KR20230169227A - Copolymer, resin composition for injection molding, molded article, and method for producing copolymer - Google Patents

Abstract

Provided is a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit, and a resin for injection molding containing the copolymer, which is excellent in strength and chemical resistance, and has excellent color and transparency when used as a molded article. It is a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit, and the peak intensity detected at UV 254 nm within the peak half width of the weight average molecular weight (MwRI) of the copolymer determined by a differential refractive index detector using gel permeation chromatography. When P(UV) is set to P(UV) and the peak intensity detected by the differential refractive index detector in the peak half width of MwRI is set to P(RI), the difference between the maximum and minimum values of P(UV)/P(RI) is 0.15 or less. , a copolymer is provided.

Description

Copolymer, resin composition for injection molding, molded article, and method for producing copolymer

The present invention relates to a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit, a resin composition for injection molding containing the copolymer, and a molded article molded from the resin composition.

Copolymers containing aromatic vinyl monomer units and cyano monomer units have various properties such as excellent chemical resistance, rigidity, and moldability, and are used in a wide range of fields. These copolymers can be produced by various polymerization methods such as emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization. However, in the case of emulsion polymerization, an emulsifier is used, and in the case of suspension polymerization, a dispersant, etc. are used, so there are problems with the appearance quality in terms of transparency and discoloration of the polymerization product. Therefore, non-aqueous bulk polymerization or solution polymerization is often adopted from quality, cost, and environmental aspects.

When performing bulk polymerization or solution polymerization continuously on an industrial production scale, the latent heat of evaporation is used, that is, heat removal by evaporation from the gas-liquid interface of the gas phase and the polymerization liquid, or, if necessary, the evaporated solvent and the Since heat can be removed more efficiently by cooling the reaction monomer in a condenser outside the reaction tank and refluxing it into the reaction tank, polymerization with a high conversion rate is possible, and is therefore widely used as a polymerization method on an industrial production scale.

A method of adjusting the concentration of the condensate refluxing from the condenser of the polymerization reactor and spraying it back to the gas phase portion of the polymerization reactor (Patent Document 1), or spraying the raw material liquid into the upper gas phase portion of the reaction tank using a spray nozzle, etc. Additionally, a method (Patent Document 2) of mixing the condensate refluxing from the condenser with the raw material liquid and supplying it to the polymerization reactor is disclosed.

Japanese Patent Publication No. 2000-226417 Japanese Patent Publication No. 2004-262987

However, it cannot be said that the copolymers obtained by the above-mentioned conventional techniques are achieving satisfactory results in response to the demand for reducing the incidence of defects in terms of physical properties including transparency, strength, color, etc., which have recently been increasing.

Therefore, the present invention provides a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit and a resin for injection molding containing the copolymer that are excellent in strength, chemical resistance, color, and transparency when used as a molded article. The task is to provide.

As a result of extensive research by the present inventors and others to solve the above problems, when a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit satisfies the following configuration with respect to the molecular weight distribution of the copolymer, It was discovered that the resulting molded article was excellent in strength, chemical resistance, color, and transparency, and the present invention was completed.

That is, the present invention:

(1) It is a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit, and is detected at UV 254 nm within the peak half width of the weight average molecular weight (MwRI) of the copolymer as determined by a differential refractive index detector using gel permeation chromatography. When the peak intensity detected by the differential refractive index detector within the peak half width of MwRI is set to P(UV), and the peak intensity detected by the differential refractive index detector within the peak half width of MwRI is set to P(RI), the difference between the maximum and minimum values of P(UV)/P(RI) copolymers with a value of 0.15 or less;

(2) In (1), when the total of the aromatic vinyl monomer unit and the cyano monomer unit is 100 mass%, 50 to 90 mass% of the aromatic vinyl monomer unit and 10 to 50 mass% of the cyano monomer unit copolymer, containing %;

(3) The copolymer according to (1) or (2), wherein the aromatic vinyl monomer unit is a styrene monomer unit and the cyano monomer unit is an acrylonitrile monomer unit;

(4) A resin composition for injection molding containing the copolymer according to any one of (1) to (3);

(5) Molded articles molded from the resin composition for injection molding according to (4); and

(6) A method for producing a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit, comprising the steps of supplying a feed liquid containing an aromatic vinyl monomer and a cyano monomer to the liquid phase of a polymerization solution in a reaction tank, and generating a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit. A method for producing a copolymer, comprising the step of condensing the evaporated gas in a heat exchanger outside the reaction tank and returning the obtained condensate to the liquid phase of the reaction tank,

It's about.

According to the present invention, a copolymer that is excellent in strength, chemical resistance, color, and transparency when used as a molded article is provided. The resin composition according to the present invention can be suitably used in containers such as cosmetics or miscellaneous goods such as stationery that require high design.

<Regulations on molecular weight distribution of copolymers>

The copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit according to the present embodiment has a weight average molecular weight determined by a differential refractive index detector using gel permeation chromatography (hereinafter sometimes abbreviated as "GPC"). When the peak intensity detected at UV 254 nm in the peak half width of (MwRI) is P(UV), and the peak intensity detected by the differential refractive index detector in the peak half width of MwRI is P(RI), P(UV) The difference between the maximum and minimum values of /P(RI) is 0.15 or less, preferably 0.10 or less. Specifically, for example, it is 0.15 or less, 0.13 or less, 0.11 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less. If the difference between the maximum and minimum values of P(UV)/P(RI) exceeds 0.15, the color of the molded product may deteriorate. A copolymer in which the difference between the maximum and minimum values of P(UV)/P(RI) is 0.15 or less can be obtained, for example, by the production method described later, but is not limited to this.

In the GPC measurement, tetrahydrofuran (hereinafter sometimes abbreviated as "THF") can be used as a mobile phase. MwRI is a polystyrene conversion value and can be measured under the following conditions.

Device name: SYSTEM-21 Shodex (manufactured by Showa Denko Co., Ltd.)

Column: 3 PL gel MIXED-B (manufactured by Polymer Laboratories) in series

Temperature: 40℃

Solvent: Tetrahydrofuran

Concentration: 0.4% by mass

Calibration curve: prepared using standard polystyrene (PS) (manufactured by Polymer Laboratories)

In the GPC measurement in this embodiment, a GPC device is used that has a differential refractive index detector and an absorption photometric detector and can simultaneously perform measurements using these detectors. The absorbance photometric detector is configured to measure absorbance at a wavelength of 254 nm. In the molecular weight distribution obtained by GPC measurement, the concentration of each component included in each molecular weight in the distribution is measured with a differential refractive index detector, and the absorbance of each molecular weight component (measurement wavelength 254 nm) is measured with an absorbance photometric detector. Additionally, the measurement wavelength of 254 nm is derived from the structure of the benzene ring. The absorbance photometric detector may be a detector that measures the absorption of ultraviolet light of a specific wavelength, or may be a detector that spectrally measures the absorption of ultraviolet light of a wavelength in a specific range.

The peak half width of weight average molecular weight (MwRI) is half of the highest peak intensity value when the elution time representing the highest peak intensity value among the chromatograms obtained by plotting the values measured with a differential refractive index detector is set as the peak. Among the elution times corresponding to the value, it refers to the width of the elution time before and after the peak. Additionally, even in cases where the peak is multimodal, the elution time representing the highest peak intensity value is used as the standard. In addition, there are cases where there are more than two elution times corresponding to half the value of the highest peak intensity, but among such elution times, the width of the elution time before and after the furthest distance from the peak shall be indicated.

The peak intensities P(RI) and P(UV) plot the values measured with a differential refractive index detector and the absorbance photometric detector (measurement wavelength 254 nm), respectively, with respect to the molecular weight of the resin converted from the GPC elution capacity. Among the chromatograms thus obtained, the peak intensities within the range of the half width mentioned above are shown, respectively.

<Copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit>

The copolymer according to the present embodiment contains an aromatic vinyl monomer unit and a cyano monomer unit. Additionally, within the range that does not impair the effect of the present invention, it may contain monomer units other than aromatic vinyl monomer units and cyano monomer units.

Hereinafter, the monomer units constituting the copolymer containing the aromatic vinyl monomer unit and the cyano monomer unit according to the present embodiment will be described.

<Aromatic vinyl monomer unit>

The monomer from which the aromatic vinyl monomer unit contained in the copolymer according to the present embodiment is obtained is not particularly limited, but includes styrene, α-methylstyrene, p-methylstyrene, 3,5-dimethylstyrene, 4-methoxystyrene, 2- Examples include substituted styrenes with substituents such as hydroxystyrene, halogenated styrenes such as α-bromine styrene and 2,4-dichlorostyrene, and 1-vinylnaphthalene. Among these, styrene is preferable from the viewpoint of polymerizability, moldability, mechanical properties, etc.

<Cyano-based monomer unit>

The monomer from which the cyano-based monomer unit contained in the copolymer according to the present embodiment is obtained is not particularly limited, and examples include acrylonitrile, methacrylonitrile, α-chloracrylonitrile, and α-ethylacrylonitrile. . Among these, acrylonitrile is preferable from the viewpoint of polymerizability, mechanical properties, etc.

The content ratio of the aromatic vinyl monomer unit and the cyano monomer unit in the copolymer in this embodiment can be arbitrarily selected, but the amount of the aromatic vinyl monomer unit contained in 100 mass% of the copolymer is 50 mass% to 90 mass%. is preferable, more preferably 55 mass% to 88 mass%, and even more preferably 60 mass% to 85 mass%. Specifically, for example, it is 50 mass%, 55 mass%, 60 mass%, 65 mass%, 70 mass%, 75 mass%, 80 mass%, 85 mass%, or 90 mass%, and the values exemplified here It may be within a range between any two of these. The amount of vinyl cyanide monomer contained in 100% by mass of the copolymer is preferably 10% by mass to 50% by mass, more preferably 12% by mass to 45% by mass, and still more preferably 15% by mass to 40% by mass. am. Specifically, for example, it is 10 mass%, 15 mass%, 20 mass%, 25 mass%, 30 mass%, 35 mass%, 40 mass%, 45 mass%, or 50 mass%, and the values exemplified here It may be within a range between any two of these. If each monomer is outside the above composition range, it may become difficult to achieve the appearance, chemical resistance, transparency, mechanical properties, etc. of the molded article, which are the objectives of the present invention.

<Monomer units other than aromatic vinyl monomer units and cyano monomer units>

The copolymer in this embodiment may be copolymerized with copolymerizable monomers other than vinyl cyanide monomers and aromatic vinyl monomers, as long as the effects of the present invention are not impaired. Other vinyl compounds copolymerizable with vinyl cyanide monomers and aromatic vinyl monomers include, for example, acrylic acid esters such as methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, and butyl acrylate, acrylic acid, and metacrylate. Unsaturated carboxylic acids or anhydrides thereof such as acrylic acid, maleic anhydride, and itaconic acid; maleimide compounds such as N-phenylmaleimide and N-cyclohexylmaleimide; and especially ethyl acrylate and butylacrylate. is preferable, and two or more types thereof may be mixed and used.

The content of these monomer units contained in the copolymer in the present embodiment is 100 mass% when the total of monomer units derived from vinyl cyanide monomer units, aromatic vinyl monomer units, and monomers copolymerizable with these is set to 100% by mass. It may be 0 mass% to 20 mass%, preferably 0 mass% to 5 mass%.

<Resin composition>

The resin composition in this embodiment is a resin composition containing a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit. In the resin composition, the content of a copolymer of an aromatic vinyl monomer unit and a cyano monomer unit in 100 mass% of the resin composition is, for example, 50 mass% or more. In one aspect, the content of the copolymer in the resin composition is preferably 80 mass% or more, and more preferably 90 mass% or more. Specifically, for example, it is 50, 55, 60, 65, 70, 75, 80, 85, 90% by mass or more. In one aspect, the resin composition may consist substantially only of a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit.

The resin composition in this embodiment may contain mineral oil in a range that does not impair the effect of the present invention. In addition, internal lubricants such as stearic acid and ethylenebisstearylamide, phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, lactone-based antioxidants, ultraviolet absorbers, hindered amine stabilizers, antistatic agents, external lubricants, etc. Additives may be included. These additives include a method of adding and mixing in the polymerization process, devolatilization process, and granulation process, and a method of adding and mixing in an extruder or injection molding machine during molding processing, etc., and are not particularly limited.

Ultraviolet absorbers have the function of suppressing deterioration and coloring caused by ultraviolet rays, for example, benzophenone-based, benzotriazole-based, triazine-based, benzoate-based, salicylate-based, cyanoacrylate-based, and oxalic acid anilide. Examples include ultraviolet absorbers such as UV absorbers, malonic acid ester series, and formamidine series. These can be used individually or in combination of two or more, and light stabilizers such as hindered amine may be used together.

In order to express various design properties, the resin composition in this embodiment may contain various dyes and pigments within a range that does not impair the effects of the present invention. For example, coumarin-based fluorescent dye, benzopyran-based fluorescent dye, perylene-based fluorescent dye, anthraquinone-based fluorescent dye, thioindigo-based fluorescent dye, xanthene-based fluorescent dye, xanthone-based fluorescent dye, thioxanthene-based fluorescent dye, and thioxane. Tone-based fluorescent dye, thiazine-based fluorescent dye, diaminostilbene-based fluorescent dye, etc. can be mentioned. The content of the dye and pigment is preferably 0.00001 to 1 part by mass, more preferably 0.00003 to 0.3 parts by mass, based on a total of 100 parts by mass of additives such as antioxidants in the resin composition.

<Method for producing a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit>

As a method for producing a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit in the present embodiment, suspension polymerization method, solution polymerization method, bulk polymerization method, etc. can be used, but mixing of a dispersant into the resin is avoided. For the purpose of prevention, a solution polymerization method or a bulk polymerization method is preferably used.

<Polymerization device>

The polymerization apparatus used in this embodiment consists of a completely mixed tank polymerization reactor (I) equipped with a heat exchanger for condensing the vapor of the gas phase portion, or the polymerization reactor (I) and one or more polymerization reactors (II) connected thereto. As the polymerization reactor (II), a complete mixing tank polymerization reactor, a tube type polymerization reactor, an extruder type polymerization reactor, a kneader type polymerization reactor, etc. can be used.

There are no particular limitations on the embodiment for substantially uniformizing the polymerization liquid in the polymerization reactor (I), but ribbon-type stirring blades such as helical ribbon blades, turbine-type stirring blades, screw-type stirring blades, anchor blades, and inclined In addition to stirring and mixing using paddle blades such as paddle blades or flat paddle blades, Full Zone blades (brand name), Max Blend blades (brand name), or Sanmera blades (brand name), for example, the polymerizer (I) Circulating mixing using an externally provided pump or the like can also be combined.

Examples of the heat exchanger used in this embodiment include spray condensers, shell & tube type condensers, etc.

The solvent used in this embodiment is an inert polymerization solvent usually used in radical polymerization, for example, ethylbenzene, toluene, xylene, o-xylene, m-xylene, p-xylene, cumene, n-propylbenzene, Aromatic hydrocarbons such as isopropylbenzene, ketones such as 2-butanone and methyl isobutyl ketone, and amide compounds such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone. there is. Among these solvents, ethylbenzene is preferable from the viewpoint of evaporation property and economic efficiency.

The amount of solvent used is preferably 5 to 40 parts by mass, more preferably 10 to 35 parts by mass, per 100 parts by mass of the monomer mixture liquid. In the case of less than 5 parts by mass, the viscosity of the polymerization liquid increases, so the polymerization rate cannot be sufficiently increased, resulting in insufficient productivity. On the other hand, when it exceeds 40 parts by mass, the amount of devolatilizing solvent increases, so it is not economical.

As the polymerization initiator added in this embodiment, known polymerization initiators can be used, for example, ketone peroxides such as methyl ethyl ketone peroxide, 1,1-bis(t-butylperoxy)3, Peroxyketals such as 3,5-trimethylcyclohexane and 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, hydroperoxides such as cumene hydroperoxide, and dicumyl peroxide. dialkyl peroxides such as dialkyl peroxides, diacyl peroxides such as benzoyl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxy esters such as t-butyl peroxyisopropyl carbonate, 2,2' -Azonitriles such as azobisisobutyronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), t-butylperoxyallyl carbonate, t-butyltrimethylsilyl peroxide, 3,3' and organic peroxides such as ,4,4'-tetra(t-butylperoxycarbonyl)benzophenone. Among these polymerization initiators, t-butylperoxyisopropyl carbonate is preferable from the viewpoint of color and economic efficiency. These polymerization initiators may be used individually, or two or more types may be mixed and used.

As for the amount of polymerization initiator used, as long as the removal of reaction heat in the polymerization apparatus is within a controllable range, it is advantageous to increase the reaction rate, but if the reaction rate is fast, problems such as coloring occur. The practical usage amount varies depending on the type of polymerization initiator and the polymerization temperature, but is preferably 0.005 to 0.5 parts by mass, more preferably 0.01 to 0.4 parts by mass, based on 100 parts by mass of the total amount of monomers.

In the production of the copolymer according to the present embodiment, examples of the chain transfer agent include t-dodecyl mercaptan, n-dodecyl mercaptan, unsaturated dimer of α-methylstyrene, terpinolene, and thioglycolic acid. Octyl, etc. may be used.

The amount of the chain transfer agent used varies depending on the type of chain transfer agent, but is preferably 5 parts by mass or less, more preferably 0 to 3 parts by mass, and even more preferably 1 to 0.001 parts by mass, based on 100 parts by mass of the total amount of monomers. am. If it exceeds 5 parts by mass, the molecular weight of the copolymer of the aromatic vinyl monomer unit and the cyano monomer unit becomes too small, causing problems such as not developing practical strength.

Polymerization of the copolymer according to this embodiment is carried out, for example, as follows.

<Preparation of supply>

First, a supply solution containing a solvent, polymerization monomer, polymerization initiator, chain transfer agent, etc. in a predetermined ratio is prepared.

<Supply of feed liquid to reaction tank>

The supply liquid is supplied to the reaction tank by continuously supplying it to the liquid phase of the polymerization liquid. The supply speed when supplying the supply liquid to the liquid phase of the polymerization liquid depends on the temperature described later and the controlled polymerization rate, but it is preferably adjusted so that the residence time in the polymerization can is 2 to 6 hours. If the residence time is too short, the color may deteriorate, and if the residence time is too long, productivity problems may occur.

<Polymerization of monomers>

The polymerization temperature is maintained within a predetermined range and polymerization is performed. The polymerization temperature varies depending on the type of initiator used, but is preferably 120 to 180°C. If the polymerization temperature is within this range, polymerization control is easy and color deterioration can be suppressed while increasing the polymerization rate.

<Control of filling rate of reaction solution>

The filling rate of the reaction liquid is maintained within a predetermined range, and an amount of the reaction liquid equal to the amount of the supplied liquid is continuously extracted. The filling rate of the reaction solution in the reaction tank is preferably 50 to 100 vol%, and if polymerization is performed within this range, productivity is excellent.

<Condensation of evaporating gas>

The evaporated gas generated in the reaction tank enters a heat exchanger outside the reaction tank via a steam line, where it condenses and becomes a condensate. This condensate is returned to the liquid phase of the reaction tank via the supply line.

<Recovery of copolymer>

From the extracted reaction liquid, unreacted monomers and organic solvents are degassed and recovered, and the copolymer is recovered as pellets.

The copolymer in the present embodiment is produced, for example, by the above-mentioned production method, so that the peak intensity detected at UV 254 nm in the peak half width of the weight average molecular weight (MwRI) is P(UV), and MwRI When the peak intensity detected by the differential refractive index detector in the peak half width of is set to P(RI), the difference between the maximum and minimum values of P(UV)/P(RI) is 0.15 or less.

The difference between the maximum and minimum values of P(UV)/P(RI) indicates the composition distribution of the aromatic vinyl monomer unit and the cyano monomer unit in the resin. The peak intensity of P(UV) detected in absorbance (measurement wavelength 254 nm) changes depending on the concentration of the monomer having a benzene ring, that is, the aromatic vinyl monomer unit. On the other hand, since P(RI) depends on the concentration of the entire molecule, the fact that P(UV)/P(RI) shows a constant value regardless of molecular weight shows that there is no difference in composition distribution even if the molecular weight changes.

The mechanism by which the difference between the maximum and minimum values of P(UV)/P(RI) of the copolymer becomes 0.15 or less by this manufacturing method has not been fully elucidated, but in the conventional manufacturing method, supply from the meteorological department In contrast to the fact that the composition distribution of the copolymer occurs due to the presence of This doesn't exist. For this reason, it is thought that the composition distribution of the copolymer became smaller, and the difference in composition distribution even when the molecular weight of the copolymer changed became smaller.

<Method for producing a resin composition comprising a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit>

If necessary, mineral oil, additives, dyes, pigments, etc. are added to the copolymer of the aromatic vinyl monomer unit and the cyano monomer unit obtained as described above to obtain a resin composition. Additives include, but are not limited to, a method of adding and mixing in the polymerization process, devolatilization process, or granulation process, or a method of adding and mixing in an extruder or injection molding machine during molding processing.

The molded body obtained by molding the resin composition according to the present embodiment can be processed into miscellaneous goods such as stationery, cosmetic containers, home appliance cases, etc. that require particularly high design. In addition, the resin composition according to the present embodiment is preferably used alone or as a mixed resin blended with other resins such as ABS resin and PC resin.

Example

Hereinafter, details will be explained using examples, but the present invention is not limited to the following examples.

<Example 1>

The feed liquid supplied to the 50 L reaction tank was 70 parts by mass of styrene, 15 parts by mass of acrylonitrile, 15 parts by mass of ethylbenzene, 0.02 parts by mass of t-butylperoxyisopropyl carbonate as a polymerization initiator, and n-dodecyl mer as a chain transfer agent. Captan was adjusted to 0.01 parts by mass. This supply liquid is bubbled with nitrogen gas, passed through a mixer, and then continuously supplied to the reaction tank in the liquid phase of the polymerization liquid at a rate of 10.8 L/hour, so that the polymerization temperature is 145°C and the filling rate of the reaction liquid in the reaction tank is 70 vol%. In order to maintain this, an amount of reaction liquid equal to the amount of supplied liquid was continuously extracted. Additionally, the evaporated gas generated within the reaction tank was condensed in a heat exchanger outside the reaction tank, and the condensate was returned to the liquid phase of the reaction tank. The extracted reaction liquid was introduced into a volatile matter removal device maintained at 250°C and a high vacuum of 10 mmHg, and unreacted monomers and organic solvents were degassed and recovered, and the copolymer was recovered as pellets.

<Example 2>

The feed liquid supplied to the 50 L reaction tank was 58 parts by mass of styrene, 22 parts by mass of acrylonitrile, 20 parts by mass of ethylbenzene, 0.02 parts by mass of t-butylperoxyisopropyl carbonate as a polymerization initiator, and n-dodecyl mer as a chain transfer agent. Captan was adjusted to 0.04 parts by mass. This supply liquid is bubbled with nitrogen gas, passed through a mixer, and then continuously supplied to the liquid phase of the polymerization liquid into the reaction tank at a rate of 8 L/hour, so that the polymerization temperature is 145°C and the filling rate of the reaction liquid in the reaction tank is 60 vol. % was maintained, and an amount of reaction liquid equal to the amount of supplied liquid was continuously extracted. Additionally, the evaporated gas generated within the reaction tank was condensed in a heat exchanger outside the reaction tank, and the condensate was returned to the liquid phase of the reaction tank. The extracted reaction liquid was introduced into a volatile matter removal device under the same conditions as in Example 1, unreacted monomers and organic solvents were degassed and recovered, and the copolymer was recovered as pellets.

<Example 3>

The feed liquid supplied to the 50 L reaction tank was 49 parts by mass of styrene, 29 parts by mass of acrylonitrile, 23 parts by mass of ethylbenzene, 0.02 parts by mass of t-butylperoxyisopropyl carbonate as a polymerization initiator, and n-dodecyl mer as a chain transfer agent. Captan was adjusted to 0.12 parts by mass. After bubbling this supply liquid with nitrogen gas and passing through a mixer, the liquid phase of the polymerization liquid is continuously supplied to the reaction tank at a rate of 9.8 L/hour, and the polymerization temperature is 145°C and the filling rate of the reaction liquid in the reaction tank is By maintaining 80 vol%, an amount of reaction liquid equal to the amount of supplied liquid was continuously extracted. Additionally, the evaporated gas generated within the reaction tank was condensed in a heat exchanger outside the reaction tank, and the condensate was returned to the liquid phase of the reaction tank. The extracted reaction liquid was introduced into a volatile matter removal device under the same conditions as in Example 1, unreacted monomers and organic solvents were degassed and recovered, and the copolymer was recovered as pellets.

<Example 4>

The feed liquid supplied to the 50 L reaction tank was 78 parts by mass of styrene, 7 parts by mass of acrylonitrile, 15 parts by mass of ethylbenzene, 0.02 parts by mass of t-butylperoxyisopropyl carbonate as a polymerization initiator, and n-dodecyl mer as a chain transfer agent. Captan was adjusted to 0.01 parts by mass. This supply liquid is bubbled with nitrogen gas, passed through a mixer, and then continuously supplied to the reaction tank in the liquid phase of the polymerization liquid at a rate of 10.8 L/hour, so that the polymerization temperature is 145°C and the filling rate of the reaction liquid in the reaction tank is 70 vol%. In order to maintain this, an amount of reaction liquid equal to the amount of supplied liquid was continuously extracted. Additionally, the evaporated gas generated within the reaction tank was condensed in a heat exchanger outside the reaction tank, and the condensate was returned to the liquid phase of the reaction tank. The extracted reaction liquid was introduced into a volatile matter removal device under the same conditions as in Example 1, unreacted monomers and organic solvents were degassed and recovered, and the copolymer was recovered as pellets.

<Comparative Example 1>

Resin pellets were obtained in the same manner as in Example 1, except that the feed liquid was continuously introduced from the vapor phase of the polymerization liquid.

<Comparative Example 2>

The evaporated gas generated in the reaction tank was condensed in a heat exchanger outside the reaction tank, and resin pellets were obtained in the same manner as in Example 1, except that the condensate was returned to the reaction tank gas phase.

<Comparative Example 3>

Resin pellets were obtained in the same manner as in Example 1, except that the supply liquid was continuously introduced by spraying from the vapor phase of the polymerization liquid and that it was introduced from the liquid phase.

<Comparative Example 4>

Resin pellets were obtained in the same manner as in Example 1 except that the supply liquid was styrene only.

<GPC measurement>

Pellets collected after 360 hours of continuous operation under the conditions described in Examples and Comparative Examples were subjected to GPC measurement under the above-mentioned conditions, and the maximum and minimum values and differences in P(UV)/P(RI) were measured.

<GPC measurement conditions>

Device name: SYSTEM-21 Shodex (manufactured by Showa Denko Co., Ltd.)

Column: 3 PL gel MIXED-B (manufactured by Polymer Laboratories) in series

Temperature: 40℃

Solvent: Tetrahydrofuran

Concentration: 0.4% by mass

Calibration curve: prepared using standard polystyrene (PS) (manufactured by Polymer Laboratories)

<Sample preparation>

A sample was prepared by dissolving 60 mg of the copolymer in 15 mL of THF (tetrahydrofuran) at room temperature and filtering it through a 0.45 μm syringe filter. Additionally, the injection volume was 10 μL.

<Measurement of peak intensity P(RI) and P(UV)>

Among the chromatograms obtained by plotting the values measured with a differential refractive index detector and the values measured with an absorbance photometric detector (measurement wavelength 254 nm), respectively, with respect to the molecular weight of the resin converted from the GPC elution capacity in the GPC measurement described above, The peak intensities in one half width range were designated as P(RI) and P(UV), respectively.

<Preparation of test piece of resin composition>

Antioxidant 4,4',4''-(1-methylpropanyl-3-iriden)tris (6) was added to 100% by mass of pellets collected after continuous operation for 360 hours under the conditions described in Examples and Comparative Examples. -tert-butyl-m-cresol) (ADEKA STAB AO-30, manufactured by ADEKA Co., Ltd.) at 0.15% by mass, tris (2,4-di-tert-butylphenyl) phosphite (AO-30, manufactured by ADEKA Co., Ltd.) After blending 0.05% by mass of ADEKA STAB 2112), it was extruded into pellets using a single-screw extruder (MS-40 manufactured by IKG Corporation). Using this pellet, a test piece was produced using an injection molding machine, and each physical property value was measured.

<Charpy impact strength>

Using the obtained pellets, a test piece without a notch was used in accordance with JIS K-7111, and the hitting direction was measured using edge wise at a relative humidity of 50% and an ambient temperature of 23°C. Additionally, a digital impact tester manufactured by Toyo Seiki Seisakusho Co., Ltd. was used as the measuring instrument.

<Transmittance, YI value>

Using the obtained pellets, a plate-shaped molded article with a thickness of 127Х127Х3 mm was molded at a molding temperature of 230°C using an injection molding machine (J140AD-180H, manufactured by Japan Steel Works Co., Ltd.). A test piece with a thickness of 115Х85Х3 mm was cut from the plate-shaped molded product, and the cross section was polished by buffing to produce a plate-shaped molded product having a mirror surface on the cross section. For the plate-shaped molded product after polishing, using an ultraviolet-visible spectrophotometer V-670 manufactured by JASCO Corporation, for incident light with a size of 20Х1.6mm and a diffusion angle of 0°, the wavelength of 350nm to 800nm at an optical path length of 115mm was measured. The spectral transmittance was measured, and the YI value at a viewing angle of 2° for a wavelength C light source was calculated according to JIS K7105. Additionally, the transmittance refers to the total light transmittance in the range of 430 to 700 nm. The results are shown in Table 1.

<Haze>

In accordance with ASTM D-1003, a plate-shaped molded product with a thickness of 127Х127Х3 mm molded under the above-mentioned conditions was used and measured using a HAZE meter (NDH-2000) manufactured by Nippon Denshoku Industries.

<Chemical resistance>

To exclude the influence of molding deformation, the test piece was manufactured by press-molding each pellet at 260°C to a thickness of 4mm and cutting it into 50mm x 50mm. After being immersed in each chemical set at 40°C for 14 days, they were classified as follows based on weight change and appearance change. Salad oil was used as the medicine.

◎: Little effect such as change in weight or appearance is observed, ○: Slight clouding or discoloration is confirmed, △: Minor cracking or crazing occurs, Х: Dissolution or significant effect

Examples 1 to 4, where the difference between the maximum and minimum values of P(UV)/P(RI) was small, had excellent strength, transparency, YI value, and Haze value. Comparative Examples 1 to 3, where the difference between the maximum and minimum values of P(UV)/P(RI) was large, resulted in low intensity and high YI values, resulting in poor color.

The resin composition containing the copolymer of the present invention and the molded article molded from the resin composition are excellent in strength and chemical resistance, and have excellent color and transparency, so they can be suitably used for applications requiring high design. Specifically, it can be suitably used for containers such as cosmetics and miscellaneous goods such as stationery.

Claims (6)

It is a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit, and the peak intensity detected at UV 254 nm within the peak half width of the weight average molecular weight (MwRI) of the copolymer determined by a differential refractive index detector using gel permeation chromatography. When P(UV) is set to P(UV) and the peak intensity detected by the differential refractive index detector in the peak half width of MwRI is set to P(RI), the difference between the maximum and minimum values of P(UV)/P(RI) is 0.15 or less. , copolymer. According to paragraph 1,
A copolymer containing 50 to 90 mass% of the aromatic vinyl monomer unit and 10 to 50 mass% of the cyano monomer unit, when the total of the aromatic vinyl monomer unit and the cyano monomer unit is 100 mass%. According to claim 1 or 2,
A copolymer wherein the aromatic vinyl monomer unit is a styrene monomer unit, and the cyano-based monomer unit is an acrylonitrile monomer unit. A resin composition for injection molding, comprising the copolymer according to any one of claims 1 to 3. A molded article molded from the resin composition for injection molding according to claim 4. A method for producing a copolymer containing an aromatic vinyl monomer unit and a cyano monomer unit, comprising:
A process of supplying a supply liquid containing an aromatic vinyl monomer and a cyano monomer to the liquid phase of the polymerization liquid in the reaction tank, and
A process of condensing the boil-off gas generated in the reaction tank in a heat exchanger outside the reaction tank and returning the obtained condensate to the liquid phase of the reaction tank,
Method for producing a copolymer, including.