JPH08176997A - Recyclable water-resistant transparent paper and film for window envelope - Google Patents

Abstract

PURPOSE: To produce water-resistant transparent paper giving water resistance sufficient for window envelopes, handleable similarly as normal paper, and exhibiting an excellent recycling properties by readily transferable to a recycling process after the use. CONSTITUTION: Transparent paper having a transparency of >=60% produced by using cellulosic fibers is impregnated with an alkali-soluble resin composition containing at least one kind of a thermosetting alkali-soluble resin selected from thermosetting carboxyl group-containing resins and thermosetting phenolic hydroxyl group-containing resins as principal components, and cured by heat to afford the object recyclable water-resistant transparent paper and the film for window envelopes using this transparent paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to transparent paper, and particularly when used or processed, it has excellent curling properties and transparency, and has water resistance, elongation resistance, oil resistance, scratch resistance and is easy to handle. After use, unlike the synthetic resin film, it does not use incombustibles, and the cured product of water resistant resin can be easily detached from transparent paper and decomposed, making it possible to reuse and recycle the paper. It is used for transparent transparent paper.

[0002]

2. Description of the Related Art In recent years, with the increasing awareness of environmental protection, paper is being collected and reused. However, as compared with the reuse of newspapers, magazines, cardboards, copy paper, etc., the reuse of window envelopes is technically very difficult and has not been recycled until now. An envelope with a window here means to make an envelope by providing an opening corresponding to a window in a part of high-quality paper or coated paper,
By attaching a transparent film to the opening, a part of the written portion of the document contained in the envelope, such as an address and a name, can be seen in the state of the envelope. In addition, an envelope in which a part of the envelope paper is impregnated with a chemical such as wax to be transparent (a wax envelope is distinguished from an envelope with a window formed by attaching a film) is not recycled because it is difficult to recycle.

These envelopes with windows are not only recycled, but are also mixed in, for example, high-quality paper which occupies most of paper waste in office, or newspaper and advertisement paper which occupy most of paper waste in home. Although it is easy and is collected together as resource waste, it is not suitable as a raw material for recycled paper when envelopes with windows are mixed in, so it is currently sorted and removed manually after collection. Naturally, these operations not only require a great deal of labor, but also increase the cost of waste paper as a raw material for recycled paper.

Even with such an effort, the window envelope is mixed in the recycled paper raw material to some extent, but the recycled paper raw material mixed with the window envelope is deinked in the same manner as general waste paper. When reproduced, the following problems occur.

When the window is made of a transparent synthetic resin film, the separated synthetic resin film is not mixed with the paper fibers in the deinking process to form a good waste paper pulp, which cannot be recycled or laminated. There was a problem that the paper of the part and the synthetic resin film were not separated. The synthetic resin film attached to the paper fibers remains in the waste paper pulp, and the printability of the recycled paper is extremely deteriorated, which is a fatal problem for printing paper.

Further, since synthetic resin films generally have poor adhesiveness, strong adhesives and hot melt adhesives are used for bonding with high quality paper, but such adhesives are generally used. Complete separation / decomposition is extremely difficult with an alkaline bath for recycling waste paper, and when separated under conditions that are severe enough to cause peeling or decomposition (high alkali concentration, high temperature bath, mechanical agitation), the support itself There is a problem that the suitability as a waste paper pulp decreases due to decomposition and deterioration.

In the case of a wax envelope, the problem of such a strongly adhesive adhesive can be avoided, but the wax component remains in the waste paper pulp in the pulp recovery process, and the wax component causes ink in recycled paper. There was a fatal problem of using it for printing paper, that is, flipping.

When the film for the envelope with window is made of transparent paper such as tracing paper or glassine paper, although the troubles caused by the recycled paper process are eliminated, firstly, the transparency is insufficient, and secondly, Has no water resistance, and the window envelope may wrinkle or tear if it gets wet with rain,
Furthermore, there is a problem that wrinkles are likely to occur when the product is attached to the window frame by gluing.

[0009]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a recyclable transparent paper having high transparency and water resistance and having good workability that can be handled like plain paper. It is in.

[0010]

Means for Solving the Problems The present inventors have accomplished the present invention as a result of extensive studies on the above problems. That is, a high-quality paper having a transparency of 60% or more produced by using cellulose fibers is selected from a thermosetting carboxyl group-containing resin or a thermosetting phenolic hydroxyl group-containing resin.
It is an invention of a recyclable water-resistant transparent paper, characterized in that it is obtained by impregnating an alkali-soluble resin composition containing at least one kind of thermosetting alkali-soluble resin as a main component and thermally curing it.

The recyclable waterproof transparent paper of the present invention preferably has a gram equivalent of acid per unit weight of 0.3 gram equivalent / kg or more.

The recyclable waterproof transparent paper of the present invention can be used as a substitute for a film for window opening envelopes.

The present invention will be described in detail below.

Generally, a method of producing waste paper, waste paper pulp or deinked pulp (DIP) constituting the waste paper, that is, recycling of paper, is performed by the following steps.

1) Disintegration step with pulper, step of decomposing waste paper into fibrous form by mechanical force and chemicals such as alkali to separate ink components from waste paper.

2) Dust removal process, rough selection, flotation,
Screen, cleaner, and cleaning processes that remove plastic, metal, and inorganic substances contained in waste paper.

3) Deinking step, a step of separating the printing ink separated from the waste paper outside the system by a flotation method or a washing method. It is created by a composite technology of these steps.

As a result of studying recycling of envelopes with windows, the present inventors have found that a part of a paper support (coated paper such as cast paper, art paper, coated paper, and fine paper) has an opening corresponding to a window. It has been confirmed that the envelope with a window provided with a section and having a synthetic resin film attached thereto with an adhesive cannot produce good waste paper pulp in the process for producing waste paper pulp as shown above. That is, when the window is made of a transparent synthetic resin film, the separated synthetic resin film is not mixed with the paper fibers in the deinking process to form good waste paper pulp,
There is a problem that the paper cannot be recycled or the synthetic resin film is not separated from the laminated paper, and the printability of the recycled paper is greatly deteriorated by the synthetic resin film remaining in the waste paper pulp.

Generally, a strong adhesive adhesive or a hot-melt adhesive is used for bonding a synthetic resin film having poor adhesiveness to high-quality paper or coated paper. It is very difficult to completely separate and disintegrate the agent in an alkaline bath for recycling general waste paper. When separated under severe conditions (high alkali concentration, high temperature bath, mechanical agitation) such that the support is peeled and decomposed, the support itself is decomposed and deteriorated, and the suitability as waste paper pulp is reduced. If you use high-quality paper such as tracing paper or glassine paper instead of synthetic resin film, the problem before recycling is that the transparency is insufficient and it will not be a good window envelope, and it will not have water resistance and window envelope. There are problems such as wrinkles and tears when it gets wet with rain.

However, in the case of high-quality paper impregnated with the alkali-soluble resin composition as shown in the present invention, when treated after use, general waste paper, or waste paper pulp or deinked pulp (DIP) step constituting the waste paper is used. It has been found that it is possible to recover very good waste paper pulp.

The high-quality paper used in the present invention is preferably a high-quality paper made of cellulose fibers and having a transparency of 60% or more. The fine paper of the present invention may have any grammage in terms of recovery, but it is preferably 10 to 45 g / m ² from the viewpoint of easy handling and transparency.

The transparency referred to in the present invention is expressed as a value obtained by subtracting the opacity value from 100. What is the opacity value?
It is the opacity (%) measured by IS P8138.
The thickness is a value measured by a test method for the thickness and density of paper and paperboard specified by JIS P8118.

Raw materials commonly used in papermaking such as wood pulp, synthetic pulp, fillers, sizing agents, paper-strengthening agents, and dyes can be used in the woodfree paper of the present invention as required. Although it is possible to use the high-quality paper itself by coloring, it is necessary to use a coloring method that can sufficiently maintain the transparency after coloring.

The high-quality paper of the present invention has a basis weight of 10 to 45 g / m ^2.
It is preferred that When the basis weight of the high-quality paper is less than 10 g / m ² , the dimensional stability is poor, tension control is difficult during processing, wrinkles are likely to occur, and the paper may be broken when it is attached to the window frame, which is not preferable. If the basis weight is greater than 45 g / m ² , the thickness after impregnation with the alkali-soluble resin composition will be thick, and the paper will not be supple, or will have irregularities after being enveloped and will have documents inside. In addition to being an obstacle, it is not preferable in terms of cost.

Examples of the carboxyl group-containing resin and the phenolic hydroxyl group-containing resin (hereinafter, both are collectively referred to as an alkali-soluble resin) used as a resin for impregnating high-quality paper of the present invention include, for example, nitrocellulose resin and fatty acid, Resin mixed with fatty acid ester, acrylic resin consisting of methacrylic acid ester or copolymer resin of acrylic acid ester and acrylic acid, resin containing maleic acid in rosin / maleic acid resin or aminoalkyd resin, polyparavinylphenol and other phenolic resins A resin containing a hydroxyl group can be used.

The alkali-soluble resin of the present invention has a thermosetting property and can be used without a solvent or together with a solvent. As the alkali-soluble resin, a thermosetting alkali-soluble resin having an acryloyl group, a methacryloyl group, an epoxy group, or an isocyanate group that can be easily impregnated into high-quality paper and dried (cured) can be preferably used.

The thermosetting alkali-soluble resin as used herein is one having a thermosetting functional group and a carboxyl group or a phenolic hydroxyl group at the same time at the molecular end or side chain, and includes trimethylolpropane diacrylate fumarate, Trimethylolpropane difumarate monoacrylate, acryloyloxyethyl salicylate, methacryloyloxyethyl salicylate, acryloyloxyethyl monophthalate, methacryloyloxyethyl monophthalate, acryloyloxypropyl monophthalate, methacryloyloxypropyl monophthalate, acryloyloxyethyl monophthalate. Succinate, methacryloyloxyethyl monosuccinate, acryloyloxypropyl monosuccinate, methacryloyloxypropy Monosuccinate, acryloyloxyethyl monotetrahydrophthalate, methacryloyloxyethyl monotetrahydrophthalate, acryloyloxypropyl monotetrahydrophthalate, methacryloyloxypropyl monotetrahydrophthalate, acryloyloxyethyl monohexahydrophthalate, methacryloyloxyethyl monohexahydrophthalate, acryloyloxy Propyl monohexahydrophthalate, methacryloyloxypropyl monohexahydrophthalate, trimethylolpropane diacrylate monosalicylate, pentaerythritol diacrylate monofumarate, and other polyfunctional acrylates and polycarboxylic acids, or their complexes, carboxyl groups Or has a phenolic hydroxyl group Such as mono acrylate, and the like.

In the present invention, a phenol resin can be used if it is used in a state of low crosslinkability. In the present invention, cresol, xylenol, trimethylphenol, allylphenol, alkenylphenol, polyhydric phenol, polyphenol belonging to phenols such as polyphenols, the term phenol resin as a generic term for resins that cure by reacting with aldehydes such as formaldehyde. To use.

Examples of the phenol resin include dry oil-modified phenol resin, dry oil / aromatic hydrocarbon formaldehyde-modified phenol resin, polybutadiene-modified phenol resin, and alkylphenol-modified phenol resin. The phenols that are the basis of the phenol resin can also be used without limitation, such as phenol, m-cresol, 3,5-xylenol, p-alkylphenol, and resorcin. These resins can be used as a phenol resin solution dissolved in a solvent such as alcohol, or as an aqueous emulsion, or as a water-soluble phenol resin (resole). There is no problem in diluting the phenol resin with water, an organic solvent such as alcohol or toluene, or using the binder resin in combination.

To cure the phenolic resin, a crosslinking agent such as formaldehyde, a modifier such as aniline, an acid catalyst such as hydrochloric acid or oxalic acid, a basic catalyst such as ammonia or hexamethylenetetramine, and a curing agent are mixed and used. It doesn't matter.

The alkali-soluble resin of the present invention may be used in combination with a cross-linking thermosetting resin which does not exhibit alkali-solubility as another binder component, to exhibit appropriate cross-linking property, and is used as a polyfunctional resin. Thermosetting resin as a cross-linking agent, diluent,
Alternatively, it can be used as a binder component together with an alkali-soluble thermosetting resin. As the crosslinkable thermosetting resin, any compound that has a polymerizable unsaturated bond that is commonly used in this field can be used. That is, an acryloyl group, a methacryloyl group,
A compound containing an epoxy group, an acrylamide group, an allyl group, an isocyanate group, a vinyl ether group, a vinyl thioether group, and the like, for example, an alkyl acrylate ester, an alkyl methacrylate ester, acrylonitrile, methacrylonitrile, acrylamide, vinyl acetate, propionic acid. Examples thereof include vinyl, vinylpyrrolidone, and various isocyanates, but it is suitable that the number of crosslinkable bonds in the molecule is 2 or more, and more preferably 3 or more in order to improve the crosslinkability.

Specific examples of the crosslinkable thermosetting resin include
Unsaturated esters of polyols such as ethylene diacrylate, diethylene glycol diacrylate, glycerol triacrylate, trimethylol propane triacrylate, pentaerythritol tetraacrylate and the like can be mentioned. A compound having one or more epoxy rings, such as glycidyl acrylate, is also preferable. Furthermore, these compounds may be high molecular weight compounds. Particularly preferred is a compound having an acrylate group at the terminal or side chain of the polymer chain, which has a polyester skeleton, a polyurethane skeleton, an epoxy resin skeleton,
Polyether skeleton, polyether acrylamide resin,
Examples thereof include a prepolymer having a polycarbonate skeleton. These monomers and prepolymers may be used alone or as a mixture. When a role as a cross-linking agent is required, a good cross-linking property can be obtained by mixing a tri- or higher functional cross-linking compound.

The alkali-soluble resin-impregnated paper obtained by impregnating high-quality paper has a strong resin film in a neutral or acidic atmosphere, and is an adhesive containing some moisture, water and solvent. The resin hard structure having water resistance will not be destroyed by the agent, sweat, oil, or the like, or will not fall off from the high-quality paper, and may be used as transparent paper for window frames. However, when treated with an alkali bath after use, the thermosetting alkali-soluble resin forms a water-soluble salt, and the coating film is immediately destroyed, and the alkali-soluble resin is dispersed / dissolved in the alkali bath. Since high-quality paper is relatively stable in an alkaline bath, when only the water-resistant resin cured product is dispersed and dissolved in the alkaline bath, it can be treated with the impregnated resin due to the difference in specific gravity or the action of a surfactant. Separation of fine paper becomes very easy.

In particular, the water-resistant transparent paper obtained in the present invention has a structure in which the alkali-soluble water-resistant resin cured product is impregnated and cured in the entire voids of the high-quality paper. The cured water-resistant resin component is not adhered to the recovered cellulose fiber obtained by the dissolution. For this reason, even if the collected high-quality paper is used to make paper again, ink repellency and stains due to the water-resistant resin cured product component do not occur, and a good printing support can be made.

When the composition is a mixture of a thermosetting alkali-soluble resin and a crosslinkable thermosetting resin, the alkali-soluble resin is 5% by weight or more based on the solid content of the composition. Is preferred. This is because if the proportion of the alkali-soluble resin is less than 5%, the desorption suitability in the alkaline bath is poor.

The impregnation amount of water resistance of the cured resin component comprising an alkali-soluble resin composition used in the present invention is preferably ^{1~40g / m 2, 6~20g / m} 2 is more preferable. If the amount of the water-resistant resin cured product component is less than this amount, it is not possible to fill the voids of the entire high-quality paper, uneven transparency appears, and good transparency cannot be obtained. Desorption in the bath is poor, and the suitability for collecting fine paper deteriorates.

In the method of the present invention, the base paper containing natural pulp as a main component, which is advantageously used, may contain various polymer compounds and additives. For example, starch derivative, polyacrylamide, polyvinyl alcohol derivative, dry paper strengthening agent such as gelatin, fatty acid salt,
Rosin derivatives, sizing agents such as dialkyl ketene dimer emulsions, melamine resins, urea resins, wet paper strength enhancers such as epoxidized polyamides, stabilizers, pigments, dyes, antioxidants, optical brighteners, various latexes, inorganics Electrolyte, p
An H regulator and the like can be contained in an appropriate combination. Further, in the present invention, treatments such as corona treatment, ozone treatment, and flame treatment may be performed in order to improve the adhesion between the high-quality paper and the water resistant component.

As a method of impregnating the high-quality paper with the alkali-soluble resin composition, a method of dispersing the alkali-soluble resin in white water as referred to in the paper industry from the papermaking stage and adsorbing it on the cellulose fiber, a tab after the papermaking process, etc. There are three types of methods, namely, a method of adsorbing the cellulose fiber by immersing it by the method described above, and a method of applying, impregnating and drying the alkali-soluble resin on the paper support. In these cases, the alkali-soluble resin can be used alone for improving the impregnation, or can be used in the state of being dissolved in a solution or in the state of emulsion.

Although the alkali-soluble resin composition of the present invention can be used without a solvent, it can be used by dissolving or dispersing it in water or an organic solvent. Further, it does not matter that the alkali-soluble resin composition contains a thermal polymerization initiator. Examples of the thermal polymerization (reaction) initiator include peroxides and azo compounds,
Specific examples include benzoyl peroxide, t-butyl perbenzoate, and azobisisobutyronitrile.

The high-quality paper of the present invention can be provided with a resin layer imparting functionality such as curl prevention and antistatic after impregnation with an alkali-soluble resin. The resin layer contains an antistatic agent,
A hydrophilic binder, a latex, a hardener, a pigment, a surfactant, an adhesive and the like can be contained in appropriate combination. When the water-resistant transparent paper of the present invention is used as a substitute for a film for window envelopes, the adhesive for attachment is preferably alkali-decomposable or alkali-soluble.

[0041]

In the transparent paper of the present invention, high-quality paper can be imparted with a high degree of water resistance by impregnating the high-quality paper with an alkali-curable resin having good curability. Alternatively, in an acidic condition, a strong coating layer is formed, and the resin does not detach from the fine paper,
It can be used as a transparent paper having water resistance, and when it is treated with an alkaline bath after use, the high-quality paper impregnated with a water-resistant resin cured product made of an alkali-soluble resin is swollen and destroyed between the cellulose fibers, and the cellulose content is alkalinized. By dispersing in a bath, the cellulose fiber component can be easily and efficiently recovered. Since the water-resistant resin cured product dissolves in the alkaline bath at the molecular level, the recovered cellulose fiber component does not have the components of the water-resistant resin cured product attached to it, and is a raw material that can produce good recycled paper. Become.

[0042]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the content of the present invention is not limited to the Examples. In the examples, "parts" means "parts by weight" and% means "% by weight", which are solid content values after drying.

Example 1 As a support, a high-quality paper having a basis weight of 15 g / m ² and a transparency of 85% was used, and an alkali-soluble resin composition 1 having the following constitution was used.
Was impregnated with a tab press to an average weight of 8 g / m ² , dried with an explosion-proof hot-air drier and cured to obtain a water-resistant resin cured product, and a target recyclable water-resistant transparent paper was obtained.

[Alkali-soluble resin composition 1] trimethylolpropane diacrylate monosalicylate: 70 parts Isocyanuric acid triacrylate monosalicylate: 30 parts Reaction initiator (benzoyl peroxide): 2 parts Toluene: 200 parts

Example 2 As a support, a high-quality paper having a basis weight of 25 g / m ² and a transparency of 72% was used, and an alkali-soluble resin composition 2 having the following composition was impregnated with a tab press to an average weight of 10 g / m ^2. Then, the product was dried by an explosion-proof hot air dryer and cured to obtain a target recyclable water-resistant transparent paper as a water-resistant resin cured product.

[Alkali-soluble resin composition 2] Acrylic acid dimer (Toagosei Chemical Industry product, trade name Aronix M-5600): 68 parts propylene oxide modified ethylene glycol acrylate (Toagosei Chemical Industry product, trade name Aronix M- 220): 30 parts Reaction initiator (benzoyl peroxide): 2 parts Ethyl acetate: 200 parts

Example 3 The paper support was a high-quality paper having a basis weight of 30 g / m ² and a transparency of 60%.
Alkali-soluble resin composition 3 having the composition shown below is impregnated with a tab press to an average weight of 15 g / m ² , dried with an explosion-proof hot-air dryer and cured to obtain a water-resistant resin cured product for the intended recycling. A possible waterproof transparent paper was obtained.

[Alkali-Soluble Resin Composition 3] Phenol Resin Alcohol Solution (Sumilite Resin PR-50087, manufactured by Sumitomo Durez): 49 parts Pentaerythritol diacrylate monofumarate: 49 parts Reaction initiator: (benzoyl peroxide) 2 Part Ethyl acetate / industrial alcohol mixed solvent: 200 parts

Example 4 As the support, a high-quality paper having a basis weight of 45 g / m ² and a transparency of 70% was used, and an alkali-soluble resin composition 4 having the following composition ratio was formed by tab pressing so that the average weight was 20 g / m ^2. Impregnate,
It was dried with a hot air dryer and cured to obtain the desired recyclable waterproof transparent paper as a cured waterproof resin.

[Alkali-soluble resin composition 4] Styrene / polyacrylic acid copolymer emulsion: 70 parts Urethane acrylic emulsion: 30 parts

Example 5 As a support, a high-quality paper having a basis weight of 40 g / m ² and a transparency of 72% was used, and an alkali-soluble resin composition 5 having the following composition ratio was formed by tab pressing so that the average weight was 20 g / m ^2. Impregnate,
It was dried with a hot air dryer and cured to obtain the desired recyclable waterproof transparent paper as a cured waterproof resin.

[Alkali-soluble resin composition 5] Rosin / maleic acid resin alcohol solution (manufactured by Dainippon Ink and Chemicals, trade name Beckasite J-896): 48 parts phenol resin alcohol solution (manufactured by Sumitomo Dures, Sumilite Resin PR- 50087): 47 copies

Example 6 A window opening envelope was prepared using the water resistant transparent paper obtained in Examples 1 to 5. An envelope having a window portion was prepared using a single-sided coated paper (made by Mitsubishi Paper Mills, Pearl Coat), and four sides of water-resistant transparent paper slightly larger than the window portion were attached to the window portion to form a window opening envelope.

Comparative Example 1 Comparative Example 1 was carried out in the same manner as in Example 1 except that the crosslinked alkali-soluble resin was impregnated and the water resistant resin cured product was not provided.
I got a sample of.

Comparative Example 2 The same high-quality paper as in Example 1 was used as the support, and the thickness was 1
A sample of Comparative Example 2 was obtained by melt extrusion coating polypropylene at 5 μm.

Comparative Example 3 A sample of Comparative Example 3 was obtained in the same manner as in Example 2 except that the crosslinked alkali-soluble resin was impregnated and the cured product of the water resistant resin was not provided.

Comparative Example 4 The same high-quality paper as in Example 2 was used as the support, and the thickness was 12
A biaxially oriented polypropylene film of μm was attached using an adhesive to obtain a sample of Comparative Example 4.

Comparative Example 5 A sample of Comparative Example 5 was obtained in the same manner as in Example 3 except that the crosslinked alkali-soluble resin was impregnated and the cured water resistant resin was not provided.

Comparative Example 6 A sample of Comparative Example 6 was obtained by using a high-quality paper similar to that used in Example 3 as a support and performing melt extrusion coating of low-density polyethylene to a thickness of 15 μm.

Comparative Example 7 A sample of Comparative Example 7 was obtained in the same manner as in Example 4 except that the crosslinked alkali-soluble resin was impregnated and the water resistant resin cured product was not provided.

Comparative Example 8 The same transparent paper as in Example 4 was used as the support, and the thickness was 1
A 2 μm cellophane film was attached using an adhesive to obtain a sample of Comparative Example 8.

Comparative Example 9 A sample of Comparative Example 9 was obtained in the same manner as in Example 5 except that the crosslinked alkali-soluble resin was impregnated and the water resistant resin cured product was not provided.

Comparative Example 10 The same high-quality paper as in Example 5 was used as the support, and the thickness was 1
A 2 μm biaxially stretched polyester film was attached using an adhesive to obtain a sample of Comparative Example 10.

Comparative Example 11 The same high quality paper as in Example 1 was used as a support, and a toluene solution of trimethylolpropane triacrylate (containing 2% benzoyl peroxide as a reaction initiator) was used as a thermosetting resin in a tab press. Impregnation was performed so that the average weight was 8 g / m ^2, and the product was cured with an explosion-proof hot-air dryer to provide a water-resistant resin cured product. The crosslinkability of the water resistant resin cured product provided by this method was very high.

Comparative Example 12 A biaxially stretched polypropylene film having a thickness of 30 μm was used as it was.

Comparative Example 13 A biaxially stretched polyester film having a thickness of 39 μm was used as it was.

Comparative Example 14 A window opening envelope was prepared using the transparent paper, the water resistant transparent paper and the film obtained in Comparative Examples 1 to 13. A single-sided coated paper (made by Mitsubishi Paper Mills, Pearl Coat) was used to make an envelope with a window, and the window had a transparent paper slightly larger than the window.
A water resistant transparent paper and four sides of the film were attached to form a window opening envelope.

The following tests were carried out on the transparent paper or water-resistant transparent paper obtained in the above Examples and Comparative Examples, and the results are shown in Tables 1 and 2.

Test 1 (Transparent) In the window opening envelope to which the obtained transparent paper or film is attached, the internal address column and the sender's column can be easily seen and can be used without any trouble in the mailing work. When it was difficult to see through the fluoroscopy, address, name, etc., the fluoroscopy was judged to be poor. Although the transparency of this judgment is about 80%, the transparency may be affected by the unevenness of the fibers.

Test 2 (Water resistance) The water resistance of the obtained transparent paper was evaluated by rubbing it with a cotton swab moistened with water. Rub with a cotton swab until a hole is opened in the transparent paper,
Water resistance was judged by the number of times. If the number of times is 100 or more, it is judged that the film has sufficient water resistance and has water resistance strength equivalent to that of a film.

Test 3 (Recoverability) The window-opening envelopes obtained by adhering the transparent paper obtained in Example 5 and Comparative Example 13 were used as 70 ° C., 0.5N sodium hydroxide, and a nonionic surfactant. The waste paper pulp recovery step was reproduced by immersing in a solution containing 1% polyoxyethylene alkyl ether and stirring, and it was judged by the time taken for desorption of the water resistant resin cured product. The faster the detachment of the cured product of the water-resistant resin, the easier the recovery treatment, but the detachment within 3 minutes enables the treatment in the waste paper pulp recovery process without any trouble. If it takes more than 5 minutes, an efficient waste paper pulp recovery process cannot be expected. The results are shown in Tables 1 and 2 in the section of the original examples and comparative examples.

Test 4 (Printability of Recovered Support) In Test 3, after separating the water resistant resin cured product, the water resistant resin cured product was discharged by the flotation method to recover the remaining support. 50% of the recovered support (waste paper pulp) and 50% of virgin pulp were mixed, the paper was strained, press-dried, and then printed on the entire surface to measure the printability. The number of print irregularities that can be visually recognized in the area of 1 m square was measured.
When paper is made only with virgin pulp, printing unevenness is 1
There are 0 places on the m square. The allowable range was 1 m square and 2 pieces were used as a reference.

Test 5 (blocking property) The sample was wound up and slit into a width of 10 cm, set in a window-opening envelope manufacturing apparatus (FWC-1 manufactured by Fujibagki Kogyo Co., Ltd.) and continuously produced at 220 sheets / minute. The window portion was attached to 10,000 envelopes at a speed. The number of sheets in which the water-resistant transparent paper or film was not accurately attached to the window due to double feeding was expressed as blocking property. The smaller the number of sheets, the better the blocking property, and the better the workability of making a window opening envelope.

Test 6 (Window sticking property) In 10000 sheets of the window opening envelope prepared in Test 5, the number of sheets in which the water-resistant transparent paper or film was stretched by the adhesive or the like caused sticking or wrinkling on the window was measured. Expressed as stickiness. The smaller the number, the better the window sticking property,
Good workability in making window envelopes and easy handling thereafter.

[0075]

[Table 1]

[0076]

[Table 2]

Evaluation As is clear from Table 1 above, the transparent paper according to the present invention not only has good transparency, transparency, and water resistance due to the effect of imparting water resistance by impregnation with an alkali-soluble resin. Swelling and destruction between cellulose fibers occur rapidly in the alkaline bath at the time of recovery, and the cellulose content is dispersed in the alkaline bath, and the cellulose fiber component can be easily and efficiently recovered. Since the water-resistant resin cured product dissolves in the alkaline bath at the molecular level, it can be discharged by the action of the surfactant, and the recovery of only the cellulose support is easy. Therefore, the component of the water-resistant resin cured product does not adhere to the obtained recovered cellulose fiber component, and it becomes a raw material that can produce good recycled paper, and even if paper is made with the obtained waste paper pulp, it is good. It has printability. Further, due to the action of the water-resistant resin cured product, wrinkles and tars are not generated even when it is attached to a window opening envelope, the window portion has sufficient water resistance, and it is okay to be wet with rain. Further, since the high-quality paper is impregnated with resin, not only the transparency is improved but also it can be handled like plain paper, so that workability at the time of manufacturing the window opening envelope is high.

On the other hand, as is clear from Table 2, the samples of Comparative Examples which do not have a water resistant resin cured product in the same experiment are not only inferior in transparency but also in water resistance. If water resistance is imparted by melt extrusion coating or laminating of polypropylene, polyethylene, polyester, etc., or if these films are used directly, the recyclability is poor, and if used for window envelopes etc., recycled as paper. Is difficult or only poor quality waste paper is obtained. When water resistance is imparted only with a thermosetting resin that is not alkali-soluble, transparency, paper permeability, and water resistance are good, but peelability due to alkali is poor, and cured water resistant resin and laminate layers are recovered. Since it adheres to and is mixed with the prepared support, the printability is poor even if a paper is made from the obtained waste paper pulp. When the transparency of the high-quality paper of the support is lower than 60%, even if the alkali-soluble resin is impregnated to impart water resistance, there is a limit to the improvement of the transparency, and good transparency cannot be obtained. Is difficult to use.

[0079]

INDUSTRIAL APPLICABILITY The recycled transparent paper produced by the method of the present invention has a high adhesiveness between the water-resistant resin cured product and the support when used, and has good water resistance and transparency. In the case of recycling used transparent paper that can be used for, the cured product of the waterproof resin can be easily separated from the support, and it is easy to collect and reuse only the support. If it is used as a film for envelopes, it will be sent to the recovery process like fine paper without any sort of separation, so it will be of great industrial value in terms of environmental protection and resource saving, or in terms of reducing the amount of waste products. It is a thing.

Claims (3)

[Claims] 1. A high-quality paper having a transparency of 60% or more produced by using cellulose fibers, and one or more kinds of thermosetting resin selected from thermosetting carboxyl group-containing resin or thermosetting phenolic hydroxyl group-containing resin. A recyclable water-resistant transparent paper, which is obtained by impregnating an alkali-soluble resin composition containing a water-soluble alkali-soluble resin as a main component and thermosetting. 2. The recyclable waterproof transparent paper has a gram equivalent of acid per unit weight of 0.3 gram equivalent / k.
The recyclable water-resistant transparent paper according to claim 1, which is g or more. 3. A window opening envelope film using the recyclable water-resistant transparent paper according to claim 1 or 2.