JP2012214990A - Thrust transmitting material and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thrust transmitting material having excellent compression strength.SOLUTION: In a pipe-thrusting method, a thrust transmitting material disposed between thrusting pipes is formed of a molded foam body of a plurality of fused foam resin particles containing a polystyrene resin component and a toluene insoluble gel component derived from a copolymer of a styrene monomer and a monomer having 3 to 10 vinyl groups and ester groups in a molecule. The molded foam body contains 1 to 70 mass% toluene insoluble gel component. The measured infrared absorption spectra for the vicinity of the boundary between the foam resin particles by ATR infrared spectroscopy show an absorbance ratio (D/D) in the range of 0.1 to 2 at 1735 cmand 1600 cm. The absorbance ratio (D/D) for the center of the foam resin particle is lower than the absorbance ratio (D/D) for the vicinity of the boundary between the foam resin particles by 0.6 or more.

Description

  The present invention relates to a thrust transmission material and a manufacturing method thereof. More specifically, the present invention relates to a thrust transmission material excellent in compressive strength and a method for manufacturing the same.

As a method for burying pipes such as water and sewage and gas pipes in the ground, an open-cut method and a non-cut-open method are known. Among them, the non-opening method has a small area for excavating the ground surface, and therefore can reduce the construction area, noise, vibration, etc., compared to the open-cut method, and has been widely used in recent years.
A propulsion method is known in which a propulsion unit performs excavation in the ground during the non-open cutting method, and a tube is continuously inserted into a space formed by the propulsion unit, thereby realizing a desired pipe arrangement. In the propulsion method, the pipe is continuously inserted into the space by thrust generated by a pressing machine. A pipe inserted by the propulsion method is generally called a propulsion pipe.

  Since the propulsion tube is inserted by a pressing machine, if a change in thrust occurs at the contact portion between the propulsion tube and the propulsion tube, pressure concentrates on the changed portion, and the propulsion tube may be damaged. In order to suppress this damage, it has been proposed to interpose a cushion material between the propulsion pipe and the propulsion pipe (Japanese Patent Laid-Open No. 61-8320: Patent Document 1).

JP-A-61-8320

The cushion material plays a role of preventing the breakage of the propulsion pipes and transmitting thrust between the propulsion pipes. In the latter sense, the cushion material is also referred to as a thrust transmission material.
The thrust transmission material is required to be a foamed molded article having a high compression strength and a high expansion ratio in order to transmit thrust and reduce raw material costs. However, the improvement in compressive strength and the increase in the expansion ratio are usually in conflict with each other, and it has been difficult to achieve them at the same time.
Therefore, it has been desired to provide a thrust transmission material in which an improvement in compressive strength and a high expansion ratio are realized at the same time.

  Inventors of the present invention, in order to simultaneously improve the compressive strength of the thrust transmission material and increase the foaming ratio, in a plurality of foamed resin particles fused to each other in the foam molded body constituting the thrust transmission material. The presence of the resin component was reviewed. As a result, it has a ratio of toluene-insoluble gel in a specific range, and a styrene monomer in the vicinity of the foamed resin particle interface defined by the absorbance ratio by the ATR method, and 3 to 10 vinyl groups and esters in the molecule. The content ratio of the toluene insoluble gel derived from the copolymer with the monomer having a group is larger than the content ratio relative to the total amount of the foamed molded product, in other words, the toluene insoluble gel content is unevenly distributed on the surface of the resin particles. As a result, it has been found that excellent compression strength can be imparted to the foamed molded article even at a high expansion ratio, and the present invention has been achieved.

Thus, according to the present invention, the thrust transmission material installed between the propulsion pipes in the propulsion method is
A plurality of foamed resins comprising a polystyrene resin component, and a toluene-insoluble gel component derived from a copolymer of a styrene monomer and a monomer having 3 to 10 vinyl groups and ester groups in the molecule It is a foamed molded article made of a fused product of particles,
The foamed molded article contains a toluene-insoluble gel content of 1 to 70% by mass,
Range absorbance ratio (D ₁₇₃₅ / D ₁₆₀₀₎ of 0.1 to 2 at 1735 cm ^-1 and 1600 cm ^-1 obtained from an infrared absorption spectrum around the expanded resin particles surface measured by ATR method infrared spectroscopy Yes,
Provided is a thrust transmission material characterized in that the absorbance ratio (D ₁₇₃₅ / D ₁₆₀₀ ) at the center of the expanded resin particles is 0.6 or more lower than the absorbance ratio (D ₁₇₃₅ / D ₁₆₀₀ ) near the interface of the expanded resin particles Is done.

Furthermore, according to the present invention, there is provided a method for producing the thrust transmission material.
A step of allowing a seed particle containing a polystyrene resin to absorb a styrene monomer and a monomer having 3 to 10 vinyl groups and an ester group in the molecule, and at or after absorption, the styrene monomer A step of obtaining polystyrene resin particles by polymerizing monomers having 3 to 10 vinyl groups and ester groups in the body and molecule, and foaming into the polystyrene resin particles after polymerization or while polymerizing A thrust transmission material comprising: a step of impregnating an agent to obtain expandable resin particles; and a step of foam-molding the expandable resin particles directly or after pre-expanding the expandable resin particles. A manufacturing method is provided.

ADVANTAGE OF THE INVENTION According to this invention, the thrust transmission material which has the outstanding compressive strength also at high foaming ratio, and its manufacturing method can be provided. The inventors believe that this effect is exhibited by the fact that the toluene-insoluble gel content is unevenly distributed near the interface of the foamed resin particles.
The toluene-insoluble gel content is a component derived from a copolymer of a styrene monomer and a monomer selected from a (meth) acrylate monomer and a vinyl monomer having a urethane bond. In this case, a thrust transmission material having excellent compressive strength even at a higher expansion ratio can be provided.

  Furthermore, the (meth) acrylate monomer is trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane trimethacrylate, ethoxylated isocyanuric acid triacrylate, tetramethylolmethane tetraacrylate, ditrimethylolpropane tetraacrylate. When the monomer is selected from dipentaerythritol hexaacrylate, a thrust transmission material having excellent compressive strength can be provided even at a higher expansion ratio.

Moreover, when a thrust transmission material has a density of 0.05-0.67 g / cm < ³ >, the thrust transmission material which has the outstanding compressive strength can be provided even at higher foaming ratio.

2 is an infrared absorption spectrum image of a cross section of the foamed molded product of Example 1. FIG. 7 is an infrared absorption spectrum image of a resin particle cross section of Comparative Example 5.

(Thrust transmission material)
The thrust transmission material of the present invention is a toluene-insoluble gel fraction derived from a copolymer of a polystyrene resin component, a styrene monomer, and a monomer having 3 to 10 vinyl groups and ester groups in the molecule. Is a foam-molded product comprising a fusion product of a plurality of foamed resin particles.
The outer shape of the thrust transmission material is not particularly limited, and can be appropriately set according to the shape of the propulsion pipe. Generally, it has a ring-shaped outer shape.
In addition, the thrust transmission material can be made thinner by about 15% if it has the same compressive strength as compared with a material not containing a toluene insoluble gel.

Hereinafter, the components of the thrust transmission material will be described.
(1) Polystyrene-based resin component The polystyrene-based resin component is not particularly limited, and examples thereof include styrene-based single components such as styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, and bromostyrene. Examples include a component derived from a homopolymer of a monomer or a copolymer thereof.

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) Toluene-insoluble gel fraction derived from a copolymer of a styrene monomer and a monomer having 3 to 10 vinyl groups and an ester group in the molecule 3 to 3 in the molecule The monomer having 10 vinyl groups and ester groups is not particularly limited as long as it is a monomer that can give a foamed molded article having excellent compressive strength. Examples thereof include monomers selected from styrene monomers, (meth) acrylate monomers, and vinyl monomers having a urethane bond.

Examples of the styrene monomer include styrene, α-methyl styrene, vinyl toluene, chlorostyrene, ethyl styrene, isopropyl styrene, dimethyl styrene, bromostyrene, and the like.
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 vinyl monomer having a urethane bond, NK oligo series available from Shin-Nakamura Chemical Co., Ltd. can be used. Specifically, NK oligo U-6HA, NK oligo UA-32P, etc. are mentioned.
The monomers exemplified above may be used alone or in combination.

(3) Toluene-insoluble gel content The foam-molded article of the present invention contains 1 to 70% by mass of a toluene-insoluble gel content. The inventor believes that this gel is derived from a monomer having 3 to 10 vinyl groups and an ester group in the molecule, and a styrene monomer optionally copolymerized with this monomer. When the ratio of a gel part is less than 1 mass%, the strength improvement of a foaming molding is not enough. When it is more than 70% by mass, the toluene-insoluble gel content is increased, the foamability of the resulting foamable resin particles is lowered, and the expansion ratio may not be improved. A more preferable range is 1 to 65% by mass.

(4) Absorbance ratio Next, the absorbance ratio at 1735 cm ^-1 and 1600 cm ^-1 obtained from an infrared absorption spectrum around the foamed resin particles surface measured by ATR method infrared spectroscopy (D ₁₇₃₅ / D ₁₆₀₀₎ is 0 In the range of 1-2. Here, the absorption at 1735 cm ⁻¹ indicates a peak derived from stretching vibration between C═O of the ester group contained in the acrylate ester, and indicates the presence of a toluene-insoluble gel 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. The absorbance ratio within this range means that the toluene-insoluble gel component is present in the vicinity of the foamed resin particle interface at 1% by mass or more. When the absorbance ratio is less than 0.1, the toluene-insoluble gel content does not exist. When more than 2, a toluene insoluble gel content will increase and the foaming magnification of a foaming molding may fall. A more preferable range of the absorbance ratio is 0.2-1.

Furthermore, the foamed molded product has an absorbance ratio (D ₁₇₃₅ / D ₁₆₀₀ ) at the center of the foamed resin particles that is 0.6 or more lower than the absorbance ratio (D ₁₇₃₅ / D ₁₆₀₀ ) near the interface of the foamed resin particles. It can be understood that the toluene-insoluble gel content is unevenly distributed at the interface of the foamed resin particles because the foamed resin particles have a center of an absorbance ratio lower than that in the vicinity of the interface. A more preferable difference in absorbance ratio is 0 to 0.6.
The absorbance ratio (D ₁₇₃₅ / D ₁₆₀₀ ) at the center of the foamed resin particles is preferably in the range of 0 to 0.4, and more preferably in the range of 0 to 0.3.

(5) Additives In the foamed molded product, flame retardants, flame retardant aids, foaming aids, plasticizers, lubricants, anti-bonding agents, adhesion promoters, antistatic agents, exhibitions, as long as physical properties are not impaired Additives such as an adhesive, a bubble regulator, a crosslinking agent, a filler, and a colorant may be contained.
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 air conditioner include ethylene bis stearamide, polyethylene wax and the like.

(Manufacturing method of thrust transmission material)
The foam molded body as a thrust transmission material is, for example, an impregnation step of obtaining foamable resin particles by impregnating a foaming agent into resin particles, directly after foamable resin particles or after prefoaming the foamable resin particles, It can be manufactured through a foam molding process. Here, it is preferable that the pre-expansion of the expandable resin particles is performed under conditions that give pre-expanded particles having a bulk density corresponding to the density of the foam molded body constituting the thrust transmission material. For example, when a thrust transmission material having a density of 0.05 to 0.67 g / cm ³ is desired, the preliminarily expanded particles having a relatively low bulk density of 0.05 to 0.67 g / cm ³ are used. Foaming is preferably performed. The foam molding can be performed after appropriately filling the foamed resin particles or the pre-foamed particles in the molded product cavity of the foam molding die.

(1) Expandable resin particles The production method of the expandable resin particles is not particularly limited.
(A) After a monomer mixture containing styrene and a crosslinkable monomer is subjected to bulk polymerization in the presence of a polymerization initiator, the resulting bulk is pelletized into resin particles, and foamed on the resin particles A method for producing expandable resin particles by impregnating an agent (bulk polymerization method),
(B) Suspension polymerization of the monomer mixture in the presence of a polymerization initiator to obtain resin particles, and after the polymerization or polymerization, the resin particles are impregnated with a foaming agent to produce expandable resin particles. Method (suspension polymerization method),
(C) The seed particles are allowed to absorb the monomer mixture, and after or after being absorbed, the monomer mixture is polymerized to obtain resin particles. After the polymerization or polymerization, the resin particles are expanded. For producing expandable resin particles by impregnating with an agent (seed polymerization method)
Etc. Among these production methods, the above-mentioned methods (b) and (c) are preferred because they do not require a pelletizing step and are excellent in production efficiency and are difficult to decompose the flame retardant and flame retardant aid. In addition, when a flame retardant or a flame retardant aid is contained in the resin particles, the flame retardant is added to the reaction system or the resin when the monomer mixture is polymerized or when pelletized in the method (a). Or a flame retardant aid may be added.

  Among the above methods, the resin is derived from a monomer selected from the above (meth) acrylate monomer and a vinyl monomer having a urethane bond at the specific absorbance ratio and from a styrene monomer. A seed polymerization method in which a resin can be present is preferable.

The method for producing expandable resin particles by the seed polymerization method is, for example,
In aqueous medium, the seed particles are selected from styrene, 3-10 vinyl groups and ester groups in the molecule, for example, (meth) acrylate monomers and vinyl monomers having urethane bonds A step of absorbing a monomer mixture containing a monomer (however, if the seed particles contain a component derived from styrene, the monomer mixture may not contain styrene);
A method comprising a step of obtaining polystyrene resin particles by polymerizing a monomer mixture after absorbing or absorbing and a step of impregnating a polystyrene resin particle with a foaming agent after or after polymerization. Can be adopted.

  In addition, the monomer which has 3-10 vinyl groups and ester groups in a molecule | numerator is 1: 0.001-0.015 (mass ratio) with respect to all the monomers for manufacturing a foaming molding. ) Is preferably included. If it is less than 0.001, the strength of the foamable molded article obtained by reducing the toluene-insoluble gel content may be lowered. When more than 0.015, toluene insoluble gel content increases and the foamability of the foamable resin particle obtained may fall. A more preferable ratio is 1: 0.0015 to 0.010.

(A) Seed particles In the monomer mixture, it is not necessary to supply all of the constituent monomers simultaneously into the aqueous medium, and all or part of the monomer is supplied into the aqueous medium at different timings. May be. When the flame retardant or flame retardant aid is contained in the expandable resin particles, the flame retardant or flame retardant aid may be added to the monomer mixture or aqueous medium, or may be contained in the seed particles. May be.

  Specifically, the resin constituting the seed particles includes any of components derived from monomers selected from styrene, the above (meth) acrylate monomers, and vinyl monomers having a urethane bond. In this case, it is preferable to adjust the use amount of each monomer in the monomer mixture so that the ratio of the component derived from the monomer constituting the expandable resin particle is within the specific range. .

  In particular, when the resin constituting the seed particles includes a component derived from styrene, the proportion of the component derived from the monomer constituting the expandable resin particle obtained is within the specific range as described above. Thus, although the usage-amount of each monomer in a monomer mixture is adjusted, the usage-amount of styrene may be 0 mass part in that case.

  In addition, a part of or all of the seed particles may be a polystyrene resin recovered product. Further, the seed particles are styrene monomers such as vinyl toluene, chlorostyrene, ethyl styrene, i-propyl styrene, dimethyl styrene, bromo styrene, o-divinylbenzene copolymerizable with these styrene monomers, polyfunctional monomers such as divinylbenzene such as m-divinylbenzene and p-divinylbenzene, alkylene glycol di (meth) acrylate such as ethylene glycol di (meth) acrylate and polyethylene glycol di (meth) acrylate, α-methyl Styrene, (meth) acrylonitrile, methyl (meth) acrylate, etc. are mentioned. These other monomers may be used alone or in combination.

The average particle diameter of the seed particles can be appropriately adjusted according to the average particle diameter of the foamable resin particles to be produced. For example, the average particle diameter of the seed particles can be 40 to 70% of the average particle diameter of the expandable resin particles. Specifically, when producing expandable 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 0.4 to 0.7 mm.
The weight average molecular weight of the seed particles is not particularly limited, but is preferably 150,000 to 700,000, more preferably 200,000 to 500,000.

  The seed particles are not particularly limited and can be produced by a known method. For example, a suspension polymerization method or a method in which a raw material resin is melt-kneaded with an extruder, extruded into a strand shape, and cut with a desired particle diameter can be mentioned. Further, the particles obtained by the suspension polymerization method or obtained by the cutting method may be classified into particles having a desired average particle diameter by appropriately sieving. By using classified seed particles, expandable resin particles having a narrow particle size distribution and a desired particle size can be obtained.

  The seed particles may be particles obtained by impregnating and polymerizing particles obtained by suspension polymerization or cutting with a styrene monomer in an aqueous medium. Examples of the aqueous medium include water and a mixed medium of water and a water-soluble solvent (for example, a lower alcohol such as methyl alcohol or ethyl alcohol). The amount of the styrenic monomer used in this method can be in the range of 7.0 to 100.0 parts by mass with respect to 100 parts by mass of the particles. When the amount is less than 7.0 parts by mass, heat resistance during molding may decrease, and when the amount exceeds 100.0 parts by mass, foamability may decrease.

  The amount of seed particles used is preferably 10 to 75% by mass with respect to the total amount of resin particles obtained at the end of polymerization. When the amount of seed particles used is less than 10% by mass, it may be difficult to control the polymerization rate of the monomer mixture during seed polymerization within an appropriate range. As a result, the resulting resin may have a high molecular weight, which may reduce the foamability of the foamable resin particles. In this case, a large amount of fine resin powder may be generated, resulting in a decrease in production efficiency. On the other hand, when the amount of seed particles used is more than 75% by mass, the appearance of the foamed molded product may be deteriorated. A more preferable usage amount is 15 to 50% by mass.

(B) Aqueous medium In the aqueous medium, a dispersant may be used in order to stabilize the dispersibility of the droplets and seed particles of the monomer mixture. Examples of such a dispersant include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone, and poorly soluble inorganic compounds such as tricalcium phosphate and magnesium pyrophosphate. A combination of a water-soluble polymer and a hardly soluble inorganic compound is preferred. Moreover, when using a poorly soluble inorganic compound, an anionic surfactant is usually used together.

  Examples of the anionic surfactant include fatty acid soaps, N-acyl amino acids or salts thereof, carboxylates such as alkyl ether carboxylates, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyls Sulfates, such as sulfoacetates, α-olefin sulfonates, higher alcohol sulfates, secondary higher alcohol sulfates, alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates, Examples thereof include phosphoric acid ester salts such as alkyl ether phosphoric acid ester salts and alkyl phosphoric acid ester salts.

(C) Polymerization of monomer mixture Polymerization of the monomer mixture can be performed, for example, by heating at 60 to 150 ° C for 2 to 40 hours. The polymerization can be carried out after the monomer mixture is absorbed into the seed particles or while the monomer mixture is absorbed into the seed particles.

  The monomer mixture is usually polymerized in the presence of a polymerization initiator. The polymerization initiator is usually impregnated into the seed particles simultaneously with the monomer mixture. The polymerization initiator is not particularly limited as long as it is conventionally used for the polymerization of styrene monomers. For example, benzoyl peroxide, t-butyl peroxybenzoate, t-butyl peroxypivalate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, 2, 2-t-butylperoxybutane, t-butylperoxy-3,3,5-trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate, 2,5-dimethyl-2,5-bis (benzoyl) Peroxy) organic peroxides such as hexane and dicumyl peroxide. These polymerization initiators may be used alone or in combination. The usage-amount of a polymerization initiator is the range of 0.05-0.5 mass part with respect to 100 mass parts of monomer mixtures, for example.

  In particular, in order to adjust the weight average molecular weight and reduce the residual monomer, it is preferable to use two kinds of polymerization initiators having different 10-hour half-life temperatures. Specifically, the 10-hour half-life temperature of the polymerization initiator having a higher 10-hour half-life temperature is 80 to 120 ° C. and the polymerization initiator having a lower 10-hour half-life temperature is 10-hour half-life temperature. Is preferably 70 to 110 ° C.

  In order to uniformly absorb the polymerization initiator from the seed particles or the seed particles to the growing particles, the polymerization initiator is suspended or emulsified and dispersed in advance in the aqueous medium when the polymerization initiator is added to the aqueous medium. It is preferable to add it to the dispersion liquid above, or to add the polymerization initiator to the aqueous medium after dissolving it in the monomer of the monomer mixture or the monomer mixture in advance.

(D) Step of impregnating foaming agent Foamable resin particles are obtained by impregnating resin particles with a foaming agent (hereinafter also simply referred to as a foaming agent). The impregnation with the foaming agent may be performed after polymerization or may be performed while polymerization.
Impregnation can be performed by a method known per se. For example, the impregnation during the polymerization can be performed by performing the polymerization reaction in a closed container and press-fitting a foaming agent into the container. Impregnation after completion of the polymerization is performed by press-fitting a foaming agent in a closed container.

(I) 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. Among the carbon hydrogens, 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, the content of the foaming agent is preferably in the range of 0.5 to 15% by mass. When the amount is less than 0.5% 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 15% by mass, the time required for the cooling step in the production process of the foam molded article becomes long, and the productivity may be lowered. A more preferable content of the blowing agent is 1 to 14% by mass.

(Ii) Method for Producing Expandable Resin Particles When the temperature when impregnating the resin particles with the foaming agent and the foaming aid is low, the time required for impregnating the resin particles with the foaming agent and the foaming aid becomes long. If the production efficiency is lowered, and if it is too high, the resin particles may be fused with each other to generate bonded grains, so that the temperature is preferably 60 to 120 ° C, more preferably 70 to 110 ° C. You may use a foaming adjuvant and a plasticizer together with a foaming agent. Examples of the foaming aid / plasticizer include diisobutyl adipate, toluene, cyclohexane, and ethylbenzene.

(2) Pre-expanded particles Pre-expanded particles are obtained by pre-expanding 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 0.05 to 0.67 g / cm ³ . When the bulk density of the pre-expanded particles is less than 0.05 g / cm ³ , the foamed molded product cannot have sufficient strength and long-term durability. On the other hand, when the bulk density is larger than 0.67 g / cm ³ , the variation of the bulk foaming factor becomes large, uniform particles cannot be obtained, and the lightweight property of the foamed molded product may be lowered.

In addition, it is preferable to apply | coat a lubricant to the surface of an expandable resin particle before foaming. By applying, the bonding between the pre-expanded particles can be reduced in the expansion step of the expandable resin particles.
The foaming agent content in the pre-expanded particles is preferably in the range of 0.5 to 15% by mass. When it is less than 0.5% by mass, pre-expanded particles having a desired density may not be obtained. In addition, since the effect of increasing the secondary foaming force when the pre-expanded particles are subjected to in-mold foam molding is reduced, the appearance of the foam molded article may not be improved. When the amount is more than 15% by mass, the time required for the cooling step in the production process of the foam molded article becomes long, and the productivity may be lowered. A more preferable content of the blowing agent is 1 to 14% by mass.

(3) Foamed molded body Filled with foamable resin particles or pre-expanded particles in a closed mold having a large number of small holes, heated and foamed again with pressurized steam, etc., filling the gaps between the pre-expanded particles and pre-expanded A foam-molded article can be produced by integrating the particles by fusing them together. 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.
<Absorbance ratio>
(1) Absorbance ratio X near the interface of the expanded resin particles
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. In the present specification, the vicinity of the interface between the expanded resin particles means a region within 200 μm from the interface where the two expanded resin particles are fused to each other toward the center. 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 (1735 cm ⁻¹ / ^{1) of} each set of polystyrene resin component and a copolymer component of a monomer having 3 to 10 vinyl groups and ester groups in the molecule and a styrene monomer. 1600 cm ⁻¹ ) is calculated. The average value of the 10 sets of absorbance ratios obtained is defined as the absorbance ratio X. The measurement apparatus and measurement conditions used for measuring the absorbance are described below.
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

(2) Absorbance ratio Y at the center of foamed resin particles
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. The center of the foamed resin particle is analyzed by a microscopic IR imaging mapping method along a straight line connecting one center and the other center of the two foamed resin particles. In the present specification, the center of the expanded resin particle means a region having a radius of 200 μm or less from the center of the particle in the cross section including the particle center from the interface where the expanded resin particle is fused with the adjacent expandable resin particle. From the results, the absorbance ratio (1735 cm ⁻¹ / ^{1) of} each set of polystyrene resin component and a copolymer component of a monomer having 3 to 10 vinyl groups and ester groups in the molecule and a styrene monomer. 1600 cm ⁻¹ ) is calculated. The average value of the 10 sets of absorbance ratios obtained is defined as the absorbance ratio Y. The measurement apparatus and measurement conditions used for measuring the absorbance are the same as the apparatus and conditions for the absorbance ratio X.

<Content of toluene insoluble gel content>
Let the content rate of a toluene insoluble gel part be the value measured on condition of the following.
The measurement sample W1 of the foamed molded product (weighed precisely at 1.00 g ± 0.02 g) is immersed in 100 ml of toluene at 130 ° C. for 24 hours. After soaking, the mixture is filtered using an 80-mesh wire mesh, and the residue is dried under reduced pressure at 80 ° C. and −60 cmHg for 2 hours. After drying, it is naturally cooled to room temperature in a desiccator, and the mass W2 of the dry residue is measured.
The toluene-insoluble gel content is calculated from the measured value according to the following formula.
Toluene insoluble gel content (mass%) = 100 × W2 / W1

<Bulk density>
The bulk density 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>
The mass (a) and volume (b) of a test piece (example 300 × 400 × 30 mm) cut out from a foamed molded product (after being molded and dried at 40 ° C. for 20 hours or more) each have three or more significant figures. And the density (kg / m ³ ) of the foamed molded product is obtained from the formula (a) / (b).

<Compressive strength>
The 5% compressive strength of the foamed molded product is measured according to the method described in JIS K9511: 1999 “Foamed plastic heat insulating material”. Specifically, a rectangular parallelepiped test piece having a length of 100 mm, a width of 100 mm, and a thickness of 30 mm is cut out from a foam molded body having a density of 200 kg / m ³ . Thereafter, the 5% compressive strength of the test piece is measured under a compression speed of 10 mm / min using a compressive strength measuring device (trade name “UCT-10T” manufactured by Orientec Co., Ltd.). Three test pieces are prepared, and the 5% compressive strength of each test piece is measured in the same manner, and the arithmetic average is taken as the average 5% compressive strength.
Evaluation: Average 5% compression strength 1.5 MPa or more: ○
Less than 1.5 MPa: ×

Example 1
120 g of tribasic calcium phosphate (manufactured by Ohira Chemical Co., Ltd.), 0.2 g of sodium hydrogen sulfite and 0.2 g of potassium persulfate were added to an autoclave with a stirrer having an internal volume of 100 liters, and 140 g of benzoyl peroxide (purity 75%), After supplying 20 g of t-butylperoxy-2-ethylhexyl monocarbonate, 40 kg of ion-exchanged water and 40 kg of styrene monomer, the stirring blade was rotated at a rotational speed of 100 rpm and stirred to form an aqueous suspension. .

Next, the temperature in the autoclave is increased to 90 ° C. while stirring the aqueous suspension by rotating the stirring blade at a rotation speed of 200 rpm, and maintained at 90 ° C. for 6 hours. Was raised to 125 ° C. and held at 125 ° C. for 2 hours and 15 minutes, whereby the styrene monomer was subjected to suspension polymerization.
Thereafter, the temperature in the autoclave is cooled to 25 ° C., the polystyrene particles are taken out from the autoclave, washed and dehydrated repeatedly, and after passing through the drying step, the polystyrene particles are classified, and the particle size is reduced. Polystyrene particles having 0.2 to 1.2 mm and a weight average molecular weight of 300,000 were obtained.

Next, another 25 liter autoclave with a stirrer is supplied with 10 kg of ion-exchanged water and the above polystyrene resin as 2350 g of seed particles, supplied with 30 g of magnesium pyrophosphate and 1 g of calcium dodecylbenzenesulfonate and heated to 75 ° C. while stirring. A dispersion was prepared.
Subsequently, 33.0 g of benzoyl peroxide and 3.2 g of t-butylperoxybenzoate were dissolved in 1000 g of styrene monomer, and all of the styrene monomer was supplied to the dispersion while stirring.

And 30 minutes after supplying the styrene monomer in the dispersion, 13.3 g of trimethylolpropane trimethacrylate (trifunctional monomer, molecular weight 338) was dissolved in 2650 g of styrene monomer. The temperature inside the autoclave was raised from 75 ° C. to 88 ° C. while supplying the product at a constant supply rate over 60 minutes.
Next, while maintaining the dispersion at 88 ° C., by performing seed polymerization while supplying 20 g of trimethylolpropane trimethacrylate dissolved in 4000 g of styrene monomer at a constant supply rate over 90 minutes, Resin particles were obtained. Subsequently, the reaction vessel was sealed, heated to 120 ° C. over 30 minutes, held for 90 minutes, and then cooled to 60 ° C.

Next, the dispersion liquid in which the resin particles are dispersed is held at 120 ° C., and subsequently, 47.5 g of toluene, 125 g of pentane, and 90 g of butane are pressed into the polymerization vessel and held for 5 hours. It was impregnated with pentane and 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 prefoamed to a bulk density of 0.20 g / cm ³ to obtain prefoamed 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 room at 50 ° C. for 6 hours, the density was measured and found to be 0.20 g / cm ³ (200 kg / m ³ ). The foamed molded article was excellent in appearance without shrinkage.
The toluene-insoluble gel content of the foamed molded product was 60% by mass.

(Examples 2-7 and Comparative Examples 1-5)
A foamed molded article was obtained in the same manner as in Example 1 except that a monomer giving the toluene-insoluble gel content shown in Table 1 was used. In Comparative Example 5, the cross-linking component was unevenly distributed, and a foamed molded article could not be obtained.
The foamed molded bodies of Examples 2 to 7 were excellent in appearance without shrinkage.
On the other hand, in the foamed molded products of Comparative Examples 1 to 4, the foamed molded products had a compressive strength of less than 1.5 Mpa.
The result of Examples 1-7 and Comparative Examples 1-5 is put together in Table 1, and is shown.

From Table 1, it can be seen that if the number of vinyl groups providing the toluene-insoluble gel content is in the range of 3 to 10, the compressive strength can be significantly improved.
The infrared absorption spectrum image of the cross section of the foamed molded product of Example 1 and the infrared absorption spectrum image of the cross section of the resin particle of Comparative Example 5 are shown in FIGS. 1 and 2, respectively. 1 and 2, it can be seen that the foam-molded product of Example 1 has a toluene-insoluble gel content unevenly distributed at the particle interface.

Claims (6)

The thrust transmission material installed between the propulsion pipes in the propulsion method is
A plurality of foamed resins comprising a polystyrene resin component, and a toluene-insoluble gel component derived from a copolymer of a styrene monomer and a monomer having 3 to 10 vinyl groups and ester groups in the molecule It is a foamed molded article made of a fused product of particles,
The foamed molded article contains a toluene-insoluble gel content of 1 to 70% by mass,
Range absorbance ratio (D ₁₇₃₅ / D ₁₆₀₀₎ of 0.1 to 2 at 1735 cm ^-1 and 1600 cm ^-1 obtained from an infrared absorption spectrum around the expanded resin particles surface measured by ATR method infrared spectroscopy Yes,
A thrust transmission material, wherein the absorbance ratio (D ₁₇₃₅ / D ₁₆₀₀ ) at the center of the foamed resin particles is 0.6 or more lower than the absorbance ratio (D ₁₇₃₅ / D ₁₆₀₀ ) near the interface of the foamed resin particles.   The toluene-insoluble gel component is a component derived from a copolymer of a styrene monomer and a monomer selected from a (meth) acrylate monomer and a vinyl monomer having a urethane bond. Item 2. The thrust transmission material according to Item 1.   The (meth) acrylate monomer is trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane trimethacrylate, ethoxylated isocyanuric acid triacrylate, tetramethylolmethane tetraacrylate, ditrimethylolpropane tetraacrylate and The thrust transmitting material according to claim 2, wherein the thrust transmitting material is a monomer selected from dipentaerythritol hexaacrylate. The thrust transmission material according to claim 1, wherein the thrust transmission material has a density of 0.05 to 0.67 g / cm ³ . It is the manufacturing method of the thrust transmission material as described in any one of Claims 1-4,
A step of allowing a seed particle containing a polystyrene resin to absorb a styrene monomer and a monomer having 3 to 10 vinyl groups and an ester group in the molecule, and at or after absorption, the styrene monomer A step of obtaining polystyrene resin particles by polymerizing monomers having 3 to 10 vinyl groups and ester groups in the body and molecule, and foaming into the polystyrene resin particles after polymerization or while polymerizing A thrust transmission material comprising: a step of impregnating an agent to obtain expandable resin particles; and a step of foam-molding the expandable resin particles directly or after pre-expanding the expandable resin particles. Manufacturing method. The method for producing a thrust transmission material according to claim 5, wherein the pre-expansion of the expandable resin particles is performed under conditions that provide pre-expanded particles having a bulk density of 0.05 to 0.67 g / cm ³ .