JP2019214801A - Uncoated paper - Google Patents

Abstract

To provide an uncoated paper that is excellent in uniform ink receptivity, a texture similar to that of painting paper, and writing properties.SOLUTION: An uncoated paper comprises pulp, at least 80 mass% of which is LBKP, and comprises an internal sizing agent and a surface sizing agent, wherein the basis weight is 130 g/mor more and 210 g/mor less, the density is 0.75 g/cmor less, and a skewness (Rsk) of a roughness curve obtained in accordance with JIS B0601:2001 is -0.6 or more and 0 or less and a kurtosis (Rku) of the roughness curve is 3 or more and 4.5 or less.SELECTED DRAWING: None

Description

  The present invention relates to an uncoated paper used for offset printing, which is suitable for a coloring book or a picture book.

  Not only coloring books and picture books, but paper used in books tends to be bulky. The reasons are various. Generally, the reason is to save forest resources, improve the opacity of paper, improve the appearance and texture of books, and reduce the weight of books.

Low-weight, low-density, high-opacity, excellent printability and processability, and at least one layer of clear paper on one or both sides of the base paper, especially for high-quality, high-quality paper with an appropriate size. A high quality paper having a coating layer, a basis weight of 30 to 62 g / m ² , a paper thickness of 90 μm or more, and an ash content of 20% by weight or less is known (for example, see Patent Document 1).

JP-A-2017-017239A

Conventionally, coloring book books and picture books have been sold. In particular, coloring books and picture books for adults are popular. Picture books require excellent print quality related to artistry. The printing quality is, for example, uniform ink deposition. Hobbyists, tasters and lovers of coloring books or picture books demand not only the smooth white paper used for mere notebooks, but also the feel that is perceived in art material paper while having a smoothness. . In addition, writing is required for coloring. The high-quality paper described in Patent Literature 1 intended for a notebook cannot satisfy the above-described ink inking property and touch feeling.
If the uncoated paper is made bulky in order to obtain a feeling of touch as seen in the art material paper, the paper will have a low density and it will be difficult to obtain uniform ink deposition. However, if the ink is simply smoothed by calendering or the like in order to obtain a uniform ink inking property, the writability deteriorates, and it is difficult to achieve both.

An object of the present invention is to provide an uncoated paper in which the following items are good.
(1) Uniform ink inking property (2) Hand feeling as seen on painting material paper (3) Writability

  The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, the object of the present invention is achieved as follows.

80% by mass or more of the pulp is LBKP, has an internal sizing agent and a surface sizing agent, has a basis weight of 130 g / m ² or more and 210 g / m ² or less, a density of 0.75 g / cm ³ or less, and JIS B0601. : Uncoated paper having a skewness (Rsk) of a roughness curve determined in accordance with 2001 of not less than -0.6 and not more than 0 and a kurtosis (Rku) of a roughness curve of not less than 3 and not more than 4.5.

  According to the present invention, it is possible to provide a non-coated paper having a uniform ink deposition property, a good touch feeling and a good writability, which are recognized on an image material paper.

The present invention is described in detail below.
In the present invention, "uncoated paper" refers to paper that does not have a clear layer that can be distinguished from the base paper when the cross section of the paper is observed with an electron microscope. For example, a resin component or a polymer component is coated, and the coated component is absorbed in the base paper in a small amount, and as a result, a clear layer that can be distinguished from the base paper when the cross section of the paper is observed by an electron microscope. If it does not have one, it falls under “uncoated paper”.

Uncoated paper can be obtained as follows.
Uncoated papers include chemical pulp such as LBKP (Leaf Bleached Kraft Pulp), NBKP (Needle Bleached Kraft Pulp), GP (Groundwood Pulp), PGW (Pressure GroundWood pulp), RMP (Refiner Mechanical Pulp), and TMP (ThermoMechanical Pulp). ), CTMP (ChemiThermoMechanical Pulp), CMP (ChemiMechanical Pulp), mechanical pulp such as CGP (ChemiGroundwood Pulp), and at least one pulp selected from waste paper pulp such as DIP (DeInked Pulp), calcium carbonate, talc and clay. Conventional fillers such as, kaolin and calcined kaolin, and various additives such as internal sizing agent, fixing agent, retention agent, cationizing agent, paper strength agent, and coloring dye, as needed. It can be produced by making a paper using a known paper machine. Non-coated papers include those that have been subjected to calendering, surface sizing with a size press solution having a surface sizing agent, or surface treatment after papermaking. Further, the uncoated paper includes those subjected to a calendar treatment and a surface sizing or surface treatment.

  In paper stock, other additives such as binders, pigment dispersants, thickeners, flow improvers, defoamers, foam inhibitors, release agents, foaming agents, penetrants, coloring pigments, fluorescent whitening One or two or more selected from agents, ultraviolet absorbers, antioxidants, preservatives, anti-binders, water-proofing agents, wet strength agents, dry strength agents, and the like, to achieve the desired effect of the present invention. Can be appropriately compounded within a range not to impair.

  The papermaking is performed by adjusting the stock to acidic, neutral or alkaline. Examples of conventionally known paper machines include a fourdrinier paper machine, a twin-wire paper machine, a combination paper machine, a round paper machine, and a Yankee paper machine.

  In the present invention, in the uncoated paper, at least one kind of pulp is LBKP, and LBKP is 80% by mass or more based on the pulp.

In the present invention, the uncoated paper has an internal sizing agent and a surface sizing agent.
The internal sizing agent is a sizing agent that is incorporated into paper stock and contained in paper. The surface sizing agent is a sizing agent to be contained in paper by being blended with a size press solution and blended with a size press or a surface treatment solution and subjected to surface treatment.
The internal sizing agent is a conventionally known sizing agent in the papermaking field, for example, rosin-based sizing agent for acidic paper, alkenyl succinic anhydride-based sizing agent for neutral paper, alkylketene dimer-based sizing agent, Examples include a neutral rosin-based sizing agent, a fatty acid-based sizing agent, and a cationic styrene-acrylic sizing agent. As the internal sizing agent, an alkyl ketene dimer sizing agent is preferable because a sizing effect can be obtained with a relatively small amount.
Surface sizing agents are conventionally known in the papermaking field, and include, for example, various starches, various modified starches, various polyvinyl alcohols, various modified polyvinyl alcohols, styrene-acrylic sizing agents, olefinic sizing agents, styrene-maleic acid. And the like. As the surface sizing agent, various starches or various modified starches are preferable from the viewpoint of material cost.

The size press is a conventionally known method.For example, there are an in-line size press, a horizontal size press, a rod metaling size press, a roll metaling size press, a blade metaling size press as a film transfer method, and a rod metaling size. Presses include a simsizer, an opticsizer, a speed sizer, and a film press, and a roll metaling size press includes a gate roll coater. Other examples include a bill blade coater, a twin blade coater, a bellvapa coater, a tab size press, and a calendar size press. Preferably, an inclined size press, a horizontal size press, a gate roll coater, a shim sizer, and a film press are used.
The surface treatment method is a method using a conventionally known coating apparatus, for example, a roll coater, an air knife coater, a bar coater, various blade coaters such as a rod blade coater, a short dwell coater, a curtain coater and the like. it can.

The basis weight of the uncoated paper is 130 g / m ² or more and 210 g / m ² or less. The grammage is a value obtained according to JIS P8124: 2011 “Paper and paperboard-measuring method of grammage”.
The density of the uncoated paper is 0.75 g / cm ³ or less. The density is preferably 0.40 g / cm ³ or more and 0.75 g / cm ³ or less. The density is a value determined according to JIS P8118: 1998 "Paper and paperboard-Test method for thickness and density".

The uncoated paper has a roughness curve Rsk determined according to JIS B0601: 2001 of -0.6 or more and 0 or less, and a roughness curve Rku of 3 or more and 4.5 or less. The measurement of Rsk and Rku based on JIS B0601: 2001 of the present invention can be performed, for example, using a color 3D laser microscope VK-8700 manufactured by KEYENCE (magnification: 10 × objective, full-screen measurement mode, Z-direction pitch: 0.2 μm, Cutoff setting: λs = 8 μm and λc = 2.5 mm).
Rsk means skewness, and represents the symmetry between the peak and the valley with respect to the average line.
Rsk = 0: symmetric with respect to the average line. normal distribution.
Rsk> 0: biased downward with respect to the average line. The convex portion is larger than the concave portion.
Rsk <0: biased upward with respect to the average line. The protrusions are smaller than the recesses (wear surface).
Rku means kurtosis which is a measure of the sharpness of the surface, and represents the sharpness (sharpness) of the height distribution.
Rku = 3: normal distribution.
Rku> 3: The height distribution is sharp.
Rku <3: A shape in which the height distribution of the surface irregularities is crushed.
The roughness indicated by Rsk and Rku relates to the state of the unevenness. And, as is clear from the above, the meaning is completely different.
Since Rsk is -0.6 or more and 0 or less, a somewhat worn surface is shown. Since Rku is 3 or more and 4.5 or less, a somewhat sharp surface is shown. The fact that Rsk and Rku are seemingly contradictory trends is presumed to be a state in which the surface is relatively thin and has a sharply worn surface. Uncoated paper in such a state has never existed.

The uncoated paper contains (1) at least one kind of pulp is LBKP, and 80% by mass or more of the pulp is LBKP, (2) containing an internal sizing agent and a surface sizing agent, 3) The basis weight is 130 g / m ² or more and 210 g / m ² or less, (4) the density is 0.75 g / cm ³ or less, and (5) the Rsk of the roughness curve is -0.6 or more and 0 or less. As a result of the synergistic effect that the Rku of the roughness curve is 3 or more and 4.5 or less, it is possible to obtain good uniform ink inking property, and a feeling of touch and writability as recognized on an image material paper. it can.
The reason for this is unknown. However, the present inventors have obtained uniform ink inking properties by the above (1), (2) and (5), and have the touch as seen in the art material paper by the above (3), (4) and (5). It is inferred that a feeling is obtained, and that the above-described (2), (4) and (5) can provide the writability.

The basis weight and density are physical properties of paper conventionally known in the papermaking field, and can be adjusted by a conventionally known method. The basis weight and density can be adjusted by, for example, the density of the stock, the supply amount of the stock to the paper machine, the control of the press part of the paper machine, and the calendering process. In the present invention, a bulking agent is not used to reduce the density, and the uncoated paper preferably contains no bulking agent.
Rsk and Rku are preferably adjusted by controlling the J / W ratio and / or L / B ratio of the paper machine, controlling the press part of the paper machine, and calendering. For example, in order to obtain Rsk and Rku within the scope of the present invention, it is preferable to use a method in which the press part of the paper machine is set to 3 nips or more, each linear pressure is adjusted, and calendering is performed lightly or not. The J / W ratio is the ratio between the speed J of the stock ejected from the headbox and the wire speed W. The L / B ratio is the ratio of the projection distance L of the lower lip with respect to the upper lip in the slice portion of the head box where the stock is discharged, and the distance B between the lips in the slice portion of the head box.

  Hereinafter, the present invention will be described in more detail with reference to examples. Note that 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 substantial component amount, respectively. The amount adhered by the size press indicates the amount of dry solid content.

<Preparation of uncoated paper>
LBKP having a freeness of 450 ml CSF, NBKP having a freeness of 500 ml CSF and DIP derived from mechanical pulp were added in a total of 100 parts by mass, as a filler, 8 parts by mass of calcium carbonate, 0.2 parts by mass of an alkyl ketene dimer sizing agent, and cationized starch. A stock was prepared by mixing 1 part by mass, 0.01 part by mass of polyacrylamide resin, 0.8 part by mass of a sulfuric acid band, and a red coloring dye. The obtained stock was paper-formed using a fourdrinier paper machine to obtain a paper-made paper.
The obtained paper was treated with oxidized starch by a size press such that the amount of adhesion per one side of the paper was 1 g / m ² to obtain an uncoated paper.
By controlling the supply amount of the stock, the J / W ratio of the paper machine and the press part of the paper machine, and controlling the conditions of the calendering process after the size press, the uncoated paper finally has a predetermined basis weight. The paper was made to have the amount, density, Rsk and Rku. Here, it is expected that Rsk and Rku change depending on the amount of adhesion in the size press. However, if the adhesion amount is several g, it is absorbed and its change is small, and there is no problem in control.

  Further, as Comparative Example 9, an uncoated paper was prepared except for the above-mentioned alkyl ketene dimer sizing agent which is an internal sizing agent. Further, as Comparative Example 10, an uncoated paper was prepared without adhering the oxidized starch as the surface sizing agent from the above.

  The parts by weight of each of LBKP, NBKP and DIP are described in Table 1.

  As a comparison of similar conventional products, a commercial product A was used in Comparative Example 11, a commercial product B was used in Comparative Example 12, and a commercial product C was used in Comparative Example 13.

  Table 1 shows the basis weight, density, Rsk and Rku of each uncoated paper.

<Evaluation of ink adhesion>
The obtained uncoated paper was printed under the following printing conditions using "RI-1 printing tester" manufactured by Ishikawajima Sangyo Kikai Co., Ltd.
Ink: Dainippon Ink "Space Color FusionG Ink S"
Drum rotation speed: 30 rpm
The printed matter was visually observed, and the following criteria were used to evaluate whether or not the ink deposition on the solid image portion was uniform. In the present invention, if the evaluation is 3 to 5, the uncoated paper is assumed to have good uniform ink inking property.
5: Ink deposition is uniform.
4: There is very slight unevenness in the ink deposition.
3: Inferior to 4 above, with slight unevenness in ink deposition.
2: Inferior to 3 above, with unevenness to the extent that there is no practical problem in depositing the ink.
1: There is unevenness in ink deposition to such an extent that it cannot be used practically.

<Evaluation of texture>
Twenty test subjects evaluated the feeling of touch to the obtained uncoated paper. The subjects sensory-evaluated the feeling of touch on the following five scales from the viewpoint of the degree of the feeling of touch that is perceived on the image material paper while being smooth, that is, the degree of rough touch. The results were expressed as the average value (rounded off to the decimal point) of 20 subjects. In the present invention, if the evaluation is 4 or 5, the uncoated paper has a good touch feeling.
5: Rough feel is felt.
4: It has some rough touch feeling.
3: It has a slight rough touch feeling.
2: Does not have a rough touch feeling.
1: Has a smooth feeling.

<Evaluation of writability>
Twenty test subjects evaluated the writability of the obtained uncoated paper. As a writing instrument, recycled pencil tree story (registered trademark) HB manufactured by Dragonfly Pencil Co., Ltd. was used. The test subject placed one uncoated paper on a steel office desk, and evaluated the feeling of writing on a five-point scale as described below. The results were expressed as the average value (rounded off to the decimal point) of 20 subjects. In the present invention, if the evaluation is 3 to 5, the uncoated paper has good writing properties.
5: Very good.
4: good.
3: Somewhat good.
2: Normal.
1: Poor.

  The evaluation results are shown in Table 1.

  From the results shown in Table 1, it can be seen that the uncoated papers of Examples 1 to 15, which correspond to the present invention, have good ink inking property, and good touch feeling and writability as seen in the art material paper. It can be seen that the uncoated papers of Comparative Examples 1 to 13 which do not correspond to the uncoated paper of the present invention cannot satisfy all of these effects.

Claims (1)

80% by mass or more of the pulp is LBKP, has an internal sizing agent and a surface sizing agent, has a basis weight of 130 g / m ² or more and 210 g / m ² or less, a density of 0.75 g / cm ³ or less, and JIS B0601. : Uncoated paper having a skewness (Rsk) of a roughness curve determined in accordance with 2001 of not less than -0.6 and not more than 0 and a kurtosis (Rku) of a roughness curve of not less than 3 and not more than 4.5.