Abstract: A polymerization apparatus used, particularly, in suspension polymerization of vinyl chloride, comprising a polymerization vessel (1) having a substantially cylindrical inner space, said inner space of said polymerization vessel being provided with a plurality of baffles (5) comprising vertically extending pipes, and serpentine pipelines (6) each of which is placed between two adjacent baffles and is extended in a serpentine fashion along the polymerization vessel inner wall from the lower part to the upper part of the polymerization vessel, and a refrigerant being passed through said baffles and said serpentine pipelines. High-cooling performance can be obtained, a high-speed reaction in a large-sized polymerization vessel becomes possible, and a stable polymerization reaction can be carried out. A high-quality and uniform polymer that has few fish eyes and has a high bulk specific gravity can be obtained.

Abstract: A vinyl chloride polymer is produced by subjecting vinyl chloride or a monomer mixture made up mainly of vinyl chloride to suspension polymerization in an aqueous medium using a polymerization apparatus equipped with a polymerization vessel. The polymerization apparatus used comprises a polymerization vessel (1) having a substantially cylindrical inner space, said inner space of said polymerization vessel being provided with a plurality of baffles (5) comprising vertically extending pipes, and serpentine pipelines (6) each of which is placed between two adjacent baffles and is extended in a serpentine fashion along the polymerization vessel inner wall from the lower part to the upper part of the polymerization vessel, and a refrigerant being passed through said baffles and said serpentine pipelines. High-cooling performance can be obtained, a high-speed reaction in a large-sized polymerization vessel becomes possible, and a stable polymerization reaction can be carried out.

Abstract: A signal level display unit which makes adjustment for correcting of deviation unnecessary and enables cost reduction. An input analog audio signal 26 is divided into seven signals having different frequency bands, converted into digital signal by an A/D converter 22, input to a display controller 25, and temporarily stored in a storage unit 32. A preset recovery time which is input to the display controller 25 through an A/D converter 28 is also stored in the storage unit 32. The value of each signal newly input from the A/D converter 22 is compared with the current value stored in the storage unit 32. When the value of a newly input signal is higher than the current value, the value displayed by a liquid crystal indicator 23 is immediately renewed. On the other hand, when no signal having a higher value than the current value is input, the displayed value is renewed after the preset recovery time stored in the storage init 32 has elapsed.

Abstract: In a voltage drop detecting circuit, when voltage Vcc being monitored is at a steady-state value, reference voltage B is classified by divided voltages Va to Vc from detection voltage generation circuit group for classification of reference voltage. In accordance with the result of that classification, one of the divided voltages Va to Vc from detection voltage generation circuit group for detection of a drop in the voltage being monitored is selected as detection voltage A. Since the resistance ratio can be expressed fairly correctly in ICs, the circuit structure of the voltage drop detecting circuit is capable of reducing the apparent range of variation of reference voltage B, whereby the precision of detection is improved.

Abstract: An improvement is proposed in the method for the preparation of a polyvinyl chloride resin by the suspension polymerization of the monomer in a polymerization reactor system comprising a reactor and an external heat exchanger connected to the reactor by a pipe line through a pumping means in order to supplement the deficiency in the cooling capacity of the jacket of the reactor and/or reflux condenser installed thereto when the capacity of the reactor is greatly increased.

Abstract: An apparatus for producing a vinyl chloride-based polymer which comprises a polymerization vessel for carrying out suspension polymerization of a monomeric material containing at least vinyl chloride dispersed in an aqueous suspension, and a circulating passage extended from said polymerization vessel and through a heat exchanger back to said polymerization vessel for circulating a polymerization reaction mixture, wherein the polymerization reaction mixture returning from said circulating passage into said polymerization vessel is sprayed inside the polymerization vessel so that the inside wall portion of said polymerization vessel in a gas-phase zone is entirely wetted with the polymerization reaction mixture.

Abstract: A polymerization apparatus that is equipped with a circulation path for the flow of a reaction mixture that comprises a polymerization vessel, a heat exchanger arranged outside said polymerization vessel, and a pipeline that is extended from said polymerization vessel, is returned to said polymerization vessel through said heat exchanger, and is provided with a strainer in the course thereof, wherein the surface of a filter provided in said strainer that is located upstream has rodlike projections, and a method of producing a polymer of a monomer having an ethylenically unsaturated double bond by using said apparatus. Scale and polymers in the form of blocks can be prevented from mixing into the reaction mixture. Therefore, where the obtained sheet is molded into a sheet or the like, fish eyes can be reduced and even if the polymerization is repeated, clogging of the tubes of the heat exchanger and dropping in the flow velocity of the reaction mixture can be prevented.

Abstract: A process for producing a vinyl chloride-based polymer by suspension polymerizing vinyl chloride monomer or the like while circulating a reaction mixture in a polymerization vessel by a circulating pump through a circulation line led out from the polymerization vessel to extend through a heat exchanger back to the vessel, wherein the pump comprises a conical hub and an impeller comprised of a spirally shaped single blade provided on the hub, and, during polymerization, the stirring energy (A) applied to the reaction mixture by the stirrer in the polymerization vessel and the circulating energy (B) exerted to the reaction mixture by the circulating pump in the circulation line are controlled so as to satisfy the relationships(A)+(B)=from 1.5 to 4.0 kW/t (1)and(B)/[(A)+(B)]=from 0.1 to 0.6 (2)Polymer scale is prevented from being deposited on inner surfaces of the heat exchanger, circulation piping, circulating pump or the like.

Abstract: A process for producing a vinyl chloride-based polymer, which comprises suspension polymerizing vinyl chloride monomer or a vinyl chloride-containing monomeric mixture in an aqueous medium in the presence of an oil-soluble polymerization initiator, wherein the initiator comprises (A) at least one compound having a 10-hour half-life temperature, at a concentration of 0.1 mol/l in benzene, of not lower than 35.degree. C., and (B) at least one compound having a 10-hour half-life temperature, at a concentration of 0.1 mol/l in benzene, of lower than 35.degree. C., with the amount of the initiator (B) being from 0.01 to 0.07% by weight based on the monomer or monomeric mixture and being from 10 to 30% by weight based on the total amount of the initiators (A) and (B). The process makes it possible to shorten easily the time required for raising temperature, and to produce vinyl chloride-based polymers which have a good particle size distribution and which have few fish eyes when formed into sheets or the like.

Abstract: A polymerizing apparatus for polymerizing a monomer having an ethylenically unsaturated double bond which is equipped with a polymerization vessel having an agitator and a return nozzle to a gaseous phase part and with a circulating pipeline extending from said polymerization vessel and connected to said return nozzle of the polymerization vessel through a heat exchanger, in which said return nozzle is installed such that it discharges a reaction mixture in the direction which is tangential to the circumferential wall of the vessel and in which the agitator is rotated. Scale of a polymer can be prevented from depositing in the polymerization vessel and it is possible to reduce the number of fish eyes of a molded product such as a sheet into which the polymer obtained by the present polymerizing apparatus can be worked.

Abstract: In a polymerizing apparatus which comprises a polymerization vessel and a circulating line comprising a heat exchanger installed outside said polymerization vessel and a circulating pipeline extending from said polymerization vessel and returning to said polymerization vessel through said heat exchanger, the improvement comprising a strainer installed in the course of said circulating pipeline. Since polymer scale and a polymer in the form of blocks formed in the circulating line can be trapped, the circulating pipeline and tubes of the heat exchanger can be prevented from being blocked up. Further, since they can be prevented from mixing with a reaction mixture in the polymerization vessel, when the obtained polymer is worked into a molded item such as a sheet, fish eyes can be prevented from increasing. Therefore, a polymer can be produced efficiently with high productivity.

Abstract: A process for producing a vinyl chloride-based polymer in which an aqueous suspension of a vinyl chloride-based monomeric material placed in a polymerization vessel equipped with an agitating element is subjected to suspension polymerization by introducing a polymerization initiator to the aqueous suspension at a position located inside the diameter of the agitating element being rotated. By this process it is possible to prevent totally the deposition of polymer scale on the inside wall of the polymerization vessel, particularly in the vicinity of a gas-liquid interface. Therefore, troubles arising from polymer scale formation and labor needed for removing such polymer scale are obviated, and a vinyl chloride-based polymer of high quality can be produced efficiently.

Abstract: An apparatus for continuous polymerization of vinyl chloride or a vinyl chloride-based monomeric mixture, comprising a pre-mixer 1 for preparing an aqueous suspension of the vinyl chloride or vinyl chloride-based monomeric mixture, and a polymer slurry tank 5 connected to the pre-mixer 1 through a polymerization passage comprising a piping 3, wherein a pump comprising a conical hub and an impeller mounted thereon comprised of a single spiral blade is used for drawing out the aqueous suspension from the pre-mixer into the polymerization passage and for discharging a polymer slurry formed in the passage into the slurry tank, and the polymerization passage has a length sufficient for permitting the vinyl chloride or vinyl chloride-based monomeric mixture contained in the aqueous suspension flowing through the passage to be polymerized to a predetermined extent while passing through the passage.