JP2023115374A - Styrene-based resin composition and molded article - Google Patents

Abstract

To provide a styrene-based resin composition that generates an extremely small amount of a gelled substance and produces a molded article having excellent appearance.SOLUTION: The styrene-based resin composition includes a styrene-based resin and an ether compound. In the styrene-based resin composition, the styrene-based resin is produced by copolymerizing a monomer mixture including a styrene-based monomer and a (meth)acrylic acid-based monomer and the ether compound has a specific structure.SELECTED DRAWING: None

Description

The present invention relates to a styrenic resin composition and molded articles.

Styrene-(meth)acrylic acid copolymer resins are superior in heat resistance to general polystyrene, and are mainly used as raw materials for food packaging materials for microwave heating. Specifically, after being formed into an extruded foam sheet or a biaxially oriented sheet, it is used as a food container or lid. In addition, since it has an excellent balance of transparency and heat resistance, it is also suitable for a light diffusing resin plate containing a light diffusing agent, such as a lighting cover or a light diffusing plate for a transmissive display.

A drawback of styrene-(meth)acrylic acid copolymer resin is that the carboxyl groups in the polymer may cause a condensation reaction between polymer molecules due to the heat history during processing into sheets, etc., resulting in the formation of a gel-like substance. It has been pointed out that a gel-like substance may be generated by a similar reaction in the production process of a copolymer resin.

Patent Literature 1 discloses a technique for suppressing the formation of gel-like substances by adding polyoxyethylene alkyl ether.

WO2007/034789

However, even if the technique disclosed in Patent Document 1 is employed, it is not possible to completely suppress the formation of the gel-like substance, and it is desired to further suppress the formation of the gel-like substance.

The present invention has been made in view of such circumstances, and provides a styrenic resin composition capable of effectively suppressing the formation of gel-like substances.

According to the present invention, there is provided a styrenic resin composition containing a styrenic resin and an ether compound, wherein the styrenic resin is a monomer mixture containing a styrenic monomer and a (meth)acrylic acid-based monomer. is obtained by copolymerizing, and the ether compound is represented by the general formula (1) to provide a styrene resin composition.

As a result of intensive studies by the present inventors, it was found that the addition of the ether compound represented by the general formula (1) can effectively suppress the formation of a gel-like substance, and the present invention has been completed. arrived.

1. Styrene-Based Resin Composition The styrene-based resin composition of the present invention contains a styrene-based resin A and an ether compound B. Each component will be described in detail below.

<<Styrene-based resin A>>
The styrene-based resin A is obtained by copolymerizing a monomer mixture containing a styrene-based monomer and a (meth)acrylic acid-based monomer.

Styrenic monomers are monocyclic or polycyclic aromatic vinyl monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, 2,5 -dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, o-ethylstyrene, p-tert-butylstyrene, 1-vinylnaphthalene, 2-vinylnaphthalene, 1,1-diphenylethylene, isopropenylbenzene (α-methylstyrene), isopropenyltoluene, isopropenylethylbenzene, isopropenylpropylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, isopropenylhexylbenzene, isopropenyloctylbenzene, etc. alone or in a mixture of two or more, preferably styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethyl Styrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, o-ethylstyrene and p-tert-butylstyrene may be used singly or as a mixture of two or more, and styrene is more preferred.

The (meth)acrylic acid-based monomer is one or both of acrylic acid monomers such as acrylic acid and methacrylic acid, preferably methacrylic acid.

The monomer mixture may contain only the styrene-based monomer and the (meth)acrylic acid-based monomer, and may contain other monomers copolymerizable therewith within a range that does not impair the effects of the present invention. OK. Other monomers include vinyl cyanide monomers such as acrylonitrile and methacrylonitrile, acrylic monomers such as butyl acrylate, ethyl acrylate, methyl acrylate and methyl methacrylate, and α-monomers such as maleic anhydride and fumaric acid. , β-ethylenically unsaturated carboxylic acids, phenylmaleimide, cyclohexylmaleimide and other imide monomers.

The monomer mixture preferably contains styrene-based monomers and (meth)acrylic monomers as main components. The total proportion of the body is preferably 50% by mass or more, for example 50 to 100% by mass, specifically for example 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100 % by weight and may be in a range between any two of the values exemplified herein.

The content of the structural unit derived from the (meth)acrylic acid-based monomer is preferably 0.1 to 30% by mass with respect to 100% by mass of the styrene resin composition. A structural unit derived from a (meth)acrylic acid-based monomer is, for example, a (meth)acrylic acid-based monomer unit. This is because if this value is too small, the heat resistance may be insufficient, and if this value is too large, the fluidity during melting may decrease and the moldability may deteriorate. Specifically, this ratio is, for example, 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30% by mass, and may be within a range between any two of the numerical values exemplified here.

The weight average molecular weight (Mw) of the styrene resin A is preferably 150,000 to 700,000, more preferably 150,000 to 400,000. Specifically, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 700,000, a range between any two of the numerical values exemplified here may be within If the Mw is too small, the strength of the molded product will be insufficient, and if the Mw is too large, the moldability will deteriorate. The weight average molecular weight of the styrene resin A is controlled by the reaction temperature and residence time in the polymerization process, the type and amount of polymerization initiator added, the type and amount of chain transfer agent used, and the type and amount of solvent used during polymerization. be able to.

The weight average molecular weight (Mw) can be measured using gel permeation chromatography (GPC) under the following conditions.
GPC model: Shodex GPC-101 manufactured by Showa Denko K.K.
Column: PLgel 10 μm MIXED-B manufactured by Polymer Laboratories
Mobile phase: Tetrahydrofuran Sample concentration: 0.2% by mass
Temperature: oven 40°C, inlet 35°C, detector 35°C
Detector: Differential refractometer The molecular weight was obtained by calculating the molecular weight at each elution time from the elution curve of monodisperse polystyrene and calculating the molecular weight in terms of polystyrene.

<<ether compound B>>
Ether compound B is represented by general formula (1).

Z1 to Z5 in general formula (1) are the same or different, and are hydrogen atoms or hydrocarbon groups which may have a heteroatom. Three or four of Z1 to Z5 are preferably hydrogen atoms, and the rest are preferably hydrocarbon groups which may have heteroatoms.

Examples of the heteroatoms include oxygen, nitrogen, sulfur, and fluorine. The hydrocarbon group preferably has 1 to 30 carbon atoms, more preferably 2 to 20 carbon atoms. Specifically, the number of carbon atoms is, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 , 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, and may be in the range between any two of the numerical values exemplified herein.

The hydrocarbon group is preferably an aliphatic hydrocarbon group which may have a substituent. Examples of aliphatic hydrocarbon groups include alkyl groups having 1 to 20 carbon atoms, allyl groups, and vinyl groups. Specifically, the number of carbon atoms in the aliphatic hydrocarbon group is, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, and may be in the range between any two of the numbers exemplified here. A substituent of the aliphatic hydrocarbon group includes an aromatic hydrocarbon group such as a phenyl group. The aromatic hydrocarbon group may be substituted with a substituent such as a hydroxyl group. A substituent is preferably bonded to the 1-position carbon of the aliphatic hydrocarbon group.

The hydrocarbon group may be an aromatic hydrocarbon group optionally having a substituent. A phenyl group, a tolyl group, etc. are mentioned as an aromatic-hydrocarbon group. Substituents include aliphatic hydrocarbon groups such as alkyl and hydroxyl groups.

At least two of Z1 to Z5 may be crosslinked to form an alicyclic or aromatic ring.

At least one of Z1 to Z5 is preferably an optionally substituted alkyl group having 1 to 20 carbon atoms. This substituent is preferably a hydrocarbon group having 1 to 20 carbon atoms which may have a heteroatom, more preferably containing an aromatic ring, further preferably a phenyl group, more preferably a 1-phenylethyl group.

n in the general formula (1) represents the number of carbon atoms in the alkylene oxide structure and is an integer of 1-10 (preferably 2-4). Specifically, n is, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and may be within a range between any two of the numerical values exemplified here. .

X in the general formula (1) represents the average number of alkylene oxide units added and is an integer of 1 to 100 (preferably 5 to 50). Specifically, X is, for example, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100 and may be in the range between any two of the numerical values exemplified here.

Examples of the ether compound B include polyoxyethylene distyrenated phenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene phenyl ether, polyoxyethylene β-naphthyl ether, polyoxyethylene bisphenol A ether, polyoxyethylene bisphenol F ether and the like.

The content of the ether compound B is preferably 0.001 to 10% by mass with respect to 100% by mass of the styrene resin composition. If this value is too small, the formation of a gel-like substance may not be sufficiently suppressed, and if this value is too large, the heat resistance may decrease. Specifically, the above content is, for example, 0.001, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 , 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10% by mass, and within the range between any two of the numerical values exemplified here good too.

<<Other Additives>>
Various additives can be blended into the styrene-based resin composition as necessary within a range that does not impair the characteristics of the present invention. The types of additives are not particularly limited as long as they are commonly used in plastics, but antioxidants, flame retardants, lubricants, processing aids, antiblocking agents, antistatic agents, antifogging agents, and improving light resistance. agents, softeners, plasticizers, inorganic reinforcing agents, cross-linking agents, pigments, dyes, etc. or mixtures thereof. The styrenic resin composition may contain only the ether compound B as an ether compound, or may contain an ether compound other than the ether compound B (eg, polyoxyethylene alkyl ether).

2. Method for Producing Styrenic Resin Composition The styrenic resin composition of the present invention can be produced by adding the ether compound B to the styrenic resin A. Polymerization methods for styrene resins include known styrene polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. In terms of quality and productivity, bulk polymerization and solution polymerization are preferred, and continuous polymerization is preferred. Examples of solvents that can be used include alkylbenzenes such as benzene, toluene, ethylbenzene and xylene, ketones such as acetone and methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and cyclohexane.

During the polymerization of the styrene-(meth)acrylic acid copolymer resin, polymerization aids such as polymerization initiators, chain transfer agents, cross-linking agents, and other polymerization aids can be used as necessary. As the polymerization initiator, radical polymerization initiators are preferred, and known and commonly used ones include, for example, 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t-butylperoxy)butane, 2,2- Peroxyketals such as di(4,4-di-t-butylperoxycyclohexyl)propane, 1,1-di(t-amylperoxy)cyclohexane, cumene hydroperoxide, t-butyl hydroperoxide and the like Hydroperoxides, alkyl peroxides such as t-butyl peroxyacetate, t-amyl peroxy isononanoate, t-butyl cumyl peroxide, di-t-butyl peroxide, dicumyl peroxide, di-t - dialkyl peroxides such as hexyl peroxide, peroxyesters such as t-butyl peroxyacetate, t-butyl peroxybenzoate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxyisopropyl carbonate, polyethers Peroxycarbonates such as tetrakis(t-butylperoxycarbonate), N,N'-azobis(cyclohexane-1-carbonitrile), N,N'-azobis(2-methylbutyronitrile), N,N' -azobis(2,4-dimethylvaleronitrile), N,N'-azobis[2-(hydroxymethyl)propionitrile] and the like, and these can be used alone or in combination of two or more. . Chain transfer agents include aliphatic mercaptans, aromatic mercaptans, pentaphenylethane, α-methylstyrene dimer, terpinolene, and the like.

In the case of continuous polymerization, the styrenic resin composition can be produced by a method comprising a polymerization step, a devolatilization step, and a granulation step.

First, in the polymerization step, the polymerization reaction is controlled by adjusting the polymerization temperature or the like, using a well-known complete mixing tank type stirring tank, tower type reactor, or the like, so as to achieve the target molecular weight, molecular weight distribution, and reaction conversion rate.

The polymerization solution containing the polymer exiting the polymerization step is transferred to the devolatilization step to remove unreacted monomers and polymerization solvent. The devolatilization process consists of a vacuum devolatilization tank with a heater and a devolatilization extruder with a vent. The molten polymer that has exited the devolatilization step is transferred to the granulation step. In the granulation step, the molten resin is extruded in strands from a multi-hole die and processed into pellets by a cold cut method, an air hot cut method, or an underwater hot cut method.

The ether compound B is preferably added before the devolatilization step or during the devolatilization step. Specifically, the ether compound B is preferably added by any one of the following methods (1) to (4).
(1) Add to the raw material monomer mixture.
(2) added during the polymerization process;
(3) Add to the polymerization solution after completion of the polymerization process.
(4) When the devolatilization process is composed of two stages and the resin temperature in the first stage is less than 200°C, it is added between the first stage and the second stage.

3. Use of Styrene-Based Resin Composition The styrene-based resin composition of the present invention can be formed into a molded product by a molding method according to the purpose, such as injection molding, extrusion molding, compression molding, blow molding, etc., and the shape thereof is not limited. not something. For example, if it is a plate-shaped molded article, it can be processed into a light guide plate or the like.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples.

1. Measurement method (1) Measurement of methacrylic acid unit content 0.5 g of a styrenic resin composition was weighed and dissolved in a mixed solution of toluene/ethanol = 8/2 (volume ratio), and then potassium hydroxide was added to 0.1 mol/L. Neutralization titration was performed with an ethanol solution, the end point was detected, and the mass-based content of methacrylic acid units was calculated from the amount of potassium hydroxide ethanol solution used.

(2) Measurement of Content of Ether Compound 5 g of the styrene-based resin composition is weighed and dissolved in THF. After dissolution, reprecipitate the polymer with methanol and a small amount of hydrochloric acid, and remove the reprecipitate by filtration. The filtrate was concentrated to finally obtain a concentrate of 10 ml methanol solution, and the ether compound was quantified by high performance liquid chromatography (HPLC). Quantification was carried out by preparing three points of methanol solutions with known ether compound concentrations and preparing a calibration curve.
HPLC model: Japan Waters alliance system 2695 separation module Detector: Differential refractometer (RI)
Column: TSKgel ODS-120T manufactured by Tosoh Corporation 4.6 mm (ID) × 15 cm (L)
Mobile phase: 0.2% by mass of phosphoric acid added to methanol/water = 80/20 (volume ratio) Flow rate: 1.0 ml/min Column oven temperature: 40°C
Detector temperature: 30°C

(3) Measurement of Vicat softening temperature It was obtained according to JIS K-7206 with a heating rate of 50°C/hr and a test load of 50N.

(4) Measurement of MEK insoluble content <before heating>
1 g of a styrenic resin composition is weighed, 35 ml of methyl ethyl ketone is added and dissolved, and the solution is centrifuged at 10,000 rpm for 30 minutes in a centrifuge (Kokusan H-2000B (rotor: H)) to remove insoluble matter. is allowed to settle, and the supernatant is removed by decantation to obtain an insoluble matter, which is pre-dried in a safety oven at 90°C for 2 hours, further dried in a vacuum dryer at 120°C for 1 hour under reduced pressure, and placed in a desiccator for 20 minutes. After cooling at , the mass G of the dried insoluble matter was measured to calculate the mass % of the insoluble matter.

<After heating>
1 g of the styrene-based resin composition was weighed and heat-treated in an oven at 230° C. for 3 hours under vacuum. After that, the insoluble matter was measured by the same method as before heating, and the mass % of the insoluble matter was calculated.
The gel-like substance is considered to be produced by a condensation reaction between polymer molecules of carboxyl groups in the styrene resin, and is an insoluble component in methyl ethyl ketone.

(5) Measurement of HAZE Pellets of a styrene resin composition were injection molded at a cylinder temperature of 250°C and a mold temperature of 50°C using an injection molding machine (IS130FII-3A) manufactured by Toshiba Machine Co., Ltd. Using the obtained test piece (thickness 2 mm, dimensions 40 mm × 40 mm), HAZE (unit: %) was measured using a haze meter (NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K-7105. .

2. Examples/Comparative Examples Examples/Comparative Examples were carried out by the methods described below.

<Example 1>
A polymerization process was constituted by connecting in series a first reactor that was a complete mixing type stirring tank with an internal volume of 39 liters and a second reactor that was a complete mixing type stirring tank with an internal volume of 39 liters. A raw material solution was prepared from a mixed solution of 71% by mass of styrene, 12% by mass of methacrylic acid, and 17% by mass of ethylbenzene.

This raw material solution was continuously supplied to the first reactor at a rate of 12.6 kg per hour, and flowed through each reactor in a fully liquid state. At the inlet of the first reactor, 250 ppm by mass of 1,1-bis(t-butylperoxy)cyclohexane (Perhexa C manufactured by NOF Corporation) with respect to the total amount of styrene and methacrylic acid in the raw material solution. Mixed. Also, the ether compound [B-1] was continuously added at the inlet of the first reactor. The reaction temperature of each reactor was adjusted to 130°C in the first reactor and 140°C in the second reactor.

Subsequently, the solution containing the copolymer resin continuously taken out from the second reactor is introduced into a vacuum devolatilization tank equipped with a preheater installed in two stages in series, and after separating unreacted monomers and ethylbenzene, a strand is obtained. A styrenic resin composition was obtained by extruding and cooling, and then cutting into pellets. For the first-stage vacuum devolatilization tank with a preheater, the temperature of the preheater was set at 175°C, the pressure of the vacuum devolatilization tank was set at 500 mmHg, and the jacket temperature of the vacuum devolatilization tank was set at 185°C. For the second-stage vacuum devolatilization tank with a preheater, the temperature of the preheater was set at 240°C, the pressure of the vacuum devolatilization tank was set at 8 mmHg, and the jacket temperature of the vacuum devolatilization tank was set at 240°C. The resin temperature in the first-stage vacuum devolatilization tank was 168°C, and the resin temperature in the second-stage vacuum devolatilization tank was 231°C.

Various physical properties were measured for the obtained styrenic resin composition. Table 1 shows the results.

Details of the components in Table 1 are as follows.
Ether compound B
B-1: Polyoxyethylene distyrenated phenyl ether (manufactured by Kao Corporation, Emulgen A-90, average number of ethylene oxide units added: 18)
B-2: Polyoxyethylene distyrenated phenyl ether (manufactured by Kao Corporation, Emulgen A-60, average addition number of ethylene oxide units: 12)
B-3: Polyoxyethylene distyrenated phenyl ether (manufactured by Kao Corporation, Emulgen A-500, average addition number of ethylene oxide units: 50)
B-4: Polyoxyethylene styrenated phenyl ether (KTSP-16, manufactured by Aoki Yushi Kogyo Co., Ltd., average addition number of ethylene oxide units: 16)
B-5: Polyoxyethylene nonylphenyl ether (manufactured by Aoki Yushi Kogyo Co., Ltd., Braunon N-513, average addition number of ethylene oxide units: 13)
Polyoxyethylene alkyl ether (polyoxyethylene lauryl ether) (manufactured by Kao Corporation, Emulgen 109P, average number of ethylene oxide units added: 9)

<Examples 2 to 9>
A styrenic resin composition was produced in the same manner as in Example 1, except that the type and/or amount of ether compound B was changed as shown in Table 1, and various physical properties were measured.

<Example 10>
A styrenic resin composition was produced in the same manner as in Example 1, except that the raw material solution was changed to a mixed solution of 77.1% by mass of styrene, 5.9% by mass of methacrylic acid, and 17% by mass of ethylbenzene. was measured.

<Example 11>
A styrenic resin composition was produced in the same manner as in Example 3, except that the raw material solution was changed to a mixed solution of 63.5% by mass of styrene, 19.5% by mass of methacrylic acid, and 17% by mass of ethylbenzene. was measured.

<Comparative Examples 1 to 3>
Styrene-based resin compositions were produced in the same manner as in Examples 1, 10 and 11 except that no ether compound was added, and various physical properties were measured.

<Comparative Examples 4 to 6>
Styrenic resin compositions were produced in the same manner as in Examples 1, 4 and 10, except that polyoxyethylene alkyl ether was added instead of ether compound B, and various physical properties were measured.

3. Discussion All examples showed a very small increase in MEK insoluble content upon heating. Since the MEK-insoluble matter is mainly a gel-like substance, it was demonstrated that the formation of the gel-like substance was suppressed.
Further, when comparing Examples 1, 4 and 10 with Comparative Examples 4 to 6, when polyoxyethylene alkyl ether was added in place of ether compound B, the Vicat softening temperature decreased significantly.

By using the styrenic resin composition of the present invention, it is possible to produce a resin composition and a molded article with very little gel, and to obtain a molded article excellent in appearance. In addition, it is possible to suppress the generation of gel in the manufacturing process more than before, and to increase the production efficiency.

Claims (11)

A styrenic resin composition containing a styrenic resin and an ether compound,
The styrene-based resin is obtained by copolymerizing a monomer mixture containing a styrene-based monomer and a (meth)acrylic acid-based monomer,
The styrenic resin composition, wherein the ether compound is represented by the general formula (1).


(Z1 to Z5 in the formula are the same or different and are hydrogen atoms or hydrocarbon groups which may have a heteroatom. At least two of Z1 to Z5 are bridged to form an alicyclic or may form an aromatic ring.n represents the number of carbon atoms in the alkylene oxide structure and is an integer of 1 to 10.X represents the average number of alkylene oxide units added and is an integer of 1 to 100 .) The styrenic resin composition according to claim 1,
A styrenic resin composition, wherein the content of the structural unit derived from the (meth)acrylic acid-based monomer is 0.1 to 30% by mass with respect to 100% by mass of the styrenic resin composition. The styrenic resin composition according to claim 1 or 2,
A styrenic resin composition, wherein the content of the ether compound is 0.001 to 10% by mass with respect to 100% by mass of the styrenic resin composition. The styrene resin composition according to any one of claims 1 to 3,
A styrenic resin composition wherein at least one of Z1 to Z5 is an optionally substituted alkyl group having 1 to 20 carbon atoms. The styrenic resin composition according to claim 4,
The styrenic resin composition, wherein the substituent is a hydrocarbon group having 1 to 20 carbon atoms which may have a heteroatom. The styrenic resin composition according to claim 5,
6. The styrenic resin composition according to claim 5, wherein said substituent contains an aromatic ring. The styrenic resin composition according to claim 6,
The styrenic resin composition, wherein the aromatic ring of the substituent is a phenyl group bonded to the alkyl group. The styrenic resin composition according to claim 7,
The styrenic resin composition, wherein the substituent is a 1-phenylethyl group. The styrenic resin composition according to any one of claims 1 to 8,
A styrenic resin composition, wherein the number of carbon atoms n in the alkylene oxide structure is 2 to 4. The styrene resin composition according to any one of claims 1 to 9,
The styrenic resin composition, wherein the average number of alkylene oxide units to be added is 5 to 50. A molded article made of the styrene-based resin composition according to any one of claims 1 to 10.