JP7057218B2 - Laminate - Google Patents

Description

The present invention relates to a laminate having an anion-modified cellulose nanofiber layer that can be used as a packaging material, a coating agent, a functional laminate material, and the like.

In the fields of packaging and shielding materials such as foods, pharmaceuticals and automobiles, in order to protect the contents, gas barrier properties that block oxygen, water vapor, hydrogen and other gases that permeate the materials are required. Conventionally, aluminum and polyvinylidene chloride, which are less affected by temperature and humidity, have been used as gas barrier materials, but from the viewpoints of environmental pollution, occupational safety and health, resource saving, non-hazardous materials, etc., organic solvent type to aqueous type The conversion to is in progress. In recent years, materials using water-insoluble fibers derived from biomass, which are naturally present in large quantities, have been attracting attention.

For example, as a material using cellulose fibers, a technique related to cellulose fibers having a nano-sized fiber diameter is attracting attention. In addition to having biodegradability, it is also excellent in physical properties such as strength, elastic modulus, dimensional stability, heat resistance, and crystallinity, and is expected to be applied to functional materials. In particular, the anion-modified cellulose nanofibers obtained by dispersing cellulose obtained from an oxidation reaction catalyzed by 2,2,6,6-tetramethyl-1-piperidin-N-oxy radical (hereinafter referred to as TEMPO) are described above. In addition to the properties of cellulosic materials, it is known to form a film having excellent transparency and gas barrier properties under dry conditions (Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2008-1728 Japanese Unexamined Patent Publication No. 2009-57552

However, the coating film formed by using the anion-modified cellulose nanofibers as described above has a problem that the adhesion to the substrate is low due to the rigid properties of the cellulose nanofibers and the high elastic modulus. If the adhesion is low, peeling between layers occurs when the film is used as a laminated material on a substrate. Although studies have been made to introduce an adhesive layer for improving the peeling, it is not always sufficient because the adhesion to the film varies depending on the type of the base material.

In addition, many of these anion-modified cellulose nanofibers have polar groups such as a carboxyl group, a sulfonic acid group, a sulfate group, a phosphoric acid group, and a hydroxyl group introduced, and water is used as the solvent, so that the base material is used. There are problems with repelling, wettability, and coatability such as unevenness.

The present invention has been made in view of the above problems, and anion-modified cellulose nanofiber dispersion is applied to various types of substrates such as polypropylene resin, polycarbonate resin, polyester resin, and polyamide resin, which are often used as film substrates and shielding materials. It is an object of the present invention to improve the coatability of the liquid and to provide a laminate having excellent adhesion between the base material and the anion-modified cellulose nanofiber layer and capable of maintaining the adhesion for a long period of time.

As a means for solving the above problems, one aspect of the present invention is a laminate having an adhesive layer between the anion-modified cellol nanofiber layer and the base material, and the adhesive layer is a cationic polyolefin resin. It is a laminate characterized by being an emulsion-based resin containing a cationic polyurethane resin and a cationic polyurethane resin.

Further, the anionic group of the anion-modified cellulose nanofiber is preferably one or more selected from a carboxyl group, a sulfonic acid group, a sulfate group, and a phosphoric acid group.

The content of the anionic group of the anion-modified cellulose nanofiber is preferably 0.05 mmol / g or more and 5.5 mmol / g or less.

It is preferable that the anionic group of the anion-modified cellulose nanofiber forms one or more salt types selected from sodium salts, potassium salts, ammonium salts, and amine salts.

According to the present invention, the coatability of an anionic cellulose nanofiber dispersion liquid to form a coating of various functional materials such as a gas barrier layer and a water vapor barrier layer by effectively utilizing cellulose, which is a natural resource having a small environmental load, on a substrate. It is possible to provide a laminate having excellent adhesion between the base material and the anionic cellulose nanofiber layer. In particular, the anionic cellulose nanofiber dispersion has excellent coatability on various base materials having different polarities such as polypropylene base material, polyethylene base material, polycarbonate base material, polyester base material, and polyamide base material, and anionic cellulose is excellent. It is possible to provide a laminate that has excellent adhesion to the nanofiber layer and can maintain the adhesion for a long period of time.

Hereinafter, embodiments of the present invention will be described in detail.

First, anionic-modified cellulose nanofibers having an anionic group (hereinafter, may be simply referred to as cellulose nanofibers) will be described. Anionic-modified cellulose nanofibers are cellulose nanofibers in which an anionic group is introduced into cellulose. The anion-modified cellulose nanofibers are cellulose fibers having a fiber diameter of nanometer level, and the number average fiber diameter thereof is preferably 1 nm or more. Further, 200 nm or less is preferable, 50 nm or less is more preferable, and 10 nm or less is further preferable. When the number average fiber diameter is within the above range, it is preferable in that it exhibits high gas barrier characteristics when used as a packaging or shielding material.

Here, the number average fiber diameter can be measured as follows. That is, an aqueous dispersion of cellulose nanofibers having a solid content of 0.05 to 0.1% by mass is prepared, and the dispersion is cast onto a hydrophilized carbon film-coated grid to transmit transmission electrons. Use as a sample for observation with a microscope (TEM). When a fiber having a large fiber diameter is included, a scanning electron microscope (SEM) image of the surface cast on the glass may be observed. Then, observation is performed using an electron microscope image at a magnification of 5000 times, 10000 times, or 50,000 times depending on the size of the constituent fibers. At that time, an axis having an arbitrary vertical and horizontal image width is assumed in the obtained image, and the sample and observation conditions (magnification, etc.) are adjusted so that 20 or more fibers intersect the axis. Then, after obtaining an observation image satisfying this condition, two random axes are drawn vertically and horizontally for each image, and the fiber diameters of the fibers intersecting the axes are visually read. In this way, images of at least three non-overlapping surface portions are taken with an electron microscope and the value of the fiber diameter of the fibers intersecting each of the two axes is read (hence, at least 20 fibers × 2 × 3 = 120). Information on the fiber diameter of the book can be obtained). From the fiber diameter data obtained in this way, the number average fiber diameter is calculated.

In the anion-modified cellulose nanofiber, it is preferable that the constituent cellulose has an I-type crystal structure. Here, the fact that the cellulose constituting the cellulose nanofibers has an I-type crystal structure means that, for example, in the diffraction profile obtained by wide-angle X-ray diffraction image measurement, 2 theta = 14 to 17 ° and 2 theta = 22 to. It can be identified by having typical peaks at two positions near 23 °.

Examples of the anion-modified cellulose nanofibers include those in which an anionic group is introduced into a glucose unit in a cellulose molecule on the surface. Examples of the anionic group include a carboxyl group, a sulfonic acid group, a sulfuric acid group, a phosphoric acid group, and salts thereof, and any one or more of these may be contained. Examples of the salt include alkali metal salts such as lithium salt, sodium salt and potassium salt, alkaline earth metal salts such as magnesium salt, calcium salt and barium salt, and onium salts such as ammonium salt, amine salt and phosphonium salt. , Sodium salt and potassium salt are more preferable in that they exhibit high gas barrier properties.

The anionic group preferably contains a salt-type anionic group. That is, as described above, the anionic group includes acid types such as carboxyl group, sulfonic acid group, sulfate group, and phosphoric acid group, and carboxyl base, sulfonic acid base, sulfate base, and phosphoric acid group. There is a salt type, but a preferred embodiment is to include a salt type anionic group, the salt type anionic group may be used alone, and the salt type anionic group and the acid type anionic group are mixed. May be. By including the salt-type anionic group, cellulose nanofibers can be uniformly arranged at the time of film formation as described later, a film with less coarseness and density can be obtained, and the gas barrier property can be enhanced. The ratio of the salt-type anionic group to the acid-type anionic group is 10% or more and 100% or less as the ratio (molar ratio) of the salt-type anionic group to the total anionic group. It is preferable because it can be uniformly dispersed.

In one embodiment, the anion-modified cellulose nanofiber having a carboxylic acid group or a salt thereof as an anionic group comprises, for example, oxidized cellulose (A) formed by oxidizing the hydroxyl group of a glucose unit constituting cellulose, and cellulose. Examples thereof include carboxymethylated cellulose (B) obtained by carboxymethylating the hydroxyl group of the glucose unit.

As the cellulose oxide (A), for example, it is preferable that the hydroxyl group at the 6-position of the glucose unit is selectively oxidized. It can be confirmed, for example, by the ¹³ C-NMR chart that the hydroxyl group at the 6-position on the glucose unit is selectively oxidized in the cellulose oxide (A). The cellulose oxide (A) has an aldehyde group and / or a ketone group together with a carboxylic acid group (COOH) and / or a carboxylic acid base (COOX, where X is a cation forming a salt with a carboxylic acid). It may be, but preferably it has substantially no aldehyde group and / or ketone group.

The cellulose oxide (A) can be produced, for example, by (1) oxidation reaction step, (2) reduction step, (3) purification step, (4) dispersion step (micronization treatment step), and the like. Is preferably manufactured by the following steps.

(1) Oxidation reaction step After dispersing natural cellulose and an N-oxyl compound in water (dispersion medium), an copolymer is added to start the reaction. During the reaction, a 0.5 M aqueous sodium hydroxide solution is added dropwise to keep the pH at 10 to 11, and when the pH does not change, the reaction is considered to be completed. Here, the copolymer is not a substance that directly oxidizes the cellulose hydroxyl group, but a substance that oxidizes an N-oxyl compound used as an oxidation catalyst.

Natural cellulose means purified cellulose isolated from the biosynthetic system of cellulose such as plant, animal and bacterial gels. More specifically, softwood pulp, broadleaf pulp, cotton linter, cotton lint and other cotton pulp, straw pulp, bagus pulp and other non-wood pulp, bacterial cellulose (BC), cellulose isolated from squirrel, seaweed. Examples thereof include cellulose isolated from. These may be used alone or in combination of two or more. Among these, cotton-based pulp such as softwood-based pulp, hardwood-based pulp, cotton linter, and cotton lint, and non-wood-based pulp such as straw pulp and bagas pulp are preferable.

Examples of the N-oxyl compound include compounds having a nitroxy radical, which is generally used as an oxidation catalyst. As the N-oxyl compound, a water-soluble compound is preferable, and a piperidine nitroxyoxy radical is preferable, and 2,2,6,6-tetramethylpiperidinooxy radical (TEMPO) or 4-acetamide-TEMPO is particularly preferable. .. The amount of the catalyst is sufficient for the addition of the N-oxyl compound, and the N-oxyl compound may be added to the reaction aqueous solution in the range of 0.1 to 4 mmol / L, for example.

Examples of the cooxidant include hypohalogenic acid or a salt thereof, subhalogenic acid or a salt thereof, perhalogenic acid or a salt thereof, hydrogen peroxide, a perorganic acid and the like, and these may be used alone or in combination of two or more. It is also used. Of these, alkali metal hypohalites such as sodium hypochlorite and sodium hypobromous acid are preferable. When sodium hypochlorite is used, it is preferable to proceed the reaction in the presence of an alkali bromide metal such as sodium bromide from the viewpoint of reaction rate.

The pH of the reaction aqueous solution in the oxidation reaction is preferably maintained in the range of about 8 to 11. The temperature of the aqueous solution is arbitrary at about 4 to 40 ° C., and no particular temperature control is required. In order to obtain a desired amount of carboxyl groups and the like, the degree of oxidation is controlled by the amount of the copolymer added and the reaction time. Reaction times are usually about 5 to 120 minutes and are usually completed within 240 minutes at the longest.

(2) Reduction Step The oxidized cellulose (A) is preferably further subjected to a reduction reaction after the above oxidation reaction. As a result, a part or all of the aldehyde group and the ketone group formed by the oxidation reaction can be reduced back to a hydroxyl group. Specifically, the finely oxidized cellulose after the oxidation reaction is dispersed in purified water, the pH of the aqueous dispersion is adjusted to about 10, and the reduction reaction is carried out with various reducing agents. As the reducing agent, a general one can be used, and examples thereof include LiBH ₄ , NaBH ₃ CN, and NaBH ₄ .

The amount of the reducing agent is preferably in the range of 0.1 to 4% by mass based on the fine cellulose oxide. The reaction is usually carried out at room temperature or a temperature slightly higher than room temperature for 10 minutes to 10 hours, preferably 30 minutes to 2 hours. After completion of the reaction, the pH of the reaction mixture is adjusted to about 2 with various acids, and solid-liquid separation is performed with a centrifuge while sprinkling purified water to obtain cake-like fine oxidized cellulose.

(3) Purification step Next, purification is performed for the purpose of removing unreacted copolymers (hypochlorous acid, etc.) and various by-products. Since the reactant fibers are not usually dispersed in nanofiber units at this stage, they can be obtained with high-purity (99% by mass or more) reactant fibers by repeating the usual purification method, that is, washing with water and filtration. It is a dispersion of water. As the purification method in the purification step, any device may be used as long as it can achieve the above-mentioned object, such as a method using centrifugal dehydration (for example, a continuous decander).

(4) Dispersion process (miniaturization process)
The reaction fiber (aqueous dispersion) impregnated with water obtained in the purification step is dispersed in a dispersion medium and subjected to a dispersion treatment. The viscosity increases with the treatment, and a dispersion of finely divided (that is, defibrated) cellulose nanofibers can be obtained. Dispersers used in the dispersion process include a homomixer under high-speed rotation, a high-pressure homogenizer, an ultrasonic disperser, a beater, a disc type refiner, a conical type refiner, a double disc type refiner, a grinder, etc. Certain devices can be used.

On the other hand, the above-mentioned carboxymethylated cellulose (B) can be produced, for example, by the following method using the above-mentioned cellulose raw material. That is, using cellulose as a raw material, a dispersion medium containing a lower alcohol 3 to 20 times by mass, specifically methanol, ethanol, n-propyl alcohol, isopropyl alcohol, etc. alone or a mixture of two or more kinds and water is used. To use. The mixing ratio of the lower alcohol is 60 to 95% by mass. As the mercerizing agent, 0.5 to 20 times mol of alkali metal hydroxide per glucose residue of cellulose, specifically sodium hydroxide or potassium hydroxide is used. Cellulose, a dispersion medium, and a mercerizing agent are mixed to perform a mercerization treatment. The reaction temperature at this time is 0 to 70 ° C., preferably 10 to 60 ° C., and the reaction time is 15 minutes to 8 hours, preferably 30 minutes to 7 hours. Then, a carboxymethylating agent is added in an amount of 0.05 to 10 times by mole per glucose residue to carry out an etherification reaction. The reaction temperature at this time is 30 to 90 ° C., preferably 40 to 80 ° C., and the reaction time is 30 minutes to 10 hours, preferably 1 hour to 4 hours. Examples of the carboxymethylating agent include sodium monochloroacetate and the like. After the above etherification reaction, nanofibers of carboxymethylated cellulose (B) can be obtained by dispersion treatment (miniaturization treatment) with a high-pressure homogenizer or the like.

In one embodiment, the anionic modified cellulose nanofiber having a phosphoric acid group or a salt thereof as an anionic group can be produced, for example, by the following method. That is, a method of mixing a powder or an aqueous solution of phosphoric acid or a phosphoric acid derivative with a dry or wet cellulose fiber raw material, a method of adding an aqueous solution of phosphoric acid or a phosphoric acid derivative to a dispersion liquid of a cellulose fiber raw material, and the like can be mentioned. .. In these methods, usually, after mixing or adding a powder or an aqueous solution of phosphoric acid or a phosphoric acid derivative, dehydration treatment, heat treatment and the like are performed. Here, examples of the phosphoric acid or the phosphoric acid derivative include at least one compound selected from oxo acids containing phosphorus atoms, polyoxo acids, and derivatives thereof. As a result, the compound containing a phosphoric acid group or a salt thereof undergoes a dehydration reaction at the hydroxyl group of the glucose unit constituting the cellulose to form a phosphoric acid ester, and the phosphoric acid group or a salt thereof is introduced. Cellulose fibers into which a phosphoric acid group or a salt thereof has been introduced become cellulose nanofibers by performing the same dispersion treatment (miniaturization treatment) as in the case of the above-mentioned oxidized cellulose (A).

The amount of the anionic group in the anion-modified cellulose nanofiber is not particularly limited, and is preferably 0.05 mmol / g or more, more preferably 0.6 mmol / g or more, for example. Further, 5.5 mmol / g or less is preferable, 3.0 mmol / g or less is more preferable, and 2.5 mmol / g or less is more preferable. When the amount of the anionic group is within the above range, it is preferable in that the cellulose nanofibers can be uniformly dispersed.
The amount of anionic groups is, for example, for carboxylic acid groups and / or carboxylic acid bases, prepare 60 mL of 0.5 to 1% by mass slurry from a cellulose sample whose dry mass has been precisely weighed, and use a 0.1 M aqueous solution of hydrochloric acid. After setting the pH to about 2.5, add a 0.05 M aqueous solution of sodium hydroxide to measure the electrical conductivity, continue until the pH reaches about 11, and in a weak acid in which the change in electrical conductivity is gradual. From the amount of sodium hydroxide (V) consumed in the sum stage, it can be obtained according to the following formula (1). The phosphoric acid group and / or a salt thereof can also be measured by the same electric conductivity measurement. Other anionic groups may be measured by a known method.

Anionic group amount (mmol / g) = V (mL) × [0.05 / cellulose mass]… (1)

The concentration of the anion-modified cellulose nanofiber in the anion-modified cellulose nanofiber dispersion is not particularly limited, and is, for example, preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and further preferably 0.05% by mass or more. preferable. Further, 5% by mass or less is preferable, 3% by mass or less is more preferable, and 2% by mass or less is further preferable. When the concentration is within the above range, it is preferable in terms of achieving both coatability and drying efficiency when forming the anion-modified cellulose nanofiber layer.

Next, the adhesive layer will be described.

By providing the above-mentioned adhesive layer, the anionic cellulose nanofiber dispersion liquid is manufactured due to problems related to wettability and coatability, as well as chemical instability of the base material, bleeding of low molecular weight molecules, crystallization, and surface deterioration. To solve the problem that the base material and the film deteriorate over time after the film, and the adhesion is deteriorated, the coating liquid consisting of the dispersion liquid of cellulose nanofibers is uniformly applied, and various base materials having different polarities are used. It is possible to secure the adhesion of the cellulose and further suppress the adhesion over time and the deterioration of the base material and the anion-modified cellulose nanofiber layer.

The adhesive layer is characterized by containing one or more types of a cationic polyolefin resin and a cationic polyurethane resin (hereinafter, may be simply referred to as a polyolefin resin and a polyurethane resin, respectively).

By containing a polyolefin resin having a low polarity and a polyurethane resin having a high polarity in the adhesive layer, the adhesion to various substrates having different polarities is improved. The blending ratio (mass ratio) of the resin is preferably polyurethane resin: polyolefin resin = 10: 90 to 90:10, and more preferably 30:70 to 70:30.

The cationic polyolefin resin can suppress moisture absorption even under high humidity while maintaining adhesion between the base material and the adhesive layer due to the interaction between polarities, and can maintain high film cohesive force.

By containing a resin having a cationic group in the adhesive layer, the cationic group forms an ion complex with the anionic group present in the cellulose nanofibers, and has coatability, adhesion, wettability, and stability over time. Is improved. The cationic group includes a tertiary ammonium group, a quaternary ammonium group, a quaternary pyridyl group, a quaternary piperidinyl group, a quaternary pyrazinyl group, a quaternary piperazinyl group, a quaternary pyrimidinyl group, and a quaternary pyrimidinyl group. Examples thereof include a quaternary pyridazinyl group, a quaternary imidazolyl group, a quaternary morpholinyl group, a quaternary phosphonium group, a sulfonium group and salts thereof.

As the cationic group, a tertiary ammonium group, a quaternary ammonium group, a quaternary ammonium base, and a quaternary ammonium base are preferable in that they enhance the adhesion to the cellulose nanofibers.

As the cationic polyurethane emulsion resin, commercially available ones can be used. There are no particular restrictions, but specifically, Pateracol Series (DIC Corporation), Parasurf UP-28, Parasurf UP-36 (Ohara Palladium Chemical Co., Ltd.), Passcall JK-830 (Meisei Chemical Works, Ltd.), Superflex 620. , Superflex 650 (Daiichi Kogyo Seiyaku Co., Ltd.) and the like.

As the cationic polyolefin emulsion resin, commercially available ones can be used. Although not particularly limited, commercially available Arrow Base C series (manufactured by Unitika Ltd.), Aquatex EC series, AC series, MC series (Japan Coating Resin Co., Ltd.) and the like can be mentioned.

As the resin contained in the adhesive layer, a polyester resin, a polyamide resin, a polyacrylic acid resin, or a polymaleic acid resin may be contained in addition to the polyolefin resin and the polyurethane resin. Further, the resin may have a functional group other than the cationic group as long as it does not inhibit the above-mentioned effect.

The particle size of the emulsion resin used for the adhesive layer is preferably 2 μm or less, more preferably 0.5 μm or less. The smaller the particle size, the easier it is to melt, and the temperature applied for heating can be lowered, which is advantageous in terms of energy. Further, the smaller the particle size, the easier it is to form a smooth film, the easier it is to uniformly apply the coating liquid containing the anion-modified cellulose nanofiber dispersion liquid, and the easier it is to secure the adhesion to the substrate.

The minimum film-forming temperature of the resin contained in the adhesive layer is preferably 80 ° C. or lower from the viewpoint of laminating with the base material.

As the emulsion resin, one to which a hydrophilic liquid medium having a boiling point higher than that of water (hereinafter referred to as a high boiling point medium) is added may be used. The high boiling point medium is a liquid hydrophilic medium having a boiling point higher than that of water. Here, the hydrophilic medium means a medium having a hydrophilic group such as a hydroxyl group in the molecule. As the high boiling point medium, a water-soluble, that is, an organic compound having a boiling point higher than that of water can be used, for example, n-butanol, 2-methyl-1-propanol, propylene glycol methyl. Ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol isopropyl ether, propylene glycol methyl ether acetate, propylene glycol-n-propyl ether, propylene glycol propyl ether, ethylene glycol -T-butyl ether, ethylene glycol ethyl ether acetate, propylene glycol monobutyl ether, ethylene glycol monobutyl ether, 3-methyl-3-methoxybutanol, dipropylene glycol dimethyl ether, dipropylene glycol monomethyl ether, propylene glycol, dipropylene glycol methyl ether, Propylene glycol diacetate, diethylene glycol monomethyl ether, ethylene glycol, diethylene glycol monoethyl ether, benzyl alcohol, ethylene glycol monohexyl ether, 1,3-butylene glycol, dipropylene glycol methyl ether acetate, dipropylene glycol propyl ether, diethylene glycol monoethyl ether Acetate, 1,4-butylene glycol, ethylene glycol-2-ecylhexyl ether, diethylene glycol monobutyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, propylene glycol monophenyl ether (ie, phenoxypropanol), ethylene glycol monophenyl Ether (ie, phenoxyethanol), propylene glycol-mono-2-ethylhexanoate, triethylene glycol, triethylene glycol monomethyl ether, diethylene glycol-n-hexyl ether, triethylene glycol monobutyl ether, tripropylene glycol-n-butyl ether, Diethylene glycol-2-ethylhexyl ether, polyoxyethylene monophenyl ether, polyethylene glycol, polypropylene glycol monomethyl ether, cyclohexylamine, si Examples thereof include organic solvents such as clohexylamine, 2,2'? (Cyclohexylimino) bisethanol, N-methylpyrrolidone, dimethyl sulfoxide, dimethylacetamide, and dimethylformamide. Preferably, propylene glycol methyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol isopropyl ether, propylene glycol-n-propyl ether, propylene glycol propyl ether, ethylene glycol. -T-butyl ether, ethylene glycol ethyl ether acetate, ethylene glycol monobutyl ether, 3-methyl-3-methoxybutanol, dipropylene glycol monomethyl ether, propylene glycol, dipropylene glycol methyl ether, diethylene glycol monomethyl ether, ethylene glycol, diethylene glycol monoethyl Ether, 1,3-butylene glycol, diethylene glycol monoethyl ether acetate, 1,4-butylene glycol, diethylene glycol monobutyl ether, triethylene glycol, tripropylene glycol monomethyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, polyethylene glycol , Ethylene glycol monophenyl ether and the like. Any one of these may be used alone, or two or more thereof may be used in combination. The boiling point (1 atm) of the high boiling point medium is not particularly limited as long as it is higher than the boiling point of water, but is preferably 110 to 260 ° C, more preferably 130 to 250 ° C.

The content of the high boiling point medium is not particularly limited. In one embodiment, the content of the high boiling point medium with respect to the solid content of the resin in the emulsion resin is preferably, for example, 1 to 300% by mass. It is preferably 1 to 100% by mass, and more preferably 1 to 10% by mass. When the content of the high boiling point medium is within the above range, it is preferable because the film-forming property of the resin can be improved.

Next, the base material will be described.

As the base material, a wide range of base materials that can be used in the technical field of the present invention can be used. Although not particularly limited, specifically, polypropylene, polyethylene, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, nylon 6, nylon 11, nylon 12, nylon 66, nylon 610, nylon 612, nylon 6T, nylon 6I, nylon 9T, Nylon such as nylon M5T, derivatives thereof, or composite materials of two or more of these can be mentioned, and examples of the metal include aluminum plated steel plate, stainless steel plate, aluminum plate, aluminum alloy plate, copper plate, iron plate, and brass. And so on.

Next, a method for manufacturing the laminate of the present invention will be described.

One embodiment of the above-mentioned manufacturing method includes a step of forming a coating film on one surface of the above-mentioned base material using a coating liquid containing a cation resin emulsion, and a step of drying the above-mentioned coating film to form an adhesive layer. It is a method of manufacturing a laminated body including the step and the step of forming the anion-modified cellulose nanofiber layer on the adhesive layer.

In the step of forming a coating film on one surface of the base material using a coating liquid containing a cationic resin emulsion, a cationic resin emulsion constituting an adhesive layer is coated or cast by a predetermined method on the base material. Do it by doing.

The above coating or casting method is not particularly limited, but specifically, a letterpress printing method, an intaglio printing method, an offset printing method, a screen printing method, a spray painting method, a doctor blade method, a knife coater method, a die coater method, etc. Examples include a dipping method and a bar coater method.

The thickness of the adhesive layer is preferably 3 nm or more. Further, 10 μm or less is preferable, 5 μm or less is more preferable, and 2 μm or less is more preferable. When the thickness is within the above range, excellent adhesion can be exhibited by preventing the adhesive layer from warping or curling, which is preferable in terms of drying efficiency of the adhesive layer.

The step of drying the coating film to form the adhesive layer is not particularly limited as the drying method, but specifically, a heat drying method, a vacuum drying method, a blast drying method, a microwave drying method, and infrared rays. A drying method, a freeze-drying method, a filtration dehydration method, or the like can be used.

Under the drying conditions in the above drying method, the drying temperature is preferably 0 ° C. or higher and 150 ° C. or lower, more preferably 80 ° C. to 120 ° C. The drying time is preferably 1 to 3000 minutes.

In the step of forming the anion-modified cellulose nanofiber layer on the adhesive layer, an anion-modified cellulose nanofiber dispersion liquid is applied or cast on the adhesive layer by a predetermined method, and then dried under predetermined conditions. Can be molded.

The coating methods for the cellulose nanofiber dispersion liquid include letterpress printing method, intaglio printing method, offset printing method, screen printing method, spray coating method, doctor blade method, knife coater method, die coater method, dipping method, and bar coater method. And so on.

As the drying method, for example, a heat drying method, a vacuum drying method, a blast drying method, a microwave drying method, an infrared drying method, a freeze drying method, a filtration dehydration method and the like are used, but the drying temperature is not particularly limited. To exemplify the case of the heat drying method, it may be 60 to 150 ° C. or 80 to 120 ° C. Further, the drying time is not particularly limited, and may be, for example, 1 to 3,000 minutes or 5 to 180 minutes. The heating temperature may be constant at all times or may be gradually increased.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

<Manufacturing method of anion-modified cellulose nanofibers and coating liquid>
[TEMPO Oxidized Cellulose Fiber]
To 2 g of coniferous pulp, 150 mL of water, 0.25 g of sodium bromide, and 0.025 g of TEMPO are added, and after sufficiently stirring and dispersing, a 13 mass% sodium hypochlorite aqueous solution (cooxidant) is added. Sodium hypochlorite was added to 1.0 g of the above pulp so that the amount of sodium hypochlorite was 6.5 mmol / g, and the reaction was started. Since the pH decreases as the reaction progresses, a 0.5 N aqueous sodium hydroxide solution was added dropwise to maintain the pH at 10 to 11, and the reaction was carried out until no change in pH was observed (reaction time: 120 minutes). ). After completion of the reaction, 0.1N hydrochloric acid was added to adjust the pH to 7.0, and filtration and washing with water were repeated for purification to obtain TEMPO-oxidized cellulose fibers having an oxidized fiber surface.

The TEMPO-oxidized cellulose fiber was separated into solid and liquid by a centrifuge, and pure water was added to adjust the solid content concentration to 4% by mass. Then, the pH of the slurry was adjusted to 10 with a 24 mass% NaOH aqueous solution. Sodium borohydride was added to the TEMPO-oxidized cellulose fiber at a temperature of 30 ° C. of the slurry, and the mixture was reacted for 2 hours for reduction treatment. After the reaction, 0.1N hydrochloric acid was added for neutralization, and then filtration and washing with water were repeated for purification to obtain a reduction-treated TEMPO-oxidized cellulose fiber.

Then, pure water was added to the above-mentioned TEMPO-oxidized cellulose fiber to adjust the solid content concentration to 2% by mass, and the treatment was carried out 5 times at 20 ° C. and 140 MPa with a high-pressure homogenizer to obtain an aqueous dispersion of TEMPO-oxidized cellulose nanofiber.
The obtained TEMPO-oxidized cellulose nanofibers had a sodium carboxylate base (COONa) as an anionic group, had a number average fiber diameter of 6 nm, and had an anionic group amount of 1.83 mmol / g.

[Carboxymethylated Cellulose Fiber]
To 20 g of softwood pulp (LBKP) ground with a household mixer, 160 g of a mixed solvent of 112 g of isopropyl alcohol (IPA) and 48 g of water was added, then 8.8 g of sodium hydroxide was added, and the mixture was stirred and mixed, and then 30. The mixture was stirred at ° C for 60 minutes. Then, the temperature of the reaction solution was raised to 70 ° C., and 12 g (in terms of active ingredient) of sodium monochloroacetate was added. After reacting for 1 hour, the reaction was taken out, neutralized and washed to obtain a carboxymethylated cellulose fiber having a degree of substitution of 0.05 per glucose unit. Then, water was added to bring the solid content concentration to 2%, and the treatment was carried out 5 times at a pressure of 140 MPa using a high-pressure homogenizer. An aqueous dispersion was obtained. The obtained carboxymethylated cellulose nanofibers had a number average fiber diameter of 25 nm and an anionic group (carboxyl group) amount of 0.30 mmol / g.

[Phosphorylated cellulose fiber]
20 g of urea, 12 g of sodium dihydrogen phosphate dihydrate, 8 g of disodium hydrogen phosphate, and 20 g of water were used to prepare a phosphorylating agent, and 20 g of coniferous tree pulp (LBKP) crushed with a household mixer was used. The phosphate was spray-sprayed with stirring with a kneader to obtain a phosphate-impregnated pulp. Next, the phosphorylated pulp was obtained by heat-treating the phosphorylated pulp in a blower dryer equipped with a damper heated to 140 ° C. for 60 minutes. Water was added to the obtained phosphorylated pulp to adjust the solid content concentration to 2%, and the pulp was stirred, mixed and uniformly dispersed, and then the operations of filtration and dehydration were repeated twice to obtain recovered pulp. Next, water was added to the obtained recovered pulp to bring the solid content concentration to 2%, and a 1N aqueous sodium hydroxide solution was added little by little with stirring to obtain a pulp slurry having a pH of 12 to 13. Subsequently, this pulp slurry was filtered and dehydrated, and further water was added to repeat the operations of filtration and dehydration twice. Water is added to the recovered product of phosphorylated pulp obtained by this series of operations to form an aqueous dispersion having a solid content concentration of 2%, and the phosphorus used in the present invention is treated three times at a pressure of 140 MPa using a high-pressure homogenizer. An aqueous dispersion of cellulose oxide nanofibers was obtained. The obtained phosphorylated cellulose nanofibers had a sodium phosphate base (-PO ₄ Na ₂ ) as an anionic group, and had a number average fiber diameter of 5 nm.

<Manufacturing method of coating liquid for adhesive layer>
A cationic polyurethane resin emulsion and a cationic polyolefin resin emulsion were mixed at a predetermined ratio to prepare 200 g. After stirring at 3000 rpm for 10 minutes with a homomixer, degassing treatment was performed to obtain a coating liquid for an adhesive layer.

<Method of manufacturing laminated body>
As a base material, a biaxially stretched polyester film (OPP), a polycarbonate film (PC), a polyethylene terephthalate film (PET), and a nylon 6 film were prepared.

The coating liquid for forming an adhesive layer was applied with a # 10 bar coater and then dried at 80 ° C. and 120 ° C. for 10 minutes each to form an adhesive layer of about 2 μm. Further, anionic-modified cellulose nanofibers were coated on the adhesive layer with a # 50 bar coater and naturally dried to obtain a desired laminate.

<Evaluation of coatability>
The coatability of the laminate coated with the anion-modified cellulose nanofibers was evaluated by the following method.
⊚: The film is laminated on the substrate, and no unevenness is observed on the film surface.
◯: The film is laminated on the base material, but some peeling is observed.
Δ: Part of the film is peeled off and uneven.
X: The film is peeled off from the base material.

[Example 1]
Superflex 620 (product name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a cationic polyurethane resin emulsion and Arrowbase CB-1200 (product name, manufactured by Unitika Co., Ltd.) as a cationic polyolefin resin emulsion have a solid content mass ratio of 50: A coating liquid for an adhesive layer was prepared by mixing and stirring at 50.

The coating liquid for the adhesive layer was applied onto each substrate with a bar coater under the above conditions and dried. The drying conditions were 80 ° C. for 10 minutes and then 120 ° C. for 10 minutes.

After allowing the dried adhesive layer to cool for 3 hours, a TEMPO-oxidized cellulose nanofiber aqueous dispersion was applied thereto under the above conditions and dried at 70 ° C. for 3 hours to obtain a laminate.

[Example 2]
The same operation as in Example 1 was performed except that the ratio of Superflex 620 and Arrow Base CB-1200 was changed to a solid content mass ratio of 70:30 to obtain a laminated body.

[Example 3]
The same operation as in Example 1 was carried out except that the cationic polyurethane resin emulsion was changed to Superflex 650 (product name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) to obtain a laminate.

[Example 4]
The same operation as in Example 3 was performed except that the ratio of Superflex 650 and Arrow Base CB-1200 was changed to a solid content mass ratio of 70:30 to obtain a laminated body.

[Example 5]
The same operation as in Example 1 was carried out except that Superflex 620, Arrow Base CB-1200 and Phenoxyethanol were mixed and stirred at a solid content mass ratio of 50:50:10 to prepare a coating liquid for an adhesive layer, and a laminate was obtained. rice field.

[Example 6]
The same operation as in Example 1 was carried out except that the TEMPO oxidized cellulose nanofiber aqueous dispersion was changed to the carboxymethylated cellulose nanofiber aqueous dispersion to obtain a laminate.

[Example 7]
The same operation as in Example 3 was carried out except that the TEMPO oxidized cellulose nanofiber aqueous dispersion was changed to the carboxymethylated cellulose nanofiber aqueous dispersion to obtain a laminate.

[Example 8]
The same operation as in Example 1 was carried out except that the TEMPO oxidized cellulose nanofiber aqueous dispersion was changed to the phosphorylated cellulose nanofiber aqueous dispersion to obtain a laminate.

[Example 9]
The same operation as in Example 3 was carried out except that the TEMPO oxidized cellulose nanofiber aqueous dispersion was changed to the phosphorylated cellulose nanofiber aqueous dispersion to obtain a laminate.

[Comparative Example 1]
A laminate was obtained by performing the same operation as in Example 1 except for the step of directly forming the cellulose nanofiber layer on the substrate without using the adhesive layer coating liquid.

[Comparative Example 2]
The same operation as in Example 1 was performed except that only Superflex 620 was used as the coating liquid for the adhesive layer to obtain a laminated body.

[Comparative Example 3]
The same operation as in Example 1 was performed except that only the arrow base CB-1200 was used as the coating liquid for the adhesive layer to obtain a laminated body.

表１より、セルロースナノファイバー層と基材間にカチオン性ポリオレフィン樹脂およびカチオン性ポリウレタン樹脂を含有するエマルジョン系樹脂を含有する接着層を設けることにより、多種基材に対しセルロースナノファイバーの塗工性が向上した（実施例１ないし９）。高沸点媒体であるフェノキシエタノールの添加下においても塗工性が良好な結果となった（実施例５）。

From Table 1, by providing an adhesive layer containing an emulsion resin containing a cationic polyolefin resin and a cationic polyurethane resin between the cellulose nanofiber layer and the base material, the coatability of the cellulose nanofibers to various base materials is provided. Was improved (Examples 1 to 9). Even under the addition of phenoxyethanol, which is a high boiling point medium, the coatability was good (Example 5).

On the other hand, when the adhesive layer is not provided, the coatability to a specific base material is poor. (Comparative Examples 1 to 3)

<Measurement of adhesion (go board test)>
Cut each laminate with a width of 2 mm in length and width with an 11 x 11 cutter to make a test piece of 10 x 10 = 100 squares. A cellophane tape was attached onto the test piece and pressed down from above, and a grid test was performed in accordance with JIS-K-5600. Adhesion was evaluated by the following method. The test environment was 25 ° C. and 40% RH.
⊚: Number of peeled sheets is 10 or less ○: Number of peeled sheets is 11 to 30 sheets Δ: Number of peeled sheets is 31 to 50 sheets ×: Number of peeled sheets is 51 or more <Stability test over time>
The laminate was stored in an environment of 25 ° C. and 80% for 1 week, and the adhesion was evaluated in the same manner as the above-mentioned adhesion test method.

From Table 2, by providing the adhesive layer containing the cationic polyolefin resin and the cationic polyurethane resin, the adhesion of the cellulose nanofibers over time to various substrates was improved (Examples 1, 3, 5, 6). 8). On the other hand, when it does not have an adhesive layer, it can be seen that the adhesiveness is poor with respect to the base material (Comparative Example 1). Further, when the adhesive layer was either polyolefin or polyurethane, the stability of adhesion over time was poor (Comparative Examples 2 and 3).

<Oxygen gas permeation test>
The adhesive layer coating liquid described in Example 1 is applied onto "Cosmo Shine A-4300" manufactured by Toyobo Co., Ltd. with a # 10 bar coater, and then dried at 80 ° C. and 120 ° C. for 10 minutes each. Formed an adhesive layer of about 2 μm. Further, an anion-modified cellulose nanofiber aqueous dispersion was applied onto the adhesive layer with a # 50 bar coater and naturally dried to obtain the desired laminate.

[Example 10]
Anionic-modified cellulose nanofiber aqueous dispersion using Superflex 620 and Arrow Base CB-1200 (product name, manufactured by Unitika Co., Ltd.) mixed and stirred at a solid content mass ratio of 50:50 as the coating liquid for the adhesive layer. As a result, a laminate was obtained using a TEMPO-oxidized cellulose nanofiber aqueous dispersion.

[Example 11]
The same operation as in Example 10 was performed except that Superflex 620 was changed to Superflex 650 to obtain a laminated body.

[Example 12]
The same operation as in Example 10 was carried out except that Superflex 620, Arrow Base CB-1200 and Phenoxyethanol were mixed and stirred at a solid content mass ratio of 50:50:10 to prepare a coating liquid for an adhesive layer, and a laminate was obtained. rice field.

[Comparative Example 4]
"Cosmo Shine A-4300" manufactured by Toyobo Co., Ltd. was used.
A sample cut to a diameter of 10 cm was prepared from the above laminate, and an oxygen permeability measuring device "MODEL8001" (cc / (m2day · atm)) manufactured by ILLINOIS was used.
Oxygen gas permeability was measured under the conditions of 23 ° C. and 0% RH. The average value of 3 samples was calculated. The results are shown in Table 3 below.

From the results in Table 3, it was found that the system having an adhesive layer also showed low oxygen gas permeability and the gas barrier characteristics of the laminated body were high.

INDUSTRIAL APPLICABILITY The present invention can be widely and suitably used in fields such as packaging materials, coating agents, and functional laminated materials.

Claims (4)

A laminate having an adhesive layer between an anion-modified cellulose nanofiber layer and a base material, wherein the adhesive layer is an emulsion-based resin containing a cationic polyolefin resin and a cationic polyurethane resin. body. The laminate according to claim 1, wherein the anionic group of the anion-modified cellulose nanofiber is one or more selected from a carboxyl group, a sulfonic acid group, a sulfate group, and a phosphoric acid group. body. The laminate according to claim 1 or 2, wherein the content of the anionic group of the anionic-modified cellulose nanofiber is 0.05 mmol / g or more and 5.5 mmol / g or less. Claim 1 characterized in that the anionic group of the anion-modified cellulose nanofiber forms one or more salt types selected from sodium salt, potassium salt, ammonium salt, and amine salt. The laminated body according to any one of 3 to 3.