JP6694685B2 - Acrylic polymer and method for producing the same - Google Patents

Description

  The present invention relates to an acrylic polymer having a ring structure in its main chain and a method for producing the same.

  Acrylic polymers represented by polymethylmethacrylate (PMMA) are widely used as optical materials because of their excellent transparency. The optical material is generally used as a bulk body such as a lens and also as a resin film (optical film) made of a thermoplastic resin containing the polymer. In recent years, optical films have been increasingly used for image display devices such as liquid crystal display devices (LCD) and organic light emitting display devices (OLED).

  Due to the design of the image display device, the optical film is arranged close to a heating element such as a power source section, a light emitting section, and a circuit board. Therefore, the optical film is required to have heat resistance. However, the glass transition temperature of polymethylmethacrylate is around 100 ° C., and the heat resistance thereof sometimes falls below the required level. Therefore, the heat resistance of the optical film has been improved by introducing a ring structure into the main chain of the polymer (for example, Patent Document 1). An acrylic polymer having a glutarimide ring structure in its main chain has also been proposed as an acrylic resin having excellent heat resistance and high optical properties (for example, Patent Documents 2 and 3).

  However, when an acrylic polymer having a ring structure in the main chain is used, the heat resistance is improved, but at the same time, the polymer changes to be hard and brittle. Therefore, when an optical film is formed from such a polymer, the breaking strength of the optical film may decrease, and the handling property may decrease.

JP, 2005-127361, A International Publication No. 2005/054311 Pamphlet JP, 2011-225699, A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an acrylic polymer having high heat resistance and breaking strength, and further excellent in moldability and productivity, and a method for producing the same. Especially.

  The acrylic polymer of the present invention capable of solving the above-mentioned problems is an acrylic polymer having a ring structure in the main chain, has a weight average molecular weight of 17,000 or more, and a temperature of 240 ° C. The melt flow rate measured under a load of 98 N is 7.1 g / 10 min or more and 12.0 g / 10 min or less, and the glass transition temperature is 110 ° C. or more. Since the acrylic polymer of the present invention has a ring structure in the main chain and has a glass transition temperature of 110 ° C. or higher, it has excellent heat resistance. By setting the weight average molecular weight to be 17,000 or more, the breaking strength can be increased and the hardness and brittleness can be improved. Further, since the melt flow rate is 7.1 g / 10 min or more and 12.0 g / 10 min or less, the moldability and productivity are excellent.

  The ring structure of the main chain is preferably at least one selected from the group consisting of a lactone ring structure, a glutarimide ring structure, and a maleimide ring structure from the viewpoint of improving heat resistance.

  The acrylic polymer preferably has a structure in which the main chain is branched. When the acrylic polymer has a structure in which the main chain is branched, the melt flow rate can be increased while increasing or maintaining the weight average molecular weight. Generally, when the weight average molecular weight of a polymer is increased, the melt viscosity shown by the melt flow rate and the like decreases, and the moldability tends to decrease. However, by making the main chain of the acrylic polymer have a branched structure, it becomes possible to increase both the weight average molecular weight and the melt flow rate.

  The present invention also has a step of polymerizing a monomer component (A) containing a (meth) acrylic acid ester monomer, and using a trifunctional or higher functional initiator (C) during the polymerization, and / or Also provided is a method for producing an acrylic polymer having a ring structure in the main chain, characterized in that the polymerization is carried out in the presence of a trifunctional or higher functional chain transfer agent (B). According to the method for producing an acrylic polymer of the present invention, an acrylic polymer having a high glass transition temperature and a high weight average molecular weight and a high melt flow rate can be easily obtained. Therefore, the obtained acrylic polymer has high heat resistance and breaking strength, and is excellent in molding processability and productivity.

  The ring structure is preferably at least one selected from the group consisting of a lactone ring structure, a glutarimide ring structure, and a maleimide ring structure. Further, it is preferable to use 0.02 parts by mass or more and 0.6 parts by mass or less of the trifunctional or higher functional chain transfer agent (B) with respect to 100 parts by mass of the monomer component (A). Further, in 100 parts by mass of the monomer component (A), it is preferable to include 50 parts by mass or more of the (meth) acrylic acid ester monomer. The monomer component (A) may contain a vinyl monomer other than the (meth) acrylic acid ester monomer.

  The present invention further provides a resin composition containing the acrylic polymer of the present invention.

  Since the acrylic polymer of the present invention has a ring structure in the main chain and has a glass transition temperature of 110 ° C. or higher, it has excellent heat resistance. Further, when the weight average molecular weight is 17,000 or more, the breaking strength can be increased and the hardness and brittleness can be improved. Furthermore, since the melt flow rate is 7.1 g / 10 min or more and 12.0 g / 10 min or less, the moldability and productivity are excellent.

  The acrylic polymer of the present invention has a main chain composed of units derived from a (meth) acrylic monomer, and has a ring structure in this main chain. Since the acrylic polymer of the present invention has a ring structure in the main chain, it can increase the glass transition temperature (Tg).

  The unit derived from the (meth) acrylic monomer is formed by homopolymerization or copolymerization of the (meth) acrylic monomer, and the (meth) acrylic monomer includes (meth) acrylic acid and its derivative. Is included. The form of the carboxylic acid contained in the unit derived from the (meth) acrylic monomer is not particularly limited, and examples thereof include free acids, esters, salts, acid anhydrides and acid amides.

  The ring structure of the main chain of the acrylic polymer may contain a part or all of the (meth) acrylic monomer in the ring structure, and it was introduced separately from the (meth) acrylic monomer. It may have a ring structure. When a part or all of the (meth) acryl-based monomer is contained in the ring structure, for example, two carboxylic acid groups of adjacent (meth) acryl-based monomers are acid-anhydrided or imidized. It may be connected by such as. When one of the adjacent (meth) acrylic monomers has a protic hydrogen atom-containing group such as a hydroxy group or an amino group, the protic hydrogen atom of the one (meth) acrylic monomer A ring structure can also be formed by condensing the containing group and the carboxylic acid group of the other (meth) acrylic monomer.

  When the ring structure is introduced separately from the unit derived from the (meth) acrylic monomer, for example, a (meth) acrylic monomer and a monomer having a polymerizable double bond in the ring structure are used. It may be copolymerized.

  The ring structure may be any of a 4-membered ring structure, a 5-membered ring structure, a 6-membered ring structure, a 7-membered ring structure, an 8-membered ring structure and the like, preferably a 5-membered ring structure or a 6-membered ring structure.

  Examples of the ring structure include a lactone ring structure, a glutaric anhydride ring structure, a glutarimide ring structure, a maleimide ring structure, and a maleic anhydride ring structure. Only one kind of these ring structures may be contained in the main chain of the acrylic polymer, or two or more kinds thereof may be contained. The ring structure of the main chain is preferably at least one selected from the group consisting of a lactone ring structure, a glutarimide ring structure, and a maleimide ring structure from the viewpoint of improving heat resistance. Further, when the ring structure is introduced into the main chain, the birefringence of the acrylic polymer can be shifted to the positive side, and the optical characteristics can be adjusted.

  When having a lactone ring structure as the ring structure, the number of ring members in the lactone ring structure is not particularly limited, and may be, for example, any of a 4-membered ring to an 8-membered ring. The lactone ring structure is preferably a 5-membered ring or a 6-membered ring, more preferably a 6-membered ring, from the viewpoint of excellent stability of the ring structure.

Examples of the lactone ring structure include structures represented by the following formula (1). In the following formula (1), R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

In the lactone ring structure of the formula (1), examples of the organic residue of R ¹ , R ² and R ³ include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t An alkyl group having 1 to 20 carbon atoms such as -butyl group, n-pentyl group, isopentyl group, n-hexyl group, 2-ethylhexyl group; 3 to 3 carbon atoms such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group 20 cycloalkyl group; alkenyl group having 2 to 20 carbon atoms such as ethenyl group and propenyl group; aryl group having 6 to 20 carbon atoms such as phenyl group, tolyl group, xylyl group, naphthyl group, biphenyl group; benzyl group And an aralkyl group having 7 to 20 carbon atoms such as a phenylethyl group. These groups may have an arbitrary substituent (for example, a hydroxy group, a carboxyl group, an alkoxy group, an ester group, etc.). In addition, R ¹ and R ³ are each independently preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ² is 1 carbon atom from the viewpoint of easy production of the acrylic polymer having a lactone ring structure. Alkyl groups of 6 are preferred.

  When the lactone ring structure is included as the ring structure, the content of the lactone ring structure in the acrylic polymer is not particularly limited, but is, for example, preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 20% by mass or more. Further, 90% by mass or less is preferable, 80% by mass or less is more preferable, 70% by mass or less is further preferable, and 60% by mass or less is particularly preferable. If the content of the lactone ring structure is too low, the effect of introducing a ring structure into the main chain becomes difficult to obtain, while if it is too high, the moldability at the time of molding the acrylic polymer into a film or the like may decrease. is there. The content of the lactone ring structure in the acrylic polymer can be determined, for example, by the method described in JP2007-070607A.

As the glutarimide ring structure, for example, a structure represented by the following formula (2) is preferably exemplified. In the following formula (2), R ⁴ and R ⁵ each independently represent a hydrogen atom or a methyl group, and R ⁶ is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a cycloalkyl having 3 to 12 carbon atoms. It represents an alkyl group, an aryl group having 6 to 10 carbon atoms or an aralkyl group having 7 to 12 carbon atoms.

In the glutarimide ring structure of the formula (2), examples of the alkyl group having 1 to 18 carbon atoms of R ⁶ include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t -Butyl group, n-pentyl group, isopentyl group, n-hexyl group, 2-ethylhexyl group and the like. Examples of the cycloalkyl group having 3 to 12 carbon atoms of R ⁶ include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group and the like. Examples of the aryl group having 6 to 10 carbon atoms for R ⁶ include a phenyl group, a tolyl group, a xylyl group, a naphthyl group and a biphenyl group. Examples of the aralkyl group having 7 to 12 carbon atoms of R ⁶ include a benzyl group and a phenylethyl group.

  When the acrylic polymer has a glutarimide ring structure as the ring structure, the content of the glutarimide ring structure in the acrylic polymer is not particularly limited, but is preferably 5% by mass or more, more preferably 10% by mass or more, and 20% by mass or more. More preferably, it is preferably 90% by mass or less, more preferably 70% by mass or less, further preferably 60% by mass or less, particularly preferably 50% by mass or less. If the content of the glutarimide ring structure is too low, it becomes difficult to obtain the effect of introducing the ring structure into the main chain, while if it is too high, the moldability at the time of molding the acrylic polymer into a film or the like may decrease. There is. The content of the glutarimide ring structure in the acrylic polymer can be determined, for example, by the method described in JP 2006-131689 A.

Preferred examples of the maleimide ring structure include structures represented by the following formula (3). In the following formula (3), R ⁷ and R ⁸ each independently represent a hydrogen atom or a methyl group, and R ⁹ is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a cycloalkyl having 3 to 12 carbon atoms. It represents an alkyl group, an aryl group having 6 to 10 carbon atoms or an aralkyl group having 7 to 12 carbon atoms.

Specific examples of R ⁹ in the maleimide ring structure of the formula (3) include the groups exemplified for R ⁶ of the glutarimide ring structure. Examples of the maleimide ring structure of the formula (3) include structural units derived from N-methylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-benzylmaleimide and the like.

  When having a maleimide ring structure as the ring structure, the content of the maleimide ring structure in the acrylic polymer is not particularly limited, but for example, 5 mass% or more is preferable, 10 mass% or more is more preferable, and 20 mass% or more is further preferable. Further, 90% by mass or less is preferable, 70% by mass or less is more preferable, 60% by mass or less is further preferable, and 50% by mass or less is particularly preferable. If the content of the maleimide ring structure is too low, the effect of introducing a ring structure into the main chain becomes difficult to obtain, while if it is too high, the moldability at the time of molding the acrylic polymer into a film or the like may decrease. is there. The content rate of the maleimide ring structure in the acrylic polymer can be determined from the copolymerization amount of maleimide (N-substituted maleimide).

  The acrylic polymer preferably contains a unit derived from a (meth) acrylic acid ester (hereinafter sometimes referred to as “(meth) acrylic acid ester unit”). By introducing the (meth) acrylic acid ester unit into the acrylic polymer, the glass transition temperature and fluidity of the acrylic polymer can be adjusted. Examples of the (meth) acrylic acid ester unit include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and t- (meth) acrylate. -Butyl, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, dicyclopentanyloxyethyl (meth) acrylate, (meth) Dicyclopentanyl acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and (meth) acrylic acid 2 , 3,4,5,6-pentahydroxyhexyl, 2,3,4,5-tetrahydroxypentyl (meth) acrylate, and other structural units derived from monomers. The acrylic polymer may contain only one type of these (meth) acrylic acid ester units, or may include two or more types thereof. Among them, it is preferable that the acrylic polymer contains a methyl methacrylate (MMA) unit, which makes it easier to increase the heat resistance of the acrylic polymer.

  The acrylic polymer may include a structural unit in which the α-position and / or the β-position of the acrylate ester is substituted. However, those in which the α-position is substituted with a methyl group are (meth) acrylic acid esters, and are therefore excluded. Examples of such structural units include methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, methyl 2- (hydroxyethyl) acrylate, and ethyl 2- (hydroxyethyl) acrylate. 2- (hydroxyalkyl) acrylic acid ester; structural units derived from monomers such as 2-halogenated acrylic acid ester such as 2-chloroacrylic acid ester.

  The acrylic polymer may further contain other constitutional units other than the above. As other structural units, for example, styrene, vinyltoluene, α-methylstyrene, α-hydroxymethylstyrene, α-hydroxyethylstyrene, acrylonitrile, methacrylonitrile, methallyl alcohol, allyl alcohol, ethylene, propylene, 4- Structural units derived from monomers such as methyl-1-pentene, vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinyl pyrrolidone, N-vinyl carbazole, vinyl pyridine, and vinyl imidazole are mentioned. ..

  Acrylic polymers have high transparency and can be used as optical materials. However, while the ring structure of the main chain of acrylic polymers shows positive birefringence, styrene, vinyltoluene, α-methylstyrene, α Since a structural unit (styrene unit) derived from a styrene-based monomer such as -hydroxymethylstyrene or α-hydroxyethylstyrene exhibits negative birefringence, if the acrylic polymer contains a styrene unit, both The birefringences of 1 and 2 may cancel each other out to provide low birefringence as a whole. In this respect, it is also preferable that the acrylic polymer contains a styrene unit. The content of styrene units in the acrylic polymer is preferably 10% by mass or less, more preferably 8% by mass or less, still more preferably 5% by mass or less. The content of styrene units in the acrylic polymer can be determined from the copolymerization amount of styrene monomer.

  The acrylic polymer of the present invention preferably has a glass transition temperature of 110 ° C. or higher, more preferably 115 ° C. or higher, even more preferably 120 ° C. or higher. When the acrylic polymer has such a glass transition temperature, the acrylic polymer can be applied to applications requiring heat resistance, such as image display devices. For example, the glass transition temperature of poly (methyl methacrylate) is usually about 100 ° C., but the glass transition temperature of the acrylic polymer can be set to 110 ° C. or higher by introducing a ring structure into the main chain. On the other hand, the upper limit of the glass transition temperature of the acrylic polymer is preferably 250 ° C. or lower, more preferably 230 ° C. or lower, still more preferably 210 ° C. or lower, and 200 ° C. from the viewpoint of ensuring moldability into a film or the like. The following are particularly preferred. The glass transition temperature of the acrylic polymer is determined according to JIS K 7121.

  The acrylic polymer of the present invention has a weight average molecular weight of 17,000 or more. By setting the weight average molecular weight of the acrylic polymer to be 17,000 or more, the hardness and brittleness of the acrylic polymer can be improved, and the breaking strength of a molded article obtained by molding the acrylic polymer can be increased. On the other hand, from the viewpoint of improving moldability, the weight average molecular weight of the acrylic polymer is preferably 250000 or less, more preferably 230000 or less, and further preferably 200000 or less. As the weight average molecular weight, a polystyrene-converted value measured by gel permeation chromatography (GPC) is used.

  The acrylic polymer of the present invention has a melt flow rate of 7.1 g / 10 min or more measured at a temperature of 240 ° C. and a load of 98 N. When the acrylic polymer has such a melt flow rate, the melt viscosity of the acrylic polymer is lowered and the moldability can be improved. Further, when removing the foreign matter from the melt of the acrylic polymer through the filter prior to the molding process, it is possible to suppress the pressure loss of the filter to a low level and improve the productivity. The melt flow rate is more preferably 7.2 g / 10 min or more, further preferably 7.3 g / 10 min or more. On the other hand, if the melt viscosity is too low, the molding process such as film molding and stretching may become difficult. Therefore, the melt flow rate is preferably 12.0 g / 10 min or less, and 11.5 g / 10 min or less. More preferable. The melt flow rate of the acrylic polymer is determined according to JIS K 7210 (method B).

  Since the acrylic polymer of the present invention has the above glass transition temperature, weight average molecular weight and melt flow rate, it has high heat resistance and breaking strength, and is excellent in moldability and productivity. .. Therefore, for example, it becomes possible to manufacture more precise optical components than ever.

The breaking energy (E) when the acrylic polymer of the present invention is melted at a temperature of glass transition temperature (Tg) + 150 ° C. and formed into an unstretched film having a thickness of 100 μm is preferably 18 mJ or more. , 19 mJ or more is more preferable, and 20 mJ or more is still more preferable. The breaking energy was measured by dropping a ball having a mass of 0.0054 kg from a certain height on an unstretched film having a thickness of 100 μm formed as described above 15 times, and the height at which the film was broken ( The breaking energy (E) is calculated from the average value of the breaking heights according to the following formula: breaking energy E (mJ) = sphere mass (kg) × breaking height average value (mm) × 9.8 (m / s) ² ). Destruction of the film is judged visually. The larger the breaking energy (E), the more preferable, and the upper limit thereof is not particularly limited, but may be 50 mJ or less, for example.

  The acrylic polymer preferably has a structure in which the main chain is branched. If the main chain of the acrylic polymer has a branched structure, the melt flow rate can be increased while increasing or maintaining the weight average molecular weight. For example, a method of adding a plasticizer can be considered as a method of improving the fluidity of the polymer in a molten state, but the addition of a plasticizer is not preferable because it easily causes a bleed-out problem during melt molding. However, by giving the main chain of the acrylic polymer a branched structure, it is possible to improve the fluidity of the polymer in a molten state without adding a plasticizer. In the present invention, a continuous portion of a unit derived from a (meth) acrylic monomer containing a ring structure is referred to as a main chain, and an acrylic polymer having a branched main chain has a branched main chain. It is preferable that there is a continuous portion of units derived from a (meth) acrylic monomer containing a ring structure.

  It is preferable that the acrylic polymer does not have too many branch points in order to secure fluidity in a molten state and prevent gelation. In this respect, the branched structure of the main chain is preferably formed by a trifunctional or higher functional polymerization initiator (C) and / or a trifunctional or higher functional chain transfer agent (B). That is, the acrylic polymer has one or more branch units formed by a polymerization initiator and / or a chain transfer agent, and has a branched structure in which three or more main chains having a ring structure are bonded to the branch units. Preferably. By thus forming a structure in which the main chain is branched, it is possible to control so that the number of branch points does not become excessive. Further, it can be easily applied to various conventional uses without significantly changing the physical properties of the conventional acrylic polymer having a cyclic structure in the linear main chain.

  Examples of the tri- or more functional polymerization initiator (C) include tris (t-butylperoxy) triazine, tris (t-amylperoxy) triazine, tris (di-t-butylperoxycyclohexyl) triazine, tris ( Trifunctional peroxides such as dicumylperoxycyclohexyl) triazine; 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-) Hexylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-octylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-amylperoxycyclohexyl) propane, 2 , 2-bis (4,4-dicumylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) butane, 3,3 ′, 4,4′-tetra ( t-butylperoxycarbonyl) benzophenone, 3,3 ′, 4,4′-tetra (t-amylperoxycarbonyl) benzophenone, 3,3 ′, 4,4′-tetra (t-hexylperoxycarbonyl) benzophenone , 3,3 ′, 4,4′-tetra (t-cumylperoxycarbonyl) benzophenone and other tetrafunctional peroxides; and the like.

The acrylic polymer preferably has a trifunctional or higher functional peroxide-derived branching unit, specifically, a branching unit represented by the following formula (4). In the following formula (4), L _S represents an m + 3 valent organic residue (initiator residue), and m represents a number of 0 or more. m is preferably 0-5.

  As the trifunctional or higher functional chain transfer agent (B), it is preferable to use a polyvalent mercaptan. For example, trimethylolpropane tristhioglycolate, trimethylolpropane tristhiopropionate, trimethylolpropane tristhiobutanate, 1, Trifunctional mercaptans such as 3,5-triazine-2,4,6-trithiol; pentaerythritol tetrakisthioglycolate, pentaerythritol tetrakisthiopropionate, pentaerythritol tetrakis (4-mercaptobutanate), and pentaerythritol tetrakis. Examples thereof include tetrafunctional mercaptans such as (6-mercaptohexanate); hexafunctional mercaptans such as dipentaerythritol hexakis (3-mercaptopropionate); and the like.

The acrylic polymer also preferably has a trifunctional or higher functional mercaptan-derived branching unit, and specifically, preferably has a branching unit (chain transfer agent residue) represented by the following formula (5). In the following formula (5), L _T represents an n + 3 valent organic residue, and n represents a number of 0 or more. n is preferably 0-5.

  The acrylic polymer may contain only one or both of a branch unit derived from a trifunctional or higher functional polymerization initiator and a branch unit derived from a trifunctional or higher functional chain transfer agent. The branching unit derived from a tri- or more functional polymerization initiator may be contained in only one kind, or may be contained in two or more kinds. The branching unit derived from a trifunctional or higher functional chain transfer agent may be contained in only one kind or in two or more kinds.

  The content of the trifunctional or more functional polymerization initiator and the branch unit derived from the chain transfer agent in the acrylic polymer is preferably 0.02 parts by mass or more, and 0.05 parts by mass in 100 parts by mass of the acrylic polymer. It is more preferably at least 0.1 part by mass, still more preferably at least 0.1 part by mass, preferably at most 0.6 part by mass, more preferably at most 0.5 part by mass, still more preferably at most 0.4 part by mass. The content of the branching unit is determined by dividing the amounts of the trifunctional or higher functional polymerization initiator and the trifunctional or higher functional chain transfer agent by the mass of the solid content of the obtained acrylic polymer.

  The degree of branching of the polymer contained in the acrylic polymer of the present invention is preferably 1.0 or more, more preferably 1.4 or more, and preferably 10.0 or less, more preferably 6.0 or less, 4 It is more preferably 0.0 or less. By setting the degree of branching to 1.0 or more, the branched structure of the main chain is sufficiently contained in the polymer, and it becomes easy to improve the fluidity of the acrylic polymer in the molten state to a desired degree. The branching degree obtained by the branching degree quantification method corresponds to the average number of branching points per polymer molecule. Theoretically, for example, a straight-chain polymer without branching has a degree of branching of 0, and a polymer in which three polymer chains extend from a single branching point has a degree of branching of 1 and has four polymer chains. The degree of branching of the polymer in which is extended is 2, and the degree of branching of the polymer in which five polymer chains are extended is 3.

  The branching degree quantification method is a linear structure obtained by extrapolating the linear region of the analytical value of the absolute molecular weight Mw of 400,000 or less of the branching standard polymer having the same composition as the linear structure, and the analytical value of the polymer having the branched structure is randomly polydispersed. It can be calculated and calculated using a model. The detailed theory is described in the following document, and the description is incorporated by reference: "GPC School Handbook" (text for training), published by Malvern; Hirohide Matsushita, "Polymer Chemistry II Physical Properties" Published by Maruzen Co., Ltd. The measuring instrument is not particularly limited. For example, a GPC system HLC-8320 manufactured by Tosoh Corporation is connected to a Viscotek TDA (light scattering / viscosity / refractive index detector) manufactured by Malvern, and a Mark-Houwink Plot is created from the obtained measurement results. It can be calculated by doing. The developing solvent is not particularly limited as long as it can dissolve the polymer, and examples thereof include tetrahydrofuran and chloroform.

  The method for producing the acrylic polymer of the present invention will be described. The method for producing an acrylic polymer of the present invention has a step of polymerizing a monomer component (A) containing a (meth) acrylic acid ester monomer, and a trifunctional or higher functional initiator (C) is added during polymerization. It is characterized in that it is used and / or the polymerization is carried out in the presence of a trifunctional or higher functional chain transfer agent (B). In the said process, the main chain comprised from the unit derived from the (meth) acrylic-type monomer containing a (meth) acrylic acid ester is formed, At this time, a trifunctional or more than trifunctional initiator (C) and / or trifunctional By using the above chain transfer agent (B), a structure having a branched main chain can be obtained. Hereinafter, this step is referred to as "main chain forming step". According to the production method of the present invention, a decrease in melt flow rate can be prevented even when the molecular weight is increased.

  In the main chain forming step, the main component is formed by polymerizing the monomer component (A) containing the (meth) acrylic acid ester monomer. The monomer component (A) contains at least a (meth) acrylic acid ester monomer, and if necessary, a monomer other than the (meth) acrylic acid ester may be used. The acrylic polymer of the present invention has a ring structure in the main chain, and this ring structure may be introduced at the stage of forming the main chain or after the formation of the main chain. For example, in the case of copolymerizing a (meth) acrylic monomer and a monomer having a polymerizable double bond in the ring structure, the ring structure can be introduced at the stage of forming the main chain. When a monomer having a polymerizable double bond in such a ring structure is not used, a main chain is formed in advance by homopolymerizing or copolymerizing a (meth) acrylic monomer. A ring structure can be introduced after the main chain is formed by appropriately cyclizing a portion of the chain adjacent to the unit derived from the (meth) acrylic monomer. Details of the cyclization method will be described later.

  Examples of the (meth) acrylic acid ester monomer that can be used in the main chain forming step include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and n- (meth) acrylate. Butyl, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, dicyclo (meth) acrylate Pentanyloxyethyl, dicyclopentanyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxy (meth) acrylate Examples include propyl, 2,3,4,5,6-pentahydroxyhexyl (meth) acrylic acid, and 2,3,4,5-tetrahydroxypentyl (meth) acrylic acid. The (meth) acrylic acid ester monomers may be used alone or in combination of two or more.

  When producing an acrylic polymer having a lactone ring structure in the main chain, it is preferable to use a (meth) acrylic monomer having a hydroxy group as the monomer component (A). The (meth) acrylic monomer having a hydroxy group may be a (meth) acrylic acid ester monomer.

It is preferable to use a monomer represented by the following formula (6) as the (meth) acrylic monomer having a hydroxy group. Therefore, when producing an acrylic polymer having a lactone ring structure in the main chain, use a (meth) acrylic acid ester monomer and a monomer represented by the following formula as the monomer component (A). Is preferred. In the following formula (6), R ¹⁰ and R ¹¹ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms.

  Examples of the monomer represented by the formula (6) include methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, and 2- (hydroxymethyl). Examples include n-butyl acrylate and t-butyl 2- (hydroxymethyl) acrylate. These monomers may be used alone or in combination of two or more. Of these monomers, methyl 2- (hydroxymethyl) acrylate and ethyl 2- (hydroxymethyl) acrylate are preferable, and methyl 2- (hydroxymethyl) acrylate has a high effect of improving heat resistance. Is more preferable.

  The acrylic polymer having a lactone ring structure in the main chain is a monomer containing a (meth) acrylic monomer having a hydroxy group and a (meth) acrylic acid ester or (meth) acrylic acid in the main chain forming step. After polymerizing the body component (A) to introduce a substituent having a hydroxy group into the main chain and an ester group or a carboxyl group, dealcoholization or dehydration between the hydroxy group and the ester group or the carboxyl group in the cyclization step. A lactone ring structure can be formed in the main chain by causing cyclocondensation.

  When producing an acrylic polymer having a glutarimide ring structure in the main chain, a monomer component (A) containing a (meth) acrylic acid ester monomer is polymerized in the main chain forming step to produce (meth). After obtaining the acrylic acid ester polymer, the glutarimide ring structure can be formed in the main chain by reacting with an imidizing agent such as amine or ammonia in the cyclization step to imidize. Further, after using (meth) acrylic acid ester and (meth) acrylamide as the monomer component (A) and copolymerizing them in the main chain forming step to introduce an amide group and an ester group into the main chain, A glutarimide ring structure can also be formed in the main chain by cyclocondensing an amide group and an ester group in the cyclization step.

  In the case of producing an acrylic polymer having a maleimide ring structure in the main chain, N-methylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-benzylmaleimide, or another N-type monomer is used as the monomer component (A). By using a substituted maleimide together with a (meth) acrylic acid ester and copolymerizing an N-substituted maleimide and a (meth) acrylic acid ester in the main chain forming step, a maleimide ring structure can be introduced into the main chain.

  The monomer component (A) may contain a vinyl monomer other than the (meth) acrylic acid ester monomer. Examples of other vinyl monomers include (meth) acrylic acid, styrene, vinyltoluene, α-methylstyrene, α-hydroxymethylstyrene, α-hydroxyethylstyrene, acrylonitrile, methacrylonitrile, methallyl alcohol, and allyl. Examples thereof include alcohol, ethylene, propylene, 4-methyl-1-pentene, vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinylpyrrolidone, N-vinylcarbazole, vinylpyridine and vinylimidazole.

  It is preferable that the monomer component (A) contains a (meth) acrylic acid ester monomer as a main component, whereby it is easy to increase the transparency or heat resistance of the resulting acrylic polymer. Become. Specifically, in 100 parts by mass of the monomer component (A), the (meth) acrylic acid ester monomer is preferably contained in an amount of 50 parts by mass or more, more preferably 55 parts by mass or more, and 60% by mass or more. More preferable. The upper limit of the ratio of the (meth) acrylic acid ester monomer in the monomer component (A) is not particularly limited, and the (meth) acrylic acid ester monomer is 100 parts by mass in 100 parts by mass of the monomer component (A). It may be less than or equal to parts by mass, for example, less than or equal to 90 parts by mass.

  The monomer component (A) may contain a styrene-based monomer such as styrene, vinyltoluene, α-methylstyrene, α-hydroxymethylstyrene, α-hydroxyethylstyrene. Acrylic polymers have high transparency and can be used as optical materials. However, while the ring structure of the main chain of acrylic polymers shows positive birefringence, structural units derived from styrene monomers (styrene Since a unit) shows negative birefringence, if a styrene-based monomer is used as a part of the monomer component (A), the birefringences of the both cancel each other out, resulting in an acrylic birefringence as a whole. It becomes easy to obtain a polymer. The content of the styrene-based monomer is preferably 10% by mass or less, more preferably 8% by mass or less, still more preferably 5% by mass or less, in 100 parts by mass of the monomer component (A). If the content of the styrene-based monomer is more than 10% by mass, the cyclization reaction may be hindered in the cyclization step described later, and the monomer component (A) may not contribute to cyclization. Therefore, problems such as deterioration of physical properties and productivity due to insufficient cyclization reaction may occur.

  The monomer component (A) can be polymerized by a known polymerization method such as a bulk polymerization method, a solution polymerization method, an emulsion polymerization method or a suspension polymerization method, but it is a polymerization method using a solvent. The solution polymerization method is preferred. By using the solution polymerization method, it is possible to suppress the mixing of minute foreign substances into the acrylic polymer, and it becomes easy to suitably apply the acrylic polymer to optical material applications and the like.

  As the polymerization method, for example, either a batch polymerization method or a continuous polymerization method can be used. During the polymerization, the monomer component (A) may be charged all at once or may be added in portions.

  The polymerization solvent can be appropriately selected according to the composition of the monomer component (A), and an organic solvent used in a usual radical polymerization reaction can be used. Specifically, aromatic hydrocarbons such as toluene, xylene and ethylbenzene; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ethers such as tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and anisole; acetic acid Esters such as ethyl, butyl acetate, propylene glycol monomethyl ether acetate, 3-methoxybutyl acetate; alcohols such as methanol, ethanol, isopropanol, n-butanol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether; acetonitrile, propionitrile , Butyronitrile, benzonitrile and the like; chloroform; dimethyl sulfoxide and the like. These solvents may be used alone or in combination of two or more.

  The concentration of the monomer component (A) in the polymerization solvent may be appropriately set depending on the polymerization conditions, the desired molecular weight of the resulting acrylic polymer, and the like. The concentration of the monomer component (A) in the polymerization solvent is, for example, preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and preferably 300 parts by mass or less, relative to 100 parts by mass of the solvent. It is more preferably 200 parts by mass or less.

  In the main chain forming step, a trifunctional or higher functional initiator (C) is used during the polymerization of the monomer component (A), or the polymerization is carried out in the presence of a trifunctional or higher functional chain transfer agent (B). Only one or both of the trifunctional or higher functional initiator (C) and the trifunctional or higher functional chain transfer agent (B) may be used. By using a trifunctional or higher functional initiator (C) and / or a trifunctional or higher functional chain transfer agent (B), an acrylic polymer having a branched main chain structure can be obtained. As a result, the weight average molecular weight was 17,000 or more, the melt flow rate measured at a temperature of 240 ° C. and a load of 98 N was 7.1 g / 10 min or more and 12.0 g / 10 min or less, and the glass transition temperature was 110 ° C. or more. It is possible to easily obtain the acrylic polymer.

  As the trifunctional or higher functional initiator (C), for example, a trifunctional or higher functional peroxide can be used. Specific examples of the trifunctional or higher functional peroxide are as described above. Considering availability, the initiator (C) is preferably trifunctional or more and octafunctional or less.

  The initiator (C) may be added all at once during the polymerization of the monomer component (A) or may be added in portions. The amount of the initiator (C) used (total amount used in the case of divided addition) may be appropriately set according to the desired physical properties of the resulting acrylic polymer, for example, 100 parts by mass of the monomer component (A). It is preferable to use 0.02 parts by mass or more of the trifunctional or higher functional initiator (C), more preferably 0.05 parts by mass or more, further preferably 0.1 parts by mass or more, and 2 parts by mass. The following is preferable, 0.8 parts by mass or less is more preferable, 0.7 parts by mass or less is further preferable, and 0.6 parts by mass or less is particularly preferable.

  In the main chain forming step, a difunctional or lower functional initiator may be used as a polymerization initiator. The difunctional or lower functional initiator may be used in combination with the trifunctional or higher functional initiator (C), or may be used alone. In the latter case, the use of a trifunctional or higher functional chain transfer agent (B) is essential. As the bifunctional or lower initiator, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amylperoxy- Organic peroxides such as 2-ethylhexanoate; 2,2'-azobis (isobutyronitrile), 1,1'-azobis (cyclohexanecarbonitrile), 2,2'-azobis (2-methylisobutyrate) And azo compounds such as 2,2′-azobis (2,4-dimethylvaleronitrile); and the like.

  As the trifunctional or higher functional chain transfer agent (B), for example, a trifunctional or higher functional mercaptan can be used. Specific examples of trifunctional or higher functional mercaptans are as described above. The chain transfer agent (B) is preferably trifunctional or more and octafunctional or less in consideration of availability.

  The chain transfer agent (B) may be added all at once during the polymerization of the monomer component (A) or may be added in portions. The amount of the chain transfer agent (B) used (total amount used in the case of divided addition) may be appropriately set according to the desired physical properties of the resulting acrylic polymer, and for example, the monomer component (A) 100 It is preferable to use 0.02 parts by mass or more of the trifunctional or higher functional chain transfer agent (B), more preferably 0.05 parts by mass or more, further preferably 0.1 parts by mass or more, and 0 The amount is preferably 0.6 parts by mass or less, more preferably 0.5 parts by mass or less, still more preferably 0.4 parts by mass or less.

  In the main chain forming step, a chain transfer agent having a functionality of 2 or less may be used. The bifunctional or lower functional chain transfer agent may be used in combination with the trifunctional or higher functional chain transfer agent (B), or may be used alone. In the latter case, the use of a trifunctional or higher functional initiator (C) is essential. Examples of the bifunctional or less chain transfer agent include butanethiol, octanethiol, octadecanethiol, cyclohexylmercaptan, thiophenol, octyl thioglycolate, octyl 2-mercaptopropionate, octyl 3-mercaptopropionate, and 2-ethylhexyl mercaptopropionate. Ester, octanoic acid 2-mercaptoethyl ester, 1,8-dimercapto-3,6-dioxaoctane, dodecyl mercaptan, ethylene glycol bisthioglycolate and other bifunctional or lower mercaptans; carbon tetrachloride, carbon tetrabromide, Halogen compounds such as methylene chloride, bromoform and bromotrichloroethane; and the like.

  The temperature of the polymerization reaction may be appropriately adjusted depending on the type of the polymerization solvent and the degree of progress of the polymerization reaction, but is preferably 50 ° C. or higher, more preferably 55 ° C. or higher, and 160 ° C. or lower, preferably 145 ° C. The following is more preferable. The time of the polymerization reaction may be appropriately adjusted according to the degree of progress of the polymerization reaction, and may be, for example, 1 to 48 hours (preferably 3 to 24 hours).

  When the acrylic polymer has a lactone ring structure or a glutarimide ring structure in the main chain, the method for producing an acrylic polymer of the present invention is It is preferable to perform a cyclization step of introducing a ring structure.

  In the cyclization step, the lactone ring structure or glutarimide ring structure can be formed in the main chain by heating the uncyclized polymer obtained in the main chain formation step. When obtaining an acrylic polymer having a lactone ring structure in the main chain, the uncyclized polymer having a substituent having a hydroxy group in the main chain and an ester group or a carboxyl group obtained in the main chain forming step is heated. By doing so, a dealcoholization or a dehydration cyclization condensation reaction occurs between the hydroxy group and the ester group or the carboxyl group, and a lactone ring structure can be formed in the main chain. When obtaining an acrylic polymer having a glutarimide ring structure in the main chain, an imidizing agent is added to the uncyclized polymer containing the (meth) acrylic acid ester unit obtained in the main chain formation step and heated. As a result, an imidization reaction occurs and a glutarimide ring structure can be formed in the main chain. Alternatively, by heating an uncyclized polymer containing a (meth) acrylic acid ester unit and a (meth) acrylamide unit obtained in the main chain forming step, a cyclized condensation reaction of an amide group and an ester group occurs, A glutarimide ring structure can be formed in the main chain.

  As the imidizing agent, amine or ammonia can be used. It is preferable to use a primary amine as the amine, for example, an alkylamine having an alkyl group having 1 to 18 carbon atoms: a cycloalkylamine having a cycloalkyl group having 3 to 12 carbon atoms; an aryl group having 6 to 10 carbon atoms And arylamines (eg, aniline, toluidine, trichloroaniline, etc.); aralkylamines having an aralkyl group having 7 to 12 carbon atoms (eg, benzylamine, etc.) and the like can be used. These imidizing agents may be used alone or in combination of two or more.

  A catalyst is preferably used in the cyclization reaction. As a catalyst for the cyclization reaction, at least one selected from the group consisting of acids, bases and salts thereof can be used. The acid, base and salts thereof may be organic or inorganic and are not particularly limited.

  An organic phosphorus compound is preferably used as a catalyst for forming the lactone ring structure. By using the organic phosphorus compound as the cyclization catalyst, the cyclization reaction rate of the lactone ring can be improved, and coloring of the resulting acrylic polymer having a lactone ring structure can be significantly reduced. Examples of the organic phosphorus compound that can be used as the cyclization catalyst include alkyl (aryl) phosphonous acid and monoesters or diesters thereof; dialkyl (aryl) phosphinic acid and esters thereof; alkyl (aryl) phosphonic acid and these Alkyl (aryl) phosphinic acid and their esters; phosphorous monoesters, diesters or triesters; methyl phosphate, ethyl phosphate, 2-ethylhexyl phosphate, octyl phosphate, isodecyl phosphate , Lauryl phosphate, stearyl phosphate, isostearyl phosphate, phenyl phosphate, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, distearyl phosphate, diphosphate Phosphate monoesters, diesters or triesters such as isostearyl, diphenyl phosphate, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate, triphenyl phosphate; Mono-, di- or tri-alkyl (aryl) phosphines; alkyl (aryl) halogen phosphines; mono-, di- or tri-alkyl (aryl) phosphines; tetraalkyl (aryl) phosphonium halides; These organic phosphorus compounds may be used alone or in combination of two or more. Among these, phosphoric acid monoesters or diesters are particularly preferable because they have high catalytic activity and low colorability.

  As a catalyst for forming the glutarimide ring structure, it is preferable to use a compound having an alkali metal because the cyclization reaction rate of the glutarimide ring is high. Examples of the compound having an alkali metal include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide; sodium methoxide, sodium ethoxide, sodium phenoxide, potassium methoxide, potassium ethoxide and potassium phenoxide. Alkali metal alkoxides such as; and organic acid alkali metal salts such as lithium acetate, sodium acetate, potassium acetate, sodium stearate, and the like. Among these compounds having an alkali metal, sodium hydroxide, sodium methoxide, lithium acetate and sodium acetate are preferable, and sodium methoxide and lithium acetate are more preferable.

  The amount of the catalyst used is not particularly limited, but it is preferably used within a range that does not adversely affect the obtained acrylic polymer such as coloring and does not reduce the transparency of the acrylic polymer. The amount of the catalyst used is preferably, for example, about 0.001 to 1 part by mass with respect to 100 parts by mass of the uncyclized polymer.

  The heating in the cyclization step, the polymerization solution containing the polymerization solvent obtained in the main chain forming step may be heated as it is, may be heated after devolatilizing the polymerization solvent, or both of them in combination. You can go. Examples of the reactor used for the cyclization reaction include an autoclave, a kettle type reactor, a device including a heat exchanger and a devolatilizing tank, an extruder with a vent, and the like. The heating temperature may vary depending on the presence or absence of the polymerization solvent and the type of reactor, but may be set in the range of 40 ° C to 380 ° C, for example.

  In the cyclization step, it is preferable to perform the cyclization reaction while devolatilizing. The devolatilization may be performed throughout the cyclization reaction or may be performed during a part of the cyclization reaction. The devolatilization removes the polymerization solvent used in the main chain formation step brought into the cyclization step and the alcohol by-produced by the cyclization reaction, thereby reducing the residual volatile content in the resulting acrylic polymer. You can Further, since alcohol and the like produced as a by-product in the cyclization reaction are removed, the reaction equilibrium tends to the production side, which is advantageous. Examples of the reactor in this case include a device including a heat exchanger and a devolatilizing tank, a vented extruder, a device in which a devolatilizing device and an extruder are arranged in series, and the like.

  When the cyclization reaction is carried out while devolatilization, the heating temperature is preferably 150 ° C. or higher, more preferably 200 ° C. or higher, whereby the cyclization reaction can be favorably advanced and the obtained acrylic polymer It is possible to reduce the residual volatile content in the inside. On the other hand, the heating temperature is preferably 380 ° C. or lower, more preferably 350 ° C. or lower, further preferably 300 ° C. or lower, whereby the decomposition of the acrylic polymer due to excessive heat history can be suppressed, and a decrease in molecular weight can be suppressed. it can. In addition, the transparency of the acrylic polymer can be easily ensured.

  When carrying out the cyclization reaction while devolatilizing, it is preferable to carry out the cyclization reaction under reduced pressure from the viewpoint of efficiently devolatilizing. The reduced pressure in the cyclization reaction is, for example, preferably 90 kPa or less in absolute pressure, more preferably 80 kPa or less, further preferably 70 kPa or less. On the other hand, from the viewpoint that the equipment for realizing the depressurized state does not have excessive specifications and the equipment cost is kept low, the absolute pressure when depressurizing is preferably 0.1 kPa or more, more preferably 1 kPa or more.

  When a vented extruder is used, the extruder preferably has a cylinder, a screw provided in the cylinder, and a heating unit. The cylinder is provided with one or more vents. The vent is preferably provided at least on the downstream side of the raw material charging section with respect to the transport direction in the extruder, and may also be provided on the upstream side of the raw material charging section.

  The cyclization reaction progresses in the process of transferring the uncyclized polymer supplied into the extruder from the upstream side to the downstream side of the extruder while kneading with the screw, and the acrylic polymer is discharged from the downstream side of the extruder. To be done. It is preferable that a die part for discharging the acrylic polymer from the extruder is provided on the downstream side of the extruder, and by discharging the acrylic polymer from the die part, a predetermined shape (film shape or rod shape) can be obtained. ). For example, pellets can be produced by finely cutting a rod-shaped acrylic polymer. The acrylic polymer after the cyclization reaction may be supplied to an extruder to form the acrylic polymer into any shape, and in this case, an extruder without a vent can be used. is there.

  A polymer filter is preferably provided in the die part of the extruder. As the polymer filter, for example, at least one selected from a leaf disc filter, a candle filter, a pack disc filter, and a cylindrical filter can be used. Of these, a leaf disc filter or a candle filter is preferable because of its high effective filtration area. Among them, the leaf disc filter is suitable for filtering a high-viscosity body, but due to its structure, it is easily damaged by a load. However, according to the production method of the present invention, since it is possible to suppress the pressure loss of the filter by suppressing the decrease in the melt flow rate of the acrylic polymer, even when using a leaf disk filter for the polymer filter, It is easy to prevent damage.

  The type of filter medium is not particularly limited, and may be a type obtained by sintering a metal fiber non-woven fabric, a type obtained by sintering metal powder, a type obtained by laminating wire mesh, or a hybrid type obtained by combining these. Of these, a type obtained by sintering a metal fiber nonwoven fabric is most preferable.

  The filtration accuracy (pore diameter) of the polymer filter is not particularly limited, but is usually 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less. The lower limit of filtration accuracy is not limited, but is, for example, 1 μm. If the filtration accuracy is excessively small, the demerit (for example, thermal deterioration of the acrylic polymer) due to the acrylic polymer staying in the polymer filter for a long time becomes greater than the effect of removing the foreign matter. On the other hand, if the filtration accuracy is excessively high, it becomes difficult to remove foreign substances contained in the acrylic polymer.

  The shape of the polymer filter is not particularly limited, and includes, for example, an internal flow type having a plurality of resin (polymer) flow ports and a resin (polymer) flow path inside the center pole; In the above, there is an external flow type which is in contact with the inner peripheral surface of the filter medium and has a resin (polymer) flow path on the outer surface of the center pole. In order to suppress the retention of the acrylic polymer in the polymer filter, it is preferable to use an external flow type in which the acrylic polymer retains less. The residence time of the acrylic polymer in the polymer filter is not particularly limited, but is preferably 20 minutes or less, more preferably 10 minutes or less, and further preferably 5 minutes or less.

  Since the acrylic polymer according to the present invention has a high melt flow rate, it is possible to suppress the pressure loss of the filter when removing foreign matters through the filter, and it is possible to suitably perform the filter operation.

  The acrylic polymer of the present invention can be used as a resin composition. The resin composition contains at least the acrylic polymer of the present invention and may contain other thermoplastic resin. The other thermoplastic resin may be used as, for example, a polymer blend with an acrylic polymer, or may be used as a polymer alloy.

  Examples of the other thermoplastic resin include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, poly (4-methyl-1-pentene); polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride, etc. A vinyl halide polymer; an acrylic polymer such as polymethylmethacrylate (excluding the acrylic polymer of the present invention); polystyrene, styrene-methylmethacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile -Styrene polymers such as butadiene-styrene block copolymers; polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; cellulose acylates such as cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate; nylon 6 Polyamide, nylon 66, nylon 610, etc .; Polyacetal; Polycarbonate; Polyphenylene oxide; Polyphenylene sulfide; Polyether ether ketone; Polysulfone; Polyether sulfone; Polyoxybenzylene; Polyamideimide; ABS blended with polybutadiene rubber or acrylic rubber Examples thereof include resins and rubber polymers such as ASA resins.

  The blending amount of the other thermoplastic resin in the resin composition of the present invention may be appropriately adjusted according to the application of the resin composition, and is not particularly limited, but with respect to 100 parts by mass of the resin composition, For example, it is preferably 0 to 50 parts by mass, more preferably 0 to 40 parts by mass, further preferably 0 to 30 parts by mass, particularly preferably 0 to 20 parts by mass.

  The resin composition may contain various additives. Examples of the additives include antioxidants such as hindered phenol-based antioxidants, phosphorus-based antioxidants and sulfur-based antioxidants; stabilization of light resistance stabilizers, weather resistance stabilizers, heat stabilizers, etc. Agents: Reinforcing agents such as glass fibers and carbon fibers; Near-infrared absorbers: Ultraviolet absorbers such as phenylsalicylate, (2,2′-hydroxy-5-methylphenyl) benzotriazole, 2-hydroxybenzophenone; Tris ( Flame retardants such as dibromopropyl) phosphate, triallyl phosphate, antimony oxide; antistatic agents such as anionic surfactants, cationic surfactants, nonionic surfactants; inorganic pigments, organic pigments, dyes, etc. Colorants; fillers such as organic fillers and inorganic fillers; resin modifiers; plasticizers; lubricants and the like.

  The blending amount of each additive in the resin composition may be appropriately adjusted according to the application of the resin composition and is not particularly limited, but is, for example, 0 to 100 parts by mass of the resin composition. It is preferably 5 parts by mass, more preferably 0 to 2 parts by mass, further preferably 0 to 0.5 parts by mass.

  Since the resin composition of the present invention has excellent heat resistance and breaking strength, and also has excellent transparency and molding processability, it can be applied to various uses. For example, signboards / displays, light electric / industrial parts, vehicle parts centering on automobiles, building materials / store equipment, coating materials, protective films for depainting, lighting equipment, large water tanks, optical lenses, optical prisms, optical films, optical fibers. , Optical discs and other miscellaneous goods such as mirrors, stationery, tableware, and the like, and of these applications, optical components such as optical lenses, optical prisms, optical films, optical fibers, and optical discs are particularly preferable.

  The resin composition of the present invention can be molded into various shapes depending on the application. Examples of moldable shapes include films, sheets, plates, disks, blocks, balls, lenses, rods, strands, cords and fibers. The molding method may be appropriately selected from conventionally known molding methods according to the shape, and is not particularly limited. Hereinafter, the method for producing an optical film from the resin composition of the present invention will be described by taking an optical film as an example.

  The optical film can be produced using a resin composition by a melt extrusion molding method such as a T-die method, an inflation method, a cast molding method, a press molding method, or the like. When the optical film is produced by the melt extrusion molding method, for example, a single screw extruder, a twin screw extruder or the like can be used.

  The optical film formed from the resin composition may be either an unstretched film or a stretched film. When it is a stretched film, it may be either a uniaxially stretched film or a biaxially stretched film. When it is a biaxially stretched film, it may be either a simultaneous biaxially stretched film or a sequential biaxially stretched film. When biaxially stretched, the mechanical strength is improved and the film performance is improved.

  The stretching temperature is preferably near the glass transition temperature (Tg) of the resin composition, specifically, (Tg-20 ° C) to (Tg + 80 ° C), more preferably (Tg-10 ° C) to. It is within the range of (Tg + 60 ° C.). When the stretching temperature is lower than (Tg-20 ° C), a sufficient stretching ratio may not be obtained. On the other hand, when the stretching temperature exceeds (Tg + 80 ° C.), the fluidity of the resin composition becomes too high, and stable stretching may not be performed.

  The stretching ratio of the optical film is about 1.5 to 3.0 times in each of the longitudinal direction and the transverse direction orthogonal to the longitudinal direction from the viewpoint of ensuring mechanical strength. It is more preferably about 1.5 times to 2.8 times.

  The thickness of the optical film cannot be unconditionally determined because it depends on its application. For example, when the optical film is used for a protective film, an antireflection film, a polarizing film or the like used in an image display device such as a liquid crystal display device or an organic EL display device, the thickness of the optical film is 1 μm or more. Is preferable, 10 μm or more is more preferable, 20 μm or more is further preferable, 250 μm or less is preferable, 100 μm or less is more preferable, and 80 μm or less is further preferable. Further, for example, when the optical film is used for an ITO film, a silver nanowire film, a transparent conductive film used for a metal mesh film or the like, the thickness of the optical film is preferably 20 μm or more, and 30 μm or more. Is more preferable, 40 μm or more is further preferable, 400 μm or less is preferable, 350 μm or less is more preferable, and 300 μm or less is further preferable. The thickness of the optical film is measured using, for example, a Digimatic Micrometer (manufactured by Mitutoyo).

  A coating layer may be formed on at least one surface of the optical film, if necessary. Examples of the coating layer include an antistatic layer, an adhesive layer, an adhesive layer, an easy-adhesion layer, an antiglare (non-glare) layer, a photocatalyst layer, an antifouling layer, an antireflection layer, a hard coat layer, an ultraviolet shielding layer, and a heat ray. Examples include a shielding layer, an electromagnetic wave shielding layer, a gas barrier layer and the like.

  The optical film is, for example, a protective film for an optical disc, a polarizer protective film used for a polarizing plate of an image display device such as a liquid crystal display device, a retardation film, a viewing angle compensation film, a light diffusion film, a reflection film, an antireflection film, It is expected to be used for applications such as an antiglare film, a brightness enhancement film, a conductive film for a touch panel, a diffusion plate, a light guide and a prism sheet. Therefore, the optical film is expected to be suitably used for applications such as an image display device such as a liquid crystal display device and a capacitive touch panel.

  An optical adjustment layer may be formed on the surface of the optical film. The optical adjustment layer is a layer for appropriately adjusting the transmittance or reflectance of incident light rays. The optical adjustment layer can be formed by alternately stacking a low refractive index layer having a relatively low refractive index and a high refractive index layer having a relatively high refractive index.

  The optical film having the transparent conductive layer formed on the surface of the optical film can be used as a transparent conductive film. Examples of the transparent conductive layer include an inorganic compound layer having a property of reflecting infrared rays, such as an indium-tin oxide (ITO) layer, and a metal mesh layer made of a metal such as silver, copper, nickel, or tungsten. ..

  Hereinafter, the present invention will be described in more detail by showing examples. However, the scope of the present invention is not limited to these, and it is entirely the case that modifications are made without departing from the spirit of the present invention. It is included in the technical scope of the invention.

(1) Analysis method (1-1) Weight average molecular weight (Mw)
The weight average molecular weight of the acrylic polymer was determined by gel permeation chromatography (GPC) in terms of polystyrene. The apparatus and measurement conditions used for the measurement are as follows.
-System: Tosoh GPC system HLC-8220
-Measurement side column configuration Guard column: Tosoh Corp., TSKguardcolumn SuperHZ-L
Separation column: Tosoh Corp., TSKgel SuperHZM-M 2 series connection-reference side column configuration Reference column: Tosoh Corp., TSKgel SuperH-RC
-Developing solvent: chloroform (manufactured by Wako Pure Chemical Industries, special grade)
-Flow rate of developing solvent: 0.6 mL / min-Standard sample: TSK standard polystyrene (Tosoh Corporation, PS-oligomer kit)
-Column temperature: 40 ° C

(1-2) Melt flow rate (MFR)
The melt flow rate was measured according to JIS K 7210 B method at a temperature of 240 ° C. and a load of 10 kgf (98 N).

(1-3) Glass transition temperature (Tg)
The glass transition temperature was determined according to the regulations of JIS K 7121. Specifically, using a differential scanning calorimeter (Thermo plus EVO DSC-8230, manufactured by Rigaku Co., Ltd.), about 10 mg of a sample was heated from room temperature to 200 ° C. under a nitrogen gas atmosphere (heating rate 20 ° C./min). The obtained DSC curve was evaluated by the starting point method. Α-alumina was used as a reference.

(1-4) Destructive energy (E)
The breaking energy (E) was obtained as follows. First, the acrylic polymer was melt-molded at a temperature of glass transition temperature + 150 ° C. to obtain a film (unstretched film) having a thickness of 100 μm. Next, a test in which a ball having a mass of 0.0054 kg was dropped from a certain height on the film was carried out 15 times, and the average value of the height when the film was broken (breaking height) was obtained. Specifically, the height was set in several stages, and when the sphere was dropped in order from the lowest height, the height at which the film was cracked was obtained, and this was repeated 15 times to crack the film. The height was obtained 15 times, and the average value was obtained as the breaking height. Whether or not the film was broken was judged by visually checking the cracks of the film after falling onto the film. If cracks were seen, the film was considered broken. The breaking energy (E) was calculated according to the following formula: breaking energy E (mJ) = sphere mass (kg) × breaking height average value (mm) × 9.8 (m / s ² ).

(2) Production of acrylic polymer (2-1) Example 1
12 parts by mass of methyl 2- (hydroxymethyl) acrylate, 83.5 parts by mass of methyl methacrylate, 82.3 parts by mass of toluene were placed in a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen introducing pipe and a dropping pump. 0.150 parts by mass of pentaerythritol tetrakis (mercaptoacetate) (A-1) was charged as a tetrafunctional chain transfer agent, and the temperature was raised to 105 ° C. while passing nitrogen. 0.076 parts by mass of t-amyl peroxyisononanoate (manufactured by Arkema Yoshitomi Co., Luperox (registered trademark) 570) was added as an initial initiator, and after 5 minutes, 4.5 parts by mass of styrene and 5.05 parts by mass of toluene. And 0.152 parts by mass of a dropping initiator t-amyl peroxyisononanoate (Arkema Yoshitomi Co., Luperox (registered trademark) 570) are added dropwise over 2 hours at 100 ° C. to 110 ° C. while performing solution polymerization. And aging was performed for 4 hours. To the obtained polymerization solution, 0.21 parts by mass of stearyl phosphate (Pholex A-18 manufactured by Sakai Chemical Industry Co., Ltd.) was added as a catalyst for the cyclization condensation reaction (cyclization catalyst), and the temperature was adjusted to about 90 ° C to 110 ° C. The cyclization condensation reaction for forming a lactone ring structure was allowed to proceed for 2 hours under reflux, and the cyclization condensation reaction was completed by passing through a multitubular heat exchanger heated to 240 ° C.

  The cyclized and condensed polymer has a barrel temperature of 250 ° C., one rear vent, four for vents (first to second, third, and fourth vents from the upstream side) and a third vent. 31.2 in a vent type screw twin-screw extruder (L / D = 52) equipped with a side feeder between the second vent and the fourth vent, and a leaf disk type polymer filter (filter pore diameter 5 μm) arranged at the tip. It was introduced at a processing rate of parts by mass / hour (converted to the amount of resin). At that time, ion-exchanged water was charged from the rear of the second, third, and fourth vents at a charging rate of 0.47 parts by mass / hour to carry out devolatilization. After the devolatilization was completed, the resin composition in a heat-melted state left in the extruder was discharged from the tip of the extruder while being filtered with a polymer filter, passed through a provided die, and further filtered with a pore diameter of 1 μm ( It was filtered by Organo Micropore Filter 1 EU) and cooled by discharging the strands into a water tank filled with cooling water maintained at a temperature within the range of 30 ± 10 ° C. By introducing this strand into a cutting machine (pelletizer), an acrylic polymer (P-1) having a lactone ring structure in its main chain and having a branched structure in its main chain formed by a polyfunctional chain transfer agent is obtained. It was

  The acrylic polymer (P-1) has a weight average molecular weight (Mw) of 176,000, a melt flow rate (MFR) of 7.4 g / 10 min, a glass transition temperature (Tg) of 124 ° C., and a breaking energy (E). Was 22.0 mJ.

(2-2) Example 2
A polyfunctional chain having a lactone ring structure in the main chain was prepared in the same manner as in Example 1 except that the amounts of the initial initiator and the dropping initiator were changed to 0.086 parts by mass and 0.172 parts by mass, respectively. An acrylic polymer (P-2) having a branched structure formed in the main chain by the transfer agent was obtained. The weight average molecular weight (Mw) of the acrylic polymer (P-2) is 171,000, the melt flow rate (MFR) is 9.0 g / 10 min, the glass transition temperature (Tg) is 124 ° C., and the breaking energy (E) is Was 20.0 mJ.

(2-3) Example 3
The procedure of Example 1 was repeated except that the amount of the tetrafunctional chain transfer agent (A-1) used was changed to 0.338 parts by mass. An acrylic polymer (P-3) having a branched structure in the chain was obtained. The weight average molecular weight (Mw) of the acrylic polymer (P-3) is 175,000, the melt flow rate (MFR) is 9.7 g / 10 min, the glass transition temperature (Tg) is 123 ° C., and the breaking energy (E) is Was 22.0 mJ.

(2-4) Comparative Example 1
The amount of toluene initially used was changed to 76.8 parts by mass, the amounts of the initial initiator and the dropping initiator were changed to 0.060 parts by mass and 0.12 parts by mass, respectively, and the chain transfer agent was changed to penta The acrylic polymer (P-4) was prepared in the same manner as in Example 1 except that 0.07 parts by mass of n-dodecyl mercaptan which was a monofunctional chain transfer agent was used instead of erythritol tetrakis (mercaptoacetate). Obtained. The acrylic polymer (P-4) was a lactone ring-containing acrylic polymer whose main chain was linear. The acrylic polymer (P-4) has a weight average molecular weight (Mw) of 165,000, a melt flow rate (MFR) of 6.2 g / 10 min, a glass transition temperature (Tg) of 123 ° C., and a breaking energy (E). Was 17.0 mJ.

(2-5) Comparative Example 2
Except that the amounts of the initial initiator and the dropping initiator used were changed to 0.072 parts by mass and 0.143 parts by mass, respectively, the main chain had a lactone ring structure in the same manner as in Comparative Example 1, and the main chain was A linear acrylic polymer (P-5) was obtained. The acrylic polymer (P-5) has a weight average molecular weight (Mw) of 146,000, a melt flow rate (MFR) of 9.0 g / 10 min, a glass transition temperature (Tg) of 123 ° C., and a breaking energy (E). Was 15.4 mJ.

(2-6) Comparative Example 3
Comparative Example 1 except that the amount of toluene used initially was changed to 85.8 parts by mass and the amounts of the initial initiator and the dropping initiator were changed to 0.090 parts by mass and 0.180 parts by mass, respectively. Similarly, an acrylic polymer (P-6) having a lactone ring structure in the main chain and a straight main chain was obtained. The acrylic polymer (P-6) has a weight average molecular weight (Mw) of 131,000, a melt flow rate (MFR) of 14.0 g / 10 min, a glass transition temperature (Tg) of 123 ° C., and a breaking energy (E). Was 14.2 mJ.

(2-7) Results The results of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Table 1. The glass transition temperature (Tg) of each of the acrylic polymers was 123 ° C. to 124 ° C., but the acrylic polymers (P-1) to (P-3) polymerized by using the tetrafunctional chain transfer agent were The weight average molecular weight (Mw) was 17,000 or more, and the melt flow rate (MFR) was 7.1 g / 10 min or more. As a result, the acrylic polymers (P-1) to (P-3) had a breaking energy (E) of 20.0 mJ or more, which was excellent in breaking strength. In the acrylic polymers (P-1) to (P-3), as a result of using the tetrafunctional chain transfer agent, it is possible to increase the melt flow rate (MFR) while maintaining the weight average molecular weight (Mw) high. did it.

  On the other hand, the acrylic polymers (P-4) to (P-6) polymerized by using the monofunctional chain transfer agent have a weight average molecular weight (Mw) of 165,000 or less, which is equal to the weight average molecular weight (Mw). A negative correlation was found with the melt flow rate (MFR). A certain degree of melt flow rate (MFR) is required to secure molding processability and productivity of the acrylic polymer, but in Comparative Examples 1 to 3, the melt flow rate (MFR) is 7.1 g / It was not possible to set the weight average molecular weight (Mw) to 17,000 or more while setting it to 10 min or more.

  The acrylic polymer of the present invention can be particularly preferably used as a raw material for optical parts such as optical lenses, optical prisms, optical films, optical fibers and optical disks.

Claims (16)

An acrylic polymer having at least one ring structure selected from the group consisting of a lactone ring structure, a glutarimide ring structure, and a maleimide ring structure in its main chain,
A weight average molecular weight of 17,000 or more,
The melt flow rate measured at a temperature of 240 ° C. and a load of 98 N is 7.1 g / 10 min or more and 12.0 g / 10 min or less,
Has a glass transition temperature of 110 ° C. or higher,
An acrylic polymer having a branched main chain structure. The ring structure, the acrylic polymer of claim 1 which is a lactone ring structure. Content of the said ring structure is 5 mass% or more and 90 mass% or less, The acrylic polymer of Claim 1 or 2.   The acrylic polymer according to any one of claims 1 to 3, which has a breaking energy of 18 mJ or more when formed into an unstretched film having a thickness of 100 µm.   The degree of branching is 1.0 or more and 10.0 or less, The acrylic polymer according to any one of claims 1 to 4.   A resin composition comprising the acrylic polymer according to any one of claims 1 to 5. A method for producing an acrylic polymer having in the main chain at least one kind of ring structure selected from the group consisting of a lactone ring structure, a glutarimide ring structure, and a maleimide ring structure ,
A step of polymerizing a monomer component (A) containing a (meth) acrylic acid ester monomer,
The polymerization is carried out in the presence of a trifunctional or higher functional chain transfer agent (B),
An acrylic polymer characterized by using 0.02 parts by mass or more and 0.6 parts by mass or less of the trifunctional or higher functional chain transfer agent (B) with respect to 100 parts by mass of the monomer component (A). Production method. A method for producing an acrylic polymer having in the main chain at least one kind of ring structure selected from the group consisting of a lactone ring structure, a glutarimide ring structure, and a maleimide ring structure ,
A step of polymerizing a monomer component (A) containing a (meth) acrylic acid ester monomer,
The polymerization is carried out in the presence of a trifunctional or higher functional chain transfer agent (B),
The method for producing an acrylic polymer, wherein the acrylic polymer has a melt flow rate of 7.1 g / 10 min or more and 12.0 g / 10 min or less measured at a temperature of 240 ° C. and a load of 98 N. A method for producing an acrylic polymer having in the main chain at least one kind of ring structure selected from the group consisting of a lactone ring structure, a glutarimide ring structure, and a maleimide ring structure ,
A step of polymerizing a monomer component (A) containing a (meth) acrylic acid ester monomer,
The polymerization is carried out in the presence of a trifunctional or higher functional chain transfer agent (B),
The method for producing an acrylic polymer, wherein the acrylic polymer is a thermoplastic resin.   The manufacturing method according to claim 8 or 9, wherein the trifunctional or higher functional chain transfer agent (B) is used in an amount of 0.02 parts by mass or more and 0.6 parts by mass or less with respect to 100 parts by mass of the monomer component (A). .. Said ring structure, a manufacturing method according to any one of claims 7 to 10 is a lactone ring structure. The content rate of the said ring structure in an acrylic polymer is 5 mass% or more and 90 mass% or less, The manufacturing method as described in any one of Claims 7-12 .   The manufacturing method according to any one of claims 7 to 12, which comprises 50 parts by mass or more of a (meth) acrylic acid ester monomer in 100 parts by mass of the monomer component (A).   The method according to any one of claims 7 to 13, wherein the monomer component (A) contains a vinyl monomer other than the (meth) acrylic acid ester monomer.   The production method according to any one of claims 7 to 14, wherein a trifunctional mercaptan, a tetrafunctional mercaptan or a hexafunctional mercaptan is used as the chain transfer agent (B).   As the chain transfer agent (B), trimethylolpropane tristhioglycolate, trimethylolpropane tristhiopropionate, trimethylolpropane tristhiobutanate, 1,3,5-triazine-2,4,6-trithiol, Pentaerythritol tetrakis thioglycolate, pentaerythritol tetrakis thiopropionate, pentaerythritol tetrakis (4-mercaptobutanoate), pentaerythritol tetrakis (6-mercaptohexanate), or dipentaerythritol hexakis (3-mercaptopropionate). Nate) is used, The manufacturing method as described in any one of Claims 7-15.