Laminate

Abstract

To provide a laminate which satisfies all performance required for use in wrapping food products, including water resistance, oil resistance, seasoning resistance, blocking resistance, and a microwave oven resistance and which has an excellent food flavor retention property.SOLUTION: Provided is a laminate comprising a coating layer on at least one surface of a paper substrate. The coating layer (L) comprises a polymer (A) comprising an ethylenic unsaturated monomer (a), a wax (B), and a silicone-based antifoamer (C). The wax (B) comprises a paraffin wax (b1) and / or a polyethylene wax (b2) and, based on 100 pts.mass of the coating layer (L), a total content of the paraffin wax (b1) and the polyethylene wax (b2) is 0.1 to 10 pts.mass. A coating weight of the coating layer is 0.5 to 10 g / m2. The laminate has an air shielding property of 20 kPa or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminate. [Background technology]

[0002] There are various methods for simply packaging food, one of which is to use a laminate containing paper. In this case, a laminate is used instead of a paper substrate alone because a typical paper substrate cannot prevent the penetration of water or oil, and the moisture and oil in the food will seep out of the packaging, staining hands and reducing the strength of the packaging itself. Therefore, it is necessary to laminate a water-resistant and oil-resistant layer onto the paper substrate. Polyethylene is often used as this water-resistant and oil-resistant layer, and laminates in which polyethylene is laminated onto a paper substrate have been widely used.

[0003] In recent years, paper recycling has been accelerating due to the global trend toward reducing environmental impact. However, the polyethylene-laminated laminates described above require expensive capital investment to remove the polyethylene film layer during the paper recycling process, making them difficult to recycle and hindering the promotion of recycling. Against this background, laminates in which a coating agent is applied to a paper substrate are being actively studied as laminates that are easier to recycle. For example, Patent Documents 1, 2 and 3 disclose laminates formed by applying a coating agent containing an aqueous acrylic resin emulsion to a paper substrate in order to impart oil resistance and water resistance to the paper substrate.

[0004] Food packaging applications require laminates with various functions. In addition to water resistance and oil resistance to minimize the penetration of moisture and oil contained in food, condiments such as ketchup and sauce, which contain multiple ingredients such as water, oil, salt, acid, and amino acids, are more likely to penetrate than simple water or oil. Therefore, resistance to the penetration of these condiments (hereinafter referred to as "condiment resistance") is required. Blocking resistance is also required so that laminates can be stacked and stored and then removed one by one when packaging food. Furthermore, after packaging food and taking it home, the food may be heated in a microwave oven. Therefore, even if the food is reheated in a microwave oven and exposed to oil or steam at high temperatures, it is necessary for the laminate to resist penetration of water or oil and prevent food from sticking to the laminate (hereinafter referred to as "microwave resistance"). Conventional laminates have struggled to satisfy all of these various performance requirements at once.

[0005] Furthermore, the inventors thought that, in addition to these functions, by imparting a function of trapping the food aroma and preventing it from permeating, the flavor of the food can be felt more strongly when eating, thereby providing a high-value-added laminate. However, the idea of ​​trapping the food aroma in a laminate having a paper base material and maintaining the deliciousness for a long period of time had not been conceived, and it was difficult to design a laminate with such a function. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-303475 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-241716 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-214250 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a laminate that satisfies all of the performance requirements required for food packaging applications, such as water resistance, oil resistance, seasoning resistance, blocking resistance, and microwave resistance, and that also has excellent food aroma retention properties. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. That is, the present invention provides a paper substrate having a coating layer (L) on at least one surface thereof, the coating layer (L) comprising a polymer (A) composed of an ethylenically unsaturated monomer (a), a wax (B), and a silicone antifoaming agent (C), the wax (B) comprising a paraffin wax (b1) and / or a polyethylene wax (b2), the total content of the paraffin wax (b1) and the polyethylene wax (b2) being 0.1 to 10 parts by mass based on 100 parts by mass of the coating layer (L), and the coating weight of the coating layer (L) being 0.5 to 10 g / m 2 and the laminate has an air barrier property of 20 kPa or less.

[0009] The present invention relates to the laminate described above, which contains 0.005 to 1 part by mass of a silicon-based antifoaming agent (C) based on 100 parts by mass of the coating layer (L).

[0010] The present invention relates to the laminate, wherein the aromatic ethylenically unsaturated monomer (a-1) is contained in an amount of 35 to 80 parts by mass based on 100 parts by mass of the ethylenically unsaturated monomer (a).

[0011] The laminate satisfies all of the performance requirements for food packaging, such as water resistance, oil resistance, seasoning resistance, blocking properties, and microwave resistance, and further has excellent air barrier properties. After extensive research, the inventors have found that a laminate with excellent air barrier properties also has excellent food aroma retention properties. In other words, the laminate satisfies all of the performance requirements for water resistance, oil resistance, seasoning resistance, blocking properties, and microwave resistance, and has excellent food aroma retention properties. [Effects of the Invention]

[0012] The laminate of the present invention satisfies all of the performance requirements for food packaging, such as water resistance, oil resistance, seasoning resistance, blocking resistance, and microwave resistance, and further provides a laminate that is excellent in retaining the aroma of food. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a front view of an air barrier property measuring device according to the present invention. [Figure 2] FIG. 2 is a plan view of a glass filter in the air barrier property measuring device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below. Needless to say, other embodiments are also included within the scope of the present invention as long as they are consistent with the spirit of the present invention. Furthermore, in this specification, a numerical range specified using "to" includes the numerical values ​​before and after "to" as the lower and upper limit values ​​of the range. Furthermore, in this specification, "film" and "sheet" are not distinguished by thickness. In other words, in this specification, "sheet" includes thin film-like materials, and "film" includes thick sheet-like materials. Unless otherwise noted, the various components appearing in this specification may be used independently either alone or in combination of two or more.

[0015] In this specification, unless otherwise specified, the terms "(meth)acrylic acid" and "(meth)acrylate" refer to "acrylic acid or methacrylic acid" and "acrylate or methacrylate," respectively. Furthermore, "(meth)acrylic acid ester monomer" is a general term for "acrylic acid ester monomer" and "methacrylic acid ester monomer." The monomer refers to an ethylenically unsaturated double bond-containing monomer.

[0016] <Laminate> The laminate of the present invention is obtained by applying a coating liquid to a paper substrate and drying the applied coating liquid to form a coating layer (L), and the coating layer (L) is provided on at least one side of the paper substrate. By forming such a laminate, the paper substrate can be endowed with various properties, such as water resistance, oil resistance, seasoning resistance, and blocking resistance. The laminate of the present application can be particularly suitable for use in forming a sheet for packaging food (hereinafter referred to as a food packaging sheet), and can also be used in applications where the coating layer comes into direct contact with food.

[0017] <Paper base material> The paper base material is obtained by papermaking a paper stock containing pulp, fillers, various auxiliaries, etc. That is, the paper support used in the present invention is not particularly limited, and examples thereof include bleached or unbleached kraft paper (acid paper or neutral paper), fine paper, medium-quality paper, lightly coated paper, coated paper, paperboard, white paperboard, liner, semi-glassine paper, glassine paper, one-sided glazed paper, parchment paper, etc. Any type of paper commercially available for food packaging can be used. The basis weight of the paper base material is 5 to 100 g / m 2 is preferable, and 10 to 50 g / m 2 is preferable, and 15 to 30 g / m 2 When the basis weight is in this range, a uniform coating film without unevenness can be formed on the substrate, and the printing speed can be improved, thereby increasing productivity.

[0018] ≪Coating layer (L)≫ The coating layer (L) can be formed by applying a coating liquid containing a polymer (A) made of an ethylenically unsaturated monomer (a), a wax (B), and a silicone antifoaming agent (C) to a paper substrate and drying the coating liquid. The coating liquid may be water-based or solvent-based, but is preferably water-based from the viewpoints of environmental impact and safety when in contact with food.

[0019] <Polymer (A) composed of ethylenically unsaturated monomer (a)> The polymer (A) (hereinafter also referred to simply as polymer (A)) made of the ethylenically unsaturated monomer (a) can be obtained by polymerizing the ethylenically unsaturated monomer (a) in water or a solvent using a radical polymerization initiator according to a conventional method. The polymerization method is not particularly limited, but emulsion polymerization is preferably used because it allows for the easy production of a resin dispersion with a high molecular weight, low viscosity, and high solid content in an aqueous medium.

[0020] (Radical polymerization initiator) As the radical polymerization initiator used in the polymerization reaction of the ethylenically unsaturated monomer (a), a known oil-soluble polymerization initiator or water-soluble polymerization initiator can be used, and these may be used alone or in combination of two or more. The radical polymerization initiator is preferably used in an amount of 0.1 to 4 parts by mass, more preferably 0.2 to 2 parts by mass, based on 100 parts by mass of the total amount of the ethylenically unsaturated monomer (a).

[0021] The oil-soluble polymerization initiator is not particularly limited, and examples thereof include organic peroxides such as benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl hydroperoxide, tert-butyl peroxy(2-ethylhexanoate), tert-butyl peroxy-3,5,5-trimethylhexanoate, di-tert-butyl peroxide, and dilauroyl peroxide; Examples include azobis compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), and 1,1'-azobis-cyclohexane-1-carbonitrile.

[0022] In emulsion polymerization, it is preferable to use a water-soluble polymerization initiator. As the water-soluble polymerization initiator, for example, conventionally known ones such as ammonium persulfate (APS), sodium persulfate (NPS), potassium persulfate (KPS), hydrogen peroxide, and 2,2'-azobis(2-methylpropionamidine) dihydrochloride can be suitably used.

[0023] (reducing agent) In emulsion polymerization, a reducing agent may be used in combination with the polymerization initiator. The use of a reducing agent in combination accelerates the emulsion polymerization rate and facilitates emulsion polymerization at low temperatures. Examples of the reducing agent include reducing organic compounds such as ascorbic acid, erythorbic acid, tartaric acid, citric acid, glucose, formaldehyde sulfoxylate, Rongalite, and metal salts of thiourea dioxide; Reducing inorganic compounds such as sodium thiosulfate, sodium sulfite, sodium bisulfite, sodium metabisulfite, and ferrous chloride; Examples include: These reducing agents are preferably used in an amount of 0.05 to 5 parts by mass based on 100 parts by mass of the total amount of the ethylenically unsaturated monomer (a).

[0024] The polymerization temperature may be equal to or higher than the polymerization initiation temperature of the polymerization initiator, and for example, when a peroxide-based polymerization initiator is used, the polymerization temperature is usually about 80°C. The polymerization time is not particularly limited, but is usually 2 to 24 hours. The ethylenically unsaturated monomer (a) may be polymerized by photochemical reaction or radiation irradiation without using the above-mentioned polymerization initiator.

[0025] (buffering agent) In the polymerization of the ethylenically unsaturated monomer (a), a buffer may be further used as needed. Examples of the buffer include sodium acetate, sodium citrate, and sodium bicarbonate. The buffer is preferably used in an amount of 0 to 1 part by mass, more preferably 0.05 to 0.5 parts by mass, based on 100 parts by mass of the total amount of the ethylenically unsaturated monomer (a).

[0026] (basic compounds) During the polymerization of the ethylenically unsaturated monomer (a), a basic compound may be used as a neutralizing agent to enhance the stability of the polymer (A). Examples of the basic compound include aqueous ammonia; Various organic amines such as dimethylaminoethanol, diethanolamine, and triethanolamine; Inorganic alkaline agents such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide; However, from the viewpoint of water resistance, aqueous ammonia is preferred.

[0027] <Ethylenically unsaturated monomer (a)> Examples of the ethylenically unsaturated monomer (a) include aromatic ethylenically unsaturated monomers (a-1), carboxyl group-containing ethylenically unsaturated monomers (a-2), alkyl group-containing ethylenically unsaturated monomers having 1 to 8 carbon atoms (a-3), and other ethylenically unsaturated monomers (a-4).

[0028] Examples of the aromatic ethylenically unsaturated monomer (a-1) include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, vinylnaphthalene, benzyl acrylate, benzyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenoxydiethylene glycol acrylate, phenoxydiethylene glycol methacrylate, phenoxytetraethylene glycol acrylate, phenoxytetraethylene glycol methacrylate, phenoxyhexaethylene glycol acrylate, phenoxyhexaethylene glycol methacrylate, phenyl acrylate, and phenyl methacrylate.

[0029] In 100 parts by mass of the ethylenically unsaturated monomer (a), 35 to 80 parts by mass of the aromatic ethylenically unsaturated monomer (a-1) Mass part It is preferable that the content is 45 to 75 Mass part , more preferably 50 to 70 Mass part By being in this range, a coating film with excellent microwave resistance can be formed. The reason why the aromatic ethylenically unsaturated monomer (a-1) improves microwave resistance is thought to be that it can maintain a hard film even when the temperature rises in a microwave oven, and because it is hydrophobic, it is less likely to absorb moisture or swell, which prevents water and oil from penetrating and food from sticking during microwave cooking.

[0030] Examples of the carboxy group-containing ethylenically unsaturated monomer (a-2) include maleic acid (including anhydride), fumaric acid, itaconic acid, citraconic acid, or alkyl or alkenyl monoesters thereof, hexahydrophthalic acid β-(meth)acryloxyethyl monoester, succinic acid β-(meth)acryloxyethyl monoester, acrylic acid, methacrylic acid, crotonic acid, and cinnamic acid.

[0031] Examples of the alkyl group-containing ethylenically unsaturated monomer (a-3) having 1 to 8 carbon atoms include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, heptyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and octyl (meth)acrylate.

[0032] Other ethylenically unsaturated monomers (a-4) include, for example, alicyclic alkyl group-containing ethylenically unsaturated monomers such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate; (Meth)acrylamide, N-methoxymethyl-(meth)acrylamide, N-ethoxymethyl-(meth)acrylamide, N-propoxymethyl-(meth)acrylamide, N-butoxymethyl-(meth)acrylamide, N-pentoxymethyl-(meth)acrylamide, N,N-di(methoxymethyl)acrylamide, N-ethoxymethyl-N-methoxymethyl(meth)acrylamide, N,N-di(ethoxymethyl)acrylamide, N-ethoxymethyl-N-propoxymethyl(meth)acrylamide, N,N-di(propoxymethyl)acrylamide Amide group-containing ethylenically unsaturated monomers such as acrylamide, N-butoxymethyl-N-(propoxymethyl)acrylamide, N,N-di(butoxymethyl)acrylamide, N-butoxymethyl-N-(methoxymethyl)(meth)acrylamide, N,N-di(pentoxymethyl)acrylamide, N-methoxymethyl-N-(pentoxymethyl)(meth)acrylamide, N,N-dimethylaminopropylacrylamide, N,N-diethylaminopropylacrylamide, N,N-dimethylacrylamide, and N,N-diethylacrylamide; Hydroxyl group-containing ethylenically unsaturated monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycerol mono(meth)acrylate, 4-hydroxyvinylbenzene, 1-ethynyl-1-cyclohexanol, and allyl alcohol; Allyl (meth)acrylate, 1-methylallyl (meth)acrylate, 2-methylallyl (meth)acrylate, 1-butenyl (meth)acrylate, 2-butenyl (meth)acrylate, 3-butenyl (meth)acrylate, 1,3-methyl-3-butenyl (meth)acrylate, 2-chloroallyl (meth)acrylate, 3-chloroallyl (meth)acrylate, o-allylphenyl (meth)acrylate, 2-(allyloxy)ethyl (meth)acrylate, allyl lactyl (meth)acrylate, citronellyl (meth)acrylate, geranyl (meth)acrylate, rosinyl (meth)acrylate, cinnamyl (meth)acrylate, diallyl maleate, diaryl itaconic acid, vinyl (meth)acrylate Acrylate, vinyl crotonate, vinyl oleate, vinyl linoleate, 2-(2'-vinyloxyethoxy)ethyl (meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol (meth)acrylate, tetraethylene glycol (meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, 1,1,1-trishydroxymethylethane diacrylate, 1,1,1-trishydroxymethylethane triacrylate, 1,1,1-trishydroxymethylpropane triacrylate, divinylbenzene, divinyl adipate, diallyl isophthalate, diallyl phthalate, diallyl maleate, etc. an ethylenically unsaturated monomer having an ethylenically unsaturated group; Epoxy group-containing ethylenically unsaturated monomers such as glycidyl (meth)acrylate and 3,4-epoxycyclohexyl (meth)acrylate; Alkoxysilyl group-containing ethylenically unsaturated monomers such as γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltributoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-acryloxypropylmethyldimethoxysilane, γ-methacryloxymethyltrimethoxysilane, γ-acryloxymethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, and vinylmethyldimethoxysilane; These may be used alone or in combination of two or more.

[0033] <Glass transition temperature (Tg)> The polymer (A) preferably has a glass transition temperature Tg in the low-temperature range of -40 to 45°C and a high-temperature range of 90 to 150°C. The polymer may also have a glass transition temperature Tg outside these temperature ranges. Having a low-temperature Tg in this range improves resistance to seasonings in particular. This is thought to be because the inclusion of a flexible component in the polymer (A) allows the formation of a dense coating film, preventing the penetration of seasonings containing various components. On the other hand, having a high-temperature Tg in this range improves blocking resistance in particular. The lower temperature Tg is more preferably in the range of -35 to 40°C, and even more preferably -10 to 35°C. The higher temperature Tg is more preferably in the range of 100 to 140°C, and even more preferably 110 to 130°C.

[0034] Examples of methods for preparing polymers (A) having different glass transition temperatures (Tg) include multi-stage polymerization in which, during emulsion polymerization, monomers are added dropwise to a reaction system in multiple stages, and the compositions of ethylenically unsaturated monomers are changed and added dropwise so that the Tg of the resulting polymers differs in each stage; and a method in which an acrylic resin is synthesized in advance by bulk polymerization or solution polymerization, dissolved or dispersed in an aqueous phase, and then an ethylenic monomer is added dropwise and polymerized so that a polymer having a Tg different from that of the acrylic resin is produced.

[0035] In the case of two-stage polymerization in which monomers are added dropwise in two stages of multistage polymerization, the monomer added dropwise in the first stage preferably contains a carboxyl group-containing ethylenically unsaturated monomer (a-2). In this case, the stability of the polymer (A) can be enhanced by neutralizing the carboxyl group with the aforementioned basic compound at the end of the first stage polymerization. The monomer added dropwise in the second stage polymerization is then incorporated into the first stage polymer stabilized by neutralization. This results in the formation of particles with a so-called core-shell structure, in which the polymer formed by the first stage monomer exists like a shell around the particles of the polymer formed by the second stage monomer. When the glass transition temperature (Tg) of a polymer (A) with such a structure is measured, different Tg values ​​are observed for the particle and shell portions. The Tg of the shell portion of the polymer (A) (the portion formed by the first stage polymerization) is preferably in the high-temperature range of 90 to 150°C, while the Tg of the core portion (the portion formed by the second stage polymerization) is preferably in the low-temperature range of -40 to 45°C.

[0036] Even when a method is used in which an acrylic resin is synthesized by bulk polymerization or solution polymerization, dissolved or dispersed in an aqueous phase, and then a monomer is added dropwise to polymerize, the monomer used in the bulk polymerization or solution polymerization preferably contains a carboxyl group-containing ethylenically unsaturated monomer (a-2), and the carboxyl group is preferably neutralized with a basic compound. Then, the monomer is added dropwise to polymerize, thereby forming particles with the above-mentioned core-shell structure.

[0037] The glass transition temperature in the present invention refers to the glass transition temperature measured by differential scanning calorimetry (DSC) for a resin obtained by drying the polymer (A) to a nonvolatile content of 100% by mass. Details are described in the Examples section.

[0038] <Acid value> The acid value of the polymer (A) was calculated from the value obtained by subjecting a pre-dried resin to potentiometric titration according to the method described in JIS K2501: 2003. Details are described in the Examples section. The acid value of the polymer (A) is preferably 40 to 120 mgKOH / g, more preferably 60 to 120 mgKOH / g, and even more preferably 70 to 95 mgKOH / g. Having an acid value within this range improves oil resistance. The inventors believe that the polar acidic functional groups exert an effect of preventing oil from penetrating into the coating layer (L), thereby improving oil resistance.

[0039] <Wax (B)> The coating layer (L) contains a wax (B). Examples of waxes include paraffin wax (b1), polyethylene wax (b2), polypropylene wax, amide wax, ethylene / vinyl acetate copolymer wax, and ethylene / acrylic acid copolymer wax. In the present invention, at least one of paraffin wax (b1) and polyethylene wax (b2) is used. The total content of paraffin wax (b1) and polyethylene wax (b2) is 0.1 to 10 parts by weight, more preferably 0.5 to 8 parts by weight, and even more preferably 1 to 6 parts by weight, based on 100 parts by weight of the coating layer. By keeping the content within these ranges, water resistance can be particularly improved without adversely affecting other properties.

[0040] <Silicone-based defoaming agent (C)> The coating layer (L) contains a silicone-based antifoaming agent (C). Antifoaming agents are typically added to coating solutions to suppress foaming, and are typically substances with low surface free energy. If the antifoaming agent used is appropriate, it can suppress foaming during coating, reducing coating film defects due to foaming and improving air barrier properties. At the same time, it also reduces coating film defects due to cissing, which is caused by the antifoaming agent's low surface free energy, improving air barrier properties. After extensive research, the inventors discovered that improved air barrier properties improve the laminate's ability to retain food aromas. Specifically, they discovered that the use of a silicone antifoaming agent (C) improves the laminate's air barrier properties, thereby imparting the laminate with the ability to retain food aromas.

[0041] The silicone-based antifoaming agent (C) used in the present invention may be, for example, an oil type whose components are all silicone oil, an oil compound type in which silica is added to silicone oil, an emulsion type in which an oil or oil compound antifoaming agent is dispersed in water with a surfactant, or a powder (solid) type. Commercially available oil-type products include KF-96 and KF-6701 manufactured by Shin-Etsu Chemical Co., Ltd., DOWSIL SH200 manufactured by Dow-Toray Industries, Inc., and AIRASE5655 and TEGO Foamex840 manufactured by Evonik Industries. Examples of oil compound types include KS-66 and KS-69 manufactured by Shin-Etsu Chemical Co., Ltd., DOWSIL ACP-3073, ACP-3258, and XIAMETER ACP-1500 manufactured by Dow-Toray Industries, Inc., and TEGO Foamex 810, TEGO Foamex 830, TEGO Foamex 832, TEGO Foamex 852, and TEGO Foamex 3062 manufactured by Evonik Industries. Examples of emulsion-type defoamers include KM-70, KM-71, KM-72, KM-75, and KM-85 manufactured by Shin-Etsu Chemical Co., Ltd., DOWSIL SM5571 Emulsion, XIAMETER AFE-1520, and DOWSIL SH5507 Emulsion manufactured by Dow-Toray Industries, Inc., and TEGO Foamex 815N, TEGO Foamex 822, TEGO Foamex 823, TEGO Foamex 825, and TEGO Foamex 1488 manufactured by Evonik Industries, Ltd. Among these, oil-type, oil-compound-type, and emulsion-type defoamers thereof are preferred, and oil-compound-type and emulsion-type defoamers thereof are more preferred.

[0042] The amount of the silicon-based antifoaming agent (C) in the coating layer (L) is preferably 0.005 to 1 part by mass, more preferably 0.075 to 0.5 parts by mass, and even more preferably 0.01 to 0.3 parts by mass, based on 100 parts by mass of the coating layer. By using the amount of the silicon-based antifoaming agent (C) within these ranges, the air barrier properties of the laminate can be further improved.

[0043] <Optional ingredients> The coating layer (L) of the laminate of the present invention can contain additives such as extender pigments, leveling agents, and preservatives as optional components. It is preferable that the optional components do not adversely affect health. When a leveling agent or preservative is contained as an optional component, it is preferable that the leveling agent is contained in an amount of 0.1 to 5 parts by mass and the preservative is contained in an amount of 0.001 to 1 part by mass, based on 100 parts by mass of the coating layer.

[0044] The extender pigment is preferably one approved as a food or food additive. Specific examples include talc, kaolin, bentonite, silica, calcium carbonate, barium sulfate, titanium oxide, diatomaceous earth (white carbon), cellulose powder, etc. When an extender pigment is included as an optional component, it is preferable that the extender pigment be contained in an amount of 1 to 50 parts by mass per 100 parts by mass of the coating layer.

[0045] <Coating amount in laminate> The coating amount of the coating layer (L) in the laminate is the unit area (1 m) after drying. 2 In the present invention, the coating amount of the coating layer (L) is 0.5 to 10 g / m 2 and 1.0 to 8 g / m 2 More preferably, it is 1.5 to 6 g / m 2 It is more preferable that the total coating amount is 0.5 g / m. 2 If the total coating weight is 10 g / m or more, the coating layer will be sufficient to cover the paper substrate, and uneven coating can be prevented. 2 By satisfying the above condition, the manufacturing cost of the laminate can be reduced.

[0046] <Coating method> Conventional methods can be used to apply the coating liquid to the laminate, but flexographic and gravure methods are preferred. The flexographic method involves first transferring the coating material from an intaglio plate called an anilox roll to a resin or rubber plate, and then transferring the coating material from the resin or rubber plate to the base material. It is also possible to pattern the resin or rubber plate. The gravure method includes a method in which the coating material is transferred directly from the intaglio plate to the base material, and a so-called gravure offset method in which the coating material is first transferred from the intaglio plate to a planographic plate and then transferred to the base material. It is also possible to pattern the intaglio plate. In the case of the gravure method, it is preferable to press the coating with a smoothing roll after coating. Of these methods, the flexographic method is more preferred. The flexographic method makes it easier to form a more uniform film on the paper substrate.

[0047] <Air barrier properties> The air barrier property in this application is the value of the degree of vacuum measured using a vacuum device under conditions where the degree of vacuum is 70 kPa when a copy paper is placed in the opening. 2 The hydraulic pump was set so that the degree of vacuum was 70 kPa when copy paper (product name: Multi Paper Super White+, manufactured by Askul Corporation) was placed in the opening, and the value of the degree of vacuum was measured by placing a laminate in the opening. The smaller the value, the higher the degree of airtightness, meaning that a film is formed on the paper base material without any gaps.

[0048] The laminate of the present invention has an air barrier strength of 20 kPa or less, more preferably 10 kPa or less, and even more preferably 5 kPa or less. A laminate with an air barrier strength of 20 kPa or less can retain the aroma components of food without letting them escape. This allows the food to taste better when eaten.

[0049] The air barrier property is measured using the apparatus shown in Figure 1. A glass filter 2 is installed on top of a glass container 1, and a rubber tube 3 is attached to the side of the glass container, to which a hydraulic pump 4 and a vacuum gauge 5 are connected. The hydraulic pump 4 is used to reduce the pressure, and the degree of pressure reduction is measured using the vacuum gauge 5. Only the filter section 6 at the top of the device is allowed to pass air; the rest of the device is completely sealed. The filter section 6 is circular and 4 cm in diameter, and the glass filter section is flat relative to the glass section around the glass filter, with no protrusions or dents. If the glass filter section is not flat, an accurate degree of pressure reduction cannot be measured when the laminate is placed. The laminate 7 is placed on the glass filter section with the coated side facing down, and the degree of pressure reduction is measured; the value obtained is the air barrier property. [Example]

[0050] The present invention will be described in more detail below with reference to examples, but the following examples do not limit the scope of the invention in any way. Unless otherwise specified, "parts" in the examples represent "parts by mass," "%" represents "% by mass," and the values ​​in the tables represent the mass of solid content, with blank spaces indicating that no space is used. The glass transition temperature and acid value of the polymer (A) are measured by the following methods.

[0051] <Glass transition temperature> The glass transition temperature of polymer (A) was measured using a DSC (differential scanning calorimeter, manufactured by TA Instruments). Specifically, an aluminum pan containing approximately 10 mg of dried resin was precisely weighed and placed in it, and an empty aluminum pan serving as a reference was placed in a DSC measurement holder. The pan was rapidly cooled to -100°C in a nitrogen stream, and then heated to 200°C at a rate of 20°C / min, and a DSC curve was plotted. The temperature at the intersection of the baseline on the low-temperature side of the endothermic phenomenon in the DSC curve and the tangent at the inflection point was taken as the glass transition temperature (Tg).

[0052] <Acid value> The acid value of polymer (A) was calculated from the value obtained by potentiometric titration of 0.1 to 5 g of pre-dried resin according to the method described in JIS K2501:2003 (the amount of sample was adjusted depending on the acid value of polymer (A)). Specifically, the sample was dissolved in a titration solvent containing toluene, 2-propanol, and a small amount of water, and potentiometric titration was performed with potassium hydroxide in 2-propanol using a glass electrode and a reference electrode. The relationship between the pH meter reading and the corresponding titration amount of potassium hydroxide in 2-propanol was plotted, and the inflection point on the titration curve was taken as the endpoint. The acid value was calculated using the amount (mL) of potassium hydroxide in 2-propanol used in the titration as described in JIS K2501:2003, "7.8.3 Calculation Method."

[0053] <Synthesis of Polymer (A1)> A reaction vessel (reaction tank) equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 100 parts of propylene glycol methyl ether acetate and heated to 145 ° C. 2 parts of di-t-butyl peroxide as a polymerization initiator, 30 parts of styrene, 30 parts of methyl methacrylate, and 40 parts of methacrylic acid as first-stage monomer components were continuously added over 2 hours. After a further 43 hours of reaction, the solvent was removed by vacuum distillation, and 31.6 parts of 25% aqueous ammonia and water were added to adjust the nonvolatile content, resulting in an aqueous solution of polymer (A1') with a nonvolatile content of 40%. A separate reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube was charged with 20 parts of water and 107.1 parts of the polymer (A1') solution and heated to 70 ° C. 0.43 parts of ammonium persulfate was added as a polymerization initiator, and an emulsion prepared by emulsifying 30 parts of styrene, 14 parts of methyl methacrylate, 56 parts of 2-ethylhexyl acrylate, and 58.6 parts of water as second-stage reaction monomer components in an emulsifier was continuously added over 2 hours under a nitrogen stream, and the reaction was continued for a further 3 hours to polymerize, yielding an emulsion solution of polymer (A1) with a nonvolatile content of 48.5%, a high-temperature Tg of 113°C, a low-temperature Tg of -6°C, and an acid value of 78.2 mgKOH / g.

[0054] <Synthesis of polymers (A2) to (A17)> Polymers (A2) to (A17) were prepared in the same manner as for polymer (A1), except that in preparing polymer (A1), the monomer components in the first reaction step, the parts by mass of 25% ammonia water, and the monomer components in the second reaction step were replaced with the amounts shown in Table 1, and emulsion solutions of each polymer were obtained. The acid value, high-temperature Tg, and low-temperature Tg of each polymer are shown in Table 1.

[0055] [Table 1]

[0056] <Wax (B)> The following waxes were used as wax (B): Paraffin wax (b1-1): Dispersion of paraffin wax with a melting point of 60°C dispersed in water (non-volatile content 30%) Paraffin wax (b1-2): Dispersion of modified paraffin with a melting point of 90°C in water (non-volatile content 30%) Polyethylene wax (b2-1): A water dispersion of polyethylene with a melting point of 125°C and a non-volatile content of 30% Polyethylene wax (b2-2): A water dispersion of polyethylene with a melting point of 110°C and a non-volatile content of 30%

[0057] <Other Waxes (X)> Polypropylene wax (x1): A water dispersion of polypropylene with a melting point of 160°C and a non-volatile content of 20% Polytetrafluoroethylene wax (x2): A water dispersion of polytetrafluoroethylene with a melting point of 321°C and a non-volatile content of 20%

[0058] <Silicone-based antifoaming agent (C)> The following silicone antifoaming agents (C) were used: Emulsion-type silicone antifoaming agent (c1): An emulsion containing 20% ​​polysiloxane (oil type) and 2% surfactant, with a non-volatile content of 22%. Compound type silicone defoamer (c2): A compound type silicone defoamer containing polysiloxane (oil type) and fumed silica, with a non-volatile content of 100%.

[0059] <Production of coating fluid> [Manufacturing Example 1] The polymer (A1) solution, the water dispersion of paraffin wax (b1-1), and the compound type silicone antifoaming agent (c2) were mixed so that the mass ratio of the nonvolatile content of each was 95.9:4:0.1, and the mixture was stirred uniformly using a disperser. Water was then added so that the nonvolatile content of the coating liquid was 43%, to give coating liquid 1. (The nonvolatile content ratio is also shown in Table 2.)

[0060] [Manufacturing Examples 2-47, 49-50] Coating Liquids 2 to 47 and 49 to 50 were obtained in the same manner as in Production Example 1, except that the blending compositions were changed as shown in Tables 2, 3 and 4.

[0061] [Manufacturing Example 48] Water was added to the polymer (A6) solution so that the nonvolatile content was 43%, to prepare coating liquid 48.

[0062] [Table 2]

[0063] [Table 3]

[0064] [Table 4]

[0065] <Preparation of laminate> [Example 1] Coating liquid 1 was applied to the glossy side of commercially available sanitary paper (21 g weight, gloss-treated on one side) at a coating speed of 150 m / min using a Windmiller & Hoelscher "SOLOFLEX" central impression (CI) type 6-color flexographic printing press. Two separate units, each with a capacity of 7 cc, were used to apply the coating twice to the glossy side. The result was then dried in an oven at 80°C to obtain laminate 1. The coating weight of the coating layer (L) in laminate 1 was measured to be 2 g / m. 2 It was.

[0066] [Example 2~ 7、10~ 37, Reference examples 8, 9, Comparative Examples 1 to 13 Each laminate was produced in the same manner as in Example 1 except that coating liquids 2 to 50 shown in Tables 5, 6 and 7 were used. However, in Table 5, examples described as Example 8 and Example 9 refer to Reference Example 8 and Reference Example 9, respectively.

[0067] Evaluation items and evaluation methods The evaluation items and evaluation methods for the laminate are as follows.

[0068] <Oil resistance test> A drop of castor oil was dropped onto the coating layer (L) of the resulting laminate in an environment of 23°C, and after 30 seconds, it was confirmed whether the castor oil had soaked into the laminate. Evaluation was made based on the percentage of the area onto which the castor oil had soaked and discolored the paper. [Evaluation criteria] 5: No penetration at all (very good) 4: Less than 10% of the area has been soaked (good) 3: The area soaked is between 10% and 30% (fairly good) 2: The area soaked is between 30% and 50% (usable) 1: Over 50% of the surface area is saturated (very poor)

[0069] <Blocking resistance test> The surface of the coating layer (L) of the obtained laminate was placed on the surface of the paper substrate in an environment of 23°C, and the blocking resistance was evaluated using the following device and conditions. Equipment: CO-201 permanent deformation testing machine (Tester Sangyo Co., Ltd., upper and lower plate heating) Pressure: 2kg / cm 2 Temperature: 40℃ Hours: 24 hours [Evaluation criteria] 5: There is absolutely no resistance when peeling off, and the glossy paper is not damaged on one side (very good) 4: There is almost no resistance when peeling off, and one side of the glossy paper is not damaged (good) 3: There is some resistance when peeling, but one side of the glossy paper is not damaged (fairly good) 2: There is some resistance when peeling, but one side of the glossy paper is not damaged (usable) 1: There is resistance when peeling off, and one side of the glossy paper is missing (unusable)

[0070] <Seasoning tolerance test> In an environment of 23°C, a drop of a mixture of ketchup / vinegar / salad oil = 1 / 1 / 1 (mass ratio) was dropped onto the coating layer (L) of the obtained laminate, and the time it took for the drop on the surface to pass through one side of the glossy paper and reach the back side was measured. [Evaluation criteria] 5: Over 90 minutes (very good) 4: Over 70 minutes, under 90 minutes (good) 3: Over 50 minutes, under 70 minutes (fairly good) 2: 30 minutes or more, less than 50 minutes (allowed) Less than 1:30 minutes (unavailable)

[0071] <Microwave resistance test> One piece of "Tokukara Fried Chicken" manufactured by Nichirei Foods Corporation was placed on the coating layer (L) of the laminate, and heated in a microwave oven at 500W for 180 seconds, then left for 20 minutes to return to room temperature.The piece of fried chicken was then removed and the state of penetration of oil and moisture into the sheet surface and whether or not the fried chicken was sticking to the sheet (blocking between the food and the sheet) was checked. [Evaluation criteria] 5: No oil or moisture penetrates the sheet, and the fried chicken does not stick to the sheet. (Excellent) 4: Some oil and water seep in, but it doesn't penetrate to the back, and the fried chicken doesn't stick to the sheet. (Good) 3: Oil and water seep in, but not to the back, and the fried chicken does not stick to the sheet. (Fairly good) 2: Oil and water have penetrated, but not to the back side. The fried chicken is slightly sticking to the sheet (less than 10% of the contact area). (Can be used) 1: Oil or moisture has penetrated to the backside of the sheet, or the fried chicken is stuck to the sheet (more than 10% of the sheet contact area). (Cannot be used)

[0072] <Water resistance> A drop of water was dropped onto the coated surface (L) of the obtained laminate in an environment of 23°C, and after 30 seconds, it was confirmed whether the water had soaked into the laminate. Evaluation was made based on the percentage of the area onto which the water had soaked and discolored the paper. [Evaluation criteria] 5: No penetration at all (very good) 4: Less than 10% of the area has been soaked (good) 3: The area soaked is between 10% and 30% (fairly good) 2: The area soaked is between 30% and 50% (usable) 1: Over 50% of the surface area is saturated (very poor)

[0073] <Air barrier properties> The air barrier property in the present invention was measured by the method described in the section on air barrier property above. The obtained laminate was cut into a piece of 5 cm x 5 cm, and the laminate was placed under reduced pressure so that the coated surface was aligned with the glass filter surface. At this time, the laminate and the glass filter surface were brought into complete contact with each other to prevent the laminate from folding and wrinkling. After placing the laminate in the measurement location, the vacuum level was read once the vacuum gauge reading had stabilized, and this was used as the air barrier value. The measurement was carried out in a constant temperature and humidity chamber at a temperature of 25°C and a humidity of 60%. The obtained values ​​were evaluated as follows: [Evaluation criteria] 5: Air barrier value is 2 kPa or less (very good) 4: Air barrier value is greater than 2kPa and less than 5kPa (good) 3: Air barrier value is greater than 5 kPa and less than 10 kPa (fairly good) 2: Air barrier value is greater than 10kPa and less than 20kPa (usable) 1: Air barrier value is greater than 20 kPa (very poor)

[0074] [Table 5]

[0075] [Table 6]

[0076] [Table 7]

[0077] [Examples 38 to 48, Comparative Examples 14 to 19] <Food flavor retention> Laminates 18-20, 23, 26, 11, 27, 32-34, 36, and 38-43 were cut into 30cm x 30cm pieces, and one piece of "Original Chicken" manufactured by Kentucky Fried Chicken Japan, preheated to 50°C, was placed in the center of the piece. The piece was then wrapped from all sides to ensure there were no gaps, and left to stand for 20 minutes in an environment of 23°C. Ten subjects then opened the packaging, ate the contents, and compared the taste with that of an unwrapped piece (control) left to stand for 20 minutes at 23°C, and were scored as follows: 3 points: The flavor was stronger than normal. 2 points: The flavor was slightly stronger than normal. 1 point: The flavor was about the same as the standard. The average scores of the 10 subjects were judged according to the following criteria and designated Examples 38 to 48 and Comparative Examples 14 to 19. These results are shown in Table 8. ◎: Average value is 2.5 points or more (good) 〇: Average value is 1.5 points or more and less than 2.5 points (usable) ×: Average value is less than 1.5 points (extremely poor)

[0078] [Table 8]

[0079] As shown in Table 8, the laminate with good air-barrier properties was able to lock in the aroma of food. After evaluating the aroma retention of the food, the contents were actually eaten, and those that had retained their aroma had a stronger flavor than those that had not. Thus, the laminate of the present invention is considered to have high added-value functions that can contribute to the deliciousness of food. [Explanation of symbols]

[0080] 1 glass container 2 glass filters 3 rubber tubes 4 Hydraulic pump 5 Vacuum gauge 6 Filter part 7 Laminate (measurement sample)

Claims

1. A coating layer (L) is provided on at least one surface of the paper substrate, the coating layer (L) contains a polymer (A) composed of an ethylenically unsaturated monomer (a), a wax (B), and a silicone-based defoaming agent (C), the polymer (A) is an aromatic ethylenically unsaturated monomer (a-1) and / or a copolymer of an ethylenically unsaturated monomer composed of a (meth)acrylic acid ester and (meth)acrylic acid, the (meth)acrylic acid ester is composed solely of a (meth)acrylic acid ester containing an alkyl group having 1 to 8 carbon atoms, the polymer (A) has a glass transition temperature in the range of −24 to 45° C. and a glass transition temperature in the range of 90 to 150° C., The wax (B) includes a paraffin wax (b1) and / or a polyethylene wax (b2), the total content of the paraffin wax (b1) and the polyethylene wax (b2) is 0.1 to 10 parts by mass based on 100 parts by mass of the coating layer (L); The coating amount of the coating layer (L) is 0.5 to 10 g / m 2 and A laminate having an air barrier property of 20 kPa or less.

2. 2. The laminate according to claim 1, comprising 0.005 to 1 part by mass of a silicon-based antifoaming agent (C) based on 100 parts by mass of the coating layer (L).

3. 3. The laminate according to claim 1, wherein the aromatic ethylenically unsaturated monomer (a-1) is contained in an amount of 35 to 80 parts by mass per 100 parts by mass of the ethylenically unsaturated monomer (a).

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