Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1996-11-01
2000-08-15
Szekely, Peter A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524 35, C08L 102
Patent
active
061037907
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to polymer matrixes reinforced with cellulose fibers, to their production in the form of aqueous suspensions, and to certain uses.
BACKGROUND OF THE INVENTION
Industry generally calls for composite materials consisting of a polymer matrix whose properties, in particular the mechanical properties, must be adapted by incorporation of fillers or reinforcements. Certain of these composite materials are produced from copolymer latexes and fibers. These are the materials to which the present invention relates. With regard to reinforcement, the advantage of cellulose, in particular particles of microcrystalline cellulose, has already been recognized, for the reinforcement of polymers from using their solutions, for example, the aqueous solutions of carbamide resins mentioned in WO 93/10172, or else for the production of compositions for nail polishes (U.S. Pat. No. 4,891,213) of which the secondary but important properties such as transparency or luster of the composite have been assessed. Also envisaged has been the filling or reinforcing with cellulose by the ordinary methods of compounding of thermoplastic resins (for examples see: Composite Systems from Natural and Synthetic Polymers, by Kalson et al. in Materials Science Monographs, 36, Elsevier 1986, or else Future Prospects for Wood Cellulose as Reinforcement in Organic Polymer Composites, by Zadorecki et al. in Polymer Composites, 10/2, p. 69, 1989).
DISCLOSURE OF THE INVENTION
It has now been found that it is possible to produce composites of completely unexpected quality consisting of a thermoplastic polymer and a reinforcement of individualized cellulose microfibrils, with as means of production, latexes incorporating said cellulose microfibrils. For the convenience of language, these latexes will be described in the shortened form of reinforced latexes.
In the sense of the present invention, individualized cellulose microfibrils is understood to mean forms of cellulose which are present in the form of more or less rigid elements, with an average length greater than a micrometer, whose diameter is between approximately 2-30 nm, and preferably greater than 7 nm, with a aspect ratio, that is to say the length/diameter ratio which is always greater than 60, and whose degree of crystallinity is greater than 20%, and preferably greater than 70%.
Generally, cellulose is present in the form of a hierarchy of structures. The cellulose molecules are always biosynthesized in the form of microfibrils, which are in turn assembled into fibers, films, walls, etc. The cellulose microfibril can be considered to be an important structural element of natural cellulose. It consists of an assembly of cellulose chains whose average degree of polymerization is greater than 1,000 and whose degree of perfection in their parallel organization is expressed in its crystallinity percentage. It is obtained from crude cellulose whose content with respect to the dry weight of the cell walls of which it constitutes the reinforcement ranges from 30% (parenchymal cellulose) to 95% (tunicin cellulose). It is therefore necessary to apply a dilaceration, bleaching and cleansing treatment to the cellulose raw material in order to obtain a crude cellulose, and then to obtain the microfibrils from it by powerful shearing in a homogenizer. The plant cellulose microfibrils are associated together in a parallel manner in the secondary walls of interlaced in a disordered manner in the primary walls. The dissociation of the secondary walls is difficult; in contrast, in the primary walls, it is much easier. The parenchyma is an example of a tissue only containing the primary wall. A model for treatment of animal cellulose is given in Examples 1 and 1bis for obtaining tunicin microfibrils. For obtaining parenchymal microcellulose, it is possible to apply the treatments recommended by Weibel (U.S. Pat. No. 4,831,127) for obtaining crude cellulose.
All the microfibrils do not develop the quality of reinforcement which is currently looked for
REFERENCES:
patent: 4452722 (1984-06-01), Turbak et al.
patent: 4483743 (1984-11-01), Turbak et al.
patent: 4487634 (1984-12-01), Turbak et al.
patent: 4842924 (1989-06-01), Farris et al.
patent: 5102601 (1992-04-01), Farris et al.
Polymer Composites, vol. 10, No. 2, Apr. 1989, pp. 69-77, Future Prospects for Wood Cellulose as Reinforcement in Organic Polymer Composites, P. Zandrecki, et al.
"Cellulose in Polymeric Composites", Klason, et al., Composite Systems From Natural and Synthetic Polymers, L. Salmen, pp. 65-74.
PCT/IB338 with English Translation of PCT/IPEA/409 dated Feb. 28, 1996.
Cavaille Jean-Yves
Chanzy Henri
Ernst Benoit
Favier Veronique
Elf Atochem S.A.
Szekely Peter A.
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