JPH07224102A - Method for producing acrylic polymer - Google Patents

Abstract

PURPOSE:To obtain the subject high-molecular weight polymer with low content of residual monomer by feeding an extruder with a polymerizable composition comprising an acrylic monomer, thermal polymerization initiator and photopolymerization initiator followed by thermal polymerization to a specified conversion rate followed by photopolymerization under ultraviolet light irradiation. CONSTITUTION:A polymerizable composition comprising an acrylic monomer such as methyl methacrylate, butyl acrylate or acrylic acid, a thermal polymerization initiator such as 2,2'-azobisisobutyronitrile or 2,2'-azobis(2,4- dimethylvaleronitrile) and a photopolymerization initiator such as benzyl dimethyl ketal or 1-hydroxycyclohexyl phenyl ketone is fed to a twin-screw extruder made up of self-wiping type double screw element and kneading disc element where the composition is heated to a temperature at or higher than the decorfzposition temperature of the thermal polymerization initiator to conduct a thermal polymerization of the acrylic monomer so as to come to 50-99% in the conversion rate of the monomer followed by conducting a photopolymerization under ultraviolet light irradiation, thus the aimed high-molecular weight polymer with trace amounts of residual monomer is obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an acrylic polymer.

[0002]

2. Description of the Related Art When an acrylic polymer is produced by bulk polymerization, the viscosity of the reaction system rapidly increases as the polymerization reaction progresses, and mechanical stirring becomes impossible. The large amount of heat generated by polymerization, which is peculiar to the above, cannot be properly removed, and the reaction becomes difficult to control. Therefore, solution polymerization, suspension polymerization, or emulsion polymerization using an organic solvent or water as a medium is generally used for producing the acrylic polymer.

However, since an organic solvent and water are used, it is necessary to remove the organic solvent and water in order to obtain an acrylic polymer, and when an organic solvent is used, there is a health problem. .

On the other hand, Japanese Patent Publication No. 37-6744 discloses that
Without using water or organic solvent, a methylmethacrylate-based polymerizable substance, a radical polymerization initiator, etc. are continuously supplied to the extruder, and the polymer is continuously supplied through a zone maintained at a constant temperature. Disclosed is a method for producing a methylmethacrylate polymer and a copolymer discharged to the above.

However, in such a method, since the reaction rate of the polymerizable substance is limited, the conversion rate of the polymerizable substance was low.

Therefore, a method for achieving the polymerization reaction by making the extruder flow rate extremely small, making the extruder extremely long, increasing the addition amount of the radical polymerization initiator, and raising the reaction temperature. However, there is a limit to the extremely small flow rate of the extruder, which leads to a decrease in productivity, and it is impossible to make the extruder extremely long due to the mechanism of the extruder. Increasing the addition amount of and increasing the reaction temperature has a problem that the molecular weight of the obtained polymer is lowered because the concentration of free radical increases in the polymerization reaction. Further, Japanese Patent Publication No. 2-55448 discloses a method for polymerizing an alkyl acrylate ester monomer in which a raw material for polymerization containing an acrylic acid alkyl ester monomer as a main component is fed into an extruder and bulk polymerized under a certain condition. It is disclosed. However, such a polymerization method has a problem that the obtained polymer has a wide distribution width.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing an acrylic polymer, which can obtain a high conversion of a high molecular weight acrylic polymer having a narrow distribution width.

[0008]

The polymerizable composition used in the present invention comprises an acrylic monomer, a thermal polymerization initiator and a photopolymerization initiator.

The acrylic monomer used in the present invention means (meth) acrylic acid esters, (meth) acrylic acid, acrylonitrile, (meth) acrylamide, N-
A substituted (meth) acrylamide and a mixture thereof, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, (meth)
(Meth) acrylic acid esters such as butyl acrylate, octyl (meth) acrylate, stearyl (meth) acrylate, glycidyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate; hydroxyethyl (meth) acrylate, Hydroxy (meth) acrylate such as hydroxypropyl (meth) acrylate; N-methyl (meth) acrylamide, N, N-dimethyl (meth)
N-substituted (meth) acrylamides such as acrylamide, N, N-diethyl (meth) acrylamide, N-methyl (meth) acrylamide and the like, acrylic acid,
Methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and acrylonitrile are preferable.

The acrylic monomer may include, if necessary, one or more vinyl compounds copolymerizable with the acrylic monomer, a synthetic resin, a chain transfer agent, a stabilizer, as long as the physical properties are not impaired. Crosslinking agents, plasticizers, tackifiers; inorganic fillers such as glass fiber, mica, talc may be added, and the addition amount thereof is 30 parts by weight or less based on 100 parts by weight of the acrylic monomer. Is preferred.

Examples of the vinyl compound include styrene; styrene derivatives such as methylstyrene, α-methylstyrene, ethylstyrene, dimethylstyrene, butylstyrene and chlorostyrene; maleic anhydride; N-vinylpyrrolidone; vinyl acetate and the like. , Styrene,
Maleic anhydride, vinyl acetate and N-vinylpyrrolidone are preferred.

The above thermal polymerization initiator is generally an acrylic monomer.
It is not particularly limited as long as it is used in the thermal polymerization reaction of the monomer.
Without, for example, benzoyl peroxide, 2,4 dicarboxylic acid
Lorbenzoyl peroxide, p-chlorobenzoyl
Peroxide, o-methylbenzoyl peroxide
De, bis-3,5,5-trimethylhexanol pero
Diacyl peroxides such as quiside; dicumyl peroxide
Xide, 2,5-dimethyl-2,5-di- (tert-
Butyl peroxy) -hexane, tert-butyl Kumi
Ruperoxide, di-tert-butyl peroxide
1,3-bis- (tert-butylperoxyiso)
Propyl) -dialkyl peroxide such as benzene;
1,1-di-tert-butylperoxycyclohexa
Peroxyketal such as tert-butyl peroxy
Alkyl peresters such as cibenzoate; diisopro
Percarbonate such as pirperoxydicarbonate
Organic peroxide of 2,2^'-Azobis (2,4-dimethyl)
Luvaleronitrile), 2, 2 ^'-Azobisisobutyroni
Trill 2,2^'-Azobiscyclohexyl nitrile, etc.
The azonitrile compound of
Soluble in acrylic monomers and has a half-life of 1 hour
It is preferable that the temperature is 60 to 150 ° C.
Zoyl peroxide, 2, 2^'-Azobisisobutyro
Nitrile, 2,2^'-Azobiscyclohexyl nitrile
Etc.

When the half-life temperature of 1 hour is high, the polymerization reaction rate is low and the conversion rate of the acrylic monomer in the extruder is low, and when it is low, the polymerization reaction rate is too fast and the reaction This makes it difficult to control. The half-life temperature of 1 hour refers to a temperature at which a substance dissolved in benzene or toluene has a half-life of 1 hour. For example, diphenyl-1-picrylhydrazyl (DP) which is a kind of a polymerization inhibitor is used.
PH) to measure the disappearance rate by an ultraviolet absorption spectrum.

If the amount of the thermal polymerization initiator added is too large, the free radicals increase too much, and the molecular weight of the resulting acrylic polymer decreases, and if it is too small, the acrylic polymer is used up at the beginning of the polymerization reaction. Since the conversion rate of the monomer is lowered, 0.005-1 is added to 100 parts by weight of the acrylic monomer.
Part by weight is preferable, and 0.02 to 0.5 part by weight is more preferable. The thermal polymerization initiator may be used alone or in combination.

The photopolymerization initiator is not particularly limited as long as it is generally used for photopolymerization of acrylic monomers and can withstand the heat history in the extruder, and for example, 4- (2-Hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2,2-
Dimethylacetophenone, methoxyacetophenone,
Acetophenone-based photopolymerization initiators such as 2,2-dimethoxy-2-phenylacetophenone; Benzoin ether-based photopolymerization initiators such as benzoin ethyl ether and benzoin isopropyl ether; Ketal-based photopolymerization initiators such as benzyl dimethyl ketal; Examples thereof include halogenated ketones, acylphosphinoxides, and acylphosphonates, and 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexylphenyl ketone, and benzyldimethylketal are preferable. .

If the amount of the photopolymerization initiator added is large, unreacted photopolymerization initiator or free radicals may remain in the resulting acrylic polymer, and the resulting acrylic polymer is deteriorated. In addition, if it is small, the integrated irradiation amount of ultraviolet rays is required to be large, so 0.001 to 2 parts by weight is preferable with respect to 100 parts by weight of the acrylic monomer, and 0.1.
01 to 1 part by weight is particularly preferred.

In the present invention, first, the polymerizable composition is fed to an extruder and heated to a temperature above the decomposition temperature of the thermal polymerization initiator to polymerize the acrylic monomer.

The extruder used in the present invention is not particularly limited, and a single-screw extruder, a twin-screw extruder, a multi-screw extruder having three or more screws, and the like can be used. As, for example, those having a full flight type screw, those having a discontinuous flight type screw, a pin barrel, a mixing head, and the like,
As the twin-screw extruder, for example, a meshing type same-direction rotating type, a meshing different-direction rotating type, a non-meshing different-direction rotating type, and the like can be cited. Wiping) A co-rotating twin screw extruder is preferably used.

The method of supplying the polymerizable composition to the screw extruder is not particularly limited, and for example, an acrylic monomer, a thermal polymerization initiator, a photopolymerization initiator and the like can be previously prepared by using a stirring tank or the like. The mixture may be supplied from one supply port, or some of these may be mixed in advance, or each of them may be supplied individually from different supply ports.

When supplying the polymerizable composition, the polymerizable composition is dissolved by nitrogen substitution or the like in order to prevent oxygen inhibition of the polymerization reaction and further to prevent the formation of by-products such as oligomers. It is preferable that oxygen is sufficiently removed, and the dissolved oxygen concentration is preferably removed so as to be 1 ppm or less, more preferably 0.5 ppm or less.

The barrel temperature of the screw extruder may be higher than the decomposition temperature of the thermal polymerization initiator, but in the pre-stage of the extruder, within a range where the acrylic monomer does not boil or vaporize,
Heating above the decomposition temperature of the thermal polymerization initiator, the polymerization reaction proceeds at the central part while preventing runaway of the reaction, and at the latter part, the screw and pumping are in a completely filled state that is stable and stable. It is preferably set in consideration of the types of the system monomer and the thermal polymerization initiator and the average residence time.

As a method of measuring the average residence time, for example, a suitable tracer may be injected in a small amount from the supply port and the residence time distribution at the discharge port of the extruder may be measured to obtain the average residence time. Specifically, an organic dye is used as a tracer, and the change over time in the dye concentration in the substance to be ejected is quantified by absorption spectrometry or the like to obtain a distribution function and obtain an average residence time.

The desired average residence time is determined by the operating conditions such as the monomer feed rate and barrel temperature, the barrel diameter and length of the screw extruder, the screw shape and rotation speed, the breaker at the screw extruder outlet, and the die head. ,
It can be set according to the shape of the die and the like.

The acrylic monomer is thermally polymerized so that the conversion rate is 50 to 99%. For such control, the amount of the thermal polymerization initiator added, the barrel temperature, the average residence time, etc. are appropriately adjusted. Achieved by

The conversion rate in the present invention is expressed by the following equation. Conversion = 100-100 x Unreacted acrylic monomer /
Acrylic monomer supplied

If the conversion rate of the acrylic monomer due to thermal polymerization is low, oxygen will dissolve into the thermal polymerization product to inhibit the photopolymerization reaction, and if it is increased, the polymerization temperature will be increased. Or, it is necessary to lengthen the extruder, and when the polymerization temperature is raised, the molecular weight of the resulting acrylic polymer decreases, and it is impossible to lengthen the extruder because of the mechanism of the extruder. Limited to 99%, 70 ~
99% is preferable.

The product discharged from the screw extruder may be formed into a desired shape by a die die provided at the exit of the extruder, and may have a sheet shape, a film shape, a rod shape,
In addition to forming a strand, it may be multilayer extruded with another substrate or applied to another substrate and impregnated to form a laminate,
It is preferable to have a shape that matches the shape of the final product because the step of shaping the obtained acrylic polymer can be omitted.

In the present invention, after the thermal polymerization, a step of further irradiating with ultraviolet rays and photopolymerizing to obtain an acrylic polymer.

The method of irradiating with ultraviolet rays is not particularly limited, and examples thereof include a low pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a metal halide lamp,
There is a method of irradiating with a black light, etc.The ultra-high pressure mercury lamp efficiently emits light in the active wavelength region of the photopolymerization initiator, and causes short-wavelength components that cause cross-linking and heat evaporation of raw materials. Since the long-wavelength component that becomes

When irradiating with ultraviolet rays, it is possible to obtain a certain amount of the product obtained by the thermal polymerization reaction and then collectively irradiate with the ultraviolet ray. However, the product obtained from the extruder is kept in a certain shape. It is preferable to continuously irradiate the ultraviolet ray while taking it off while improving the production efficiency.

When the irradiation intensity of ultraviolet rays is high, the starting radical concentration is increased and the molecular weight of the resulting acrylic polymer is lowered, and when the irradiation intensity is low, the reaction efficiency of the photopolymerization reaction is lowered. 100 mW / cm ² is preferable, 1 to 4
0 mW / cm ² is particularly preferred.

When the irradiation time of ultraviolet rays is long, the polymer is broken by the ultraviolet rays, and when it is short, the conversion rate of the acrylic monomer is lowered, so that it is preferably 10 seconds to 10 minutes.
20 seconds to 4 minutes are particularly preferred.

Therefore, the irradiation of ultraviolet rays is 0.1 to 100.
Irradiation with mW / cm ² for 10 seconds to 10 minutes is preferable, and irradiation with 1 to 40 mW / cm ² for 20 seconds to 4 minutes is particularly preferable.

[0034]

In the present invention, the production of the acrylic polymer is carried out in two steps of the thermal polymerization reaction and the photopolymerization reaction in the extruder. That is, a part of the acrylic monomer is polymerized in an extruder that is easy to control and has a high processing efficiency within a range that does not reduce the conversion rate of the acrylic monomer. Next, since the unreacted acrylic monomer in the product obtained by the thermal polymerization reaction is photopolymerized, it is generally a problem in photopolymerization, which is characteristic of oxygen inhibition and polymerization reaction of acrylic monomer. The problem of removing the heat of polymerization does not occur.

[0035]

【Example】

(Examples 1 to 3 and Comparative Example 1) A meshing type co-rotating twin-screw extruder equipped with a screw of self-wiping type two-row screw element and kneading disc element with a diameter of 39 mm and L / D = 42 ( Product name BT-4 manufactured by Plastic Engineering Laboratory Co., Ltd.
A coat hanger die having a sheet-like ejection port having a width of 17 cm and a thickness of 2 mm was attached to the tip of 0).

The front part of the barrel of the screw extruder (first
~ 3 barrel section), middle stage section (4th-6th barrel section), rear stage section (7th barrel section and die section) are set to the temperatures shown in Table 1, and the screw rotation speed is shown in Table 1. Set to.

In a 100 liter tank, the prescribed amounts of methyl methacrylate (MMA), butyl acrylate (BA), acrylic acid (AA) and 2,2'-azobisisobutyronitrile (AIBN) shown in Table 1 were used. ), 2,2 ^'- azobis - (2,4-dimethylvaleronitrile (ADMV
N), benzyl dimethyl ketal, and 1-hydroxycyclohexyl phenyl ketone were supplied to prepare a raw material solution.

Next, while maintaining the temperature of the raw material solution at less than 25 ° C., a nitrogen gas (purity 99.9%) having a flow rate of 4 liters per minute was blown into the raw material solution to dissolve a dissolved oxygen meter (Central Chemical Co., Ltd.). The amount of dissolved oxygen in the acrylic monomer was measured using a trade name UC-12-SOL type manufactured by the company), and nitrogen substitution was stopped when the dissolved oxygen concentration reached 0.1 ppm.

Next, the nitrogen-substituted raw material solution was treated with a chemical gear pump (GX-12SZKC- manufactured by Iwaki Co., Ltd.).
04N1) was continuously supplied to the screw extruder in a predetermined amount shown in Table 1 to initiate bulk polymerization.

When the bulk polymerization reaction reached a steady state, a part of the product discharged from the screw extruder was sampled to obtain a sample (a), and the width was 17 cm, the length was 10 cm, and the thickness was 2 mm. Intermediate product, the inner surface 4
The sample was placed in an ultraviolet irradiation device, which is a cube composed of a 0 cm reflector, and was irradiated with ultraviolet rays at an intensity of 8 mW / cm ² for 2 minutes to obtain a sample (b). In addition, the irradiation intensity of ultraviolet rays is measured by an illuminometer (trade name: UVR-3 manufactured by Tokyo Engineering Co., Ltd.).
6) was used.

From the obtained sample (a), the conversion of acrylic monomer by thermal polymerization and the weight average molecular weight (Mw)
And the distribution width (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the sample (b), the conversion rate of the acrylic monomer, the weight average molecular weight and the distribution width were measured by the following methods, and The results are shown in Table 2.

(Conversion rate) The conversion rate of the acrylic monomer is
For convenience, it was obtained from the following formula. Conversion rate (%) = 100 × acrylic polymer amount / sample amount The acrylic polymer amount was measured using gas chromatography (Shimadzu Corporation trade name LC9A). The column name is PE manufactured by Shimadzu Corporation.
The column temperature was 140 ° C. using G20M.

(Weight average molecular weight, distribution width) Using gel per chromatography consisting of liquid chromatography (Shimadzu Corporation trade name LC9A) and detector (Shimadzu Corporation trade name RYD6A), the polystyrene equivalent weight average molecular weight and The number average molecular weight was obtained, and the distribution width was obtained from these values. In addition, product name 80 manufactured by Showa Denko
5, product name 804, product name 801 columns 2, 1,
One column connected in series was used as a column, tetrahydrofuran (THF) was used as a solvent, the flow rate was 1 cc / min, and the temperature was 45 ° C.

Comparative Example 2 A screw extruder equipped with the same coat hanger die as that used in Example 1 was used.

The front part of the barrel of the screw extruder (first
~ 3 barrel section), middle stage section (4th-6th barrel section), rear stage section (7th barrel section and die section) are set to the temperatures shown in Table 1, and the screw rotation speed is shown in Table 1. Set to.

A predetermined amount of methyl methacrylate (MMA) and 2,2'-azobisisobutyronitrile (AIBN) shown in Table 1 were supplied to a 100 liter tank to prepare a raw material solution.

Next, while maintaining the temperature of the raw material solution at less than 25 ° C., nitrogen gas (purity 99.9%) at a flow rate of 4 liters per minute was blown into the raw material solution, and a dissolved oxygen meter (Central Chemical Co., Ltd.) was used. The amount of dissolved oxygen in the acrylic monomer was measured using a trade name UC-12-SOL type manufactured by the company), and nitrogen substitution was stopped when the dissolved oxygen concentration reached 0.1 ppm.

Next, the nitrogen-substituted raw material solution was treated with a chemical gear pump (GX-12SZKC- manufactured by Iwaki Co., Ltd.).
04N1) was continuously supplied to the screw extruder in a predetermined amount shown in Table 1 to initiate bulk polymerization.

When the bulk polymerization reaction reached a steady state, a part of the product discharged from the screw extruder was sampled to obtain a sample (a).

From the obtained sample (a), the conversion of acrylic monomer by thermal polymerization, the weight average molecular weight (Mw)
And distribution width (weight average molecular weight (Mw) / number average molecular weight (Mn)) were measured by the same method as in Example 1, and the results are shown in Table 2.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

The method for producing an acrylic polymer according to the present invention is as described above, and according to the present invention, a high molecular weight acrylic polymer having a very small amount of residual monomer and a narrow distribution width. Can be easily produced at a high conversion rate and continuously as required.

Claims (1)

[Claims] 1. A polymerizable composition comprising an acrylic monomer, a thermal polymerization initiator and a photopolymerization initiator is fed to an extruder and heated to a temperature not lower than the decomposition temperature of the thermal polymerization initiator to obtain a single acrylic monomer. A method for producing an acrylic polymer, which comprises subjecting the polymer to thermal polymerization so that the conversion rate of the body is 50 to 99%, further irradiating with ultraviolet rays, and photopolymerizing to obtain an acrylic polymer.