JP5240118B2 - Coating packaging paper - Google Patents

Description

  The present invention relates to a coated wrapping paper blended with waste paper pulp, and more particularly to a wrapping paper that is excellent in flexographic printing suitability and has bag making suitability.

  In recent years, the number of colors of printed materials has been increasing, so that the required printing quality has been improved and the printing speed has been increased, and the development of packaging paper corresponding to these has been required. There is also a strong demand for higher printing quality in packaging paper used for paper handbags such as shopping bags. As a technique for improving the print quality, for example, printing by high-speed and high-definition offset printing or gravure printing is generally used. However, in the case of wrapping paper, flexo printing is still used in many situations, and it cannot be denied that its print quality is inferior to that of offset printing or gravure printing. On the other hand, flexographic printing technology has also made remarkable progress, and with the recent wave of digitization, attention has been paid to innovative and innovative technologies against market issues such as multi-lot production, environmental and safety issues, and cost reductions. Has been. Furthermore, the print quality has also been improved to a level comparable to other printing methods. As described above, flexographic printing has a great advantage in terms of water-based and solvent-free printing. Flexographic printing has already become mainstream in the packaging field in Europe and the United States, and there are signs of widespread use in Japan. Even if flexographic printing is performed on commonly used offset or gravure printing paper by using such flexographic technology, it is inferior in ink color development and cannot be printed with high density. The ink in the image area does not adsorb to the paper, causing a phenomenon of flowing, which is insufficient to improve the print quality.

  On the other hand, from the viewpoint of reducing waste and saving resources, it is a major social issue and a strong social issue to recycle and reuse the end of the purpose of use rather than discarding it as it is. It is also a request. Paper and paperboard that have ended their intended use fall under this category, and if they can be recycled as used paper pulp, it will be a great cost advantage.

  In addition, since the packaging paper needs to have a role of packaging and holding the goods, not only the printing quality but also the quality such as strength and rigidity is one of the important factors. However, waste paper pulp is weaker than virgin pulp, and in order to blend waste paper pulp as a wrapping paper, it has been unavoidable to reduce the blending ratio within a practically acceptable range. In addition, the addition of a paper strength agent has been conventionally performed. However, since there is a limit to the effect of improving the paper strength, there is a limit to the ratio of waste paper pulp. On the other hand, there has been proposed a technique for suppressing a decrease in strength due to the combination of waste paper pulp by more efficiently treating a used paper pulp treatment process, for example, a dust removal process and a deinking process. (Patent Document 1 and Patent Document 2)

  As a technique for achieving both printing quality and strength, for example, an amphoteric polyacrylamide type paper strength agent and a polyamide epichlorohydrin type paper strength agent are contained in the base paper, and a pigment layer is formed on one side of the base paper with wet strength. Is exemplified (Patent Document 3).

It has been proposed that the fiber orientation angle difference between the front and back sides and the fiber orientation ratio are adjusted to a certain range during base paper making, and a coating layer of 1 to 10 g / m ² is provided on at least one surface (Patent Document 4). .

In addition, a coating layer containing a pigment and an adhesive is formed on at least one side of a base paper which is formed by using 50% by weight or more of softwood kraft pulp and the longitudinal / lateral tensile strength ratio is adjusted to 1.7 or more. basis weight formed by ² coated packaging material of 100 to 500 g / ^{m 2} are presented (Patent Document 5). None of Patent Documents 3 to 5 assumes flexographic printing.

JP 2000-336590 A JP 2004-124281 A JP 2005-248394 A JP 2006-83487 A JP 2006-97149 A

  Although the present invention is a base paper using waste paper pulp, it is excellent in flexo ink color development at the time of flexographic printing, and is suitable for varnishing, laminating, etc., which is applied as packaging paper, and for bag making. It provides excellent coated packaging paper.

The present invention provides a coated and wrapping paper having a coating layer containing a pigment and an adhesive on at least one side of a base paper, wherein the base paper is 5 to 50% by weight of waste paper pulp deinked, and cationized starch and anionic It contains polyacrylamide as a paper strength agent, and further contains calcined kaolin as a pigment in the coating layer, and the specific tear strength in the machine direction and the transverse direction measured according to JIS P8116: 2000 is 6.5 to 5, respectively. It is a coated and wrapping paper characterized by being 18.0 mN · m ² / g and 7.0 to 19.0 mN · m ² / g.
The content of the calcined kaolin is preferably 20 to 100 parts by mass with respect to 100 parts by mass of the pigment.
It is preferable that talc contains 80 parts by mass or less with respect to 100 parts by mass of the pigment.
It is preferable that 2-40 mass parts of starch derivatives are contained with respect to 100 mass parts of pigments in the coating layer.

  According to the present invention, it has become possible to provide a coated and wrapping paper that is excellent in ink color development in flexographic printing and excellent in suitability for bag making even if used paper pulp is used.

  Pulp (hereinafter referred to as DIP) obtained by deinking used paper used in the present invention is, for example, used paper such as magazine used paper, flyer used paper, newspaper used paper, office used paper, information paper used paper, cardboard used paper, paper container used paper, Used after dedusting and deinking.

  Examples of pulps other than DIP include softwood unbleached kraft pulp (hereinafter referred to as NUKP), hardwood unbleached kraft pulp (hereinafter referred to as LUKP), softwood bleached kraft pulp (hereinafter referred to as NBKP), and hardwood bleached kraft pulp (hereinafter referred to as NBKP). , LBKP), softwood oxygen-bleached kraft pulp (NOKP), bleached oxygen bleached kraft pulp (NOKP) that has been subjected to the bleaching process using conifers and broadleaf trees, or semi-bleaching that has been bleached from one to two stages Pulp and the like.

  In order to supplement the paper strength required for the packaging paper after coating, which must be reduced due to the use of DIP, cationized starch and anionic polyacrylamide are selected from the commonly known paper strength agents in the base paper. In addition, appropriate blending is necessary. When the DIP content is less than 5% by mass, paper strength is easily obtained, but the environmental load is large and the cost is high. On the other hand, if the number of blended parts of DIP exceeds 50% by mass, it is necessary to add a large amount of the above paper strength agent in order to obtain a paper strength suitable for bag making, which is economically disadvantageous. As a result of intensive studies by the inventors, 5 to 50% by mass of DIP is blended in the base paper, and a balance between environmental load and cost can be achieved by appropriately mixing and blending cationized starch and anionic polyacrylamide as a paper strength agent. It was also found that the paper strength required for the packaging paper after coating could be secured. A preferable blending amount of DIP is 10 to 40% by mass. As content of paper strength agent, cationized starch is 0.1-1.0 mass% with respect to pulp mass, and anionic polyacrylamide is 0.05-0.5 mass% with respect to pulp mass. It is desirable to do. The addition amount of the sulfuric acid band is preferably 1.0 to 2.0% by mass with respect to the pulp mass.

  Internally added chemicals other than those described above can be used as necessary. For example, a sizing agent such as rosin, a drainage retention improver, a water-resistant agent such as polyamide polyamine epichlorohydrin, a dye, and the like are used.

There are no particular limitations on the paper making conditions of the base paper, and for example, commercial scale paper machines such as long net paper machines, gap former paper machines, round net paper machines, short net paper machines, etc. It can be appropriately selected and used. As the papermaking method, any method such as acidic papermaking, neutral papermaking, and weak alkali papermaking can be used. The basis weight of the base paper made under these papermaking conditions is 30 to 180 g / m ^{2, which} is a basis weight suitable for bag making, and is preferable as packaging paper. More preferably 60 to 150 g / ^{m 2.}

  In general, flexographic printing is performed using a water-type ink, so that the ink penetration varies depending on the degree of water absorption of the printed surface. For this reason, ink color development and halftone dot reproducibility in flexographic ink are greatly affected by the degree of water absorption on the printed surface and the amount of flexographic ink. When calcined kaolin is present in the coating layer formed on the surface of the packaging paper, the flexographic ink absorbability is extremely improved. By adjusting the blended quantity of this calcined kaolin and other pigments, various flexographic printing machines can be used. Applicable ink color development and excellent quality can be obtained.

  The reason why the calcined kaolin is contained in the coating layer to improve the flexibility of flexographic printing is not necessarily clear. However, the calcined kaolin is produced by treating kaolin produced in nature with a kiln or the like at a high temperature of about 800 ° C. The crystal water that is present in the crystal structure is released, the crystal structure is collapsed to become an amorphous structure, and it is opaque, porous, and has excellent ink absorbability. From this, the porosity of the calcined kaolin allows the ink to be taken into the pigment, and the solvent in the ink is absorbed uniformly, resulting in ink color development and uniformity, and a halftone dot due to improved adhesion. It is considered that reproducibility can be obtained. The content of the calcined kaolin is preferably 20 to 100 parts by mass, more preferably 40 to 90 parts by mass.

  Examples of pigments other than calcined kaolin used in the present invention include pigments commonly used in the papermaking field, such as clay, structured kaolin, engineered kaolin, talc, aluminum hydroxide, titanium dioxide, light calcium carbonate, heavy One or more of calcium carbonate, barium sulfate, zinc oxide, satin white, calcium sulfate and the like can be used. Among these, it is preferable to mix talc. When foreign material comes into contact with the coating surface and is rubbed during post-processing or bag-making processing, dirt due to adhesion of foreign material is likely to occur, whereas talc is a flat pigment that reduces frictional resistance when present in the coating layer. Since it has properties, it is possible to reduce contamination due to foreign matter. Generally, talc for papermaking has an average particle size of 1 to 5 μm measured by sedigraph and a chlorite content of 0 to 90%. Among them, the use of talc with a chlorite content of 5 to 50% is This is more preferable because the balance between the dispersibility of the pigment and the effect of reducing dirt during processing is balanced. The number of talc blending parts is preferably 80 parts by mass or less per 100 parts by mass of the pigment. When 5 parts by mass or more is blended, the effect is remarkably exhibited. Although the talc content varies depending on the chlorite content, it is more preferably 15 to 60 parts by mass. In addition, it is desirable to use pigments other than calcined kaolin in a range that does not impair the desired effect of the present invention from the viewpoint of the absorbability of flexographic inks. Absent.

  It is known that calcined kaolin significantly reduces the water retention of the paint. If the paint water retention is low, the paint is likely to penetrate into the base paper, and it becomes difficult to form a uniform coating layer on the base paper surface. Further, depending on the coating apparatus, coating stripes may be generated or coating may not be performed at all. Therefore, it is preferable to use a starch derivative. In addition, since the base paper using a large amount of DIP has a poor surface size and the paint easily penetrates into the base paper, the adhesive in the paint moves into the base paper and has the effect of improving the strength. In order to exert an effect, a starch derivative is desirable. Examples thereof include oxidized starch, esterified starch, etherified starch, dextrin, and cold water-soluble starch. The blending amount is preferably 2 to 40 parts by mass per 100 parts by mass of the pigment. 10-35 mass parts is further more preferable, and it is most preferable to mix | blend in the ratio of 15-30 mass parts.

  In addition, an additive such as an anti-slip agent and a dye may be used in combination in the paint used in the present invention as long as the effect on the ink color development is not impaired.

  As an adhesive in the paint, a water-dispersible resin or a water-soluble polymer can be used. As the water-dispersible resin, a known adhesive used in a general coated paper manufacturing field is appropriately used. For example, styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, conjugated diene copolymer latex such as styrene-methyl methacrylate-butadiene copolymer latex, acrylic ester and / or methacrylate ester Acrylic polymer latex such as a polymer or copolymer latex, vinyl polymer latex such as ethylene-vinyl acetate polymer latex, or these various polymer latexes were modified with a functional group-containing monomer such as a carboxyl group. A water-dispersible adhesive such as a polymer or copolymer latex can be used, and one or two or more can be appropriately selected and used. Of the water-dispersible resins exemplified, it is more preferable to use a styrene-butadiene copolymer latex having a good balance between cost and adhesive strength. Moreover, as a compounding quantity in the coating layer of a water dispersible adhesive agent, 8-30 mass parts is preferable with respect to 100 mass parts of pigments, More preferably, it is 10-25 mass parts. This is a range sufficient to sufficiently develop the strength of the coating layer since the fired kaolin has a porous characteristic as described above. Examples of the water-soluble resin include starches such as polyvinyl alcohol, oxidized starch, positive starch, esterified starch, and dextrin. One or more of these water-dispersible and / or water-soluble adhesives can be appropriately selected and used.

In the present invention, the coating layer of the paint containing calcined kaolin may be a single layer or a multilayer, but the total coating amount is preferably 0.5 to 10 g / m ² . When the coating amount is within this range, it is possible to obtain a coated and wrapping paper that is excellent in economic efficiency and excellent in water-colored flexographic ink color development. A more preferable coating amount is 1.5 to 7 g / m ² .

When applying the coating material of the present invention to a base paper, a coating device generally used for coated paper production can be used, for example, blade coater, air knife coater, roll coater, reverse roll coater, bar coater, curtain coater. , Die-slot coater, gravure coater, champlex coater, 2-roll size press coater, gate roll size press coater, film metering size press coater, etc. The surface is coated in a single layer or multiple layers. The solid content concentration of the pigment composition at the time of coating can be selected in the range of 10 to 75% by mass, but is applied so that the coating amount remains in the range of 0.5 to 10 g / m ^2. It is preferable to adjust appropriately considering the coater.
In the case of coated wrapping paper, since only the surface corresponding to the outer surface of the bag is printed, it is economically preferable for the present invention to coat only one side. However, when only one side is coated, the paper has a property of curling to the coated surface side, so it is preferable to correct the curl. For curl correction, a conventional method can be selected. If a gate roll coater is selected as the coater to apply the paint, the surface can be coated with a baked kaolin-containing paint and the back side can be applied simultaneously with a curl correction paint in one pass. It is more economically preferable to apply.

  The coated packaging paper coated according to the present invention can be subjected to a calendar process in order to further improve the coated surface and printability. For example, a machine calender that nips between metal rolls, a super calender that uses a cotton roll as an elastic roll, and a soft nip that uses a synthetic resin roll as an elastic roll. The soft nip calender can set the heat-resistant temperature on the surface of the synthetic resin roll higher than that of the cotton roll, so it can be processed at high temperatures, and compared with the super calender when the same smoothness is targeted. This is a preferred embodiment because the treatment linear pressure can be set low.

As the strength of the coated wrapping paper of the present invention, the longitudinal specific tear strength is 6.5 to 18.0 mN · m ² / g, and the lateral specific tear strength is 7.0 to 19.0 mN · m ^2. The range of / g is important. If the specific tear strength in the machine direction is less than 6.5 mN · m ² / g and the specific tear strength in the transverse direction is less than 7.0 mN · m ² / g, Problems such as tearing occur in the bottom pasting process, making bag making difficult. In order to produce such that the specific tear strength in the longitudinal direction exceeds 18.0 mN · m ² / g or the specific tear strength in the lateral direction exceeds 19.0 mN · m ² / g, A large amount of force agent is required, which is economically disadvantageous. As the more preferable range of the ratio tear, in the longitudinal direction 8~13mN · ^m 2 / g, in the transverse direction is 9~14mN · ^m 2 / g.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these ranges. In the examples, “parts” and “%” indicate parts by mass and mass% unless otherwise specified.

Example 1
(Creation of paint)
Baked kaolin (trade name: Ancilex 93, manufactured by BASF) 90 parts, Kaolin (trade name: Milagros J, manufactured by BASF) 10 parts, adhesive (trade name: PA-8064, manufactured by A & L), oxidation A paint composed of 20 parts of starch (trade name: GRS-T110, manufactured by Oji Cornstarch Co., Ltd.) (both in terms of solid content) was prepared to a concentration of 40%.

Blended with 35% NBKP of 560 ml CSF, 30% of LBKP of 460 ml CSF, and 35% waste paper pulp from deinked newspaper waste paper, and cationized starch (trade name: Pillar P3YK, manufactured by Pillar Starch Co., Ltd.) ) 0.35%, sulfuric acid band 1.3%, sizing agent (trade name: Perosa E3655, manufactured by Toho Chemical Industry Co., Ltd.) 0.4%, anionic polyacrylamide (trade name: Polystron 117, manufactured by Arakawa Chemical Industries, Ltd.) ) Paper is made with the stock prepared by adding 0.2%, and then the above coating is applied on one side with a gate roll coating device so that the dry mass is 3 g / m ² (solid content). Coated with oxidized starch (trade name: GRS-T110, manufactured by Oji Cornstarch Co., Ltd.) to 0.5 g / m ² , dried and calendered to give 6.0% paper moisture. A coated packaging paper having a basis weight of 80 g / m ² was obtained.

Example 2
In Example 1, coated wrapping paper was obtained in the same manner as in Example 1 except that the pigment in the paint was 70 parts of calcined kaolin and 30 parts of talc (trade name: Microtouch, manufactured by Nippon Mystron).

Example 3
In Example 1, the pigment in the paint was 30 parts of calcined kaolin, 70 parts of talc, 5 parts of adhesive, 35 parts of oxidized starch, and the coating amount was 12 g / m ^2. Coated packaging paper was obtained in the same manner as in Example 1 except that the product name: Gohsenal KS (manufactured by Nippon Synthetic Chemical Co., Ltd.) was applied and dried to 0.5 g / m ² .

Example 4
In Example 1, a coated packaging paper was obtained in the same manner as in Example 1, except that the surface coating amount was 0.5 g / m ² and the starch coating amount on the opposite surface was 0.2 g / m ² . .

Example 5
In Example 1, except that the pigment in the paint was 15 parts of calcined kaolin, 25 parts of kaolin, 60 parts of heavy calcium carbonate (trade name: Hydrocurve 90 manufactured by Bokuhoku Kasei Co., Ltd.) and 1 part of oxidized starch, Coated packaging paper was obtained in the same manner as in Example 1.

Comparative Example 1
In Example 1, it was carried out except that the base paper pulp was NBKP 10%, the waste paper pulp was deinked 90%, polyacrylamide was not added, and the oxidized starch was double-sided coating amount 0.4 g / m ^2. Wrapping paper was obtained in the same manner as in Example 1.

Comparative Example 2
A coated wrapping paper was obtained in the same manner as in Example 2 except that the base paper of Comparative Example 1 was used and the paint of Example 2 was applied to the surface.

Comparative Example 3
In Example 1, coated wrapping paper was obtained in the same manner as in Example 1 except that the pigment in the coating solution was 50 parts kaolin and 50 parts heavy calcium carbonate.

Comparative Example 4
In Example 1, a coated packaging paper was obtained in the same manner as in Example 1 except that the anionic polyacrylamide was not blended in the pulp for base paper.

Comparative Example 5
In Example 1, a coated packaging paper was obtained in the same manner as in Example 1 except that the cationized starch was not blended in the pulp for base paper.

  The obtained coated packaging paper was evaluated by the following evaluation method, and the obtained results are shown in Table 1. The measurement and evaluation in the present invention were performed in an environment of 23 ° C. and 50% RH unless otherwise specified.

(Specific tear strength)
Calculation was performed according to JIS P8116.

(Color development of ink in flexographic printing)
K printing proofer (manufactured by RK Print-Coat Instruments), an anilox plate engraved at 100 lines / inch, and water-based flexo indigo ink (trade name: Wraptone HR, manufactured by Sakata Inks) Printed on craft paper. The printed surface was measured for cyan ink density with a color reflection densitometer (Model 404G, manufactured by X-Rite).

(Printing part ink flow)
The portion printed by the K printing proofer was observed, and whether or not the ink on the printed surface was uniformly fixed was visually evaluated with a magnifying glass.
[Evaluation criteria]
(Double-circle): The ink is uniformly fixed with a magnifier and visual observation.
○: When magnifying and observing the printed part, there are some non-uniform parts, but they are fixed uniformly by visual inspection.
X: The ink is difficult to absorb on the paper, the excess ink is swimming, and the ink fixing surface is uneven by visual observation.

(Bag making suitability)
Using an automatic bag making machine, it was processed into a square bottom bag (hand bag) having a bottom width of 115 mm, a bag width of 315 mm, and a bag length of 315 mm. After processing, a visual evaluation was performed on the cracks in the folded portion and the printed portion.
[Evaluation criteria]
(Double-circle): A crack does not generate | occur | produce at all.
○: A very small crack occurred.
X: The crack generate | occur | produced regularly.

As is apparent from Table 1 above, Examples 1 to 5 satisfying the requirements of the present invention have no ink flow in the printing portion and ink colorability compared to Comparative Examples 1 to 5 that lack any of the requirements of the present invention. The bag making suitability was also good. That is, Comparative Examples 1 and 3 are inferior in flexographic printing suitability because they do not have a coating layer containing calcined kaolin, and Comparative Examples 2, 4 and 5 contain 70 parts of calcined kaolin in the coating layer. Although excellent in ink coloring property, Comparative Example 2 contains 90% DIP, and Comparative Examples 4 and 5 contain only one of cationized starch and anionic polyacrylamide in the base paper pulp. However, the specific tear strength was insufficient, cracking occurred at the folded part and printed part during bag making, and the bag making suitability was poor.
As described above, according to the present invention, it is possible to obtain a coated and wrapping paper having excellent ink color development and printing surface finish with respect to flexographic printing inks, particularly aqueous flexographic inks, and excellent in bag making suitability.

Claims (4)

A coated and wrapping paper having a coating layer containing a pigment and an adhesive on at least one side of a base paper, wherein the base paper is 5-50% by weight of deinked waste paper pulp, and cationized starch and anionic polyacrylamide are paper In addition, it contains calcined kaolin as a pigment in the coating layer, and the specific tear strength in the machine direction and the transverse direction measured according to JIS P8116: 2000 is 6.5 to 18.0 mN, respectively.・ Coated packaging paper characterized by m ² / g and 7.0 to 19.0 mN · m ² / g.   The coated packaging paper according to claim 1, wherein the content of the calcined kaolin is 20 to 100 parts by mass with respect to 100 parts by mass of the pigment.   The coated packaging paper according to claim 1 or 2, wherein talc contains 80 parts by mass or less with respect to 100 parts by mass of the pigment.   The coated packaging paper according to any one of claims 1 to 3, wherein the coating layer contains 2 to 40 parts by mass of a starch derivative with respect to 100 parts by mass of the pigment.