JPH09314759A - Moistureproof paper and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain moistureproof paper having sufficient moistureproofness with specific water vapor transmission and specific water absorbing capacity and capable of performing adhesion with a water-base adhesive by forming a layer containing a water-insoluble synthetic resin on at least one of faces of paper, forming a layer of wax on the surface of its layer, and further forming a layer of a surface-active agent on the surface of the wax layer. SOLUTION: A layer containing a water-insoluble synthetic resin prepared from an acrylic polymer, etc., is formed on at least one of faces of paper, and a layer of wax composed of one kind of, or a mixture of, paraffin wax, synthetic resin wax, etc., is formed on the surface of the layer containing the water-insoluble synthetic resin. Further, a layer of a surface-active agent such as an anionic surfactant is formed on the surface of the wax layer, and water vapor transmission is made to be 50g/m<2> .24h or below, while water absorbing capacity on a layer forming face is made to be 10g/m<2> or above. Accordingly, moistureproofness is maintained, and adhesion by using a water-base adhesive is made possible. Thus, productivity of making boxes which employ this moistureproof paper as a material can be enhanced.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a moisture-proof paper and a method for producing the same. More specifically, the present invention relates to a moisture-proof paper which has moisture-proof property and can be bonded with an aqueous adhesive, and a method for producing the same.

[0002]

2. Description of the Related Art There are demands for moisture-proof papers for various uses such as wrapping paper. In recent years, the demand has been increasing, and various moisture-proof papers have been proposed. Among them, there is a reusable moisture-proof paper in which a wax-containing emulsion is applied to paper and dried to provide a uniform wax layer as an outermost layer. In such a moisture-proof paper, the wax film of the outermost layer exhibits a moisture-proof effect despite the relatively low wax content.

[0003]

However, when a box is manufactured from these moisture-proof papers, since the adhesive used in the manufacturing process is generally a water-based adhesive, the outermost layer to be applied is formed. Wax repels the water-based adhesive, and the adhesive becomes water droplets on the wax layer. That is, the adhesive does not spread on the surface to be adhered, and it is difficult to bond these moisture-proof papers with the water-based adhesive. In particular, in recent years, the speed has been increasing in the box making process, and it has been strongly required that moisture-proof paper can be easily bonded with a water-based adhesive.

An object of the present invention is to provide a moisture-proof paper which has sufficient moisture-proof property and can be bonded with an aqueous adhesive, and a method for producing the same.

[0005]

In view of the above-mentioned circumstances, as a result of intensive studies by the present inventors, a surfactant layer is formed on the outermost wax layer of conventional moisture-proof paper. As a result, the above problems have been solved, and it is needless to say that it has sufficient moisture resistance, and at the same time, it was discovered that bonding can be performed using a water-based adhesive, and the present invention has been completed.

That is, according to the present invention, (1) a layer containing a water-insoluble synthetic resin is formed on at least one side of a paper, a wax layer is formed on the surface side thereof, and a surfactant layer is further formed on the surface thereof. The water vapor transmission rate is 50g / m ²
・ In 24 hours or less, the water absorption of the layer forming surface is 10 g / m ²
The moisture-proof paper as described above, (2) the moisture-proof paper as described in (1) above, wherein the surfactant is an anionic surfactant, and (3) at least one surface of the paper is coated with an emulsion containing a wax and a water-insoluble synthetic resin. To form a first layer, the surface of which is coated with a mixed solution containing an emulsion containing a water-insoluble synthetic resin and a surfactant released to form a second layer, A method for producing a moisture-proof paper comprising heat-treating to form a layer of the above-mentioned surfactant on the outermost layer, (4) The method for producing a moisture-proof paper according to the above (3), wherein the surfactant is an anionic surfactant. And (5) the method for producing a moisture-proof paper according to the above (3), wherein the first layer contains a pigment.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The moisture-proof paper of the present invention has a moisture permeability of 50 g.
/ M ² · 24h or less. Water vapor transmission rate is JIS Z 0
208 (cup method) in accordance with the B method, the measurement is a synthetic resin layer
The measurement is performed with the surface on which the wax layer and the surfactant layer are formed as the inside.

The moisture-proof paper of the present invention has a water absorption of 10 g /
m ² or more. The water absorption is based on JIS P 8140 (Cup method) on the surface on the side of the outermost surfactant layer,
The contact time with water is measured as 2 minutes. Water absorption is 10g
If it is less than / m ² , the adhesiveness with a water-based adhesive tends to be lowered. The preferred range of water absorption is 10 to 50 g / m
² and more preferably 20 to 40 g / m ² .

The paper used in the present invention is not particularly limited, and packaging paper, printing paper, cardboard base paper, paperboard board and the like can be used. The paper may or may not be sized. Further, a surface treatment with a resin or the like may be performed. Furthermore, smoothness (JIS P 81
19), for example, a paperboard having a particularly low smoothness of 50 seconds or less, more preferably about 10 to 20 seconds.

As the wax, those derived from natural products and petroleum can be used without particular limitation. For example, paraffin wax, low melting point polyethylene wax, fatty acid ester wax, fatty acid wax, petroleum oil wax, synthetic resin wax, microcrystalline wax and the like can be mentioned. These may be used alone or as a mixture. Of these, paraffin wax and synthetic resin wax are preferred. The molecular weight (Mn) of the wax is 300-
The melting point is preferably 500, and the melting point is preferably 100 ° C or lower, more preferably 50 to 70 ° C.

Examples of the water-insoluble synthetic resin include acrylic polymers, synthetic rubbers, vinyl acetate polymers and the like. Specifically, as the acrylic polymer, for example,
Methyl acrylate polymer, ethyl acrylate polymer, butyl acrylate polymer, 2-ethylhexyl acrylate polymer, butyl acrylate-methyl methacrylate copolymer, butyl acrylate-styrene copolymer, ethylene-
2-ethylhexyl acrylate copolymer etc. are mentioned. Examples of the synthetic rubber include styrene-butadiene copolymers, nitrile-butadiene copolymers, vinylpyridine-styrene-butadiene copolymers, butadiene-based polymers such as methylmethacrylate-butadiene copolymers, and isoprene such as isoprene polymers. A system polymer etc. are mentioned. Examples of vinyl acetate polymers include vinyl acetate polymers, vinyl acetate-methyl acrylate copolymers, vinyl acetate-ethyl acrylate copolymers, vinyl acetate-butyl acrylate copolymers, vinyl acetate-acrylic acid-2. -Ethylhexyl copolymer, vinyl acetate-dibutyl maleate copolymer, vinyl acetate-ethylene copolymer and the like can be mentioned. In addition to this, styrene-based polymers such as styrene polymers,
Ethylene polymers such as ethylene polymers and ethylene-vinyl acetate polymers can also be used.

The melting point of the surfactant is preferably the same as or higher than the melting point of the wax used. If the melting point is too low, the workability may be impaired due to stickiness of the coating layer. The molecular weight can be used without any particular limitation, and includes a general surfactant having a molecular weight of about 300 to 1,000 to a surfactant having a molecular weight of 1,000 or more classified as a so-called high molecular surfactant.

The HLB of the surfactant is not particularly limited, but it is preferably in the range of 10 to 50, and more preferably 13 to 40 from the viewpoint of solubility in water. Here, HLB is calculated by the formula: HLB = ΣJ _W −ΣJ _O +7 (wherein, J _W is the number of hydrophilic groups and J _O is the number of hydrophobic groups).

As the surfactant, anionic surfactants and some nonionic surfactants are preferable. Among them, the anionic surfactant causes electrical repulsion with the water-insoluble synthetic resin, and as a result, it easily floats to the upper layer, so the amount used is small, and initial adhesion during box making is good and productivity is improved. However, it is preferable. Specifically, examples of the anionic surfactant include alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, dialkylsulfosuccinates such as sodium dialkylsulfosuccinate, and alkyl sulfates such as sodium lauryl sulfate. Further, as the nonionic surfactant,
Examples thereof include polyoxyethylene alkylaryl ethers such as polyoxyethylene nonylphenyl ether, polyoxyethylene alkyl ethers, polyoxyethylene glycerin fatty acid esters, polyethylene glycol fatty acid esters and the like.

A pigment may be contained as a component other than these. Any pigment can be used as long as it is usually used for paper coating. Examples thereof include kaolinite, sericite, mica, talc, chlorite, pyrophyllite, titanium oxide, calcium carbonate, silica, color pigments, organic pigments, and the like, and preferable examples include calcium carbonate, clay and the like. The particle size of the pigment is preferably about 0.1 to 5 μm. A particle diameter within this range is suitable for forming a layer, and a smooth coating layer can be obtained. The appropriate content of the pigment is
The amount is preferably up to about 2 times (weight), more preferably about 1.3 to 1.7 times the water-insoluble polymer. Inclusion of the pigment can reduce the amount of the water-insoluble polymer, is advantageous in terms of cost, and can improve the disintegration property.

Next, the method for producing the moisture-proof paper of the present invention will be described. As a production method, an emulsion containing wax and a water-insoluble synthetic resin among the above-mentioned essential components is applied to at least one side of paper to form a layer (first layer), and a water layer is formed on the obtained layer. A two-layer coating is preferred, in which an emulsion of an insoluble synthetic resin, which is a water-insoluble synthetic resin and a liberated surfactant, is applied to form the second layer.

The two-layer coating will be described below. In addition to the above essential components, a pigment may be added to the emulsion forming the first layer. The emulsion is prepared by conventional methods. For example, an emulsion of wax, a water-insoluble synthetic resin, and optionally a pigment is prepared, and these are mixed simultaneously or sequentially. As the emulsifier used when preparing the emulsion, a surfactant,
A water-soluble resin or the like can be used without any special limitation. For example, polyoxyalkylene monoalkylate (having 10 to 1 carbon atoms)
8 obtained by reacting the alcohol of 8 with ethylene oxide or propylene oxide), dodecylbenzene sulfonate, dodecylamine hydrochloride, sodium polyacrylate, polyvinyl alcohol and the like. The amount of emulsifier used is usually 1 with respect to 100 parts by weight of the resin solid content.
It is about 3 parts by weight.

The weight ratio of the wax, the water-insoluble synthetic resin and the pigment (wax (solid content) / water-insoluble synthetic resin (solid content) / pigment) in the emulsion forming the first layer is not particularly limited, and the required performance can be obtained. It is appropriately determined according to A preferred weight ratio is 1/1 to 30/0 to 200, more preferably 1/3 to 20/10 to 100. Further, the solid content concentration in the emulsion is preferably in the range of 30 to 70% by weight.

Stabilizers, defoamers, water resistance agents, viscosity improvers, water retention agents, preservatives, colorants and the like may be added to the emulsion.

The minimum film-forming temperature of the emulsion is preferably 30 ° C. or lower. When an emulsion having a minimum film forming temperature of 30 ° C. or lower is used, a layer having high moisture resistance can be obtained. Here, “minimum film forming temperature of 30 ° C. or lower” means that the polymer aqueous dispersion has film forming ability at a temperature of 30 ° C. or lower. The lower limit of the minimum film forming temperature is not particularly limited.

The coating amount of the emulsion for forming the first layer can be arbitrarily changed according to the required performance and the like, but is generally 3
˜20 g / m ² (dry weight) is preferable, and particularly preferably 5 to 10 g / m ² (dry weight). The coating method is performed by a known method. For example, the coating liquid, roll coater,
A known coater such as a blade coater or an air knife coater is used to coat the paper, and a drying step (for example, 80 to 130) is performed.
To form a layer.

After the first layer is formed, a mixed solution, which is an emulsion of a water-insoluble synthetic resin and contains the water-insoluble synthetic resin and the liberated surfactant, is applied thereon to form the second layer. The method for producing the mixed solution for forming the second layer is also a usual method. For example, a surfactant is mixed with the above water-insoluble synthetic resin emulsion. In the mixed solution forming the second layer, in addition to the above synthetic resin emulsion and surfactant, other substances such as a stabilizer, a defoaming agent, a water resistant agent, a viscosity improver, a water retention agent, an antiseptic, a colorant, etc. Although it may be added, it is essential that it does not prevent the migration of the wax in the first layer.

Weight ratio of water-insoluble synthetic resin and surfactant (excluding surfactant added to form emulsion) in the mixture [water-insoluble synthetic resin (solid content)
/ Surfactant] is not particularly limited and may be appropriately determined depending on the required performance. A preferred weight ratio is 1 / 0.01-0.
5, more preferably 1 / 0.03 to 0.3. The solid content concentration in the mixed solution is preferably in the range of 20 to 60% by weight.

The minimum film-forming temperature of the mixed solution for forming the second layer is 3 as in the emulsion for forming the first layer.
It is preferably 0 ° C or lower.

The coating amount of the mixed liquid is preferably ^{2 to 5} g / m ² (dry weight). When the coating amount is within this range, a sufficient moisture-proof effect can be obtained and it is advantageous in terms of cost.

The coating method for the second layer is also carried out in the same manner as the coating method for the first layer. After forming the second layer, a heat treatment at 80 to 130 ° C. is applied to form the layer.

In order to emulsify wax or water-insoluble synthetic resin, of course, a surfactant is used as an emulsifying agent, but usually the amount used is the minimum necessary amount, and most of them are wax or synthetic resin. Attached to the particles. On the other hand, the surfactant constituting the outermost layer of the moisture-proof paper of the present invention is added for the purpose other than the emulsification of particles, and most of it is in a free state in water in the mixed solution, The agents form micelles. By drying the first layer of the two-layer coating, a uniform wax layer is formed on the surface of the layer. In the process of coating and drying a mixed solution containing a surfactant as the second layer,
The surfactant is present in water that evaporates due to heat, and is left on the surface as the drying proceeds, and remains on the uniform wax layer that transfers to the surface due to heat. Further, a surface-active agent layer is formed on the surface thereof. It is not impossible to prepare a mixed solution containing the above essential components and apply it to paper, but it does not form a uniform wax layer in advance. Only part of them can be deposited on the surface of the wax layer, and as a result, it is difficult to increase the water absorption. Further, if it is attempted to make the water absorption capable of being bonded with a water-based adhesive, the required amount of the surfactant is increased, which may adversely affect the moisture resistance. For this reason, coating is more difficult to control in terms of production, and it is difficult to use a pigment, which is not advantageous in terms of cost.

[0028]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Example 1 A coated white ball having a rice basis weight of 330 g / m ² was used as a base material, and a wet heavy calcium carbonate [trademark: H was used as a pigment on the back surface thereof.
-60, manufactured by Bihoku Koka Kogyo Co., Ltd., solid content: 75% by weight] 1
00 parts by weight, 30 parts by weight of SBR emulsion as an adhesive [Asahi Kasei Kogyo KK, solid content 48% by weight] and paraffin wax emulsion [Arakawa Chemical Industry Co., Ltd.]
Manufactured, solid content 30% by weight] A mixed liquid containing 10 parts by weight as a main component is coated with a wire rod so as to be 11 g / m ² and dried at 100 ° C. for 30 seconds to form an undercoat layer (first layer). ) Was formed. Next, 92 parts by weight of SBR emulsion [manufactured by Nippon Zeon Co., Ltd., solid content 45% by weight] and 8 parts by weight of sodium dodecylbenzenesulfonate [manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., solid content 20% by weight] were used as main components. The mixed liquid was coated with a wire rod so as to be 5 g / m ² , dried at 100 ° C. for 30 seconds to form an overcoat layer (second layer), and a moisture-proof paper was manufactured.

Example 2 The second layer of Example 1 was mixed with 82 parts by weight of the same SBR emulsion as in Example 1 and sodium dialkylsulfosuccinate [manufactured by Yatasha Yushi Kogyo Co., Ltd., solid content: 17.5% by weight].
A moisture-proof paper was produced in the same manner as in Example 1 except that a mixed solution containing 18 parts by weight as a main component was used.

Example 3 The second layer of Example 1 was mixed with 95 parts by weight of the same SBR emulsion as in Example 1 and polyoxyethylene nonyl phenyl ether [trademark: Eleminol HA-161, manufactured by Sanyo Chemical Industry Co., Ltd., solid content. 100 wt%] A moisture-proof paper was produced in the same manner as in Example 1 except that a mixed solution containing 5 parts by weight as a main component was used.

Comparative Example 1 A mixed solution containing 5 parts by weight of the paraffin wax emulsion and 93 parts by weight of the SBR emulsion used in Example 1 on the back surface of the same base material as in Example 1 was used as a wire rod at 16 g / m ² . It was coated as described above and dried at 100 ° C. for 30 seconds to produce a moisture-proof paper.

Comparative Example 2 A moisture-proof paper was produced in the same manner as in Example 1 except that sodium dodecylbenzenesulfonate was not used.

Experimental Example 1 When a water drop was dropped on the outermost layer of the moisture-proof paper obtained in Example 1 and Comparative Example 1, the contact angle of the water drop to the surface of the moisture-proof paper of Comparative Example 1 was 90 ° or more. On the other hand, the moisture-proof paper of Example 1 was uniformly wet and spread on the surface. Further, from the analysis by surface infrared absorption spectrum analysis (ATR) and X-ray photoelectron spectroscopy (ESCA), the moisture-proof paper of Example 1 was found to have a layer containing wax as the main component on the surface side, and further the surface active layer on top of it. It was confirmed that the agent layer was formed. On the other hand, in the moisture-proof paper of Comparative Example 1, a layer containing wax as a main component could be confirmed on the surface side, but no surfactant layer could be confirmed above it.

Experimental Example 2 The moisture-proof papers obtained in Examples 1 to 3 and Comparative Examples 1 to 2 were used as samples to measure moisture permeability, adhesiveness with a water-based adhesive, and water absorption of a moisture-proof coated surface. Each measuring method is as follows. [Moisture Permeability] The moisture permeability was measured in accordance with the method described in JIS Z 0208 (cup method) B method with the moisture-proof coated surface inside. [Adhesiveness with water-based adhesive] Synthetic rubber water-based emulsion adhesive [Konishi Co., Ltd.]
[Production], and allowed to stand for 24 hours and then peeled by hand to confirm the adhesiveness of the moisture-proof paper. The evaluation is as follows. ⊚: Complete paper break ○: 90% paper break ×: Interface peeling [Water absorption] The water absorption of the moisture-proof coated surface is JIS P 814.
0 (cup method), and the contact time with water was 2 minutes.

Tables 1 and 2 summarize the moisture vapor transmission rates of the moisture-proof papers obtained in Examples 1 to 3 and Comparative Examples 1 to 2, the adhesiveness to water-based adhesives, and the water absorption of the moisture-proof coated surface.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

The moisture-proof paper of the present invention has a uniform wax layer and a surfactant layer formed on the surface thereof.
The moisture-proof property is maintained, and at the same time, adhesion by a water-based adhesive is made possible, which contributes to improvement in productivity of a box made of the moisture-proof paper. Further, according to the manufacturing method of the present invention, it is possible to easily manufacture the moisture-proof paper having the above-mentioned moisture-proof property and adhesiveness with the water-based adhesive at the same time.

Claims (5)

[Claims] 1. A water vapor-permeable material in which a layer containing a water-insoluble synthetic resin is formed on at least one surface of a paper, a wax layer is formed on the surface side thereof, and a surfactant layer is further formed on the surface thereof. Is 50 g / m ² · 24 h or less, and the water absorption of the layer forming surface is 10 g / m ² or more. 2. The moisture-proof paper according to claim 1, wherein the surfactant is an anionic surfactant. 3. An emulsion containing a water-insoluble synthetic resin on at least one side of a paper to form a first layer, the emulsion containing a water-insoluble synthetic resin on the surface thereof. A method for producing a moisture-proof paper, which comprises applying a mixed solution containing a resin and a free surfactant to form a second layer and heat-treating it to form the surfactant layer as the outermost layer. 4. The method for producing a moisture-proof paper according to claim 3, wherein the surfactant is an anionic surfactant. 5. The method for producing a moisture-proof paper according to claim 3, wherein the first layer contains a pigment.