US 3450256 A
Description (OCR text may contain errors)
C. G. CHANDLER ET AL HEAT-SEALED BLISTER PACKAGE Filed Jan. 23, 1967 June 17, 1969 I Il Il Il Il Il f'f'la Charles G. Chandler Rex Eells INVENTORS o As l Warsaw.
I PRIOR ART FIG. 2
United States Patent O 3,450,256 HEAT-SEALED BLISTER PACKAGE Charles G. Chandler and Rex Eells, Kingsport, Tenn.,
assignors to Eastman Kodak Company, Rochester, N.Y.,
a corporation of New Jersey Filed Jan. 23, 1967, Ser. No. 610,896 Int. Cl. B65d 73/00; B32b 27/10; C08f 45 04 U.S. Cl. 206-73 3 'Claims ABSTRACT F THE DISCLOSURE A package consisting of a thermoplastic cover having blisters formed therein which is heat-sealed to a coated, paperboard substrate. The coating on the paperboard consists of a mixture of clay, pigment, and a heat activatable resin binder. As the thermoplastic cover is placed in contact with the coated substrate, heat and pressure are applied thereto to activate the resin binder and form an adhesive bond between the cover and substrate.
This invention relates to a container for packaging articles and more particularly to a container comprising a plastic blister attached to a paperboard backing.
Plastic films and sheets are widely used today as a construction material for containers employed chiefiy in the marketing of relatively small, inexpensive articles. It is obvious that the cost of packaging an inexpensive article must be negligible in order for the Cost of the packaged article to be reasonable. One of the simplest packages for such articles is a fiat, paperboard Substrate covered on one side with a plastic lm formed into a blister-like enclosure or enclosures over the article or articles resting on or secured to the substrate. Such containers may be fabricated and subsequently loaded with an article by way of an entrance cut through the substrate or, preferably, the article and the paperboard may be simultaneously covered with a formed plastic film to produce the final package. In either event, it has been found necessary to utilize an adhesive or primer on the substrate to produce good adhesion between the plastic film and the paperboard substrate. One of the principal difficulties in the past has been to find a combination of plastic and paperboard which will provide the necessary adhesion a a low cost. e
The substrate generally employed in the above described package is paperboard made from the lightly beaten pulp of unbleached, softwood sulfate stock or mixtures of such stock with a hardwood sulfate stock. Paperboard manufactured from lightly beaten pulp and without bleaching is usually somewhat coarse and dark in color; accordingly, when paperboard is employed to make ornamental or decorative containers, it is coated to provide a smooth, white, finished appearance. The most common coating utilized for such a finish is a mixture of clay and pigment with a binder which is applied to the paperboard by calendaring. While the appearance of the nished paperboard is acceptable and its receptivity to printing is good, attempts to cover its surface with a thermoplastic lm formed into a blister-like enclosure have been unsuccessful because of lack of adhesion between the cover and the clay coating. One method for overcoming this difiiculty has been to prime the surface of the coated paperboard before the film is applied with cellulose nitrate. Priming is, however, undesirable because it adds an additional time consuming step to the package forming process.
In accordance with this invention, it has been found that the above enumerated difficulties can be overcome if the coated paperboard is treated with an acrylic resin composition so as to incorporate a small amount of acrylic resins solids in the surface of the paperboard. A thermoplastic film can then be readily heat sealed to the treated paperboard with a high degree of adhesion. The acrylic resin coating composition may be applied to the clay- Coated paperboard, or preferably, the resin composition may be incorporated as the binder into the clay and pigment mixture employed as a coating. The latter method is preferred since with only one manufacturing step, the paperboard is coated to provide a white, smooth surface containing an acrylic resin binder which will readily heat seal to a thermoplastic film covering.
It is, therefore, an object of this invention to provide an improved, economical, plastic, blister container.
Another object of this invention is to provide a blisterlike package which is fabricated without the use of a primer or adhesive between the cover and the substrate.
These and other objects and advantages of this invention will be more apparent upon reference to the following specification, appended claims, and drawing wherein:
FIGURE l is a perspective View of a blister package constructed in accordance with the instant invention;
FIGURE 2 is a cross sectional fragmentary View showing the various components of a blister package in accordance with the prior art; and
FIGURE 3 is a view similar to FIGURE 2 but showing a fragmentary, cross-sectional view of the components required to form a blister package in accordance with the instant invention.
In order to better understand the construction and use of this novel covered article, it will be described in relation to a blister package. It is to be understood, however, that a substrate covered in accordance with the instant invention may be utilized in other ways. For example, the substrate could be a sign or decorative element which is protected from weathering by the plastic coating. Furthermore, a coating may be applied to a paperboard substrate which can be formed into weather-proof packaging. Other uses will be readily apparent to those skilled in the art.
With continued reference to the accompanying figures wherein like numerals designate similar parts throughout the various views, and with initial attention directed to FIGURE l, reference numeral 10 designates generally a blister package including a paperboard substrate 12 and a thermoplastic covering 14. The thermoplastic cover 14 has been previously formed into a blister 16 which will cover and protect an article resting on or secured to the substrate 12.
As shown in FIGURE 2, in prior art blister-packages, the substrate 12 having a clay-coat finish 20` on the surface thereof must have a primer coating or adhesive coating 22 applied to its coated surface before the thermoplastic covering 14 can be secured thereto. As illustrated in FIGURE 3, however, there is no primer or adhesive coating needed in accordance with our invention since the clay-coat finish applied to the substrate 12 contains an acrylic resin binder which also acts as an adhesive when heat activated.
The acrylic resins which have been found to be satisfactory as a binder and heat activatable adhesive are the polymeric acrylic acid esters and the polymeric alkacrylic acid esters. These materials are available commercially as coating compositions in the form of solutions or emulsions which, as slated above, can be applied directly to the paperboard or blended with the clay coating mixture so as to leave a deposit of resins solids when the liquid phase of the solution or emulsion is removed. A typical composition is latex in which the acrylic resins content may be from about l5 to 25% by weight of the composition, while the remainder is a liquid vehicle with a small portion of additives such as stabilizers, emulsifiers, and the like. The amount of acrylic resin which is necessary in order to provide an acceptable level of heat scalability is from about 2% to about 35% by weight of the clay and pigment mixture employed in coating the paperboard.
The thermoplastic materials which can be employed to prepare the covering film in accordance with this invention are those which are suitable for being formed into blisters as described above. Included among these materials are polyolefins, cellulose esters, vinyl polymers, and the like. A-mong the preferred materials are polyethylene, polypropylene, copolymers of propylene and butene-l, copolymers of ethylene and ethylacrylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate proppropionate, polyesters such as polyethylene terephthalate film or Kodar poly(cyclohexylenedimethylene terephthalate-isophthalate) lm, and blends or paraffin Wax with any of the above polymers or copolymers. lt is to be understood that the foregoing listing of polymers and copolymers also include such materials as modifiers, plasticizers, stabilizers and other additives which are employed to provide The foregoing plastic materials can be made to adhere to substrates coated with the clay resin mixture as described above by means of a heat-sealing operation. Sealing is accomplished by applying heat and pressure to the preformed film as it rests on the substrate at the point at which a seal is desired. The heat and pressure applied to the film and the substrate cause the acrylic resin and the lm to become activated resulting in an adhesive bond being formed between the two. Good adhesion is obtained, therefore, between the substrate and film Without the use of a priming material or separate adhesive and without destroying the individual characteristics or properties of either the film or the coated substrate.
The heat sealing quality of the products made in accordance with this invention are tested by comparing them to products obtained employing paperboard which has been coated with a clay and pigment mixture primed with a film of cellulose nitrate, and covered with a plastic blister heat sealed thereto. In the case of the cellulose nitrate-coated paperboard, a heat seal is obtained employing 80 pounds per square inch of pressure for one second at 400 F. or for 2 seconds at 325 F. An excellent bond is obtained between a cover film of polyvinyl acetate and a paperboard substrate coated with a clay-acrylic resin mixture, by applying 80 pounds per square inch of pressure for one second at 415 F., or for two seconds at 375 F. It is apparent that in order to obtain a film cover to substrate bond with acrylic resin binder in accordance with this invention, a temperature 50 to 75 F. higher than the temperature required to obtain a bond on cellulose nitrate-coated paperboard is required. Even though slightly higher temperatures are required, it is more economical to employ the combination of this invention since the replacement of the cellulose nitrate coating with an acrylic resin binder in the clay coating greatly reduces the cost of manufacturing the package while the requirement of a slightly higher temperature is the addition of a negligible expense.
The container of this invention may include decorative designs or printing on the paperboard, transparent or opaque thermoplastic film, or any of several other the material with special characteristics. y
variations which may be apparent to those skilled in the packaging art.
It will be apparent that by following the teachings of this invention a blister package which is economical and yet highly protective to the enclosed article can be produced. No primer or adhesive is necessary to promote a bond between the cover and the substrate. Since the potential utilization of blister board packaging is extremely wide-spread, the savings which can be realized both to the consumer and the packager by employing our invention are of great significance.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrated and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
What is claimed and desired to be secured by United States Letters Patent is:
1, A protective package for one or more articles, comprismg:
(a) a paperboard substrate having a finish coating on at least one side of a composition consisting essentially of clay and 2% to 35% of acrylic resin solids, based on the weight of the clay;
(b) a solid, shaped thermoplastic cover attached by means of a heat seal bond between said cover and said acrylic resins to at least a portion of said coated surface of said paperboard;
(c) said shaped cover having at least one portion spaced from said substrate adapted to form a protective container for an article.
2. A protective package according to claim 1 wherein said thermoplastic of said cover is selected from the group consisting of cellulose acetate, cellulose acetate butyrate, or cellulose acetate propionate.
3. A protective package according to claim 1 in which said acrylic resin is a polymeric acrylic acid ester or a polymeric alkacrylic acid ester.
References Cited UNITED STATES PATENTS 1,982,946 12/ 1934 Bauer. 2,101,107 12/1937 Strain. 2,750,719 6/ 1956 Wandelt. 2,992,203 7/ 1961 Protzman. 3,100,760 8/1963 Brown et al. 3,253,705 5/ 1966 Stoker et al.
FOREIGN PATENTS 1,048,706 11/1966 Great Britain.
OTHER REFERENCES Modern Packaging Encyclopedia, 1962, pp. 300, 301, 306 and 307.
DAVIS T. MOORHEAD, Primary Examiner.
U.S. Cl. X.R.