Stock material or miscellaneous articles – Structurally defined web or sheet – Nonplanar uniform thickness material
Reexamination Certificate
2002-06-27
2004-09-21
Loney, Donald J. (Department: 1772)
Stock material or miscellaneous articles
Structurally defined web or sheet
Nonplanar uniform thickness material
C428S212000, C428S324000, C428S328000, C428S330000, C428S331000, C428S363000, C428S402000
Reexamination Certificate
active
06794016
ABSTRACT:
TECHNICAL FIELD
The present invention relates to recyclable water-resistant corrugated fiberboard sheets suitable for use as materials for corrugated fiberboard containers for transporting substances while keeping the freshness thereof, particularly materials for corrugated fiberboard containers for transporting perishable foods such as fresh fishes, vegetables, fruits and meats together with ice, which sheets can be easily produced and also easily macerated or disintegrated.
BACKGROUND ART
Corrugated fiberboard containers are widely used for the transportation. However, ordinary corrugated fiberboard containers have a disadvantage in that they are not resistant to water. Therefore, water-repellency and water resistance are imparted to corrugated fiberboard sheets to be used for making containers for water-containing foods such as fruits, vegetables, fresh fishes, meats and frozen foods, as well as contents which must be transported at a low temperature for keeping them fresh and thereby causing the moisture condensation.
As such corrugated fiberboards, those prepared by applying a molten wax to the surface of them or by impregnating them with the wax are known.
However, the corrugated fiberboards having such a wax applied thereto in a large amount cannot be recycled as waste papers. When such a corrugated fiberboard containing wax is collected together with the ordinary corrugated fiberboards as waste paper by mistake, it causes problems such as that a paper is broken in a regenerated paper-making step and that black spots of the wax appear on the regenerated product to seriously reduce the commercial value of the product.
Corrugated fiberboards produced by combining a corrugated fiberboard linerboard with a synthetic resin film such as a polyolefin film are also known. Also such corrugated fiberboard linerboards cannot be recovered as waste paper to be used as the starting pulp material and, they are burnt or buried for a landfill at present.
As strong demand for recycling resources is grown recently under these circumstances, various corrugated fiberboards which have water-repellency and water-resistance and which can be recycled and used as starting materials for waste paper pulp have been proposed.
For example, a method wherein a synthetic resin emulsion and a wax emulsion are applied to the surface of a linerboard to impart both water resisting function and water-repelling function to the corrugated fiberboards was proposed [see Japanese Patent Unexamined Published Application (hereinafter referred to as “J. P. KOKAI”) No. Sho 59-15596].
The corrugated fiberboards having the water-repellent layer prepared from such synthetic resin emulsion and wax emulsion have the water-repellent function and, in addition, they can be macerated and, therefore, they can be recycled.
Further, J. P. KOKAI No. Hei 10-226001 discloses a recyclable water-resistant corrugated fiberboard sheet prepared by imparting the water repellency to the surface of a corrugated fiberboard sheet linerboard to be adhered to a corrugated, water-resistant core sheet and also to the surface of the core sheet, so as to especially prevent the corrugated fiberboard sheet from wetting with water through the flute surface of the fiberboard and also to improve the water resistance of the corrugated fiberboard sheet.
However, when even such a corrugated fiberboard sheet is used as a material for boxes to be brought into contact with a large amount of water for a long period of time, such as boxes for frozen fishes or boxes in which perishable foods are to be packaged together with ice, water penetrates through the linerboard surface of the corrugated fiberboard sheet to reduce the strength of the sheet and thereby to cause the crushing of the boxes.
Therefore, the object of the present invention is to provide a water-resistant corrugated fiberboard sheet having a high water resistance and capable of being recycled after the use.
DISCLOSURE OF THE INVENTION
After intensive investigations made for the purpose of attaining the above-described objective, the inventors have found that the objective can be attained by constructing the corrugated fiberboard sheet as follows. The present invention has been completed on the basis of this finding.
Namely, the present invention relates to a recyclable, water-resistant corrugated fiberboard sheet comprising a water-resistant linerboard adhered to both surfaces of a corrugated, water-resistant core sheet (or corrugating medium), wherein the water repellency (JIS P8137) of at least one surface selected from the group consisting of both surfaces of the corrugated, water-resistant core sheet and the core sheet-side surface of the water-resistant linerboard is at least R 6 and that the Cobb water-absorption (JIS P8140; contact time: 30 minutes) of the surface of the corrugated fiberboard sheet (the surface of the water-resistant linerboard on the side not adhered to the corrugated, water-resistant core sheet) (i.e. at least one of both sides of the corrugated fiberboard sheet) is not higher than 30 g/m
2
.
In a preferred embodiment of the present invention, a water-resistant layer is formed on at least one of the surfaces of the corrugated fiberboard sheet by applying a water-resistant coating containing a synthetic resin emulsion or this emulsion and a pigment.
In another preferred embodiment of the present invention, the water-resistant coating contains 30 to 60% by mass, based on the solid content, of the pigment.
In still another preferred embodiment of the present invention, the pigment in the water-resistant coating comprises 5 to 40% by mass of a pigment having an average particle diameter of 5 to 15 &mgr;m and 95 to 60% by mass of a pigment having an average particle diameter of not larger than 3 &mgr;m.
In a further preferred embodiment of the present invention, the water-resistant coating contains a synthetic resin emulsion having a gel content of at least 90%.
In a further preferred embodiment of the present invention, the water repellency of each of the single facer side of the water-resistant core sheet and the surface of the water-resistant linerboard on the side adhered to the water-resistant corrugated core sheet is not higher than R 2, and the water repellency of each of the double facer side of the water-resistant core sheet and the surface of the corrugated fiberboard sheet is at least R 6.
In a further preferred embodiment of the present invention, at least one surface of the water-resistant core sheet carries 0.01 to 2.0 g/m
2
of a water repellent.
In a further preferred embodiment of the present invention, the water repellent comprises a wax having a melting point of not higher than 70° C.
In a further preferred embodiment of the present invention, the adhesive for bonding each of both surfaces of the corrugated water-resistant core sheet with the water-resistant linerboard is a water-resistant adhesive comprising a starch, an agent for making the starch water-resistant and a synthetic resin emulsion.
MODE FOR CARRYING OUT THE INVENTION
The water-resistant core sheet and the water-resistant linerboard used for producing the recyclable water-resistant corrugated fiberboard sheet of the present invention are those having a ring crush strength (residual strength after water immersion) after immersing them in water at 20° C. for 24 hours of at least 10%, when the ring crush strength of them in dry state is set 100% as determined according to JIS P8126.
The water-resistant core sheet and the water-resistant linerboard are prepared from a pulp which is usually used for preparing ordinary core sheets and linerboards. They are prepared by incorporating a water-resisting agent in the paper-making step or by impregnating the paper with the water-resisting agent or applying this water-resisting agent to the paper prior to the drying and then drying them in a paper-making machine. Concretely, HP 200 and MMS 200 (products of Hokuyo Seishi K.K.), etc. are available as the water-resisting core sheet on the market. As the water-resistant linerboard, for example, non-
Kumabe Masahiro
Nishiyauchi Tatsuhiko
Ogawa Fumito
Yamakoshi Masaru
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