JP2009178898A - Polystyrene resin laminated foam sheet and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polystyrene resin laminated foam sheet that is excellent in printing characteristics such that no delamination between foam layers will occur. <P>SOLUTION: The polystyrene resin laminated foam sheet produced by coextrusion foaming comprises a polystyrene resin low density foam layer 11 having a density of 0.07 to 0.17 g/cm<SP>3</SP>and laminated and integrated with a polystyrene resin high density foam layer 12 having density of 0.18 to 0.45 g/cm<SP>3</SP>and a polystyrene resin non-foam layer in this order. The average bubble diameter of the polystyrene resin low density foam layer 11 is 200 to 500 μm, the average bubble diameter of the polystyrene resin high density foam layer 12 is 70 to 180 μm, and the ratio of the average bubble diameter of the polystyrene resin high density foam layer 12 to the average bubble diameter of the polystyrene resin low density foam layer 11 is 0.33 to 0.6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polystyrene-based resin laminated foam sheet and a method for producing the same.

  Today, instant noodle containers are provided in a wide variety. Containers for packaging or cooking instant noodles are strong against impacts applied during transportation or storage, and have excellent appearance. In order to satisfy such a requirement, a material in which a polystyrene resin non-foamed sheet is laminated on one surface of a polystyrene resin foam sheet is widely used as a raw material for instant noodle containers.

  The outer surface of the instant noodle container is printed, and the printing procedure is as follows. In addition to the method of forming the original noodles, there is a method in which the raw fabric is formed into an instant noodle container shape and then printed directly on the outer surface of the instant noodle container using a curved surface printing machine.

  However, when printing is performed on the outer surface of the instant noodle container using a curved surface printing machine, depending on the state of the outer surface of the container, there has been a problem that printed characters and patterns are blurred or the printing is faint.

  Therefore, in Patent Document 1, a polystyrene resin non-foamed layer is laminated by coextrusion on one surface of a polystyrene resin foamed sheet layer obtained by extrusion foaming, in which a low foamed sheet layer and a high foamed sheet layer are laminated. It is a long polystyrene-based resin laminated foam sheet formed integrally, and when heated at 125 ° C. for 150 seconds, the surface of the polystyrene-based resin non-foamed layer is −45 to −15% in the width direction. A long polystyrene-based resin-laminated foam sheet is proposed, which shrinks at a dimensional change rate and is configured to deform in a circular arc shape in the width direction with the polystyrene-based resin non-foamed layer inside. Yes.

  However, although the above-mentioned polystyrene-based resin laminated foam sheet has excellent printing characteristics, it may cause delamination between the foamed sheet layers, especially when the polystyrene-based resin laminated foam sheet is thermoformed into a container shape and used. In addition, a sealing sheet is usually stretched at the opening of the container, but there is a problem that delamination occurs between the foamed sheet layers due to the peeling force when peeling the sealing sheet. .

  In addition, containers are usually stored in a transport storage box arranged vertically and horizontally and transported to a predetermined location, but adjacent containers rub against each other due to vibrations generated during transport. May cause delamination between the foam sheet layers.

  In addition to the above, although a sheet formed by laminating and integrating a plurality of foam layers is also proposed in Patent Documents 2 and 3, it does not solve the above problems.

JP 2006-264024 A JP-A-9-141773 JP 2001-162735 A

  The present invention provides a polystyrene-based resin laminated foam sheet excellent in printing characteristics that does not cause delamination between foamed layers, and a method for producing this polystyrene-based resin laminated foam sheet.

As shown in FIG. 1, the long polystyrene-based resin laminated foam sheet A of the present invention is a polystyrene-based resin laminated foam sheet manufactured by coextrusion foaming, and is a polystyrene system manufactured by coextrusion foaming. High density foam of polystyrene resin having a density of 0.18 to 0.45 g / cm ^{3 on} a polystyrene resin low density foam layer having a density of 0.07 to 0.17 g / cm ^3. Layers and a polystyrene resin non-foamed layer are laminated and integrated in this order. The polystyrene resin low-density foam layer has an average cell diameter of 200 to 500 μm, and the polystyrene resin high-density foam layer The average cell diameter is 70 to 180 μm, and the average cell diameter of the polystyrene resin high-density foam layer and the average cell diameter of the polystyrene resin low-density foam layer are (Average cell diameter of polystyrene resin density foam layer average cell diameter / polystyrene resin low density foam layer of the) is characterized by a 0.33 to 0.6.

  Hereinafter, the polystyrene-based resin low-density foam layer may be simply referred to as “low-density foam layer” and the polystyrene-based resin high-density foam layer may be simply referred to as “high-density foam layer”.

  The polystyrene resin constituting the low density foam layer 11 and the high density foam layer 12 of the polystyrene resin laminate foam sheet A of the present invention is not particularly limited, and examples thereof include styrene, α-methylstyrene, vinyltoluene, and chlorostyrene. , Homopolymers of styrenic monomers such as ethyl styrene, i-propyl styrene, t-butyl styrene and dimethyl styrene, or copolymers thereof.

  The polystyrene resin includes a copolymer of the styrene monomer containing 50% by weight or more of the styrene monomer and a vinyl monomer copolymerizable with the styrene monomer. Such vinyl monomers may be, for example, alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cetyl (meth) acrylate, (Meth) acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate and the like can be mentioned.

The polystyrene-based resin laminated foam sheet of the present invention is a high-density foam having a density of 0.18 to 0.45 g / cm ^{3 on} the low-density foam layer 11 having a density of 0.07 to 0.17 g / cm ³ . The layer 12 and the polystyrene-based resin non-foamed layer 2 (hereinafter sometimes simply referred to as “non-foamed layer”) are laminated and integrated in this order.

  In the polystyrene-based resin laminated foam sheet A of the present invention, the non-foamed layer 2 is laminated and integrated on the high-density foamed layer 12 by the coextrusion method. It is necessary to extrude from the coextrusion die after setting the heating temperature higher than that of the high density foam layer 12 and the low density foam layer 11, lowering the resin viscosity, and approaching the resin viscosity of the high density foam layer 12.

  However, if the resin temperature at the time of co-extrusion is set to the temperature matched with the non-foamed layer 2, the resin viscosity of the polystyrene resin constituting the low-density foam layer 11 and the high-density foam layer 12 becomes too low and bubbles break. On the other hand, if the resin temperature at the time of coextrusion is set to the temperature matched to the low density foam layer 11 and the high density foam layer 12, the resin viscosity of the polystyrene resin constituting the non-foam layer 2 becomes too high. Thus, the extrusion stability of the non-foamed layer 2 is lowered.

  Therefore, when the non-foamed layer 2 is laminated and integrated on the high-density foam layer 12 by coextrusion, the high-density foam layer 12 is less plasticized than the low-density foam layer 11 by the amount of the foaming agent. And coextruding at a temperature higher than that of the low density foamed layer 11 and coextruding at a temperature lower than that of the non-foamed layer 2 as much as the foaming agent is contained. Yes.

  In other words, the temperature suitable for coextrusion of the high density foam layer 12 is between the temperature suitable for coextrusion of the low density foam layer 11 and the temperature suitable for coextrusion of the non-foamed layer 2. I have to.

  By comprising in this way, the temperature difference suitable for coextrusion between the low density foamed layer 11 and the non-foamed layer 2 is relieved by the high density foamed layer 12, and each layer is a temperature suitable for coextrusion. The high-density foam layer 12 and the low-density foam layer 11 in the polystyrene-based resin laminated foam sheet A have low open cell ratio and excellent mechanical strength. Excellent surface smoothness.

  The non-foamed layer 2 laminated and integrated on the high-density foam layer 12 having excellent surface smoothness is also excellent in surface smoothness, and the high-density foam layer 12 has mechanical strength as described above. Since it is strong, a printing process can be stably performed on the non-foamed layer 2.

Here, if the density of the high-density foam layer 12 is small, the open cell ratio of the high-density foam layer is increased and the mechanical strength is lowered, so that the printing characteristics on the non-foamed layer may be deteriorated. If it is large, when the basis weight of the polystyrene resin laminated foam sheet is made the same, the thickness of the high-density foam layer becomes thin, the surface smoothness of the non-foam layer decreases, or the high density during coextrusion The temperature difference between the foam layer and the low-density foam layer becomes large, and the bubbles on the low-density foam layer side in the vicinity of the interface between the high-density foam layer and the low-density foam layer become open cells, and the polystyrene-based resin laminated foam sheet since the mechanical strength of the drops are limited to ^{0.18~0.45g / cm 3, 0.19~0.41g / cm} 3 are preferred.

Further, if the density of the low density foam layer 11 is small, the mechanical strength of the polystyrene resin laminated foam sheet may be reduced, while if large, the basis weight of the polystyrene resin laminate foam sheet is tried to be the same. In this case, the thickness of the low-density foam layer is reduced, and the mechanical strength and heat insulating property of the polystyrene-based resin laminated foam sheet may be reduced. Therefore, the thickness is limited to 0.07 to 0.17 g / cm ³ , and 0 0.08 to 0.15 g / cm ³ is more preferable.

  Further, if the ratio of the density of the low density foam layer 11 to the density of the high density foam layer 12 (density of the low density foam layer 11 / density of the high density foam layer 12) is small, the low density foam layer and the high density foam layer are low. Even if the average cell diameter is adjusted, delamination between the low-density foam layer and the high-density foam layer may occur. Therefore, 0.30 to 0.7 is preferable, 0.31 to 0.55 is more preferable, and 0.32 to 0.50 is particularly preferable.

The density of the low density foam layer 11 and the high density foam layer 12 in the polystyrene resin laminated foam sheet can be calculated in the following manner. First, the basis weight W of the polystyrene-based resin laminate foam sheet A of (g / cm ²⁾ was measured, extrusion rate E ₀ (kg / time) of the non-foamed layer 2, the extrusion amount of the low-density foam layer 11 E ₁ (kg / time) and in accordance with the following formula from the extrusion rate E ₂ of the high density foam layer 12 (kg / hour), to calculate the basis weight W ₂ of the basis weight W ₁ and the high density foam layer 12 of low density foam layer 11.
The basis weight W ₁ (g / cm ² ) of the low density foamed layer 11 = W × E ₁ / (E ₀ + E ₁ + E ₂ )
The basis weight W ₂ (g / cm ² ) of the high-density foam layer 12 = W × E ₂ / (E ₀ + E ₁ + E ₂ )

Next, to measure the thickness T ₁ of the low-density foam layer 11 (cm) and high-density foam layer 12 having a thickness T ₂ (cm), on the basis of the following equation, the density D ₁ and the high density foam of low density foam layer The density D ₂ of the layer can be calculated.
Density D ₁ (g / cm ³ ) = W ₁ / T _{1 of} low density foamed layer
Density D ₂ (g / cm ³ ) = W ₂ / T _{2 of} high-density foam layer

  Furthermore, when the total thickness of the low density foam layer 11 and the high density foam layer 12 is thin, the mechanical strength of the molded product obtained by molding the polystyrene-based resin laminated foam sheet may decrease, Since the moldability of the polystyrene-based resin laminated foam sheet may be lowered, 1.0 to 3 mm is preferable, 1.5 to 3 mm is more preferable, and 1.8 to 2.8 mm is particularly preferable.

  Further, if the thickness of the high-density foam layer 12 of the polystyrene resin foam sheet layer 1 is thin, the surface smoothness of the polystyrene resin non-foam layer of the polystyrene resin laminate foam sheet may be lowered. The above is preferable, 0.2 mm or more is more preferable, and 0.2 to 0.5 mm is particularly preferable.

  Furthermore, if the ratio of the thickness of the high density foam layer 12 to the thickness of the low density foam layer 11 (thickness of the high density foam layer 12 / thickness of the low density foam layer 11) in the polystyrene resin laminated foam sheet A is small, When the non-foamed layer is laminated and integrated on the density foamed layer, the surface smoothness of the non-foamed layer may decrease, or the mechanical strength of the polystyrene resin laminated foam sheet may decrease, Since the heat insulation and moldability of the polystyrene-based resin laminated foam sheet may be lowered, 0.08 to 0.2 is preferable.

  When the average cell diameter of the low-density foam layer 11 is small, the mechanical strength and thermoformability of the polystyrene resin laminated foam sheet are lowered, while when large, the thermoformability of the polystyrene resin laminate foam sheet is lowered. Alternatively, since the appearance of the obtained thermoformed product is deteriorated, it is limited to 200 to 500 μm, preferably 250 to 400 μm, and more preferably 250 to 350 μm.

  If the average cell diameter of the high-density foam layer 12 is small, bubbles near the surface of the high-density foam layer are destroyed when the non-foam layer is layered and integrated. While there is a risk that the thermal fusion strength between the layers will decrease, or the open cell ratio of the high-density foam layer will increase and the mechanical strength will decrease. When the layers are laminated and integrated, the surface property of the non-foamed layer is lowered, and the printing characteristics of the polystyrene-based resin laminated foamed sheet are lowered. Therefore, the layer is limited to 70 to 180 μm, and preferably 70 to 150 μm.

  The ratio of the average cell diameter of the high-density foam layer 12 to the average cell diameter of the low-density foam layer 11 (average cell diameter of the high-density foam layer 12 / average cell diameter of the low-density foam layer 11) is 0.33. It is limited to -0.6, and 0.35-0.55 is preferable.

  This is because when the ratio of the average cell diameter of the high-density foam layer 12 to the average cell diameter of the low-density foam layer 11 (average cell diameter of the high-density foam layer 12 / average cell diameter of the low-density foam layer 11) is small, Although the action is not clearly clarified, formation of bubbles having a small diameter is completed first in extrusion foaming, and formation of bubbles having a large diameter is completed later. Here, at the interface between the low-density foam layer 11 and the high-density foam layer 12, a bubble film having a small diameter formed in the high-density foam layer 12 is caused by the bubbles of the low-density foam layer 11 formed thereafter. As a result, the bubbles in the high-density foam layer 12 are broken, and as a result, the contact state at the interface between the low-density foam layer 11 and the high-density foam layer 12 deteriorates, and the low-density foam layer 11 and the high-density foam layer 12 This is presumably because the heat-fusibility at the interface with the foam layer 12 is lowered.

  On the other hand, when the ratio of the average cell diameter of the high-density foam layer 12 to the average cell diameter of the low-density foam layer 11 (average cell diameter of the high-density foam layer 12 / average cell diameter of the low-density foam layer 11) is large, Air bubbles in the density foam layer become too large, the surface property of the non-foamed layer laminated and integrated on the high density foam layer is lowered, and the printability of the polystyrene-based resin laminated foam sheet is lowered, or low density This is because the mechanical strength of the foamed layer is lowered, and the mechanical strength of the polystyrene-based resin laminated foam sheet is lowered.

  Here, in the present invention, the average cell diameters of the low-density foam layer 11 and the high-density foam layer 12 are those measured in the following manner. That is, the average cell diameters of the low density foam layer 11 and the high density foam layer 12 are those calculated based on the average chord length measured according to the test method of ASTM D2842-69. Specifically, the low-density foam layer 11 or the high-density foam layer 12 of the polystyrene-based resin laminated foam sheet A is cut along a surface along the direction in which the average cell diameter is desired to be measured, and the outer peripheral portion of the cut surface is formed. The removed central portion is arbitrarily enlarged at four places using a scanning electron microscope, and magnified 17 to 20 times (in some cases, 200 times), and an electron micrograph is taken.

Next, a straight line with a length of 60 mm is drawn on each photograph taken in the direction in which the average bubble diameter is to be measured, and the average chord length t of the bubbles is calculated based on the following formula 1 from the number of bubbles on the straight line. To do. 6 straight lines are drawn for each photograph, the average chord length t is calculated for each straight line, the arithmetic mean of the average chord length t is calculated for each photograph, and this arithmetic mean value is taken as the average chord length t of the bubbles. . If a straight line with a length of 60 mm cannot be drawn on the straight line, draw a straight line with a length of 20 mm or 30 mm on the photograph and measure the number of bubbles on this straight line to obtain the number of bubbles on the straight line with a length of 60 mm. Convert proportionally. Note that when counting the number of bubbles, even a portion of the bubbles located on a straight line or a bubble whose shape was unclear and could not be specified were counted as one.
Average chord length t = 60 / (number of bubbles × photo magnification) Formula 1

Then, the bubble diameter D is calculated by the following formula 2, and the arithmetic average of the bubble diameters D of each photograph is set as the average bubble diameter in the desired direction of the low density foam layer 11 or the high density foam layer 12.
Bubble diameter D = average chord length t / 0.616 Equation 2

  In addition, the average cell diameter of the low density foam layer 11 or the high density foam layer 12 is perpendicular to the average cell diameter of MD and the extrusion direction (MD) and is along the surface of the polystyrene-based resin laminated foam sheet in the manner described above. It can be calculated by measuring the average bubble diameter in the direction (TD) and the average bubble diameter in the direction (VD) orthogonal to MD and TD, respectively, and arithmetically averaging the average bubble diameter in MD, TD, and VD. it can.

  If the entire open cell ratio of the entire polystyrene resin laminated foam sheet A, that is, the low density foam layer 11, the high density foam layer 12 and the non-foamed layer 2 is large, the machine of the polystyrene resin laminated foam sheet is large. Less than 20% is preferable because the mechanical strength and thermoformability may be reduced.

  In addition, the open cell rate of the whole polystyrene resin laminated foam sheet A says what was measured by the 1-1 / 2 atm method based on ASTM D-2856-87. Specifically, the polystyrene-based resin laminated foam sheet A is cut into a planar square shape having a side of 25 mm, and a plurality of the cut pieces are stacked in the thickness direction to produce a test piece having a thickness of about 25 mm. Five test pieces were prepared in this manner, and the open cell ratio of each test piece was determined by using the air comparison type hydrometer (trade name “1000 type” manufactured by Tokyo Science Co., Ltd.). The arithmetic average value is defined as the open cell ratio of the entire polystyrene resin laminated foam sheet.

  As shown in FIG. 1, the polystyrene resin non-foamed layer 2 is laminated and integrated on the high-density foamed layer 12. As the polystyrene resin constituting the non-foamed polystyrene resin layer, in addition to the above-mentioned polystyrene resin, an impact resistant polystyrene resin in which a rubber component is added to the above polystyrene resin to improve impact resistance, A mixed resin obtained by adding a polystyrene elastomer such as a styrene-butadiene-styrene copolymer to a polystyrene resin may be used. In addition, as for the melt flow rate of the polystyrene resin which comprises the polystyrene resin non-foaming layer 2, 1-15 g / 10min is preferable.

  Furthermore, when the thickness of the polystyrene-based resin non-foamed layer 2 is thin, the mechanical strength of the polystyrene-based resin laminated foamed sheet may be lowered. On the other hand, when the thickness is thick, the moldability of the polystyrene-based resin laminated foamed sheet is lowered. Therefore, 60 to 200 μm is preferable, and 100 to 160 μm is more preferable.

  Furthermore, on the polystyrene resin non-foamed layer 2 of the polystyrene resin laminated foam sheet, a polystyrene resin sheet having a surface printed may be laminated and integrated as a print layer. A general-purpose method is used as a method for laminating and integrating the printed layer on the polystyrene-based resin non-foamed layer 2. Moreover, since it is the same as that of the polystyrene resin which comprises a polystyrene resin non-foaming layer as a polystyrene resin which comprises a printing layer, the description is abbreviate | omitted.

  Next, the manufacturing method of the said polystyrene-type resin laminated foam sheet is demonstrated. First, in order to manufacture a polystyrene-based resin laminated foam sheet, as shown in FIGS. 2 and 3, a coextrusion die 6 including a joining die 61 and an annular die 62 connected to the joining die 61, ~ Third extruders 3 to 5 are prepared, and all of the three extruders 3 to 5 are connected to the merge die 61 of the same coextrusion die 6.

  And while supplying polystyrene-type resin, a foaming agent, and a bubble regulator to the 1st extruder 3 and the 2nd extruder 4 and melt-kneading, it supplies a polystyrene-type resin to the 3rd extruder 5, and a bubble regulator In the presence of a foaming agent that does not foam, or in the absence of a foaming agent. The amount of foaming agent relative to the polystyrene resin is such that the first extruder 3 is higher than the second extruder 4, that is, the first extruder 3 is higher than the second extruder 4. It is necessary to adjust so that the foam is extruded and foamed.

  Here, in addition to the polystyrene resin, it is preferable to supply the third extruder 5 with an amount of foaming agent that does not foam. However, when supplying a foaming agent to the 3rd extruder 5, a bubble regulator is not supplied. Specifically, the amount of the blowing agent supplied to the third extruder 5 is preferably 2 parts by weight or less with respect to 100 parts by weight of the polystyrene-based resin. Then it does not foam. The foaming agent supplied to the third extruder 5 is not intended to foam the polystyrene resin, but plasticizes the polystyrene resin to lower the resin temperature during extrusion, and the high-density foam layer 12 is extruded and foamed. This is to prevent the open cell ratio of the high-density foam layer 12 from increasing as close as possible to the temperature.

  In addition, as said foaming agent, a general purpose thing is used, for example, aliphatic hydrocarbons, such as propane, butane, and pentane; 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1 , 1-difluoroethane (HCFC-142b), 2-chloro-1,1,1,2-tetrafluoroethane (HCFC-124), 1,1,1,2-tetrafluoroethane (HFC-134a), 1, Fluorocarbon blowing agents such as 1-difluoroethane (HFC-152a) can be mentioned, and aliphatic hydrocarbons are preferable.

  And if the quantity of the foaming agent supplied to the 1st extruder 3 and the 2nd extruder 4 is small, while it may not foam, if there is much, there exists a possibility of producing foam breakage, 100 weight of polystyrene resin 0.5-5 weight part is preferable with respect to a part.

  Further, the bubble regulator is not particularly limited. For example, inorganic powder such as talc and silica; acidic salt such as polyvalent carboxylic acid; reactive mixture of polyvalent carboxylic acid and sodium carbonate or sodium bicarbonate Inorganic powder is preferable, and talc is more preferable.

  If the amount of the air conditioner supplied to the first extruder 3 is small, the cell diameter of the resulting polystyrene resin low-density foam layer may not be reduced. In addition, since the open cell ratio of the obtained polystyrene-based resin low-density foam layer may increase, 0.03 to 4 parts by weight is preferable with respect to 100 parts by weight of the polystyrene-based resin.

  If the amount of the air conditioner supplied to the second extruder 4 is small, the cell diameter of the resulting polystyrene resin high-density foam layer may not be reduced. In addition, since the open cell ratio of the resulting polystyrene resin high-density foam layer may be high, 0.05 to 5 parts by weight is preferable with respect to 100 parts by weight of the polystyrene resin.

  Next, the high-extrusion polystyrene resin from the first extruder 3, the low-expansion polystyrene resin from the second extruder 4, the non-expanded polystyrene resin from the third extruder 5, and the coextrusion die 6 are joined together. Extruded into the die 61, and these polystyrene resins are merged in the merge die 61, and a low-expandable polystyrene resin layer and a polystyrene resin non-foamed coating are formed on the outer peripheral surface of the high-expandable polystyrene resin layer having a circular cross section. A foamable laminate having a circular cross section in which layers are laminated in this order.

  Then, this foamable laminate is supplied to the annular die 62 of the coextrusion die 6 so that the foamable laminate is cylindrical, and this cylindrical foamable laminate is extruded and foamed from the front end opening of the annular die 62. A foam layer obtained by extrusion foaming a highly foamable polystyrene resin is used as a high foam layer, and a foam layer obtained by extrusion foaming a low foam polystyrene resin is used as a low foam layer. A cylindrical foam in which a coating layer, a low foam layer and a high foam layer are laminated and integrated in layers from the outside to the inside is manufactured.

  At this time, the polystyrene-based resin non-foamed coating layer does not contain a foaming agent, or it is an amount that does not foam even if a foaming agent is contained, and does not contain a cell regulator. While there is no or little plasticization by the agent, the low foam layer and the high foam layer are plasticized by containing the foaming agent, and the high foam layer has a greater degree of plasticization than the low foam layer.

  Therefore, when the resin temperature during coextrusion is the same as that of the polystyrene resin non-foamed coating layer, the low foam layer and the high foam layer have a melt viscosity that is too low by the amount plasticized by the foaming agent. Therefore, it is necessary to set the temperature lower than that of the polystyrene-based resin non-foamed coating layer.

  Therefore, the resin temperature when extruding the low foam layer and the high foam layer from the coextrusion die is set to a temperature lower than the resin temperature of the polystyrene resin non-foamed coating layer, and the low foam layer is extruded from the coextrusion die. The temperature of the resin is set to a higher temperature than that of the high foam layer, and the resin temperature of the low foam layer is brought close to the resin temperature of the polystyrene resin non-foamed coating layer. The difference in the resin temperature when extruding from the coextrusion die to the layer is alleviated by the presence of the low foam layer, and the resin is extruded from the coextrusion die between the polystyrene resin non-foamed coating layer and the high foam layer. The difference in melt viscosity at the time is also mitigated by the presence of the low foam layer.

  Therefore, it is possible to give a wide range of conditions when the foamable laminate is extruded and foamed from the coextrusion die, and to obtain a cylindrical foam by stably extruding and foaming the foamable laminate from the coextrusion die. In addition, this cylindrical foam has a high foam layer, a low foam layer and a polystyrene resin non-foamed coating layer laminated and integrated in a beautiful state from the inside to the outside in this order. The foam coating layer has excellent surface smoothness.

  Since both the high foam layer and the low foam layer are extruded and foamed at a resin temperature suitable for each foaming, unnecessary strain is hardly generated in the high foam layer and the low foam layer during coextrusion foaming. The low-density foam layer 11 and the high-density foam layer 12 obtained by developing the high foam layer and the low foam layer are less distorted and rich in flexibility, and have excellent moldability. .

  Furthermore, the resin temperature at the time of extruding the polystyrene resin (high foaming layer) from the first extruder 3 from the coextrusion die is the same as that of the polystyrene resin (low foaming layer) from the second extruder 4 from the coextrusion die. Although adjusted so that it may become lower than the resin temperature at the time of extrusion, the resin temperature at the time of extruding the polystyrene-type resin (high foaming layer) from the 1st extruder 3 from a coextrusion die, and a 2nd extruder If the difference in resin temperature when extruding polystyrene resin (low foaming layer) from No. 4 from the coextrusion die is large, the open cell ratio of the resulting low density foaming layer will be high, Since the integrity by heat fusion with the density foam layer is reduced and delamination is likely to occur between them, the temperature is preferably less than 23 ° C, more preferably 5 to 20 ° C.

  And if the resin temperature at the time of extruding the polystyrene resin (low foam layer) from the second extruder 4 from the coextrusion die is high, the open cell ratio of the high density foam layer becomes high, and the polystyrene resin laminate Since there exists a possibility that the mechanical strength of a foam sheet may fall and printing characteristics may fall, below 172 degreeC is preferable and 150-170 degreeC is more preferable.

  Then, cooling air is blown to the outer peripheral surface of the cylindrical foam obtained by extruding and foaming the foamable laminate from the tip opening of the annular die 62 of the coextrusion die 6 to cool the cylindrical foam. While preventing the foam layer from foaming more than necessary, the low density foam layer may be adjusted so that the open cell ratio is less than 20%. In addition, you may spray cooling air also on the inner surface of a cylindrical foam.

If the amount of cooling air blown to the outer peripheral surface of the cylindrical foam is small, the cooling of the low foam layer becomes insufficient, resulting in a low density of the resulting high density foam layer, or the resulting high density foam layer. Since the open cell ratio may be high, it is preferably 0.1 m ³ or more per 1 m ² of the outer peripheral surface of the cylindrical foam, and more preferably 0.2 to 0.8 m ³ per 1 m ² .

  Moreover, if the temperature of the cooling air blown to the outer peripheral surface of the cylindrical foam is low, the low foam layer may be excessively cooled, and foaming of the low foam layer may be inhibited. Since the cooling of the layer becomes insufficient and the density of the resulting high-density foamed layer may be low, or the open cell ratio of the resulting high-density foamed layer may be high, 10 to 70 ° C. is preferable, and 20 to 50 is preferable. ° C is more preferred.

  Next, after gradually expanding the diameter of the cylindrical foam and supplying the cooling mandrel 7 to cool the cylindrical foam, the cylindrical foam is stretched between the inner and outer peripheral surfaces in the extrusion direction. A high-density foam layer 12 obtained by cutting a low foam layer and a polystyrene resin non-foam coating layer on a low density foam layer 11 obtained by continuously cutting and opening a high foam layer. Produce a long polystyrene-based resin laminated foam sheet in which resin non-foamed layers are laminated and integrated directly in this order by thermal fusion, and this long polystyrene-based resin laminated foam sheet is a take-up shaft. Continuously wound up.

  And the said polystyrene-type resin laminated foam sheet can be shape | molded in desired thermoformed goods, such as packaging containers, such as instant noodles, by general-purpose thermoforming methods, such as plug assist vacuum forming. When an instant noodle packaging container is thermoformed from a polystyrene resin laminated foam sheet, a flange is formed at the upper opening of the packaging container, and the opening of the packaging container is sealed using this flange. It is closed by the seat.

  When removing the sealing sheet from the opening of the packaging container and opening the opening of the packaging container, the sealing sheet is peeled off and removed from the flange portion of the packaging container. Since the low-density foam layer 11 and the high-density foam layer 12 of the polystyrene resin laminated foam sheet are firmly heat-sealed and integrated, the low-density foam layer 11 and the high-density foam are formed by the peeling force of the sealing sheet. The layer 12 does not delaminate between the two.

  In addition, the packaging container is stored in a transport storage box vertically and horizontally and transported to a predetermined place, but adjacent containers rub against each other due to vibration generated during transport, but the polystyrene-based resin laminate Since the low-density foam layer 11 and the high-density foam layer 12 of the foam sheet are firmly heat-sealed and integrated, the low-density foam layer 11 and the high-density foam layer 12 are separated from each other by the frictional force between the packaging containers. There is no delamination at.

  Since the polystyrene resin laminated foam sheet of the present invention is configured as described above, the polystyrene resin low density foam layer and the polystyrene resin high density foam layer are firmly heat-sealed and integrated, No delamination occurs.

  And, the polystyrene resin non-foamed layer is laminated and integrated on the polystyrene resin high density foam layer of the polystyrene resin laminated foam sheet, but the polystyrene resin high density foam layer is excellent in surface smoothness, Excellent surface smoothness of non-foamed polystyrene resin layer.

  Furthermore, since the high density foamed polystyrene resin layer has excellent mechanical strength, it can sufficiently withstand the pressure applied during printing, and can be printed beautifully on the non-foamed polystyrene resin layer. .

Example 1
As the first extruder 3, a first-stage single-screw extruder having a diameter of 115 mm, and a second-stage single-screw extruder having a diameter of 150 mm connected to the first-stage single-screw extruder, A tandem type extruder consisting of A single screw extruder with a diameter of 90 mm was prepared as the second extruder 4, while a single screw extruder with a diameter of 115 mm was prepared as the third extruder 5. Further, as the coextrusion die 6, there is prepared a confluence die 61 and an annular die 62 connected to the confluence die 61, and the first to third extruders 3 are added to the confluence die 61 of the coextrusion die 6. All of ~ 5 were connected.

  The first-stage single-screw extruder in the first extruder 3 has 100 parts by weight of polystyrene (trade name “G0002” manufactured by PS Japan Co., Ltd.) and a particle size of 5 to 15 μm as a foam regulator in polystyrene. A master batch (trade name “SMA-01”, manufactured by Kihara Kasei Co., Ltd., talc: about 40% by weight) with 1.5 parts by weight of talc and a dispersant added thereto was melt-kneaded at a resin temperature of 220 ° C. Then, 3.0 parts by weight of butane (normal butane: 65% by weight, isobutane: 35% by weight) as a foaming agent was press-fitted into the first stage single-screw extruder, and a polystyrene resin was melt-kneaded to achieve high foaming. Next, the high-expandable polystyrene melt-kneaded by the first-stage single-screw extruder is continuously supplied to the second-stage single-screw extruder and the resin temperature is 152 ° C. while melt-kneading. Cooling to It was.

  Furthermore, 100 parts by weight of polystyrene (trade name “GPPS, HRM18” manufactured by Toyo Styrene Co., Ltd.) and a talc having a particle diameter of 5 to 15 μm and a dispersing agent as a foam regulator are added to the second extruder 4. After feeding 3.4 parts by weight of the master batch (trade name “SMA-01” manufactured by Kihara Kasei Co., Ltd., talc: about 40% by weight) and melt-kneading at a resin temperature of 220 ° C., butane (normal butane: 65% by weight) %, Isobutane: 35 parts by weight) 1.9 parts by weight were press-fitted and melt-kneaded to form low-expandable polystyrene. The melt-kneaded low-expandable polystyrene was cooled to a resin temperature of 169 ° C.

  Further, impact-resistant polystyrene (trade name “HIPS, E641” manufactured by Toyo Styrene Co., Ltd., melt flow rate: 3.6 g / 10 min) is supplied to the third extruder 5 and melt-kneaded at a resin temperature of 220 ° C. Then, 1.0 part by weight of butane was press-fitted into the third extruder 5 with respect to 100 parts by weight of impact-resistant polystyrene, and further melted and kneaded, and then cooled to a resin temperature of 181 ° C.

  The high-expandable polystyrene from the first extruder 3 to the coextrusion die, the low-expandable polystyrene from the second extruder 4, and the impact-resistant polystyrene from the third extruder 5, respectively. The resin is extruded into the joining die 61 of the coextrusion die 6 to which 3 to 5 are connected, and these resins are joined in the joining die 61, and the low-foaming property is formed on the outer peripheral surface of the highly foamed polystyrene layer having a circular cross section. A foamable laminate comprising a polystyrene layer and an impact-resistant polystyrene coating layer laminated in this order, and the foamable laminate is continuously supplied to the annular die 62 of the coextrusion die 6 to form a cylindrical shape. Obtained by extruding and foaming a cylindrical foamable laminate from the tip opening of the annular die 62, extruding and foaming high-expandable polystyrene as a high-foamed layer, and extruding and foaming low-expandable polystyrene. The foamed layer is a low foam layer Te, high impact polystyrene unfoamed coating layer, low foaming layer and high foam layer to produce a laminated cylindrical foam in layers from the outside to the inside. The extrusion rate from the first extruder 3 was 130 kg / hour, the extrusion rate from the second extruder 4 was 43 kg / hour, and the extrusion rate from the third extruder 5 was 87 kg / hour. Further, the annular die 62 of the coextrusion die 6 had a tip surface 621a diameter of the inner die 621 of 215 mm and an opening clearance of 0.76 mm.

Then, the wind amount of 1 m ² per 0.48 m ³ / min the cylindrical foam on its outer peripheral surface gradually while spraying a 40 ° C. cooling air at a set air volume of 1 m ² per 0.21 m ³ on the inner peripheral surface After the diameter is expanded, the cylindrical foam is continuously supplied to a cylindrical cooling mandrel 7 (diameter: 670 mm) having a constant diameter to cool the cylindrical foam, and then the cylindrical foam is inserted in the extrusion direction. A low-density foam layer 11 formed by cutting a low-foamed layer on a low-density foam layer 11 formed by continuously cutting and cutting between peripheral surfaces, and a high-foamed layer, and non-foaming polystyrene A long polystyrene-based resin laminated foam sheet A in which the impact-resistant polystyrene non-foamed layer 2 formed by opening the coating layer is laminated and integrated in this order by heat fusion is manufactured, and this long polystyrene-based resin is produced. Winding shaft for laminated foam sheet A Rolled up continuously.

  Next, one month after the extrusion, the long polystyrene-based resin laminated foam sheet A was unwound, and a bowl-shaped molded product was thermoformed by plug-assisted vacuum forming. The molded product had an inside diameter of 13.5 cm, an outside diameter of 14.5 cm, a depth of 7.5 cm, and the impact-resistant polystyrene non-foamed layer 2 was on the outside.

(Example 2)
A master batch (trade name “SMA-01” manufactured by Kihara Kasei Co., Ltd., talc: about 40% by weight) made by adding talc having a particle diameter of 5 to 15 μm and a dispersing agent to polystyrene as a bubble adjusting agent is used as the first extruder 3. In the same manner as in Example 1 except that 1.1 parts by weight was supplied instead of 1.5 parts by weight, a polystyrene-based resin laminated foam sheet and a bowl-shaped molded product were obtained.

(Comparative Example 1)
A master batch (trade name “SMA-01” manufactured by Kihara Kasei Co., Ltd., talc: about 40% by weight) made by adding talc having a particle diameter of 5 to 15 μm and a dispersing agent as a foam regulator to polystyrene is used as the second extruder 4. In the same manner as in Example 1 except that 5.0 parts by weight was supplied instead of 3.4 parts by weight, a polystyrene resin laminated foam sheet and a bowl-shaped molded product were obtained.

(Comparative Example 2)
A master batch (trade name “SMA-01” manufactured by Kihara Kasei Co., Ltd., talc: about 40% by weight) made by adding talc having a particle diameter of 5 to 15 μm and a dispersing agent to polystyrene as a bubble adjusting agent is used as the first extruder 3. In the same manner as in Example 1 except that 0.65 part by weight was supplied instead of 1.5 part by weight, a polystyrene-based resin laminated foam sheet and a bowl-shaped molded product were obtained.

(Comparative Example 3)
A master batch (trade name “SMA-01” manufactured by Kihara Kasei Co., Ltd., talc: about 40% by weight) made by adding talc having a particle diameter of 5 to 15 μm and a dispersing agent to polystyrene as a bubble adjusting agent is used as the first extruder 3. 1.1 parts by weight instead of 1.5 parts by weight, a master batch (trade name “manufactured by Kihara Kasei Co., Ltd.”, in which talc having a particle size of 5 to 15 μm and a dispersant are added as polystyrene to the polystyrene. SMA-01 ", talc: about 40% by weight), in the same manner as in Example 1, except that 2.5 parts by weight instead of 3.4 parts by weight was supplied to the second extruder. And the molded product of the bowl shape was obtained.

(Comparative Example 4)
A master batch (trade name “SMA-01” manufactured by Kihara Kasei Co., Ltd., talc: about 40% by weight) made by adding talc having a particle diameter of 5 to 15 μm and a dispersing agent to polystyrene as a bubble adjusting agent is used as the first extruder 3. In addition to 1.5 parts by weight, 2.5 parts by weight of polystyrene was added, and a master batch prepared by adding talc having a particle diameter of 5 to 15 μm and a dispersant as a bubble regulator to the polystyrene (trade name “manufactured by Kihara Kasei Co., Ltd.” SMA-01 ", talc: about 40% by weight) is the same as in Example 1 except that 5.0 parts by weight is supplied to the second extruder instead of 3.4 parts by weight. And the molded product of the bowl shape was obtained.

  In the low-density foam layer and the high-density foam layer of the obtained polystyrene-based resin laminated foam sheet, the thickness, basis weight, density, and average cell diameter were measured as described above. The thickness of the foamed layer was measured, and the open cell ratio, peelability, printing characteristics and moldability of the polystyrene-based resin laminated foamed sheet were measured in the following manner, and the results are shown in Tables 1 and 2. In Table 1, the average cell diameter ratio is the ratio of the average cell diameter of the high-density foam layer to the average cell size of the low-density foam layer (average cell diameter of the high-density foam layer / average cell diameter of the low-density foam layer). Means.

(Peelability)
At any location of the polystyrene-based resin-laminated foam sheet, only the impact-resistant polystyrene sheet layer 2 is peeled from the high-density foam layer 12 over the entire length in the extrusion direction (MD) of 50 mm and the width direction (TD). “○” indicates that only the impact-resistant polystyrene sheet layer 2 can be peeled off, and “×” indicates that some delamination occurs between the low-density foam layer 11 and the high-density foam layer 12. As evaluated.

(Print characteristics)
Printing was performed on the outer peripheral surface of the bowl-shaped molded product using a curved surface printing machine. This print was visually observed, and a case where it was not faint was indicated as “◯”, and a case where it was faint was indicated as “X”.

(Formability)
When the obtained bowl-shaped molded product is visually observed, the molded product is torn, and no cracks or through holes are generated. The case where it was present was designated as “×”.

It is the schematic cross section which showed an example of the polystyrene-type resin laminated foam sheet of this invention. It is the schematic diagram which showed the manufacturing apparatus of the polystyrene-type resin laminated foam sheet. It is the longitudinal cross-sectional view which showed an example of the coextrusion die.

Explanation of symbols

1 Polystyrene resin foam sheet layer
11 High density foam layer
12 Low-density foam layer 2 Polystyrene resin non-foam layer 3 First extruder 4 Second extruder 5 Third extruder 6 Coextrusion die
61 Junction die
62 Ring die 7 Mandrel A Polystyrene resin laminated foam sheet

Claims (5)

A polystyrene-based resin laminated foam sheet produced by coextrusion foaming, on a polystyrene-based resin low-density foam layer having a density of 0.07 to 0.17 g / cm ³ , a density of 0.18 to 0.45 g / A polystyrene resin high-density foam layer of cm ³ and a polystyrene resin non-foamed layer are laminated and integrated in this order, and the average cell diameter of the polystyrene resin low-density foam layer is 200 to 500 μm, The polystyrene-based resin high-density foam layer has an average cell diameter of 70 to 180 μm, and the ratio of the average cell diameter of the polystyrene-based resin high-density foam layer to the average cell size of the polystyrene-based resin low-density foam layer (polystyrene resin). Polystyrene characterized in that the average cell diameter of the high-density foam layer / average cell diameter of the polystyrene resin low-density foam layer) is 0.33 to 0.6. Resin laminate foam sheet. 2. The polystyrene-based resin laminated foam sheet according to claim 1, wherein an open cell ratio of the entire polystyrene-based resin laminated foam sheet is less than 20%. A container obtained by thermoforming the polystyrene-based resin laminated foam sheet according to claim 1 or 2. The polystyrene resin is supplied to the first extruder and melt kneaded in the presence of the foaming agent and the air conditioner, and the polystyrene resin is supplied to the second extruder and in the presence of the foaming agent and the air conditioner. Melt-kneaded, and polystyrene resin is supplied to the third extruder, melt-kneaded, and from the co-extrusion die connecting the first to third extruders, A foamed layer, a low-foamed layer extruded from the second extruder, and a non-foamed layer extruded from the third extruder are extruded and foamed into layers in this order to produce a cylindrical foam. After the cylindrical foam is expanded and supplied to a mandrel and cooled, the cylindrical foam is continuously cut in the extrusion direction to open the high foam layer, and the density is 0. .07~0.15g / cm ³ of the polystyrene-based resin On the low-density foam layer, the low-polystyrene resin density foam layer of the foamed layer density made to open up the 0.16~0.45g / cm ^3, and, polystyrene resin non made to open up the non-foamed layer The foam layer is laminated and integrated in this order. The polystyrene resin low density foam layer has an average cell diameter of 200 to 500 μm, and the polystyrene resin high density foam layer has an average cell diameter of 70 to 180 μm. Yes, the ratio of the average cell diameter of the polystyrene resin high density foam layer to the average cell diameter of the polystyrene resin low density foam layer (average cell diameter of polystyrene resin high density foam layer / polystyrene resin low density foam layer Production of polystyrene-based resin laminated foam sheet having an average cell diameter) of 0.33 to 0.6 Method. The difference between the resin temperature when extruding the polystyrene resin from the first extruder from the coextrusion die and the resin temperature when extruding the polystyrene resin from the second extruder from the coextrusion die is less than 23 ° C. It is, The manufacturing method of the polystyrene-type resin laminated foam sheet of Claim 4 characterized by the above-mentioned.

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