Foamable laminate and heat-insulating container

Abstract

To provide a foamable laminate for applications such as foamed heat-insulating cups.SOLUTION: The present invention provides a foamable laminate comprising: a foam material having base paper, a first resin layer covering one surface of the base paper, and a second resin layer that covers the other surface of the base paper, has a lower melting point than the first resin layer, and foams by heat treatment, wherein a printed layer is included on the surface of the second resin layer, and the printed layer contains a printing pattern using a printing ink satisfying (1) and (2). The present invention also provides a heat-insulating container using the foamable laminate. (1) The printing ink A forming a printed layer A in contact with the surface of the second resin layer is included. (2) The printing ink A contains a colorant, a polyurethane resin, a vinyl chloride-vinyl acetate copolymer, a plasticizer, and a chelating agent; the mass mixing ratio of the polyurethane resin to the vinyl chloride-vinyl acetate copolymer is from 49:50 to 1:99; and the plasticizer is contained in an amount of 1 to 20 mass% with respect to the total solid content of the printing ink A.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention mainly relates to a foamed laminate that can be used as a heat-insulating container for food.

Background Art

[0002] From the viewpoints of de-oiling resources and recycling, paper substrates have attracted attention, and for example, paper containers are increasingly being used for food cups and beverage cups called "cup noodles". A general paper cup is coated with polyethylene on the inner surface of the cup and has a structure that does not leak water. However, since the outer surface of the cup is not coated, if a beverage is left in the cup for a long time, the strength of the cup tends to weaken due to condensation. Also, since heat is easily transmitted, it is not suitable for use with hot contents. Therefore, recently, foamed heat-insulating cups that impart heat insulation, a feeling of fit when held in the hand, and anti-slip properties have been developed. The foamed heat-insulating cup has its inner and outer surfaces coated with polyethylene. By heating the outer polyethylene during cup molding to cause it to foam, an air layer is formed to block the heat transmitted to the hand. With this structure, it is possible to suppress a decrease in cup strength due to condensation and apply it to hot contents.

[0003] The foamed laminate used for the foamed heat-insulating cup is obtained by laminating low-density polyethylene on one side of the base paper and high-density or medium-density polyethylene on the opposite side, and then heating it in an oven to overheat the laminate layer and cause it to foam due to the moisture in the base paper. When molding the foamed heat-insulating cup, it is required to provide a printing layer for design patterns, product names, manufacturer names, product barcodes, etc. on the surface of the low-density polyethylene that becomes the outer surface of the container.

[0004] Here, it has been a conventional problem that the printing layer suppresses the foaming of low-density polyethylene. In particular, in the printed and non-printed portions of the printing layer, or when a multi-color overprinting portion is formed by overprinting two colors, three colors, or more on the printed portion, there are often differences in the thickness of the low-density polyethylene after foaming. When such a printed portion or the overprinted portion becomes a concave portion and a step is generated, particularly small characters, characters with a large number of strokes, barcodes, etc. become unclear, which causes problems in visibility and barcode reading. On the other hand, as a printing ink composition for a foamed paper container that improves the suppression of foaming of low-density polyethylene and enables both smoothness and foamability to the extent that it does not interfere with reading, an ink composition using a polyurethane resin, a vinyl chloride-vinyl acetate copolymer, or a nitrocellulose resin such as nitrocellulose as a binder resin is known (see, for example, References 1 to 3).

[0005] More recently, as a measure for preventing infectious diseases, resistance to disinfectants such as alcohol has also been required. The methods described in References 1 to 3 do not describe any findings regarding alcohol resistance, and there are also examples where the ink layer swells due to alcohol and affects visibility. Furthermore, nitrocellulose resins are regarded as having a problem with flammability, and an ink design that does not use nitrocellulose resins is desired.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] The problem to be solved by the present invention is to improve the suppression of foaming of low-density polyethylene by a printing layer, to achieve both smoothness and foamability, and alcohol resistance, and to provide a foamable laminate that can be used for foamed heat-insulating cups and the like, using an ink that does not use a nitrocellulose-based resin.

Means for Solving the Problem

[0008] That is, the present invention provides a foamable laminate having a base paper, a first resin layer covering one surface of the base paper, a second resin layer covering the other surface of the base paper, having a melting point lower than that of the first resin layer and foaming by heat treatment, and including a printing layer on the surface of the second resin layer, the printing layer containing a printing pattern of a printing ink that satisfies (1) and (2). (1) It has printing ink A that forms a printing layer A in contact with at least the surface of the second resin layer. (2) The printing ink A contains a coloring material, a polyurethane resin, a vinyl chloride-vinyl acetate copolymer, a plasticizer, and a chelating agent, the mass mixing ratio of the polyurethane resin to the vinyl chloride-vinyl acetate copolymer is 49:50 to 1:99, and the plasticizer is contained in an amount of 1 to 20% by mass based on the total solid content of the printing ink A.

[0009] The present invention also provides a heat-insulating container using the foamable laminate described above.

Effects of the Invention

[0010] According to the present invention, it is possible to provide a foamable laminate that improves the suppression of foaming of low-density polyethylene by a printing layer, achieves both smoothness and foamability, and alcohol resistance, and uses an ink that does not use a nitrocellulose-based resin, and can be used for foamed heat-insulating cups and the like.

Modes for Carrying Out the Invention

[0011] (Definition of Terms) In the present invention, the liquid printing ink refers to a liquid ink applied to a printing method using a printing plate, such as gravure ink or flexographic ink, and is preferably gravure ink or flexographic ink. Further, the liquid printing ink of the present invention does not contain an active energy curable component, that is, it is a liquid ink non-reactive to active energy rays. In the following description, all "inks" refer to "printing inks". Further, all "parts" refer to "parts by mass", "total ink amount" refers to the total amount of ink including all volatile components such as organic solvents, and "total ink solid content" refers to the total amount of only non-volatile components without volatile components.

[0012] (Base paper) The base paper used in the present invention is not particularly limited, but from the viewpoints of the capacity and strength of the heat insulating container, it is preferably a base paper having a basis weight of 80 g / m 2 ~500 g / m 2 Also, since the laminate layer overheats when the foamed laminate is heated in an oven and the moisture contained in the base paper becomes water vapor and foams, it is preferable to maintain a moisture content of about 5 to 10% by mass of the total amount of the base paper.

[0013] (Resin layer) Both the first resin layer and the second resin layer used in the present invention are layers of thermoplastic synthetic resins, and specifically, they can be obtained by laminating a thermoplastic synthetic resin film on the base paper. The thermoplastic synthetic resin film may be a film made of a resin material known as a container material. For example, it can be appropriately selected and used from films made of thermoplastic synthetic resins such as stretched and unstretched polyolefins such as polyethylene and polypropylene, polyesters, nylons, cellophane, and vinylon. Among them, films made of polyolefin resins are preferably used.

[0014] The second resin layer is a resin layer having a melting point lower than that of the first resin layer. Specifically, when manufacturing a heat-insulating container using the foaming laminate of the present invention, a high-melting-point resin film forming the first resin layer is used on the inner wall of the body of the heat-insulating container, and a low-melting-point resin film forming the second resin layer is used as the outer wall of the body of the heat-insulating container. For example, when using a polyethylene film, as the high-melting-point resin film forming the first resin layer, a high-melting-point polyethylene film having a melting point of about 130°C to 135°C is used, and as the low-melting-point resin film forming the second resin layer, a low-melting-point polyethylene film having a melting point of about 105°C to 110°C can be laminated and used respectively. It is preferable to use high-density polyethylene as the high-melting-point polyethylene film. It is preferable to use low-density polyethylene as the low-melting-point polyethylene film.

[0015] The thickness of each film laminated on the front and back of the base paper is not particularly limited. However, the thickness of the low-melting-point resin film constituting the outer wall of the body of the heat-resistant container is preferably adjusted appropriately so that the film layer after foaming functions sufficiently as a heat-insulating layer. For example, if it is a low-density polyethylene film, a thickness of 25 to 80 μm is preferable. Also, when using a medium-density or high-density polyethylene film on the inner wall of the body of the heat-resistant container, the thickness of the film is not particularly limited, but it is preferable to appropriately set the thickness of the film so that the contents do not penetrate and leak.

[0016] (Printing layer) The foaming laminate of the present invention includes a first resin layer covering one surface of the base paper, and a second resin layer covering the other surface of the base paper, having a melting point lower than that of the first resin layer and foaming by heat treatment. The surface of the second resin layer of the foaming material includes a printing layer, and the printing layer is characterized by containing a printing pattern of printing ink that satisfies (1) and (2). (1) It has printing ink A that forms at least a printing layer A in contact with the surface of the second resin layer. (2) It contains a coloring material, a polyurethane resin, a vinyl chloride-vinyl acetate copolymer, a plasticizer, and a chelating agent. The mass mixing ratio of the polyurethane resin to the vinyl chloride-vinyl acetate copolymer is 49:50 to 1:99, and the plasticizer is contained in an amount of 1 to 20% by mass based on the total solid content of the printing ink A.

[0017] A printing layer B may be further formed on the surface of the printing layer A. The printing layer B may be overprinted on a part or the whole of the printing layer A. The printing ink B for forming the printing layer B satisfies (3). (3) It contains a coloring material, a polyurethane resin, a vinyl chloride-vinyl acetate copolymer, and a plasticizer. The mass mixing ratio of the polyurethane resin to the vinyl chloride-vinyl acetate copolymer is 49:50 to 1:99, and the plasticizer is contained in an amount of 1 to 20% by mass based on the total solid content of the printing ink A.

[0018] The printing layer A or the printing layer B is formed by gravure printing or flexographic printing. Therefore, the printing ink A or the printing ink B can be printed by each printing method using a liquid printing ink such as gravure ink or flexographic ink.

[0019] As the binder resin used for the printing ink A and the printing ink B used in the foamed laminate of the present invention, a polyurethane resin and a vinyl chloride-vinyl acetate copolymer are essential.

[0020] (Polyurethane resin) The polyurethane resin used in the printing ink of the present invention is not particularly limited as long as it is a polyurethane resin obtained by reacting a polyol and a polyisocyanate. As the polyol, for example, various known polyols generally used in the production of polyurethane resins can be used, and one kind or two or more kinds may be used in combination.For example, saturated or unsaturated low molecular weight polyols (1) such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butynediol, 1,4-butylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol, pentaerythritol, etc.; polyester polyols (2) obtained by dehydration condensation or polymerization of these low molecular weight polyols (1) and polycarboxylic acids such as sebacic acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, trimellitic acid, pyromellitic acid or anhydrides thereof; polyester polyols (3) obtained by ring-opening polymerization of cyclic ester compounds such as lactones like polycaprolactone, polyvalerolactone, poly(β-methyl-γ-valerolactone), etc.; polycarbonate polyols (4) obtained by reaction of the above low molecular weight polyols (1), etc. with, for example, dimethyl carbonate, diphenyl carbonate, ethylene carbonate, phosgene, etc.; polybutadiene glycols (5); glycols (6) obtained by adding ethylene oxide or propylene oxide to bisphenol A; acrylic polyols (7) obtained by copolymerizing one or more hydroxyethyl, hydroxypropyl acrylate, hydroxybutyl acrylate, etc. in one molecule, or corresponding methacrylic acid derivatives thereof with, for example, acrylic acid, methacrylic acid or esters thereof, etc.

[0021] Examples of the polyisocyanate include various known aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, etc., which are generally used in the production of polyurethane resins. For example, aromatic polyisocyanates such as 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 1-methyl-2,4-phenylene diisocyanate, 1-methyl-2,6-phenylene diisocyanate, 1-methyl-2,5-phenylene diisocyanate, 1-methyl-2,6-phenylene diisocyanate, 1-methyl-3,5-phenylene diisocyanate, 1-ethyl-2,4-phenylene diisocyanate, 1-isopropyl-2,4-phenylene diisocyanate, 1,3-dimethyl-2,4-phenylene diisocyanate, 1,3-dimethyl-4,6-phenylene diisocyanate, 1,4-dimethyl-2,5-phenylene diisocyanate, diethylbenzene diisocyanate, diisopropylbenzene diisocyanate, 1-methyl-3,5-diethylbenzene diisocyanate, 3-methyl-1,5-diethylbenzene-2,4-diisocyanate, 1,3,5-triethylbenzene-2,4-diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, 1-methyl-naphthalene-1,5-diisocyanate, naphthalene-2,6-diisocyanate, naphthalene-2,7-diisocyanate, 1,1-dinaphthyl-2,2'-diisocyanate, biphenyl-2,4'-diisocyanate, biphenyl-4,4'-diisocyanate, 3-3'-dimethylbiphenyl-4,4'-diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, diphenylmethane-2,4-diisocyanate;Aliphatic or alicyclic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, 1,3-cyclopentylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, 1,3-di(isocyanatomethyl)cyclohexane, 1,4-di(isocyanatomethyl)cyclohexane, lysine diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate, 2,2'-dicyclohexylmethane diisocyanate, 3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate, etc. can be used. These polyisocyanates may be used alone or in combination of two or more. Among these, these diisocyanate compounds can be used alone or as a mixture of two or more.;

[0022] A chain extender can also be used. Examples of the chain extender include ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, etc. In addition, amines having a hydroxyl group in the molecule such as 2-hydroxyethyl ethylenediamine, 2-hydroxyethyl propylenediamine, 2-hydroxyethyl propylenediamine, di-2-hydroxyethyl ethylenediamine, di-2-hydroxyethylenediamine, di-2-hydroxyethyl propylenediamine, 2-hydroxypyrropyl ethylenediamine, di-2-hydroxypyrropyl ethylenediamine, di-2-hydroxypropyl ethylenediamine can also be used. These chain extenders can be used alone or in combination of two or more. In addition, a monohydric active hydrogen compound can also be used as a terminal blocking agent for the purpose of terminating the reaction. Examples of such compounds include dialkylamines such as di-n-butylamine, and alcohols such as ethanol and isopropyl alcohol. Further, when it is particularly desired to introduce a carboxyl group into the polyurethane resin, amino acids such as glycine and L-alanine can be used as the reaction terminator. These terminal blocking agents can be used alone or in admixture of two or more.

[0023] The weight average molecular weight of the polyurethane resin is preferably from 10,000 to 100,000, more preferably in the range of 15,000 to 80,000. Also, the addition amount of the polyurethane resin is preferably 0.15 to 40% by mass, more preferably 1.0 to 35% by mass, based on the total amount of the ink.

[0024] (Vinyl chloride-vinyl acetate copolymer) The vinyl chloride-vinyl acetate copolymer resin used in the printing ink of the present invention is not particularly limited as long as it is a copolymer of vinyl chloride and vinyl acetate. The weight average molecular weight of the vinyl chloride-vinyl acetate copolymer resin is preferably from 5,000 to 100,000, more preferably from 10,000 to 70,000. In 100% by mass of the solid content of the vinyl chloride-vinyl acetate copolymer resin, the structure derived from the vinyl acetate monomer is preferably from 1 to 30% by mass, and the structure derived from the vinyl chloride monomer is preferably from 70 to 95% by mass. In this case, the solubility in an organic solvent is improved, and the adhesion to a substrate, the film physical properties, the scratch resistance, etc. are good. Also, those containing a hydroxyl group derived from a vinyl alcohol structure are preferable from the viewpoint of solubility in an organic solvent. The hydroxyl value is preferably from 20 to 200 mgKOH / g. Further, the glass transition temperature is preferably from 50°C to 90°C. The addition amount of the vinyl chloride-vinyl acetate copolymer resin is preferably 0.15 to 40% by mass, more preferably 1.0 to 35% by mass, based on the total amount of the ink.

[0025] The mass mixing ratio of the polyurethane resin and the vinyl chloride-vinyl acetate copolymer is preferably such that the ratio of urethane resin:vinyl chloride-vinyl acetate copolymer is 49:51 to 1:99. In this range, and by using a plasticizer described later in combination, it is possible to suppress and improve the foaming of low-density polyethylene by the printing layer and achieve both smoothness and foamability, as well as alcohol resistance, without using a nitrocellulose resin. Among these, a range of 51:49 to 70:30 is more preferable, and a range of 55:45 to 65:35 is most preferable.

[0026] In the present invention, within a range that does not impair the effects of the present invention, it may contain resins other than the urethane resin and the vinyl chloride-vinyl acetate copolymer. However, it is preferable not to use a nitrocellulose resin from the viewpoint of flammability. Specifically, for example, polyamide resins, acrylic resins, chlorinated polypropylene resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, vinyl chloride resins such as polyvinyl chloride resins, polyester resins, alkyd resins, rosin resins, rosin-modified maleic resins, ketone resins, cyclized rubbers, chlorinated rubbers, butyrals, petroleum resins, etc. can be mentioned. Among these, it is preferable to use a rosin resin in combination.

[0027] (Rosin resin) The rosin resin is not particularly limited as long as it has a rosin skeleton, but rosin-modified maleic resins, rosin esters, rosin phenols, polymerized rosins, etc. are preferable. The softening point (by the ring and ball method) is preferably 90 to 200°C. When using a rosin resin in combination, it is preferably 0.5 to 10% by mass, more preferably 1.0 to 5% by mass, based on the total amount of the ink.

[0028] (Plasticizer) The plasticizer used in the printing ink of the present invention is not particularly limited, and known plasticizers can be used. Specifically, castor oil, epoxidized soybean oil, tributyl acetylcitrate, dioctyl sebacate, fatty acid triglyceride, ethyltoluene sulfonamide, 2-ethylhexyl stearate, 2-ethylhexyl palmitate, etc. can be mentioned. Among them, castor oil, epoxidized soybean oil, or tributyl acetylcitrate is preferable. The addition amount of the plasticizer is 1 to 20% by mass based on the total solid content of the printing ink A and / or the total solid content of the printing ink B. By setting it within this range, it is possible to suppress and improve the foaming of low-density polyethylene by the printing layer without using a nitrocellulose resin, and to achieve both smoothness and foamability, and alcohol resistance. Among them, the addition amount is preferably 1.0 to 15.0% by mass, and more preferably 2.0 to 10.0% by mass.

[0029] (Chelating agent) In order to increase the thickness of the foaming region accompanying foaming by improving the cohesive force, it is preferable to add a chelating agent to the printing ink B, and a metal chelating agent is particularly preferable. As the metal chelating agent, a titanium-based chelating agent, a zirconium-based chelating agent, or an aluminum-based chelating agent can be used. Among them, a titanium-based chelating agent and a zirconium-based chelating agent are preferable. Titanium-based chelating agents are classified into alkoxides, acylates, and chelate complexes. As the chelating agent used in the foamed laminate of the present invention, chelate complexes are more preferable than alkoxides and acylates. Specific examples of chelate complexes include titanium acetylacetonate, titanium tetraacetylacetonate, titanium ethylacetoacetate, and phosphate ester titanium complexes. The titanium ethylacetoacetate and phosphate ester titanium complexes can achieve acetylacetone-free and have higher safety. Zirconium-based chelating agents are similarly classified into alkoxides, acylates, and chelate complexes. As the chelating agent used in the foaming laminate of the present invention, a chelate complex is preferred over alkoxides and acylates. Specifically, zirconium tetraacetylacetonate can be mentioned.

[0030] By using the chelating agent, the cross-linking reaction is completed at a low temperature and hydrolysis at room temperature hardly occurs, and a stable cross-linking reaction can be obtained. When a chelating agent is added, physical properties such as alcohol resistance can be further improved, but the redissolubility of the ink tends to decrease. For example, taking gravure printing as an example, the phenomenon of "plate clogging" is likely to occur where the ink clogs the cells of the gravure printing plate and the ink is difficult to transfer to the printed matter, making it difficult to obtain stable printing suitability and tending to reduce the reproducibility of fine lines and highlight dots. In the present invention, the printing ink A forming the printing layer A contains a chelating agent, but the inclusion of a chelating agent in the printing ink B forming the printing layer B is optional. The blending amount of the chelating agent is preferably 0.1 to 5.0% by mass, more preferably 0.5 to 3.0% by mass of the total amount of the ink as the active ingredient of the chelating agent.

[0031] (Wax) It is also preferable to add wax to the printing ink in the present invention. By adding wax, blocking during laminate production can be suppressed. As the wax, polyolefin-based wax and fatty acid amide-based wax are preferred, and each may be used alone or in combination. When each is used alone, it is preferable to contain 0.5 to 10% by mass of the polyolefin-based wax with respect to the ink solid content and 1.0 to 5% by mass of the fatty acid amide-based wax with respect to the ink solid content. When the polyolefin-based wax and the fatty acid amide-based wax are used in combination, the mass ratio of both is preferably in the range of 0.1:1.0 to 4.5:1.0.

[0032] (Organic solvent) The printing ink in the present invention contains an organic solvent. There is no particular limitation on the organic solvent. For example, aromatic hydrocarbon-based organic solvents such as toluene, xylene, Solvesso #100, Solvesso #150, etc., aliphatic hydrocarbon-based organic solvents such as hexane, methylcyclohexane, heptane, octane, decane, etc., and various ester-based organic solvents such as methyl acetate, ethyl acetate, isopropyl acetate, normal propyl acetate, butyl acetate, amyl acetate, ethyl formate, butyl propionate, etc. can be mentioned. In addition, as water-miscible organic solvents, alcohol-based ones such as methanol, ethanol, propanol, butanol, isopropyl alcohol, etc., ketone-based ones such as acetone, methyl ethyl ketone, cyclohexanone, etc., and various glycol ether-based organic solvents such as ethylene glycol (mono, di) methyl ether, ethylene glycol (mono, di) ethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, monobutyl ether, diethylene glycol (mono, di) methyl ether, diethylene glycol (mono, di) ethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, triethylene glycol (mono, di) methyl ether, propylene glycol (mono, di) methyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol (mono, di) methyl ether, etc. can be mentioned. These can be used alone or in a mixture of two or more.

[0033] In addition, from the perspectives of both work hygiene during printing and the harmfulness of packaging materials, it is more preferable to use ethyl acetate, propyl acetate, isopropanol, normal propanol, etc., and not to use aromatic solvents such as toluene and ketone-based solvents such as methyl ethyl ketone. Among them, from the perspective of solubility in polyurethane resin and nitrocellulose, a mixed solution of isopropyl alcohol / ethyl acetate / methoxypropanol is more preferable. Also, glycol ethers can be added if it is less than 10% by mass of the total ink amount for drying adjustment.

[0034] (Colorant) The printing ink in the present invention contains a colorant used for design printing or the like for the purpose of imparting cosmetic properties or the like as a coloring material. Examples of the colorant include inorganic pigments, organic pigments, and dyes used in general inks, paints, and recording agents, and pigments are preferred.

[0035] Examples of the organic pigment include pigments such as soluble azo-based, insoluble azo-based, azo-based, phthalocyanine-based, halogenated phthalocyanine-based, anthraquinone-based, ansanthrone-based, dianthraquinonyl-based, anthrapyrimidine-based, perylene-based, perinone-based, quinacridone-based, thioindigo-based, dioxazine-based, isoindolinone-based, quinophthalone-based, azomethine azo-based, flavanthrone-based, diketopyrrolopyrrole-based, isoindoline-based, indanthrone-based, carbon black-based, etc. Further, for example, carmine 6B, lake red C, permanent red 2B, disazo yellow, pyrazolone orange, carmine FB, chromophthal yellow, chromophthal red, phthalocyanine blue, phthalocyanine green, dioxazine violet, quinacridone magenta, quinacridone red, indanthrone blue, pyrimidine yellow, thioindigo Bordeaux, thioindigo magenta, perylene red, perinone orange, isoindolinone yellow, aniline black, diketopyrrolopyrrole red, daylight fluorescent pigment, etc. can be mentioned. Also, either unacid-treated pigment or acid-treated pigment can be used.

[0036] Examples of inorganic pigments include white inorganic pigments such as titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, lithopone, antimony white, and gypsum. Among the inorganic pigments, the use of titanium oxide is particularly preferred. Titanium oxide exhibits white color and is preferred in terms of coloring power, hiding power, chemical resistance, and weather resistance. From the perspective of printing performance, it is preferred that the titanium oxide is treated with silica and / or alumina. Examples of inorganic pigments other than white ones include, for example, aluminum particles, mica, bronze powder, chrome vermilion, lead yellow, cadmium yellow, cadmium red, ultramarine, dark blue, red iron oxide, iron black, and zircon. Aluminum is in the form of powder or paste, but it is preferably used in the form of paste from the viewpoints of handleability and safety. Whether to use leafing or non-leafing is appropriately selected from the viewpoints of brightness and density.

[0037] The above pigments are preferably contained in an amount sufficient to ensure the density and coloring power of the printing ink, that is, in a proportion of 1 to 60% by mass based on the total mass of the liquid printing ink and 10 to 90% by mass in terms of the solid content weight ratio in the liquid printing ink. These pigments can be used alone or in combination of two or more.

[0038] The printing ink in the present invention can further contain, if necessary, extender pigments, leveling agents, defoaming agents, plasticizers, infrared absorbers, ultraviolet absorbers, fragrances, flame retardants, and the like.

[0039] The printing ink in the present invention can be produced by dissolving and / or dispersing a binder resin, pigments, etc. in an organic solvent. Specifically, a pigment dispersion in which pigments are dispersed in an organic solvent by a binder resin is produced, and the obtained pigment dispersion is blended with other compounds, etc. as necessary to produce the ink.

[0040] The particle size distribution of the pigment in the pigment dispersion can be adjusted by appropriately adjusting the size of the grinding media of the disperser, the filling rate of the grinding media, the dispersion treatment time, the discharge rate of the pigment dispersion, the viscosity of the pigment dispersion, etc. As the disperser, generally used ones such as a roller mill, a ball mill, a pebble mill, an attritor, a sand mill, etc. can be used. When the ink contains bubbles or unexpectedly large particles, etc., it is preferable to remove them by filtration or the like in order to reduce the print quality. As the filter, a conventionally known one can be used.

[0041] The viscosity of the ink produced by the above method is preferably in the range of 10 mPa·s or more from the viewpoint of preventing the sedimentation of the pigment and dispersing it appropriately, and 1000 mPa·s or less from the viewpoint of the workability efficiency during ink production or printing. The above viscosity is the viscosity measured at 25 °C with a B-type viscometer manufactured by Tokimec Co., Ltd. The viscosity of the ink can be adjusted by appropriately selecting the types and amounts of the raw materials used, the binder resin, the pigment, the organic solvent, etc. Also, the viscosity of the ink can be adjusted by adjusting the particle size and particle size distribution of the pigment in the ink.

[0042] The printing ink in the present invention belongs to so-called liquid printing ink, and is useful as an ink for gravure printing using a gravure printing plate such as an electron engraved intaglio plate, or for flexographic printing using a flexographic printing plate such as a resin plate. The printing inks A and B used in the foaming laminate of the present invention are made into a printed matter by once closely adhering and transferring the printing ink to a printing plate or a printing pattern, and then closely adhering only the ink to the base material again and drying it as necessary. The film thickness of the printing ink formed from the gravure printing method or the flexographic printing method using the printing inks A and B used in the foaming laminate of the present invention is, for example, 10 μm or less, preferably 5 μm or less.

Examples

[0043] The present invention will be described more specifically by way of examples. Hereinafter, "parts" and "%" are both based on mass. In addition, the measurement of the weight average molecular weight (polystyrene conversion) by GPC (gel permeation chromatography) in the present invention was carried out under the following conditions using an HLC8220 system manufactured by Tosoh Corporation. Separation column: 4 TSKgel GMHHR-N columns manufactured by Tosoh Corporation were used. Column temperature: 40 °C. Mobile phase: Tetrahydrofuran manufactured by Wako Pure Chemical Industries, Ltd. Flow rate: 1.0 ml / min. Sample concentration: 0.4 mass%. Sample injection volume: 100 microliters. Detector: Differential refractometer. The viscosity was measured at 25 °C using a B-type viscometer manufactured by Tokimec. In addition, the measurement of the glass transition temperature (Tg) was carried out by scanning using a differential scanning calorimeter ("DSC Q100" manufactured by TA Instruments, Inc.) under a nitrogen atmosphere, with a temperature range of -80 to 450 °C and a heating rate of 10 °C / min using a cooling device.

[0044] (Preparation of polyurethane resin solution Pu) 264.20 parts of a polyester polyol having a number average molecular weight of 5100 obtained from adipic acid and 3-methyl-1,5-pentanediol were charged into a 1-liter four-necked flask equipped with a stirrer, a thermometer, a Dimroth-type reflux condenser, and a nitrogen gas inlet tube. Nitrogen gas was passed through, and the temperature was raised to 50 °C while stirring. Subsequently, 28.01 parts of isophorone diisocyanate were added, and the reaction was carried out at 90 °C until the residual rate of isocyanate groups, NCO%, reached 1.99%. After cooling, 157.34 parts of n-propyl acetate were added to obtain a urethane prepolymer solution (B2) having isocyanate groups at the terminals. Subsequently, 10.96 parts of 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 1.37 parts of monoethanolamine, 411.00 parts of n-propyl acetate, 142.00 parts of n-propyl alcohol, and 449.55 parts of urethane prepolymer solution (B2) were added to a 1-liter four-necked flask equipped with a stirrer, a thermometer, a Dimroth condenser, and a nitrogen gas inlet tube, and reacted at 45 °C for 4 hours to obtain a polyurethane resin solution Pu having a solid content of 30% and a weight average molecular weight of 48,000.

[0045] (Preparation of vinyl chloride-vinyl acetate copolymer resin solution Ev) A vinyl chloride-vinyl acetate copolymer resin having a hydroxyl group (resin monomer composition: vinyl chloride / vinyl acetate / vinyl alcohol = 92 / 3 / 5 by mass%, hydroxyl value (mgKOH) = 64) was made into a 25% solution with methyl ethyl ketone, and this was used as the vinyl chloride-vinyl acetate copolymer resin solution Ev.

[0046] (Preparation of nitrocellulose resin solution N) To 37.5 parts of industrial nitrocellulose L1 / 8 (nitrocellulose, solid content 30%, viscosity at a solution concentration of 25.0% according to JIS K-6703: 1.6 to 2.9% product, manufactured by Taihei Chemical Products Co., Ltd.), 62.5 parts of a mixed solution of isopropyl alcohol / ethyl acetate / n-propyl acetate (ratio of 40 / 30 / 30 by mass) was added and thoroughly mixed to prepare a nitrocellulose resin solution N.

[0047] [Ink Production Example 1] 30 parts of the solid content of the obtained vinyl chloride-vinyl acetate copolymer resin Ev, 3 parts of rosin-modified maleic acid, 60 parts of titanium oxide R-830 (manufactured by Ishihara Sangyo Co., Ltd.), 3 parts of titanium acetylacetonate, 4 parts of polyethylene wax / amide wax = 2 / 1, and 200 parts of a total of 300 parts consisting of the solvents contained in each resin and the adjusting solvent methyl ethyl ketone / n-propyl acetate = 50 / 50 (mass ratio) were kneaded in a bead mill to prepare a white gravure printing ink.

[0048] [Ink Production Examples 2 to 6, Production Comparative Examples 1 to 6] According to the composition of Table 1, gravure printing inks of Production Examples 2 to 6 and Production Comparative Examples 1 to 6 were prepared in the same manner as in Production Example 1 of the ink.

[0049] Table 1 shows the compositions of Ink Production Examples 1 to 6 and Production Comparative Examples 1 to 6. The blanks indicate non-formulation.

[0050]

Table 1

[0051] 〔Example 1〕 Using a gravure proofing machine equipped with a gravure plate with a plate depth of 35 μm, the white gravure printing ink prepared in Production Example 1 was printed on a foamed polyethylene base paper in which a polyethylene film with a melting point of 133 °C was laminated on one side of the paper base paper and a polyethylene film with a melting point of 106 °C was laminated on the other side, in a solid pattern of 240 mm in length and 80 mm in width on the polyethylene film with a melting point of 106 °C to form a printing layer A. Then, it was heat-treated in a constant temperature bath at 120 °C for 5 minutes to foam the polyethylene film with a melting point of 106 °C, and a foaming laminate was obtained.

[0052] 〔Examples 2 to 3, 5, 6, Comparative Examples 1 to 6〕 Regarding Examples 2 to 3, 5, 6, and Comparative Examples 1 to 6, using the white gravure printing ink prepared in each production example, a foaming laminate was obtained in the same manner as in Example 1.

[0053] 〔Example 4〕 Regarding Example 4, using a gravure proofing machine equipped with a gravure plate with a plate depth of 35 μm, the white gravure printing ink obtained in Production Example 2 was printed on the foamed polyethylene base paper in a solid pattern of 240 mm in length and 80 mm in width on the polyethylene film with a melting point of 106 °C to form a printing layer A. Then, the blue gravure printing ink obtained in Production Example 4 was overprinted on the printing layer A in a solid pattern of 30 mm in length and 30 mm in width and 10-point character line drawing data to form a printing layer B. Then, it was heat-treated in a constant temperature bath at 120 °C for 5 minutes to foam the polyethylene film with a melting point of 106 °C, and a foaming laminate was obtained.

[0054] For the foaming laminate by single-color printing of the obtained white gravure printing ink and the foaming laminate by overprinting of white gravure printing ink / blue gravure printing ink, the foaming property, smoothness, scratch resistance, and alcohol resistance after molding processing were evaluated respectively.

[0055] 〔Evaluation item 1: Foaming property〕 For the obtained foaming laminate, the foaming property was evaluated in five grades by visual inspection and touch. (Evaluation criteria) 5: Foaming is sufficient. 4: Foaming occurs. 3: Foaming occurs to an extent that it can be used. 2: Foaming is slightly insufficient. 1: Foaming is insufficient.

[0056] 〔Evaluation item 2: Smoothness〕 For the obtained foaming laminate, the step difference between the polyethylene film laminate (melting point 106°C) serving as the base of the printed surface after heat treatment, the foaming layer, and the printing layer A (white ink layer), and the step difference between the printing layer A (white ink layer) and the printing layer B (blue ink layer) were felt by touch, and the smoothness was evaluated in five grades based on the size of the step difference. (Evaluation criteria) 5: No step difference is felt between the foaming layer of the base and the printing layer A, or between the printing layer A and the printing layer B. 4: A slight step difference is felt between the foaming layer of the base and the printing layer A, or between the printing layer A and the printing layer B. 3: The step difference between the foaming layer of the base and the printing layer A, or between the printing layer A and the printing layer B is felt to an acceptable extent. 2: A large step difference is felt between the foaming layer of the base and the printing layer A, or between the printing layer A and the printing layer B. 1: A very large step difference is felt between the foaming layer of the base and the printing layer A, or between the printing layer A and the printing layer B.

[0057] 〔Evaluation item 3: Scratch resistance〕 For the obtained foaming laminate, it was scratched with a sapphire needle of a Clements type scratching tester (Toyosha Seiki) under a load of 100 g, and the state of the coating film was evaluated. (Evaluation criteria) 5: The film does not peel off after 4 times. 4: The film peels off after 4 times. 3: The film peels off after 3 times. 2: The film peels off after 2 times. 1: The film peels off after 1 time.

[0058] 〔Evaluation Item 4: Alcohol Resistance〕 Regarding the obtained foamed laminate, using a Kagaku-Shinko type friction tester (Toyosyoki), a mixed solution of ethanol / water = 80 / 20 was used to wet a cotton cloth, and it was reciprocated 5 times with a load of 200 g to evaluate the state of ink pickup of the coating film. (Evaluation Criteria) 5: No ink is picked up. 4: The ink pickup is less than 10%. 3: The ink pickup is 10% or more and less than 50%. 2: The ink pickup is 50% or more and less than 80%. 1: The ink pickup is 80% or more.

[0059] The evaluation results are shown in Table 2.

[0060]

Table 2

[0061] As a result, the foamed laminate of the present invention was excellent in the balance of foamability, smoothness, scratch resistance, and alcohol resistance.

Claims

1. A foaming material having a base paper, a first resin layer covering one surface of the base paper, and a second resin layer covering the other surface of the base paper, having a melting point lower than that of the first resin layer and foaming by heat treatment, wherein a printing layer is included on the surface of the second resin layer, The foaming laminate is characterized in that the printing layer contains a printing pattern of printing ink satisfying (1) and (2). (1) It has printing ink A that forms at least a printing layer A in contact with the surface of the second resin layer. (2) The printing ink A contains a coloring material, a polyurethane resin, a vinyl chloride-vinyl acetate copolymer, a plasticizer, and a chelating agent, and the mass mixing ratio of the polyurethane resin to the vinyl chloride-vinyl acetate copolymer is 49:50 to 1:99, and the plasticizer is contained in an amount of 1 to 20% by mass based on the total solid content of the printing ink A.

2. The foaming laminate according to claim 1, wherein printing ink B that forms a printing layer B provided on the surface of the printing layer A formed by the printing ink A satisfies (3). (3) The printing ink B contains a coloring material, a polyurethane resin, a vinyl chloride-vinyl acetate copolymer, and a plasticizer, and the mass mixing ratio of the polyurethane resin to the vinyl chloride-vinyl acetate copolymer is 49:50 to 1:99, and the plasticizer is contained in an amount of 1 to 20% by mass based on the total solid content of the printing ink A.

3. The foaming laminate according to claim 1, wherein the plasticizer is castor oil, epoxidized soybean oil, or tributyl acetylcitrate.

4. The foaming laminate according to claim 1, wherein the printing ink A contains a rosin-based resin.

5. The foaming laminate according to claim 2, wherein the printing ink B contains a rosin-based resin.

6. A heat-insulating container using the foaming laminate according to any one of claims 1 to 5.

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