JP7599306B2 - Styrenic resin extrusion foam - Google Patents

Description

The present invention relates to an extruded styrene-based resin foam.

Styrene-based resin extruded foams are used, for example, as insulation for structures due to their good workability and insulating properties. In recent years, there has been an increasing demand for energy conservation in homes and buildings, and there is a demand for technological development of foams with higher insulating properties than ever before.

As examples of highly insulating foams, there have been proposed extruded styrene-based resin foams to which a prescribed amount of graphite or titanium oxide has been added as a heat radiation suppressant (see, for example, Patent Document 1), and extruded styrene-based resin foams that use, as a foaming agent, environmentally friendly fluorinated olefins (hydrofluoroolefins and hydrochlorofluoroolefins) that have an ozone depletion potential of zero and a small global warming potential, or alkyl chlorides such as methyl chloride and ethyl chloride (see, for example, Patent Documents 2 to 4).

On the other hand, brominated styrene-butadiene block copolymers have been proposed as a flame retardant to be added to styrene-based resin extruded foams to impart flame retardancy, instead of the conventionally used hexabromocyclododecane (HBCD). However, brominated styrene-butadiene block copolymers have problems with thermal stability. Therefore, techniques have been proposed to improve the thermal stability of the brominated styrene-butadiene block copolymers themselves, and to improve thermal stability by adding epoxy compounds (for example, Patent Documents 5-6).

JP 2013-221110 A Special Publication No. 2008-546892 JP 2019-189811 A JP 2019-108416 A International Publication No. 2007/058736 International Publication No. 2010/080285

The object of the present invention is to provide an extruded styrene-based resin foam that has excellent heat insulation performance, flame retardancy, and thermal stability.

In order to solve the above problems, the present inventors have conducted intensive research and found that when a thermal radiation inhibitor is added to a styrene-based resin foam to improve its heat insulation, the effect of improving the thermal stability by using an epoxy compound as a stabilizer in combination with an aliphatic bromine-containing polymer as a flame retardant is reduced. As a result of further investigation, the inventors have succeeded in producing a styrene-based resin foam having excellent heat insulation performance, flame retardancy, and thermal stability, and have arrived at the present invention. The present invention includes the following aspects.
<1> An extruded styrene-based resin foam satisfying the following (I) to (III):
(I) containing 0.5 to 5.0 parts by weight of a heat radiation inhibitor based on 100 parts by weight of a styrene-based resin;
(II) Contains an aliphatic bromine-containing polymer as a flame retardant;
(III) The composition contains, as a stabilizer, 21 to 50 parts by weight of an epoxy compound (A) based on 100 parts by weight of the aliphatic bromine-containing polymer.
<2> The stabilizer comprises 0 to 20 parts by weight of (B) a polyhydric alcohol partial ester relative to 100 parts by weight of the aliphatic bromine-containing polymer,
The extruded styrene-based resin foam according to <1>, comprising: (C) 4 to 20 parts by weight of a phenol-based stabilizer; and (D) 0 to 0.9 parts by weight of a phosphite-based stabilizer.
<3> The extruded styrene-based resin foam according to <1> or <2>, wherein the epoxy compound comprises at least one selected from the group consisting of bisphenol A diglycidyl ether type epoxy resins, cresol novolac type epoxy resins, and phenol novolac type epoxy resins.
<4> The stabilizer contains (B) a polyhydric alcohol partial ester,
The extruded styrene-based resin foam according to any one of <1> to <3>, wherein the polyhydric alcohol partial ester comprises a reaction product of dipentaerythritol and adipic acid.
<5> The stabilizer contains (D) a phosphite-based stabilizer,
The extruded styrene-based resin foam according to any one of <1> to <4>, wherein the phosphite stabilizer comprises at least one selected from the group consisting of 3,9-bis(2,4-di-tert-butylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, and tetrakis(2,4-di-tert-butyl-5-methylphenyl)-4,4'-biphenylene diphosphonite).
<6> The extruded styrene-based resin foam according to any one of <1> to <5>, further comprising a phosphoric acid ester.
<7> The extruded styrene-based resin foam according to <6>, wherein the phosphoric acid ester contains tetrakis(2,6-dimethylphenyl)-m-phenylene bisphosphate.
<8> The extruded styrene-based resin foam according to any one of <1> to <7>, containing hydrofluoroolefin and/or hydrochlorofluoroolefin as a foaming agent.
<9> The extruded styrene-based resin foam according to <8>, containing 1.0 part by weight or more and 12.0 parts by weight or less of the hydrofluoroolefin and/or hydrochlorofluoroolefin per 100 parts by weight of the styrene-based resin.
<10> The extruded styrene-based resin foam according to any one of <1> to <9>, wherein the heat radiation inhibitor contains graphite and/or titanium oxide.
<11> The extruded styrene-based resin foam according to any one of <1> to <10>, wherein the extruded styrene-based resin foam has a thermal conductivity of 0.0244 W/mK or less.
<12> The extruded styrene-based resin foam according to any one of <1> to <11>, wherein the extruded styrene-based resin foam has a density of 20 to 60 kg/m3.
<13> The extruded styrene-based resin foam according to any one of <1> to <12>, wherein the extruded styrene-based resin foam has a thickness of 10 mm or more and 150 mm or less.

The extruded styrene-based resin foam of the present invention exhibits excellent heat insulation performance, flame retardancy, and thermal stability.

One embodiment of the present invention is described below, but the present invention is not limited to this. The present invention is not limited to each configuration described below, and various modifications are possible within the scope of the claims, and embodiments and examples obtained by appropriately combining the technical means disclosed in different embodiments and examples are also included in the technical scope of the present invention. In addition, all academic literature and patent documents described in this specification are incorporated herein by reference. In addition, unless otherwise specified in this specification, "A to B" representing a numerical range is intended to mean "greater than or equal to A and less than or equal to B."

[1. Extruded styrene resin foam]
The extruded styrene-based resin foam according to one embodiment of the present invention satisfies the following (I), (II), and (III).
(I) containing 0.5 to 5.0 parts by weight of a heat radiation inhibitor based on 100 parts by weight of a styrene-based resin;
(II) Contains an aliphatic bromine-containing polymer as a flame retardant;
(III) The composition contains, as a stabilizer, 21 to 50 parts by weight of an epoxy compound (A) based on 100 parts by weight of the aliphatic bromine-containing polymer.

In the case where the styrene-based resin extruded foam contains an aliphatic bromine-containing polymer as a flame retardant, the thermal stability is improved by using an epoxy compound in combination. However, if an excessive amount of epoxy compound is added, the stabilizing effect of the epoxy compound becomes excessive, and there is a problem that the flame retardant performance is reduced, so an excessive amount of epoxy compound is not usually used. Even in the case of a styrene-based resin extruded foam with improved flame retardant performance and thermal stability, when a heat radiation inhibitor such as graphite or titanium oxide is added to reduce the thermal conductivity, it has been found that the flame retardant tends to deteriorate more in the case where the graphite is added than in the case where the heat radiation inhibitor is not added. This is assumed to be because the thermal stability of the aliphatic bromine-containing polymer is further deteriorated by the impurities contained in the heat radiation inhibitor. As described above, the excessive addition of epoxy compounds usually causes a decrease in flame retardant performance, but in the case where the heat radiation inhibitor is added, it has been found that the decrease in flame retardant performance can be suppressed even if the amount of epoxy compound added to the aliphatic bromine-containing polymer is more than the normal amount. Specifically, by controlling the content of the epoxy compound to 21 to 50 parts by weight per 100 parts by weight of the aliphatic bromine-containing polymer, it is possible to achieve a good balance between thermal stability, flame retardancy, and heat insulation. For example, even when a styrene-based resin extrusion foam is recycled by reducing the volume through heat shrinkage and/or thermal melting, it has good moldability and thermal stability that allows recycling. In addition, it passes the JIS A9511 combustion test method and/or exhibits flame retardancy with an oxygen index of 26% or more, and also has excellent heat insulation.

(1-1. Styrene-based resin)
As the styrene -based resin, it is preferable to use one having an MFR of 0.1 to 50 g/10 min, because (i) it is excellent in molding processability during extrusion foaming, (ii) it is easy to adjust the discharge amount during molding, the thickness, width, apparent density, and closed cell ratio of the obtained styrene-based resin extruded foam to desired values, (iii) it is excellent in foamability (the thickness, width, apparent density, closed cell ratio, and surface properties of the foam are easily adjusted to desired conditions), (iv) it is possible to obtain an extruded styrene-based resin foam with excellent appearance, and (v) it is possible to obtain an extruded styrene-based resin foam with a good balance of properties (for example, mechanical strength such as compressive strength, bending strength, or bending deflection amount, toughness, etc.). Furthermore, the MFR of the styrene-based resin is more preferably 0.3 to 30 g/10 min, and particularly preferably 0.5 to 25 g/10 min, from the viewpoint of the balance between molding processability and foamability, and mechanical strength and toughness. In one embodiment of the present invention, the MFR is measured by JIS K7210 (1999) Method A and test condition H. The styrene -based resin is preferably polystyrene , high- impact polystyrene, etc. From the viewpoint of economy, polystyrene is particularly preferable .

(1-2. Flame retardants)
The styrene-based resin extruded foam of the present invention uses an aliphatic bromine-containing polymer as a flame retardant. Examples of the aliphatic bromine-containing polymer include brominated styrene-butadiene block copolymer, brominated styrene-butadiene random copolymer, brominated styrene-butadiene graft polymer, brominated butadiene polymer, and brominated epoxidized styrene-butadiene block copolymer. These may be used alone or in combination of two or more. Among these, brominated styrene-butadiene block copolymer is preferred from the viewpoints of performance, economy, and supply stability.

In one embodiment of the present invention, the content of the aliphatic bromine-containing polymer is preferably 0.5 to 10 parts by weight per 100 parts by weight of the styrene-based resin, and in consideration of the economical efficiency and the effect on other required physical properties, a more preferable range is 0.5 to 5 parts by weight.

In one embodiment of the present invention, other brominated flame retardants can be used in combination to further improve flame retardant performance.

Specific examples of other bromine-based flame retardants include hexabromocyclododecane, tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl)ether, tetrabromobisphenol A-bis(2,3-dibromopropyl)ether, and tris(2,3-dibromopropyl)isocyanurate. These may be used alone or in combination of two or more. Among these other bromine-based flame retardants, from the viewpoint of the flame retardant performance and thermal stability performance of the foam, mixed bromine-based flame retardants consisting of tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl)ether and tetrabromobisphenol A-bis(2,3-dibromopropyl)ether, and hexabromocyclododecane are preferred. The preferred amount of the other bromine-based flame retardant to be added is 0 to 3.0 parts by weight per 100 parts by weight of the styrene-based resin.

In one embodiment of the present invention, a radical generator can be used in combination with the styrene-based resin extrusion foam to improve the flame retardant performance. Specific examples of the radical generator include 2,3-dimethyl-2,3-diphenylbutane, poly-1,4-diisopropylbenzene, 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. Peroxides such as dicumyl peroxide are also used. Among them, those that are stable under the resin processing temperature conditions are preferred, specifically 2,3-dimethyl-2,3-diphenylbutane and poly-1,4-diisopropylbenzene, and the preferred amount of the radical generator to be added is 0.05 to 0.8 parts by weight per 100 parts by weight of the styrene-based resin.

In one embodiment of the present invention, phosphorus-based flame retardants such as phosphate esters and phosphine oxides can be used in combination to improve flame retardant performance, in other words, as flame retardant assistants, to the extent that the thermal stability performance is not impaired.

Examples of the phosphate esters used in one embodiment of the present invention include condensed phosphate esters such as triphenyl phosphate, tris(tributylbromoneopentyl)phosphate, tricresyl phosphate, trixylyleneyl phosphate, cresyl diphenyl phosphate, 2-ethylhexyl diphenyl phosphate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, tris(2-ethylhexyl)phosphate, tris(butoxyethyl)phosphate, and tetrakis(2,6-dimethylphenyl)-m-phenylene bisphosphate. As a phosphine oxide type phosphorus-based flame retardant, triphenylphosphine oxide is preferred. These phosphate esters and phosphine oxides may be used alone or in combination of two or more. Among these phosphorus-based flame retardants, triphenyl phosphate, tris(tributylbromoneopentyl)phosphate, and tetrakis(2,6-dimethylphenyl)-m-phenylene bisphosphate are preferred from the viewpoint of the flame retardant performance and thermal stability performance of the foam, and tetrakis(2,6-dimethylphenyl)-m-phenylene bisphosphate is particularly preferred. The preferred amount of phosphorus-based flame retardant to be added is 0.1 to 2 parts by weight per 100 parts by weight of the styrene-based resin.

(1-3. Stabilizer: (A) Epoxy Compound)
In one embodiment of the present invention, by containing an epoxy compound as a stabilizer, it is possible to improve the thermal stability without impairing the flame retardant performance of the flame retardant.

As the epoxy compound used in one embodiment of the present invention, an epoxy compound generally used as a stabilizer for the aliphatic bromine-containing polymer can be used, and from the standpoints of cost, performance, and supply stability, it is preferable that the epoxy compound contains at least one selected from the group consisting of bisphenol A diglycidyl ether type epoxy resin, phenol novolac type epoxy resin, and phenol novolac type epoxy resin.

An example of a bisphenol A diglycidyl ether type epoxy resin is represented by the following structural formula (1):

An example of a cresol novolac type epoxy resin is represented by the following structural formula (2):

An example of a phenol novolac type epoxy resin is represented by the following structural formula (3):

In one embodiment of the present invention, an epoxy compound having a bromine atom added to a bisphenol A skeleton, as shown in the following structural formula (4), can also be used.

These epoxy compounds may be used alone or in combination of two or more.

The epoxy compound used in one embodiment of the present invention preferably has an epoxy equivalent of less than 1000 g/eq. Since it is believed that the epoxy group inhibits the decomposition of the bromine-based flame retardant and improves the thermal stability of the styrene-based resin, if the epoxy equivalent is 1000 g/eq or more, the effect of inhibiting the decomposition of the flame retardant is very low, and as a result, a large amount must be added, which is not economically realistic. In consideration of the balance between cost and performance, it is more preferable that the epoxy equivalent is less than 500 g/eq, and even more preferably less than 400 g/eq.

The content of the epoxy compound in the styrene-based resin extruded foam of the present invention is 21 to 50 parts by weight per 100 parts by weight of the aliphatic bromine-containing polymer. From the viewpoint of economy and performance, it is preferably 25 to 50 parts by weight, more preferably 25 to 48 parts by weight, and even more preferably 25 to 47 parts by weight. If the content of the epoxy compound is less than 21 parts by weight, the stabilizing effect of the flame retardant is not fully exerted, and the flame retardant and resin decompose, and the molecular weight of the resin tends to decrease, resulting in the bubble diameter of the bubbles forming the foam becoming larger, and the heat insulating performance tends to deteriorate. In addition, with the decrease in molecular weight distribution, the smoothness of the foam surface tends to deteriorate, and moldability tends to deteriorate. Furthermore, the decomposition of the flame retardant causes other additives or resin to turn black, leading to poor appearance. In addition, even during recycling in which scraps generated during product cutting, etc. are heated, melted, and kneaded, the decomposition of the flame retardant and resin tends to cause the resin to turn black and the molecular weight distribution to decrease, resulting in difficult recycling and increased costs. On the other hand, if the content of the epoxy compound exceeds 50 parts by weight, the stabilizing effect of the stabilizer becomes excessive, and the flame retardant cannot be effectively decomposed when the foam is burned, which tends to reduce the flame retardant performance.

(1-4. Stabilizer: (B) Polyhydric alcohol partial ester)
In one embodiment of the present invention, the thermal stability of the flame retardant can be improved by using a polyhydric alcohol partial ester in combination as a stabilizer. In particular, even in the case of repeated recycling, decomposition of the resin and the flame retardant can be suppressed, thereby making it possible to obtain a foam having excellent moldability, flame retardancy, and heat insulation performance.

The polyhydric alcohol partial ester used in the present invention is a partial ester that is a reaction product of a polyhydric alcohol such as pentaerythritol, dipentaerythritol, or tripentaerythritol with a monovalent carboxylic acid such as acetic acid or propionic acid, or a divalent carboxylic acid such as adipic acid or glutamic acid, and is a mixture of compounds having one or more hydroxyl groups in the molecule, and may contain a small amount of the raw material polyhydric alcohol. From the viewpoints of performance and economy, the partial ester that is a reaction product of dipentaerythritol and adipic acid is preferable as the polyhydric alcohol partial ester, and an example of a commercially available product is Plainlyzer (registered trademark) ST-210 manufactured by Ajinomoto Fine-Techno Co., Ltd.

In one embodiment of the present invention, the content of the polyhydric alcohol partial ester is preferably 0 to 20 parts by weight, and more preferably 0 to 17 parts by weight, per 100 parts by weight of the aliphatic bromine-containing polymer. If the content of the polyhydric alcohol partial ester exceeds 20 parts by weight, the stabilizing effect is exerted excessively, which may reduce the flame retardant performance of the flame retardant itself.

(1-4. Stabilizer: (C) Phenol-based stabilizer)
In one embodiment of the present invention, the thermal stability can be improved without impairing the flame retardant performance of the flame retardant by using a phenol-based stabilizer in combination.

The phenol-based stabilizer used in one embodiment of the present invention is not particularly limited, and commercially available substances can be used. Specific examples include triethylene glycol-bis-3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate, pentaerythritol tetrakis[3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate], and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, which may be used alone or in combination of two or more. Of these, pentaerythritol tetrakis[3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate] is preferably used in terms of cost and performance.

In one embodiment of the present invention, the content of the phenolic stabilizer is preferably 4 to 20 parts by weight, and more preferably 5 to 20 parts by weight, per 100 parts by weight of the aliphatic bromine-containing polymer. If the content of the phenolic stabilizer exceeds 20 parts by weight, it tends to affect the bubble formation of the foam, making it difficult to control the moldability and heat insulation. On the other hand, if the content of the phenolic stabilizer is less than 4 parts by weight, the stabilizing effect of the flame retardant may not be fully exerted.

(1-5. Stabilizer: (D) Phosphite-based stabilizer)
In one embodiment of the present invention, the thermal stability can be improved without impairing the flame retardant performance of the flame retardant by using a phosphite stabilizer in combination.

As examples of phosphite stabilizers used in one embodiment of the present invention, 3,9-bis(2,4-di-tert-butylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, and tetrakis(2,4-di-tert-butyl-5-methylphenyl)-4,4'-biphenylene diphosphonite) are suitable because they do not reduce the flame retardant performance of the foam and improve the thermal stability of the foam.

In one embodiment of the present invention, the content of the phosphite stabilizer is preferably 0 to 0.9 parts by weight, and more preferably 0 to 0.8 parts by weight, per 100 parts by weight of the aliphatic bromine-containing polymer. If the content of the phosphite stabilizer exceeds 0.9 parts by weight, the stabilizing effect is exerted to a great extent, which may reduce the flame retardant performance of the flame retardant itself.

(1-6. Foaming Agent)
The blowing agent used in one embodiment of the present invention is not particularly limited, but in order to improve heat insulation, it is preferable to use hydrofluoroolefin and/or hydrochlorofluoroolefin (hereinafter, "hydrofluoroolefin and/or hydrochlorofluoroolefin" may be referred to as "hydro(chloro)fluoroolefin").

The hydrofluoroolefin used in one embodiment of the present invention is not particularly limited, but tetrafluoropropene is preferred from the viewpoint of low gas thermal conductivity and safety. Specific examples include trans-1,3,3,3-tetrafluoropropene (trans-HFO-1234ze), cis-1,3,3,3-tetrafluoropropene (cis-HFO-1234ze), and 2,3,3,3-tetrafluoropropene (trans-HFO-1234yf). The hydrochlorofluoroolefin used in the present invention is not particularly limited, but hydrochlorotrifluoropropene is preferred from the viewpoint of low gas thermal conductivity and safety. Specific examples include trans-1-chloro-3,3,3-trifluoropropene (trans-HCFO-1233zd). These hydrofluoroolefins and hydrochlorofluoroolefins may be used alone or in combination of two or more.

The content of the hydro(chloro)fluoroolefin in one embodiment of the present invention is preferably 0.5 to 13.0 parts by weight, more preferably 1.0 to 12.0 parts by weight, and particularly preferably 1.5 to 11.0 parts by weight, per 100 parts by weight of the styrene-based resin. If the content of the hydro(chloro)fluoroolefin is less than 0.5 parts by weight per 100 parts by weight of the styrene-based resin, the effect of improving the heat insulating properties due to the hydro(chloro)fluoroolefin tends not to be very promising. On the other hand, if the content of the hydro(chloro)fluoroolefin is more than 13.0 parts by weight per 100 parts by weight of the styrene-based resin, the hydro(chloro)fluoroolefin may separate from the resin melt during extrusion foaming, causing spot holes (traces where a localized mass of the hydro(chloro)fluoroolefin breaks through the surface of the extruded foam and is released into the outside air) to occur on the surface of the extruded foam, or the closed cell ratio may decrease, resulting in impaired heat insulating properties.

In the present invention, by using other foaming agents, a plasticizing effect and/or a co-foaming effect can be obtained during foam production, reducing the extrusion pressure and enabling stable production of foams.

Other blowing agents include, for example, saturated hydrocarbons having 3 to 5 carbon atoms, such as propane, n-butane, i-butane, n-pentane, i-pentane, and neopentane; ethers, such as dimethyl ether, diethyl ether, methyl ethyl ether, isopropyl ether, n-butyl ether, diisopropyl ether, furan, furfural, 2-methylfuran, tetrahydrofuran, and tetrahydropyran; dimethyl ketone, methyl ethyl ketone, diethyl ketone, methyl n-propyl ketone, methyl n-butyl ketone, methyl i-butyl ketone, methyl n-amyl ketone, methyl n-hexyl ketone, and ethyl n-propyl ketone. Examples of the foaming agents that can be used include ketones such as ethyl n-butyl ketone and ethyl n-butyl ketone; saturated alcohols having 1 to 4 carbon atoms such as methanol, ethanol, propyl alcohol, i-propyl alcohol, butyl alcohol, i-butyl alcohol, and t-butyl alcohol; carboxylic acid esters such as methyl formate, ethyl formate, propyl formate, butyl formate, amyl formate, methyl propionate, and ethyl propionate; organic foaming agents such as alkyl halides such as methyl chloride and ethyl chloride; inorganic foaming agents such as water and carbon dioxide; and chemical foaming agents such as azo compounds and tetrazole. These other foaming agents may be used alone or in combination of two or more.

Among other blowing agents, saturated alcohols with 1 to 4 carbon atoms, dimethyl ether, diethyl ether, methyl ethyl ether, methyl chloride, ethyl chloride, etc. are preferred from the standpoint of foaming property and foam moldability, while water and carbon dioxide are preferred from the standpoint of the flammability of the blowing agent and the flame retardancy or heat insulating property of the foam. Of these, dimethyl ether and ethyl chloride are preferred from the standpoint of plasticizing effect, while water is particularly preferred from the standpoint of economy and the effect of improving heat insulating property by controlling the bubble diameter.

In one embodiment of the present invention, when water and/or alcohols are used as the other blowing agent, it is preferable to add a water-absorbing substance in order to perform stable extrusion foam molding. Specific examples of water-absorbing substances used in one embodiment of the present invention include water-absorbing polymers such as polyacrylate polymers, starch-acrylic acid graft copolymers, polyvinyl alcohol polymers, vinyl alcohol-acrylate copolymers, ethylene-vinyl alcohol copolymers, acrylonitrile-methyl methacrylate-butadiene copolymers, polyethylene oxide copolymers, and derivatives thereof, as well as fine powders having hydroxyl groups on the surface such as anhydrous silica (silicon oxide) having silanol groups on the surface [for example, AEROSIL manufactured by Nippon Aerosil Co., Ltd. is commercially available]; water-absorbing or water-swelling layered silicates such as smectite and swelling fluoromica, and organically treated products thereof; and porous substances such as zeolite, activated carbon, alumina, silica gel, porous glass, activated clay, diatomaceous earth, and bentonite. The content of the water-absorbing substance is adjusted as appropriate by adding water and/or alcohols, but is preferably 0.01 to 5 parts by weight, and more preferably 0.1 to 3 parts by weight, per 100 parts by weight of the styrene-based resin.

In the method for producing an extruded styrene resin foam according to one embodiment of the present invention, the pressure at which the foaming agent is added or injected is not particularly limited, and may be any pressure higher than the internal pressure of the extruder, etc.

(1-7. Heat radiation suppressant)
To the extruded styrene resin foam of the present invention, a heat radiation inhibitor is added in order to improve the heat insulating property.

The heat radiation inhibitor refers to a substance that has the properties of reflecting, scattering, and absorbing light in the near infrared or infrared region. By containing a heat radiation inhibitor, a foam with high thermal insulation properties can be obtained. Heat radiation inhibitors that can be used in the present invention include black particles such as graphite and carbon black, and white particles such as titanium oxide, barium sulfate, zinc oxide, aluminum oxide, and antimony oxide. These may be used alone or in combination of two or more. In terms of the large heat radiation inhibitory effect, graphite, titanium oxide, and barium sulfate are preferred, and it is more preferred to contain graphite and/or titanium oxide.

Examples of graphite include scaly (flake) graphite, clayey graphite, spherical graphite, and artificial graphite. Of these, it is preferable to use graphite whose main component is scaly (flake) graphite because of its high heat radiation suppression effect. Graphite with a fixed carbon content of 80% or more is preferable, and graphite with a fixed carbon content of 85% or more is more preferable. By setting the fixed carbon content within the above range, a foam with high thermal insulation properties can be obtained.

The average particle size of the graphite is preferably 15 μm or less, more preferably 10 μm or less. By setting the average particle size within the above range, the specific surface area of the graphite increases, and the probability of collision with heat radiation increases, resulting in a higher heat radiation suppression effect. The average particle size refers to the particle size at which the cumulative volume of the total particle volume is 50% (volume average particle size by laser diffraction scattering method) when the particle size distribution is measured and analyzed by a laser diffraction scattering method based on the Mie theory in accordance with ISO13320:2009 and JIS Z8825:2013.

Examples of titanium oxide include common rutile-type titanium oxide, anatase-type titanium oxide, and conductive rutile-type titanium oxide and conductive anatase-type titanium oxide that have been imparted with electrical conductivity.

There are no particular limitations on the average particle size of the white particles, but in terms of effectively reflecting infrared rays and taking into consideration color development in resins, for example, for titanium oxide, 0.1 μm to 10 μm is preferable, and 0.15 μm to 5 μm is even more preferable.

In one embodiment of the present invention, the content of the heat radiation suppressant is 0.5 parts by weight or more and 5.0 parts by weight or less, more preferably 1.0 parts by weight or more and 4.5 parts by weight or less, and even more preferably 1.0 parts by weight or more and 4.0 parts by weight or less, relative to 100 parts by weight of the styrene-based resin. If the content is less than 0.5 parts by weight, a sufficient heat radiation suppression effect cannot be obtained. On the other hand, if the content exceeds 5.0 parts by weight, the heat radiation suppression effect corresponding to the content cannot be obtained, and there is no cost benefit.

(1-8. Moldability improver)
In one embodiment of the present invention, a polyhydric alcohol fatty acid ester and/or polyethylene glycol may be added as a moldability improver, if necessary, which can impart an attractive surface to the extruded foam and increase the thickness of the extruded foam (i.e., improve the moldability of the extruded foam).

The polyhydric alcohol fatty acid ester used in one embodiment of the present invention includes, for example, esters of higher fatty acids having 10 to 24 carbon atoms with polyhydric alcohols such as ethylene glycol, glycerin, 1,2,4-butanetriol, diglycerin, pentaerythritol, sorbitol, erythritol, and hexanetriol. These polyhydric alcohol fatty acid esters may be used alone or in combination of two or more kinds.

Among these, glycerin fatty acid esters, particularly mono-, di-, tri-, or tetra-fatty acid esters of glycerin, are preferred in terms of availability, price, etc.

As the glycerin fatty acid ester, it is preferable to use at least one selected from the group consisting of, for example, lauric acid monoglyceride, lauric acid diglyceride, lauric acid triglyceride, palmitic acid monoglyceride, palmitic acid diglyceride, palmitic acid triglyceride, stearic acid monoglyceride, stearic acid diglyceride, stearic acid triglyceride, and stearic acid tetraglyceride.

The melting point of the glycerin fatty acid ester used in the present invention is preferably 150°C or less, more preferably 130°C or less, and particularly preferably 110°C. When the melting point of the glycerin fatty acid ester is 150°C or less, it is excellent in handleability, for example, in the dry blending process during the production of extruded foam, and since it exists as a liquid during extrusion foam molding, it can also impart a plasticizing effect to the styrene-based resin during extrusion foam molding, so that a sufficient thickening effect of the extruded styrene-based resin foam can be exhibited. On the other hand, when the melting point is higher than 150°C, it exists as a solid during extrusion foam molding, and it cannot impart a plasticizing effect to the styrene-based resin during extrusion foam molding, so there is a risk that a sufficient thickening effect of the extruded styrene-based resin foam cannot be exhibited.

The content of the polyhydric alcohol fatty acid ester used in one embodiment of the present invention is preferably 0.05 parts by weight or more and 5.0 parts by weight or less, more preferably 0.1 parts by weight or more and 3.0 parts by weight or less, and particularly preferably 0.5 parts by weight or more and less than 2.0 parts by weight, relative to 100 parts by weight of the styrene-based resin. If the content of the polyhydric alcohol fatty acid ester is less than 0.05 parts by weight, the effect of thickening the extruded foam tends to be insufficient. On the other hand, if it exceeds 5.0 parts by weight, the excessive amount may impair extrusion, foaming, and molding stability during production, or may deteriorate various properties such as the heat resistance of the extruded foam.

The average molecular weight of the polyethylene glycol used in one embodiment of the present invention is not particularly limited, but is preferably 1000 to 25000, more preferably 1500 to 20000, and particularly preferably 3000 to 15000. These polyethylene glycols with different average molecular weights may be used alone or in combination of two or more. If the molecular weight of the polyethylene glycol is 1000 to 25000, the freezing point of the polyethylene glycol is higher than room temperature and the polyethylene glycol is in a solid state at room temperature. Depending on the amount used, the polyethylene glycol has excellent handleability in, for example, a dry blending process during the production of an extruded foam, does not bleed out from the inside of the extruded foam to the surface, and has a freezing point lower than the extrusion foam molding temperature, and can impart a plasticizing effect to the styrene-based resin during extrusion foam molding. Therefore, the polyethylene glycol can exert a sufficient surface property imparting effect and a sufficient thickness-imparting effect to the styrene-based resin extruded foam.

In one embodiment of the present invention, the content of polyethylene glycol is preferably 0.05 parts by weight or more and 5.0 parts by weight or less, more preferably 0.1 parts by weight or more and 3.0 parts by weight or less, and particularly preferably 0.2 parts by weight or more and 1.0 parts by weight or less, relative to 100 parts by weight of the styrene-based resin. If the content of polyethylene glycol is less than 0.05 parts by weight, the surface property imparting effect and the thickness-imparting effect tend to be insufficient. On the other hand, if the content of polyethylene glycol is more than 5.0 parts by weight, the content of polyethylene glycol is excessive, which may impair the extrudability, foamability, and molding stability during production, or may deteriorate various properties such as the heat resistance of the extruded foam.

In one embodiment of the present invention, when polyethylene glycol and polyhydric alcohol fatty acid ester are used in combination as a moldability improving agent, the total amount of polyethylene glycol and polyhydric alcohol fatty acid ester is preferably 0.05 parts by weight to 5.0 parts by weight, more preferably 0.1 parts by weight to 3.0 parts by weight, and particularly preferably 0.2 parts by weight to 2.0 parts by weight, per 100 parts by weight of styrene-based resin. If the content is less than 0.05 parts by weight, the surface property imparting effect and the thickness-imparting effect tend to be insufficient. On the other hand, if the content is more than 5.0 parts by weight, the content is excessive, which may impair extrudability, foamability, and molding stability during production, or may deteriorate various properties such as the heat resistance of the extruded foam.

(1-9. Other Additives)
In one embodiment of the present invention, further, as necessary, additives such as inorganic compounds such as silica, calcium silicate, wollastonite, kaolin, clay, mica, calcium carbonate, sodium stearate, calcium stearate, magnesium stearate, barium stearate, liquid paraffin, olefin wax, stearylamide compounds, phenolic antioxidants, phosphorus stabilizers, nitrogen stabilizers, sulfur stabilizers, light resistance stabilizers such as benzotriazoles and hindered amines, bubble size regulators such as talc, flame retardants other than the above, antistatic agents, colorants such as pigments, and plasticizers may be contained in the styrene resin, as long as the effects of one embodiment of the present invention are not impaired. In addition, as necessary, other resins may be used in combination with the styrene resin, as long as the effects of one embodiment of the present invention are not impaired.

(1-8. Physical Properties)
The thermal conductivity of the styrene-based resin extruded foam according to one embodiment of the present invention is not particularly limited, but from the viewpoint of thermal insulation considering that the foam functions, for example, as a thermal insulation material for building, or as a thermal insulation material for refrigerators or refrigerated vehicles, the thermal conductivity measured at an average temperature of 23° C. one week after production is preferably 0.0284 W/mK or less, more preferably 0.0244 W/mK or less, and particularly preferably 0.0224 W/mK or less.

The apparent density of the extruded styrene-based resin foam according to one embodiment of the present invention is preferably 20 kg/m or more and 60 kg/m or less, more preferably 25 kg/m ^{or more} and 40 kg/m ^{or less} , from the viewpoints of heat insulation property and light weight, taking into consideration that the foam functions as a heat insulation material for construction, or a heat insulation ^material for a refrigerator or a ^refrigerator car.

The closed cell ratio of the extruded styrene-based resin foam according to one embodiment of the present invention is preferably 90% or more, and more preferably 95% or more. If the closed cell ratio is less than 90%, the foaming agent will dissipate from the extruded foam prematurely, resulting in reduced thermal insulation.

The average bubble diameter in the thickness direction of the styrene-based resin extruded foam according to one embodiment of the present invention is preferably 0.05 mm or more and 0.5 mm or less, more preferably 0.05 mm or more and 0.4 mm or less, and particularly preferably 0.05 mm or more and 0.3 mm or less. In general, the smaller the average bubble diameter, the shorter the distance between the bubble walls of the foam, so that the range of movement of the bubbles of the extruded foam when shaping the extruded foam during extrusion foaming is narrow, making deformation difficult, and it tends to be difficult to impart a beautiful surface to the extruded foam and to achieve a thick extruded foam. If the average bubble diameter in the thickness direction of the styrene-based resin extruded foam is smaller than 0.05 mm, it becomes particularly difficult to impart a beautiful surface to the extruded foam and to achieve a thick extruded foam. On the other hand, if the average bubble diameter in the thickness direction of the styrene-based resin extruded foam exceeds 0.5 mm, there is a risk that sufficient heat insulation cannot be obtained.

The average cell diameter of the styrene-based resin extruded foam according to one embodiment of the present invention can be evaluated using a microscope (DIGITAL MICROSCOPE VHX-900, manufactured by KEYENCE CORPORATION) as described below.

The obtained styrene resin extrusion foam was observed from the extrusion direction at a total of three vertical cross sections in the thickness direction center, namely, the center in the width direction and a location 150 mm from one end in the width direction to the opposite end (the same location for both ends in the width direction), using the microscope, and a 100x magnified photograph was taken. Similarly, the three vertical cross sections in the thickness direction center of the width direction were observed from the width direction using the microscope, and a 100x magnified photograph was taken. Three 2 mm straight lines were drawn in the thickness direction of the magnified photograph (three lines for each observation point and each observation direction), and the number a of bubbles in contact with the straight lines was measured. From the measured number a of bubbles, the average bubble diameter A in the thickness direction for each observation point was calculated using the following formula (1). The average value of the three points (two directions at each point) was taken as the average bubble diameter A (average value) in the thickness direction of the styrene resin extrusion foam.

Average bubble diameter A (mm) in the thickness direction at each observation point = 2 x 3 / number of bubbles a
...(1).

The obtained styrene-based resin extruded foam was observed from the width direction using the microscope at three locations in the center of the thickness direction, namely, the center of the width direction and a location 150 mm from one end of the width direction to the opposite end (the same location for both ends of the width direction), and a vertical cross section in the extrusion direction was taken from the width direction. A 100x magnified photograph was taken. Three 2 mm straight lines were drawn in the extrusion direction of the enlarged photograph (three lines for each observation location), and the number b of bubbles in contact with the lines was measured. From the measured number b of bubbles, the average bubble diameter B in the extrusion direction for each observation location was calculated using the following formula (2). The average value of the three locations was taken as the average bubble diameter B (average value) in the extrusion direction of the styrene-based resin extruded foam.

Average bubble diameter B (mm) in the extrusion direction at each observation point = 2 x 3 / number of bubbles b
...(2).

The obtained styrene-based resin extruded foam was observed with the microscope from the extrusion direction at three locations in the width direction center and at a location 150 mm from one end in the width direction to the opposite end (the same location for both ends in the width direction), and a vertical cross section in the width direction at the center of the thickness direction was taken. A 100x magnification photograph was taken. Three 2 mm straight lines were drawn at random in the width direction of the enlarged photograph (three lines for each observation location), and the number c of bubbles in contact with the lines was measured. From the measured number c of bubbles, the average bubble diameter C in the width direction for each observation location was calculated using the following formula (3). The average value of the three locations was taken as the average bubble diameter C (average value) in the width direction of the styrene-based resin extruded foam.

Average bubble diameter C (mm) in the width direction at each observation point = 2 x 3 / number of bubbles c
...(3).

The bubble deformation ratio of the styrene-based resin extruded foam according to one embodiment of the present invention is preferably 0.7 to 2.0, more preferably 0.8 to 1.5, and even more preferably 0.8 to 1.2. If the bubble deformation ratio is less than 0.7, the compressive strength is low, and the extruded foam may not have a strength suitable for the intended use. In addition, the bubbles tend to return to a spherical shape, which tends to result in poor dimensional (shape) retention of the extruded foam. On the other hand, if the bubble deformation ratio exceeds 2.0, the number of bubbles in the thickness direction of the extruded foam decreases, and the effect of improving the insulation due to the bubble shape is reduced.

The cell deformation rate of the extruded styrene resin foam according to one embodiment of the present invention can be calculated from the average cell diameter described above using the following formula (4).

Bubble deformation rate (unitless) = A (average value) / {[B (average value) + C (average value)] / 2} ... (4).

The thickness of the styrene-based resin extruded foam according to one embodiment of the present invention is preferably 10 mm or more and 150 mm or less, more preferably 20 mm or more and 130 mm or less, and particularly preferably 30 mm or more and 120 mm or less, from the viewpoint of thermal insulation, bending strength, and compressive strength, taking into consideration the functioning of the foam as, for example, a thermal insulation material for buildings, or a thermal insulation material for refrigerators or refrigerated vehicles.

As described in the examples and comparative examples of the present invention, the styrene-based resin extruded foam may be shaped by extrusion foaming, and then both surfaces of a plane perpendicular to the thickness direction may be cut to a depth of about 5 mm on each side in the thickness direction to obtain the product thickness. However, unless otherwise specified, the thickness of the styrene-based resin extruded foam according to one embodiment of the present invention refers to the uncut thickness after extrusion foaming to give the shape.

Thus, one embodiment of the present invention makes it possible to easily obtain an extruded styrene resin foam that has excellent heat insulation and flame retardancy, a beautiful appearance, and a sufficient thickness suitable for use.

2. Method for producing extruded styrene resin foam
The method for producing a styrene-based resin extrusion foam according to one embodiment of the present invention includes a melting step in which a resin composition containing a styrene-based resin, a heat radiation inhibitor, a flame retardant, and a stabilizer is heated and melted in an extruder equipped with a die slit section, and a foaming step in which the foamable melt obtained in the melting step is extruded from the die slit section into a low pressure region to foam the foamable melt, the flame retardant containing an aliphatic bromine-containing polymer, the stabilizer containing an epoxy compound, and the resin composition containing 21 to 50 parts by weight of the epoxy compound per 100 parts by weight of the aliphatic bromine-containing polymer. The configuration already described in [1. Styrene-based resin extrusion foam] is used by reference, and the description thereof is omitted here.

As an example of a method for producing a styrene-based resin extrusion foam, the following method can be mentioned. First, a styrene-based resin, a radiation suppressant, a flame retardant, a stabilizer, and, if necessary, the above-mentioned various additives are supplied to a heat-melting section of an extruder having a die slit section (in other words, a resin composition is supplied to the heat-melting section of an extruder). At this time, a foaming agent can be mixed into the resin composition under high pressure conditions at any stage (for example, before the resin composition is heated and melted, during the resin composition is heated and melted, or after the resin composition is heated and melted). Then, the resin composition is made into a fluid gel. The above is the melting process.
Thereafter, the foamable molten material obtained in the melting step is cooled to a temperature suitable for extrusion foaming, and then the fluid gel is extruded through the die slit into a low pressure region (e.g., an atmospheric pressure region) to form an extruded styrene resin foam.

In the melting process, methods for blending various additives with styrene-based resin include, for example, a method of adding various additives to styrene-based resin and mixing them by dry blending; a method of adding various additives to molten styrene-based resin from a supply section installed midway through the extruder; a method of preparing a master batch in which various additives are incorporated into styrene-based resin at high concentrations using an extruder, kneader, Banbury mixer, rolls, etc., and mixing the master batch with styrene-based resin by dry blending; a method of feeding various additives to the extruder using a feed facility separate from the styrene-based resin.

The heating temperature in the heat melting section is equal to or higher than the temperature at which the styrene resin used melts. The heating temperature is preferably a temperature at which molecular deterioration of the resin due to the influence of additives and the like is suppressed as much as possible (for example, about 150°C to 260°C). The melt kneading time in the heat melting section cannot be uniquely defined because it differs depending on the amount of styrene resin extruded per unit time and/or the type of extruder used as the heat melting section and as the melt kneading section, and can be appropriately set as the time required for the styrene resin, the foaming agent, and the additives to be uniformly dispersed and mixed.

As the melt-kneading section, any mechanism used in normal extrusion foaming can be used without particular limitations, such as a screw-type extruder.

There are no particular limitations on the pressure at which the foaming agent is added or injected, as long as it is higher than the internal pressure of the extruder, etc.

In the foaming process, an example of a method for extrusion foaming is a method in which the above-mentioned fluid gel is released from a high-pressure region to a low-pressure region through a die slit section having a straight slit-shaped opening used for extrusion molding. In this way, an extruded foam is obtained. Note that there are no particular limitations on the shape of the die slit section, and various die slit sections in this technical field can be used.

In the foaming process, the foaming pressure in the extrusion foaming (in other words, the pressure applied to the foamable molten material before (e.g., immediately before) it is extruded from the die slit) is preferably 3.5 MPa or more and 10.0 MPa or less, more preferably 3.5 MPa or more and 8.0 MPa or less, and even more preferably 3.5 MPa or more and 6.0 MPa or less. If the foaming pressure is within this range, the advantageous effect of being able to reduce the thin skin ratio of the styrene-based resin extruded foam can be obtained. The foaming pressure can be adjusted by adjusting the opening of the slit in the die slit section and/or the temperature of the die slit section.

The styrene-based resin extruded foam may be molded into a plate-shaped foam, i.e., an extruded foam plate. For example, the extruded foam obtained as described above can be molded into a plate-shaped foam with a large cross-sectional area using a molding die installed in close contact with or in contact with a slit die and a molding roll installed adjacent to the downstream side of the molding die. The desired cross-sectional shape, surface properties, and foam quality can be obtained by adjusting the flow surface shape of the molding die and the die temperature.

The following describes examples of the present invention, but the present invention is not limited to these.

[Raw materials]
The raw materials used in the examples and comparative examples are as follows.
○Base resin
Styrene-based resin A [PS Japan Co., Ltd., G9401; MFR 2.2 g/10 min]
Styrene-based resin B [PS Japan Co., Ltd., 680; MFR 7.0 g/10 min]
Thermal radiation suppressant - graphite [Marutoyo Foundry Manufacturing Co., Ltd., M-885; flake graphite, average particle size 5.5 μm, fixed carbon content 89%]
Titanium oxide [(Sakai Chemical Industry Co., Ltd., R-7E; average particle size 0.23 μm)]
Flame retardant: Brominated styrene-butadiene block copolymer [Chemtura, EMERALD INNOVATION #3000]
Stabilizer (A) Epoxy compound, bisphenol-A-glycidyl ether [manufactured by ADEKA Corporation, EP-13]
Cresol novolac epoxy resin [EPICLON N-680, manufactured by DIC Corporation]
Stabilizer (B) Polyhydric alcohol partial ester, dipentaerythritol-adipic acid reaction mixture [Ajinomoto Fine-Techno Co., Ltd., Plainlyzer ST210]
Stabilizer (C) Phenol-based stabilizer: Pentaerythritol tetrakis [3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate] [ANOX20 manufactured by Chemtura]
Stabilizer (D) Phosphite stabilizer: 3,9-bis(2,4-di-tert-butylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane [Ultranox (registered trademark) 626 manufactured by Chemtura]
Flame retardant assistant: Condensed phosphate ester (tetrakis(2,6-dimethylphenyl)-m-phenylene bisphosphate) [PX-200, manufactured by Daihachi Chemical Industry Co., Ltd.]
Radical generator: Poly-1,4-diisopropylbenzene [United Initiators, CUROX CC-P3].
Other additives: Talc [Talc Powder PK-Z, manufactured by Hayashi Kasei Co., Ltd.]
Calcium stearate [Sakai Chemical Industry Co., Ltd., SC-P]
Bentonite [Hojun Co., Ltd., Bengelbright 11K]
Silica [Evonik Degussa Japan Co., Ltd., Carplex BS-304F]
Ethylene bis stearic acid amide [NOF Corporation, Alflow H-50S]
Stearic acid monoglyceride [Rikemal S-100P, manufactured by Riken Vitamin Co., Ltd.]
○Foaming agent
・HFO-1234ze [Honeywell Japan Co., Ltd.]
HCFO-1233zd [Honeywell Japan Co., Ltd.]
- Isobutane [Mitsui Chemicals, Inc.]
- Dimethyl ether [Mitsui Chemicals, Inc.]
Ethyl chloride [Nippon Specialty Chemical Industry Co., Ltd.]
・Water [Settsu City, Osaka Prefecture tap water]

[Measurement method]
In the examples and comparative examples, various parameters were measured and evaluated according to the following measurement methods.

(1) Apparent density (kg/m3)
The weight of the resulting extruded styrene resin foam was measured, and the length, width and thickness of the foam were also measured.
From the measured weight and each dimension, the apparent density of the extruded styrene resin foam was calculated based on the following formula: Then, the unit of the apparent density was converted into kg/ ^m3 .
Apparent density (g/cm ³ )=foam weight (g)/foam volume (cm ³ ).

(2) Closed cell ratio Test pieces measuring 40 mm thick x 25 mm long (in the extrusion direction) x 25 mm wide were cut out from three locations of the obtained extruded styrene-based resin foam: the widthwise center, a location 150 mm from one end in the widthwise direction toward the opposite end, and a location 150 mm from the other end in the widthwise direction toward the opposite end. Using the test pieces, measurements were performed according to procedure C of ASTM-D2856-70, and the closed cell ratio of each test piece was calculated according to the following formula. The average value of the closed cell ratios at the three locations was taken as the closed cell ratio of the extruded styrene-based resin foam.
Closed cell ratio (%) = (V1-W/ρ) x 100/(V2-W/ρ)
Here, V1 (cm ³ ) is the true volume (excluding the volume of the portion that is not an independent cell) of the test piece measured using an air comparison type specific gravity meter [Tokyo Science Co., Ltd., air comparison type specific gravity meter, Model 1000]. V2 (cm ³ ) is the apparent volume calculated from the outer dimensions of the test piece measured using a caliper [M-type standard vernier caliper N30, Mitutoyo Corporation]. W (g) is the total weight of the test piece. In addition, ρ (g/cm ³ ) is the density of the styrene-based resin that constitutes the extruded foam, which was set to 1.05 (g/cm ³ ).

(3) Average cell diameter in the thickness direction and cell deformation rate The average cell diameter in the thickness direction and cell deformation rate of the obtained styrene-based resin extruded foam were determined using a microscope [DIGITAL MICROSCOPE VHX-900, manufactured by KEYENCE CORPORATION] as described above.

(4) HFO-1234ze/HCFO-1233zd Content per 100 g of Styrenic Resin in Extruded Foam The obtained styrenic resin extruded foam was allowed to stand under standard temperature condition class 3 (23° C.±5° C.) and standard humidity condition class 3 (50+20, −10% R.H.) conditions specified in JIS K 7100, and the HFO-1234ze/HCFO-1233zd content 7 days after production was evaluated using the following equipment and procedures.
a) Equipment used: Gas chromatograph GC-2014 [manufactured by Shimadzu Corporation]
b) Column used: G-Column G-950 25UM [manufactured by Chemicals Evaluation and Research Institute, Inc.]
c) Measurement conditions;
・Inlet temperature: 65℃
Column temperature: 80°C
Detector temperature: 100°C
Carrier gas: High purity helium Carrier gas flow rate: 30 mL/min Detector: TCD
Current: 120mA
A test piece of about 1.2 g (depending on the apparent density) cut out from the foam was placed in a sealable glass container of about 130 cc (hereinafter referred to as "sealed container"), and the air in the sealed container was removed using a vacuum pump. The sealed container was then heated at 170° C. for 10 minutes, and the foaming agent in the foam was removed into the sealed container. After the sealed container returned to room temperature, helium was introduced into the sealed container to return it to atmospheric pressure, and then 40 μL of a mixed gas containing HFO-1234ze/HCFO-1233zd was removed using a microsyringe, and evaluation was performed using the above-mentioned instruments and measurement conditions a) to c).

(5) Thermal conductivity: According to JIS A 9521, a test piece cut from a styrene-based resin extruded foam with a thickness of 50 mm, a length (extrusion direction) of 300 mm, and a width of 300 mm was used to measure the thermal conductivity at an average temperature of 23°C using a thermal conductivity measuring device [Eiko Seiki Co., Ltd., HC-074]. Specifically, after the production of the styrene-based resin extruded foam, a test piece with the above dimensions was cut out, and the test piece was left to stand under the conditions of standard temperature condition class 3 (23°C ± 5°C) and standard humidity condition class 3 (50 + 20, -10% R.H.) specified in JIS K 7100, and then the thermal conductivity was measured one week (7 days) after the production of the styrene-based resin extruded foam. (6) JIS flammability: According to JIS A 9521, a test piece with a thickness of 10 mm, a length of 200 mm, and a width of 25 mm was used to evaluate the flammability according to the following criteria. The produced styrene-based resin extrusion foam was cut into a test piece having the above dimensions, and the test piece was left to stand under the conditions of standard temperature condition class 3 (23°C ± 5°C) and standard humidity condition class 3 (50 + 20, -10% R.H.) specified in JIS K 7100. One week (seven days) after the production of the styrene-based resin extrusion foam, the flammability was evaluated using the test piece.
○: Meets the criteria of "flame goes out within 3 seconds, there is no residual fuel, and the fire does not burn beyond the flammability limit indicator line."
×: Does not meet the above criteria.

(7) Oxygen index: Measured by a method in accordance with JIS K 7201:1999.

(8) Weight average molecular weight retention of foam (hereinafter abbreviated as "Mw retention")
In order to evaluate the degree of resin deterioration due to the thermal history in the extruder, the weight average molecular weight Mw of the foam obtained after each number of recycling was determined by gel permeation chromatography according to the following procedure.
a) Sample concentration: 2.5 mg/mL (solvent: chloroform)
b) Equipment used: Waters e2695
c) Column used: Two GPC-K-806M columns directly connected, manufactured by Shodex d) Measurement conditions: Temperature; 40° C., Solvent; Chloroform, Sample injection amount; 50 μL, Flow rate; 1.0 mL/min, Detection method; UV (254 nm), Standard polystyrene; “Shodex STANDARD SM-105” manufactured by Showa Denko K.K.
The weight average molecular weight Mw of the foam obtained after five recycling cycles was divided by the weight average molecular weight Mw of the foam obtained after zero recycling cycles, and the value was evaluated as the Mw retention rate.
◯: Mw retention is 0.90 or more ×: Mw retention is less than 0.90

[Examples and Comparative Examples]
For the examples and comparative examples, graphite and titanium oxide were added via masterbatches prepared according to the following procedures.

[Preparation of graphite master batch]
In a Banbury mixer, 100 parts by weight of styrene resin B [manufactured by PS Japan Co., Ltd., 680; MFR 7.0 g / 10 min], which is a base resin, and 100 parts by weight of graphite [manufactured by Marutoyo Casting Co., Ltd., M-885] 102 parts by weight and ethylene bisstearic acid amide [manufactured by NOF Corp., Alflow H-50S] 2.0 parts by weight were added and melt-kneaded for 20 minutes without heating and cooling under a load of 5 kgf / cm2. At this time, the resin temperature was measured and was 190 ° C. The strand-shaped resin extruded at a discharge rate of 250 kg / hr through a die with a small hole attached to the tip of the ruder was cooled and solidified in a water tank at 30 ° C., and then cut to obtain a master batch.

[Preparation of titanium oxide master batch]
In a Banbury mixer, 100 parts by weight of styrene resin B [manufactured by PS Japan Co., Ltd., 680], which is a base resin, and 154 parts by weight of titanium oxide [manufactured by Sakai Chemical Industry Co., Ltd., R-7E] and 2.6 parts by weight of ethylene bisstearic acid amide [manufactured by NOF Corp., Alflow H-50S] were added to the Banbury mixer, and the mixture was melt-kneaded for 20 minutes without heating or cooling under a load of 5 kgf/ ^cm2 . At this time, the resin temperature was measured to be 180 ° C. The strand-shaped resin extruded at a discharge rate of 250 kg/hr through a die having a small hole attached to the tip of the ruder was cooled and solidified in a water tank at 30 ° C., and then cut to obtain a master batch.

Example 1
[Preparation of resin mixture]
The materials (materials other than the foaming agent) shown in Table 1 were dry-blended in the ratio shown in Table 1 to obtain a resin mixture. This dry blend is abbreviated as [GP].

[Preparation of extruded foam]
The obtained GP was supplied at about 800 kg/hr to an extruder in which a single screw extruder (first extruder) with a diameter of 150 mm, a single screw extruder (second extruder) with a diameter of 200 mm, and a cooler were connected in series.
The resin composition fed to the first extruder was heated to a resin temperature of about 240° C. to melt or plasticize, and kneaded, and a foaming agent (2.0 parts by weight of HFO-1234ze, 1.8 parts by weight of isobutane, 2.5 parts by weight of dimethyl ether, and 0.9 parts by weight of water, relative to 100 parts by weight of the base resin) was pressed into the resin composition near the tip of the first extruder. Thereafter, in the second extruder and the cooler connected to the first extruder, the temperature of the resin composition was cooled to the foaming temperature shown in Table 1, and the resin composition was extruded and foamed into the atmosphere at the foaming pressure shown in Table 1 from a die (slit die) with a rectangular cross section and a thickness shown in Table 1 provided at the tip of the cooler, and then, using a molding die installed in close contact with the die and a molding roll installed downstream of the die, an extruded foam plate with a cross-sectional shape of 60 mm thick x 1000 mm wide was obtained, and cut to a thickness of 50 mm, width of 910 mm, and length of 1820 mm with a cutter. The foam is the foam recycled 0 times.

[Production of recycled resin]
The foam obtained was crushed by a crusher and the cut waste generated when the foam was cut to a predetermined size by a cutter, and fed to a single screw extruder with a diameter of 120 mm, where the resin temperature was heated to about 230°C to melt or plasticize, knead, and the foam was discharged from a die and pelletized by strand cutting under open vent conditions after the remaining blowing agent in the foam was removed. The pellets are called [RP] (recycled styrene resin).

[Preparation of recycled resin-containing extruded foam]
A foam was obtained under the same conditions and operations as in the above [Preparation of extruded foam], except that the RP and GP obtained as above were fed in a weight ratio of 50:50 to an extruder in which a single screw extruder with a diameter of 150 mm, a single screw extruder with a diameter of 200 mm, and a cooler were connected in series, at about 800 kg/hr. The foam obtained was used as the foam for the first recycling run. Thereafter, recycling was carried out five times by repeating [Preparation of recycled resin] and [Preparation of extruded foam containing recycled resin]. The evaluation results of the obtained foam are shown in Table 1. (Examples 2 to 12)
Extruded foams were obtained in the same manner as in Example 1, except that the production conditions were changed as shown in Table 1. The physical properties of the obtained extruded foams are shown in Table 1. The cross-sectional shape and the thickness, width and length after cutting of the obtained extruded foams were the same as in Example 1.

(Comparative Examples 1 to 3)
Extruded foams were obtained in the same manner as in Example 1, except that the production conditions were changed as shown in Table 2. The physical properties of the obtained extruded foams are shown in Table 2. The cross-sectional shape and the thickness, width, and length after cutting of the obtained extruded foams were the same as in Example 1.

As shown in Table 1, foams with excellent flame retardancy and Mw retention were obtained in Examples 1 to 12. On the other hand, as shown in Table 2, foams with poor flame retardancy and/or Mw retention were obtained in Comparative Examples 1 to 3.

The styrene-based resin extruded foam according to one embodiment of the present invention can be used, for example, as a heat insulating material, a sound absorbing material, a core material for vacuum insulation materials, a cushioning material, and a filler material.

Claims (13)

A styrene-based resin extrusion foam, which is a foam of a resin composition containing a polystyrene resin, a heat radiation inhibitor, a flame retardant, and a stabilizer ,
The resin composition comprises
It contains recycled resin made by melting and kneading styrene-based resin extrusion foam.
The flame retardant comprises one or more aliphatic bromine-containing polymers selected from the group consisting of brominated styrene-butadiene block copolymers, brominated styrene-butadiene random copolymers, brominated styrene-butadiene graft polymers, brominated butadiene polymers, and brominated epoxidized styrene-butadiene block copolymers;
The stabilizer includes an epoxy compound,
The composition contains 0.5 to 5.0 parts by weight of the heat radiation inhibitor and 0.5 to 10 parts by weight of the aliphatic bromine-containing polymer relative to 100 parts by weight of the polystyrene resin,
The epoxy compound is contained in an amount of 21 to 50 parts by weight based on 100 parts by weight of the aliphatic bromine-containing polymer .
Styrenic resin extruded foam. The resin composition further contains a phenol-based stabilizer and a phosphite-based stabilizer as the stabilizer,
The phenol- based stabilizer is contained in an amount of 4 to 20 parts by weight, and the phosphite-based stabilizer is contained in an amount of 0 to 0.9 parts by weight, based on 100 parts by weight of the aliphatic bromine-containing polymer .
The extruded styrene resin foam according to claim 1. 3. The extruded styrene-based resin foam according to claim 2, wherein the resin composition further comprises, as the stabilizer, 20 parts by weight or less of a polyhydric alcohol partial ester which is a reaction product of dipentaerythritol and adipic acid per 100 parts by weight of the aliphatic bromine-containing polymer. The extruded styrene-based resin foam according to claim 2 or 3, wherein the phosphite-based stabilizer comprises at least one selected from the group consisting of 3,9-bis(2,4-di-tert-butylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, and tetrakis(2,4-di-tert-butyl-5-methylphenyl)-4,4'-biphenylene diphosphonite). The extruded styrene-based resin foam according to any one of claims 1 to 4, wherein the epoxy compound comprises at least one selected from the group consisting of bisphenol A diglycidyl ether type epoxy resins, cresol novolac type epoxy resins, and phenol novolac type epoxy resins. The extruded styrene-based resin foam according to any one of claims 1 to 5, wherein the resin composition further contains a phosphoric acid ester. The extruded styrenic resin foam according to claim 6, wherein the phosphate ester is tetrakis (2,6-dimethylphenyl)-m-phenylene bisphosphate. The extruded styrene-based resin foam according to any one of claims 1 to 7, wherein the resin composition further contains a hydrofluoroolefin and/or a hydrochlorofluoroolefin as a foaming agent. The extruded styrene resin foam according to claim 8, wherein the total content of the hydrofluoroolefin and the hydrochlorofluoroolefin in the resin composition is 1.0 part by weight or more and 12.0 parts by weight or less per 100 parts by weight of the polystyrene resin. The extruded styrene-based resin foam according to any one of claims 1 to 9, comprising graphite and/or titanium oxide as the heat radiation inhibitor. The extruded styrene-based resin foam according to any one of claims 1 to 10, having a thermal conductivity of 0.0244 W / mK or less. The extruded styrene-based resin foam according to any one of claims 1 to 11, having a density of 20 to 60 kg/ ^m3 . The extruded styrene-based resin foam according to any one of claims 1 to 12, having a thickness of 10 mm or more and 150 mm or less.