JP7031445B2 - Manufacturing method of foam laminate - Google Patents

Description

The present invention relates to a method for producing a foamed laminate in a shorter time than a conventional technique for producing a foamed laminate.

Conventionally, synthetic resins, particularly polystyrene-foamed ones, have been widely used as heat-insulating containers and interleaving papers. However, expanded polystyrene has drawbacks such as high environmental load at the time of disposal and inferior printability, and alternatives to other materials are being considered.

Therefore, a high melting point thermoplastic synthetic resin film is laminated on one surface of a water-containing base material, a low melting point thermoplastic synthetic resin film is laminated on the other side, and the base material is heated with hot air. A technique for foaming a low melting point thermoplastic synthetic resin film using the contained water has been devised (see, for example, Patent Documents 1 and 2). However, as a condition for such a laminate to foam, the temperature of the laminate must rise to a temperature at which the low melting point thermoplastic synthetic resin film melts and the moisture contained in the substrate evaporates. Therefore, the hot air heating method in which the object is heated by heat conduction has a drawback that it requires long-time heating in order to obtain the foamed laminate, resulting in high cost.

Japanese Unexamined Patent Publication No. 2007-21724 Japanese Unexamined Patent Publication No. 2009-196200

An object of the present invention is to provide a manufacturing method capable of shortening the time of the foaming process, which is the manufacturing process of the foamed laminate, as compared with the prior art.

As a result of diligent studies to solve the above problems, the present inventors have found that the foaming time can be shortened by producing the foamed laminate by a specific method, and have completed the present invention.

That is, it is a method for producing a foamed laminate containing at least (A) layer, base material layer, and (B) layer in this order, in which the (A) layer is made of a polyethylene resin (a) and the (B) layer is. It is a moisture-proof layer and relates to a method for producing a foamed laminate, which is characterized by undergoing the following steps (i) to (ii).
(I) Laminating (i) by dielectric heating with a lower output than the steps (ii) and (i) of softening the polyethylene-based resin (a) in the layer (A) by heating the laminate before foaming by dielectric heating. Step of foaming the polyethylene-based resin (a) of the layer (A) by heating the body The present invention will be described in detail below.

The polyethylene-based resin (a) constituting the (A) layer of the foaming laminate of the present invention is not particularly limited as long as the object of the present invention is achieved, and is low-density polyethylene, high-density polyethylene, or linear. Examples thereof include low-density polyethylene, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer and the like. These polyethylene-based resins (a) may be used alone or in combination of two or more. Of these, low-density polyethylene, linear low-density polyethylene, ethylene / vinyl acetate copolymers, ethylene / acrylic acid copolymers, ethylene / methacrylic acid copolymers, or compositions thereof are available because of their excellent foaming stability. preferable.

Low-density polyethylene can be obtained by a conventionally known high-pressure radical polymerization method.

Linear low-density polyethylene is obtained by copolymerizing ethylene and α-olefin by a high-pressure ion polymerization method using a Ziegler-Natta catalyst, a Phillips catalyst, or a metallocene catalyst, a medium-pressure ion polymerization method, or a low-pressure ion polymerization method. be able to.

The α-olefins used for linear low-density polyethylene include propylene, 1-butene, 4-methyl-1-pentene, 3-methyl-1-butene, 1-pentene, 1-hexene, 1-hexene, 1-. Octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene and the like can be mentioned, and one or more of these can be used.

The ethylene-vinyl acetate copolymer can be obtained by a conventionally known high-pressure radical polymerization method.

The density (hereinafter, simply abbreviated as density) measured by JIS K6922-1 (1997) of low-density polyethylene or linear low-density polyethylene used for the polyethylene-based resin (a) is 910 because it has excellent foaming stability. The range is preferably from 930 kg / m ³ , more preferably from 914 to 925 kg / m ³ , and even more preferably from 916 to 920 kg / m ³ .

The vinyl acetate content measured by JIS K7192 (1999) of the ethylene-vinyl acetate copolymer used for the polyethylene-based resin (a) is preferably 2 to 42% by weight, and more preferably 3 because it is excellent in foaming stability. It is in the range of ~ 20%, more preferably 4 ~ 15%.

The content of acrylic acid in the ethylene / acrylic acid copolymer used in the polyethylene resin (a) is preferably 2 to 30% by weight, more preferably 5 to 20%, because it is excellent in foaming stability.

The content of methacrylic acid in the ethylene / methacrylic acid copolymer used in the polyethylene resin (a) is preferably 2 to 30% by weight, more preferably 5 to 20%, because it is excellent in foaming stability.

The melt mass flow rate (hereinafter, simply abbreviated as MFR) measured by JIS K6922-1 (1997) of the polyethylene resin (a) is preferably in the range of 6.0 to 30 g / 10 minutes and has excellent foaming stability. Therefore, it is more preferably in the range of 7.0 to 27 g / 10 minutes, and further preferably in the range of 8.0 to 25 g / 10 minutes.

In order to improve the efficiency of dielectric heating, another resin may be blended with the polyethylene-based resin (a) constituting the layer (A) of the effervescent laminate of the present invention.

The resin to be blended is not limited to these, but is not limited to these, but is limited to chlorine group-containing polymer, vinyl acetate-containing polymer, acrylic acid-containing polymer, methacrylic acid-containing polymer, acrylonitrile-based polymer, hydroxyl group-containing polymer, acrylic-based or acrylate-based polymer. , Epoxy group-containing polymer, maleic anhydride-containing or maleic anhydride-modified polymer, acetate-based polymer, polyether-based polymer, polyketone-based polymer, polyamide-based polymer, polyurethane-based polymer and the like.

When another resin is mixed with the polyethylene-based resin (a) constituting the laminate of the present invention, it may be a mixture of the pellets of the polyethylene-based resin (a) and the pellets of the other resin in a solid state. However, a mixture melt-kneaded with a single-screw extruder, a twin-screw extruder, a kneader, a Banbury or the like is preferable because a product with stable quality can be obtained. When a melt-kneading device is used, the melting temperature is preferably about 300 ° C. from the melting point of the polyolefin resin or lower than the decomposition temperature of the other resin to be mixed.

Further, the low-density polyethylene (a) constituting the laminate of the present invention is generally used as a polyolefin resin such as an antioxidant, a light stabilizer, an antistatic agent, a lubricant, and an antiblocking agent, if necessary. The additive may be added as long as the object of the present invention is not impaired.

A microwave-sensitive substance may be added to the polyethylene-based resin (a) constituting the layer (A) of the effervescent laminate of the present invention in order to improve the efficiency of dielectric heating.

The microwave-sensitive substance is not limited to this, for example, carbon compound, metal, metal salt, metal oxide, zeolite, hydrated mineral, hydrated salt of metal compound, clay, silicate, ceramic, sulfide. , Titanate, carbide, sulfur, inorganic solid acid or salt, inorganic or polymer ion exchange resin, glycerin and the like, these may be used alone or in combination of two or more.

When the microwave-sensitive substance is mixed with the polyethylene-based resin (a), it may be a mixture of the pellets of the polyethylene-based resin (a) and the microwave accepting substance, but it may be a single-screw extruder or a twin-screw extruder. , A mixture melt-kneaded with a kneader, Banbury or the like is preferable because a product with stable quality can be obtained. When a melt-kneading device is used, the melting temperature is preferably about 300 ° C. from the melting point of the polyolefin resin or lower than the temperature at which the microwave-sensitive substance is decomposed.

Examples of the (B) layer, which is the moisture-proof layer of the foaming laminate of the present invention, include layers formed from synthetic polymer polymers, woven fabrics, non-woven fabrics, metal foils, cellophane and the like. For example, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyamide resins such as nylon 6 and nylon 66, high density polyethylene, low density polyethylene, linear low density polyethylene, ethylene / ethyl acrylate copolymers, ethylene / Methacrylic acid copolymer, ethylene / vinyl acetate copolymer, ethylene / vinyl alcohol copolymer, polyethylene resin such as ionomer, polypropylene resin, polybutene, acrylic resin, polyvinyl alcohol, polymethylpentene, polyvinyl chloride, Examples thereof include a layer formed from a synthetic polymer polymer such as polyvinyl chloride, polystyrene, polycarbonate, polyurethane, and a cellulose-based resin. Further, these polymer polymer films and sheets may be further subjected to aluminum vapor deposition, alumina vapor deposition, silicon dioxide vapor deposition, or acrylic treatment. Further, these polymer polymer films and sheets may be further printed using urethane-based ink or the like. Examples of the metal foil include aluminum foil and copper foil.

Since the moisture permeability of such a moisture-proof layer is excellent in the thickness of foam, it is preferably 15 g / m ^2/24 hr or less, more preferably 12 g / m ^2/24 hr or less, and further preferably 10 g / m ^2/24 hr or less. ..

Here, the moisture permeability was measured in accordance with the humidification sensor method described in JIS K7129 A method (2008), and a value converted to 40 μm was used.

Among these, since the foaming thickness is excellent, the layer (B) is made of polyethylene-based resin (b), polypropylene-based resin, polyester-based resin, polyamide-based resin, and aluminum vapor deposition and alumina vapor deposition on these polymer polymer films. , A film on which silicon dioxide is vapor-deposited, a film coated with an inorganic substance such as clay, and a metal foil are preferable, and a polyethylene-based resin (b) is more preferable.

The density of the polyethylene-based resin (b) is preferably in the range of 930 to 970 kg / m ³ , more preferably in the range of 935 to 970 kg / m ³ , and most preferably in the range of 935 to 970 kg / m 3, because the polyethylene-based resin (b) is excellent in foaming stability. It is in the range of 945 to 965 kg / m ³ .

The polyethylene-based resin (b) is an ethylene homopolymer, an ethylene / α-olefin copolymer or a composition thereof, and the form of the molecular chain thereof may be linear or may have branches. .. Such a polyethylene-based resin (b) is not particularly limited, and may not be out of the density range.

Examples of the ethylene homopolymer include medium-pressure method or low-pressure method ethylene homopolymer, and high-pressure method low-density polyethylene. Medium-pressure method or low-pressure method The ethylene homopolymer can be obtained by a conventionally known medium-pressure ion polymerization method or low-pressure ion polymerization method. Further, the high-pressure method low-density polyethylene can be obtained by a conventionally known high-pressure radical polymerization method.

Examples of the α-olefin used for the ethylene / α-olefin copolymer include propylene, 1-butene, 4-methyl-1-pentene, 3-methyl-1-butene, 1-pentene, 1-hexene, 1-heptene, and the like. 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene and the like can be mentioned, and one or more of these can be used.

The method for obtaining the ethylene / α-olefin copolymer is not particularly limited, and examples thereof include high / medium / low pressure ion polymerization methods using a Ziegler-Natta catalyst, a Phillips catalyst, and a metallocene catalyst. Such a copolymer can be conveniently selected from commercially available products.

When a polyolefin such as polypropylene is mixed with such a polyethylene resin (b), it may be a pellet mixture in which the pellets of the polyethylene resin (b) and the pellets of the polyolefin are mixed in a solid state, but it is uniaxially extruded. A mixture melt-kneaded with a machine, a twin-screw extruder, a kneader, a Banbury or the like is preferable because a product with stable quality can be obtained. When a melt-kneading device is used, the melting temperature is preferably about 300 ° C., which is the melting point of the polyethylene resin.

Further, the object of the present invention is to add to the polyethylene-based resin (b), if necessary, additives generally used for polyolefin resins, such as antioxidants, light stabilizers, antistatic agents, lubricants, and antiblocking agents. May be added as long as it does not impair.

Regarding the paper base material constituting the foaming laminate of the present invention, the basis weight of the paper base material is preferably in the range of 30 to 400 g / m ² , and more preferably 60 because the thickness after foaming is excellent. It is ~ 350 g / m ² , more preferably 90 to 320 g / m ² . When the basis weight of the paper is 30 g / m ² or more, the thickness after foaming is large, and when it is less than 400 g / m ² , the heat sealability and flexibility are excellent, which is preferable.

The moisture content of such a paper substrate is preferably in the range of 5 to 33 g / m ² and more preferably 7 to 30 g / m because the foaming ratio of the polyethylene resin (a) is improved. ² , most preferably 9 to 28 g / m ² . When the water content of the paper substrate is 5 g / m ² or more, the thickness after foaming is large, and when the water content is 33 g / m ² or less, the foam film does not break during foam molding due to excessive water content, and the appearance does not deteriorate. preferable.

The effervescent laminate of the present invention contains at least a layer (A) which is a polyethylene resin (a), a paper base material, and a layer (B) which is a moisture-proof layer in this order.

The thickness of the layer (A) constituting the foaming laminate of the present invention before foaming is not particularly limited as long as the object of the present invention is achieved, but the foaming appearance is excellent, and the thickness is in the range of 30 to 150 μm. It is preferably more preferably 50 to 120 μm, still more preferably 60 to 100 μm.

The thickness of the layer (B) constituting the foaming laminate of the present invention is not particularly limited as long as the object of the present invention is achieved, but it is excellent in foamability and has few problems such as breakage. The thickness is preferably 100 μm, and the range of 20 to 50 μm is most preferable from the viewpoint of economy.

As a method for obtaining the foaming laminate of the present invention, a method of extrusion laminating the polyethylene resin (a) is exemplified.

As a method for obtaining a laminate by an extrusion laminating method, various extrusion laminating methods such as a single laminating method, a tandem laminating method, a sandwich laminating method, and a coextrusion laminating method can be exemplified. The temperature of the resin in the extrusion laminating method is preferably in the range of 240 to 350 ° C., and the surface temperature of the cooling roll is preferably in the range of 10 to 50 ° C.

Further, in the extrusion laminating molding method, the processing speed when forming the layer (A) made of the polyethylene resin (a) is preferably in the range of 50 to 200 m / min because it is excellent in foaming appearance and productivity.

The method for forming the layer (B) constituting the foaming laminate of the present invention is not particularly limited, and various laminating methods such as an extrusion laminating method, a dry laminating method, a thermal laminating method, and a wet laminating method are used. Can be exemplified.

In such an extrusion laminating process, immediately after the polyethylene resin is made into an extruded layer in a molten state, the substrate adhesive surface of the layer is exposed to an oxygen-containing gas or an ozone-containing gas and bonded to the substrate. It is preferable because it has excellent adhesion to the base material layer. When improving the adhesiveness between the thermoplastic resin and the substrate by using ozone-containing gas, the amount of ozone gas treated is 0.5 mg or more of ozone per 1 m ² of the film made of the thermoplastic resin extruded from the die. It is preferable to spray it.

In the extrusion laminating method in the method for obtaining the foaming laminate of the present invention, in order to further improve the adhesiveness between the thermoplastic resin layer and the base material layer, the temperature at which the polyethylene-based resin does not foam, for example, 3 to 60 It can be heat-treated at a temperature of ° C. for 10 hours or more. Further, if necessary, a known surface treatment such as a corona treatment, a frame treatment, or a plasma treatment may be applied to the adhesive surface of the paper substrate. Further, if necessary, an anchor coating agent may be applied to the paper substrate.

As a method for obtaining the foaming laminate of the present invention, in order to improve the heat insulating property and economy of the foamed laminate, the paper base is used before the polyethylene-based resin (a) to the moisture-proof layer (B) is laminated on the paper substrate layer. Water may be applied to the material.

The method of applying water is not particularly limited as long as the object of the present invention is achieved, and a method using a roll coat device, a lip coat device, a spray device, a die coat device, a gravure device, a dampening device and the like is exemplified. be able to. Since the amount of water applied is uniform, a method using a dampening device is preferable.

For example, the product name "High Rotor S" from Suzuki Sangyo Co., Ltd., the product name "WEKO Rotor Damping" from Nikka Co., Ltd., and the product name "WEKO Rotor Damping" from Toki Electronics Co., Ltd. "TSD-3000" is on sale.

The amount of water applied in the present invention is not particularly limited as long as the object of the present invention is achieved, but the foaming ratio of the polyethylene-based resin (a) can be increased, and the paper substrate and the polyethylene-based resin (a) can be applied. 1.5 to 30 g / m ² is preferable, and 3 to 15 g / m ² is more preferable, because the adhesive strength with the material does not decrease.

The surface to which water is applied can be the surface of the paper in contact with the layer (A), the surface of the paper in contact with the layer (B), or both sides thereof, but the foam layer after foam molding has high smoothness and cushioning. It is preferable to apply it only on the surface of the paper in contact with the layer (B) because of its excellent properties.

Further, before applying water, it is preferable to perform corona treatment on the paper base material in order to improve the wettability of the paper.

The foaming laminate of the present invention is characterized by containing at least the (A) layer / paper base material / (B) layer, and has three layers: (A) layer, paper base material layer, and (B) layer. It may contain not only a layer but also another layer, for example, the layer (C). Specifically, (A) layer / paper base material layer / (B) layer, (A) layer / paper base material layer / (B) layer / (A) layer, (B) layer / paper base material layer / (A) layer / (B) layer, (A) layer / paper base material layer / (B) layer / (B) layer, (A) layer / (A) layer / paper base material layer / (B) layer, (A) layer / paper base material layer / (B) layer / (C) layer, (B) layer / paper base material layer / (A) layer / (C) layer, (C) layer / (B) layer / Paper substrate layer / (A) layer / (B) layer / (C) layer, (A) layer / paper substrate layer / (B) layer / (C) layer / (B) layer / (A) layer, Examples thereof include (B) layer / paper base material layer / (A) layer / (C) layer / (A) layer / (B) layer. The symbol / between the layers indicates that they are adjacent layers.

Examples of the layer (C) include layers formed from synthetic polymer polymers, woven fabrics, non-woven fabrics, metal foils, papers, cellophane and the like. For example, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyamide resins such as nylon 6 and nylon 66, high density polyethylene, low density polyethylene, linear low density polyethylene, ethylene-ethyl acrylate copolymer, and ethylene-. Methacrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyethylene resin such as ionomer, polypropylene resin, polybutene, acrylic resin, polyvinyl alcohol, polymethylpentene, polyvinyl chloride, Examples thereof include a layer formed from a synthetic polymer polymer such as polyvinyl chloride, polystyrene, polycarbonate, polyurethane, and a cellulose-based resin. Further, these polymer polymer films and sheets may be further subjected to aluminum vapor deposition, alumina vapor deposition, silicon dioxide vapor deposition, or acrylic treatment. Further, these polymer polymer films and sheets may be further printed using urethane-based ink or the like. Examples of the metal foil include aluminum foil and copper foil, and examples of papers include kraft paper, high-quality paper, stretched paper, glassin paper, and paperboard such as cup base paper and stamp paper base paper.

The foamed laminate of the present invention can be obtained by heating the foamed laminate by a dielectric heating method to foam the layer (A).

In the present invention, the foamed laminate is produced through the following steps (i) to (ii).
(I) Laminating (i) by dielectric heating with a lower output than the steps (ii) and (i) of softening the polyethylene-based resin (a) in the layer (A) by heating the laminate before foaming by dielectric heating. Step of foaming polyethylene resin (a) in layer (A) by heating the body Examples of the method of dielectric heating in steps (i) and (ii) include high-frequency heating and microwave heating, which are preferable. It is microwave heating. Further, other heating means such as hot air, electric heating, and electron beam may be used in combination with the dielectric heating. The output of the microwave heating device is preferably in the range of 200 to 300,000 W, more preferably 500 to 35,000 W.

In the step (i), the polyethylene resin (a) in the layer (A) is heated until it softens, and in the step (ii), the polyethylene resin (a) in the layer (A) is heated until it foams.

The output of the dielectric heating is preferably switched in steps (i) and (ii) because a foamed laminate having a high foaming ratio can be obtained in a short time and the appearance of the foamed layer is excellent. After heating with a high-power microwave, it is heated with a dielectric heating having a lower power than that of (i) in the step (ii).

Specifically, in the step (i), the polyethylene-based resin (a) of the laminated body before foaming is softened by a high-power microwave. In the step (i), it is preferable to heat the polyethylene resin (a) until it reaches the melting point to an appropriate foaming temperature. In the step (ii), the polyethylene resin (a) is foamed with a microwave having a lower output than the step (i). In the step (ii), it is preferable to foam the layer (A) while maintaining an appropriate foaming temperature. If the heating is continued with the high output microwave of the step (i), the temperature of the polyethylene resin (a) exceeds the appropriate foaming temperature, and the foaming appearance deteriorates due to the foam breaking due to the decrease in the melt tension of the foam layer. Further, when the polyethylene-based resin (a) is heated only with a low-power microwave, it takes time for the polyethylene-based resin (a) to start foaming, so that the effect of shortening the foaming time is small.

Here, the appropriate foaming temperature of the polyethylene-based resin (a) is not particularly limited as long as the foam can be foamed in a good appearance, but is preferably the melting point of the polyethylene-based resin (a). The temperature is 200 ° C. or lower, more preferably 150 ° C. or higher than the melting point of the polyethylene resin (a), and further preferably 135 ° C. or higher than the melting point of the polyethylene resin (a).

The heating can be performed by a method of performing batch-type in an oven, a method of continuously performing in a conveyor-type facility, or the like.

The heating time is not particularly limited as long as the object of the present invention is achieved, and is generally 10 seconds to 6 minutes.

The foamed laminate of the present invention is used as a cushioning material for wrapping paper, cushioning wrapping paper, wrapping bag, etc., as a non-slip material, a sound insulating material, a heat insulating material, a food container, a heat insulating paper container, etc. It is commonly used for paper containers.

According to the production method of the present invention, a foamed laminate can be produced in a shorter time than the conventional foaming method.

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(1) Density Density was measured according to JIS K6922-1 (1997).

(2) Melt mass flow rate (MFR)
MFR was measured according to JIS K6922-1 (1997).

(3) Vinyl acetate content The vinyl acetate content was measured in accordance with JIS K7192 (1999).

(4) Melting point The melting point was measured according to JIS K6922-2 (2010).

(5) Moisture Permeability The moisture permeability was measured according to JIS K7129 A method (2008). The sample was extruded and laminated so that the resin temperature directly under the T-die was 320 ° C, the take-up speed was 50 m / min, the air gap length was 130 mm, and the thickness was 40 μm. Using.

(6) Heat foaming A sample obtained by cutting the laminate obtained in the example into a 10 cm × 20 cm shape and forming it into a cylindrical shape is produced in a microwave oven (MR M-25 manufactured by Hitachi, Ltd.) or a gear aging tester (Yasuda Seiki) with an output of 700 to 500 W. After heating for a predetermined time using No. 102-SHF-77) manufactured by Mfg. Co., Ltd., it was taken out and cooled to room temperature in the air.

(7) Moisture content of the paper substrate The moisture content of the paper substrate after the polyethylene resin was laminated was measured using a Karl Fischer method moisture measuring device (manufactured by Mitsubishi Chemical Corporation, trade name CA-05). The measurement temperature is 165 ° C.

(8) Temperature of layer (A) after heating The surface temperature of layer (A) after heating with a microwave oven or a gear aging tester was measured with a non-contact thermometer (IT-540 manufactured by Horiba, Ltd.). The measurement was performed immediately after the heating was completed.

(9) Foam layer thickness A cross-sectional photograph of the foam obtained in the examples was taken with an optical microscope. The thickness of the layer (A) after foaming (hereinafter abbreviated as DA) was measured from the cross-sectional photograph and measured at 5 points. The foam layer thickness (DA ₆₀ ) at a heating time of 60 seconds was good when it was 450 μm or more.

(10) Appearance after foaming The appearance of the foam obtained in the examples was visually evaluated. The one having good smoothness of the (A) layer after foaming was evaluated as ◯, and the one having poor smoothness of the (A) layer of the foamed layer or the one in which the (B) layer after foaming was melted was evaluated as x.

Example 1
High-density polyethylene (manufactured by Tosoh Corporation, A1) having an MFR of 14 g / 10 minutes and a density of 918 kg / m3 as the resin for the layer ⁽ A) is used, and MFR is 7.0 g as the resin for the layer (B). High-density polyethylene (trade name Petrosen LW04-1 manufactured by Tosoh Corporation) (B1) having a density of 940 kg / m ³ for 10 minutes was used.

First, (A1) is supplied to a single-screw extrusion laminator (manufactured by Musashinokikai Co., Ltd.) having a screw with a diameter of 90 mmφ, extruded from the T-die so that the resin temperature directly under the T-die becomes 320 ° C., and the basis weight is 300 g / m. Extrusion laminating was performed on the cup base paper base material of No. ² so that the take-up speed was 50 m / min, the air gap length was 130 mm, and the thickness was 70 μm. Further, (B1) is supplied to a single-screw extruder (manufactured by Musashinokikai Co., Ltd.) having a screw having a diameter of 90 mmφ, and at a temperature of 320 ° C., a take-up speed of 50 m / min, and an air gap length of 130 mm, (B1). Was extruded to a thickness of 40 μm to obtain a foaming laminate in which the high-pressure method low-density polyethylene (A1), the paper substrate, and the high-density polyethylene (B1) were laminated in this order. The obtained effervescent laminate was heated in a microwave oven (MR M-25 manufactured by Hitachi, Ltd.) at an output of 700 W for 20 seconds, immediately switched to an output of 500 W and further heated for 40 seconds to foam the effervescent laminate. .. The foamed layer thickness (DA ₆₀ ) and the foamed appearance of the obtained foamed laminate were evaluated. The results of the evaluation are shown in Table 1. The foam layer thickness (DA ₆₀ ) and the foam appearance were excellent.

Example 2
The same as in Example 1 except that high-pressure low-density polyethylene (manufactured by Tosoh Corporation, A2) having an MFR of 24 g / 10 min and a density of 918 kg / m ³ was used as the resin of the layer (A). A foamed laminate was obtained by the method. The foamed layer thickness (DA ₆₀ ) and the foamed appearance of the obtained foamed laminate were evaluated. The results of the evaluation are shown in Table 1. The foam layer thickness (DA ₆₀ ) and the foam appearance were excellent.

Example 3
A foamed laminate was obtained by the same method as in Example 2 except that (B1) was laminated after applying 5 g / m ² of water to the paper substrate on the surface on which (B1) was laminated. The foamed layer thickness (DA ₆₀ ) and the foamed appearance of the obtained foamed laminate were evaluated. The results of the evaluation are shown in Table 1. The foam layer thickness (DA ₆₀ ) and the foam appearance were excellent.

Example 4
As the resin of the layer (A), an ethylene-vinyl acetate copolymer (manufactured by Tosoh Corporation, A3) having an MFR of 8.5 g / 10 minutes, a density of 925 kg / m ³ , and a vinyl acetate content of 6% was used. A foamed laminate was obtained by the same method as in Example 1 except that it was used. The foamed layer thickness (DA ₆₀ ) and the foamed appearance of the obtained foamed laminate were evaluated. The results of the evaluation are shown in Table 1. The foam layer thickness (DA ₆₀ ) and the foam appearance were excellent.

Example 5
A foamed laminate was obtained by the same method as in Example 3 except that kraft paper having a basis weight of 100 g / m ² was used as the paper base material. The foamed layer thickness (DA ₆₀ ) and the foamed appearance of the obtained foamed laminate were evaluated. The results of the evaluation are shown in Table 1. The foam layer thickness (DA ₆₀ ) and the foam appearance were excellent.

Comparative Example 1
Same as Example 2 except that the foaming laminate was foamed by heating it in a gear aging tester (No. 102-SHF-77 manufactured by Yasuda Seiki Seisakusho) heated to 120 ° C. for 60 seconds while applying hot air. A foamed laminate was obtained by the above method. The foamed layer thickness (DA ₆₀ ) and the foamed appearance of the obtained foamed laminate were evaluated. The results of the evaluation are shown in Table 2. Although the foamed appearance was excellent, the foamed layer thickness (DA ₆₀ ) was inferior.

Comparative Example 2
Same as Example 2 except that the foaming laminate was foamed by heating it in a gear aging tester (No. 102-SHF-77 manufactured by Yasuda Seiki Seisakusho) heated to 140 ° C. for 60 seconds while applying hot air. A foamed laminate was obtained by the above method. The foamed layer thickness (DA ₆₀ ) and the foamed appearance of the obtained foamed laminate were evaluated. The results of the evaluation are shown in Table 2. It was inferior in foam layer thickness (DA ₆₀ ) and foam appearance.

Comparative Example 3
A foamed laminate was obtained by the same method as in Example 2 except that it was heated in a microwave oven (MR M-25 manufactured by Hitachi, Ltd.) at an output of 700 W for 60 seconds. The foamed layer thickness (DA ₆₀ ) and the foamed appearance of the obtained foamed laminate were evaluated. The results of the evaluation are shown in Table 2. Although the foam layer thickness (DA ₆₀ ) was excellent, the foam appearance was inferior.

Comparative Example 4
A foamed laminate was obtained by the same method as in Example 2 except that it was heated in a microwave oven (MR M-25 manufactured by Hitachi, Ltd.) at an output of 500 W for 60 seconds. The foamed layer thickness (DA ₆₀ ) and the foamed appearance of the obtained foamed laminate were evaluated. The results of the evaluation are shown in Table 2. Although it was excellent in foamed appearance, it was inferior in foam layer thickness (DA ₆₀ ).

The foamed laminate of the present invention is used as a cushioning material for wrapping paper, cushioning wrapping paper, wrapping bag, etc., as a non-slip material, a sound insulating material, a heat insulating material, a food container, a heat insulating paper container, etc. It is commonly used for paper containers.

Claims (8)

A method for producing a foamed laminate containing at least a (A) layer, a base material layer, and a (B) layer in this order. The (A) layer is made of a polyethylene resin (a), and the (B) layer is a moisture-proof layer. A method for producing a foamed laminate, which comprises going through the following steps (i) to (ii).
(I) Laminating (i) by dielectric heating with a lower output than the steps (ii) and (i) of softening the polyethylene-based resin (a) of the layer (A) by heating the laminate before foaming by dielectric heating. A step of foaming the polyethylene-based resin (a) of the layer (A) by heating the body. The method for producing a foamed laminate according to claim 1, wherein in the step (i), the polyethylene-based resin (a) in the layer (A) is heated at a melting point or higher and 200 ° C. or lower . The method for producing a foamed laminate according to claim 1 or 2, wherein in the step (ii), the temperature is maintained at 200 ° C. or higher, which is equal to or higher than the melting point of the polyethylene resin (a). The method for producing a foamed laminate according to any one of claims 1 to 3, wherein the thickness of the layer (A) before foaming is 30 μm to 150 μm. (B) The method for producing a foamed laminate according to any one of claims 1 to 4, wherein the moisture permeability of the layer is 15 g / m ^2/24 hr or less. The method for producing a foamed laminate according to any one of claims 1 to 5, wherein the basis weight of the paper base material is 30 g / m ² to 400 g / m ² . The method for producing a foamed laminate according to any one of claims 1 to 6, wherein the dielectric heating is a heating method using microwaves. The method for producing a foamed laminate according to claim 7, wherein the microwave output of the dielectric heating is 200 W to 300,000 W.