JP2008296514A - Polystyrene resin foam sheet manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a polystyrene resin foam sheet which has almost no uneven stripe, improved thermal adhesiveness, and low density. <P>SOLUTION: The polystyrene resin foam sheet manufacturing method comprises supplying a polystyrene resin to an extruder and extrusion foaming it with fusion kneading under the existence of foaming agent to manufacture a cylindrical foamed body, cooling the outer surface of the cylindrical foamed body, and then crushing the cylindrical foamed body in its radial direction and thermally fusing the inner faces of the cylindrical foamed body to be bonded to each other to form the face-to-face polystyrene resin foam sheet. The polystyrene resin has a melt flow rate of 0.5-3.0g/ten minutes and a Z average molecular weight (Mz) of 6.0×10<SP>5</SP>to 10.0×10<SP>5</SP>, wherein the ratio (Mz/Mw) of the Z average molecular weight (Mz) to a weight average molecular weight (Mw) is 2.0 to 4.0. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a polystyrene resin foam sheet.

  Conventionally, a polystyrene resin foam sheet has been used as a base material for large panels, and a paper with a design applied by printing or the like is pasted on the surface of the polystyrene resin foam sheet, or the surface of the polystyrene resin foam sheet After being silk-printed, it is displayed on the storefront or at the sales floor or pasted at a predetermined location and used for commercial advertisement.

  As a method for producing such a polystyrene resin foam sheet, Patent Document 1 discloses that a polystyrene resin having a melt tension of 39.2 to 107.8 mN at 200 degrees is extruded and foamed into a cylindrical shape, and immediately after extrusion. A method for producing a polystyrene-based resin foam is disclosed that includes a step of cooling the outer surface of a cylinder and a step of crushing the cooled cylinder and fusing it in two layers.

  However, since the polystyrene resin used in the above production method has a relatively low molecular weight, in order to produce a polystyrene resin foam sheet having a low density, it is necessary to increase the amount of foaming agent. When the amount of the agent is increased, the melt viscosity of the polystyrene resin decreases due to the plasticizing effect of the foaming agent, making it difficult to maintain the pressure for good foaming in the mold, resulting in bubble breakage. Alternatively, a wavy striped pattern as shown in FIG. 1 is likely to occur in the cylindrical foam, and when such a cylindrical foam is crushed in the radial direction, as shown in FIG. The resulting polystyrene-based resin foam sheet has uneven heat-sealing and uneven stripes, resulting in a problem that a product having good appearance and physical properties cannot be obtained.

  Therefore, the resin temperature when extruding polystyrene resin from the extruder is lowered, but when the extrusion foaming temperature is lowered, the cylindrical foam is crushed in the radial direction and the inner surfaces are heat-sealed. Another problem was that the heat-sealing property was lowered and the resulting polystyrene-based resin foam sheet was easily peeled off from the heat-sealing interface.

  In addition, when the amount of the foaming agent is large, heat is taken from the cylindrical foam by the heat of vaporization accompanying the evaporation of the foaming agent from the cylindrical foam, and the cylindrical foam is easily cooled. Thus, when the extrusion foaming temperature is lowered, when the cylindrical foam is crushed in the radial direction and the inner surfaces are heat-sealed, the inner surfaces of the cylindrical foam are heat-sealed. There was also a problem that the sex decreased.

JP 2003-220639 A

  The present invention provides a method for producing a low-density polystyrene-based resin foam sheet having almost no uneven stripe pattern and excellent heat fusion properties.

In the method for producing a polystyrene resin foam sheet of the present invention, a polystyrene resin is supplied to an extruder, melt kneaded in the presence of a foaming agent, extruded and foamed to produce a cylindrical foam, and this cylindrical foam is produced. After the outer surface of the body has been cooled, the cylindrical foam is crushed in the radial direction, and the inner surfaces of the cylindrical foam are heat-sealed to produce a polystyrene-based resin foam sheet that is a two-sheet laminate. A method for producing a resin foam sheet, wherein the polystyrene-based resin has a melt flow rate of 0.5 to 3.0 g / 10 min and a Z average molecular weight (Mz) of 6.0 × 10 ^{5 to} 10.0. X 10 ⁵ , and the ratio (Mz / Mw) of Z average molecular weight (Mz) to weight average molecular weight (Mw) is 2.0 to 4.0.

  The polystyrene resin used in the present invention is not particularly limited as long as it has the above-mentioned predetermined characteristics. For example, styrene, α-methylstyrene, vinyltoluene, chlorostyrene, isopropylstyrene, dimethylstyrene, etc. Examples include homopolymers of styrene monomers or copolymers thereof.

  The polystyrene resin includes a copolymer of the styrene monomer and a vinyl monomer copolymerizable with the styrene monomer, containing 50% by weight or more of the styrene monomer. Examples of such vinyl monomers include alkyls such as acrylic acid, methacrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and cetyl (meth) acrylate. (Meth) acrylate, (meth) acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, maleic anhydride, (meth) acrylamide and the like. In addition, (meth) acryl means a methacryl or an acryl.

  If the melt flow rate of the polystyrene resin is low, the melt viscosity of the polystyrene resin becomes too high and the load on the extruder increases, resulting in a decrease in productivity, or obtained by extrusion foaming from the extruder. While it is not possible to produce a wide polystyrene-based resin foam sheet due to insufficient elongation of the cylindrical foam, if high, it is necessary to lower the extrusion foaming temperature because the melt tension at the time of extrusion foaming is insufficient. As a result, the foamability of the polystyrene-based resin is lowered and the foaming ratio of the cylindrical foam is lowered, or the heat-fusibility between the inner surfaces when the cylindrical foam is crushed in the radial direction is lowered. Therefore, it is limited to 0.5 to 3.0 g / 10 minutes, preferably 1.0 to 2.8 g / 10 minutes, and more preferably 2.0 to 2.5 g / 10 minutes.

  The melt flow rate of polystyrene resin is measured in accordance with the method described in JIS K7210: 1999 “Testing method for melt mass flow rate (MFR) and melt volume flow rate (MVR) of plastic-thermoplastic plastic” B method. What you did.

  Specifically, for example, using a measuring device commercially available from Toyo Seiki Seisakusho Co., Ltd. under the trade name “Semi-Auto Melt Indexer”, 3-8 g of the sample is filled in the cylinder of this measuring device, and a filling rod is used. The sample is compressed, and the melt flow rate of the polystyrene resin is measured under the measurement conditions of a test temperature of 200 ° C., a load of 49.03 N, and a preheating time of 4 minutes. And let the number of tests be 3 or more, and let the arithmetic average value of the melt flow rate of the polystyrene resin obtained by each measurement be the melt flow rate of the polystyrene resin.

Then, Z-average molecular weight of the polystyrene resin (Mz) is limited to ^{6.0 × 10 5 ~10.0 × 10 5} . In the present invention, by setting the Z-average molecular weight of the polystyrene-based resin higher than usual, even when the extrusion foaming temperature is set high, the polystyrene-based resin maintains a melt tension suitable for foaming at the time of extrusion foaming, Extrusion foaming can be performed satisfactorily.

  That is, when the Z-average molecular weight (Mz) of the polystyrene-based resin is low, when the extrusion foaming temperature is increased, the melt tension of the polystyrene-based resin is lowered at the time of extrusion foaming, and the foaming speed at the time of extrusion foaming is increased. A problem arises in that a wavy striped pattern occurs in the cylindrical foam extruded from the mold and the appearance is deteriorated.

  On the other hand, if the Z-average molecular weight (Mz) of the polystyrene resin is high, the melt viscosity of the polystyrene resin becomes high and the foam is difficult to extend, and the cylindrical foam is difficult to expand, and the polystyrene resin has a wide width. There arises a problem that a foam sheet cannot be obtained.

  Moreover, the ratio (Mz / Mw) of the Z average molecular weight (Mz) and the weight average molecular weight (Mw) in the polystyrene resin is limited to 2.0 to 4.0, and preferably 2.0 to 3.0.

  This is because, when the ratio (Mz / Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) in the polystyrene resin is low, the extrusion resin is melted at the time of extrusion foaming when the extrusion foaming temperature is increased. This is because the tension is lowered, the foaming speed at the time of extrusion foaming is increased, and a problem arises in that a wavy striped pattern is generated in the cylindrical foam extruded from the mold and the appearance is deteriorated.

  On the other hand, if the ratio (Mz / Mw) of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw) in the polystyrene resin is high, the melt tension of the polystyrene resin at the time of extrusion foaming becomes too large, and the cylindrical foam This is because the body cannot be sufficiently expanded in diameter and a wide polystyrene resin foam sheet cannot be obtained.

  The foaming agent is not particularly limited as long as it is used for extrusion foaming. For example, hydrocarbons such as propane, butane and pentane, halogenated carbonization such as tetrafluoroethane, chlorodifluoroethane, and difluoroethane. Volatile foaming agents such as hydrogen; organic foaming agents such as azodicarbonamide and dinitropentamethylenetetramine; inorganic foaming agents composed of organic acids such as citric acid or salts thereof and bicarbonates such as sodium bicarbonate Decomposable foaming agents such as carbon dioxide, nitrogen, water and the like, butane is preferred. As for butane, either normal butane or isobutane may be used, or normal butane and isobutane may be used in combination. In addition, a foaming agent may be used independently or 2 or more types may be used together.

  Further, additives such as foaming nucleating agents such as talc and calcium stearate, ultraviolet absorbers, antioxidants, colorants, lubricants, flame retardants and antistatic agents may be added to the polystyrene resin. The foam nucleating agent is preferably 0.5 to 5.0 parts by weight with respect to 100 parts by weight of the polystyrene resin.

  Here, an example of the manufacturing apparatus used with the manufacturing method of the polystyrene-type resin foam sheet of this invention is demonstrated. As shown in FIG. 3, a circular die 2 is attached to the tip of the extruder 1, and air is blown in front of the circular die 2 to cool the outer surface of the cylindrical foam over its entire circumference. An air ring 3 is disposed.

  Further, in front of the air ring 3, a pair of guide plates 4, 4 are disposed for pressing the cylindrical foam from the upper and lower directions into a flat shape, and in front of the guide plates 4, 4. Are provided with pinch rolls 5 and 5 for pressing the flattened foam from above and below to thermally fuse the inner surfaces.

  Further, in front of the pinch rolls 5 and 5, a roller with a needle (not shown) is provided on each of both side surfaces of the cylindrical foam to penetrate through the inner and outer peripheral surfaces. ing. As described in JP-A-2005-238686, by adjusting the gas pressure in the cylindrical foam by adjusting the gas pressure in the cylindrical foam by removing the gas in the cylindrical foam through the through hole, The width of the resulting polystyrene-based resin foam sheet can be adjusted.

  In front of the pinch rolls 5 and 5, a take-up machine 6 for taking up the manufactured polystyrene resin foam sheet and a cutting device 7 for cutting the polystyrene resin foam sheet at predetermined lengths are sequentially arranged. It is installed.

  The polystyrene-based resin is supplied to the extruder 1 of the manufacturing apparatus configured as described above and melt-kneaded in the presence of a foaming agent. In addition, what is necessary is just to press-fit a foaming agent from the middle of an extruder according to the kind of foaming agent, or just to supply an extruder with a polystyrene-type resin.

  And cylindrical foam A is manufactured by extrusion foaming the polystyrene resin from the circular die 2 attached to the tip of the extruder 1. In this case, as described above, the polystyrene resin has a melt flow rate, a Z average molecular weight (Mz), and a ratio of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) within a predetermined range. Therefore, even if the extrusion foaming temperature is set high, the polystyrene resin has a melt tension suitable for foaming, and the cylindrical foam A has almost no wavy striped pattern, and the inner and outer peripheral surfaces are smooth. An arcuate surface can be obtained.

  When the resin temperature at the time of extruding and foaming a polystyrene resin from an extruder is low, the heat-fusibility at the time of crushing the cylindrical foam in the radial direction and heat-bonding the inner surfaces to each other is reduced, while being high Since the melt tension of the polystyrene-based resin is lowered and the cylindrical foam may be expanded in diameter, cracks may occur, so 140 to 160 ° C. is preferable.

  The cylindrical foam A obtained by extruding and foaming a polystyrene-based resin from the circular die 2 is cooled by the air discharged from the air ring 3 over the entire circumference, and the cylindrical foam is obtained. Emission of the foaming agent and volatile components from the outer peripheral surface of A is suppressed.

  On the other hand, since the cylindrical foam A is crushed in the radial direction in front of the cylindrical foam A, the space surrounded by the inner peripheral surface of the cylindrical foam A is in a closed state. The space is filled with the foaming agent and volatile components contained in the cylindrical foam A, and the cylindrical foam A is expanded by the pressure of the foaming agent and volatile components. The On the other hand, if the melt tension of the cylindrical foam A is too high, the diameter of the cylindrical foam A due to the pressure of the foaming agent or volatile component is insufficient, and a polystyrene-based resin foam sheet having a desired width can be obtained. Can not.

  The cylindrical foam A is pressed between the guide plates 4 and 4 in the vertical direction, is gradually deformed into a flat state and is superposed on two sheets, and is supplied between the pinch rolls 5 and 5. The Then, as described above, the cylindrical foam A is expanded in diameter by the pressure of the foam material or volatile component, and the cylindrical foam A is sized so as to obtain a desired foam sheet width. The cylindrical foam A is brought into contact with a roll with a needle disposed in front of 5, and through-holes are formed on both side surfaces of the cylindrical foam A so as to penetrate between the inner and outer surfaces. While removing excess gas from the foam A, the inner peripheral surfaces of the cylindrical foam A, that is, the opposing surfaces of the foams superimposed on each other, are bonded together by heat sealing and integrated. A sheet-fitted polystyrene resin foam sheet can be produced.

  At this time, the inner peripheral surface of the cylindrical foam A was sufficiently expanded in diameter so that the inner peripheral surface was a smooth peripheral surface, and the cylindrical foam A was flattened and superimposed on two sheets. Since the two foams are facing each other, the opposing faces of the foam are both smooth and the resin temperature during extrusion foaming is set high using a specific polystyrene resin. Therefore, the foam supplied between the pinch rolls 5 and 5 maintains a state heated to a high temperature, and the overlapped foam is uniformly pressed in the width direction by the pinch rolls 5 and 5. The two-layered polystyrene resin foam sheet is manufactured by heat-sealing uniformly and firmly over the entire surface. And the said polystyrene-type resin foam sheet is supplied to the cutting device 7 arrange | positioned ahead, and is cut | disconnected for every desired length.

If the density of the polystyrene resin foam sheet is low, the lightness of the polystyrene resin foam sheet is reduced. On the other hand, if the density is high, the mechanical strength of the polystyrene resin foam sheet may be reduced. -0.060 g / cm < ³ > is preferable.

  In addition, the density of a polystyrene-type resin foam sheet is measured in the following way. First, a polystyrene-based resin foam sheet that has been manufactured for more than 5 days is prepared. From the polystyrene-based resin foam sheet, a test piece having a width and thickness that matches the entire width and thickness of the polystyrene-based resin foam sheet and having a length of 200 mm. Cut out.

And while measuring the weight W (g) of a test piece, the thickness of the center part of the length direction in a test piece is measured every 25 mm in the width direction, The arithmetic mean value is made into the thickness of a test piece, and a test is carried out. The volume V (cm) of the piece is calculated, the density of the test piece is calculated based on the following formula, and this density is taken as the density of the polystyrene resin foam sheet.
Density of polystyrene resin foam sheet (g / cm ³ )
= Weight W of test piece / volume V of test piece

In the method for producing a polystyrene-based resin foam sheet of the present invention, the melt flow rate is 0.5 to 3.0 g / 10 minutes, and the Z average molecular weight (Mz) is 6.0 × 10 ^{5 to} 10.0 × 10 ⁵ . In addition, since a polystyrene resin having a ratio (Mz / Mw) of Z-average molecular weight (Mz) to weight-average molecular weight (Mw) of 2.0 to 4.0 is used, the resin temperature at the time of extrusion foaming Even if the height is increased, the polystyrene-based resin has a melt tension suitable for foaming.

  Therefore, the cylindrical foam obtained by extrusion foaming has almost no wavy striped pattern, and if it occurs, it is a slight one. Can be eliminated.

  In addition, since the polystyrene resin has an appropriate melt tension, the diameter of the cylindrical foam can be increased, and a wide range of polystyrene resin foam sheets can be obtained.

  And, as described above, the cylindrical foam can be smoothly expanded in diameter and extended in the circumferential direction. Therefore, the inner and outer peripheral surfaces of the cylindrical foam in the expanded state, in particular, the inner peripheral surface is The opposing surface of the foam, which is a smooth arc-shaped surface and is crushed in the radial direction by crushing the cylindrical foam in the radial direction, is a smooth flat surface, and is extruded by using a specific polystyrene resin. Since the resin temperature at the time of foaming is increased, when the cylindrical foam is crushed in the radial direction and the inner surfaces are heat-sealed, the foam has a sufficient amount of heat, and the two sheets are overlapped By sandwiching the foam in the thickness direction, the opposing surfaces of the foam can be firmly heat-sealed and integrated, and a polystyrene resin foam sheet having excellent mechanical strength and appearance can be produced. .

(Molecular weight and molecular weight distribution of polystyrene resin)
About 30 mg of polystyrene resin is dissolved in 10 ml of chloroform, filtered through a non-aqueous 0.45 μm chromatographic disk, and then measured for polystyrene equivalent molecular weight using high pressure liquid chromatography (HPLC, trade name “Detector 484, Pump 510” manufactured by Water). did.

Measurement conditions were set as follows.
Column: Product name “ShodexGPCK-806L (φ8.0 × 300) manufactured by Showa Denko KK
mm) ”Two column temperature: 40 ° C.
Mobile phase: Chloroform Mobile phase flow rate: 1.2 ml / min Injection / pump temperature: Room temperature Detection: UV at 254 nm Injection amount: 50 microliter Standard polystyrene for calibration curve: Showa Denko Co., Ltd. trade name “Shodex”, molecular weight: 1030000
Made by Tosoh Corporation
Molecular weight: 540000,3840000,355000,102000,37900,9100
2630,495

(Average cell diameter of polystyrene resin foam sheet)
The cell diameter of the polystyrene resin foam sheet was measured based on the method described in ASTM D2842-69. Specifically, the polystyrene-based resin foam sheet is cut over the entire thickness in the extrusion direction (MD) and in the direction orthogonal to the extrusion direction (TD direction), and an enlarged photograph of each cut surface is taken with a scanning electron microscope (Hitachi). Photo was taken using a trade name “S-3000N”.

  In the enlarged photograph of the cut surface cut along the extrusion direction, draw one straight line with a length of 60 mm parallel to the extrusion direction, count the number of bubbles present on this straight line, and average the extrusion direction based on the following formula The chord length (t) was calculated.

  Similarly, in the enlarged photograph of the cut surface cut along the direction orthogonal to the extrusion direction, one straight line with a length of 60 mm parallel to the direction orthogonal to the extrusion direction is drawn, and the number of bubbles existing on this line is calculated. The average chord length (t) in the direction orthogonal to the extrusion direction was calculated based on the following formula.

Furthermore, in both the enlarged photograph of the cut surface cut along the extrusion direction and the enlarged photograph of the cut surface cut along the direction orthogonal to the extrusion direction, a straight line having a length of 60 mm parallel to the thickness direction (VD) is shown. Draw one, count the number of bubbles on these straight lines, calculate the average chord length (t) in the thickness direction for each cut surface based on the following formula, and calculate the phase of these average chord lengths (t) The arithmetic average value was calculated, and this average value was defined as the average chord length (t) in the thickness direction.
Average chord length (t) = 60 / (number of bubbles × photo magnification)

  When drawing a straight line, the straight line was penetrated as much as possible without making point contact with the bubbles. Also, if some of the bubbles come into point contact with a straight line, this bubble is included in the number of bubbles, and if both ends of the straight line are located in the bubble without penetrating the bubbles Included the number of bubbles including both ends of the straight line.

Based on the calculated average chord length (t) in each direction, the average bubble diameter in each direction was calculated by the following equation.
Average bubble diameter (mm) D = t / 0.616

(Open cell ratio)
The open cell ratio of the polystyrene resin foam sheet was measured based on the measurement method described in ASTM D2856-87. A plurality of planar square sheet pieces each having a side of 25 mm were cut out from the polystyrene-based resin foam sheet, and the plurality of sheet pieces were overlapped so as to have a thickness of about 25 mm to prepare a test piece.

Thereafter, the dimensions of this test piece are measured using a caliper to calculate the apparent volume of each test piece, while using an air comparison hydrometer (trade name “1000 type” manufactured by Tokyo Science Co., Ltd.) 1-1. The volume of the test piece was measured based on the / 2-1 atmospheric pressure method, and the open cell ratio of the polystyrene resin foam sheet was calculated based on the following formula.
Open cell ratio (%) = 100 × (apparent volume−air comparison type hydrometer) / apparent volume

(Fusion strength and fusing property)
Ten planar rectangular test pieces having a width of 30 mm and a length of 300 mm were cut out from the polystyrene resin foam sheet over the entire length. Then, a cut having a depth of 100 mm was made from the end face over the entire width of 30 mm at the heat fusion interface at the center in the thickness direction at the end in the length direction of each test piece. One of the foams stacked on top and bottom of each test piece is fixed to a jig, the peel strength is measured at a test speed of 300 mm / min, and the arithmetic average value of the peel strength of each test piece is measured. Was the fusion strength. Note that the peel strength was measured only when the foams could be peeled apart without destroying the foams at the heat fusion interface between the foams stacked one above the other.

And the fusion property of the polystyrene-type resin foam sheet was judged based on the following reference | standard.
○. In all the test pieces, the foam was destroyed at the heat-sealing interface between the foams.
× ·· At least one of the test pieces was able to peel off the foams without breaking the foams at the heat-sealing interface between the foams.

Example 1
The manufacturing apparatus shown in FIG. 3 was used as the manufacturing apparatus. Specifically, a tandem type extruder having a φ150 mm second single screw extruder connected to the tip of a φ115 mm first single screw extruder is used as the extruder 1, and the second single unit of the tandem type extruder 1 is used. A circular die 2 having an annular slit having a diameter of 160 mm and a width of 1.0 mm is attached to the tip of the axial extruder, and an air ring 3 is disposed in front of the circular die 2, and in front of the air ring 3 and A pair of upper and lower pinch rolls 5, 5 are disposed at a position 93 cm forward from the circular die 2, and a pair of upper and lower guide plates 4, 4 are disposed between the pinch rolls 5, 5 and the circular die 2. Further, a take-up machine 6 and a cutting device 7 are sequentially arranged in front of the pinch rolls 5 and 5. In front of the pinch rolls 5 and 5, a roller with a needle (not shown) is provided on each of both side surfaces of the cylindrical foam to penetrate through the inner and outer peripheral surfaces. The distance between the opposing surfaces of the pair of upper and lower pinch rolls 5 and 5 was 4 mm.

And polystyrene resin (trade name “HRM-48N” manufactured by Toyo Styrene Co., Ltd., melt flow rate: 2.1 g / 10 min, weight average molecular weight (Mw): 3.3 × 10 ⁵ , Z average molecular weight average molecular weight (Mz ): 7.1 × 10 ⁵ , Mz / Mw = 2.2) 100 parts by weight and 2.4 parts by weight of dry talc as a foam nucleating agent were dry-blended to prepare a polystyrene resin composition.

  Next, the polystyrene resin composition is supplied to a first single-screw extruder of a tandem extruder and melt-kneaded. Further, butane (100 parts by weight of polystyrene resin from the middle of the first single-screw extruder) (Isobutane: 35% by weight, normal butane: 65% by weight) were injected at a ratio of 7 parts by weight, melted and kneaded, and the polystyrene-based resin composition was continuously supplied to the second single-screw extruder.

  Next, the cylinder temperature of the second single screw extruder is gradually lowered so that the temperature of the polystyrene resin measured on the breaker plate disposed at the tip of the second single screw extruder is 150 ° C. The cylinder temperature of the screw extruder was gradually lowered. In addition, the temperature of the cylinder front-end | tip part of a 2nd single screw extruder was 104 degreeC.

  And the polystyrene-type resin composition was extrusion-foamed from the circular die | dye 2 attached to the front-end | tip part of a 2nd single screw extruder, and the cylindrical foam A was obtained. The tip temperature of the circular die was 122 ° C.

  After cooling by blowing air at 36 ° C. from the air ring 3 over the entire circumference of the cylindrical foam A immediately after being extruded and foamed from the circular die 2, the cylindrical foam A is The diameter was expanded in the radial direction by the pressure of butane and volatile substances diffused in the space surrounded by the surface.

  Thereafter, the expanded cylindrical foam A is supplied between a pair of upper and lower guide plates 4 and 4 and the cylindrical foam A is pressed from the upper and lower directions to be gradually deformed into a flat state. The foam is overlapped vertically, and a through hole penetrating between the inner and outer peripheral surfaces is formed on both side surfaces of the cylindrical foam A with a needle roller, and then supplied between the pinch rolls 5 and 5. The inner surface of the cylindrical foam, that is, the opposing surfaces of the two foams stacked one above the other are heat-sealed and integrated to produce a polystyrene-based resin foam sheet. This polystyrene-based resin foam sheet Was cut into predetermined lengths using a cutting device 7 disposed in front.

The obtained polystyrene-based resin foam sheet has a width of 630 mm, an average thickness of 5.0 mm, a basis weight of 260 g / m ² and a density of 0.052 g / cm ³ , and has no uneven stripe pattern. Had an excellent appearance. In addition, the average thickness of the polystyrene-type resin foam sheet measured the thickness of the polystyrene-type resin foam sheet every 25 mm in the width direction, and made it the arithmetic mean value.

(Example 2)
The polystyrene resin has a melt flow rate of 2.2 g / 10 min, a weight average molecular weight (Mw) of 3.2 × 10 ⁵ , a Z average molecular weight (Mz) of 8.2 × 10 ⁵ , a Z average molecular weight and a weight average. Using a polystyrene resin having a molecular weight ratio (Mz / Mw) of 2.6 (product name “G9401” manufactured by PS Japan), the amount of butane is 6.6 parts by weight with respect to 100 parts by weight of the polystyrene resin. A polystyrene resin foam sheet was obtained in the same manner as in Example 1 except that.

The obtained polystyrene-based resin foam sheet has a width of 630 mm, an average thickness of 5.0 mm, a basis weight of 290 g / m ² and a density of 0.058 g / cm ³ , and has no uneven stripe pattern. Had an excellent appearance.

(Comparative Example 1)
As a polystyrene resin, the melt flow rate is 2.2 g / 10 min, the weight average molecular weight (Mw) is 2.5 × 10 ⁵ , the Z average molecular weight (Mz) is 4.2 × 10 ⁵ , the Z average molecular weight and the weight average. A polystyrene resin having a molecular weight ratio (Mz / Mw) of 1.7 (trade name “HRM-13N” manufactured by Toyo Styrene Co., Ltd.) was used, and the amount of butane with respect to 100 parts by weight of the polystyrene resin. A polystyrene resin foam sheet was produced in the same manner as in Example 1 except that the amount was 6 parts by weight. As a result, a wavy striped pattern was generated in the cylindrical foam A, and the resulting polystyrene resin foam sheet was uneven. The stripe pattern was generated.

The obtained polystyrene-based resin foam sheet had a width of 630 mm, an average thickness of 4.9 mm, a basis weight of 279 g / m ² and a density of 0.057 g / cm ³ .

  Therefore, except that the cylinder temperature of the second single-screw extruder was gradually lowered so that the temperature of the polystyrene resin measured at the breaker plate disposed at the tip of the second single-screw extruder was 145 ° C. A polystyrene resin foam sheet was produced in the same manner.

No wavy striped pattern was generated on the cylindrical foam, and no uneven striped pattern was formed on the resulting polystyrene-based resin foam sheet, but the density could not be reduced to 0.064 g / cm ³ . .

(Comparative Example 2)
As polystyrene resin, melt flow rate is 5.0 g / 10 min, weight average molecular weight (Mw) is 2.7 × 10 ⁵ , Z average molecular weight (Mz) is 6.4 × 10 ⁵ , Z average molecular weight and weight average. Using a polystyrene resin (trade name “HRM-18” manufactured by Toyo Styrene Co., Ltd.) having a molecular weight ratio (Mz / Mw) of 2.4, measured on a breaker plate disposed at the tip of a second single screw extruder Except that the cylinder temperature of the second single-screw extruder was gradually lowered so that the temperature of the polystyrene-based resin was 145 ° C., and the butane amount was 7.3 parts by weight with respect to 100 parts by weight of the polystyrene-based resin. Obtained a polystyrene-based resin foam sheet in the same manner as in Example 1.

The obtained polystyrene resin foam sheet had a width of 630 mm, an average thickness of 5.0 mm, a basis weight of 320 g / m ² , and a density of 0.064 g / cm ³ . Since the melt viscosity of the polystyrene resin composition was high, the melt viscoelasticity was low, and it was not possible to reduce the density of the polystyrene resin foam sheet.

Therefore, when a polystyrene resin foam sheet was produced in the same manner as described above except that the amount of butane was 7.9 parts by weight with respect to 100 parts by weight of the polystyrene resin, polystyrene having a density of 0.060 g / cm ³ was obtained. Although a resin-based resin foam sheet could be obtained, a wavy striped pattern was generated on the cylindrical foam, and an uneven striped pattern was also generated on the polystyrene-based resin foam sheet. In addition, although polystyrene resins have a high Z average molecular weight (Mz), the melt flow rate is also high, so that the melt tension of the polystyrene resin composition during extrusion foaming is lowered and the foaming force in the thickness direction is maintained. The polystyrene-based resin foam sheet was thin.

  Furthermore, when the thickness of the polystyrene resin foam sheet is reduced to 5.0 mm by lowering the take-up speed by the take-up machine 6 of the polystyrene resin foam sheet, the density of the polystyrene resin foam sheet increases and the density can be reduced. There wasn't.

(Comparative Example 3)
As polystyrene resin, melt flow rate is 7.9 g / 10 min, weight average molecular weight (Mw) is 2.0 × 10 ⁵ , Z average molecular weight (Mz) is 3.5 × 10 ⁵ , Z average molecular weight and weight average. Using a polystyrene resin (trade name “HRM-10N” manufactured by Toyo Styrene Co., Ltd.) having a molecular weight ratio (Mz / Mw) of 1.8, measured on a breaker plate disposed at the tip of a second single screw extruder A polystyrene resin foam sheet was obtained in the same manner as in Example 1 except that the cylinder temperature of the second single-screw extruder was gradually lowered so that the temperature of the polystyrene resin thus obtained was 136 ° C.

The obtained polystyrene resin foam sheet had a width of 630 mm, an average thickness of 5.0 mm, a basis weight of 290 g / m ² and a density of 0.058 g / cm ^3. The heat fusion between the bodies was weak, and the foams could be easily peeled from the heat fusion interface by hand.

It is the longitudinal cross-sectional view which showed the state which the wavy striped pattern produced in the cylindrical foam. It is the longitudinal cross-sectional view which showed the state in which the fusion | fusion nonuniformity and the uneven stripe pattern produced in the polystyrene-type resin foam sheet. It is the model side view which showed an example of the manufacturing apparatus of the polystyrene-type resin foam sheet of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Extruder 2 Circular die 3 Air ring 3 Comparative example 4 Guide plate 5 Pinch roll 6 Picker 7 Cutting device A Cylindrical foam

Claims (2)

A polystyrene resin is supplied to an extruder, melt-kneaded in the presence of a foaming agent, extruded and foamed to produce a cylindrical foam, and after cooling the outer surface of the cylindrical foam, the cylindrical foam is A method for producing a polystyrene-based resin foam sheet, which is crushed in the radial direction and heat-bonds the inner surfaces of the cylindrical foam to produce a two-piece polystyrene-based resin foam sheet, the polystyrene-based resin Has a melt flow rate of 0.5 to 3.0 g / 10 min, a Z average molecular weight (Mz) of 6.0 × 10 ^{5 to} 10.0 × 10 ⁵ , and a Z average molecular weight (Mz) of A method for producing a polystyrene-based resin foam sheet, wherein the ratio (Mz / Mw) to the weight average molecular weight (Mw) is 2.0 to 4.0. The method for producing a polystyrene resin foam sheet according to claim 1, wherein the density of the polystyrene resin foam sheet is 0.045 to 0.060 g / cm ³ .

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