JP4195591B2 - Polyethylene resin laminated foam board - Google Patents

Description

【００３３】
実施例２〜３、比較例１〜３
表１に示すように芯層の厚み、表層の厚み、見掛け密度、引張弾性率の異なるものを用いた他は実施例１と同様にして積層発泡板を得た。得られた積層発泡板の曲げ弾性率Ａ、厚み方向への２５％圧縮強さＢ、及び曲げ弾性率と厚み方向への２５％圧縮強さとの比（Ａ／Ｂ）の値、積層発泡板の軽量性、自立性、剛性を評価した結果を表１にあわせて示す。尚、比較例２、３は表層を積層していない単層の発泡体であるが、比較例２、３の発泡体の曲げ弾性率、厚み方向への２５％圧縮強さ、曲げ弾性率と厚み方向への２５％圧縮強さの比の値を、便宜上表１の積層発泡板の相当する欄に記載する。
【００３４】
表１における自立性、軽量性、剛性の評価は、縦１２００ｍｍ、幅１０００ｍｍ、厚みは発泡性成形品厚みのトラックボード形状の板材を実施例及び比較例にて得られた成形品から切り出して以下の通り判断した。
自立性：縦方向を上下にしてトラックボード形状の板材を立てた場合の様子により以下の基準にて評価した。
○：撓まない
△：若干撓む
×：大きく撓む
軽量性：
○：長さ方向の端部付近を手で持っても軽く作業性に問題が無い。
△：長さ方向の端部付近を手で持つと重いと感じるが作業性に問題は無い程度である。
×：長さ方向の端部付近を手で持つと重く作業性に問題がある。
剛性：
○：長さ方向の端部付近を手で持って地面と水平にしたときに撓みが殆どない。
△：長さ方向の端部付近を手で持って地面と水平にしたときに撓みはあるが、作業性に問題が無い。
×：長さ方向の端部付近を手で持って地面と水平にしたときに撓みが大きく、作業性に問題がある。
【００３５】
【発明の効果】
以上説明したように、本発明のポリエチレン系樹脂積層発泡板は、平均厚みが１０ｍｍ以上、見掛け密度が２０〜９０ｇ／Ｌのポリエチレン系樹脂押出発泡体からなる芯層の両面に、平均厚みが１．５〜８ｍｍ、見掛け密度が１００〜６００ｇ／Ｌのポリエチレン系樹脂発泡体からなる表層が接着積層されている積層発泡板であって、該積層発泡板の曲げ弾性率Ａが５ＭＰａ以上、圧縮強さＢ（厚み方向への２５％圧縮）が０．０３〜０．１ＭＰａであり、かつ曲げ弾性率と厚み方向への２５％圧縮強さとの比（Ａ／Ｂ）が１５０以上であることにより、軽量性、保形性、耐久性、表面硬度、そして厚み方向への圧縮力に対する適度な緩衝性を兼備した板状の優れた緩衝材が得られる。したがって、本発明の積層発泡板は軽量でありながら曲げ力に対して強く、また表面は硬いものの圧縮に対しては変形し易く、トラックボード等の強い力の加わる箇所に用いる緩衝材として好適なものである。
【図面の簡単な説明】
【図１】本発明のポリエチレン系樹脂積層発泡板の一実施例を示す縦断面図である。
【図２】発泡体幅方向垂直断面の厚み厚薄の１周期内における厚みの最大値及び最小値の測定方法の説明図である。
【図３】引張弾性率の算出方法の説明図で仮定荷重とチャート長さの関係の一例を示すグラフである。
【符号の説明】
１ ポリエチレン系樹脂押出発泡体
２ 芯層
３、４ 表層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyethylene resin laminated foam plate suitable as a track board or the like.
[0002]
[Prior art and problems to be solved by the invention]
A pallet transportation method is known in which, when a cargo is transported by truck, the cargo loaded on the pallet is loaded and transported on a truck for each pallet. The pallet transportation method can be easily loaded and unloaded onto a truck by a forklift, but there is a possibility that a gap is generated between the loads on adjacent pallets, and the loads may be damaged due to shaking during transportation. For this reason, a method is adopted in which a plate-shaped cushioning material (hereinafter referred to as a track board) is sandwiched and transported as a cushioning slip between the loads.
[0003]
Conventionally, as a track board, polystyrene foam particles formed into a plate shape are known. However, the track board made of a polystyrene foam particle molded plate has a problem that the foam particles are easily chipped off, easily broken, easily dented, and easily soiled. On the other hand, a track board in which polyethylene foam particles are formed into a plate shape is also known. However, the track board made of the polyethylene foam particle molded plate has solved the above-mentioned problems of the polystyrene foam particle molded plate to some extent, but still has problems in shape retention and surface hardness.
In this way, a plate-like cushioning material that is suitable for truck boards and the like and has appropriate cushioning properties against lightness, shape retention, durability, surface hardness, and compressive force in the thickness direction has not been realized. There wasn't.
[0004]
The present invention has been made to solve the above problems, and is a polyethylene-based resin laminate that is lightweight, strong against bending force, and easily deforms against compression force even though the surface is hard. It aims at providing a foam board.
[0005]
[Means for Solving the Problems]
The present inventors have intensively studied to solve the above-mentioned problems, and have completed the present invention by combining a specific polyethylene-based resin extruded foam and a polyethylene-based resin foam.
That is, the present invention
(1) An average thickness of 1.5 to 8 mm and an apparent density of 100 to 600 g / L on both surfaces of a core layer made of a polyethylene resin extruded foam having an average thickness of 10 mm or more and an apparent density of 20 to 90 g / L A laminated foam plate having an average thickness of 15 to 120 mm to which a surface layer made of a polyethylene resin foam is bonded, wherein the laminated foam plate has a flexural modulus (A) of 5 MPa or more and a 25% compressive strength in the thickness direction. is (B) is 0.03～0.1MPa, and the ratio (a / B) over 150 der the flexural modulus and the compressive strength is, the polyethylene resin extruded foam which constitutes the core layer When the thickness of the foam is measured at intervals of 1 cm in the width direction perpendicular to the extrusion direction at any position along the extrusion direction, periodic thin thickness is not observed, or the thickness is thin Is accepted , The value obtained by dividing the maximum value of the thickness at the minimum value in one cycle of the thick-thin thickness, a polyethylene-based resin laminate foam boards, characterized in der Rukoto either 1.07 or less,
(2) The polyethylene-based resin laminated foam plate according to (1), wherein the polyethylene-based resin foam constituting the surface layer has a tensile modulus of 10 to 100 MPa,
(3) In the above (2), the base resin of the polyethylene resin foam constituting the surface layer contains 30 to 90% by weight of a polyethylene resin having a density of 0.93 to 0.97 g / cm ^3. The polyethylene-based resin laminated foam plate according to the description ,
(4) The polyethylene resin laminate according to any one of the above (1) to (3) , wherein the polyethylene resin foam constituting the core layer is a multilayer foam comprising a plurality of foam layers. Foam board,
Is a summary.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIG. 1, the polyethylene resin laminated foam plate 1 of the present invention is formed by bonding and laminating surface layers 3 and 4 on both surfaces of a core layer 2.
[0007]
The core layer 2 is composed of a polyethylene resin extruded foam having an average thickness of 10 mm or more and an apparent density of 20 to 90 g / L. Examples of the base resin of the polyethylene resin extruded foam constituting the core layer 2 include ethylene homopolymers such as high-density polyethylene, medium-density polyethylene, and low-density polyethylene, and ethylene-propylene copolymers having an ethylene component exceeding 50 mol%. Polymer, ethylene-propylene-butene-1 copolymer, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-4-methylpentene-1 copolymer, ethylene-octene-1 copolymer An ethylene copolymer such as a polymer may be mentioned. In particular, an ethylene homopolymer or an ethylene copolymer having a density of 900 g / L or more and less than 930 g / L and a melt index: MI (190 ° C./21.18N) of 0.1 to 10 g / 10 min. Is preferred.
[0008]
The core layer 2 has an average thickness of 10 mm or more, more preferably more than 10 mm and 150 mm or less. The upper limit of the average thickness of the core layer 2 is approximately 200 mm.
The polyethylene resin foam constituting the core layer may be a single layer or a multilayer foam composed of a plurality of foam layers. In particular, it is preferable to form the core layer with a multilayer foam in order to obtain a high-thickness one.
When the core layer is composed of a multilayer foam, methods for obtaining the multilayer foam include (1) a method of laminating and bonding two or more foams, and (2) a method of multilayer co-extrusion foaming. Can be mentioned. However, in order to obtain the polyethylene-based resin laminated foam of the present invention using the multilayer foam obtained by the method (1) as a core layer, a plurality of conventional foam sheets having a large thickness and a small thickness can be simply laminated and bonded. The surface irregularities are large, and a product satisfying the desired physical properties cannot be obtained. Therefore, when the multilayer foam is used as the core layer, it is desirable to laminate and bond ones in which periodic thickness is not recognized, or those in which periodic thickness is hardly recognized. The core layer made of the multi-layered foam obtained in this way can have a periodic thickness as described later, or only a very small thickness. When the core layer is constituted by a multilayer foam by the method (1), the thickness of each layer constituting the multilayer foam is particularly preferably from 10 mm to 30 mm in view of buffering properties.
Moreover, although the apparent density of the core layer 2 is 20-90 g / L, 25-60 g / L is more preferable. If the thickness of the core layer 2 is less than 10 mm, the buffering property is insufficient. Moreover, when the apparent density is less than 20 g / L, the surface smoothness of the laminated foam plate of the present invention and the buffering property against heavy objects become insufficient. When the apparent density exceeds 90 g / L, the lightness, buffering property, and buffering against light objects. The property becomes insufficient. In addition, the polyethylene-based resin extruded foam constituting the core layer is preferably non-crosslinked when recycled.
[0009]
The surface layers 3 and 4 laminated and bonded to both surfaces of the core layer 2 are composed of polyethylene resin foam having an average thickness of 1.5 to 8 mm and an apparent density of 100 to 600 g / L. It is preferable that the average thickness of the polyethylene-based resin foam constituting the resin is 2 to 6 mm and the apparent density is 120 to 400 g / L. Examples of the base resin of the polyethylene resin foam constituting the surface layers 3 and 4 include the same resin as the base resin of the polyethylene resin extruded foam constituting the core layer 2.
The polyethylene resin foam constituting the surface layers 3 and 4 preferably has a tensile elastic modulus of 10 to 100 MPa, more preferably 50 to 100 MPa. In order to set the tensile elastic modulus of the polyethylene resin foam to 10 to 100 MPa, a material containing 30 to 90% by weight of a polyethylene resin having a density of 0.93 to 0.97 g / cm ³ is used as the base resin. Is preferred. Above, as the density of 0.93~0.97g / cm ³ than polyethylene resin together with polyethylene resin density 0.93~0.97g / cm ³ are incorporated into the base resin, constituting the core layer 2 The polyethylene resin is selected from the polyethylene resins exemplified as the base resin of the extruded polyethylene resin foam.
When the thickness of the surface layers 3 and 4 is less than 1.5 mm, the smoothness and bending elastic modulus of the laminated foam plate of the present invention are insufficient, and when the thickness exceeds 8 mm, the laminated foam plate lacks lightness. In the bending elastic modulus, the quality becomes excessive. Further, when the apparent density of the surface layers 3 and 4 is less than 100 g / L, the shape retention and surface hardness of the laminated foam plate of the present invention are insufficient, and when it exceeds 600 g / L, the lightweight property of the laminated foam plate, Buffering becomes insufficient. In addition, the polyethylene-type resin extrusion foam which comprises said surface layer has a non-crosslinked thing when recycling. Moreover, the surface layers 3 and 4 may also be comprised from a multilayer foam.
[0010]
In this specification, the average thickness of the said core layer 2, the average thickness of each foam layer in case the core layer 2 is a multilayer foam, the average thickness of the surface layers 3 and 4, etc. are measured as follows.
In the vertical cross section of the polyethylene-based resin laminated foam plate, the thickness of the target layer of the cross section is measured at 10 points at regular intervals over the entire width of the vertical cross section, and the arithmetic average value of these values is the thickness of the target layer. To do.
Further, in this specification, the apparent density of the core layer 2 and the surface layers 3, 4 and the like is obtained by dividing a test piece for measurement from the target layer and dividing the weight of the cut test piece by the volume of the test piece. It is a value obtained by doing. However, this operation is performed by cutting out 10 or more test pieces over the entire thickness of the target layer as much as possible, and the arithmetic average value of the apparent density of each test piece is set as the apparent density of the target layer. .
[0011]
In this specification, the tensile elastic modulus of the polyethylene resin foam constituting the surface layers 3 and 4 is measured based on the JIS K6767 (1976) A method to obtain a graph showing the tensile load curve shown in FIG. . And based on the obtained graph, it is computable with the following formula. The shape of the test piece was a dumbbell-shaped No. 1 test piece described in JIS K6767 (1976), with a distance between chucks of 30 mm and a test speed of 10 mm / min.
Tensile modulus (kgf / cm ² ) = Δσ / Δε
Δσ = load corresponding to a straight line between points A and B in FIG. 3 “assumed load” (kgf) / [width D of test piece parallel portion: (cm) × thickness I of test piece parallel portion I: (cm) ]
Δε = [Chart moving distance “chart length” (cm) × [test speed (mm / min) / chart speed (mm / min)] corresponding to a straight line between points A and B in FIG. 3] / between chucks: 3 (cm)
The tensile modulus was measured five times in each of the extrusion direction and the width direction, and the average value of these was taken as the tensile modulus. The tensile modulus (kgf / cm ² ) was multiplied by 0.1 to convert the unit to the tensile modulus (MPa).
[0012]
The laminated foam board 1 of the present invention uses a polyethylene resin extruded foam obtained by an extrusion foaming method as a core layer 2, and foams obtained separately on both surfaces of the core layer 2 as surface layers 3, 4 (surface layers 3, No. 4 is not necessarily an extruded foam.) And is laminated and bonded by a hot air bonding method or a bonding method using an adhesive. In addition, as the above laminating and bonding method, a thermal bonding method is preferable for recycling.
In order to improve the adhesion with the surface layers 3 and 4 laminated on the core layer 2 and the surface smoothness of the laminated foamed plate 1 obtained by adhering the surface layers 3 and 4 is excellent, When the thickness is measured at intervals of 1 cm in the width direction perpendicular to the extrusion direction, even if the thickness is not recognized, or even if the thickness is recognized, the maximum value of the thickness within one cycle of the thickness is the minimum value. It is preferable that all the values divided by are 1.07 or less. In other words, the core layer 2 has no periodic thickness irregularity, or is almost negligible even if there is a thickness irregularity.
[0013]
In the present specification, the term “thickness having a periodic thickness” means that in the width direction (the width direction of the foam) perpendicular to the extrusion direction of the foam constituting the core layer 2, the locations where the thickness is thick and the locations where the thickness is thin In addition, it means a thickness that appears at a substantially constant interval (usually 2 to 7 cm). Usually, this thickness is called a corrugate.
[0014]
The thickness of the above thickness is measured at intervals of 1 cm from one end to the other end in the width direction of the foam in the vertical cross section with respect to the foam extrusion direction, that is, the vertical cross section indicating the total width and thickness of the foam. To do. From the measurement results, it is determined whether or not periodic thickness is recognized. When periodic thickness is recognized, the maximum value of the thickness within one cycle is determined to be the minimum value. Find the value divided by.
However, if no periodic thickness is recognized, this means that no cogate has occurred, and a value obtained by dividing the maximum value of the thickness within one cycle of the thickness by the minimum value cannot be obtained. .
[0015]
A value obtained by dividing the maximum value of the thickness within one cycle by the minimum value is obtained as follows.
Thickness and thinness periodically appearing in the width direction of the foam has alternating thickness peaks and valleys at substantially constant intervals. FIG. 2 schematically shows the foam cut surface in the width direction orthogonal to the extrusion direction of the foam. As shown in FIG. 2, the peak of the peak located closest to one edge of the foam is shown in FIG. The thickness at P1 is T1, the thickness at the apex P2 of the mountain adjacent to this mountain is T2, and the period from P1 to P2 is one cycle of thickness.
[0016]
Next, the thickness t1 of the valley having the thinnest thickness in the first period is measured. Further, P2 and the peak P3 of the mountain next to this mountain are set as the second period, and the thickness at P3 and the thickness t2 of the valley part with the smallest thickness in the second period are measured. The same measurement is performed for all of the thin and thin periods such as the third period and the fourth period. From these results, a value obtained by dividing the maximum value of the thickness by the minimum value is obtained for each period. That is, in the first period, a value obtained by dividing the larger of T1 and T2 by t1 is obtained, and in the second period, a value obtained by dividing the larger of T2 and T3 by t2. Thus, in all the cycles, a value obtained by dividing the value of the larger thickness at the apex of the two peaks by the thickness of the valley having the thinnest thickness is obtained. The core layer 2 used in the present invention usually has no periodic thickness, but even if it exists, the above value is preferably 1.07 or less in all periods of the thickness. More preferably, it is 1.05 or less.
[0017]
In addition, the part cut | disconnected and excluded in order to equalize a product width | variety in the vicinity of the width direction both ends part of a foam is excluded from the object which calculates | requires the maximum value and minimum value of the thickness for every above-mentioned period.
[0018]
When trying to obtain a polyethylene-based resin extruded foam having a small apparent density and a thick thickness like the foam constituting the core layer 2, the obtained foam has periodic thickness unevenness called corrugated, This corrugate appears as a wavy phenomenon of the entire foam or as a striped stripe pattern in the size of the bubbles. Corrugates tend to appear more prominently as the apparent density decreases, the thickness increases, and the bubble diameter decreases.
[0019]
The polyethylene-based resin extruded foam used as the core layer 2 in the present invention has substantially no corrugate as described above or can be almost ignored even if it exists. As described in Japanese Patent Application No. 2001-364485 previously proposed, it can be obtained by adjusting the shape while cooling the foam immediately after extrusion foaming from the die.
[0020]
Examples of the foaming agent used to obtain the polyethylene resin extruded foam constituting the core layer 2 include the same inorganic physical foaming agent and organic physical foaming agent as those conventionally used in the production of polyethylene resin foams. Can be used. Examples of the inorganic physical foaming agent include oxygen, nitrogen, carbon dioxide, air, and water. Examples of the organic physical foaming agent include propane, normal butane, isobutane, normal pentane, isopentane, normal hexane, isohexane, and cyclohexane. Aliphatic hydrocarbons, chlorinated hydrocarbons such as methyl chloride, ethyl chloride, fluorinated hydrocarbons such as 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, dimethyl ether, methyl ethyl ether, diethyl ether, etc. Ethers, dimethyl carbonate, methanol, ethanol and the like. A chemical foaming agent such as azodicarbonamide can also be used. The above foaming agents can be used in combination of two or more. Of these, foaming agents mainly composed of normal butane, isobutane or a mixture thereof are preferred.
[0021]
In obtaining the extruded foam, a cell regulator is usually added to the base resin supplied to the extruder. As the bubble adjusting agent, either an organic type or an inorganic type can be used. Examples of the inorganic foam regulator include borate metal salts such as zinc borate, magnesium borate, borax, sodium chloride, aluminum hydroxide, talc, zeolite, silica, calcium carbonate, sodium bicarbonate, and the like. Examples of the organic bubble regulator include sodium phosphate-2,2-methylenebis (4,6-tert-butylphenyl), sodium benzoate, calcium benzoate, aluminum benzoate, and sodium stearate. A combination of citric acid and sodium bicarbonate, an alkali salt of citric acid and sodium bicarbonate, or the like can also be used as the bubble regulator. These bubble regulators can be used in combination of two or more.
[0022]
The amount of the foaming agent added is adjusted according to the type of foaming agent and the apparent density of the desired foam. Moreover, the addition amount of a bubble regulator is adjusted according to the target bubble diameter. In general, when butane is used as the foaming agent and talc is used as the cell regulator, the amount of butane added is 2 to 20 parts by weight, preferably 3 to 18 parts by weight, more preferably 4 parts per 100 parts by weight of the resin. The amount of talc added is 0.05 to 3 parts by weight, preferably 0.1 to 2 parts by weight, and more preferably 0.15 to 1 part by weight per 100 parts by weight of the resin.
[0023]
When butane is used as a foaming agent and talc is used as the cell regulator, the amount of butane added in the foamable composition for forming the core layer 2 is less than 2 parts by weight per 100 parts by weight of the resin The apparent density of the core layer 2 becomes difficult to be 90 g / L or less, and if it exceeds 20 parts by weight, the corrugation may not be suppressed.
[0024]
The polyethylene resin foam constituting the surface layers 3 and 4 is not particularly limited as to the method for producing the foam, but as a preferred production method, an extrusion foaming method, particularly the same extrusion foaming method as that of the core layer 2 described above. Is mentioned.
[0025]
Examples of the method for adhering the surface layers 3 and 4 to the core layer 2 include conventionally known laminating and bonding methods such as a hot air laminating method and a method using a hot melt adhesive as described above.
[0026]
The laminated foam board 1 of the present invention has a flexural modulus (A) of 5 MPa or more, a 25% compressive strength (B) in the thickness direction of 0.03 to 0.1 MPa, and the flexural modulus and the 25 The ratio (A / B) to% compressive strength is 150 or more. If the flexural modulus is less than 5 MPa, the shape retention is insufficient. Further, when the 25% compressive strength is less than 0.03 MPa, the buffering property against a heavy object becomes insufficient, and when it exceeds 0.1 MPa, the buffering property against a light object becomes insufficient. When the ratio (A / B) between the flexural modulus and the compressive strength is less than 150, even if the shape retention is sufficient, the compressive strength is too large, so that the buffering property is insufficient, or the buffering Even if the properties are sufficient, the bending elastic modulus is too small, so that the shape retention is poor.
The laminated foamed board 1 of the present invention has a balance between the flexural modulus and the compressive strength and exhibits an appropriate buffering property. In particular, the flexural modulus is 10 to 70 MPa, and the 25% compressive strength in the thickness direction. Is more preferably 0.035 to 0.08 MPa, and the ratio (A / B) between the flexural modulus and the compressive strength is more preferably 300 or more. Further, the upper limit of the flexural modulus is preferably 100 MPa, and the upper limit of (A / B) is preferably 2000, and more preferably 1500.
[0027]
In this specification, the bending elastic modulus of the laminated foam board 1 is based on the bending strength test method of JIS A9511 (1989), cut out a test piece having a width of 75 mm, a length of 300 mm, and a total thickness of the laminated foam board, This is a value measured at a fulcrum distance of 200 mm, (support base tip R = 10 mm), and a test speed of 30 mm / min.
[0028]
Moreover, in this specification, the 25% compressive strength to the thickness direction of the laminated foam board 1 is based on JISK7220 (1983), and is a test piece of width 50mm, length 50mm, thickness: thickness of the laminated foam 1. Is a value obtained by compressing at a compression speed of 10 mm / min in the thickness direction so that the thickness is reduced to 25% of the total thickness, that is, 75% of the total thickness of the laminated foam 100%.
The laminated foam board 1 of the present invention preferably has an overall apparent density of 40 to 150 g / L and a thickness of 15 to 120 mm for achieving the intended purpose. When the laminated foam board of the present invention is used as a track board, it is particularly preferable that the length is 1000 to 2500 mm, the width is 800 to 1200 mm, the thickness is 20 to 100 mm, and the overall apparent density is 50 to 120 g / L.
[0029]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
[0030]
Example 1
Low-density polyethylene resin (low density polyethylene manufactured by Nippon Unicar Co., Ltd .: MI: 0.3 g / 10 min, density: 0.921 g / cm ³ ) per 100 parts by weight of mixed butane of normal butane and isobutane as a blowing agent ( Weight ratio 7: 3) 9.5 parts by weight of a foaming agent and 0.3 parts by weight of talc as a foam regulator were heated and melt-kneaded in an extruder to prepare a foamable composition. The foamable composition was adjusted to an extrusion resin temperature of 110 ° C., and then extruded from a circular die at a discharge rate of 230 kg / hour and discharged from a die lip portion (open portion to atmospheric pressure). After cooling by contact with an external cooling device from the surface side of the cylindrical foam immediately after extrusion foaming from the die, this cylindrical foam was passed over the mandrel and cooled from the inner surface side. Next, the cylindrical foam was cut along the extrusion direction to obtain a sheet-like extruded foam.
As the core layer, two sheet-like extruded foams obtained by the above-mentioned method having a thickness of about 15 mm are prepared, set in a feeding machine, and laminated with the foams fed out simultaneously from the feeding machine. A hot air of 350 ° C. was blown onto the surface, and the foam laminated surface was melted and bonded, and was formed by a method of continuously pressing and bonding (hereinafter referred to as a continuous hot air lamination method). A multilayer foam was used.
Table 1 shows the average thickness, apparent density, and presence / absence of periodic thickness in the direction orthogonal to the extrusion direction.
[0031]
Using the multilayer foam as a core layer, a high-density polyethylene resin (high-density polyethylene “130J” manufactured by Idemitsu Petrochemical Co., Ltd .: MI: 19 g / 10 min, density: 0.955 g / cm ³ ) as a surface layer on both surfaces; As a foaming agent, 100% by weight of a low density polyethylene resin (low density polyethylene manufactured by Nihon Unicar: MI: 0.3 g / 10 min, density: 0.921 g / cm ³ ) in a weight ratio of 7: 3 is used as a foaming agent. Obtained by mixing 1.1 parts by weight of a mixed butane (weight ratio 7: 3) foaming agent of rubane and isobutane and 0.3 parts by weight of talc as a foam regulator by heating, melting and kneading in an extruder and extrusion foaming. The foamed sheet shown in Table 1 was bonded and laminated on both surfaces of the core layer obtained by the above method by a continuous hot air lamination method to obtain a laminated foamed plate.
Table 1 shows the average thickness, apparent density, and tensile modulus of the polyethylene foam sheet of the surface layer. Further, the flexural modulus A, 25% compressive strength B in the thickness direction, and ratio (A / B) of the flexural modulus and 25% compressive strength in the thickness direction of the obtained laminated foamed plate are obtained. The results of evaluating the lightness, independence and rigidity of the plate are shown in Table 1.
[0032]
[Table 1]

[0033]
Examples 2-3 and Comparative Examples 1-3
As shown in Table 1, a laminated foam plate was obtained in the same manner as in Example 1 except that the core layer thickness, surface layer thickness, apparent density, and tensile modulus were different. Bending elastic modulus A, 25% compressive strength B in the thickness direction, and ratio (A / B) of bending elastic modulus and 25% compressive strength in the thickness direction of the obtained laminated foam plate, laminated foam plate Table 1 also shows the results of evaluating the lightness, self-supporting property, and rigidity. In addition, Comparative Examples 2 and 3 are single layer foams in which the surface layer is not laminated, but the flexural modulus, the 25% compressive strength in the thickness direction, the flexural modulus of the foams of Comparative Examples 2 and 3 The value of the ratio of 25% compressive strength in the thickness direction is described in the corresponding column of the laminated foam plate in Table 1 for convenience.
[0034]
The evaluation of the self-supporting property, lightness, and rigidity in Table 1 is as follows: the length of 1200 mm, the width of 1000 mm, and the thickness of the foamed molded product thickness of the track board-shaped plate material cut out from the molded products obtained in the examples and comparative examples. Judged as follows.
Independence: Evaluation was made according to the following criteria depending on the state of standing a board material in the shape of a track board with the vertical direction up and down.
○: not bent Δ: slightly bent ×: lightly bent
○: Even if the vicinity of the end in the length direction is held by hand, there is no problem in workability.
Δ: Holding the vicinity of the end in the length direction with a hand feels heavy, but there is no problem in workability.
X: When the vicinity of the end in the length direction is held by hand, there is a problem in workability because of heavy weight.
rigidity:
◯: There is almost no bending when the vicinity of the end in the length direction is held by hand and leveled with the ground.
Δ: There is bending when the vicinity of the end in the length direction is held by hand and is level with the ground, but there is no problem in workability.
X: Deflection is large when the vicinity of the end in the length direction is held by hand and level with the ground, and there is a problem in workability.
[0035]
【The invention's effect】
As described above, the polyethylene resin laminated foam plate of the present invention has an average thickness of 1 on both sides of a core layer made of a polyethylene resin extruded foam having an average thickness of 10 mm or more and an apparent density of 20 to 90 g / L. A laminated foam board in which a surface layer made of a polyethylene resin foam having an apparent density of 100 to 600 g / L is adhesively laminated, and the flexural modulus A of the laminated foam board is 5 MPa or more, compression strength The thickness B (25% compression in the thickness direction) is 0.03 to 0.1 MPa, and the ratio (A / B) between the flexural modulus and the 25% compression strength in the thickness direction is 150 or more. Thus, an excellent plate-like cushioning material having light weight, shape retention, durability, surface hardness, and moderate cushioning against compressive force in the thickness direction can be obtained. Therefore, the laminated foam plate of the present invention is lightweight but strong against bending force, and has a hard surface, but is easily deformed against compression, and is suitable as a cushioning material used in places where strong force is applied such as track boards. Is.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an embodiment of a polyethylene resin laminated foam plate of the present invention.
FIG. 2 is an explanatory view of a method for measuring the maximum value and the minimum value of the thickness within one cycle of the thickness of the foam width direction vertical cross section.
FIG. 3 is an explanatory diagram of a method for calculating a tensile elastic modulus and is a graph showing an example of a relationship between an assumed load and a chart length.
[Explanation of symbols]
1 Polyethylene resin extruded foam 2 Core layer 3, 4 Surface layer

Claims (4)

Polyethylene resin having an average thickness of 1.5 to 8 mm and an apparent density of 100 to 600 g / L on both sides of a core layer made of a polyethylene resin extruded foam having an average thickness of 10 mm or more and an apparent density of 20 to 90 g / L A laminated foam plate having an average thickness of 15 to 120 mm to which a surface layer made of a foam is adhered, wherein the laminated foam plate has a flexural modulus (A) of 5 MPa or more and a 25% compressive strength (B ) is 0.03～0.1MPa, and the ratio (a / B) over 150 der the flexural modulus and the compressive strength is, the polyethylene resin extruded foam constituting the core layer, When the thickness of the foam is measured at intervals of 1 cm in the width direction orthogonal to the extrusion direction at any position along the extrusion direction, periodic thickness thinness is not recognized, or thickness thinness is recognized. If the thickness Polyethylene-based resin laminate foam boards value obtained by dividing the minimum value of the maximum value of the thickness in one cycle, characterized in that both at 1.07 or less thick-thin.   The polyethylene-based resin laminated foam plate according to claim 1, wherein the polyethylene-based resin foam constituting the surface layer has a tensile elastic modulus of 10 to 100 MPa. The polyethylene-based resin according to claim 2, wherein the base resin of the polyethylene-based resin foam constituting the surface layer contains 30-90 wt% of a polyethylene-based resin having a density of 0.93-0.97 g / cm ^3. Resin laminated foam board.   The polyethylene-based resin laminated foam plate according to any one of claims 1 to 3, wherein the polyethylene-based resin foam constituting the core layer is a multi-layered foam composed of a plurality of foam layers.

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