JP2003194289A - Pipe thermal insulating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pipe thermal insulating material made of styrene-based resin foam molding element, stabilizing dimensions thereof under high temperature atmosphere for the long term, and including a finite amount of volatile organic compound. <P>SOLUTION: Styrene-based resin reserve foaming grains obtained by impregnating styrene-based resin grains with carbon dioxide gas is in-mold foamed to be a pipe thermal insulating material. When being heated at 85 for 168 hours, the rate of change in dimensions is made to be within ±0.5%. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat insulating material for a pipe mainly used for keeping the temperature of a pipe for water supply or hot water supply. 2. Description of the Related Art Pipes for water supply and hot water supply are provided from inside a cold water source or a hot water source to inside and outside a building, and cold water and hot water are led to a consumption place. In order to reduce the heat loss in the pipeline, a heat insulating material is attached to the water supply / hot water supply pipe (see JP-A-2000-154900). For example, FIG. 3 shows an example of a heat insulating material made of a resin foam molded article having a shape obtained by dividing a cylindrical body into two parts in a radial direction.
The heat insulating materials 52, 52 formed so as to have an inner diameter that can be closely adhered to the periphery of the pipe 51 are fixed to the outer peripheral surface of the pipe 51 using an adhesive or an appropriate fixing tool such as an adhesive tape. . [0003] Due to its excellent heat insulating properties, excellent strength and moldability, and low cost, a styrene-based resin foam molded article is often used. Have been. These heat insulating materials are filled with pre-expanded particles obtained by heating expandable styrene resin particles containing butane or pentane as a foaming agent by heat such as steam, into the cavity of the in-mold foam molding die, It is manufactured by subjecting the pre-expanded particles to foam molding in a mold by heating with steam or the like. However, those using butane or pentane as the blowing agent have a dimensional change rate of ± 1.5% when exposed to a high-temperature environment of about 85 ° C., which is the maximum temperature of hot water flowing in the hot water supply vibrator, for a long time. It turned out to be large. Generally, even if a hot water supply pipe is designed for flowing hot water of about 80 ° C., if hot water of up to about 85 ° C. flows for some reason, as described above. Since the dimensional change rate is as large as about ± 1.5%, a gap is formed between the pipe and the heat insulating material, and sometimes a crack occurs in the heat insulating material for the pipe, thereby impairing the heat insulating performance. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a heat insulating material for pipes according to the present invention is obtained by impregnating styrene resin particles with carbon dioxide gas. Cylindrical molded article obtained by heating at 85 ° C. for 168 hours, the dimensional change before and after heating is within ± 0.5%. Alternatively, it is a pipe heat insulating material having a shape obtained by dividing a cylindrical body in a radial direction. In the present invention, the condition of “heating at 85 ° C. for 168 hours” is one of the indices required by those skilled in the art as a heat insulating material such as a hot water supply pipe. In addition, when the dimensional change rate at this time satisfies ± 0.5% or less, it is possible to prevent the heat insulation state from being lowered for the above-described reason. A foamed styrene-based resin having a dimensional change rate in the above range (ie, a heat insulating material for pipes) is obtained by in-mold foaming of pre-expanded styrene-based resin particles produced as follows. be able to. That is,
First, styrene-based resin particles are impregnated with carbon dioxide to form expandable styrene-based resin particles, and in the next step, the expandable styrene-based resin particles are charged into a pre-foaming machine having a steam input line and an exhaust line, and steam is injected. Steam from the input line
The gas is supplied at an input pressure of 5 to 5.0 kg / cm ² G, and the atmosphere gas containing steam is exhausted from the exhaust line.
Pre-expanded while maintaining a low 1.0 kg / cm ² G to obtain pre-expanded styrene resin particles. By using the above-mentioned styrene-based resin pre-expanded particles, it is possible to obtain a styrene-based resin foam molded article by in-mold foaming having the dimensional change rate of ± 0.5% or less. Therefore, the heat insulating material for pipes manufactured in this way becomes a heat insulating material for pipes that satisfies the above-described required properties of the heat insulating material for pipes, and can suppress a decrease in heat insulation performance for a long time. At the same time, the content of the residual volatile organic compound can be suppressed to an extremely small amount. The in-mold foam molding conditions may be the same as the conventional in-mold foam molding conditions using styrene resin pre-expanded particles. The details will be described below. As the styrene resin particles, generally known styrene resin particles can be used. Specifically, such resin particles include styrene, α-methylstyrene, paramethylstyrene, t
-Homopolymer particles of styrene monomers such as butylstyrene, chlorostyrene, divinylbenzene (bifunctional monomer) or copolymer particles obtained by combining two or more of these monomers, methyl acrylate, butyl acrylate, Methyl methacrylate, ethyl methacrylate, esters of acrylic acid and methacrylic acid such as cetyl methacrylate,
Alternatively, copolymer particles with a monomer other than a styrene-based monomer such as acrylonitrile, dimethyl fumarate, ethyl fumarate, and alkylene glycol dimethacrylate (a bifunctional monomer) may be used. Further, resin particles obtained by extrusion blending with a resin other than the styrene resin within a range in which the styrene component in the styrene resin particles exceeds 50% by weight may be used. Examples of the resin other than the styrene resin include a polyphenyl ether resin, a polyolefin resin, and a rubber component. In particular, polystyrene resin particles are preferable as the styrene resin particles. Resin particles having a particle size of, for example, 0.2 to 5 mm can be used. The styrene-based resin particles are preferably those in which the residual styrene-based monomer is suppressed to a small extent.
Those having a concentration of from 500 to 500 ppm are particularly preferred. In order to reduce the residual styrene-based monomer in the styrene-based resin particles, for example, in suspension polymerization, a high-temperature-initiated polymerization catalyst of 0.05% by weight or more based on the styrene-based monomer is used. Is preferably 115 ° C. or higher. Examples of the high temperature initiation type polymerization catalyst include t-butyl peroxybenzoate, t-butyl peroxypivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxy acetate, 2,2-t-butyl peroxybutane, and the like. Temperature to obtain a half-life of 10 hours
Those at 15 ° C. are particularly preferred. However, if these are used more than necessary, they will contain decomposition by-products such as t-butanol, so that they vary depending on the type of polymerization catalyst, but the upper limit of the amount used is preferably 0.5% by weight. The molecular weight of the styrene-based resin particles is preferably 200,000 to 400,000 in terms of weight average molecular weight according to the GPC method. If it is less than 200,000, the strength of the foamed molded article may be reduced.
If it exceeds 10,000, it is difficult to obtain a sufficient foaming property, which is not preferable. The styrene resin particles are impregnated with carbon dioxide as a foaming agent to obtain expandable styrene resin particles. The carbon dioxide gas as the foaming agent may be 100% carbon dioxide gas, but other foaming agents may be added as long as the effects of the present invention are not impaired. Other blowing agents include air, inorganic blowing agents such as nitrogen, aliphatic hydrocarbons such as propane, butane, pentane, and hexane; cycloaliphatic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane; and fluorocarbons. Organic blowing agents can also be mixed. As the fluorinated hydrocarbon, it is preferable to use difluoroethane, tetrafluoroethane, or the like having an ozone depletion potential of zero. Here, the organic foaming agent is preferably used in a range not exceeding 20% by weight of the total amount of the foaming agent. The content ratio of carbon dioxide in the styrene resin particles is 1 to 15% by weight.
Is preferred. In order to impregnate the styrene-based resin particles with carbon dioxide gas, for example, after putting the styrene-based resin particles into a pressure-resistant closed container, carbon dioxide gas is injected and the resin particles are brought into contact with the pressurized carbon dioxide gas. This can be done by causing The impregnation temperature may be raised to a temperature at which the styrene resin particles do not coalesce and agglomerate with each other,
４０40 ° C. The pressure at which the styrene resin particles are impregnated with carbon dioxide gas is preferably 10 kg / cm ² G or more, more preferably 15 to 40 kg / cm ² G. The impregnation time can be appropriately adjusted so that the styrene-based resin particles have the above-mentioned carbon dioxide content.
0 hours is preferable, and 2 to 8 hours is more preferable. When impregnating the styrene resin particles with carbon dioxide, various surface treatment agents can be applied to the surfaces of the resin particles. Examples of such a surface treatment agent include an anti-binding agent for preventing the bonding of the pre-expanded particles at the time of heat expansion, a fusion promoting agent at the time of molding, an antistatic agent, and a spreading agent. Examples of the binding inhibitor include talc, calcium carbonate, silica, zinc stearate, aluminum hydroxide, ethylene bisstearic acid amide, tribasic calcium phosphate, dimethyl silicon and the like. As the fusion promoter, for example, stearic acid, stearic acid triglyceride, hydroxystearic acid triglyceride,
And sorbitan stearate, polyethylene wax and the like. 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. [0016] As other additives, flame retardants such as hexabromocyclododecane and tetrabromocyclooctane, methacrylic acid ester copolymers, ethylenebisstearic acid amide, and polyethylene wax may be incorporated into the styrene resin particles, if desired. And a cell regulator such as ethylene-vinyl acetate copolymer or the like. The above-mentioned binding inhibitor, fusion promoter during molding, antistatic agent, spreading agent and other additives can be used alone or in combination of two or more. The above-mentioned expandable styrene resin particles may contain a flame retardant. As a method for obtaining styrene-based resin pre-expanded particles containing a flame retardant, for example, in a suspension of styrene-based resin particles and water, the resin in a temperature atmosphere above the melting point of the flame retardant dissolved or suspended in water Styrene resin particles containing a flame retardant are obtained by a method of including a flame retardant in particles, or a method of including a flame retardant in styrene resin particles by extrusion blending, and impregnation and prefoaming of a foaming agent using this. Method. Examples of the flame retardant that can be used at this time include hexabromocyclododecane and tetrabromocyclooctane. The content of the flame retardant is preferably from 0.1 to 4% by weight, particularly preferably from 0.5 to 3.0% by weight, based on the whole resin particles. When the content of the flame retardant is less than 0.1% by weight, it is difficult to obtain a sufficient flame retarding effect, which is not preferable. On the other hand, if the flame retardant content exceeds 4% by weight, the tendency of the pre-expanded particles of the styrene resin to coalesce with each other increases, which is not preferable. The particle diameter of the styrene resin pre-expanded particles is preferably about 0.3 to 10 mm. The styrene resin pre-expanded particles are preferably produced as follows. That is, as described above, the styrene-based resin particles are impregnated with carbon dioxide to form expandable styrene-based resin particles, and in the next step, the expandable styrene-based resin is placed in a preliminary foaming machine having a steam input line and an exhaust line. The particles are charged, steam is supplied from a steam charging line at a charging pressure of 0.5 to 5.0 kg / cm ² G, and an atmosphere gas containing steam is exhausted from an exhaust line,
In the meantime, the pressure in the foaming machine is set at 0.0
Pre-foaming is performed while maintaining a low level of 5 to 1.0 kg / cm ² G to obtain pre-foamed styrene resin particles. In this method, it is preferred that prefoaming be performed immediately after the step of impregnating with carbon dioxide gas. Further, in this method, it is necessary to control the pressure in the preliminary foaming machine to be always lower than the supply pressure by using an exhaust control valve or the like so that the steam is always supplied to the foaming machine. For example, if the steam input pressure is set to 1.2 kg / cm ² G and the pressure in the prefoaming machine is set to 0.8 kg / cm ² G, the pressure is reduced while removing 0.4 kg / cm ² G pressure from the exhaust line. Is performed. In particular,
The pressure can be adjusted by linking and controlling the pressure inside the foaming machine and the exhaust control valve. The difference between the input pressure and the pressure inside the foaming machine is 0.0
If it is less than 5 kg / cm ² G, not only is it difficult to obtain styrene resin pre-expanded particles having a low bulk density, but the appearance and internal fusion of the expanded molded article are poor, and the commercial value is low. On the other hand, if it exceeds 1.0 kg / cm ² G, the bonding at the time of preliminary foaming increases, which is not preferable. A more preferred pressure difference is
0.1 to 0.7 kg / cm ² G. The expandable styrene resin particles in the prefoaming machine are preferably heated to about 110 to 160 ° C., more preferably 110 to 130 ° C. When the heating temperature is lower than 110 ° C., the bulk density is 0.5 g /
Pre-expanded styrene resin particles of cm ³ or less are not preferred because they are difficult to obtain. On the other hand, when the heating temperature is higher than 160 ° C., the tendency of the styrene-based resin pre-expanded particles to coalesce increases, which is not preferable. FIG. 1 shows an example of a pre-expansion machine which can be used for producing the pre-expanded styrene resin particles as described above. In the figure, 2 is a stirring motor, 3 is a stirring blade, 4 is a baffle bar, 5 is a detector for the top of the foaming tank, 6 is a foaming particle transporter, 7
Is an expandable particle measuring tank, 8 is an expandable particle injector, 9 is a steam blowing control valve, 10 is a steam chamber, 11 is a condensed water discharge valve, 12 is an exhaust control valve, 13 is a pre-expanded particle discharge port,
4 is a pre-expanded particle temporary receiver, 15 is a pneumatic transportation facility, 16
Denotes an internal pressure detection / control device, 17 denotes a steam injection hole, 18 denotes a steam input pressure gauge, 19 denotes a pressure reducing valve, and 20 denotes a steam source pressure gauge. The foam molded article obtained by foam molding the above-mentioned styrene resin pre-expanded particles has excellent long-term dimensional stability. As described in the examples, 8
The dimensional change when heated at 5 ° C. for 168 hours is ± 0.1%.
It can be within 5%. Further, the content of the volatile organic compound can be extremely reduced to 1000 ppm or less. The foam molding method is not particularly limited, and any known method can be used. For example, by filling styrenic resin pre-expanded particles into the cavity of the foaming mold and heating the pre-expanded particles by blowing steam, the particles adhere to each other and are fused and integrated to form the desired foamed molding. You can get the body. The density of the foam molded body is preferably about 0.015 to 0.5 g / cm ³ . The present invention will be described below in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples, the dimensional change rate and the content of the volatile organic compound were evaluated as follows. <Dimensional change rate> A styrenic resin foam molded article taken out of a foaming mold (actually, as shown in FIG. 2, thickness h: 30 mm, inner diameter a: 200 mm, outer diameter b: 260 mm, After leaving a semi-cylindrical styrene resin foam molded product having a length c: 1000 mm in a semi-cylindrical shape) in a constant temperature and humidity room (standard temperature and humidity condition of JIS-K7100) at a temperature of 23 ° C. and a relative humidity of 50% for 24 hours, This foamed molded article is
A test sample according to IS-K6767 was used. The test sample was placed horizontally in a hot air circulating drier kept at 85 ° C., subjected to a heating test for 168 hours, taken out, and left again in a constant temperature and humidity room for 1 hour.
JI measures dimensions of test samples before and after heating
It carried out based on SK6767. The dimensional change P was determined according to the following equation. Here, the dimension is the length c of the test sample. Dimensional change rate P (%) = (c2−c1) × 100 / c1 (where c1 is 23 ° C. and 50% relative humidity after in-mold molding)
%, The dimension of the test sample left for 24 hours, c2 is the dimension of the test sample after heating the test sample at 85 ° C. for 168 hours). <Content of Volatile Organic Compound> After the foamed molded article taken out of the foaming mold was dried in a constant temperature room at 50 ° C. for 7 days, the values obtained by the following three measurement methods were measured. The total was determined. a. (Measurement of hydrocarbons having 5 or less carbon atoms) The foamed molded article was placed in a pyrolysis furnace at 150 ° C, and volatile hydrocarbons were measured by gas chromatography. Gas chromatography (GC): G manufactured by Shimadzu Corporation
C-14B Pyrolysis furnace: PYR-1A manufactured by Shimadzu Corporation Column: Polapack Q 80/100 (3 mmφ × 1.
5m) Column temperature: 100 ° C Detector (FID) temperature: 120 ° C b. (A hydrocarbon having 6 or more carbon atoms,
Measurement of Hydrocarbon Up to Styrene Peak Appearing in Gas Chromatogram) The foamed molded product was dissolved in dimethylformamide, and an internal standard solution (cyclopentanol) was added. However, peaks that could not be identified were quantified in terms of the amount of toluene detected. GC: GC-14A manufactured by Shimadzu Corporation Column: PEG-20M PT25% 60/80
(2.5 m) Column temperature: 105 ° C. Detector (FID) temperature: 220 ° C. c. (From the next peak of styrene appearing in the gas chromatogram, the carbon number is 16 (n-hexadecane)
Measurement of hydrocarbon up to) The foamed molded product was dissolved in chloroform, and measured with a gas chromatograph mass spectrometer (GCMS). However, a blank test using only a solvent that did not dissolve the test sample was performed, and the amount of the detected substance in the blank test was subtracted. Further, unspecified peaks were quantified in terms of the amount of toluene detected. GCMS: QP5000 manufactured by Shimadzu Corporation Column: DB-1 manufactured by J & W Scientific
(1 μm × 60 m 0.25 mmφ) Measurement conditions: column temperature (after holding at 60 ° C. for 1 minute, 10
(The temperature was raised to 300 ° C. at a rate of 300 ° C./min.) Split ratio: 10 Carrier gas: He (1 ml / min) Interface temperature: 260 ° C. Example 1 In a 100-liter reactor, 40 kg of pure water, dodecylbenzene sulfone Acid soda 1.8
g and 70 g of magnesium pyrophosphate were used as an aqueous medium. Next, benzoyl peroxide (purity 75%) 18
2 g, 30 g of t-butyl peroxybenzoate and 44 kg of styrene in which 22 g of polyethylene wax (molecular weight 1000) were dissolved were added with stirring and suspended.
The temperature was raised to 0 ° C. to initiate polymerization. When the polymerization conversion measured by the specific gravity method reached 95% by weight, the reactor was cooled to 12%.
After heating to 2 ° C and holding for 2 hours, cool to room temperature,
The styrene resin particles were taken out. The residual styrene in the styrene resin particles obtained here was measured by gas chromatography and found to be 460 ppm, and the weight average molecular weight measured by GPC was 222000. [0036] Of the styrene resin particles, a particle size of 0.7 to
After putting 15 kg of 1.0 mm into a rotary pressure-resistant container having a content of 30 liters, 7.5 g of polyethylene glycol 300 as a spreading agent, 7.5 g of glycerin monostearate, and carbonic acid as a binding inhibitor are used. 30 g of calcium was added, and the container was rotated to adhere to the surface of the resin particles. Next, after stopping the rotation, carbon dioxide gas was injected into the container and kept at 25 ° C. and 30 kg / cm ² G for 6 hours to impregnate the resin particles with carbon dioxide gas to obtain expandable styrene resin particles. The expandable styrene resin particles thus obtained were taken out of the pressure-resistant container, and charged in a foaming machine with a stirrer in the next step, and steam having a charging pressure of 1.2 kg / cm ² G was introduced into the foaming machine can. . Excess pressure was released to the outside using the exhaust line while controlling the opening of the exhaust control valve with an electric signal so that the pressure in the foaming machine at this time was 0.8 kg / cm ² G (input pressure). Is 0.4 kg / cm ² G). In this way, pre-foaming was performed while continuously introducing steam into the foaming machine to obtain styrene resin pre-foamed particles. The particle size of the pre-expanded particles was 2.3 to 4.0 mm. Six hours after the pre-foaming, the styrene resin pre-foamed particles are placed in a foaming mold designed so that the cavity shape after mold clamping is the shape of a semi-cylindrical pipe heat insulating material shown in FIG. And heated with steam to obtain a styrene resin foam molded article having a shape shown in FIG. Density 0.020g /
cm ³ . With respect to the obtained foamed molded article, the dimensional change rate and the content of the volatile organic compound were evaluated by the evaluation method described above. Table 1 shows the obtained results. [Example 2] Immediately after the expandable styrene resin particles were taken out of the pressure-resistant container, the charging pressure was 1.5 kg / c.
m ² G steam was introduced into the foaming machine, and the pressure in the foaming machine was adjusted to 0.8 kg / cm ² G (the difference between the input pressure and the pressure in the foaming machine was 0.7 kg / cm ² G). Except for the above, pre-expanded particles and a semi-cylindrical foamed molded product were obtained in the same manner as in Example 1. Table 1 shows the evaluation results of the dimensional change rate and the content of the volatile organic compound of the obtained foamed molded article. In addition, the particle diameter of the pre-expanded particles is 2.3 to 4.0 mm.
The density of the foam molded article was 0.025 g / cm ³ . [Comparative Example 1] Immediately after the expandable styrene resin particles were taken out of the pressure-resistant container, the charging pressure was 2.0 kg / c.
m ² G steam was introduced into the foaming machine, and the pressure inside the foaming machine was adjusted to 0.8 kg / cm ² G (the difference between the input pressure and the pressure inside the foaming machine was 1.2 kg / cm ² G). Except for the above, pre-expanded particles and a semi-cylindrical foamed molded product were obtained in the same manner as in Example 1. Table 1 shows the evaluation results of the obtained foamed molded articles. The particle size of the pre-expanded particles is 2.2 to 3.
At 6 mm, the density of the foam molded article was 0.025 g / cm ³ . [Comparative Example 2] Immediately after the expandable styrene resin particles were taken out of the pressure-resistant container, the charging pressure was 0.8 kg / c.
m ² G steam was introduced into the foaming machine, and the pressure in the foaming machine was adjusted to 0.8 kg / cm ² G (the difference between the input pressure and the pressure in the foaming machine was 0 kg / cm ² G), except that In the same manner as in Example 1, pre-expanded particles and a semi-cylindrical foam molded article were obtained. Table 1 shows the evaluation results of the obtained foamed molded articles. The particle size of the obtained pre-expanded particles was 1.
8 to 2.8 mm, the density of the foam molded article is 0.050 g /
cm ³ . Comparative Example 3 2.0 kg of the styrene resin particles obtained in Example 1 having a particle size of 0.7 to 1.0 mm and ion-exchanged water were placed in a pressure-resistant container having an internal volume of 5 liters and equipped with a stirrer. 2.2 liters, tricalcium phosphate 6.0
g, and sodium dodecylbenzenesulfonate 0.2
g was added and stirring was started. Next, after heating to 90 ° C,
140 g of butane was injected and held for 5 hours. Then 3
After cooling to 0 ° C., expandable styrene resin particles were obtained. After the taken out particles were dried, they were aged in a thermostatic chamber at 15 ° C. for 5 days. Then, zinc stearate as a binding inhibitor at the time of prefoaming and hydroxystearic acid triglyceride as a fusion promoter are coated on the surface of the particles, and then charged into a foaming machine equipped with a stirrer.
² G steam was introduced into the foaming machine. Excess pressure was released to the outside using the exhaust line while controlling the opening of the exhaust control valve with an electric signal so that the pressure in the foaming machine at this time was 0.1 kg / cm ² G (input pressure). Is 0.4 kg / cm ² G). In this way, pre-foaming was performed while continuously introducing steam into the foaming machine to obtain styrene resin pre-foamed particles. The particle size of the pre-expanded particles was 2.3 to 4.0 mm. Six hours after the prefoaming, foaming was performed using the same foaming mold used in Example 1 to obtain a foamed molded article having a density of 0.020 g / cm ³ and the same shape as in Example 1. . Table 1 shows the evaluation results of the obtained foamed molded articles. [Table 1] From the above results, in the in-mold foamed product of the styrene-based resin pre-expanded particles obtained by impregnating the styrene-based resin particles with carbon dioxide, as the styrene-based resin pre-expanded particles, expandable styrene having carbon dioxide was used. A styrene-based resin molded article that has excellent dimensional stability over a long period of time even in a high-temperature atmosphere by foaming using pre-expanded particles by adjusting the difference between the input pressure and the pressure in the foaming machine. Is obtained. Further, the content of the volatile organic compound can be extremely reduced. The heat insulating material for pipes according to the present invention has excellent heat insulating properties, excellent strength and moldability, and is a low-cost expanded polystyrene product. The dimensions are very stable over. Therefore, in the cold water / hot water pipe in which the heat insulating material for the pipe is mounted around, high heat insulation performance can be maintained for a long period of time. Further, the content of the residual volatile organic compound can be extremely small.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic explanatory view of a pre-expansion machine used for producing pre-expanded Tylene resin particles usable in the present invention. FIG. 2 is a view showing a heat insulating material for a pipe used in Examples and Comparative Examples. FIG. 3 is a view for explaining a usage mode of a conventional pipe heat insulating material. [Description of Signs] 2 Stirring motor 3 Stirring blade 4 Baffle bar 5 Foaming tank top detector 6 Foaming particle transporter 7 Foaming particle measuring tank 8 Foaming particle injector 9 Steam blowing control valve 10 Steam chamber 11 Condensate discharge Valve 12 Exhaust control valve 13 Pre-expanded particle outlet 14 Pre-expanded particle temporary receiver 15 Air transport facility 16 Internal pressure detection / control device 17 Steam blow-in hole 18 Steam input pressure gauge 19 Pressure reducing valve 20 Steam source pressure gauge 51 Pipe 52 For pipe Insulation material

Claims (1)

Claims 1. An in-mold foam molded article of styrene-based resin pre-expanded particles obtained by impregnating styrene-based resin particles with carbon dioxide gas, which is heated at 85 ° C. for 168 hours. The dimensional change before and after heating is within ± 0.5%,
A heat insulator for pipes having a cylindrical shape or a shape obtained by dividing a cylindrical body in a radial direction.