JP2013071996A - Expandable thermoplastic resin particle, process for producing the same, thermoplastic resin prefoamed particle, and thermoplastic resin foam molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an expandable thermoplastic resin particle having excellent heat resistance, mechanical strength and foaming properties; a prefoamed particle thereof; and a foam molded product.SOLUTION: The expandable thermoplastic resin particle consists of a particle of a thermoplastic resin containing a foaming agent. The thermoplastic resin is a styrene-methacrylate-methyl methacrylate copolymer.

Description

  TECHNICAL FIELD The present invention relates to expandable thermoplastic resin particles, pre-expanded particles, and a foam-molded product using a thermoplastic resin mainly composed of a styrene-methacrylic acid-methyl methacrylate copolymer having excellent heat resistance and mechanical strength. .

  Polystyrene-based resin foam moldings are lightweight, have excellent heat insulation, relatively good mechanical strength, excellent moldability, and low cost, so various containers, packing materials, cushioning materials It is widely used as a heat insulating material. Conventionally, as resin used for polystyrene resin foam moldings, resin materials with better heat resistance than polystyrene resins have been proposed, and the heat resistance of foam moldings has been improved to further improve performance and expand applications. ing.

  For example, in Patent Document 1, a volatile foaming agent is added to a heat-resistant resin having a glass transition temperature measured by a DSC method of 110 ° C. or higher, or a thermoplastic resin composed of a mixed resin of the heat-resistant resin and a polystyrene resin. Foamed thermoplastic resin particles contained, characterized in that 0.01 to 1.0 parts by mass of a higher fatty acid-based lubricant having a melting point of 65 ° C. or higher is contained with respect to 100 parts by mass of the thermoplastic resin. Expandable thermoplastic resin particles are disclosed. In Patent Document 1, as the heat-resistant resin, a styrene-methacrylic acid copolymer, or a styrene-maleic anhydride copolymer, a styrene-maleimide copolymer, a polyphenylene ether resin, and a styrene-polyphenylene ether copolymer. Resins selected from are listed.

JP 2010-229205 A

  However, although the foamable thermoplastic resin particles according to the above-mentioned prior art can contribute to the reduction of heat resistance and volatile organic compounds, it is still insufficient for achieving both the strength and foamability of the obtained foamed molded product. It was.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the foamable thermoplastic resin particle which was excellent in heat resistance, mechanical strength, and foamability, its pre-expanded particle, and a foamable form.

  In order to achieve the above object, the present invention is an expandable thermoplastic resin particle comprising thermoplastic resin particles containing a foaming agent, wherein the thermoplastic resin is a styrene-methacrylic acid-methyl methacrylate copolymer. An expandable thermoplastic resin particle is provided.

  In the foamable thermoplastic resin particles of the present invention, the copolymer has a total content of styrene monomer units, methacrylic acid monomer units, and methyl methacrylate monomer units of 100% by mass. The content of the methyl methacrylate monomer unit is preferably in the range of 2 to 20% by mass.

  In the foamable thermoplastic resin particles of the present invention, the copolymer has a total content of styrene monomer units, methacrylic acid monomer units, and methyl methacrylate monomer units of 100% by mass. The content of the methyl methacrylate monomer unit is preferably in the range of 5 to 10% by mass.

  In the foamable thermoplastic resin particles of the present invention, the residual amount of styrene dimer and trimer in the thermoplastic resin is 0.6 mass%, and the residual amount of styrene monomer is the thermoplastic resin. The content is preferably 700 ppm or less.

  In the foamable thermoplastic resin particles of the present invention, the thermoplastic resin has a weight average molecular weight (Mw) in the range of 100,000 to 350,000, and a Z average molecular weight (Mz) with respect to the weight average molecular weight (Mw). The ratio (Mz / Mw) is preferably in the range of 1.6 to 3.5.

  In the foamable thermoplastic resin particles of the present invention, the thermoplastic resin preferably contains an aliphatic primary alcohol having 14 or more carbon atoms in a range of 0.02 to 1.0 mass%.

  The present invention also provides a die in which a styrene-methacrylic acid-methyl methacrylate copolymer is melted in a resin supply device, a foaming agent is press-fitted and kneaded, and a molten resin containing the foaming agent is attached to the tip of the resin supply device. There is provided a method for producing expandable thermoplastic resin particles, characterized in that expandable thermoplastic resin particles are obtained by a melt extrusion method in which particles are formed by extrusion from small holes.

  The present invention also provides a die in which a styrene-methacrylic acid-methyl methacrylate copolymer is melted in a resin supply device, a foaming agent is press-fitted and kneaded, and a molten resin containing the foaming agent is attached to the tip of the resin supply device. The extrudate is extruded with a high-speed rotary blade at the same time as it is extruded into the cooling liquid directly from the small holes of the material, and the extrudate is cooled and solidified by contact with the liquid to obtain expandable thermoplastic resin particles. A method for producing expandable thermoplastic resin particles is provided.

  In the method for producing expandable thermoplastic resin particles of the present invention, the copolymer has a total content of styrene monomer units, methacrylic acid monomer units, and methyl methacrylate monomer units as 100% by mass. When it does, it is preferable that content of a methyl methacrylate monomer unit exists in the range of 2-20 mass%.

  In the method for producing expandable thermoplastic resin particles of the present invention, the copolymer has a total content of styrene monomer units, methacrylic acid monomer units, and methyl methacrylate monomer units as 100% by mass. When it does, it is preferable that content of a methyl methacrylate monomer unit exists in the range of 5-10 mass%.

  In the method for producing expandable thermoplastic resin particles of the present invention, the residual amount of styrene dimer and trimer in the thermoplastic resin is 0.6% by mass, and the residual amount of styrene monomer is It is preferably 700 ppm or less in the thermoplastic resin.

  In the method for producing expandable thermoplastic resin particles of the present invention, the thermoplastic resin has a weight average molecular weight (Mw) in the range of 100,000 to 350,000 and a weight average molecular weight of Z average molecular weight (Mz) ( The ratio (Mz / Mw) to Mw) is preferably in the range of 1.6 to 3.5.

  In the method for producing expandable thermoplastic resin particles of the present invention, the thermoplastic resin preferably contains an aliphatic primary alcohol having 14 or more carbon atoms in the range of 0.02 to 1.0% by mass.

  The present invention also provides thermoplastic resin pre-expanded particles obtained by heating and foaming the expandable thermoplastic resin particles.

  The present invention also provides a thermoplastic resin foam molded article obtained by filling the thermoplastic resin pre-expanded particles in a cavity of a molding die and heating to form in-mold foam molding.

  The expandable thermoplastic resin particles of the present invention are composed of thermoplastic resin particles containing a foaming agent, and since the thermoplastic resin is a styrene-methacrylic acid-methyl methacrylate copolymer, it is excellent in heat resistance and high. Pre-expanded particles having a multiple of expansion can be obtained, and a foamed molded article having a light weight and sufficient mechanical strength can be produced.

  The method for producing the foamable thermoplastic resin particles of the present invention comprises melting a styrene-methacrylic acid-methyl methacrylate copolymer in a resin supply apparatus, press-fitting and kneading the foaming agent, Expandable thermoplastic resin particles are obtained by a melt extrusion method in which particles are formed by extruding from a small hole in a die attached to the tip of the resin supply device, so that pre-expanded particles with excellent heat resistance and high expansion ratio can be obtained. It is possible to efficiently produce foamable thermoplastic resin particles that can be obtained and can produce a foamed molded article that is lightweight and has sufficient mechanical strength.

It is a block diagram which shows an example of the manufacturing apparatus of the foamable thermoplastic resin particle by a melt extrusion method.

(Foaming thermoplastic resin particles)
The expandable thermoplastic resin particles of the present invention are expandable thermoplastic resin particles made of thermoplastic resin particles containing a foaming agent, and the thermoplastic resin is a styrene-methacrylic acid-methyl methacrylate copolymer. It is characterized by that.

The thermoplastic resin may be a copolymer containing a styrene monomer unit, a methacrylic acid monomer unit, and a methyl methacrylate monomer unit in an arbitrary ratio, and the ratio of each monomer unit is There is no particular limitation.
In a preferred embodiment of the present invention, the copolymer contains methacrylic acid when the total content of styrene monomer units, methacrylic acid monomer units, and methyl methacrylate monomer units is 100% by mass. The methyl monomer unit content is preferably in the range of 2 to 20% by mass.
By setting the content of the methyl methacrylate monomer unit in the thermoplastic resin within the range of 2 to 20% by mass, it is possible to obtain pre-expanded particles having excellent heat resistance and a high expansion ratio. A foamed molded article having a high mechanical strength can be obtained.

  In a further preferred embodiment of the present invention, the copolymer has a methacrylic acid content when the total content of styrene monomer units, methacrylic acid monomer units, and methyl methacrylate monomer units is 100% by mass. The content of the acid methyl monomer unit is preferably in the range of 5 to 10% by mass.

  In the thermoplastic resin, the residual amount of styrene dimer and trimer in the thermoplastic resin is 0.6% by mass, and the residual amount of styrene monomer is 700 ppm or less in the thermoplastic resin. It is preferable. When the residual amount of styrene dimer and trimer exceeds 0.6% by mass, the heat resistance of the thermoplastic resin may be deteriorated. The residual amount of styrene dimer and trimer is more preferably 0.5% by mass or less, and further preferably 0.4% by mass or less. Further, when the residual amount of the styrene monomer exceeds 700 ppm, the heat resistance of the thermoplastic resin may be deteriorated.

  In the foamable thermoplastic resin particles of the present invention, the thermoplastic resin preferably has a weight average molecular weight (Mw) in the range of 100,000 to 350,000, and preferably in the range of 130,000 to 300,000. More preferably, it is still more preferably in the range of 160,000 to 250,000. If the weight average molecular weight (Mw) is less than 100,000, the mechanical strength of the resulting foamed molded article may be lowered. When the weight average molecular weight (Mw) exceeds 350,000, the foamability deteriorates when the foamed thermoplastic resin particles are heated to prepare the pre-foamed particles, and it becomes difficult to obtain a foamed molded article having a high expansion ratio.

  In the foamable thermoplastic resin particles of the present invention, the thermoplastic resin has a ratio (Mz / Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) in the range of 1.6 to 3.5. It is preferably within a range of 1.7 to 3.0, more preferably within a range of 1.7 to 2.5. If the ratio (Mz / Mw) is less than 1.6, the mechanical strength of the obtained foamed molded article may be lowered. When the ratio (Mz / Mw) exceeds 3.5, the foamability deteriorates when the foamable thermoplastic resin particles are heated to prepare the prefoamed particles, and it becomes difficult to obtain a foamed molded article having a high expansion ratio. .

In the foamable thermoplastic resin particles of the present invention, it is preferable that the thermoplastic resin contains an aliphatic primary alcohol having 14 or more carbon atoms. The aliphatic primary alcohol having 14 or more carbon atoms can be selected from linear aliphatic primary alcohols having 14 or more carbon atoms, branched aliphatic primary alcohols, etc., for example, isohexadecanol, isooctadecanol, Examples include eicosanol.
The content of the aliphatic primary alcohol is preferably in the range of 0.02 to 1.0% by mass in the thermoplastic resin, preferably in the range of 0.05 to 0.9% by mass. More preferably, the range of 0.1-0.8 mass% is further more preferable. When the content of the aliphatic primary alcohol is less than 0.02% by mass, the effect of improving foamability due to the addition of the alcohol becomes insufficient. When the content of the aliphatic primary alcohol exceeds 1.0% by mass, the resulting foamed molded product tends to be melted, which may cause poor appearance.
Moreover, when the number of carbon atoms of the aliphatic primary alcohol is less than 14, the resulting foamed molded product is likely to be melted, which may cause poor appearance.

  Examples of the foaming agent contained in the expandable thermoplastic resin particles of the present invention include propane, n-butane, isobutane, n-pentane, isopentane, neopentane and other aliphatic hydrocarbons, 1,1-dichloro-1-fluoroethane ( HCFC-141b), 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123), chlorodifluoromethane (HCFC-22), 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124) and other chlorofluorocarbons, 1,1-difluoroethane (HFC-152a), 1,1,1-trifluoroethane (HFC-143a), 1,1,1,2-tetrafluoroethane (HFC- 134a), fluorocarbons such as difluoromethane (HFC-32), various alcohols, carbon dioxide, water, and Include physical blowing agents such as iodine, it can be used in combination one or more of these. Among these, preferable foaming agents include n-butane, isobutane, n-pentane, isopentane, and a foaming agent obtained by mixing two or more thereof. The addition amount of a foaming agent shall be the range of 1-15 mass parts with respect to 100 mass parts of polystyrene-type resins, More preferably, it shall be the range of 3-12 mass parts.

The foamable thermoplastic resin particles of the present invention preferably contain an inorganic foam nucleating agent in addition to the foaming agent and the aliphatic primary alcohol. Examples of the inorganic foam nucleating agent include talc, silica, and other inorganic powders. Among these, talc is preferable.
The amount of the inorganic foam nucleating agent is preferably in the range of 0.05 to 5 parts by mass, more preferably in the range of 0.1 to 2 parts by mass with respect to 100 parts by mass of the polystyrene resin.
The average particle diameter of the inorganic foam nucleating agent to be used is preferably in the range of 0.1 to 30 μm, and more preferably in the range of 0.5 to 10 μm.
By making the expandable thermoplastic resin particles contain an inorganic foam nucleating agent such as talc together with the plasticizer, the effect of increasing the bulk expansion ratio of the pre-expanded particles and the effect of improving the mechanical strength of the foamed molded product can be enhanced.
The inorganic foam nucleating agent needs to be uniformly contained throughout the foamable thermoplastic resin particles. If the inorganic foam nucleating agent is unevenly distributed in a local part of the resin particle, for example, a surface layer part of the resin particle, the mechanical strength of the obtained foamed molded product may be lowered.

  The foamable thermoplastic resin particles of the present invention may be added with additives such as a crosslinking agent, a plasticizer, a filler, a flame retardant, a flame retardant aid, a lubricant, and a colorant, as long as the physical properties are not impaired. In addition, if powder metal soaps such as zinc stearate are coated on the surface of the expandable styrene resin particles, the bonding between the preexpanded particles is reduced in the prefoaming step of the expandable thermoplastic resin particles. This is preferable.

  The particle diameter of the expandable thermoplastic resin particles of the present invention is not particularly limited, but is usually preferably in the range of 0.5 to 3.0 mm, more preferably in the range of 0.7 to 2.0 mm. The shape of the particles is not particularly limited, but is preferably spherical or substantially spherical.

  The expandable thermoplastic resin particles of the present invention are composed of thermoplastic resin particles containing a foaming agent, and since the thermoplastic resin is a styrene-methacrylic acid-methyl methacrylate copolymer, it is excellent in heat resistance and high. Pre-expanded particles having a multiple of expansion can be obtained, and a foamed molded article having a light weight and sufficient mechanical strength can be produced.

(Method for producing foamable thermoplastic resin particles)
The method for producing the foamable thermoplastic resin particles of the present invention comprises melting a styrene-methacrylic acid-methyl methacrylate copolymer in a resin supply apparatus, press-fitting and kneading the foaming agent, It is characterized in that expandable thermoplastic resin particles are obtained by a melt extrusion method in which particles are formed by extruding from a small hole of a die attached to the tip of a resin supply device.
In this production method, the foaming agent-containing molten resin extruded from the small holes of the die may be immediately guided into water and cut, and directly formed into particles, or may be extruded into strands. A strand cut method may be employed in which the particles are cooled and cut after cooling to form particles.

  In the method for producing foamable thermoplastic resin particles of the present invention, a styrene-methacrylic acid-methyl methacrylate copolymer is melted in a resin supply apparatus, and a foaming agent is press-fitted and kneaded to obtain a foaming agent-containing molten resin. Extrude directly into the cooling liquid through a small hole in the die attached to the tip of the resin supply device, and at the same time extrude is cut with a high-speed rotary blade, and the extrudate is cooled and solidified by contact with the liquid. A method of obtaining plastic resin particles is more preferable.

  As a manufacturing method of styrene-methacrylic acid-methyl methacrylate copolymer which is a raw material resin, a radical polymerization method, more specifically, a radical polymerization method by a bulk polymerization method or a solution polymerization method, and the like can be given. The production of this copolymer preferably includes a polymerization step for polymerizing a polymerization raw material (monomer component) and a devolatilization step for removing volatile components such as unreacted monomers and polymerization solvent from the product. .

In the production of the copolymer, when the polymerization raw material is polymerized, a polymerization initiator is blended in the polymerization raw material composition. As this polymerization initiator, 2,2-bis (4,4-ditertiarybutylperoxycyclohexyl) propane, 2,2-bis (t-butylperoxy) butane, 2,2-bis (t-butylperoxy) Octane, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate , Di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α, α′-bis (t-butylperoxyisopropyl) benzene, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, diisopropyl peroxide Carbonate, 2-ethylhexyl peroxydi -Bonate, di-n-propyl peroxydicarbonate, t-butyl peroxyacetate, t-butyl peroxyisobutyrate, acetylacetone peroxide, methyl ethyl ketone peroxide, t-butyl hydroperoxide, cumene hydroperoxide, diisopropyl perbenzene hydroperoxide, etc. it can.
In the polymerization raw material composition, together with the polymerization initiator, chain transfer of n-dodecyl mercaptan, t-dodecyl mercaptan, α-methylstyrene linear dimer, n-octyl mercaptan, 1-phenyl-2-fluorene, dibenten and the like An agent may be added.

  Examples of the polymerization solvent added to the polymerization raw material composition include aromatic hydrocarbons such as toluene, xylene, ethylbenzene, dialkyl ketones and, for example, methyl ethyl ketone, each alone or in combination of two or more. Can be used.

A styrene-methacrylic acid-methyl methacrylate copolymer produced by a bulk polymerization method or a radical polymerization method by a solution polymerization method is put into a resin supply apparatus together with a desired additive such as an inorganic foam nucleating agent, and melt extrusion. Expandable thermoplastic resin particles are obtained by the method.
In addition, when adding the said aliphatic primary alcohol, you may add in the middle of manufacture of a styrene-methacrylic acid-methyl methacrylate copolymer, and you may throw in into a resin supply apparatus with this copolymer. .

  FIG. 1 is a configuration diagram showing an example of a production apparatus used in the method for producing expandable thermoplastic resin particles of the present invention. The production apparatus of this example includes an extruder 1 as a resin supply apparatus, and an extruder 1. A die 2 having a large number of small holes attached to the tip of the resin, a raw material supply hopper 3 for introducing a resin raw material or the like into the extruder 1, and a foaming agent through the foaming agent supply port 5 to the molten resin in the extruder 1. A high pressure pump 4 to be press-fitted, a cutting chamber 7 provided so that cooling water is brought into contact with a resin discharge surface in which a small hole of the die 2 is formed, and cooling water is circulated and supplied into the chamber; a small hole of the die 2 The cutter 6 is rotatably provided in the cutting chamber 7 so as to cut the resin extruded from the chamber, and the foaming thermoplastic resin particles carried along with the flow of the cooling water from the cutting chamber 7 are separated from the cooling water. And dehydrated and dried to foam A dehydration dryer 10 with a solid-liquid separation function for obtaining thermoplastic resin particles, a water tank 8 for storing cooling water separated by the dehydration dryer 10 with a solid-liquid separation function, and a cutting chamber 7 for cooling water in the water tank 8 And a storage container 11 for storing foamable thermoplastic resin particles dehydrated and dried by a dehydration dryer 10 having a solid-liquid separation function.

  As the extruder 1, either an extruder using a screw or an extruder not using a screw can be used. Examples of the extruder using a screw include a single-screw extruder, a multi-screw extruder, a vent-type extruder, and a tandem extruder. Examples of the extruder that does not use a screw include a plunger type extruder and a gear pump type extruder. Moreover, any extruder can use a static mixer. Among these extruders, an extruder using a screw is preferable from the viewpoint of productivity. Moreover, the conventionally well-known thing used in the granulation method by melt extrusion of resin can also be used for the cutting chamber 7 which accommodated the cutter 6. FIG.

  In order to produce foamable thermoplastic resin particles using the production apparatus shown in FIG. 1, first, desired additives such as the raw material styrene-methacrylic acid-methyl methacrylate copolymer and inorganic foam nucleating agent are added. Weigh and put into the extruder 1 from the raw material supply hopper 3. The raw polystyrene resin may be pelletized or granulated and mixed well in advance and then fed from one raw material supply hopper. For example, when multiple lots are used, the supply amount for each lot may be reduced. A plurality of adjusted raw material supply hoppers may be charged and mixed in an extruder.

  While supplying desired additives such as a styrene-methacrylic acid-methyl methacrylate copolymer and an inorganic foam nucleating agent into the extruder 1, the resin is heated and melted, and the molten resin is transferred to the die 2 side. The foaming agent is injected from the foaming agent supply port 5 by the high-pressure pump 4 to mix the foaming agent with the molten resin, and the melt is further kneaded through a foreign matter removing screen provided in the extruder 1 as necessary. It moves to the front end side, and the melted material to which the foaming agent is added is pushed out from the small hole of the die 2 attached to the front end of the extruder 1.

  The resin discharge surface in which the small holes of the die 2 are drilled is disposed in the cutting chamber 7 in which cooling water is circulated and supplied into the chamber, and the resin extruded from the small holes of the die 2 is placed in the cutting chamber 7. A cutter 6 is provided so as to be rotatable. Extruding the melt with the blowing agent added through a small hole in the die 2 attached to the tip of the extruder 1 causes the melt to be cut into granules, and at the same time, brought into contact with cooling water and rapidly cooled to solidify while suppressing foaming. Thus, expandable thermoplastic resin particles are obtained.

  The formed expandable thermoplastic resin particles are transferred from the cutting chamber 7 to the flow of cooling water and carried to the dehydrating dryer 10 with a solid-liquid separation function, where the expandable thermoplastic resin particles are separated from the cooling water. And dehydrated and dried. The dried foamable thermoplastic resin particles are stored in the storage container 11.

  The method for producing the foamable thermoplastic resin particles of the present invention comprises melting a styrene-methacrylic acid-methyl methacrylate copolymer in a resin supply apparatus, press-fitting and kneading the foaming agent, Expandable thermoplastic resin particles are obtained by a melt extrusion method in which particles are formed by extruding from a small hole in a die attached to the tip of the resin supply device, so that pre-expanded particles with excellent heat resistance and high expansion ratio can be obtained. It is possible to efficiently produce foamable thermoplastic resin particles that can be obtained and can produce a foamed molded article that is lightweight and has sufficient mechanical strength.

(Thermoplastic resin pre-expanded particles and thermoplastic resin foam molding)
The foamable thermoplastic resin particles of the present invention are pre-foamed by heating with steam or the like using a well-known apparatus and method in the field of foamed resin moldings, and are pre-foamed thermoplastic resin particles (hereinafter referred to as pre-foamed particles). ). The pre-expanded particles are pre-expanded so as to have a bulk density equivalent to the density of the foamed molded product to be manufactured. In the present invention, its bulk density is not limited, usually in the range of 0.010~0.10g / cm ^3, preferably in the range of 0.015~0.050g / cm ^3.

In the present invention, the bulk density of the pre-expanded particles refers to those measured in accordance with JIS K6911: 1995 “General Test Method for Thermosetting Plastics”.
<Bulk density of pre-expanded particles>
First, Wg was sampled from pre-expanded particles as a measurement sample, this measurement sample was naturally dropped into a graduated cylinder, and the volume Vcm ³ of the measurement sample dropped into the graduated cylinder was measured using an apparent density measuring instrument based on JIS K6911. The bulk density of the pre-expanded particles is measured based on the following formula.
Bulk density (g / cm ³ ) = mass of measurement sample (W) / volume of measurement sample (V)

<Bulk expansion ratio of pre-expanded particles>
Moreover, the bulk expansion ratio of the pre-expanded particles is a numerical value calculated by the following equation.
Bulk foaming factor = 1 / bulk density (g / cm ³ )

The pre-expanded particles are filled in a cavity of a mold using a well-known apparatus and method in the field of manufacturing a foamed resin molded body, heated by steam heating or the like, and subjected to in-mold foam molding, A plastic resin foam molded article (hereinafter referred to as a foam molded article) is produced.
Although the density of the foamed molded article of the present invention is not particularly limited, usually in the range of 0.010~0.10g / cm ^3, preferably in the range of 0.015~0.050g / cm ^3.

In the present invention, the density of the foamed molded product refers to the density of the foamed molded product measured by the method described in JIS K7122: 1999 “Measurement of foamed plastic and rubber-apparent density”.
<Density of foam molding>
A test piece of 50 cm ³ or more (100 cm ³ or more in the case of semi-rigid and soft materials) was cut so as not to change the original cell structure of the material, its mass was measured, and calculated by the following formula.
Density (g / cm ³ ) = Test piece mass (g) / Test piece volume (cm ³ )
Test specimen condition adjustment and measurement specimens were cut from a sample that had passed 72 hours or more after molding, and were subjected to atmospheric conditions of 23 ° C ± 2 ° C x 50% ± 5% or 27 ° C ± 2 ° C x 65% ± 5%. It has been left for more than an hour.

<Folding multiple of foamed molded product>
Further, the expansion factor of the foamed molded product is a numerical value calculated by the following equation.
Foaming factor = 1 / density (g / cm ³ )

  The foamed molded article of the present invention is obtained by heating and foaming the expandable thermoplastic resin particles according to the present invention described above, and the resulting pre-foamed particles are obtained by in-mold foam molding. You can get a body. In addition, a foamed molded article that is lightweight and excellent in mechanical strength such as bending strength can be obtained.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention in detail, this invention is not necessarily limited to these Examples. In addition, the analysis and evaluation methods for the resin, the expandable resin particles, and the like in Examples and Comparative Examples are as follows.

[Properties of resin]
(1) Heat loss method The mass of the foamable thermoplastic resin particles was set to A (g), wrapped in an aluminum foil and weighed again, and this was set to B (g). It heat-processed for 1 hour in 145 degreeC oven, and the gas in this particle | grain was blown completely. After that, it is allowed to stand for 10 minutes with a desiccator to adsorb the gas component adhering to the resin surface from which gas has been released, and the resin from which gas has been released is weighed again in an aluminum foil, and this is measured as C (g) And the amount of residual gas remaining in the expandable particles was calculated by the following formula.
Residual gas amount (%) = (B (g) −C (g)) / A (g) × 100
The resin from which the gas was completely removed was used as a measurement resin sample for the following measurement items (2) to (5).

(2) Content of each monomer unit of styrene, methacrylic acid and methyl methacrylate The resin composition was quantified from the integral ratio of the spectrum measured with a proton nuclear magnetic resonance ( ₁ H-NMR) measuring machine.
Sample preparation: 30 mg of a resin sample was dissolved in 0.75 mL of d6-DMSO by heating at 60 ° C. for 4 to 6 hours.
Measuring instrument: JNMECA-500, manufactured by JEOL Ltd.
Measurement conditions: Measurement temperature 25 ° C., observation nucleus 1H, integration number 64 times, repetition time 11 seconds, spectrum assignment: spectrum assignment measured in dimethyl sulfoxide heavy solvent has a peak of 0.5 to 1.5 ppm. Α-methyl group hydrogen of methacrylic acid, methyl methacrylate and 6-membered cyclic acid anhydride, peak of 1.6 to 2.1 ppm is hydrogen of methylene group of polymer main chain, peak of 3.5 ppm is methyl methacrylate The hydrogen of the carboxylic acid ester (—COOCH ₃ ), the peak at 12.4 ppm is the hydrogen of the carboxylic acid of methacrylic acid. The peak at 6.5 to 7.5 ppm is hydrogen in the aromatic ring of styrene.

(3) Measurement of Vicat softening temperature It measured based on ISO306. The load was 49N.

(4) Styrene dimer (dimer) and trimer (trimer) when the total content of styrene monomer units, methacrylic acid monomer units, and methyl methacrylate monomer units is 100% by mass Preparation of measurement sample of residual amount: 0.2 g of resin sample is weighed, 0.2 g of this resin is dissolved in 10 mL of methyl ethyl ketone, and dropped into 40 mL of methanol for reprecipitation. Next, 1 mL of an internal standard solution (a solution obtained by dissolving 0.2 g of Eicosane in 100 mL of methyl ethyl ketone) was added to a 50 mL eggplant flask, and the reprecipitation liquid was No. 1 Filter with 5A filter paper and make up to the internal standard solution. This was measured by GC / MC (manufactured by Shimadzu Corporation, trade name GC17A), and the area of five dimer peaks in the column chromatogram and the relative sensitivity of the internal standard substance were measured to be the same. Confirmation of dimer and trimer peaks was performed using a standard substance manufactured by Kanto Chemical.
Apparatus: Product name GC17A manufactured by Shimadzu Corporation
Column: Product name DB-1 (manufactured by J & W, 0.25 mmφ × 30 m, membrane pressure 0.1 μm)
Inlet temperature: 240 ° C
Detector (FID) temperature: 260 ° C
Carrier gas (He): Pressure 80 psi
Column temperature: 40 ° C. (1 minute) to 50 ° C./minute to 150 ° C. (1 minute) to 5 ° C./minute to 250 ° C. (3 minutes) to 50 ° C./minute to 320 ° C. (8 minutes)
The amount of oligomer was the sum of styrene dimer and trimer.

(5) Measurement sample preparation of the content of the styrene monomer when the total content of the styrene monomer unit, the methacrylic acid monomer unit, and the methyl methacrylate monomer unit is 100% by mass: resin sample Weigh precisely 1 g, add 1 mL of dimethylformamide solution containing 0.1% by volume of cyclopentanol as an internal standard solution to 1 g of this resin, and then add dimethylformamide to prepare a 25 mL measurement solution. did. And 1.8 microliters of this measurement solution was supplied to the gas chromatograph (Shimadzu Corporation make, brand name "GC-14A"), and it measured on the following measurement conditions, and obtained the chart of the compound in a measurement solution. And based on the calibration curve of the styrene monomer measured in advance, the amount of styrene monomer (ppm) remaining in the resin is calculated by calculating the amount of styrene monomer in the measurement solution. did.
Detector: FID
Column: manufactured by GL Sciences Inc. (inner diameter 3 mm × length 2.5 m)
Liquid phase (PEG-20M PT 25%)
Carrier (Chromosorb W AW-DWCS)
Mesh: 60/80
Column temperature: 100 ° C
DET temperature: 230 ° C
Detector temperature: 230 ° C
Carrier gas: Nitrogen Carrier gas flow rate: 40ml / min

(6) Preparation of measurement sample of weight average molecular weight and Z average molecular weight: A resin sample was dissolved in tetrahydrofuran so as to be about 0.05% by mass.
Measurement condition equipment: TOSHOHHLC-8220GPC
(Gel permeation chromatography)
Column: super HZM-H
Temperature: 40 ° C
Carrier: THF 0.35 mL / min
Detector: RI, UV: 254 nm
Calibration curve: Standard PS made by TOSOH

(7) Preparation of measurement sample of aliphatic primary alcohol in resin: Expandable particles A (g) containing 0.5 g of resin calculated by the following formula were dissolved in 20 mL of methyl ethyl ketone and measured under the following measurement conditions. .
Amount of foaming resin added: A (g)
= Resin 0.5g / [1- [Residual gas amount calculated by (1) (%)] / 100]
Measurement condition equipment: Shimadzu Corporation gas chromatography GC2010
Column: DB-WAX 30 m, 0.25 mmφ, df = 0.5 μm
Temperature: 100 ° C. → 5 ° C./min→130° C. → 10 ° C./min→180° C.-12 min → 20 ° C./min→220° C.-20 min

(8) Evaluation of foamability by prefoaming The foamable thermoplastic resin particles were allowed to stand for 72 hours in a 15 ° C. cool box and then supplied to a cylindrical batch prefoaming machine. The number of seconds required for heating with water vapor to reach 40 times the bulk foaming ratio is measured, and the following evaluation criteria:
120 seconds or more: Defect (x)
100 seconds or more and less than 110 seconds: Somewhat bad (△)
90 seconds or more, less than 100 diseases: Good (○)
Less than 90 seconds: Particularly good (◎)
Was evaluated for foamability.

(9) Manufacture of foam molded article The foamable thermoplastic resin particles are allowed to stand for 72 hours in a 15 ° C cool box, and then supplied to a cylindrical batch type pre-foaming machine. Pre-expanded particles having a bulk expansion ratio of 40 times were obtained by heating with water vapor. Subsequently, the pre-expanded particles obtained were allowed to stand for 24 hours in a room temperature atmosphere, and after filling the pre-expanded particles in a mold having a rectangular parallelepiped cavity of 400 mm × 300 mm × 25 mm, the mold The inside of the cavity was heated with water vapor at a gauge pressure of 0.9 MPa for 20 seconds, and then cooled until the pressure in the cavity of the mold became 0.15 MPa. A 300 mm × 25 mm rectangular foam molded body was obtained. The density of the obtained foamed molded product was 0.028 g / cm ³ .

(10) Evaluation of flexural strength of foamed molded product The flexural strength of the foamed molded products obtained in the examples (and comparative examples) was measured according to the method described in JIS A9511: 2006 “Foamed plastic heat insulating material”.
That is, using a Tensilon universal testing machine UCT-10T (manufactured by Orientec Co., Ltd.), the specimen size is 75 mm × 300 mm × 25 mm, the compression speed is 10 mm / min, the tip jig is a pressure wedge 10R, and a support base 10R. Measurement was performed under the condition of a distance between supporting points of 200 mm, and the bending strength was calculated by the following formula. The number of test pieces was three, and the average value was obtained.
Bending strength (MPa) = 3FL / 2bh ²
[Where F represents the maximum bending load (N), L represents the distance between supporting points (mm), b represents the width (mm) of the test piece, and h represents the thickness (mm) of the test piece. ]
In this way, the average value of the bending strength is obtained, and the following evaluation criteria:
Bending strength is 0.38 MPa or more: particularly good (◎),
Bending strength is 0.36 MPa or more and less than 0.38 MPa: good (◯),
Bending strength is 0.35 MPa or more and less than 0.36 MPa: Somewhat poor (Δ),
Bending strength is less than 0.35 MPa: defective (x)
In light of the above, the strength was evaluated.

(11) Evaluation of heat resistance (change in heating dimensions)
A flat foam molded body having a length of 400 mm, a width of 300 mm, and a thickness of 25 mm was taken out of the mold, and left in a constant temperature and humidity chamber (standard temperature and humidity state of JIS-K7100) at a temperature of 23 ° C. and a relative humidity of 50% for 24 hours. Thereafter, a flat plate (length 150 mm, width 150 mm, thickness 25 mm) whose upper and lower surfaces are parallel is cut out from the central portion of the foamed molded body, and three straight lines are parallel to each other in the vertical and horizontal directions at the central portion. The test piece according to JIS-K 6767 was formed so that the distance was 50 mm. After measuring the dimensions of this test piece (dimension before heating: L1), place it horizontally in a hot-air circulating drier kept at 100 ° C., take it out after heating for 168 hours, and leave it in a constant temperature and humidity room for 1 hour again. Then, the dimension of the test piece (dimension after heating: L2) was measured. The dimensional measurement before and after the heating test was performed according to JIS-K6767, and the dimensional change rate was determined according to the following equation.
Dimensional change rate (%) = (L2-L1) × 100 / L1
(However, L1 is the size of a test piece obtained from a foamed molded product that was allowed to stand for 24 hours at 23 ° C. and 50% relative humidity after molding in the mold, and L2 is the value after heating the molded product at 100 ° C. for 168 hours. It is the size of the test piece)
In addition, a dimension is the average value of the length of three straight lines each written in the test piece obtained from the foaming molding.

[Example 1]
(Production of styrene-methacrylic acid-methyl methacrylate copolymer)
76.9 parts by mass of styrene, 5.4 parts by mass of methacrylic acid, 2.7 parts by mass of methyl methacrylate, 15.0 parts by mass of ethylbenzene as a polymerization solvent, and 2,2-bis (4,4-ditertiary as a polymerization initiator A polymerization raw material composition solution comprising 0.02 part by weight of butylperoxycyclohexyl) propane is supplied from a fully mixed reactor having a capacity of 4 liters at a rate of 1.2 liters / hour and then from a 2 liter laminar flow reactor. Then, the copolymer was prepared by successively supplying the polymerizer continuously with a devolatilizer connected to a single-screw extruder for removing volatile components such as unreacted monomers and polymerization solvent. The polymerization reaction conditions in the polymerization step were a polymerization temperature of 122 to 130 ° C. for the complete mixing reactor and a temperature of 125 to 145 ° C. for the laminar flow reactor. The devolatilized unreacted gas was condensed by a condenser through which a refrigerant of -5 ° C was passed, and recovered as an unreacted liquid. The polymer content in the final polymerization solution was measured by (sample weight after drying / sample weight before drying × 100%) after drying the polymer solution at 215 ° C. under a reduced pressure of 3 kPa for 30 minutes. %Met. Resin pellets obtained by extruding the final polymerization liquid into pellets are put into a short-shaft extruder and kneaded with an aliphatic primary alcohol of the type shown in Table 1 to obtain a styrene-methacrylic acid-methyl methacrylate copolymer. Obtained. The alcohol content (% by mass) in the resin shown in Table 1 was quantified by gas chromatography. The product name “Fine Oxocol 180” manufactured by Nissan Chemical Co., Ltd. was used as the isoaliphatic primary alcohol in Table 1.

(Manufacture of foamable thermoplastic resin particles)
160 kg per hour is obtained by uniformly mixing 0.3 parts by mass of fine powder talc in advance with a tumbler mixer with respect to 100 parts by mass of a thermoplastic resin composed of a copolymer kneaded with the aliphatic primary alcohol. After feeding into a single-screw extruder having a diameter of 90 mm at a rate of / hr and heating and melting the resin, 6 parts by weight of pentane (isopentane / normal pentane = 20/80 as a blowing agent with respect to 100 parts by weight of the resin) The mixture was pressed from the middle of the extruder. Then, while kneading the resin and the foaming agent in the extruder, while cooling so that the resin temperature at the tip of the extruder is 190 ° C., it is connected to the extruder and held at 320 ° C. by a heater, diameter 0.6 mm Then, through a granulation die having 200 nozzles with a land length of 3.0 mm, it is extruded into a chamber in which cooling water at 50 ° C. circulates, and at the same time, a high-speed rotary cutter having 10 blades in the circumferential direction is used as a die. Adhered, cut at 3000 rpm, dehydrated and dried to obtain spherical foamable thermoplastic resin particles.

Each measurement and evaluation mentioned above were performed about the obtained expandable thermoplastic resin particle, the pre-expanded particle obtained from this resin particle, and the foaming molding. The results are shown in Table 1.
The composition ratio of each monomer unit in the resin of the expandable thermoplastic resin particles obtained in Example 1 was 82.1% by mass of the styrene (ST) monomer unit, and methacrylic acid (MAA) unit. The monomer unit was 11.9% by mass, and the methyl methacrylate (MMA) monomer unit was 6.0% by mass.

[Example 2]
The blending amount of each monomer is such that the composition ratio of each monomer unit in the resin of the obtained foamable thermoplastic resin particles is 81.9% by mass of a styrene (ST) monomer unit, methacrylic acid (MAA ) The monomer unit was changed to 8.2% by mass, and the methyl methacrylate (MMA) monomer unit was changed to 9.9% by mass. Otherwise, the expandable thermoplastic resin particles were obtained in the same manner as in Example 1. The foamed thermoplastic resin particles produced and obtained, the pre-foamed particles obtained from the resin particles, and the foamed molded article were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Example 3]
The blending amount of each monomer is such that the composition ratio of each monomer unit in the resin of the obtained foamable thermoplastic resin particles is 88.8% by mass of a styrene (ST) monomer unit, methacrylic acid (MAA) The foamed thermoplastic resin particles were changed in the same manner as in Example 1 except that the monomer unit was 6.0% by mass and the methyl methacrylate (MMA) monomer unit was 3.1% by mass. The foamed thermoplastic resin particles produced and obtained, the pre-foamed particles obtained from the resin particles, and the foamed molded article were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Example 4]
The blending amount of each monomer is such that the composition ratio of each monomer unit in the resin of the obtained foamable thermoplastic resin particles is 71.8% by mass of styrene (ST) monomer unit, methacrylic acid (MAA ) The monomer unit was changed to 13.7% by mass and the methyl methacrylate (MMA) monomer unit was 14.5% by mass. Otherwise, the expandable thermoplastic resin particles were obtained in the same manner as in Example 1. The foamed thermoplastic resin particles produced and obtained, the pre-foamed particles obtained from the resin particles, and the foamed molded article were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Example 5]
The blending amount of each monomer is such that the composition ratio of each monomer unit in the resin of the obtained foamable thermoplastic resin particles is 81.9% by mass of a styrene (ST) monomer unit, methacrylic acid (MAA ) The monomer unit was changed to 8.2% by mass, and the methyl methacrylate (MMA) monomer unit was changed to 9.9% by mass. Otherwise, the expandable thermoplastic resin particles were obtained in the same manner as in Example 1. The foamed thermoplastic resin particles produced and obtained, the pre-foamed particles obtained from the resin particles, and the foamed molded article were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.
The expandable thermoplastic resin particles produced in Example 5 had the same composition ratio of each monomer unit in the resin as that of Example 2, but the obtained resin had Mz / Mw of It was different.

[Example 6]
The blending amount of each monomer is such that the composition ratio of each monomer unit in the resin of the obtained foamable thermoplastic resin particles is 85.9% by mass of a styrene (ST) monomer unit, methacrylic acid (MAA ) The monomer unit was changed to 8.1% by mass and the methyl methacrylate (MMA) monomer unit to 6.0% by mass. The foamed thermoplastic resin particles produced and obtained, the pre-foamed particles obtained from the resin particles, and the foamed molded article were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Example 7]
The blending amount of each monomer is such that the composition ratio of each monomer unit in the resin of the obtained foamable thermoplastic resin particles is 85.8% by mass of a styrene (ST) monomer unit, methacrylic acid (MAA) ) Monomer unit 8.1% by mass, methyl methacrylate (MMA) monomer unit 6.1% by mass, and 2-ethylhexyl alcohol (carbon number) instead of iso fatty acid primary alcohol 8), and other than that, expandable thermoplastic resin particles were produced in the same manner as in Example 1, and the obtained expandable thermoplastic resin particles, and pre-expanded particles and foamed molded products obtained from the resin particles were obtained. The above measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[Example 8]
The blending amount of each monomer is such that the composition ratio of each monomer unit in the resin of the obtained foamable thermoplastic resin particles is 85.8% by mass of a styrene (ST) monomer unit, methacrylic acid (MAA) ) The monomer unit was changed to 8.1% by mass and the methyl methacrylate (MMA) monomer unit was 16.5% by mass. Otherwise, the foamable thermoplastic resin particles were prepared in the same manner as in Example 1. The foamed thermoplastic resin particles produced and obtained, the pre-foamed particles obtained from the resin particles, and the foamed molded article were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
Instead of the copolymer in Example 1, a heat-resistant polystyrene resin (manufactured by Toyo Styrene Co., Ltd., styrene-methacrylic acid copolymer, trade name “T-080”) and polystyrene resin (manufactured by Toyo Styrene Co., Ltd., polystyrene, commodity The thermoplastic resin which mix | blended name "HRM-10N" by mass ratio 40:60 was used. A mixture obtained by uniformly mixing 0.31 part by mass of stearic acid monoglyceride in advance with a tumbler mixer with respect to 100 parts by mass of this thermoplastic resin was supplied into a single screw extruder. Thereafter, production of foamable thermoplastic resin particles by melt extrusion, pre-foaming and production of a foamed molded article were carried out in the same manner as in Example 1, and each measurement and evaluation was carried out in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
Without using methacrylic acid, the composition ratio of each monomer unit in the resin of the obtained foamable thermoplastic resin particles is the same as the styrene (ST) monomer unit 93.6. The foamable thermoplastic resin particles were produced in the same manner as in Example 1 except that the content was changed to be mass%, and methyl methacrylate (MMA) monomer unit was 6.4 mass%. The thermoplastic resin particles, the pre-foamed particles obtained from the resin particles, and the foamed molded article were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

  From the results of Table 1, the expandable thermoplastic resin particles produced in Examples 1 to 8 using a styrene-methacrylic acid-methyl methacrylate copolymer as the thermoplastic resin have good foamability at the time of preliminary foaming. The resulting foamed molded article had high bending strength and excellent heat resistance.

On the other hand, in Comparative Example 1 using a thermoplastic resin containing a styrene-methacrylic acid copolymer without using methyl methacrylate (MMA), the bending strength of the obtained foamed molded product was low.
Moreover, the comparative example 2 which did not use methacrylic acid (MAA), and used the thermoplastic resin containing a styrene-methyl methacrylate copolymer, the bending strength of the obtained foaming molding became low.

  TECHNICAL FIELD The present invention relates to expandable thermoplastic resin particles, pre-expanded particles, and a foam-molded product using a thermoplastic resin mainly composed of a styrene-methacrylic acid-methyl methacrylate copolymer having excellent heat resistance and mechanical strength. .

  DESCRIPTION OF SYMBOLS 1 ... Extruder (resin supply apparatus), 2 ... Die, 3 ... Raw material supply hopper, 4 ... High pressure pump, 5 ... Foam supply port, 6 ... Cutter, 7 ... Cutting chamber, 8 ... Water tank, 9 ... High pressure pump, 10: Dehydration dryer with solid-liquid separation function, 11: Storage container.

Claims (15)

Expandable thermoplastic resin particles comprising thermoplastic resin particles containing a foaming agent,
Expandable thermoplastic resin particles, wherein the thermoplastic resin is a styrene-methacrylic acid-methyl methacrylate copolymer.   The copolymer has a methyl methacrylate monomer unit content when the total content of the styrene monomer unit, the methacrylic acid monomer unit, and the methyl methacrylate monomer unit is 100% by mass. The expandable thermoplastic resin particles according to claim 1, wherein is in the range of 2 to 20% by mass.   The copolymer has a methyl methacrylate monomer unit content when the total content of the styrene monomer unit, the methacrylic acid monomer unit, and the methyl methacrylate monomer unit is 100% by mass. The foamable thermoplastic resin particles according to claim 1 or 2, wherein the content is in the range of 5 to 10 mass%.   The residual amount of styrene dimer and trimer in the thermoplastic resin is 0.6% by mass, and the residual amount of styrene monomer is 700 ppm or less in the thermoplastic resin. The expandable thermoplastic resin particle according to any one of the above items.   The thermoplastic resin has a weight average molecular weight (Mw) in the range of 100,000 to 350,000, and a ratio (Mz / Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) of 1.6 to The expandable thermoplastic resin particles according to any one of claims 1 to 4, which are within a range of 3.5.   The foamable thermoplastic resin according to any one of claims 1 to 4, wherein the thermoplastic resin contains an aliphatic primary alcohol having 14 or more carbon atoms in a range of 0.02 to 1.0 mass%. particle.   Styrene-methacrylic acid-methyl methacrylate copolymer is melted in a resin supply device and a foaming agent is press-fitted and kneaded, and the molten resin containing the foaming agent is extruded from a small hole in a die attached to the tip of the resin supply device. A foamable thermoplastic resin particle production method, comprising: obtaining foamable thermoplastic resin particles by a melt extrusion method to form particles.   Styrene-methacrylic acid-methyl methacrylate copolymer is melted in a resin supply device, and a foaming agent is press-fitted and kneaded, and the molten resin containing the foaming agent is directly from the small hole of the die attached to the tip of the resin supply device. Foaming thermoplastic, characterized by extruding into a cooling liquid, cutting the extrudate with a high-speed rotating blade at the same time as extrusion, and cooling and solidifying the extrudate by contact with the liquid to obtain expandable thermoplastic resin particles A method for producing resin particles.   The copolymer has a methyl methacrylate monomer unit content when the total content of the styrene monomer unit, the methacrylic acid monomer unit, and the methyl methacrylate monomer unit is 100% by mass. The method for producing expandable thermoplastic resin particles according to claim 7 or 8, wherein is in the range of 2 to 20% by mass.   The copolymer has a methyl methacrylate monomer unit content when the total content of the styrene monomer unit, the methacrylic acid monomer unit, and the methyl methacrylate monomer unit is 100% by mass. The method for producing expandable thermoplastic resin particles according to any one of claims 7 to 9, wherein is in the range of 5 to 10% by mass.   The residual amount of styrene dimer and trimer in the thermoplastic resin is 0.6 mass%, and the residual amount of styrene monomer is 700 ppm or less in the thermoplastic resin. The manufacturing method of the foamable thermoplastic resin particle of any one of Claims 1.   The thermoplastic resin has a weight average molecular weight (Mw) in the range of 100,000 to 350,000, and a ratio (Mz / Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) of 1.6 to It is in the range of 3.5, The manufacturing method of the expandable thermoplastic resin particle of any one of Claims 7-11.   The foamable thermoplastic resin according to any one of claims 7 to 12, wherein the thermoplastic resin contains an aliphatic primary alcohol having 14 or more carbon atoms in a range of 0.02 to 1.0 mass%. Particle production method.   Thermoplastic resin pre-expanded particles obtained by heating and foaming the expandable thermoplastic resin particles according to any one of claims 1 to 6.   A thermoplastic resin foam molded article obtained by filling the thermoplastic resin pre-foamed particles according to claim 14 into a cavity of a molding die and heating and molding in-mold foam molding.

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