JPH0629290B2 - Gas phase polymerization of vinyl chloride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention obtains a product of good quality at a high growth ratio by gas phase polymerization with a vinyl chloride monomer (hereinafter abbreviated as VCM) or a comonomer mainly copolymerizable with the vinyl chloride monomer. It relates to an improved polymerization method. The growth ratio refers to the ratio of the amount of gas phase polymer including the seed polymer / the amount of seed polymer.

Regarding the gas phase polymerization of VCM, Japanese Patent Publication No. 52-4491
8, JP-B-48-14666, U.S. Pat. No. 3,578,6
No. 46, it is known that the obtained gas phase polymerized product has poor porosity and lacks homogeneity, resulting in poor gelation at the time of processing and fish-eye characteristics (hereinafter abbreviated as FE characteristics). Worse, it is believed to have little industrial value, despite the many process advantages as if it were only a sandy polymer.

As a result of earnest research, the inventors of the present invention have found that a vapor phase polymerization method has a high porosity comparable to that of a conventional two-stage mass polymerization method or a suspension polymerization method, good FE characteristics, and high bulk density. Successful, though limited, (patent pending).

That is, since the characteristics of the seed polymer are dominant, in order to improve the porosity and the FE characteristics, (a) the bulk prepolymerization is performed at a polymerization rate of 14 to 25%.

(B) In the polymerization, a VCM-soluble polymer substance is preferably added as an initial additive, preferably, a lubricant component, a stabilizer and the like are added and polymerized to sharpen the particle size distribution and modify the internal structure of the particle.

Further, (c) at the end of the polymerization, a VCM-soluble polymer substance as a particle surface coating agent is added.

Further, in order to improve the bulk specific gravity as well, (d) when recovering the unreacted VCM and pulverizing it, the internal temperature is adjusted to 45
The temperature is raised to -60 ° C and the mixture is stirred with an anchor blade at 100 to 300 rpm to give a smooth surface without increasing agglomeration of individual polymer particles by applying heat and shear to increase bulk density.

(E) Using a seed polymer made with the above requirements, Pr0.65 ~
Gas phase polymerization is performed in the range of 0.85.

However, according to the knowledge of the present inventors, even if gas phase polymerization is carried out while satisfying the above requirements, the product obtained will gradually change as follows when the growth ratio is increased by 6 times or more.

The particle size gradually shifts toward the coarse direction and increases on the sieve.

The bulk specific gravity also gradually increases, while the porosity decreases.

When polymerization is carried out for a long time, the hue and thermal stability during processing gradually decrease.

The FE characteristics also deteriorate as the growth ratio increases.

Therefore, if the growth ratio is kept in the range of 5 to 6 times as a batch reaction, a good quality product can be obtained as described above, but since there is a step of producing a powdered seed polymer,
It is hard to say that the rationality of the process is excellent.

Therefore, the present inventors have completed the present invention as a result of intensive studies to eliminate these drawbacks.

That is, a new seed polymer is added after the growth ratio exceeds 3.5 times to keep the growth ratio at 3.5 to 5.5 times, and the amount exceeding the holding capacity of the reactor is intermittently or continuously withdrawn.

As a method of supplying this new seed polymer, (1) a method of adding a seed polymer which has been powdered in advance by collecting unreacted monomers.

(2) Add VCM to powdered seed polymer and return to slurry,
Slurry transport A method of feeding with a pressure pump and spraying from a spray nozzle to supply to a reaction can.

(3) A method in which bulk prepolymerization is performed and the polymerization rate is from 10% to 25% (range that can be handled as a slurry) by a slurry-conveying pressure pump, and is sprayed from a spray nozzle and supplied to a reactor.

There are three possible methods, and any of them can be used, but there is no problem as described below.

In the method (1), if a double lock hopper or the like is used, the deaerated powder seed polymer can be supplied to the pressure system, and problems such as agglomeration do not occur, but the equipment becomes slightly complicated, and the seed polymer is also used. It takes time and effort to powder.

In the method (2), there is no problem in liquid transfer if the flow velocity in the pipe is 1.5 times or more the sedimentation velocity of the slurry. In addition, when examining the slurry spray nozzle, the inlet 1.0 mmφ,
The swirl flow type spray nozzle that does not reach the outlet of 1.5 mmφ is occasionally clogged, resulting in insufficient performance.
If the inlet is 1.5 mmφ and the outlet is 2.0 mmφ or more, there is no problem in performance. If the nozzle hole diameter is large, it is difficult to form a spray. After all, 1.5mmφ inlet and 2.0mmφ outlet are the best. In addition, a slurry concentration of up to 15 wt% is sufficient for liquid delivery and spraying. Therefore, the supply of the seed polymer by this reconstituted slurry is facility simple compared to the method of (1), and if coarse particles are removed through a 48-mesh sieve as a powdered seed polymer in advance, clogging troubles during liquid transfer will occur. No, performance is good. In addition, since particles having a strong shape due to heat and shearing force are preliminarily collected at the time of recovering the monomer, and particles having an independent shape even after spraying, problems such as generation of agglomerated coarse particles hardly occur. However, it takes a lot of time to pulverize the powder, and there remains a problem in terms of process rationality.

The direct spraying of the polymerized slurry of (3) is the best in terms of process rationality, but some problems occurred when it was actually tried.

The problem and the solution method will be described below.

Polymerization Slurry Spray Polymerization Problems (1) Liquid-Feeding Concentration Since the polymerized slurry has a smaller particle size and higher slurry viscosity than the reconstitution slurry, the liquid-delivery sprayable concentration is 12 wt%. Therefore, when the polymerization rate exceeds 12 wt%, the concentration of the polymerized slurry inevitably exceeds 12 wt%.
It is advisable to add 7% to 12% by weight for dilution.

(B) Closure of slurry / spray nozzle Even if the amount is small, the spray nozzle is clogged because some coarse particles or particles from which the scale in the can has peeled off are mixed in the polymerized slurry. It suffices to remove this, but in an ordinary static strainer or the like, even if the mesh is a large mesh as a property peculiar to the slurry, deposition occurs one after another and the layer is completely blocked. Normally, it is necessary to use a vibrating sieve for the excess of the slurry, but in the case of this process,
If the pressure resistance is required and the space volume is large, dry polymer is precipitated, which is not preferable. From this point of view, a strainer equipped with a stirrer was devised, and by removing a small amount of aggregated particles contained in the polymerized slurry and scale peeling matters, the clogging trouble of the liquid feed pump and the spray nozzle was solved.

The structure is simple as shown in Fig. 1.
In an autoclave with a stirrer of 0.5 to 1, insert an appropriate wire mesh cylinder (about 20 mesh) into the inner cylinder and pass the slurry while stirring.

(C) Agglomerated particle generation problem In spray gas phase polymerization of aggregated slurry, unlike the above-mentioned reconstitution slurry, heat and shearing force are not applied, so particles are soft and a large amount of fine particles are present. It was found that the formation of agglomerated coarse particles was promoted probably because the polymer particles play a role of a binder in the polymerization.

Then, the countermeasures for preventing the generation of the aggregated coarse particles were examined and the following matters were found.

(1) It is preferable that the spray nozzles are spread as widely as possible and the droplets are small. In other words, if the nozzle diameter is large, the risk of clogging is small, but if the flow rate is small, the particles will drop and coarse particles will be generated, so the nozzle has a limit of 1.5 mmφ at the inlet and 2.0 mmφ at the outlet so that trouble does not occur in liquid feeding of the slurry. If a whirling flow type spray nozzle is suitable and the flow rate is large and the pressure loss is large, a plurality of nozzles may be used.

(2) The higher the saturated vapor pressure ratio Pr of the monomer at the polymerization pressure / polymerization temperature, the less the formation of aggregated coarse particles. That is, P
When r is high, the reaction is vigorous and unreacted VCM evaporates immediately due to the heat of reaction, but since Pr is high and it is not completely dried, agglomerated coarse particles are difficult to form. However, if Pr exceeds 0.85, the FE characteristics of the product deteriorate, so Pr is 0.65 to 0.
85 is good.

(3) Coarse particles are less likely to be formed when the mixing shearing force is uniformly applied in the production of the seed polymer.

In agitation gas phase polymerization, since the particles are a discontinuous phase, if the stirring speed is high, only the vicinities of the blades will be stirred, and the center will not be stirred. Therefore, coarse particles cannot be obtained when the whole is slowly stirred at a low speed (20 to 100 rpm) with an anchor type stirring blade. As the powder layer height increases as it is, the stirring of the upper part becomes insufficient when the stirring blade is buried in the powder layer.

A stirring blade length equivalent to or 0.5 times the maximum powder layer surface is preferable. When the can diameter is large, stirring at the top and center tends to be inadequate, and it is desirable to install auxiliary blades for stirring at the center.

In the rogas flow gas phase polymerization, the fluidization rate is 10 to 1
5 cm / sec, but 1 with slurry spraying
Coarse particles are not generated when the fluidization speed is increased to about 2 to 18 cm / sec.

Furthermore, gas flow with a stirrer is most desirable for preventing local non-uniform flow.

(4) Effect of bulk specific gravity The bulk prepolymerization is performed with the same composition, and the higher the recovery temperature of the unreacted VCM, the higher the bulk specific gravity of the seed polymer.

When vapor phase polymerization is carried out and spray polymerization of the polymerized slurry is carried out at the same growth ratio, the use of a seed polymer having a high bulk specific gravity causes less generation of agglomerated coarse particles. Therefore, it is better to spray after the growth ratio has increased to some extent and the bulk specific gravity has increased.
Therefore, it is better to add additional seed polymer after the growth ratio exceeds 3.5.

(5) Anticoagulant additive A substance that has an anticoagulant action as a coating agent at the end of the polymerization, which is slightly different from that at the time of preparation of the polymer powder, that is, a so-called lubricant such as higher fatty acid, higher alcohols, higher fatty acid metal soaps, etc. 10 to 10.000pp per polymer
The addition of m is effective.

When satisfying the above requirements, in the polymerization slurry spray polymerization,
It is possible to suppress the generation of aggregated coarse particles to less than 3%, and even if the initial growth ratio of seed polymer exceeds 6 times, the growth ratio of the added polymerization slurry to seed polymer is in the range of 3.5 to 5.5 times. By pressing it, it is possible to obtain a gas phase polymerized product having a high bulk density, good porosity and good FE characteristics.

Therefore, it is possible to carry out semi-continuous or continuous polymerization to obtain a product of good quality only by intermittently extracting the product so as to keep the powder layer level constant.

In bulk polymerization, the polymer produced is polymerized in the presence of 10 to 10,000 ppm of a polymeric substance soluble in a vinyl chloride monomer, and after the completion of the polymerization, a vinyl chloride monomer is added to the produced polymerization slurry. Polymer soluble in body 30-10,000pp
When the polymer obtained by adding m is used as a seed polymer, a gas phase polymerized product having extremely good porosity and FE characteristics can be obtained. In order to prevent aggregation, the above-mentioned lubricant and stabilizer may be present at 10 to 5.000 ppm with respect to the polymer produced during the bulk polymerization, and the lubricant may be added at 30 to 5.000 ppm at the end of the polymerization.

Examples of the above include oil-soluble cellulose derivative pairs such as nitrocellulose, cellulose acetate (preferably cellulose triacetate) and ethyl cellulose; ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, methyl methacrylate homopolymer. Or copolymer,
Examples thereof include aromatic or aliphatic petroleum resins, modified polyvinyl alcohol having a low saponification degree, polyvinyl acetate, unvulcanized chloroprene rubber, unvulcanized nitrile rubber, chlorinated polyethylene and the like. You may mix and use these.

In addition, as a stabilizer, metal soaps of higher fatty acids such as salts of calcium stearate, zinc, barium and aluminum; octyl tin derivatives, butyl tin derivatives,
Organotin compounds such as methyltin derivatives; antimony derivatives and the like can be mentioned.

Next, examples of the present invention will be described. However, the present invention is not limited to the examples.

Example 1 Preparation of type polymer Evans Blue 0.2 g / m ² / sodium lauryl sulfate 0.1 g / m ² / polyvinyl alcohol (Japan Synthetic N- Three
00) A scale inhibitor was applied so as to have a concentration of ² g / m ² and dried.

Ethyl Cellulose (Etocel) T-50 3.0g, Stearic Acid (Hst) 3.0g, Higher Alcohol (Kao Soap Calcol 68) 3.0g, Dioctyltin Dilaurate (TVS)
8105) 3.0 g was deaerated, 56 kg of VCM was charged, the mixture was stirred at 180 rpm and warm water was passed through the jacket to raise the temperature, and isobutyl peroxide (I
B) 25.0 ml of 25% isoparaffin solution and 10.0 ml of 2,4,4 trimethyl-pentyl-2-peroxyphenooxyacetate (TMP-PA) 30% isoparaffin solution were VC
M4kg is washed into a polymerization vessel to start polymerization. Adjust the cooling water through the jacket to keep the internal temperature constant. 1.
Ethylcellulose T-100 in VCM in advance in 5 hours 10.
The product dissolved in 0 g is charged with ² kg of VCM, mixed for 5 minutes, and then recovered under constant pressure at an internal temperature of 50 ° C. and an internal pressure of 7.2 kg / cm ² . For the first 60 minutes, warm water of 54 ° C. is passed through the jacket, and then 52 ° C., and the collection rate is slightly reduced. When the internal temperature rises to 52 ° C., self-pressure recovery is carried out, and then a reduced pressure is recovered by a provider (made by Fujikin) to remove residual VCM and then take out the polymer. Polymerization rate 17.1
% Was 1.5% on a 48 mesh screen.

Gas-phase polymerization A 100-rustless steel polymerization can equipped with a stirrer equipped with an anchor-shaped blade with a rising blade length of 400 m / m and a strip blade in the middle stage, with an inlet 1.
VCM nozzle with 0mmφ and outlet 1.5mmφ, and inlet 1.5mmφ,
Attach a 2.0 mmφ outlet slurry spray nozzle. The above scale inhibitor is applied in advance and dried to obtain the seed polymer.
3.8 kg was put and stirred at 80 rpm, and after deaeration, warm water was passed through the jacket to raise the temperature, and VCM was gradually added from the VCM nozzle to raise the pressure. When the temperature reaches 7.0 kg / cm ² (Pr0.75) at 60.5 ° C, 3.0 ml of 50% toluene solution of initiator di-2-ethoxy-ethylperoxydicarbonate (EEP) is put in a charging vessel, degassed, and VCM is pressurized. Spray from VCM nozzle with a pump. The polymerization reaction begins. Keep the jacket constant at 61.0 ° C.

To remove the heat of polymerization, the stroke of the VCM pressurizing pump is adjusted to keep the internal temperature constant. On the other hand, the internal pressure is adjusted to collect the excess vaporized VCM gas. Liquefaction cooler liquefies and recycles. The reaction amount can be known from the VCM reduction of the measuring tank when the diameter is changed. When the reaction rate decreases, an initiator is added.

Preparation of polymerized slurry On the other hand, 30 scale stainless steel polymerization can equipped with a stirrer with two stages of turbine blades was coated with the above scale inhibitor and dried, and then ethyl cellulose T-50 0.55 g, TVS8105 0.55
g, stearic acid (HST) 0.55g, Calcol 68 0.18
g, degassed, add 9 kg of VCM under vacuum (5 Torr or less), and stir at 700 rpm. Warm water is passed through the jacket to raise the temperature. At 56.0 ° C, 3.6 ml of IB 20% isoparaffin solution and 1.6 ml of TMP-PA 30% isoparaffin solution are VCM.
Charge with 2 kg. Polymerization starts. Cooling water is adjusted through the jacket so that the inner temperature is constant. Polymerization time is 2.0 hours,
1.6 g of stearic acid, 0.8 g of barium stearate, and 0.5 g of ethyl cellulose T-100 were charged and diluted with 5 kg of VCM, cooled, and prepared for slurry feed.

Polymerized Slurry Spray Polymerization When the growth ratio reached 3.5 times in the above-mentioned stirred gas phase polymerization, the polymerized slurry prepared in 30 polymerized cans is sent to 100 polymerized cans with a double tire flam metering pump through a slurry line that has been filled with VCM in advance. Spray from the slurry nozzle. The stirring strainer shown in FIG. 1 is installed on the suction side of the slurry pump. At the third hour, 30 polymerization cans were sprayed with 2.0 kg of VCM from the top to wash the inside. Stirring 5
Drop to 00 rpm. The liquid transfer of the slurry is completed in 4 hours.
The average concentration of the liquid transfer slurry is 9.17%. Wash the slurry line with VCM. Inhibitors stopped at an apparent growth ratio of 7.5 times (see Note in Table 1) and dissolved in VCM beforehand
3.5 g of 4,4'-britidenbis (3-methyl-6-tert-butyl) phenol and 1.5 g of diphenylmonodecyl phosphite were spray-charged with VCM, recovered, and recovered under reduced pressure to remove the residual VCM and take out the product. The results are shown in Table 1.

Comparative Example 1 Using the same seed polymer as in Example 1, vapor phase polymerization was performed under the same conditions. However, the polymerization slurry was not sprayed with 30 polymerization cans and stopped at a growth ratio of about 7.5 times. The results are shown in Table 1.

Comparative Example 2 A polymerization operation was performed in exactly the same manner as in Example 1. However, no stirring strainer was installed on the suction side of the slurry pump.

45 minutes after the slurry feed was started, the slurry nozzle was closed. Inevitably, 30 polymerized cans were collected with unreacted VCM and the polymerized polymer was taken out. Based on the remaining amount, it is estimated that the amount of liquid-fed polymer is 0.15 kg. The results are shown in Table 1.

Comparative Example 3 The same procedure as in Example 1 was performed. However, in the case of 30 polymerization cans, when the seed slurry was prepared, only 0.5 g of ethyl cellulose T-50 was added as the coating agent after the polymerization was completed.

Example 2 Gas phase polymerization was carried out under the same conditions as in Example 1.

However, instead of polymerized slurry, 1.60 kg of powder type polymer
After degassing in 0 can, VCM 9.40 kg was added and stirred back to prepare a slurry. Otherwise the same.

Example 3 Polymerization is carried out under the same conditions as in Example 1 except for using the same equipment. However, 3
Transfer the polymerized slurry prepared with 0 can to the stirrer slurry storage tank. Add late additives to 30 cans and wash with 5 kg of VCM and deliquorate 100 cans. The remaining VCM of 30 cans was recovered and decompressed, and the can was opened to check the remaining amount, but there was no remaining amount and scaling. A polymerized slurry was continuously prepared with the same composition as in Example 1.

100 cans for performing gas phase polymerization are provided with a 1B insertion pipe, and an outlet is provided with a 1B automatic valve 1-measuring pipe-1B automatic valve 2;
0 Connect to a stirring tank. In addition, 1 / 4B 12kg / cm for the measuring pipe
It is equipped with a ² G nitrogen automatic valve. These automatic valves open the 1B automatic valve 1 at the highest setting point of the ultrasonic level meter attached to the gas-phase polymerization can, close it at the lowest setting point, and open the automatic valve 2 to set the powder in the measuring tube to 2 kg / cm. Pump to a ₂ G stirring tank.

After a certain time, the 1B automatic valve 2 is closed. This operation is performed once every tens of times, the 1/4 BN ₂ automatic valve is opened, the 1B automatic valve is closed, and the automatic valve 1 is opened to purge the polymerization vessel side for a certain period of time to prevent the scale from adhering to the inside of the extraction pipe. When the powder layer reaches a certain level with this device, the product is extracted intermittently, an inhibitor is added in an 80-stirring tank, VCM is collected, and the product is decompressed under vacuum to remove V.
Perform CM.

[Brief description of drawings]

FIG. 1 is a view showing the inside of the stirring strainer used in the examples. The meanings of the symbols in the figure are as follows. 1 ... Body part, 4 ... stirring blade 2 ... wire mesh cylinder, 5 ... slurry inlet 3 ... stirring shaft, 6 ... slurry outlet

Claims (11)

[Claims] 1. In a gas phase polymerization of a vinyl chloride monomer or a monomer copolymerizable therewith and a vinyl chloride monomer, the growth ratio exceeds 3.5 times for the first time after the initiation of the polymerization, and then the seed polymer is added. A homopolymerization method or a copolymerization method of vinyl chloride, characterized in that the supply ratio is adjusted to maintain the growth ratio at 3.5 to 5.5 times. 2. A vinyl chloride homopolymer or copolymer powdered in bulk polymerization is supplied as a seed polymer.
The method according to item (1). 3. A seed polymer prepared by adding vinyl chloride monomer to a homopolymer or copolymer of vinyl chloride powdered in bulk polymerization to form a slurry, (1)
Method described in section. 4. A slurry containing a vinyl chloride homopolymer or copolymer obtained by bulk polymerization is fed as a seed polymer without recovering unreacted monomers therefrom. Method. 5. The concentration of the seed polymer slurry is 7 to 12 w.
The method according to item (4), which is supplied as t%. 6. The method according to claim 4 or 5, wherein coarse particles are removed by passing through a strainer equipped with a stirrer before feeding the slurry of the seed polymer to the gas phase polymerization apparatus. 7. The method according to (4), (5) or (6), wherein the slurry of the seed polymer is fed through a whirling flow type nozzle having an inlet diameter of 1.5 mm and an outlet diameter of 2.0 mm. 8. The ratio (4) to (7) of the saturated vapor pressure ratio of the monomer at the polymerization pressure / polymerization temperature is 0.65 to 0.85.
The method described in any of the sections. 9. An anchor type stirring blade having a blade length of 0.5 to 1.0 times the height of the highest powder layer is used as the polymer in the polymerization apparatus in an amount of 20 to 100 r.
The method according to any one of items (4) to (8), which comprises stirring at a rotation speed of pm. 10. The gas phase polymerization is gas flow gas phase polymerization,
Fluidization speed is 10 to 15 cm / sec, (4) to
The method according to any one of (8). 11. The method according to any one of (4) to (8), wherein the gas phase polymerization is slurry atomizing gas fluidized gas phase polymerization and the fluidization rate is 12 to 18 cm / sec.