Manufacturing method of coated paper for heat sealing

Abstract

To provide a method for producing a heat sealing coated paper having excellent printability and good heat-sealability.SOLUTION: A method for producing a heat sealing coated paper of the invention comprises the steps of: preparing a base paper; preparing a coating for the coating layer; and coating at least one side of the base paper with the coating for the coating layer to provide one coating layer, wherein the coating for the coating layer contains pigments and an adhesive, and the adhesive contains styrene-butadiene rubber copolymer latex having an average particle size of 100 nm or larger.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for producing a coated paper for heat sealing which has excellent printability and good heat sealing properties. [Background technology]

[0002] Heat sealing is one of the sealing methods, which melts and bonds plastic films by applying a certain amount of heat and pressure. Conventionally, heat sealing processing has been used for bonding bags for packaging materials and molding paper cups. For paper cups with heat sealing properties, there have been proposals such as using biaxially oriented polyethylene terephthalate as a heat seal layer, or using multiple resins in a specific ratio (see, for example, Patent Documents 1 to 4). However, when applying high-quality printing to the opposite side of the heat seal layer, a pigment coating layer is provided, but the adhesion to this coating layer cannot be made satisfactory. There has been a proposal to provide a water-resistant and oil-resistant resin layer on a prescribed amount of undercoat layer containing pigment (see, for example, Patent Document 5). This method does not provide good print quality because there is no pigment coating layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-43388 A [Patent Document 2] JP 2011-79584 A [Patent Document 3] JP 2009-149351 A [Patent Document 4] JP 2006-256643 A [Patent Document 5] Japanese Patent Application Publication No. 9-158089 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a method for producing a coated paper for heat sealing which overcomes the above-mentioned problems and has excellent printability and good heat sealing properties.

[0005] Another object of the present invention is to provide a method for producing coated paper for heat sealing in which, when the coated paper for heat sealing is broken, the base paper or base paper portion and the coating layer do not peel off at the interface, but break as one piece.

[0006] Further objects and advantages of the present invention will become readily apparent to those skilled in the art by reading the following description. [Means for solving the problem]

[0007] As a result of extensive investigations into the manufacturing method of coated paper for heat sealing, the inventors have found that the object can be achieved by the following configuration: That is, the manufacturing method of coated paper for heat sealing according to the present invention comprises the steps of preparing a base paper, preparing a coating layer paint, and applying the coating layer paint to at least one surface of the base paper to provide a coating layer, wherein the coating layer paint contains a pigment and an adhesive, and the adhesive contains a styrene-butadiene rubber copolymer latex having an average particle size of 100 nm or more.

[0008] According to this method, it is possible to produce a relatively thin heat-sealable coated paper having excellent printability.

[0009] Also, a different embodiment of the method for producing coated paper for heat sealing according to the present invention includes the steps of preparing a base paper, preparing a paint for an outermost coating layer, preparing a paint for an inner coating layer, applying the paint for the inner coating layer to at least one surface of the base paper to provide one or more inner coating layers, and applying the paint for the outermost coating layer on the inner coating layer to provide an outermost coating layer, wherein the paint for the outermost coating layer contains a pigment and an adhesive, and the adhesive of the paint for the outermost coating layer contains a styrene-butadiene rubber copolymer latex having an average particle size of 100 nm or more.

[0010] According to this method, it is possible to produce a relatively thick heat-sealable coated paper having excellent printability.

[0011] In a preferred embodiment of the present invention, the coating layer paint and the outermost coating layer paint preferably contain 5 to 30 parts by mass of the styrene-butadiene rubber copolymer latex having an average particle size of 100 nm or more per 100 parts by mass of the pigment. With this configuration, it is possible to produce a heat-sealable coated paper that has good heat-sealing suitability in addition to printability.

[0012] In a preferred embodiment of the present invention, the styrene-butadiene rubber copolymer latex having an average particle size of 100 nm or more preferably has an average particle size in the range of 100 to 200 nm, which can provide better heat sealability.

[0013] In a preferred embodiment of the present invention, the disintegrated freeness of the base paper is preferably in the range of 300 to 550 ml. With this configuration, a coated paper for heat sealing having an excellent balance between paper strength and processing suitability can be obtained.

[0014] In a preferred embodiment of the present invention, one or more intermediate coating layers may be formed between the inner coating layer and the outermost coating layer.

[0015] The present invention can also be understood as an invention of coated paper for heat sealing.

[0016] The present invention can also be seen as an invention relating to paper cup containers and packaging paper using the heat-sealable coated paper. Effect of the Invention

[0017] The present invention can provide a method for producing a coated paper for heat sealing which has excellent printability and good heat sealing properties. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a coated paper for heat sealing according to the present invention. [Diagram 2] FIG. 2 is a diagram showing an example of the configuration of a base paper of a heat-sealing coated paper according to the present invention. [Diagram 3] 1 is a table showing the configuration and evaluation of coated papers for heat sealing according to Examples and Comparative Examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Next, the present invention will be described in detail with reference to an embodiment, but the present invention is not limited to the description. Various modifications of the embodiment may be made as long as the effects of the present invention are achieved.

[0020] An example of the configuration of the heat-sealing coated paper according to the present invention is shown in Figure 1. In the figure, 10 is a base paper, 20 is a size layer, 30 is a base paper, 31 is a base paper surface, 40 is a coating layer, 41 is an inner coating layer, 42 is an intermediate coating layer, 43 is an outermost coating layer, 50 is an outer surface of the heat-sealing coated paper, and 100 is a heat-sealing coated paper. Figure 1(a) shows an example of the configuration of the heat-sealing coated paper when there is one coating layer, in which a size layer 20 is provided on both sides of the base paper 10, and a coating layer 40 is provided on the size layer 20. Figure 1(b) shows an example of the configuration of the heat-sealing coated paper when there are three coating layers, in which a size layer 20 is provided on one side of the base paper 10, and a size layer is provided on the surface of the base paper 10 to form the base paper 30. On the base paper surface 31, coating layers 40 are provided in the order of an inner coating layer 41, an intermediate coating layer 42, and an outermost coating layer 43. In the example of Fig. 1(b), three coating layers are provided, but if there are two coating layers, intermediate coating layer 42 is not necessary, and conversely, if there are four or more coating layers, it is preferable to provide multiple intermediate coating layers 42. Note that Fig. 1 is a schematic representation of the structure of the heat-sealing coated paper according to the present invention, and the thicknesses of the layers in the figure are not based on the actual ratio of the layers.

[0021] An example of the structure of the base paper of the heat-sealing coated paper according to the present invention is shown in Figure 2. In the figure, 10 is the base paper, 11 is the middle layer, 12 is the white underlayer, 13 is the white layer, and 14 is the surface of the base paper. The structure shown in Figure 2 is an example of a multi-layered base paper, in which the layer exposed on both base paper surfaces 14 is the white layer 13, the layer adjacent to the inside of the white layer 13 is the white underlayer 12, and the layer provided inside the white underlayer 12 is the inner layer 11. In this example, the base paper has a five-layer structure, but if it has a three-layer structure, it is possible to omit the white underlayer 12 or the inner layer 11. On the other hand, if it has a six-layer structure or more, it is preferable to appropriately increase the number of layers of the white underlayer 12 or the inner layer 11.

[0022] In the present invention, known pulps such as bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), bleached hardwood sulfite pulp (LBSP), bleached softwood sulfite pulp (NBSP), mechanical pulp (GP, TMP, BCTMP), and deinked pulp (DIP) can be used as the pulp for the base paper. In addition, in addition to wood pulp, non-wood pulp, synthetic pulp, synthetic fiber, etc. may be used as appropriate, if necessary. In order to give whiteness and a clean feeling to the heat-sealing coated paper, it is preferable to use LBKP or NBKP in the white layer that becomes the surface, and when using mechanical pulp, it is preferable to not mix it in the white layer but mix it in the white underlayer or middle layer from the viewpoint of fading. In addition, deinked pulp (DIP) may be mixed in the white layer if it is a high-quality waste paper, but in the case of medium-quality waste paper, it is preferable to not mix it in the white layer but mix it in the white underlayer or middle layer.

[0023] The disintegration freeness of the pulp of each layer used in the base paper of the heat-sealing coated paper is preferably in the range of 300 to 550 ml, and more preferably in the range of 350 to 500 ml. If the disintegration freeness is less than 300 ml, the base paper becomes dense and too hard, which may cause cracks when molded into a paper cup, or cracks at creases when processed into packaging paper. On the other hand, if it exceeds 550 ml, the interfiber bond is weakened, the paper strength is reduced, and the strength is low after processing into a container or when used as packaging paper, which may cause problems in use. The disintegration freeness of the pulp of each layer in the present invention is obtained by measuring with a Canadian Standard Type Freeness Tester (based on JIS P 8121:1995 "Testing Method for Freeness of Pulp").

[0024] The base paper of the heat-sealing coated paper according to the present invention may contain a filler, such as light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, calcined clay, titanium dioxide, or aluminum hydroxide.

[0025] The base paper of the heat-sealing coated paper according to the present invention may contain raw materials other than pulp and fillers. Examples of such raw materials include aluminum sulfate, sizing agents, internal paper strength enhancers such as cationic starch or polyacrylamide, retention improvers, drainage improvers, coloring dyes, coloring pigments, fluorescent brighteners, and fluorescent decolorizers, and other auxiliary agents that may be suitably blended according to the product. In addition, chemicals required in the papermaking process, such as pitch control agents and defoamers, may be used as necessary.

[0026] In the case of the heat-sealing coated paper of the present invention, when the application is to be used as packaging paper, the base paper is made of a single layer or two layers, and the basis weight of the finished heat-sealing coated paper is 50 to 150 g / m 2 The basis weight is preferably in the range of 50 g / m 2 If the paper weight is less than 150 g / m, it will not have sufficient strength for use as wrapping paper and will be prone to tearing. 2 If the basis weight exceeds 150 g / m, the thickness of the base paper will also increase, making the heat-sealing coated paper harder and causing it to lack flexibility as packaging paper. 2 If the thickness is less than this, it is preferable for the base paper to be single-ply or two-ply; the more layers there are, the harder the paper itself becomes, and in the case of a multi-layer structure, there is a possibility of delamination occurring due to the gaps between the layers, so a single layer is more preferable.

[0027] In addition, when the application is for paper cups, the base paper should be made of three or more layers, and the basis weight of the finished heat-sealing coated paper should be 150 to 400 g / m. 2 The basis weight is preferably in the range of 150 g / m 2 If the basis weight is less than 400 g / m, the strength is insufficient and the paper cup may be crushed when picked up. 2If it exceeds this value, the thickness of the base paper will also increase, so the heat-sealing coated paper will become hard, and the flexibility suitable for processing into paper cups will not be obtained, which may result in processing defects. In addition, if a single-layer or two-layer base paper is to be made to a thickness suitable for paper cup applications, it is necessary to increase the inlet concentration, which is the concentration at the inlet of the papermaking machine, to increase the basis weight per layer, which results in large flocs of the raw material, poor texture, and a base paper with poor printability. For this reason, when increasing the basis weight of the base paper for use in applications such as paper cups, it is preferable to make it a multi-layer paper with three or more layers.

[0028] The method for producing the base paper of the heat-sealing coated paper according to the present invention is not particularly limited and can be produced by known production methods, but when producing a relatively thin heat-sealing coated paper for use in packaging paper, etc., it is preferable to use a paper machine suitable for single-layer or two-layer papermaking. On the other hand, when producing a relatively thick heat-sealing coated paper for use in paper cups, etc., among these known production methods, various devices that are paper machines capable of three or more layers of multi-layer papermaking, such as a Fourdrinier multi-layer papermaking machine, a cylinder wire multi-layer papermaking machine, and a Fourdrinier cylinder wire combination multi-layer papermaking machine, are preferred.

[0029] In the heat-sealing coated paper according to the present invention, a surface sizing liquid may be applied to the front and / or back of the base paper. The surface sizing liquid used here is not particularly limited, but examples thereof include known water-soluble polymers such as starch, polyvinyl alcohol, and polyacrylamide. The method of applying the surface sizing liquid is also not particularly limited, and known applicators such as a type equipped with a pond such as a size press, a film metering type such as a gate roll size press or a shim sizer, a rod coater, or an air knife coater can be used.

[0030] In the coated paper 100 for heat sealing according to the present invention, the coating layer 40 is provided on the front and / or back surface of the base paper 10 or base paper 30. The coating layer 40 may be provided directly on either the front or back outer surface 14 of the base paper 10, or the outer surface 14 of the base paper 10 may be subjected to a surface sizing treatment to provide a size layer 20, and the coating layer 40 may be provided on the outer surface 31 of the base paper 30 including the size layer 20. When coating layers are provided on both the front and back surfaces, the compositions of the coating layers on the front and back sides may be the same or different depending on the purpose.

[0031] In the present invention, when the coating layer has a single layer structure or a multilayer structure, the pigment to be used in the outermost coating layer is preferably kaolin clay, which is flat and therefore oriented on the coating layer surface to improve smoothness and printability, heavy calcium carbonate (ground calcium carbonate), light calcium carbonate, titanium oxide, etc., which have high whiteness, and it is desirable to use one or more of these in combination. In particular, when the object of packaging is white food such as yogurt or ice cream, the packaging container is often required to have high whiteness.

[0032] The preferred blending ratios of these pigments are as follows. The kaolin clay is preferably in the range of 10 to 30% based on the total amount of pigments. If the blending ratio of kaolin clay is less than 10%, sufficient ink receptivity may not be obtained, resulting in a decrease in printability. If the blending ratio of kaolin clay is more than 30%, the blending ratio of pigments that contribute to whiteness relatively decreases, resulting in a decrease in whiteness, and depending on the application, the required whiteness may not be obtained. The heavy calcium carbonate is preferably in the range of 50 to 90% based on the total amount of pigments. If the blending ratio of heavy calcium carbonate is less than 50%, the whiteness may decrease, resulting in a decrease in whiteness, and depending on the application, the required whiteness may not be obtained. If the blending ratio of heavy calcium carbonate is more than 90%, the blending ratio of kaolin clay relatively decreases, resulting in a decrease in sufficient ink receptivity, resulting in a decrease in printability. The light calcium carbonate is preferably in the range of 0 to 20% based on the total amount of pigments. If the blending ratio of light calcium carbonate exceeds 20%, the blending ratio of kaolin clay decreases relatively, so that sufficient ink receptivity may not be obtained, and printability may decrease, and the fluidity of the paint may decrease, so that the processing suitability may decrease. The blending of light calcium carbonate is not essential, but if the blending ratio of pigments that contribute to whiteness, including light calcium carbonate, is small, the required whiteness may not be obtained depending on the application. The titanium oxide is preferably in the range of 5 to 30% with respect to the total amount of pigments. If the blending ratio of titanium oxide is less than 5%, the whiteness may decrease, and the required whiteness may not be obtained depending on the application. If the blending ratio of titanium oxide exceeds 30%, the blending ratio of kaolin clay decreases relatively, so that sufficient ink receptivity may not be obtained, and printability may decrease, and the fluidity of the paint may decrease, so that the processing suitability may decrease.

[0033] In the present invention, the pigment used in the intermediate coating layer or the inner coating layer is not particularly limited, and any general pigment can be used as appropriate. However, since it is desirable for the pigment in these layers to improve whiteness and have an anchoring effect on the overcoated layer, it is preferable that 90% or more of the total amount of pigment contained in the layer is heavy calcium carbonate.

[0034] In the present invention, other pigments may be used in each coating layer as necessary, and are not particularly limited, but examples of such pigments include talc, satin white, lithopone, titanium dioxide, silica, alumina, aluminum hydroxide, zinc oxide, magnesium carbonate, calcined kaolin, and colored pigments.

[0035] In the heat-sealing coated paper according to the present invention, the adhesive used in the coating layer includes a styrene-butadiene copolymer latex having an average particle size of 100 nm or more (hereinafter, styrene-butadiene copolymer latex will be referred to as SBR latex). In addition, adhesives other than SBR latex may be used alone or in combination of two or more types as long as the effects of the present invention are not impaired. Other adhesives that can be used here include various copolymer latexes such as acrylic, polyvinyl acetate, or ethylene-vinyl acetate, polyvinyl alcohol, modified polyvinyl alcohol, polyacrylamide, urea or melamine / formalin resin, polyethyleneimine or polyamidepolyamine / epichlorohydrin, and other water-soluble compounds. Further examples include starch purified from natural plants, hydroxyethylated starch, oxidized starch, etherified starch, phosphate esterified starch, enzyme-modified starch, cold water soluble starch obtained by flash drying these, natural polysaccharides such as dextrin, mannan, chitosan, arabinogalactan, glycogen, inulin, pectin, hyaluronic acid, carboxymethylcellulose, hydroxyethylcellulose, or their oligomers or modified forms. Other examples include natural proteins such as casein, gelatin, soybean protein, collagen, or their modified forms, and synthetic polymers or oligomers such as polylactic acid and peptides. When the coating layer has a multi-layer structure, the SBR latex having an average particle size of 100 nm or more may be contained in the outermost coating layer.

[0036] Even if SBR latex is blended in the coating layer, if the average particle size of the SBR latex is less than 100 nm, the desired heat seal strength will not be achieved. Although there is no particular upper limit to the average particle size, if the maximum particle size of the SBR latex exceeds 200 nm, there is a risk of a decrease in print strength, so it is preferable to set the upper limit at 200 nm.

[0037] In the present invention, the coating layer may contain SBR latex having an average particle size of less than 100 nm, as long as the effect of the invention is not impaired. In the present invention, the average particle size of the SBR latex can be measured by a known method. As an example, in this embodiment, the measurement is performed using ELSZ-1000 (manufactured by Otsuka Electronics Co., Ltd.) using a dynamic light scattering method, and the volume average value D50 is taken as the average particle size.

[0038] In the present invention, it is preferable to add 5 to 30 parts by weight of SBR latex per 100 parts by weight of pigment. If the amount of SBR latex having an average particle size of 100 nm or more is less than 5 parts by weight, sufficient coating layer strength cannot be obtained, and there is a risk of interfacial peeling occurring between the coating layer and the base paper, resulting in material breakage from the base paper or base paper. On the other hand, if the amount exceeds 30 parts by weight, the ink absorbency of the coating layer during printing may decrease, causing problems in terms of printability.

[0039] In the present invention, the paint for forming the coating layer may suitably contain, as necessary, various commonly used auxiliary agents such as dispersants, defoamers, water-resistant agents, coloring dyes, coloring pigments, thickeners, etc., or cationized products of these various auxiliary agents.

[0040] In the present invention, the coating layer may be formed as one layer or as two or more layers. When the coating layer is a multi-layer structure of two or more layers, it is composed of an inner coating layer 41 provided on the front and back sides of the base paper or base paper, one or more intermediate layers 42 provided as necessary on the inner coating layer 41, and an outermost coating layer 43 provided on the inner coating layer 41 or the intermediate layer 42. When two or more layers are used, the inner coating layer 41 and the outermost coating layer 43 are essential, but the intermediate layer 42 is not essential. The inner coating layer 41, the intermediate layer 42, and the outermost coating layer 43 may all have the same composition, or each layer may have a different composition. When the coating layer is two or more layers, it is preferable to form the coating layer so that the total coating amount of all the coating layers is within the range of the dry coating amount per one side described later. When no coating is required on the back side, a water-soluble polymer such as starch may be applied to prevent curling and dried only.

[0041] In the present invention, the method of applying the coating material for forming the coating layer is not particularly limited, and various methods can be appropriately used, such as a size press having a liquid pool, a metering size press, various film transfer coaters such as a gate roll or a shim sizer, an air knife coater, a rod coater, a blade coater, a direct fountain coater, a spray coater, a curtain coater, etc. When the coating layer has a multi-layer structure, the coating method may be different for each layer.

[0042] In the present invention, the dry coating weight of the coating layer per side is 7 to 30 g / m 2 It is preferable that the thickness is 12 to 26 g / m 2 It is more preferable that the dry coating weight per side is 7 g / m. If the desired coating weight cannot be achieved by one coating, the desired coating weight may be achieved by applying two or more coats. 2 If the dry coating weight per side is less than 30 g / m, the desired whiteness may not be achieved. 2 If it exceeds this limit, the strength of the coating layer will decrease, causing paper dust or powder falling during processing, which may be a serious problem.

[0043] The mainstream approach for heat-sealing coated paper is to have one side printed and the other side laminated with polyethylene, etc. In this case, the printed side should have two or more coating layers in consideration of the finish of the printed side, and the dry coating weight per side should be 17 to 28 g / m. 2 On the other hand, the lamination surface side is coated with one layer for the purpose of providing a certain degree of whiteness and lamination processability, and the dry coating amount per side is 7 to 15 g / m. 2 It is preferable to set the above.

[0044] The internal bond strength of the heat-sealable coated paper is preferably 100 to 500 mJ, and more preferably 200 to 400 mJ. If the internal bond strength is less than 100 mJ, the paper may tear during processing, such as when it is molded into a packaging bag, or may crack during top curl molding of a cup. On the other hand, if the internal bond strength exceeds 500 mJ, the material may not easily break, which is a requirement for heat sealing. EXAMPLES

[0045] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" refer to "parts by mass" and "% by mass", respectively, unless otherwise specified. The number of parts added is a value calculated as a solid content.

[0046] Example 1 <Preparation of base paper> Pulp consisting of 90% hardwood pulp (L-BKP) and 10% softwood pulp (N-BKP) was adjusted to 450 ml of CSF, to which was added 0.5% cationic starch (Neotack 40T, manufactured by Nihon Shokuhin Kako Co., Ltd.) as a paper strength enhancer, 0.5% aluminum sulfate as a flocculation aid, and 0.5% neutral rosin emulsion sizing agent (New Size 738, manufactured by Harima Kasei Co., Ltd.) as a sizing agent to prepare the raw material for the white layer. Next, pulp consisting of 100% hardwood pulp (L-BKP) was adjusted to 450 ml of CSF, to which was added 0.5% cationic starch (Neotack 40T, manufactured by Nihon Shokuhin Kako Co., Ltd.) as a paper strength enhancer, 0.5% aluminum sulfate as a coagulation aid, and 0.5% neutral rosin emulsion sizing agent (New Size 738, manufactured by Harima Chemical Co., Ltd.) as a sizing agent to prepare the raw material for the middle layer. The prepared white layer raw material and middle layer raw material were used to make a three-layer base paper with a total of three layers, one middle layer and white layers on both sides of the middle layer, at a speed of 300 m / min on a fourdrinier combination papermaking machine. The total basis weight of this base paper was 200 g / m 2 It was.

[0047] <Size press treatment (formation of size layer)> A 7% starch paste (MS3800, manufactured by Nippon Shokuhin Kako Co., Ltd.) was applied to both sides of the obtained base paper using a pond size press at a solid content of 2 g / m per side. 2 The resulting mixture was dried to form a size layer, thereby obtaining a base paper.

[0048] <Formation of coating layer on the surface> A paint for the inner coating layer was prepared by blending 100 parts of wet heavy calcium carbonate (Carbital 90, manufactured by Imerys Minerals Japan Co., Ltd.) as a pigment, 8 parts of a styrene-butadiene rubber latex (BA-333, average particle size 90 nm, manufactured by Asahi Kasei Chemical Co., Ltd.) which is a styrene-butadiene copolymer latex as an adhesive, and 3 parts of phosphated starch. The paint for the inner coating layer was applied to a solid content of 10 g / m2 using a rod coater. 2 The inner coating layer was formed by applying the coating solution to the surface side of the base paper so as to obtain the above-mentioned inner coating layer. Next, 15 parts of kaolin (Amazon SB, manufactured by Kadam) as a pigment, 65 parts of wet heavy calcium carbonate (Carbital 90, manufactured by Imerys Minerals Japan Co., Ltd.), and 20 parts of titanium oxide (RPS-Vantage, manufactured by DuPont) were mixed, and 18 parts of styrene-butadiene rubber latex (B-1230, manufactured by Asahi Kasei Chemical Corporation, average particle size 150 nm), which is a styrene-butadiene copolymer latex, were mixed as an adhesive to prepare a paint for the outermost coating layer. The paint for the outermost coating layer was applied to a thickness of 10 g / m2 solids using a rod coater. 2 The mixture was applied onto the inner coating layer so as to form a surface coating layer by drying.

[0049] <Forming a coating layer on the back side> On the back side of the base paper, apply the paint for the outermost coating layer with a rod coater at a solid content of 10 g / m 2 The coated paper was then dried to form a coating layer on the back side. The basis weight of the finished coated paper for heat sealing was 234 g / m 2 It is.

[0050] <Smoothing processing> A calendaring treatment was carried out at a linear pressure of 50 kg / cm, and then the surface was treated with a luster press at 80 kg / cm and 140° C. to obtain a heat-sealable coated paper according to Example 1.

[0051] Example 2 A heat-sealable coated paper according to Example 2 was obtained in the same manner as in Example 1, except that the amount of styrene-butadiene rubber latex added in the paint for the outermost coating layer was changed from 18 parts to 5 parts.

[0052] Example 3 A heat-sealable coated paper of Example 3 was obtained in the same manner as in Example 1, except that the amount of styrene-butadiene rubber-based latex added in the paint for the outermost coating layer was changed from 18 parts by mass to 30 parts by mass.

[0053] Example 4 The heat-sealable coated paper of Example 4 was obtained in the same manner as Example 1, except that the adhesive in the paint for the outermost coating layer was changed from a styrene-butadiene rubber-based latex (B-1230 manufactured by Asahi Kasei Chemical Corporation) to a styrene-butadiene rubber-based latex (L1432X manufactured by Asahi Kasei Chemical Corporation, average particle size 170 nm).

[0054] Example 5 The heat-sealable coated paper of Example 5 was obtained in the same manner as Example 1, except that the adhesive in the paint for the outermost coating layer was changed from a styrene-butadiene rubber-based latex (B-1230 manufactured by Asahi Kasei Chemical Corporation) to a styrene-butadiene rubber-based latex (B1335 manufactured by Asahi Kasei Chemical Corporation, average particle size 130 nm).

[0055] Example 6 The heat-sealable coated paper of Example 6 was obtained in the same manner as Example 1, except that the adhesive in the paint for the outermost coating layer was changed from a styrene-butadiene rubber-based latex (B-1230 manufactured by Asahi Kasei Chemical Corporation) to a styrene-butadiene rubber-based latex (T2788K manufactured by JSR Corporation, average particle size 130 nm).

[0056] Example 7 A heat-sealable coated paper of the present example was obtained in the same manner as in Example 1, except that no inner coating layer was provided on the surface side, and only one coating layer was provided using a paint for the outermost coating layer.

[0057] Example 8 The base paper is made of three layers with a total weight of 200g / m 2 From the one with a single layer, the basis weight is 200g / m 2 A heat-sealable coated paper according to the present example was obtained in the same manner as in Example 1, except that the composition was changed to the above.

[0058] Example 9 The base paper is made of three layers with a total weight of 200g / m 2 From this, the basis weight is 67g / m for single layer paper. 2 A heat-sealable coated paper according to the present example was obtained in the same manner as in Example 1, except that the composition was changed to the above.

[0059] Comparative Example 1 The heat-sealable coated paper of the present embodiment was obtained in the same manner as in Example 1, except that the adhesive in the paint for the outermost coating layer was changed from a styrene-butadiene rubber-based latex (B-1230 manufactured by Asahi Kasei Chemical Co., Ltd.) to a styrene-butadiene rubber-based latex (PA6033 manufactured by Japan A&L Co., Ltd., average particle size 95 nm).

[0060] Comparative Example 2 A coated paper for heat sealing according to this example was obtained in the same manner as in Example 1, except that no coating layer was formed on the surface layer.

[0061] The heat-sealing coated papers obtained in each of the Examples and Comparative Examples were evaluated under the following conditions. The evaluation results are shown in FIG.

[0062] <Heat seal suitability evaluation> The heat-sealing coated paper obtained in each Example and Comparative Example was cut into two pieces with a width of 8 mm and a length of 15 cm, and the front and back sides of the two heat-sealing coated papers were overlapped and heat-sealed using a heat-sealing device (Palmec, model number: PTS-100) under the following conditions: adhesion width: 4 mm, temperature: 180°C, pressure: 0.4 MPa, pressing time: 0.5 seconds, pitch: 4 mm to obtain each sample. Next, each sample was peeled using a peel strength tester (Shimadzu, model number: Autograph AGS-X) under the following conditions: peel speed: 100 mm / min, peel length: 10 cm, and the peeled surface was visually evaluated. ⊚: The entire seal portion is broken away from the base paper of the paper substrate and can be used. ◯: Most of the seal portion is broken away from the base paper of the paper substrate, and is usable. △: Part of the seal is torn from the base paper of the paper base material, and it is still usable (lower limit of usability). ×: The seal portion is peeled off at the interface between the coating layer and the size layer, or is not adhered (not practical).

[0063] <Printability Evaluation 1: Smoothness> For the heat-sealing coated papers obtained in each Example and Comparative Example, the total area of ​​the non-contact parts was measured using PST2600 (manufactured by FIBRO system ab) under the following conditions: clamping pressure: 7.6 MPa, clamping time: 0.02 seconds. This measurement was performed on the front side. ⊚: The total area of ​​non-contact parts is 6% or less, which is very good. ◯: The total area of ​​non-contact parts is 6 to 7%, which is good. △: The total area of ​​non-contact parts is 7 to 8% (lower practical limit). ×: The total area of ​​non-contact parts is 8% or more (not practical).

[0064] <Printability Evaluation 2: Ink setting> For the heat-sealing coated paper obtained in each Example and Comparative Example, 0.4 cc of process ink red (manufactured by Toyo Ink Co., Ltd.) was used to print once on the front side at a printing speed of 30 rpm using an RI printing machine (manufactured by Akira Seisakusho). After that, a transfer paper (MuCoat Neos, manufactured by Hokuetsu Corporation) was placed on the front side (printed surface) of the heat-sealing coated paper, and the rubber roll and metal roll of the printing machine were pressed against the impression cylinder, and the state of ink transfer to the transfer paper was visually confirmed. The impression cylinder was rotated by 1 / 3 (about 10 cm) at 30 seconds, 60 seconds, and 90 seconds after printing, and the measurement was performed three times. Note that this measurement was performed on the front side. .circle-solid.: The ink transfer to the transfer paper is minimal and good. ◯: Some ink transfer onto the transfer paper, but good. △: Ink transfer to transfer paper (lower practical limit) ×: A large amount of ink is transferred to the transfer paper. (Not practical)

[0065] As is clear from FIG. 3, all of the heat-sealable coated papers obtained in Examples 1 to 9 were excellent in both printability and heat-sealability.

[0066] On the other hand, the heat-sealing coated paper obtained in Comparative Example 1 had poor heat-sealing suitability because the average particle size of the SBR latex used was smaller than 100 nm. Also, the heat-sealing coated paper obtained in Comparative Example 2 had large surface irregularities because no coating layer was provided on the surface side where printing was performed, and also had slow ink setting, resulting in poor printability.

Claims

1. providing a base paper; A step of preparing a paint for an outermost coating layer; A step of preparing a paint for an inner coating layer; applying the inner coating paint to the printing surface of the base paper to provide one or more inner coating layers; A step of applying the paint for the outermost coating layer onto the inner coating layer on the printed surface to provide an outermost coating layer; and applying the outermost coating layer paint to a non-printing surface side of the base paper to provide a non-printing surface coating layer, the paint for the outermost coating layer contains a pigment and an adhesive, and the adhesive of the paint for the outermost coating layer contains a styrene-butadiene rubber copolymer latex having an average particle size of 100 nm or more; A method for producing coated paper for heat sealing, characterized in that the total dry coating weight of the coating layers provided on the printed side is 17 to 28 g / m2, and the total dry coating weight of the coating layers provided on the non-printed side is 7 to 15 g / m2.

2. The method for producing coated paper for heat sealing as described in claim 1, characterized in that the paint for the outermost coating layer contains 5 to 30 parts by mass of styrene-butadiene rubber copolymer latex having an average particle diameter of 100 nm or more per 100 parts by mass of the pigment.

3. The method for producing coated paper for heat sealing according to claim 1, characterized in that the styrene-butadiene rubber copolymer latex having an average particle size of 100 nm or more has an average particle size in the range of 100 to 200 nm.

4. 2. The method for producing coated paper for heat sealing according to claim 1, wherein the disintegrated freeness of the base paper is in the range of 300 to 550 ml.

5. 2. The method for producing coated paper for heat sealing according to claim 1, further comprising forming one or more intermediate coating layers between the inner coating layer and the outermost coating layer.

6. A coated paper for heat sealing, one side of which is printed and the other side is non-printed, The printed surface is provided with two or more coating layers including one or more inner coating layers obtained by applying an inner coating paint to a base paper, and an outermost coating layer obtained by applying an outermost coating paint onto the inner coating layer, The non-printing surface is provided with one non-printing surface coating layer obtained by applying a coating material to a base paper, the paint for the outermost coating layer contains a pigment and an adhesive, and the adhesive of the paint for the outermost coating layer contains a styrene-butadiene rubber copolymer latex having an average particle size of 100 nm or more; The coated paper for heat sealing is characterized in that the total dry coating weight of the coating layers provided on the printed side is 17 to 28 g / m2, and the total dry coating weight of the coating layers provided on the non-printed side is 7 to 15 g / m2.

7. A coated paper for heat sealing as described in Claim 6, characterized in that the coating layer paint used for the non-printing surface coating layer is a coating layer paint for the outermost coating layer.

8. A paper cup container using the heat-sealable coated paper according to claim 6 or 7.

9. A packaging paper using the heat-sealable coated paper according to claim 6 or 7.

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