Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Production of continuous or running length
Patent
1997-02-28
2000-09-05
Silbaugh, Jan H.
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Production of continuous or running length
264561, 264562, 264564, 2642095, 26421111, 26421119, B29C 4788, B29C 4904
Patent
active
061138428
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for manufacturing oriented cellulose films by extruding a cellulose solution in a regenerating bath, to films manufactured according to the method, and their utilisation.
At present large number of products are being made world-wide from regenerated cellulose, such as fibres, films and other shaped bodies, predominantly by the viscose method. The viscose method however is disadvantageous because of the high degree of environmental stress and the high investment costs involved.
Proceeding from this point many efforts are being made to propose alternative methods. As regards the generation of cellulose fibres, a promising method is the spinning of solutions of cellulose in amino oxides. From DE 28 30 605, DD 142 000 and U.S. Pat. No. 3,767,756 is it known that cellulose is soluble in a N-methyl-morpholin-N-oxide (NMMNO)-water system, and can be processed to produce textile fibres by spinning in a normally aqueous NMMO solution. The composition of solutions and regenerating bath is further known from DD 201 703. In the abovenamed publication it is also disclosed that additives can be added to the regenerating bath.
SUMMARY OF THE INVENTION
The manufacture of cellulose blown films from NMMO solutions however has not previously been known in prior art.
Proceeding from this prior art it is the object of the present invention to indicate a method for manufacturing cellulose films, and the films themselves, and in which in particular the mechanical properties of the films are to be adjustable.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Surprisingly, the applicant was able to show for the first time that it is possible to obtain cellulose blown films when cellulose dissolved in amino oxide is extruded downwards into a regenerating bath through a film blower nozzle and an external air gap. The method according to the invention is characterised in particular in that it is possible by varying the parameters of the method to produce variously-oriented blown films. On the one hand, by varying the draw ratio and blow-up ratio, the longitudinal and cross stretch ratios can be adjusted. In this respect the draw and blow-up ratios can be varied within a range from 1 to 10. The films produced thereby then either have a unipolar-axial, a biaxial or a unipolar-biaxial orientation. A factor which is particularly surprising and could not have been foreseen is that the cellulose films can also have a uniplanar-biaxial orientation, the (101)-interplanar group (Meyer/Misch nomenclature) to the film surface and the chain axes being present to a varying degree, preferably oriented in the film's direction of travel and transversely thereto. The method according to the invention is further characterised in that an additional control of the mechanical properties is also possible by means of variation of the external air gap. The external air gap can in this case be varied within a range of 1 to 5 mm.
Tests have shown that with a maximum draw ratio of 5 and a blow ratio of 1, preferably weakly oriented uniplanar-axial structures result. By definition known in the art, the draw ratio is the ratio of the linear velocity of the tube being pulled through the precipitating bath and the linear velocity of the solution exiting the film-blower nozzle. By definition known in the art, the blow up ratio is the ratio between the circumference or diameter of the performed tube at the film-blower nozzle and the circumference or diameter of the blown-up tube. Since the circumference and diameter are proportional to each other, thus the ratio is the same.
When the air gap is set to more that 5 mm, uniplanar-biaxially oriented films are obtained, whose degree of orientation can be increased by increasing the withdrawal and cross stretch ratio.
Accordingly the method according to the invention is particularly characterised in that the mechanical properties of the blown films which can be produced can be altered both by varying the longitudinal and cross stretch in the air gap, and additiona
REFERENCES:
patent: 4416698 (1983-11-01), McCorsley, III
patent: 5451364 (1995-09-01), Ducharme, Jr. et al.
"Kunststoff-Lexikon", 7th edition, Cals Hanser Verlag Munich, Vienna 1981, p. 454-455.
Fink Hans-Peters
Frigge Konrad
Schwarz Wolfgang
Weigel Peter
Fraunhofer-Gesellschaft Zur Forderung Der Angewandten Forschung
Jones Kenneth M.
Silbaugh Jan H.
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