JP7084213B2 - Styrene-based resin composition for extrusion foam, foam sheet, container, and plate-like foam - Google Patents

Description

The present invention relates to a styrene-based resin composition capable of obtaining an extruded foamed sheet and a plate-shaped foam having a high foaming ratio, fine bubble cells, and excellent surface smoothness.

Extruded foam sheets made of styrene resin are widely used in food packaging containers such as grocery trays, lunch boxes, instant noodle containers, natto containers, and cups because of their excellent lightness, rigidity, and moldability. In addition, since the plate-shaped extruded foam of styrene resin has excellent heat insulating properties and mechanical strength, it is used in various fields such as flooring materials such as general buildings, wall materials, ceiling materials, and tatami heart materials. ing.

As a method for improving the appearance, heat insulating property, and strength of the extruded foam sheet or plate-shaped extruded foam, miniaturization of the bubble cell is effective. Generally, inorganic fine particles such as talc and calcium carbonate are used as a foam nucleating agent. As often, the bubble cell is adjusted.

In addition, carbon dioxide or nitrogen as a foaming agent is impregnated into a thermoplastic resin in a supercritical state, and the pressure is rapidly reduced from a pressure higher than the critical pressure to atmospheric pressure to generate bubble nuclei, and then the growth of bubbles is controlled in the cooling process. By doing so, a method for obtaining a fine bubble cell is disclosed (Patent Documents 1 to 3).

Japanese Unexamined Patent Publication No. 10-175249 U.S. Pat. No. 4,473,665 U.S. Pat. No. 5,158,986

However, with the above-mentioned conventional technique, the bubble cell of the extruded foam could not be sufficiently miniaturized.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a styrene-based resin composition for extrusion effervescence capable of miniaturizing bubble cells of an extruded foam.

That is, the present invention is as shown in the following (1) to (9).
(1) A styrene-based resin composition containing a styrene-based resin (A) and a fatty acid amide compound (B) having a melting point of 170 to 300 ° C., the fatty acid amide based on 100% by mass of the styrene-based resin composition. A styrene-based resin composition for extrusion foaming containing 0.001 to 10% by mass of the compound (B).
(2) The styrene-based resin composition for extrusion foaming according to (1) above, wherein the fatty acid amide compound (B) is a condensate of a fatty acid, a diamine, and a dicarboxylic acid.
(3) The styrene-based resin composition for extrusion foaming according to claim 1 or 2, wherein the fatty acid amide compound (B) is N, N'-bis (2-stearoamide ethyl) -sevacamide.
(4) The styrene resin composition for extrusion foaming according to any one of (1) to (3) above, wherein the methanol-soluble content of the styrene resin (A) is 0.2 to 3.0% by mass.
(5) The styrene resin composition for extrusion foaming according to any one of (1) to (4) above, wherein the styrene resin (A) has a weight average molecular weight of 100,000 to 700,000.
(6) The ratio (Mz / Mw) of the Z average molecular weight (Mz) and the weight average molecular weight (Mw) of the styrene resin (A) is 1.5 to 3.5, as described in (1) to (5) above. The styrene resin composition for extrusion foaming according to any one.
(7) A foamed sheet obtained by molding the styrene resin composition for extrusion foaming according to any one of (1) to (6) above.
(8) A container formed by molding the foam sheet according to (7) above.
(9) A plate-shaped foam obtained by molding the styrene resin composition for extrusion foam according to any one of (1) to (6) above.

By using the styrene resin composition for extrusion foaming of the present invention, the bubble cells of the extrusion foam can be miniaturized.

Hereinafter, the present invention will be described in detail.

<Styrene-based resin composition>
The styrene-based resin composition of the present invention contains a styrene-based resin (A) and a fatty acid amide compound (B), and may contain components such as a fatty acid metal salt (C) and inorganic fine particles (D). Details of each component will be described later.

The melt mass flow rate (MFR) of the styrene-based resin composition of the present invention measured under the conditions of 200 ° C. and 49 N load is preferably 0.1 to 30 g / 10 minutes, preferably 0.5 to 25 g / 10 minutes. Is more preferable, and 1 to 15 g / 10 minutes is even more preferable. When the melt mass flow rate (MFR) is less than 0.1 g / 10 minutes, the productivity of the extruded foam deteriorates, and when it exceeds 30 g / 10 minutes, the pressure in the die increases when the amount of the foaming agent is increased. It becomes difficult to maintain, and the foaming ratio may not increase.

The Vicat softening temperature of the styrene resin composition of the present invention is preferably 93 to 130 ° C, more preferably 95 to 125 ° C, still more preferably 100 to 110 ° C. When the Vicat softening temperature is less than 93 ° C., the heat resistance of the extruded foam becomes insufficient, and when the Vicat softening temperature exceeds 130 ° C., the moldability of the extruded foam is lowered.

The Charpy impact strength of the styrene-based resin composition of the present invention is preferably 1.2 kJ / m ² or more, more preferably 1.4 kJ / m ² or more, and further preferably 1.6 kJ / m ² or more. When the Charpy impact strength is less than 1.2 kJ / m ² , the impact resistance of the extruded foam becomes insufficient. The upper limit of the Charpy impact strength is not particularly specified, but is, for example, 2.5 kJ / m ² .

<Styrene resin (A)>
The styrene-based resin (A) of the present invention preferably has a weight average molecular weight (Mw) of 100,000 to 700,000 as measured by gel permeation chromatography (GPC), and more preferably 150,000 to 600,000. preferable. If the Mw is less than 100,000, the strength of the extruded foam is lowered, and if the Mw is more than 700,000, the fluidity is lowered, which is not preferable. The Mw of the styrene resin (A) should be adjusted according to the reaction temperature and residence time of the polymerization step, the type and amount of the polymerization initiator, the type and amount of the chain transfer agent, and the type and amount of the solvent used during the polymerization. Can be done.

The styrene-based resin (A) of the present invention preferably has a ratio (Mz / Mw) of Z average molecular weight (Mz) to weight average molecular weight (Mw) of 1.5 to 3.5, preferably 1.7 to 3. It is more preferably 0.0. If the ratio (Mz / Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) is less than 1.5, the foaming ratio may decrease, and if (Mz / Mw) exceeds 3.5, the foaming ratio may decrease. , The moldability of the extruded foam deteriorates.

The methanol-soluble content of the styrene-based resin (A) of the present invention is preferably 0.2 to 3.0% by mass, more preferably 0.3 to 2.5% by mass, and 0.4 to 0.4 to 2.5% by mass. It is particularly preferably 2.0% by mass. If the methanol-soluble content is less than 0.2% by mass, the moldability of the extruded foam may deteriorate. If the soluble content of methanol exceeds 3.0% by mass, the strength and heat resistance of the foam may decrease. The methanol-soluble component here refers to a component soluble in methanol in the styrene-based resin, for example, other than styrene oligomers (styrene dimer, styrene trimmer) by-produced in the polymerization step and the devolatilization step of the styrene-based resin. Contains various additives such as liquid paraffin and silicon oil, residual styrene monomer, and low molecular weight components such as a polymerization solvent. As a method for adjusting the soluble content of methanol, a method for adjusting the amount of styrene oligomer (styrene dimer, styrene trimmer) generated as a by-product in the polymerization step depending on the type and amount of the initiator, and the amount of liquid paraffin and silicone oil added. There is a method of adjusting by.

The styrene-based resin (A) of the present invention contains a styrene monomer as an essential component (essential contained component) as a raw material, but in addition to the styrene homopolymer, 50% by mass or less of a vinyl-based monomer copolymerizable with styrene is used. It may be included in the ratio of. Examples of vinyl-based monomers include substituted styrenes such as α-methylstyrene and p-methylstyrene, acrylic monomers such as acrylic acid, butyl methacrylate, butyl acrylate and methyl methacrylate, and vinyl cyanide such as acrylonitrile and methacrylonitrile. Monomers, maleic anhydride and the like can be mentioned.

Examples of the polymerization method of the styrene-based resin (A) of the present invention include known styrene polymerization methods such as a bulk polymerization method, a solution polymerization method, and a suspension polymerization method. Further, as the solvent, for example, alkylbenzenes such as benzene, toluene, ethylbenzene and xylene, ketones such as acetone and methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and cyclohexane can be used. As a mode of the reactor, a continuous polymerization method in which a completely mixed reactor, a plug flow reactor, a loop reactor and the like are combined is preferably used.

When producing the styrene-based resin (A) of the present invention, a polymerization solvent, a polymerization initiator such as an organic peroxide, or a chain transfer agent such as an aliphatic mercaptan may be used, if necessary, from the viewpoint of controlling the polymerization reaction. Can be used.

As the polymerization initiator, a radical polymerization initiator is preferable, and for example, 1,1-di (t-butylperoxy) cyclohexane, 2,2-di (t-butylperoxy) butane, 2,2-di (t-butylperoxy) butane, which are known and commonly used, are preferable. Peroxyketals such as di (4,4-di-t-butylperoxycyclohexyl) propane, 1,1-di (t-amylperoxy) cyclohexane, cumenehydroperoxide, t-butylhydroperoxide and the like. Hydroperoxides, alkyl peroxides such as t-butylperoxyacetate, t-amylperoxyisononanoate, t-butylcumyl peroxide, di-t-butyl peroxide, dicumyl peroxide, di-t -Dialkyl peroxides such as hexyl peroxide, peroxyesters such as t-butylperoxyacetate, t-butylperoxybenzoate, t-butylperoxyisopropyl monocarbonate, t-butylperoxyisopropylcarbonate, polyether 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 can be mentioned, and one or a combination of two or more of these can be used. ..

Examples of the chain transfer agent include monofunctional chain transfer agents such as aliphatic mercaptan, aromatic mercaptan, pentaphenylethane, α-methylstyrene dimer and terpinolene, ethylene glycol, tetraethylene glycol, neopentyl glycol and trimethylolpropane. , Pentaerythritol, dipentaerythritol, tripentaerythritol, sorbitol and other polyhydric alcohol hydroxyl groups are esterified with thioglycolic acid or mercaptopropionic acid, and polyfunctional chain transfer agents such as polyfunctional mercaptans are mentioned. Species or a combination of two or more can be used.

<Fatile amide compound (B)>
The fatty acid amide compound (B) of the present invention has a melting point of 170 to 300 ° C., more preferably 180 to 290 ° C., and particularly preferably 200 to 270 ° C. When the melting point is less than 170 ° C., the effect of miniaturizing the bubble cell is small, and when the melting point exceeds 300 ° C., the dispersibility of the fatty acid amide compound (B) in the styrene resin (A) deteriorates, which is not preferable.

The fatty acid amide compound (B) of the present invention is preferably a condensate of a fatty acid, a diamine and a dicarboxylic acid. The melting point can be adjusted by changing the type and amount of fatty acid, diamine, and dicarboxylic acid.

The fatty acid is not limited to, but is not limited to, for example, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, pentadecic acid, stearic acid, hydroxystearic acid, nonadecanoic acid, and araginic acid. , Bechenic acid, lignoseric acid, cellotic acid, heptaconic acid, laxel acid, undecylenic acid, oleic acid, ellagic acid, setreic acid, erucic acid, brushzic acid, linoleic acid, linolenic acid, arachidonic acid, stearolic acid carbon number Examples thereof include monovalent fatty acids of 12 to 27.

The diamine is not limited to the following, but is not limited to, for example, ethylene diamine, propylene diamine, tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, heptamethylene diamine, octamethylene diamine, nonamethylene diamine, decamethylene, and un. Linear aliphatic diamines having 2 to 20 carbon atoms such as decamethylenediamine, dodecamethylenediamine, and tridecamethylenediamine, 2-methylpentamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2-methyl-1, Branched aliphatic diamines having 3 to 20 carbon atoms such as 8-octanediamine and 2,4-dimethyloctamethylenediamine, and alicyclics such as 1,4-cyclohexanediamine, 1,3-cyclohexanediamine and 1,3-cyclopentanediamine. Examples thereof include aromatic diamines such as group diamines, m-xylylene diamines, p-xylylene diamines, p-phenylenediamines and m-phenylenediamines.

The dicarboxylic acid is not limited to the following, but is, for example, malonic acid, dimethylmalonic acid, succinic acid, 2,2-dimethylsuccinic acid, 2,3-dimethylglutaric acid, 2,2-diethyl succinic acid. Acid, 2,3-diethylglutaric acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, Linear or branched aliphatic dicarboxylic acids such as tetradecanedioic acid, hexanedecanedioic acid, octadecanedioic acid, eicosandioic acid, and diglycols having 3 to 20 carbon atoms, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, An aromatic dicarboxylic acid having 8 to 20 carbon atoms substituted with an unsubstituted or predetermined substituent such as 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylterephthalic acid, 5-sodiumsulfoisophthalic acid, etc. Can be mentioned.

Specific examples of the fatty acid amide compound (B) include N, N'-bis (2-stearoamide ethyl) -sevacamide, N, N'-bis (stearoamide ethyl) azelaicamide, N, N'-bis ( Examples thereof include stearoamide-m-xylylene) sebacamide, and N, N'-bis (2-stearoamide ethyl) -sebacamide is particularly preferable. Typical of these are trade names: "Light Amide WH-255" and "Light Amide WH-215" (both manufactured by Kyoeisha Chemical Co., Ltd.). Further, the fatty acid amide compound (B) may be used alone or in combination of two or more.

The fatty acid amide compound (B) is 0.001 to 10% by mass, preferably 0.002 to 9% by mass, preferably 0.005 to 8% by mass, based on 100% by mass of the styrene resin composition. Is more preferable, and 0.01 to 5% by mass is particularly preferable. When the fatty acid amide compound (B) is less than 0.001% by mass, the effect of miniaturizing the bubble cell of the foam cannot be obtained. Further, when the fatty acid amide compound (B) exceeds 10% by mass, the strength, the expansion ratio of the foam, and the heat resistance are lowered, which is not preferable.

In order to obtain the effect of the present invention, it is preferable that the fatty acid amide compound (B) is dispersed in the styrene resin composition in the form of particles. The dispersed particles of the fatty acid amide compound (B) can be observed by, for example, a transmission electron microscope, and the particle size corresponding to the weight average circle of the dispersed particles is preferably 1 to 1000 nm. The dispersed particles of the fatty acid amide compound (B) are considered to act as a nucleating agent in the formation of bubbles in the foam, and when the particle size corresponding to the weight average circle of the dispersed particles is 1 to 1000 nm, the foam The effect of refining the bubble cell is particularly effective. As a method of adjusting the particle size equivalent to the weight average circle of the dispersed particles of the fatty acid amide compound (B), a styrene-based resin composition containing the fatty acid amide compound (B) is melted at a temperature equal to or higher than the melting point of the fatty acid amide compound (B). In the process of cooling to room temperature, a method of adjusting by the cooling rate is effective. If the cooling rate is increased, the coarsening of the dispersed particles can be suppressed, so that the dispersed particles become smaller, and conversely, if the cooling rate is decreased, the dispersed particles can be increased.

<Fataceous acid metal salt (C)>
The fatty acid metal salt (C) of the present invention is a metal of a higher fatty acid represented by the chemical formula R ³ -COOH (R ³ in the formula is an alkyl group having 7 to 21 carbon atoms, an alkenyl group, an alkynyl group, a hydroxyalkyl group). Refers to salt, specifically zinc stearate, calcium stearate, magnesium stearate, aluminum stearate, calcium oleate, calcium palmitate, zinc hydroxystearate, aluminum hydroxystearate, zinc behenate, behenic acid. Examples thereof include calcium and calcium montanate.

The styrene-based resin composition of the present invention preferably has a fatty acid metal salt (C) content of 0 to 0.1% by mass with respect to 100% by mass of the styrene-based resin composition. The content of the fatty acid metal salt (C) is preferably 0 to 0.05% by mass, and more preferably no fatty acid metal salt (C). When the content of the fatty acid metal salt (C) exceeds 0.1% by mass, the effect of reducing the cell diameter of the foam may be inferior. It is considered that the fatty acid metal salt (C) suppresses the formation of fine particles of the fatty acid amide compound (B). In another expression, the content of the fatty acid metal salt (C) / the mass ratio of the fatty acid amide compound (B) is preferably 0.6 or less, more preferably 0.5 or less, and 0.4 or less. Is more preferable, and 0.3 or less is further preferable. When the content of the fatty acid amide compound (B) is relatively high, the miniaturization effect may be exhibited even if the content of the fatty acid metal salt (C) exceeds 0.1% by mass. In that case, By setting the mass ratio to 0.6 or less, the miniaturization effect is more effectively exhibited. The content of the fatty acid metal salt (C) is 0 to 0.1% by mass, and the content of the fatty acid metal salt (C) / the mass ratio of the fatty acid amide compound (B) is 0.6 or less. More preferred.

<Inorganic fine particles (D)>
The inorganic fine particles (D) of the present invention are fine particles of an inorganic compound, and examples thereof include talc, calcium carbonate, and clay.

The average particle size of the inorganic fine particles (D) is, for example, 0.1 to 100 μm, preferably 0.5 to 30 μm, more preferably 1 to 20 μm, still more preferably 5 to 15 μm. The average particle size of the inorganic fine particles (D) means the particle size at an integrated value of 50% in the particle size distribution obtained by the laser diffraction / scattering method.

The content of the inorganic fine particles (D) in the styrene-based resin composition is preferably 0.01 to 10% by mass, preferably 0.02 to 5% by mass, based on 100% by mass of the styrene-based resin composition. More preferably, 0.05 to 1% by mass is further preferable, and 0.1 to 0.5% by mass is further preferable.

<Other additives>
The styrene resin composition of the present invention contains, as additives, antioxidants such as phosphorus, phenol and amine, plasticizers such as liquid paraffin, silicone oil and polyethylene wax, ultraviolet absorbers and antistatic agents. Flame retardants, colorants, pigments, deodorants, antifogging agents and the like can be added as needed.

<Manufacturing method of styrene resin composition>
The method for producing the styrene-based resin composition of the present invention is not particularly limited, and a known blending method can be used. For example, a method of dry blending with a tumbler, a henschel mixer, a hopper blender, etc., and melting compounding with a single-screw extruder, a twin-screw extruder, a multi-screw screw extruder, a Banbury mixer, a kneader, etc. can be mentioned. A method in which a masterbatch in which the compound (B) is adjusted in an amount larger than a predetermined amount is prepared in advance and blended with the styrene resin (A) at the time of producing the foam, or the fatty acid amide compound (B) is mixed with the styrene resin (B). A method of adhering to the pellet surface of A) and adding it can also be adopted.

For the purpose of increasing heat resistance, strength, and oil resistance, another thermoplastic resin or rubber reinforcing material can be added to the styrene-based resin composition of the present invention as long as the effects of the present invention are not impaired.

Specific examples of the thermoplastic resin include polyolefin resins such as polypropylene and propylene-α-olefin copolymers, polyphenylene ether, modified polyphenylene ether, poly L-lactic acid, poly D-lactic acid, poly D and L-lactic acid. Examples thereof include aliphatic polyester resins, and one type or a combination of two or more of these can be used.

Specific examples of the rubber reinforcing material include natural rubber, polybutadiene, polyisoprene, polyisobutylene, polychloroprene, polysulfide rubber, thiocol rubber, acrylic rubber, urethane rubber, silicone rubber, epichlorohydrin rubber, styrene-butadiene block copolymer, and the like. Styrene-butadiene-styrene copolymer, styrene-isoprene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-butadiene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, hydrogen Styrene-based rubber such as added styrene-isoprene block copolymer and hydrogenated styrene-isoprene-styrene block copolymer, and olefin-based rubber such as ethylene propylene rubber, ethylene propylene diene rubber, and linear low-density polyethylene-based elastomer. Or butadiene-acrylonitrile-styrene-coreshell rubber, methylmethacrylate-butadiene-styrene-coreshell rubber, methylmethacrylate-butylacrylate-styrene-coreshell rubber, octylacrylate-butadiene-styrene-coreshell rubber, alkylacrylate-butadiene-acrylonitrile-styrene -Core-shell rubber and high-impact polystyrene can be mentioned, and one or a combination of two or more of these can be used.

<Manufacturing method of foam sheet and container>
The styrene-based resin composition of the present invention can be processed into a foamed sheet by using a known method for producing an extruded foamed sheet. Specifically, two single-screw extruders and twin-screw extruders are arranged in series, and the resin temperature is 120 by melting and kneading with a foaming agent in the first extruder and cooling in the second extruder. Examples thereof include a method in which the temperature is adjusted to ℃ to 180 ° C., and then the mixture is released into the atmosphere with a circular die and foamed under reduced pressure.

Examples of the effervescent agent include aliphatic hydrocarbons such as propane, normal butane, isobutane, pentane, and hexane, cyclic aliphatic hydrocarbons such as cyclobutane and cyclopentane, trichlorofluoromethane, dichlorodifluoromethane, 1,1-difluoroethane, and the like. Physical foaming agents such as halogenated hydrocarbons such as 1,1-difluoro-chloride and methylene chloride can be used. Further, a decomposable foaming agent such as azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, sodium bicarbonate and citric acid, an inorganic gas such as carbon dioxide and nitrogen, and water can also be used. Although these foaming agents can be appropriately mixed and used, butane is often used industrially, and is a mixture of isobutane and normal butane from the viewpoint of foam extrudability, secondary moldability of foam sheet, and foamability. It is preferable to use butane. Since butane has a slow permeation rate with respect to polystyrene resin, it usually remains in the foamed sheet in an amount of about 0.5 to 3% by mass immediately after foam extrusion. Since this residual amount affects the secondary foam thickness and thermoforming property in the secondary molding, it is appropriately adjusted by providing a certain aging period.

The thickness of the foamed sheet of the present invention is preferably 0.5 to 4.0 mm, more preferably 1.0 to 3.0 mm. If the thickness of the foam sheet is less than 0.5 mm, the strength and heat insulating properties of the container after the secondary molding are lowered. When the thickness of the foamed sheet exceeds 4.0 mm, temperature unevenness of the sheet is likely to occur during secondary molding, and the moldability deteriorates.

The density of the foamed sheet of the present invention is preferably 30 to 500 kg / m ³ , and more preferably 50 to 300 kg / m ³ . If the density of the extruded foam sheet is less than 30 kg / m ³ , the strength is lowered, and if it exceeds 500 kg / m ³ , the heat insulating property is insufficient.

The average cell diameter X in the thickness direction, the average cell diameter Y in the extrusion direction, and the average cell diameter Z in the width direction of the foamed sheet of the present invention are preferably 0.01 to 500 μm, respectively, and are 0.1 to 300 μm, respectively. It is more preferable to have. If the average cell diameter is less than 0.01 μm, the density of the extruded foamed sheet increases, which is not preferable in terms of heat insulating properties. When the average cell diameter exceeds 500 μm, the strength, heat insulating property, and planar smoothness of the foamed sheet are lowered.

Further, in the foamed sheet of the present invention, a surface layer called a so-called skin layer, which has a higher density than the central portion in the thickness direction, can be provided on the front and back surfaces of the sheet. By providing a skin layer, the strength of the sheet can be increased and the appearance is beautifully finished. The skin layer can be adjusted by air cooling the surface of the foam sheet immediately after leaving the circular die.

The foamed sheet of the present invention can be improved in moldability, strength and rigidity by laminating a thermoplastic resin sheet or a film on one side or both sides thereof. The thermoplastic resins constituting the sheets and films include polystyrene-based resins such as polystyrene and high-impact polystyrene, polypropylene-based resins, polyester-based resins, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ethylene-vinyl acetate. Examples thereof include a copolymer, but a polystyrene-based resin that can be laminated without using an adhesive layer and has good recyclability is preferable.

The thickness of the thermoplastic resin sheet or film laminated as described above is not particularly limited, but is preferably 10 to 300 μm, more preferably 50 to 250 μm, and particularly preferably 70 to 200 μm. A thick sheet or film is advantageous for deep drawing, but if it is too thick, the weight of the container increases, which is not desirable.

The foamed sheet of the present invention can be secondarily molded into a container such as a tray, an instant noodle container, a natto container, a cup, etc. by thermoforming such as vacuum forming or pressure forming.

<Manufacturing method of plate-shaped foam>
The styrene-based resin composition of the present invention can be processed into a plate-shaped foam by using a die having a slit having a rectangular cross section instead of a circular die in the above-mentioned method for producing an extruded foam sheet.

Further, when producing a plate-shaped foam, a known flame retardant can be used, for example, hexabromocyclododecane, dibromoneopentyl glycol, decabromodiphenyloxide, tetrabromobisphenol A, tetrabromophthalic acid. Examples thereof include brominated flame retardants such as diol, tetrabromophenol and polypentabromobenzyl acrylate, and phosphorus flame retardants such as guanyated urea phosphate, polyphosphazene, ammonium phosphate, ammonium polyphosphate and red phosphorus.

The density of the plate-shaped foam of the present invention is preferably 5 to 100 kg / m ³ , and more preferably 10 to 50 kg / m ³ . If the density of the plate-shaped foam is less than 5 kg / m ³ , the strength is lowered, and if it exceeds 100 kg / m ³ , the heat insulating property is insufficient.

Since the plate-shaped foam of the present invention is excellent in strength and heat insulating properties, it can be suitably used for floor materials such as general buildings, wall materials, ceiling materials, and core materials for tatami mats.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

<Manufacturing of styrene resins A-1 to A-3>
(1) Production of Styrene-based Resin A-1 The following first to third reactors were connected in series to form a polymerization step.

1st reactor: Completely mixed reactor with stirring blade of 39 L volume 2nd reactor: Completely mixed reactor with stirring blade of 39 L volume 3rd reactor: Plug flow reactor with static mixer of 16 L volume

The conditions for each reactor were as follows.

First reactor: [Reaction temperature] 117 ° C
Second reactor: [Reaction temperature] 125 ° C
Third reactor: [Reaction temperature] Adjusted so that a temperature gradient of 130 to 140 ° C is formed in the flow direction.

The following materials were used as the raw material liquid.

Raw material solution in which 0.02 parts by mass of 1,1-di (t-butylperoxy) cyclohexane was mixed with 90 parts by mass of styrene and 10 parts by mass of ethylbenzene.

The raw material liquid was continuously supplied to the first reactor set at 117 ° C. at a supply rate of 13.5 kg / hr for polymerization, and then continuously charged into the second reactor set at 125 ° C. for polymerization. .. The polymerization conversion rate at the outlet of the second reactor was 55%. Further, the polymerization was allowed to proceed until the polymerization conversion rate reached 70% in the third reactor adjusted so as to have a temperature gradient of 130 to 140 ° C.
This polymerization solution was introduced into a vacuum devolatilization tank equipped with a preheater composed of two stages in series, and unreacted styrene and ethylbenzene were separated, extruded into strands, cooled, and then cut into pellets. The temperature of the first stage preheater is set to 200 ° C., the pressure of the vacuum devolatilization tank is set to 66.7 kPa, the temperature of the second stage preheater is set to 240 ° C., and the pressure of the vacuum devolatilization tank is set. Was 0.9 kPa. The characteristics of the obtained styrene resin A-1 are shown in Table 1.

(2) Production of styrene resin A-2 A except that the temperature conditions of the 1st to 3rd reactors were changed as follows using the following raw material liquids and the supply speed of the raw material liquid was set to 17.6 kg / hr. It was the same as the production of -1. The characteristics are shown in Table 1.

<Raw material solution>
Raw material liquid in which 90 parts by mass of styrene and 10 parts by mass of ethylbenzene are mixed.

<Conditions>
First reactor: [Reaction temperature] 150 ° C
Second reactor: [Reaction temperature] 156 ° C
Third reactor: [Reaction temperature] Adjusted so that a temperature gradient of 170 to 180 ° C is formed in the flow direction.

(3) Production of styrene resin A-3 Using the following raw material liquid, the temperature conditions of the first to third reactors were changed as follows, the supply speed of the raw material liquid was set to 16.5 kg / hr, and the third reaction. The same as the production of A-1 was carried out except that liquid paraffin was added in an amount of 0.8% by mass based on 100% by mass of the resin at the outlet of the reactor. The characteristics are shown in Table 1.

<Raw material solution>
Raw material liquid in which 90 parts by mass of styrene and 10 parts by mass of ethylbenzene are mixed.

<Conditions>
First reactor: [Reaction temperature] 130 ° C
Second reactor: [Reaction temperature] 150 ° C
Third reactor: [Reaction temperature] Adjusted so that a temperature gradient of 140 to 150 ° C is formed in the flow direction.

<Examples 1 to 9, Comparative Examples 1 to 3>
The styrene resins (A-1 to A-3) produced by the above method and the fatty acid amide compounds (B-1 to B-3) are mixed in a mass% ratio shown in Tables 2 to 3 with a Henschel mixer. The melt compound was used in a twin-screw extruder (KTX30α manufactured by Kobe Steel, Ltd.) set at 150 to 210 ° C. The die resin temperature at this time was 220 ° C. The resin properties are shown in Tables 2 and 3.

The following was used as the fatty acid acid amide compound (B).
<Fatile amide compound (B)>
B-1: N, N'-bis (2-stearoamide ethyl) -sebacamide (Light Amide WH-255 manufactured by Kyoei Kagaku Co., Ltd.)
Melting point: 252 ° C
B-2: N, N'-bis (2-stearoamide ethyl) -sebacamide (Light Amide WH-215 manufactured by Kyoei Kagaku Co., Ltd.)
Melting point: 210 ° C
B-3: Ethylene bisstearic acid amide (Kao-Wax EBFF)
Melting point: 140 ° C

Next, extruded foam sheets were manufactured by tandem extruders having screw diameters of 40 mmφ and 50 mmφ. First, the melt-compounded resin was supplied to an extruder having a screw diameter of 40 mmφ. Further, butane gas as a foaming agent was press-fitted from the tip of the extruder at a ratio of 2.0 parts by mass with respect to 100 parts by mass of the resin and melt-mixed. At this time, the cylinder temperature was 230 to 270 ° C, the resin temperature was 235 to 250 ° C, and the pressure was 12 to 18 MPa.
After that, it is transferred to an extruder having a screw diameter of 50 mmφ via a connecting pipe set at 210 ° C., the cylinder temperature is adjusted to 150 to 170 ° C., the resin temperature at the outlet is adjusted to 140 ° C., and the resin pressure is adjusted to 15 MPa. An extruded foam sheet was obtained by extruding from a circular die having a diameter of 6 mm and a diameter of 40 mm at a discharge rate of 10 kg / hr along with a cylinder having a diameter of 152 mm and incising with a cutter at one point at the lower part of the circumference. The characteristics are shown in Tables 2 and 3.

<Example 10>
In the above embodiment, hexabromocyclododecane is blended by 4 parts by mass with respect to 100 parts by mass of the melt-compounded resin, then supplied to an extruder having a screw diameter of 40 mmφ, and butane gas is press-fitted by 5.0 parts by mass to have a screw diameter. Adjust the resin temperature at the outlet of the 50 mmφ extruder to 120 ° C and the resin pressure to 12 MPa, change to a circular die, and use a die with a rectangular cross section of 4 mm in thickness and 40 mm in width, and extrude in a plate shape. A foam was obtained. The characteristics are shown in Table 3.

Various physical properties and performance evaluations were performed by the following methods.

The resin properties were evaluated by the following method.
(1) Molecular Weight The number average molecular weight (Mn), weight average molecular weight (Mw), and Z average molecular weight (Mz) were measured by gel permeation chromatography (GPC) under the following conditions.
GPC model: Showa Denko Corporation Shodex GPC-101
Column: Polymer Laboratories PLgel 10 μm MIXED-B
Mobile phase: Tetrahydrofuran Sample concentration: 0.2% by mass
Temperature: Oven 40 ° C, inlet 35 ° C, detector 35 ° C
Detector: Differential refractometer In the measurement of the molecular weight of the present invention, the molecular weight at each elution time was calculated from the elution curve of monodisperse polystyrene, and the molecular weight was calculated as the polystyrene equivalent.
(2) Methanol-soluble content The methanol-soluble content was measured under the following conditions. 1.00 g of styrene-based resin is precisely weighed (P), 40 ml of methyl ethyl ketone is added to dissolve it, and 400 ml of methanol is rapidly added to precipitate and precipitate an insoluble methanol (resin component). After allowing to stand for about 10 minutes, it was gradually filtered through a glass filter to separate the methanol-soluble component, dried under reduced pressure at 120 ° C. for 2 hours in a vacuum dryer, then allowed to cool in a desiccator for 25 minutes, and dried. The mass N of the insoluble matter of methanol is measured and determined as follows.
Methanol-soluble content (% by mass) = (PN) / P × 100
(3) Content of fatty acid amide compound (B) The content of the fatty acid amide compound (B) in the resin composition was measured under the following conditions. First, the styrene-based resin composition was frozen and pulverized, weighed 0.05 g, and then dissolved and constant volume in 25 mL of chloroform. Next, the obtained solution was diluted with chloroform, the diluted solution was adjusted, filtered through a PTFE disk filter (0.45 μm), and measured by LC / MS / MS analysis under the following conditions.
LC: LC20A (Shimadzu Corporation)
MS: API4000 (AB / MDS Six)
Column: Cadenza CD-C18 2.0 x 150 mm 3 μm
Column temperature: 45 ° C
Mobile phase: A = 0.1 vol% formic acid, water / methanol = 1/9 solution
B = chloroform flow rate: 0.3 mL / min
Injection volume: 3 μL
Ionization: ESI method MS detection: Cation extraction (SRM method)
The commercially available fatty acid amide compound is usually a mixture of components having different chain lengths (for example, in the case of ethylene bisstearic acid amide, a mixture of C16-C16, C16-C18, and C18-C18). .. Therefore, a calibration curve for each component having a different chain length is prepared from the component ratio for each chain length obtained in advance by GC or the like, the quantitative values of each component are calculated individually, and the total amount thereof is used as the amount of the fatty acid amide compound. do.
(4) Melt mass flow rate Obtained based on JIS K7210 under the conditions of 200 ° C. and 49N load.
(5) Vicat softening temperature A test piece was prepared using an injection molding machine, and the temperature was determined based on JIS K7206 under the condition of a 50 N load.
(6) Charpy impact strength A test piece was prepared using an injection molding machine and obtained by JIS K7111.

The foam properties were evaluated by the following method.
(7) Thickness Except for 5 mm at both ends of the extruded foam, the measurement points were located at intervals of 10 mm in width. Using a dial thickness gauge Peacock Model G (manufactured by Ozaki Works Paper Gauge), measure this measurement point to a minimum unit of 0.01 mm, taking care not to deform the test piece, and use this average value for the extruded foam. The thickness was (mm).
(8) Density A test piece of 10 cm in length × 10 cm in width was carefully cut out from the extruded foam so as not to break the cell structure of the material, and calculated from the weight and thickness of the test piece by the following formula.
Density (kg / m ³ ) = weight of test piece (g) / thickness of test piece (mm) x 100
(9) Effervescence Magnification The effervescence ratio of the extruded foam was the value obtained by dividing the density of the base polystyrene resin (1,050 kg / m ³ ) by the density of the extruded foam obtained above.
(10) Average cell diameter The average cell diameter X in the thickness direction, the average cell diameter Y in the extrusion direction, and the average cell diameter Z in the width direction of the foamed foam are based on the average chord length measured by the test method of ASTM D2842-06. Was calculated.
The average cell diameter X in the thickness direction draws a vertical straight line over the entire thickness of the foam in the vertical cross section in the extrusion direction observed with a scanning electron microscope, and is an average chord based on the length of the straight line and the number of cells intersecting the straight line. The length X1 was obtained and calculated from X1 / 0.616.
The average cell diameter Y in the extrusion direction is obtained by dividing the vertical cross section in the extrusion direction observed with a scanning electron microscope into four equal parts in the thickness direction, and in each of a total of three line segments near the surface layer, the central portion in the thickness direction, and the back surface. , The average chord length Y1 is obtained from the length of the straight line and the number of cells intersecting the straight line, the average cell diameter of each line segment is calculated from Y1 / 0.616, and the average cell in the extrusion direction is used as the arithmetic average value. The diameter was Y.
The average cell diameter Z in the width direction divides the vertical cross section in the width direction observed with a scanning electron microscope into four equal parts in the thickness direction, and in each of a total of three line segments near the surface layer, the central part in the thickness direction, and the back surface. , The average chord length Z1 is obtained from the length of the straight line and the number of cells intersecting the straight line, the average cell diameter of each line segment is calculated from Z1 / 0.616, and the average cell in the width direction is used with these arithmetic average values. The diameter was Z.
(11) Gloss Based on JIS K7105, the upper and lower surfaces (in the case of a foam sheet, the contact surface and the non-contact surface of the cooling mandrel) were measured under the condition of an incident angle of 60 degrees, and the average value was taken as the gloss. The higher the glossiness, the better the smoothness of the surface.

By using the styrene-based resin composition of the example, the bubble cell diameter can be made finer while maintaining a low foam density, and the obtained foam has excellent surface smoothness.

By using the styrene-based resin composition of the present invention, it is possible to obtain a foamed sheet and a plate-shaped foam having a high foaming ratio and fine bubble cells, and the heat insulating property, strength and plane smoothness of the foam are higher than those in the past. Can improve sex.

Claims (7)

A styrene-based resin composition containing a styrene-based resin (A) and a fatty acid amide compound (B) having a melting point of 170 to 300 ° C., wherein the fatty acid amide compound (B) is based on 100% by mass of the styrene-based resin composition. ) In an amount of 0.001 to 10% by mass , and the fatty acid amide compound (B) is N, N'-bis (2-stearoamide ethyl) -sebacamide, a styrene-based resin composition for extrusion foaming. The styrene-based resin composition for extrusion foaming according to claim 1 , wherein the methanol-soluble content of the styrene-based resin (A) is 0.2 to 3.0% by mass. The styrene-based resin composition for extrusion foaming according to claim 1 or 2 , wherein the styrene-based resin (A) has a weight average molecular weight of 100,000 to 700,000. Any one of claims 1 to 3 , wherein the ratio (Mz / Mw) of the Z average molecular weight (Mz) and the weight average molecular weight (Mw) of the styrene resin (A) is 1.5 to 3.5. The styrene resin composition for extrusion foaming according to the above. A foamed sheet obtained by molding the styrene resin composition for extrusion foaming according to any one of claims 1 to 4 . A container formed by molding the foam sheet according to claim 5 . A plate-shaped foam obtained by molding the styrene resin composition for extrusion foam according to any one of claims 1 to 4 .