WO2021149648A1

WO2021149648A1 - Foam paper laminate, method for producing same, and container made of foam paper

Info

Publication number: WO2021149648A1
Application number: PCT/JP2021/001520
Authority: WO
Inventors: 里穂羽山; 哲哉佐井; 博明高位; 嘉貢西野
Original assignee: 日清食品ホールディングス株式会社; 東洋インキＳｃホールディングス株式会社; 東洋インキ株式会社
Priority date: 2020-01-20
Filing date: 2021-01-18
Publication date: 2021-07-29
Also published as: CN115038581A; JP2021112873A; BR112022014281A2; JP7418220B2

Abstract

This foam paper laminate has: a foam paper having, in the following order, a thermoplastic resin layer (A), a paper substrate, and a foam thermoplastic resin layer (B); and a printing layer formed on the surface of the foam thermoplastic resin layer (B) of the foam paper, wherein the number of foam cells per unit area of the foam thermoplastic resin layer (B) is at least 1000 cells/1 cm2, the printing layer includes a binder resin containing a polyurethane resin, and the residual rate of the printing layer after immersion in ethanol at 25 °C for 30 minutes is at least 50 mass%.

Description

Foam paper laminate and its manufacturing method, foam paper container

An embodiment of the present invention relates to a foamed paper laminate and a method for producing the same. Further, another embodiment of the present invention relates to a foamed paper container provided with the foamed paper laminate.

Foam containers are widely used as containers for storing foods containing high-temperature or low-temperature liquids because they have excellent heat insulating properties. Among them, foam containers are indispensable for products generally called "cup noodles" that can be eaten in a few minutes by simply pouring an appropriate amount of boiling water into instant noodles such as ramen, udon, and soba noodles contained in a container. I can't. Styrofoam containers and foamed paper containers are known as foamed containers for cup noodles, but in recent years, foamed paper containers have been attracting attention from the viewpoint of environmental load and safety.

The foamed paper container is manufactured by using a foamed paper material having a paper base material and a thermoplastic resin layer that foams by heating at the time of manufacturing the container to form a heat insulating layer. Usually, a printing layer including a decorative pattern, a company name, a printing pattern such as a barcode is formed on the surface of a foamed paper container (foamed paper material). Therefore, it is desirable that the printing layer has excellent foaming followability without hindering foaming when the thermoplastic resin layer of the foamed paper material foams by heating to form a heat insulating layer. Further, it is desirable that the surface (printing surface) of the printing layer after the thermoplastic resin layer is foamed is smooth, has no cracks or swelling, and has an excellent appearance. Further, it is desirable that the printed surface is excellent in various resistances such as abrasion resistance and heat resistance required for manufacturing the container.

Conventionally, oil-based inks such as oil-based gravure ink and oil-based flexo ink have been used to form the printing layer of the foamed paper container. The oil-based ink usually contains an organic solvent such as toluene from the viewpoint of solubility and drying property of the binder resin. However, in recent years, from the viewpoint of environmental load and occupational safety and health, regulations on the use of organic solvents have become stricter, so that there is an increasing demand for water-based inks. Therefore, in the field of food containers used for cup noodles and the like, development of a foamed paper laminate having a printing layer formed by using water-based ink and which can be suitably used as a material for foamed paper containers has been promoted. ing.

For example, Patent Document 1 discloses a water-based flexographic ink for a foam cup, which contains a binder resin, a pigment, and water as an ink for forming a print layer of a foamed paper laminate, and the binder resin contains a polyurethane resin. .. Further, Patent Document 2 discloses that the foaming of the foaming layer is suppressed within a predetermined range by the coating portion (printing layer) of the water-based ink. The water-based ink disclosed in Patent Document 2 contains a colorant and a binder resin, and contains 30% by mass or more of a urethane resin having a glass transition point of −20 ° C. or higher and 30 ° C. or lower in the resin solid content of the binder resin. do. Further, Patent Document 3 discloses a water-based ink containing an acrylic resin, an acrylic-urethane copolymer resin, a styrene-maleic acid copolymer resin, or a polyurethane resin as a binder resin.

Japanese Unexamined Patent Publication No. 2018-058955 International Publication No. 2018/066031 Japanese Unexamined Patent Publication No. 2011-068381

The heat insulating property of the foamed paper container mainly depends on the foamability of the thermoplastic resin layer constituting the foaming layer (heat insulating layer) in the foamed paper laminate. However, as the foamability of the thermoplastic resin layer during heat processing increases, appearance defects such as cracks and swelling tend to occur on the surface of the printing layer formed on the thermoplastic resin layer. Therefore, it is desirable that the printed layer can uniformly suppress the foaming so as not to prevent the foaming of the thermoplastic resin layer, while preventing the appearance defects such as cracks and swelling.

However, in comparison with the conventional oil-based ink used for forming the print layer of the foamed paper laminate, when the water-based ink is used, the foam followability, abrasion resistance, and heat resistance desired in the print layer are obtained. It is difficult to obtain the properties, and the quality of the foamed paper laminate tends to deteriorate. Further, it is difficult to uniformly suppress the foaming of the thermoplastic resin layer by the printing layer. Therefore, defects such as cracks and swelling in the appearance of the printed surface after foaming of the thermoplastic resin layer (hereinafter referred to as foamed appearance) are likely to occur. Further, in the food field, since a solvent such as ethanol is widely used for disinfection, chemical resistance such as ethanol resistance of the printed layer is also required.

However, it is difficult to obtain excellent ethanol resistance because the print layer formed by using a water-based ink is usually highly hydrophilic. For example, even when a print layer is formed using the water-based inks disclosed in Patent Documents 1 to 3, it is necessary to provide a foamed paper laminate that can sufficiently satisfy various characteristics required in the food container industry. Is difficult and further improvement is desired.

Therefore, in view of the above situation, the embodiment of the present invention is a foamed paper laminate having a printing layer formed by using a water-based ink, and the printing layer prevents the thermoplastic resin layer from foaming during heat processing. Provided are a foamed paper laminate having excellent foaming followability and a surface of a printing layer having excellent foaming appearance, abrasion resistance, heat resistance, and ethanol resistance, and a method for producing the same.

In order to solve the above problems, the present inventors have diligently studied the relationship between the foamability of the thermoplastic resin layer during heat processing and the foaming suppressing force of the printing layer. As a result, by forming the printing layer using an aqueous ink composition containing a specific binder resin, the foamability of the thermoplastic resin layer and the printed surface such as foamed appearance, abrasion resistance, heat resistance, and ethanol resistance are obtained. We have found that good results can be obtained in terms of the characteristics of the above, and have completed the present invention. That is, the present invention relates to the following embodiments, but includes various embodiments without limitation.

One embodiment is formed on a foam paper having a thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer (B) in that order, and on the surface of the foamed thermoplastic resin layer (B) of the foamed paper. A foamed paper laminate having a printed layer,
The number of foamed cells per unit area of the foamed thermoplastic resin layer (B) is 1000 cells / cm ² or more.
The printing layer relates to a foamed paper laminate containing a binder resin containing a polyurethane resin and having a residual ratio of the printing layer of 50% by mass or more after being immersed in ethanol at 25 ° C. for 30 minutes.

In the foamed paper laminate, the binder resin preferably has a stress of 0.1 mPa to 50 mPa at an elongation rate of 50 to 4,000%. The binder resin preferably has a glass transition temperature of −100 to 0 ° C.

In the foamed paper laminate, the printing layer preferably has a film thickness of 0.5 to 5.0 μm.

In the foamed paper laminate, the printing layer is a cured product formed from a binder resin containing a polyurethane resin having an acid value of 1 to 100 mgKOH / g and at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent. It is preferable to include it.

In the foamed paper laminate, it is preferable that the printing layer has a plurality of layers and the outermost layer is a transparent layer.

In the foamed paper laminate, the thickness of the foamed thermoplastic resin layer (B) is preferably 500 to 950 μm.

One embodiment relates to a foam paper container provided with the foam paper laminate of the above embodiment.

One embodiment is formed on a foam paper having a thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer (B) in that order, and on the surface of the foamed thermoplastic resin layer (B) of the foamed paper. by having a printed layer, the number of foam cells per unit area of the foamed thermoplastic resin layer (B) is at 1,000 / 1 cm ² or more, after immersion for 30 minutes in a 25 ° C. ethanol A method for producing a foamed paper laminate, wherein the residual ratio of the printed layer is 50% by mass or more.
It has a thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer forming layer (B ₀ ) having a melting point lower than that of the thermoplastic resin layer (A) and foaming by heating. , Preparing foam paper material,
Preparing a water-based ink composition containing a binder resin containing a polyurethane resin and water,
Applying the water-based ink composition to the surface of the foamed thermoplastic resin layer forming layer (B _{0) of the foamed paper material to form a printing layer.}
By heating the foamed paper material having the printed layer, the foamed thermoplastic resin layer forming layer (B ₀ ) of the foamed paper material is foamed to form the foamed thermoplastic resin layer (B). , The method for manufacturing a foamed paper laminate.

In the above production method, the aqueous ink composition contains a binder resin containing a polyurethane resin having an acid value of 1 to 100 mgKOH / g, water, and at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent. It is preferable to prepare the composition.

In the above manufacturing method, it is preferable that the printing layer has a plurality of layers and the outermost layer is a transparent layer.

In the above manufacturing method, the film thickness of the foamed thermoplastic resin layer forming layer (B ₀ ) is preferably 40 to 150 μm.
The disclosure of the present application is related to the subject matter described in Japanese Patent Application No. 2020-006574 filed on January 20, 2020, the entire disclosure of which is incorporated herein by reference.

According to the present invention, a foamed paper laminate having a printing layer, which is excellent in foaming followability without hindering the foaming of the thermoplastic resin layer during heat processing, and is excellent in foaming appearance, abrasion resistance, heat resistance, and ethanol resistance. A body and a method for producing the body can be provided. Further, according to the present invention, it is possible to provide a foam paper container provided with the foam paper laminate.

FIG. 1 is a perspective view showing a structural example of a foamed paper container provided with the foamed paper laminate according to the embodiment. FIG. 2 is a schematic cross-sectional view showing a part (reference numeral I part) of the foamed paper container shown in FIG. 1 in an enlarged manner.

Hereinafter, embodiments of the present invention will be specifically described. However, the present invention is not limited to the embodiments described below, and includes various embodiments.

<1> Foamed Paper Laminated Material One embodiment relates to a foamed paper laminated body. The foamed paper laminate is formed on a foamed paper having a thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer (B) in that order, and on the surface of the foamed thermoplastic resin layer (B) of the foamed paper. The foamed thermoplastic resin layer (B) has a formed printing layer, and the number of foamed cells per unit surface area is 1000 cells / 1 cm ² or more, and the printed layer is a binder resin containing a polyurethane resin. It is characterized in that the residual ratio of the printed layer after being immersed in ethanol at 25 ° C. for 30 minutes is 50% by mass or more.

As for the number of foamed cells per unit surface area of the foamed thermoplastic resin layer (B) (hereinafter, also referred to as foamed layer (B)), the larger the number, the smaller the bubbles existing in the foamed layer (B), and the smaller the number. It means that the bubbles existing in the foamed layer (B) are large. When the bubbles existing in the foam layer (B) become large, appearance defects such as cracks and swelling of the printed surface are likely to occur.

In one embodiment, the number of foamed cells per unit surface area of the foamed layer (B) ^{is preferably 1000 cells / 1 cm 2} or more, and more preferably 1250 cells / 1 cm ² or more. When the number of foamed cells is in the above range, an excellent foamed appearance without cracks and swelling can be easily obtained in the printed layer formed on the foamed layer (B). On the other hand, the upper limit of the number of foamed cells is not particularly limited. In one embodiment, the number of foamed cells may be 1600 cells / cm ² or less from the viewpoint of manufacturing conditions and the like.

Here, the "number of foamed cells per unit area" is an independent cell (air bubble) existing in a range defined by a constant length in the vertical and horizontal (XY) directions on the surface of the foamed layer (B). It means a value calculated as the number of independent cells per ^{1 cm 2} by counting the number of. The number of independent cells is determined by removing the print layer of the foamed paper laminate with a solvent, exposing the surface of the foamed layer (B), and then observing the surface of the foamed layer (B) using an optical microscope. NS.

The thickness of the foam layer (B) is preferably 500 μm or more, more preferably 630 μm or more, from the viewpoint of heat insulating properties. If the thickness of the foamed layer (B) is 500 μm or more, the foamed paper laminate is formed into a cup-shaped container, and even when hot water of about 100 ° C. is poured into the container, the container is continuously held with bare hands. It becomes easy to hold in. On the other hand, from the viewpoint of resource saving, it is preferable that the amount of resin used is as small as possible. Further, from the viewpoint of heat insulating property, the heat insulating layer does not need to be thick enough to have excessive quality. Therefore, the thickness of the foamed layer (B) is preferably 950 μm or less, more preferably 900 μm or less, and extremely preferably 800 μm or less.

From the above viewpoint, in one embodiment, the thickness of the foamed layer (B) is preferably 500 to 950 μm, more preferably 500 to 900 μm, and even more preferably 500 to 800 μm. The thickness of the foamed layer (B) is determined by observing the cross section of the foamed paper laminate with an optical micrograph and measuring the height from the upper surface of the paper substrate to the lower surface of the printed layer.

In the foamed paper laminate of the above embodiment, the foamed paper foam layer (B) means a state after the thermoplastic resin layer is foamed by heating. That is, the foamed layer (B) is formed by heating and foaming an unfoamed thermoplastic resin layer (foamed thermoplastic resin layer forming layer (B _{0)) as a precursor.} In one embodiment, in order to form the foamed paper laminate, it has a thermoplastic resin layer (A), a paper base material, and a melting point lower than that of the thermoplastic resin layer (A), and is foamed by heat treatment. A foamed paper material (foamed paper before heating) having a foamed thermoplastic resin layer forming layer (B _{0) in sequence can be used.} The foamed paper material can be composed of materials known in the art. Hereinafter, the constituent materials of the foamed paper laminate will be specifically described.

(Paper base material)
The paper base material constituting the foamed paper laminate is not particularly limited. For example, kraft paper or woodfree paper can be used. From the viewpoint of achieving sufficient toughness when used as a container, the basis weight of the paper base ^{material is preferably 150 to 450 g / m 2} , and more preferably 250 to 400 g / m ² . Further, from the viewpoint of obtaining suitable foamability of a thermoplastic resin such as polyethylene, the amount of water contained in the paper base material is preferably 4 to 10% by mass, more preferably 5 to 8% by mass.

(Thermoplastic resin layer, foam layer forming layer)
In one embodiment, the thermoplastic resin layer (A) and the foamed thermoplastic resin layer forming layer (B ₀ ) (hereinafter, also referred to as the foamed layer forming layer (B ₀ )) have been conventionally known as container materials. It may be a film made of a resin material. For example, a film (thermoplastic resin film) made of at least one thermoplastic resin selected from the group consisting of stretched and unstretched polyolefins such as polyethylene and polypropylene, polyester, nylon, cellophane, and vinylon can be used. can. In one embodiment, a polyethylene film can be preferably used because it is excellent in laminating suitability and foamability.

The foamed paper material can be constructed by laminating thermoplastic resin films having different melting points on a paper base material. Here, the melting point of the thermoplastic resin film provided on the other surface of the paper substrate as _{the foam layer forming layer (B 0} ) is higher than that of the thermoplastic resin film provided on one surface of the paper substrate as the thermoplastic resin layer (A). The material is selected so that (Mp) is low. In the foamed paper material, the water content in the paper base material evaporates during the heat treatment, and the evaporated water content is _{extruded to the softened foam layer forming layer (B 0} ) (low Mp resin film) side. Then, with such extrusion, the low Mp resin film swells (foams) outward, and a foamed layer (B) is formed. The foamed layer (B) thus formed functions as a heat insulating layer in the container. On the other hand, for the thermoplastic resin layer (A) (high Mp resin film), a material that does not melt or soften when the low Mp resin film foams by heat treatment is selected.

From the viewpoint of producing a foam paper container using the foam paper laminate, the foam paper material is, for example, a high Mp polyethylene film having a melting point of about 125 ° C. to 140 ° C. on one surface (inside of the container) of the paper base material. _{(Thermoplastic resin layer (A)) and a low Mp polyethylene film (foam layer forming layer (B 0} )) having a melting point of about 105 ° C. to 120 ° C. on the other surface (outside of the container) of the paper base material, respectively. It may have a laminated structure. The low Mp polyethylene film foams to form a foamed layer by heating during the production of a foamed paper container or the like. On the other hand, the high Mp polyethylene film preferably functions as a coating layer. That is, the coating layer can suppress the evaporation of the water content in the paper base material to the outside during the foaming of the low Mp polyethylene film, and can efficiently contribute the water content in the paper base material to the foaming.

In one embodiment, the material of the foam layer forming layer (B ₀ ) preferably contains a low-density polyethylene resin (density 910 to 925 kg / m ³ , melting point 105 to 120 ° C.) among the polyethylene resins. The density of the low-density polyethylene resin is more preferably 910 to 922 kg / m ³ , and even more preferably 910 to 918 kg / m ³ . As the material of the foam layer forming layer (B ₀ ), a medium density polyethylene resin (density 925 to 940 kg / m ³ , melting point 115 to 130 ° C.) and a high density polyethylene resin (density 940 to 970 kg / m ³ , melting point 125 to 140). When ℃) is used, the melting point is high and it tends to be difficult to obtain sufficient foamability. Further, from the viewpoint of obtaining a uniformly foamed layer, the melt flow rate of the polyethylene resin (hereinafter referred to as "MFR") is preferably 8 to 28 g / 10 minutes, and preferably 10 to 20 g / 10 minutes. More preferred.

Although not particularly limited, in one embodiment, _{the film thickness of the foamed cambium (B 0} ) is preferably 40 μm or more, and more preferably 60 μm or more. By adjusting the film thickness to 40 μm or more, sufficient heat insulating properties can be obtained after the heat treatment.

On the other hand, from the viewpoint of resource saving, it is preferable that the amount of resin used is as small as possible. Also, from the viewpoint of heat insulation, it is not necessary to have a thickness sufficient for excessive quality. Therefore, the film thickness of the foamed cambium (B ₀ ) is preferably 150 μm or less, more preferably 100 μm or less, and extremely preferably 80 μm or less.

(Print layer)
In the foamed paper laminate of the above embodiment, the printing layer is a coating film obtained by applying an aqueous ink composition to the surface of _{the foamed layer forming layer (B 0) of the foamed paper material.} The main component of the coating film constituting the print layer is a binder resin in the water-based ink composition, and the binder resin preferably contains at least a polyurethane resin.

Since the printing layer contains at least a polyurethane resin as the binder resin, when the foam layer forming layer (B ₀ ) foams by heating to form the foam layer (B), it does not hinder the foaming and has excellent foaming followability. Can be easily obtained. Further, the foamability of the foam layer forming layer (B ₀ ) can be appropriately suppressed, and the number of foam cells per unit surface area of the foam layer (B) described above can be easily obtained. From these facts, by using the polyurethane resin, an excellent foamed appearance can be obtained, and further, excellent abrasion resistance and heat resistance of the printed layer can be easily obtained.

In one embodiment, the thickness of the printed layer (coating film after drying) is preferably 0.5 to 5.0 μm from the viewpoint of the foaming suppressing power of the printed layer and the abrasion resistance. The thickness of the print layer may be more preferably 0.5 to 4.0 μm, and even more preferably 0.5 to 3.5 μm.

From the viewpoint of ethanol resistance, the printed layer preferably has a residual ratio of 50% by mass or more after being immersed in ethanol at 25 ° C. for 30 minutes. When the residual ratio of the printing layer is 50% by mass or more, even if ethanol is used for disinfection and cleaning in the manufacturing process of food containers, problems such as unclear printing can be suppressed. The print layer can be maintained well. Considering the use in food containers, the residual ratio of the printed layer after being immersed in ethanol at 25 ° C. for 30 minutes is more preferably 60% by mass or more, further preferably 70% by mass or more. ..

The residual ratio of the printed layer described in the present specification does not require strict adjustment of the immersion conditions in ethanol. That is, conditions such as temperature and immersion time may be slightly changed. For example, "immersion for 30 minutes" means that the print layer may be immersed in ethanol for approximately 30 minutes. Therefore, for example, the immersion time may be extended by 5 to 10 minutes by operations before and after immersion, post-treatment, and the like. As an operation before and after immersion, for example, a stirring step may be provided. The stirring condition is preferably 50 to 150 rpm.

Generally, when forming a water-based ink composition, it is preferable to increase the hydrophilicity of the binder resin from the viewpoint of printability. However, if the hydrophilicity of the binder resin is increased, the ethanol resistance of the print layer tends to decrease. On the other hand, by adjusting the structure and physical properties of the polyurethane resin used as the binder resin, in addition to the desired properties such as foaming followability, foaming suppressing force, friction resistance, and heat resistance, as described above, It is possible to realize the desired ethanol resistance. Hereinafter, specific embodiments of the water-based ink composition containing the polyurethane resin as the binder resin will be described.

<2> Water-based ink composition One embodiment relates to a water-based ink composition that can be suitably used for forming a print layer of the foamed paper laminate of the above embodiment. The water-based ink composition contains a binder resin and water, and may further contain a colorant such as a pigment. The water-based ink composition may further contain various additives in addition to the above components, if necessary. Hereinafter, the composition of the water-based ink composition will be described.

(Binder resin)
At the time of heat processing for forming the foam layer (B), it is preferable that the printed layer does not inhibit the foaming of the _{foam layer forming layer (B 0) and has excellent foam followability.} On the other hand, in order to suppress foaming appearance defects such as cracks and fire swelling on the printed surface, _{it is preferable that the foaming of the foam layer forming layer (B 0} ) can be appropriately controlled by the printing layer. On the other hand, since the binder resin is the main component of the printing layer (coating film), the foaming followability and the foaming suppressing power of the printing layer can be satisfactorily adjusted by selecting an appropriate binder resin. ..

In one embodiment, the binder resin in the water-based ink composition forming the print layer preferably has an elongation rate of 50 to 4,000% from the viewpoint of foaming followability. On the other hand, if the stress is too small even if the elongation rate of the binder resin is 50 to 4,000%, the printed layer follows the foaming, but the foaming cannot be properly controlled, and cracks and swelling occur. The foamed appearance tends to deteriorate. Therefore, from the viewpoint of achieving both the foamability and the foamed appearance of the printed surface, the binder resin preferably has an elongation rate of 50 to 4,000% and a stress of 0.1 mPa or more.

The term "elongation rate" described in the present specification refers to a sample having dimensions of 0.3 mm in thickness and 15 mm in width, using a small tensile tester manufactured by Intesco, with a tensile speed of 100 mm / min and a room temperature of 25. It means a value obtained by measuring at ° C.

In one embodiment, the binder resin preferably has a stress of 0.1 mPa or more, more preferably 1 mPa or more, and even more preferably 5 mPa or more at an elongation rate of 50 to 4,000%. On the other hand, the stress at an elongation rate of 50 to 4,000% is preferably 50 mPa or less, more preferably 40 mPa or less, and even more preferably 30 mPa or less. The stress at an elongation rate of 50 to 4,000% of the binder resin may be 0.1 mPa to 50 mPa.

When the binder resin has an elongation rate and stress in the above range, it becomes easy to obtain good results in terms of foaming appearance in addition to foaming followability. Further, a binder resin having an elongation rate and stress in the above range is preferable from the viewpoint of enhancing ethanol resistance because it is easy to obtain a desired residual rate of the printed layer.

In one embodiment, the binder resin preferably has a glass transition temperature (Tg) of −100 ° C. to 0 ° C. The Tg of the binder resin may be more preferably −10 ° C. or lower, and even more preferably −25 ° C. or lower. When the Tg of the binder resin is within the above range, excellent foaming followability can be obtained during heat treatment of the foamed paper material, and deterioration of heat insulating property can be suppressed. In addition, it is possible to suppress defective foam appearance such as cracks and swelling on the printed surface. The Tg may be −100 ° C. or higher, preferably −90 ° C. or higher, and more preferably −80 ° C. or higher. A binder resin having a Tg in the above range is preferable from the viewpoint of ethanol resistance because it is easy to obtain a desired residual ratio of the printed layer.

As described above, the binder resin preferably contains at least a polyurethane resin from the viewpoint of foaming followability of the printed layer during foaming. When a polyurethane resin is used, it is excellent in various resistances such as light resistance, heat resistance, abrasion resistance, and blocking resistance, and further, it is resistant to a low Mp resin film (foam layer forming layer (B ₀ )) which is a base material during printing. A water-based ink composition capable of forming a print layer having excellent adhesiveness can be easily constructed. Further, by using a polyurethane resin as a binder resin, even when the water-based ink composition is stored for a long period of time in an environment where heat or light is applied, it becomes a friction resistance, a blocking resistance, and a base material of the printing layer. Good results can also be obtained in various properties such as adhesion to low Mp resin films.

As the binder resin, a conventionally known resin can be used in addition to the polyurethane resin. By using various resins having an elongation rate and stress in the above range and Tg, excellent printing characteristics can be easily obtained. The elongation rate and stress of the binder resin can be controlled by combining various resins, controlling the molecular weight during resin synthesis, changing the Tg of the monomer, adjusting the crosslink density, and the like. From this point of view, examples of resins that can be used as binder resins in addition to polyurethane resins include acrylic resins, styrene-acrylic copolymer resins, and styrene-maleic acid copolymer resins.

In one embodiment, the content of the polyurethane resin is preferably 50% by mass or more, more preferably 70% by mass or more, and 85% by mass or more, based on the total mass of the resin components in the binder resin. It is more preferable to have. In one embodiment, the binder resin may be composed only of the polyurethane resin.

The term "polyurethane resin" used in the present specification means a polyurethane resin in a broad sense including a general polyurethane resin conventionally used in the art or a modified polyurethane resin such as a polyurethane urea resin. The polyurethane resin used in the present specification is not particularly limited depending on the production method thereof, and may be various polyurethane resins obtained by applying a known or well-known method for polyurethane resin. Hereinafter, the polyurethane resin that can be suitably used as the binder resin will be described in more detail.

(Polyurethane resin)
Although not particularly limited, one preferred embodiment of the polyurethane resin is a polyurethane resin obtained by reacting at least a polyol with a polyisocyanate. In addition, as another embodiment, a polyurethane urea resin obtained by extending a chain of a prepolymer of a polyurethane resin with an amine compound can be mentioned.

In one embodiment, the polyurethane resin used as the binder resin is preferably an aqueous polyurethane resin (also referred to as an aqueous polyurethane resin) from the viewpoint of preparing an aqueous ink composition. As used herein, the term "aqueous polyurethane resin" means that the polyurethane resin is soluble in water or a water-soluble solvent, or easily dispersible. That is, in one embodiment, the polyurethane resin has an acid value (acidic functional group) and takes either a "water-soluble" or "emulsion" form by neutralizing or modifying the acidic functional group. It is preferable to obtain. The acidic functional group may be a carboxyl group, a sulfonic acid group, or the like, but a carboxyl group is preferable. Although not particularly limited, the polyurethane resin used as the binder resin is preferably water-soluble.

On the other hand, when an aqueous polyurethane resin is usually used to form an aqueous ink composition, it tends to be difficult to obtain sufficient ethanol resistance in the printed layer in consideration of its use in food containers. Therefore, from the viewpoint of imparting the desired ethanol resistance to the printed layer, the polyurethane resin used as the binder resin preferably has a structure or physical properties that are difficult to dissolve in ethanol. Although not particularly limited, the ethanol resistance of the printed surface can be easily improved by the method described below.

For example, as the polyol that is the main constituent of the polyurethane resin, there is a method of selecting a polyol having a structure that is difficult to dissolve in ethanol. In this method, it is preferable to use at least one of a polycarbonate diol and a polyester polyol as the polyol.

Another method is to increase the weight average molecular weight of the polyurethane resin. In one embodiment, when the weight average molecular weight of the polyurethane resin is larger than 20,000, the ethanol resistance can be easily increased. However, the weight average molecular weight of the polyurethane resin is not particularly limited. Even when the weight average molecular weight of the polyurethane resin is 20,000 or less, excellent ethanol resistance can be easily obtained by using, for example, a curing agent in combination.

Another method is to raise the glass transition temperature (Tg) of the polyurethane resin. The preferable range of Tg of the polyurethane resin may be −100 ° C. to 0 ° C., as described above as the characteristics of the binder resin. In one embodiment, from the viewpoint of ethanol resistance, the Tg of the polyurethane resin is preferably −80 ° C. or higher, more preferably −70 ° C. or higher, and even more preferably −60 ° C. or higher. On the other hand, the Tg of the polyurethane resin is preferably −10 ° C. or lower, more preferably −20 ° C. or lower.

Another method is to adjust the hardness (elongation rate and stress) of the polyurethane resin. Along with this, a method of adjusting the urethane bond concentration or the urea bond concentration in the polyurethane resin is also conceivable. In the preferable range of the elongation rate and the stress of the polyurethane resin, as described above as the characteristics of the binder resin, the stress at the elongation rate of 50 to 4,000% may be 0.1 mPa or more. In one embodiment, from the viewpoint of ethanol resistance, the elongation rate of the polyurethane resin is preferably 100 to 2,500%, more preferably 300 to 1,500%, and more preferably 300 to 1,200%. Is even more preferable. The stress is preferably 1 to 40 mPa, more preferably 3 to 30 mPa, and even more preferably 5 to 25 mPa.

By using a polyurethane resin constructed by applying any one of the above methods or a combination of a plurality of methods as a binder resin, the residual rate after immersion in ethanol at 25 ° C. for 30 minutes is 50% by mass or more. The print layer is easily formed.

Hereinafter, the raw material and the manufacturing method of the polyurethane resin will be described.
(Polyol)
Various polyols can be used to produce polyurethane resins. For example, various polyols shown below can be preferably used. The various polyols shown below may be used alone or in combination of two or more.
(1) Polymers such as ethylene oxide, propylene oxide and tetrahydrofuran, or polyether polyols such as copolymers;
(2) Ester glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl1,3-propanediol, neopentyl glycol, pentandiol , 3-Methyl-1,5-pentanediol, hexanediol, octanediol, nonanediol, methylnonanediol, diethylene glycol, triethylene glycol, dipropylene glycol and other saturated and unsaturated low molecular weight glycols, and n-butyl Alkyl glycidyl ethers such as glycidyl ethers and 2-ethylhexyl glycidyl ethers, monocarboxylic acid glycidyl esters such as versatic acid glycidyl esters, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, Polyester polyols obtained by dehydration-condensing dibasic acids such as oxalic acid, malonic acid, glutaric acid, pimeric acid, azelaic acid, sebacic acid, and dimer acid or anhydrides thereof;
(3) Others Polycarbonate diols, polybutadiene glycols, bisphenol A glycols obtained by adding ethylene oxide or propylene oxide;
(4) Dimerdiols.

In one embodiment, the polyurethane resin is preferably made from at least one polyol selected from a polyether polyol, a polyester polyol, and a polycarbonate diol, and preferably has a structural unit derived from these raw materials. It is more preferable to use a polyether polyol and / or a polyester polyol as the polyol. That is, in one embodiment, the polyurethane resin may be a polyether polyurethane resin, a polyester polyurethane resin, or a polyether / polyester polyurethane resin.

The polyether polyol preferably contains at least one selected from polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and more preferably contains polyethylene glycol.
The polyester polyol preferably contains a polyester polyol which is a condensate of a low molecular weight diol and a dibasic acid. The low molecular weight diol is preferably a branched diol. The “branched diol” means that at least one hydrogen atom of the alkylene group contained in the alkylene glycol is substituted with a group other than the hydrogen atom. The substituent is preferably an alkyl group having 1 to 10 carbon atoms.

In one embodiment, when the polyester-based polyurethane resin is constructed by using the polyester polyol exemplified as (2) above, up to 5 mol% of the polyol compounding amount can be replaced with various other polyols. Examples of other various polyols include glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, and pentaerythritol.

The structure and number average molecular weight of the polyol are appropriately determined in consideration of properties such as ethanol resistance, dryness, elongation and stress of the polyurethane resin obtained as a reaction product. Although not particularly limited, the number average molecular weight of the polyol is usually preferably in the range of 500 to 10,000, more preferably in the range of 500 to 6,000.

(Polyisocyanate)
The polyisocyanate that can be used in the production of the polyurethane resin is preferably a diisocyanate compound. Specific examples include aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates. The polyisocyanate may be a compound having an isocyanurate ring structure formed by forming various diisocyanates into trimers.

Examples of aromatic diisocyanates include 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, and tetraalkyl. Examples thereof include diphenylmethane diisocyanate, 1,3-phenylenediocyanate, 1,4-phenylenediocyanate and tolylene diisocyanate.

Examples of the aliphatic diisocyanate include butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate.

Examples of the alicyclic diisocyanate include cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, methylcyclohexanediisocyanate, and norbornan diisocyanate. , M-Tetramethylxylylene diisocyanate, hydrogenated 4,4-diphenylmethane diisocyanate, diisocyanate obtained by converting the carboxyl group of dimer acid into an isocyanate group, and the like.

Among the above-mentioned polyisocyanates, at least one selected from the group consisting of trimers of tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, bis (isocyanatomethyl) cyclohexane, hexamethylene diisocyanate, and hexamethylene diisocyanate is preferable. The polyisocyanate can be used alone or in combination of two or more.

(Dihydroxyic acid)
When dihydroxyic acid is used in addition to polyol and polyisocyanate in the production of polyurethane resin, an acidic functional group (carboxyl group) derived from dihydroxyic acid is introduced, and a polyurethane resin having an acid value can be obtained. Since the polyurethane resin having an acid value can be easily made water-based, it can be suitably used as the water-based polyurethane resin for forming the water-based ink composition.

The dihydroxyic acid may be a compound having two hydroxy groups and an acidic group in the molecule. Well-known diol compounds containing a carboxyl group can be preferably used. Examples thereof include dimethylolalkanoic acids such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, and 2,2-dimethylolvaleric acid, and these can be preferably used. These may be used alone or in combination of two or more.

In one embodiment, when a polyurethane urea resin is produced as a polyurethane resin, it is desirable that the molar equivalent ratio of isocyanate groups / hydroxyl groups be in the range of 1.2 / 1 to 3/1. In another embodiment, when a polyurethane resin containing no urea bond is produced, it is desirable that the molar equivalent ratio of isocyanate groups / hydroxyl groups is in the range of 0.5 / 1 to 0.98 / 1. When the raw materials are blended within the above molar equivalent ratio, it becomes easy to control the elongation rate and stress of the polyurethane resin and the ethanol resistance. The polyurethane-forming reaction in the production of the polyurethane resin is usually carried out at a reaction temperature in the range of 80 ° C. to 200 ° C., preferably 90 ° C. to 150 ° C.

The polyurethane-forming reaction may be carried out in a solvent or in a solvent-free atmosphere. When a solvent is used, the solvent exemplified later can be appropriately selected from the viewpoint of controlling the reaction temperature, viscosity and side reaction. When the polyurethane-forming reaction is carried out in a solvent-free atmosphere, it is desirable to raise (heat) the temperature to such an extent that sufficient stirring is possible and lower the viscosity in order to obtain a uniform polyurethane resin. The reaction time of the polyurethane-forming reaction is preferably 10 minutes to 5 hours. The end point of the reaction can be determined by a method such as viscosity measurement, confirmation of NCO peak by IR measurement, and NCO% measurement by titration.

In one embodiment, a suitable usable polyurethane urea resin is prepared by reacting the polyol exemplified above with an organic diisocyanate to synthesize a prepolymer of a polyurethane resin having an isocyanate group at the terminal, followed by a chain extender and a reaction. It is a resin obtained by using an amine compound as a stopping agent and introducing a urea bond into the prepolymer of the polyurethane resin. Among the polyurethane resins, when the above polyurethane urea resin is used, various characteristics of the coating film (printed surface) formed by using the water-based ink composition can be further enhanced.

(Chain extender)
As an example of the chain extender that can be used to introduce a urea bond, various known polyamines can be mentioned. The polyamine means a compound having a plurality of amino groups in the molecule.
Specific examples of polyamines include ethylenediamine, propylenediamine, hexamethylenediamine, triethylenetetramine, diethylenetriamine, isophoronediamine, and dicyclohexylmethane-4,4'-diamine. Other specific examples include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine and the like. Examples thereof include diamines having a hydroxyl group in the molecule and dimerdiamine obtained by converting the carboxyl group of dimer acid into an amino group.

(Reaction terminator)
A reaction terminator can also be used in combination with polyamines. Examples of the reaction terminator include dialkylamines such as di-n-dibutylamine, monoethanolamine, diethanolamine, 2-amino-2-methyl-1-propanol, tri (hydroxymethyl) aminomethane, and 2-amino-. Amino acids having hydroxyl groups such as 2-ethyl-1,3-propanediol, N-di-2-hydroxyethylethylenediamine, N-di-2-hydroxyethylpropylenediamine, N-di-2-hydroxypropylethylenediamine, and further. Examples thereof include monoamine-type amino acids such as glycine, alanine, glutamic acid, taurine, aspartic acid, aminobutyric acid, valine, aminocaproic acid, aminobenzoic acid, aminoisophthalic acid and sulfamic acid.

When a urea bond is introduced into the prepolymer of a polyurethane resin, the production method thereof is not particularly limited. For example, assuming that the number of free isocyanate groups present at both ends of the prepolymer is 1, the total number of amino groups in the chain extender and reaction terminator used is in the range of 0.5 to 1.3. It is preferable to do so.

The solvent used in each production of the polyurethane resin and the polyurethane urea resin may be a well-known compound that can be usually used as a solvent for ink forming a printing layer. For example, alcohol solvents such as methanol, ethanol, isopropanol, n-propanol, n-butanol; ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; ester solvents such as ethyl acetate, propyl acetate and butyl acetate; methylcyclohexane. , Non-aromatic hydrocarbon solvents such as ethylcyclohexane. These solvents may be used alone or in combination of two or more.

When the above-mentioned ketone solvent is used during production, ketimine is generated between the ketone and the amine used as the chain extender, which hinders the smooth progress of the reaction. Therefore, it is desirable to use a small amount of water in combination in order to suppress the generation of ketimine and allow the reaction to proceed smoothly. When an organic solvent is used in the synthesis reaction, it is preferable to provide a step of removing the organic solvent by distillation under reduced pressure and replacing it with water in order to prepare an aqueous solution of the polyurethane resin.

In one embodiment, the polyurethane resin is preferably a polyurethane resin having an acid value because it can be easily made water-based by neutralization. In one embodiment, the polyurethane resin preferably has an acid value of 1-100 mgKOH / g. The acid value is more preferably 10 to 70 mgKOH / g, and even more preferably 20 to 60 mgKOH / g. Although not particularly limited, the hydroxyl value of the polyurethane resin is preferably 1 to 20 mgKOH / g. Here, the acid value and the hydroxyl value are measured by the method described in JIS K0070 (1992).

(Neutralizer)
Various neutralizing agents can be used to make the polyurethane resin having an acid value water-based by neutralization. For example, a basic compound can be used to neutralize the carboxyl group in the polyurethane resin.
Specific examples of basic compounds that can be used as neutralizers include sodium hydroxide, potassium hydroxide, ammonia, methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, ethanolamine, propanolamine, diethanolamine, N- Examples thereof include methyldiethanolamine, dimethylamine, diethylamine, triethylamine, N, N-dimethylethanolamine, 2-dimethylamino-2-methyl-1-propanol, 2-amino-2-methyl-1-propanol, and morpholin. One of these may be used alone, or two or more thereof may be used in combination. Ammonia is preferable from the viewpoint of water resistance of printed matter and residual odor.

The production of the water-based polyurethane resin can be carried out by applying a conventionally known or well-known method, and is not particularly limited. For example, the methods for producing an aqueous polyurethane resin described in JP-A-2013-234214, JP-A-2013-249401, JP-A-2015-67818, and JP-A-2018-184512 can be referred to.

In one embodiment, when an aqueous polyurethane resin is used as the binder resin, its weight average molecular weight may be in the range of 5,000 to 100,000, more preferably 10,000 to 90,000. It is good, more preferably 20,000 to 80,000. When the weight average molecular weight of the polyurethane resin is within the above range, it becomes easy to obtain desired properties such as elongation and stress. Further, in one embodiment, from the viewpoint of enhancing ethanol resistance, the weight average molecular weight of the polyurethane resin is preferably 21,000 to 80,000, more preferably 25,000 to 75,000, and 30,000 to 70, 000 is particularly preferable.

Although not particularly limited, in one preferred embodiment, the polyurethane resin used as the binder resin may be a polyurethane resin aqueous solution obtained as follows.
(1) First, poly (3-methyl-1,5-pentaneadipate) diol, polyethylene glycol, and dimethylolbutanoic acid are mixed and stirred, and isophorone diisocyanate is further added and reacted to react with the terminal isocyanate pre. Form a polymer. Next, an organic solvent such as 2-aminoethylethanolamine and isopropyl alcohol is added to the terminal isocyanate prepolymer (I) to form a solvent-type polyurethane resin solution.
(2) Next, ammonia water and ion-exchanged water are gradually added to the solvent-type polyurethane resin solution to neutralize the solution to form an aqueous polyurethane resin solution. Further, after distilling off the organic solvent in the aqueous polyurethane resin solution under reduced pressure, water is added to adjust the solid content to obtain an aqueous solution of the aqueous polyurethane resin (polyurethane resin aqueous solution).

In one embodiment, the urethane resins (A) to (G) described later in the examples can be preferably used as the binder resin constituting the water-based ink composition. The urethane resins (A) to (G) may be used individually, but it is more preferable to use two or more in combination because various characteristics can be easily adjusted. For example, when the urethane resin (A) and the urethane resin (B) are used in combination, more suitable characteristics tend to be obtained.

In one embodiment, the total content of the binder resin is preferably 30% by mass or less, more preferably 5 to 25% by mass, based on the total mass of the aqueous ink composition (solid content). When the amount of the binder resin used is adjusted within the above range, an appropriate ink viscosity can be easily obtained, so that the work efficiency during ink production and printing can be improved.

(Hardener)
In one embodiment, the aqueous ink composition preferably further comprises a curing agent for the resin used as the binder resin. When the water-based ink composition contains a curing agent, the printing layer is formed from the cured coating film, but the reaction form thereof is not particularly limited. That is, the printing layer may be a cured coating film formed from the resin in the binder resin and the curing agent. Alternatively, the printing layer may be a cured coating film formed from the curing agent itself.

In one embodiment, when a polyurethane resin having an acid value is used as the binder resin, it is preferable that the aqueous ink composition further contains a curing agent. In one embodiment, the polyurethane resin preferably has an acid value of 1-100 mgKOH / g. The acid value is more preferably 10 to 70 mgKOH / g, and even more preferably 20 to 60 mgKOH / g.

In one embodiment, when a polyurethane resin having an acid value of 1 to 100 mgKOH / g and a curing agent are used in combination, a printing layer having a residual ratio of 50% or more after being immersed in ethanol at 25 ° C. for 30 minutes is formed. It can be easily formed. Therefore, excellent ethanol resistance can be easily realized in the printed layer. Further, according to the embodiment in which the water-based ink composition contains a polyurethane resin having an acid value of 1 to 100 mgKOH / g and a curing agent, in addition to ethanol resistance, abrasion resistance of the printed surface, foamed appearance, etc. Good results can be obtained with various characteristics.

A compound well known in the art can be used as a curing agent for a polyurethane resin having an acid value. Among them, it is preferable to use at least one selected from the group consisting of an epoxy-based curing agent, a carbodiimide-based curing agent, and an isocyanate-based curing agent as the curing agent. In one embodiment, it is more preferable to use at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent. It is more preferable to use at least a carbodiimide-based curing agent.

In one embodiment, the aqueous ink composition for forming the printing layer may contain an aqueous polyurethane resin having an acid value of 1 to 100 mgKOH / g and at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent. preferable. The printing layer formed by using such an aqueous ink composition is a curing formed from an aqueous polyurethane resin having an acid value of 1 to 100 mgKOH / g and at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent. Includes objects (cured coating).

The carbodiimide-based curing agent may be a compound having a carbodiimide group in the molecule. Compounds having two or more carbodiimide groups in the molecule are preferable. Specific examples of carbodiimide-based curing agents include p-phenylene-bis (2,6-xylylcarbodiimide), tetramethylene-bis (t-butylcarbodiimide), and cyclohexane-1,4-bis (methylene-t-butylcarbodiimide). ). The carbodiimide-based curing agent may be a polycarbodiimide compound which is a polymer having a carbodiimide group. These may be used alone or in combination of two or more.

In one embodiment, the compound used as the carbodiimide-based curing agent preferably has a chemical formula amount (NCN equivalent) per 1 mol of carbodiimide group of 250 to 700, more preferably 300 to 600. Commercially available products can also be used as the carbodiimide-based curing agent. For example, Nisshinbo's Carbodilite series V-02, V-02-L2, SV-02, V-04, V-10, SW-12G, E-02, E-03A, E-05, etc. Be done. One of these may be used alone, or two or more thereof may be used in combination.

The isocyanate-based curing agent may be a compound having an isocyanate group in the molecule. A compound having two or more isocyanate groups in the molecule is preferable. The compound used as the isocyanate-based curing agent is preferably aqueous, that is, dispersed in water or diluted with water. Such an aqueous isocyanate-based curing agent can also be obtained as a commercially available product, for example, Aquanate 100, Aquanate 110, Aquanate 200 and Aquanate 210 (all trade names, manufactured by Nippon Polyurethane Industry Co., Ltd.); Baihijour TPLS-2032, SUB-Isocyanate L801, Baihijour VPLS-2319, Baihijour 3100, VPLS-2336 and VPLS-2150 / 1 (trade name, manufactured by Sumika Bayer Urethane Co., Ltd.); Takenate WD-720, Takenate WD-725 , Takenate WD-220 (trade name, manufactured by Mitsui Takeda Chemical Co., Ltd.); isocyanate D-56 (trade name, manufactured by Dainichiseika Kogyo Co., Ltd.) and the like. One of these may be used alone, or two or more thereof may be used in combination.

In one embodiment, in the aqueous ink composition for forming the printing layer, the blending amount of the curing agent is preferably 100: 1 to 100: 100 in terms of the mass ratio of the binder resin: the curing agent, 100: It is more preferably 2 to 100:60, and even more preferably 100: 3 to 100:30.

It is preferable to adjust the blending amount of the curing agent according to the composition of the printing layer. More specifically, in one embodiment, the blending amount of the curing agent when the printing layer is formed as a single layer is preferably 100: 2 to 100: 100 in terms of the mass ratio of the binder resin: the curing agent. It is more preferably 100: 2 to 100: 60, and even more preferably 100: 5 to 100:30.

In one embodiment, when the printing layer is formed as a plurality of layers, the blending amount of the curing agent is preferably 100: 1.5 to 100: 100 in the mass ratio of the binder resin: the curing agent in each layer. It is more preferably 100: 2 to 100: 60, and even more preferably 100: 3 to 100:30.

By adjusting the blending amount of the curing agent within the above range, it is possible to easily form a printed layer having a residual ratio of 50% or more after being immersed in ethanol at 25 ° C. for 30 minutes. As a result, excellent foam followability, excellent foam appearance, abrasion resistance, heat resistance, and ethanol resistance of the printed surface can be easily realized.

(Colorant)
The colorant used in the water-based ink composition may be various inorganic pigments and organic pigments generally used in printing inks and paints. Examples of inorganic pigments include white pigments such as titanium oxide, colored pigments such as red iron oxide, dark blue, ultramarine blue, carbon black, and graphite, and extender pigments such as calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, and talc. Be done. Further, examples of organic pigments include colored pigments such as soluble azo pigments, insoluble azo pigments, azo chelate pigments, condensed azo pigments, copper phthalocyanine pigments, and condensed polycyclic pigments. The content of these pigments can be appropriately selected in consideration of the desired color tone of the ink and the like, but is generally in the range of 0.5 to 50% by mass based on the total mass of the aqueous ink composition. It is preferable to do so.

In one embodiment, when a white water-based ink composition is prepared, the blending amount of the white pigment is preferably in the range of 20 to 50% by mass based on the total mass of the water-based ink composition. From the viewpoint of hiding property, pigment concentration, and light resistance, it is preferable to use titanium dioxide as the white pigment. On the other hand, when preparing a colored water-based ink composition, colored organic pigments and colored inorganic pigments such as red iron oxide, prussian blue, ultramarine blue, carbon black, and graphite can be appropriately selected and used. Organic pigments are preferable from the viewpoint of color development and light resistance. The blending amount of the colored pigment is preferably in the range of 10 to 30% by mass based on the total mass of the water-based ink composition.

In the water-based ink composition, an organic solvent may be used in addition to water as the solvent as long as the effect is not hindered. When an organic solvent is used, an alcohol-based organic solvent is preferable. Specific examples of the organic solvent include ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, t-butanol, 2-methyl-2-propanol and the like. Can be mentioned. When these organic solvents are used, it is preferable in the water-based ink composition because the wettability to the base material can be controlled. In one embodiment, the substrate may be a foamed paper material. The water-based ink composition is applied to the upper surface of _{the foam layer forming layer (B 0) of the foam paper material to form a print layer.}

When the water-based ink composition contains an organic solvent, the blending amount thereof is preferably 30% by mass or less, more preferably 20% by mass or less, and 10% by mass, based on the total mass of the water-based ink composition. It is more preferably less than or equal to%. In one embodiment, the content of the organic solvent in the water-based ink composition is most preferably 5% by mass or less, and the water-based ink composition may not contain the organic solvent.

(Other additives)
The water-based ink composition may contain various additives, if necessary. Preferable examples of the additive include an antiblocking agent, various waxes, a thickener, a rheology adjuster, a defoamer, a leveling agent, a preservative, a surface tension adjuster, an adhesion aid, and a pH adjuster.

(Adhesive aid)
The water-based ink composition may further contain an adhesion aid from the viewpoint of improving the adhesion between the printing layer and the substrate. It is preferable to use at least one of a hydrazine-based compound and an epoxy compound as the adhesion aid.
As the hydrazine-based compound, adipic acid dihydrazide, sebacic acid dihydrazide, isophthalic acid dihydrazide, and other dihydrazide compounds are preferable.
The epoxy compound means a compound having an epoxy group. For example, alicyclic epoxies such as ADEKA ADEKA Resin EP-4000, EP-4005, 7001 can be mentioned.
These adhesive aids are preferably used in an amount of 0.1 to 5% by mass, more preferably 0.1 to 3% by mass, based on the total mass of the aqueous ink composition.

In one embodiment, when a white ink composition is formed as the water-based ink composition, the preferable composition is 10 to 50% by mass of the white inorganic pigment and 5 to 35% of the polyurethane resin (solid content) based on the total mass of the white ink. % By mass and 5 to 30% by mass of water. More preferable compositions of the white ink composition are 20 to 50% by mass of the white inorganic pigment, 5 to 30% by mass of the polyurethane resin (solid content), and 5 to 25% by mass of water. As another embodiment, in addition to the composition of the white ink composition, 0.5 to 15% by mass of a curing agent may be further contained. The curing agent preferably contains at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent.

In one embodiment, when a color ink composition such as magenta, yellow, and cyan is formed as the water-based ink composition, the preferable composition is 10 to 25% by mass of an organic pigment and a polyurethane resin based on the total mass of the color ink. (Solid content) 5 to 35% by mass and 5 to 30% by mass of water. More preferable compositions of the color ink are organic pigment 10 to 20% by mass, polyurethane resin (solid content) 5 to 30% by mass, and water 5 to 25% by mass. As another embodiment, in addition to the composition of the color ink, 0.5 to 15% by mass of a curing agent may be further contained. The curing agent preferably contains at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent.

The water-based ink composition forming the print layer can be produced by applying a well-known technique and mixing the above-mentioned various components. More specifically, first, the binder resin, water, and, if necessary, a pigment, a pigment dispersant, a surfactant, and the like are stirred and mixed, and then, for example, a bead mill, a ball mill, a sand mill, an attritor, a roll mill, and the like. Examples thereof include a method of kneading meat using various kneading machines such as a pearl mill, and further adding and mixing the remaining materials.

<3> Method for manufacturing foamed paper laminate One embodiment relates to a method for producing a foamed laminate. That is, one embodiment includes a foam paper having a thermoplastic resin layer (A), a paper base material, and a foam layer (B) in that order, and a printing layer formed on the surface of the foam layer (B) of the foam paper. The number of foamed cells per unit surface area of the foamed layer (B) is 1000 cells / cm ² or more, and the residual ratio of the printed layer after being immersed in ethanol at 25 ° C. for 30 minutes is 50% by mass or more. The present invention relates to a method for producing a foamed paper laminate. This production method has the following steps (i) to (iv), that is, (i) a thermoplastic resin layer (A), a paper substrate, and a melting point lower than that of the thermoplastic resin layer (A). To prepare a foamed paper material which sequentially has a foamed layer forming layer (B _{0) that foams by heating.}
(Ii) Preparing a water-based ink composition containing a binder resin containing a polyurethane resin and water.
(iii) Applying the water-based ink composition to the surface of the foam layer forming layer (B _{0) of the foam paper material to form a printing layer.}
(iv) By heating the foamed paper material having the printed layer, the foamed layer forming layer (B ₀ ) of the foamed paper material is foamed to form the foamed layer (B).

In the above manufacturing method, each step relating to (i) preparation of foam paper material, (ii) preparation of water-based ink composition, (iii) formation of printing layer, and (iv) formation of foam layer (B) by heating is performed. It can be carried out according to a method well known in the art. Hereinafter, each step will be described.

(Step (i): Preparation of foam paper material)
(I) The preparation of the foamed paper material can be carried out, for example, according to the extrusion laminating method. The constituent materials of the paper base material, the thermoplastic resin layer (A), and the foamed layer forming layer (B ₀ ) constituting the foamed paper material are as described above. As the extrusion laminating method, a well-known method such as a single laminating method, a tandem laminating method, a sandwich laminating method, and a coextrusion laminating method can be appropriately selected. In one embodiment, polyethylene resins having different melting points can be preferably used as the constituent materials of the thermoplastic resin layer (A) and the foamed layer forming layer (B _0).

The foam layer forming layer (B ₀ ) is constructed by using a polyethylene resin (low Mp polyethylene resin) having an Mp lower than the melting point (Mp) of the polyethylene resin constituting the thermoplastic resin layer (A). The foamed paper material is obtained by extruding a low Mp polyethylene resin into a film on one side of a paper base material and a high Mp polyethylene resin into a film on the other side of a paper base material through a T-die extruder. Can be manufactured by

The temperature of the polyethylene resin at the time of laminating (the temperature immediately below the T die) is preferably 300 to 350 ° C, more preferably 320 ° C to 340 ° C. Within this temperature range, sufficient lamination strength can be realized between each polyethylene resin layer (A, B _{0) and the paper base material.} The surface temperature of the cooling roll passed after laminating is preferably controlled in the range of 10 to 50 ° C.

In one embodiment, the laminating speed is preferably 50 to 130 m / min, more preferably 60 to 110 m / min. If the laminating speed is too slow, the productivity will be low, while if the laminating speed is too fast, the neck-in tends to reduce the yield. Neck-in is a phenomenon in which the width of the extruded polyethylene resin film is smaller than the effective width of the T-die when the polyethylene resin is extruded into a film by a T-die extruder. At this time, both ends of the film become thicker than the central portion. When the thickness of both ends deviates from the standard, it is common to cut and remove both ends, but when the neck-in is severe, the area deviating from the standard increases and the yield decreases.

In one embodiment, the air gap is preferably 300 mm or less, more preferably 200 mm or less. If the air gap is widened too much, the polyethylene resin will neck in and the yield will tend to decrease. The air gap refers to the distance from the T-die extrusion port to the nip roll. It is preferable to surface-treat the polyethylene resin with ozone gas and / or oxygen gas while the polyethylene resin is passing through the air gap. By performing the surface treatment using ozone gas and / or oxygen gas, the formation of an oxide film can be promoted and the adhesive force with the base material layer can be improved. The amount of ozone gas and / or oxygen gas to be treated is not particularly limited, but 0.5 mg / m ² or more is preferable from the viewpoint of promoting the oxidation of the polyethylene resin.

(Step (ii): Preparation of water-based ink composition)
In the production method of the above-described embodiment, the specific configuration and preparation method of (ii) the water-based ink composition are as described above in the embodiment of the water-based ink composition.
In one embodiment, it is preferable to prepare a water-based ink composition (ii-1) containing a binder resin containing a water-based polyurethane resin and water as the water-based ink composition. Here, the binder resin is preferably an aqueous polyurethane resin having an acid value, and more preferably water-based by neutralization. Further, the stress at an elongation rate of 50 to 4,000% is preferably 0.1 mPa to 50 mPa.

In another embodiment, instead of the water-based ink composition (ii-1), a binder resin containing an water-based polyurethane resin having an acid value of 1 to 100 mgKOH / g, water, a carbodiimide-based curing agent, and a polyisocyanate-based curing agent are used. It is preferable to prepare an aqueous ink composition (ii-2) containing at least one of the agents. Here, the polyurethane resin having an acid value of 1 to 100 mgKOH / g is preferably made aqueous by neutralization.

(Step (iii): Formation of print layer)
The formation of the print layer (iii) is not particularly limited, and a well-known technique can be applied. For example, when printing a white water-based ink composition on the entire surface of the foam layer forming layer (B ₀ ) (low Mp resin film) as the base layer, a coater such as a bar coater, a roll coater, or a reverse roll coater is used. May be good. In addition, various printing methods can be applied.

Among various printing methods, it is preferable to apply a printing method by flexographic printing or gravure printing. When forming the printing layer by these printing methods, the water-based ink compositions (ii-1) and (ii-2) of the above-described embodiments can be preferably used. In particular, when the printing method by flexographic printing is applied, it is possible to form a printing layer with good productivity and high yield. Hereinafter, a typical form of the flexographic printing method will be described.

(Flexographic printing method)
(1) Anilox roll Anilox can be used in the flexographic printing method. For example, ceramic anilox rolls with cell engraving, chrome-plated anilox rolls, and the like can be used.
In order to obtain a printed layer (printed matter) having excellent dot reproducibility, anilox roll having a line number of 5 times or more, preferably 6 times or more of the number of lines of the plate used at the time of printing is used. For example, when the number of lines of the plate to be used is 75 lpi, Anilox having a number of lines of 375 lpi or more is required. When the number of lines of the plate is 150 lpi, anilox roll having a number of lines of 750 lpi or more is required. Capacity of the anilox roll, from the viewpoint of drying properties and blocking property of the aqueous ink composition used may be 1 ~ 8cc / m ^2, preferably, may be ² ~ 6cc / m 2.

(2) Flexographic plate In the flexographic printing method, a photosensitive resin plate that utilizes ultraviolet curing by a UV light source can be used as the plate. As the plate, an elastomer material plate that uses a direct laser engraving method can also be used. Regardless of the method of forming the image portion of the flexographic plate, a plate having a screening line number of 75 lpi or more is used. Any sleeve or cushion tape can be used to attach the plate.

(3) Printing Machine Specific examples of the flexographic printing machine include a CI type multicolor flexographic printing machine and a unit type multicolor flexographic printing machine. Specific examples of the ink supply method include a chamber method and a two-roll method. A printing machine applicable to the flexographic printing method can be appropriately selected and used.

In one embodiment, the print layer preferably comprises a plurality of layers. The print layer may have a base layer that covers the entire surface of the foam layer forming layer (B ₀ ) and a print pattern provided on at least a part of the surface of the base layer. For example, the base layer is composed of a white water-based ink composition, and the print pattern is formed of a water-based color ink composition.

In one embodiment, the thickness of the printed layer is adjusted so that the film thickness of the dry coating film is 0.5 to 5.0 μm from the viewpoint of the foaming suppressing force of the printed layer and the abrasion resistance. Is preferable. The film thickness of the printing layer (dry coating film) may be more preferably 0.5 to 4.0 μm, and further preferably 0.5 to 3.5 μm. Here, when the print layer is composed of a plurality of layers, the film thickness of the print layer is preferably adjusted so that the thickness of the entire print layer is within the above range.

In another embodiment, the printing layer may include a plurality of layers, and it is preferable to have a transparent layer as the outermost layer thereof. The lucidum can be constructed using a pigment-free clear ink composition. In one embodiment, the clear ink composition can be configured in the same manner as the water-based ink compositions (ii-1) and (ii-2) described above, except that it does not contain a pigment.

When a transparent layer is provided, the friction resistance, ethanol resistance, and water friction resistance of the printed surface can be easily improved. In one embodiment, the thickness of the transparent layer (dry film thickness) is preferably 0.1 to 3.0 μm, more preferably 0.1 to 2.5 μm, and even more preferably 0.1 to 2. It is 0.0 μm. Here, when the print layer has a transparent layer, it is preferable to adjust the thickness of the entire print layer including the thickness of the transparent layer to be within the range of 0.5 to 5.0 μm.

When the printing layer includes a plurality of layers, the water-based ink constituting at least one of the plurality of layers preferably contains a binder resin containing a polyurethane resin and a curing agent. In one embodiment, the aqueous ink composition constituting at least the base layer and / or the outermost layer preferably contains a binder resin containing a polyurethane resin and a curing agent. It is more preferable to form the base layer (white) ink layer and the outermost layer (ink layer or transparent layer) by using the above-mentioned water-based ink composition, and it is most preferable to form all of the plurality of layers.

(Step (iv): Formation of foam layer (B))
In the formation of the foamed layer (B) by the above (iv) heating, the appropriate heating temperature and heating time vary depending on the characteristics of the paper base material used and the thermoplastic resin film. A person skilled in the art can determine the combination conditions of the optimum heating temperature and heating time according to the material such as the thermoplastic resin film to be used. Although not particularly limited, the heat treatment is generally carried out in the process of molding the container. If the heating temperature during the heat treatment is too low, sufficient foamability cannot be obtained, and if the heating temperature is too high, the foam cells are combined and swelling is likely to occur.

Although not particularly limited, when the foamed layer forming layer is composed of a low-density polyethylene film, the heating temperature may be preferably 100 to 125 ° C, more preferably 110 to 120 ° C. The heating time can be appropriately adjusted according to the heating temperature, but is preferably 3 to 10 minutes, more preferably 5 to 7 minutes. In one embodiment, when the foam layer forming layer is composed of a low density polyethylene film and the printed layer is formed on the foam layer forming layer by using the water-based ink composition (ii-1) or (ii-2) described above. It is preferable to adjust the heating temperature to 110 to 123 ° C. and the heating time to 5 to 7 minutes. It is more preferable to adjust the heating temperature to 115 to 121 ° C. and the heating time to 5 to 7 minutes. When heating is performed under the above conditions, it becomes easy to appropriately control the foaming of the foam layer forming layer during heat processing by the printing layer.

Any means such as hot air, electric heat, and electron beam can be used as the heating means. A large amount of heat treatment can be carried out at low cost by heating with hot air, electric heat, or the like in a tunnel provided with a transport means by a conveyor.

<4> Foam Paper Container One embodiment relates to a foam paper container provided with the foam paper laminate of the above embodiment. The foamed paper container is composed of a container body member and a bottom plate member, and the container body member is formed from the foamed paper laminate of the above embodiment. FIG. 1 is a perspective view showing the structure of a foamed paper container 10A obtained by performing a heat treatment after assembling and molding the container. As shown in FIG. 1, the foamed paper container 10A is composed of a container body member 10 made of a foamed paper laminate and a bottom plate member 12. In the container body member (foamed paper laminate) 10, the high Mp resin film forms the inner wall surface 10a of the container, and the printing layer on the low Mp resin film (foamed layer) forms the outer wall surface 10b of the container.

FIG. 2 is a schematic cross-sectional view showing an enlarged reference code I portion of the container body member of the foam paper container shown in FIG. The container body member (foamed paper laminate) 10 includes a high Mp resin film 20, a paper base material 30, and a low Mp resin film (foamed layer) 40 after foaming, in this order from the inner wall surface 10a side (see FIG. 1) of the container. And a print layer 50, and the print layer 50 has a base layer 50a and a print pattern 50b.

Molding of foamed paper containers can be carried out by applying well-known technology. For example, a foamed paper laminate (foamed paper laminate before heating) on which a printing layer is first formed is punched into a predetermined shape along a mold to obtain a container body member. Similarly, the bottom plate material is punched into a predetermined shape to obtain a bottom plate member. Next, the container body member and the bottom plate member are assembled and molded into the shape of the container by using a conventional container manufacturing apparatus. In the assembly molding of the container by the container manufacturing apparatus, the high Mp resin film of the container body member forms the inner wall surface, the low Mp resin film forms the outer wall surface, and the laminated surface of the bottom plate member is on the inside. To carry out. By assembling and molding the container with the container manufacturing apparatus in this way and then performing heat treatment, the low Mp resin film is foamed to form a foam layer (heat insulating layer), and a foamed paper container having heat insulating properties can be obtained. can.

In one embodiment, when the inner wall surface of the body and the outer wall surface of the body of the foamed paper container are each made of polyethylene film, one surface of the paper base material (inner wall surface of the container) is made of medium-density or high-density polyethylene film. It is preferable to laminate the other surface (outer wall surface of the container) with a low-density polyethylene film. The thickness of each film laminated on the paper substrate is not particularly limited. However, the thickness of the low Mp resin film constituting the outer wall surface of the container body is appropriately set so that the foamed film has a sufficient thickness to function as a heat insulating layer when the film is foamed. Is preferable.

For example, when the outer wall surface of the container body is made of a low-density polyethylene film, the thickness of the film to be laminated on the paper substrate may be 40 to 150 μm. On the other hand, when the inner wall surface of the container body is made of a medium-density or high-density polyethylene film, the thickness of the film to be laminated on the paper substrate is not particularly limited. However, it is preferable to appropriately set the thickness of the film so that the permeation resistance of the contents is ensured when used as a heat-insulating foamed paper container. Since the thickness of the film to be laminated on the paper substrate varies depending on the resin material of the film used, it is desirable for those skilled in the art to appropriately set the thickness in consideration of the characteristics of the resin material.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. The "parts" and "%" described below represent "parts by mass" and "% by mass" unless otherwise specified.

<1> Measurement method of various characteristics The various characteristics of the binder resin and the water-based ink composition, which will be described later, represent values obtained by the following measurement methods.

(Glass-transition temperature)
Each of the polyurethane resin aqueous solutions obtained in the synthetic examples described later was applied onto a polyethylene substrate and then dried at 40 ° C. for 3 days to obtain a dry coating film having a thickness of 0.5 mm. For each dry coating film, the peak top temperature of loss tangent tan δ measured using a dynamic viscoelastic automatic measuring machine (DDV-GP series (Leo Vibron) manufactured by A & D Co., Ltd.) is Tg (° C.). And said. The measurement was carried out in a temperature range of −120 ° C. to 40 ° C. and a heating rate of 10 ° C./min.

(Elongation rate and stress of binder resin)
Each of the polyurethane resin aqueous solutions obtained in the synthetic example described later was dried to prepare a coating film test sample (thickness 0.30 mm, width 5.0 mm, length 20.0 mm). For each sample, the elongation and stress were measured using a small tensile tester manufactured by Intesco. The measurement was carried out under the conditions of a tensile speed of 100 mm / min and a room temperature of 25 ° C.
In the embodiment in which the water-based ink composition contains a curing agent, a binder resin and a curing agent are used in combination in the same manner as in the blending ratio in the water-based ink composition, and a coating film test sample (thickness 0.30 mm, width 5) is used. .0 mm, length 20.0 mm) was prepared. Using this sample, the elongation and stress of the binder resin (cured product) were measured according to the same method as described above.

(Residual rate of print layer)
The residual ratio of the printed layer was a test for evaluating the ethanol resistance of the printed layer (the surface of the foamed paper laminate) formed on the foamed paper, and was carried out as follows.
First, as a test piece (sample), a foamed paper laminate was cut into dimensions of 100 mm in length and 100 mm in width. The mass of the cut-out test piece was measured and used as the sample mass before immersion in ethanol. Then, for convenience of the immersion work, the test piece was pulverized to a size of about 20 mm in length and 20 mm in width.
Next, ethanol (25 ° C.) and the crushed test piece were placed in a container so that the mass ratio of ethanol: test piece was 100: 4.5, and the test piece was immersed in ethanol. Immersion was carried out in ethanol at 25 ° C. under the conditions of stirring the test piece at a stirring rotation speed of 100 rpm for 2 minutes, then allowing it to stand for 30 minutes, and further stirring the test piece at a rotation speed of 100 rpm for 1 minute. did. The test piece was taken out, and the mass of the test piece after drying was measured and used as the sample mass after immersion.
Further, from the sample mass before immersion and the sample mass after immersion measured as described above, the residual ratio of the printed layer was calculated according to the following formula.
Residual rate of printed layer = (sample mass after immersion / sample mass before immersion) x 100

(Film thickness of print layer)
The thickness of the print layer was determined from a scanning electron microscope (SEM) photograph (magnification 5000) of a cross section of the foamed paper laminate. The print layer was measured at any five points, and the average value thereof was taken as the film thickness of the print layer.

(Number of foam cells)
The printed layer of the foamed paper laminate was removed with methyl ethyl ketone (MEK) to expose the surface of the foamed thermoplastic resin layer (foamed layer). Next, the surface of the foam layer was observed using an optical microscope (AZ100M manufactured by Nikon Corporation) (magnification: 25 times), and independent cells existing within a range partitioned by a certain length in the vertical and horizontal (XY) directions. Was obtained, and a value calculated as the number of independent cells per ^{1 cm 2 was obtained.} Observation was performed at any 5 points, and the average value of these was taken as the number of foamed cells.

(Film thickness of foam layer)
The film thickness of the foamed layer was determined by observing the cross section of the foamed paper laminate with an optical micrograph and measuring the height from the upper surface of the paper substrate to the lower surface of the printed layer. The film thickness before foaming corresponds to the film thickness of the foamed layer forming layer. Therefore, the value obtained by measuring the film thickness of the low-density polyethylene resin formed as the foam layer forming layer was used.

(Binder resin)
(Synthetic Example 1) Polyurethane resin (A)
Poly (3-methyl-1,5-pentaneadipate) diol (PMPA2000, number) while introducing nitrogen gas into a reactor equipped with a reflux condenser, a dropping funnel, a gas introduction tube, a stirrer, and a thermometer. 328.16 parts with an average molecular weight of 2,000), 10.0 parts of polyethylene glycol (PEG2000, number average molecular weight of 2,000), 57.81 parts of dimethylolbutanoic acid (DMBA), and 350 parts of methyl ethyl ketone (MEK) were added. .. While mixing and stirring these, further 200.76 parts of isophorone diisocyanate (IPDI) was added dropwise over 1 hour. These were then reacted at reflux temperature for 6 hours to form a terminal isocyanate prepolymer. Then, the reaction solution was cooled to 30 ° C., and then 100 parts of isopropyl alcohol was added to obtain a solvent solution of the terminal isocyanate prepolymer.
To the obtained terminal isocyanate prepolymer, a mixed solution of 28.21 parts of 2-aminoethylethanolamine (AEA) and 150 parts of isopropyl alcohol (IPA) was gradually added at room temperature (25 ° C.) and at 40 ° C. A solvent-type polyurethane resin solution was obtained by reacting for 3 hours.
Next, an aqueous polyurethane resin solution was obtained by gradually adding 23.69 parts of 28% ammonia water and 1800 parts of ion-exchanged water to the solvent-type polyurethane resin solution to neutralize the solution. Further, MEK and IPA in the aqueous polyurethane resin solution were distilled off under reduced pressure, and then water was added to adjust the solid content to 25%.
As described above, an aqueous solution (solid content 25%) of the polyurethane resin (A) having an acid value of 35 mgKOH / g and a weight average molecular weight of 35,000 was obtained. According to the method described above, the elongation rate and stress of the polyurethane resin (A) and other characteristics were measured. The results are shown in Table 1.

(Synthesis Examples 2 to 8)
In the same manner as in Synthesis Example 1, except that the raw materials and the blending amounts described in Synthesis Example 1 were changed so as to have the characteristics shown in Table 1 according to the synthesis method described in JP-A-2018-184512. Aqueous solutions of polyurethane resins (B) to (H) having a solid content of 25% were obtained (hereinafter, may be abbreviated as polyurethane resins (B) to (H)). Table 1 shows the results of measuring the elongation and stress of the polyurethane resins (B) to (H) and other properties according to the method described above.

<2> Production Example of Aqueous Ink Composition (Production Example 1) Production of White Ink (W1) 10 parts of polyurethane resin (A) aqueous solution, 20 parts of polyurethane resin (B) aqueous solution, according to the formulation shown in Table 2. 40 parts of white pigment (titanium oxide, Titanics JR808 (manufactured by Teika Co., Ltd.), 0.1 part of antifoaming agent, 0.2 part of adipate dihydrazide (ADH), 1 part of N-propanol, and 5 parts of water are mixed by stirring. Then, the mixture was dispersed with a sand mill. Next, 4 parts of a polyurethane resin (A) aqueous solution, 14 parts of a polyurethane resin (B) aqueous solution, and 6 parts of water were added to the mixture obtained by the dispersion treatment, and the mixture was stirred. By mixing, a white ink (W1) was obtained.

(Production Examples 2 to 9) Production of White Inks (W2) to (W9) All described in Production Example 1 except that the two types of polyurethane resin aqueous solutions used in Production Example 1 were changed according to the formulation shown in Table 2. White inks (W2) to (W9) were obtained in the same manner as in the above production method.
The binder resins shown in Table 2 are as follows.
Polyurethane resins A to H: Aqueous solutions of polyurethane resins (A) to (H) prepared in Synthesis Examples 1 to 8 (each having a solid content of 25%).
Polyurethane resin I: Product name "Uriano W321" manufactured by Arakawa Chemical Industry Co., Ltd. (an aqueous solution of a polyurethane resin having a resin elongation rate of 600% and a stress of 7.0 mPa).
Acrylic resin: Product name "Joncryl7100" manufactured by BASF Co., Ltd. (weight average molecular weight is 200,000, glass transition temperature is -10 ° C, acid value is 51 mgKOH / g, resin elongation is 180%, stress is 6. Emulsion of acrylic resin at 5 mPa).
Vinyl chloride resin: Product name "Viniblanc 700" manufactured by Nissin Chemical Industry Co., Ltd. (a vinyl chloride resin emulsion having a glass transition temperature of 70 ° C. and an acid value of 57 mgKOH / g).

(Manufacturing Example 10) Production of indigo ink (B1) According to the formulation shown in Table 2, 20 parts of a polyurethane resin (B) aqueous solution, 20 parts of a polyurethane resin (C) aqueous solution, and an indigo pigment (LIONOL BLUE FG-7358-). 20 parts of G (manufactured by Toyo Color Co., Ltd.), 0.10 part of defoamer, 0.20 part of ADH, 2.5 parts of N-propanol, and 10 parts of water were stirred and mixed, and dispersed with a sand mill. Next, 4 parts of the polyurethane resin (B) aqueous solution, 16 parts of the polyurethane resin (C) aqueous solution, and 8 parts of water were added to the mixture obtained by the dispersion treatment, and the mixture was stirred and mixed to obtain indigo ink (indigo ink). B1) was obtained.

(Production Examples 11 to 18) Production of Indigo Inks (B2) to (B9) All of Production Examples 10 except that the two types of polyurethane resin aqueous solutions described in Production Example 10 were changed to the formulations shown in Table 2. Indigo inks (B2) to (B9) were obtained in the same manner as in the production method described.

(Manufacturing Example 19) Production of Clear Ink (C1) According to the formulation shown in Table 2, 82 parts of the polyurethane resin (C) aqueous solution, 0.1 part of the defoamer, 0.2 part of ADH, and 1 part of N-propanol. , 17 parts of water was stirred and mixed to obtain a clear ink (C1) for overprinting.

(Production Examples 20 to 27) Production of Clear Inks (C2) to (C9) All the production methods described in Production Example 19 except that the polyurethane resin aqueous solution described in Production Example 19 was changed to the formulation shown in Table 2. In the same manner as above, clear inks (C2) to (C9) were obtained.

<3> Production example of foamed paper laminate (1) Production example of foamed paper material The foamed paper material is (step 1) extruded and laminated with a medium-density polyethylene resin (M) on one side of a paper base material to form a water vapor blocking layer. Then, the low-density polyethylene resin (L) was extruded and laminated on the other surface (non-laminated surface) of the paper base material (step 2).

Various conditions in steps 1 and 2 are as follows.
(Step 1)
Paper substrate: Moisture content 23 kg / m ³ , Basis weight 320 kg / m ³
Medium density polyethylene resin (M): Tosoh's "Petrosen LW04-1", MFR 4.3 g / 10 minutes, density 940 kg / m ³
Extrusion temperature (T die outlet temperature): 320 ° C
Pick-up speed (lamination speed): 50 m / min Air gap: 130 mm
Thickness: 40 μm (thickness of the central part of the polyethylene resin layer)

(Step 2)
Low density polyethylene resin (L); extrusion temperature (T die outlet temperature) described later: 310 ° C.
Pick-up speed (lamination speed): 60 m / min Air gap: 130 mm

The low-density polyethylene resin (L) used in the above step 2 is a foam layer forming layer (B ₀ ). As the low-density polyethylene resin (L), the low-density polyethylene resin (L2) was used in Example 18, and the other low-density polyethylene resin (L1) was used to produce a foam paper material. Details of the low-density polyethylene resins (L1) and (L2) are as follows.
Low-density polyethylene resin (L1): Tosoh's "Petrosen 07C03C", density 918 kg / m ³ , melting point 106 ° C, MFR 15 g / 10 minutes Low-density polyethylene resin (L2): Japan Polyethylene "Novatec LDLC720", density 922 kg / m ³ , melting point 110 ° C, MFR 9 g / 10 minutes

(2) Production example of forming a printing layer on foamed paper material (foamed paper laminate before foaming) White inks (W1 to W9), indigo inks (B1 to B9), and clear inks (C1) prepared above. -C9) was used to form a print layer on the foam paper material as described below.

(Example 1)
As shown in Table 3, carbodilite SV-02 (manufactured by Nisshinbo Co., Ltd.) was used as a carbodiimide-based curing agent for 100 parts by mass of white ink (W1), indigo ink (B1), and clear ink (C1). ) Was added in an amount of 3 parts by mass to obtain a printing ink. The curing agent had a chemical formula amount of 430 and a solid content of 40% by mass per 1 mol of carbodiimide group.
Printing ink (W1), printing ink (B1), and printing on low-density polyethylene resin (L), which is a foam paper material, using a central impression (CI) type flexographic printing machine using anilox rolls and a resin plate. Overprinting was performed in the order of ink (C1) to form a print layer. The printing speed was 150 m / min.

(Examples 2 to 19 and Comparative Examples 1 to 4)
As shown in Table 3, in the embodiment in which the curing agent is added to the white ink, the indigo ink, and the clear ink, the curing agent is further added to obtain each printing ink. The amount of Carbodilite SV-02 (manufactured by Nisshinbo Holdings Inc.) added was 5.0 parts by mass in Example 3, 1.0 parts by mass in Example 12, 5.0 parts by mass in Example 13, and the others were carried out. As in Example 1, 3 parts by mass was used. In Example 11, Takenate WD-725 (manufactured by Mitsui Chemicals, Inc., aqueous isocyanate-based curing agent, solid content 50% by mass) was used as the curing agent, and the amount added was 3 parts by mass. Overprinting was performed in the same manner as in Example 1 except that the printing inks were used in combination as shown in Table 3, to form a printing layer.

(3) Production Example of Foam Paper Laminate The foam paper material (foam paper laminate before foaming) having a printing layer produced as described above is heat-treated under the following conditions to obtain a low-density polyethylene resin layer (a low-density polyethylene resin layer). L) was foamed to form a foamed layer to produce a foamed paper laminate (post-foam laminate). In Examples and Comparative Examples other than Examples 14 and 15 and Comparative Example 4, heat treatment was performed under standard conditions.
Standard conditions: Heat in an oven at 120 ° C for 6 minutes Example 14: Heat in an oven at 120 ° C for 9 minutes Example 15: Heat in an oven at 122 ° C for 6 minutes Comparative Example 4: Heat in an oven at 124 ° C for 6 minutes

<4> Evaluation of Foam Paper Laminates Various characteristics of the foam paper laminates of Examples 1 to 19 and Comparative Examples 1 to 4 produced as described above were evaluated according to the methods described below. The results of each are shown in Table 3.

<Foam followability>
On each surface of the foamed paper laminates of Examples 1 to 19 and Comparative Examples 1 to 4, the step between the white ink printing portion and the indigo ink printing portion after the heat treatment (after foaming of the low Mp film) was touched to indigo. The degree of dent in the ink printed portion was evaluated according to the following criteria. The higher the evaluation value, the better the foam followability and the flatter the printed surface.
(Evaluation criteria)
5: Almost no step with the white ink printing part is felt.
4: I feel a slight step with the white ink printing part.
3: I feel a considerable difference in level with the white ink printing part.
2: I feel that the step with the white ink printing part is quite large.
1: I feel that the step with the white ink printing part is very large.

<Foam appearance: Fire swelling>
With respect to the foam paper laminates of Examples 1 to 19 and the foam paper laminates of Comparative Examples 1 to 4, the printed surface of the foam paper laminate was visually observed. The evaluation criteria are as follows. The results shown in Table 3 are the most frequent values in the results of randomly preparing 10 samples of the foamed paper laminate and observing and evaluating each sample. When there are multiple modes, the value with the lower evaluation is adopted.
(Evaluation criteria)
5: No swelling (no swelling can be confirmed).
4: There is one swelling with a major axis of less than 5 mm ^{per 100 cm 2.}
^{3: There are two} swellings with a major axis of less than 5 mm per 100 cm 2.
2: There are 3 to 5 swells with a major axis of less than 5 mm ^{per 100 cm 2.} Alternatively, there is one swelling with a major axis of 5 to 20 mm ^{per 100 cm 2.}
1: There are 6 swells with a major axis of less than 5 mm ^{per 100 cm 2.} Alternatively, there are two or more swellings having a major axis of 5 to 20 mm ^{per 100 cm 2.} Alternatively, there is one or more swellings having a major axis of more than 20 mm ^{per 100 cm 2.}
If multiple swells with different major axes are mixed, a lower evaluation is adopted. Specifically, if there are ^two swellings with a major axis of less than 5 mm and one swelling with a major axis of 5 to 20 mm per 100 cm 2, the evaluation is "2".

<Foam appearance: cracks>
With respect to the foamed paper laminates of Examples 1 to 19 and Comparative Examples 1 to 4, the printed surface of the foamed paper laminate was visually observed in the same manner as in the evaluation of fire swelling. The evaluation criteria are as follows. The results shown in Table 3 are the most frequent values in the results of randomly preparing 10 samples of the foamed paper laminate and observing and evaluating each sample. When there are multiple modes, the value with the lower evaluation is adopted.
(Evaluation criteria)
5: No cracks (no cracks can be confirmed).
4: There is one crack with a length of less than 2 mm ^{per 100 cm 2.}
3: There are 2 to 4 cracks with a length of less than 2 mm ^{per 100 cm 2.}
2: There are 5 to 10 cracks with a length of less than 2 mm ^{per 100 cm 2.} Alternatively, there is one crack with a length of 2 to 5 mm ^{per 100 cm 2.}
1: There are 11 or more cracks with a length of less than 2 mm ^{per 100 cm 2.} Alternatively, there are two or more cracks having a length of 2 to 5 mm ^{per 100 cm 2.} Alternatively, there is one or more cracks having a length of more than 5 mm ^{per 100 cm 2.}
If a plurality of cracks having different lengths are mixed, a lower evaluation is adopted. Specifically, if there is one crack having a length of 1 mm and one crack having a length of 4 mm per ^{100 cm 2, the evaluation is “2”.}

<Ethanol resistance>
With respect to the foamed paper laminates of Examples 1 to 19 and Comparative Examples 1 to 4, 70% ethanol (ethanol: water = 70) was added to the friction element with respect to the surface of the printing layer (coating film) on the low melting point film foamed by heat treatment. : 30) The kanakin (JIS L 0803) containing the mixture was loaded and reciprocated once. When reciprocating in Kanakin, a load of 200 g was applied by a Gakushin tester (manufactured by Tester Sangyo Co., Ltd.). Then, the coating film was visually observed, the ratio of the area where the coating film (ink) was peeled off was calculated based on the total area of the coating film before the test, and the ethanol resistance was evaluated. The evaluation criteria are as follows.
(Evaluation criteria)
5: Ink peeling is less than 30%.
4: Ink peeling is 30% or more and less than 40%.
3: Ink peeling is 40% or more and less than 60%.
2: Ink peeling is 60% or more and less than 70%.
1: Ink peeling is 70% or more.

<Abrasion resistance>
For the foam paper laminates of Examples 1 to 19 and Comparative Examples 1 to 4, the white ink printed surface or the white ink and clear ink printed surfaces (coating film surface) of each laminate was used as a friction element. The coating film surface was reciprocated once with a load of 200 g using a Gakushin tester (manufactured by Tester Sangyo Co., Ltd.). The abrasion resistance was evaluated from the degree of color transfer of the indigo ink to the white ink printing surface.
(Evaluation criteria)
5: There is no color transfer of ink.
4: There is some ink color transfer (less than 1%).
3: There is color transfer of ink (1% or more and less than 10%).
2: There is considerable color transfer of the ink (10% or more, less than 30%).
1: There is a great deal of ink color transfer (30% or more).

<Insulation>
The heat resistance was evaluated by placing the foamed paper laminate on a hot plate heated to 90 ° C. with the foamed surface facing up and measuring the temperature of the foamed surface (non-contact surface) after 4 minutes. More specifically, the temperature of 10 samples of the foamed paper laminate after the heating process was measured as described above, and the average temperature of these was determined. From the obtained average temperature, the heat resistance was evaluated according to the following evaluation criteria.
(Evaluation criteria)
5: The temperature of the foamed surface is less than 80 ° C.
4: The temperature of the foamed surface is 80 ° C. or higher and lower than 82 ° C.
3: The temperature of the foamed surface is 82 ° C. or higher and lower than 84 ° C.
2: The temperature of the foamed surface is 84 ° C. or higher and lower than 88 ° C.
1: The temperature of the foamed surface is 88 ° C. or higher.

From the results shown in Examples and Comparative Examples as described above, the residual ratio of the printed layer after immersion in ethanol at 25 ° C. is 50% by mass or more, and the number of foamed cells in the foamed layer is 1,000 /. According to the foamed paper laminate having a size of 1 cm ² or more (Examples 1 to 19), it can be seen that excellent foamed appearance, abrasion resistance, heat resistance, and ethanol resistance can be realized. Further, as is clear from the comparison between Examples 1 to 19 and Comparative Example 1, it is preferable to contain at least a polyurethane resin as the binder resin in order to form the water-based ink composition for forming the printing layer. I understand. As seen in Comparative Example 1, when only the acrylic resin was used as the binder resin (without the polyurethane resin), the elongation rate and stress of the resin were lower than those when the polyurethane resin was used, and the foaming followability and foaming ability were improved. The foamed appearance is significantly reduced. Further, as is clear from the comparison between Examples 1 to 19 and Comparative Examples 2 and 3, excellent foam followability and foam appearance can be realized by adjusting the weight average molecular weight and other configurations of the polyurethane resin. At the same time, it can be seen that the ethanol resistance and abrasion resistance of the printed layer can be improved.

From the above description, it is clear that a wide variety of different embodiments can be constructed without violating the spirit and scope of the invention, and the invention is a particular embodiment thereof, except as limited by the claims. Not constrained by.

(Explanation of code)
10 Foamed paper laminate (container body member)
10A Foamed paper container 10a Outer wall surface of container 10b Inner wall surface of container 12 Bottom plate member 12
20 High Mp resin film (thermoplastic resin layer (A))
30 Paper base material 40 Low Mp resin film after foaming (foamed thermoplastic resin layer (B), foamed layer (B))
50 print layer 50a base layer 50b print pattern

Claims

A foamed paper having a thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer (B) in that order, and a printing layer formed on the surface of the foamed thermoplastic resin layer (B) of the foamed paper. It is a foamed paper laminate having
The number of foamed cells per unit area of the foamed thermoplastic resin layer (B) is 1000 cells / cm 2 or more.
The printed layer is a foamed paper laminate containing a binder resin containing a polyurethane resin and having a residual ratio of the printed layer of 50% by mass or more after being immersed in ethanol at 25 ° C. for 30 minutes.
The foamed paper laminate according to claim 1, wherein the binder resin has a stress of 0.1 mPa to 50 mPa at an elongation rate of 50 to 4,000%.
The foamed paper laminate according to claim 1 or 2, wherein the binder resin has a glass transition temperature of -100 to 0 ° C.
The foamed paper laminate according to any one of claims 1 to 3, wherein the print layer has a film thickness of 0.5 to 5.0 μm.
Claims 1 to 4 wherein the printing layer contains a cured product formed from a binder resin containing a polyurethane resin having an acid value of 1 to 100 mgKOH / g and at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent. The foamed paper laminate according to any one of the above items.
The foamed paper laminate according to any one of claims 1 to 5, wherein the printing layer has a plurality of layers and the outermost layer is a transparent layer.
The foamed paper laminate according to any one of claims 1 to 6, wherein the foamed thermoplastic resin layer (B) has a thickness of 500 to 950 μm.
A foam paper container comprising the foam paper laminate according to any one of claims 1 to 7.
A foamed paper having a thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer (B) in that order, and a printing layer formed on the surface of the foamed thermoplastic resin layer (B) of the foamed paper. The number of foamed cells per unit area of the foamed thermoplastic resin layer (B) is 1000 cells / cm 2 or more, and the residual rate of the printed layer after being immersed in ethanol at 25 ° C. for 30 minutes is A method for producing a foamed paper laminate, which is 50% by mass or more.
The thermoplastic resin layer (A), the paper base material, and the foamed thermoplastic resin layer forming layer (B 0 ) having a melting point lower than that of the thermoplastic resin layer (A) and foaming by heating are sequentially provided. , Preparing foam paper material,
Preparing a water-based ink composition containing a binder resin containing a polyurethane resin and water,
Applying the water-based ink composition to the surface of the foamed thermoplastic resin layer forming layer (B 0) of the foamed paper material to form a printing layer.
By heating the foamed paper material having the printed layer, the foamed thermoplastic resin layer forming layer (B 0 ) of the foamed paper material is foamed to form the foamed thermoplastic resin layer (B). , A method for manufacturing a foamed paper laminate.
As the water-based ink composition, a water-based ink composition containing a binder resin containing a polyurethane resin having an acid value of 1 to 100 mgKOH / g, water, and at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent is prepared. The method for producing a foamed paper laminate according to claim 9.
The method for producing a foamed paper laminate according to claim 9 or 10, wherein the printing layer has a plurality of layers and the outermost layer is a transparent layer.
The method for producing a foamed paper laminate according to any one of claims 9 to 11, wherein the foamed thermoplastic resin layer forming layer (B 0) has a thickness of 40 to 150 μm.