JP6398179B2 - Method for producing foam laminate and foam laminate - Google Patents

Description

  The present invention relates to a method for producing a foam laminate having a thick foam layer and excellent heat insulation.

  Conventionally, as a container having a heat insulating property, a synthetic resin, in particular, a polystyrene foamed one is often used. However, the expanded polystyrene container has drawbacks such as high environmental load at the time of disposal and poor printability, and alternatives to other materials are being studied. Under such circumstances, a container in which corrugated paper is pasted on the outer peripheral surface of the paper cup body to form a heat insulating layer, a container in which a laminate of pulp nonwoven fabric and coated paper is bonded to the outer peripheral surface of the paper cup, etc. Has been developed and used.

  However, each method has a drawback that it is not easy to process and mold, and the cost is high. Therefore, by laminating and heating a low-melting-point thermoplastic synthetic resin film on at least one surface of the moisture-containing base material, the synthetic resin film is foamed into irregularities using the moisture contained in the base material. Has been devised (see, for example, Patent Documents 1 to 3). However, the material thus obtained has a thin foam layer and insufficient heat insulation.

  Further, as a means for obtaining a foam having a thick foam layer, a technique has been proposed in which at least a part of the foam surface is vacuum-sucked to thicken the foam layer of the foam cell (see, for example, Patent Document 4). The container body member and the bottom plate member are composed of a high-melting point thermoplastic synthetic resin film laminated on the inner wall surface of the base material of the container body member and the bottom plate member, and the low melting point heat is applied to the outer wall surface of the base material of the container body member. There has been proposed a heat-insulating paper container in which a plastic synthetic resin film is laminated and the low-melting thermoplastic synthetic resin film is foamed by heat treatment (see, for example, Patent Document 5). Furthermore, a method has been proposed in which water is applied to a paper substrate to thicken the foam layer (see, for example, Patent Document 6).

  However, the method of thickening the foamed layer by vacuum suction has a problem that it is inferior in cost performance because a vacuum suction device is necessary and a step of performing vacuum suction is required in the manufacturing process. Further, in the heat insulating paper container having a high melting point thermoplastic synthetic resin on the inner wall surface and the technique of applying water to the paper substrate, the foam layer is thin and the heat insulating property is insufficient.

Japanese Patent Publication No. 48-32283 JP-A-57-110439 JP 2001-270571 A JP 2004-58534 A Japanese Patent Laid-Open No. 2007-217024 JP 2013-78928 A

  The objective of this invention is providing the manufacturing method of the foaming laminated body which a foaming layer is thick and shows the outstanding heat insulation.

  As a result of intensive studies to solve the above problems, the present inventors have found that a foamed laminate produced by a specific method exhibits excellent heat insulation properties, and have completed the present invention.

That is, it is a method for producing a foam laminate which is laminated in the order of at least (A) layer / paper substrate / (B) layer, and is characterized by at least the following steps (i) to (iii). This relates to a method for producing a foam laminate.
(I) The process of apply | coating the solution containing a foaming agent to the single side | surface or both surfaces of a paper base material.
(Ii) Polyethylene resin (a) having a density measured by JIS K6922-1 (2011) as layer (A) of 935 kg / m ³ or more and 970 kg / m ³ or less, and JIS K6922-1 as layer (B). laminating high-pressure measured density of 910 kg / ^{m 3} or more 930 kg / ^{m 3} or less by (2011) a low density polyethylene (b) a paper substrate (iii) polyethylene resin (a) / a paper The process which heat-processes to the laminated body which consists of material / high pressure method low density polyethylene (b), and foams high pressure method low density polyethylene (b) Hereinafter, this invention is demonstrated in detail.

The density (hereinafter simply abbreviated as density) measured by JIS K6922-1 (2011) of the polyethylene resin (a) constituting the laminate of the present invention is excellent in heat insulation and foam stability. in the range of 935~970kg / ^{m 3,} more preferred 945~970kg / ^{m 3,} is most preferably 950~965kg / ^{m 3.} When the density of the polyethylene-based resin (a) is less than 935 kg / m ^3, it is not preferable because of poor heat insulation, and when it exceeds 970 kg / m ³ , it is not preferable because of poor foam appearance.

  The polyethylene resin (a) constituting the laminate of the present invention is an ethylene homopolymer or an ethylene / α-olefin copolymer and a composition thereof, and the molecular chain form is linear. Alternatively, it may have a long chain branch having 6 or more carbon atoms. Such a polyethylene-based resin (a) is not particularly limited, and may be as long as the density range is not exceeded.

  Examples of such ethylene homopolymers include low pressure ethylene homopolymers and high pressure low density polyethylene.

  Such a low-pressure ethylene homopolymer can be obtained by a conventionally known low-pressure ion polymerization method.

  Such a high pressure method low density polyethylene can be obtained by a conventionally known high pressure radical polymerization method.

  Examples of the α-olefin used in such an ethylene / α-olefin copolymer include propylene, 1-butene, 4-methyl-1-pentene, 3-methyl-1-butene, 1-pentene, 1-hexene, -Heptene, 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.

  A method for obtaining such an ethylene / α-olefin copolymer is not particularly limited, and examples thereof include a high / medium / low pressure ion polymerization method using a Ziegler-Natta catalyst, a Philips catalyst, or a metallocene catalyst. Can do. Such a copolymer can be conveniently selected from commercially available products.

  In addition, the polyolefin resin (a) constituting the present invention may be blended with other polyolefins such as polypropylene, and the blending ratio of these polyolefins is 1 to 30% by weight of laminate moldability and laminate appearance. It is preferable from the point.

  When the polyolefin is mixed with the polyethylene resin (a) constituting the laminate of the present invention, a pellet mixture in which the pellets of the polyethylene resin (a) and the polyolefin pellets are mixed in a solid state may be used. A mixture obtained by melt kneading with a screw extruder, twin screw extruder, kneader, Banbury or the like is preferable because a product with stable quality can be obtained. When using a melt-kneading apparatus, the melting temperature is preferably about the melting point of polyethylene resin to about 300 ° C.

  Furthermore, for the polyethylene resin (a) constituting the present invention, additives generally used for polyolefin resins, such as an antioxidant, a light stabilizer, an antistatic agent, a lubricant, and an antiblocking agent, as necessary. May be added as long as the object of the present invention is not impaired.

  Among these, since it is excellent in laminate moldability, the high-density polyethylene (c) 10 to 90% by weight and the high-pressure method low-density polyethylene (d) 90 to 10% by weight (the total of (c) and (d) It is preferable that it is an ethylene resin composition (e) containing (weight%).

  Examples of such high-density polyethylene (c) include low-pressure ethylene homopolymers and ethylene / α-olefin copolymers.

  Moreover, in such a high density polyethylene (c), since it is excellent in the laminating property of ethylene-type resin composition (e), it is the melt mass flow rate (henceforth only MFR) measured by JISK6922-1 (2011). Abbreviated) is preferably in the range of 6 to 100 g / 10 min, more preferably in the range of 8 to 60 g / 10 min.

Furthermore, in such a high density polyethylene (c), the ethylene resin composition (e) is excellent in laminate processability and productivity, and therefore the density is preferably in the range of 935 to 980 kg / m ³ , more preferably 945 to 945. The range is 975 kg / m ³ .

  Such a high pressure method low density polyethylene (d) can be obtained by a conventionally known high pressure radical polymerization method.

  In such a high pressure method low density polyethylene (d), since the extrusion laminating property of the ethylene resin composition (e) is excellent, the MFR is preferably in the range of 0.1 to 20 g / 10 min, more preferably 0.8. It is in the range of 3 to 10 g / 10 minutes, most preferably 1 to 4 g / 10 minutes.

Moreover, in such a high-pressure method low-density polyethylene (d), since the film-forming stability of the ethylene-based resin composition (e) is excellent, the density is preferably in the range of 910 to 935 kg / m ³ .

  Since MFR of such an ethylene-based resin composition (d) is excellent in laminate moldability, it is preferably in the range of 1 to 50 g / 10 minutes, and more preferably in the range of 3 to 20 g / 10 minutes.

  The high pressure method low density polyethylene (b) constituting the laminate of the present invention can be obtained by a conventionally known high pressure method radical polymerization method.

High-pressure low-density polyethylene (b) is excellent in heat insulating property and foam appearance, density in the range of 910~930kg / ^{m 3,} more preferably 914~926kg / ^{m 3,} more preferably 916~924kg / m ³ range. When the density of the high-pressure low-density polyethylene (b) is less than 910 kg / m ^3, it is not preferable because the foam appearance is inferior, and when it exceeds 930 kg / m ³ , it is not preferable because the heat insulating property is poor.

  The MFR of the high-pressure method low-density polyethylene (b) is preferably in the range of 10 to 30 g / 10 minutes because of excellent heat insulation and foam appearance, more preferably 12 to 30 g / 10 minutes, and still more preferably 13 It is in the range of ˜24 g / 10 minutes, most preferably 13 to 18 g / 10 minutes.

  The high-pressure low-density polyethylene (b) constituting the present invention may be blended with another polyolefin such as an ethylene / α-olefin copolymer.

  When the polyolefin is mixed with the high-pressure method low-density polyethylene (b) constituting the laminate of the present invention, the pellet mixture obtained by mixing the high-pressure method low-density polyethylene (b) pellets and the polyolefin pellets in a solid state may be used. Although a mixture obtained by melt-kneading with a single screw extruder, twin screw extruder, kneader, Banbury or the like is preferable, a product with stable quality can be obtained. When using a melt kneader, the melting temperature is preferably about the melting point of the polyolefin resin to about 300 ° C.

  In addition, the high-pressure low-density polyethylene (b) constituting the laminate of the present invention is generally used for polyolefin resins such as an antioxidant, a light stabilizer, an antistatic agent, a lubricant, and an antiblocking agent as necessary. The additives that have been used may be added within a range that does not impair the object of the present invention.

The manufacturing method of the foaming laminated body of this invention is characterized by passing through the process of following (i)-(iii).
(I) The process of apply | coating the solution containing a foaming agent to the single side | surface or both surfaces of a paper base material.
(Ii) Step of laminating a polyethylene resin (a) as a layer (A) and a high-pressure method low density polyethylene (b) as a layer (B) on a paper substrate (iii) Polyethylene resin (a) / paper substrate / The process of applying heat treatment to the laminate comprising the high-pressure method low-density polyethylene (b) and foaming the high-pressure method low-density polyethylene (b) The method of applying a solution containing a foaming agent is as long as the object of the present invention is achieved. In the method, there is no particular limitation, and a technique using a roll coater, a lip coater, a spray device, a die coater, a gravure device, a dampening device, etc. can be exemplified. A method using a dampening device is preferable because the amount of water applied is uniform.

  Such a dampening apparatus includes, for example, a product name “High Rotor S” from Suzuki Sangyo Co., Ltd., a product name “WEKO Rotor Dampening” from Nikka Co., Ltd., and a trade name “Toko Electronics Co., Ltd.” "TSD-3000" is sold.

The coating amount of the solution containing the foaming agent in the present invention is not particularly limited as long as the object of the present invention is achieved, but the high-pressure method low-density polyethylene (b) can have a high expansion ratio, and the paper substrate and Since the adhesive strength with the polyethylene resin (a) and / or the high pressure method low density polyethylene (b) does not decrease, ² to 30 g / m ² is preferable, more preferably 3 to ²⁰ g / m ² , and most preferably 3. I am a ~10g / ^{m 2.}

  The foaming agent in the present invention is a compound that generates a gas when subjected to heat treatment, can be dissolved in a solvent, and is not particularly limited as long as the object of the present invention is achieved.

  Examples of such foaming agents include sodium hydrogen carbonate, maleic acid, glutaric acid, azodicarbonamide, hydrazodicarbonamide, N, N′-dinitrosopentamethylenetetramine, p, p′-oxybisbenzenesulfonylhydrazide. Etc. are exemplified.

  The solvent used in the solution containing the foaming agent in the present invention is not particularly limited as long as the object of the present invention is achieved. Water, acetone, methanol, isopropanol, dimethylformamide, tetrahydrofuran, 1,4-dioxane , Benzene, toluene, xylene and the like.

  The concentration of the solution containing the foaming agent in the present invention is not particularly limited as long as the object of the present invention is achieved.

  In these, since it is excellent in foaming stability, it is preferable to use the aqueous solution of sodium hydrogencarbonate and sodium carbonate as a solution containing a foaming agent. When sodium carbonate is dissolved in water, it becomes sodium hydrogen carbonate by the reaction of the following formula (2).

Na ₂ CO ₃ + H ₂ O → NaHCO ₃ + NaOH (2)
Such sodium hydrogen carbonate generates carbon dioxide gas and water by the reaction of the following formula (3) during the heat treatment. These generated gases cause the high-pressure low-density polyethylene (b) to foam.

2NaHCO ₃ → Na ₂ CO ₃ + H ₂ O + CO ₂ (3)
In the production method of the present invention, the method for laminating the polyethylene resin (a) and the high-pressure low-density polyethylene (b) is not particularly limited as long as the object of the present invention is achieved, and the laminate of the present invention is molded. Examples of the method include an extrusion laminate molding method, a dry laminate molding method, a wet laminate molding method, a thermal laminate molding method, a hot melt laminate molding method, and a compression molding method. The molding methods for the polyethylene resin (a) and the high-pressure method low-density polyethylene (b) may be the same method or different methods.

  Among these molding methods, the extrusion lamination molding method is preferable from the viewpoints of production efficiency and the quality of the molded laminate.

  Examples of the method for obtaining a laminate by an extrusion laminate molding method include various extrusion lamination methods such as a single lamination method, a tandem lamination method, a sandwich lamination method, and a coextrusion lamination method. The temperature of the resin in the extrusion laminating method is preferably in the range of 260 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 process, immediately after forming the extruded layer in a molten state in the thermoplastic resin, the substrate adhesion surface of the layer is exposed to an oxygen-containing gas or an ozone-containing gas, and a method of bonding to the substrate is used. It is preferable because of its excellent adhesiveness with the material layer. When the adhesiveness between the thermoplastic resin and the substrate is improved by the ozone-containing gas, the ozone gas treatment amount 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.

  The extrusion laminating method in the method for obtaining the laminate used in the present invention further improves the adhesiveness between the thermoplastic resin layer and the base material layer, so that the temperature at which the thermoplastic resin does not foam, for example, 30 ° C.-60 ° Heat treatment can be performed at a temperature of 10 ° C. for 10 hours or more. Moreover, you may perform well-known surface treatments, such as a corona treatment, a flame treatment, and a plasma treatment, with respect to the adhesive surface of a base material as needed. If necessary, an anchor coating agent may be applied to the substrate.

  In the heating method for obtaining the laminate used in the present invention, the heat source to be heated is not particularly limited as long as this object is achieved. Examples of the laminate and the molded container include hot air, electric heat, and electron beam. For example, in a container in which a body is molded, a high-temperature object is filled and the heat of the filling is used. Further, the heating method can be performed by a batch method in an oven, a continuous method using a conveyor, or the like.

Conditions such as heating temperature and heating time are not particularly limited as long as the object of the present invention is achieved. Generally, when hot air is used as a heat source, the heating temperature is the melting point of the high-pressure method low-density polyethylene (b). And 150 ° C. or less, the air volume is 0.5 to 2.0 m ³ / hour, and the heating time is 10 seconds to 6 minutes.

Since the heating conditions of the present invention are excellent in heat insulation, it is preferable that the water reduction rate constant k (min− ¹ ) satisfies the condition of 0.60 to 1.30, more preferably 0.65 to 1.30. Most preferably, it is 0.80-1.10.

Here, the water decrease rate constant k (min− ¹ ) is the amount of water change dW per unit time in a certain heating time t (min) in the step (iii) of foaming the high pressure method low density polyethylene (b). It is a proportionality constant in the first-order velocity equation represented by the following equation (1), which is a relational expression between / dt and the moisture concentration W in the paper substrate at a certain heating time t (minutes).

dW / dt = −kW (1)
Specifically, the water reduction rate constant k (min− ¹ ) is laminated in the order of paper base / polyethylene resin, the density of the polyethylene resin is 940 kg / m ³ , and the thickness of the polyethylene resin is 40 μm. It can obtain | require using the weight change at the time of the heating of a certain laminated body. Derived from weight loss ΔW _t (g / m ² ) per unit area after heating at a certain time t (min) obtained when heat-treating a laminate comprising paper base material / polyethylene resin and formula (1) The weight reduction amount ΔW _{t, cal} (g / m ² ) per unit area at a certain time t (minute) obtained by calculating the following equation (4) is 0.5 to 6 every 0.5 minutes. When calculating up to minutes, the water decrease rate constant k (minutes) is such that the total value from 0.5 minutes to 6 minutes of the error ε _t at a certain time t (minutes) expressed by the following equation (5) is minimized. ^-1 ).

ΔW _{t, cal} = W ₀ [1-exp (−kt)] (4)
ε _t = [(ΔW _t −ΔW _{t, cal} ) / ΔW _t ] ² (5)
Here, W ₀ is the moisture content (g / m ² ) per unit area before heating in the paper base material / polyethylene resin.

Although there is no limitation in particular about the paper base material which comprises the laminated body of this invention, since the expansion ratio of a high pressure method low density polyethylene (b) can be improved, the basic weight of a paper base material is 150-400 g / m. ² is more preferable, and 250 to 350 g / m ² is more preferable.

Moisture contained in such a paper base causes foaming of the high-pressure low-density polyethylene (b) by heating. Since the expansion ratio of the high-pressure method low-density polyethylene (b) is improved, the water content of the paper substrate after laminating the polyethylene resin (a) and the high-pressure method low-density polyethylene (b) is 20 to 40 g / m ^2. Is preferable, more preferably 25 to 40 g / m ² , and most preferably 27 to 35 g / m ² .

  In the production method of the present invention, as long as the object of the present invention is achieved, other steps may be included, and other layers such as paper and thermoplastic resin are formed on the surface of the high pressure method low density polyethylene (b). Step of laminating, step of printing on high pressure method low density polyethylene (b) or / and paper, step of boxing polyethylene resin (a) / paper substrate / high pressure method low density polyethylene (b) into container shape Etc. can be exemplified.

  The thickness of the layer (A) and the thickness before foaming of the layer (B) constituting the laminate of the present invention are not particularly limited as long as the object of the present invention is achieved. Since the problem is small, the thickness is preferably 30 μm to 5 mm, and the range of 30 μm to 150 μm is most preferable from the viewpoint of economy.

  About the foaming laminated body of this invention, since it is excellent in heat insulation, 1600 micrometers or more are preferable for the sum total of the thickness of a foaming layer, More preferably, it is 1700 micrometers or more, Most preferably, it is 1800 micrometers or more.

  The foamed laminate of the present invention is characterized in that at least (A) layer / paper substrate / (B) layer is laminated in order, and (A) layer, paper substrate, and (B) layer. In addition to the above three components, other components such as the (C) layer may be included. Specifically, (A) layer / paper substrate / (B) layer, (A) layer / paper substrate / (B) layer / (A) layer, (B) layer / paper substrate / (A) Layer / (B) layer, (A) layer / paper substrate / (B) layer / (B) layer, (A) layer / (A) layer / paper substrate / (B) layer, (A) layer / Paper substrate / (B) layer / (C) layer, (B) layer / paper substrate / (A) layer / (C) layer, (C) layer / (B) layer / paper substrate / (A) Layer / (B) layer / (C) layer, (A) layer / paper substrate / (B) layer / (C) layer / (B) layer / (A) layer, (B) layer / paper substrate / Examples include (A) layer / (C) layer / (A) layer / (B) layer.

  Examples of the layer (C) include layers formed from synthetic polymer, woven fabric, non-woven fabric, metal foil, 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, 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 such as polyvinylidene chloride, polystyrene, polycarbonate, polyurethane, and cellulose resin. Further, these 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 films and sheets may be further printed using urethane ink or the like. Examples of the metal foil include aluminum foil and copper foil, and examples of paper include kraft paper, fine paper, stretched paper, glassine paper, paperboard such as base paper for cups and photographic paper.

  The container of the present invention comprises at least a trunk member and a bottom member punched into a predetermined shape and size, and has excellent heat insulation properties. Therefore, the foamed laminate produced by the production method of the present invention is used for at least the trunk member. It is preferable to do. There is no particular limitation on the method for producing the container as long as the object of the present invention is achieved.

  The order of the steps for boxing the container is not particularly limited, but is preferably performed immediately before the step of foaming the high-pressure low-density polyethylene (b) because of high production efficiency.

  According to the production method of the present invention, a foam laminate having a thick foam layer and excellent heat insulation can be produced.

Hereinafter, although an example and a comparative example explain the present invention, the present invention is not limited to these.
(1) Density Density was measured based on JIS K6922-1 (2011).
(2) Melt mass flow rate (MFR)
MFR was measured according to JIS K6922-1 (2011).
(3) Heat-foaming Gear type aging tester (No. 102-SHF-77 manufactured by Yasuda Seiki Seisakusakusho Co., Ltd.) obtained by heating a sample obtained by cutting the laminate obtained in the example into 10 cm × 20 cm and forming it into a cylindrical shape. ) Was left standing for a predetermined time while applying hot air, and then taken out and cooled in air to room temperature. Also, the air volume during heating was adjusted by “HIGH” and “LOW” of the “AGING” button.
(4) Moisture content of paper substrate The paper substrate before and after the lamination of the polyethylene resin was measured using a Karl Fischer method moisture measurement device (trade name CA-05, manufactured by Mitsubishi Chemical Corporation). The measurement temperature is 165 ° C.
(5) Water decrease rate constant k
A high-density polyethylene (product name Petrocene manufactured by Tosoh Corporation) having a MFR of 7 g / 10 min and a density of 940 kg / m ³ on a paper substrate having a water content of 24 g / m ² and a basis weight of 320 g / m ² LW04-1) is supplied to a single-screw extrusion laminator (manufactured by Musashinokikai Co., Ltd.) having a screw with a diameter of 90 mmφ, extruded from a T-die at a temperature of 320 ° C., the take-up speed on a paper substrate is 60 m / min, After performing extrusion lamination molding so that the length is 130 mm and a thickness of 40 μm, using a constant temperature and humidity chamber (EC-25MHP, manufactured by Hitachi Appliances, Inc.), the moisture content described in the examples and comparative examples The laminated body adjusted in humidity was used. These laminates are heat-treated every 0.5 minutes up to 6 minutes in the same manner as (3) heating foaming, using an electronic balance (BP210S, manufactured by Sartorius Co., Ltd.) that can measure up to the fourth digit of the decimal point. The weight change before and after the heat treatment was measured, and the weight loss ΔW _t (g / m ² ) was calculated. Using this weight reduction amount ΔW _t , the water reduction rate constant (min ⁻¹ ) was calculated using the method exemplified in the specification.
(6) Foam Layer Thickness Samples were taken of the foam obtained in Examples and the laminate laminate before foaming as a blank, and a cross-sectional photograph was taken with an optical microscope. The thickness of the foam layer was measured from the cross-sectional photograph and measured at five locations.

Example 1
As the polyethylene-based resin (a), high-density polyethylene (trade name Petrocene LW04-1 manufactured by Tosoh Corporation) having an MFR of 7 g / 10 min and a density of 940 kg / m ³ is used. b) High-pressure method low-density polyethylene (trade name Petrocene 212 manufactured by Tosoh Corporation) (B1) having an MFR of 13 g / 10 min and a density of 918 kg / m ³ , and sodium bicarbonate (Wako Pure Chemical Industries, Ltd.) as a blowing agent Kogyo Co., Ltd., reagent grade) (C1) was used.

First, (A1) is supplied to a paper base having a water content of 24 g / m ² and a basis weight of 320 g / m ² to a single-screw extrusion laminator (manufactured by Musashinokikai Co., Ltd.) having a screw having a diameter of 90 mm. Extrusion was performed from a T-die at a temperature of 0 ° C., and extrusion lamination was performed on a paper substrate so that the take-up speed was 60 m / min, the air gap length was 130 mm, and the thickness was 40 μm. Furthermore, before laminating (B1), using a high rotor S (manufactured by Suzuki Sangyo Co., Ltd.) on the surface on which (B1) is laminated, 10 g / After coating m ² , (B1) is fed to a single-screw extruder (Musashi no Kikai Co., Ltd.) having a screw with a diameter of 90 mmφ, temperature of 320 ° C., take-up speed of 60 m / min, air gap length of 130 mm Extrusion lamination was carried out to obtain a laminate having a laminate of polyethylene resin (A1), paper base material, and high-pressure low-density polyethylene (B1). The obtained laminate was heated for 5 minutes at a temperature of 120 ° C. and an air volume of HIGH for foaming to obtain a foam laminate. About the obtained laminated body before and behind foaming, the thickness of the foamed layer was evaluated. The evaluation results are shown in Table 1.

Example 2
A laminate before and after foaming was obtained in the same manner as in Example 1 except that the polyethylene resin and the foaming agent used in Example 1 were used and the foaming temperature was 130 ° C. About the obtained laminated body, the thickness of the foaming layer was evaluated. The results are shown in Table 1.

Example 3
A laminate before and after foaming was obtained in the same manner as in Example 1 except that the polyethylene resin and the foaming agent used in Example 1 were used and the concentration of the aqueous sodium hydrogen carbonate solution was 4% by weight. About the obtained laminated body, the thickness of the foaming layer was evaluated. The results are shown in Table 1.

Example 4
A laminate before and after foaming was obtained in the same manner as in Example 3 except that the polyethylene-based resin used in Example 3 was used and the air volume during foaming was changed to LOW. About the obtained laminated body, the thickness and smoothness of the foamed layer were evaluated. The results are shown in Table 1.

Comparative Example 1
A laminate before and after foaming was obtained in the same manner as in Example 1 except that sodium bicarbonate was not added to the water to be applied. About the obtained laminated body, the thickness of the foaming layer was evaluated. The results are shown in Table 1. The foam layer thickness after foaming was inferior.

Comparative Example 2
A laminate before and after foaming was obtained in the same manner as in Example 1 except that the aqueous sodium hydrogen carbonate solution was not applied. About the obtained laminated body, the thickness of the foaming layer was evaluated. The results are shown in Table 1. The foam layer thickness after foaming was inferior.

  The foamed laminate of the present invention is suitably used for containers that require heat insulation, such as paper containers for high-temperature beverages such as coffee and soup, and containers for instant foods such as instant noodles.

Claims (7)

A method for producing a foam laminate in which at least (A) layer / paper base material / (B) layer is laminated in order, wherein at least the following steps (i) to (iii) are performed: A method for producing a foam laminate.
(I) Step of applying an aqueous solution of sodium bicarbonate or sodium carbonate on one side or both sides of a paper substrate (ii) The density measured by JIS K6922-1 (2011) as a layer (A) is 935 kg / m ³ above 970 kg / ^{m 3} or less is polyethylene resin (a), (B) high-pressure density measured by JIS K6922-1 (2011 years) is not more than 910 kg / ^{m 3} or more 930 kg / ^{m 3} as layer low density Step of laminating polyethylene (b) on paper substrate (iii) Heat treatment is performed on a laminate comprising polyethylene resin (a) / paper substrate / high pressure method low density polyethylene (b), and high pressure method low density polyethylene ( b) foaming step ^{2. The} method for producing a foam laminate according to claim 1, wherein the amount of sodium bicarbonate or an aqueous solution of sodium carbonate applied to the paper substrate is 2 g / m ² or more and 30 g / m ² or less. The manufacturing method of the foaming laminated body of Claim 1 or 2 which apply | coats the aqueous solution of sodium hydrogencarbonate or sodium carbonate to a paper base material using a dampening apparatus. Method for producing a foam laminate according to any one of claims 1 to 3, wherein the basis weight of the paper substrate is 150 g / ^{m 2} or more 400 g / ^{m 2} or less. In the step (iii) of foaming the high-pressure method low-density polyethylene (b), a heating condition that satisfies the condition that the water reduction rate constant k (min− ¹ ) is 0.60 or more and 1.30 or less is applied. The manufacturing method of the foaming laminated body in any one of Claims 1-4 .
Here, the water decrease rate constant k (min− ¹ ) is the amount of water change dW per unit time in a certain heating time t (min) in the step (iii) of foaming the high pressure method low density polyethylene (b). It is a proportionality constant in the first-order velocity equation represented by the following equation (1), which is a relational expression between / dt and the moisture concentration W in the paper substrate at a certain heating time t (minutes).
dW / dt = −kW (1) In the step (iii) of foaming the high-pressure method low-density polyethylene (b), a heating condition that satisfies the condition that the water reduction rate constant k (min− ¹ ) is 0.65 or more and 1.30 or less is applied. The manufacturing method of the foaming laminated body of Claim 5 . In the step (iii) of foaming the high-pressure method low-density polyethylene (b), a heating condition is applied that satisfies the condition that the water reduction rate constant k (min− ¹ ) is 0.80 or more and 1.10 or less. The manufacturing method of the foaming laminated body of Claim 6 .