JP3139550B1 - Barrier paper - Google Patents

Abstract

[Summary] [Problem] Moistureproofness and gas barrier properties can be dramatically improved.
An object of the present invention is to provide a barrier paper which has high mechanical properties and can be easily cut at the time of recycling. SOLUTION: This is a barrier paper comprising a base paper and a barrier layer having a moisture-proof property and a gas barrier property, wherein the barrier layer comprises a water-disintegrating polymer and an inorganic filler, and is molecularly dispersed as the inorganic filler. Characterized in that a layered clay mineral is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a barrier paper having a moisture-proof property and a gas barrier property and capable of being made on recycled paper.

[0002]

2. Description of the Related Art At present, as a barrier paper including a moisture-proof paper, a gas barrier paper and the like, a barrier layer is formed on a base paper by coating and laminating a synthetic resin such as polyethylene, polypropylene and vinyl chloride. It is generally used to impart properties, waterproofness, and gas barrier properties. Such barrier papers can sufficiently exhibit functions such as moisture proofing properties, but have poor disintegration properties when recovered and used as used paper, and are difficult to reuse. Therefore, it was a big problem from the viewpoint of resource saving and effective utilization.

On the other hand, there has been disclosed a method of laminating a water-disintegrating barrier layer on a base paper by applying a liquid mixture of a wax emulsion alone or a synthetic rubber-based latex as a recyclable barrier paper. (See Japanese Patent Publication No. 10759/1991) Further, a method has been developed in which a flat inorganic filler is blended with the resin composition for forming such a barrier layer to improve the moisture-proof property and the barrier property (Japanese Patent Application Laid-Open No. 9-1997). No. 21096).

Mica having an aspect ratio of 5 or more and an average particle size of 5 μm to 50 μm is used as the flat inorganic filler. The reason why the blending of the flat inorganic filler is that the barrier performance is improved. As a result, the permeation area of gas such as water vapor becomes small, and the flat inorganic filler is arranged in parallel to the barrier layer surface and many layers are laminated. As a result of the permeation while bypassing the filler, the required permeation distance of the gas may be increased, and it is presumed that the permeation amount of the gas per unit time is extremely small.

[0005]

When a barrier paper using the above wax is wound into a roll, the wax contained in the surface of the barrier layer adheres to the back surface of the barrier paper in contact with the barrier paper. For this reason, the back surface of the barrier paper becomes very slippery, and when the packaging of the barrier paper is lined up, it becomes irregular, slips off, and when wrapping heavy items, it slips off during transportation and falls off. Problems may occur.

[0006] When the barrier paper is recycled as waste paper, it is common to cut the paper into small pieces of a predetermined size before defibration in order to facilitate defibration into water. However, the above-mentioned conventional recyclable barrier paper has a flat inorganic filler compounded in the resin composition constituting the barrier layer, and is arranged in parallel to the barrier layer surface, and is laminated in multiple layers. Therefore, in order to cut such barrier paper, it is necessary to shear the flat inorganic filler. Therefore, the blade used for cutting the barrier paper at the time of such recycling is easily damaged.

The present invention has been made in view of these disadvantages, and an object of the present invention is to provide a barrier paper that can dramatically improve moisture-proof and gas-barrier properties, has high mechanical properties, and is easy to cut during recycling. It is assumed that.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that it is not sufficient to add only an inorganic filler such as calcium carbonate, but a layered structure in which at least a part of the inorganic filler is molecularly dispersed. By replacing with clay minerals of
They have found that the barrier properties of the barrier layer can be further enhanced.

As a result, the invention made to solve the above-mentioned problem is a barrier paper comprising a base paper and a barrier layer, wherein the barrier layer contains a water-disintegrating polymer and an inorganic filler. The water-disintegrating polymer is formed from a synthetic rubber-based latex and an acrylic emulsion, and a layered clay mineral dispersed molecularly is used as the inorganic filler, and the layered clay mineral has an organic onium on its surface. It is characterized in that the ions are bonded. Here, “molecularly dispersed” means that the water-disintegrating polymer or the like intrudes between layers of the clay mineral, and each layer is molecularly dispersed.

According to this means, the moisture-proof property and the gas barrier property can be remarkably improved. This is presumably because the layered clay mineral dispersed in the barrier layer in a molecular form prevents gas such as water vapor from permeating at the molecular level, resulting in a smaller gas permeation area. In addition, since the inorganic filler added in the barrier layer is a layered clay mineral in which the inorganic filler is dispersed in a molecular state, cutting at the time of recycling is easy.

Further, the resin has a structure in which a layered clay mineral and a polymer are bonded by a strong interaction such as an ionic bond and the resin is crosslinked. In other words, the clay mineral exceeds the binding force between the layers (Vande-Awars force, electrostatic attraction, etc.), is completely separated by layer, exists alone, and has the negative charge of the layer and the resin. Positive charges (onium ions) at the terminals or side chains are bound by ionic bonds. Therefore, the mechanical properties of the barrier paper can be significantly improved. Further, since a clay mineral modified with an organic onium ion is used, a polymer easily enters between layers of the clay mineral, and a barrier layer in which the clay mineral is uniformly dispersed in the water-disintegrating polymer can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. The barrier paper according to the embodiment has a structure in which a base paper and a barrier layer are stacked.

The paper material constituting the base paper is not particularly limited, and various paper materials can be used.
However, in consideration of recyclability, it is preferable to be easily dispersible in water due to mechanical disaggregation.For example, chemical pulp such as hardwood kraft pulp and softwood kraft pulp, high-quality paper made from mechanical pulp, and medium-grade paper Kraft paper, kraft paper, kraft stretch paper and the like. There is no particular limitation on the basis weight of this base paper.
It is preferable to select about 00 g / m ² according to the purpose.

The barrier layer is formed from a resin composition having a specific composition, and the resin composition contains a water-disintegrable polymer and an inorganic filler. As the water-disintegrating polymer, conventionally used wax-based emulsions, latexes, mixtures thereof and the like can be used, but considering the balance between barrier properties and water-disintegrating properties, synthetic rubber-based latex And an acrylic emulsion and a mixture are optimal.

Examples of the synthetic rubber-based latex include styrene butadiene latex, methacrylate butadiene latex, and acrylonitrile butadiene latex, which have good water resistance, good elongation, and hardly cause cracks in the coating layer due to breakage. For this reason, styrene butadiene latex is preferred. Here, the polymerizable monomer is mainly composed of styrene and 1,3-butadiene, but other monomers copolymerizable with styrene and 1,3-butadiene are used within a range not to impair the object of the present invention. be able to. Other monomers copolymerizable with styrene and 1,3-butadiene include aromatic vinyl monomers such as α-methylstyrene, vinyltoluene, pt-butyltoluene, and chlorostyrene; (meth) acrylic Methyl acid,
Ethyl (meth) acrylate, propyl (meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) ) (Meth) acrylate monomers such as n-octyl acrylate, 2-hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; cyano group-containing ethylenically unsaturated monomers such as (meth) acrylonitrile Glycidyl esters of ethylenically unsaturated acids such as glycidyl acrylate and glycidyl methacrylate; glycidyl ethers of unsaturated alcohols such as allyl glycidyl ether; (meth) acrylamide, N-methylol (meth)
(Meth) acrylamide-based monomers such as acrylamide, N-methylol (meth) acrylamide, and N-butoxymethyl (meth) acrylamide; and the like. These polymerizable monomers may be used alone or in combination of two or more. Can be used.

The acrylic emulsion specifically includes styrene and styrene derivatives, acrylic acid (methacrylic acid), acrylic acid (methacrylic acid)
A copolymer system such as an acrylic copolymer or an acrylic-styrene copolymer obtained by copolymerizing an ester or the like can be used.

The compounding ratio of the synthetic rubber latex and the acrylic emulsion is 50: 100 by weight.
The ratio should be 100: 50. This is because, when the blending ratio of the acrylic emulsion is smaller than the above range, it is soft, the water disintegration and the blocking property are deteriorated, and conversely, when the blending ratio of the acrylic emulsion exceeds the above range, it is hard,
This is because the barrier properties deteriorate.

Further, the glass transition temperature (Tg) of the water-disintegrating polymer is preferably in the range of 15 ° C. to 40 ° C., particularly preferably in the range of 20 ° C. to 30 ° C. This is Tg
Is less than 15 ° C., the hardness of the polymer forming the coating layer at the time of defibration is not sufficient, and the polymer is flexible and has a large elongation. It is difficult to separate and disperse, the disintegration property is poor, and the blocking property is also poor. Conversely, if the Tg exceeds 40 ° C., the polymer forming the coating layer becomes very hard and the disintegration becomes very good, but the moisture resistance and heat sealability at the time of bending deteriorate. It is.

The inorganic filler compounded in the barrier layer has a function of further improving the moisture-proof and gas-barrier properties of the barrier layer. Such inorganic fillers include, for example, one or more selected from the group consisting of silicates such as calcium carbonate, calcium sulfate, magnesium oxide, aluminum hydroxide, titanium oxide, zinc oxide, talc and clay, and silica. Can be used. The present invention is characterized in that a layered clay mineral molecularly dispersed in at least a part of the inorganic filler is used. By containing such a layered clay mineral, the moisture-proof property and gas-barrier property of the barrier layer are further enhanced.

Examples of the clay mineral include montmorillonite, saponite, hectorite, beidellite,
There are smectite-based clays such as stevensite and nontronite, vermiculite, halloysite and the like.
It may be natural or synthetic.

In order to molecularly disperse the layered clay mineral in the water-disintegrating polymer, it is preferable to use a clay mineral having an organic onium ion bonded to the surface. The polymer easily enters between the layers of the clay mineral to which the organic onium ions are bonded, and a barrier layer in which the clay mineral is uniformly dispersed in the water-disintegrating polymer is obtained. By using a clay mineral modified with an organic onium ion in this way, by mixing it with a water-disintegrating polymer, the layered clay mineral is dispersed molecularly in the water-disintegrating polymer, and the water-disintegrating property is added to the layered clay mineral. A polymer can be included. At the time of this mixing, the inorganic filler of the present invention can also be added.

Generally, since montmorillonite clay contains impurities other than montmorillonite, clay minerals having organic onium ions bonded thereto also contain impurities. By using the organically modified clay mineral containing this impurity as the inorganic filler, a layered clay mineral in which at least a part of the inorganic filler is molecularly dispersed as in the present invention can be obtained. This method is less costly than binding organic onium ions to the refined clay mineral,
This is a preferred embodiment of the present invention.

Examples of the organic onium ion include hexyl ammonium ion, octyl ammonium ion, 2-ethylhexylammonium ion, dodecyl ammonium ion, lauryl ammonium ion, octadecyl ammonium ion, stearyl ammonium ion, dioctyl dimethyl ammonium ion, and trioctyl ammonium ion. Ions, distearyl dimethyl ammonium ion, ammonium laurate ion, or the like can be used. The organic onium ion preferably has 6 or more carbon atoms. When the number of carbon atoms is less than 6, the hydrophilicity of the organic onium ion is increased, and the compatibility with the polymer may be reduced.

It is preferable to use a clay mineral having a large contact area with a polymer. Thereby, the interlayer of the clay mineral can be largely swollen. Specifically, the cation exchange capacity of the clay mineral is preferably 50 to 200 meq / 100 g. When the amount is less than 50 meq / 100 g, the organic onium ions are not sufficiently exchanged, and it may be difficult to swell between the layers of the clay mineral. On the other hand, when it exceeds 200 meq / 100 g, the bonding force between the layers of the clay mineral becomes strong, and it may be difficult to swell between the layers of the clay mineral.

The organic onium ion is preferably used in an amount of 0.3 to 3 equivalents of the ion exchange capacity of the clay mineral.
If the ion exchange capacity of the clay mineral is less than 0.3 equivalent, it may be difficult to swell between the clay mineral layers, and if it exceeds 3 equivalents, it may cause deterioration of the polymer and cause coloring of the barrier layer. is there. More preferably, the organic onium ion has an ion exchange capacity of 0. 0% of the clay mineral.
Use 5 to 2 equivalents. Thereby, the clay mineral layers can be further swollen, and the deterioration and discoloration of the resin composite material can be further prevented.

As the above-mentioned clay mineral to which the organic onium ion is bonded, it is preferable to use a clay mineral in which a polymerizable monomer is polymerized in the presence of the clay mineral. As the polymerizable monomer, a monomer used in a synthetic resin latex or emulsion described later is preferable, but methacrylic acid,
Copolymer components such as acrylic acid, acrylonitrile and acrylamide are also suitable for improving the affinity between the polymer and the clay mineral.

Further, as the clay mineral to which the organic onium ion is bonded, (a) a compound having both an organic onium ion and a compound having a polymerizable functional group;
In the presence of a compound having both an organic onium ion and a polymerizable functional group, another polymerizable monomer is polymerized,
(C) a combination of a compound having both an organic onium ion and a polymerizable functional group and a polymer containing an organic onium ion synthesized by polymerization of another polymerizable monomer;
Is preferred. Examples of the compound having both the organic onium ion and the polymerizable functional group include quaternary methyl chloride salt of dimethylaminoethyl methacrylic acid, quaternary methyl chloride salt of dimethylaminoethylstyrene, and bromide of dimethylaminopropylethylene. Methyl quaternary salts and the like can be mentioned, and a polymer obtained by combining these can be used in the presence of another polymerizable monomer or a polymer obtained by polymerizing these with another polymerizable monomer.

The mixing ratio of the above-mentioned inorganic filler and the water-disintegrating polymer is preferably in the range of 1:99 to 60:40 by weight. This is because if the inorganic filler is less than 1%, the barrier properties become insufficient, and blocking tends to occur,
Conversely, if it exceeds 60%, the voids between the inorganic filler and the polymer in the barrier layer will be very large, and the barrier properties will be degraded.

The coating amount for forming these barrier layers is preferably in the range of 5 to 50 g / m ² , and more preferably 10 to 30 g / m ^2.
/ M ² is particularly preferred. If the coating amount is less than 5 g / m ² , the barrier properties will be significantly deteriorated, and if it exceeds 50 g / m ² , the improvement in moisture permeability will level off, which is uneconomical.

The coating liquid for forming the barrier layer is as follows:
(A) a method in which an inorganic filler is dispersed in water and mixed with a latex or emulsion; (b) a method in which the inorganic filler is dispersed in a latex or emulsion; (c) polymerization in the presence of a clay mineral to which an organic onium ion is bonded. When an acidic monomer is polymerized, it can be obtained by a method of mixing a latex or emulsion containing a clay mineral or the like. At this time, if necessary, it is possible to use a water-soluble resin such as starch or polyvinyl alcohol as a protective colloid, or to add a dispersant such as polycarboxylic acid, an antifoaming agent, a surfactant, or a color adjusting agent. it can. When the coating liquid prepared in this manner is applied to the base paper and dried, the drying temperature is sufficient if the coating liquid is given a sufficient amount of heat to form a film. Conditions are fine.

When a barrier layer is formed only on one side, it is preferable to apply water on the opposite side of the coated surface to prevent curling.

The coating equipment for forming the barrier layer is not particularly limited, but may be an air knife coater,
It can be arbitrarily selected from a bar coater, a roll coater, a blade coater, a gate roll coater and the like.

[0033]

Hereinafter, the present invention will be described in detail with reference to Examples.
Of course, the present invention should not be construed as being limited based on the description of this embodiment.

Example 1 In terms of solid content, 4 parts by weight of montmorillonite bound with octadecyl ammonium ion and 6 parts by weight of talc were mixed with styrene-butadiene latex 4
5 parts by weight and 45 parts by weight of an acrylic emulsion were mixed and dispersed to prepare a coating liquid for forming a barrier layer. The coating liquid was applied to about 20 g / m ² on a 75 g / m ² kraft paper using a bar coater to obtain a barrier paper of Example 1. The Tg of this coating solution was 26 ° C.

Example 2 Montmorillonite 4 was added to 10 parts by weight of an acrylic emulsion obtained by copolymerizing a quaternary methyl chloride of dimethylaminoethyl methacrylic acid as a coating liquid.
Example 2 was prepared in the same manner as in Example 1 except that a mixture of a mixture of 6 parts by weight of talc and a mixture of 40 parts by weight of styrene butadiene latex and 40 parts by weight of an acrylic emulsion was used. Barrier paper was obtained. The Tg of the coating solution was 22 ° C.

Comparative Example A barrier of Comparative Example was prepared in the same manner as in Example 1 except that 10 parts by weight of talc was mixed and dispersed in 45 parts by weight of styrene butadiene latex and 45 parts by weight of acrylic emulsion. I got the paper.

[Evaluation of Characteristics] Using the barrier papers of Examples 1 and 2 and the barrier paper of Comparative Example, water disintegration and moisture permeability were measured by the following methods, and the results are shown in Table 1. .

(1) Disintegration 1.5 g (pulp concentration: 0.3%) was added to 500 ml of water and a household mixer having a rounded blade (National MX-
1200 G) at room temperature for 3 minutes (voltage 60 V).
8, (590 μm)) and hand-printed with a print heater (1
(50 ° C., mirror surface) for about 10 minutes, and then visually check the resin residue on the surface and the heat melting property, and evaluated it on a three-point scale.

(2) Moisture Permeability The moisture permeability was measured based on the cup method (JIS-Z-0208-B method).

[0040]

[Table 1]

As shown in Table 1 above, the barrier paper of Example 1 had good water disintegration properties, and exhibited better moisture barrier properties than the barrier paper of the comparative example. In addition, the barrier paper of Example 2 also had good water disintegration properties, and exhibited better moisture permeability than the barrier paper of the comparative example.

[0042]

As described above, according to the barrier paper of the present invention, the basic properties of the barrier paper such as moisture proof property, gas barrier property and mechanical properties can be remarkably improved.
In addition, it can be easily recycled as used paper.

Claims (5)

(57) [Claims] 1. A barrier paper comprising a base paper and a barrier layer, wherein the barrier layer comprises a water-disintegrable polymer and an inorganic filler, wherein the water-disintegratable polymer comprises a synthetic rubber-based latex and an acrylic resin.
And a layered clay mineral dispersed molecularly as the above-mentioned inorganic filler, and organic onium ions are bonded to the surface of the above-mentioned layered clay mineral.
Barrier sheet, characterized in that to those were. 2. The barrier paper according to claim 1 , wherein the organic onium ion has a polymerizable functional group. 3. The barrier paper according to claim 1 , wherein the layered clay mineral to which the organic onium ion is bonded is obtained by polymerizing a polymerizable monomer in the presence of the clay mineral. 4. The barrier paper according to claim 3 , wherein the polymerizable monomer is a water-disintegrable polymer constituting a barrier layer. 5. The barrier paper according to claim 1, wherein the glass transition temperature of the water-disintegratable polymer is from 15 ° C. to 40 ° C.