Preparation of vinyl chloride polymer

• US 6,274,690 B1
• Filed: 08/11/2000
• Issued: 08/14/2001
• Est. Priority Date: 08/11/1999
• Status: Expired due to Fees

• Current Assignee: Shin-Etsu Chemical Company Limited
• Original Assignee: Shin-Etsu Chemical Company Limited
• Inventors: Ishii, Tatsuo, Hoshida, Shigehiro, Noguki, Genji
• Primary Examiner(s): Wu, David W.
• Assistant Examiner(s): CHEUNG, WILLIAM K
• Application Number:
  US09/636,745
• Time in Patent Office: 368 Days
• Field of Search: 526/62, 526/344.2, 526/344
• US Class Current: 526/344
• CPC Class Codes: C08F 14/06 Vinyl chloride
• CPC Class Codes: C08F 2/18 Suspension polymerisation

Abstract

A vinyl chloride polymer is prepared by charging a reactor with a vinyl chloride monomer, effecting polymerization, removing a slurry of the polymer from the reactor, and washing the reactor interior with water, and repeating the series of steps. The reactor has an internal volume of at least 40 m³. A cylinder-guided lift type washer assembly having a nozzle is secured to the reactor at its top in a sealed manner such that the nozzle can be moved downward and upward in the reactor. Water is fed to the nozzle through the assembly for injecting water from the nozzle into the reactor for cleaning. The large size reactor can be effectively washed with water in the closed state, and vinyl chloride polymers of quality with least fisheyes are produced batchwise, leading to an improved productivity.

Claims

1. A process for preparing a vinyl chloride polymer, comprising the steps of

providing a reactor having an internal volume of at least 40 m³ and a cylinder-guided lift type washer assembly with a nozzle movable downward and upward in the reactor, said assembly being secured to the reactor at its top in a sealed manner,

charging said reactor with water, and with a vinyl chloride monomer alone or with a mixture of a vinyl chloride monomer and a monomer copolymerizable therewith, to form an aqueous medium,

effecting polymerization in said aqueous medium to form a polymer,

removing a slurry of the polymer from the rector,

washing the interior of the reactor with water by feeding water to the nozzle through the assembly and injecting said water from the nozzle into the reactor while moving the nozzle downward and then upward over a stroke of at least 1 meter, and

repeating the charging, polymerization, polymer removal, and washing steps.

2. The process of claim 1, wherein the reactor is maintained at an internal pressure of 0 to 7 kg/cm²G (0.101 to 0.0788 MPa·

Gauge) during the washing step.

3. The process of claim 1, wherein the nozzle is moved downward and then upward at least twice.

4. The process of claim 1, wherein the vinyl chloride polymer produced has no more than 12 fisheyes per 100 cm².

5. The process of claim 1, wherein the wash water is fed under a pressure of 1 to 50 kg/cm²G.

6. The process of claim 5, wherein the wash water is fed under a pressure of 1 to 40 kg/cm²G.

7. The process of claim 6, wherein the wash water is fed under a pressure of 1 to 25 kg/cm²G.