JP7211140B2 - White ball and coated white ball - Google Patents

Description

The present invention relates to a white board containing waste paper and a coated white board.

White balls used for packaging boxes and the like are generally multi-layered and have a surface layer, an intermediate layer and a back layer. In some cases, a coated white ball is provided with a pigment coating layer on one or both sides of the white ball.

Printed waste paper pulp is often used as a raw material for white board from the viewpoint of utilization of waste paper resources, economic efficiency at the time of production, and the like. For this reason, when printed waste paper is used as a raw material for the backing layer, the quality of the white ball is deteriorated. In order to solve this problem, the deinking process for removing the residual substances contained in the waste printed paper may be strengthened, but new problems such as an increase in cost arise.

Therefore, in Patent Document 1, printed waste paper is not used as a raw material for the back layer, and the back layer is colored with a coloring agent to make it a specific absorption coefficient, thereby increasing the shielding property of the back layer. White paperboard (white ball) has been proposed to cover dust, dullness, and the like. However, in the proposal of Patent Document 1, printed waste paper cannot be used as a raw material for the back layer of the white board, and a new technique is required from the viewpoint of resource utilization.

JP 2015-132023 A

The present invention provides a white board and a coated white board which have a good appearance on the back side of the back layer while containing printed waste paper pulp in the back layer of the multilayer base paper.

[1] A multi-layered white ball having a surface layer, a middle layer and a back layer, wherein the back layer contains waste paper pulp obtained by dispersing printed waste paper, and the back layer has an ERIC value of 200 to 500. In a plan view of the back layer, the number of dust particles of 0.01 mm ² or more and less than 0.05 mm ² is 500 to 15,000/m ² , and the number of dust particles of 0.05 mm ² or more is 50 to 2,000/m ² . There is a white ball.
[2] The content of the waste paper pulp is 90 to 100% by mass relative to the mass of the total pulp contained in the back layer, and the content of the waste paper pulp is 95 to 100 mass% relative to the mass of the total pulp contained in the intermediate layer. %, the white ball according to [1].
[3] The white ball of [1] or [2], wherein the back layer has a specific absorption coefficient of 50 cm ² /g or more.
[4] The white ball according to any one of [1] to [3], wherein the ISO whiteness of the back layer is in the range of 45 to 60%.
[5] The white ball according to any one of [1] to [4], wherein the back layer has a basis weight of 15 to 40 g/m ² .
[6] A coated white ball comprising a coating layer provided on at least one surface of the white ball of any one of [1] to [5].

The white ball and coated white ball of the present invention can be used for various purposes because the back surface of the back layer has a good appearance even though the back layer contains printed waste paper pulp.

≪White ball≫
The white ball of the first aspect of the present invention is multi-layered and has at least a surface layer, a middle layer and a back layer. The back layer contains waste paper pulp obtained by dispersing printed waste paper. Furthermore, the ERIC value of the back layer is in the range of 200 to 500, and the number of dust particles of 0.01 mm ² or more and less than 0.05 mm ² is 500 to 15,000/m ² or more than 0.05 mm ² in the plan view of the back layer. The dust count is in the range of 50 to 2000/m ² .

The surface layer is a layer constituting the outermost surface of the multilayer paper. The surface layer may or may not contain waste paper pulp made from waste paper, but desirably contains waste paper.
The middle layer is a layer having a lower degree of whiteness than the surface layer. The middle layer may be a single layer, or may have a multi-layer structure of about 2 to 9 layers. The middle layer may or may not contain waste paper pulp, but preferably contains waste paper, and more preferably contains waste printed paper. When the intermediate layer has a multi-layer structure, the raw material composition of each layer of the intermediate layer may be the same or different.
The white ball may or may not have a lower surface layer in contact with the surface layer between the surface layer and the middle layer. The whiteness of the lower surface layer is preferably higher than that of the middle layer and lower than that of the surface layer.
The white ball has a back layer on the side opposite to the surface layer of the middle layer. Since the raw material composition forming the back layer is different from the raw material composition of the middle layer, the whiteness of each is also usually different.
The white ball may or may not have a lower back layer in contact with the back layer between the middle layer and the back layer. The whiteness of the lower back layer is preferably higher than that of the intermediate layer and lower than that of the back layer.

^The basis ^weight of the white ball is not particularly limited, and is ^{appropriately} set according to the application. may be

Each layer will be described in detail below. The surface layer other than the back layer, the front and bottom layers, the middle layer, and the back and bottom layer may be the same as those of a known white ball.

[Back layer]
Since the back layer contains waste paper pulp obtained by dispersing printed waste paper, ink remains on the back layer. As a method for quantifying this residual ink, JIS P 8254:2013 "Pulp and paper-Test method for effective residual ink concentration (ERIC value) by infrared reflectance measurement" is known.
In this embodiment, the JIS standard ERIC value is specified as one of the physical properties of the back layer. Specifically, the range of the ERIC value of the back layer of the white ball of this embodiment is 200-500, preferably 250-490, more preferably 300-480.
When the ERIC value of the back layer is equal to or higher than the above lower limit, the shielding property of the back layer is enhanced, and dust and dullness of the middle layer can be sufficiently covered. When the ERIC value of the back layer is equal to or less than the above upper limit value, the whiteness of the back layer is further improved, and the appearance is further improved.

The ERIC value of the backing layer is measured by the following method.
First, after immersing a white ball (for example, A5 size) in water or warm water at 50±20°C for 1 to 3 hours, use tweezers to pinch the edge of the back layer to peel it off before it dries, and place it in a rotary dryer. and dried to obtain the backing layer. After obtaining a plurality of back layers in this way, a plurality of back layers are stacked, and visually confirmed that they are not transparent, and the surface (back surface) opposite to the surface on the middle layer side (peeled surface) is peeled as described above. ERIC value is obtained by measuring according to JIS standards.
Here, a method for obtaining the ERIC value by peeling the backing layer from the white ball is shown. It was equivalent to the ERIC value measured on the backside of the chisel. Therefore, the ERIC value of the present invention may be a value obtained by measuring the back layer as a sample before the paper is combined, which is obtained during the manufacture of the white ball.

Dirt of various sizes may be present in the backing layer due to raw materials and manufacturing processes. The number of dust particles (the number of dust particles) can be measured for each size of dust particles by viewing the back layer from above.
The dust count of the backing layer is measured by the following method.
As in the case of measuring the ERIC value described above, the back layer is peeled off from the white ball, and the back side opposite to the middle layer side is measured. Also, as an alternative method that yields equivalent measurement results, a method of measuring the back surface of the backing layer before the sheets are combined may be used.
For measuring the number of dust particles on the back layer, a fine foreign matter measuring device (model number: DIP-200) manufactured by Oji Keisoku Kiki Co., Ltd. is used. The back surface of the back layer is set on the reading side of the scanner provided in the device, and an image of 10 cm×10 cm is taken in at a resolution of 1600 dpi and analyzed by attached software.

The number of dust particles of 0.01 mm ² or more and less than 0.05 mm ² in the back layer is 500 to 15,000/m ² , preferably 1,000 to 15,000/m ² , more preferably 5,000 to 15,000/m ² . , more preferably 10,000 to 15,000/m ² .
When the number of dust particles having the above size is equal to or more than the above lower limit value, the shielding property of the back layer is enhanced, and the dust and dullness of the middle layer can be sufficiently covered. The cost of a manufacturing process can be reduced as it is below said upper limit.

The number of dust particles of 0.05 mm ² or more in the back layer is 50 to 2,000/m ² , preferably 100 to 1,000/m ² , more preferably 150 to 500/m ² . The upper limit of the dust size counted here can be, for example, less than 10 mm ² , and may be less than 2 mm ² .
When the number of dust particles having the above size is equal to or greater than the above lower limit, the cost of the manufacturing process can be reduced. If it is at most the above upper limit, the whiteness of the backing layer will be further improved, and the appearance will be much more excellent.

The number of dust particles of 0.004 mm ² or more and less than 0.01 mm ² in the back layer is preferably 1,000 to 100,000/m ² , more preferably 10,000 to 70,000/m ² , and 30,000 to 50,000/m 2 . ² is more preferred.
When the number of dust particles having the above size is equal to or greater than the above lower limit, the cost of the manufacturing process can be reduced. If it is at most the above upper limit, the whiteness of the backing layer will be further improved, and the appearance will be much more excellent.

The specific absorption coefficient of the backing layer is preferably 40 cm ² /g or more, more preferably 45 cm ² /g or more, and even more preferably 50 cm ² /g or more.
The upper limit of the specific absorption coefficient is not particularly limited, and can be, for example, 60 cm ² /g or less.
When the specific absorption coefficient is at least the above lower limit, the shielding property of the back layer is enhanced, and the dust and dullness of the middle layer can be sufficiently covered.

The specific absorption coefficient of the backing layer is measured by the following method.
As in the case of measuring the ERIC value described above, the back layer is peeled off from the white ball, and the back side opposite to the middle layer side is measured. Also, as an alternative method that yields equivalent measurement results, a method of measuring the back surface of the backing layer before the sheets are combined may be used.
The specific absorption coefficient K and the specific scattering coefficient S of the backing layer are obtained by measuring the single sheet luminous reflectance R ₀ and the intrinsic luminous reflectance R _∞ at a wavelength of 457 nm in accordance with the method of JIS P 8149:2000, Using the R ₀ , R _∞ and the basis weight W (g/m ² ) of the paper, the following three equations (1) were obtained.

The specific scattering coefficient of the backing layer is preferably 300 cm ² /g or more, more preferably 350 cm ² /g or more, and even more preferably 380 cm ² /g or more.
The upper limit of the specific scattering coefficient is not particularly limited, and can be, for example, 400 cm ² /g or less.
When the specific scattering coefficient is at least the above lower limit, the shielding property of the back layer is enhanced, and dust and dullness of the middle layer can be sufficiently covered.

The ISO whiteness of the backing layer is preferably 40-70%, more preferably 45-65%, even more preferably 50-60%.
If the ISO whiteness is above the lower limit, the appearance of the back layer will be excellent. be able to.

The ISO brightness of the back side of the backing layer is measured by the following method.
As in the case of measuring the ERIC value described above, the back layer is peeled off from the white ball, and the back side opposite to the middle layer side is measured. Also, as an alternative method that yields equivalent measurement results, a method of measuring the back surface of the backing layer before the sheets are combined may be used.
The ISO whiteness of the back surface of the backing layer is determined as the whiteness in the measurement including ultraviolet rays in accordance with JIS P 8148:2001.

Waste paper pulp, which is the raw material of the back layer, is waste paper pulp obtained by dispersing printed waste paper. Printed waste paper includes, for example, printed waste paper such as high-quality paper, medium-quality paper, newspaper, fliers, magazines, corrugated cardboard, and paper packs. Among these, sorted waste paper from which corrugated cardboard and paper packs have been previously removed is preferable.
The waste paper pulp may be deinked pulp that has been deinked, but from the viewpoint of reducing production costs, waste paper pulp that has not been deinked is preferable.
The ISO whiteness of the waste paper pulp used as the raw material is preferably about 30 to 50% from the viewpoint of improving the appearance of the back side of the back layer.

The content of waste paper pulp contained in the back layer is, for example, preferably 80 to 100% by mass, more preferably 90 to 100% by mass, and 95 to 100% by mass relative to the total mass of all pulp contained in the back layer. is more preferred, and 98 to 100% by mass is particularly preferred.
Higher waste paper pulp content facilitates waste paper recycling. When fresh pulp is blended, it becomes easier to make the physical properties of the backing layer within the ranges described above.

Examples of fresh pulp include chemical pulp such as kraft pulp and sulfite pulp; mechanical pulp such as thermomechanical pulp and pressure groundwood pulp; semi-chemical pulp such as chemical thermomechanical pulp.

The basis weight of the back layer is preferably, for example, 15 to 40 g/m ² , more preferably 25 to 40 g/m ² , from the viewpoint of reliably preventing white unevenness in the lower back layer and middle layer from affecting the appearance of the back surface of the back layer. is more preferred, 30 to 40 g/m ² is even more preferred, and 35 to 40 g/m ² is particularly preferred.

[surface]
Pulp with high whiteness is usually used for the surface layer. For example, the above-mentioned fresh pulp and deinked pulp of used paper can be mainly used. As the waste paper, highly white waste paper such as high white card, special white, middle white, white manila, and imitation, high color can be preferably used.

[middle class]
The middle layer is usually composed of multiple layers. Pulp constituting each layer of the middle layer may be the same or different.
Since the middle layer is a layer sandwiched between the surface layer and the back layer, pulp of a lower grade than that of the surface layer and the back layer is generally used. For example, disaggregated pulp from newspapers, magazines, tickets, medium-quality rolls, brown imitations, corrugated cardboard, mounts, coupons, balls, and the like.

When a lower surface layer is provided between the surface layer and the middle layer, the pulp used for the surface layer may be used for the lower surface layer, but usually low-grade waste paper compared to the surface layer, that is, a large amount of medium fiber Retained waste paper is used. For example, it is common to use deinked waste paper pulp from newspapers, magazines, colored paper, balls, and the like.

When a lower back layer is provided between the back layer and the middle layer, the pulp used in the back layer may be used for the lower back layer, but usually low-grade waste paper compared to the back layer, that is, medium-density fiber Waste paper containing a large amount of is used.
For example, it is common to use deinked waste paper pulp from newspapers, magazines, colored paper, balls, and the like.

<Effect>
Since the back layer of the white ball of the present invention has the ERIC value and the number of dust particles within a specific range, the back layer can sufficiently shield white unevenness and dullness of the middle layer and the lower back layer. Therefore, the back layer of the white ball of the present invention exhibits a good appearance.

≪Coated white ball≫
The coated white ball of the second aspect of the present invention is obtained by forming a coating layer on at least one surface of the white ball of the first aspect.
[Coating layer]
The coating layer formed on the surface of the surface layer or the back layer of the white ball may be a pigment coating layer containing a pigment and an adhesive, or a clear coating layer containing no pigment in a substantial amount. There may be. By providing the coating layer, it is possible to improve the appearance of the coated surface, increase the rigidity of the coated white ball, and suppress curling.
The coating layer formed on the surface of the surface layer or the back layer of the white ball may be one layer or two or more layers. If the backing layer is provided with a coating layer, one layer is sufficient, as the backing layer of the white ball has an excellent appearance.

The ERIC value of the back layer of a coated white ball provided with a coating layer on the surface side is measured in the same manner as the measurement of the ERIC value of the back layer of the white ball described above.
The ERIC value of the back layer of a coated white ball provided with a coating layer on the back layer side is measured by the following method.
First, a coated white ball (for example, A5 size) is immersed in water or hot water at 50±20° C. for 1 to 3 hours. It is divided into a release body 1 on the coating layer side and a release body 2 on the middle layer side. Usually, the back layer remains without being peeled off on the coating surface (the surface in contact with the back layer) of the coating layer of the release body 1 . In this case, the stripping body 2 consists of a white ball from which the backing layer has been removed.
Next, after the release body 1 is dried, a transparent adhesive tape is attached to the back layer remaining on the release body 1, and the back layer is peeled off to transfer the surface layer to the adhesive surface of the transparent adhesive tape. A plurality of backing layers transferred to the adhesive surface are superimposed and visually confirmed to be opaque, and the surface on the coating layer side is measured according to the above JIS standard to determine the ERIC value.
Here, the method for obtaining the ERIC value by peeling off the backing layer from the coated white ball is shown. It was equivalent to the ERIC value measured on the surface of only the backing layer before papermaking. Therefore, the ERIC value of the present invention may be a value obtained by measuring the back layer as a sample before the white ball is combined, which is obtained during the manufacture of the coated white ball.

The dust count, specific absorption coefficient, specific scattering coefficient, and ISO whiteness of the back layer of the coated white ball are measured by peeling off the back layer from the coated white ball in the same way as when measuring the ERIC value. do. In addition, as an alternative method of obtaining the same result, the back layer obtained during the manufacture of the coated white ball before the white ball is combined may be used as a sample for measurement. Specific measurements are carried out in accordance with the above-mentioned measurement methods and conditions for white balls.

The coating weight (basis weight) of the coating layer provided on the back layer can be, for example, 0.1 to 10 g/m ² in terms of dry solid content, preferably 0.5 to 5 g/m ² .
When the coating amount is equal to or higher than the above lower limit, the surface of the backing layer can be sufficiently covered and a good appearance can be exhibited. When the coating amount is equal to or less than the above upper limit, the excellent appearance of the back layer is likely to be reflected in the appearance of the coating layer, which is advantageous in terms of cost.

The coating amount of the coating layer is obtained by the following method.
A coated white paperboard (for example, A5 size) and a transparent polyethylene film (weight known) larger than the coated white paperboard are superimposed and thermocompressed, and then the pressed product is immersed in a 0.5 mol copper ethylenediamine solution. , After dissolving the paper layer, the integrated product of the film and the coating layer is separated from the white paperboard by washing with water and air-drying. The coating weight of the pigment coating layer is obtained by subtracting the film mass from the combined mass of the film and coating layer. In addition, as a simple measurement method, the coating amount (g/m ² ) of the coating liquid applied when forming the coating layer, the ratio of the solid content of the coating liquid (content of non-volatile components) can also be calculated by accumulating . Alternatively, it may be calculated by subtracting the basis weight of the white ball from the basis weight of the coated white ball.

When the coated white ball has a coating layer on the surface of the surface layer, the opacity of the coating layer is preferably 50 to 100%, more preferably 55 to 80%, more preferably 55 to 65%. % is more preferred.
The above opacity is linked to the pigment content and the basis weight of the coating layer. When the opacity is above the lower limit, the appearance of the coated white ball is less likely to be affected by the surface layer. If the basis weight is equal to or less than the above upper limit, it is advantageous in terms of cost.

When the coated white ball has a coating layer on the surface of the back layer, the opacity of the coating layer is preferably 0 to 50%, more preferably 5 to 30%, and more preferably 10 to 50%. 20% is more preferred. When the coating layer does not contain pigment, the opacity of the coating layer is 0% or close to 0%.
The above opacity is linked to the pigment content and the basis weight of the coating layer. When the opacity is above the lower limit, the appearance of the coated white ball is less likely to be affected by the backing layer. When the opacity is equal to or less than the above upper limit, the excellent appearance of the back layer is likely to be reflected in the appearance of the coating layer, which is advantageous in terms of cost.

The opacity of the coating layer is measured by the following method.
The opacity is measured from the surface opposite to the surface in contact with the back layer or surface layer of the coating layer of the integrated product of the transparent polyethylene film and the coating layer obtained by the above method.
The opacity is measured according to JIS P 8149:2000.

The pigment contained in the pigment coating layer is not particularly limited, and examples thereof include diatomaceous earth, talc, kaolin, calcined kaolin, delaminated kaolin, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, barium carbonate, titanium dioxide, oxide Inorganic fillers such as zinc, silicon oxide, amorphous silica, calcium sulfite, gypsum, white carbon, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, paper sludge, recycled inorganic particles from deinking floss, Known pigments such as urea-formalin resin, polystyrene resin, vinyl chloride resin, melamine resin, phenol resin, and organic fillers such as plastic fine hollow particles can be used.
The pigment contained in the pigment coating layer may be one kind, or two or more kinds.

The adhesive contained in the pigment coating layer or clear coating layer is not particularly limited, and examples thereof include styrene-butadiene, styrene-acrylic, ethylene-vinyl acetate, butadiene-methyl methacrylate, and vinyl acetate-butyl acrylate. and other copolymers, synthetic adhesives such as polyvinyl alcohol, maleic anhydride copolymer, and acrylic acid-methyl methacrylate copolymer; proteins such as casein, soybean protein, synthetic protein; oxidized starch, positive Starch, etherified starch such as urea phosphate esterified starch, hydroxyethyl etherified starch, starches such as dextrin; cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, etc. known adhesives for pigment coating layers. mentioned. One type of adhesive may be contained in the coating layer, or two or more types may be used.

The content ratio of the pigment and the adhesive contained in the pigment coating layer is not particularly limited. Part is more preferred. When it is at least the above lower limit, the strength of the pigment coating layer is sufficiently increased, and when it is at most the above upper limit, the cost can be suppressed.

The coating liquid forming the coating layer may optionally contain known binders, dispersants, viscosity improvers, water retention agents, antifoaming agents, water resistance agents, fluorescent dyes, coloring dyes, coloring pigments, interface Activators, pH adjusters, cationic resins, anionic resins, UV absorbers, metal salts, etc. may be blended.

The coating weight (basis weight) of the coating layer provided on the surface of the surface layer can be, for example, 5 to 50 g/m ² , preferably 10 to 35 g/m ² , in terms of dry solid content.

<Effect>
When the coated white ball of the present invention has a coating layer on the back layer side, the appearance when observed from the coating layer side is greatly affected by white unevenness due to dust and dullness of the back layer. Since the back layer in the present invention has the ERIC value and the number of dust particles within a specific range, the back layer can sufficiently shield white unevenness and dullness of the lower back layer and the middle layer. Therefore, the coated white ball of the present invention exhibits a good appearance regardless of the shielding properties of the coating layer.

≪Manufacturing method of white ball≫
The white ball of the present invention can be manufactured in the same manner as the conventional white ball, except that the back layer is formed so that the physical properties such as the ERIC value and the number of dust particles fall within specific ranges.

When manufacturing a white ball, as a method of forming a back layer having the above-described physical properties, for example, the blending amount of the printed waste paper as a raw material is adjusted based on the ratio of the printed portion possessed by the printed waste paper, or A method of adjusting the strength of the deinking process and the number of times of the kneading process can be mentioned.
If the printed waste paper has less printed areas, the ERIC value of the waste paper pulp can be reduced. In addition, if the intensity of the deinking treatment is increased by increasing the concentration of chemicals used for the deinking treatment of waste paper pulp or increasing the deinking treatment time, the ink remaining on the deinked pulp will be reduced, so the ERIC value can be lowered.
By increasing the number of times of kneading the waste paper pulp or increasing the defibration force of the device used for the kneading process, the foreign matter adhering to the waste paper pulp can be made finer, so that the above-mentioned dust number condition can be satisfied.

The content of waste paper pulp contained in the raw material slurry used when making the back layer is, for example, preferably 80 to 100% by mass, preferably 90 to 100% by mass, based on the total mass of all pulp contained in the raw material slurry. is more preferred, and 95 to 100% by mass is even more preferred.
Higher waste paper pulp content facilitates waste paper recycling. When fresh pulp is blended, it becomes easier to make the physical properties of the backing layer within the ranges described above.
Generally, the pulp composition of the backing layer after papermaking is the same as that of the raw material slurry.

The content of the waste paper pulp contained in the raw material slurry used when making the middle layer is each independently based on the total mass of all pulp contained in the raw material slurry. 100% by mass is more preferable, and 98 to 100% by mass is even more preferable.
Higher waste paper pulp content facilitates waste paper recycling. When fresh pulp is added, the appearance of the middle layer is improved.
Usually, the pulp composition of the paper-making middle layer is the same as the pulp composition of the raw material slurry.
The pulp composition of the raw material slurry for forming the other layers is appropriately adjusted according to the purpose of use.

There are no particular restrictions on the papermaking method of the white board, and for example, paperboard using a Fourdrinier paper machine including a top wire, an on-top former, a gap former, a cylinder paper machine, and a combination of a Fourdrinier paper machine and a cylinder paper machine. It can be carried out using a paper machine, a Yankee dryer machine, or the like.
The pH of the raw material slurry during papermaking may be acidic, neutral or alkaline, preferably neutral or alkaline.

The drying method after paper making is not particularly limited, and for example, various methods such as a steam heating cylinder, a heated hot air dryer, a gas heater dryer, an electric heater dryer, and an infrared heater dryer can be used alone or in combination.

A filler may be internally added to the raw material slurry of each layer.
The filler is not particularly limited, and examples thereof include diatomaceous earth, talc, kaolin, calcined kaolin, delaminated kaolin, ground calcium carbonate, ground calcium carbonate, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous Inorganic fillers such as silica, calcium sulfite, gypsum, white carbon, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, papermaking sludge, inorganic particles recycled from deinked floss, urea-formalin resin, polystyrene resin , vinyl chloride resins, melamine resins, phenolic resins, organic fillers such as hollow plastic microparticles, and fillers contained in used paper and broken paper.
The type of filler internally added to the raw material slurry of each layer may be one type or two or more types.
When the raw material slurry contains a filler, it can be added so that the content of the filler is, for example, 1 to 20% by mass with respect to the total mass of each layer dried after papermaking.

The raw material slurry for each layer may optionally contain a flocculation aid, paper strength agent, dye, pigment, sizing agent, retention aid, drainage improver, and antifoaming agent.

<<Manufacturing method of coated white ball>>
A coated white ball can be produced by coating at least one of the surface layer and the back layer of a white ball with a coating liquid that will form a coating layer. Preferred coating amounts are as described above.

The coating method for forming the coating layer on the white ball is not particularly limited, and known methods such as curtain coating, blade coating and wet-on-wet coating can be applied.

After providing the coating layer on the white ball, the white ball is appropriately dried to adjust the water content to obtain the coated white ball. Moreover, you may perform well-known smoothing processing with respect to a coating layer as needed.

[Example 1]
<Creating the back layer of the white ball>
50% of both sides are the printing part, finely cut colored waste paper into length x width = 3 cm x 3 cm, and hot water are put into a tabletop disintegrator, disintegration treatment is performed at 40 ° C for 10 minutes, and pulp is obtained. A slurry was obtained. The pulp concentration was adjusted to 2% by mass during the defibration treatment.
After concentrating the pulp slurry to a pulp concentration of 25% by mass, kneading treatment is performed 500 times using a PFI mill, and the obtained pulp is washed with running water on a 150-mesh wire mesh, and used paper A pulp was obtained.
Using the above waste paper pulp as a raw material, hand-made paper was prepared with a basis weight of 37.2 g/m ² according to JIS8222:2015 using 150-mesh wire, and used as the back layer of the white ball.

<Measurement of the number of dust particles on the back layer>
The "number of dust particles" present on the surface of the hand-made paper prepared above was measured for each dust size of 1) to 6) below.
To measure the number of dust particles, a fine foreign matter measuring device (model number: DIP-200) manufactured by Oji Scientific Instruments Co., Ltd. is used to set the surface of the hand-made paper on the reading side of the scanner, and a resolution of 1600 dpi and a size of 10 cm × 10 cm. Images were captured and analyzed by the attached software.
1) 0.004 mm ² or more and less than 0.01 mm ² 2) 0.01 mm ² or more and less than 0.05 mm ² 3) 0.05 mm ² or more and less than 0.20 mm ² 4) 0.20 mm ² or more and less than 0.30 mm ² 5) 0.30 mm ² or more and less than 0.50 mm ² 6) 0.50mm2 or ^more

<Measurement of ERIC value of back layer>
The ERIC value of the handmade paper prepared above was measured according to JIS P 8254:2013. The standard stipulates that the basis weight of the hand-made paper used as the test sheet should be 60 g/m ² . In order to comply with this standard, two sheets of hand-made paper prepared above were piled up and used as a test sheet.

<Measurement of whiteness of back layer>
The hand-made paper prepared above was measured for whiteness in a measurement including ultraviolet rays in accordance with JIS P 8148:2001.

<Measurement of specific scattering coefficient/specific absorption coefficient of back layer>
For the handmade paper prepared above, the single sheet luminous reflectance R ₀ and the intrinsic luminous reflectance R _∞ at a wavelength of 457 nm were measured according to the method of JIS P ₈₁₄₉ :2000. Using R _∞ and basis weight W (g/m ² ) of the paper, the specific absorption coefficient K and the specific scattering coefficient S were obtained from the above-mentioned three equations (1).

<Measurement of Opacity of Backing Layer>
The opacity of the handmade paper prepared above was measured according to JIS P 8149:2000.

<Visual evaluation of the appearance of the back layer>
The hand-made paper prepared above was visually observed from a distance of about 10 cm, and the appearance of the backing layer was evaluated according to the following criteria.
A: Dust and dullness cannot be observed.
○: Dust and dullness can be slightly observed.
x: A large amount of dust and dullness can be confirmed.

<Visual evaluation of hiding property of back layer>
The surface of the hand-made paper was pressed from a distance of about 10 cm to the hand-made paper prepared above, with the middle layer containing the waste paper pulp separated from the commercially available white ball and containing the waste paper pulp dispersed with the printed waste paper pressed against the back side. Visual observation was performed, and the concealability of the handmade paper was evaluated according to the following criteria.
A: No dust or dullness in the middle layer was observed, and the whiteness of the middle layer was hardly affected.
◯: Dust and dullness in the middle layer cannot be confirmed, but are affected by the whiteness of the middle layer.
x: Dust and dullness in the middle layer can be confirmed, and the whiteness of the middle layer is affected.

Table 1 shows the results of the above measurements and evaluations.
In the back layer of Example 1 showing the results in Table 1, the dust and dullness of the middle layer were sufficiently hidden by the back layer, and the back layer exhibited a good appearance.

[Example 2]
As the raw material waste paper, hand-made paper (back layer) was prepared in the same manner as in Example 1, except that colored waste paper with 70% of the printed part on both sides was used, and the results were measured and evaluated. are shown in Table 1.
The reason why Example 2 shows a higher ERIC value than Example 1 in the results of Table 1 is that the waste printed paper used as the raw material contains more ink.
In the back layer of Example 2 showing the results in Table 1, the dust and dullness of the middle layer were sufficiently concealed, and the back layer exhibited a good appearance.

[Example 3]
As the raw material waste paper, hand-made paper (back layer) was prepared in the same manner as in Example 1, except that colored waste paper with 90% of the printed part on both sides was used, and the results were measured and evaluated. are shown in Table 1.
In the results of Table 1, the reason why Example 3 shows a higher ERIC value than Examples 1 and 2 is that the waste printed paper used as the raw material contains more ink.
The reason why Example 3 shows more dust than Example 1 and less than Example 2 (0.004 mm ² or more and less than 0.01 mm ² and 0.01 mm ² or more and less than 0.05 mm ² ) in the results of Table 1 The reason for this is that the coating amount of waste paper is large and the amount of ink that directly adheres to the pulp fibers is small.
In the back layer of Example 3 showing the results in Table 1, dust and dullness in the middle layer were sufficiently concealed, and the back layer exhibited a good appearance.

[Comparative Example 1]
A hand-made paper (back layer) was prepared in the same manner as in Example 1 except that bleached hardwood pulp (LBKP) was used instead of waste paper as a raw material, and the results of measurement and evaluation are shown. 1.
As shown in Table 1, the ERIC value of Comparative Example 1 was less than 200. As a result, in the back layer of Comparative Example 1, the concealment of dust and dullness in the middle layer was insufficient.

[Comparative Example 2]
A hand-made paper (back layer) was prepared in the same manner as in Example 2 except that the kneading treatment was not performed, and the results of measurement and evaluation are shown in Table 1.
As shown in Table 1, the ERIC value of Comparative Example 2 was less than 200. As a result, in the back layer of Comparative Example 2, the concealment of dust and dullness in the middle layer was insufficient.

[Comparative Example 3]
Hand-made paper (back layer) was prepared in the same manner as in Comparative Example 2, except that colored waste paper with 90% of the printed portion on both sides was used as the raw material waste paper, and the results were measured and evaluated. are shown in Table 1.
As shown in Table 1, the number of dust particles (0.01 mm ² or more and less than 0.05 mm ² ) in Comparative Example 3 was more than 15,000, and the number of dust particles (0.05 mm ² or more) was more than 2,000. As a result, in the surface layer of Comparative Example 3, the evaluation of dust and dullness of the back layer itself was poor, and the appearance was poor.

Claims (8)

A multi-layered white ball having a surface layer, a middle layer and a back layer,
The back layer contains waste paper pulp obtained by dispersing printed waste paper,
The ERIC value of the backing layer is in the range of 200 to 500,
A white ball, wherein the number of dust particles of 0.01 mm ² or more and less than 0.05 mm ² is in the range of 500 to 15,000/m ² and the number of dust particles of 0.05 mm ² or more is in the range of 50 to 2,000/m ² in plan view of the back layer. . The content of the waste paper pulp is 90 to 100% by mass with respect to the mass of the total pulp contained in the backing layer,
2. The white ball according to claim 1, wherein the content of the waste paper pulp is 95 to 100% by mass with respect to the total mass of pulp contained in the intermediate layer. 3. The white ball according to claim 1, wherein the back layer has a specific absorption coefficient of 50 cm ² /g or more. A white ball according to any one of claims 1 to 3, wherein the ISO whiteness of the backing layer is in the range of 45-60%. The white ball according to any one of claims 1 to 4, wherein the back layer has a basis weight of 15 to 40 g/ ^m2 . 6. The white ball according to any one of claims 1 to 5, except when the printed waste paper is only waste newspaper. A white ball according to any one of claims 1 to 6, wherein the printed waste paper comprises colored waste paper. A coated white ball, comprising a coating layer provided on at least one surface of the white ball according to any one of claims 1 to 7 .