Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Woven fabric – Including a paper or wood pulp layer
Reexamination Certificate
1997-07-24
2001-04-24
Raimund, Christopher (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Woven fabric
Including a paper or wood pulp layer
C442S401000, C442S412000, C428S537500, C156S176000, C156S308800
Reexamination Certificate
active
06221798
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods for making multi-layer composites containing layers of fibrous materials laminated with synthetic films and the like.
BACKGROUND OF THE INVENTION
Laminated webs may be made from a variety of materials for a variety of applications. When one of the layers of laminate is a fibrous web to which a synthetic sheet or film is to be attached, conventional practice is to first prepare the fibrous web and then apply the synthetic sheet or film to the web. Accordingly, the layers of the laminate are made separately and then combined in a separate lamination step.
The use of separate forming and lamination steps for laminating synthetic sheets or films to fibrous webs requires separate equipment to store and handle each component. These separate steps add to the cost and complexity of the process.
Accordingly, it is an object of the invention to provide a method for making a laminate comprising a synthetic sheet or film and a fibrous web.
Another object of the invention is to provide a lamination method of the character described which is carried out during formation of the web.
A further object of the invention is to reduce the number of process steps and the time required to form a laminated fibrous web.
An additional object of the invention is to provide a lamination method of the character described which enables simplified, high speed production of laminated fibrous webs.
Still another object of the invention is to provide a laminating method of the character described which is versatile and enables production of laminates with a desirable range of aesthetic and functional characteristics.
SUMMARY OF THE INVENTION
With regard to the above and other objects, the invention provides a method for laminating a synthetic film or sheet to a fibrous web. The method comprises continuously depositing an aqueous slurry of fibers on a moving foraminous support equipped to drain water from the slurry leaving fibers deposited thereon as a continuous fibrous web and pressing the web to consolidate the fibers to provide a pressed web having a moisture content of at least about 40% by weight. A continuous layer containing a heat-softenable polymeric material is combined with the pressed web in interfacial contact with fibers of the web to provide an at least two-layer continuous composite having opposed outer surfaces. The composite is continuously conducted through an extended nip dryer and pressure is applied substantially simultaneously to the opposed outer surfaces of the composite in the dryer while applying heat to at least one of the surfaces to cause evaporation of water from the fibrous web, reducing the moisture content of the web to below about 40% by weight water and plasticizing the heat-softenable polymeric material so that at least a mechanical bond is achieved between the layer and the fibrous web characterized by an intermingling of fibers in the fibrous web with the polymeric material in the layer.
According to another aspect of the invention, an on-line lamination process is provided for fibrous webs. The process comprises continuously conducting a continuous fibrous web having a moisture content ranging from about 40 to about 70% by weight water and a continuous layer comprising a heat-softenable polymeric material in interfacial contact therewith through an extended nip dryer to provide a continuous at least two-layer composite having opposed outer surfaces. In the dryer, pressure is applied substantially simultaneously to the opposed outer surfaces of the composite and heat is applied to at least one of the surfaces of the composite to cause evaporation of water therefrom substantially reducing the water content of the web. The heat applied to the composite together with steam generated by water vaporized from the web causes the polymeric material to soften so that fibers from the web intermingle with the material forming a bond therebetween. In one embodiment, water is applied to the web before it passes through the dryer to provide the necessary moisture content for steam generation in the dryer.
An additional aspect of the invention involves a process for making a three or more layer composite by an on-line lamination process. In the process, an elongate bonding layer containing a heat-softenable material provided as a powder, spray, film or sheet is continuously combined with an elongate first fibrous web. An elongate second fibrous web is combined in interfacial contact with the bonding layer to provide an at least three-layer composite with the bonding layer sandwiched between the first and second fibrous webs. Heat and pressure are applied to the composite in an extended nip dryer unit sufficient to cause the fibers of the first and second webs to become intermingled with the bonding layer in order to bond the first and second webs together. The first and second fibrous webs may comprise natural or synthetic fibers and at least one of the first or second webs has a moisture content from about 40% by weight to about 70% by weight. The other web preferably have a moisture content no higher than about 80% by weight. The bond layer disposed between the webs may comprise a fibrous web containing a heat-softenable material in particulate or powder form or a sheet or film comprised of a heat-softenable material. Additional layers and webs may be applied to the three layer composite to produce multi-layer composite webs.
Conventionally, laminated webs comprised of different materials are produced by combining pre-formed sheets or webs and then bonding the materials together in a separate step using heat, pressure and/or an adhesive with conventional laminating equipment such as press-rolls and the like. The process of the invention departs from such prior practices in the case of fibrous web components of such laminates by using a wetted web in an extended nip dryer enabling the composites to be produced on-line while the fibrous web is being made thereby achieving an efficient and economical mode of production and an improved product with a more tenacious and uniform bond between the layers. The process therefore provides a significant advance in the art of laminating materials to fibrous webs and provides substantial savings in terms of equipment costs and process time.
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Tampella Papertech; “The Basic Condebelt Process Can be Modified to Satisfy a Variety of Special Quality Demands”; Jukka Lehtinen,World Pulp & Paper Technology1993 1992, pp. 105-110.
Karles George
Mahale Anant D.
Srivatsa Narendra
Yu Xiang
International Paper Company
Luedeka Neely & Graham P.C.
Raimund Christopher
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