JP6031378B2 - Expandable styrene resin particles, expanded particles and lightweight concrete - Google Patents

Description

The present invention, expandable styrene resin particles, relates to foamed particles and lightweight concrete. The expandable styrene resin particles of the present invention can be suitably used as lightweight concrete such as an outer wall.

  Conventionally, lightweight concrete includes lightweight aggregate instead of heavy aggregate such as gravel. As lightweight aggregates, porous materials such as perlite, vermiculite, pumice / coal slag, and volcanic ash are used. However, these lightweight aggregates are irregular in shape and have poor fluidity, and therefore have the drawback of reducing the workability of ready-mixed concrete containing lightweight aggregates. Further, since these lightweight aggregates are inorganic, they remain in the concrete without being decomposed even when the concrete is fired. As a result, there is a drawback that it is not possible to produce lighter concrete having voids inside.

  On the other hand, the technique which uses an expanded styrene resin particle (expanded particle) for manufacture of a lightweight concrete is proposed (Unexamined-Japanese-Patent No. 2011-74242: patent document 1). The expanded particles are spherical and have a uniform shape. Further, since the expanded particles are organic, they are decomposed by baking at a high temperature. Therefore, when the foamed particles are used for the production of lightweight concrete, the above disadvantages can be solved.

JP 2011-74242 A

For foamed particles used for lightweight concrete, it is desired to reduce the particle diameter in order to improve the design properties (for example, surface smoothness) of lightweight concrete. Reducing the particle diameter of the expanded particles means reducing the particle diameter of the expandable particles for obtaining the expanded particles. Expandable particles with a small particle size have a large specific surface area, and the dissipation of the foaming agent is easy to proceed quickly, so the foamability is low (the foaming speed is slow), and it takes time to foam to the desired multiple. there were.
Moreover, it can be considered that foamability is improved by adding a plasticizer such as a solvent to the foamable particles, but there is a problem that the plasticizer may deteriorate the lightweight concrete.

  The inventor of the present invention has found that the foamable styrene resin particles in which the resin component derived from the acrylate ester is unevenly distributed can secure sufficient foamability even if the particle diameter is small, and has led to the present invention.

Thus, according to the present invention, expandable styrenic resin particles for lightweight concrete production comprising a resin component derived from an acrylate ester and a foaming agent,
The expandable styrenic resin particles are
(1) having an average particle diameter of 200 to 500 μm,
(2) the respective infrared absorption spectrum of the surface layer and the central portion was measured by microscopic transmission imaging method, the obtained absorbance D1600 absorbance D1730 and 1600 cm ^-1 in 1730 cm ^-1 from the infrared absorption spectrum, from the absorbance D1730 and the absorbance D1600 When the absorbance ratio of the surface layer (D1730 / D1600) (A) and the absorbance ratio of the central part (D1730 / D1600) (B) are calculated,
(I) The absorbance ratio (A) is greater than the absorbance ratio (B),
(Ii) Expandable styrene resin particles are provided, wherein the absorbance ratio (A) is in the range of 0.15 to 0.5.
Moreover, according to this invention, the foamed particle obtained by making the said expandable styrene-type resin particle foam and used for manufacture of a lightweight concrete is provided.
Furthermore, according to this invention, the lightweight concrete obtained by hardening the ready-mixed concrete composition containing the said foaming particle, or baking and decomposing | disassembling the said foaming particle after hardening is provided.

  ADVANTAGE OF THE INVENTION According to this invention, even if a particle diameter is small, the expandable styrene-type resin particle which can ensure sufficient foamability can be provided. The inventor believes that this effect is exhibited when the resin component derived from the acrylate ester is unevenly distributed in the expandable styrene resin particles. In the expandable styrene resin particles of the present invention, the resin component derived from the acrylate ester is present more in the surface layer than in the center due to the magnitude relationship between the absorbance ratios (A) and (B). For this reason, the softening of the surface layer of the expandable particles is caused at the lower temperature than the expandable particles made of a styrene homopolymer by heating at the time of foaming. The inventor believes that the foaming property can be increased (the foaming speed can be increased) by softening the surface layer at a lower temperature.

Expandable styrenic resin particles
If the absorbance ratio (A) is larger than the absorbance ratio (B), sufficient foamability can be secured even if the particle diameter is small.
Moreover, since the expanded particle of this invention is obtained by foaming the said expandable styrene-type resin particle with a sufficiently small particle diameter, the design property of lightweight concrete can be improved.
Furthermore, the lightweight concrete of the present invention is obtained by curing the ready-mixed concrete composition containing the foamed particles, or by baking and decomposing the foamed particles after curing. Variations in physical properties such as mass can be suppressed.

It is the schematic for demonstrating the measurement procedure of the light absorbency ratio by an infrared absorption spectrum method.

(Expandable styrene resin particles)
Expandable styrene resin particles (hereinafter, expandable particles) include a styrene resin component, a resin component derived from an acrylate ester, and a foaming agent. In addition, expandable particles
(A) having an average particle size of 200-500 μm,
(B) the absorbance ratio (A) is greater than the absorbance ratio (B);
(C) Particles having an absorbance ratio (A) in the range of 0.15 to 0.5.
The absorbance ratio (A) is a ratio (D1730 / D1600) of absorbance D1730 and absorbance D1600 of the surface layer of the expandable particles. On the other hand, the absorbance ratio (B) is a ratio (D1730 / D1600) of absorbance D1730 and absorbance D1600 at the center of the expandable particle. Absorbance D1730 and the absorbance D1600 were obtained from each of the infrared absorption spectrum of the surface layer and the central portion as measured by microscopic transmission imaging method, it refers to a value of at the absorption wavelength of 1730 cm ^-1 and 1600 cm ^-1.

(1) Component (a) Styrenic resin component The styrene resin component is not particularly limited, and any resin component derived from a known styrene monomer can be used. Examples thereof include resin components derived from styrene, α-methylstyrene, vinyl toluene, chlorostyrene, ethyl styrene, isopropyl styrene, dimethyl styrene, bromostyrene, and the like. These styrene resin components may be one kind or a mixture of plural kinds. A preferred styrenic resin component is a homopolymer of styrene.
(B) Resin component derived from acrylate ester The resin component derived from the acrylate ester is not particularly limited, but a resin component derived from a monomer copolymerizable with a styrene monomer is preferable. The acrylic ester is preferably an ester having 3 to 20 carbon atoms. By using a monomer having a carbon number within this range, it is possible to provide expandable particles having improved expandability.

  Specific acrylic esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, and hexyl (meth) acrylate. , Heptyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, undecyl (meth) acrylate, tridecyl (meth) acrylate, Examples include tetradecyl (meth) acrylate and heptadecyl (meth) acrylate. The alkyl group having 3 or more carbon atoms includes not only a linear alkyl group but also an alkyl group having a structural isomer such as an iso structure, a sec structure or a tert structure.

(C) Ratio of styrene resin component and resin component derived from acrylate ester The ratio of styrene resin component and resin component derived from acrylate ester is in the range of 1: 0.005 to 0.031 (mass ratio). It is preferable.
If the resin component derived from the acrylate ester is less than 0.005, the foamability may not be sufficiently improved. When the amount is more than 0.031, the resin is softened by heating with steam and contraction and coalescence occur, and it may be difficult to obtain high-magnification expanded particles. A more preferable ratio is in the range of 1: 0.005 to 0.021, and a further preferable ratio is in the range of 1: 0.01 to 0.016.
In addition, the ratio of the styrene resin component and the resin component derived from the acrylate ester substantially matches the ratio of the monomer as the raw material.

(D) Other resin components Expandable particles are resin components derived from styrene-based resins and acrylate esters within a range that does not impair the effects of the present invention (for example, 5 parts by mass or less with respect to 100 parts by mass of all resin components). In addition to the above, other resin components may be included.
Examples of other resin components include resin components derived from polyfunctional vinyl monomers, polyolefin resins such as polyethylene and polypropylene, and resin components such as polycarbonate resins and polyesters.
Multifunctional vinyl monomers include bifunctional monomers such as divinylbenzene, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, and ethoxylated trimethylolpropane. Trifunctional monomers such as trimethacrylate and ethoxylated isocyanuric acid triacrylate are listed.

(E) Additives Within the range that does not impair the physical properties, flame retardants, flame retardant aids, plasticizers, lubricants, anti-blocking agents, fusion accelerators, antistatic agents, spreading agents, bubble regulators, fillers, Additives such as colorants may be included.
As flame retardants, tetrabromocyclooctane, hexabromocyclododecane, trisdibromopropyl phosphate, tetrabromobisphenol A, tetrabromobisphenol A-bis (2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol A- Examples thereof 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 anti-blocking agent 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, stearic acid monoglyceride, polyethylene glycol and the like.
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.

(2) Average particle diameter The expandable particles have an average particle diameter of 200 to 500 µm. If it is this range, the expanded particle which can obtain lightweight concrete with favorable design property, ensuring sufficient foamability can be provided. When the average particle size is less than 200 μm, it may be difficult to obtain sufficient foamability. When it is larger than 500 μm, it may be difficult to obtain sufficient design properties. A preferable average particle diameter is 250-400 micrometers, and a more preferable average particle diameter is 330-380 micrometers. Furthermore, in order to ensure sufficient foamability and good design properties, it is preferable to remove in advance foamable particles of less than 200 μm and greater than 500 μm.
In addition, when the shape of an expandable particle is not spherical, an average particle diameter means the average value of a maximum diameter.

(3) Absorbance ratio (A) and (B)
The absorbance ratio here is obtained from an infrared absorption spectrum measured by an infrared absorption spectrum method.
Absorbance ratio is in the measured infrared absorption spectrum, the ratio D1730 / D1600 absorbance D1730 at 1730 cm ^-1 to the absorbance D1600 at 1600 cm ^-1. Here, the absorption at 1730 cm ⁻¹ indicates a peak derived from stretching vibration between C═O of ester groups contained in a resin derived from an acrylate ester. 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 styrene resin.
Incidentally, the absorbance D1600 and absorbance D1730, when light having a wavelength of 1600 cm ^-1 and 1730 cm ^-1 which is incident from the surface to be measured reaches the measuring instrument passes through the measurement object, the degree of absorption of light (amount ).

The absorbance ratio (A) of the surface layer is larger than the absorbance ratio (B) of the central portion. This means that the resin component derived from the acrylate ester is contained more in the surface layer than in the center. Here, the surface layer in the absorbance ratio (A) means a region within about 20% of the particle radius from the particle outermost layer. The central portion in the absorbance ratio (B) means a region within about 15% of the particle radius from the particle center.
It is preferable that the absorbance ratio has a tendency to decrease from the surface of the expandable particle toward the center. The tendency of the decrease may be, for example, a tendency to decrease linearly from the surface toward the center portion, or may decrease in a region close to the surface or a region close to the center portion and thereafter become a substantially constant value.

The absorbance ratio (A) of the surface layer is preferably in the range of 0.15 to 0.5. When the absorbance ratio (A) is less than 0.15, it may be difficult to obtain a sufficient foaming rate. If the absorbance ratio is greater than 0.5, the surface layer resin may be too soft, making it difficult to obtain high-magnification expanded particles. More preferable absorbance ratio (A) is in the range of 0.2 to 0.4, and still more preferable absorbance ratio (A) is in the range of 0.25 to 0.35.
The absorbance ratio (B) at the center is preferably in the range of 0.05 to 0.4. When the absorbance ratio (B) is less than 0.05, it may be difficult to obtain a sufficient foaming rate. When the absorbance ratio (B) is larger than 0.4, it may be difficult to obtain high-magnification expanded particles. More preferable absorbance ratio (B) is in the range of 0.08 to 0.3, and still more preferable absorbance ratio (B) is in the range of 0.1 to 0.2.
The difference between the absorbance ratios (A) and (B) is preferably in the range of 0.05 to 0.3. When the difference is larger than 0.3, the bubble diameter at the time of foaming varies, and the appearance of foamed particles may be deteriorated. A more preferable difference is in the range of 0.05 to 0.2, and a further preferable difference is in the range of 0.05 to 0.1.

(4) Foaming speed of expandable particles The expandable particles are placed in a foaming tank heated to 80 ° C and heated by steam of 0.07 MPa to raise the temperature in the foaming tank to 90 ° C. When foamed particles are obtained after one minute has passed after reaching 90 ° C., the particles are preferably particles that give the foamed particles a bulk multiple in the range of 65 to 50 times.

(Method for producing expandable particles)
The method for producing the expandable particles is not particularly limited. For example, resin particles are obtained by absorbing and polymerizing a monomer mixture containing at least an acrylate ester into seed particles made of a styrene resin, and obtained by impregnating the resin particles with a foaming agent simultaneously with or after the polymerization. be able to. The monomer mixture usually contains a styrenic monomer.
(A) Seed particles As the seed particles, those produced by a known method can be used. For example, (i) a styrene resin is melt-kneaded with an extruder, extruded into a strand, and the strand is cut. An extrusion method for obtaining seed particles, (ii) an aqueous medium, a styrene monomer, or a styrene monomer in which a part of polystyrene resin is dissolved, and a polymerization initiator are supplied into the autoclave, and heated and stirred in the autoclave. A suspension polymerization method in which seed particles are produced by suspension polymerization of a styrene monomer; (iii) an aqueous medium and styrene resin particles are supplied into an autoclave, and the styrene resin particles are dispersed in the aqueous medium; While heating and stirring the inside of the autoclave, the styrenic monomer is continuously or intermittently supplied to the styrenic resin particles. Examples thereof include a seed polymerization method in which seed particles are produced by polymerizing in the presence of a polymerization initiator while absorbing a lenic monomer.
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 350 μm, it is preferable to use seed particles having an average particle diameter of about 330 to 340 μm. Furthermore, the weight average molecular weight of the seed particles is not particularly limited, but is preferably 100,000 to 500,000, and more preferably 150,000 to 400,000.

(B) Impregnation step The monomer mixture is absorbed by the seed particles by supplying the monomer mixture into a dispersion obtained by dispersing the seed particles in an aqueous medium. The acrylic acid ester in the monomer mixture is preferably used in the range of 0.5 to 3.4 parts by mass with respect to 100 parts by mass of the seed particles. The acrylic ester is preferably contained in the monomer mixture in an amount of 5.0 to 30.0% by mass.
Examples of the aqueous medium include water and a mixed medium of water and a water-soluble solvent (for example, alcohol).

  A polymerization initiator may be included in the monomer mixture. 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. to obtain a half-life of 10 hours. In addition, a polymerization initiator may be used independently or 2 or more types may be used together.

  A suspension stabilizer may be included in the aqueous medium to stabilize the dispersion of monomer droplets and seed particles. 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.

(C) 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 60-130 degreeC heating for 2 to 10 hours. The polymerization step may be performed while impregnating the monomer mixture.
In the polymerization step, the entire amount of the monomer mixture 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 process is usually performed in two stages. The polymerization temperature and time of the polymerization process divided into two or more steps may be the same or different.

For example, when it is performed in one stage, it is preferable to adjust the polymerization process as follows.
A styrene resin seed particle is allowed to absorb a monomer mixture containing a styrene monomer and an acrylate ester and polymerize in the seed particle. Here, the monomer mixture is preferably added to the polymerization vessel over 1 to 30 minutes.
The resin particles obtained through the polymerization step preferably have a weight average molecular weight in the range of 100,000 to 700,000. When the weight average molecular weight is less than 100,000, the strength of the foamed particles may decrease. If it exceeds 700,000, sufficient foaming may not be obtained. A more preferred weight average molecular weight is in the range of 100,000 to 500,000, and a more preferred weight average molecular weight is in the range of 150,000 to 300,000.

(D) Foaming agent impregnation step Foamable particles are obtained by impregnating the resin particles with a foaming agent.
The foaming agent is not particularly limited, and any known foaming agent can be used. In particular, a gaseous or liquid organic compound having a boiling point equal to or lower than the softening point of the styrene resin 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 2-14 mass%. If the amount is less than 2% by mass, expanded particles having a desired bulk density may not be obtained from the expandable particles. If it is more than 14% by mass, the resin may be softened and foamed during foaming. A more preferable content of the blowing agent is 3 to 13% by mass.

The impregnation with the foaming agent may be performed wet simultaneously with the polymerization of the monomer mixture, 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.
In particular, expandable particles are obtained by absorbing and polymerizing a monomer mixture containing at least an acrylate ester into seed particles composed of a styrene resin in an aqueous medium to obtain resin particles, and impregnating the resin particles with a foaming agent. Obtained,
The acrylic ester is used in an amount of 0.5 to 3.4 parts by mass with respect to 100 parts by mass of the seed particles, and 0.5 to 100 parts by mass with respect to 100 parts by mass of the styrene resin constituting the expandable styrene resin particles. It is preferable that the particles are obtained by using 3.1 parts by mass.

(Foamed particles)
The average particle diameter of the expanded particles obtained from the expandable particles is preferably 1.0 to 2.0 mm. The average particle diameter is more preferably 1.1 to 1.5 mm, and still more preferably 1.2 to 1.3 mm.
In addition, when the shape of the expanded particles is not spherical, the average particle diameter means an average value of the maximum diameters.
The bulk magnification of the expanded particles is preferably in the range of 50 to 65 times. When the bulk multiple is larger than 65 times, the foaming speed is too fast, and the foam multiple may vary. On the other hand, when the bulk multiple is smaller than 50 times, the foaming time may take time. A more preferable bulk magnification is 55 to 60 times.

(Method for producing expanded particles)
The expanded particles are obtained by expanding the expandable particles to a desired bulk density using water vapor or the like. In the present invention, the foaming speed can be increased by about 1.1 to 1.5 times that of expandable particles made of a homopolymer of styrene. In addition, foaming can be implemented by heating for 1-3 minutes, for example, using 0.06-0.08 MPa water vapor | steam, pressurizing as needed.
Before foaming, it is preferable to apply a powdered metal soap such as polyethylene glycol as an antistatic agent or zinc stearate as an antiblocking agent to the surface of the foamable particles.

(Lightweight concrete)
The lightweight concrete can be obtained by curing the ready-mixed concrete composition containing the foamed particles, or by firing and then decomposing the foamed particles after curing.
The ready-mixed concrete composition may contain components usually used in addition to the foamed particles. For example, water and binders (cement, asphalt, etc.) are essential components, and other components such as gravel as aggregates, shrinkage inhibitors as chemical admixtures, and freeze inhibitors are included as necessary. May be.
Lightweight concrete can be obtained, for example, by the following method. That is, the ready-mixed concrete composition is obtained by mixing expanded particles, water, a binder and other components. The obtained ready-mixed concrete composition is placed in a predetermined formwork. After placing, lightweight concrete can be obtained by compacting and curing as necessary.
The foamed particles may be decomposed and removed by firing the obtained lightweight concrete. By decomposing and removing, lightweight concrete can be further provided with functions such as humidity control and water permeability.
The lightweight concrete can be used, for example, as a concrete for filling relatively thin members such as wall surfaces, floor surfaces, and ceiling boards of buildings, and relatively thick plate-like structures and columnar structures.

  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.

<Weight average molecular weight>
“Weight average molecular weight (Mw)” means a polystyrene (PS) equivalent weight average molecular weight measured using gel permeation chromatography (GPC).
Specifically, 3 mg of a sample is dissolved in 10 mL of tetrahydrofuran (THF) (completely dissolved), and measured by filtration through a non-aqueous 0.45 μm chromatodisc. The weight average molecular weight of the sample is obtained from a standard polystyrene calibration curve that has been measured and prepared in advance. The chromatographic conditions are as follows.
・ Device: High-speed GPC device ・ Product name: HLC-8320GPC EcoSEC-WorkStation (built-in RI detector) manufactured by Tosoh Corporation
・ Analysis conditions Column: TSKgel SuperHZM-H × 2 (4.6 mm ID × 15 cmL × 2)
Guard column: TSK guard column Super HZ-H x 1 (4.6 mm ID x 2 cm L)
Flow rate: Sample side 0.175 ml / min, Reference side 0.175 ml / min
Detector: Built-in RI detector Concentration: 0.3 g / L
Injection volume: 50 μL
Column temperature: 40 ° C
System temperature: 40 ° C
Eluent: THF

(Create a calibration curve)
Standard polystyrene samples for calibration curves include standard polystyrene samples having a weight-average molecular weight of 500, 2630, 9100, 37900, 102000, 355000, 3840000, and 5480000 as trade name “TSK standard POLYSYRENE” manufactured by Tosoh Corporation; A standard polystyrene sample having a weight average molecular weight of 1030000 with a trade name “Shodex STANDARD” manufactured by the company is used.
The method of creating a calibration curve is as follows. First, the standard polystyrene samples for calibration curves are group A (with a weight average molecular weight of 1030000), group B (with a weight average molecular weight of 500, 9100, 102000, and 3480000) and group C (with a weight average molecular weight of 2630, 37900). 355,000 and 5480000). 5 mg of a standard polystyrene sample belonging to group A having a weight average molecular weight of 1030000 is weighed and then dissolved in 20 mL of THF, and 50 μL of the resulting solution is injected into the sample side column. Standard polystyrene samples belonging to group B having weight average molecular weights of 500, 9100, 102000, and 3480000 are weighed 10 mg, 5 mg, 5 mg, and 5 mg, respectively, dissolved in 50 mL of THF, and 50 μL of the resulting solution is injected into the sample side column. . Standard polystyrene samples having a weight average molecular weight of 2630, 37900, 355000, and 5480000 belonging to group C were weighed 5 mg, 5 mg, 5 mg, and 1 mg, respectively, dissolved in 40 mL of THF, and 50 μL of the resulting solution was injected into the sample side column. . A calibration curve (tertiary equation) is prepared from the retention time of these standard polystyrene samples with a data analysis program GPC workstation (EcoSEC-WS) dedicated to HLC-8320GPC, and this is used as a calibration curve for polystyrene-equivalent weight average molecular weight measurement.

<Average particle size of various particles>
The average particle size is measured by the following method. That is, JIS standard sieve opening 2360 μm (7.5 mesh), opening 2000 μm (8.6 mesh), opening 1700 μm (10 mesh), opening 1400 μm (12 mesh), opening 1180 μm (14 mesh), opening Opening 1000 μm (16 mesh), opening 850 μm (18 mesh), opening 710 μm (22 mesh), opening 600 μm (26 mesh), opening 500 μm (30 mesh), opening 425 μm (36 mesh), opening 355 μm (42 mesh), mesh opening 300 μm (50 mesh), mesh opening 250 μm (60 mesh), mesh opening 212 μm (70 mesh), mesh opening 180 μm (83 mesh) and classification based on cumulative weight distribution curve , Average particle size (median) with a cumulative mass of 50% And child size.
<Absorbance ratio of central part and surface layer>
The absorbance ratio (D1730 / D1600) of the center portion and the surface layer portion of the styrene resin particles is measured in the following manner.
(A) Preparation of measurement sample Ten particles selected at random are fixed to a plastic sample support (manufactured by Nissin EM). Next, a slice sample is obtained by slicing the particles with a diamond knife using an ultramicrotome (LEICA ULTRACUT UCT, manufactured by Leica Microsystems) to a thickness of about 10 μm through the center. The obtained slice sample is sandwiched between two barium fluoride crystals (manufactured by Pier Optics). This is used as a measurement sample. The image of the slice sample is captured by the CCD attached to the following measuring device. Image capture is performed with the advancing direction of the blade of the ultramicrotome as the Y axis and the vertical direction as the X axis. The particles in the slice sample are slightly crushed in the moving direction of the blade. By matching the Y-axis of the captured image with the direction of travel of the blade, the measured absorbance ratio is prevented from varying.
Absorbances D1730 and D1600 use an apparatus sold by Perkin Elmer under the trade name “High-Speed IR Imaging System Spectrum Spotlight 300”. Using this apparatus, an image of a slice sample is obtained under the following conditions. From the obtained image, an infrared absorption spectrum at each location is obtained under the following measurement conditions.

(Measurement condition)
Mode: Microscopic transmission imaging Pixel size: 6.25 μm
Measurement region: 4000 cm ^{−1 to} 650 cm ⁻¹
Detector: MCT
Resolution: 8cm-1
Scan / pixel: 2 times (background measurement condition)
Mode: Microscopic transmission imaging Pixel size: 6.25 μm
Measurement region: 4000 cm ^{−1 to} 650 cm ⁻¹
Detector: MCT
Resolution: 8cm-1
Scan / pixel: 60 times Others: A process that does not participate in the measurement spectrum is performed using the infrared absorption spectrum obtained by measuring the barium fluoride crystal in the vicinity of the sample without the sample as a background.

  As shown in FIG. 1, the minimum value and the maximum value of the X coordinate value and the minimum value and the maximum value of the Y coordinate value of the Y axis are connected by a line from the captured image, and the intersection of the lines is set as a center point A. In image processing, the X and Y coordinate values of the center point are set within a range of ± 20 μm from the center point A.

  Next, a straight line passing through the center point A and parallel to the X axis is drawn in the image. A point where this straight line intersects with the position of the end where the particle (resin) exists (maximum value on the X axis) is defined as a point D. An infrared absorption spectrum on a line connecting the points A and D is extracted every 12 ± 2 μm as an X coordinate value. In the present invention, the central portion refers to within 15% of the distance from point A to point D, while the surface layer portion refers to the portion of 20% of the distance from point D to point A.

  Absorbances D1730 and D1600 are read from the extracted infrared absorption spectrum, respectively, and the absorbance ratio (D1730 / D1600) in the center part and the surface layer part is calculated. The arithmetic average of the individual absorbance ratios calculated for 10 particles is taken as the absorbance ratio.

The absorbance D 1730 at 1730 cm ⁻¹ obtained from the infrared absorption spectrum is the absorbance corresponding to the absorption spectrum derived from the stretching vibration between C═O of the ester group contained in the ester. In this measurement of absorbance, no peak separation is performed even when other absorption spectra overlap at 1730 cm ⁻¹ . Absorbance D1730 is a straight line connecting the 1680 cm ^-1 and 1785 cm ^-1 as a baseline, means the maximum absorbance between 1680 cm ^-1 and 1785 cm ^-1. Further, the absorbance D1600 at 1600 cm ⁻¹ obtained from the infrared absorption spectrum is an absorbance corresponding to the absorption spectrum derived from the in-plane vibration of the benzene ring contained in the styrene resin. In this absorbance measurement, peak separation is not performed even when other absorption spectra overlap at 1600 cm ⁻¹ . Absorbance D1600 is a straight line connecting the 1565Cm ^-1 and 1640 cm ^-1 as a baseline, means the maximum absorbance between 1565cm ^-1 and 1640 cm ^-1.

<Initial foaming speed>
The initial foaming speed is measured by measuring the foamable particles to be measured into steam and heating them with steam in a foaming tank. The foaming tank used for measurement is 1120 mm wide, 635 mm high, and 900 mm deep. Steam flows from the steam inlets installed at the bottom and side of the tank, and a φ140 mm opening is installed at the top of the tank. Water vapor is discharged to the outside from the part. In addition, a thermometer is installed in the tank so that the measurement part of the thermometer is located at a position 50 mm from the ceiling, and the temperature in the tank can be measured.
The measurement was performed by opening the door of the foaming tank heated to 90 ° C. or more with water vapor, and confirming that the temperature in the tank reached 80 ° C., and then weighing 3 g of the foamable particles to be measured into the steam. Place in the center of the foaming tank. After leaving the foamable particles in the foaming tank, the foaming tank door is immediately closed, and heating in the foaming tank is started with 0.07 MPa water vapor. After 1 minute has elapsed since the temperature in the foaming tank reached 90 ° C., the water vapor was stopped, the door was immediately opened, and the foamed particles were collected.
Subsequently, the bulk magnification of the obtained expanded particles is measured according to JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. Specifically, first, the foamed particles are naturally dropped into the graduated cylinder. The volume Vcm ³ of the expanded particles dropped into the graduated cylinder is measured using an apparent density measuring device in accordance with JIS K6911. By substituting Vcm ³ into the following equation, the bulk multiple of the expanded particles is calculated.
Volume multiple (times) of expanded particles = volume of expanded particles (V) / mass of expanded particles 3 g
The initial foaming speed is expressed as bulk times / 1 minute.

Example 1
After supplying 120 kg of tricalcium phosphate, 4 g of sodium dodecylbenzenesulfonate, 105 g of benzoyl peroxide, 30 g of t-butylperoxybenzoate, 40 kg of ion-exchanged water and 40 kg of styrene to an autoclave with a stirrer having an internal volume of 100 L, 200 rpm A stirring blade was stirred at a stirring speed to prepare a suspension.
Subsequently, the internal temperature of the autoclave was heated to 90 ° C. and held for 6 hours. Next, the temperature in the autoclave is raised to 125 ° C. and held for 2 hours, then the temperature in the autoclave is cooled to 25 ° C., and the produced particles are recovered, dehydrated and dried, and then polystyrene particles. To obtain polystyrene particles having an average particle diameter of 350 μm and a weight average molecular weight of 200,000.

Add 1800 g of the polystyrene resin as seed particles, 5 g of magnesium pyrophosphate and 0.2 g of sodium dodecylbenzenesulfonate to a polymerization vessel equipped with a stirrer with an internal volume of 5 L and heat to 75 ° C. with stirring to produce a dispersion. did.
Subsequently, 80 g of styrene and 20 g of butyl acrylate were all added to the dispersion while stirring.
Then, 15 minutes after the supply of the solution into the dispersion, a solution in which 1.2 g of benzoyl peroxide and 0.2 g of t-butylperoxybenzoate were dissolved in 100 g of styrene was added to the dispersion. All were added to the dispersion with stirring. After the addition, the polymerization reaction was carried out for 40 minutes while maintaining the dispersion at 75 ° C.
Next, the temperature of the polymerization vessel is raised to 120 ° C. and held for 1 hour, and then the temperature in the autoclave is cooled to 25 ° C., and the generated particles are recovered, dehydrated and dried to obtain an average particle size. Resin particles having 360 μm and a weight average molecular weight of 200,000 were obtained.

Next, the dispersion liquid in which the resin particles are dispersed is maintained at 90 ° C., and 20 g of propane, 150 g of pentane (n-pentane / isopentane (mass ratio) = 4) and 100 g of isobutane are injected into the polymerization vessel over 3 hours. The resin particles were impregnated with a foaming agent to obtain expandable particles. Thereafter, the inside of the polymerization vessel was cooled to 25 ° C., and the expandable particles were taken out.
Polyethylene glycol was applied as an antistatic agent to the surface of the expandable particles. Thereafter, zinc stearate as an antiblocking agent was further applied to the surface of the expandable particles. After coating, the expandable particles were left in a thermostatic chamber at 13 ° C. for 7 days.
Then, the initial foaming speed was measured using the foamable particles.
(Example 2)
Expandable particles were obtained in the same manner as in Example 1 except that 80 g of styrene and 20 g of butyl acrylate were replaced with 90 g of styrene and 10 g of butyl acrylate, and the initial foaming rate was measured in the same manner as in Example 1.
Example 3
Expandable resin particles were obtained in the same manner as in Example 1 except that 80 g of styrene and 20 g of butyl acrylate were replaced with 40 g of styrene and 60 g of butyl acrylate, and the initial foaming rate was measured in the same manner as in Example 1.

(Comparative Example 1)
Expandable resin particles were obtained in the same manner as in Example 1 except that 80 g of styrene and 20 g of butyl acrylate were changed to 100 g of styrene and 0 g of butyl acrylate, and the initial foaming rate was measured in the same manner as in Example 1.
(Comparative Example 2)
Expandable resin particles were obtained in the same manner as in Example 1 except that 80 g of styrene and 20 g of butyl acrylate were replaced with 94 g of styrene and 6 g of butyl acrylate, and the initial foaming rate was measured in the same manner as in Example 1.
(Comparative Example 3)
Expandable resin particles were obtained in the same manner as in Example 1 except that 80 g of styrene and 20 g of butyl acrylate were changed to 30 g of styrene and 70 g of butyl acrylate, and the initial foaming rate was measured in the same manner as in Example 1.
The results of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Table 1.

  From Table 1, the average particle diameter is 200 to 500 μm, the absorbance ratio (A) is larger than the absorbance ratio (B), and the absorbance ratio (A) satisfies the requirements of the range of 0.15 to 0.5. It can be seen that the example expandable particles have a faster expansion rate than the comparative example expandable particles that do not meet any of these requirements. On the other hand, when the absorbance ratio (A) exceeds 0.5, although the initial foaming speed is fast, the foamed particles contract and the appearance of the foamed particles is deteriorated.

Claims (5)

It is an expandable styrene resin particle for lightweight concrete production comprising a resin component derived from an acrylate ester and a foaming agent,
The expandable styrenic resin particles are
(1) having an average particle diameter of 200 to 500 μm,
(2) the respective infrared absorption spectrum of the surface layer and the central portion was measured by microscopic transmission imaging method, the obtained absorbance D1600 absorbance D1730 and 1600 cm ^-1 in 1730 cm ^-1 from the infrared absorption spectrum, from the absorbance D1730 and the absorbance D1600 When the absorbance ratio of the surface layer (D1730 / D1600) (A) and the absorbance ratio of the central part (D1730 / D1600) (B) are calculated,
(I) The absorbance ratio (A) is greater than the absorbance ratio (B),
(Ii) Expandable styrene resin particles, wherein the absorbance ratio (A) is in the range of 0.15 to 0.5.   The expandable styrene resin particles according to claim 1, wherein the absorbance ratio (B) is in a range of 0.05 to 0.4. The foamable styrenic resin particles are placed in a foaming tank heated to 80 ° C. and heated with 0.07 MPa steam to raise the temperature in the foaming tank to 90 ° C. The expandable styrenic resin particle according to claim 1 or 2 , which is a particle that gives the expanded particle a bulk factor of 50 to 65 times when the expanded particle is obtained after a lapse of 1 minute after reaching the temperature. Foamed particles obtained by foaming the expandable styrenic resin particles according to any one of claims 1 to 3 and used for the production of lightweight concrete. The lightweight concrete obtained by hardening the ready-mixed concrete composition containing the foamed particle of Claim 4 , or baking after hardening and decomposing | disassembling the said foamed particle.