JPH0885183A - Moisture-proof laminate - Google Patents

Abstract

PURPOSE: To improve resistance to folding and breakage by a method wherein an undercoating layer, containing a synthetic resin having a specified value of glass transition temperature, is formed on one surface of a supporting body while a moistureproof layer, consisting of unsoluble synthetic resin and emulsified wax, having a specified value of emulsifying grain size of wax, is formed thereon. CONSTITUTION: A moistureproof laminated body is obtained by a method wherein an undercoating layer, containing a synthetic resin having a glass transition temperature of -30-0 deg.C, is formed on base paper while a moistureproof layer, consisting of unsoluble synthetic resin and emulsified wax, having an emulsifying grain size of 0.1-0.5μm, is formed on the undercoating layer. When the glass transition temperature of the synthetic resin, used for the undercoating layer, exceeds 0 deg.C, resistance to folding and breakage becomes insufficient and when the same temperature is lower than -30 deg.C, the resistance to folding and breakage reaches the top value and scratch or contamination is generated upon coating. When the moistureproof layer on the undercoating layer, which is constituted of the soluble synthetic resin and the emulsified wax, is heated and dried so as to obtain a surface temperature, higher than the melting point of the wax, the configuration of grain of wax, buried in the moistureproof layer, will never be changed and weak contacting condition exists mutually since the film making property of the synthetic resin is quick.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moistureproof paper which has excellent moistureproofness and can be reused as waste paper.

[0002]

2. Description of the Related Art Conventionally, for winding high-quality paper, bleached kraft paper, unbleached kraft paper, various coated papers, etc., and for packaging high-quality papers and coated plain papers, to prevent moisture absorption of the product A wrapping paper is used in which a high molecular weight polyolefin compound such as polyethylene or polypropylene is applied to paper, laminated or internally added to provide moisture resistance and water resistance. In addition, in heavy-duty base paper such as cement bags, salt bags, feed bags, fertilizer bags, and garbage bags, it is necessary to carry heavy goods while preventing moisture absorption and water absorption of the contents after bag making and bagging. , Moisture resistance and strength are required. For this reason, polyolefin laminated paper (hereinafter referred to as poly-laminated paper) obtained by laminating polyethylene, polypropylene or the like on kraft paper is overlapped with kraft paper and is usually used as a bag.

However, these poly-laminated papers have a problem in that they cannot be reused as waste paper because they are not sufficiently disintegrated in water even if they are collected for reuse as waste paper after use. In addition, the used poly-laminated paper is inconvenient to dispose of because it costs the user even if it is discarded, and also causes environmental pollution due to incineration or landfill.

There is also known an attempt to disintegrate a used moisture-proof wrapping paper with water and reuse it as a raw material for paper. For example, Japanese Patent Application Laid-Open No. 50-67711 discloses a paraffin wax having a specific melting point. To a petroleum resin having a specific softening point, rosin and higher alcohol are added, emulsified with an organic amine or aqueous ammonia solution, and saponified with an alkali to prepare an aqueous emulsion, and the aqueous emulsion is applied to one side or both sides of kraft paper. A method of applying to produce a moisture proof wrapping paper is disclosed. However, when the moisture-proof wrapping paper obtained by this method is heated above the softening point, the wax film melts and soaks into the paper, and since the wax film is prone to plastic deformation, it is likely to be folded in flat-format packaging. There is a problem in that moisture cannot permeate from the folds and the moisture-proof property cannot be exhibited.

Japanese Unexamined Patent Publication (Kokai) No. 53-41511 discloses a method for producing a moisture-proof wrapping paper using an aqueous emulsion composed of a synthetic rubber latex and a wax emulsion. This method is intended to eliminate the deterioration of the moisture proof property and the deterioration of the moisture proof property due to bending during use of the product, by performing high temperature drying when manufacturing the moisture proof wrapping paper. However, with this method, the moisture resistance is considerably high and the moisture permeability at the fold is also good, but it is still insufficient. For this reason, it is necessary to increase the amount of the moisture-proofing agent applied, and the processed paper tends to cause blocking (a phenomenon in which the coated surface and the non-coated surface adhere to each other due to heat and pressure causing adhesion). After winding up after production, the wax in the moisture-proof layer is transferred to the back surface and becomes slippery, and it is disadvantageous in terms of cost.

Further, JP-A-56-148997 discloses a moisture-proofing composition for paper comprising a mixture of a wax emulsion and a thermoplastic acrylic emulsion obtained by dispersing in water in the presence of at least a saponification equivalent of alkali. The thing is disclosed.

Japanese Unexamined Patent Publication No. 61-47896 discloses a wax containing a paraffin wax having a specific melting point, an esterified product of a maleinized or fumarized rosin and a polyhydric alcohol, liquid polybutene, and rosin as main components. Disclosed is a method for producing a moisture-proof paper in which an emulsion or a mixture of the wax emulsion and a synthetic rubber-based latex is applied to the surface of a fibrous base material such as high-quality paper or kraft paper and dried under heating.

However, in all of the above-mentioned prior arts, the crease resistance in moisture-proof packaging (reduction in moisture resistance when folds are made) is insufficient, and the folds at the corners of the package cause It was never used for wrapping plain paper or for making bags because it absorbs moisture and the wax is transferred to the back surface to make it slippery.

Further, in Japanese Patent Laid-Open No. 4-334447, there is one in which a moisture-proof property is enhanced by providing a first layer made of a synthetic resin having a minimum film forming temperature of 1 ° C. or higher and a second layer made of a wax and a polymer. However, due to the large deformation of the first layer, the moisture resistance to breakage is not sufficient yet under the present circumstances.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a moisture-proof paper having improved breakage resistance as compared with conventional ones.

[0011]

That is, according to the present invention, an undercoat layer containing a synthetic resin having a glass transition temperature of -30 ° C to 0 ° C as a main component is provided on a base paper, and a water-insoluble synthetic material is further provided on the undercoat layer. A moisture-proof laminate, comprising a moisture-proof layer made of a resin and a wax having an emulsion particle size of 0.1 μm to 0.6 μm.

[0012]

It is possible to use a synthetic resin having a low glass transition temperature (Tg) for the moisture-proof layer in order to impart break resistance to the moisture-proof layer, but blocking tends to occur when the glass transition temperature becomes low. On the other hand, if the glass transition temperature is too high, the synthetic resin becomes brittle, and when a crease is formed, defects such as cracks occur in the moisture-proof layer, and there is a problem that the crease resistance is lost. Therefore, it is difficult to achieve both the blocking resistance and the breakage resistance of the moisture-proof layer.

In order to solve this problem, the inventors of the present invention have earnestly studied and, as a result, have a glass transition temperature of -30 ° C. to 0 on the base paper.
It has been found that it is sufficient to form an undercoat layer containing a synthetic resin at 0 ° C. and provide a moisture-proof layer containing a wax having an emulsion particle size of 0.1 μm to 0.6 μm on the undercoat layer.

The first important point of the present invention is that the synthetic resin used for the undercoat layer has a glass transition temperature of -30 ° C to 0 ° C. The synthetic resin is generally used as a latex or an aqueous emulsion, and is composed of an aromatic vinyl monomer, an aliphatic conjugated diene monomer, an ethylenically unsaturated fatty acid monomer and other copolymerizable monomers. As the copolymer, for example, a synthetic rubber latex such as a styrene / butadiene latex or a methyl methacrylate / butadiene latex or an acrylic emulsion can be used. Of these, styrene-butadiene latex, which is excellent in flexibility, is preferable. If the glass transition temperature of the synthetic resin used exceeds 0 ° C., the resulting moisture-proof paper will have insufficient crack resistance. It is preferably -5 ° C or lower in order to impart sufficient folding crack resistance. In addition, when the temperature is -30 ° C or lower, the effect on the fold crack resistance reaches a peak, and
It is not preferable because scratches and stains are generated during coating. There is a close relationship between the glass transition temperature and the minimum film forming temperature, and if the glass transition temperature is 0 ° C. or lower, the minimum film forming temperature may be 0 ° C. or lower.

Inorganic pigments may be added to the undercoat layer in order to improve coatability and prevent blocking.
For example, calcium carbonate, kaolin, clay, amorphous silica, aluminum hydroxide, zinc oxide, titanium oxide, etc. are used in a weight ratio of synthetic resin to pigment of 10:90 to 70: 3.
0, preferably 30; 70 to 50; 50 is added. The coating amount of this undercoat layer is not particularly limited, but is 0.1 to 20 g.
/ M ^{2 and} the range of 0.5 to 10 g / m ² is preferable. The coating amount is O. If it is 1 g / m ² or less, the effect on the fold cracking resistance is lost, and if it is 20 g / m ² or more, the effect reaches the ceiling and the cost is increased, which is uneconomical.
Furthermore, moisture permeability of the undercoat layer is generally sufficient if the 200~4000g / m ² / 24hr about not particularly limited.

The second important point of the present invention is that the wax is used as an emulsion, but the moisture resistance of the fold is greatly changed depending on the emulsion particle size of the wax. According to a detailed observation by the present inventor, even if a moisture-proof layer made of a synthetic resin and a wax emulsion is dried by heating so as to have a surface temperature higher than the melting point of the wax, the synthetic resin has a rapid film-forming property and is buried therein. The particle shape of the wax thus formed does not change, and the waxes are present in weak contact with each other while maintaining the initial particle shape. Therefore, the emulsified particle size of the wax is 0.6 μm
It is considered that the moisture resistance is greatly reduced, probably because the distance between the waxes becomes large due to plastic deformation when cracking occurs when the size is large and peeling occurs at the boundary between the synthetic resin and the wax. Further, when the emulsified particle diameter of the wax is 0.1 μm or less, the amount of the emulsifier contained in the emulsion becomes very large, and as a result, the moisture resistance is lowered.

The wax emulsion used in the present invention contains a paraffin component composed of an aliphatic hydrocarbon having a wax melting point of 50 ° C to 80 ° C. For example, paraffin wax and those containing an esterified product of a modified rosin and a polyhydric alcohol as a main component, or waxes such as microcrystalline wax and polyethylene wax are generally used in the same manner as the paraffin wax. In addition to the above, a wax emulsion containing liquid polybutene, rosin, an etherified product of polyoxyalkylene, etc., in addition to the above components in order to prevent the moisture-proof layer from slipping (see JP-A-61-47896). Those containing other components compatible with the wax are preferable.

In order to emulsify these paraffin component-containing substances in water, (1) a molten wax and an emulsifier are mixed and heated water is injected into the emulsified water-in-oil (W / O) type emulsion. A solubilization method in which the substance is in a solubilized state, and when further injected, it is inverted to form an oil-in-water (O / W) type emulsion state.
(2) A method in which a melted wax and an emulsifier in order to lower the interfacial tension is poured into boiling water while stirring to obtain an emulsion. (3) There is a method of emulsifying by applying a force equal to or higher than the interfacial tension by a mechanical force such as a homogenizer or a homomixer.

In order to exert the effects of the present invention using the wax thus emulsified, there is no particular limitation as long as the emulsified particle size of the wax is 0.6 μm or less, more preferably 0.3 μm or less. Emulsified particle size 0.1μm
If the amount is less than the above, a large amount of emulsifier is required, and a large amount of micelles containing only an emulsifier containing no wax component is generated, which reduces the effective amount of wax, which is not preferable.

The moisture permeability of the cracks also depends on the minimum film-forming temperature of the water-insoluble synthetic resin used for the moisture-proof layer. That is, the minimum film forming temperature (MFT) of the water-insoluble synthetic resin is 40.
When the temperature is higher than 0 ° C, the moisture-proof paper obtained has insufficient moisture-proof property. This is because when the minimum film forming temperature is higher than 40 ° C., a high drying temperature is required for a long time, so that the film forming property becomes insufficient under normal drying conditions, and the moisture-proof layer after production is lower than the minimum film forming temperature. It is considered that when this happens, the moisture-proof layer is prone to cracking, so that a continuous film cannot be obtained and the moisture-proof property deteriorates. Therefore, the minimum film-forming temperature of the water-insoluble synthetic resin generally used for the moisture-proof layer is 40 ° C. or lower, preferably 30 ° C. or lower.

The water-insoluble synthetic resin used in the moisture-proof layer is generally used as a latex or an aqueous emulsion, and it is used as an aromatic vinyl monomer, an aliphatic conjugated diene monomer, an ethylenically unsaturated fatty acid monomer. And copolymers composed of other copolymerizable monomers, such as styrene-butadiene latex, methyl methacrylate
A synthetic rubber latex such as a butadiene latex or an acrylic emulsion may be used.

The above-mentioned aromatic vinyl monomer imparts appropriate hardness and water resistance to the resulting copolymer resin,
For example, it can be selected from styrene, α-methylstyrene, monochlorostyrene, vinyltoluene and the like. Styrene is especially preferred.

The aliphatic conjugated diene-based monomer imparts appropriate flexibility to the resulting water-insoluble copolymer resin, for example, 1,3-butadiene, 2-methyl-1,3-.
Examples thereof include butadiene and 2-chloro-1,3-dibutadiene, and 1,3 butadiene is particularly preferable.

The ethylenically unsaturated acid monomer is effective for enhancing the adhesive force of the copolymer resin to be obtained and improving the stability of the copolymer latex as a colloid. At least one of unsaturated carboxylic acids such as methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid and butenetricarboxylic acid, itaconic acid monoethyl ester, fumaric acid monobutyl ester and maleic acid monobutyl ester. Unsaturated sulfonic acids such as unsaturated polycarboxylic acid alkyl ester having one carboxyl group, acrylamidopropanesulfonic acid, acrylic acid sulfoethyl sodium salt, and methacrylic acid sulfopropyl sodium salt, or a salt thereof can be used. Of which, acrylic acid, methacrylic acid, and itacone And fumaric acid are preferably used.

Other monomers (comonomers) copolymerizable with the above monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, and ethylenically unsaturated carboxylic acid alkyl esters such as butyl acrylate, Ethylenically unsaturated nitriles such as acrylonitrile and methacrylonitrile, β-hydroxyethyl acrylate,
Ethylenically unsaturated carboxylic acid hydroxyalkyl esters such as β-hydroxypropyl acrylate and β-hydroxyethyl methacrylate, ethylenically unsaturated carboxylic acid amides such as acrylamide, methacrylamide, N-methylol acrylamide, and diacetone acrylamide, and Its derivative, glycidyl acrylate,
And unsaturated carboxylic acid glycidyl esters such as glycidyl methacrylate, and vinyl compounds such as acrolein and allyl alcohol.
Among these monomers (comonomer), methyl methacrylate as an unsaturated carboxylic acid alkyl ester, acrylonitrile as an ethylenically unsaturated nitrile, β-hydroxyethyl acrylate as an unsaturated carboxylic acid hydroxyalkyl ester, and unsaturated carboxylic acid. Acrylamide is preferably used as the amide and its derivative.

The blending amount of the water-insoluble synthetic resin emulsion and the wax emulsion is, in terms of solid content, the water-insoluble synthetic resin emulsion: wax emulsion = 95:
A weight ratio of 5 to 50:50 is suitable, but if the weight ratio of the wax emulsion is less than 5%, sufficient moisture resistance cannot be obtained, and if it exceeds 50, the resistance to folds becomes small, and as a result, Moisture resistance of the portion where the fold is generated deteriorates.

The coating amount of the moistureproofing agent is 5 to 30 in terms of solid content.
It is g / m ² . If the coating amount is less than 3 g / m ² , the moisture resistance becomes insufficient, and if it exceeds 30 g / m ² , the moisture resistance obtained will only slightly improve as the coating amount increases, and it will reach the ceiling and the cost will increase. It is uneconomical because it invites

It is desirable to form an anti-slip layer on the back surface of the support in order to prevent the back surface from slipping due to the transfer of the wax component on the surface of the moisture-proof layer. The anti-slip agent is formed by applying a coating liquid containing a fine particle diameter powder having an anti-slip property such as zinc oxide, calcium carbonate, aluminum hydroxide, silicon dioxide, polystyrene, and acrylic styrene. Usually, the coating amount of this anti-slip layer is about 0.02 to 3 g / m ² . When the coating amount is 0.02 g / m ² or less, the slip preventing effect is small, and when the coating amount is more than 3 g / m ² , the anti-slip effect reaches the ceiling and it is uneconomical.

The coating equipment for the undercoat layer, the moisture-proof layer, and the anti-slip layer is not particularly limited, but may be arbitrarily selected from an air knife coater, bar coater, roll coater, blade coater, gate roll, size press and the like. .

The base paper is not particularly limited as long as it is easily dispersible in water by a mechanical disaggregation action. For example, a pulp selected from chemical pulp such as hardwood kraft pulp and softwood kraft pulp, mechanical pulp and the like. Examples of the raw material include high-quality paper, medium-quality paper, single-gloss kraft paper, Ryosara kraft paper, and kraft extended paper. There is no particular limitation on the basis weight of these base papers, and those having a basis weight of 30 to 300 g / m ² are appropriately selected and used according to the purpose.

The present invention will be specifically described below with reference to examples, but the following examples do not limit the present invention.

[0032]

【Example】

Example 1 Styrene butadiene latex having a glass transition temperature of 0 ° C. (trade name: SSB1008C, manufactured by Nippon Zeon, solid content 4)
(5% by weight) is hand-coated on unbleached kraft paper with a basis weight of 70 g / m ^{2 to} a solid content of 5 g / m ² with a Meyer bar, and then dried at 105 ° C. using a hot air circulation dryer. An undercoat layer was formed. Next, styrene-butadiene latex with a minimum film forming temperature of 27 ° C (trade name: OX1007
W, manufactured by Nippon Zeon Co., Ltd., solid content 50% by weight) 100 parts by weight and emulsified particle size 0.25 μm wax emulsion (trade name: OKW-40, manufactured by Arakawa Chemical Co., Ltd., solid content 40%, wax melting point 70 ° C.) 90 The moisture-proofing agent obtained by mixing 1 part by weight is hand-coated on the above undercoat layer with a Meyer bar so that the solid content is 12 g / m ² , and then dried at 105 ° C using a hot-air circulating dryer to prevent moisture-proofing. Layers were formed. Next, a polystyrene emulsion (trade name: AT-938, made by Japan PMC, solid content 5%) was hand-coated on the back surface of the support with a Mayer bar to a solid content of 0.5 g / m ^2, and then dried with hot air circulation. Using a machine, it was dried at 105 ° C. to form an anti-slip layer to produce a moisture-proof paper.

Example 2 A synthetic resin used for the undercoat layer was a styrene butadiene latex having a glass transition temperature of -8 ° C. (trade name: T-258).
No. 0, made by Japan Synthetic Rubber, solid content 50%), a moisture-proof paper was produced in the same manner as in Example 1.

Example 3 The synthetic resin used for the undercoat layer was a styrene acrylic emulsion having a glass transition temperature of -9 ° C. (trade name: X-591-).
620E, manufactured by Saiden Chemical Co., Ltd., solid content: 45%) to produce a moisture-proof paper in the same manner as in Example 1.

Example 4 The synthetic resin used for the undercoat layer was made to have a glass transition temperature of -12 ° C.
Styrene butadiene latex (trade name PL-518
B, manufactured by Mitsui Toatsu Co., Ltd., solid content 50%), and a moisture-proof paper was manufactured in the same manner as in Example 1.

Example 5 The synthetic resin used for the undercoat layer had a glass transition temperature of -30 ° C.
Styrene butadiene latex (trade name L-139
2, a moisture-proof paper was manufactured in the same manner as in Example 1 except that the solid content was 50% made by Asahi Kasei.

Example 6 A wax emulsion used in the moisture-proof layer was emulsified. A wax emulsion having a particle diameter of 0.55 μm (trade name: OKW
Modified-BN-1, manufactured by Arakawa Chemical Co., Ltd., solid content 40%, melting point of wax 70 ° C.), except that moisture-proof paper was manufactured in the same manner as in Example 1.

Comparative Example 1 A moisture-proof paper was produced in the same manner as in Example 1 except that the undercoat layer was not provided.

Comparative Example 2 The synthetic resin used for the undercoat layer was a styrene butadiene latex having a glass transition temperature of 5 ° C. (trade name: SSB).
1005, manufactured by Nippon Zeon Co., Ltd., solid content: 45%) to produce a moisture-proof paper in the same manner as in Example 1.

Comparative Example 3 The synthetic resin used for the undercoat layer was a styrene butadiene latex having a glass transition temperature of 27 ° C. (trade name: OX).
A moisture-proof paper was produced in the same manner as in Example 1 except that 1007 W, manufactured by Nippon Zeon Co., Ltd., solid content: 50%) was used.

Comparative Example 4 The wax used in the moisture-proof layer was a wax emulsion having an emulsified particle size of 0.77 μm (trade name: OKW Kai-BN-3,
A moisture-proof paper was produced in the same manner as in Example 1 except that Arakawa Chemical Co., Ltd., solid content 40%, melting point of wax 70 ° C.).

Comparative Example 5 The wax used in the moisture-proof layer was a wax emulsion having an emulsified particle size of 1.01 μm (trade name: OKW Kai-BN-4,
A moisture-proof paper was produced in the same manner as in Example 1 except that Arakawa Chemical Co., Ltd., solid content 40%, melting point of wax 70 ° C.).

Comparative Example 6 A wax emulsion having an emulsified particle size of less than 0.1 μm (trade name: OKW Kai-BN-
5, Arakawa Chemical, solid content 40%, melting point of wax 70
A moisture-proof paper was produced in the same manner as in Example 1 except that (.degree. C.) was used.

The moisture-proof papers obtained in Examples 1 to 5 and Comparative Examples 1 to 7 were subjected to a test for evaluating moisture permeability and blocking resistance. These test methods were as follows.

<Test Method> 1) Moisture Permeability Measured by JIS Z0208 (cup method) B method with the coated surface facing outward. If it has a crease, fold the sample in half and use a mini-machine calender to load 50kg / c linear pressure.
After making a crease at m, the sample was opened and the crease was made again in the cross direction using a minimachine calender. 50 g / m ² · 2 without folds as a standard for the value of moisture permeability
4 hours or less, with creases 100 g / m ² · 24 hours
The following is sufficiently practical.

2) Particle size Shimadzu laser diffraction particle size distribution analyzer SALD-110
0 V2.10 (manufactured by Shimadzu Corporation) was used to measure the emulsified particle size of the wax emulsion under the following conditions. In addition,
In the present invention, the particle size is the average particle size (the cumulative volume ratio is 5
0% particle size). Measurement range: 0.1 to 45 μm Refractive index: 1.7 Calculation method: Direct calculation method Number of measurements: 4 times Measurement interval: 2 seconds

[0047]

[Table 1]

As is clear from Table 1, the moisture-proof paper of the present invention has improved crease resistance.

[0049]

The moisture-proof paper of the present invention has improved resistance to folds.

Claims (1)

[Claims] 1. A moisture-proof laminate comprising a support, on one surface of which an undercoat layer containing a synthetic resin is formed, and a moisture-proof layer comprising a water-insoluble synthetic resin and a wax emulsion formed on the undercoat layer. (1) Undercoat layer Glass transition temperature of synthetic resin of -30 ℃
˜0 ° C., (2) The emulsion particle diameter of the wax of the moisture-proof layer is 0.1 μm
A moisture-proof laminate having a thickness of 0.6 μm.