Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-09-15
2004-11-16
Davis, Robert (Department: 1722)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S207000, C523S210000, C385S143000
Reexamination Certificate
active
06818683
ABSTRACT:
BACKGROUND OF THE INVENTION
Semi-crystalline polymers have been used to form fibers for textile applications for many years. The physical properties of a fiber is dependent on polymer molecular orientation and structural morphology developed during fiber spinning. The mechanical properties for the fibers are directly related to molecular orientation. Resins with higher molecular weight produce higher strength fibers if processed under the same processing conditions. The higher the degree of orientation the higher the tensile strength for a given fiber. However, the degree of crystallinity and crystalline structure play a very important role in producing fibers with good dimensional stability. Selecting high molecular weight polyolefin polymers with narrow molecular weight distribution keep the impurities to a minimum. These polymers can easily be extruded and drawn into extremely transparent fibers with controlled morphology. The high molecular weight allows the formation of strong fibers and obtain a very high degree of both amorphous and crystalline orientation. The high degree of crystallinity obtained by using such polymer provides dimensional stability that cannot be obtained using amorphous polymers.
Since polyolefins melt at low temperatures, extruding and processing of these polymers requires minimum energy as compared to all other polymers. For example, glass melts at 1200 C. and other amorphous polymers melt at much higher temperatures as compared to polyolefins. Therefore, it is much cheaper to produce optical fibers from polyolefin semi-crystalline fibers than those from glass and other amorphous polymers. These fibers are much lighter due to their inherent low densities and have excellent flexibility for handling. Glass fibers are simply too heavy and too fragile for handling and they require sophisticated claddings and end-to-end attachment devices.
In the manufacture of synthetic fibers including polypropylene, nylon and polyester, molten polymer is extruded through small holes to form filaments which are drawn down and solidified on rotating rolls. In a second stage the solidified filaments are passed from a slow roll to a fast roll drawing them down several times in diameter. The filaments formation process is known as melt spinning, the solid state stretching process as drawing.
It has been well established in the melt spinning process that polymer melts are converted to uniaxially oriented filaments. The orientation in melt spun filaments has been investigated by various researchers using wide angle x-ray scattering (WAXS), birefringence and small angle x-ray scattering (SAXS). Generally molecular orientation has been expressed in terms of Hermans-Stein orientation factors, with WAXS being applied to crystalline orientation and birefringence to detect amorphous orientation [Kitao, T., Yamada K., Yamazaki, T., Ohya S.: Sen-i-Gakkashi, 28, p. 61 (1972); Kitao, T. Ohya. S., Furukawa. J. Yamashita. S.: J. Polym. Sci. Polym. Phys. 11, p. 1091 (1973); Abbott, L. E. White, J. L.: Appl. Polym. Symp. 20, p. 247 (1973); Dees, J. R., Spritiell, J. E.: J. Appl. Polym. Sci. 18, p. 1055 (1974); Spruiell, J. E., White, J. L.: Polym. Enj. Sci. 15, p. 660(1975); Nadella, H. P., Henson, H. M. Spruiell J. E., White, J. L.: J. Appl. Polym. Sci. 21, p. 3003 (1977); Bankar, V. G., Spruiell. J. E., White. J. L. J. Appl. Polym. Sci. 21, p. 2341 (1977); Shimizu. J., Toriumi, K., Imai, Y.: Sen-i-Gakkashi 33, p. T-255 (1977); Danford M. D., Spruiell. J. E. White, J. L.: J. Appl. Polym. Sci. 22, p. 3351 (1978); Heuvel, H. M., Huisman, R.: J. Appl. Polym. Sci. 22, p. 2229 (1978)]. This orientation is found to be a unique function of the spinline stress. For the case of polyolefins WAXS has generally detected a lamellar structure which at high spinline stresses is oriented perpendicular to the fiber axis [Dees, J. R., Spruiell J. E.: J. Appl. Polym. Sci. 18, p. 1055 (1974); Spruiell J. E., White. J. L.: Polym. Enj. Sci. 15, p. 660 (1975); Nadella, H. P., Henson, H.M., Spruiell J. E., White, J. L.: J. Appl. Polym. Sci. 21, p. 3003 (1977); Katayama, K., Amano, T., Nukamura, K.: Koll Z—Z Polym. 226, p. 125 (1967), Noether, H. D., Whitney, W. Koll Z—Z Polym. 251, p. 991 (1973); Sprague, B. S., Macromol, J.: Sci. Phys. B8, p. 157 (1973)]. From the work of Keller and Machin [Keller, A., Machin. M. J. J.: Macromol. Sci. Phys. 131, p. 41 (1967)], Dees and Spruiell [Dees, J. R., Spruiell J. E.: J. Appl. Polym. Sci. 18, p. 1055 (1974)] and later investigators it is generally hypothesized that the structure observed by SAXS and WAXS consists of folded chain lamellae. These lamellae are arranged in aggregates to form a spherulitic superstructure when melt spinning is carried out at low spinline stresses but at higher spinning stresses they nucleate along lines parallel to the filament axes and grow radially outward to form a so called “row structure” or cylindrite morphology.
In the drawing process, filaments first exhibit local necking but they eventually become uniform at a point known as the natural draw ratio. The necked regions and drawn out filaments exhibit significantly increased levels of polymer chain orientation [Fankuchen, I., Macrk, H.: J. Appl. Phys. 15, p. 364 (1944); Wyckoff H. W.: J. Polym. Sci. 62, p. 83 (1962); Kasai, N., Kakudo, M.: J. Polym. Sci., pt. A2, p. 1955 (1961); Samules, R. J.: J. Polym. Sci. A-26, p. 2021 (1968); White, J. L., Dharod, K. C., Clark. E. S.: J. Appl. Polym. Sci. 18, p. 2539 (1974); Sze, G. M., Spruiell, J. E., White, J. L.: J. Appl. Polym. Sci. 20, p. 1823 (1976); Nadella, H. P., Spruiell, J. E., White, J. L.: J. Appl. Polym. Sci. 22, p. 3121 (1978); Kitao, T., Spruiell, J. E., White, J. L.: Polym. Eng. Sci. 19, p. 761 (1979)]. Another phenomenon occurring during the drawing process is the development of fibrillation which transforms the initially solid homogenous filament into a non-homogenous structure containing many “fibrils” together with elongated voids [Samuels, R. J.: J. Polym. Sci. A-26, p. 2021 (1968); White, J. L., Dharod, K. C., Clark, E. S.: J. Appl. Polym. Sci. 18, p. 2539 (1974); Sze. G. M., Spruiell. J. E., White, J. L.: J. Appl. Polym. Sci. 20, p. 1823 (1976), Nadella, H. P., Spruiell, J. E., White, J. L.: J. Appl. Polym. Sci. 22, p. 3121 (1978); Kitao, T., Spruiell, J. E., White, J. L.: Polym. Eng. Sci. 19, p. 761 (1979); Statton, W. O.: J. Polym. Sci. 41, p. 143: Sakaoku. K., Peterline, A.: J. Polym. Sci. A-29, p. 895 (1974); Glenz, W., Morossoff, N., Peterlin, A.: Polymer Letters 9, p. 211 (1971); Muzzy, J. E., Hansen, D.: Textile Res. J. 41, p. 436 (1971); Vonk, C. G.: Colloid Polym. Sci. 257, p. 1021 (1979)]. It is this problem and its interaction with melt spinning that is a concern. In general, observations of fibrillation have been qualitative in character, with authors noting the existence of this phenomenon, and sometimes hypothesizing mechanisms [Sakaoku, K., Peterline, A. J. Polym. Sci. A-29, p. 895 (1971); Peterlin, A.: J. Polym. Sci. 9, p. 61 (1965)]. Investigations [Sze, G. M., Spruiell J. E., White, J. L.: J. Appl. Polym. Sci. 20, p. 1823 (1976); Kitao, T., Spruiell, J. E., White, J. L.: Polym. Eng.Sci. 19, p. 761 (1979)] using SAXS and scanning electron microscopy (SEM) have indicated that in high density polyethylene and polypropylene fibrillation tends to increase with draw ratio and decrease with increasing draw temperature.
SUMMARY OF THE INVENTION
The present invention is an optical fiber made of semi-crystalline polymer. By “semi-crystalline” it is meant that the final fiber product produced by the teaching herein has from about 30% to about 99% crystallinity.
The apparatus for manufacturing optical fiber made of semi-crystalline polymers includes: An extruder heats polymer resin to produce molten polymer and supplies the molten polymer at a constant pressure. A gear pump is in fluid communication with the extruder, receives the molten polymer and controls the polymer flow rate. A spinneret is in fluid communication with the gear pump a
Davis Robert
Del Sole Joseph S
First Quality Fibers, LLC
Morgan & Lewis & Bockius, LLP
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