JP5537918B2 - Styrene resin extruded foam - Google Patents

Description

  The present invention relates to a styrenic resin foam by extrusion foaming, which 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 it has a zero ozone depletion factor, 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-mentioned problems, and by using a suitable amount of a combustible gas and making the surface hardness a certain level or more, the styrene system has good flame retardancy (particularly gas combustion). An object is to provide a resin extruded foam.

[1] The surface hardness (Type-A) measured by the measurement method specified in JIS K6253 is 23 degrees or more, passes the flammability measurement method A specified in JIS A9511: 2006R, and the fire spread length is Styrenic resin extrusion foam which is 10 mm or less.

[2] The styrene resin extruded foam according to [1], wherein the surface is melted by heat treatment.

[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], having a density of 30 to 40 kg / m ³ and a cell diameter (cell size) of 0.1 to 0.4 mm. body.

  According to a preferred embodiment of the present invention, for example, there is provided a styrene resin extruded foam having excellent flame retardancy (especially gas combustion) and further maintaining the conventional foam density and cross section and having excellent physical properties. can do.

Styrene Resin Extruded Foam The styrene resin extruded foam according to the present invention has a surface hardness (Type-A) measured by a measurement method defined in JIS K6253 of 23 degrees or more, and is defined in JIS A9511: 2006R. It is a styrene resin extruded foam having passed the flammability measurement method A and having a fire spread length of 10 mm or less.

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.

  Examples of a method for increasing the surface hardness of the obtained foam (a method for forming a surface hardened layer) include a method in which the surface of the foam is heated and melted. Good. As a device to be used, a desk-top heat press or the like can be used at the laboratory level, and a heating roll or the like can be used at the plant. Also, in general, when foam is extruded and foamed from the die of an extruder, the surface is often called a skin layer, which is often a different foam from the inside of the foam. The surface hardened layer may be formed after forming a form called a board, or when the skin layer satisfies the requirements of the present invention, it may be used as it is as the surface hardened layer without being scraped off.

Physical Properties of Styrenic Resin Extruded Foam The density, bubble diameter (cell size), surface hardness, and flammability 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 0.5 mm, more preferably 0.18 to 0.4 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.

(surface hardness)
The surface hardness is measured according to JIS K6253 by using a durometer and selecting the type of push needle that is most suitable for the resin to be measured.

  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. Although the gas surface combustion mechanism is not limited to this, the fire source ignites the foam, and at the same time, the melting of the foam film resin on the surface layer of the foam is promoted, and then the foam film melts. At the same time, it is considered that gas combustion occurs with oxygen in the air when the bubbles are broken and the combustible gas filled in the bubble structure is released to the atmosphere. Therefore, if the surface layer portion of the foam is weak against heat, it is considered that gas discharge from the surface layer portion of the foam is facilitated 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.

  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.

  As for the surface hardness for clearing the problem of gas combustion based on these, the surface hardness (Type-A) measured by the measuring method specified in JIS K6253 is 23 degrees or more, desirably 30 degrees or more.

  As described above, the optimum value of the surface hardness 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 value of the surface hardness for clearing increases.

(Flammability and fire spread length of foam)
The flammability of the foam is measured by a method in accordance with JIS A9511: 2006R (measurement method A is adopted). As a result of the flammability test, the flame extinguishing time is within 3 seconds and there is no residue. The standard of acceptance was taken. About the fire spread length, a fire spread length of 10 mm or less is preferable, and it is particularly preferable that there is no fire spread (fire spread length 0 mm).

<Examples 1 to 10, Comparative Examples 1 to 4>
Based on a styrene resin having a weight average molecular weight of 210,000 as the main raw material, barium stearate (manufactured by NOF Corporation) as a lubricant for the extruder and magnesium oxide (as a flame retardant stabilizer) with the addition amount shown in Table 1 or 2. Kamijima Chemical Co., Ltd .: Starmag L-10), those having a high flame retardant addition amount are epoxy stabilizers (manufactured by Huntsman: Araldite ECN1280), polyethylene (Dow Chemical Co .: Daurex 2047G) or talc as the air conditioner (Manufactured by Fuji Talc), phthalocyanine blue (manufactured by Toyo Ink: Lionol Blue SM) as a colorant, hexabromocyclododecane (HBCD) (manufactured by Albemarle: SAYTEX HP-900) as a flame retardant, and a flame retardant aid Triphenyl phosphate (TPP) (manufactured by Daihachi Chemical Co., Ltd.), radiation Graphite (manufactured by Ito Graphite Industries Co., Ltd .: artificial graphite AGB-5) and titanium oxide (manufactured by DuPont: R-104) as the reducing agent, when water is used as the blowing agent, bentonite is charged into the extruder hopper, After adding isobutane, ethyl chloride, carbon dioxide, methyl chloride, dimethyl ether and water as foaming agents with the addition amount shown in Table 1 or 2 and kneading, the gel is cooled uniformly with a cooler, and the atmospheric pressure from the die And foamed. 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 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.

  The skin layer was cut and removed from the foam obtained as described above (production of a so-called cut board), and a test piece of 200 mm × 200 mm × 30 mm (thickness) was prepared from the foam from which the skin layer was removed. Next, about Examples 1-10, the surface of the test piece was processed according to the hot press method demonstrated below, and the surface hardening layer was formed.

(Formation of hardened surface layer)
Using a desktop test heat press (manufactured by Shindo Metal Industry Co., Ltd.), set the lower surface of the main body to 200 ° C., press the test piece against the main body of the press through a PET film, and melt the surface. A hardened layer was formed (a surface of 200 mm × 200 mm constituting the test piece is a surface on which a hardened surface layer was formed). The contact time was from about 2 seconds to about 1 minute, and a hardened surface layer with higher density and higher surface hardness was obtained as the contact time was longer. The PET film is used because the hot-melted surface does not adhere to the desktop press, and does not particularly contribute to surface improvement.

  Note that this time, a desktop test heat press was used to collect foams with different surface hardness. However, a similar hardened surface layer can be obtained by a heating roll installed in the finishing process of the foam production line in the plant. Is possible. In a heating roll, surface melting can be reproduced by passing a foam between upper and lower rolls whose surfaces are heated. The surface temperature can be in the range of 160 to 250 ° C, preferably in the range of 200 to 230 ° C. The production line speed is 5 to 70 m / min, desirably 5 to 40 m / min. The pressing thickness is about 0 to 8 mm, preferably about 1 to 2 mm.

  The density, bubble diameter, skin density, moisture permeability coefficient, surface hardness, local compression modulus and flammability of the test pieces (surface-treated and untreated) 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 the foam of the dual cell structure, the size of secondary bubbles and the ratio (%) of the number of secondary bubbles to the total number of bubbles are also listed in the table.

(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 conducted after 10 days had passed since the foam was produced.

(Surface layer density)
The density of 2 mm from the surface of the test piece is defined as the density of the surface hardened layer. The test piece was 3 cm wide × 5 cm long and the thickness was uniformly sliced with a meat slicer at 2 mm, and the total weight (kg) was calculated by dividing by the volume (m ³ ). In addition, about the test piece of the comparative example which is not performing surface treatment, the density of a surface hardening layer is the same as a normal density.

(Moisture permeability coefficient)
The moisture permeability coefficient was measured according to JIS A9511 (JIS K7225: 2005). The test piece was cut into 90 mmφ, and the thickness of the test piece was set in a designated container containing a hygroscopic agent (calcium chloride) with the heat-melted surface facing up. In order to make the moisture permeable area (80 mmφ) constant, the periphery of the end portion and upper surface of the test piece was fixed with a sealing agent (paraffin). An acceleration test was carried out in a constant temperature layer. The test conditions were a temperature of 23 ± 1 ° C. and a relative humidity gradient of 0% to (50 ± 2)%. The measurement was continued for one week, and the moisture permeability coefficient was determined from the increase rate of the hygroscopic agent. The measurement result was an average value of two measurements.
Originally, in the plant equipment, the surface subjected to the heat roll treatment is the upper and lower surfaces, but this measurement is a test piece subjected to the one-side heat melting treatment, and the effect is estimated to be about half the effect. Moreover, since the obtained numerical value differs, it is the numerical value converted per thickness 25mm.

(surface hardness)
The surface hardness was measured according to JIS K6253.
The following measuring instruments were used.
Type-A: TECLOCK Durometer (Rubber Plastic Hardness Meter) GS-719N (manufactured by TECLOCK, serial number: 78339)
Type-C: Cellular Rubber & Yarn Durometer hardness Asker (manufactured by Kobunshi Keiki Co., Ltd., production number: 025129)
As for the size of the test piece, the thickness was at least 15 mm or more, and the measurement point was measured at least 20 mm or more away from the end. A test piece having a standard size measured this time of 30 mm in thickness and a width and length of 200 mm was prepared. The measurement procedure is to place the test piece on a hard, rigid flat surface and hold the measuring instrument so that the push needle is perpendicular to the measurement surface of the test piece. The pressure surface was brought into close contact with the measurement surface of the test piece as quickly as possible without impact, and the scale was read within 1 second to determine the hardness of the test piece. The measurement result was an average value of three measurements.

(Local compression modulus)
The local compression modulus was measured in accordance with JIS A9511 and JIS K7220. A 10 mmφ cylindrical (0.785 cm ² ) jig was placed on the test piece, and a local compression test at 10 mmφ was performed using Tensilon TMI-RTM-500 (manufactured by TOYO BALDWIN CO. LTD). The measurement conditions of the autograph were the test speed: 5 mm / min, and the measurement result was the result of the compression modulus. As for the size of the test piece, the thickness was at least 15 mm or more, and the measurement point was measured at least 20 mm or more away from the end. A test piece having a standard size measured this time of 30 mm in thickness and a width and length of 200 mm was prepared. The measurement result was an average value of three measurements.

(Flammability, fire spread length)
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 10 days 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 are prepared from the above-mentioned test pieces (200 mm × 200 mm × 30 mm (thickness): a surface-cured product has a surface of 200 mm × 200 mm as a treated surface). It cut out and attached the ignition limit indicator line and the combustion limit indicator line to this test piece. A surface constituting a thickness of 10 mm in the test piece is a surface subjected to surface hardening treatment. 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, then quickly retreat the flame, and set the extinction time (seconds) from that moment until the flame disappears. Measurement was made to confirm the presence of dust and the combustion stop position. The flame extinction time was an average value after measuring five test pieces.

  As a result of the flammability test, it was determined that the flame extinguishing time was within 3 seconds and there was no residual dust.

  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 (mm) of the flame spread beyond the combustion limit indicating line is expressed as “fire spread length”. Was measured. The “fire spread length” was also measured as an average value after measuring five test pieces. When the fire was extinguished without exceeding the limit indicator line (without reaching the limit indicator line), the remaining distance from the limit indicator line was obtained as a negative value. In general, this minus amount is regarded as zero, but is expressed in the minus direction in order to clarify the effect of the present invention.

  As is clear from the test results of the foams according to the examples and comparative examples, even if almost the same amount of flammable residual gas is present, the surface of the foam is increased by the flammable gas by increasing the surface hardness. It is possible to suppress the spread of fire. For example, the fire spread length can be reduced to 10 mm or less by adjusting the surface hardness (Type-A) to 23 degrees or more. Of course, the fire spread length is short and preferably negative, and the fire spread length can be reduced to 0 mm or less by adjusting the surface hardness (Type-A) to 30 degrees or more.

Claims (6)

It has a surface hardened layer formed by melting by heat treatment , has a surface hardness (Type-A) measured by a measuring method specified in JIS K6253 of 23 degrees or more, and combustibility specified in JIS A9511: 2006R A styrene resin extruded foam having passed the measurement method A and having a fire spread length of 10 mm or less.   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, wherein a 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.   The styrene resin extruded foam according to any one of claims 1 to 4, comprising 4 to 8 parts by weight of a flame retardant with respect to 100 parts by weight of the foam. A density of 30-40 kg / ^{m 3,} a cell diameter (cell size) is 0.1 to 0.4 mm, a styrene resin extruded foam according to any one of claims 1 to 5.