JP2000212895A - Moistureproof paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a moistureproof paper readily recyclable as waste paper while a maintaining moisture resistance by forming a moistureproof layer containing a synthetic rubber-based latex and a granular filler on the surface of a base paper. SOLUTION: A synthetic rubber-based latex of a styrene-butadiene-based copolymer, or the like, in an amount of 100 pts.wt. is mixed with 30-150 pts.wt. of a filler 5 having 3-30 μm particle diameter such as talc subjected to surface hydrophilization treatment with a fatty acid such as stearic acid to prepare a resin composition having 15-40 deg.C, preferably 20-30 deg.C glass transition temperature. The resin composition is applied to the surface of a base paper 2 in a coated amount (calculated as solid content) of 5-50 g/m2, preferably 10-30 g/m2 while scraping the coated surface by a blade coater, or the like, to give a moistureproof paper 1 formed with a moistureproof layer 3.

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 which can be made on recycled paper.

[0002]

2. Description of the Related Art Currently, polyethylene,
It is generally used that a moisture-proof layer is formed on a base paper by extruding and laminating a synthetic resin such as polypropylene, vinyl chloride, or the like to impart moisture-proof and waterproof properties. Such moisture-proof paper can sufficiently exhibit its function with respect to moisture-proof properties, but has poor disintegration properties when recovered and used as waste paper, and has been difficult to reuse. Therefore, this is a major problem from the viewpoint of resource saving and effective utilization.

On the other hand, there has been disclosed a method of laminating a disintegrating moisture-proof layer on a base paper by coating a resin composition such as a synthetic rubber-based latex as a recyclable moisture-proof paper (Japanese Patent Publication (Kokai) No. HEI 10-301). Further, a method has been developed in which a flat inorganic filler is added to the resin composition for forming the moisture-proof layer to improve the moisture-proof property (see JP-A-9-21096).

[0004] The reason why the moisture-proof performance is improved by blending such a flat inorganic filler is that the permeation area of water vapor is reduced and the flat inorganic filler is arranged in parallel to the surface of the moisture-proof layer. Since the layers are also laminated, the water vapor in the moisture-proof layer permeates while bypassing the flat inorganic filler, resulting in an increase in the required permeation distance of the water vapor. It is presumed to be smaller.

[0005]

On the other hand, it is necessary to cut the above moisture-proof paper into a predetermined shape at the time of finishing the product. When recycling moisture-proof paper as used paper, it is common to cut the moisture-proof paper into small pieces of a predetermined size before disaggregation in order to facilitate disaggregation into water.

[0006] However, in the above conventional moisture-proof paper, a flat inorganic filler is blended in the resin composition constituting the moisture-proof layer, and is arranged in parallel to the surface of the moisture-proof layer, and is laminated in multiple layers. Therefore, in order to cut such a moisture-proof paper, it is necessary to shear the flat inorganic filler. Therefore, the blade used for cutting such moisture-proof paper is easily damaged.

[0007] The present invention has been made in view of these disadvantages, and an object of the present invention is to provide a moisture-proof paper which is recyclable as used paper and which is easily cut while maintaining high moisture-proof properties. Things.

[0008]

The invention made to solve the above-mentioned problem is a moisture-proof paper having a base paper and a moisture-proof layer, wherein the moisture-proof layer comprises a synthetic rubber-based latex and a particulate filler. It is formed from the contained resin composition. Here, the term “granular” literally means a granular state, and specifically includes a columnar shape, a confetti-like shape, a spherical shape, a barrel shape, and the like, but does not include a flat shape, a flake shape, a long rod shape, and the like. is there.

According to this means, since the filler compounded in the resin composition forming the moisture-proof layer is granular, the effect of promoting moisture-proof property per unit weight is lower than that of the flat filler, but the synthetic rubber type By using latex or wax in combination, the effect of promoting moistureproofness can be maintained. Moreover, since the filler is granular, the risk of damaging the blade during cutting is reduced. As a result, recycling as used paper becomes easy while maintaining the moisture-proof property, which is the basic performance of the moisture-proof paper.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings as appropriate. FIG. 1 is a schematic sectional view showing a moisture-proof paper according to one embodiment of the present invention. 1 includes a base paper 2 and a moisture-proof layer 3.

The paper material constituting the base paper 2 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 action.For example, chemical pulp such as hardwood kraft pulp and softwood kraft pulp, high-quality paper made from mechanical pulp, medium quality Examples of the paper include kraft paper, single gloss kraft paper, Ryoso kraft paper, and kraft stretch paper. The basis weight of the base paper 2 is not particularly limited, and may be appropriately selected depending on the purpose at about 30 to 300 g / m ² .

The moisture-proof layer 3 is formed of a resin composition having a specific composition, and this resin composition contains a synthetic rubber-based latex 4 and a particulate filler 5.

The glass transition temperature of the resin composition forming the moisture-proof layer 3 is preferably between 15 ° C. and 40 ° C. When the glass transition temperature is lower than the above range, the resin is soft and has a large elongation, and this elongation becomes a resistance to a shearing force applied at the time of defibration, so that it is difficult to be finely separated and dispersed, and the defibration property is extremely poor. . Conversely, when the glass transition temperature exceeds the above range, the material becomes very hard, brittle, and has a small elongation, so that the disintegration becomes very good, but the moisture resistance, particularly the moisture resistance at the time of bending deteriorates. Therefore, the glass transition temperature of the resin composition constituting the moisture-proof layer 3 needs to be in the above range, preferably in the range of 20 ° C to 30 ° C.

Specific examples of the synthetic rubber latex 4 used in the resin composition include styrene butadiene latex, methacrylate butadiene latex, and acrylonitrile butadiene latex.
Styrene butadiene latex which has good water resistance and good elongation and is less likely to be cracked by breaking 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 styrene and 1,
Examples of the monomer copolymerizable with 3-butadiene include (a)
aromatic vinyl monomers such as α-methylstyrene, vinyltoluene, pt-butyltoluene, chlorostyrene,
(B) methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, ( (Meth) acrylic acid 2-
Ethylhexyl, n-octyl (meth) acrylate,
(Meth) acrylate monomers such as 2-hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; (c) cyano group-containing ethylenically unsaturated monomers such as (meth) acrylonitrile; d) glycidyl esters of ethylenically unsaturated acids such as glycidyl acrylate and glycidyl methacrylate; (e) glycidyl ethers of unsaturated alcohols such as allyl glycidyl ether; (f) (meth) acrylamide; N-methylol (meth) acrylamide , N-methylol (meth) acrylamide, (meth) acrylamide monomers such as N-butoxymethyl (meth) acrylamide and the like,
These polymerizable monomers can be used alone or in combination of two or more.

As the granular filler 5 used in the resin composition, specifically, (a) an inorganic filler such as calcium carbonate, talc, barium sulfate, titanium oxide, kaolin;
(B) One or more of organic fillers such as acrylic resin beads, styrene resin beads, polyethylene resin beads, and urethane resin beads can be used. As described above, the moisture resistance can be improved by blending the filler.

The particle size of the filler 5 is preferably 3 μm or more and 30 μm or less. If the particle size of the filler 5 is smaller than the above range, the effect of improving the moisture-proof property is small. Conversely, if the particle size exceeds the above range, irregularities may occur on the surface of the moisture-proof layer 3 or the blade may be damaged during shearing. Because there is.

The compounding ratio of the filler 5 is preferably 30 parts by weight or more and 150 parts by weight or less based on 100 parts by weight of the synthetic rubber latex. This is because if the compounding ratio of the filler 5 is smaller than the above range, the distance between the fillers 5 is too large, and the effect of promoting the moisture-proof property becomes insufficient, and it becomes necessary to increase the coating amount, which is uneconomical. On the other hand, if the compounding ratio of the filler 5 exceeds the above range, the resin matrix composed of the synthetic rubber-based latex 4 becomes small, so that a)
The moisture-proof layer itself becomes very hard and brittle, and the moisture-proof property, especially when folded, deteriorates. B) The convex portion becomes large,
This is because inconveniences such as a possibility of damaging the package contents occur.

It is preferable to use the filler 5 whose surface has been subjected to a lipophilic treatment. Here "lipophilic treatment"
Means a treatment for making the surface of the filler 5 having hydrophilicity lipophilic. When the particles become fine, the surface energy increases, and it becomes extremely difficult to disperse the particles in the synthetic resin. Therefore, as in the case of this means, the granular filler 5
By subjecting the surface to a lipophilic treatment, affinity with the synthetic rubber-based latex 4 is improved, and dispersion in the synthetic rubber-based latex 4 can be facilitated.

The lipophilic treatment is preferably a fatty acid treatment. The surface treatment of the particles using a higher fatty acid represented by stearic acid can not only improve the affinity with the synthetic rubber-based latex 4 as described above, but also can positively modify the moisture-proof layer. That is, a functional group is provided on the surface of the filler 5 by a fatty acid treatment using acrylic acid or a derivative thereof, an organic titanate coupling agent, a silane coupling agent, or the like, and bonding between the functional group and the synthetic rubber-based latex 4 The functionality can be improved by the reaction.

Next, a method of manufacturing the moisture-proof paper 1 will be described. First, a filler 5 is dispersed in a synthetic rubber-based latex 4 to prepare a resin composition constituting the moisture-proof layer 3. 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. The resin composition prepared in this manner is applied onto the base paper 2 and dried to form the moisture-proof layer 3. This drying temperature is sufficient if it gives a sufficient amount of heat for forming a film of the resin composition, and therefore, the same drying conditions as those of general coated paper may be used. Further, it is preferable to coat the surface of the base paper 2 on the side opposite to the moisture-proof layer 3 with water to prevent curling.

The coating amount of the resin composition for forming the moisture-proof layer 3, in terms of solid content, preferably in the range of 5 to 50 g / m ^2, the range of 10 to 30 g / m ² is particularly preferred.
If the coating amount is less than 5 g / m ² , the moisture-proof property will be significantly deteriorated, and if it exceeds 50 g / m ² , the improvement in moisture permeability will level off, which is uneconomical.

As described above, the equipment for applying the resin composition is not particularly limited, and for example, an air knife coater, a bar coater, a roll coater, a blade coater, a gate roll coater and the like can be used. In particular, a coating method such as a blade coater, a bar coater, or an air knife coater that scrapes the coating surface is preferable because it tends to promote the smoothness of the surface of the moisture-proof layer 3.

The moisture-proof paper of the present invention is not limited to the above embodiment. For example, a moisture-proof paper in which the moisture-proof layers 3 are formed on both sides of the base paper 2 is also possible. In addition to the synthetic rubber-based latex 4 and the filler 5, a wax, a dispersant, an antifoaming agent, a blocking agent, and the like may be added to the resin composition forming the moisture-proof layer 3.

[0024]

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.

(Experiment 1) [Example 1] 100 parts by weight of SBR having a Tg of 20 ° C., 50 parts by weight of calcium carbonate having a particle size of 5 μm, and wax 4
The coating liquid was prepared by mixing the coating liquid and the coating solution with a weight part of 20 g / m ² on a dry conversion basis on the surface of a base paper having a basis weight of 75 g / m ² to obtain the moisture-proof paper of Example 1. Was.

Example 2 A moisture-proof paper of Example 2 was obtained in the same manner as in Example 1 except that SBR having a Tg of 15 ° C. was used.

Example 3 A moisture-proof paper of Example 3 was obtained in the same manner as in Example 1 except that SBR having a Tg of 40 ° C. was used.

Example 4 A moisture-proof paper of Example 4 was obtained in the same manner as in Example 1 except that 50 parts by weight of SBR having a Tg of 15 ° C. and 50 parts by weight of SBR having a Tg of 20 ° C. were mixed.

Example 5 A moisture-proof paper of Example 5 was obtained in the same manner as in Example 1 except that SBR having a Tg of 10 ° C. was used.

Example 6 A moisture-proof paper of Example 6 was obtained in the same manner as in Example 1 except that SBR having a Tg of 50 ° C. was used.

[Evaluation of Characteristics] The first embodiment having different Tg.
Using moisture-proof papers of Nos. 6 to 6, moisture permeability and defibration properties were evaluated by the following methods. The results are shown in Table 1 below. (1) Method of measuring moisture permeability The moisture permeability was measured according to JIS-Z-0208 (Method B). The unit of the numerical values shown in Table 1 is g / m ² · 24h
And the evaluation of moisture permeability was 以下, 40 to 6 at 40 or less.
At 0, it was evaluated as Δ, and at 60 or more, it was evaluated as ×. (2) Method of evaluating disintegration 1.5 g of sample in 500 ml of water (pulp concentration 0.3%)
, And a household mixer with a rounded blade (National M
X-1200G) at room temperature for 3 minutes (voltage 60V)
After dissociation, the dissociated sample is hand-crafted with a standard sieve (mesh 28 (590 μm)), dried for about 10 minutes by a printer heater (150 ° C., mirror surface), and visually checked for resin residue on the surface. 1mm or less is ○, 1m
m to 5 mm were evaluated as △, and 5 mm or more was evaluated as x.

[0032]

[Table 1]

As can be seen from Table 1 above, Examples 1-6
Is excellent in both moisture permeability and disintegration. Examples 1 to 4 having a Tg of 15 ° C to 40 ° C are particularly excellent.

(Experiment 2) [Example 7] 100 parts of the above calcium carbonate was used as a filler.
A moisture-proof paper of Example 7 was obtained in the same manner as in Example 3 except that the parts by weight were mixed.

Example 8 A moisture-proof paper of Example 8 was obtained in the same manner as in Example 3 except that 150 parts by weight of the above calcium carbonate was mixed as a filler.

Example 9 The particle size was 10 μm as a filler.
Was obtained in the same manner as in Example 3 except that 50 parts by weight of talc was mixed.

Example 10 The filler had a particle size of 20 μm.
The moisture-proof paper of Example 10 was obtained in the same manner as in Example 3 except that 50 parts by weight of m acrylic beads were mixed.

Example 11 A moisture-proof paper of Example 11 was obtained in the same manner as in Example 3 except that 20 parts by weight of the above calcium carbonate and 20 parts by weight of the talc were mixed as fillers.

Example 12 A moisture-proof paper of Example 12 was obtained in the same manner as in Example 3 except that 50 parts by weight of the calcium carbonate and 5 parts by weight of the acrylic beads were mixed as fillers.

Example 13 A moisture-proof paper of Example 13 was obtained in the same manner as in Example 3 except that 20 parts by weight of the above calcium carbonate was mixed as a filler.

Example 14 A moisture-proof paper of Example 14 was obtained in the same manner as in Example 3 except that 200 parts by weight of the above calcium carbonate was mixed as a filler.

Example 15 The particle size was 2 μm as a filler.
Example 15 was obtained in the same manner as in Example 3 except that 50 parts by weight of the above calcium carbonate was mixed.

Example 16 The particle size of the filler was 30 μm.
A moisture-proof paper of Example 16 was obtained in the same manner as in Example 3 except that 50 parts by weight of acrylic beads were mixed.

[Evaluation of Characteristics] The moisture-proof paper of Example 3 and
Based on this, moisture permeability, disintegration, and damage to the cutting blade were evaluated using the moisture-proof papers of Examples 7 to 16 in which fillers having different particle sizes were mixed. The results are shown in Table 2 below. Note that the moisture permeability and the disintegration properties are the same as in the evaluation method of Experiment 1. The degree of damage to the cutting blade was determined by repeatedly cutting the moisture-proof paper by a length of 10 cm using a commercially available cutter 20 times, and visually checking the degree of damage to the cutting blade.

[0045]

[Table 2]

As can be seen from Table 2 above, Examples 3 and 7
The moisture-proof papers No. to No. 16 both had good moisture permeability and good disintegration properties, and the cutting blades were well damaged, with little damage. Note that the moisture-proof papers of Examples 3 and 7 to 12 in which the compounding ratio of the filler is in the range of 50 parts by weight to 150 parts by weight with respect to 100 parts by weight of the synthetic rubber-based latex are particularly preferable. The moisture-proof papers of Examples 3 and 7 to 12 in the range of ３０30 μm are particularly preferred.

[0047]

As described above, according to the moisture-proof paper of the present invention, the risk of damaging the blade at the time of cutting is small since the filler mixed with the resin composition forming the moisture-proof layer is granular. Become. As a result, recycling as used paper becomes easy while maintaining the moisture-proof property, which is the basic performance of the moisture-proof paper.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a moisture-proof paper according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Moisture-proof paper 2 Base paper 3 Moisture-proof layer 4 Synthetic rubber latex 5 Filler

Claims (6)

[Claims] 1. A moisture-proof paper having a base paper and a moisture-proof layer, wherein the moisture-proof layer is formed from a resin composition containing a synthetic rubber-based latex and a particulate filler. paper. 2. The moisture-proof paper according to claim 1, wherein the glass transition temperature (Tg) of the resin composition forming the moisture-proof layer is 15 ° C. or more and 40 ° C. or less. 3. The filler has a particle size of 3 μm or more and 30 μm or more.
The moisture-proof paper according to claim 1 or 2, wherein: 4. The moisture-proof paper according to claim 1, wherein the compounding ratio of the filler is 30 parts by weight or more and 150 parts by weight or less based on 100 parts by weight of the synthetic rubber-based latex. . 5. The moisture-proof paper according to claim 1, wherein the filler has a surface subjected to a lipophilic treatment. 6. The moisture-proof paper according to claim 5, wherein the lipophilic treatment is a fatty acid treatment.