JP2019151576A - Sheet paper - Google Patents

Abstract

To provide a sheet paper excellent in antibacterial property, water resistance, printability, interlaminar strength, powder dropping resistance, and rigid degree.SOLUTION: The problem is achieved by a sheet paper having a base paper by combining 3 or more layers having a surface layer, a back surface layer, and one or more core layer between the surface layer and the back surface layer, and a coating layer containing a pigment on a single side of the base paper, in which each layer of the surface layer, the back surface later and the core layer contains a sizing agent of 0.8 mass% to 1.5 mass% of a pulp solid content, the base paper contains an antibacterial agent of 0.05 g/mto 1.50 g/mper a single side on double side by coating, and coating weight of the coating layer is 10 g/mto 30 g/m.SELECTED DRAWING: None

Description

  The present invention relates to paperboard. More specifically, the present invention relates to a paperboard having excellent antibacterial properties, water resistance, printability, interlayer strength, dust resistance, and rigidity.

  Paperboard such as white paperboard is used in fields such as medical wrapping paper and food wrapping paper. In recent years, in such fields, there has been an increasing demand for paperboard having antibacterial properties from the viewpoint of hygiene.

  Antibacterial paper carrying a specific antibacterial phosphate is known as an antibacterial paper that does not cause discoloration even after being used for a long time and exhibits permanent antibacterial, antifungal and algal control effects (for example, Patent Document 1). Patent Document 1 discloses, as a method for producing the antibacterial paper, a method of applying a liquid composition containing an antibacterial agent and a binder to a paperboard after paper making, a method of impregnating a paperboard after paper making, and a method of spraying the paperboard after paper making A method and a method of making a paper by adding a flocculant to a slurry containing an antibacterial agent and pulp are disclosed. In addition, as a method of producing paperboard with excellent antibacterial properties, in the process of producing paperboard by making two or more wet paper layers made of waste paper pulp as the main raw material, it is combined between at least one layer. A method is known in which an antibacterial agent is retained in the paperboard by spraying the antibacterial agent in advance (see, for example, Patent Document 2).

JP 05-32512 A JP-A-10-96195

  The antibacterial paper produced by the method of coating the liquid composition containing the antibacterial agent and the binder on the paperboard after paper making, the method of impregnating the paperboard after paper making, and the method of spraying on the paperboard after paper making, Has the problem of falling. By increasing the binder content, the problem of antibacterial agent powdering off can be reduced. However, by increasing the binder content, the binder has the problem of blocking the antimicrobial action of the antimicrobial agent. Antibacterial paper produced by a method of making paper by adding an antibacterial agent to pulp slurry has a problem of wastewater treatment because the yield of the antibacterial agent is poor. Paperboard produced by a method in which an antibacterial agent is sprayed before interlaminating between layers has a problem that the antibacterial ability of the paperboard surface is somewhat inferior because the antibacterial agent exists between the layers.

  Since the paperboard is used for a box making package, information on the contents is printed. Accordingly, the paperboard having the base papers that have been combined together is required to have printability, rigidity that can withstand box making, and interlayer strength.

  The paperboard is also used for food packaging applications. In food packaging applications, various moistures are generated due to food. Therefore, the paperboard having the base papers that have been combined together is required to have the performance of suppressing the penetration of moisture into the paperboard and the capability of suppressing the strength reduction due to moisture.

In view of the above problems, an object of the present invention is to provide a paperboard having the following performance.
(1) Excellent antibacterial properties.
(2) Excellent water resistance.
(3) Excellent printability.
(4) Excellent interlayer strength of the base paper.
(5) Excellent anti-powder resistance of the antibacterial agent.
(6) Excellent rigidity.

The object of the present invention is achieved by the following.
[1] A base paper in which three or more layers having one or more core layers are formed between the surface layer and the back layer, and between the surface layer and the back layer, a coating layer containing a pigment on one side of the base paper, Each of the surface layer, the back layer, and the core layer contains a sizing agent in an amount of 0.8% by mass or more and 1.5% by mass or less based on the pulp solid content, and the base paper is contains an antimicrobial agent in per side 0.05 g / ^{m 2} or more 1.50 g / ^{m 2} or less by coating on both surfaces, paperboard coating amount of the coating layer is not more than 10 g / ^{m 2} or more 30 g / ^{m 2} .

  [2] The paperboard according to [1], wherein the antibacterial agent is a silver antibacterial agent.

  According to the present invention, it is possible to provide a paperboard excellent in antibacterial properties, water resistance, printability, interlayer strength, dust resistance, and rigidity.

  Hereinafter, the board of the present invention will be described in detail.

  The paperboard comprises a base paper in which three or more layers having a surface layer and a back layer, and one or more core layers between the surface layer and the back layer, and a coating layer containing a pigment on one side of the base paper, Have Each of the surface layer, the back layer and the core layer contains a sizing agent, and the base paper contains an antibacterial agent by coating on both sides.

Each layer of the base paper consists of chemical pulp such as LBKP (Leaf Bleached Kraft Pulp) and NBKP (Needle Bleached Kraft Pulp), GP (Groundwood Pulp), PGW (Pressure Ground Wood Pulp), RMP (Refiner Mechanical Pulp), TMP (ThermoMechanical Pulp) At least one pulp selected from mechanical pulp such as CTMP (ChemiThermoMechanical Pulp), CMP (ChemiMechanical Pulp), CGP (ChemiGroundwood Pulp) and DIP (DeInked Pulp), calcium carbonate, talc, clay, Paper materials containing various fillers such as kaolin and various additives such as a fixing agent, a retention agent, a cationizing agent, and a paper strength agent can be obtained by papermaking.
The base paper can be obtained, for example, by making a paper stock for each layer, making the surface layer, the back layer, and the core layer together in a wet paper state and drying. Prior to combining, it is preferable to apply adhesives such as various starches and modified products thereof between the surface layer and the core layer, between the core layer and the back layer, and between the core layer and the core layer. . This is because the interlayer strength is improved.

  Paper making is performed using a conventionally known paper machine by adjusting the stock to acidity, neutrality or alkalinity. Examples of the paper machine include various paper machines capable of making three or more layers, such as a long net multilayer paper machine, a circular net multilayer paper machine, and a long net multi-layer combination paper machine.

  In the paper stock, other additives include pigment dispersants, thickeners, fluidity improvers, antifoaming agents, foam inhibitors, mold release agents, foaming agents, penetrants, colored dyes, colored pigments, fluorescent One or more of whitening agents, ultraviolet absorbers, antioxidants, preservatives, antibacterial agents, water resistance agents, wet paper strength enhancers, dry paper strength enhancers, and the like are desired effects of the present invention. In the range which does not impair this, it can mix | blend suitably.

  Each of the surface layer, the back layer, and the core layer contains a sizing agent in a range of 0.8% by mass to 1.5% by mass with respect to the pulp solid content. In any one of the surface layer, the back layer and the core layer, when the content of the sizing agent is less than 0.8% by mass with respect to the pulp solid content, the paperboard cannot obtain water resistance. When the content of the sizing agent exceeds 1.5% by mass with respect to the pulp solid content in any one of the surface layer, the back layer, and the core layer, the paperboard cannot obtain interlayer strength.

  The sizing agent is conventionally known in the papermaking field. Examples of the sizing agent include alkyl ketene dimers, fatty acid metal salts, alkenyl or alkyl succinic anhydrides, rosin derivatives, epoxidized higher fatty acid amides, and organic fluoro compounds.

The base paper contains an antibacterial agent by coating on both sides.
“Containing antibacterial agent by coating” means that (A) an antibacterial agent is blended in the surface sizing liquid composition, and the surface sizing liquid composition is subjected to size press treatment by a conventionally known size pressing apparatus to be a base paper (B) The antibacterial agent is blended with the surface treatment liquid composition, and the surface treatment liquid composition is used for surface treatment with a conventionally known coating apparatus to give the antibacterial agent to the base paper. It means that the base paper becomes a state containing an antibacterial agent by the method. Conventionally known size press apparatuses include, for example, an incline size press, a horizontal size press, a rod metalling size press, a roll metalling size press, and a blade metalling size press as a film transfer system, A gate roll coater can be cited as an optical sizer, a speed sizer, a film press, and a roll metering size press. Other examples include a bill blade coater, a twin blade coater, a bellbapa coater, a tab size press, and a calendar size press. Examples of conventionally known coating apparatuses include a blade coater, a rod coater, an air knife coater, a comma coater, a gravure coater, a bar coater, an E bar coater, and a curtain coater. After applying the liquid composition, it can be dried using a conventionally known drying apparatus. Examples of the drying device include a straight tunnel dryer, an arch dryer, an air loop dryer, a hot air dryer such as a sine curve air float dryer, a dryer using an infrared heating dryer, a microwave, and the like.

  The surface sizing liquid composition is a liquid composition for the purpose of size effect, surface paper quality improvement or paper surface processing. The surface sizing liquid composition preferably contains a water-soluble polymer for improving the surface paper quality. The water-soluble polymer is conventionally known in the papermaking field. Examples of the water-soluble polymer include various starches and modified products thereof, various polyvinyl alcohols and modified products thereof, and polyacrylamide.

In the present invention, the base paper contains 0.05 g / m ² or more and 1.50 g / m ² or less of the antibacterial agent by coating. When the content of the antibacterial agent is less than 0.05 g / m ² per side, the paperboard cannot obtain antibacterial properties. When the content of the antibacterial agent exceeds 1.50 g / m ² per side, the paperboard cannot obtain anti-powder resistance.

  The antibacterial agent is an inorganic antibacterial agent or an organic antibacterial agent. Examples of the inorganic antibacterial agent include a silver antibacterial agent, a mercury antibacterial agent, a cadmium antibacterial agent, a copper antibacterial agent, a gold antibacterial agent, a cobalt antibacterial agent and a nickel antibacterial agent. Organic antibacterial agents include, for example, phenolic antibacterial agents, pyridine / quinoline antibacterial agents, triazine antibacterial agents, isothiazolone antibacterial agents, anilide antibacterial agents, nitrile antibacterial agents, imidazole / thiazole antibacterial agents, carboxylic acids Antibacterial agents, fatty acid ester antibacterial agents and fatty acid ether antibacterial agents. The antibacterial agent is preferably a silver antibacterial agent. This is because it has excellent antibacterial properties and high safety.

The paperboard has a coating layer containing a pigment on one side of the base paper.
The method for providing the coating layer on one side of the base paper is not particularly limited. Examples of the method of providing the coating layer on one side of the base paper include a method of applying and drying the coating solution of the coating layer using a conventionally known coating apparatus and drying apparatus in the papermaking field. Examples of conventionally known coating apparatuses include gate roll coaters, film transfer coaters, blade coaters, rod coaters, air knife coaters, comma coaters, gravure coaters, bar coaters, E bar coaters, curtain coaters, and the like. Examples of dryers include various dryers such as straight tunnel dryers, arch dryers, air loop dryers, sine curve air float dryers, hot air dryers, infrared heating dryers, dryers using microwaves, etc. Can do.

The coating amount of the coating layer on one side of the base paper is 10 g / m ² or more and 30 g / m ² or less. When the coating amount of the pigment coating layer is less than 10 g / m ² , the paperboard cannot obtain printability. When the coating amount of the pigment coating layer exceeds 30 g / m ² , the paperboard cannot obtain rigidity.

  The pigment of a coating layer is a conventionally well-known thing. Examples of the pigment include organic pigments such as kaolin, calcium carbonate, talc, satin white, lithopone, titanium oxide, zinc oxide, silica, alumina, aluminum hydroxide, activated clay, diatomaceous earth, and plastic pigments. Can do.

  The coating layer preferably contains a conventionally known binder in the coated paper field. Examples of conventionally known binders include various starches and modified products thereof, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, natural polymer resins such as casein, gelatin, soybean protein, pullulan, gum arabic, karaya gum and albumin and derivatives thereof. , Polyvinylpyrrolidone, various polyvinyl alcohols and modified products thereof, polyacrylamide, polyethyleneimine, polypropylene glycol, polyethylene glycol, maleic anhydride resin, acrylic resin, methacrylic acid ester-butadiene copolymer and styrene-butadiene copolymer, ethylene -Thermosetting of functional group-modified copolymers, melamine resins and urea resins with vinyl acetate copolymers or monomers containing functional groups such as carboxy groups of these various copolymers Synthetic resin binder, a polyurethane resin, unsaturated polyester resin, polyvinyl butyral, and the like alkyd resin latex. The coating layer is preferably one or more selected from the group consisting of these binders.

  The coating layer can contain various conventionally known additives in the coated paper field as required. Examples of additives include dispersants, fixing agents, thickeners, fluidity improvers, antifoaming agents, mold release agents, foaming agents, penetrating agents, coloring pigments, colored dyes, fluorescent whitening agents, UV absorbers , Antioxidants, preservatives, antifungal agents and the like.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples. Here, “parts by mass” and “% by mass” represent “parts by mass” and “% by mass” of the dry solid content or the amount of substantial components, respectively. The coating amount of the coating layer represents the dry solid content.

A pulp slurry was prepared from the following pulp and internal chemicals, and a base paper was made. The paper machine used was a long-mesh paper machine with a surface layer, a 5-layer paper machine with a core layer, and a 1-layer paper machine with a back layer, and was made at a speed of 160 m / min. In addition, 0.6 g / m < ² > of each commercially available urea phosphate esterified starch was made to adhere between each layer with the spray.

<Surface>
LBKP (freeness 440 mlcsf) 75 parts by weight NBKP (freeness 480 mlcsf) 25 parts by weight Sizing agent of rosin derivative Content with respect to pulp solid content is listed in Table 1. Sulfuric acid band 1.5 parts by weight Basis weight 40 g / m ²

<Core layer>
LBKP (freeness 440 mlcsf) 50 parts by mass CGP (freeness 400 mlcsf) 50 parts by weight Sizing agent of rosin derivative Content with respect to pulp solid content is shown in Table 1. Sulfuric acid band 1.5 parts by weight Basis weight Table 1

<Back layer>
LBKP (freeness 440 mlcsf) 100 parts by mass Size of rosin derivative Content relative to pulp solid content is listed in Table 1. Sulfuric acid band 1.5 parts by mass Basis weight 40 g / m ²

<Antimicrobial application>
A surface sizing composition was prepared using the following materials so as to have a predetermined content, and a base paper containing an antibacterial agent and a base paper containing no antibacterial agent were obtained using a horizontal size press.
Oxidized starch 2.6 g / m ² per side
Antibacterial agent type and content per side are listed in Table 1.

<Preparation of coating solution and paperboard for coating layer>
The coating solution for the coating layer was adjusted according to the following contents.
Kaolin 60 parts by weight Heavy calcium carbonate 40 parts by weight Phosphate esterified starch 10 parts by weight Styrene-butadiene copolymer 10 parts by weight Ammonia water 0.1 part by weight It adjusted to 60 mass%, the coating amount of Table 1 was coated on the single side | surface of the base paper with the rod coater, and the paperboard of the Example and the comparative example was produced. The coating layer was provided on the surface layer side of the base paper.

  The board produced as described above was evaluated by the following evaluation method.

<Evaluation of antibacterial properties>
The antibacterial property was evaluated by a test method according to JIS Z 2801: 2012 “Antimicrobial processed product-antibacterial test method / antibacterial effect (film adhesion method)”. However, a paperboard immersed in a 1/500 NB medium for about 1 minute was used. In the film adhesion method, the number of surviving bacteria after 24 hours of antibacterial treated paperboard is 1 / 100th of the number of surviving bacteria after 24 hours of untreated (antibacterial agent content 0.00 g / m ² ) paperboard. If it is below, the antibacterial treated paperboard has antibacterial properties. Escherichia coli and Staphylococcus aureus were used for the bacterial solution. The evaluation was performed on the side of the paperboard that does not have a coating layer, that is, the surface of the base paper. In the present invention, the paperboard is excellent in antibacterial properties when the evaluation result is poor and the evaluation is 2 to 4 points as a result of the test of Escherichia coli or Staphylococcus aureus.
4 points: R is 5 or more 3 points: R is 3 or more and less than 5 2 points: R is 2 or more and less than 3 1 point: R is less than 2 Here, R is a value obtained from the following formula.
R = Ut-At
R: antibacterial activity value Ut: logarithm of the number of surviving bacteria after 24 hours of untreated paperboard At: logarithm of the number of surviving bacteria after 24 hours of antibacterial treated paperboard

<Evaluation of water resistance>
The water resistance was evaluated by the water absorbency (edge wick test) from the end faces of the four circumferences of the paperboard. The edge wick test is the amount of water absorbed when a paperboard is cut into 5cm x 10cm paper pieces, water-resistant tape is attached to the front and back surfaces of the paper pieces, and immersed in water at a predetermined water temperature for 10 minutes. This is a test for In the present invention, the edge wick value determined by the edge wick test is calculated by the formula of ([weight after immersion in water at 23 ° C. for 10 minutes] − [weight before immersion]) / [total area of the four peripheral end faces]. Numerical value (mg / mm ² ). In the present invention, the paperboard is excellent in water resistance if the evaluation is 2 to 4 points.
4 points: Edge wick value is less than 0.15 mg / mm ² 3 points: Edge wick value is 0.15 mg / mm ² or more and less than 0.25 mg / mm ² 2 points: Edge wick value is 0.25 mg / mm ² or more and 0 .. Less than 40 mg / mm ² 1 point: Edge wick value is 0.40 mg / mm ² or more

<Evaluation of printability>
Using a RI printing aptitude tester, red (ink amount 0.3 cc) solid printing was applied to the paperboard, and then printing aptitude was visually observed and evaluated from the viewpoint of printing unevenness. In the present invention, the paperboard is excellent in printability if the evaluation is 2 to 4 points.
4 points: printing unevenness is not observed at all and good 3 points: printing unevenness is observed very slightly, but generally good 2 points: printing unevenness is observed, but a level that is acceptable as a product 1 point: printing unevenness Observed and unusable level as product

<Evaluation of interlayer strength>
The evaluation of interlayer strength is based on JAPAN TAPPI No. It was evaluated by a test method according to 18-2 “Paper and paperboard—Internal bond strength test method—Part 2: Internal bond tester method”. In the present invention, the paperboard has an excellent interlayer strength if the evaluation is 2 to 3 points.
3 points: Internal bond strength of 150 mJ or more 2 points: Internal bond strength of 110 mJ or more and less than 150 mJ 1 point: Internal bond strength of less than 110 mJ

<Evaluation of dust resistance>
The evaluation of dust resistance was performed using Sauzaland Love Tester (Toyo Seiki Seisakusho). First, the base paper surface on which the coating layer coating liquid was not applied was set up in a lab tester. Next, black rush paper was attached to a 1 kg weight, and the weight was set on a lab tester so that the base paper surface and the black lash paper were rubbed. After setting, the base paper surface and the black lasha paper were rubbed together by automatic reciprocation 10 times. After rubbing, the state of the powder adhering to the black lasha paper was visually judged. In the present invention, the paperboard is excellent in anti-powder resistance if the evaluation is 2 to 3 points.
3 points: no powder falling 2 points: slightly powder falling 1 point: powder falling

<Evaluation of rigidity>
The rigidity was evaluated by a test method according to JIS P 8125: 1994 “Paper and paperboard—Stiffness test method—Taber stiffness tester method”. The measurement direction was a direction perpendicular to the papermaking flow direction (MD direction) (CD direction). In the present invention, the paperboard is excellent in rigidity if the evaluation is 2 to 3 points.
3 points: stiffness is 4.5 mN · m or more 2 points: stiffness is 3.0 mN · m or more and less than 4.5 mN · m 1 point: stiffness is less than 3.0 mN · m

  The evaluation results are shown in Table 1.

From the evaluation results of Table 1, it can be seen that Examples 1 to 16 corresponding to the present invention are excellent in antibacterial properties, water resistance, printability, interlayer strength, dust resistance and rigidity. However, it can be seen that Comparative Examples 1 to 8 that do not satisfy the configuration of the present invention cannot satisfy all of these effects.
Moreover, from the comparison between Example 1 and Examples 15 and 16, it can be seen that the antibacterial agent is preferably a silver antibacterial agent.

Claims (2)

A paperboard having a surface layer, a back layer, a base paper obtained by combining three or more layers having one or more core layers between the surface layer and the back layer, and a coating layer containing a pigment on one side of the base paper Each of the surface layer, the back layer and the core layer contains a sizing agent in an amount of 0.8% by mass or more and 1.5% by mass or less based on the pulp solid content, and the base paper is coated on both sides. Engineering by containing an antimicrobial agent in per side 0.05 g / ^{m 2} or more 1.50 g / ^{m 2} or less, the coating layer of the coated amount is less than 10 g / ^{m 2} or more 30 g / ^{m 2} paperboard.   The paperboard according to claim 1, wherein the antibacterial agent is a silver-based antibacterial agent.