JP2000309601A - Production of methyl methacrylate syrup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for stably producing a methyl methacrylate syrup. SOLUTION: This method for producing a methyl methacrylate syrup is (1) to perform the warm-up of 20-70 wt.% of the total quantity of raw materials principally comprising methyl methacrylate, (2) to add the total quantity of a chain transfer agent after temperature rise up to reaction temperature, (3) to add the rest of the raw materials together with a polymerization initiator having a half-life of 10-300 seconds at the reaction temperature while spending 0.1 to 5 h., (4) to continue to additionally heat for 0.01 to 5 h. after the end of the addition and (5) to add a hindered phenol-based polymerization inhibitor after the end of the heating.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a methyl methacrylate syrup comprising a monomer having methyl methacrylate as a main component and a polymer obtained by polymerizing a monomer having methyl methacrylate as a main component. And a method for producing the same.

[0001]

2. Description of the Related Art Methyl methacrylate syrup is a methacrylic resin casting plate, an optical material such as an optical transmission fiber or an optical waveguide,
It has been conventionally used as an intermediate raw material for acrylic artificial marble, artificial stamping materials, flooring materials, adhesives, adhesives, restoration materials such as cultural properties and stuffed goods, and medical materials.

Among them, a method for producing a syrup containing methyl methacrylate as a main component is disclosed in JP-B-36-3392.
JP-B-40-3701, JP-B-46-40693
JP, JP-B-53-2189, JP-A-55-4
A number of applications have been filed, such as Japanese Patent No. 3111 and Japanese Patent Laid-Open No. 9-255714. Also, JP-A-49-10493
7, Japanese Patent Publication No. 1-11652, Japanese Patent Application Laid-Open No. 9-6
No. 7,495, JP-A-9-19467 and the like describe methyl methacrylate syrup having a carboxylic acid as a polymer in the syrup.

[0003] Methods for producing methyl methacrylate syrup are roughly classified into two. One is a method disclosed in Japanese Examined Patent Publication No. Hei 11-16652, in which a monomer is partially bulk-polymerized, and is also called a partial polymerization method. The partial polymerization method is further divided into a batch method and a continuous method. The other is a method in which a separately prepared polymer is dissolved in a monomer.
Although it is disclosed in Japanese Patent Application Laid-Open No. 104937 and Japanese Patent Application Laid-Open No. 9-194673, the production method is basically different from that of the present invention. It is disadvantageous both economically and economically.

In polymerization methods other than bulk polymerization, that is, solution polymerization and emulsion polymerization, besides the batch method and the continuous method, for example, as described by Kuwano (Polymer Processing, 47 (3), 125, 1998), A method of dividingly adding a monomer material containing a polymerization initiator to a solvent, that is, a semi-batch method is generally used. However, in this case, a solvent for dissolving the monomer is required for solution polymerization, and a dispersion solvent and an emulsifier are required for emulsion polymerization. There is no known example of industrially producing methyl methacrylate syrup by the batch method.

As a production method by the first batch method among the partial polymerization methods, for example, Japanese Patent Publication No. 36-3392 discloses
The raw material comprising a monomer having methyl methacrylate as a main component and a chain transfer agent is heated to 80 ° C, a small amount of azobisisobutyronitrile or benzoyl peroxide is added as a polymerization initiator, and the temperature is raised to 100 ° C at the same time. It discloses a method for producing methyl methacrylate syrup by adding 27 to 50 minutes of polymerization at a temperature and then quenching by adding cold methyl methacrylate containing hydroquinone as a polymerization inhibitor when a predetermined viscosity is reached. . However, in this method, since the polymerization is stopped in a state where the polymerization initiator is not completely decomposed, the polymerization initiator remains in the obtained syrup, and the storage stability is poor even if the polymerization inhibitor is added. It will be. For example, benzoyl peroxide used as a polymerization initiator has a half-life at 100 ° C. of about 22 minutes, and when a predetermined viscosity is reached, 42 to 20% of the polymerization initiator based on the added amount is contained in the product. It remains. In addition, it is difficult to control the reaction because the amount of polymerization initiator required for the reaction is added at once, and there is no effective means other than keeping the temperature constant once the polymerization initiator is added. Therefore, stable production cannot be performed because the polymerization rate and viscosity of the product are greatly changed by the influence of the change in the viscosity. In Japanese Patent Publication No. 1-11652, SM
In producing syrup as an intermediate material of C or BMC, 89% by weight of methyl methacrylate and 5% of methacrylic acid were used.
% By weight, trimethylolpropane trimethacrylate 6
A raw material containing 0.4 part of n-dodecyl mercaptan and 0.05 part of 2,2′-azobisisobutyronitrile was charged with respect to 100 parts by weight of a monomer consisting of 100% by weight, and polymerization was carried out at 80 ° C. By the method of adding hydroquinone and p-methoxyphenol as a polymerization inhibitor when the viscosity reaches a predetermined viscosity, and quickly cooling to room temperature to inhibit polymerization, a method for producing methyl syrup methacrylate containing carboxylic acid is disclosed. I have. However, in this method, the polymerization initiator remains in the obtained syrup, and even if a polymerization inhibitor is added, the storage stability becomes poor. In addition, it is difficult to control the reaction because the amount of the polymerization initiator required for the reaction is added all at once. Once the polymerization initiator is added, there is no effective means other than keeping the temperature constant, and stable production cannot be performed because the polymerization rate and viscosity of the product change greatly due to a slight change in temperature. Also, JP-A-9-674
No. 95, in producing syrup as an intermediate material of SMC or BMC, 90 parts of methyl methacrylate,
The monomer composed of 10 parts of methacrylic acid was heated to 80 ° C.
0.05 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator and 0.8 parts of n-dodecyl mercaptan as a chain transfer agent were added to carry out polymerization. When the reaction solution reached a predetermined viscosity, methacrylic acid was added. A method for producing methyl methacrylate syrup containing a carboxylic acid in the polymer in the syrup by adding 50 parts of methyl acrylate and quenching is disclosed. However, in this method, the polymerization initiator remains in the obtained syrup, resulting in poor storage stability. In addition, it is difficult to control the reaction because the amount of the polymerization initiator required for the reaction is added all at once. Once the polymerization initiator has been added, there is no effective means other than keeping the temperature constant, and stable polymerization cannot be performed because the polymerization rate and viscosity of the product greatly change due to a slight change in temperature.

[0006] As described above, in the batch method, it is difficult to control the reaction because the amount of polymerization initiator required for the reaction is added all at once. Once the polymerization initiator has been added, there is no effective means other than keeping the temperature constant, and the polymerization rate and viscosity of the product change significantly due to slight temperature changes, so that products of stable quality can be obtained. It is hard. Moreover, the polymerization initiator remains in the obtained syrup, and even if a polymerization inhibitor is added, the storage stability becomes poor.

As a production method by the second batch method among the partial polymerization methods, for example, Japanese Patent Publication No. 40-3701 discloses
A method for continuously producing methyl methacrylate syrup by extracting a part while continuously supplying methyl methacrylate in which benzoyl peroxide 0.1% by weight is dissolved as a polymerization initiator to a reactor is disclosed. I have. However, the above-described continuous method using a complete mixing tank is not suitable for small-quantity multi-kind production for producing products suitable for various uses, even if it is suitable for large-volume small-kind production such as for continuous cast plates.

On the other hand, regarding the progress of polymerization by mercaptans, for example, Japanese Patent Publication No. 46-40693 discloses a method in which a sulfur compound having an active hydrogen such as mercaptans is used as a chain transfer agent, and 65 to 65 without adding a polymerization initiator.
A method for producing methyl methacrylate syrup by partial polymerization at 105 ° C. is disclosed. However, a large amount of a chain transfer agent is required to polymerize to a desired polymerization rate, and it is not possible to obtain methyl methacrylate syrup containing a polymer having a high molecular weight. To obtain methyl methacrylate syrup containing a high molecular weight polymer, it is necessary to react for a long time using a small amount of chain transfer agent,
It is not practical in either case.

As a method for treating the remaining unreacted mercaptan after polymerization using a mercaptan as a polymerization initiator and a chain transfer agent, for example, JP-B-53-2189
In the publication, when producing a methyl methacrylate for casting, at least 0.3 to 5 equivalents of maleic anhydride and 0.01 to 1 equivalent of an amine compound, a diaza compound or a triazole compound with respect to mercaptans are used. A method of adding one kind of basic compound at 10 to 90 ° C. is disclosed. However, in this method, the steps are complicated because the additives are added during or after cooling, and the product produced from methyl methacrylate methacrylate is not practical because the basic compound containing nitrogen causes coloring. JP-A-55-43111 discloses that a basic organic compound is added to 100 parts by weight of methyl methacrylate under the condition that unreacted acrylate remains in an amount of 0.5 wt% or more.
A method for inactivating mercaptans in methyl methacrylate syrup by adding 02 to 4.0 parts by weight is disclosed. However, even in this method, the step of adding the additives during or after cooling becomes complicated, and the product produced from methyl methacrylate methacrylate is not practical because the basic organic compound causes coloring. JP-A-9-255714 discloses a method for treating mercaptans by adding vinyl ether and / or vinyl thioether to methyl methacrylate syrup containing carboxylic acid obtained by partial polymerization in the presence of mercaptans. I have. However, in this method, the addition of an additive after the completion of the polymerization step complicates the process, and the residual vinyl ether and / or vinyl thioether is not preferable because the weather resistance of the product obtained from methyl methacrylate syrup deteriorates. Moreover, compounds in which mercaptans are added to vinyl ether and / or vinyl thioether are vulnerable to heat. Since it is decomposed, molding conditions are extremely restricted, which is not preferable.

[0010] As described above, in the method of polymerizing using mercaptans as a chain transfer agent in the presence of a polymerization initiator and then adding some additives to deactivate the remaining mercaptans, a method is used after completion of the polymerization step. The process becomes complicated due to the addition of additives, and even if the mercaptans can be inactivated, coloring or weather resistance is sacrificed and the physical properties of methyl methacrylate methacrylate are reduced, which is not practical.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional method and to obtain methacrylic acid of stable quality suitable for various uses, which cannot be obtained by the batch method or the continuous method. An object of the present invention is to provide a method for efficiently and easily producing methyl syrup.

[0012]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that methyl methacrylate methacrylate suitable for various uses and of stable quality can be efficiently and easily produced by a specific production method. The present invention has been completed.

That is, the present invention relates to a process for producing a syrup from a mixture containing a monomer containing methyl methacrylate as a main component, a polymerization initiator and a chain transfer agent, wherein (1) 90 to 100% by weight of methyl methacrylate and acrylic acid One or two or more unsaturated carboxylic acids selected from acids or methacrylic acids are heated at a temperature corresponding to 20 to 70% by weight based on the total amount of the raw material comprising 10 to 0% by weight, and (2) the temperature is raised to the reaction temperature. Thereafter, the entire amount of the chain transfer agent is added, (3) Then, the remaining raw materials are added over 0.1 to 5 hours together with a polymerization initiator having a half-life at the reaction temperature of 10 to 300 seconds,
(4) Heating is further continued for 0.01 to 5 hours after the addition is completed, and (5) Weight average molecular weight measured by GPC obtained by adding a hindered phenol polymerization inhibitor at the end of heating is 2 (2). The present invention relates to a method for producing methyl methacrylate syrup having a viscosity at 25 ° C of 10 to 20,000 mPa · s.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing methyl methacrylate syrup of the present invention will be specifically described below.

In the present invention, a part of the raw material (monomer mixture) is heated to a reaction temperature using a single reaction tank, and after reaching the reaction temperature, the entire amount of the chain transfer agent is added to the reaction solution. Then, polymerization is carried out by a semi-batch method in which the remaining raw materials and the specific polymerization initiator are continuously or dividedly added at a constant rate,
After heating for a certain period of time after the addition is completed, a specific polymerization inhibitor is added to stably produce methyl methacrylate syrup.

In the present invention, methyl methacrylate is essential as a monomer component, and acrylic acid and / or methacrylic acid can be optionally added and used.

The concentration of acrylic acid and / or methacrylic acid is 10% by weight or less based on 100% by weight of the total amount of monomers. In the method of the present invention, methyl methacrylate syrup comprising a monomer of methyl methacrylate alone and an unsaturated carboxylic acid (acrylic acid and / or methacrylic acid)
Any of the methyl methacrylate syrups containing In the case of methyl methacrylate syrup obtained from a monomer of methyl methacrylate alone, for applications that can take advantage of the excellent optical properties of poly (methyl methacrylate), such as casting plates, optical transmission fibers or optical waveguides Can be used. Methyl methacrylate syrup having an unsaturated carboxylic acid can be used for applications requiring a reaction by a carboxyl group, such as compounds for artificial marble such as BMC or SMC, adhesives, and the like. In this case, according to our knowledge, the viscosity of the obtained syrup is lower than that of the unsaturated carboxylic acid in the polymer when compared at the same molecular weight and the same polymer concentration due to the action of the carboxylic acid present as a side chain in the polymer. It increases almost exponentially with respect to the unit mole fraction. For this reason, if the concentration of the unsaturated carboxylic acid exceeds 10% by weight, the polymer content must be set low in order to obtain the same viscosity.
The original effect of producing a syrup, that is, a reduction in shrinkage when producing a final product, cannot be expected and is not practical.

In the present invention, when an unsaturated carboxylic acid is used, it is preferable to charge at least a part of the unsaturated carboxylic acid in advance, and it is more preferable to charge the entire amount in advance. By increasing the initial concentration of the unsaturated carboxylic acid relative to the initial charge, the unsaturated carboxylic acid can be efficiently copolymerized.

The polymerization initiator used in the present invention includes:
It is added at a constant rate, either continuously or divided. It is also possible to perform the addition in a state where the polymerization initiator is dissolved in the monomer to be added. In order to minimize polymerization after completion of the addition, a polymerization initiator having a half-life at a polymerization temperature of 10 to 300 seconds, preferably 15 to 120 seconds, is selected. If the half-life is less than 10 seconds, most of the initiator is decomposed before the added raw material and / or the added polymerization initiator is completely mixed, so that it is necessary to use a large amount of the polymerization initiator. It is not preferable to use a large amount of, because coloring by a polymerization initiator or impurities contained in the polymerization initiator occurs. If the half-life is longer than 300 seconds, the time required for the polymerization initiator present at the end of the addition to decompose and disappear is long, and the polymerization reaction proceeds by batch polymerization. For this reason, the polymerization rate and viscosity of the product change due to the influence of temperature change after the addition is completed, and it is difficult to obtain a product of stable quality, which is not preferable. The half-life is, for example, Nippon Oil & Fats Co., Ltd.
"Organic peroxide" material 13th edition, Atochem Yoshitomi technical data and Wako Pure Chemical Industries, Ltd. "Azo Polym"
and the like. For example, 2,2′-azobis (2,4
-Dimethylvaleronitrile), 2,2′-azobis (2,4 dimethyl-4-methoxyvaleronitrile), t
-Butyl pivalate, diisopropyl peroxydicarbonate and / or bis (4-tert-butylcyclohexyl) peroxydicarbonate are used.

The polymerization initiator may be used alone or in combination of two or more.
The desired polymerization can be performed in each polymerization reaction tank.
The amount required to obtain the rate is added. Also a polymerization initiator
Method by itself, mixed with monomer material and added
Any of the methods can be used. Meta according to the invention
The viscosity of methyl acrylate syrup depends on the conversion,
And the carboxylic acid unit fraction in the polymer.
However, in order to satisfy the required viscosity range,
2.0 × 10 ^-Four~ 3.
2 wt% is preferable, and 1.0 × 10^-3~ 1.0wt%
More preferred.

Any chain transfer agent can be used as long as it can obtain a product having a desired molecular weight without inhibiting the polymerization reaction.
Usually, mercaptans are used. In the present invention, the chain transfer agent is added to the remaining raw materials (monomer mixture) and the polymerization initiator at a predetermined time immediately before the addition is started, preferably at a predetermined time from 0 to 60 minutes after the start of the addition, More preferably, the entire amount used is added to the reaction tank at a predetermined time from 0 to 15 minutes after the start of the addition. As described above, it is known that bulk polymerization proceeds when mercaptans are used as a chain transfer agent. If the temperature is increased in a state where mercaptans are added to the raw materials to be charged first, the concentration of the polymer before the start of the addition varies due to the variation in the heating pattern, and therefore the polymerization rate of the product varies, so that stable production cannot be performed. Further, if the chain transfer agent is added while the monomer and the polymerization initiator are added, the polymerization may occur in the raw material tank due to a redox reaction between the polymerization initiator and the chain transfer agent, which is not preferable. In addition, the residual ratio of the chain transfer agent to the amount used is higher than when the chain transfer agent is added before the addition. For this reason, in order to set the required molecular weight, the amount of the chain transfer agent must be increased, which is not economical.

It is well known that polymerization of methyl methacrylate has a polymerization accelerating effect called a gel effect, and this phenomenon makes it difficult to control the reaction, especially in batch polymerization. The present invention has the following three features as compared with batch polymerization. First, the polymerization initiator is supplied separately rather than all at once, and has a half-life of 10 to 10 at the reaction temperature.
Since it is as short as 300 seconds, the radical concentration in the system can be kept extremely low throughout the addition period. This allows
Even if an abnormal acceleration phenomenon of polymerization occurs due to any cause, by stopping the addition of the raw materials, the progress of the subsequent polymerization reaction can be minimized and the polymerization can be safely performed. Second, at least a part of the polymerization heat can be removed by sensible heat by adding the raw materials containing the monomer separately instead of all at once. Third, since the half-life at the reaction temperature is as short as 10 to 300 seconds, the polymerization initiator already in an extremely low concentration is rapidly decomposed and disappears after the addition.
Because of the above three features, the control of the reaction is easy because the runaway of the polymerization reaction can be suppressed, and the production of methyl methacrylate methacrylate can be performed safely and under stable conditions.

In the present invention, the polymerization temperature is usually atmospheric pressure,
The polymerization is performed at a temperature set at 95 to 110 ° C, and more preferably at the boiling point of the in-system composition. The heat of polymerization can be removed by sensible heat and latent heat of evaporation, and the sensible heat can be set large by conducting the polymerization reaction at 110 to 180 ° C. Although it is possible to remove the heat of polymerization from the jacket of the reaction tank, it is preferable to use the jacket for keeping the temperature warm because there is a possibility that the scale may adhere to the inside of the reaction tank. 180
It is possible to carry out the polymerization at a temperature of not lower than ° C, but this is not preferred because the amount of oligomers produced increases. If the temperature is lower than 80 ° C., the sensible heat and the latent heat of vaporization cannot be set large, and the viscosity in the system during the reaction becomes high, so that even if the polymerization rate is relatively low, the effect of the gel effect becomes large, which is not preferable.

In the present invention, the raw materials are roughly divided into raw materials charged from the beginning, that is, an initial charge, and remaining raw materials added later together with the polymerization initiator, that is, additional components. The weight ratio of the initial charge and the additional charge is 2
0:80 to 70:30, preferably 25:70.
75-67: 33, more preferably 30:67.
The range is 70 to 65:35. Addition is 30w
If it is less than t%, the effect of removing the heat of polymerization by the sensible heat of the added raw material is poor, and the heat generation is maximized immediately after the start of the addition having a high monomer concentration. Conversely, when the amount of addition exceeds 80% by weight, heat generation immediately after the start of the addition can be suppressed, but the amount of monomer in the system increases immediately before the end of the addition, and the heat generation becomes maximum at the end of the addition. In any case, the calorific value in the system greatly changes during the addition, and the amount of reflux greatly fluctuates during polymerization at the boiling point, and stable operation cannot be performed. Is difficult to keep constant, which is not preferable. In order to average the reflux amount throughout the addition period as much as possible with respect to the setting of the polymerization rate of 15 to 50%, it is desirable that the weight ratio of the initially charged portion and the added portion be in the range of 20:80 to 70:30.

The feed rate of the additive material is controlled so as to be substantially constant throughout the addition. The addition time is 0.1 to 5
Time, preferably 0.3 to 4 hours, more preferably 0.5 to 3 hours. If the addition time is less than 0.1 hour, a large amount of heat is generated, and the rate of increase in the amount of liquid in the reaction tank is large. On the other hand, if the time exceeds 5 hours, the process time from preparation to product removal becomes longer, which is not preferable in terms of productivity.

After the addition is completed, heating is continued for 0.01 to 5 hours, preferably 0.01 to 1 hour. The reaction time is desirably a time at which the polymerization initiator is decomposed by 99% or more. If the polymerization initiator remains, the polymerization rate and viscosity of the final product fluctuate due to the effect of cooling, and it becomes difficult not only to stably produce methyl methacrylate syrup, but also to obtain the obtained methyl methacrylate syrup. Storage stability is undesirably reduced. Although it is possible to continue heating for more than 5 hours, the process time from preparation to product removal becomes longer, which is not preferable from the viewpoint of productivity. The final polymerization rate is 15 to 50% by weight, depending on the set molecular weight and the unsaturated carboxylic acid concentration.

In the present invention, after heating is continued for a certain period of time, a polymerization inhibitor is added, and then the product is cooled and the product is taken out. By adding a polymerization inhibitor at the end of heating, it is possible to suppress the progress of polymerization by mercaptans during the cooling operation,
Further, methyl methacrylate syrup can be produced safely and under stable conditions. Even when mercaptans are used as a chain transfer agent by adding a polymerization inhibitor at the end of heating, the storage stability of methyl methacrylate syrup becomes good, and the deactivation treatment of mercaptans remaining in methacrylic syrup is achieved. No need to do.

In order to avoid coloring of the obtained syrup, it is preferable to use a hindered phenol-based polymerization inhibitor as the polymerization inhibitor. Examples of the hindered phenol polymerization inhibitor include 2,6-di-t-butyl-4-methylphenol (BHT) and 6-t-butyl-2,4-
Dimethylphenol, 4,4'-thiobis- (6-t-
Butyl-3-methylphenol) and / or 2,
2'-methylenebis- (4-methyl-6-t-butylphenol) and the like. These hindered phenol-based polymerization inhibitors can be used alone or in combination of two or more. In addition, in the presence of the hindered phenol-based polymerization inhibitor, for example, a polymerization inhibitor, such as a phosphorus-based polymerization inhibitor, is used in combination with a hindered phenol-based polymerization inhibitor, which is known to further suppress coloration. It is also possible.

The methyl methacrylate syrup obtained as described above has a weight average molecular weight measured by GPC (gel permeation chromatography) of 20,000 to 200,000 and a viscosity at 25 ° C. of 10 to 20,000 mPa · s.
s.

The resulting methyl methacrylate syrup is used as a casting plate, an optical material such as an optical transmission fiber or an optical waveguide, an acrylic artificial marble, an artificial stamping material, a flooring material, an adhesive, a pressure-sensitive adhesive, a cultural property or a restoring material such as a stuffing. It can be used as an intermediate material such as a medical material. Filler, fiber reinforcement,
Low-shrinkage agents, lubricants, plasticizers, thickeners, diluents such as organic solvents, crosslinking agents, leveling agents, defoamers, anti-settling agents, release agents, antioxidants, UV absorbers, pigments and / or Known additives such as dyes and the methyl methacrylate syrup of the present invention can be mixed and used.

[0031]

The present invention will now be described in more detail with reference to Examples, but it should not be construed that the invention is limited thereto. The polymerization rate can be determined by the gravimetric method by pouring the sample into a large amount of cold hexane and purifying the resulting precipitate.
It was dried under reduced pressure. The molecular weight of the polymer is 8 from Tosoh Corporation.
It was measured by type 010 gel permeation chromatography. The acid value was determined using a 10% solution of methylene chloride as a sample, and phenolphthalein as an indicator, 0.05 mol /
It measured using L ethanolic potassium hydroxide solution.
The viscosity was measured at 25 ° C. using a B-type viscometer.

Example 1 930 g of methyl methacrylate and 9.4 g of methacrylic acid were charged into a 3 L separable flask equipped with a stirrer, a condenser and a metering pump, and heated. When the temperature reached 100 ° C., 11.3 g of 1-dodecanethiol was added, 940 g of methyl methacrylate and 0.14 g of 2,2′-azobis (2,4-dimethylvaleronitrile) (10
(Half-life at 0 ° C. = 96 seconds) was added using a metering pump over 3 hours. After the addition was completed, heating was continued for 1 hour. At this time, the polymerization rate was 35.1%.
One hour after the completion of the addition, the heating was terminated, and 2.98 g of 2,6-di-t-butyl-4-methylphenol was added, followed by cooling to room temperature. The acid value of the obtained syrup is 2.5 mg KOH
/ G. This syrup was added to cold hexane, and the precipitated polymer was purified and dried under reduced pressure. The acid value was measured as a 10% solution in methylene chloride, and the acid value was measured.
gKOH / g. The acid value of methylene chloride is 0.00
It was 1 mgKOH / g or less. The weight average molecular weight measured by GPC was 51,000, and the viscosity at 25 ° C. was 2100 mPa · s. After storing the obtained syrup in a dark place at 40 ° C. for one month, the viscosity at 25 ° C. was measured and found to be 2.2 Pa · s, indicating no change in color tone.

Reference Example 1 1 kg of methyl methacrylate syrup obtained in Example 1
1.8 with respect to aluminum hydroxide (average particle size 20 μm)
kg, glass frit 0.2 kg, magnesium oxide 7
g, trimethylolpropane trimethacrylate 50
g, t-butylperoxy (2-ethylhexanoate) 10 g, zinc stearate 10 g, tinuvin P (2
5 g of-(5-methyl-2-hydroxyphenyl) benzotriazole (manufactured by Nippon Ciba Geigy) was added and kneaded at 30 ° C for the first hour and then at 40 ° C. Viscosity started immediately after kneading, and tackiness disappeared after 3 hours.
This compound was aged for 24 hours at 40 ° C.
Molding was performed at 5 ° C., a lower surface of 130 ° C., and a molding pressure of 3.0 MPa for 3 minutes, and then at 10.0 MPa for 3 minutes to obtain an artificial marble plate having a good surface smoothness. 40 ° C
For 10 days, and molded in the same manner to obtain an artificial marble plate having good surface smoothness.

Examples 2 to 5 The reaction was carried out in the same manner as in Example 1 under the conditions shown in Table 1. The methyl methacrylate syrup obtained in Examples 2 to 4 was evaluated under the same conditions as in Reference Example 1. All of the methyl methacrylate syrups after 3 hours had a sufficiently thickened compound without stickiness.

Reference Example 2 1k of methyl syrup of methyl methacrylate obtained in Example 5
g, 2 g of lauroyl peroxide and degassed.
The syrup was injected into a glass cell in which a polyvinyl chloride gasket was set between two pieces of tempered glass of × 300 × 10 mm. 2 hours at 55 ° C, 2 hours at 60 ° C, 6
After polymerization at 5 ° C. for 2 hours and 135 ° C. for 0.25 hours, 70
After cooling at ℃, the methacrylic resin plate was taken out. A methacrylic resin plate which was colorless and transparent and had a good appearance was obtained.

Comparative Example 1 0.09 g of t-butylperoxy (2-ethylhexanoate) as an initiator (half-life at 100 ° C. = 1550)
The reaction was carried out in the same manner as in Example 1 except that One hour after completion of the addition, the polymerization rate was 35.0%. The acid value of the obtained syrup was 2.5 mgKOH / g. This syrup was added to cold hexane, and the precipitated polymer was purified and dried under reduced pressure, and the acid value was measured as a 10% solution of methylene chloride. The acid value was 3.5 mgKOH / g. The acid value of methylene chloride was 0.001 mgKOH / g or less. The weight average molecular weight measured by GPC was 51,000, and the viscosity at 25 ° C. was 2100 mPa · s.
Met. When this syrup was stored in a dark place at 40 ° C. for one month, it was solidified throughout.

Comparative Example 2 A syrup was obtained by carrying out the reaction in the same manner as in Example 1 except that no polymerization inhibitor was used. At this time, the polymerization rate was 35.1%. The acid value of the obtained syrup was 2.5 mg KOH /
g. Also add this syrup in cold hexane,
The precipitated polymer was purified and dried under reduced pressure, and the acid value was measured as a 10% solution in methylene chloride.
OH / g. The acid value of methylene chloride is 0.001m
gKOH / g or less. The weight average molecular weight measured by GPC was 51,000, and the viscosity at 25 ° C was 2.
It was 1 Pa · s. When this syrup was stored for one month in a dark place at 40 ° C., about 上部 of the upper part was left, and the rest was solidified.

Comparative Example 3 1870 g of methyl methacrylate, 9.4 g of methacrylic acid
At once and the temperature was raised while stirring. Upon reaching 80 ° C., 29.1 g of 1-dodecanethiol and 2,2
0.25 g of 2′-azobisisobutyronitrile (80 ° C.
(Half life at 5230 seconds) was added to initiate polymerization. Three hours after the start of the polymerization, 2.98 g of 2,6-di-t-butyl-4-methylphenol was added and cooled. Polymerization rate is 3
5.5%, and the resulting syrup had an acid value of 2.5 mg.
KOH / g. This syrup was added to cold hexane, and the precipitated polymer was purified and dried under reduced pressure. The acid value was measured as a 10% solution in methylene chloride.
It was 9 mgKOH / g. The acid value of methylene chloride is 0.1.
001 mgKOH / g or less. The weight average molecular weight measured by GPC was 51,000, and the viscosity at 25 ° C. was 2,400 mPa · s. 40 of this syrup
When stored for one month in the dark at ℃, it was solidified throughout.

[0039]

According to the present invention, methyl methacrylate syrup having desired properties can be stably produced, and is of great industrial significance.

[0040]

[Table 1]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) (C08F 220/14 220: 06) F term (reference) 4J011 BA07 BB01 BB02 BB08 FA04 FA05 FB05 FB10 FB19 4J100 AJ02Q AL03P CA01 CA04 DA01 DA09 EA01 FA03 FA04 FA06 FA18 FA28 FA37 FA39 JA03 JA32 JA51 JA67

Claims (4)

[Claims] When producing a syrup from a mixture containing a monomer having methyl methacrylate as a main component, a polymerization initiator and a chain transfer agent, (1) methyl methacrylate 90
To 100% by weight and one or two unsaturated carboxylic acids selected from acrylic acid or methacrylic acid
20-70% by weight based on the total amount of the raw material consisting of ０0% by weight
(2) After the temperature was raised to the reaction temperature, the entire amount of the chain transfer agent was added, and (3) the remaining raw materials were then polymerized to have a half-life at the reaction temperature of 10 to 300 seconds. It is obtained by adding over 0.1 to 5 hours together with the initiator, (4) heating is further continued for 0.01 to 5 hours after the addition is completed, and (5) a hindered phenol polymerization inhibitor is added at the end of heating. (6) The weight average molecular weight measured by GPC is from 20,000 to 200,000, and the viscosity at 25 ° C is from 10 to 2
A method for producing methyl methacrylate syrup having a viscosity of 0000 mPa · s. 2. The method according to claim 1, wherein the reaction temperature is 95 to 110 ° C. 3. The method according to claim 1, wherein the reaction temperature is a boiling point of the composition in the system. 4. The chain transfer agent according to claim 1, wherein the chain transfer agent is a mercaptan, and the addition of the remaining raw materials and the polymerization initiator is started at a predetermined time 0 to 60 minutes after the addition of the chain transfer agent. Manufacturing method.