JP2008189805A - Heat-resistant thermoplastic resin foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a thick-walled heat-resistant thermoplastic resin foam excellent in heat resistance, surface properties and moldability, also excellent in material-recyclable environmental adaptability, and appropriate for construction material applications. <P>SOLUTION: The heat-resistant thermoplastic resin foam is obtained by heating and melting a thermoplastic resin composition comprising 0.1-90 wt.% of (A) a copolymer composed of aromatic vinyl units, unsaturated dicarboxylic acid anhydride units and N-alkyl-substituted maleimide units and 99.9-10 wt.% of (B) a second copolymer composed of aromatic vinyl units and vinyl cyanide units followed by addition of a foaming agent and then conducting an extrusive expansion, wherein the foaming agent is such as to contain 0.5 pt.wt. or more of carbon dioxide based on 100 pts.wt. of the resin composition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thermoplastic foam excellent in heat resistance, and in particular, a copolymer (A) comprising an aromatic vinyl unit, an unsaturated dicarboxylic anhydride unit and an N-alkyl-substituted maleimide unit, and an aromatic vinyl unit. And a foam obtained by foaming a resin composition containing a copolymer (B) comprising vinyl cyanide units.

  Conventionally, polystyrene-based resin foams, rigid polyurethane foams, and the like have been widely used as heat insulating materials for buildings due to their favorable workability and heat insulating properties.

  Polystyrene resin foam is inexpensive and useful as a heat insulating material excellent in environmental compatibility in consideration of material recycling, but the heat resistant temperature of styrene as a base resin is around 80 ° C., for example, relatively When applied to rooftop insulation applications exposed to high temperatures, or to warm cars or greenhouses, there is a risk of deformation of the insulation.

  On the other hand, rigid polyurethane foams are generally known to have high heat resistance because rigid polyurethane is a thermosetting resin. However, the rigid polyurethane foam has high water absorption and has the disadvantage that deformation is large when impregnated with water, and the disadvantage that it is low in strength and difficult to handle. In addition, since hard polyurethane is a thermosetting resin, it cannot be said that it has poor material recyclability and excellent environmental compatibility.

  By the way, chlorine atom-containing halogenated carbon (hereinafter abbreviated as CFC), which has low toxicity and is nonflammable and chemically stable, has been used as a foaming agent in producing these foams. For example, Patent Document 1 discloses the use of dichlorodifluoroethane as a blowing agent. However, it is pointed out that these CFCs may destroy the ozone layer, and as a safer foaming agent than CFCs, a method using a chlorine atom-containing halogenated hydrocarbon (hereinafter abbreviated as HCFC) in which the CFC chlorine atoms are partially hydrogenated. However, this is disclosed in Patent Document 2. However, more suitable foaming agents have been studied from the viewpoint of protecting the global environment.

From this point of view, compared to foaming agents such as CFC and HCFC, it is more environmentally friendly and inexpensive, and uses a volatile liquid such as water or an inorganic gas such as nitrogen or carbon dioxide as a foaming agent. A press-fitting method has been studied (for example, Patent Document 3 and Patent Document 4).
Japanese Patent Publication No.41-672 Japanese Patent Publication No.57-7175 JP-A 51-7068 JP-A-3-81346

  Under the circumstances described above, a thermoplastic foam that uses a foaming agent that has excellent heat resistance, is inexpensive and can be recycled, and is friendly to the global environment is desired. The present invention has been made in view of such circumstances, and an object thereof is to provide a foam excellent in heat resistance and environmental compatibility and suitable for use as a heat insulating material.

  As a result of intensive studies to solve the above-described problems, the present inventors have found that a resin composition containing a heat-resistant copolymer and a fluidity-free copolymer in producing a foam. In addition, by using mainly carbon dioxide as a foaming agent, it is found that the foam is excellent in heat resistance and environmental compatibility and suitable for use as a heat insulating material, and the present invention is completed. It came.

That is, the present invention
[1] Copolymer (A) 0.1 to 90% by weight of an aromatic vinyl unit, an unsaturated dicarboxylic anhydride unit, and an N-alkyl-substituted maleimide unit, an aromatic vinyl unit, and a vinyl cyanide unit A heat-resistant thermoplastic resin foam obtained by heating and melting a thermoplastic resin composition comprising 99.9 to 10% by weight of a copolymer (B), adding a foaming agent, and extrusion-foaming, As an agent, it contains 0.5 part by weight or more of carbon dioxide with respect to 100 parts by weight of the resin composition.
[2] The aromatic vinyl unit constituting each of the copolymer (A) and the copolymer (B) preferably includes a styrene unit.
[3] The unsaturated dicarboxylic anhydride unit constituting the copolymer (A) is preferably a maleic anhydride unit.
[4] The N-alkyl-substituted maleimide unit constituting the copolymer (A) is preferably an N-phenylmaleimide unit.
[5] As the vinyl cyanide unit constituting the copolymer (B), acrylonitrile is preferable.
[6] The foaming agent may be a mixture of one or more selected from the group consisting of (a) carbon dioxide, (b) a lower alcohol, and water.
[7] Examples of the foaming agent include ethanol as a lower alcohol.
[8] It is preferable that the density of the foam is 20 to 100 kg / m ³ .
[9] The average diameter of the bubbles forming the vapor foam is preferably 0.05 to 2.0 mm.

  Thus, according to the present invention, 0.1 to 90% by weight of a copolymer (A) comprising an aromatic vinyl unit, an unsaturated dicarboxylic anhydride unit and an N-alkyl-substituted maleimide unit, an aromatic vinyl unit and Copolymer (B) composed of vinyl cyanide units A thermoplastic resin composition comprising 99.9 to 10% by weight of a heat-resistant thermoplastic resin foam obtained by heating and melting, adding a foaming agent, and extrusion-foaming. And, as a foaming agent, by making carbon dioxide 0.5 parts by weight or more with respect to 100 parts by weight of the resin composition, a foam having excellent heat resistance and environmental compatibility and suitable for use as a heat insulating material is obtained. Obtainable.

  Embodiments of the present invention will be described below. In addition, this embodiment is only a part of this invention, and it cannot be overemphasized that this embodiment can be suitably changed in the range which does not change the summary of this invention.

  The foam according to the present invention comprises a copolymer (A) comprising an aromatic vinyl unit, an unsaturated dicarboxylic anhydride unit and an N-alkyl-substituted maleimide unit, and a copolymer comprising an aromatic vinyl unit and a vinyl cyanide unit. A resin composition containing the coalescence (B) is foamed.

  Examples of the aromatic vinyl unit constituting the copolymer (A) include styrene, α-methylstyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, bromostyrene, chlorostyrene, vinyltoluene, and vinylxylene. Of these, styrene and α-methylstyrene are preferable from the viewpoint of compatibility with the copolymer (B) and ease of polymerization, and styrene, which is cheaper, is most preferable.

  Examples of the unsaturated dicarboxylic anhydride unit constituting the copolymer (A) include maleic anhydride, itaconic anhydride, and citraconic anhydride. Of these, maleic anhydride is preferred from the viewpoint of compatibility with the copolymer (B), ease of polymerization, and low cost. In consideration of water absorbency and hygroscopicity of the obtained foam, the total amount of the copolymer (A) comprising an aromatic vinyl unit, an unsaturated dicarboxylic anhydride unit, and an N-alkyl-substituted maleimide unit is 100% by weight. The unsaturated dicarboxylic acid anhydride unit is preferably 5% by weight or less.

Examples of N-alkyl-substituted maleimide units constituting the copolymer (A) include N-methylmaleimide, N-butylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-4-diphenylmaleimide, and N-2-chlorophenyl. Examples thereof include maleimide, N-4-bromophenylmaleimide, and N-1-naphthylmaleimide, and N-phenylmaleimide is most preferable from the viewpoint of compatibility with the copolymer (B), ease of polymerization, and low cost. .
In consideration of the heat resistance of the obtained foam, the total amount of the copolymer (A) comprising an aromatic vinyl unit, an unsaturated dicarboxylic anhydride unit, and an N-alkyl-substituted maleimide unit was 100% by weight. In this case, the N-alkyl-substituted maleimide unit is preferably 40% by weight or more.

  The chemical formulas of preferred embodiments as the copolymer (A) are shown below. In the following chemical formula, “NPMI” is N-phenylmaleimide as an N-alkyl time maleimide unit, “St” is styrene as an aromatic vinyl unit, and “MAH” is an unsaturated dicarboxylic anhydride unit. Of maleic anhydride.

  Examples of the aromatic vinyl unit constituting the copolymer (B) include styrene, α-methylstyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, bromostyrene, chlorostyrene, vinyltoluene, and vinylxylene. Of these, styrene and α-methylstyrene are preferable from the viewpoint of compatibility with the copolymer (A) and ease of polymerization, and styrene, which is cheaper, is most preferable.

  Examples of the vinyl cyanide unit constituting the copolymer (B) include acrylonitrile, methacrylonitrile, and α-chloroacrylonitrile. Of these, acrylonitrile is preferred from the viewpoint of compatibility with the copolymer (A) and ease of polymerization.

  Below, the chemical formula of a preferable aspect as a copolymer (B) is shown. In the chemical formula below, “St” represents styrene as an aromatic vinyl unit, and “AN” represents acrylonitrile as a vinyl cyanide unit.

  The thermoplastic resin composition in the present invention is a thermoplastic resin composition containing a thermoplastic resin mixture comprising the copolymer (A) and the copolymer (B). The thermoplastic resin composition in the present invention is one in which the resin mixture is contained in an amount of preferably 50% by weight or more, more preferably 70% by weight or more based on the entire thermoplastic resin composition.

  The weight ratio of the copolymer (A) to the copolymer (B) in the resin composition is such that the copolymer (A) is 0.1 to 90% by weight and the copolymer (B) is 99.9 to 99.9%. 10% by weight is preferred. Within this range, the fluidity and moldability of the resin composition are maintained.

  In order to obtain the thermoplastic resin foam according to the present invention, the foaming agent added to the molten resin composition is 100 weights of the thermoplastic resin mixture comprising the copolymer (A) and the copolymer (B). 3 to 15 parts by weight of the foaming agent can be used with respect to parts. Moreover, as such a foaming agent, at least 1 sort (s) or 2 or more types chosen from the group which consists of a physical foaming agent and a chemical foaming agent can be used. Although it is preferable that the foaming agent does not have a chlorine atom, the burden on the environment is reduced. However, in order to achieve the object of the present invention, it is not always necessary that the foaming agent does not contain a chlorine atom.

  As the foaming agent used in the present invention, (a) one containing carbon dioxide is preferable from the viewpoint of environmental compatibility and combustibility.

  The amount of (ii) carbon dioxide used as the blowing agent in the present invention is preferably 0.5 parts by weight or more, more preferably 0.5 to 7.0 parts by weight, with respect to 100 parts by weight of the resin mixture. 2.0-5.0 weight part is further more preferable. By making the usage-amount of carbon dioxide into the said range, the gas dispersibility in a foam is good and the foamability of a resin composition can be improved. (I) When the amount of carbon dioxide used is less than the above range, a high foaming ratio and a fine foam tends to be not obtained. Conversely, (i) if the amount of carbon dioxide used exceeds 7.0 parts by weight, internal foaming may occur and a foam with a high expansion ratio may not be obtained.

  In addition, carbon dioxide used as a foaming agent in the present invention may be in a gas or liquid state, but in consideration of solubility in thermoplastic resin, permeability, diffusivity, etc. It is preferable to use carbon dioxide in a supercritical state at or above the critical pressure.

  As a foaming agent used in the present invention, by combining at least one selected from the group consisting of (b) carbon dioxide and (b) a lower alcohol and water, a reduction in the closed cell ratio of the foam obtained is prevented, The shrinkage | contraction of the bubble to comprise can be suppressed or the moldability of a foam can be improved.

  The lower alcohol is an alcohol having 1 to 4 carbon atoms, and examples thereof include methanol, ethanol, propanol, n-butanol, i-butanol, t-butanol, and the like. From the viewpoint of influence, ethanol is preferred.

  The amount of at least one selected from the group consisting of (b) lower alcohol and water in the present invention is preferably 0-7 parts by weight, more preferably 1.0-5. 0 parts by weight. (B) By setting the amount of at least one selected from the group consisting of a lower alcohol and water within the above range, the dispersibility of the gas in the foam is good, and the foamability of the resin composition is improved.

  As the foaming agent used in the present invention, (i) as long as it contains carbon dioxide, other foaming agents may be combined. As other blowing agents, specifically, hydrocarbons such as propane, n-butane, i-butane, n-pentane, i-pentane, neopentane, cyclopentane, hexane, cyclohexane and the like as physical blowing agents; 1-difluoroethane, 1,2-difluoroethane, 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2- Fluorinated hydrocarbons such as tetrafluoroethane, 1,1,1,2,2-pentafluoroethane, difluoromethane and trifluoromethane; inorganic gases such as nitrogen, argon and helium; dimethyl ether, diethyl ether, methyl ethyl ether, isopropyl Ether, n-butyl ether, diisoamyl ether, furan, furfural, 2-methylphenol Ethers such as methyl, tetrahydrofuran, tetrahydropyran; alkyl chlorides such as methyl chloride, ethyl chloride, propyl chloride, isopropyl chloride; formic acid methyl ester, formic acid ethyl ester, formic acid propyl ester, formic acid butyl ester, formic acid amyl ester, propionic acid Carboxylic acid esters such as methyl ester and propionic acid ethyl ester; dimethyl ketone, methyl til ketone, diethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, methyl-i-butyl ketone, methyl-n-amyl ketone, methyl And ketones such as -n-hexyl ketone, ethyl-n-propyl ketone, and ethyl-n-butyl ketone. Examples of the chemical foaming agent include N, N′-dinitrosopentamethylenetetramine, p, p′-oxybis-benzenesulfonylhydrazide, hydrazodicarbonamide, sodium carbonate, azodicarbonamide, terephthalazide, and 5-phenyl. Examples include tetrazole and p-toluenesulfonyl semicarbazide. These can be used alone or in admixture of two or more.

  Of the other blowing agents described above, from the viewpoint of protecting the ozone layer, hydrocarbons such as propane, n-butane, i-butane, n-pentane, i-pentane, neopentane, cyclopentane, hexane, cyclohexane, nitrogen Inorganic gases such as argon and helium, and ethers such as dimethyl ether, diethyl ether, methyl ethyl ether, isopropyl ether, n-butyl ether and diisoamyl ether are preferred.

  In the present invention, additives such as a nucleating agent, a stabilizer, a lubricant, a flame retardant, an antistatic agent, a plasticizer, a water absorbing agent, and a radiation inhibitor are blended in the resin composition as necessary. Also good.

  Since the thermoplastic resin foam of the present invention is characterized by being a plate-like foam, the thickness of the thermoplastic resin foam of the present invention is preferably 10 to 150 mm, more preferably 20 to 100 mm. For example, in the case of a heat insulating material used for applications such as building materials, in order to give preferable heat insulating properties, it tends to be difficult to obtain with a sheet-like foam having a thickness of less than 10 mm. Even if the thickness of the foam exceeds 150 mm, it is possible to manufacture on a small scale such as an experimental machine, but because the thickness increases, the temperature difference between the foam surface layer and the inner layer is added, so the internal The closed cell ratio tends to decrease due to the effect of heat storage, and as a result, the heat insulating properties, dimensional stability, strength, and the like may decrease.

Density of the thermoplastic resin foam in the present invention is preferably in the range of 20 and 100 kg / ^{m 3,} and more preferably in the range of 25 to 60 kg / ^{m 3.} If the density is in the range of 20 to 100 kg / m ³ , it is preferable from the viewpoint of expression of surface compressive strength represented by plane compressive strength.

  Examples of the cell structure forming the thermoplastic resin foam of the present invention include a uniform cell structure and a composite cell structure in which large and small cells are mixed, but the cell structure is not particularly limited.

  The average diameter of the bubbles in the thermoplastic resin foam of the present invention is preferably preferably from 0.05 to 2.0 mm, more preferably from 0.1 to 1.0 mm. The bubble diameter is measured, for example, according to ASTM D-3576 from a photograph obtained by sampling a part of the cross-section of the extruded foam and magnifying it with a scanning electron microscope. be able to. All of the bubble diameters are not necessarily in the above range, and at least the average value of the bubble diameters is in the above range. When the average diameter of the bubbles is less than 0.05 mm, the moldability is greatly lowered, and stable production tends to be difficult. Moreover, when an average diameter exceeds 2.0 mm, there exists a tendency for the external appearance of the product surface to deteriorate.

  The extruded foam according to the present invention is obtained by a known extrusion foaming method using the above resin composition. For example, the thermoplastic resin mixture is supplied to a known heat-melting and kneading apparatus such as an extruder and heated and melted, and a foaming agent is added under high-temperature and high-pressure conditions to form a foamable gel substance. Subsequently, the gel-like substance is cooled to a resin temperature suitable for extrusion foaming, and is extruded and foamed from a high pressure region to a low pressure region through a die such as a slit die to obtain a plate-like thermoplastic resin foam.

  Before the foaming agent is added, the resin composition is heated and melted. The heating temperature in that case should just be more than the glass transition temperature or melting | fusing point of a thermoplastic resin. The foaming agent may be added by a method that can disperse in the heat-melted resin. That is, the melted resin composition can be mixed, press-fitted or compounded by means known in the field related to the production and / or development of foams, for example, an extruder, a mixer and the like. The blowing agent component may be in the liquid, gas, or supercritical state above the critical temperature and above the critical pressure, and may be added individually or simultaneously to the extruder.

  As a procedure for adding various additives such as a flame retardant to the thermoplastic resin mixture, for example, (1) after adding and mixing various additives such as a flame retardant to the thermoplastic resin mixture, A procedure for supplying to a melt-kneading apparatus and heating and melting, and further adding and mixing a foaming agent. (2) After supplying a thermoplastic resin mixture to a melt-kneading apparatus such as an extruder and heating and melting, a flame retardant, etc. Procedures of adding and mixing various additives, and further adding and mixing a foaming agent, (3) obtained by previously adding various additives such as flame retardant to the thermoplastic resin mixture and melt-kneading The resin composition is again supplied to an extruder, heated and melted, and then added with a foaming agent and mixed. The timing of adding various additives to the thermoplastic resin mixture is slightly kneaded Is not particularly limited. Also, the heating temperature and melt kneading time when the resin composition is heated and melted cannot be uniquely defined because it varies depending on the amount of the resin composition extruded per unit time and the type of the extruder. The time required for uniformly dispersing and mixing the mixture and the foaming agent or additive is appropriately set.

  Examples of the heat-melt kneading means for the resin composition include, for example, screw type extruders such as a single screw and a twin screw, but there are no particular restrictions as long as they are used for normal extrusion foaming. Absent. However, when the dispersibility of the foam is required, the extruder is preferably a twin screw type. In order to suppress degradation and degradation of the resin as much as possible, the screw shape of the extruder is preferably a low shear type.

  As the extrusion conditions in the present invention, it is preferable to maintain the internal pressure of the extrusion system at a high pressure so that the foaming agent does not vaporize in the extruder or the mold and is sufficiently dissolved in the resin. Specifically, the pressure in the slit die is preferably 3 MPa or more, and more preferably 4 MPa or more. If the pressure in the slit die is out of the above range, phenomena such as gas blowing, void generation in the foam, pressure fluctuation in the extruder system, and accompanying foam cross-sectional profile tend to occur.

  Regarding the temperature for cooling the heated and melted gel-like substance, the resin temperature at the outlet of the extruder is preferably 20 to 70 ° C. higher than the glass transition temperature of the thermoplastic resin mixture, more preferably, The temperature is 30-60 ° C higher. By setting the temperature for cooling the gel substance in the above range, the gel substance can be introduced into the die in a state where there is almost no increase in die slit pressure or temperature unevenness, and the extrudability becomes good. Moreover, the surface property of the foam is improved.

  The set temperature of the die is preferably controlled at a temperature 5 to 50 ° C. lower than the resin temperature, and more preferably 10 to 40 ° C. lower. By setting the set temperature of the die within the above range, it is possible to maintain a die slit pressure and obtain a foam having good surface properties.

  The foam molding method is not particularly limited. For example, an extruded foam obtained by releasing pressure from a high pressure region to a low pressure region through a slit die in which an opening used for extrusion molding has a linear slit shape. Is formed into a flat foam using a molding die placed in close contact with or in contact with the slit die and a molding roll placed adjacent to the downstream side of the molding die.

  As the shape of the slit die, a rectangular shape, a coat hanger shape, a fish tail shape, a tee shape, etc. can be adopted, but when a wide plate-like foam is to be obtained, a coat hanger shape, a tee shape slit die Is preferred.

  In order to obtain a plate-like foam having a thickness of 10 to 150 mm, from the viewpoint of suppressing the size expansion rate in the thickness direction and the size expansion rate in the width direction of the molding die shape relative to the slit die exit shape, A method of forming a desired foam width by using a slit die whose die outlet is enlarged in a flat plate shape is advantageous. In particular, since the thermoplastic resin comprising the copolymer (A) and the copolymer (B) in the present invention tends to be brittle with respect to the polystyrene resin, a molding method in which the expansion ratio in the width direction is suppressed as much as possible. Is preferably selected.

  Since the thermoplastic resin mixture comprising the copolymer (A) and the copolymer (B) cannot be expected to elongate a resin such as a polystyrene resin, the surface properties of the resulting extruded foam are favorably retained. Further, it is preferable to reduce the resistance between the surface of the extruded foam and the molding die. Specifically, a material with low surface resistance such as a sheet made of a fluororesin such as a polytetrafluoroethylene resin can be placed at the interface between the extruded foam surface and the molding die by heating the molding die. Can be mentioned.

  Moreover, in order to ensure the surface property and physical property of the obtained foam, it is preferable to cool slowly the foam extruded and foamed from the slit die. Even when the surface of the foam extruded from the slit die is cooled and solidified, the surface portion can withstand the foaming force inside when the foam has a force to foam in a fluid state. Since it cannot do, there exists a possibility that the surface of a foam may produce defects, such as a crack. In addition, the closed cell ratio of the obtained foam may be lowered, and as a result, the heat insulation properties, dimensional stability, strength, and the like of the foam are lowered. The conditions for gently cooling the foam are affected by the resin temperature at the time of foaming, so it is set as appropriate. The length of the mold, the heating temperature of the mold, and the installation of materials with low surface resistance. It is set in consideration of distance.

  Thus, according to the present invention, 0.1 to 90% by weight of the copolymer (A) comprising an aromatic vinyl unit, an unsaturated dicarboxylic anhydride unit and an N-alkyl-substituted maleimide unit, and the aromatic vinyl unit. And a thermoplastic resin composition containing 99.9 to 10% by weight of a copolymer (B) comprising a vinyl cyanide unit and heat-melting, adding a foaming agent, and extrusion-foaming heat resistance It is a thermoplastic resin foam, and by using 0.5 parts by weight or more of carbon dioxide as a foaming agent with respect to 100 parts by weight of the resin mixture, it has excellent heat resistance and environmental compatibility, and is used as a heat insulating material. A suitable foam can be obtained.

  Hereinafter, specific examples of the thermoplastic resin foam according to the present invention will be described. Needless to say, the present invention is not limited to the following examples. In the following Examples and Comparative Examples, “part” represents “part by weight” and “%” represents “% by weight” unless otherwise specified.

  About the characteristics of the foams obtained in Examples 1 to 1 and Comparative Examples 1 to 4 shown below, the foam density, the average cell diameter in the extrusion direction, the width direction and the thickness direction, the cell deformation rate, 100 C. heat resistance, 120.degree. C. heat resistance, 140.degree. C. heat resistance, glass transition temperature, and thermal conductivity were measured according to the following methods.

(1) Extrudability
The extrusion moldability was evaluated by visual inspection for the occurrence of gas ejection from the die and the occurrence of fluctuations in the slit pressure under the conditions described in Examples, Comparative Examples or Reference Examples. Judgment criteria are as follows. Somewhat good is a pass level.
Good: Gas ejection from the die per hour and occurrence of fluctuations in slit pressure are less than once.
Slightly good: The gas ejection from the die per hour and the occurrence of fluctuation of the slit pressure are 1 to 2 times.
Defective: The gas ejection from the die per hour and the occurrence of fluctuations in the slit pressure are 3 times or more.

(2) Foam density (kg / m ³ )
The foam density was determined based on the following formula, and the unit was shown in terms of kg / m ³ .

（３）平均セル径（ｍｍ）
得られた発泡体の押出方向、巾方向および厚み方向の各方向のセル径を、ＡＳＴＭ Ｄ−３５７６に準じて測定した。
すなわち、発泡体の巾方向の断面を５０〜１００倍に拡大投影し、厚み方向のセル径（ＨＤ）と巾方向のセル径（ＴＤ）を測定する。次に、押出方向の断面を拡大投影し、押し出し方向のセル径（ＭＤ）を測定した。
平均セル径は、各方向のセル径の積を３乗根した値を以下の式より算出した。

(3) Average cell diameter (mm)
The cell diameter in each of the extrusion direction, the width direction, and the thickness direction of the obtained foam was measured according to ASTM D-3576.
That is, the cross-section in the width direction of the foam is magnified and projected 50 to 100 times, and the cell diameter (HD) in the thickness direction and the cell diameter (TD) in the width direction are measured. Next, the cross section in the extrusion direction was enlarged and projected, and the cell diameter (MD) in the extrusion direction was measured.
The average cell diameter was calculated from the following formula by taking the cube of the product of the cell diameters in each direction.

（４）１００℃耐熱性（発泡体の体積変化率）、１２０℃耐熱性（発泡体の体積変化率）
発泡体作成後、２３℃、湿度５５％の恒温室内にて１０日間状態調整した後、厚み２５ｍｍ×幅１００ｍｍ×長さ１００ｍｍの試験片を切り出し、１００℃±２℃（１２０℃耐熱性の場合は、１２０℃±２℃）に設定した熱風乾燥機内で２４時間加熱し、加熱前と加熱後の体積変化率（％）を算出し、以下の基準により耐熱性の有無を判断した。
◎：発泡体の体積変化率が１％以下である。
○：発泡体の体積変化率が１％を超え３％以下である。
△：発泡体の体積変化率が３％を超え５％以下である。
×：発泡体の体積変化率が５％を超える。

(4) 100 ° C. heat resistance (volume change rate of foam), 120 ° C. heat resistance (volume change rate of foam)
After creating the foam, after conditioning for 10 days in a constant temperature room at 23 ° C. and 55% humidity, a test piece having a thickness of 25 mm × width of 100 mm × length of 100 mm was cut out to 100 ° C. ± 2 ° C. Were heated in a hot air dryer set at 120 ° C. ± 2 ° C. for 24 hours, the volume change rate (%) before and after heating was calculated, and the presence or absence of heat resistance was judged according to the following criteria.
A: Volume change rate of the foam is 1% or less.
A: The volume change rate of the foam is more than 1% and 3% or less.
(Triangle | delta): Volume change rate of a foam exceeds 3% and is 5% or less.
X: Volume change rate of the foam exceeds 5%.

(5) Glass transition temperature After preparation of the foam, after conditioning for 10 days in a constant temperature room at 23 ° C. and 55% humidity, a differential scanning calorimeter (manufactured by Shimadzu Corporation: DSC-) according to JIS K7121 60A), the temperature is raised to 250 ° C. at a temperature rising rate of 10 ° C./min, held for 10 minutes, and then cooled to 30 ° C. at 10 ° C./min. The step change when the temperature was raised again to 250 ° C. was measured according to the method for obtaining the transition temperature of JIS K7121.

(Example 1)
Product name: Denka IP (265 ° C. × 10 kg condition, melt flow rate MFR = 0.2 g / min) as copolymer (A), and Toyostyrene as copolymer (B) Product name: Toyo AS (220 ° C. × 10 kg condition, MFR = 1.8 g / min) is used, and the copolymer (A) / copolymer (B) is 90% / 10%. Mixed in ratio. For 100 parts of this thermoplastic resin mixture, 0.1 part of talc (produced by Hayashi Kasei Co., Ltd., trade name: Talcan powder) and 0.2 part of calcium stearate (manufactured by Sakai Kogyo Co., Ltd.) are dried as nucleating agents. The resin composition was blended to supply the resin composition to a two-stage connection type extruder. The resin composition supplied to the first stage extruder is heated to about 280 ° C. and melt-kneaded, and then 3.0 parts of carbon dioxide (made by Showa Carbon Co., Ltd.) and ethanol (made by Wako Pure Chemical Industries, Ltd.) as a foaming agent. ) 2.0 parts were pressed into the molten resin near the tip of the first stage extruder. Thereafter, while kneading and cooling in the connected second-stage extruder, the resin temperature is cooled to about 195 ° C., and the slit pressure is 11.8 MPa and the discharge amount is 45 kg / hour from the slit die provided at the tip of the extruder. Extruded foam having a cross-sectional shape having a thickness of about 30 mm and a width of about 100 mm was obtained using a molding die and a molding roll. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam was 55 kg / m ³ , the average cell diameter was 0.1 mm, the heat resistance at 100 ° C. and the heat resistance at 120 ° C. were both “◎”, and the glass transition temperature was 183 ° C. It was.

(Example 2)
60% of copolymer (A) and 40% of copolymer (B) are mixed, the heating temperature in the first stage extruder is 250 ° C., and the resin temperature in the second stage extruder is 176 ° C. The foam was obtained under the same conditions as in Example 1 except that the slit pressure was 10.2 MPa and the discharge rate was 44 kg / hour. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam was 44 kg / m ³ , the average cell diameter was 0.15 mm, the heat resistance at 100 ° C. and the heat resistance at 120 ° C. were both “◎”, and the glass transition temperature was 143 ° C. It was.

(Example 3)
30% of copolymer (A) and 70% of copolymer (B) are mixed, the heating temperature in the first stage extruder is 240 ° C., and the resin temperature in the second stage extruder is 159 ° C. The foam was obtained under the same conditions as in Example 1 except that the slit pressure was 10.2 MPa and the discharge rate was 46 kg / hour. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam is 39 kg / m ³ , the average cell diameter is 0.2 mm, the heat resistance at 100 ° C. is “◎”, the heat resistance at 120 ° C. is “◯”, and the glass transition temperature is 123. ° C.

Example 4
20% of copolymer (A) and 80% of copolymer (B) are mixed, the resin temperature in the second stage extruder is cooled to 149 ° C., the slit pressure is 8.8 MPa, and the discharge amount A foam was obtained under the same conditions as in Example 3 except that was set to 48 kg / hour. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam is 38 kg / m ³ , the average cell diameter is 0.2 mm, the heat resistance at 100 ° C. is “◎”, the heat resistance at 120 ° C. is “◯”, and the glass transition temperature is 117. ° C.

(Example 5)
The copolymer (A) is mixed at a ratio of 10% and the copolymer (B) at a ratio of 90%, the resin temperature in the second-stage extruder is cooled to 138 ° C., the slit pressure is 8.5 MPa, the discharge amount A foam was obtained under the same conditions as in Example 3 except that the amount was 47 kg / hour. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam is 35 kg / m ³ , the average cell diameter is 0.25 mm, the heat resistance at 100 ° C. is “◯”, the heat resistance at 120 ° C. is “Δ”, and the glass transition temperature is 113. ° C.

(Example 6)
The blowing agent is 4.0 parts of carbon dioxide and ethanol is 1.0 part, the nucleating agent is 0.05 part of talc, the resin temperature in the second stage extruder is cooled to 155 ° C., and the slit pressure is 9.8 MPa. A foam was obtained under the same conditions as in Example 3 except that the discharge rate was 51 kg / hour. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam was 42 kg / m ³ , the average cell diameter was 0.2 mm, the heat resistance at 100 ° C. was “◎”, the heat resistance at 120 ° C. was “◯”, and the glass transition temperature was 122 ° C.

(Example 7)
The blowing agent is 2.0 parts of carbon dioxide and 3.5 parts of ethanol, the nucleating agent is 0.2 part of talc, the resin temperature in the second stage extruder is cooled to 157 ° C., and the slit pressure is 9.2 MPa. A foam was obtained under the same conditions as in Example 3 except that the discharge rate was 47 kg / hour. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam is 36 kg / m ³ , the average cell diameter is 0.2 mm, the heat resistance at 100 ° C. is “◎”, the heat resistance at 120 ° C. is “◯”, and the glass transition temperature is 123. ° C.

(Example 8)
The blowing agent is 4.5 parts carbon dioxide, talc is not added, the resin temperature in the second stage extruder is cooled to 158 ° C., the slit pressure is 10.8 MPa, and the discharge rate is 51 kg / hour. A foam was obtained under the same conditions as in Example 3. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam is 43 kg / m ³ , the average cell diameter is 0.1 mm, the heat resistance at 100 ° C. is “◎”, the heat resistance at 120 ° C. is “◯”, and the glass transition temperature is 124. ° C.

Example 9
The blowing agent is 3.5 parts of carbon dioxide and 1.0 part of water, and the water-absorbing agent is bentonite (manufactured by Hojun Co., Ltd., trade name: Bengel Bright 11) and silicon dioxide (manufactured by DSL Japan Co., Ltd., trade name). : Carplex) Example 3 except that 0.5 part was added, the resin temperature in the second stage extruder was cooled to 154 ° C., the slit pressure was 9.6 MPa, and the discharge rate was 45 kg / hour. A foam was obtained under the same conditions. The properties of the obtained foam are shown in Table 1.
The density of the foam is 40 kg / m ³ , the average cell diameter is 0.2 mm, the heat resistance at 100 ° C. is “◎”, the heat resistance at 120 ° C. is “◯”, and the glass transition temperature is 122 ° C. It was.

(Example 10)
The blowing agent is 3.0 parts of carbon dioxide, 1.5 parts of ethanol, 1.0 part of water, 1.0 part of bentonite and 0.5 part of silicon dioxide are added as the water-absorbing agent, and the resin in the second stage extruder is added. A foam was obtained under the same conditions as in Example 3 except that the temperature was cooled to 154 ° C., the slit pressure was 9.6 MPa, and the discharge rate was 45 kg / hour. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam is 40 kg / m ³ , the average cell diameter is 0.2 mm, the heat resistance at 100 ° C. is “◎”, the heat resistance at 120 ° C. is “◯”, and the glass transition temperature is 123. ° C.

(Example 11)
The blowing agent is 3.0 parts of carbon dioxide and 2.0 parts of n-butane (made by Mitsui Chemicals), the resin temperature in the second stage extruder is cooled to 153 ° C., the slit pressure is 10.2 MPa, and the discharge A foam was obtained under the same conditions as in Example 3 except that the amount was 46 kg / hour. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam is 39 kg / m ³ , the average cell diameter is 0.2 mm, the heat resistance at 100 ° C. is “◎”, the heat resistance at 120 ° C. is “◯”, and the glass transition temperature is 123. ° C.

(Example 12)
The blowing agent is 3.0 parts of carbon dioxide and 2.0 parts of dimethyl ether (manufactured by Mitsui Chemicals), the resin temperature in the second stage extruder is cooled to 155 ° C., the slit pressure is 9.6 MPa, and the discharge amount is A foam was obtained under the same conditions as in Example 3 except that the amount was 48 kg / hour. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam is 38 kg / m ³ , the average cell diameter is 0.2 mm, the heat resistance at 100 ° C. is “◎”, the heat resistance at 120 ° C. is “◯”, and the glass transition temperature is 122 ° C.

(Example 13)
The blowing agent is 1.0 part of carbon dioxide, 2.5 parts of n-butane, 1.5 parts of dimethyl ether, 0.2 part of talc as a nucleating agent, and the resin temperature in the second stage extruder is 156. A foam was obtained under the same conditions as in Example 3 except that it was cooled to 0 ° C., the slit pressure was 7.5 MPa, and the discharge rate was 47 kg / hour. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam is 34 kg / m ³ , the average cell diameter is 0.3 mm, the heat resistance at 100 ° C. is “◎”, the heat resistance at 120 ° C. is “◯”, and the glass transition temperature is 123. ° C.

(Comparative Example 1)
Polystyrene (PS) resin (PS Japan Co., Ltd., trade name: G9401, 200 ° C. × 5 kg, MFR = 0.2 g / min) is used as the base resin, and nucleating agent is used for 100 parts of PS resin. As a resin composition, 0.3 part of talc and 0.2 part of calcium stearate were dry blended, and this resin composition was supplied to a two-stage connection type extruder. After the resin composition supplied to the first-stage extruder is melt-kneaded by heating to about 230 ° C., 3.0 parts of carbon dioxide and 2.0 parts of ethanol are used as a blowing agent in the vicinity of the front end of the first-stage extruder. Press fit inside. Then, while kneading and cooling in the connected second stage extruder, the resin temperature is cooled to about 128 ° C., and the slit pressure is 8.1 MPa and the discharge amount is 50 kg / hour from the slit die provided at the tip of the extruder in the atmosphere. Extruded foam having a cross-sectional shape having a thickness of about 30 mm and a width of about 100 mm was obtained using a molding die and a molding roll. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam was 32 kg / m ³ , the average cell diameter was 0.3 mm, the heat resistance at 100 ° C. and the heat resistance at 120 ° C. were both “x”, and the glass transition temperature was 98 ° C. It was.

(Comparative Example 2)
Using only copolymer (B) as the base resin, 100 parts of copolymer (B) is dry blended with 0.3 part of talc and 0.2 part of calcium stearate as a nucleating agent. The resin composition was supplied to a two-stage connection type extruder. After the resin composition supplied to the first stage extruder is melt-kneaded by heating to about 240 ° C., 3.0 parts of carbon dioxide and 2.0 parts of ethanol are used as a blowing agent in the vicinity of the front end of the first stage extruder. Press fit inside. Thereafter, while kneading and cooling in the connected second stage extruder, the resin temperature is cooled to about 135 ° C., and the slit pressure is 8.3 MPa and the discharge amount is 47 kg / hour from the slit die provided at the end of the extruder. Extruded foam having a cross-sectional shape having a thickness of about 30 mm and a width of about 100 mm was obtained using a molding die and a molding roll. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam was 33 kg / m ³ , the average cell diameter was 0.3 mm, the heat resistance at 100 ° C. and the heat resistance at 120 ° C. were both “x”, and the glass transition temperature was 109 ° C. It was.

(Comparative Example 3)
Foaming was performed under the same conditions as in Example 3 except that 4.0 parts of ethanol, the resin temperature in the second-stage extruder was cooled to 155 ° C., the slit pressure was 13.2 MPa, and the discharge rate was 48 kg / hour. Got the body. The properties of the obtained foam are shown in Table 1.
The density of the obtained foam is 115 kg / m ³ , the average cell diameter is 1.2 mm, the heat resistance at 100 ° C. is “◎”, the heat resistance at 120 ° C. is “◯”, and the glass transition temperature is 123. ° C.

  As shown in Table 1, in Examples 1 to 13, a foaming agent containing carbon dioxide is added to a resin composition in which a copolymer (A) and a copolymer (B) are mixed at a predetermined ratio. In Examples 1 to 4 and Examples 6 to 13, the heat resistance at 100 ° C. and the heat resistance at 120 ° C. are “◎” or “◯”, and in Example 5, 100 ° C. Good results were obtained with heat resistance “◯” and 120 ° C. heat resistance “Δ”.

  On the other hand, in Comparative Example 1 and Comparative Example 2, although a foaming agent containing carbon dioxide was used, a foam was obtained from a resin composition containing only PS resin or copolymer (B). In Example 1, both the 100 ° C. heat resistance and the 120 ° C. heat resistance are “x”, and in Comparative Example 2, the 100 ° C. heat resistance is “Δ”, and the 100 ° C. heat resistance is “x”. Was confirmed to be inferior.

In Comparative Example 3, a foam is obtained from the resin composition in which the copolymer (A) and the copolymer (B) are mixed using only ethanol without containing carbon dioxide as a foaming agent. However, the extrudability was poor, the density of the foam was as high as 112 kg / m ³ , and the cell diameter was 1.2 mm. Only a foam suitable as a coarse heat insulating material was obtained.

Claims (9)

  Copolymer (A) 0.1 to 90% by weight of an aromatic vinyl unit, an unsaturated dicarboxylic anhydride unit and an N-alkyl substituted maleimide unit, and a copolymer of an aromatic vinyl unit and a vinyl cyanide unit (B) A heat-resistant thermoplastic resin foam obtained by heating and melting a thermoplastic resin composition containing a thermoplastic resin mixture comprising 99.9 to 10% by weight, adding a foaming agent, and extrusion-foaming. The foamed thermoplastic resin composition comprises 0.5 parts by weight or more of carbon dioxide with respect to 100 parts by weight of the thermoplastic resin mixture.   The thermoplastic resin foam according to claim 1, wherein the aromatic vinyl units constituting the copolymer (A) and the copolymer (B) are styrene units.   The thermoplastic resin foam according to claim 1 or 2, wherein the unsaturated dicarboxylic anhydride unit constituting the copolymer (A) is a maleic anhydride unit.   The thermoplastic resin foam according to any one of claims 1 to 3, wherein the N-alkyl-substituted maleimide unit constituting the copolymer (A) is an N-phenylmaleimide unit.   The thermoplastic resin foam according to any one of claims 1 to 4, wherein the vinyl cyanide unit constituting the copolymer (B) is acrylonitrile.   The heat according to any one of claims 1 to 5, wherein the blowing agent is a mixture of (b) carbon dioxide and (b) at least one selected from the group consisting of lower alcohols and water. Plastic resin foam.   The thermoplastic resin foam according to claim 6, wherein the lower alcohol is ethanol. The thermoplastic foam according to any one of claims 1 to 7, wherein the density of the foam is 20 to 100 kg / m ³ .   The thermoplastic foam according to any one of claims 1 to 8, wherein an average diameter of bubbles forming the foam is 0.05 to 2.0 mm.