US 3323206 A
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F. N. CLARK June 6, 1967 PROCESS FOR THE MANUFACTURE OF AN AEROSOL CONTAINER Filed May '7, 1964 FIGZ.
INVENTOR FRANK N.CLARK SEQ/6&4
ATTORNEY United States Patent 3,323,206 PROCESS FOR THE MANUFACTURE OF AN AEROSOL CONTAINER Frank N. Clark, Scotch Plains, N.J., assignor to Allied Chemical Corporation, New York, N.Y., a corporation of New York Filed May 7, 1964. Ser. No. 365,645 4 Claims. (Cl. 29--509) The present invention relates to a novel process for manufacturing an aerosol container. In particular, it concerns a process for manufacturing an aerosol container with a nylon bag insert.
Nylon film has been suggested as a material for bag inserts in aerosol containers; however, it has been found deficient in that a high number of failures occurred through contamination of the product by the propellant and the propellant by the product.
In the past, aerosol containers with nylon bag inserts have been prepared by inserting a preformed, e.g., vacuum formed or blow molded, nylon bag into a container and hermetically sealing the container by crimping, i.e., compressing the edge of the nylon bag insert between two rigid edges, one edge belonging to the container and the other edge to the valve assembly. It was found that rupturing of the nylon bag in the crimping area occurs immediately or during the shelf life of the container causing contamination. In addition to rupturing, the permeability qualities of the original nylon film were not retained which resulted in further contamination during the shelf life of the aerosol container.
It is an object of the present invention to provide a method of manufacturing aerosol containers with nylon bag inserts which will remain substantially rupture-free during their shelf life. It is another object of the invention to provide a method of manufacturing aerosol containers with nylon bag inserts which will retain the permeability properties of the original nylon film. It is still another object to provide a process for the manufacture of aerosol containers with nylon bag inserts which will remain rupture-free and retain the original permeability properties of the nylon film. Other objects and advantages will become apparent hereinafter.
In accordance with the invention, an aerosol container, comprising a rigid container having an opening at one end, the edge of the opening being adapted for crimping; a valve assembly with an edge adapted for crimping in conjunction with the edge of the container; and a nylon film bag insert with an opening in one end, the edge of the opening being adapted for crimping between the edges of the container and valve assembly, is manufactured by a process comprising the following steps: (a) humiditying the nylon bag; (b) inserting the humidified nylon bag and valve assembly into the container; and (c) crimping the edges of the container, valve assembly, and humidified nylon bag so that the edge of the nylon bag is compressed between the edges of the container and valve assembly forming a hermetic seal, said crimping being initiated while the nylon bag is in a humidified state.
It has been unexpectedly discovered that when a nylon bag is humidified and crimped while in the humidified state, the nylon bag insert remains rupture-free for the shelf life of the aerosol container.
It has further been discovered that when an unpreformed nylon film bag insert, such as a fiat nylon film bag insert, is used the nylon bag insert retains the permeability properties of the original nylon film for the shelf life of the aerosol container.
Referring to the drawing:
FIGURE 1 shows the finished aerosol container with a flat nylon film bag insert expanded to simulate product inclusion.
FIGURE 2 is a cross section of FIGURE 1 taken at the line 2-2.
FIGURE 3 shows a fiat nylon film bag insert.
FIGURE 4 is a cross section of FIGURE 3 taken at the line 4-4.
A detailed account of the process with reference to the drawing is as follows:
Rigid container 1 is preferably made of metal, but can be constructed of a variety of materials, such as plastics, e.g., nylon and phenolic resins; paper, such as heavy corrugated paper in the form of a carton; and glass. It is desirable that the materials are such that they can be subjected to low temperatures and high pressures and will not be corroded by the propellants, the product to be dispensed, or the external environment. The shape of the container is immaterial, the convetnional types commercially available being adequate. The typical shape used is cylindrical with the longitudinal axis of the cylinder perpendicular to the fiat surface on which the container usually rests. One side of the container, usually the top, has an opening with edge 2 which is receptive to crimping.
Valve assembly 3 has an edge 4 which is adapted to be crimped together with edge 2 of container 1 to form a hermetic seal. The valve assembly materials can be the same as those used for the container except that the valve itself is preferably a flexible material such as various plastics, rubber, plastisols, and compressible polyethylene. Flexible gaskets of similar materials can be used to insure that the valve assembly is leakproof. The valve assembly can be constructed as -a top portion of the container as in FIGURE 1 of the drawing or restricted to a small area within the upper surface of the container.
The nylon film bag insert can be preformed, e.g., vacuum formed or blow molded by well-known processes; however, the nature of the process is such that the preformed bag wall does not have a uniform thickness, but thins out in various areas increasing the permeability of the original nylon film. A preferred embodiment of the invention is the use of an unpreformed nylon film bag insert, e.g., a flat nylon film bag insert, which has been found to retain the properties of the original nylon film throughout the shelf life of the aerosol container. Nylon bag inserts such as flat nylon film bag insert 5, which is also shown in its fiat state before insertion in the container, in FIGURES 3 and 4, is prepared from nylon film which has the necessary permeability properties to provide a sufficient barrier against contamination. A thickness of about 1 to about 4 mils has been found to be satisfactory, but the important factor is the permeability property for the desired purpose. The film as a matter of practice is tested before the nylon bag insert is prepared and if its is found to be impermeable to the product to be dispensed and the propellant, it can be used in the aerosol container with the knowledge that if it is unpreformed, the original permeability properties will be retained throughout the shelf life of the container. The film can be crystalline or amorphous and, typically, a 1 mil film, has a tensile strengthof 6,000 to 10,000 p.s.i., a moisture content at 50% relative humidity at 23 C. of 2 to 4% by weight and a maximum moisture absorption (saturation) of 8 to 12% by weight. The nylon film can be made from any film forming nylon such as nylon 11, nylon 6/6, nylon 6/10 and nylon 8. Nylon 6 which is obtained by the polycondensation of caprolactam, is especially suitable. The term nylon as used herein includes unsupported film or nylon laminates. The nylon can be laminated with foil, cellophane, polyolefins such as polyethylene, polypropylene, polycarbonate resin, polyvinyl chloride, or polymer coated paper. The unpreformed nylon bag insert can be prepared from the nylon film by heat sealing tubular or flat film. Heat sealing, wherein a flat nylon bag is prepared from two flat plastic films, is
preferred. An impulse heat sealer, such as the Sentinel sealer made by Packaging Industries, Inc., of Montclair, N.J., or a fiat impulse wire sealer, series C, made by Weldotron, Inc., of Newark, N.]., can be used. A typical example makes use of Weldotrons series C impulse sealing unit which employs a /8" x .002" Nichrome wire mounted with the wire standing on its .002 edge. The wire is held in this on edge position by ceramic side supports and it can be shaped to conform to almost any configuration. As the impulse is fired, it seals and cuts the flat bag from a double Web of film, one superimposed upon the other. The seal is approximately ,4, to wide, about as wide as the thickness of a pencil line. Ultrasonic and dielectric sealing techniques are also satisfactory sealing methods. In addition, solvents and/or adhesives can be used for sealing.
Whether the propellant and product are introduced before or after the crimping step is optional, although it is preferable to do so before crimping.
Propellant 6 can be selected from a wide variety of compositions such as dichlorodifluoromethane, trichloromonofiuoromethane, dichlorotetrafluoroethane, monochlorodifluoroethane, trichlorotrifluoroethane, monochlorodifluoromethane, difluoroethane, and mixtures thereof. Nylon is permeated to a certain extent by nitrogen, propane, butane, and ethylene oxide; however, if the nylon is laminated with aluminum foil or other suitable lamination, the lamination can serve as a barrier for these gases. In this case, bag would be positioned so that the barrier lamination was on the outside adjacent to the propellant with the nylon on the inside adjacent to the product.
Cavity 7 receives the product to be dispensed by the aerosol container, which can be selected from a wide variety of materials. Examples are peanut butter, catsup, mustard, cheese spreads, hair cream, hair colorants and sprays, cold cream, shaving creams, toothpaste, shampoos, insecticides, mineral oil, perfumes, miscellaneous oil, fats, waxes. and greases, emulsion based products, concentrat d paint pigments, and paints.
Humidification is accomplished by the use of water vapor, steam, or water. For best results, the humidification is performed in an enclosed area so that the bag will be fully immersed in a cloud of vapor.
The nylon film bag insert can be humidified for an unlimited length of time before the crimping step, the minimum humidification time being sufficient to increase the moisture content of the nylon film bag insert to at least 3.5% by weight. A practical maximum time limit is that required for saturation of the nylon film bag. The preferred moisture content is from about 6% by weight to saturation, which is generally, about 10.5% by weight. It has been found that for thin nylon films, e.g., /2 to 3 mils, a humidification time of about 1 to about 2 minutes is sufiicient to give a moisture content of at least 3.5% by weight. If a stack of bags is being humidified, more time will be required for the inner bags to absorb a sufficient amount of moisture. To avoid diminution of the moisture content, the crimping step should take place as soon as possible after the completion of humidification. In practice, a machine operation is used .wherein the crimping step takes place so soon after the completion of the humidification step that the problem of dehumidification does not arise.
Nylon film will absorb limited amounts of moisture depending upon the temperature and relative humidity of the surrounding medium. These factors can be taken into consideration in the humidification step; however, immersion in water vapor or steam is most practical because temperature and relative humidity does not have to be measured.
Flat humidified nylon bag and valve assembly 3 are then placed in the rigid container. The bag is usually pre-attached to the valve assembly so that the edges of both are in position for the crimping step.
The crimping step must take place while the nylon bag is in a humidified state, i.e., where the moisture content is at least 3.5% by weight. Various machines can be used for crimping, both hand and power operated, such as those manufactured by the Kartridg Pak Co. of Mount Prospect, Ill.; LG. Machine Works, Inc., of Little Ferry, N.J.; and PMC Industries .of Hackensack, NJ. Crimping provides a hermetic seal with the edge of the nylon bag compressed in between the edge of the container opening and the edge of the valve assembly. The crimped area of bag 5 is designated as reference character 8. Trimming the edge of the nylon bag which might protrude from the crimped area can be accomplished after the crimping step.
Simultaneous with, before, or after humidification or even after the crimping step, propellant 7 can be introduced into rigid container 1 in liquid form. Suflicient pressure or refrigeration must be used to maintain the propellant in its liquid state. Pressure filling may be desirable with aqueous-base formulations such as non-foaming shaving creams or shampoos. If the propellant is introduced before the insertion of the valve assembly, the opening can be plugged to assist in retaining the propellant until the proper time. If the propellant is introduced after the crimping step, an aperture must be provided in the container to permit insertion of the propellant after which the aperture must be sealed.
After humidification, and before or after crimping, the product can be introduced into the container. This is preferably accomplished before the crimping step, but if desired, it can take place after crimipng wherein the product must be forced through the valve under pressure.
The resulting unpreformed nylon bag insert is not affected by temperatures from up to about 250 F. and humidity from up to about and the aerosol container prepared by this process should have a shelf life of at least 2 years, which is more than satisfactory for commercial purposes. Additional advantages of the unpreformed nylon bag over the vacuum formed bag are freedom from entrapped air, lower cost, and compatibility with a wide variety of materials to form laminated film.
The following examples are illustrative of the invention.
Examples I-VI V The same procedure was followed in the six examples. A flat nylon 6 film bag insert (3%" x 3% and open at one end), prepared using Weldotrons series C impulse sealing unit as explained supra, was humidified with steam in an enclosed area for 5 minutes. 40 cc. of a propellant comprising 65% by weight dichlorodifluoromethane and 35% by weight vinyl chloride was introduced, under pressure, into a standard 6 02. metal aerosol can with a 1" diameter opening. The product .to be dispensed was placed in the nylon bag, which was attached to a standard aerosol valve assembly. The bag and valve assembly were inserted in the can and the edges were crimped 60 seconds after humidification. Four such aerosol containers were prepared for each example. Each container was structurally similar to the aerosol container shown in FIGURE 1 of the drawing.
Ex. No. Film Product to be dispensed I 3 mil nylon 6 1% 025. of Colgate lather shaving cream.
II mil nylon 6 laminated 1% ozs. of Colgate lather with mil polyethylene shaving cream. on the inside of the bag.
III 2 mil nylon 6 Mineral oil and blue dye (soluble in mineral oil and propellant).
IV 1 mil nylon 6 laminated Mineral oil and blue dye with 1 mil polyethylene (soluble in mineral oil and on the inside of the bag. propellant).
V Same as Example III except blue dye added to propellant rather than mineral oil.
VI Same as Example IV except blue dye added to propellant rather than mineral oil.
After 16 months the shaving cream used in Examples I and II was dispensed evenly without a trace of propellant; the propellant used in Examples III and IV was found to contain no traces of blue dye; and the mineral oil used in Examples V and VI was found to contain no traces of blue dye.
Examples I-VI were repeated without humidification. Blobs and spurts of shaving cream and propellant were dispensed and traces of blue dye appeared in the mineral oil and propellant.
During the 16 months, all of the aerosol containers were subjected to a temperature of 15 C. and 30 C. and a relative humidity of 20% and 50% to similate two years of shelf life.
1. A process for the manufacture of an aerosol container comprising a rigid container having an opening at one end, the edge of the opening being adapted for crimping; a valve assembly with an edge adapted for crimping in conjunction with the edge of the container; and a nylon film bag insert with an opening in one end, the edge of the opening being adapted for crimping between the edges of the container and valve assembly, comprising the following steps: (a) humidifying said nylon bag until said nylon bag has a moisture content of at least 3.5% by weight; (b) inserting the humidified nylon bag and valve assembly into the container; and
'(c) crimping the edges of the container, valve assembly, and humidified nylon bag so that the edge of the nylon bag is compressed between the edges of the container and valve assembly, forming a hermetic seal, said crimping being initiated while the nylon bag is in a humidified state.
2. The process for the manufacture of an aerosol container as defined in claim 1 wherein the nylon film bag insert is unpreformed.
3. The process for the manufacture of an aerosol container as defined in claim 2 wherein the unpreformed nylon film bag insert is a flat nylon film bag insert.
4. A process for the manufacture of an aerosol container as defined in claim 1 wherein said nylon bag is humidified until said nylon bag has a moisture content of from about 6 to 10.5% by weight.
References Cited UNITED STATES PATENTS 2,397,455 3/ 1946 Chmielowiec 222-95 X 2,671,578 3/1954 McBean. 2,889,078 1/1959 Thomas. 3,080,094 3/1963 Modderno 222394 X 3,169,670 2/ 1965 Hrebenak et a1 222-95 CHARLIE T. MOON, Primary Examiner.