Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Patent
1997-03-27
1998-12-08
Bell, James J.
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
427 229, 427195, 427336, 4273898, 4283044, 442180, B05D 300
Patent
active
058466401
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for the preparation of a fibre product pre-impregnated with a polymer (prepreg). The invention relates further to a novel prepreg, a method for the manufacture of fibre reinforced composite based on the use of said prepreg, the novel composites and their use.
BACKGROUND OF THE INVENTION
The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.
Dental devices made from polymers are prone to fracture in the oral conditions. For instance, it is well documented that a removable denture can fracture after the denture has been worn for some years, (1-4). Consequently, an ideal reinforcement of a denture should be used both in the fabrication of a new denture and in repairing of an old denture. The polymer devices and constructions in dentistry have traditionally been reinforced with metal inclusions of the polymer (5-7). The effect of the metal inclusions in the strength of the polymer device or construction is, however, inadequate. Attempts have been made to develop a polymer-fibre composite which can easily be used as reinforcement of dentures. Before the date of the present invention, no fibre-composite products fulfilling the requirements of the clinical dentistry and the dental laboratory technology have been achieved, even though one fibre ribbon product exists on the market for use in dentistry (Ribbond.RTM., Ribbon Inc., Seattle, Wash., U.S. Pat. No. 5,176,951).
Known polymer-fibre composites for prosthetic dentistry have been made by dipping the fibre bundle, ribbon or weave in methylmethacrylate (MMA) monomer or in a mixture of polymethylmethacrylate (PMMA) powder and its monomer (MMA). Composites made by this method are, however, not suitable for use in dentures because of the following shortcomings: PMMA to be used in denture repairing, i.e. autopolymerizing PMMA (8), compression moulding of the PMMA (12), fibres on the denture surface (14).
Attempts have also been made to manufacture a pre-impregnated fibre bundle with a polymer (which is called a polymer-fibre prepreg). Three general methods for the manufacture of such thermoplastic polymer-fibre prepregs have been reported (15): whereby the monomer is incorporated into a fibrous preform, layers of polymer film, and powder which is then melted.
These methods have, however, some shortcomings in terms of dental requirements. The in situ polymerization, even though it can be used with PMMA, results in a composite having polymerization shrinkage voids in the structure, wherein said voids will be filled with saliva and oral microbes. The film stacking method yields a composite with poor degree of impregnation (i.e. the fibre bundle is not sufficiently impregnated by the polymer). The insufficient degree of impregnation will also cause voids in the structure of the composite. The powder coating method includes melting of the polymer powder. This method results in a prepreg of a dense structure which is difficult to plasticize before the usage by dissolving the polymer. Consequently, any of the methods used in general plastic industry to produce fiber composites are not suitable for use in fabrication or repairing of dentures.
OBJECT AND SUMMARY OF THE INVENTION
The requirements imposed by clinical dentistry and dental technology on a prepreg useful in dentistry reinforcement are the following: of the oral cavity, i.e. the prepreg should be plastic at room's temperature when used in denture fabrication or repairing, with unfilled (i.e. fibre free) polymer, surrounding polymer, irrespective of whether it is a heat-curing polymer or an autopolymerizing polymer, and as autopolymerizing polymer.
One object of the invention is a prepreg fulfilling the aforementioned requirements 1) to 5).
Another object of the invention is the use of said prepreg in the manufacture of fibre reinforced composites. Said composites are suitable for use in any tec
REFERENCES:
patent: 4919978 (1990-04-01), Winkler et al.
patent: 4954304 (1990-09-01), Ohtake et al.
patent: 5011721 (1991-04-01), Decker et al.
International Preliminary Examination Report for PCT/FI96/00095.
Bell James J.
Bioxid Oy
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