JPS63146907A - Production of vinyl chloride resin - Google Patents

Abstract

PURPOSE:To produce a vinyl chloride resin for sheets free from fish-eye, by removing vinyl chloride polymer dust collected with multicyclones to the outside of the system in drying and transporting processes in the production of vinyl chloride resin by a suspension polymerization method. CONSTITUTION:In the production of vinyl chloride resin by a suspension polymerization method, vinyl chloride dust collected with multicyclones 2, 4 and 6 equipped in process of drying the vinyl chloride polymer and of transporting the vinyl chloride polymer to a vinyl chloride resin product tank is removed to the outside of the system to give the objective resin. Namely, e.g., a vinyl chloride polymer slurry is continuously sent to a centrifugal separator 10 and water is separated from the slurry to give a cake with a water content of 15-25%. When the cake is dried and by-produced fine polymer particles are collected with multicyclones 2, 4 and 6, rotary valves 7, 8 and 9 are closed to store the fine polymer particles in stock tanks 11, 12 and 13. When the drying operation is finished, the rotary valves 7, 8 and 9 are opened to remove the fine polymer particles to the outside of the system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to the production of vinyl chloride resin for sheets with good fisheye properties.

(Prior art) Fish eyes (hereinafter abbreviated as rFEJ) impair the appearance of products made from vinyl chloride resin and lower their commercial value.Furthermore, when printing on a sheet of vinyl chloride resin, the printing may occur on the FE portion. Particularly in the field of hard sheets where the amount of plasticizer is small, there is a high demand for vinyl chloride resins with low FE.

As a method to achieve the objective of reducing F'E'r, there is a method of devising various types and combinations of initiators and dispersants used in the polymerization of vinyl chloride. Since the combined particles absorb the plasticizer and become easily crushed, the effect of reducing FE is enhanced. However, if only a small amount of plasticizer can be used, the porosity of the vinyl chloride polymer particles will not be improved because the amount of plasticizer that can be absorbed is small.

Next, various measures have been taken to prevent the contamination of particles with a higher degree of polymerization than vinyl chloride polymer particles. In other words, polymerization is carried out using various techniques such as thorough cleaning and rinsing of the polymerization vessel after completion of polymerization, slurry transport piping, cleaning of slurry tanks before grade switching, rinsing with water, cleaning of drying pipes, centrifugal separators, product tanks, and rinsing with water. Measures are taken to prevent the contamination of high-grade polymer particles.

However, despite the above measures, the reality is that a hard vinyl chloride resin with low FE has not been obtained.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a method for producing a vinyl chloride resin with low F'E.

[Means for solving problems]

The present invention removes the vinyl chloride polymer dust collected by Multichron, which is present during the drying process of the vinyl chloride polymer and the transportation process to the vinyl chloride resin product tank in the production of vinyl chloride resin by suspension polymerization, out of the system. The gist is a method for producing vinyl chloride resin.

The inventors conducted various studies for the above purpose, and as a result of measuring the FE of the vinyl chloride polymer collected from the polymerization vessel and the vinyl chloride resin collected from the product tank immediately after the completion of polymerization, it was found that the FE was always collected from the product tank. It was discovered that vinyl chloride resin has less FE. This was completely unexpected since it was common knowledge in the industry that vinyl chloride resin, which has a higher degree of polymerization than the vinyl chloride resin produced as described above, was mixed in as a cause of deterioration of hard FE. .

As a result of further research, the present inventors found that vinyl chloride polymers obtained by suspension polymerization are usually dried by hot air drying.

For this reason, a cyclone or multiclone is always installed at the hot air outlet to separate the air and vinyl chloride polymer. Fine vinyl chloride polymer powder that could not be captured by the cyclone is captured by the multi-clone, and only air exits from the outlet. However, the vinyl chloride polymer (hereinafter abbreviated as "Multicron product") captured by Multichron
When mixed with vinyl chloride resin, which was tested in a comparatively small amount in the total hard FE test, it was found that the number of FE increased dramatically. In other words, it was discovered that this multi-chlorine product was the cause of the deterioration of hard vinyl chloride FEi.

From the above, the polyvinyl chloride resins produced by not returning the polyvinyl chloride polymers to the drying process or product production had low FE, as expected.

The configuration of the present invention will be explained in detail below.

A flow sheet of the transportation process to the tank will be illustrated and explained along this flow sheet.

The vinyl chloride polymer slurry was continuously centrifuged in the centrifugal direction 1 from A.
It is sent to a machine 10 and mechanically separated from water to have a water content of 15 to 25.
% cake. This cake is 15% in Sunzu primary drying system.
The moisture content is lowered to about 3-4% with hot air at 0°C to 160"C, and the powder is collected in cyclone 1 as a powder that is difficult to adhere to.
Transfer to secondary drying system. At this time, the fine particles further go to the MultiCron 2 and are captured there. Normally, the captured fine particles are transferred to a secondary drying system via a rotary valve 7.

In the secondary drying system, hot air at 60°C to 80°C is blown from below to fluidize the polymer particles and reduce the moisture content to 0.3%.
Lower it below. At this time, fine particles are captured by the secondary drying system MultiClon 4, but usually they are all returned to the system from above the vibrating sieve. The thus dried vinyl chloride polymer particles are sent to a product tank after coarse particles are removed using a vibrating sieve.

At this time, a suction multi-cron 6 is also installed on the tank to capture fine particles, which are also returned to the vibrating sieve and into the system.

The present invention provides a process that does not return the fine vinyl chloride polymer particles captured by the MultiClon in each of 2.4.6 above into the system.
'. Specifically, the rotary valve 7.8.9 under the multicolon is stopped, the polymer fine particles are stored in the stock tanks 11, 12, 13, and after the vinyl chloride polymer is dried, the rotary pulp 7.8.9 is This is a method of moving it out of the system.

Furthermore, the amount of slurry fed to the drying system is preferably smaller than the normal amount. This is because by increasing the collection efficiency of the Multichron, it is possible to reduce the particles that degrade F E fK in the product.

The dispersant used in the suspension polymerization in the present invention may be a known dispersant, such as cellulose derivatives such as methylcellulose, ethylcellulose, flobylcellulose, hydroxyethylcellulose, and hydroxypropylcellulose, partially saponified 1? Synthetic polymers such as RI & vinyl, polyacrylic acid, maleic anhydride-vinyl ether copolymer, propylene glycol fatty acid ester, glycerin
et? Esters such as fatty acid H ester, saccharide acid ester, and sorbitan fatty acid ester can be used alone or in combination.

The present invention includes 1. Id, 2,2'-azobis-2,4-dimethylvaleronitrile, 2,2'-7:/bis-4-methoxy2,4-dimethylvaleronitrile as an oil-soluble polymerization initiator used in suspension polymerization in - , azo compounds such as 2,2'-azobisisobutyronitrile, peroxides such as lauroyl peroxide, benzoyl peroxide, t-butylperoxypivalate, t-butylperoxyneodecanate, di-isopropyl Peroxydicarbonate, di-5ec-butyl peroxycarbonate, di-2-ethylhexyl quine dicarbonate, di-3-methoxybutyl peroxydicarbonate, di-methoxyisopropyl peroxydicarbonate, di-ethoxyethyl peroxydicarbonate carbonate, peroxydicarbonates such as di-cyclohexyl peroxydicarbonate, bis(4-butylcyclohexyl)peroxydicarbonate, acetylcyclohexylsulfonyl peroxide, acetyl-2-ethylhexylsulfonyl peroxide, etc. One or more types of sulfur-containing peroxides may be used.

〔Example〕

Examples are described below, but the present invention is not limited thereto.

Note that hard FE was determined under the following conditions.

1) Formulation (PHR) P V C100 Dibutyltin maleate stabilizer 4 Butyl stearate 0.5 Ethylene glycol monostearate lubricant 0. s Calcium stearate 0.2 Ultramarine 0.01 2) 20 scrap shoulder extrusion conditions die: inflation, compression ratio 2.5, screw length 500
11N Temperature 1i: cl: 185°C, C2: 195°C, C9: 2
00°C, DI: 190°C, D2: 195°C rotation speed
90 rpm Screen 1 piece of 60 mesh wire mesh, 1 piece of 100 mesh wire mesh 3) FE judgment Number of ungelled particles per 100 aJ of inflated membrane Example 1 Pure water 31200 in a stainless steel polymerization vessel with a content of 65 nl
kg, partially saponified polyvinyl acetate (saponification degree 80%)
18 kg, 2.21-azobis-2゜4-dimethylvaleronitrile 9 and vinyl chloride 22,850 kQ1r were charged, and heated with stirring to maintain the temperature inside the polymerization system at 67°C at 7.3 kti/dG. The slurry obtained by stopping the polymerization and discharging all unreacted vinyl chloride is sent to the centrifugal separator 10 from A using the apparatus shown in Figure 1, where it is mechanically separated from water to form a cake with a water content of 24%. did.

This cake has a moisture content of 3% with hot air at 150℃ in the primary drying system.
This becomes a powder that is difficult to adhere to, is captured by the cyclone 1, and transferred to the secondary drying system.

At this time, the fine particles further went to the MultiCron 2, but the rotary pulp 7 was stopped to prevent them from returning to the system.

The polymer particles transferred to the secondary drying system were fluidized by hot air at 80°C blown from below, and the water content reached 0.25%. At this time, fine particles were collected by the secondary drying system MultiClon 4, but the rotary valve 8 was stopped to prevent them from returning into the system.

The vinyl chloride polymer powder thus dried was sent to a product tank after coarse particles were removed using a vibrating sieve. The rotary valve 9 was stopped to prevent fine particles captured by the suction multi-clon 6 installed on the tank from returning to the system.

The degree of polymerization of the dried vinyl chloride resin was 700.

Further, the drying amount at this time was 4 T/Hr (based on dry resin).

The hard FEO numbers of the vinyl chloride fat thus obtained were as shown in Table 1 below.

Example 2 The same method as in Example 1 was carried out except that the drying amount was 3 T/Hr (based on dry resin).

The number of hard FE in the obtained vinyl chloride resin was as shown in Table 1.

Comparative Example 1 The same method as in Example 1 was carried out except that the vinyl chloride polymer particles captured by rotating the 0-tally valve 7 were returned to the system.

Comparative Example 2 The same method as in Example 1 was carried out except that the vinyl chloride polymer particles collected by rotating the 0-tally valve 8 were returned to the system.

Comparative Example 3 The same method as in Example 1 was carried out except that the vinyl chloride polymer particles captured by rotating the 0-tally valve 9 were returned to the system.

Comparative Example 4 The same method as in Example 1 was carried out except that all seven Multichrome products were returned to the system.

The hard FE number of the vinyl chloride resins obtained in Comparative Examples 1 to 4 was the first
It was as shown in the table.

Comparative Example 5 The hard FE number of the resin obtained by collecting and drying the slurry after polymerization in Example 1 was as shown in Table 1.

Comparative Example 6 The same method as Comparative Example 4 was carried out except that the drying amount was changed to 3 T/Hr (dry resin base).

The hard FE numbers were as shown in Table 1.

From the actual paddle examples 1.2 and Comparative Examples 1 to 6, it is clear that the FE reduction effect when cutting multichrome products is obvious.

Also, even when cutting, if the amount of drying is reduced, it will be even more F.
It can be seen that it is effective in lowering the level of E (Example 1
, from the comparison of Example 2).

However, it is clear that no matter how much the amount of drying is suppressed, returning the multi-chlorine product to the system will not lead to an improvement in FE (from a comparison of Example 2 and Comparative Example 6).

Example 3 Example 1 except that the dispersant used in the polymerization was partially saponified polyvinyl acetate (saponification degree 70%) and the amount added was 13 kg.
It was carried out in exactly the same way.

The degree of polymerization of the dried vinyl chloride resin was 710.

The hard FE properties of the obtained vinyl chloride resin were as shown in Table 2.

13-Example 4 The same method as Example 3 was carried out except that the drying amount was changed to f 3 T/Hr (dry resin base). The number of hard FE in the obtained vinyl chloride resin was as shown in Table 2.

Comparative Example 7 The same method as in Example 3 was carried out except that the vinyl chloride polymer captured by rotating the 0-tally valve 7 was returned to the system.

Comparative Example 8 The same method as in Example 3 was carried out except that the 0-tally valve 8 was rotated and the captured vinyl chloride resin was returned to the system.

Comparative Example 9 The same method as in Example 3 was carried out except that the 0-tally valve 9 was rotated and the captured vinyl chloride resin was returned to the system.

Comparative Example 10 The same method as in Example 3 was carried out except that all seven Multichrome products were returned to the system.

The hard FE numbers of the vinyl chloride resins obtained in Comparative Examples 7 to 10 were as shown in Table 2.

Comparative Example 11 The slurry obtained in Example 3 after the completion of polymerization was collected and dried.

The hard FE numbers of the resins were as shown in Table 2.

Comparative Example 12 The same method as Comparative Example 10 was carried out except that the drying amount was changed to 3 T/Hr (dry resin base).

The hard FE numbers were as shown in Table 2.

From Example 3.4 and Comparative Examples 7 to 12, even in the case of a polyvinyl chloride resin polymerized with the addition of a dispersant with a saponification degree of 70%, the polymerization product was compared with one polymerized with the addition of a dispersant with a saponification degree of 80%. It is clear that the FE level is slightly good when cut, but when the Multichrome product is returned to the system, the FE level deteriorates significantly.

It is clear from the above that regardless of the type of dispersant, multi-chlorine cut is effective in improving hard FE.

Table 1 Table 2

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of an example of the process of drying a vinyl chloride polymer and the process of transporting it to a vinyl chloride resin product tank for carrying out the method of the present invention. In the figure, 1 is a primary drying cyclone, 2 is a primary drying multiclone, 3 is a secondary drying cyclone, 4 is a secondary drying multiclone, 6 is a suction cyclone, 6 is a suction multiclone, and 7 .8.9 is a rotary pulp, 10 is a centrifugal separator, and 11.12.13 is a stock tank. that's all

Claims (1)

[Claims] Production of vinyl chloride resin by suspension polymerization, which is characterized by removing the vinyl chloride polymer dust collected by Multi-Cron during the drying process and the transportation process to the vinyl chloride resin product tank from the system. Method.