JP2012207097A - Foamed molding and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foamed molding excellent in compressive elasticity modulus.SOLUTION: There is provided the foamed molding comprising a fusion bonded product of plural foamed resin particles containing (A) a polystyrene-based resin ingredient and (B) a copolymer ingredient of a monomer having an ester group and 3-10 vinyl groups in a molecule and a styrene-based monomer, wherein the absorbance ratio (D/D) at 1,735 cmand 1,600 cmobtained from an infrared absorption spectrum near the fusion interface of the foamed resin particles, measured by infrared spectroscopic analysis of the ATR method, is within a range of 0.06-0.25, the z average molecular weight of the foamed resin particle surface is 900,000-2,000,000, the density is 0.010-0.100 g/cm, and the compressive elasticity modulus is ≥1,000 KPa.

Description

  The present invention relates to a foam molded article and a method for producing the same. More specifically, the present invention relates to a foamed molded article excellent in compression modulus and a method for producing the same.

Conventionally, it is known to use a foam-molded body as a heat insulating structure for buildings.
For example, floor insulation structures, wall insulation structures, and the like are used as insulation structures for wooden buildings. Specifically, Japanese Patent Application Laid-Open No. 2004-36089 discloses that as a conventional floor heat insulating structure, a heat insulating material made of a flat foam molded body such as a foam resin board can be used between joists.

JP 2004-36089 A

  However, the foam molded body used between the joists like the floor heat insulating structure has a problem that it is easily bent. In order to solve this problem, there is a demand for a foam molded article having high strength.

Moreover, as a foaming molding which comprises a floor heat insulating material, the weight reduction for improving workability | operativity other than intensity | strength is calculated | required. This weight reduction can be realized by increasing the foaming ratio of the foamed molded product, but the strength decreases when the foaming ratio is increased. In order to suppress the decrease in strength, the foamed molded product is placed between non-foamed structures. There is a way to insert. In this case, in order to prevent the dent of the heat insulating material or the like when walking on the heat insulating material, there is a demand for a foamed molded article having high compression characteristics, mainly a high compression elastic modulus.

The inventors of the present invention reviewed the presence of the resin component in the plurality of foamed resin particles fused to each other constituting the foam molded body in order to improve the compression modulus of the foam molded body. As a result, the content ratio of the copolymer component of the styrene monomer in the expanded resin particles and the monomer having an ester group and 3 to 10 vinyl groups in the molecule is 0.1 to 50% by mass. And the absorbance ratio (D ₁₇₃₅ / D ₁₆₀₀ ) in the vicinity of the fused interface of the expanded resin particles is in the range of 0.06 to 0.25 (in other words, the copolymer component is unevenly distributed in the vicinity of the interface of the expanded resin particles. ), It was found that an excellent compression elastic modulus can be obtained with the foamed molded article composed of the expanded resin particles, and the present invention has been achieved.

Thus, according to the present invention, a polystyrene resin component (A), a copolymer component (B) of a monomer having an ester group, 3 to 10 vinyl groups in the molecule, and a styrene monomer. A foamed molded article comprising a fusion product of a plurality of foamed resin particles,
Absorbance ratio at 1735 cm ^-1 and 1600 cm ^-1 obtained from an infrared absorption spectrum around fusing interface of said measured foamed resin particles by ATR method infrared spectroscopy (D ₁₇₃₅ / D ₁₆₀₀₎ is 0.06 to 0 .25 range,
The z-average molecular weight of the surface of the foamed resin particles is 900,000 to 2,000,000,
There is provided a foamed molded article having a density of 0.010 to 0.100 g / cm ³ and a compression modulus of 1000 KPa or more.

Further, according to the present invention, there is provided a method for producing the above foam molded article,
A step of allowing a seed particle containing a polystyrene resin to absorb a monomer having an ester group and 3 to 10 vinyl groups in the molecule and a styrene monomer;
A step of obtaining resin particles by copolymerizing an ester group and a monomer having 3 to 10 vinyl groups and a styrene monomer in or after absorption,
A step of impregnating resin particles with a foaming agent to obtain expandable resin particles;
Pre-foaming expandable resin particles, and then foam-molding by foam-molding,
Absorption of a monomer having an ester group, 3 to 10 vinyl groups and a styrene monomer in the molecule is performed under a polymerization conversion of 70 to 85% styrene monomer. A method for producing a foamed molded product is provided.

ADVANTAGE OF THE INVENTION According to this invention, the foaming molding excellent in the compression elastic modulus and its manufacturing method can be provided. The foamed molded product of the present invention is particularly useful as a foamed molded product for floor insulation. The inventors consider that this effect is exhibited by the fact that the copolymer component is unevenly distributed in the vicinity of the fusion interface of the foamed resin particles in the fusion product constituting the foamed molded product.
Furthermore, the slope of the correlation equation with the log (RMS radius) measured by the GPC / MALLS method on the surface of the foamed resin particle as the y axis and the log (Mw) as the x axis is 0.55 or less. In this case, it is possible to provide a foamed molded article having more excellent compression modulus and moldability.

Moreover, when it is the copolymerization component of the monomer selected from a (meth) acrylate type monomer, and a styrene-type monomer, the foaming molding which was more excellent in the compression elastic modulus can be provided.
Furthermore, the (meth) acrylate monomer is trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane trimethacrylate, ethoxylated isocyanuric acid triacrylate, tetramethylolmethane tetraacrylate, ditrimethylolpropane tetraacrylate. And when it is a monomer selected from dipentaerythritol hexaacrylate, it is possible to provide a foamed molded article having a more excellent compression modulus.

It is a graph which shows the light absorbency ratio of the melt | fusion interface of the foamed resin particle which comprises a foaming molding.

(Foamed molded product)
The foamed molded article of the present invention comprises a polystyrene resin component (A), a copolymer component (B) of a monomer having an ester group and 3 to 10 vinyl groups in the molecule, and a styrene monomer. It consists of the fusion | melting body of the several foamed resin particle which contains as base resin.
(1) Polystyrene resin component (A)
The polystyrene resin component is not particularly limited. For example, a homopolymer of a styrene monomer such as styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, bromostyrene, or the like The component derived from these copolymers etc. is mentioned.
Moreover, as a polystyrene-type resin component, the component derived from the copolymer of the said styrene-type monomer and the vinyl monomer copolymerizable with this styrene-type monomer may be sufficient. Examples of such vinyl monomers include alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and cetyl (meth) acrylate, (meth) acrylonitrile, and dimethyl maleate. And monofunctional monomers such as acrylate, dimethyl fumarate, diethyl fumarate and ethyl fumarate, and bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate.
Of the polystyrene resin components, a polystyrene resin component is more preferable.

(2) A copolymer component of a monomer having an ester group and 3 to 10 vinyl groups in the molecule and a styrene monomer (B)
The monomer having an ester group and 3 to 10 vinyl groups in the molecule is not particularly limited as long as it is a monomer that can give an excellent compression elastic modulus to the foam molded article. For example, the monomer selected from a (meth) acrylate type monomer is mentioned.
Examples of (meth) acrylate monomers include trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane trimethacrylate, ethoxylated isocyanuric acid triacrylate, tetramethylolmethane tetraacrylate, ditrimethylolpropane tetraacrylate, Examples include dipentaerythritol hexaacrylate.
As the styrene monomer, any of the monomers listed in the above item (1) can be used.

(3) Presence state of the copolymer component of the monomer having an ester group and 3 to 10 vinyl groups in the molecule and the styrene monomer The existence state is foaming measured by ATR infrared spectroscopy. It can be inferred from the absorbance ratio at 1735 cm ^-1 and 1600 cm ^-1 obtained from an infrared absorption spectrum of the resin particles (D ₁₇₃₅ / D _1600). Here, the absorption at 1735 cm ⁻¹ indicates a peak derived from an ester group contained in a monomer having 3 to 10 vinyl groups in the molecule, indicating the presence of a copolymer component. The absorption at 1600 cm ⁻¹ indicates the presence of a peak derived from the in-plane vibration of the benzene ring contained in the polystyrene resin.

  In the foamed molded product of the present invention, the absorbance ratio near the fusion interface of the foamed resin particles constituting the foamed molded product is in the range of 0.06 to 0.25. The absorbance ratio in this range means that the copolymer component is present in the vicinity of the surface of the foamed resin particle by 60% by mass or more. When the absorbance ratio is less than 0.06, since the copolymer component is very small, the effect of improving the compression modulus is not observed. When more than 0.25, a copolymer component increases and the foam moldability of a foaming molding may fall. A more preferable range of the absorbance ratio is 0.07 to 0.23. In this specification, the interface means a contact surface between two adjacent foamed resin particles fused together, and the vicinity of the interface means a region from the interface to 100 μm toward the particle center.

Furthermore, the absorbance ratio (D ₁₇₃₅ / D ₁₆₀₀ ) near the center of the foamed resin particles is preferably 0.05 or less. It can be understood that the resin component is unevenly distributed in the vicinity of the interface of the foamed resin particles because the foamed resin particles have the vicinity of the center of the absorbance ratio lower than that in the vicinity of the interface. A more preferable absorbance ratio near the center is 0.04 or less. In the present specification, the vicinity of the center means a region from the center of the foamed resin particle to 100 μm.

Further, the copolymer component is present in the foamed resin particles so that the z-average molecular weight (Mz1) on the surface of the foamed resin particles is 900,000 to 2,000,000.
As understood from the above numerical range, the foamed resin particles preferably have a copolymer component unevenly distributed on the surface and a z-average molecular weight in a specific range.
When the z-average molecular weight at the interface of the expanded resin particles is less than 900,000, a sufficient compression modulus may not be obtained. On the other hand, if it is larger than 2 million, moldability, particularly heat fusion between the pre-expanded particles may be lowered. A more preferable z-average molecular weight is 900,000 to 1,700,000.
Here, it is preferable that the z-average molecular weight (Mz2) of the entire foamed molded product is also in a specific range. For example, it can be in the range of 500,000 to 1.1 million. Furthermore, it is preferable to set Mz1 / Mz2 to a specific range, specifically, a range of 1.5 to 2.0. By adjusting the z-average molecular weight, it is possible to obtain a foamed molded article having an excellent compression modulus.

  The copolymer component has a slope of a correlation equation with the log (RMS radius) measured by the GPC / MALLS method on the surface of the foamed resin particles as the y axis and the log (Mw) as the x axis. Preferably it is present to be .55 or less. If it exceeds 0.55, the moldability, particularly the thermal fusion between the foamed resin particles is lowered, and a sufficient compression elastic modulus cannot be obtained. A preferable range is 0.53 or less. The lower limit of the slope is preferably 0.40.

(4) Other resins The foamed molded product may contain other resins as necessary and within a range not impairing the effects of the present application.
Examples of other resins include polyolefin resins such as polyethylene and polypropylene, polycarbonate resins, and polyesters.

(5) Additives In the foamed molded product, flame retardants, flame retardant aids, plasticizers, lubricants, anti-binding agents, fusion accelerators, antistatic agents, spreading agents, and bubbles are within the range that does not impair the physical properties. Additives such as a regulator, a crosslinking agent, a filler, a colorant, and an infrared shielding agent may be included.
As flame retardants, tetrabromocyclooctane, hexabromocyclododecane, trisdibromopropyl phosphate, tetrabromobisphenol A, tetrabromobisphenol A-bis (2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol A- Examples of the flame retardant include bis (2,3-dibromopropyl ether).
Examples of the flame retardant aid include organic peroxides such as 2,3-dimethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, dicumyl peroxide, and cumene hydroperoxide. .

Examples of the plasticizer include glycerin fatty acid esters such as phthalic acid ester, glycerin diacetomonolaurate, glycerin tristearate and diacetylated glycerin monostearate, and adipic acid esters such as diisobutyl adipate.
Examples of the lubricant include paraffin wax and zinc stearate.
Examples of the binding inhibitor include calcium carbonate, silica, zinc stearate, aluminum hydroxide, ethylene bis stearamide, tricalcium phosphate, dimethyl silicon and the like.
Examples of the fusion accelerator include stearic acid, stearic acid triglyceride, hydroxystearic acid triglyceride, stearic acid sorbitan ester, and polyethylene wax.

Examples of the antistatic agent include polyoxyethylene alkylphenol ether and stearic acid monoglyceride.
Examples of the spreading agent include polybutene, polyethylene glycol, and silicone oil.
Examples of the bubble regulator include methacrylic acid ester copolymer, ethylene bis stearamide, polyethylene wax, ethylene-vinyl acetate copolymer, and the like.

(6) Shape of foam molded body The shape of the foam molded body is not particularly limited, and can be appropriately determined according to the application. For example, in the use of a floor heat insulating material, a plate shape and a rectangular parallelepiped are mentioned.

(Method for producing foamed molded article)
The foam-molded product can be obtained by pre-foaming expandable resin particles to obtain pre-foamed particles, and then foam-molding the pre-foamed particles. The expandable resin particles can be obtained, for example, by impregnating resin particles obtained by seed polymerization with a foaming agent.
(1) Method for Producing Resin Particles The resin particles are not particularly limited. For example, a seed particle containing a polystyrene resin is a single particle having an ester group and 3 to 10 vinyl groups in a styrene monomer and molecule. It can be obtained by so-called seed polymerization in which a monomer is absorbed and polymerized.
(I) Seed particles The seed particles can be produced by a known method. For example, (1) a polystyrene resin is melt-kneaded with an extruder, extruded into a strand, and the strand is cut. (2) An aqueous medium, a styrene monomer and a polymerization initiator are fed into an autoclave, and the styrene monomer is subjected to suspension polymerization while being heated and stirred in the autoclave, thereby seed particles. (3) After supplying the aqueous medium and polystyrene resin particles into the autoclave and dispersing the polystyrene resin particles in the aqueous medium, the autoclave is heated and agitated while stirring. The polymer is supplied continuously or intermittently and polymerized in the presence of a polymerization initiator while the polystyrene resin particles absorb the styrene monomer. And seed polymerization method for producing seed particles.
In addition, the resin particles can be used for part or all of the seed particles. In the case of using a recovered product, production of seed particles by an extrusion method is suitable.

  The average particle size of the seed particles can be adjusted as appropriate according to the average particle size of the resin particles. For example, when obtaining resin particles having an average particle diameter of 1.0 mm, it is preferable to use seed particles having an average particle diameter of about 0.7 mm to 0.9 mm. Furthermore, the weight average molecular weight of the seed particles is not particularly limited, but is preferably 100,000 to 700,000, and more preferably 150,000 to 500,000.

(Ii) Impregnation step In a dispersion obtained by dispersing seed particles in an aqueous medium, a styrene monomer and a monomer having an ester group and 3 to 10 vinyl groups in the molecule are supplied. Each monomer is absorbed by the seed particles. A monomer having an ester group and 3 to 10 vinyl groups in the supplied molecule is almost equivalent to a monomer having an ester group and 3 to 10 vinyl groups in the molecule contained in the resin particle. is doing.
Here, the absorption of the monomer having an ester group and 3 to 10 vinyl groups in the molecule and the styrene monomer is carried out under a polymerization conversion of 70 to 85% of the styrene monomer. Is called. By carrying out within this range, a foamed molded article in which the copolymer component is unevenly distributed can be obtained.
Examples of the aqueous medium include water and a mixed medium of water and a water-soluble solvent (for example, alcohol).

  Each monomer to be used may contain a polymerization initiator. The polymerization initiator is not particularly limited as long as it is conventionally used for monomer polymerization. For example, benzoyl peroxide, t-butyl peroxybenzoate, t-butyl peroxy-2-ethylhexanoate, lauryl peroxide, t-butyl peroxide, t-butyl peroxypivalate, t-butyl peroxyisopropyl Organics such as carbonate, t-butyl peroxyacetate, 2,2-t-butylperoxybutane, t-butylperoxy-3,3,5-trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate Examples thereof include peroxides, azo compounds such as azobisisobutyronitrile, azobisdimethylvaleronitrile, and the like. Among these initiators, in order to reduce the residual monomer, it is preferable to use two or more different polymerization initiators having a decomposition temperature of 80 to 120 ° C. for obtaining a half-life of 10 hours. In addition, a polymerization initiator may be used independently or 2 or more types may be used together.

  The aqueous medium may contain a suspension stabilizer to stabilize the dispersion of monomer droplets and seed particles that provide the copolymer component. The suspension stabilizer is not particularly limited as long as it is conventionally used for monomer suspension polymerization. Examples thereof include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone, and poorly soluble inorganic compounds such as tricalcium phosphate, magnesium pyrophosphate, and magnesium oxide. And when using a sparingly soluble inorganic compound as said suspension stabilizer, it is preferable to use an anionic surfactant together, and as such anionic surfactant, for example, fatty acid soap, N-acylamino acid or its Salts, carboxylates such as alkyl ether carboxylates, alkyl benzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl sulfoacetates, sulfonates such as α-olefin sulfonates; higher alcohol sulfuric acid Ester salts, secondary higher alcohol sulfates, sulfates such as alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates, etc .; phosphates such as alkyl ether phosphates, alkyl phosphates, etc. Is mentioned.

(Iii) Polymerization process Although a polymerization process changes with monomer types to be used, a polymerization initiator seed | species, a polymerization atmosphere seed | species, etc., it is normally performed by maintaining a 70-130 degreeC heating for 3 to 10 hours. The polymerization step may be performed while impregnating the monomer.
In the polymerization step, the entire amount of the monomer to be used may be polymerized in one stage, or may be polymerized in two or more stages. When polymerizing in two or more stages, the impregnation step is usually performed in two or more stages. The polymerization temperature and time of the polymerization process divided into two or more steps may be the same or different.

(2) Method for Producing Expandable Resin Particles Expandable resin particles can be obtained by impregnating the above resin particles with a foaming agent.
The foaming agent is not particularly limited, and any known foaming agent can be used. Particularly, a gaseous or liquid organic compound having a boiling point equal to or lower than the softening point of the polystyrene resin and normal pressure is suitable. For example, hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane, cyclopentadiene, n-hexane, petroleum ether, ketones such as acetone and methyl ethyl ketone, methanol, ethanol, isopropyl alcohol, etc. Low boiling point ether compounds such as alcohols, dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, halogen-containing hydrocarbons such as trichloromonofluoromethane, dichlorodifluoromethane, inorganic gases such as carbon dioxide, nitrogen, ammonia, etc. Can be mentioned. These foaming agents may be used alone or in combination of two or more. Among these, it is preferable to use hydrocarbons from the viewpoint of preventing the destruction of the ozone layer and from the viewpoint of quickly replacing with the air and suppressing the time-dependent change of the foamed molded product. Of the hydrocarbons, hydrocarbons having a boiling point of −45 to 40 ° C. are more preferable, and propane, n-butane, isobutane, n-pentane, isopentane and the like are more preferable.

  Furthermore, it is preferable that content of a foaming agent is the range of 2-12 mass%. When the amount is less than 2% by mass, a foamed molded article having a desired density may not be obtained from the expandable resin particles. In addition, since the effect of increasing the secondary foaming power at the time of in-mold foam molding is reduced, the appearance of the foam molded article may not be good. When the amount is more than 12% by mass, the time required for the cooling step in the production process of the foamed molded product becomes long, and the productivity may decrease. A more preferable content of the blowing agent is 3 to 10% by mass.

The impregnation with the foaming agent may be performed simultaneously with the polymerization, or may be performed wet or dry after the polymerization. When it is carried out in a wet manner, it may be carried out in the presence of a suspension stabilizer and a surfactant exemplified in the polymerization step.
The impregnation temperature of the foaming agent is preferably 60 to 120 ° C. When the temperature is lower than 60 ° C., the time required for impregnating the resin particles with the foaming agent becomes long, and the production efficiency may decrease. On the other hand, when the temperature is higher than 120 ° C., the resin particles may be fused to generate bonded particles. A more preferable impregnation temperature is 70 to 110 ° C.
A foaming aid may be used in combination with a foaming agent. Examples of the foaming aid include isobutyl adipate, toluene, cyclohexane, and ethylbenzene.

(3) Method for producing pre-expanded particles Pre-expanded particles are obtained by foaming expandable resin particles to a desired bulk density using water vapor or the like.
The bulk density of the pre-expanded particles is preferably in the range of 0.01 to 0.100 g / cm ³ . When the pre-expanded particles have a bulk density of less than 0.01 g / cm ³ , shrinkage may occur in the foamed molded product to be obtained next and appearance may be deteriorated. In addition, the heat insulation performance and mechanical strength of the foamed molded product may deteriorate. On the other hand, if the bulk density is greater than 0.100 g / cm ³ , the lightweight property of the foamed molded product may be reduced.
In addition, it is preferable to apply powdered metal soaps such as zinc stearate to the surface of the expandable resin particles before foaming. By applying, the bonding between the foamed particles can be reduced in the foaming process of the foamable resin particles.

(4) Foam molding method In the foam molding method, pre-foamed particles are filled in a closed mold having a large number of small holes, and again heated and foamed with pressurized steam, etc., filling the gaps between the pre-foamed particles and pre-foaming. In this method, the particles are integrated by fusing each other. At that time, the density of the foamed molded product can be adjusted, for example, by adjusting the filling amount of the pre-expanded particles in the mold.
The pre-expanded particles may be aged, for example, at normal pressure before forming the foamed molded product. The aging temperature of the pre-expanded particles is preferably 20 to 60 ° C. When the aging temperature is low, the aging time of the pre-expanded particles may be long. On the other hand, if it is high, the foaming agent in the pre-expanded particles may be dissipated and the moldability may be lowered.

Hereinafter, specific examples of the present invention will be described by way of examples. However, the following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples. In the following, “part” and “%” are based on mass unless otherwise specified.
<Polymerization conversion>
The method for measuring the amount of monomer contained in seed particles in the course of nuclear polymerization (hereinafter referred to as growing particles) refers to those measured in the following manner.
That is, the growing particles are taken out from the dispersion, and the water adhering to the surface is wiped off with gauze. 0.08 g of the growing particles are collected, and the collected growing particles are dissolved in 24 ml of toluene to prepare a toluene solution. Next, 10 ml of the Wis reagent, 30 ml of 5% by weight potassium iodide aqueous solution and 30 ml of 1% by weight starch aqueous solution are added to the toluene solution. The result obtained by titrating the obtained solution with an N / 40 sodium thiosulfate solution is defined as a titration constant (milliliter) of the sample. The Wis reagent is obtained by dissolving 8.7 g of iodine and 7.9 g of iodine trichloride in 2 liters of glacial acetic acid.
On the other hand, without dissolving the growing particles, 10 ml of Wis reagent, 30 ml of 5% by weight potassium iodide aqueous solution and 30 ml of 1% by weight starch aqueous solution are added to 24 ml of toluene. The resulting solution was titrated with a N / 40 sodium thiosulfate solution to give a blank titration (in milliliters).
From the obtained droplet constant, the amount of unreacted monomer in the growing particles is calculated based on the following formula.
Amount of monomer in growing particles (% by mass) = 0.1322 × (blank drop constant−sample drop constant) / sample drop constant Further, the polymerization conversion is calculated by the following equation.
Polymerization conversion rate (%) = 100 × (sample mass−monomer amount of growing particles) / sample mass

<Absorbance ratio>
A foam sample is sliced at a thickness of 0.1 to 0.15 mm to obtain a slice sample, and 10 sets of two foamed resin particles fused to each other in the obtained slice sample are arbitrarily selected. Analysis is performed by a microscopic IR imaging mapping method along a straight line connecting one center and the other center of the two foamed resin particles. From the results, the absorbance ratio of the copolymer component of the each pair of polystyrene-based resin component, a monomer having 3 to 10 vinyl groups in the molecule and a styrene monomer (1730cm ^-1 / 1600cm ^-1 ) Is calculated. The average value of the 10 sets of absorbance ratios obtained is taken as the absorbance ratio in this specification.
Measuring apparatus: Fourier transform infrared spectrophotometer Spectrum One (manufactured by Perkin Elmer)
High-speed IR imaging system Spectrum Spotlight 300
Measurement mode: Imaging Transmission method Measurement conditions: Resolution = 8 cm ⁻¹ Number of scans 2, 8 Pixel size 6.25 × 6.25 μm
Pretreatment method: A slice sample is sandwiched between fluorinated Ba plates, measured by the transmission method, and then intensity ratio mapping of absorbance is performed.
Slice sample preparation: Ultramicrotome ULTRACUT-UCT (Leica)
Slicing knife: Diamond knife Cutting thickness 10μm

<Z average molecular weight>
The z-average molecular weight (Mz1) on the surface of the foam-molded product and the z-average molecular weight (Mz2) of the entire foam-molded product are measured as follows.
That is, a foamed molded product having a density of 0.02 g / cm ³ is prepared, the surface portion is sliced at 0.1 to 0.15 mm, and the z-average molecular weight is measured by gel permeation chromatography (GPC). Since the surface portion is an aggregate of expanded resin particles, it has the same z-average molecular weight as the interface of the expanded molded body.
On the other hand, the z-average molecular weight of the entire foamed molded product is measured by the GPC method in the same manner using the sample as a sample.

<GPC / MALLS method>
A foam molded article having a density of 0.02 g / cm ³ is prepared, and the surface portion is sliced at 0.1 to 0.15 mm to obtain a sample.
(Measurement conditions for THF-based GPC-MALLS)
・ GPC device: HLC-8120GPC (manufactured by Tosoh Corporation)
-MALLS: DAWN HELEOS (manufactured by Wayat Technology)
Concentration detector: differential refractometer (RI detector)
-MALLS laser wavelength: 658 nm
Column: TSKgelGMH _HR- H (7.8 mm ID × 30 cm) × 2 pieces (manufactured by Tosoh Corporation)
・ Eluent: THF (1st grade, manufactured by Kishida Chemical Co.)
・ Flow rate: 1.0 ml / min
Sample concentration: 1 mg / ml
・ Injection volume: 100 μl
-Column temperature: 40 ° C
Detector temperature: RI detector: 40 ° C., MALLS: room temperature Sample pretreatment: The sample is weighed, and a predetermined amount of eluent is added and allowed to stand overnight to dissolve. Shake gently just before the measurement and filter through a 0.5 μm Teflon cartridge filter.

<Bulk density>
The bulk magnification of the pre-expanded particles is measured according to JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. Specifically, first, Wg is collected using pre-expanded particles as a measurement sample, and this measurement sample is naturally dropped into a measuring cylinder. The volume Vcm ³ of the measurement sample dropped into the graduated cylinder is measured using an apparent density measuring instrument based on JIS K6911. By substituting Wg and Vcm ³ into the following formula, the bulk density of the pre-expanded particles is calculated.
Bulk density of pre-expanded particles (g / cm ³ ) = mass of measurement sample (W) / volume of measurement sample (V)

<Density of foam molding>
Mass (a) and volume (b) of test pieces (example 100 × 100 × thickness of molded product (mm)) cut out from a foamed molded product (after molding and dried at 40 ° C. for 20 hours or more) are significant figures. The measurement is carried out so that it is 3 digits or more, and the density (g / cm ³ ) of the foamed molded product is obtained by the formula (a) / (b).

<Compressive modulus>
The compression elastic modulus of the foamed molded product is measured in accordance with the method described in JIS K9511: 1999 “Foamed plastic heat insulating material”.
That is, a rectangular test piece having a density of 0.0166 g / cm ³ , a length of 100 mm, a width of 100 mm, and a thickness of 30 mm is cut out. This test piece was subjected to a compression test under the conditions of 23 ° C., humidity 50%, compression speed 10 mm / min using a product name (UCT-10T) manufactured by Orientec Co., and the average of five compression elastic moduli of the test pieces. Find the value.
In the examples and comparative examples, the evaluation was performed with a density of 0.0166 g / cm ³ and a value of 5000 KPa or more as ◯ and a value of less than 5000 KPa as x.

Example 1
2350 g of seed particles of polystyrene resin (average particle diameter of 0.75 mm) having a weight average molecular weight of 300,000, 30 g of magnesium pyrophosphate and 10 g of calcium dodecylbenzenesulfonate are supplied to a polymerization vessel equipped with a stirrer having an internal volume of 25 L and stirred. While being heated to 75 ° C., a dispersion was prepared.
Subsequently, a solution prepared by dissolving 32.6 g of benzoyl peroxide and 3.0 g of t-butylperoxybenzoate in 1000 g of styrene monomer was supplied to the dispersion while stirring (first step).
Then, 30 minutes after supplying the solution into the dispersion, 20 g of trimethylolpropane trimethacrylate (trifunctional monomer, molecular weight 338) was dissolved in 6650 g of styrene monomer in this dispersion. The solution was supplied from 75 ° C. to 88 ° C. at a constant supply rate over 60 minutes, and then the dispersion was supplied at a constant supply rate over 90 minutes while maintaining the dispersion at 88 ° C. for polymerization. . (Second step).

From the first step to the second step, the polymerization conversion rate of the seed particles changed between 73% and 85%.
Subsequently, the reaction vessel was sealed, heated to 120 ° C. over 30 minutes, allowed to stand for 60 minutes, and then cooled to room temperature (about 25 ° C.).
Next, the dispersion liquid in which the resin particles are dispersed is maintained at 100 ° C., and then 80 g of cyclohexane, 70 g of diisobutyl adipate and 800 g of butane are pressed into the polymerization vessel and held for 3 hours. Was impregnated with butane. Thereafter, the inside of the polymerization vessel was cooled to 25 ° C. to obtain expandable resin particles.

Polyethylene glycol was applied as an antistatic agent to the surface of the expandable resin particles. Thereafter, zinc stearate and hydroxystearic acid triglyceride were further applied to the surface of the expandable resin particles. After coating, the expandable resin particles were left in a thermostatic chamber at 13 ° C. for 5 days.
Then, the expandable resin particles were heated and pre-expanded to a bulk density of 0.0166 g / cm ³ to obtain pre-expanded particles. Pre-expanded particles were aged at 20 ° C. for 24 hours. Next, the pre-expanded particles were filled in a mold and heated and foamed to obtain a foamed molded product having a length of 400 mm × width of 300 mm × thickness of 30 mm. After the foamed molded product was dried in a drying chamber at 50 ° C. for 6 hours, the density was measured and found to be 0.0166 g / cm ³ (16.6 kg / m ³ ). The foamed molded article was excellent in appearance without shrinkage.
The absorbance ratio with respect to the center-to-center distance of the interface of the foamed resin particles constituting the foamed molded product is shown in FIG. In FIG. 1, the peak position of the absorbance ratio corresponds to the interface.

(Example 2)
In Example 1, a foamed molded article was obtained in the same manner as in Example 1 except that 88 ° C in the second step was changed to 86 ° C.
The obtained foamed molded article was excellent in appearance without shrinkage.
(Example 3)
A foam molded article was obtained in the same manner as in Example 1, except that 16 g of trimethylolpropane trimethacrylate (trifunctional monomer, molecular weight 338) was used.
The obtained foamed molded article was excellent in appearance without shrinkage.
Example 4
A foam molded article was obtained in the same manner as in Example 1 except that 24 g of trimethylolpropane trimethacrylate (trifunctional monomer, molecular weight 338) was used.
The obtained foamed molded article was excellent in appearance without shrinkage.
(Comparative Example 1)
In Example 1, a foamed molded article was obtained in the same manner as in Example 1 except that trimethylolpropane trimethacrylate was not added.
The obtained foamed molded article was inferior in compression modulus.
(Comparative Example 2)
In Example 1, a foamed molded article was obtained in the same manner as in Example 1 except that 75 ° C in the first step was 72 ° C and 88 ° C in the second step was 86 ° C.
The obtained foamed molded article was inferior in compression modulus.
(Comparative Example 3)
In Example 1, a foamed molded article was obtained in the same manner as in Example 1 except that 75 ° C in the first step was 77 ° C and 88 ° C in the second step was 90 ° C.
The obtained foamed molded article had poor foam moldability, poor adhesion between foamed grains, and poor compression modulus.
(Comparative Example 4)
A foam molded article was obtained in the same manner as in Example 1, except that 10 g of trimethylolpropane trimethacrylate (trifunctional monomer, molecular weight 338) was used.
The obtained foamed molded article was inferior in compression modulus.
(Comparative Example 5)
Molding was performed in the same manner as in Example 1 except that 30 g of trimethylolpropane trimethacrylate (trifunctional monomer, molecular weight 338) was used. However, the adhesion between the expanded particles was very poor, and a foamed molded product could not be obtained.
The results of Examples 1 to 4 and Comparative Examples 1 to 5 are summarized in Table 1.

Claims (7)

A plurality of foamed resin particles comprising a polystyrene resin component (A), a monomer having an ester group and 3 to 10 vinyl groups in the molecule, and a copolymer component (B) of a styrene monomer. It is a foamed molded body made of a fused body,
Absorbance ratio at 1735 cm ^-1 and 1600 cm ^-1 obtained from an infrared absorption spectrum around fusing interface of said measured foamed resin particles by ATR method infrared spectroscopy (D ₁₇₃₅ / D ₁₆₀₀₎ is 0.06 to 0 .25 range,
The z-average molecular weight of the surface of the foamed resin particles is 900,000 to 2,000,000,
A foamed molded article having a density of 0.010 to 0.100 g / cm ³ and a compression modulus of 1000 KPa or more.   The slope of the correlation equation with the log (RMS radius) measured by the GPC / MALLS method on the surface of the foamed resin particle as the y axis and the log (Mw) as the x axis is 0.55 or less. Item 2. The foamed molded article according to Item 1.   The foam molded article according to claim 1 or 2, wherein the copolymer component is a copolymer of a monomer selected from (meth) acrylate monomers and a styrene monomer.   The (meth) acrylate monomer is trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane trimethacrylate, ethoxylated isocyanuric acid triacrylate, tetramethylolmethane tetraacrylate, ditrimethylolpropane tetraacrylate and The foamed molded product according to claim 3, which is a monomer selected from dipentaerythritol hexaacrylate.   The foamed molded article according to any one of claims 1 to 5, which has an insoluble content of 0.1% by mass or less when dissolved in toluene at 23 ° C.   The foamed molded product according to any one of claims 1 to 5, wherein the foamed molded product is a foamed molded product for floor insulation. It is a manufacturing method of a foaming fabrication object given in any 1 paragraph of Claims 1-6,
A step of allowing a seed particle containing a polystyrene resin to absorb a monomer having an ester group and 3 to 10 vinyl groups in the molecule and a styrene monomer;
A step of obtaining resin particles by copolymerizing an ester group and a monomer having 3 to 10 vinyl groups and a styrene monomer in or after absorption,
A step of impregnating resin particles with a foaming agent to obtain expandable resin particles;
Pre-foaming expandable resin particles, and then foam-molding by foam-molding,
Absorption of a monomer having an ester group, 3 to 10 vinyl groups and a styrene monomer in the molecule is performed under a polymerization conversion of 70 to 85% styrene monomer. A method for producing a foamed molded product.

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