JP2012082440A - Polystyrene-based resin-extruded foamed plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polystyrene-based resin-extruded foamed plate with a low apparent density, excellent in flame resistance, comprising a foaming agent using carbon dioxide as principal ingredient.SOLUTION: The polystyrene-based resin-extruded foamed plate is obtained by kneading a base resin comprising a polystyrene-based resin blended with an ethylenic copolymer having carbonyl group, a foaming agent comprising 60-100 mol% of carbon dioxide and 40-0 mol% of other physical foaming agent (excluding chlorofluorocarbons) to the total foaming agent, and a flame retardant, and extruding, wherein 2-8 pts.wt. of the ethylenic copolymer having carbonyl group is contained in the 100 pts.wt. of the polystyrene-based resin in the polystyrene-based resin-extruded foamed plate, the polystyrene based resin composition constituting the polystyrene-based resin-extruded foamed plate has 1.5×10-2.5×10of the weight-average molecular weight and a ratio of Mw/Mn of weight-average molecular weight (Mw) to number-average molecular weight (Mn) of 2.3 or more, having thickness of 10 mm or more and at least 50 cmof cross section, 20-50 kg/mof apparent density, 0.1-0.7 mm of average diameter of the foam in thickness direction, and having at least 80% of closed cell ratio.

Description

  The present invention relates to a polystyrene resin extruded foam plate mainly used for heat insulating materials such as walls, floors, and roofs of buildings, tatami core materials, and the like, and more specifically, it is excellent in environmental suitability and has a low apparent density. It relates to a foam board.

  Conventionally, polystyrene-based resin foams have excellent heat insulating properties and suitable mechanical strength, so that those molded into a plate shape have been widely used as heat insulating materials. As a method for producing such an extruded foam plate, a polystyrene-based resin material is heated and melt-kneaded, a physical foaming agent is added, the mixture is extruded from a high-pressure region to a low-pressure region, and, if desired, at the die outlet of the extruder. A method of manufacturing a foam by connecting shaping apparatuses is known.

  Conventionally, as a foaming agent used for the production of the extruded foam plate, chlorofluorocarbons (hereinafter referred to as CFC) such as dichlorodifluoromethane, hydrogen atom-containing fluorinated hydrocarbons (hereinafter referred to as HCFC), molecules. Fluorocarbons such as fluorinated hydrocarbons having no chlorine atom (hereinafter referred to as HFC) and lower saturated hydrocarbons such as propane, butane and pentane have been used as blowing agents.

  However, the CFC and HCFC may destroy the ozone layer, and the HFC has a large global warming potential although the ozone depletion coefficient is 0. Therefore, their use is not preferable in terms of protecting the global environment.

  On the other hand, lower saturated hydrocarbons as described above have an ozone depletion coefficient of 0, a lower global warming coefficient than fluorocarbons, and are excellent foaming agents. However, since lower saturated hydrocarbons are flammable gases, there is a high risk of foam production, such as the risk of fire accidents when electrostatic ignition occurs, and they are obtained when used in large quantities as foaming agents. Since it tends to be difficult to impart flame retardancy to foams as compared with chlorofluorocarbons, it is desirable to reduce the amount used. In addition, due to recent volatile organic compound (VOC) emission control measures, lower hydrocarbons other than methane have been subject to emission control. There is a need to reduce emissions.

  From such a background, it is desired to produce a polystyrene resin foam using a foaming agent that is environmentally friendly and less dangerous. In recent years, the global warming potential is very small compared to fluorocarbons. Since it does not destroy the ozone layer and is nonflammable, studies have been made using carbon dioxide as a foaming agent that is friendly to the global environment and highly safe.

  However, when carbon dioxide is used as the main component in the foaming agent, carbon dioxide has lower solubility in polystyrene resins than the above-mentioned chlorofluorocarbons and lower saturated hydrocarbons. At the same resin pressure as that used, the foaming agent separates from the resin inside the lip of the die, vaporizes, and foaming starts (hereinafter also referred to as internal foaming), and gas is ejected from the die. Or voids that cause poor appearance occur, making it difficult to obtain a good foam. Furthermore, in order to obtain a foam having a low apparent density, the amount of the physical foaming agent used must be increased. However, when carbon dioxide is used, the above-described separation and vaporization of the foaming agent becomes more remarkable. Therefore, in order to obtain a good foam, it is necessary to maintain the resin pressure near the lip higher than when using chlorofluorocarbons or lower saturated hydrocarbons.

  The pressure can be maintained by reducing the distance between the die lips or the opening cross-sectional area, but in that case, it becomes practically impossible to obtain a polystyrene resin extruded foam plate having a large thickness and a large cross-sectional area. End up. On the other hand, it is possible to increase the resin pressure by further cooling the resin and extruding it at a low temperature, but in this case, shaping after extrusion foaming becomes impossible. Furthermore, maintaining a high resin pressure in the vicinity of the lip causes finer bubbles in the resulting extruded foam, and there is a possibility that the bubbles may become continuous bubbles or that shaping may be impossible.

  Carbon dioxide has a smaller plasticizing effect on polystyrene resins than fluorocarbons and hydrocarbons, so it is difficult to maintain a good foamed state due to the heat generated by the resin, and the load on the extruder is extremely high. There is also a problem of becoming higher.

  Attempts have been made to overcome the above-mentioned problems that occur when using a foaming agent composed mainly of carbon dioxide and to produce a polystyrene-based extruded foam having a low apparent density.

  For example, by using carbon dioxide as a foaming agent and using a polystyrene resin with a specific relationship between melt flow rate and melt tension, a method for producing a polystyrene resin extruded foam plate with a high expansion ratio (low apparent density) has been reported. (Patent Document 1).

  In addition, a method using polystyrene having a low average molecular weight has been reported in order to suppress the problem of heat generation due to insufficient plasticization effect of carbon dioxide (Patent Document 2).

  Furthermore, it has been reported that polyphenylene ether (hereinafter also referred to as PPE) is added in order to improve the compatibility between carbon dioxide and polystyrene resin (Patent Document 3).

JP 2000-17097 A JP-T-9-503813 JP 2000-248107 A

However, the apparent density of the extruded foamed plate obtained by the production method of Patent Document 1 is as high as 40 kg / m ³ , and the high expansion ratio was insufficient. Furthermore, if the amount of carbon dioxide, which is a foaming agent, is increased for the purpose of increasing the foaming ratio, not only will the bubbles become finer and molding becomes difficult, but if the amount is increased too much, internal foaming occurs and the foam has a high foaming ratio. The problem that cannot be obtained remains.

  Moreover, although the foam of comparatively low apparent density is obtained by the manufacturing method of patent document 2, the cross-sectional area is very small, and it is large cross-sectional area to obtain the width | variety and thickness required as a heat insulating material. When extrusion foaming is performed using a die having an opening, a pressure necessary for foaming cannot be ensured, and internal foaming occurs and a foam having a low apparent density cannot be obtained. In addition, since the molecular weight of the base resin constituting the foam is too small, there is a disadvantage that a foam excellent in mechanical strength cannot be obtained.

  Furthermore, in the production method of Patent Document 3, a foam having a low apparent density is obtained by adding a large amount of PPE. However, since a large amount of PPE is added, if a large amount of flame retardant is not added, JIS A 9511 ( (2006), the problem remains that it is difficult to obtain an extruded foam board that satisfies the flammability standard of measurement method A.

  The present invention is an extruded foam plate using carbon dioxide having a ozone depletion coefficient of 0 and a low global warming potential as a main component of a foaming agent in view of the drawbacks of conventional polystyrene resin extruded foam boards, An object of the present invention is to provide a polystyrene resin extruded foam plate having excellent properties and low apparent density.

  As a result of intensive research to solve the above problems, the present inventors have used a specific resin for a polystyrene resin having a specific average molecular weight when a foaming agent mainly composed of carbon dioxide is used as a foaming agent. By adding, it has excellent mechanical strength, moderately fine bubble diameter, low apparent density, width and thickness necessary for heat insulation, excellent flame resistance, low thermal conductivity, and appearance However, the present inventors have found the fact that a good styrene resin foam plate can be easily produced, and have completed the present invention.

According to this invention, the polystyrene-type resin extrusion foam board shown below is provided.
[1] A base resin obtained by blending a polystyrene resin with an ethylene copolymer having a carbonyl group, 60 to 100 mol% of carbon dioxide with respect to the total amount of foaming agent, and other physical foaming agents (fluorocarbons) A polystyrene resin extruded foam plate obtained by kneading together with a foaming agent consisting of 40 to 0 mol% and a flame retardant and extrusion foaming, wherein the carbonyl group is contained in the polystyrene resin extruded foam plate. 2-8 parts by weight of an ethylene copolymer having 100 parts by weight of polystyrene resin is contained, and the polystyrene resin composition constituting the polystyrene resin extruded foam plate has a weight average molecular weight of 1. .5 × and at ¹⁰ 5 to 2.5 × 10 number average molecular weight with a ⁵ (Mn) weight ratio Mw / Mn of average molecular weight (Mw) of 2.3 or more with respect to, the less the thickness At least 50 cm ² cross-sectional area with a 10 mm, an apparent density of 20 to 50 kg / ^{m 3,} a thickness direction average cell diameter 0.1 to 0.7 mm, closed cell ratio is 80% or more A polystyrene resin extruded foam board characterized by that.
[2] The polystyrene-based resin extruded foam plate as described in 1 above, wherein the apparent density of the foam plate is 20 to 35 kg / m ³ .
[3] The polystyrene-based resin extruded foam plate as described in 1 or 2 above, wherein the foamed plate has a closed cell ratio of 90% or more.
[4] The above-mentioned 1 characterized in that the foaming agent comprises 80 to 100 mol% of carbon dioxide and 20 to 0 mol% of other physical foaming agents (excluding chlorofluorocarbons) with respect to the total amount of foaming agent. The polystyrene-type resin extrusion foam board in any one of -3.
[5] The ethylene copolymer having a carbonyl group is one or more selected from an ethylene-vinyl acetate copolymer and an ethylene-acrylic acid copolymer. The polystyrene-type resin extrusion foam board in any one.

The polystyrene resin extruded foam plate of the present invention is an extrusion of a base resin obtained by blending a specific amount of an ethylene copolymer having a carbonyl group into a polystyrene resin using a foaming agent mainly composed of carbon dioxide. Extruded foam plate having a specific weight average molecular weight and molecular weight distribution obtained by foaming, excellent mechanical strength, low apparent density, moderately fine bubble diameter, width required as a heat insulating material, It has a thickness, excellent flame retardancy, small thermal conductivity, and good appearance.

The present invention will be described in detail below.
In the present invention, in an extruder, a polystyrene resin is kneaded together with a flame retardant and a foaming agent to form a foamable melt-kneaded product, and after adjusting the foamable melt-kneaded product to a temperature suitable for foaming, By extrusion foaming, a polystyrene resin extruded foam plate (hereinafter also simply referred to as an extruded foam plate) is obtained.

  In the extrusion foaming method, the foamable melt-kneaded product is extruded through a flat die into a low-pressure region from the inside of a high-pressure extruder and foamed, and a molding die disposed at the outlet of the die (parallel or from the inlet to the outlet). Passing a molding tool such as a molding roll or the like composed of a plate made of two fluoropolymers such as polytetrafluoroethylene resin (hereinafter also referred to as guider) installed so as to expand gently. A method for obtaining an extruded foam board can be employed.

  Such a method for producing an extruded foam plate is conventionally known, but the method of the present invention is a specific polystyrene type in an extruded foam plate production technique using a foaming agent mainly composed of carbon dioxide, which is difficult to achieve a high expansion ratio. A resin obtained by adding a specific amount of a specific ethylene copolymer to a resin is used as a raw material resin.

  Examples of the polystyrene resin supplied to the extruder in the present invention include a styrene homopolymer, a styrene-methylstyrene copolymer containing styrene as a main component, a styrene-dimethylstyrene copolymer, and a styrene-ethylstyrene copolymer. And styrene-diethylstyrene copolymer. The styrene component content in the styrene copolymer is preferably 50 mol% or more, more preferably 80 mol% or more, and particularly preferably 90 mol% or more.

The weight average molecular weight (Mw) of the polystyrene-based resin used in the present invention is 1.7 × 10 ^{5 to} 2.8 × 10 ⁵ , preferably 1.8 × 10 ^{5 to} 2.8 × 10 ⁵ , more preferably from ^{1.8 × 10 5 ~2.5 × 10 5} . When the polystyrene-based resin has an Mw that is too small, internal foaming in the die due to a decrease in the die pressure is extremely likely to occur, and a good extruded foam plate having a large cross-sectional area cannot be obtained. On the other hand, when the polystyrene-based resin has an excessively large Mw, it is impossible to mold after extrusion foaming due to heat generation, and a good extruded foam plate cannot be obtained.

  The ratio Mw / Mn of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polystyrene resin used in the present invention is 2.5 or more, preferably 2.8 or more. When Mw / Mn is too small, foamability is deteriorated and a good foam cannot be obtained. The upper limit of Mw / Mn is not particularly limited, but is about 5 in general.

The number average molecular weight (Mn) of the polystyrene-based resin used in the present invention satisfies the above Mw / Mn relationship and is preferably 9.0 × 10 ⁴ or less. It is preferable for Mn to be in the above-mentioned range since it will be further excellent in extrusion foamability. In addition, although the minimum of Mn is not specifically limited, it is about 5.0 * 10 < ⁴ > in general.

  Furthermore, the ratio Mz / Mn of the Z average molecular weight (Mz) to the number average molecular weight (Mn) of the polystyrene resin used in the present invention is preferably 5.5 or more, more preferably 5.7 or more, and still more preferably. Is 5.9 or more. When the Mz / Mn of the polystyrene resin is within the above range, the resin pressure in the vicinity of the lip tip can be maintained at a moderately high level while suppressing the heat generation of the resin during extrusion, so that the Mz / Mn is 5.5. The above polystyrene resins are suitable for producing extruded foam plates having a large cross-sectional area. The upper limit of Mz / Mn is not particularly limited, but is approximately 30.

The number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) of the polystyrene resin in this specification are all values obtained by gel permeation chromatography (GPC method). . Specifically, after dissolving 30 mg of polystyrene-based resin in 20 mL of tetrahydrofuran (THF) (however, when insoluble matter in THF exists, the insoluble matter is removed by filtration), the analysis shown below The measurement is performed under the GPC method under the conditions, and the chart obtained by this measurement is horizontal (horizontal) with respect to the peak start position by the polystyrene resin (in the present invention, the molecular weight of 1.9 × 10 ⁷ position is adopted for convenience). Each molecular weight is calculated by a standard calibration curve drawn using standard polystyrene with a baseline drawn parallel to the axis.

Equipment used: GPC high performance liquid chromatograph manufactured by GL Sciences Inc. Column: Column manufactured by Showa Denko KK, trade name Shodex GPC KF-806, KF-805, KF-803 are connected in series in this order. Temperature: 40 ° C
Solvent: THF
Flow rate: 1.0 mL / min Concentration: 0.15 w / v%
Injection volume: 0.2ml
Detector: UV-visible detector manufactured by GL Sciences Inc., trade name UV702 type (measurement wavelength 254 nm)
Molecular weight range of calibration curve used for calculation of molecular weight distribution: 1.9 × 10 ^{7 to} 5.4 × 10 ³

  A polystyrene resin having an average molecular weight in the above range can be obtained by adjusting the temperature conditions during polymerization and the addition amount of the polymerization initiator. Grade name “679” from Toyo Styrene Co., Ltd. Is commercially available as grade name “G220” or the like.

  Furthermore, in this invention, raw material resin can also be prepared so that an average molecular weight may become in the said range by mixing 2 or more types of polystyrene resin.

  In addition, when mixing two or more kinds of polystyrene resins, in determining the molecular weight of the polystyrene resin by the above method, depending on the ratio of mixing two or more kinds of polystyrene resins used as the base resin, The molecular weight of the mixed polystyrene resin is specified by dissolving the mixture in tetrahydrofuran to obtain a measurement sample. For example, when the polystyrene resin (A) and the polystyrene resin (B) are mixed at a ratio of 8 to 2, 24 mg of the polystyrene resin (A) and 6 mg of the polystyrene resin (B) are added to 20 ml of tetrahydrofuran. It is dissolved and used as a measurement sample, and the molecular weight of the polystyrene resin is determined.

  In the present invention, when a foaming agent mainly composed of carbon dioxide, which will be described later, is used, an ethylene copolymer having a carbonyl group in the polystyrene resin is used to increase the foamability of the polystyrene resin extruded foam plate. Added. By adding the copolymer to a polystyrene-based resin, the effect of increasing the resin pressure in the vicinity of the die internal lip compared to the case where the copolymer is not added even when the addition amount is small (hereinafter, In addition, an effect of expanding the bubble diameter (hereinafter also referred to as a bubble expansion effect) can be obtained even when the resin pressure is increased.

  Examples of the ethylene copolymer having a carbonyl group include copolymers of ethylene and vinyl ester, acrylic ester, other acrylic compounds, and the like, specifically, ethylene-vinyl acetate copolymer, Ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer Ionomer in which a part of the intermolecular molecule of the polymer, ethylene-acrylic acid copolymer such as ethylene-glycidyl methacrylate, ethylene-acrylic acid copolymer or ethylene-methacrylic acid copolymer is intermolecularly bonded by a metal ion or the like. , Maleic acid modified polyethylene, maleic acid modified ethylene-ethyl acrylate copolymer And the like.

  Among the ethylene-based copolymers having a carbonyl group, the internal foam suppression effect and the bubble expansion effect are remarkable, and therefore one type selected from an ethylene-vinyl acetate copolymer and an ethylene-acrylic acid copolymer. The above is preferable.

  Further, the ethylene-based copolymer having a carbonyl group is more preferably at least one selected from an ethylene-acrylic acid alkyl ester copolymer and an ethylene-methacrylic acid alkyl ester copolymer. Since the copolymer has a higher thermal stability than other ethylene-based copolymers having a carbonyl group, the resulting foam is preferable because it is excellent in flame retardancy. Further, among the above copolymers, an ethylene-methyl acrylate copolymer and an ethylene-methyl methacrylate copolymer are particularly preferable.

  The content of the compound having a carbonyl group such as vinyl acetate, methacrylic acid, methyl methacrylate, etc. in the copolymer is preferably 10 to 50% by weight with respect to the copolymer. %, More preferably 20 to 35% by weight. When the content of the compound having a carbonyl group is within the above range, the dispersibility of the copolymer in a polystyrene-based resin is improved, so that a good foam can be obtained, which is preferable.

  The copolymer has a melt flow rate (MFR) of 0.1 to 30 g / 10 minutes (provided that the test condition of method A of JIS K7210-1976 is MFR measured by 190 ° C. and a load of 21.2 N). It is preferably 1 to 25 g / 10 min, more preferably 2 to 10 g / 10 min. When the MFR of the copolymer is too high, the effect of increasing the pressure of the die at the time of extrusion is reduced, and internal foaming is likely to occur, so that a foam having a low apparent density may not be obtained. On the other hand, if the MFR is too low, the dispersion state is deteriorated and a good foam may not be obtained. That is, when the MFR is within the above range, a foam having a low apparent density and moderately fine bubbles can be obtained.

  The addition amount of the copolymer is 2 to 8 parts by weight, preferably 2 to 7 parts by weight, and more preferably 3 to 6 parts by weight with respect to 100 parts by weight of the polystyrene resin. If the amount added is too small, internal foaming suppression effect and bubble expansion effect cannot be obtained, and molding failure occurs when shaping into internal foam or plate shape. On the other hand, if the added amount is too large, it is difficult to stably obtain a good extruded foam plate because the foam tends to be clogged in the guider. Even if an extruded foam plate is obtained, the obtained foam plate is flame retardant. Not only decreases or becomes too flexible, but the mechanical strength decreases due to a decrease in the closed cell ratio.

  In addition, in this invention, what mixed the other polymer with the polystyrene-type resin may be sufficient in the range in which the objective of this invention, an effect | action, and an effect are achieved. Other polymers include styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer water. Additives, styrene-ethylene copolymers and the like can be mentioned, and they can be mixed depending on the purpose in a range of generally less than 50% by weight, further less than 30% by weight, and particularly less than 10% by weight.

  The foaming agent used in the present invention is composed of 60 to 100 mol% carbon dioxide and 40 to 0 mol% other physical foaming agent with respect to the total amount of the foaming agent. A foaming agent composed mainly of carbon dioxide has a low global warming potential and does not destroy the ozone layer. If the content of carbon dioxide is too small, the effect of reducing the environmental load by using carbon dioxide as a foaming agent is greatly reduced, and the characteristics by using carbon dioxide as a foaming agent are largely lost. From this viewpoint, the content of carbon dioxide is preferably 80 to 100 mol%, more preferably 85 to 100 mol%, still more preferably 90 to 100 mol%, and particularly preferably 95 to 100 mol%.

  In the present invention, other physical foaming agents are used in order to alleviate problems when carbon dioxide is used alone as a foaming agent. That is, it is used when an extruded foam plate having a lower apparent density is to be obtained. The blending amount is determined from the viewpoint of achieving the target apparent density.

  In the present invention, examples of other physical foaming agents include saturated hydrocarbons, ethers, aliphatic alcohols, inorganic gases, and ketones. These may be used alone or in combination of two or more.

  Examples of the saturated hydrocarbon include ethane, propane, isobutane, normal butane, isopentane, cyclopentane, normal pentane and the like. These may be used alone or in combination of two or more. In addition, saturated hydrocarbons having 3 to 5 carbon atoms are preferable from the viewpoints of compatibility with polystyrene resins and ease of handling, and normal butane and isobutane are particularly preferably used.

  Examples of ethers include diethyl ether, methyl ethyl ether, dimethyl ether, and methyl vinyl ether. These may be used alone or in combination of two or more. In addition, dialkyl ethers having 1 to 3 carbon atoms in the alkyl chain are preferable from the viewpoint of compatibility with polystyrene resins and ease of handling, and dimethyl ether is particularly preferably used.

  Examples of aliphatic alcohols include methanol, ethanol, propyl alcohol, isopropyl alcohol, butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, aryl alcohol, crotyl alcohol, propargyl alcohol and the like. These may be used alone or in combination of two or more. In addition, C1-C4 aliphatic alcohol is preferable from points, such as compatibility with a polystyrene-type resin and ease of handling, and also ethanol is used suitably.

  Moreover, water is mentioned as another foaming agent. Since water has a high foaming power and a high cooling capacity, water is preferable because an extruded foam board having a low apparent density can be obtained.

  By using a foaming agent mainly composed of carbon dioxide, in addition to protecting the global environment and ensuring safety, the thermal insulation of the resulting polystyrene resin extruded foam plate is minimized, and long-term insulation is achieved. Sex can be stabilized. In recent years, lower saturated hydrocarbons that have been used as foaming agents for polystyrene resin extruded foam plates are sustained release foaming agents for polystyrene resins, so they are gradually released from the extruded foam plates over time. There is a drawback that the heat insulating property of the extruded foam plate changes. However, carbon dioxide has a very high permeation rate to polystyrene resin, and almost all of it escapes from the extruded foam plate immediately after extrusion, so air enters the bubbles in the extruded foam plate up to atmospheric pressure. For example, since the heat insulating property of the extruded foam board does not change with time, long-term stabilization of the heat insulating property is achieved.

The amount of foaming agent added in the present invention varies depending on the type of foaming agent, the apparent density of the target extruded foam plate, the type of polystyrene resin, etc., and is difficult to specify. It is preferably added in a range of about 0.7 to 2.0 moles per 1 kg of a base resin composed of an ethylene copolymer having a group (hereinafter also simply referred to as a base resin), more preferably. Is added in the range of 0.9 to 1.8 mol, more preferably in the range of 1.0 to 1.6 mol.
However, the amount of foaming agent added when carbon dioxide and other foaming agents are used in combination is determined by the total number of moles of the physical foaming agent.

  In the present invention, a bubble regulator for adjusting the bubble diameter of the extruded foam plate may be added. Examples of the bubble regulator include inorganic powders such as talc, kaolin, mica, silica, calcium carbonate, barium sulfate, titanium oxide, clay, aluminum oxide, bentonite, and diatomaceous earth. In the present invention, two types of bubble regulators are used. It can also be used in combination. Among the various bubble regulators, talc is preferably used because it is easy to adjust the bubble diameter and does not hinder flame retardancy, and it is easy to reduce the bubble diameter. Talc having a median particle diameter of 0.1 to 10 μm, more preferably 0.5 to 5 μm is preferable.

  When talc is used as the bubble regulator, the amount added is preferably 0.05 to 3 parts by weight, more preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of the base resin.

  In order to impart flame retardancy to the extruded foam of the present invention, a flame retardant is kneaded into the polystyrene resin. A brominated flame retardant is preferably used as the flame retardant kneaded with the polystyrene resin. Examples of brominated flame retardants include tetrabromobisphenol A, tetrabromobisphenol A bis (2,3-dibromopropyl ether), tetrabromobisphenol A bis (2-bromoethyl ether), tetrabromobisphenol A bis (allyl ether). ), 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, hexabromocyclododecane, tetrabromocyclooctane, tris (2,3-dibromopropyl) isocyanurate, tribromophenol, decabromodiphenyl Examples thereof include oxide, tris (tripropylneopentyl) phosphate, brominated bisphenol ether derivatives and the like. These compounds can be used alone or in admixture of two or more.

  The content of the flame retardant in the extruded foam plate of the present invention is 1 per 100 parts by weight of the polystyrene-based resin in order to improve the flame retardancy and minimize the decrease in foamability and mechanical properties. 10 to 10 parts by weight is preferred, 1.5 to 7 parts by weight is more preferred, and 2 to 5 parts by weight is even more preferred.

  Furthermore, in the present invention, a flame retardant aid can be used in combination with the brominated flame retardant for the purpose of further improving the flame retardancy of the extruded foam plate. Examples of the flame retardant aid include 2,3-dimethyl-2,3-diphenylbutane, 2,3-diethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, 3,4 -Diphenylalkanes such as diethyl-3,4-diphenylhexane, 2,4-diphenyl-4-methyl-1-pentene, 2,4-diphenyl-4-ethyl-1-pentene, diphenylalkene, triphenyl phosphate, cresyldi Nitrogen-containing cyclic compounds such as 2,6-xylenyl phosphate, antimony trioxide, diantimony pentoxide, ammonium sulfate, zinc stannate, cyanuric acid, isocyanuric acid, triallyl isocyanurate, melamine cyanurate, melamine, melam, melem , Silicone compounds, boron oxide, zinc borate, zinc sulfide, etc. , Red phosphorus-based, ammonium polyphosphate, phosphorus-based compounds such as phosphazene and the like. These compounds can be used alone or in admixture of two or more.

  In the present invention, various additives such as a colorant, a heat stabilizer, a fluidity improver, and a filler are appropriately added to the base resin as necessary within a range not hindering the object and effect of the present invention. Can do.

  Next, the polystyrene resin extruded foam plate of the present invention will be described. The extruded foam plate is obtained by kneading and extruding a base resin obtained by adding the ethylene copolymer having the carbonyl group to the polystyrene resin together with a foaming agent and a flame retardant mainly composed of carbon dioxide. Is obtained.

  As described above, carbon dioxide, which is the main component of the blowing agent, is contained in an amount of 60 mol% or more, preferably 80 mol% or more, preferably 85 mol% or more, more preferably 90 mol%, based on the total amount of the blowing agent. Above, most preferably 95 mol% or more is contained. However, when a foaming agent other than carbon dioxide is used, chlorofluorocarbons are excluded as the foaming agent for the above reasons.

  The polystyrene-based extruded foam plate of the present invention comprises 2 to 8 parts by weight of an ethylene-based copolymer having a carbonyl group in the extruded foamed plate, based on 100 parts by weight of the polystyrene-based resin, preferably 2 to 7 parts. It contains 3 parts by weight, more preferably 3 to 6 parts by weight. When a foaming agent mainly composed of carbon dioxide is used as a foaming agent, the plasticizing effect to a styrene resin cannot be obtained as in the case of using a foaming agent mainly composed of a lower saturated hydrocarbon. The bending deflection of the plate is reduced. Therefore, by including an ethylene-based copolymer having a flexible carbonyl group in the extruded foamed plate, an extruded foamed plate having improved balance of foamability while improving foamability is obtained. can get.

The content of the ethylene copolymer having a carbonyl group in the extruded foam plate of the present invention can be measured by a known method by ¹³ C nuclear magnetic resonance spectroscopy.

In the polystyrene resin composition constituting the extruded foam plate of the present invention, that is, a mixture of the polystyrene resin and the ethylene copolymer having a carbonyl group, the weight average molecular weight (Mw) is 1.5 × 10 ⁵ to 2. 0.5 × 10 ⁵ , preferably 1.6 × 10 ^{5 to} 2.5 × 10 ⁵ , and more preferably 1.7 × 10 ^{5 to} 2.3 × 10 ⁵ . If the molecular weight is too low, the mechanical strength of the polystyrene resin itself, which is a base resin, is inferior to that of a polystyrene resin having a general molecular weight, so that the mechanical strength of the extruded foam plate is lowered. On the other hand, if the molecular weight is too high, it becomes impossible to obtain an extruded foam plate having a low apparent density due to defective molding due to heat generation.

  Furthermore, the ratio Mw / Mn of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polystyrene-based resin composition constituting the extruded foam board of the present invention is 2.3 or more, preferably 2.5 or more. If the Mw / Mn of the composition is too small, the extruded foam board itself that satisfies the object physical properties of the present invention cannot be obtained because the extrusion foaming is inferior. The upper limit of Mw / Mn is not particularly limited, but is about 4 in general. The Mw / Mn of the polystyrene-based resin composition after extrusion foaming is the Mw of the polystyrene-based resin before extrusion because the molecular chain on the high molecular weight side of the polystyrene-based resin is cut by the shear and thermal history received during extrusion. It tends to be smaller than the value of / Mn.

Further, the number average molecular weight (Mn) of the polystyrene resin composition constituting the extruded foam plate of the present invention satisfies the above Mw / Mn relationship for the same reason as the number average molecular weight of the polystyrene resin, and is 8.0. × 10 ⁴ or less is preferable.

  The average molecular weight (Mn, Mw and Mz) of the polystyrene-based resin composition constituting the extruded foam plate is that of the polystyrene-based resin described above, except that a 30 mg test piece cut out from the extruded foam plate is used as a measurement sample. It can be measured by the same method as the method for measuring the average molecular weight.

  The thickness of the extruded foam plate of the present invention is at least 10 mm or more, but usually the upper limit is 150 mm, preferably 20 to 120 mm, more preferably 25 to 100 mm. When this thickness is too thin, there exists a possibility that it may become an extruded foam board with difficulty in manufacture and inadequate mechanical strength and heat insulation. On the other hand, if the thickness is too thick, the bubble diameter in the thickness direction tends to be large, so there is a possibility that sufficient heat insulation may not be ensured, and a large size is required for stable production of extruded foam plates. An extruder is required.

Furthermore, the cross-sectional area of the extruded foam plate of the present invention is at least 50 cm ² or more, preferably 60 cm ² or more, more preferably 100 cm ² or more. Usually, the upper limit of the cross-sectional area is about 3000 cm ² , but the upper limit is 2000 cm ² or less. If the cross-sectional area is less than 50 cm ² , the enforcement efficiency and the production efficiency are lowered.

Further, the apparent density of the extruded foamed plate of the present invention is 20 to 50 kg / m ³ , preferably 25 to 40 kg / m ³ , more preferably 25 to 38 kg / m ³ , and particularly preferably 25 to 35 kg / m ² . is there. If the apparent density is too low, it is considerably difficult to produce an extruded foam plate having such an apparent density, and the mechanical properties of the obtained extruded foam plate are also compared with those of a conventional foam insulation board. Therefore, the applications that can be used are limited. On the other hand, when the apparent density is too large, it is difficult to exhibit sufficient heat insulation unless the thickness is increased more than necessary, and the lightness is insufficient. The apparent density is measured in accordance with JIS K 6767 (1999).

  Moreover, the thickness direction average cell diameter of the extrusion foamed board of this invention is 0.1-0.7 mm, Preferably it is 0.15-0.6 mm, More preferably, it is 0.28-0.6 mm. . When the average cell diameter is within this range, an extruded foam plate having excellent mechanical strength and higher heat insulation can be obtained. An extruded foam plate having an excessively small cell diameter is thick and it is difficult to obtain an extruded foam plate having a low apparent density. On the other hand, if it is too large, it is not possible to obtain an extruded foam plate having the desired heat insulating property.

The measurement method of the average bubble diameter in this specification is as follows. The average cell diameter (D _T : mm) in the thickness direction of the extruded foam plate and the average cell diameter (D _W : mm) in the width direction of the extruded foam plate are perpendicular to the cross section in the width direction of the extruded foam plate (perpendicular to the extrusion direction of the extruded foam plate). The average cell diameter in the longitudinal direction of the extruded foam plate (D _L : mm) was bisected at the longitudinal section of the extruded foam plate (parallel to the extrusion direction of the extruded foam plate and at the center in the width direction). Project a magnified image (vertical section) onto a screen or monitor using a microscope, draw a straight line in the direction to be measured on the projected image, count the number of bubbles intersecting the straight line, and calculate the length of the straight line (however, , This length is not the length of the straight line on the enlarged projected image, but the length of the true straight line considering the magnification of the projected image)) divided by the number of counted bubbles, respectively. The average bubble diameter in the direction is determined.

The measurement method of the average bubble diameter will be described in detail. The measurement of the average bubble diameter in the thickness direction (D _T : mm) is performed by measuring a straight line extending over the entire thickness in the thickness direction at a total of three locations at the center and both ends of the vertical cross section in the width direction. From the length of each straight line and the number of bubbles intersecting the straight line, the average diameter of the bubbles existing on each straight line (the length of the straight line / the number of bubbles intersecting the straight line) is obtained, and Let the arithmetic mean value of an average diameter be the average bubble diameter ( _DT : mm) of the thickness direction.

The average bubble diameter (D _W : mm) in the width direction is a width of a straight line having a length of 3 mm at a position that bisects a total of three extruded foam plates in the center and both ends in the width direction. From the straight line of 3 mm length and (number of bubbles crossing the straight line minus 1), the average diameter of bubbles existing on each straight line (3 mm / (number of bubbles crossing the straight line minus 1)) The arithmetic average value of the obtained average diameters at the three locations is taken as the average cell diameter in the width direction (D _W : mm).

The average cell diameter in the longitudinal direction (D _L : mm) is obtained by dividing the extruded foam plate into two equal parts in the thickness direction at a total of three locations in the center and both ends of the longitudinal vertical section obtained by cutting the test piece. A straight line having a length of 3 mm is drawn in the longitudinal direction at a position where the average diameter of bubbles existing on each straight line from the straight line having a length of 3 mm and (the number of bubbles crossing the straight line −1) (3 mm / (the straight line) The number of bubbles intersecting -1)) is obtained, and the arithmetic average value of the obtained average diameters at the three locations is defined as the average bubble diameter in the longitudinal direction (D _L : mm). The average cell diameter in the horizontal direction of the extruded foam plate _(D H: mm) is the arithmetic mean value of _{D W} and _{D L.}

Furthermore, in the extruded foam plate of the present invention, the bubble deformation rate is preferably 0.7 to 2.0. The cell strain rate, refers to the D _T obtained by the measuring method is calculated by dividing the D _H value (D T _{/ D H),} bubbles as bubble deformation ratio is less than 1 flat The larger the value is, the longer the image is. If the bubble deformation ratio is less than 0.7, the compression strength may be reduced because the bubbles are flat, and the flat bubbles tend to return to a spherical shape, so the dimensional stability of the extruded foam plate also decreases. There is a fear. If the bubble deformation rate exceeds 2.0, the number of bubbles in the thickness direction decreases, and there is a possibility that the desired high heat insulation property cannot be obtained. From such a viewpoint, the bubble deformation rate is preferably 0.8 to 1.5, and more preferably 0.8 to 1.2. When the bubble deformation rate is within the above range, an extruded foam plate having excellent mechanical strength and high heat insulating properties can be obtained.

  The extruded foam plate of the present invention has a closed cell ratio of 80% or more, preferably 85% or more, preferably 90% or more from the viewpoint of improving heat insulation and further improving mechanical strength as described above. Is more preferable.

  The closed cell ratio of the extruded foam plate in the present specification was measured using an air comparison type hydrometer 930 type manufactured by Toshiba Beckman Co., Ltd. according to ASTM-D2856-70 Procedure C (25 mm × 25 mm × 20 mm from the extruded foam plate). A cut sample without a molded skin cut to a size of 5 mm is accommodated in a sample cup and measured, but when the thickness is thin and a cut sample of 20 mm cannot be cut in the thickness direction, for example, 25 mm × 25 mm × It is sufficient that two cut samples having a size of 10 mm are stored in the sample cup at the same time and measured. (%) Is calculated and obtained as an average value of N = 3.

S (%) = (Vx−W / ρ) × 100 / (VA−W / ρ) (1)
Vx: the true volume (cm ³ ) of the cut sample measured by the above method (corresponding to the sum of the volume of the resin constituting the cut sample of the extruded foam plate and the total volume of bubbles in the closed cell portion in the cut sample) .)
VA: apparent volume (cm ³ ) of the cut sample calculated from the outer dimensions of the cut sample used for the measurement
W: Total weight of cut sample used for measurement (g)
ρ: Density of resin constituting the extruded foam plate (g / cm ³ )

Since the extruded foam board of this invention is mainly used as a heat insulation board, it is preferable that the heat conductivity is 0.040 W / mK or less. Such thermal conductivity is achieved by controlling the bubble diameter and bubble deformation rate within the above ranges.
According to the description of JIS A 9511 (2006) 5.7, the thermal conductivity of the extruded foam in the present invention is a plate heat flow meter method (two heat flow meters, high temperature side) described in JIS A 1412-2 (1999). 35 ° C., low temperature side 5 ° C., average temperature 20 ° C.).

  Since the extruded foam board of the present invention is mainly used as a heat insulating board for construction, it satisfies the flammability standard for the extruded polystyrene foam thermal insulation board described in measuring method A of JIS A 9511 (2006). It is particularly preferred that That is, when the flammability was measured according to 5.13.1 “Measurement method A” described in JIS A 9511 (2006), the flame disappeared within 3 seconds, there was no residue, and the combustion limit was supported. It is preferable that it does not burn beyond the line. Such an extruded foam board has the safety required as an extruded polystyrene foam heat insulating board for building materials because the possibility of fire burning is small even when ignited. Such an extruded foam board satisfying the flammability standard is achieved by blending the flame retardant.

  When the extruded foam board of the present invention is produced only with carbon dioxide, the carbon dioxide is dissipated at an early stage, so that the gases present in the bubbles are mainly nitrogen and oxygen. However, when manufactured using the said other foaming agent, possibility that the foaming agent remains in an extrusion foam is large.

In that case, the content of the other foaming agent can be measured using a gas chromatograph. Specifically, a sample cut out from the center of the extruded foam plate is placed in a sample bottle with a lid containing toluene, and after the lid is closed, the sample is thoroughly stirred and the foaming agent in the extruded foam plate is added to toluene. The content dissolved in the extruded foam plate can be determined by performing gas chromatography analysis on the sample dissolved in the sample and quantifying the sample by an internal standard method.

  Next, the present invention will be described in more detail with reference to specific examples and comparative examples.

[Manufacturing equipment]
A first extruder with an inner diameter of 65 mm, a second extruder with an inner diameter of 90 mm, and a third extruder with an inner diameter of 150 mm are connected in series, and a blowing agent injection port is attached near the end of the first extruder, with a gap of 1 mm × A production apparatus was used in which a flat die having a resin discharge port (tip of the die lip) having a width of 90 mm (rectangular cross section) or a gap of 2 mm × width of 65 mm (rectangular cross section) was connected to the outlet of the third extruder. A guider made of a plate made of a pair of upper and lower polytetrafluoroethylene resins installed in parallel was attached to the resin outlet of the extruder.

[material]
PS1: Polystyrene “679” manufactured by PS Japan Co., Ltd. (Mn = 7.3 × 10 ⁴ , Mw = 2.0 × 10 ⁵ , Mz / Mn = 5.2)
PS2: Polystyrene “HH32” manufactured by PS Japan Co., Ltd. (Mn = 1.1 × 10 ⁵ , Mw = 3.2 × 10 ⁵ , Mz / Mn = 6.7)
PS3: The above-mentioned “PS1” is supplied to an extruder having a cylinder diameter of 65 mm, extruded into a strand at a discharge of 80 kg / hr and a resin temperature of 230 ° C., cooled and cut, and Mn = 6.5 × 10 ⁴ , Mw = 1. A pellet of 6 × 10 ⁵ and Mz / Mn = 5.5 was produced.

Resin A: Ethylene-vinyl acetate copolymer “NUC-3195” manufactured by Nippon Unicar Co., Ltd. (Amount of vinyl acetate component: 25 wt%, MFR: 4 g / 10 min)
Resin B: Ethylene-methacrylic acid copolymer “Nucrel N1525” manufactured by Mitsui Sumitomo DuPont Polychemical Co., Ltd. (methacrylic acid component amount: 15 wt%, MFR: 25 g / 10 min)
Resin C: ethylene-methyl methacrylate copolymer “Acrylift WK307” manufactured by Sumitomo Chemical Co., Ltd. (methyl methacrylate component amount: 25 wt%, MFR: 7 g / 10 min)
Resin D: Ethylene-methyl methacrylate copolymer “Acrylift WH206” (Sumitomo Chemical Co., Ltd.) (methyl methacrylate component amount: 20% by weight, MFR: 2 g / 10 min)
Resin E: Nippon Unicar Low Density Polyethylene “NUC-8008” (MFR: 4.7 g / 10 min)

Bubble regulator: A talc masterbatch comprising 35 parts by weight of polystyrene, 60% by weight of talc (High Filler # 12 manufactured by Matsumura Sangyo Co., Ltd.) and 5% by weight of a dispersant was used.
Flame retardant: A flame retardant masterbatch containing 93% by weight of hexabromocyclododecane was used.

Examples 1-6, Comparative Examples 1-6
A polystyrene resin, an ethylene copolymer having a carbonyl group, a flame retardant, and a bubble regulator are supplied to the first extruder so as to have the blending amounts shown in Tables 1 to 4, heated to 220 ° C., melted, Kneading is carried out, and a foaming agent having the composition shown in Tables 1 to 4 is press-fitted into the foamable melt mixture in the vicinity of the tip of the first extruder, and the resin temperature is changed to Tables 1 to 4 in the subsequent second and third extruders. The foaming temperature is shown in the table (indicated in the table as foaming resin temperature. This foaming temperature is the temperature of the foamable molten mixture measured at the position of the junction between the extruder and the die), and then the foaming is performed. The extrudable molten mixture was extruded from the die lip into the guider (low pressure region) at a discharge rate of 50 kg / hr (the tip of the die lip: width 90 mm, gap 1 mm).

  The foamable molten mixture extruded from the die lip is passed through a guider arranged in parallel at an interval of 28 mm in the thickness direction of the extruded foam plate while foaming, and is formed into a plate shape while being filled in the guider. An extruded foam board was produced.

Examples 7-12, Comparative Examples 7-10
Production similar to Examples 1-6 and Comparative Examples 1-6 above, except that the tip of the die lip was changed from 90 mm wide, 1 mm gap to 65 mm wide, 2 mm gap, and the gap between guiders was changed from 28 mm to 50 mm. A polystyrene-based extruded foam plate was produced by this method.

Mn, Mw, Mz / Mn of styrene resin supplied to the extruder, evaluation of foamed state of the obtained extruded foam plate, evaluation of moldability, apparent density, thickness, width direction vertical cross-sectional area, each average cell diameter, Tables 1 to 4 show the bubble deformation rate, closed cell rate, evaluation of heat insulation, and evaluation of flame retardancy. The weight of the table represents parts by weight per 100 parts by weight of polystyrene resin, CO ₂ represents CO, Bu represents isobutane.

The evaluation of the foamed state in Tables 1 to 4 was evaluated according to the following evaluation criteria.
○: No internal foaming occurs.
X: Internal foaming occurred.

The moldability evaluation in Tables 1 to 4 was evaluated according to the following evaluation criteria.
◯: Extruded foam plate having good surface condition and good sliding between the foam and the guider can be obtained stably.
Δ: The foam is easily clogged in the guider, and a stable and excellent extruded foam plate cannot be obtained.
X: The foam is clogged in the guider, and an extruded foam board cannot be obtained.

In the heat insulation evaluation in Tables 1 to 4, a test piece not having a molded skin of 200 mm × 200 mm × 25 mm was cut out from an extruded foamed plate 4 days after production, and the thermal conductivity was measured by the above method using the test piece. And evaluated according to the following criteria.
○: Thermal conductivity is 0.040 W / mK or less.
X: Thermal conductivity exceeds 0.040 W / mK.

In the flame retardancy evaluation in Tables 1 to 4, the test piece cut out from the extruded foamed plate after 1 hour from the production was measured by the above method. In addition, this measurement cut out five test pieces with respect to one extrusion foaming board, and evaluated it with the following evaluation criteria.
○: Flame disappears in all test pieces within 3 seconds.
(Triangle | delta): Although the average burning time of five test pieces is less than 3 second, a flame does not disappear within 3 seconds in one or more test pieces.
X: The average burning time of 5 test pieces exceeds 3 seconds.

The results of Examples 1 to 12 show that when a polystyrene resin extruded foam is produced based on the method of the present invention, a polystyrene resin extruded foam having a low apparent density and excellent flame retardancy can be easily produced. Yes. Even when carbon dioxide, which is poorly soluble in polystyrene resin, is used as a foaming agent, by adding an ethylene copolymer having a specific carbonyl group to the polystyrene resin, its internal foaming suppression effect, bubble expansion Due to the effect, an extruded foam having a low apparent density, moderately fine bubbles, and excellent flame retardancy was obtained.
In particular, in Examples 7 to 12, by using a polystyrene resin having a specific Mz / Mn ratio, even when an extruded foam plate having a larger thickness and a larger cross-sectional area is produced, the apparent density is low. Thus, an extruded foam having moderately fine bubbles and excellent flame retardancy was obtained.

  Comparative Example 1 is contrasted with Example 1 and shows an example in which an ethylene-based copolymer having a carbonyl group is not used. Since the copolymer was not used in Comparative Example 1, when the same amount of foaming agent as in Example 1 was added, internal foaming occurred and an extruded foam board could not be obtained.

  Comparative Example 2 is contrasted with Example 1 and shows an example in which the addition amount of the ethylene-based copolymer having a carbonyl group is reduced. In Comparative Example 2, since the blending amount of the copolymer is too small, when the same amount of foaming agent as in Example 1 is added, internal foaming occurs near the lip without showing the effect of suppressing internal foaming, and the extruded foam plate Could not get.

  Comparative Example 3 is contrasted with Example 1, and is an example in which low-density polyethylene was blended in place of the ethylene-based copolymer having a carbonyl group. In Comparative Example 3, since low density polyethylene was blended, the internal foaming suppression effect was not seen and internal foaming occurred near the lip, and an extruded foam board could not be obtained.

  The comparative example 4 is contrasted with Examples 3-6, Comprising: The example which does not use the ethylene-type copolymer which has a carbonyl group is shown. In Comparative Example 4, since a polystyrene resin having a higher molecular weight than Comparative Example 1 was used, the die pressure increased and internal foaming did not occur, but the copolymer was not used. When the same amount as in Examples 3 to 6 was added, although it was able to be shaped into a plate shape, the bubbles were excessively refined as the die pressure increased, so the strength of the extruded foam plate itself decreased, The extruded foam plate was easily broken in the guider, and a stable extruded foam plate could not be obtained.

  Comparative Example 5 is contrasted with Example 4 and shows an example in which the blending amount of the ethylene copolymer having a carbonyl group is too large. In Comparative Example 5, since the blended amount of the copolymer was too large, it could be molded into a plate shape, but the foam was easily clogged in the guider and a stable extruded foam plate could not be obtained. Moreover, even if the addition amount of the flame retardant was increased, the flame retardancy of measuring method A of JIS A 9511 (2006) was not satisfied.

  Comparative Example 6 is contrasted with Example 1 and shows an example in which the number average molecular weight (Mn) and the weight average molecular weight (Mw) of the polystyrene-based resin are too low. In Comparative Example 6, since Mn and Mw of the polystyrene resin are too low, even when an ethylene copolymer having a carbonyl group is blended, internal foaming in the vicinity of the lip cannot be suppressed, and an extruded foam plate is obtained. I couldn't.

  Comparative Example 7 is contrasted with Examples 7 to 9, and Comparative Example 8 is compared with Example 10. The ethylene-based copolymer having a thick carbonyl group at the time of producing an extruded foam plate having a large cross-sectional area was used. An example that is not used is shown below. Since the copolymer is not used in Comparative Examples 7 and 8, when the same amount of foaming agent as in Examples 7 to 10 is added, internal foaming occurs near the lip, and an extruded foam plate can be obtained. There wasn't.

  Comparative Example 9 is contrasted with Example 7 and shows an example in which the blending amount of the ethylene-based copolymer having a carbonyl group is too large at the time of producing an extruded foam plate having a large thickness and a large cross-sectional area. In Comparative Example 9, since the blended amount of the copolymer was too large, it could be molded into a plate shape, but the foam was easily clogged in the guider and a stable extruded foam plate could not be obtained.

  Comparative Example 10 is contrasted with Example 10 and shows an example in which the number average molecular weight (Mn) and the weight average molecular weight (Mw) of the polystyrene resin are too high. In Comparative Example 10, since the Mn and Mw of the polystyrene-based resin were too high, the resin temperature could not be cooled to the desired temperature, so that the foam was clogged in the guider without slipping with the guider, and the extruded foam plate was Couldn't get.

Claims (5)

A base resin obtained by blending a polystyrene resin with an ethylene copolymer having a carbonyl group is 60 to 100 mol% of carbon dioxide and other physical foaming agents (excluding chlorofluorocarbons) with respect to the total amount of foaming agent. ) A polystyrene resin extruded foam plate obtained by kneading together with a foaming agent composed of 40 to 0 mol% and a flame retardant and extrusion foaming, and the ethylene having the carbonyl group in the polystyrene resin extruded foam plate 2-8 parts by weight of the copolymer based on 100 parts by weight of the polystyrene resin, and the weight average molecular weight of the polystyrene resin composition constituting the polystyrene resin extruded foam plate is 1.5 ×. 10 ^{5 to} 2.5 × 10 ⁵ , the ratio Mw / Mn of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 2.3 or more, and the thickness is at least 10 m. m, the cross-sectional area is at least 50 cm ² , the apparent density is 20 to 50 kg / m ³ , the thickness direction average bubble diameter is 0.1 to 0.7 mm, and the closed cell ratio is 80% or more. A polystyrene resin extruded foam board characterized by that. The polystyrene resin extruded foam plate according to claim 1, wherein the apparent density of the foam plate is 20 to 35 kg / m ³ .   The polystyrene-based resin extruded foam plate according to claim 1 or 2, wherein the foamed plate has a closed cell ratio of 90% or more.   The foaming agent is composed of 80 to 100 mol% carbon dioxide and 20 to 0 mol% of other physical foaming agents (excluding chlorofluorocarbons) with respect to the total amount of foaming agent. The polystyrene-type resin extrusion foam board in any one of.   The ethylene copolymer having the carbonyl group is at least one selected from an ethylene-vinyl acetate copolymer and an ethylene-acrylic acid copolymer. 2. A polystyrene-based resin extruded foam plate according to 1.