JPH02293499A - Composition for liner coating and coating liner - Google Patents

Abstract

PURPOSE:To obtain the title composition containing a pigment ingredient consisting of an inorganic pigment having hardness being specific value or above, inorganic pigment having hardness being specific value or below and organic pigment each contained at a specific ratio and having excellent optical characteristics, printability and corrugated board producing ability. CONSTITUTION:The aimed composition containing a pigment ingredient consisting of 0-10wt.%, preferably 0-2wt.% inorganic pigment (e.g. calcium carbonate, aluminum hydroxide or titanium dioxide) having >=3 Mohs hardness, 60-95wt.% inorganic pigment (e.g. talc, kaolinite or clay) having <3 Mohs hardness and 5-30wt.% organic pigment (e.g. PS). Furthermore, the lowest film- forming temperature of the organic pigment is preferably <=75 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a liner coating composition, and more specifically to a coated liner having excellent optical properties, printability, and corrugated board manufacturing suitability, and a coated liner using the same. This invention relates to a liner coating composition for manufacturing. (Prior Art) Corrugated board is composed of liners that form the front and back sides of the corrugated board, and core base paper that forms corrugated corrugations to support the front and back liners at regular intervals. There are various types of corrugated cardboard such as single-sided corrugated cardboard, double-sided corrugated cardboard, double-sided corrugated cardboard, and double-sided corrugated cardboard. Single-sided corrugated board is made by laminating a liner on one side of corrugated core paper, and is rarely used alone for exterior packaging, but is primarily used as a cushioning material. Double-sided corrugated board is made by laminating liners on both sides of corrugated core paper, and is most commonly used for the exterior of boxes and other items. Double-sided corrugated board or double-sided corrugated board is a multilayered corrugated board containing multiple corrugated core base papers and is used for heavy goods packaging. Corrugated boxes made from corrugated cardboard are lightweight, yet have a certain level of strength and cushioning properties due to the use of a corrugated corrugated core, so they can be used for various industrial products, It is prized for packaging agricultural products, marine products, etc.

Incidentally, in recent years, it has become common practice to print multicolors on the exterior of cardboard boxes in order to accurately display products packaged in cardboard boxes and to stimulate consumers' desire to purchase. ing. When such multicolor printing is performed, a white liner is generally used as the liner for manufacturing corrugated boxes. However, ordinary liners are yellow-brown in color because they are usually made from unbleached kraft bulp by combining sheets. Therefore, in order to manufacture white liners for corrugated boxes, there are two methods: ■ Using bleached kraft pulp on the surface layer of the paperboard to whiten the color, ■
Two methods are used: one is to apply pigment coating to a tan liner made from normal unbleached kraft pulp, and the other is to apply pigment coating to a white liner using bleached kraft pulp for the surface layer. On the other hand, it is well known that paper products with excellent optical properties and printability can be obtained by applying a pigment coating composition containing a white pigment as a main component to paper. Namely, clays such as kaolinite clay and hydrated halloysite, aqueous dispersions of white pigments such as calcium carbonate, aluminum hydroxide, titanium dioxide, and talc; synthetic rubber latex, polyacrylate latex, and polyvinyl acetate latex. Excellent optical aptitude and printing can be achieved by coating a base paper with a pigment coating composition whose main component is an adhesive consisting of a synthetic polymer latex such as; and an aqueous solution of a water-soluble polymer such as starch or casein. Coated papers such as art paper and coated paper, as well as coated white bonore and coated manila, can be obtained. Therefore, by adopting the method described above, it is possible to improve the optical properties and printability of the coated liner to a certain level. However, conventional coated liners often cause black stains on the coated surface during the manufacture of corrugated cardboard, which is a major problem as it reduces the commercial value of the corrugated cardboard. (Problems to be Solved by the Invention) The purpose of the present invention is to provide a coated liner that does not stain the coated surface during the production of corrugated board and has excellent optical properties and printability, and a liner coating for producing the same. The objective is to provide a composition. In order to achieve the above object, the inventors of the present invention have conducted extensive studies on the causes of stains on the coated surface, and have found that the composition of the pigment in the liner coating composition is related. As a result of further investigation into the structure of the present invention, we have arrived at the present invention. (Means for Solving the Problems) Thus, according to the present invention, 0 to 10% by weight of an inorganic pigment with a Mohs hardness of 3 or more, and 60 to 9% by weight of an inorganic pigment with a Mohs hardness of less than 3.
A liner coating composition characterized by containing a pigment component consisting of 5% by weight and 5 to 30% by weight of an organic pigment, and a coated liner obtained by coating this liner coating composition. provided.

In the liner coating composition of the present invention, the pigment component 10
The content of inorganic pigments with a Mohs hardness of 3 or more in 0 parts by weight is 1
It is essential that the amount is 0'ffit parts or less, preferably 5 parts by weight or less, and more preferably 2 parts by weight or less. If the amount of the inorganic pigment with a Mohs hardness of 3 or more exceeds 10 parts by weight, the coated surface will become extremely dirty, significantly reducing the commercial value of the corrugated board. Inorganic pigments with a Mohs hardness of 3 or higher include calcium carbonate (calcite), aluminum hydroxide, and
Examples include titanium dioxide having a Mohs hardness of 5.5 to 7, but are not limited thereto. Furthermore, in the liner coating composition of the present invention, 60 parts by weight of an inorganic pigment having a Mohs hardness of less than 3 is contained in 100 parts by weight of the pigment component.
It is necessary to use ~95 parts by weight. This results in
Contamination on the coated surface of cardboard is reduced or eliminated. Pigments with a Mohs hardness of less than 3 include, but are not limited to, talc with a Mohs hardness of 1 and kaolinite clay with a Mohs hardness of 1.5 to 2.

Furthermore, as examples of inorganic pigments other than those exemplified above, the Japan Powder Industry Association [r Powder Measurement Handbook] 230-23
The one described on page 2 (published by Nippon Kogyo Shimbun, 1982) can be mentioned. Note that even inorganic pigments with the same chemical composition have different Mohs hardnesses due to differences in crystal shape, so it is necessary to select an inorganic pigment with a hardness that satisfies the purpose of the present invention. In the present invention, the mechanism by which staining on the coated surface can be prevented by controlling the amount of inorganic pigment is not clear, but it can be estimated as follows. In other words, corrugated board is first corrugated on a core base paper using corrugated rolls heated to 150°C or higher, and after applying adhesive to the top of the corrugations, this and a liner are bonded together using press rolls to form a single corrugated board. It is then manufactured by applying adhesive to the top of one corrugated board, attaching the liner on the opposite side, and drying it on a hot plate. However, in the bonding step and drying step, the pigment-coated surface of the liner coated with the M material comes into contact with a press roll or a hot plate.

At this time, the part of the core that corresponds to the step top is strongly subjected to heat, pressure, and frictional force, and therefore the pigment-coated surface of this part wears the roll surface and hot plate surface, and although it is very slight, the roll surface It is thought that this scrapes the surface of the hot plate and transfers it to the coated surface, causing black stains on the coated surface. In contrast, in the present invention, by appropriately selecting the composition of the inorganic pigment, the hardness of the pigment-coated surface is maintained at an appropriate level, thereby preventing the roll surface and hot plate surface from being scraped. It is thought that there are. Next, in the present invention, it is also an essential requirement that 5 to 30 parts by weight of the organic pigment be contained in 100 parts by weight of the pigment component. The use of organic pigments can provide coated liners with excellent optical properties and printability such as ink receptivity and image reproducibility. In the present invention, there are restrictions on the inorganic pigments that can be used from the perspective of preventing staining of the coated surface, so it is essential to use organic pigments to provide excellent optical properties and printability. Additionally, by using organic raw materials, staining on the coated surface can be kept to an even lower level. This is thought to be because organic pigments are inherently more flexible than inorganic pigments, making it less likely that the roll surface or hot plate surface will be scraped off. The organic pigment used in the present invention is a pigment made of polymer particles, that is, a plastic pigment in a broad sense. ``Plastic pigments in a broad sense can be classified into plastic pigments in a narrow sense (hereinafter simply referred to as plastic pigments) and binder pigments. The plastic pigment used in the present invention is an organic pigment without film-forming properties. As a specific example,
“Coating pigments and papermaking fillers” translated by Reisaburo Oe and Saburo Yoshimura
(22 Publishing, published in 1989), but the most common one is boristyrene. The binder/vidament used in the present invention may be any plastic pigment in a broad sense that has the function of a binder, that is, an adhesive. Here, having the function of an adhesive means that it has film-forming properties, that is, it can form a film. In order to form a film, it is necessary for the polymer particles to fuse with each other, and the lowest temperature at which this fusion can occur is called the minimum film-forming temperature. Whether or not the organic pigment functions as a binder can be determined by the minimum film-forming temperature of the organic pigment. The minimum film-forming temperature of the binder pigment used in the present invention is not particularly limited, but is preferably below the temperature in the drying process after the liner coating composition is applied to the substrate. Generally, the above temperature is 7
In other words, in the present invention, the minimum film forming temperature for the binder pigment is about 75°C.
It is preferable to use the following: The usage form of the organic pigment used in the present invention is not particularly limited, but it is usually used as a latex obtained by an emulsion polymerization method.

In addition, methods for producing these binders and pigments are disclosed in Japanese Patent Publication No. 57-26692 and Japanese Patent Publication No. 62-3111.
5, JP 62-61720, JP 54-13101
3. JP-A-55-45724, JP-A-63-30319
Examples include, but are not limited to, the methods disclosed in No. 5 and the like. Furthermore, the particle structure of these binder pigments is known to have a two-layer structure with a core of polystyrene and a shell of styrene-butadiene (Paper Vulp Technology Association Journal, Vol. 43, No. 2, pp. 159-166). , 1989)
However, I don't mind anything else. In the present invention, the blending amount of the organic pigment is 5 to 30 parts by weight per 10 parts by weight of the pigment component. If the amount is less than 5 parts by weight, the effect of improving optical properties and printability will be insufficient;
If it exceeds 0 parts by weight, the coating cost will increase and it is not practical. The amount of organic raw material to be blended is determined based on the quality required of the resulting coated liner; for example, when high gloss is required, it is preferable to increase the amount of organic pigment blended. In the liner coating composition of the present invention, a binder is usually used to bond the pigments to each other and to bond the pigments to the base paper. Specific examples include so-called styrene-butadiene copolymer latex such as carboxylated styrene-butadiene copolymer latex and carboxylated styrene-methyl methacrylate butadiene copolymer latex, polyvinyl acetate latex, and polyacrylic acid. Known binders include synthetic polymer latexes such as ester latex; water-soluble polymers such as starch, casein, and polyvinyl alcohol. These binders can be used alone or in combination of two or more. When using a binder pigment as an organic pigment, the above-mentioned ordinary binder may not be used as long as its adhesive strength is sufficient. The liner coating composition of the present invention further includes a dispersant for improving the dispersibility of the inorganic pigment, a viscosity modifier and a water retention agent for controlling the flow characteristics of the coating composition. Known additives such as pH adjusters, antifoaming agents, dyes, coloring pigments, fluorescent dyes, and preservatives can be used. By applying the liner coating composition of the present invention to a liner, which is a base material, it is possible to obtain a coated liner that has excellent optical properties and printability, and does not cause stains during corrugated board production. In order to apply the liner coating composition of the present invention to a liner, a known coating device such as a roll coater, an air knife coater, a bar coater, a blade coater, etc. can be employed. The preferred composition coating amount is 5 to 5 by dry weight.
It is 25g/m2. The method for applying the liner coating composition of the present invention may be single coating or double coating. In double coating, as long as the liner coating composition of the present invention is used in the top coating layer, it is also possible to use a material other than the liner coating composition of the present invention in the undercoating layer. This is because the purpose of the present invention, which is to solve stains during the production of corrugated board and to improve the optical properties and printability of the coated surface, mainly depends on the top coating layer. A known drying device such as a cylinder dryer or an air dryer can be used to dry the liner coating composition of the present invention after it has been applied. If necessary, a gloss treatment can be applied to the coated surface after one coat has dried, thereby further improving the gloss and printability of the coated surface. Super calendar as a glossing device,
Known calenders such as gloss calenders and soft nip calenders can be used. (Effects of the Invention) Thus, the present invention provides a liner coating that does not cause stains on the coated surface during corrugated board production, provides excellent gloss and whiteness to the coated surface, and also exhibits excellent ink receptivity during printing. An industrial composition is obtained. By using this liner coating composition, a coated liner can be obtained which has excellent optical properties and printability, and which does not cause stains on the coated surface during the production of corrugated board. Furthermore, the products packaged with the cardboard can be accurately and beautifully printed on the cardboard manufactured using this coated liner. (Example) The present invention will be explained in more detail with reference to Examples below. However, the present invention is not limited to the following examples. Note that parts and percentages in the examples are based on weight unless otherwise specified. Example 1 (Preparation of liner coating composition) A liner coating composition with a concentration of 50% was prepared by vR using the formulation shown in Table 1. (The number of copies.). Each liner coating composition contained 0.2 parts of Aron T40 (manufactured by Toagosei Co., Ltd.) as a dispersant and 5 parts of New Zealand casein as a binder. As the binder latex, Nipol Lx407C (manufactured by Nippon Zeon Co., Ltd.), a styrene-butadiene copolymer latex commercially available as a latex for clay coating, was used. The blending amounts are shown in Table 1. The Mohs hardness of the inorganic pigments used in the formulation is shown in Table 2 based on the catalog description of each product. [See below for margins] Also, the organic pigments A to D used in the formulation were synthesized by emulsion polymerization and used in a latex state. Organic pigment A
, B and C are all binder pigments. Organic pigments A and B both have a two-layer copolymer structure in which a shell is formed by copolymerizing a monomer composition of styrene, butadiene, and methacrylic acid on the core of polystyrene particles obtained by polymerizing styrene. It is a coalesced particle. Organic pigment C is obtained by copolymerizing a monomer composition consisting of styrene and methacrylic acid on the core of copolymer particles obtained by copolymerizing a monomer composition consisting of styrene, butadiene and methacrylic acid. These are two-layer structure copolymer particles that form a shell. Organic pigment D is a plastic pigment made of polystyrene particles obtained by one-step polymerization of styrene. Table 3 shows the monomer composition, number average particle diameter, and minimum film forming temperature of each copolymer constituting these organic pigments. The number average particle diameter is the value measured using an electron micrograph of the organic pigment particles, and the minimum film forming temperature is the value measured using a film forming tester (manufactured by Tester Sangyo Co., Ltd.). Table 3 Example 2 (Manufacture of coated liner) Liner coating compositions 1 to 16 prepared according to the formulations shown in Table 1 were used as a white liner (with bleached kraft valves on the surface layer). Coated using a wire bar (manufactured by Kumagai Riki Kogyo Co., Ltd.) and heated in a hot air oven (130°C).
Dry for 30 seconds. The dried paper was glossed using a gloss calendar (Yuri Roll Kikai Co., Ltd.'R) to obtain coated liners L1 to L16 corresponding to each liner coating composition. The coating amount was 7 g/m2 (dry weight, t) in each case. (Evaluation of Coated Liners) Each characteristic of the coated liners L1 to L16 obtained above was evaluated. The evaluation method is as follows. In addition, for each property other than wear staining, the larger the value, the better the property. - Abrasion stains on the coated surface of the coated liner: The coated surface was scratched with a copper and nickel round rod (1 cm in diameter), and judgment was made based on whether stains appeared on the scratched area. A 0 mark means that no stain has occurred, and an x mark means that a stain has occurred.・White paper gloss: Gloss meter (manufactured by Murakami Color Technology Research Institute)
It was measured using - Printing gloss: The offset ink was printed solidly using an RI tester (manufactured by Mei Seisakusho), and after drying, it was measured using a gloss meter. - Whiteness: Measured with a Hunter whiteness needle (manufactured by Mura-E Color Technology Research Institute).・Ink receptivity: Apply K&N ink to the coating surface,
The whiteness was measured after wiping it off after a few minutes, and calculated using the following formula. Ink receptivity (%) K&N Ink K&N Ink Whiteness and surface strength before application of K&N Ink: Acceleration printing is performed using pinking test ink with R etester (manufactured by Mei Seisakusho), and the degree of peeling It was determined. Judgment was made using a 5-point system. The intermediate value was determined based on the degree of occurrence of a shock, with 5 indicating no shock and 1 indicating a significant occurrence. The evaluation results are shown in Table 4. [Space below] The following can be pointed out from Table 4. Coated liners L1 to L8 coated with liner coating compositions 1 to 8 of the present invention did not generate any stains in the abrasion stain test on the coated surface, and also showed white paper gloss, print gloss, whiteness, ink It showed good results in each test of acceptability and surface strength. Coated liner L7 coated with liner coating composition 7 using a plastic pigment made of boristyrene as organic pigment D has the same properties as organic pigments in terms of abrasion stains, white paper gloss, printing gloss, and ink receptivity. amount of binder pigment (organic pigment B)
or Coated liner L2 or L coated with liner coating composition 2 or 5 having the same composition except that C) was used.
5, but inferior in surface strength.
Coated liner L coated with liner coating composition 8, which has an increased amount of binder latex in liner coating composition 7.
Although good surface strength was obtained with No. 8, ink receptivity decreased. On the other hand, in coated liners L9 to L12 (control examples) coated with a liner coating composition containing more than 10 parts by weight of an inorganic pigment with a Mohs hardness of 3 or more,
It can be seen that stains occur in the abrasion stain test regardless of the amount of organic pigment. In addition, coated liners L13 to L15 were coated with liner coating compositions 13 to 15, which did not contain any pigments with a Mohs hardness of 3 or higher as inorganic pigments, but had an organic pigment content of less than 5 parts by weight (control liners L13 to L15). For example,
There were no abrasion stains or stains, but the white paper was glossy and
The whiteness, printing gloss, and ink receptivity were inferior to the coated liner coated with the liner coating composition of the present invention. Furthermore, the coated liner L16 is coated with a liner coating composite 16 in which the content of an inorganic pigment with a Mohs hardness of 3 in the pigment component is less than 10%, but does not contain an organic pigment.
(Contrast Example) Abrasion stains occurred. The uncoated white liner Ll7 used as a control had no problems in terms of abrasion stains, but it showed significant differences in white paper gloss, print gloss, whiteness, and surface strength. It was inferior to the coated liner of the invention example.

Example 3 (Evaluation of coated liner manufactured using an actual machine) Liner coating compositions 2 and 10 were applied to a liner using an actual air knife coater, and the resulting coated liner and uncoated white liner were used to coat corrugated cardboard. The resulting cardboard was printed. The evaluation results are shown in Table 5. Table 5 The results show that by using the liner coating composition of the present invention, a coated liner that has excellent optical properties and printability and does not cause stains during corrugated board production can be obtained. It can be seen that when a liner coating composition with a pigment composition outside the range specified in the present invention is used, the resulting coated liner is inferior in all properties. *
In addition, when an uncoated white liner was used, although there was no stain during corrugated board manufacturing, it was found that the white paper gloss, whiteness, and printing gloss were inferior. In addition, when an uncoated white liner was used in Example 2, although it showed good ink receptivity, bleeding occurred during printing on an actual machine, resulting in poor image reproducibility. I understand. Patent applicant Zeon Corporation

Claims (3)

[Claims] (1) It is characterized by containing a pigment component consisting of 0 to 10% by weight of an inorganic pigment with a Mohs hardness of 3 or more, 60 to 95% by weight of an inorganic pigment with a Mohs hardness of less than 3, and 5 to 30% by weight of an organic pigment. Composition for liner coating. (2) The liner coating composition according to claim (1), wherein the organic pigment has a minimum film-forming temperature of 75° C. or lower. (3) A coated liner obtained by coating the liner coating composition of claim (1).