JP2000080593A - Water-repulpable moisture-proof paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a moisture-proof paper excellent in moisture-proof and water-proof properties, hardly causing slipping between the moisture-proofing face and the opposite face, and having water-repulpable properties allowing the recovery as a waste paper by forming a moisture-proof resin layer consisting of a mixture of an α-olefin-unsaturated carboxylic acid copolymer with a specific vinyl-based emulsion-polymerized material, on a base paper. SOLUTION: A coating liquid for moisture proof is obtained by blending 100 pts.wt. α-olefin-unsaturated carboxylic acid copolymer with a low molecular weight, e.g. an ethylene-(meth)acrylic acid copolymer having 10,000-50,000 molecular weight, with 10-100 pts.wt. vinyl-based emulsion-polymerized material having >=10 deg.C glass transition temperature, e.g. a polystyrene latex. The water repulpable moisture-proof paper is obtained by coating the obtained moisture- proof coating liquid on a base paper while regulating the moisture-proof resin layer so as to be 5-30 g/m2 expressed in terms of solid.

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, and more specifically, to a moisture-proof paper required for a moisture-proof paper.
Not only is it excellent in waterproofness, it does not cause slippage between the moisture-proof surface and the opposite surface, it is easy to handle in printing or using adhesives, and has water disintegration properties that can be recovered as waste paper. It is about paper. That is, the present invention belongs to the papermaking technique.

[0002]

2. Description of the Related Art Conventionally, winding of high quality paper, bleached kraft paper, unbleached kraft paper, various coated papers, etc. and packaging of high quality paper and coated paper plain paper have been conducted to prevent moisture absorption of products. A wrapping paper roll obtained by coating, laminating or internally adding a polyolefin-based polymer compound such as polyethylene or polypropylene onto paper, and winding the wrapping paper having moisture resistance and water resistance into a roll shape in the same form or as desired. Cut to size and used. Also, cement bags, salt bags,
For base paper for heavy bags such as feed bags, fertilizer bags, garbage bags, etc., after bags are made and packed, moisture-proofing and strength are required to transport heavy objects while preventing moisture absorption and water absorption of the contents. A laminate of kraft paper and polyolefin laminate paper (hereinafter referred to as polylaminate paper) obtained by laminating kraft paper with polypropylene or the like is used. However, these polylaminate papers are problematic because they are not sufficiently disintegrated in water even if collected and reused as used paper after use, and cannot be reused as used paper. In addition, even if used poly-laminate paper is discarded, there is a concern that it may cause environmental pollution because it can only be disposed of by incineration or landfill, and there are many problems at present.

As described above, the conventional moisture-proof papers have problems in any of them, and development of alternative moisture-proof papers is urgent. One of the techniques for this purpose is a butadiene latex 10
A technique for obtaining a moisture-proof paper by applying a composition obtained by blending 5-200 parts by weight of wax with 0 parts by weight has been proposed (Japanese Patent Publication No. 55-22597). However, since this technique uses wax, there is a problem of "slip" which occurs when processing papers are stacked and a problem of printability when printing on the processing paper. Also, with respect to moisture resistance, it is difficult to obtain moisture resistance comparable to that of polyethylene laminated paper by applying it to paper with a low coating amount. Also, a paraffin wax having a specific melting point, an esterified product of maleated or fumarated rosin and a polyhydric alcohol, a wax emulsion mainly containing liquid polybutene and rosin, or a mixture of the wax emulsion and a synthetic rubber-based latex A method for producing a moisture-proof paper, which is applied to the surface of a fibrous base material such as high-quality paper or kraft paper and dried under heating, has also been proposed (JP-A-61-47896). However, when the moisture-proof wrapping paper obtained by this method is in the form of a roll, the back surface of the support is less slippery because even a small amount of the wax component contained in the moisture-proof layer is leached out, and is wrapped with the moisture-proof wrapping paper. When loading, unloading, or transporting a heavy roll of rolled paper, there is a serious problem such as a gap between the wrapping paper and its contents, and in severe cases, the wrapping paper may be torn or fall. appear. In addition, there is a problem such as peeling off immediately when trying to attach a label to the surface processed in such a way,
Other than hot-melt adhesives that have a strong adhesive strength that is liquid at room temperature, adhesion to wax-containing moisture-proof surfaces is poor, and when they can be attached, the open time is very short. Is also very limited. Particularly, a vinyl acetate emulsion used for general purposes is repelled and cannot be applied. Even if it can be applied, there is no adhesiveness at all. There is also a method of using a pressure-sensitive adhesive tape with re-dispersing properties.However, when using an adhesive tape as compared to hot-melt bonding, there is a serious drawback that the workability at the time of packaging is significantly inferior. It is currently not used.

[0004] In order to solve these problems,
Moisture proof provided with an anti-slip layer made of an amphoteric compound on the back of the support,
Waterproof paper has been proposed (Japanese Patent Publication No. 56-18712). However, when the sheet of the moisture-proof laminate having the moisture-proof layer on the support surface and the slip-resistant layer on the back surface is finished as a roll, when the winding pressure is increased, the pigment of the slip-proof layer may damage the surface of the moisture-proof layer. Deterioration of moisture proof performance occurs. For this reason, it is necessary to set the winding pressure to a low pressure.However, a decrease in the winding pressure makes it impossible to manufacture a long winding due to the occurrence of winding slip at the time of winding, or in a subsequent process due to irregular winding side surfaces. There is a problem that the workability is greatly reduced. As described above, there is no moisture-proof paper that has a conventional re-disaggregation property and has a moisture-proof property superior to that of a plastic film and does not cause a problem due to slippage of a package.

[0005]

SUMMARY OF THE INVENTION The inventors of the present invention have developed a moisture-proof paper in which the above-mentioned problems have been solved, that is, not only the moisture-proof and waterproof properties required for the moisture-proof paper, but also the distance between the moisture-proof surface and the opposite surface. Research was conducted to find a moisture-proof paper having water disintegration properties that does not cause slippage, is easy to handle in printing and use of an adhesive, and can be recovered as waste paper. That is, the present invention has been made to provide an excellent moisture-proof paper which has not been achieved in the past.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve the problems, and the above-mentioned problems are solved by providing a moisture-proof resin layer made of a specific component on the surface of paper. Thus, the present invention has been completed.
That is, the present invention provides a water-disintegrating moisture-proof paper, characterized by having a moisture-proof resin layer comprising a mixture of an α-olefin / unsaturated carboxylic acid low molecular weight copolymer and a vinyl emulsion polymer on the surface, The water disintegrating moisture-proof paper, wherein the α-olefin / unsaturated carboxylic acid low molecular weight copolymer is ethylene / acrylic acid or ethylene / methacrylic acid copolymer having a molecular weight of 10,000 to 50,000, The vinyl emulsified polymer is a polymer having a glass transition point (Tg) of 10 ° C. or more, and relates to the water disintegratable moisture-proof paper.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. ○ α-olefin / unsaturated carboxylic acid low molecular weight copolymer The present inventors have proposed α-olefin / unsaturated carboxylic acid low molecular weight copolymer, particularly ethylene and acrylic acid or methacrylic acid (hereinafter referred to as both ) Acrylic acid) low molecular weight copolymer, and ethylene and (meth) acrylic acid low molecular weight copolymer having a molecular weight of 10,000 to 50,000, even without using wax, the same moisture-proof properties as polyethylene It has been found that it can be imparted to paper, and at the same time can satisfy printing and adhesive properties, and is one of the components forming the moisture-proof resin layer of the present invention. Examples of the α-olefin constituting the α-olefin / unsaturated carboxylic acid low molecular weight copolymer include ethylene and propylene.
Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, and the like. Preferred for the present invention is ethylene, and acrylic acid and methacrylic acid. As the α-olefin / unsaturated carboxylic acid low molecular weight copolymer in the present invention, those having a copolymerization ratio of α: olefin and unsaturated carboxylic acid of 75:25 to 90:10 are preferable, and : 20 to 87:13, more preferably 8
Those having a ratio of 0:20 to 85:15 are particularly preferred. If the amount of the unsaturated carboxylic acid is low, it is difficult to satisfy the printing and adhesion performance, and if the amount is high, the problem may be caused in the moisture resistance. The molecular weight of the α-olefin / unsaturated carboxylic acid low molecular weight copolymer is preferably from 5,000 to 50,000, and particularly preferably from 10,000 to 50,000. If the molecular weight is low, the coefficient of friction may be low and slippage may occur. The α-olefin / unsaturated carboxylic acid low molecular weight copolymer of the present inventor is a latex (emulsion) dispersed in an aqueous medium.
It is preferable from the viewpoint of mixing with a synthetic resin described later and the efficiency of imparting properties to paper. As the latex type α-olefin / unsaturated carboxylic acid low molecular weight copolymer as described above, a commercially available product can be used. An example of a commercially available product is Hitec S-312
1, 7024, 3125, 3123 and 312
7 (all are trade names manufactured by Toho Chemical Industry Co., Ltd.).

○ Vinyl Emulsion Polymer The vinyl emulsion polymer used in the present invention is obtained by emulsion polymerization of a vinyl monomer, and the α-olefin / unsaturated carboxylic acid low molecular weight copolymer Unlike polymers,
Although not specifically measured, it has a high molecular weight of several hundred thousand to several million. These vinyl-based emulsion polymers are those in which the above α-olefin / unsaturated carboxylic acid low molecular weight copolymer can impart the same moisture resistance as polyethylene to paper, and can also satisfy printing and adhesive performance. However, it is used to solve the problem that the disintegration property is as bad as polyethylene. As in the case of the above α-olefin / unsaturated carboxylic acid low molecular weight copolymer, the vinyl emulsion polymer is also dispersed in an aqueous medium and in a latex (emulsion) state, that is, as it is obtained by emulsion polymerization. Is preferred for the present invention. The vinyl monomers used to obtain the vinyl emulsion polymer include aromatic vinyl monomers, aliphatic conjugated diene monomers, unsaturated carboxylic acid monomers and other copolymerizable monomers. And styrene-butadiene-based latex, and synthetic rubber-based latex such as methyl methacrylate-butadiene-based latex and styrene-acrylic emulsion, and the like. . The aromatic vinyl monomer is capable of imparting appropriate hardness and water resistance to the obtained vinyl emulsion polymer, and can be selected from, for example, styrene, α-methylstyrene, monochlorostyrene, vinyltoluene, and the like. Styrene is particularly preferred, and a vinyl emulsion polymer containing styrene as a constituent monomer in an amount of 30% is particularly preferred because the intended effects of the present invention can be efficiently exhibited. Aliphatic conjugated diene-based monomers are those that impart appropriate flexibility to the resulting vinyl-based emulsion polymer, for example, 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro- Examples thereof include 1,3-butadiene, and 1,3-butadiene is particularly preferable. The unsaturated carboxylic acid monomer is effective for increasing the adhesive strength of the obtained vinyl emulsion polymer and improving the stability of the vinyl emulsion polymer latex as a colloid. Unsaturated carboxylic acids such as acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, butenetricarboxylic acid, monoethyl itaconate, monobutyl fumarate and monobutyl maleate; Unsaturated polycarboxylic acid alkyl esters having at least one carboxyl group, and other acidic monomers for the same purpose, such as acrylamidopropanesulfonic acid, sodium sulfoethyl acrylate, sodium sulfopropyl methacrylate. Unsaturated sulfonic acids such as salts or salts thereof Can be mentioned, among these acrylic acid, methacrylic acid, itaconic acid, fumaric acid are preferably used in the present invention. Examples of other copolymerizable monomers include methyl acrylate, methyl methacrylate, unsaturated carboxylic acid alkyl esters such as ethyl acrylate and butyl acrylate, unsaturated nitriles such as acrylonitrile and methacrylonitrile, and acrylic acid β. Unsaturated hydroxycarboxylic acid esters such as -hydroxyethyl, β-hydroxypropyl acrylate, and β-hydroxyethyl methacrylate; carboxylic acid amides such as acrylamide, methacrylamide, N-methylolacrylamide and diacetoneacrylamide; Derivatives, unsaturated carboxylic acid glycidyl esters such as glycidyl acrylate and glycidyl methacrylate, and vinyl compounds such as acrolein and allyl alcohol can be mentioned. Among these monomers, methyl methacrylate as an unsaturated carboxylic acid alkyl ester, acrylonitrile as an unsaturated nitrile, β-hydroxyethyl acrylate as an unsaturated carboxylic acid hydroxyalkyl ester, and acrylamide as an unsaturated carboxylic acid amide and derivatives thereof Is preferably used. The vinyl emulsion polymer of the present invention preferably has a glass transition point (Tg) of 10 ° C. or higher, and the glass transition point (Tg) has some differences depending on the measurement method, but is not essential and has an error. However, in the present invention, a value measured by a differential calorimeter was used as a reference. If the glass transition temperature is less than 10 ° C., the disintegration properties are remarkably poor, and may not be suitable for the purpose of the present invention.

○ Method for Preparing Moisture-Proof Paper The moisture-proof paper of the present invention is obtained from a mixture of an α-olefin / unsaturated carboxylic acid low molecular weight copolymer and a vinyl emulsion polymer on the surface of paper such as kraft paper or woodfree paper. The mixture ratio of the α-olefin / unsaturated carboxylic acid low molecular weight copolymer and the vinyl emulsion polymer is an effective and effective object of the present invention. In order to achieve the above effect, it is preferable to use 10 to 100 parts by weight of the vinyl emulsion polymer per 100 parts by weight of the α-olefin / unsaturated carboxylic acid low molecular weight copolymer.
In order to mix both, as described above, it is preferable that both the α-olefin / unsaturated carboxylic acid low molecular weight copolymer and the vinyl emulsion polymer are in a latex (emulsion) state. If both α-olefin / unsaturated carboxylic acid low molecular weight copolymer and vinyl emulsion polymer are latex (emulsion), latex (emulsion)
The solid content is regarded as a resin component, and the two components are mixed so that the two resin components are in the above-mentioned ratio to form a moisture-proof coating solution. The coating solution is applied to the surface of paper, dried, and then cooled. By doing so, a moisture-proof resin layer is provided on the surface of the paper, whereby the moisture-proof paper of the present invention is easily prepared. The amount of the moisture-proof resin layer applied to the paper surface is preferably 5 to 30 g / m ² (solid content). If the amount of construction is less than 5 g / m ^2, it will not be possible to sufficiently cover the irregularities of the support, and the moisture-proof property will be insufficient, and even if it exceeds 30 g / m ² , the obtained moisture-proof property will not be sufficient. Despite the increase, there is only a slight improvement and the price levels out, leading to high costs and uneconomical. The coating equipment for forming the moisture-proof resin layer with the moisture-proof coating liquid is not particularly limited, but an air knife coater, a bar coater, a roll coater, a blade coater, a gate roll coater and the like can be used. As the paper of the moisture-proof paper of the present invention, fine pulp selected from pulp selected from chemical pulp such as hardwood kraft pulp and softwood kraft pulp, and mechanical pulp as a material easily dispersed in water by mechanical disaggregation action is used. Examples include paper, medium quality paper, single gloss kraft paper, Ryoso kraft paper, kraft stretch paper, and the like. There is no particular limitation on the basis weight of these base papers.
One having a flow rate of 00 g / m ² is appropriately selected and used according to the purpose.

[0010]

The moisture-proof paper obtained as described above is not only moisture-proof and waterproof, but also has no slippage particularly between the moisture-proof surface and the opposite surface, and can be used for printing or adhesive. It has recoverable water disintegration properties.

[0011]

EXAMPLES The present invention will be specifically described below with reference to examples, but the following examples do not limit the present invention. Unless otherwise specified, parts in the examples are parts by weight. ○ Example 1 As a moisture-proof coating solution, polystyrene latex (trade name “L8801”: manufactured by Asahi Kasei Corporation, Tg = 109 ° C.)
25 parts in terms of solid content and an ethylene acrylic acid copolymer emulsion (trade name “S-3121”):
Toho Chemical Co., Ltd., molecular weight 27500, acrylic acid /
(Ethylene copolymerization ratio = 15/85) is 10
0 parts of the mixture were prepared. This moisture-proof coating solution was applied with a basis weight of 70 g /
It was applied to an unbleached kraft paper of m ^{2 with} a Meyer bar so as to have a solid content of 25 g / m ^2, and dried at 120 ° C. for 40 seconds to obtain a moisture-proof paper. ○ Example 2 Instead of the polyethylene acrylic acid copolymer emulsion S-3121 used in Example 1, Hitec S-702 was used.
4 (trade name: Toho Chemical Co., Ltd., molecular weight 16000,
A moisture-proof paper was obtained in exactly the same manner as in Example 1 except that acrylic acid / ethylene copolymerization ratio = 15/85) was used. Example 3 The same as Example 1 except that SBR latex (trade name “L1537”: manufactured by Asahi Kasei Corporation, Tg = 16 ° C., solid content 50%) was used instead of the polystyrene latex used in Example 1. To obtain a moisture-proof paper. Example 4 The same as Example 1 except that SBR latex (trade name “L1638”: manufactured by Asahi Kasei Corporation, Tg = 16 ° C., solid content 48%) was used in place of the polystyrene latex used in Example 1. To obtain a moisture-proof paper. ○ Example 5 The ratio of the polystyrene latex and the ethylene acrylic acid copolymer emulsion used in Example 1 was 12:
A moisture-proof paper was obtained in exactly the same manner as in Example 1 except that it was changed to 100. ○ Example 6 The ratio of polystyrene latex and ethylene acrylic acid copolymer emulsion used in Example 1 was 10
A moisture-proof paper was obtained in exactly the same manner as in Example 1 except that the ratio was set to 0: 100. Example 7 A moisture-proof paper was obtained in exactly the same manner as in Example 1 except that an acrylic emulsion (styrene / 2-ethylhexyl acrylate copolymer emulsion, Tg = 30 ° C.) was used instead of the polystyrene latex used in Example 1. Was.

Comparative Example 1 Only the ethylene acrylic acid copolymer emulsion S-3121 used in Example 1 was applied to a solid content of 25 g / m ² and dried at 120 ° C. for 40 seconds to obtain a moisture-proof paper. Was. Comparative Example 2 65 parts by weight of an acrylic emulsion MI-300 (styrene / 2-ethylhexyl acrylate copolymer, Tg = 0 ° C.) at a solid content ratio and wax emulsion Cerosol H-908 (paraffin wax, manufactured by Chukyo Yushi Co., Ltd.) ) Was manually applied to unbleached kraft paper with a Mayer bar so as to have a coating amount of 25 g / m ² as a solid content to obtain a moisture-proof paper. Comparative Example 3 SBR latex (trade name “L1201”, manufactured by Asahi Kasei Corporation, Tg = −7 ° C., solid content 50%) was used at a solid content ratio of 10%.
0 parts by weight and wax emulsion CEROLOL H-908
(Paraffin wax, manufactured by Chukyo Yushi Co., Ltd.) Hand-painted with unblown kraft paper as a solid by hand using a Meyer bar so as to have a coating amount of 25 g / m ² , mixed with 20 parts by weight of solid content ratio. Then, a moisture-proof paper was manufactured.

Characteristic evaluation test The properties of the moisture-proof papers obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were evaluated by the following test methods, and the results are shown in Table 1.
Test method 1) Moisture permeability Laminated surface of moisture-proof layer and unbleached kraft paper are superposed on each other.
I passed the super calender once with m. Transfer each moisture-proof paper sample to JIS-Z-0208 (cup method)
The measurement was performed by the method B with the moisture-proof coated surface facing outward. As a criterion for the value of the lithographic moisture permeability, if it is 50 g / m ² · 24 hours or less, it is practical. The moisture permeability was measured in the same manner after the moisture-proof surface was folded in a cross inward. As a criterion for the value of the moisture permeability, it is practical if it is 100 g / m ² · 24 hours or less. 2) Coefficient of friction The coefficient of friction between the untransferred surfaces of the unbleached kraft paper obtained in the above measurement of the moisture permeability was determined by a method based on JIS-P-8147 (however, the pulling speed was 150 mm / min).
If the dynamic friction coefficient is 0.5 or less and the static friction coefficient is 0.3 or less, there is a possibility that rolling slippage may occur when carrying heavy objects. 3) Disaggregation Small household mixer (contents: 1.2 liters, rotation speed: 1)
(1,000 rpm), the moisture-proof paper obtained in this example was added to ordinary-temperature tap water in an amount such that the pulp concentration became 1% by weight, and the mixture was stirred for 3 minutes. The obtained slurry was used as a handmade sheet having a basis weight of 60 g / m ^{2 in} a laboratory handmade machine. The presence or absence of undisintegrated materials (film pieces, paper pieces) was visually evaluated. 4) Adhesiveness A peeling test was performed after applying the poly vinegar emulsion to the coated surface and laminating the uncoated surface for 2 days at room temperature. The paper was evaluated as ○, and the paper peeled off on the adhesive surface was evaluated as ×.

[0014]

[Table 1]

[0015]

As described above in detail, according to the present invention, there is provided a moisture-proof paper which has sufficient moisture-proofness and has no problem with slippage even though it can be recovered and reused as waste paper. can get.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4L055 AG59 AG63 AG71 AG76 AG89 AG97 AJ02 BE08 EA20 EA30 FA11 FA19 FA30 GA47

Claims (3)

[Claims] 1. A water-disintegrating moisture-proof paper having a moisture-proof resin layer comprising a mixture of an α-olefin / unsaturated carboxylic acid low molecular weight copolymer and a vinyl emulsion polymer on the surface. 2. The α-olefin / unsaturated carboxylic acid low molecular weight copolymer is ethylene / acrylic acid or ethylene / methacrylic acid copolymer having a molecular weight of 10,000 to 50,000. The water disintegratable moisture-proof paper as described in the above. 3. A vinyl emulsion polymer having a glass transition point (T
The water disintegratable moisture-proof paper according to claim 1, wherein g) is a polymer having a temperature of 10 ° C or higher.