JP2010229575A - Multilayered paper obtained by papermaking, and having colored layer with less decoloration - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayered paper obtained by paper making, used for producing bags and corrugated board cases, equipped with a touch feeling of a pulp raw material having less surface staining (decoloration) caused by wetting with water, moisture and abrasion. <P>SOLUTION: This multilayered paper obtained by the papermaking, and having a colored layer on its surface contains a sulfide dyestuff, a direct dyestuff and/or a coloring pigment in the colored layer, and has 1.3 to 24.2 ΔEa obtained by immersing the multilayered paper obtained by the papermaking, having 5 cm×5 cm square in water at 20°C for 30 sec, then nipping the multilayered paper with filter paper (manufactured by ADVANTECH Φ18) for 30 sec by a sheet press in accordance with the JIS P8222 (1998), drying and then calculating by using the calculating method of a color difference in accordance with the JIS Z8730 (2002), method for showing the color-the color difference of a material color, regarding the filter paper brought in contact with the colored layer side of the multilayered paper. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a multilayer paper used for corrugated cardboard cases and bag making applications, and more particularly to a multilayer paper having a colored layer with little color fading in a multilayer paper board.

  The wrapping paper for bag making is a paper used for a packaging base material for shopping such as a handbag, a square bottom bag, or an envelope. In recent years, it has been desired that such wrapping paper has not only protection of contents but also fashionability and functionality. In particular, handbags used for shopping purposes are favored for colorful and dark colors, and papers with printed or pulp-colored paper are used. In the printing type, glossy varnish or lamination is applied on the printing surface to prevent surface contamination (color loss) due to water wetting, moisture, or rubbing.

  However, a handbag of a papermaking type using colored pulp has a problem that the color of the colored pulp elutes and is transferred to the clothes worn by water. Compared with printing type bag making, the paper making type bag making is superior in that it has a good texture without impairing the texture of the pulp, and paper making type paper with less color fading is desired. .

  For example, in Patent Document 1, it is necessary to use a reducing agent, an oxidizing agent, and a chemical with a high electrolyte concentration in order to dye conventional fibers, which causes a problem in treating these waste liquids after dyeing. However, there is a disclosure of a method for producing a water-soluble sulfur dye that can be used without the addition of a reducing agent. However, the invention of Patent Document 1 is a method of directly dyeing a cotton fabric or a fabric such as a woven fabric in which cotton and polyester are mixed, and the dyeing temperature is 50 to 75 ° C. In the papermaking process, setting the wet paper temperature to the above condition requires excessive energy, which is problematic in terms of cost.

  Patent Document 2 discloses a technique in which coloring properties are improved in a pH range of 7.5 to 11.0 and a temperature range of 60 to 120 ° C. in order to color a polyamide or a polyamide-containing substrate with a sulfur dye. is there.

  Further, Patent Document 3 describes any combination of fibers or fiber structures (cellulose fibers such as cotton and hemp, animal fibers such as hair and silk, synthetic fibers such as nylon, polyester and acetate, and regenerated fibers such as rayon. In order to dye cotton, yarn, woven fabric, knitted fabric, non-woven fabric, and paper sheet, a pre-treatment is performed by immersing in a mixed solution of a cationizing agent and an alkaline auxiliary agent at 60 to 80 ° C., and then fixing with a dye. There is a disclosure of a technique in which dyeing is performed by immersing in a mixed solution in which one or both of a colorant and a color former are mixed.

  However, both require heating and require excessive energy.

Japanese Patent Laid-Open No. 5-140879 Special table 2003-504532 gazette JP-A-11-158785

  The present invention has been made in view of the above-described circumstances, and is a multilayer paper for bag making and corrugated cardboard cases having a texture of pulp material with less surface contamination (color loss) due to water wetting, moisture, and rubbing. The purpose is to provide paper. It is another object of the present invention to provide a multi-layer paper that has good dye fixing properties while suppressing the elution of other dyes while the dyeing temperature is as low as less than 50 ° C. (45 ° C.).

The present invention is a multilayer paper having a colored layer on the surface,
The colored layer contains a sulfur dye, a direct dye and / or a color pigment,
After immersing the multilayer paper of 5 cm × 5 cm square in water at 20 ° C. for 30 seconds, the multilayer paper is filtered with a sheet press according to JISP8222 (1998) for 30 seconds (Φ18 manufactured by ADVANTEC). ΔEa calculated by a color difference calculation method according to JISZ8730 (2002) color display method-color difference of object color is 1.3 to It is a multilayer paper characterized by being 24.2 or less.

In the present invention, the sulfur dye is an anionic sulfur dye,
The direct dye is an anionic direct dye;
The ratio (mass ratio) of the anionic sulfur dye and the anionic direct dye is 50:50 to 30:70, and the total amount of the dye added to the dry mass of the pulp contained in the colored layer is 1 to 12 mass. %
Using a light resistance tester according to JISB7751 (2007), the test piece of the multilayer paper is irradiated with an ultraviolet carbon arc at 45 ° C. for 4 hours, and the color tone of the test piece after irradiation and the test piece before irradiation is measured. The calculated ΔEb is preferably 1.73 or less.

The present invention is also a method for producing the multilayer paper,
Add components to the raw pulp slurry for forming the colored layer in the order of anionic sulfur dye and / or color pigment, aluminum sulfate, anionic direct dye, and aluminum sulfate. The pulp slurry has a pH of 4.2 to 6.8, and the pulp slurry after the final addition of aluminum sulfate has a pH of 4.0 to 5.0. is there.

  INDUSTRIAL APPLICABILITY The present invention can provide a multi-layer paper having a texture of a pulp material with less surface contamination (color loss) due to water wetting, moisture, and rubbing. When producing this multi-layer paper, it is possible to provide a multi-layer paper having good dye fixing property while suppressing the elution of other dyes while the dyeing temperature is as low as less than 50 ° C. (45 ° C.). .

  Hereinafter, an embodiment of the multi-layer paper according to the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, It cannot be overemphasized that the structure can be variously changed in the range which does not deviate from a claim.

  The multi-layer paper according to the present embodiment (hereinafter referred to as “the multi-layer paper”) is composed of three paper layers, a front colored layer, an intermediate layer, and a back layer.

[Raw material pulp]
Raw material pulp used for forming each layer constituting this multilayer paper is hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), softwood unbleached kraft pulp ( NUKP), pulp and chips chemically processed from wood fibers such as softwood hardwood sulfite pulp and softwood sulfite pulp, or non-wood fibers such as kenaf and hemp as non-wood fiber materials. Pulp after mechanically pulping treated pulp and chips, chemi-ground pulp mechanically pulped with chemicals added to wood or chips, and digesters until chips are softened, then refiner, etc. Virgin pulp such as semi-chemical pulp and kraft pulp, semi-chemical pulp Office waste paper including enzyme-bleached pulp is deinked, bleached pulp, milk pack waste paper, high quality cut waste paper, coat cut waste paper, upper white, special white, medium white, etc. Examples include kraft envelopes, imitations, recovered pulp obtained from magazine waste paper, and the like. In addition, there is an advantage that an environmental load is reduced when much waste paper pulp is used.

  This multi-layer paper is colored by coloring the surface of the multi-layer paper by forming a colored layer by blending and dyeing sulfur dyes and direct dyes and / or color pigments into the raw material pulp of the surface layer. is doing. The present multi-layer paper can achieve a desired purpose by mixing a sulfur dye and a direct dye and / or a color pigment in at least the surface layer raw material pulp. A sulfur dye and a direct dye and / or color pigment may be blended in the middle layer and / or the back layer as a colored layer.

  Sulfurized dye is a water-insoluble dye containing many sulfur bonds in the dye molecule. It is reduced by a reducing agent (usually sodium sulfide) in the dye bath, adsorbed on the fiber in the form of leuco dye, and then oxidized to water. It is a dye that completes dyeing as an insoluble dye. Specifically, vulcanized diformyl metatoluidine and benzine, vulcanized metatoluylenediamine, vulcanized 3-amino-7-oxyphenazine, 2-4 dinitro-4-oxydiphenylamine And vulcanized 1,5 dinitronaphthalene, and the like. Of these, anionic sulfur dyes are preferred because they are less likely to lose color due to water wetting and moisture, and those obtained by vulcanizing 2,4 dinitrophenol and picric acid are particularly preferred. For example, “Kayaku Sulfur” series manufactured by Nippon Kayaku Co., Ltd., “Mitsui Sulfur” series manufactured by Mitsui BSF Dye Co., Ltd., and the like can be used.

  The direct dye is a dye having a relatively large molecular weight and affinity for cellulose fibers among water-soluble anionic dyes. Specifically, an anionic direct dye, a cationic direct dye, or the like is used, but an anionic direct dye is more preferable because of less color fading due to water wetting or moisture.

  Anionic direct dyes are originally made for the purpose of dyeing cellulose fibers and are dyed directly on cellulose fibers from a dye bath containing a neutral salt. From the chemical structure, it can be divided into azo, stilbene, thiazole, dioxazine, phthalocyanine and the like. As the anionic direct dye, those composed of an azo dye having an azo group (—N═N—) as a chromophore are generally used, but any anionic direct dye can be used. Cationic direct dyes are those in which the end of the chromophore is a cationic group, for example, a molecule having a sulfone group, a phenolic hydroxyl group, a carboxyl group, etc. in the molecule, in the form of a sodium, potassium or ammonium salt It is a dye of structure. Examples of anionic direct dyes include Clariant Japan Co., Ltd., Derma Carbon BFN and Cartasol Yellow 5GE liq, and Nippon Kayaku Co., Ltd. Kayaft Yellow G.

  The color pigment is a general term for those unnecessary for water and oil, and includes inorganic pigments, organic pigments, and lake pigments. In the present invention, Grand Black YT-100 manufactured by Gokoku Dye Co., Ltd. may be mentioned.

  The sulfur dye (especially anionic sulfur dye) is preferably added in an amount of 0.5 to 6.0% by weight, more preferably, based on the dry weight of the raw pulp used for forming the surface colored layer of the multilayer paper. 0.6 mass% to 3.6 mass% is added. If the addition amount of the sulfur dye is less than 0.5% by mass, the color becomes light, so even if it is eluted, it is not known. If it exceeds 6.0% by mass, it will be difficult for the color fading to occur due to the auxiliary effect of the anionic sulfur dye, but there will be a difference in the color fading due to water wetting, moisture, and rubbing even when the proportion is increased. There is no excess quality and the manufacturing cost is high.

  Further, the total amount of direct dyes and / or color pigments (in particular, only an anionic direct dye) is preferably added, preferably 0.5 to 8.4% by mass, more preferably 1.0 to 6.0% by mass. . If the added amount is less than 0.5% by mass, the color becomes light, so it is not known even if it is eluted. Also, by using a combination of sulfur dyes (especially anionic sulfur dyes) and direct dyes and / or color pigments, the fixability of the dye is good and the elution of other dyes is less than 50 ° C., which is the subject of the present invention. It is possible to produce a multi-layer paper that suppresses the above. Even if it is added in excess of 8.4% by mass, the dye does not stay in the raw material pulp, making it difficult to exhibit the dyeing effect.

  The total addition amount of the dye and the color pigment with respect to the dry mass of the raw material pulp contained in the front colored layer is preferably 1 to 14 mass%, more preferably 2 to 12 mass%. If the total addition amount is less than 1% by mass, the color becomes light, so it is not known even if it is eluted. On the other hand, even if added in excess of 14% by mass, the dye does not stay in the raw material pulp, making it difficult to exhibit the dyeing effect.

  The mass ratio of the addition amount of the sulfur dye (particularly anionic sulfur dye) and the direct dye and / or color pigment (particularly anionic direct dye) contained in the surface coloring layer is preferably 50:50 to 30:70. When the ratio of the anionic sulfur dye is less than 30, the auxiliary effect of the anionic sulfur dye as a fixing agent is weakened, so that the color of the dye is easily lost due to water wetting, moisture, or rubbing. Conversely, if the ratio of the anionic sulfur dye exceeds 50, it will be difficult to discolor due to the auxiliary effect of the anionic sulfur dye as a fixing agent, but it may be caused by water wetting, moisture, or rubbing compared to when the ratio is increased. There is no difference in color fading, resulting in excessive quality and high manufacturing costs.

As described above, in the present invention, the raw material pulp of the surface layer is dyed with a sulfur dye and a direct dye and / or a color pigment to form a colored layer, and further, a sulfur dye (especially anionic sulfur). Dye) and direct dyes and / or color pigments (especially anionic direct dyes) are added in a predetermined ratio at a predetermined ratio, so that this multilayer paper having less surface contamination (color loss) due to water wetting, moisture and rubbing can be obtained. As a scale, ΔEa was obtained to be 1.3 to 24.2 or less. Moreover, preferably ΔEa can be set to 1.3 to 15.3 or less. On the other hand, in the case of a comparative example which does not take the configuration of the present invention, the dye elution is particularly large when wet, and ΔEa exceeds 24.5. ΔEa is obtained by immersing the multilayer paper of 5 cm × 5 cm square in 20 ° C. water for 30 seconds and then filtering the multilayer paper for 30 seconds with a sheet press according to JISP8222 (1998). It is calculated by the color difference calculation method according to JISZ8730 (2002) color display method-color difference of the object color for the filter paper which is sandwiched between ADVANTEC Φ18), dried, and in contact with the surface coloring layer side of this multilayer paper. This is the difference between the color tone of the multilayer paper before contact with the multilayer paper and the color tone of the filter paper after contact with the multilayer paper. A smaller value of ΔEa indicates that color fading due to water wetting is less likely. The multilayer paper made by the conventional method had a ΔEa exceeding 24.2.
ΔEa = {(L1-L2) ² (a1-a2) ² (b1-b2) ² } ^1/2
L1, a1 and b1 are the color tones of the filter paper before contact with the present multilayer paper L2, a2 and b2 are the color tones of the filter paper after contact with the present multilayer paper. Further, as described above, the configuration of the present invention is adopted. Thus, the multilayer paper can be prevented from fading even when exposed to light. Specifically, an ultraviolet carbon arc was irradiated to the test piece of this multilayer paper for 4 hours at 45 ° C. with a light resistance tester according to JISB7751 (2007), and a test piece after irradiation and a test piece before irradiation The calculated ΔEb can be 1.73 or less, and more preferably ΔEb can be 0.96 to 1.45 or less. ΔEb is a value calculated from the difference between the color tone of the multi-layer paper before the light resistance test and the color tone of the multi-layer paper before the light resistance test. The smaller this value is, the less fading is caused by exposure.
ΔEb = {(L1-L2) ² (a1-a2) ² (b1-b2) ² } ^1/2
L1, a1 and b1 are the color tones of the colored layer of the multilayer paper before ultraviolet irradiation L2, a2 and b2 are the tones of the colored layer of the multilayer paper after ultraviolet irradiation Surface coloring of the multilayer paper The layer is formed by dyeing the raw pulp by adding a sulfur dye and a direct dye and / or color pigment to the raw pulp slurry. At this time, in obtaining the multilayer paper having less surface contamination (color loss) due to water wetting, moisture and rubbing of the obtained multilayer paper, a sulfur dye, a direct dye and / or a color pigment, and further aluminum sulfate are used. The addition method of is important. Rather than adding each component to the pulp slurry at once, by adding them individually in the following order, the dyes and / or dyes can be effectively used under normal temperature conditions (approximately 20 ° C.) to less than 50 ° C. The pigment is firmly fixed on the raw material pulp fiber, and as a result, the present multilayer paper can be made with less surface contamination (color loss) due to water wetting, moisture and rubbing. When no color pigment is added, an anionic sulfur dye, aluminum sulfate (i) (the first addition of aluminum sulfate), an anionic direct dye, aluminum sulfate (ii) (a second addition of aluminum sulfate) It is preferable to perform coloring in the order of addition. When adding a color pigment, it is preferable to color in the order of addition of an anionic sulfur dye, aluminum sulfate (i), a color pigment, an anionic direct dye, and aluminum sulfate (ii). In addition, after adding an anionic sulfur dye, it is preferable to adjust pH to 4.5-6.8 and leave it for 3 minutes or more.

  The amount of aluminum sulfate (i) added is preferably 1.5 to 4.0% by mass, more preferably 2.0 to 3.5% by mass. When the added amount of aluminum sulfate (i) is less than 1.5% by mass, the auxiliary effect of the anionic sulfur dye as a fixing agent is weakened, so that the color of the dye is easily lost due to water wetting, moisture and rubbing. . Conversely, if it exceeds 4.0% by mass, it will be difficult to discolor due to the auxiliary effect of the anionic sulfur dye as a fixing agent, but the color due to water wetting, moisture and rubbing will be higher than when the additive is increased. There will be no difference in drop, resulting in excessive quality and high manufacturing costs.

  In addition, the amount of aluminum sulfate (sulfuric acid band) added is preferably within the above addition range in consideration of the influence on the pH of the raw slurry. That is, the addition range exhibits a synergistic effect both in the role of the anionic sulfur dye as a fixing agent and in the dyeability in the pH range described later.

  The pH of the raw pulp slurry after the addition of aluminum sulfate (i) is preferably 4.0 to 8.0, more preferably 4.5 to 6.8. When the pH is less than 4.5, the oxidation reaction is instantaneously performed, so that the reaction does not spread over the whole, resulting in hair dyeing or fixing failure, and the color of the dye is easily lost due to water wetting, moisture, or rubbing. On the other hand, if the pH exceeds 8.0, the oxidizing agent (aluminum sulfate) necessary for the oxidation reaction is insufficient, and unreacted parts and poor fixing can be made. Therefore, the color of the dye is easily lost due to water wetting, moisture, and rubbing. .

  The addition amount of aluminum sulfate (ii) is preferably 3.0 to 7.0 mass%, more preferably 4.0 to 6.0 mass%. When the added amount of aluminum sulfate (ii) is less than 3.0% by mass, the auxiliary effect of the anionic sulfur dye as a fixing agent is weakened, so that the color of the dye is easily lost due to water wetting, moisture, or rubbing. . On the other hand, when the content exceeds 7.0% by mass, the acidity is high, so the cellulose molecules are decomposed by sulfate ions generated from aluminum sulfate, and are easily discolored and deteriorated. There is a tendency that it is not suitable as a packaging base material for shopping.

  The pH of the raw pulp slurry after adding aluminum sulfate (ii) is preferably 3.8 to 5.4, more preferably 4.0 to 5.0. If the pH is less than 3.8, the acidity is high, so cellulose molecules are easily decomposed and deteriorated by sulfate ions generated from aluminum sulfate, resulting in poor storage stability and the cause of ruled cracks. It is not suitable as a packaging substrate for shopping purposes. If the pH exceeds 5.4, the anionic direct dye lacks sufficient oxidizing agent (aluminum sulfate), so the fixing is poor and unreacted parts remain, and the dye discolors due to water wetting, moisture and rubbing. As a result, the auxiliary effect of the sulfur dye as a fixing agent is reduced.

  In addition, the multi-layered paper is provided with a filler, a yield improver, a freeness improver, a paper strength enhancer, a fixing agent, a fluorescent whitening agent, an antifoaming agent, a pitch control agent, and a slime control agent as necessary. Further, an internal additive for papermaking such as a bulking agent and a foaming agent can be appropriately blended.

  As the paper strength enhancer, various materials such as PAM, oxidized starch, modified starch, PVA, polyethyleneimine, and epichlorohydrin resin are used. The addition amount of the paper strength enhancer is preferably 0.5 to 4.0% by mass with respect to the dry mass of the pulp.

  It is preferable that the raw material pulp used for the surface layer is adjusted to a freeness of 200 to 370 ml, particularly 250 to 320 ml. When the freeness of the surface layer is less than 200 ml, the fibers are likely to become dense, and the dewatering failure of the multilayer paper is generated. On the other hand, if it exceeds 370 ml, the dewaterability will be good, but the fibers will tend to be loose, and the texture of the multilayer paper will be poor. That is, the cosmetic properties of the multi-layered paper are deteriorated.

  The raw material pulp used for the middle layer and the back layer is preferably adjusted to a freeness of 250 to 500 ml, particularly 300 to 400 ml. If the freeness of the middle layer is less than 250 ml, the fibers are likely to become dense, resulting in poor dewatering of the multilayer paper and poor drying. On the other hand, if the freeness of the middle layer exceeds 500 ml, the fibers tend to become sparse, resulting in poor texture of the multilayer paper.

  In addition, as a method for adjusting the freeness of the raw material pulp, a known beating machine such as a single disc refiner (SDR), a double disc refiner (DDR), or a conical refiner can be used.

  In addition, in this specification, freeness is based on the freeness test method of a JIS-P8121 (1995) pulp after disintegrating a sample with a standard disintegrator based on the JIS-P8220 (1998) disaggregation method. This is a value measured by a Canadian standard freeness tester.

Although the basic weight of this multilayer paper is not specifically limited, Usually, 80-320 g / m < ² >, Preferably it is 120-280 g / m < ² >. When the basis weight is less than 80 g / m ² , it is difficult to ensure the strength when the multilayer paper is processed into corrugated base paper. On the other hand, when the basis weight exceeds 320 g / m ² , not only is the quality excessive, but the manufacturing cost is increased. In addition, the basic weight in this specification is the value measured based on the basic weight measuring method of JIS-P8124 (1998).

Further, in making the multilayer paper, JIS-P8140 (1998) is used by adding a known sizing agent such as an acidic rosin sizing agent, a neutral rosin sizing agent, or an alkyl ketene dimer in order to adjust water absorption. 15 to 80 g / ^{m 2} Cobb sizing degree of the measured paper with a contact time of 120 seconds in accordance with), is preferably adjusted preferably so that 20 to 50 g / ^{m 2.}

  The paper machine used for the production of the multilayer paper is not particularly limited. For example, a long net paper machine, a twin wire paper machine, a circular net paper machine, a short net combination machine, a Yankee Various paper machines known in the art such as a paper machine and an inclined wire paper machine can be appropriately used.

  Further, the moisture content of the wet paper immediately after the pressing step in making the multilayer paper is more preferably 55 to 65%. If the wet paper moisture is less than 55%, there is a problem of curling after drying after drying in a subsequent dryer process. If the moisture content of the wet paper exceeds 65%, color transfer may occur due to insufficient drying when winding the paper with a reel. The wet paper moisture is measured in accordance with JISP8127 moisture test method-dryer method.

  Furthermore, the subject of the present invention is dried by bringing the colored layer side surface of the wet paper immediately after the pressing step into contact with a mirror-finished cylindrical dryer surface of 3 m or more at a holding angle of 180 to 270 °. Can be solved efficiently. When the drip angle of the dryer is less than 180 °, it is difficult to press and dry the paper, and when the paper is taken up with a reel, the paper may be transferred due to insufficient drying. Also, if the drip angle of the dryer exceeds 270 °, there is a problem of curling after drying due to the problem of time and angle for pressure bonding to the paper on only one side.

  The multilayer paper according to the present invention has been described for the case where the paper layer is composed of three layers. However, the middle layer may be composed of two or more layers, and may be composed of four or more paper layers.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

  In order to confirm the effect of this multilayer paper, the following various samples were produced and the test which evaluates the quality with respect to each of these samples was done. In addition, in a present Example, the numerical value which shows a mixing | blending, a density | concentration, etc. is a numerical value based on the mass of a solid active ingredient. Moreover, since the pulp, chemical | medical agent, etc. which are shown in a present Example are only examples, it cannot be overemphasized that this invention is not restrict | limited by these Examples, and can be selected suitably.

  In order to compare with 18 types of multi-layer papers (referred to as “Example 1” to “Example 18”) according to the present invention and these Examples 1 to 18, three types of paperboards are used. (This is referred to as “Comparative Example 1” to “Comparative Example 3”) was fabricated with the configuration shown in Table 1.

[Examples 1 to 18]
(Creation of base paper)
<Surface>
Using 100% by mass of hardwood bleached kraft pulp (LBKP), a double pulp refiner was used to adjust the raw pulp so that the freeness (CSF) was 300 ml, thereby preparing a raw pulp slurry. To this raw material pulp slurry, 1.0% by mass of an anionic sulfide dye (Clearant Japan Co., Ltd., Direul Black PFT Liquid) is added, and 3.0% by mass of aluminum sulfate is added, followed by an anionic direct dye (Clariant Japan Co., Ltd.) 1.0% by mass of Derma Carbon BFN) manufactured by the company was added, and 4.0% by mass of aluminum sulfate was further added. The temperature when the anionic sulfur dye and the anionic direct dye were added was 45 ° C. As a sizing agent, 0.75% by mass of an acidic rosin sizing agent (manufactured by Modern Chemical Industry Co., Ltd., R50) is added, and a paper strength enhancer (Harima Kasei Co., Ltd., Hermide RB32) is added by 0.4% by mass. A raw material pulp slurry for the surface layer was prepared.

Example 2
As a pigment, Grand Black YT100 manufactured by Mikuni Color Co., Ltd. was used.

<Middle layer>
The raw pulp was prepared by using 100% by mass of the waste paper pulp that had been cut off from the coat and adjusting the freeness (CSF) to 350 ml with a double disc refiner. A fixing agent, a sizing agent, and a paper strength enhancer were added to the raw pulp slurry. 0.4% by mass of a sulfuric acid band was added as a fixing agent. Further, 0.75% by mass of an acidic rosin sizing agent was added as a sizing agent, and 0.4% by mass of a paper strength enhancer was further added to prepare an intermediate layer raw material pulp slurry.

<Back layer>
The raw pulp was adjusted by using 100% by mass of the waste paper pulp and the double disc refiner so that the freeness (CSF) was 400 ml, thereby preparing a raw pulp slurry. A fixing agent and a sizing agent were added to the raw pulp slurry. In addition, 0.4% by mass of a sulfuric acid band was added as a fixing agent. Further, 0.75% by mass of an acidic rosin sizing agent was added as a sizing agent, and 0.4% by mass of a paper strength enhancer was further added to prepare a raw material pulp slurry for the back layer.

Using the surface layer, middle layer, and back layer raw pulp slurries, using a circular mesh 5-layer paper machine, the surface layer, the middle layer, and the back layer raw pulp slurries were combined and mirror-finished with a dryer The colored layer surface was pressure-dried and multilayer paper (paperboard) having a colored layer composed of a five-layer base paper having a basis weight of 170 g / m ² was made.

  The color difference ΔEa and the color difference ΔEb were measured by the following method.

(Comparative Examples 1-3)
The test was conducted in the same manner as in the example.

  In Comparative Example 1, an anionic direct dye (manufactured by Clariant Japan Co., Ltd., Derma Carbon BFN), aluminum sulfate, the same anionic direct dye as in Example, and aluminum sulfate were added in this order, and color difference ΔEa and color difference ΔEb were measured.

  In Comparative Example 2, a cationic direct dye (manufactured by Clariant Japan Co., Ltd., Cartazole Turkis K-RL), aluminum sulfate, the same anionic direct dye as that used in the example, and aluminum sulfate were added in this order, and color difference ΔEa and color difference ΔEb were added. Was measured.

  In Comparative Example 3, a cationic direct dye (manufactured by Clariant Japan Co., Ltd., Cartazole Turkis K-RL), aluminum sulfate, the same cationic direct dye, and aluminum sulfate were added in this order, and color difference ΔEa and color difference ΔEb were measured. .

  “Color difference ΔEa” is obtained by using a 5 cm × 5 cm square multi-layer paper as a sample, immersing the sample in water at 20 ° C. for 30 seconds, and then using a sheet press according to JISP8222 (1998) for 30 seconds. The sample is sandwiched between filter papers (Φ18 manufactured by ADVANTEC), dried, and then the color tone of the filter paper in contact with the colored layer surface of this sample is measured using a colorimetric color difference meter (ZE2000, manufactured by Nippon Denshoku Industries Co., Ltd.). The color tone of the filter paper before coming into contact with the sample was measured, and the color difference was calculated by a color difference calculation method according to JISZ8730 color display method-object color difference.

“Color difference ΔEb” is obtained by using a multi-layer paper having a size of 6 cm × 4.5 cm or more as a sample, using a light resistance tester (Suga Test Instruments Co., Ltd. Model: FAL-3D) in accordance with JIS B 7751 (2007). Irradiate an arc (400 to 500 W / m ² ) at 45 ° C. for 4 hours, measure the color tone of the test piece after irradiation and the test piece before irradiation, and display the color difference according to the color display method of the JISZ8730 color Calculated by the calculation method.

Claims (3)

A multilayer paper having a colored layer on the surface,
The colored layer contains a sulfur dye, a direct dye and / or a color pigment,
After immersing the multilayer paper of 5 cm × 5 cm square in water at 20 ° C. for 30 seconds, the multilayer paper is filtered with a sheet press according to JISP8222 (1998) for 30 seconds (Φ18 manufactured by ADVANTEC). ΔEa calculated by a color difference calculation method according to JISZ8730 (2002) color display method-color difference of object color is 1.3 to Multi-layered paper characterized by being 24.2 or less. The sulfur dye is an anionic sulfur dye;
The direct dye is an anionic direct dye;
The ratio (mass ratio) of the anionic sulfur dye and the anionic direct dye is 50:50 to 30:70, and the total amount of the dye added to the dry mass of the pulp contained in the colored layer is 1 to 12 mass. %
Using a light resistance tester according to JISB7751 (2007), the test piece of the multilayer paper is irradiated with an ultraviolet carbon arc at 45 ° C. for 4 hours, and the color tone of the test piece after irradiation and the test piece before irradiation is measured. The multilayer paper according to claim 1, wherein the calculated ΔEb is 1.73 or less. A method for producing the multilayer paper according to claim 1 or 2,
Add components to the raw pulp slurry for forming the colored layer in the order of anionic sulfur dye and / or color pigment, aluminum sulfate, anionic direct dye, and aluminum sulfate. The pulp slurry has a pH of 4.2 to 6.8, and the pulp slurry has a pH of 4.0 to 5.0 after the final addition of aluminum sulfate.