JP2023158345A - Method for manufacturing polystyrene-based resin extrusion foam plate - Google Patents

Abstract

To provide a method for manufacturing a polystyrene-based resin extrusion foam plate which can maintain low thermal conductivity over a long period of time, is excellent in manufacturing stability and has good appearance.SOLUTION: A method for manufacturing a polystyrene-based resin extrusion foam plate having apparent density of 20 kg/m3 or more and 50 kg/m3 or less includes a step of extrusion foaming a foamable molten resin composition obtained by kneading a base material resin containing a polystyrene-based resin as a main component, a flame retardant and a physical foaming agent, and molding the molten resin composition into a plate shape, wherein the physical foaming agent contains a foaming agent A composed of 1,1,1,4,4,4-hexafluoro-2-butene, a foaming agent B composed of dialkyl ether having 1 to 3 carbon atoms, and a foaming agent C composed of water and/or aliphatic alcohol having 1 to 5 carbon atoms, the total addition amount of the physical foaming agent is 0.9 mol or more and 1.8 mol or less with respect to 1 kg of the base material resin, an addition amount of the foaming agent A is 0.2 mol or more with respect to 1 kg of the base material resin, an addition amount of the foaming agent B is 0.05 mol or more and 0.8 mol or less with respect to 1 kg of the base material resin, an addition amount of the foaming agent C is 0.1 mol or more and 0.7 mol or less with respect to 1 kg of the base material resin, and the total of the addition amount of the foaming agent A and the addition amount of the foaming B with respect to 100 mol% of the total addition amount of the physical foaming agent is 50 mol% or more.SELECTED DRAWING: None

Description

Application for application of Article 30, Paragraph 2 of the Patent Act Publisher: Invention Promotion Association Publication: Invention Promotion Association Public Technical Report Public Technical Number: 2021-500600 Publication date: April 19, 2021

The present invention relates to a method for producing an extruded polystyrene foam board, and more particularly, to a method for producing an extruded polystyrene foam board that can be suitably used as a heat insulating material for walls, floors, roofs, etc. of buildings.

Polystyrene resin extruded foam board (hereinafter also simply referred to as "foam board") has excellent heat insulation properties and mechanical strength, and is therefore widely used as a thermal insulation material for buildings. Such plate-shaped foam boards are generally produced by heating and melting polystyrene resin in an extruder, then press-feeding a physical foaming agent into the resulting melt and kneading it. It is manufactured by extruding it into a low-pressure region through a flat die attached to the tip of the machine, foaming it, and then forming it into a plate shape using a molding tool.

In recent years, there has been an increasing demand for energy saving in houses, buildings, etc., and there is an increasing demand for polystyrene resin extruded foam boards with excellent heat insulation properties. One of the methods for manufacturing extruded polystyrene resin foam board with excellent heat insulation properties is to use hydrofluoroolefins (such as 1,3,3,3-tetrafluoropropene and 1-chloro-3,3,3-trifluoropropene). Hereinafter, a foaming agent consisting of "HFO" (also simply referred to as "HFO") is used (for example, Patent Documents 1 and 2). These HFOs are nonflammable, have low thermal conductivity, and can provide high heat insulation properties. Furthermore, it is an environmentally friendly blowing agent because it has very low ozone layer depletion potential and global warming potential.

In Patent Documents 1 and 2, 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz) is used as HFO alone or in combination with other blowing agents. HFO-1336mzz used in these Patent Documents 1 and 2 has an excellent effect of keeping the thermal conductivity of the foam board low for a long period of time (long-term low thermal conductivity). Therefore, it is desired to produce a foam board that can maintain low thermal conductivity by using HFO-1336mzz as a foaming agent.

Special Publication No. 2010-522808 Special table 2019-515112 publication

However, when manufacturing foam boards, if the amount of HFO-1336mzz added is set excessively in an attempt to maintain a low thermal conductivity, there is a problem that the foaming agent separates from the resin, deteriorating moldability, and There was a problem in that moldability deteriorated depending on the blending ratio when -1336mzz and other blowing agents were used in combination. As mentioned above, when HFO-1336mzz was used, manufacturing stability was poor, and there was a possibility that a foam board with a good appearance could not be obtained.

The present invention has been made in view of this background, and an object of the present invention is to provide a method for manufacturing a polystyrene resin foam board that can maintain low thermal conductivity over a long period of time, has excellent manufacturing stability, and has a good appearance. The challenge is to

According to the present invention, the following method for manufacturing an extruded polystyrene resin foam board is provided.

[1] Apparent density: 20 kg/m, including the step of extruding and foaming a foamable molten resin composition obtained by kneading a base resin mainly composed of polystyrene resin, a flame retardant, and a physical foaming agent and molding it into a plate shape. A method for producing an extruded polystyrene resin foam board having a weight of ³ or more and 50 kg/m and ³ or less,
The physical blowing agents include a blowing agent A consisting of 1,1,1,4,4,4-hexafluoro-2-butene, a blowing agent B consisting of a dialkyl ether having 1 to 3 carbon atoms, and water and/or A blowing agent C consisting of an aliphatic alcohol having 1 to 5 carbon atoms,
The total amount of the physical foaming agent added is 0.9 mol or more and 1.8 mol or less per 1 kg of the base resin,
The amount of the blowing agent A added is 0.2 mol or more per 1 kg of base resin,
The amount of the blowing agent B added is 0.05 mol or more and 0.8 mol or less per 1 kg of base resin,
The amount of the foaming agent C added is 0.1 mol or more and 0.7 mol or less per 1 kg of base resin,
Production of an extruded polystyrene resin foam board, characterized in that the total amount of the foaming agent A and the foaming agent B added is 50 mol% or more with respect to the total amount of the physical foaming agent added of 100 mol%. Method.

[2] The method for producing an extruded polystyrene resin foam board according to the invention [1] above, characterized in that the amount of the blowing agent A added is 0.2 mol or more and 0.7 mol or less per 1 kg of base resin. do.

[3] In the method for producing an extruded polystyrene resin foam board according to the invention [1] or [2], the molar ratio between the amount of the foaming agent B added and the amount of the foaming agent C added (foaming agent B: foaming The ratio of agent C) is 25:75 to 90:10.

[4] In the method for producing an extruded polystyrene foam board according to the invention according to any one of [1] to [3], the blowing agent C contains 60 to 95 mol% of water and 5 to 40 mol% of carbon atoms. It is characterized by being an aliphatic alcohol having 1 to 5 carbon atoms (however, the total of water and aliphatic alcohol having 1 to 5 carbon atoms is 100 mol%).

[5] The method for producing an extruded polystyrene foam board according to any one of the inventions [1] to [4], characterized in that the extruded polystyrene foam board has a thickness of 20 mm or more.

According to the manufacturing method of the present invention, it is possible to provide a method for manufacturing a polystyrene resin foam board that can maintain low thermal conductivity over a long period of time, has excellent manufacturing stability, and has a good appearance.

Hereinafter, the method for producing an extruded polystyrene foam board of the present invention will be explained in detail.
The method for producing an extruded polystyrene foam board of the present invention involves extruding and foaming a foamable resin composition obtained by kneading a base resin mainly composed of polystyrene resin, a flame retardant, and a physical foaming agent, and forming it into a board shape. The method includes the step of manufacturing an extruded polystyrene resin foam board having an apparent density of 20 kg/m ³ or more and 50 kg/m ³ or less.

Specifically, a base resin consisting of polystyrene resin and other resins added as necessary, a flame retardant, and other additives added as necessary are melted under heat in an extruder. , a physical foaming agent is press-injected into the resulting melt-kneaded product, which is further kneaded to form a foamable resin melt, the foamable resin melt is adjusted to an appropriate foaming temperature, and then extruded at high pressure through a flat die. The foam is extruded from inside the machine into a low pressure area, and the mold is placed at the outlet of a flat die (for example, two pieces of polytetrafluoroethylene resin are placed in parallel or in a manner that gently expands from the inlet to the outlet). A shaping device (hereinafter also referred to as a guider) consisting of plates such as the above and forming tools such as forming rolls are arranged, and the extruded foamed composition is formed into a plate shape by passing through the forming tools. .

In the present invention, the following specific components (1,1,1,4,4,4-hexafluoro-2-butene, dialkyl ether having 1 to 3 carbon atoms, water and/or fat having 1 to 5 carbon atoms) are used. By using a physical foaming agent containing a specific amount of alcohol (group alcohol), it is possible to maintain low thermal conductivity for a long period of time, and it is possible to obtain a foamed board with excellent production stability and good appearance.

<Base material resin>
(Polystyrene resin)
Examples of the polystyrene resin used in the production method of the present invention include polystyrene (general purpose polystyrene: GPPS), styrene-methyl acrylate copolymer containing 50 mol% or more of styrene unit components, and styrene-ethyl acrylate copolymer. , styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-maleic anhydride copolymer, styrene-polyphenylene ether copolymer one or two selected from styrene-acrylonitrile copolymer, styrene-methylstyrene copolymer, styrene-dimethylstyrene copolymer, styrene-ethylstyrene copolymer, styrene-diethylstyrene copolymer, etc. The above can be exemplified, and among these, polystyrene can be preferably used. Note that the polystyrene resin may contain a unit component formed by a branching agent such as a polyfunctional monomer or a polyfunctional macromonomer. The content of styrene component units in the copolymer is preferably 60 mol% or more, more preferably 80 mol% or more, and still more preferably 90 mol% or more.

The melt viscosity of the polystyrene resin used in the production method of the present invention is preferably 500 to 3000 Pa·s, more preferably 1000 to 2500 Pa·s, and still more preferably 1200 Pa·s, since it has excellent foamability and moldability. ~2300Pa・s. In this specification, melt viscosity is a value measured at a temperature of 200° C. and a shear rate of 100 sec ⁻¹ based on JIS K7199:1999.

(Other polymers)
The base resin may contain a polymer other than the polystyrene resin within the range in which the objects and effects of the present invention are achieved. Other polymers include polyethylene resins (one type or a mixture of two or more selected from the group of ethylene homopolymers and ethylene copolymers with an ethylene unit component content of 50 mol% or more), polypropylene resins (One or a mixture of two or more selected from the group of propylene homopolymers and propylene copolymers with a propylene unit component content of 50 mol% or more), polyphenylene ether resin, polymethyl methacrylate, amorphous Thermoplastic resins such as polyethylene terephthalate resins (heat of fusion less than 5 J/g: measured by heat flux differential scanning calorimetry in JIS K7122-1987), styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene Examples include thermoplastic elastomers such as block copolymers, hydrogenated styrene-butadiene-styrene block copolymers, hydrogenated styrene-isoprene-styrene block copolymers, and styrene-ethylene copolymers. These other polymers can be blended within a range that does not impede the objective effects of the present invention.

In addition, in the manufacturing method of the present invention, the base resin whose main component is polystyrene resin means that 50% by mass or more of the base resin is polystyrene resin, preferably 70% by mass or more, and more. Preferably it is 80% by mass or more, more preferably 90% by mass or more.

<Physical foaming agent>
The physical blowing agents used in the present invention are a blowing agent A made of 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz) and a blowing agent A made of a dialkyl ether having 1 to 3 carbon atoms. The agent B and the blowing agent C consisting of water and/or an aliphatic alcohol having 1 to 5 carbon atoms are essential components.

(Blowing agent A)
Among hydrofluoroolefins, 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz), which is the blowing agent A, has moderate solubility in polystyrene resins and excellent foaming properties. It is possible to produce a foamed board that remains in the body and has excellent low thermal conductivity over a long period of time. Furthermore, since it is non-flammable, the risk of ignition due to static electricity during foam board manufacturing can be reduced. Furthermore, it has a low ozone depletion potential and a very low global warming potential, making it a blowing agent that places less of a burden on the environment.

(Blowing agent B)
Examples of the dialkyl ether having 1 to 3 carbon atoms as the blowing agent B include dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, etc., and these may be used alone or in combination of two or more. I can do it. From the viewpoint of improving production stability, dimethyl ether can be preferably used among these. Note that the dialkyl ether having 1 to 3 carbon atoms means a dialkyl ether having 1 to 3 carbon atoms in the alkyl chain.

By using dialkyl ether with 1 to 3 carbon atoms together with blowing agent A, it has excellent low thermal conductivity over a long period of time, has excellent surface smoothness, suppresses the occurrence of gas spots, and has excellent manufacturing stability. The present invention can be used as a method for manufacturing an extruded foam board.

(Blowing agent C)
The blowing agent C is at least one of water and an aliphatic alcohol having 1 to 5 carbon atoms. By using the blowing agent C together with the blowing agent A and the blowing agent B, it is possible to more easily obtain an extruded polystyrene resin foam board that satisfies the above apparent density range.

The water of the foaming agent C does not destroy the ozone layer, does not cause global warming, and quickly dissipates from the foam board, so the dimensions of the obtained foam board can be stabilized quickly. I can do it.

Examples of aliphatic alcohols having 1 to 5 carbon atoms as blowing agent C include methyl alcohol (methanol), ethyl alcohol (ethanol), n-propyl alcohol, isopropyl alcohol, butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol. , aryl alcohol, crotyl alcohol, propargyl alcohol, n-amyl alcohol, sec-amyl alcohol, isoamyl alcohol, tert-amyl alcohol, neopentyl alcohol, 3-pentanol, 2-methyl-1-butanol, 3-methyl Examples include monohydric alcohols such as -2-butanol, which can be used alone or in combination of two or more. From the viewpoint of improving the appearance, ethanol can be preferably used among these. The ratio of ethanol to 100% by weight of aliphatic alcohol having 1 to 5 carbon atoms is preferably 60% by weight or more, more preferably 70% by weight or more, and still more preferably 85% by weight or more.

Aliphatic alcohols with 1 to 5 carbon atoms, like water, do not destroy the ozone layer or cause global warming, and because they quickly dissipate from the foam board, the shape of the foam board has been changed. It can be stabilized early.

In the present invention, blowing agent A, blowing agent B, and blowing agent C are used as essential components in the physical blowing agent, but various other blowing agents may be added to the physical blowing agent as appropriate to the extent that the effects of the present invention are not impaired. Can be blended. Examples of other blowing agents include carbon dioxide, nitrogen, saturated hydrocarbons having 3 to 5 carbon atoms (such as isobutane and n-butane), and chlorinated hydrocarbons (such as methyl chloride and ethyl chloride). These can be used alone or in combination of two or more.

<Additional amount of physical foaming agent>
In the present invention, the total amount of physical foaming agents added is 0.9 mol or more and 1.8 mol or less per 1 kg of base resin. From the viewpoint of obtaining a foam board that has excellent appearance, low apparent density, and can maintain low thermal conductivity over a long period of time, the total amount of physical foaming agents added is 1.0 mol per 1 kg of base resin. The amount is preferably 1.6 mol or more, and more preferably 1.2 mol or more and 1.5 mol or less.

The amount of blowing agent A (1,1,1,4,4,4-hexafluoro-2-butene) added is 0.2 mol or more per 1 kg of base resin. By adjusting the amount of foaming agent A added within the above range, the thermal conductivity can be maintained low for a long period of time. From the viewpoint of maintaining low thermal conductivity over a long period of time, the amount of blowing agent A added is preferably 0.3 mol or more, more preferably 0.4 mol or more, and 0.5 mol per 1 kg of base resin. It is more preferable that it is above.

On the other hand, from the viewpoint of improving mechanical strength such as bending strength and bending failure deflection of the extruded foam board, the amount of foaming agent A added is preferably 1.0 mol or less per 1 kg of base resin, and 0. It is more preferably .8 mol or less, even more preferably 0.7 mol or less, even more preferably 0.6 mol or less.

In addition, in the present invention, a high kneading type extruder such as a screw or twin screw with a large ratio of the axial length of the screw to the diameter of the screw, or a first extruder and a second extruder connected in series are used. In a tandem extruder, a continuous static mixer (static mixer) may be installed at the connection between the first extruder and the second extruder, or between the second extruder and the die. By using the same, it is possible to easily produce an extruded foam board with excellent appearance even when the amount of foaming agent A added is increased.

If the amount of blowing agent B (dialkyl ether having 1 to 3 carbon atoms) is too small, there is a risk of deterioration of surface smoothness and generation of gas spots. Further, since the blowing agent B is a flammable gas, if the amount of the blowing agent B added is too large, there is a risk of ignition during molding after extrusion foaming, and there is a possibility that manufacturing stability may be reduced. Therefore, the amount of foaming agent B added is 0.05 mol or more and 0.8 mol or less, preferably 0.1 mol or more and 0.7 mol or less, and more preferably 0.2 mol or more and 0.6 mol or less, per 1 kg of the base resin. More preferably, the amount is 0.3 mol or more and 0.5 mol or less.

The total amount of blowing agent C (water and/or aliphatic alcohol having 1 to 5 carbon atoms) is 0.1 mol or more and 0.7 mol per 1 kg of base resin, from the viewpoint of manufacturing stability and good appearance. The amount is preferably from 0.2 mol to 0.7 mol, more preferably from 0.3 mol to 0.6 mol, and even more preferably from 0.4 mol to 0.55 mol. When the physical foaming agent contains the foaming agent C, it becomes easier to maintain an appropriate pressure during extrusion. Note that the amount of blowing agent C added is the total of the amount of water added and the amount of aliphatic alcohol having 1 to 5 carbon atoms added.

The blowing agent C is preferably both water and an aliphatic alcohol having 1 to 5 carbon atoms, from the viewpoint of achieving a low apparent density and improving the appearance by reducing gas spots. More preferably, 95 mol% of water and 5 to 40 mol% of an aliphatic alcohol having 1 to 5 carbon atoms (however, the total of water and aliphatic alcohol having 1 to 5 carbon atoms is 100 mol%); More preferably, it is ~85 mol% water and 15-35 mol% aliphatic alcohol having 1 to 5 carbon atoms.

The amount of foaming agent A (1,1,1,4,4,4-hexafluoro-2-butene) and foaming agent B (having 1 to 3 carbon atoms) is calculated based on the total amount of physical foaming agents added of 100 mol%. From the viewpoint of maintaining manufacturing stability and low thermal conductivity over a long period of time, the total amount including the amount of dialkyl ether) is 50 mol% or more, preferably 55 mol% or more. On the other hand, the upper limit of the total addition amount of blowing agent A and blowing agent B is preferably 90 mol%, more preferably 80 mol%, and even more preferably 70 mol%.

The molar ratio between the amount of blowing agent B (dialkyl ether having 1 to 3 carbon atoms) and the amount of blowing agent C (water and/or aliphatic alcohol having 1 to 5 carbon atoms) added (Blowing agent B: blowing agent C) is preferably 15:85 to 95:5. The above molar ratio (Blowing agent B:Blowing agent C) is more preferably 25:75 to 90:10, from the viewpoint of further improving manufacturing stability and maintaining low thermal conductivity over a long period of time. More preferably, the ratio is from 75 to 75:25.

In the present invention, the total amount of physical foaming agents added, the amount of foaming agent A added, the amount of foaming agent B added, the amount of foaming agent C added, and the ratio of the amounts of foaming agent A and foaming agent B added are as described above. By setting the specific range, it is possible to maintain low thermal conductivity for a long period of time, and it is possible to obtain a foam board with good manufacturing stability and appearance (surface smoothness and gas spots).

<Other ingredients>
(Flame retardants)
The foam board obtained by the manufacturing method of the present invention is mainly used as a heat insulating material for building materials, and is imparted with flame retardancy by blending a flame retardant into the base resin. The flame retardant used in the present invention is not particularly limited, but it is preferable to use a brominated flame retardant. Examples of the brominated flame retardant include brominated butadiene polymers such as brominated butadiene-styrene copolymers, tetrabromobisphenol-A-bis(2,3-dibromo-2-methylpropyl ether), and tetrabromobisphenol-A-bis(2,3-dibromo-2-methylpropyl ether). Bromobisphenol-S-bis(2,3-dibromo-2-methylpropyl ether), Tetrabromobisphenol-F-bis(2,3-dibromo-2-methylpropyl ether), Tetrabromobisphenol-A-bis(2 , 3-dibromopropyl ether), tetrabromobisphenol-S-bis(2,3-dibromopropyl ether), and brominated bisphenol compounds represented by tetrabromobisphenol-F-bis(2,3-dibromopropyl ether), Tris(2,3-dibromopropyl)isocyanurate, mono(2,3,4-tribromobutyl)isocyanurate, di(2,3,4-tribromobutyl)isocyanurate, tris(2,3,4- Examples include brominated isocyanurates represented by tribromobutyl) isocyanurate. Moreover, these brominated flame retardants can be used alone or in combination of two or more.

In addition to these brominated flame retardants, we also use cresyl di-2,6-xylenyl phosphate, antimony trioxide, diantimony pentoxide, ammonium sulfate, zinc stannate, cyanuric acid, pentabromotoluene, isocyanuric acid, triallylisocyanurate. , nitrogen-containing cyclic compounds such as melamine cyanurate, melamine, melam, melem, silicone compounds, inorganic compounds such as boron oxide, zinc borate, and zinc sulfide, phosphate esters such as triphenyl phosphate, and red phosphorus compounds. , ammonium polyphosphate, phosphazene, phosphorous compounds such as hypophosphite, etc. can be used in combination.

Among these flame retardants, it can impart high flame retardancy, is difficult to decompose polystyrene resin during extrusion, has a low apparent density (high expansion ratio), and is stable even in the case of a large cross-sectional area. Tetrabromobisphenol A-bis(2,3-dibromopropyl ether) and tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) It is more preferable to use a flame retardant used in combination or a flame retardant containing a brominated butadiene-styrene copolymer.

The amount of flame retardant to be added is 0.00 parts by mass based on 100 parts by mass of the base resin, since it can impart high flame retardancy to the foam board and also suppress deterioration of extrusion foaming properties and deterioration of mechanical properties. It is preferably 1 to 10 parts by weight, more preferably 1 to 9 parts by weight, and even more preferably 1.5 to 7 parts by weight. If it is within this range, the flame retardant will not inhibit foaming properties, and the extruded polystyrene foam insulation material according to "Test Method A" specified for flammability in the test method for foamed plastic insulation materials of JIS A9521:2022. It is possible to obtain a foam board that has a high degree of flame retardancy that meets the flammability standards that apply to flammability standards.

(Flame retardant aid)
Furthermore, in the method of the present invention, a flame retardant aid can be used in combination with the flame retardant for the purpose of further improving the flame retardancy of the foam board. Examples of flame retardant aids include 2,3-dimethyl-2,3-diphenylbutane, 2,3-diethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, and 3,4-dimethyl-2,3-diphenylbutane. -Diphenylalkanes and diphenylalkenes such as diethyl-3,4-diphenylhexane, 2,4-diphenyl-4-methyl-1-pentene, 2,4-diphenyl-4-ethyl-1-pentene, poly-1,4 Examples include one or more selected from polyalkylated aromatic compounds such as -diisopropylbenzene. The amount of the flame retardant aid added is approximately 0.01 to 1 part by mass, more preferably 0.05 to 0.5 part by mass, per 100 parts by mass of the base resin.

(Radiation suppressant)
In the production method of the present invention, graphite can be added to the foamable resin composition as a radiation suppressant in order to improve the heat insulation properties. Graphite can improve the insulation properties of foam boards by reflecting infrared rays.

Examples of graphite include scaly graphite, scaly graphite, artificial graphite, earthy graphite, etc., and it is preferable to use a graphite whose main component is scaly graphite. As will be described later, graphite is preferably used as a masterbatch blended with polystyrene resin at a high concentration. Graphite with a fixed carbon content of 80% or more is preferred because it has good workability when producing a masterbatch and has an excellent effect of improving the heat insulation properties of the resulting foam board. Further, in order to further improve the heat insulation properties of the foam board, a fixed carbon content of 90% or more is more preferable, and a fixed carbon content of 95% or more is even more preferable. Incidentally, the fixed carbon content of the graphite refers to a value measured by the method described in JIS M8511:2014.

When graphite is blended, the amount of graphite added is preferably 0.2 to 10 parts by weight based on 100 parts by weight of the base resin. When the amount added is within this range, the heat insulation properties are improved and a foam board with a desired low thermal conductivity can be obtained. From this point of view, the amount of graphite added is more preferably 0.3 parts by mass or more, and even more preferably 0.4 parts by mass or more, based on 100 parts by mass of the base resin of the foam board. On the other hand, from the viewpoint of maintaining flame retardancy of the foam board, the upper limit of the amount of graphite added is more preferably 5 parts by mass, and 3 parts by mass based on 100 parts by mass of the base resin of the foam board. It is even more preferable that the amount is 1 part by mass.

Moreover, in the manufacturing method of the present invention, in order to further improve the heat insulation properties, the foam board can contain a radiation suppressant other than the graphite. Examples of radiation suppressants other than graphite include one or more selected from metal oxides such as titanium oxide, metals such as aluminum, ceramics, carbon black, graphite, infrared shielding pigments, hydrotalcite, etc. I can give an example. Among these, titanium oxide can be preferably used. The amount of the radiation suppressant other than graphite added is approximately 0.5 to 5 parts by weight, more preferably 1 to 4 parts by weight, based on 100 parts by weight of the base resin.

In addition, in the method of the present invention, other known additives may be appropriately blended into the base resin, if necessary. Examples of other additives include various additives such as cell regulators, colorants such as pigments and dyes, heat stabilizers, and fillers.

(Bubble regulator)
In the production method of the present invention, it is preferable to mix a cell regulator with the base resin to form a foamable resin composition. Inorganic powders such as talc, kaolin, mica, silica, calcium carbonate, barium sulfate, titanium oxide, clay, aluminum oxide, bentonite, and diatomaceous earth can be used as the bubble regulator. Among these, talc is suitable because it is easy to adjust the bubble size and the bubble size can be easily reduced without impairing flame retardancy, and in particular, talc has a 50% particle size (light transmission centrifugal sedimentation method) of 0.1 to 20 μm. A fine talc of 0.5 to 15 μm is preferred, and a fine talc of 0.5 to 15 μm is preferred. The amount of the foam regulator to be added varies depending on the type of regulator, the intended bubble diameter, etc., but when using talc as the foam regulator, it is preferably 0.1 to 7 parts by mass per 100 parts by mass of the base resin. , more preferably 0.2 to 5 parts by weight, and even more preferably 0.3 to 3 parts by weight.

(thermal stabilizer)
Thermal stabilizers improve the thermal stability of the brominated flame retardant by adding them to raw materials and offcuts when manufacturing foam boards or recycling offcuts from foam boards to re-pelletize them. can be done. Examples of the heat stabilizer include bisphenol-type epoxy compounds such as EPICLON series manufactured by DIC Corporation, novolak-type epoxy compounds, (pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) )propionate]), and phosphite compounds such as (bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol-diphosphite). Heat stabilizers may be mentioned. The amount of heat stabilizer added is preferably 0.1 to 40 parts by weight based on 100 parts by weight of the total flame retardant.

In the manufacturing method of the present invention, the flame retardant and other additives are added to the base resin in a predetermined proportion together with the base resin in a supply unit provided upstream of the extruder. It is possible to adopt a method of supplying the mixture to an extruder and kneading it in an extruder. In addition, a method of supplying the flame retardant and other additives into the molten resin from a supply section provided in the middle of the extruder can also be adopted. Specifically, a method in which a dry blend of a flame retardant, other additives, and a base resin is supplied to an extruder and melt-kneaded, and a method in which a flame retardant, other additives, and a base resin are kneaded using a kneader, etc. A method of feeding a melt-kneaded product to an extruder: A masterbatch is prepared by blending a highly concentrated flame retardant and other additives into the base resin in advance, and this is fed to the extruder and melt-kneaded with the base resin. method etc. can be adopted. In particular, from the viewpoint of dispersibility, it is preferable to prepare a flame retardant masterbatch and supply it to an extruder. To prepare a flame retardant masterbatch, use a polystyrene resin with a melt flow rate of about 0.5 to 30 g/10 min at 200°C and a load of 5 kg as the base resin, and adjust the flame retardant content to 10 to 95 g/10 min at 200°C and a load of 5 kg. The content is preferably adjusted to be contained in % by mass, more preferably adjusted to be contained in 30 to 90% by mass, and still more preferably adjusted to be contained in 50 to 85% by mass.

<Physical properties of foam board>
Next, a polystyrene resin extruded foam board obtained by the manufacturing method of the present invention will be explained.

(apparent density)
The apparent density of the foam board of the present invention is 20 kg/m ³ or more and 50 kg/m ³ or less, preferably 25 kg/m ³ or more and 45 kg/m ³ or less, and more preferably 30 kg/m ³ or more and 40 kg/m ³ or less. It is. When the apparent density is within the above range, it can be suitably used as a heat insulating material that has sufficient mechanical strength and is lightweight.

(closed cell ratio)
The closed cell ratio of the foam board is preferably 85% or more, more preferably 90% or more, and even more preferably 93% or more. When the closed cell ratio is within this range, the foaming agent tends to remain in the cells, and the high heat insulation performance of the foam board can be maintained over a long period of time.

The closed cell ratio of the extruded foam board in this specification is measured using an air comparison hydrometer model 930 manufactured by Toshiba Beckman Corporation in accordance with ASTM-D2856-70 procedure C (25 mm x 25 mm x 20 mm from the foam board). A cut sample without a molded skin cut to size is stored in a sample cup and measured.However, if the thickness is too thin and a cut sample of 20 mm in the thickness direction cannot be cut, for example, 25 mm x 25 mm x 10 mm. It is sufficient to measure two cut samples with the size of %) and obtain the average value of N=3.

S (%) = (Vx-W/ρ) x 100/(V _A -W/ρ)...(1)
Vx: true volume (cm ³ ) of the cut sample measured by the above method (corresponds to the sum of the volume of the resin constituting the cut sample of the extruded foam board and the total volume of the cells in the closed cell portion in the cut sample .)
_VA : Apparent volume of the cut sample (cm ³ ) calculated from the outer dimensions of the cut sample used for measurement
W: Total weight of cut sample used for measurement (g)
ρ: Density of resin constituting the extruded foam board (g/cm ³ )

(Thermal conductivity after 7 days)
In the foam board of the present invention, the thermal conductivity after 7 days of manufacture is preferably 0.028 W/m·K or less, more preferably 0.025 W/m·K or less.

(Thermal conductivity after 300 days)
Further, the thermal conductivity after 300 days of production is preferably 0.032 W/m·K or less, more preferably 0.027 W/m·K or less.

The thermal conductivity shall be measured based on the heat flow meter method described in JIS A1412-2:1999 (one test piece, symmetrical configuration, high temperature side 38°C, low temperature side 8°C, average temperature 23°C). I can do it.

(bending failure deflection)
In the foam board of the present invention, the bending failure deflection is preferably 10 mm or more, more preferably 20 mm or more, and even more preferably 30 mm or more. The bending failure deflection is the bending deflection when the test piece breaks.

(bending strength)
In the foam board of the present invention, the bending strength (maximum bending stress) is preferably 40 N/cm ² or more, more preferably 50 N/cm ² or more, and preferably 55 N/cm ² or more. More preferred.

Note that the bending failure deflection and bending strength can be measured in accordance with JIS K7221-2:2006. A test piece without a molded skin is cut out from the extruded foam board 7 days after manufacture so that the test piece has dimensions of 250 mm in length, 75 mm in width, and 25 mm in thickness. The test pieces were three test pieces cut out so that the length direction was along the extrusion direction of the extruded foam and at the midpoint in the width direction; Then, cut out three test pieces so that the midpoint in the width direction is the center of the length. Using these test pieces, a test was conducted with a radius of 10 mm at the tip of the pressure wedge and support, a distance between fulcrums of 200 mm, and a test speed of 20 mm/min, and the bending strength was calculated by arithmetic averaging of the measured values of each test piece. , the bending failure deflection can be determined.

(cross-sectional area, dimensions, etc.)
The foam board of the present invention is plate-shaped, and its cross-sectional area perpendicular to the extrusion direction is preferably 100 cm ² or more, more preferably 200 cm ² or more. The upper limit of its cross-sectional area is approximately 1500 cm ² . In this specification, the cross-sectional area perpendicular to the extrusion direction refers to the area of the cross section of the foam board perpendicular to the extrusion direction.

The foamed board of the present invention is usually manufactured by creating a base plate one size or more larger than the desired size, cutting the base plate, and adjusting the width, length, and thickness in some cases.

However, if the width of the original plate fluctuates greatly during manufacturing and becomes narrower than the specified width, it becomes impossible to obtain a foam board of the specified size, resulting in poor yield. In addition, in the production of foamed boards, there is a tendency that the smaller the apparent density and the larger the cross-sectional area, the more difficult it is to foam. According to the manufacturing method of the present invention, since manufacturing stability is excellent, even when manufacturing a foam board that is thick and has a large cross-sectional area, a foam board with a good appearance can be stably manufactured. An extruded foam board that is well-foamed and has excellent surface smoothness can be suitably used as a foam board with a molded skin without cutting the surface in the thickness direction.

In the case of a foam board used as a heat insulating material, the thickness thereof is preferably 20 mm or more, more preferably 30 mm or more, and even more preferably 50 mm or more. On the other hand, the upper limit of the thickness is approximately 150 mm. Since the present invention includes the step of extruding and foaming a foamable molten resin composition and molding it into a plate shape, it is possible to stably produce a foam board even if the board is thick.

Further, the width is preferably 800 mm or more, more preferably 900 mm or more. The upper limit is approximately 1200 mm.

(Bubble structure: average bubble diameter in the thickness direction)
The average cell diameter in the thickness direction of the foam board is preferably 50 to 200 μm, more preferably 70 to 170 μm, and still more preferably 80 to 150 μm. When the average cell diameter is within the above range, the foamed board has even higher heat insulation properties and superior mechanical strength.

The method for measuring the average bubble diameter in the thickness direction is as follows. The average cell diameter in the thickness direction is determined by increasing the magnification from 50x to 200x so that the number of cells in the photograph is approximately 200 to 500 at three locations in the center and near both ends of the vertical cross section in the width direction of the foam board. Obtain enlarged photographs that have been adjusted within a range of about 100%, and measure the maximum diameter of each bubble in the thickness direction on each photograph using image processing software NS2K-pro manufactured by Nanosystems Co., Ltd., and calculate these values. It can be obtained by taking the arithmetic average of each.

(Bubble structure: bubble deformation rate)
Further, in the foam board, it is preferable that the cell deformation rate is 0.7 to 1.5. The bubble deformation rate refers to the average bubble diameter in the thickness direction determined by the above measurement method, as well as the average bubble diameter in the thickness direction. Measure the maximum diameter of each bubble in the width direction, calculate the average bubble diameter in the width direction by taking the arithmetic average of each value, and divide the average bubble diameter in the thickness direction by the average bubble diameter in the width direction. The smaller the bubble deformation rate is than 1, the flatter the bubble is, and the more the bubble deformation rate is greater than 1, the longer the bubble is. When the cell deformation rate is within the above range, the foamed board has excellent mechanical strength and higher heat insulation properties. The lower limit of the cell deformation rate is more preferably 0.8 from the viewpoint of dimensional stability of the foam board. Further, the upper limit of the cell deformation rate is more preferably 1.1, and even more preferably 1.05, from the viewpoint of improving heat insulation properties.

EXAMPLES Below, the present invention will be explained in more detail with reference to Examples. However, the present invention is not limited in any way by the examples.

In the Examples and Comparative Examples, the following equipment and raw materials were used.

A first extruder of high kneading type with an inner diameter of 115 mm and a second extruder with an inner diameter of 180 mm are connected in series, and a physical blowing agent injection port is provided near the end of the first extruder, so that a cross section with a gap of 1 mm x width of 440 mm is formed. An extrusion device was used in which a flat die equipped with a rectangular resin outlet (die lip) was connected to the outlet of a second extruder. Furthermore, a molding device (guider) was attached to the resin outlet of the second extruder, in which a pair of upper and lower plates made of polytetrafluoroethylene resin were installed horizontally at a substantially constant interval.

(1) Base resin (1-1) Polystyrene resin: Polystyrene “HP600ANJ” manufactured by DIC Corporation, melt viscosity (200°C, 100sec ^-1 ) 1400 Pa・s
The melt viscosity is a value measured using a flow characteristic measuring device such as Capillograph 1D (manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a temperature of 200° C. and a shear rate of 100 sec ⁻¹ .

(2) Flame retardant (2-1) Tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether): Daiichi Kogyo Seiyaku "SR-130"/Tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) - dibromopropyl ether): using a flame retardant masterbatch (GR-134BG manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) containing a mixed flame retardant of Daiichi Kogyo Seiyaku "SR-720" = 60% by mass / 40% by mass, The masterbatch was added so as to have the amount of flame retardant shown in Tables 1 and 2.

(3) Cell conditioner talc (manufactured by Matsumura Sangyo Co., Ltd., product name “High Filler #12”, particle size (d50) 7.5 μm)

(4) Radiation suppressor (4-1) Graphite (graphite: manufactured by Resino Color Industries Co., Ltd., product name: SBF-T-1683, flaky graphite powder, average particle size 17 μm, 40% masterbatch)
(4-2) Titanium oxide (manufactured by Nikko Bix Co., Ltd.)

(5) Physical foaming agent (a) HFO-1336mzz: Mitsui Chemours Fluoro Products Co., Ltd. (b) Dimethyl ether: Mitsubishi Gas Chemical Co., Ltd. (c1) Water (c2) Alcohol (ethanol/isopropyl alcohol/1-propanol = 90 (wt%/6wt%/4wt%): Manufactured by Yamaichi Chemical Industry Co., Ltd. Carbon dioxide: Manufactured by Showa Tanso Co., Ltd.

Examples 1 to 9, Comparative Examples 1 to 5
The types and amounts of the base resin, flame retardant masterbatch, and foam regulator shown in Table 1 (Examples 1 to 9) and Table 2 (Comparative Examples 1 to 5) are supplied to the first extruder and heated to 200°C. A physical blowing agent of the type and amount shown in Tables 1 and 2 was supplied from the physical blowing agent injection port provided in the first extruder, and the mixture was further kneaded to form a foamable resin melt. . Next, the obtained foamable resin melt is transferred to a second extruder to adjust the resin temperature, and then extruded into a guider at a discharge rate of 400 kg/hr, and passed through the guider while foaming to form a plate. A master plate with a thickness of 30 mm was produced by molding (shaping), and the width and length of the master plate were adjusted by cutting, and the molded skins on both sides were equally cut to form a rectangular parallelepiped without a molded skin. A polystyrene resin foam board (width: 910 mm, length: 1820 mm, thickness: 25 mm, area of cross section perpendicular to the extrusion direction: 227.5 cm ² ) was manufactured. In Example 4, ethanol (Reagent Ethanol (99.5) Shika 1st grade, manufactured by Kanto Kagaku Co., Ltd.) was used as the (c2) alcohol.

For the foamed boards obtained under the conditions of Examples and Comparative Examples, the cell structure (average cell diameter in the thickness direction, cell deformation rate), thickness, apparent density, closed cell ratio, and thermal conductivity (after 7 days and 300 days) are as follows. Flammability, bending failure deflection, bending strength (maximum bending stress), manufacturing stability, and appearance (surface smoothness, gas spots) were evaluated using the following criteria. The results are shown in Tables 1 and 2.

(Bubble structure: average bubble diameter in the thickness direction)
The average cell diameter in the thickness direction was determined by the following method. Enlarged photographs with the magnification magnification adjusted to 100x were obtained at a total of three locations near the center and both ends of the widthwise vertical section of the obtained foam board, and an image manufactured by Nano System Co., Ltd. The maximum diameter of each bubble in the thickness direction was measured using processing software NS2K-pro, and the values were calculated by taking the arithmetic average of each value.

(Bubble structure: bubble deformation rate)
The bubble deformation rate was determined by measuring the maximum diameter of each bubble in the width direction using image processing software NS2K-pro manufactured by Nano System Co., Ltd. on an enlarged photograph of the bubbles, in the same way as the method for measuring the bubble diameter in the thickness direction. The average cell diameter in the width direction was determined by taking the arithmetic mean of these values, and the average cell diameter in the thickness direction was determined by dividing the average cell diameter in the width direction.

(thickness)
The obtained foam board was measured at three positions where the foam board was divided into four equal parts in the width direction, and the measurements were arithmetic averaged.

(apparent density)
The apparent density of the foam board was determined by the following method. A rectangular parallelepiped sample measuring 50 mm long x 50 mm wide x 20 mm thick was cut out from the center and both ends of the obtained foam board in the width direction at the position where the obtained foam board was divided into two equal parts in the length direction. The apparent density of each sample was determined by measuring the mass and dividing the mass by the volume, and the arithmetic mean value thereof was taken as the apparent density.

(closed cell ratio)
The closed cell ratio of the foam board is measured using an air comparison hydrometer (manufactured by Toshiba Beckman Corporation, model: 930) in accordance with procedure C of ASTM-D2856-70. It was determined from the above equation (1) using the true volume Vx of the plate.

(Thermal conductivity: 7 days after production)
A test piece measuring 200 mm long x 200 mm wide x 20 mm thick was cut from the widthwise center of the foam board immediately after manufacture, and the test piece was stored in a constant temperature and humidity chamber at a temperature of 23°C and a relative humidity of 50% for 7 days after manufacture. Thereafter, the thermal conductivity of each was measured based on the flat plate heat flow meter method (two heat flow meter method, high temperature side 38°C, low temperature side 8°C, average temperature 23°C) described in JIS A1412-2 (1999).

(Thermal conductivity: 300 days after production)
The thermal conductivity after 300 days of manufacture is the value obtained by measuring the thermal conductivity of an extruded foam board subjected to test method A of the long-term accelerated change in thermal resistance test in accordance with JIS A1486:2014. be. Specifically, a rectangular parallelepiped measuring 200 mm long x 200 mm wide x 25 mm thick was cut from the widthwise center of the extruded foam board immediately after manufacture, and then evenly shaved from both sides to create a rectangular parallelepiped of 200 mm long x 200 mm wide x 10 mm thick. A test piece was cut out and stored in a constant temperature and humidity room at a temperature of 23°C and a relative humidity of 50%, and the test piece was used after 48 days of manufacture (equivalent to 300 days after manufacture of a 25 mm thick extruded foam board) according to JIS A1412-2 ( Thermal conductivity was measured based on the flat plate heat flow meter method (two heat flow meter method, high temperature side: 38°C, low temperature side: 8°C, average temperature: 23°C) as described in (1999).

(Combustion quality)
The foam board immediately after manufacture was stored in a constant temperature and humidity chamber at a temperature of 23°C and a relative humidity of 50%, and 4 weeks after manufacture, five test pieces were randomly cut out from the foam board (N = 5) and tested according to JIS A9521: The flammability was measured based on "Test Method A" specified for flammability in the test method for foamed plastic insulation materials of 2022, and the flame retardance of the foam board was evaluated according to the following criteria.
○: Average burning time of 5 test pieces is 3 seconds or less ×: Average burning time of 5 test pieces exceeds 3 seconds (not applicable)

(manufacturing stability)
Manufacturing stability was evaluated based on the following criteria.
◎: Can be continuously and stably extruded into a plate shape during extrusion foaming 〇: Catch rarely occurred during extrusion foaming, but stable extrusion molding into a plate shape is possible △: No catch during extrusion foaming Occasionally occurred, but extrusion molding into a plate shape is possible ×: Catch frequently occurs during extrusion foaming, making extrusion molding into a plate shape difficult.

(Appearance: surface smoothness)
The surface smoothness of the original plate and the extruded foam board was visually evaluated according to the following criteria. The original board is a foam board with a molded skin that is one size or more larger than the desired size, and extruded foam board is made by cutting the original board to remove the molded skin whose width, length, and in some cases thickness have been adjusted. It is made of foam board.
◎: The surfaces of the original board and extruded foam board are extremely good. ○: Roughness rarely occurs on the surface of the original board, and the surface of the extruded foam board is extremely good. △: Roughness rarely occurs on the surface of the extruded foam board. ×: Extruded foam board. A lot of roughness occurs on the surface of

(Appearance: gas spot)
Gas spots (excessively large bubbles seen on the surface of the foam board and in the cross section of the foam board due to separation of the foaming agent generated during extrusion foaming) were evaluated according to the following criteria.
◎: No spot holes are observed on the original board and extruded foam board ○: No spot holes are generally observed on the original board, and no spot holes are observed on the extruded foam board △: Spot holes are found in some parts of the extruded foam board ×: Multiple spot holes are observed in the extruded foam board, and a good foam board cannot be obtained.

From the results of the above measurements and evaluations, it was found that 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz) (foaming agent A) as a physical blowing agent, and Examples 1 to 9 containing a dialkyl ether (Blowing agent B) and water and/or an aliphatic alcohol having 1 to 5 carbon atoms (Blowing agent C) under the conditions of the present invention have the following properties: apparent density, closed cell ratio, foaming It was confirmed that the thermal conductivity, bending properties (bending failure deflection, bending strength), manufacturing stability, and appearance (surface smoothness, gas spots) of the board (after 7 days and 300 days) were all good. .

Furthermore, from Examples 1 to 5, it was confirmed that production stability was higher when the molar ratio of blowing agent B and blowing agent C was 25:75 to 75:25. Furthermore, by comparing Example 3 with Examples 6 and 9, it was confirmed that when both water and an aliphatic alcohol having 1 to 5 carbon atoms were used as the blowing agent C, the generation of gas spots could be further suppressed. . By comparing Examples 1 to 5 with Examples 7 and 8, it was confirmed that the bending strength was even better when the amount of blowing agent A added was 0.7 mol or less per 1 kg of base resin. Ta.

In contrast to Examples 1 to 9, in Comparative Examples 1 to 5, the cell structure, apparent density, closed foam ratio, thermal conductivity of the foam board, bending properties, manufacturing stability, and appearance were all improved. I couldn't do that. Specifically, it is as follows.

In Comparative Example 1, a dialkyl ether having 1 to 3 carbon atoms (blowing agent B) was not used. As a result, although it was possible to manufacture a foam board, the foamability was poor, and the manufacturing stability and appearance were also poor. In Comparative Example 2, the amount of blowing agent A added was set to be larger than the conditions of the present invention. As a result, in Comparative Example 2, foaming was unstable and it was difficult to manufacture a foam board. In Comparative Example 3, blowing agent C was not used. As a result, in Comparative Example 3, it was difficult to manufacture the foam board. In Comparative Example 4, carbon dioxide was used instead of blowing agent C. As a result, in Comparative Example 4, the bubbles were too small, making it difficult to manufacture a foam board. In Comparative Example 5, the amount of blowing agent B added was set lower than the conditions of the present invention. As a result, in Comparative Example 5, although a foam board could be manufactured, the foamability was poor, and the manufacturing stability and appearance were also poor.

Claims (5)

Apparent density: 20 kg/m ³ or more 50 kg, including the step of extruding and foaming a foamable molten resin composition obtained by kneading a base resin mainly composed of polystyrene resin, a flame retardant, and a physical foaming agent to form a plate shape. /m ³ or less A method for producing an extruded polystyrene resin foam board, the method comprising:
The physical blowing agents include a blowing agent A consisting of 1,1,1,4,4,4-hexafluoro-2-butene, a blowing agent B consisting of a dialkyl ether having 1 to 3 carbon atoms, and water and/or A blowing agent C consisting of an aliphatic alcohol having 1 to 5 carbon atoms,
The total amount of the physical foaming agent added is 0.9 mol or more and 1.8 mol or less per 1 kg of the base resin,
The amount of the blowing agent A added is 0.2 mol or more per 1 kg of base resin,
The amount of the blowing agent B added is 0.05 mol or more and 0.8 mol or less per 1 kg of base resin,
The amount of the foaming agent C added is 0.1 mol or more and 0.7 mol or less per 1 kg of base resin,
Production of an extruded polystyrene resin foam board, characterized in that the total amount of the foaming agent A and the foaming agent B added is 50 mol% or more with respect to the total amount of the physical foaming agent added of 100 mol%. Method. 2. The method for producing an extruded polystyrene resin foam board according to claim 1, wherein the amount of the blowing agent A added is 0.2 mol or more and 0.7 mol or less per 1 kg of the base resin. Claim 1 or Claim 2, characterized in that the molar ratio between the amount of the foaming agent B added and the amount of the foaming agent C added (foaming agent B: foaming agent C) is 25:75 to 90:10. A method for producing an extruded polystyrene foam board as described in . The blowing agent C is 60 to 95 mol% of water and 5 to 40 mol% of an aliphatic alcohol having 1 to 5 carbon atoms (provided that the total of water and aliphatic alcohol having 1 to 5 carbon atoms is 100 mol%). 3. The method for producing an extruded polystyrene foam board according to claim 1 or 2, characterized in that: 3. The method for producing an extruded polystyrene foam board according to claim 1 or 2, wherein the extruded polystyrene foam board has a thickness of 20 mm or more.