JP5042654B2 - Thermoplastic resin foam - Google Patents

Description

The present invention relates to a method for producing a thermoplastic resin extruded foam that is excellent in heat resistance and flame retardancy and is also used for architectural heat insulating materials.

  Conventionally, styrenic resin foams and rigid polyurethane foams have been widely used as heat insulating materials for construction because of their workability and heat insulating properties. However, the styrene resin foam is 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., and is about 200 to 250 ° C. There is no heat resistance to the heated hot melt asphalt, and the foam is deformed so that the shape cannot be maintained. On the other hand, hard polyurethane foam does not cause deformation like the styrene resin foam, and has high heat resistance against hot melt asphalt, but because it is a thermosetting resin itself, it has poor material recyclability and is environmentally friendly. It is hard to say that it is excellent. Each of the two types of foams has advantages and disadvantages, and it is difficult to have both characteristics.

Some examples of styrene resin foams having excellent environmental compatibility such as material recyclability and improved heat resistance have been disclosed so far (for example, Patent Documents 1 to 7).
For example, efforts have been made to improve heat resistance by copolymerizing methacrylic acid or the like with styrene (see Patent Document 1). In this approach, it is recognized that the heat distortion temperature is increased and the heat resistance is improved by increasing the glass transition temperature (Tg) as compared with a general styrene resin foam. However, since the main component of the base resin is made of styrene, the heat resistance is naturally limited, and even when the methacrylic acid component is contained at about 10%, only a heat resistance of about 100 ° C. can be obtained. Therefore, short-time heat resistance and long-term heat resistance at 140 ° C. cannot be obtained.

  In addition, efforts have been made to improve heat resistance by incorporating a maleimide compound into a styrene resin or bonding at a molecular level (see Patent Documents 2 to 5). In the field of injection molding, heat resistance has been improved by introducing maleimide compounds for a long time, and it has been used mainly in the automotive field as a heat resistance improver for ABS resins.

  However, a resin composition in which a maleimide compound is introduced into a styrene resin has improved heat resistance, but tends to decrease fluidity and elongation in a molten state. When obtaining a foam from the resin composition, the fluidity and elongation of the molten resin composition containing the foaming agent are reduced, and thus it is particularly difficult to form a thick plate-like foam molded article. It was.

  Moreover, the approach which makes a maleimide-type compound flame-retardant is made (refer patent documents 6-8). In this approach, a resin composition using a maleimide compound is used, particularly for the purpose of imparting flame retardancy in an injection-molded product. However, in this approach, nothing is described regarding a plate-like foam. In particular, in the case of a foam, the heat transfer rate after the flame is ignited is significantly faster than that of an injection-molded body. In addition, when the foaming agent remaining in the foam is a combustible gas, Since it is necessary to suppress the ignition or combustion of the flammable gas that evaporates from the foam, it is very difficult to satisfy the requirements specified in JIS A9511, in particular the flame retardancy required for building material applications. It was difficult.

  Therefore, it is very difficult to make full use of a resin composition using a maleimide compound, to produce a thick plate-like foamed molded article, and to achieve a quality that matches the flame retardancy required for building materials. Met.

Because of these, it has the advantages of styrene resin foam and rigid polyurethane foam, has excellent heat resistance and moldability, is also excellent in environmental compatibility that can be recycled, and is also difficult for building materials. The development of a plastic resin foam that matches the flammability is awaited.
JP-A-57-72830 JP-A-61-78846 JP-A-5-93082 JP-A-60-184546 Japanese Patent Laid-Open No. 4-25532 Japanese Patent Laid-Open No. 7-53833 JP-A-10-168261 JP-A-10-182905

The object of the present invention is a thick-walled thermoplastic resin extruded foam that has excellent heat resistance, moldability, environmental compatibility that enables material recycling, and further meets the flame retardancy required for building materials. It is in providing the manufacturing method of. Furthermore, it is providing the manufacturing method of the thermoplastic resin extrusion foam which has the heat resistance which maintains a shape, even if it applies a hot-melt asphalt.

As a result of diligent research in view of the prior art, the present inventors, as a result, a heat comprising a copolymer imparted with heat resistance from the viewpoint of heat resistance, and a copolymer imparted with fluidity from the viewpoint of fluidity. A step of heating and melting a thermoplastic resin composition to be added to a specific flame retardant into a plastic resin mixture, adding a foaming agent to form a foamable gel material, a step of cooling the gel material,
To step extruding the gel-like substance through a slit die lower pressure region, and, by Fugata using a molding die installed close contact or contact with the slit die including as engineering of forming the extruded foam, thermoplastic In the method for producing a resin extruded foam, the resin temperature of the gel substance at the outlet of the cooling step is controlled to a specific temperature, and the resistance between the surface of the extruded foam and the molding die in the step of forming the extruded foam. be reduced, and by gradual cooling in the molding die to foam, reduction in the thermal stability, lowering of heat resistance, the moldability defects have few have thermoplastic resin foam such like reduction is obtained The headline and the present invention were completed.

That is, the present invention
[1] 50 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, and a copolymer comprising an aromatic vinyl unit and a vinyl cyanide unit For 100 parts by weight of the thermoplastic resin mixture comprising 50% to 10% by weight of the combined body (B),
Thermoplastic resin composition comprising 5 to 15 parts by weight of at least one flame retardant selected from brominated flame retardants having a 5% thermogravimetric decrease starting temperature of 270 ° C. or higher and a melting point or softening point of 150 ° C. or higher. A process of heating and melting a product, adding a foaming agent, and forming a foamable gel material,
Cooling the gelled material;
Extruding the gel-like material through a slit die into a lower pressure region; and
A method for producing an extruded foam of a thermoplastic resin having a foam thickness of 10 to 150 mm, comprising a step of forming an extruded foam by molding using a molding die placed in close contact with or in contact with a slit die. ,
In the step of forming the extruded foam, the resin foam of the gel substance at the outlet of the cooling step is 20 to 70 ° C. higher than the glass transition temperature of the thermoplastic resin mixture. The present invention relates to a method for producing an extruded foam of a thermoplastic resin, characterized by reducing resistance between a body surface and a molding die and gradually cooling the foam in the molding die .
Furthermore, the present invention relates to [2] the method for producing a thermoplastic resin extruded foam according to [1] , wherein the die temperature is 5 to 50 ° C. lower than the resin temperature .
Furthermore, the present invention is characterized in that [3] the resistance between the extruded foam and the molding die is reduced by installing a material with less surface resistance at the interface between the extruded foam surface and the molding die. The present invention relates to a method for producing an extruded foam of a thermoplastic resin according to [1] or [2] .
[4] The thermoplastic resin according to any one of [1] to [3], wherein the foam is gradually cooled in the molding die by adjusting the temperature of the molding die. The present invention relates to a method for producing an extruded foam .
Furthermore, the present invention relates to [5] the method for producing a thermoplastic resin extruded foam according to any one of [1] to [4], wherein the aromatic vinyl unit is a styrene unit.
Furthermore, the present invention relates to [6] the method for producing an extruded foam according to any one of [1] to [5], wherein the unsaturated dicarboxylic anhydride unit is a maleic anhydride unit. .
Furthermore, the present invention provides the method for producing an extruded foam according to any one of [1] to [6] , wherein the [7] N-alkyl-substituted maleimide unit is an N-phenylmaleimide unit.
Furthermore, the present invention relates to a method for producing an extruded foam of a thermoplastic resin according to any one of [1] to [7] , wherein the [8] vinyl cyanide unit is acrylonitrile.
Further, the present invention provides [9] a brominated flame retardant having a 5% thermal weight loss onset temperature of 270 ° C. or higher and a melting point or softening point of 150 ° C. or higher, decabromodiphenyl ether, ethylenebis (pentabromophenyl), Bis (2,4,6-tribromophenoxy) ethane, tetrabromobisphenol A diglycidyl ether copolymer, tribromophenol adduct of tetrabromobisphenol A diglycidyl ether copolymer, 2,4,6-tris (2,4,4 6-tribromophenoxy) 1,3,5-triazine or tris (tribromoneopentyl) phosphate, The thermoplastic resin extruded foam according to any one of [1] to [8] It relates to the manufacturing method .

According to the present invention, a thick thermoplastic resin foam having excellent heat resistance, moldability, environmental compatibility capable of material recycling, and flame retardance required for building materials is obtained. be able to. In particular, a thermoplastic resin extruded foam that cannot be filled with a styrene-based resin foam and that requires heat resistance against hot melt asphalt can be obtained.

  Hereinafter, the present invention will be described in detail.

  The copolymer (A) used in the present invention comprises an aromatic vinyl unit, an unsaturated dicarboxylic anhydride unit, and an N-alkyl-substituted maleimide unit.

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

  Further, examples of the unsaturated dicarboxylic acid anhydride unit include maleic anhydride, itaconic anhydride, and citraconic anhydride. From the viewpoint of compatibility with the copolymer (B), ease of polymerization, and low cost, maleic anhydride. Acid is preferred.

  Furthermore, as N-alkyl substituted maleimide units, N-methylmaleimide, N-butylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-4-diphenylmaleimide, N-2-chlorophenylmaleimide, N-4-bromo Examples thereof include phenylmaleimide and N-1-naphthylmaleimide, and N-phenylmaleimide is optimal from the viewpoint of compatibility with the copolymer (B), ease of polymerization, and low cost.

  When the total amount of the aromatic vinyl unit, unsaturated dicarboxylic acid anhydride unit and N-alkyl substituted maleimide unit is 100% by weight, the N-alkyl substituted maleimide unit is 40% by weight or more in view of heat resistance. In view of water absorption and moisture absorption resistance, the unsaturated dicarboxylic acid anhydride unit is preferably 5% by weight or less.

  The copolymer (B) used in the present invention comprises an aromatic vinyl unit and a vinyl cyanide unit. As the aromatic vinyl unit, as described above, styrene and α-methylstyrene are preferable from the viewpoint of compatibility with the copolymer (A) and ease of polymerization, and styrene which is inexpensive in price. Is the best.

Examples of the vinyl cyanide unit include acrylonitrile, methacrylonitrile, and α-chloroacrylonitrile, and acrylonitrile is preferred from the viewpoint of compatibility with the copolymer (A) and ease of polymerization. In view of compatibility with the copolymer (A), ease of polymerization, and low cost, a copolymer of styrene and acrylonitrile is preferable.
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 preferably such that the resin mixture is contained in an amount of 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 mixture (the total amount of (A) and (B) is 100% by weight) is that the copolymer (A) is 50 to 90% by weight. % And the copolymer (B) are preferably 50 to 10% by weight, the copolymer (A) is more preferably 50 to 85% by weight, and the copolymer (B) is more preferably 50 to 15% by weight. More preferably, A) is 55 to 80% by weight and the copolymer (B) is 45 to 20% by weight. A copolymer (A) in the range of 50 to 90% by weight is preferable because strength retention, fluidity and moldability, and heat resistance against hot melt asphalt can be aligned.

  As the foaming agent for obtaining the thermoplastic resin foam in the present invention, a foaming agent containing no chlorine atom is used for the thermoplastic resin mixture comprising the copolymer (A) and the copolymer (B). Can do. Moreover, as such a foaming agent, 1 type chosen from the group chosen from a physical foaming agent and a chemical foaming agent can be used, or 2 or more types can be mixed and used. By not containing a chlorine atom, it is preferable because the burden on the environment is reduced. However, in order to achieve the object of the present invention, it is not always necessary to contain no chlorine atom.

  Examples of the physical blowing agent include hydrocarbons such as propane, n-butane, i-butane, n-pentane, i-pentane, neopentane, cyclopentane, hexane, cyclohexane, 1,1-difluoroethane, 1,2 -Difluoroethane, 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1 , 1,2,2-pentafluoroethane, fluorinated hydrocarbons such as difluoromethane, trifluoromethane, dimethyl ether, diethyl ether, methyl ethyl ether, isopropyl ether, n-butyl ether, diisoamyl ether, furan, furfural, 2- Ethers such as methylfuran, tetrahydrofuran and tetrahydropyran Alkyl chlorides such as methyl chloride, ethyl chloride, propyl chloride and isopropyl chloride, methyl formate, ethyl formate, propyl formate, butyl formate, amyl formate, methyl propionate, ethyl propionate, etc. Carboxylic acid esters, methanol, ethanol, propyl alcohol, i-propyl alcohol, butyl alcohol, i-butyl alcohol, t-butyl alcohol and other alcohols, dimethyl ketone, methyl ethyl ketone, diethyl ketone, methyl-n-propyl ketone, methyl Ketones such as -n-butyl ketone, methyl-i-butyl ketone, methyl-n-amyl ketone, methyl-n-hexyl ketone, ethyl-n-propyl ketone, ethyl-n-butyl ketone, or Carbon oxides, nitrogen, water, argon, include inorganic foaming agents such as helium, these can be used alone or in combination.

  Examples of the chemical foaming agent include N, N′-dinitrosopentamethylenetetramine, p, p′-oxybis-benzenesulfonylhydrazide, hydrazodicarbonamide, sodium carbonate, azodicarbonamide, terephthalazide, and 5-phenyltetrazole. , P-toluenesulfonyl semicarbazide and the like, and these can be used alone or in admixture of two or more.

  Among these foaming agents, hydrocarbons such as propane, n-butane, i-butane, n-pentane, i-pentane, neopentane, cyclopentane, dimethyl ether, diethyl ether, and methyl ethyl ether are used to protect the ozone layer. Ethers such as methanol, ethanol, propyl alcohol, i-propyl alcohol, alcohols such as butyl alcohol, i-butyl alcohol and t-butyl alcohol, alkyl chlorides such as methyl chloride and ethyl chloride, carbon dioxide, nitrogen, An inorganic foaming agent such as water is preferred.

  Of the foaming agents described above, the foaming agent is mainly selected from the group consisting of (a) ethers and alkyl chlorides in consideration of weight reduction of the foam and stability of extrusion foaming. What contains 0.5-10 weight part of at least 1 sort (s) and (b) 0-6 weight part of hydrocarbons is preferable.

  Examples of the ether in the foaming agent of the present invention include the ethers described above, and among these, dimethyl ether reduces the extrusion pressure during extrusion foaming, and can stably produce an extruded foam. preferable. The amount of ether used is preferably 0.5 to 10 parts by weight, more preferably 1.5 to 6 parts by weight, and more preferably 3 to 5 parts by weight with respect to 100 parts by weight of the thermoplastic resin mixture. Is particularly preferred. When the amount of ether used is in the range of 0.5 to 10 parts by weight, the foamability and gas dispersibility in the foam are good, and the foamability is good.

  Examples of the alkyl chloride in the foaming agent of the present invention include the above-mentioned alkyl chlorides. Among these, methyl chloride and ethyl chloride reduce the extrusion pressure during extrusion foaming, and the extruded foam can be stably formed. It is preferable at the point manufactured. The amount of alkyl chloride used is preferably 0.5 to 10 parts by weight, more preferably 1.5 to 6 parts by weight, and more preferably 3 to 5 parts by weight with respect to 100 parts by weight of the thermoplastic resin mixture. Part is particularly preferred. When the amount of alkyl chloride used is in the range of 0.5 to 10 parts by weight, the foamability and gas dispersibility in the foam are good, and the foamability is good.

  Examples of the hydrocarbon in the foaming agent of the present invention include the hydrocarbons described above, but if the boiling point is too low, the vapor pressure becomes high, and a high pressure is required for handling, which tends to be a problem in production. If the boiling point is too high, the foaming agent remains as a liquid in the foam bubbles and tends to lower the heat resistant temperature of the foam. Therefore, a saturated hydrocarbon having a boiling point in the range of −50 ° C. to 85 ° C. is preferable. Examples of the saturated hydrocarbon having a boiling point in the range of −50 ° C. to 85 ° C. include propane, cyclopropane, n-butane, i-butane, cyclobutane, n-pentane, i-pentane, neopentane, cyclopentane, hexane, Examples include 2-methylpentane, 3-methylpentane, 1,2-dimethylbutane, cyclohexane and the like. Of these, propane, n-butane, i-butane, n-pentane, i-pentane, neopentane, cyclopentane, n-hexane and cyclohexane are preferred from the viewpoint of production stability. The amount of hydrocarbon used is preferably 0 to 6 parts by weight and more preferably 2 to 5 parts by weight with respect to 100 parts by weight of the thermoplastic resin mixture. If the usage-amount of hydrocarbon exists in the range of 0-6 weight part, the gas dispersibility to a foam is good and foamability is good.

  The brominated flame retardant used in the present invention preferably has a 5% thermogravimetric decrease starting temperature of 270 ° C. or higher and a melting point or softening point of 150 ° C. or higher.

  The 5% thermal weight loss starting temperature of the brominated flame retardant is more preferably 275 ° C. or higher, and further preferably 280 ° C. or higher. If the 5% thermal weight reduction start temperature of the brominated flame retardant is in the range of 270 ° C. or higher, the thermal stability is lowered due to the decomposition of the flame retardant in the extruder, and the heat resistance of the obtained foam is lowered. It is preferable because it does not have an adverse effect. On the other hand, for the expression of flame retardancy, the bromine-based flame retardant preferably has a 5% thermogravimetric decrease starting temperature of 400 ° C. or lower.

  Moreover, as melting | fusing point or softening point of a brominated flame retardant, 160 degreeC or more is more preferable, and 170 degreeC or more is further more preferable. If the melting point or softening point of the brominated flame retardant is in the range of 150 ° C. or higher, there will be no adverse effects such as instability of extrusion due to melting or softening of the brominated flame retardant, and reduced heat resistance of the obtained foam. ,preferable.

In addition, the softening point of the brominated flame retardant in the present invention is a value measured according to JIS K7234 (Method for testing softening point of epoxy resin).
Among the brominated flame retardants described below, epoxy polymer flame retardants such as tetrabromobisphenol A diglycidyl ether copolymer and tribromophenol adduct of tetrabromobisphenol A diglycidyl ether copolymer do not have a clear melting point, so they are solid. A softening point at which the material softens was substituted.

  Examples of the brominated flame retardant having a 5% thermal weight loss starting temperature of 270 ° C. or higher and a melting point or softening point of 150 ° C. or higher used in the present invention include, for example, hexabromobenzene, decabromodiphenyl ether, ethylene bis (pentabromo Phenyl), bis (2,4,6-tribromophenoxy) ethane, pentabromobenzyl acrylate polymer, tetrabromobisphenol A diglycidyl ether copolymer, tribromophenol adduct of tetrabromobisphenol A diglycidyl ether copolymer, tetrabromobisphenol S, tetrabromobisphenol A polycarbonate oligomer, ethylenebistetrabromophthalimide, 2,4,6-tris (2,4,6-tribromophenoxy) 1,3,5-triazine, tris (to Such as bromo neopentyl) phosphate can be mentioned.

  Among the brominated flame retardants, decabromodiphenyl ether and ethylene bis (pentabromophenyl) are preferable because they have good dispersibility with the thermoplastic resin composition, little adverse effect on heat resistance, and high flame retardant effect. ), Bis (2,4,6-tribromophenoxy) ethane, tris (tribromoneopentyl) phosphate are preferred.

  The brominated flame retardant content in the present invention is appropriately adjusted so that the flammability of JIS A9511 is satisfied and the oxygen index of the foam is 26% or more, but is approximately 100 parts by weight of the thermoplastic resin mixture. On the other hand, the range of 5 to 15 parts by weight is preferable, more preferably 6 to 14 parts by weight, and still more preferably 7 to 13 parts by weight.

  If the content of the brominated flame retardant is within the above range, the present invention does not cause problems such as a decrease in physical stability such as a decrease in thermal stability and a decrease in heat resistance, a decrease in extrusion stability, and a decrease in foam moldability. It is preferable because the desired flame retardancy is satisfied.

The JIS A9511 corresponds to the Japanese Industrial Standard applied to the foamed plastic heat insulating material. The flammability specified in JIS A9511 includes three measurement methods A to C. In this test, among the foamed plastic heat insulating materials, bead method polystyrene foam heat insulating material, extrusion method polystyrene foam heat insulating material. It conformed to measurement method A applied to.
The measurement method is as follows. A flame of the candle for the fire source is moved horizontally to the ignition limit indicating line at a constant speed over about 5 seconds on a test piece (thickness 10 mm, length 200 mm, width 25 mm) inclined at 45 °. After reaching the ignition limit indicator line, the flame is quickly retracted, and the time from the moment until the flame disappears and the combustion stop position are confirmed.
Judgment criteria for flame retardancy are as follows: 1) The average flame extinguishing time of 5 test specimens is within 3 seconds, 2) no residual dust, 3) each test specimen has a combustion limit indicating line (ignition limit) It is required not to burn more than 20 mm from the indicated line.

  In the present invention, a nucleating agent, a stabilizer, a lubricant, an antistatic agent, a plasticizer, a water absorbing agent are added to the thermoplastic resin composition as necessary within the scope of assuming the effects of the present invention. You may mix | blend additives, such as an agent and a radiation inhibitor.

  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. In addition, when the foam thickness exceeds 150 mm, the closed cell ratio tends to decrease, 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 foam density is within the above range, it is preferable from the viewpoint of expression of surface compressive strength represented by plane compressive strength.

  Examples of the cell structure of the thermoplastic resin foam in 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 the sample 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 may be in the above range. If the bubble diameter is less than the above range, the heat-insulating material has poor moldability, and stable production tends to be difficult. When the bubble diameter exceeds the above range, the appearance of the surface of the heat insulating material tends to deteriorate.

  The thermoplastic resin foam of the present invention can be obtained by a known method using the resin composition. For example, the thermoplastic resin mixture is supplied to a known heat-melting and kneading apparatus such as an extruder and melted by heating, and a step of adding a foaming agent under a high-pressure condition, a step of forming a foamable gel substance Then, the step of cooling the gel-like substance, the step of extruding and foaming the gel-like substance into the low-pressure region through a die such as a slit die from the high-pressure region, and the molding die placed in close contact with or in contact with the die A thick plate-like thermoplastic resin foam can be obtained through the step of forming the foam to be shaped.

  Prior to adding the blowing agent, the resin composition is heated to its glass transition temperature or melting point or higher. 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. Moreover, each foaming agent component can be put into an extruder individually or simultaneously. Furthermore, each foam component may be blended in either a liquid or gas state.

  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 and melted by heating, and then a procedure for adding and mixing a foaming agent is included, but the timing of adding various additives to the thermoplastic resin mixture is particularly limited. Not.

  In the production of the thermoplastic resin foam of the present invention, the heating temperature, melt kneading time, and melt kneading means when the thermoplastic resin mixture, foaming agent, and various additives added as necessary are heated and melt kneaded. There is no particular limitation on the above.

  The heating temperature may be equal to or higher than the temperature at which the thermoplastic resin mixture melts (glass transition temperature or melting point), but is preferably a temperature at which decomposition and deterioration of the resin due to the influence of a flame retardant and the like are suppressed as much as possible.

  The melt-kneading time varies depending on the amount of extrusion per unit time, the type of melt-kneading equipment, etc., so it cannot be determined unconditionally, but the thermoplastic resin mixture and the foaming agent or additive are uniformly dispersed and mixed. The time required is set as appropriate.

  Examples of the melt-kneading means include a screw type extruder such as a single screw or a twin screw, but there is no particular limitation as long as it is used for normal extrusion foaming. However, when the dispersibility of the foaming agent is required, the twin screw type is preferable as the extruder. 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.

  As one means thereof, the pressure in the slit die (hereinafter sometimes referred to as “slit pressure”) is preferably 3 MPa or more, and more preferably 4 MPa or more. It is preferable that the pressure in the slit die be 3 MPa or more because phenomena such as gas blowing, void generation in the foam, pressure fluctuation in the extruder system, and accompanying foam cross-sectional profile fluctuation are less likely to occur.

  The resin temperature of the gel substance at the exit of the step of cooling the gel substance is preferably 20 to 70 ° C. higher than the glass transition temperature of the thermoplastic resin mixture, More preferably, the temperature is higher by 30 to 60 ° C. By setting the resin temperature at the process outlet to cool the gel-like substance to a temperature suitable for foaming within the above range, the gel substance is introduced into the die in a state where there is almost no increase in the slit pressure of the die and temperature unevenness. And good extrusion moldability and surface properties can be obtained.

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

  The foam molding method is not particularly limited, and can be obtained, for example, by releasing pressure from the high pressure region to the low pressure region through a die such as a slit die having a slit shape used for extrusion molding. The extrusion foaming method of forming a thermoplastic resin extruded foam using a molding die installed in close contact with or in contact with the slit die and a molding roll installed adjacent to the downstream side of the molding die. For example, it is possible to obtain a plate-like foam that is thick and has a large cross-sectional area.

  Examples of the shape of the slit die include a rectangular shape, a coat hanger shape, a fish tail shape, and the like, but when a wide plate-like foam is to be obtained, a coat hanger shape or a fish tail shape slit die is preferable. .

  Furthermore, when trying to obtain a plate-like foam having a thickness of 10 to 150 mm, from the viewpoint of suppressing the dimensional enlargement ratio in the thickness direction and the dimensional enlargement ratio 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 slit die outlet is enlarged in a flat plate shape is advantageous. In particular, the thermoplastic resin mixture composed of the copolymer (A) and the copolymer (B) in the present invention tends to be brittle with respect to the polystyrene-based resin, so that the expansion rate in the width direction is suppressed as much as possible. It is preferred to select a method.

  In addition, when the resin composition is used, since the elongation of a resin such as a polystyrene resin cannot be expected from its resin characteristics, the surface of the extruded foam and molding are required to ensure the surface properties of the obtained extruded foam. It is important to reduce the resistance to the mold.

  Means for reducing the resistance between the extruded foam and the molding die include, for example, (1) heating the molding die by using steam, oil, an electric heater, etc., (2) polytetrafluoroethylene resin, etc. It is conceivable to install a material having a low surface resistance such as a sheet made of a fluororesin at the interface between the extruded foam surface and the molding die.

  Furthermore, it is important to gradually cool the foam obtained by extrusion foaming from the slit die in order to ensure the surface properties and physical properties of the obtained thermoplastic resin foam. That is, even when the surface of the foam is cooled and solidified, in the state where the inside of the foam is still fluid and has a foaming force, the surface portion cannot withstand the foaming force inside, The surface of the foam may cause defects such as cracks. In addition, as described above, the closed cell ratio of the obtained foam tends to decrease, and as a result, the heat insulating properties, dimensional stability, strength, and the like may decrease. Slow cooling conditions are also affected by the resin temperature at the time of foaming and may be adjusted as appropriate.However, depending on the length of the molding die, the heating temperature for the molding die, the installation distance of the material with low surface resistance, etc. Can be adjusted.

  The thermoplastic resin foam of the present invention is superior in heat resistance and chemical resistance compared to conventional styrene-based extruded foams, for example, a roof insulation part that is susceptible to direct heat from sunlight, asphalt during construction, etc. In addition to being used in building materials such as rooftop waterproof insulation parts that are in contact with hot-melted molten materials and waterproof insulation parts that are in contact with adhesives during construction, industrial materials are also used in harsh environments where there is a large temperature difference between high and low temperatures. Is preferably used.

  Hereinafter, the thermoplastic resin foam having both heat resistance and flame retardancy of the present invention will be described in detail by way of specific examples. However, the present invention is not limited to such examples. Unless otherwise specified, “parts” represents parts by weight and “%” represents% by weight.

  As the properties of the foams obtained in Examples 1 to 16, Comparative Examples 1 to 7, and Reference Examples 1 to 4 shown below, the foam density, average cell diameter, JIS A9511 combustibility, foam oxygen index, and heat melting Asphalt coating heat resistance, 140 ° C. heat resistance, and surface properties were examined according to the following methods.

1) 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 .

2) Average cell diameter (mm)
The cell diameter in each direction was measured according to ASTM D-3576.

The cross-section in the width direction of the foam is enlarged 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.

3) Flammability (JIS A9511)
About the foam which passed 7 days after preparation, according to JISA9511, the combustion test was done by n number 5 using the test piece of thickness 10mm * length 200mm * width 25mm, and judged by the following references | standards.
<Burning time>
A: All five flame extinguishing times are within 3 seconds.
○: Among 5 flame extinguishing times, at least one exceeds 3 seconds, but the average flame extinguishing time of 5 falls within 3 seconds.
X: The average flame-out time of five exceeds 3 seconds.
<Combustion status>
A: Combustion stops within the combustion limit indication line, and no foaming agent combustion is observed.
○: Combustion stops within the combustion limit indication line, but some of the foaming agent is observed.
X: Combustion continues beyond the combustion limit indicating line.

4) Foam oxygen index About the foam which passed 7 days after manufacture, according to JISK7201, it measured using the test piece of thickness 10mm * length 150mm * width 10mm.

5) Hot melt asphalt coating heat resistance (shape retention ratio of foam cross section after heating)
After creating the foam, it was conditioned for 10 days in a constant temperature room at 23 ° C. and 55% humidity, then cut out into a thickness of 25 mm × length of 300 mm × width of 100 mm, and uniformly applied hot melt asphalt heated to 200 ° C., 30 After cooling for a minute, the foam cross-section in the thickness direction x length direction was cut out, the cross-sectional area was determined, and the presence or absence of heat resistance was judged according to the following criteria.
(Circle): The cross-sectional area of a foam cross section is 90% or more of the original cross-sectional area.
Δ: The cross-sectional area of the cross-section of the foam is 80% or more and less than 90% of the original cross-sectional area.
X: The cross-sectional area of the foam cross-section is less than 80% of the original cross-sectional area.

6) 140 ° C. heat resistance (volume change rate of foam)
After creating the foam, it was conditioned for 10 days in a constant temperature room at 23 ° C. and 55% humidity, then cut into a thickness of 25 mm × length 100 mm × width 100 mm and heated in a hot air dryer set at 140 ° 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: The volume change rate of the foam is 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%.

7) Surface properties
The surface property of the obtained foam was visually determined according to the following criteria.
Good: A foam having a beautiful skin layer having 3 or less cracks, cracks, dents and voids (pores) per 1 m in the extrusion flow direction of the foam surface.
Defect: Foam surface is a foam capable of forming only a poor skin layer having more than 3 cracks, cracks, dents and voids (pores) per 1 m in the extrusion direction of the foam surface.

Example 1
As a copolymer (A), manufactured by Denki Kagaku Kogyo Co., Ltd., trade name: DENKA IP (265 ° C. × 10 kg, MFR = 0.2 g / min), and as a copolymer (B) manufactured by Toyo Styrene Co., Ltd. , Trade name: Toyo AS (220 ° C. × 10 kg condition, MFR = 1.8 g / min) was used, and copolymer (A) / copolymer (B) were mixed at a ratio of 60% / 40%. . With respect to 100 parts of the obtained thermoplastic resin mixture, 7.0 parts of decabromodiphenyl ether (manufactured by Albemarle, trade name: SAYTEX102E 5% thermogravimetric decrease starting temperature: 326 ° C., melting point: 304 ° C.) as a brominated flame retardant, As a nucleating agent, 0.3 parts of talc (trade name: Talcan powder, manufactured by Hayashi Kasei Co., Ltd.) is dry blended, and the resulting resin composition is a single screw extruder (first stage extruder) having a diameter of 65 mm and a diameter. A 90 mm single-screw extruder (second-stage extruder) was supplied to a two-stage connected extruder connected in series. The resin composition supplied to the first stage extruder was melted and kneaded by heating to about 250 ° C., and then 4.0 parts of dimethyl ether as a foaming agent was pressed into the resin near the tip of the first stage extruder. Then, while kneading and cooling with the connected second stage extruder, the resin temperature at the outlet of the second stage extruder is cooled to about 190 ° C., and from the die lip of the rectangular slit die provided at the tip of the second stage extruder Extrusion into the atmosphere, and 0.8 MPa steam is passed through the molding die, so that the molding die temperature is set to 170 ° C. (surface material: iron surface-treated with polytetrafluoroethylene resin: height 25 mm × width 120 mm) and a forming roll, an extruded foam plate having a cross-sectional shape having a thickness of about 30 mm and a width of about 100 mm was obtained. The die lip was set at 170 ° C., and the gap was a rectangular cross section having a thickness direction of 2 mm and a width direction of 50 mm.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

(Example 2)
Extruded foams were obtained under the same conditions as in Example 1 except that the addition amount of the brominated flame retardant decabromodiphenyl ether was changed to 10 parts.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

(Example 3)
Extruded foam was obtained under the same conditions as in Example 1 except that the addition amount of the brominated flame retardant decabromodiphenyl ether was changed to 13 parts.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

Example 4
The mixing ratio of copolymer (A) / copolymer (B) was changed to 50% / 50%, the heating temperature in the first stage extruder was about 240 ° C., and the resin temperature at the outlet of the second stage extruder was about Extrusion was performed under the same conditions as in Example 2 except that the temperature was set to 160 ° C. by cooling the die lip to 160 ° C. and allowing 0.7 MPa steam to pass through the molding die. A foam was obtained.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

(Example 5)
The mixing ratio of copolymer (A) / copolymer (B) was changed to 80% / 20%, the heating temperature in the first stage extruder was about 270 ° C., and the resin temperature at the outlet of the second stage extruder was about Extruded foam was obtained under the same conditions as in Example 2 except that the temperature was lowered to 200 ° C. and the die lip temperature was 190 ° C.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

(Example 6)
The mixing ratio of copolymer (A) / copolymer (B) was changed to 90% / 10%, the heating temperature in the first stage extruder was about 280 ° C., and the resin temperature at the outlet of the second stage extruder was about Extruded foam was obtained under the same conditions as in Example 2 except that the temperature was lowered to 210 ° C and the die lip temperature was 195 ° C.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

(Example 7)
Extruded foams were obtained under the same conditions as in Example 2 except that the blowing agent was changed to 2.0 parts of dimethyl ether and 3.0 parts of isobutane.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

(Example 8)
Extruded foams were obtained under the same conditions as in Example 2, except that the blowing agent was changed to 3.0 parts of dimethyl ether and 3.0 parts of normal butane, and talc was changed to 0.2 parts.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

Example 9
Extruded foam was obtained under the same conditions as in Example 8, except that the blowing agent was changed to 4.0 parts of dimethyl ether and 2.0 parts of isobutane.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

(Example 10)
Extruded foam was obtained under the same conditions as in Example 8, except that the blowing agent was changed to 4.0 parts of dimethyl ether and 2.0 parts of normal butane.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

(Example 11)
Extruded foam was obtained under the same conditions as in Example 2 except that 4.0 parts of dimethyl ether and 3.5 parts of normal butane were used and the talc was changed to 0.1.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

(Example 12)
Extruded foams were obtained under the same conditions as in Example 11 except that the blowing agent was changed to 3.0 parts of dimethyl ether, 3.5 parts of normal butane, and 1.0 part of ethanol.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

(Example 13)
Example 2 except that the brominated flame retardant was changed to 10 parts ethylene bis (pentabromophenyl) (manufactured by Albemarle, trade name: SAYTEX 8010, 5% thermogravimetric decrease starting temperature: 344 ° C., melting point: 350 ° C.) An extruded foam was obtained under the conditions described above.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

(Example 14)
The brominated flame retardant was changed to 10 parts of bis (2,4,6-tribromophenoxy) ethane (manufactured by Great Lakes, trade name: FF680, 5% thermogravimetric decrease starting temperature: 276 ° C., melting point: 225 ° C.). Obtained an extruded foam under the same conditions as in Example 2.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

(Example 15)
Except that the brominated flame retardant was changed to 10 parts of tris (tribromoneopentyl) phosphate (manufactured by Daihachi Chemical Industry, trade name: CR900, 5% thermal weight reduction start temperature: 310 ° C., melting point: 180 ° C.) An extruded foam was obtained under the same conditions as in Example 2.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

(Example 16)
Extruded foam was obtained under the same conditions as in Example 2 except that the brominated flame retardant was changed to 8.0 parts of tris (tribromoneopentyl) phosphate.
The properties of the obtained foam are shown in Table 1. Compared with Comparative Examples 1-7, the foam which was excellent in heat resistance and a flame retardance was obtained.

(Comparative Example 1)
Extruded foams were obtained under the same conditions as in Example 2, except that the brominated flame retardant was changed to 4.0 parts of decabromodiphenyl ether.
The properties of the obtained foam are shown in Table 2. Compared with Examples 1-16, although heat resistance is satisfied, flame retardance cannot be satisfied.

(Comparative Example 2)
Extruded foam was obtained under the same conditions as in Example 2 except that the brominated flame retardant was changed to 17 parts of decabromodiphenyl ether.
The properties of the obtained foam are shown in Table 2. Compared with Examples 1-16, although flame retardance is satisfied, heat resistance could not be satisfied, and in addition, as the amount of brominated flame retardant added increased, molding defects due to fluctuations in extrusion occurred. .

(Comparative Example 3)
Extruded foams were obtained under the same conditions as in Example 2 except that the brominated flame retardant was changed to 20 parts of decabromodiphenyl ether.
The properties of the obtained foam are shown in Table 2. Compared with Examples 1-16, although flame retardance is satisfied, heat resistance could not be satisfied, and in addition, as the amount of brominated flame retardant added increased, molding defects due to fluctuations in extrusion occurred. .

(Comparative Example 4)
Example 2 except that the brominated flame retardant was changed to 8.0 parts of hexabromocyclododecane (manufactured by Albemarle, trade name: SAYTEX HP900, 5% thermogravimetric decrease starting temperature: 244 ° C., melting point: 180 ° C.) An extruded foam was obtained under the conditions described above.
The properties of the obtained foam are shown in Table 2. Although flame retardance is satisfied as compared with Examples 1 to 16, resin deterioration due to decomposition of the flame retardant occurs, and heat resistance cannot be satisfied.

(Comparative Example 5)
The brominated flame retardant was changed to 10 parts of tetrabromobisphenol A bis (2,3-dibromopropyl ether) (manufactured by Albemarle, trade name: SAYTEX HP800A 5% thermogravimetric decrease starting temperature: 312 ° C., melting point: 110 ° C.) Obtained an extruded foam under the same conditions as in Example 2.
The properties of the obtained foam are shown in Table 2. Compared with Examples 1-16, although flame retardance is satisfied, heat resistance cannot be satisfied. In addition, due to the low melting point of brominated flame retardants, molding defects due to poor resin feed occurred.

(Comparative Example 6)
As a base resin, polystyrene resin (manufactured by PS Japan Co., Ltd., trade name: G9401, 200 ° C. × 5 kg, MFR = 0.2 g / min) is used. 10 parts decabromodiphenyl ether as a fuel and 0.3 parts talc as a nucleating agent were dry blended, and the resulting resin composition was a 65 mm single screw extruder (first stage extruder) and a 90 mm single screw extruder. (Second-stage extruder) was supplied to a two-stage connected extruder connected in series. After the resin composition supplied to the first stage extruder having a diameter of 65 mm is heated to about 220 ° C. and melt-kneaded, 4.0 parts of dimethyl ether is press-fitted into the resin near the tip of the first stage extruder as a foaming agent. did. The resin temperature at the outlet of the second stage extruder is cooled to about 125 ° C. while being kneaded and cooled by the connected second stage extruder with a diameter of 90 mm, and the die lip of the rectangular slit die provided at the tip of the second stage extruder The extruded foam plate 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 that were further extruded into the atmosphere and set at a molding die temperature of 100 ° C. The temperature of the die lip was set to 115 ° C., and the gap was a rectangular cross section having a thickness direction of 2 mm and a width direction of 50 mm.
The properties of the obtained foam are shown in Table 2. Compared with Examples 1-16, a flame retardance and heat resistance cannot be satisfied.

(Comparative Example 7)
Extruded foam was obtained under the same conditions as in Comparative Example 5 except that the brominated flame retardant was changed to 5.0 parts of hexabromocyclododecane.
The properties of the obtained foam are shown in Table 2. Compared with Examples 1-16, although flame retardance is satisfied, heat resistance cannot be satisfied.

(Reference Example 1)
Extrusion was carried out under the same conditions as in Example 2 except that the resin temperature at the outlet of the second stage extruder was cooled to 230 ° C. and the temperature of the die lip was changed to 200 ° C. However, since the resin temperature is high, the slit pressure decreases due to gas ejection and foaming inside the die, the extrusion moldability deteriorates, and only a poor shape / surface can be obtained, and a satisfactory foam cannot be obtained. .

(Reference Example 2)
Extrusion was performed under the same conditions as in Example 2 except that the temperature of the molding die was set to 50 ° C. by passing water through the molding die. However, since the mold temperature is low, the cracks on the surface due to the occurrence of blistering from the inside of the foam become extremely large, and only a poor shape / surface can be obtained, and a satisfactory foam cannot be obtained. It was.

(Reference Example 3)
Extrusion was carried out under the same conditions as in Example 9, except that the resin temperature at the outlet of the second stage extruder was cooled to 230 ° C. and the temperature of the die lip was changed to 200 ° C. However, since the resin temperature is high, the slit pressure decreases due to gas ejection and foaming inside the die, the extrusion moldability deteriorates, and only a poor shape / surface can be obtained, and a satisfactory foam cannot be obtained. .

(Reference Example 4)
Extrusion was performed under the same conditions as in Example 9 except that the temperature of the molding die was set to 50 ° C. by passing water through the molding die. However, since the mold temperature is low, the cracks on the surface due to the occurrence of blistering from the inside of the foam become extremely large, and only a poor shape / surface can be obtained, and a satisfactory foam cannot be obtained. It was.

Claims (9)

Copolymer (A) composed of aromatic vinyl unit, unsaturated dicarboxylic anhydride unit and N-alkyl-substituted maleimide unit (A) 50 to 90% by weight and copolymer composed of aromatic vinyl unit and vinyl cyanide unit (B ) For 100 parts by weight of the thermoplastic resin mixture consisting of 50 to 10% by weight,
Thermoplastic resin composition comprising 5 to 15 parts by weight of at least one flame retardant selected from brominated flame retardants having a 5% thermogravimetric decrease starting temperature of 270 ° C. or higher and a melting point or softening point of 150 ° C. or higher. A process of heating and melting a product, adding a foaming agent, and forming a foamable gel material,
Cooling the gelled material;
Extruding the gel-like material through a slit die into a lower pressure region; and
A method for producing an extruded foam of a thermoplastic resin having a foam thickness of 10 to 150 mm, comprising a step of forming an extruded foam by molding using a molding die placed in close contact with or in contact with a slit die. ,
In the step of forming the extruded foam, the resin foam of the gel substance at the outlet of the cooling step is 20 to 70 ° C. higher than the glass transition temperature of the thermoplastic resin mixture. A method for producing an extruded foam of a thermoplastic resin, comprising reducing resistance between a body surface and a molding die, and gradually cooling the foam in the molding die . The method for producing a thermoplastic resin extruded foam according to claim 1, wherein the die temperature is 5 to 50 ° C lower than the resin temperature . The heat according to claim 1 or 2, wherein a resistance of the extruded foam and the molding die is reduced by installing a material having a small surface resistance at an interface between the surface of the extruded foam and the molding die. A method for producing an extruded foam of a plastic resin . The method for producing a thermoplastic resin extruded foam according to any one of claims 1 to 3, wherein the foam is gradually cooled in the mold by adjusting the temperature of the mold . The method for producing a thermoplastic resin extruded foam according to any one of claims 1 to 4, wherein the aromatic vinyl unit is a styrene unit. The method for producing an extruded foam according to any one of claims 1 to 5, wherein the unsaturated dicarboxylic anhydride unit is a maleic anhydride unit. The method for producing an extruded foam according to any one of claims 1 to 6, wherein the N-alkyl-substituted maleimide unit is an N-phenylmaleimide unit. The method for producing an extruded foam according to any one of claims 1 to 7 , wherein the vinyl cyanide unit is acrylonitrile. Brominated flame retardants having a 5% thermal weight loss starting temperature of 270 ° C. or higher and a melting point or softening point of 150 ° C. or higher are decabromodiphenyl ether, ethylene bis (pentabromophenyl), bis (2,4,6-tri Bromophenoxy) ethane, tetrabromobisphenol A diglycidyl ether copolymer, tribromophenol adduct of tetrabromobisphenol A diglycidyl ether copolymer, 2,4,6-tris (2,4,6-tribromophenoxy) 1,3 The method for producing an extruded foam according to any one of claims 1 to 8 , which is 1,5-triazine or tris (tribromoneopentyl) phosphate.