JP5642365B2 - Styrene resin extruded foam - Google Patents

Description

  The present invention relates to a styrenic resin foam by extrusion foaming, which has excellent heat insulation performance and has improved combustibility, particularly gas surface combustion problems.

  Styrenic resin is added to an extruder and melted by heating, then a foaming agent is injected, the gel is cooled to a temperature suitable for foaming, and the foam is continuously extruded to produce a foam. How to do is known. Moreover, the foam manufactured in this way is known as a styrene resin foam having a low thermal conductivity.

  As the blowing agent, chlorine atom-containing fluorinated hydrocarbons (hereinafter abbreviated as CFC) such as dichlorodifluoromethane and chlorine atom-containing fluorinated hydrocarbons (hereinafter referred to as HCFC) obtained by partially hydrogenating chlorine atoms such as monochlorodifluoroethane. Fluorocarbons such as fluorinated hydrocarbons (hereinafter abbreviated as HFC) having no chlorine atom in the molecule such as 1,1,1,2-tetrafluoroethane have been used.

  Fluorocarbons have a low thermal conductivity as a gas and have low gas permeability with respect to the styrene resin, so that they remain in the bubbles for a long time, and are effective in reducing the thermal conductivity of the foam. However, regarding the use of CFCs and HCFCs, there are concerns about the protection of the ozone layer, and HFC has a large global warming potential although its ozone depletion coefficient is 0, so there is room for improvement in terms of protecting the global environment. It was. On the other hand, combustible hydrocarbons such as propane, butane, and pentane have come to be used as a substitute for chlorofluorocarbons.

JP-A-10-237210 JP-A-10-265604

  As mentioned above, flammable hydrocarbons such as propane, butane, and pentane have come to be used as a substitute for chlorofluorocarbons, but the thermal conductivity when these hydrocarbon-based blowing agents are gasified is air. While combusting lower the foam's thermal conductivity, these combustible gases worsen the foam's combustion resistance. Here, in the flammability test of the foam (here, the flammability test of JIS A9511: 2006R), the combustion of the foam is roughly divided into resin combustion and gas surface combustion. Resin combustion can be suppressed to some extent by increasing the amount of flame retardant, but gas surface combustion, which is a phenomenon that spreads only the foam surface due to the use (injection) of a large amount of flammable gas, increases the amount of flame retardant. However, there are limits to suppression. That is, there is a problem that the foam does not satisfy the combustion resistance and it is difficult to obtain good thermal conductivity.

  The present invention has been made in view of the above-described problems. By using a suitable amount of combustible gas, the thickness of the bubble film is set to a certain level or more, so that the thermal conductivity and flame retardancy (particularly gas combustion) are good. An object of the present invention is to provide an extruded foam of a styrene resin.

[1] The thickness of the bubble film is 2 μm or more, the thermal conductivity measured by the measurement method specified in JIS A1412-2: 1999 is 28 mW / m · K or less, and specified in JIS A9511: 2006R. Styrenic resin extruded foam that passes flammability measurement method A.

[2] The styrene resin extruded foam according to [1], wherein the thermal conductivity is 26 mW / m · K or less.

[3] The styrene resin extruded foam according to the above [1] or [2], comprising at least one selected from the group consisting of graphite, titanium oxide and carbon black as a radiation reducing agent.

[4] The styrene-based resin extrusion foam according to any one of [1] to [3], wherein an addition amount of the radiation reducing agent is 0.1 to 10 parts by weight with respect to 100 parts by weight of the foam. body.

[5] The styrene according to any one of [1] to [4], wherein the remaining amount of the combustible gas in the foam is 3 to 4.5 parts by weight with respect to 100 parts by weight of the foam. -Based resin extruded foam.

[6] The styrene resin extruded foam according to any one of the above [1] to [5], comprising 4 to 8 parts by weight of a flame retardant with respect to 100 parts by weight of the foam.

[7] The styrene resin extruded foam according to any one of the above [1] to [6], wherein the density is 30 to 40 kg / m ³ and the cell diameter (cell size) is 0.1 to 0.3 mm. body.

  According to a preferred embodiment of the present invention, for example, a styrene resin extruded material that has good thermal conductivity and flame retardancy (particularly gas combustion), and has excellent physical properties while maintaining the conventional foam density and cross section. A foam can be provided.

Styrene Resin Extruded Foam The styrene resin extruded foam according to the present invention has a cell membrane thickness of 2 μm or more, and a thermal conductivity measured by the measurement method defined in JIS A1412-2: 1999 is 28 mW / It is a styrene resin extruded foam that is m · K or less and passes the flammability measuring method A defined in JIS A9511: 2006R.

Styrenic resin The styrene resin used in the present invention is not particularly limited, and is a polystyrene homopolymer obtained only from a styrene monomer, a monomer copolymerizable with styrene monomer and styrene, or a derivative thereof. And modified polystyrene such as post-brominated polystyrene and rubber-reinforced polystyrene.

  Examples of monomers that can be copolymerized with styrene include methylstyrene, dimethylstyrene, ethylstyrene, diethylstyrene, isopropylstyrene, bromostyrene, dibromostyrene, tribromostyrene, chlorostyrenedichlorostyrene, trichlorostyrene, and other styrene derivatives, vinyl. Vinyl compounds such as toluene, vinyl xylene, divinylbenzene, unsaturated compounds such as acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butadiene, acrylonitrile, or derivatives thereof, maleic anhydride, Examples include itaconic anhydride. These can be used alone or in admixture of two or more. Of the styrenic resins, polystyrene homopolymer is particularly preferred.

  The weight average molecular weight of the styrene resin is 100,000 to 300,000, preferably 150,000 to 250,000, and more preferably 180,000 to 220,000.

Blowing agent As the blowing agent used in the present invention, one or more kinds of saturated hydrocarbons having 3 to 5 carbon atoms can be used, and other blowing agents can be used as necessary.

  Examples of the saturated hydrocarbon having 3 to 5 carbon atoms include propane, n-butane, i-butane, n-pentane, i-pentane, neopentane and the like. In the case of a saturated hydrocarbon having 3 to 5 carbon atoms, n-butane and i-butane are preferable from the viewpoint of foamability and heat insulation performance of the foam, and i-butane is particularly preferable. Moreover, it is preferable that content of 1 type (s) or 2 or more types of C3-C5 saturated hydrocarbon is 2-10 weight part with respect to 100 weight part of foams, More preferably, a saturated hydrocarbon compound 3 to 9 parts by weight, particularly preferably 4 to 8 parts by weight for propane, 2.5 to 9 parts by weight for n-butane and i-butane, particularly preferably 3 to 8 parts by weight, -In pentane, i-pentane, and neopentane, 3-9 weight part is preferable from the point of heat insulation performance and a flame retardance.

  Other foaming agents are not particularly limited. Examples of organic foaming agents include alkyl chlorides such as methyl chloride and ethyl chloride, dimethyl ether, diethyl ether, methyl ethyl ether, isopropyl ether, n-butyl ether, Ethers such as diisopropyl ether, furan, furfural, 2-methylfuran, tetrahydrofuran, tetrahydropyran, dimethyl ketone, methyl ethyl ketone, diethyl ketone, methyl n-propyl ketone, methyl n-butyl ketone, methyl i-butyl ketone, methyl n-amyl ketone, Ketones such as methyl n-hexyl ketone, ethyl n-propyl ketone, ethyl n-butyl ketone, methanol, ethanol, propyl alcohol, i-propyl alcohol, butyl alcohol, -Alcohols such as butyl alcohol and t-butyl alcohol, carboxylic acid esters such as formic acid methyl ester, formic acid ethyl ester, formic acid propyl ester, formic acid butyl ester, formic acid amyl ester, propionic acid methyl ester, propionic acid ethyl ester, etc. Can be used. Further, for example, carbon dioxide and water can be used as the inorganic foaming agent, and azo compounds can be used as the chemical foaming agent. These can be used individually or in mixture of 2 or more types. By using these other foaming agents, a good plasticizing effect and a foaming aid effect can be obtained, the extrusion pressure can be reduced, and the foam can be stably produced.

  In particular, as other foaming agents, methyl chloride, ethyl chloride, and dimethyl ether are preferable from the viewpoint of foamability, foam moldability, and the like. The other blowing agent is a compound other than a saturated hydrocarbon having 3 to 5 carbon atoms, but not only does not contain a saturated hydrocarbon having 3 to 5 carbon atoms, but also a saturated hydrocarbon having 2 or less carbon atoms. Or a saturated hydrocarbon having 6 or more carbon atoms, and preferably no unsaturated hydrocarbons regardless of the number of carbon atoms.

  About the ratio of each foaming agent in the case of adding a several foaming agent, C3-C5 saturated hydrocarbon is 20-100 weight% with respect to the total weight of a foaming agent, Preferably it is 25-100 weight%, More preferably, it is 30 to 100% by weight. The other blowing agent is 0 to 80% by weight, preferably 0 to 75% by weight, and more preferably 0 to 70% by weight. The other foaming agent is preferably 80% by weight or less in order to improve the heat insulation performance of the foam.

  The amount of the foaming agent added to the styrenic resin when producing the foam is 6 to 10 parts by weight, preferably 7 to 9 parts by weight, more preferably 7 to 8 parts by weight, based on 100 parts by weight of the styrene resin. Part.

  The foaming agent used in the present invention includes a combustible material. In this case, the amount of combustible gas remaining in the foam (in the bubbles) is 3 with respect to 100 parts by weight of the foam. It is preferably ˜4.5 parts by weight, and more preferably 3.4 to 4.3 parts by weight.

Flame retardant As the flame retardant used in the present invention, a flame retardant usually used for thermoplastic resins can be used without any particular limitation, and a halogen flame retardant is preferred. For example, brominated products of aliphatic or alicyclic hydrocarbons such as hexabromocyclododecane, hexabromobenzene, ethylene bispentabromodiphenyl, decabromodiphenyl ether, octabromodiphenyl ether, 2,3-dibromopropylpentabromophenyl ether, etc. Brominated aromatic compounds, tetrabromobisphenol A, tetrabromobisphenol A bis (2,3-dibromopropyl ether), tetrabromobisphenol A (2-bromoethyl ether), tetrabromobisphenol A diglycidyl ether, tetrabromobisphenol Brominated bisphenols such as A diglycidyl ether and tribromophenol adducts and derivatives thereof, tetrabromobisphenol A polycarbonate oligomer Brominated bisphenol derivatives oligomers such as tetrabromobisphenol A diglycidyl ether and brominated bisphenol adduct epoxy oligomer, ethylene bistetrabromophthalimide, ethylene bisdibromonorbornane dicarboximide, bis (2,4,6-tribromophenoxy) Examples include ethane, brominated SBS block polymers, brominated aromatic compounds such as brominated acrylic resins, chlorinated paraffin, chlorinated naphthalene, perchloropentadecane, chlorinated aromatic compounds, and chlorinated alicyclic compounds. These compounds can be used individually or in mixture of 2 or more types.

  Of the halogen-based flame retardants, bromine-based flame retardants are preferable from the viewpoint of flame retardancy, and hexabromocyclododecane, brominated SBS block polymer, 2,2-bis (4 ′) are particularly preferable from the viewpoint of compatibility with styrene resins. (2 ″, 3 ″ -dibromoalkoxy) -3 ′, 5′-dibromophenyl) -propane is preferred.

  The content of the flame retardant in the foam is preferably 4 to 10 parts by weight, more preferably 4 to 8 parts by weight, and particularly preferably 7 to 8 parts by weight with respect to 100 parts by weight of the foam. If the amount is less than 4 parts by weight, the flame retardancy targeted by the present invention cannot be obtained. If the amount exceeds 10 parts by weight, the moldability during production of the foam may be impaired.

  By coexisting a phosphate ester with a halogen-based flame retardant, combustion can be suppressed even in the case of high flammability containing titanium oxide (as a radiation reducing agent), achieving high heat insulation and JIS. A high degree of flame retardancy as defined in A9511: 2006R can be achieved.

  The phosphate ester used in the present invention is not limited to triphenyl phosphate (TPP), but includes tricresyl phosphate, trixylylenyl phosphate, cresyl diphenyl phosphate, 2-ethylhexyl diphenyl phosphate, trimethyl. As the phosphate, triethyl phosphate, tributyl phosphate, tris (2-ethylhexyl) phosphate, tris (butoxyethyl) phosphate, or condensed phosphate ester, an aromatic phosphate ester is preferable, and triphenyl phosphate is particularly preferable.

  Examples of the radiation reducing agent that can be used in the present invention include white pigments such as titanium oxide described below, black pigments such as graphite and carbon black, and other colored pigments. The amount of the radiation reducing agent added to the styrene resin is preferably 0.1 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, and more preferably 0.1 to 4 parts by weight with respect to 100 parts by weight of the styrene resin. Part is particularly preferred.

White pigments As white pigments used in the present invention, for example, lead white (basic lead carbonate: (PbCO ₃ ) ₂ .Pb (OH) ₂ ), zinc white (zinc oxide), titanium oxide, zinc sulfide, Examples include lithopone (a mixture of zinc sulfide and barium sulfate), antimony white, mica, aluminum oxide, alumina white, and white carbon. Among these, titanium oxide is preferable.

  The average particle diameter of the white pigment (for example, titanium oxide) is not particularly limited, but is preferably 0.1 μm to 0.5 μm (0.15 μm to 0.005 μm) in consideration of the color developability to the resin. 3 μm is more preferable). If the average particle diameter is in this range, the dispersibility and color developability are good, and the whiteness in the visible light region of 400 to 800 nm can be improved. On the other hand, when it is desired to suppress infrared absorption to the resin in the near infrared to far infrared region, 0.8 μm to 1.5 μm is preferable (0.8 μm to 1.0 μm is more preferable). By mixing these white pigments having different average particle diameters in the range of 10 wt% to 90 wt%, it is possible to obtain a mixed titanium oxide with improved reflection in the infrared region and whiteness in the visible light region. .

  The amount of the white pigment added to the styrene resin is 0.1 to 10 parts by weight, preferably 1 to 8 parts by weight, and more preferably 2 to 4 parts by weight with respect to 100 parts by weight of the styrene resin.

Black pigments Examples of the black pigment used in the present invention include graphite, carbon black, chromium black, copper chromate, and the like. Among these, graphite and carbon black are preferable. The graphite may be natural graphite such as flaky graphite, scaly (lumpy) graphite, earthy graphite, artificial graphite, or pyrolytic graphite. Graphite desirably has a fixed carbon number of 80% or more, more preferably 90% or more.

  The average particle size of the black pigment is not particularly limited, but for example, carbon black is preferably 10 to 300 nm (0.01 to 0.3 μm), and 200 to 290 nm (0.2 to 0.29 μm). Is more preferable. Moreover, 1-30 micrometers is preferable in a graphite, and 3-15 micrometers is more preferable. The average particle size of graphite is preferably set to an average particle size of 10 μm or more in order to affect the color developability and the degree of infrared absorption / reflection in the infrared region in the same manner as titanium oxide. On the other hand, if the average particle diameter of graphite exceeds 30 μm, the connectivity of the bubbles in the foam increases and the heat insulation performance is remarkably lowered.

  The amount of the black pigment added to the styrenic resin is 0.1 to 2.5 parts by weight, preferably 0.3 to 2.0 parts by weight, and more preferably 0.8 to 100 parts by weight of the styrenic resin. 5 to 1.2 parts by weight.

Colored pigment The colored pigment used in the present invention is preferably an organic colored pigment having an average particle size of 0.5 μm or less (preferably 0.1 to 0.3 μm). For example, phthalocyanine blue is preferable for a blue pigment. Further, some inorganic colored pigments have an average particle diameter of 1 μm or more, and exhibit an effective reflecting action at locations where the wavelength is large in the infrared region. However, note that inorganic colored pigments, unlike organic pigments, often have poor color developability and dispersibility, and may require a larger amount (for example, 5 times or more) than organic pigments. There is a need to. In general, an increase in the amount of additive added is not preferable because it may act as a nucleating agent when the foam is molded to significantly reduce the bubble diameter, and is not preferable from the viewpoint of cost.

  The amount of the colored pigment added to the styrenic resin is 0.01 to 0.5 parts by weight, preferably 0.03 to 0.2 parts by weight, more preferably 0.05 to 100 parts by weight of the styrenic resin. ~ 0.15 parts by weight.

In the present invention, a styrene resin is heated and melted, a foaming agent, a radiation reducing agent, a flame retardant, and the like are added to the styrene resin, and the resultant is extruded and foamed. -Based resin extruded foam can be produced. For example, the main raw material styrenic resin and various other additives are put into the hopper of the extruder, the foaming agent is injected and kneaded, the gel is cooled uniformly with a cooler, and the pressure is reduced from the die to atmospheric pressure. It can be produced by extrusion foaming.

The melting temperature for heating and melting the styrene resin is 160 to 240 ° C., preferably 170 to 230 ° C., more preferably 180 to 220 ° C., and the solid raw material is melt-kneaded by an extruder. The pressure at the time of press-fitting the blowing agent, 110~200kg / cm ^2, more preferably 120~185kg / cm ^2. The solid raw material and the foaming agent melted by the extruder are kneaded by a mixer (rotational speed: 20 to 40 rpm, more preferably 25 to 35 rpm) and slowly cooled by a cooler. Moreover, the optimal temperature when cooling and foaming a gel is 100-130 degreeC, More preferably, it is 110-127 degree | times.

  In addition, the white pigment (for example, titanium oxide), black pigment (for example, graphite), colored pigment, and phosphate ester (for example, triphenyl phosphate) are added in advance before being added to the heat-melted styrene resin. It is preferable to prepare a master batch with a styrene resin.

  When producing a master batch of pigment, in order to ensure the stability of the extruder, metal-based stearic acid such as about 5% magnesium stearate may be used. In some cases, the flame retardant performance was lowered or the bubble diameter was changed. On the other hand, the melting point of triphenyl phosphate is around 49 ° C., and if it is directly fed into the extruder during the foam production process, surging of the extruder occurs or the discharge amount is not good at an addition amount of 0.3 parts by weight or more. In some cases, it becomes stable and the productivity is significantly reduced.

  Therefore, as a substitute for stearic acid, 0.1% to 10%, preferably around 5% of triphenyl phosphate is added in advance in the masterbatch production process of the pigment, so that the mixing ratio of these raw materials is made uniform. As well as good addition of triphenyl phosphate. Also, in the masterbatch manufacturing process, the meltability of polystyrene can be further improved by the plasticizing effect of triphenyl phosphate, so that each of the pigment and triphenylphosphate is fed into the masterbatch rather than directly into the extruder. Thus, it is possible to easily disperse uniformly, and it is possible to obtain a stable dispersibility after extrusion.

  In addition, as a method of adjusting the bubble diameter, generally, there is a method of adjusting by adding or decreasing the amount of foaming agent added (influence of solubility), such as polyethylene or talc. Moreover, as a method of adjusting the density of a foam, the method performed by adjusting the addition amount of a foaming agent or foaming temperature is mention | raise | lifted generally.

Physical Properties of Styrene Resin Extruded Foam The density, cell diameter (cell size), cell membrane thickness, thermal conductivity, and combustibility of the styrene resin extruded foam according to the present invention will be described.

(Foam density)
The density of the foam is calculated excluding the skin layer, and can be calculated by dividing the weight (Kg) of the foam by the volume (m ³ ) of the foam. The density of the styrene resin extruded foam according to the present invention is 20 to 45 Kg / m ³ , preferably 25 to 40 Kg / m ³ , and more preferably 30 to 39 Kg / m ³ .

(Bubble diameter of foam)
The cell diameter of the foam is measured by a method according to ASTM D 3567, and is 0.1 to 0.6 mm, preferably 0.15 to 0.3 mm, more preferably 0.18 to 0.23 mm. It is. Note that, in the foam of the dual cell structure, the bubble diameter is defined for the primary bubbles and the secondary bubbles. In this case, the primary bubble diameter is 0.2 to 0.5 mm, preferably 0.25 to 0.4 mm, and more preferably 0.25 to 0.3 mm. Moreover, the secondary bubble diameter is 0.03-0.1 mm, Preferably it is 0.05-0.08 mm.

(Bubble film thickness)
The thickness of the bubble film is theoretically calculated as a regular hexahedron model, and is calculated from the density of the foam, the bubble diameter (cell size), and the density of the foam resin. The calculation of the thickness of the cell membrane of the regular hexahedron model in the closed-cell foam is theoretically calculated by the following formula (Plastic Foam Handbook, February 28, 1973, Nikkan Kogyo Shimbun, page 43). In addition, the density of the resin represented by ρs means the density of the resin used for the production of the foam, and in the case of polystyrene, it is 1050 Kg / m ³ . When a resin other than polystyrene is used, the density of the resin is used in the calculation formula as ρs.

  In order to improve the gas surface combustion of the foam in the flammability test, the increase in the flame retardant alone cannot be solved. The mechanism of gas surface combustion is not limited to this, but as the fire source ignites the foam, the melting of the resin in the bubble film is promoted first, and then the bubble film is melted and the bubbles are destroyed. Then, it is considered that gas combustion occurs together with oxygen in the air when the combustible gas filled in the bubble structure is released to the atmosphere. Therefore, if the structure of the bubble film is thin or weak, it is considered that the bubble film can be easily broken and gas combustion is promoted. Gas combustion generally occurs only on the surface layer of the specimen, and the fire spread of the fire source may reach the top in an instant.

  The problem of gas combustion is related to the amount of flammable gas remaining in the foam, the amount of flame retardant added, and the thickness of the bubble film. The cell membrane depends on the density of the foam and the cell diameter.

  Although the above-mentioned flame retardant can be used, it is particularly preferable to use hexabromocyclododecane (HBCD). The amount of the flame retardant added is limited to 10 parts by weight with respect to 100 parts by weight of the foam, and if it is more than that, there is a concern that foam molding may occur. There is no big difference. If the amount is less than 4 parts by weight, flame retardancy cannot be obtained. When HBCD is used, it is desirable to use it together with triphenyl phosphate (TPP), which is a flame retardant aid. For example, the addition ratio of 6.5 parts by weight of HBCD and 1.0 part by weight of TPP is the most. Good. In addition, this addition ratio is about 3.4 to 3.7 parts by weight (the amount of foam is 100 parts by weight) of the addition amount or the residual amount of a combustible gas (for example, isobutane) as a foaming agent in consideration of long-term heat insulation performance maintenance. In contrast, it is the optimal flame retardant formulation. As other foaming agent (flammable gas), ethyl chloride is used, and about 1.2 parts by weight is added. The gas permeability of ethyl chloride is larger than that of isobutane, and the residual amount in the foam varies greatly depending on the number of aging days. The sample evaluation is based on aging for about 7 days, and after that, the amount of combustible gas decreases, which can be said to be safer.

  The thickness of the bubble film for clearing the problem of gas combustion on the basis of these is about 2 μm or more, preferably 2.2 μm or more. In order to improve the thermal conductivity, the bubble diameter should be small, but if the bubble is small when the density is constant, the bubble film becomes thin and gas combustion becomes remarkable. To deal with these, the density must be increased, and the balance with economy is worsened. Therefore, in consideration of these balances, the bubble diameter and density must be designed to satisfy the thermal conductivity and gas combustion.

  As described above, the optimum thickness of the bubble film varies depending on the remaining amount of the combustible gas. For example, when the added amount is larger than the above set value, or when the ambient temperature is lowered and the gas permeability is lowered in winter curing, in these cases, the remaining amount of combustible gas is increased, which causes the problem of surface gas combustion. The optimum thickness of the bubble film to clear increases.

  When the bubbles have a dual-cell structure, the area% (Dc small%) of the small bubble structure and the area% (Dc large%) of the large bubble structure are calculated in advance, and the respective bubble film thicknesses (t The thickness of the bubble film may be calculated by a weighted average of small and large t). In the examples and comparative examples described below, the thickness of the bubble film is calculated in this way in the case of the dual cell structure.

(The thermal conductivity of the foam)
The thermal conductivity ( mW / m · K ) of the foam is measured by a method according to JIS A1412-2: 1999, and is 28 mW / m · K or less, preferably 26 mW / m · K or less. More preferably, it is 24 mW / m · K or less.

(Flammability of foam)
The flammability of the foam is measured by a method according to JIS A9511: 2006R (measurement method A is adopted). As a result of the flammability test, there is no residue, and the flame extinguishing time is within 3 seconds. There was no fire spread (fire spread length 0 mm) as a criterion for acceptance.

<Example 1>
A styrene resin having a weight average molecular weight of 210,000 is used as a main raw material, 0.15 parts by weight of barium stearate (manufactured by NOF Corporation) as a lubricant for an extruder, and magnesium oxide (manufactured by Kamishima Chemical Co., Ltd .: Starmag as a flame retardant stabilizer). L-10) 0.08 part by weight, 0.5 part by weight of polyethylene (Daulex 2047G: manufactured by Dow Chemical Co.) as a bubble regulator, and hexabromocyclododecane (HBCD, Albemarle SAYTEX HP-900) as a flame retardant 6. 5 parts by weight, 1.0 part by weight of triphenyl phosphate (TPP, manufactured by Daihachi Chemical Co., Ltd.) as a flame retardant adjuvant, 0.9 part by weight of graphite (GA98 / 10: manufactured by Timcal Japan) as a radiation reducing agent, and Charge 3.0 parts by weight of titanium oxide (R-104: DuPont) into the extruder hopper. As a blowing agent, 3.7 parts by weight of isobutane, 1.2 parts by weight of ethyl chloride, and 2.7 parts by weight of carbon dioxide were press-fitted and kneaded, and then the gel was cooled uniformly with a cooler and extruded and foamed from a die under atmospheric pressure. did. The pressure in the gel system from the extruder outlet to the die inlet was within the pressure resistance of the current equipment and was not a problem. The density of the foam obtained in Example 1 was collected at a foaming temperature of 122 ° C.

  The total weight of all the raw materials charged in the extruder was set to 100 parts by weight. In addition, graphite, titanium oxide and TPP were previously charged in the form of a styrene resin masterbatch. The mixing concentration of the master batch was 70% by weight / 30% by weight of styrene resin / graphite or titanium oxide, and 90% by weight / 10% by weight of styrene resin / TPP.

<Examples 2-7, Comparative Examples 1-9>
The foams according to Examples and Comparative Examples were prepared according to the method described in Example 1 according to the amount of each raw material and the foaming temperature shown in Tables 1 and 2. The foams according to Example 7 and Comparative Example 7 have a dual cell structure, and as this manufacturing method, water is indispensable for forming the dual cell structure, so 0.6 parts by weight of water is used instead of ethyl chloride. It was used as a foaming agent, and clay, 0.14 parts by weight of bentonite and 0.46 parts by weight of halloysite, were added as water retaining agents. In addition to existing magnesium oxide, 0.2 parts by weight of dibutyltin maleate and 0.05 parts by weight of hydrotalcite were added as stabilizers in order to reduce the reaction between water and the flame retardant.

  The density, bubble diameter, bubble film thickness, thermal conductivity, residual gas amount and flammability of the obtained foam were measured by the following methods. The results are shown in Tables 3 and 4.

(density)
The density of the foam (excluding the skin layer) was calculated by dividing the weight (Kg) of the foam by the volume (m ³ ) of the foam.

(Bubble diameter)
The bubble diameter of the foam was measured by a method according to ASTM D 3567, and was taken as the average value of the size in the thickness direction, the width direction, and the length direction (each corresponding to each direction of the extruded foam). In addition, in the foam of the dual cell structure, the ratio (%) of the number of secondary bubbles to the total number of bubbles is also listed in the table.

(Bubble film thickness)
The thickness of the bubble film was calculated from the obtained density and bubble diameter according to the following equation. In addition, the density of the resin represented by ρs means the density of the resin used for the production of the foam, and in the case of polystyrene, it is 1050 Kg / m ³ . When a resin other than polystyrene is used, the density of the resin is used in the calculation formula as ρs.

(Thermal conductivity)
The thermal conductivity ( mW / m · K ) of the foam was measured by a method based on JIS A1412-2: 1999. In addition, this measurement was performed after one week passed at normal temperature after manufacturing a foam. The thermal conductivity was 28 mW / m · K or less as a criterion for acceptance.

(Residual gas amount)
The amount of residual gas contained in the bubbles of the foam was quantitatively analyzed with a gas chromatograph for the residual gas collected by melting the foam. This analysis was performed after 1 week at room temperature after the foam was produced.

(Combustion quality)
The combustibility of the foam was measured by a method based on JIS A9511: 2006R (measurement method A was adopted). In addition, this measurement was performed after one week passed at normal temperature after manufacturing a foam. First, five test pieces having a thickness of about 10 mm, a length of about 200 mm, and a width of about 25 mm were cut out from the foam, and an ignition limit indicator line and a combustion limit indicator line were attached to the test piece. Next, apply the flame of the candle to the end of the test piece, apply the flame to the ignition limit indicator line for about 5 seconds, quickly retreat the flame, and measure the time (seconds) from that moment until the flame disappears Then, the presence of residual dust and the combustion stop position were confirmed.

  The “flame extinguishing time” was an average value after measuring five test pieces. In addition, regarding the gas surface combustion, which is a phenomenon in which only the foam surface is spread by the combustible gas contained in the foam (in the bubbles), the length of the fire spread beyond the combustion limit indicator line is measured as the “fire spread length”. did. The “fire spread length” was also measured as an average value after measuring five test pieces.

  As a result of the flammability test, there were no residue, flame extinguishing time was within 3 seconds, and there was no fire spread (fire spread length 0 mm).

As is clear from the test results of the foams according to the examples and the comparative examples, the flammable gas can be obtained by adjusting the thickness of the bubble film to 2 μm or more even when almost the same amount of flammable residual gas is present. Can prevent the foam surface from spreading. The foam according to Comparative Example 8 has a bubble film thickness of 4.02 μm that is 2 μm or more and can prevent the spread of fire, but the thermal conductivity is 28 mW / m · K or less, which is an acceptance criterion. Does not meet.

Claims (5)

The cell membrane has a thickness of 2 μm or more, is not a foam having a dual cell structure, and has a thermal conductivity of 26 mW / m · K or less measured according to the measurement method defined in JIS A1412-2: 1999. JIS A9511: A styrene resin extruded foam that passes the flammability measurement method A defined in 2006R,
The residual amount of the combustible gas in the foam is 3 to 4.5 parts by weight with respect to 100 parts by weight of the foam , and the styrene resin extruded foam contains the combustible gas containing alkyl chloride . The styrene resin extruded foam according to claim 1 , comprising at least one selected from the group consisting of graphite, titanium oxide and carbon black as a radiation reducing agent. The styrene resin extruded foam according to claim 1 or 2 , wherein an addition amount of the radiation reducing agent is 0.1 to 10 parts by weight with respect to 100 parts by weight of the foam. The styrene resin extruded foam according to any one of claims 1 to 3 , comprising 4 to 8 parts by weight of a flame retardant with respect to 100 parts by weight of the foam. The styrene resin extruded foam according to any one of claims 1 to 4 , having a density of 30 to 40 kg / m ³ and a cell diameter (cell size) of 0.1 to 0.3 mm.