FI56850C - FOERFARANDE FOER SUSPENSION-POLYMERISERING AV VINYLKLORID I NAERVARO AV ETT OXIDATIONSMEDEL - Google Patents

Description

., f · »- I rRl ADVERTISEMENT„ „Λ _ Λ TOMA ™ (11) UTLÄGGN I NGSSKRI FT 56850 C (45) Patent cycr.n? tty 10 Λ 1930 Patent meddelat v (51) Kv.ik. '/ intci. * C 08 F 14/06 C 08 P 2/18 SUO MI — FI N LAN D <*) Pttunttlhakamus - Pat «nttn * 6knlng 1332/72 (22) Hakamltplivi - Ansttknlnpdag 10.03 * 72 (23) Alkupllvi — Glttlghuudag 10.05.72 (41) Interpreters slipped - Blivlc offuntlig 11.11.73

Patent and Registration Office ............. , . ,,,. , _ '(44) Date of issue and date of issue. -

Patent · och registerstyrelsen 7 Antökan utiagd och utUkrifUn pubikerad 31.12.79 (32) (33) (31) Pyydatty etuolkau »—Begird priorct (71) Shinetsu Chemical Company, 6-1 Otemachi 2-chome, Chiyoda-ku, Tokyo, ' Japan-Japan (JP) (72) Shunichi Koyanagi, Kanagawa-ken, Shigenobu Tajima, Niigata-ken,

Toshihide Shimizu, Ibaragi-ken, Yoshitaka Kiri, Ibaragi-ken,

The present invention relates to an improved process for the suspension polymerization of vinyl chloride. The present invention relates to an improved process for the polymerization of vinyl chloride in suspension in the presence of an oxidizing agent. The present invention relates to an improved process for the suspension polymerization of vinyl chloride.

A process for the suspension polymerization of vinyl chloride or a mixture containing predominantly vinyl chloride and at least one other vinyl monomer copolymerizable therewith in the aqueous phase in the presence of an oil-soluble catalyst usually results in polymer scaffold the yield decreases, but also the cooling capacity of the reactor decreases. The quality of the products also deteriorates due to the granular impurities formed in the flakes and mixed with the product. Besides, more work is needed, time to remove the layered scales. To overcome these disadvantages, various proposals have been made for the selection of suspending agents or additives to be used in the polymerization system and also for adjusting the pH of the polymerization medium. In fact, 56850 of them have all been found to be quite effective in reducing flake deposits to a large extent on reactor walls below the liquid phase level, but none of them have been effective in reducing flake deposits near the gas-liquid phase interface in the reactor, so the problem remains unresolved.

In addition, it is detrimental that, in general, when a film or sheet is made from a vinyl chloride polymer, "fish eyes" are easily formed due to the very small, spherical, indigestible particles present in the film or sheet. This phenomenon has been considered inevitable.

It is an object of the present invention to provide a process for the suspension polymerization of vinyl chloride which is free from the disadvantages described above.

It is a further object of the present invention to provide a process for the suspension polymerization of vinyl chloride, which process successfully prevents the deposition of polymer flakes on the reactor walls in the vicinity of the gas-liquid phase interface.

It is a further object of the invention to provide an improved process for the suspension polymerization of vinyl chloride by which vinyl chloride polymers are prepared which are free of "fisheye" formation.

The process according to the present invention is characterized in that water and / or an aqueous solution of a dispersant and / or an aqueous solution of a dispersant in which the alkali is sodium, potassium, sodium, alkali, , calcium or barium hydroxide or sodium or calcium oxide, and / or an aqueous solution or suspension of an inorganic oxidant in which the oxidant is permanganic, chromic, dichromic or nitric acid or their salts, nitric oxide, nitrous oxide, nitrous oxide, nitric oxide, cuprous oxide, silver nitrate, ammonium nitrate, cerium oxide, copper oxide or lead oxide, wherein the addition of liquid is carried out continuously from the beginning of the polymerization so that the gas-liquid interface at the beginning of the polymerization in the planar polymerization reactor does not decrease until at least 50% monomer and that the alkali content of the aqueous alkali solution is at least 0.001% by weight based on the weight of the vinyl chlorodimonomer or said mixture, and that the content of the inorganic oxide in the aqueous solution of the inorganic oxidant is at least 0.0001% by weight. calculated on the weight of the vinyl chloride monomer or said mixture.

Using the process of the invention, hardly any polymer flakes are deposited on the reactor walls, and it is surprising that the vinyl chloride polymers or copolymers produced have very few "fish eyes".

56850 3

As a further explanation, when the suspension polymerization is carried out by a conventional method, the volume of the polymerization medium decreases as the polymerization progresses. For example, if the polymerization medium contains 100 parts of vinyl chloride monomer, 200 parts of water, 0.1 parts of partially saponified polyvinyl acetate, and 0.15 parts of lauroyl peroxide at the beginning of the polymerization, its total volume decreases to about $ 85 when the polymerization is complete. That is, the level of the interface between the gaseous phase and the liquid phase in the reactor gradually decreases as the polymerization progresses and the vinyl chloride polymer or copolymer deposited on the exposed surfaces on the reactor walls increasingly solidifies into flakes. On the other hand, according to the process of the invention, water or the above-mentioned aqueous solutions are added as their polymerization systems in such amounts that the gaseous and liquid phase interfaces in the reactor always remain at a level not lower than at the beginning so that the suitable interface is in constant contact with the suspension medium. As a result, this part of the reactor walls is protected from the formation of scales, which has been considered an inevitable phenomenon.

In the practice of the process of the invention, the time-added liquid to the polymer reactor may be water, preferably deionized, or more preferably a dispersion solution containing the same suspending agent initially introduced into the polymerization system, an aqueous alkali solution which is particularly effective in preventing scaling, and / or an aqueous solution of an inorganic oxidizing agent.

Examples of the alkali include hydroxides or oxides of metals such as sodium hydroxide, lithium hydroxide, potassium hydroxide and sodium oxide; alkaline earth metal hydroxides or oxides such as barium hydroxide, calcium hydroxide and calcium oxide. Examples of inorganic oxidizing agents include permanganic acid and its salt; chromic acid, bichromic acid and their salts; nitric acid, nitric acid, nitric oxide, nitrous oxide, nitrous oxide; nitrates such as copper nitrate, lead nitrate, silver nitrate and ammonium nitrate; as well as oxides such as cerium, silver, copper and lead oxide.

The addition of water or aqueous solutions is not particularly limited in amounts as long as the initial level of the interface between the gas and liquid phases in the reactor does not decrease. In addition, such addition of water or aqueous solutions can advantageously be carried out continuously after the start of the polymerization and until the amount of change reaches at least 50%. In addition, the alkali can be correspondingly at least 0.001 by weight of J? and inorganic oxide 0.0001 w / w calculated on the weight of vinyl chloride monomer used.

The addition of water or aqueous solutions to the polymerization system described above can be accomplished in any suitable manner by introducing the liquid into the reactor under pressure by a pump located outside the reactor and, preferably, spraying the reactor interior walls near the liquid-gas interface 56850.

For this purpose, a suitable jet is provided by means of nozzles of either centrifugal pressure type or helical pressure chamber type and has a wide spray angle. For pumping liquids into the reactor, a pressure is preferably used which exceeds the pressure inside the reactor by 2 to 20 kg / cm, which, however, depends on the droplets to be obtained as well as the required spray area.

The process according to the invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 is a vertical section of a polymerization apparatus showing a general arrangement of the embodiment of the invention, Figure 2 is a partial section along line AA in Figure 1, and Figure 3 is a partial enlarged sectional view. embodiment.

In Figures 1 and 2, inside the reactor 1, there is a stirrer 2 and a sprayer 3. The sprayer 3 comprises an annular tube mounted horizontally around the axis of the rake device 2, which is above the surface of the liquid phase and has several nozzles on its outer surface. Water or an aqueous solution of alkali and / or inorganic oxidizing agent is introduced from the tank 6 by means of a pump 5 into the annular tube of the sprayer 3 for spraying through nozzles k to the inner walls of the reactor 1 near the gas-liquid interface. Fig. 3 shows another embodiment of the spray device of Figs. 1 and 2, in which the shaft 7 of the stirrer is hollow and the tube 8 is connected at one end to the hollow shaft so that water or aqueous solution passes through a nozzle 9 fitted to the other end of the tube 8. According to the embodiment shown in Fig. 3, the tube '8 and the nozzle 9 rotate as the shaft 7 of the stirrer rotates, thereby providing higher pressure jets and resulting in a similar prevention of scale build-up with a smaller amount of liquids used compared to the embodiment of Figs.

The process according to the invention is generally applicable to the suspension polymerization of vinyl chloride, in which any known suspending agents and polymerization catalysts can be used. Examples of suspending agents are fully saponified polyvinyl acetate, partially saponified polyvinyl acetate, copolymer of vinyl acetate and maleic anhydride, copolymer of styrene and maleic anhydride, aqueous polyacrylate, gelatin, polyvinylpyrrolidine, polyvinylpyrrolidine. Examples of polymerization catalysts include organic peroxides such as lauroyl peroxide, 2, 4-dichlorobenzoyl peroxide, diisopropyl peroxydicarbonate and acetylcyclohexylsulfonyl peroxide, and azo compounds such as o, **'-azobisisobutyronitrile and azilobutyronitrile.

Furthermore, the process according to the invention is applicable not only to the homopolymerization of vinyl chloride but also to the formation of vinyl monomers.

G G 6S O

for the copolymerization of a mixture containing vinyl chloride as the main component. Examples of monomers copolymerizable with vinyl chloride include various vinyl esters, vinyl ether, acrylic acid, methacrylic acid and their esters, maleic acid, fumaric acid and their anhydrides and esters, vinyl chloride halide, vinylidene halide, vinylidene halide, vinylidene halide, vinylidene halide, vinyl

The following are some examples of the practice of the invention.

Example 1

A stainless steel reactor with a capacity of 23,000 liters, equipped with a stirrer with 3 layers of melodic superimposed stirrers, each with a diameter of 1200 mm, was evacuated, filled with nitrogen and then charged with 7,000 kilos of vinyl chloride, 12,000 pounds of deionized water, 7 pounds of partially saponified polyvinyl acetate, and 7 pounds of lauroyl peroxide. While stirring the reaction mixture with a stirrer with a rotational speed. . . o. .

was 100 rpm, the mixture polymerized at 57 ° C for 16 hours and resulted in a 91% yield of polyvinyl chloride.

In this example, the sprayer shown in Figs. 1 and 2 was equipped with eight centrifugal pressure type nozzles, each nozzle having a hole diameter of 0.5 mm. For the entire time from the beginning of the polymerization until the rate of conversion reached 60%, water or the aqueous solution indicated in Table 1 below was introduced into the sprayer 2 by means of a pump with an outlet pressure of 20 kg / cm and sprayed through the nozzles onto the reactor walls. and in the vicinity of the interface between the liquid phase at a rate of 300 liters / hour. The results are shown in the table. In this case, it is observed that the number of scales deposited on the reactor walls around the interface between the gas and liquid phases and the number of "fish eyes" formed on the polymer plate were much smaller than in the comparative experiment without water and aqueous solution spraying.

6 56850

table 1

particle size

Shower- Layered distribution ($) "Fisheye"

Number of showers —— · ———————

Try t ^ tu liquid scales 60 100 200 (pieces) *) no. ®amount of content _ meshin meshin meshin • * (liters) (weight- $) (g) sieve through the sieve through the sieve through through 3 3 ', 000 water, 10 99-9 50.6 1.1' 3 2 3,000 80 $: english 10 99.8 51.3 1.3 4 saponified polyvinyl acetate $ 0.05

3 3,000 NaOH

0.002 $ 5 99.7 50.1 · 1.6 2 4 3,000 NaOH 0 99.9 55.4 1.2 1 0.002 $ + K2Cr2 ° 7 0.0002 $ 5 3,000 K2Cr20? 7 99.8 51.2 1.1 2 0.002 $ 6 3,000 KMn04 10 99.6 56.4 1.4 4 0.002 $ 7 3,000 Ce02 12 99.9 55.7 1.2 1 0.002 $ 8 3,000 NaNO-j 15 99.7 51.2 1.8 3 0.002 $ comparison 0 - 3,200 99.7 56.3 1.3 51 test n (k) The number of "fish s" was calculated as follows: This is applicable to Examples 2 below, and to 50 parts by weight of vinyl chloride polymer was added 50 parts by weight of dioctyl xalate, 2 parts by weight. difcutyltin analeate, 0.8 part by weight of cetyl alcohol, 0.1 part by weight of barium stearate, 0.1 part by weight of cadmium stearate, 7 56850 0.5 part by weight of titanium oxide and 0.05 part by weight of carbon. This mixture was formed into a sheet after kneading at 150 ° C for 7 minutes. The number of "fish eyes" was calculated with the naked eye from a plate sample of size p 10 cm.

Example 2

A stainless steel reactor with a capacity of 1000 liters, equipped with the atomizer shown in Fig. 5, a stirrer with melodic stirrers arranged in three overlapping layers, and a hollow shaft, was subjected to a vacuum, filled with 250 ml of nitrogen and then 500 kg of deionized water, 250 g of partially (80 mol) saponified polyvinyl acetate and 50 g of α, α'-atobisdimethylvaleronitrile. While the stirrer was rotated at 160 rpm, the mixture was PC-polymerized at 57 ° C for 10 hours. Throughout the time from the start of the polymerization until the rate of change reached 50%, water or aqueous solutions were continuously sprayed at a rate of 15 liters / hour by means of a pump with an outlet pressure of 13 kg / cm G, a centrifugal pressure nozzle. through a hole with a diameter of 0.5 mm, intentionally to prevent the level of the interface between the gas and liquid phases from decreasing from what it was at the beginning of the polymerization. The results are shown in Table 2.

Table 2

Experiment Shower- Shower- Floor- Particle size "Fisheye" stretched tune distribution ($) number of liquid scales 60 100 200 (pieces) (liters) content (g) mesh mesh mesh (weight ^) through the sieve through the sieve 9, 75 water 8 99.9 45.1 1.2 5 10 75 «90 Rye 7.5 99 * 9 50.3 1 * 7 4 saponified polyvinyl acetate 25 11 75 NaOH 1.5 99.7 41.3 0.9 1 25 12 75 NaOH 0 99.8 40.2 0.6 0 25 + K2Cr207 25 0 - 780 99 * 9 48.2 1.4 83 Reading No. 2 56850

Example 5

A stainless steel reactor with a capacity of 1000 liters and equipped with a stirrer equipped with melodic humanners with a diameter of 600 mm was charged with 255 kg of vinyl chloride, 15 kg of vinyl acetate, 500 kg of pure water, 250 kg of partial (80 molar) $) saponified polyvinyl acetate and 50 E α, α'-azobis-dime-valivalonitrile. While stirring the mixture with a stirrer at 160 rpm, the mixture was polymerized at 60 ° C for 10 hours · For the entire time from the start of the polymerization until the conversion to 50? 6 was reached, water or aqueous solution was sprayed continuously at 15 liters / hour through the sprayer shown in Figure 5 and at an inlet pressure of 13 kg / cm G so that the level of the interface between the gas and liquid phases did not decrease from what it was at the beginning of the polymerization. The results are shown in Table 3 *

Table 3

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Experiment Sprayed Sprayed Layering Distribution ($) - No. No. (blue liquor of the liquid) contains (weight and (g) neshin meAJe meohln no sieve through sieve through sieve through 13 75 NaOH 1 92.1 18.2 0.1 Ο.196 14 65 NaOH 1.5 95-3 23.0 0.5 Ο.Ο596 15 75 NaOH 2 99.6 43.1 · 1.5 O.OI96 16 75 K2Cr207 1.5 95.4 35 * 9 0.9 0.01 $ 17 75 K2Cr2 ° 7 1 99.6 48, 2 1.1 0.005 $ 18 75 K2Cr207 1 99.8 54.1 1.5 0.001 $ 19 75 water 15 99 * 9 55.1 1 * 7

Example 4

A stainless steel reactor with a capacity of 1000 liters and equipped with a stirrer with three layers of melodic stirrers, each 600 mm in diameter, was charged 9,56850 250 kg of vinyl chloride, 500 kg of water, 250 g in part (80 mol- $) saponified polyvinyl acetate, 55 g of isopropyl peroxydicarbonate and 15 g of α'-azobisdimethylvaleronitrile. While stirring the mixture with a stirrer rotating at 10 rpm, the mixture was polymerized at 57 ° C for 10 hours.

During the dusting of the dust, water or aqueous solution was added in the amount and rate indicated in Table 4 below directly to the polymerization system under pressure through a pipe so that the level of the gas-liquid phase interface did not decrease from what was at the beginning of the polymerization. The results obtained are shown in Table 4.

The addition of additional liquids was performed at a rate of more than 10 liters / hour in the above experiments, so that the initial liquid phase level did not decrease. For comparison, comparative experiments Nos. 5, 5, 5, and 6 were performed in which no water or aqueous solutions were added or these were added at lower rates, and all of these experiments gave unsatisfactory results, as also shown in Table 4.

Table 4

Experience Added Addition- Added Layer- Particle Size "Fish No. Liquid Speed Liquid Tuned Distribution of Eyes" Number (liters / content of scales 60,100,200 Number (liters) per hour) (weight- $) (g) meshin meshin meshin (pieces) sieve sieve through sieve through through 20 150 15 water 5 99.9 47.3 1.8 3 21 150 15 Ca (0H) 2 1 99.6 42.1 1.2 1 0'.01 $ 22 150 15 K2Cr20? 0.8 99.7 50.1 1.1 2 0.005 $ 23 100 10 K2Cr20? 3 99-3 .49.3 0.9 21 0.005 $ 24,150 15 Hydroxy- 4.5 99.8 39.2 1.9 4 Propylmethylcellulose $ 0.1 (continued) 10,56850 25,150 15 Vinyl 4,99.7 45.6 1.6 7 Acetate-maleic anhydride kopclymeeriä.

0.1 / 26 150 15 NaOH 1 99.4 43.7 2.1 1 0.1 / 27 150 15 K2Cr 2 O? 0.5 99-5 51.2 1.8 1 0.005 ° / ..

NaOH

0.01 / 28 150 15 KMn04 1 99.2 49.8 1.6 2 0.1 / + methylcellulocea 0.1 / 29 150 15 NaOH 0.4 99.4 47.2 1.7 2 0.01 / +

Ca (OH) 2 0.01 / 30 100 10 water 15 99.9 49.5 2.3 10 comparison test

Well. 3 0 O - 850 99.9 49.1 1.9 54

Ro. 4 50 5 K2Cr207 50 99.6 50.2 2.4 30 0.005 /

Well. 5 75 7.5 νθβ1 200 99.9 47.8 1.5 28

Well. 6 50 5 water 400 99.9 48.2 1.9 35

Example 5

A stainless steel reactor with a capacity of 1 GC0 liters and equipped with a stirrer with three layers of melodic stirrers with a diameter of 600 mm was charged with 250 kg of vinyl chloride, 250 g of partially (80 mol / l) saponified polyvinyl and 56850 acetate. 65 g of α, α * -dimethylvaleronitrile. While the mixture was quenched with a stirrer rotated at 160 rpm, the mixture was polymerized at 57 ° C for 10 hours.

In the polymerization, an aqueous solution of sodium hydroxide was injected at the interface between the liquid phase in the reactor by means of a pump with an outlet pressure of 13 kg / cm through a sprayer shown in Fig. 3 with an orifice diameter of 0.3 mm. The results obtained are shown in Table 3 *

As is clear from the results, good efficiency was obtained when spraying was continued until the amount of change had reached at least 30 #, while in the case where spraying was stopped before the change value of 50 # was reached, no satisfactory result was obtained.

Table 3

Experiment Shower- Variable- Spray- Layered- Partial size No. number of known shielding (#) number of sprays (g) 60 100 200 (liters) its final content meshin meshin meshin ees (#) (weight #) sieve through the sieve through the sieve through 31 75 20 NaOH 550 95.0 31.3 0.1 0.01 # 32 75 40 NaOH 28 99.8 49.3 1.1. 0.01 # 33 75 50 NaOH 0.7 99.9 48.2 0.9 0.01 # 34 75 70 NaOH 0 99-9 51.3 0.6 0.01 # 35 75 90 NaOH 0 99.9 52.1 0.7 0.01.

Claims (1)

56850 Claim: A process for the suspension polymerization of vinyl chloride or a monomer mixture containing predominantly vinyl chloride in the aqueous phase in the presence of an oil-soluble catalyst and dispersant so as to minimize the formation of a polymeric water and / or an aqueous solution of a dispersant and / or an aqueous alkali solution in which the alkali is sodium, potassium, lithium, calcium or barium hydroxide or sodium or calcium oxide, and / or an aqueous solution or suspension of an inorganic oxidant in which the oxidant is permanganese, chromium -, dichromic or nitric acid or their salts, or cerium oxide, the addition of the liquid being carried out continuously from the beginning of the polymerization so that the level of the interface between the gas and liquid phases at the beginning of the polymerization is p does not decrease to the point where at least SO% of the monomers have reacted and that the alkali content of the aqueous alkali solution is at least 0.001% by weight based on the weight of the vinyl chloride monomer or said mixture and that the inorganic oxide content of the aqueous inorganic oxidant solution is at least 0, 0001% by weight based on the weight of the vinyl chloride monomer or said mixture.