JP2003096690A - Pigment-coated paperboard for active energy-curable resin coating use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pigment-coated paperboard for curable resin coating use affording a cured resin layer surface of high gloss thereon even if coated with a water-based active energy ray-curable resin either directly or indirectly via printing ink, followed by curing. SOLUTION: This pigment-coated paperboard for active energy-curable resin coating use is such one as to be coated with a water-soluble or water-dispersible active energy ray-curable resin composition either directly or indirectly via printing ink, wherein a pigment 0.25-7.00 μm in mean particle size and <=2.00 ml/g pigment in specific sedimentation volume is included at >=30 mass% in 100 mass% of the total pigment in the pigment coating layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pigment-coated paperboard for coating a cured resin, and more specifically to an active energy ray-curable composition, particularly an aqueous type by introducing a hydrophilic group in an amount of 0.05% by mass or more. Even if you apply and cure the
The present invention relates to a pigment-coated paperboard for coating a cured resin, which gives a cured resin layer surface having excellent gloss.

[0002]

2. Description of the Related Art As paperboard used for packaging, white paperboard mainly used in carton boxes and inner and outer liners and cores mainly used as cardboard boxes are used.
It is representative. The pigment-coated paperboard for coating a cured resin of the present invention is mainly intended for the field in which white paperboard and exterior liner are used. The main purpose of packaging is to protect the contents, but in recent years, there has been a strong demand for cosmetics for carton boxes and cardboard boxes in order to improve the display effect of packaging.

For this reason, in the case of a paper container box, overprint varnish or press coat is often applied after printing, and in the case of a cardboard box as well, in the case of a cosmetic box, it is overprinted by a preprint method in which printing is performed before bonding. Print varnish may be applied.

Here, the overprint varnish can be formed by a printing machine, but the effect of improving gloss which affects the aesthetic appearance is just a step further, and press coating is performed for those requiring high gloss. Although high gloss can be obtained with the press coat, it cannot be carried out by the printing machine and must be carried out in a separate step, and the processing speed is about 1/10 of that of the printing machine, which is a major drawback. Further, both the overprint varnish and the press coat dry slowly, which may be a problem.

In order to deal with the above-mentioned problems, treatment with a composition which cures with active energy such as ultraviolet rays and electron beams has come to be performed in recent years. Compared with overprint varnish, this treatment gives high gloss and
When it is irradiated with active energy rays, it cures instantly, so it has the advantage of good drying properties.

Here, there are two types of the curable composition, an oily type and an aqueous type (water-soluble and water-dispersible). Comparing these, the gloss is superior to the oil type,
This naturally contains a lot of solvent, and when it is used, a large amount of solvent is discharged. Therefore, the working environment becomes worse, and the equipment requires local exhaust gas collection equipment, explosion-proof specifications, dangerous goods warehouse, etc., and there is some drawback in handling. In particular, when an aromatic compound-based solvent such as toluene is used, there is also a problem in health, and in recent years offset inks have also been directed to inks that do not use aromatic compounds, and from these points, Aqueous type is excellent. However, as described above, the water-based type has a poor gloss-developing property as compared with the oil-based type, so that improvement in gloss has been strongly desired.

In order to improve this, from the viewpoint of the curing composition, the chemicals used are reviewed, the coating amount is increased, etc.
From the aspect of operation, improvement of smoothness and application of chemicals have been considered from the viewpoint of the type and strength of active energy rays and the board of cured resin coating, but the effects are limited, and they are still satisfactory. The current situation is that we have not obtained a satisfactory standard.

[0008]

According to the present invention, a surface of a cured resin layer having excellent gloss can be obtained even when an aqueous type active energy ray-curable resin is applied or cured directly or indirectly through a printing ink. It is to provide a pigment-coated paperboard for coating a cured resin.

[0009]

[Means for Solving the Problems] The present invention has the following configuration. (1) The water-soluble or water-dispersible active energy ray-curable composition is directly or indirectly applied via a printing ink, and the average particle diameter is 100% by weight of all pigments in the pigment coating layer. Of 0.25 to 7.00 [mu] m and a specific sedimentation volume of 2.00 ml / g of pigment or less is contained in an amount of 30% by mass or more of a pigment.

(2) The water-soluble or water-dispersible active energy ray-coin composition contains a hydrophilic group in an amount of 0.05% by mass or more, and the pigment-coated paperboard for coating an active energy ray-curable resin according to (1).

(3) The pigment coating for active energy ray-curable resin coating according to (1), wherein the pigment coating layer contains 10 to 60% by mass of a polymer resin having a glass transition temperature of -50 to 0 ° C. Paperboard.

Although it is not clear why this means can achieve the object, it is presumed as follows. It is considered that the cause of inhibiting gloss when the active energy ray-curing composition, especially the aqueous type, is applied to a paperboard and cured, is as follows.

That is, a portion of the cured composition will penetrate into the paper layer of the paperboard. The curing composition, which is a glossy substance,
If it penetrates into the paper layer, it does not contribute to the gloss development.
The greater the amount of the composition that remains on the paperboard surface, the higher the gloss. When the pulp fibers absorb and swell the cured composition, the surface of the paperboard to be coated becomes rough. As a result, the glossiness is deteriorated. Further, since the pulp fiber has a particularly large degree of swelling when it absorbs water, this effect is particularly strong in the case of an aqueous type curing composition in which the solvent is water. Therefore, when comparing the oil-based type curable composition with the aqueous type, the glossiness of the aqueous type is worse.

When the pigment coating material is applied to the paperboard as in the present invention, the pigment coating material fills the voids in the paper layer, and the pigment coating layer formed on the paper surface is compared with the void diameter of the paper layer. Then, it is considered that the permeation of the liquid can be suppressed because the pore diameter is as small as one digit or less and the void amount is small. Also,
When coated with pigment paint, pulp fibers near the coated surface are coated with pigment. Since the pigment is a non-absorbent liquid, the coating prevents the pulp fibers from swelling. Further, as described above, the permeation of the liquid is suppressed and the swelling of the pulp fiber is suppressed. These swelling suppressing effects suppress the roughening of the paperboard coated surface, and as a result, it is considered that the gloss of the cured composition surface becomes high.

Furthermore, it is considered that the pigment having a small specific sedimentation volume has a high effect of preventing liquid permeation since it forms a dense coating layer. On the other hand, when the pigment particle size becomes smaller, the number of voids having a small pore size increases, and it is considered that the liquid permeation prevention effect tends to decrease. Further, it is considered that when the particle size becomes large, the gloss on the surface coated with the pigment decreases, and thus the gloss on the surface of the cured composition also decreases. From the above factors, it is considered that there is a certain preferable range for the pigment particle size.

Further details will be described below. Here, the pigment coating layer is provided by coating the base paper board with pigment paint. Pigment paints are composed of pigments, adhesives, and other auxiliaries. The type of pigment is not limited, and examples of the inorganic pigment include clay (including various modified clays such as calcined clay and chemically modified clay [structured clay]), heavy calcium carbonate, light calcium carbonate, titanium dioxide, and hydroxide. Examples include aluminum, silica, satin white, talc, mica, muscovite, and the like. Examples of organic pigments include polystyrene or polyacrylic resin-based solid or hollow pigments and urea resin-based pigments. These may be used alone or in combination of two or more.

Regarding the properties of the pigment, the specific sedimentation volume is preferably 2.00 ml / g of pigment or less. If the specific sedimentation volume exceeds 2.00 ml / g of pigment, the gloss of the surface coated with the cured composition will decrease. The particle size is 0.25
7.00 μm is good, preferably 0.5-5.00 μm
Is. Even if the particle size is less than 0.25 μm, 7.00 μm
Even if it exceeds the range, the gloss of the surface coated with the cured composition decreases, which is not preferable. Furthermore, the amount of the pigment having this property to be blended is required to be 30% by mass or more based on 100% by mass of all the pigments, and if it is less than this, the gloss of the surface coated with the cured composition is lowered, which is not preferable.

There is no limitation on the kind of the adhesive, and for example, starch (including various modified starch such as phosphate esterified starch and cationized starch), polyvinyl alcohol, casein, polyacrylamide, polystyrene-butadiene emulsion, polyvinyl acetate. System emulsion, polyacrylic emulsion, polyurethane emulsion and the like.
These may be used alone or in combination of two or more.

Here, a polymer resin having a glass transition temperature of -50 to 0 ° C. has a good film-forming property and has a high effect of filling voids in a coating layer or a base paper. ~
It is preferable to contain 60% by mass, preferably 10 to 40% by mass. When it is less than 10% by mass, it is insufficient to fill the coating layer and voids, and when it exceeds 60% by mass, the gloss development effect is rather deteriorated, which is not preferable.

Any of the auxiliaries may be used if necessary, and examples thereof include a dispersant, a pH adjusting agent such as sodium hydroxide and ammonia, an antifoaming agent, a fluorescent dye, a coloring pigment, a release agent, and a water-proofing agent. , Fluidity improvers, water retention agents, preservatives and the like.

The coating amount of the pigment paint is preferably 5 to 25 g / m ² . Here, if it is less than 5 g / m ² , the gloss developing property tends to be low, and if it is more than 25 g / m ² , the gloss developing effect reaches a ceiling and the coating layer cracking tends to occur easily.

The coating of the pigment paint may be a single coating or a multi-stage coating of double coating or more. If necessary, a chemical such as starch, polyvinyl alcohol, or a surface sizing agent containing polyacrylamide may be applied before the pigment paint is applied. Various types of coating equipment can be used, and examples thereof include a bar coater, a blade coater, an air knife coater, a rod blade coater, a roll coater such as a gate roll coater and a size press, a bill blade coater, and a vervapa coater.

The method for drying the pigment coating material is not limited, and examples thereof include hot air drying, infrared ray drying and dryer roll drying.

Smoothing the coated surface after coating and drying the pigment coating with a calendar or the like is a preferable treatment method because it has the effect of accelerating the gloss development effect. For example, there are gloss calender treatment, soft nip calender treatment, machine calender treatment and the like.

The base paper coated with the pigment coating may be a single-layer paper or a multi-layer paper made by combining single layers. There is no limitation on the pulp used for this purpose, for example, unbleached or bleached mechanical pulp or chemical pulp wood pulp, non-wood pulp such as kenaf or bagasse, and used paper such as magazines, newspapers, offices, information paper, corrugated cardboard, paper containers, etc. There are pulps and synthetic pulps such as polyethylene and polypropylene. These may be used alone or in combination of two or more.

Further, when the base paper is made into paper, if necessary, a sizing agent, a filler, a paper strength enhancer, a water resistance agent, a water repellent, an oil resistance agent, a drainage retention improver, an antifoaming agent, an anticorrosive agent. , Conductive agents, flame retardants, softeners, dyes, etc.

The active energy ray is a radiation which acts on an organic compound having an unsaturated bond to cause a polymerization reaction or a crosslinking reaction. Generally, an electron beam or an ultraviolet ray is often used. Also in the present invention, electron beams and ultraviolet rays are mainly targeted.

The active energy ray-curable composition is a single or mixture of active energy ray-curable compounds, and if necessary, does not cure with a polymerization initiator, an ultraviolet sensitizer, a pigment or an active energy ray. It may contain a water-soluble or oil-based resin, a water-dispersible or oil-based dispersed resin, or the like.
The total amount of active energy ray-curable compounds in the active energy ray-curable composition is 30% by mass or more, preferably 50% by mass or more, and most preferably 80% by mass or more.

The active energy ray-curable compound that can be used may be any of a monomer, an oligomer and a polymer. Specific examples thereof include the following. (1) Aliphatic, alicyclic, aromatic, araliphatic polyhydric alcohols and (poly) acrylates of polyalkylene glycols (2) Aliphatic, alicyclic, aromatic, araliphatic polyhydric alcohols Poly (meth) acrylate of polyhydric alcohol to which alkylene oxide is added (3) Polyester poly (meth) acrylate (4) Polyurethane poly (meth) acrylate (5) Epoxy poly (meth) acrylate (6) Polyamide poly (meth) Acrylate (7) Poly (meth) acryloyloxyalkyl phosphate ester (8) Vinyl- or diene-based compound having a (meth) acryloyloxy group at the side chain or terminal (9) Monofunctional (meth) acrylate, vinylpyrrolidone, (Meth) acryloyl compound (10) Cyanation having ethylenically unsaturated bond (11) Mono- or polycarboxylic acids having an ethylenically unsaturated bond, and their alkali metal salts, ammonium salts, amine salts, etc. (12) Ethylenically unsaturated (meth) acrylamides or alkyl-substituted (meth) acrylamides and the like Polymer (13) Vinyl lactam and vinyl lactam compound (14) Polyether having ethylenically unsaturated bond and ester thereof (15) Alcohol ester having ethylenically unsaturated bond (16) Polyester having ethylenically unsaturated bond Alcohol and its ester (17) Aromatic compound having one or more ethylenically unsaturated bonds such as styrene and divinylbenzene (18) Polyorganosiloxane compound having a (meth) acryloyloxy group at the side chain or terminal (19) ) Ethylenic Silicone compounds having a sum coupling (20) above (1) to (19) multimeric or oligoester (meth) acrylate modified compounds of the compounds described

In order to make the active energy ray-curable composition aqueous, it is necessary to introduce a hydrophilic group, and examples thereof include a carboxyl group, a sulfonate group, a carboxylate group, a sulfonate group and a hydroxyl group. , Ether groups, acid amide groups, primary to tertiary amino groups, quaternary ammonium groups, alkylene oxide groups and the like. Further, examples of the acid used for introducing the carboxyl group include dimethylpropionic acid, maleic acid, phthalic acid, oxalic acid, succinic acid and the like.

Further, in order to make this active energy ray-curable composition into an aqueous type, it is necessary that the amount of hydrophilic groups contained in the cured resin is 0.05 mass% or more.

Further, a curable composition containing 40 to 90% by mass of an acrylate having three or more unsaturated bonds in one molecule, that is, trifunctional or more, or a resin having a glass transition temperature of 60 after curing.
A curable composition having a temperature of up to 250 ° C. is a preferable use because a cured resin layer having excellent heat resistance, blocking resistance and slip resistance can be obtained.

An aqueous solution of a water-soluble polymer or an aqueous dispersion of a synthetic resin may be added to the active energy ray-curable composition. As the water-soluble polymer, polyvinyl alcohol,
Polyethylene oxide, methyl cellulose, polyvinylpyrrolidone and the like can be mentioned. Examples of the synthetic resin aqueous dispersion include acrylic emulsions, polyvinyl acetate emulsions, polystyrene-butadiene emulsions and polyurethane emulsions.

The active energy ray-curable composition layer is preferably formed in a continuous process after being provided with a printing layer in a printing machine without being wound, but it may of course be formed in another process. Here, any printing method may be used, and examples thereof include offset printing, flexographic printing, and gravure printing.

When electron beam irradiation is used for curing, the accelerating voltage is 100 to 1000 KV, more preferably 100 to 300 KV in terms of penetrating power and curing power, more preferably 100 to 300 KV electron beam accelerator, and the absorbed dose in one pass is 0.1. 5-20 Mrad
It is preferable that If the accelerating voltage or the electron beam irradiation dose is lower than this range, the electron beam penetrating power is too low to sufficiently cure the inside of the support, and if it is higher than this range, the energy efficiency deteriorates. In addition, unfavorable influences on the quality such as the strength of the support and the decomposition of the resin and the additives appear. The electron accelerator may be, for example, an electro-curtain system, a scanning type, a double scanning type, or the like, but a curtain beam system that is relatively inexpensive and obtains a large output is preferable. The preferred acceleration voltage in this system is 100 to 300 KV, and the absorbed dose is 0.5 to 1
It is 0 Mrad.

When the oxygen concentration is high during electron beam irradiation, curing of the electron beam curable resin is hindered, so replacement with an inert gas such as nitrogen, helium, carbon dioxide, etc. is carried out to reduce the oxygen concentration to 600 ppm or less. Preferably 500
Irradiation is preferably performed in an atmosphere in which the concentration is suppressed to ppm or less.

If UV irradiation is used for curing, 80
It is preferable to use a lamp of W / cm or more. For example, there are a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a metal halide lamp and the like. There is also an ozoneless type that produces less ozone. Further, a photoreaction initiator can be mixed and used in the resin.

Further, when ultraviolet rays are used for curing,
A photoinitiator is required in the resin. Examples that can be used include acetophenones such as di- and trichloroacetophenone, benzophenone, Michler's ketone, benzyl, benzoin, benzoin alkyl ether, benzyl dimethyl ketal, tetramethyl thiuram monosulfide, thioxanthone and azo compounds.

Here, a solution or dispersion of a polymer substance may be applied under the active energy ray-curable composition in order to enhance the effect of improving gloss. In this case, it is preferable to apply an aqueous solution of a water-soluble polymer or a synthetic resin aqueous emulsion and dry it. Examples of the water-soluble polymer include starches, cellulose derivatives, polyvinyl alcohols, casein, gelatin and the like. Starches include raw starch and modified starch, and cellulose derivatives include methyl cellulose and
Examples include carboxymethyl cellulose and hydroxyethyl cellulose. Examples of polyvinyl alcohols include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxylic acid-modified polyvinyl alcohol, and silyl-modified polyvinyl alcohol.
Examples of the synthetic resin include polyvinyl acetate resin, polyethylene-vinyl acetate resin, polyacrylic resin, polystyrene-butadiene resin, and the like.

[0040]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Numerical values indicating the composition, concentration, etc. are based on the mass of the solid content or the active ingredient.

Example 1 <Papermaking of base paper> As the surface layer pulp, LBKP / NBK
Prepare a mixed pulp slurry of P / super white waste paper pulp = 5/2/3, and add 3 kg / sulphuric acid band / pulp-t and 2 kg / size Pine G (rosin size, Arakawa Chemical Co., Ltd.).
Pulp-t addition, and as the back layer pulp, NUKP
/ Prepared mixed pulp slurry of corrugated cardboard = 8/2,
Sulfuric acid band was added thereto in an amount of 2 kg / pulp-t, and Polystron 117 (paper strength agent, manufactured by Arakawa Chemical Co., Ltd.) was added in an amount of 3 kg / pulp-t. A base paper having a basis weight of 220 g / m ² was obtained.

<Preparation of Pigment Paint> NUCL as a pigment blend
Y (specific sedimentation volume: 1.01 ml / g of pigment, particle diameter: 0.
72 μm, clay, manufactured by Engelhard Co., Ltd., 90 parts, Tamapearl TP-121 (specific sedimentation volume: 1.40 ml / pig g, particle size: 1.20 μm, calcium carbonate, manufactured by Okutama Kogyo Co., Ltd.), 10 parts by weight. Alon T40 as a dispersant
0.3 parts of Toagosei Co., Ltd. and 0.1 parts of sodium hydroxide as a pH adjuster were added and dispersed to obtain a pigment slurry. B-1525 (Tg =-
16 parts, polystyrene-butadiene copolymer latex, manufactured by Asahi Kasei) 19 parts, SN thickener 920 (special carboxylic acid salt, manufactured by San Nopco) as a fluidity improver
Was added and mixed to obtain a pigment paint.

<Production of Pigment-Coated Paperboard> This pigment coating material was applied to a base paper with a bar coater so that the coating amount was 12 g / m ² .
The pigment-coated paperboard 1 was obtained by coating, drying and soft calendering.

<Preparation of active energy ray-curable composition 1> 60 parts of dipentaerythritol pentaacrylate with 1 mol of succinic acid added, 35 parts of polyethylene glycol diacrylate, polymerization initiator Irgacure 2959 (Ciba Specialty) Chemicals Co., Ltd.) to 100 parts of the active energy ray-curable composition composed of 5 parts, water / isopropyl alcohol = 50
A water-soluble active energy ray-curable composition 1 was obtained by mixing 25 parts of a 50/50 dilution.

<Preparation of Cured Resin Coated Paperboard> Pigment coated paperboard 1 was first coated with ² g / m ^{2 of} polystyrene-acrylic acid ester resin (PW-62K, manufactured by Nippon Kako Paint Co., Ltd.), dried, and then activated energy. 5 g / m ^{2 of} radiation curable composition
It was coated and then cured by ultraviolet irradiation to obtain a cured resin-coated paperboard 1. This effect makes the gloss of the resin surface glossy.
-VGS-ID (manufactured by Nippon Denshoku Industries Co., Ltd.)
The angle of 45 ° / 45 ° was measured according to S Z-8741. The results are shown in Table 2.

Examples 2, 3, 4 Samples were obtained in the same manner as in Example 1 except that the conditions shown in Table 1 were used, and the same measurements as in Example 1 were performed. The results are shown in Table 2.

Comparative Examples 1, 2, 3, 4 Samples were obtained in the same manner as in Example 1 except that the conditions shown in Table 1 were used, and the same measurements as in Example 1 were performed. The results are shown in Table 2.

Comparative Example 5 A sample was obtained in the same manner as in Example 1 except that the pigment paint was not applied, and the same measurement as in Example 1 was carried out. The results are shown in Table 2.

Comparative Example 6 A sample was obtained in the same manner as in Comparative Example 1 except that the active energy ray-curable composition prepared by the method described below was used. The same measurement was performed. The results are shown in Table 2. (Preparation of active energy ray-curable composition) 60 parts of dipentaerythritol pentaacrylate, 35 parts of polyethylene glycol diacrylate, and 5 parts of polymerization initiator Irgacure 2959 in an active energy ray-curable composition 100. 10 parts of a diluted solution of ethyl acetate was mixed with 10 parts to obtain a water-insoluble active energy ray-curable composition.

Table 1 shows the results of measuring the glossiness of the cured resin-coated paperboards obtained in Examples 1 to 4 and Comparative Examples 1 to 6. The particle size and sedimentation volume of the pigment used are shown in Table 2.

[Table 1]

[0051]

[Table 2]

(Measurement Method of Specific Sedimentation Volume) 0.1 part by mass of the dispersant Aron T-40 (manufactured by Toagosei Co., Ltd.) was added to the dispersion water,
100 parts by mass of the pigment is added with stirring at 1500 rpm, and the mixture is stirred for 10 minutes to obtain a 10% by mass pigment slurry. A predetermined amount of this pigment slurry was placed in a centrifuge tube with a volume scale, and centrifuged at a rotation speed of 1800 rpm for 60 minutes to measure the volume of the precipitated pigment, and the specific sedimentation volume was calculated from this. (Measurement method of average particle diameter) The average particle diameter was measured by a sedimentation method (Cedigraph). The particle size at which the cumulative mass was 50% was defined as the average particle size.

In an embodiment satisfying the requirements of the present invention,
Aqueous type (water-soluble
Even when a water-dispersible composition is used, high gloss equivalent to that obtained by using an oil-based (water-insoluble) composition can be obtained.

Continued front page    F-term (reference) 4L055 AA02 AA03 AA11 AC06 AC09                       AG04 AG12 AG18 AG27 AG63                       AG71 AG76 AG89 AH02 AH37                       AH50 AJ01 AJ02 AJ04 BD18                       BE09 EA15 EA16 EA32 FA12                       GA05

Claims (3)

[Claims] 1. A water-soluble or water-dispersible active energy ray-curable composition is directly or indirectly applied through a printing ink, and the average amount is 100% by weight of all pigments in a pigment coating layer. 30% by mass of pigment having a particle diameter of 0.25 to 7.00 μm and a specific sedimentation volume of 2.00 ml / g of pigment or less
A pigment-coated paperboard for coating an active energy ray-curable resin, which is characterized by containing the above. 2. The active energy ray-curable resin coating composition according to claim 1, wherein the water-soluble or water-dispersible active energy ray curable composition contains 0.05% by mass or more of a hydrophilic group. Pigment coated paperboard. 3. The glass transition temperature in the pigment coating layer is −
The pigment-coated paperboard for applying an active energy ray-curable resin according to claim 1, which contains a polymer resin at 50 to 0 ° C in an amount of 10 to 60% by mass.