JP2014189766A - Polystyrenic resin composition for foaming, polystyrenic resin foam sheet, and foam molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polystyrenic resin composition for foaming capable of inhibiting attenuations of mechanical strengths even if the weight thereof is reduced.SOLUTION: The problem-solving polystyrenic resin composition for foaming includes, as constituent components of a matrix resin, a polyfunctional vinyl aromatic compound and a component derived from a styrenic monomer, whereas the polyfunctional vinyl aromatic compound has a molecular weight of 100 or higher and lower than 1000, whereas the matrix resin is obtained by polymerizing a monomer mixture including 50-500 ppm of the polyfunctional vinyl aromatic compound within the styrenic monomer, whereas the matrix resin is a resin exhibiting a ratio of the gradient (a) of the linear approximation line of a non-linear region specific to a logarithmically plotted time-elongational viscosity curve ascertained by measuring the monoaxial elongational viscosity thereof under conditions of temperature=160°C and fixed strain rate=0.1/sec with respect to the gradient (a) of the linear approximation line of a linear region specific to the same curve (a/a) greater than 2.0 and 6.0 or less.

Description

  The present invention relates to a polystyrene-based resin composition for foaming, a polystyrene-based resin foam sheet, and a foam-molded article. More specifically, the present invention relates to a polystyrene-based resin composition for foaming, a polystyrene-based resin foamed sheet, and a foam-molded product that can suppress a decrease in mechanical strength even when the weight is reduced.

Polystyrene resin foam sheets of polystyrene resin are lightweight but have excellent mechanical strength, heat insulation and thermal insulation properties, and excellent moldability, so they are molded into shapes such as dishes, cups, and bowls. It is widely used as various food packaging materials and simple containers.
From the viewpoints of enforcement of the Container Recycling Law, consideration for environmental issues, promotion of resource saving, cost reduction, etc., the above containers are required to be lighter. In order to reduce the weight, it is conceivable to reduce the thickness of the container. However, simply reducing the thickness of the container may reduce the strength of the container.

It is also conceivable to reduce the weight by increasing the foaming ratio with the same thickness. However, with this weight reduction, the open cell ratio increases as the magnification increases, and the moldability at the time of container molding may deteriorate.
As a technique for reducing the weight, a technique described in Japanese Patent Application Laid-Open No. 2012-207172 is known. In this technique, when the uniaxial extensional viscosity of a polystyrene resin composition is measured under predetermined conditions, the slope of the first-order approximation line in the non-linear region in the logarithmic plot of the time-elongation viscosity curve and the first-order approximation line in the linear region in the above curve. We focus on the ratio to the slope of Specifically, by setting this ratio in the range of 1.2 to 2.0, it is said that weight reduction of the container can be realized while suppressing the formation of open cells.

JP 2012-207172 A

  Even with the technique described in the above publication, a certain amount of weight reduction can be achieved, but in recent years, further weight reduction of containers has been demanded, and the technique of the above publication is sufficient for such a demand. It wasn't.

  The inventor of the present invention has intensively studied to meet the above demands. As a result, the polystyrene-based resin composition for foaming has a styrene-based polyfunctional vinyl-based aromatic compound as a branching agent having a specific molecular weight. A polystyrene resin composition for foaming containing a base resin derived from a monomer mixture contained in the monomer, wherein the ratio of the base resin described in the above publication is greater than 2.0 and 6.0 or less. For example, the present inventors have found that it is possible to provide a polystyrene-based resin foam sheet that can be reduced in weight without deteriorating the physical properties of the container.

Thus, according to the present invention, a polyfunctional vinyl aromatic compound and a component derived from a styrene monomer are included as a base resin,
The polyfunctional vinyl-based aromatic compound has a molecular weight of 100 or more and less than 1000;
The base resin is obtained by polymerizing a monomer mixture containing 50 to 500 ppm of a polyfunctional vinyl aromatic compound in the styrene monomer.
The base resin has a slope (a ₁ ) of a first-order approximation line in a non-linear region in a logarithmic plot of a time-extension viscosity curve obtained by measuring uniaxial extensional viscosity at a temperature of 160 ° C. and a constant strain rate of 0.1 / second. ) And the slope (a ₂ ) of the first-order approximate straight line in the linear region in the above curve is a resin having a ratio (a ₁ / a ₂ ) of more than 2.0 and not more than 6.0 A polystyrene resin composition is provided.

Moreover, according to this invention, the polystyrene-type resin foam sheet obtained by carrying out extrusion foaming of the said polystyrene-type resin composition is provided.
Furthermore, according to this invention, the foaming molded article obtained using the said polystyrene-type resin foam sheet is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the polystyrene-type resin foam sheet which can implement | achieve weight reduction without reducing the physical property of a container can be provided.

Moreover, according to the present invention,
(1) The polyfunctional vinyl aromatic compound is divinylbenzene. (2) The base resin is dissolved in toluene at 23 ° C. for 1 hour under shaking so that the base resin has a concentration of 5% by mass. (3) When the base resin shows a toluene insoluble content of 5% by mass or more when dissolved, the base resin is dissolved in tetrahydrofuran at a concentration of 0.3 g / L at 23 ° C. for 72 hours, (4) The base resin having a tetrahydrofuran insoluble content of 0% (completely dissolved) contains a branching agent, which is a polyfunctional vinyl aliphatic compound, dispersed in an aqueous suspension, and a styrene monomer. (5) The base resin obtained by suspension polymerization with the monomer mixture is branched into a polystyrene resin seed particle dispersed in an aqueous suspension, which is a polyfunctional vinyl aliphatic compound. Mixing agent and monomer containing styrenic monomer It is possible to provide a polystyrene-based resin foam sheet that can be reduced in weight without further degrading the physical properties of the container, by providing either one obtained intermittently or continuously by polymerizing the product. .

2 is a time-elongation viscosity curve of Example 1.

(Polystyrene resin composition for foaming)
The polystyrene-based resin composition for foaming of the present invention contains a polyfunctional vinyl-based aromatic compound and a component derived from a styrene-based monomer as a base resin.
(1) Base resin (a) Ratio (a ₁ / a ₂ )
The base resin has a slope of a first-order approximation line (a ₁ ) in a non-linear region in a logarithmic plot of a time-extension viscosity curve obtained by measuring uniaxial extensional viscosity at a temperature of 160 ° C. and a constant strain rate of 0.1 / second. And a ratio (a ₁ / a ₂ ) between the slope (a ₂ ) of the first-order approximate straight line in the linear region in the above curve and a resin that is greater than 2.0 and 6.0 or less.

When the ratio (a ₁ / a ₂ ) is 2.0 or less, the effect of strain hardening is small and the extrusion foamability and moldability may be deteriorated. When it is larger than 6.0, productivity and extrusion foamability may be deteriorated. The preferred ratio (a ₁ / a ₂₎ greater than 2.0 5.0 or less, and more preferably the ratio (a ₁ / a ₂₎ greater than 2.0 is 4.0 or less, more preferably the ratio (a ₁ / a ₂ ) Is greater than 2.0 and less than or equal to 3.5. It is difficult to measure this physical property from the structure in which molecular chains of polystyrene resin are cross-linked with a polyfunctional vinyl aromatic compound. For this reason, the inventor believes that the base resin having this physical property has a structure in which the molecular chain of the polystyrene resin is branched by a polyfunctional vinyl aromatic compound.

The above “nonlinear region” is intended to indicate a region that appears after the inflection point (the point at which the slope of the plot that separates the nonlinear region and the linear region of the logarithmic plot changes). The slope of the linear approximation line in the “nonlinear region” (A ₁ ) is between 8.0 × 10 ^{0 and} 2.0 × 10 ¹ seconds, and is observed after the inflection point and before the maximum point, and has an interval of 5.0 × 10 ⁰ seconds The inclination of the regression line based on the two points of data is intended.
In addition, the “linear region” is intended to be a region where linearity is relatively obtained in data appearing before the inflection point, and the slope (a ₂ ) of the linear approximation line in the “linear region” is 1. Intended for the slope of the regression line based on any two points of data observed between 0 × 10 ^{0 to} 2.0 × 10 ⁰ s and before the inflection point and having an interval of 5.0 × 10 ⁻¹ s doing.

(B) Mn, Mw and Mz
The base resin preferably has Mn in the range of 60,000 to 150,000, Mw in the range of 200,000 to 500,000, and Mz in the range of 500,000 to 3,000,000. When the average molecular weight is smaller than these ranges, the strength of the molded product and the moldability may be deteriorated. In the case of a large average molecular weight, since the resin fluidity is deteriorated, extrusion foamability and productivity may be deteriorated. More preferably, it is Mn in the range of 70,000 to 130,000, Mw in the range of 300,000 to 500,000, and Mz in the range of 1 million to 2.5 million.

(C) Melt tension It is preferable that the base resin has a melt tension of 10 cN or more. When the melt tension is less than 10 cN, the extrusion foamability may be deteriorated. A more preferable melt tension is 13 cN or more.
(D) MFR
The base resin preferably has an MFR in the range of 0.5 to 5 g / 10 minutes. When MFR is smaller than 0.5 g / 10 minutes, fluidity may be poor and productivity may be poor. When it is larger than 5 g / 10 minutes, the appearance defect of the sheet may occur. A more preferred MFR is in the range of 0.8 to 4.0 g / 10 min.
(E) Toluene-insoluble content The base resin preferably has a toluene-insoluble content of 5% by weight or more. A toluene insoluble content of 5% by weight means that a high molecular weight component is present in the polystyrene resin. A more preferable toluene insoluble content is 7% by weight, and a still more preferable toluene insoluble content is 8% by weight.

(F) Solubility in Tetrahydrofuran When the base resin is added with 0.3 g of polystyrene resin in 1 liter of tetrahydrofuran and allowed to stand for 72 hours, it is preferably completely dissolved in tetrahydrofuran. Complete dissolution means that the cross-linking component is not substantially present in the polystyrene-based resin.

(2) Component derived from styrene monomer Examples of the component derived from styrene monomer include, for example, styrene, α-methylstyrene, vinyltoluene, ethylstyrene, i-propylstyrene, t-butylstyrene, dimethylstyrene, Homopolymers of styrenic monomers such as bromostyrene and chlorostyrene, or copolymers thereof, or methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cetyl (meth) acrylate Alkyl (meth) acrylates such as, alkyl methacrylates such as (meth) acrylonitrile, dimethyl maleate and diethyl maleate, alkyl fumarate such as dimethyl fumarate, diethyl fumarate and ethyl fumarate, maleic anhydride, N-phenyl Maleimide, (meth) acrylic acid If, copolymer of styrene monomer.

(3) Polyfunctional vinyl aromatic compound The polyfunctional vinyl aromatic compound has a role as a branching agent.
In general, with a general polystyrene resin obtained by simply polymerizing the above monomer, an inflection point is observed in the vicinity of 3 to 7 seconds when the uniaxial elongation viscosity is measured, but the inflection point is the boundary. The inclination tends to be small. Therefore, it is difficult to satisfy the above ratio (a ₁ / a ₂ ).

  On the other hand, in a polystyrene resin having a plurality of branching structures derived from the above-mentioned branching agent in the molecule (hereinafter also referred to as “multi-branched polystyrene resin”), an inflection point is exhibited at the same location as a general polystyrene resin. . However, the inclination tends to increase at the inflection point.

The polyfunctional vinyl-based aromatic compound is not particularly limited as long as a base resin having a molecular weight of 100 or more and less than 1000 and satisfying the above ratio (a ₁ / a ₂ ) can be obtained. When the molecular weight is 1000 or more, the number of functional groups per unit mass is reduced, and the effect as a branching agent may be reduced, or it may be difficult to be absorbed by the seed particles when nuclear polymerization is performed.

In the polyfunctional vinyl-based aromatic compound, polyfunctional means that the compound contains two or more vinyl groups. Multifunctional includes bifunctional, trifunctional, tetrafunctional, pentafunctional, hexafunctional or more.
The vinyl group contained in the polyfunctional vinyl aromatic compound means a group composed of a polymerizable carbon-carbon double bond. The vinyl group may have a structure in which a hydrogen atom bonded to carbon constituting the vinyl group is substituted with another group (for example, a methyl group). In addition, when the hydrogen atom of the carbon atom in which the bond of the vinyl group is located is substituted with another group, the vinyl group is also referred to as a vinylidene group. The vinyl group in the polyfunctional vinyl aromatic compound may be contained in the (meth) acryloyl group located at the molecular end.

As the polyfunctional vinyl aromatic compound, for example,
(I) divinylbenzene, trivinylbenzene, divinyltoluene, divinylxylene, bis (vinylphenyl) methane, bis (vinylphenyl) ethane, bis (vinylphenyl) propane, bis (vinylphenyl) butane, divinylnaphthalene, divinylanthracene, A compound in which a vinyl group is bonded directly to a polyfunctional benzene ring such as divinylbiphenyl,
(Ii) Bifunctional (meth) acrylate compounds such as ethylene oxide adduct di (meth) acrylate of bisphenol A, propylene oxide adduct di (meth) acrylate of bisphenol A,
Etc.

  The base resin is obtained by polymerizing a monomer mixture containing 50 to 500 ppm of a polyfunctional vinyl aromatic compound in a styrene monomer. When the content is less than 50 ppm, extrusion foamability and moldability may be deteriorated. When it is more than 500 ppm, a cross-linked product is generated, which may give poor appearance during extrusion foaming. A preferable content is 75 to 400 ppm, and a more preferable content is 100 to 300 ppm. In addition, content of the said compound respond | corresponds substantially with content of the component derived from the polyfunctional vinyl-type aromatic compound in base-material resin.

(4) Other additives The polystyrene-based resin composition for foaming may contain other additives in addition to the base resin, if necessary. Other additives include foaming agents, plasticizers, other resins, flame retardants, flame retardant aids, antistatic agents, spreading agents, foam control agents, fillers, colorants, weathering agents, anti-aging agents, Examples include lubricants, antifogging agents, and fragrances.
Examples of blowing agents include hydrocarbons (for example, propane, normal butane, isobutane, normal pentane, isopentane), water, dimethyl ether, methyl chloride, ethyl chloride, nitrogen, carbon dioxide, argon and other physical blowing agents, azodicarbonamide, Examples include chemical blowing agents such as sodium bicarbonate or a mixture of sodium bicarbonate and citric acid.
Examples of the plasticizer include aromatic hydrocarbons such as styrene, toluene, and xylene, and aliphatic hydrocarbons such as cyclohexane, hexane, and heptane. Adipic acid esters such as diisobutyl adipate, dioctyl adipate, diisononyl adipate, glycerin fatty acid esters such as glycerin diacetomonolaurate, phthalic acid esters such as dioctyl phthalate, diisononyl phthalate, diisobutyl phthalate, liquid paraffin, white oil High boiling point compounds such as

Other resins include rubber modified with addition of diene rubbery polymer such as polyolefin resin such as polyethylene and polypropylene, polybutadiene, styrene-butadiene copolymer, ethylene-propylene-nonconjugated diene three-dimensional copolymer, etc. High impact polystyrene resin, polycarbonate resin, polyester resin, polyamide resin, polyphenylene ether, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, polymethyl methacrylate, styrene- (meth) acrylic acid copolymer And a styrene- (meth) acrylic acid ester copolymer.
As flame retardants, tetrabromocyclooctane, hexabromocyclododecane, trisdibromopropyl phosphate, tetrabromobisphenol A, tetrabromobisphenol A-bis (2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol A- Examples thereof include bis (2,3-dibromopropyl ether).
Examples of the flame retardant aid include organic peroxides such as 2,3-dimethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, dicumyl peroxide, and cumene hydroperoxide. .

Examples of the antistatic agent include polyoxyethylene alkylphenol ether, stearic acid monoglyceride, polyethylene glycol and the like.
Examples of the spreading agent include polybutene, polyethylene glycol, glycerin, and silicone oil.
As the air conditioner, talc, mica, silica, diatomaceous earth, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, potassium sulfate, Barium sulfate, glass beads, polytetrafluoroethylene, tribasic calcium phosphate, magnesium pyrophosphate, zinc stearate, magnesium stearate and other metal soaps, ethylene bis stearamide, bisamide compounds such as methylene bis stearamide, stearamide Amide compounds such as 12-hydroxystearic acid amide, higher fatty acid glycerides such as stearic acid triglyceride, stearic acid monoglyceride, and the like.
As the lubricant, metal soap such as zinc stearate and magnesium stearate, bisamide compound such as ethylene bis stearamide, methylene bis stearamide, stearamide, amide compound such as 12-hydroxystearic amide, stearic acid triglyceride, Examples thereof include higher fatty acid glycerides such as stearic acid monoglyceride, polyethylene wax, liquid paraffin, and white oil.

(5) Production method of polystyrene-based resin composition for foaming The polystyrene-based resin composition for foaming is made of polystyrene-based resin foamed with styrene-based monomers, polyfunctional vinyl aromatic compounds and other additives as raw materials. It can be manufactured by putting into an extruder for obtaining a sheet, polymerizing and mixing. This production method will be described again in the column of polystyrene-based resin foam sheets. In addition to this production method, a method in which a styrene monomer, a polyfunctional vinyl aromatic compound and other additives are placed in an aqueous medium and polymerization and crosslinking are carried out under suspension conditions (suspension weight). legal). In this method, the components constituting the polystyrene-based resin composition for foaming can be uniformly dispersed. Among suspension polymerization methods, there may be mentioned a method in which separately produced styrene resin particles are impregnated with a styrene monomer, a polyfunctional vinyl aromatic compound and other additives, and then polymerized and crosslinked ( Seed polymerization method). In this method, components constituting the foaming polystyrene-based resin composition can be selectively dispersed as compared with the suspension polymerization method.

More specifically,
(I) The suspension polymerization method is a method in which a styrenic monomer is continuously or intermittently supplied into an aqueous medium and suspension polymerization is performed in the presence of a polymerization initiator,
(Ii) In the seed polymerization method, polystyrene resin seed particles (hereinafter referred to as seed particles) are dispersed in an aqueous medium to form an aqueous suspension, and a styrene monomer is continuously or intermittently supplied thereto for polymerization. This is a method of suspension polymerization in the presence of an initiator.

  The polymerization initiator used in the suspension polymerization method and the seed polymerization method is not particularly limited, and examples thereof include benzoyl peroxide, lauryl peroxide, t-butyl peroxybenzoate, t-butyl peroxide, and t-butyl peroxide. Oxypivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-butyl peroxy-2-ethylhexanate, isopropyl carbonate, t-butyl peroxyacetate, 2,2- Organic peroxides such as bis (t-butylperoxy) butane, t-butylperoxy-3,3,5-trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate, and azobisisobutyronitrile Azobisdimethylvalero Include azo compounds tolyl or the like, they may be also alone, or two or more are used alone.

  The seed particles can be obtained by a known method such as a method obtained using an extruder or a suspension polymerization method (including a seed polymerization method). When obtaining seed particles by the suspension polymerization method, the aqueous suspension obtained by dispersing the seed particles in an aqueous medium may be used as the aqueous suspension as it is as a reaction solution after polymerization by the suspension polymerization method. Alternatively, seed particles obtained by the suspension polymerization method may be separated from the reaction solution, and an aqueous suspension obtained by suspending the seed particles in an aqueous medium separately prepared may be used. In addition, it does not specifically limit as an aqueous medium, For example, water, alcohol, etc. are mentioned, Water is preferable.

  In the above suspension polymerization method or seed polymerization method, a suspension stabilizer is used to stabilize the dispersibility of the styrene monomer droplets or seed particles when the styrene monomer is polymerized. Also good. Examples of such a suspension stabilizer include water-soluble polymers such as polyvinyl alcohol, methylcellulose, polyacrylamide, and polyvinylpyrrolidone, and poorly water-soluble inorganic salts such as tricalcium phosphate, hydroxyapatite, and magnesium pyrophosphate. In the case of using a poorly water-soluble inorganic salt, an anionic surfactant is usually used in combination.

Examples of the anionic surfactant include alkyl sulfates such as sodium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate, higher fatty acid salts such as sodium oleate, and β-tetrahydroxynaphthalene sulfonate. And alkylbenzene sulfonates are preferred.
In the suspension polymerization method or seed polymerization method, a water-soluble polymerization inhibitor is added for the purpose of preventing the generation of fine powder due to polymerization of styrene dissolved in water when the styrene monomer is polymerized. May be.

(Polystyrene resin foam sheet)
Polystyrene resin composition for foaming obtained by suspension polymerization or seed polymerization is kneaded with a foaming agent in an extruder and extruded and foamed from a flat die or a circular die attached to the tip of the extruder. A resin foam sheet can be obtained. When a polystyrene-based resin composition for foaming is obtained by reacting and kneading raw materials in an extruder, a foaming agent is added during kneading, and a polystyrene-based resin foamed sheet can be obtained by extrusion foaming from a die.
The polystyrene-based resin foam sheet preferably has a density of 0.035 g / cm ^{3 to} 0.065 g / cm ³ . Moreover, thickness is 0.8-3.0 mm normally, Preferably it is 1.0-2.5 mm, More preferably, it is 1.5-2.0 mm.

(Foam molded product)
A foamed molded product can be obtained by molding a polystyrene resin foam sheet by a known method. As the foamed molded product, it can be used for food containers such as dishes, cups, bowls, cushioning materials, packaging materials and the like.

EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.
<Average molecular weight>
Number average molecular weight (Mn), weight average molecular weight (Mw), and z average molecular weight (Mz) mean polystyrene (PS) equivalent average molecular weight measured using gel permeation chromatography (GPC).
Specifically, 3 mg of a sample is dissolved in 10 mL of tetrahydrofuran (THF) for 72 hours by standing (complete dissolution), and filtered through a non-aqueous 0.45 μm chromatodisc to measure the molecular weight. The average molecular weight of the sample is obtained from a standard polystyrene calibration curve that has been measured and prepared in advance. The chromatographic conditions are as follows.
・ Device: High-speed GPC device ・ Product name: HLC-8320GPC EcoSEC-WorkStation (built-in RI detector) manufactured by Tosoh Corporation
・ Analysis conditions Column: TSKgel SuperHZM-H × 2 (4.6 mm ID × 15 cmL × 2)
Guard column: TSK guard column Super HZ-H x 1 (4.6 mm ID x 2 cm L)
Flow rate: 0.175 mL / min on the sample side, 0.175 mL / min on the reference side Detector: Built-in RI detector Concentration: 0.3 g / L
Injection volume: 50 μL
Column temperature: 40 ° C
System temperature: 40 ° C
Eluent: Tetrahydrofuran

(Create a calibration curve)
Standard polystyrene samples for calibration curves include standard polystyrene samples having a weight-average molecular weight of 500, 2630, 9100, 37900, 102000, 355000, 3840000, and 5480000 as trade name “TSK standard POLYSYRENE” manufactured by Tosoh Corporation; A standard polystyrene sample having a weight average molecular weight of 1030000 with a trade name “Shodex STANDARD” manufactured by the company is used.

The method of creating a calibration curve is as follows. First, the standard polystyrene samples for calibration curves are group A (with a weight average molecular weight of 1030000), group B (with a weight average molecular weight of 500, 9100, 102000, and 3480000) and group C (with a weight average molecular weight of 2630, 37900). 355,000 and 5480000). 5 mg of a standard polystyrene sample belonging to group A having a weight average molecular weight of 1030000 is weighed and then dissolved in 20 mL of tetrahydrofuran, and 50 μL of the resulting solution is injected into the sample side column. Standard polystyrene samples belonging to Group B with weight average molecular weights of 500, 9100, 102000, and 3480000 were weighed 10 mg, 5 mg, 5 mg, and 5 mg, respectively, dissolved in 50 mL of tetrahydrofuran, and 50 μL of the resulting solution was injected into the sample side column. To do. Standard polystyrene samples belonging to Group C having weight average molecular weights of 2630, 37900, 355000, and 5480000 were weighed 5 mg, 5 mg, 5 mg, and 1 mg, respectively, dissolved in 40 mL of tetrahydrofuran, and 50 μL of the resulting solution was injected into the sample side column. To do. A calibration curve (tertiary equation) is prepared from the retention time of these standard polystyrene samples with a data analysis program GPC workstation (EcoSEC-WS) dedicated to HLC-8320GPC, and this is used as a calibration curve for polystyrene-equivalent weight average molecular weight measurement.
The measurement is performed in an environment with a temperature of 23 ± 2 ° C. and a humidity of 50 ± 5%.

<Measurement of uniaxial elongation viscosity>
Uniaxial extensional viscosity is measured with a viscoelasticity measuring device PHYSICA MCR301 (manufactured by Anton Paar) and a temperature control system CTD450. First, a strip sample having a width of 10 mm and a thickness of about 0.8 mm is prepared using a resin hot press machine at a temperature of 190 ° C. Next, a strip-shaped sample was cut into a length of 20 to 25 mm and set on a uniaxial extensional viscosity measuring jig (SER2) heated to a measurement temperature of 160 ° C., and then 160 ° C. ± 0 in a nitrogen atmosphere. After waiting for 10 seconds at a temperature of 5 ° C., the uniaxial extensional viscosity is measured at a strain rate of 0.1 / second. The measurement point interval is set to “Acquire measurement point interval logarithmically”, and the start is 0.01 seconds and the end is 26 seconds. The measurement point is 300.

<Toluene insoluble matter>
The weight was measured, 10 g of toluene and 0.5 g of a polystyrene-based resin composition for foaming were added to a 30 ml Erlenmeyer flask, and the memory of a shaker TAIYO ROTARY SHAKER R-II (manufactured by Taiyo Kagaku Kogyo Co., Ltd.) was set to 10. Shake at 23 ° C. for 1 hour. After shaking, the insoluble content of toluene is calculated from the difference between the weight after drying the conical flask from which toluene has been removed at 60 ° C. under reduced pressure for 24 hours and the weight of the conical flask before addition.

<Tetrahydrofuran soluble>
When 0.3 g of a polystyrene-based resin is added to 1 liter of tetrahydrofuran and allowed to stand for 72 hours, the case where it is completely dissolved in tetrahydrofuran is marked with ◯, and the case where undissolved residue is caused is marked with ×.

<Measurement of MFR>
Melt mass flow rate (MFR) is a semi-auto melt indexer 2A manufactured by Toyo Seiki Seisakusho Co., Ltd. B) Measured by a method of measuring the time for which the piston moves a predetermined distance described in the method B. The measurement conditions are 3 to 8 g of sample, preheating 270 seconds, load hold 30 seconds, test temperature 200 ° C., test load 49.03 N, and piston moving distance (interval): 25 mm. The number of test of the sample is 3 times, and the average is the value of melt mass flow rate (g / 10 minutes).

<Melting tension>
Measurement is performed using a twin-bore capillary-rheometer-Rheological 5000T (Chiast, Italy). That is, after filling a measurement sample resin in a 15 mm diameter barrel heated to a test temperature of 200 ° C. and preheating for 5 minutes, the capillary die of the above measurement apparatus (caliber 2.095 mm, length 8 mm, inflow angle 90 degrees (conical) ) While keeping the piston descending speed (0.07730 mm / s) constant and extruding it into a string, the string is passed through a tension detection pulley located 27 cm below the capillary die, and then wound up. Using a roll, the winding speed is gradually increased at an initial speed of 3.94388 mm / s and an acceleration of 12 mm / s ² , and the maximum value and minimum value of the tension immediately before the point at which the string-like object is cut are taken. The average value is taken as the melt tension (MT) of the sample resin.

Example 1
(Preparation of seed particles)
In a 106 liter autoclave with a stirrer (hereinafter also referred to as a reactor), as a polymerization initiator, 150 g of benzoyl peroxide (purity 75%, manufactured by NOF Corporation, trade name Nyper BW), t-butylperoxy-2- Dissolve 20 g of ethyl hexyl monocarbonate (trade name Perbutyl E, manufactured by NOF Corporation) in 44 kg of styrene, add 130 g of magnesium pyrophosphate, 6.5 g of sodium dodecylbenzenesulfonate, and 40 kg of distilled water, and then dissolve under stirring at 60 rpm. And dispersed to form a suspension.
Subsequently, the temperature in the autoclave was raised to 90 ° C. and then held at 90 ° C. for 6 hours.

  Then, after stirring at 120 rpm, the temperature in the autoclave was further raised to 120 ° C., held at 120 ° C. for 2 hours, then the temperature in the autoclave was cooled to 60 ° C., the contents were taken out from the autoclave, and dehydrated. -Dried and classified to obtain seed particles composed of a styrene polymer having a particle diameter of 0.5 to 0.8 mm and a weight average molecular weight of 300,000.

(Preparation of polystyrene-based resin composition for foaming)
Next, 12.2 kg of the seed particles, 37.8 kg of distilled water, 160 g of magnesium pyrophosphate, and 22 g of sodium dodecylbenzenesulfonate were placed in an autoclave with a stirrer having an internal volume of 106 liters, and stirred and suspended at 150 rpm.
Next, 2.6 kg of distilled water prepared in advance, 16 g of magnesium pyrophosphate, 4.6 g of sodium dodecylbenzenesulfonate, divinylbenzene as a branching agent (81% pure, manufactured by Nippon Steel Chemical Co., Ltd., trade name DVB-810) 1 A suspension was prepared by stirring 0.6 g and 1.5 kg of styrene with a homomixer, and this suspension was added to a reactor maintained at 75 ° C., and styrene was absorbed by the seed particles for 15 minutes.

Next, 2.1 kg of styrene was added to the reactor over 15 minutes, and the mixture was further left for 15 minutes to be absorbed by the seed particles.
Next, 240 g of benzoyl peroxide (purity 75%, manufactured by NOF Corporation, trade name Nyper BW) and 21 g of t-butylperoxy-2-ethylhexyl monocarbonate (trade name: Perbutyl E, manufactured by NOF Corporation) were used as polymerization initiators. A suspension prepared by dissolving in 2.0 kg of styrene and stirring with a homomixer together with 16 g of magnesium pyrophosphate, 4.6 g of sodium dodecylbenzenesulfonate, and 1.7 g of distilled water was placed in a reactor maintained at 75 ° C. for 15 minutes. Added over.

The temperature inside the reactor was maintained at 75 ° C. for 60 minutes from the start of adding the suspension containing the polymerization initiator to the reactor, and the styrene and the polymerization initiator were absorbed by the seed particles. Thereafter, as a branching agent, a mixture of 13.1 g of divinylbenzene (81% pure, manufactured by Nippon Steel Chemical Co., Ltd., trade name DVB-810) and 34.0 kg of styrene was continuously fed into the reactor for 2 hours and 30 minutes. The temperature in the reactor was continuously raised to 108 ° C. at the end of the styrene supply, and further raised to 112 ° C. in 20 minutes.
Subsequently, the temperature was raised to 125 ° C. and held for 90 minutes, then cooled to 60 ° C., styrene resin particles were taken out, washed, dehydrated, and dried to obtain a polystyrene resin composition for foaming.
The amount of branching agent used was 230 ppm with respect to the polystyrene-based resin composition for foaming.

Example 2
1.6 g of divinylbenzene used for preparing a suspension by stirring with a homomixer is 2.1 g, and 17.1 g of divinylbenzene used when 34 kg of styrene is continuously dropped into the reactor. A polystyrene-based resin composition for foaming was obtained in the same manner as in Example 1 except that the amount was 3 g.
The amount of the branching agent used is 300 ppm with respect to the polystyrene-based resin composition for foaming.

Example 3
1.1 g of divinylbenzene used for preparing a suspension by stirring with a homomixer is 1.1 g, and 13.1 g of divinylbenzene used when 34 kg of styrene is continuously dropped into the reactor. A polystyrene-based resin composition for foaming was obtained in the same manner as in Example 1 except that the amount was 6 g.
The amount of the branching agent used is 150 ppm with respect to the polystyrene-based resin composition for foaming.

Example 4
1.3 g of divinylbenzene used for preparing a suspension by stirring with a homomixer and 1.3 g of divinylbenzene, and 10.9 g of divinylbenzene used for continuously dropping 34 kg of styrene into the reactor are added. A polystyrene-based resin composition for foaming was obtained in the same manner as in Example 1 except that the amount was 6 g.
The amount of branching agent used was 75 ppm with respect to the polystyrene-based resin composition for foaming.

Example 5
In a 106 liter autoclave with a stirrer (hereinafter also referred to as a reactor), as a polymerization initiator, benzoyl peroxide (purity 75%, manufactured by NOF Corporation, trade name Nyper BW) 205 g, t-butylperoxy-2 -Dissolve 20 g of ethylhexyl monocarbonate (trade name Perbutyl E, manufactured by NOF Corporation) and 16.3 g of divinylbenzene (81% pure, manufactured by Nippon Steel Chemical Co., trade name DVB-810) as a branching agent in 44 kg of styrene. did. Next, 130 g of magnesium pyrophosphate, 6.5 g of sodium dodecylbenzenesulfonate, and 40 kg of distilled water were added to the reactor, and then dissolved and dispersed with stirring at 60 rpm to form a suspension.
Subsequently, the temperature in the autoclave was raised to 90 ° C. and then held at 90 ° C. for 6 hours.

Thereafter, stirring was performed at 120 rpm, and the temperature in the autoclave was further increased to 120 ° C. Next, after maintaining at 120 ° C. for 2 hours, the temperature in the autoclave is cooled to 60 ° C., the styrene resin particles are taken out from the autoclave, dehydrated, dried, and classified so that the particle diameter is 0.5 to 0.8 mm. A polystyrene-based resin composition for foaming composed of a range of styrene-based resin particles was obtained.
The amount of the branching agent used is 300 ppm with respect to the polystyrene-based resin composition for foaming.

Example 6
A polystyrene-based resin composition for foaming was obtained in the same manner as in Example 5 except that 16.3 g of divinylbenzene was changed to 21.7 g.
The amount of branching agent used was 400 ppm with respect to the polystyrene-based resin composition for foaming.

Example 7
A polystyrene-based resin composition for foaming was obtained in the same manner as in Example 5 except that 16.3 g of divinylbenzene was changed to 27.2 g.
The amount of the branching agent used is 500 ppm with respect to the polystyrene-based resin composition for foaming.

Example 8
A polystyrene-based resin composition for foaming was obtained in the same manner as in Example 5 except that 16.3 g of divinylbenzene was changed to 10.8 g.
The amount of the branching agent used was 200 ppm with respect to the polystyrene-based resin composition for foaming.

Example 9
A polystyrene resin composition for foaming was obtained in the same manner as in Example 5 and the polystyrene resin composition for foaming except that 16.3 g of divinylbenzene was changed to 5.4 g.
The amount of the branching agent used is 100 ppm with respect to the polystyrene-based resin composition for foaming.

Example 10
A polystyrene resin composition for foaming was obtained in the same manner as in Example 5 except that 16.3 g of divinylbenzene was changed to 13.2 g of light acrylate BP-4EAL (Kyoeisha Chemical Co., Ltd., ethylene oxide adduct diacrylate of bisphenol A). It was.
The amount of the branching agent used is 300 ppm with respect to the polystyrene-based resin composition for foaming.

Example 11
A polystyrene resin composition for foaming was obtained in the same manner as in Example 5 except that 16.3 g of divinylbenzene was changed to 22.0 g of light acrylate BP-4EAL (manufactured by Kyoeisha Chemical Co., Ltd., ethylene oxide adduct diacrylate of bisphenol A). It was.
The amount of the branching agent used is 500 ppm with respect to the polystyrene-based resin composition for foaming.

Comparative Example 1
A polystyrene resin composition for foaming was obtained in the same manner as in Example 5 except that 16.3 g of divinylbenzene was changed to 32.6 g.
The amount of branching agent used was 600 ppm with respect to the polystyrene-based resin composition for foaming.

Comparative Example 2
A polystyrene-based resin composition for foaming was obtained in the same manner as in Example 5 except that 16.3 g of divinylbenzene was changed to 43.5 g.
The amount of the branching agent used is 800 ppm with respect to the polystyrene-based resin composition for foaming.

Comparative Example 3
4.2 g of divinylbenzene used for preparing a suspension by stirring with a homomixer is 4.2 g, and 34 g of divinylbenzene used when 34 kg of styrene is continuously dropped into the reactor. A polystyrene-based resin composition for foaming was obtained in the same manner as in Example 1 except that the amount was 0 g.
The amount of branching agent used was 600 ppm with respect to the polystyrene-based resin composition for foaming.

Comparative Example 4
A polystyrene-based resin composition for foaming was obtained in the same manner as in Example 5 except that 16.3 g of divinylbenzene was changed to 1.6 g.
The amount of branching agent used was 30 ppm with respect to the polystyrene-based resin composition for foaming.

Comparative Example 5
1.6 g of divinylbenzene used for preparing a suspension by stirring with a homomixer is 0.2 g, and 13.1 g of divinylbenzene used when 34 kg of styrene is continuously dropped into the reactor. A polystyrene-based resin composition for foaming was obtained in the same manner as in Example 1 except that the amount was 7 g.
The amount of branching agent used was 30 ppm with respect to the polystyrene-based resin composition for foaming.

Comparative Example 6
A polystyrene-based resin composition for foaming was obtained in the same manner as in Example 5 except that divinylbenzene was not used.
The amount of the branching agent used is 0 ppm with respect to the polystyrene-based resin composition for foaming.

Comparative Example 7
A polystyrene-based resin composition for foaming was obtained in the same manner as in Example 5 except that 16.3 g of divinylbenzene was changed to 1.6 g, 205 g of benzoyl peroxide was changed to 120 g, and the reaction time was changed from 6 hours to 9 hours. .
The amount of branching agent used was 30 ppm with respect to the polystyrene-based resin composition for foaming.

From the above Tables 1 to 3, a polystyrene-based resin composition for foaming containing a base resin showing a specific ratio (a ₁ / a ₂ ) containing a specific amount of a component derived from a polyfunctional vinyl aromatic compound having a specific molecular weight. It can be confirmed that the product has excellent physical properties.

Claims (8)

Including a component derived from a polyfunctional vinyl aromatic compound and a styrene monomer as a base resin,
The polyfunctional vinyl-based aromatic compound has a molecular weight of 100 or more and less than 1000;
The base resin is obtained by polymerizing a monomer mixture containing 50 to 500 ppm of a polyfunctional vinyl aromatic compound in the styrene monomer.
The base resin has a slope (a ₁ ) of a first-order approximation line in a non-linear region in a logarithmic plot of a time-extension viscosity curve obtained by measuring uniaxial extensional viscosity at a temperature of 160 ° C. and a constant strain rate of 0.1 / second. ) And the slope (a ₂ ) of the first-order approximate straight line in the linear region in the above curve is a resin having a ratio (a ₁ / a ₂ ) of more than 2.0 and not more than 6.0 Polystyrene resin composition.   The polystyrene-based resin composition for foaming according to claim 1, wherein the polyfunctional vinyl-based aromatic compound is divinylbenzene.   The said base resin shows the toluene insoluble content amount of 5 mass% or more when the base resin is dissolved in toluene at 23 ° C. for 1 hour so as to have a concentration of 5 mass%. Or the polystyrene-type resin composition for foaming of 2.   The said base resin shows the tetrahydrofuran insoluble content of 0% (complete dissolution) when the base resin is dissolved in tetrahydrofuran at a concentration of 0.3 g / L at 23 ° C. for 72 hours. 4. The polystyrene-based resin composition for foaming according to any one of 3.   The base resin is obtained by suspension polymerization of a branching agent, which is a polyfunctional vinyl aliphatic compound, dispersed in an aqueous suspension and a monomer mixture containing a styrene monomer. The polystyrene-type resin composition for foaming as described in any one of Claims 1-4.   A branching agent, which is a polyfunctional vinyl aliphatic compound, and a monomer mixture containing a styrene monomer are added to polystyrene resin seed particles in which the base resin is dispersed in an aqueous suspension. The polystyrene-type resin composition for foaming as described in any one of Claims 1-4 obtained by supplying or polymerizing intermittently or continuously.   A polystyrene-based resin foam sheet obtained by extrusion foaming the polystyrene-based resin composition according to any one of claims 1 to 6.   A foam molded product obtained using the polystyrene resin foam sheet according to claim 7.