Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-06-29
2001-08-28
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C523S200000, C524S500000, C524S513000, C524S522000, C524S523000
Reexamination Certificate
active
06281278
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a modified thermoplastic resin composition and a process for preparing it. More specifically, the present invention relates to a process for continuous preparation of a modifier-containing thermoplastic resin wherein a modifier useful for fibers, films and other molded products is added and/or copolymerized therewith to give high uniformity and good dispersing properties, and to a thermoplastic resin composition obtained by the process.
BACKGROUND ART
Polyesters, polyamides, polyolefins and other representative thermoplastic resins (Throughout this specification, the simple term “resin” will sometimes be used to refer to such “thermoplastic resins”.) have excellent physical and chemical properties and are therefore widely used as fibers, films and other molded products. Despite their superior properties, however, such resins are associated with such undesirable problems as poor workability during molding, or poor manageability as a result of unsatisfactory sliding properties of the molded products themselves during their handling.
Several techniques have already been developed in order to solve these problems. For example, numerous methods have been proposed for improving the surface slidability of molded products by including fine particles in the resins to provide suitable irregularities on the surfaces of the molded properties, and a few of these methods are being employed. Taking polyesters as an example, there is a process whereby silicon oxide, titanium dioxide, calcium carbonate, talc, kaolinite or other inactive inorganic particles are added to the polyesters (see, for example, Japanese Unexamined Patent Publication No. 55-133431), and a process whereby heat-resistant polymer particles such as silicon particles or polystyrene particles are added to the polyesters (see, for example, Japanese Unexamined Patent Publication No. 3-115354).
The aforementioned thermoplastic resins are also used, in a wide range of industrial fields, as modified resins endowed with new properties such as flame retardance, electrostatic properties, dyeability, dyeing clarity and heat resistance which cannot be obtained by resins alone, while still maintaining the original excellent properties of the resins. Techniques for producing resins which meet the demands for such a wide range of uses include, in addition to the inclusion of particles as mentioned above, also methods of copolymerization or blending of the resins with different functional substances for different purposes, and such methods provide good results in terms of high performance and high functionability of the final products.
One process which has been attempted as a technique for giving various functions to thermoplastic resins involves providing a mixing apparatus in the polymer transport line of the molding step for reeling or film formation, to uniformly add and mix different additives with the resins. However in most cases, since the thermoplastic resins are highly viscous when in a molten state, addition and mixture of particulate, liquid or pasty additives directly with the resins results in poor dispersability of the additives in the resins and insufficient quality when used as fibers or films.
Thus, in order to improve the dispersability of additives, inclusion of such additives to resins has been accomplished by a method wherein a “master batch” containing a given additive at high concentration is prepared first and kneaded into the molten resin to improve the dispersability of the additive in the resin. According to this method, preparation of the master batch allows the viscosity and surface tension of the master batch to be adjusted to match that of the resin with which it will be kneaded, for kneading of the master batch with the resin, and thus allows the state of admixture to be improved. In the kneading systems for such master batch processes, static mixing apparatuses used as part of the transport line up to molding of the resin are a publicly known type of mixing apparatus. An example of a known process where such a static mixing apparatus is employed is one in which two types of chips, for the resin and the master batch, are blended prior to the kneading extruder for melting of the chipped resin, and after loading and melting, they are passed through a static mixing apparatus and sent to a reeling machine (see Japanese Unexamined Patent Publication No. 59-126457). According to this process, however, mixture of the resin is accomplished not dynamically but statically, and therefore since there is no external energy during mixing there has been a limit to the extent of admixture of the additives. As a result, the density and quality of obtained products have been non-uniform, the dispersion of additives in resins has been inadequate, and their uses have been limited to a narrow range including those which do not demand high performance products.
Incidentally, systems for polymerization of thermoplastic resins are gradually shifting from the conventional batch systems to continuous polymerization systems. This is because continuous polymerization systems give products with less quality variation than batch polymerization systems, are suitable for mass production of specific grades over long periods, and are overwhelmingly advantageous in terms of cost. In addition, products discharged from batch polymerization systems have lower intrinsic viscosity with time, more quality variation between different batches resulting in poor color, and more variation in stocked materials and quality variation between batches due to differences in reaction conditions, etc. In order to solve these problems, such as the problem that once the resin has been chipped it must be blended with chips obtained from a different batch, continuous polymerization systems achieve low quality variation by keeping constant and consistent control of the operating conditions in each step. Also, when disturbances or other variations occur, it is relatively easy with continuous polymerization systems to minimize changes in resulting products with time during the polymerization step by appropriately controlling the process conditions so as to eliminate such disturbances. In addition, while it is difficult to increase the performance of existing equipment for each batch in a batch system, in the case of continuous polymerization systems the advantages have been multiplied by recent progress in technological innovations which allow scaled-up production.
Despite the advantages described above, continuous polymerization systems have a disadvantage in that they are not adaptable for small-scale production of different product types. In particular, for production of modified thermoplastic resins containing various modifiers such as those mentioned above, changing the type of modifier requires cleaning of the entire massive continuous polymerization apparatus, resulting in a huge loss which includes that of polymer waste, cleaning chemicals and time. With the rapid progress in scaled-up size and product diversity in recent years, these disadvantages of continuous polymerization systems have become ever more serious.
In light of this background, the greatest technical issue in the field of producing resin compositions has recently become that of determining how to achieve production with increased dispersion of modifiers in different modified thermoplastic resin compositions without losing the cost merit of continuous polymerization, and how to diversify for different final needs.
In addition, with the development of continuous polymerization systems it has recently become practical to accomplish direct film formation and spinning for formation of films and spinning of fibers. With developing techniques, continuous polymerization-based direct film formation and direct spinning systems are being employed in the attempt to eliminate steps which are essential in batch systems, such as transport of the fully polymerized polymer to the film formation or spinning step after first being chipped, stored in a silo and d
Kurihara Hideshi
Maekawa Tatsuji
Nakao Takuo
Takase Toru
Cain Edward J.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Teijin Limited
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