JP4358601B2 - Paperboard - Google Patents

Description

  The present invention relates to paperboard. In particular, the present invention relates to a paperboard having both water repellent processing suitability and printability.

  Conventionally, water repellency has been imparted to the surface of paperboard used in cardboard cases and paper containers. In order to impart water repellency to paperboard, it is widely performed to apply a water repellent or a surface treatment agent containing a water repellent to the surface of the paperboard or by spraying.

  On the other hand, paperboard is printed on the surface and used as a packaging material. In recent years, cosmetic printing has been performed to differentiate content products, and there has been an increasing demand for an exhibition function, and high printability has been demanded. For example, when performing unimarque printing, if the ink is not absorbed to some extent by the paperboard, uneven ink deposition occurs, so that the ink absorbability is increased to improve the printability. As described above, when water repellency is imparted to the paperboard, in order to obtain a high water repellency effect (suitability for water repellency), a coating agent such as a resin is applied to the surface of the paperboard to absorb the water repellant. Although suppression is performed, the ink absorbability is also reduced at the same time, and printability is lowered.

  Here, if the concentration of the coating agent applied to the base paper surface of the paperboard is lowered, the ink absorbency is increased and the printability is improved, but conversely, the water repellent finishability is lowered. It was difficult to obtain a paperboard having both printability and printability. At present, two types of paperboard for water-repellent processing and for printing without water-repellent processing are prepared, and they are used properly according to the application, which is suitable for water-repellent processing in terms of stock burden. A paperboard having both printability and printability is desired.

  Accordingly, an object of the present invention is to provide a paperboard having both water-repellent processing suitability and printability.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that a paperboard having a specific range of water absorption at a contact time of 120 seconds as defined in JIS-P8140 and a density within a specific range. The present invention has been completed by obtaining the knowledge that the above object can be achieved.

The present invention has been made on the basis of the above findings, and has a Cobb water absorption of 20 to 60 g / m ² at a contact time of 120 seconds as defined in JIS-P8140, and a density of 0.5 to 0.9 g / m. The paperboard is characterized by being cm ³ .
The paperboard is preferably coated with a cationic surface sizing agent, and the required amount of cation of the paper layer coated with the cationic surface sizing agent is -0.02 to -0.46 mmol / L. Is preferred.
The paperboard preferably has a multilayer structure of two or more layers, and the density of the surface layer is preferably 0.5 to 0.9 g / cm ³ .
When it has a multilayer structure of two or more layers, the density of the lower and lower layers is preferably 0.5 to 0.9 g / cm ³ .

  According to the present invention, a paperboard having both water-repellent processing suitability and printability is provided. Since the paperboard of the present invention has both water repellent processing suitability and printability, it is not necessary to prepare two types of paperboard for water repellent processing and printing depending on the use of the paperboard, and only one type of paperboard is sufficient. Therefore, the user's stock burden can be reduced.

Hereinafter, the paperboard of the present invention will be described.
The paperboard of the present invention preferably has a multilayer structure of two or more layers. The multilayer structure may be a two-layer structure, but a paperboard having a multilayer structure of three or more layers is more preferable. The paperboard of the present invention is preferably formed by papermaking, and the materials forming a multilayer structure of two or more layers may be the same or different. Hereinafter, a paper board having a five-layer structure composed of the front and lower layers and the three back layers will be described in detail.

In general, paperboard is manufactured by multilayer papermaking. Accordingly, each layer having a multilayer structure of paperboard is independently formed and combined with a paper layer. In the present invention, the layer on the most front side is referred to as a surface layer, and the layer below the surface layer is referred to as a surface lower layer.
As a fiber material used when producing the paperboard of the present invention, as virgin pulp, groundwood pulp (GP), thermomechanical pulp (TMP), semi-chemical pulp (SCP), semi-ground pulp (CGP), kraft pulp Known pulp such as wood pulp such as (KP) and sulfite pulp (SP), and non-wood pulp made from kenaf, hemp, flax, straw and the like is used. In addition, as waste paper pulp, recovered pulp obtained from unprinted waste paper such as milk-packed waste paper, coated waste paper, upper white, special white, medium white, newspaper waste paper, magazine waste paper, corrugated paper waste, waste paper waste paper, etc. Is used.

  In addition, high-quality plant fibers made of polyethylene, polypropylene, etc. as raw materials, mixed with synthetic pulp, etc. In addition to synthetic pulp, organic fibers such as rayon fiber, acrylic fiber, polyamide fiber, glass fiber, carbon fiber, etc. It is also possible to mix various fibers.

  In the above-mentioned surface layer, front surface lower layer, middle layer, and back layer, all of additives that are usually used when producing paperboard may be added. Examples of such additives include polyacrylamide, polyvinyl alcohol polymer, urea / formalin resin, melamine / formalin resin, paper strength enhancer such as starch; chemical fixing agent such as sulfuric acid band, polyacrylamide, acrylamide / amino. Freezing agent or yield improver such as methyl acrylamide copolymer salt, cationized starch, polyethyleneimine, polyethylene oxide, acrylamide / sodium acrylate copolymer; water-resistant agent such as polyamide, polyamine, epichlorohydrin; antifoaming agent And fillers such as talc; dyes; color pigments; antibacterial agents;

  As the paper machine used for producing the paperboard of the present invention, a paper machine conventionally used for producing paperboard can be used. Examples of such a paper machine include a circular net paper machine, an ultra former paper machine, and a bell bond former paper machine. Examples of the method for drying the combined raw materials include a Yankee dryer, a multi-cylinder dryer, a hot air dryer, and an infrared dryer.

Basis weight of the paperboard of the present ^invention, it is preferably, commercialization, and 150g ^{/ m 2} ~300g ^/ m 2 in terms of the corrugator bonding suitability during cardboard working is 100g / ^{m 2} ~400g / m 2 It is preferable.

In the paperboard of the present invention, the density of the surface layer and the surface layer is preferably 0.5 to 0.9 g / cm ³ . The density of the surface layer and the surface lower layer is lower than the density of each layer constituting a normal paperboard. That is, the density of the surface layer and the surface layer is lower than the density of the back layer. By making the density of the surface layer and the surface lower layer lower than the density of each layer constituting the normal paperboard, the ink absorbability of the paperboard is improved and the printability is improved. In order to improve printability, the density of the surface layer and the surface layer is more preferably 0.55 to 0.86 g / cm ³ . Note that the density of the surface layer and the density of the surface layer are not necessarily the same, as long as both are within the above range.

The paperboard of the present invention has a Cobb water absorption of 20 to 60 g / m ² , preferably 30 to 50 g / m ² at a contact time of 120 seconds, as defined in JIS-P8140. If the Cobb water absorption at a contact time of 120 seconds defined by JIS-P8140 is less than 20 g / m ² , the ink absorbency is too low, and the printability is not good, while if it exceeds 60 g / m ² , the ink Absorbability becomes too high, and printability is not good.

  In order to make the Cobb water absorption of the paperboard of this invention into the said range, it can achieve by adjusting content of the internal sizing agent in a surface layer and a surface lower layer, for example. For example, in the surface layer and the lower layer, the internal sizing agent is preferably 0.4% by mass per absolute dry mass of the pulp (hereinafter, unless otherwise specified, the addition amount and application amount of the chemical are expressed in terms of solid content) or less More preferably, the content may be 0.38% by mass or less. As the internal sizing agent to be used, those conventionally used for producing paperboard can be used without particular limitation, and examples thereof include an acidic rosin size, a neutral rosin size, and an acrylic sizing agent. . The internal sizing agent may be used alone or in combination of two or more.

  In addition, by setting the content of the internal sizing agent in the surface layer and the surface lower layer in the above range, the Cobb water absorption can be set in a specific range, and the size effect can be reduced. Therefore, when a surface sizing agent is applied on the surface layer to provide a layer having the surface sizing agent, the surface sizing agent is absorbed in the surface layer and the lower layer, and thus the surface sizing agent is absorbed in the surface layer and the lower layer. The surface layer and the lower layer swell and the density decreases. For this reason, the absorptivity of an ink becomes high and printability can be improved.

Further, the board of the present invention has a density of 0.5 to 0.9 g / cm ³ , preferably 0.55 to 0.86 g / cm ³ . If the density is less than 0.5 g / cm ³ , the ink absorbability becomes too high, and drying after printing is unfavorable. On the other hand, if it exceeds 0.9 g / cm ³ , the paper layer is too tight, so that the ink absorbability is lowered and the printability is poor. The density of the paperboard is adjusted by the press roll nip pressure installed in the paper machine or the nip pressure of the calendar roll.

In the paperboard of the present invention, the cation requirement of the paper layer coated with the cationic surface sizing agent is preferably −0.02 to −0.46 mmol / L, more preferably −0.1 to −0. 4 mmol / L. By increasing the application amount of the cationic surface sizing agent, the required cation amount can be lowered from −0.46 mmol / L, but the suitability for water repellent processing is not improved any more. When the required amount of cation exceeds −0.02 mmol / L, the water repellent agent is not fixed on the paper surface and penetrates too much into the paper layer, resulting in a low water repellent effect.
In the present invention, the required cation amount means that the surface layer of the paperboard is peeled off to make a 5 g sample, 1 liter of distilled water is added thereto, and the sample is removed using a standard disaggregator used in the handsheet adjustment method for pulp testing. It is the value measured for the disaggregation.

  There is no particular limitation on the method for setting the cation requirement of the paperboard within the above range, but the cation requirement can be adjusted within the above range by applying a cationic surface sizing agent to the surface. As the water repellent used for water repellent processing of the paperboard, an anionic one is mainly used. Therefore, in order to keep the cation requirement of the paperboard of the present invention within the above range, the surface of the paperboard is made cationic. It is preferable to apply a surface sizing agent. By using a cationic surface sizing agent, it is possible to completely fix the water repellent on the surface of the paperboard during water repellent processing, and to prevent the water repellent from penetrating into the paper layer. Therefore, higher water repellency can be imparted.

As the cationic surface sizing agent used in the present invention, those conventionally used for producing paper can be used without particular limitation. Examples of such a cationic surface sizing agent include Seiko PMC Co., Ltd., BLS720; Arakawa Chemical Industries, Ltd., Polymeron 360, and the like. By applying a cationic surface sizing agent on the surface layer of the paperboard, the cationic surface sizing agent is absorbed by the surface layer and the lower layer on the surface layer.
Further, as the coating agent, in addition to the cationic surface sizing agent, a surface paper strength enhancer such as starch, polyvinyl alcohol (PVA), polyacrylamide (PAM) or the like may be mixed and used.

The cationic surface sizing agent is absorbed by the surface layer and the lower layer, so that when the paperboard of the present invention is subjected to a water repellent treatment, a large amount of water repellent agent can be retained on the surface layer of the paperboard, thereby providing high water repellency. can do. To obtain the above effects, the coating amount onto the surface of the cationic surface sizing agent is preferably 0.05~0.50g / ^{m 2,} more preferably 0.25~0.50g / ^{m 2} It is.

  There is no particular limitation on the method of applying the cationic surface sizing agent to the surface of the paperboard, and for example, the cationic surface sizing agent can be applied using a coating device installed in a paper machine. Examples of the coating apparatus include a blade coater, a bar coater, a gate roll coater, and a calendar coat.

The back layer in contact with the upper and lower layers is a layer for making the paperboard a predetermined thickness and economically ensuring the strength of “strain”. Usually, the density is larger than the upper and lower layers, 0.5 About 1.1 g / cm ³ may be sufficient.

The back layer not in contact with the front and lower layers is the back side of the paperboard, and usually has a higher density than the front and lower layers, and may be about 0.6 to 1.1 g / cm ³ .

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited thereto.
Example 1
The paperboard having both water-repellent processing suitability and printing suitability in this example has a paper layer of 5 layers consisting of a surface layer, a front layer, a bottom layer, a middle layer, and a back layer. A paperboard of / m ² was produced.
Surface pulp blending: NBKP, LBKP and high quality waste paper (blending ratio 20/40/40)
Surface chemicals: internal sizing agent 0.20%, sulfuric acid band 3%
Top and bottom pulp blend; Colored waste paper and Kent waste paper (blend ratio 50/50)
Subsurface chemicals: 0.10% internal sizing agent, 3% sulfuric acid band
Middle layer pulp mix; corrugated waste paper Middle layer chemicals; 0.08% internal sizing agent, 3% sulfuric acid band
Back layer pulp composition; waste corrugated paper Back layer chemicals: 0.15% internal sizing agent, 3% sulfuric acid band
Surface coating: A cationic surface sizing agent and polyvir alcohol were mixed at a weight ratio of 2 to 1 (solid content) and coated with a bar coater installed in a paper machine. The coating amount of the cationic surface sizing agent 0.40 g / ^{m 2,} and a polyvinyl alcohol 0.20 g / ^{m 2.}
Chemicals used Internal sizing agent: Size Pine N771 manufactured by Arakawa Chemical Industries, Ltd.
Cationic surface sizing agent: BLS720 manufactured by Seiko PMC Co., Ltd.
Polyvinyl alcohol (PVA): Nippon Synthetic Chemical Co., Ltd. P7400

In this example, the paperboard was evaluated by the following method.
(1) Printability Using an IGT printability tester stipulated in JIS-P8129, printing is performed on the paperboard surface using Unimarki USW RED1 manufactured by Kyokuto International Co., Ltd. And evaluated.
Evaluation was performed according to the following evaluation criteria. The evaluation results are shown in Table 1 (Examples 1 to 6) and Table 2 (Comparative Examples 1 to 6)).
A: There was no printing blur and ink absorption was good.
○: Although there was no printing blur, the ink print was thin due to less ink absorption.
Δ: Ink is absorbed but blurring is noticeable.
X: The ink is not absorbed and the ink is swimming on the paper surface, and the blur is severe. Or
The ink absorbed too much and the ink was not dry after 4 hours of printing.

(2) Water-repellent processing suitability Using a IGT print suitability tester specified in JIS-P8129, 0.2 g / m ² of water-repellent agent (Ripax A240 manufactured by Modern Chemical Industry Co., Ltd.) is applied to the surface of the paperboard, and water-repellent The degree of water was measured using the water repellency test method specified in JIS-P8137.
Evaluation was performed according to the following evaluation criteria. The evaluation results are shown in Table 1 (Examples 1 to 6) and Table 2 (Comparative Examples 1 to 6)).
A: The water repellency was R8 or more.
○: The water repellency was R6 or more and less than R8.
Δ: The water repellency was R4 or more and less than R6.
X: The water repellency was less than R4.

(3) Cation requirement The surface layer of the paperboard is peeled off, 5 g of the peeled surface layer is collected, 1 kg of distilled water is added thereto, and the sample is disaggregated with a standard disaggregator used for the handsheet preparation method for pulp test. The required amount of cation was measured by the company's particle surface charge measuring device name Cyber Charge. The results are shown in Table 1 (Examples 1 to 6) and Table 2 (Comparative Examples 1 to 6).

(4) Density The density of the surface layer and the lower layer was measured as follows.
Photographs of the cross-sectional view of the paperboard were taken using an optical microscope, the thicknesses of the surface layer and the lower layer were measured at 10 locations, and the measurement results at these 10 locations were averaged to obtain the thicknesses of the surface layer and the lower layer. Next, the paperboard was cut into a size of 30 cm × 30 cm and immersed in distilled water for 24 hours. The board immersed in distilled water was taken out, the surface layer and the lower layer were peeled off, and dried at a temperature of 102 to 108 ° C. for 2 hours using a hot air dryer. Next, pretreatment was performed based on the pretreatment of the test paper defined in JIS P 8111, and the weight was measured in a standard state (temperature 23 ° C., humidity 55%). The density of the surface layer and the lower layer was calculated from the thickness and weight. The results are shown in Table 1 (Examples 1 to 6) and Table 2 (Comparative Examples 1 to 6).
The density of the paperboard was determined by measuring the thickness of the paperboard at 10 locations, averaging the measurement results at the 10 locations to obtain the thickness of the paperboard, then measuring the weight, and calculating the density from the thickness and weight. The results are shown in Table 1 (Examples 1 to 6) and Table 2 (Comparative Examples 1 to 6).

Example 2
A paperboard was obtained in the same manner as in Example 1 except that the amount of the internally added sizing agent in the surface layer was 0.40% by mass per the absolute dry mass of pulp. The obtained paperboard was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 3
The amount of the internally added sizing agent in the surface layer was set to 0.16% by mass per pulp dry mass, and the same operation as in Example 1 was performed except that 0.5 g / m ^{2 of} the cationic surface sizing agent was applied. Got. The obtained paperboard was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4
The same procedure as in Example 1 was carried out except that the amount of the internal sizing agent added in the surface layer was 0.38% by mass based on the dry pulp mass, and the cationic surface sizing agent was applied at 0.25 g / m ^2. Got. The obtained paperboard was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 5
The same procedure as in Example 1 was carried out except that the amount of the internal sizing agent added in the surface layer was 0.32% by mass per pulp dry mass, and the cationic surface sizing agent was applied at 0.30 g / m ^2. Got. The obtained paperboard was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 6
The amount of the internal sizing agent added to the surface layer was 0.20% by mass based on the dry pulp mass, and the same operation as in Example 1 was performed except that 0.05 g / m ^{2 of} the cationic surface sizing agent was applied. Got. The obtained paperboard was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1
The operation was carried out in the same manner as in Example 1 except that the amount of the internal sizing agent added to the surface layer was 0.12% by mass per pulp dry mass and 0.01 g / m ² of the cationic surface sizing agent was applied as the coating agent. A paperboard was obtained. The obtained paperboard was evaluated in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 2
The same procedure as in Example 1 was performed except that the amount of the internally added sizing agent in the surface layer was 0.30% by mass per the dry dry mass of the pulp, and a cationic surface sizing agent was applied and applied as a coating agent in an amount of 0.04 g / m ^2. The board was obtained. The obtained paperboard was evaluated in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 3
The operation was carried out in the same manner as in Example 1 except that the amount of the internally added sizing agent in the surface layer was 0.10% by mass per the absolute dry weight of the pulp, and 0.03 g / m ² of the cationic surface sizing agent was applied as the coating agent. A paperboard was obtained. The obtained paperboard was evaluated in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 4
The addition amount of the internal sizing agent in the surface layer is 0.52% by mass per the dry pulp mass, 0.20 g / m ² of PVA as the coating agent, and 0% of Polymeron 1329 manufactured by Arakawa Chemical Industries, Ltd. A board was obtained in the same manner as in Example 1 except that 50 g / m ^{2 was} applied. The obtained paperboard was evaluated in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 5
Example 1 except that the amount of the internally added sizing agent in the surface layer was 0.58% by mass based on the absolute dry mass of the pulp, and 0.50 g / m ^{2 of} PAM polymer set HP710 manufactured by Arakawa Chemical Industries, Ltd. was applied as the coating agent. In the same manner as described above, a paperboard was obtained. The obtained paperboard was evaluated in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 6
The amount of addition of the internal sizing agent in the surface layer was 0.42% by mass per dry pulp mass, and polyacrylamide (Polytron 320 manufactured by Arakawa Chemical Co., Ltd.) was applied as a coating agent at 0.50 g / m ^2. Were the same as in Example 1 to obtain paperboard. The obtained paperboard was evaluated in the same manner as in Example 1. The results are shown in Table 2.

  As is clear from Tables 1 and 2, the paperboards of Examples 1 to 6 have both printability and water repellency.

Claims (4)

It has a multilayer structure of two or more layers, the surface layer contains an internal additive, and a surface layer cationic surface sizing agent is applied, and the cation requirement of the paper layer coated with the cationic surface sizing agent is − 0.02 to −0.46 mmol / L, surface layer density of 0.5 to 0.9 g / cm ³ , and Cobb water absorption at a contact time of 120 seconds as defined in JIS-P8140 is 20 to 60 g. A paperboard characterized by being / m ² . The paperboard of Claim 1 whose application amount on the surface layer of the said cationic surface sizing agent is 0.05-0.50 g / m < ² > . The paperboard of Claim 1 or 2 contained so that the said internal addition size may be 0.4 mass% or less in a surface layer. The paperboard of any one of Claims 1-3 whose density of a surface lower layer is 0.5-0.9 g / cm < ³ >.