JPH10266096A - Production of moistureproof paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a moistureproof paper that maintains high moistureproof properties and enables the adhesion with a water-based adhesive, thus can largely contribute to the practical use in the fields requiring moistureproofness and adhesion such as moistureproof cardboard or moistureproof carton paper. SOLUTION: In the production of moistureproof paper, paper is coated on at least one face with a mixture of wax emulsion, water-insoluble synthetic resin emulsion and a surfactant to form a layer and the layer is heat-treated to form a layer of surfactant on the outermost layer. The water vapor permeability of the resultant paper is <=50 g/m<2> /24 h and the water absorption of the layer-forming face is >=10 g/m<2> .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing moisture-proof paper. More specifically, the present invention relates to a method for producing moisture-proof paper having moisture-proof properties and capable of being bonded with a water-based adhesive.

[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 method for producing a moisture-proof paper which has sufficient moisture-proof properties and can be bonded with an aqueous adhesive.

[0005]

That is, the present invention provides:
(1) At least one side of the paper is coated with a mixture obtained by adding a surfactant together with a wax emulsion and a water-insoluble synthetic resin emulsion to form a layer. A method for producing a moisture-proof paper having a moisture permeability of 50 g / m ² · 24 h or less and a water absorption of the layer-forming surface of 10 g / m ² or more, characterized by forming a layer of an agent, (2) surfactant Is from 2 to 25% by weight based on the total solid content of the wax emulsion and the water-insoluble synthetic resin emulsion, and (3) the surfactant is an anionic surfactant. The present invention relates to the method for producing a moisture-proof paper according to the above (1), which is an activator.

[0006]

According to the method of the present invention, a mixed solution containing the following essential components is applied to at least one side of paper,
The obtained layer is heat-treated. As the wax emulsion, which is an essential component of the above-mentioned liquid mixture, those derived from natural products and petroleum can be used without any particular limitation. For example, paraffin wax, low melting point polyethylene wax, fatty acid ester wax, fatty acid wax, petroleum oil wax,
Emulsions such as synthetic resin wax and microcrystalline wax are exemplified. 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 preferably from 300 to 700, and the melting point is 1
00 ° C or less is preferable, and 50 to 80 ° C is more preferable.
It is.

The water-insoluble synthetic resin emulsion includes, for example, emulsions of acrylic polymers, synthetic rubbers, vinyl acetate polymers and the like. In particular,
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 Emulsions such as copolymers and ethylene-2-ethylhexyl acrylate copolymers may be mentioned. As synthetic rubbers, for example, styrene-butadiene copolymer, nitrile-butadiene copolymer, vinylpyridine-
Emulsions such as butadiene-based polymers such as styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer, and isoprene-based polymers such as isoprene polymer are exemplified. As the vinyl acetate polymer, for example, vinyl acetate polymer, vinyl acetate-methyl acrylate copolymer,
Vinyl acetate-ethyl acrylate copolymer, vinyl acetate-
Butyl acrylate copolymer, vinyl acetate-acrylic acid-
Emulsions such as 2-ethylhexyl copolymer, vinyl acetate-dibutyl maleate copolymer, and vinyl acetate-ethylene copolymer are exemplified. In addition, emulsions of a styrene polymer such as a styrene polymer, an ethylene polymer, and an ethylene polymer such as an ethylene-vinyl acetate polymer can also be used.

The surfactant preferably has a melting point equal to 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 is preferably in the range of 5 to 50, more preferably 7 to 40, from the viewpoint of compatibility with water. Where H
LB is calculated by the formula: HLB = ΣJ _W −ΣJ _O +7 (where J _W represents the number of hydrophilic groups and J _O represents the number of hydrophobic groups).

As the surfactant, an anionic surfactant and a nonionic surfactant are preferred. Above all, anionic surfactants cause electrical repulsion with water-insoluble synthetic resin, which makes it easy to float to the upper layer.Thus, only a small amount of the anionic surfactant is required. However, it is particularly preferred. 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. Examples of the nonionic surfactant include, for example, polyoxyethylene alkylaryl ethers such as polyoxyethylene nonylphenyl ether, polyoxyethylene alkyl ether, polyoxyethylene glycerin fatty acid ester, and polyethylene glycol fatty acid ester.

A surfactant is added together with the wax emulsion and the water-insoluble synthetic resin emulsion to obtain a mixed solution.

The mixture contains a stabilizer, an antifoaming agent, a waterproofing agent,
Viscosity improvers, water retention agents, preservatives, coloring agents and the like may be added.

The solid content weight ratio of the wax emulsion and the water-insoluble synthetic resin emulsion [wax emulsion (solid content) / water-insoluble synthetic resin emulsion (solid content)] in the mixed solution thus obtained is not particularly limited.
It is appropriately determined according to the required performance. The preferred weight ratio is 1
/ 1 to 50, more preferably 1/10 to 40. The amount of the surfactant to be added is appropriately determined according to the required performance, and is preferably [surfactant (solid content)] / [wax emulsion (solid content) + water-insoluble synthetic resin emulsion (solid content)] × 100. It is 2 to 25% by weight, more preferably 3 to 20% by weight. If it is less than 2% by weight, it may be insufficient to form a layer on the coated surface of the moisture-proof paper, and if it exceeds 25% by weight, water resistance may be adversely affected. The solid content in the mixture is 10 to 50% by weight.
Is more preferably in the range of 20 to 50% by weight.

[0014] The minimum film forming temperature of the mixed solution is preferably 30 ° C or lower. When a mixture having a minimum film-forming temperature of 30 ° C. or lower is used, a layer having high moisture-proof properties can be obtained. Here, the “minimum film forming temperature of 30 ° C. or less” means that the polymer aqueous dispersion is 3
This means that the film can be formed at a temperature of 0 ° C. or lower. The lower limit of the minimum film forming temperature is not particularly limited.

The coating amount of the mixed solution for forming the layer can be arbitrarily changed depending on the required performance and the like.
m ² (wet weight) is preferred, and particularly preferably 15 to 25.
g / m ² (wet weight). The coating method is performed by a known method. For example, the coating liquid is applied to the paper using a known coater such as a roll coater, a blade coater, or an air knife coater, and a layer is formed through a drying process (for example, at 80 to 130 ° C. for 30 seconds).

The moisture-permeable paper thus obtained has a moisture permeability of 5
0 g / m ² · 24 h or less. The moisture permeability is JIS Z
0208 (cup method) According to the B method, the measurement is performed with the surface on which the synthetic resin layer, the wax layer and the surfactant layer are formed inside.

The moisture absorption of the moisture-proof paper is 10 g / m ² or more. The degree of water absorption is the surface on the surfactant layer side which is the outermost layer,
Based on JIS P 8140 (cup method), the contact time with water is measured as 2 minutes. If the water absorption is less than 10 g / m ² , the adhesiveness of the aqueous adhesive tends to decrease. The preferred range of water absorption degree is 10 to 50 g / m ^2, more preferably from 20 to 40 g / m ^2.

There is no particular limitation on the paper used in the present invention, and packaging paper, printing paper, cardboard, paperboard for paper containers, 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.

[0019]

The mixed liquid of the wax emulsion, the water-insoluble synthetic resin emulsion and the surfactant exists as a stable mixture in a liquid state, but when coated on paper and dried by heating,
First, the surfactant dissolved in the water is separated from the wax and the resin by water evaporation, and is deposited on the coating surface. Also, the action of heat causes the wax component to melt, become compatible with the synthetic resin component, and mix well. And when the heating and drying of the coated surface is finished and the surface temperature is lowered, the wax solidifies and the compatibility with the resin is reduced, and a synthetic resin layer and a wax layer are formed,
The wax precipitates on the surface of the synthetic resin layer. At this time, the surface of the synthetic resin layer is formed with a surfactant layer first, and the compatibility with the surfactant layer is low, so that the wax pushes up the surfactant layer and forms an interface with the synthetic resin layer. A layer is formed between the activator layers. In other words, the final configuration of the moisture-proof paper is such that a layer mainly composed of a synthetic resin layer is formed on the innermost layer on the side of the coated base paper, a wax layer is formed on the intermediate layer, and a surfactant layer is formed on the outermost layer. Become. The innermost synthetic resin layer prevents the penetration of the wax into the paper, the middle wax layer imparts moisture resistance, and the outermost surfactant layer dissolves in the water of the water-based adhesive. It acts to re-emulsify the layer and provide adhesion.

The wax emulsion and the water-insoluble synthetic resin emulsion usually contain a small amount of a surfactant added during emulsification. In the method of the present invention, the emulsion is obtained by further adding a surfactant to the emulsion. It is characterized by using the obtained mixed liquid. The amount of the surfactant contained in the emulsion is small, and most of the surfactant is physically adsorbed on the surface of the emulsion particles. It is considered that the surface active agent is hardly fixed on the surface of the emulsion particles, and therefore, has a strong property of easily phase-separating from the emulsion particles during coating and heating and drying, and bleeding to the surface.

[0021]

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 paraffin wax emulsion (manufactured by Arakawa Chemical Industries, Ltd., solid content concentration: 30% by weight) having a base weight of coated white balls having a basis weight of 330 g / m ² and having a melting point of 58 ° C. 5
Parts by weight, SBR emulsion (manufactured by Zeon Corporation,
93 parts by weight of a solid content concentration of 48% by weight and sodium dodecylbenzenesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.)
A mixture containing 2 parts by weight of a solid content of 65% by weight (anionic) was applied using a wire rod so as to be 16 g / m ^2, and dried at 100 ° C. for 30 seconds to produce a moisture-proof paper.

Example 2 4 parts by weight of the same paraffin wax emulsion as in Example 1, 88 parts by weight of the same SBR emulsion as in Example 1, and dodecylbenzene as in Example 1 on the back of the same substrate as in Example 1. A mixture containing 8 parts by weight of sodium sulfonate was applied with a wire rod so as to be 17 g / m ^2, and dried at 100 ° C. for 30 seconds to produce a moisture-proof paper.

Example 3 6 parts by weight of the same paraffin wax emulsion as in Example 1, 84 parts by weight of the same SBR emulsion as in Example 1, and sodium dialkyl sulfosuccinate (on the other hand, A mixture containing 10 parts by weight (manufactured by Kogyo Co., Ltd., solid content concentration: 20% by weight, anionic) is coated with a wire rod at 17 g / m ² and dried at 100 ° C. for 30 seconds to produce a moisture-proof paper. did.

Example 4 4 parts by weight of a paraffin wax emulsion as in Example 1, 91 parts by weight of SBR emulsion as in Example 1, and polyoxyethylene nonylphenyl ether (trademark) : Eleminor HA-
161 manufactured by Sanyo Kasei Kogyo Co., Ltd., a solid content of 100% by weight, nonionic), and a mixture containing 5 parts by weight was applied with a wire rod to 17 g / m ² at 100 ° C.
After drying for 30 seconds, a moisture-proof paper was produced.

Example 5 On the back surface of the same base material as in Example 1, 6 parts by weight of the same paraffin wax emulsion as in Example 1, 74 parts by weight of the same SBR emulsion as in Example 1, and polyoxyethylene alkyl ether (trade name: Sanmorin 11, manufactured by Sanyo Chemical Industries, Ltd., solid content concentration 40% by weight, nonionic)
The mixture containing 20 parts by weight was mixed with a wire rod at 18 g /
m ^2, and dried at 100 ° C. for 30 seconds to produce a moisture-proof paper.

Comparative Example 1 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 droplet was dropped on the coating surface of the moisture-proof paper obtained in Example 1 and Comparative Example 1, the contact angle of the water droplet with the moisture-proof paper of Comparative Example 1 was 90 ° or more. On the other hand, the moisture-proof paper of Example 1 spread uniformly on the surface. Further, from the analysis by surface infrared absorption spectrum analysis (ATR) and X-ray photoelectron spectroscopy (ESCA), a layer mainly composed of wax is formed on the surface side of the moisture-proof paper of Example 1, and the outermost layer is formed on the outermost layer. It was confirmed that a layer composed of a surfactant was formed. On the other hand, in the moisture-proof paper of Comparative Example 1, a layer mainly composed of wax could be confirmed on the surface side, but a layer composed of a surfactant could not be confirmed as the outermost layer.

Experimental Example 2 The moisture-proof papers obtained in Examples 1 to 5 and Comparative Example 1 were used as samples to test the moisture permeability and the adhesiveness with an adhesive. Each measuring method is as follows. [Moisture Permeability] The moisture permeability was measured with the coated surface inside, according to the method described in JIS Z 0208 (cup method) B method. [Adhesiveness with water-based adhesive] The coated and uncoated surfaces of the moisture-proof paper are bonded with a synthetic rubber-based water-based emulsion adhesive (manufactured by Konishi Co., Ltd.), left for 24 hours, and then peeled off by hand to adhere the moisture-proof paper. Was confirmed. The evaluation is as follows. ：: Completely broken paper ×: Interfacial peeling [Water absorption] The water absorption of the moisture-proof coated surface is JIS P814.
0 (cup method), and the contact time with water was 2 minutes.

Table 1 summarizes the moisture permeability of the moisture-proof papers obtained in Examples 1 to 5 and Comparative Example 1, the adhesiveness to a water-based adhesive, the water absorption of the moisture-proof coated surface, and the like.

[0031]

[Table 1]

[0032]

The moisture-proof paper obtained by the production method of the present invention comprises:
Layers mainly composed of synthetic resin in the innermost layer on the base paper side, wax in the middle layer, and surfactant in the outermost layer maintain high moisture resistance and enable adhesion with water-based adhesives. . For this reason, it greatly contributes to practical use in fields requiring moisture proof and adhesiveness, such as moisture proof corrugated cardboard and moisture proof carton paper.

Claims (3)

[Claims] 1. A layer formed by applying a mixed solution obtained by adding a surfactant together with a wax emulsion and a water-insoluble synthetic resin emulsion to at least one side of paper to form a layer,
The layer is heat-treated to form the above-mentioned surfactant layer as the outermost layer. The layer has a water permeability of 50 g / m ² · 24 h or less and a water absorption of the layer-forming surface of 10 g / m ² or more. A method of manufacturing a moisture-proof paper. 2. The method for producing a moisture-proof paper according to claim 1, wherein the amount of the surfactant is 2 to 25% by weight based on the total solid content of the wax emulsion and the water-insoluble synthetic resin emulsion. 3. The method according to claim 1, wherein the surfactant is an anionic surfactant.