JP7418220B2 - Foamed paper laminate and its manufacturing method, foamed paper container - Google Patents

Description

Embodiments of the present invention relate to a foamed paper laminate and a method for manufacturing the same. Further, another embodiment of the present invention relates to a foam paper container including the foam paper laminate described above.

Foam containers have excellent heat insulation properties and are therefore widely used as containers for storing foods containing high-temperature or low-temperature liquids. In particular, foam containers are essential for products commonly called "cup noodles," which can be eaten within a few minutes by simply pouring an appropriate amount of boiling water over instant noodles such as ramen, udon, and soba stored in a container. I can't. Foamed polystyrene containers and foamed paper containers are known as foamed containers for cup noodles, but in recent years, foamed paper containers have attracted attention from the viewpoint of environmental impact and safety.

Foamed paper containers are manufactured using a foamed paper material having a paper base material and a thermoplastic resin layer that is foamed by heating during container manufacturing to form a heat insulating layer. Usually, a printed layer containing a printed pattern such as a decorative pattern, a company name, a bar code, etc. is formed on the surface of a foamed paper container (foamed paper material). Therefore, when the thermoplastic resin layer of the foamed paper material is foamed by heating to form a heat insulating layer, the printed layer desirably has excellent foaming followability without hindering foaming. Further, it is desirable that the surface (printed surface) of the printed layer after the thermoplastic resin layer is foamed is smooth, free of cracks and blisters, and has an excellent appearance. Furthermore, it is desirable that the printed surface be excellent in various resistances such as abrasion resistance and heat resistance that are required during container manufacturing.

Conventionally, oil-based inks such as oil-based gravure inks and oil-based flexo inks have been used to form printing layers on foamed paper containers. Oil-based inks usually contain an organic solvent such as toluene from the viewpoint of solubility and drying properties of the binder resin. However, in recent years, regulations on the use of organic solvents have become stricter from the viewpoint of environmental impact and occupational safety and health, and therefore the demand for water-based inks has increased. Therefore, in the field of food containers used for cup noodles and the like, progress is being made in the development of foam paper laminates that have a printed layer formed using water-based ink and can be suitably used as a material for foam paper containers. ing.

For example, Patent Document 1 discloses a water-based flexographic ink for foamed cups that contains a binder resin, a pigment, and water as an ink forming a printing layer of a foamed paper laminate, and the binder resin contains a polyurethane resin. . Moreover, Patent Document 2 discloses that foaming of a foaming layer is suppressed within a predetermined range by a coating portion (printed layer) of water-based ink. The water-based ink disclosed in Patent Document 2 includes 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 more and 30°C or less 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.

JP2018-058955A International Publication No. 2018/066031 JP2011-068381A

The heat insulation properties of a foam paper container mainly depend on the foamability of the thermoplastic resin layer that constitutes the foam layer (insulation layer) in the foam paper laminate. However, as the foamability of the thermoplastic resin layer increases during heat processing, poor appearance such as cracking and blistering becomes more likely to occur on the surface of the printed layer formed on the thermoplastic resin layer. Therefore, it is desirable that the printing layer be able to uniformly suppress foaming so as not to impede foaming of the thermoplastic resin layer and, on the other hand, to prevent appearance defects such as cracking and blistering.

However, in contrast to the conventional oil-based ink used to form the printing layer of foam paper laminates, when water-based ink is used, it is difficult to achieve the desired foam followability, abrasion resistance, and heat resistance in the printing layer. It is difficult to obtain the desired properties, and the quality of the foamed paper laminate tends to deteriorate. In addition, it is difficult to uniformly suppress foaming of the thermoplastic resin layer by the printed layer. Therefore, defects in the appearance of the printed surface after foaming the thermoplastic resin layer (hereinafter referred to as foamed appearance), such as cracking and blistering, are likely to occur. Furthermore, in the food field, since solvents such as ethanol are commonly used for disinfection, chemical resistance such as ethanol resistance of the printed layer is also required.

However, since the printed layer formed using water-based ink is usually highly hydrophilic, it is difficult to obtain excellent ethanol resistance. To provide a foamed paper laminate that can sufficiently satisfy various characteristics required in the food container industry, even when a printing layer is formed using the water-based ink disclosed in Patent Documents 1 to 3, for example. is difficult, and further improvements are desired.

Therefore, in view of the above-mentioned situation, an embodiment of the present invention is a foamed paper laminate having a printed layer formed using water-based ink, wherein the printed layer prevents foaming of the thermoplastic resin layer during heat processing. To provide a foamed paper laminate which has excellent foaming followability without any problem, and the surface of a printed layer has an excellent foamed appearance, abrasion resistance, heat resistance, and ethanol resistance, and a method for producing the same.

In order to solve the above-mentioned problem, the present inventors conducted intensive studies on the relationship between the foamability of the thermoplastic resin layer during heat processing and the foaming suppressing power of the printed layer. As a result, by forming a printing layer using a water-based ink composition containing a specific binder resin, it is possible to improve the foamability of the thermoplastic resin layer and the print surface's properties such as foamed appearance, abrasion resistance, heat resistance, and ethanol resistance. The present inventors have discovered that good results can be obtained in terms of the characteristics, and have completed the present invention. That is, the present invention relates to the following embodiments, but includes various embodiments without being limited to these.

One embodiment includes a foamed paper having a thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer (B) in this order, and a foamed thermoplastic resin layer (B) formed on the surface of the foamed paper. A foam paper laminate having a printed layer,
The number of foamed cells per unit area of the foamed thermoplastic resin layer (B) is 1000 cells/1cm ² or more,
The printed layer includes a binder resin containing a polyurethane resin, and the printed layer has a residual rate 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 printed layer preferably has a thickness of 0.5 to 5.0 μm.

In the foamed paper laminate, the printing layer comprises 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 curing agent and an isocyanate curing agent. It is preferable to include.

In the foamed paper laminate, the printed layer preferably has a plurality of layers, and the outermost layer is preferably a transparent layer.

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

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

One embodiment includes a foamed paper having a thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer (B) in this order, and a foamed thermoplastic resin layer (B) formed on the surface of the foamed paper. The foamed thermoplastic resin layer (B) has a printed layer with a foamed cell count of 1000 cells/ ^1cm2 or more per unit area, and the printed layer is immersed in ethanol at 25°C for 30 minutes. A method for producing a foamed paper laminate, wherein the residual rate of the layer is 50% by mass or more,
A thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer forming layer (B ₀ ) that has a lower melting point than the thermoplastic resin layer (A) and foams when heated, sequentially. , 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;
The foamed thermoplastic resin layer forming layer (B ₀ ) of the foamed paper material is foamed by heating the foamed paper material having the printed layer to form a foamed thermoplastic resin layer (B). , relates to a method for producing a foamed paper laminate.

In the above manufacturing method, the aqueous ink composition includes 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 curing agent and an isocyanate curing agent. Preferably, a composition is provided.

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

In the above manufacturing method, the thickness of the foamed thermoplastic resin layer forming layer (B ₀ ) is preferably 40 to 150 μm.

According to the present invention, a foamed paper laminate having a printed layer has excellent foaming followability without hindering foaming of the thermoplastic resin layer during heat processing, and has excellent foamed appearance, abrasion resistance, heat resistance, and ethanol resistance. and a method for producing the same. Further, according to the present invention, it is possible to provide a foam paper container comprising the foam paper laminate described above.

FIG. 1 is a perspective view showing an example of the structure of a foam paper container including a foam paper laminate according to an embodiment. FIG. 2 is a schematic cross-sectional view showing an enlarged part of the foam paper container shown in FIG. 1 (reference numeral I section).

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

<1> Foamed paper laminate One embodiment relates to a foamed paper laminate. The foamed paper laminate includes a foamed paper having a thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer (B) in this order, and a foamed paper having a foamed thermoplastic resin layer (B) on the surface of the foamed thermoplastic resin layer (B) of the foamed paper. The foamed thermoplastic resin layer (B) has a foamed cell count of 1000 cells/ ^1cm2 or more per unit surface area, and the printed layer has a binder resin containing a polyurethane resin. and the residual rate of the printed layer after being immersed in ethanol at 25° C. for 30 minutes is 50% by mass or more.

Regarding 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 present in the foamed layer (B); This means that the bubbles present in the foam layer (B) are large. When the bubbles present in the foam layer (B) become larger, poor appearance such as cracking and blistering on the printed surface is likely to occur.

In one embodiment, the number of foam cells per unit surface area of the foam 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 within the above range, it is possible to easily obtain an excellent foamed appearance without cracking or blistering 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, from the viewpoint of manufacturing conditions and the like, the number of foamed cells may be 1600 cells/1 cm ² or less.

Here, "the number of foamed cells per unit area" refers to the closed cells (bubbles) that exist within a range defined by a certain length in the vertical and horizontal (XY) directions on the surface of the foamed layer (B). It means the value calculated as the number of independent cells per 1 cm ² by counting the number of cells. The number of closed cells is determined by removing the printed layer of the foam paper laminate with a solvent to expose the surface of the foam layer (B), and then observing the surface of the foam layer (B) using an optical microscope. Ru.

The thickness of the foam layer (B) is preferably 500 μm or more, more preferably 630 μm or more, from the viewpoint of heat insulation. If the foam layer (B) has a thickness of 500 μm or more, even if the foam paper laminate is formed into a cup-shaped container and hot water of about 100°C is poured into the container, the container can be continuously opened with bare hands. This makes it easy to hold. On the other hand, from the viewpoint of resource saving, it is preferable that the amount of resin used be as small as possible. In addition, from the viewpoint of heat insulation properties, it is not necessary to have a thickness that would result in excessive quality as a heat insulation layer. Therefore, the thickness of the foam layer (B) is preferably 950 μm or less, more preferably 900 μm or less, and extremely preferably 800 μm.

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 foam layer (B) is determined by observing a cross section of the foam paper laminate using an optical microscope and measuring the height from the top surface of the paper base to the bottom surface of the printing layer.

In the foamed paper laminate of the above embodiment, the foamed layer (B) of the foamed paper means the 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 )) serving as a precursor. In one embodiment, the foamed paper laminate includes a thermoplastic resin layer (A), a paper base material, which has a melting point lower than that of the thermoplastic resin layer (A), and which 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. Foamed paper materials can be constructed from materials known in the art. Hereinafter, the constituent materials of the foam paper laminate will be specifically explained.

(Paper base material)
The paper base material constituting the foamed paper laminate is not particularly limited. For example, kraft paper or high quality 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 , more preferably 250 to 400 g/m ² . Further, from the viewpoint of obtaining suitable foamability of thermoplastic resin such as polyethylene, the water content 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 foamed layer-forming layer (B ₀ )) are each conventionally well-known container materials. It may be a film made of a resin material. For example, it is possible to use a film (thermoplastic resin film) made of at least one thermoplastic resin selected from the group consisting of polyethylene, stretched and unstretched polyolefins such as polypropylene, polyester, nylon, cellophane, and vinylon. can. In one embodiment, polyethylene film can be preferably used because it has excellent lamination suitability and foamability.

The foamed paper material can be constructed by laminating thermoplastic resin films having different melting points to a paper base material. Here, the melting point of the thermoplastic resin film provided on the other side of the paper base material as the foamed layer forming layer (B ₀ ) is higher than that of the thermoplastic resin film provided on one side of the paper base material as the thermoplastic resin layer (A). Materials are selected so that (Mp) is low. In foamed paper materials, water in the paper base material evaporates during heat treatment, and the evaporated water is extruded to the softened foamed layer forming layer (B ₀ ) (low Mp resin film) side. As a result of such extrusion, the low Mp resin film swells (foams) outward, forming a foam layer (B). The foam 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 is selected that does not melt or soften when the low Mp resin film is foamed by heat treatment.

From the point of view of manufacturing foam paper containers using foam paper laminates, 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 side of the paper substrate (inside the container). (thermoplastic resin layer (A)), and a low Mp polyethylene film (foamed layer forming layer (B ₀ )) having a melting point of about 105°C to 120°C on the other side (outside of the container) of the paper base material. It may have a laminated structure. The low Mp polyethylene film foams to form a foam layer by heating during the manufacture of foam paper containers. On the other hand, the high Mp polyethylene film preferably functions as a covering layer. That is, the coating layer can suppress moisture in the paper base material from evaporating to the outside during foaming of the low Mp polyethylene film, and can make the moisture in the paper base material efficiently contribute to foaming.

In one embodiment, the material of the foamed layer forming layer (B ₀ ) preferably includes a low-density polyethylene resin (density 910-925 kg/m ³ , melting point 105-120° C.) among polyethylene resins. The density of the low density polyethylene resin is more preferably 910 to 922 kg/m ³ , even more preferably 910 to 918 kg/m ³ . As materials for the foam layer forming layer (B ₀ ), medium density polyethylene resin (density 925 to 940 kg/m ³ , melting point 115 to 130°C) and high density polyethylene resin (density 940 to 970 kg/m ³ , melting point 125 to 140°C) are used. ℃), the melting point is high and it tends to be difficult to obtain sufficient foamability. In addition, from the viewpoint of obtaining a uniformly foamed layer, the melt flow rate (hereinafter referred to as "MFR") of the polyethylene resin 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 thickness of the foamed layer forming layer (B ₀ ) is preferably 40 μm or more, more preferably 60 μm or more. By adjusting the film thickness to 40 μm or more, sufficient heat insulation properties can be obtained after heat treatment.

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

(Printing layer)
In the foamed paper laminate of the above embodiment, the printed 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 printing layer is a binder resin in the aqueous ink composition, and the binder resin preferably contains at least a polyurethane resin.

Since the printing layer contains at least a polyurethane resin as a binder resin, when the foamed layer forming layer (B ₀ ) foams by heating to form the foamed layer (B), excellent foaming followability is achieved without hindering foaming. can be easily obtained. Moreover, the foamability of the foamed layer forming layer (B ₀ ) can be appropriately suppressed, and the number of foamed cells per unit surface area of the foamed layer (B) described above can be easily obtained. For these reasons, by using a polyurethane resin, an excellent foamed appearance can be obtained, and furthermore, 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 foaming suppressing ability of the printed layer and abrasion resistance. The thickness of the printed 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 rate of 50% by mass or more after being immersed in 25° C. ethanol for 30 minutes. If the residual rate of the printing layer is 50% by mass or more, even when ethanol is used for disinfection and cleaning in the manufacturing process of food containers, problems such as printing becoming unclear can be suppressed, The printed layer can be maintained well. Considering the use in food containers, the residual rate of the printed layer after immersion in 25°C ethanol for 30 minutes is more preferably 60% by mass or more, and even more preferably 70% by mass or more. .

The print layer survival rate described herein does not require strict adjustment of the ethanol immersion conditions. That is, conditions such as temperature and immersion time may be changed to some extent. For example, "immersed for 30 minutes" means that the printed layer only needs to 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, and by post-treatment. For example, a stirring step may be provided as the operation before and after immersion. The stirring conditions are preferably 50 to 150 rpm.

Generally, when constituting a water-based ink composition, it is preferable to increase the hydrophilicity of the binder resin from the viewpoint of printability. However, increasing the hydrophilicity of the binder resin tends to reduce the ethanol resistance of the printed layer. 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 foamability, foaming suppression ability, abrasion resistance, and heat resistance, as described above, It becomes possible to achieve desired ethanol resistance. Hereinafter, specific embodiments of a water-based ink composition containing a polyurethane resin as a binder resin will be described.

<2> Water-based ink composition One embodiment relates to a water-based ink composition that can be suitably used to form the printing layer of the foamed paper laminate of the above embodiment. The aqueous ink composition contains a binder resin and water, and may further contain a colorant such as a pigment. In addition to the above components, the aqueous ink composition may further contain various additives, if necessary. The structure of the water-based ink composition will be explained below.

(binder resin)
During the heating process to form the foamed layer (B), the printed layer preferably does not inhibit foaming of the foamed layer forming layer (B ₀ ) and has excellent foaming followability. On the other hand, in order to suppress foaming appearance defects such as cracks and blisters on the printed surface, it is preferable that the foaming of the foamed layer forming layer (B ₀ ) can be appropriately controlled by the printed layer. On the other hand, the binder resin is the main component of the printing layer (coating film), so by selecting an appropriate binder resin, the foaming followability and foaming suppressing power of the printing layer can be adjusted well. .

In one embodiment, the binder resin in the aqueous ink composition forming the printing layer preferably has an elongation rate of 50 to 4,000% from the viewpoint of foaming followability. On the other hand, even if the elongation rate of the binder resin is 50 to 4,000%, if the stress is too small, the printed layer will follow the foaming, but the foaming will not be properly controlled, causing cracks and blisters. The appearance of foam tends to deteriorate. Therefore, from the viewpoint of achieving both foam followability and a foamed appearance on the printed surface, it is preferable that the binder resin has an elongation rate of 50 to 4,000% and a stress of 0.1 mPa or more.

In addition, the term "elongation rate" described in this 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, at a tensile rate of 100 mm/min, and at a room temperature of 25 mm. Means the value obtained when measured at °C.

In one embodiment, the stress of the binder resin at an elongation rate of 50 to 4,000% is preferably 0.1 mPa or more, more preferably 1 mPa or more, and even more preferably 5 mPa or more. 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 the binder resin of 50 to 4,000% may be 0.1 mPa to 50 mPa.

When the binder resin has an elongation rate and stress within the above ranges, it is easy to obtain good results not only in foam followability but also in foam appearance. Further, a binder resin having an elongation rate and stress within the above range is preferable from the viewpoint of improving ethanol resistance since 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 less, and still more preferably -25°C or less. 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 in heat insulation properties can be suppressed. In addition, it is possible to suppress appearance defects caused by foaming, such as cracks and blistering on the printed surface. 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 within the above range is preferable from the viewpoint of ethanol resistance since it is easy to obtain a desired residual rate of the printed layer.

As mentioned above, the binder resin preferably contains at least a polyurethane resin from the viewpoint of the foaming followability of the printed layer during foaming. When polyurethane resin is used, it has excellent resistance such as light resistance, heat resistance, abrasion resistance, and blocking resistance, and is also highly resistant to the low Mp resin film (foamed layer forming layer (B ₀ )) that serves as the base material during printing. A water-based ink composition that can form a printed layer with excellent adhesiveness can be easily constructed. In addition, by using a polyurethane resin as a binder resin, even when the water-based ink composition is stored for a long time in an environment where heat or light is applied, the abrasion resistance and blocking resistance of the printing layer, and it becomes a base material. Good results can also be obtained in various properties such as adhesion to low Mp resin films.

As the binder resin, conventionally known resins can be used in addition to polyurethane resins. By using various resins having elongation, stress, and Tg within the above ranges, excellent printing characteristics can be easily obtained. Control of the elongation rate and stress of the binder resin can be achieved by combining various resins, controlling the molecular weight during resin synthesis, changing the Tg of the monomer, adjusting the crosslink density, etc. From this viewpoint, examples of resins other than polyurethane resins that can be used as binder 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 even more preferable that there be. In one embodiment, the binder resin may consist solely of polyurethane resin.

The term "polyurethane resin" as used herein refers to polyurethane resins in a broad sense, including common polyurethane resins conventionally used in the art or modified polyurethane resins such as polyurethane urea resins. Moreover, the polyurethane resin used in this specification is not particularly limited by its manufacturing method, and may be various polyurethane resins obtained by applying known or well-known methods related to polyurethane resins. Hereinafter, the polyurethane resin that can be suitably used as the binder resin will be explained in more detail.

(Polyurethane resin)
Although not particularly limited, a preferred embodiment of the polyurethane resin includes a polyurethane resin obtained by reacting at least a polyol and a polyisocyanate. Another embodiment is a polyurethane urea resin obtained by chain-extending a polyurethane resin prepolymer with an amine compound.

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. "Aqueous polyurethane resin" as described herein means that the polyurethane resin is soluble or readily dispersible in water or a water-soluble solvent. That is, in one embodiment, the polyurethane resin has an acid value (acidic functional group), and when the acidic functional group is neutralized or modified, it takes the form of either "water-soluble" or "emulsion". It is preferable to obtain. The acidic functional group may be a carboxyl group, a sulfonic acid group, etc., but a carboxyl group is preferable. Although not particularly limited, it is preferable that the polyurethane resin used as the binder resin is water-soluble.

On the other hand, when a water-based polyurethane resin is normally used to constitute a water-based ink composition, it tends to be difficult to obtain sufficient ethanol resistance in the printing layer when considering use in food containers. Therefore, from the viewpoint of imparting 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, there is a method of selecting a polyol having a structure that is difficult to dissolve in ethanol as the polyol that is the main component of the polyurethane resin. 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 greater 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, for example, by using a curing agent in combination.

Another example is a method of increasing the glass transition temperature (Tg) of polyurethane resin. The preferred range of Tg of the polyurethane resin may be -100°C to 0°C, as described above as the properties 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 example is a method of adjusting the hardness (elongation rate and stress) of the polyurethane resin. In conjunction with this, a method of adjusting the urethane bond concentration or urea bond concentration in the polyurethane resin may also be considered. Note that the preferable range of the elongation rate and stress of the polyurethane resin is, as described above as the properties of the binder resin, that the stress at an 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 2500%, more preferably 300 to 1500%, and even more preferably 300 to 1200%. . The stress is preferably 1 to 40 mPa, more preferably 3 to 30 mPa, even more preferably 5 to 25 mPa.

By using a polyurethane resin constructed by applying any one of the above-mentioned methods or a combination of multiple methods as a binder resin, the residual rate after immersion in ethanol at 25°C for 30 minutes is 50% by mass or more. It is possible to easily construct a printing layer that is .

The raw materials and manufacturing method of polyurethane resin will be explained below.
(polyol)
Various polyols can be used to make polyurethane resins. For example, various polyols shown below can be suitably used. The various polyols shown below may be used alone or in combination of two or more.
(1) Polyether polyols such as polymers or copolymers of ethylene oxide, propylene oxide, tetrahydrofuran, etc.;
(2) Ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl 1,3-propanediol, neopentyl glycol, pentanediol , 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 ether and 2-ethylhexyl glycidyl ether, monocarboxylic acid glycidyl esters such as versatile acid glycidyl ester, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, Polyester polyols obtained by dehydration condensation with dibasic acids such as oxalic acid, malonic acid, glutaric acid, pimelic acid, azelaic acid, sebacic acid, dimer acid, or anhydrides thereof;
(3) Other glycols obtained by adding polycarbonate diols, polybutadiene glycols, bisphenol A ethylene oxide or propylene oxide;
(4) Dimer diols.

In one embodiment, the polyurethane resin is preferably made from at least one polyol selected from polyether polyols, polyester polyols, and polycarbonate diols, and preferably has structural units derived from these raw materials. It is more preferable to use polyether polyol and/or 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 that is a condensate of a low molecular diol and a dibasic acid. The low molecular weight diol is preferably a branched diol. "Branched diol" means an alkylene glycol in which at least one hydrogen atom of the alkylene group is substituted with a group other than a hydrogen atom. The substituent is preferably an alkyl group having 1 to 10 carbon atoms.

In one embodiment, when a polyester polyurethane resin is constructed using the polyester polyol exemplified as (2) above, up to 5 mol% of the polyol blending amount can be replaced with other various polyols. Other various polyols include, for example, 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 the properties of the polyurethane resin obtained as a reaction product, such as ethanol resistance, drying properties, elongation rate, and stress. Although not particularly limited, the number average molecular weight of the polyol is preferably in the range of 500 to 10,000, more preferably in the range of 500 to 6,000.

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

Aromatic diisocyanates include 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzylisocyanate, dialkyldiphenylmethane diisocyanate, and tetraalkyl Examples include diphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, and tolylene diisocyanate.

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

Examples of alicyclic diisocyanates include cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, and norbornane diisocyanate. , m-tetramethylxylylene diisocyanate, hydrogenated 4,4-diphenylmethane diisocyanate, and dimer diisocyanate obtained by converting the carboxyl group of dimer acid into an isocyanate group.

Among the above polyisocyanates, at least one selected from the group consisting of tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, bis(isocyanatomethyl)cyclohexane, hexamethylene diisocyanate, and a trimer of hexamethylene diisocyanate is preferred. Polyisocyanates can be used alone or in combination of two or more.

(dihydroxy acid)
When a dihydroxy acid is used in addition to a polyol and a polyisocyanate in the production of a polyurethane resin, an acidic functional group (carboxyl group) derived from the dihydroxy acid is introduced, and a polyurethane resin having an acid value can be obtained. Polyurethane resins having an acid value can be easily converted into water-based resins, and therefore can be suitably used as water-based polyurethane resins for forming water-based ink compositions.

The dihydroxy acid may be a compound having two hydroxy groups and an acidic group in the molecule. Well-known carboxyl group-containing diol compounds can be suitably used. Examples 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 producing a polyurethane urea resin as the polyurethane resin, it is desirable that the molar equivalent ratio of isocyanate groups/hydroxyl groups be within the range of 1.2/1 to 3/1. In another embodiment, when producing a polyurethane resin that does not contain urea bonds, it is desirable that the molar equivalent ratio of isocyanate groups/hydroxyl groups be within the range of 0.5/1 to 0.98/1. When the raw materials are blended within the above molar equivalent ratio range, it becomes easy to control the elongation rate, stress, and ethanol resistance of the polyurethane resin. The polyurethanization reaction in the production of polyurethane resins is usually carried out at a reaction temperature in the range of 80°C to 200°C, preferably in the range of 90°C to 150°C.

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

In one embodiment, the polyurethane urea resin that can be suitably used is produced by reacting the polyol exemplified above with an organic diisocyanate to synthesize a polyurethane resin prepolymer having isocyanate groups at the terminals, and then reacting with a chain extender and reacting with the polyurethane resin. This resin is obtained by using an amine compound as a terminator and introducing a urea bond into the prepolymer of the polyurethane resin described above. Among polyurethane resins, when the above-mentioned polyurethane urea resin is used, various properties of the coating film (printed surface) formed using the water-based ink composition can be further improved.

(chain extender)
Examples of the chain extenders that can be used to introduce urea bonds include various known polyamines. Polyamine means a compound having multiple amino groups within 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, etc. diamines having a hydroxyl group in the molecule, and dimer diamines obtained by converting the carboxyl group of dimer acid into an amino group.

(reaction terminator)
A reaction terminator can also be used in conjunction with the polyamine. 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- Amines having a hydroxyl group such as 2-ethyl-1,3-propanediol, N-di-2-hydroxyethylethylenediamine, N-di-2-hydroxyethylpropylenediamine, N-di-2-hydroxypropylethylenediamine, and Examples 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 introducing a urea bond into a polyurethane resin prepolymer, the manufacturing method is not particularly limited. For example, if 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 should be within the range of 0.5 to 1.3. It is preferable to do so.

Solvents used in the production of polyurethane resins and polyurethane urea resins may be generally known compounds that can be used as solvents for inks forming printing layers. For example, alcohol solvents such as methanol, ethanol, isopropanol, n-propanol, and n-butanol; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester solvents such as ethyl acetate, propyl acetate, butyl acetate; methyl cyclohexane and 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 a chain extender, which prevents the reaction from proceeding smoothly. Therefore, in order to suppress the generation of ketimine and allow the reaction to proceed smoothly, it is desirable to use a small amount of water in combination. When using an organic solvent 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 to 100 mgKOH/g. The acid value is more preferably 10 to 70 mgKOH/g, 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 hydroxyl value are values measured by the method described in JIS K0070 (1992).

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

The aqueous polyurethane resin can be produced by applying conventionally known or well-known methods, and is not particularly limited. For example, reference can be made to the methods for producing aqueous polyurethane resins described in JP-A No. 2013-234214, JP-A No. 2013-249401, JP-A No. 2015-67818, and JP-A No. 2018-184512.

In one embodiment, when a water-based 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. more preferably from 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. Furthermore, in one embodiment, from the viewpoint of improving 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, 30,000 to 70, 000 is particularly preferred.

Although not particularly limited, in a preferred embodiment, the polyurethane resin used as the binder resin may be an aqueous polyurethane resin solution obtained as follows.
(1) First, poly(3-methyl-1,5-pentane adipate) diol, polyethylene glycol, and dimethylolbutanoic acid are mixed and stirred, and isophorone diisocyanate is added and reacted to form a terminal isocyanate precipitate. 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-based polyurethane resin solution to neutralize it, thereby forming an aqueous polyurethane resin solution. Furthermore, after the organic solvent in the aqueous polyurethane resin solution is distilled off 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, urethane resins (A) to (G) described later in Examples can be suitably used as the binder resin constituting the aqueous ink composition. The urethane resins (A) to (G) may be used alone, but it is more preferable to use two or more of them in combination because it facilitates adjustment of various properties. For example, when urethane resin (A) and urethane resin (B) are used together, 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 from 5 to 25% by mass, based on the total mass of the aqueous ink composition (solid content). When the amount of binder resin used is adjusted within the above range, it is possible to easily obtain a suitable ink viscosity, thereby increasing the work efficiency during ink production and printing.

(hardening agent)
In one embodiment, the aqueous ink composition preferably further includes 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 a cured coating film, but the form of the reaction is not particularly limited. That is, the printing layer may be a cured coating formed from a resin in a binder resin and a curing agent. Alternatively, the printed layer may be a cured coating 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 to 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 together, a printed layer with a residual rate of 50% or more after being immersed in ethanol at 25°C for 30 minutes is formed. Can be easily formed. Therefore, excellent ethanol resistance can be easily achieved in the printed layer. Further, according to an 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, the abrasion resistance and foamed appearance of the printed surface can be improved. Good results can also be obtained in various properties.

As curing agents for acid-valued polyurethane resins, compounds well known in the art can be used. Among these, it is preferable to use at least one selected from the group consisting of epoxy curing agents, carbodiimide curing agents, and isocyanate curing agents as the curing agent. In one embodiment, it is more preferable to use at least one of a carbodiimide curing agent and an isocyanate curing agent. It is more preferable to use at least a carbodiimide curing agent.

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

The carbodiimide curing agent may be any compound having a carbodiimide group in its molecule. Compounds having two or more carbodiimide groups in the molecule are preferred. Specific examples of carbodiimide curing agents include p-phenylene-bis(2,6-xylylcarbodiimide), tetramethylene-bis(t-butylcarbodiimide), and cyclohexane-1,4-bis(methylene-t-butylcarbodiimide). ). The carbodiimide 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 curing agent preferably has a chemical formula weight (NCN equivalent) per mol of carbodiimide group of 250 to 700, more preferably 300 to 600. Commercially available products can also be used as the carbodiimide 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. It will be done. One of these may be used alone or two or more may be used in combination.

The isocyanate curing agent may be any compound having an isocyanate group in its molecule. Compounds having two or more isocyanate groups in the molecule are preferred. The compound used as the isocyanate curing agent is preferably in a water-based state, that is, in a water-dispersed state or in a water-diluted state. Such water-based isocyanate curing agents can also be obtained as commercial products, such as Aquanate 100, Aquanate 110, Aquanate 200, and Aquanate 210 (all trade names, manufactured by Nippon Polyurethane Industries, Ltd.); Byhydur TPLS-2032, SUB-Isocyanate L801, Byhydur VPLS-2319, Byhydur 3100, VPLS-2336 and VPLS-2150/1 (all product names, manufactured by Sumika Bayer Urethane Co., Ltd.); Takenate WD-720, Takenate WD-725 and Takenate WD-220 (both trade names, manufactured by Mitsui Takeda Chemical Co., Ltd.); Rezamin D-56 (trade name, produced by Dainichiseika Chemical Industries, Ltd.), and the like. One of these may be used alone or two or more may be used in combination.

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

It is preferable that the amount of the curing agent is adjusted depending on the configuration of the printed layer. More specifically, in one embodiment, when the printing layer is formed as a single layer, the blending amount of the curing agent is preferably 100:2 to 100:100 in terms of binder resin: curing agent mass ratio, The ratio 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 multiple layers, the blending amount of the curing agent is preferably 100:1.5 to 100:100 in terms of binder resin:curing agent mass ratio in each layer, The ratio 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 rate of 50% or more after being immersed in 25° C. ethanol for 30 minutes. As a result, it is possible to easily achieve excellent foaming followability, as well as excellent foamed appearance on the printed surface, abrasion resistance, heat resistance, and ethanol resistance.

(colorant)
The colorant used in the aqueous ink composition may be any of the various inorganic and organic pigments commonly used in printing inks and paints. Examples of inorganic pigments include white pigments such as titanium oxide, colored pigments such as red iron, deep blue, ultramarine, carbon black, and graphite, and extender pigments such as calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, and talc. It will be done. 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 selected as appropriate in consideration of the desired color tone of the ink, but generally it is 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 preparing a white aqueous ink composition, the amount of white pigment blended is preferably in the range of 20 to 50% by mass based on the total mass of the aqueous ink composition. From the viewpoints of hiding power, pigment concentration, and light resistance, it is preferable to use titanium dioxide as the white pigment. On the other hand, when preparing a colored aqueous ink composition, colored organic pigments and colored inorganic pigments such as red iron, deep blue, ultramarine blue, carbon black, and graphite can be appropriately selected and used. From the viewpoint of color development and light resistance, organic pigments are preferred. The content of the colored pigment is preferably in the range of 10 to 30% by weight based on the total weight of the aqueous ink composition.

In addition to water, an organic solvent may be used as a solvent in the water-based ink composition within a range that does not adversely affect its effectiveness. When using an organic solvent, an alcohol-based organic solvent is preferred. Specific examples of organic solvents include ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, t-butanol, and 2-methyl-2-propanol. Can be mentioned. The use of these organic solvents is preferable in that the wettability to the substrate can be controlled in the aqueous ink composition. In one embodiment, the substrate may be a foam paper material. The aqueous ink composition is applied to the upper surface of the foamed layer forming layer (B ₀ ) of the foamed paper material to form a printed layer.

When the aqueous ink composition contains an organic solvent, the amount thereof is preferably 30% by mass or less, more preferably 20% by mass or less, and 10% by mass or less, based on the total mass of the aqueous ink composition. % or less is more preferable. In one embodiment, the content of organic solvent in the aqueous ink composition is most preferably 5% by mass or less, and the aqueous ink composition may be free of organic solvents.

(Other additives)
The aqueous ink composition may contain various additives as necessary. Suitable additives include antiblocking agents, various waxes, thickeners, rheology modifiers, antifoaming agents, leveling agents, preservatives, surface tension modifiers, adhesion aids, pH modifiers, and the like.

(adhesion aid)
The aqueous ink composition may further contain an adhesion auxiliary agent 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 compound and an epoxy compound as the adhesion aid.
As the hydrazine 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, cycloaliphatic epoxies such as Adeka Resin EP-4000, EP-4005, and 7001 manufactured by ADEKA may be mentioned.
These adhesion aids are preferably used in an amount of 0.1 to 5% by weight, more preferably 0.1 to 3% by weight, based on the total weight of the aqueous ink composition.

In one embodiment, when a white ink composition is constituted as an aqueous ink composition, a preferable composition is 10 to 50 mass % of white inorganic pigment, 5 to 35 mass % of polyurethane resin (solid content), based on the total mass of white ink. % by mass, and 5 to 30% by mass of water. A more preferable composition of the white ink composition is 20 to 50% by mass of white inorganic pigment, 5 to 30% by mass of polyurethane resin (solid content), and 5 to 25% by mass of water. In another embodiment, in addition to the composition of the white ink composition, it may further contain 0.5 to 15% by mass of a curing agent. The curing agent preferably contains at least one of a carbodiimide curing agent and an isocyanate curing agent.

In one embodiment, when constituting a color ink composition such as magenta, yellow, and cyan as an aqueous ink composition, the preferable composition is 10 to 25% by weight of organic pigment, polyurethane resin, based on the total weight of the color ink. (Solid content) 5 to 35% by mass, water 5 to 30% by mass. A more preferable composition of the color ink is 10 to 20% by weight of organic pigment, 5 to 30% by weight of polyurethane resin (solid content), and 5 to 25% by weight of water. In another embodiment, in addition to the above color ink composition, it may further contain 0.5 to 15% by mass of a curing agent. The curing agent preferably contains at least one of a carbodiimide curing agent and an isocyanate curing agent.

The aqueous ink composition that forms the printing layer can be manufactured by applying well-known techniques and mixing the various components described above. More specifically, first, a binder resin, water, and, if necessary, a pigment, a pigment dispersant, a surfactant, etc. are stirred and mixed, and then, for example, a bead mill, ball mill, sand mill, attritor, roll mill, or Examples include a method of kneading the meat using various kneading machines such as a pearl mill, and then adding and mixing the remaining ingredients.

<3> Method for manufacturing a foamed paper laminate One embodiment relates to a method for manufacturing a foamed laminate. That is, one embodiment includes a foamed paper having a thermoplastic resin layer (A), a paper base material, and a foamed layer (B) in this order, and a printed layer formed on the surface of the foamed layer (B) of the foamed paper. and the number of foamed cells per unit surface area of the foamed layer (B) is 1000 cells/ ^1cm2 or more, and the residual rate 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 manufacturing method includes the following steps (i) to (iv): (i) a thermoplastic resin layer (A), a paper base material, and a thermoplastic resin layer (A) having a melting point lower than that of the thermoplastic resin layer (A); preparing a foamed paper material which sequentially has a foamed layer-forming layer (B ₀ ) that foams upon heating;
(ii) preparing a water-based ink composition comprising 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) foaming the foamed layer forming layer (B ₀ ) of the foamed paper material by heating the foamed paper material having the printed layer to form a foamed layer (B);

In the above manufacturing method, each step regarding (i) preparation of foamed paper material, (ii) preparation of aqueous ink composition, (iii) formation of a printed layer, and (iv) formation of foamed layer (B) by heating is performed respectively. It can be carried out according to methods well known in the art. Each step will be explained below.

(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 lamination method. The constituent materials of the paper base material, thermoplastic resin layer (A), and foamed layer forming layer (B ₀ ) that constitute the foamed paper material are as described above. As the extrusion lamination method, well-known methods such as a single lamination method, a tandem lamination method, a sandwich lamination method, and a coextrusion lamination method can be appropriately selected. In one embodiment, polyethylene resins having different melting points can be preferably used as constituent materials of the thermoplastic resin layer (A) and the foamed layer forming layer (B ₀ ).

The foam layer forming layer (B ₀ ) is formed 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 produced by extruding a low Mp polyethylene resin into a film on one side of the paper substrate and extruding a high Mp polyethylene resin into a film on the other side of the paper substrate through a T-die extruder. It can be manufactured by

The temperature of the polyethylene resin during lamination (temperature directly below the T-die) is preferably 300 to 350°C, more preferably 320 to 340°C. Within this temperature range, sufficient lamination strength can be achieved between each polyethylene resin layer (A, B ₀ ) and the paper base material. The surface temperature of the cooling roll passed through after lamination is preferably controlled within the range of 10 to 50°C.

In one embodiment, the lamination speed is preferably between 50 and 130 m/min, more preferably between 60 and 110 m/min. If the laminating speed is too slow, productivity will be low, while if the laminating speed is too fast, the yield will tend to decrease due to neck-in. Neck-in is a phenomenon in which when polyethylene resin is extruded into a film using a T-die extruder, the width of the extruded polyethylene resin film becomes smaller than the effective width of the T-die. At this time, both ends of the film are thicker than the center. When the thickness of both ends deviates from the standard, it is common to cut and remove both ends, but if the neck-in is severe, the area outside the standard increases, resulting in a decrease in yield.

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 tends to neck in, resulting in a decrease in yield. The air gap refers to the distance from the extrusion port of the T-die to the nip roll. While the polyethylene resin is passing through the air gap, it is preferable to perform surface treatment on the polyethylene resin using ozone gas and/or oxygen gas. By performing 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 from the viewpoint of promoting oxidation of the polyethylene resin, it is preferably 0.5 mg/m ² or more.

(Step (ii): Preparation of water-based ink composition)
In the manufacturing method of the above embodiment, the specific structure and preparation method of the aqueous ink composition (ii) are as described above in the embodiment of the aqueous ink composition.
In one embodiment, as the aqueous ink composition, it is preferable to prepare an aqueous ink composition (ii-1) containing a binder resin containing an aqueous polyurethane resin and water. Here, the binder resin is preferably an aqueous polyurethane resin having an acid value, and more preferably is made aqueous 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, in place of the aqueous ink composition (ii-1), a binder resin containing an aqueous polyurethane resin having an acid value of 1 to 100 mgKOH/g, water, a carbodiimide-based curing agent, and a polyisocyanate-based curing agent is used. It is preferable to prepare an aqueous ink composition (ii-2) containing at least one of the above agents. Here, the polyurethane resin having an acid value of 1 to 100 mgKOH/g is preferably made water-based by neutralization.

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

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

(Flexo printing method)
(1) Anilox roll Anilox can be used in the flexographic printing method. For example, a ceramic anilox roll with cell engraving, a chrome plated anilox roll, etc. can be used.
In order to obtain a printing layer (printed material) with excellent dot reproducibility, an anilox roll having a line count of at least 5 times, preferably at least 6 times, the line count of the plate used during printing is used. For example, if the plate used has a line count of 75 lpi, an anilox with a line count of 375 lpi or more is required. Furthermore, if the plate has a line count of 150 lpi, an anilox roll with a line count of 750 lpi or more is required. The capacity of the anilox roll may be 1 to 8 cc/m ² , preferably 2 to 6 cc/m ² from the viewpoint of drying properties and blocking properties of the aqueous ink composition used.

(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 a plate, it is also possible to use an elastomer material plate using a direct laser engraving method. Regardless of the method of forming the image area of the flexo plate, a plate with a screening line count 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 flexo printing machines include CI type multicolor flexo printing machines and unit type multicolor flexo printing machines. Specific examples of ink supply methods include a chamber method and a two-roll method. A printing machine applicable to the flexo printing method can be appropriately selected and used.

In one embodiment, the printed layer preferably includes multiple layers. The printed layer may include a base layer that covers the entire surface of the foamed layer forming layer (B ₀ ) and a printed pattern provided on at least a portion of the surface of the base layer. For example, the base layer is composed of a white water-based ink composition, and the printed pattern is formed from a water-based color ink composition.

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

In other embodiments, the printed layer may include multiple layers, preferably having a transparent layer as its outermost layer. The transparent layer 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 abrasion resistance, ethanol resistance, and water abrasion resistance of the printed surface can be easily improved. In one embodiment, the thickness of the transparent layer (dry thickness) is preferably 0.1 to 3.0 μm, more preferably 0.1 to 2.5 μm, and even more preferably 0.1 to 2.0 μm. .0 μm. Here, when the printing layer has a transparent layer, it is preferable to adjust the thickness of the entire printing 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, it is preferable that the aqueous ink constituting at least one layer among the plurality of layers 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 use the above water-based ink composition to form the base layer (white) ink layer and the outermost layer (ink layer or transparent layer), and most preferably to form all of the plurality of layers.

(Step (iv): Formation of foam layer (B))
In the above (iv) formation of the foamed layer (B) by heating, the appropriate heating temperature and heating time vary depending on the paper base material used and the properties of the thermoplastic resin film. Those skilled in the art can determine the optimal combination of heating temperature and heating time depending on the material used, such as the thermoplastic resin film. Although not particularly limited, heat treatment is generally performed during the container forming process. If the heating temperature during the heat treatment is too low, sufficient foamability will not be obtained, and if the heating temperature is too high, the foamed cells will bond and blistering will likely occur.

Although not particularly limited, when the foam 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 adjusted as appropriate depending on the heating temperature, but is preferably 3 to 10 minutes, more preferably 5 to 7 minutes. In one embodiment, the foam layer-forming layer is composed of a low-density polyethylene film, and the printing layer is formed thereon 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 foaming of the foamed layer forming layer during heating processing by the printed layer.

As the heating means, any means such as hot air, electric heating, and electron beam can be used. By heating with hot air or electric heat in a tunnel equipped with a conveyor conveyance means, a large amount of heat treatment can be carried out at low cost.

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

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

Forming of a foamed paper container can be carried out by applying well-known techniques. For example, a foamed paper laminate on which a printing layer has been formed (a foamed paper laminate before heating) is punched into a predetermined shape along a die to obtain a container body member. Similarly, the bottom plate material is punched out 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 a container using a commonly used container manufacturing apparatus. When assembling and molding the container using the container manufacturing device, 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. Implemented. After assembling and molding the container using the container manufacturing device, the low Mp resin film is foamed by heat treatment to form a foam layer (insulating layer) and to obtain a foamed paper container with heat insulating properties. can.

In one embodiment, when the inner wall surface and outer wall surface of the body of the foam paper container are each made of polyethylene film, one surface of the paper base material (the inner wall surface of the container) is made of medium density or high density polyethylene film. It is preferable that the other surface (outer wall surface of the container) be laminated with a low-density polyethylene film. The thickness of each film laminated to the paper base material 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 when the film is foamed, the foamed film has a sufficient thickness to function as a heat insulating layer. It is preferable that

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

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

<1> Methods for measuring various properties Various properties of the binder resin and water-based ink composition described below represent values determined by the following measuring methods.

(Glass-transition temperature)
Each polyurethane resin aqueous solution obtained in the synthesis example described below was coated on a polyethylene base material, and then dried at 40° C. for 3 days to obtain a dry coating film with a thickness of 0.5 mm. For each dry coating film, the peak top temperature of the loss tangent tan δ was measured using an automatic dynamic viscoelasticity measuring machine (manufactured by A&D Co., Ltd., DDV-GP series (Rheovibron)) as Tg (°C) And so. The measurements were carried out at a temperature range of -120°C to 40°C and a heating rate of 10°C/min.

(Binder resin elongation rate and stress)
Each polyurethane resin aqueous solution obtained in the synthesis example described below was dried to prepare a coating film test sample (thickness: 0.30 mm, width: 5.0 mm, length: 20.0 mm). For each sample, elongation and stress were measured using a small tensile tester manufactured by Intesco. The measurements were carried out at a tensile rate of 100 mm/min and a room temperature of 25°C.
In addition, regarding the embodiment in which the water-based ink composition contains a curing agent, a binder resin and a curing agent are used together in the same proportion as in the water-based ink composition, and a coating film test sample (thickness 0.30 mm, width 5 .0 mm and length 20.0 mm). Using this sample, the elongation rate and stress of the binder resin (cured product) were measured according to the same method as above.

(Residual rate of printed layer)
The residual rate of the printed layer is a test for evaluating the ethanol resistance of the printed layer formed on the foamed paper (the surface of the foamed paper laminate), and was conducted as follows.
First, a foamed paper laminate was cut out to a size of 100 mm in length and 100 mm in width as a test piece (sample). The mass of the cut out test piece was measured and used as the sample mass before immersion in ethanol. Thereafter, for convenience of dipping work, the test piece was crushed into a size of approximately 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 to test piece was 100:4.5, and the test piece was immersed in ethanol. The immersion was carried out in ethanol at 25°C for 2 minutes while stirring the test piece at a stirring speed of 100 rpm, then allowed to stand for 30 minutes, and then for 1 minute while stirring the test piece at a speed of 100 rpm. did. The test piece was taken out, and the mass of the test piece after drying was measured, which was taken as the sample mass after immersion.
Furthermore, the residual rate of the printed layer was calculated from the sample mass before immersion and the sample mass after immersion, which were measured as described above, according to the following formula.
Remaining rate of printed layer = (sample mass after immersion/sample mass before immersion) x 100

(Thickness of printed layer)
The thickness of the printed layer was determined from a scanning electron microscope (SEM) photograph (magnification: 5000) of a cross section of the foam paper laminate. Measurements were made at five arbitrary locations on the printed layer, and the average value thereof was taken as the film thickness of the printed 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) (25x magnification), and independent cells existing within a range defined by a certain length in the vertical and horizontal (X-Y) directions were observed. The number of cells was determined, and a value calculated as the number of independent cells per 1 cm ² was obtained. Observations were made at five arbitrary locations, and the average value was taken as the number of foamed cells.

(Thickness of foam layer)
The thickness of the foam layer was determined by observing the cross section of the foam paper laminate using an optical microscope and measuring the height from the top surface of the paper base to the bottom surface of the printing layer. Moreover, the film thickness before foaming corresponds to the film thickness of the foam 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)
(Synthesis Example 1) Polyurethane resin (A)
Poly(3-methyl-1,5-pentane adipate) diol (PMPA2000, number 328.16 parts of polyethylene glycol (PEG2000, number average molecular weight 2,000), 57.81 parts of dimethylolbutanoic acid (DMBA), and 350 parts of methyl ethyl ketone (MEK) were added. . While mixing and stirring these, 200.76 parts of isophorone diisocyanate (IPDI) was further added dropwise over 1 hour. These were then reacted at reflux temperature for 6 hours to form a terminal isocyanate prepolymer. Thereafter, the reaction solution was cooled to 30° C., and 100 parts of isopropyl alcohol was added to obtain a solvent solution of the terminal isocyanate prepolymer.
A mixed solution of 28.21 parts of 2-aminoethylethanolamine (AEA) and 150 parts of isopropyl alcohol (IPA) was gradually added to the obtained terminal isocyanate prepolymer at room temperature (25°C), and the mixture was heated at 40°C. A solvent-type polyurethane resin solution was obtained by reacting for 3 hours.
Next, 23.69 parts of 28% ammonia water and 1800 parts of ion-exchanged water were gradually added to the above solvent-based polyurethane resin solution for neutralization, thereby obtaining a water-based polyurethane resin solution. Furthermore, after MEK and IPA in the aqueous polyurethane resin solution were distilled off under reduced pressure, water was added to adjust the solid content to 25%.
As described above, an aqueous solution (solid content 25%) of 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, stress, and other properties of the polyurethane resin (A) were measured. The results are shown in Table 1.

(Synthesis examples 2 to 8)
According to the synthesis method described in JP 2018-184512A, in the same manner as Synthesis Example 1, except that the raw materials and blending amounts described in Synthesis Example 1 were changed to have the characteristics described in Table 1. Aqueous solutions of polyurethane resins (B) to (H) each having a solid content of 25% were obtained (hereinafter sometimes abbreviated as polyurethane resins (B) to (H)). The elongation rate, stress, and other properties of the polyurethane resins (B) to (H) were measured according to the method explained to the measurement site, and the results are shown in Table 1.

<2> Production example of water-based ink composition (Production example 1) Production of white ink (W1) According to the formulation shown in Table 2, 10 parts of polyurethane resin (A) aqueous solution, 20 parts of polyurethane resin (B) aqueous solution, Stir and mix 40 parts of white pigment (titanium oxide, Titanix JR808 (manufactured by Teika Co., Ltd.), 0.1 part of antifoaming agent, 0.2 part of adipic acid dihydrazide (ADH), 1 part of N-propanol, and 5 parts of water. Then, to the mixture obtained by the dispersion treatment, 4 parts of the polyurethane resin (A) aqueous solution, 14 parts of the polyurethane resin (B) aqueous solution, and 6 parts of water were added, and the mixture was stirred. By mixing, white ink (W1) was obtained.

(Production Examples 2 to 9) Production of white inks (W2) to (W9) Everything is 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 formulations listed in Table 2. White inks (W2) to (W9) were obtained in the same manner as in the manufacturing method.
The binder resins listed 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 with a solid content of 25%).
Polyurethane resin I: Product name "Yuliano W321" manufactured by Arakawa Chemical Industry Co., Ltd. (aqueous solution of polyurethane resin with a resin elongation rate of 600% and a stress of 7.0 mPa).
Acrylic resin: Product name "Joncryl 7100" manufactured by BASF Corporation (weight average molecular weight 200,000, glass transition temperature -10°C, acid value 51 mgKOH/g, resin elongation rate 180%, stress 6. 5 mPa of acrylic resin emulsion).
Vinyl chloride resin: Product name “Vinibran 700” manufactured by Nissin Chemical Industry Co., Ltd. (emulsion of vinyl chloride resin with a glass transition temperature of 70° C. and an acid value of 57 mgKOH/g).

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

(Production Examples 11 to 18) Production of indigo inks (B2) to (B9) All procedures were performed in accordance with Production Example 10, except that the two types of polyurethane resin aqueous solutions described in Production Example 10 were changed to the formulations listed in Table 2. Indigo inks (B2) to (B9) were obtained in the same manner as the production method described above.

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

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

<3> Manufacturing example of foamed paper laminate (1) Manufacturing example of foamed paper material Foamed paper material is made by (Step 1) extrusion laminating medium density polyethylene resin (M) on one side of the paper base material to form a water vapor barrier layer. was formed, and then (Step 2) a low density polyethylene resin (L) was extrusion laminated on the other side (non-laminated side) of the paper base material.

Various conditions in Step 1 and Step 2 are as follows.
(Step 1)
Paper base material: moisture content 23 kg/m ³ , basis weight 320 kg/m ³
Medium density polyethylene resin (M): “Petrocene LW04-1” manufactured by Tosoh Corporation, MFR 4.3 g/10 minutes, density 940 kg/m ³
Extrusion temperature (T die exit temperature): 320℃
Take-up speed (laminate speed): 50m/min Air gap: 130mm
Thickness: 40μm (thickness at the center of the polyethylene resin layer)

(Step 2)
Low-density polyethylene resin (L); described later Extrusion temperature (T-die exit temperature): 310°C
Take-up speed (laminate speed): 60m/min Air gap: 130mm

Note that the low density polyethylene resin (L) used in the above step 2 becomes the foam layer forming layer (B ₀ ). As the low-density polyethylene resin (L), low-density polyethylene resin (L2) was used in Example 18, and low-density polyethylene resin (L1) was used in other cases to produce foamed paper materials. Details of the low density polyethylene resins (L1) and (L2) are as follows.
Low density polyethylene resin (L1): "Petrocene 07C03C" manufactured by Tosoh Corporation, density 918 kg/m ³ , melting point 106 ° C., MFR 15 g/10 minutes Low density polyethylene resin (L2): "Novatec LDLC720" manufactured by Japan Polyethylene Co., Ltd., density 922 kg/m 3 ^m3 , melting point 110°C, MFR9g/10min

(2) Production example of forming a printing layer on foam paper material (foam paper laminate before foaming) The white ink (W1 to W9), indigo ink (B1 to B9), and clear ink (C1) prepared previously -C9) were used to form printed layers on foamed paper materials as described below.

(Example 1)
As shown in Table 3, Carbodilite SV-02 (manufactured by Nisshinbo Co., Ltd.) was added as a carbodiimide curing agent to 100 parts by mass of white ink (W1), blue ink (B1), and clear ink (C1). ) was added to obtain a printing ink. The curing agent had a chemical formula weight of 430 per mol of carbodiimide group and a solid content of 40% by mass.
Printing ink (W1), printing ink (B1), and printing are applied onto low-density polyethylene resin (L), which is a foamed paper material, using a central impression (CI) type flexo printing machine, using an anilox roll and a resin plate. Overprinting was performed in the order of ink (C1) to form a printed layer. The printing speed was 150 m/min.

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

(3) Manufacturing example of foamed paper laminate The foamed paper material having the printed layer manufactured as described above (foamed paper laminate before foaming) was heat-treated under the following conditions, and the low-density polyethylene resin layer ( L) was foamed to form a foamed layer to produce a foamed paper laminate (post-foamed laminate). Note that in Examples and Comparative Examples other than Examples 14 and 15 and Comparative Example 4, the heat treatment was performed under standard conditions.
Standard conditions: Heated in an oven at 120°C for 6 minutes Example 14: Heated in an oven at 120°C for 9 minutes Example 15: Heated in an oven at 122°C for 6 minutes Comparative example 4: Heated in an oven at 124°C for 6 minutes

<4> Evaluation of foamed paper laminates Various properties of the foamed 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 are shown in Table 3.

<Foam followability>
For each surface of the foamed paper laminates of Examples 1 to 19 and Comparative Examples 1 to 4, touch the level difference between the white ink printed area and the indigo ink printed area after heat treatment (after foaming the low Mp film), and The degree of depression of the ink printed area was evaluated according to the following criteria. The higher the evaluation value, the better the foaming followability and the flatter the printed surface.
(Evaluation criteria)
5: Almost no difference in level from the white ink printed area is felt.
4: A slight difference in level from the white ink printed area is felt.
3: There is a noticeable difference in level from the white ink printed area.
2: The level difference with the white ink printed area is felt to be quite large.
1: The level difference with the white ink printed area is felt to be very large.

<Foam appearance: blistering>
Regarding the foamed paper laminates of Examples 1 to 19 and the foamed paper laminates of Comparative Examples 1 to 4, the printed surfaces of the foamed paper laminates were visually observed. The evaluation criteria are as follows. The results shown in Table 3 are the most frequent values obtained by randomly preparing 10 samples of foamed paper laminates and observing and evaluating each sample. If there were multiple mode values, the value with the lowest evaluation was adopted.
(Evaluation criteria)
5: There is no swelling at all (no swelling can be confirmed).
4: There is one blister with a major axis of less than 5 mm per 100 ^cm2 .
3: There are 2 blisters with a major axis of less than 5 mm per 100 ^cm2 .
2: There are 3 to 5 blisters with a major axis of less than 5 mm per 100 ^cm2 . Or, there is one bulge with a major axis of 5 to 20 mm per 100 ^cm2 .
1: There are 6 blisters with a major axis of less than 5 mm per 100 ^cm2 . Or, there are two or more bulges with a major axis of 5 to 20 mm per 100 ^cm2 . Or, there is one or more bulges with a major diameter exceeding 20 mm per 100 ^cm2 .
In addition, if multiple bulges with different major axes are present, a lower evaluation will be adopted. Specifically, if there are two blisters with a major axis of less than 5 mm and one blister with a major axis of 5 to 20 mm per 100 cm ² , the evaluation will be "2".

<Foam appearance: cracks>
Regarding the foamed paper laminates of Examples 1 to 19 and Comparative Examples 1 to 4, the printed surfaces of the foamed paper laminates were visually observed in the same manner as the blistering evaluation. The evaluation criteria are as follows. The results shown in Table 3 are the most frequent values obtained by randomly preparing 10 samples of foamed paper laminates and observing and evaluating each sample. If there were multiple mode values, the value with the lowest evaluation was adopted.
(Evaluation criteria)
5: No cracks at all (cracks cannot be confirmed).
4: One crack with a length of less than 2 mm exists per 100 ^cm2 .
3: There are 2 to 4 cracks with a length of less than 2 mm per 100 ^cm2 .
2: There are 5 to 10 cracks with a length of less than 2 mm per 100 ^cm2 . Or, there is one crack with a length of 2 to 5 mm per 100 ^cm2 .
1: There are 11 or more cracks with a length of less than 2 mm per 100 ^cm2 . Or, there are two or more cracks with a length of 2 to 5 mm per 100 ^cm2 . Or, there is one or more cracks with a length exceeding 5 mm per 100 ^cm2 .
Note that if there are multiple cracks of different lengths, a lower evaluation will be adopted. Specifically, if there is one crack with a length of 1 mm and one crack with a length of 4 mm per 100 cm ² , the evaluation will be "2".

<Ethanol resistance>
Regarding the foam paper laminates of Examples 1 to 19 and Comparative Examples 1 to 4, 70% ethanol (ethanol:water = 70 :30)) was applied back and forth once while applying a load. When traveling back and forth between Kanakin, a load of 200 g was applied using a Gakushin testing machine (manufactured by Tester Sangyo Co., Ltd.). Thereafter, the coating film was visually observed, and 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: Peeling of ink is 70% or more.

<Abrasion resistance>
For the foamed 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 surface (coated film surface) of each laminate was used as a friction element. Using a Gakushin testing machine (manufactured by Tester Sangyo Co., Ltd.), the coating surface was made to reciprocate once under a load of 200 g. Abrasion resistance was evaluated based on the degree of color transfer of the indigo ink to the white ink printed surface.
(Evaluation criteria)
5: No ink color transfer.
4: There is some color transfer of the ink. (less than 1%)
3: There is color transfer of ink. (1% or more, less than 10%)
2: There is considerable color transfer of ink. (10% or more, less than 30%)
1: There is a lot of ink color transfer. (30% or more)

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

As mentioned above, from the results shown in Examples and Comparative Examples, the residual rate 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 cells/ It can be seen that the foamed paper laminates (Examples 1 to 19) having a size of 1 cm ² or more can achieve excellent foamed appearance, abrasion resistance, heat resistance, and ethanol resistance. Further, as is clear from the comparison between Examples 1 to 19 and Comparative Example 1, it is preferable that at least a polyurethane resin is included as a binder resin in order to constitute the aqueous ink composition for forming the above-mentioned printing layer. I understand. As seen in Comparative Example 1, when only acrylic resin is used as the binder resin (does not contain polyurethane resin), the elongation rate and stress of the resin are lower than when polyurethane resin is used, and the foaming followability and The appearance of the foam is significantly reduced. Furthermore, 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 achieved by adjusting the weight average molecular weight and other compositions of the polyurethane resin. It is also found that the ethanol resistance and abrasion resistance of the printed layer can be improved.

From the foregoing description, it is clear that widely different embodiments may be constructed without departing from the spirit and scope of the invention, and the invention is not limited to the specific embodiments thereof, except as limited in the scope of the claims. It is not restricted by.

(Explanation of symbols)
10 Foam paper laminate (container body member)
10A Foam paper container 10a Outer wall surface of the container 10b Inner wall surface of the 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 Printing layer 50a Base layer 50b Printing pattern

Claims (10)

A foamed paper having a thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer (B) in this order; and a printed layer formed on the surface of the foamed thermoplastic resin layer (B) of the foamed paper. A foam paper laminate having:
The number of foamed cells per unit area of the foamed thermoplastic resin layer (B) is 1000 cells/1 cm ² or more,
The printing layer includes 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 curing agent and an isocyanate curing agent, and ethanol at 25°C. A foamed paper laminate having a residual rate of a printed layer of 50% by mass or more after being immersed in a foamed paper 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 printed layer has a thickness of 0.5 to 5.0 μm. The foam paper laminate according to any one of claims 1 to 4, 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 5, 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 6. A foamed paper having a thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer (B) in this order; and a printed 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/ ^1cm2 or more, and the residual rate of the printed layer after being immersed in ethanol at 25°C for 30 minutes is 50% by mass or more, a method for producing a foamed paper laminate,
A thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer-forming layer (B ₀ ) that has a lower melting point than the thermoplastic resin layer (A) and foams when heated. , preparing foam paper material;
preparing a water-based ink composition containing a binder resin containing a polyurethane resin having an acid value of 1 to 100 mg KOH/g, water, and at least one of a carbodiimide-based hardener and an isocyanate-based hardener;
Applying the aqueous 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;
Foaming the foamed thermoplastic resin layer forming layer (B ₀ ) of the foamed paper material by heating the foamed paper material having the printed layer to form a foamed thermoplastic resin layer (B). A method for producing a foamed paper laminate, comprising: The method for producing a foamed paper laminate according to claim 8, wherein the printed layer has a plurality of layers, and the outermost layer is a transparent layer. The method for producing a foamed paper laminate according to claim 8 or 9, wherein the foamed thermoplastic resin layer forming layer (B ₀ ) has a thickness of 40 to 150 μm.

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