JPH07189183A - Recyclable type erasable writing sheet - Google Patents

Abstract

PURPOSE:To obtain a recyclable type erasable writing sheet excellent in writing quality and repetitive writing quality/erasability. CONSTITUTION:The characteristic of this recyclable type erasable writing sheet comprises an alkali-soluble radiation curing resin having (meth)acryloyl groups and one or more functional groups selected from carboxyl groups or phenolic hydroxyl groups in the molecule in a radiation curing resin-coated layer in an erasable writing sheet having the radiation curing resin-coated layer cured with radiation on at least one surface of a substrate. The writing quality/ erasability with a marking pen are good and the resin-coated layer is readily removed in deinking the sheet without mixing the components in the resin-coated layer in the obtained recovered substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an erasable writing sheet, and more specifically, a cast paper, art paper, coated paper, lightly coated paper, fine paper, synthetic paper, or film sheet. By forming a support and providing a resin coating layer on at least one side of the support, writing / erasing can be repeated using a marking pen for whiteboard, printing is easy, and the resin coating layer can be easily separated when discarded. The present invention relates to a reusable erasable writing sheet.

[0002]

2. Description of the Related Art Using white or colored chalk,
There is a blackboard for writing / erasing characters and figures, but the conventional blackboard has a problem that it sucks the chalk powder scattered when erasing characters and figures and stains clothes. .

Instead of a blackboard, write on a white writing surface with an erasable marking pen that is water-based or oil-based, a so-called white-board marking pen, and then lightly rub with a dry cloth or soft paper. In recent years, a white plate that is wiped from the writing surface to erase the handwriting, that is, a so-called whiteboard, has been rapidly spread.

As the whiteboard, a non-absorbent or non-permeable base material, that is, a plastic plate, a metal plate, an enamel plate, a glass plate or the like is used. Whiteboard
The ink composition of the marking pen for white plate (hereinafter, simply referred to as a marking pen) does not penetrate into the surface of the base material, water and organic solvent in the ink composition volatilize from the surface of the base material, and the remaining dye Only the other composition remains, and writing such as letters is possible. The handwriting such as written characters can be easily erased by lightly rubbing it with a dry cloth or flexible paper. This whiteboard can be replaced with the size of the conventional blackboard itself,
The mainstream type is a stationary type, such as an electronic blackboard that can immediately copy written records. You can also see various blackboard-shaped objects that are smaller than this.

However, when using the conventional whiteboard, it is necessary to use it in a place where it is installed or to prepare a size that is easy to carry, and it is used in a place close to the user. It was often restricted when doing. In addition, when used personally at school or at home, there are some aspects that are difficult to use due to size, weight, price, and other restrictions.

As a means for solving such a problem,
Although it is possible to use a white board (referred to as an erasable writing sheet in the present invention) using paper, paper is basically used as compared with the case where a non-absorbent or non-permeable rigid metal plate or enamel plate is used. Due to the permeability of the solvent and the dye due to the inherent porosity, there are fatal drawbacks that writing with a marking pen is possible but it is difficult to erase, or that handwriting remains. There may also be erasable writing sheets in which polyethylene, polypropylene, polyvinyl chloride, etc. are laminated using paper as a base material, but these are basically incombustible materials (even if they are combustible materials, they have high combustion heat and damage the incinerator). Therefore, it is collected as non-combustible material and generally disposed of in landfill, which is not preferable from the standpoint of environmental protection.

Further, as shown in JP-A-4-264000 and JP-A-4-353585, an ultraviolet curable resin or an electron beam curable resin is applied on a synthetic resin sheet or coated paper and cured. Although erasable writing sheets have been proposed, they are ultimately discarded as combustible or non-combustible materials. From the viewpoint of resource conservation, it is desired to reuse the support used.

However, newspapers, magazines, cardboards,
Alternatively, the reuse of the sheet coated with the resin coating layer is technically very difficult as compared with the reuse of copy paper and the like, and the recycling thereof has not been made so far. When the sheet coated with the resin coating layer is deinked and recycled in the same manner as general waste paper, the following problems occur. That is, when the support is coated with a polyolefin resin, there is a problem that the separated polyolefin resin is not mixed with the paper fibers in the deinking process to form a good waste paper pulp, or the support and the resin coating layer are not separated. there were. Even when a resin coating layer coated with thermosetting resin or radiation curing resin is directly provided on the paper, the resin coating layer attached to the paper fibers remains in the waste paper pulp and is printed when it is reused as printing paper. There was a fatal problem that the aptitude was extremely deteriorated.

[0009]

From the above, it is an object of the present invention to have sufficient flexibility, can be handled like ordinary paper, and can be easily carried and recorded with a marking pen. It is an object of the present invention to provide a rewritable erasable writing sheet in which the erasing of records can be repeated and the resin coating layer can be easily separated from the support when the used erasable writing sheet is recycled.

[0010]

Means for Solving the Problems The inventors of the present invention have made the following inventions as a result of earnest research for solving the above problems. That is, in an erasable writing sheet provided with a radiation-curable resin coating layer obtained by curing at least one surface of a support by irradiation with radiation, the radiation-curable resin contains a radiation-curable (meth) acryloyl group and a carboxyl group in the molecule. Or selected from phenolic hydroxyl groups 1
It is an invention of a rewritable erasable writing sheet characterized by containing an alkali-soluble radiation-curable resin containing at least one kind of functional group.

In the alkali-soluble radiation-curable resin constituting the radiation-curable resin coating layer, the radiation-curable (meth) acryloyl group and the carboxyl group or the phenolic hydroxyl group have a molar ratio of 100/5 to 100 /. Three
It is preferably 00. More preferably 100/5
It is used in the range of up to 100/100.

Further, the invention of the rewritable erasable writing sheet is characterized in that the surface of the resin coating layer is the surface obtained by transferring the surface shape of the synthetic resin film.

The present invention will be described in detail below. In the present invention, ultraviolet rays and electron beams are collectively called radiation.

Generally, a method for producing waste paper, waste paper pulp or deinked pulp (DIP) constituting the waste paper is based on the following steps. That is, 1) a disintegration step using a pulper, a step in which the waste paper is decomposed into fibers by a mechanical force and a chemical such as an alkali, and an ink component is separated from the waste paper. 2) Dust removal process, rough selection, flotation, screen,
The process of removing plastics, metals, and inorganic substances contained in waste paper in each step of cleaning and cleaning. 3) Deinking step, a step of separating the printing ink separated from the waste paper outside the system by a flotation method or a cleaning method. It is created by a composite technology of these steps.

In the case of a sheet coated with a resin coating layer containing a radiation-curable and alkali-soluble resin as a main component as shown in the present invention, when treated after use, general waste paper or waste paper pulp constituting the waste paper is used. By the process of deinking pulp (DIP), very good waste paper pulp can be recovered.

In the recyclable erasable writing sheet of the present invention, when a support that cannot be reused as a waste paper such as laminated paper, synthetic paper or film sheet is used, the erasable writing sheet is treated with an alkaline bath. Since the resin coating layer containing a radiation-curable and alkali-soluble resin as a main component can be easily removed by immersing in a substrate, the support is recovered and reused as laminated paper, synthetic paper, film sheet, etc. It is possible.

The support used in the present invention is a natural pulp paper whose main component is wood pulp of softwood pulp, hardwood pulp, mixed wood of hardwood and hardwood, fine paper, art paper, coated paper, kraft paper, Kent paper, pure white roll. Paper, general-purpose paper mainly composed of wood pulp such as glassine paper, polymer films such as polyethylene terephthalate, polyethylene, polyvinyl chloride, polypropylene, or laminated products of these synthetic resin films and paper, or synthetic A non-woven fabric or a synthetic paper containing polymer fibers as a main component, or a composite material thereof, most preferably a base paper containing wood pulp as a main component is used. Regarding the thickness of the support is not particularly limited, smoothness good support is preferably the basis weight 40g / m ² ~250g / m ² is preferred.

In the method of the present invention, the raw 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,
Sizing agents such as rosin derivatives and 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 An electrolyte, a pH adjusting agent and the like can be contained in an appropriate combination.
Further, in the present invention, in order to improve the wettability with the base paper, the surface of the base paper may be subjected to a surface treatment such as corona treatment.

The resin used in the resin coating layer of the present invention is
An alkali-soluble radiation-curable resin (hereinafter referred to as an alkali-soluble radiation-curable resin), a (meth) acryloyl group which is a radiation-curable functional group at a molecular end or a side chain, and a functional group which exhibits alkali-solubility. Which have a carboxyl group or a phenolic hydroxyl group, trimethylolpropane diacrylate fumarate, trimethylolpropane difumarate monoacrylate, acryloyloxyethyl salicylate, trimethylolpropane diacrylate monosalicylate, pentaerythritol diacrylate Acrylate monofumarate, trimellitic acid monohydroxyethyl acrylate, trimellitic acid dihydroxyethyl acrylate, trimellitic acid monohydroxypropyl acrylate, trimellitic acid dihydroxypropyiate Acrylate, pyromellitic acid mono hydroxyethyl acrylate, pyromellitic dihydroxyethyl acrylate, pyromellitic acid mono- hydroxypropyl acrylate, and pyromellitic acid dihydroxypropyl acrylate. These resins may be modified with ethylene oxide or propylene oxide. The product names of Toagosei Chemical Industry Co., Ltd. are Aronix M-5300 and Aronix M-.
5400, Aronix M-5500, Aronix M
-5600 etc. are mentioned.

The erasable writing sheet of the present invention has a molar ratio of (meth) acryloyl group to carboxyl group or phenolic hydroxyl group of 100/5 in the alkali-soluble radiation-curable resin constituting the resin coating layer on the support. -10
It is characterized by being 0/100. If the proportion of the carboxyl group or the phenolic hydroxyl group is less than the above range, the removability of the support and the resin coating layer when placed in an alkaline bath is poor, and there is a problem in reusing the support for use. Further, when the proportion of the carboxyl group or the phenolic hydroxyl group exceeds the above range, the radiation-curability is weakened, so that the hardness, rigidity, etc. of the resin coating layer are weakened, and when used as an erasable writing sheet, a writing It is not preferable because the surface is easily scratched and a problem occurs in repeated use of writing / erasing.

Further, the alkali-soluble radiation-curable resin constituting the resin coating layer is mixed with the radiation-curable resin in such a range that the molar ratio of the (meth) acryloyl group and the carboxyl group or the phenolic hydroxyl group does not exceed the above range. Can be used. The radiation curable resin referred to here is
A resin that has a (meth) acryloyl group, which is a radiation-curable functional group, at the molecular end or side chain and does not have a carboxyl group or a phenolic hydroxyl group, and has an affinity with an alkali-soluble radiation-curable resin. It can be selected in consideration. It can be roughly classified as follows regardless of the number of radiation-curable functional groups. Incidentally, the number of functional groups of the radiation curable resin is usually 1 to 6 per molecule.

(1) Aliphatic, alicyclic, aromatic, araliphatic polyhydric alcohol and (meth) acrylate of (poly) alkylene glycol (2) Aliphatic, alicyclic, aromatic, araliphatic (Meth) acrylate of polyhydric alcohol obtained by adding alkylene oxide to polyhydric alcohol of (3) (poly) ester (meth) acrylate (4) (poly) urethane (meth) acrylate (5) epoxy (meth) acrylate ( 6) (Poly) amide (meth) acrylate (7) (meth) acryloyloxyalkyl phosphate ester and its salt (8) Vinyl-based or diene-based compound having a (meth) acryloyloxy group at the side chain or terminal (9) ) Monofunctional (meth) acrylate, vinylpyrrolidone, (meth) acryloyl compound (10) Ethylenic fatigue Cyano compound having a bond (11) Vinyl lactam and polyvinyl lactam compound (12) Acrylamide compound (13) (Poly) ether having an ethylenically unsaturated bond and its ester (14) Alcohol ester having an ethylenically unsaturated bond ( 15) Polyalcohol having ethylenically unsaturated bond and ester thereof (16) Aromatic compound having one or more ethylenically unsaturated bonds such as styrene and divinylbenzene (17) Side chain having (meth) acryloyloxy group, or (Poly) organosiloxane-based compound having a terminal (18) Silicone compound having an ethylenically unsaturated bond (19) Amino-modified or carbamate-modified (meth) acrylate (20) Of the compounds described in the above (1) to (19) Multimers or ori Ester (meth) acrylate-modified products

The resin coating layer made of an alkali-soluble radiation-curable resin provided on the support forms a strong coating layer in a neutral or acidic atmosphere, and some moisture, moisture, sweat, Alternatively, the resin coating layer will not be broken or peeled off from the support by oil or the like.
However, when treated with an alkaline bath after use,
The radiation-curable and alkali-soluble resin forms a water-soluble salt, the film is quickly destroyed, and the resin is dispersed and dissolved in an alkaline bath.

Although the coating amount of the resin coating layer is not limited, it is preferably 2 g / m ^{2 to} 30 g / for the purpose of maintaining sufficient adhesive strength with the support and ensuring surface smoothness.
m ^2, more preferably ^{5g / m 2 ~25g / m 2} , and most preferably in the range of ^{8g / m 2 ~22g / m 2} .
If the coating amount of the resin coating layer is less than this range, the adhesiveness may be insufficient, and pinholes may be generated, which may result in poor ink erasability of the marking pen. If the amount exceeds this range, not only does it not contribute to the improvement of the adhesiveness, but also the handleability may deteriorate from the viewpoint of rigidity and the like.

In the erasable writing sheet of the present invention, as a method for providing the resin coating layer, the resin composition for forming the resin coating layer can be directly applied on the support. In this case, it is preferable to smooth the surface with a smoothing roll or the like.

Further, the resin composition is applied onto a synthetic resin film, the synthetic resin film and the support are brought into close contact with each other via the resin composition, and cured by irradiation with radiation in the close contact state, and then the film is peeled off. By doing so, a resin coating layer to which the smooth surface shape of the synthetic resin film is transferred may be produced. By transferring the surface shape of the synthetic resin film onto the surface of the resin coating layer, the writing surface of the erasable writing sheet can be made smooth and the writing by the marking pen can be made smooth.

The synthetic resin film used in the above method is a synthetic resin film such as a polyethylene film, a polypropylene film, a polyethylene terephthalate film, etc., preferably a biaxially oriented polypropylene film having good processability and heat resistance, a biaxial A stretched polyethylene terephthalate film is desirable.

The thickness of the synthetic resin film used is not particularly limited, but is 5 to 100 μm,
In particular, from the viewpoint of handling, it is preferably 10 μm or more,
From the viewpoint of electron beam absorption loss when the electron beam is irradiated from the film side, it is preferably 150 μm or less.

As a method for bringing the synthetic resin film and the support into close contact with each other via the resin composition, two methods capable of appropriately pressure-bonding the coated synthetic resin film and the support according to a method which has been widely used in the past. It can be easily done by passing between rolls.

In order to achieve a good balance between the ink erasability of the resin coating layer and the adhesiveness to the support, an anchor layer may be provided on the support, and a resin coating layer may be further provided thereon. The coating amount of the anchor layer resin that forms the anchor layer is
Depending on the type of support that will be the erasable writing sheet,
0.5 to 10 g / m ² , more preferably 1.0 to 5 g / m ² .
m ² . If the amount of the anchor layer resin is less than this range, it is difficult to evenly cover the support with the anchor layer, and the adhesion between the support and the resin coating layer forming the writing surface is deteriorated. Further, even if the coating amount of the anchor layer resin is increased beyond this range, the characteristics will not change and only the cost will be improved. As the resin forming the anchor layer, a binder, a pigment or the like used in general coated paper can be used. A water-soluble polymer can also be used in consideration of recoverability. Examples of the water-soluble polymer include the following substances. As natural polymers and semi-synthetic polymers, modified starch compounds such as starch, oxidized starch, etherified starch, dialdehyde starch, esterified starch, alginic acid compounds such as sodium alginate and propylene glycol alginate, casein,
Examples thereof include modified cellulose compounds such as gelatin, pullulan, dextran, chitin, chitosan, gum latex, gum arabic, funori, natural gum, dextrin, methylcellulose, ethylcellulose, hydroxycellulose and carboxymethylcellulose. As the synthetic polymer, completely saponified or partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, esterification products of polyvinyl alcohol and polyvalent carboxylic acid, carboxy modified polyvinyl alcohol, sulfonic acid modified polyvinyl alcohol, olefin modified Modified polyvinyl alcohol compounds such as polyvinyl alcohol, nitrile modified polyvinyl alcohol, amide modified polyvinyl alcohol, pyrrolidone modified polyvinyl alcohol, polyethylene glycol, polyacrylic acid amide, polyacrylic acid, ammonium polyacrylate, sodium polyacrylate, etc. Polyacrylic acid compound, polyvinylpyrrolidone, polyethyleneimine, polyvinyl ether, polymaleic acid copolymer, polyacrylamide, Such as soluble alkyd resins. In addition, a water-soluble polymer solution as an emulsion in which a synthetic polymer such as styrene / maleic anhydride copolymer, styrene / butadiene copolymer, butadiene / methacrylate copolymer, acrylonitrile / butadiene / acrylic acid latex is dispersed in water. Can be used instead of.
As the water-soluble polymer, the above-mentioned polymer alone,
Alternatively, as a mixed aqueous solution, an antifoaming agent, a dispersant and the like can be used in combination if necessary.

The method for applying the radiation curable resin of the present invention includes a gravure coater, a gravure offset coater, a bar coater, a roll coater, an air knife coater, a U comma coater, an AKKU coater, a smoothing coater, a micro gravure coater, a reverse roll coater, Any coater such as a four or five roll coater, a blade coater, a dip coater, a falling curtain coater, a slide coater, a die coater and a squeeze coater may be used.

The electron beam accelerator used to cure the resin coating layer by electron beam irradiation is a curtain system,
The scanning method and the double scanning method can be adopted, but the curtain method is preferable because it is relatively inexpensive and can easily obtain a large output. The acceleration voltage of the electron beam is 100 to 1000 kV, preferably 150 to 300 kV, and the irradiation dose is 0.5 to 10 Mrad in absorbed dose. Accelerating voltage is 1
If it is less than 00 kV, the amount of transmitted energy is insufficient, and 100
If the voltage exceeds 0 kV, the energy efficiency is reduced and it is not economical. If the irradiation dose is less than this range, the curing reaction becomes insufficient and a tough layer cannot be obtained. When the irradiation dose is more than this range, not only the energy efficiency is lowered, but also unfavorable effects on the quality such as deterioration of the support, decomposition of the resin and additives, strength reduction and coloring appear, which is not preferable.

The electron beam may be irradiated from either the support side or the resin coating layer coating side, but it is preferably from the resin coating layer coating side from the viewpoint of preventing deterioration of the support.

Since the energy of ultraviolet rays is smaller than that of electron beams, it is difficult to cure the entire resin coating layer even if the ultraviolet rays are irradiated from the support side. Therefore, the irradiation direction of the ultraviolet rays is from the resin coating layer coating side. Irradiation is preferred.

In the present invention, the radiation-curable resin can be cured by irradiation with ultraviolet rays, if necessary. Examples of the ultraviolet irradiation device used include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, and a metal halide lamp.
There is also an ozoneless type that produces less ozone. Generally, a plurality of lamps having an output of 80 w / cm or more are used in parallel.

In the present invention, as the photoinitiator used when the radiation curable resin is cured by irradiation with ultraviolet rays, acetophenones such as di- and trichloroacetophenone, benzophenone, Michler's ketone, benzyl, benzoin, benzoin alkyl ether and benzyl are used. There are dimethyl ketal, tetramethyl thiuram monosulfide, thioxanthones, azo compounds and the like, and they are selected from the viewpoints of the type of curing reaction of the curable resin, stability, and suitability with an ultraviolet irradiation device. The amount of the photoinitiator used is usually in the range of 0.1 to 5% with respect to the ultraviolet curable resin. Further, a storage stabilizer such as hydroquinone may be used in combination with the photoinitiator.

As the sensitizer used in the present invention, an aliphatic amine, an amine containing an aromatic group, a nitrogen heterocyclic compound,
Allyl urea, O-tolylthiourea, sodium diethyldithiophosphate, soluble salts of aromatic sulfinic acid,
N, N-disubstituted P-aminobenzonitrile compounds, tree n
-Butylphosphine, sodium diethylthiophosphate, Michler's ketone, N-nitrosohydroxylamine derivatives, oxazoline compounds, carbon tetrachloride, hexachloroethane, etc. are available, and commonly used as a photoinitiator, the curing rate can be improved.

Curing by irradiation with ultraviolet rays or electron beams is a radical reaction and depends on the oxygen concentration in the atmosphere. Therefore, replacement with an inert gas such as nitrogen, helium or carbon dioxide is carried out, and the oxygen concentration is 600 ppm or less, preferably 400 ppm. Irradiation is preferably performed in an atmosphere suppressed below.

In the erasable writing sheet of the present invention, it is the non-penetrable resin coating layer composed of a radiation-curable and alkali-soluble resin that exhibits the function of repeatedly writing / erasing a record with a marking pen. It is preferable that the erasable writing sheet obtained has a Gurley air permeability of 1000 seconds or more as defined in JIS P8117. When the air permeability is 1000 seconds or more, the ink composition of the marking pen does not penetrate into the erasable writing sheet,
It is possible to write a record by evaporating water or an organic solvent in the ink composition from the surface of the base material. Here, if the air permeability is less than 1000 seconds, the solvent in the marking pen ink easily penetrates, and the ink component reaches the support, which makes it difficult to erase the record on the erasable writing sheet. In addition, there is a drawback that the resin coating layer easily comes off from the support.

[0040]

The erasable writing sheet of the present invention has a function of writing and erasing with a marking pen. Writing and erasability are the functions of a radiation-curable, radiation-curable, non-permeable resin coating layer made of an alkali-soluble resin, but the solvent smoothness of the support is eliminated because no solvent or solvent is used to form the resin coating layer. Is maintained, and there is almost no change in water content because heat is not applied during curing,
After the resin coating layer is provided, curling or wrinkling does not occur, and the dimensional stability is excellent.
When the resin coating layer is cured by irradiation with radiation, unsaturated bonds between carbon and carbon are three-dimensionally cross-linked and firmly bonded to each other, so that scratch resistance is obtained on the writing surface and ink non-fixing property of the marking pen is prevented. Thus, the reusability of writing / erasing the record is improved. Furthermore, since the resin coating layer is a radiation-curable and alkali-soluble resin, if the resin coating layer is treated with an alkaline bath after use, the resin coating layer will be immediately destroyed and dispersed / dissolved in the alkaline bath to recover the support. It can be performed easily and efficiently.

[0041]

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".

Example 1 Acrylic acid dimer as an alkali-soluble radiation-curable resin (Aronix M-560 manufactured by Toagosei Kagaku Kogyo Co., Ltd.)
0), the molar ratios of acryloyl group and carboxyl group are 100/3, 100/5, 100/2, respectively.
Radiation curable resin (Aronix M-3, manufactured by Toagosei Kagaku Kogyo Co., Ltd.) so as to be 0, 100/50, 100/100.
09) was mixed (when the molar ratio was 100/100, the radiation-curable resin was not mixed) and kneaded well with a three-roller to obtain a resin composition. This resin composition was coated with a gravure coater at a coating amount of 10 g / m ² using a commercially available cast-coated paper (LK Color White, 157 g / m ² ) as a support. Then, the support coated with this resin composition was placed in a nitrogen atmosphere (oxygen concentration: 20%).
Electron beam irradiation (Nisshin High Voltage Co., Ltd., trade name Curetron) at an acceleration voltage of 200 kV in an amount of 0 ppm or less) so that the absorbed dose becomes 2 Mrad, and the resin composition is cured to coat the resin. As a layer, an erasable writing sheet was obtained.

Example 2 As the alkali-soluble radiation-curable resin, trimellitic acid monohydroxyethyl acrylate obtained by esterifying trimellitic acid and acrylic acid was used.
The molar ratio of acryloyl group and carboxyl group is 100 /
Radiation curable resin (Toagosei Kagaku Kogyo, M-220) was mixed so as to be 50, 100/100, 100/200 (when the molar ratio is 100/200, the radiation curable resin is not mixed. The resin composition was thoroughly kneaded with three rollers. This resin composition was coated on a biaxially oriented polyethylene terephthalate (PET) film with a gravure coater at a coating amount of 5 g / m ² , and was used as a support for commercially available high-quality paper (Mitsubishi Paper Mills, 60 g / m 2).
² ) Adhered to and adhered to an electron beam (Nisshin High Voltage Co., Ltd.) so that the absorbed dose becomes 3 Mrad at an accelerating voltage of 200 kV in a nitrogen atmosphere (oxygen concentration of 200 ppm or less). , Product name Curetron)
Was performed, and the PET film was peeled off after the resin composition was cured to obtain an erasable writing sheet having a resin coating layer to which the surface properties of the PET film were transferred.

Example 3 Glassine paper having a basis weight of 50 g / m ² was used as a support,
Using an air knife coater as the aqueous polymer layer on the front and back surfaces, a 5% gelatin solution containing formaldehyde mixed with a hardener was applied to each of the front and back surfaces so that the dry weight was 2 g / m ^2, and after setting with cold air, Heat dried. On this support, 7 g of isocyanuric acid diacrylate (Toagosei Kagaku Kogyo Kogyo Kogyo, Aronix M-215, acryloyl group / phenolic hydroxyl group molar ratio 100/50) was used as an alkali-soluble radiation-curable resin with a gravure coater.
The coating amount of / m ² was applied to obtain a support having an anchor layer made of a water-soluble polymer and a resin coating layer made of an alkali-soluble radiation-curable resin. This support was irradiated with 200 KV, 1.5 Mr by an electron beam irradiation device with nitrogen substitution.
Curing was performed with an absorbed dose of ad to obtain an erasable writing sheet.

Example 4 As a support, the surface was clay-coated and the basis weight was 70 g / m 2.
^{Using 1} side glossy paper, 100 parts of acrylic acid dimer (Aronix M-5600 manufactured by Toagosei Kagaku Kogyo Co., Ltd.) as an alkali-soluble radiation curable resin is used as a photoreaction initiator (product of Ciba Geigy Co., Ltd., product name Irgacure). 90
After mixing 2 parts of 5) and applying the adjusted resin composition, the resin composition is introduced into an ultraviolet irradiation device (120 W / cm, manufactured by Ushio Denki Co., Ltd.) and irradiated with ultraviolet rays to cure the resin coating layer for erasability writing. Got the sheet. The molar ratio of the acryloyl group to the carboxyl group in the resin composition is 100/100, and the coating amount on the support is 10 g / m ² .

Example 5 Pyromellitic acid monohydroxyethyl acrylate obtained by esterifying pyromellitic acid and acrylic acid (molar ratio of acryloyl group to carboxyl group is 100/300) was used as an alkali-soluble radiation-curable resin. , Biaxially oriented polyethylene terephthalate (hereinafter PE
T) Coating amount on the film by gravure coater 8g / m ²
The coated paper (made by Mitsubishi Paper Mill,
Pearl deluxe, 165 g / m ² ) is adhered and adhered, and as it is, in a nitrogen atmosphere (oxygen concentration 200 pp
m or less), the absorbed dose is 5 at an acceleration voltage of 200 kV.
By irradiating an electron beam (manufactured by Nisshin High Voltage Co., Ltd., trade name Curetron) so as to give Mrad, curing the resin composition, and then peeling off the PET film, PE
An erasable writing sheet having a resin coating layer to which the surface properties of the T film were transferred was obtained.

Example 6 As a support, a tracing paper (Deluxe Strepée made by Mitsubishi Paper Mills, 75 g / m ² ) having a molar ratio of acryloyl groups to carboxyl groups of 10 used in Example 1 was used.
An erasable writing sheet was obtained by applying a resin composition of 0/50 with a gravure coater at an application amount of 6 g / m ² and irradiating with an electron beam in the same manner as in Example 1.

Example 7 As a support, a biaxially stretched polyethylene terephthalate film (made of dia foil, thickness 50 μm, abbreviated as PET) was used, and the molar ratio of acryloyl group to carboxyl group used in Example 2 was 100 /. An erasable writing sheet was obtained by applying a resin composition of 100 with a gravure coater at an application amount of 5 g / m ² and irradiating with an electron beam in the same manner as in Example 2.

Comparative Example 1 The sample of Comparative Example 1 was obtained by applying the radiation curable resin used in Example 1 onto the same support as in Example 1 and curing it.

Comparative Example 2 A sample of Comparative Example 2 was obtained by applying the radiation curable resin used in Example 2 onto the same support as in Example 2 and curing it.

Comparative Example 3 On the paper support used in Example 1, polypropylene was melt-extruded and laminated at a coating amount of 15 g / m ² , and Comparative Example 3
I got a sample of.

The erasable writing sheets obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were subjected to the following tests. The results are shown in Table 1. The molar ratio in the table is the molar ratio of the acryloyl group and the carboxyl group or the phenolic hydroxyl group contained in the resin composition. The test method is as follows.

Test 1 [Writability] A pattern is written on the writing surface of the erasable writing sheet obtained with a marking pen and left for 10 minutes, after which the shape of the written pattern is retained as it is and can be read completely. The inks were repelled, and the ink was repelled, or the resin coating layer, which is the writing surface, penetrated and bleeded, and the pattern handwriting was not maintained.

Test 2 [Writing / Erasing Property] On the writing surface of an erasable writing sheet, recording was written with a marking pen, and the handwriting was erased with a commercially available eraser for whiteboard. Repeat this operation until the handwriting cannot be completely erased. If the number of repetitions is greater than 300, excellent writing / erasing ability, 50
Those with a range of up to 300 times were rated as average, and those with less than 50 times were rated poor.

Test 3 [Non-Fixing Property] Erasable Writing Sheet Recording was written on the writing surface with a marking pen, left for 1 week, and then erased with a commercially available eraser for whiteboard. . Those in which the handwriting could be completely erased were evaluated as excellent in non-fixing property, those in which some marks remained and the handwriting could not be completely erased without strong rubbing, and those in which 10% or more of the handwriting could not be erased were judged as poor.

Test 4 (Recoverability) The erasable writing sheets of Examples and Comparative Examples were cut with a shredder, 70 ° C., 0.5N sodium hydroxide, and 1% polyoxyethylene as a nonionic surfactant. The waste paper pulp recovery step was reproduced by immersing in a solution containing an alkyl ether and stirring, and the time was determined by the time of desorption of the resin coating layer. ○ If the resin coating layer detaches within 1 minute
A mark indicates that the resin coating layer was released from the mold within 3 minutes but was longer than 1 minute, and a mark indicates that it took longer than 3 minutes.

[0056]

[Table 1]

Evaluation: The erasable writing sheets prepared in the examples have good writing performance with a marking pen, and the writing operation was performed by the resin composition constituting the resin coating layer which is the writing surface. It can be done smoothly without scratching the ink or repelling ink, and even when erasing the handwriting, it can be completely erased without leaving handwriting even after a lapse of time after writing, and the resin coating accompanying scratching of the eraser for whiteboard Repeated writing / erasing could be done without dropping layers. Furthermore, since the resin coating layer is alkali-soluble, good desorption of the resin coating layer occurs in the alkaline bath at the time of collection, and high support recoverability is exhibited. Since the desorbed resin coating layer has a low specific gravity, it can float when left standing and can be discharged by the action of the surfactant, and it is easy to collect only the support. On the other hand, in a similar experiment, the sample of the comparative example in which the resin coating layer was provided with the radiation-curable resin having no alkali solubility had a poor alkali releasability, and thus the support could not be recovered after use. It has to be disposed of, which is not preferable from an environmental point of view.

[0058]

As is clear from the results of Table 1, the erasable writing sheet of the present invention has a function of writing and erasing with a marking pen, and can be repeatedly used for writing / erasing recording. And when recycling the used erasable writing sheet, the resin coating layer can be easily separated from the support, it is easy to recover and reuse only the support, from the viewpoint of environmental protection, resource saving, or In terms of reducing the amount of waste products, it has great industrial value.

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Claims (3)

[Claims] 1. An erasable writing sheet having a radiation-curable resin coating layer obtained by curing at least one surface of a support by irradiation with radiation, wherein the radiation-curable resin coating layer contains a radiation-curable (meta ) 1 selected from an acryloyl group and a carboxyl group or a phenolic hydroxyl group
A recyclable erasable writing sheet comprising an alkali-soluble radiation-curable resin having at least one kind of functional group. 2. An alkali-soluble radiation-curable resin,
The molar ratio of the radiation-curable (meth) acryloyl group to the carboxyl group or the phenolic hydroxyl group is 100/5 to 1
The rewritable erasable writing sheet according to claim 1, which is 00/300. 3. The rewritable erasable writing sheet according to claim 1, wherein the radiation curable resin coating layer has the surface obtained by transferring the surface shape of the synthetic resin film.