Flexible container packaging, such as collapsible tube packaging, presently is made from single and multilayer films. These usually are polyolefin containing films. Suitable polyolefins are polyethylene and polypropylene. When a multilayer film, the film structure, in addition to polyolefins, will contain layers of polymers such as ethylene vinyl alcohols, ethylene vinyl acetates, ethylene-propylene copolymers, metal foils, paper and other materials. In these packages the polyolefins provide a good moisture barrier. However, they have poor organic barrier properties, and for a given weight are not as strong as other materials.
It has been found that packaging tubes having a high strength can be produced from polyester resins, such as polyethylene terephthalate resins, and in particular from biaxially oriented polyethylene terephthalate. However, such tube packages do not have good moisture barrier properties. They are effective to package nonaqueous compositions. When used to package aqueous compositions, there is a transfer of moisture from the composition through the package wall and a change in the physical properties of the composition. This problem of providing a polyester tube package, such as a polyethylene terephthalate tube package, with effective moisture barrier properties is addressed in the present application for patent. As used in this application tube includes those that are crimp sealed at the end opposite the nozzle and those that are continuous throughout the tube body and which are filled through the upper shoulder/nozzle region.
It is known to coat polyester container surfaces with polyvinylidene chloride solutions or emulsions to make the containers less permeable to contained gases such as carbon dioxide. The interior surface can be coated but usually the exterior surface is coated. Also there can be a polyvinylidene chloride or other polymer coated onto the polyester surface of a container preform or as a outer layer of a container preform and the preform then blown to form a container. In the latter instance, the resulting container will have a barrier layer of a polyvinylidene chloride film.
The concept of having a polyester preform coated with a vinylidene chloride or other polymeric coating, and then blowmolding this preform to a container is shown in U.S. Pat. No. 4,254,170; U.S. Pat. No. 4,267,143; U.S. Pat. No. 4,267,743; U.S. Pat. No. 4,714,5830 and U.S. Pat. No. 4,615,925. Coating the preform is preferred when the container is to be produced on a high speed blowmolding line. It removes a relatively slow subsequent coating step. U.S. Pat. No. 4,478,889 discloses that the polyvinylidene chloride layer should be highly crystallized in order to improve the adhesion of the coating to the polyester surface. U.S. Pat. No. 4,505,951 discloses to cure polyvinylidene chloride water based emulsion coatings with infrared energy to prevent the entrapment of water in the coating. And U.S. Pat. No. 4,515,836 discloses the coating of polyvinylidene chloride emulsions onto a container by using airless spray nozzles. This forms coatings with good gas barrier properties. None of these patents are directed to producing a container that has good moisture barrier properties. The concern is a gas barrier for beverage bottles. None of the references discloses how to put an effective moisture barrier onto a tube container.
The moisture barrier properties of a polyester tube can be increased by means of a coating, such as a polyvinylidene chloride latex or solvent coating, on the exterior surface of the tube package. The polyvinylidene chloride coating can be on the entire surface of the tube package, i.e. both on the tube body and the tube shoulder or only on the tube body which is the sidewall of the tube. The outer layer decoration material also can have moisture barrier properties. One technique is to first put a decoration on at least part of the exterior surface of the tube package, cause the material of the decoration to bind to the polyethylene terephthalate surface the tube package, and then to coat the entire surface with the polyvinylidene chloride composition. However, this has several disadvantages. One is a gradual discoloration of the polyvinylidene chloride outer layer. The preferred technique is to coat substantially all of the tube package with the polyvinylidene chloride coating and then to apply the tube decoration onto this coating as the outer layer. A primary requirement then is that the decoration form a good bond to the polyvinylidene chloride coating and that the polyvinylidene chloride coating form a good bond to the polyester tube wall.
It has been found that when the transmission of the moisture is from within a polyester container to the exterior that a polyvinylidene chloride coating cannot be applied directly to the surface of the tube to effectively prevent moisture transmission. Upon the moisture from within the tube contacting the polyvinylidene coating, the coating peels away from and flakes off the polyester surface of the tube. This is not the case where moisture is from the exterior and first contacts the polyvinylidene chloride layer and then the polyester wall of the container. This problem is solved using the inventions disclosed herein.
This problem is more severe for tube containers, and in particular, collapsible tube containers. In dispensing products from tube containers, the sidewalls are flexed whether the tube walls remain in the dispensed shape or return to their original shape. The flexing of the sidewalls increases the cracking and peeling of a polyvinylidene chloride coating on a tube which contains an aqueous composition.
Another problem is that polyvinylidene chloride coatings upon exposure to ultraviolet and visible radiation tend to form a yellow tint. The yellow tint increases with time. The addition of a blue tint to remove the yellow tint is not effective for tubes and other containers that are white since the degree of yellow tint increases with time. This problem likewise is solved using the inventions disclosed herein.