JP3013953B2 - Acrylic resin manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an acrylic resin useful as a plastic material having excellent transparency.

[0002]

2. Description of the Related Art Acrylic resin is a plastic excellent in transparency, light resistance, mechanical strength, moldability and workability, and is used for signboards, lighting equipment, vehicle parts and various decorative articles. Have been. In recent years, lenses, optical disks,
Applications in the optical field such as optical fibers are expanding, and there is a need for a method for producing a high-quality acrylic resin having a narrow molecular weight distribution and excellent optical properties.

Conventionally, suspension polymerization, bulk polymerization, solution polymerization, and the like have been known as methods for industrially producing an acrylic resin used for a molding material. In the suspension polymerization method, since the polymerization reaction is easily controlled, an acrylic resin having a relatively narrow molecular weight distribution can be produced, but the dispersant or dispersion stabilizer used in the production remains in the resin, and the There are drawbacks such as deterioration of properties, batch production is mainly performed, the production process is complicated, productivity is low, and a large amount of wastewater treatment is required.

[0004] The bulk polymerization method does not use a dispersant or a dispersion stabilizer, does not require a large amount of wastewater treatment, is relatively easy to maintain good productivity, and is relatively easy to achieve good productivity. There are advantages, such as easiness, as compared with the suspension polymerization method. However, when the monomer conversion rate (hereinafter, referred to as the conversion rate) increases, the phenomenon of acceleration of the polymerization rate, which is generally known as the gel effect, occurs, and the viscosity and the temperature rise rapidly during the polymerization reaction, so that the heat of polymerization is removed. It is difficult to control the polymerization reaction on an industrial scale, it is difficult to increase the conversion to 60% or more, the molecular weight distribution of the acrylic resin to be produced is wide, and oligomers and gelled products are difficult to control. There are drawbacks, such as easy formation of impurities as by-products and deterioration of optical properties.

In order to improve these disadvantages of the bulk polymerization method, Japanese Patent Application Laid-Open No. 49-37993 discloses a conversion rate of 50%.
After reaching ~ 80%, a method has been proposed in which a viscosity reducing agent such as toluene and a radical polymerization initiator are additionally added to increase the conversion to 85% or more. However, it is usually very difficult to control the polymerization reaction until the conversion reaches 50 to 80% by the bulk polymerization method, and the amount of the radical polymerization initiator and the polymerization temperature are limited to specific ranges. The range of manufacturable conditions is very narrow and it is extremely difficult to implement on an industrial scale. Also, the addition of a viscosity reducing agent and the addition and addition of a radical polymerization initiator change polymerization conditions such as polymerization temperature,
There are drawbacks such as broadening the molecular weight distribution of the obtained acrylic resin and deteriorating the optical properties.

JP-A-63-77909 discloses that a specific monomer mixture consisting of methyl methacrylate, vinyl aromatic, maleic anhydride and alkyl acrylate is converted to a conversion of 60% in the presence or absence of a solvent. Production methods have been proposed in which about 15 to 33% by weight of a solvent is added after polymerization to a polymerization rate of 80% or more.
However, usually, the gel effect is suppressed in the absence of a solvent,
It is difficult to control the polymerization reaction up to a conversion of 60%.
On the other hand, if the conversion is 60% or more, the viscosity of the polymerization reaction solution becomes extremely high, it is difficult to uniformly mix the solvent with the solvent, the polymerization temperature becomes uneven, and the molecular weight distribution of the obtained acrylic resin becomes wide. There are drawbacks.

In the solution polymerization method, when the amount of the solvent used is small, a gel effect occurs, and the molecular weight distribution of the obtained acrylic resin is widened. The molecular weight can be easily adjusted, and since no dispersant or the like is used, the optical properties are good and a resin having a narrow molecular weight distribution can be produced. However, as is well known, the use of a large amount of a solvent equal to or more than the amount of the monomer reduces the polymerization rate, particularly the polymerization rate at the initial stage of the polymerization, and lowers the productivity and increases the polymer of high molecular weight. There are drawbacks such as being difficult to obtain.

[0008]

DISCLOSURE OF THE INVENTION The present invention eliminates the drawbacks of the prior art relating to the polymerization of acrylic resins, makes it easy to control the polymerization reaction, has a narrow molecular weight distribution, and has excellent optical properties. It is an object of the present invention to provide a method for producing a.

According to the present invention, a monomer comprising 70 % by weight to 95% by weight of methyl methacrylate and another copolymerizable vinyl compound is converted into a radical polymerization initiator using two or more polymerization reactors. (1) In the first polymerization reactor, a monomer and a solvent are mixed at a weight ratio of 70 to 95/30 to 5 to produce an acrylic resin, and the conversion of the monomer is 10 to 10. Polymerizing to a range of 50 %, and transferring the resulting polymer-containing mixture to a subsequent polymerization reactor including a final polymerization reactor; (2) mixing the polymer-containing mixture and the solvent by weight in the latter polymerization reactor; 30-70 /
Mixing at a ratio of 70 to 30; (3) polymerizing until the conversion of the monomer becomes 80% or more in the subsequent polymerization reactor; and (4) adjusting the polymerization temperature in the first and second polymerization reactors. (5) removing the solvent, unreacted monomer and low molecular weight polymer from the polymer mixture obtained in the final polymerization reactor, and keeping the temperature change within the range of ± 10 ° C. To a method for producing an acrylic resin.

Other vinyl compounds copolymerizable with methyl methacrylate include alkyl acrylates such as methyl acrylate, ethyl acrylate and butyl acrylate, alkyl methacrylates such as ethyl methacrylate, butyl methacrylate and lauryl methacrylate, acrylonitrile and methacrylonitrile. And unsaturated nitriles such as α-chloroacrylonitrile, styrene compounds such as styrene and α-methylstyrene, acrylamide, methacrylamide, acrylic acid, methacrylic acid, vinyl chloride, vinylidene chloride and the like. These may be used alone or in combination of two or more.

Methyl methacrylate is JIS K671
A product having the product quality described in No. 6 and removing dissolved oxygen to an amount that does not affect the polymerization reaction, usually to 100 ppm or less can be used. The other copolymerizable vinyl compound may be of a quality equivalent to methyl methacrylate.
If the amount of methyl methacrylate is less than 70% by weight, the transparency, mechanical strength and the like are lowered, and the inherent properties of the acrylic resin are lost.

As the radical polymerization initiator, an organic peroxide or an azo compound can be used. Examples of the organic peroxide include diacyl peroxides such as lauroyl peroxide and benzoyl peroxide;
1-bis (t-butylperoxy) cyclohexane,
Peroxyketals such as 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, peroxydicarbonates such as diisopropylperoxydicarbonate and di-2-ethylhexylperoxydicarbonate; Examples include peroxyesters such as t-butylperoxy-2-ethylhexanoate and t-butylperoxyisobutyrate. Examples of the azo compound include azobisisobutyronitrile and 1,1-azo Biscyclohexane-t-carbonitrile and the like can be mentioned. These may be used alone or in combination of two or more. The radical polymerization initiator is monomer 1
It is used in an amount of 0.0005 to 1 part by weight, preferably 0.001 to 0.5 part by weight, per 100 parts by weight.

The solvent has a solubility in the monomer and the acrylic resin to be formed and does not substantially inhibit the polymerization reaction, and has a boiling point of about 40 to 225 ° C., preferably 60 to 225 ° C.
What is in the range of about 150 ° C. can be used. Specific examples include tetrahydrofuran, methyl ethyl ketone, hexane, heptane, octane, benzene, methyl isobutyrate, toluene, xylene, cyclohexane, cyclododecane, isooctane, decalin, dimethyl sulfoxide, ethylene carbonate, and normal butanol. These solvents are used after the dissolved oxygen is removed to an amount that does not affect the polymerization reaction.

In the first polymerization reactor, these solvents are used in a weight ratio to the monomer (monomer / solvent) of 70 to 95/30.
-5, preferably 75-90 / 25-10. If the amount of the solvent is less than the above lower limit, the viscosity increases as the polymerization reaction proceeds, and it is difficult to control the polymerization reaction up to a conversion of 50%, which is not preferable. In the latter polymerization reactor, the solvent is a polymer-containing mixture produced in the first polymerization reactor and a weight ratio of (polymer-containing mixture / solvent) 3.
0-70 / 70-30, preferably 35-60 / 65-
It is adjusted to the range of 40 and mixed uniformly. If the amount of the solvent used is less than the above lower limit, the viscosity of the polymerization reaction liquid becomes high due to the gel effect, control of the polymerization reaction becomes difficult, and the molecular weight distribution becomes unfavorably wide. Conversely, when the amount of the solvent is larger than the upper limit, there is no difference in the ease of controlling the polymerization reaction, but it takes a long time to remove the solvent, the unreacted monomer, the low molecular weight polymer, and the like from the produced polymerization mixture. This is not preferable because productivity is deteriorated.

In the present invention, the conversion to a polymer is made 10 to 50%, preferably about 20 to 40% in the first polymerization reactor, and the polymerization is carried out to a high conversion in the subsequent polymerization reactor. Unlike the conventional solution polymerization method, the amount of solvent in the first polymerization reactor is small, so that the polymerization rate in the first polymerization reactor is high, and the presence of the solvent prevents the gel effect up to a conversion of 50%. it can. Furthermore, in the latter polymerization reactor where the conversion exceeds 50% and the gel effect is apt to occur, the viscosity of the polymerization reaction solution does not sharply increase due to the action of the added solvent, and the temperature change due to polymerization heat is small. Control of the polymerization reaction is easy,
An acrylic resin having a narrow molecular weight distribution can be obtained, and generation of impurities such as a low molecular weight polymer can be suppressed. Further, the viscosity of the polymerization reaction liquid in the first polymerization reactor is low, and mixing with a solvent in the subsequent polymerization reactor is easy and has little effect on the polymerization reaction. Furthermore, since the viscosity of the polymerization reaction solution is low, expensive special equipment such as used in bulk polymerization is not required in the polymerization reactor.

If the conversion is less than 80% in the latter polymerization reactor, the amount of unreacted monomer increases and the recovery apparatus and operation become complicated, which is not preferable. Therefore, it is preferable to increase the conversion in the latter polymerization reactor as much as possible. The polymerization temperature was 60 to 18 in both the first and second polymerization reactors.
A range of 0 ° C, preferably 80-150 ° C is suitable.
At this time, the polymerization temperature in each polymerization reactor is set to be the same, and polymerization is performed while maintaining the temperature fluctuation within a range of ± 10 ° C., preferably within a range of ± 5 ° C. When the polymerization temperature is 50 ° C. or lower, the polymerization rate is low, and a large amount of radical polymerization initiator is required, which is not economical. On the other hand, if the temperature exceeds 180 ° C., the amount of impurities such as a low molecular weight polymer increases, which is not preferable.
On the other hand, if the temperature change exceeds ± 10 ° C., it becomes difficult to control the polymerization rate, and the molecular weight distribution becomes unfavorable.

In the present invention, mercaptans such as n-butyl mercaptan, isobutyl mercaptan, n-octyl mercaptan and lauryl mercaptan, and octyl thioglycolate are used for the purpose of controlling the molecular weight of the acrylic resin to be formed and improving the thermal stability. A chain transfer agent such as thioglycolic acid esters can be used. The amount of the chain transfer agent used is 0.02 per 100 parts by weight of the mixture.
To 1.0 part by weight, preferably 0.05 to 0.8 part by weight. Further, the raw material mixed solution used in the present invention is an additive that does not inhibit the polymerization reaction at the start of the reaction or during the reaction, for example, a plasticizer such as dioctyl phthalate,
Adds lubricants such as stearyl alcohol, dyes such as anthraquinone / red, pigments such as phthalocyanine blue and titanium dioxide, antioxidants such as hindered phenol or UV inhibitors such as resorcinol compounds, benzotriazine and benzotriazole. You can also.

The acrylic resin of the present invention can be produced in two or more stirred tank polymerization reactors. One example of the method for producing the acrylic resin of the present invention will be described in detail below with reference to FIG. 1 using two polymerization reactors. A mixture of a monomer mixture of a predetermined amount of methyl methacrylate or another vinyl compound copolymerizable with methyl methacrylate, a radical polymerization initiator and, if necessary, a chain transfer agent, a mixture of various additives, and a solvent in the raw material adjusting tank 1; (Mixture / solvent = 70-
Mix uniformly at a temperature of about 20 ° C. The mixture is withdrawn by a first metering pump 2, dust having a diameter of 0.2 μm or more is removed by a filter 3, and the temperature of the resulting polymerization reaction solution is reduced by a first heater 4 to 5 μm.
The temperature is raised to the range of 0 to 180 ° C., preferably 80 to 150 ° C., and is supplied to the first polymerization reactor 5 which has been adjusted to the same temperature. In the first polymerization reactor 5, polymerization is carried out to a conversion of 10 to 50%, preferably 20 to 40%. The change in the conversion can be known by measuring the temperature change and / or the viscosity change of the polymerization reaction solution during the polymerization reaction.

After the completion of the polymerization reaction in the first polymerization reactor 5, the produced polymer-containing mixture and a predetermined amount of the solvent heated to a temperature slightly lower than the boiling point are supplied to a second metering pump 7 and a solvent metering pump 8, respectively. To the second polymerization reactor 10. The solvent is a polymer-containing mixture / solvent = 30 to 70/7.
It is supplied so as to have a weight ratio of 0 to 30. If necessary, an additional copolymerizable vinyl compound or chain transfer agent is supplied to the reactor from the additional raw material line 11. The temperature of the polymer-containing mixture and the solvent supplied to the second polymerization reactor 10 are adjusted by the second heater 9. The polymerization temperature in the second polymerization reactor 10 is the same as that in the first polymerization reactor. The polymer-containing mixture and the solvent may be supplied to the second polymerization reactor 10 while mixing using a static mixer or the like. Second
The conversion in the polymerization reactor 10 is 80% or more, preferably 9%.
The polymerization is carried out until it becomes 5% or more, and substantially all of the radical polymerization initiator is consumed. The temperature of the polymerization reaction solution is controlled by the fact that the evaporated solvent is condensed in the condenser 12 and refluxed to the second polymerization reactor 10 and the temperature is controlled by the jacket of the polymerization reactor, and is ± 10 ° C., preferably ± 5 ° C. Is maintained within the range. The reaction pressure in both the first and second polymerization reactors is preferably slightly higher than the saturated vapor pressure of methyl methacrylate.

After the completion of the polymerization reaction in the second polymerization reactor 10, the resulting polymerization reaction mixture is sent to a heater 14 by a metering pump 13, and the heater 14 cools the mixture to about 220 to 260 ° C. in as short a time as possible. Raise the temperature. The pressure at this time is set slightly higher than the saturated vapor pressure of the solvent to prevent a decrease in the heating function due to foaming of the reaction mixture and the like. The heated polymerization reaction mixture is flushed by a deaerator 16 through a needle valve at the lower part of the line 15 and is cooled to a temperature of 220 to 2.
The solvent, unpolymerized components, low-boiling polymer and the like are removed from the polymerization reaction mixture under the conditions of 60 ° C. and a pressure of 10 to 150 mmHg. When the temperature is 220 ° C. or lower, the temperature of the acrylic resin after flashing is lowered, and the removal of the solvent, unpolymerized components, and the like becomes insufficient, which is not preferable. On the other hand, if the temperature is 270 ° C. or higher, an oligomer or a gel is formed, and the acrylic resin is deteriorated by thermal decomposition, which is not preferable. The removed solvent, unpolymerized components, low-boiling polymer and the like are sent to a recycling line via a line 17. Due to this deaeration, the content of the solvent, low molecular weight polymer, etc. in the acrylic resin becomes 1
The polymer is drawn out from the lower part of the deaerator 16 by a fourth metering pump 18 and pelletized by a pelletizer 19.

Here, the raw material adjusting tank 1 and the first polymerization reactor 3
May be the same. A solvent from the polymer-containing mixture,
For removal of low molecular weight polymers, etc., besides a flash-type device, a thin film evaporator for high viscosity (for example, trade name "EXEV")
A ″, manufactured by Shinko Pantech Co., Ltd.) or an extruder with a vent may be used, and it is more preferable to use them together with the deaerator of the present invention. Acrylic resin can be supplied to a single-screw or multi-screw extruder.The raw material adjustment tank, polymerization reactor, line and metering pump of this device are all temperature-controlled by passing a heating medium or refrigerant through the jacket. In addition, the line for transferring the acrylic resin mixture is designed to be as short as possible so that no sediment is generated.The raw material adjusting tank and the polymerization reactor are sufficiently replaced with an inert gas. In addition, the space in the polymerization reactor during the polymerization reaction is preferably an inert gas atmosphere.As described above, two polymerization reactors are used, but in the present invention, three or more reactors are used. Can also be continuous .3 Oru is also possible to operate Te
When two or more polymerization reactors are used, the operation is performed with the ultimate conversion set in each of the polymerization reactors subsequent to the second polymerization reactor being sequentially set higher.

[0022]

The present invention will be described in more detail with reference to the following examples and comparative examples. The following methods were used to measure the monomer conversion, total light transmittance, molecular weight, and molecular weight distribution of the acrylic resin in the examples. (1) Monomer conversion ratio The polymer-containing mixture 5 from the first and second polymerization reactors was used.
10 g is taken as a sample in a test tube and cooled with liquid nitrogen. After measuring the weight of the sample, the sample is completely dissolved in chloroform, and the solution is poured into methanol of about 20 times the weight of the sample with stirring to precipitate the acrylic resin.
The acrylic resin is separated by filtration, dried under reduced pressure at about 60 ° C. for 16 hours, and the weight of the obtained acrylic resin is measured. The conversion was determined from the ratio between the weight of the acrylic resin after drying and the weight of the sample. The solvent content in the polymer-containing mixture was determined by gas chromatography. (2) Total light transmittance Injection molding of the produced acrylic resin (resin temperature 230
° C, injection pressure 750 Kgf / cm ² )
It is formed into a plate having a size of 100 mm x 3 mm (thickness), and the total light transmittance is measured according to ASTM D1003 using the plate as a sample. (3) Molecular weight, molecular weight distribution GPC apparatus (Tosoh HLC-8020 type, column is S
(Hodex KF-80M), a sample prepared by dissolving 0.3 g of the produced acrylic resin in 100 ml of tetrahydrofuran was measured, and the number average molecular weight, weight average molecular weight and molecular weight distribution were determined based on a calibration curve prepared with standard polymethyl methacrylate. Ask.

Example 1 4750 g of methyl methacrylate, 250 g of methyl acrylate, and 882 g of toluene were mixed at 20 ° C. in a raw material adjusting tank 1, and nitrogen gas was blown into the mixture at a flow rate of 150 ml / min for about 10 minutes to remove dissolved oxygen. did. The dissolved oxygen in this mixture is measured with a DO meter (Central Scientific, UC
-12-SOL type) was 5 ppm or less. To this mixture, 10 g of lauroyl peroxide and 15 g of lauroyl mercaptan were added and mixed uniformly.
To remove dust and the like having a diameter of 0.2 μm or more. The first heater 4 raised the temperature to 105 ° C. and adjusted the temperature to 105 ° C.
The solution was transferred to the polymerization reactor 5 at a temperature of 105 ° C. and 150
Polymerization was performed for 90 minutes at rpm. At this time, the conversion was 32%. The temperature change during this period was within ± 2 ° C.
The polymer-containing mixture was withdrawn by the second metering pump 7 and transferred to the second polymerization reactor 10 whose temperature was adjusted to 105 ° C. Subsequently, 3618 g of toluene heated to 105 ° C. by the solvent metering pump 8 was supplied to the second polymerization reactor 10, mixed, and polymerized at the same temperature for 3 hours while stirring at a rotation speed of 100 rpm. At this time, the conversion was 91%. The temperature change during this period was within ± 3.5 ° C.

The polymer-containing mixture is pumped to a third metering pump 13
And heated to 245 ° C. under pressure, and then flushed to a deaerator 16 at a temperature of 240 ° C. and a reduced pressure of 50 mmHg or less to remove a solvent, a low molecular weight polymer and the like. The acrylic resin was taken out from the nozzle of the fourth metering pump 18 below the deaerator 16 with a strand, cooled in a water tank of the pelletizer 19, and cut with a cutter to form pellets. The total light transmittance of the produced acrylic resin was as good as 93%, the number average molecular weight measured by GPC was 39500, the weight average molecular weight was 75840, and the molecular weight distribution was 1.92.

Comparative Example 1 To a mixed solution of 4750 g of methyl methacrylate and 250 g of methyl acrylate in the raw material adjusting tank 1 was added 4500 g of toluene.
And the polymerization was carried out in the same manner as in Example 1 except that toluene was not added in the second polymerization reactor 10. The addition rate after polymerization for 90 minutes was 7%, and the conversion rate after polymerization for 3 hours in the second polymerization reactor 10 was 31%. The polymerization rate was lower than that in Example 1 and was not practical. Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 except that toluene was not added in the first polymerization reactor 5. However, the temperature of the polymerization reaction liquid began to rise from the time when the polymerization was continued for 60 minutes, and the temperature of the heating medium in the jacket of the first polymerization reactor 5 was lowered. However, it became difficult to control the temperature, and 80 minutes after the start of the polymerization. Since the temperature of the polymerization reaction solution reached 153 ° C., 4500 g of toluene at a temperature of about 10 ° C. was added and mixed to lower the temperature of the polymerization reaction solution.
Immediately after cooling, the reaction solution was withdrawn into a stainless steel container. At this time, the conversion was 56%. The acrylic resin obtained by removing toluene, unreacted monomers, and the like had a number average molecular weight of 38,800, a weight average molecular weight of 112,700, a molecular weight distribution of 2.9, and a wide molecular weight distribution. The total light transmittance was 89%.

[0026]

According to the present invention, when producing an acrylic resin containing methyl methacrylate as a main component, the polymerization is carried out by adding a solvent in both the first and second polymerization reactors, and the amount of the solvent is small. 10 to 50% conversion of the first stage,
After increasing the amount of the solvent to a conversion rate of 80% or more after the removal, the solvent, low molecular weight components, etc. are removed. (1) Even at a high conversion rate of 80% or more, the change in viscosity is small, Is easy to control. (2) A high-quality acrylic resin having a high total light transmittance and a narrow molecular weight distribution can be obtained. (3) Since the viscosity of the polymerization reaction solution is low, an inexpensive polymerization reactor can be used. And so on.

[0027]

[Brief description of the drawings]

FIG. 1 is a flow sheet according to a method for producing an acrylic resin of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 raw material adjusting tank 2 first metering pump 3 filter 4 first heater 5 first polymerization reactor 6 first condenser 7 second metering pump 8 solvent metering pump 9 second heater 10 second Polymerization reactor 11 Line for additional raw material 12 Second condenser 13 Third pump 14 Third heater 15 Liquid transfer line 16 Degassing device 17 Removal line for solvent etc. 18 Fourth constant pump 19 Pelletizer

Claims (1)

(57) [Claims] 1. The method of claim 1 wherein two or more polymerization reactors are used.
In producing an acrylic resin by polymerizing a monomer composed of methyl methacrylate by weight to 95% by weight and another vinyl compound copolymerizable by the action of a radical polymerization initiator, (1) a first polymerization reaction In a vessel, the monomer and the solvent are mixed at a weight ratio of 70 to 95/30 to 5, and the conversion of the monomer is polymerized to a range of 10 to 50%. (2) mixing the polymer-containing mixture and the solvent in the latter polymerization reactor at a weight ratio of 30 to 70/70 to 30; and (3) mixing the latter in the latter polymerization reactor. Polymerizing in a polymerization reactor until the conversion of the monomer is 80% or more;
(4) keeping the polymerization temperature in the first and second polymerization reactors the same, and keeping the temperature change within a range of ± 10 ° C .;
(5) Solvent from the polymer mixture obtained in the final polymerization reactor,
A method for producing an acrylic resin, comprising removing unreacted monomers and a low molecular weight polymer.