Styrene copolymer, feed liquid, and method for producing styrene copolymer

Abstract

To provide a styrenic copolymer having excellent weather resistance, a feed solution for producing a styrenic copolymer and a method for producing a styrenic copolymer using the feed solution.SOLUTION: There is provided a styrenic copolymer which is a copolymer containing an α-methylstyrene unit and a vinyl aromatic monomer unit represented by the following general formula (1) obtained by a living anionic polymerization method, wherein the amount of change in the total light transmittance is 5% or less and the amount of change in yellowness is 5 or less after 1000 hours of irradiation in a weather resistance test using a sunshine weather meter, (wherein, R1 represents a hydrogen atom, an alkyl group having 2 or more carbon atoms or a phenyl group, R2 represents a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a carboxyl group or a haloalkyl group having 1 to 6 carbon atoms.)SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a styrene copolymer excellent in weather resistance, a feed liquid for producing the styrene copolymer, and a method for producing the styrene copolymer using the feed liquid.

Background Art

[0002] Styrene resins are not only excellent in material properties such as transparency, rigidity, and dimensional stability, but also can be subjected to various molding processes such as injection molding, stretched sheet, film, foamed sheet, foamed board, and blow molding. Moreover, many styrene resins can be produced in large quantities at low cost by bulk polymerization by radical polymerization method, solution polymerization at high monomer concentration, suspension polymerization, and emulsion polymerization, and thus are used in a very wide variety of applications.

[0003] Generally, styrene resins are produced by living anionic polymerization. However, this living anionic polymerization is a polymerization method that is easily affected by impurities contained in raw materials (Patent Document 1). In particular, it is known that active anions easily react with polar substances such as water, aldehyde, ketone, and alcohol. Even if a trace amount of polar substance is present in the reaction system of anionic polymerization, the active anion reacts with the polar substance to form a stable bond, resulting in a problem that polymerization stops. Therefore, when performing living anionic polymerization, it is necessary to reduce the polar substances in the raw materials and suppress the contamination of polar substances into the reaction system as much as possible.

[0004] As a method for purifying α-methylstyrene to solve the above problems, a method has been proposed in which polar substances contained in α-methylstyrene are reacted in the presence of a basic substance, and low-boiling by-products generated by the reaction are separated from the reactants of the polar substances to purify α-methylstyrene (for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In recent years, the effective utilization of resins has been emphasized, and various recycling methods have been established and implemented. The ability to recycle, rework, and reuse resins will become an essential need in the future resin market.

[0007] Resin materials to be developed in the future should be resins that hardly cause a decrease in molecular weight due to the cleavage of polymer chains or the generation of monomers even after several melt processes, have little weathering deterioration of physical properties due to long-term use, and can be effectively reused.

[0008] Therefore, the development of resin materials with higher melt stability and excellent weather resistance than conventional styrene copolymers has been desired.

[0009] An object of the present invention is to provide a styrene copolymer excellent in weather resistance, a feed liquid for producing the styrene copolymer, and a method for producing a styrene copolymer produced using the feed liquid by controlling the content of a specific compound in the feed liquid to be subjected to polymerization within a specific range.

Means for Solving the Problems

[0010] As a result of intensive studies to solve the above problems, the present inventors have found that a styrene copolymer excellent in weather resistance can be obtained by controlling the content of a specific compound contained in trace amounts in the feed liquid to be subjected to polymerization within a specific range, and have completed the present invention. That is, the present invention has the following aspects.

[0011] (1) A copolymer obtained by living anionic polymerization and containing α-methylstyrene units and vinyl aromatic monomer units represented by the following general formula (1), wherein the change in total light transmittance after 1000 hours of irradiation in a weather resistance test using a sunshine weather meter is 5% or less, and the change in yellowness is 5 or less. A styrene copolymer.

Chemical formula

[0012] (2) The content of α-methylstyrene units in the copolymer is 10 to 65% by mass, the weight average molecular weight (Mw) is in the range of Mw = 50,000 to 300,000, and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) is in the range of 1.6 to 2.5. And the total mass of the remaining monomers and polymerization solvent is 500 ppm or less. The styrene copolymer according to (1) above.

[0013] (3) A feed liquid for producing a styrene copolymer, which consists of a monomer and a polymerization solvent, wherein the content of acetylacetone in the feed liquid is 2 ppm or less, the content of benzaldehyde is 10 ppm or less, and the content of phenylacetylene is 15 ppm or less. A feed liquid for producing a styrene copolymer.

[0014] (4) A method for producing a styrene copolymer using a feed liquid composed of a monomer and a polymerization solvent, wherein the content of acetylacetone in the feed liquid is 2 ppm or less, the content of benzaldehyde is 10 ppm or less, and the content of phenylacetylene is 15 ppm or less. A method for producing a styrene copolymer produced using a feed liquid.

Advantages of the Invention

[0015] The styrene copolymer of the present invention has excellent weather resistance by controlling the content of a specific compound in the feed liquid to be polymerized within a specific range. Further, a molded article containing the styrene copolymer of the present invention can be extremely suitably used as a food container for heating, a housing part, an interior part for an automobile, or an optical part.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, the present invention will be described in detail.

[0017] <Styrene Copolymer> The styrene copolymer of the present invention will be described. The styrene copolymer in the present invention is a copolymer obtained by controlling the content of a specific compound in the feed liquid to be polymerized, and contains an α-methylstyrene unit and a vinyl aromatic monomer unit represented by the following formula (1) as constituent units, and the change amount of the total light transmittance after 1000 hours of irradiation time in the weather resistance test by a sunshine weather meter is 5% or less, and the change amount of the yellowness is 5 or less. This styrene copolymer has excellent weather resistance. Further, it also has excellent properties in heat resistance, melt stability, moldability, strength, and rigidity.

Chemical formula

[0018] As used herein, the term "C1-C6 alkyl group" means a linear or branched alkyl group having 1 to 6 carbon atoms, specifically, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, 1-ethylpropyl group, n-hexyl group, 1-ethyl-2-methylpropyl group, 1,1,2-trimethylpropyl group, 1-ethylbutyl group, 1-methylbutyl group, 2-methylbutyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 2,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,3-dimethylbutyl group, 2-ethylbutyl group, 2-methylpentyloxy group, 3-methylpentyloxy group, etc., preferably methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, n-hexyl group, etc.

[0019] As used herein, the term "C1-C6 alkoxy group" means an oxy group bonded to the "C1-C6 alkyl group" as defined above, specifically, methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n-butoxy group, iso-butoxy group, sec-butoxy group, tert-butoxy group, n-pentyloxy group, iso-pentyloxy group, sec-pentyloxy group, n-hexyloxy group, iso-hexyloxy group, 1,1-dimethylpropoxy group, 1,2-dimethylpropoxy group, 2,2-dimethylpropoxy group, 2-methylbutoxy group, 1-ethyl-2-methylpropoxy group, 1,1,2-trimethylpropoxy group, 1,1-dimethylbutoxy group, 1,2-dimethylbutoxy group, 2,2-dimethylbutoxy group, 2,3-dimethylbutoxy group, 1,3-dimethylbutoxy group, 2-ethylbutoxy group, 2-methylpentyloxy group, 3-methylpentyloxy group, etc., preferably methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, and more preferably methoxy group, ethoxy group.

[0020] As used herein, the term "alkyl group having 2 or more carbon atoms" means a linear or branched alkyl group having 2 or more (preferably 2 to 6) carbon atoms. Specifically, examples include ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, 1-ethylpropyl group, n-hexyl group, 1-ethyl-2-methylpropyl group, 1,1,2-trimethylpropyl group, 1-ethylbutyl group, 1-methylbutyl group, 2-methylbutyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 2,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,3-dimethylbutyl group, 2-ethylbutyl group, 2-methylpentyl group, 3-methylpentyl group, etc. Preferably, examples include ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, etc.

[0021] As used herein, the term "halogen atom" means a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.

[0022] As used herein, the term "halo C1-C6 alkyl group" means a group in which the "halogen atom" as defined above is bonded to the "C1-C6 alkyl group" as defined above.

[0023] The vinyl aromatic monomers used in the present invention include, for example, alkyl-substituted styrenes such as styrene, p-methylstyrene, m-methylstyrene, o-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, o-ethylstyrene, etc., and other styrene derivatives such as p-hydroxystyrene, p-methoxystyrene, p-chlorostyrene, 1,1-diphenylethylene, etc. The preferred vinyl aromatic monomer is styrene. These vinyl aromatic monomers may be used one by one, or two or more of them may be mixed and used. In the present invention, the most preferred combination is a combination of α-methylstyrene and styrene.

[0024] The content of α-methylstyrene units contained in the styrene copolymer is preferably 10 to 65% by mass (hereinafter also referred to as wt%), more preferably 12 to 63 wt%, and even more preferably 15 to 60 wt%. When the α-methylstyrene units are 10 wt% or more, the effect of improving heat resistance in actual use is greater, and when they are 65 wt% or less, the thermal stability during melt molding processing is higher, the generation of gas during molding can be more suppressed, and the amount of monomer components accompanying the decomposition in the resin can also be more suppressed.

[0025] In addition to the above monomers, other polymerizable monomers can be used together within the range that does not impair the object of the present invention. Examples of copolymerizable monomers include conjugated diene monomers such as butadiene and isoprene; alkyl methacrylate esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate; and acrylate esters such as methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate. These monomers are useful when improving or adjusting the impact strength, elongation, chemical resistance, etc. of the resin.

[0026] The styrenic copolymer in the present invention is synthesized by a living anionic polymerization method. As the living anionic polymerization method, a known method can be used. For example, an organolithium compound is used as an initiator. Specifically, n-butyllithium, sec-butyllithium, t-butyllithium, ethyllithium, benzyllithium, 1,6-dilithiohexane, styryllithium, butadienyllithium, etc. are used. Among these, n-butyllithium and sec-butyllithium are preferably used.

[0027] As the polymerization solvent, a hydrocarbon-based compound containing no heteroatoms is preferable. Specifically, aliphatic hydrocarbon compounds such as n-hexane, cyclohexane, and heptane, and aromatic hydrocarbon compounds such as benzene, toluene, ethylbenzene, and xylene are exemplified. These hydrocarbon compounds may be used alone or in combination of two or more. In particular, a preferable compound is cyclohexane.

[0028] The polymerization temperature is preferably in the range of 40°C to 110°C, more preferably in the range of 50°C to 100°C, and even more preferably in the range of 55°C to 95°C, from the viewpoints of productivity and coloring and weather resistance of the resin after production.

[0029] The styrenic copolymer in the present invention can be produced, for example, by a continuous living polymerization method using a completely mixed type polymerization reactor. Or, a combination of a completely mixed type polymerization reactor and an incompletely mixed type polymerization reactor may also be used. In particular, for obtaining a random copolymer, a completely mixed type polymerization reactor is preferable. The completely mixed type polymerization refers to a method of polymerization using a continuous type completely mixed reactor in which the concentrations of α-methylstyrene, vinyl aromatic monomer, and living copolymer present in the reaction system of living polymerization are always constant.

[0030] When it is desired to increase the productivity by increasing the monomer concentration in the raw material solution, it is desirable to attach a condenser to the polymerization reactor in order to efficiently remove the heat of polymerization, and remove the heat of polymerization with the latent heat of vaporization of the solvent. In particular, when cyclohexane (n - hexane may be mixed) is mainly used as the polymerization solvent, since the boiling point is 82°C, it is easy to control the polymerization temperature in the vicinity of 80°C to 90°C.

[0031] When using an imperfectly mixed tube - type polymerization reactor, for example, when the ratio L / D of the length (L) to the inner diameter (D) of the reactor is 1 or more, or when the stirring efficiency is poor, etc., when it is difficult to achieve a perfect mixing state in the polymerization reactor, the styrene - based copolymer of the present invention can be produced by adding a solution of a vinyl aromatic monomer from the middle of the reactor.

[0032] Also, two or more imperfectly mixed polymerizers can be connected in series, and the copolymer of the present invention can be obtained by adding a solution of a vinyl aromatic monomer to the second polymerization reactor after the first polymerization. Further, only the vinyl aromatic monomer is polymerized in the first polymerization reactor, and then the copolymerization of α - methylstyrene and the vinyl aromatic monomer is carried out in the second polymerization reactor to obtain a block copolymer of a homopolymer of the vinyl aromatic unit and the copolymer.

[0033] Among the trace components contained in the monomers used to obtain the styrene - based copolymer of the present invention, the specific compounds to be controlled in the present invention are carbonyl - group - containing compounds, phenol, catechols including t - butylcatechol which is a polymerization inhibitor, and phenylacetylene. Specific examples of the carbonyl - group - containing compounds include acetonylacetone, 3 - methyl - 2 - cyclopentenone, benzaldehyde, acetophenone, etc.

[0034] These compounds tend to cause polymerization inhibition, polymer coloring, and deterioration of weather resistance when producing polyα - methylstyrene and its copolymers by anionic polymerization or the like, so it is preferably removed as much as possible.

[0035] As a method for removing a specific compound to be controlled from α-methylstyrene, a method of adding a specific basic substance to α-methylstyrene and separating the high-boiling compound and the low-boiling compound generated by the reaction from α-methylstyrene by distillation is preferable.

[0036] As the basic substance used in this case, basic compounds containing alkali metals or alkaline earth metals such as metal alkoxides such as sodium ethoxide, potassium ethoxide, and sodium methoxide, metal hydroxides such as sodium hydroxide, potassium hydroxide, and magnesium hydroxide, metal oxides such as sodium oxide, potassium oxide, and magnesium oxide, metal amides such as lithium diisopropylamide, and alkyl metals such as butyllithium and methyllithium can be used.

[0037] As a method for removing a specific compound to be controlled from styrene and a polymerization solvent, ordinary purification methods can be applied. For example, after nitrogen bubbling, the purification can be carried out by passing through a purification column filled with activated alumina.

[0038] By the above methods and the like, it is possible to control the content of a specific compound in the feed liquid for polymerization composed of a monomer and a polymerization solvent. When these specific compounds are controlled within a certain range, it is effective for polymerization control and prevention of polymer yellowing, and particularly very effective for improving the weather resistance of the polymer.

[0039] Regarding the content of the specific compound in the feed liquid to be controlled, the less the better. However, it is preferably 2 ppm or less for acetonylacetone, 10 ppm or less for benzaldehyde, and 15 ppm or less for phenylacetylene. Furthermore, it is more preferably 10 ppm or less for phenylacetylene. Note that ppm in this specification is a mass unit. If these values are exceeded, the weather resistance of the obtained polymer will be significantly reduced, and in some cases, living polymerization will be inhibited.

[0040] The value of the Yellow Index of the styrene copolymer in the present invention is preferably 3 or less, more preferably 2 or less, and most preferably 1.5 or less. In order to reduce the yellow index, as described above, it is effective to reduce the content of specific compounds in the feed liquid. In particular, when manufacturing biaxially stretched sheets (OPS) or foamed sheets (PSP) used in the food packaging field, yellowing of the resin becomes particularly noticeable when winding and recovering the sheets, which may cause quality problems. Therefore, users of such applications are particularly sensitive to yellowing of the resin and regard it as one of the important required performances.

[0041] In the styrene copolymer of the present invention, in the weather resistance test using a sunshine weather meter, the change amount of the total light transmittance after 1000 hours of irradiation time is 5% or less, and the change amount of the yellow index is 5 or less. In this specification, the change amount of the total light transmittance and the change amount of the yellow index after 1000 hours of irradiation time in the weather resistance test using a sunshine weather meter are the values measured by the method described in the examples below.

[0042] The weight average molecular weight (Mw) of the styrene copolymer of the present invention is preferably in the range of Mw = 50,000 to 300,000, more preferably in the range of Mw = 60,000 to 290,000, and still more preferably in the range of Mw = 70,000 to 280,000. From the viewpoint of mechanical strength, it is preferable that Mw is 50,000 or more, and from the viewpoint of the fluidity of the resin during molding, it is preferable that Mw is 300,000 or less. As a result, not only is it easier to mold precision parts, but also the molecular orientation of the polymer chains is more suppressed, and various problems such as the manifestation of anisotropy in optical properties, the decrease in surface impact strength of sheet-like extrusion molded products and sheet-like injection molded products, and the difficulty of molding large-sized molded products can be more suppressed.

[0043] Furthermore, it is preferable that the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is in the range of 1.6 to 2.5. More preferably, the range of Mw / Mn = 1.8 to 2.4 is good. When Mw / Mn is in the range of 1.6 to 2.5, the balance between the fluidity and mechanical properties of the resin is improved, sufficient performance can be achieved as a resin molded body, and the occurrence of the above problems can be suppressed simultaneously.

[0044] The glass transition temperature in the present invention can be determined by DSC, and the temperature determined by the method shown in JIS-K7121 is taken as the glass transition temperature.

[0045] The bonding mode of the α-methylstyrene unit and the vinyl aromatic monomer unit in the styrene-based copolymer in the present invention is not particularly limited, but the most preferable bonding mode is a copolymer composed of random bonding. Generally, when there are many chains of α-methylstyrene units, it tends to be easily thermally decomposed. Therefore, depending on the application, it is preferable to control the chains of α-methylstyrene units to 2 to 4 chains or less.

[0046] The vinyl aromatic monomer unit, even if it forms a chain, is not particularly likely to impair thermal stability, so it may have a long-chain structure. The inventors have found that a long-chain structure of the vinyl aromatic monomer unit exists at the end of the molecular chain of the copolymer in the form of an AB type or ABA type block copolymer (A is a homopolymer component mainly composed of a vinyl aromatic monomer unit component; B is a random copolymer component containing an α-methylstyrene unit and a vinyl aromatic monomer unit), and its other properties including heat resistance, thermal stability, mechanical properties, and fluidity are equivalent to those of a random copolymer, and moreover, it has extremely good compatibility with a homopolymer having the same structure as the vinyl aromatic monomer unit which is one component of the block. Taking advantage of this property, when the styrene-based copolymer of the present invention is to be reused as a recycling material, for example, when it is desired to be melt-kneaded with polystyrene for reuse, a copolymer having a polystyrene chain blocked at the end of the polymer chain of the copolymer can be used.

[0047] The block chain length of the vinyl aromatic monomer unit is not particularly limited, and preferably, the number average molecular weight of the block chain portion is in the range of 1,000 to 250,000. Further, the Mw / Mn of the block component composed of vinyl aromatic monomer units is preferably in the range of 1.0 to 2.5.

[0048] The method for producing a copolymer having a vinyl aromatic monomer unit as a block component is, for example, producing a homopolymer composed of vinyl aromatic monomer units in a batch reactor, a continuous tube reactor, a continuous static mixer reactor, a continuous stirred tank reactor with blades, a continuous coil reactor, etc., and then feeding and copolymerizing α-methylstyrene, a vinyl aromatic monomer, and a homopolymer composed of living vinyl aromatic monomer units into a continuous complete mixing reactor to obtain an AB-type block copolymer. When obtaining an ABA-type block copolymer, it can be produced by living polymerizing vinyl aromatic monomer units in another reactor after producing the AB-type block copolymer. Or, after producing an AB-type living copolymer, an ABA-type block copolymer can be obtained by adding a bifunctional compound that reacts with the living growth species in another reactor.

[0049] As a result of further intensive research, the present inventors have found that a copolymer containing α-methylstyrene units and vinyl aromatic monomer units obtained by a continuous living polymerization method, in which the composition ratio of α-methylstyrene and the vinyl aromatic monomer represented by the above formula (1) in the raw material is continuously or intermittently changed and fed into a polymerization reactor, has a styrenic copolymer composed of at least two or more different copolymers, and its other properties including heat resistance, thermal stability, mechanical properties, and fluidity are equivalent to those of a random copolymer, and it has extremely good compatibility with a polymer mainly composed of vinyl aromatic monomer units.

[0050] When the molded article of the copolymer is recycled, it is suggested that it can be blended and reused as a recycled material with a polymer mainly composed of vinyl aromatic monomer units, such as polystyrene. Different copolymers refer to copolymers with a glass transition temperature difference of at least 3 °C or more.

[0051] The continuous or intermittent change of the composition ratio of α-methylstyrene and vinyl aromatic monomer in the monomer and feeding it into the polymerization reactor means that the concentration of each monomer introduced into the polymerization reaction system changes continuously or intermittently. As a result, the composition ratio of each aromatic unit of the obtained copolymer changes continuously, and copolymers composed of at least two or more different constitutional composition ratios are sequentially obtained.

[0052] Copolymers having two or more different constitutional composition ratios may be mixed in a batch-type tank in a solution state, and then flash into a tank heated under vacuum to remove the solvent, or the solvent can be removed using an extruder or a kneader and recovered in a pellet state. Or, it can be directly recovered in a pellet state without being stored in a batch-type tank, and the pellets can be mixed and homogenized in a batch-type or continuous-type mixing container. Or, after making the pellets in a uniform state in the mixing container, it is also possible to further perform melt mixing using an extruder.

[0053] Taking a specific production example, after feeding and polymerizing a raw material with a component composition ratio of α-methylstyrene (M1) and vinyl aromatic monomer (M2) of M1 / M2 = 50 / 50 (wt%) into the reactor, it is switched to a raw material with a different composition ratio, for example, M1 / M2 = 40 / 60 (wt%), and continuously introduced into the reactor for polymerization. In this case, the raw material composition is changed intermittently. When polymerized in this way, copolymers with a continuously changing composition from the composition of the copolymer obtained by polymerizing at M1 / M2 = 50 / 50 (wt%) to the composition of the copolymer obtained at M1 / M2 = 40 / 60 (wt%) are sequentially obtained. The obtained copolymer is solution-mixed in a batch-type tank or stirred and mixed in a pellet state, and then melt-kneaded to obtain a copolymer with a certain composition.

[0054] The copolymer obtained by such a method can be considered as a composition of copolymers with different composition ratios of α-methylstyrene unit components and vinyl aromatic monomer unit components. The copolymer obtained thereby is extremely compatible with a homopolymer of a vinyl aromatic monomer, and it has been found that it is a copolymer with extremely high utility value as a recycled material because it can maintain transparency without causing a decrease in mechanical properties.

[0055] In the living anionic polymerization method which is the method for producing the copolymer of the present invention, it is preferable to carry out the completion of the polymerization reaction when the reaction rate of the vinyl aromatic monomer reaches 99% or more, and α-methylstyrene may remain in the reaction system. The termination of the polymerization reaction can be achieved by adding a compound having an oxygen-hydrogen bond such as water, alcohol, phenol, carboxylic acid, etc. as a terminator, and epoxy compounds, ester compounds, ketone compounds, carboxylic anhydrides, compounds having a carbon-halogen bond, etc. can also be expected to have the same effect. The amount of these additives used is preferably about 10 times the equivalent of the growing species. If it is too much, it is not only disadvantageous in terms of cost, but also the mixing of the remaining additives often becomes an obstacle.

[0056] It is also possible to carry out a coupling reaction with a polyfunctional compound using a living growing species to increase the polymer molecular weight and further to make the polymer chain into a branched structure. The polyfunctional compound used for such a coupling reaction can be selected from known ones. Examples of the polyfunctional compound include polyhalogen compounds, polyepoxy compounds, mono- or polycarboxylic acid esters, polyketone compounds, mono- or polycarboxylic anhydrides, etc. Specific examples include silicon tetrachloride, di(trichlorosilyl)ethane, 1,3,5-tribromobenzene, epoxidized soybean oil, tetraglycidyl 1,3-bis(aminomethyl)cyclohexane, dimethyl oxalate, tri-2-ethylhexyl trimellitate, pyromellitic dianhydride, diethyl carbonate, etc.

[0057] After the coincidence ends, unreacted monomers and solvents are volatilized and removed from the polymer for recovery and reuse. Known methods can be used for volatilization and removal. As the volatilization and removal device, for example, a method of flashing into a vacuum tank and / or a method of heating and evaporating under vacuum using an extruder or a kneader can be preferably used. Depending on the volatility of the solvent, generally, volatile components such as the solvent and residual monomers are volatilized and removed at a temperature of 180 to 300 °C and a vacuum degree of 100 Pa to 50 KPa.

[0058] A method of connecting volatilization and removal devices in series and arranging them in two or more stages is also effective. In addition, a method of adding water between the first stage and the second stage to enhance the monomer volatilization ability of the second stage can also be used. After removing the volatile components in the flashing tank, a vented extruder can be further used to remove the remaining volatile components. The styrene-based copolymer from which the solvent has been removed can be finished into pellets by a known method.

[0059] In the present invention, it is preferable that the total mass of the monomers and polymerization solvent remaining in the pellet-shaped styrene-based copolymer is 500 ppm or less. More preferably, it is 400 ppm or less.

[0060] For the styrene-based copolymer of the present invention, known compounds used in styrene-based resins can be added, if necessary, for the purpose of improving thermal, mechanical stability, fluidity, and colorability. Examples thereof include, as primary antioxidants, for example, 2,6-di-t-butyl-4-methylphenol, triethylene glycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], pentaerythritol tetrakis[-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, n-octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2[1-(2-hydroxy 3,5-di-t-pentylphenyl)]-4,6-di-t-pentylphenyl acrylate, tetrakis[methylene 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, 3,9-bis[2-{3-(t-butyl-4-hydroxy-5-methylphenyl)propynyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxa[5,5]undecane, 1,3,5-tris(3’,5’-di-t-butyl-4’-hydroxybenzyl)-s-triazine-2,4,6(1H,2H,3H)-trione, 1,1,4-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 4,4’-butylidenebis(3-methyl-6-t-butylphenol), and other 2,4,6-trisubstituted phenols.

[0061] In addition, it is also possible to add phosphorus-based antioxidants as secondary antioxidants, sulfur-based antioxidants, hindered amine stabilizers as weathering agents, and UV absorbers. Furthermore, it is also possible to add plasticizers such as mineral oil, lubricants such as long-chain aliphatic carboxylic acids and / or their metal salts, organic dyes, and organic pigments for improving colorability.

[0062] Anthraquinone-based organic dyes for improving coloring are particularly preferred because they rarely impair the thermal stability of the copolymer.

[0063] Known techniques such as silicone-based and fluorine-based release agents and antistatic agents used in styrene resins can be directly applied as they are.

[0064] These stabilizers can be added and mixed into the polymer solution after the polymerization is completed or melt-mixed using an extruder after polymer recovery.

[0065] The styrene copolymer of the present invention is preferably processed by a melt processing method that enables mass production at low cost, and injection molding, extrusion molding, foam extrusion molding, blow molding, etc. can be suitably used.

[0066] In addition, the styrene copolymer of the present invention is a material with excellent transparency, heat resistance, weather resistance, dimensional stability, and rigidity, and is therefore suitably used as optical parts. Examples of optical parts include light guide plates, diffusion plates, reflector plates, reflection films, antireflection films, polarizing plates, polarizing films, retardation films, lenses, Fresnel lenses, etc. With the increase in the size of liquid crystal displays and projectors, these optical parts are required to have higher dimensional stability and processability than before, and because they are used closer to the light source, light resistance and heat resistance are becoming increasingly important. The styrene copolymer of the present invention is an excellent material that can solve conventional problems at once and meet future performance needs, and it can be expected that there are many other applications besides uses such as food containers for heating, housing parts, interior parts for automobiles, and optical parts.

Examples

[0067] Hereinafter, the embodiments of the present invention will be specifically described with reference to examples and comparative examples. However, these are examples and do not limit the scope of the present invention in any way.

[0068] The analysis and evaluation methods used in the examples and comparative examples will be described.

[0069] <Analysis and Evaluation Methods> (1) Content of Specific Compounds in the Feed Liquid Acetonylacetone, benzaldehyde, and phenylacetylene in the feed liquid were quantified by gas chromatography (equipment: GC-14A manufactured by Shimadzu Corporation, column: DB-WAX 30m).

[0070] (2) Residual Volatiles in Pellets (Total Mass of Monomers and Polymerization Solvents) Measurement was performed using a GC-MS manufactured by Shimadzu Corporation under the following conditions. Equipment: GC-2010, MS-QP2010, with a headspace sampler Column: Rtx-1, 0.25 mm, 1.00 μm, 60 m (manufactured by Shimadzu GL Sciences Inc.) Temperature conditions: Held at 60°C for 2 minutes, then heated to 145°C at a rate of 10°C / min, and then heated to 160°C at a rate of 3°C / min. Preparation of measurement sample: 0.4 g of the polymer was placed in a dedicated vial, 1 ml of chloroform containing 10 ml of DMF and an internal standard (n-nonane) was added, sealed, and the sample was dissolved. Then, trace monomers and cyclohexane (weight ppm) in the resin were measured. The calibration curve was prepared using styrene, α-methylstyrene, and cyclohexane.

[0071] (3) Molecular Weight Measurement (Mn, Mw, Mw / Mn) Two columns (TSKgel SuperHZM-H, 40°C) were connected to an HLC-8220 manufactured by Tosoh Corporation, and measurement was performed using an SEC apparatus equipped with an RI detector. The mobile phase used was THF. The molecular weight was calculated by preparing a calibration curve using a polystyrene standard (manufactured by Tosoh Corporation) and performing the calculation in terms of polystyrene conversion.

[0072] (4) Glass Transition Temperature (Tg) It was determined in accordance with JIS-K-7121 using a DSC-7 manufactured by PerkinElmer, Inc. Specifically, under nitrogen, the temperature was raised from room temperature to 250 °C at 10 °C / min, then returned to room temperature at 10 °C / min, and then raised to 250 °C again at 10 °C / min. The glass transition temperature measured during the second heating process was defined as Tg.

[0073] (5) Composition of α-methylstyrene in the styrene copolymer It was determined using an NMR (DPX-400) manufactured by BRUKER. The composition (mass %) of α-methylstyrene in the styrene copolymer was determined by measuring the 1H-NMR of the styrene copolymer and calculating from the peak area ratio of methyl, methylene, and methine. 1 It was determined by measuring the 1H-NMR of the styrene copolymer and calculating from the peak area ratio of methyl, methylene, and methine.

[0074] (6) Injection molding method It was molded under the following conditions using PNX60 (manufactured by Nissei Plastic Industrial Co., Ltd.). The cylinder temperature was set to 215 °C, 225 °C, 230 °C, and 230 °C from the hopper side. The mold temperature was set to 50 °C, the injection time was set to 10 seconds, and the cooling time was set to 10 seconds. The molten resin was filled by applying a pressure 5 MPa higher than the injection pressure at which the resin fills the mold. The shape of the test piece was a flat plate shape of 80 mm × 80 mm × 3 mm and was used as a sample for the weather resistance test.

[0075] (7) Total light transmittance Tt It was measured using Haze-Gard II (manufactured by Toyo Seiki Seisaku-sho, Ltd.) under the conditions of light source D65 in accordance with ASTM D1003.

[0076] (8) Yellowness Yi It was measured using SD6000 (manufactured by Nippon Denshoku Industries Co., Ltd.) under the conditions of light source: D65 and viewing field: 10°.

[0077] (9) Weather resistance evaluation (SWOM irradiation test) Using a dual-cycle sunshine weather meter model S80DHBBR (manufactured by Suga Test Instruments Co., Ltd.), with a light source: sunshine carbon arc, a black panel temperature of 63 °C, and irradiation was carried out under rainfall conditions of 18 min / 120 min. The total light transmittance Tt and yellowness Yi before irradiation and after 1000 hours of irradiation were measured.

[0078] [Production Example] (1) Raw materials Styrene (St) and cyclohexane (CH: manufactured by Idemitsu Kosan Co., Ltd.) were stored in a storage tank and nitrogen bubbling was carried out. Then, the solution was passed through a 5 L volume purification column filled with activated alumina (KHD-24 manufactured by Sumika Alkem Co., Ltd.) for purification. As St, those manufactured by Sumitomo Chemical Co., Ltd. and Taiwan Chemical Fiber Co., Ltd. were used.

[0079] α-Methylstyrene (αMeSt) was purified under the following conditions. As αMeSt, those manufactured by Mitsui Chemicals, Inc. and Shin Chang Chemical Industry Co., Ltd. were used.

[0080] <αMeSt Purification Method> Distillation was carried out by simple distillation. Specifically, a 300 ml reaction flask with a rotor was equipped with a thermometer for measuring the liquid temperature, and a Claisen head, a Liebig condenser, a Y-shaped adapter, and a receiving flask equipped with a thermometer for measuring the vapor temperature were connected thereto. Further, a vacuum pump was connected to the adapter part via a vacuum controller (VC-30S manufactured by Okano Seisakusho Co., Ltd.) so that the degree of vacuum could be adjusted. An oil bath was used as the heat source.

[0081] 200 ml of αMeSt was placed in the reaction flask, and the liquid temperature was raised to 80 °C. Then, 0.08% by mass of sodium ethoxide (20% by mass ethanol solution, manufactured by FUJIFILM Wako Pure Chemical Corporation) as a basic substance was added to the reaction flask while stirring with a rotor. The degree of vacuum was adjusted to 230 mmHg, and the temperature was slowly raised until the liquid temperature reached 120 °C to 125 °C.

[0082] During the temperature increase, when the boiling point was reached, the cooled low-boiling fraction was recovered as the initial fraction. When the liquid temperature reached 120°C to 125°C and the vapor temperature also reached 120°C to 125°C, it was recovered as the main fraction. The main fraction was divided into 10 fractions for recovery. In the examples, only fractions with an acetonylacetone content of 2 ppm or less, a benzaldehyde content of 10 ppm or less, and a phenylacetylene content of 15 ppm or less were used.

[0083] (2) Adjustment of the feed liquid The raw materials purified by the method in (1) above were mixed at a ratio of St / αMeSt / CH = 12.5 / 19.5 / 68 (wt%) to obtain a feed liquid for polymerization.

[0084] (3) Initiator n-Butyllithium (a 15 wt% n-hexane solution, manufactured by Wako Pure Chemical Industries, Ltd.) was diluted 1 / 61 times with cyclohexane.

[0085] (4) Terminator Methanol (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) was diluted with cyclohexane to a concentration of 3 wt%.

[0086] (5) Polymerization method The polymerization reactor was a 5 L reactor (R1) with a jacket equipped with a stirring blade (Max Blend blade manufactured by Sumitomo Heavy Industries, Ltd.) and a condenser, and further equipped with a raw material inlet nozzle, an initiator inlet nozzle, and a polymerization solution discharge nozzle. The outlet of the condenser was sealed with nitrogen gas to prevent external air from mixing in. The volume of the polymerization solution in the polymerization reactor was always controlled to be 3 L. A part of the solution in the polymerization solution was always kept in a boiling state, and the internal temperature was controlled between 79°C and 81°C. The rotation speed of the stirring blade was 320 rpm. Gear pumps were attached to the raw material inlet and outlet of the polymerization reactor, respectively, and were controlled so that the adjusted feed liquid could flow at a constant flow rate of 1.5 L / Hr. Also, the initiator solution was introduced into the polymerization reactor at 0.09 L / Hr.

[0087] The solution of the living polymer discharged from the coincidence reactor was further led by a gear pump through a 10-mm diameter pipe to the inlet of the polymerization terminator solution. The length of the pipe from the reactor to the terminator mixing point was about 2 m, and the pipe was heat-insulated at 65 - 70 °C. The terminator solution was introduced into the polymerization reaction solution at a flow rate of 0.13 L / Hr, and then the polymerization reaction was completely terminated through a static mixer (SMX type, manufactured by Sulzer Co., Ltd.) with a capacity of 1.2 L. Further, the polymer solution was heated to 260 °C in a preheater, and then flushed into a container of about 50 L heated to 260 °C under a reduced pressure of 60 torr to separate and recover the solvent and unreacted monomer from the polymer. The temperature of the polymer in the flushing container was about 240 - 250 °C, and the residence time of the polymer in the tank was about 20 - 30 minutes. The polymer from which the volatile components had been sufficiently removed was then discharged in a rope shape, cooled under water, and pelletized with a cutter to recover the styrene-based copolymer.

[0088] [Examples 1 - 3, Comparative Examples 1 - 3] Using the pellets obtained by polymerizing the feed solution adjusted by changing the raw material lot, various analyses and evaluations were carried out. The results are shown in Table 1 and Table 2. The composition of the αMeSt units in the obtained copolymer was 52% by mass.

[0089]

Table 1

[0090]

Table 2

[0091] As is clear from Table 1 and Table 2, it can be seen that the styrene-based copolymer of the present invention is excellent in weather resistance.

Industrial Applicability

[0092] The styrenic copolymer of the present invention has excellent weather resistance characteristics by controlling the content of a specific compound in the feed liquid to be polymerized within a specific range. Further, molded articles containing the styrenic copolymer of the present invention can be very suitably used as food containers for heating, housing parts, automotive interior parts, and optical parts.

Claims

1. A copolymer obtained by living anionic polymerization and containing α-methylstyrene units and vinyl aromatic monomer units represented by the following general formula (1), wherein the change in total light transmittance after 1000 hours of irradiation in a weather resistance test using a sunshine weather meter is 5% or less, and the change in yellowness is 5 or less. A styrene-based copolymer. 【Chemical 1】 (In the formula, R １ represents a hydrogen atom, an alkyl group having 2 or more carbon atoms, or a phenyl group, and R ２ represents a hydrogen atom, a halogen atom, a hydroxyl group, a C1-C6 alkyl group, a C1-C6 alkoxy group, a carboxyl group, or a halo C1-C6 alkyl group.)

2. The content of α-methylstyrene units in the copolymer is 10 to 65% by mass, the weight average molecular weight (Mw) is in the range of Mw = 50,000 to 300,000, and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) is in the range of 1.6 to 2.5, and the total mass of the remaining monomers and polymerization solvent is 500 ppm or less. The styrene-based copolymer according to Claim 1.

3. A feed liquid for producing a styrene-based copolymer, comprising a monomer and a polymerization solvent, wherein the monomer contains α-methylstyrene and a vinyl aromatic monomer represented by the following general formula (1), and the content of acetylacetone in the feed liquid is 2 ppm or less, the content of benzaldehyde is 10 ppm or less, and the content of phenylacetylene is 15 ppm or less. A feed liquid for producing a styrene-based copolymer. 【Chemical 2】

4. A method for producing a styrene-based copolymer using a feed liquid composed of a monomer and a polymerization solvent, wherein the monomer contains α-methylstyrene and a vinyl aromatic monomer represented by the following general formula (1), and the content of acetylacetone in the feed liquid is 2 ppm or less, the content of benzaldehyde is 10 ppm or less, and the content of phenylacetylene is 15 ppm or less. A method for producing a styrene-based copolymer using the feed liquid. [Chemical Formula 2]

Images