KR100371273B1 - Barrier paper - Google Patents

Abstract

It is an object of the present invention to provide a barrier paper that can drastically improve moisture resistance and gas barrier properties, has excellent mechanical properties, and is easily cut during recycling (recycling).

A barrier layer having a matrix and a barrier layer having moisture resistance and gas barrier properties, the barrier layer containing a water-decomposable polymer and an inorganic filler. In the above, the inorganic filler is characterized in that a layered clay mineral dispersed in a molecular form is used.

Description

Barrier {BARRIER PAPER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a barrier paper having moisture resistance and gas barrier properties and recyclable as recycled paper.

As barrier papers including moisture-proof papers, gas barrier papers, etc., substrates are currently known by coating or bonding synthetic resins such as polyethylene, polypropylene, and vinyl chloride. A barrier layer is formed on i) to provide moisture resistance, water resistance and gas barrier properties. Such barrier paper can exhibit sufficient function with respect to moisture-proof property, etc., but when it is collected and used as old paper, degradability is bad and it is difficult to reuse. Therefore, there was a big problem in terms of resource saving and utilization.

On the other hand, as a recyclable barrier paper, a method of laminating a barrier layer having water degradability on a substrate by coating a wax emulsion alone or a mixed liquid with a synthetic rubber latex is disclosed. Also, a method of improving the moisture resistance and barrier properties by mixing a flat inorganic filler with a resin composition forming such a barrier layer has been developed. See JP-A 9-21096).

As such a plate-shaped inorganic filler, mica and the like having an aspect ratio of 5 or more and an average particle diameter of 5 µm to 50 µm are used. The reason why the barrier performance is improved by the combination of such flat inorganic fillers is that the permeation area of gas such as water vapor is reduced, and the flat inorganic fillers are arranged in parallel with the barrier layer surface so that they are stacked in multiple layers. As the gas in the barrier layer is permeated while bypassing the plate-shaped inorganic filler, the permeation distance of the gas becomes long, and it is thought that the permeation amount of the gas per unit time becomes very small due to coordination with each other.

By the way, when winding up the barrier paper using wax as a roll as mentioned above, the wax contained in the surface of a barrier layer adheres to the back surface of the barrier paper which contact | connects it. As a result, the back surface of the barrier paper is very slippery, and the barrier paper becomes uneven or slips when aligned, and moreover, when the heavy material is packaged, it is shifted and dropped during transportation. There are times when serious problems arise.

In addition, when the barrier paper is recycled as old paper, it is generally cut into small pieces of a predetermined size before decomposition to facilitate the decomposition into water. However, since the conventional recyclable barrier paper is blended with a plate-shaped inorganic filler in the resin composition constituting the barrier layer, and further, is arranged in parallel with the surface of the barrier layer and laminated in multiple layers, the barrier paper can be cut. In order to do this, it is necessary to shear the inorganic filler on the plate. Therefore, the blade used for cutting the barrier paper is easily damaged during such recycling.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a barrier paper that can drastically improve moisture resistance and gas barrier properties, and is excellent in mechanical properties and easily cut during recycling (recycling).

As a result of earnest examination, the present inventors have found that the addition of inorganic fillers such as calcium carbonate is insufficient. However, the barrier layer barrier property is changed by replacing at least a portion of the inorganic filler with a layered clay mineral dispersed in a molecular form. It was found to be further improved.

As a result, the present invention devised to solve the above problems comprises a matrix having a matrix and a barrier layer, the barrier layer comprising a water-decomposable polymer and an inorganic filler. As the inorganic filler, a layered clay mineral dispersed in a molecular form is used. Here, "dispersed in molecular form" means that the water-decomposable polymer or the like penetrates into the interlayer of clay minerals, and each layer is dispersed in a molecular form.

According to such a present invention, moisture resistance and gas barrier property can be improved remarkably. The reason for this is presumably because layered clay minerals dispersed in the barrier layer in the barrier layer prevent permeation of gas such as water vapor at the molecular level, and as a result, the permeation area of the gas becomes small. In addition, since the inorganic filler added in the barrier layer is a layered clay mineral dispersed in a molecular form, cutting is easy at the time of recycling.

In addition, the layered clay mineral and the polymer have a structure in which the resin is crosslinked by bonding by strong interaction such as ionic bonding. In other words, the clay minerals, beyond the layer-to-layer bonds (van der Waals forces, electrostatic forces, etc.), are completely separated and present as a single layer, and the negative charge and terminal or side chains of the layer The positive charge (onium ion) in i) is bound by ionic bonds. Therefore, the mechanical property of the barrier paper can be remarkably improved.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail. The barrier paper according to this embodiment has a structure in which a matrix and a barrier layer are stacked.

The branch material which comprises a base is not specifically limited, Various branch materials can be used. However, in consideration of recyclability, it is preferable to disperse in water by mechanical decomposition, for example, chemical pulp such as hardwood kraft pulp, softwood kraft pulp, or mechanical pulp Examples thereof include upper-quality paper, heavy paper, single-kraft kraft paper, biplane kraft paper, and kraft paper. The weight of the matrix is not particularly limited, and may be appropriately selected depending on the purpose of about 30 to 300 g / m 2.

The barrier layer is formed of a resin composition having a specific composition, and the resin composition contains a water decomposable polymer and an inorganic filler. As such a water-decomposable polymer, emulsions such as waxes, latexes, and mixtures thereof, which are conventionally used, may be used. However, in consideration of the balance between barrier properties (barrier properties) and water decomposability, synthetic rubber latex and acrylic emulsion mixtures may be used. It is optimal.

Examples of the synthetic rubber latex include styrene butadiene latex, methacrylate butadiene latex, acrylonitrile butadiene latex, and the like. However, the water-resistant surface is good and the stretching force is good, so that the coating layer due to cutting Styrene butadiene latex is suitable because it is difficult to produce cracks in industrial processes. Here, the polymerizable monomer mainly consists of styrene and 1,3-butadiene, but other monomers copolymerizable with styrene and 1,3-butadiene can be used within the scope of not impairing the object of the present invention. Do. Examples of the monomer copolymerizable with styrene and 1,3-butadiene include aromatic vinyl monomers such as α-methylstyrene, vinyltoluene, p-t-butyltoluene, and chlorostyrene; Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (Meth) acrylic acid ester monomers, such as (meth) acrylic acid n-octyl, (meth) acrylic acid 2-hydroxyethyl, and (meth) acrylic acid hydroxypropyl; 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 aryl glycidyl ether; (Meth) acrylamide type monomers, such as (meth) acrylamide, N-metholol (meth) acrylamide, N-metholol (meth) acrylamide, and N-butoxymethyl (meth) acrylamide, etc. are mentioned, These polymerizable monomers can be used alone or in combination of two or more thereof.

Moreover, as said acrylic emulsion, the copolymer system, such as an acrylic copolymer which copolymerized styrene and a styrene derivative, acrylic acid (methacrylic acid), acrylic acid (methacrylic acid) ester, etc. can be used specifically ,. .

The blending ratio of the synthetic rubber latex and the acrylic emulsion is preferably 50: 100 ~ 100: 50 by weight. It is soft when the blending ratio of the acrylic emulsion is smaller than the above range, and the water decomposability and blocking properties are worse. On the contrary, when the blending ratio of the acrylic emulsion exceeds the above range, it is hard and blocked. This is because the sex (barrier) is worsened.

In addition, the glass transition temperature (Tg) of the water-decomposable polymer is preferably in the range of 15 ° C. to 40 ° C., particularly in the range of 20 ° C. to 30 ° C. When the Tg is less than 15 ° C, the rigidity of the polymer forming the coating layer at the time of decomposition is not sufficient, and it is flexible and the stretching force is increased, which is a resistance to the shear force at the time of decomposition, and the density It is high, so it is difficult to separate and disperse, degrading deterioration and blocking performance deteriorate. Conversely, if the Tg exceeds 40 ° C, the polymer forming the coating layer becomes very hard and decomposable becomes very good, but moisture-proofing and heat sealability at bending are poor. Because it falls out.

The inorganic filler compounded in the barrier layer functions to further increase the moisture barrier property and gas barrier property of the barrier layer. As the inorganic filler, for example, one or two or more selected from the group of silicates such as calcium carbonate, calcium sulfate, magnesium oxide, aluminum hydroxide, titanium oxide, zinc oxide, talc, clay, silica, and the like can be used. . The present invention is characterized by using a layered clay mineral dispersed in at least a part of the inorganic filler in a molecular form. By containing such layered clay minerals, the moisture barrier property and gas barrier property of the barrier layer are further improved.

Examples of the clay minerals include smectite-based clays such as montmorillonite, saponite, hectorite, heidelite, stevensite, nontronite, and the like. , Vermiculite, halloysite, and the like. It may be natural or synthesized.

In order to disperse a layered clay mineral in molecular form in a water-decomposable polymer, the clay mineral which combined organic onium ion on the surface is used. It is good. The polymer easily penetrates into the interlayer 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-decomposable polymer can be obtained. By mixing clay minerals modified with organic onium ions and mixing them with water-decomposable polymers, the clay minerals are dispersed in the water-decomposable polymer molecularly, and the water-decomposable polymer is contained in the layered clay minerals. It is possible. It is also possible to add the inorganic filler of the present invention at the time of such mixing.

In general, since montmorillonite clay contains impurities other than montmorillonite, impurities in clay minerals in which organic onium ions are bound to it also contain impurities. By using the organic clay mineral containing this impurity as an inorganic filler, it is possible to set it as the layered clay mineral which disperse | distributed at least a part of inorganic filler to molecular form like this invention. This method is cheaper than bonding organic onium ions to purified clay minerals and is a preferred embodiment of the present invention.

As said organic onium ion, hexyl ammonium ion, octyl ammonium ion, 2-ethylhexyl ammonium ion, dodecyl ammonium ion, lauryl ammonium ion, octadecyl ammonium ion, stearyl ammonium ion, dioctyl dimethyl ammonium, for example. Ions, trioctyl ammonium ions, distearyl dimethylammonium ions, ammonium laurate or the like can be used. Moreover, as said organic onium ion, a C6 or more thing is preferable. When carbon number is less than 6, there exists a problem that the hydrophilicity of organic onium ion becomes high and compatibility with a polymer falls.

As clay minerals, those having a large contact area with the polymer are preferably used. This makes it possible to greatly swell the interlayers of clay minerals. Specifically, it is preferable that the exchange capacity of the cation of clay mineral is 50-200 milliliter equivalent / 100 g. In the case of less than 50 milliequivalents / 100g, the exchange of organic onium ions is not performed sufficiently, and it is difficult to swell the interlayer of clay minerals, On the other hand, when it exceeds 200 milliequivalents / 100g, it is a clay mineral The interlayer bonding strength is strengthened, and it may be difficult to swell the interlayers of clay minerals.

In addition, it is preferable to use organic onium ion for 0.3-3 equivalents of the ion-exchange capacity of a clay mineral. If the ion exchange capacity of clay minerals is less than 0.3 equivalents, it may be difficult to swell the clay mineral layers, and if it exceeds 3 equivalents, it may cause deterioration of the polymer and cause coloring of the barrier layer. More preferably, organic onium ions use 0.5 to 2 equivalents of the ion exchange capacity of the clay mineral. As a result, the clay mineral layer can be further swollen, and further degradation and discoloration of the resin composite can be further prevented.

As the clay mineral to which the above organic onium ions are bonded, it is preferable to use a polymer in which the polymerizable monomer is polymerized in the presence of the clay mineral. As this polymerizable monomer, the monomer used for the synthetic resin latex and emulsion demonstrated below is suitable, but copolymerization components, such as methacrylic acid, acrylic acid, acrylonitrile, and acrylamide, are also suitable in order to improve the affinity of a polymer and a clay mineral. Do.

As the clay mineral to which the organic onium ions are bonded, (a) a compound having both organic onium ions and a polymerizable functional group is bonded, (b) a compound having both an organic onium ion and a polymerizable functional group. Suitably polymerized with another polymerizable monomer in the presence of (c) a compound containing (c) 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. Do. As a compound which has both this organic onium ion and a polymerizable functional group, For example, the methyl chloride quaternary salt of dimethylaminoethyl methacrylate, the methyl quaternary salt of dimethylaminoethyl styrene, the methyl bromide quaternary salt of dimethylaminopropylethylene, etc. These can be mentioned, The thing which combined these can superpose | polymerize in presence of another polymerizable monomer, or can couple the polymer which superposed | polymerized these and another polymerizable monomer.

As for the compounding ratio of the above-mentioned inorganic filler and a water-decomposable polymer, the range of 1: 99-60: 40 is suitable by weight ratio. This is because when the inorganic filler is less than 1%, the barrier property is insufficient, and it is easy to cause blocking. On the contrary, when the inorganic filler is more than 60%, there is a large amount of air gap between the inorganic filler and the polymer in the barrier layer. Because sex deteriorates.

The coating amount for forming these barrier layers is preferably in the range of 5 to 50 g / m 2, and particularly preferably in the range of 10 to 30 g / m 2. When the coating amount is less than 5 g / m 2, the barrier property is greatly deteriorated, and when the coating amount is more than 50 g / m 2, the improvement of moisture permeability becomes a limit point, which is uneconomical.

The coating solution for forming the barrier layer is (a) a method of dispersing an inorganic filler in water and mixing with a latex or emulsion, (b) a method of dispersing an inorganic filler in a latex or emulsion, (c) In the case of polymerizing a polymerizable monomer in the presence of clay minerals bonded with organic onium ions, it can be obtained by a method of mixing a latex or an emulsion containing clay minerals or the like. At this time, if necessary, water-soluble resins such as starch and polyvinyl alcohol may be used as a protective colloid, and dispersants such as polycarboxylic acid, antifoaming agents, surfactants, and color tone composition agents may be used. It is possible to add. In the case where the coating liquid thus formed is coated on a known substrate and dried, the drying temperature is sufficient to give a heat amount in which the coating liquid is sufficiently formed, so that drying conditions equivalent to those of the general coating liquid may be used.

In the case where the barrier layer is formed on only one surface, water is preferably applied on the opposite side of the coated surface to prevent curl.

The coating equipment for forming the barrier layer is not particularly limited, and can be arbitrarily selected from air knife coaters, bar coaters, roll coaters, blade coaters, gate roll coaters, and the like.

Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited based on description of this Example of course.

Example 1

In terms of solid content, 4 parts by weight of montmorillonite combined with octadecyl ammonium ion and 6 parts by weight of talc were mixed and dispersed in 45 parts by weight of styrenebutadiene latex and 45 parts by weight of an acrylic emulsion to prepare a coating solution for forming a barrier layer. This coating solution was coated on a 75 g / m 2 kraft paper by using a bar coater at about 20 g / m 2 to obtain the barrier paper of Example 1. Here, Tg of the coating liquid was 26 degreeC.

Example 2

As the coating liquid, 4 parts by weight of montmorillonite was mixed and dispersed in 10 parts by weight of an acrylic emulsion copolymerized with a methyl chloride quaternary salt of dimethylaminoethylmethacrylic acid, and 6 parts by weight of talc and 40 parts by weight of styrene-butadiene latex and 40 parts by weight of an acrylic emulsion. A barrier paper of Example 2 was obtained in the same manner as in Example 1, except that a mixture of mixed dispersions was used. Here, Tg of the coating liquid was 22 degreeC.

[Comparative Example]

A barrier paper of Comparative Example was obtained 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.

[Evaluation of Characteristics]

Using the barrier paper of the said Example 1, 2 and the barrier paper of a comparative example, water decomposability and water vapor transmission rate were measured by the method described below, and the result is shown in Table 1.

(1) degradability

1.5 g (0.3% pulp concentration) was added to 500 ml of water, and the resultant was decomposed at room temperature for 3 minutes (voltage 60 V) using a domestic mixer (MX-1200G manufactured by National Instruments). The paper was scooped up with a standard sieve (mesh 28 (590 μm)) and dried for about 10 minutes by a printer heater (150 ° C.), and then visually confirmed residual resin and thermal meltability on the surface and evaluated in three steps. .

(2) moisture permeability

The moisture permeability was measured according to the cup method (JIS-Z-0208-B method).

Degradable Water vapor permeability (g / ㎡ ・ 24hr) Example 1 32 Example 2 35 Comparative example 45

As shown in Table 1, the barrier paper of Example 1 had good degradability, and the moisture permeability exhibited good moisture barrier property more than that of the comparative example. Moreover, the barrier map of Example 2 also had good degradability, and the water vapor transmission rate showed the favorable moisture barrier property more than the barrier paper of a comparative example.

As described above, according to the barrier paper of the present invention, not only the moisture barrier property, gas barrier property, and mechanical properties, which are the basic performances of the barrier paper, can be dramatically improved, but also recycled as old paper (recycle). ) Can be facilitated.

Claims (7)

In the barrier paper which has a base and a barrier layer, this barrier layer contains a water-decomposable polymer and an inorganic filler, A barrier paper characterized in that a layered clay mineral dispersed in a molecular form is used as the inorganic filler. The barrier paper according to claim 1, wherein the layered clay mineral is composed of organic onium ions bound to a surface thereof. The barrier finger according to claim 2, wherein the organic onium ion has a polymerizable functional group. The barrier paper according to claim 2 or 3, wherein the layered clay mineral to which the organic onium ions are bonded is polymerized with a polymerizable monomer in the presence of the clay mineral. The barrier paper according to claim 4, wherein the polymerizable monomer is a water decomposable polymer constituting the barrier layer. The barrier paper according to any one of claims 1 to 3, wherein the glass transition temperature of the water-decomposable polymer is 15 ° C or more and 40 ° C or less. The barrier paper according to any one of claims 1 to 3, wherein the water-decomposable polymer is formed of a synthetic rubber latex and an acrylic emulsion.