an improvement over the presently known extrusion blow molded tubes. The injection stretch blow molded tubes of this invention are also being longitudinally stretched while the tube is being blown. This produces a biaxially oriented tube structure with new and improved barrier and strength properties. This tube can be of a monolayer or multilayer construction. It also can be comprised of a single chamber or be a multichamber tube. Material-wise it can be of any polymer that can be injection stretch blow molded. The tubes can have thin but yet strong walls, can readily be produced in a form where they are collapsible and have good barrier properties.
In the present invention, the tubular container can be produced in essentially any shape. The shape will be determined by the shape of the mold. Thus these can be produced in circular, elliptical or essentially any polygonal shape. In most uses they will be produced in a circular or elliptical form. Also they can be produced for top filling in order to preserve and take advantage of the enhanced strength properties of injection stretch blow molding. If modified for bottom filling by severing a portion of the bottom of the tubular container, filling, and then crimp sealing the bottom, a weak point will be the crimp seal. This crimp seal will tend to fail prior to other parts of the tubular container. It is an option to bottom fill the tubular container by severing the bottom end, filling and then sealing the bottom of the tube with a crimp or other seal.
Bottles are made by injection stretch blow molding processes. This includes single and multichamber bottles. Polyethylene terephthalate (PET) bottles such as those used for carbonated beverages are produced by injection stretch blow molding. These range in size from less than one liter to more than two liters. The blow molding of multichamber bottles is shown in U.S. Pat. No. 5,232,108. In this patent there is shown the blow molding of a multichamber bottle from a multichamber preform with a stretch rod for each chamber. However, tubular containers have not been made by this process. Such tubular containers have been made by extrusion blow molding processes, but without stretching. Tubular containers made by these other processes do not have the same desirable barrier and strength properties, and cannot use some of the plastic materials that can be used in injection stretch blow molding processes.
The processes of the present invention solve the problems of how to produce tubular containers having improved barrier properties, increased strengths, relatively thin walls, and which are collapsible with a decreased suckback of air and product back into the tube after a dispensing.
BRIEF SUMMARY OF THE INVENTION
It has been found that collapsible, relatively thin wall, high strength tubular containers, including multichamber tubular containers, can be produced using injection stretch blow molding techniques. In this process a preform is injection molded. This preform will have the same number of chambers of the final tubular container. This preform is heated to about the glass transition temperature and placed in a mold that has the desired shape of the tubular container. Stretch rods are placed into each chamber and a gas or fluid is injected as the stretch rods move downwardly to longitudinally stretch the tube preform while blowing the tube preform to laterally stretch the tube preform. The final shape of the tube will be the shape of the mold. The tubular container is formed with the shoulder and nozzle fully formed and in place. The bottom end optionally can be severed from the tubular container to provide a larger opening for bottom filling the tube with a sealing of the tube bottom end after filling. However, where high strength is required, it is preferred that there be a sufficiently large top opening for the top filling of the tubular container. This preserves the high strength properties resulting from injection stretch blow molding.
The injection stretch blow molded tubular containers should have a total orientation of greater than about 10, preferably greater than about 12 and most preferably greater than about 14. The wall thickness, which is the point of least thickness of the tubular container should be less than about 250 microns, preferably less than about 200 microns and most preferably less than about 170 microns. The burst strength for such a tubular container will be greater than about 6 kg/cm
2
, preferably greater than about 8.5 kg/cm
2
, and most preferably greater than about 10 kg/cm
2
. This is a strength of about 3 to 5 times or more than that of other tubular containers.
The tensile strength in Newtons per micron thickn
Berger Kenneth R.
Connan Patrick A.
Readdy Robert L.
Colgate-Palmolive Company
McGreal Michael
Moy Joseph M.
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