Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Patent
1994-08-12
1997-12-23
Ryan, Patrick
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
428508, 428516, 4287033, 264171, 15624411, B32B 900
Patent
active
057005869
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to a laminate according to the preamble of claim 1.
Such a laminate incorporates at least one first layer comprised of cellulose fibers, at least one second layer spaced apart the first layer, said second layer being comprised of a material which is at least substantially insoluble in water, and at least one third layer which is arranged between said first and said second layer and is capable of interbonding said layers.
The invention also concerns a method for producing this laminate, and the use thereof.
2. Description of the Related Art
Growing environmental problems, limited capacities of dump sites and resultant constraints imposed by the tightening regulatory measures require an increasing degree of recycling in all activities, including the packaging sector. Traditionally, paper and paperboard have been utilized in recycling by way of repulping, that is, defibering of an aqueous waste paper slush. The industry also makes use of repulping methods compatible with combination fiber/plastic systems. The goal has been to separate plastic from fibre to the highest degree so that the fibre fraction can be reused.
Prior-art technology suffers, however, from the problem that conventional combination plastic/fiber products frequently contain plastics of low molecular weight (e.g., hot-melt glues), which in aqueous defibering are easily carried through into the fiber reuse process and cause impairment of paperboard or paper product produced by such a process. Furthermore, detachment of a pure polymer coating or plastic layer from a laminate structure is extremely difficult in aqueous defibering due to the strong adherence of plastic on cellulose fibres. In pulping, such combination materials must be treated so vigorously that the detached plastic is torn into small pieces that, despite the long washing times employed, still contain plenty of paper fibres. The resultant plastic scrap finds hardly any recycling use, and consequently, its typical fate is combustion or dumping. Finally, the fibre fragmentation into so-called fines is promoted by the elongated aqueous defibering and relatively high temperature employed in waste paper furnish preparation process.
To overcome the above-described drawbacks, the plastics industry has developed polymers soluble in acidic or basic conditions. Such polymers have also been used in different types of laminates and similar products.
The EP Patent Specification No. 316,676 describes adhesive layers for labels etc. that are soluble in basic conditions. The adhesive layers employed here are copolymers of acrylic or methacrylic acid and acrylate or methacrylate, respectively. The solubility property is designed to aid removal of labels from, e.g., bottles and similar objects.
Polymer layers made of corresponding copolymers have also been used for binding notebooks and similar items as is described in the EP Patent Specification No. 330,997. For recycling the pages of such notebooks, soaking in an alkaline aqueous solution is used for unbinding of the pages. A paperboard or paper sheet can be bonded onto such an adhesive layer so forming the cover or front page of a notebook. The above-described polymer-paper laminate is made using wide-slot lip die extrusion. The publication does not make it clear that the laminate structure would also be decomposable under alkaline wash treatment or that this prior-art method would aim at recovery of the polymer component.
The EP Published Patent Application No. 88,373 describes the binding of a book with the help of a polymer layer comprised of a polyvinyl alcohol layer and an adhesive layer. Such a mere PVA layer is soluble in hot water, of course, but while also being sensitive to moisture, it is not suited to, e.g., the conditions occurring in the use of conventional packages.
The U.S. Pat. No. 3,968,310 describes the coating of a paper web with a hot-melt type composition by way of brush application of said composition onto the web. The applied polymer
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Laiho Erkki
Sainio Markku
Borealis Polymers OY
Ryan Patrick
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