JPH03111408A - Preparation of methacrylic polymer - Google Patents

Abstract

PURPOSE:To stably prepare a colorless, transparent polymer excellent in the moldability by bulk polymerizing methyl methacrylate using only one complete mixing type reactor in an inert gas in the presence of a radical initiator in a specific manner. CONSTITUTION:A monomer mixture mainly comprising methyl methacrylate is bulk-polymerized continuously using only one complete mixing type reactor without using any solvent in such a manner that: an inert gas is blown into the monomer mixture to reduce the dissolved oxygen content to 1ppm or lower; in the presence of a radical initiator having a half-life at the polymn. temp. of 0.5-120sec and under stirring with a stirrer consuming 0.5-20kW power per cubic meter of the reaction soln. stirred, the mean residence time is set such that the ratio of the half-life of the radical initiator at the polymn. temp. to the mean residence time is 1/200-1/10000; and then the monomer mixture is polymerized at 130-160 deg.C to a monomer conversion of 45-70%. Thus, a target polymer is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing methacrylic polymers. More specifically, the present invention includes:
When polymerizing a monomer mixture containing methyl methacrylate as the main component, continuous bulk polymerization is carried out using special reaction conditions in a single stirred tank reactor (completely mixed reactor). The present invention relates to a method of industrially advantageously carrying out polymerization to obtain a methacrylic polymer with excellent moldability.

(Prior Art) Methacrylic polymers (hereinafter referred to as PHMA) are used for signboards, nameplates, etc. due to their excellent transparency, surface gloss, excellent light resistance, mechanical strength, moldability, and machinability.
It has been used for vehicle parts, etc. Recently, polymers have been used in large quantities in optical fields such as optical disc substrates, and there is a demand for highly pure polymers that are free from the contamination of microscopic foreign matter, which has not been a problem in the past.

The start of industrial production of PMM^ is the oldest among the currently used polymers, and it is similar to polyvinyl chloride, polystyrene,
It began in the 1930s with polyethylene. After that, Ike's three polymers grew rapidly and came to be called general-purpose resins, but the biggest reason why only PMM^ was left behind is that other polymers were quick to use monomer raw materials for petrochemical products. PM
This is because, until very recently, the monomer of M^, methyl methacrylate-1~ (hereinafter referred to as M^), was limited to cyanide gas, a special raw material that was extremely difficult to handle.

However, several years ago, Japan became the first country in the world to convert its raw material to isobutylene, one of the leading petrochemical products. Furthermore, in Europe, as a synthesis method from ethylene and propylene was developed and plans were made for its industrialization, it became certain that the major cause that had prevented PMM^ from becoming a general-purpose resin would disappear. In this way, PM has various excellent properties that are unrivaled by other products.
Rapid growth of +4^ is expected in the future.

The conventional industrial method for producing PMM^ has been a batch polymerization method using a suspension polymerization method. This method is similar to the conventional PMM
It was suitable for high-mix, low-volume production like Industry A, but this is expected to happen in the future! This method is not suitable for mass production as PM+4^ becomes a general-purpose resin. That is, disadvantages such as the complexity of batch operations, increased energy consumption due to repeated heating and cooling, and the necessity of treating a large amount of wastewater become more noticeable as the size increases. These disadvantages have usually been overcome by converting batch operations to continuous operations, but continuous suspension polymerization is difficult due to the problem of slurry sedimentation in the slurry transfer line, making it difficult to implement in industrial applications. As a continuous polymerization method, a so-called bulk polymerization method is adopted. Unlike the suspension polymerization method, this method does not require the addition of dispersants or stabilizers, so it is superior to the suspension polymerization method in handling high-purity products, which have recently become increasingly demanding. . Therefore, it can be considered that the bulk polymerization method will continue to be adopted as an industrial continuous polymerization method for 88^.

Continuous bulk polymerization methods that have been proposed so far can be roughly divided into the following two types. One is Special Public Service 1974-22, 200. Using methods such as Japanese Patent Publication No. 55-7,845, Japanese Patent Publication No. 54-42,035, and Japanese Patent Publication No. 58132.002, the solvent is
This is a method in which the monomer conversion rate is 90z or more using a complete mixing reactor and a plug flow reactor in series (hereinafter referred to as the high conversion rate method), and strictly speaking, it should be called a solution polymerization method. It is. The other one is Special Public Service 52-
32,665 and JP-A-53-147.788, a method of polymerizing using unreacted monomers as a solvent without adding a solvent and using a complete mixing reactor with a conversion rate of about 60z or less (hereinafter referred to as high conversion In the history of FM, the high conversion method is older, while the low conversion method is relatively new. This is because it was modeled after the styrene bulk process that had previously been developed. The industrialization of bulk polymerization was first carried out, and the polymerization of styrene is currently carried out on the largest scale, and most of the polymerization methods employed there are high conversion methods.

Both have their advantages and disadvantages. In the high conversion rate method, it is possible to handle high viscosity liquids by applying special innovations to the second stage piston flow reactor.
hjukusaitl14141%輛、rツ2JAtbfpH桙A
, 1. -1+: The polymer content including the additive can be made higher than in the case of a complete mixing type reactor. the result,
Since the productivity of one bath increases, the main equipment becomes more compact. There is also less monomer and solvent that must be recovered and recycled, resulting in smaller recovery equipment and lower utility usage. However, this method requires a special reactor in the second stage, which increases equipment costs and makes operation and operation complicated.

The technical point of this method is how to achieve a high monomer conversion rate with a small amount of solvent added, but this depends on developing technology that can handle even high viscosity reaction liquids in the second stage reactor. There is. However, this method has an essential drawback in that the concentration of the radical initiator (hereinafter simply referred to as initiator) in the first stage and second stage is different, so that the degree of polymerization distribution of the final product becomes slightly broader.

Also, a solvent separation device is required.

On the other hand, in the low conversion method, one bath of monomer a;-7
17! T! Fortune telling (Yih6＾da1g φHigashi Mata na me, I have to recycle the Jushome Rinoma - $N, L money,
There is no need to separate the solvent and monomer, and in the bulk polymerization of 814^, the difference in boiling point between the monomer and impurities in the recovered monomer is large, so the utility cost required for recovering and recycling the monomer is not very large.The advantages of this method are: A general stirred tank can be used as a reactor, the sensible heat of the feed monomer can be effectively used to cool the polymerization heat, so the need for heat removal equipment can be reduced, and the degree of polymerization distribution allows for two-stage reactions. It is slightly sharper than the high conversion rate method used.

The low conversion method was originally widely adopted as a method for producing prepolymer (syrup) in the Cath 1 polymerization method, but in that case, the monomer conversion rate was at most 30 to 40%.
There is $1'. In the above-mentioned Japanese Patent Application Laid-Open No. 53-147,788, the monomer conversion rate is 25 to 60 in the claims.
1, but looking at the examples, all conversion rates are 4H.
It is as follows. The low conversion method was implemented with a relatively high monomer conversion of around 6 oz.
665 is the first.

In this Japanese Patent Publication No. 52-32,685, the type and amount of initiator added are limited, and the monomer conversion rate is 50 at a polymerization reaction (hereinafter sometimes simply referred to as reaction) temperature of 130 to 160°C.
-782, in which initiators are claimed to have half-lives from 2 minutes to 5.6 hours at the reaction temperature. The average residence time (hereinafter simply referred to as residence time) is not limited, but according to the examples, it is 3 to 6.
The half-life of the initiator used at the reaction temperature is 18 minutes, or 33 minutes.

From this, the ratio of the half-life of the initiator to the residence time is 1/6
~l/45. The ratio of the minimum half-life in the claims to the maximum residence time in the examples is 17,180. According to this patent, if an initiator with a shorter half-life is used, the thermal decomposition temperature of the product polymer will be lowered and the temperature range in which molding can be performed will be narrowed (hereinafter, this will be simply referred to as
(sometimes described as having poor moldability),
There is no mention of the reason.

(Problems to be Solved by the Invention) Under the polymerization conditions of Japanese Patent Publication No. 52-32.685, a so-called self-acceleration effect (hereinafter referred to as gel effect) is expressed, and the method is characterized in that it is utilized. However, according to our experiments according to the embodiments of this patent, we found that it was difficult to react with a stable monomer conversion rate, and that there was a problem in that it was only possible to operate with a wide range of conversion rate fluctuations. In addition, the range of fluctuation may become too large, causing the reaction to run out of control. If the monomer conversion rate fluctuates, the amount of reaction heat generated, the amount of polymer production, the amount of recovered monomer produced, etc. will fluctuate, which will impede the stable operation of the entire 10 process.

Furthermore, if a problem occurs in the process after the first reactor, continuous operation will have to be temporarily stopped for repairs, but during this temporary interruption of continuous reaction, the monomer conversion rate will increase rapidly. It was discovered that there was a problem in that the system could go out of control.

The purpose of the present invention is to avoid the above-mentioned difficult problems when carrying out continuous bulk polymerization of a monomer mixture containing methyl methacrylate as a main component in a single complete mixing reactor without using a solvent. The object of the present invention is to provide a method for obtaining a colorless and transparent polymer with excellent moldability while achieving stable operation at any monomer conversion rate between 45 and 701.

(Means for Solving the Problems) As a result of intensive research to achieve the above object, the present inventors have developed an initiator with a specific half-life after reducing the dissolved oxygen in the monomer to ippm or less. The present inventors have discovered that the objective can be achieved by stirring with a specific power consumption and reacting at a specific monomer conversion rate at a specific temperature and residence time, and have completed the present invention.

That is, in the present invention, a monomer mixture containing methyl methacrylate as a main component is produced using one complete mixing reactor.
When performing continuous bulk polymerization without using a solvent, (1) introducing an inert gas into the monomer to reduce the dissolved oxygen in the monomer to 1 pp- or less, (2) half-life at the polymerization temperature. (3) Using a radical initiator with a time of 0.5 to 120 seconds, while stirring with a stirrer having a stirring power consumption of 0.5 to 20 KH per 11) of the reaction solution, (4) the radical initiator at the polymerization temperature. τ to the ratio of half-life and average residence time of
The average residence time is set so that 17□10) is i/zoo to I/10,000, and (5) polymerization is carried out at 130 to 160°C so that the monomer conversion rate is 45 to 701. This is a method for producing a colorless and transparent methacrylic polymer with excellent moldability.

The present invention will be explained in more detail below.

The methacrylic polymer of the present invention refers to a monopolymer of 1 to 15 fH (hereinafter referred to as H
It is a copolymer containing ethyl acrylate (hereinafter referred to as E^) or ethyl acrylate (hereinafter referred to as E^).

The present invention consists of the steps of seven-mer preparation, polymerization, heating, deaerating extrusion, and monomer recovery in the order of steps. The steps will be explained in order below.

In the monomer mixing process, a tank (blending tank) with an agitator is used.
Then, 88^, a predetermined amount of H^ or E^, a chain transfer agent, and an initiator are mixed and dissolved, and the mixture is continuously supplied to a polymerization reactor.

Since the polymerization activities of 814^ and H^ or E^ are different, the monomer composition to be charged is slightly different from the copolymer composition in the polymer, but the relationship between the two can be easily determined by testing in advance. 7 to monomer 100B
+) The amount of heavy chain transfer agent added is 0, O1 to 0.1. The target average molecular weight is selected from the range of . The amount of initiator added ranges from 0.001 to 0.1 g,
It is selected so that the target monomer conversion rate can be achieved at the polymerization temperature at that time.

The chain transfer agent used is mercaptans, especially n-
Butyl, n-octyl and n-dodecyl mercaptan are preferred.

The initiator used is a radical initiator with a half-life of 0.5 to 120 seconds, preferably 1 to 60 seconds at any reaction temperature between 130 and 160°C, which is the most important aspect of the present invention. This is a point. If an initiator with a half-life of more than 120 seconds is used, the monomer conversion rate will fluctuate widely, making it difficult to ensure stable operation. Also, the half-life is 0.5
If it is less than 2 seconds, the amount of initiator used will be too large, causing problems with the colorless transparency of the product polymer. Examples of initiators used in the present invention include 2.2-azobisisobutyronitrile, 2. 2-azobis(2,4-dimethylvaleronitrile), 2,2-azobis(2-methylbutyronitrile)
Azo compounds such as 1.1-bis([-butylperoxy)]3. (,5-1-limethylcyclohexane, L-butylperoxyisobutyrate, benzoyl peroxide, lauroyl peroxide, and other organic peroxides are preferred. In the present invention, the value of the half-life of the initiator For azo compounds, Wako Pure Chemical Industries, Ltd.
Regarding published technical bis-lethane and organic peroxide, values from the catalog (12th edition) published by Nippon Oil & Fats Co., Ltd. were adopted.

There are two methods for seven-timer mixing: batch and continuous, and either method may be used. In the batch method, two mixing tanks are installed and batches are mixed alternately and used. In continuous blending, each component stream 1 is automatically controlled in a predetermined amount in separate lines, then mixed and fed to the reactor. Among these, only the initiator is continuously supplied as a monomer solution of 0.1 to 5z.

To reduce the dissolved oxygen in the monomer to less than ippm, in the case of batch mixing, it may be carried out by bubbling inert gas into the mixing tank for a certain period of time, but when the monomer is charged into the mixing tank, it may be carried out by bubbling inert gas into the mixing tank. A method of mixing inert gas in a line mixer and separating gas and liquid in the mixing tank (unfruitful). It is preferable to use a motionless mixer such as a static mixer as the line mixer, in the case of continuous mixing. After mixing each component, a line mixer and a small gas-liquid separator are installed, and inert gas is continuously supplied to the line mixer and released from the gas-liquid separator to remove dissolved oxygen in the monomer. It is preferable to carry an amount of inert gas in the range of 2 to 10 parts by volume per 1 part by volume of monomer.If the dissolved oxygen in the monomer exceeds 1 pp+s, the conversion of the 7-mer in the reaction will be poor. It becomes stable.

It is preferable that the liquid mixture prepared as described above is filtered through a filter of 0.5 microns or less before being fed to a reactor.

In the polymerization step, the temperature is 130-160°C, preferably 140-160°C.
Monomer conversion of 45 to 155°C at a temperature range of 155°C
701, preferably in the range of 55 to 65. If the reaction temperature exceeds 160°C, the polymerization of oligomers such as dimers and trimers, and compounds of monomers and mercaptans will occur. In addition, if it is less than j3qp, the viscosity of the reaction solution will increase and the contribution of the gel effect will increase, making it difficult to maintain a stable monomer conversion rate, and also from the point of view of reaction heat removal. A disadvantage arises. When the monomer conversion rate exceeds 701, the viscosity increases and it becomes difficult to maintain stable operation.
If it is less than 5z, not only will the load on the degassing step and the monomer recovery step increase, which is disadvantageous, but also the self-In nature of the reaction described below will disappear, which will be disadvantageous for stable operation.

The present invention originates from the discovery of the fact that when polymerization is performed using a specific initiator under specific conditions, the higher the reaction temperature, the lower the monomer conversion rate, which is contrary to common knowledge in chemical reaction kinetics. The initiator was 2.2-
Figure 1 shows the results of an experiment using azobisin butyronitrile (hereinafter referred to as Al0N) at a reaction temperature of 150°C, a residence time of 3.0 hours, and a stirring speed of 200 rpm (stirring power consumption of 9 and H7m'). When the monomer conversion rate is 45z or less, the common sense result is that the conversion rate is higher at a higher temperature at the same initiator concentration, but the opposite is true when the monomer conversion rate is 451 or higher. With this figure, it is possible to explain the self-controllability of the polymerization reaction, which is the basis of the present invention. That is, suppose that the reaction temperature rises for some reason. According to FIG. 1, as a result, the monomer conversion rate decreases, so the amount of reaction heat generated decreases, and the reaction temperature automatically decreases and returns to the original temperature. Conversely, the same applies when the reaction temperature decreases. According to the first factor, the higher the monomer conversion rate, the stronger this reversal phenomenon becomes.The reason why such a reversal phenomenon occurs is that a gel effect occurs at a monomer conversion rate of 451 or higher, resulting in low temperature and high conversion. The stability of the monomer conversion rate in continuous polymerization achieved by the present invention is due to such self-controllability.

The residence time for the reaction may be selected from the range of 1 to 6 hours, but the ratio of the half-life of the initiator used at the reaction temperature to the residence time (t+zi10) should be 17200 to 1/10.
,000 is essential. There has never been an example of a polymerization reaction using such a small (t+, zlo) value, and the fact shown in figure p1 is that such a (t+, zlo) value is
This can only be obtained by adopting the value of t, /210). The reason why stable operation at a monomer conversion rate of 60 to 701 could be achieved during a short residence time of 1 to 3 hours was due to such a small (t + z2/θ
), and the present invention provides a process with unprecedentedly high productivity.

There is no particular limitation on the polymerization pressure, but if the reaction solution is boiled, the polymer will adhere to the walls of the gas phase inside the reactor 2 due to entrainment, which will hinder long-term operation. It is preferable to pressurize with an inert gas so that the reaction pressure is higher than the reaction pressure and to suppress the boiling of the reaction solution.The inert gas is introduced directly below the seal part of the stirring shaft such as a mechanical seal, It is used to prevent monomer vapor from rising to the sealing area and to prevent problems caused by polymer adhesion inside the sealing machine.

This gas passes through a reflux condenser to condense and remove monomer vapor, and then is released after controlling the pressure to a constant level with a pressure control valve. The pressure may be selected from 3 to 9 kgr/cm2G, but it does not need to be too high, although the purpose is to suppress boiling of the reaction liquid.

Excessive pressure reduces the monomer composition in the gas phase of the reactor, resulting in less condensation of the steam vapor in the reflux condenser, which is disadvantageous in terms of heat removal.

Regarding stirring of the reaction liquid, the stirring power consumption is 1 m' of reaction liquid.
0.5 to 20 KIl per unit, preferably 1 to 10 -
It is essential to do so. If it is less than 0.5 KM, the amount of initiator required to obtain a predetermined monomer conversion rate will increase, which will adversely affect the moldability and colorless transparency of the polymer. In addition, if it exceeds 20KllI, the power consumption becomes too large and it is not economical.As a TA stirring blade, a general paddle blade, double helical ribbon blade, or Sumitomo FFEIR is used.
In the method of the present invention, it is necessary to suppress the boiling of the reaction liquid and evaporate the monomer, so a double helical ribbon blade or a Maxblend blade, which has a large liquid level renewal effect, is preferably used. is recommended. When using these stirring blades, there is an advantage that the evaporation of the monomer can be dramatically accelerated by stirring the liquid at a level lower than the upper end of the blade.

There are three conventionally used methods for removing the reaction heat: a method that utilizes the sensible heat of the monomers supplied, a method that uses heat transfer to remove heat from the reaction solution using a heating medium, and a method that uses heat transfer from the reaction solution. It is desirable to use a method that utilizes latent heat of vaporization in combination.8 According to the method of the present invention, the amount of heat removed by the sensible heat can be increased by cooling the monomer to be supplied, so it is not dependent on the other two methods. The amount of heat that must be removed is reduced. As a result, it is no longer necessary to insert a heat exchanger inside the reactor or to install an external heat exchanger and circulate the reaction liquid externally using a circulation pump, which not only simplifies the reactor, but also makes it possible to The size of the reflux condenser is also compact, reducing installation costs.

In the heating step, the reaction solution obtained by the above polymerization reaction is heated to 220 to 270°C in the shortest possible time,
This is a step in which the latent heat of vaporization necessary for gasifying unreacted monomers in the next degassing step is clearly imparted to the reaction solution. The heating step and the degassing step are separated by a needle valve, and the pressure in the heating step is set slightly higher than the saturated vapor pressure of the monomer at the heating temperature. Otherwise, gas may be generated in the heater, which not only reduces the heat exchange capacity but also generates char in the heater.

If the heating temperature is lower than 220℃, the polymer temperature after being flushed with the needle valve will become too low.
This is not preferable because it increases the degassing load on the degassing extruder, and if the temperature is higher than 270°C, the amount of high-boiling by-products such as dimers and trimers increases, which is not preferable.

In the heating process, the temperature of the reaction solution is raised by 60 to 120°C, so it is inevitable that the polymerization reaction and side reactions that produce dimers and trimers will proceed to some extent. Since the degree of polymerization of the polymer is slightly different from that of the polymer produced in the reactor, the distribution of degree of polymerization of the product polymer becomes wider, which is undesirable.Also, if dimers, trimers, etc. sit in the heater, the purity of the polymer decreases. However, in the present invention, the concentration of initiator in the reaction solution in the heater is several tenths of the concentration of initiator in the monomer supplied to one reactor, so polymerization in the heater does not occur. The progress of the reaction becomes negligible. This is one of the advantages of the present invention. In order to suppress the formation of dimers and trimers in the heater, the volume of the heater must be made as small as possible and the temperature must be raised to the target temperature in a short residence time.To do this, heating with a large heat transfer coefficient is required. Preference is given to using equipment, advantageously the use of double-tube or shell-and-tube heat exchangers of motionless mixers such as Noritake static mixers. This allows residence times of 1 to 3 minutes and minimizes the formation of by-products in the heater.

In the degassing step, the reaction solution heated in this manner is flashed using the needle valve, and unreacted monomers are separated from the polymer as a gas.

Preferably, the degassing is carried out in two stages, the needle valve installed at the outlet of the heater being connected to the first stage degassing device. As for this device, it is preferable to use the following filtration extruder.A two dollar valve is connected to the barrel of the deep groove part (feed zone) of the screw to flush the reaction liquid from the heater, and the polymer is transferred to the feed zone. The gasified monomer is not forced out of the guide through the compression zone and metering zone following the needle valve, but is stored in a back vent installed in the barrel of the deep screw part on the opposite side of the polymer flow direction with respect to the needle valve. ) The gas is extracted from the hole at normal pressure and can be fed as is to the distillation tower.At this stage, the monomers in the polymer are usually 1 to 5z.

In the second stage of degassing, the monomer content of 1 to 5z is reduced to 0.1z.
The purpose is to reduce it to below. The equipment used is a vacuum tank with a polymer discharge screw at the bottom or an extruder with one to three vacuum vents (front vents). In either case, the degree of vacuum is selected from the range of 1 to 301. It is preferable that the clearance is small, but they must not touch each other.Practically, a clearance in the range of 2 to 5 is used. When using an extruder, the first stage described above and the second stage deaerator may be integrated. In either case, the deaerator is equipped with a jacket and heated using a heat medium, but the deaerator is It is preferable to select the wall temperature of the device from the range of 200 to 260°C for both the first stage and the second stage.If this temperature is below 200°C, degassing will be insufficient, and if it is above 260°C, the degassing device will not work properly. Thermal decomposition of the polymer occurs within the polymer, and in any case, the monomer content in the product polymer will not be less than 0.1z. The polymer thus obtained is ultimately extruded from the goo as a strand or plate;
In this case, it is preferable to attach a filter such as a 400-mesh wire mesh to the die breaker plate.

In the monomer recovery process, a high-boiling cut device is used to remove high-boiling compounds such as mercaptans, dimers, and trimers from the vapor extracted from the first-stage deaerator and recover them as monomers that can be reused in polymerization reactions. A general distillation tower is used for this purpose, but in order to prevent polymerization within the tower, it is preferable to introduce a small amount of air from a reboiler and release it from a condenser at the top of the tower. It is preferable to cool it to 0 to 20°C and set it as an air atmosphere.

(Example) Next, the present invention will be explained in more detail with reference to Examples, but these Examples do not limit the present invention in any way. A flow sheet of the apparatus used in the Example is shown in Fig. 2. The specifications of the main equipment are as follows.

Nitrogen mixer: Noritake static mixer - 810 type inner diameter 41.2 + m ring - 10.77 m (12 elements)%
/ ? -411 combined tank: 400F-SUS-: 116.
, paddle included, jacket included, 2 filters: Enfron filter HCY-10 manufactured by Ball Co., Ltd.
01FRE Reactor: 200fjUS-316, Maq 9 Suf 1
/ 7 F
-φ, 1II (number of elements 30) x 3 in series, 5O
S-316 Deaerator = (-stage) Single screw extruder with back vent, (Second stage) Wiper type falling thin film evaporator Contents: 1i30J (SOS31B), Heat transfer area: 0.2+m
”, high-boiling cut tower equipped with an extraction screw at the bottom: inner diameter 71 m @ length 1.2 in. 172 inch SUS rasp ring filled. Also, the polymer evaluation method is as follows.

(1) Measurement of heat decomposition resistance Product pellets were continuously injection molded under the following conditions.
Ten plates of m-x70amx3mm were obtained, and the monomer concentration therein was measured by gas chromatography and found to be 0.5
A value of z or less was considered to have good heat decomposition resistance.

Injection molding machine: Toshiba 81 machine 1s-80EPH-2 Injection pressure 400 kg 47 am” Injection and pressure holding time 8 seconds Barrel temperature 270°C Mold temperature 55°C Cycle time 180 seconds (2) MFH Measurement Takara Kogyo Co., Ltd. Melt Using an indexer, ASTM-
Based on 01238, 230℃, load 3.80kg, extrusion distance (f) 2.54cs+, cylinder diameter (D)
The extrusion time (in seconds) was measured under the conditions of 5.08 cm and a nozzle diameter of 0.2095 cs+, and was determined by the following formula.

MF to (1/4) D″fX (specific gravity) xaoo eight (3)
For molecular weight measurement using PC, Shimabara LC-5^ was equipped with Shimabara+1sG-15 as a column.
-30 and -50 are used, polymer 0.12
g was determined from an elution curve obtained using a sample dissolved in tetrahydrofuran 201 using a calibration curve prepared using a-quasi-polystyrene.

(4) Measurement of average molecular weight by intrinsic viscosity method - sample 1 le 0
．． 6 g was dissolved in 251 chloroform and the viscosity at 20°C was measured using an Uppelohde viscometer. 2 of this liquid
Several viscosity points diluted to ~6 times were determined, and from these values, the intrinsic viscosity [η] at infinite dilution was determined, and the average molecule fM was determined using the following formula.

[,] = 0.485X10-'X14'-" (5) Measurement of hue Using an SN color computer manufactured by Suga Test Instruments Co., Ltd., the hue of a 3--thick plate was calculated using Hunter's chromaticity coordinates. It was determined as a b value.

(6) Measurement of minute foreign matter 111 Using an AC-ROYCOMocle 346 automatic particle counter, 6 g of sample was
0.5-10. The number of foreign objects of size was measured.

Example 1 91.5 ffIli parts of methyl methacrylate (HMA), 8.5 parts by weight of ethyl acrylate (E^), 0.36 parts by weight of n-octylmercaptan (ON), 2.2-azoisobutyronitrile (^IIIN) ) was charged into a mixing tank which had been previously purged with nitrogen and cooled to 0° C., and mixed with stirring. Of these, 814^ and E^ are each pumped from the raw material tank by 1,
At a flow rate of 5007/b, the gas was fed through a heat exchanger cooled with a -5°C refrigerant and a nitrogen mixer, but was it mixed with nitrogen at that time? The amount of nitrogen used in - was 5,000878. While stirring the mixture of 88^ and E^, turn ON and ^.
ION was separately introduced through the nozzle in the upper tube of the mixing tank and mixed and dissolved. Dissolved oxygen in this preparation was measured using DOMe-9-IC-12-SQL manufactured by Sephura Hy Kagaku Co., Ltd., and found to be below the detection limit (0.6 ppm).

The blended liquid is transferred to the reactor by a plunger pump 33.3
kg/b was continuously fed to two mixing tanks while being alternately switched every 8 hours. The piping from the mixing tank to the reactor was jacketed and cooled with a -5°C refrigerant, and the above-mentioned filter was installed. Removed more trash.

The liquid mixture was directly flowed down from the nozzle of the upper mirror of the reactor onto the surface of the reaction liquid.

A multi-tubular heat exchanger with a heat transfer area of 5 m' is installed in the upper part of the reactor, and Jacquera I is installed on the upper mirror, the body, and the lower mirror of the reactor. The lower mirror was cooled with a heating medium to control the reaction temperature at 150°C. ta
A double mechanical seal is used for the shaft seal of the stirrer. 38 m of nitrogen is supplied from the connection between this seal box and the upper mirror.
It was introduced in August 2010, and was discharged after controlling the internal pressure to 4 kgr/cya"G via the shell-and-tube heat exchanger with a pressure control valve.

The amount of reaction liquid in the reactor was 100K, and the half-life of the initiator was 3.6 seconds and the residence time was 3.0 hours. Therefore, the ratio of the half-life of the initiator to the residence time (τ1, 210) is 1/300G. 11! The rotation speed of the stirrer is 200 rpm
It was set as m.

The stirring power was 1.0 KW/m', which was calculated by subtracting the rotating power from the value on the stirrer motor's wattmeter.The reaction liquid was drawn out by the gear pump at the bottom of the reactor, and the liquid level in the reactor was kept constant. Don't control it.

A heating medium at 245°C was passed through the heater jacket as an alternating current to heat the reaction liquid from the gear pump to 235°C.

The pressure inside the heater is set to 24k by the needle valve at the outlet.
I made 7J4!I to Bf/cm”c.

The needle valve was directly connected to the barrel of the 3rd pitch <pitch R from the rgA moving side) of the deep groove screw (lead 130 mm) of the single screw extruder, and the monomer paper was extracted from the back vent hole provided at the 2nd pitch. . The polymer, from which most of the monomers have been removed, is advanced by a screw flight to the compression zone,
It was extruded through the metering zone to the feed nozzle of a single-film evaporator.

The temperature of the heating medium in the jacket of this evaporator was 230°C, the pressure was 10 Torr, the clearance between the wiper and the vessel wall was 3 mm, and the rotation speed of the wiper was 150 rpm. It was extruded as a strand, cooled in a water bath, and then cut with a cutter to obtain a pellet-shaped molding material. A 400 mesh wire mesh was attached to the breaker route of this die.

The yield of pellets was measured hourly and averaged over 24 hours, and the result was 120.4 after 15 days of continuous operation.
~20.8kg/l+(%/?-conversion rate ti, t
61.9 io, 62).

The monomer paper taken out from the back vent is directly fed to the lower end of the packed section of the high boiling cut tower,
With a reflux ratio of 0.5, high boilers (consisting of high boilers concentration of about 401 and monomers of about 601) are cut into the bottom of the column and
-Octyl mercaptan, dimer, trimer, etc., which do not contain high boiling points, were collected, and air was also collected from the tower of this tower! , 5 f/b was introduced and the recovered monomer was discharged from the condenser at the top of the tower and was put into a jacketed tank, purged with air, stored, and reused.

Melt flow rate of the molding material obtained as above (
MFR) is 20.5, E^ in the pellet by gas chromatography analysis is 7.2 times ff1z, and residual monomers, dimers and trimers are each 0.0B,
They were 0.09 and 0.08 heavy duty. The number average molecular weight measured using cpc is 36,000. ff1ffl
The average molecular weight was 67.000, and the value of molecule 1 distribution Hw/Hn was 1.9.

In addition, the average molecular weight measured by the intrinsic viscosity method was 84,000.
Met. The monomer in the injection molding machine was 0.331, and the hue of the molded plate was 0.19, both of which were good. The number of minute foreign particles of 0.5 to 10 microns per gram of polymer was 10,800 particles/g.

Example 2 Ethyl acrylate (E^) 8.5f in Example 1
Methyl acrylate (M^)9 instead of fiffi part
．． Using 0111 parts, ^l[lN addition amount is 0.009
Operation 4 was carried out in exactly the same manner as in Example 1 except for the 5-fold leg and the shingles, and the monomer conversion rate remained constant at 61.8±0.5z during 15 days of continuous operation. In addition, HFR2O,1, of the obtained pellet (in Ly but) MA8
．． 2ffiffil, mo/-i'-0,09fflf
Fi! , dimer 0.087 heavy JH, toIJ -i'-
0,084% by weight, Mw/Hn1.9. Average molecule [84
, (too, the number 7 in the injection molding machine is 0.381.
The number of micron foreign particles was 12,500 pieces/g.

Example 3 The same operation as in Example 1 was performed except that the type and amount of the initiator used in Example 1 was changed to 0.0825 parts by weight of lauroyl peroxide. The conversion rate became constant at 62.2±0]4z. At this time, since the half-life of the initiator is 1.8 seconds, ([, 7□10) becomes 1/6000. In addition, HFR2O,3 of the obtained pellet, E in the pellet
^7.2 weight 2, 7-mer 0.094 weight 1z, dimer 0.093 weight%, To IJ 7-0, 080 weight JiLI
Mw/Mn1.9, average molecular weight 84.000. The monomer in the injection molding machine is 0.38Z, the hue value of the molding plate is 0.21, the number of minute foreign particles between 0.5 and 10 microns is 14,
000 pieces/g.

Example 4 The type and amount of the initiator used in Example 1 were
When the same operation as in Example 1 was carried out except that the amount was changed to 1.5 parts, the monomer conversion rate remained constant at 62.2±0.5 $ during 15 days of continuous operation. At this time, the half-life of the initiator is 45 seconds, so (τ+7-10) is l72
It will be 40. Furthermore, the MFI of the obtained pellets was +20.
0, Beret Nakano EA7.2fffffi! , -E/
? -0,1) 85-fold ff1z, dimer 0.086f
fiffi$, l-tsum-0,0fufujuffllHw/
Mn1.9, average molecular ff184,000, monomer in injection molding machine 0.40! , the hue value of the molded plate is 0
．． 20. The number of minute foreign particles between 0.5 and 10 microns is 11.3
00 pieces/g.

Comparative Example 1 Except for changing the type and amount of the initiator used in Example 1 to 0.0026 parts by weight of di-butyl peroxide.
The same operation as in Example 1 was performed. Since the half-life of the initiator at this time is 30 minutes, (r+z□10) is I/6
becomes. Over 15 days of continuous operation, monomer conversion varied between 158 g and 651 g for 20-30:1 m cycles. In addition, the 14PR of the obtained pellets is 19~
23, Heret Nakano E^ is 7~7.5fffffl! ,
Mo/? -0,08~0.111! fit$, die 7-0
．． 08~0.1ffiffi! ,bird? -0,08~0
．． 12 layers R$, Mw/Mn2. O~2.2, average molecular i 82,000~86.000. The monomer in the injection molding machine has a value of 0.4 to 0.6z, and the hue value of the molded plate is 0.
It varied between 20 and 0.25.

In addition, the number of minute foreign particles of 0.5 to 10 microns is approximately 15.0
00 pieces/g.

[Brief explanation of drawings]

FIG. 1 is a graph showing a reversal phenomenon in which when the special polymerization conditions of the present invention are employed, the monomer conversion rate is 451 or higher and the conversion rate becomes lower at high temperatures. Figure 2 shows the equipment and flow sheet used in the examples of the present invention, in which reference numeral 1 is a static mixer for nitrogen mixing, 2 is a monomer mixing tank, 3 is a metering pump, and 4 is a static mixer for nitrogen mixing. Filter, 5 is reactor, 6 is reflux condenser, 7 is automatic pressure control valve, 8 is mechanical seal, 9 is gear pump, 10 is double pipe heater with built-in static mixer, 11 is 21 dollar valve 12 is back Vented single screw extruder, 13 wiper type thin film evaporator, 1
4 is an extraction screw, 15 is a guide, 16 is a vacuum pump, 17 is a water tank, 1st is a cutter, 19 is a shifter, 2
0 is a smoke distillation tank, 21 is a reboiler, 22 is a condenser, and 23 is a recovered monomer tank.

Claims (1)

[Claims] When carrying out continuous bulk polymerization of a monomer mixture containing methyl methacrylate as a main component in a single complete mixing reactor without using a solvent, (1) an inert gas is introduced into the monomer; After reducing the dissolved oxygen in the monomer to 1 ppm or less, (2) using a radical initiator with a half-life of 0.5 to 120 seconds at the polymerization temperature, (3) using 0.5 to 20 KW per 1 m^3 of the reaction solution. (4) Adjust the average residence time so that the ratio of the half-life of the radical initiator at the polymerization temperature to the average residence time is 1/200 to 1/10,000 (5) The monomer conversion rate is 45 at 130-160°C.
1. A method for producing a colorless and transparent methacrylic polymer with excellent molding processability, characterized by polymerizing the polymer to a concentration of ~70%.