JP2009184138A - Gas-barrier laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a gas-barrier laminate which is excellent in the strength of adhesion to a heat sealing layer and oxygen-barrier properties as a packaging bag, allows the use of a metal detector, and can be scrapped as paper. <P>SOLUTION: In the gas-barrier laminate, a first gas-barrier layer containing an ethylene-modified polyvinyl alcohol resin and an inorganic laminar compound on a paper support and a second gas-barrier layer made of ethylene-modified polyvinyl alcohol are formed in turn. The mass ratio between the ethylene-modified polyvinyl alcohol resin and the inorganic laminar compound of the first gas-barrier layer is 100/5-100/50. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a packaging material for packaging foods, in particular, a packaging material for packaging contents that may react with oxygen and cause oxidation or deterioration, and a metal detector can be used. The present invention provides a packaging material that can be separated as paper after use.

In general, when food comes into contact with oxygen, oily components contained in the food react (oxidize) with oxygen, causing the food to change its taste or cause discoloration. For this reason, many food packages are packaged with a packaging material having gas barrier properties (particularly oxygen barrier properties).
Conventionally, as such a packaging material, a gas barrier film in which PVDC or PVA layer is provided on OPP (biaxially stretched polypropylene), a PET (polyethylene terephthalate) film, a nylon film, an inorganic oxide layer of silica or alumina, or an aluminum metal There are a gas barrier film provided with a layer, a paper base material and an aluminum foil, or a gas barrier laminate in which a paper base material and the gas barrier film are bonded. Gas barrier laminates using paper as a base material are characterized by excellent printability, moderate rigidity, and a high-class feeling, and are widely used as packaging materials.

However, when a film having an aluminum foil or an aluminum vapor deposition layer and a paper substrate are bonded, there is a problem that a metal detector for inspection of foreign matter after food packaging cannot be used because it contains metal. Moreover, since it contains metal, it cannot be incinerated as paper and cannot be reused as waste paper. On the other hand, when a film having a gas barrier layer such as PVA, PVDC, or an inorganic oxide is used, the cost is increased, and the laminate of the film and paper is often inferior in packaging suitability and workability. The present situation is that most of the gas barrier laminates of the paper base material use an aluminum foil and paper base laminate.
On the other hand, techniques for forming a gas barrier layer on the surface of a paper substrate have been proposed. Patent Document 1 proposes a method of providing polyvinyl alcohol and an inorganic layered compound on a paper substrate. Patent Document 2 proposes, similarly to Patent Document 1, a laminated paper for packaging provided with a paper layer and a resin composition layer having an inorganic layer compound on the paper layer. Patent Document 3 proposes a paper composite having, on at least one surface of paper, a resin composition layer containing 0.01 to 200 parts by weight of a layered inorganic compound with respect to 100 parts by weight of a water-soluble polymer compound. Yes. Patent Document 4 discloses an ethylene-vinyl ester copolymer saponified product (A) having an ethylene content of 1 to 15 mol%, an ethylene-vinyl ester copolymer saponified product (B) having an ethylene content of 15 to 70 mol%, and A resin composition comprising an inorganic layered compound (C) has been proposed. In Patent Document 5, in a laminate comprising a coating layer 1, a barrier layer 2 and a paper base material 3, the barrier layer 2 is a base material B of paper or a biaxially stretched film and vinyl having an ethylene content of 0 to 15 mol%. A laminate comprising a layer A of an alcohol polymer has been proposed. Patent Document 6 discloses a gas barrier laminate in which a first gas barrier layer and a second gas barrier layer containing a water-soluble polymer and an inorganic layered compound are provided in this order on a paper support. The mass ratio of the water-soluble polymer to the inorganic stratiform compound is 75/25 to 50/50, and the mass ratio of the water-soluble polymer to the inorganic stratiform compound in the second gas barrier layer is 95/5 to 75 / A gas barrier laminate of 25 is proposed. In Patent Document 7, in a gas barrier laminate in which a gas barrier layer containing a water-soluble polymer, an inorganic layered compound, and a synthetic resin is provided on a paper support, the inorganic layered compound is used with respect to 100 parts by mass of the water-soluble polymer. Proposed is a gas barrier laminate in which 10 to 150 parts by mass and 5 to 100 parts by mass of a synthetic resin are proposed.
JP 11-129381 A JP-A-11-309817 JP-A-13-214396 Japanese Patent Application Laid-Open No. 14-069255 Japanese Patent Laid-Open No. 15-094574 JP 2007-216592 A JP 2007-216593 A

However, when such a gas barrier laminate is used, the adhesion between the gas barrier layer and the heat seal layer such as a polyethylene resin layer is insufficient, and the oxygen barrier property when finished in the final packaging bag There was a problem of being bad.
Therefore, it has been required to improve the oxygen barrier property of the package by increasing the adhesion strength between the gas barrier layer and the heat seal layer.

The present invention adopts the following method in order to solve the above problems.
The first of the present invention is a gas barrier laminate in which a first gas barrier layer containing an ethylene-modified polyvinyl alcohol resin and an inorganic layered compound and a second gas barrier layer made of ethylene-modified polyvinyl alcohol are sequentially provided on a paper support. is there.

  The second aspect of the present invention is the gas barrier laminate according to the first aspect of the present invention, wherein the mass ratio of the ethylene-modified polyvinyl alcohol and the inorganic stratiform compound in the first gas barrier layer is 100/5 to 100/50.

  According to the present invention, it is possible to obtain a gas barrier laminate that has excellent adhesion strength with a heat seal layer, excellent oxygen barrier properties as a packaging bag, can be used as a metal detector, and can be discarded as paper. .

The present invention is described in detail below.
When a barrier layer is formed by applying an aqueous paint mixed with a water-soluble polymer such as polyvinyl alcohol and a swellable inorganic layered compound such as montmorillonite onto a paper support, the barrier effect of the inorganic layered compound causes the barrier. The characteristics are greatly improved.
However, in order to exhibit high barrier properties, it is necessary to increase the blending amount of the inorganic layered compound, but when the inorganic layered compound exceeds a certain amount, the adhesion strength and coating strength of the barrier layer are significantly reduced. The present inventors have found that. Here, the adhesion strength of the barrier layer refers to the adhesion strength between the barrier layer and the sealant layer when the barrier layer and the sealant layer are laminated. If the adhesion strength is weak, not only the heat seal strength after packaging will be weak, but also an air gap will be created at the interface between the sealant layer and the barrier layer, and air will permeate through that part, greatly reducing the oxygen barrier properties as a packaging bag. Turned out to be.

  Therefore, the present inventors have conducted intensive studies, and as a result, a first gas barrier layer containing an ethylene-modified polyvinyl alcohol resin and an inorganic layered compound and a second gas barrier layer made of ethylene-modified polyvinyl alcohol are sequentially provided on the paper substrate surface. Thus, the present inventors have found that the adhesion strength between the barrier layer and the sealant layer is greatly improved, and have reached the present invention.

  The ethylene-modified polyvinyl alcohol in the present invention is polyvinyl alcohol obtained by copolymerization of an ethylene monomer and a vinyl acetate monomer. The ethylene unit content is preferably 1 to 20 mol%, more preferably 2 to 15 mol%, particularly preferably 3 to 10 mol%. If the ethylene unit content of the ethylene-modified PVA is less than 1 mol%, the stretchability of the PVA may not be sufficient. On the other hand, if the ethylene unit content exceeds 20 mol%, the solubility in water is lowered and it is difficult to obtain an aqueous paint, which is not preferable. The ethylene unit content is expressed in mol% with respect to the entire monomer unit (ethylene unit + vinyl alcohol unit) (the vinyl alcohol unit includes a vinyl acetate unit which is not saponified).

  Since ethylene-modified polyvinyl alcohol contains hydrophobic ethylene units, it is considered that it has excellent adhesion to polyolefin-based substrates such as polyethylene films and polypropylene films that are sealants.

  In addition, the degree of “saponification” of ethylene-modified polyvinyl alcohol is preferably 70% or more and 99.9% or less, and more preferably 80% or more and less than 99% in terms of mole percentage. The degree of polymerization is preferably 100 or more and 3000 or less, and more preferably 200 or more and 2000 or less. If the saponification degree is less than 70%, the oxygen barrier property is lowered, and if it exceeds 99.9%, the miscibility between the inorganic layered compound and polyvinyl alcohol is lowered, which is not preferable. On the other hand, when the degree of polymerization is less than 100, the coating film strength is lowered, and when the degree of polymerization exceeds 3000, the coating suitability is lowered, which is not preferable.

The first gas barrier layer may contain unmodified polyvinyl alcohol or modified polyvinyl alcohol. Examples of the modified polyvinyl alcohol include polyvinyl alcohol modified with a functional group such as a silanol group (—Si (OH) ₃ ), an amino group, a carboxyl group, and a 1,2 glycol group. Further, synthetic resins such as styrene-butadiene latex and acrylic-styrene emulsion may be included. Furthermore, polysaccharides such as starch, water-soluble polymers such as casein, polyacrylic acid, and polyethyleneimine may be included.

  As described above, the second gas barrier layer is mainly composed of ethylene-modified polyvinyl alcohol having excellent adhesion to a polyolefin-based substrate, but various water-soluble polymers can be used as necessary within the range not hindering the effect. It is possible to add a synthetic resin or the like. As the water-soluble polymer or synthetic resin that can be added and used, those that can be used in the first gas barrier layer can be used. In the present invention, the inorganic layered compound is not added to the second gas barrier layer because it interferes with the polyolefin base material.

  In the present invention, a hydrogen bonding group crosslinking agent can be added to the gas barrier layer for the purpose of improving the coating strength.

Although it does not specifically limit as a crosslinking agent for hydrogen bondable groups which can be used by this invention, For example, a titanium coupling agent, a silane coupling agent, a melamine coupling agent, an epoxy coupling agent, an isocyanate type cup Examples thereof include a ring agent, a copper compound, a zirconium compound, a boron compound, and colloidal silica. Among these, a zirconium compound and a boron compound are more preferably used.
Specific examples of the zirconium compound include zirconium halides such as zirconium oxychloride, hydroxyzirconium chloride, zirconium tetrachloride and zirconium bromide, zirconium salts of mineral acids such as zirconium sulfate, basic zirconium sulfate and zirconium nitrate, and formic acid. Zirconium salt, zirconium salt of organic acid such as zirconium acetate, zirconium propionate, zirconium caprylate, zirconium stearate, ammonium zirconium carbonate, sodium zirconium sulfate, ammonium zirconium acetate, sodium zirconium oxalate, sodium zirconium citrate, zirconium ammonium citrate, etc. And zirconium complex salts thereof.

  The gas barrier layer may contain an antifoaming agent, a wetting agent, a dye, a color adjusting agent, a thickener, and the like as necessary.

The coating amount of the first gas barrier layer is preferably from 0.1 to 3.0 g / ^{m 2,} more preferably 0.5 to 2.5 g / ^{m 2.} If the coating amount of the first gas barrier layer exceeds 3.0 g / m ² , the coating strength may be significantly reduced, and if it is less than 0.1 g / m ² , the oxygen barrier property may be insufficient. is there.
Further, the coating amount of the second gas barrier layer is preferably from 0.1 to 3.0 g / ^{m 2,} more preferably 0.5 to 2.5 g / ^{m 2.} If the coating amount of the second gas barrier layer exceeds 3.0 g / m ² , the coating strength may decrease, and if it is less than 0.1 g / m ² , the adhesion strength with the sealant layer becomes insufficient, and oxygen There is also a possibility that the barrier property is also lowered.
The total coating amount of the first gas barrier layer and the second gas barrier layer is preferably 0.5 to 5 g / m ² . If the total coating amount is less than 0.5 g / m ² , the oxygen barrier property may be lowered or the coating film strength may be lowered. Moreover, when it exceeds 5 g / m < ² >, there exists a possibility that adhesive strength and coating-film strength may fall, and it is not preferable.

Specific examples of inorganic layered compounds that can be used in the present invention include graphite, phosphate derivative compounds (such as zirconium phosphate compounds), chalcogenides, hydrotalcite compounds, lithium aluminum composite hydroxides, clays. Minerals, synthetic mica, synthetic smectite and the like can be mentioned.
Graphite, phosphate derivative compounds (zirconium phosphate compounds, etc.), chalcogenides, hydrotalcite compounds, and lithium aluminum composite hydroxides are compounds or substances in which unit crystal layers are stacked on each other and have a layered structure. Here, the layered structure refers to a structure in which surfaces in which atoms are strongly bonded by a covalent bond or the like and densely arranged are stacked substantially in parallel by a weak binding force such as van der Waals force.

A “chalcogenide” is a dichalcogenide of a group IV (Ti, Zr, Hf), group V (V, Nb, Ta) and / or group VI (Mo, W) element, which has the formula MX ₂ (M is The above element, X represents a chalcogen (S, Se, Te).
Clay-based minerals generally have a two-layer structure having an octahedral layer with aluminum, magnesium, etc. as the central metal at the top of the silica tetrahedral layer, and a silica tetrahedral layer, with aluminum, magnesium, etc. It is classified into a type having a three-layer structure in which an octahedral layer made of a central metal is sandwiched from both sides. Examples of the former two-layer structure type include kaolinite group and antigolite group. Examples of the latter three-layer structure type include smectite group, vermiculite group, mica group, etc. depending on the number of interlayer cations. Can do.
Examples of these clay minerals include clay minerals such as smectite group and vermiculite group. More specifically, kaolinite, dickite, nacrite, halloysite, antigolite, chrysotile, pyrophyllite, montmorillonite, hectorite, tetrasilic mica, sodium teniolite, margarite, talc, vermiculite, xanthophyllite, Chlorite and the like can be mentioned. References can also be made to articles such as Haruo Shiramizu, “Clay Mineralogy”, 1988, Asakura Shoten. Smectite is particularly preferable, and examples of the smectite include montmorillonite, hydelite, nontronite, saponite, iron saponite, hectorite, soconite, and stevensite.

In addition to the clay mineral (natural product), it may be a synthetic product or a processed product (for example, a surface-treated product of a silane coupling agent). As the synthetic smectite, the formula Na _{0.1-1.0 mg 2.4~2.9 Li 0.0~0.6 Si 3.5~4.0 O 9.0~10.6} (OH and / or _F) those represented by _{1.5 to 2.5} Is mentioned. There are three methods for producing synthetic smectite and synthetic mica, namely, a hydrothermal reaction method (JP-A-6-345419), a solid-phase reaction method, and a melting method (see JP-A-5-270815).
In the hydrothermal reaction method, an aqueous solution or aqueous slurry containing various raw materials such as silicate, magnesium salt, alkali metal ion, alkali metal salt, and fluorine ion is heated at a high temperature and high pressure of 100 to 400 ° C. in an autoclave or a pipe reactor. It is the method of reacting and synthesizing at the beginning. In the hydrothermal reaction method, since the crystal growth is slow and large particles cannot be obtained, in general, most particles have a particle size of 10 to 100 nm. Of course, the hydrothermal reaction can produce large particles having a particle diameter of 1 μm or more if they are synthesized under conditions of low concentration, low temperature and long time, but there is a problem that the production cost becomes extremely high.

The solid phase reaction method is a method for producing synthetic mica by reacting with talc, alkali silicofluoride and other raw materials for several hours in the range of 400 to 1000 ° C. In solid phase reaction, element migration occurs while leaving the talc structure of the raw material, and mica is produced (topotaxy), so the quality of the resulting synthetic mica depends on the talc physical properties of the raw material and its impurities, or the element transfer is completely Since it cannot be controlled, there is a problem that the purity and crystallinity of synthetic mica are low.
In the melting method, anhydrous silicic acid, magnesium oxide, aluminum oxide, potassium silicofluoride, potassium carbonate, and other raw materials are melted at a melting point (for example, 1500 ° C.) or higher of mica and then slowly cooled to crystallize synthetic mica and synthetic smectite. It is a manufacturing method. Also, depending on the heating method, there are an external heating type melting method and an internal heating type melting method. The external heating type melting method is a method in which the crucible containing the raw material is put into a chamber having a temperature higher than the melting point and the temperature is raised, and then moved to a chamber having a temperature lower than the melting point. There is a point. The internal heating type melting method is a method in which a raw material is heated and melted by energization in a vessel equipped with a graphite (carbon) electrode or a metal electrode, and then cooled. In the fusion method, the internal heating type melting method is generally used. It is. The melt fusion method can produce a synthetic product having a controlled particle size by pulverizing and classifying the cooled and crystallized mass. The fusion method can use raw materials with high purity as raw materials, and since the raw materials can be mixed uniformly, it produces high-crystallinity, large particle size, high-purity synthetic mica and synthetic smectite. There is an advantage that can be done.

Examples of the synthetic inorganic layered compound include fluorine phlogopite (KMg ₃ AlSi ₃ O ₁₀ F, melting method or solid phase reaction method), potassium tetrasilicon mica (KMg _2.5 Si ₄ O ₁₀ F ₂ , melting method), sodium tetra Silicon mica (NaMg _2.5 Si ₄ O ₁₀ F ₂ , melting method), sodium teniolite (NaMg ₂ LiSi ₄ O ₁₀ F ₂ , melting method), lithium teniolite (LiMg ₂ LiSi ₄ O ₁₀ F ₂ , melting method) ), Etc., sodium hectorite (Na _0.33 Mg _2.67 Li _0.33 Si _4.0 O ₁₀ (OH or F) ₂ , hydrothermal reaction method or melting method), lithium hectorite (Na _{0) .33 Mg 2.67 Li 0.33 Si 4.0 O} 10 (OH or F) _2, hydrothermal reaction method or a fusion method), saponite _{(Na 0.33} Mg _{.67 AlSi 4.0 O 10 (OH)} 2, hydrothermal reaction method) and synthetic smectite such.
As commercial products of clay minerals, natural bentonite generally called sodium bennite, Kunipia (natural montmorillonite, manufactured by Kunimine Industry), Smecton (hydrothermal reaction method synthetic smectite, manufactured by Kunimine Industry Co., Ltd.), Veegum (Trademark: Vanderbilt) Laponite (Trademark: Laporte), DM Clean A, DMA-350, Na-Ts, NTO-5 (Melting Method, Sodium Tetrasilicon Mica, Trademark: Topy Industries), Bengel (Trademark: Toyoshun) Yoko Co., Ltd.), Somasif ME-100 (solid phase reaction method synthetic mica, trademark: Co-op Chemical) and the like can be used, and these can be used alone or in admixture of two or more.

Preferred according to the invention are swellable inorganic layered compounds that readily swell, open and disperse in water. The degree of the “swelling / cleavage” property of the swellable inorganic layered compound to the solvent can be evaluated by the following “swelling / cleavage” test. The swellability of the swellable inorganic layered compound is preferably about 5 mL or more (more preferably about 20 mL or more) in the following swellability test. Specific examples of the swelling property include the above Kunipia (swelling force: 65 mL / 2 g or more), smecton (swelling force: 60 mL / 2 g or more), DM Clean A, DMA-350, Na-Ts (swelling force: 30 mL / 2 g or more), ME-100 (trademark: manufactured by Coop Chemical Co., swelling power: 20 mL / 2 g or more), Bengel (swelling power: 38 mL / 2 g or more), and the like.
On the other hand, the cleavage property of the swellable inorganic layered compound is preferably about 5 mL or more (more preferably about 20 mL or more) in the following cleavage test. In these cases, a solvent having a density smaller than that of the swellable inorganic layered compound is used as the solvent. As the solvent, water is preferably used.

The swelling test will be described in detail. Slowly add 2 g of swellable inorganic layered compound to 100 mL of solvent (100 mL graduated cylinder as container). The volume of the former (swellable inorganic layered compound dispersion layer) is read from the scale of the interface between the swellable inorganic layered compound dispersion layer and the supernatant after 24 hours at 23 ° C. The larger this value, the higher the swelling property.
The cleavage test will be described in detail. Slowly add 30 g of the swellable inorganic layered compound to 1500 mL of the solvent, and using a disperser (manufactured by Asada Tekko Co., Ltd., Desper MH-L, blade diameter 52 mm, rotation speed 3100 rpm, container capacity 3 L, bottom-blade distance 28 mm) After dispersing for 90 minutes at a peripheral speed of 8.5 m / sec (23 ° C.), take 100 mL of the dispersion, place it in a graduated cylinder and let stand for 60 minutes, then read the volume of the swellable inorganic layered compound dispersion layer from the interface with the supernatant .

The swellable inorganic layered compound preferred for use in the present invention has a cation exchange capacity of 30 to 300 meq, more preferably 50 to 250 meq, particularly preferably 60 to 200 meq per 100 g. When the cation exchange capacity is less than 30 meq / 100 g, the effect of the nitrogen-containing compound is reduced and the moisture resistance is not excellent. On the other hand, if it exceeds 300 meq / 100 g, the coating tends to aggregate, which is not preferable. In general, natural and synthetic squametites having a cation exchange capacity of 85 to 130 meq / 100 g are particularly preferred in the present invention.
The cation exchange capacity is generally measured by an alcohol washing method (Schollenberger method or its improved method, see Mitsufumi Wada (1981) Clay Science 21, 160-163). Collect 0.2 to 1.0 g of the swellable inorganic layered compound powder or about 10 to 30 ml of about 1 to 3% aqueous dispersion in a 100 ml capacity centrifuge tube. Add 1N ammonium acetate (CH ₃ COONH ₄ ) solution (pH 7) to make about 80 ml, shake well, then centrifuge and discard the supernatant (centrifuge washing). After centrifuge washing is repeated 4 times, centrifuge washing is performed 3 times with 80% ethanol aqueous solution (pH 7) in order to remove excess salt remaining in the centrifuge tube. Next, the centrifuge washing is repeated 4 times using a 10% NaCl aqueous solution, and all the supernatant of the centrifuge tube is collected to obtain an extract. NH4 in the extract is quantified by distillation, and the number of milligram equivalents (meq) per dry mass (100 g) of the sample is taken as the value of cation exchange capacity (CEC). The measurement is performed in an environment of 23 ° C. The measurement was performed at 7 points, and the average of 5 points excluding the maximum value and the minimum value was used as the measurement value.

  The swellable inorganic layered compound preferably has an aspect ratio of 50 to 5000. The aspect ratio (Z) is indicated by the relationship Z = L / a, where L is the average particle diameter of the swellable inorganic layered compound in water (measured by laser diffraction method. HORIBA, Ltd. LA-910, refractive index). 1.3, median diameter of 50% volume distribution), and a is the thickness of the swellable inorganic layered compound. Thickness is the value which calculated | required the cross section of the moisture-proof layer by the photograph observation by SEM or TEM. The average particle size is preferably 0.1 μm to 100 μm, particularly preferably 0.5 μm to 50 μm. When the particle diameter is less than 0.1 μm, the aspect ratio becomes small, and it becomes difficult to align the moisture-proof layer in parallel to the moisture-proof surface, resulting in insufficient moisture-proof effect. When the particle diameter exceeds 100 μm, the swellable inorganic layered compound protrudes from the moisture-proof layer, which is not preferable.

Among these swellable inorganic layered compounds, sodium tetrasilicon mica, sodium teniolite, lithium teniolite, sodium hectorite, lithium hectorite, saponite, and natural smectite (montmorillonite) are preferable. Among these, sodium tetrasilicon mica (manufactured by Topy Kogyo Co., DMA350) and talc produced by the fusion method from the viewpoint of particle size, aspect ratio, and crystallinity, and silicon fluoride are intercalated and fired at about 800 ° C. Swellable fluorine mica obtained in this way is particularly preferred.
In addition, the inorganic layered compound used in the present invention preferably has an average particle diameter of 20 nm to 100 μm, preferably 0.1 μm to 50 μm, more preferably dispersed in water or a solvent. Is 1 μm to 30 μm. When the average particle size is less than 20 nm, the aspect ratio becomes small, and the effect of improving moisture resistance is small. On the other hand, when the thickness exceeds 100 μm, the pigment protrudes from the surface of the coating layer, which leads to poor appearance and reduced moisture resistance.

The average particle diameter of the inorganic layered compound used in the present invention dispersed in water or solvent is a value measured by a laser diffraction particle size distribution measuring apparatus applying light scattering theory when the average particle diameter is 0.1 μm or more. . In addition, the value measured by the dynamic light scattering method is used when the average particle size dispersed in water or solvent is 0.1 μm.
The preferred aspect ratio of the inorganic layered compound used in the present invention is 5 or more, and particularly preferred is an aspect ratio of 10 or more. When the aspect ratio is less than 5, the moisture resistance is lowered because the curved path effect is small. The higher the aspect ratio, the higher the number of layers in the coating layer of the inorganic stratiform compound, and the higher the moisture-proof performance. The thickness of the inorganic layered compound is measured from a cross-sectional photograph of the moisture-proof film. Thickness of 0.1 μm or more is obtained by image analysis from an electron micrograph. Those having a thickness of less than 0.1 μm are obtained by image analysis from a transmission electron micrograph. The aspect ratio referred to in the present invention is obtained by dividing the average particle size dispersed in the water or solvent by the thickness obtained from the cross-sectional photograph of the moisture-proof film.

  The blending amount of the ethylene-modified polyvinyl alcohol and the inorganic stratiform compound in the first gas barrier layer is preferably 99/1 to 30/70 in terms of mass, more preferably 93/7 to 35/65, particularly preferably 95/5. 40/60. When the compounding amount of the inorganic layered compound is less than 1%, the moisture resistance improving effect and the disaggregation improving effect become small. If the inorganic layered compound exceeds 70%, the resin that fills the space between the inorganic layered compounds is insufficient, leading to an increase in voids and pinholes, resulting in deterioration of moisture resistance.

  The gas barrier paint in the present invention is a water-based paint, but if necessary, an alcohol solvent such as ethanol or isopropyl alcohol, or a solvent such as methyl ethyl ketone or toluene may be added.

  In the present invention, a gas barrier coating is applied to a paper support to form a gas barrier layer. The coating equipment is not particularly limited, but a blade coater, bar coater, air knife coater, slit die coater, gravure coater, micro gravure coater, gate roll coater or the like is preferable. In particular, a coater that scrapes the coating surface such as a blade coater, a bar coater, an air knife coater, or a slit die coater is preferable for forming the gas barrier layer in terms of promoting the orientation of the inorganic layered compound.

  The substrate used in the present invention is not particularly limited as long as it contains plant-derived pulp as a main component, but is not limited to high quality paper, medium quality paper, fine coated paper, coated paper, glossy paper, bleached paper. Alternatively, unbleached kraft paper (acidic paper or neutral paper), paperboard used for corrugated cardboard, building material, whiteball, chipboard, etc., white paperboard, etc. are suitable.

Further, a pigment layer containing a pigment and a resin may be provided between the paper support and the moisture-proof layer in order to reduce the coating suitability and the coating amount of the moisture-proof layer. Alternatively, a pigment layer containing a pigment and a resin may be provided on the surface of the paper support opposite to the gas barrier layer in order to improve printability.
The pigments are calcium carbonate, kaolin and clay. Firing clay, talc, barium sulfate and the like are preferably used. As the resin, a styrene-butadiene copolymer, an acrylic-styrene copolymer, polyvinyl alcohol, starch, or the like is preferably used.
The mixing ratio of the pigment and the resin is preferably pigment / resin = 50/50 to 99/1 in terms of mass.

  The structure of the gas barrier laminate of the present invention is as follows: paper support / first gas barrier layer / second gas barrier layer, paper support / pigment layer / first gas barrier layer / second gas barrier layer, pigment layer / paper Examples thereof include support / first gas barrier layer / second gas barrier layer, pigment layer / paper support / pigment layer / first gas barrier layer / second gas barrier layer.

  Moreover, a sealant layer such as polyethylene or polypropylene is provided on the second gas barrier layer of the gas barrier laminate of the present invention to form a packaging laminate. The sealant can be laminated by a melt extrusion lamination method, a dry lamination method, or a coating method. An anchor layer may be provided in order to improve adhesion between the gas barrier layer and the sealant layer. The anchor layer is preferably a urethane resin or a polyester resin, and may contain a curing agent such as isocyanate.

  Hereinafter, the present invention will be described in detail by way of examples.

<Modified PVA1>
A pressure-resistant reaction vessel equipped with a stirrer, a thermometer, an ethylene introduction tube, a nitrogen introduction tube, and a cooler was charged with 100 parts of vinyl acetate and 30 parts of methanol, and after replacing with nitrogen, the pressure became 5 kg / cm ² . Was injected with ethylene. A solution in which 2,2′-azobisisobutyronitrile was dissolved in methanol as an initiator was prepared, and nitrogen substitution was performed by bubbling with nitrogen gas. The temperature of the reaction vessel charged with the monomer was raised, and when the internal temperature reached 60 ° C., an initiator solution was injected to start polymerization. Cooled after 3 hours. Then, it was deethyleneated, and then the unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of ethylene-modified polyvinyl acetate. To this, a methanol solution of NaOH (NaOH content 10 mass%) was added to initiate the saponification reaction. After 1 minute from the addition of the alkaline solution, the resulting gelled product is pulverized with a pulverizer, and further allowed to stand for 1 hour to allow the saponification reaction to proceed. Then, methyl acetate is added to the reaction system to leave the remaining alkali. Was partially neutralized. White solid-modified polyvinyl alcohol was filtered off, methanol was added thereto, and the mixture was allowed to stand at room temperature for 3 hours, washed, and drained by centrifugation. The denatured polyvinyl alcohol after washing is centrifuged and then dried for 1 day under a nitrogen stream (oxygen concentration 8%) using a drier whose internal temperature is kept at 90 ° C. Got alcohol. This is designated as modified PVA1.
The modified PVA1 had a polymerization degree of 1200, a saponification degree of 98.6 mol%, and an ethylene content of 6.2 mol%.
In the present invention, the polymerization degree and the saponification degree were determined according to “3.7 Average polymerization degree” and “3.5 Saponification degree” of JIS K 6725 “Testing methods for polyvinyl acetate”. The ethylene content was determined by analysis by ¹ H-NMR and ¹³ C-NMR. Regarding ethylene content, commercially available ethylene vinyl alcohol (such as “Eval L101” manufactured by Kuraray) was used as a standard substance.

<Modified PVA2>
Modified polyvinyl alcohol was produced in the same manner as modified PVA1, except that ethylene was injected so that the pressure was 5.5 kg / cm ² . This is designated as modified PVA2.
The modified PVA2 had a polymerization degree of 1200, a saponification degree of 98.2 mol%, and an ethylene content of 11.2 mol%.

<Modified PVA3>
Modified polyvinyl alcohol was produced in the same manner as modified PVA1, except that ethylene was injected so that the pressure was 6.0 kg / cm ² . This is designated as modified PVA3.
The modified PVA3 had a polymerization degree of 1200, a saponification degree of 98.4 mol%, and an ethylene content of 18.2 mol%.

<Modified PVA4>
Modified polyvinyl alcohol was produced in the same manner as modified PVA1, except that ethylene was injected so that the pressure was 4.0 kg / cm ² . This is designated as modified PVA4.
The modified PVA4 had a polymerization degree of 1200, a saponification degree of 98.0 mol%, and an ethylene content of 4.5 mol%.

<Modified PVA5>
Modified polyvinyl alcohol was produced in the same manner as modified PVA1, except that ethylene was injected so that the pressure was 3.0 kg / cm ² . This is designated as modified PVA5.
The modified PVA5 had a polymerization degree of 1200, a saponification degree of 98.8 mol%, and an ethylene content of 2.1 mol%.

<Modified PVA6>
A modified polyvinyl alcohol is produced in the same manner as the modified PVA1 except that ethylene is injected so that the internal temperature during polymerization is 100 ° C. and the pressure is 6.0 kg / cm ² , and cooling is performed 5 hours after the start of polymerization. did. This is designated as modified PVA6.
The modified PVA6 had a polymerization degree of 2400, a saponification degree of 98.5 mol%, and an ethylene content of 9.2 mol%.
<Example 1>
Coated paper with a basis weight of 84 g / m ² (manufactured by Oji Paper Co., Ltd .: product name OK top coat, pigment layer / paper support / pigment layer, the coating amount of the pigment layer is 15 g / m ² on one side) 33.3 parts of an aqueous dispersion of an inorganic stratiform compound (NTO-5, solid content 6%, sodium tetrasilicate mica), 100 parts of an aqueous solution of alcohol-modified PVA1 (solid content 10%), water Add 16.7 parts and stir the first gas barrier paint (solid content 8%, pH 7.4, viscosity 350 cps) obtained by stirring so that the solid content is 1.5 g / m ^2. And dried with a hot air dryer at 120 ° C. for 1 minute to form a first gas barrier layer.
Next, a second gas barrier coating material composed of an aqueous solution (solid content: 10%) of modified PVA1, which is ethylene-modified polyvinyl alcohol, is 1.5 g / m ² in solid content on the first gas barrier layer. Coating was performed using a Mayer bar, and drying was performed at 120 ° C. for 1 minute with a hot air dryer to form a second gas barrier layer to obtain a gas barrier laminate.

<Example 2>
A gas barrier laminate was obtained in the same manner as in Example 1 except that PVA2 was used as the ethylene-modified polyvinyl alcohol used for the first gas barrier layer and the second gas barrier layer.

<Example 3>
A gas barrier laminate was obtained in the same manner as in Example 1 except that PVA3 was used as the ethylene-modified polyvinyl alcohol used for the first gas barrier layer and the second gas barrier layer.

<Example 4>
A gas barrier laminate was obtained in the same manner as in Example 1 except that PVA4 was used as the ethylene-modified polyvinyl alcohol used for the first gas barrier layer and the second gas barrier layer.

<Example 5>
A gas barrier laminate was obtained in the same manner as in Example 1 except that PVA5 was used as the ethylene-modified polyvinyl alcohol used for the first gas barrier layer and the second gas barrier layer.

<Example 6>
A gas barrier laminate was obtained in the same manner as in Example 1 except that the ethylene-modified polyvinyl alcohol used for the first gas barrier layer and the second gas barrier layer was PVA6.

<Example 7>
Coated paper with a basis weight of 84 g / m ² (manufactured by Oji Paper Co., Ltd .: product name OK top coat, pigment layer / paper support / pigment layer, the coating amount of the pigment layer is 15 g / m ² on one side) 83.3 parts of an aqueous dispersion of an inorganic layered compound (NTO-5, solid content 6%, sodium tetrasilicate mica), 100 parts of an aqueous solution (solid content 10%) of modified PVA1 that is alcohol, water 4.2 parts are added and the first gas barrier paint (solid content 8%, pH 7.4, viscosity 350 cps) obtained by stirring is added to a Mayer bar so that the solid content is 1.5 g / m ^2. And dried with a hot air dryer at 120 ° C. for 1 minute to form a first gas barrier layer.
Next, a second gas barrier coating material composed of an aqueous solution (solid content: 10%) of modified PVA1, which is ethylene-modified polyvinyl alcohol, is 1.5 g / m ² in solid content on the first gas barrier layer. Coating was performed using a Mayer bar, and drying was performed at 120 ° C. for 1 minute with a hot air dryer to form a second gas barrier layer to obtain a gas barrier laminate.

<Example 8>
Coated paper with a basis weight of 84 g / m ² (manufactured by Oji Paper Co., Ltd .: product name OK top coat, pigment layer / paper support / pigment layer, the coating amount of the pigment layer is 15 g / m ² on one side) 58.3 parts of an aqueous dispersion of inorganic layered compound (Topy Industries, NTO-5, solid content 6%, sodium tetrasilicate mica) in 100 parts of an aqueous solution (solid content 10%) of modified PVA1 that is alcohol, water Add 10.4 parts and stir the first gas barrier coating (solid content 8%, pH 7.4, viscosity 350 cps) obtained by stirring so that the solid content is 1.5 g / m ^2. And dried with a hot air dryer at 120 ° C. for 1 minute to form a first gas barrier layer.
Next, a second gas barrier coating material composed of an aqueous solution (solid content: 10%) of modified PVA1, which is ethylene-modified polyvinyl alcohol, is 1.5 g / m ² in solid content on the first gas barrier layer. Coating was performed using a Mayer bar, and drying was performed at 120 ° C. for 1 minute with a hot air dryer to form a second gas barrier layer to obtain a gas barrier laminate.

<Example 9>
Coated paper with a basis weight of 84 g / m ² (manufactured by Oji Paper Co., Ltd .: product name OK top coat, pigment layer / paper support / pigment layer, the coating amount of the pigment layer is 15 g / m ² on one side) 16.7 parts of an aqueous dispersion of an inorganic layered compound (Topy Industries, NTO-5, solid content 6%, sodium tetrasilicate mica) in 100 parts of an aqueous solution (solid content 10%) of modified PVA1 that is alcohol, water Add 20.8 parts and stir the first gas barrier paint (solid content 8%, pH 7.4, viscosity 350 cps) obtained by stirring so that the solid content is 1.5 g / m ^2. And dried with a hot air dryer at 120 ° C. for 1 minute to form a first gas barrier layer.
Next, a second gas barrier coating material composed of an aqueous solution (solid content: 10%) of modified PVA1, which is ethylene-modified polyvinyl alcohol, is 1.5 g / m ² in solid content on the first gas barrier layer. Coating was performed using a Mayer bar, and drying was performed at 120 ° C. for 1 minute with a hot air dryer to form a second gas barrier layer to obtain a gas barrier laminate.

<Example 10>
Coated paper with a basis weight of 84 g / m ² (manufactured by Oji Paper Co., Ltd .: product name OK top coat, pigment layer / paper support / pigment layer, the coating amount of the pigment layer is 15 g / m ² on one side) 8.3 parts of an aqueous dispersion of inorganic layered compound (Topy Industries, NTO-5, solid content of 6%, sodium tetrasilicate mica) in 100 parts of an aqueous solution of alcohol-modified PVA1 (solid content of 10%), water Add 22.9 parts and stir the first gas barrier coating (solid content 8%, pH 7.4, viscosity 350 cps) obtained by stirring so that the solid content is 1.5 g / m ^2. And dried with a hot air dryer at 120 ° C. for 1 minute to form a first gas barrier layer.
Next, a second gas barrier coating material composed of an aqueous solution (solid content: 10%) of modified PVA1, which is ethylene-modified polyvinyl alcohol, is 1.5 g / m ² in solid content on the first gas barrier layer. Coating was performed using a Mayer bar, and drying was performed at 120 ° C. for 1 minute with a hot air dryer to form a second gas barrier layer to obtain a gas barrier laminate.

<Comparative Example 1>
A gas barrier laminate was obtained in the same manner as in Example 1 except that the second gas barrier layer was not provided.

<Comparative Example 2>
Coated paper with a basis weight of 84 g / m ² (manufactured by Oji Paper Co., Ltd .: product name OK top coat, pigment layer / paper support / pigment layer, the coating amount of the pigment layer is 15 g / m ² on one side) 33.3 parts of an aqueous dispersion of an inorganic stratiform compound (NTO-5, solid content 6%, sodium tetrasilicate mica), 100 parts of an aqueous solution of alcohol-modified PVA1 (solid content 10%), water Add 16.7 parts and stir the first gas barrier paint (solid content 8%, pH 7.4, viscosity 350 cps) obtained by stirring so that the solid content is 1.5 g / m ^2. And dried with a hot air dryer at 120 ° C. for 1 minute to form a first gas barrier layer.
Next, the first gas barrier paint is applied on the first gas barrier layer so as to have a solid content of 1.5 g / m ² using a Mayer bar, and then heated at 120 ° C. for 1 minute using a hot air dryer. It dried and formed the 2nd gas barrier layer and obtained the gas-barrier laminated body.

<Comparative Example 3>
Unmodified polyvinyl on one side of coated paper with a basis weight of 84 g / m ² (Oji Paper Co., Ltd .: product name OK top coat, pigment layer / paper support / pigment layer, the coating amount of the pigment layer is 15 g / m ² on one side) To 100 parts of an aqueous solution (solid content 10%) of PVA (part number PVA105, manufactured by Kuraray Co., Ltd., degree of polymerization 500) as an alcohol, an aqueous dispersion of inorganic layered compound (Topy Industries, NTO-5, solid content 6) 33.3 parts of sodium tetrasilicate mica) and 16.7 parts of water were added and stirred to obtain a first gas barrier paint (solid content 8%, pH 7.4, viscosity 320 cps). The first gas barrier layer was formed by coating using a Mayer bar so as to be 1.5 g / m ² and drying at 120 ° C. for 1 minute using a hot air dryer.
Next, a second gas barrier paint composed of an aqueous solution (solid content 10%) of PVA (product number PVA105, manufactured by Kuraray, complete saponification, polymerization degree 500), which is an unmodified polyvinyl alcohol, is formed on the first gas barrier layer. Coating with a Mayer bar so that the solid content is 1.5 g / m ^2, and drying with a hot air dryer at 120 ° C. for 1 minute to form a second gas barrier layer to obtain a gas barrier laminate. It was.

The gas barrier laminates obtained in Examples and Comparative Examples were evaluated by the following methods, and the results are shown in Table 1.
[Evaluation methods]
1) Oxygen permeability On the gas barrier layer of the gas barrier laminate produced in Examples 1 to 10 and Comparative Examples 1 to 3, an anchoring agent for laminating (manufactured by Toyo Morton, polyester-based main polyester polyester EL557A / polyisocyanate-based curing agent / (Mixed at a solid ratio of ethyl acetate = 1.6 / 0.8 / 12.5 parts) and coated so that the coating amount is 4 cc / m ² and dried at 80 ° C. for 30 seconds. I let you. On the obtained anchor layer, polyethylene (manufactured by Nippon Polychem, LC522, low density polyethylene, MFR 3.5 g / 10 min) was melt-extruded and laminated to a thickness of 20 μm. The obtained polyethylene laminate laminate sample was subjected to JIS-K-7126 B method (isobaric method) with the polyethylene lamination side as the oxygen detector side (nitrogen side) and the oxygen side and nitrogen side at 23 ° C. and 90% RH conditions. (Oxygen permeability measuring device: OX-TRAN100 type, manufactured by MOCON). After setting the sample, the value after 24 hours was defined as the oxygen permeability. The oxygen permeability is preferably 30 cc / m ² · 24 hr or less, particularly preferably 20 cc / m ² · 24 hr or less.
Further, when the measurement conditions were 23 ° C. and 0% RH on both the oxygen side and the nitrogen side, the oxygen permeability was 1 cc / m ² · 24 hr or less in all Examples and Comparative Examples.
2) Adhesive strength On the gas barrier layers of the gas barrier laminates produced in Examples 1 to 10 and Comparative Examples 1 to 3, an anchoring agent for lamination (manufactured by Toyo Morton, polyester-based main component polyester EL557A / polyisocyanate-based curing agent / acetic acid) (Ethyl = 1.6 / 0.8 / 12.5 parts by mixing in a solid ratio) was applied so that the coating amount was 4 cc / m ² in solid form and dried at 80 ° C. for 30 seconds. It was. On the obtained anchor layer, polyethylene (manufactured by Nippon Polychem, LC522, low density polyethylene, MFR 3.5 g / 10 min) was melt-extruded and laminated to a thickness of 20 μm. A cross tape (width 3 cm, length 10 cm) was applied to the surface of the polyethylene laminate surface of the obtained polyethylene laminate laminate, and after 10 reciprocations with a rubber roller, the cloth tape was peeled off by hand. The adhesion strength was evaluated as follows.
◎: Laminate breaks 100% material ○: Part peels between polyethylene laminate layer and gas barrier layer, part breaks material △: All peels between polyethylene laminate layer and gas barrier layer, but resistance Strong feeling x: Peels without resistance between the polyethylene laminate layer and the gas barrier layer.
3) Barrier property of packaging bag On the gas barrier layer of the gas barrier laminate produced in Examples 1 to 10 and Comparative Examples 1 to 3, an anchoring agent for lamination (manufactured by Toyo Morton, polyester-based main polyester polyester EL557A / polyisocyanate-based curing) Agent / ethyl acetate = 1.6 / 0.8 / 12.5 parts by mixing in a solid ratio) and coated so that the coating amount is 4 cc / m ² in a solid state at 80 ° C. and 30 ° C. Dry for 2 seconds. On the obtained anchor layer, polyethylene (manufactured by Nippon Polychem, LC522, low density polyethylene, MFR 3.5 g / 10 min) was melt-extruded and laminated to a thickness of 20 μm. The obtained polyethylene laminate was sampled to a predetermined size (160 mm × 65 mm), and the long side was folded in half so that the size was 80 mm × 65 mm. Using a heat sealing machine, both sides on the 65 mm side were heat sealed. Next, vacuum evacuation was performed, nitrogen filling was performed, and heat sealing on the 80 mm side was performed to obtain a packaging bag filled with nitrogen. As a filling machine, a vacuum gas filling sealer “VG-400” manufactured by Fuji Impulse was used.
The packaging bag was allowed to stand in an environment of 23 ° C. and 50%, and the oxygen concentration in the packaging bag was measured every week until 4 weeks later. The oxygen concentration was measured using an oxygen concentration meter “RO-112” manufactured by Iijima Electronics. The oxygen concentration was measured for three points of the package. Measurement was made to the second decimal place, the average value was rounded off, and the first decimal place was taken as the oxygen concentration.

As is clear from Table 1, a layer containing ethylene-modified polyvinyl alcohol and synthetic mica is used as the first gas barrier layer, and ethylene-modified polyvinyl alcohol is used as the second gas barrier layer. Adhesion strength is greatly improved.
Further, as apparent from Table 2, the oxygen barrier property as a package is obtained by using a layer containing ethylene-modified polyvinyl alcohol and synthetic mica as the first gas barrier layer and ethylene-modified polyvinyl alcohol as the second gas barrier layer. Is greatly improved.
As is clear from Tables 1 and 2, the correlation between the oxygen permeability of the laminate provided with the polyethylene laminate layer in the gas barrier layer and the gas barrier property of the package using the laminate is low. The correlation between the adhesive strength with the laminate layer and the gas barrier property is high, and improving the adhesive strength as in the present invention is effective in improving the oxygen barrier property of the package.

Claims (2)

A gas barrier laminate comprising a paper support and a first gas barrier layer containing an ethylene-modified polyvinyl alcohol resin and an inorganic layered compound, and a second gas barrier layer made of ethylene-modified polyvinyl alcohol. 2. The gas barrier laminate according to claim 1, wherein the mass ratio of the ethylene-modified polyvinyl alcohol and the inorganic stratiform compound in the first gas barrier layer is 100/5 to 100/50.