JP2007320264A - Extruded multilayer foam sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably provide a foam sheet having the property of a continuous air bubble foam sheet and also being excellent in surface property in an extruded foam sheet obtained using an extrusion foaming process. <P>SOLUTION: The continuous air bubble foam sheet excellent in surface property and having an stably uniform performance can be prepared by making the foam sheet using different type of substrate resin having a different thermal characteristic into a multilayer foam sheet integrally laminated with an independent air bubble layer on the outside and a continuous air bubble layer on the center part using a co-extrusion process. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an extruded foam sheet used for buildings, vehicle interior materials, floors or walls, heat insulating materials, food packaging materials, and the like.

  Conventionally, there are many sheets obtained by laminating a plurality of foam layers by coextrusion. Co-extrusion is a method in which an extruded resin is fused by passing it through a converging die to form a sheet. For example, as a method of obtaining a high strength tray container, a method of laminating sheets having different foaming densities by coextrusion (Patent Document 1), in order to obtain a packaging material having a low open cell ratio and excellent mechanical properties, and having a beautiful surface appearance In order to obtain a packaging container in which foamed sheets having different cell diameters are laminated by coextrusion (Patent Document 2), compatibility between rigidity and buffering property, and excellent moldability and water resistance, polystyrene-based resin foaming which is a closed cell layer A laminated sheet obtained by coextrusion of a mixed resin foam layer of a polystyrene resin and a polyethylene resin having an open cell ratio of 40% or more (Patent Document 3), etc. is widely used in the market It has become. However, in the laminated sheet as described above, the base foam layer is composed of cells having closed cells.

  On the other hand, foams in which the base foam layer is composed of open-celled cells are also widely used due to the required qualities such as air permeability, sound absorption, water absorption, water retention, flexibility, buffering property, and microorganism supportability. There are almost no cases where the foam having both surface properties is stably obtained by the extrusion foaming method.

  Moreover, it is not sufficient to suppress the foaming agent dissipation from the surface and improve the surface property by blowing air or the like onto the surface of the foamed sheet after the foamed sheet is discharged from the extrusion die.

As shown in Patent Document 4, there is a method of obtaining a polyphenylene ether-based resin extruded foam sheet in which the surface layer is a closed cell layer and the center layer is an open cell layer by adjusting the extrusion temperature condition, not the coextrusion method, Since it is necessary to control extrusion foaming conditions in a very narrow temperature range, it is difficult to stably produce a sheet having uniform performance.
JP 2000-25088 A JP-A-6-23895 JP 2001-26079 A JP 2005-88873 A

  The present invention is an extruded foam sheet obtained by using an extrusion foaming method, the breathability unique to the open-cell foamed sheet, the sound absorption, the mold determination and terminal crushability during molding, water absorption, water retention, flexibility, An object of the present invention is to stably provide a foam sheet having excellent surface properties while having performances such as buffering properties and microbial supportability.

  In the extrusion foaming method, it is not possible to produce an open-cell foamed sheet having excellent surface properties and stable uniform performance. The foaming agent escapes from the surface during the process of forming foamed cells by extruding the resin into the atmosphere. This is thought to be due to scattering and the cells breaking and crushing from the surface layer.

  Therefore, as a result of intensive studies to solve the above problems, the present inventors made an extruded multilayer foam sheet in which a closed cell layer is laminated on the outside and an open cell layer is laminated on the center using a coextrusion method. Thus, it has been found that an open-cell foamed sheet having excellent surface properties and uniform performance can be stably obtained. In order to form the said structure, although it considered many as a resin composition, it discovered that co-extrusion of the foam sheet which consists of a different resin composition was effective.

That is,
[1] Consisting of a thermoplastic resin that is different from the thermoplastic resin constituting the first foamed layer by coextrusion on both sides of the first foamed layer having an open cell ratio of 60 to 90%. An extruded multi-layer foam sheet, characterized in that it is formed by laminating a second foam layer having an open cell ratio of less than 40%,
[2] The melting point or glass transition temperature of the thermoplastic resin constituting the first foamed layer is lower than the melting point or glass transition temperature of the thermoplastic resin constituting the second foamed layer, [1] Extruded multilayer foam sheet,
[3] The melting point or glass transition temperature of the thermoplastic resin constituting the first foam layer is 10 ° C. or more lower than the melting point or glass transition temperature of the thermoplastic resin constituting the second foam layer. The extruded multilayer foam sheet according to Item 1 or 2, the extruded multilayer foam sheet according to Item [1] or [2], and
[4] The extruded multilayer foam sheet according to any one of [1] to [3], wherein the thermoplastic resin constituting the foam layer is a modified polyphenylene ether.

  In extruded foam sheets obtained using the extrusion foaming method, for example, when molding and processing interior materials for automobiles, etc., the mold determinism indicating whether the material is processed according to the design dimensions, and each interior material It is possible to obtain a foam sheet having a stable and excellent surface property while having the performance of an open-cell foam sheet such as a terminal crushing property necessary for connecting materials (for example, a ceiling material and a pillar) with a good appearance. it can.

  As shown in FIG. 1, the extruded multilayer foam sheet of the present invention is made of a thermoplastic resin and has heat different from the composition of the first foam layer on both sides of the first foam layer having an open cell ratio of 60 to 90%. A second foamed layer made of a plastic resin and having an open cell ratio of less than 40% is laminated by a coextrusion method. FIG. 1 is a cross-sectional view showing an example of an extruded multilayer foam sheet according to the present invention, wherein 1 is a first foam layer, 2 is a second foam layer, and 3 is a multilayer foam sheet.

  As the base resin constituting the foamed layer of the extruded foam sheet of the present invention, any thermoplastic resin, that is, any plastic that can be softened reversibly at high temperatures can be used. Specific examples of the thermoplastic resin include, for example, polyolefin resins such as polyethylene and polypropylene, polyamide resins, polyester resins such as polybutylene terephthalate (PBT) and polyethylene terephthalate (PET), vinyl chloride, polyphenylene ether (PPE), and modified PPE. PPE resins such as styrene resins, styrene resins such as polystyrene and heat-resistant polystyrene, acrylic resins, acrylonitrile / butadiene / styrene resins (ABS), polycarbonate, and the like. These resins may be used alone or in combination of two or more.

Among these resins, polyolefin resins such as polyethylene and polypropylene, styrene resins such as polystyrene and heat-resistant polystyrene, and PPE resins such as modified PPE resins are preferable.
Furthermore, a modified PPE resin is particularly preferred from the viewpoints of excellent quality such as heat resistance and rigidity, processability and easy production. Examples of the modified PPE resin include a mixture of a PPE resin and a PS resin, and a styrene / phenylene ether copolymer such as a graft copolymer of a styrene monomer to PPE. The PPE resin is low in cost, and by changing its mixing ratio, it is easy to obtain a resin with excellent quality such as heat resistance, rigidity, etc., and having processability changed. A mixed resin with a PS resin is preferable.

  Specific examples of the PPE resin in the modified PPE resin include, for example, poly (2,6-dimethylphenylene-1,4-ether), poly (2-methyl-6-ethylphenylene-4-ether), and poly (2,6-diethylphenylene-1,4-ether), poly (2,6-diethylphenylene-1,4-ether), poly (2-methyl-6-n-propylphenylene-1,4-ether) Poly (2-methyl-6-n-butylphenylene-1,4-ether), poly (2-methyl-6-chlorophenylene-1,4-ether), poly (2-methyl-6-bromophenylene- 1,4-ether), poly (2-ethyl-6-chlorophenylene-1,4-ether), and the like. These may be used alone or in combination of two or more.

  Examples of PS resins that form mixed resins with PPE resins in modified PPE resins include styrene or derivatives thereof, such as α-methylstyrene, 2,4-dimethylstyrene, monochlorostyrene, dichlorostyrene, p-methyl. Examples thereof include resins mainly composed of styrene, ethyl styrene and the like. Accordingly, the PS-based resin is not limited to a homopolymer composed of only styrene or a styrene derivative, but may be a copolymer made by copolymerizing with another monomer.

  Specific examples of the styrene monomer that is polymerized on the PPE resin, preferably graft-polymerized, include, for example, styrene, α-methylstyrene, 2,4-dimethylstyrene, monochlorostyrene, dichlorostyrene, p-methyl. Examples include styrene and ethylstyrene. Among these, styrene is preferable in terms of versatility and cost. These may be used alone or in combination of two or more.

  In the present invention, the thermoplastic resin constituting the first foam layer and the second foam layer (hereinafter sometimes referred to as “base resin”) is separate, but has a melting point and / or a glass transition temperature. If the thermal properties are different, the material resin itself may be of a different type, and even if it is the same, means for changing the molecular weight, the resin mixing ratio, and the like may be used. For example, in the case of a modified PPE resin, since the compatibility of the PPE resin and the PS resin at the time of melting is high, the glass transition temperature can be changed only by changing the mixing ratio.

  As the thermoplastic resin constituting the first foam layer in the present invention, it is possible to use a resin whose melting point and / or glass transition temperature is lower than those of the thermoplastic resin constituting the second foam layer. The extrusion foaming conditions can be set without greatly differing, and it is preferable in that an open-cell foamed sheet having good surface properties can be obtained. Further, the melting point and / or the glass transition temperature of the thermoplastic resin constituting the first foam layer may be lower by 10 ° C. than those of the thermoplastic resin constituting the second foam layer. It is more preferable because the foaming conditions can be set without greatly different, and the open-cell foamed sheet having a good surface property can be obtained with a higher open-cell ratio of the first foam layer.

  In the present invention, from the viewpoint of processability and productivity, the thermoplastic resin constituting the first foam layer and the thermoplastic resin constituting the second foam layer are different in the mixing ratio of PPE resin / PS resin. It is preferable to use modified PPE.

  In the present invention, when a modified PPE resin is used as the thermoplastic resin (base resin) used for the extruded multilayer foam sheet 1, the PPE resin is 25 to 70% by weight and the PS resin is 75 to 30% by weight. %, More preferably 35 to 60% by weight of PPE resin and 65 to 40% by weight of PS resin. If the PPE resin in the modified PPE resin is less than 25% by weight, the heat resistance tends to be inferior. If the PPE resin exceeds 70% by weight, the viscosity at the time of heat flow increases and foam molding becomes difficult. Tend.

  In the present invention, in order to lower the glass transition temperature of the modified PPE resin constituting the first foamed layer by 10 ° C. or more than the glass transition temperature of the modified PPE resin constituting the second foamed layer, specifically, The PPE ratio in the modified PPE resin constituting the first foam layer is preferably 10% or more smaller than that of the second foam layer.

  In the present invention, the first foamed layer is an open-cell foamed cell, and the second foamed layer laminated on both sides thereof is a closed-cell foamed cell. By covering the surface of the first foam layer with a layer having a good surface (closed cell layer) by the second foam layer, the surface property of the extruded multilayer foam sheet having the performance of an open-cell foam sheet can be improved. . Moreover, since it becomes a 3 layer sandwich structure, the bending rigidity of an extrusion multilayer foamed sheet can also be increased.

  The open cell ratio (1-closed cell ratio) of the first foam layer in the extruded multilayer foam sheet of the present invention is preferably 60 to 90%, more preferably 70 to 90%. When the open cell ratio of the first foam layer is less than 60%, the performance as the open cell layer may not be exhibited. On the other hand, if it is larger than 90%, the mechanical strength tends to decrease.

  The closed cell ratio of the second foam layer in the extruded multilayer foam sheet of the present invention is preferably 70% or more, and more preferably 80% or more. When the closed cell ratio of the second foam layer is lower than 70%, the heat insulation and rigidity are inferior, and good surface properties may not be obtained.

  In the present invention, the closed cell ratio is a ratio of the cells in which the foamed cells are completely isolated from the other foamed cells by the cell membrane to the total foamed cells, and is a multi-pynometer (manufactured by Beckman Co., Ltd.). ) And measured according to ASTM D-2859. Further, the open cell ratio is a value obtained from 100 (%) − closed cell ratio (%) using the value of the closed cell ratio (%).

  The thickness of the first foam layer in the extruded multilayer foam sheet of the present invention is preferably 1.5 to 8.0 mm, and more preferably 2.5 to 4.0 mm. If the thickness of the first foamed layer is less than 1.5 mm, the function as an open cell layer tends to be hardly exhibited. If the thickness is greater than 8.0 mm, molding becomes difficult or the volume becomes large and transportation, etc. Productivity tends to decrease.

  On the other hand, the thickness per layer of the second foam layer in the extruded multilayer foam sheet of the present invention is preferably 0.2 mm to 2.0 mm, and more preferably 0.3 mm to 1.0 mm. If the thickness per layer of the second foamed layer is less than 0.2 mm, stable supply as a foamed sheet may be difficult, or a desired surface property may not be obtained. In developing the performance of the bubble layer, there is a tendency to become an obstacle in many cases.

  The total thickness of the extruded multilayer foam sheet of the present invention is preferably 2.0 to 10.0 mm, more preferably 2.5 to 6.0 mm.

Basis weight of the first foam layer in the extrusion multilayer foamed sheet of the present invention is preferably ^{100~300g / m 2, 120~250g / m} 2 is more preferable. When the basis weight of the first foamed layer is smaller than 100 g / m ² , the rigidity tends to be insufficient, and when it exceeds 300 g / m ² , the lightness tends to decrease.

On the other hand, the basis weight of the second foam layer in the extruded multilayer foam sheet of the present invention is preferably 30 to 100 g / m ² . When the basis weight of the second foamed layer is smaller than 30 g / m ^2, there may be cases where sufficient surface properties cannot be stably provided. When the basis weight exceeds 100 g / m ^{2, this} may hinder the performance of the open cell layer. Tend to increase.

  The expansion ratio in the extruded multilayer foam sheet of the present invention is preferably 3 to 25 times, more preferably 5 to 15 times for both the first foam layer and the second foam layer. When the foaming ratio of the first foamed layer or the second foamed layer is lower than 3 times, the flexibility is inferior, damage due to bending or the like tends to occur, and the effect of weight reduction tends to be reduced. On the other hand, when the expansion ratio exceeds 25 times, the strength decreases, and the moldability tends to decrease due to difficulty in heating to the center.

  The extruded multilayer foam sheet in the present invention is preferably obtained by extrusion foam molding using a hydrocarbon-based foaming agent as a foaming agent from the viewpoint of compatibility with the resin used, foamability, and the like.

  The hydrocarbon-based foaming agent used when obtaining the extruded multilayer foamed sheet 3 is preferably a volatile foaming agent, and specific examples include ethane, propane, butane, pentane and the like. Especially, the hydrocarbon type foaming agent whose Kauri butanol value (KB value) which shows the solubility of a foaming agent is 20-50 is preferable. In addition, it is also possible to use those having the above range by appropriately mixing two or more types having a KB value higher and lower than this range.

  In the present invention, among the specific examples of the foaming agent, butane is suitable in that the moderate solubility of the foaming agent and the dissipative property of the foaming agent are small, and the change in foamability with the aging of the foamed layer is small. preferable. The butane may be isobutane, normal butane, or a mixture of isobutane and normal butane.

  The press-fitting amount of the carbonized foaming agent at the time of extrusion foaming in the present invention is preferably 2.0 to 6.0 parts by weight, and 2.5 to 4.5 parts by weight with respect to 100 parts by weight of the constituent resin. Is more preferable. When the amount of the foaming agent injected is less than 2.0 parts by weight, the foaming power for the resin tends to be too small and a good open cell foam cell or closed cell foam cell tends to be obtained, exceeding 5.0 parts by weight. And extrusion foaming becomes unstable, and the surface roughness of the foam sheet tends to occur greatly in the second foam layer.

  The method of laminating the first foam layer 1 and the second foam layer 2 in the extruded multilayer foam sheet 3 of the present invention is performed by a co-extrusion method. That is, the molten resin mixture for forming the first foamed layer 1 and the molten resin mixture for forming the second foamed layer 3 are laminated by a method in which they are fused in a die and integrally extruded into a sheet shape and foamed. .

  By adopting the co-extrusion method as the method of laminating the first foam layer and the second foam layer, the foaming step and the laminating step are performed continuously at the same time. Obtainable.

  The method for obtaining an extruded multilayer foamed sheet 3 comprising two or more layers by the coextrusion method includes (i) lamination by laminating each layer in a die using a flat die and then coextrusion into a plate shape. (Ii) An extruded multilayer foam sheet obtained by laminating each layer in a die using a circular die and then co-extruding it into a cylindrical shape, and then cutting the cylindrical foam and stacking the layers. (Iii) While coextruding into a cylindrical shape using an annular die, and while the inner surface of the foam is in an adhesive state, the foam is sandwiched using a rolling roll, and the inner surface is There is a method in which the foamed sheet 3 is laminated by pressure bonding. Among these coextrusion methods, (ii) a method of obtaining a foamed sheet 1 by coextrusion into a cylindrical shape using an annular die and then cutting the cylindrical foam to obtain a foamed sheet 1, although depending on the application, is a wide extrusion multilayer foaming. It is preferable from the viewpoint that the sheet 1 can be easily manufactured.

  The extruded multilayer foam sheet used in the present invention can be produced, for example, as follows.

  That is, what mixed the various additives as needed with respect to the base resin constituting the first foamed layer 1 is a resin temperature of 150 to 400 ° C. using the first stage extruder of the first extruder. Melt and knead. Next, 2.0 to 6.0 parts by weight of a foaming agent is injected into 100 parts by weight of the base resin into an extruder under high temperature and high pressure (resin temperature 150 to 400 ° C. and resin pressure 3 to 50 MPa). After that, the heat-resistant resin mixed with the foaming agent and introduced into the molten state is introduced into the second stage extruder of the first extruder, and the resin temperature is adjusted to the optimum foaming temperature range (150 to 300 ° C.). Introduce into the inner channel.

  Here, in the extrusion step, in order to increase the open cell ratio of the first foam layer 1, for example, (i) temperature conditions in the extruder, (ii) amount of foaming agent, and (iii) low heat resistance ( The mixing amount of the resin having a low Tg may be adjusted. More specifically, regarding (i), by setting the cooling temperature in the second-stage extruder to the high temperature side, an open cell layer can be provided as a whole in the thickness direction of the sheet. With regard to (ii), the foaming agent press-fitting amount may be set to about 1.5 to 2.0 times the normal use amount with respect to 100 parts by weight of the base resin. However, if the foaming agent press-fitting amount is too large, plasticization proceeds and shear heat generation between the polymers is less likely to occur, so that the open cell ratio may decrease. Regarding (iii), the amount of the resin having low heat resistance may be increased. For example, when the base resin is a modified PPE resin, the mixing ratio of polystyrene is increased, and when the base resin is a heat-resistant polystyrene resin, high impact polystyrene (hereinafter sometimes referred to as HIPS). What is necessary is just to mix 1-20 weight part with respect to 100 weight part of heat-resistant polystyrene resins. These (i) to (iii) may be combined.

  On the other hand, the base resin constituting the second foam layer 2 is introduced into the flow path in the die under an extrusion condition that increases the closed cell ratio using an extruder different from the first foam layer. In this case, in the present invention, since the melting point or glass transition temperature of the base resin of the first foam layer is lower than those of the second foam layer, the first foam is used as the extrusion condition of the second foam layer. Even when the same conditions as the layer extrusion conditions are employed, a second foam layer having a high closed cell ratio can be obtained. In order to further increase the closed cell ratio of the second foam layer, for example, compared to the extrusion conditions in the first foam layer, for example, the amount of foaming agent press-fitted is reduced, or the cooling set temperature in the second stage extruder It is also possible to perform operations such as lowering or increasing the slip clearance at the die.

  After integrating the base resin constituting the second foamed layer in the molten state on both sides of the base resin constituting the first foamed layer in the molten state in the flow path in the die, from the annular die , Extruded into a low pressure zone (usually in the atmosphere) and foamed. Then, it is manufactured by a method such as winding it after it is formed into a sheet shape by taking it at a speed of 0.5 to 40 m / min while being brought into contact with a mandrel (cylindrical cooling cylinder), cut, and cut. it can.

  In addition, the base resin constituting the extruded multilayer foam sheet of the present invention includes various additives such as a nucleating agent, an antioxidant, and a thermal stability, as long as the object of the present invention is not significantly impaired. An agent, an antistatic agent, a conductivity imparting agent, a weathering agent, an ultraviolet absorber, a flame retardant, an inorganic filler, and the like can be added.

  In the extruded multilayer foamed sheet 3 of the present invention, a non-foamed layer and / or a design material is provided on at least one surface of the second foamed layer with or without an adhesive layer in accordance with the use and required quality. You may laminate.

  As the resin used for the non-foamed layer in the present invention, a resin having the same composition as described in the foamed sheet can be used. In the present invention, when a modified PPE resin is used as the base resin for the second foam layer, from the viewpoint of adhesiveness, the thermoplastic resin constituting the non-foam layer may be a modified PPE resin or a heat-resistant PS resin. Is preferred.

  In the present invention, when a modified PPE resin is used as the non-foamed layer, the same materials as those described for the foamed sheet can be used. In addition to these, a rubber-based resin, specifically, a styrene-butadiene copolymer represented by high impact polystyrene (HIPS) may be mixed for improving impact resistance.

In the present invention, when a heat-resistant PS resin is used as the non-foamed layer, examples of the heat-resistant PS resin used include a copolymer of styrene or a derivative thereof and another monomer. As a monomer having an effect of improving heat resistance and copolymerizable with styrene or a derivative thereof, for example, an unsaturated carboxylic acid such as maleic acid, fumaric acid, acrylic acid, methacrylic acid, itaconic acid or a derivative thereof And nitrile compounds such as acid anhydrides, acrylonitrile, methacrylonitrile, and derivatives thereof. These may be used alone or in combination of two or more.
In addition, when polymerizing styrene or a styrene derivative, a polymer obtained by adding synthetic rubber or rubber latex, an unsaturated carboxylic acid such as maleic acid, fumaric acid, acrylic acid, methacrylic acid, itaconic acid or the like Derivatives and acid anhydrides thereof, and copolymers with nitrile compounds such as acrylonitrile and methacrylonitrile may also be used. Among these, styrene-maleic anhydride copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, acrylonitrile-butadiene-styrene copolymer are the heat resistance improving effect, versatility and This is preferable from the viewpoint of cost.
The heat resistant PS resin may be used alone or in combination of two or more.

  In the present invention, the heat-resistant PS resin may be blended with other thermoplastic resins. Examples of the thermoplastic resin to be blended include polystyrene, HIPS, polycarbonate, polyester, polyamide, and copolymers thereof. Etc. Among these, HIPS is preferable from the viewpoints of versatility, uniform dispersion, a large effect of improving the impact resistance of the non-foamed layer, and cost. A known HIPS can be used, and the content of the rubber component is usually 1 to 15% by weight.

Basis weight of the non-foamed layer in the present invention is preferably ^{50~300g / m 2, 90~120g / m} 2 is more preferable. When the basis weight of the non-foamed layer is lower than 50 g / m ² , the strength, rigidity, heat resistance and the like tend to decrease. When the basis weight is higher than 300 g / m ² , the moldability of the foam laminated sheet tends to be inferior. is there.

The material used for the design material in the present invention is a woven fabric, non-woven fabric, knitted fabric, felt, pad material, flexible foam, or a laminate of them, and has a design property. Anything can be used. Design material, in consideration of quality and cost, preferably has a basis weight of 100 to 300 g / m ^2, and more preferably has a basis weight of 120~200g / m ^2. When the basis weight of the skin material is less than 100 g / m ^2, there is a tendency that a sufficient feel as an interior material cannot be obtained. On the other hand, if the basis weight of the skin material exceeds 300 g / m ² , the molding distortion of the skin material tends to affect thermal deformation.

  Examples of the adhesive layer include thermoplastic adhesives such as vinyl acetate, cellulose, polyamide, and polyvinyl acetate; thermosetting adhesives such as urethane, melamine, phenol, epoxy, and acrylic. Rubber adhesives such as chloroprene rubber, nitrile rubber, and silicone rubber; natural product adhesives such as starch, protein, and natural rubber; polyolefin, modified polyolefin, ethylene-vinyl acetate copolymer resin, Hot melt adhesives such as polyamide, polyester, thermoplastic rubber, styrene-butadiene copolymer, styrene-isoprene copolymer; PS resin latex, styrene-butadiene (SB) resin latex, carboxy-modified SB Water-soluble emulsions such as resin latexes.

  In the case of undergoing a molding process for shaping the extruded multilayer foam sheet of the present invention, for example in the case of automobile interior materials, the primary foam laminate sheet is clamped in the center of a heating furnace having upper and lower heaters. After being heated to a temperature suitable for molding (for example, the surface temperature of the foamed laminated sheet is 135 to 155 ° C.) and softening so as to be deformable, it is press-cooled with a temperature-controlled mold and applied. The method of shaping is mentioned. Specific examples of molding methods include plug molding, free drawing molding, plug and ridge molding, ridge molding, matched molding, straight molding, drape molding, reverse draw molding, air slip molding, plug assist molding. Examples of the method include plug assist reverse draw molding.

  Next, although the foam sheet regarding this invention is demonstrated based on an Example and a comparative example, this invention is not limited only to this Example.

  The evaluation method of the obtained foamed sheet is shown below.

(Closed cell rate)
In the obtained primary foamed sheet, the part that is the first foamed layer and the part that is the second foamed layer are cut out with a razor and measured according to ASTM D-2859 using a multi-pynometer (manufactured by Beckman). The closed cell ratio of each layer was determined.

(Open cell ratio)
The value of 1-closed cell rate was defined as the open cell rate.

(Foaming ratio)
In the obtained primary foamed sheet, a portion that is clearly the first foam layer and a portion that is the second foam layer are cut out with a razor, and the density df of each is measured in accordance with JIS K 7222. The density dp of the modified PPE-based resin was measured according to JIS K 7112, and calculated by the formula: foaming ratio = dp / df.

(Thickness of foam layer and molded body)
For the obtained primary foamed sheet and molded product, using a magnifying loupe (manufactured by PEAK, zoom scale magnifying glass, magnification 15 times), the thickness at any 20 locations in the width direction was measured and measured. The average value was calculated.

(Weight)
In the obtained primary foamed sheet, test pieces having a size of 100 mm × 100 mm were cut out from arbitrary five locations in the extrusion direction, and after measuring their weights, an average value was calculated and converted to 1 m ^2. The basis weight of the entire sheet was used. On the other hand, the discharge at the time of independent operation of each extruder (the amount of resin discharged from the extruder per unit <unit: kg / hr>) is measured, and the basis weight of each layer is determined from the ratio and the basis weight of the entire sheet. Calculated.

(Surface property)
The surface state of the obtained primary foamed sheet was visually observed and evaluated in the following three stages.
○: Beautiful surface. It is glossy, has small unevenness, and has no skin-like resin mass on the surface.
Δ: Concavities and convexities are small, and the skin-like resin mass is fine.
X: A large lump-like resin lump is distributed on the surface, and the unevenness is large.

(Terminal crushability in molding)
From the obtained primary foamed sheet, a sample of 430 mm × 430 mm was cut out, and heated with an infrared heater for 30 seconds using a compressed air vacuum forming machine (manufactured by Asano Laboratory Co., Ltd.), the sheet surface temperature was 145 ° C. did. Next, after 3 seconds from the end of heating, it was sandwiched for 15 seconds between two parallel molds (430 mm square flat plate) and finally crushed until a gap of 1.5 mm (mold clearance) was obtained. The thickness of the sample taken out was measured at five locations in the sample width direction, and the average value was taken as the thickness.
The ratio of the average thickness of the sample after removal and the mold clearance of 1.5 mm was taken to evaluate the terminal crushability during the molding process. When the obtained primary foamed sheet exhibits the characteristics of the open cell layer, the sample thickness does not return much after being taken out of the mold, whereas when it exhibits the characteristics of the closed cell layer, The return tends to be large.
○: The ratio between the average thickness of the sample after removal and the mold clearance is less than 1.3.
(Triangle | delta): Ratio of the average thickness of a sample after taking-out and a mold clearance is 1.3 or more.

Example 1
As the first foam layer, 28.6 parts by weight of PPE resin (manufactured by GE Japan, EFN-4230) and PS resin (manufactured by PS Japan Co., Ltd.) so as to be 20% by weight of PPE resin component and 80% by weight of PS resin component. G8102) A mixture obtained by stirring and mixing 71.4 parts by weight and 0.32 parts by weight of talc with a ribbon blender is supplied to a barrel diameter φ65-90 mm tandem extruder, and the first stage so that the resin temperature becomes 270 ° C. After being melted in an extruder (φ65 mm), a hydrocarbon-based blowing agent containing iso-butane as a main component (iso-butane / n-butane = 85/15% by weight) with respect to 100 parts by weight of the resin as a blowing agent ) 4.0 parts by weight of the mixture was mixed. Then, it cooled in the 2nd stage extruder (phi90mm), the resin temperature was adjusted to 190 degreeC (tandem extruder A), and it flowed into the merge die.
On the other hand, by using an extruder (tandem extruders B and C) different from the above-mentioned extruder as the second foam layer, PPE resin (Japan) is obtained so that the PPE resin component is 40% by weight and the PS resin component is 60% by weight. GE, EFN-4230) 57.1 parts by weight, PS resin (PS Japan, G8102) 42.9 parts by weight and talc 0.32 parts by weight were mixed in a ribbon blender. It is supplied to a φ65-90 mm tandem extruder and melted in a first stage extruder (φ65 mm) so that the resin temperature becomes 270 ° C. Then, iso-butane is mainly used as a blowing agent for 100 parts by weight of the resin. The hydrocarbon-based foaming agent (iso-butane / n-butane = 85/15 wt%) as a component was 4.0 parts by weight mixed by pressing. Then, it cooled in the 2nd stage extruder (phi90mm), the resin temperature was adjusted to 190 degreeC, and it laminated | stacked in the form which flows in into a confluence | merging die and pinches | interposes a 1st foam layer.
As described above, the laminated sheet of the first foamed layer and the second foamed layer joined by the joining die flows into a die slip mold having a diameter of φ75 mm, and is extruded under the atmospheric pressure from the slit (die slip clearance). Molding was performed using a mandrel having a length of 200 mm and a main body length of 200 mm and temperature-controlled at 15 ° C. by circulating water. Further, while taking up the sheet, a cylindrical foam was obtained, and this was cut open with a cutter to obtain a primary foam sheet having a width of 626 mm.
Various evaluations are performed on the obtained primary foamed sheet, and the results are shown in Table 1.

(Comparative Example 1)
As the first foamed layer, 57.1 parts by weight of PPE resin (manufactured by GE Japan, EFN-4230) and PS resin (manufactured by PS Japan, so as to be 40% by weight of PPE resin component and 60% by weight of PS resin component) G8102) The following foamed sheet was obtained in the same manner as in Example 1 except that 42.9 parts by weight and 0.32 parts by weight of talc were blended.
Various evaluations are performed on the obtained primary foamed sheet, and the results are shown in Table 1.

(Comparative Example 2)
As the first foamed layer, 57.1 parts by weight of PPE resin (manufactured by GE Japan, EFN-4230) and PS resin (manufactured by PS Japan, so as to be 40% by weight of PPE resin component and 60% by weight of PS resin component) G8102) Example except that 42.9 parts by weight of talc and 0.32 part by weight of talc were blended and cooled in the second stage extruder (φ90 mm) in tandem extruder A to adjust the resin temperature to 200 ° C. In the same manner as in Example 1, a primary foamed sheet was obtained.
Various evaluations are performed on the obtained primary foamed sheet, and the results are shown in Table 1.

Sectional drawing which shows an example of the foam sheet of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st foam layer 2 2nd foam layer 3 Extrusion multilayer foam sheet

Claims (4)

  It is made of a thermoplastic resin, and is formed of a thermoplastic resin different from the thermoplastic resin constituting the first foamed layer by coextrusion on both sides of the first foamed layer having an open cell ratio of 60 to 90%. An extruded multilayer foam sheet comprising a second foam layer having a rate of less than 40%.   The extruded multilayer according to claim 1, wherein a melting point or glass transition temperature of the thermoplastic resin constituting the first foam layer is lower than a melting point or glass transition temperature of the thermoplastic resin constituting the second foam layer. Foam sheet.   The melting point or glass transition temperature of the thermoplastic resin constituting the first foam layer is 10 ° C or lower than the melting point or glass transition temperature of the thermoplastic resin constituting the second foam layer, or 3. The extruded multilayer foam sheet according to 2.   The extruded multilayer foam sheet according to any one of claims 1 to 3, wherein the thermoplastic resin constituting the foam layer is a modified polyphenylene ether.

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