JP5716266B2 - Method for producing methacrylic resin - Google Patents

Description

  The present invention relates to a method for producing a methacrylic resin.

  Methacrylic resins are used in various fields because of their excellent transparency, weather resistance, heat resistance, and mechanical strength. Recently, a product obtained by molding a methacrylic resin into an arbitrary shape has been widely used as an optical component such as a light guide plate, various video lenses, and optical lenses.

  In recent years, the production of injection molding and extrusion molding has increased due to the increase in the size of optical components, but in order to increase the productivity, the cooling time until solidification of the heated and melted resin is shortened and the molding cycle is shortened. Therefore, improvement of the fluidity of the resin is demanded so that it can be molded.

  However, when the molecular weight of the resin is lowered to improve the fluidity, there is a problem that the heat resistance and the mechanical strength are lowered.

  Therefore, a method is known in which a low molecular weight polymer is mixed with a high molecular weight polymer, and fluidity is imparted with the low molecular weight polymer while maintaining heat resistance and mechanical strength with the high molecular weight polymer. . For example, in Patent Document 1, after polymerizing a low molecular weight polymer B by suspension polymerization, a monomer as a raw material for the high molecular weight polymer A is added, and the polymer A is subjected to suspension polymerization. A method for producing a methacrylic resin containing A and polymer B is described.

  In addition, as a method for producing a methacrylic resin excellent in transparency as an optical application, preventing a decrease in transparency due to a foreign substance caused by a dispersant used in suspension polymerization, for example, Patent Document 2 and Patent Document 3 include A method is described in which polymerization is carried out continuously using a polymerization apparatus in which a fully mixed reactor and a plug flow reactor are connected in series.

JP 2007-291230 A JP-A-8-253507 JP 2000-26507 A

  However, in the method described in Patent Document 1, the transparency tends to be insufficient due to foreign matters caused by the dispersant used in suspension polymerization, and the productivity is not sufficient.

  In addition, the method described in Patent Document 2 is to produce a resin having a uniform molecular weight by specifying an initiator concentration, a chain transfer agent concentration, etc. in order to improve thermal decomposition resistance. Absent.

  The method described in Patent Document 3 defines the initiator type, the chain transfer agent concentration, etc., and prevents a decrease in productivity due to the gel effect when the polymerization rate becomes high in bulk polymerization, and improves fluidity. It is not what was done.

  An object of the present invention is to provide a method for efficiently producing a methacrylic resin having excellent heat resistance and mechanical strength and high fluidity.

The method for producing a methacrylic resin of the present invention comprises a methacrylic resin by bulk polymerization or polymerization containing a solvent of less than 5% by mass using a fully mixed reactor and subsequently a plug flow reactor connected in series. A method of manufacturing
A monomer mixture containing 70% by mass or more of methyl methacrylate is polymerized in the complete mixing reactor until the polymerization rate (R1) becomes 40% to 65%, and a polymer having a weight average molecular weight of 50,000 to 100,000. Obtaining (P1);
A resin composition containing the polymer (P1) is extracted from the complete mixing reactor, and 0.1 to 2.0 parts by mass of a chain transfer agent and 0.0005 to 0 with respect to 100 parts by mass of the monomer mixture. After supplying 0.01 parts by mass of the polymerization initiator, polymerization is performed in the plug flow reactor until the polymerization rate (R2) at the outlet of the plug flow reactor becomes 0.65 <R1 / R2 <0.9. And a process of
And a step of removing volatile components from the obtained resin composition.

  By the method for producing a methacrylic resin according to the present invention, a methacrylic resin having excellent heat resistance and mechanical strength and high fluidity can be provided with high productivity.

  In the present invention, a monomer mixture containing methyl methacrylate is polymerized in a complete mixing reactor to obtain a resin composition containing polymer P1, and a chain transfer agent and a polymerization initiator are supplied to the resin composition. It has the process of superposing | polymerizing with a plug flow type reactor, and the process of removing a volatile matter from the obtained resin composition.

[Polymerization in a fully mixed reactor]
In the present invention, a monomer mixture containing 70% by mass or more of methyl methacrylate is polymerized to a polymerization rate (R1) of 40% to 65% in a fully mixed reactor, and a weight average molecular weight of 50,000 to 100,000 is obtained. Combine (P1) is obtained.

  In the monomer mixture, it is necessary to contain 70% by mass or more of methyl methacrylate with respect to the total monomer amount from the viewpoint of transparency and weather resistance of the methacrylic resin.

  Examples of the monomer other than methyl methacrylate in the monomer mixture include alkyl acrylates having an alkyl group having 1 to 18 carbon atoms, such as methyl, ethyl, n-propyl, n-butyl, -Alkyl acrylate having an alkyl group such as ethylhexyl, dodecyl, stearyl and the like.

  Moreover, as an alkyl methacrylate, it has a C2-C18 alkyl group, for example, the alkyl methacrylate which has alkyl groups, such as ethyl, n-propyl, n-butyl, 2-ethylhexyl, dodecyl, stearyl, is mentioned. . These may be used alone or in combination of two or more.

  Moreover, in this invention, it superposes | polymerizes to a polymerization rate (R1) 40%-65% with a perfect mixing type | mold reactor. If R1 is less than 40%, the amount of initiator used in the plug flow reactor increases, and the mechanical strength decreases. If it exceeds 65%, mixing and heat transfer become insufficient, and the polymerization stability decreases.

  Furthermore, in this invention, it is required that the weight average molecular weight of the polymer obtained by a complete mixing type reactor is 50,000-100,000. When the weight average molecular weight is less than 50,000, the mechanical strength of the methacrylic resin is lowered, and when the weight average molecular weight is more than 100,000, the fluidity of the methacrylic resin is lowered. A preferable range of the weight average molecular weight is 60,000 to 80,000.

  The polymerization rate (R1) and the weight average molecular weight were measured by the method described later for the resin composition extracted from the complete mixing reactor.

  The polymerization in the complete mixing reactor may be carried out under known polymerization conditions using a known chain transfer agent, polymerization initiator or the like.

  As the chain transfer agent, a mercaptan compound can be used. Examples of mercaptan compounds include primary, secondary, and primary alkyl groups or substituted alkyl groups such as n-butyl, isobutyl, n-octyl, n-dodecyl, sec-butyl, sec-dodecyl, and tert-butyl mercaptan. Tertiary mercaptans; aromatic mercaptans such as phenyl mercaptan, thiocresol, 4-tert-butyl-o-thiocresol; thioglycolic acid and esters thereof; and mercaptans having 2 to 18 carbon atoms such as ethylenethioglycol. These can be used alone or in combination of two or more. Among these mercaptans, tert-butyl, n-butyl, n-octyl, and n-dodecyl mercaptan are preferable.

  The amount of the chain transfer agent used is preferably 0.01% by mass to 2% by mass with respect to the total monomer amount in order to achieve the target weight average molecular weight. When the amount is less than 0.01% by mass, polymerization in a complete mixing type reactor may become unstable. On the other hand, when it is more than 2% by mass, the polymer (P1) has a weight average molecular weight of less than 50,000.

  The polymerization initiator may be a general radical polymerization initiator, and is not particularly limited. For example, tert-butylperoxy-3,5,5-trimethylhexanate, tert-butylperoxylaurate. Tert-butyl peroxyisopropyl monocarbonate, tert-hexyl peroxyisopropyl monocarbonate, tert-butyl peroxyacetate, 1,1-bis (tert-butylperoxy) 3,3,5-trimethylcyclohexane, 1, 1-bis (tert-butylperoxy) cyclohexane, tert-butylperoxy 2-ethylhexanate, tert-butylperoxyisobutyrate, tert-hexylperoxy-2-ethylhexanate, di-tert-butylperoxy Id, di-tert-hexyl peroxide, organic peroxides such as 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane, or 2- (carbamoylazo) -isobutyronitrile, , 1'-azobis (1-cyclohexanecarbonitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), dimethyl 2,2'-azobisisobuty An azo compound such as a rate, 2,2′-azobis (2,4,4-trimethylpentane), and 2,2′-azobis (2-methylpropane) can be appropriately selected in consideration of the polymerization temperature. These can be used alone or in combination of two or more.

  The amount of the polymerization initiator used is preferably 0.001% by mass to 1% by mass with respect to the total monomer amount in order to achieve the target weight average molecular weight. If it is less than 0.001% by mass, the target polymerization rate may not be obtained. Moreover, when more than 1 mass%, raw material cost may become high.

  The polymerization temperature is preferably 110 to 170 ° C. When the polymerization temperature is lower than 110 ° C., the acceleration phenomenon of the polymerization rate due to the gel effect becomes large, so that it can be operated stably only under a condition with a low polymerization rate, which is disadvantageous economically because productivity is lowered. More preferably, it is 120 ° C. or higher. On the other hand, when the polymerization temperature is higher than 170 ° C., the polymerization reaction becomes stable and the polymerization rate can be increased. However, the transparency of the polymer, the mechanical strength, the thermal deformation temperature, and the thermal decomposition resistance are reduced. Since it falls, it is not preferable. More preferably, it is 150 degrees C or less.

  Polymerization in the fully mixed reactor of the present invention is preferably bulk polymerization without using a solvent, but may contain less than 5% by mass of solvent. As the solvent, known solvents such as methanol, ethanol, toluene, xylene, acetone, methyl isobutyl ketone, ethylbenzene, methyl ethyl ketone, and butyl acetate can be used. Among these, methanol, toluene, ethylbenzene, butyl acetate and the like are preferable.

[Polymerization in plug flow reactor]
Next, the resin composition containing the polymer (P1) is extracted from the complete mixing reactor, a chain transfer agent and a polymerization initiator are supplied to the resin composition, and then polymerization is performed in a plug flow reactor. .

  As the chain transfer agent, the same mercaptan compound as that used in the polymerization in the complete mixing reactor can be used, and these can be used alone or in combination of two or more. The amount of the chain transfer agent is required to be 0.1 to 2.0 parts by mass with respect to 100 parts by mass of all monomers. If it is less than 0.1 part by mass, the molecular weight of the resulting polymer is insufficiently lowered and the fluidity becomes insufficient. If it exceeds 2.0 parts by mass, the molecular weight of the resulting polymer becomes too low and the mechanical strength is lowered.

  As the polymerization initiator, the same radical polymerization initiator as the polymerization in the complete mixing reactor can be used, and the polymerization initiator can be used alone or in combination of two or more. The amount of the polymerization initiator is required to be 0.0005 to 0.01 parts by mass with respect to 100 parts by mass of all monomers. If it is less than 0.0005 parts by mass, the fluidity is insufficient, and if it exceeds 0.01 parts by mass, the mechanical strength is insufficient. In addition, when using 2 or more types of polymerization initiators, the total amount should just be in a regulation range.

  Furthermore, in the present invention, it is necessary that the polymerization rate (R2) at the outlet of the plug flow reactor is 0.65 <R1 / R2 <0.9. When R1 / R2 is 0.65 or less, the ratio of the polymer having a high molecular weight in the obtained resin composition is low, so that the mechanical strength becomes insufficient. Moreover, when R1 / R2 is 0.9 or more, since the ratio of the low molecular weight polymer in the obtained resin composition is low, the fluidity becomes insufficient.

  The outlet temperature of the plug flow reactor is preferably 170 ° C to 200 ° C. When the viscosity of the resin composition as the reactant increases, the pressure loss in the plug flow reactor and piping increases, so the pressure resistance of the apparatus needs to be increased. Therefore, it is preferable to lower the viscosity by setting the outlet temperature to 170 ° C. or higher. Thereby, in this invention, it becomes possible to manufacture a methacrylic resin with high productivity. In addition, in the polymerization of methyl methacrylate, it is known that the depolymerization proceeds as the temperature increases, so that the ultimate polymerization rate decreases. Therefore, in order to increase the ultimate polymerization rate, the outlet temperature is preferably 200 ° C. or lower in the present invention.

  Although there is no restriction | limiting in particular as a plug flow type reactor, The tubular reactor which equipped the static mixer internally is preferable. The plug flow reactor preferably has as little pressure loss as possible from the viewpoint of pressure resistance of the apparatus. When the plug flow reactor includes a static mixer, it is preferable to use a static mixer with a small pressure loss. As a means for reducing the pressure loss, there is a method of reducing a value L / D obtained by dividing the length (L) of the static mixer by the diameter (D) of the static mixer. However, in order to quickly mix the polymerization initiator and chain transfer agent supplied to the plug flow reactor into the resin composition, the plug flow reactor increases the linear velocity in order to increase the mixing speed, that is, It is preferable to increase L / D.

  For this reason, it is preferable to use a plug flow reactor having a large diameter after rapidly mixing a chain transfer agent and a polymerization initiator in a static mixer having a small diameter with the resin composition extracted from the complete mixing reactor. .

  That is, the plug flow reactor connected to the complete mixing reactor comprises a static mixer having a diameter Dm and a plug flow reactor having a diameter Dr, where Dm <Dr, and the complete mixing reactor, A static transfer mixer having a diameter Dm and a plug flow reactor having a diameter Dr are connected in series. In the static mixer having the diameter Dm, a chain transfer agent is added to the resin composition extracted from the complete mixing reactor. In order to reduce the pressure loss, it is preferable to perform polymerization in the plug flow reactor having the diameter Dr after supplying and mixing the polymerization initiator.

  The static mixer for mixing the chain transfer agent and the polymerization initiator may be used in combination when the mixing speed is sufficiently high. However, the static mixer for mixing the chain transfer agent and the static mixer for mixing the polymerization initiator are used. It is preferable to use it. Specifically, a chain transfer agent mixing static mixer and a polymerization initiator mixing static mixer are connected to a complete mixing reactor, and the diameter is larger than that of a chain transfer agent mixing static mixer and a polymerization initiator mixing static mixer. It is preferable to connect a plug flow reactor. Note that the same chain transfer agent mixing static mixer and polymerization initiator mixing static mixer can be used.

  In the case of using the reactor, first, after supplying the chain transfer agent to the resin composition extracted from the complete mixing type reactor in the chain transfer agent mixing static mixer, the polymerization initiator is subsequently added to the polymerization initiator mixing static mixer. The mixture is fed to a mixer and polymerized in a plug flow reactor having a diameter larger than that of a static mixer for mixing a chain transfer agent and a static mixer for mixing a polymerization initiator. Thereby, while being able to use a chain transfer agent efficiently, it becomes possible to also suppress consumption by the redox reaction of a chain transfer agent and a polymerization initiator.

  L / D of the chain transfer agent mixing static mixer and the polymerization initiator mixing static mixer is preferably 3 to 36. When L / D is smaller than 3, the pressure loss is small but mixing may be insufficient. On the other hand, if L / D is greater than 36, mixing may be sufficient but pressure loss may increase.

[Removal of volatile matter]
In the present invention, the resin composition extracted from the plug flow reactor is sent to a volatile matter removing step to remove volatile matter mainly composed of unreacted monomers to obtain a methacrylic resin.

  As a method for introducing the volatile matter, the reaction mixture having a predetermined polymerization rate that is continuously sent is heated to 200 to 290 ° C. under reduced pressure, and most of the volatile matter mainly composed of monomer is continuously obtained. It is preferable to separate and remove. Specific examples include a devolatilizing extruder.

  The physical properties of the polymers of the examples were evaluated by the following methods.

(Weight average molecular weight)
The weight average molecular weight was measured by gel permeation chromatography (GPC). The GPC method was measured by dissolving a methacrylic resin in tetrahydrofuran (THF) and then using liquid chromatography “HLC-8020” (trade name, manufactured by Tosoh Corporation), and the separation column was “TSK-Gel GMHXL”. (Trade name, manufactured by Tosoh Corporation) 2 in series, solvent is THF, flow rate is 1.0 ml / min, detector is differential refractometer, measurement temperature is 40 ° C., injection amount is 0.1 ml, polymethyl methacrylate as standard polymer Was carried out.

(Polymerization rate)
The polymerization rate is determined from the mass (mass A) of the resin composition from which volatile components have been removed at 230 ° C. and −20 KPa, and the mass (mass B) of the monomer mixture to be supplied.
[Polymerization rate] (%) = [mass A] / [mass B] × 100 (%)
Determined by

(Bending strength)
Conforms to JIS standard K6911. The specimen thickness was 4 mm. If the bending break strength was 75 Mpa or more, it was judged that the mechanical strength was sufficient.

(Fluidity (MFR))
MFR was measured using a capillograph (manufactured by Toyo Seiki Co., Ltd.) under the conditions of capillary: L / D = 10/1 mm, temperature: 230 ° C., shear rate: 600 (Sec ⁻¹ ). If the MFR was 15 or more, it was judged that the fluidity was sufficient.

[Example 1]
Nitrogen was introduced into a monomer mixture consisting of 95 parts by mass of methyl methacrylate (MMA) and 5 parts by mass of methyl acrylate (MA), and then 100 parts by mass of this monomer mixture was used as a chain transfer agent with 0.32 n-octyl mercaptan. The polymerization monomer was controlled at a polymerization temperature of 135 ° C. with a raw material monomer mixed with 0.009 part by mass of 1,1-bis (t-butylperoxy) -3,5,5-trimethylcyclohexane as a polymerization initiator. Polymerization was carried out while continuously feeding to the complete mixing reactor while stirring and mixing, and continuously taking out the resin composition with a gear pump. Polymerization was carried out at a residence time of the reaction solution in the reaction zone of 60 kg and an average residence time of 2.0 hours. The polymerization rate of the high molecular weight resin sampled at the outlet of the complete mixing reactor was 50%, and the weight average molecular weight was 75,000.

  Subsequently, to a chain transfer agent mixing static mixer (trade name: “SMX Through the Mixer”, manufactured by Sumitomo Heavy Industries, Ltd., diameter: 27.2 mm, length: 650 mm) connected in series to the complete mixing reactor. The extracted resin composition was supplied. Furthermore, in the chain transfer agent mixing static mixer, 0.26 parts by mass of n-octyl mercaptan was supplied as a chain transfer agent and mixed with the resin composition.

  Thereafter, the mixture was supplied to a polymerization initiator mixing static mixer connected to a chain transfer agent mixing static mixer. As the polymerization initiator mixing static mixer, the same one as the chain transfer agent mixing static mixer was used. Further, in the static mixer for mixing the polymerization initiator, 0.001-35 parts by mass of 1,1-bis (t-butylperoxy) -3,5,5-trimethylcyclohexane as a polymerization initiator, di-t-hexyl peroxide 0 0035 parts by mass was diluted 100 times with methyl methacrylate and mixed with the mixture.

  Thereafter, the polymerization initiator was connected to a plug flow reactor (trade name: “SMX Through the Mixer”, manufactured by Sumitomo Heavy Industries, Ltd., diameter 65.9 mm, length 5000 mm) connected to a static mixer for mixing polymerization initiators. Polymerization was carried out by feeding the mixture that passed through the static mixer for mixing. The jacket temperature of the plug flow reactor was adjusted so that the outlet temperature of the plug flow reactor was 190 ° C. In addition, the polymerization rate was calculated | required from the mass of the raw material monomer and the obtained polymer composition.

  The obtained polymer composition was devolatilized with an extruder to obtain a methacrylic resin. The polymerization rate of the obtained methacrylic resin was 71%. The evaluation results are shown in Table 1.

[Examples 2 to 6]
The same procedure as in Example 1 was performed except that the amounts of the polymerization initiator and the chain transfer agent were changed as shown in Table 1. The evaluation results are shown in Table 1.

[Comparative Example 1]
The same procedure as in Example 1 was performed except that the amounts of the polymerization initiator and the chain transfer agent were changed as shown in Table 1. The polymerization rate of the high molecular weight resin sampled at the outlet of the complete mixing reactor was as low as 38%, and the mechanical strength was lowered.

[Comparative Example 2]
The same procedure as in Example 1 was performed except that the amounts of the polymerization initiator and the chain transfer agent were changed as shown in Table 1. The weight average molecular weight of the polymer obtained in the fully mixed reactor was high, and the fluidity was insufficient.

[Comparative Example 3]
The same procedure as in Example 1 was performed except that the amounts of the polymerization initiator and the chain transfer agent were changed as shown in Table 1. The weight average molecular weight of the polymer obtained in the complete mixing reactor was low, and the bending fracture strength was insufficient.

[Comparative Example 4]
The same procedure as in Example 1 was performed except that the amounts of the polymerization initiator and the chain transfer agent were changed as shown in Table 1. Since R1 / R2 is as low as 0.65, the ratio of the high molecular weight polymer is small, so that the bending rupture strength is insufficient.

[Comparative Example 5]
The same procedure as in Example 1 was performed except that the amounts of the polymerization initiator and the chain transfer agent were changed as shown in Table 1. Since R1 / R2 was as high as 0.9, the ratio of the high molecular weight polymer was large and the fluidity was insufficient.

[Comparative Example 6]
The same procedure as in Example 1 was performed except that the amounts of the polymerization initiator and the chain transfer agent were changed as shown in Table 1. Since the amount of the chain transfer agent supplied to the resin composition obtained in the fully mixed reactor was large, the molecular weight of the low molecular weight polymer was too low, and the breaking strength was insufficient.

[Comparative Example 7]
The same procedure as in Example 1 was performed except that the amounts of the polymerization initiator and the chain transfer agent were changed as shown in Table 1. Since the amount of the chain transfer agent supplied to the resin composition obtained in the fully mixed reactor was small, the molecular weight of the low molecular weight polymer was not sufficiently lowered, and the fluidity was insufficient.

* 1: 1,1-di (t-butylperoxy) -3,5,5-trimethylcyclohexane * 2: Di-t-hexyl peroxide.

Claims (1)

A method for producing a methacrylic resin by bulk polymerization or polymerization containing less than 5% by weight of a solvent using a fully mixed reactor and subsequently a plug flow reactor connected in series,
A monomer mixture containing 70% by mass or more of methyl methacrylate is polymerized in the complete mixing reactor until the polymerization rate (R1) becomes 40% to 65%, and a polymer having a weight average molecular weight of 50,000 to 100,000. Obtaining (P1);
A resin composition containing the polymer (P1) is extracted from the complete mixing reactor, and 0.1 to 2.0 parts by mass of a chain transfer agent and 0.0005 to 0 with respect to 100 parts by mass of the monomer mixture. After supplying 0.01 parts by mass of the polymerization initiator, polymerization is performed in the plug flow reactor until the polymerization rate (R2) at the outlet of the plug flow reactor becomes 0.65 <R1 / R2 <0.9. And a process of
Removing volatiles from the resulting resin composition;
A method for producing a methacrylic resin having