WO2021149648A1 - 発泡紙積層体及びその製造方法、発泡紙製容器 - Google Patents
発泡紙積層体及びその製造方法、発泡紙製容器 Download PDFInfo
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- WO2021149648A1 WO2021149648A1 PCT/JP2021/001520 JP2021001520W WO2021149648A1 WO 2021149648 A1 WO2021149648 A1 WO 2021149648A1 JP 2021001520 W JP2021001520 W JP 2021001520W WO 2021149648 A1 WO2021149648 A1 WO 2021149648A1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B27/10—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of paper or cardboard
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/40—Layered products comprising a layer of synthetic resin comprising polyurethanes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B29/00—Layered products comprising a layer of paper or cardboard
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
- B32B5/18—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by features of a layer of foamed material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
- B32B7/02—Physical, chemical or physicochemical properties
- B32B7/022—Mechanical properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
- B32B7/02—Physical, chemical or physicochemical properties
- B32B7/027—Thermal properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D65/00—Wrappers or flexible covers; Packaging materials of special type or form
- B65D65/38—Packaging materials of special type or form
- B65D65/40—Applications of laminates for particular packaging purposes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D81/00—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents
- B65D81/38—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents with thermal insulation
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D11/00—Inks
- C09D11/02—Printing inks
- C09D11/10—Printing inks based on artificial resins
- C09D11/102—Printing inks based on artificial resins containing macromolecular compounds obtained by reactions other than those only involving unsaturated carbon-to-carbon bonds
Definitions
- An embodiment of the present invention relates to a foamed paper laminate and a method for producing the same. Further, another embodiment of the present invention relates to a foamed paper container provided with the foamed paper laminate.
- Foam containers are widely used as containers for storing foods containing high-temperature or low-temperature liquids because they have excellent heat insulating properties.
- foam containers are indispensable for products generally called "cup noodles" that can be eaten in a few minutes by simply pouring an appropriate amount of boiling water into instant noodles such as ramen, udon, and soba noodles contained in a container. I can't.
- Styrofoam containers and foamed paper containers are known as foamed containers for cup noodles, but in recent years, foamed paper containers have been attracting attention from the viewpoint of environmental load and safety.
- the foamed paper container is manufactured by using a foamed paper material having a paper base material and a thermoplastic resin layer that foams by heating at the time of manufacturing the container to form a heat insulating layer.
- a printing layer including a decorative pattern, a company name, a printing pattern such as a barcode is formed on the surface of a foamed paper container (foamed paper material). Therefore, it is desirable that the printing layer has excellent foaming followability without hindering foaming when the thermoplastic resin layer of the foamed paper material foams by heating to form a heat insulating layer.
- the surface (printing surface) of the printing layer after the thermoplastic resin layer is foamed is smooth, has no cracks or swelling, and has an excellent appearance. Further, it is desirable that the printed surface is excellent in various resistances such as abrasion resistance and heat resistance required for manufacturing the container.
- oil-based inks such as oil-based gravure ink and oil-based flexo ink have been used to form the printing layer of the foamed paper container.
- the oil-based ink usually contains an organic solvent such as toluene from the viewpoint of solubility and drying property of the binder resin.
- organic solvents such as toluene from the viewpoint of solubility and drying property of the binder resin.
- regulations on the use of organic solvents have become stricter, so that there is an increasing demand for water-based inks. Therefore, in the field of food containers used for cup noodles and the like, development of a foamed paper laminate having a printing layer formed by using water-based ink and which can be suitably used as a material for foamed paper containers has been promoted. ing.
- Patent Document 1 discloses a water-based flexographic ink for a foam cup, which contains a binder resin, a pigment, and water as an ink for forming a print layer of a foamed paper laminate, and the binder resin contains a polyurethane resin. ..
- Patent Document 2 discloses that the foaming of the foaming layer is suppressed within a predetermined range by the coating portion (printing layer) of the water-based ink.
- the water-based ink disclosed in Patent Document 2 contains a colorant and a binder resin, and contains 30% by mass or more of a urethane resin having a glass transition point of ⁇ 20 ° C. or higher and 30 ° C. or lower in the resin solid content of the binder resin.
- 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.
- the heat insulating property of the foamed paper container mainly depends on the foamability of the thermoplastic resin layer constituting the foaming layer (heat insulating layer) in the foamed paper laminate.
- the foamability of the thermoplastic resin layer during heat processing increases, appearance defects such as cracks and swelling tend to occur on the surface of the printing layer formed on the thermoplastic resin layer. Therefore, it is desirable that the printed layer can uniformly suppress the foaming so as not to prevent the foaming of the thermoplastic resin layer, while preventing the appearance defects such as cracks and swelling.
- the embodiment of the present invention is a foamed paper laminate having a printing layer formed by using a water-based ink, and the printing layer prevents the thermoplastic resin layer from foaming during heat processing.
- a foamed paper laminate having excellent foaming followability and a surface of a printing layer having excellent foaming appearance, abrasion resistance, heat resistance, and ethanol resistance, and a method for producing the same.
- the present inventors have diligently studied the relationship between the foamability of the thermoplastic resin layer during heat processing and the foaming suppressing force of the printing layer.
- the foamability of the thermoplastic resin layer and the printed surface such as foamed appearance, abrasion resistance, heat resistance, and ethanol resistance are obtained.
- good results can be obtained in terms of the characteristics of the above, and have completed the present invention. That is, the present invention relates to the following embodiments, but includes various embodiments without limitation.
- One embodiment is formed on a foam paper having a thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer (B) in that order, and on the surface of the foamed thermoplastic resin layer (B) of the foamed paper.
- a foamed paper laminate having a printed layer The number of foamed cells per unit area of the foamed thermoplastic resin layer (B) is 1000 cells / cm 2 or more.
- the printing layer relates to a foamed paper laminate containing a binder resin containing a polyurethane resin and having a residual ratio of the printing layer of 50% by mass or more after being immersed in ethanol at 25 ° C. for 30 minutes.
- 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.
- the printing layer preferably has a film thickness of 0.5 to 5.0 ⁇ m.
- the printing layer is a cured product formed from a binder resin containing a polyurethane resin having an acid value of 1 to 100 mgKOH / g and at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent. It is preferable to include it.
- the printing layer has a plurality of layers and the outermost layer is a transparent layer.
- the thickness of the foamed thermoplastic resin layer (B) is preferably 500 to 950 ⁇ m.
- One embodiment relates to a foam paper container provided with the foam paper laminate of the above embodiment.
- One embodiment is formed on a foam paper having a thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer (B) in that order, and on the surface of the foamed thermoplastic resin layer (B) of the foamed paper.
- the number of foam cells per unit area of the foamed thermoplastic resin layer (B) is at 1,000 / 1 cm 2 or more, after immersion for 30 minutes in a 25 ° C.
- thermoplastic resin layer (A) a paper base material, and a foamed thermoplastic resin layer forming layer (B 0 ) having a melting point lower than that of the thermoplastic resin layer (A) and foaming by heating.
- Preparing foam paper material Preparing a water-based ink composition containing a binder resin containing a polyurethane resin and water, Applying the water-based ink composition to the surface of the foamed thermoplastic resin layer forming layer (B 0) of the foamed paper material to form a printing layer.
- the foamed thermoplastic resin layer forming layer (B 0 ) of the foamed paper material is foamed to form the foamed thermoplastic resin layer (B).
- the aqueous ink composition contains a binder resin containing a polyurethane resin having an acid value of 1 to 100 mgKOH / g, water, and at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent. It is preferable to prepare the composition.
- the printing layer has a plurality of layers and the outermost layer is a transparent layer.
- the film thickness of the foamed thermoplastic resin layer forming layer (B 0 ) is preferably 40 to 150 ⁇ m.
- the disclosure of the present application is related to the subject matter described in Japanese Patent Application No. 2020-006574 filed on January 20, 2020, the entire disclosure of which is incorporated herein by reference.
- a foamed paper laminate having a printing layer which is excellent in foaming followability without hindering the foaming of the thermoplastic resin layer during heat processing, and is excellent in foaming appearance, abrasion resistance, heat resistance, and ethanol resistance.
- a body and a method for producing the body can be provided. Further, according to the present invention, it is possible to provide a foam paper container provided with the foam paper laminate.
- FIG. 1 is a perspective view showing a structural example of a foamed paper container provided with the foamed paper laminate according to the embodiment.
- FIG. 2 is a schematic cross-sectional view showing a part (reference numeral I part) of the foamed paper container shown in FIG. 1 in an enlarged manner.
- the foamed paper laminate is formed on a foamed paper having a thermoplastic resin layer (A), a paper base material, and a foamed thermoplastic resin layer (B) in that order, and on the surface of the foamed thermoplastic resin layer (B) of the foamed paper.
- the foamed thermoplastic resin layer (B) has a formed printing layer, and the number of foamed cells per unit surface area is 1000 cells / 1 cm 2 or more, and the printed layer is a binder resin containing a polyurethane resin. It is characterized in that the residual ratio of the printed layer after being immersed in ethanol at 25 ° C. for 30 minutes is 50% by mass or more.
- the larger the number the smaller the bubbles existing in the foamed layer (B), and the smaller the number. It means that the bubbles existing in the foamed layer (B) are large. When the bubbles existing in the foam layer (B) become large, appearance defects such as cracks and swelling of the printed surface are likely to occur.
- the number of foamed cells per unit surface area of the foamed layer (B) is preferably 1000 cells / 1 cm 2 or more, and more preferably 1250 cells / 1 cm 2 or more.
- the upper limit of the number of foamed cells is not particularly limited. In one embodiment, the number of foamed cells may be 1600 cells / cm 2 or less from the viewpoint of manufacturing conditions and the like.
- the "number of foamed cells per unit area” is an independent cell (air bubble) existing in a range defined by a constant length in the vertical and horizontal (XY) directions on the surface of the foamed layer (B). It means a value calculated as the number of independent cells per 1 cm 2 by counting the number of. The number of independent cells is determined by removing the print layer of the foamed paper laminate with a solvent, exposing the surface of the foamed layer (B), and then observing the surface of the foamed layer (B) using an optical microscope. NS.
- the thickness of the foam layer (B) is preferably 500 ⁇ m or more, more preferably 630 ⁇ m or more, from the viewpoint of heat insulating properties. If the thickness of the foamed layer (B) is 500 ⁇ m or more, the foamed paper laminate is formed into a cup-shaped container, and even when hot water of about 100 ° C. is poured into the container, the container is continuously held with bare hands. It becomes easy to hold in. On the other hand, from the viewpoint of resource saving, it is preferable that the amount of resin used is as small as possible. Further, from the viewpoint of heat insulating property, the heat insulating layer does not need to be thick enough to have excessive quality. Therefore, the thickness of the foamed layer (B) is preferably 950 ⁇ m or less, more preferably 900 ⁇ m or less, and extremely preferably 800 ⁇ m or less.
- the thickness of the foamed layer (B) is preferably 500 to 950 ⁇ m, more preferably 500 to 900 ⁇ m, and even more preferably 500 to 800 ⁇ m.
- the thickness of the foamed layer (B) is determined by observing the cross section of the foamed paper laminate with an optical micrograph and measuring the height from the upper surface of the paper substrate to the lower surface of the printed layer.
- the foamed paper foam layer (B) means a state after the thermoplastic resin layer is foamed by heating. That is, the foamed layer (B) is formed by heating and foaming an unfoamed thermoplastic resin layer (foamed thermoplastic resin layer forming layer (B 0)) as a precursor.
- the foamed paper laminate in order to form the foamed paper laminate, it has a thermoplastic resin layer (A), a paper base material, and a melting point lower than that of the thermoplastic resin layer (A), and is foamed by heat treatment.
- a foamed paper material (foamed paper before heating) having a foamed thermoplastic resin layer forming layer (B 0) in sequence can be used.
- the foamed paper material can be composed of materials known in the art. Hereinafter, the constituent materials of the foamed paper laminate will be specifically described.
- the paper base material constituting the foamed paper laminate is not particularly limited.
- kraft paper or woodfree paper can be used.
- the basis weight of the paper base material is preferably 150 to 450 g / m 2 , and more preferably 250 to 400 g / m 2 .
- the amount of water contained in the paper base material is preferably 4 to 10% by mass, more preferably 5 to 8% by mass.
- thermoplastic resin layer, foam layer forming layer the thermoplastic resin layer (A) and the foamed thermoplastic resin layer forming layer (B 0 ) (hereinafter, also referred to as the foamed layer forming layer (B 0 )) have been conventionally known as container materials.
- It may be a film made of a resin material.
- a film (thermoplastic resin film) made of at least one thermoplastic resin selected from the group consisting of stretched and unstretched polyolefins such as polyethylene and polypropylene, polyester, nylon, cellophane, and vinylon can be used.
- a polyethylene film can be preferably used because it is excellent in laminating suitability and foamability.
- the foamed paper material can be constructed by laminating thermoplastic resin films having different melting points on a paper base material.
- the melting point of the thermoplastic resin film provided on the other surface of the paper substrate as the foam layer forming layer (B 0 ) is higher than that of the thermoplastic resin film provided on one surface of the paper substrate as the thermoplastic resin layer (A).
- the material is selected so that (Mp) is low.
- the water content in the paper base material evaporates during the heat treatment, and the evaporated water content is extruded to the softened foam layer forming layer (B 0 ) (low Mp resin film) side.
- the low Mp resin film swells (foams) outward, and a foamed layer (B) is formed.
- the foamed layer (B) thus formed functions as a heat insulating layer in the container.
- thermoplastic resin layer (A) high Mp resin film
- a material that does not melt or soften when the low Mp resin film foams by heat treatment is selected for the thermoplastic resin layer (A) (high Mp resin film).
- the foam paper material is, for example, a high Mp polyethylene film having a melting point of about 125 ° C. to 140 ° C. on one surface (inside of the container) of the paper base material.
- the low Mp polyethylene film foams to form a foamed layer by heating during the production of a foamed paper container or the like.
- the high Mp polyethylene film preferably functions as a coating layer. That is, the coating layer can suppress the evaporation of the water content in the paper base material to the outside during the foaming of the low Mp polyethylene film, and can efficiently contribute the water content in the paper base material to the foaming.
- the material of the foam layer forming layer (B 0 ) preferably contains a low-density polyethylene resin (density 910 to 925 kg / m 3 , melting point 105 to 120 ° C.) among the polyethylene resins.
- the density of the low-density polyethylene resin is more preferably 910 to 922 kg / m 3 , and even more preferably 910 to 918 kg / m 3 .
- the material of the foam layer forming layer (B 0 ) As the material of the foam layer forming layer (B 0 ), a medium density polyethylene resin (density 925 to 940 kg / m 3 , melting point 115 to 130 ° C.) and a high density polyethylene resin (density 940 to 970 kg / m 3 , melting point 125 to 140).
- the melt flow rate of the polyethylene resin (hereinafter referred to as "MFR”) is preferably 8 to 28 g / 10 minutes, and preferably 10 to 20 g / 10 minutes. More preferred.
- the film thickness of the foamed cambium (B 0 ) is preferably 40 ⁇ m or more, and more preferably 60 ⁇ m or more. By adjusting the film thickness to 40 ⁇ m or more, sufficient heat insulating properties can be obtained after the heat treatment.
- the film thickness of the foamed cambium (B 0 ) is preferably 150 ⁇ m or less, more preferably 100 ⁇ m or less, and extremely preferably 80 ⁇ m or less.
- the printing layer is a coating film obtained by applying an aqueous ink composition to the surface of the foamed layer forming layer (B 0) of the foamed paper material.
- the main component of the coating film constituting the print layer is a binder resin in the water-based ink composition, and the binder resin preferably contains at least a polyurethane resin.
- the printing layer contains at least a polyurethane resin as the binder resin
- the foam layer forming layer (B 0 ) foams by heating to form the foam layer (B)
- it does not hinder the foaming and has excellent foaming followability. Can be easily obtained.
- the foamability of the foam layer forming layer (B 0 ) can be appropriately suppressed, and the number of foam cells per unit surface area of the foam layer (B) described above can be easily obtained. From these facts, by using the polyurethane resin, an excellent foamed appearance can be obtained, and further, excellent abrasion resistance and heat resistance of the printed layer can be easily obtained.
- the thickness of the printed layer (coating film after drying) is preferably 0.5 to 5.0 ⁇ m from the viewpoint of the foaming suppressing power of the printed layer and the abrasion resistance.
- the thickness of the print layer may be more preferably 0.5 to 4.0 ⁇ m, and even more preferably 0.5 to 3.5 ⁇ m.
- the printed layer preferably has a residual ratio of 50% by mass or more after being immersed in ethanol at 25 ° C. for 30 minutes.
- the residual ratio of the printing layer is 50% by mass or more, even if ethanol is used for disinfection and cleaning in the manufacturing process of food containers, problems such as unclear printing can be suppressed.
- the print layer can be maintained well.
- the residual ratio of the printed layer after being immersed in ethanol at 25 ° C. for 30 minutes is more preferably 60% by mass or more, further preferably 70% by mass or more. ..
- the residual ratio of the printed layer described in the present specification does not require strict adjustment of the immersion conditions in ethanol. That is, conditions such as temperature and immersion time may be slightly changed. For example, "immersion for 30 minutes” means that the print layer may be immersed in ethanol for approximately 30 minutes. Therefore, for example, the immersion time may be extended by 5 to 10 minutes by operations before and after immersion, post-treatment, and the like. As an operation before and after immersion, for example, a stirring step may be provided. The stirring condition is preferably 50 to 150 rpm.
- the hydrophilicity of the binder resin when forming a water-based ink composition, it is preferable to increase the hydrophilicity of the binder resin from the viewpoint of printability. However, if the hydrophilicity of the binder resin is increased, the ethanol resistance of the print layer tends to decrease.
- the structure and physical properties of the polyurethane resin used as the binder resin in addition to the desired properties such as foaming followability, foaming suppressing force, friction resistance, and heat resistance, as described above, It is possible to realize the desired ethanol resistance.
- specific embodiments of the water-based ink composition containing the polyurethane resin as the binder resin will be described.
- Water-based ink composition One embodiment relates to a water-based ink composition that can be suitably used for forming a print layer of the foamed paper laminate of the above embodiment.
- the water-based ink composition contains a binder resin and water, and may further contain a colorant such as a pigment.
- the water-based ink composition may further contain various additives in addition to the above components, if necessary.
- the composition of the water-based ink composition will be described.
- the printed layer does not inhibit the foaming of the foam layer forming layer (B 0) and has excellent foam followability.
- the foaming of the foam layer forming layer (B 0 ) can be appropriately controlled by the printing layer.
- the binder resin is the main component of the printing layer (coating film)
- the foaming followability and the foaming suppressing power of the printing layer can be satisfactorily adjusted by selecting an appropriate binder resin. ..
- the binder resin in the water-based ink composition forming the print layer preferably has an elongation rate of 50 to 4,000% from the viewpoint of foaming followability.
- the binder resin preferably has an elongation rate of 50 to 4,000% and a stress of 0.1 mPa or more.
- the term "elongation rate" described in the present specification refers to a sample having dimensions of 0.3 mm in thickness and 15 mm in width, using a small tensile tester manufactured by Intesco, with a tensile speed of 100 mm / min and a room temperature of 25. It means a value obtained by measuring at ° C.
- the binder resin preferably has a stress of 0.1 mPa or more, more preferably 1 mPa or more, and even more preferably 5 mPa or more at an elongation rate of 50 to 4,000%.
- the stress at an elongation rate of 50 to 4,000% is preferably 50 mPa or less, more preferably 40 mPa or less, and even more preferably 30 mPa or less.
- the stress at an elongation rate of 50 to 4,000% of the binder resin may be 0.1 mPa to 50 mPa.
- the binder resin has an elongation rate and stress in the above range, it becomes easy to obtain good results in terms of foaming appearance in addition to foaming followability. Further, a binder resin having an elongation rate and stress in the above range is preferable from the viewpoint of enhancing ethanol resistance because it is easy to obtain a desired residual rate of the printed layer.
- the binder resin preferably has a glass transition temperature (Tg) of ⁇ 100 ° C. to 0 ° C.
- Tg of the binder resin may be more preferably ⁇ 10 ° C. or lower, and even more preferably ⁇ 25 ° C. or lower.
- the Tg may be ⁇ 100 ° C. or higher, preferably ⁇ 90 ° C. or higher, and more preferably ⁇ 80 ° C. or higher.
- a binder resin having a Tg in the above range is preferable from the viewpoint of ethanol resistance because it is easy to obtain a desired residual ratio of the printed layer.
- the binder resin preferably contains at least a polyurethane resin from the viewpoint of foaming followability of the printed layer during foaming.
- a polyurethane resin is used, it is excellent in various resistances such as light resistance, heat resistance, abrasion resistance, and blocking resistance, and further, it is resistant to a low Mp resin film (foam layer forming layer (B 0 )) which is a base material during printing.
- a water-based ink composition capable of forming a print layer having excellent adhesiveness can be easily constructed.
- a polyurethane resin as a binder resin, even when the water-based ink composition is stored for a long period of time in an environment where heat or light is applied, it becomes a friction resistance, a blocking resistance, and a base material of the printing layer. Good results can also be obtained in various properties such as adhesion to low Mp resin films.
- the binder resin a conventionally known resin can be used in addition to the polyurethane resin.
- various resins having an elongation rate and stress in the above range and Tg excellent printing characteristics can be easily obtained.
- the elongation rate and stress of the binder resin can be controlled by combining various resins, controlling the molecular weight during resin synthesis, changing the Tg of the monomer, adjusting the crosslink density, and the like.
- examples of resins that can be used as binder resins in addition to polyurethane resins include acrylic resins, styrene-acrylic copolymer resins, and styrene-maleic acid copolymer resins.
- the content of the polyurethane resin is preferably 50% by mass or more, more preferably 70% by mass or more, and 85% by mass or more, based on the total mass of the resin components in the binder resin. It is more preferable to have.
- the binder resin may be composed only of the polyurethane resin.
- polyurethane resin used in the present specification means a polyurethane resin in a broad sense including a general polyurethane resin conventionally used in the art or a modified polyurethane resin such as a polyurethane urea resin.
- the polyurethane resin used in the present specification is not particularly limited depending on the production method thereof, and may be various polyurethane resins obtained by applying a known or well-known method for polyurethane resin.
- the polyurethane resin that can be suitably used as the binder resin will be described in more detail.
- polyurethane resin Although not particularly limited, one preferred embodiment of the polyurethane resin is a polyurethane resin obtained by reacting at least a polyol with a polyisocyanate. In addition, as another embodiment, a polyurethane urea resin obtained by extending a chain of a prepolymer of a polyurethane resin with an amine compound can be mentioned.
- 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 means that the polyurethane resin is soluble in water or a water-soluble solvent, or easily dispersible. That is, in one embodiment, the polyurethane resin has an acid value (acidic functional group) and takes either a "water-soluble” or “emulsion” form by neutralizing or modifying the acidic functional group. It is preferable to obtain.
- the acidic functional group may be a carboxyl group, a sulfonic acid group, or the like, but a carboxyl group is preferable.
- the polyurethane resin used as the binder resin is preferably water-soluble.
- the polyurethane resin used as the binder resin preferably has a structure or physical properties that are difficult to dissolve in ethanol.
- the ethanol resistance of the printed surface can be easily improved by the method described below.
- the polyol that is the main constituent of the polyurethane resin there is a method of selecting a polyol having a structure that is difficult to dissolve in ethanol. In this method, it is preferable to use at least one of a polycarbonate diol and a polyester polyol as the polyol.
- Another method is to increase the weight average molecular weight of the polyurethane resin.
- the weight average molecular weight of the polyurethane resin is larger than 20,000, the ethanol resistance can be easily increased.
- the weight average molecular weight of the polyurethane resin is not particularly limited. Even when the weight average molecular weight of the polyurethane resin is 20,000 or less, excellent ethanol resistance can be easily obtained by using, for example, a curing agent in combination.
- Tg glass transition temperature
- the preferable range of Tg of the polyurethane resin may be ⁇ 100 ° C. to 0 ° C., as described above as the characteristics of the binder resin.
- 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.
- the Tg of the polyurethane resin is preferably ⁇ 10 ° C. or lower, more preferably ⁇ 20 ° C. or lower.
- the stress at the elongation rate of 50 to 4,000% may be 0.1 mPa or more.
- the elongation rate of the polyurethane resin is preferably 100 to 2,500%, more preferably 300 to 1,500%, and more preferably 300 to 1,200%. Is even more preferable.
- the stress is preferably 1 to 40 mPa, more preferably 3 to 30 mPa, and even more preferably 5 to 25 mPa.
- the residual rate after immersion in ethanol at 25 ° C. for 30 minutes is 50% by mass or more.
- the print layer is easily formed.
- polyol Various polyols can be used to produce polyurethane resins.
- various polyols shown below can be preferably used.
- the various polyols shown below may be used alone or in combination of two or more.
- Polymers such as ethylene oxide, propylene oxide and tetrahydrofuran, or polyether polyols such as copolymers;
- the polyurethane resin is preferably made from at least one polyol selected from a polyether polyol, a polyester polyol, and a polycarbonate diol, and preferably has a structural unit derived from these raw materials. It is more preferable to use a polyether polyol and / or a polyester polyol as the polyol. That is, in one embodiment, the polyurethane resin may be a polyether polyurethane resin, a polyester polyurethane resin, or a polyether / polyester polyurethane resin.
- the polyether polyol preferably contains at least one selected from polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and more preferably contains polyethylene glycol.
- the polyester polyol preferably contains a polyester polyol which is a condensate of a low molecular weight diol and a dibasic acid.
- the low molecular weight diol is preferably a branched diol.
- the “branched diol” means that at least one hydrogen atom of the alkylene group contained in the alkylene glycol is substituted with a group other than the hydrogen atom.
- the substituent is preferably an alkyl group having 1 to 10 carbon atoms.
- polyester-based polyurethane resin when the polyester-based polyurethane resin is constructed by using the polyester polyol exemplified as (2) above, up to 5 mol% of the polyol compounding amount can be replaced with various other polyols.
- various polyols include glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, and pentaerythritol.
- the structure and number average molecular weight of the polyol are appropriately determined in consideration of properties such as ethanol resistance, dryness, elongation and stress of the polyurethane resin obtained as a reaction product.
- the number average molecular weight of the polyol is usually preferably in the range of 500 to 10,000, more preferably in the range of 500 to 6,000.
- the polyisocyanate that can be used in the production of the polyurethane resin is preferably a diisocyanate compound. Specific examples include aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates.
- the polyisocyanate may be a compound having an isocyanurate ring structure formed by forming various diisocyanates into trimers.
- aromatic diisocyanates examples include 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, and tetraalkyl.
- MDI 4,4'-diphenylmethane diisocyanate
- 4,4'-diphenyldimethylmethane diisocyanate 4,4'-dibenzyl isocyanate
- dialkyldiphenylmethane diisocyanate examples include diphenylmethane diisocyanate, 1,3-phenylenediocyanate, 1,4-phenylenediocyanate and tolylene diisocyanate.
- aliphatic diisocyanate examples include butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate.
- alicyclic diisocyanate examples include cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, methylcyclohexanediisocyanate, and norbornan diisocyanate.
- polyisocyanates at least one selected from the group consisting of trimers of tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, bis (isocyanatomethyl) cyclohexane, hexamethylene diisocyanate, and hexamethylene diisocyanate is preferable.
- the polyisocyanate can be used alone or in combination of two or more.
- dihydroxyic acid When dihydroxyic acid is used in addition to polyol and polyisocyanate in the production of polyurethane resin, an acidic functional group (carboxyl group) derived from dihydroxyic acid is introduced, and a polyurethane resin having an acid value can be obtained. Since the polyurethane resin having an acid value can be easily made water-based, it can be suitably used as the water-based polyurethane resin for forming the water-based ink composition.
- the dihydroxyic acid may be a compound having two hydroxy groups and an acidic group in the molecule.
- Well-known diol compounds containing a carboxyl group can be preferably used. Examples thereof include dimethylolalkanoic acids such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, and 2,2-dimethylolvaleric acid, and these can be preferably used. These may be used alone or in combination of two or more.
- the molar equivalent ratio of isocyanate groups / hydroxyl groups be in the range of 1.2 / 1 to 3/1.
- the molar equivalent ratio of isocyanate groups / hydroxyl groups is in the range of 0.5 / 1 to 0.98 / 1.
- the polyurethane-forming reaction may be carried out in a solvent or in a solvent-free atmosphere.
- a solvent used, the solvent exemplified later can be appropriately selected from the viewpoint of controlling the reaction temperature, viscosity and side reaction.
- the polyurethane-forming reaction is carried out in a solvent-free atmosphere, it is desirable to raise (heat) the temperature to such an extent that sufficient stirring is possible and lower the viscosity in order to obtain a uniform polyurethane resin.
- the reaction time of the polyurethane-forming reaction is preferably 10 minutes to 5 hours.
- the end point of the reaction can be determined by a method such as viscosity measurement, confirmation of NCO peak by IR measurement, and NCO% measurement by titration.
- a suitable usable polyurethane urea resin is prepared by reacting the polyol exemplified above with an organic diisocyanate to synthesize a prepolymer of a polyurethane resin having an isocyanate group at the terminal, followed by a chain extender and a reaction. It is a resin obtained by using an amine compound as a stopping agent and introducing a urea bond into the prepolymer of the polyurethane resin.
- the polyurethane resins when the above polyurethane urea resin is used, various characteristics of the coating film (printed surface) formed by using the water-based ink composition can be further enhanced.
- Chain extender As an example of the chain extender that can be used to introduce a urea bond, various known polyamines can be mentioned.
- the polyamine means a compound having a plurality of amino groups in the molecule. Specific examples of polyamines include ethylenediamine, propylenediamine, hexamethylenediamine, triethylenetetramine, diethylenetriamine, isophoronediamine, and dicyclohexylmethane-4,4'-diamine.
- Examples thereof include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine and the like.
- Examples thereof include diamines having a hydroxyl group in the molecule and dimerdiamine obtained by converting the carboxyl group of dimer acid into an amino group.
- reaction terminator can also be used in combination with polyamines.
- the reaction terminator include dialkylamines such as di-n-dibutylamine, monoethanolamine, diethanolamine, 2-amino-2-methyl-1-propanol, tri (hydroxymethyl) aminomethane, and 2-amino-.
- Amino acids having hydroxyl groups such as 2-ethyl-1,3-propanediol, N-di-2-hydroxyethylethylenediamine, N-di-2-hydroxyethylpropylenediamine, N-di-2-hydroxypropylethylenediamine, and further.
- Examples thereof include monoamine-type amino acids such as glycine, alanine, glutamic acid, taurine, aspartic acid, aminobutyric acid, valine, aminocaproic acid, aminobenzoic acid, aminoisophthalic acid and sulfamic acid.
- 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.
- the production method thereof is not particularly limited.
- the number of free isocyanate groups present at both ends of the prepolymer is 1, the total number of amino groups in the chain extender and reaction terminator used is in the range of 0.5 to 1.3. It is preferable to do so.
- the solvent used in each production of the polyurethane resin and the polyurethane urea resin may be a well-known compound that can be usually used as a solvent for ink forming a printing layer.
- alcohol solvents such as methanol, ethanol, isopropanol, n-propanol, n-butanol
- ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone
- ester solvents such as ethyl acetate, propyl acetate and butyl acetate
- methylcyclohexane Non-aromatic hydrocarbon solvents such as ethylcyclohexane.
- ketimine is generated between the ketone and the amine used as the chain extender, which hinders the smooth progress of the reaction. Therefore, it is desirable to use a small amount of water in combination in order to suppress the generation of ketimine and allow the reaction to proceed smoothly.
- an organic solvent is used in the synthesis reaction, it is preferable to provide a step of removing the organic solvent by distillation under reduced pressure and replacing it with water in order to prepare an aqueous solution of the polyurethane resin.
- the polyurethane resin is preferably a polyurethane resin having an acid value because it can be easily made water-based by neutralization.
- the polyurethane resin preferably has an acid value of 1-100 mgKOH / g.
- the acid value is more preferably 10 to 70 mgKOH / g, and even more preferably 20 to 60 mgKOH / g.
- the hydroxyl value of the polyurethane resin is preferably 1 to 20 mgKOH / g.
- the acid value and the hydroxyl value are measured by the method described in JIS K0070 (1992).
- Neutralizer Various neutralizing agents can be used to make the polyurethane resin having an acid value water-based by neutralization.
- a basic compound can be used to neutralize the carboxyl group in the polyurethane resin.
- Specific examples of basic compounds that can be used as neutralizers include sodium hydroxide, potassium hydroxide, ammonia, methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, ethanolamine, propanolamine, diethanolamine, N- Examples thereof include methyldiethanolamine, dimethylamine, diethylamine, triethylamine, N, N-dimethylethanolamine, 2-dimethylamino-2-methyl-1-propanol, 2-amino-2-methyl-1-propanol, and morpholin. One of these may be used alone, or two or more thereof may be used in combination. Ammonia is preferable from the viewpoint of water resistance of printed matter and residual odor.
- the production of the water-based polyurethane resin can be carried out by applying a conventionally known or well-known method, and is not particularly limited.
- a conventionally known or well-known method for example, the methods for producing an aqueous polyurethane resin described in JP-A-2013-234214, JP-A-2013-249401, JP-A-2015-67818, and JP-A-2018-184512 can be referred to.
- the weight average molecular weight of the polyurethane resin when used as the binder resin, its weight average molecular weight may be in the range of 5,000 to 100,000, more preferably 10,000 to 90,000. It is good, more preferably 20,000 to 80,000.
- 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.
- the weight average molecular weight of the polyurethane resin is preferably 21,000 to 80,000, more preferably 25,000 to 75,000, and 30,000 to 70, 000 is particularly preferable.
- the polyurethane resin used as the binder resin may be a polyurethane resin aqueous solution obtained as follows. (1) First, poly (3-methyl-1,5-pentaneadipate) diol, polyethylene glycol, and dimethylolbutanoic acid are mixed and stirred, and isophorone diisocyanate is further added and reacted to react with the terminal isocyanate pre. Form a polymer. Next, an organic solvent such as 2-aminoethylethanolamine and isopropyl alcohol is added to the terminal isocyanate prepolymer (I) to form a solvent-type polyurethane resin solution.
- 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.
- the urethane resins (A) to (G) described later in the examples can be preferably used as the binder resin constituting the water-based ink composition.
- the urethane resins (A) to (G) may be used individually, but it is more preferable to use two or more in combination because various characteristics can be easily adjusted. For example, when the urethane resin (A) and the urethane resin (B) are used in combination, more suitable characteristics tend to be obtained.
- the total content of the binder resin is preferably 30% by mass or less, more preferably 5 to 25% by mass, based on the total mass of the aqueous ink composition (solid content).
- the amount of the binder resin used is adjusted within the above range, an appropriate ink viscosity can be easily obtained, so that the work efficiency during ink production and printing can be improved.
- the aqueous ink composition preferably further comprises a curing agent for the resin used as the binder resin.
- the printing layer is formed from the cured coating film, but the reaction form thereof is not particularly limited. That is, the printing layer may be a cured coating film formed from the resin in the binder resin and the curing agent. Alternatively, the printing layer may be a cured coating film formed from the curing agent itself.
- the aqueous ink composition 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.
- the polyurethane resin preferably has an acid value of 1-100 mgKOH / g. The acid value is more preferably 10 to 70 mgKOH / g, and even more preferably 20 to 60 mgKOH / g.
- a printing layer having a residual ratio of 50% or more after being immersed in ethanol at 25 ° C. for 30 minutes is formed. It can be easily formed. Therefore, excellent ethanol resistance can be easily realized in the printed layer.
- the water-based ink composition contains a polyurethane resin having an acid value of 1 to 100 mgKOH / g and a curing agent, in addition to ethanol resistance, abrasion resistance of the printed surface, foamed appearance, etc. Good results can be obtained with various characteristics.
- a compound well known in the art can be used as a curing agent for a polyurethane resin having an acid value.
- the aqueous ink composition for forming the printing layer may contain an aqueous polyurethane resin having an acid value of 1 to 100 mgKOH / g and at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent.
- the printing layer formed by using such an aqueous ink composition is a curing formed from an aqueous polyurethane resin having an acid value of 1 to 100 mgKOH / g and at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent. Includes objects (cured coating).
- the carbodiimide-based curing agent may be a compound having a carbodiimide group in the molecule. Compounds having two or more carbodiimide groups in the molecule are preferable. Specific examples of carbodiimide-based curing agents include p-phenylene-bis (2,6-xylylcarbodiimide), tetramethylene-bis (t-butylcarbodiimide), and cyclohexane-1,4-bis (methylene-t-butylcarbodiimide). ).
- the carbodiimide-based curing agent may be a polycarbodiimide compound which is a polymer having a carbodiimide group. These may be used alone or in combination of two or more.
- the compound used as the carbodiimide-based curing agent preferably has a chemical formula amount (NCN equivalent) per 1 mol of carbodiimide group of 250 to 700, more preferably 300 to 600.
- NCN equivalent chemical formula amount
- Commercially available products can also be used as the carbodiimide-based curing agent.
- the isocyanate-based curing agent may be a compound having an isocyanate group in the molecule.
- a compound having two or more isocyanate groups in the molecule is preferable.
- the compound used as the isocyanate-based curing agent is preferably aqueous, that is, dispersed in water or diluted with water.
- Such an aqueous isocyanate-based curing agent can also be obtained as a commercially available product, for example, Aquanate 100, Aquanate 110, Aquanate 200 and Aquanate 210 (all trade names, manufactured by Nippon Polyurethane Industry Co., Ltd.); Baihijour TPLS-2032, SUB-Isocyanate L801, Baihijour VPLS-2319, Baihijour 3100, VPLS-2336 and VPLS-2150 / 1 (trade name, manufactured by Sumika Bayer Urethane Co., Ltd.); Takenate WD-720, Takenate WD-725 , Takenate WD-220 (trade name, manufactured by Mitsui Takeda Chemical Co., Ltd.); isocyanate D-56 (trade name, manufactured by Dainichiseika Kogyo Co., Ltd.) and the like. One of these may be used alone, or two or more thereof may be used in combination.
- the blending amount of the curing agent is preferably 100: 1 to 100: 100 in terms of the mass ratio of the binder resin: the curing agent, 100: It is more preferably 2 to 100:60, and even more preferably 100: 3 to 100:30.
- the blending amount of the curing agent when the printing layer is formed as a single layer is preferably 100: 2 to 100: 100 in terms of the mass ratio of the binder resin: the curing agent. It is more preferably 100: 2 to 100: 60, and even more preferably 100: 5 to 100:30.
- the blending amount of the curing agent is preferably 100: 1.5 to 100: 100 in the mass ratio of the binder resin: the curing agent in each layer. It is more preferably 100: 2 to 100: 60, and even more preferably 100: 3 to 100:30.
- the colorant used in the water-based ink composition may be various inorganic pigments and organic pigments generally used in printing inks and paints.
- inorganic pigments include white pigments such as titanium oxide, colored pigments such as red iron oxide, dark blue, ultramarine blue, carbon black, and graphite, and extender pigments such as calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, and talc. Be done.
- examples of organic pigments include colored pigments such as soluble azo pigments, insoluble azo pigments, azo chelate pigments, condensed azo pigments, copper phthalocyanine pigments, and condensed polycyclic pigments.
- the content of these pigments can be appropriately selected in consideration of the desired color tone of the ink and the like, but is generally in the range of 0.5 to 50% by mass based on the total mass of the aqueous ink composition. It is preferable to do so.
- the blending amount of the white pigment is preferably in the range of 20 to 50% by mass based on the total mass of the water-based ink composition. From the viewpoint of hiding property, pigment concentration, and light resistance, it is preferable to use titanium dioxide as the white pigment.
- titanium dioxide as the white pigment.
- colored organic pigments and colored inorganic pigments such as red iron oxide, prussian blue, ultramarine blue, carbon black, and graphite can be appropriately selected and used. Organic pigments are preferable from the viewpoint of color development and light resistance.
- the blending amount of the colored pigment is preferably in the range of 10 to 30% by mass based on the total mass of the water-based ink composition.
- an organic solvent may be used in addition to water as the solvent as long as the effect is not hindered.
- an organic solvent an alcohol-based organic solvent is preferable.
- Specific examples of the organic solvent include ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, t-butanol, 2-methyl-2-propanol and the like. Can be mentioned.
- these organic solvents it is preferable in the water-based ink composition because the wettability to the base material can be controlled.
- the substrate may be a foamed paper material. The water-based ink composition is applied to the upper surface of the foam layer forming layer (B 0) of the foam paper material to form a print layer.
- the blending amount thereof is preferably 30% by mass or less, more preferably 20% by mass or less, and 10% by mass, based on the total mass of the water-based ink composition. It is more preferably less than or equal to%.
- the content of the organic solvent in the water-based ink composition is most preferably 5% by mass or less, and the water-based ink composition may not contain the organic solvent.
- the water-based ink composition may contain various additives, if necessary.
- the additive include an antiblocking agent, various waxes, a thickener, a rheology adjuster, a defoamer, a leveling agent, a preservative, a surface tension adjuster, an adhesion aid, and a pH adjuster.
- the water-based ink composition may further contain an adhesion aid from the viewpoint of improving the adhesion between the printing layer and the substrate. It is preferable to use at least one of a hydrazine-based compound and an epoxy compound as the adhesion aid.
- a hydrazine-based compound adipic acid dihydrazide, sebacic acid dihydrazide, isophthalic acid dihydrazide, and other dihydrazide compounds are preferable.
- the epoxy compound means a compound having an epoxy group.
- alicyclic epoxies such as ADEKA ADEKA Resin EP-4000, EP-4005, 7001 can be mentioned. These adhesive aids are preferably used in an amount of 0.1 to 5% by mass, more preferably 0.1 to 3% by mass, based on the total mass of the aqueous ink composition.
- the preferable composition when a white ink composition is formed as the water-based ink composition, is 10 to 50% by mass of the white inorganic pigment and 5 to 35% of the polyurethane resin (solid content) based on the total mass of the white ink. % By mass and 5 to 30% by mass of water. More preferable compositions of the white ink composition are 20 to 50% by mass of the white inorganic pigment, 5 to 30% by mass of the polyurethane resin (solid content), and 5 to 25% by mass of water.
- 0.5 to 15% by mass of a curing agent may be further contained.
- the curing agent preferably contains at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent.
- the preferable composition is 10 to 25% by mass of an organic pigment and a polyurethane resin based on the total mass of the color ink. (Solid content) 5 to 35% by mass and 5 to 30% by mass of water. More preferable compositions of the color ink are organic pigment 10 to 20% by mass, polyurethane resin (solid content) 5 to 30% by mass, and water 5 to 25% by mass.
- a curing agent in addition to the composition of the color ink, 0.5 to 15% by mass of a curing agent may be further contained.
- the curing agent preferably contains at least one of a carbodiimide-based curing agent and an isocyanate-based curing agent.
- the water-based ink composition forming the print layer can be produced by applying a well-known technique and mixing the above-mentioned various components. More specifically, first, the binder resin, water, and, if necessary, a pigment, a pigment dispersant, a surfactant, and the like are stirred and mixed, and then, for example, a bead mill, a ball mill, a sand mill, an attritor, a roll mill, and the like. Examples thereof include a method of kneading meat using various kneading machines such as a pearl mill, and further adding and mixing the remaining materials.
- One embodiment relates to a method for producing a foamed laminate. That is, one embodiment includes a foam paper having a thermoplastic resin layer (A), a paper base material, and a foam layer (B) in that order, and a printing layer formed on the surface of the foam layer (B) of the foam paper.
- the number of foamed cells per unit surface area of the foamed layer (B) is 1000 cells / cm 2 or more, and the residual ratio of the printed layer after being immersed in ethanol at 25 ° C. for 30 minutes is 50% by mass or more.
- the present invention relates to a method for producing a foamed paper laminate.
- This production method has the following steps (i) to (iv), that is, (i) a thermoplastic resin layer (A), a paper substrate, and a melting point lower than that of the thermoplastic resin layer (A).
- a foamed paper material which sequentially has a foamed layer forming layer (B 0) that foams by heating.
- (Ii) Preparing a water-based ink composition containing a binder resin containing a polyurethane resin and water.
- (iii) Applying the water-based ink composition to the surface of the foam layer forming layer (B 0) of the foam paper material to form a printing layer.
- the foamed layer forming layer (B 0 ) of the foamed paper material is foamed to form the foamed layer (B).
- each step relating to (i) preparation of foam paper material, (ii) preparation of water-based ink composition, (iii) formation of printing layer, and (iv) formation of foam layer (B) by heating is performed. It can be carried out according to a method well known in the art. Hereinafter, each step will be described.
- Step (i): Preparation of foam paper material The preparation of the foamed paper material can be carried out, for example, according to the extrusion laminating method.
- the constituent materials of the paper base material, the thermoplastic resin layer (A), and the foamed layer forming layer (B 0 ) constituting the foamed paper material are as described above.
- the extrusion laminating method a well-known method such as a single laminating method, a tandem laminating method, a sandwich laminating method, and a coextrusion laminating method can be appropriately selected.
- polyethylene resins having different melting points can be preferably used as the constituent materials of the thermoplastic resin layer (A) and the foamed layer forming layer (B 0).
- the foam layer forming layer (B 0 ) is constructed by using a polyethylene resin (low Mp polyethylene resin) having an Mp lower than the melting point (Mp) of the polyethylene resin constituting the thermoplastic resin layer (A).
- the foamed paper material is obtained by extruding a low Mp polyethylene resin into a film on one side of a paper base material and a high Mp polyethylene resin into a film on the other side of a paper base material through a T-die extruder.
- the temperature of the polyethylene resin at the time of laminating is preferably 300 to 350 ° C, more preferably 320 ° C to 340 ° C. Within this temperature range, sufficient lamination strength can be realized between each polyethylene resin layer (A, B 0) and the paper base material.
- the surface temperature of the cooling roll passed after laminating is preferably controlled in the range of 10 to 50 ° C.
- the laminating speed is preferably 50 to 130 m / min, more preferably 60 to 110 m / min. If the laminating speed is too slow, the productivity will be low, while if the laminating speed is too fast, the neck-in tends to reduce the yield.
- Neck-in is a phenomenon in which the width of the extruded polyethylene resin film is smaller than the effective width of the T-die when the polyethylene resin is extruded into a film by a T-die extruder. At this time, both ends of the film become thicker than the central portion. When the thickness of both ends deviates from the standard, it is common to cut and remove both ends, but when the neck-in is severe, the area deviating from the standard increases and the yield decreases.
- the air gap is preferably 300 mm or less, more preferably 200 mm or less. If the air gap is widened too much, the polyethylene resin will neck in and the yield will tend to decrease.
- the air gap refers to the distance from the T-die extrusion port to the nip roll. It is preferable to surface-treat the polyethylene resin with ozone gas and / or oxygen gas while the polyethylene resin is passing through the air gap. By performing the surface treatment using ozone gas and / or oxygen gas, the formation of an oxide film can be promoted and the adhesive force with the base material layer can be improved.
- the amount of ozone gas and / or oxygen gas to be treated is not particularly limited, but 0.5 mg / m 2 or more is preferable from the viewpoint of promoting the oxidation of the polyethylene resin.
- Step (ii): Preparation of water-based ink composition In the production method of the above-described embodiment, the specific configuration and preparation method of (ii) the water-based ink composition are as described above in the embodiment of the water-based ink composition.
- the binder resin is preferably an aqueous polyurethane resin having an acid value, and more preferably water-based by neutralization.
- the stress at an elongation rate of 50 to 4,000% is preferably 0.1 mPa to 50 mPa.
- a binder resin containing an water-based polyurethane resin having an acid value of 1 to 100 mgKOH / g, water, a carbodiimide-based curing agent, and a polyisocyanate-based curing agent are used. It is preferable to prepare an aqueous ink composition (ii-2) containing at least one of the agents.
- the polyurethane resin having an acid value of 1 to 100 mgKOH / g is preferably made aqueous by neutralization.
- the formation of the print layer (iii) is not particularly limited, and a well-known technique can be applied.
- a coater such as a bar coater, a roll coater, or a reverse roll coater is used. May be good.
- various printing methods can be applied.
- the printing method by flexographic printing or gravure printing it is preferable to apply a printing method by flexographic printing or gravure printing.
- the water-based ink compositions (ii-1) and (ii-2) of the above-described embodiments can be preferably used.
- the printing method by flexographic printing it is possible to form a printing layer with good productivity and high yield.
- a typical form of the flexographic printing method will be described.
- Anilox roll Anilox can be used in the flexographic printing method.
- ceramic anilox rolls with cell engraving, chrome-plated anilox rolls, and the like can be used.
- anilox roll having a line number of 5 times or more, preferably 6 times or more of the number of lines of the plate used at the time of printing is used.
- anilox roll having a number of lines of 375 lpi or more is required.
- anilox roll having a number of lines of 750 lpi or more is required.
- Capacity of the anilox roll, from the viewpoint of drying properties and blocking property of the aqueous ink composition used may be 1 ⁇ 8cc / m 2, preferably, may be 2 ⁇ 6cc / m 2.
- a photosensitive resin plate that utilizes ultraviolet curing by a UV light source can be used as the plate.
- an elastomer material plate that uses a direct laser engraving method can also be used.
- a plate having a screening line number of 75 lpi or more is used. Any sleeve or cushion tape can be used to attach the plate.
- the flexographic printing machine include a CI type multicolor flexographic printing machine and a unit type multicolor flexographic printing machine.
- Specific examples of the ink supply method include a chamber method and a two-roll method. A printing machine applicable to the flexographic printing method can be appropriately selected and used.
- the print layer preferably comprises a plurality of layers.
- the print layer may have a base layer that covers the entire surface of the foam layer forming layer (B 0 ) and a print pattern provided on at least a part of the surface of the base layer.
- the base layer is composed of a white water-based ink composition
- the print pattern is formed of a water-based color ink composition.
- the thickness of the printed layer is adjusted so that the film thickness of the dry coating film is 0.5 to 5.0 ⁇ m from the viewpoint of the foaming suppressing force of the printed layer and the abrasion resistance. Is preferable.
- the film thickness of the printing layer (dry coating film) may be more preferably 0.5 to 4.0 ⁇ m, and further preferably 0.5 to 3.5 ⁇ m.
- the film thickness of the print layer is preferably adjusted so that the thickness of the entire print layer is within the above range.
- the printing layer may include a plurality of layers, and it is preferable to have a transparent layer as the outermost layer thereof.
- the lucidum can be constructed using a pigment-free clear ink composition.
- 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.
- the thickness of the transparent layer (dry film thickness) is preferably 0.1 to 3.0 ⁇ m, more preferably 0.1 to 2.5 ⁇ m, and even more preferably 0.1 to 2. It is 0.0 ⁇ m.
- the print layer has a transparent layer, it is preferable to adjust the thickness of the entire print layer including the thickness of the transparent layer to be within the range of 0.5 to 5.0 ⁇ m.
- the water-based ink constituting at least one of the plurality of layers preferably contains a binder resin containing a polyurethane resin and a curing agent.
- the aqueous ink composition constituting at least the base layer and / or the outermost layer preferably contains a binder resin containing a polyurethane resin and a curing agent. It is more preferable to form the base layer (white) ink layer and the outermost layer (ink layer or transparent layer) by using the above-mentioned water-based ink composition, and it is most preferable to form all of the plurality of layers.
- the appropriate heating temperature and heating time vary depending on the characteristics of the paper base material used and the thermoplastic resin film.
- a person skilled in the art can determine the combination conditions of the optimum heating temperature and heating time according to the material such as the thermoplastic resin film to be used.
- the heat treatment is generally carried out in the process of molding the container. If the heating temperature during the heat treatment is too low, sufficient foamability cannot be obtained, and if the heating temperature is too high, the foam cells are combined and swelling is likely to occur.
- the heating temperature may be preferably 100 to 125 ° C, more preferably 110 to 120 ° C.
- the heating time can be appropriately adjusted according to the heating temperature, but is preferably 3 to 10 minutes, more preferably 5 to 7 minutes.
- the foam layer forming layer is composed of a low density polyethylene film and the printed layer is formed on the foam layer forming layer by using the water-based ink composition (ii-1) or (ii-2) described above. It is preferable to adjust the heating temperature to 110 to 123 ° C. and the heating time to 5 to 7 minutes. It is more preferable to adjust the heating temperature to 115 to 121 ° C. and the heating time to 5 to 7 minutes.
- Any means such as hot air, electric heat, and electron beam can be used as the heating means.
- a large amount of heat treatment can be carried out at low cost by heating with hot air, electric heat, or the like in a tunnel provided with a transport means by a conveyor.
- FIG. 1 is a perspective view showing the structure of a foamed paper container 10A obtained by performing a heat treatment after assembling and molding the container.
- the foamed paper container 10A is composed of a container body member 10 made of a foamed paper laminate and a bottom plate member 12.
- the high Mp resin film forms the inner wall surface 10a of the container
- the printing layer on the low Mp resin film forms the outer wall surface 10b of the container.
- FIG. 2 is a schematic cross-sectional view showing an enlarged reference code I portion of the container body member of the foam paper container shown in FIG.
- the container body member (foamed paper laminate) 10 includes a high Mp resin film 20, a paper base material 30, and a low Mp resin film (foamed layer) 40 after foaming, in this order from the inner wall surface 10a side (see FIG. 1) of the container. And a print layer 50, and the print layer 50 has a base layer 50a and a print pattern 50b.
- Molding of foamed paper containers can be carried out by applying well-known technology. For example, a foamed paper laminate (foamed paper laminate before heating) on which a printing layer is first formed is punched into a predetermined shape along a mold to obtain a container body member. Similarly, the bottom plate material is punched into a predetermined shape to obtain a bottom plate member. Next, the container body member and the bottom plate member are assembled and molded into the shape of the container by using a conventional container manufacturing apparatus. In the assembly molding of the container by the container manufacturing apparatus, the high Mp resin film of the container body member forms the inner wall surface, the low Mp resin film forms the outer wall surface, and the laminated surface of the bottom plate member is on the inside. To carry out.
- the low Mp resin film is foamed to form a foam layer (heat insulating layer), and a foamed paper container having heat insulating properties can be obtained. can.
- one surface of the paper base material is made of medium-density or high-density polyethylene film. It is preferable to laminate the other surface (outer wall surface of the container) with a low-density polyethylene film.
- the thickness of each film laminated on the paper substrate is not particularly limited. However, the thickness of the low Mp resin film constituting the outer wall surface of the container body is appropriately set so that the foamed film has a sufficient thickness to function as a heat insulating layer when the film is foamed. Is preferable.
- the thickness of the film to be laminated on the paper substrate may be 40 to 150 ⁇ m.
- the thickness of the film to be laminated on the paper substrate is not particularly limited. However, it is preferable to appropriately set the thickness of the film so that the permeation resistance of the contents is ensured when used as a heat-insulating foamed paper container. Since the thickness of the film to be laminated on the paper substrate varies depending on the resin material of the film used, it is desirable for those skilled in the art to appropriately set the thickness in consideration of the characteristics of the resin material.
- the water-based ink composition contains a curing agent
- a binder resin and a curing agent are used in combination in the same manner as in the blending ratio in the water-based ink composition, and a coating film test sample (thickness 0.30 mm, width 5) is used. .0 mm, length 20.0 mm) was prepared. Using this sample, the elongation and stress of the binder resin (cured product) were measured according to the same method as described above.
- the residual ratio of the printed layer was a test for evaluating the ethanol resistance of the printed layer (the surface of the foamed paper laminate) formed on the foamed paper, and was carried out as follows. First, as a test piece (sample), a foamed paper laminate was cut into dimensions of 100 mm in length and 100 mm in width. The mass of the cut-out test piece was measured and used as the sample mass before immersion in ethanol. Then, for convenience of the immersion work, the test piece was pulverized to a size of about 20 mm in length and 20 mm in width.
- the thickness of the print layer was determined from a scanning electron microscope (SEM) photograph (magnification 5000) of a cross section of the foamed paper laminate. The print layer was measured at any five points, and the average value thereof was taken as the film thickness of the print layer.
- 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).
- MEK methyl ethyl ketone
- the surface of the foam layer was observed using an optical microscope (AZ100M manufactured by Nikon Corporation) (magnification: 25 times), and independent cells existing within a range partitioned by a certain length in the vertical and horizontal (XY) directions. was obtained, and a value calculated as the number of independent cells per 1 cm 2 was obtained. Observation was performed at any 5 points, and the average value of these was taken as the number of foamed cells.
- the film thickness of the foamed layer was determined by observing the cross section of the foamed paper laminate with an optical micrograph and measuring the height from the upper surface of the paper substrate to the lower surface of the printed layer.
- the film thickness before foaming corresponds to the film thickness of the foamed layer forming layer. Therefore, the value obtained by measuring the film thickness of the low-density polyethylene resin formed as the foam layer forming layer was used.
- Polyurethane resin (Synthetic Example 1) Polyurethane resin (A) Poly (3-methyl-1,5-pentaneadipate) diol (PMPA2000, number) while introducing nitrogen gas into a reactor equipped with a reflux condenser, a dropping funnel, a gas introduction tube, a stirrer, and a thermometer. 328.16 parts with an average molecular weight of 2,000), 10.0 parts of polyethylene glycol (PEG2000, number average molecular weight of 2,000), 57.81 parts of dimethylolbutanoic acid (DMBA), and 350 parts of methyl ethyl ketone (MEK) were added. ..
- a solvent-type polyurethane resin solution was obtained by reacting for 3 hours.
- an aqueous polyurethane resin solution was obtained by gradually adding 23.69 parts of 28% ammonia water and 1800 parts of ion-exchanged water to the solvent-type polyurethane resin solution to neutralize the solution.
- MEK and IPA in the aqueous polyurethane resin solution were distilled off under reduced pressure, and then water was added to adjust the solid content to 25%.
- an aqueous solution (solid content 25%) of the polyurethane resin (A) having an acid value of 35 mgKOH / g and a weight average molecular weight of 35,000 was obtained. According to the method described above, the elongation rate and stress of the polyurethane resin (A) and other characteristics were measured. The results are shown in Table 1.
- Synthesis Examples 2 to 8 In the same manner as in Synthesis Example 1, except that the raw materials and the blending amounts described in Synthesis Example 1 were changed so as to have the characteristics shown in Table 1 according to the synthesis method described in JP-A-2018-184512. Aqueous solutions of polyurethane resins (B) to (H) having a solid content of 25% were obtained (hereinafter, may be abbreviated as polyurethane resins (B) to (H)). Table 1 shows the results of measuring the elongation and stress of the polyurethane resins (B) to (H) and other properties according to the method described above.
- Acrylic resin Product name "Joncryl7100” manufactured by BASF Co., Ltd. (weight average molecular weight is 200,000, glass transition temperature is -10 ° C, acid value is 51 mgKOH / g, resin elongation is 180%, stress is 6. Emulsion of acrylic resin at 5 mPa).
- Vinyl chloride resin Product name "Viniblanc 700” manufactured by Nissin Chemical Industry Co., Ltd. (a vinyl chloride resin emulsion having a glass transition temperature of 70 ° C. and an acid value of 57 mgKOH / g).
- indigo ink (B1) According to the formulation shown in Table 2, 20 parts of a polyurethane resin (B) aqueous solution, 20 parts of a polyurethane resin (C) aqueous solution, and an indigo pigment (LIONOL BLUE FG-7358-). 20 parts of G (manufactured by Toyo Color Co., Ltd.), 0.10 part of defoamer, 0.20 part of ADH, 2.5 parts of N-propanol, and 10 parts of water were stirred and mixed, and dispersed with a sand mill.
- G manufactured by Toyo Color Co., Ltd.
- foamed paper laminate (1) Production example of foamed paper material The foamed paper material is (step 1) extruded and laminated with a medium-density polyethylene resin (M) on one side of a paper base material to form a water vapor blocking layer. Then, the low-density polyethylene resin (L) was extruded and laminated on the other surface (non-laminated surface) of the paper base material (step 2).
- M medium-density polyethylene resin
- L low-density polyethylene resin
- Step 1 Paper substrate: Moisture content 23 kg / m 3 , Basis weight 320 kg / m 3
- Thickness 40 ⁇ m (thickness of the central part of the polyethylene resin layer)
- Step 2 Low density polyethylene resin (L); extrusion temperature (T die outlet temperature) described later: 310 ° C.
- the low-density polyethylene resin (L) used in the above step 2 is a foam layer forming layer (B 0 ).
- the low-density polyethylene resin (L) was used in Example 18, and the other low-density polyethylene resin (L1) was used to produce a foam paper material. Details of the low-density polyethylene resins (L1) and (L2) are as follows.
- Example 1 As shown in Table 3, carbodilite SV-02 (manufactured by Nisshinbo Co., Ltd.) was used as a carbodiimide-based curing agent for 100 parts by mass of white ink (W1), indigo ink (B1), and clear ink (C1). ) was added in an amount of 3 parts by mass to obtain a printing ink.
- the curing agent had a chemical formula amount of 430 and a solid content of 40% by mass per 1 mol of carbodiimide group.
- Examples 2 to 19 and Comparative Examples 1 to 4 As shown in Table 3, in the embodiment in which the curing agent is added to the white ink, the indigo ink, and the clear ink, the curing agent is further added to obtain each printing ink.
- the amount of Carbodilite SV-02 (manufactured by Nisshinbo Holdings Inc.) added was 5.0 parts by mass in Example 3, 1.0 parts by mass in Example 12, 5.0 parts by mass in Example 13, and the others were carried out. As in Example 1, 3 parts by mass was used.
- Example 11 Takenate WD-725 (manufactured by Mitsui Chemicals, Inc., aqueous isocyanate-based curing agent, solid content 50% by mass) was used as the curing agent, and the amount added was 3 parts by mass. Overprinting was performed in the same manner as in Example 1 except that the printing inks were used in combination as shown in Table 3, to form a printing layer.
- the evaluation criteria are as follows. (Evaluation criteria) 5: Ink peeling is less than 30%. 4: Ink peeling is 30% or more and less than 40%. 3: Ink peeling is 40% or more and less than 60%. 2: Ink peeling is 60% or more and less than 70%. 1: Ink peeling is 70% or more.
- the heat resistance was evaluated by placing the foamed paper laminate on a hot plate heated to 90 ° C. with the foamed surface facing up and measuring the temperature of the foamed surface (non-contact surface) after 4 minutes. More specifically, the temperature of 10 samples of the foamed paper laminate after the heating process was measured as described above, and the average temperature of these was determined. From the obtained average temperature, the heat resistance was evaluated according to the following evaluation criteria. (Evaluation criteria) 5: The temperature of the foamed surface is less than 80 ° C. 4: The temperature of the foamed surface is 80 ° C. or higher and lower than 82 ° C. 3: The temperature of the foamed surface is 82 ° C. or higher and lower than 84 ° C. 2: The temperature of the foamed surface is 84 ° C. or higher and lower than 88 ° C. 1: The temperature of the foamed surface is 88 ° C. or higher.
- the residual ratio of the printed layer after immersion in ethanol at 25 ° C. is 50% by mass or more, and the number of foamed cells in the foamed layer is 1,000 /.
- the foamed paper laminate having a size of 1 cm 2 or more (Examples 1 to 19), it can be seen that excellent foamed appearance, abrasion resistance, heat resistance, and ethanol resistance can be realized.
- Comparative Example 1 when only the acrylic resin was used as the binder resin (without the polyurethane resin), the elongation rate and stress of the resin were lower than those when the polyurethane resin was used, and the foaming followability and foaming ability were improved. The foamed appearance is significantly reduced. Further, as is clear from the comparison between Examples 1 to 19 and Comparative Examples 2 and 3, excellent foam followability and foam appearance can be realized by adjusting the weight average molecular weight and other configurations of the polyurethane resin. At the same time, it can be seen that the ethanol resistance and abrasion resistance of the printed layer can be improved.
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Abstract
Description
上記発泡熱可塑性樹脂層(B)の単位面積あたりの発泡セル数が1000個/1cm2以上であり、
上記印刷層は、ポリウレタン樹脂を含有するバインダー樹脂を含み、かつ25℃のエタノール中に30分間浸漬した後の印刷層の残存率が50質量%以上である、発泡紙積層体に関する。
熱可塑性樹脂層(A)と、紙基材と、上記熱可塑性樹脂層(A)よりも低い融点を有し、加熱によって発泡する、発泡熱可塑性樹脂層形成層(B0)とを順次有する、発泡紙材料を準備すること、
ポリウレタン樹脂を含むバインダー樹脂と、水とを含む水性インキ組成物を準備すること、
上記発泡紙材料の上記発泡熱可塑性樹脂層形成層(B0)の表面に、上記水性インキ組成物を塗布して印刷層を形成すること、
上記印刷層を有する上記発泡紙材料を加熱することによって、上記発泡紙材料の上記発泡熱可塑性樹脂層形成層(B0)を発泡させ、発泡熱可塑性樹脂層(B)を形成することを含む、発泡紙積層体の製造方法に関する。
本願の開示は、2020年1月20日に出願された特願2020-006574号に記載の主題と関連しており、その全ての開示内容は引用によりここに援用される。
一実施形態は、発泡紙積層体に関する。発泡紙積層体は、熱可塑性樹脂層(A)、紙基材、及び発泡熱可塑性樹脂層(B)を順次有する発泡紙と、上記発泡紙の上記発泡熱可塑性樹脂層(B)の表面に形成された印刷層とを有し、上記発泡熱可塑性樹脂層(B)は、単位表面積あたりの発泡セル数が1000個/1cm2以上であり、上記印刷層は、ポリウレタン樹脂を含有するバインダー樹脂を含み、かつ25℃のエタノール中に、30分間浸漬した後の印刷層の残存率が50質量%以上であることを特徴とする。
発泡紙積層体を構成する紙基材は、特に限定されない。例えば、クラフト紙、又は上質紙を使用することができる。容器として使用する時に十分な強靭さを実現する観点から、紙基材の坪量は、150~450g/m2であることが好ましく、250~400g/m2であることがより好ましい。また、ポリエチレンなどの熱可塑性樹脂の好適な発泡性を得る観点から、紙基材に含まれる水分量は4~10質量%が好ましく、5~8質量%がより好ましい。
一実施形態において、熱可塑性樹脂層(A)、及び発泡熱可塑性樹脂層形成層(B0)(以下、発泡層形成層(B0)ともいう)は、それぞれ、従来から容器材料として周知の樹脂材料からなるフィルムであってよい。例えば、ポリエチレン、及びポリプロピレンなどの延伸及び無延伸ポリオレフィン、ポリエステル、ナイロン、セロファン、及びビニロンからなる群から選択される少なくとも1種の熱可塑性樹脂からなるフィルム(熱可塑性樹脂フィルム)を使用することができる。一実施形態において、ラミネート適性及び発泡性に優れることから、ポリエチレンフィルムを好適に使用することができる。
上記実施形態の発泡紙積層体において、印刷層は、発泡紙材料の発泡層形成層(B0)の表面に水性インキ組成物を塗布して得られる塗膜である。印刷層を構成する塗膜の主成分は、水性インキ組成物中のバインダー樹脂であり、バインダー樹脂は少なくともポリウレタン樹脂を含有することが好ましい。
一実施形態は、上記実施形態の発泡紙積層体の印刷層を形成するために好適に使用できる水性インキ組成物に関する。水性インキ組成物は、バインダー樹脂及び水を含み、顔料などの着色剤をさらに含んでもよい。水性インキ組成物は、上記成分に加えて、必要に応じて、各種添加剤をさらに含んでもよい。以下、水性インキ組成物の構成について説明する。
発泡層(B)を形成する加熱加工時に、印刷層は、発泡層形成層(B0)の発泡を阻害せず、発泡追随性に優れることが好ましい。その一方で、印刷面のひび割れ及び火膨れといった発泡外観不良を抑制するためには、発泡層形成層(B0)の発泡を印刷層によって適切に制御できることが好ましい。これに対し、バインダー樹脂は、印刷層(塗膜)の主成分となるため、適切なバインダー樹脂を選択することによって、印刷層の発泡追随性と発泡抑制力とを良好に調整することができる。
特に限定するものではないが、ポリウレタン樹脂の好ましい一実施形態として、少なくともポリオールとポリイソシアネートとを反応させて得られるポリウレタン樹脂が挙げられる。また、他の実施形態として、ポリウレタン樹脂のプレポリマーをアミン化合物によって鎖延長して得られる、ポリウレタンウレア樹脂が挙げられる。
(ポリオール)
ポリウレタン樹脂を製造するために、各種ポリオールを使用することができる。例えば、以下に示す各種ポリオールを好適に使用することができる。以下に示す各種ポリオールは、単独で使用しても、2種以上を組合せて使用してもよい。
(1)酸化エチレン、酸化プロピレン、テトラヒドロフランなどの重合体又は共重合体などのポリエーテルポリオール類;
(2)エチレングリコール、1,2-プロパンジオール、1,3-プロパンジオール、1,3-ブタンジオール、1,4-ブタンジオール、2-メチル1,3-プロパンジオール、ネオペンチルグリコール、ペンタンジオール、3-メチル-1,5-ペンタンジオール、ヘキサンジオール、オクタンジオール、ノナンジオール、メチルノナンジオール、ジエチレングリコール、トリエチレングリコール、ジプロピレングリコールなどの飽和及び不飽和の低分子グリコール類と、n-ブチルグリシジルエーテル、2-エチルヘキシルグリシジルエーテルなどのアルキルグリシジルエーテル類、バーサティック酸グリシジルエステルなどのモノカルボン酸グリシジルエステルと、アジピン酸、フタル酸、イソフタル酸、テレフタル酸、マレイン酸、フマル酸、こはく酸、しゅう酸、マロン酸、グルタル酸、ピメリン酸、アゼライン酸、セバシン酸、ダイマー酸などの二塩基酸もしくはこれらの無水物とを脱水縮合せしめて得られるポリエステルポリオール類;
(3)その他ポリカーボネートジオール類、ポリブタジエングリコール類、ビスフェノールA酸化エチレン又は酸化プロピレンを付加して得られるグリコール類;
(4)ダイマージオール類。
ポリエステルポリオールは、低分子ジオールと二塩基酸との縮合物であるポリエステルポリオールを含むことが好ましい。低分子ジオールとしては、分岐ジオールであることが好ましい。「分岐ジオール」とは、アルキレングリコールの有するアルキレン基のうち、少なくとも1つの水素原子が水素原子以外の基に置換されたものを意味する。置換基としては炭素数1~10のアルキル基であることが好ましい。
ポリウレタン樹脂の製造に使用できるポリイソシアネートは、ジイソシアネート化合物であることが好ましい。具体例として、芳香族ジイソシアネート、脂肪族ジイソシアネート、脂環族ジイソシアネートなどが挙げられる。ポリイソシアネートは、各種ジイソシアネートが3量体となって形成されるイソシアヌレート環構造を有する化合物であってもよい。
ポリウレタン樹脂の製造において、ポリオール及びポリイソシアネートに加えて、ジヒドロキシ酸を使用した場合は、ジヒドロキシ酸由来の酸性官能基(カルボキシル基)が導入され、酸価を有するポリウレタン樹脂を得ることができる。酸価を有するポリウレタン樹脂は、水性化が容易であることから、水性インキ組成物を構成するための水性ポリウレタン樹脂として好適に使用することができる。
尿素結合を導入するために使用できる上記鎖延長剤の一例として、各種公知のポリアミンが挙げられる。ポリアミンとは、分子内に複数のアミノ基を有する化合物を意味する。
ポリアミンの具体例として、エチレンジアミン、プロピレンジアミン、ヘキサメチレンジアミン、トリエチレンテトラミン、ジエチレントリアミン、イソホロンジアミン、ジシクロヘキシルメタン-4,4’-ジアミンが挙げられる。その他の具体例として、2-ヒドロキシエチルエチレンジアミン、2-ヒドロキシエチルプロピレンジアミン、ジ-2-ヒドロキシエチルエチレンジアミン、ジ-2-ヒドロキシエチルプロピレンジアミン、2-ヒドロキシプロピルエチレンジアミン、ジ-2-ヒドロキシプロピルエチレンジアミンなどの分子内に水酸基を有するジアミン類、及びダイマー酸のカルボキシル基をアミノ基に転化したダイマージアミンが挙げられる。
ポリアミンと併用して反応停止剤を使用することもできる。反応停止剤としては、例えば、ジ-n-ジブチルアミンなどのジアルキルアミン類、モノエタノールアミン、ジエタノールアミン、2-アミノ-2-メチル-1-プロパノール、トリ(ヒドロキシメチル)アミノメタン、2-アミノ-2-エチル-1,3-プロパンジオール、N-ジ-2-ヒドロキシエチルエチレンジアミン、N-ジ-2-ヒドロキシエチルプロピレンジアミン、N-ジ-2-ヒドロキシプロピルエチレンジアミンなどの水酸基を有するアミン類、さらにグリシン、アラニン、グルタミン酸、タウリン、アスパラギン酸、アミノ酪酸、バリン、アミノカプロン酸、アミノ安息香酸、アミノイソフタル酸、スルファミン酸などのモノアミン型アミノ酸類が挙げられる。
酸価を有するポリウレタン樹脂を中和によって水性化するために、種々の中和剤を使用することができる。例えば、ポリウレタン樹脂におけるカルボキシル基を中和するために塩基性化合物を使用することができる。
中和剤として使用できる塩基性化合物の具体例として、水酸化ナトリウム、水酸化カリウム、アンモニア、メチルアミン、エチルアミン、プロピルアミン、ブチルアミン、ヘキシルアミン、オクチルアミン、エタノールアミン、プロパノールアミン、ジエタノールアミン、N-メチルジエタノールアミン、ジメチルアミン、ジエチルアミン、トリエチルアミン、N,N-ジメチルエタノールアミン、2-ジメチルアミノ-2-メチル-1-プロパノール、2-アミノ-2-メチル-1-プロパノール、及びモルホリンなどが挙げられる。これらの1種を単独で使用しても、又は2種以上を組合せて使用してもよい。印刷物の耐水性、及び残留臭気などの点から、アンモニアが好ましい。
(1)先ず、ポリ(3-メチル-1,5-ペンタンアジペート)ジオールと、ポリエチレングリコールと、ジメチロールブタン酸とを混合及び撹拌し、さらに、イソホロンジイソシアネートを加えて反応させて、末端イソシアネートプレポリマーを形成する。次に、末端イソシアネートプレポリマー(I)に対し、2-アミノエチルエタノールアミン、及びイソプロピルアルコールなどの有機溶剤を加え、溶剤型のポリウレタン樹脂溶液を形成する。
(2)次に、上記溶剤型ポリウレタン樹脂溶液に対して、アンモニア水、及びイオン交換水を徐々に添加して中和し、水性ポリウレタン樹脂溶液を形成する。さらに、水性ポリウレタン樹脂溶液中の有機溶剤を減圧留去した後、水を加えて固形分を調整し、水性ポリウレタン樹脂の水溶液(ポリウレタン樹脂水溶液)を得る。
一実施形態において、水性インキ組成物は、バインダー樹脂として使用される樹脂に対する硬化剤をさらに含むことが好ましい。水性インキ組成物が硬化剤を含む場合、印刷層は硬化塗膜から形成されるが、その反応形態は特に限定されない。すなわち、印刷層は、バインダー樹脂中の樹脂と硬化剤とから形成される硬化塗膜であってよい。又は、印刷層は、硬化剤自身から形成される硬化塗膜であってもよい。
水性インキ組成物に使用する着色剤は、一般に印刷インキや塗料で使用される各種無機顔料、及び有機顔料であってよい。無機顔料の一例として、酸化チタンなどの白色顔料、ベンガラ、紺青、群青、カーボンブラック、黒鉛などの有色顔料、及び炭酸カルシウム、カオリン、クレー、硫酸バリウム、水酸化アルミニウム、タルクなどの体質顔料が挙げられる。また、有機顔料の一例として、溶性アゾ顔料、不溶性アゾ顔料、アゾキレート顔料、縮合アゾ顔料、銅フタロシアニン顔料、及び縮合多環顔料などの有色顔料が挙げられる。これら顔料の含有量は、所望とするインキの色調などを考慮して適宜選択することができるが、一般的に水性インキ組成物の全質量を基準として、0.5~50質量%の範囲とすることが好ましい。
水性インキ組成物は、必要に応じて各種添加剤を含んでもよい。添加剤としては、ブロッキング防止剤、各種ワックス、増粘剤、レオロジー調整剤、消泡剤、レベリング剤、防腐剤、表面張力調整剤、接着補助剤、pH調整剤などが好適に挙げられる。
水性インキ組成物は、印刷層と基材との密着性を向上させる観点から、接着補助剤をさらに含んでもよい。接着補助剤として、ヒドラジン系化合物、及びエポキシ化合物の少なくとも一方を使用することが好ましい。
ヒドラジン系化合物としては、アジピン酸ジヒドラジド、セバシン酸ジヒドラジド、イソフタル酸ジヒドラジド、及びその他のジヒドラジド化合物が好ましい。
エポキシ化合物としては、エポキシ基を有する化合物を意味する。例えば、ADEKA社製アデカレジンEP-4000、EP-4005、7001などの脂環式エポキシが挙げられる。
これらの接着補助剤は、水性インキ組成物の全質量に対して、0.1~5質量%で使用することが好ましく、0.1~3質量%で使用することがより好ましい。
一実施形態は、発泡積層体の製造方法に関する。すなわち、一実施形態は、熱可塑性樹脂層(A)、紙基材、及び発泡層(B)を順次有する発泡紙と、上記発泡紙の発泡層(B)の表面に形成された印刷層とを有し、上記発泡層(B)の単位表面積あたりの発泡セル数が1000個/1cm2以上であり、25℃のエタノール中に30分間浸漬した後の印刷層の残存率が50質量%以上である発泡紙積層体を製造するための方法に関する。この製造方法は、以下の工程(i)~(iv)、すなわち
(i)熱可塑性樹脂層(A)と、紙基材と、上記熱可塑性樹脂層(A)よりも低い融点を有し、加熱によって発泡する、発泡層形成層(B0)とを順次有する、発泡紙材料を準備すること、
(ii)ポリウレタン樹脂を含有するバインダー樹脂、及び水を含む、水性インキ組成物を準備すること、
(iii)上記発泡紙材料の上記発泡層形成層(B0)の表面に、上記水性インキ組成物を塗布して印刷層を形成すること、
(iv)上記印刷層を有する上記発泡紙材料を加熱することによって、上記発泡紙材料の上記発泡層形成層(B0)を発泡させ、発泡層(B)を形成することを含む。
(i)発泡紙材料の準備は、例えば、押出ラミネート法に従って実施することができる。発泡紙材料を構成する、紙基材、熱可塑性樹脂層(A)、及び発泡層形成層(B0)の構成材料は先に説明したとおりである。押出ラミネート法として、シングルラミネート法、タンデムラミネート法、サンドウィッチラミネート法、及び共押出ラミネート法などの周知の方法を適宜選択することができる。一実施形態において、熱可塑性樹脂層(A)、及び発泡層形成層(B0)の構成材料として、それぞれ融点の異なるポリエチレン樹脂を好適に使用することができる。
上記実施形態の製造方法において、上記(ii)水性インキ組成物の具体的な構成、調製方法については、先に水性インキ組成物の実施形態で説明したとおりである。
一実施形態において、水性インキ組成物として、水性ポリウレタン樹脂を含むバインダー樹脂と、水とを含有する水性インキ組成物(ii-1)を調製することが好ましい。ここで、バインダー樹脂は、酸価を有する水性ポリウレタン樹脂であることが好ましく、中和によって水性化されていることがより好ましい。また、伸び率50~4,000%における応力が0.1mPa~50mPaであることが好ましい。
上記(iii)印刷層の形成については、特に限定されるものではなく、周知の技術を適用することができる。例えば、下地層として、発泡層形成層(B0)(低Mp樹脂フィルム)の全面に白色の水性インキ組成物を印刷する場合、バーコーター、ロールコーター、リバースロールコーターなどのコーターを使用してもよい。その他、各種印刷方法を適用することができる。
(1)アニロックスロール
フレキソ印刷方法では、アニロックスを使用することができる。例えば、セル彫刻が施されたセラミックアニロックスロール、及びクロムメッキアニロックスロールなどを使用することができる。
優れたドット再現性を有する印刷層(印刷物)を得るために、印刷時に使用する版の線数の5倍以上、好ましくは6倍以上の線数を有するアニロックスロールが使用される。例えば、使用する版の線数が75lpiの場合は、線数が375lpi以上のアニロックスが必要である。また、版の線数が150lpiの場合は、線数が750lpi以上のアニロックスロールが必要である。アニロックスロールの容量は、使用する水性インキ組成物の乾燥性とブロッキング性との観点から、1~8cc/m2であってよく、好ましくは、2~6cc/m2であってよい。
フレキソ印刷方法では、版として、UV光源による紫外線硬化を利用する感光性樹脂版を使用できる。版として、ダイレクトレーザー彫刻方式を使用するエラストマー素材版を使用することもできる。フレキソ版の画像部の形成方法に関わらず、スクリーニング線数において75lpi以上の版が使用される。版を貼るスリーブ、又はクッションテープについては、任意のものを使用できる。
フレキソ印刷機の具体例として、CI型多色フレキソ印刷機、及びユニット型多色フレキソ印刷機などが挙げられる。インキ供給方式の具体例として、チャンバー方式、及び2ロール方式が挙げられる。フレキソ印刷方法に適用可能な印刷機を適宜選択して使用することができる。
上記(iv)加熱による発泡層(B)の形成において、適切な加熱温度及び加熱時間は、使用する紙基材、及び熱可塑性樹脂フィルムの特性に依存して変化する。当業者であれば、使用する熱可塑性樹脂フィルムなどの材料に応じて、最適な加熱温度と加熱時間との組合せ条件を決定することができる。特に限定するものではないが、一般的に、加熱処理は、容器の成形工程において実施される。加熱処理時の加熱温度が低すぎると十分な発泡性が得られず、加熱温度が高すぎると発泡セルが結合し火脹れが生じやすくなる。
一実施形態は、上記実施形態の発泡紙積層体を具備する発泡紙製容器に関する。発泡紙製容器は、容器胴体部材と底板部材とから構成され、容器胴体部材が上記実施形態の発泡紙積層体から形成されることを特徴とする。図1は、容器の組み立て成形後に加熱処理を実施することによって得られる発泡紙製容器10Aの構造を示す斜視図である。図1に示すように、発泡紙製容器10Aは、発泡紙積層体から構成される容器胴体部材10と底板部材12とから構成される。容器胴体部材(発泡紙積層体)10において、高Mp樹脂フィルムが容器の内壁面10aを形成し、低Mp樹脂フィルム(発泡層)上の印刷層が容器の外壁面10bを形成する。
後述するバインダー樹脂、及び水性インキ組成物の各種特性は、以下の測定方法によって求めた値を表す。
後述する合成例で得た各々のポリウレタン樹脂水溶液をポリエチレン基材上に塗工し、次いで40℃で3日間にわたって乾燥させ、厚さ0.5mmの乾燥塗膜を得た。それぞれの乾燥塗膜について、動的粘弾性自動測定機(エー・アンド・デー株式会社製、DDV-GPシリーズ(レオバイブロン))を用いて測定した、損失正接tanδのピークトップ温度をTg(℃)とした。測定は、温度範囲-120℃~40℃、昇温速度10℃/分で実施した。
後述する合成例で得た各々のポリウレタン樹脂水溶液を乾燥させて、塗膜試験サンプル(厚さ0.30mm、幅5.0mm、長さ20.0mm)を作製した。各サンプルについて、インテスコ社製の小型引張り試験機を使用し、伸び率、及び応力を測定した。測定は、引張り速度100mm/分、室温25℃の条件下でそれぞれ実施した。
なお、水性インキ組成物が硬化剤を含む実施形態については、水性インキ組成物における配合比率と同様にしてバインダー樹脂と硬化剤とを併用し、塗膜試験サンプル(厚さ0.30mm、幅5.0mm、長さ20.0mm)を作製した。このサンプルを使用して、上記と同様の方法に従って、バインダー樹脂(硬化物)の伸び率及び応力を測定した。
印刷層の残存率は、発泡紙上に形成された印刷層(発泡紙積層体の表面)の耐エタノール性を評価するための試験であり、以下のとおりに実施した。
先ず、試験片(サンプル)として、発泡紙積層体を縦100mm、横100mmの寸法に切り出した。切り出した試験片の質量を測定し、エタノール浸漬前のサンプル質量とした。その後、浸漬作業の便宜上、試験片を縦20mm、横20mm程度のサイズに粉砕した。
次に、エタノール:試験片が100:4.5の質量比となるように、容器内にエタノール(25℃)と粉砕した試験片とを容器に入れ、試験片をエタノールに浸漬させた。浸漬は、25℃のエタノール中で、撹拌回転数100rpmで試験片を撹拌しながら2分間、その後30分間静置し、さらに、回転数100rpmで試験片を撹拌しながら1分間の条件下で実施した。試験片を取り出して、乾燥後の試験片の質量を測定し、浸漬後のサンプル質量とした。
さらに、上述のようにして測定した、浸漬前のサンプル質量、及び浸漬後のサンプル質量から、下式に従い、印刷層の残存率を算出した。
印刷層の残存率=(浸漬後のサンプル質量/浸漬前のサンプル質量)×100
印刷層の膜厚は、発泡紙積層体の断面の走査型電子顕微鏡(SEM)の写真(倍率5000)から求めた。印刷層について任意の5箇所について測定し、これらの平均値を印刷層の膜厚とした。
発泡紙積層体の印刷層をメチルエチルケトン(MEK)で除去し、発泡熱可塑性樹脂層(発泡層)の表面を露出させた。次いで、光学顕微鏡(ニコン社製、AZ100M)を用いて発泡層の表面を観察し(倍率25倍)、縦横(X-Y)方向に一定の長さで区画される範囲内に存在する独立セルの数を求め、さらに1cm2あたりの独立セル数として算出される値を得た。任意の5箇所について観察を行い、これらの平均値を発泡セル数とした。
発泡層の膜厚は、発泡紙積層体の断面を光学顕微鏡写真で観察し、紙基材の上面から、印刷層の下面までの高さを測定することによって決定した。また、発泡前の膜厚は、発泡層形成層の膜厚に対応する。そのため、発泡層形成層として形成した低密度ポリエチレン樹脂の膜厚を測定して得た値とした。
(合成例1)ポリウレタン樹脂(A)
還流冷却管、滴下漏斗、ガス導入管、撹拌装置、及び温度計を備えた反応器中に、窒素ガスを導入しながら、ポリ(3-メチル-1,5-ペンタンアジペート)ジオール(PMPA2000、数平均分子量2,000)328.16部、ポリエチレングリコール(PEG2000、数平均分子量2,000)10.0部、ジメチロールブタン酸(DMBA)57.81部、及びメチルエチルケトン(MEK)350部を入れた。これらを混合及び撹拌しながら、さらに、イソホロンジイソシアネート(IPDI)200.76部を1時間かけて滴下した。その後、これらを還流温度で6時間にわたって反応させて、末端イソシアネートプレポリマーを形成した。その後、反応液を30℃まで冷却してからイソプロピルアルコール100部を加えて、末端イソシアネートプレポリマーの溶剤溶液を得た。
得られた末端イソシアネートプレポリマーに対し、2-アミノエチルエタノールアミン(AEA)28.21部及びイソプロピルアルコール(IPA)150部の混合液を、室温(25℃)で徐々に添加し、40℃で3時間にわたって反応させることによって、溶剤型ポリウレタン樹脂溶液を得た。
次に、上記溶剤型ポリウレタン樹脂溶液に対して、28%アンモニア水23.69部及びイオン交換水1800部を徐々に添加して中和することによって、水性化ポリウレタン樹脂溶液を得た。さらに、上記水性化ポリウレタン樹脂溶液中のMEK及びIPAを減圧留去した後、水を加えて固形分を25%に調整した。
以上のようにして、酸価が35mgKOH/gであり、重量平均分子量が35,000である、ポリウレタン樹脂(A)の水溶液(固形分25%)を得た。先に説明した方法に従い、上記ポリウレタン樹脂(A)の伸び率及び応力、並びにその他の特性について測定した。その結果を表1に示す。
特開2018-184512号公報に記載された合成方法に従って、合成例1に記載した原料及び配合量を表1に記載した特性となるように変更したことを除き、合成例1と同様にして、それぞれ固形分25%のポリウレタン樹脂(B)~(H)の水溶液を得た(以下、ポリウレタン樹脂(B)~(H)と略記する場合もある)。ポリウレタン樹脂(B)~(H)の伸び率及び応力、並びにその他の特性について、測定先に説明した方法に従い測定したその結果を表1に示す。
(製造例1)白色インキ(W1)の製造
表2に記載する配合に従い、ポリウレタン樹脂(A)水溶液を10部、ポリウレタン樹脂(B)水溶液を20部、白色顔料(酸化チタン、チタニックス JR808(テイカ株式会社製)40部、消泡剤0.1部、アジピン酸ジヒドラジド(ADH)0.2部、N-プロパノール1部、及び水5部を撹拌混合し、サンドミルで分散処理した。次いで、分散処理によって得られた混合物に、さらに、ポリウレタン樹脂(A)水溶液を4部、ポリウレタン樹脂(B)水溶液を14部、及び水6部を加えて、撹拌混合することによって、白色インキ(W1)を得た。
製造例1で使用した2種のポリウレタン樹脂水溶液を表2に記載する配合に従って変更したことを除き、全て製造例1に記載の製造方法と同様にして白色インキ(W2)~(W9)を得た。
なお、表2に記載したバインダー樹脂は、以下のとおりである。
ポリウレタン樹脂A~H:合成例1~8で調製したポリウレタン樹脂(A)~(H)の水溶液(それぞれ、固形分25%)。
ポリウレタン樹脂I:荒川化学工業株式会社製の製品名「ユリアーノW321」(樹脂の伸び率が600%で、応力が7.0mPaであるポリウレタン樹脂の水溶液)。
アクリル樹脂:BASF株式会社製の製品名「Joncryl7100」(重量平均分子量が200,000、ガラス転移温度が-10℃、酸価が51mgKOH/g、樹脂の伸び率が180%で、応力が6.5mPaであるアクリル樹脂のエマルジョン)。
塩化ビニル樹脂:日信化学工業株式会社製の製品名「ビニブラン700」(ガラス転移温度が70℃、酸価が57mgKOH/gの塩化ビニル樹脂のエマルジョン)。
表2に記載する配合に従い、ポリウレタン樹脂(B)水溶液を20部、ポリウレタン樹脂(C)水溶液を20部、藍顔料(LIONOL BLUE FG-7358-G(トーヨーカラー社 製))を20部、消泡剤0.10部、ADHを0.20部、N-プロパノール2.5部、及び水10部を撹拌混合し、サンドミルで分散処理した。次いで、分散処理によって得られた混合物に、さらに、ポリウレタン樹脂(B)水溶液を4部、ポリウレタン樹脂(C)水溶液を16部、及び水8部を追加し、撹拌混合することによって、藍インキ(B1)を得た。
製造例10に記載の2種のポリウレタン樹脂水溶液を表2に記載の配合に変更したことを除き、全て製造例10に記載の製造方法と同様にして、藍色インキ(B2)~(B9)を得た。
表2に記載の配合に従い、ポリウレタン樹脂(C)水溶液を82部、消泡剤0.1部、ADHを0.2部、N-プロパノール1部、水17部を撹拌混合することによって、重ね刷り用のクリアインキ(C1)を得た。
製造例19に記載のポリウレタン樹脂水溶液を表2に記載の配合に変更したことを除き、全て製造例19に記載の製造方法と同様にして、クリアインキ(C2)~(C9)を得た。
(1)発泡紙材料の製造例
発泡紙材料は、(工程1)紙基材の片面に、中密度ポリエチレン樹脂(M)を押出ラミネートして水蒸気遮断層を形成し、次いで、(工程2)紙基材の他面(非ラミネート面)に低密度ポリエチレン樹脂(L)を押出ラミネートしてすることによって、製造した。
(工程1)
紙基材:水分量23kg/m3、坪量320kg/m3
中密度ポリエチレン樹脂(M):東ソー社製「ペトロセンLW04-1」、MFR4.3g/10分、密度940kg/m3
押出温度(Tダイ出口温度):320℃
引取速度(ラミネート速度):50m/分
エアギャップ:130mm
厚さ:40μm(ポリエチレン樹脂層の中央部の厚さ)
低密度ポリエチレン樹脂(L);後述
押出温度(Tダイ出口温度):310℃
引取速度(ラミネート速度):60m/分
エアギャップ:130mm
低密度ポリエチレン樹脂(L1):東ソー社製「ペトロセン07C03C」、密度918kg/m3、融点106℃、MFR15g/10分
低密度ポリエチレン樹脂(L2):日本ポリエチレン社製「ノバテックLDLC720」、密度922kg/m3、融点110℃、MFR9g/10分
先に調製した白色インキ(W1~W9)、藍色インキ(B1~B9)、及びクリアインキ(C1~C9)を使用して、以下に記載するようにして発泡紙材料に印刷層を形成した。
表3に記載するように、白色インキ(W1)、藍色インキ(B1)、及びクリアインキ(C1)の100質量部に対し、それぞれ、カルボジイミド系硬化剤としてカルボジライトSV-02(日清紡株式会社製)を3質量部添加して印刷インキを得た。上記硬化剤は、カルボジイミド基1molあたりの化学式量が430、固形分40質量%であった。
発泡紙材料の低密度ポリエチレン樹脂(L)上に、セントラルインプレッション(CI)型のフレキソ印刷機を利用し、アニロックスロール、及び樹脂版によって、印刷インキ(W1)、印刷インキ(B1)、及び印刷インキ(C1)の順で、重ね刷りを行い、印刷層を形成した。印刷速度は150m/分で行った。
表3に記載するように、白色インキ、藍色インキ、及びクリアインキに対して、硬化剤を添加する実施形態については、さらに硬化剤を添加して、それぞれの印刷インキを得た。なお、カルボジライトSV-02(日清紡株式会社製)の添加量は、実施例3では5.0部、実施例12では1.0質量部、実施例13では5.0質量部とし、その他は実施例1と同様に3質量部とした。実施例11では、硬化剤としてタケネートWD-725(三井化学社製、水性イソシアネート系硬化剤、固形分50質量%)を使用し、添加量は3質量部とした。表3に記載するように各印刷インキを組合せて使用したことを除き、実施例1と同様の方法で重ね刷りを行い、印刷層を形成した。
上述のようにして製造した印刷層を有する発泡紙材料(発泡前の発泡紙積層体)について、以下の条件で加熱処理を行い、低密度ポリエチレン樹脂層(L)を発泡させて、発泡層を形成し、発泡紙積層体(発泡後積層体)を製造した。なお、実施例14、15及び比較例4以外の実施例及び比較例では、標準条件下で加熱処理を行った。
標準条件 :120℃のオーブンで6分間加熱
実施例14:120℃のオーブンで9分間加熱
実施例15:122℃のオーブンで6分間加熱
比較例4 :124℃のオーブンで6分間加熱
上述のようにして製造した実施例1~19及び比較例1~4の発泡紙積層体について、以下に記載の方法に従い、各種特性を評価した。それぞれの結果を表3に示す。
実施例1~19及び比較例1~4の発泡紙積層体の各表面について、加熱処理後(低Mpフィルム発泡後)の白インキ印刷部と藍インキ印刷部との段差を指触し、藍インキ印刷部の凹み度合いを以下の基準に従って評価した。評価の数値が高いほど、発泡追随性に優れ、印刷面が平坦であることを意味する。
(評価基準)
5:白インキ印刷部との段差をほとんど感じない。
4:白インキ印刷部との段差をわずかに感じる。
3:白インキ印刷部との段差をかなり感じる。
2:白インキ印刷部との段差をかなり大きく感じる。
1:白インキ印刷部との段差を非常に大きく感じる。
実施例1~19の発泡紙積層体、及びび比較例1~4の発泡紙積層体について、目視にて発泡紙積層体の印刷面を観察した。評価基準は以下の通りである。なお、表3に示した結果は、発泡紙積層体のサンプルを無造作に10個準備し、各サンプルを観察及び評価した結果における最頻値である。最頻値が複数存在する場合は、より低い評価となる値を採用した。
(評価基準)
5:火脹れが全くない(火脹れが確認できない)。
4:長径5mm未満の火脹れが、100cm2あたり1個存在する。
3:長径5mm未満の火脹れが、100cm2あたり2個存在する。
2:長径5mm未満の火脹れが、100cm2あたり3~5個存在する。又は、長径5~20mmの火脹れが、100cm2あたり1個存在する。
1:長径5mm未満の火脹れが、100cm2あたり6個存在する。又は、長径5~20mmの火脹れが、100cm2あたり2個以上存在する。又は、長径20mmを超える火脹れが、100cm2あたり1個以上存在する。
なお、長径が異なる複数の火脹れが混在している場合は、より低い評価を採用する。具体的には、100cm2あたり、長径5mm未満の火脹れが2個、及び長径5~20mmの火脹れが1個存在する場合は、評価は「2」となる。
実施例1~19及び比較例1~4の発泡紙積層体について、火膨れの評価と同様に、目視にて発泡紙積層体の印刷面を観察した。評価基準は以下の通りである。なお、表3に示した結果は、発泡紙積層体のサンプルを無造作に10個準備し、各サンプルを観察及び評価した結果における最頻値である。最頻値が複数存在する場合は、より低い評価となる値を採用した。
(評価基準)
5:ひび割れが全くない(ひび割れが確認できない)。
4:長さ2mm未満のひび割れが、100cm2あたり1本存在する。
3:長さ2mm未満のひび割れが、100cm2あたり2~4本存在する。
2:長さ2mm未満のひび割れが、100cm2あたり5~10本存在する。又は、長さ2~5mmのひび割れが、100cm2あたり1本存在する。
1:長さ2mm未満のひび割れが、100cm2あたり11本以上存在する。又は、長さ2~5mmのひび割れが、100cm2あたり2本以上存在する。又は、長さ5mmを超えるひび割れが、100cm2あたり1本以上存在する。
なお、長さの異なる複数のひび割れが混在している場合には、より低い評価を採用する。具体的には、100cm2あたり、長さ1mmのひび割れが1本、及び長さ4mmのひび割れが1本存在する場合は、評価は「2」となる。
実施例1~19及び比較例1~4の発泡紙積層体について、加熱処理によって発泡した低融点フィルム上の印刷層(塗膜)表面に対し、摩擦子に70%エタノール(エタノール:水=70:30)を含ませたカナキン(JIS L 0803)を荷重しながら1往復した。カナキンを往復する時、学振試験機(テスター産業社製)により、200gの荷重を加えた。その後、塗膜を目視で観察し、試験前の塗膜の全面積を基準として、塗膜(インキ)が剥がれた面積の割合を算出し、耐エタノール性について評価した。評価基準は以下のとおりである。
(評価基準)
5:インキの剥がれが30%未満である。
4:インキの剥がれが30%以上、40%未満である。
3:インキの剥がれが40%以上、60%未満である。
2:インキの剥がれが60%以上、70%未満である。
1:インキの剥がれが70%以上である。
実施例1~19及び比較例1~4の発泡紙積層体について、各積層体の白インキ印刷面、又は白インキ、及びクリアインキの印刷面(塗膜表面)を摩擦子として使用した。学振試験機(テスター産業社製)により、荷重200gで塗膜表面を1往復させた。白インキ印刷面への藍インキの色移り度合いから、耐摩擦性を評価した。
(評価基準)
5:インキの色移りがない。
4:インキの色移りがややある(1%未満)。
3:インキの色移りがある(1%以上、10%未満)。
2:インキの色移りがかなりある(10%以上、30%未満)。
1:インキの色移りが非常にある(30%以上)。
90℃に加熱したホットプレートに、発泡面が上になるように発泡紙積層体を置き、4分経過後の発泡面(非接触面)の温度を測定することによって耐熱性を評価した。より具体的には、発泡紙積層体のサンプル10個について上記のようにして加熱経過後の温度を測定し、これらの平均温度を求めた。得られた平均温度から、以下の評価基準に従い、耐熱性を評価した。
(評価基準)
5:発泡面の温度が80℃未満である。
4:発泡面の温度が80℃以上、82℃未満である。
3:発泡面の温度が82℃以上、84℃未満である。
2:発泡面の温度が84℃以上、88℃未満である。
1:発泡面の温度が88℃以上である。
10 発泡紙積層体(容器胴体部材)
10A 発泡紙製容器
10a 容器の外壁面
10b 容器の内壁面
12 底板部材12
20 高Mp樹脂フィルム(熱可塑性樹脂層(A))
30 紙基材
40 発泡後の低Mp樹脂フィルム(発泡熱可塑性樹脂層(B)、発泡層(B))
50 印刷層
50a 下地層
50b 印刷パターン
Claims (12)
- 熱可塑性樹脂層(A)、紙基材、及び発泡熱可塑性樹脂層(B)を順次有する発泡紙と、前記発泡紙の前記発泡熱可塑性樹脂層(B)の表面に形成された印刷層とを有する発泡紙積層体であって、
前記発泡熱可塑性樹脂層(B)の単位面積あたりの発泡セル数が1000個/1cm2以上であり、
前記印刷層は、ポリウレタン樹脂を含有するバインダー樹脂を含み、かつ25℃のエタノール中に30分間浸漬した後の印刷層の残存率が50質量%以上である、発泡紙積層体。 - 前記バインダー樹脂は、伸び率50~4,000%における応力が0.1mPa~50mPaである、請求項1に記載の発泡紙積層体。
- 前記バインダー樹脂は、-100~0℃のガラス転移温度を有する、請求項1又は2に記載の発泡紙積層体。
- 前記印刷層の膜厚が0.5~5.0μmである、請求項1~3のいずれか1項に記載の発泡紙積層体。
- 前記印刷層が、1~100mgKOH/gの酸価を有するポリウレタン樹脂を含むバインダー樹脂と、カルボジイミド系硬化剤及びイソシアネート系硬化剤の少なくとも一方とから形成される硬化物を含む、請求項1~4のいずれか1項に記載の発泡紙積層体。
- 前記印刷層が、複数の層を有し、最外層が透明層である、請求項1~5のいずれか1項に記載の発泡紙積層体。
- 前記発泡熱可塑性樹脂層(B)の厚さが500~950μmである、請求項1~6のいずれか1項に記載の発泡紙積層体。
- 請求項1~7のいずれか1項に記載の発泡紙積層体を具備してなる発泡紙製容器。
- 熱可塑性樹脂層(A)、紙基材、及び発泡熱可塑性樹脂層(B)を順次有する発泡紙と、前記発泡紙の前記発泡熱可塑性樹脂層(B)の表面に形成された印刷層とを有し、前記発泡熱可塑性樹脂層(B)の単位面積あたりの発泡セル数が1000個/1cm2以上であり、25℃のエタノール中に30分間浸漬した後の前記印刷層の残存率が50質量%以上である、発泡紙積層体の製造方法であって、
熱可塑性樹脂層(A)と、紙基材と、前記熱可塑性樹脂層(A)よりも低い融点を有し、加熱によって発泡する、発泡熱可塑性樹脂層形成層(B0)とを順次有する、発泡紙材料を準備すること、
ポリウレタン樹脂を含むバインダー樹脂と、水とを含む水性インキ組成物を準備すること、
前記発泡紙材料の前記発泡熱可塑性樹脂層形成層(B0)の表面に、前記水性インキ組成物を塗布して印刷層を形成すること、
前記印刷層を有する前記発泡紙材料を加熱することによって、前記発泡紙材料の前記発泡熱可塑性樹脂層形成層(B0)を発泡させ、発泡熱可塑性樹脂層(B)を形成することを含む、発泡紙積層体の製造方法。 - 前記水性インキ組成物として、1~100mgKOH/gの酸価を有するポリウレタン樹脂を含むバインダー樹脂と、水と、カルボジイミド系硬化剤及びイソシアネート系硬化剤の少なくとも一方とを含む水性インキ組成物を準備する、請求項9に記載の発泡紙積層体の製造方法。
- 前記印刷層が複数の層を有し、最外層が透明層である、請求項9又は10に記載の発泡紙積層体の製造方法。
- 前記発泡熱可塑性樹脂層形成層(B0)の膜厚が40~150μmである、請求項9~11のいずれか1項に記載の発泡紙積層体の製造方法。
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- 2021-01-18 WO PCT/JP2021/001520 patent/WO2021149648A1/ja active Application Filing
- 2021-01-18 BR BR112022014281A patent/BR112022014281A2/pt unknown
- 2021-01-18 CN CN202180010163.6A patent/CN115038581A/zh active Pending
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JP7418220B2 (ja) | 2024-01-19 |
BR112022014281A2 (pt) | 2022-09-20 |
CN115038581A (zh) | 2022-09-09 |
JP2021112873A (ja) | 2021-08-05 |
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