CS250035B1 - A method for demnominizing vinyl chloride copolymers or copolymers and apparatus for its implementation - Google Patents

Abstract

The invention relates to a method and a device for the demonomerization of suspension polymers or copolymers of vinyl chloride. The demonomerization is carried out in a column-type device by fluidizing the suspension with steam, while in order to improve the operability of the device, the undersides of the mechanical dividing partitions are continuously homogeneously sprayed with water in an amount of 50 to 300 kg/h. Homogeneous spraying is ensured by at least one suitably located nozzle.

Description

250035

The present invention provides a method and apparatus for continuously removing monomers from aqueous suspension of homopolymers and copolymers of vinyl chloride.

It is known that prolonged exposure of a human organism to a few de-ppm ppm of vinyl chloride in the air has a carcinogenic effect. As a result, in addition to the production of polyvinyl chloride and copolymer vinyl chloride, the requirements for removing residual vinyl chloride from these polymers are increasing, and for example, hygienic regulations for direct contact with foodstuffs exist as a permissible limit of 1 ppm of monomeric vinyl chloride in polyvinyl chloride. In addition, the careful grinding of the vinyl chloride ipol represents a significant economic benefit when the monomer content of the polymer dispersion is 2 to 4% by weight. (a known dry product is known from the literature. Removal of residual vinyl chloride monomer from polymer systems is known in some cases to demonomerize column systems. Recently, multi-patent applications have emerged that address the demo-polymerization of polyvinyl chloride. The NSR 2 441 304 demonomeration column contains a series of thaw-flat surfaces with a slope of 45 to 80% from the vertical inside, and the treated slurry is applied to the head of the column and passed through a layer in the countercurrent flow. The contact of the suspension with the water in this type of column is relatively small and a substantial high column is required to achieve the desired efficiency.

Improved contact is achieved in a grate column (German Patent No. 2,714,438), where the steam entering the bottom of the column is bubbled through the top-flowing polyvinyl chloride suspension. As an example in the 25th floor column, 200-400 ppm of vinyl chloride o-monomer in a demonomerized suspension is achieved, which is a lack of efficacy since, in order to obtain a 1 ppm of vinyl chloride monomer, The subsequent product needs to extend the drying degree, which may cause other major problems in continuous operations. (Better results in efficiency (~ 100 to 200 ppmj are reported by NSR No. 2,714,685, wherein the column consists of a cylindrical vessel equipped with sieve bottoms with a thickness of 5 to 15% and vellkoet holes 4 to 30 mm, on the surface of which is a drop-cyclone separator) A very effective hitherto known demineralisation device includes a sieve coil of H & chst AG (NSR 2 550 023) and (NSR no. It is a sieve wheel which, according to the examples, has 14 to 17 levels of sieves (~ 6% gap, 0 holes 2 mm) provided with 1 to 3 overflow tubes with an overflow height of 12 cm. about 10 ppm of the monomeric vinyl chloride in the suspension treated therein.

Very good effect is achieved by the procedure on the device according to MS. No. 204,533, but some of the drawbacks are that power barriers are introduced over time with a demonomerized suspension. Last but not least, the reduction in labor time is due to striking and cleansing, with cleaning being laborious. These drawbacks are eliminated by the present invention.

According to the present invention, the de-monomerization of the suspension polymers or copolymers of vinyl chloride is carried out by fluidizing the overheated or saturated water vapor in an amount of 30 to 100 kg of steam per m 3 of the feed suspension so that the mechanical partition above which the suspension is suspended is sprayed from below with water 5 to 85 ° C, preferably homogeneously flat, in an amount of 50 to 500 kg / h, preferably 100 to 250 kg / h per m 2 of mechanical separating partition.

The apparatus for making this method is made up of a multi-sieve sieve with an overflow height of 150 to 600 mm, wherein at least one spraying nozzle having a hole diameter of 0.3 to 1.5 mm is placed below the tray sieve at 100 to 400 mm, wherein the spray nozzle axis with the axis of the screen column is sharp.

Among the most advantageous advantages of the present invention is the fact that, despite the relative low operating and investment costs, a high demonomerization efficiency is achieved when the free monomer content of the 1 ppm product is even in the compact, hardly demo-non -izable types of suspension polymers. The demonomerization operating mode is manageable and exhibits consistently high iconic efficiency and operability.

The process and apparatus of the invention provide a high level of utilization of the working time, which is also very favorable to the process economics. The high efficiency of demo-ionization is also very important from an ecological and hygienic point of view.

All types of suspension polyvinyl chloride and suspension-produced vinyl chloride copolymer types can be processed by the process and apparatus of the present invention. As an example. mention may be made of vinyl chloride copolymers with vinyl acetate, olefins, acid-α-crystals and / or esters thereof, as well as suspension of chlorinated polyvinyl chloride, such as a suspension of tough polyvinyl chloride. Typically, the β-β 3 is between 10 and 50 percent by weight. It is preferred to be suspended in the demonomerization column by heating it close to the boiling point (at a given pressure) boiling point.

The pre-heated suspension is sprayed into the multi-stage sieve column, where it is fluidized with saturated or saturated streams. pre-heated steam. Due to the intensely turbulent mode, which, when fluidized, achieves the desorption of the monomeric vinyl, the chloride is very effective.

The slurry in the column gradually overflows from the tray to the final monomeric suspension containing about 1 mm of monomeric vinyl chloride leaving the column for further processing. By means of a demonomerization column, a device consisting of at least two stages is meant. Each stage of the demonomerization device is formed by a mechanical separating baffle, which is a sewn bottom, having a thickness of 0.1 to 4%, preferably 0.5 to 2%, through which at least one overflow passes, the total surface The ratio of the resin is 2 to 10%, preferably 4 to 7%, of the column cross-sectional area.

Linear saturated or resp. The pre-heated steam in the openings is 15 to 35 m / s, preferably 20 to 30 m / s. The overflow height of the sewn partition is 150 to 600 mm, thereby providing the desired contact time of the fluidized suspension with the vapor in the range of 40 to 300 s, preferably 60 to 150 s. over the lower deck floor, the ipod overflow area is unwelcome and is equal to or larger than the overflow surface itself.

At least one nozzle with apertures of 0.3 to 1.5 mm is placed under the screen bar, the axis of which is angled with the axis of the screen column. The nozzle edge is 100 to 400 mm away from the screen.

Said nozzle, respectively. The nozzles are also used to spray off the bottom of the screen which is fluidized with water, at a temperature of 5 to 85 ° C, preferably homogeneously flat, in an amount of 50 to 500 kg / h per m 2 of mechanical partition. By permanently spraying the bottom of the screen, the polymer particles are deposited on the lower part of the partition, and the demonomerization column and the whole monomer line are extended and uniformly spaced. Example 1

A suspension of porous type ipolyvinyl chloride containing about 30% dry matter and about 18,000 ppm residual vinyl chloride (dry matter) is passed at 8 m 3 / h through a heat exchanger and a heater (steam injector) at 96 ° C per head of the demonomer columns of the following parameters: 6 column diameter 900 mm number of trays 8 distance between screen bars 1 000 mm overflow height 400 mm spacing 1% diameter of holes 1,9 mm

The surface of the sewn compartments is polished, the entire device is made of 'stainless steel'. Under each tray, heads are fitted with five nozzles with a diameter of 0.4 mm disposed on the head so that one hundred angles with the column axis such an acute angle to achieve uniform spray surfaces. screen. The nozzles are at a distance of 200 mm from the bottom of the screen. The total amount of conduit supplied to the nozzles at a temperature of 10 ° C under each tray is 100 kg / h per 1 m2 of strainer.

Saturated vapor (0.5 MPa) is fed under the bottom tray in an amount of 450 kg / h. The head temperature of the column is 98 ° C, the temperature at the bottom of the column is 103 degrees C. The suspension from the demineralization column contains less than 1 µm of residual vinyl chloride. The liberated monomeric vinyl chloride and waterone are passed off from the top of the column to a condenser, where the vapor is predominantly condensed, and the ethyl chloride-enriched gas is recycled.

The demonomerization column in such an arrangement operated evenly for 3 months without purification, while only 1 week without the use of spray nozzles. Example 2

A demonomerization column as in Example 1 was used, except that the height of the pads was increased to 500 mm.

A pre-heated suspension of compact, hard demo-polymerizable type polyvinyl chloride in an amount of 6 m 3 / h was injected onto the column head. The dry matter content was about 32%, the residual vinyl chloride content was about 22,000 ppm. The amount of saturated steam (0.5MPa) fed under the bottom sieve tray was 350 kg / h, the column head temperature was 99 ° C, and the 106 ° C bottom tray. Spraying the lower parts of the sewn compartments provided a single 1.2 mm orifice nozzle positioned eccentrically at 250 millimeters below the screen bar, which provided such an acute angle with the column axis that the entire bottom surface was evenly sprayed. Water at 45 ° C was fed to the nozzle at 250 lkg / h per m 2 of screen screen.

The monomerized suspension leaving the column contained 1.8 ppm of residual vinyl chloride. Released monomeric

Claims (2)

1. A process for demonomerizing suspension polymers or copolymers of vinyl chloride by fluidizing by flowing superheated or saturated water vapor in an amount of 30 to 100 kilograms of steam per m ^{3 of} feed suspension, characterized in that the mechanical partition over which the suspension is fluidized is sprayed from below. a temperature of 5 to 85 ^Q C, preferably uniformly over the entire flat, in an amount of 50-500 kg / h, preferably 100-250 kg / h, per 1 m ² of the mechanical subdivision bulkheads. INVENTION 2. Apparatus for carrying out the method according to claim 1, formed from a multi-stage sieve column with an overflow height of 150 to 600 mm, characterized in that at least one spray nozzle with a bore size of 0.3 to 1 is located below the sieve at 100 to 400 mm. 5 mm, the axis of the spray nozzle being at an acute angle to the axis of the sieve column.