JP7576984B2 - Method for producing extruded thermoplastic resin foam - Google Patents

Description

The present invention relates to an extruded thermoplastic resin foam board and a method for manufacturing the same, and more specifically to an extruded thermoplastic resin foam board that can be suitably used as an insulating material for the walls, floors, roofs, etc. of buildings, and a method for manufacturing the same.

Polyester resin is known as a resin that can be used to make foam boards. Polyester resin has a high performance in preventing air from entering the foam board, but it is difficult to mold polyester resin alone into a foam board.

On the other hand, styrene-(meth)acrylic acid ester copolymers are known as resins that have a high performance in preventing air from flowing into foam boards. However, although it is possible to manufacture foam boards using styrene-(meth)acrylic acid ester copolymers as the sole raw material, there is still room for further improvement in terms of reducing thermal conductivity.

In Patent Document 1, the present inventors proposed an extruded thermoplastic resin foam board (hereinafter also referred to simply as extruded foam board) that contains polystyrene resin and a specific polyester resin (including a styrene-(meth)acrylic acid ester copolymer) and has a mass ratio of polystyrene resin to polyester resin of 95:5 to 50:50. This extruded foam board has a foam surface free of uneven waves, has a good appearance, is sufficiently thick, and has a high expansion ratio.

In addition, in Patent Document 2, the present inventors proposed a styrene-based resin foam consisting of a mixed resin of polystyrene resin, a styrene-(meth)acrylic acid ester copolymer, and an amorphous polyester resin (in the examples, the content of amorphous polyester resin is 22 to 44% by mass). This extruded foam had little change in thermal conductivity over time and was excellent in flame retardancy and mechanical strength such as bending fracture strain.

JP 2013-082805 A JP 2019-189666 A

However, the extruded foams in Patent Documents 1 and 2 contain a specific ratio of ordinary polystyrene in the base resin, and since this polystyrene has a relatively high air permeability coefficient, there is still room for further improvement in terms of maintaining thermal insulation properties over the long term.

The objective of the present invention is to provide an extruded thermoplastic resin foam board that can maintain low thermal conductivity for a long period of time and has excellent heat insulation and flame retardancy, and a method for producing the same.

The present invention provides the following extruded thermoplastic resin foam insulation board and a method for producing the same.
<1> A method for producing an extruded thermoplastic resin foam plate having an apparent density of 20 to 50 kg/m ³ and a thickness of 10 to 150 mm, comprising the steps of extruding and foaming a foamable resin composition obtained by kneading a base resin, a physical foaming agent, and a flame retardant, and molding the composition into a plate shape using a molding tool,
the base resin contains a styrene-(meth)acrylic acid ester copolymer and a polyester resin having a heat of fusion of less than 5 J/g based on JIS K7122-1987;
The blending amount of the polyester resin in the base resin is 5 to 50% by mass,
The method for producing an extruded thermoplastic resin foam board, wherein the content of a (meth)acrylic acid ester component derived from a styrene-(meth)acrylic acid ester copolymer in the base resin is 20 to 40 mass %.
<2> The method for producing an extruded thermoplastic resin foam board according to <1>, wherein the physical foaming agent contains a hydrofluoroolefin, and the amount of the hydrofluoroolefin added is 0.5 mol or more and 1.5 mol or less per 1 kg of the base resin.
<3> The method for producing an extruded thermoplastic resin foam board according to <2>, wherein the ratio of the amount of the hydrofluoroolefin added to the total amount of the physical foaming agents added (100 mol %) is 50 mol % or more.
<4> The method for producing an extruded thermoplastic resin foam plate according to <2> or <3>, characterized in that the hydrofluoroolefin contains 1,3,3,3-tetrafluoropropene and 1-chloro-3,3,3-trifluoropropene, and the molar ratio of 1,3,3,3-tetrafluoropropene to 1-chloro-3,3,3-trifluoropropene is 20:80 to 80:20.
<5> An extruded thermoplastic resin foam board containing a flame retardant, having an apparent density of 20 to 50 kg/m ³ and a thickness of 10 to 150 mm,
the base resin of the extruded thermoplastic resin foam board is a mixture of a styrene-(meth)acrylic acid ester copolymer and a polyester resin having a heat of fusion of less than 5 J/g based on JIS K7122-1987;
The content of the polyester resin in the base resin is 5 to 50% by mass,
The content of the (meth)acrylic acid ester component derived from the styrene-(meth)acrylic acid ester copolymer in the base resin is 20 to 40 mass %.

The present invention is a method for producing an extruded thermoplastic resin foam board, the base resin of which is a polyester resin having a heat of fusion of less than 5 J/g and a styrene-(meth)acrylic acid ester copolymer. By setting the ratio of the polyester resin in the base resin and the ratio of the (meth)acrylic acid ester component derived from the styrene-(meth)acrylic acid ester copolymer in the base resin within a specific range, it is possible to provide a method for producing an extruded thermoplastic resin foam board with excellent flame retardancy, low thermal conductivity that can be maintained for a long period of time, and excellent thermal insulation.

The extruded thermoplastic resin foam board of the present invention and its manufacturing method are described below. The extruded thermoplastic resin foam board (hereinafter also referred to as extruded foam board) manufactured by the present invention contains a foamable resin composition obtained by kneading a base resin, a physical foaming agent, and a flame retardant, has an apparent density of 20 to 50 kg/m ³ , and a thickness of 10 to 150 mm, and the base resin contains a styrene-(meth)acrylic acid ester copolymer and a polyester resin having a heat of fusion of less than 5 J/g.

(1) Styrene-(meth)acrylic acid ester copolymer The styrene-(meth)acrylic acid ester copolymer used in the base resin is a copolymer of styrene and a lower alkyl ester of (meth)acrylic acid. Specific examples include styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-propyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, and styrene-propyl methacrylate copolymer. Among these, styrene-methyl acrylate copolymer and styrene-methyl methacrylate copolymer, which have a remarkable desired effect, are preferred, and styrene-methyl methacrylate copolymer is more preferred. These styrene-(meth)acrylic acid ester copolymers can be used alone or in a mixture of two or more kinds. In this specification, "(meth)acrylic acid" is a concept including "acrylic acid" and "methacrylic acid", and means one or both of them.

The content of the (meth)acrylic acid ester component derived from the styrene-(meth)acrylic acid ester copolymer in the base resin is 20 to 40% by mass, preferably 25 to 38% by mass, and more preferably 30 to 36% by mass. Two or more types of styrene-(meth)acrylic acid ester copolymers having different contents of the (meth)acrylic acid ester component can be used in combination. When two or more types of styrene-(meth)acrylic acid ester copolymers are used in combination, the total of the (meth)acrylic acid ester component contents contained in each styrene-(meth)acrylic acid ester copolymer is regarded as the (meth)acrylic acid ester component content of the styrene-(meth)acrylic acid ester copolymer.

If the amount of (meth)acrylic ester in the base resin is too small, the effect of lowering the thermal conductivity of the extruded foam board is reduced. On the other hand, if the amount of (meth)acrylic ester is too large, the thermal conductivity of the extruded foam board is sufficient, but the flame retardancy is deteriorated and the flame retardancy standard required for building materials cannot be met. However, the flame retardancy is also affected by the type and amount of flame retardant used in production, the density of the extruded foam, and the amount of foaming agent remaining in the extruded foam. In addition, if the amount of (meth)acrylic ester in the base resin is within an appropriate range, the styrene-(meth)acrylic ester copolymer and the polyester resin with a heat of fusion of less than 5 J/g in the base resin are easily dispersed in layers, which has the advantage of making it easier to achieve low thermal conductivity.

The thermal conductivity reducing effect of styrene-(meth)acrylic acid ester copolymer is due to the (meth)acrylic acid ester component preventing the escape of the blowing agent, which has low thermal conductivity, from the extruded foam plate and preventing air, which has high thermal conductivity, from entering the extruded foam plate. Therefore, as the (meth)acrylic acid ester component in the styrene-(meth)acrylic acid ester copolymer decreases, the thermal conductivity of the extruded foam plate increases. However, if an extruded foam is manufactured using only styrene-(meth)acrylic acid ester copolymer, which has a high (meth)acrylic acid ester component, it will be difficult to meet flame retardant standards.

Therefore, when using a styrene-(meth)acrylic acid ester copolymer with a high (meth)acrylic acid ester content, it is preferable to use a styrene-(meth)acrylic acid ester copolymer with a low (meth)acrylic acid ester content in combination to set the content of the (meth)acrylic acid ester component within the range described above. A styrene-(meth)acrylic acid ester copolymer with a low (meth)acrylic acid ester content has relatively excellent compatibility with both a styrene-(meth)acrylic acid ester copolymer with a high (meth)acrylic acid ester content and a polyester resin. Therefore, in the case of a resin composition consisting of a styrene-(meth)acrylic acid ester copolymer with a high (meth)acrylic acid ester content, a styrene-(meth)acrylic acid ester copolymer with a low (meth)acrylic acid ester content, and a polyester resin, the resins constituting the resulting extruded foam board form a continuous layer with a complex dispersion state, and it is believed that by efficiently suppressing the escape of the blowing agent from the extruded foam board and the inflow of air into the extruded foam board, it is possible to reduce the thermal conductivity of the extruded foam board while maintaining flame retardancy.

The styrene-(meth)acrylic acid ester copolymer having a high (meth)acrylic acid ester content preferably contains 40 to 75% by mass, more preferably 50 to 75% by mass of the (meth)acrylic acid ester component in the styrene-(meth)acrylic acid ester copolymer. The styrene-(meth)acrylic acid ester copolymer having a low (meth)acrylic acid ester content preferably contains 5% by mass or more and less than 40% by mass, more preferably 15% by mass or more and 30% by mass or less of the (meth)acrylic acid ester component in the styrene-(meth)acrylic acid ester copolymer.

The content of the (meth)acrylic acid ester component in the styrene-(meth)acrylic acid ester copolymer can be determined by known methods such as pyrolysis gas chromatography analysis.

The amount of styrene-(meth)acrylic acid ester copolymer in the base resin is adjusted according to the amount of (meth)acrylic acid ester component contained in the styrene-(meth)acrylic acid ester copolymer, but is preferably 50% by mass or more, and more preferably 60% by mass or more. In order to maintain a low thermal conductivity of the extruded foam board, the amount of styrene-(meth)acrylic acid ester copolymer in the base resin is preferably 90% by mass or less, and more preferably 80% by mass or less.

(2) Polyester Resin Examples of the polyester resin used in the base resin include polyester copolymers produced by polycondensation of a dicarboxylic acid component and a diol component, or by transesterification of a polyester homopolymer and/or a polyester copolymer.

The polyester resin satisfies the condition that the endothermic peak heat quantity associated with melting of the polyester resin is less than 5 J/g (including 0) based on the DSC curve obtained by heating the polyester resin to a temperature 30°C higher than the end of the glass transition at a heating rate of 10°C/min using a heat flux differential scanning calorimeter (hereinafter referred to as DSC device) based on the heat flux differential scanning calorimetry method in JIS K7122 (1987) at a heating rate of 10°C/min, maintaining the temperature at that temperature for 10 minutes, cooling to a temperature 50°C lower than the glass transition temperature at a cooling rate of 10°C/min, and heating again to a temperature 30°C higher than the end of the glass transition at a heating rate of 10°C/min. The endothermic peak heat quantity of this polyester resin is preferably less than 2 J/g (including 0), more preferably less than 1 J/g (including 0), from the viewpoint of the foaming characteristics of the base resin in which the polyester resin is blended with a styrene-(meth)acrylic acid ester copolymer.

An example of the polyester resin is an amorphous polyethylene terephthalate copolymer in which some of the ethylene glycol component units are replaced with a diol component that is bulkier than the ethylene glycol component in order to prevent crystallization of the polyethylene terephthalate.

Aliphatic and aromatic diols (including dihydric phenols) or their ester-forming derivatives can be used as the diol component of the polyester resin.

The diol component units in the polyester resin include aliphatic diols such as ethylene glycol, propylene glycol, trimethylene glycol, diethylene glycol, 1,4-butanediol, and neopentyl glycol, alicyclic diols such as 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,6-cyclohexanediol, aromatic diols such as bisphenol A, and diols having a cyclic ether skeleton such as 3,9-bis(1,1-dimethyl-2-hydroxyethyl)2,4,8,10-tetraoxaspiro[5.5]undecane (hereinafter referred to as spiro glycol) and 2-(5-ethyl-5-hydroxymethyl-1,3-dioxane-2-yl)-2-methylpropane-1-ol (hereinafter referred to as dioxane glycol). These diol components may be used alone or in combination of two or more kinds.

As the polyethylene terephthalate resin modified with the diol component, particularly preferred are spiroglycol-modified polyethylene terephthalate resin, dioxane glycol-modified polyethylene terephthalate resin, neopentyl glycol-modified polyethylene terephthalate resin, and 1,4-cyclohexanedimethanol-modified polyethylene terephthalate resin.

The polyester resin preferably contains, as the main dicarboxylic acid component unit, an acid component unit consisting of an aromatic dicarboxylic acid or its acid anhydride, or a derivative thereof, such as a terephthalic acid component unit, an isophthalic acid component unit, a naphthalenedicarboxylic acid component unit, or one or more of these dicarboxylic acid components.

The degree of crystallinity of the polyester resin can be adjusted by using two or more dicarboxylic acid components, such as terephthalic acid and isophthalic acid, and changing the molar ratio of the dicarboxylic acid component units, or by using two or more diol components, such as ethylene glycol and cyclohexanedimethanol, and changing the molar ratio of the diol component units.

In order for the base resin constituting the extruded foamed insulation board of the present invention to have a preferable morphology, the melt viscosity of the polyester resin is preferably close to the melt viscosity of a styrene-(meth)acrylic acid ester copolymer, and the melt viscosity (η) under the conditions of a temperature of 200° C. and a shear rate of 100 sec ⁻¹ is preferably within the range of 500 to 10,000 Pa s, more preferably 700 to 8,000 Pa s, and particularly preferably 1,000 to 6,000 Pa s.

The amount of the polyester resin in the base resin is 5 to 50% by mass. If the amount of polyester resin is too small, it is difficult to obtain an extruded foam insulation board with a large cross-sectional area. On the other hand, if the amount of polyester resin is too large, the melt tension of the base resin decreases, making foam molding difficult, and there is a risk that an extruded foam insulation board with a high expansion ratio cannot be obtained. In addition, depending on the type of polyester resin, there is a risk that the heat resistance of the obtained extruded foam insulation board may be inferior to that of a conventional general polystyrene resin foam insulation board. In addition, from the viewpoint of obtaining an extruded foam insulation board with a large cross-sectional area and having both a high expansion ratio and a high closed cell ratio, it is preferable that the amount of the polyester resin in the base resin is 10 to 45% by mass, and more preferably 20 to 40% by mass.

The mass ratio of the styrene-(meth)acrylic acid ester copolymer to the polyester resin in the base resin (styrene-(meth)acrylic acid ester copolymer:polyester resin) is preferably 95:5 to 50:50, more preferably 85:15 to 45:55, and even more preferably 80:20 to 40:60.

In the present invention, other polymers such as polystyrene resin, polyolefin resin, styrene-based elastomer, and polyphenylene ether resin can be mixed into the base resin according to the purpose of blending, within the scope that does not impair the object of the present invention. The amount of such other polymers used in the base resin (base resin being 100% by mass) is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less. The polystyrene resin refers to a polystyrene resin in which the (meth)acrylic acid ester component is less than 5% by mass and the styrene component is more than 50% by mass.

(3) Physical Foaming Agent The physical foaming agent is preferably one having zero or extremely low ozone depletion potential and low global warming potential. For the purpose of reducing the thermal conductivity of the thermoplastic resin extruded foam insulation board, it is preferable to use at least hydrofluoroolefin (HFO) as the physical foaming agent.

Specific examples of the HFO include 1,3,3,3-tetrafluoropropene (hereinafter also referred to as HFO1234ze), 1-chloro-3,3,3-trifluoropropene (hereinafter also referred to as HFO1233zd), 1-chloro-2,3,3,3-tetrafluoropropene (hereinafter also referred to as HFO1224yd), 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz), and the like. These blowing agents can be used alone or in combination of two or more. The hydrofluoroolefins have an ozone depletion potential of zero, a very small global warming potential, low thermal conductivity in the gas state, and are non-flammable.

The HFO is more effective at plasticizing the (meth)acrylic acid ester component derived from the styrene-(meth)acrylic acid ester copolymer in the base resin than a hydrocarbon-based blowing agent. Therefore, in relation to the content of the (meth)acrylic acid ester component, it is thought that it becomes easier to adjust the foaming suitability to a good range and that the styrene-(meth)acrylic acid ester copolymer and polyester resin tend to form a complex continuous layer.

Furthermore, among the above-mentioned HFOs, from the viewpoint of obtaining an extruded foam board with particularly low thermal conductivity, it is preferable to use one or more HFOs selected from HFO1234ze, HFO1233zd, and HFO1224yd, which have low permeability into styrene-(meth)acrylic acid ester copolymers and low thermal conductivity.

When HFO1234z and HFO1233zd are used as the HFO, from the viewpoint of obtaining an extruded foam board with long-term insulation properties due to an effective amount of HFO remaining in the foam board after extrusion foaming, the molar ratio of HFO1234ze to HFO1233zd (HFO1234ze:HFO1233zd) is preferably 20:80 to 80:20, and more preferably 30:70 to 70:30.

The amount of HFO added is preferably 0.5 mol or more and 1.5 mol or less per 1 kg of the base resin. Within this range, an effective amount of HFO remains in the foamed insulation board after extrusion foaming, resulting in an extruded foam board with long-term insulation properties. From this viewpoint, the amount of HFO added is more preferably 0.7 mol or more and 1.4 mol or less, and even more preferably 0.8 mol or more and 1.3 mol or less per 1 kg of the base resin.

The ratio of the amount of the hydrofluoroolefin added to the total amount of the physical foaming agent added (100 mol%) is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more.

It is also preferable to use aliphatic alcohols with 1 to 5 carbon atoms, water, dialkyl ethers with alkyl chains with 1 to 3 carbon atoms, carbon dioxide, etc., in combination with the physical foaming agent, as long as this does not impair long-term heat insulation, as this reduces the amount of HFO added and allows for cheaper production.

In addition, from the viewpoint of facilitating the production of an extruded foam board having a low apparent density and a high closed cell ratio, the amount of saturated hydrocarbons having 3 to 5 carbon atoms added as the physical foaming agent is preferably 0.3 mol or less per 1 kg of the base resin, more preferably 0.2 mol or less per 1 kg of the base resin, and even more preferably 0.1 mol% or less per 1 kg of the base resin. Saturated hydrocarbons having 3 to 5 carbon atoms have a weak effect of plasticizing the styrene-(meth)acrylic acid ester copolymer contained in the base resin. Therefore, in the present invention, it is believed that by reducing the amount of saturated hydrocarbons having 3 to 5 carbon atoms added or by not adding them at all, an extruded foam board having a low apparent density and a high closed cell ratio can be easily produced.

(4) Flame retardant As the flame retardant, a bromine-based flame retardant can be suitably used. Examples of the bromine-based flame retardant include tetrabromobisphenol A, tetrabromobisphenol-A-bis(2,3-dibromopropyl ether), tetrabromobisphenol-A-bis(2-bromoethyl ether), tetrabromobisphenol-A-bis(allyl ether), tetrabromobisphenol-A-bis(2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol S, tetrabromobisphenol-S-bis(2,3-dibromopropyl ether), hexabromocyclododecane, tetrabromocyclooctane, tris(2,3-dibromopropyl)isocyanurate, tribromophenol, decabromodiphenyl oxide, tris(tribromoneopentyl)phosphate, brominated polystyrene, and brominated styrene-butadiene copolymer. These compounds can be used alone or in combination of two or more. Among the above brominated flame retardants, from the viewpoint of high thermal stability and high flame retardancy, it is particularly preferable to use brominated compounds of tetrabromobisphenol-A-bis(2,3-dibromopropyl ether), tetrabromobisphenol-A-bis(2,3-dibromo-2-methylpropyl ether), tris(2,3-dibromopropyl)isocyanurate, and styrene-butadiene copolymers. These compounds can be used alone or in combination of two or more kinds.

The amount of flame retardant to be blended is preferably 1 part by mass, more preferably 3 parts by mass, per 100 parts by mass of base resin, from the viewpoint of satisfying a high level of flame retardancy such as the flammability standard for extruded polystyrene foam insulation boards described in "Test Method A" in the flammability test method of JIS A9521:2017. In addition, from the viewpoint of minimizing the deterioration of foamability during extrusion and the deterioration of the mechanical properties of the thermoplastic resin foam, the upper limit of the amount of flame retardant to be blended is preferably 10 parts by mass, more preferably 7 parts by mass, per 100 parts by mass of thermoplastic resin.

Furthermore, in the present invention, a flame retardant auxiliary can be blended in combination with the flame retardant in order to further improve the flame retardancy of the extruded foam board. Examples of the flame retardant auxiliary include diphenylalkanes and diphenylalkenes such as 2,3-dimethyl-2,3-diphenylbutane, 2,3-diethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, 3,4-diethyl-3,4-diphenylhexane, 2,4-diphenyl-4-methyl-1-pentene, and 2,4-diphenyl-4-ethyl-1-pentene; nitrogen-containing cyclic compounds such as triphenylphosphate, cresyl di-2,6-xylenyl phosphate, antimony trioxide, diantimony pentoxide, ammonium sulfate, zinc stannate, cyanuric acid, isocyanuric acid, triallyl isocyanurate, melamine cyanurate, melamine, melam, and melem; silicone compounds; inorganic compounds such as boron oxide, zinc borate, and zinc sulfide; and phosphorus compounds such as red phosphorus, ammonium polyphosphate, and phosphazene. These compounds can be used alone or in combination of two or more.

The method of blending the flame retardant into the thermoplastic resin includes a method of feeding a predetermined ratio of the flame retardant together with the thermoplastic resin to a raw material feed section provided upstream of the extruder and kneading the flame retardant together with the thermoplastic resin in the extruder. In addition, the flame retardant can be fed into the thermoplastic resin melt from a flame retardant feed section provided in the extruder. When feeding the flame retardant into the extruder, a method of feeding a dry blend of the flame retardant and the thermoplastic resin into the extruder, a method of feeding a liquid flame retardant that has been heated and melted in advance into the extruder, or a method of preparing a master batch containing the flame retardant and the thermoplastic resin as the base resin and feeding it to the extruder can be adopted. In particular, from the viewpoint of dispersibility, it is preferable to adopt a method of preparing a master batch containing the flame retardant and feeding it to the extruder. The blending method of the flame retardant assistant is the same as the above method.

(5) Heat Insulation Improver In the present invention, a heat insulation improver can be blended with the base resin to further improve the heat insulation. Examples of heat insulation improvers include metal oxides such as titanium oxide, metals such as aluminum, ceramics, fine powders such as carbon black and graphite, infrared shielding pigments, and hydrotalcite. These can be used alone or in combination. The amount of the heat insulation improver added is in the range of 0.5 to 5 parts by mass, preferably 1 to 4 parts by mass, per 100 parts by mass of the base resin.

(6) Other Additives In the present invention, various additives such as cell regulators, colorants such as pigments and dyes, heat stabilizers, and fillers may be appropriately blended with the base resin, if necessary.

As the bubble regulator, for example, inorganic powders such as talc, kaolin, mica, silica, calcium carbonate, barium sulfate, aluminum oxide, clay, bentonite, and diatomaceous earth, and conventionally known chemical foaming agents such as azodicarbodiamide can be used. Among them, talc is preferable because it does not inhibit flame retardancy and allows easy adjustment of bubble size. It is particularly preferable to use talc having a particle size of 0.1 to 20 μm, and more preferably 0.5 to 15 μm, as specified in JIS Z8901 (2006). The amount of the bubble regulator to be added varies depending on the type of the bubble regulator, the desired bubble size, and the like, but is generally 0.01 to 8 parts by mass, more preferably 0.01 to 5 parts by mass, and particularly preferably 0.05 to 3 parts by mass, relative to 100 parts by mass of the base resin.

The method for producing the extruded thermoplastic resin foam plate of the present invention is, for example, a method for producing an extruded thermoplastic resin foam plate by extruding and foaming a foamable resin composition obtained by kneading the thermoplastic resin, the physical foaming agent, and the flame retardant through a die attached to the outlet of an extruder, and forming the composition into a plate shape. Specifically, the extruded thermoplastic resin foam plate is produced by feeding the thermoplastic resin and additives added as necessary to an extruder, further feeding a physical foaming agent through a physical foaming agent supply port, melt-kneading the mixture, extruding the mixture from a die lip at the tip of the extruder under atmospheric pressure, and then forming the mixture into a predetermined shape (plate shape) with a forming tool (such as a guider). The forming tool can be, for example, a forming device consisting of a pair of upper and lower polytetrafluoroethylene plates.

The physical properties of the extruded thermoplastic resin foam board will be described in detail below.
[Apparent density]
From the viewpoint of improving the manufacturing stability and mechanical strength of the foam board, the lower limit of the apparent density of the extruded thermoplastic resin foam board of the present invention is preferably 20 kg/ ^m3 , more preferably 25 kg/ ^m3 , and even more preferably 30 kg/ ^m3 . From the viewpoint of improving the heat insulating properties and ensuring the light weight, the upper limit of the apparent density is preferably 50 kg/ ^m3 , more preferably 45 kg/ ^m3 , and even more preferably 40 kg/ ^m3 .

[Thickness]
The thickness of the extruded foam board is appropriately set depending on the purpose of use, and is not particularly limited, but from the viewpoint of use as a heat insulating material, it is preferably 25 mm or more, more preferably 35 mm or more, and even more preferably 45 mm or more. The upper limit of the thickness is about 150 mm. In the present invention, since the base resin contains a polyester resin, it is easy to obtain the thick extruded foam board.

[Closed bubble ratio]
From the viewpoint of long-term heat insulation, the closed cell ratio of the extruded foam board is preferably 85% or more, more preferably 90% or more, and even more preferably 92% or more.

The closed cell ratio of the extruded foam board is measured by cutting out cut samples from a total of five randomly selected locations of the extruded foam board, determining the closed cell ratio for each measurement sample, and adopting the arithmetic average value of the closed cell ratios at the five locations. The cut samples are samples without a skin cut into a size of 45 mm length x 20 mm width x 25 mm thickness from the extruded foam board. If the sample is too thin to cut out a 25 mm sample in the thickness direction, for example, two cut samples cut into a size of 45 mm length x 20 mm width x 12.5 mm thickness are stacked and measured. The closed cell ratio S (%) is calculated according to the following formula (1) using the true volume Vx of the thermoplastic resin foam measured using an air comparison type specific gravity meter (for example, Toshiba Beckman Co., Ltd., air comparison type specific gravity meter, model: 930) in accordance with procedure C of ASTM-D2856-70.

S (%) = (Vx-W/ρ) x 100/(VA-W/ρ)...(1)
Vx: true volume (cm ³ ) of a cut sample determined by measurement using an air-comparison specific gravity meter (the sum of the volume of the resin constituting the cut sample of the foam and the total volume of the air bubbles in the closed cell portion of the cut sample) It is equivalent to.)
VA: Apparent volume (cm ³ ) of the cut sample calculated from the outer dimensions of the cut sample used in the measurement
W: total weight (g) of cut sample used for measurement
ρ: density of base resin constituting thermoplastic resin foam (g/cm ³ )

[Thermal conductivity]
The thermal conductivity of the extruded foam board of the present invention 10 days after production is preferably 0.024 W/(m·K) or less, more preferably 0.023 W/(m·K) or less, and even more preferably 0.022 W/(m·K) or less.

The extruded foam of the present invention preferably has a thermal conductivity of 0.028 W/(m·K) or less 1500 days after production, more preferably 0.027 W/(m·K) or less, and even more preferably 0.026 W/(m·K) or less. Furthermore, from the viewpoint of the long-term insulation properties of the extruded foam board, it is preferable that the difference between the thermal conductivity 10 days after production, 1500 days after production, and the thermal conductivity 10 days after production is smaller.

The thermal conductivity is measured by cutting test pieces of 200 mm length x 200 mm width x thickness without any skin from the extruded foam board immediately after production, storing the test pieces for 10 days in an atmosphere of 23°C and 50% humidity, and storing the test pieces for 10 days and 1500 days in accordance with 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 A 1412-2 (1999).

The thermal conductivity 1500 days after manufacture is measured on samples that have undergone accelerated testing in accordance with JIS A1486 (2014). According to this method, for example, the thermal conductivity measured 60 days after manufacture using a sample obtained by slicing a 50 mm thick extruded foam board to a thickness of 10 mm corresponds to the thermal conductivity of the extruded foam board approximately 1500 days after manufacture.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.
The thermoplastic resins, flame retardants, cell regulators and physical foaming agents used in the examples and comparative examples are shown below.

<Thermoplastic resin>
(Styrene-(meth)acrylic acid ester copolymer) (MS raw material) (Hereinafter, the (meth)acrylic acid ester component derived from the styrene-(meth)acrylic acid ester copolymer may be referred to as M component)
MS1: styrene-methyl (meth)acrylate copolymer, manufactured by Toyo Styrene Co., Ltd., MS600 M component-60% by mass, styrene component-40% by mass, melt viscosity (200°C, 100 sec ^-1 ) 2570 Pa·s, air permeability coefficient 5.9 (cc·mm/( ^m2 ·day·atm))
MS2: styrene-methyl (meth)acrylate copolymer, manufactured by Toyo Styrene Co., Ltd., MS200 M component-20% by mass, styrene component-80% by mass, melt viscosity (200°C, 100 sec ^-1 ) 1750 Pa·s, air permeability coefficient 22.9 (cc·mm/( ^m2 ·day·atm))

(Polyester resin) (PET raw material)
PET1: (spiroglycol) modified PET, Altester 3012 manufactured by Mitsubishi Gas Chemical Co., Inc., dicarboxylic acid component - terephthalic acid 100% by mass, glycol component - spiroglycol (SPG)/ethylene glycol (EG) = 30% by mass/70% by mass, endothermic peak heat quantity 0 J/g, melt viscosity (200°C, 100 sec ^-1 ) 2000 Pa·s, air permeability coefficient 4.1 (cc·mm/( ^m2 ·day·atm))
PET2: glycol-modified PET, PN100 manufactured by SK Chemical Co., Ltd., dicarboxylic acid component-terephthalic acid 100% by mass, glycol component-1,4-cyclohexanedimethanol (CHDM)/ethylene glycol (EG)=43% by mass/57% by mass, endothermic peak heat quantity 0 J/g, melt viscosity 3170 Pa·s, air permeability coefficient 2.4 (cc·mm/( ^m2 ·day·atm))

The type, manufacturer, product name, melt viscosity, and air permeability coefficient of each of the above resins are shown in Tables 1 and 2.

The melt viscosity of the resin was measured by the following method using a Capillograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. A capillary with a hole diameter of 1.0 mm and a length of 10.0 mm was attached to the tip of a cylinder with a diameter of 9.55 mm and a length of 350 mm, and the cylinder and the capillary were heated to 200° C., after which a measurement sample (resin pellets) was filled in the cylinder and sufficiently melted by preheating for 4 minutes, and the melt viscosity of the resin was measured under the condition of a shear rate of 100 sec ⁻¹ .

The air permeability coefficient of the resin was measured using a gas permeability tester BT-3 manufactured by Toyo Seiki Co., Ltd., in accordance with JIS K7126-1:2006 Plastics - Films and sheets - Gas permeability test method - Part 1: Differential pressure method.

<Flame retardants>
As a flame retardant, a bromide butadiene-styrene block copolymer "Emerald innovation 3000" manufactured by LANXESS KK was used.

<Foam Regulator>
As the bubble adjusting agent, talc: "Hi-Filler #12" manufactured by Matsumura Sangyo Co., Ltd. was used.

<Physical foaming agent>
Blowing agent 1: Hydrofluoroolefin (HFO): 1,3,3,3-tetrafluoropropene (HFO-1234ze)
Blowing agent 2: Hydrofluoroolefin (HFO): 1-chloro-3,3,3-trifluoropropene (HFO1233zd)
Blowing agent 3: Ethanol (EtOH)
Blowing agent 4: Water

The mixed resin, flame retardant, and cell regulator were each fed to the extruder in the blending ratios shown in Tables 3 and 4 below (where the total blending amount of the MS raw material and the PET raw material is 100% by mass), and the physical foaming agent was further fed from the physical foaming agent feed port, melted and kneaded, and the molten mixture was extruded from the die lip at the tip of the extruder under atmospheric pressure under the conditions shown in Tables 3 and 4, and then molded into a predetermined shape (plate-like) using a shaping device (guider), which is a molding tool, to obtain a base plate with a thickness of 55 mm. The surface skins on both sides of the base plate were then evenly scraped off to produce the plate-like thermoplastic resin extruded foam plates of Examples 1 to 6 and Comparative Examples 1 to 3, each with a width of 600 mm, length of 2000 mm, and thickness of 50 mm.

The extruded foam boards thus produced were measured for apparent density, closed cell ratio, and cell structure (cell diameter in the thickness direction, cell deformation rate) by the following methods.
<Apparent density>
The apparent density was measured in accordance with JIS K6767 (1999). Rectangular samples measuring 50 mm long x 50 mm wide x 50 mm thick were cut from three locations, namely, the center and both ends in the width direction of each extruded foam plate, and the apparent density of each sample was measured. The arithmetic mean of the measurements at the three locations was taken as the apparent density.

<Closed bubble ratio>
The cut samples were cut from three locations, namely, the center and both ends in the width direction of the extruded foam plate, to prepare measurement samples, and the closed cell ratio of each measurement sample was measured, and the arithmetic average value of the closed cell ratios at the three locations was used. The cut samples were cut from the extruded foam plate to a size of 25 mm length x 25 mm width x 25 mm thickness.
The closed cell ratio of the sample was measured using an air comparison type pycnometer (Model: 930, manufactured by Toshiba Beckman Co., Ltd.) according to Procedure C of ASTM-D2856-70, and calculated from the above formula (1). The arithmetic average value of three points was defined as the closed cell ratio.

<Flame retardancy evaluation>
The extruded thermoplastic resin foam boards 7 days after production were subjected to a flammability test in accordance with the measurement method A of the flammability test method of JIS A9521: 2017. For the measurement, five test pieces were randomly cut out from one extruded foam board, and the flame retardancy was evaluated according to the following criteria.
◯: For all test pieces, the flame goes out within 3 seconds, no residual dust remains, and the test piece does not burn beyond the flammability limit line.
×: The average burning time of the five test pieces exceeds 3 seconds.

<Surface properties>
The surface properties were visually evaluated as follows.
◯: A base plate with a smooth surface was stably produced, and a good extruded foam plate was obtained.
×: Cracks or splits were observed on the surface of the original plate, and good extruded foam plates could not be stably obtained.

<LOI (Oxygen Index)>
Immediately after production, the extruded foam board was moved to a room with an air temperature of 23°C and a relative humidity of 50%, and left in that room for 4 weeks. After that, a test piece was cut out from the extruded foam board and measured in accordance with JIS K7201-2007. The flammability was evaluated. The type of heat source of the igniter was liquefied petroleum gas (LPG), the ignition procedure was method A, and the test piece was placed in a designated position inside the test machine. The temperature in the room was 23° C. and the humidity was 50%.

<Thermal Conductivity>
A test piece without a skin, measuring 200 mm in length, 200 mm in width, and 50 mm in thickness, was cut out from the extruded foam plate immediately after production, and stored for 10 days in an atmosphere at a temperature of 23°C and a humidity of 50%. The thermal conductivity of the test piece was measured in accordance with JIS A1412-2 (1999) flat plate heat flow meter method (two heat flow meter plates method, high temperature side 38°C, low temperature side 8°C, average temperature 23°C).

The thermal conductivity after 1500 days of manufacture was measured on a test piece subjected to test method A of the accelerated long-term change test of thermal resistance in accordance with JIS A1486 (2014). Specifically, a test piece without a molded skin measuring 200 mm x 200 mm x 10 mm was cut evenly from both sides of the center of a 50 mm-thick extruded foam board immediately after manufacture, and stored in a constant temperature and humidity room at a temperature of 23°C and a relative humidity of 50%. The thermal conductivity of the test piece after 60 days of manufacture (corresponding to 1500 days after the manufacture of a 50 mm-thick extruded foam board) 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).

<Evaluation Results>
From the evaluation and measurement results of the physical properties shown in Table 5, the extruded foam boards of Examples 1 to 6, as shown in Table 3, contain a base resin containing a styrene-(meth)acrylic acid ester copolymer and a polyester resin having a heat of fusion of less than 5 J/g based on JIS K7122-1987, and the blending amount of the polyester resin in the base resin is in the range of 5 to 50% by mass, and the content of the (meth)acrylic acid ester component in the base resin is in the range of 20 to 40% by mass. Therefore, it was confirmed that the extruded foam boards exhibit good flame retardancy and maintain low thermal conductivity even after 1500 days.

In contrast, the extruded foams of Comparative Examples 1 to 3, in which the content of the (meth)acrylic acid ester component in the base resin was not within the range of 20 to 40% by mass, either had poor flame retardancy or were unmoldable.

Claims (3)

A method for producing an extruded thermoplastic resin foam plate having an apparent density of 20 to 50 kg/m ³ and a thickness of 10 to 150 mm, comprising the steps of extruding and foaming a foamable resin composition obtained by kneading a base resin, a physical foaming agent, and a flame retardant, and molding the composition into a plate shape using a molding tool,
the base resin comprises a styrene-(meth)acrylic acid ester copolymer and a polyester resin having a heat of fusion of less than 5 J/g based on JIS K7122-1987;
The blending amount of the polyester resin in the base resin is 5 to 50% by mass,
the content of the (meth)acrylic acid ester component derived from a styrene-(meth)acrylic acid ester copolymer in the base resin is 20 to 40% by mass,
The physical blowing agent comprises a hydrofluoroolefin,
A method for producing an extruded thermoplastic resin foam board, wherein the ratio of the amount of said hydrofluoroolefin added to the total amount of said physical foaming agents added (100 mol %) is 50 mol % or more . 2. The method for producing an extruded thermoplastic resin foam board according to claim 1, wherein the amount of the hydrofluoroolefin added is 0.5 mol or more and 1.5 mol or less per 1 kg of the base resin. The method for producing an extruded thermoplastic resin foam plate according to claim 1 or 2, characterized in that the hydrofluoroolefin contains 1,3,3,3-tetrafluoropropene and 1-chloro-3,3,3-trifluoropropene, and the molar ratio of 1,3,3,3-tetrafluoropropene to 1-chloro-3,3,3-trifluoropropene is 20:80 to 80:20 .