JP3273393B2 - Moisture proof paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moisture-proof paper used for a moisture-proof packaging or the like obtained by coating paper with a synthetic resin.

[0002]

2. Description of the Related Art Conventionally, moisture-proof processing of paper is performed by laminating a synthetic resin film using a synthetic resin such as polyethylene as an adhesive, or directly coating a molten resin on the paper. However, when collecting and recycling used paper, these moisture-proof treated papers have a strong bond between the paper and the synthetic resin film. There have been problems in that the fibers of the paper are hardly detached from the residual resin, the yield of the fibers is reduced, or the resin portion is hardly removed in the unnecessary material removing step.

In order to obtain a moisture-proof paper which can be recycled as used paper, a wax-based emulsion is applied (JP-B-63-39022, JP-B-63-39023, etc.), and a wax-based emulsion and a synthetic rubber-based emulsion are used. There is a method of applying a mixed coating (Japanese Patent Publication No. 55-22597) or a method of mixing and applying a wax-based emulsion and a water-soluble emulsion. There were drawbacks such as blocking. Also,
Even if they can be defibrated, it is difficult to completely remove the resin, and when paper is made after recycling, the resin re-floats. Problems occur in copy quality and print quality.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has the same moisture-proof property and usability as conventional moisture-proof paper coated with a synthetic resin such as polyethylene. An object of the present invention is to obtain a moisture-proof paper in which the yield of fibers at the time is equal to that of unprocessed paper and the pulp to be recycled can be used without any problem similarly to used newspaper.

[0005]

According to the present invention, firstly, there is provided a moisture-proof paper in which a base paper and a moisture-proof synthetic resin film are bonded together with a polyvinyl alcohol-based water-soluble synthetic resin adhesive . Second, there is provided a moisture-proof paper in which a polyvinyl alcohol-based water-soluble synthetic resin layer and a moisture-proof synthetic resin layer are sequentially coated on a base paper by coating . Hereinafter, the present invention will be described in detail. In the first moisture-proof paper, since a polyvinyl alcohol-based water-soluble synthetic resin was interposed between the base paper and the moisture-proof synthetic resin film,
Water penetrates from the end face of the base paper and dissolves the polyvinyl alcohol-based water-soluble synthetic resin. Thereby, the moisture-proof synthetic resin film is peeled off from the base paper before being subdivided by the disintegrator, and is easily removed from the system by a wire or a filter. In the case of the second moisture-proof paper, since the material of each layer is the same as that of the first moisture-proof paper, the water-soluble synthetic resin layer dissolves and the moisture-proof synthetic resin similarly to the case of the first moisture-proof paper. The film layer is peeled off from the base paper and removed.

[0006] Even if the moisture-proof synthetic resin film or film layer cannot be removed as described above, the film or film layer is separated from the paper fibers and can be easily removed in the deinking step. On the other hand, the base paper from which the film or film layer has been peeled is regenerated with the same efficiency and yield as the paper before processing. In addition, even if the water-soluble synthetic resin remains in the recycled pulp while being dissolved in water even after the rinsing process, it is originally used as a paper strength agent or a sizing agent. Does not occur. Hereinafter, the materials used in the present invention will be described.

First, as a moisture-proof synthetic resin film,
For example, 8 to 40 μm biaxially oriented polypropylene (OP
P) film, biaxially oriented polyethylene terephthalate (OPET) film of 3 to 60 μm, unstretched polypropylene (CPP) film of 10 to 40 μm, high-density or low-density polyethylene film, and the like. The material, thickness, and the like are determined by accuracy, moisture-proof performance, and the like. Moreover, co in the second moistureproof paper
As a moisture-proof synthetic resin for coating, such as polyvinylidene chloride, it has good film-forming properties by coating,
Further, those having high moisture-proof properties are preferable. When coating polyvinylidene chloride, toluene, ethyl acetate,
A coating solution dissolved in a solvent such as methyl ethyl ketone, cyclohexanone, and tetrahydrofuran is used. When coating polyvinylidene chloride with an aqueous emulsion, it is desirable to coat an anchor coat agent in advance or to coat a solvent type polyvinylidene chloride.

Next, examples of the water-soluble synthetic resin adhesive include those modified with polyvinyl alcohol of a partially saponified type (degree of saponification: about 80 to 90 mol%), styrene, acryl, or the like.

[0009]

The present invention will be described more specifically with reference to the following examples. [Examples 1 to 4] A 60 g / m ² bleached kraft paper was used as a base paper, and a polyvinyl alcohol-based water-soluble synthetic resin and a moisture-proof synthetic resin (film) shown in Table 1 below were coated on the base paper. To produce a moisture-proof paper.

[0010]

[Table 1] (Note) In Examples 1 and 2, after bonding the base paper and the moisture-proof synthetic resin film, a hot plate at 150 ° C. was applied from the base paper side at a pressure of 3 kg for 1.0 second and bonded. In Examples 3 and 4, a polyvinyl alcohol-based water-soluble synthetic resin and then a moisture-proof synthetic resin were sequentially coated on a base paper. All coatings were by Meyer bar coating. · Table in (1) is 2 a solvent coating type 5 g / m ²
One-time application.・ (Note 2) in the table means that the solvent coating type was applied at ² g / m ² and the aqueous emulsion type was applied at 5 g / m ² .

The obtained samples were tested for moisture permeability, disintegration of paper fibers, presence or absence of residual resin, and blocking resistance. The test results are shown in Table 2. For comparison, a low-density polyethylene laminated paper (laminated film thickness: 20 μm) was similarly tested, and the results were also described. In this case, the same kraft paper as in the example was used as the base paper.

[Test Method] "Moisture Permeability": Measured at 40 ° C., 90% to 40 ° C., 0% using a L80-4000 moisture permeability meter manufactured by Lyssy, Switzerland. Unit: g / m ² · 24hr "defibration properties", "residual resin" cut into 30 m m square pieces of paper, after maceration for 30 minutes by a laboratory size disintegrator 2% pulp concentration in terms, air bubbles flow tester The resin content was removed by hand, and the remaining pulp liquor was hand-made. The degree of fiber disintegration was visually compared with the case of the copied paper, and a 180 ° C. hot plate was applied for 3 seconds to check the residual resin.

Evaluation of "disintegration" 〇: no fiber lump
×: There is a lump of fibers Evaluation of “residual resin” 〇: No ×: Yes “Blocking resistance” A 10 cm square sample is put together in a thermostat at 50 ° C. with moisture-proof synthetic resin films (or layers). After applying a load of 10 kg and allowing to stand for 24 hours, both are peeled off and the condition of peeling is confirmed. Evaluation 〇: Sounds but peels off lightly.

[0014]

[Table 2] Comparative Example 1: Copied paper Comparative Example 2: Low density polyethylene laminated paper

As is clear from Table 2, the OPP film or OPET film according to the present invention was bonded to a base paper with modified PVA (Examples 1 and 2),
PVA and polyvinylidene chloride were sequentially coated on a base paper (Examples 3 and 4), and the moisture permeability (moisture proof) was not inferior to that of a conventional polyethylene laminated paper (Comparative Example 2). The disintegration and the presence or absence of the residual resin (recyclability of used paper) are remarkably improved as compared with the conventional one, and there is no problem. Furthermore, the blocking resistance is also good.

In addition, when the moisture-proof synthetic resin film is laminated, it can be laminated with a small amount of resin used, and high moisture-proof performance can be obtained at low cost. , High precision printing quality, high mechanical strength,
Stable quality is obtained. When the water-soluble synthetic resin layer and the moisture-proof synthetic resin layer are provided by coating, they can be performed in one pass in the same process together with other processing such as printing by gravure printing or the like.

Incidentally, in Comparative Example 1 in the table, "copied paper" was used, and was compared as an example of unprocessed paper. In the examples, bleached kraft paper was used as the base paper,
Of course, unbleached kraft paper can be used.

[0018]

As described above, according to the present invention, the moisture-proof property is equivalent to that of a conventional moisture-proof paper coated with a synthetic resin such as polyethylene, and the fiber disintegration property and the like at the time of recycling used paper are unprocessed paper. Thus, a moisture-proof paper which can be used without any problem in the same manner as used newspaper is obtained.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) D21H 11/00-27/42 B32B 1/00-35/00

Claims (2)

(57) [Claims] 1. A moisture-proof paper comprising a base paper and a moisture-proof synthetic resin film bonded together with a polyvinyl alcohol-based water-soluble synthetic resin adhesive . 2. A polyvinyl alcohol-based water-soluble synthetic resin layer and a moisture-proof synthetic resin layer are sequentially coated on a base paper by coating.
Proof paper, characterized in that formed by coating.