Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1999-03-18
2001-07-24
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C206S531000, C428S324000, C428S325000, C428S329000, C428S330000, C428S331000, C428S522000
Reexamination Certificate
active
06265041
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a cover sheet for press-through-package (hereinafter referred to as “PTP”) used for packaging of pharmaceuticals in the form of tablets, capsules, etc., foods, and others.
BACKGROUND ART
Pharmaceuticals and foods are usually packaged in the following manner. That is, a base material is made by forming a plastic sheet into a sheet having pockets, contents are put in the pocket portions, and an aluminum foil cover coated with an adhesive is allowed to adhere to the flat part of the base material other than the pocket portions by heating, etc. This package is called PTP. The aluminum foil is broken through by pressing the pocket portions of the base material by fingers to take out the content. Thus, this packaging is very convenient and widely used.
However, in the conventional PTP, the cover material comprises an aluminum foil (inorganic material) and the base material comprises a plastic (organic material), which utterly differ from each other. Therefore, they must be separated after use, and it is very difficult to perform recycling or incineration of them after use. Under the circumstances, it has been desired to use plastics also for the cover material in place of the aluminum foil. However, usual plastic sheets are too strong as cover materials, and lack push-through property in use (when the content is to be taken out). The push-through property here means easiness to break the cover material adhering to the base material in taking out the contents such as tablets which are packed in the pockets of the base material formed by molding. For imparting the push-through property to plastic sheets, there is a method of filling the sheets with fillers such as inorganic fillers, but if the particle size of the fillers is large, the appearance of sheets becomes rough to cause sometimes non-uniformity of the push-through property.
DISCLOSURE OF INVENTION
The object of the present invention is to provide a cover sheet for PTP which is convenient in recycling and incineration for disposal after use to inhibit production of rubbish and which is excellent in push-through property.
The present invention is a cover sheet for PTP characterized in that the sheet of 0.01-1 mm thickness comprises a resin composition containing 5-250 parts by weight of an inorganic filler for 100 parts by weight of a polyvinyl chloride based resin, said polyvinyl chloride based resin has an average polymerization degree of 500-1300, and the sheet has a bursting strength of 0.01-5.0 kg/cm
2
measured by Muller low pressure test method specified in JIS P8112. According to a more preferred embodiment, the sheet has a flex temperature of 50-100° C. measured by Clash-Berg test method specified in JIS K6734, the inorganic filler is at least one of talc, silica, kaolin, mica, alumina, wollastonite, clay and calcium carbonate, the inorganic filler has an average particle size of 0.5-100 &mgr;m, and the polyvinyl chloride based resin contains a vinyl chloride-vinyl acetate copolymer having a vinyl acetate content of 3-15% by weight.
The polyvinyl chloride based resin used in the present invention is excellent in moldability and formability, transparency, heat resistance, electrical insulation properties and cost. Especially, regarding the moldability and formability, the temperature range at which it can be thermoformed is wider than that of other resins, and furthermore, it is superior in transparency and the content can be readily seen. Thus, the resin is particularly suitable for PTP in view of these points.
The polyvinyl chloride based resin used has an average polymerization degree of 500-1300. If it is less than 500, melt viscosity at the time of sheet formation decreases to cause reduction in stiffness and deterioration in processability, and if it is more than 1300, melt viscosity increases and high temperatures are required for sheet formation from the resin with inorganic fillers and, thus, troubles occur in making the sheet. The average polymerization degree is more preferably 500-1100.
The polyvinyl chloride based resins used in the present invention may be straight polyvinyl chloride resins, copolymers with ethylene, vinyl acetate or the like, mixtures thereof or chlorinated polyvinyl chloride resins. Especially, vinyl chloride-vinyl acetate copolymer resins are superior to polyvinyl chloride resin in that processing temperature decreases and thermoplastic fluidity increases, and, simultaneously, the range of proper processing temperature is broadened, and solubility of the resin in solvents is improved to result in decrease of melt viscosity. The content of vinyl acetate in the vinyl chloride-vinyl acetate copolymer resin is preferably 3-15% by weight. If the content is less than 3% by weight, the effect of improvement is not developed, and if it is more than 15% by weight, the softening temperature decreases too much, heat distortion becomes larger and a sheet having a sufficient heat resistance cannot be obtained, and furthermore, water resistance, chemical resistance and oil resistance are apt to be deteriorated. The vinyl acetate content is more preferably 3-10% by weight.
As the polyvinyl chloride based resin used in the present invention, preferred is a resin which comprises 1-80% by weight of a polyvinyl chloride resin and 20-99% by weight of a vinyl chloride-vinyl acetate copolymer resin. If the content of the vinyl chloride-vinyl acetate copolymer resin is less than 20% by weight, the processing temperature increases too much and thermoplastic fluidity decreases, the proper processing temperature range is not broadened, and troubles are apt to occur at the time of PTP formation. The content of the vinyl chloride-vinyl acetate copolymer resin is more preferably 30-99% by weight.
In order for the PTP cover sheet to have push-through property, it is necessary to fill the sheet with inorganic fillers. As the inorganic fillers, there may be cited talc, silica, kaolin, mica, alumina, wollastonite, clay, calcium carbonate, asbestos, glass fiber, aluminum sulfate, and the like. Among them, talc, silica, kaolin, mica, alumina, wollastonite, clay, and calcium carbonate are suitable from the point of easiness in handling.
Average particle size of the inorganic fillers is 0.5-100 &mgr;m, preferably 0.5-20 &mgr;m, and more preferably 0.5-5 &mgr;m. If the average particle size is more than 100 &mgr;m, roughness of the sheet increases because the particles are large, and the push-through property is apt to become non-uniform. If it is less than 0.5 &mgr;m, the size is too small and the effect of push-through property decreases.
Amount of the inorganic fillers is suitably 5-250 parts by weight based on 100 parts by weight of the polyvinyl chloride based resin. If it is less than 5 parts by weight, the sheet is strong and the content in the pocket cannot be taken out, and the desired push-through property cannot be obtained. If it is more than 250 parts by weight, the sheet is too fragile and problems often occur. The amount of the inorganic fillers is preferably 10-200 parts by weight.
Thickness of the sheet of the present invention is 0.01-1 mm. If it is thinner than 0.01 mm, this is practically not suitable and if it is thicker than 1 mm, the push-through property can hardly be obtained. The thickness is preferably 0.02-0.4 mm.
The sheet of the present invention has a flex temperature of 50-100° C., preferably 55-85° C. measured by Clash-Berg test method specified in JIS K6734. The sheet of the higher flex temperature is higher in heat resistance, that is, undergoes less change in appearance when heat is applied. However, if it exceeds 1000° C., there often occur problems in calender processability or moldability or formability in the later steps. If it is lower than 500° C., the sheet is inferior in heat resistance and shows a large change in appearance when heat is applied or sticks to sealing plate at the time of heat sealing. Thus, problems are apt to occur in the later steps.
With regard to the push-through property, the sheet has a bursting strength of 0.
Nakarani D. S.
Rickman Holly C.
Smith Gambrell & Russell
Sumitomo Bakelite Company Limited
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