JP3199274B2 - Paper coating composition, coated paper and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coating composition for moisture-proof paper. More specifically, waste paper or broke of paper coated with the composition has good reusability as a raw material for papermaking, and is excellent in terms of moisture resistance, folding resistance, disintegration and blocking resistance. The present invention relates to a coating composition for a moisture-proof paper suitable for producing a moisture-proof paper having excellent performance. Furthermore, the present invention provides a moisture-proof paper having excellent performance in terms of wastepaper and waste paper having good reusability as a raw material for papermaking, and moisture-proof, folding resistance, disintegration and blocking resistance. It relates to the manufacturing method.

[0002]

2. Description of the Related Art Conventionally, as moisture-proof papers mainly used for moisture-proof packaging, there are mentioned paraffin paper impregnated with molten wax, polyethylene laminate paper obtained by melt-extruding polyethylene, and tarpaulin paper melt-impregnated with asphalt. Can be Among these moisture-proof papers, polyethylene laminated paper is widely used because of its low cost and good performance, but it is difficult to remove wax and polyethylene from pulp when reusing waste paper or waste paper of moisture-proof paper. There was a point. Furthermore, a composition comprising the wax emulsion (A) and the polyvinyl alcohol (B) (the mixing ratio (A) /
It is known to apply (B) 0/100 to 23/77) to paper (Japanese Patent Application Laid-Open No. S59-144693).
However, the obtained paper had insufficient moisture resistance and folding resistance. Further, a slurry composed mainly of a pigment obtained by adding a small amount of a composition comprising a wax emulsion and polyvinyl alcohol (11 parts by weight of the composition to 100 parts by weight of the pigment) as a binder for the pigment is applied to paper. It is known to work (Japanese Patent Publication No. 34-1066)
No. 1), however, the obtained paper was insufficient in moisture resistance and folding resistance. Further, it is known to apply a wax emulsion to paper (JP-A-57-155253).
However, the obtained paper was insufficient in moisture resistance, folding resistance, disintegration and blocking resistance. Further, it is known to apply a composition comprising a wax emulsion and a synthetic rubber emulsion to paper (Japanese Patent Laid-Open No.
No.-41511), but the obtained paper did not have sufficient folding resistance and disintegration. Further, it is known to apply rosin emulsion obtained by emulsifying and dispersing polyvinyl alcohol as a dispersion stabilizer to paper (Japanese Unexamined Patent Publication No.
8-69251), but the obtained paper was not sufficient in moisture resistance and folding resistance.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide waste paper and broke of moisture-proof paper, in particular, which have good reusability as a raw material for papermaking, and which have moisture resistance, folding resistance, disintegration and resistance to moisture. An object of the present invention is to provide a coating composition for a moisture-proof paper suitable for producing a moisture-proof paper having excellent performance in terms of blocking property and the like. A further object of the present invention is to provide a moisture-proof paper in which waste paper or waste paper has good reusability as a raw material for papermaking and has excellent properties in terms of moisture resistance, folding resistance, disintegration and blocking resistance. And a method for producing the same.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have a specific wax-based emulsion (A) and a water-soluble resin (B) as main components.
The weight-based compounding ratio (A) / (B) in terms of solid content is 25.
/ 75-80 / 20, a moisture-proof paper obtained by applying the moisture-proof paper coating composition to base paper, and a method for producing the same. The present invention has been completed.

That is, the present invention firstly provides a melt viscosity of 50
Wax emulsion (A) having a particle size of 0.01 to 2000 centipoise, a particle diameter of 0.01 to 10 μm and a solid content of 5 to 50% by weight, and at least one selected from a polyvinyl alcohol resin having a polymerization degree of 200 to 3000, carboxymethyl cellulose and soluble starch. It is a coating composition for a moisture-proof paper having a water-soluble resin (B) of a kind as a main component and a weight-based mixing ratio (A) / (B) of 25/75 to 80/20 in terms of solid content.

Further, the present invention secondly provides the above-mentioned coating composition for moisture-proof paper on a base paper in an amount of 1 to 50 g / m in terms of solid content.
A ² coated moistureproof paper, the third, moisture permeability 50 g / m ²
Fourth, the moisture-proof paper has the following thickness. Fourth, the moisture-proof paper has a thickness of 30 to 300 μm.

Fifthly, the present invention is characterized in that the above-mentioned coating composition for moisture-proof paper is applied to base paper and then dried at a temperature higher than the melting point of wax by 10 ° C. or more for 5 seconds to 10 minutes. This is a method for producing moisture-proof paper.

[0008] In the present invention, the wax emulsion (A) is an aqueous emulsion containing a wax component as a dispersoid, and specific examples thereof include paraffin wax,
Aqueous emulsion containing a single component such as microcrystalline wax or polyethylene wax as a dispersoid; aqueous emulsion containing a blend of these wax components as a dispersoid; aqueous emulsion containing a modified wax component such as a maleated petroleum resin An aqueous emulsion containing rosin or an unsaturated higher alcohol as a dispersoid. The melting point of the wax which is a dispersoid of the wax emulsion (A) is not particularly limited, but is preferably 40 to 12
0 ° C. is preferred, 40 to 100 ° C. is more preferred, and 40 ° C.
~ 80 ° C is even more preferred. The melting point of wax is 40
When the temperature is lower than 0 ° C, a blocking phenomenon of the coated paper may easily occur depending on the use of the coated paper. The melt viscosity of the wax as a dispersoid of the wax emulsion (A) is 50 to 2000 at 100 ° C. (hereinafter, the melt viscosity means a viscosity measured at 30 rpm using a B-type viscometer). It is a centipoise (cp), and 100 to 1500 cp is more preferable. When the melt viscosity of the wax at 100 ° C. is within the above range, the moisture resistance of the coated paper is further improved. The particle size of the wax which is the dispersoid of the wax-based emulsion (A) is 0.1.
01 to 10 μm. The wax dispersant is not particularly limited, and has an emulsifier such as a nonionic emulsifier, an anionic emulsifier, and a cationic emulsifier; a water-soluble polymer dispersant such as polyvinyl alcohol and carboxmethylcellulose; and has a self-emulsifying property such as a maleated petroleum resin. And a polymer dispersant.

[0009] The water-soluble resin (B) in the present invention is preferably 5 to
A stable aqueous solution is obtained in a temperature range of 100 ° C., and is at least one water-soluble resin selected from a polyvinyl alcohol-based resin, carboxymethyl cellulose, and soluble starch such as oxidized starch. Among these water-soluble resins (B), polyvinyl alcohol-based resins are preferred from the viewpoint of the folding resistance and the disintegration properties of the obtained paper. As the polyvinyl alcohol-based resin, ordinary polyvinyl alcohol obtained by saponifying polyvinyl acetate;
Modified polyvinyl alcohol obtained by saponifying a copolymer obtained by copolymerizing another copolymerizable monomer with a vinyl acetate monomer; by reacting another reactive group with a part of the hydroxyl group of polyvinyl alcohol The resulting post-modified polyvinyl alcohol is included. As for the degree of polymerization of the polyvinyl alcohol-based resin, the lower the degree of polymerization is, the higher the degree of polymerization is preferable from the viewpoint of increasing the concentration of the coating solution and the phase separation between the wax and the polyvinyl alcohol-based resin after coating on the paper surface.
From the viewpoint of preventing the wax of the surface layer portion (outermost layer) of the coating layer from seeping into the paper layer, the higher the degree of polymerization, the better. The degree of polymerization of the polyvinyl alcohol-based resin is 200 to 3000 in view of the balance between the two. And 300 to 200
0 is more preferred. The degree of saponification of the polyvinyl alcohol-based resin is not particularly limited, but is preferably higher from the viewpoint of phase separation between the polyvinyl alcohol-based resin and the wax, and the saponification degree of the polyvinyl alcohol-based resin is preferably 80 mol% or more. preferable.

[0010] The weight-based compounding ratio (A) of the wax-based emulsion (A) and the water-soluble resin (B) in terms of solid content.
(B) is from 25/75 to 80/20, and from 35/65 to
80/20 is preferred, and 40/60 to 70/30 is more preferred. When the compounding ratio is out of the range of the present invention, the moisture-proof property of the paper obtained by applying the coating composition for moisture-proof paper decreases.

The coating composition for moisture-proof paper of the present invention requires the above-mentioned components (A) and (B) as main components, and the component (A) based on the total solid content in the coating composition for moisture-proof paper. And the total content of component (B) is 50
% By weight or more, more preferably 70% by weight or more, even more preferably 90% by weight or more. When the total content of the component (A) and the component (B) with respect to the total solids in the coating composition for moisture-proof paper is in the above-mentioned preferred range, the moisture-proof property and the folding resistance are further improved. The coating composition for a moisture-proof paper of the present invention needs to contain the component (A) and the component (B) as main components, but additives such as extender pigments and coloring pigments as long as the effects of the present invention are not impaired. May be contained.

The coating composition for moisture-proof paper of the present invention is characterized by being aqueous, and has a solid content of 5 to 50% by weight, more preferably 7 to 40% by weight. The coating amount of the moisture-proof paper coating composition in the present invention is preferably 1 to 50 g / m ² in terms of solid content, 2~25g / m ² is more preferable.

The coating composition for moisture-proof paper of the present invention comprises:
It has the effect of improving the moisture resistance, folding resistance, disintegration and blocking resistance of the object to be coated, and is particularly useful when the object to be coated is a base paper mainly composed of cellulose. When the coating composition of the present invention is applied to base paper, a moisture-proof paper having remarkably excellent moisture resistance, folding resistance, disintegration and blocking resistance can be obtained.

The coating layer of the moisture-proof paper of the present invention needs to contain wax and a water-soluble resin as main components. However, additives such as extender pigments and coloring pigments may be used as long as the effects of the present invention are not impaired. May be contained.

The coating layer in the moisture-proof paper of the present invention may be present substantially on the surface of the base paper so that the surface of the base paper is not exposed. A case where a part of the coating layer has penetrated into the base paper may be used. The thickness (thickness including the coating layer) of the moisture-proof paper of the present invention is 300 μm or less, preferably 250 μm or less, and more preferably 200 μm or less. 30 μm as the lower limit of the thickness of the moisture-proof paper
Or more, preferably 40 μm or more. Therefore, the thickness of the moisture-proof paper of the present invention is preferably from 30 to 300 μm, more preferably from 40 to 250 μm. When the thickness of the moisture-proof paper of the present invention is larger than 300 μm, the folding resistance tends to decrease.

The base paper of the moisture-proof paper of the present invention is not particularly limited, but base paper containing cellulose as a main component is preferable, and kraft paper is particularly preferable.

In the case of producing the moisture-proof paper of the present invention, it is preferable to apply the coating composition for moisture-proof paper of the present invention to base paper and then heat and dry at a temperature higher than the melting point of the wax by 10 ° C. or more. That is, the drying temperature is 65 to 17
0 ° C is preferred, and 80 to 150 ° C is more preferred. The drying time is appropriately selected from the range of 5 seconds to 10 minutes.

[0018]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the examples, unless otherwise noted,
“%” And “parts” mean on a weight basis.

Examples 1 to 9 and Comparative Examples 1 to 10 Kraft base paper (basis weight: 76 g / m
² , to a strength of 0.6), the composition shown in Table 1 was applied in an amount of 20 g / m ^{2 in} terms of solid content, followed by hot-air drying under the drying conditions shown in Table 2, and 24 hours at 20 ° C. and 65% RH. After humidity control, the following evaluation was performed. Table 2 summarizes the results.

(Evaluation method) Moisture permeability: Measured by the cup method described in JIS Z-0208 (measurement conditions: 40 ° C., 90% RH, 24)
Hr) Disintegration: Waste paper corresponding to a pulp slurry concentration of 1% was put into a small household mixer together with water, stirred for 1 minute, dropped into 5 times the amount of water, and the dispersion state of pulp fibers was observed. (○: well dispersed, △: a little floc,
×: Many flocs) Folding resistance: The sample for measuring moisture permeability was folded with the coated surface inside, pressed at 150 g / cm ² for 10 seconds, and then folded with the coated surface outside to form a cross. The moisture permeability of the creased sample was measured. Blocking resistance: The coated surface and the uncoated surface of the moisture permeability measurement sample were overlapped, and a load of 150 g / cm ² was applied.
After standing at 40 ° C. and 90% RH for 24 hours, the blocking state of the superposed surfaces was observed. (○: no blocking, Δ: slight blocking occurred, ×: blocking occurred almost all over)

[0021]

[Table 1] Description of abbreviations in Table 1 WE-1: Obtained by emulsifying and dispersing paraffin wax having a melting point of 57 ° C. and a melt viscosity of 950 cp at 100 ° C. using a maleated petroleum resin having self-emulsifiability in water as a dispersant. Aqueous emulsion having an average particle size of the dispersoid of 0.13 μm WE-2: a microparticle having a melting point of 74 ° C. and a melt viscosity of 980 cp at 100 ° C. using a maleated petroleum resin having self-emulsifiability in water as a dispersant. The average particle size of the dispersoid obtained by emulsifying and dispersing the crystallin wax is 0.51 μm.
m aqueous emulsion ST: Oxidized starch (manufactured by Nippon Shokuhin Co., Ltd., trade name: MS)
-3800) CMC: carboxymethylcellulose (Daiichi Kogyo Seiyaku Co., Ltd., trade name: Cellogen-7A) PVA-1: polyvinyl alcohol (polymerization degree 350, saponification degree 98.5 mol%, manufactured by Kuraray Co., Ltd.) Name: PVA
-103) PVA-2: polyvinyl alcohol (degree of polymerization 1750,
Saponification degree 98.5 mol%, manufactured by Kuraray Co., Ltd., trade name: PV
A-117) PVA-3: polyvinyl alcohol (degree of polymerization 1750,
Saponification degree 96.0 mol%, manufactured by Kuraray Co., Ltd., trade name: PV
A-CST) AE: methyl methacrylate-butadiene latex (manufactured by Mitsui Toatsu Co., Ltd., trade name: Polylac-707) RE: content of lauryl vinyl ether unit 0.5 mol%, content of itaconic acid unit 3. 0 mol%, saponification degree 9
An acid value of 195 was obtained by using 6.5 mol% of a modified polyvinyl alcohol having a viscosity of 34 cp at 4% viscosity at 20 ° C. of 34 cp.
Aqueous emulsion having an average particle size of 0.65 μm of a dispersoid obtained by emulsifying and dispersing an acid-modified rosin having a softening point of 101 ° C.

[0022]

[Table 2]

[0023]

The coating composition for moisture-proof paper of the present invention has the effect of improving the moisture-proof property, folding resistance, defibration property and blocking resistance of the object to be coated. This is useful for base papers. When the coating composition for a moisture-proof paper of the present invention is applied to base paper, a moisture-proof paper having remarkably excellent moisture resistance, folding resistance, disintegration and blocking resistance can be obtained. Moisture proof paper obtained by coating the coating composition for moisture proof paper of the present invention,
Moistureproofness comparable to conventionally used polyethylene laminated paper is obtained, and the reusability of waste paper is good.

Claims (5)

(57) [Claims] A melt viscosity of 50 to 2000 centipoise;
Wax emulsion (A) having a particle diameter of 0.01 to 10 μm and a solid content of 5 to 50% by weight, and a degree of polymerization of 2
The main component is at least one water-soluble resin (B) selected from the group consisting of a polyvinyl alcohol-based resin, carboxymethylcellulose and soluble starch of from 00 to 3000, and the weight-based compounding ratio (A) / (B) in terms of solid content is: 25/7
A coating composition for moisture-proof paper, which has a ratio of 5 to 80/20. 2. A moisture-proof paper coated with the coating composition for moisture-proof paper according to claim 1 in an amount of 1 to 50 g / m ^{2 in} terms of solid content. 3. The moisture-proof paper according to claim 2, which has a moisture permeability of 50 g / m ² or less. 4. The moisture-proof paper according to claim 2, wherein the thickness of the moisture-proof paper is 30 to 300 μm. 5. A coating composition for moisture-proof paper according to claim 1, which is applied to a base paper, and then 10 ° C. below the melting point of the wax.
A method for producing a moisture-proof paper, comprising drying at a high temperature for 5 seconds to 10 minutes.