JP5613609B2 - Method for producing methacrylic resin and molded product - Google Patents

Description

  The present invention is excellent in transparency, heat resistance, chemical resistance, mechanical strength, and a method capable of producing a methacrylic resin excellent in moldability with high production efficiency, and excellent optical characteristics comprising the methacrylic resin obtained by the method. Related to molded products.

  Molded products made of methacrylic resin have excellent transparency and low optical distortion. Therefore, optical products such as lenses, prisms, retardation films, light guide plates, light diffusion films, and polarizing plate protective films provided in various optical products such as display devices. Widely used as a member. In particular, as the display device has a larger screen, the optical member has been increased in size and thickness. Therefore, further improvement in moldability is required for the methacrylic resin.

In order to improve the moldability of methacrylic resins, Patent Document 1 discloses a methacrylic copolymer having an intrinsic viscosity of 0.010 to 0.050 l / g and a methacrylic copolymer having an intrinsic viscosity of 0.050 to 0.090 l / g. A good flowable acrylic resin composition containing
Patent Document 2 proposes a resin composition containing a methacrylic copolymer having a weight average molecular weight of 130,000 to 250,000 and a methacrylic copolymer having a weight average molecular weight of 30,000 to 19,000. doing.
Patent Document 3 contains a methacrylic copolymer (1) having a weight average molecular weight of 50,000 to 250,000 and a methacrylic copolymer (2) having a weight average molecular weight of 6,000 to 40,000. The copolymer does not contain any of a dispersion stabilizer and an emulsifier, and the copolymer has a mass fraction of repeating units derived from (meth) acrylic acid alkyl esters other than methyl methacrylate contained in the copolymer (1). A methacrylic resin composition smaller than the mass fraction of repeating units derived from (meth) acrylic acid alkyl esters other than methyl methacrylate contained in (2) is proposed.

JP 58-101140 A JP 2006-193647 A JP 2010-59305 A

Nippon Oil & Fats Co., Ltd. Technical document “Organic peroxide hydrogen abstraction and initiator efficiency” (created in April 2003)

In these Patent Documents 1 to 3, a high molecular weight or high intrinsic viscosity methacrylic copolymer and a low molecular weight or low intrinsic viscosity methacrylic copolymer are produced separately and kneaded with a biaxial kneader or the like. A method for producing a methacrylic resin is described. In such a production method, it is difficult to keep the production cost low, and coloring and burning due to high heat applied during kneading; In addition, since a methacrylic copolymer having a low molecular weight or a low intrinsic viscosity starts to melt earlier in kneading than a methacrylic copolymer having a high molecular weight or a high intrinsic viscosity, a methacrylic polymer having a high molecular weight or a high intrinsic viscosity is used. A sufficient shear force may not be transmitted to the copolymer. For this reason, a part of the methacrylic copolymer having a high molecular weight or a high intrinsic viscosity cannot be completely melted and may cause poor appearance when a methacrylic resin is molded.
The object of the present invention is to achieve high production efficiency of a methacrylic resin with improved moldability without impairing the excellent properties such as transparency, heat resistance, chemical resistance and mechanical strength inherent in the methacrylic resin. And a molded article having excellent optical properties made of a methacrylic resin obtained by the method.

  The present inventors have made various studies in order to achieve the above object. As a result, the reaction mixture (I) containing the polymer (a) having a weight average molecular weight exceeding 50,000 by bulk polymerization or solution polymerization of the monomer mixture (I) containing methyl methacrylate in a specific amount. Then, the monomer mixture (II) containing methyl methacrylate in a specific amount is mixed with the reaction liquid (I) by 0.02 to 1.0 times by mass of the monomer mixture (I). To obtain a reaction solution (II) containing the polymer (a) and a polymer (b) having a weight average molecular weight of 20,000 to 50,000 in a specific mass ratio and concentration by bulk polymerization or solution polymerization. It is possible to produce methacrylic resins with improved moldability with high production efficiency without impairing the excellent properties such as transparency, heat resistance, chemical resistance and mechanical properties inherent in methacrylic resins. I found it. The present invention has been completed by further studies based on this finding.

That is, the present invention includes the following.
[1] In the first stage, a monomer mixture (I) containing 50% by mass or more of methyl methacrylate and 50% by mass or less of a vinyl monomer copolymerizable therewith is subjected to bulk polymerization or solution polymerization. To obtain a reaction solution (I) containing a polymer (a) having a weight average molecular weight of more than 50,000, and then, in the second stage, the reaction solution (I) contains more than 50% by mass of methyl methacrylate. A monomer mixture containing less than 50% by mass of a copolymerizable vinyl monomer and containing methyl methacrylate at a higher content than the content of methyl methacrylate in the monomer mixture (I) ( II) is mixed in an amount of 0.02 to 1.0 times the monomer mixture (I), and bulk polymerization or solution polymerization is performed, so that the polymer (a) and the weight average molecular weight are 20,000 or more and 50,000 or less. Of the polymer (b) in a mass ratio (a / b) of 60/40 to 90 The reaction solution containing a total of 100 parts by mass 10 (II) 105 to 300 manufacturing method of the methacrylic resin comprising obtaining a mass parts.
[2] The first stage is performed in the tank reactor (1), the second stage is performed in the tank reactor (2), and the amount of the reaction solution (II) obtained is 125 to 300 parts by mass. The method according to [1] above.
[3] In the first stage, the polymerization temperature T1 is 110 to 170 ° C., and in the second stage, the polymerization temperature T2 is 130 ° C. or more and (T1 + 30) ° C. or less. ] Manufacturing method.
[4] The second stage is carried out in a tank reactor (2a) and a tubular reactor (2b) connected downstream thereof, and a reaction liquid (II ₀ ) obtained in the tank reactor (2a) Is a method for producing a methacrylic resin according to [1] above, which comprises 70 to 95 parts by mass of the polymer, and the amount of the reaction solution (II) obtained is 105 to 250 parts by mass.
[5] In the first stage, the polymerization temperature T1 is 110 to 170 ° C, and in the second stage, the polymerization temperature T2a in the tank reactor (2a) is 130 ° C or higher and (T1 + 30) ° C or lower, The production method of the above-mentioned [4], wherein the polymerization temperature T2b in the tubular reactor (2b) is 140 to 190 ° C.
[6] Content a _m [mass%] of repeating units derived from methyl methacrylate in polymer (a) and content b _m [mass of repeating units derived from methyl methacrylate in polymer (b) %] Is any one of the above [1] to [5].
[7] A molded article made of a methacrylic resin obtained by any one of the production methods [1] to [6].

  According to the production method of the present invention, a methacrylic resin having improved moldability is obtained without impairing excellent properties such as transparency, heat resistance, chemical resistance, and mechanical strength inherent in the methacrylic resin. It can be obtained with high production efficiency. Further, by using the methacrylic resin obtained by the production method of the present invention, a molded product having excellent optical properties and the like can be easily obtained.

  The method for producing a methacrylic resin of the present invention includes at least a first stage and a second stage. In the first stage and the second stage, a polymer is obtained by bulk polymerization or solution polymerization of the monomer mixture.

  The bulk polymerization method is a method in which a monomer mixture is polymerized without using a solvent. The solution polymerization method is a method in which a monomer mixture is dissolved in a solvent to cause a polymerization reaction. The amount of the solvent used is preferably 0 to 100 parts by mass, more preferably 0 to 90 parts by mass with respect to 100 parts by mass of the monomer mixture. The greater the amount of solvent used, the lower the viscosity of the reaction solution and the better the handleability but the lower the productivity. The solvent that can be used in the solution polymerization is not particularly limited as long as it has a solubility in the monomer mixture as a raw material and the polymer as a product, but aromatic hydrocarbons such as benzene, toluene, and ethylbenzene are not limited. preferable. These solvents can be used alone or in combination of two or more. When two or more solvents are used in combination as a mixed solvent, as long as the mixed solvent has a solubility in a monomer mixture as a raw material and a methacrylic resin as a product, alcohol such as methanol, ethanol, butanol, Solvents having low solubility in the monomer mixture and the polymer, such as ketones such as acetone and methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and cyclohexane, may be included.

〔the first stage〕
First, in the first stage, the reaction mixture (I) containing the polymer (a) is obtained by bulk polymerization or solution polymerization of the monomer mixture (I).
The monomer mixture (I) used in the first stage contains 50% by mass or more of methyl methacrylate, preferably 80 to 99% by mass, more preferably 90 to 98% by mass.
In the monomer mixture (I) used in the first stage, the vinyl monomer copolymerizable with methyl methacrylate is 50% by mass or less, preferably 1 to 20% by mass, more preferably 2%. -10 mass% may be contained. The vinyl monomer is a monomer having at least one polymerizable alkenyl group in one molecule. Preferred examples of the vinyl monomer include alkyl acrylates such as methyl acrylate, ethyl acrylate and butyl acrylate; alkyl methacrylates other than methyl methacrylate such as ethyl methacrylate and butyl methacrylate; acrylamide , Methacrylamide, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, and other vinyl monomers; non-crosslinkable vinyl monomers having only one polymerizable alkenyl group in one molecule It is done. A vinyl monomer can be used individually by 1 type or in combination of 2 or more types.

Among the vinyl monomers, the alkyl acrylate ester has an effect of improving the light resistance of the resulting methacrylic resin and further reducing the birefringence and improving the optical uniformity.
Styrene has the effect of increasing the refractive index and decreasing the hygroscopicity of the resulting methacrylic resin.
α-Methylstyrene has the effects of increasing the heat resistance and increasing the refractive index of the resulting methacrylic resin.
It is preferable that the monomer mixture (I) contains a monomer corresponding to characteristics required for various uses of the molded article of the present invention.

  The monomer mixture (I) is subjected to bulk polymerization or solution polymerization as a raw material liquid (I) containing the monomer mixture (I). Such raw material liquid (I) can further contain an initiator, a chain transfer agent, and a solvent.

  The bulk polymerization or solution polymerization in the first stage is referred to as a reactor including at least one tank reactor (hereinafter referred to as tank reactor (1)). > Is preferable. The tank reactor (1) may be a batch type or a flow type, but a flow type is preferable.

The batch tank reactor (1) is charged with a raw material liquid (I) containing a necessary amount of the monomer mixture (I) in a tank reactor and subjected to a polymerization reaction in the tank reactor. When the conversion rate is reached, the reaction liquid is discharged from the tank reactor.
The flow-through tank reactor (1) supplies the raw material liquid (I) containing the monomer mixture (I) to the tank reactor at a constant flow rate, and keeps the inside of the tank reactor in a steady state for the polymerization reaction. The reaction solution is discharged from the tank reactor at a flow rate balanced with the supply amount.
The tank reactor is usually provided with stirring means such as a stirring blade. In the tank reactor, the raw material liquid (I) is preferably mixed almost uniformly by stirring means, more preferably completely mixed. As the tank reactor, a commercially available complete mixing tank reactor can be used. The flow-through tank reactor (1) may be composed of one tank reactor, or may be composed of two or more tank reactors connected in series. Also good. When two or more tank reactors are connected in series, the raw material liquid (I) containing the monomer mixture (I) is added all at once to the most upstream tank reactor. Or you may divide | segment and add to the tank reactor located upstream, and the tank reactor located downstream.

  As the chain transfer agent used in the first stage, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, 1,4-butanedithiol, 1,6-hexanedithiol, ethylene glycol bisthiopropionate, butane Diol bisthioglycolate, butanediol bisthiopropionate, hexanediol bisthioglycolate, hexanediol bisthiopropionate, trimethylolpropane tris (β-thiopropionate), pentaerythritol tetrakisthiopropionate, etc. Alkyl mercaptans; α-methylstyrene dimer; terpinolene. These can be used alone or in combination of two or more. The amount of the chain transfer agent used in the first stage is not particularly limited as long as the polymer (a) having a weight average molecular weight described later can be obtained.

  The polymerization initiator used in the first stage has a hydrogen abstraction ability of preferably 30% or less, more preferably 20% or less, and further preferably 10% or less. If a polymerization initiator having an excessively high hydrogen abstraction capability is used, the proportion of the low molecular weight polymer in the resulting methacrylic resin increases, so that mold fouling or the like tends to be reduced.

  The hydrogen abstraction ability can be known from the technical data of the polymerization initiator manufacturer (for example, Non-Patent Document 1). Further, it can be measured by a radical trapping method using α-methylstyrene dimer, that is, α-methylstyrene dimer trapping method. The measurement is generally performed as follows. First, a polymerization initiator is cleaved in the presence of α-methylstyrene dimer as a radical trapping agent to generate radical fragments. Among the generated radical fragments, radical fragments having a low hydrogen abstraction ability are added to and trapped by the double bond of α-methylstyrene dimer. On the other hand, a radical fragment having a high hydrogen abstraction capacity abstracts hydrogen from cyclohexane to generate a cyclohexyl radical, which is added to the double bond of α-methylstyrene dimer and captured to generate a cyclohexane trapping product. Therefore, by quantifying cyclohexane or cyclohexane-trapped product, the molar fraction of radical fragments having a high ability to extract hydrogen relative to the theoretical amount of radical fragments generated is obtained, and this is used as the hydrogen abstraction ability. More specifically, it is performed by the method described in the examples.

  The polymerization initiator used in the first stage has a one-hour half-life temperature of preferably 60 to 140 ° C, more preferably 80 to 120 ° C.

  As a polymerization initiator having a hydrogen drawing ability of 30% or less, di-t-hexyl peroxide (for example, manufactured by NOF Corporation, perhexyl D: hydrogen drawing ability 19%, 1 hour half-life temperature 136.2 ° C.), t- Hexyl peroxyisopropyl monocarbonate (for example, manufactured by NOF Corporation, perhexyl I: hydrogen abstraction capacity 18%, 1 hour half-life temperature 114.0 ° C.), t-hexyl hydroperoxide (for example, manufactured by NOF Corporation, perhexyl Z : Hydrogen abstraction capacity 27%, 1 hour half-life temperature 114.2 ° C., t-butyl peroxy 2-ethylhexanoate (for example, manufactured by NOF Corporation, Perbutyl O: Hydrogen abstraction capacity 22%, 1 hour half-life Temperature 92.1 ° C.), t-hexylperoxy 2-ethylhexanoate (for example, manufactured by NOF Corporation, perhexyl O: hydrogen abstraction capacity 11%, 1 hour (Deterioration temperature 90.1 ° C.), 1,1,3,3-tetramethylbutyl peroxy 2-ethylhexanoate (for example, manufactured by NOF Corporation, Perocta O: hydrogen abstraction capacity 4%, 1 hour half-life temperature 84.4 ° C.), t-butyl peroxypivalate (for example, manufactured by NOF Corporation, perbutyl PV: hydrogen abstraction capacity 12%, 1 hour half-life temperature 72.7 ° C.), t-hexyl peroxypivalate (for example, Manufactured by NOF CORPORATION, perhexyl PV: hydrogen abstraction capacity 8%, 1 hour half-life temperature 71.3 ° C., t-butyl peroxyneodecanoate (for example, manufactured by NOF Corporation, perbutyl ND: hydrogen abstraction capacity) 12%, 1-hour half-life temperature 64.8 ° C.), t-hexyl peroxyneodecanoate (for example, manufactured by NOF Corporation, perhexyl ND: hydrogen abstraction capacity 7%, 1-hour half-life temperature 62.8 ° C. ), 1,1, 3,3-tetramethylbutylperoxyneodecanoate (for example, manufactured by NOF Corporation, perocta ND: hydrogen abstraction capacity 2%, 1 hour half-life temperature 57.5 ° C.), 1,1-bis (t-hexyl) Peroxy) cyclohexane (for example, manufactured by NOF Corporation, perhexa HC: hydrogen abstraction capacity 10%, 1 hour half-life temperature 107.3 ° C.), benzoyl peroxide (for example, manufactured by NOF Corporation, Nyper BW: hydrogen abstraction capacity 15) %, 1 hour half-life temperature 92.0 ° C.), 3,5,5-trimethylhexanoyl peroxide (for example, manufactured by NOF Corporation, Parroyl 355: hydrogen abstraction capacity 2%, 1 hour half-life temperature 76.8 ° C. ), Lauroyl peroxide (for example, manufactured by NOF Corporation, Parroyl L: hydrogen abstraction capacity 1%, 1 hour half-life temperature 79.5 ° C.); 2,2′-azobis ( -Methylpropionitrile) (for example, manufactured by Otsuka Chemical Co., Ltd., AIBN: hydrogen abstraction capacity 1%, 1 hour half-life temperature 82.6 ° C.), 2,2′-azobis (2-methylbutyronitrile) (for example, Otsuka Manufactured by Chemical Co., Ltd., AMBN: hydrogen abstraction ability 1%, 1 hour half-life temperature 86.0 ° C.), dimethyl 2,2′-azobis (2-methylpropionate) (for example, manufactured by Wako Pure Chemical Industries, Ltd., V601) Azo compounds such as: hydrogen abstraction ability 1%, 1 hour half-life temperature 83.9 ° C.); A polymerization initiator can be used individually by 1 type or in combination of 2 or more types. In the parentheses after the compound name, the representative commercial name of the compound, hydrogen abstraction ability and 1 hour half-life temperature are shown. A polymerization initiator can be used individually by 1 type or in combination of 2 or more types.

  Among these, t-hexylperoxyisopropyl monocarbonate, t-hexylperoxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, t-butylperoxy Pivalate, t-hexylperoxypivalate, t-butylperoxyneodecanoate, t-hexylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate 1,1-bis (t-hexylperoxy) cyclohexane, benzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide, 2,2′-azobis (2-methylpropionitrile), 2,2'-azobis (2-methylbutyronitrile), dimethyl 2,2'-azobis 2-methylpropionate) is preferred; t-hexylperoxy 2-ethylhexanoate, 1,1-bis (t-hexylperoxy) cyclohexane, dimethyl 2,2′-azobis (2-methylpropionate) ) Is more preferable.

  The amount of the polymerization initiator used in the first stage is preferably 0.00001 to 0.02 parts by mass, more preferably 0.0001 to 0.01 parts by mass with respect to 100 parts by mass of the monomer mixture (I). It is. If the amount of the polymerization initiator used is too small, the reaction rate tends to be slow and the productivity tends to decrease. If there are too many polymerization initiators, the polymerization rate tends to be too high and control tends to be difficult.

  The polymerization temperature T1 in the first stage is preferably 110 to 170 ° C, more preferably 120 to 150 ° C, still more preferably 130 to 150 ° C. When the temperature T1 is too low, the viscosity of the reaction solution becomes high, and a large power tends to be required for mixing. When temperature T1 is too high, the amount of terminal double bonds of the obtained polymer (a) increases, and the thermal stability of the resulting methacrylic resin tends to decrease.

  The polymerization reaction in the first stage is preferably carried out for an average residence time of 0.5 to 4 hours, more preferably 1 to 3 hours. As the average residence time becomes shorter, the required amount of the polymerization initiator tends to increase. When the required amount of the polymerization initiator increases, it tends to be difficult to control the polymerization reaction and to adjust the molecular weight. On the other hand, the longer the average residence time, the longer it takes for the reaction to reach a steady state, and the productivity tends to decrease.

  The weight average molecular weight of the polymer (a) produced in the first stage is more than 50,000, preferably more than 50,000 and not more than 200,000, more preferably more than 50,000 and not more than 150,000. When the weight average molecular weight of the polymer (a) is too low, the mechanical strength and chemical resistance of the resulting methacrylic resin tend to decrease. On the other hand, when the weight average molecular weight of the polymer (a) is too high, the moldability of the resulting methacrylic resin tends to decrease.

  The polymer (a) produced in the first stage has a mass ratio of a repeating unit derived from methyl methacrylate and a repeating unit derived from a vinyl monomer copolymerizable therewith, preferably from 50/50 to 50/50. 100/0, more preferably 80/20 to 99/1, still more preferably 90/10 to 98/2.

  In the reaction liquid (I) obtained in the first stage, the polymer (a) is preferably contained in an amount of 10% by mass or more, more preferably 30 to 70% by mass, and further preferably 40 to 60% by mass. If the proportion of the polymer (a) contained in the reaction liquid (I) is too small, the productivity tends to decrease. When the ratio of the polymer (a) contained in the reaction liquid (I) is too large, the viscosity of the reaction liquid (I) increases, and there is a tendency that a large power is required for mixing.

[Second stage]
Next, in the second stage, the polymer (a) and the polymer (b) are included by mixing the monomer mixture (II) with the reaction liquid (I) and performing bulk polymerization or solution polymerization. Reaction liquid (II) is obtained. In the second stage, the unreacted monomer mixture (I) and the monomer mixture (II) newly added in the second stage are polymerized.

The monomer mixture (II) used in the second stage contains methyl methacrylate in excess of 50% by mass, preferably 80 to 100% by mass, more preferably 90 to 100% by mass. In the monomer mixture (II) used in the second stage, the vinyl monomer copolymerizable with methyl methacrylate is less than 50% by mass, preferably 0 to 20% by mass, more preferably 0. -10 mass% may be contained.
The content of methyl methacrylate in the monomer mixture (II) is set higher than the content of methyl methacrylate in the monomer mixture (I). The difference between the content of methyl methacrylate in the monomer mixture (II) and the content of methyl methacrylate in the monomer mixture (I) is preferably 1% by mass or more, more preferably 2% by mass. Above, more preferably 3% by mass or more, particularly preferably 4% by mass or more. When the content of methyl methacrylate in the monomer mixture (II) is lower than the content of methyl methacrylate in the monomer mixture (I), the transparency and heat resistance of the resulting methacrylic resin are There is a tendency to decrease.

  The monomer mixture (II) is subjected to bulk polymerization or solution polymerization as a raw material liquid (II) containing the monomer mixture (II). Such raw material liquid (II) can further contain an initiator, a chain transfer agent, and a solvent.

  The amount of the monomer mixture (II) mixed with the reaction liquid (I) is 0.02 to 1.0 times by mass of the monomer mixture (I) subjected to the first stage, preferably 0.03 to It is 0.5 mass times, More preferably, it is 0.05-0.3 mass times.

The polymerization in the second stage is a reaction apparatus including at least one tank type reactor (hereinafter referred to as a tank type reaction apparatus (2)). > Is preferable. The tank reactor (2) may be a batch type or a flow type, but is preferably a flow type. When two or more reactors are connected in series, the raw material liquid (II) containing the monomer mixture (II) can be added to one of the reactors at a time. You may divide and add to a vessel.
The polymerization in the second stage is referred to as a reaction apparatus including at least one tank reactor (hereinafter referred to as a tank reaction apparatus (2a)). > And the tubular reactor (2b) connected downstream thereof. The tank reactor (2a) may be a batch type or a flow type, but a flow type is preferable.

The batch tank reactor (2) and the batch tank reactor (2a) are composed of a reaction liquid (I) containing the polymer (a) obtained in the tank reactor (1) and a monomer mixture ( II) containing raw material liquid (II) is charged into a tank reactor, polymerized in the tank reactor, and when the predetermined polymerization conversion rate is reached, the reaction liquid is completely transferred from the tank reactor. It is a device for discharging.
The flow tank reactor (2) and the flow tank reactor (2a) are composed of a reaction liquid (I) containing the polymer (a) obtained in the tank reactor (1) and a monomer mixture ( The raw material liquid (II) containing II) is supplied to the tank reactor at a constant flow rate, and the polymerization reaction is performed while maintaining the inside of the tank reactor in a steady state, and the flow rate is balanced with the supply amount from the tank reactor. This is a device for discharging the reaction liquid.
The tank reactor is usually provided with stirring means such as a stirring blade. In the tank reactor, the mixed solution in the reactor is preferably mixed almost uniformly by stirring means, and more preferably completely mixed. As the tank reactor, a commercially available complete mixing tank reactor can be used. Even if the flow tank reactor (2) and the flow tank reactor (2a) are composed of one tank reactor, two or more tank reactors are connected in series. It may be configured.

The tubular reactor <2b> is composed of at least one tubular or tower flow reactor. The tubular reactor <2b> is a constant flow rate of the reaction liquid (II ₀ ) containing the polymer obtained in the tank reactor (2a) and the raw material liquid containing the monomer mixture (II) if necessary. A flow rate that is supplied to a tube-type or column-type flow reactor, increases the polymerization conversion rate while passing through the flow-type reactor, and balances the supply amount from the tube-type or column-type flow reactor. This is a device for discharging the reaction liquid. In such a flow reactor, when the tube diameter or column diameter is very small compared to the tube length or column height, the liquid flowing in the flow reactor is theoretically a complete plug flow (plug flow). A baffle plate or a packing may be provided in the flow reactor. As the tower-type flow reactor, for example, a reactor having a tower height / column diameter (L / D) ratio of 3 or more having a multistage stirring blade inside and a heat transfer tube for heat removal between each stage. Can be used. As the tubular flow reactor, for example, a reactor having a tube length / tube diameter (L / D) ratio of 5 or more with a built-in heat transfer tube for heat removal and mixing, specifically Sumitomo Heavy Industries An SMR reactor manufactured by Kogyo Co., a reactor with a built-in static mixer manufactured by Noritake Company, and a reactor with a built-in high mixer manufactured by Toray are listed. Among these, a static reactor built-in type tubular reactor is preferable.

  The tubular reactor <2b> is preferably divided into two or more regions so that the inner wall temperature gradually increases from the raw material liquid inlet side toward the reaction liquid outlet side. For example, in a single pipe-type flow reactor, the inner wall temperature in the upstream part is lowered and the inner wall temperature in the downstream part is raised; the pipe-type flow reactor with a low inner wall temperature and the pipe type with a high inner wall temperature In which the flow reactors are connected in series. In the present invention, the tubular reactor is divided into two regions, the inner wall temperature on the reaction liquid introduction side is set to 140 to 160 ° C., the inner wall temperature on the reaction liquid discharge side is set to 150 to 200 ° C. It is more preferable that the height is gradually increased from the side toward the reaction solution outlet side.

In bulk polymerization or solution polymerization in the second stage, polymerization auxiliary materials such as a polymerization initiator and a chain transfer agent can be added as necessary.
The method for adding the polymerization auxiliary material is not particularly limited, but a mixer is connected immediately upstream of the reaction apparatus, and the mixture is reacted with the raw material liquid (II) containing the polymerization auxiliary material and the monomer mixture (II). Liquid (I); or such monomer mixture (II), raw material liquid (II) containing a polymerization auxiliary material, and reaction liquid (I) are preferably mixed and then introduced into the reactor. As the mixer, a static mixer is preferable. In the case of a flow reactor, a polymerization auxiliary material can be added from an intermediate portion of the flow reactor.

  Examples of the chain transfer agent used in the second stage can include the same chain transfer agents as those used in the first stage. The amount of the chain transfer agent used in the second stage is not particularly limited as long as a polymer (b) having a weight average molecular weight described later is obtained.

  The polymerization initiator used when polymerizing in the tank reactor in the second stage has a hydrogen abstraction ability of preferably 30% or less, more preferably 20% or less, and even more preferably 10% or less. When the hydrogen abstraction ability of the polymerization initiator used is too high, the amount of the low molecular weight polymer contained in the resulting methacrylic resin increases so that mold fouling tends to occur and the heat resistance tends to decrease. is there. Such a polymerization initiator has a one-hour half-life temperature of preferably 60 to 140 ° C, more preferably 80 to 120 ° C. Specific examples of such a polymerization initiator can include the same ones listed as those used in the first stage. The amount of the polymerization initiator is preferably 0.00001 to 0.02 parts by mass, more preferably 0 with respect to 100 parts by mass of the total amount of the monomer mixture (I) and the monomer mixture (II). 0.0001 to 0.01 parts by mass. If it is less than 0.00001 parts by mass, the reaction rate may be slow and productivity may be reduced. If it is used in excess of 0.02 parts by mass, the polymerization rate may become too fast, making control difficult.

  The polymerization initiator used when polymerizing in the tubular reactor in the second stage has a hydrogen abstraction capacity of preferably 40% or less, more preferably 35% or less. When the hydrogen abstraction ability of the polymerization initiator used is too high, the amount of the low molecular weight polymer contained in the resulting methacrylic resin increases so that mold fouling tends to occur and the heat resistance tends to decrease. is there. Such a polymerization initiator has a one-hour half-life temperature of preferably 100 to 160 ° C, more preferably 110 to 150 ° C. Specific examples of such a polymerization initiator include t-butyl peroxyacetate (for example, manufactured by NOF Corporation, perbutyl A, hydrogen abstraction capacity 38%, 1 hour half-life temperature 120.9 ° C.), t-butyl peroxy- 3,5,5-trimethylhexanoate (for example, manufactured by NOF Corporation, perbutyl 335, hydrogen abstraction ability 36%, 1 hour half-life temperature 119.3 ° C.), 2,2-di (t-butylperoxy) Butane (for example, manufactured by NOF Corporation, Perhexa 22, hydrogen abstraction capacity 35%, 1 hour half-life temperature 121.7 ° C.), 1,1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane (For example, manufactured by NOF Corporation, Perhexa 3M, hydrogen abstraction ability 38%, 1 hour half-life temperature 109.2 ° C.), 1,1-di (t-butylperoxy) cyclohexane (eg manufactured by NOF Corporation) Perhexa C, hydrogen drawing capacity 35%, 1 hour half-life temperature 111.1 ° C., 2,2-di (4,4-di-t-butylperoxycyclohexyl) propane (for example, Pertetra A manufactured by NOF Corporation) , Hydrogen abstraction capacity 34%, 1 hour half-life temperature 114.0 ° C., di-t-butylperoxy-2-methylcyclohexane (for example, manufactured by NOF Corporation, Perhexa MC, hydrogen abstraction capacity 33%, 1 hour half) Period temperature 102.4 ° C.), t-hexyl hydroperoxide (for example, manufactured by NOF Corporation, perhexyl Z: hydrogen abstraction capacity 27%, 1 hour half-life temperature 114.2 ° C.), 1,1-di (t- (Hexylperoxy) cyclohexane (for example, manufactured by NOF Corporation, Perhexa HC: hydrogen abstraction capacity 10%, 1 hour half-life temperature 107.3 ° C.), t-hexylperoxyisopropyl monocarbonate Doo (e.g. NOF Corp., Perhexyl I: hydrogen abstraction ability of 18%, 1 hour half-life temperature 114.0 ° C.) include organic peroxides such as. These polymerization initiators can be used alone or in combination of two or more. In the parentheses after the compound name, the representative commercial name of the compound, hydrogen abstraction ability and 1 hour half-life temperature are shown. Among these, 1,1-di (t-butylperoxy) cyclohexane, 2,2-di (4,4-di-t-butylperoxycyclohexyl) propane, 1,1-di (t-hexylper) Oxy) cyclohexane is preferred. Such a polymerization initiator is preferably used after being dissolved in an inert solvent at a concentration of 1 to 50% by mass. Examples of the inert solvent include alcohols such as methanol and ethanol; aromatic hydrocarbons such as toluene, ethylbenzene and xylene; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone. Of these, toluene, ethylbenzene, and xylene are preferable, and toluene and ethylbenzene are more preferable. These inert solvents can be used alone or in combination of two or more. The amount of the polymerization initiator is preferably 0.001 to 100 parts by mass of the total amount of the monomer mixture (II) and the unreacted monomer mixture (I) in the reaction liquid (I). 0.1 parts by mass, more preferably 0.002 to 0.02 parts by mass. If it is less than 0.001 part by mass, the reaction rate may be slow and the productivity may decrease. If it exceeds 0.1 parts by mass, the polymerization rate may become too fast and control may be difficult, or the molecular weight may tend to decrease. The unreacted monomer mixture (I) in the reaction liquid (I) is calculated from the polymerization conversion measured by a gas chromatograph described later.

  The lower limit of the polymerization temperature T2 or T2a in the tank reactor (2) or tank reactor (2a) is preferably 130 ° C., more preferably 140 ° C., and the upper limit thereof is (T1 + 30) ° C., more preferably (T1 + 20) ° C., more preferably (T1 + 10) ° C. If the polymerization temperature T2 or T2a is too high, the initiator that has not been used up in the first stage may be decomposed all at once in the second stage, making it difficult to control the reaction. The polymerization temperature T2 or T2a in the second stage is preferably higher than the polymerization temperature T1 in the first stage. If the polymerization temperature T2 or T2a in the second stage is lower than the polymerization temperature T1 in the first stage, energy loss may increase, which may be disadvantageous from the viewpoint of production efficiency.

The polymerization temperature T2b in the tubular reactor (2b) is preferably 140 to 190 ° C, more preferably 150 to 170 ° C, and further preferably 150 to 160 ° C. When the polymerization temperature is too low, the viscosity of the reaction solution tends to increase. On the other hand, when the polymerization temperature is too high, the amount of terminal double bonds in the polymer increases, and the thermal stability of the resulting methacrylic resin tends to decrease.
The difference between the polymerization temperature T2b in the tubular reactor (2b) and the polymerization temperature T2a in the tank reactor (2a) is preferably 30 ° C. or less, more preferably 20 ° C. or less, and even more preferably 10 ° C. or less. . If the difference in polymerization temperature is too large, the initiator remaining without being used up in the polymerization reaction in the tank reactor (2a) decomposes all at once in the tubular reactor (2b), making it difficult to control the reaction temperature. There is a case.
The polymerization temperature T2b in the tubular reactor (2b) is preferably higher than the polymerization temperature T2a in the tank reactor (2a). If the polymerization temperature T2b in the tubular reactor (2b) is lower than the polymerization temperature T2a in the tank reactor (2a), energy loss increases, which may be disadvantageous in terms of production efficiency.

  In the case of a tank reactor, the polymerization reaction in the second stage is preferably carried out for an average residence time of 0.2 to 3 hours, more preferably 0.5 to 2 hours. The shorter the average residence time, the smaller the volume of the reactor and the more difficult it is to remove heat. On the other hand, the longer the average residence time, the longer it takes for the reaction to reach a steady state, and the productivity tends to decrease.

  In the case of a tubular reactor, the polymerization reaction in the second stage is preferably carried out as an average residence time of 10 minutes to 3 hours, more preferably 10 minutes to 1 hour. As the average residence time becomes shorter, the required amount of the polymerization initiator tends to increase. When the required amount of the polymerization initiator is increased, it is difficult to control the reaction and it may be difficult to adjust the molecular weight. On the other hand, the longer the average residence time, the higher the equipment cost and the lower the productivity.

  The polymer contained in the reaction liquid (II) obtained in the second stage includes the polymer (a) polymerized in the first stage (tank reactor (1)) and the second stage (tank reactor ( 2)) containing the polymer polymerized in (b), or polymer (a) polymerized in the first stage (tank reactor (1)) and the second stage (tank reactor) (2a) and the polymer (b) polymerized in the tubular reactor (2b)).

Further, the polymer contained in the reaction liquid (II ₀ ) obtained in the tank reactor (2a) is composed of the polymer (a) polymerized in the first stage (tank reactor (1)), It is presumed to contain the polymer (b) polymerized in the two-stage tank reactor (2a).

  The polymer (b) produced in the second stage has a weight average molecular weight of 20,000 to 50,000, preferably 20,000 to 40,000, more preferably 30,000 to 40,000. When the weight average molecular weight of the polymer (b) is too low, the mechanical strength and chemical resistance of the resulting methacrylic resin tend to decrease. On the other hand, when the weight average molecular weight of the polymer (b) is too high, the moldability of the resulting methacrylic resin tends to decrease.

In the polymer (b) produced in the second stage, the mass ratio of the repeating unit derived from methyl methacrylate and the repeating unit derived from a vinyl monomer copolymerizable therewith is preferably 50/50 to It is in the range of 100/0, more preferably in the range of 80/20 to 99/1, still more preferably in the range of 90/10 to 98/2.
Further, the content a _m (% by mass) of repeating units derived from methyl methacrylate in the polymer (a) produced in the first stage and the methacryl in the polymer (b) produced in the second stage The difference from the content b _m (% by mass) of the repeating unit derived from methyl acid is preferably within ± 1% by mass, more preferably within ± 0.8% by mass, and ± 0.5 More preferably, it is within mass%. when the difference between a _m and b _m is large, there is a tendency that transparency of the obtained methacrylic resin is lowered. Further, a _m ≦ b _m is preferable from the viewpoint of heat resistance.

The breakdown of 100 parts by mass of the polymer contained in the reaction liquid (II) obtained in the second stage is 60 to 90 parts by mass of the polymer (a) and 10 to 40 parts by mass of the polymer (b), preferably the polymer ( a) 60 to 85 parts by mass and polymer (b) 15 to 40 parts by mass, more preferably 65 to 85 parts by mass of polymer (a) and 25 to 35 parts by mass of polymer (b), still more preferably polymer ( a) 70 to 85 parts by mass and polymer (b) 15 to 30 parts by mass.
When there is too little quantity of a polymer (b), the improvement effect of the moldability of the methacrylic resin obtained is small. On the other hand, when the amount of the polymer (b) is too large, the mechanical strength and chemical resistance of the resulting methacrylic resin are extremely lowered.
In addition, since it is difficult to isolate the polymer (a) and the polymer (b) contained in the reaction liquid (II), 100 mass of the polymer contained in the reaction liquid (II) obtained in the second stage. The breakdown of the part is calculated from the amount of the polymer (a) produced in the first stage and the amount of the polymer contained in the reaction liquid (II) obtained in the second stage. The weight average molecular weight and monomer unit composition ratio of the polymer (b) are the same as the weight average molecular weight and monomer unit composition ratio measured for the polymer (a) produced in the first stage. The weight average molecular weight and monomer unit composition ratio measured for the polymer contained in the reaction liquid (II) obtained in the above and the breakdown of 100 parts by mass of the polymer contained in the reaction liquid (II) obtained in the second stage And calculated from

The amount of the reaction liquid (II) obtained in the second stage is 105 to 300 parts by mass, preferably 125 to 250 parts by mass, as the total of the polymer (a) and the polymer (b) contains 100 parts by mass. When the second stage is carried out in the tank reactor (2), it is preferably 125 to 300 parts by mass, more preferably 140 to 250 parts by mass, and the second stage is a tank reactor (2a). ) And a tubular reactor (2b) connected downstream thereof, preferably 105 to 250 parts by mass, more preferably 125 to 200 parts by mass. In addition, the amount of the polymer contained in the reaction liquid (II ₀ ) obtained in the tank reactor (2a) is the amount of the polymer (polymer (a) and polymer (b) contained in the reaction liquid (II). The total amount is preferably 70 to 95 parts by mass, more preferably 75 to 90 parts by mass with respect to 100 parts by mass.

[Methacrylic resin]
In the method for producing a methacrylic resin according to the present invention, it is preferable to separate and remove volatile components mainly composed of unreacted monomers and / or solvents after completion of the multistage polymerization reaction as described above. The removal method is not particularly limited, but the reaction solution (II) sent continuously is heated under reduced pressure, preferably 180 to 300 ° C., more preferably 200 to 270 ° C. The method of separating and removing is preferable. If the heating temperature is too low, it may take time to separate and remove the volatile matter, or the separation and removal of the volatile matter may be insufficient, resulting in appearance defects such as silver in the molded product. If the heating temperature is too high, the methacrylic resin may be colored due to oxidation or burning. Examples of the apparatus for separating and removing volatile components include a flash drum, a biaxial devolatilizer, a thin film evaporator, and an extruder. The amount of residual volatile components after separating and removing volatile components is preferably 0.5% by mass or less, more preferably 0.4% by mass or less, and further preferably 0.3% by mass or less. If the amount of residual volatile components exceeds 0.5% by mass, the heat distortion temperature or the like tends to decrease, or the molded product may have poor appearance such as silver. A methacrylic resin can be obtained as described above.

  The molecular weight distribution (= weight average molecular weight / number average molecular weight) of the methacrylic resin obtained by the production method of the present invention is preferably 1.6 or more, more preferably 1.7 or more, still more preferably 1.8 or more, particularly Preferably it is 1.9 or more, most preferably 2 or more. If the molecular weight distribution is too narrow, the fluidity of the methacrylic resin tends to be insufficient. The weight average molecular weight and molecular weight distribution of the methacrylic resin can be controlled by adjusting the types and amounts of the polymerization initiator and the chain transfer agent.

  The methacrylic resin obtained by the production method of the present invention includes an ultraviolet absorber, a light stabilizer, an antioxidant, a thermal degradation inhibitor, a release agent, a polymer processing aid, an organic dye, light as necessary. A diffusing agent, a phosphor, an impact resistance modifier, a flame retardant, a lubricant, an antistatic agent, and the like can be added. Moreover, the methacrylic resin obtained by the production method of the present invention can be used after diluted with a methacrylic resin obtained by another production method. In addition, other resins such as AS resin, ABS resin, AES resin, AAS resin, MS resin, MBS resin, styrene resin, high impact polystyrene resin, and vinyl chloride resin can be used.

  Examples of the ultraviolet absorber include benzophenones, benzotriazoles, triazines, benzoates, salicylates, cyanoacrylates, succinic anilides, malonic esters, and formamidines. These can be used alone or in combination of two or more.

Among these, any one or a combination of a benzotriazole ultraviolet absorber and an ultraviolet absorber having a maximum value ε _max of a molar extinction coefficient at a wavelength of 380 to 450 nm of 1200 dm ³ · mol ⁻¹ cm ⁻¹ or less is preferable. . A benzotriazole-based ultraviolet absorber has a high effect of suppressing deterioration of the resin due to ultraviolet rays, particularly a decrease in optical properties due to coloring, and is suitable for adding such properties to the methacrylic resin obtained by the production method of the present invention. Further, an ultraviolet absorber having a maximum value ε _max of a molar extinction coefficient at a wavelength of 380 to 450 nm of 1200 dm ³ · mol ⁻¹ cm ⁻¹ or less is required to have such characteristics because the yellowness of the obtained molded product can be suppressed. It is suitable for the use.

In addition, the maximum value ε _max of the molar extinction coefficient of the ultraviolet absorber was calculated as follows. First, 10.00 mg of a UV absorber having a molecular weight of M _UV was sufficiently dissolved in 1 L of cyclohexane so that there was no undissolved substance by visual observation. This solution was poured into a 1 cm × 1 cm × 3 cm quartz glass cell, and the absorbance at a wavelength of 380 to 450 nm was measured using a U-3410 spectrophotometer manufactured by Hitachi, Ltd. The maximum value ε _max of the molar extinction coefficient was calculated from the maximum absorbance (A _max ) using the following equation.

ε _max = [A _max / (10 × 10 ⁻³ )] × M _UV

As an ultraviolet absorber having a maximum molar extinction coefficient ε _{max at a} wavelength of 380 to 450 nm of 1200 dm ³ · mol ⁻¹ cm ⁻¹ or less, 2-ethyl-2′-ethoxy-oxalanilide (Clariant Japan, Inc .; product) Name Sundeyuboa VSU).

  The amount of the ultraviolet absorber used is preferably 0.001 to 1 part by mass, more preferably 0.01 to 0.5 part by mass, and still more preferably 0.1 to 0.100 parts by mass with respect to 100 parts by mass of the methacrylic resin. 3 parts by mass. If the amount of the ultraviolet absorber used is too small, there is a tendency that the effect of suppressing resin deterioration due to ultraviolet rays is not sufficiently exhibited. If the amount of UV absorber used is too large, the mold will be easily soiled during molding, which may lead to a decrease in yield and productivity due to mold cleaning. It tends to occur.

In the present invention, a light stabilizer such as a compound having a 2,2,6,6-tetraalkylpiperidine skeleton or a hindered amine may be further contained.
Examples of hindered amines include dimethyl succinate / 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, poly ((6- (1,1,3 , 3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl) ((2,2,6,6-tetramethyl-4-pipedyl) imino) hexamethylene ((2,2, 6,6-tetramethyl-4-pipedyl) imino)), 2- (2,3-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2, 6,6-pentamethyl-4-piperidyl), 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl) -4-piperidyl), N, N′-bis (3-a Minopropyl) ethylenediamine / 2,4-bis (N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino) -6-chloro-1,3,5-triazine condensate Examples thereof include bis (2,2,6,6-tetra-methyl-4-pipedyl) sebacate and bis (2,2,6,6-tetramethyl-4-piperidyl) succinate. These can be used alone or in combination of two or more.
The amount of the light stabilizer used is preferably 0.001 to 0.5 parts by mass, more preferably 0.005 to 0.1 parts by mass with respect to 100 parts by mass of the methacrylic resin.

  Examples of the antioxidant include phosphorus antioxidants, hindered phenol antioxidants, and thioether antioxidants. These can be used alone or in combination of two or more. Among these, phosphorus antioxidants and hindered phenol antioxidants are preferably used from the viewpoint of preventing the deterioration of optical properties due to coloring.

  Examples of phosphorus antioxidants include 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite and bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphos. Phyto, tris (2,4-di-t-butylphenyl) phosphite, tetrakis (2,4-di-t-butylphenyl) [1,1-biphenyl] -4,4′-diylbisphosphonite, bis [ 2,4-bis (1,1-dimethylethyl) -6-methylphenyl] ethyl ester phosphorous acid. Among these, 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite and tris (2,4-di-t-butylphenyl) phosphite are preferable.

  Examples of the hindered phenol antioxidant include triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3 , 5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis (n-octyl) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3, 5-triazine, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,2-thio-diethylenebis [3- (3,5-di-t -Butyl-4-hydroxyphenylpropionate), octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexameth Tylene bis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-t-butyl-4-hydroxybenzyl phosphonate-diethyl ester, 1,3,5-trimethyl -2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, octyl Diphenylamine, 2,4-bis [(octylthio) methyl] -o-cresol, isooctyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate. Among these, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (trade name “IRGANOX1010”, manufactured by Ciba Special Chemicals), octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (trade name “IRGANOX1076”, manufactured by Ciba Special Chemicals) is preferable.

  The amount of the antioxidant used is preferably 0.001 to 1 part by mass, more preferably 0.005 to 0.5 part by mass, and still more preferably 0.01 to 0.100 parts by mass with respect to 100 parts by mass of the methacrylic resin. 3 parts by mass. If the amount of the antioxidant used is too small, the effect of preventing coloring when exposed to high temperatures of the molded product tends to be insufficient. On the other hand, if the amount of antioxidant used is too large, it will cause a decrease in yield due to mold contamination and a decrease in productivity due to mold cleaning. There is a tendency for the burn to occur and the hue to decrease, or foreign matter to be generated in the molded product.

Examples of the thermal degradation inhibitor include a compound having a structure represented by the formula (α), specifically, 2-t-butyl-6- (3′-t-butyl-5′-methyl-hydroxybenzyl)- 4-methylphenyl acrylate (Sumitomo Chemical Co., Ltd .; trade name “Sumilyzer GM”), 2,4-di-t-amyl-6- (3 ′, 5′-di-t-amyl-2′-hydroxy-) α-methylbenzyl) phenyl acrylate (Sumitomo Chemical Co., Ltd .; trade name “Sumilyzer GS”), 2-t-butyl-6- (3′-t-butyl-2′-hydroxy-5′-methyl-methylbenzyl) ) -4-methylphenyl acrylate, 2,5-di-t-butyl-6- (3′-5′-di-t-butyl-2′-hydroxymethylbenzyl) -phenyl acrylate.
Among these, 2-t-butyl-6- (3′-t-butyl-5′-methyl-hydroxybenzyl) -4-methylphenyl acrylate, 2,4-di-t-amyl-6- (3 ′ , 5'-di-t-amyl-2'-hydroxy-α-methylbenzyl) phenyl acrylate, 2,4-di-t-amyl-6- (3 ', 5'-di-t-amyl- 2′-hydroxy-α-methylbenzyl) phenyl acrylate is more preferred.

（式（α）中、Ｒ¹〜Ｒ⁴は、それぞれ独立に、１〜５個の炭素原子を有するアルキル基を示し、Ｒ⁵は１〜５個の炭素原子を有するアルキル基または水素原子を示す。）

(In formula (α), R ^{1 to} R ⁴ each independently represents an alkyl group having 1 to 5 carbon atoms, and R ⁵ represents an alkyl group having 1 to 5 carbon atoms or a hydrogen atom. Show.)

  The amount of the heat degradation inhibitor used is preferably 0.001 to 1 part by weight, more preferably 0.005 to 0.5 part by weight, and still more preferably 0.01 to 0 part per 100 parts by weight of the methacrylic resin. .2 parts by mass. When there is too little usage-amount of a heat deterioration inhibiting agent, there exists a tendency for the heat deterioration preventing effect to be hard to be acquired. On the other hand, if the amount of the heat deterioration inhibitor used is too large, it tends to cause a decrease in yield due to mold contamination and a decrease in productivity due to mold cleaning during injection molding. There is a tendency that eyes are easily formed at the time of extrusion molding.

Examples of the mold release agent include higher alcohol and / or glycerin monoester. Examples of the higher alcohol include cetyl alcohol and stearyl alcohol. Examples of the glycerin monoester used in the present invention include glycerides of higher fatty acids such as stearic acid monoglyceride and stearic acid diglyceride. When the higher alcohol and glycerol monoester are used in combination, the ratio is not particularly limited, but the mass ratio of higher alcohol / glycerol monoester is preferably 2.5 / 1 to 3.5 / 1, more preferably 2.8. / 1 to 3.2 / 1.
The amount of the release agent used is preferably 0.5 parts by mass or less, more preferably 0.3 parts by mass or less, and 0.1 parts by mass or less with respect to 100 parts by mass of the methacrylic resin. More preferably it is. Excessive use of mold release agent tends to reduce yield due to mold contamination and productivity due to mold cleaning, and may cause defects in molded products due to the occurrence of silver, and extrusion molding. There is a tendency that the eyes and the eyes of time are likely to occur.

The polymer processing aid is effective in improving thickness accuracy and thin film moldability when molding a methacrylic resin. The intrinsic viscosity of the polymer processing aid is preferably 3 to 6 dl / g. When the intrinsic viscosity is too small, a sufficient improvement effect on moldability is not recognized. When the intrinsic viscosity is too large, the melt fluidity tends to be lowered.
The polymer processing aid can be produced, for example, by an emulsion polymerization method. The polymer processing aid obtained by this emulsion polymerization method is usually polymer particles having a particle size of 0.05 to 0.5 μm. The polymer particles may be single layer particles composed of polymers having a single composition ratio and single intrinsic viscosity, or multilayer particles composed of two or more polymers having different composition ratios or intrinsic viscosities. Among these, particles having a two-layer structure having a low intrinsic viscosity polymer in the inner layer and a high intrinsic viscosity polymer having an intrinsic viscosity of 5 dl / g or more in the outer layer are preferable.
The amount of the polymer processing aid used is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the methacrylic resin. If the amount of the polymer processing aid used is too small, a sufficient improvement effect is not recognized in the thickness accuracy during molding. On the other hand, if the amount of the polymer processing aid used is too large, the melt fluidity tends to be lowered.

Examples of the organic dye include terphenyl having a function of converting ultraviolet light, which is considered harmful to the resin, into visible light.
Examples of the light diffusing agent include glass fine particles, polysiloxane-based crosslinked fine particles, and crosslinked polymer fine particles.
Examples of the phosphor include fluorescent pigments, fluorescent dyes, fluorescent white dyes, fluorescent whitening agents, and fluorescent bleaching agents.

  Examples of the impact resistance modifier include a core-shell type modifier that includes acrylic rubber or diene rubber as a core layer component, and a modifier that includes a plurality of rubber particles. The impact modifier is preferably added in less than normal levels to improve some properties.

  Examples of the flame retardant include organic halogen flame retardants such as tetrabromobisphenol A, decabromodiphenyl oxide, and brominated polycarbonate; non-halogen flame retardants such as antimony oxide, aluminum hydroxide, zinc borate, and tricresyl phosphate. Etc.

  Examples of the lubricant include stearic acid, behenic acid, stearamic acid, methylene bisstearamide, hydroxystearic acid triglyceride, paraffin wax, ketone wax, octyl alcohol, and hardened oil.

  Examples of the antistatic agent include stearoamidopropyldimethyl-β-hydroxyethylammonium nitrate.

  If the methacrylic resin obtained by the production method of the present invention is used, a molded article having excellent transparency can be obtained. For example, molded articles having various shapes can be obtained by known melt-heating molding such as injection molding, compression molding, extrusion molding, and vacuum molding.

  Since the methacrylic resin obtained by the production method of the present invention is excellent not only in transparency but also in heat resistance, chemical resistance and moldability, it is suitable for various applications. Applications include, for example, billboard supplies such as advertising towers, stand signboards, sleeve signboards, billboard signs, and rooftop signs; display supplies such as showcases, dividers, and store displays; fluorescent lamp covers, mood lighting covers, lamp shades, and light. Lighting products such as ceilings, light walls, and chandeliers; interior items such as pendants and mirrors; building parts such as doors, domes, safety window glass, partitions, staircases, balconies, roofs of leisure buildings; aircraft windshields, Transportation parts such as pilot visors, motorcycles, motorboat windshields, bus shading plates, automobile side visors, rear visors, head wings, headlight covers, meter covers, tail lamp covers; nameplates for audio visuals, stereo covers, TV protection Electronic devices such as masks and vending machines Parts: Medical equipment parts such as incubators and X-ray parts; equipment-related parts such as machine covers, instrument covers, experimental devices, rulers, dials, observation windows; LCD protective plates, light guide plates, light guide films, Fresnel lenses, lenticulars Optical parts such as lenses, front plates and diffusers for various displays; traffic-related parts such as road signs, guide boards, curve mirrors, and sound barriers; surface materials for automobile interiors, surface materials for mobile phones, films such as marking films Materials: Household appliances such as washing machine canopy and control panels, rice cooker top panels; other greenhouses, large water tanks, box water tanks, clock panels, bathtubs, sanitary, desk mats, game parts, toys, welding For example, a face protection mask.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.
The measurement or evaluation of physical property values in Examples and Comparative Examples was performed by the following method.

(Hydrogen abstraction ability of polymerization initiator)
α-Methylstyrene dimer (1.0 mol), cyclohexane (6.9 mol) and a polymerization initiator (0.05 mol) were placed in a glass ampoule and purged with nitrogen to be substantially oxygen-free and sealed. The temperature was raised to the following temperature corresponding to the 10-hour half-life temperature of the polymerization initiator and left at that temperature for 60 hours.
For polymerization initiators with a 10-hour half-life temperature exceeding 80 ° C: 140 ° C
In the case of a polymerization initiator having a 10-hour half-life temperature of 60 ° C to 80 ° C: 100 ° C
In the case of a polymerization initiator having a 10-hour half-life temperature of less than 60 ° C: 80 ° C
The number of moles of cyclohexane (H [mol]) in the reaction solution after being allowed to stand was measured with a gas chromatograph, and the hydrogen abstraction ability was determined by the following equation.
Hydrogen abstraction capacity (%) = [(6.9−H) / (0.05 × 2)] × 100

(Measurement of polymerization conversion of monomer mixture)
A gas chromatograph GC-14A manufactured by Shimadzu Corporation was added to GL Sciences Inc. Column INERT CAP 1 (df = 0.4 μm, 0.25 mm ID × 60 m) is set, injection temperature is 180 ° C., detector temperature is 180 ° C., column temperature is 60 ° C. (maintained for 5 minutes) → heating rate is 10 The measurement was carried out by controlling the temperature from ° C./min to 200 ° C. (held for 10 minutes). The polymerization conversion rate was calculated based on this measured value and a calibration curve for each monomer.

(Mass of polymer in reaction solution and mass ratio of polymer (a) and polymer (b))
The mass of the polymer in the reaction solution was calculated from the polymerization conversion rate and the amount of the monomer mixture used.
Further, from the mass of the polymer (a) in the reaction liquid (I) after the first stage calculated as described above and the mass of the polymer in the reaction liquid (II) after the second stage, the polymer (a ) And the polymer (b).

(Measurement of number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn))
Tosoh's gel permeation chromatograph (HLC-8020) is connected to Tosoh's column TSKgel G2000HHR (one) and GMHRHR-M (two) in series, and tetrahydrofuran is used as the eluent. Measurement was performed using a differential refractive index (RI) meter for detection under conditions of a flow rate of 1.0 ml / min and a column temperature of 40 ° C. By converting the measured value into the molecular weight of standard polystyrene, the number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) of the polymer were determined.

  According to this measurement method, when the reaction liquid A collected from the tank reactor A is analyzed, the weight average molecular weight (Mwa) of the polymer (a) can be obtained, and the reaction liquid B collected from the tank reactor B is analyzed. By doing so, the weight average molecular weight (MwB) of the polymer B can be determined. In Example 4, the weight average molecular weight (MwC) of the polymer C can be determined by analyzing the reaction solution C collected from the tubular reactor C.

The polymer B is considered to contain the polymer (a) polymerized in the tank reactor A and the polymer (b) polymerized in the tank reactor B.
The polymer C is considered to contain the polymer B and the polymer (b) polymerized in the tubular reactor C (hereinafter referred to as polymer (c)). That is, the polymer C is considered to contain the polymer (a), the polymer (b), and the polymer (c).

The weight average molecular weight (Mw _b ) of the polymer (b) can be calculated by the following formula.

_{Mw b = [100 × Mw B} - (Mw a × Cont a)] / Cont b

Here, Cont _a, the polymer in the polymer B taken from the tank reactor B content of (a) [mass%], Cont _b is in the polymer B taken from the tank reactor B The content (% by mass) of the polymer (b) is shown. Cont _a and Cont _b can be calculated from the polymerization conversion rates in the tank reactor A and the tank reactor B, and the amounts of the monomer mixture (I) and the monomer mixture (II) used.

The weight average molecular weight (Mw _c ) of the polymer (c) can be calculated by the following formula.

Mw _c = [100 × Mw _C − (Mw _B × Cont _B )] / Cont _c

Here, Cont _B represents the content [% by mass] of the polymer B in the polymer C collected from the tubular reactor C, and Cont _c represents the content of the polymer C collected from the tubular reactor C. The content (% by mass) of the polymer (c) is shown. Cont _B and Cont _c can be calculated from the polymerization conversion rates in the tank reactor B and the tubular reactor C, and the amounts of the monomer mixture (I) and the monomer mixture (II) used.
Further, the number average molecular weight and molecular weight distribution of the polymer (a), the polymer (b) and the polymer (c) can be determined by the same method as described above.

(Measurement of the content of repeating units derived from methyl methacrylate)
A gas chromatograph GC-14A manufactured by Shimadzu Corp. E. G. A column BPX-5 (30 m × 0.25 mmφ, film thickness 0.5 μm) made by the company was set and decomposed at a decomposition temperature of 500 ° C. and analysis conditions: 40 ° C. (PYR-2A, manufactured by Shimadzu Corporation) Measurement was performed at a rate of temperature increase of 5 ° C./minute→250° C., and the content of repeating units derived from methyl methacrylate was calculated from the measurement results.

According to this measuring method, by analyzing the reaction liquid A collected from tank reactor A, it is possible to determine the content of the repeating unit derived from methyl methacrylate in the polymer (a) (a _m), By analyzing the reaction solution B collected from the tank reactor B, the content (B _m ) of repeating units derived from methyl methacrylate in the polymer B can be determined. By analyzing the reaction liquid C collected from the type reactor C, the content (C _m ) of repeating units derived from methyl methacrylate in the polymer C can be determined.

The content (b _m ) of repeating units derived from methyl methacrylate in the polymer (b) can be calculated by the following formula.

_{b m = [100 × B m} - (a m × Cont a)] / Cont b

Here, Cont _a, the polymer in the polymer B taken from the tank reactor B content of (a) [mass%], Cont _b is in the polymer B taken from the tank reactor B The content (% by mass) of the polymer (b) is shown. Cont _a and Cont _b can be calculated from the polymerization conversion rates in the tank reactor A and the tank reactor B, and the amounts of the monomer mixture (I) and the monomer mixture (II) used.

The content ( _cm ) of the repeating unit derived from methyl methacrylate in the polymer (c) can be calculated by the following formula.

c _m = [100 × C _m − (B _m × Cont _B )] / Cont _c

Here, Cont _B represents the content [% by mass] of the polymer B in the polymer C collected from the tubular reactor C, and Cont _c represents the content of the polymer C collected from the tubular reactor C. The content (% by mass) of the polymer (c) is shown. Cont _B and Cont _c can be calculated from the polymerization conversion rates in the tank reactor B and the tubular reactor C, and the amounts of the monomer mixture (I) and the monomer mixture (II) used.

(Evaluation of fluidity-1 (MFR))
Based on ISO1133, the melt flow rate (MFR) was measured at a temperature of 230 ° C. and a load of 37.3 N.

(Evaluation of fluidity-2 (Spiral flow length))
In a SE-180DU-HP molding machine manufactured by Sumitomo Heavy Industries, a spiral flow mold (with a clamping pressure of 180 tons, a screw diameter of 36 mm, a mold temperature of 80 ° C., a molding temperature of 285 ° C., an injection speed of 400 mm / sec, a filling pressure of 274 MPa) Injection molding was performed using a product thickness of 0.4 mm and a width of 10 mm. The spiral flow length of the methacrylic resin at that time was measured.

(Formability evaluation of thin light guide plate)
In a SE-180DU-HP molding machine manufactured by Sumitomo Heavy Industries, a clamping pressure of 180 tons, a screw diameter of 36 mm, a mold temperature of 85 ° C., a molding temperature of 290 ° C., an injection speed of 300 mm / sec, a filling pressure of 300 MPa, and a length of 31.5 mm An attempt was made to injection-mold a thin light guide plate having a width of 23.0 mm and a thickness of 0.65 mm.
As a result, the case where molding was possible without difficulty was evaluated as A, the case where sinking occurred at the end of the material to be filled was evaluated as B, and the case where molding was not possible due to unfilling was evaluated as C.

(Measurement of light transmittance and chromaticness index b ^* of molded product)
A test piece of 190 mm × 50 mm × 5 mm was cut out from a plate-like molded product obtained by molding with an injection molding machine, and using a spectrophotometer (UV-2550; manufactured by Shimadzu Corporation), wavelengths of 400 nm and 500 nm at an optical path length of 190 mm. The light transmittance (%) at 600 nm and the chromaticness index b ^* were measured.

(Measurement of tensile fracture stress of molded products)
The tensile fracture stress was measured based on ISO527-2 / 1A / 5.

(Measurement of heat resistance of molded products)
Based on ISO75-2, the deflection temperature under a load of 1.80 MPa was measured.

(Chemical resistance of molded products)
Chemical resistance was evaluated by a test generally called a cantilever method (based on ASTM F791-82). That is, a test piece for measuring tensile fracture stress in accordance with ISO 527-2 / 1A / 5 is supported by a linear fulcrum perpendicular to the length direction at the center in the length direction and placed in a horizontal state. Is fixed at one end, and a load of 400 g is applied near the other end 84 mm away from the central portion in the length direction, while bending elongation stress on the surface opposite to the support portion in the central portion in the length direction is concentrated. A 10 mm square filter paper soaked with ethanol was brought into contact. As a result, cracks were easily generated. The time until the test piece broke was measured. This test was repeated 7 times, and the average value was calculated.

(manufacturing device)
The production apparatus used in this example is an autoclave with a stirrer (I), an autoclave with a stirrer (II), a fully mixed tank reactor A and a fully mixed tank reactor B connected in series. The tank-type flow polymerization reactor and the twin screw extruder are provided. In addition, the tank reactor A and the tank reactor B are provided with a stirrer and a sampling tube, and have a volume such that a desired flow rate and an average residence time are obtained.
In the autoclaves (I) and (II), raw material liquids (I) and (II) containing the monomer mixture (I) and the monomer mixture (II) are prepared, respectively. The raw material liquid (I) is supplied to the tank reactor A via a pipe. The reaction liquid A discharged from the tank reactor A is mixed with the raw material liquid (II) in a pipe equipped with a static mixer manufactured by Noritake Engineering Co., supplied to the tank reactor B, and discharged from the tank reactor B. The reaction liquid B is supplied to a twin screw extruder through a pipe.

  Furthermore, a pipe in which a Noritake Engineering static mixer and a tubular reactor C Noritake Engineering static mixer are connected in series between the tank reactor B and the twin screw extruder. A mold flow type polymerization reactor can be attached. As a result, the reaction liquid B discharged from the tank reactor B is supplied to the tubular reactor C via a pipe equipped with a static mixer manufactured by Noritake Engineering Co., and the reaction liquid C discharged from the tubular reactor C is It is supplied to the twin screw extruder by piping. Each reactor is provided with a collection tube, and a small amount of reaction solution can be extracted from the collection tube to measure the properties of the polymer and the like.

Example 1
In an autoclave (I) with a stirrer, 94.5 parts by mass of purified methyl methacrylate, 5.5 parts by mass of methyl acrylate, 2,2′-azobis (2-methylpropionitrile) (“AIBN” Otsuka Chemical) Made by the company, hydrogen drawing ability: 1%, 1 hour half-life temperature: 82.6 ° C.) 0.006 parts by mass and 0.37 parts by mass of n-octyl mercaptan were charged and uniformly dissolved to obtain a raw material liquid (I). It was.
An autoclave with a stirrer (II) was charged with 100 parts by weight of purified methyl methacrylate, 0.015 parts by weight of 2,2′-azobis (2-methylpropionitrile) and 1.13 parts by weight of n-octyl mercaptan. The raw material liquid (II) was obtained by uniformly dissolving.
Next, the inside of the production apparatus was replaced with nitrogen to expel oxygen.

  The raw material liquid (I) is supplied from the autoclave (I) to the tank reactor A controlled at a temperature of 130 ° C. at a rate of 2 kg / hr, bulk polymerization is performed with an average residence time of 90 minutes, and the tank is charged at a rate of 2 kg / hr. The reaction liquid A containing the polymer (a) was discharged from the mold reactor A.

  Following this, the raw material liquid (II) is added from the autoclave (II) at 0.3 kg / hr to a pipe part equipped with a static mixer manufactured by Noritake Engineering Co., thereby flowing into the pipe part at 2 kg / hr. The reaction solution A containing the polymer (a) was continuously mixed. The mixed solution is supplied to a tank reactor B controlled at 140 ° C. at 2.3 kg / hr, bulk polymerization is performed with an average residence time of 60 minutes, and a polymer is transferred from the tank reactor B at 2.3 kg / hr. Reaction solution B containing B was discharged.

  Subsequently, the reaction solution B containing the polymer B discharged from the tank reactor B at 2.3 kg / hr is heated to 230 ° C., and the reaction solution B is supplied to the twin screw extruder controlled at 260 ° C. It was supplied at 3 kg / hr. In the twin-screw extruder, volatile components mainly composed of unreacted monomers were separated and removed, and the polymer B was extruded into a strand shape. The strand was cut with a pelletizer to obtain a pellet-shaped methacrylic resin.

When the continuous production operation was in a steady state, a small amount of the reaction solution was withdrawn from each sampling tube, and the physical properties were measured.
As a result, the polymer content in the reaction solution obtained in the tank reactor A was 46% by mass. The polymer (a) polymerized in the tank reactor A is composed of 95.9% by mass of repeating units derived from methyl methacrylate and 4.1% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 60,700.
The content of the polymer in the reaction solution obtained in the tank reactor B was 53% by mass. The polymer B contained in the reaction liquid B obtained in the tank reactor B is composed of 96.1% by mass of repeating units derived from methyl methacrylate and 3.9% by mass of repeating units derived from methyl acrylate, And the weight average molecular weight was 53,500.
The breakdown of 100 parts by mass of the polymer B was 76 parts by mass of the polymer (a) and 24 parts by mass of the polymer (b).
The polymer (b) polymerized in the tank reactor B is composed of 96.7% by mass of repeating units derived from methyl methacrylate and 3.3% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 30,700.
The obtained pellet-like methacrylic resin had a residual volatile content of 0.1% by mass.
A molded product was produced by injection molding using the pellet-like methacrylic resin and used for the above evaluation. The evaluation results are shown in Table 1.

Example 2
In an autoclave with a stirrer (I), 94.5 parts by mass of purified methyl methacrylate, 5.5 parts by mass of methyl acrylate, 0.006 parts by mass of 2,2′-azobis (2-methylpropionitrile) and A raw material liquid (I) was obtained by charging 0.37 parts by mass of n-octyl mercaptan and dissolving it uniformly.
An autoclave with a stirrer (II) was charged with 100 parts by mass of purified methyl methacrylate, 0.008 parts by mass of 2,2′-azobis (2-methylpropionitrile) and 4.49 parts by mass of n-octyl mercaptan. It was made to melt | dissolve uniformly and the raw material liquid (II) was obtained.
Next, the inside of the production apparatus was replaced with nitrogen to expel oxygen.

  The raw material liquid (I) is supplied from the autoclave (I) to the tank reactor A controlled at a temperature of 130 ° C. at a rate of 2 kg / hr, bulk polymerization is performed with an average residence time of 90 minutes, and the tank is charged at a rate of 2 kg / hr. The reaction liquid A containing the polymer (a) was discharged from the mold reactor A.

  Following this, the raw material liquid (II) is added from the autoclave (II) at a rate of 0.1 kg / hr to a pipe part equipped with a static mixer manufactured by Noritake Engineering Co., thereby flowing into the pipe part at a rate of 2 kg / hr. The reaction solution A containing the polymer (a) was continuously mixed. The mixed liquid is supplied to a tank reactor B controlled at 140 ° C. at 2.1 kg / hr, bulk polymerization is performed with an average residence time of 60 minutes, and a heavy polymerization is performed from the tank reactor B at 2.1 kg / hr. Reaction solution B containing coalescence B was discharged.

  Following this, the reaction solution B containing the polymer B discharged from the tank reactor B at 2.1 kg / hr is heated to 230 ° C., and the mixture is fed to a twin screw extruder controlled at 260 ° C. It was supplied at 1 kg / hr. In the twin-screw extruder, volatile components mainly composed of unreacted monomers were separated and removed, and the polymer B was extruded into a strand shape. The strand was cut with a pelletizer to obtain a pellet-shaped methacrylic resin.

When the continuous production operation was in a steady state, a small amount of the reaction solution was withdrawn from each sampling tube, and the physical properties were measured.
As a result, the polymer content in the reaction solution obtained in the tank reactor A was 46% by mass. The polymer (a) polymerized in the tank reactor A is composed of 95.9% by mass of repeating units derived from methyl methacrylate and 4.1% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 60,700.
The content of the polymer in the reaction solution obtained in the tank reactor B was 53% by mass. The polymer B contained in the reaction solution B obtained in the tank reactor B is composed of 95.9% by mass of repeating units derived from methyl methacrylate and 4.1% by mass of repeating units derived from methyl acrylate, And the weight average molecular weight was 55,500.
The breakdown of 100 parts by mass of the polymer B was 83 parts by mass of the polymer (a) and 17 parts by mass of the polymer (b).
The polymer (b) polymerized in the tank reactor B is composed of 95.9% by mass of repeating units derived from methyl methacrylate and 4.1% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 30,100.
The obtained pellet-like methacrylic resin had a residual volatile content of 0.1% by mass.
A molded product was produced by injection molding using the pellet-like methacrylic resin and used for the above evaluation. The evaluation results are shown in Table 1.

Example 3
In an autoclave (I) with a stirrer, 94.5 parts by mass of purified methyl methacrylate, 5.5 parts by mass of methyl acrylate, 0.004 parts by mass of 2,2′-azobis (2-methylpropionitrile) and The raw material liquid (I) was obtained by charging 0.14 parts by mass of n-octyl mercaptan and dissolving it uniformly.
An autoclave with a stirrer (II) was charged with 100 parts by weight of purified methyl methacrylate, 0.012 parts by weight of 2,2′-azobis (2-methylpropionitrile) and 0.22 parts by weight of n-octyl mercaptan. The raw material liquid (II) was obtained by uniformly dissolving.
Next, the inside of the production apparatus was replaced with nitrogen to expel oxygen.

  The raw material liquid (I) is supplied from the autoclave (I) to the tank reactor A controlled at a temperature of 130 ° C. at a rate of 2 kg / hr, bulk polymerization is performed with an average residence time of 90 minutes, and the tank is charged at a rate of 2 kg / hr. The reaction liquid A containing the polymer (a) was discharged from the mold reactor A.

  Following this, the raw material liquid (II) is added from the autoclave (II) at a rate of 0.1 kg / hr to a pipe part equipped with a static mixer manufactured by Noritake Engineering Co., thereby flowing into the pipe part at a rate of 2 kg / hr. The reaction solution A containing the polymer (a) was continuously mixed. The mixed liquid is supplied to a tank reactor B controlled at 140 ° C. at 2.1 kg / hr, bulk polymerization is performed with an average residence time of 60 minutes, and a heavy polymerization is performed from the tank reactor B at 2.1 kg / hr. Reaction solution B containing coalescence B was discharged.

  Following this, the reaction solution B containing the polymer B discharged from the tank reactor B at 2.1 kg / hr is heated to 230 ° C., and the mixture is fed to a twin screw extruder controlled at 260 ° C. It was supplied at 1 kg / hr. In the twin-screw extruder, volatile components mainly composed of unreacted monomers were separated and removed, and the polymer B was extruded into a strand shape. The strand was cut with a pelletizer to obtain a pellet-shaped methacrylic resin.

When the continuous production operation was in a steady state, a small amount of the reaction solution was withdrawn from each sampling tube, and the physical properties were measured.
As a result, the polymer content in the reaction solution obtained in the tank reactor A was 41% by mass. The polymer (a) polymerized in the tank reactor A is composed of 96.0% by mass of repeating units derived from methyl methacrylate and 4.0% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 149,800.
The content of the polymer in the reaction solution obtained in the tank reactor B was 53% by mass. The polymer B contained in the reaction liquid B obtained in the tank reactor B is composed of 96.0% by mass of repeating units derived from methyl methacrylate and 4.0% by mass of repeating units derived from methyl acrylate, And the weight average molecular weight was 121,200.
The breakdown of 100 parts by mass of the polymer B was 73 parts by mass of the polymer (a) and 27 parts by mass of the polymer (b).
The polymer (b) polymerized in the tank reactor B comprises 96.0% by mass of repeating units derived from methyl methacrylate and 4.0% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 44,000.
The obtained pellet-like methacrylic resin had a residual volatile content of 0.1% by mass.
A molded product was produced by injection molding using the pellet-like methacrylic resin and used for the above evaluation. The evaluation results are shown in Table 1.

Example 4
In an autoclave with a stirrer (I), 94.5 parts by mass of purified methyl methacrylate, 5.5 parts by mass of methyl acrylate, 0.006 parts by mass of 2,2′-azobis (2-methylpropionitrile) and A raw material liquid (I) was obtained by charging 0.37 parts by mass of n-octyl mercaptan and dissolving it uniformly.
An autoclave with a stirrer (II) was charged with 100 parts by weight of purified methyl methacrylate, 0.01 parts by weight of 2,2′-azobis (2-methylpropionitrile) and 1.13 parts by weight of n-octyl mercaptan. The raw material liquid (II) was obtained by uniformly dissolving.
Next, the inside of the production apparatus was replaced with nitrogen to expel oxygen.

  The raw material liquid (I) is supplied from the autoclave (I) to the tank reactor A controlled at a temperature of 130 ° C. at a rate of 2 kg / hr, bulk polymerization is performed with an average residence time of 90 minutes, and the tank is charged at a rate of 2 kg / hr. The reaction liquid A containing the polymer (a) was discharged from the mold reactor A.

  Subsequently, the raw material liquid (II) is added from the autoclave (II) at a rate of 0.2 kg / hr to a pipe part equipped with a static mixer manufactured by Noritake Engineering Co., thereby flowing through the pipe part at a rate of 2 kg / hr. The reaction solution A containing the polymer (a) was continuously mixed. The mixed solution is supplied to a tank reactor B controlled at 140 ° C. at 2.2 kg / hr, bulk polymerization is performed with an average residence time of 60 minutes, and a heavy polymerization is performed from the tank reactor B at 2.2 kg / hr. Reaction solution B containing coalescence B was discharged.

  Following this, 1,1-di (t-butylperoxy) cyclohexane (“Perhexa C”, NOF Corporation, hydrogen abstraction capacity: 35%, 1 hour half-life temperature: 111.1 ° C.) and n-octyl Mercaptan is added to a pipe part equipped with a static mixer manufactured by Noritake Engineering Co., Ltd. at a rate of 0.008 parts by mass and 0.20 part by mass with respect to the whole raw material liquid, whereby 2.2 kg / hr is added to the pipe part. The mixture was continuously mixed with the reaction solution B containing the polymer B flowing therethrough. The mixed solution is supplied to a tubular reactor C controlled at an inner wall temperature of 140 ° C. at 2.21 kg / hr, bulk polymerization is performed with an average residence time of 12 minutes, and from the tubular reactor C at 2.21 kg / hr. The reaction liquid C containing the polymer C was discharged.

  Following this, the reaction liquid C containing the polymer C discharged from the tubular reactor C at 2.21 kg / hr was heated to 230 ° C., and the mixture was fed to a twin screw extruder controlled at 260 ° C. It was supplied at 21 kg / hr. In the twin-screw extruder, volatile components mainly composed of unreacted monomers were separated and removed, and the polymer C was extruded in a strand shape. The strand was cut with a pelletizer to obtain a pellet-shaped methacrylic resin.

When the continuous production operation was in a steady state, a small amount of the reaction solution was withdrawn from each sampling tube, and the physical properties were measured.
As a result, the polymer content in the reaction solution obtained in the tank reactor A was 46% by mass. The polymer (a) polymerized in the tank reactor A is composed of 95.9% by mass of repeating units derived from methyl methacrylate and 4.1% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 60,700.
The content rate of the polymer in the reaction liquid obtained in the tank reactor B was 49 mass%. The polymer B contained in the reaction liquid B obtained in the tank reactor B is composed of 96.0% by mass of repeating units derived from methyl methacrylate and 4.0% by mass of repeating units derived from methyl acrylate, And the weight average molecular weight was 55,900.
The breakdown of 88 parts by mass of the polymer B was 74 parts by mass of the polymer (a) and 14 parts by mass of the polymer (b).
The polymer (b) polymerized in the tank reactor B is composed of 96.3% by mass of repeating units derived from methyl methacrylate and 3.7% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 31,000.

The content of the polymer in the reaction solution obtained in the tubular reactor C was 55% by mass. The polymer C contained in the reaction liquid C obtained in the tubular reactor C is composed of 96.0% by mass of repeating units derived from methyl methacrylate and 4.0% by mass of repeating units derived from methyl acrylate, And the weight average molecular weight was 52,900.
The breakdown of 100 parts by mass of the polymer C was 74 parts by mass of the polymer (a) and 14 parts by mass of the polymer (b) 12 parts by mass of the polymer (c).
The polymer (c) polymerized in the tubular reactor C is composed of 95.9% by mass of repeating units derived from methyl methacrylate and 4.1% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 30,200.
The obtained pellet-like methacrylic resin had a residual volatile content of 0.1% by mass.
A molded product was produced by injection molding using the pellet-like methacrylic resin and used for the above evaluation. The evaluation results are shown in Table 1.

<< Comparative Example 1 >>
In an autoclave with a stirrer (I), 94.5 parts by mass of purified methyl methacrylate, 5.5 parts by mass of methyl acrylate, 0.006 parts by mass of 2,2′-azobis (2-methylpropionitrile) and A raw material liquid (I) was obtained by charging 0.37 parts by mass of n-octyl mercaptan and dissolving it uniformly.
Next, the inside of the production apparatus was replaced with nitrogen to expel oxygen.

  The raw material liquid (I) is supplied from the autoclave (I) to the tank reactor A controlled at a temperature of 130 ° C. at a rate of 2 kg / hr, bulk polymerization is performed with an average residence time of 90 minutes, and the tank is charged at a rate of 2 kg / hr. The reaction liquid A containing the polymer (a) was discharged from the mold reactor A.

  Subsequently, by adding n-octyl mercaptan at a constant flow rate at a rate of 0.175 parts by mass with respect to the raw material liquid (I), the pipe is provided with a static mixer manufactured by Noritake Engineering Co., Ltd. The mixture was continuously mixed with the reaction solution A containing the polymer (a) flowing at 2 kg / hr in the part. The mixed solution is supplied to a tank reactor B controlled at 140 ° C. at 2 kg / hr, bulk polymerization is performed with an average residence time of 30 minutes, and the reaction including the polymer B from the tank reactor B at 2 kg / hr. Liquid B was discharged.

  Following this, the reaction solution B containing the polymer B discharged from the tank reactor B at 2 kg / hr is heated to 230 ° C., and then fed into a twin screw extruder controlled at 260 ° C. at 2 kg / hr. Supplied. In the twin-screw extruder, volatile components mainly composed of unreacted monomers were separated and removed, and the polymer B was extruded into a strand shape. The strand was cut with a pelletizer to obtain a pellet-shaped methacrylic resin.

When the continuous production operation was in a steady state, a small amount of the reaction solution was withdrawn from each sampling tube, and the physical properties were measured.
As a result, the polymer content in the reaction solution obtained in the tank reactor A was 47% by mass. The polymer (a) polymerized in the tank reactor A is composed of 95.9% by mass of repeating units derived from methyl methacrylate and 4.1% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 60,700.
The content of the polymer in the reaction solution obtained in the tank reactor B was 50% by mass. The polymer B contained in the reaction solution B obtained in the tank reactor B is composed of 95.9% by mass of repeating units derived from methyl methacrylate and 4.1% by mass of repeating units derived from methyl acrylate, And the weight average molecular weight was 58,800.
The breakdown of 100 parts by mass of the polymer B was 94 parts by mass of the polymer (a) and 6 parts by mass of the polymer (b).
The polymer (b) polymerized in the tank reactor B is composed of 95.9% by mass of repeating units derived from methyl methacrylate and 4.1% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 29,600.
The obtained pellet-like methacrylic resin had a residual volatile content of 0.1% by mass.
A molded product was produced by injection molding using the pellet-like methacrylic resin and used for the above evaluation. The evaluation results are shown in Table 1.

<< Comparative Example 2 >>
In an autoclave (I) with a stirrer, 94.5 parts by mass of purified methyl methacrylate, 5.5 parts by mass of methyl acrylate, 0.002 parts by mass of 2,2′-azobis (2-methylpropionitrile) and n-Octyl mercaptan (0.36 parts by mass) was charged and uniformly dissolved to obtain a raw material liquid (I).
An autoclave with a stirrer (II) was charged with 100 parts by weight of purified methyl methacrylate, 0.04 parts by weight of 2,2′-azobis (2-methylpropionitrile) and 3.25 parts by weight of n-octyl mercaptan. The raw material liquid (II) was obtained by uniformly dissolving.
Next, the inside of the production apparatus was replaced with nitrogen to expel oxygen.

  The raw material liquid (I) is supplied from the autoclave (I) to the tank reactor A controlled at a temperature of 130 ° C. at a rate of 2 kg / hr, bulk polymerization is performed with an average residence time of 90 minutes, and the tank is charged at a rate of 2 kg / hr. The reaction liquid A containing the polymer (a) was discharged from the mold reactor A.

  Subsequently, the raw material liquid (II) is added from the autoclave (II) at a rate of 0.2 kg / hr to a pipe part equipped with a static mixer manufactured by Noritake Engineering Co., thereby flowing through the pipe part at a rate of 2 kg / hr. The reaction solution A containing the polymer (a) was continuously mixed. The mixed solution is supplied to a tank reactor B controlled at 140 ° C. at 2.2 kg / hr, bulk polymerization is performed with an average residence time of 60 minutes, and the polymer is transferred from the tank reactor B at 2.2 kg / hr. Reaction solution B containing B was discharged.

  Following this, the reaction solution B containing the polymer B discharged from the tank reactor B at 2.2 kg / hr was heated to 230 ° C., and the mixture was fed to a twin screw extruder controlled at 260 ° C. It was supplied at 2 kg / hr. In the twin-screw extruder, volatile components mainly composed of unreacted monomers were separated and removed, and the polymer B was extruded into a strand shape. The strand was cut with a pelletizer to obtain a pellet-shaped methacrylic resin.

When the continuous production operation was in a steady state, a small amount of the reaction solution was withdrawn from each sampling tube, and the physical properties were measured.
As a result, the polymer content in the reaction solution obtained in the tank reactor A was 29% by mass. The polymer (a) polymerized in the tank reactor A comprises 96.2% by mass of repeating units derived from methyl methacrylate and 3.8% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 59,100.
The content rate of the polymer in the reaction liquid obtained in the tank reactor B was 49 mass%. The polymer B contained in the reaction liquid B obtained in the tank reactor B consists of 96.2% by mass of repeating units derived from methyl methacrylate and 3.8% by mass of repeating units derived from methyl acrylate, And the weight average molecular weight was 45,600.
The breakdown of 100 parts by mass of the polymer B was 54 parts by mass of the polymer (a) and 46 parts by mass of the polymer (b).
The polymer (b) polymerized in the tank reactor B comprises 96.2% by mass of repeating units derived from methyl methacrylate and 3.8% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 29,800.
The obtained pellet-like methacrylic resin had a residual volatile content of 0.1% by mass.
A molded product was produced by injection molding using the pellet-like methacrylic resin and used for the above evaluation. The evaluation results are shown in Table 1.

<< Comparative Example 3 >>
In an autoclave with a stirrer (I), 94.5 parts by mass of purified methyl methacrylate, 5.5 parts by mass of methyl acrylate, 0.006 parts by mass of 2,2′-azobis (2-methylpropionitrile) and 0.29 parts by mass of n-octyl mercaptan was charged and uniformly dissolved to obtain a raw material liquid (I).
An autoclave with a stirrer (II) was charged with 100 parts by mass of purified methyl acrylate, 0.0008 parts by mass of 2,2′-azobis (2-methylpropionitrile) and 3.32 parts by mass of n-octyl mercaptan. The raw material liquid (II) was obtained by uniformly dissolving.
Next, the inside of the production apparatus was replaced with nitrogen to expel oxygen.

  The raw material liquid (I) is supplied from the autoclave (I) to the tank reactor A controlled at a temperature of 130 ° C. at a rate of 2 kg / hr, bulk polymerization is performed with an average residence time of 90 minutes, and the tank is charged at a rate of 2 kg / hr. The reaction liquid A containing the polymer (a) was discharged from the mold reactor A.

  Following this, the raw material liquid (II) is added from the autoclave (II) at 0.3 kg / hr to a pipe part equipped with a static mixer manufactured by Noritake Engineering Co., thereby flowing into the pipe part at 2 kg / hr. The reaction solution A containing the polymer (a) was continuously mixed. The mixed liquid is supplied to a tank reactor B controlled at 140 ° C. at 2.3 kg / hr, bulk polymerization is performed with an average residence time of 30 minutes, and a polymer is transferred from the tank reactor B at 2.3 kg / hr. Reaction solution B containing B was discharged.

  Subsequently, the reaction solution B containing the polymer B discharged from the tank reactor B at 2.3 kg / hr is heated to 230 ° C., and the reaction solution B is supplied to the twin screw extruder controlled at 260 ° C. It was supplied at 3 kg / hr. In the twin-screw extruder, volatile components mainly composed of unreacted monomers were separated and removed, and the polymer B was extruded into a strand shape. The strand was cut with a pelletizer to obtain a pellet-shaped methacrylic resin.

When the continuous production operation was in a steady state, a small amount of the reaction solution was withdrawn from each sampling tube, and the physical properties were measured.
As a result, the polymer content in the reaction solution obtained in the tank reactor A was 46% by mass. The polymer (a) polymerized in the tank reactor A is composed of 95.9% by mass of repeating units derived from methyl methacrylate and 4.1% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 76,500.
The content of the polymer in the reaction solution obtained in the tank reactor B was 46% by mass. The polymer B contained in the reaction liquid B obtained in the tank reactor B is composed of 93.9% by mass of repeating units derived from methyl methacrylate and 6.1% by mass of repeating units derived from methyl acrylate, The weight average molecular weight was 69,000.
The breakdown of 100 parts by mass of the polymer B was 87 parts by mass of the polymer (a) and 13 parts by mass of the polymer (b).
The polymer (b) polymerized in the tank reactor B is composed of 80.6% by mass of repeating units derived from methyl methacrylate and 19.4% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 18,900.
The obtained pellet-like methacrylic resin had a residual volatile content of 0.1% by mass.
A molded product was produced by injection molding using the pellet-like methacrylic resin and used for the above evaluation. The evaluation results are shown in Table 2.

<< Comparative Example 4 >>
In an autoclave (I) with a stirrer, 94.5 parts by mass of purified methyl methacrylate, 5.5 parts by mass of methyl acrylate, 0.004 parts by mass of 2,2′-azobis (2-methylpropionitrile) and A raw material liquid (I) was obtained by charging 0.31 parts by mass of n-octyl mercaptan and dissolving it uniformly.
An autoclave with a stirrer (II) was charged with 100 parts by mass of purified methyl acrylate, 0.005 parts by mass of 2,2′-azobis (2-methylpropionitrile) and 3.68 parts by mass of n-octyl mercaptan. It was made to melt | dissolve uniformly and the raw material liquid (II) was obtained.
Next, the inside of the production apparatus was replaced with nitrogen to expel oxygen.

  The raw material liquid (I) is supplied from the autoclave (I) to the tank reactor A controlled at a temperature of 130 ° C. at a rate of 2 kg / hr, bulk polymerization is performed with an average residence time of 90 minutes, and the tank is charged at a rate of 2 kg / hr. The reaction liquid A containing the polymer (a) was discharged from the mold reactor A.

  Following this, the raw material liquid (II) is added from the autoclave (II) at 0.3 kg / hr to a pipe part equipped with a static mixer manufactured by Noritake Engineering Co., thereby flowing into the pipe part at 2 kg / hr. The reaction solution A containing the polymer (a) was continuously mixed. The mixed liquid is supplied to a tank reactor B controlled at 140 ° C. at 2.3 kg / hr, bulk polymerization is performed with an average residence time of 30 minutes, and a polymer is transferred from the tank reactor B at 2.3 kg / hr. Reaction solution B containing B was discharged.

  Subsequently, the reaction solution B containing the polymer B discharged from the tank reactor B at 2.3 kg / hr is heated to 230 ° C., and the reaction solution B is supplied to the twin screw extruder controlled at 260 ° C. It was supplied at 3 kg / hr. In the twin-screw extruder, volatile components mainly composed of unreacted monomers were separated and removed, and the polymer B was extruded into a strand shape. The strand was cut with a pelletizer to obtain a pellet-shaped methacrylic resin.

When the continuous production operation was in a steady state, a small amount of the reaction solution was withdrawn from each sampling tube, and the physical properties were measured.
As a result, the polymer content in the reaction solution obtained in the tank reactor A was 41% by mass. The polymer (a) polymerized in the tank reactor A is composed of 95.9% by mass of repeating units derived from methyl methacrylate and 4.1% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 70,500.
The content of the polymer in the reaction solution obtained in the tank reactor B was 47% by mass. The polymer B contained in the reaction liquid B obtained in the tank reactor B is composed of 94.9% by mass of repeating units derived from methyl methacrylate and 5.1% by mass of repeating units derived from methyl acrylate, And the weight average molecular weight was 58,200.
The breakdown of 100 parts by mass of the polymer B was 76 parts by mass of the polymer (a) and 24 parts by mass of the polymer (b).
The polymer (b) polymerized in the tank reactor B is composed of 91.7% by mass of repeating units derived from methyl methacrylate and 8.3% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 19,300.
The obtained pellet-like methacrylic resin had a residual volatile content of 0.1% by mass.
A molded product was produced by injection molding using the pellet-like methacrylic resin and used for the above evaluation. The evaluation results are shown in Table 2.

<< Comparative Example 5 >>
In an autoclave with a stirrer (I), 94.7 parts by mass of purified methyl methacrylate, 5.3 parts by mass of methyl acrylate, 0.006 parts by mass of 2,2′-azobis (2-methylpropionitrile) and A raw material liquid (I) was obtained by charging 0.38 parts by mass of n-octyl mercaptan and dissolving it uniformly.
Next, the inside of the production apparatus was replaced with nitrogen to expel oxygen.

  The raw material liquid (I) is supplied from the autoclave (I) to the tank reactor A controlled at a temperature of 150 ° C. at a constant flow rate, and bulk polymerization is performed with an average residence time of 150 minutes. The reaction liquid A containing the polymer (a) was discharged from the vessel A.

  Following this, the reaction solution A containing the polymer (a) discharged from the tank reactor A at a constant flow rate is heated to 230 ° C., and is fed to a twin screw extruder controlled at 260 ° C. at a constant flow rate. Supplied. In the twin-screw extruder, volatile components mainly composed of unreacted monomers were separated and removed, and the polymer (a) was extruded into a strand shape. The strand was cut with a pelletizer to obtain a pellet-shaped methacrylic resin.

When the continuous production operation was in a steady state, a small amount of the reaction solution was withdrawn from each sampling tube, and the physical properties were measured.
As a result, the polymer content in the reaction solution obtained in the tank reactor A was 52% by mass. The polymer (a) polymerized in the tank reactor A is composed of 96.0% by mass of repeating units derived from methyl methacrylate and 4.0% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 58,400.
The obtained pellet-like methacrylic resin had a residual volatile content of 0.1% by mass.
A molded product was produced by injection molding using the pellet-like methacrylic resin and used for the above evaluation. The evaluation results are shown in Table 2.

<< Reference Example 1 >>
In an autoclave with a stirrer (I), 94.7 parts by mass of purified methyl methacrylate, 5.3 parts by mass of methyl acrylate, 0.005 parts by mass of 2,2′-azobis (2-methylpropionitrile) and The raw material liquid (I) was obtained by charging and uniformly dissolving 0.1 parts by mass of n-octyl mercaptan. Next, the inside of the production apparatus was replaced with nitrogen to expel oxygen.

  The raw material liquid (I) is supplied from the autoclave (I) to the tank reactor A controlled at a temperature of 150 ° C. at a constant flow rate, and bulk polymerization is performed with an average residence time of 150 minutes. The reaction liquid A containing the polymer (a) was discharged from the vessel A.

  Following this, the reaction solution A containing the polymer (a) discharged from the tank reactor A at a constant flow rate is heated to 230 ° C., and is fed to a twin screw extruder controlled at 260 ° C. at a constant flow rate. Supplied. In the twin-screw extruder, volatile components mainly composed of unreacted monomers were separated and removed, and the polymer (a) was extruded into a strand shape. The strand was cut with a pelletizer to obtain a pellet-shaped methacrylic resin.

When the continuous production operation was in a steady state, a small amount of the reaction solution was withdrawn from each sampling tube, and the physical properties were measured.
As a result, the polymer content in the reaction solution obtained in the tank reactor A was 48% by mass. The polymer (a) polymerized in the tank reactor A is composed of 96.0% by mass of repeating units derived from methyl methacrylate and 4.0% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 19,000.
The obtained pellet-like methacrylic resin had a residual volatile content of 0.1% by mass.

<< Reference Example 2 >>
In an autoclave with a stirrer (I), 94.7 parts by mass of purified methyl methacrylate, 5.3 parts by mass of methyl acrylate, 0.006 parts by mass of 2,2′-azobis (2-methylpropionitrile) and The raw material liquid (I) was obtained by charging 0.14 parts by mass of n-octyl mercaptan and dissolving it uniformly. Next, the inside of the production apparatus was replaced with nitrogen to expel oxygen.

  The raw material liquid (I) is supplied from the autoclave (I) to the tank reactor A controlled at a temperature of 150 ° C. at a constant flow rate, and bulk polymerization is performed with an average residence time of 150 minutes. The reaction liquid A containing the polymer (a) was discharged from the vessel A.

  Following this, the reaction solution A containing the polymer (a) discharged from the tank reactor A at a constant flow rate is heated to 230 ° C., and is fed to a twin screw extruder controlled at 260 ° C. at a constant flow rate. Supplied. In the twin-screw extruder, volatile components mainly composed of unreacted monomers were separated and removed, and the polymer (a) was extruded into a strand shape. The strand was cut with a pelletizer to obtain a pellet-shaped methacrylic resin.

When the continuous production operation was in a steady state, a small amount of the reaction solution was withdrawn from each sampling tube, and the physical properties were measured.
As a result, the polymer content in the reaction solution obtained in the tank reactor A was 52% by mass. The polymer (a) polymerized in the tank reactor A is composed of 96.0% by mass of repeating units derived from methyl methacrylate and 4.0% by mass of repeating units derived from methyl acrylate, and has a weight average molecular weight. Was 150,000.
The obtained pellet-like methacrylic resin had a residual volatile content of 0.1% by mass.

<< Comparative Example 6 >>
80 parts by mass of the pellet-like methacrylic resin obtained in Comparative Example 5 and 20 parts by mass of the pellet-like methacrylic resin obtained in Reference Example 1 were mixed using a Henschel mixer. Thereafter, the mixture was kneaded and extruded at 250 ° C. with a twin-screw extruder (trade name: KZW20TW-45MG-NH-600, manufactured by Technobel Co., Ltd.) to obtain a pellet-shaped methacrylic resin. The methacrylic resin was composed of 96.0% by mass of repeating units derived from methyl methacrylate and 4.0% by mass of repeating units derived from methyl acrylate, and had a weight average molecular weight of 50,500.
A molded product was produced by injection molding using the pellet-like methacrylic resin and used for the above evaluation. The evaluation results are shown in Table 2.

<< Comparative Example 7 >>
80 parts by mass of the pellet-like methacrylic resin obtained in Reference Example 2 and 20 parts by mass of the pellet-like methacrylic resin obtained in Reference Example 1 were mixed using a Henschel mixer. Thereafter, the mixture was kneaded and extruded at 250 ° C. with a twin-screw extruder (trade name: KZW20TW-45MG-NH-600, manufactured by Technobel Co., Ltd.) to obtain a pellet-shaped methacrylic resin. The methacrylic resin was composed of 96.0% by mass of repeating units derived from methyl methacrylate and 4.0% by mass of repeating units derived from methyl acrylate, and had a weight average molecular weight of 123,500. This strand was found to be unmelted and could not withstand melt molding.

  From the above results, it can be seen that the methacrylic resin obtained by the production method of the present invention has excellent transparency, heat resistance, moldability, durability, chemical resistance, thermal stability and the like.

Claims (7)

In the first stage, the monomer mixture (I) containing 50% by mass or more of methyl methacrylate and 50% by mass or less of the copolymerizable vinyl monomer is subjected to bulk polymerization or solution polymerization. To obtain a reaction solution (I) containing a polymer (a) having a weight average molecular weight of more than 50,000,
In the second stage, the reaction liquid (I) contains more than 50% by weight of methyl methacrylate and less than 50% by weight of a vinyl monomer copolymerizable therewith, and methacrylic acid in the monomer mixture (I). Monomer mixture (II) containing methyl methacrylate at a higher content than methyl acid content is mixed 0.02-1.0 mass times of the monomer mixture (I), and bulk polymerization is performed. Alternatively, by polymerizing the solution, the polymer (a) and the polymer (b) having a weight average molecular weight of 20,000 or more and 50,000 or less are in a mass ratio (a / b) of 60/40 to 90/10 in a total amount of 100 parts by mass. A method for producing a methacrylic resin, comprising obtaining 105 to 300 parts by mass of a reaction liquid (II) containing. The first stage is performed in a tank reactor (1), the second stage is performed in a tank reactor (2),
The method for producing a methacrylic resin according to claim 1, comprising obtaining 125 to 300 parts by mass of the reaction liquid (II). In the first stage, the polymerization temperature T1 is 110 to 170 ° C.,
The production method according to claim 1 or 2, wherein the second stage has a polymerization temperature T2 of 130 ° C or higher and (T1 + 30) ° C or lower. The second stage is carried out in a tank reactor (2a) and a tubular reactor (2b) connected downstream thereof,
After obtaining the reaction liquid (II ₀ ) containing 70 to 95 parts by mass of the polymer in the tank reactor (2a),
The method for producing a methacrylic resin according to claim 1, comprising obtaining 105 to 250 parts by mass of the reaction liquid (II). In the first stage, the polymerization temperature T1 is 110 to 170 ° C.,
In the second stage, the polymerization temperature T2a in the tank reactor (2a) is 130 ° C. or higher and (T1 + 30) ° C. or lower, and the polymerization temperature T2b in the tubular reactor (2b) is 140 to 190 ° C. 4. The production method according to 4. The content a _m [mass%] of repeating units derived from methyl methacrylate in the polymer (a) and the content b _m [mass%] of repeating units derived from methyl methacrylate in the polymer (b) The manufacturing method according to claim 1, wherein the difference is within ± 1% by mass. Carrying out the production method according to claim 6 to obtain a methacrylic resin,
A method for producing a molded article , comprising melt-molding the obtained methacrylic resin.