JP2007314643A - Extrusion foamed styrene resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for producing an extrusion foamed styrene resin having excellent environmental compatibility and heat-insulation and desired mechanical properties. <P>SOLUTION: The extrusion foamed styrene resin has a foam diameter distribution diagram characterized in that the areal ratio of the foam diameter in the whole range has multiple peaks, the foam anisotropy ratio of the foam existing in a region having a foam diameter larger than the first region having the smallest area ratio existing between the first peak existing in a region having smallest foam diameter among the multiple peaks and the second peak existing in a region having a foam diameter larger than that of the first peak and positioned closest to the first peak is 0.5-1.0. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a styrene resin extruded foam, and particularly to a styrene resin extruded foam excellent in good heat insulation and environmental compatibility.

  The styrenic resin composition is heated and melted in an extruder, and then a foaming agent having a low thermal conductivity such as chlorinated hydrocarbon, fluorinated hydrocarbon, or chlorine fluorinated hydrocarbon is added, A method of continuously producing a styrene resin extruded foam by cooling to a resin temperature and extruding it to a low pressure region is known. Styrenic resin extruded foam is used as a heat insulating material for structures, for example, because of good workability and heat insulating properties.

  As a foaming agent used in the styrene resin extruded foam, there is a chlorofluorocarbon containing chlorine atoms (hereinafter referred to as “CFC”). CFC contributes to excellent heat insulation properties because it forms a good extruded foam that does not generate pores or voids and is easy to control the bubble diameter, and tends to remain in the extruded foam and has low thermal conductivity. To do.

  By the way, in the global environment, the destruction of the ozone layer and the influence of chemical substances on the atmosphere or water quality are regarded as problems. The above-mentioned chlorofluorocarbons such as CFC are considered as causative substances that destroy the ozone layer. In addition, methyl chloride and ethyl chloride are obligated to be reported as a Class 1 Designated Substance in the Chemical Substances Emission Control Management Promotion Act (PRTR Law), and their emissions are controlled. Therefore, it is desired to adopt a foaming agent used for manufacturing a styrene resin extruded foam that does not adversely affect the global environment.

  As a blowing agent that replaces CFCs, hydrochlorofluorocarbons (hereinafter referred to as “HCFC”) in which some of the chlorine atoms of CFC are replaced with hydrogen atoms and hydrofluorocarbons that do not have chlorine atoms (hereinafter referred to as “HFC”) Is proposed). However, although HCFC and HFC have less influence on the ozone layer than CFC, there is a concern about the influence on global warming, so reduction of the usage amount is desired.

  Under such circumstances, a foaming agent such as propane, butane, or pentane having a low ozone destruction coefficient and a little influence on global warming has been proposed (for example, Patent Document 1). In addition to environmental compatibility, it is also desired to further improve the heat insulation of the styrene resin extruded foam.

  For example, it is known that the heat insulation performance is improved by configuring the cell structure of a styrene resin extruded foam from small cells and large cells (for example, Patent Document 2). Further, by reheating and stretching the extruded foam after extrusion, the average cell diameter in the thickness direction with respect to the average cell diameter in the extrusion direction is set to 1 or less, that is, the heat insulation is improved as a horizontally long flat cell in the extrusion direction. It is known (for example, Patent Document 3). Similarly, in order to improve the heat insulation performance, it is known to orient the bubbles of the extruded foam in different directions (for example, Patent Document 4 and Patent Document 5).

JP-A-1-174540 Japanese Patent Laid-Open No. 2001-200087 International Publication No. 1999/33625 Pamphlet JP 2005-528494 A JP 2001-316508 A

  However, when the bubbles are flattened in the extruded foam, there is a problem that although the heat insulation performance is improved, the mechanical properties such as the plane compressive strength are deteriorated. Therefore, flattening bubbles as in each of the above-mentioned patent documents has the adverse effect of deteriorating mechanical properties and is not suitable for applications that require both heat insulation and strength, such as building materials. Occurs. In order to solve such a problem, that is, as an extruded foam used for a desired application such as a building material, how to balance heat insulation and mechanical properties is described in each of the aforementioned patent documents. Are not disclosed at all.

  This invention is made | formed in view of this situation, and it aims at providing the means to obtain the styrene-type resin extrusion foam which is excellent in environmental compatibility and heat insulation, and has a desired mechanical characteristic.

  As a result of earnest research to solve the above-mentioned problems, the present inventors have controlled environmental anisotropy, heat insulation, by controlling the anisotropy rate in a specific range of cell diameters of the styrene resin extruded foam. The present inventors have found that a styrene resin extruded foam satisfying desired mechanical properties can be obtained, and have completed the present invention.

(1) The present invention is a styrene resin extruded foam obtained by extrusion foaming a styrene resin composition to which a non-halogen foaming agent is added as a foaming agent, the extrusion of the styrene resin extruded foam A predetermined range of the cross section along the direction is sampled, the bubble diameter and area of each bubble in the obtained sample cross section are obtained, and the horizontal axis is the bubble diameter divided into sections of 0.02 mm from 0 mm to the maximum bubble diameter. In the bubble diameter distribution diagram in which the vertical axis represents the area ratio for each section obtained by the following formula (1), the area ratio in the entire section of the bubble diameter has a plurality of peaks, and any one of the plurality of peaks is not included. The area ratio between the first peak existing in the section where the bubble diameter is smaller than the first peak and the second peak closest to the first peak in the section where the bubble diameter is larger than the first peak is the lowest. 1 The bubble anisotropy ratio calculated | required by following formula (2) of the bubble which exists in an area where a bubble diameter is larger than an area is 0.5-1.0.
Formula (1): Area ratio for each section = sum of the areas of the bubbles having the bubble diameter belonging to the section / sum of the areas of all the bubbles (2): Bubble anisotropic ratio = average bubble diameter in the thickness direction / extrusion direction Average bubble diameter

  (2) In the above bubble diameter distribution diagram, the bubble anisotropy rate obtained by the above equation (2) of the bubbles existing from the second section where the bubble diameter is 0 mm or more and less than 0.02 mm to the first section is 0. .8 or more is preferable.

  (3) In the bubble diameter distribution diagram, the total area ratio from the second section to the first section is preferably 0.05 to 0.90.

  (4) The plurality of peaks are at least one peak existing in a section where the bubble diameter is 0 mm or more and less than 0.20 mm, and at least one peak present in a section where the bubble diameter is 0.20 mm or more and less than 0.42 mm. It is preferable that it contains.

  (5) The non-halogen foaming agent preferably contains at least water.

  (6) It is preferable that the non-halogen-based blowing agent further contains a saturated hydrocarbon having 3 to 5 carbon atoms.

  (7) The saturated hydrocarbon may be selected from the group consisting of propane, n-butane and i-butane.

  (8) The thermal conductivity of the styrene resin extruded foam is preferably 0.025 W / mK or less.

(9) The plane compressive strength of the styrene resin extruded foam is preferably 15 N / m ² or more.

(10) The foam density of the styrene resin extruded foam is preferably ³⁰ to 60 kg / m ³ .

  (11) The thickness of the styrene resin extruded foam is preferably 10 to 150 mm.

  As described above, according to the present invention, in the above bubble diameter distribution diagram, the formula of bubbles existing in a section where the bubble diameter is larger than the first section where the area ratio existing between the first peak and the second peak is the lowest ( Since the bubble anisotropy ratio calculated | required by 2) was 0.5-1.0, it is excellent in heat insulation and environmental compatibility, and the styrene-type resin extrusion foam which has a desired mechanical characteristic can be obtained. Such a styrene resin extruded foam is particularly useful as a building material, a heat insulating material for a cold box or a cold car.

  The styrenic resin used in the present invention is not particularly limited, and is obtained from a styrene homopolymer obtained only from a styrene monomer, a monomer copolymerizable with styrene monomer and styrene, or a derivative thereof. A random copolymer, a block copolymer, or a graft copolymer, a modified polystyrene such as brominated polystyrene or rubber-reinforced polystyrene, a styrene resin having a branched structure, or the like can be used.

  Examples of monomers copolymerizable with styrene include styrene derivatives such as methyl styrene, dimethyl styrene, ethyl styrene, diethyl styrene, isopropyl styrene, bromo styrene, dibromo styrene, tribromo styrene, chloro styrene, dichloro styrene, and trichloro styrene. , Polyfunctional vinyl compounds such as divinylbenzene, (meth) acrylic compounds such as acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, acrylonitrile, diene compounds such as budadiene or Examples thereof include unsaturated carboxylic acid anhydrides such as derivatives thereof, maleic anhydride, and itaconic anhydride. These may be used alone or in combination of two or more.

  The styrenic resin used in the present invention preferably has a melt flow rate (hereinafter referred to as “MFR”) in the range of 0.1 to 50 g / 10 min. By using a styrene resin having an MFR in the above range, adjustment of the discharge amount of the styrene resin composition when molding the extruded foam, and the thickness, width and density of the obtained styrene resin extruded foam There is an advantage that the closed cell ratio or the surface property can be easily adjusted. That is, there is an advantage that the moldability of the extruded foam is excellent. In addition, by using a styrene resin having an MFR in the above range, the appearance of the styrene resin extruded foam is excellent, and the balance of properties such as mechanical strength and toughness expressed by compressive strength, bending strength, and bending deflection is achieved. Becomes better. Further, the MFR of the styrenic resin is more preferably 0.3 to 30 g / 10 minutes, particularly 0.5 to 20 g / 10 minutes, from the viewpoint of the balance of moldability, mechanical strength of the extruded foam, toughness and the like. preferable. In addition, MFR is measured by A method of JISK7210 (1999), and test conditions are set according to the composition of styrene resin. For example, for polystyrene, it is measured under test condition H.

  Among the styrene resins described above, it is preferable to use a styrene homopolymer (polystyrene) from the viewpoints of economy and moldability. Moreover, when high heat resistance is requested | required by an extrusion foam, it is preferable to use a styrene-acrylonitrile copolymer, a (meth) acrylic acid copolymer polystyrene, and a maleic anhydride modified polystyrene. Moreover, when high impact resistance is calculated | required by an extrusion foam, it is preferable to use rubber reinforced polystyrene. These styrenic resins may be used alone, or two or more styrenic resins having different molecular weight, MFR, composition, degree of branching and the like may be mixed and used.

  In the present invention, a non-halogen foaming agent is used as the foaming agent. Specifically, (a) one or more saturated hydrocarbons having 3 to 5 carbon atoms, (b) a compound selected from dimethyl ether, diethyl ether, and methyl ethyl ether, and (c) other non-halogen type What contains a foaming agent is used. Thus, by using a non-halogen-type foaming agent, the environmental compatibility of the extrusion foam molding method and the obtained extruded foam is improved. Moreover, the thickness, width, density, or closed cell ratio, thermal conductivity of the obtained styrene-based resin extruded foam is obtained by using a combination of the foaming agents (i), (b), and (c) above. It becomes easy to adjust the bubble diameter and surface property to desired values. That is, it is excellent in the moldability of the extruded foam. Also, a styrene resin extruded foam having a good appearance can be obtained.

  Examples of the one or more saturated hydrocarbons having 3 to 5 carbon atoms include propane, n-butane, i-butane, n-pentane, cyclopentane, and the like. 1 or more types selected from the group consisting of n-butane and i-butane are preferred. Moreover, since the heat insulation of an extrusion foam becomes favorable, the 1 or more types selected from n-butane and i-butane are preferable, and i-butane is especially preferable.

  The saturated hydrocarbon having 3 to 5 carbon atoms as the blowing agent is preferably 100 to 20 parts by weight, more preferably 80 to 30 parts by weight, particularly preferably 60 to 40 parts by weight based on 100 parts by weight of the total amount of the blowing agent. It is. By setting the content of the saturated hydrocarbon having 3 to 5 carbon atoms in the above range, the extruded foam can have both high heat insulating properties and flame retardancy. Further, the plasticity is set to an appropriate range, and the styrene resin and the foaming agent are uniformly kneaded in the extruder, and the pressure control of the extruder becomes easy.

  The compound selected from dimethyl ether, diethyl ether and methyl ethyl ether as the blowing agent is preferably 0 to 80 parts by weight, more preferably 20 to 70 parts by weight, particularly preferably 40 to 40 parts by weight based on 100 parts by weight of the total amount of the blowing agent. 60 parts by weight. By making content of the said compound into the said range, high heat insulation, a flame retardance, and a moldability can be made to have in an extruded foam. In addition, other ethers used as a blowing agent in the same manner as the above compound include isopropyl ether, n-butyl ether, diisopropyl ether, furan, furfural, 2-methylfuran, tetrahydrofuran, tetrahydropyran and the like.

  Examples of other non-halogen foaming agents include those selected from the group consisting of water, carbon dioxide, and alcohol. By using these as blowing agents, (a) the amount of a compound selected from (b) saturated hydrocarbons having 3 to 5 carbon atoms and (b) dimethyl ether, diethyl ether, and methyl ethyl ether, that is, a flammable blowing agent The amount used is reduced, and the combustibility of the resulting styrene resin extruded foam is improved.

  As other non-halogen foaming agents, water is preferably 0 to 80 parts by weight, more preferably 3 to 70 parts by weight, particularly preferably 3 to 30 parts by weight, based on 100 parts by weight of the total amount of the foaming agent. Most preferably, it is 5 to 20 parts by weight. By setting the water content in the above range, an extruded foam having a good surface and high heat insulating properties and good moldability can be obtained. Due to the use of water as the foaming agent, there are multiple peaks in the bubble size distribution diagram described below, depending on the type, composition, amount of use of the foaming agent, type and amount of the water-absorbing substance described below, and extrusion foaming molding conditions. A bubble structure with is obtained. Thereby, compared with the bubble structure which has a single peak, the styrene resin extrusion foam excellent in heat insulation can be obtained.

  When water is used as the other non-halogen foaming agent, it is preferable to add a water-absorbing substance in order to stably perform extrusion foam molding. The water-absorbing substance refers to a compound that absorbs water, absorbs, adsorbs, swells with water, or a compound that reacts with water to form a hydrate. The water-absorbing substance absorbs, absorbs, or reacts with water having low compatibility with the styrenic resin to form a gel, and is uniformly dispersed in the styrenic resin in the gel state. It is considered that stable extrusion foaming can be realized without generating pores or voids in the foam.

  When carbon dioxide is used as the other non-halogen-based foaming agent, the amount is preferably 3 to 40 parts by weight, more preferably 5 to 30 parts by weight with respect to 100 parts by weight of the total amount of the foaming agent. By setting the carbon dioxide content in the above range, the heat insulating property and moldability of the extruded foam are improved, which is preferable.

  In the present invention, other foaming agents may be used. Specific examples of other blowing agents include 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, ethyl n. Ketones such as propyl ketone and ethyl n-butyl ketone, alcohols such as methanol, ethanol, propyl alcohol, i-propyl alcohol, butyl alcohol, i-butyl alcohol and t-butyl alcohol, formic acid methyl ester, formic acid ethyl ester, Organic acids such as carboxylic acid esters such as propyl formate, butyl formate, amyl formate, methyl propionate and ethyl propionate, and alkyl halides such as methyl chloride and ethyl chloride Agents, inorganic blowing agents such as nitrogen, azo compounds, and chemical blowing agents such as tetrazoles.

  The addition amount of the other foaming agent in the styrene resin extruded foam may be appropriately determined in consideration of heat insulation, foam moldability, and foam density, but 0 to 4 with respect to 100 parts by weight of the styrene resin composition. A weight part is preferable, More preferably, it is 0-3 weight part.

  The total amount of the foaming agent relative to the styrene resin is preferably 4.5 to 10 parts by weight with respect to 100 parts by weight of the styrene resin composition.

  The content of the foaming agent contained in the styrene resin extruded foam is the gas extracted from the obtained extruded foam by heating a test piece with all surfaces cut out by 2 mm or more in a closed container, or styrene. Depending on the type of the system resin, it can be measured by gas chromatography using a gas extracted by dissolving in a solvent as a sample.

  The water-absorbing substance used in the present invention is one or two selected from silicon oxide, layered silicate, porous substance, sulfate, carbonate, phosphate, other metal salts, boron compounds, and water-absorbing polymers. More than a seed. Specifically, a fine powder having a particle diameter of 1000 nm or less having a hydroxyl group on the surface, such as anhydrous silica having a silanol group (silicon oxide) on the surface, can be mentioned. Examples of such anhydrous silica include Nippon Aerosil Co., Ltd .: AEROSIL (trade name), DSL. Japan Co., Ltd .: Carplex (trade name) is commercially available. Examples of the layered silicate include smectite, swellable fluorinated mica, and organically treated products thereof. Examples of the porous material include zeolite, activated carbon, alumina, silica gel, porous glass, activated clay, diatomaceous earth, and the like. Examples of the sulfate include sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, barium sulfate, aluminum sulfate, zinc sulfate, and ammonium sulfate. Examples of the carbonate include sodium carbonate, sodium hydrogen carbonate, magnesium carbonate, and ammonium carbonate. Examples of phosphates include sodium phosphate, magnesium phosphate, aluminum phosphate, ammonium phosphate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, triammonium phosphate, calcium dihydrogen phosphate, Examples thereof include calcium hydrogen phosphate. Other metal salts include calcium citrate, trisodium citrate, tripotassium citrate, calcium lactate, ammonium oxalate, potassium oxalate, disodium succinate, sodium acetate, sodium pyrophosphate, magnesium chloride, barium chloride, etc. Is mentioned. Examples of the boron compound include boron oxide and sodium borate. As the water-absorbing polymer, polyacrylate polymer, starch-acrylic acid graft copolymer, polyvinyl alcohol polymer, vinyl alcohol-acrylate copolymer, ethylene-vinyl alcohol copolymer, Examples thereof include polyacrylonitrile-methyl methacrylate-butadiene copolymer, polyethylene oxide copolymer, and derivatives thereof. These water-absorbing substances can be used alone or in admixture of two or more.

  Among the water-absorbing substances mentioned above, anhydrous layered silica, polyacrylate polymer, smectite, swellable fluorinated mica and other layered silicates, sulfates, carbonates, phosphates that are water-absorbable or water-swellable Porous materials such as metal salts, zeolite, etc. are stabilized by extrusion foaming, the generation of pores and voids is suppressed, and a cell structure having a characteristic cell diameter distribution, which will be described later, is formed. This is preferable because an extruded foam having heat insulation performance is realized.

  The amount of the water-absorbing substance used in the present invention is appropriately adjusted according to the amount of water added as a foaming agent, but is 0.1 to 10 parts by weight with respect to 100 parts by weight of the styrenic resin. Preferably, it is 0.1-8 weight part, More preferably, it is 0.2-7 weight part. By setting the amount of the water-absorbing substance in the above range, there is an advantage that water dispersion in the extruder is improved, extrusion foaming is stabilized, and generation of pores and voids is suppressed. In addition, there is an advantage that a bubble structure having a characteristic bubble diameter distribution, which will be described later, is formed, a desired heat insulation performance is expressed, and the quality is stabilized.

The layered silicate is mainly composed of a tetrahedral sheet of silicon oxide and an octahedral sheet of mainly metal hydroxide. A tetrahedral sheet and an octahedral sheet form a unit layer, and a unit layer is formed alone, or a plurality of layers are laminated via a cation between unit layers to form primary particles, or an aggregate of primary particles. It exists by forming particles (secondary particles). Examples of layered silicates include smectite clay and swellable mica. Smectite group clay has chemical formula (1): X _0.2-0.6 Y _2-3 Z ₄ O ₁₀ (OH) ₂ .nH ₂ O (wherein X is composed of K, Na, 1 / 2Ca and 1 / 2Mg). One or more selected from the group, Y is one or more selected from the group consisting of Mg, Fe, Mn, Ni, Zn, Li, Al and Cr, and Z is from the group consisting of Si and Al It is at least one selected from the above, and H ₂ O represents a water molecule bonded to an interlayer ion, and n is about 0.5 to 10, but n varies significantly depending on the interlayer ion and relative humidity. Therefore, it is not limited to this range.) Specific examples of the smectite group clay include, for example, montmorillonite, beidellite, nontronite, saponite, iron saponite, hectorite, soconite, stevensite and bentonite, and substitutions, derivatives, or mixtures thereof.

The swellable mica has the chemical formula (2): X _0.5-1.0 Y _2-3 (Z ₄ O ₁₀ ) (F, OH) ₂ (where X is Li, Na, K, Rb, Ca, Ba and One or more selected from the group consisting of Sr, Y is one or more selected from the group consisting of Mg, Fe, Ni, Mn, Al and Li, and Z is Si, Ge, Al, Fe and 1 or more selected from the group consisting of B.) or natural or synthesized. These have the property of swelling in water, a polar organic compound compatible with water at an arbitrary ratio, and a mixed solvent of water and the polar organic compound. Specific examples of the swellable mica include lithium-type teniolite, sodium-type teniolite, lithium-type tetrasilicon mica, sodium-type tetrasilicon mica, and substitutes, derivatives, or mixtures thereof.

Some of the above swellable mica have a structure similar to vermiculites, and such vermiculite equivalents can also be used. The vermiculite such equivalent has a 3 octahedral type and dioctahedral, chemical formula (3) :( Mg, Fe, Al) 2 ~3 (Si 4-x Al x) O 10 (OH) 2 · ( M ⁺ , M ²⁺ _1/2 ) _x · nH ₂ O (wherein M is an alkaline earth metal such as Na and Mg or an exchangeable cation of an alkaline earth metal, x = 0.6 to 0.9) N = 3.5 to 5.). These layered silicates are used alone or in combination of two or more.

  In the layered silicate, smectite clay and swellable mica are preferable from the viewpoint of dispersibility in the obtained extruded foam and stability of extrusion foam molding when water is used as a foaming agent, and more preferably montmorillonite. Swellable mica having sodium ions between layers such as smectite group clays such as bentonite, hectorite, synthetic smectite, and swellable fluorine mica.

  Typical examples of bentonite include natural bentonite and purified bentonite. Organic bentonite can also be used. A representative example of hectorite is synthetic hectorite. Smectites also include montmorillonite-modified products such as anionic polymer-modified montmorillonite, silane-treated montmorillonite, and highly polar organic solvent composite montmorillonite.

  The content of the layered silicate is appropriately adjusted depending on the amount of water added as a foaming agent, but is preferably 0.1 to 10 parts by weight, more preferably 0 with respect to 100 parts by weight of the styrenic resin. 2 to 7 parts by weight. The mixing ratio (weight ratio) of water to the layered silicate is preferably 0.02 to 20, more preferably 0.1 to 10, particularly preferably 0.15 to 5, most preferably 0.25 to 2. It is a range. By setting the amount of the layered silicate within the above range, the water absorption or adsorption amount of the layered silicate is sufficiently greater than the amount of water added, and the water dispersibility is improved. Is stabilized, and there is an advantage that generation of pores and voids is suppressed. In addition, there is an advantage that bubbles are not uneven due to excessive layered silicate and closed cells are formed well. Further, there is an advantage that a bubble structure having a characteristic bubble diameter distribution, which will be described later, is formed, and desired heat insulation performance is exhibited.

  In the present invention, for example, a flame retardant may be added to the styrene resin in order to meet the demand in the use of a styrene resin extruded foam such as a heat insulating material for buildings. Examples of the flame retardant include a halogen-based flame retardant, a phosphate ester compound, and a nitrogen-containing compound.

  Specific examples of the halogen-based flame retardant include (a) tetrabromoethane, tetrabromocyclooctane, hexabromocyclododecane, dibromoethyldibromocyclohexane, dibromodimethylhexane, 2- (bromomethyl) -2- (hydroxymethyl) -1,3-propanediol, dibromoneopentyl glycol, tribromoneopentyl alcohol, pentaerythrityl tetrabromide, monobromodipentaerythritol, dibromodipentaerythritol, tribromodipentaerythritol, tetrabromodipentaerythritol, pentabromodi Brominated aliphatic compounds such as pentaerythritol, hexabromodipentaerythritol, hexabromotripentaerythritol, polybrominated polypentaerythritol, etc. Is a derivative thereof, or a brominated alicyclic compound or a derivative thereof, (b) hexabromobenzene, pentabromotoluene, ethylenebispentabromodiphenyl, decabromodiphenyl ether, octabromodiphenyl ether, bis (2,4,6-tribromo Brominated aromatic compounds such as phenoxy) ethane, tetrabromophthalic anhydride, octabromotrimethylphenylindane, pentabromobenzyl acrylate, tribromophenyl allyl ether, 2,3-dibromopropyl pentabromophenyl ether, or derivatives thereof, (c) Tetrabromobisphenol A, tetrabromobisphenol A diallyl ether, tetrabromobisphenol A dimethallyl ether, tetrabromobisphenol A diglycidyl ether, tetrabromide Tribromophenol adduct of bisphenol A diglycidyl ether, tetrabromobisphenol A bis (2,3-dibromopropyl ether), tetrabromobisphenol A bis (2-bromoethyl ether), tetrabromobisphenol A bis (2,3- Dibromo-2-methylpropyl ether), tetrabromobisphenol S bis (2,3-dibromopropyl ether), tetrabromobisphenol S and the like brominated bisphenols and derivatives thereof, (d) tetrabromobisphenol A polycarbonate oligomer, tetra Brominated bisphenol derivatives oligomers such as bromobisphenol A diglycidyl ether and brominated bisphenol adduct epoxy oligomer, (e) pentabromobenzyl acrylate Brominated acrylic resins such as polymers, (f) ethylenebistetrabromophthalimide, ethylenebisdibromonorbornanedicarboximide, 2,4,6-tris (2,4,6-tribromophenoxy) 1,3,5-triazine Bromine and nitrogen atom containing compounds such as tris (2,3-dibromopropyl) isocyanurate, (g) bromine and phosphorus atom containing compounds such as tris (tribromoneopentyl) phosphate, tris (bromophenyl) phosphate, (h ) Chlorinated paraffin, chlorinated naphthalene, perchloropentadecane, chlorinated aromatic compounds, chlorinated alicyclic compounds, and the like, and (i) brominated inorganic compounds such as ammonium bromide. These compounds can be used alone or in admixture of two or more. Furthermore, a brominated polystyrene resin which is a kind of styrene resin in the present invention can also be used as a flame retardant.

  Among these, from the viewpoint of flame retardancy, hexabromocyclododecane, tetrabromocyclooctane, tetrabromobisphenol A bis (2,3-dibromopropyl ether), and tris (2,3-dibromopropyl) isocyanurate are preferable.

  The content of the halogen-based flame retardant in the styrene resin extruded foam is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the styrene resin. In addition, the flame retardancy specified in JIS A9511 measuring method A is appropriately adjusted according to the type or amount of the additive having the foaming agent addition amount, the foam density, and the flame retardant synergistic effect. The amount is preferably 1 to 20 parts by weight, more preferably 1 to 15 parts by weight, and still more preferably 2 to 8 parts by weight with respect to 100 parts by weight of the styrenic resin. By setting the content of the halogen-based flame retardant within the above range, various desirable characteristics such as intended flame retardancy can be obtained. Further, the heat resistance and surface properties of the extruded foam and the stability during the production of the foam are improved.

  For the purpose of improving the flame retardancy of the styrene resin extruded foam, a flame retardant aid having a synergistic effect with the halogen flame retardant may be added. Examples of such flame retardant aids include metal compounds, phosphorus-containing compounds, nitrogen-containing compounds, boron-containing compounds, and sulfur-containing compounds. Among these, from the viewpoint of flame retardancy, iron oxide as a metal compound, triphenyl phosphate and tris (tribromoneopentyl) phosphate as a phosphorus-containing compound, cyanuric acid, isocyanuric acid and their derivatives, boron-containing compounds as a nitrogen-containing compound Most preferred are boron oxide as the sulfur-containing compound and sulfanilic acid as the sulfur-containing compound and derivatives thereof. In addition, as a cyanuric acid derivative and an isocyanuric acid derivative, the thing of Unexamined-Japanese-Patent No. 2002-30174 ([0069] paragraph-[0079] paragraph) can be used, for example. The content of such a flame retardant aid in the styrene resin extruded foam is 0 with respect to 100 parts by weight of the styrene resin, although it depends on the type of flame retardant aid having a synergistic effect with the halogen flame retardant. 0.0001 to 10 parts by weight is preferred.

  In the present invention, inorganic compounds such as silica, calcium silicate, wollastonite, kaolin, clay, mica, zinc oxide, titanium oxide, and calcium carbonate, sodium stearate, as long as the effects of the present invention are not inhibited as necessary. , Magnesium stearate, Barium stearate, Liquid paraffin, Olefin wax, Stearylamide compound, etc. Processing aids, Phenol antioxidant, Phosphorus stabilizer, Nitrogen stabilizer, Sulfur stabilizer, Benzotriazoles Additives such as light-resistant stabilizers such as hindered amines, flame retardants other than the above flame retardants, colorants such as antistatic agents and pigments may be contained.

  The styrene resin extruded foam according to the present invention has a composite cell (bubble) structure in which small bubbles having a small bubble diameter and large bubbles having a large bubble diameter are mixed in a sea-island shape. Thereby, the heat insulation and the mechanical characteristic which were excellent in the extrusion foam can be provided. More specifically, if the extruded foam has a single cell (bubble) structure composed of bubbles having a substantially uniform diameter, the heat insulation performance of the extruded foam is improved by reducing the bubble diameter. In order to obtain a thick extruded foam by reducing the bubble diameter, a large amount of resin is required. As a result, the pressure during extrusion increases and the moldability deteriorates. On the other hand, in the composite cell structure, heat insulation is improved by the presence of small bubbles, and a thick extruded foam can be easily formed at a low resin density by the presence of large bubbles.

The composite cell structure has a structure specified by a bubble size distribution diagram shown below. The bubble diameter distribution chart samples a predetermined range of the cross section along the extrusion direction of the styrene resin extruded foam, obtains the bubble diameter and area of each bubble in the obtained sample cross section, the horizontal axis from 0 mm to the maximum bubble diameter The bubble diameter is divided into sections of 0.02 mm until the vertical axis, and the vertical axis is the area ratio of each section obtained by the following formula (1).
Formula (1): Area ratio for each section = sum of the areas of bubbles having bubble diameters belonging to the section / sum of the areas of all bubbles

  The detailed method of creating the bubble diameter distribution chart is as follows. A predetermined range of the cross section along the extrusion direction of the styrene resin extruded foam is sampled. The cross section along the extrusion direction is a cross section extending in the thickness direction in the extrusion direction of the extruded foam. Each predetermined range of this cross section is sampled. The predetermined range to be sampled may be sampled at any position of the extruded foam except for the special cell structure at the end of the extruded foam, but preferably at the center in the width direction of each cross section. Sampling is performed at about three points at the center of the height and the vertical symmetry position.

  Each sampled sample is photographed using a scanning electron microscope (SEM) to obtain an SEM image. The imaging magnification of the SEM image is set to about 30 to 40 times. The photographing range is, for example, about several mm to several cm in length × width. Each SEM image is processed using an image processing apparatus (for example, product name: PIAS-II, manufactured by Pierce Co., Ltd.) with the thickness direction as the vertical direction and the extrusion direction as the horizontal direction, and individual bubbles in the SEM image. (A) (hereinafter referred to as “bubble area”). Moreover, the maximum diameter (Feret diameter) of the vertical direction (thickness direction: Zf) and horizontal direction (extrusion direction: Xf) of each bubble is calculated | required. Note that the measurement of the bubble area and the maximum diameter is for only the bubble in which the entire view of the bubble is projected in the SEM image, and a part of the bubble is missing at the edge of the SEM image, or the edge of the SEM image. Even if it is not a part, a part of the bubble wall is missing, or a bubble integrated with an adjacent bubble or the like is excluded. This excluded bubble is also excluded from the total measurement area. The number of bubbles to be measured is preferably at least 200. Therefore, in some cases, 200 or more bubbles can be measured with one SEM image, but in other cases, two or more SEM images may be used.

Each bubble in the SEM image is assumed to be elliptical, and the bubble diameter Z in the thickness direction of each bubble and the bubble diameter X in the extrusion direction are determined according to the following equations (3) and (4).
Formula (3): X = [{(4 × a) / (π × xf × zf)} ^1/2 ] × xf
Formula (4): Z = [{(4 × a) / (π × xf × zf)} ^1/2 ] × zf

The representative bubble diameter D of each bubble is obtained by geometrically averaging the obtained bubble diameter Z in the thickness direction and the bubble diameter X in the extrusion direction of each bubble according to the equation (5).
Formula (5): D = (X × Z) ^1/2

  In the range from zero to the section including the maximum bubble diameter, the abscissa represents the representative bubble diameter D divided by 0.02 mm, and the ordinate represents the area ratio for each section represented by the above formula (1). Is made into a bubble diameter distribution chart in the present invention. For example, in the bubble diameter distribution chart, the representative bubble diameter D is classified such that, in the smallest section, the representative bubble diameter D is zero or more and less than 0.02 mm. In the present specification, when “bubble diameter” is simply described, the representative bubble diameter D is indicated unless otherwise specified. The horizontal axis of the bubble diameter distribution chart, that is, the range of each section of the representative bubble diameter D includes the minimum representative bubble diameter D of the section, and the bubble diameter larger by 0.02 mm than the minimum representative bubble diameter D is included. Make it not exist. That is, the bubble diameter belonging to the section is not less than the minimum bubble diameter of the section and less than the minimum bubble diameter of the section + 0.02 mm.

  In the above bubble diameter distribution diagram, from the section where the bubble diameter is from zero to less than 0.02 mm, the area ratio in that section is compared with the area ratio of the adjacent section. In the present invention, when the area ratio is larger than the area ratio in one section (the section where the bubble diameter is 0.02 mm smaller and 0.02 mm larger), the peak is recognized in the present invention, the area ratio of the section is the peak area ratio, and the section is the peak. It is called a section. When the area ratio in one or both of the two adjacent sections is equal, the area ratio of the adjacent section of the equal side section is compared. A plurality of sections are combined to be a peak section. When the area ratio in either one or both of the adjacent sections is larger, it is not determined as a peak.

The styrene-based resin extruded foam according to the present invention has a plurality of peaks in the area ratio of the entire cell diameter in the cell diameter distribution diagram. In addition, among the plurality of peaks, a first peak that exists in a section where the bubble diameter is smaller than any other peak, and a second peak that is in a section where the bubble diameter is larger than the first peak and is closest to the first peak. The bubble anisotropy rate obtained by the following formula (2) of the bubbles existing in the section having the bubble diameter larger than the first section having the lowest area ratio between and 0.5 is 1.0.
Formula (2): Bubble anisotropic ratio = average bubble diameter in the thickness direction / average bubble diameter in the extrusion direction Note that the average bubble diameter is the addition of the bubble diameter Z in the thickness direction of each bubble and the bubble diameter X in the extrusion direction. The average value.

  The bubbles present in the section having a larger bubble diameter than the first section are the aforementioned large bubbles. Hereinafter, when simply referred to as “large bubble”, it means a bubble present in a section having a larger bubble diameter than the first section. As described above, the bubble anisotropy ratio of large bubbles is preferably 0.5 to 1.0, more preferably 0.6 to 1.0, and particularly preferably 0.7 to 0.9. is there. When the bubble anisotropy rate of the large bubbles is within the above range, the decrease in the plane compressive strength is suppressed and the thermal conductivity is improved. In addition, a decrease in heat-resistant dimensional stability due to the restoring force of the flat bubbles returning to a circular shape can be suppressed.

  In the bubble diameter distribution diagram, the bubbles existing from the second section to the first section where the bubble diameter is 0 mm or more and less than 0.02 mm are the small bubbles described above. Hereinafter, when simply referred to as “small bubbles”, it means bubbles existing from the second section to the first section. In the small bubbles, the bubble anisotropy ratio obtained by the above formula (2) is preferably 0.8 or more, more preferably 0.8 to 1.3, and particularly preferably 0.9 to 1. .2. By making the bubble anisotropy rate of the small bubbles within the above range, a decrease in the plane compressive strength and a decrease in the heat resistant dimensional stability can be suppressed. In other words, in the small bubbles, the flat compressive strength is greatly reduced by flattening the bubbles, and the restoring force of the flat bubbles to return to a circle is strong. A shape close to is suitable.

  The styrene resin extruded foam according to the present invention preferably has a total area ratio from the second section to the first section of 0.05 to 0.90 in the cell diameter distribution diagram. Preferably it is 0.1-0.9, Most preferably, it is 0.2-0.8, Most preferably, it is 0.25-0.7. By setting the sum of the area ratios from the second section to the first section in the above range, the heat insulation is improved and the thickness of the extruded foam is easily increased, and the moldability is improved.

  The styrene-based resin extruded foam according to the present invention has a plurality of peaks in the above bubble diameter distribution diagram, at least one peak existing in a section where the bubble diameter is 0 mm or more and less than 0.20 mm, and the bubble diameter is 0.20 mm. It is preferable that at least one peak existing in a section of 0.42 mm or less and more preferably, at least one peak present in a section of a bubble diameter of 0.02 mm or more and less than 0.16 mm, and a bubble diameter. And at least one peak existing in a section of 0.20 mm or more and less than 0.38 mm. When the peak of the composite cell structure exists in the above range, the improvement of the heat insulating performance and the improvement of the mechanical properties of the extruded foam are balanced.

  The present styrene resin extruded foam supplies a styrene resin by supplying the styrene resin to the melt kneading means, and supplying the additive containing the nucleating agent and the foaming agent to the melt kneading means and kneading with the styrene resin. A composition is obtained by extruding and foaming the styrenic resin composition from a high pressure region through a die lip to a low pressure region.

  As a method of adjusting the cell diameter distribution of the styrene resin extruded foam, water is used as the foaming agent, depending on the type and amount of the other foaming agent, the type and amount of the water-absorbing substance, the molding conditions for extrusion foaming, etc. Can be adjusted. As such molding conditions, for example, adjustment of the enlargement ratio of the thickness when the molten styrene resin composition is discharged into the atmosphere, that is, the die lip slit thickness and the molding die for making a rectangle Height adjustment can be mentioned. Moreover, the method of adjusting molding resistance is mentioned.

  As a procedure for adding various additives to the styrenic resin, for example, after adding and mixing various additives to the styrenic resin, the mixture is supplied to an extruder, heated and melted, and further added with a foaming agent and mixed. The timing for adding various additives to the styrenic resin and the kneading time are not particularly limited.

  The heating temperature of the styrenic resin may be higher than the temperature at which the used styrenic resin is melted, but the temperature at which the molecular degradation of the resin due to the influence of additives and the like is suppressed as much as possible, for example, about 150 to 260 ° C. preferable. The melt-kneading time varies depending on the amount of styrene-based resin extruded per unit time and the type of extruder used as the melt-kneading means, so it cannot be uniquely defined. The styrene-based resin and the blowing agent or additive are uniform. The time required for the dispersion and mixing is appropriately set.

  Examples of the melt-kneading means include a screw type extruder, but are not particularly limited as long as they are used for ordinary extrusion foaming. However, in order to suppress the molecular degradation of the resin as much as possible, it is preferable that the screw shape of the extruder is of a low shear type.

  The foam molding method is, for example, a method in which an extruded foam obtained by releasing pressure from a high pressure region to a low pressure region through a slit die having a linear slit shape used for extrusion molding is in close contact with the slit die. A method of molding a plate-like foam having a large cross-sectional area is used by using a molding die placed in contact and a molding roll installed adjacent to the downstream side of the molding die. By adjusting the flow surface shape and the mold temperature of the molding die, a desired foam cross-sectional shape, foam surface property, and foam quality can be obtained.

  Examples of a method for controlling the bubble anisotropy rate include a method of stretching an extruded foam while heating. Specifically, using a heating and stretching device that performs stretching with a roll while heating the extruded foam with heated air, the roll is rotated faster than the rotational speed of the take-up machine while heating the resulting extruded foam. To apply a stretching process. Thereby, an extrusion foam is extended | stretched in an extrusion direction and the said bubble anisotropic rate becomes small.

  Considering that the styrene-based resin extruded foam according to the present invention functions as, for example, a heat insulating material for a building, a cold storage, or a cold car, a thermal conductivity on the seventh day after manufacture is 0.025 W / It is preferably mK or less. This thermal conductivity is measured according to JIS A9511.

Considering that the styrene-based resin extruded foam according to the present invention functions as, for example, a heat insulating material for buildings, a cold storage or a cold storage vehicle, the plane compressive strength is preferably 15 N / m ² or more. . This plane compressive strength is measured according to JIS A9511.

The styrene-based resin extruded foam according to the present invention has a foam density from the viewpoint of heat insulation, strength, and light weight considering that it functions as, for example, a heat insulating material for buildings, a cold storage or a cold car. is preferably 30~60kg / ^{m 3,} more preferably from 35~50kg / ^{m 3.}

  The thickness of the styrene-based resin extruded foam according to the present invention is 10 from the viewpoint of heat insulation, bending strength, and compressive strength in consideration of functioning as, for example, a heat insulating material for buildings, a cold storage or a cold car. It is preferable that it is -150mm, More preferably, it is 15-120mm, Most preferably, it is 20-100mm.

  Thus, according to the styrene resin extruded foam according to the present invention, the bubble diameter is larger than the first section where the area ratio existing between the first peak and the second peak is the lowest in the above bubble diameter distribution diagram. Since the bubble anisotropy ratio obtained by the formula (2) of the bubbles existing in the section is set to 0.5 to 1.0, the styrene resin extruded foam has excellent heat insulation and environmental compatibility and has desired mechanical properties. The body can be obtained. Such a styrene resin extruded foam is particularly useful as a building material, a heat insulating material for a cold box or a cold car.

  Examples of the present invention will be described below. Needless to say, the present invention is not limited to the following examples. In the following examples, “%” represents “% by weight” unless otherwise specified.

  For Examples 1 to 3 and Comparative Examples 1 to 3, foam density, closed cell ratio, residual foaming agent amount, thermal conductivity, plane compressive strength, bubble diameter distribution, bubble anisotropy according to the following methods Rate was evaluated.

(1) Foam density (kg / m ³ )
The styrene resin extruded foam is cut into a rectangular parallelepiped shape of approximately 200 mm (extrusion direction) x 100 mm (width direction) x 25 mm (thickness direction), and the weight is measured, and the vertical dimensions, horizontal dimensions, and height dimensions are measured with calipers. It was measured. The foam density was determined from the measured weight and each dimension based on the following formula, and the unit was converted to kg / m ³ .
Foam density (g / cm ³ ) = foam weight (g) / foam volume (cm ³ )

(2) Closed cell ratio (%)
It measured according to ASTM D-2856 using a multi-pynometer (Yuasa Ionics Co., Ltd.).

(3) Residual foaming agent amount (parts by weight)
About 1 g of a test piece having all surfaces cut away by 2 mm or more was precisely weighed from a styrene resin extruded foam 7 days after the production, put in a sealed container, and heated at 200 ° C. for 15 minutes. The gas in a container was extract | collected and content of the foaming agent was measured using the gas chromatography (Shimadzu Corporation, brand name: GC-14A).

(4) Thermal conductivity (unit: W / mK)
The thermal conductivity of the extruded styrene resin foam 7 days after the production was measured according to JIS A9511.

(5) Plane compressive strength (N / cm ² )
The thermal conductivity of the styrene resin extruded foam 7 days after production was measured according to JIS A9511.

(6) Bubble diameter distribution A bubble diameter distribution chart was prepared for the styrene resin extruded foam according to the method described above. Using this bubble diameter distribution chart, the number of peaks, peak position, and total area ratio from the first section to the second section (hereinafter referred to as “small bubble area ratio”) are obtained according to the method described above. It was.

(7) Cell Anisotropy Rate The bubble diameter Z in the thickness direction of each bubble and the bubble diameter X in the extrusion direction in the SEM image obtained by the method described above in the cross section along the extrusion direction of the styrene resin extruded foam It calculated | required based on Formula (3) and Formula (4) mentioned above, and calculated | required the average large bubble diameter and average small bubble diameter about each of an extrusion direction and the thickness direction about each of the large bubble and the small bubble. From these, the bubble anisotropy rate was determined for each of the large bubbles and the small bubbles based on the above-described equation (2).

Example 1
Hexabromocyclododecane (Albemarle Corporation, trade name: SAYTEX HP-900) as a halogen-based flame retardant with respect to 100 parts by weight of polystyrene (PS Japan Corporation, trade name: G9401, MFR = 2.5 g / 10 min) 3.5 parts by weight, talc (Hayashi Kasei Co., Ltd., trade name: Talcan powder) 0.15 parts by weight, barium stearate (Sakai Chemical Industry Co., Ltd., trade name: barium stearate), 0.5 parts by weight, bentonite ( Hojun Co., Ltd., trade name: Bengel 23) 1 part by weight, triphenyl phosphate (Daihachi Chemical Industry Co., Ltd., trade name: TPP) 1 part by weight, epoxy resin (Asahi Denka Kogyo Co., Ltd., trade name: EP-13) 0.2 parts by weight, trisodium phosphate dodecahydrate (Taihei Chemical Industry Co., Ltd., trade name: triato phosphate) 0.1 parts by weight of rhodium (crystal), 0.1 parts by weight of hydrous amorphous silicon dioxide (DSL Japan Co., Ltd., trade name: Carplex), stabilizer (Ciba Specialty Chemicals Co., Ltd., trade name: IRGANOX) B911 (hindered phenol antioxidant IRGANOX1076: octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate and phosphorus stabilizer IRGAFOS168: tris (2,4-di-t-butyl Phenyl) 1: 1 mixture of phosphite)) A 0.4 weight part mixture is dry blended into a styrenic resin composition, and the styrenic resin composition is passed through a first extruder and a second extruder. It was fed at 750 kg / hour to a two-stage extruder connected in series. The styrenic resin composition supplied to the first extruder is heated to 200 ° C. and kneaded. In the vicinity of the tip of the first extruder (the side connected to the second extruder), as a foaming agent, 100 weight polystyrene. Styrene resin composition in which 4 parts by weight of i-butane (Mitsui Chemicals), 1.5 parts by weight of dimethyl ether (Mitsui Chemicals), and 0.75 parts by weight of water (tap water) are melted Press-fitted into. In addition, the composition of the used blowing agent is 64% i-butane, 24% dimethyl ether, and 12% water with respect to the total amount of the blowing agent. Under the present circumstances, the resin pressure in the front-end | tip of a 1st extruder was 8-15 MPa, and the press injection pressure of the foaming agent was set to + 0.5-3 MPa with respect to this. In the second extruder connected to the first extruder, the resin temperature is cooled to 120 ° C., and the styrenic resin composition is extruded into the atmosphere from a die lip provided at the tip of the second extruder. A rectangular parallelepiped having a width of about 35 mm and a width of about 1000 mm. Next, while the extruded rectangular extruded foam is heated to 90 to 110 ° C. using a heating and stretching apparatus, the take-up roll provided on the downstream side of the forming roll provided on the downstream side of the die lip is set to 0. The foam was rotated at a speed of 5 to 2.0 m / min and subjected to heat stretching treatment (post-expansion) to obtain an extruded foam.

  The evaluation results of the obtained extruded foam are shown in Table 1. Moreover, the SEM image of the cross section along the extrusion direction of an extrusion foam is shown in FIG. Furthermore, the bubble diameter distribution map of the extruded foam is shown in FIG.

  As shown in FIG. 1, in the SEM image of the cross section along the extrusion direction of the extruded foam, it was confirmed that large diameter bubbles and small diameter bubbles were formed in a sea-island shape. Moreover, as shown in FIG. 2, four peaks were confirmed in the bubble diameter distribution chart. Further, as shown in Table 1, since the bubble anisotropy rate of large bubbles was 0.76, it was within the range of 0.5 to 1.0. The bubble anisotropy rate of the small bubbles was 0.85, which was 0.8 or more. The small bubble area ratio was 0.39, which was in the range of 0.05 to 0.90.

  In Example 1, the peak existing in the section where the bubble diameter is 0.08 mm or more and less than 0.10 mm is the first peak in the present invention, and the bubble diameter is present in the section where the bubble diameter is 0.26 mm or more and less than 0.28 mm. The peak is the second peak in the present invention. Moreover, the section where the bubble diameter is 0.14 mm or more and less than 0.16 mm is the first section in the present invention, and the section where the bubble diameter is 0 mm or more and less than 0.02 mm is the second section in the present invention. And a thing with a larger bubble diameter than a 1st area is a large bubble, and a thing contained from a 2nd area to a 1st area is a small bubble.

As shown in Table 1, the foam density of the entire extruded foam obtained was 35 kg / m ³ , the thermal conductivity was 0.024 W / mK, and the plane compressive strength was 22 N / m ² . . The amount of foaming agent remaining in the extruded foam was 3.0% for isobutane, 1.0% for dimethyl ether, and 0.2% for air. The closed cell ratio of the extruded foam was 99%.

(Example 2)
Extruded foam was obtained in the same manner as in Example 1 except that the styrene resin composition was supplied to the two-stage extruder at 600 kg / hour. The evaluation results are shown in Table 1.

  As shown in Table 1, four peaks were confirmed in the bubble size distribution diagram. Moreover, since the bubble anisotropy rate of large bubbles was 0.64, it was in the range of 0.5 to 1.0. The bubble anisotropy rate of the small bubbles was 0.80, which was 0.8 or more. The small bubble area ratio was 0.23, which was in the range of 0.05 to 0.90.

As shown in Table 1, the foam density of the entire extruded foam obtained was 35 kg / m ³ , the thermal conductivity was 0.024 W / mK, and the plane compressive strength was 25 N / m ² . . The amount of foaming agent remaining in the extruded foam was 3.0% for isobutane, 1.1% for dimethyl ether, and 0.3% for air. The closed cell ratio of the extruded foam was 98%.

(Example 3)
For 100 parts by weight of polystyrene, 4 parts by weight of hexabromocyclododecane, 1 part by weight of talc, 0.2 part by weight of calcium stearate (Sakai Chemical Industry Co., Ltd., trade name: calcium stearate), 0.75 part by weight of triphenyl phosphate , Epoxy resin 0.3 part by weight, synthetic hectorite (Rockwood, trade name: Laponite) 0.3 part by weight, aerosil (Nippon Aerosil Co., Ltd., trade name: AEROSIL) 0.2 part by weight, stabilizer 0.4 A mixture consisting of parts by weight was dry blended to obtain a styrene resin composition, and the styrene resin composition was supplied to a two-stage extruder at 800 kg / hour. Moreover, 3.7 parts by weight of i-butane, 2 parts by weight of dimethyl ether, and 0.4 parts by weight of water were injected into the melted styrene resin composition with respect to 100 parts by weight of polystyrene as a foaming agent. Moreover, the heat-stretching process (post expansion) after foaming was not performed in the present Example. Otherwise, an extruded foam was obtained in the same manner as in Example 1. The evaluation results are shown in Table 1.

  As shown in Table 1, two peaks were confirmed in the bubble size distribution diagram. Moreover, since the bubble anisotropy rate of large bubbles was 0.93, it was in the range of 0.5 to 1.0. The bubble anisotropy rate of the small bubbles was 0.99, which was 0.8 or more. The small bubble area ratio was 0.29, which was in the range of 0.05 to 0.90.

As shown in Table 1, the foam density of the entire extruded foam obtained was 40 kg / m ³ , the thermal conductivity was 0.024 W / mK, and the plane compressive strength was 20 N / m ² . . The amount of blowing agent remaining in the extruded foam was 3.2% for isobutane, 1.2% for dimethyl ether, and 0.4% for air. The closed cell ratio of the extruded foam was 97%.

(Comparative Example 1)
For 100 parts by weight of polystyrene, 3.5 parts by weight of hexabromocyclododecane, 0.15 parts by weight of talc, 0.5 parts by weight of barium stearate, 1 part by weight of bentonite, 1 part by weight of triphenyl phosphate, 0. A mixture comprising 2 parts by weight and 0.1 part by weight of water-containing amorphous silicon dioxide was dry blended to obtain a styrene resin composition, and the styrene resin composition was supplied to a two-stage extruder at 900 kg / hour. Moreover, 4 parts by weight of i-butane, 1.5 parts by weight of dimethyl ether, and 0.6 parts by weight of water were pressed into the melted styrene resin composition with respect to 100 parts by weight of polystyrene as a foaming agent. Further, in Comparative Example 1, no heat stretching treatment (post-expansion) after foaming was performed. Otherwise, an extruded foam was obtained in the same manner as in Example 1. The evaluation results are shown in Table 1.

As shown in Table 1, Comparative Example 1 has a single cell structure that does not have a plurality of peaks in the bubble diameter distribution diagram, and has a bubble structure that includes only bubbles corresponding to small bubbles (small bubble area ratio). 100). Further, the foam density of the entire extruded foam was 34 kg / m ³ , the thermal conductivity was 0.027 W / mK, and the plane compressive strength was 18 N / m ² . The amount of blowing agent remaining in the extruded foam was 3.3% for isobutane, 0.7% for dimethyl ether, and 0.2% for air. The closed cell ratio of the extruded foam was 94%.

(Comparative Example 2)
For 100 parts by weight of polystyrene, 4 parts by weight of hexabromocyclododecane, 0.2 parts by weight of talc, 0.5 parts by weight of barium stearate, 1 part by weight of bentonite, 0.2 parts by weight of epoxy resin, hydrous amorphous dioxide A mixture comprising 0.1 part by weight of silicon and 0.2 part by weight of a stabilizer was dry blended to obtain a styrene resin composition, and the styrene resin composition was supplied to a two-stage extruder at 1000 kg / hour. Moreover, 3.7 parts by weight of i-butane, 1.9 parts by weight of dimethyl ether, and 0.6 parts by weight of water were pressed into the melted styrene resin composition with respect to 100 parts by weight of polystyrene as a foaming agent. In Comparative Example 2, the heat-stretching treatment (post-expansion) after foaming was not performed. Otherwise, an extruded foam was obtained in the same manner as in Example 1. The evaluation results are shown in Table 1.

As shown in Table 1, since the bubble anisotropy rate of large bubbles was 1.63, it was out of the range of 0.5 to 1.0. The foam density of the entire extruded foam was 35 kg / m ³ , the thermal conductivity was 0.029 W / mK, and the plane compressive strength was 29 N / m ² . The amount of foaming agent remaining in the extruded foam was 3.3% for isobutane, 0.8% for dimethyl ether, and 0.3% for air. The closed cell ratio of the extruded foam was 97%.

(Comparative Example 3)
Hexabromocyclododecane 4 parts by weight, talc 1 part by weight, calcium stearate 0.2 parts by weight, triphenyl phosphate 0.75 parts by weight, epoxy resin 0.3 parts by weight, synthetic hectorite 0 .3 parts by weight, 0.2 parts by weight of aerosil and 0.4 parts by weight of stabilizer were dry blended to obtain a styrene resin composition, and the styrene resin composition was transferred to a two-stage extruder. It was supplied at 900 kg / hour. Moreover, 3.7 parts by weight of i-butane, 2 parts by weight of dimethyl ether, and 0.4 parts by weight of water were injected into the melted styrene resin composition with respect to 100 parts by weight of polystyrene as a foaming agent. Others were obtained in the same manner as in Example 1 to obtain an extruded foam that was subjected to a heat-stretching treatment (post-expansion) after foaming. The evaluation results are shown in Table 1.

As shown in Table 1, since the bubble anisotropy rate of large bubbles was 1.20, it was out of the range of 0.5 to 1.0. The foam density of the entire extruded foam was 35 kg / m ³ , the thermal conductivity was 0.026 W / mK, and the plane compressive strength was 28 N / m ² . The amount of foaming agent remaining in the extruded foam was 3.0% for isobutane, 1.4% for dimethyl ether, and 0.1% for air. The closed cell ratio of the extruded foam was 94%.

When the styrene resin extruded foam is used as, for example, a heat insulating material for a building material, a cold box or a cold car, the thermal conductivity is 0.025 W / mK or less and the plane compressive strength is 15 N / m. It is preferable that it is ² or more. In Example 1 to Example 3, it was confirmed that such heat insulation performance and planar compressive strength were satisfied, and Comparative Example 1 to Comparative Example 3 were not satisfied.

1 is a view showing an SEM image of a cross section along the extrusion direction in Example 1. FIG. FIG. 2 is a bubble diameter distribution diagram in the first embodiment.

Claims (11)

A styrene resin extruded foam obtained by extrusion foaming a styrene resin composition to which a non-halogen foaming agent is added as a foaming agent,
A predetermined range of the cross section along the extrusion direction of the styrene resin extruded foam is sampled, the bubble diameter and area of each bubble in the obtained sample cross section are obtained, and the horizontal axis is from 0 mm to the maximum bubble diameter every 0.02 mm. In the bubble diameter distribution diagram, the bubble diameter is divided into sections, and the vertical axis is the area ratio for each section obtained by the following formula (1).
The area ratio in all sections of the bubble diameter has multiple peaks,
Of the plurality of peaks, a first peak that exists in a section where the bubble diameter is smaller than any other peak, and a second peak that is in a section where the bubble diameter is larger than the first peak and is closest to the first peak A styrenic resin having a bubble anisotropy ratio of 0.5 to 1.0 determined by the following formula (2) of bubbles existing in a section having a larger bubble diameter than the first section having the lowest area ratio between them Extruded foam.
Formula (1): Area ratio for each section = sum of the areas of the bubbles having the bubble diameter belonging to the section / sum of the areas of all the bubbles (2): Bubble anisotropic ratio = average bubble diameter in the thickness direction / extrusion direction Average bubble diameter   In the bubble diameter distribution diagram, the bubble anisotropy ratio determined by the above formula (2) of the bubbles existing from the second section to the first section where the bubble diameter is 0 mm or more and less than 0.02 mm is 0.8 or more. The styrenic resin extruded foam according to claim 1.   The styrene resin extruded foam according to claim 1 or 2, wherein, in the bubble diameter distribution diagram, the sum of the area ratios from the second section to the first section is 0.05 to 0.90.   The plurality of peaks include at least one peak existing in a section having a bubble diameter of 0 mm or more and less than 0.20 mm and at least one peak existing in a section having a bubble diameter of 0.20 mm or more and less than 0.42 mm. The styrene resin extruded foam according to any one of claims 1 to 3.   The styrene resin extruded foam according to any one of claims 1 to 4, wherein the non-halogen foaming agent contains at least water.   The styrene resin extruded foam according to claim 5, wherein the non-halogen foaming agent further contains a saturated hydrocarbon having 3 to 5 carbon atoms.   The styrene resin extruded foam according to claim 6, wherein the saturated hydrocarbon is selected from the group consisting of propane, n-butane and i-butane.   The styrene resin extruded foam according to any one of claims 1 to 7, wherein the thermal conductivity of the styrene resin extruded foam is 0.025 W / mK or less. 9. The styrene resin extruded foam according to claim 1, wherein the styrene resin extruded foam has a plane compressive strength of 15 N / m ² or more. The styrene resin extruded foam according to any one of claims 1 to 9, wherein a foam density of the styrene resin extruded foam is 30 to 60 kg / m ³ .   The styrene resin extruded foam according to any one of claims 1 to 10, wherein the styrene resin extruded foam has a thickness of 10 to 150 mm.