Transparent paper

Abstract

To provide transparent paper having excellent visibility.SOLUTION: A transparency paper according to the present invention has a base paper with haze of 90% or less and total light transmission of 70% or more, and a transparency layer provided on at least one surface of the base paper, wherein the transparency layer contains at least one kind of polyolefin resin, melamine resin, polyester resin, silicone, silane coupling agent, and fatty acid ester.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to transparencies. [Background technology]

[0002] In recent years, in consideration of the environment, transparent paper using a paper base material has been used instead of plastic packaging materials. Such transparent paper is generally formed by treating a paper base material with a clarifying agent such as liquid paraffin. For example, Patent Document 1 discloses a packaging material having a base paper containing pulp and resin layers on both sides of the base paper, in which the base paper contains polyalkylene glycol. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-154603 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, further study is needed to achieve visibility that allows the packaged contents to be confirmed even when the paper and the object are separated. The present invention has been made in consideration of the above circumstances, and has an object to provide a transparent paper having excellent visibility. [Means for solving the problem]

[0005] The present invention provides a transparent paper comprising a base paper having a haze of 90% or less and a total light transmittance of 70% or more, and a transparent layer provided on at least one surface of the base paper, the transparent layer containing at least one of polyolefin resin, melamine resin, polyester resin, silicone, a silane coupling agent, and a fatty acid ester.

[0006] The polyolefin resin is preferably an ethylene-vinyl acetate copolymer or polyethylene, and the fatty acid ester is preferably a sorbitan fatty acid ester.

[0007] It is preferable that a transparent layer is further provided on the other surface of the base paper.

[0008] The base paper has a beating degree of 70°SR or more and 100°SR or less, and a compactness of 1.0 g / cm 3 More than 1.5g / cm 3 It is preferable that:

[0009] The transparent layer is preferably a laminate layer containing a polyolefin resin.

[0010] The thickness of the laminate layer is preferably 5 μm or more and 40 μm or less.

[0011] The clarifying layer is preferably a coating layer containing at least one of a melamine resin, a polyester resin, a silicone, a silane coupling agent, and a fatty acid ester.

[0012] The content of at least one of the melamine resin, polyester resin, silicone, silane coupling agent, and fatty acid ester in the coating layer is 0.5 g / m 2 More than 20g / m 2 It is preferable that: Effect of the Invention

[0013] According to the present invention, a transparent paper having excellent visibility can be obtained. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] [Transparent paper] The transparent paper of the present invention comprises a base paper having a haze of 90% or less and a total light transmittance of 70% or more, and a transparent layer provided on at least one surface of the base paper, the transparent layer containing at least one of polyolefin resin, melamine resin, polyester resin, silicone, a silane coupling agent, and a fatty acid ester.

[0015] (base paper) The base paper used in the present invention has a haze (hereinafter, sometimes referred to as Haze) of 90% or less and a total light transmittance (hereinafter, sometimes referred to as TT) of 70% or more. With a haze of 90% or less and a total light transmittance of 70%, the transparency is high, and by forming a transparent layer described below, a transparent paper with even higher transparency can be provided. The beating degree of the base paper is 70°SR or more and 100°SR or less, and the tension is 1.0 g / cm 3 More than 1.5g / cm 3 It is preferable that the beating degree and the compactness of the base paper are within the above ranges, so that light scattering in voids inside the paper can be suppressed, and high transparency can be obtained. More preferably, the beating degree is 75° SR or more and 95° SR or less, and the compactness is 1.1 g / cm or less. 3 More than 1.4g / cm 3 The following is the result.

[0016] The base paper preferably contains chemical pulp such as bleached hardwood kraft pulp (LBKP (L material)), bleached softwood kraft pulp (NBKP (N material)), bleached hardwood sulfite pulp (LBSP), or bleached softwood sulfite pulp (NBSP).

[0017] The base paper may contain wood pulp or non-wood pulp other than bleached hardwood kraft pulp / bleached softwood kraft pulp. In addition, as long as the haze and total light transmittance are within the above ranges, the base paper may contain conventional additives, such as paper strength agents (starch, polyacrylamide, polyamidoamine epichlorohydrin, etc.), retention aids, drainage aids, aluminum sulfate, pH adjusters, defoamers, pitch control agents, slime control agents, etc., which may be appropriately selected and used as necessary. Furthermore, the base paper includes treated base paper that has been subjected to a calendaring process, and treated base paper that has been subjected to a surface sizing process or surface treatment with starch, polyvinyl alcohol, etc. Furthermore, the base paper includes treated base paper that has been subjected to a calendaring process after surface sizing or surface treatment. Calendering is a process in which paper is passed between rolls to make the surface glossy, smooth, and even out the thickness. Examples of calendering devices include machine calenders and super calenders, and the super calenders include soft nip calenders and hard nip calenders. From the viewpoint of improving transparency, the base paper is preferably a treated base paper that has been subjected to a calendering treatment using a machine calender and a super calender. In addition, the base paper is preferably subjected to a damping process before the calendaring process. In the damping process, it is more preferable to attach moisture of 5 to 25% of the base paper's mass, and then heat the base paper at 70°C to 150°C to perform the calendaring process. The reason for this is that the moisture absorbed in the damping process breaks the hydrogen bonds between the pulp, making the pulp flexible, and in this state, applying pressure with the calendar crushes the base paper, reducing the voids. If heat is applied at this time, the base paper is dried while maintaining its crushed state, reducing the void ratio of the base paper (increasing compactness) and improving transparency.

[0018] The thickness of the base paper is preferably 20 μm or more and 150 μm or less. The lower limit of the thickness of the base paper is more preferably 25 μm or more, even more preferably 30 μm or more, and even more preferably 35 μm or more. The upper limit of the thickness of the base paper is more preferably 80 μm or less, even more preferably 70 μm or less, and even more preferably 60 μm or less.

[0019] (transparent layer) The transparent paper of the present invention has a transparent layer provided on at least one surface of the base paper. The transparent layer contains at least one of polyolefin resin, melamine resin, polyester resin, silicone, silane coupling agent, and fatty acid ester. These may be used alone or in combination of two or more. The polyolefin resin is not particularly limited, and examples thereof include ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, and ethylene-methyl methacrylate, etc. Among them, the polyolefin resin is preferably an ethylene-vinyl acetate copolymer or polyethylene.

[0020] The melamine resin is not particularly limited, and examples thereof include methylated melamine, methylolated melamine, iminated melamine, methoxymethylated melamine, and butylated melamine.

[0021] The polyester resin is not particularly limited, and examples thereof include those produced by known polymerization methods such as polylactic acid, polyhydroxybutyrate, polycaprolactone, polyglycolic acid, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polytrimethylene terephthalate. In addition, a commercially available polyester resin water dispersion may be used as the polyester.

[0022] The silicone is not particularly limited, and examples thereof include silicone oil, solvent-type silicone, solventless silicone, etc. The weight-average molecular weight of the silicone is preferably 2,000 to 500,000, from the viewpoint that the silicone easily penetrates into the inside of the base paper, thereby reducing the porosity inside the base paper and making it easier to express transparency.

[0023] The silane coupling agent is not particularly limited, and examples thereof include compounds having an alkoxy group bonded to a silicon atom and a reactive group that chemically bonds with an adherend such as a metal or various synthetic resins within one molecule, such as methyltrimethoxysilane oligomer, vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-isocyanatopropyltriethoxysilane.

[0024] The fatty acid ester is not particularly limited, and examples thereof include sorbitan fatty acid esters (e.g., sorbitan monooleate, sorbitan monostearate, sorbitan monomyristate, sorbitan monolaurate, sorbitan dioleate, sorbitan distearate, sorbitan dimyristate, sorbitan dilaurate, etc.), glycerin fatty acid esters (e.g., glycerin monooleate, glycerin monostearate, glycerin monomyristate, glycerin monolaurate, glycerin dioleate, glycerin distearate, glycerin dimyristate, glycerin dilaurate, etc.), sucrose fatty acid (e.g., sucrose oleate, sucrose behenate, sucrose stearate, sucrose palmitate, sucrose myristate, sucrose laurate, sucrose erucate, etc.), and the like.

[0025] Among them, it is preferable that the polyolefin resin is laminated on the base paper to form the transparent layer. When the transparent layer is a laminate layer, the film thickness of the transparent layer is preferably 5 μm or more and 40 μm or less, more preferably 12 μm or more and 16 μm or less. By having a film thickness of 5 μm or more, the unevenness of the paper surface can be made flat, and high transparency can be obtained. In addition, by having a film thickness of 40 μm or less, it is possible to prevent the front and back surfaces of the transparent paper from sticking together after production, that is, so-called blocking. There is no particular limit to the method of laminating the transparent layer on the base paper. For example, the transparent layer can be provided on the base paper using a general melt extrusion die, a T die, a multi-layer simultaneous extrusion die, a conventionally known laminator device, or the like.

[0026] The transparent layer is preferably formed by forming a coating layer containing at least one of a melamine resin, a polyester resin, a silicone, a silane coupling agent, and a fatty acid ester. The content of at least one of a melamine resin, a polyester resin, a silicone, a silane coupling agent, and a fatty acid ester in the coating layer is preferably 0.5 g / m or less. 2 More than 20g / m 2 Preferably, the content is 1.0 g / m or less. 2 More than 15g / m 2 More preferably, it is 1.5 g / m or less. 2 More than 10g / m 2 The coating weight of the clarifying layer is more preferably 0.5 g / cm or less. 2 By providing the above amount, the voids in the base paper and the unevenness of the base paper surface can be flattened, thereby obtaining high transparency. 2 If the thickness exceeds this range, no difference in transparency is observed, or blocking or tack occurs, which is undesirable.

[0027] Examples of the coating method include a size press, a gate roll coater, a film transfer coater, a blade coater, a rod coater, an air knife coater, a Comma Coater (registered trademark), a gravure coater, a bar coater, an E-bar coater, and a curtain coater. The heating temperature for drying the coating film is preferably 100° C. or higher and 200° C. or lower, and the drying time is preferably 0.5 minutes or higher and 5 minutes or lower. Examples of the drying device include hot air dryers such as a linear tunnel dryer, an arch dryer, an air loop dryer, and a sine curve air float dryer, an infrared heating dryer, and a dryer using microwaves, etc.

[0028] From the viewpoint of obtaining even higher transparency, it is preferable that a transparent layer is also provided on the other side of the base paper, that is, it is preferable that a transparent layer is provided on both sides of the base paper.

[0029] Because the transparent paper of the present invention has the above-mentioned configuration, it can achieve a haze of 75% and a total light transmittance of 75%, and therefore has high transparency. When used as wrapping paper, envelope windows, etc., the contents can be clearly seen even from a distance. EXAMPLES

[0030] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0031] Details of the materials listed in Table 1 are as follows: (laminating resin) PE: Polyethylene resin (thickness 12 μm, product name "LC8001", manufactured by Japan Polyethylene Co., Ltd.) EVA: Ethylene-vinyl acetate copolymer resin (thickness 13 μm, product name "Ultrathene 537", manufactured by Tosoh Corporation)

[0032] (coating resin) A1: Methylated melamine (product name "Nicalac MW-30", manufactured by Nippon Carbide Industries Co., Ltd.) A2: Silicone (weight average molecular weight 30,000 to 500,000, product name "KNS3300", manufactured by Shin-Etsu Chemical Co., Ltd.) A3: Polyester resin (product name "Pluscoat Z-730", manufactured by GOO Chemical Industry Co., Ltd.) A4: Methyltrimethoxysilane oligomer (product name "KR-400N", manufactured by Shin-Etsu Chemical Co., Ltd.) A5: Polyoxyethylene sorbitan monooleate (product name "Leodol SP-O10V", manufactured by Kao Corporation)

[0033] [Example 1] (base paper) Pulp slurry with a beating degree of 70 to 100°SR is used to make paper using a fourdrinier multi-cylinder papermaking machine, and after a damping process, it is calendered using a machine calender and a super calender to make a paper with a tightness of 1.25 g / cm. 3 A base paper with a haze of 82% and a total light transmittance of 81% was produced. (transparent layer) Next, polyethylene resin was laminated on both sides of the base paper using a laminator equipped with a melt extrusion device to form a polyethylene layer (transparent layer, 12 μm per side) on both sides. The base paper laminated with polyethylene resin was heat-treated using a flat plate heat press set at 140°C to produce transparent paper.

[0034] [Example 2] A transparent paper was prepared in the same manner as in Example 1, except that polyethylene resin was laminated on one side of the base paper.

[0035] [Example 3] A transparent paper was prepared in the same manner as in Example 1, except that the resin to be laminated was changed to ethylene-vinyl acetate copolymer resin (EVA) and the lamination thickness was changed to 13 μm per side.

[0036] [Example 4] The A1 resin was bar-coated on both sides of the same base paper as in Example 1, and dried in a hot air oven at 140° C. for 1 minute to prepare transparent paper.

[0037] [Example 5] A2 resin was bar-coated on both sides of the same base paper as in Example 1, and dried in a hot air oven at 150° C. for 30 seconds to prepare transparent paper.

[0038] [Example 6] A3 resin was bar-coated on both sides of the same base paper as in Example 1, and dried in a hot air oven at 120° C. for 1 minute and 30 seconds to prepare transparent paper.

[0039] [Example 7] A mixture of 3 parts of titanium catalyst (product name "D-25", manufactured by Shin-Etsu Chemical Co., Ltd.) per 100 parts by mass of A4 resin was bar-coated on both sides of the same base paper as in Example 1, and the mixture was dried in a hot air oven at 140°C for 1 minute to produce transparent paper.

[0040] [Example 8] A mixture of 30 parts by mass of methylated melamine (product name "Nikarac MW-30", manufactured by Nippon Carbide Industries Co., Ltd.) as a crosslinking agent and 100 parts by mass of p-toluenesulfonic acid (product name "D-900", manufactured by Sakuramiya Chemical Co., Ltd.) as a catalyst per 100 parts by mass of A5 resin was bar coated on both sides of the same base paper as in Example 1, and then dried in a hot air oven at 140°C for 1 minute to produce transparent paper. [Comparative Example 1] Pulp slurry with a beating degree of 70 to 100°SR was used to make paper using a fourdrinier multi-cylinder papermaking machine, and the paper was calendered using a machine calender and a super calender to obtain a paper with a density of 1.1 g / cm. 3 A base paper with a haze of 76% and a total light transmittance of 82% was produced. No transparent layer was formed on the base paper.

[0041] [Comparative Example 2] Tightness: 1.1g / cm 3 A transparent paper was prepared in the same manner as in Example 1, except that a base paper having a haze of 91% and a total light transmittance of 68% was used.

[0042] [Comparative Example 3] Pulp slurry with a beating degree of 70 to 100°SR is made into paper using a fourdrinier multi-cylinder papermaking machine, and calendered using a machine calender and a super calender to obtain a paper with a tightness of 0.7 g / cm. 3 A base paper with a haze of 94% and a total light transmittance of 62% was produced. Next, the base paper was impregnated with polyethylene glycol using a size press coater. Next, polyethylene resin was laminated on both sides of the base paper. The base paper laminated with polyethylene resin was heat-treated in a lithographic hot press set at 140°C to produce transparent paper.

[0043] [Comparative Examples 4 to 8] Pulp slurry with a beating degree of 70 to 100°SR was used to make paper using a fourdrinier multi-cylinder papermaking machine, and the paper was calendered using a machine calender and a super calender to obtain a paper with a density of 1.1 g / cm. 3 A base paper with a haze of 91% and a total light transmittance of 68% was produced. Next, the coating resins shown in Table 1 were applied to prepare transparent papers.

[0044] [evaluation] The base papers and transparencies of the above-mentioned Examples and Comparative Examples were evaluated as follows. The evaluation results are shown in Table 1.

[0045] (Measurement of Beating Degree) The beating degree of the base paper was measured using a J-type Schopper-Riegler freeness tester based on the JIS P8121-1:2012 Schopper-Riegler method.

[0046] (Haze and total light transmittance measurements) The haze and total light transmittance of the transparent paper were measured using a haze meter NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0047] (Visibility) We evaluated whether an object (paper with 10-point characters printed on it) could be seen from a distance when viewed through a transparent piece of paper. <Evaluation criteria> 5: Visible from 5cm to 7cm 4: Visible at 3cm to 5cm 3: Visible at 1cm to 3cm 2: Visible at 0.5cm to 1cm Visible at 1:0cm

[0048] [Table 1]

[0049] As shown in Table 1, the transparent paper of the present invention, which uses base paper having a haze of 90% or less and a total light transmittance of 70% or more and has a transparency layer containing polyolefin resin, melamine, polyester, silicone, silane coupling agent, or fatty acid ester, has excellent transparency and good visibility.

Claims

1. A base paper having a haze of 90% or less and a total light transmittance of 70% or more; A transparent layer is provided on at least one surface of the base paper, The transparent paper, wherein the transparent layer contains at least one of a polyolefin resin, a melamine resin, a polyester resin, a silicone, a silane coupling agent, and a fatty acid ester.

2. 2. The transparent paper according to claim 1, wherein the polyolefin resin is an ethylene-vinyl acetate copolymer or polyethylene, and the fatty acid ester is a sorbitan fatty acid ester.

3. 2. The transparent paper according to claim 1, wherein the transparent layer is further provided on the other surface of the base paper.

4. The base paper has a beating degree of 70°SR or more and 100°SR or less, and a tightness of 1.0 g / cm ３ 1.5g / cm or more ３ 2. The transparency of claim 1, wherein:

5. 2. The transparent paper according to claim 1, wherein the transparent layer is a laminate layer containing a polyolefin resin.

6. 6. The transparent paper according to claim 5, wherein the thickness of the laminate layer is 5 to 40 μm or more.

7. 2. The transparent paper according to claim 1, wherein the transparent layer is a coating layer containing at least one of a melamine resin, a polyester resin, a silicone, a silane coupling agent, and a fatty acid ester.

8. The content of at least one of a melamine resin, a polyester resin, a silicone, a silane coupling agent, and a fatty acid ester in the coating layer is 0.5 g / m ２ 20g / m or more ２ 8. The transparency of claim 7, wherein:

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