Method for producing polymers having structural units derived from α-methylene lactone

Abstract

To provide a method for producing a polymer having a structural unit derived from α-methylene lactone excellent in productivity.SOLUTION: A method for producing a polymer having a structural unit derived from α-methylene lactone includes: a suspension liquid producing step of stirring a mixture including α-methylene lactone monomer, a dispersion medium, and a first surfactant to obtain a suspension liquid; and a polymerization step of heating the suspension liquid to obtain a polymer. A second surfactant is added to the suspension liquid between the suspension liquid producing step and the polymerization step.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a method for producing a polymer having a structural unit derived from α-methylene lactone.

Background Art

[0002] Polymers (resins) having a structural unit derived from α-methylene lactone are excellent in transparency, heat resistance and optical isotropy, and are expected to be applied to optical members. Such resins can be obtained, for example, by suspension polymerization as shown in Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] Polymer particles obtained after suspension polymerization are usually recovered by filtration, centrifugation or the like. If the particle diameter of the polymer particles becomes excessively small, the recovery rate decreases or the recovery time increases, leading to lower productivity.

[0005] An object of the present disclosure is to provide a method for producing a polymer having a structural unit derived from α-methylene lactone, which is excellent in productivity.

Means for Solving the Problems

[0006] The present disclosure provides the method for producing a polymer described in the following [1] to [4]. [1] A method for producing a polymer having structural units derived from α-methylene lactone, comprising: a suspension production step of stirring a mixture containing an α-methylene lactone monomer, a dispersion medium, and a first surfactant to obtain a suspension; and a polymerization step of heating the suspension to obtain the polymer, wherein a second surfactant is added to the suspension between the suspension production step and the polymerization step. [2] The method for producing a polymer according to [1], wherein the first surfactant and / or the second surfactant comprises an anionic surfactant. [3] The method for producing a polymer according to [1] or [2], wherein the first surfactant and the second surfactant are the same surfactant. [4] The method for producing a polymer according to any one of [1] to [3], wherein the stirring peripheral speed in the suspension production step is 4 m / s or more and 15 m / s or less. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a method for producing polymers having structural units derived from α-methylene lactone that are highly productive. [Modes for carrying out the invention]

[0008] Embodiments of this disclosure will be described in detail below. However, this disclosure is not limited to the embodiments described below. In the following description, "(meth)acrylic" is used as a term that encompasses both methacrylic and acrylic. Resin and polymer are used as synonymous terms. When a numerical range is indicated as X to Y, it means X or more and Y or less. For example, "5 to 60 mass%" means 5 mass% or more and 60 mass% or less.

[0009] [Method for producing polymers] The method for producing a polymer having structural units derived from α-methylene lactone according to this embodiment comprises a suspension production step of stirring a mixture containing an α-methylene lactone monomer, a dispersion medium, and a first surfactant to obtain a suspension, and a polymerization step of heating the suspension to obtain a polymer, wherein the method includes a step of adding a second surfactant to the suspension between the suspension production step and the polymerization step.

[0010] <Suspension Manufacturing Process> The suspension of this embodiment is obtained by stirring a mixture containing an α-methylene lactone monomer, a dispersion medium, and a first surfactant.

[0011] (monomer) α-Methylenelactone monomers are a general term for compounds in which a methylene group is bonded to the α-carbon of a lactone ring. The number of members in the lactone ring is not particularly limited, but from the viewpoint of compound stability, a 5-membered ring (γ-lactone) or a 6-membered ring (δ-lactone) is preferred.

[0012] Representative examples of α-methylenelactone monomers that are 5-membered or 6-membered rings are α-methylene-γ-butyrolactone and α-methylene-δ-valerolactone.

[0013] The α-methylene lactone monomer is preferably a compound such as the one shown in formula (1) below.

[0014] [ka]

[0015] R in equation (1) 1 ~R 4 These are, independently of each other, a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms.

[0016] The hydrocarbon group is an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group is, for example, an alkyl group. The number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 8. The alkyl group may be linear, branched, or cyclic. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, t-butyl group, n-pentyl group, n-hexyl group, cyclopentyl group, cyclohexyl group and the like.

[0017] The aromatic hydrocarbon group is, for example, a phenyl group, a tolyl group, a benzyl group or the like.

[0018] R 1 to R 4 are preferably, independently of each other, a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and more preferably all are hydrogen atoms.

[0019] The suspension may contain only one type of α-methylene lactone monomer, or may contain two or more types thereof.

[0020] The suspension of the present embodiment may contain any other monomer in addition to the α-methylene lactone monomer. The optional other monomers are, for example, alkyl (meth)acrylate, benzyl (meth)acrylate, chloromethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, styrene, vinyltoluene, α-methylstyrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, vinyl acetate and the like. The suspension may contain only one type of optional other monomer, or may contain two or more types thereof.

[0021] Among any other monomers, alkyl (meth)acrylate is preferred from the viewpoint of further improving the heat resistance, transparency, etc., of the film obtained using the polymer of this embodiment, alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms is more preferred, alkyl (meth)acrylate having an alkyl group having 1 to 3 carbon atoms is even more preferred, and methyl (meth)acrylate is even more preferred. The suspension may contain only one type of alkyl (meth)acrylate or may contain two or more types.

[0022] The alkyl groups having 1 to 6 carbon atoms in alkyl (meth)acrylates include, for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, t-butyl, n-pentyl, n-hexyl, cyclopentyl, and cyclohexyl groups.

[0023] From the viewpoint of further improving heat resistance and other properties, the content of α-methylene lactone monomers in the suspension is preferably 5 to 60% by mass, more preferably 7.5 to 50% by mass, and even more preferably 10 to 45% by mass, relative to the total amount of monomers in the suspension.

[0024] The content of alkyl (meth)acrylate having an alkyl group with 1 to 6 carbon atoms in the suspension is preferably 40 to 95% by mass, more preferably 45 to 92.5% by mass, and even more preferably 50 to 90% by mass, based on the total amount of monomers in the suspension.

[0025] The content of monomers other than α-methylene lactone monomers and alkyl (meth)acrylates having an alkyl group with 1 to 6 carbon atoms in the suspension is preferably 0 to 30% by mass, more preferably 0 to 25% by mass, and even more preferably 0 to 20% by mass, relative to the total amount of monomers in the suspension.

[0026] (dispersion medium) The dispersion medium is preferably an aqueous solvent. The aqueous solvent may also contain a non-aqueous solvent (especially a water-soluble organic solvent). Examples of water-soluble organic solvents include alcohol solvents such as methanol, ethanol, propanol, butanol, 2-methylpropyl alcohol, and 2-methyl-2-propanol; ketone solvents such as acetone and methyl ethyl ketone; ester solvents such as ethyl acetate; and ether solvents such as dioxane, diethyl ether, and tetrahydrofuran.

[0027] The amount of dispersion medium contained in the suspension is, for example, 50 to 300 parts by mass, or 100 to 200 parts by mass, per 100 parts by mass of the total amount of monomer.

[0028] (First surfactant) The first surfactant is, for example, a fatty acid salt such as sodium oleate or potassium castor oil; an alkyl sulfate ester salt such as sodium lauryl sulfate or ammonium lauryl sulfate; an alkylbenzene sulfonate such as sodium dodecylbenzenesulfonate; an alkylnaphthalene sulfonate; an alkane sulfonate; a dialkyl sulfosuccinate; an alkyl phosphate ester salt; a formalin condensate of naphthalene sulfonic acid; an anionic surfactant such as polyoxyalkylene alkyl ether sulfate such as polyoxyethylene alkyl ether sulfate; an anionic surfactant such as polyoxyalkylene alkyl sulfate such as polyoxyethylene phenyl ether sulfate; an alkylamine salt such as laurylamine acetate or stearylamine acetate; a cationic surfactant such as quaternary ammonium salt such as lauryltrimethylalkylammonium chloride; an amphoteric surfactant such as lauryldimethylamine oxide; or a nonionic surfactant such as polyoxyethylene alkyl ether. The suspension may contain only one of the first surfactants, or it may contain two or more. The first surfactant preferably contains an anionic surfactant, and more preferably contains a polyoxyethylene phenyl ether sulfate salt such as polyoxyethylene distyrylphenyl ether sulfate ammonium salt.

[0029] The content of the first surfactant in the suspension is preferably 0.01 to 20 parts by mass, more preferably 0.05 to 10 parts by mass, per 100 parts by mass of the total monomer.

[0030] When dispersing the α-methylene lactone monomer, the first surfactant, etc., in a dispersion medium, the dispersion may be carried out by stirring with paddle blades or the like, or by using an emulsification and dispersion device such as a high-speed shear turbine type disperser, a high-pressure jet homogenizer, an ultrasonic emulsification and dispersion machine, a media stirring disperser, or a forced gap-passing type disperser.

[0031] From the viewpoint of increasing polymer productivity, the stirring peripheral speed in the suspension manufacturing process is preferably 4 m / s to 15 m / s, more preferably 6 m / s to 13 m / s, and even more preferably 7 m / s to 12 m / s. The stirring peripheral speed can be appropriately adjusted within the above range depending on the scale of polymer production, and the time required for stirring can also be appropriately adjusted depending on the scale of polymer production.

[0032] In the suspension manufacturing process of this embodiment, additives such as polymerization initiators, chain transfer agents, and dispersants may be added as needed.

[0033] Polymerization initiators include, for example, organic peroxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butyl peroxyisopropyl carbonate, t-amyl peroxy-2-ethylhexanoate, and t-butyl peroxy-2-ethylhexanoate; and azo compounds such as 2,2'-azobis(isobutyronitrile), 1,1'-azobis(cyclohexanecarbonile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl-2,2'-azobis(2-methylpropionate). The amount of polymerization initiator added can be adjusted as needed, but is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, and even more preferably 0.1 to 2 parts by mass per 100 parts by mass of monomer.

[0034] Examples of chain transfer agents include monofunctional thiol compounds such as n-dodecyl mercaptan and β-mercaptopropionic acid; difunctional thiol compounds such as polysiloxanes with mercapto-modified ends; and polyfunctional mercapto-modified polysiloxanes with mercapto-modified side chains. The amount of chain transfer agent added can be adjusted as needed, but preferably 0.001 to 1 part by mass, and more preferably 0.01 to 0.3 parts by mass, per 100 parts by mass of monomer.

[0035] Examples of dispersants include water-soluble polymer-based dispersion stabilizers such as polyvinyl alcohol (PVA), polyvinylpyrrolidone, cellulose, gelatin, sodium polyacrylate, and sodium polymethacrylate; alginates, zein, and casein; and inorganic dispersants such as barium sulfate, calcium sulfate, barium carbonate, magnesium carbonate, calcium phosphate, talc, clay, diatomaceous earth, bentonite, titanium hydroxide, thorium hydroxide, and metal oxide powders. The amount of dispersant added can be adjusted as needed, but 0.1 to 3 parts by mass, and more preferably 0.2 to 1 part by mass, is preferred per 100 parts by mass of monomer.

[0036] Other additives besides polymerization initiators, chain transfer agents, and dispersants include, for example, ultraviolet absorbers such as benzophenone compounds, salicylate compounds, benzoate compounds, triazole compounds, and triazine compounds; antioxidants such as phenolic, phosphorus, and sulfur compounds; polymerization inhibitors such as 4-tert-butylcatechol (TBC), hydroquinone, and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4H-TEMPO); 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; phase difference adjusters such as phase difference enhancers, phase difference reducers, and phase difference stabilizers; antistatic agents such as hydrophilic polymers and conductive fillers; colorants such as inorganic pigments, organic pigments, and dyes; organic and inorganic fillers; resin modifiers; organic and inorganic fillers; and the like. The proportion of these additives may be adjusted as needed, but it may be 0 to 5 parts by mass or 0 to 3 parts by mass per 100 parts by mass of monomer.

[0037] <Polymerization process> When the above suspension is heated, the polymerization reaction begins.

[0038] The method for heating the suspension can be appropriately selected depending on the scale of polymer production. For example, one method involves heating the suspension to 50-90°C, maintaining a constant temperature, and then heating it to 70-100°C as the polymer reaction progresses. The heating temperature and heating time can be appropriately adjusted depending on the type of monomer, the scale of polymer production, etc.

[0039] In the polymerization step, the suspension may be heated while being stirred. The stirring speed of the suspension in the polymerization step is not particularly limited, but it is preferably slower than the stirring speed in the suspension preparation step. From the viewpoint of promoting the polymerization reaction, the stirring speed in the polymerization step is, for example, 0.1 m / s to 3 m / s, or 1.0 m / s to 2.0 m / s.

[0040] <Step of adding a second surfactant to the suspension> The polymer production method of this embodiment includes a step of adding a second surfactant to the suspension between the suspension production step and the polymerization step. The period between the suspension production step and the polymerization step refers to the period from when stirring in the suspension production step is stopped until when heating in the polymerization step is started.

[0041] (Second surfactant) Specific examples of the second surfactant are the same as specific examples of the first surfactant. Only one type of the second surfactant may be added to the suspension, or two or more types may be added. Furthermore, the first and second surfactants may be the same type of surfactant, or they may be different types of surfactants. In particular, from the viewpoint of ease of manufacture, the first and second surfactants may be the same surfactant. The second surfactant preferably contains an anionic surfactant, and more preferably contains a polyoxyethylene phenyl ether sulfate salt such as polyoxyethylene distyrylphenyl ether sulfate ammonium salt.

[0042] The amount of the second surfactant added can be adjusted as appropriate considering the content of the first surfactant in the suspension, but preferably 0.01 to 20 parts by mass, and more preferably 0.05 to 10 parts by mass, per 100 parts by mass of the total monomer amount. Furthermore, the amount of the second surfactant added is preferably 10 to 1000 parts by mass, and more preferably 20 to 800 parts by mass, per 100 parts by mass of the total first surfactant amount.

[0043] The second surfactant may be added after being dissolved in the above-mentioned dispersion medium. The amount of dispersion medium should be adjusted as appropriate depending on the type and amount of the second surfactant added.

[0044] <Solid-liquid separation process> After the polymerization process, the polymer can be recovered by solid-liquid separation. The solid-liquid separation method can be selected from, for example, filtration, centrifugation, or a combination thereof. The recovered polymer may be dried as needed. The drying temperature is preferably 60°C or higher, more preferably 70°C or higher, and also preferably 90°C or lower. Drying can be carried out until the moisture content in the polymer is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less. The drying time is preferably 10 hours or more, more preferably 12 hours or more, and also preferably 20 hours or less, and more preferably 18 hours or less.

[0045] The water content in a polymer can be measured using a water content measuring device. One method of measurement using a water content measuring device is to disperse approximately 0.5 g of dry polymer in methanol solution and measure the amount of water introduced into the methanol solution by the polymer using a Karl Fischer volume titrator (automatic water content measuring device "AQV-300" manufactured by Hiranuma Sangyo Co., Ltd.). Aquamicron SS-Z 3 mg (manufactured by Mitsubishi Chemical Corporation) can be used as the titrant, and deionized water can be used to test the titrant's potency.

[0046] The average particle size of the polymer obtained by the above method is preferably 1.1 μm or larger, more preferably 1.5 μm or larger, and even more preferably 2.0 μm or larger, from the viewpoint of facilitating solid-liquid separation after polymerization. Furthermore, from the viewpoint of obtaining a uniform polymer, it is preferably 50 μm or smaller, more preferably 20 μm or smaller, and even more preferably 10 μm or smaller.

[0047] In the method for producing polymers having structural units derived from α-methylene lactone described above, a portion of the surfactant used in suspension polymerization is added to the suspension after the suspension has been prepared. This allows for optimization of the particle size of the polymer obtained by the polymerization step of suspension polymerization. As a result, the efficiency in the solid-liquid separation step is improved.

[0048] Conventionally, the entire amount of surfactant used in suspension polymerization is added to the mixture for producing the suspension. This can lead to the particle size of the polymer obtained by the polymerization process in suspension polymerization becoming excessively small. Conversely, if the amount of surfactant used is reduced to accommodate the particle size, the dispersion of monomers in the suspension may become insufficient.

[0049] In contrast, the method for producing a polymer having structural units derived from α-methylene lactone according to this disclosure reduces the surfactant content in the mixture for producing the suspension compared to conventional methods, thus optimizing the particle size of the polymer obtained by the suspension polymerization step. Furthermore, since the surfactant is added to the produced suspension, the dispersion state of the monomers in the suspension is well maintained. [Examples]

[0050] The present disclosure will be explained in more detail below with reference to examples, but the present disclosure is not limited to these examples. Furthermore, various physical properties were measured and evaluated as follows.

[0051] [Average particle size of polymer] The average particle size of the polymer was determined by measuring the particle size of 30,000 particles using a precision particle size distribution analyzer (Beckman Coulter's "Coulter Multisizer III") after dispersing the polymer in the suspension following the completion of the polymerization reaction by irradiating it with ultrasound, and then calculating the average particle size per unit volume.

[0052] The materials used in the examples are described below. Methyl methacrylate (MMA) and α-methylene-γ-butyrolactone (ML) are commercially available products from Tokyo Chemical Industry Co., Ltd. Perloyl L (dilauroyl peroxide, LPO) is a commercially available product from NOF Corporation. Polyoxyethylene distyrylphenyl ether sulfate ammonium salt (trade name "Hytenol® NF-08") is a commercially available product from Daiichi Kogyo Seiyaku Co., Ltd. t-amyl peroxy 2-ethylhexanoate (trade name "Luperox® 575 (R575)") is a commercially available product from Arkema Yoshitomi Co., Ltd. Polyoxyethylene 2-ethylhexyl ether (trade name "Newcol® 1020") is a commercially available product from Nippon Emulsifier Co., Ltd.

[0053] (Example 1) A reactor equipped with a stirring device (Shinto Chemical Co., Ltd. Three One Motor, anchor-type stirring blade), a temperature sensor, a cooling tube, and a nitrogen inlet tube was prepared. 150 parts by mass of deionized water containing 0.25 parts by mass of Hythenol (registered trademark) NF-08 as the first surfactant was charged into a container. A pre-prepared solution containing 75 parts by mass of MMA, 25 parts by mass of ML, 0.5 parts by mass of LPO, and 0.01 parts by mass of nDM (n-dodecyl mercaptan) was then charged into the container. The mixture in the reactor was then stirred using a TK homomixer MARK II model 2.5 (Primix Corporation) at a peripheral speed of 12 m / s for a predetermined time to obtain a homogeneous suspension.

[0054] 250 parts by mass of deionized water containing 1.75 parts by mass of Hi-Tenol NF-08 as a second surfactant was added to the suspension and then transferred to the reactor. After transfer, nitrogen gas was blown in while stirring and the suspension was heated until it reached 70°C. The point when the internal temperature reached 70°C was used as the reference time, and the reactor was kept at 70°C until the internal temperature reached its peak temperature due to self-heating, at which point it was maintained at 75°C. Two hours after the reference time, the suspension was further heated to 90°C and stirred for 4 hours to complete the polymerization reaction. After that, the reaction solution (suspension) was cooled and centrifuged at 4000 rpm for 10 minutes using a benchtop centrifuge H-36α (manufactured by Kokusan Co., Ltd.) to separate the solid and liquid to obtain the polymer, which was then dried using a hot air dryer to obtain the polymer (powder).

[0055] (Examples 2-3, Comparative Example 1) A polymer (powder) was obtained in the same manner as in Example 1, except that the amount of surfactant added and the stirring speed were changed as shown in Table 1.

[0056] (Example 4) A reactor equipped with a stirring device (Shinto Chemical Co., Ltd. Three One Motor, anchor-type stirring blade), a temperature sensor, a cooling tube, and a nitrogen inlet tube was prepared. 0.15 parts by mass of Newcol (registered trademark) 1020 as the first surfactant and 150 parts by mass of deionized water containing 0.1 parts by mass of sodium lauryl sulfate were charged into a container. A pre-prepared solution containing 75 parts by mass of MMA, 25 parts by mass of ML, 0.5 parts by mass of LPO, and 0.01 parts by mass of nDM was then charged into the container. The mixture in the reactor was then stirred using a TK homomixer MARK II model 2.5 (Primix Corporation) at a peripheral speed of 7.5 m / s for a predetermined time to obtain a homogeneous suspension.

[0057] To the suspension, 0.15 parts by mass of Newcol 1020 as a second surfactant and 250 parts by mass of deionized water containing 0.1 parts by mass of sodium lauryl sulfate were added, and then the mixture was transferred to the reactor. After transfer, nitrogen gas was blown in while stirring, and the suspension was heated until it reached 70°C. The point when the internal temperature reached 70°C was used as the reference time, and the reactor was kept at 70°C until the internal temperature reached its peak temperature due to self-heating, at which point it was maintained at 75°C. Two hours after the reference time, the suspension was further heated to 90°C and stirred for 4 hours to complete the polymerization reaction. After that, the reaction solution (suspension) was cooled, and centrifugal separation was performed using a benchtop centrifuge H-36α (manufactured by Kokusan Co., Ltd.) at a rotation speed of 4000 rpm for 10 minutes to obtain the polymer by solid-liquid separation, and then the polymer (powder) was obtained by drying using a hot air dryer.

[0058] The average particle size and recovery rate of the obtained polymer are shown in Table 1. The polymer recovery rate is calculated with the theoretically obtainable polymer mass as 100% by mass.

[0059] [Table 1]

Claims

1. A method for producing a polymer having structural units derived from α-methylene lactone, A suspension preparation step involves stirring a mixture containing an α-methylene lactone monomer, a dispersion medium, and a first surfactant to obtain a suspension. The process includes a polymerization step of heating the suspension to obtain the polymer, A method for producing a polymer, comprising adding a second surfactant to the suspension after stopping the stirring in the suspension production step and before starting the heating in the polymerization step.

2. The method for producing a polymer according to claim 1, wherein the first surfactant and / or the second surfactant includes an anionic surfactant.

3. The method for producing a polymer according to claim 1, wherein the first surfactant and the second surfactant are the same surfactant.

4. A method for producing a polymer according to any one of claims 1 to 3, wherein the stirring peripheral speed in the suspension production step is 4 m / s or more and 15 m / s or less.

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