JP2023104649A - Laminate and manufacturing method thereof - Google Patents

Abstract

To provide a laminate with excellent adhesion and heat resistance between paper and a polypropylene layer and no odor.SOLUTION: A laminate containing paper, an adhesive layer and a polypropylene layer in this order. The adhesive layer contains an acid-modified polyolefin resin containing an unsaturated carboxylic acid component and an olefin component, where the propylene component in the olefin component of the acid-modified polyolefin resin is 50 mass% or more. It is preferable that the olefin component contain a butene component and/or an ethylene component.SELECTED DRAWING: None

Description

The present invention relates to a laminate and its manufacturing method.

Many packaging materials and containers including paper are used for beverages, liquid seasonings, cup noodles, cup ice cream, and the like. A polyolefin resin layer (for example, a polyethylene resin layer) is sometimes laminated on the surface of these packaging materials and paper containers for the purpose of imparting water resistance and for the purpose of easy box-making by heat sealing. However, polyethylene resin is poor in heat resistance, so if it is filled with high-temperature content or heated in a microwave oven after being filled, the resin layer may foam, resulting in poor heat resistance. However, its application in high temperature applications has been limited.

Therefore, in applications where heat resistance is required, polypropylene resin is used as the polyolefin resin layer. For example, in Patent Document 1, by extrusion-laminating polypropylene resin to paper, paper having excellent heat resistance and a polypropylene layer are combined. A laminate having

JP-A-11-130042

In Patent Document 1, the polypropylene layer is directly laminated on the paper by extrusion laminating the polypropylene layer on the paper, and due to the low adhesive strength of the polypropylene resin, the lamination strength between the paper and the polypropylene layer is low. Sometimes it wasn't enough. In particular, when paper is molded into a packaging material or container having a complicated shape, there is a problem that the interface between the paper and the polypropylene layer is peeled off due to localized stress.

The present invention solves the above problems, and provides a laminate containing a paper and a polypropylene layer, which has excellent lamination strength between the paper and the polypropylene layer and can withstand use at high temperatures. The task is to

That is, the gist of the present invention is as follows.
(1) A laminate containing paper, an adhesive layer, and a polypropylene layer in this order,
A laminate, wherein the adhesive layer contains an acid-modified polyolefin resin containing an unsaturated carboxylic acid component and an olefin component, and the content of the propylene component in the olefin component of the acid-modified polyolefin resin is 50% by mass or more.
(2) The laminate of (1), wherein the olefin component contains a butene component and/or an ethylene component.
(3) The laminate of (1) or (2), wherein the adhesive layer contains a polyurethane resin and/or a cross-linking agent.
(4) The laminate according to any one of (1) to (3), wherein the adhesive layer does not substantially contain a nonvolatile water-improving aid.
(5) The laminate according to any one of (1) to (4), wherein the adhesive layer has a thickness of 1 μm or less.
(6) A method for producing a laminate according to any one of (1) to (5), wherein the paper surface is coated with a liquid acid-modified polyolefin resin to form an adhesive layer.
(7) The method for producing a laminate according to (6), wherein the liquid is an acid-modified polyolefin resin dispersed or dissolved in an aqueous medium.
(8) A packaging material comprising the laminate according to any one of (1) to (5).
(9) A container comprising the laminate according to any one of (1) to (5).

The laminate of the present invention includes a paper and a polypropylene layer, and by containing an adhesive layer having a specific composition between these layers, the adhesiveness and heat resistance between the paper and the polypropylene layer can be improved. It is possible to obtain an excellent laminate. In addition, when an aqueous resin dispersion is used to form the adhesive layer, it is possible to reduce the environmental load and odor caused by organic solvents and the like.

The present invention will be described in detail below.
The laminate of the present invention contains paper, an adhesive layer, and a polypropylene layer in this order.

The paper that constitutes the laminate of the present invention will be described.
In the present invention, as the paper, any paper having various formability, bending resistance, stiffness, stiffness, strength, etc. can be used. Unbleached paper, pure white roll paper, kraft paper, Japanese paper, liner paper, art paper, coated paper, carton paper, glassine paper, semi-glassine paper, etc. Paperboard, processed paper, milk base paper, etc. Various paper and synthetic paper can be used. The paper in the present invention may be obtained by laminating a plurality of layers of these papers.

Paper of any thickness can be used. The thickness of the paper is, for example, a basis weight of 20-300 g/m ² , preferably a basis weight of 30-200 g/m ² . On the surface opposite to the side on which the adhesive layer is laminated on the paper, for example, a desired pattern printed layer such as letters, figures, symbols, etc. can be arbitrarily formed.
A surface protective layer made of nitrocellulose or the like may be provided on the surface of the paper. Further, an aluminum layer or an inorganic oxide layer may be provided to improve barrier properties.

When synthetic paper is used as the paper, its structure is not particularly limited, and may be a single-layer structure or a multi-layer structure. Examples of multilayer structures include a two-layer structure of paper and a surface layer, a three-layer structure in which surface layers exist on the front and back surfaces of paper, and a multilayer structure in which another resin film layer exists between the paper and the surface layer. can be done. Each layer may or may not contain inorganic or organic fillers. A microporous synthetic paper with many fine voids can also be used.

The adhesive layer constituting the laminate of the present invention will be described.
The adhesive layer contains an acid-modified polyolefin resin with a specific composition.
The acid-modified polyolefin resin contains an unsaturated carboxylic acid component and an olefin component. The main component of the olefin component is the propylene component from the viewpoint of improving the adhesion between the adhesive layer and the polypropylene layer and providing excellent lamination strength between the paper and the polypropylene layer. That is, the content of the propylene component is 50% by mass or more, preferably 60% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, and 100% by mass. is particularly preferred.

The olefin component may contain an olefin component other than the propylene component.
Olefin components other than the propylene component include alkenes such as ethylene, 1-butene, isobutene, 1-pentene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-hexene, 1-octene and norbornenes. and dienes such as butadiene and isoprene. Among them, the ethylene component and the butene component (1-butene, isobutene, etc.) are preferable from the viewpoints of ease of resin production, ease of making the resin water-based, and particularly adhesion between the adhesive layer and the polypropylene layer.

In the acid-modified polyolefin resin, the form of copolymerization of the olefin component is not limited and includes random copolymerization, block copolymerization, graft copolymerization and the like, but random copolymerization is preferred from the viewpoint of ease of polymerization. Moreover, you may mix and use multiple types of polyolefin resin as needed.

If necessary, the acid-modified olefin resin may contain other components than those mentioned above. Other components include (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate and butyl (meth)acrylate, and maleins such as dimethyl maleate, diethyl maleate and dibutyl maleate. Acid esters, (meth)acrylic acid amides, alkyl vinyl ethers such as methyl vinyl ether and ethyl vinyl ether, vinyl esters and vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate and vinyl versatate Vinyl alcohol obtained by saponifying with a basic compound or the like, 2-hydroxyethyl acrylate, glycidyl (meth) acrylate, (meth) acrylonitrile, styrene, substituted styrene, vinyl halides, vinylidene halides, carbon monoxide, Sulfur dioxide and the like may be mentioned, and mixtures thereof may also be used.

The content (mass ratio) of the other components is preferably 10% by mass or less based on the total acid-modified polyolefin resin.

The acid-modified polyolefin resin of the present invention may be a commercially available unmodified polyolefin resin that has not been acid-modified and acid-modified. Examples of commercially available products include the Toughmar series manufactured by Mitsui Chemicals, the APAO series (amorphous polyalphaolefin) manufactured by REXtac, the Ricothene PP series manufactured by Clariant, and the Bestplast manufactured by Evonik Degussa. .

The acid-modified polyolefin resin in the present invention must contain an unsaturated carboxylic acid component from the viewpoint of improving the dispersibility of the aqueous dispersion described later and the viewpoint of improving the adhesion to paper. The acid-modified polyolefin resin preferably contains 0.1 to 10% by mass of the unsaturated carboxylic acid component, more preferably 0.5 to 10% by mass, even more preferably 1 to 7% by mass, and 1.5 to 5% by mass. % is most preferred. If the unsaturated carboxylic acid content is less than 0.1% by mass, it may be difficult to make the acid-modified polyolefin resin water-based or to adhere it sufficiently to paper. On the other hand, if it exceeds 10% by mass, the resin can be easily made water-based, but the adhesion to the polypropylene layer may be lowered, and the heat resistance and water resistance of the laminate may be lowered. When using a commercially available polyolefin resin that has not been acid-modified, an unsaturated carboxylic acid component may be introduced, for example, by the method described later.

Examples of unsaturated carboxylic acid components include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, aconitic acid, aconitic anhydride, fumaric acid, crotonic acid, citraconic acid, mesaconic acid, and allylsuccinic acid. In addition, compounds having at least one carboxyl group or acid anhydride group in the molecule (in the monomer unit) such as half esters and half amides of unsaturated dicarboxylic acids can also be used. Among them, maleic anhydride, acrylic acid, and methacrylic acid are preferred, and maleic anhydride is more preferred, from the viewpoint of ease of introduction into the unmodified polyolefin resin.

The unsaturated carboxylic acid component is, for example, copolymerized in a polyolefin resin, and its form is not limited. Examples include random copolymerization, block copolymerization, graft copolymerization, and the like. In addition, the acid anhydride unit introduced into the polyolefin resin tends to take an acid anhydride structure in a dry state, and in an aqueous medium containing a basic compound described later, part or all of it is ring-opened to form a carboxylic acid. or its salt.

The method of introducing the unsaturated carboxylic acid component into the unmodified polyolefin resin is not particularly limited. Graft copolymerization of an unsaturated carboxylic acid component to an unmodified polyolefin resin by a method of reacting the unmodified polyolefin resin, or a method of dissolving the unmodified polyolefin resin in an organic solvent and then heating and stirring the resin in the presence of a radical generator. can be done. The former method is particularly preferable because the operation is simple. Radical generators used in graft copolymerization include, for example, di-tert-butyl peroxide, dicumyl peroxide, tert-butyl hydroperoxide, tert-butyl cumyl peroxide, benzoyl peroxide, dilauryl peroxide, Organic peroxides such as cumene hydroperoxide, tert-butyl peroxybenzoate, ethyl ethyl ketone peroxide, di-tert-butyl diperphthalate, and azonitriles such as azobisisobutyronitrile can be used. These may be appropriately selected and used depending on the reaction temperature.

In the present invention, the acid-modified polyolefin resin is specifically a propylene/maleic anhydride binary copolymer, a propylene/butene/maleic anhydride terpolymer, or a propylene/ethylene/maleic anhydride terpolymer. , a propylene/butene/ethylene/maleic anhydride tetrapolymer, etc., and among them, a propylene/maleic anhydride binary copolymer is preferable from the viewpoint of heat resistance.

The weight average molecular weight of the acid-modified polyolefin resin is preferably 15,000 or more, more preferably 20,000 or more, and particularly preferably 30,000 or more. If the weight-average molecular weight is less than 15,000, not only the adhesiveness to paper and polypropylene layer is lowered, but also the heat resistance may be deteriorated. On the other hand, if the weight-average molecular weight exceeds 200,000, it may become difficult to make the resin water-soluble, which will be described later. Therefore, the weight-average molecular weight is preferably 200,000 or less. The weight average molecular weight of the resin can be determined by gel permeation chromatography (GPC) using polystyrene resin as a standard.

The adhesive layer constituting the laminate of the present invention may further contain a polyurethane resin and/or a cross-linking agent in addition to the acid-modified polyolefin resin described above.

As the polyurethane resin, a polymer containing urethane bonds in the main chain can be used, for example, a polymer obtained by reaction of a polyol component and a polyisocyanate component can be used.

In the present invention, the polyol component constituting the polyurethane resin is not particularly limited. Propanediol, 1,3-propanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, methyl-1,5-pentanediol, 1,8-octanediol, 2-ethyl-1 , 3-hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol and other low molecular weight glycols, trimethylolpropane, glycerin, pentaerythritol and other low molecular weight polyols, polyol compounds having ethylene oxide or propylene oxide units, polyethers Examples include diols, high molecular weight diols such as polyester diols, bisphenols such as bisphenol A and bisphenol F, and dimer diol obtained by converting the carboxyl group of dimer acid to hydroxyl group.

As the polyisocyanate component, one or a mixture of two or more known aromatic, aliphatic or alicyclic diisocyanates can be used. Specific examples of diisocyanates include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,3-phenylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 1,5-naphthalene diisocyanate, isophorone diisocyanate, dimethyl diisocyanate, and lysine diisocyanate. . Moreover, tri- or more functional polyisocyanates such as triphenylmethane triisocyanate and polymethylene polyphenyl isocyanate may be used as diisocyanates.

In the present invention, commercially available water-based polyurethane resins include the Takelac series manufactured by Mitsui Chemicals (product numbers: W-615, W-6010, W-511, etc.), and the ADEKA BONTITTER series manufactured by ADEKA CORPORATION (product number: HUX). -232, HUX-320, HUX-380, HUX-401, etc.), Superflex series manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (product numbers: 500, 550, 610, 650, etc.), Hydran manufactured by Dainippon Ink and Chemicals. series (product numbers: HW-311, HW-350, HW-150, etc.).

As the cross-linking agent used in the present invention, a cross-linking agent having self-crosslinking properties, a compound having a plurality of functional groups that react with the unsaturated carboxylic acid component in the molecule, a metal having a polyvalent coordination site, or the like can be used. can.

Specific examples include oxazoline group-containing compounds, carbodiimide group-containing compounds, isocyanate group-containing compounds, melamine compounds, urea compounds, epoxy compounds, zirconium salt compounds, silane coupling agents, and the like. A mixture may be used. Among them, oxazoline group-containing compounds and/or carbodiimide group-containing compounds are preferable from the viewpoint of ease of handling and adhesion.

As the oxazoline group-containing compound, those having two or more oxazoline groups in the molecule can be preferably used. For example, 2,2'-bis(2-oxazoline), 2,2'-ethylene-bis(4,4'-dimethyl-2-oxazoline), 2,2'-p-phenylene-bis(2-oxazoline) , compounds having an oxazoline group such as bis(2-oxazolinylcyclohexane)sulfide, and polymers containing an oxazoline group. These 1 type(s) or 2 or more types can be used. Among these, the oxazoline group-containing polymer is preferable because of its ease of handling.

Oxazoline group-containing polymers are generally obtained by polymerizing addition polymerizable oxazolines such as 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline and 2-isopropenyl-2-oxazoline. The oxazoline group-containing polymer may contain other monomers as necessary. A polymerization method for the oxazoline group-containing polymer is not particularly limited, and a known polymerization method can be employed. Examples of commercially available oxazoline group-containing polymers include Epocross series manufactured by Nippon Shokubai Co., Ltd., and the like. Specific trade names include, for example, water-soluble types "WS-500" and "WS-700"; emulsion types "K-1010E", "K-1020E", "K-1030E", "K- 2010E”, “K-2020E”, “K-2030E” and the like.

The carbodiimide group-containing compound is not particularly limited as long as it has at least two carbodiimide groups in its molecule. For example, compounds having a carbodiimide group such as p-phenylene-bis(2,6-xylylcarbodiimide), tetramethylene-bis(t-butylcarbodiimide), cyclohexane-1,4-bis(methylene-t-butylcarbodiimide) and polycarbodiimide, which is a polymer having carbodiimide groups. These 1 type(s) or 2 or more types can be used. Among these, polycarbodiimide is preferred because of its ease of handling.

The method for producing polycarbodiimide is not particularly limited, and for example, it can be produced by a condensation reaction accompanied by decarbonization of an isocyanate compound. The isocyanate compound is also not limited, and may be aliphatic isocyanate, alicyclic isocyanate, or aromatic isocyanate. The isocyanate compound may contain polyfunctional liquid rubber, polyalkylenediol, or the like, if necessary. Commercially available products of polycarbodiimide include Carbodilite series manufactured by Nisshinbo. Specific products include, for example, water-soluble type “SV-02”, “V-02”, “V-02-L2”, “V-04”; emulsion type “E-01”, “E -02”; organic solution type “V-01”, “V-03”, “V-07”, “V-09”; solvent-free type “V-05” and the like.

The isocyanate group-containing compound is not particularly limited as long as it has at least two isocyanate groups in its molecule. For example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane 2,4′- or 4,4′-diisocyanate, polymethylene polyphenyl diisocyanate, tolidine diisocyanate, 1,4-diisocyanatobutane, hexamethylene diisocyanate, 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,10-diisocyanatodecane, 1,3- or 1,4-diisocyanatocyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane, 4,4′-diisocyanatodicyclohexylmethane, hexahydrotoluene 2, 4- or 2,6-diisocyanate, perhydro-2,4'- or 4,4'-diphenylmethane diisocyanate, naphthalene 1,5-diisocyanate, xylylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, tetra Examples include polyfunctional isocyanate compounds such as methylxylylene diisocyanate, or modified products thereof. Here, the modified product is obtained by modifying a diisocyanate among polyfunctional isocyanate compounds by a known method. Polyfunctional isocyanate compounds having an isocyanurate group and the like, and adduct-type polyfunctional isocyanate compounds modified with polyfunctional alcohols such as trimethylolpropane can be mentioned. The isocyanate group-containing compound may contain monoisocyanate within a range of 20% by mass.

The isocyanate group-containing compound can usually be obtained by reacting a polyfunctional isocyanate compound with a monovalent or polyvalent nonionic polyalkylene ether alcohol. Commercial products of such water-based polyfunctional isocyanate compounds include Bayhydur 3100, Bayhydur VPLS2150/1, SBU Isocyanate L801, Desmodur N3400, Desmodur VPLS2102 and Desmodur manufactured by Sumitomo Bayer Urethane Co., Ltd. VPLS2025/1, SBU isocyanate 0772, Desmodur DN, Takenate WD720 manufactured by Takeda Pharmaceutical Co., Ltd., Takenate WD725, Takenate WD730, Duranate WB40-100 manufactured by Asahi Chemical Industry Co., Ltd., Duranate WB40-80D, Duranate WX-1741, BASF and Basonat HW-100, Basonat LR-9056, etc. manufactured by the company.

When a polyurethane resin is used in the adhesive layer without using a cross-linking agent, the content is 300 parts by mass or less with respect to 100 parts by mass of the acid-modified polyolefin resin from the viewpoint of adhesion to paper and polypropylene layers and heat resistance. is preferably 1 to 150 parts by mass, more preferably 2 to 130 parts by mass, and particularly preferably 3 to 100 parts by mass. If the content of the polyurethane resin exceeds 300 parts by mass, the adhesion between the polypropylene layer and the adhesive layer tends to be insufficient, making it difficult to obtain heat resistance. If the polyurethane resin content is less than 1 part by mass, the heat resistance may be poor.

When a cross-linking agent is used in the adhesive layer without using a polyurethane resin, its content is 50 parts by mass or less with respect to 100 parts by mass of the acid-modified polyolefin resin, from the viewpoint of adhesion to paper and polypropylene layers and heat resistance. is preferably 1 to 40 parts by mass, and more preferably 1 to 30 parts by mass. If the content of the cross-linking agent exceeds 50 parts by mass, the adhesion between the polypropylene layer and the adhesive layer tends to be insufficient, and heat resistance may be difficult to obtain. If the content of the cross-linking agent is less than 1 part by mass, the heat resistance may be poor.

When the adhesive layer contains both a polyurethane resin and a cross-linking agent, 50 parts by mass of the cross-linking agent is added to 100 parts by mass of the acid-modified polyolefin resin from the viewpoint of adhesion to the paper or polypropylene layer and dimensional stability at high temperatures. or less and 300 parts by mass or less of the polyurethane resin, and preferably contains 1 part by mass or more of either component. If either component exceeds 300 parts by mass, the adhesion between the polypropylene layer and the adhesive layer tends to be insufficient, and heat resistance may be difficult to obtain.

In addition, the adhesive layer in the present invention may contain other polymers other than the above, from the viewpoint of improving adhesion with paper or polypropylene layer, etc., as long as the effects of the present invention are not impaired. .

Other polymers include polyester resin, acrylic resin, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, ethylene-vinyl acetate copolymer, styrene-maleic acid resin, styrene. -Resins such as butadiene resin, butadiene resin, acrylonitrile-butadiene resin, poly(meth)acrylonitrile resin, (meth)acrylamide resin, chlorinated polyethylene resin, chlorinated polypropylene resin, modified nylon resin, phenolic resin, silicone resin, epoxy resin, etc. Ingredients are given. These other polymers are preferably used within a range that does not impair the adhesion to the paper or polypropylene layer. % or less, more preferably 5% by mass or less.

The amount of the adhesive layer is preferably in the range of 0.001 to 5 g/m ² , more preferably 0.01 to 3 g/m ² , and 0.02 to 2 g with respect to the area of the adhesive surface. /m ² is more preferred, 0.03 to 1 g/m ² is particularly preferred, and 0.05 to 1 g/m ² is most preferred. If it is less than 0.001 g/m ² , sufficient adhesion tends not to be obtained, while if it exceeds 5 g/m ² , it tends to be economically disadvantageous.

The polypropylene layer constituting the laminate of the present invention will be described. By providing the polypropylene layer, heat-sealing properties, water resistance, waterproofness, and oil resistance can be imparted to the paper, and packaging materials, containers, etc., which will be described later, can be formed.

The polypropylene layer in the laminate of the present invention is preferably a polyolefin resin containing 70% by mass or more of a propylene component (hereinafter sometimes referred to as a propylene-based resin). Examples of the resin composition of the polypropylene include homopolypropylene, propylene-vinyl acetate copolymer, propylene-α-olefin copolymer, etc. Examples of the α-olefin include ethylene, 1-butene, 1 -pentene, 1-hexene, 4-methyl-1-pentene and the like.

From the viewpoint of heat resistance, the content of the propylene component in the propylene-based resin constituting the polypropylene layer is preferably 70% by mass or more, more preferably 85% by mass or more, and even more preferably 95% by mass or more.

Further, the polypropylene layer in the present invention may have a multilayer structure, and materials other than the polypropylene-based resin may be used for the structure other than the outermost layer of the multilayer structure.

The polypropylene layer contains a light stabilizer, an ultraviolet absorber, an antioxidant, a plasticizer, a flame retardant, an inorganic filler, a pigment (colorant), a lubricant, and a silane cup within a range that does not impair the effects obtained from the present invention. A ring agent or the like may be added.

Moreover, you may surface-process a polypropylene layer as needed. There are several surface treatment methods, including kneaded matting, chemical matting, sand matting, embossing, and the like. In particular, embossing is preferable because by optimizing the embossing mold, the surface roughness can be controlled in a wide range and a highly uniform roughened surface can be obtained. The laminate of the present invention can be produced by extrusion lamination of a propylene-based resin, which is polypropylene, on an adhesive layer provided on paper. Polypropylene surface treatment such as treatment can be performed at the same time, and productivity can be improved.

The method of providing the polypropylene layer is not particularly limited. For example, a method of laminating a film-shaped propylene-based resin and a base material in advance, a method of laminating a propylene-based resin on a base material by extrusion lamination, and the like. can be used.

The paper, adhesive layer, and polypropylene in the laminate of the present invention may optionally contain antistatic agents, antioxidants, light stabilizers, ultraviolet absorbers, heat stabilizers, colorants, foaming agents, etc. may be contained in any amount.

A preferred method for manufacturing the laminate of the present invention will be described, but is not limited thereto.
In the method for producing a laminate of the present invention, an adhesive layer is provided on the paper surface. The method of providing the adhesive layer is not particularly limited, but for example, a method of preparing a liquid material containing an acid-modified polyolefin resin, applying this liquid material to the surface of paper, and drying the liquid medium serving as a medium for the liquid material. preferable. The form of the liquid is preferably a solution in which the acid-modified polyolefin resin is dissolved or a dispersion in which the acid-modified polyolefin resin is dispersed, and the liquid medium may be either an aqueous medium or an organic solvent. It is preferred to utilize an aqueous dispersion in which the polyolefin resin is dispersed in an aqueous medium. However, in the present invention, the adhesive layer may be formed directly from a resin or other solid material by means of hot-melt or the like without being processed into a liquid material. Although this is not excluded, a liquid material may be used. This is preferable in that the amount of the adhesive layer can be easily adjusted, the thickness of the adhesive layer can be controlled to be thin, and mass production is possible at low cost. Among the liquid substances, the use of an aqueous dispersion is preferable from the viewpoint of environment and performance, and since there is no residual solvent, the product can be produced without odor.

The method for preparing the liquid containing the acid-modified polyolefin resin is not particularly limited, and for example, it can be prepared as a dispersion or solution of the acid-modified polyolefin resin. In the present invention, it is particularly preferred to prepare an aqueous dispersion of the acid-modified polyolefin resin.

In addition, if necessary, the above-mentioned liquid substances include various agents such as leveling agents, antifoaming agents, anti-popping agents, antistatic agents, pigment dispersants, and ultraviolet absorbers, as well as titanium oxide, zinc oxide, carbon black, and the like. Pigments or dyes may be added. Further, organic or inorganic compounds other than those mentioned above can be added to the liquid as long as they do not impair the stability of the liquid.

When a liquid material is used to form the adhesive layer, the solid content is not particularly limited, and can be appropriately selected according to lamination conditions, the desired thickness and performance of the adhesive layer, and the like. However, from the viewpoint of maintaining an appropriate viscosity of the liquid and forming a good adhesive layer, the solid content is preferably 1 to 60% by mass, more preferably 1 to 50% by mass. It is preferably 2 to 45% by mass, particularly preferably 3 to 40% by mass, and most preferably 5 to 30% by mass.

A method for obtaining an aqueous dispersion of an acid-modified polyolefin resin is not particularly limited, but the acid-modified polyolefin resin, an aqueous medium, and if necessary an organic solvent, a basic compound, etc. are heated in a sealable container, A method of stirring can be employed, and this method is most preferred.

As the container, a known solid/liquid stirring device or emulsifier can be used, and it is preferable to use a device capable of applying a pressure of 0.1 MPa or more. The method of stirring and the rotational speed of stirring are not particularly limited. High-speed stirring (for example, 1000 rpm or more) is not essential, and the aqueous dispersion can be prepared even with a simple apparatus.

For example, raw materials such as an acid-modified polyolefin resin and an aqueous medium are put into the apparatus described above and stirred and mixed, preferably at a temperature of 40° C. or lower. Then, the temperature in the tank is kept at 70 to 240° C., preferably 100 to 220° C., more preferably 100 to 200° C., particularly preferably 110 to 190° C., preferably until coarse particles disappear (for example, 5-300 minutes) continue stirring. Here, when the temperature in the tank is lower than 70°C, it becomes difficult to make the acid-modified polyolefin resin water-based. On the other hand, if the temperature in the tank exceeds 240°C, the molecular weight of the acid-modified polyolefin resin may decrease.

In this method, a basic compound, an organic solvent, and water may be added as appropriate, and the proportion at that time may be appropriately determined according to the desired solid content concentration, particle size, degree of dispersion, and the like. The method of additionally blending a basic compound, an organic solvent or water is not particularly limited, but there are a method of blending under pressure using a gear pump, and a method of once opening the system and blending after lowering the temperature in the system. The solid content concentration after blending can be adjusted by the total amount of the basic compound, organic solvent, or water to be additionally blended. From the viewpoint of promoting water-based conversion of the acid-modified polyolefin resin and reducing the dispersed particle size, it is preferable to add an organic solvent when making water-based.

The content of the organic solvent is preferably 50% by mass or less, more preferably 1 to 45% by mass, even more preferably 2 to 40% by mass, and particularly preferably 3 to 35% by mass, relative to the entire aqueous medium. If the content of the organic solvent exceeds 50% by mass, the stability of the aqueous dispersion may deteriorate depending on the organic solvent used.

The organic solvent preferably has a solubility in water at 20° C. of 10 g/L or more, more preferably 20 g/L or more, and more preferably 50 g/L or more, in order to obtain an aqueous dispersion with good dispersion stability. is more preferred.

The organic solvent preferably has a boiling point of 150° C. or lower from the viewpoint of efficient removal from the adhesive layer during the film forming process. An organic solvent with a boiling point exceeding 150° C. tends to be difficult to scatter from the adhesive layer when dried, and in particular, the adhesiveness of the adhesive layer may deteriorate.

Preferred organic solvents include, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-amyl alcohol, isoamyl alcohol, sec-amyl alcohol, tert-amyl alcohol. , 1-ethyl-1-propanol, 2-methyl-1-butanol, n-hexanol, cyclohexanol and other alcohols, methyl ethyl ketone, methyl isobutyl ketone, ethyl butyl ketone, cyclohexanone and other ketones, tetrahydrofuran, dioxane and other ethers , ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, 3-methoxybutyl acetate, methyl propionate, ethyl propionate, diethyl carbonate, dimethyl carbonate, etc. esters, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, glycol derivatives such as ethylene glycol ethyl ether acetate, further, 1-methoxy-2-propanol, 1-ethoxy -2-propanol, 3-methoxy-3-methyl-1-butanol, methoxybutanol, acetonitrile, dimethylformamide, dimethylacetamide, diacetone alcohol, ethyl acetoacetate, 1,2-dimethylglycerin, 1,3-dimethylglycerin, and trimethylglycerin. In the present invention, a plurality of these organic solvents may be mixed and used.

Among the above organic solvents, ethanol, n-propanol, isopropanol, n-butanol, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, and diethylene glycol monomethyl ether are It is more effective in accelerating water conversion, and is preferable.

When the above organic solvent is used in the preparation of the aqueous dispersion, after making the resin water-based as described above, part of it is distilled out of the system by a solvent removal treatment generally called "stripping". , the content of the organic solvent may be reduced. By stripping, the organic solvent content in the aqueous dispersion can be reduced to 10% by weight or less, and 5% by weight or less is environmentally preferable. In the stripping process, it is possible to distill off substantially all of the organic solvent used in the aqueous conversion process. Taking this into consideration, the lower limit of the organic solvent content is preferably about 0.01% by mass. However, even if it is less than 0.01% by mass, there is no particular effect on performance and there is no problem in use.

As a stripping method, there is a method of heating the aqueous dispersion under normal pressure or reduced pressure while stirring to distill off the organic solvent. In addition, since the solid content concentration increases by distilling off the aqueous medium, for example, when the viscosity increases and the workability deteriorates, water may be added to the aqueous dispersion in advance. good.

By adopting the above preparation method, the acid-modified polyolefin resin can be efficiently dispersed or dissolved in the aqueous medium and can be prepared in a uniform liquid state. Here, being in a uniform liquid state means that the aqueous dispersion is in a state in which there is no local difference in solid content concentration from other portions, such as precipitation, phase separation, or skinning, in appearance. Say.

The weight average particle size of the acid-modified polyolefin resin in the aqueous dispersion of the acid-modified polyolefin resin is preferably 0.15 μm or less. Incidentally, the resin particle size in the aqueous dispersion of the acid-modified polyolefin resin usually does not change even when it is mixed with the aqueous dispersion or aqueous solution of the cross-linking agent or the polyurethane resin.

The aqueous dispersion of the acid-modified polyolefin resin can be prepared without the use of non-volatile water conversion aids, and is preferably substantially free of non-volatile water conversion aids. Although the use of a non-volatile water-improving aid is not excluded, it is possible to stably disperse the polyolefin resin in an aqueous medium with a weight-average particle size of 0.15 µm or less without using a water-improving aid. can. When a film is formed using such an aqueous dispersion, an adhesive layer having excellent water resistance, adhesion to a polypropylene layer, and heat resistance is obtained, and these properties hardly change even over a long period of time.

Here, the term "aqueous agent" refers to a drug or compound added for the purpose of promoting the aqueous dispersion or stabilizing the aqueous dispersion in the preparation of the aqueous dispersion. It means having no boiling point at normal pressure or having a high boiling point (for example, 300° C. or higher) at normal pressure.

The phrase "substantially free of non-volatile water-improving aid" means that the content of the non-volatile water-improving aid is less than 0.5% by mass relative to the acid-modified polyolefin resin component. It is particularly preferred that they contain no auxiliaries. Examples of the non-volatile water-improving aid in the present invention include emulsifiers, compounds having a protective colloid action, modified waxes, acid-modified compounds with a high acid value, and water-soluble polymers.

Examples of emulsifiers include cationic emulsifiers, anionic emulsifiers, nonionic emulsifiers, and amphoteric emulsifiers, and include surfactants in addition to those generally used for emulsion polymerization. For example, anionic emulsifiers include higher alcohol sulfates, higher alkylsulfonates, higher carboxylates, alkylbenzenesulfonates, polyoxyethylene alkylsulfates, polyoxyethylene alkylphenyl ether sulfates, vinyl sulfosuccinates, and the like. Examples of nonionic emulsifiers include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyethylene glycol fatty acid esters, ethylene oxide propylene oxide block copolymers, polyoxyethylene fatty acid amides, ethylene oxide-propylene oxide copolymers and other poly Examples thereof include compounds having an oxyethylene structure and sorbitan derivatives such as polyoxyethylene sorbitan fatty acid esters. Amphoteric emulsifiers include lauryl betaine, lauryldimethylamine oxide and the like.

Compounds having a protective colloid action, modified waxes, acid-modified compounds with a high acid value, and water-soluble polymers include polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, modified starch, Polyvinylpyrrolidone, polyacrylic acid and its salts, carboxyl group-containing polyethylene wax, carboxyl group-containing polypropylene wax, carboxyl group-containing polyethylene-propylene wax and other acid-modified polyolefin waxes having a number average molecular weight of usually 5000 or less and salts thereof, acrylic acid - maleic anhydride copolymer and its salt, styrene - (meth) acrylic acid copolymer, ethylene - (meth) acrylic acid copolymer, isobutylene - maleic anhydride alternating copolymer, (meth) acrylic acid - ( Carboxyl group-containing polymers and salts thereof having an unsaturated carboxylic acid content of 10% by mass or more, such as meth)acrylic acid ester copolymers, polyitaconic acid and salts thereof, water-soluble acrylic copolymers having amino groups, gelatin, Examples include compounds generally used as dispersion stabilizers for fine particles, such as gum arabic and casein.

Further, basic compounds include ammonia, triethylamine, N,N-dimethylethanolamine, isopropylamine, aminoethanol, dimethylaminoethanol, diethylaminoethanol, ethylamine, diethylamine, isobutylamine, dipropylamine, 3-ethoxypropylamine, 3-diethylaminopropylamine, sec-butylamine, propylamine, n-butylamine, 2-methoxyethylamine, 3-methoxypropylamine, 2,2-dimethoxyethylamine, monoethanolamine, morpholine, N-methylmorpholine, N-ethylmorpholine , pyrrole, pyridine and the like. The blending amount of the basic compound is preferably 0.5 to 10 equivalents, more preferably 0.8 to 5 equivalents, and 0.9 to 3.0 times the equivalents of the carboxyl groups in the polyolefin resin. Equivalents are particularly preferred. If the amount is less than 0.5 equivalents, the effect of addition of the basic compound may not be observed. may occur.

The liquid material thus obtained is applied to the paper surface to form an adhesive layer. As a coating method at this time, a conventionally known method can be adopted. Examples thereof include gravure roll coating, reverse roll coating, wire bar coating, lip coating, air knife coating, curtain flow coating, spray coating, dip coating, brush coating and the like. The coated surface of the paper may be surface-activated, and the form of the liquid is preferably an aqueous dispersion. In addition, an undercoat layer may be provided on the coated surface of the paper, if necessary.

By such a method, the liquid can be uniformly applied to the paper surface. Then, after setting at around room temperature as necessary, an adhesive layer can be formed on the paper by subjecting it to a drying treatment or a heat treatment for drying.

As a heating device at this time, an ordinary hot air circulation type oven, an infrared heater, or the like may be used. The heating temperature and heating time may be appropriately determined in consideration of the characteristics of the paper to be coated and the degree of addition of the above-mentioned various organic solvents and additives that can be arbitrarily blended with the liquid. As an example, from the viewpoint of economy, the heating temperature is preferably 30 to 250°C, more preferably 60 to 180°C, and particularly preferably 80 to 150°C. On the other hand, the heating time is preferably 1 second to 20 minutes, more preferably 5 seconds to 60 seconds, particularly preferably 5 seconds to 30 seconds.

According to the present invention, by laminating a polypropylene layer on an adhesive layer provided on paper, a laminate having excellent adhesion between the paper and the polypropylene layer can be obtained.

Specifically, in forming the polypropylene layer, when the propylene-based resin is melt-extruded from the T-die, the temperature of the resin immediately after being extruded from the T-die is preferably set to 230 to 300°C. In particular, from the viewpoint of suppressing thermal decomposition of the propylene-based resin, the resin temperature is desirably low, specifically 230 to 270°C. Furthermore, from the viewpoint of improving adhesion and suppressing thermal decomposition, it is more preferably 240 to 260°C.

In the present invention, an extrusion lamination method is preferable as a method of laminating an adhesive layer on paper and then laminating a polypropylene layer thereon. may be adopted. Methods other than the extrusion lamination method include, for example, a method of thermally laminating an adhesive layer and a propylene-based resin film (dry lamination method).

After laminating the propylene-based resin on the surface of the adhesive layer, the resulting laminate may be subjected to aging treatment for the purpose of improving adhesion. The aging treatment is preferably performed at a temperature of about room temperature to 100°C, more preferably 30 to 60°C from the viewpoint of heat damage to the laminate and economic efficiency, and further preferably at 40 to 50°C. preferable.

The lamination strength can be evaluated by performing a 180 degree peel test using a tensile tester under the conditions of a constant temperature of 25° C. and a tensile strength of 300 mm/min. Although the lamination strength varies depending on the material of the paper, it is preferable that the paper breaks during the measurement.

(Structure of laminate)
Examples of the structure of the laminate of the present invention include paper/adhesive layer/polypropylene layer and polypropylene layer/adhesive layer/paper/adhesive layer/polypropylene layer.
The laminate of the present invention may optionally contain layers other than the paper, the adhesive layer, and the polypropylene layer within a range that does not impair the effects of the present invention.

(Application)
The laminate of the present invention can be used as a packaging material and a molding material for paper containers.
Since the polypropylene layer has excellent heat-sealing properties, the laminate of the present invention can be molded by bending or rolling into a cylindrical shape, overlapping the ends, and heat-sealing. Further, since the polypropylene layer is excellent in workability, it can be bent or rolled into a cylindrical shape.

In addition, since the polypropylene layer of the laminate of the present invention has excellent heat resistance, the packaging material and paper container molded using the laminate of the present invention are suitable for applications in which hot beverages and foods are stored (so-called hot applications), Especially suitable for applications that are heated in a microwave oven or hot water bath.

The form of the paper container is not particularly limited, and includes paper packaging materials, paper plates, paper cups, and the like. A paper cup is manufactured by folding the bottom portion, fixing the joint portion to form pleats, and rounding and bonding the upper end portion. Since the resin layer has excellent workability, it can conform to such a shape and can be heat-sealed well.

EXAMPLES The present invention will be specifically described below by way of examples, but the present invention is not limited to these. Various properties were measured or evaluated by the following methods.

1. Polyolefin Resin (1) Content of Unsaturated Carboxylic Acid Component Content was determined by infrared absorption spectroscopy (Perkin Elmer System-2000 Fourier transform infrared spectrophotometer, resolution 4 cm ⁻¹ ).

(2) Structure of resin other than unsaturated carboxylic acid component Determined by ¹ H-NMR and ¹³ C-NMR analysis (manufactured by Varian, 300 MHz) at 120°C in ortho-dichlorobenzene (d ₄ ). ^{The 13} C-NMR analysis was based on a gated decoupling method in consideration of quantification.

(3) Weight-average molecular weight of resin The weight-average molecular weight was measured using a GPC apparatus (HLC-8020 manufactured by Tosoh Corporation, two columns of KF-804L manufactured by SHODEX, and one KF-805L column manufactured by SHODEX.) was used, and an eluent was used. Tetrahydrofuran was used as the catalyst, and the measurement was carried out under the conditions of a flow rate of 1 ml/min and 40°C. About 10 mg of the resin was dissolved in 5.5 mL of tetrahydrofuran and filtered through a PTFE membrane filter to obtain a measurement sample. A weight-average molecular weight was determined from a calibration curve prepared from polystyrene standard samples. When it was difficult to dissolve in tetrahydrofuran, it was dissolved in ortho-dichlorobenzene.

2. Laminate (1) Amount of adhesive layer (coating amount)
The aqueous dispersion obtained in the production example was applied to paper whose area and weight had been measured in advance, and dried at 100° C. for 1 minute. The mass of the obtained laminate was measured, and the coating amount was obtained by subtracting the mass of the substrate before coating. A coating amount per unit area (g/m ² ) was calculated from the coating amount and the coating area.

(2) Laminate strength (adhesion evaluation)
A test piece with a width of 15 mm is taken from the obtained laminate, and a tensile tester (manufactured by Intesco, precision universal material testing machine 2020 type) is used to perform T-type peeling from the end of the test piece to separate the paper and polypropylene layer. The interface was peeled off and measured in a constant temperature room at 25° C. with a tensile tester (manufactured by Intesco, precision universal material testing machine, 2020 type). The peeling speed was 100 mm/min.

(3) Microwave resistance (heat resistance)
Using the laminate, 100 cup-shaped paper containers (bottom diameter: 50 mm, height: 80 mm) were prepared, filled with water, heated in a microwave oven at 500 W for 3 minutes, and the presence or absence of foaming at the laminated part was checked as follows. was evaluated according to the criteria of
◎: No foaming observed in all ○: No foaming was observed in 99 pieces, and a very small amount of foaming was observed in 1 piece ×: 98 or less in which no foaming was observed, or many bubbles were observed 1 or more samples present

(4) Presence or Absence of Odor As in (3) above, a paper container was prepared using the laminate, filled with water, heated in a microwave oven at 500 W for 3 minutes, and judged by a sensory test for the presence or absence of odor.

(Production Example 1: Production of acid-modified polyolefin resin P-1)
280 g of a propylene-butene copolymer (mass ratio: propylene/1-butene = 80/20) was heated and dissolved in 470 g of xylene in a four-necked flask under a nitrogen atmosphere. With stirring, 40.0 g of maleic anhydride as an unsaturated carboxylic acid and 28.0 g of dicumyl peroxide as a radical generator were added over 2 hours, and then reacted for 6 hours. After completion of the reaction, the obtained reactant was put into a large amount of acetone to precipitate a resin. This resin was dried in a vacuum dryer under reduced pressure to obtain an acid-modified polyolefin resin P-1.

(Production Examples 2, 4, 7: Production of acid-modified polyolefin resins P-2, P-4, P-7)
The mass ratio of propylene/1-butene is propylene/1-butene = 65/35 for P-2, propylene/1-butene = 100/0 for P-4, and propylene/1-butene = 40/60 for P-7. Acid-modified polyolefin resins P-2, P-4, and P-7 were obtained in the same manner as in Production Example 1, except that each was changed to .

(Production Example 3: Production of acid-modified polyolefin resin P-3)
Acid-modified polyolefin resin P-3 was prepared in the same manner as in Production Example 1, except that a propylene-ethylene copolymer (mass ratio: propylene/ethylene = 92/8) was used instead of the propylene-butene copolymer. Obtained.

(Production Example 5: Production of acid-modified polyolefin resin P-5)
Acid-modified polyolefin resin P-5 was obtained in the same manner as in Production Example 4, except that the amount of maleic anhydride added was 26.0 g and the amount of dicumyl peroxide added was 50.0 g.

(Acid-modified polyolefin resin P-6)
Bondine LX-4110 (manufactured by Arkema Co., Ltd., maleic anhydride-modified polyolefin resin), which is a commercially available acid-modified polyolefin resin, was used as acid-modified polyolefin resin P-6.

Table 1 shows the properties of the obtained acid-modified polyolefin resins P-1 to P-7.
P-6 was difficult to dissolve in tetrahydrofuran and orthodichlorobenzene, and the weight average molecular weight could not be measured.

(Preparation Example 1)
60.0 g of acid-modified polyolefin resin (P-1), 45.0 g of ethylene glycol monobutyl ether (manufactured by Wako Pure Chemical Industries, Ltd.), 8 0 g of N,N-dimethylethanolamine and 137.0 g of distilled water were placed in a glass container and stirred at a rotation speed of 300 rpm with a stirring blade. It was confirmed that Therefore, while maintaining this state, after 10 minutes, the power of the heater was turned on to heat. Then, the temperature in the system was kept at 160° C. and the mixture was further stirred for 60 minutes. Then, cool with air until the internal temperature reaches 80 ° C., open, 45.0 g of tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.), 5.0 g of N,N-dimethylethanolamine and 30.0 g of distillation. Water was added. After that, the system was sealed, and the rotation speed of the stirring blade was set to 300 rpm, and the temperature in the system was kept at 140° C., and the system was further stirred for 60 minutes. Then, after cooling to room temperature (about 25°C) while stirring at a rotation speed of 300 rpm with air cooling, pressure filtration (air pressure 0.2 MPa) was performed through a 300 mesh stainless steel filter (wire diameter 0.035 mm, plain weave). , to obtain a slightly cloudy aqueous dispersion E-1. At this time, almost no resin remained on the filter.

(Preparation Examples 2-5, 7)
Aqueous dispersions E-2 to E-5 and E-7 were obtained in the same manner as in Preparation Example 1 except that P-2 to P-5 and P-7 were used as acid-modified polyolefin resins.

(Preparation Example 6)
60.0 g of acid-modified polyolefin resin (P-7), 90.0 g of isopropanol, 3.0 g of triethylamine and 147.0 g of Distilled water was charged into a glass container. Then, the rotation speed of the stirring blade was set to 300 rpm, and the temperature in the system was kept at 140 to 145° C., and the mixture was stirred for 30 minutes. After that, it was placed in a water bath and cooled to room temperature (approximately 25° C.) while stirring at a rotational speed of 300 rpm. Furthermore, pressure filtration (air pressure 0.2 MPa) was performed with a 300-mesh stainless steel filter (wire diameter 0.035 mm, plain weave). This gave a milky white uniform aqueous dispersion E-6.

(Example 1)
E-1 was applied to cup base paper (200 g/m ² ) using a gravure coater so that the coating amount after drying was 0.5 g/m ² , and then dried at 100° C. for 10 seconds to remove the adhesive layer. formed. Then, using an extrusion laminator, polypropylene (Novatec PP FL02A, manufactured by Nippon Polypro Co., Ltd.) is melt-extruded as a propylene-based resin on the surface of the adhesive layer, and the laminate having a 25 μm polypropylene layer is cooled with a cooling roll and then wound. took it. At this time, the temperature of the propylene-based resin extruded from the T-die was 240°C.

(Examples 2 to 5, Comparative Examples 1 and 2)
The same as in Example 1 except that the aqueous dispersions to be coated were E-2 to E-5 (Examples 2 to 5), E-6 (Comparative Example 1), and E-7 (Comparative Example 2). A laminate was obtained by the method.

(Example 6)
Aqueous Dispersion E-5 and a polyurethane resin aqueous dispersion (Takelac W-6010, manufactured by Mitsui Chemicals, Inc., solid content concentration 30% by mass) were mixed so that the content of the polyurethane resin was 30 parts by mass with respect to 100 parts by mass of the polyolefin resin. A coating solution was prepared by mixing so that A laminate was obtained in the same manner as in Example 1, except that the main coating solution was used as the aqueous dispersion to be applied.

(Example 7)
Using an aqueous solution of an oxazoline group-containing compound (manufactured by Nippon Shokubai Co., Ltd., Epocross WS-700, solid content concentration 25% by mass) instead of the polyurethane resin aqueous dispersion, and adjusting the content of the oxazoline group-containing compound to that of the acid-modified polyolefin resin A laminate was obtained in the same manner as in Example 6, except that the amount was 5 parts by mass with respect to 100 parts by mass.

(Example 8)
Using an aqueous solution of a carbodiimide group-containing compound (manufactured by Nisshinbo Co., Ltd., Carbodilite V-02-L2, solid content concentration 40% by mass) instead of the polyurethane resin aqueous dispersion, A laminate was obtained in the same manner as in Example 6, except that the amount was 5 parts by mass with respect to 100 parts by mass of the resin.

(Example 9)
Using a 10% by mass aqueous solution of an isocyanate group-containing compound (Basonato HW-100, manufactured by BASF, solid content concentration: 100% by mass) instead of the polyurethane resin aqueous dispersion, acid-modified the content of the isocyanate group-containing compound A laminate was obtained in the same manner as in Example 6, except that the amount was 5 parts by mass with respect to 100 parts by mass of the polyolefin resin.

(Example 10)
Aqueous Dispersion E-5, Polyurethane Resin Aqueous Dispersion (manufactured by Mitsui Chemicals, Takelac W-6010, solid content concentration 30% by mass) and aqueous solution of oxazoline group-containing compound (manufactured by Nippon Shokubai Co., Ltd., Epocross WS-700, solid concentration of 25% by mass) was mixed so that the content of the polyurethane resin was 30 parts by mass and the content of the oxazoline group-containing compound was 5 parts by mass with respect to 100 parts by mass of the polyolefin resin, and the coating liquid was obtained. prepared. A laminate was obtained in the same manner as in Example 1, except that the main coating solution was used as the aqueous dispersion to be applied.

(Comparative Examples 3-6)
Except that the aqueous dispersion E-7 was used instead of the aqueous dispersion E-5, Comparative Example 3 was performed in the same manner as in Example 6, and Comparative Example 4 was performed in the same manner as in Example 7. In Example 5, a laminate was obtained in the same manner as in Example 8, and in Comparative Example 6, a laminate was obtained in the same manner as in Example 9.

(Comparative Example 7)
The cup base paper was subjected to corona treatment without using an aqueous dispersion, and polypropylene was directly melt-extruded onto the corona-treated surface of the cup base paper in the same manner as in Example 1 to obtain a laminate having no adhesive.

Table 2 shows the properties of the laminates obtained in Examples 1-10 and Comparative Examples 1-7.

As shown in Table 2, the laminates obtained in Examples 1 to 10 had excellent lamination strength and excellent microwave resistance because the peeling form was paper material failure, and even in a high temperature environment. , which can be suitably used as a laminate. In addition, since there is no odor, these laminates can be suitably used as heat-resistant paper containers.

On the other hand, as shown in Table 2, in Comparative Examples 1 to 6 in which the propylene component in the olefin component in the acid-modified polyolefin resin contained in the adhesive layer was less than 50% by mass, the laminate strength tended to be inferior. Furthermore, it was also inferior in microwave resistance. In particular, in Comparative Example 1, when the laminate strength was measured, delamination occurred and could not be measured, and the microwave oven resistance could not be measured and the presence or absence of odor could not be evaluated. Also, in Comparative Examples 3 to 6, the adhesive layer contained a polyurethane resin and a cross-linking agent, but was inferior in adhesiveness and resistance to microwave ovens.

In Comparative Example 7, a laminate was obtained by directly melt extruding polypropylene onto the paper surface to laminate a polypropylene layer without forming an adhesive layer. This laminate tends to be inferior in laminate strength.

Claims (9)

A laminate containing paper, an adhesive layer, and a polypropylene layer in this order,
A laminate, wherein the adhesive layer contains an acid-modified polyolefin resin containing an unsaturated carboxylic acid component and an olefin component, and the content of the propylene component in the olefin component of the acid-modified polyolefin resin is 50% by mass or more. 2. The laminate according to claim 1, wherein the olefin component contains a butene component and/or an ethylene component. 3. The laminate according to claim 1, wherein the adhesive layer contains a polyurethane resin and/or a cross-linking agent. A laminate according to any one of claims 1 to 3, wherein the adhesive layer is substantially free of non-volatile water-retaining aids. The laminate according to any one of claims 1 to 4, wherein the adhesive layer has a thickness of 1 µm or less. A method for producing a laminate according to any one of claims 1 to 5, wherein an adhesive layer is formed by applying a liquid acid-modified polyolefin resin to the paper surface. 7. The method for producing a laminate according to claim 6, wherein the liquid is an acid-modified polyolefin resin dispersed or dissolved in an aqueous medium. A packaging material comprising the laminate according to any one of claims 1-5. A container comprising the laminate according to any one of claims 1 to 5.