Base paper for release paper and release paper

Abstract

The present invention aims to provide a base paper for release paper that can be easily disintegrated and easily recycled, even when using conventional polyolefin resins such as ethylene. [Solution] The present invention provides a base paper 1 for release paper, wherein a sealing layer 3 and another sealing layer 3 are sequentially laminated on at least one surface 2b of a base paper 2, and the sealing layer 3 is formed from a sealing layer forming composition mainly composed of an aqueous acrylic emulsion. Furthermore, in the release paper of the present invention, a release layer 4 is laminated on the surface 3b of the base paper 1 for release paper, opposite to the surface 3a of the sealing layer 3 on which the base paper 2 is provided.

Description

[Technical Field]

[0001] This invention relates to base paper for release paper and release paper. [Background technology]

[0002] Release paper is used as a backing to protect the adhesive surface of adhesive labels, adhesive stickers, adhesive tapes, etc., from the adhesion of dirt and other debris. The surface that comes into contact with the adhesive surface is coated with a release agent such as silicone resin. Conventional release paper is manufactured by coating the surface of a base paper such as polyethylene laminate paper, glassine paper, clay coated paper, or clear coated paper with a release agent. These release agents are used after being diluted with organic solvents such as toluene, which poses a problem of environmental damage. Therefore, in recent years, there has been a growing demand for water-based emulsion type silicone resins and solvent-free silicone resins.

[0003] Furthermore, since silicone resin used as a release agent is very expensive, it is necessary for the base paper for release paper to minimize the penetration of the silicone resin coating liquid into the base paper in order to enable the uniform application of a small amount of silicone resin coating liquid. However, in recent years, from the perspective of resource conservation, recyclability has also become a requirement.

[0004] To suppress the penetration of release agents such as silicone resin, a release paper base in which polyethylene is laminated to the base paper is preferable. However, it has the disadvantage that it is difficult to separate the release paper after use, making it unsuitable for recycling.

[0005] To improve upon the above drawbacks, a base paper for release paper is known, comprising a sealing layer containing at least a pigment component and an adhesive component on at least one surface of the base paper, wherein the median diameter (D50) of the pigment component measured by laser diffraction using a scattering particle size distribution analyzer is 2.0 to 7.0 μm, the adhesive component contains at least synthetic resin latex, and the amount of synthetic resin latex blended with 100 parts by mass of the pigment component (absolutely dry) is 8 to 20 parts by mass (absolutely dry) (see Patent Document 1).

[0006] Furthermore, there is a known release paper for adhesive labels characterized by having a tightness of 0.9 to 1.1 when an underlayer containing a tackifier with a softening point of 170°C or lower, a sealing layer containing a water-soluble resin, and a release layer are sequentially formed on the surface of ordinary paper made from wood pulp with a freeness of 350 to 500 ml CSF (see Patent Document 2).

[0007] Furthermore, there is a known release paper characterized by sequentially providing a sealing layer made of a water-soluble resin, an intermediate layer made of a water-soluble resin, and a release layer on at least one surface of a base paper made of pulp with a beaten degree of 20 to 44°SR (see Patent Document 3).

[0008] Furthermore, an acrylate-based latex containing a copolymer of ethyl acrylate and butyl acrylate is added to a water-dispersible paper substrate at a solid content of 0.5 to 10 g / m². 2 Apply to form a sealing layer, and then apply solvent-free silicone at a solid content equivalent of 0.3 to 3 g / m² on top of the sealing layer. 2 Release paper is known that is characterized by having a release layer formed by coating (see Patent Document 4). [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2016-223036 [Patent Document 2] Japanese Patent Publication No. 2005-010513 [Patent Document 3] Japanese Patent Publication No. 2002-166504 [Patent Document 4] Japanese Patent Application Publication No. 06-305087 [Overview of the project] [Problems that the invention aims to solve]

[0010] The present invention provides a base paper for release paper and release paper that allows the sealing layer to be easily separated and reused. [Means for solving the problem]

[0011] As a result of diligent research to solve the aforementioned problems, the inventors discovered that the above problems could be solved by using a specific resin as a sealing layer, and thus completed the present invention.

[0012] In other words, the present invention relates to a base paper for release paper, wherein a sealing layer is laminated on at least one surface of a base paper, and the sealing layer is a resin layer formed of a sealing layer-forming composition mainly composed of an aqueous acrylic emulsion. The present invention also relates to a release paper in which a release layer is laminated on the side of the base paper for the release paper that is opposite to the side of the sealing layer on which the base paper is provided. [Effects of the Invention]

[0013] By using the release paper base paper of the present invention, the decomposition properties of the sealing layer are good, so the release paper can be easily reused. [Brief explanation of the drawing]

[0014] [Figure 1] This figure schematically shows a cross-section of a release liner and a base paper for release liner according to one embodiment of the present invention. [Modes for carrying out the invention]

[0015] Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG. 1. Note that the scope of the present invention is not limited to the release paper shown in FIG. 1. As shown in FIG. 1, the base paper 1 for release paper of the present invention is formed by laminating a blocking layer 3 on at least one surface 2b of the base paper 2, and the blocking layer 3 is a resin layer formed of a composition for forming a blocking layer mainly composed of an aqueous acrylic emulsion.

[0016] The base paper 2 used for the base paper 1 for release paper of the present invention is mainly composed of wood pulp fibers. As the wood pulp fibers, chemical pulps such as softwood kraft pulp, hardwood kraft pulp, and sulfite pulp, mechanical pulps such as stone ground pulp, thermomechanical pulp, and refiner ground pulp, and recycled pulp obtained from newspapers, coated paper, fine paper, etc. can be appropriately blended and used. Further, if necessary, non-wood pulp such as kenaf, hemp, and bamboo, and fiber materials other than cellulose fibers such as glass fibers and polyethylene fibers may be blended.

[0017] When forming the base paper 2, internal additives such as sizing agents, paper strength enhancers, fixing agents, yield improvers, and dyes, and internal fillers such as talc, kaolin, titanium dioxide, aluminum hydroxide, and calcium carbonate can be added, or during the papermaking process, paper strength improvers such as starch and polyvinyl alcohol, surface sizing agents, and dyes can be applied using a size press, gate roll, etc. Surface treatment may be appropriately performed.

[0018] The base paper 2 preferably has a thickness of 40 μm or more and 300 μm or less. If the thickness of the base paper 2 is less than 40 μm, the occurrence of wrinkles during the production of the release paper increases. On the other hand, if the thickness of the base paper 2 exceeds 300 μm, the rigidity becomes too high and the handleability decreases.

[0019] The basis weight of the base paper 2 is preferably 40 g / m 2 or more and 200 g / m 2 or less, more preferably 50 g / m 2 or more and 160 g / m 2 or less. If the basis weight of the base paper 2 is 40 g / m2 If the basis weight is less than 200 g / m², the paper strength will be weak and the paper may not be suitable for processing. On the other hand, the basis weight of base paper 2 is 200 g / m². 2 Exceeding this limit may result in poor handling.

[0020] The aqueous acrylic emulsion used in the sealing layer 3 of the present invention is, for example, a (meth)acrylic acid-based unsaturated monomer as an essential component, and other copolymerizable unsaturated monomers are emulsion-polymerized and dispersed in water as needed. Examples of the (meth)acrylic acid-based unsaturated monomers include alkyl (meth)acrylate ester compounds such as (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; aromatic ring-containing (meth)acrylic acid ester compounds such as allyl (meth)acrylate, benzyl (meth)acrylate, and naphthyl (meth)acrylate; and hydroxyalkyl (meth)acrylate ester compounds such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate. Examples of copolymerizable unsaturated monomers used as needed include styrene-based unsaturated monomers such as styrene, α-methylstyrene, and vinyltoluene; and (meth)acrylamide.

[0021] The sealing layer 3 preferably has a thickness of 0.5 μm to 50 μm, and more preferably 5 μm to 50 μm. If the thickness of the sealing layer 3 is less than 0.5 μm, it becomes difficult to suppress the penetration of the release agent into the base paper 2. On the other hand, if the thickness of the sealing layer 3 exceeds 50 μm, it becomes unnecessarily thick and is not practically suitable.

[0022] In addition to the aqueous acrylic emulsion, other additives may be added to the composition for forming the plugging layer of the present invention. Specific examples of the other additives include additives generally usable in the production of polyurethane foams, such as plasticizers, foam stabilizers, fillers, antioxidants, defoamers, compatibilizers, colorants, stabilizers, ultraviolet absorbers, and the like. The addition amount of the other additives may be appropriately selected within a range that does not inhibit the effects of the present invention.

[0023] The plugging layer 3 may be formed on both surfaces 2a and 2b of the base paper 2. The method for forming the plugging layer 3 on one surface 2b or both surfaces 2a and 2b of the base paper 2 is not particularly limited, and conventionally known methods can be used, for example, a method of applying a coating liquid containing a resin constituting the plugging layer 3 on the base paper 2 and drying it to form the plugging layer 3, or a method of laminating the base paper 2 and the plugging layer 3 via an adhesive.

[0024] Examples of the release agent that can be used for the release paper 10 of the present invention include silicone resins, fluorine compounds, amino alkyd compounds, polyester compounds, etc., and among them, silicone resins are preferably mentioned. Specific examples of the silicone resin include solvent-free silicone resins, solvent-based silicone resins, water-based emulsion silicone resins, solvent-free UV-curable silicone resins, and the like.

[0025] The release paper 10 of the present invention is obtained by coating a release agent, for example, at 0.5 to 2.0 g / m, on the surface 3b of the release paper base paper 1, which is opposite to the surface 3a of the plugging layer 3 where the base paper 2 is in contact, to provide a release layer (also referred to as a release layer) 4. Also, as a method for applying the release agent to the release paper base paper 1, various coating apparatuses such as a blade coater, an air knife coater, a rod blade coater, a bar blade coater, a gravure coater, etc. can be appropriately selected and used. 2

[0026] ​Furthermore, the 75° gloss of the surface 4b of the release layer 4 of the release paper 10 of the present invention is preferably 70-90%, and more preferably 75-85%. If the 75° gloss is less than 70%, a uniform coating surface of the release agent cannot be obtained. Also, if the 75° gloss exceeds 90%, the release layer 4 becomes excessively thick, resulting in insufficient adhesion between the release paper base 1 and the release layer 4. [Examples]

[0027] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way to these examples. [Examples]

[0028] 5 g / m² on PET and CPP films 2 Test specimens 1 and 2 were prepared by coating a water-based acrylic emulsion adhesive with the material and dry laminating it with fine paper. When the adhesive strength was measured in accordance with JIS Z 0237, both test specimens 1 and 2 showed a result of 1.0 N / 15 mm. It was determined that the cohesive force between the layer formed from the water-based acrylic emulsion adhesive and the fine paper, and the cohesive force within the layer formed from the water-based acrylic emulsion adhesive, were stronger than the cohesive force within the fine paper, as the peeling interface became a wall-breaking point in the fine paper.

[0029] The manufacturing process for release paper involves coating it with a release agent. Since a drying process is required during the release agent coating, heat resistance is necessary. Therefore, test specimens 1 and 2 were subjected to a test in which they were stored for 2 minutes in an air bath set to 120°C, 140°C, and 160°C. As a result, neither melting nor foaming was observed in test specimens 1 and 2.

[0030] To improve recyclability, it is desirable that the base paper or release paper for release liner be easily peelable by immersion in water or hot water. Therefore, the condition of test pieces 1 and 2 after immersion in water (25°C) and hot water (80°C) for 24 hours, respectively, was observed. The results are shown in Table 1.

[0031] [Table 1]

[0032] From the above results, it was found that test pieces 1 and 2 could be easily peeled off without applying force by immersing them in water or hot water. Only the sample of test piece 1 that was immersed in hot water for 24 hours showed partial wall breakage, but the others showed cohesive peeling, indicating that the high-quality paper, PET, and CPP could be easily peeled off compared to before immersion. Therefore, it was suggested that the base paper and release paper for release paper of the present invention will be easier to separate during recycling, and an improvement in recyclability can be expected. [Industrial applicability]

[0033] The base paper for release paper of the present invention can be suitably used in release paper on which various seals and the like can be attached.

Claims

1. A base paper for release paper, comprising a base paper with a sealing layer laminated on at least one surface thereof, wherein the sealing layer is a resin layer formed from a sealing layer-forming composition mainly composed of an aqueous acrylic emulsion.

2. A release paper comprising a release layer laminated on the side of the base paper for release paper according to claim 1, opposite to the side of the sealing layer on which the base paper is provided.

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