JP6069846B2 - FOAM LAMINATE, PROCESS FOR PRODUCING THE SAME, FOAMED PAPER AND INSULATION CONTAINER USING THE SAME - Google Patents

Description

  The present invention relates to a foamable laminate, a method for producing the same, and a foamed paper and a heat insulating container using the same, more specifically, the foamed paper after foaming and the surface of the heat insulating container are excellent in smoothness, and the foamed layer is thick. Excellent thermal insulation, foamable laminate with good foam appearance and heat-sealability during shaping, foamed paper and heat-insulated containers using the laminate, and simple post-treatment to improve economy and high quality The present invention relates to a method for producing a foamable laminate that can stably provide a product.

  Conventionally, as a container having heat insulation properties such as a cup for hot beverages, a container for instant noodles and the like, many containers such as made of expanded polystyrene have been used, but the expanded polystyrene container has a high environmental load at the time of disposal, There are drawbacks such as poor printability, and alternatives to other materials are being considered.

  Therefore, by laminating a low-melting point thermoplastic synthetic resin film on at least one surface of the moisture-containing paper base material and heating it, the synthetic resin film is foamed into irregularities using the moisture contained in the base material. A technique 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 formed by laminating a plastic synthetic resin film and foaming the thermoplastic synthetic resin film having a low melting point by heat treatment (see, for example, Patent Document 5).

  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. Also, in a heat-insulated paper container having a high-melting-point thermoplastic synthetic resin on the inner wall surface, large protrusions are generated on the surface of the foam layer during foaming, foam cell bonding or bubble breakage, and foam cell shrinkage during cooling There is a problem that the surface appearance is likely to deteriorate due to a reason that a large concave portion is formed on the surface for the reason described above.

  Further, as a method of obtaining a foam layer having a good foam appearance, in a paper container composed of a bottom plate member and a body member, foaming of a low melting point thermoplastic resin from the surface side of the paper to at least one wall surface of the body member There has been proposed a heat insulating container in which a two-layered heat insulating film composed of an outer layer of a non-foamed layer of a thermoplastic resin having a melting point higher than the melting point of the inner layer and the thermoplastic resin, for example, 5 ° C. is applied (for example, a patent Reference 6).

  However, the heat insulating container has a problem that the thickness of the foam layer is thin and the heat insulating property is insufficient. Further, if the MFR is increased in order to improve the foaming property, there are problems that the appearance of the foamed layer becomes poor and the workability at the time of extrusion laminating becomes unstable.

  Further, as a method for obtaining a foam layer having good smoothness of foam appearance, the heat insulation container has at least two foam layers, and is a laminate comprising (a) layer / (b) layer / base material layer. Thus, a heat insulating container made of a thermoplastic resin in which the (a) layer has a remarkably higher melting point than the (b) layer has been proposed (see, for example, Patent Document 7).

  However, in the above heat insulating container, since a resin having a high melting point is used for the outermost surface layer, the problem that the (A) layer does not expand and contract during foaming and foam floating occurs and heat sealability during shaping There were problems such as lowering.

  Accordingly, it is economically stable to produce foamed paper and a heat-insulated container using the same, made of thermoplastic resin, with a thick foam layer, excellent heat insulation, excellent surface appearance, and good workability. There has been a demand for a foamable laminate.

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 05-42929 A JP 2010-46881 A

  In view of the above circumstances, the object of the present invention is excellent in the smoothness of foamed paper after foaming and the surface of the heat insulating container, the foamed layer is thick, and exhibits excellent heat insulation, as well as the foam appearance and heat sealability during shaping. The present invention provides a foamable laminate having good quality, a foamed paper using the same, a heat-insulated container, and a method for producing a foamable laminate capable of stably providing a high-quality one with excellent economic efficiency by simple post-treatment. There is.

  As a result of intensive studies to solve the above problems, the present inventors laminated a foamable resin layer (A) made of polyethylene resin A on one surface of a base material layer mainly composed of paper, A foamable laminate obtained by laminating a non-foamed resin layer (B) made of polyethylene-based resin B on the other surface of the base material layer, and performing a specific post-treatment to form the foamable resin layer (A). The present inventors have found that a foamed laminate having a modified surface can solve the above-mentioned problems and has completed the present invention.

That is, according to the first aspect of the present invention, at least one foamable resin layer (A) made of polyethylene-based resin A is laminated on one surface of a base material layer mainly composed of paper, A foamable laminate formed by laminating a non-foamed resin layer (B) made of polyethylene resin B on the other surface of the layer,
By performing the following post-treatment (a) and / or (b), a foamable laminate is provided in which the surface of the foamable resin layer (A) is modified.
(A) A corona treatment of 20 W · min / m ² or more is performed on the surface of the foamable resin layer (A).
(B) An aging treatment is performed in which the foamable laminate is left in an environment of 40 ° C. or higher for 1 hour or longer.

  According to the second invention of the present invention, in the first invention, the polyethylene resin A has a melt mass flow rate (MFRa) measured in accordance with JIS K6922-2: 2005 of 1 to 50 g / A foamable laminate is provided that is 10 minutes long.

  According to the third invention of the present invention, in the first or second invention, the polyethylene resin A has a melting temperature measured in accordance with JIS K6922-2: 2005 of 80 to 125 ° C. A foamable laminate is provided.

  According to the fourth invention of the present invention, in any one of the first to third inventions, the polyethylene resin A contains 50 to 99% by weight of high-pressure low-density polyethylene and 1 to 50% by weight of other polyolefins. The foamable laminate according to any one of claims 1 to 3 is provided.

  According to a fifth invention of the present invention, in any one of the first to fourth inventions, the foamable resin layer (A) has a thickness before foaming of 30 μm or more. The body is provided.

According to the sixth aspect of the present invention, the foamable resin layer is formed by laminating at least the foamable resin layer (A) made of the polyethylene resin A on one surface of the base material layer mainly composed of paper. There is provided a method for producing a foamable laminate comprising a laminating step and a post-treatment step in which the following (a) and / or (b) post-treatment is performed.
(A) A corona treatment of 20 W · min / m ² or more is performed on the surface of the foamable resin layer (A).
(B) An aging treatment is performed in which the foamable laminate is left in an environment of 40 ° C. or higher for 1 hour or longer.

  Further, according to the seventh invention of the present invention, in the sixth invention, the aging treatment is performed in at least two stages, left in an environment of 40 ° C. or higher in the former stage for 1 hour or more, and then humidified in the latter stage. There is provided a method for producing a foamable laminate, which is left in an atmosphere.

  According to the eighth invention of the present invention, in the sixth or seventh invention, a non-foamed layer in which a non-foamed resin layer (B) made of polyethylene resin B is laminated on the other surface of the base material layer. A method for producing a foamable laminate comprising a lamination step is provided.

  According to the ninth invention of the present invention, the foamable laminate of any one of the first to fifth inventions is heated, and the foamable resin layer is foamed mainly using the moisture contained in the paper substrate. A foamed paper is provided that is obtained.

  According to a tenth aspect of the present invention, in the ninth aspect, the height of the foamed cell formed by foaming the foamable resin layer (A) is 500 μm or more. Processed paper is provided.

  Moreover, according to the eleventh invention of the present invention, after forming the container shape so that the foamable resin layer (A) is outside using the foamable laminate of any one of the first to fifth inventions, There is provided an insulated container obtained by heating to foam a foamable resin layer.

The foamed laminate of the present invention is a foamed paper and a heat insulating container after foaming, and the foamed layer is thick, exhibits excellent heat insulation properties, has excellent smoothness on the surface of the foamed layer, and has a good surface appearance. A foamed laminate having good heat sealability during shaping, a foamed paper and a heat insulating container using the foamed laminate.
In addition, the method for producing a foam laminate of the present invention is excellent in smoothness of foamed paper after foaming and the surface of the heat insulating container, the foam layer is thick, exhibits excellent heat insulation, and is economical by simple post-treatment. A foamed laminate, foamed paper and a heat-insulated container having a stable foam appearance can be obtained.

FIG. 1 is an ultra-deep color 3D shape measurement micrograph showing an example of the foam layer surface of the foamable laminate of the present invention. FIG. 2 is an ultra-deep color 3D shape measurement micrograph showing an example of the foam layer surface of a conventional foam laminate.

In the present invention, at least one foamable resin layer (A) made of polyethylene resin A is laminated on one surface of a base material layer containing paper as a main component, and the other surface of the base material layer is polyethylene-based. It is a foamable laminate formed by laminating a non-foamed resin layer (B) made of resin B, and the surface of the foamable resin layer (A) is modified by performing a specific post-treatment. The present invention relates to a foamable laminate and a method for producing the same.
Moreover, this invention relates to the foamed paper and heat insulation container which use the said foamable laminated body.
Hereinafter, the details of the post-treatment method, layer structure, raw material resin and the like of the foamable laminate will be described.

1. In the present invention, at least one foamable resin layer (A) made of polyethylene resin A is laminated on one surface of a base material layer containing paper as a main component, and the other surface of the base material layer. And a non-foamed resin layer (B) made of polyethylene-based resin B, the foamable laminate being subjected to the following post-treatment (a) and / or (b): It is a foamable laminate in which the surface of the layer (A) is modified.
(A) A corona treatment of 20 W · min / m ² or more is performed on the surface of the foamable resin layer (A).
(B) An aging treatment is performed in which the foamable laminate is left in an environment of 40 ° C. or higher for 1 hour or longer.

  As a result of studying to solve the above-mentioned problems, the present inventors have conducted surface corona treatment and aging treatment on the foamable resin layer, whereby the surface smoothness of the foamable laminate having the foamable resin layer formed on the surface thereof. Found to improve. That is, for example, in the known literature, as the polyethylene resin (a) used for the surface layer laminated on the foamable resin layer, a resin whose melting temperature is much higher than the polyethylene resin (b) used for the foamable resin layer is used. In the present invention, the foamable resin layer (A) made of the polyethylene resin A is subjected to corona treatment and / or aging treatment, so that foaming processing with excellent surface smoothness and heat insulation is achieved by subsequent foaming. It has been found that a foamed laminate can be obtained from paper, and the present invention has been completed.

  That is, in the present invention, the foamable resin layer (A) containing the polyethylene resin A is subjected to corona treatment and / or aging treatment, thereby modifying the surface of the foamable resin layer (A), that is, By promoting crosslinking and improving the viscosity of the surface, cell growth is suppressed by the surface when the polyethylene-based resin A melts and foams, so the surface smoothness of the foamed layer can be improved. It is done.

  The “foaming” and “non-foaming” as used in the present invention refers to a heat treatment step (about 110 ° C. to about 200 ° C.) after forming a molded body such as a heat insulating container using the laminate obtained in the present invention. ), A layer that mainly foams using moisture contained in the paper base material is referred to as “foaming”, and a layer that does not mainly foam is referred to as “non-foaming”. Whether or not the resin layer foams is determined by the subsequent heat treatment temperature and the melting point of the resin used for the resin layer.

(1) Expandable resin layer (A)
The foamable resin layer (A) of the present invention needs to contain at least a polyethylene resin A.
The polyethylene resin A used in the present invention preferably has a melt mass flow rate (MFRa) measured in accordance with JIS K6922-2: 2005 of 1 to 50 g / 10 minutes. In particular, the range of 5 to 20 g / 10 min is preferable because of excellent foamability.

  In addition, the polyethylene resin A used in the present invention preferably has a melting temperature measured in accordance with JIS K6922-2: 2005 of 80 to 125 ° C. In particular, the range of 100 to 110 ° C. is preferable because the heat sealability is improved.

The density of the polyethylene-based resin A used in the present invention is preferably in the range of 870 to 935 kg / m ³ because of excellent foamability. More preferably, it is the range of 890-930 kg / m < ³ >.

  As the polyethylene resin A of the present invention that satisfies the above requirements, high-pressure method low density polyethylene A, ethylene / α-olefin copolymer A, ethylene / vinyl acetate copolymer, ethylene / ethyl acrylate copolymer, ethylene -An acrylic acid copolymer, an ethylene-methacrylic acid copolymer, etc. are mentioned. In particular, when high-pressure low-density polyethylene is used for the layer (A), foaming growth is not suppressed, the expansion ratio can be improved, and surface smoothness is excellent, which is preferable.

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

  A method for obtaining such an ethylene / α-olefin copolymer A 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. be able to.

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

  Moreover, you may mix | blend other polyolefin with the polyethylene-type resin A which comprises this invention. At this time, since the foamability is excellent, the mixing ratio is preferably 50 to 99% by weight for the high-pressure method low-density polyethylene A and 1 to 50% by weight for the other polyolefins.

Examples of the polyolefin to be mixed with the high-pressure method low-density polyethylene A include ethylene / α-olefin copolymers, polypropylene, polybutene, and the like, and since it has excellent foaming properties, the density is 850 kg / m ³ or more and less than 920 kg / m ^3. The ethylene / α-olefin copolymer is preferred.

  In the polyethylene resin A of the present invention, additives generally used in polyolefin resins such as an antioxidant, a light stabilizer, an antistatic agent, a lubricant, an antiblocking agent, etc. are added to the polyethylene resin A of the present invention as necessary. You may add in the range which does not impair.

  When the polyethylene resin A constituting the laminate of the present invention is composed of two or more types of polyolefin, the mixing may be a pellet mixture in which pellets of high-pressure low-density polyethylene A and polyolefin pellets are mixed in a solid state. 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 polyethylene resin to about 200 ° C.

  The thickness of the foamable resin layer (A) of the present invention comprising the polyethylene resin A is preferably 30 μm or more as the thickness at the time of lamination before heating and foaming in order to obtain a good foam thickness and foam appearance. If it is less than 30 micrometers, since it is inferior to a foaming external appearance, it is not preferable.

After the foamable resin layer (A) of the present invention is formed on the substrate, the surface of the foamable resin layer (A) is subjected to the following post-treatment (a) and / or (b). It must be modified.
(A) A corona treatment of 20 W · min / m ² or more is performed on the surface of the foamable resin layer (A).
(B) An aging treatment is performed in which the foamable laminate is left in an environment of 40 ° C. or higher for 1 hour or longer.

In the post-treatment (a), the corona treatment performed on the surface of the foamable resin layer (A) needs to be performed in a discharge amount range of 20 W · min / m ² or more. Preferably it is 30 W · min / m ² or more, more preferably 40 W · min / m ² or more. By performing this treatment, the foamed surface smoothness of the foamable resin layer (A) is significantly improved when the laminate of the present invention is subjected to a subsequent heating step to foam the foamable resin layer (A). . In general, in a laminate used for printing, the surface of the laminate before printing may be subjected to corona treatment in order to improve printability, but the corona treatment of the present invention is stronger than such normal pre-printing corona treatment. Corona treatment in range. Upper limit, since the characteristics improving change in surface is too strong is lowered, 80W · min / ^{m 2} or less, preferably 75W · min / ^{m 2} or less, and more preferably not more than 70W · min / ^{m 2.} By such corona treatment, the wetting tension according to JIS K6768 is improved by about 30% from the value before the treatment.
As a method for performing corona treatment on the foamable resin layer (A), a usual method for performing corona treatment on the film surface can be employed. Specifically, a film in which a foamable resin layer (A) is laminated is passed between an insulated electrode and a dielectric roll, and a high frequency high voltage is applied from the surface of the foamable resin layer (A) to corona discharge. Can be used.

In the post-treatment (b), the aging treatment performed for modifying the surface of the foamable resin layer (A) is to leave the whole foamable laminate in an environment of 40 ° C. or more for 1 hour or more. is necessary. By performing this treatment, there is an effect of promoting the modification of the resin surface, and the foamable resin layer when the laminate of the present invention is subjected to a subsequent heating step to foam the foamable resin layer (A). The foamed surface smoothness of (A) is remarkably improved.
The upper limit of the temperature needs to be controlled to a temperature at which the foamed layer resin does not foam at least, and is preferably 40 to 100 ° C, more preferably 40 to 85 ° C, and further preferably 45 to 80 ° C. The standing time is 1 hour or longer, preferably 6 hours or longer, more preferably 1 day or longer, but can be appropriately controlled according to the relationship with the set temperature. For example, if it is 40 ° C., it is 8 hours or longer and 80 ° C. If it exists, it is preferable when it is 2 hours or more.
The upper limit of the standing time is not particularly limited because the reforming effect is improved as the standing time is longer. However, since the change in improvement becomes small even when left for a long time, it is suitably within 3 months, preferably 1 month. Within two weeks, more preferably within two weeks.
The aging treatment atmosphere may be in the air, but other atmospheres may be used. Further, it may be in a normal atmosphere or in a humidified atmosphere. As the humidification in the humidified atmosphere, the relative humidity is 55% or more, preferably 70% or more, more preferably 90% or more. The range is preferable. When the moisture content contained in the paper substrate of the laminate is kept at about 5 to 8% in a humidified atmosphere, foaming is caused by the action of the moisture contained in the paper substrate when subjected to the subsequent heating and foaming step. Foaming of the conductive resin layer (A) is performed well.

Moreover, you may perform an aging process in steps. When performing an aging process in steps, it can be performed in at least two stages. For example, the aging process may be performed in two stages of initial aging and late humidification. In this case, as the initial aging, it can be left in an environment of 40 ° C. or higher in the former stage for 1 hour or more, and then it can be left in a humidified atmosphere in the latter stage as the latter humidification treatment. Thereby, the process of initial aging can be simplified and the effect of keeping the water | moisture content contained in a paper base material can also be ensured. In this case, the initial aging can be performed in a normal air atmosphere, and then the subsequent humidification treatment can be performed in a humidified atmosphere.
The humidification in the latter humidification treatment is preferably in the range where the moisture content in the air is 55% or more, preferably 70% or more, more preferably 90% or more. Although the temperature is not particularly limited, it is preferably carried out in a heated atmosphere in the range of 25 to 100 ° C. because it is in a water vapor atmosphere. By performing this latter humidification treatment, it becomes possible to restore the amount of moisture contained in the paper substrate of the laminate, which was lost during the initial aging treatment, and when subjected to the subsequent heating and foaming process, Foaming of the foamable resin layer (A) is favorably performed by the action of moisture contained in the substrate.

In addition, the corona treatment and the aging treatment may be performed independently or in combination. When they are used in combination, whichever may be performed first, it is preferable to perform the corona treatment first because there is a synergistic effect of further accelerating the cross-linking of the surface by the corona treatment by the aging treatment.
By the corona treatment and / or aging treatment, the surface of the foamable resin layer (A) containing the polyethylene resin A is modified, the surface is promoted to be crosslinked, and the viscosity of the surface is improved. It is considered that the surface smoothness of the foamed layer can be improved because cell growth is suppressed on the surface when the resin A melts and foams.
Moreover, it is thought that the effect is further accelerated | stimulated by using the said corona treatment and aging treatment together.

(2) Base material layer The base material layer which comprises the laminated body of this invention needs to be a base material layer which has paper as a main component. In the present invention, the base material layer mainly composed of paper includes paper itself and paper appropriately processed.
In the present invention, by subjecting the laminate of the present invention to a subsequent heating step, water contained in the paper mainly becomes water vapor by heating, and the foamable resin layer (A) is foamed by its action.

The moisture contained in the base material layer is for foaming the foamable resin layer (A) by heating, and the moisture content is 5-8 wt% because the expansion ratio can be improved and the laminate appearance is also excellent. preferable.
As a base material layer constituting such a laminate of the present invention, a paper mainly composed of natural pulp such as fine paper, cup base paper, kraft paper (hereinafter simply referred to as “paper”), synthetic fiber or Examples include so-called synthetic paper made of synthetic resin film, foamed sheets, sheets made of porous inorganic materials such as zeolite and calcium carbonate, and the adjustment of the amount of water contained in the substrate is relatively easy. Therefore, paper is preferable.
When using paper substrate, since the easy adjustment of water content, it is preferred that the basis weight 150~500g / ^{m 2,} more preferably from 200 to 400 g / ^{m 2.}

(3) Non-foamed resin layer (B)
It is necessary to form and laminate a non-foamed resin layer (B) made of polyethylene-based resin B on the other substrate wall surface of the substrate constituting the laminate of the present invention. Formation and lamination of the non-foamed resin layer (B) can be performed by a conventionally known technique.
This polyethylene-based resin B is a resin having a higher density and a higher melting temperature than the polyethylene-based resin A constituting the foamable resin layer (A) provided on the other surface of the base material, and the laminate is heated later. Even when subjected to the process, it is a resin that does not mainly foam. By providing the non-foamed resin layer (B) made of the polyethylene resin B on the side opposite to the surface on which the (A) layer of the base material is provided, water vapor generated from the paper base material during heating is the (B) layer. It acts on the (A) layer side instead of the side, and the foamability of the foamable resin layer (A) is improved.
Examples of the polyethylene resin B include polyolefins such as high-pressure low-density polyethylene B, ethylene / α-olefin copolymers, and polypropylene.

The MFR of the polyethylene resin B is preferably in the range of 1 to 50 g / 10 minutes because of excellent workability.
Moreover, since it is necessary for the density of the polyethylene-type resin B not to melt at the time of a heating, it is preferable that it is 920-970 kg / m < ³ >.
For the polyethylene resin B constituting the laminate of 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, are added as necessary. You may add in the range which does not impair the objective of this invention.

Furthermore, other polyolefins may be mixed with the polyethylene resin B.
Examples of the polyolefin to be mixed with the high-pressure method low-density polyethylene B include ethylene / α-olefin copolymer B, polypropylene, polybutene, and the like. Processability, non-foaming to MFR range from 1 to 50/10 minutes, density Is preferably an ethylene / α-olefin copolymer having a molecular weight of 920 to 970 kg / m ³ .

  Furthermore, the method for obtaining such an ethylene / α-olefin copolymer B is not particularly limited, and a high / medium / low pressure ionic polymerization method using a Ziegler-Natta catalyst, a Phillips catalyst, or a metallocene catalyst is used. Such a copolymer can be conveniently selected from commercially available products.

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

  When another polyolefin is mixed with the polyethylene resin B constituting the laminate of the present invention, a pellet obtained by mixing, in a solid state, pellets of the polyethylene resin B such as high-pressure low-density polyethylene B and other polyolefins. A mixture may be used, but a mixture obtained by melt-kneading 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 using a melt-kneading apparatus, the melting temperature is preferably about the melting point of polyethylene resin B to about 300 ° C.

(4) Other layers In the foamable laminate of the present invention, other layers may be present in some or all of the layers or outermost layers of the laminate as long as the effects of the present invention are not impaired. That is, a base material layer and a foamable resin layer (A), or a laminate provided with a non-foamed resin layer (B), and / or an outer layer, or a single layer or a plurality of film layers or a decorative layer between the layers. A reinforcing layer, an adhesive layer, a barrier layer, and the like may be provided.
Examples of the decorative layer include printed paper, film, nonwoven fabric, and woven fabric.
The reinforcing layer plays a role such as giving mechanical strength. The resin is not particularly limited, and may be a polyolefin resin such as polyethylene or polypropylene, a polyamide resin, a polyester resin, or the like.
The resin forming the adhesive layer includes a copolymer of ethylene and an unsaturated carboxylic acid or a derivative thereof, a modified polyolefin resin obtained by grafting an unsaturated carboxylic acid or the like onto a polyolefin resin, an ethylene-vinyl acetate copolymer, etc. And usual adhesives.

Also, as the resin forming the barrier layer, polyamide resin, polyester resin, saponified ethylene-vinyl acetate copolymer (EVOH), polyvinylidene chloride resin, polycarbonate resin, expanded polypropylene (OPP), stretched polyester (OPET), stretched polyamide, alumina vapor deposition film, inorganic oxide vapor deposition film such as silica vapor deposition film, metal vapor deposition film such as aluminum vapor deposition, and metal foil.
Further, printing or the like may be performed on any of the layers as necessary. The printing may be performed partially or entirely with colored ink. Moreover, you may provide a foaming site | part partially or entirely using a foamable ink as needed. For the printing position, the size of the printing area, the printing method, the ink used, etc., a conventionally known technique can be appropriately selected and used.

2. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamable resin layer laminating step in which at least a foamable resin layer (A) made of polyethylene resin A is laminated on one surface of a base material layer mainly composed of paper. And (a) and / or (b) a post-treatment step for performing a post-treatment step.
(A) A corona treatment of 20 W · min / m ² or more is performed on the surface of the foamable resin layer (A).
(B) An aging treatment is performed in which the foamable laminate is left in an environment of 40 ° C. or higher for 1 hour or longer.

  As a method for obtaining the foamable laminate of the present invention, there are various extrusion laminating methods such as a method in which polyethylene resin A and polyethylene resin B can be extrusion laminated to a base material, a single laminating method and a tandem laminating method. It can be illustrated. 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 the polyethylene-based resin A is made into an extruded layer in a molten state, the base material adhesion surface of the layer is exposed to an oxygen-containing gas or an ozone-containing gas, and a method of bonding to the base material is used. It is preferable because of excellent adhesiveness with the base material layer. If improving the adhesion to the polyethylene resin A and the base material by containing ozone gas, forming a processing amount of the ozone gas, the flow rate of 1.5 Nm 3 / ^hr, ozone concentration in ozone atmosphere of 10 g / Nm ³ or more It is preferable to do.

Above 1. As described in (1) above, at least a foamable resin layer (A) made of polyethylene resin A is laminated on one surface of the base material layer, and a polyethylene resin is formed on the other surface of the base material layer. The foamable laminate obtained by laminating the non-foamed resin layer (B) made of B is subjected to a corona treatment of (a) 20 W · min / m ² or more on the surface of the foamable resin layer (A), and / or (B) The foamable laminate of the present invention is produced by performing an aging treatment in which the foamable laminate is left in an environment of 40 ° C. or higher for 1 hour or longer.
The aging treatment is preferably carried out in at least two stages, and is allowed to stand in an environment of 40 ° C. or higher for 1 hour or more in the former stage and then left in a humidified atmosphere in the latter stage.
The other layers may be formed before the post-treatment (a) and / or (b) or after the post-treatment as required.

3. Foamed paper and heat insulating container The foamed paper of the present invention is obtained by heating the foamable laminate of the present invention and foaming the foamable resin layer mainly using moisture contained in the paper substrate. Features.
Since the foamed paper of the present invention has a thick foam layer and exhibits excellent heat insulation properties, the height of the foamed cell formed by foaming the foamable resin layer (A) is 500 μm or more. It is preferable.
In addition, the heat insulating container of the present invention uses the foamable laminate of the present invention to shape the container shape so that the foamable resin layer (A) is on the outside, and then heats to foam the foamable resin layer. It is characterized by being obtained.

As a heating method in the method of obtaining foamed paper or a heat-insulated container using the foamable laminate of the present invention by heat foaming, the foamable laminate of the present invention is formed into a container shape in addition to hot air, electric heat, and electron beam. Arbitrary means can be used, such as using a heat of the filling by filling a hot object. The heating can be performed by a batch method in an oven, a continuous method using a conveyor, or the like.
The heating temperature and the heating time vary depending on the base material to be used and the kind of the thermoplastic resin. Generally, the heating temperature is 110 to 130 ° C., and the heating time is 10 seconds to 10 minutes.

  As an example of the manufacturing method of the heat insulation container of this invention, the manufacturing method of a cup-shaped heat insulation container is mentioned below. First, the foamable laminate of the present invention is rolled out continuously or continuously, and a blank for a trunk member and a blank for a bottom plate member are punched out from the foamable laminate, and a trunk member is used with a conventional cup molding machine. After the bottom plate members are joined and molded into a cup shape, etc., they are transported to a batch or transfer belt conveyor and transferred to a heating furnace, oven tunnel, etc. equipped with irradiation means such as hot air, microwave, high frequency, infrared, and far infrared Heat insulation foams to form an insulated container.

The foamable laminate, foamed paper and heat-insulating container of the present invention are 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. The In particular, the foamable laminate, foamed paper and heat insulation container of the present invention are excellent in smoothness of the foamed paper and heat insulation container surface after foaming, the foam layer is thick, exhibiting excellent heat insulation, Since the heat-sealability at the time of shaping is good, it is suitably used for applications where surface smoothness is required.
The foamed paper of the present invention is used not only as a heat insulating and heat insulating material for a heat insulating container, but also as a buffer material, a sound insulating material, a foamed paper, etc., and a sleeve material, a paper plate, a tray, a non-slip material, a fruit It can be used as agricultural materials such as packaging materials and foamed paper, industrial materials, and daily life materials.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

1. Measurement Method Various physical properties of the polyethylene resin were measured by the following methods.
(1) Melt mass flow rate (MFR)
The measurement was performed at 190 ° C. and 2.16 kg in accordance with JIS K6922-2.
(2) Density The density was measured by a density gradient tube method at a test temperature of 23 ° C. according to JIS K7112.
(3) Melting point (melting temperature)
Measured according to JIS K7121.
The pellet was formed into a sheet by hot pressing and punched out to obtain a sample.
The measurement was carried out under the following conditions under the procedure of first temperature rise, temperature drop, and second temperature rise, and the temperature at the maximum peak height of the second temperature rise was defined as the melting point (melting temperature).
(A) Apparatus: DSC7020 manufactured by Seiko Instruments Inc.
(B) Heating temperature conditions:
First temperature rise: 10 ° C / min from 30 ° C to 200 ° C Temperature drop: 10 ° C / min from 200 ° C to 20 ° C Second temperature rise: 10 ° C / min from 20 ° C to 200 ° C (c) Temperature retention Time: 5 minutes after the first temperature increase, 5 minutes after the temperature decrease (d) Sample amount: 5 mg
(E) Reference: Aluminum (f) Atmosphere: N ₂ 50 mL / min
(4) Moisture content of base material The laminate before foaming obtained in the Examples was cut into 10 cm × 10 cm and stored in a perfect oven (PH-102 type Espec) heated to 50 ° C. for 1 week, and the weight change The weight loss was calculated from the sample that could not be seen, and the water content was determined.
(5) Thickness of foam layer The laminates obtained in the examples were cut into 10 cm × 10 cm, left standing in a perfect oven (PH-102 type ESPEC) heated to 115 ° C. for 360 seconds, then taken out and in the air At room temperature. A sample of the laminated body after foaming was taken, and a cross-sectional photograph of the cross section of the laminated body after foaming was taken with a hybrid digital microwatcher (manufactured by SCARA, HDM-2100). The thickness of the foamed layer was measured from the cross-sectional photograph, and the thickness of the average foamed layer ((A) layer) measured at 10 locations was defined as the foamed layer thickness.
(6) Foamed surface state (surface smoothness)
The laminates obtained in the examples were cut into 10 cm × 10 cm, allowed to stand for 360 seconds in a perfect oven (PH-102 type ESPEC) heated to 115 ° C., then taken out and cooled to room temperature in air. The smoothness of the surface of the obtained foam was measured visually.
Visual surface smoothness was performed according to the following evaluation criteria.
Evaluation of visual surface smoothness Good smoothness: ○, Slightly smooth: Δ, Surface irregularities many: ×
(7) Gloss (Glossiness)
The laminates obtained in the examples were cut into 10 cm × 10 cm, allowed to stand for 360 seconds in a perfect oven (PH-102 type ESPEC) heated to 115 ° C., then taken out and cooled to room temperature in air. The glossiness of the surface of the obtained foam was measured with a digital variable gloss meter (UGV-4D, manufactured by Suga Test Instruments Co., Ltd., light receiving angle 60 °, reflection angle 60 °, standard 91.2 °).

2. Examples and Comparative Examples (Comparative Example 1)
As the polyethylene-based resin A, high-pressure low-density polyethylene having an MFR of 14 g / 10 minutes, a density of 918 kg / m ³ , and a melting temperature of 106 ° C. was used. In addition, the non-foamed polyethylene resin B on the opposite side of the paper base layer to the resin layer is a medium density polyethylene having an MFR of 6 g / 10 min, a density of 942 kg / m ³ , and a melting temperature of 130 ° C. It was used.

First, polyethylene resin B is supplied to a single-screw extrusion laminator (manufactured by Sumitomo Heavy Industries Modern Co., Ltd.) having a screw with a diameter of 90 mmφ, extruded from a T die at a temperature of 320 ° C., and has a moisture content of about 5.6%. Extrusion lamination was performed on a paper substrate having an amount of 320 g / m ² so that the take-up speed was 100 m / min, the air gap length was 120 mm, and the thickness was 40 μm.
Furthermore, the polyethylene resin A is supplied to a single screw extruder (manufactured by Sumitomo Heavy Industries Modern Co., Ltd.) having a 90 mmφ screw, at a temperature of 320 ° C., a take-up speed of 50 m / min, and an air gap length of 120 mm. Extrusion lamination is performed on the back side of the base material layer with respect to the resin layer of the polyethylene resin B of the laminate so that the thickness becomes 70 μm, and the polyethylene resin A (high pressure method low density polyethylene), paper base material, polyethylene resin B The foamable laminated body laminated | stacked in order of these was obtained.
This foamable laminate was stored at room temperature for 8 days and then foamed by heating at 115 ° C. for 6 minutes to evaluate the thickness of the foamed layer and the state of the foamed surface. The results of foamability evaluation are shown in Table 1. Although the surface smoothness was inferior, the foam layer height was good.
Moreover, the photograph which image | photographed the surface of this foaming layer using the ultra-depth color 3D shape measuring microscope (the Keyence company make, VK-9500) by 10-times multiplication factor is shown in FIG.

( Reference Example 1 )
On the surface of the polyethylene-based resin A side of the foamable laminate obtained by laminating a polyethylene-based resin A made of a high-pressure method low-density polyethylene, a paper base material, and a polyethylene-based resin B in the same manner as in Comparative Example 1. As a post-treatment, a corona treatment was performed at a processing speed of 50 m / min and an output of 1.5 kW using a corona treatment bar having a width of 500 mm. That is, the corona treatment was performed under the condition of 60 W · min / m ² . Thereafter, the foamable laminate was stored at room temperature for 8 days, and then heated and foamed at 115 ° C. for 6 minutes to evaluate the thickness of the foamed layer and the state of the foamed surface. The results are shown in Table 1. Both surface smoothness and foam layer height were good.

(Comparative Example 2)
The foamable laminate obtained by the same method as in Comparative Example 1 was stored at room temperature for 3 months and then heated to foam, and the thickness of the foamed layer and the state of the foamed surface were evaluated. The results are shown in Table 1. The height of the foamed layer was good, but the surface smoothness was poor.

( Reference Example 2 )
The foamable laminate subjected to corona treatment by the same method as in Reference Example 1 is stored at room temperature for 3 months, and then the foamable laminate is heated and foamed in the same manner as in Reference Example 1 to obtain the thickness of the foamed layer, foaming The surface condition was evaluated. The results are shown in Table 1. Both surface smoothness and foam layer height were good.

( Example 1 )
The foamed laminate not subjected to the corona treatment obtained by the same method as in Comparative Example 1 was subjected to an aging treatment at 50 ° C. for 6 days in an aging oven, and then at 40 ° C. and 90% in a constant temperature and humidity oven. After humidifying for days, the foam was heated for 6 minutes at 115 ° C. in the same manner as in Reference Example 1, and the thickness of the foam layer and the state of the foam surface were evaluated. The results are shown in Table 1. Although the foam layer height was low, the surface smoothness was good.

( Example 2 )
After the corona-treated foamed laminate was subjected to aging treatment at 50 ° C. for 6 days in the same manner as in Reference Example 1, it was humidified at 40 ° C. and 90% for 1 day in a constant temperature and humidity oven. Then, as in Reference Example 1 , heating was performed at 115 ° C. for 6 minutes for foaming, and the thickness of the foamed layer and the state of the foamed surface were evaluated. The results are shown in Table 1. Although the foam layer height was low, the surface smoothness was good.
Moreover, the photograph which image | photographed the surface of this foaming layer using the ultra-deep color 3D shape measuring microscope (the Keyence company make, VK-9500) by 10-times multiplication factor is shown in FIG.

3. Evaluation As described above, from the results shown in Table 1, when Reference Examples 1 and 2, Examples 1 and 2 are compared with Comparative Example 1 or 2, it is a specific matter of the foamable laminate of the present invention "(a). The surface of the foamable resin layer (A) is subjected to a corona treatment of 20 W · min / m ² or more, and / or (b) the foamable laminate is left in an environment of 40 ° C. or more for 1 hour or more. The foamable laminate shown in Comparative Example 1 or 2 by a method that does not satisfy the requirement of “performing aging treatment” has a surface smoothness and glossiness obtained by visual observation and an ultra-deep color 3D shape measurement microscope . 2, It is inferior to the foamable laminated body of Examples 1-2 .
Compared with these comparative examples, the foamable laminates according to the present invention have sufficient foam layer total thickness, smoothness and glossiness as shown in Reference Examples 1-2 and Examples 1-2. It was confirmed to be good.
Therefore, the foamable laminate, the foamed paper and the heat-insulated container of the present invention have excellent smoothness of the foamed paper surface after foaming, the foamed layer is thick, and exhibits excellent heat insulation, as well as foam appearance and shaping It is confirmed that the heat-sealing property is a foamed laminate and the like excellent in economic efficiency, and can be particularly suitably used for a container that requires surface smoothness as well as heat insulation.

The foamable laminate, foamed paper and heat insulation container of the present invention have excellent smoothness of the foamed paper and heat insulation container surface after foaming, the foamed layer is thick, exhibiting excellent heat insulation, foam appearance and shaping Is a foamable laminate having good heat sealability at the time, and is excellent in economic efficiency by a foamed paper and a heat insulating container using the same and simple post-treatment, and can stably provide the above-mentioned quality Since it is a method for producing a foam laminate, it is particularly suitable for paper containers for high-temperature beverages such as coffee and soup that are required to have surface smoothness as well as heat insulation, and containers for instant food such as instant noodles. It can be used suitably and is very useful industrially.

Claims (12)

A foamable resin layer laminating step of forming a foamable laminate by laminating at least a foamable resin layer (A) made of polyethylene-based resin A on one surface of a base material layer mainly composed of paper; and
The manufacturing method of the foamable laminated body characterized by including the post-processing process of performing the aging process which leaves the said foamable laminated body for 1 hour or more in a humidified atmosphere ( 40 degreeC or more) .   2. The foamable laminate according to claim 1, wherein the polyethylene-based resin A has a melt mass flow rate (MFRa) measured in accordance with JIS K6922-2: 2005 of 1 to 50 g / 10 minutes. Body manufacturing method.   The method for producing a foamable laminate according to claim 1 or 2, wherein the polyethylene resin A has a melting temperature measured in accordance with JIS K6922-2: 2005 of 80 to 125 ° C. .   4. The foam according to claim 1, wherein the polyethylene-based resin A contains 50 to 99 wt% of high-pressure low-density polyethylene and 1 to 50 wt% of another polyolefin. For producing a conductive laminate.   The method for producing a foamable laminate according to any one of claims 1 to 4, wherein the foamable resin layer (A) has a thickness before foaming of 30 µm or more.   The aging treatment is performed in at least two stages, and is allowed to stand in an environment of 40 ° C. or higher in the former stage for 1 hour or more and then left in a humidified atmosphere in the latter stage. A process for producing an expandable laminate according to claim 1. The method for producing a foamable laminate according to any one of claims 1 to 6 , wherein a relative humidity of the humidified atmosphere is 70 % or more. A foamable resin layer laminating step of forming a foamable laminate by laminating at least a foamable resin layer (A) made of polyethylene-based resin A on one surface of a base material layer mainly composed of paper; and
Including a post-treatment step in which the foamable laminate is left to stand for 1 hour or longer in a humidified atmosphere , and before the aging treatment, 20 W · min with respect to the surface of the foamable resin layer (A) method for producing a foamed laminate you and performs / m ² or more corona treatment. On the other surface of the base material layer, according to any one of claims 1-8, characterized in that it comprises a non-foamed layer lamination step of laminating a polyethylene comprising the resin B non-foamed resin layer (B) A method for producing a foamable laminate. The foamable laminate obtained by the production method according to any one of claims 1 to 9 is heated, and the foamable resin layer (A) is foamed mainly using moisture contained in a paper substrate. A process for producing foamed paper, characterized in that The method for producing foamed paper according to claim 10 , wherein the foamed cell layer formed by foaming the foamable resin layer (A) has a height of 500 μm or more. Using the foamable laminate obtained by the production method according to any one of claims 1 to 9 , the container shape is molded so that the foamable resin layer (A) is on the outside, and then heated. The foamable resin layer (A) is foamed.