JP4570504B2 - Method for producing extruded polystyrene resin foam - Google Patents

Description

  The present invention relates to a method for producing a plate-like polystyrene-based resin extruded foam used for, for example, heat insulating materials such as walls, floors, and roofs of buildings, and tatami core materials.

  Conventionally, polystyrene resin extruded foam has been widely used as a heat insulating material because it has excellent heat insulating properties and suitable mechanical strength, and is molded into a plate having a constant width. As a method for producing such a foam plate, a foam regulator is added to a polystyrene resin material, and after heating and melt-kneading, a physical foaming agent is added, and the mixture (foamable melt mixture) is extruded from a high pressure region to a low pressure region and foamed. In addition, a method of obtaining a foam by connecting a shaping device to a die outlet of an extruder as required is known (see Patent Documents 1, 2, and 3).

JP 2003-292664 A JP 2004-59595 A JP 2004-196907 A

  However, in the method for producing a polystyrene resin extruded foam as described above, in order to obtain a foam having a large thickness and a low density (high expansion ratio), the amount of the physical foaming agent must be increased.

  Here, in the production of the polystyrene resin foam as described above, in the vicinity of the lip (outlet) of the die so that foaming starts after the foamable molten mixture is extruded into a low pressure region (usually under atmospheric pressure). The pressure is adjusted so as not to drop below a predetermined pressure. If foaming occurs inside the vicinity of the lip of the die due to separation and vaporization before the foamable molten mixture is extruded from the die lip, not only uniform bubbles are obtained, but the appearance of the foam is significantly deteriorated. Moreover, the operating conditions of the extruder become unstable, and a good foam cannot be obtained. For this reason, although the pressure value of the foamable molten mixture in the vicinity of the lip of the die varies depending on the type and amount of the foaming agent used, separation of the foaming agent before the mixture is extruded from the lip of the die It is necessary to maintain the pressure higher than a certain level so that vaporization does not occur.

  However, if the amount of foaming agent used is increased to obtain a foam having a large thickness and a low density, the viscosity of the foamable molten mixture decreases, and foaming tends to occur near the lip of a normally used flat die. This tendency becomes more prominent as the amount of the foaming agent used increases, and it becomes difficult to maintain the pressure of the foamable molten mixture near the lip of the die. Therefore, there is a problem that it is difficult to obtain a foam having a low density because a foaming agent in a sufficient amount necessary for obtaining a low-density polystyrene resin foam cannot be added. However, if the gap (clearance) or cross-sectional area of the die lip is reduced, the pressure can be maintained even if the amount of foaming agent used is increased, but in that case, the plate-shaped polystyrene is thick and has a large cross-sectional area. It becomes practically impossible to obtain a resin foam.

On the other hand, by lowering the extrusion temperature and increasing the viscosity of the foamable melt mixture, the resin pressure near the lip in the extruder can be kept high to prevent separation of the foaming agent and vaporization. It is.
However, in this case, since the temperature of the foamable composition is low, the temperature falls below the thermal deformation temperature of the raw material resin in a short time after extrusion foaming, and the time from the start to the end of foaming is short, While the expansion force of the foaming agent remains, the temperature of the foamable composition becomes lower than the heat deformation temperature of the raw material resin. For this reason, it reaches the temperature at which foaming is completed before the foaming agent is sufficiently vaporized, and the low density foaming is sufficiently foamed until the desired density is reached without fully utilizing the expansion force of the foaming agent. There is a problem that the body cannot be obtained.

Further, if a raw material resin having a small MFR (melt flow rate measured at 200 ° C./5 kgf load) is used, the viscosity of the foamable composition is increased and the resin pressure near the lip of the die is maintained high without lowering the extrusion temperature. Seems to be able to.
However, in this case, the MFR of the raw resin must be made extremely small. As a result, the fluidity of the raw resin is impaired and the flow of the resin extruded from the lip is disturbed. There is a problem that moldability is deteriorated, and in particular, it becomes difficult to form a foam into a smooth plate shape.

  Therefore, in order to solve the above-mentioned problems, the present inventors have conducted extensive studies, and as a result, when polystyrene foam containing an ultrahigh molecular weight component is used and extrusion foaming is performed while suppressing decomposition of the ultra high molecular weight component. In addition, the inventors have found that it is easy to produce a foamed plate having a high foaming ratio, a large cross-sectional area, and a high thickness, thereby completing the present invention.

That is, the present invention provides (1) As the foaming molten mixture thickness physical blowing agent into a molten polystyrene resin, which are mixed is at least 10 mm, and the cross-sectional area is at least 50 cm ^2, an extruder tip In the method of producing a plate-like polystyrene-based resin extruded foam by passing through a shaping apparatus connected to a flat die of the above and extruding and foaming, the polystyrene-based resin has a weight average molecular weight (Mw) of 1.4 × 10 ^5. Mz obtained by pre-melting and kneading a polystyrene resin having ˜5.0 × 10 ^{5 and} a polystyrene resin having Mw of 1.0 × 10 ^{6 to} 5.0 × 10 ⁶ is 2.0 × 10 ^6. It is a mixture of the ultra-high molecular weight polystyrene masterbatch as described above and a polystyrene-based resin (main PS) having an Mw of 1.4 × 10 ^{5 to} 5.0 × 10 ⁵ . The blending ratio of the ultrahigh molecular weight polystyrene masterbatch is 1 to 100 parts by weight with respect to 100 parts by weight of the polystyrene resin (main PS), and the Z average molecular weight (Mz) of the polystyrene resin constituting the extruded foam obtained. ) And the number average molecular weight (Mn) (Mz / Mn) is 8.0 or more, a method for producing a plate-like polystyrene resin extruded foam,
(2) The method for producing a plate-like polystyrene resin extruded foam according to (1), wherein a heat stabilizer is added to the ultrahigh molecular weight polystyrene masterbatch,
(3) The method for producing a plate-like polystyrene resin extruded foam according to the above (1) or (2), wherein a brominated flame retardant is added to the molten polystyrene resin,
(4) The plate-shaped polystyrene in any one of said (1)-(3) whose number average molecular weights of the polystyrene-type resin which comprises the said extrusion foam are 8.0 * 10 < ⁴ > -1.5 * 10 < ⁵ >. Method for manufacturing a resin-based extruded foam,
(5) The production method of a plate-like polystyrene resin extruded foam according to any one of (1) to (4) above, wherein the apparent density of the polystyrene resin extruded foam is 20 to 35 kg / m ^3. To do.

  According to the production method of the present invention, extrusion foaming is performed so that the ratio Mz / Mn between the Z average molecular weight (Mz) and the number average molecular weight (Mn) of the obtained polystyrene resin foam does not decrease to less than 8.0. Thus, even when the amount of the foaming agent used is large, there is an effect that a polystyrene resin extruded foam plate having a high thickness, a large cross-sectional area, and a high expansion ratio can be easily produced.

  The method for producing a polystyrene resin extruded foam (hereinafter referred to as an extruded foam) of the present invention is similar to the conventional method for producing a polystyrene resin extruded foam, in which a physical foaming agent is mixed with a molten polystyrene resin. This is a method of extrusion-foaming the foamable molten mixture. The foamable molten mixture is extruded through a flat die from an extruder into a low-pressure region and foamed, and a molding die arranged on the downstream side of the die (upper and lower installed so as to gradually expand from the inlet to the outlet). A method of forming a plate by passing a forming tool such as a sheet made of a fluororesin such as polytetrafluoroethylene resin (hereinafter referred to as guider) or a forming roll is preferable. Adopted. The foamable molten mixture is prepared by supplying a polystyrene resin into an extruder and melting the mixture, cooling the foaming agent, and adding and kneading the other additives as necessary (the type of polystyrene resin used, The presence or absence of the addition of the fluidity improver, the type and amount of the fluidity improver, and further the amount of the mixed foaming agent added and the components of the foaming agent, etc. After cooling to 130 ° C. and adjusting the melt viscosity to be suitable for foaming, it can be foamed by extrusion from within the extruder.

Examples of the polystyrene resin supplied to the extruder in the present invention include a styrene homopolymer and a styrene copolymer mainly composed of styrene. Examples of the styrene copolymer include styrene-acrylic acid copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer. Polymer, styrene-ethyl methacrylate copolymer, styrene-maleic anhydride copolymer, styrene-polyphenylene ether copolymer, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer Examples thereof include styrene-methylstyrene copolymer, styrene-dimethylstyrene copolymer, styrene-ethylstyrene copolymer, and styrene-diethylstyrene copolymer. The styrene component content in the styrenic copolymer is 50 mol% or more, preferably 80 mol% or more.
The polystyrene resin may be a mixture of other polymers within the range in which the object, action and effect of the present invention are achieved. Other polymers include polyethylene resins, polypropylene resins, styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, styrene-butadiene-styrene block copolymer hydrogenated products, styrene- Examples include hydrogenated isoprene-styrene block copolymer, styrene-ethylene copolymer, and the like. The amount of such other polymer used is less than 100 parts by weight based on 100 parts by weight of the polystyrene resin, preferably 0-60 parts by weight, more preferably 0-20 parts by weight, and 0-10. Part by weight is more preferred.

Although the thickness of the polystyrene resin extruded foam obtained by the production method of the present invention is at least 10 mm or more, the upper limit is usually 250 mm, preferably 20 to 200 mm. When the thickness is less than 10 mm, the heat insulating performance is insufficient when used as a heat insulating material, and the construction efficiency is greatly reduced when used as a light weight embedding material for a lightweight embankment method.
The cross-sectional area of the polystyrene resin extruded foam obtained by the production method of the present invention (the cross-sectional area of the vertical cross section perpendicular to the extrusion direction (vertical cross section in the width direction)) is at least 50 cm ² or more, preferably 60 cm ² or more. More preferably, it is 100 cm ² or more. Usually, the upper limit of the cross-sectional area is 3000 cm ^2, 2500 cm ² following items are common. Moreover, it becomes easy to obtain a foam having a large cross-sectional area as the extrusion capability of the extruder increases. When the cross-sectional area is less than 50 cm ² , the construction efficiency is greatly reduced when it is used for the heat insulation work or the laying work of the lightweight embedding material.

  In order to achieve the object of the present invention, extrusion foaming is carried out so that the ratio of Z average molecular weight (Mz) / number average molecular weight (Mn) of the polystyrene-based resin constituting the obtained extruded foam does not fall below 8.0. There must be. If the Mz / Mn ratio of the polystyrene-based resin constituting the resulting extruded foam is less than 8.0, the object of the present invention cannot be achieved, and an extruded foam having a high foaming ratio and a large cross-sectional area is produced. Can not do it. When the Mz / Mn ratio of the polystyrene-based resin constituting the obtained extruded foam is 8.0 or more, the polystyrene-based resin constituting the extruded foam has a large Mz and / or a small Mn. (It means that the decrease in Mz is also within the allowable range). By using a large amount of foaming agent, the pressure of the foamable molten resin in the vicinity of the lip in the extruder is reduced by the internal foaming. It becomes possible to maintain high so as not to occur, and since the fluidity of the foamable molten resin is not impaired by the small Mn, an extruded foam having a large cross-sectional area can be produced at a high expansion ratio. In addition, when the Mz / Mn ratio of the polystyrene resin constituting the obtained extruded foam is less than 8.0, the ratio can be maintained at 8.0 or more (in this case, except for the amount of foaming agent used). The other production conditions are the same), and the maximum foaming ratio of the obtained foam can be improved. In general, the higher the extrusion capacity of the extruder, the greater the resin pressure in the die, so the maximum foaming of the resulting foam than the relatively low extrusion capacity of the extruder Since the magnification can be increased, the manufacturing conditions must be matched for comparison. In the method of the present invention, when the production and production conditions other than the foaming temperature are the same, the foaming temperature can be further increased because the ultrahigh molecular weight component is effectively present, and as a result, the foam obtained The maximum expansion ratio can be improved. In the method of the present invention, when the production conditions other than the amount of foaming agent used are the same, the amount of foaming agent used can be further increased because the ultra-high molecular weight component is effectively present, As a result, the maximum expansion ratio of the obtained foam can be improved.

In general, even when a polystyrene resin having a large Z average molecular weight (Mz) and a Mz / Mn ratio of 8.0 or more is used, the molecular chain of the high molecular weight component is broken when melt-kneaded, resulting in a high molecular weight. As a result, the polystyrene-based resin constituting the extruded foam obtained by reducing the components has a Mz / Mn ratio of less than 8.0. In order to set the Mz / Mn ratio to 8.0 or more, it is important to select a raw polystyrene resin used for extrusion foaming and to suppress thermal decomposition of the polystyrene resin.
The selection of the raw material polystyrene resin used in the present invention, among the following (A) to (d), can be most cheaply and efficiently carried out (c) is selected.

  (A) A polystyrene resin having a very large molecular weight (hereinafter referred to as “UHMW-PS”) is used in combination with a polystyrene resin having a general molecular weight (hereinafter referred to as “NMW-PS”) as compared with NMW-PS. In this case, the amount of UHMW-PS used is preferably 0.4 to 50 parts by weight, more preferably 0.5 to 40 parts by weight, and still more preferably 1 to 35 parts by weight with respect to 100 parts by weight of NMW-PS. If the amount of UHMW-PS used is small, it will be difficult to maintain the Mz / Mn ratio of the polystyrene resin constituting the resulting extruded foam at 8.0 or more, and conversely, the amount of UHMW-PS used is large. When it becomes too much, the fluidity at the time of melt-kneading deteriorates, and there is a possibility that cooling cannot be performed sufficiently, and there is a possibility that coarse bubbles are formed in the obtained extruded foam. In order to maintain the Mz / Mn ratio of the obtained extruded foam at 8.0 or more, the larger the Mz of UHP used, the smaller the amount used, and the smaller the Mz of UHMW-PS used, the smaller There is a tendency to require a large amount of use.

(A) A polystyrene resin having a Mz / Mn ratio of 9.0 or more, preferably 10.0 to 16.0, obtained by previously melt-kneading NMW-PS and UHMW-PS. use. In this case, in the polystyrene-based resin obtained by melt-kneading in advance, Mn is usually 7.0 × 10 ^{4 to} 1.4 × 10 ⁵ , and Mz is 6.5 × 10 ^{5 to} 1.9 ×. 10 ⁶ and the Mw / Mn ratio is 3.0 to 6.0. If the Mz / Mn ratio is less than 9.0, the Mz / Mn ratio of the polystyrene resin constituting the extruded foam obtained may be less than 8.0.

(C) A polystyrene resin mixture having a Z average molecular weight of 2.0 × 10 ⁶ or more obtained by previously melt-kneading NMW-PS and UHMW-PS is used as at least one component of the polystyrene resin. This polystyrene-based resin mixture preferably has a Mz / Mn ratio of more than 16.0, more preferably 17.0 to 60.0. That is, the above polystyrene-based resin mixture having a Z average molecular weight of 2.0 × 10 ⁶ or more obtained by previously melt-kneading NMW-PS and UHMW-PS was used as an ultrahigh molecular weight polystyrene master batch, An appropriate amount is used with NMW-PS to produce an extruded foam . In this case, in the polystyrene-based resin mixture of the master batch, usually, Mn is 7.0 × 10 ^{4 to} 1.6 × 10 ⁵ , and Mz is 2.0 × 10 ^{6 to} 4.5 × 10 ⁶ . The Mw / Mn ratio is 4.0-15.0. In this case, the NMW-PS for producing the master batch has a melt flow rate (200 ° C./5 kgf load) of 1 to 50 (g / g) in order to suppress thermal decomposition of UHMW-PS described later. 10 minutes), preferably 5 to 45 (g / 10 minutes), and more preferably 10 to 30 (g / 10 minutes). The ratio of NMW-PS and UHMW-PS in the master batch is preferably NMW-PS 15 to 95% by weight, UHMW-PS 85 to 5% by weight, and NMW-PS 25 to 90% by weight when the total of both is 100% by weight. %, UHMW-PS 75 to 10% by weight is more preferable, NMW-PS 35 to 85% by weight, and UHMW-PS 65 to 15% by weight are more preferable. In addition, the amount of the master batch used in the production of the extruded foam is preferably small in terms of economy. Therefore, at the time of manufacturing the extruded foam, the blending ratio of the master batch and NMW-PS is 1 to 100 parts by weight, more preferably 3 to 80 parts by weight, with respect to 100 parts by weight of NMW-PS. Part by weight is more preferred. As the Mz of the polystyrene-based resin mixture of the masterbatch becomes smaller, that is, as the ratio of Mz / Mn of the polystyrene-based resin of the masterbatch becomes smaller, the amount of the masterbatch used must be increased. Since it becomes difficult to maintain the Mz / Mn ratio of the resin based on 8.0 or more, the polystyrene resin mixture constituting the master batch preferably has Mz of 2.0 × 10 ⁶ or more. It is preferable that the ratio of / Mn exceeds 16.0.

(D) A polystyrene resin having a Mz / Mn ratio of 9.0 or more, preferably 10.0 to 16.0, obtained by suspension polymerization, seed polymerization, emulsion polymerization, or multistage polymerization is used. . In this case, in this polystyrene resin, Mn is usually 7.0 × 10 ^{4 to} 1.4 × 10 ⁵ , Mz is 6.5 × 10 ^{5 to} 2.0 × 10 ⁶ , and Mw / Mn The ratio is 3.0 to 6.0. If the Mz / Mn ratio is less than 9.0, the Mz / Mn ratio of the polystyrene-based resin constituting the extruded foam obtained may be less than 8.0.

Note that the above, the NMW-PS, usually, the weight average molecular weight (Mw) refers to the ^{1.4 × 10 5 ~5.0 × 10 5} . NMW-PS having a Mw of 1.5 × 10 ^{5 to} 4.5 × 10 ⁵ is preferable from the viewpoint of good extrusion foaming workability and good mechanical properties of the resulting extruded foam . That is, when the Mw of NMW-PS is small, the mechanical properties of the obtained extruded foam tend to deteriorate, and when the Mw of NMW-PS is large, the extrusion foaming processability tends to deteriorate. NMW-PS usually has a number average molecular weight (Mn) of 7.0 × 10 ^{4 to} 1.2 × 10 ⁵ and a Z average molecular weight (Mz) of 5.0 × 10 ^{5 to} 1.5 ×. 10 ⁶ , the Mw / Mn ratio is 2.0 to 4.0, and the Mz / Mn ratio is 5.0 to 7.5. Since NMW-PS is a general-purpose polystyrene, it is generally available from the manufacturer of polystyrene.

On the other hand, UHMW-PS usually refers to those having Mw of 1.0 × 10 ^{6 to} 5.0 × 10 ⁶ . UHMW-PS preferably has a Mw of 1.1 × 10 ^{6 to} 4.8 × 10 ⁶ , and more preferably 1.2 × 10 ^{6 to} 4.5 × 10 ⁶ . If the Mw of the UHMW-PS is small, it is difficult to achieve the object of the present invention, and if the Mw of the UHMW-PS is large, melt kneading with the NMW-PS is difficult. UHMW-PS usually has Mn of 1.6 × 10 ^{5 to} 1.0 × 10 ⁶ , Mz of 2.5 × 10 ^{6 to} 7.0 × 10 ⁶ , and Mw / Mn ratio is The Mz / Mn ratio is 6.0 to 16.0. UHMW-PS can be produced, for example, by adopting a continuous polymerization method, adding an organic peroxide in an appropriate amount divided into a plurality of stages, and polymerizing a styrene monomer within a range where no gel is generated. UHMW-PS can also be produced by employing a suspension polymerization, seed polymerization or emulsion polymerization method. In any case, if a polymerization agent (usually an organic peroxide) remains in the obtained UHMW-PS, depending on the amount remaining, the molecular weight is greatly reduced during subsequent thermal processing. Therefore, it is necessary to deactivate the polymerization agent completely or almost completely. UHMW-PS is sold as trade names BLENDEX 865, BLENDEX 28270, etc. from Crompton as ultra-high molecular weight polystyrene, and may be obtained and used.

Next, suppression of thermal decomposition of polystyrene resin will be described. In the present invention, it is important to suppress the thermal decomposition of the high molecular weight component contained in the polystyrene resin within an allowable range. The following is a list of effective means for suppressing the thermal decomposition of the high molecular weight component within an allowable range.
When melt-kneading, the heating temperature is preferably in the range of 160 ° C to 240 ° C, and more preferably in the range of 170 ° C to 225 ° C. It is also effective to add a heat stabilizer to the polystyrene resin. In this case, the amount of heat stabilizer added is preferably 0.05 to 2 parts by weight per 100 parts by weight of the polystyrene resin. As the heat stabilizer, a lactone heat stabilizer is particularly preferable. It is also effective to shut off oxygen when the polystyrene-based resin is charged into the extruder (for example, charged under a nitrogen stream) or exhaust air from the vent port of the extruder. In the most preferable (c), when a master batch is produced from NMW-PS and UHMW-PS, for example, after the NMW-PS is first melted in an extruder, a side feeder or the like is used. An effective method is to add UHMW-PS from the middle of the extruder and knead them together. In this case, if the NMW-PS is melted first, the mixing with the UHMW-PS can be performed efficiently, so the heating time of the UHMW-PS can be shortened, and as a result, the decrease in Mz is minimized. be able to.

  Specific examples of the heat stabilizer include pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl- 4-hydroxyphenyl) propionate, ethylenebis (oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate], 1,3,5-tris (3,5-tert-butyl) -4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 2,6-di-tert-butyl-4- (4,6-bis (octylthio) ) -1,3,5-triazin-2-ylamino) phenol, tris (2,4-di-tert-butylphenyl) phosphite, 5,7- -tert- butyl-3- (3,4-di - methyl phenyl) -3H- benzofuran-2-one and the like. In addition, since these heat stabilizers have the effect of suppressing the decomposition of the polystyrene-based resin itself and also suppressing the thermal decomposition of the flame retardant described later, it is suitable for stably obtaining a good foam. Used. The heat stabilizer may be used alone or in admixture of two or more.

In the present invention, the polystyrene resin constituting the extruded foam must be extruded and foamed so that the Mz / Mn ratio of the polystyrene resin constituting the resulting extruded foam does not drop below 8.0. The Mn of is preferably 8.0 × 10 ^{4 to} 1.5 × 10 ⁵ (Claim 2), more preferably 8.0 × 10 ^{4 to} 1.3 × 10 ⁵ . If Mn is less than 8.0 × 10 ⁴ , the resulting foam may have low mechanical properties. On the other hand, even if Mn of the polystyrene-based resin constituting the obtained extruded foam exceeds 1.5 × 10 ⁵ , there is no big problem, but since the raw material cost tends to be high, it is 1.5 × 10 ⁵ or less. It is preferable.

In the present invention, Mz, Mw, and Mn are all values obtained by gel permeation / chromatography (GPC method). Specifically, a polystyrene resin or a polystyrene resin extruded foam is dissolved in 20 mL of tetrahydrofuran (THF) (or, if there is an insoluble content in THF, after removing the insoluble content by filtration), The measurement is performed by the GPC method under the analysis conditions shown in FIG. 4, and the chart obtained by this measurement is based on the peak start position by the styrene resin (in the present invention, the molecular weight of 1.9 × 10 ⁷ position is adopted for convenience). Draw a baseline horizontally (parallel to the horizontal axis) and calculate each molecular weight with a standard calibration curve generated using standard polystyrene.

Equipment used: GPC high performance liquid chromatograph manufactured by GL Sciences Inc.
Column: Showa Denko Co., Ltd. column, trade name Shodex GPC KF-806,
The KF-805 and KF-803 are used in series in this order.
Column temperature: 40 ° C.
Solvent: THF.
Flow rate: 1.0 mL / min.
Concentration: 0.2% by weight.
Injection volume: 0.2 ml.
Detector: UV-Vis detector manufactured by GL Sciences Inc., trade name UV702 type (measurement wave
Length 254 nm).
The molecular weight range of the calibration curve used to calculate the molecular weight distribution: 1.9 × 10 ^{7 to} 5.4 × 10 ³ .

Apparent density of the extruded polystyrene resin foams produced by the process of the present invention is preferably from 20 to 35 kg / m ^3, more preferably 22~33kg / m ^3. When the apparent density is less than 20 kg / m ^3, it is difficult to produce a plate-like extruded foam having such an apparent density, but a plate-like extruded foam having such an apparent density was obtained. However, it is expected that the closed cell ratio will be greatly reduced and the mechanical properties will be greatly reduced. On the other hand, when the apparent density exceeds 35 kg / m ³ , it is difficult to exhibit sufficient heat insulation unless the thickness is increased more than necessary, which may be insufficient in terms of lightness.

  In order to impart flame retardancy to the extruded foam obtained by the present invention, a flame retardant can be kneaded into the polystyrene resin. A brominated flame retardant is preferably used as the flame retardant kneaded with the polystyrene resin. Examples of brominated flame retardants include tetrabromobisphenol A, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, hexabromocyclododecane, tris (2,3-dibromopropyl) isocyanurate, Examples thereof include tribromophenol, decabromodiphenyl oxide, brominated bisphenol ether derivatives and the like. These brominated flame retardants are melted and kneaded with polystyrene resin in an extruder, so that a part of them is decomposed due to thermal degradation, but the molecular chain of the polystyrene resin is broken by the generated radicals. , Molecular weight may be reduced. When the molecular weight of the polystyrene resin is reduced, foaming occurs near the lip and a good foam cannot be obtained, or even if a foam is obtained, it is possible to obtain a foam with a large thickness and a large cross-sectional area. It becomes very difficult. In the present invention, even when such a brominated flame retardant is added, the ratio of the Z average molecular weight (Mz) and the number average molecular weight (Mn) of the resin constituting the polystyrene resin extruded foam obtained is 8 The target extruded foam can be obtained by extruding and foaming so that it does not become less than 0.0. In order to prevent it as much as possible, it is preferable to use the heat stabilizer described above.

  In the production method of the present invention, various additives such as a bubble regulator, a colorant, a fluidity improver, a filler and the like are added to the resin melt mixture as necessary, as long as the objects and effects of the present invention are not hindered. May be added as appropriate.

  Examples of the physical blowing agent used in the present invention include aliphatic hydrocarbons such as propane, isopentane, cyclopentane, isobutane and normal butane, fluorine such as methyl chloride, ethyl chloride, 1,1,1,2-tetrafluoroethane and the like. Hydrocarbons, aliphatic alcohols such as methanol and ethanol, aliphatic ethers such as dimethyl ether, ether-based fluorine-containing compounds such as 1,1,1,2-tetrafluoroethyl-trifluoromethyl ether, water, carbon dioxide, etc. A well-known physical foaming agent is mentioned. In addition, a small amount of a known chemical foaming agent such as azodicarbonamide can be used in combination with a bubble adjusting function for adjusting the bubble diameter of the extruded foam to be small.

  The addition amount of the physical foaming agent is difficult to specify because it varies depending on the type of foaming agent, the apparent density of the target extruded foam, the type of polystyrene resin, etc. Usually, 0.8 to 3.0 moles per 1 kg of polystyrene resin (in the case where a plurality of physical foaming agents are used in combination, the total number of moles of each physical foaming agent; the same shall apply hereinafter), preferably 0.9. It is added in a range of ˜2.7 mol, more preferably 1.0 to 2.2 mol. Moreover, it is better not to use a chemical foaming agent in combination, but when a small amount of chemical foaming agent is used in combination, the chemical foaming agent is usually added in the range of 0.05 to 5 parts by weight with respect to 100 parts by weight of the polystyrene resin. However, it is preferably added in the range of 0.1 to 3 parts by weight, and more preferably in the range of 0.1 to 2 parts by weight.

  Further, the plate-like foam obtained by the method of the present invention (hereinafter, the plate-like foam may be referred to as a foamed plate or an extruded foamed plate) has an average cell diameter in the thickness direction of usually 0.1 to 0.1. The thickness is 2.0 mm, preferably 0.12 to 1.5 mm, and more preferably 0.15 to 1.3 mm. When the average cell diameter is in the above range, a foam plate having high heat insulation can be obtained. If the bubble diameter is less than 0.1 mm, it is difficult to obtain a foam plate having a large thickness and a small apparent density. On the other hand, when it exceeds 2.0 mm, it will become a foam board with low heat insulation performance. In order to obtain a foam plate having a high thermal insulation property such that the thermal conductivity of the three types of extruded polystyrene foam heat insulating plates described in JIS A9511 (1995) is 0.028 W / mK or less, the average bubble diameter is In addition to 0.1 to 0.5 mm, the foamed plate contains some foaming agent with low thermal conductivity such as isobutane and 1,1,1,2-tetrafluoroethane and low gas permeability to polystyrene resin. It is important to ensure that However, if the content of isobutane is too large, the flame retardancy of the foamed plate will decrease, so care must be taken not to overload. Further, if the content of 1,1,1,2-tetrafluoroethane is too large, that is, if the amount of addition is too large, molten polystyrene resin and 1,1,1,2-tetrafluoroethane are formed in the extruder. Since it becomes easy to separate and a good foamed plate may not be obtained, care must be taken so that it is not too much. In order to eliminate such problems, in general, a blowing agent having a low thermal conductivity such as isobutane or 1,1,1,2-tetrafluoroethane and a low gas permeability to a polystyrene resin is chlorinated. It is used in combination with a foaming agent having a high gas permeability to an aliphatic ether such as methyl, ethyl chloride or dimethyl ether, or a polystyrene resin such as water or carbon dioxide.

The measurement method of the average bubble diameter in this specification is as follows. The average cell diameter in the thickness direction (D _T : mm) and the average cell size in the width direction of the foam plate (D _W : mm) of the foamed plate obtained as an extruded foam are: A vertical cross section perpendicular to the direction) is magnified and projected onto a screen or monitor using a microscope, etc., a straight line is drawn in the direction to be measured on the projected image, the number of bubbles intersecting the straight line is counted, Divide the length (however, this length is not the length of the straight line on the enlarged projected image but the length of the true straight line considering the magnification of the projected image) by the number of counted bubbles. Each is required.
The average cell diameter (D _L : mm) in the foam plate extrusion direction is the vertical cross section in the extrusion direction of the foam plate (vertical cross section that bisects the foam plate in the width direction and perpendicular to the width direction of the foam plate). Is magnified and projected onto a screen or a monitor using a microscope, and is obtained in the same manner as in the case of D _T and D _W described above.
However, for the measurement of the average bubble diameter (D _T : mm) in the thickness direction, a straight line extending over the entire thickness in the thickness direction is drawn at a total of three locations in the center and both ends of the vertical cross section in the width direction. The average diameter of the bubbles existing on each straight line (the length of the straight line / the number of bubbles crossing the straight line) is obtained from the number of bubbles intersecting the straight line, and the arithmetic average value of the average diameters of the three obtained positions is obtained. The average cell diameter in the thickness direction (D _T : mm) is used.
The average bubble diameter in the width direction (D _W : mm) is a width of 3000 μm in a straight line at a position that bisects the total of three foam plates in the thickness direction in the center and both ends of the vertical cross section in the width direction. The average diameter of the bubbles existing on each straight line (3000 μm / (number of bubbles intersecting the straight line-1)) from the straight line having a length of 3000 μm and (number of bubbles intersecting the straight line-1) The arithmetic average value of the obtained average diameters at the three locations is taken as the average cell diameter in the width direction (D _W : mm).

The average bubble diameter in the extrusion direction (D _L : mm) is a straight line having a length of 3000 μm at the position where the total three foamed plates at the center and both ends of the extrusion direction vertical section are equally divided in the thickness direction. Pulling in the direction, the average diameter of the bubbles (3000 μm / (number of bubbles intersecting the straight line) -1) from the straight line having a length of 3000 μm and (number of bubbles intersecting the straight line-1) is calculated. The arithmetic average value of the obtained average diameters at the three locations is taken as the average cell diameter in the longitudinal direction (D _L : mm). The average bubble diameter (D _H : mm) in the horizontal direction of the foamed plate is an arithmetic average value of D _W and D _L.

The foamed plate obtained by the method of the present invention preferably has a cell deformation rate of 0.7 to 2.0. The cell strain rate, the D _T obtained by the measuring method means a value calculated by dividing the _{D H (D T / D H} ), small enough bubbles flat than bubbles deformation rate 1 The larger the value is, the longer the image is. If the bubble deformation rate is less than 0.7, the compression strength may be reduced because the bubbles are flat, and the flat bubbles are more likely to return to a circle, so the dimensional stability of the extruded foam plate is also reduced. There is a fear. If the bubble deformation rate exceeds 2.0, the number of bubbles in the thickness direction decreases, and there is a possibility that the desired high heat insulation property cannot be obtained. From such a viewpoint, the bubble deformation rate is preferably 0.8 to 1.5, and more preferably 0.8 to 1.2. When the bubble deformation rate is within the above range, a foamed plate having high heat insulation can be obtained.

  Examples of the method for obtaining the foam plate obtained by the method of the present invention in which the average cell diameter is adjusted to be small as described above include a method of adding a cell regulator such as talc. Even if the added amount is increased to adjust the bubble diameter to be small, the open cell ratio of the foamed plate increases, and as a result, it cannot be easily obtained that exhibits the desired high heat insulation. Therefore, for example, in consideration of the relationship between the MFR of the polystyrene resin and the melt viscosity, a polystyrene resin that does not reduce the MFR even when the melt viscosity is high (the above (A) to (A) to (D)) to increase the amount of addition of the bubble regulator, or by using an inorganic physical foaming agent such as carbon dioxide as a physical foaming agent while avoiding excessive addition of the bubble regulator. A foamed plate having a small average cell diameter can be obtained.

  Since the extruded foam obtained by the method of the present invention is mainly used as a heat insulating plate, it is particularly preferable that the extruded foam satisfies the flammability standard for the extruded polystyrene foam heat insulating plate described in JIS A9511 (1995). . That is, when the flammability measurement of 4.13.1 “Measurement method A” described in JIS A9511 (1995) was performed, the flame disappeared within 3 seconds, there was no residue, and the combustion limit indicator line was displayed. It is preferable that it does not burn over. Such an extruded foam board has the safety required as an extruded polystyrene foam heat insulating board for building materials because the possibility of fire burning is small even when ignited.

As described above, the extruded foam obtained by the method of the present invention preferably has a closed cell ratio of 90% or more, more preferably 93% or more from the viewpoint of improving heat insulation and further improving mechanical strength. preferable. The higher the closed cell ratio, the higher the heat insulation performance and the longer it can be maintained.
In the present specification, the closed cell ratio of the extruded foam is measured using an air comparison type hydrometer 930 type manufactured by Toshiba Beckman Co., Ltd. according to the procedure C of ASTM-D2856-70 (25 mm × 25 mm × 20 mm from the extruded foam). A cut sample without a molded skin cut to a size of 5 mm is accommodated in a sample cup and measured, but when the thickness is thin and a cut sample of 20 mm cannot be cut in the thickness direction, for example, 25 mm × 25 mm × It is sufficient that two cut samples having a size of 10 mm are stored in a sample cup and measured at the same time.) Using the true volume Vx of the extruded foam (cut sample) thus obtained, the closed cell ratio S is calculated according to the following equation (1). (%) Was calculated and obtained as an average value of N = 3.

(Equation 1)
S (%) = (Vx−W / P) × 100 / (VA−W / P) (1)
Vx: the true volume (cm ³ ) of the cut sample measured by the above method, which is the sum of the volume of the resin constituting the cut sample of the extruded foam and the total volume of bubbles in the closed cell portion in the cut sample Equivalent to.
VA: apparent volume (cm ³ ) of the cut sample calculated from the outer dimensions of the cut sample used for the measurement.
W: Total weight (g) of cut sample used for measurement.
P: Density (g / cm ³ ) of the resin constituting the extruded foam.

  Next, the present invention will be described in more detail with specific examples.

-Manufacture of master batch to which ultra high molecular weight polystyrene resin is added [Production Example 1 (Examples 1 to 5)]
Mn: 7.3 × 10 ⁴ , Mw: 2.0 × 10 ⁵ , Mz: 3.8 × 10 ⁵ polystyrene (PS Japan, polystyrene, grade name 679) 74 parts by weight and thermal stabilizer (Ciba Specialty)・Thermal stabilizer for styrene resin of Chemicals Co., Ltd., grade name IRGASTAB STYL66) is supplied to a twin screw extruder at a ratio of 1 part by weight, melt kneaded so as not to exceed 220 ° C., and 2 Using a side feeder from the middle of the screw extruder, polystyrene (Mn: 7.9 × 10 ⁵ , Mw: 3.1 × 10 ⁶ , Mz: 5.7 × 10 ⁶ , ultra high molecular weight polystyrene manufactured by Crompton) Grade name: BLENDEX 865) is supplied at a rate of 25 parts by weight, melt kneaded so as not to exceed 220 ° C., extruded into a strand, and cooled. Cut ^{from, Mn: 8.3 × 10 4,} Mw: 7.3 × 10 5, Mz: to prepare a 3.8 × 10 ⁶ pelleted masterbatch. Hereinafter, this is referred to as a master batch A. Incidentally, the Mz / Mn ratio of the master batch A is calculated to be 45.8.

[Production Example 2 (Comparative Example 2)]
Mn: 7.3 × 10 ⁴ , Mw: 2.0 × 10 ⁵ , Mz: 3.8 × 10 ⁵ polystyrene (PS Japan, polystyrene, grade name 679) 75 parts by weight with respect to Mn: 7. 9 × 10 ⁵ , Mw: 3.1 × 10 ⁶ , Mz: 5.7 × 10 ⁶ polystyrene (Crompon ultra-high molecular weight polystyrene, grade name: BLENDEX 865) 25 parts by weight supplied to the twin screw extruder Then, it was melt-kneaded at 250 ° C., extruded into a strand shape, cooled and cut, and Mn: 1.1 × 10 ⁵ , Mw: 4.5 × 10 ⁵ , Mz: 1.4 × 10 ⁶ A pellet-shaped master batch was prepared. Hereinafter, this is referred to as a master batch B.
The Mz / Mn ratio of the master batch B is calculated to be 12.7.

  In Masterbatch B, no heat stabilizer was used, both polystyrene resins were supplied to the twin screw extruder at the same time, and the used polystyrene resin was Masterbatch A because the heating temperature was 250 ° C. However, it is considered that the decomposition of the high molecular weight component progressed, and as a result, Mz was greatly reduced.

Production of ultra high molecular weight polystyrene resin [Production Example 3 (Comparative Example 7) ]
350 kg of ion exchange water, 1.4 kg of tricalcium phosphate, and 17.5 g of sodium dodecylbenzenesulfonate are added to a reactor equipped with a stirrer having an internal volume of 1.2 m ³ . Next, a styrene solution in which the following auxiliary agent was dissolved in advance was added, and the inside of the system was purged with nitrogen. Then, heating was started and suspension polymerization was performed to produce true spherical polystyrene beads. Specific polymerization (heating) conditions at that time were as follows. The reactor contents were further heated for 1 hour to 90 ° C. from 25 ° C.. Subsequently, the temperature was raised from 90 ° C. to 100 ° C. over 15 hours. Subsequently, the temperature was raised from 100 ° C. to 120 ° C. over 1.5 hours, held at 120 ° C. for 5 hours, then cooled to room temperature, and the resulting spherical polystyrene beads were taken out from the reactor.
The styrene solution was prepared by adding 350 kg of styrene monomer, 175 g of t-butylperoxy-2-ethylhexanoate, 245 g of t-butylperoxy-2-ethylhexyl monocarbonate, divinylbenzene (purity of about 55% product).
Subsequently, the true spherical polystyrene beads were washed and dried. These spherical spherical beads have Mn: 2.6 × 10 ⁵ , Mw: 1.3 × 10 ⁶ , Mz: 3.4 × 10 ⁶ , and the Mz / Mn ratio is calculated to be 13.1. Hereinafter, the ultrahigh molecular weight polystyrene beads obtained in Production Example 3 are referred to as polystyrene C.

Extruded foam production [Extruded foam production equipment and production conditions (Examples 1 to 6 , Comparative Examples 1 to 5, 7)]
The following apparatus was used as an apparatus for producing an extruded foam plate.
The extruder has a cylinder diameter of 65 mm (hereinafter referred to as “first extruder”), a cylinder diameter of 90 mm (hereinafter referred to as “second extruder”), and a cylinder diameter of 150 mm extruder (hereinafter referred to as “second extruder”). What was referred to as “third extruder”) was connected in series, and the mixed foaming agent was press-kneaded into the molten resin near the end of the first extruder. Further, the flat die connected to the third extruder uses a die lip having a resin outlet having a width of 65 mm and an interval of 2 mm (rectangular cross section) (however, in Example 4 and Comparative Example 3) (Changed to the one described later) The discharge amount per hour was 50 kg.
[Extruded Foam Manufacturing Equipment and Manufacturing Conditions (Example 7 , Comparative Example 6)]
The following apparatus was used as an apparatus for producing an extruded foam plate.
The extruder used what connected the 1st extruder with a cylinder diameter of 150 mm and the 2nd extruder with a cylinder diameter of 200 mm in series, and provided the blowing agent injection port near the terminal end of the 1st extruder. Further, flat die connected to a second extruder, using what tip of the die lip is provided with a resin outlet of width 440 mm, distance 3 mm (rectangular cross section), and 1300kg the discharge rate per hour did.

As manufacturing conditions, the following manufacturing conditions were adopted.
Using the above manufacturing equipment, supply raw materials such as polystyrene resin to the first extruder, heat to 220 ° C, melt knead, press-fit the mixed foaming agent near the tip of the first extruder, and expand and melt a resin mixture, followed by a second extruder at (nice contrast, examples 1 to 6 and Comparative examples 1 to at the 5 and 7 a third extruder) resin temperature foaming suitability temperature (in the table was expressed as foaming temperature This foaming temperature is the temperature of the foamable molten resin mixture measured at the position of the junction between the extruder and the die.), And then the foamable molten resin mixture adjusted to the foaming suitable temperature is removed from the die lip to the atmosphere. Extruded into. The foamable molten resin mixture extruded from the die lip was compressed while being foamed by passing through the guider while being foamed, and then formed into a plate shape while being filled in a molding apparatus to produce an extruded foam.

[Details of Production of Extruded Foams of Examples 1 to 3]
The raw materials were 88 parts by weight of polystyrene (polystyrene manufactured by Idemitsu Petrochemical Co., Ltd., grade name: HH32), 12 parts by weight of the above masterbatch A, talc masterbatch (35% by weight of polystyrene and talc (Matsumura Sangyo) 0.5% by weight of master filler made of High Filler # 12) 60% by weight and 5% by weight of dispersant), master batch of flame retardant (50% by weight of polystyrene, and 50% by weight of hexabromocyclododecane) 4 parts by weight in a ratio shown in Table 1, and an amount of foaming agent obtained by mixing isobutane and methyl chloride in a molar ratio of 15:85 as a foaming agent is shown in Table 1 (per 1 kg of polystyrene). The blowing agent injection amount (expressed as mol / kg)) was used. The main raw material HH32 (shown as “polystyrene (HH32)” in the table) was Mn: 1.2 × 10 ⁵ , Mw: 3.5 × 10 ⁵ , and Mz: 7.9 × 10 ⁵ . .
Apparent density, Mn, Mw, Mz / Mn (all of polystyrene resin Mn, Mw, Mz / Mn measured using the obtained extruded foam as a sample), thickness, width direction vertical section Table 1 shows the evaluation of area, thickness direction average cell diameter, cell deformation rate, closed cell rate, and moldability. In Tables 1 to 4, “resin pressure near the lip” means the pressure of the foamable molten resin mixture measured by a pressure sensor attached to the inner wall of the die 150 mm inside from the lip tip toward the die.

成形性の○は発泡体外観が良好、×は発泡体表面に亀裂が生じて外観が悪いことを示す。 (Table 1)

Formability (circle) shows that the foam appearance is good, and x shows that the foam surface is cracked and the appearance is bad.

[Details of Production of Extruded Foams of Comparative Examples 1 and 2]
In Comparative Example 1, an extruded foam was produced in the same manner as in Example 1 except that Master Batch A was not used. The results are shown in Table 2.
In Comparative Example 2, an extruded foam was produced in the same manner as in Example 1 except that Master Batch B was used instead of Master Batch A. The results are also shown in Table 2.

(Table 2)

[Details of Production of Extruded Foam of Example 4]
In Example 4, the die lip has a width of 115 mm, a gap of 1 mm, a foam regulator talc master batch compounding ratio of 0.17 parts by weight, a foaming agent composition of HFC134a (1,1,1,2-tetrafluoroethane), isobutane, Extruded foams were produced using the same extruded foam plate production apparatus and production conditions as in Example 1 except that the mixture was changed to a methyl chloride mixed system. The results are shown in Table 3.

[Details of Production of Extruded Foam of Comparative Example 3]
In Comparative Example 3, an extruded foam was produced in the same manner as in Example 4 except that Master Batch A was not added. The results are also shown in Table 3.

(Table 3)

[Details of Production of Extruded Foams of Example 5 and Comparative Example 4]
In Example 5, the foaming agent was changed to a mixed foaming agent of isobutane, ethanol and carbon dioxide as shown in Table 4, and the amount of talc masterbatch used was changed from 0.5 parts by weight to 0.2 parts by weight. In the same manner as in Example 1, an extruded foam was produced. The results are shown in Table 4.
In Comparative Example 4, an extruded foam was produced in the same manner as in Example 5 except that master batch A was not used. The results are also shown in Table 4.

(Table 4)

[Details of production of extruded foams of Examples 6 and 7 and Comparative Examples 5, 6 , and 7]
In Example 6, the foaming agent was changed to a mixed foaming agent of isobutane and dimethyl ether as shown in Table 5, the amount of talc masterbatch used was changed from 0.5 parts by weight to 0.17 parts by weight, and the foaming temperature was 0. Extruded foam was produced in the same manner as in Example 1 except that the temperature was raised by 5 ° C. The results are shown in Table 5.
In Example 7, an extruded foam was produced in the same manner as in Example 6 except that the above-described large-sized extrusion apparatus in which two extruders were connected in series was used and the foaming temperature was lowered by 0.5 ° C. The results are shown in Table 5.
Comparative Example 5 produced an extruded foam in the same manner as in Example 6 except that master batch A was not used. The results are also shown in Table 5.
Comparative Example 6 produced an extruded foam in the same manner as in Example 7 except that master batch A was not used. The results are also shown in Table 5.
In Comparative Example 7, an extruded foam was produced in the same manner as in Example 6 except that the combination of polystyrene raw materials was changed and the blending amount of polystyrene C was reduced. The results are also shown in Table 5.

The results of Examples 1 to 7 show that when a polystyrene resin extruded foam is produced based on the method of the present invention, a polystyrene resin extruded foam having a high thickness, a large cross-sectional area and a high expansion ratio can be easily produced. ing.

  Examples 1 to 3 show examples in which ultrahigh molecular weight polystyrene was added to increase the amount of foaming agent used. In Example 1, since the ultra-high molecular weight component is effectively present (determined from the Mz / Mn ratio of the foamed plate obtained as an extruded foam), the foaming property is high despite the large amount of foaming agent used. The viscosity of the molten mixture is increased compared to Comparative Example 1 and Comparative Example 2. As a result, the resin pressure near the lip is maintained at a pressure at which internal foaming does not occur, and extrusion foaming with excellent extrusion moldability (no surface cracks) The body was obtained.

  In Examples 2 and 3, although the amount of the foaming agent used was larger than that in Example 1, the ultrahigh molecular weight component was effectively present (determined from the Mz / Mn ratio of the foam plate). As a result, the resin pressure in the vicinity of the lip was maintained at a pressure at which internal foaming did not occur, and an extruded foam excellent in extrudability (no surface cracks) was obtained.

  On the other hand, Comparative Example 1 is contrasted with Example 1 and shows an example in which no ultrahigh molecular weight polystyrene is added. In Comparative Example 1, the ultrahigh molecular weight component was not added, that is, because the ultrahigh molecular weight component was not effectively present (judged from the Mz / Mn ratio of the foamed plate), the foaming agent was the same amount as in Example 1. When added, the resin pressure in the vicinity of the lip does not increase, so internal foaming occurs in the vicinity of the lip, cracks occur on the surface of the obtained foam, and the appearance is poor.

  Comparative Example 2 is in contrast to Example 1 because, despite the use of ultra-high molecular weight polystyrene, the master batch used contained few ultra-high molecular weight components (Mz and Mz of the master batch). As a result, the resin pressure near the lip in the extruder does not increase, and as a result, the ultra high molecular weight component does not exist effectively (determined from the Mz / Mn ratio of the foamed plate). Internal foaming occurred, cracks occurred on the surface of the obtained foam, and the appearance was poor. For Comparative Example 2, the foamed plate was the same as in Example 1 except that the composition of 88 parts by weight of HH32 and 12 parts by weight of masterbatch B was changed to 100 parts by weight of masterbatch B without using HH32. Is produced, a foam comparable to that of Example 1 is obtained.

  Example 4 shows an example in which ultrahigh molecular weight polystyrene was added and the foaming agent composition was changed to a mixed system of HFC134a, isobutane, and methyl chloride. Example 4 is a comparative example in which the viscosity of the foamable melt mixture is high despite the large amount of foaming agent used due to the effective presence of the ultra-high molecular weight component (determined from the Mz / Mn ratio of the foamed plate). As a result, the resin pressure in the vicinity of the lip was maintained at a pressure at which internal foaming did not occur, and an extruded foam excellent in extrusion moldability (no surface cracks) was obtained.

  Comparative Example 3 is contrasted with Example 4 and is an example in which no ultrahigh molecular weight polystyrene is added. However, since the ultra high molecular weight component contained in the raw material resin is small (Mz / Since the resin pressure in the vicinity of the die lip does not increase, internal foaming occurs in the vicinity of the lip, cracks are generated on the surface of the obtained foam, and the appearance is poor.

  Example 5 shows an example in which ultrahigh molecular weight polystyrene was added and the foaming agent composition was changed to a mixed system of isobutane, ethanol and carbon dioxide. In Example 5, the ultrahigh molecular weight component was present effectively (determined from the Mz / Mn ratio of the foamed plate), and the viscosity of the foamable melt mixture was comparative, despite the large amount of foaming agent used. As a result, the resin pressure in the vicinity of the lip was maintained at a pressure at which internal foaming did not occur, and an extruded foam excellent in extrudability (no surface cracks) was obtained.

  Comparative Example 4 is contrasted with Example 5 and is an example in which no ultrahigh molecular weight polystyrene is added. However, since the ultra high molecular weight component contained in the raw material resin is small (Mz / Since the resin pressure in the vicinity of the die lip did not increase, internal foaming occurred in the vicinity of the lip, cracks occurred on the surface of the obtained extruded foam, and the appearance was poor.

  Example 6 shows an example in which ultrahigh molecular weight polystyrene was added and the foaming agent composition was changed to a mixed system of isobutane and dimethyl ether. Example 6 is a comparative example in which the viscosity of the foamable melt mixture is high despite the large amount of foaming agent used due to the effective presence of the ultra-high molecular weight component (determined from the Mz / Mn ratio of the foamed plate). As a result, the resin pressure in the vicinity of the lip was maintained at a pressure at which internal foaming did not occur, and an extruded foam excellent in extrusion moldability (no surface cracks) was obtained.

  Comparative Example 5 is contrasted with Example 6 and is an example in which no ultrahigh molecular weight polystyrene is added. However, since the ultra high molecular weight component contained in the raw material resin is small (Mz / Since the resin pressure in the vicinity of the die lip did not increase, internal foaming occurred in the vicinity of the lip, cracks occurred on the surface of the obtained extruded foam, and the appearance was poor.

  Example 7 shows an example of producing a foam having a large cross-sectional area and a high thickness with the same composition as Example 6 using a large extruder having a large discharge amount. Example 7 is a comparative example in which the viscosity of the foamable melt mixture is high despite the large amount of foaming agent used due to the effective presence of the ultra-high molecular weight component (determined from the Mz / Mn ratio of the foamed plate). As a result, the resin pressure in the vicinity of the lip was maintained at a pressure at which internal foaming did not occur, and an extruded foam excellent in extrusion moldability (no surface cracks) was obtained.

  Comparative Example 6 is contrasted with Example 7 and is an example in which ultrahigh molecular weight polystyrene is not added, but since the ultrahigh molecular weight component contained in the raw material resin is small (Mz / Since the resin pressure in the vicinity of the die lip did not increase, internal foaming occurred in the vicinity of the lip, cracks occurred on the surface of the obtained extruded foam, and the appearance was poor.

In Comparative Example 7 , ultrahigh molecular weight polystyrene (polystyrene C) was added, but since the ultrahigh molecular weight component contained in the raw material resin was small (determined from the Mz / Mn ratio of the foamed plate), the resin pressure near the die lip increased. Therefore, internal foaming occurred near the lip, cracks were generated on the surface of the obtained extruded foam, and the appearance was poor.

The resin pressure near the lip where internal foaming occurs near the lip differs depending on the type and composition of the foaming agent, the amount added, the lip spacing, the foaming temperature, and the like. In the cases of Examples 1 to 3, Comparative Example 1 and Comparative Example 2, internal foaming tends to occur when the resin pressure near the lip falls below 22 kgf / cm ^{2. In} the cases of Example 4 and Comparative Example 3, resin pressure in the vicinity of the lip tends internal foaming occurs when falls below the 55 kgf / cm ^2, in the case in example 5 and Comparative example 4, the internal foam the resin pressure in the vicinity of the lip is below a 34kgf / cm ² In the cases of Examples 6 to 7 and Comparative Examples 5 to 7, internal foaming was likely to occur when the resin pressure near the lip fell below 25 kgf / cm ² . Therefore, in the cases of Example 4 and Example 5, there is a margin to the resin pressure at which internal foaming occurs, and therefore it is possible to further increase foaming by further increasing the amount of foaming agent to the extent that internal foaming does not occur. Conceivable. In addition, if the foamable molten resin mixture is extruded with a larger discharge rate by changing to an extruder having a larger extrusion capacity, it becomes easier to maintain a high resin pressure near the lip. It is considered that the expansion ratio of the body can be further improved.

Claims (5)

Vehicles a molten polystyrene resin in a physical blowing agent is formed by mixing the foamable molten mixture is thick is at least 10 mm, and the cross-sectional area is to be at least 50 cm ^2, which is connected to the flat die of the extruder tip In a method of producing a plate-like polystyrene resin extruded foam by passing through a molding apparatus and extrusion foaming, the polystyrene resin has a weight average molecular weight (Mw) of 1.4 × 10 ^{5 to} 5.0 × 10 ⁵ . Ultra high molecular weight polystyrene master having an Mz of 2.0 × 10 ⁶ or more obtained by previously melt-kneading a polystyrene resin and a polystyrene resin having an Mw of 1.0 × 10 ^{6 to} 5.0 × 10 ^6. It is a mixture of a batch and a polystyrene resin (main PS) having a Mw of 1.4 × 10 ^{5 to} 5.0 × 10 ⁵ , and an ultrahigh molecular weight polystyrene in the mixture The blend ratio of the master batch is 1 to 100 parts by weight with respect to 100 parts by weight of the polystyrene resin (main PS), and the Z average molecular weight (Mz) and number of the polystyrene resin constituting the extruded foam obtained. A method for producing a plate-like polystyrene-based resin extruded foam, wherein the ratio (Mz / Mn) to the average molecular weight (Mn) is 8.0 or more. The manufacturing method of the plate-shaped polystyrene-type resin extrusion foam of Claim 1 to which the heat stabilizer is added to the said ultra high molecular weight polystyrene masterbatch. The manufacturing method of the plate-shaped polystyrene-type resin extrusion foam of Claim 1 or 2 with which the brominated flame retardant is added to the said melted polystyrene-type resin. The polystyrene-based resin constituting the extruded foam has a number average molecular weight of 8.0 × 10 ^{4 to} 1.5 × 10 ^5. The plate-like polystyrene resin extruded foam according to claim 1 . Production method. The apparent density of the polystyrene resin extruded foam is 20 to 35 kg / m ^{3. The} method for producing a plate-like polystyrene resin extruded foam according to claim 1 .