JPS5921325B2 - Continuous manufacturing method for methyl methacrylate syrup - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a syrup with a high polymer content that maintains a suitable viscosity for good workability without degrading the quality of methyl methacrylate resin plates, and at the same time shortens the plate making time. .

More specifically, the present invention involves sequentially passing a methyl methacrylate monomer and a radical polymerization initiator under specified reaction conditions to achieve a narrow polymerization degree distribution, a small residual initiator concentration, and a polymer-containing polymer. This invention relates to a method for continuously producing syrup with high yield.

Methyl methacrylate resin plates are usually obtained by injecting a polymerizable liquid composition consisting of a polymerization initiator and methyl methacrylate syrup between two glass plates and polymerizing the composition under heating. At this time, a syrup containing an appropriate amount of polymer is used as the injection liquid in order to improve the workability of injecting the polymerizable liquid composition, improve the quality of the resulting resin board, and shorten the board making time. ing.
Before injection, a polymerization initiator and other necessary additives are added to the syrup, and the syrup is degassed under reduced pressure to remove dissolved air. glass plate = injected between. If the viscosity of the syrup is too low during injection, it may cause leakage, and if it is too high, the injection time will be longer, both of which will reduce the workability of injection, so the viscosity of the syrup to be injected should be appropriate. must be selected within a certain range.
In addition, by using syrup, the amount of heat generated during polymerization is reduced, and the shrinkage of the polymer during polymerization can be reduced, which improves the surface condition of the resulting resin board and makes it easier to control the board thickness. From this objective, the higher the polymer content in the waters off Shilotov, the better. Further, the higher the polymer content in the white stubble, the shorter the board making time, so from this point of view as well, it is preferable that the polymer content is as high as possible. Please note that this may not be used for such purposes.
4. The syrup used must have high storage stability, and must not inhibit polymerization during board manufacturing, nor reduce the quality of the resulting resin board (~. Manufacture of methacrylic resin board) Traditionally, this process has been carried out using the batch-type cell-casting method, which involves polymerization between two glass plates.
In recent years, there has been a shift to a continuous casting method in which plate production is performed by continuous polymerization between two consecutive moving bands.

This continuous casting method is used, for example, in Japanese Patent Publication No. 51-29916
As shown in the publication, two continuous moving bands in a vertical positional relationship are made to run in the same direction and at the same speed, and at least one continuous gasket is moved on each side of the moving bands on both sides. The composition is run in contact with the bands to seal the space between the moving bands, the polymerizable liquid composition is supplied to the space between the moving bands, and the composition is run through the zone where it polymerizes to complete the polymerization. , is a continuous plate manufacturing method in which a plate-shaped polymer is taken out from the other end between the moving bands. However, in this method, the equipment cost accounts for a large proportion of the manufacturing cost, so it is particularly required to shorten the plate manufacturing time compared to the cell casting method. Shortening the plate making time is achieved by increasing the polymer content of the syrup used as the injection liquid as high as possible within the viscosity range that ensures workability for injection, etc. As a result, if the quality of the resulting resin board deteriorates, the value of the resin board as a product will decrease accordingly, and the effect of reducing manufacturing costs by shortening the board manufacturing time will be offset by that amount. should not reduce the quality of the resin plate as much as possible, but should preferably improve the quality. If the polymer content of the syrup is increased to shorten the plate making time, the average degree of polymerization of the resulting resin plate will usually decrease, resulting in a decrease in mechanical strength. Defects such as foaming are more likely to occur during hot forming of the plate.

The viscosity of syrup under constant temperature conditions is determined by the polymer content and the weight average degree of polymerization of the polymer, and the relationship is such that the higher the content in both of them, the higher the viscosity. Therefore, in order to increase the polymer content as much as possible within the limited upper limit of viscosity from the viewpoint of workability such as injection, it is preferable that the weight average degree of polymerization is as low as possible. The low degree of polymerization in the syrup also contributes to the tendency of foaming during thermoforming of the resin plate, and its amount is approximately determined by the number average degree of polymerization. Since the amount of low molecular weight polymer decreases as the number average degree of polymerization increases, it can be said that the higher the number average degree of polymerization, the more preferable it is. In polymers with a degree of polymerization distribution, the weight average degree of polymerization is generally larger than the number average degree of polymerization, and the polydispersity expressed as the ratio of the two is used as a measure of the breadth of the distribution of degree of polymerization. It can be said that syrups with a smaller degree of dispersion are more preferable. Additionally, if the concentration of residual initiator in the syrup is high, polymerization will proceed further during cooling during syrup production and during syrup storage, increasing the polymer content and viscosity of the syrup, making it difficult to obtain a constant quality product. It has some serious drawbacks.

In addition, trace amounts of residual initiator such that the progress of polymerization is not substantially observed may cause deterioration of the syrup during storage, and residual monomers in resin plates obtained using such syrup may It is necessary to keep the residual initiator concentration as low as possible, since it may increase the content and cause quality deterioration, such as making the resin plate more likely to foam during heat molding. In addition, as a method of shortening the plate making time, it is possible to increase the concentration of the polymerization initiator used during plate making instead of increasing the polymer content of the syrup, but in this case, the average degree of polymerization of the resin plate will inevitably increase. It is difficult to say that this is an advantageous method because the quality decreases significantly. Various methods have been proposed for the production of syrup, and although all of them partially satisfy the above conditions, no method is known that satisfies all of them. Reducing the plate making time leads to quality deterioration, such as a decrease in the mechanical strength of the resulting resin plate and the tendency to foam during heat forming, which has the disadvantage that shortening the plate making time does not necessarily lead to improved economic efficiency. was. Batch production of syrup usually involves using a stirred tank reactor, heating monomers to a high temperature and then adding a predetermined amount of polymerization initiator, or using a mixture of monomers and polymerization initiator. The syrup is heated to a high temperature, allowed to polymerize for a sufficient period of time to reduce the initiator concentration to a substantially negligible amount, and then cooled to remove the syrup.

In this method, the initiator concentration is high at the beginning of the reaction and decreases relatively rapidly as the reaction progresses, and the degree of polymerization of the resulting polymer varies from a fairly low degree at the beginning to a very high degree at the end. Even things change drastically. Therefore, the polymerization degree distribution of the obtained Silozov polymer is extremely wide, with a high weight average degree of polymerization and a low number average degree of polymerization. The weight average degree of polymerization is directly related to the viscosity of the syrup, which means that the syrup has a higher viscosity when compared with the same polymer content, making it easier to pour into glass cells or between moving bands. Therefore, in order to facilitate this, it is necessary to suppress the polymer content in the syrup to a low level, and it is not expected that the plate making time will be reduced much. In addition, a low number average degree of polymerization means that it contains a relatively large amount of low polymerization degree polymers that cause quality deterioration, and the average degree of polymerization of resin plates obtained using such white stubbles may decrease. Alternatively, it may cause foaming during heat molding of the resin plate, resulting in quality deterioration, which is undesirable. Increasing the concentration of the polymerization initiator initially used in this method lowers the weight average degree of polymerization of the polymer in the syrup obtained, and the upper limit of the polymer content within the range of viscosity that is easy to pour is Although this increases the plate making time, the number average degree of polymerization also decreases correspondingly, which is not a good idea as it promotes deterioration in the quality of the resin plate. Note that the syrup obtained by this method usually has a sufficiently low concentration of residual initiator,
Storage stability is relatively good. On the other hand, in this batch production method, if polymerization is not carried out for a sufficient period of time, a syrup with a relatively narrow degree of polymerization distribution is produced, but due to the high residual initiator limit, further polymerization occurs during cooling and storage. This leads to the problem that the viscosity increases.

Additionally, polymerization inhibitors have been added for the purpose of increasing the storage stability of the syrup, but this has drawbacks such as delaying the polymerization time during plate manufacturing and causing discoloration. The method of adding a chain transfer agent during the batch production of syrup to suppress the formation of highly polymerized polymers is difficult because if the chain transfer agent remains in the syrup, it will affect the plate manufacturing process, delaying the polymerization time and reducing the yield. This is not a preferable method as it causes a decrease in the average degree of polymerization or coloring of the resin plate. On the other hand, several continuous methods of producing syrup have been proposed.

The method of continuously supplying monomers and polymerization initiator from one end of a tubular reactor and continuously taking out the produced syrup from the other end essentially completely overcomes the drawbacks of the batch method mentioned above. Can not do it. In other words, from the perspective of the time course of the polymerization reaction, the phenomenon that occurs when a reaction solution flows in the longitudinal direction of a long and narrow tubular reactor shows that, excluding the influence of back mixing, a batch tank reactor The time course of the polymerization reaction in The degree of polymerization of the polymer produced varies widely, from a fairly low degree of polymerization near the inlet to a very high degree of polymerization near the outlet, and the distribution of the degree of polymerization of the polymer in the resulting syrup is extremely wide. Become. On the other hand, if this method does not carry out polymerization at a sufficient temperature or residence time, a syrup with a relatively narrow degree of polymerization distribution is produced, but the storage stability of the syrup is poor, so a batch tank reactor is sufficient. It is the same as when you do not spend a lot of time doing it.

That is, even in a continuous tubular reactor, it is not expected that the plate making time will be reduced so much without degrading the quality of the resin plate obtained. A method has also been proposed in which monomers and polymerization initiators are continuously supplied from the inlet of a stirred tank reactor, and the produced syrup is continuously taken out from the outlet.

Japanese Patent Publication No. 38-4794 describes a method in which polymerization is carried out at a temperature and under conditions such that the polymerization initiator is just decomposed when the desired conversion is reached. In this method, if the reaction temperature is selected to be sufficiently higher than the decomposition temperature of the polymerization initiator in the batch polymerization method, rapid decomposition of the polymerization initiator will occur, and polymerization will proceed to a certain conversion rate during this time.
If the polymerization initiator is completely decomposed after a certain period of time, the reaction will proceed only thermally and will be extremely slow. Also, carrying out the polymerization at temperatures and conditions just such that the polymerization initiator is decomposed makes it easier to control the reaction and keep the conversion within predetermined limits, i.e. This study focused on the fact that under high temperature conditions, the Tromsdorf effect appears to be significantly reduced, approaching dead-end polymerization. It states that it is perfectly suitable as a polymerization control method. However, the syrup obtained by polymerizing at such temperatures and conditions in a batch production method or a production method using a continuous tubular reactor has an extremely wide distribution of polymerization degree as described in detail above. It has the disadvantage that shortening does not necessarily lead to improved economic efficiency.

On the other hand, in the production method using a continuous tank reactor, the method in which polymerization is carried out at such temperatures and conditions has drawbacks regarding the quality of the obtained syrup, which will be described later.

That is, in this method, new polymerization initiator is constantly supplied into the reactor even under temperature conditions where rapid decomposition of the initiator occurs, and the concentration of polymerization initiator rapidly decreases as the reaction time increases. There is no such thing. The steady-state initiator concentration in a continuous tank reactor under conditions where complete mixing is achieved is equal to the residual initiator concentration at the outlet of this reactor, I=
It is expressed as IO/(1+Kθ). where I is the residual initiator concentration (wt%) and 10 is the fed initiator concentration (wt%)
, K is the decomposition rate constant of the initiator (1/sec), and θ is the average residence time (sec). Now considering the temperature conditions under which rapid decomposition of the initiator occurs, K is sufficiently large, so Kθ》
1, and I-IO/Kθ is established. In other words, as the reaction time increases, the residual initiator concentration shows a decrease that is at most inversely proportional to the reaction time, and there is no reaction time condition under which the polymerization initiator is just decomposed. It is impossible for the reaction to proceed very slowly over a period of time, and in this sense it is difficult to stop the polymerization at a desired level in the case of batch production methods or production methods using continuous tubular reactors. It is quite different from that, and it cannot necessarily be said that it is easy. Therefore, in a continuous tank reactor, as mentioned above, the residual initiator concentration only shows a slow decrease with reaction time even at temperatures where rapid decomposition of the initiator occurs in batch reactions. It is,
The concentration of residual initiator in the resulting syrup is higher than in the case of a batch reaction, and it is inevitable that polymerization will proceed further during cooling or storage, increasing the viscosity of the syrup. In order to obtain a syrup with good thermal stability that does not cause such polymerization to occur, it is necessary to reduce the residual initiator concentration to a lower level, which requires rapid decomposition in batch reactions. Although it is necessary to carry out the reaction at a temperature even higher than that at which it occurs, other disadvantages arise under such conditions.

In other words, it takes a certain amount of time to uniformly mix the newly supplied monomer and polymerization initiator into the reaction mixture in the reactor, but under such temperature conditions, sufficient mixing is difficult. Before the polymerization is achieved, the decomposition of the polymerization initiator proceeds in a non-uniform state, and the resulting polymers produced in Shilotzhu have a wide range of polymerization levels, from very low polymerization degrees to very high polymerization degrees. It will have a degree distribution. Resin plates obtained using such syrups are of low quality because they contain low polymerization degree polymers, and because the polymerization degree distribution of the polymers in the syrup is wide, the viscosity is high in proportion to the polymer content. However, it has the drawback that it is a constraint in increasing the polymer content, and it is difficult to expect much reduction in plate manufacturing time. Further, Japanese Patent Publication No. 47-35307 describes a method in which two or more continuous tank reactors are arranged in series to carry out polymerization in order to improve the drawbacks of the above-mentioned method.

In this method, 40 to 95% by weight of the polymer in the syrup is produced in a first reactor, and then the remaining polymer is produced in second and subsequent reactors, and the polymer in the syrup is at least Because it is made in the presence of two concentrations of polymerization initiator, the polymer has at least two molecular weight moieties;
The weight average molecular weight of the high molecular weight portion is at least twice that of the low molecular weight portion, and the low molecular weight portion is 40% to 95% by weight of the polymer in the syrup; It is stated that when included in high proportions, syrups with relatively low useful viscosities and high solids contents are obtained. This method reduces the weight average degree of polymerization, which is directly related to the viscosity of the syrup, by increasing the proportion of the low polymerization degree portion of the polymer in the syrup, thereby increasing the polymer content at a relatively low viscosity. It can be interpreted that the intention was to obtain a high syrup. However, a low polymerization degree polymer lowers the average degree of polymerization of the obtained resin plate and causes foaming to occur easily during heat molding of the resin plate, so by increasing the proportion of the low polymerization degree part, the polymer Although the method of obtaining syrup with a high content rate can shorten the board making time, it has the disadvantage that the quality of the resulting resin board is degraded.

Furthermore, from the relationship between the polymerization degree distribution of the polymer in the syrup obtained by this method and the residual initiator concentration, a relatively low proportion of low polymerization degree polymer within this range is produced in the first reactor. If the average residence time in the first reactor is relatively short relative to the initiator half-life, the number of reactors may be increased to sufficiently reduce the residual initiator concentration in the final syrup. At this time, the average degree of polymerization of the polymer produced in each reactor increases rapidly as it progresses to subsequent reactors, as in the case of continuous tubular reactors, and the average degree of polymerization in the final syrup increases. The polymer contains a large amount of a portion with a high degree of polymerization, resulting in a wide distribution of degree of polymerization and a disadvantage that the viscosity becomes high in proportion to the polymer content. on the other hand,
Within this range, a high percentage of low polymerization degree polymer is produced in the first reactor when the reaction time in the first reactor is sufficiently long compared to the half-life of the initiator; Although the initiator concentration can be reduced relatively easily by using two or more reactors, the residual initiator concentration in the first and second reactors is extremely different, resulting in a high degree of polymerization. The weight average degree of polymerization of the portion takes a very large value, more than twice the weight average degree of polymerization of the low polymerization degree portion. Therefore, even though the content of the high degree of polymerization portion is small, the distribution of the degree of polymerization of the polymer in the resulting syrup is relatively wide. In other words, even in this method, if the residual initiator concentration is sufficiently reduced, the polymerization degree distribution ends up becoming broader, which is still unsatisfactory from the point of view of shortening the plate-making time without degrading the quality of the resulting resin plate. It's hard to say it's something that should be done. In addition, Japanese Patent Publication No. 48-35357 uses a reactor in which at least one continuous stirred tank type reactor is arranged in series in the first stage and a tubular reactor in the second stage, so that the reaction mixture at the outlet of the first stage is conversion rate of 9-12%
A method for continuously producing a prepolymerized product of a methacrylic acid ester compound is described.

This method is related to the removal of the amount of heat generated during continuous production in a tank reactor, and due to the conditions for stably controlling the exothermic reaction, the conversion rate in one tank is at most 2. They found that it was only 5%, and as a method to obtain a prepolymer with a higher conversion rate, they used multiple tank reactors arranged in series and further changed the quality by combining them with a tubular reactor. The main purpose of this system is to make it easy to adjust the production amount without causing any problems, and to prevent clogging in the tubes, which is a drawback of tubular reactors. In this method, the conversion rate in the tank-type reactor in the first stage is within the range of 9 to 12% in order to stably control the reaction, so it is suitable for shortening the manufacturing time of resin plates. It has drawbacks that make it impossible to achieve the purpose of producing white whelk.

Furthermore, since the polymerization is carried out at a temperature of 50 to 100°C, the concentration of residual initiator in the resulting syrup remains at a relatively high level. From this point of view, it is difficult to say that this method is satisfactory.
The inventors of the present invention conducted intensive studies on methods to overcome these drawbacks, and found that a syrup produced by continuously supplying a methyl methacrylate monomer and a radical polymerization initiator to a reaction zone and partially polymerizing it was developed. In a method for continuous production of syrup, which can be taken out from A polymer with a narrow degree of polymerization distribution is produced by specifying the residence time conditions, and a tubular reactor is arranged in series in the latter stage to control the temperature of the reactor.
The present invention was completed based on the discovery that by specifying the conditions of the average residence time, the degree of polymerization distribution can be kept narrow and the residual initiator concentration can be extremely effectively reduced. That is, in the present invention, a methyl methacrylate monomer and a radical polymerization initiator are continuously supplied to a first reaction zone consisting of one reaction zone where substantially complete mixing is achieved, and residual initiator in the reaction zone is The agent concentration is 1/2 to 1/1000 times the supply starting concentration, preferably 1/5 to 1/5.
1/1000 times the amount, particularly preferably 1/10 to 1/50
Conditions in the reaction zone are maintained to yield the majority of the polymer in the final syrup, and the resulting reaction mixture is then substantially extruded into a second reaction zone where flow is achieved. and maintaining temperature and average residence time conditions in the reaction zone such that a residual amount of polymer is produced during passage through the reaction zone and the residual initiator concentration is substantially negligible. A syrup whose polydispersity of the polymerization degree distribution expressed as the ratio of the weight average degree of polymerization to the number average degree of polymerization of the final syrup is 3.0 or less, preferably 2.5 or less, particularly preferably 2.2 or less. This is a continuous production method for methyl methacrylate syrup.

As the methyl methacrylate monomer used in the production of syrup according to the method of the present invention, monomers or monomer mixtures normally used in the production of this type of syrup can be used as they are, but methyl methacrylate is the main component. Particularly preferred are monomers such as methyl methacrylate used alone, or alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, etc. within a range of 20% by weight or less based on the total amount of the monomer mixture; Alkyl methacrylates such as ethyl methacrylate and lauryl methacrylate; unsaturated nitrites such as acrylonitrile and methacrylonitrile;
A methyl methacrylate monomer mixture whose main constituent is a methyl methacrylate monomer containing one or more vinyl compounds such as styrene and α-methylstyrene is used.

These unsaturated vinyl compounds are generally used in amounts within this range for various quality improvements within the range that does not impair the characteristics of the resulting resin board as a methyl methacrylate resin board. The radical polymerization initiator used for producing white whelk according to the method of the present invention includes temperatures of 90 to 200°C,
Preferably, an initiator that generates radicals relatively rapidly at 110 to 180°C is used, and a radical polymerization initiator whose half-life is 5 seconds or less at a temperature of 180°C or lower, preferably 140°C or lower is suitable, for example, Azo compounds such as azobisisobutyronitrile, azobisdimethylvaleronitrile, azobiscyclohexanenitrile, benzoyl peroxide, lauroyl peroxide, acetyl peroxide, caprylic peroxide, 2,4-
Dichlorobenzoyl peroxide, isobutyl peroxide, acetylcyclohexylsulfonyl peroxide, tert-butyl peroxypivalate, tert-butyl peroxy-2-ethylhexanoenite, isopropyl peroxydicarbonate, isobutyl peroxydicarbonate, Secondary butyl peroxydicarbonate, normal butyl peroxydicarbonate, 2-ethylhexyl oxydicarbonate, bis(4-tert-butylcyclohexyl)
Examples include peroxides such as peroxydicarbonate, and one or more of these polymerization initiators are used.

In particular, when using a polymerization initiator whose half-life is 5 seconds or less and whose temperature is 140°C or lower, the reaction temperature is preferably carried out at a low temperature of 90 to 160°C, and the preheating of the monomers and the cooling of the syrup are preferably carried out. This is preferable because not only the load is reduced but also the pressure conditions are relaxed. The amount of polymerization initiator is usually 0.001 to 1% by weight, preferably 0.001 to 1% by weight based on the methyl methacrylate monomer.
．． When a high polymer content of 0.01 to 0.5% by weight is desired, the concentration of the initiator fed is adjusted to be high, and when a high number average degree of polymerization is desired, the concentration of the fed initiator is adjusted to be low.

Although the monomer and the polymerization initiator may be mixed in advance and supplied after being preheated, it is preferable that only the monomer is preheated and the polymerization initiator solution is supplied after being cooled.

The supplied methyl methacrylate monomer or polymerization initiator solution may optionally be pre-added with one or more of ultraviolet absorbers, antioxidants, pigments, dyes, and other additives used in the production of resin plates. It's okay. In the production of syrup according to the method of the present invention, without using a chain transfer agent, by mutually adjusting the reaction temperature, the concentration of the initiator fed, and the average residence time of the reaction mixture, the number average degree of polymerization of the syrup produced by the syrup Chain transfer agents are not normally used because they have the advantage of allowing the weight average degree of polymerization or viscosity to be easily adjusted to a desired value, but chain transfer agents may be used within a range that does not reduce the quality of the resulting resin plate. .

In the present invention, the methyl methacrylate monomer and the radical polymerization initiator are first continuously supplied to the first reaction zone where substantially complete mixing is achieved.

The reaction temperature in the reaction zone is adjusted according to the decomposition temperature of the initiator so that the ratio of the concentration of the residual initiator to the concentration of the supplied initiator falls within the above range, and is usually 90 to 200°C, preferably 110 to 180°C. . The average residence time of the reaction mixture in the reaction zone is adjusted depending on the desired polymer content and number average degree of polymerization in the final syrup, as well as the feed initiator concentration, but is usually from 1 to 30 minutes, preferably. is 2~
It is 15 minutes. To maintain the temperature conditions of a tank reactor, a jacket is usually provided outside the reactor and a heat medium is circulated through the jacket to control the temperature of the heat medium, but the method of the present invention Because the reaction rate is extremely fast, it is difficult to maintain the reaction temperature at the desired conditions with this method, and it becomes thermally unstable, especially when scaled up, making stable steady operation impossible. becomes.

In the method of the present invention, the amount of heat generated by polymerization and the amount of sensible heat required to raise the temperature of the reaction mixture to the reaction temperature are approximately the same, and the amount of heat generated by polymerization is approximately the same as the amount of sensible heat required to raise the temperature of the reaction mixture to the reaction temperature. is heated or cooled to maintain the reaction temperature, and the temperature of the first reaction zone is preferably controlled by changing the preheating temperature of the monomers supplied to the reaction zone. It is more effective to use a method in which a jacket is provided outside the reaction zone to circulate the heat medium. The supplied monomer may be preheated by any method as long as there is no substantial stagnation and the preheating temperature can be adjusted. This is suitably carried out by passing the monomer at a rate of several 5,000 or more, preferably 20,000 or more, circulating a heat medium through the jacket, and adjusting the temperature of the heat medium. In the first reaction zone, the monomers and polymerization initiator supplied must be rapidly mixed into the reaction mixture to maintain substantially uniform concentration and temperature, but substantially complete mixing is required. Any reaction device and stirring method may be used as long as the method achieves this, and the stirring Reynolds number is 2000 or more, preferably 50.
00 or more is preferably used, for example a continuous stirred tank reactor equipped with a ribbon stirrer is used for this purpose. The amount of polymer produced in the first reaction zone and the number average degree of polymerization are determined by the type and concentration of the feed initiator in the reaction zone, the reaction temperature and the average residence time of the reaction mixture; Depending on the polymer content, number average degree of polymerization or viscosity, the preferred feed initiator concentration, reaction temperature and average residence time of the reaction mixture are selected.

The residual initiator concentration in the first reaction zone is 1/2 to 1/1000 times, preferably 1/5 to 1/1000 times, particularly preferably 1/1/2 to 1/1000 times the concentration of initiator fed to this reaction zone.
The conditions of reaction temperature and zero average residence time of the reaction mixture are maintained so that the volume is 10 to 1/500 times larger. When the proportion of the residual initiator concentration within this range is small, steady operation can be carried out particularly stably. At the same time, it is possible to achieve a particularly narrow distribution of the degree of polymerization of the polymer in the final syrup and a particularly low residual initiator concentration. When the residual initiator concentration in the first reaction zone is greater than this range, the reaction zone tends to become thermally unstable, and in order to perform stable steady operation, it is necessary to reduce the amount of polymer produced in the reaction zone. The amount needs to be kept very low, making it impossible to obtain a final syrup with a high polymer content and resulting in a high residual starting concentration in the final syrup.

In order to sufficiently reduce this residual initiator concentration, it is necessary to increase the average residence time in the second reaction zone.
During this time, a large amount of high polymerization degree polymer is generated, which is not a good idea as it tends to result in a wide distribution of polymerization degree of the polymer at the final stage. On the other hand, if the residual initiator concentration is below this range, the supplied initiator will decompose in a non-uniform state before being sufficiently mixed into the reaction mixture in the reaction zone, making it impossible to achieve substantially complete mixing. As a result, the resulting polymer itself already has a wide polymerization degree distribution, which is not a good idea. In order to achieve a narrow polymerization degree distribution of the polymer in the final syrup and a small residual initiator concentration, a narrow polymerization of the polymer supplied from the first reaction zone is required in the second reaction zone. It is necessary to maintain the conditions of the residual initiator concentration exiting the first reaction zone as described above so that the concentration distribution can be maintained and the residual initiator concentration can be effectively reduced.

When the above-mentioned conditions regarding the residual initiator concentration in the first reaction zone are achieved, the proportion of polymer formed in the reaction zone in the final syrup is usually between 60 and 60%.
99.5% by weight, preferably 90-99.5% by weight, particularly preferably 95-99.5% by weight. The reaction mixture leaving the first reaction zone is then conducted to a second reaction zone where a substantially extrusion flow is achieved, and during passage through said reaction zone residual amounts of polymer are formed and residual Initiator concentration is reduced.

Since the reaction mixture introduced into the reaction zone can no longer be supplied with polymerization initiator while passing through the reaction zone, substantially complete mixing with constant supply of polymerization initiator is achieved. In contrast to the case in the second reaction zone, the residual initiation degree can be very easily reduced in the second reaction zone, and since the amount of polymer produced during this period is small, a relatively high degree of polymerization can be achieved. Despite the formation of polymer, the degree of polymerization distribution of the polymer in the final syrup remains surprisingly small. The temperature of the reaction zone may be a temperature at which the residual initiator decomposes sufficiently rapidly, and is usually selected to have a half-life of 20 seconds or less, preferably 5 seconds or less. Preferably, the temperature is no lower than that, and in particular conditions are maintained such that the temperature of the reaction mixture increases substantially adiabatically during passage through the reaction zone, such as due to the heat of polymerization. Since the vapor pressure of the reaction mixture in both the first and second reaction zones is usually higher than atmospheric pressure, it is easy to control the residence time, temperature, etc. in both reaction zones, and therefore the polymer content in the final reactor, In order to maintain substantially constant quality such as viscosity and residual initiator concentration, it is desirable to apply a pressure equal to or higher than the vapor pressure so that the reaction mixture maintains a substantially liquid phase, usually from 1 to 20 atm, preferably. It is pressurized to 2 to 10 atmospheres.

The average residence time of the reaction mixture in the second reaction zone is 0.05 to 5 times the average residence time in the first reaction zone;
Preferably, 0.1 to 2 times is selected.

The average residence time only needs to be long enough so that the residual initiator concentration is essentially negligible; even if the average residence time is too long, the residual initiator concentration is no longer present in an essentially negligible amount, so that polymerization will not occur. There is no problem since the reaction progresses only thermally very slowly and therefore the increase in polymer content and viscosity is virtually negligible, but making it unnecessarily long would require a large reaction zone. There is no point in doing so.
Since the reaction mixture supplied to the second reaction zone does not have any newly supplied components, it essentially requires no mixing in terms of concentration, and also in terms of temperature. Since the amount is small, runaway will not occur even if the reaction is carried out adiabatically and it can be easily controlled. Therefore, any reaction device and stirring method may be used as long as it achieves substantially extrusion flow, but stirring is not recommended. If this is not done at all, the polymer will adhere to the reactor wall, making it difficult to achieve a substantial extrusion flow, and if it progresses further, it will cause blockage. Stirring with a Reynolds number of 2000 or more using a stirrer designed so that the coefficient is 0.2 or less, preferably 0.1 or less,
Preferably, a method of stirring at 5,000 or more, or a method of stirring using a self-wiping type stirrer with a back mixing coefficient of 0.2 or less, preferably 0.1 or less, is preferably used, such as a twin-screw one-type extruder. A tubular reactor with a similar construction is used for this purpose. Mixing that occurs in the flow direction of the fluid is called back-mixing, and the back-mixing coefficient here refers to the degree to which the flow state of the reaction fluid in the tubular reactor differs from the ideal extrusion flow. M
It is expressed as 1/M, and the smaller this value is, the closer it is to the ideal extrusion flow. The modified Péclet number M applied in the present invention is based on the M-UL/2E formula on the bottom line of page 91 of Kagaku Special Issue 36, "Reaction Engineering," published by Kagaku Doujin, October 20, 1968. Although the reaction zone may be provided with an external jacket to control the temperature with a heat medium, it is preferable to maintain the reaction zone under substantially adiabatic conditions because the residual initiator is more rapidly reduced. The residual initiator concentration in the reaction mixture passing through the second reaction zone is 1 ppm.
a substantially negligible amount of less than or equal to 0.1 ppm, preferably 0.1 ppm
The concentration of the residual initiator is particularly preferably 0.01 ppm or less, and since the concentration of the residual initiator rapidly decreases from the inlet to the outlet of the reaction zone, correspondingly, the concentration of the remaining initiator is 0.01 ppm or less. The number average degree of polymerization of the reaction zone increases rapidly from the inlet to the outlet, while its production amount rapidly decreases from the inlet to the outlet of the reaction zone, so the amount of polymer produced in the reaction zone is unexpected. also has a number average degree of polymerization that is not so large compared to the number average degree of polymerization of the polymer produced in the previous reaction zone,
It has been achieved to reduce the residual initiator concentration in the final syrup to a virtually negligible amount, while at the same time maintaining a very narrow degree of polymerization distribution of the polymer in the syrup, with the weight average degree of polymerization of the polymer The polydispersity of the degree of polymerization distribution expressed as a ratio of number average degrees of polymerization is 3 or less, preferably 2.5 or less, particularly preferably 2.2 or less.

The polymer content in the syrup produced by the method of the present invention is 5 to 40% by weight, preferably 10 to 30% by weight, and when it is lower than this range, the effect of shortening the board making time is relatively small; If the concentration is higher than this range, the polymerization rate will be accelerated due to the Tromsdorff effect, resulting in instability in terms of concentration, making stable steady operation impossible, and neither is a good idea.

On the other hand, the viscosity of syrup at 25°C is 0.5 to 500.
poise, preferably 1 to 100 poise; if it is lower than this range, it will cause liquid leakage during injection during the production of resin plates, and if it is higher than this range, the concentration will become unstable. Stable steady operation is not possible, and neither is a good idea. Particularly within this range, the polymer content is between 20 and 4.
The 0% by weight syrup remains the obtained syrup and has suitable workability for injection etc. during the production of resin boards, and can significantly increase the board manufacturing time without degrading the quality of the resulting resin board. This shortening makes it particularly suitable for use in continuous board manufacturing processes. The number average degree of polymerization of the polymers in the syrup is selected to be between 300 and 6000, especially for syrups with a high polymer content suitable for use in continuous plate making processes.
The number average degree of polymerization is selected from 0 to 2000, but it is preferable to select a number average degree of polymerization as high as possible within a range where the viscosity is not too high relative to the desired polymer content in order to improve the quality of the resulting resin plate. Even when the final syrup obtained by the above method is left under the same temperature conditions, there is almost no increase in polymer content or viscosity, but until the final syrup is used for manufacturing resin plates, During this period, the syrup should be stored to minimize deterioration, and the polymer content should be controlled during operations such as adding polymerization initiators and other additives during the production of resin plates, and pouring the syrup. It is cooled to an appropriate temperature, usually 100° C. or lower, preferably 80° C. or lower, so as not to cause an increase in viscosity that would reduce workability or deteriorate the quality of the resulting resin plate.

The syrup obtained by the process of the present invention has a residual initiator concentration in a substantially negligible amount of less than 1 ppm, preferably 0.
．． Since it is 1 ppm or less, particularly preferably 0.01 ppm or less, the increase in polymer content and viscosity after leaving the second reaction zone is negligible even without rapid cooling, and a constant quality can be achieved. It has the advantage of being easy to obtain, and no increase in polymer content or viscosity is observed during storage, and furthermore, the residual monomer content in the resin plate obtained due to deterioration of the syrup during storage increases. It has excellent storage stability, with no deterioration in quality such as easy foaming or foaming during hot molding of the resin plate.

Further, the polymerization degree distribution of the polymer in the syrup obtained by the method of the present invention is extremely narrow, and the polydispersity of the polymerization degree distribution expressed as the ratio of the weight average degree of polymerization to the number average degree of polymerization is 3 or less, preferably 2. 5 or less, particularly preferably 2.2 or less, the number average degree of polymerization, which affects the average degree of polymerization of the resin plate, should be relatively high, and the weight average degree of polymerization, which affects the viscosity of the syrup, should be selected to be relatively low. As a result, a syrup with a relatively low viscosity and a high polymer content can be obtained, which has the extremely favorable advantage of shortening the board making time without degrading the quality of the resin board. In addition, when polymerizing using this syrup under conditions that do not shorten the board-making time,
It also has the advantage that the average degree of polymerization of the resin plate can be improved and a resin plate of particularly excellent quality can be obtained. Furthermore, it is also possible to shorten the board making time by increasing the concentration of the polymerization initiator used when manufacturing resin boards using the syrup with a relatively low polymer content obtained by the method of the present invention. This case also has the advantage that the quality of the resin plate obtained is relatively small. The syrup produced by the method of the present invention may be used as a syrup having the same polymer content and viscosity as obtained in the production of resin plates, but the syrup with a polymer content of 15 to 5
0% by weight, preferably 20-40% by weight, and 25% by weight.
It may be concentrated or diluted with a monomer or similar syrup so that the viscosity at °C reaches a desired value in the range of 0.5 to 1000 poise, preferably 5 to 500 poise, Depending on the case, this can be used to advantageously improve the homogeneity or productivity of the syrup used in the production of resin plates.

Since the syrup produced by the method of the present invention has a high polymer content, low viscosity, and good storage stability, its use is not limited to the production of resin boards. It is suitably used in the production of molding materials, adhesives, paints, resin concrete compositions, and other applications in which syrups of this type are generally used. EXAMPLES Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Note that % in the examples is % by weight. In addition, the viscosity of the syrup in the examples was measured at 25°C using a B-type viscometer, and the number average degree of polymerization and polydispersity of the polymerization degree distribution of the polymer in the syrup were measured using polystyrene gel as a filler and tetrahydrofuran. The measurement was carried out by gel permeation chromatography using as an eluent. In addition, for polymerization foaming of resin plates, the presence or absence of bubbles is determined by visually observing the obtained resin plate, and for heat foaming, the obtained resin plate is placed in a circulating hot air oven for 30 minutes at 180°C.
After heating for a minute, the presence or absence of bubbles was determined by visual observation.

The reduced viscosity was determined by measuring a 0.1% chloroform solution of the obtained resin plate at 25°C, and the residual monomer concentration was measured by dissolving the obtained resin plate in methylene chloride and using gas chromatography. .

Example 1 A stirred tank reactor with a ribbon-shaped stirring blade installed in the front stage, a stirring shaft in the rear stage, and a pin installed on the stirring shaft in a direction perpendicular to the shaft and facing the axis perpendicular to the tube wall. A two-stage continuous reaction apparatus was used, which consisted of an array of fixed pins and tubular reactors arranged so as to wipe each other.

The volume ratio of the tank reactor to the tube reactor was 1:0.25. 0 of azobisisobutyronitrile, a polymerization initiator
．． Methyl methacrylate monomer containing 0.47% was continuously fed so that the average residence time in the tank reactor was 147 seconds, the temperature of each reactor was 160 ° C., and the pressure of each reactor was 6.0 atm. Maintained. The feed liquid was preheated to about 80° C. using a single tube with a jacket. The polymer content of the syrup leaving the tubular reactor was 26.6%, the viscosity at 25°C was 21.0 poise, and 95% of the total polymer was produced in the tank reactor.

Further, the concentration of the residual initiator in the tank reactor was 1/32 times the concentration of the supplied initiator. The residual initiator concentration in the final syrup was 0.01 ppm or less, and no change was observed in the polymer content or viscosity even after standing and heating at 60° C. for 5 hours. The number average degree of polymerization of the polymer in the syrup is 745, and the polydispersity of the polymerization degree distribution expressed as the ratio of the weight average degree of polymerization to the number average degree of polymerization is 2.17. The degree of polymerization and the polymer content of the syrup were high and the viscosity was low. This syrup was added with 0.0 azobisdimethylvaleronitrile as a polymerization initiator.
5% was dissolved to obtain a polymerizable liquid composition, which was degassed under reduced pressure, and then polymerization was completed using a known continuous polymerization apparatus to produce a resin board. Width 500mm, thickness 0.6m1L
The first 674 of the polymerization zone with a horizontal distance of 10,000 m 1L was
0m7! ! 217011 was a heating polymerization zone heated with 85° C. hot water, the next 217011 was a heat treatment zone heated with 120° C. hot air, and the last 1090 mm was a cooling zone that could be cooled with cold air. The interval between the upper and lower bands was adjusted to obtain a resin plate with a thickness of 3 mm, and the above polymerizable composition was continuously supplied between the bands, and the band was moved so that the composition passed through the heated polymerization zone in 18 minutes. The band was driven at a speed of 374 mm/min. This product had a reduced viscosity of 2.37 d1/7, a residual monomer concentration of 0.8%, and had a good appearance with no polymerization foaming or thermal foaming observed. Comparative Example 1 Except for using a one-stage continuous reaction apparatus consisting of only the stirred tank reactor in the first stage of Example 1, the type and concentration of the polymerization initiator, average residence time in the tank reactor, temperature, pressure, etc. The reaction was carried out under exactly the same conditions as in Example 1 to obtain a syrup having a polymer content of 25.0% and a viscosity of 10.3 poise.

The number average degree of polymerization of the polymer in the syrup was 725, and the polydispersity of the degree of polymerization distribution was 2.02, but the residual initiator concentration was as large as 15.2 ppm, and when heated at 60°C, polymerization did not occur. The process progressed rapidly and lost no fluidity within one hour, making it impossible to withstand long-term storage. 0.04% of azobisdimethylvaleronitrile was added to this syrup, and the polymerization was completed using the continuous polymerization apparatus of Example 1 under the same conditions as in Example 1, except that the syrup was passed through the heated polymerization zone for 24 minutes. A resin plate was obtained.

The reduced viscosity of this product was 2.69 d1/7, and no polymerization foaming occurred, but the residual monomer concentration was as high as 4.2%, and thermal foaming occurred. When polymerization was carried out under the same conditions as above except that the resin was passed through the heating polymerization zone for 21 minutes, significant polymerization and foaming occurred, and the resulting resin plate had no value as a commercial product. Also, this syrup? When 0.05% azobisdimethylvaleronitrile was added and the mixture was passed through the heating polymerization zone for 21 minutes, no polymerization foaming occurred, but the heating foaming was significant. Comparative Example 2 Two stirred tank reactors equipped with ribbon-shaped stirring blades were arranged in series, and the volume ratio of the first and second stage reactors was 0.25.
A two-stage continuous reactor was used, and the average residence time in the first stage reactor was 14.
7 seconds, and the temperature of each reactor was 16
The pressure in each reactor was maintained at 0° C. and 6.0 atm.

The polymer content of the syrup leaving the second reactor is 28.3
%, the viscosity was 80.9 poise, and 88% of the total polymer was produced in the first reactor. The residual initiator concentration in the syrup was 2.53 ppm, and when it was left to stand and heated at 60° C. for 3 hours, the polymer content increased to 28.7% and the viscosity increased to 780 poise. The number average degree of polymerization of the polymer in the syrup is 795, and the polydispersity of the degree of polymerization distribution is 2.
It was 55. 0.04% of azobisdimethylvaleronitrile was added to this syrup, and the polymerization was completed using the continuous polymerization apparatus of Example 1 under the same conditions as Example 1, except that the syrup was passed through the heated polymerization zone for 20 minutes. A resin plate was obtained.

The reduced viscosity of this product was 2.65 d1/V, and no polymerization foaming occurred, but the residual monomer concentration was as high as 2.7%, and thermal foaming occurred. On the other hand, 0.05% of azobisdimethylvaleronitrile was added to a syrup with a polymer content of 24.3% obtained by diluting this syrup with a monomer until it had the same viscosity as in Example 1, 21.0 poise. and heat polymerization zone 2.
Polymerization was completed under the same conditions as above except that the polymer was passed for 2 minutes, and the reduced viscosity of the product was 2.53 d1/7, the residual monomer concentration was 2.3%, and no polymerization foaming occurred. However, heating and foaming occurred. Comparative Example 3 Using the same reactor as Comparative Example 2 except that the volume ratio of the first and second stage reactors was 1:2, a reaction was carried out under exactly the same conditions as Comparative Example 2. Combined content rate is 31.4%
A syrup with a viscosity of 1100 poise was obtained.

80% of the polymer in the syrup was produced in the first reactor. Residual initiator concentration in syrup is 0.23 ppm
When the mixture was heated at 60° C. for 3 hours, the polymer content increased to 31.6% and the viscosity increased to 2500 poise. In addition, the number average degree of polymerization of the polymer in the syrup is 87.
0, and the polydispersity of the polymerization degree distribution was 3.32. 0.04% of azobisdimethylvaleronitrile was added to this syrup, and the polymerization was completed using the continuous polymerization apparatus of Example 1 under the same conditions as Example 1, except that the syrup was passed through the heated polymerization zone for 17 minutes. A resin plate was obtained. The high viscosity of this syrup made it difficult to inject between the moving bands, and the product exhibited polymeric foaming. In addition, this syrup was used in Example 1.
Add 0.05% of azobisdimethylvaleronitrile to a syrup with a polymer content of 21.5% obtained by diluting with a monomer until the viscosity is the same as that of 21.0 poise, and heat the polymerization section for 25 minutes. When the polymerization was completed under the same conditions as above except that the product was passed through, the reduced viscosity of the product was 2.74 dj/7, the residual monomer concentration was 1.9%, and no polymerization foaming occurred. Heat foaming occurred.

In addition, when 0.08% of azobisdimethylvaleronitrile was added to the same diluted syrup and the polymerization was completed under the same conditions as above except that it passed through the heating polymerization zone for 21 minutes, the reduced viscosity of the product was At 2.17 dj/t, the residual monomer concentration was 1.7%, and no polymerization foaming occurred.
Significant heat foaming occurred. Comparative Example 4 The single-stage continuous reaction apparatus of Comparative Example 1 was used.

Methyl methacrylate monomer containing 0.45% azopisisobutyronitrile is continuously fed so that the average residence time is 14.6 minutes, and the target pressure in the reactor is normal pressure and the temperature is 85°C. And so. Further, the concentration of the residual initiator at the outlet of the reaction tank was about 90/100 times the concentration of the supplied initiator. At first, a syrup with a polymer content of about 25% and a viscosity of about 12 poise was obtained, but it was difficult to maintain a constant reaction temperature, and after about an hour the syrup reached a boiling point, causing the polymerization reaction to run out of control. The material solidified and it was impossible to continue the reaction. Example 2 The volumes of both the tank type reactor and the tube type reactor are 5f! The same apparatus as in Example 1 was used except for the following.

Polymerization initiator azobisisobutyronitrile at 20℃
As a 0.7% ethyl acrylate monomer solution of 0.2
The methyl methacrylate monomer was preheated to 120°C and was continuously fed to the reactor at a rate of 1.91/min, and the temperature of each reactor was 160
℃, and the pressure in each reactor was maintained at 6.0 atm. In addition, the concentration of residual initiator in a tank reactor is 1/1/1 of the concentration of supplied initiator.
It was 32 times the amount. The syrup leaving the tubular reactor had a polymer content of 31.9%, a viscosity at 25° C. of 45.9 poise, and a residual initiator concentration of less than 0.01 ppm.

The number average degree of polymerization of the polymer in the syrup was 615, and the polydispersity of the degree of polymerization distribution was 2.18. Examples 3 to 14 The same apparatus as in Example 1 was used except that the volume ratio of the tank reactor and the tubular reactor was set to the values shown in Table 1.

Using various radical polymerization initiators in different amounts as polymerization initiators and using methyl methacrylate monomer as a monomer, the reactions were carried out at various temperatures and average residence times to produce the polymers shown in Table 1. A syrup with coalesced content, viscosity and number average degree of polymerization was obtained. Further, the ratio of the concentration of the residual initiator to the concentration of the supplied initiator in the tank reactor was the value shown in Table 1. In all cases, the residual initiator concentration in the syrup was 0.01 ppm or less, and the polydispersity of the polymerization degree distribution of the polymer in the syrup was 2.2 or less. Example 15 Polymer content 25.5% obtained in exactly the same manner as Example 3
, the polymer content obtained by diluting syrup with a viscosity of 70.0 poise with methyl methacrylate monomer was 14.3%,
A polymerizable liquid composition is prepared by dissolving 0.1% of azobisisobutyronitrile in syrup having a viscosity of 1.1 poise, and after degassing under reduced pressure, a resin plate with a thickness of 3' is obtained. The mixture was injected into the space between two glass plates sealed with a gasket with a certain distance maintained, and heated at 65°C for 4 hours to polymerize, and then heated at 120°C for 2 hours to complete the polymerization. A resin plate was obtained.

Claims (1)

[Claims] 1. A monomer mainly composed of methyl methacrylate and a radical polymerization initiator are continuously supplied to a first reaction zone consisting of one reaction zone where substantially complete mixing is achieved. , the residual initiator concentration in the reaction zone is 1 of the feed initiator concentration.
/2 to 1/1000 times the amount by maintaining the conditions in the reaction zone to produce the majority of the polymer in the final syrup;
The resulting reaction mixture is then directed to a second reaction zone where a substantially extrusion flow is achieved such that a residual amount of polymer is produced during passage through the reaction zone and a residual initiator concentration is substantially negligible. The temperature and average residence time of the reaction zone are maintained so that the polydispersity of the polymerization degree distribution expressed as the ratio of the weight average degree of polymerization to the number average degree of polymerization of the polymer in the final syrup is 3. A method for continuously producing methyl methacrylate syrup, characterized in that a syrup having a concentration of .0 or less is obtained. 2. The method according to claim 1, which uses a radical polymerization initiator whose temperature at which its half-life is 5 seconds or less is 180° C. or less. 3 Stirring Reynolds number in the first reaction zone is 200
The method according to claim 1, wherein the number is 0 or more. 4. The process according to claim 1, wherein the proportion of the polymer produced in the first reaction zone in the final syrup is from 60 to 99.5% by weight. 5. Claims in which the concentration of the residual initiator in the first reaction zone is 1/5 to 1/1000 times the concentration of the supplied initiator, and the polydispersity of the degree of polymerization distribution in the final syrup is 2.5 or less. The method described in paragraph 1. 6. Claims in which the concentration of the residual initiator in the first reaction zone is 1/10 to 1/500 times the concentration of the supplied initiator, and the polydispersity of the degree of polymerization distribution in the final syrup is 2.2 or less. The method described in paragraph 1. 7. The method of claim 1, wherein the temperature of the second reaction zone is no lower than the temperature of the first reaction zone. 8. The method of claim 1, wherein the average residence time of the reaction mixture in the second reaction zone is 0.1 to 2 times the average residence time in the first reaction zone. 9. The method according to claim 1, which uses a stirring method in which the back mixing coefficient is 0.2 or less in the second reaction zone. 10. The method of claim 1, wherein the residual initiator concentration in the final syrup is 1 ppm or less. 11 Residual initiator concentration in final syrup is 0.01pp
2. The method according to claim 1, wherein: m or less. 12 Polymer content in the final syrup is 5-40% by weight
The method according to claim 1, wherein the viscosity at 25° C. is 0.5 to 500 poise. 13. The method of claim 1, wherein the final syrup has a polymer content of 10 to 30% by weight and a viscosity of 1 to 100 poise at 25°C.