Manufacturing method of pellet

Abstract

To provide a method of manufacturing a resin pellet with high size uniformity.SOLUTION: A manufacturing method of a resin pellet includes a blending process of conducting formation of a resin pellet substantially in two or more sequences in the same condition and blending the resin pellets formed in the two or more sequences. The sequences includes: a polymerization process of polymerization of a monomer for formation of a thermoplastic resin; and a devolatilization and extrusion process of devolatilization of a volatile component including the monomer having been unreacted from a polymer obtained by the polymerization process as well as extrusion molding a resin composition including the thermoplastic resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing resin pellets. [Background technology]

[0002] Resin pellets made of a resin composition are produced, for example, by a strand cut method in which a molten resin composition is extruded into a strand shape, the strand is cooled, and cut with a strand cutter, or by a center hot cut method in which a molten resin composition extruded from a nozzle hole of a die is cut with a rotary blade and the cut pieces are cooled (e.g., Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-271928 Summary of the Invention [Problem to be solved by the invention]

[0004] However, resin pellets formed in a conventional single line often have large variations in pellet size, and when resin pellets with large variations in size are used to form a molded product such as a film, the quality of the molded product can be reduced due to the non-uniform size of the resin pellets.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing resin pellets having a high degree of size uniformity. [Means for solving the problem]

[0006] The present invention, which has solved the above problems, has the following configuration. [1] a polymerization step of polymerizing a monomer to form a thermoplastic resin; a devolatilization and extrusion step of removing volatile components including unreacted monomers from the polymer obtained in the polymerization step and extruding a resin composition including the thermoplastic resin, and forming resin pellets in two or more lines under substantially the same conditions; A method for producing resin pellets, comprising a mixing step of mixing the resin pellets formed in the two or more lines. [2] The method according to [1], wherein the thermoplastic resin constituting the resin pellets is a (meth)acrylic resin. [3] The method according to [2], wherein the (meth)acrylic resin is a resin having a ring structure in the main chain. [4] The manufacturing method according to [3], further comprising a cyclization step of forming a ring structure in the main chain of the thermoplastic resin formed in the polymerization step by a cyclization condensation reaction, prior to the devolatilization and extrusion steps. [Effects of the Invention]

[0007] According to the manufacturing method of the present invention, resin pellets with reduced size variation can be obtained. Furthermore, by using resin pellets with reduced size variation and high uniformity, molded products with consistent quality can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0008] An investigation into the size variation of resin pellets revealed significant variation in the resin pellets produced through the devolatilization and extrusion processes. During the devolatilization process, the viscosity of the molten resin changes depending on the degree of volatilization. The size of resin pellets produced by extrusion is also affected by viscosity, and changes in viscosity tend to lead to changes in pellet size. It was determined that the combination of the devolatilization and extrusion processes is the cause of the pellet size variation. Furthermore, it was found that the manufacturing method of the present invention, which forms resin pellets in two or more series under substantially identical conditions and includes a mixing process in which the resin pellets formed in the two or more series are mixed, narrows the variation rather than widening the variation due to the merging of the variations in each series, thereby producing resin pellets with improved size uniformity. The improved pellet size uniformity can be confirmed, for example, by a reduction in the standard deviation and / or coefficient of variation of the pellet size. Stable resin pellet size can also prevent deterioration in the quality of molded products and a decrease in production efficiency due to non-uniform pellet sizes. Furthermore, even for resin pellets containing a (meth)acrylic resin whose melt flow rate is prone to fluctuate, the production method of the present invention, which includes a mixing step of mixing two or more series of resin pellets, can easily reduce the variation in the melt flow rate (specifically, reduce the standard deviation and / or the coefficient of variation). In particular, when a cyclization step of forming a ring structure in the main chain of a thermoplastic resin is included, there is a risk that the variation in the melt flow rate will increase due to the generation of volatile components during the cyclization condensation reaction. However, the production method of the present invention can provide resin pellets with a stable melt flow rate. In the present invention, forming resin pellets under substantially the same conditions means producing resin pellets using the same recipe in equipment of the same design. The resin pellets produced under the same conditions will be divided into multiple series when the production equipment is cleaned or the equipment used is changed, etc.

[0009] (1) Polymerization process In the polymerization step, one or more monomers are homopolymerized or copolymerized to form a thermoplastic resin. The polymerization of the monomers may be carried out by any of bulk polymerization, solution polymerization, emulsion polymerization and suspension polymerization, but solution polymerization is preferred from the viewpoint of high safety and low risk of contamination with foreign matter. The polymerization may be carried out by batch polymerization or continuous polymerization. When the polymerization is carried out continuously by batch polymerization, the contents of the reactor are removed after the polymerization reaction, and the reactor is emptied. The raw materials (monomers, etc.) for the next batch can be charged again without cleaning the inside of the reactor, and the next production can be started.

[0010] The thermoplastic resin formed in the polymerization step of the present invention is not particularly limited, and examples thereof include (meth)acrylic resins; olefin resins such as polyethylene, polypropylene, ethylene-propylene copolymers, and poly(4-methyl-1-pentene); halogen-containing resins such as vinyl chloride and chlorinated vinyl resins; styrene resins such as polystyrene, styrene-methyl methacrylate copolymers, styrene-acrylonitrile copolymers (AS resins), and acrylonitrile-butadiene-styrene block copolymers (ABS resins); polyethylene terephthalate, polybutylene terephthalate, and the like. Examples of the resin include polyesters such as cellulose ether ketone, polyethylene naphthalate, and the like; polyamides such as nylon 6, nylon 66, and nylon 610; cellulose ester resins such as cellulose triacetate, cellulose acetate propionate, and cellulose acetate butyrate; polyacetal; polycarbonate; polyphenylene oxide; polyphenylene sulfide; polyether ether ketone; polysulfone; polyethersulfone; polyoxybenzylene; polyamideimide; and maleimide resins. Of these, (meth)acrylic resins are preferred from the viewpoint of heat resistance and transparency.

[0011] Monomers used in polymerization of (meth)acrylic resins include (meth)acrylic acid, (meth)acrylic acid esters, and derivatives thereof (hereinafter, these may be collectively referred to as (meth)acrylic monomers). In this specification, "(meth)acrylic acid" means acrylic acid or methacrylic acid.

[0012] Examples of the (meth)acrylic acid ester include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate (preferably methacrylic acid C 2-20 aralkyl); esters of (meth)acrylic acid with hydroxy cyclic saturated hydrocarbons (preferably hydroxy cyclic saturated hydrocarbons having 5 to 20 carbon atoms), such as cyclohexyl (meth)acrylate and dicyclopentanyl (meth)acrylate. The (meth)acrylic acid ester is preferably a methacrylic acid ester, more preferably an alkyl methacrylate, and even more preferably a C methacrylic acid ester. 1-10 alkyl, and even more preferably methacrylic acid C 1-7 Alkyl, particularly preferably methacrylic acid C 1-4 It is alkyl.

[0013] Examples of the (meth)acrylic acid ester derivatives include derivatives having a hydroxy group introduced therein, for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth)acrylate, and 2,3,4,5-tetrahydroxypentyl (meth)acrylate; and α-(1-hydroxyalkyl)alkyl acrylates. The hydroxyalkyl (meth)acrylate includes hydroxy (meth)acrylate C 1-20 Alkyl is preferred, and (meth)acrylic acid hydroxy C 1-15 Alkyl is more preferred, and (meth)acrylic acid hydroxy C 1-10 Alkyl is more preferred, and (meth)acrylic acid hydroxy C 1-5 Alkyl is even more preferred. α-(1-hydroxyalkyl) alkyl acrylates include α-(1-hydroxy C1-20 Alkyl)acrylic acid C 1-20 Alkyl is preferred, and α-(1-hydroxyC 1-20 Alkyl)acrylic acid C 1-20 Alkyl includes α-(hydroxymethyl)acrylic acid C such as methyl α-(hydroxymethyl)acrylate, ethyl α-(hydroxymethyl)acrylate, isopropyl α-(hydroxymethyl)acrylate, n-butyl α-(hydroxymethyl)acrylate, and t-butyl α-(hydroxymethyl)acrylate. 1-20 Alkyl; α-(1-hydroxy C) such as methyl α-(1-hydroxyethyl)acrylate 2-20 Alkyl)acrylic acid C 1-20 Alkyl and the like are included.

[0014] In addition, (meth)acrylic acid ester derivatives include β-C such as methyl crotonate. 1-10 Alkyl acrylic acid C 1-10 Also included are alkyl; halogen-introduced derivatives such as chloromethyl (meth)acrylate and 2-chloroethyl (meth)acrylate; and ether-bond-introduced derivatives such as dicyclopentanyloxyethyl (meth)acrylate.

[0015] The (meth)acrylic acid ester derivative is preferably a derivative having a hydroxy group introduced therein, more preferably an α-(1-hydroxyalkyl) alkyl acrylate, and even more preferably an α-(1-hydroxy C 1-20 Alkyl)acrylic acid C 1-20 alkyl, and even more preferably α-(hydroxymethyl)acrylic acid C 1-20 It is alkyl.

[0016] The (meth)acrylic acid derivatives include compounds obtained by hydrolyzing the ester bond of the methacrylic acid ester derivatives, such as crotonic acid, α-(hydroxymethyl)acrylic acid, 2-(1-hydroxyethyl)acrylic acid, and other α-hydroxyalkylacrylic acids.

[0017] When the cyclization step described below is included, it is preferable to use a hydroxyl group-introduced derivative of a (meth)acrylic acid ester. The amount of the hydroxyl group-introduced derivative of a (meth)acrylic acid ester used is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 8% by mass or more, and still more preferably 10% by mass or more, based on 100% by mass of the total amount of the monomer components, and is, for example, 70% by mass or less, preferably 50% by mass or less, and more preferably 30% by mass or less.

[0018] The (meth)acrylic monomer used in the polymerization of the (meth)acrylic resin may be a single monomer or a combination of two or more types. The (meth)acrylic monomer preferably contains (meth)acrylic acid or a (meth)acrylic acid ester as an essential monomer, and more preferably contains a (meth)acrylic acid ester (particularly a methacrylic acid ester) as an essential monomer. The amount of the essential monomer used is, based on 100% by mass of the total amount of the monomer components, preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 65% ​​by mass or more, even more preferably 70% by mass or more, and particularly preferably 75% by mass or more, and is, for example, 100% by mass or less, preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

[0019] The (meth)acrylic resin may be formed by copolymerizing the (meth)acrylic monomer with another monomer copolymerizable with the (meth)acrylic monomer. Examples of the other monomer include styrene-based monomers such as styrene, vinyl toluene, α-methylstyrene, α-hydroxymethylstyrene, and α-hydroxyethylstyrene; vinyl ester-based monomers such as vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate, and vinyl cinnamate; maleic acid-based monomers such as maleic anhydride, maleic acid, and monoalkyl and dialkyl esters of maleic acid; maleimide-based monomers such as maleimide, methylmaleimide, ethylmaleimide, propylmaleimide, butylmaleimide, hexylmaleimide, octylmaleimide, dodecylmaleimide, stearylmaleimide, phenylmaleimide, and cyclohexylmaleimide; fumaric acid, Examples of suitable other monomers include fumaric acid monomers such as monoalkyl esters and dialkyl esters of the above; nitrogen-containing heterocyclic vinyl compounds such as N-vinylpyrrolidone and N-vinylcarbazole; lactone ring-containing monomers such as α-methylene-γ-butyrolactone, α-methylene-4-methyl-γ-butyrolactone, α-methylene-3-methyl-γ-butyrolactone, α-methylene-4,4-dimethyl-γ-butyrolactone, and α-methylene-δ-valerolactone; vinyl nitriles such as acrylonitrile and methacrylonitrile; vinyl alcohols such as methallyl alcohol and allyl alcohol; olefins such as ethylene, propylene, and 4-methyl-1-pentene; 2-hydroxymethyl-1-butene; and methyl vinyl ketone. Preferred examples of suitable other monomers include styrene-based monomers and nitrogen-containing heterocyclic vinyl compounds, with styrene-based monomers being more preferred. Only one of these other monomers may be used as a copolymerization component, or two or more may be used as copolymerization components.

[0020] The amount of other monomers (particularly styrene-based monomers) used is, for example, 0% by mass or more, preferably 1% by mass or more, and for example, 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on 100% by mass of the total amount of the monomer components.

[0021] When the cyclization step described below is not included, it is preferable to use a maleic acid-based monomer, a maleimide-based monomer, or a lactone ring-containing monomer as the other monomer. Using a maleic acid-based monomer as the other monomer allows for the introduction of a structure derived from maleic anhydride into the main chain of the (meth)acrylic resin. Using a maleimide-based monomer allows for the introduction of a structure derived from an N-substituted maleimide into the main chain of the (meth)acrylic resin. Using a lactone ring-containing monomer allows for the introduction of a methylene lactone ring structure into the main chain of the (meth)acrylic resin. Only one type of maleic acid-based monomer, maleimide-based monomer, and / or lactone ring-containing monomer may be used as a copolymerization component, or two or more types may be used as copolymerization components. In the polymerization step, when a maleic acid-based monomer, a maleimide-based monomer, and / or a lactone ring-containing monomer is used as another monomer to incorporate a ring structure into the main chain of the (meth)acrylic resin, the amount of the maleic acid-based monomer, the maleimide-based monomer, and / or the lactone ring-containing monomer used is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, relative to 100% by mass of the total amount of the monomer components, and is, for example, 70% by mass or less, preferably 60% by mass or less, and more preferably 50% by mass or less. In the present invention, the term "having a ring structure in the main chain" refers to an embodiment in which at least one of the carbon atoms forming the ring structure is included in the main chain of the thermoplastic resin.

[0022] The structure derived from maleic anhydride or the structure derived from N-substituted maleimide is preferably, for example, a structure represented by the following general formula (1): 1 When X is an oxygen atom, the structure is derived from maleic anhydride, 1 When is a nitrogen atom, the structure is derived from an N-substituted maleimide.

[0023] [ka]

[0024] R in the above general formula (1) 1 , R 2 are each independently a hydrogen atom or a methyl group, and X 1 is an oxygen atom or a nitrogen atom. 1 is an oxygen atom, R 3 does not exist. X 1 When is a nitrogen atom, R 3 is a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms (methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group), a cyclopentyl group, a cyclohexyl group, a benzyl group, or a phenyl group.

[0025] The methylene lactone ring structure is preferably, for example, a structure represented by the following general formula (11).

[0026] [ka]

[0027] R in the above general formula (11) 11 , R 12 , R 13 and R 14 are each independently a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, and A is -(CR 11 R 12 )-and-(CR 13 R 14 )- or -(CR 15 R 16 )- and R 15 , R 16 are each independently a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms. In formula (11), when A is a single bond, the structure shown in formula (11) has a five-membered lactone ring structure, and A is -(CR 15 R 16 )-, the structure shown in formula (11) has a six-membered lactone ring structure. Examples of the hydrocarbon group in formula (11) include saturated aliphatic hydrocarbon groups (e.g., alkyl groups) having from 1 to 18 carbon atoms, such as a methyl group, an ethyl group, or a propyl group; unsaturated aliphatic hydrocarbon groups (e.g., alkenyl groups) having from 2 to 18 carbon atoms, such as an ethenyl group or a propenyl group; and aromatic hydrocarbon groups (e.g., aryl groups) having from 6 to 18 carbon atoms, such as a phenyl group or a naphthyl group. Alkyl groups are preferred, and alkyl groups having from 1 to 10 carbon atoms are more preferred.

[0028] Solvents that can be used when polymerizing the monomers by solution polymerization include aromatic hydrocarbon solvents such as toluene, xylene, and ethylbenzene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ether solvents such as tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and anisole; ester solvents such as ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; cellosolve solvents such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve; alcohol solvents such as methanol, ethanol, isopropanol, and n-butanol; nitrile solvents such as acetonitrile, propionitrile, butyronitrile, and benzonitrile; halogenated solvents such as chloroform and dichloromethane; and dimethyl sulfoxide. Preferred polymerization solvents are aromatic hydrocarbon solvents, ketone solvents, and alcohol solvents, more preferably aromatic hydrocarbon solvents and alcohol solvents, even more preferably aromatic hydrocarbon solvents, and particularly preferably toluene. These polymerization solvents may be used alone or in combination of two or more.

[0029] When the polymerization of the monomers is carried out by solution polymerization, the total concentration of the monomer components in the polymerization reaction solution is, for example, 5% by mass or more, preferably 10% by mass or more, more preferably 30% by mass or more, and for example, 90% by mass or less, preferably 80% by mass or less, more preferably 70% by mass or less. The amount of solvent used in the polymerization reaction is not particularly limited as long as the total concentration of the monomer components in the polymerization reaction solution is within the above range.

[0030] In the polymerization step, a polymerization initiator may be used as needed.

[0031] Examples of polymerization initiators that can be used include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, dimethyl-2,2'-azobis(2-methylpropionate), and 4,4'-azobis(4-cyanopentanoic acid); persulfates such as potassium persulfate; and organic peroxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexanoate, t-amylperoxyoctoate, t-amylperoxyisononanoate, t-amylperoxyisopropyl carbonate, and t-amylperoxy-2-ethylhexyl carbonate. These may be used alone or in combination of two or more. Among these, it is preferable to use organic peroxides which have a strong hydrogen abstracting power.

[0032] The amount of the polymerization initiator used is, for example, 500 ppm or more, preferably 1000 ppm or more, more preferably 1500 ppm or more, based on the total amount of the monomer components, from the viewpoint of increasing the polymerization rate and reducing the amount of unreacted monomer components remaining. The amount of the polymerization initiator used is, for example, 2% by mass or less, preferably 1% by mass or less, more preferably 0.7% by mass or less, based on the total amount of the monomer components.

[0033] In order to promote the decomposition of the polymerization initiator, a suitable amount of a decomposer for the polymerization initiator, such as a reducing agent such as sodium hydrogen sulfite or a transition metal salt such as ferrous sulfate, may be added to the reaction system.

[0034] In the polymerization step, a chain transfer agent may be used as needed. Adding a chain transfer agent to the reaction system can lower the molecular weight of the thermoplastic resin. Examples of chain transfer agents include organic thiol compounds; halogen compounds such as carbon tetrachloride, carbon tetrabromide, methylene chloride, bromoform, and bromotrichloroethane; and unsaturated hydrocarbon compounds such as α-methylstyrene dimer, α-terpinene, γ-terpinene, dipentene, and terpinolene. These chain transfer agents may be used alone or in combination of two or more. Among these, organic thiol compounds such as 1-dodecanethiol are preferred because they can prevent a decrease in conversion.

[0035] The amount of the chain transfer agent used is, for example, 200 ppm or more, preferably 400 ppm or more, more preferably 500 ppm or more, and for example, 5 mass % or less, preferably 1 mass % or less, more preferably 0.5 mass % or less, based on the total amount of the monomer components.

[0036] The method of adding the above-mentioned monomers, and the solvent, polymerization initiator, and chain transfer agent used as needed, is not particularly limited. The addition method may involve initially charging the entire amount of each into the reaction vessel, or initially charging a portion of each into the reaction vessel, with the remainder being added to the reaction system (reaction vessel) all at once or continuously during the polymerization reaction. The addition may be continuous or intermittent, such as by adding portions, but is preferably continuous or intermittent at intervals of 10 minutes or less, and more preferably continuous.

[0037] The atmosphere in which the monomers are polymerized is not particularly limited, but from the viewpoint of increasing the efficiency of the polymerization reaction, an inert gas such as nitrogen gas is preferred.

[0038] The polymerization temperature when polymerizing the monomers is, for example, 40°C or higher, preferably 60°C or higher, and more preferably 70°C or higher. When a polymerization initiator is used, the polymerization temperature is preferably equal to or higher than the 10-hour half-life temperature of the polymerization initiator used. The 10-hour half-life temperature refers to the temperature at which the half-life of the polymerization initiator is 10 hours. The polymerization temperature is, for example, 180°C or lower, preferably 150°C or lower, and more preferably 120°C or lower. When a solvent is used, the polymerization temperature is preferably equal to or lower than the reflux temperature of the solvent used.

[0039] The polymerization time for polymerizing the monomers is not particularly limited and may be set appropriately depending on the progress of the polymerization reaction, but is usually about 2 to 8 hours.

[0040] After adding all the monomers, and optionally a solvent, a polymerization initiator, and a chain transfer agent, aging may be carried out as needed. Aging further improves the monomer conversion rate. In the aging step, it is preferable to continue stirring at an appropriate temperature, for example, about ±30°C of the polymerization temperature (preferably at the polymerization temperature or above). The aging time is, for example, from 0 to 10 hours, preferably from 1 to 5 hours.

[0041] The conversion rate of the monomer at the end of the polymerization reaction is, for example, 80% or more, preferably 85% or more, and more preferably 88% or more.

[0042] The weight-average molecular weight (Mw) of the thermoplastic resin in the polymer (preferably the polymerization solution) obtained by the polymerization step is, for example, 50,000 or more, preferably 70,000 or more, more preferably 90,000 or more, and even more preferably 100,000 or more, and for example, 300,000 or less, preferably 250,000 or less, and more preferably 200,000 or less. When the weight-average molecular weight of the thermoplastic resin is within the above range, a resin composition can be obtained that maintains the strength required for a resin and also has good fluidity during molding.

[0043] When the thermoplastic resin is a (meth)acrylic resin, the total content of structural units derived from (meth)acrylic monomers (i.e., structural units derived from (meth)acrylic acid, (meth)acrylic acid esters, and derivatives thereof) in all structural units of the (meth)acrylic resin in the polymer (preferably, the polymerization solution) obtained by the polymerization step is, from the viewpoint of transparency, preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and still more preferably 75% by mass or more. There is no particular upper limit, and it may be 100% by mass. The content ratio of each structural unit in the (meth)acrylic polymer was determined by dissolving the (meth)acrylic polymer in a heavy solvent and 1 It can be determined by measuring H-NMR and calculating the peak area ratio corresponding to each structural unit.

[0044] (2) Cyclization process From the viewpoint of heat resistance, the thermoplastic resin preferably has a ring structure in the main chain. The ring structure that the thermoplastic resin has in its main chain is preferably at least one selected from the group consisting of a lactone ring structure, a glutarimide structure, a glutaric anhydride structure, a maleic anhydride structure, and an N-substituted maleimide structure. The thermoplastic resin having a ring structure in the main chain can be formed, for example, by using a maleic acid-based monomer, a maleimide-based monomer, and / or a lactone ring-containing monomer as a monomer in the polymerization step as described above, or by carrying out a cyclization condensation reaction after the polymerization reaction (cyclization step).

[0045] Examples of the main chain ring structure formed by the cyclization condensation reaction include a lactone ring structure, a glutaric anhydride structure, and a glutarimide structure.

[0046] When an optical component is produced using resin pellets formed from a resin composition containing a thermoplastic resin, the main chain ring structure of the thermoplastic resin is preferably a lactone ring structure, a glutaric anhydride structure, or a glutarimide structure, more preferably a lactone ring structure, in order to obtain an optical component with excellent optical properties. Furthermore, in terms of moist heat resistance, the main chain ring structure is preferably a lactone ring structure, a glutarimide structure, or a structure derived from an N-substituted maleimide, more preferably a lactone ring structure.

[0047] The lactone ring structure is, for example, a 4- to 8-membered ring, preferably a 5- or 6-membered ring, more preferably a 6-membered ring, due to its excellent stability. Examples of 6-membered lactone ring structures include the structure represented by the following general formula (2).

[0048] [ka]

[0049] In the above general formula (2), R 4 , R 5 and R 6 are each independently a hydrogen atom or an organic residue having 1 to 20 carbon atoms, and the organic residue may contain an oxygen atom. Examples of the organic residue in general formula (2) include saturated aliphatic hydrocarbon groups (e.g., alkyl groups) having from 1 to 20 carbon atoms, such as a methyl group, an ethyl group, or a propyl group; unsaturated aliphatic hydrocarbon groups (e.g., alkenyl groups) having from 2 to 20 carbon atoms, such as an ethenyl group or a propenyl group; aromatic hydrocarbon groups (e.g., aryl groups) having from 6 to 20 carbon atoms, such as a phenyl group or a naphthyl group; and groups in which one or more hydrogen atoms in these saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbon groups, or aromatic hydrocarbon groups have been substituted with at least one group selected from a hydroxy group, a carboxyl group, an ether group, and an ester group, with alkyl groups being preferred.

[0050] The lactone ring structure can be formed by dealcoholization or dehydration cyclocondensation (cyclization condensation reaction) between a hydroxy group and an ester group or a carboxyl group in a thermoplastic resin. Therefore, when forming a lactone ring structure by a cyclocondensation reaction, it is preferable to homopolymerize a hydroxy group-containing (meth)acrylic monomer such as an α-(1-hydroxyalkyl) alkyl acrylate in the polymerization step, or to copolymerize the hydroxy group-containing (meth)acrylic monomer with a (meth)acrylic monomer such as (meth)acrylic acid or a (meth)acrylic acid ester to form a thermoplastic resin having a hydroxy group and an ester group or a carboxyl group introduced into the molecular chain.

[0051] When a lactone ring structure is formed in the main chain of a thermoplastic resin by a cyclization condensation reaction, it is preferable to carry out the cyclization condensation reaction so that the content of the lactone ring structure in the thermoplastic resin is, for example, 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and for example, 70% by mass or less, preferably 50% by mass or less, more preferably 30% by mass or less.

[0052] The content of lactone ring structures in a thermoplastic resin can be determined by a known method, for example, nuclear magnetic resonance ( 1 This can be evaluated by 1 H-NMR and / or infrared spectroscopy (IR).

[0053] The glutaric anhydride structure or the glutarimide structure may be, for example, a structure represented by the following general formula (3): 2 When X is an oxygen atom, it becomes a glutaric anhydride structure, and 2 When is a nitrogen atom, it becomes a glutarimide structure.

[0054] [ka]

[0055] R in the above general formula (3) 7 , R 8are each independently a hydrogen atom or a methyl group, and X 2 is an oxygen atom or a nitrogen atom. 2 is an oxygen atom, R 9 does not exist, and X 2 When is a nitrogen atom, R 9 is a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms (methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group), a cyclopentyl group, a cyclohexyl group, or a phenyl group.

[0056] The glutaric anhydride structure can be formed by dealcoholization or dehydration cyclocondensation (cyclization condensation reaction) between a carboxyl group of a thermoplastic resin and an ester group or another carboxyl group. Therefore, when forming a glutaric anhydride structure by a cyclocondensation reaction, it is preferable to homopolymerize a (meth)acrylic acid ester or (meth)acrylic acid, or copolymerize a (meth)acrylic acid ester and (meth)acrylic acid in the polymerization step to form a thermoplastic resin having a carboxyl group and an ester group or another carboxyl group introduced into the molecular chain.

[0057] The glutarimide structure can be formed by forming a glutaric anhydride structure by dealcoholization or dehydration cyclocondensation (cyclocondensation reaction) between a carboxyl group of a thermoplastic resin and an ester group or another carboxyl group, followed by imidization with an imidizing agent. The imidization may be carried out immediately after the cyclocondensation reaction, or after the volatilization and extrusion steps described below after the cyclocondensation reaction, but is preferably carried out after the volatilization and extrusion steps described below after the cyclocondensation reaction.

[0058] The imidizing agent is not particularly limited, but examples thereof include aliphatic hydrocarbon group-containing amines such as methylamine, ethylamine, and n-butylamine; cycloalkylamines having a cycloalkyl group with 3 to 12 carbon atoms such as cyclohexylamine; and arylamines having an aryl group with 6 to 10 carbon atoms such as aniline, benzylamine, toluidine, and trichloroaniline. These imidizing agents may be used alone or in combination of two or more. From the viewpoint of the transparency of the resulting resin pellets, preferred imidizing agents are cyclohexylamine, aniline, and toluidine, with aniline being more preferred. The amount of imidizing agent used may be appropriately adjusted to achieve a desired imidization rate.

[0059] The imidization may be carried out by a known method, for example, by dissolving the thermoplastic resin that has undergone a cyclization condensation reaction in a solvent and adding an imidizing agent to the solution, or by melting the thermoplastic resin that has undergone a cyclization condensation reaction using an extruder or the like and adding an imidizing agent to the melt. The reaction temperature during the imidization is, for example, 160°C or higher and 400°C or lower.

[0060] The solvent used in the imidization is preferably a solvent inert to the imidization, and examples thereof include aliphatic alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol; aromatic compounds such as benzene, toluene, xylene, chlorobenzene, and chlorotoluene; ether compounds, etc. These solvents may be used alone or in combination of two or more.

[0061] After imidization, it is preferable to remove unreacted imidizing agent. For example, when imidization is performed using an extruder, the extruder can be provided with a vent that can reduce the pressure to atmospheric pressure or below, so that the imidizing agent can be removed.

[0062] When a glutaric anhydride structure or a glutarimide structure is formed in the main chain of a thermoplastic resin, it is preferable to carry out the cyclization condensation reaction and, if necessary, imidization so that the content of the glutaric anhydride structure or the glutarimide structure in the thermoplastic resin is, for example, 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and for example, 70% by mass or less, preferably 50% by mass or less, more preferably 30% by mass or less.

[0063] The content ratio of the glutaric anhydride structure and the glutarimide structure in the thermoplastic resin can be determined by a known method, for example, the method described in JP-A-2006-131689.

[0064] The cyclization condensation reaction may be carried out in the presence of a solvent. Examples of solvents that can be used in the cyclization condensation reaction include the same types of solvents that can be used in the polymerization reaction described above, and preferred embodiments are also the same. When the polymerization reaction is carried out by solution polymerization, the solvent used in the solution polymerization may be removed once and then a new solvent may be added, or the solvent used in the solution polymerization may be subsequently used as the solvent in the cyclization reaction. However, from the viewpoint of production efficiency, it is preferable to subsequently use the solvent used in the solution polymerization as the solvent in the cyclization reaction.

[0065] The concentration of the thermoplastic resin in the cyclization condensation reaction liquid is, for example, 5% by mass or more, preferably 10% by mass or more, more preferably 30% by mass or more, and for example, 90% by mass or less, preferably 80% by mass or less, more preferably 70% by mass or less. The amount of solvent used in the cyclization condensation reaction is not particularly limited as long as the concentration of the thermoplastic resin in the cyclization condensation reaction liquid is within the above range.

[0066] The cyclization condensation reaction is preferably carried out in the presence of a catalyst (cyclization catalyst). As the cyclization catalyst, at least one selected from the group consisting of acids, bases, and salts thereof can be used. The acids, bases, and salts thereof may be organic or inorganic, and are not particularly limited. In particular, it is preferable to use an organic phosphorus compound or a compound containing an alkali metal as the cyclization reaction catalyst. By using an organic phosphorus compound or a compound containing an alkali metal as the cyclization catalyst, the cyclization condensation reaction can be carried out efficiently and the coloration of the resulting thermoplastic resin can be reduced.

[0067] Examples of organic phosphorus compounds that can be used as cyclization catalysts include alkyl (aryl) phosphonous acids and their monoesters or diesters; dialkyl (aryl) phosphinic acids and their esters; alkyl (aryl) phosphonic acids and their monoesters or diesters; alkyl (aryl) phosphinic acids and their esters; phosphite 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, phosphate Examples of suitable phosphate monoesters, diesters, or triesters include diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, distearyl phosphate, diisostearyl phosphate, diphenyl phosphate, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate, and triphenyl phosphate; mono-, di-, or tri-alkyl(aryl)phosphines; alkyl(aryl)halogen phosphine; mono-, di-, or tri-alkyl(aryl)phosphine oxide; and tetraalkyl(aryl)phosphonium halides. These may be used alone or in combination of two or more. Among these, phosphate monoesters or diesters are particularly preferred due to their high catalytic activity and low coloration.

[0068] Examples of compounds containing an alkali metal that can be used as a cyclization catalyst include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; alkali metal alkoxide compounds such as sodium methoxide, sodium ethoxide, sodium phenoxide, potassium methoxide, potassium ethoxide, and potassium phenoxide; and alkali metal salts of organic carboxylic acids such as lithium acetate, sodium acetate, potassium acetate, and sodium stearate. These compounds may be used alone or in combination of two or more. Among these compounds, sodium hydroxide, sodium methoxide, lithium acetate, and sodium acetate are preferred because of their high catalytic activity and low coloration, and sodium methoxide and lithium acetate are more preferred.

[0069] The amount of the cyclization catalyst used is preferably, for example, 0.001 part by mass or more and 1 part by mass or less per 100 parts by mass of the thermoplastic resin obtained in the polymerization step.

[0070] The reaction temperature in the cyclization step is, for example, 50° C. or higher and 300° C. or lower, and the reaction time is, for example, 5 minutes to 6 hours. The cyclization step is preferably carried out in a reaction vessel in which a polymerization reaction is carried out, and furthermore, the cyclization step is preferably carried out in an autoclave, a shell-and-tube heat exchanger, or the like.

[0071] (3) Devolatilization and extrusion process Devolatilization refers to a process for removing volatile components such as solvents and residual monomers from a molten resin. When a cyclization step is included, the devolatilization process also removes alcohol produced as a by-product in the cyclization condensation reaction from the molten resin. If the devolatilization is insufficient, a large amount of volatile matter remains in the resin composition, which may cause foaming during molding and result in molding defects. On the other hand, if the devolatilized resin is extruded in a molten state to form pellets, the pellet size will vary greatly. In the present invention, resin pellets formed in two or more series are mixed, which can suppress the variation in pellet size.

[0072] The apparatus used for devolatilization is not particularly limited as long as it is an apparatus capable of handling molten resin, and examples that can be used include an autoclave, a kettle-type reactor, an apparatus consisting of a heat exchanger and a devolatilization tank, and a vented extruder.

[0073] When a vented extruder is used for devolatilization, extrusion can be carried out subsequently using the extruder. The extruder preferably has a cylinder and a screw provided in the cylinder, and is equipped with a heating means. The cylinder is preferably provided with one or more vents, and the vent is more preferably provided at least downstream of the raw material input section with respect to the transport direction within the extruder, and may also be provided upstream of the raw material input section. Devolatilization progresses as the resin composition containing the thermoplastic resin fed into the extruder is transported from the upstream side to the downstream side of the extruder while being kneaded with the screw.

[0074] The devolatilization is preferably carried out at a temperature of 150° C. to 350° C. and at a reduced pressure of 13.3 hPa or more (e.g., 13.3 hPa to 800 hPa). If the devolatilization temperature is lower than 150° C., there is a problem that the devolatilization is insufficient and a large amount of volatile matter remains, whereas if the devolatilization temperature is higher than 350° C., there is a problem that coloration and decomposition occur, which is not preferable.

[0075] The extrusion is preferably carried out at a temperature of 200° C. or more and 300° C. or less and at a pressure of 10 MPa or more and 20 MPa or less, for example.

[0076] In the polymerization step, the cyclization step, and / or the devolatilization and extrusion step, various known additives can be used as needed. Examples of the additives include ultraviolet absorbers; phenolic antioxidants (e.g., hydroquinone, 2,6-di-t-butyl-p-cresol, tocopherol, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, etc.); phosphorus-based antioxidants (e.g., triphenyl phosphite, tris(2,4-di-t-butylphenyl)phosphite, etc.); sulfur-based antioxidants (e.g., 2-mercaptobenzimidazole, dilauryl 3,3'-thiodiproline, etc.); Examples of the additives include antioxidants such as phenate; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers; near-infrared absorbers; flame retardants such as tris(dibromopropyl)phosphate, triallyl phosphate, and antimony oxide; retardation adjusters such as retardation increasers, retardation decreasers, and retardation stabilizers; antistatic agents including anionic, cationic, and nonionic surfactants; compatibilizers; stabilizers; colorants such as inorganic pigments, organic pigments, and dyes; organic and inorganic fillers; and resin modifiers. These may be used alone or in combination of two or more.

[0077] The amount of additive used is not particularly limited, but it is advisable to adjust the content of the additive to be preferably in the range of 0% by mass or more and 5% by mass or less, more preferably 0% by mass or more and 2% by mass or less, relative to 100% by mass of the solid content of the resulting resin composition.

[0078] The weight-average molecular weight (Mw) of the resin composition containing the thermoplastic resin is, for example, 50,000 or more, preferably 60,000 or more, more preferably 70,000 or more, and even more preferably 80,000 or more, and is, for example, 300,000 or less, preferably 250,000 or less, and more preferably 200,000 or less. By having the weight-average molecular weight of the resin composition within the above range, it is possible to obtain a resin composition that has good fluidity during molding while maintaining the strength required for a resin.

[0079] From the viewpoint of heat resistance, a resin composition containing a thermoplastic resin preferably has a glass transition temperature (Tg) of 100°C or higher. The resin composition may have a plurality of glass transition temperatures of 100°C or higher. The glass transition temperature of the resin composition is more preferably 110°C or higher, and even more preferably 120°C or higher. From the viewpoint of improving processability during molding, the glass transition temperature of the resin composition is preferably less than 300°C, more preferably 200°C or lower, and even more preferably 180°C or lower. The glass transition temperature of the resin composition can be determined by the starting point method in accordance with the provisions of JIS K7121.

[0080] (4) Cutting process The molten resin composition after the devolatilization and extrusion steps is cut into pellets using a cutter to form resin pellets. The cutting method is not particularly limited, and may be a strand cut method in which the molten resin composition extruded in the form of a strand is cooled and cut using a strand cutter, or a center hot cut method or underwater cut method in which the molten resin composition extruded from a nozzle hole is cut using a rotary blade.

[0081] A die is preferably provided downstream of the extruder used in the extrusion step (for example, at the tip of the cylinder), and the molten resin composition can be extruded in a desired shape from the nozzle holes of the die. The shape of the nozzle holes of the die is not particularly limited, and for example, a cylindrical shape is preferable. The number of nozzle holes of the die may be 1 or more, and may be, for example, 100 or more. The diameter of the nozzle holes of the die, for example, in the case of a cylindrical shape, can be 1 mm or more and 10 mm or less. The die is preferably provided with a polymer filter.

[0082] The molten resin composition is solidified by cooling. The cooling method may be air cooling or water cooling, but water cooling is preferred.

[0083] After cutting, post-treatments such as washing, liquid-solid separation, drying, etc. may be carried out as necessary. Examples of washing methods include washing with water, examples of liquid-solid separation methods include centrifugation and vacuum sieving, and examples of drying methods include air drying and vacuum drying.

[0084] (5) Mixing process In the mixing step, two or more series of resin pellets formed according to the same recipe are mixed under substantially the same conditions, that is, in equipment of the same design.

[0085] In the present invention, mixing does not necessarily mean that two or more series of resin pellets are uniformly mixed together, but means that two or more series of resin pellets coexist in the same space (in a container such as a hopper or silo).

[0086] The mixing method is not particularly limited, and may be, for example, a mixer. A simple and preferred method is to mix two or more series of resin pellets by charging them into the same container, such as a hopper. When two or more series of resin pellets are charged into the same container, the order of charging is not particularly limited. The two or more series of resin pellets may be charged simultaneously. Alternatively, the resin pellets of two series (A and B) (or three or more series) may be divided into multiple groups, such as A1, A2, A3, ..., B1, B2, B3, ..., and then charged in the order A1, B1, A2, B2, ..., alternately (or randomly) by group. Furthermore, the resin pellets of two series (A and B) (or three or more series) may be charged in the order of the series, such as first charging all the pellets of the A series, and then charging all the pellets of the B series. Even when charging in the order of the series, mixing occurs at the boundary between the series, and further mixing progresses due to the uneven flow of the pellets when they are discharged from the container. Furthermore, the resin pellets introduced into the container (hereinafter referred to as the first container) may be discharged and then introduced again into a container (hereinafter referred to as the second container) to further enhance the degree of mixing. For example, the resin pellets may be divided into a plurality of groups when being dispensed from the first container, and each group may be introduced into the second container in an order different from that in which they were dispensed from the first container (preferably in a random order). When re-introducing the resin pellets into the second container, not only may groups of resin pellets dispensed from the same first container be introduced, but groups of resin pellets dispensed from different first containers (provided that these are resin pellets produced under substantially the same conditions) may also be mixed into the same second container.

[0087] The more series that are mixed, the more likely it is that resin pellets with higher size uniformity can be obtained.

[0088] When mixing two or more series of resin pellets produced under substantially the same conditions, the amount of resin pellets of the other series is preferably 0.1 to 100 parts by mass, more preferably 1 to 100 parts by mass, even more preferably 10 to 100 parts by mass, and even more preferably 30 to 100 parts by mass, per 100 parts by mass of the resin pellets of the series with the largest proportion (if there are two or more series of resin pellets with the largest proportion, any one of them).

[0089] (6) Resin pellets The resin pellets obtained after the mixing step are a mixture of two or more rows of resin pellets produced under substantially the same conditions, and therefore have high pellet size uniformity.More preferably, the resin pellets obtained after the mixing step also have small variations in melt flow rate.

[0090] The shape of the resin pellets is not particularly limited, and examples thereof include spherical (including ellipsoidal) and columnar (for example, cylindrical or prismatic) shapes.

[0091] The size of the resin pellets is not particularly limited and can be appropriately set depending on the intended use and the like. The maximum diameter of the cut surface of the resin pellet (the surface formed by the cutter in the cutting step) is, for example, preferably 0.5 mm or more and 15 mm or less, and more preferably 1.0 mm or more and 10 mm or less. The length of the longest part of the cut surface of the resin pellet in a direction perpendicular to the maximum diameter (perpendicular diameter) is, for example, preferably 0.5 mm or more and 15 mm or less, and more preferably 1.0 mm or more and 10 mm or less. The length of the resin pellet in the direction perpendicular to the cut surface (pellet length or pellet thickness) is, for example, preferably 0.5 mm or more and 10 mm or less, and more preferably 1.0 mm or more and 8.0 mm or less.

[0092] The standard deviation and coefficient of variation of the maximum diameter, orthogonal diameter, and pellet length (or pellet thickness) all indicate the size uniformity of the resin pellets, and it is preferable that the value of at least one of them (preferably all of them) is small. Furthermore, it is preferable that the resin pellets after mixing have a reduced standard deviation or coefficient of variation (preferably both) of any (preferably all of) of the maximum diameter, orthogonal diameter, and pellet length (or pellet thickness) compared to the resin pellets of all series before mixing.

[0093] For example, it is preferable that the resin pellets after mixing have a small standard deviation and / or coefficient of variation in pellet size as follows. (When maximum diameter is less than or equal to pellet length) The standard deviations (mm) of the maximum diameter and the perpendicular diameter are preferably 0.65 or less, more preferably 0.60 or less, and even more preferably 0.55 or less. The coefficients of variation of the maximum diameter and the perpendicular diameter are preferably 0.014 or less, and more preferably 0.012 or less. The standard deviation (mm) of the pellet length is preferably 0.65 or less, more preferably 0.60 or less, and even more preferably 0.55 or less. The coefficient of variation of the pellet length is preferably 0.022 or less, more preferably 0.020 or less, and even more preferably 0.018 or less. (When maximum diameter > pellet thickness) The standard deviations (mm) of the maximum diameter and the perpendicular diameter are preferably 0.80 or less, more preferably 0.75 or less, and even more preferably 0.70 or less. The coefficients of variation of the maximum diameter and the perpendicular diameter are preferably 0.016 or less, and more preferably 0.014 or less. The standard deviation (mm) of the pellet thickness is preferably 0.80 or less, more preferably 0.70 or less, and even more preferably 0.60 or less. The coefficient of variation of the pellet thickness is preferably 0.035 or less, more preferably 0.030 or less, and even more preferably 0.025 or less.

[0094] The melt flow rate of the resin pellets, measured in accordance with JIS K 7210 (Method B) at a temperature of 240°C and a load of 10 kgf (98 N), is preferably 8 g / 10 min or more, more preferably 10 g / 10 min or more, from the viewpoint of molding processability, and is preferably 50 g / 10 min or less, more preferably 40 g / 10 min or less, and even more preferably 30 g / 10 min or less. The standard deviation and coefficient of variation of the melt flow rate indicate the stability of the melt flow rate, and it is preferable that these values ​​are small. Furthermore, it is preferable that the standard deviation and / or coefficient of variation of the melt flow rate of the resin pellets after mixing is lower than that of the resin pellets of all series before mixing. For example, the standard deviation (g / 10 min) of the melt flow rate is preferably 0.75 or less, more preferably 0.70 or less, and more preferably 0.60 or less. The coefficient of variation of the melt flow rate is preferably 0.050 or less, more preferably 0.045 or less, and more preferably 0.040 or less.

[0095] When the resin pellets contain volatile components such as residual monomers, alcohol by-produced by the cyclocondensation reaction, and water, the content of these volatile components is preferably low from the viewpoint of forming a molded product with excellent appearance. Furthermore, it is preferable that the resin pellets after mixing have a reduced standard deviation and / or coefficient of variation of the volatile component content compared to the resin pellets of all series before mixing.

[0096] From the viewpoint of molding processability, the amount of residual monomers (particularly methyl methacrylate residuals) in the resin pellets is preferably 3000 ppm or less, more preferably 2500 ppm or less, and even more preferably 2300 ppm or less. The amount of residual monomers in the resin pellets is a value determined by the method described in the Examples below. In the present invention, unless otherwise specified, "ppm" means a value determined in mass terms. The standard deviation (ppm) of the amount of residual monomer (particularly, methyl methacrylate residual) is, for example, preferably 120 or less, more preferably 110 or less, and more preferably 100 or less. The coefficient of variation of the amount of residual monomer (particularly, methyl methacrylate residual) is, for example, preferably 0.065 or less, more preferably 0.060 or less, and more preferably 0.055 or less.

[0097] From the viewpoint of molding processability, the amount of alcohol (particularly methanol) in the resin pellets is preferably 200 ppm or less, more preferably 180 ppm or less, and even more preferably 150 ppm or less. The amount of alcohol in the resin pellets is a value determined by the method described in the examples below. The standard deviation (ppm) of the alcohol (particularly methanol) amount is, for example, preferably 15 or less, more preferably 10 or less, and more preferably 8 or less. The coefficient of variation of the alcohol (particularly methanol) amount is, for example, preferably 0.120 or less, more preferably 0.110 or less, and more preferably 0.100 or less.

[0098] From the viewpoint of molding processability, the water content in the resin pellets is preferably 200 ppm or less, more preferably 180 ppm or less, and even more preferably 150 ppm or less. The water content in the resin pellets is a value determined by the method described in the examples below. The standard deviation (ppm) of the water content is, for example, preferably not more than 30, more preferably not more than 25, and more preferably not more than 20. The coefficient of variation of the water content is, for example, preferably not more than 0.320, more preferably not more than 0.300, and more preferably not more than 0.280.

[0099] The characteristic values ​​and their standard deviations of the resin pellets can be determined, for example, by randomly sampling 10 or more pellets and calculating the arithmetic mean (primary average) 10 or more times to determine the 10 or more primary averages for each characteristic, and then using the arithmetic mean (secondary average) of these primary averages as the characteristic values ​​and the standard deviation of the primary averages as the standard deviation of each characteristic value. The coefficient of variation of each characteristic value of the resin pellets can be determined from the secondary averages and the standard deviations.

[0100] The resin pellets produced by the production method of the present invention have high size uniformity and preferably small melt flow rate variation, so that molded products of consistent quality can be formed. Furthermore, since the occurrence of production problems caused by size non-uniformity of raw material resin pellets can be reduced, it is also possible to improve the productivity of molded products.

[0101] (7) Molded body The resin pellets produced by the production method of the present invention can be molded into various shapes and used as various products or parts. Examples of molding methods include injection molding, extrusion molding, blow molding, hollow molding, calendar molding, rotational molding, vacuum molding, and compression molding. The shape of the molded product can be appropriately determined depending on the application, and examples include sheets, films, lenses, tubes, pipes, bags, and containers. In particular, when the thermoplastic resin contained in the resin composition forming the resin pellets is a (meth)acrylic resin, the resin pellets are useful as molded products (optical components) for optical applications because of their excellent balance of various properties such as optical properties, mechanical strength, moldability, and surface hardness. Examples of molded products for optical applications include films, such as polarizer protective films, retardation films, viewing angle compensation films, light diffusion films, reflective films, antireflection films, antiglare films, brightness enhancement films, and conductive films for touch panels. The molded articles can also be used in the fields of optical communication systems, optical switching systems, and optical measurement systems, including, for example, solar cells, or sheets or plates such as light guide plates, diffusion plates, front panels, transparent substrates, and transparent conductive substrates such as touch panels in optical products such as head-mounted displays and liquid crystal projectors. Furthermore, examples of molded articles include lenses, lens arrays, lens covers, optical fibers, tail lamps, meter covers, head lamps, lamp covers, light guide rods, and the like, which can be used in optical products, in-vehicle products, and household products such as lighting equipment and office automation equipment. The molded articles can also be suitably used as interior and exterior decorations or decorative films for automobiles and various devices.

[0102] The molded body may be a molded body consisting only of resin pellets produced by the manufacturing method of the present invention, or a molded body consisting of a mixture of resin pellets produced by the manufacturing method of the present invention and other pellets.

[0103] The molding temperature is not particularly limited, but is preferably in the range of 150°C or higher and 350°C or lower, and more preferably in the range of 200°C or higher and 300°C or lower. [Example]

[0104] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples, and can of course be practiced with appropriate modifications within the scope of the above and below-described aims, all of which are included within the technical scope of the present invention. In the following, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

[0105] First, the measurement methods employed in the following examples will be explained.

[0106] (1) Weight average molecular weight The weight average molecular weight (Mw) of the resin composition was determined in terms of polystyrene using gel permeation chromatography (GPC) using the following apparatus and conditions: Measurement system: Tosoh GPC system HLC-8220 Measurement column configuration: Guard column (Tosoh, TSK guardcolumn SuperHZ-L) Separation columns (Tosoh, TSK Gel Super HZM-M), two connected in series Reference column configuration: Reference column (Tosoh, TSK gel SuperH-RC) Developing solvent: chloroform (Wako Pure Chemical Industries, special grade) Developing solvent flow rate: 0.6 mL / min Standard sample: TSK standard polystyrene (Tosoh, PS-oligomer kit) Column temperature: 40℃

[0107] (2) Glass transition temperature The glass transition temperature (Tg) of the resin composition was determined by the initial point method in accordance with JIS K7121. Specifically, a differential scanning calorimeter (Rigaku Corporation, Thermo plus EVO DSC-8230) was used to measure the glass transition temperature (Tg) of approximately 10 mg of a sample, heated from room temperature to 200°C (heating rate: 20°C / min) under a nitrogen gas flow (100 ml / min), and the DSC curve was obtained. α-Alumina was used as a reference.

[0108] (3) Cyclization rate (glutaric anhydride oxidation rate, imidization rate) The rate of oxidation or imidization of glutaric anhydride in (meth)acrylic resin is 1803 cm -1 The absorption due to the carboxylic acid anhydride group in the vicinity and the absorption at 1720 cm -1 The absorption due to the ester carbonyl group in the vicinity and the absorption at 1680cm -1 The ratio of the intensity of the absorption due to the imide carbonyl group to the intensity of the absorption due to the nearby imide carbonyl group was determined. Here, the glutaric anhydride oxidation rate or imidization rate is the ratio of the carboxylic anhydride group or imide carbonyl group to the total carbonyl groups.

[0109] (4) Size of resin pellets The maximum diameter of the cut surface of the resin pellet (the surface formed by the cutting machine in the cutting process), the length of the longest part of the cut surface in a direction perpendicular to the maximum diameter (orthogonal diameter), and the length in the direction perpendicular to the cut surface (pellet length or pellet thickness) were measured.

[0110] (5) Melt flow rate (MFR) The MFR of the resin pellets was measured using a melt indexer (manufactured by Takara Industries Co., Ltd.) in accordance with JIS K 7210 (Method B) at a temperature of 240° C. and a load of 98 N (10 kgf).

[0111] (6) Volatile component content (6-1) Methyl methacrylate (MMA) The amount of residual MMA in the resin pellets was determined by gas chromatography (Shimadzu Corporation, GC-2014) using a calibration curve prepared using diphenyl carbonate as an internal standard. (6-2) Methanol (MeOH) The amount of MeOH in the resin pellets was quantified using gas chromatography (Shimadzu Corporation, GC-2014) by creating a calibration curve using diphenyl carbonate as an internal standard. (6-3) Moisture The moisture content of the resin pellets was determined by Karl Fischer volumetric titration using a trace moisture analyzer (Mitsubishi Chemical Corporation, CA-100) connected to a moisture vaporizer (Mitsubishi Chemical Corporation, VA-100). Specifically, approximately 1.0 g of pellets was weighed out and introduced into the moisture vaporizer, which was kept at 250°C, and heated for 2 minutes. The total moisture generated was introduced into the moisture vaporizer using nitrogen gas dried through diphosphorus pentaoxide, and the moisture content was determined by Karl Fischer volumetric titration.

[0112] (7) Average values, standard deviations, and coefficients of variation for various properties of resin pellets (maximum diameter, orthogonal diameter, pellet length (pellet thickness), MFR, and volatile component content) The average values, standard deviations, and coefficients of variation for the various properties of each series of resin pellets before mixing and after mixing were measured as follows: First, the properties of 10 randomly selected pellets were examined, and the arithmetic mean (primary average value) for each property was calculated. This procedure was repeated 15 times, and the primary average value of the 15 pellets was calculated for each property. The arithmetic mean (secondary average value) and standard deviation of the 15 primary average values ​​were calculated, and these were used as the average values ​​and standard deviations for the various properties of each series of resin pellets and after mixing. The coefficient of variation was calculated from the average values ​​and standard deviations of the various properties.

[0113] Example 1 A reactor equipped with a stirrer, temperature sensor, cooling condenser, and nitrogen inlet tube was charged with 83.5 parts of methyl methacrylate, 12 parts of methyl 2-(hydroxymethyl)acrylate, 90.4 parts of toluene, 0.05 parts of tris(2,4-di-tert-butylphenyl)phosphite (ADEKA Corporation: ADK STAB® 2112), and 0.07 parts of n-dodecyl mercaptan, and the mixture was heated to 105°C while nitrogen was passed through. When refluxing began, 0.09 parts of tert-amyl peroxyisononanoate (Arkema Yoshitomi Co., Ltd.: Luperox® 570) was added as a polymerization initiator. 0.18 parts of tert-amyl peroxyisononanoate and 4.5 parts of styrene were added dropwise over 2 hours to allow solution polymerization to proceed under reflux at approximately 105-110°C. After the dropwise addition, the mixture was aged for another 4 hours at the same temperature.

[0114] Next, 0.075 parts of stearyl phosphate (Phoslex A-18, manufactured by SC Organic Chemical Co., Ltd.) was added as a cyclization catalyst to the polymerization solution in the reactor, and a cyclization condensation reaction to form a lactone ring structure was carried out for 2 hours under reflux at approximately 90 to 110 ° C. Next, the polymerization solution was passed through a multi-tube heat exchanger heated to 240 ° C. to complete the cyclization condensation reaction. After that, the mixture was introduced at a processing rate of 100 parts / h (resin amount equivalent) into a vent-type twin-screw extruder (L / D = 52.5) ​​with a barrel temperature of 250 ° C, a vacuum of 13.3 to 400 hPa (10 to 300 mmHg), one rear vent and four fore vents (referred to as the first, second, third, and fourth vents from the upstream side), a side feeder between the third and fourth vents, and a leaf disc-type polymer filter (filtration accuracy 5 μm) at the tip, and kneading and devolatilization were carried out. At that time, separately prepared ion-exchanged water was introduced from the upstream of the second and fourth vents at a rate of 1.5 parts / h, and a toluene solution consisting of a zinc octylate toluene solution (Nihon Kagaku Sangyo Co., Ltd., Nikka Octix Zinc 1.8%; cyclization catalyst deactivator), a phenolic antioxidant (ADEKA Corporation, ADK STAB (registered trademark) AO-60), and a sulfur-based antioxidant (ADEKA Corporation, ADK STAB (registered trademark) AO-412S) (mixing ratio by mass: 33.74:1:1) was introduced from the upstream of the third vent at a rate of 0.165 parts / h.

[0115] After devolatilization was complete, the resin composition in a molten state remaining in the extruder was filtered through a polymer filter and discharged from the tip of the extruder. The extrusion die at the tip of the extruder cylinder had numerous 4mm diameter holes drilled through it along its circumference, and was equipped with a watering cutter. The cooling water used therein was filtered through a 1µm pore size filter (manufactured by Organo Corporation, product name: Micropore Filter 1EU) and kept at a temperature within the range of 30±10°C. After cutting and water-cooling solidification, a centrifugal dryer was installed for dehydration, and the resulting mixture was transported to a storage silo by gas.

[0116] The resulting resin composition containing a (meth)acrylic resin having a lactone ring structure in the main chain had a glass transition temperature of 124°C and a weight average molecular weight of 132,000.

[0117] The resin pellets were formed in two lines (hereinafter referred to as line A and line B, respectively). Line A and line B were produced using the same recipe in equipment of the same design, but the specific equipment used was different. The resin pellets of line A and the resin pellets of line B were mixed by stirring in a storage silo.

[0118] The primary average value, secondary average value, standard deviation, and coefficient of variation of the sizes (maximum diameter, orthogonal diameter, pellet thickness) of the resin pellets formed in Series A and Series B, and of the resin pellets after mixing, are shown in Table 1. Table 2 also shows the primary average value, secondary average value, standard deviation, and coefficient of variation of the melt flow rate and volatile component content of the resin pellets formed in Series A and Series B, and of the resin pellets after mixing. In Table 1, the measurement unit for pellet size is "mm."

[0119] [Table 1]

[0120] [Table 2]

[0121] As shown in Table 1, the production method of Example 1, which includes a step of mixing resin pellets of series A and series B formed under substantially the same conditions, was able to produce highly uniform resin pellets with reduced standard deviation and coefficient of variation in pellet size. Furthermore, as shown in Table 2, the production method of Example 1 also reduced the standard deviation and coefficient of variation in the melt flow rate and volatile component content of the resulting resin pellets.

[0122] Example 2 Resin pellets were formed in two series (hereinafter, the two series will be referred to as series C and series D, respectively) in the same manner as in Example 1. Series C and Series D were produced using the same recipe using equipment of the same design, but the specific equipment used was different. The resin pellets of Series C were first charged into a storage silo, and then the resin pellets of Series D were charged on top of the resin pellets of Series C. Then, resin pellets in which the resin pellets of Series C and the resin pellets of Series D were mixed were obtained from a discharge outlet installed at the bottom of the storage silo.

[0123] The primary average value, secondary average value, standard deviation, and coefficient of variation of the sizes (maximum diameter, perpendicular diameter, pellet thickness) of the resin pellets formed in series C and D, and of the resin pellets after mixing, are shown in Table 3. In Table 3, the measurement unit for pellet size is "mm."

[0124] [Table 3]

[0125] As shown in Table 3, the manufacturing method of Example 2, which includes a step of mixing resin pellets of series C and series D formed under substantially the same conditions, made it possible to obtain highly uniform resin pellets with reduced standard deviation and coefficient of variation of pellet size.

[0126] Example 3 A reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen gas inlet pipe was charged with 79.4 parts of methyl methacrylate, 20.6 parts of methacrylic acid, a mixed solvent of 90.0 parts of toluene and 22.5 parts of methanol as a polymerization solvent, and 0.05 parts of an antioxidant (manufactured by ADEKA Corporation, trade name: Adekastab 2112), and the temperature was raised to 73°C while nitrogen gas was passed through the reaction vessel. When refluxing began with the temperature increase, 0.25 parts of dimethyl-2,2'-azobis(2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd., product name: V-601) was added to the reactor as a polymerization initiator, and a solution of 0.35 parts of dimethyl-2,2'-azobis(2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd., product name: V-601) dissolved in a mixed solvent of 7.3 parts of toluene and 1.8 parts of methanol was added dropwise to the reactor over 2 hours, while solution polymerization was carried out under reflux at approximately 71 to 76°C. After the dropwise addition of dimethyl-2,2'-azobis(2-methylpropionate) was completed, the mixture was aged for an additional 4 hours. The content of repeating units derived from methacrylic acid in the (meth)acrylic resin in the resulting polymerization solution was 20.6%. The weight-average molecular weight of the (meth)acrylic resin was 110,000.

[0127] Next, 10 parts of a solution prepared by dissolving 0.1 parts of sodium methoxide as a cyclization catalyst in 9.9 parts of methanol was added dropwise to the polymerization solution in the reaction vessel at a temperature of about 65 to 70°C over 20 minutes to obtain a homogeneous polymerization solution.

[0128] The polymerized solution obtained above was introduced into a vent-type twin-screw extruder (hole diameter: 15 mm, L / D: 45) with a barrel temperature of 290°C, a rotation speed of 70 rpm, a vacuum level of 13.3 to 400 hPa (10 to 300 mmHg), one rear vent, and two fore vents at a processing rate of 300 g / h in terms of resin amount, and devolatilization was carried out in this twin-screw extruder. The extruder was then extruded with a residence time in the extruder of about 0.9 minutes to obtain transparent resin pellets formed from a resin composition containing a (meth)acrylic resin having a glutaric anhydride structure in its main chain.

[0129] The resin composition containing the (meth)acrylic resin having a glutaric anhydride structure in its main chain obtained above had a glass transition temperature of 131°C and a weight average molecular weight of 100,000. The cyclization rate (glutaric anhydride oxidation rate) of the (meth)acrylic resin having a glutaric anhydride structure in its main chain obtained above was 17.5%.

[0130] The resin pellets formed from the resin composition containing the (meth)acrylic resin having a glutaric anhydride structure in its main chain obtained above were introduced from the hopper into a vent-type twin-screw extruder (hole diameter: 15 mm, L / D: 45) with one vent, a barrel temperature of 290°C, a rotation speed of 300 rpm, a reduced pressure of 13.3 to 400 hPa (10 to 300 mmHg), and at a processing rate of 420 g / h (resin amount equivalent). Aniline as an imidizing agent was injected from the rear of the hopper using a liquid addition pump at a rate of 101 g / h, and the extrusion was carried out with a residence time in the shaft of about 2.1 minutes, thereby obtaining transparent resin pellets formed from the resin composition containing the (meth)acrylic resin having a glutarimide structure in its main chain.

[0131] The resin pellets were passed through a die attached to the tip of the extruder and cooled in a water tank filled with cooling water to obtain strands of the resin composition, and the cooled strands were then introduced into a cutting machine (pelletizer). The cooling water used was filtered through a filter with a pore size of 1 μm (manufactured by Organo Corporation, product name: Micropore Filter 1EU) and maintained at a temperature within the range of 30±10°C. The cut resin pellets were transported to a storage silo.

[0132] The resin composition containing the (meth)acrylic resin having a glutarimide structure in its main chain obtained above had a glass transition temperature of 162°C and a weight average molecular weight of 90,000. The imidization rate of the (meth)acrylic resin having a glutarimide structure in its main chain obtained above was 44.1%.

[0133] The resin pellets were formed in two lines (hereinafter referred to as line E and line F, respectively). Line E and line F were produced using the same recipe in equipment of the same design, but the specific equipment used was different. The resin pellets of line E and line F were mixed by stirring in a storage silo.

[0134] The primary average value, secondary average value, standard deviation, and coefficient of variation of the sizes (maximum diameter, perpendicular diameter, pellet length) of the resin pellets formed in series E and series F, and of the resin pellets after mixing, are shown in Table 4. In Table 4, the measurement unit for pellet size is "mm."

[0135] [Table 4]

[0136] As shown in Table 4, the manufacturing method of Example 3, which includes a step of mixing resin pellets of series E and series F formed under substantially the same conditions, made it possible to obtain highly uniform resin pellets with reduced standard deviation and coefficient of variation of pellet size.

Claims

1. Step a) of obtaining a resin composition containing a (meth)acrylic resin having a ring structure in its main chain and a volatile component; a step b of removing the volatile components from the resin composition using an extruder, and then extruding the (meth)acrylic resin having a ring structure in its main chain; and step c) of pelletizing the (meth)acrylic resin having a ring structure in its main chain extruded from the extruder, The steps b and c are carried out in two or more series under substantially the same conditions to form pellets; A method for producing pellets, characterized in that the pellets obtained in at least two of the two or more lines are placed in the same vessel.

2. 2. The method for producing pellets according to claim 1, wherein the ring structure includes at least one selected from the group consisting of a lactone ring structure, a glutarimide structure, a glutaric anhydride structure, a structure derived from maleic anhydride, and a structure derived from an N-substituted maleimide.

3. The method for producing pellets according to claim 1 , wherein the ring structure includes at least one selected from the group consisting of a lactone ring structure and a glutarimide structure.

4. 2. The method for producing pellets according to claim 1, wherein the step a comprises a step a1 of subjecting a (meth)acrylic resin to a cyclization condensation reaction to introduce at least one ring structure selected from the group consisting of a lactone ring structure and a glutarimide structure into a main chain of the (meth)acrylic resin, thereby obtaining a (meth)acrylic resin having a ring structure in the main chain.

5. The method for producing pellets according to claim 4 , wherein the volatile components include an alcohol by-produced in the cyclocondensation reaction.

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