Plastic and nonmetallic article shaping or treating: processes – Forming articles by uniting randomly associated particles
Patent
1995-10-02
1997-04-08
Simmons, David A.
Plastic and nonmetallic article shaping or treating: processes
Forming articles by uniting randomly associated particles
264122, B27N 300
Patent
active
056184824
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/DK94/00378, Oct. 12, 1994.
TECHNICAL FIELD
The present invention relates to an improved method of producing fibreboard by a wet process, more specifically to a method comprising the steps of providing an aqueous slurry of lignin-containing wood fibre material, forming the aqueous fibre slurry into a mat, and pressing the formed mat by applying heat and pressure to produce the fibreboard. By the method of the invention is prepared fibreboard having improved mechanical properties.
BACKGROUND ART
Fibreboard is conventionally produced by defibration or steam explosion of wood chips to obtain wood fibres, forming a mat of the fibres, and pressing the mat while applying heat and pressure. Conventionally, the mat is prepared either by a dry process from wood fibres with a water content below 120% (by weight of the dry fibres) with addition of adhesives, or by a wet process from an aqueous slurry of wood fibres with a water content of 200-10000% (by weight of the dry fibres).
In the wet process, it is conventional to add a binder (adhesive) to the aqueous fibre slurry and/or to cure the fibreboard at high temperature after the pressing, in order to improve the mechanical properties of the fibreboard.
SU 636,311 and DD 271,078 disclose processes wherein microorganisms productive of enzymes such as laccase are cultivated on wood chips before defibration to make wood fibres for use in fibreboard.
It is the object of this invention to provide an improved wet process for producing fibreboard of improved mechanical properties without the need for the addition of binder or the final curing.
STATEMENT OF THE INVENTION
Surprisingly, we have found that fibreboard of improved mechanical properties can be produced by adding a phenol oxidizing enzyme system to the slurry in a wet process. Apart from the addition of the enzyme system, the process can be conducted at conventional conditions, without the need for any changes of equipment. The addition of the enzyme system results in improved mechanical properties of the fibreboard, such as decreased swelling, increased resistance to bending and increased transversal strength, without the need for the addition of a binder or a final curing step.
Accordingly, the invention provides a method of producing fibreboard, comprising the sequential steps of: fibreboard, improved mechanical properties of the fibreboard produced.
In the process of this invention, the enzyme system may act on lignin present on the fibres during the hot pressing and/or during an optional incubation step between steps (b) and (c).
BRIEF DESCRIPTION OF THE FIGURE
percent water uptake of the conditioned weight of the fibre board; .largecircle.: board formed from fibres treated with inactive laccase; .tangle-solidup.: board formed from fibres treated with active laccase.
DETAILED DESCRIPTION OF THE INVENTION
Wood fibre slurry
The wood fibres used in the process of this invention may be any type of lignin-containing fibres suitable for use in a conventional wet fibreboard process, e.g. softwood or hardwood produced by a mechanical or semi-chemical defibration or pulping process, i.e. grinding, TMP (thermomechanical pulping), CTMP (chemical thermomechanical pulping), NSSC (neutral sulphite semichemical); or recycled fibres. Thus, the wood fibres may be made by conventional defibration or steam explosion of wood chips for fibre board production.
The water content of the wood fibre slurry is preferably from about 200% to about 10000% (based on the weight of dry wood fibre material), more preferably from about 500% to about 5000%.
pH of the slurry is preferably from about 3 to about 10, depending on the enzyme used; pH from about 3 to about 7.5 is suitable for laccase, and pH from about 6 to about 10 is suitable for peroxidase.
Phenol oxidizing enzyme system
The enzyme system used in the method of the present invention consists of a suitable oxidase together with O.sub.2 or a suitable peroxidase together with H.sub.2 O.sub.2. Suitable enzymes are those which oxidize and p
REFERENCES:
patent: 2037522 (1936-04-01), Lundback
patent: 4194997 (1980-03-01), Edler
patent: 4432921 (1984-02-01), Haars et al.
patent: 5342765 (1994-08-01), Irvine et al.
SU 636,311, Sukhaya et al, Soviet Patent application, published May 12, 1978 Bulletin No. 45.
DD 271 078 A1, Wagenfuhr et al., Industrial Patent granted Aug. 23, 1989.
Andersen Lars H. D.
Olesen Tine
Pedersen Lars S.
Gregg, Esq. Valeta
Jones Kenneth M.
Novo Nordisk A S
Simmons David A.
Zelson Esq. Steve T.
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