Plastic and nonmetallic article shaping or treating: processes – Forming articles by uniting randomly associated particles – With liberating or forming of particles
Reexamination Certificate
2001-10-30
2003-08-12
Lechert, Jr., Stephen J. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming articles by uniting randomly associated particles
With liberating or forming of particles
C264S118000, C241S003000, C241S024280
Reexamination Certificate
active
06605242
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of producing styrenic resin granulates from styrenic resin powder, and to a shaped article produced by molding the granulates. More particularly, the invention relates to a method of producing styrenic resin granulates, with good manageability and extrudability, in a large-scale apparatus, the granulates having excellent hue and a small amount of residual organic solvent, as well as to a shaped article produced by completely melting the granulates and molding the resultant melt.
BACKGROUND ART
Styrenic polymers having a highly syndiotactic configuration (hereinafter may be abbreviated as SPS), which have been developed in recent years, have already found utility in a broad range of engineering plastics having excellent properties such as resistance to heat and chemicals.
Among methods of producing SPS, Japanese Patent Application Laid-Open (kokai) No. 187708/1987 discloses a method in which styrenic monomers are polymerized, in inert hydrocarbon solvent or in the absence of solvent, in the presence of a catalyst comprising a titanium compound and a condensation product of water and a trialkylaluminum.
In general, conventional SPS production processes employ small-scale apparatus and involve polymerization in a polymerizer; removal of volatile components and deactivation in an extruder; and pelletizing. Through such a very simple process, conventional styrenic resin granulates have been produced.
When the aforementioned SPS production process is carried out by use of a large-scale apparatus, the following problems arise in a granulation stage.
(1) High costs of a specially designed extruder and installation thereof.
(2) Requirements for use of a large motor and installation of a high-temperature heating medium for heating a jacket, thereby elevating variable costs.
(3) Cumbersome operation due to requirement for a crystallization apparatus after granulation.
(4) Increase in number of heat hysteresis cycles by melting resin during granulation, thereby readily deteriorating quality of products.
Thus, an object of the present invention is to provide, through solving the aforementioned problems arising during granulation when the scale of the SPS production process is elevated, a method of producing high-quality styrenic resin granulates in an industrially advantageous manner.
SUMMARY OF THE INVENTION
In view of the foregoing, the present inventor has conducted earnest studies on scale-up of the granulation system in the SPS production process, and has found that when a styrenic polymer (SPS) which has been removed from a polymerizer and from which volatile components are removed is subjected to a specific format of dry compression molding, SPS granulates(pellets) endowed with quality and manageability compared to those of conventional SPS granulates can be produced by means of a large-scale apparatus and in an industrially advantageous manner. The present invention has been accomplished on the basis of this finding.
Accordingly, the summary of the present invention is as follows:
[1] a method of producing styrenic resin granulates, comprising dry-compression-molding a powder of styrenic resin having a highly syndiotactic configuration at a compression pressure of 1-20 t/cm and at a molding temperature falling within a range of the glass transition temperature of the powder of styrenic resin to the melting point thereof, inclusive; and crushing the resultant molded product.
[2] a method of producing styrenic resin granulates according to above mentioned [1], wherein the produced styrenic resin granulates contain an organic solvent in an amount of 1 wt. % or less.
[3] a method of producing styrenic resin granulates according to above mentioned [1] or [2], wherein the powder of styrenic resin to be dry-compression-molded is obtained by continuously feeding styrenic resin powder containing an organic solvent to a vessel which contains styrenic resin powder and evaporating the solvent.
[4] a method of producing styrenic resin granulates according to any one of above mentioned [1] to [3], further comprising classifying particles obtained by crushing the molded product by means of a disintegrator by use of two-stage vibratory screens; disintegrating particles remaining on an upper screen by means of another disintegrator; and feeding, together with particles which have passed through a lower screen, the resultant disintegrated matter back to the upstream step performed in a dry compression molding apparatus, to thereby mix into styrenic resin powder serving as a raw material.
[5] a styrenic resin shaped article which is produced by completely melting and molding the styrenic resin granulates obtained through a method as recited in any one of above mentioned [1] to [4].
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention will next be described in more detail.
1. Styrenic Polymer Useful in the Present Invention
The styrenic polymer which is useful in the present invention has a highly syndiotactic configuration. The SPS powder removed from a polymerization tank contains residual volatile components such as unreacted monomers.
The term “syndiotactic configuration” refers to the stereochemical structure having a syndiotactic configuration; i.e., a steric structure in which side-chain phenyl groups and substituted phenyl groups are located alternately in opposite directions on a main chain comprising carbon-carbon bonds. The tacticity thereof is determined through the nuclear magnetic resonance method making use of an isotopic carbon (
13
C-NMR method).
The tacticity determined through the
13
C-NMR method can be represented by the number of existing plural continuous constitutional units. For example, in the case in which two continuous units exist, the tacticity is called a diad; in the case in which three continuous units exist, it is called a triad; and in the case in which five continuous units exist, it is called a pentad. The styrenic polymer having a syndiotactic configuration according to the present invention refers to polystyrene, poly(alkylstyrene), poly(halogenated styrene), poly(halogenated alkylstyrene), poly(alkoxystyrene), poly(vinyl benzoate), a halogenated polymer thereof, a mixture thereof, or a copolymer predominantly containing any of the above polymers, the syndiotacticity typically being 75% or more, preferably 85% or more in terms of a racemic diad, or typically 30% or more, preferably 50% or more, in terms of a racemic pentad.
Examples of the poly(alkylstyrene) include poly(methylstyrene), poly(ethylstyrene), poly(isoproylstyrene), poly(tert-butylstyrene), poly(phenylstyrene), poly(vinylnaphthalene), and poly(vinylstyrene). Examples of the poly(halogenated styrene) include poly(chlorostyrene), poly(bromostyrene), and poly(fluorostyrene). Examples of the poly(halogenated alkylstyrene) include poly(chloromethylstyrene). Examples of the poly(alkoxystyrene) include poly(methoxystyrene) and poly(ethoxystyrene).
Of these, examples of particularly preferred styrenic polymers include polystyrene, poly(p-methylstyrene), poly(m-methylstyrene), poly(p-tert-butylstyrene), poly(p-chlorostyrene), poly(m-chlorostyrene), poly(p-fluorostyrene), hydrogenated polystyrene, and a copolymer containing a moiety of any of these polymers as a structural unit.
Specific examples of preferred copolymers include styrene-p-methylstyrene copolymers containing p-methylstyrene repeating units in amounts of 3 mol % or more. No particular limitation is imposed on the molecular weight of the styrenic polymers, and the weight-average molecular weight thereof is preferably 10,000 or more, more preferably 50,000 or more. In addition, the molecular weight distribution profile is not particularly limited, and styrenic polymers having a wide variety of molecular weight distribution profiles may be employed. When the weight-average molecular weight is less than 10,000, thermal properties and mechanical properti
Idemitsu Petrochemical Co. Ltd.
Lechert Jr. Stephen J.
LandOfFree
Method of producing styrenic resin granulate and shaped article does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of producing styrenic resin granulate and shaped article, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of producing styrenic resin granulate and shaped article will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3075320