Printing paper and its manufacturing method

Abstract

To provide a technique whereby, even when collected printing paper is used as a recycled material, the printing paper does not degrade in its physical properties.SOLUTION: The present invention relates to printing paper including polyolefin resin. Relative to 100 pts.mass of the polyolefin resin, the printing paper includes 0.10-5 pts.mass of at least one of melamine and melamine derivatives.SELECTED DRAWING: None

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to printing paper suitable for recycling and a method for manufacturing such printing paper. [Background technology]

[0002] Plastics are manufactured in various forms together with other substances such as heavy metals. For example, the plastic printed matter described in Patent Document 1 contains heavy metal components derived from pigments in the ink. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-140390 Summary of the Invention [Problem to be solved by the invention]

[0004] Furthermore, given the need to reuse plastics due to environmental concerns, a common method for producing recycled plastics is to crush recovered used plastics into pellets, which are then blended with fresh resin.

[0005] Therefore, when recovered used plastics are recycled, they are usually subjected to heat history during each of the granulation, molding, and re-pelletization processes, and repeated heat history can cause the physical properties of the recycled plastic to deteriorate.

[0006] When the plastic is polyolefin, thermal degradation proceeds via a radical mechanism. Therefore, if the recovered plastic contains heavy metals such as copper or iron, the presence of these heavy metal ions is thought to accelerate the radical mechanism, making the plastic more susceptible to degradation.

[0007] Therefore, if recycled plastics that contain a large amount of heavy metals that have been mixed in from the environment in which they are used, such as printing inks, colorants, and paints, are recycled as is, they will be prone to thermal degradation.

[0008] Furthermore, when producing recycled plastic, thermal degradation already occurs during the process of crushing recovered plastic and producing recycled pellets, making it difficult to prevent degradation at that point.

[0009] An object of the present invention is to prevent deterioration of the physical properties of collected printing paper even when the paper is used as recycled raw material. [Means for solving the problem]

[0010] The inventors discovered that adding melamine or its derivatives, which are metal sealants, to printing paper at the time of manufacturing the paper can suppress deterioration caused by heat when recycled printing paper is recycled, and thus completed the present invention.

[0011] The present invention is as follows. [1] A printing paper containing a polyolefin resin, the printing paper containing 0.10 to 5 parts by mass of at least one of melamine and a melamine derivative per 100 parts by mass of the polyolefin resin. [2] The printing paper according to [1], wherein the polyolefin resin contains 5 to 80% by mass of recycled polyolefin resin. [3] The printing paper according to [1] or [2], which contains 1 to 120 parts by mass of one or more inorganic fillers selected from talc, calcium carbonate, aluminum oxide, silicon oxide, titanium oxide, barium oxide, and zeolite per 100 parts by mass of the polyolefin resin. [4] The printing paper according to [3], wherein the total content of the polyolefin resin and the inorganic filler is 75 to 99.9% by mass. [5] Surface resistivity is 1.0 × 10 9 ~1.0×10 13 The printing paper according to any one of [1] to [4], wherein the resistivity is Ω / □. [6] The printing paper according to any one of [1] to [5], wherein the melamine derivative is at least one of a melamine phosphate derivative and melamine cyanurate. [7] A method for producing printing paper, comprising a step of blending 0.10 to 5 parts by mass of at least one of melamine and a melamine derivative with 100 parts by mass of polyolefin resin, and molding the mixture. [8] A method for producing printing paper according to [7], in which a recycled polyolefin resin and at least one of melamine and a melamine derivative are added to a polyolefin resin and molded. [9] The method for producing printing paper according to [7] or [8], wherein the molding is extrusion molding, and further comprises a step of applying a coating material containing an antistatic agent to at least one surface of the sheet obtained by extrusion molding.

[10] The method for producing printing paper according to any one of [7] to [9], wherein the molding is extrusion molding, and further comprises a step of laminating a polyolefin resin film to at least one side of the sheet obtained by extrusion molding. [Effects of the Invention]

[0012] According to the present invention, it is possible to suppress deterioration in the physical properties of printing paper made from recovered printing paper as recycled raw material.

[0013] The present invention also makes it possible to increase the recycled content of printing paper. DETAILED DESCRIPTION OF THE INVENTION

[0014] The printing paper and its manufacturing method of the present invention will be described in detail below, but the explanation of the constituent elements described below is an example (representative example) of one embodiment of the present invention and is not limited to these contents.

[0015] In the present invention, polyolefin resins that are manufactured and shipped in the form of powder granules or pellets and are used for the first time as raw materials for printing paper are referred to as "fresh raw materials," while scraps and printed matter generated after the printing paper manufacturing process are collected and re-pelletized to be used as raw materials for printing paper are referred to as "recycled raw materials."

[0016] Plastic printing paper uses thermoplastic resin, and is roughly divided into those that use polyester resin and those that use polyolefin resin.

[0017] Of these, the mechanisms by which printing paper made with polyester resins undergoes thermal degradation, excluding burning and aggregation of fillers and additives contained within, include depolymerization of condensation polymers, typified by hydrolysis, and oligomerization, which proceed faster than the radical degradation mechanism.

[0018] On the other hand, the mechanism by which printing paper using polyolefin resins undergoes thermal degradation, excluding the above-mentioned burning and aggregation, is primarily due to radical degradation.

[0019] Furthermore, when polyolefin resins contain heavy metals such as cobalt, manganese, copper, and iron, the radical degradation mechanism is accelerated, and it has been frequently reported that degradation progresses even at room temperature; this phenomenon is generally referred to as copper damage.

[0020] In the case of printing paper, copper is used in indigo ink and manganese is used as a drying accelerator for oil-based ink, and these are often included in recycled raw materials.

[0021] (Melamine and melamine derivatives) The printing paper of the present invention contains a specific amount of at least one of melamine and melamine derivatives (hereinafter also referred to as "melamines.") In the present invention, the melamines function as metal deactivators. To date, commonly used metal deactivators include those that combine a structure with chelating ability, such as a salicylic acid structure or a triazole-imide structure, with a structure with radical trapping function, such as a phenol structure or a hydrazine structure. On the other hand, melamine generates nitrogen gas when it decomposes thermally, so it is used as a flame retardant alone, in combination with phosphorus-based flame retardants, or as an auxiliary agent for inorganic flame retardants such as magnesium hydroxide, but has not received much attention as a copper damage inhibitor.

[0022] The melamine used in the present invention includes simple melamine, and examples of the melamine derivatives include melamine phosphate derivatives such as melamine phosphate, melamine pyrophosphate, and melamine polyphosphate; methylol melamines such as monomethylol melamine, dimethylol melamine, and trimethylol melamine; and melamine cyanurate.

[0023] Among these, it is preferable to use melamine alone from the viewpoint of maintaining the mechanical strength of printing paper using recycled polyolefin resin.

[0024] On the other hand, from the viewpoint of suppressing discoloration over time of printing paper using recycled polyolefin resin, it is preferable to use a melamine phosphate derivative.

[0025] The content of melamines is 0.10 to 5 parts by mass as the total content of melamine and melamine derivatives per 100 parts by mass of the polyolefin resin.

[0026] The content of melamines is more preferably 1 part by mass or more, and even more preferably 3 parts by mass or more. By setting the content of melamines to 0.10 parts by mass or more, thermal degradation of printing paper using recycled polyolefin resins tends to be suppressed. From the viewpoint of the present invention, the content of melamines is preferably 4.9 parts by mass or less, and more preferably 4.8 parts by mass or less. By keeping the content of melamines at 5 parts by mass or less, it is possible to suppress a decrease in the mechanical strength of printing paper using recycled polyolefin resins.

[0027] The above-mentioned content of melamines is the total amount in the printing paper. For example, if the raw material already contains melamines, the amount of melamines added is adjusted so that the total amount of the existing melamine content and the newly added melamine content falls within the above-mentioned range.

[0028] (Polyolefin resin) Examples of the polyolefin resin used in the present invention include polyethylene resins such as high-density polyethylene, medium-density polyethylene, and low-density polyethylene; and polypropylene resins such as isotactic polypropylene, syndiotactic polypropylene, and polypropylene random polymers and polypropylene block polymers obtained by copolymerizing propylene with an α-olefin such as ethylene, 1-butene, 1-hexene, 1-heptene, and 4-methyl-1-pentene. These may be used alone or in combination of two or more.

[0029] The polyolefin resin may consist of only fresh polyolefin resin, or may contain fresh polyolefin resin and recycled polyolefin resin.

[0030] The MFR (melt flow rate, 230° C., 2.16 kg load) of the fresh polyolefin resin is preferably in the range of 0.5 g / 10 min to 20 g / 10 min from the viewpoint of film productivity.

[0031] When the printing paper contains recycled polyolefin resin, the content is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and particularly preferably 10% by mass or more, from the viewpoint of reducing the environmental impact. Furthermore, the content of recycled polyolefin resin is preferably 90% by mass or less, more preferably 80% by mass or less, from the viewpoint of suppressing thermal degradation. According to the present invention, the inclusion of melamines suppresses thermal degradation of the resin, so a high proportion of the raw polyolefin resin can be replaced with recycled polyolefin resin.

[0032] (inorganic filler) The printing paper may contain 1 to 120 parts by mass of inorganic filler per 100 parts by mass of polyolefin resin.

[0033] From the viewpoint of improving the whiteness and opacity of printing paper, the content of the inorganic filler is preferably 15 parts by mass or more, and more preferably 20 parts by mass or more, per 100 parts by mass of the polyolefin resin.

[0034] From the viewpoint of improving the mechanical strength of the printing paper, the content of the inorganic filler is preferably 100 parts by mass or less, and more preferably 80 parts by mass or less, per 100 parts by mass of the polyolefin resin.

[0035] From the viewpoint of obtaining translucent printing paper, the content of the inorganic filler is preferably 50 parts by mass or less, and more preferably 40 parts by mass or less, per 100 parts by mass of the polyolefin resin.

[0036] Furthermore, from the viewpoint of exerting the effect of suppressing thermal degradation of melamines, the total content of the polyolefin resin and inorganic filler contained in the printing paper is preferably 75 to 99.9% by mass.

[0037] The inorganic filler used in the printing paper is preferably one or more selected from talc, calcium carbonate, aluminum oxide, silicon oxide, titanium oxide, barium oxide, and zeolite.

[0038] Among these, it is more preferable to use one or more selected from talc, calcium carbonate, and titanium oxide from the viewpoint of formability and weather resistance of printing paper.

[0039] (Functional material) In order to improve formability and weather resistance, various additives such as lubricants, antioxidants, stabilizers, and antistatic agents can be used appropriately in printing paper.

[0040] Examples of lubricants include higher fatty acids such as stearic acid and oleic acid, and metal soaps such as magnesium stearate and aluminum stearate.

[0041] Examples of the antioxidant include phenol-based antioxidants, hindered phenol-based antioxidants, and phosphorus-based antioxidants.

[0042] Examples of the stabilizer include hindered amine-based heat stabilizers, benzotriazole-based light stabilizers, and benzophenone-based light stabilizers.

[0043] Examples of the antistatic agent include cationic surfactants, anionic surfactants, nonionic surfactants, cationic polymers, and anionic polymers.

[0044] When the antistatic agent is applied to the surface as a coating, it may be used in combination with a binder such as a polyimine polymer or a derivative thereof, an ethyleneimine adduct of polyamine polyamide, or an acrylic resin, a crosslinking agent, or the like.

[0045] The functional material may be used by blending it into the resin layer of the printing paper, or by applying it to the surface of the printing paper and drying it.

[0046] These functional materials can be applied independently to the printing paper in an amount of 0.01 to 5% by mass.

[0047] (molding) The printing paper can be formed by any known method, and the type is not particularly limited.

[0048] For example, molding can be performed using extrusion molding, in which a molten resin is extruded into a sheet using a single-layer or multi-layer T-die or I-die connected to an extruder, inflation molding, in which a molten resin is extruded into a cylindrical shape using an O-die connected to an extruder, calendar molding, roll molding, or a method in which a mixture of a thermoplastic resin and an organic solvent or oil is cast or calendar molded and then the solvent or oil is removed.

[0049] Among these, extrusion molding, inflation molding, and calender molding are preferred, with extrusion molding being particularly preferred.

[0050] Furthermore, a resin layer can be laminated on one or both sides of the extrusion-molded sheet by extrusion lamination, thermal lamination, dry lamination or the like.

[0051] By combining these forming methods, printing paper can have any layer structure, such as a single layer structure, ABA structure, ABC structure, or ABCBA structure.

[0052] (Stretching) Printing paper can be constructed by stretching one or more of its constituent layers. Stretching can improve mechanical strength such as Young's modulus, opacity, and whiteness, and can also reduce the density of the printing paper to make it lighter.

[0053] The stretching of each layer is not particularly limited, and may be uniaxial or biaxial.

[0054] The stretching method is not particularly limited, and examples that can be used include longitudinal stretching utilizing the difference in peripheral speed between a group of rolls, transverse stretching using a tenter oven, rolling, sequential biaxial stretching by combining longitudinal stretching and transverse stretching, simultaneous biaxial stretching by combining a tenter oven and a pantograph, simultaneous biaxial stretching by combining a tenter oven and a linear motor, and simultaneous biaxial stretching by inflation molding.

[0055] Furthermore, by combining it with lamination, any desired stretched layer configuration can be achieved, such as longitudinal uniaxial layer / sequentially biaxially stretched layer, transverse uniaxial layer / sequentially biaxially stretched layer / transverse uniaxial layer, longitudinal uniaxially stretched layer / transverse uniaxially stretched layer, or simultaneous biaxially stretched layer / unstretched layer.

[0056] The stretching temperature is not particularly limited, but is preferably equal to or lower than the melting point of the polyolefin resin from the viewpoint of uniformity of the thickness of the printing paper, and is preferably 2 to 20°C lower than the melting point of the polyolefin resin from the viewpoint of improving whiteness, opacity, and reducing density.

[0057] The stretching ratio of the uniaxial stretching is not particularly limited, but is preferably 2 to 12 times, more preferably 3 to 10 times, and even more preferably 4 to 8 times.

[0058] The stretching ratio for biaxial stretching is not particularly limited, but is usually preferably 4 to 80 times, more preferably 10 to 65 times, and even more preferably 20 to 50 times in terms of area ratio.

[0059] (Printing paper manufacturing method) The method for producing printing paper of the present invention is characterized in that 0.10 to 5 parts by mass of at least one of melamine and a melamine derivative is blended with 100 parts by mass of polyolefin resin, and then molding is carried out.

[0060] In the production of printing paper, melamines can be added to fresh raw materials, or fresh raw materials, recycled raw materials, and melamines can be mixed together. That is, recycled polyolefin resin and at least one of melamine and melamine derivatives can be added to polyolefin resin, and the mixture can be extrusion-molded.

[0061] In the present invention, the content of melamines is the total amount in the printing paper, and therefore, when the raw material already contains melamines, such as when using recycled raw materials containing melamines, the amount of melamines added is adjusted so that the total amount of the existing melamine content and the newly added melamine content falls within the above range. If the melamine content in the recycled raw material is already sufficient, there is no need to add new melamines during recycling.

[0062] From the viewpoint of stabilizing quality, it is preferable that the fresh raw materials are prepared by previously mixing polyolefin resins, melamines, and other fillers and additives and granulating them into pellets.

[0063] The MFR (melt flow rate, 230° C., 2.16 kg load) of the fresh raw material is preferably 0.5 g / 10 min or more, more preferably 1.0 g / 10 min or more, from the viewpoint of film productivity. Furthermore, the MFR (melt flow rate, 230° C., 2.16 kg load) of the fresh raw material is preferably 20 g / 10 min or less, and more preferably 10 g / 10 min or less, from the viewpoint of film formability.

[0064] When using recycled raw materials, methods such as pre-mixing fresh raw materials, recycled raw materials, and melamines and feeding the mixture into an extruder, or side-feeding recycled raw materials while melting and kneading fresh raw materials in an extruder, are used.

[0065] The recycled raw material can be made by crushing recovered printing paper and using it as is, but from the viewpoint of stabilizing the blending ratio of fresh raw material to recycled raw material, it is preferable to crush the paper and then granulate it into pellets, and from the viewpoint of reducing the number of defects and foreign matter on the surface of the printing paper, it is more preferable to crush the paper, then wash and dry it, and then granulate it into pellets, and from the viewpoint of suppressing thermal deterioration due to the recycling process, it is particularly preferable to crush the paper, then wash and dry it, and then blend melamines and, if necessary, various additives, and then granulate it into pellets.

[0066] Melamines can be added to printing paper by directly blending them with fresh or recycled raw materials, or by granulating a master batch of additives by combining the polyolefin resin and the various additives listed above.

[0067] By applying a coating containing an antistatic agent to at least one surface of the sheet obtained by extrusion molding, it is possible to impart antistatic properties to the printing paper.

[0068] The coating device is not particularly limited, but a die coater, bar coater, lip coater, roll coater, gravure coater, spray coater, blade coater, air knife coater, size press coater, etc. can be used.

[0069] The amount of coating is not particularly limited, but from the viewpoints of production costs, suppression of stickiness, and improvement of ink adhesion, it is recommended to use an amount of 0.01 to 3 g / m in terms of solid content. 2is preferable, and 0.01 to 1 g / m 2 More preferably, 0.02 to 0.5 g / m 2 is more preferable.

[0070] (printing paper) The thickness of all layers of printing paper is preferably 50 μm or more, more preferably 75 μm or more, and is preferably 500 μm or less, more preferably 300 μm or less, from the viewpoint of enabling proper printing with various printing machines. The thickness of all layers of printing paper is based on JIS K7130 (1999).

[0071] The color of the printing paper is preferably such that the increase in b* value when heated in air at 120°C for 3 days is 0.5 or less, more preferably 0.3 or less. The color is based on JIS P8150 (2004).

[0072] The surface resistivity of printing paper is set to 1.0 x 10 from the viewpoint of transportability during flatbed printing and prevention of static electricity problems during post-processing. 13 It is preferable that the resistance is Ω / □ or less, and 1.0×10 12 It is more preferable that the surface roughness is 1.0×10 Ω / □ or less. 9 It is preferable that the surface resistivity is Ω / □ or more. The surface resistivity is based on JIS K6911 (1995).

[0073] (printing) The printing methods applicable to printing paper include offset printing, letterpress printing, flexographic printing, and screen printing, and the inks used for these are of the oxidative polymerization type, solvent evaporation drying type, and ultraviolet curing type.

[0074] The resulting printed matter can be handled in the same way as conventional synthetic paper, and is useful as commercial printed matter such as posters, pamphlets, catalogs, signs, and menus; publications such as books, maps, book covers, and bookmarks; and wrapping paper. Due to its high weather resistance, it is useful in applications intended for outdoor use such as election posters and signboard posters; applications that are exposed to water such as posters used in wet areas; and applications that may come into contact with water such as menus in restaurants.

[0075] (Recycling printing paper) Scraps generated during the printing paper manufacturing process are typically crushed, fed into the extruder through a feeder, heated and melted inside the extruder, and various additives are added as needed. The scraps are then extruded as strands through a die, cooled, and cut into recycled pellets.

[0076] Used printing paper is collected and then recycled into recycled pellets in a process similar to that used in the manufacturing process, but an ink stripping, deinking or cleaning process may be added before or after crushing and before being fed into the extruder feeder.

[0077] The MFR (melt flow rate) of recycled raw materials is an indicator of thermal degradation and is generally higher than that of fresh raw materials. From the viewpoint of film formability, it is preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less. The tensile breaking stress of printing paper according to JIS K7161-1 is preferably 5 MPa or more, more preferably 5.5 MPa or more, since this is thought to be due to strength reduction caused by thermal history and the addition of a large amount of additives. [Example]

[0078] The features of the present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In other words, the materials, amounts used, proportions, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention.

[0079] (blank physical property evaluation) <Surface resistivity> The surface resistivity of the printing paper (blank paper) before printing obtained in the examples and comparative examples was measured under conditions of a temperature of 20°C and a relative humidity of 30% using a digital ultra-insulation / microcurrent meter (product name "DSM-8104", manufactured by Hioki E.E. Corporation).

[0080] <MFR after heat treatment> White printing paper was crushed and passed through a SUS mesh with 8 mm openings. The sample was divided into two, one of which was stored at room temperature (23°C) for 5 days as the sample before heat treatment, and the other was placed in a glass bottle and heat-treated in an oven at 150°C for 5 days to be used as the sample after heat treatment.

[0081] The samples before and after the heat treatment were melt-kneaded separately using a twin-screw kneading extruder with the cylinder temperature set to 230°C while degassing through the vent holes, extruded as strands from the nozzle, cooled, cut with a cutter, and formed into pellets. The MFR was then measured using a Melt Indexer L247 (manufactured by Tateyama Scientific Industry Co., Ltd.).

[0082] The increase in the MFR value of the sample after heat treatment relative to the MFR value of the sample before heat treatment was defined as ΔMFR, and the ΔMFR value was evaluated as follows: Excellent, ◯, or △ was used. ◎: ΔMFR is 10% or less ○: ΔMFR is greater than 10% and less than 20% △: ΔMFR is greater than 20% and less than 30% ×: ΔMFR is greater than 30% and less than or equal to 40%

[0083] <Hue> Ten sheets of blank printing paper were heated in an oven at 120°C in air for three days and then stacked together. Using a colorimeter (device name: Color Computer SM-T, manufactured by Suga Test Instruments Co., Ltd.), the L*a*b* color system values ​​were measured using light source C in accordance with JIS-Z8730:2009, and the difference before and after heating was determined.

[0084] <Tensile breaking stress> Before the heat treatment, the sample pellets were molded into plates with a thickness of 600 to 700 μm using a heat press machine heated to 250°C, and then punched out into the shape of test piece type 5B specified in JIS K7162 Appendix A to prepare test pieces.

[0085] Tensile tests were carried out using a tensile testing machine (Shimadzu Corporation, model: Autograph AGS-5kNJ) at a tensile speed of 200 mm / min, and the average value of the tensile breaking stress measured three times for each sample was calculated. A value of 4.0 MPa or more was considered to be good.

[0086] (Evaluation of printed matter properties) <Print> Oil-based offset printing was carried out on 100% Kiku-shi-nobi size printing paper using a four-color offset printing press (equipment name: Ryobi 524GX, manufactured by Ryobi MHI Graphic Technology Co., Ltd.) and oil-based offset ink (product name: Fusion-G MK black, indigo, red, transparent yellow, manufactured by DIC Corporation).

[0087] <MFR after heat treatment> Except for using printed matter that had been printed for 15 days or more after printing, the measurements were performed in the same manner as the MFR measurement after heat treatment in the evaluation of blank paper physical properties, and the evaluation was performed in the same manner.

[0088] <Thickness> The overall thickness (μm) of the printing paper obtained in the examples and comparative examples was measured using a paper thickness measuring device (device name: MEI-11, manufactured by Citizen Finedevice Co., Ltd.) based on JIS K7130:1999 "Plastics - Films and sheets - Thickness measurement method". The thickness (μm) of each layer constituting the printing paper was measured as follows: The printing paper was cooled to a temperature of -60°C or below with liquid nitrogen, and the sample was placed on a glass plate. A razor blade (product name: Proline Blade, manufactured by Schick Japan) was placed at a right angle to cut the sample for cross-section measurement. The cut surface of the sample was observed using a scanning electron microscope (instrument name: JSM-6490, manufactured by JEOL Ltd.), and the boundary lines of each layer were identified from the compositional appearance to determine the thickness ratio of each layer. The thickness (μm) of each layer was calculated by multiplying the total thickness (μm) by the thickness ratio of each layer.

[0089] (Materials used) The following materials were used in the examples and comparative examples. 1. Propylene homopolymer (symbol: FY6, product name: Novatec PP FY6, manufactured by Japan Polypropylene Corporation, MFR: 2.4 g / 10 min, density: 0.90 g / cm 3 ) 2. Propylene homopolymer (symbol: MA3, product name: Novatec PP MA3, manufactured by Japan Polypropylene Corporation, MFR: 11 g / 10 min, density: 0.90 g / cm 3 ) 3. High-density polyethylene (symbol: HJ580N, product name: Novatec HD HJ580N, manufactured by Japan Polyethylene Co., Ltd., MFR: 12 g / 10 min, density: 0.96 g / cm 3 ) 4. Heavy calcium carbonate particles (symbol: 1800, product name: Softon 1800, manufactured by Bihoku Funka Kogyo Co., Ltd., average particle size: 1.25 μm, density: 2.72 g / cm 3 ) 5. Rutile-type titanium dioxide particles (symbol: CR-60, product name: Typaque CR-60, manufactured by Ishihara Sangyo Kaisha, Ltd., average particle diameter: 0.21 μm, density: 4.23 g / cm) 3 ) 6. Finely powdered talc (symbol: P-6, product name: Micro Ace P-6, manufactured by Nippon Talc Co., Ltd., average particle size: 4.0 μm, BET specific surface area: 10.5 m) 2 / g) 7. Hindered phenol antioxidant (symbol: Irg1010, trade name: Irganox 1010, manufactured by BASF Japan, molecular weight: 1178, density: 1.15 g / cm 3 ) 8. Phosphorus-based antioxidant (symbol: Irg168, trade name: Irganox 168, manufactured by BASF Japan, molecular weight: 647, density: 1.03 / cm 3 ) 9. Hindered amine light stabilizer (symbol: Tnv622, trade name: Tinuvin 622, manufactured by BASF Japan Ltd., molecular weight: 3100 to 4000, density: 1.22 / cm 3 ) 10. Metal soap (symbol: AS-6, product name: aluminum stearate, manufactured by Nitto Kasei Kogyo Co., Ltd., Al2O3 content: 7.5-8.5%, melting point: 145-160°C) 11. Melamine (symbol: Wako Melamine, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., molecular weight: 126.12) 12. Melamine polyphosphate (symbol: Planelon NP, product name: Mitsui Fine Chemicals, phosphorus content: 14% or more, nitrogen content: 36% or more) 13. Melamine cyanurate (symbol: MC-6000, product name: MC-6000, manufactured by Nissan Chemical Industries, Ltd., average particle size: 2 μm or less, density: 1.52 / cm 3 )

[0090] (Production of Resin Compositions A to O) Each of the above materials 1 to 13 and either the printing paper obtained in Example 1 or the printing paper obtained in Comparative Example 3, described below, were mixed using a high-speed mixer in the proportions shown in Table 1 below, and then melt-kneaded using a twin-screw kneading extruder with the cylinder temperature set to 210°C while degassing through vent holes, extruded from the nozzle as a strand, cooled, and cut with a cutter to obtain pellets of each of Resin Compositions A to O.

[0091] [Table 1]

[0092] Example 1 [Production of longitudinally stretched resin film] Resin composition D was melt-kneaded in an extruder (1) set at 270°C, extruded from a T-die into a sheet, and further cooled by a cooling roll to obtain an unstretched sheet. Next, this unstretched sheet was reheated to 150°C, and then stretched 4.8 times in the sheet flow direction by utilizing the speed difference between the rolls to obtain a longitudinally stretched resin film.

[0093] [Preparation of Antistatic Agent Coating Solution] An aqueous solution of dimethylamine-epichlorohydrin condensate (trade name: Unisense KHE104L, manufactured by Senka Corporation, molecular weight: less than 100,000) was diluted 40 times with water to obtain an antistatic agent coating solution with a solid content of approximately 0.5%.

[0094] [Lamination] Resin composition B was melt-kneaded in an extruder (2) set at 270°C, extruded into a sheet from a T-die, laminated onto one side of a longitudinally stretched resin film, and cooled to 60°C with a cooling roll to obtain a two-layer laminate sheet. Resin composition B was melt-kneaded in an extruder (3) set at 270°C, extruded into a sheet from a T-die, laminated on the longitudinally stretched resin film side of the two-layer laminate sheet, and cooled to 60°C with a cooling roll to obtain a three-layer laminate sheet consisting of resin composition B / resin composition D / resin composition B.

[0095] [Horizontal stretching] The obtained three-layer laminate sheet was reheated to 150°C and stretched 9 times in the sheet width direction using a tenter, and then annealed at 165°C. Thereafter, it was cooled again to 60°C to obtain a three-layer stretched sheet with a total layer thickness of 110 μm (resin composition B / resin composition D / resin composition B=3 μm / 104 μm / 3 μm).

[0096] [Antistatic treatment] The obtained three-layer stretched sheet was passed through a line at a line speed of 25 m / min, while applying an energy density of 1800 J / m 2 (30W min / m 2 Both surfaces of the three-layered stretched sheet were subjected to a corona discharge treatment under the conditions of Next, a roll coater was used to coat both surfaces of the corona discharge-treated printing paper until the solid content of the coating film after drying was 0.02 g / m per side. 2 After drying and solidifying, the edge portions were slit to obtain the printing paper of Example 1.

[0097] (Examples 2 to 10, Comparative Examples 1 to 4) Printing papers of Examples 2 to 10 and Comparative Examples 1 to 4 were produced in the same manner as in Example 1, except that resin composition B and resin composition D in Example 1 were changed to the respective resin compositions shown in Table 2. The results of each example and comparative example are summarized in Table 2. In Table 2, PO represents polyolefin resin.

[0098] [Table 2]

[0099] (result) Comparative Example 3 is a printing paper made using only fresh raw materials that do not contain melamines, and the MFR of the printed material after heat treatment was worse than the MFR of the blank paper after heat treatment, indicating that the contamination of printing ink is likely to cause thermal degradation.

[0100] Examples 1 to 4, which used fresh raw materials and melamines within the specified range, had better MFR after heat treatment of blank paper and also better MFR after heat treatment of printed matter than Comparative Example 1, which had a melamine content lower than the specified range.

[0101] Comparative Example 2, in which the melamine content was higher than the specified range, showed a decrease in tensile breaking stress, but Examples 1 to 4, in which fresh raw materials and melamines within the specified range were used, showed an extremely small decrease.

[0102] Among Examples 1 to 3, which contain the same amount of the same type of calcium carbonate as a filler, Example 1 is advantageous in terms of tensile breaking stress, and Example 2 is advantageous in that it has a small increase in the hue b* value and little yellowing due to the addition of melamine.

[0103] Example 4 is an example in which a material other than calcium carbonate was used as a filler. By blending talc as a filler, an increase in the b* value was observed.

[0104] Examples 5 to 8, which used recycled raw materials, are examples in which printing paper containing melamines of the present invention was used as the recycled raw material, demonstrating that 5 to 80% by mass of the raw polyolefin can be replaced with recycled polyolefin. Furthermore, while the recycled raw material contains heavy metals derived from the printing layer, in comparison with Comparative Example 4, which uses recycled raw materials containing such heavy metals but does not contain melamines, it can be confirmed that in Examples 7 to 9, which contain melamines, the increase in the b* value was suppressed even after heating in the presence of heavy metals. Furthermore, when recycled raw materials were used, the L* value, a* value, and b* value in terms of hue all decreased compared to when recycled raw materials were not used.

[0105] Example 9, which used recycled raw materials, is an example in which printing paper that does not contain melamines is used as recycled raw materials, and it can be seen that adding melamines during recycling suppresses the decrease in tensile breaking stress, which is an indicator of thermal degradation.

[0106] Example 10 is an example in which printing paper containing melamines was used as recycled raw material, and fresh raw material was added during recycling. The MFR of the printed material after heat treatment was improved compared to Comparative Example 3, which did not contain melamines. In Example 7, which used the same recycled and fresh raw materials, as well as newly added melamines, the total content of melamines in the recycled printing paper was higher than in Example 10, and therefore the MFR after heat treatment and tensile stress at break were further improved.

Claims

1. A printing paper comprising a polyolefin resin and an inorganic filler, the printing paper containing 0.10 to 5 parts by mass of at least one of melamine and a melamine derivative per 100 parts by mass of the polyolefin resin; The printing paper has a total content of the polyolefin resin and the inorganic filler of 75 to 99.9% by mass.

2. 2. The printing paper according to claim 1, wherein the polyolefin resin contains 5 to 80% by mass of recycled polyolefin resin.

3. 3. The printing paper according to claim 1, wherein the printing paper contains 1 to 120 parts by mass of one or more inorganic fillers selected from talc, calcium carbonate, aluminum oxide, silicon oxide, titanium oxide, barium oxide, and zeolite per 100 parts by mass of the polyolefin resin.

4. Surface resistivity is 1.0 x 10 ９ ~1.0 x 10 １３ The printing paper according to any one of claims 1 to 3, wherein the resistance is Ω / □.

5. 5. The printing paper according to claim 1, wherein the melamine derivative is at least one of a melamine phosphate derivative and melamine cyanurate.

6. The method includes a step of blending 0.10 to 5 parts by mass of at least one of melamine and a melamine derivative, and an inorganic filler, with 100 parts by mass of a polyolefin-based resin, and molding the mixture; The method for producing printing paper, wherein the total content of the polyolefin resin and the inorganic filler is 75 to 99.9 mass %.

7. The method for producing printing paper according to claim 6, wherein the recycled polyolefin resin and at least one of melamine and a melamine derivative are added to the polyolefin resin and then molded.

8. 8. The method for producing printing paper according to claim 6, wherein the forming is extrusion forming, and further comprising a step of applying a coating material containing an antistatic agent to at least one surface of the sheet obtained by extrusion forming.

9. The method for producing printing paper according to any one of claims 6 to 8, wherein the molding is extrusion molding, and the method further comprises a step of laminating a polyolefin resin film on at least one surface of the sheet obtained by extrusion molding.

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