JP6436575B2 - Foam and production method thereof - Google Patents

Description

  The present invention relates to a foam and a method for producing the same. More specifically, the present invention relates to a foam excellent in heat insulation and a method for producing the same.

  Conventionally, foams are lightweight and have excellent heat insulation and mechanical strength, so heat insulation materials used in houses and automobiles, heat insulation materials used in building materials, transport packaging materials such as fish boxes and food containers, cushioning materials, etc. Is used. Among them, in-mold foam molded articles produced using foamable particles as raw materials are often used because of the advantage that a desired shape is easily obtained.

As the foam, a polystyrene foam derived from expandable polystyrene particles is widely used. Polystyrene foam is obtained by heating and pre-expanding expandable polystyrene particles to obtain pre-expanded particles, followed by heat-sealing while pre-expanding the obtained pre-expanded particles in the mold cavity. It is obtained by integrating. Polystyrene foam has various properties. For example, the polystyrene foam has excellent heat insulation properties. Excellent heat insulation is required for various applications from the viewpoint of energy saving.
Specific applications include wall insulation, floor insulation, roof insulation, automotive insulation, hot water tank insulation, piping insulation, solar system insulation, water heater insulation, food And containers for industrial products, packing materials for fish and agricultural products, embankment materials, core materials for tatami mats, and the like.

  It is desired that the thermal insulation required for the foam is further improved from the viewpoint of energy saving. As a method for improving the heat insulation, various methods such as higher magnification, change of resin composition, use of additives, and the like are known. For example, Japanese Patent Application Laid-Open No. 63-183941 (Patent Document 1) proposes a foam containing fine powder having an infrared reflectance of 40% or more as an additive. In the example of Patent Document 1, a foam using aluminum powder, silver powder and graphite powder having a reflectance of 40% or more is carbon black (for example, specially used as a blackening agent in the foam). It has been described that the heat insulation is superior to a foam containing an additive having a reflectance of less than 40% as in JP 2013-6966 A: Patent Document 2).

Japanese Unexamined Patent Publication No. 63-183941 JP 2013-6966 A

  In the technology described in the above publication, although improvement in heat insulation is seen, it is difficult to obtain a foam having heat insulation, which has been increasingly demanded in recent years, and it is possible to provide a foam having higher heat insulation. It is desired.

  In order to improve the heat insulation of the foam, the additive added to the foam was examined. As a result, the knowledge that the carbon-based infrared shielding agent contributes to the improvement of heat insulation was obtained.

Thus, according to the present invention, the foam comprises 0.5 to 25 parts by mass of a carbon-based infrared shielding agent and 100 parts by mass of a thermoplastic resin, and is composed of a plurality of expanded particles fused to each other, foam in absorbance B at absorbance a and the wave number 500 cm ^-1 in wave number 1000 cm ^-1 obtained by the transmission method infrared analysis, shows a ratio a / B of 0.8 to 2.0, and 0.5g A foam having a water absorption of less than / 100 cm ² is provided.

Moreover, according to the present invention, the foam comprises 0.5 to 25 parts by mass of a carbon-based infrared shielding agent and 100 parts by mass of a thermoplastic resin, and is composed of a plurality of expanded particles fused to each other. the foam, in the absorbance B at absorbance a and the wave number 500 cm ^-1 in wave number 1000 cm ^-1 obtained by the transmission method infrared analysis, shows a ratio a / B of 0.8 to 2.0, and 0. A method for producing a foam characterized by having a water absorption of less than 5 g / 100 cm ² , wherein the seed particles containing a carbon-based infrared shielding agent and a thermoplastic resin are dispersed in water. Among them, the step of impregnating the seed particles with the seed particle, the step of polymerizing the monomer simultaneously with or after the impregnation, and the step of impregnating the foaming agent with the foaming agent simultaneously with or after the polymerization And pre-foaming the resulting expandable particles Obtaining a foamed particles, method for producing a foam comprising the step of obtaining a resulting foam expanded beads and a mold cavity is provided.

Furthermore, according to the present invention, there is provided a foam comprising a plurality of foam particles fused to each other, comprising 0.5 to 25 parts by mass of a carbon-based infrared shielding agent and 100 parts by mass of a thermoplastic resin, foam in absorbance B at absorbance a and the wave number 500 cm ^-1 in wave number 1000 cm ^-1 obtained by the transmission method infrared analysis, shows a ratio a / B of 0.8 to 2.0, and 0.5g / A method for producing a foam characterized by having a water absorption of less than 100 cm ² , which is obtained by melt-kneading a carbon-based infrared shielding agent and a thermoplastic resin, and the melt-kneading step. A step of injecting a foaming agent into the molten resin, a step of extruding the molten resin obtained in the foaming agent injection step into a liquid, cutting, and then solidifying to obtain expandable particles, and the resulting expandable particles Pre-expanding to obtain expanded particles; The resulting method of manufacturing a foam comprising the step of obtaining a mold molding to foam expanded beads is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the foam excellent in heat insulation and its manufacturing method can be provided.

In any of the following cases, a foam having better heat insulation can be provided.
(1) Absorbance B is 0.5 or more.
(2) The foam has a density of 0.01 to 0.04 g / cm ³ .
(3) The thermoplastic resin is a styrene resin.
(4) The expanded particles constituting the foam have an average cell diameter of 150 to 350 μm.
(5) The carbon-based infrared shielding agent has conductivity.
(6) The carbon-based infrared shielding agent is acetylene black, ketjen black, or a mixture thereof.
(7) The foam has a water absorption of less than 0.5 g / 100 cm ² .
(8) The foam further contains a flame retardant.

It is an example of the electron micrograph which shows the carbon-type infrared shielding agent which formed the aggregate.

(Foam)
The foam includes a carbon-based infrared shielding agent and a thermoplastic resin, and is composed of a plurality of foam particles fused to each other.
(1) Absorbance The foam exhibits a ratio A / B of 0.8 to 2.0 in the absorbance A at a wave number of 1000 cm ⁻¹ and the absorbance B at a wave number of 500 cm ⁻¹ obtained by transmission infrared analysis. When the absorbance ratio A / B <0.8 or when the absorbance ratio A / B> 2.0, sufficient heat insulation may not be obtained. (1) The absorbance ratio A / B can be reduced by increasing the amount of the infrared shielding agent added. (2) Increasing the absorbance ratio A / B can be achieved by increasing the addition amount of the infrared shielding agent, decreasing the bubble diameter, or the like. A preferred absorbance ratio A / B is 0.81-1.80, and a more preferred absorbance ratio A / B is 0.82-1.75. Specific values of the absorbance ratio A / B are 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.9, 0.95, 1.0, 1 .1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.75, 1.76, 1.77, 1.78, 1.79, 1.8 1.85, 1.9, 1.95, 2.0 and the like.

Absorbance A means the absorbance at a wave number of 1000 cm ⁻¹ obtained by transmission infrared analysis. The preferred absorbance A is 0.8 or more. When the absorbance A is less than 0.8, the heat insulation is poor. More preferable absorbance A is 0.95 or more. Specific values of absorbance A are 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89. 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, and the like.
Further, the absorbance B means the absorbance at a wave number of 500 cm ⁻¹ obtained by transmission infrared analysis. The preferred absorbance B is 0.5 or more. When the absorbance B is less than 0.5, the heat insulating property is lowered. More preferable absorbance B is 0.55 or more. Specific values of absorbance B are 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59. , 0.6, 0.65, 0.7 and the like.
Detailed methods for measuring absorbances A and B are described in the Examples.

(2) Carbon-based infrared shielding agent The carbon-based infrared shielding agent is not particularly limited, but carbon black, activated carbon, graphite, graphene, coke, carbon nanofiber, carbon nanotube, mesoporous carbon, glassy carbon, hard carbon, and soft carbon Carbon materials such as acetylene black, ketjen black, carbon nanofibers, and conductive carbon blacks such as carbon nanotubes, and more preferably acetylene black, ketjen black, or a mixture thereof. .

  Content of a carbon-type infrared shielding agent is 0.5-25 mass parts with respect to 100 mass parts of thermoplastic resins. When content is less than 0.5 mass part, heat insulation may not fully be improved. On the other hand, when the content exceeds 25 parts by mass, the foam film may be broken, so that the moldability may be reduced and the heat insulation may be inferior. The content of the preferred carbon-based infrared shielding agent is 0.5 to 15 parts by mass, and the more preferred content of the carbon-based infrared shielding agent is 0.5 to 10 parts by mass. Specific contents include 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.01, 2, 2.56, 3, 3.13, 4, 5, 5.26, 6, 7, 7.52, 7.69, 8, 9, 10, 11, 11.11, 12, 13, 14, 15, 16, 17, 18, 19, 20 parts by mass, etc. It is done.

Preferably, the carbon-based infrared shielding agent has a volume resistivity of 1.0 × 10 ⁴ Ω · cm or less. When the volume resistivity is higher than 1.0 × 10 ⁴ Ω · cm, the heat insulation may not be sufficiently improved. A more preferred volume resistivity is 7.0 × 10 ³ Ω · cm or less, a further preferred volume resistivity is 4.0 × 10 ³ Ω · cm or less, and a most preferred volume resistivity is 2.0 × 10 ^3. Ω · cm or less. A lower limit value of the volume resistivity is not particularly provided, but is, for example, about 1.0 × 10 ⁻¹ Ω · cm or more. Specific values of volume resistivity are 1.0 × 10 ³ , 2.0 × 10 ³ , 3.0 × 10 ³ , 4.0 × 10 ³ , 5.0 × 10 ³ , 6.0 × 10 ³ , 7.0 × 10 ³ , 8.0 × 10 ³ , 9.0 × 10 ³ , 1.0 × 10 ⁴ Ω · cm and the like. Here, the volume resistivity is determined by removing the raw material carbon-based infrared shielding agent or, if the raw material carbon-based infrared shielding agent is added to the foam, removing the thermoplastic resin in the foam with an organic solvent. The carbon-based infrared shielding agent taken out is melt-kneaded with the styrene resin (carbon-based infrared shielding agent: styrene resin = 1: 4 (mass ratio)), and the surface of the kneaded plate-like foam Means the measured value. Detailed volume resistivity measurement methods are described in the Examples.
In addition, even if it uses the carbon-type infrared shielding agent of a raw material, or uses the carbon-type infrared shielding agent taken out by removing resin in a foam with an organic solvent, volume resistivity becomes a comparable value.

  Further, when the resin constituting the foam is a styrene resin, and the volume resistivity of the carbon-based infrared shielding agent contained in the resin is measured using a styrene resin as a plate-like foam-forming resin, Regarding the procedure for taking out the carbon-based infrared shielding agent by removing the resin in the foam with an organic solvent, the removal of the styrene-based resin is performed when the carbon-based infrared shielding agent: styrene-based resin = 1: 4 (mass ratio). You may stop in the middle, or you may take the method of adding (dilution) a styrene resin so that it may become carbon-type infrared shielding agent: styrene-type resin = 1: 4 (mass ratio). In the case of adopting a method of stopping the removal of the styrene-based resin in the middle, in order to adjust the carbon-based infrared shielding agent: styrene-based resin = 1: 4 (mass ratio), the amount of the carbon-based infrared shielding agent in the foam is measured. You may measure the amount of styrene resin. Although it does not specifically limit as a measuring method of the amount of carbon-type infrared shielding agents, For example, the method of using a differential thermothermal weight simultaneous measuring apparatus etc. are mentioned.

The carbon-based infrared shielding agent may be contained in a form in which primary particles of the carbon-based infrared shielding agent are dispersed in the resin, or an aggregate of a plurality of aggregated primary particles of the carbon-based infrared shielding agent in the resin. It may be contained in the form. Preferably, the primary particles of the carbon-based infrared shielding agent are contained as agglomerated masses in the resin.
FIG. 1 shows an example of a carbon-based infrared shielding agent in which aggregates observed using an electron microscope are formed. The primary particles of the carbon-based infrared shielding agent mean each of substantially circular particles as observed in FIG. By agglomerate is meant a mass of primary particles that appear to overlap each other, as observed in FIG.

The primary particles preferably have an average primary particle size of 18 to 125 nm.
An average primary particle diameter means the average value of the longest diameter of a primary particle, and can take the value of 18-125 nm. However, this does not restrict the primary particles from taking a shape other than spherical and substantially spherical, and the primary particles may take other shapes such as a cylindrical shape and a prismatic shape. When the primary particles have a shape other than a spherical shape or a substantially spherical shape, the average primary particle size means an average value of the longest diameters obtained by approximating the primary particles to a spherical shape. If the average primary particle size is less than 18 nm, moldability may be reduced due to finer bubbles, and if it is greater than 125 nm, moldability may be reduced due to tearing of the bubble film. Specific numerical ranges of the average primary particle diameter include 18 to 120 nm, 18 to 110 nm, 18 to 100 nm, 18 to 90 nm, 18 to 80 nm, 18 to 73 nm, 18 to 66 nm, 18 to 60 nm, 20 to 100 nm, 25 -80 nm, 32-66 nm, 20-125 nm, 25-125 nm, 32-125 nm, 40-125 nm, 50-125 nm, 60-125 nm, 66-125 nm, 73-125 nm, 80-125 nm and the like. Specific values of the average primary particle diameter include 18, 20, 25, 32, 40, 50, 60, 66, 73, 80, 90, 100, 110, 120, 125 nm, and the like.

The carbon-based infrared shielding agent preferably has a specific surface area of 10 to 3000 m ² / g. When the specific surface area is less than 10 m ² / g, the desired heat insulating performance may not be obtained. On the other hand, when the specific surface area exceeds 3000 m ² / g, workability may be reduced. For example, as a specific numerical range of the specific surface ^{area, 100~3000m 2 / g, 200~3000m 2} / g, 210~3000m 2 / g, 220~3000m 2 / g, 15~2500m 2 / g, 100~ ^{2500m 2 / g, 210~2500m 2 /} g, 10~2000m 2 / g, 60~2000m 2 / g, 210~2000m 2 / g, 10~1500m 2 / g, 70~1500m 2 / g, 200~1500m ² / g, 210-1500m < ² > / g, etc. are mentioned. When the carbon-based infrared shielding agent is acetylene black, a more preferable specific surface area is 20 to 300 m ² / g. When the carbon-based infrared shielding agent is ketjen black, a more preferable specific surface area is 500 to 2000 m ² / g. As specific surface area values, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 400, 500, 700, 1000, 1500, 2000, 2500, 3000 m ² / g and the like.

The agglomerates preferably have an average value of the longest diameter of 180 to 500 nm.
The longest diameter means the longest distance between any two points on the outer edge of the aggregate. For example, in FIG. 1, the diameter indicated by the solid line is defined as the longest diameter of the aggregate. .
When the average value of the longest diameter is less than 180 nm, the heat insulating property may not be improved, and when it is larger than 500 nm, bubbles may be broken at the time of foaming and the heat insulating property may not be improved and a good molded product may not be obtained. Specific numerical ranges of the average value of the longest diameter are 180 to 450 nm, 180 to 400 nm, 180 to 370 nm, 180 to 300 nm, 180 to 240 nm, 200 to 450 nm, 220 to 400 nm, 240 to 370 nm, 200 to 500 nm, 220-500 nm, 240-500 nm, 300-500 nm, 370-500 nm, 400-500 nm etc. are mentioned. Specific examples of the average value of the longest diameter include 180, 200, 220, 230, 240, 250, 300, 350, 370, 400, 420, 450, 460, 470, 480, 490, and 500 nm.
The longest diameter of the aggregate is set so as to always overlap the aggregate. That is, the longest diameter does not pass through the background (thermoplastic resin). For example, in FIG. 1, since the line shown with the broken line has a part which overlaps with a background, it cannot be set as the longest diameter.

Moreover, it is preferable that the aggregate has a ratio of the average value of the longest diameter to the average primary particle diameter of 4.0 to 10.0. When the ratio is less than 4.0, the heat insulating property may not be improved. When the ratio is more than 10.0, bubbles may be broken during foaming and a good molded product may not be obtained. Specific numerical ranges of the above ratio are 4.0 to 9.0, 5.0 to 9.0, 5.0 to 8.9, 5.0 to 8.5, 5.0 to 8. 0 , 5.0-7.0 , 5.0-6.0 , 5.2-8.9 , 5.5-8.5 , 6.0-8.0,4. 0-10.0, 5.0-10.0, 5.2-10.0, 5.5-10.0, 6.0-10.0 etc. are mentioned. The ratio of the average value of the longest diameter to the specific average primary particle diameter is 4.0, 4.5, 5.0, 5.2, 5.5, 6.0, 7.0, 8. 0, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.0, etc. are mentioned. Detailed measurement methods of the average value of the longest diameter and the average primary particle diameter are described in Examples.

(2) Thermoplastic resin A thermoplastic resin will not be specifically limited if it is resin which can obtain a foam. Examples of the thermoplastic resin include styrene resin, olefin resin (for example, ethylene resin, propylene resin, etc.) and the like. A particularly preferable thermoplastic resin is a styrene resin. Examples of such styrene resins include styrene monomers such as styrene, α-methyl styrene, vinyl toluene, ethyl styrene, i-propyl styrene, t-butyl styrene, dimethyl styrene, bromo styrene, and chloro styrene, or And resins derived from mixtures of these monomers.

The thermoplastic resin may contain a component derived from a crosslinking agent.
Examples of the crosslinking agent include divinylbenzene, trivinylbenzene, divinyltoluene, divinylxylene, bis (vinylphenyl) methane, bis (vinylphenyl) ethane, bis (vinylphenyl) propane, bis (vinylphenyl) butane, and divinylnaphthalene. , Divinyl anthracene, divinyl biphenyl, and other bifunctional benzene rings, such as a compound in which a vinyl group is bonded directly, bisphenol A ethylene oxide adduct di (meth) acrylate, bisphenol A propylene oxide adduct di (meth) acrylate, etc. A (meth) acrylate compound etc. are mentioned.

  The thermoplastic resin may be a copolymer with another monomer as long as the properties of the present invention are not impaired. Examples of other monomers include (meth) acrylic acid such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and cetyl (meth) acrylate. Esters, alkyl maleates such as (meth) acrylonitrile, dimethyl maleate and diethyl maleate, alkyl fumarates such as dimethyl fumarate, diethyl fumarate and ethyl fumarate, maleic anhydride, N-phenylmaleimide, (meth) acrylic An acid etc. are mentioned.

  Furthermore, resins other than those described above may be included. Other than the above resins, rubber-modified impact-resistant styrene resins and polycarbonate resins to which diene rubber-like polymers such as polybutadiene, styrene-butadiene copolymer, ethylene-propylene-nonconjugated diene three-dimensional copolymer are added , Polyester resin, polyamide resin, polyphenylene ether, acrylonitrile-butadiene-styrene copolymer, polymethyl methacrylate, and the like. The proportion of these other resins is preferably less than 50% by mass, more preferably 30% by mass or less, and still more preferably 10% by mass or less based on the total amount of the base resin.

  The thermoplastic resin preferably has a weight average molecular weight of 100,000 to 1,000,000. If the weight average molecular weight is less than 100,000, the strength of the foam may decrease. When larger than 1 million, foamability may fall and it may be inferior to lightness. A weight average molecular weight of 150,000 to 800,000 is more preferable, and 200,000 to 500,000 is more preferable.

  The content of the thermoplastic resin in the foam is preferably 50% by mass or more. If it is less than 50% by mass, sufficient foamability may not be obtained. A more preferable content rate is 60 mass% or more, and a still more preferable content rate is 80 mass% or more.

  The foam may be a heat insulating material for a living space in which the total content of aromatic organic compounds including styrene monomer, ethylbenzene, isopropylbenzene, normal propylbenzene, xylene, toluene, and benzene is less than 2000 ppm. If the total content of the aromatic organic compound is less than 2000 ppm, it is possible to cope with sick house syndrome which has been recently requested, and a more comfortable living space can be provided. More preferably, it is 1750 ppm or less, More preferably, it is 1500 ppm or less, Most preferably, it is 500 ppm or less, Most preferably, it is 300 ppm or less. By selecting a resin raw material with a low content of aromatic organic compounds consisting of styrene monomer, ethylbenzene, isopropylbenzene, normal propylbenzene, xylene, toluene, benzene as the raw material thermoplastic resin, during the manufacturing process Thus, it is possible to obtain a foam and a heat insulating material for living space without mixing the aromatic organic compound. As a production method for obtaining expandable particles having a small total content of the aromatic organic compound, a melt extrusion method is preferable. Detailed methods for measuring the total content of aromatic organic compounds are described in the Examples.

The foam preferably has a density of 0.01 to 0.04 g / cm ³ . If the density is greater than 0.04 g / cm ³ , the lightness may be reduced. When the density is less than 0.01 g / cm ³ , the heat insulating performance and mechanical strength may be lowered. More preferred density is 0.0125~0.04g / cm ^3, more preferred density is 0.014~0.033g / cm ^3.

The foam is 0. It preferably exhibits a thermal conductivity of 0 34 W / mk or less. Thermal conductivity is 0. When it exceeds 0 34 W / mk, a foam having sufficient heat insulation may not be provided. A more preferred thermal conductivity is 0. 0 33 W / mk or less, and more preferable thermal conductivity is 0. 0 32 W / mk or less.

The foam preferably exhibits a water absorption of less than 0.5 g / 100 cm ² . When the amount of water absorption exceeds 0.5 g / 100 cm ² , the heat insulating property may be lowered. More preferable water absorption is less than 0.4 g / 100 cm ² , still more preferable water absorption is less than 0.3 g / 100 cm ² , and even more preferable water absorption is less than 0.2 g / 100 cm ² . Specific water absorption values are 0.5, 0.45, 0.4, 0.35, 0.3, 0.25, 0.2, 0.15, 0.1, 0.05 g / 100cm < ² > etc. are mentioned.

  The foam may further contain a flame retardant. 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), and tetrabromocyclooctane or tetrabromobisphenol A-bis (2,3-dibromo-2-methylpropyl ether) is particularly preferable. Content of a flame retardant is 0.5-10 mass parts with respect to 100 mass parts of foams, Preferably it is 2-8 mass parts.

  The average diameter (average cell diameter) of the foamed particles constituting the foam is preferably 50 to 1000 μm. When the average cell diameter is less than 50 μm, the heat insulating property may be lowered. When the average bubble diameter is larger than 1000 μm, the mechanical strength may be lowered. The average cell diameter is more preferably from 100 to 400 μm, still more preferably from 150 to 350 μm.

(3) Other additives Other additives may be contained in the foam as necessary. Examples of other additives include plasticizers, flame retardant aids, antistatic agents, spreading agents, fillers, colorants, weathering agents, anti-aging agents, lubricants, antifogging agents, and fragrances.
Plasticizers include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as cyclohexane, hexane and heptane, adipic acid esters such as diisobutyl adipate, dioctyl adipate and diisononyl adipate, and glycerin diacetomonolaurate. Glycerin fatty acid esters such as glycerin fatty acid esters, dioctyl phthalate, diisononyl phthalate, diisobutyl phthalate and the like, phthalic acid esters such as liquid paraffin and white oil.

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 antistatic agent include polyoxyethylene alkylphenol ether, stearic acid monoglyceride, polyethylene glycol and the like.
Examples of the spreading agent include polybutene, polyethylene glycol, glycerin, and silicone oil.

  Examples of lubricants include metal soaps such as zinc stearate and magnesium stearate, bisamide compounds such as ethylenebisstearic acid amide and methylenebisstearic acid amide, stearic acid amides, amide compounds such as 12-hydroxystearic acid amide, stearic acid triglycerides, Examples include fatty acid glycerides such as stearic acid monoglyceride and hydroxystearic acid triglyceride, polyethylene wax, liquid paraffin, and white oil.

(4) Applications The foam can be used for various applications requiring heat insulation. For example, wall insulation, floor insulation, roof insulation, automotive insulation, warm water tank insulation, piping insulation, solar system insulation, water heater insulation, food and industrial products, etc. It can be used for containers, packing materials for fish and agricultural products, embankment materials, tatami core materials, etc. The foam can take a shape according to the intended use. In particular, it can be suitably used as a heat insulating material for living spaces such as a heat insulating material for walls, a heat insulating material for floors, a heat insulating material for roofs, and a heat insulating material for automobiles.

(5) Method for producing foam The scope of the present invention includes the method for producing the foam.
The foam can be obtained, for example, by pre-expanding expandable particles obtained according to a method known to those skilled in the art to obtain pre-expanded particles, and by pre-expanding the pre-expanded particles. Further, it is also possible to employ a method in which foamable particles obtained according to a method known to those skilled in the art are directly filled into a mold and foamed in the mold to form a molded body.

In one embodiment of the invention,
A foam comprising 0.5 to 25 parts by mass of a carbon-based infrared shielding agent and 100 parts by mass of a thermoplastic resin and composed of a plurality of expanded particles fused together,
The foam exhibits a ratio A / B of 0.8 to 2.0 in the absorbance A at a wave number of 1000 cm ⁻¹ and the absorbance B at a wave number of 500 cm ⁻¹ obtained by transmission infrared analysis. A method for producing a foam, comprising:
A step of impregnating the seed particles with a monomer in a dispersion obtained by dispersing seed particles containing a carbon-based infrared shielding agent and a thermoplastic resin in an aqueous medium;
Polymerizing the monomer simultaneously with or after impregnation;
A step of impregnating a foaming agent to obtain expandable particles simultaneously with or after the polymerization;
A step of pre-foaming the obtained expandable particles to obtain expanded particles;
And a process for producing a foam by molding the obtained foamed particles in a mold.

The aqueous medium is not particularly limited as long as it is a liquid that can dissolve a water-soluble substance at room temperature, and examples thereof include water, lower alcohols having 1 to 4 carbon atoms, and mixtures thereof. Water is particularly preferable. A person skilled in the art can appropriately set the amount of the aqueous medium used.
Resins other than thermoplastic resins may be contained in the resin obtained by polymerization. The kind, physical property, and content of such a resin are as described above.

  This embodiment is an embodiment in which expandable particles are produced using a suspension polymerization method, which is one of the typical methods for producing expandable particles in the art, and then a foam is obtained. Hereinafter, the suspension polymerization method will be described in more detail. However, the present embodiment is not limited to the conditions described below.

1. Suspension polymerization method Suspension polymerization method is a method in which a polymerization initiator is dissolved in a monomer, and with a water in which the suspending agent is dispersed, the temperature is raised in a reaction vessel, polymerized, and then cooled to obtain resin foamable particles. How to get. The method of adding a foaming agent during the polymerization and / or after the polymerization is called a one-stage method. The particles obtained by polymerization without adding a blowing agent are screened, and only the particles in the required particle size range are heated in water in which the suspending agent in the reaction vessel is dispersed, and the blowing agent is added here. The method of impregnating the particles is called a two-stage method (post-impregnation method). Further, small resin particles (seed particles) are put into a reaction vessel containing water in which a suspending agent is dispersed, and after raising the temperature, a monomer in which a polymerization initiator is dissolved is continuously added to the reaction vessel. The method of supplying to the polymer and polymerizing it to grow to the target particle size is called seed polymerization. In the seed polymerization method, the foaming agent is added during the polymerization and / or after the completion of the polymerization. Expandable particles can be produced by any one of a one-stage method, a two-stage method (post-impregnation method), and a seed polymerization method. In addition, any method has an advantage that true spherical expandable particles can be obtained. A preferable production method includes a seed polymerization method. According to the seed polymerization method, resin particles containing a carbon-based infrared shielding agent at a high concentration (for example, 20% by mass) can be used as seed particles, and there is an advantage that moldability can be improved.

Hereinafter, the seed polymerization method of the suspension polymerization method will be described in more detail. However, the present embodiment is not limited to the conditions described below.
(A) Seed polymerization method of suspension polymerization method In this method, seed particles containing a carbon-based infrared shielding agent and a thermoplastic resin are allowed to absorb monomers and polymerize to obtain resin particles. A method of obtaining expandable particles by injecting a foaming agent in the middle and / or after the completion of polymerization is mentioned. In this method, it is easy to obtain expandable particles containing a large amount of carbon-based infrared shielding agent at the center.

(I) Seed particles Seed particles produced by a known method can be used. For example, a carbon-based infrared shielding agent and a thermoplastic resin are melt-kneaded with an extruder and then extruded into a strand shape to cut the strand. There is an extrusion method for obtaining seed particles by doing so. 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. Further, 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.

  The addition amount of the carbon-based infrared shielding agent is 0.5 to 25 parts by mass with respect to 100 parts by mass in total of the addition amount of the thermoplastic resin and the monomer in the seed particles. That is, seed particles are added so that the addition amount of the carbon-based infrared shielding agent is 0.5 to 25 parts by mass. When the addition amount is less than 0.5 parts by mass, the heat insulating property may not be sufficiently improved. On the other hand, when the addition amount exceeds 25 parts by mass, the foam film may be broken, so that the moldability may be reduced and the heat insulation may be inferior. A preferable addition amount of the carbon-based infrared shielding agent is 0.5 to 15 parts by mass, and a more preferable addition amount of the carbon-based infrared shielding agent is 0.5 to 10 parts by mass. Specific contents include 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.01, 2, 2.56, 3, 3.13, 4, 5, 5.26, 6, 7, 7.52, 7.69, 8, 9, 10, 11, 11.11, 12, 13, 14, 15, 16, 17, 18, 19, 20 parts by mass, etc. It is done. In addition, the addition amount can be adjusted at the time of producing the foam so as to have a value substantially equal to the above-described content of the foam.

(Ii) Polymerization step Each monomer is absorbed by seed particles by supplying a monomer mixture into a dispersion obtained by dispersing seed particles in an aqueous medium, and then each monomer is polymerized. Resin particles can be obtained.
The addition amount of the monomer is preferably 50 parts by mass or more with respect to 100 parts by mass of the total addition amount of the seed particles and the monomer. When the amount is less than 50 parts by mass, sufficient foamability may not be obtained. A more preferable content rate is 60 mass parts or more, and a still more preferable content rate is 80 mass parts or more. In addition, the addition amount can be adjusted at the time of producing the foam so as to have a value substantially equal to the above-described content of the foam.
Examples of the aqueous medium include water and a mixed medium of water and a water-soluble solvent (for example, alcohol).

  Each monomer to be used may contain a polymerization initiator. The polymerization initiator is not particularly limited as long as it is conventionally used for monomer polymerization. For example, benzoyl peroxide, t-butyl peroxybenzoate, t-butyl peroxy-2-ethylhexanoate, lauryl peroxide, t-butyl peroxide, t-butyl peroxypivalate, t-butyl peroxyisopropyl Carbonate, t-butyl peroxyacetate, 2,2-t-butylperoxybutane, t-butylperoxy-3,3,5-trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate, 2, Examples thereof include organic peroxides such as 5-dimethyl-2,5-di (benzoylperoxy) hexane and dicumyl peroxide, and azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile. Among these initiators, in order to reduce the residual monomer, two or more different polymerization initiators having a decomposition temperature of 80 to 120 ° C. for obtaining a half-life of 10 hours may be used in combination. 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, magnesium oxide, and hydroxyapatite. 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, alkylbenzenesulfonates, alkylnaphthalenesulfonates, sulfonates such as dialkylsulfosuccinates, alkylsulfoacetates, α-olefinsulfonates; higher alcohol sulfates 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.

  Although a polymerization process changes with monomer types to be used, a polymerization initiator seed | species, superposition | polymerization atmosphere, etc., it is normally performed by maintaining 70-130 degreeC heating for 3 to 10 hours. The polymerization step may be performed while impregnating the monomer. In the polymerization step, the total amount of the monomers used may be polymerized in one step, or may be polymerized in two or more steps (including polymerization during the production of seed particles).

(Iii) Foaming agent impregnation step Expandable particles can be obtained by impregnating resin particles with a foaming agent.
The impregnation may be performed wet simultaneously with the polymerization, or may be performed wet or dry after the polymerization. When it is carried out in a wet manner, it may be carried out in the presence of a suspension stabilizer and a surfactant exemplified in the polymerization step. The impregnation temperature of the foaming agent is preferably 60 to 120 ° C. When the temperature is lower than 60 ° C., the time required for impregnating the resin particles with the foaming agent becomes long, and the production efficiency may decrease. On the other hand, when the temperature is higher than 120 ° C., the resin particles may be fused to generate bonded particles. A more preferable impregnation temperature is 70 to 110 ° C.

  The amount of the foaming agent to be impregnated is preferably in the range of 2 to 12 parts by mass with respect to 100 parts by mass of the thermoplastic resin obtained by polymerization. When the amount is less than 2 parts by mass, a foam having a desired density may not be obtained from the expandable 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 may not be good. When the amount is more than 12 parts by mass, the time required for the cooling step in the production process of the foam becomes long, and the productivity may be lowered. A more preferable content is 3 to 10 parts by mass, a still more preferable content is 4 to 9 parts by mass, and a most preferable content is 5 to 8 parts by mass. In addition, the quantity of the foaming agent to be impregnated can be adjusted so as to have a value substantially equal to the above-described content of the foam when the foam is manufactured. Further, as described above, a foaming aid may be used in combination with a foaming agent. The type of foaming aid and the like are as described above, and the amount added can be appropriately set by those skilled in the art.

In another embodiment of the invention,
A foam comprising 0.5 to 25 parts by mass of a carbon-based infrared shielding agent and 100 parts by mass of a thermoplastic resin and composed of a plurality of expanded particles fused together,
The foam exhibits a ratio A / B of 0.8 to 2.0 in the absorbance A at a wave number of 1000 cm ⁻¹ and the absorbance B at a wave number of 500 cm ⁻¹ obtained by transmission infrared analysis. A method for producing a foam, comprising:
Melting and kneading a carbon-based infrared shielding agent and a thermoplastic resin;
Injecting a foaming agent into the molten resin obtained in the melt-kneading step;
Extruding the molten resin obtained in the blowing agent injection step into a liquid, cutting, and then solidifying to obtain expandable particles;
A step of pre-foaming the obtained expandable particles to obtain expanded particles;
And a process for producing a foam by molding the obtained foamed particles in a mold.

  This embodiment is an embodiment in which expandable particles are produced using a melt extrusion method, which is one of typical methods for producing expandable particles in the art, and then a foam is obtained. Hereinafter, although the melt extrusion method will be described in more detail, the present embodiment is not limited to the conditions described below.

2. Melt extrusion method The melt extrusion method supplies resin pellets to a resin supply device, presses and kneads a foaming agent into the molten resin in the resin supply device, and attaches the molten resin containing the foaming agent to the tip of the resin supply device. This is a method of extruding from the small holes of the formed die and then cooling to obtain expandable particles. A method of directly extruding from a small hole of a die into a cooling liquid, cutting the extrudate with a rotary blade immediately after the extrusion, and cooling the cut particles in the cooling liquid is called a hot cut method. The strand is extruded from the small holes of the die into air in the form of strands, guided into the cooling water tank before the strands are foamed, and after the strands are cooled in the cooling water tank, they are cut into columnar particles. This is called the method (cold cut method). Expandable particles can be produced by either a hot cut method or a strand cut method (cold cut method). In addition, any method has an advantage that an arbitrary amount of carbon-based infrared shielding agent can be easily contained in the particles. Moreover, a carbon-type infrared shielding agent can be uniformly contained in the expandable particles. A preferable production method includes a hot cut method. According to the hot cut method, there is an advantage that substantially spherical expandable particles can be obtained.

Hereinafter, the hot-cut method of the melt extrusion method will be described in more detail, but the present embodiment is not limited to the conditions described below.
(B) Hot cut method of melt extrusion method In this method, a foaming agent was press-fitted and kneaded into a thermoplastic resin melted in a resin supply device, and a molten resin containing the foaming agent was attached to the tip of the resin supply device. Direct extrusion into the cooling liquid from a small hole in the die, and the extrudate extruded into the cooling liquid is cut with a rotating blade in the cooling liquid, and the extrudate is cooled and solidified by contact with the liquid to foam. This is a method for obtaining particles.
In this method, for example, the following manufacturing apparatus can be used. That is, an extruder as a resin supply device, a die having a large number of small holes attached to the tip of the extruder, a raw material supply hopper for charging the raw material into the extruder, and a blowing agent supply port for the molten resin in the extruder A high-pressure pump for press-fitting the foaming agent through, a cutting chamber in which cooling water is provided in contact with the resin discharge surface provided with a small hole in the die, and cooling water is circulated and supplied into the chamber, and a small hole in the die A cutter (high-speed rotating blade) that is rotatably provided in the cutting chamber so as to cut the resin extruded from the cutting chamber, and the foaming particles carried along with the flow of cooling water from the cutting chamber are separated from the cooling water. A dehydration dryer with a solid-liquid separation function that obtains foamable particles by dehydration and drying, a water tank for storing cooling water separated by the dehydration dryer with a solid-liquid separation function, and a cooling chamber for cooling water in this water tank A high pressure pump to send, include manufacturing apparatus and a storage container for storing the dewatered dried effervescent grains at the solid-liquid separation function dehydrating dryer.

  An example of a procedure for producing expandable particles using the production apparatus will be described. First, raw material thermoplastic resin and carbon-based infrared shielding agent are charged into an extruder from a raw material supply hopper. The raw material resin may be mixed in advance in the form of pellets or granules and then charged from one raw material supply hopper. For example, when a plurality of lots are used, the supply amount is adjusted for each lot. You may throw in from several raw material supply hoppers, and may mix them in an extruder. Also, when using a combination of recycled materials from multiple lots, mix the raw materials from multiple lots in advance and remove foreign matter using appropriate sorting means such as magnetic sorting, sieving, specific gravity sorting, and air blowing sorting. It is preferable to keep it. The carbon-based infrared shielding agent may be put into an extruder as a master batch prepared by melt-mixing with a thermoplastic resin in advance.

  The addition amount of the carbon-based infrared shielding agent is 0.5 to 25 parts by mass with respect to 100 parts by mass of the thermoplastic resin. When the addition amount is less than 0.5 parts by mass, the heat insulating property may not be sufficiently improved. On the other hand, when the addition amount exceeds 25 parts by mass, the foam film may be broken, so that the moldability may be reduced and the heat insulation may be inferior. A preferable addition amount of the carbon-based infrared shielding agent is 0.5 to 15 parts by mass, and a more preferable addition amount of the carbon-based infrared shielding agent is 0.5 to 10 parts by mass. Specific contents include 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.01, 2, 2.56, 3, 3.13, 4, 5, 5.26, 6, 7, 7.52, 7.69, 8, 9, 10, 11, 11.11, 12, 13, 14, 15, 16, 17, 18, 19, 20 parts by mass, etc. It is done. In addition, the addition amount can be adjusted at the time of producing the foam so as to have a value substantially equal to the above-described content of the foam.

  After supplying the raw material into the extruder, the thermoplastic resin is heated and melted, and while the molten resin is transferred to the die side, the blowing agent is injected from the blowing agent supply port with a high-pressure pump to mix the blowing agent with the molten resin, The melt is moved to the tip side while further kneading through a foreign matter removing screen provided in the extruder as needed, and the melt added with the foaming agent is pushed out from a small hole in a die attached to the tip of the extruder. .

Those skilled in the art can appropriately set the conditions for injecting the foaming agent into the molten resin obtained by melt kneading. The addition amount of the foaming agent is preferably in the range of 2 to 12 parts by mass with respect to 100 parts by mass of the molten resin. When the amount is less than 2 parts by mass, a foam having a desired density may not be obtained from the expandable 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 may not be good. When the amount is more than 12 parts by mass, the time required for the cooling step in the production process of the foam becomes long, and the productivity may be lowered. A more preferable content is 3 to 10 parts by mass, a still more preferable content is 4 to 9 parts by mass, and a most preferable content is 5 to 8 parts by mass. In addition, the quantity of the foaming agent to inject | pour can be adjusted so that it may become a value substantially the same as content mentioned above about the foam at the time of foam manufacture. Further, as described above, a foaming aid may be used in combination with a foaming agent. The type of foaming aid is as described above, and the amount of foaming aid to be added can be appropriately set by those skilled in the art.

A resin discharge surface with a small hole in the die is placed in a cutting chamber in which cooling water is circulated and supplied into the chamber, and a cutter is provided in the cutting chamber so that the resin extruded from the small hole in the die can be cut. Is rotatably provided. When the melted product with foaming agent added is extruded through a small hole in the die attached to the tip of the extruder, the melt is cut into granules and simultaneously cooled in contact with cooling water to solidify while suppressing foaming. It becomes an expandable particle.
The formed expandable particles are transferred from the cutting chamber along with the flow of cooling water to the dehydrating dryer with a solid-liquid separation function, where the expandable particles are separated from the cooling water and dehydrated and dried. The dried expandable particles are stored in a storage container.
In addition, when adding a flame retardant, the addition time is not particularly limited, but it is preferably added to the extruder together with the raw material.

3. Other Methods As an example of other methods for obtaining expandable resin particles, in the melt extrusion method, resin particles are obtained without press-fitting a foaming agent, and then the particles are subjected to a suspension polymerization method in a two-stage method ( Examples thereof include a method of producing foamable particles by impregnating a foaming agent by a post-impregnation method, or a method of producing foamable particles by seed polymerization of suspension polymerization using these particles as seed particles. Expandable particles can also be produced by these methods. In addition, any method has an advantage that an arbitrary amount of carbon-based infrared shielding agent can be easily contained in the particles by melt extrusion. As a preferable production method, there is a method in which particles containing no foaming agent are obtained by a melt extrusion method and then foamable particles are produced by a seed polymerization method using the particles as seed particles. According to this method, resin particles containing a carbon-based infrared shielding agent at a high concentration (for example, 20% by mass) can be used as seed particles, and there is an advantage that moldability is improved. There is an advantage that it can be obtained.

(Foaming agent)
It does not specifically limit as a foaming agent, All can use a well-known thing. In particular, a gaseous or liquid organic compound having a boiling point equal to or lower than the softening point of the thermoplastic resin used 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 change with time of the foam. 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.
The content of the foaming agent is preferably in the range of 2 to 12% by mass. When the amount is less than 2% by mass, a foam having a desired density may not be obtained from the expandable 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 may not be good. When the amount is more than 12% by mass, the time required for the cooling step in the foam production process becomes long, and the productivity may decrease. A more preferable content is 3 to 10% by mass, a still more preferable content is 4 to 9% by mass, and a most preferable content is 5 to 8% by mass.
A foaming aid may be used in combination with a foaming agent. Examples of the foaming aid include isobutyl adipate, toluene, cyclohexane, and ethylbenzene.

(Other additives)
The foamable particles may contain other additives as necessary. Other additives include plasticizers, flame retardants, flame retardant aids, antistatic agents, spreading agents, foam control agents, fillers, colorants, weathering agents, anti-aging agents, lubricants, antifogging agents, and fragrances. Etc. Other additives other than the bubble regulator are as described above for the foam.

  As the air conditioner, talc, mica, silica, diatomaceous earth, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, potassium sulfate, Barium sulfate, glass beads, polytetrafluoroethylene, tribasic calcium phosphate, magnesium pyrophosphate, zinc stearate, magnesium stearate and other metal soaps, ethylene bis stearamide, bisamide compounds such as methylene bis stearamide, stearamide Amide compounds such as 12-hydroxystearic acid amide, and fatty acid glycerides such as stearic acid triglyceride and stearic acid monoglyceride.

(Foamed particles)
The expanded particles are obtained by expanding the expandable particles to a desired bulk density using water vapor or the like.
The expanded particles may be aged, for example, at normal pressure, prior to the subsequent foam molding process. The aging temperature of the expanded particles is preferably 20 to 60 ° C. When the aging temperature is low, the aging time of the expanded particles may be long. On the other hand, if it is high, the foaming agent in the foamed particles may dissipate and the moldability may deteriorate.
The expanded particles can be obtained by expanding (pre-expanding) the expandable particles, and correspond to the pre-expanded particles for producing the following foam.
The carbon-based infrared shielding agent, thermoplastic resin, and other additives constituting the expanded particles are the same as the above-mentioned foam.

The expanded particles preferably have a bulk density of 0.01 to 0.04 g / cm ³ . When the bulk density is larger than 0.04 g / cm ³ , the lightness of the foam may be lowered. When the bulk density is less than 0.01 g / cm ³ , the heat insulating performance and mechanical strength of the foam may be deteriorated. More preferred bulk density of 0.0125~0.04g / cm ^3, more preferred bulk density is 0.014~0.033g / cm ^3.

  The average diameter (average cell diameter) of the bubbles constituting the expanded particles is preferably 50 to 1000 μm. When the average cell diameter is less than 50 μm, the heat insulating property may be lowered. When the average bubble diameter is larger than 1000 μm, the mechanical strength may be lowered. The average cell diameter is more preferably from 100 to 400 μm, still more preferably from 150 to 350 μm.

(In-mold foaming)
For example, the foamed body is filled with the above-mentioned foamed particles in a closed mold having a large number of small holes, and heated and foamed with a heat medium (for example, pressurized water vapor) to fill the voids between the foamed particles. Can be manufactured by fusing them together. At that time, the density of the foam can be adjusted, for example, by adjusting the filling amount of the pre-expanded particles in the mold.
Heating foaming can be performed, for example, by heating for 5 to 50 seconds with a heat medium of 110 to 150 ° C. Under these conditions, good fusing property between the expanded particles can be secured. More preferably, the heat-foaming molding can be performed by heating for 10 to 50 seconds with a heating medium (for example, water vapor) at a molding vapor pressure (gauge pressure) of 0.06 to 0.08 MPa and 90 to 120 ° C. .

EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.
<Volume resistivity of carbon-based infrared shielding agent>
The volume resistivity is determined by removing the raw carbon-based infrared shielding agent, or if the raw carbon-based infrared shielding agent is added to the foam, remove the thermoplastic resin in the foam with toluene as the organic solvent. The carbon-based infrared shielding agent taken out is melt-kneaded with a styrene resin (carbon-based infrared shielding agent: styrene resin = 1: 4 (mass ratio)), and the surface of the kneaded plate foam is Means the measured value.
Specifically, a plate-like foam of a kneaded product of carbon-based infrared shielding agent and styrene resin (carbon-based infrared shielding agent: styrene-based resin = 1: 4 (mass ratio)) is used to search for conductive plastics. Measurement is performed in accordance with a resistivity test method by a needle method (JIS K7194). The test apparatus uses a low resistivity meter Lorester GP MCP-T600 manufactured by Mitsubishi Chemical Corporation, and the sample sample has a width of 80 × length of 50 × original thickness (20 or less) mm. The sample sample is conditioned at a temperature of 20 ± 2 ° C. and a humidity of 65 ± 5% for 24 hours or more, and then measured as a test environment at a temperature of 20 ± 2 ° C. and a humidity of 65 ± 5%.
The volume resistivity is calculated from the following equation by measuring the resistance values at five measurement positions according to JIS K 7194 on the surface of the sample. The average value is defined as the volume resistivity (Ω · cm) of the carbon-based infrared shielding agent. ρv = V / I × RCF × t
ρv: Volume resistivity (Ω · cm)
V / I: Resistance (Ω)
RCF: Correction coefficient depending on measurement position and sample thickness t: Thickness of test piece (cm)

<Weight average molecular weight>
A weight average molecular weight means the polystyrene (PS) conversion average molecular weight measured using gel permeation chromatography (GPC). Specifically, 3 mg of the sample was allowed to stand and dissolved in 10 mL of tetrahydrofuran (THF) for 72 hours (complete dissolution), and the resulting solution was subjected to a non-aqueous 0.45 μm chromatodisc (13N) manufactured by Kurashiki Boseki Co., Ltd. Filter and measure. The average molecular weight of the sample is determined from a standard polystyrene calibration curve measured and prepared in advance. The chromatographic conditions are as follows.

(Measurement condition)
Equipment used: High-speed GPC equipment: HLC-8320GPC EcoSEC system manufactured by Tosoh Corporation (with built-in RI detector)
Guard column: Tosoh TSKguardcolumn SuperHZ-H (4.6 mm ID × 2 cmL) × 1 Column: Tosoh TSKgel SuperHZM-H (4.6 mm ID × 15 cmL) × 2 Column temperature: 40 ° C.
System temperature: 40 ° C
Mobile phase: Tetrahydrofuran Mobile phase flow rate: Sample side 0.175 mL / min, Reference side 0.175 mL / min Detector: RI detector Sample concentration: 0.3 g / L
Injection volume: 50 μL
Measurement time: 0-25 minutes Runtime: 25 minutes Sampling pitch: 200 msec

(Create a calibration curve)
As a standard polystyrene sample for a calibration curve, the weight average molecular weights of trade names “TSK standard POLYSTYRENE” manufactured by Tosoh Corporation are 5,480,000, 3,840,000, 355,000, 102,000, 37,900, 9 , 100, 2,630, and 500, and a standard polystyrene sample having a weight average molecular weight of 1,030,000 with a trade name “Shodex STANDARD” manufactured by Showa Denko KK

  The method of creating a calibration curve is as follows. The above standard polystyrene samples for calibration curves are group A (with a weight average molecular weight of 1,030,000), group B (weight average molecular weights of 3,840,000, 102,000, 9,100, 500) and group C. (The weight average molecular weight is 5,480,000, 355,000, 37,900, 2,630). Group A is weighed 5 mg and then dissolved in 20 mL of tetrahydrofuran, Group B is also weighed 5 to 10 mg each and then dissolved in 50 mL of tetrahydrofuran, and Group C is also weighed 1 to 5 mg each and then dissolved in 40 mL of tetrahydrofuran. The standard polystyrene calibration curve was prepared by injecting 50 μL of the prepared A, B, and C solutions. From the retention time obtained after measurement, a calibration curve (tertiary equation) was transferred to the HLC-8320GPC dedicated data analysis program GPC workstation (EcoSEC-WS). The measurement curve is obtained by using the calibration curve.

<Measurement method of average primary particle size>
A skin portion of the foam is cut out using a cutter knife and used as a measurement sample. After the cut sample is fixed to the cryosample table with an adhesive, it is ultrathin using an ultramicrotome (Leica Microsystems, LEICA ULTRACUT UCT) and a frozen section preparation system (Leica Microsystems, LEICA EM FCS). A section (thickness 90 nm) is prepared. Next, using a transmission electron microscope (H-7600, manufactured by Hitachi High-Technologies Corporation), an ultrathin section is photographed (photographing magnification: 50,000 times). At least 200 carbon-based infrared shielding agents are photographed per sample, the diameter of each particle is measured, and the average value thereof is calculated. In addition, it is desirable to measure the part which can be recognized clearly as a primary particle, without an outer edge missing.

<Measurement method of amount of carbon-based infrared shielding agent>
The amount of the carbon-based infrared shielding agent is measured using a differential thermothermal gravimetric simultaneous measurement apparatus TG / DTA6200 type (manufactured by SII Nano Technology). For example, in the case of a foam containing a foaming agent or an organic solvent in the resin, the foaming agent or the organic solvent in the resin is removed by leaving it in a thermostatic bath at 120 ° C. for 2 hours. A measurement sample is used. About 15 mg of the sample is filled so that there is no gap at the bottom of the platinum measurement container, and the measurement is performed using alumina as a reference material. As temperature conditions, the temperature is raised from 30 ° C. to 520 ° C. at a rate of 10 ° C./min and a nitrogen gas flow rate of 230 mL / min, and then raised from 520 ° C. to 800 ° C. at a rate of 10 ° C./min and an Air flow rate of 160 mL / min. A TG curve (vertical axis: TG (%), horizontal axis: temperature (° C.)) is obtained, and based on this, the weight loss of the sample when the temperature is raised from 520 ° C. to 800 ° C. is calculated. (Mass%).
At this time, the mass ratio between the carbon-based infrared shielding agent and the thermoplastic resin has the following relationship.
Carbon-based infrared shielding agent: thermoplastic resin = 1: (100 / w-1)
w: Value of mass% of carbon-based infrared shielding agent obtained from measurement results

<Bulk density of expanded particles>
The bulk density of the expanded particles is measured according to JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. Specifically, first, Wg is collected using the expanded particles as a measurement sample, and the 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 expanded particles is calculated.
Bulk density of expanded particles (g / cm ³ ) = mass of measurement sample (W) / volume of measurement sample (V)

<Foam density>
The mass (a) and volume (b) of the test piece (example 75 × 300 × 30 mm) cut out from the foam (after being molded and dried at 40 ° C. for 20 hours or more) so that the significant number is 3 digits or more respectively. And the density (g / cm ³ ) of the foam is determined by the formula (a) / (b).

<Average bubble diameter>
The average cell diameter is measured according to the test method of ASTM D2842-69. A cross-section of any part of the foam is obtained using a razor blade. Using the scanning electron microscope (JSM-6360LV, manufactured by NEC Corporation), an image obtained by enlarging the cut surface by 100 times is created.
Next, a straight line of 60 mm is drawn at an arbitrary position in the range of 20% in the radial direction of the expanded particle from the expanded particle interface on the cut surface image. The number of bubbles on the straight line is counted, and the average chord length (t) of the bubbles is calculated by the following equation.
Average chord length t (μm) = 60 / (number of bubbles × magnification multiple of image)
The average bubble diameter (D) of this bubble is calculated by the following formula.
Average bubble diameter D (μm) = t / 0.616
The above operation is performed with N number of 10, and the average value is defined as the average bubble diameter.

<Thermal conductivity>
A rectangular parallelepiped test piece having a length of 200 mm, a width of 200 mm, and a thickness of 30 mm is cut out from the foam. Next, the cut-out test piece is left still for 72 hours in a thermostat at 60 ° C. to remove the foaming agent contained in the foam. Thereafter, curing is performed for 24 hours or more at a temperature of 23 ° C. ± 1 ° C. and a humidity of 50 ± 10% to obtain a test piece for measuring thermal conductivity. The thermal conductivity (W / m · K) of the test specimen for measurement is measured at a measurement temperature of 23 ° C. by a flat plate heat flow meter method according to JIS A1412-2 (1999 “Foamed plastic insulation material”). Rate is an indicator of thermal insulation.
From the value of the obtained thermal conductivity (W / m · K), the heat insulation is evaluated according to the following criteria.
0.0310 (W / m · K) or less: Thermal insulation is further improved (A)
0.0310 and 0.0320 or less: better thermal insulation (B)
More than 0.0320 and 0.0340 or less: Excellent heat insulation (C)
Exceeds 0.0340 (W / m · K): poor heat insulation (D)
In the present invention, the value of the thermal conductivity of the foam is a value after removing the foaming agent contained in the foam. In addition, when measured without removing the foaming agent in the foam, the thermal conductivity of the foaming agent such as butane and pentane is lower than the thermal conductivity of air, so the value of the thermal conductivity of the foam is about The value is even lower by about 0.002 (W / m · K).
<Specific surface area>
The specific surface area (m ² / g) of the carbon-based infrared shielding agent is measured according to ASTM D-6556.

<Longest diameter of aggregate of carbon-based infrared shielding agent in foam>
A skin portion of the foam is cut out using a cutter knife and used as a measurement sample. After the cut sample is fixed to the cryosample table with an adhesive, it is ultrathin using an ultramicrotome (Leica Microsystems, LEICA ULTRACUT UCT) and a frozen section preparation system (Leica Microsystems, LEICA EM FCS). A section (thickness 90 nm) is prepared. Subsequently, using a transmission electron microscope (H-7600, manufactured by Hitachi High-Technologies Corporation), an ultrathin section is photographed (imaging magnification: 10,000 times). Photograph at least 200 independent separate aggregates per sample. In the photographed image, the longest distance between any two points on the outer edge of the agglomerate where the primary particles of the carbon-based infrared shielding agent appear to overlap is the longest diameter of the agglomerate, and the average value thereof is calculate. The longest diameter connecting the two points is set so as to always overlap the primary particles on the photograph. That is, the longest diameter does not pass through the background of the photograph.

<Measurement method of water absorption>
The water absorption amount of the foam was measured according to JIS A9511: 2006R foamed plastic heat insulating material measurement method B. Three test pieces having a 100 × 100 × 25 mm full-cut surface were immersed in fresh water for 10 seconds, then immersed in ethanol for 10 seconds, and further allowed to stand at room temperature (23 ° C.) for 60 minutes. The reference mass (m0) And Next, after immersing in fresh water again and allowing it to absorb water for 24 hours, the mass (m1) is measured by the same method as the reference mass measurement.
About three test pieces, W is calculated with the following formula | equation, respectively, and let the average value be water absorption (g / 100cm < ² >).
W = (m1-m0) / A × 100
m1 (g): Mass after absorbing water for 24 hours m0 (g): Reference mass A (cm ² ): Total surface area

<Measurement method and evaluation of flame retardancy>
Five test pieces having a rectangular parallelepiped shape having a length of 200 mm, a width of 25 mm, and a height of 10 mm are cut out from the obtained foam by a vertical cutter. After the cut material is cured in an oven at 60 ° C. for 1 day, the individual flame-out time is measured according to the measurement method A of JIS A9511-2006. The average value of the individual flame extinguishing times of 5 test pieces is taken as the flame extinguishing time. In addition, the flame retardance was evaluated according to the following criteria from the flame extinguishing time.
Good (○) ・ ・ ・ Extinguishing time 1.5 seconds to less than 3.0 seconds Very good (◎) ・ ・ ・ Extinguishing time less than 1.5 seconds Unmeasured (-) Absent

<Total content of aromatic organic compound>
The total content of the aromatic organic compound is a value measured by the following << Method for measuring volatile organic compound (VOC) content >>.
<< Measurement Method of Volatile Organic Compound (VOC) Content >>
Weigh precisely 1 g of foam and add 1 ml of a dimethylformamide solution containing 0.1% by volume of cyclopentanol as an internal standard solution, and then add dimethylformamide to the dimethylformamide solution to prepare 25 ml of a measurement solution. Then, 1.8 μl of this measurement solution was supplied to a 230 ° C. sample vaporization chamber, and a chart of each volatile organic compound detected by a gas chromatograph (manufactured by Shimadzu Corporation, trade name “GC-14A”) under the following measurement conditions Based on the calibration curve of each volatile organic compound measured in advance, the amount of volatile organic compound is calculated from each chart, and the amount of volatile organic compound in the foam is calculated.
Detector: FID
Column: GL Sciences (3mmφ × 2.5m)
Liquid phase: PEG-20M PT 25%
Carrier; Chromosorb W AW-DMCS
Mesh: 60/80
Column temperature: 100 ° C
Detector temperature: 230 ° C
DET temperature: 230 ° C
Carrier gas (nitrogen)
Carrier gas flow rate (40ml / min)
In addition, among the volatile organic compound (VOC) content described above, the total amount of each volatile organic compound corresponding to the aromatic organic compound is defined as “total content of aromatic organic compound”.

<Measurement method of absorbance>
A sample having a thickness of 1.0 mm ± 0.1 mm is obtained from an arbitrary portion of the obtained foam. Next, the absorbance of the transmitted infrared of the sample is measured by the following method.
・ Fourier transform infrared spectroscopic analyzer NICOLET iS5 (manufactured by Thermo Fisher Scientific Co., Ltd.)
Measurement method: Transmission method Measurement wave number region: 4000 cm ^{−1 to} 400 cm ⁻¹
-Wave number dependence of measurement depth: No correction-Detector: DTGSKBr
・ Resolution: 4cm ^-1
・ Number of integration: 16 times (same for background measurement)

Example 1
Acetylene black (manufactured by Denki Kagaku Co., Ltd .: Denka Black granular grade, average primary particle size 35 nm, specific surface area 69 m ² ) with respect to 95 parts by mass of polystyrene having a weight average molecular weight of 200,000 (trade name “HRM-10N”, manufactured by Toyo Styrene Co., Ltd.) / G) 5 parts by mass, 0.5 parts by mass of fine powder talc as an inorganic foam nucleating agent, 5 parts by mass of tetrabromobisphenol A-bis (2,3-dibromo-2-methylpropyl ether) as a flame retardant, 150 kg per hour was continuously supplied to a single screw extruder having a diameter of 90 mm. The temperature inside the extruder was set to a maximum temperature of 220 ° C., and after the resin was melted, 6 parts by mass of isopentane was injected from the middle of the extruder as a foaming agent to 100 parts by mass of the resin.

  The resin and foaming agent are kneaded and cooled in the extruder, the resin temperature at the tip of the extruder is maintained at 170 ° C., the pressure at the resin introduction part of the die is maintained at 15 MPa, the diameter is 0.6 mm, and the land length is 3 From the die having 200 small holes of 0.0 mm, the foaming agent-containing molten resin is extruded into the cutting chamber connected to the discharge side of this die and circulating water at 30 ° C. The extrudate was cut with a high-speed rotary cutter having a blade. While the cut particles were cooled with circulating water, they were conveyed to a particle separator, and the particles were separated from the circulating water. Further, the collected particles were dehydrated and dried to obtain expandable styrene resin particles.

The obtained expandable styrene resin particles were carbon-based infrared shielding agent: styrene resin = 1: 19 (mass ratio). The obtained expandable styrenic resin particles were almost spherical with no deformation or beard, and the average particle size was about 1.1 mm. Polyethylene glycol 0.03 parts by mass, zinc stearate 0.15 parts by mass, stearic acid monoglyceride 0.05 parts by mass, hydroxystearic acid triglyceride 0.05 parts by mass with respect to 100 parts by mass of the obtained expandable styrene resin particles. The part was uniformly coated on the entire surface of the expandable styrene resin particles. By heating the expandable styrene resin particles produced as described above, the foamed styrene resin particles were prefoamed to a bulk density of 0.020 g / cm ³ to obtain prefoamed particles. The 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 foam having a length of 400 mm × width of 300 mm × thickness of 30 mm.

After the foam was dried in a drying chamber at 50 ° C. for 6 hours, the density of the foam was measured and found to be 0.020 g / cm ³ . This foam was excellent in appearance without shrinkage. The obtained foam was sliced to a thickness of 1.0 ± 0.1 mm using a ham slicer to obtain a sample for absorbance measurement. Absorbance obtained by transmission infrared absorption analysis of the foam sample was calculated. The absorbance A at a wave number of 1000 cm ⁻¹ was 0.98, the absorbance B at a wave number of 500 cm ⁻¹ was 0.78, and the absorbance ratio (A / B) was 1.26. Moreover, the thermal conductivity of this foam was as excellent as 0.031 W / mk. Furthermore, the water absorption was as low as 0.08 g / 100 cm ² . The average value of the longest diameter of the aggregate was 270 nm.

(Example 2)
A polystyrene resin masterbatch (product name: EX4050B, average primary particle diameter 55 nm, manufactured by Nippon Pigment Co., Ltd.) with respect to 75 parts by mass of polystyrene (product name “HRM-10N”, manufactured by Toyo Styrene Co., Ltd.) having a weight average molecular weight of 200,000 A foam was obtained in the same manner as in Example 1 except that 25 parts by mass of carbon black having a surface area of 28 m ² / g was contained. The absorbance A at a wave number of 1000 cm ⁻¹ was 0.97, the absorbance B at a wave number of 500 cm ⁻¹ was 0.85, and the absorbance ratio (A / B) was 1.14. The foam had a thermal conductivity of 0.032 W / mk and a water absorption of 0.09 g / 100 cm ² . The average value of the longest diameter of the aggregate was 340 nm.
Example 3
Polystyrene resin masterbatch (product name: EX4050A, average primary particle size 15 nm, manufactured by Nippon Pigment Co., Ltd.) with respect to 75 parts by mass of polystyrene (product name “HRM-10N”, manufactured by Toyo Styrene Co., Ltd.) having a weight average molecular weight of 200,000 A foam was obtained in the same manner as in Example 1 except that 25 parts by mass of carbon black (containing 20% carbon black having a surface area of 254 m ² / g) was used. The absorbance A at a wave number of 1000 cm ⁻¹ was 0.98, the absorbance B at a wave number of 500 cm ⁻¹ was 0.86, and the absorbance ratio (A / B) was 1.14. The foam had a thermal conductivity of 0.032 W / mk and a water absorption of 0.11 g / 100 cm ² . The average value of the longest diameter of the aggregate was 278 nm.
(Example 4)
A foam was obtained in the same manner as in Example 1 except that an average primary particle size of 40 nm, a specific surface area of 800 m ² / g, and Ketjen Black (manufactured by Lion Corporation: EC300J) were used. The absorbance A at a wave number of 1000 cm ⁻¹ was 0.98, the absorbance B at a wave number of 500 cm ⁻¹ was 0.85, and the absorbance ratio (A / B) was 1.15. The foam had a thermal conductivity of 0.030 W / mk and a water absorption of 0.1 g / 100 cm ² . The average longest diameter of the agglomerates was 255 nm.

(Example 5)
A foam was obtained in the same manner as in Example 1 except that Ketjen Black (Lion Corporation: EC600JD) having an average primary particle size of 34 nm and a specific surface area of 1400 m ² / g was used. The absorbance A at a wave number of 1000 cm ⁻¹ was 0.98, the absorbance B at a wave number of 500 cm ⁻¹ was 1.2, and the absorbance ratio (A / B) was 0.82. The foam had a thermal conductivity of 0.030 W / mk and a water absorption of 0.15 g / 100 cm ² . The average value of the longest diameter of the aggregate was 289 nm.
(Example 6)
A foam was obtained in the same manner as in Example 1 except that graphite having an average primary particle diameter of 15 μm and an apparent density of 0.1 g / cm ³ was used instead of acetylene black (manufactured by Nippon Graphite Co., Ltd .: GR15). The absorbance A at a wave number of 1000 cm ⁻¹ was 0.96, the absorbance B at a wave number of 500 cm ⁻¹ was 0.55, and the absorbance ratio (A / B) was 1.75. The foam had a thermal conductivity of 0.033 W / mk and a water absorption of 0.35 g / 100 cm ² .

(Comparative Example 1)
A foam was obtained in the same manner as in Example 1 except that acetylene black was not added. The absorbance A at a wave number of 1000 cm ⁻¹ was 0.94, the absorbance B at a wave number of 500 cm ⁻¹ was 0.37, and the absorbance ratio (A / B) was 2.54. The water absorption of the foam was 0.2 g / 100 cm ² . The thermal conductivity of the foam was 0.038 W / mk, which was insufficient.
(Comparative Example 2)
A foam was obtained in the same manner as in Example 1 except that furnace black (Mitsubishi Chemical Corporation: # 970) having an average primary particle diameter of 16 nm and a specific surface area of 260 m ² / g was used instead of acetylene black. The absorbance A at a wave number of 1000 cm ⁻¹ was 0.88, the absorbance B at a wave number of 500 cm ⁻¹ was 0.40, and the absorbance ratio (A / B) was 2.20. The water absorption of the foam was 0.22 g / 100 cm ² . The thermal conductivity of the foam was 0.037 W / mk, which was insufficient.

  From Table 1 above, it was shown that the foam having an absorbance ratio A / B of 0.8 to 2.0 has good thermal conductivity.

Claims (10)

A foam comprising 0.5 to 25 parts by mass of a carbon-based infrared shielding agent and 100 parts by mass of a thermoplastic resin and composed of a plurality of expanded particles fused together,
The foam, in the absorbance B at absorbance A and the wave number 500 cm ^-1 in wave number 1000 cm ^-1 obtained by the transmission method infrared analysis, shows a ratio A / B of 0.8 to 2.0, and 0. A foam having a water absorption of less than 5 g / 100 cm ² .   The foam according to claim 1, wherein the absorbance B is 0.5 or more. The foam according to claim 1 or 2, wherein the foam has a density of 0.01 to 0.04 g / cm ³ .   The foam according to any one of claims 1 to 3, wherein the thermoplastic resin is a styrene resin.   The foam according to any one of claims 1 to 4, wherein the foamed particles have an average cell diameter of 150 to 350 µm.   The foam according to any one of claims 1 to 5, wherein the carbon-based infrared shielding agent has conductivity.   The foam according to any one of claims 1 to 6, wherein the carbon-based infrared shielding agent is acetylene black, ketjen black, or a mixture thereof. The foam according to any one of claims 1 to 7 , further comprising a flame retardant. A foam comprising 0.5 to 25 parts by mass of a carbon-based infrared shielding agent and 100 parts by mass of a thermoplastic resin and composed of a plurality of expanded particles fused together,
The foam, in the absorbance B at absorbance A and the wave number 500 cm ^-1 in wave number 1000 cm ^-1 obtained by the transmission method infrared analysis, shows a ratio A / B of 0.8 to 2.0, and 0. A method for producing a foam, characterized by having a water absorption of less than 5 g / 100 cm ² , comprising:
A step of impregnating the seed particles with a monomer in a dispersion obtained by dispersing seed particles containing a carbon-based infrared shielding agent and a thermoplastic resin in water;
Polymerizing the monomer simultaneously with or after impregnation;
A step of impregnating a foaming agent to obtain expandable particles simultaneously with or after the polymerization;
A step of pre-foaming the obtained expandable particles to obtain expanded particles;
And a process for producing a foam by molding the obtained foamed particles in a mold. A foam comprising 0.5 to 25 parts by mass of a carbon-based infrared shielding agent and 100 parts by mass of a thermoplastic resin and composed of a plurality of expanded particles fused together,
The foam, in the absorbance B at absorbance A and the wave number 500 cm ^-1 in wave number 1000 cm ^-1 obtained by the transmission method infrared analysis, shows a ratio A / B of 0.8 to 2.0, and 0. A method for producing a foam, characterized by having a water absorption of less than 5 g / 100 cm ² , comprising:
Melting and kneading a carbon-based infrared shielding agent and a thermoplastic resin;
Injecting a foaming agent into the molten resin obtained in the melt-kneading step;
Extruding the molten resin obtained in the blowing agent injection step into a liquid, cutting, and then solidifying to obtain expandable particles;
A step of pre-foaming the obtained expandable particles to obtain expanded particles;
And a process for producing a foam by molding the obtained foamed particles in a mold.