Stock material or miscellaneous articles – Hollow or container type article – Nonself-supporting tubular film or bag
Reexamination Certificate
2001-03-06
2003-03-18
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Hollow or container type article
Nonself-supporting tubular film or bag
C428S035600, C428S036300, C428S036400, C428S532000, C428S536000, C428S537500, C427S171000, C427S206000, C427S208600, C427S324000, C427S364000, C427S394000, C427S414000, C427S415000
Reexamination Certificate
active
06534138
ABSTRACT:
TECHNICAL FIELD
The present invention pertains to a packaging material with high printability and recyclability. The invention further relates to a method for producing such a packaging material.
The herein utilized expressions “recyclability” and “recyclable raw materials” pertains to both material and energy recovery, such as the re-use of raw materials included in the packaging material when producing new packaging material, biological recovery of nutritious substances included in the packaging material by means of composing, energy recovery when combusting the packaging material, and the like.
Before or in connection with the use of the packaging material according to the invention in a package, a distance layer, included in the packaging material and comprising a matrix material and reinforcement fibres of cellulose, is expanded, wherein both the matrix material and the reinforcement fibres of cellulose are based on renewable and recyclable raw materials. Before the expansion, the distance layer has been applied onto and bonded to one or several surface layers which comprise cellulose fibres.
The surface layer(s) of the packaging material according to the invention provide(s) one or several smooth external surfaces with high printability. Furthermore, the packaging material according to the invention can, in a simple way, be re-used as a raw material for new packaging material. The packaging material according to the invention is intended to replace corrugated board and other packaging materials with similar fields of application. The packaging material according to the invention can, for example, be utilized in boxes or in protective, sheet-shaped wrappings, and also in applications with higher demands on printability than what is normal for conventional corrugated board.
BACKGROUND OF THE INVENTION
Corrugated board is a long ago well-known packaging material and provides a number of significant advantages, such as low weight, high stiffness, recyclability and a proportionately low price.
The manufacture of corrugated board starts from liner and fluting. Thereby, liner refers to a paper grade with high tensile and tear resistance, which is intended to constitute surface layers in the finished corrugated board. Liner is preferably manufactured from unbleached sulphate pulp of softwood, but recently there has been a changeover to the utilization of recycled fibres, originating from corrugated board, as a raw material in so-called testliner.
Furthermore, with a view to improve the printability, the manufacture of multi-layered liner has been initiated, wherein the layer of the liner which is intended to be visible in a finished corrugated container is constituted of bleached chemical pulp and/or contains a filler with high brightness. As a rule, such liner is called “white top liner”.
The fluting is the undulating paper layer in corrugated board and has the task of providing the finished corrugated board with high stiffness and bulk, preferably by means of creating distance between the liner layers being part of the corrugated board. Fluting is generally manufactured from semi-chemical pulp, for example neutral sulphite pulp (NSSC).
There are corrugated board grades which have one single liner layer, which by means of a suitable adhesive has been attached to an undulating fluting layer in a corrugated board machine intended for this purpose.
However, it is occurring more frequently that two liner layers have been attached onto each side of an undulating fluting layer, or that the corrugated board consists of larger number of alternating liner and fluting layers, for example in the sequence liner/fluting/liner/fluting/liner. Thereby, the number of layers is determined, amongst other things, by the durability which is required from the finished corrugated container.
When manufacturing corrugated board, a frequently occurring chemical additive is different forms of starch or starch derivatives. Such an addition of starch can, for instance, be utilized as a dry strength agent in the liner production, or as an adhesive when converting liner and fluting into corrugated board.
The gradually increasing demand on resource economy and recycling have resulted in that corrugated board waste, and waste paper containing corrugated board, today can be recycled without any problems worth mentioning, as long as the main components included are cellulose fibres and starch and the starch content does not become too high. Certain synthetic adhesives, plastic layers, plastic particles and other additives in packaging materials, however, can render the recycling difficult and lead to disturbances in the production. Therefore, it is desirable that the recycled raw material which is re-used, for example in liner production, does not contain large amounts of such unwanted components, and that the content of starch or starch derivatives in relation to the content of cellulose fibre is not too high.
In connection with this, it may be mentioned that also other “natural” polymers, having similar properties as starch, can function well for recycling in a production process for liner, fluting or other raw material for packaging material. There are a number of such “natural” polymers, which are based on renewable raw materials and which, in principle, can be recovered in a corresponding way as starch, as long as the content of “natural” polymer in the process does not become too high. Examples of such “natural” polymers, which in this context usually can be placed on an equal footing with starch, are carboxy-methyl cellulose (CMC), alginate, casein, animal glue, polylactides (PLA), pentosanes, chitin and other polymers which have been manufactured from natural, in the short term renewable, non-fossil raw materials.
It has preciously been suggested to produce packaging material out of expanded starch. Accordingly, the patent publication U.S. Pat. No. 5,035,930 discloses a biodegradable shaped product comprising an expanded starch, having a high amylose content of at least 45%. The expanded product is claimed to have a low density, a closed cell structure, and to be compressible. In U.S. Pat. No. 5,035,930, the use of the expanded starch material in a biodegradable packaging material, such as an insert or a loose fill, is also disclosed.
Furthermore, the patent publication EP 0 696 612 A2 discloses biodegradable foamed articles and a process for their preparation. The foamed articles are claimed to have a density between 5 and 300 kg/m
3
and are obtained by means of agglomerating foamed particles having a composition comprising a themoplastic starchy material or a thermoplastic natural polymer capable of absorbing water when converted into the thermoplastic state, a thermoplastic polymer and water. The task of the thermoplastic polymer is claimed to be to improve the strength of melted composition, and to obtain foamed particles with high elasticity and low moisture sensitivity. In EP 0 696 612 A2, if is also disclosed that sandwich structures easily can be formed by means of bonding one or several sheets or panels which have been obtained by means of agglomeration of foamed particles, and that the biodegradable sheets or panels can be joined together with paper sheets, cardboard sheets or a film or a sheet of a biodegradable plastic material or of a conventional plastic material. Furthermore, its is disclosed that cellulose fibres can be included in such sheets or panels together with the foamed particles, WO 94/05492 discloses a laminate comprising hardened starch which is bound to another material. The laminate is obtained by extruding a suspension of expanded starch between two outer layers.
Something which might be perceived as a disadvantage with conventional corrugated board is that the undulating fluting layer is attached to the liner only at its wave crests. This often results in problems with so-called “washboarding effects”. This Implies that the external surface of the corrugated board, i.e. the liner, assumes a washboard-like structure with wave crests and wave troughs. This results in a heav
Jonasson Alf
Thornton Jeff
Burns Doane Swecker & Mathis
Kiliman Leszek
SCA Packaging Marketing NV
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