Aqueous barrier coating agent and coated paper

Abstract

This aqueous barrier coating agent contains a polymer of polymer components that include a (meth)acrylamide, a (meth)acrylate having a C4 or higher linear or branched alkyl group, a (meth)acrylate having a styrene and / or cyclic alkyl group, and a carboxy-group-containing vinyl monomer. The mass ratio of (meth)acrylate having a C4 or higher linear or branched alkyl group to (meth)acrylamide is 8.3 to 27.0.

Description

Water-based barrier coating agents and coated paper

[0001] The present invention relates to a water-based barrier coating agent and coated paper.

[0002] In recent years, from the viewpoint of reducing plastic consumption, the use of paper as an alternative to plastic has been considered. However, paper has low oil resistance. Therefore, from the viewpoint of imparting oil resistance to paper, it has been considered to form a barrier coating layer on the surface of paper by treating the surface of the paper with a barrier coating agent.

[0003] As such a barrier coating agent, for example, a paper overcoating and adhesive composition containing a resin including a styrene-acrylic copolymer of styrene, α-methylstyrene, and (meth)acrylate has been proposed (see, for example, Patent Document 1).

[0004] International Publication No. 2020 / 203346 Pamphlet

[0005] On the other hand, paper is required to have better oil resistance, and paper with a barrier coating layer is required to have blocking resistance.

[0006] An object of the present invention is to provide an aqueous barrier coating agent that has excellent oil resistance and blocking resistance, and coated paper having a barrier coating layer obtained using the aqueous barrier coating agent.

[0007] The present invention [1] is an aqueous barrier coating agent comprising a polymer of polymerization components including (meth)acrylamide, a (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms, a styrene and / or a (meth)acrylate having a cyclic alkyl group, and a carboxy group-containing vinyl monomer, wherein the mass ratio of the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms to the (meth)acrylamide is 8.3 or more and 27.0 or less.

[0008] The present invention [2] includes the aqueous barrier coating agent according to the above [1], in which the content of the carboxyl group-containing vinyl monomer is 0.1 parts by mass or more and 20.0 parts by mass or less per 100 parts by mass of the polymerization components.

[0009] The present invention [3] further includes the aqueous barrier coating agent according to the above [1] or [2], which contains a reaction product of a monocarboxylic acid having from 16 to 28 carbon atoms and a monoalcohol having from 24 to 34 carbon atoms.

[0010] The present invention [4] further comprises the aqueous barrier coating agent according to any one of the above [1] to [3], which further comprises cellulose nanofibers.

[0011] The present invention [5] includes a coated paper comprising paper and a barrier coating layer disposed on one side and / or the other side in the thickness direction of the paper, the barrier coating layer including a dried product of the aqueous barrier coating agent described in any one of [1] to [4] above.

[0012] In the aqueous barrier coating agent of the present invention, the mass ratio of the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms to the (meth)acrylamide is from 8.3 to 27.0, thereby enabling the formation of a barrier coating layer having excellent oil resistance and blocking resistance.

[0013] The coated paper of the present invention has a barrier coating layer containing the dried product of the aqueous barrier coating agent of the present invention, and therefore has excellent oil resistance and blocking resistance.

[0014] FIG. 1 is a graph showing the relationship between (meth)acrylamide and (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms in each example and each comparative example.

[0015] In the following description, (meth)acrylic means acrylic and / or methacrylic.

[0016] 1. Water-Based Barrier Coating Agent The water-based barrier coating agent contains a polymer of polymerization components containing a predetermined monomer.

[0017] The polymerization components contain, as essential components, (meth)acrylamide, a (meth)acrylate having a linear or branched alkyl group with 4 or more carbon atoms, a (meth)acrylate having a styrene and / or cyclic alkyl group, and a carboxy group-containing vinyl monomer. Note that the (meth)acrylamide, the (meth)acrylate having a linear or branched alkyl group with 4 or more carbon atoms, the (meth)acrylate having a styrene and / or cyclic alkyl group, and the carboxy group-containing vinyl monomer are copolymerizable with each other.

[0018] <(Meth)acrylamide> (Meth)acrylamide is a component that imparts oil resistance to the aqueous barrier coating agent. The (meth)acrylamide is methacrylamide and / or acrylamide. The (meth)acrylamide is preferably acrylamide.

[0019] The mass ratio of the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms to the (meth)acrylamide is 8.3 to 27.0, preferably 8.5 to 25.0, more preferably 8.5 to 23.0, even more preferably 8.5 to 20.0, particularly preferably 8.5 to 19.0, most preferably 8.5 to 15.0, or even 8.5 to 13.6.

[0020] Specifically, the mass ratio of the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms to the (meth)acrylamide is 8.3 or more, preferably 8.5 or more, and 27.0 or less, preferably 25.0 or less, more preferably 23.0 or less, even more preferably 20.0 or less, particularly preferably 19.0 or less, most preferably 15.0 or less, and even more preferably 13.6 or less. When the mass ratio is equal to or greater than the lower limit, oil resistance can be improved. On the other hand, when the mass ratio is less than the lower limit, oil resistance decreases. When the mass ratio is equal to or less than the upper limit, blocking resistance improves. On the other hand, when the mass ratio exceeds the upper limit, blocking resistance decreases.

[0021] The content of (meth)acrylamide is, for example, 4 parts by mass to 150 parts by mass, preferably 5 parts by mass to 70 parts by mass, more preferably 10 parts by mass to 50 parts by mass, even more preferably 12 parts by mass to 45 parts by mass, particularly preferably 13 parts by mass to 43 parts by mass, most preferably 14 parts by mass to 40 parts by mass, further 20 parts by mass to 38 parts by mass, or even 20 parts by mass to 36 parts by mass, relative to 100 parts by mass of styrenes and / or (meth)acrylate having a cyclic alkyl group.

[0022] The content of (meth)acrylamide is, for example, 20 parts by mass to 700 parts by mass, preferably 30 parts by mass to 200 parts by mass, more preferably 40 parts by mass to 180 parts by mass, even more preferably 50 parts by mass to 170 parts by mass, particularly preferably 70 parts by mass to 150 parts by mass, and most preferably 75 parts by mass to 130 parts by mass, relative to 100 parts by mass of the carboxy group-containing vinyl monomer.

[0023] The content of (meth)acrylamide is, for example, 1.0 to 20 parts by mass, preferably 2.0 to 10 parts by mass, more preferably 3.0 to 9.5 parts by mass, even more preferably 3.5 to 9.0 parts by mass, and particularly preferably 4.5 to 8.0 parts by mass, relative to 100 parts by mass of the total amount of (meth)acrylamide, (meth)acrylate having a linear or branched alkyl group with 4 or more carbon atoms, styrenes and / or (meth)acrylate having a cyclic alkyl group, and carboxy group-containing vinyl monomer (hereinafter, may be referred to as the total amount of essential components).

[0024] The content of (meth)acrylamide is, for example, 0.5 to 20.0 parts by mass, preferably 1.0 to 10.0 parts by mass, more preferably 2.0 to 9.0 parts by mass, even more preferably 3.0 to 8.0 parts by mass, particularly preferably 3.5 to 7.0 parts by mass, and most preferably 3.5 to 6.5 parts by mass, relative to 100 parts by mass of the polymerization components.

[0025] <(Meth)acrylates Having a Linear or Branched Alkyl Group with 4 or More Carbon Amounts> (Meth)acrylates having a linear or branched alkyl group with 4 or more carbon atoms are components that impart oil resistance to aqueous barrier coating agents. (Meth)acrylates having a linear or branched alkyl group with 4 or more carbon atoms do not contain cyclic branched alkyl groups and are distinguished from (meth)acrylates having cyclic alkyl groups, as described below. Examples of (meth)acrylates having a linear or branched alkyl group with 4 or more carbon atoms include n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, and stearyl (meth)acrylate. The (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms is appropriately selected from the viewpoint of adjusting the glass transition temperature in the polymer and achieving both oil resistance and blocking resistance. The (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms is preferably n-butyl(meth)acrylate or 2-ethylhexyl(meth)acrylate, and more preferably n-butyl acrylate or 2-ethylhexyl acrylate. In other words, the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms preferably consists of n-butyl(meth)acrylate, or 2-ethylhexyl(meth)acrylate, or consists of n-butyl(meth)acrylate and 2-ethylhexyl(meth)acrylate.

[0026] When the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms consists of n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate, the mass ratio of 2-ethylhexyl (meth)acrylate to n-butyl (meth)acrylate is, for example, 0.5 or more, preferably 0.8 or more, more preferably 0.9 or more, and for example, 2.0 or less, preferably 1.5 or less, more preferably 1.3 or less, and even more preferably 1.2 or less.

[0027] Specifically, the mass ratio of 2-ethylhexyl (meth)acrylate to n-butyl (meth)acrylate is, for example, 0.5 to 2.0, preferably 0.8 to 1.5, more preferably 0.9 to 1.3, and still more preferably 0.9 to 1.2.

[0028] In addition, in a (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms, the number of carbon atoms is preferably 18 or less, more preferably 14 or less, even more preferably 10 or less, and particularly preferably 8 or less.

[0029] The content ratio of the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms is, for example, 60 parts by mass to 1600 parts by mass, preferably 80 parts by mass to 1000 parts by mass, more preferably 150 parts by mass to 500 parts by mass, even more preferably 200 parts by mass to 350 parts by mass, particularly preferably 250 parts by mass to 320 parts by mass, and most preferably 260 parts by mass to 300 parts by mass, relative to 100 parts by mass of the styrenes and / or the (meth)acrylate having a cyclic alkyl group.

[0030] The content of the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms is, for example, 200 to 12,000 parts by mass, preferably 400 to 10,000 parts by mass, more preferably 800 to 1,600 parts by mass, and even more preferably 1,000 to 1,200 parts by mass, relative to 100 parts by mass of the carboxy group-containing vinyl monomer.

[0031] The content of the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms is, for example, 30 parts by mass to 90 parts by mass, preferably 40 parts by mass to 80 parts by mass, more preferably 50 parts by mass to 70 parts by mass, and even more preferably 60 parts by mass to 70 parts by mass, relative to 100 parts by mass of the essential components.

[0032] Specifically, the content of the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms is, relative to 100 parts by mass of the essential components, for example, 30 parts by mass or more, preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 60 parts by mass, from the viewpoint of oil resistance, and for example, 90 parts by mass or less, preferably 80 parts by mass or less, and more preferably 70 parts by mass or less, from the viewpoint of blocking resistance.

[0033] The content of the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms is, for example, 20.0 parts by mass to 80.0 parts by mass, preferably 30.0 parts by mass to 70.0 parts by mass, and more preferably 40.0 parts by mass to 60.0 parts by mass, relative to 100 parts by mass of the polymerization components.

[0034] Specifically, the content of the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms is, relative to 100 parts by mass of the polymerization components, for example, 20.0 parts by mass or more, preferably 30.0 parts by mass or more, and more preferably 40.0 parts by mass or more, from the viewpoint of oil resistance, and for example, 80.0 parts by mass or less, preferably 70.0 parts by mass or less, and more preferably 60.0 parts by mass or less, from the viewpoint of blocking resistance.

[0035] <Styrene and / or (meth)acrylate having a cyclic alkyl group> Examples of the styrene include styrene, α-methylstyrene, and vinyltoluene. The styrene is preferably styrene or α-methylstyrene, and more preferably styrene.

[0036] Examples of (meth)acrylates having a cyclic alkyl group include cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate. The (meth)acrylate having a cyclic alkyl group is preferably cyclohexyl (meth)acrylate, and more preferably cyclohexyl acrylate. The (meth)acrylate having a styrene and / or a cyclic alkyl group is preferably styrene or cyclohexyl acrylate, and more preferably styrene. The (meth)acrylate having a styrene and / or a cyclic alkyl group can be used alone or in combination of two or more.

[0037] The content ratio of the styrenes and / or (meth)acrylates having a cyclic alkyl group relative to 100 parts by mass of the carboxy group-containing vinyl monomer is, for example, 80 parts by mass to 5000 parts by mass, preferably 100 parts by mass to 1000 parts by mass, more preferably 200 parts by mass to 500 parts by mass, and even more preferably 300 parts by mass to 400 parts by mass.

[0038] The content of the styrenes and / or (meth)acrylates having a cyclic alkyl group is, for example, 1 part by mass to 50 parts by mass, preferably 10 parts by mass to 40 parts by mass, and more preferably 20 parts by mass to 30 parts by mass, relative to 100 parts by mass of the essential components.

[0039] The content of the styrenes and / or (meth)acrylate having a cyclic alkyl group is, for example, 4.0 parts by mass to 40.0 parts by mass, preferably 10.0 parts by mass to 30.0 parts by mass, and more preferably 15.0 parts by mass to 20.0 parts by mass, relative to 100 parts by mass of the polymerization components.

[0040] <Carboxy Group-Containing Vinyl Monomer> The carboxy group-containing vinyl monomer is a component that improves oil resistance.

[0041] Examples of the carboxyl group-containing vinyl monomer include monocarboxylic acids, dicarboxylic acids, and salts thereof. Examples of the monocarboxylic acid include (meth)acrylic acid. Examples of the dicarboxylic acid include itaconic acid, maleic acid, fumaric acid, itaconic anhydride, maleic anhydride, and fumaric anhydride.

[0042] The carboxyl group-containing vinyl monomer is preferably a monocarboxylic acid, more preferably (meth)acrylic acid, and even more preferably methacrylic acid. The carboxyl group-containing vinyl monomer can be used alone or in combination of two or more kinds.

[0043] The content of the carboxy group-containing vinyl monomer is, for example, 0.1 to 20 parts by mass, preferably 1 to 15 parts by mass, and more preferably 3 to 10 parts by mass, relative to 100 parts by mass of the essential components.

[0044] The content of the carboxy group-containing vinyl monomer relative to 100 parts by mass of the polymerization components is, for example, 0.1 parts by mass to 20.0 parts by mass, preferably 1.0 parts by mass to 15.0 parts by mass, more preferably 3.0 parts by mass to 10.0 parts by mass, and even more preferably 4.0 parts by mass to 7.0 parts by mass.

[0045] Specifically, the content of the carboxy group-containing vinyl monomer is, from the viewpoint of oil resistance, for example, 0.1 parts by mass or more, preferably 1.0 parts by mass or more, more preferably 3.0 parts by mass or more, and even more preferably 4.0 parts by mass or more, relative to 100 parts by mass of the polymerization components. Also, from the viewpoint of oil resistance, the content is, for example, 20.0 parts by mass or less, preferably 15.0 parts by mass or less, more preferably 10.0 parts by mass or less, and even more preferably 7.0 parts by mass or less.

[0046] <Copolymerizable Monomer> The polymerization components may also contain (meth)acrylamide, a (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms, a styrene and / or a (meth)acrylate having a cyclic alkyl group, and a copolymerizable monomer copolymerizable with a carboxy group-containing vinyl monomer (excluding the crosslinkable monomer described below).

[0047] The copolymerizable monomer may, for example, be a (meth)acrylate having an alkyl group having 3 or less carbon atoms.

[0048] Examples of (meth)acrylates having an alkyl group having 3 or less carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, and isopropyl (meth)acrylate.

[0049] The copolymerizable monomer is preferably methyl (meth)acrylate, more preferably methyl methacrylate. The copolymerizable monomers can be used alone or in combination of two or more kinds.

[0050] The content of the copolymerizable monomer relative to 100 parts by mass of the essential components is, for example, 1 to 70 parts by mass, preferably 3 to 60 parts by mass, more preferably 5 to 50 parts by mass, more preferably 7 to 40 parts by mass, even more preferably 8 to 30 parts by mass, and particularly preferably 10 to 25 parts by mass.

[0051] The content of the copolymerizable monomer relative to 100 parts by mass of the polymerization components is, for example, 1.0 parts by mass to 50.0 parts by mass, preferably 5.0 parts by mass to 40.0 parts by mass, more preferably 7.0 parts by mass to 30.0 parts by mass, and even more preferably 10.0 parts by mass to 20.0 parts by mass.

[0052] The copolymerizable monomer preferably does not contain a silicon-containing monomer (e.g., a polysiloxane-containing (meth)acrylate). Specifically, this polymer can achieve sufficient oil resistance even without containing a silicon-containing monomer that has excellent oil resistance.

[0053] The copolymerizable monomer preferably does not contain a fluorine-containing monomer (e.g., a perfluoroalkyl group-containing (meth)acrylate). Specifically, this polymer can achieve sufficient oil resistance even without containing a fluorine-containing monomer that has excellent oil resistance.

[0054] <Crosslinking Monomer> The polymerization components may contain a crosslinking monomer, if necessary, from the viewpoint of improving oil resistance. The crosslinking monomer is copolymerizable with (meth)acrylamide, a (meth)acrylate having a linear or branched alkyl group with 4 or more carbon atoms, a styrene and / or a (meth)acrylate having a cyclic alkyl group, a carboxy group-containing vinyl monomer, and a copolymerizable monomer to form a crosslinked structure.

[0055] Crosslinking monomers include, for example, monofunctional crosslinkers, difunctional crosslinkers, and multifunctional crosslinkers.

[0056] Examples of the monofunctional crosslinking agent include N-(hydroxymethyl)acrylamide, N-(hydroxyethyl)acrylamide, N,N'-dimethylacrylamide, diacetone acrylamide, N-(isopropyl)acrylamide, and polyethylene glycol mono(meth)acrylate. The monofunctional crosslinking agent is preferably N-(hydroxymethyl)acrylamide.

[0057] Examples of bifunctional crosslinking agents include methylene bis(meth)acrylamide, ethylene bis(meth)acrylamide, allyl (meth)acrylamide, divinylbenzene, allyl (meth)acrylate, and polyethylene glycol di(meth)acrylate. The bifunctional crosslinking agent is preferably polyethylene glycol di(meth)acrylate. Examples of polyethylene glycol di(meth)acrylate include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and triethylene glycol di(meth)acrylate.

[0058] Examples of polyfunctional crosslinking agents include triacrylformal, triallyl isocyanurate, pentaerythritol triacrylate, trimethylolpropane (meth)acrylate, and tetraallyloxyethane.

[0059] The crosslinking monomer is preferably a monofunctional crosslinker, more preferably N-(hydroxymethyl)acrylamide.

[0060] The mixing ratio of the crosslinkable monomer relative to 100 parts by mass of the polymerization components is, for example, 0.01 parts by mass to 10.0 parts by mass, preferably 0.1 parts by mass to 5.0 parts by mass, more preferably 0.5 parts by mass to 3.0 parts by mass, and even more preferably 0.8 parts by mass to 1.5 parts by mass.

[0061] Specifically, from the viewpoint of oil resistance, the blending ratio of the crosslinkable monomer is, for example, 10 parts by mass or less, preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 1.5 parts by mass or less, per 100 parts by mass of the polymerization components.

[0062] <Method for Producing Polymer> The polymer is obtained by polymerizing the polymerization components. The method for polymerizing the polymerization components is not particularly limited, but emulsion polymerization is preferred.

[0063] In emulsion polymerization, first, polymerization components, water, and an emulsifier (e.g., alkylbenzene sulfonate) are charged into a predetermined reaction vessel, and if necessary, a catalyst, a chain transfer agent, etc. are appropriately blended to prepare a mixture containing the polymerization components (monomer mixture).

[0064] The emulsifier may be any known anionic surfactant or nonionic surfactant. Examples of the anionic surfactant include alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate, fatty acid salts, rosinates, alkyl sulfates, alkyl sulfosuccinates, α-olefin sulfonates, alkylnaphthalene sulfonates, and polyoxyethylene alkyl (aryl) sulfates. The anionic surfactant is preferably an alkylbenzenesulfonate. Examples of the nonionic surfactant include ethylene oxide and / or propylene oxide adducts of C1-C20 alkanols, phenols, naphthols, bisphenols, C1-C20 alkylnaphthols, polyoxyethylene (propylene) glycols, and aliphatic amines. The emulsifier is preferably an anionic surfactant, more preferably an alkylbenzenesulfonate. The emulsifiers may be used alone or in combination.

[0065] Next, a polymerization initiator and a monomer mixture are added to the mixture containing water and an emulsifier to polymerize the polymerization components.

[0066] The polymerization initiator is prepared in advance as an aqueous solution of the polymerization initiator, and is mixed in one portion or in portions with the mixed liquid containing water and the emulsifier.

[0067] Examples of the polymerization initiator include radical polymerization initiators, and specific examples include peroxide compounds, sulfides, sulfines, sulfinic acids, etc., and more preferably peroxide compounds. Note that peroxide compounds may be used in combination with a reducing agent as a redox polymerization initiator. Examples of peroxide compounds include organic peroxides and inorganic peroxides. The peroxide compound is preferably an inorganic peroxide.

[0068] Examples of organic peroxides include benzoyl peroxide, lauroyl peroxide, and acetyl peroxide.

[0069] Examples of inorganic peroxides include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, hydrogen peroxide, bromates such as potassium permanganate, sodium bromate, and potassium bromate, perborates such as sodium perborate, potassium perborate, and ammonium perborate, percarbonates such as sodium percarbonate, potassium percarbonate, and ammonium percarbonate, and perphosphates such as sodium perphosphate, potassium perphosphate, and ammonium perphosphate. The inorganic peroxide is preferably a persulfate, more preferably potassium persulfate or ammonium persulfate, and even more preferably ammonium persulfate.

[0070] Alternatively, an azo compound can be used as the polymerization initiator, such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2-methylpropionamidine), or a salt thereof.

[0071] The polymerization initiator is preferably an inorganic peroxide, more preferably a persulfate, and even more preferably ammonium persulfate. The polymerization initiators can be used alone or in combination of two or more.

[0072] As for the polymerization conditions, the polymerization temperature is, for example, 60° C. to 100° C., or preferably 70° C. to 90° C. The polymerization time is, for example, 1 hour to 12 hours, or preferably 4 hours to 8 hours.

[0073] The polymer is preferably adjusted to a pH of 5 to 9 by neutralizing the carboxy groups derived from the carboxy group-containing vinyl monomer with a neutralizing agent.

[0074] Examples of the neutralizing agent include known basic compounds. Examples of basic compounds include amine compounds, hydroxides, and morpholine. The basic compound is preferably an amine compound. Examples of amine compounds include monoamines such as ammonia, triethylamine, and diethylamine, and alkanolamines such as 2-amino-2-methyl-1-propanol, N,N-dimethylaminoethanol, N,N-diethylaminoethanol, 2-dimethylamino-2-methyl-1-propanol, monoisopropanolamine, diisopropanolamine, triisopropanolamine, monoethanolamine, diethanolamine, triethanolamine, N-ethyldiethanolamine, and N-methyldiethanolamine. The amine compound is preferably a monoamine, and more preferably ammonia. Examples of hydroxides include sodium hydroxide and potassium hydroxide. The neutralizing agent is preferably a basic compound, more preferably an amine compound, and even more preferably ammonia. The neutralizing agents can be used alone or in combination of two or more.

[0075] The glass transition temperature of the polymer is, for example, −70° C. to 40° C., preferably −55° C. to 25° C., more preferably −40° C. to 10° C., even more preferably −30° C. to 5° C., particularly preferably −25° C. to 3° C., and most preferably −20° C. to −5° C. The glass transition temperature is calculated by the FOX formula.

[0076] The weight average molecular weight (Mw) of the polymer is, for example, 20,000 to 250,000, or preferably 30,000 to 200,000, as calculated using standard polystyrene standards by gel permeation chromatography (GPC).

[0077] <Reaction Product of Monocarboxylic Acid Having 16 to 28 Carbon Atoms and Monoalcohol Having 24 to 34 Carbon Atoms> From the viewpoint of improving oil resistance and blocking resistance, the aqueous barrier coating agent preferably contains a reaction product of a monocarboxylic acid having 16 to 28 carbon atoms and a monoalcohol having 24 to 34 carbon atoms.

[0078] Examples of monocarboxylic acids having 16 to 28 carbon atoms include palmitic acid (16 carbon atoms), margaric acid (17 carbon atoms), stearic acid (18 carbon atoms), nonadecylic acid (19 carbon atoms), arachidic acid (20 carbon atoms), heneicosylic acid (21 carbon atoms), behenic acid (22 carbon atoms), tricosylic acid (23 carbon atoms), lignoceric acid (24 carbon atoms), pentacosylic acid (25 carbon atoms), cerotic acid (26 carbon atoms), heptacosylic acid (27 carbon atoms), and montanic acid (28 carbon atoms).

[0079] The monocarboxylic acid having from 16 to 28 carbon atoms is preferably a monocarboxylic acid having from 16 to 20 carbon atoms, more preferably a monocarboxylic acid having from 16 to 18 carbon atoms, and even more preferably palmitic acid. The monocarboxylic acid having from 16 to 28 carbon atoms can be used alone or in combination of two or more kinds.

[0080] Examples of monoalcohols having 24 or more and 34 or less carbon atoms include 1-tetracosanol (24 carbon atoms), 1-pentacosanol (25 carbon atoms), 1-hexacosanol (26 carbon atoms), 1-heptacosanol (27 carbon atoms), 1-octacosanol (28 carbon atoms), 1-nonacosanol (29 carbon atoms), 1-triacontanol (30 carbon atoms), 1-hentriacontanol (31 carbon atoms), 1-dotriacontanol (32 carbon atoms), 1-tritriacontanol (33 carbon atoms), and 1-tetratriacontanol (34 carbon atoms).

[0081] The monoalcohol having from 24 to 34 carbon atoms is preferably a monoalcohol having from 26 to 32 carbon atoms, more preferably a monoalcohol having from 28 to 30 carbon atoms, and even more preferably 1-triacontanol. The monoalcohol having from 24 to 34 carbon atoms can be used alone or in combination of two or more types.

[0082] To react (esterify) a monocarboxylic acid having 16 to 28 carbon atoms with a monoalcohol having 24 to 34 carbon atoms, for example, the monocarboxylic acid having 16 to 28 carbon atoms and the monoalcohol having 24 to 34 carbon atoms are mixed together in a nitrogen atmosphere, dissolved at a temperature of, for example, 80°C to 110°C, and then heated to react them.

[0083] As for reaction conditions, the reaction temperature is, for example, 120° C. to 220° C., preferably 150° C. to 200° C. The reaction is continued until the acid value (JIS K5601-2-1 (1999)) becomes, for example, 20 mgKOH / g or less, and the reaction time is, for example, 0.5 hours to 6 hours.

[0084] This gives a reaction product of a monocarboxylic acid having 16 to 28 carbon atoms and a monoalcohol having 24 to 34 carbon atoms.

[0085] The content ratio of the reaction product of a monocarboxylic acid having 16 to 28 carbon atoms and a monoalcohol having 24 to 34 carbon atoms is, for example, 5.0 to 30.0 parts by mass, preferably 10.0 to 20.0 parts by mass, and more preferably 10.0 to 15.0 parts by mass, relative to 100 parts by mass of the polymer.

[0086] Specifically, the content of the reaction product of a monocarboxylic acid having from 16 to 28 carbon atoms and a monoalcohol having from 24 to 34 carbon atoms is, relative to 100 parts by mass of the polymer, for example, 5.0 parts by mass or more, or preferably 10.0 parts by mass or more, from the viewpoint of improving oil resistance and blocking resistance, and for example, 30.0 parts by mass or less, preferably 20.0 parts by mass or less, more preferably 15.0 parts by mass or less, from the viewpoint of oil resistance.

[0087] <Cellulose nanofibers> The aqueous barrier coating agent preferably contains cellulose nanofibers from the viewpoint of improving oil resistance and blocking resistance. The cellulose nanofibers are preferably prepared as an aqueous dispersion of cellulose nanofibers in which cellulose nanofibers are dispersed in water. A commercially available product may be used as the aqueous dispersion of cellulose nanofibers. An example of a commercially available product is Rheocrysta I-2SX.

[0088] The content ratio of the cellulose nanofibers relative to 100 parts by mass of the polymer is, for example, 0.1 to 5 parts by mass, or preferably 0.2 to 1 part by mass.

[0089] Specifically, the content of cellulose nanofibers is, from the viewpoint of improving oil resistance and blocking resistance, for example, 0.1 parts by mass or more, preferably 0.2 parts by mass or more, relative to 100 parts by mass of the polymer, and from the viewpoint of oil resistance, for example, 5.0 parts by mass or less, preferably 1.0 part by mass or less.

[0090] <Additives> The aqueous barrier coating agent may contain additives as needed, such as antifoaming agents, preservatives, chelating agents, anti-slip agents, anti-rust agents, UV inhibitors, anti-fading agents, fluorescent brighteners, viscosity stabilizers, and surface strength agents.

[0091] Furthermore, the aqueous barrier coating agent preferably does not contain a polysiloxane compound (e.g., polyether-modified polydimethylsiloxane). Specifically, this aqueous barrier coating agent can achieve sufficient oil resistance even without containing a polysiloxane compound that has excellent oil resistance.

[0092] The aqueous barrier coating agent preferably does not contain a fluorine compound. Specifically, while fluorine compounds have excellent oil resistance, they may increase the environmental load. On the other hand, this aqueous barrier coating agent can achieve sufficient oil resistance without containing a fluorine compound that has excellent oil resistance.

[0093] <Preparation of Water-Based Barrier Coating Agent> The water-based barrier coating agent is prepared by mixing a polymer, a reaction product of a monocarboxylic acid having from 16 to 28 carbon atoms and a monoalcohol having from 24 to 34 carbon atoms, which is blended as needed, cellulose nanofibers (aqueous dispersion of cellulose nanofibers), which are blended as needed, additives, and water.

[0094] Furthermore, when a reaction product of a monocarboxylic acid having 16 to 28 carbon atoms and a monoalcohol having 24 to 34 carbon atoms is blended, the reaction product of the monocarboxylic acid having 16 to 28 carbon atoms and the monoalcohol having 24 to 34 carbon atoms is preferably heated in advance at 20°C or higher and 60°C or lower.

[0095] The solids concentration of the aqueous barrier coating agent is, for example, 10% by mass to 50% by mass, preferably 20% by mass to 45% by mass, and more preferably 30% by mass to 40% by mass.

[0096] In the aqueous barrier coating agent, the mass ratio of the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms to the (meth)acrylamide is 8.3 or more and 27.0 or less, thereby enabling the formation of a barrier coating layer having excellent oil resistance and blocking resistance.

[0097] Such water-based barrier coating agents are particularly suitable for use in applications where oil resistance is to be imparted to paper.

[0098] The coated paper obtained using this aqueous barrier coating agent will be described in detail below.

[0099] 2. Coated Paper Coated paper comprises paper and a barrier coating layer disposed on one thickness side and / or the other thickness side of the paper. Specifically, coated paper comprises paper and a barrier coating layer in that order toward one thickness side (or the other thickness side), or a barrier coating layer, paper, and another barrier coating layer in that order toward one thickness side. Examples of paper include newsprint, inkjet paper, thermal recording base paper, wood-free paper, cardboard, coated paper, and kraft paper. The basis weight of the paper is, for example, 50 g / m ２ ~120g / m ２ , preferably 70 g / m ２ ~100g / m ２ is.

[0100] The barrier coat layer contains a dried product of a water-based barrier coating agent. The barrier coat layer is preferably made of a dried product of a water-based barrier coating agent.

[0101] Coated paper is obtained by applying an aqueous barrier coating agent to one surface and / or the other surface of the paper in the thickness direction, followed by drying.

[0102] Specifically, the mass of the aqueous barrier coating agent after drying is, for example, 1 g / m ２ ~20g / m ２ , preferably 5 g / m ２ ~15g / m ２ Apply the mixture so that it becomes

[0103] The coating method is not particularly limited, and examples thereof include gravure coating, reverse coating, roll coating, bar coating, spray coating, air knife coating, and dipping. The coating method is preferably bar coating.

[0104] As drying conditions, the drying temperature is, for example, 70° C. to 180° C., preferably 90° C. to 150° C., and more preferably 110° C. to 150° C. The drying time is, for example, 0.5 minutes to 10 minutes.

[0105] This results in a barrier coating, which is a dried product of the aqueous barrier coating agent, being formed on one thickness side and / or the other thickness side of the paper. In this way, coated paper is produced, which includes paper and a barrier coating layer disposed on one thickness side and / or the other thickness side of the paper.

[0106] <Effects> In the aqueous barrier coating agent, the mass ratio of the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms to the (meth)acrylamide is 8.3 to 27.0, thereby forming a barrier coating layer having excellent oil resistance and blocking resistance.

[0107] The coated paper has a barrier coating layer containing a dried product of a water-based barrier coating agent, which provides excellent oil resistance and blocking resistance.

[0108] Specific numerical values ​​of the blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be replaced with the upper limit values ​​(numerical values ​​defined as "not more than" or "less than") or lower limit values ​​(numerical values ​​defined as "not less than" or "exceeding") of the corresponding blending ratios (content ratios), physical property values, parameters, etc. described in the above "Modes for Carrying Out the Invention." Furthermore, unless otherwise specified in the following description, "parts" and "%" are based on mass.

[0109] <Details of Components> The trade names and abbreviations of the components used in each example and each comparative example are described in detail. The values ​​in parentheses indicate the glass transition temperatures of the homopolymers. AM: Acrylamide (153°C) 2EHA: 2-ethylhexyl acrylate (-85°C) nBA: n-butyl acrylate (-54°C) St: Styrene (100°C) MAA: Methacrylic acid (130°C) MMA: Methyl methacrylate (105°C) Rheocrysta I-2SX: Aqueous dispersion of cellulose nanofiber (solid content 2% by mass), manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.

[0110] <Production of Polymers> Production Examples 1 to 15 and Comparative Production Examples 1 to 6 The polymerization components shown in Tables 1 and 2, 7.1 parts by mass of a 20% by mass aqueous solution of alkylbenzenesulfonate (trade name "Neogen S-20F", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as an emulsifier, and 41.2 parts by mass of water were blended and stirred to obtain a monomer mixture. Separately, 1.2 parts by mass of ammonium persulfate as a polymerization initiator and 32.4 parts by mass of water were blended in a beaker, stirred, and dissolved to prepare an aqueous polymerization initiator solution.

[0111] Then, 112 parts by mass of water and 3.1 parts by mass of a 20% by mass aqueous solution of alkylbenzene sulfonate (Neogen S-20F) as an emulsifier were mixed into a four-neck flask equipped with a stirrer, a thermometer, and a reflux condenser, and the mixture was heated to 80°C with stirring.

[0112] Next, the monomer mixture and the polymerization initiator aqueous solution were continuously injected separately into the alkylbenzene sulfonate aqueous solution over 4 hours while maintaining the temperature at 80°C during this period to allow polymerization to proceed. After the injection, the reaction was continued at 80°C for 2.5 hours, and then cooled to 40°C.

[0113] Next, 0.2 parts by mass of 28% by mass ammonia water and 2.9 parts by mass of water were blended so that the pH of the obtained polymer was 5 to 9, and the acid groups (carboxy groups) in the polymer were neutralized with ammonia, thereby obtaining an aqueous dispersion of the polymer having a solids concentration of 35.0% by mass and a viscosity of 650 mPa s (25°C).

[0114] <Synthesis of reaction product of monocarboxylic acid having 16 to 28 carbon atoms and monoalcohol having 24 to 34 carbon atoms> Synthesis Example 1 Into a four-neck flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, a water drainage tube, and a reflux condenser, 40 parts by mass of "palmitic acid (number of carbon atoms: 16)" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. and 68.5 parts by mass of "1-triacontanol (number of carbon atoms: 30)" manufactured by Tokyo Chemical Industry Co., Ltd. were placed, and the mixture was heated to 100°C with stirring to dissolve the raw materials.

[0115] Next, the temperature was raised to 180°C while continuing stirring, and the reaction was allowed to proceed for 1 hour while maintaining the temperature. Nitrogen gas was blown in during the reaction, and water accumulated in the drain pipe was appropriately removed. After 1 hour had passed, a sample was taken. The resulting sample was subjected to acid value measurement based on JIS K 5601-2-1 (1999). Specifically, 5 g of the sample was dissolved in a 1:1 toluene / methanol mixed solvent and titrated with a 0.1 mol% aqueous KOH solution. If the acid value of the resulting sample was 20 mgKOH / g or less, the reaction was considered to be the end point, and cooling was initiated. If the acid value was 20 mgKOH / g or more, sampling and acid value measurement were performed every 30 minutes, and the reaction was continued until the acid value reached 20 mgKOH / g or less. After reaching the end point, the reaction was cooled. The resulting mixture was purified by silica gel column chromatography. As a result, a reaction product of a monocarboxylic acid having 16 to 28 carbon atoms and a monoalcohol having 24 to 34 carbon atoms was obtained (yield: 90.9%).

[0116] <Preparation of Water-Based Barrier Coating Agents> Examples 1 to 7, 10 to 17, and Comparative Examples 1 to 6 The polymers of Production Examples 1 to 15 and Comparative Production Examples 1 to 6 were used as water-based barrier coating agents as they were.

[0117] Example 8 In a four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser, reaction products of a monocarboxylic acid having 16 to 28 carbon atoms and a monoalcohol having 24 to 34 carbon atoms were blended based on the descriptions in Tables 3 and 4, and stirred at 60°C for 30 minutes. Next, a polymer was blended, and after stirring for 30 minutes, the mixture was cooled to 40°C or below. In this way, an aqueous barrier coating agent was prepared. Note that the numerical values ​​for each component in Tables 3 and 4 are "parts by mass" of the solid content.

[0118] Example 9 25 parts by mass of RHEOCRYSTA I-2SX and 75 parts by mass of water were mixed in a beaker and stirred for 15 minutes with a high-speed mixer, Labo-Lution, to prepare an aqueous dispersion containing RHEOCRYSTA I-2SX. Next, based on the descriptions in Tables 3 and 4, a polymer and the aqueous dispersion containing RHEOCRYSTA I-2SX were mixed and stirred for 15 minutes with the Labo-Lution. In this way, an aqueous barrier coating agent was prepared.

[0119] <Evaluation> (Production of Coated Paper) The solids concentration of the aqueous barrier coating agent of each Example and Comparative Example was adjusted to 35.0% by mass at 25°C.

[0120] Next, kraft paper (basis weight 83 g / m ２ The aqueous barrier coating agent of each Example and Comparative Example was applied to one surface in the thickness direction of a sheet of paper (25 cm length x 25 cm width) using a bar coater at a rate of 10 g / m2 in terms of mass after drying. ２ The coating was applied so that the coating became as follows: and the coating was dried for 1 minute at 120° C. using a hot air dryer. In this way, a barrier coating layer was disposed on one surface of the paper in the thickness direction, and coated paper was produced.

[0121] (Oil Resistance) The oil resistance of the coated paper of each Example and Comparative Example was evaluated in a constant temperature and humidity environment (23°C, relative humidity 50%) in accordance with the evaluation standard T-559cm-02 (kit method) of TAPPI (The Leading Technical Association for the Worldwide Pulp, Paper, and Converting Industry). The evaluation was on a 12-point scale from 1 to 12, with a higher number indicating better oil resistance. If even test liquid No. 1 bled within 15 seconds, the paper was evaluated as having "no oil resistance."

[0122] In Comparative Example 2, when the test liquid was wiped off with tissue paper, the tissue stuck to the coated paper due to blocking, making it impossible to confirm whether the test liquid had soaked in. However, when the surface of the coated paper was visually observed before wiping, no soaking of the test liquid into the coated paper was observed.

[0123] In Examples 1, 3, and 6 to 17, the oil resistance rating was 12, and the relative merits were unclear. Therefore, a water-based barrier coating agent was separately applied to the surface of the coated sheet in an amount of 6 g / m2 in terms of mass after drying. ２ The oil resistance of this coated paper was evaluated in the same manner.

[0124] (Blocking Resistance) The coated paper of each Example and Comparative Example was cut into a size of 7 cm length x 7 cm width to prepare a test piece. ２ ) was cut into a size of 7 cm length x 7 cm width. In an atmosphere of 23°C and 50% relative humidity, the barrier coating layer of the test piece was placed on uncoated kraft paper, and a load of 2 kg was applied from above and pressed for 24 hours. The test piece was then completely peeled away from the uncoated kraft paper in 1.5 seconds, and the blocking resistance was evaluated based on the following criteria. Regarding the presence or absence of the following criteria, the sound was checked at a position 15 cm from the ear of the experimenter. The experiment was conducted by two people, and if even one person heard the sound, it was judged that there was sound. The results are shown in Tables 3 and 4. {Criteria} A: No peeling of the barrier coating layer was observed, and no sound was heard during peeling. B: No peeling of the barrier coating layer was observed, but sound was heard during peeling. C: Peeling of less than 50% of the barrier coating layer was observed. D: Peeling of 50% or more of the barrier coating layer was observed.

[0125] <Discussion> Figure 1 is a graph showing the relationship between (meth)acrylamide and (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms in each example and each comparative example. Figure 1 shows that both oil resistance and blocking resistance can be improved when the mass ratio of (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms to (meth)acrylamide is 8.3 or more and 27.0 or less (specifically, the shaded area in Figure 1).

[0126]

[0127]

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[0129]

[0130] The above invention is provided as an exemplary embodiment of the present invention, but this is merely an example and should not be interpreted as limiting. Modifications of the present invention that are obvious to those skilled in the art are intended to be included in the scope of the following claims.

[0131] The aqueous barrier coating agent and coated paper of the present invention are suitable for use, for example, in the production of packaging materials.

Claims

1. An aqueous barrier coating agent comprising a polymer of a polymerization component containing (meth)acrylamide, (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms, styrenes and / or (meth)acrylate having a cyclic alkyl group, and a carboxy group-containing vinyl monomer, wherein the mass ratio of the (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms to the (meth)acrylamide is 8.3 or more and 27.0 or less.

2. The aqueous barrier coating agent according to claim 1, wherein the content ratio of the carboxy group-containing vinyl monomer is 0.1 part by mass or more and 20.0 parts by mass or less with respect to 100 parts by mass of the polymerization component.

3. The aqueous barrier coating agent according to claim 1, further comprising a reaction product of a monocarboxylic acid having 16 or more and 28 or less carbon atoms and a monoalcohol having 24 or more and 34 or less carbon atoms.

4. The aqueous barrier coating agent according to claim 1, further comprising cellulose nanofibers.

5. A coated paper comprising paper and a barrier coating layer disposed on one side and / or the other side in the thickness direction of the paper, wherein the barrier coating layer contains a dried product of the aqueous barrier coating agent according to any one of claims 1 to 4.

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