Lidstock material having improved sealability and peelability to wide classes of materials

Abstract

A material that can be used as a lid (12) on a container (14, 40), the lid containing a solid substrate (30) and a peelable and heat sealable film (32) which contains a mixture of at least aliphatic-aromatic copolyester, inorganic filler, butene-1 polymer and ethylene-vinyl acetate copolymer, where the substrate (30) is preferably made of aluminum.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a lidstock material suitable for making lids to be sealed over plastic containers such as pharmaceutical blisters. BACKGROUND OF THE INVENTION [0002] Many products are placed in containers covered by a lidstock material and such products can range from yogurt to disposable contact lenses. Such lidstocks must be sealable to a very wide class of materials, peelable and resistant to both hot and cold temperatures. [0003] Many pharmaceuticals and disposable contact lenses are packaged in blister packages consisting of 2 pieces: a base and a lid. The base is an injection molded plastic shaped to include a bowl-shaped or rectangular recess for receiving the contents. In the case of contact lenses, each blister pack generally contains a contact lens and enough solution to prevent drying and to maintain the contact lens ready for use. [0004] The lid covering the base is heat sealed over the recess containing the contents of the ...

AI Technical Summary

Benefits of technology

[0011] The substrate can be, for example, metal foil, plastic or paper but the preferred substrate is aluminum foil. The preferred range is from about 10 wt. % to about 30 wt. % of butene-1 polymer and about 10 wt. % to about 30 wt. % ethylene-vinyl acetate copolymer. The above composition / substrate provides excellent bonding sealing and cohesive peeling to all of PVC, PET and PVDC as well as more easily bondable packaging such as PS, PP and PE.

[0016] The substrate is preferably coated with a print primer. The print primer facilitates application of printed labeling on the substrate. A particularly preferred print primer has a coating weight of about 0.4 to 0.9 pound per 3000 square feet (0.6-1.4 g. / sq meter).

[0017] The peelable and heat sealable film has a total weight of about 17 lb per 3000 square feet (27 g / sq meter). The filler enhances peelablity of the coating by assisting the seal failure upon peeling from adhesive failure at the container-coating layer interface to cohesive failure in the coating layer itself. The filler preferably is selected from at least one of talc, silica or alumina and comprises at least about 15 wt. % of the coating, preferably about 15 wt. % to 30 wt. %, more preferably about 20 wt. % to 30 wt. %. The filler is preferably a powder having an average particle size of about 0.5-10 micrometers (microns). Talc having an average particle size of about 12 0.5 to 10 micrometers is particularly preferred. The talc or other filler is preferably provided with a surface coating comprising about 0.5 wt. % to about 5 wt. % of the filler, preferably about 1 wt. %. A carboxylic acid surface coating is particularly preferred. The surface coating contributes to talc dispersion and adhesion within the polymer. The carboxylic acid in the surface coating may be a mono or dicarboxylic acid or a mixture of such acids. Some preferred acids include stearic acid and isostearic acid, which is a liquid mixture of mostly C1-8 saturated fatty acids having the general formula C17H35COOH. Other saturated C10-C20 carboxylic acids or mixtures thereof may also be useful.

Problems solved by technology

Packaging Digest describes a lidstock containing a type ethylene acid copolymer which replaces adhesive-mounted versions having high peel strengths making them somewhat difficult to wpen with an extrusion mounted version.

The prior art lidstock materials generally suffer from one or more serious disadvantages making them less than entirely suitable for their intended purpose, including compatibility with an extensive class of substrate or blister package sealing lids, for example compatibility with polystyrene (“PS”), polypropylene (“PP”), polyethylene (“PE”) and with all three of polyvinyl chloride (“PVC”), polyethylene terepthalate (“PET”), and polyvinylidene chloride (“PVDC”).

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