Release paper and separation method of the same

Abstract

To provide release paper in which a paper substrate and a release agent layer can be separated, the paper substrate can be easily recycled, and hardening inhibition when forming a silicone-based release agent layer is suppressed.SOLUTION: There is provided release paper 100 comprising: a paper substrate 10; a filler layer 20 which is provided on at least one surface of the paper substrate 10, and includes a polyester resin whose acid value is 35 mgKOH / g or more; and a release agent layer 30 which is provided on a surface opposite to the paper substrate 10 side of the filler layer 20, and includes a silicone-based release agent. In the paper substrate 10 having the filler layer 20, air infiltration resistivity using the Oken type test machine method in accordance with JIS P 8117:2009 when measuring from the filler layer 20 side before the release agent layer 30 is arranged, is 10000 seconds or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a release paper and a method for separating the release paper. [Background technology]

[0002] 2. Description of the Related Art Release papers having a release agent layer provided on a paper substrate have been widely used for various applications.

[0003] Patent Document 1 describes a recyclable release sheet having, on at least one surface of a support, an intermediate layer mainly composed of an aqueous polymer, an anchor layer on the intermediate layer made of a resin composition mainly composed of one or more alkali-soluble resins selected from alkali-soluble resins containing a carboxyl group or a phenolic hydroxyl group, and a release agent layer on the anchor layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 05-269932 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been growing interest in recycling in order to reduce the environmental impact of treating plastic waste, and there is a demand for recycling release paper as well.

[0006] Conventionally, in a release paper having a release agent layer containing a silicone-based release agent, for example, a filler layer formed of a polyolefin resin is provided between the paper substrate and the release agent layer in order to suppress the penetration of the release agent into the paper substrate. However, when recycling a release paper provided with a filler layer formed of a polyolefin resin, it is required to separate the paper substrate from the polyolefin resin as the filler layer.

[0007] From the viewpoint of recycling of the release paper, it is preferable to manufacture the release paper without forming the polyolefin resin as a sealing layer. For example, a release paper in which a release agent layer containing a silicone-based release agent is formed directly on a paper substrate such as glassine paper is known as such a release paper. However, when a release paper in which a release agent layer containing a silicone-based release agent is formed directly on a paper substrate is recycled, the silicone-based release agent contained in the release agent layer is contained in the raw material from which the release paper is recycled. Therefore, there is a concern that the conventional release paper may cause problems with the paper manufactured from the raw material from which the release paper is recycled.

[0008] In the release sheet described in Patent Document 1, the support is essentially a paper substrate, and an anchor layer is formed on the paper substrate, the anchor layer being mainly composed of an alkali-soluble resin containing a carboxyl group or a phenolic hydroxyl group. However, the use of a polyester resin in the anchor layer is not disclosed. In addition, when a release agent layer containing a silicone-based release agent is provided as the release agent layer, the resin used in the anchor layer as the sealing layer may inhibit the curing of the silicone-based release agent when the release agent layer is formed. For this reason, further improvement of the release paper has been required.

[0009] The present invention provides a release paper that allows the paper base material to be separated from the release agent layer, allows the paper base material to be easily recycled, and suppresses curing inhibition when forming a release agent layer containing a silicone-based release agent, and a method for separating the release paper. [Means for solving the problem]

[0010] [1] A paper substrate; a sealing layer provided on at least one surface of the paper base material and containing a polyester resin having an acid value of 35 mgKOH / g or more; a release agent layer provided on a surface of the filling layer opposite to the paper substrate side and containing a silicone-based release agent; Equipped with In the paper base material provided with the filling layer, the air permeability resistance measured from the filling layer side before providing the release agent layer according to the Oken type testing machine method in accordance with JIS P 8117:2009 is 10,000 seconds or more. Release paper.

[0011] [2] In the release paper according to [1], The paper substrate comprises glassine paper. Release paper.

[0012] [3] In the release paper according to [2], The paper base material comprises the glassine paper and a pigment coating layer provided on the glassine paper. Release paper.

[0013] [4] In the release paper according to any one of [1] to [3], The amount of the polyester resin applied is 1 g / m2 in terms of solid content. 2 That's all. Release paper.

[0014] [5] In the release paper according to any one of [1] to [4], When a pressure-sensitive adhesive layer is provided on the release agent layer, the peel strength of the release agent layer to the pressure-sensitive adhesive layer is 300 mN / 50 mm or less. Release paper.

[0015] [6] In the release paper according to any one of [1] to [5], The silicone-based release agent is a solvent-free silicone-based release agent. Release paper.

[0016] [7] A method for separating the release paper according to any one of [1] to [6], comprising the steps of: providing the release paper; separating the release paper into the paper substrate and the release agent layer in an alkaline solution; having How to separate the release paper. Effect of the Invention

[0017] According to one aspect of the present invention, there is provided a release paper that allows the paper base material and the release agent layer to be separated, allows the paper base material to be easily recycled, and suppresses curing inhibition when forming a release agent layer containing a silicone-based release agent, and a method for separating the release paper. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a schematic cross-sectional view showing an example of a release paper according to the present embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing an example of a substrate provided with a sealing layer before providing a release agent layer in the release paper according to the present embodiment. [Diagram 3] 3 shows electron microscope images of the surface of the filling layer before the release agent layer is provided in the release papers according to Example 1, Example 4, and Comparative Example 3. [Figure 4] 4 shows electron microscope images showing the results of evaluation of the separation properties of the release papers according to Example 1, Example 4, and Comparative Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described in detail.

[0020] [Release paper] The release paper according to the present embodiment comprises a paper substrate, a filler layer provided on at least one side of the paper substrate, the filler layer containing a polyester resin having an acid value of 35 mgKOH / g or more, and a release agent layer provided on the side opposite to the paper substrate side of the filler layer, the release paper according to the present embodiment has an air resistance of 10,000 seconds or more when measured from the filler layer side before the release agent layer is provided, using an Oken type testing machine method according to JIS P 8117:2009. In the following description, a release agent layer containing a silicone-based release agent may be referred to as a silicone-based release agent layer.

[0021] The present inventor has focused on the acid value of polyester resin, and found that by providing a polyester resin having a specific acid value or more as a filler layer on a paper substrate, it is possible to easily separate the paper substrate and the silicone-based release agent layer.The present inventor has also found that when a filler layer is formed on a paper substrate using a polyester resin having a specific acid value or more, the air permeability resistance measured from the filler layer side by the Oken type testing machine method is a specific value or more, so that the silicone-based release agent can be prevented from penetrating into the paper substrate, and the paper substrate and the silicone-based release agent layer can be easily separated.The present inventor has also found that by using a polyester resin as the type of resin used for the filler layer, the curing inhibition when forming the silicone-based release agent layer can be suppressed.

[0022] That is, by having the above-mentioned configuration, the release paper according to this embodiment makes it possible to separate the paper substrate from the release agent layer, allowing the paper substrate to be easily recycled, and inhibiting hardening when forming the silicone-based release agent layer. The inventor believes this to be the following: The filling layer provided on the paper substrate contains a polyester resin having an acid value equal to or greater than a specific value, and therefore the polyester resin contains a large amount of carboxy groups. When the release paper according to this embodiment is placed in an alkaline solution, the polyester resin contained in the filling layer is dissolved in the cations (e.g., Na) in the alkaline solution.+ and K. + It is considered that the interfacial strength between the filling layer and the paper substrate is weakened by forming a salt with the filling layer and swelling with the filling layer. In addition, since the gel fraction of the polyester resin contained in the filling layer in a sodium hydroxide aqueous solution is about 95%, the polyester resin is considered to be in a state where it is almost not dissolved by the alkaline solution. Furthermore, it is considered that the air permeability resistance measured from the filling layer side by the Oken type testing machine method is a specific value or more, so that the filling effect when forming the silicone-based release agent layer is enhanced, and the silicone-based release agent is less likely to penetrate into the paper substrate. As a result, when the release paper according to this embodiment is recycled, it is presumed that the silicone-based release agent layer is peeled off at the interface between the filling layer and the paper substrate under the same conditions as those when the paper is disintegrated in an alkaline aqueous solution, and the silicone-based release agent layer is separated from the paper substrate together with the filling layer, so that the paper substrate and the silicone-based release agent layer can be easily separated. And, in the release paper according to this embodiment, the silicone-based release agent layer is separated from the paper substrate, so that a release paper with improved recyclability can be obtained.

[0023] The release paper according to the present embodiment will be described with reference to the drawings, in which some parts are shown enlarged or reduced in size for ease of explanation.

[0024] The release paper 100 shown in FIG. 1 includes a paper substrate 10, a sealing layer 20 laminated on one side (first paper substrate surface 11) of the paper substrate 10, and a release agent layer 30 laminated on the surface (first sealing layer surface 21) opposite to the surface (second sealing layer surface 22) of the sealing layer 20 on the paper substrate 10 side, and the paper substrate 10, the sealing layer 20, and the release agent layer 30 are laminated in this order in the thickness direction from the paper substrate 10 toward the release agent layer 30. The sealing layer 20 contains a polyester resin having an acid value of 35 mgKOH / g or more, and the release agent layer 30 contains a silicone-based release agent. In the release paper 100 shown in FIG. 1, the paper substrate 10 and the sealing layer 20 are in direct contact with each other, and the sealing layer 20 and the release agent layer 30 are in direct contact with each other. The second paper substrate surface 12 opposite to the first paper substrate surface 11 of the paper substrate 10 is not provided with the sealing layer 20 and the release agent layer 30, and the second paper substrate surface 12 is exposed. The second release agent layer surface 32 of the release agent layer 30 is in contact with the first sealing layer surface 21 of the sealing layer 20, and the first release agent layer surface 31 opposite to the second release agent layer surface 21 is exposed. In the release paper 100, the first release agent layer surface 31 is the surface of the release paper 100 that has releasability and serves as the release surface. When the release paper 100 is used with a laminate (not shown) laminated on the release agent layer 30, the laminate (not shown) is laminated on the first release agent layer surface 31, which is the release surface of the release paper 100. Here, the laminate represents an object (for example, an adhesive sheet, various resin sheets, various composite materials, synthetic leather, etc.) that is laminated on the release surface of the release paper.

[0025] 2 shows a sealed paper 200 in which a sealing layer 20 is provided on a first paper substrate surface 11 of a paper substrate 10. The sealed paper 200 comprises a paper substrate 10 and a sealing layer 20 laminated on the first paper substrate surface 11 of the paper substrate 10, and the first paper substrate surface 11 and the second sealing layer surface 22 are in direct contact with each other. That is, the sealed paper 200 is a paper substrate 10 in which a sealing layer 20 is provided before the release agent layer 30 of the release paper 100 shown in FIG. 1 is provided. The sealed paper 200 has an air resistance of 10,000 seconds or more when measured from the first sealing layer surface 21 side of the sealing layer 20 by the Oken type testing machine method in accordance with JIS P 8117:2009.

[0026] Although an example of the release paper according to the present embodiment has been described above with reference to Figures 1 and 2, the release paper according to the present embodiment is not limited to this. The release paper according to the present embodiment may take various forms as long as it has the above-mentioned configuration.

[0027] (Paper base material) The paper substrate is not particularly limited as long as it can support the filling layer. Examples of the paper substrate include kraft paper, medium-quality paper, fine paper, glassine paper, and coated paper (e.g., art paper, clay-coated paper, and cast-coated paper).

[0028] In this specification, the coated paper comprises a base paper mainly composed of pulp fibers and a pigment coating layer provided on the base paper. The base paper is obtained by adding the desired additives to, for example, pulp fibers as the main component, using a known method. The pigment coating layer is provided on the base paper by a known method. The pigment coating layer may have a single-layer structure or a multi-layer structure. The pigment coating layer contains, for example, an adhesive such as an aqueous resin in a range of 2 parts by mass or more and 50 parts by mass or less per 100 parts by mass of one or more pigments such as calcium carbonate, kaolin, clay, talc, satin white, titanium oxide, and plastic pigment. In this specification, the aqueous resin refers to a resin that can be dispersed in water or a resin that can be dissolved in water. The aqueous resin includes not only water-soluble resins, but also resins that can be dispersed in water, such as emulsion type and dispersion type.

[0029] From the viewpoint of making it possible to separate the paper base material from the release agent layer and to make it easier to recycle the paper base material, it is preferable that the paper base material contains glassine paper. Glassine paper is, for example, paper obtained by highly beating pulp fibers and processing with a super calendar or the like. Glassine paper has fewer voids between pulp fibers than general paper such as fine paper. For this reason, when the paper base material contains glassine paper, the sealing effect is enhanced. As a result, the release agent layer is less likely to penetrate into the paper base material, making it easier to separate the paper base material from the release agent layer, and making it easier to recycle the paper base material. From the same viewpoint, it is more preferable that the paper base material comprises glassine paper and a pigment coating layer provided on the glassine paper. A substrate comprising glassine paper and a pigment coating layer provided on the glassine paper is a type of coated paper. In this specification, glassine paper provided with a pigment coating layer may be referred to as clay-coated glassine paper. If the paper substrate is a clay-coated glassine paper, the glassine paper has a pigment coating layer, which further enhances the sealing effect, and as a result, the release agent layer is less likely to penetrate into the paper substrate, which makes it easier to separate the paper substrate from the release agent layer, and makes the paper substrate easier to recycle.

[0030] The basis weight of the paper substrate is not particularly limited. The basis weight of the paper substrate is, for example, 50 g / m 2 It is preferable that the thickness is 60 g / m or more. 2 More preferably, it is equal to or greater than this. The basis weight of the paper base material is, for example, 200 g / m 2 It is preferable that the thickness is less than 150 g / m 2 It is more preferable that:

[0031] (Sealing layer) The filling layer contains a polyester resin having an acid value of 35 mgKOH / g or more. The filling layer is preferably provided in direct contact with the paper substrate. In this specification, the acid value of the polyester resin (unit: mgKOH / g) is a theoretical acid value derived from the resin constituent unit ratio, and represents the mass (unit: mg) of potassium hydroxide (KOH) required to neutralize 1 g of the polyester resin. The acid value of the polyester resin is preferably 40 mgKOH / g or more, from the viewpoints of making it possible to separate the paper substrate from the release agent layer, making it easier to recycle the paper substrate, and further suppressing the inhibition of curing when forming the silicone-based release agent layer.

[0032] The upper limit of the acid value of the polyester resin is not particularly limited, and may be, for example, 300 mgKOH / g or less, 200 mgKOH / g or less, or 100 mgKOH / g or less. When, for example, a platinum catalyst is used in combination with the silicone-based release agent for forming the release agent layer, if the acid value of the polyester resin used in the sealing layer is too high, the platinum catalyst may be coordinated to the carboxyl group of the polyester resin, and curing inhibition may easily occur. Therefore, from the viewpoint of more easily suppressing curing inhibition when forming the silicone-based release agent layer, it is preferable to set the upper limit of the acid value of the polyester resin to 100 mgKOH / g or less. In addition, if there is no concern about the influence on curing inhibition when forming the silicone-based release agent layer, the upper limit of the acid value of the polyester resin is not limited.

[0033] The acid value of the polyester resin can be adjusted, for example, by changing the type and amount of a polyvalent carboxylic acid component described below.

[0034] The polyester resin can be obtained, for example, by polycondensation of a monomer component including a polyvalent carboxylic acid component and a polyhydric alcohol component. In this specification, the polycarboxylic acid component includes both polycarboxylic acids and derivatives of polycarboxylic acids. Examples of the derivatives of polycarboxylic acids include anhydrides of polycarboxylic acids, lower alkyl esters of polycarboxylic acids, and halides of polycarboxylic acids. In the present specification, the polyhydric alcohol component includes both polyhydric alcohols and derivatives of polyhydric alcohols, such as acetate compounds of polyhydric alcohols.

[0035] Specific examples of the polycarboxylic acid component include aromatic dicarboxylic acids and aliphatic dicarboxylic acids. The polycarboxylic acid component may be used alone or in combination of two or more. Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, diphenic acid, naphthalic acid, 1,2-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid. Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, maleic acid, itaconic acid, glutaric acid, adipic acid, pimelic acid, 2,2-dimethylglutaric acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, diglycolic acid, and thiodipropionic acid.

[0036] The polyvalent carboxylic acid component may be a trivalent or higher polyvalent carboxylic acid. The trivalent or higher polyvalent carboxylic acid component may be used alone or in combination of two or more kinds. When a trivalent or higher polyvalent carboxylic acid is used as the polyvalent carboxylic acid component, a polyester resin having a carboxy group is easily obtained. Examples of trivalent or higher polyvalent carboxylic acids include hemimellitic acid, trimellitic acid, trimesic acid, mellophanic acid, pyromellitic acid, benzenepentacarboxylic acid, mellitic acid, cyclopropane-1,2,3-tricarboxylic acid, cyclopentane-1,2,3,4-tetracarboxylic acid, and ethanetetracarboxylic acid.

[0037] Specific examples of the polyhydric alcohol component include aliphatic diols, alicyclic diols, and aromatic diols. The polyhydric alcohol component may be used alone or in combination of two or more. Examples of the aliphatic diol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, and neopentyl glycol. Examples of the alicyclic diol include cyclohexanediol and cyclohexanedimethanol. Examples of the aromatic diol include dihydroxybiphenol, methylenediphenol, dihydroxynaphthalene, bisphenol A, and bisphenol S.

[0038] The method of polymerizing the polyester resin is not particularly limited, and a known polymerization method can be used. The polyester resin may be prepared by selecting a polyvalent carboxylic acid component and a polyhydric alcohol component and subjecting them to condensation polymerization so that the polyester resin has an acid value of 35 mgKOH / g or more. The polyester resin may be a commercially available polyester resin or a synthesized polyester resin.

[0039] From the viewpoint of making it possible to separate the paper base material from the release agent layer, making it easier to recycle the paper base material, and further suppressing the inhibition of curing when forming the silicone-based release agent layer, the content of the polyester resin having an acid value of 35 mgKOH / g or more in the filling layer is preferably 90 mass% or more based on the total amount of the filling layer. The content of the polyester resin having an acid value of 35 mgKOH / g or more is more preferably 95 mass% or more, even more preferably 99 mass% or more, and even more preferably 100 mass% based on the total amount of the filling layer. When the content of the polyester resin in the filling layer is 100% by mass (that is, the filling layer is a layer consisting of only the polyester resin), the recyclability of the release paper is more likely to be improved.

[0040] The coating amount of the polyester resin having an acid value of 35 mgKOH / g or more is not particularly limited as long as the air permeability resistance measured from the filling layer side before the release agent layer is provided on the paper base material provided with the filling layer by the Oken type testing machine method satisfies the above-mentioned lower limit. From the viewpoint of making it easier to separate the paper base material from the release agent layer and to recycle the paper base material more easily, the coating amount of the polyester resin having an acid value of 35 mgKOH / g or more is, for example, 1 g / m2 in terms of solid content. 2 or more, and 2 or more, and 2 or more, and 2 or more, and 2 Even if the filling layer contains a component other than the polyester resin, the coating amount of the polyester resin may be within the above range. The upper limit of the coating amount of the polyester resin is not particularly limited. The upper limit of the coating amount of the polyester resin is, for example, 20 g / m in terms of solid content, from the viewpoint of saturating the sealing effect. 2 It may be the following.

[0041] The filling layer may contain various additives such as an inorganic filler and a coloring agent, if necessary.

[0042] In a paper substrate provided with a filling layer, the air resistance measured from the filling layer side before providing a release agent layer by the Oken type testing machine method according to JIS P 8117:2009 is 10000 seconds or more. The air resistance is preferably 12000 seconds or more, more preferably 15000 seconds or more, and even more preferably 20000 seconds or more. It is also preferable that the air resistance is ∞ (infinity).

[0043] (Release agent layer) The release agent layer contains a silicone-based release agent. The silicone-based release agent is not particularly limited, and can be used in any form of solvent type, solventless type, or emulsion type. From the viewpoint of the environment, the silicone-based release agent is preferably an emulsion type or a solventless type. From the viewpoint of the environment and improving the productivity of the release paper, the silicone-based release agent is preferably a solventless type.

[0044] Examples of the silicone resin used in the silicone-based release agent include homopolymers or copolymers such as trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, diphenyldichlorosilane, phenyltrichlorosilane, and methylvinyldichlorosilane. These polymers can be used alone or in combination of two or more. Examples of the silicone-based release agent include addition reaction type, condensation reaction type, ultraviolet curing type, and electron beam curing type, and any of the silicone-based release agents can be used.

[0045] When using an addition reaction type silicone resin as the silicone-based release agent, it is preferable to use a crosslinking agent and a catalyst in combination.The addition reaction type silicone resin is not particularly limited, and examples thereof include polydimethylsiloxanes having an alkenyl group such as a vinyl group or a hexenyl group as a functional group in the molecule.The crosslinking agent includes organopolysiloxanes having at least two hydrogen atoms bonded to silicon atoms in one molecule.The catalyst includes platinum metal compounds such as platinum group, palladium, and rhodium.

[0046] The release agent composition containing the silicone-based release agent may contain various additives, such as, for example, an antioxidant, an ultraviolet absorber, an inorganic or organic filler, an antistatic agent, and a surfactant, as necessary.

[0047] (peel strength) When an adhesive layer is provided on a silicone-based release agent layer, the peeling force of the release agent layer against the adhesive layer is preferably 300 mN / 50 mm or less from the viewpoint of facilitating peeling. The peeling force of the release agent layer against the adhesive layer is the force when the adhesive layer is attached on the silicone-based release agent layer and the adhesive layer is peeled off from the silicone-based release agent layer. From the same viewpoint, when an adhesive layer is provided on a silicone-based release agent layer, the peeling force of the release agent layer against the adhesive layer is more preferably 280 mN / 50 mm or less, even more preferably 260 mN / 50 mm or less, and even more preferably 240 mN / 50 mm or less. When an adhesive layer is provided on a silicone-based release agent layer, the peeling force of the release agent layer against the adhesive layer is preferably 50 mN / 50 mm or more from the viewpoint of suppressing the occurrence of unintended peeling.

[0048] The pressure-sensitive adhesive layer may be a pressure-sensitive adhesive sheet consisting of only a pressure-sensitive adhesive layer, or may be a pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive base and a pressure-sensitive adhesive layer provided on the pressure-sensitive adhesive base. The pressure-sensitive adhesive layer is preferably an acrylic pressure-sensitive adhesive.

[0049] (Production method of release paper) An example of a preferred method for producing the release paper according to this embodiment includes, for example, the steps of preparing a paper substrate, providing a sealing layer by applying a coating liquid containing a polyester resin having an acid value of 35 mgKOH / g or more to at least one surface of the paper substrate, and providing a release agent layer by applying a coating liquid of a release agent composition containing a silicone-based release agent to the surface of the sealing layer opposite to the paper substrate side.

[0050] In the step of preparing the paper base material, the paper base material described above may be prepared. The paper base material may be obtained by a known manufacturing method. The paper base material to be prepared preferably includes glassine paper, and more preferably is clay-coated glassine paper.

[0051] The step of providing the filler layer includes a step of preparing a polyester resin having an acid value of 35 mgKOH / g or more as described above for the filler layer. The polyester resin is preferably an emulsion type from the viewpoint of ease of handling. Next, a coating liquid containing the prepared polyester resin is prepared, and the coating liquid containing the polyester resin is applied to one side of the paper substrate. When applying the coating liquid containing the polyester resin, it is preferable to dilute it so that the coating amount is the desired solid content equivalent. The method of applying the coating liquid containing the polyester resin is not particularly limited, and examples of the coating methods include gravure coating, bar coating, knife coating, roll knife coating, roll coating, blade coating, die coating, and curtain coating.

[0052] The step of providing a release agent layer may include, for example, a step of applying a coating solution of a release agent composition containing a silicone-based release agent to the first sealing layer surface, which is the surface opposite to the paper substrate side of the sealing layer, to form a coating film, and a step of curing the obtained coating film to form a release agent layer. When the step of providing a release agent layer includes these steps, the coating method of the release agent composition may be, for example, a coating method such as a bar coating method, an offset gravure coating method, a multi-stage roll coating method, or an air knife coating method. The drying conditions of the coating film may be any conditions that allow the coating film to dry.

[0053] When the silicone-based release agent is a solvent-based one, a coating liquid is prepared by mixing an organic solvent such as toluene, ethyl acetate, methyl ethyl ketone, hexane, or heptane with a release agent composition containing the solvent-based silicone-based release agent. The coating liquid thus prepared is then applied onto the sealing layer by a known coating method, followed by drying and heating to obtain a release agent layer.

[0054] When the silicone-based release agent is a solventless type, the release agent composition containing the silicone-based release agent does not contain a solvent. The release agent layer is obtained by applying a solvent-free coating solution of the release agent composition onto the sealing layer by a known coating method, followed by drying and heating.

[0055] The method of curing the coating film obtained by applying the coating liquid of the stripping agent composition includes, for example, a method of curing by heat treatment, and a method of irradiating ultraviolet light after heat treatment, and either method may be used. When using a combination of heat treatment and ultraviolet light irradiation as a method of curing the coating film, it is desirable to add a photoinitiator to the stripping agent. The photoinitiator is not particularly limited, and examples thereof include benzoins, benzophenones, acetophenones, α-hydroxyketones, α-aminoketones, α-diketone, α-diketone dialkyl acetals, anthraquinones, and thioxanthones.

[0056] The amount of the silicone-based release agent applied after curing is not particularly limited. For example, the amount of the silicone-based release agent applied after curing is 0.01 g / m from the viewpoint of releasability and curing property of the coating film. 2 More than 2g / m 2 It is preferable that:

[0057] The release paper according to the present embodiment can be used for general release sheet applications, such as a protective sheet for protecting the adhesive surface of an adhesive sheet, and a process paper used in a process of forming a sheet-like object on the release surface of a release agent layer of the release paper.

[0058] [How to separate the release paper] An example of a preferred method for separating the release paper according to this embodiment includes, for example, a step of preparing the release paper according to this embodiment, and a step of separating the release paper into a paper substrate and a silicone-based release agent layer in an alkaline solution.

[0059] The release paper may be prepared by the above-described preferred method for producing the release paper.

[0060] The release paper is separated into a paper substrate and a silicone-based release agent layer in an alkaline solution. The method for separating the release paper into the paper substrate and the silicone-based release agent layer is not particularly limited. From the viewpoint of enabling the paper substrate and the release agent layer to be easily separated, it is preferable to adopt a method for separating the paper substrate and the silicone-based release agent layer by immersing the paper substrate in an alkaline solution and stirring the paper substrate in the alkaline solution. The time for separating the release paper into the paper substrate and the silicone-based release agent layer in the alkaline solution is preferably 15 minutes or less, more preferably 5 minutes or less, and even more preferably 3 minutes or less. The alkaline solution is preferably, for example, an alkaline aqueous solution having a pH of 13 or more and 15 or less. The alkaline agent for preparing the alkaline solution is not particularly limited, and examples thereof include sodium hydroxide and potassium hydroxide. The temperature of the alkaline solution is preferably, for example, 23° C. or more and 70° C. or less. The alkaline solution is preferably an alkaline aqueous solution.

[0061] In the release paper according to the present embodiment, since the filler layer contains a polyester resin having an acid value equal to or greater than a specific value, it is believed that in the process of separating the release paper, the polyester resin in the filler layer is difficult to dissolve in an alkaline solution, and is swollen by the alkaline solution, weakening the interfacial strength between the filler layer and the paper substrate. As a result, it is presumed that the filler layer peels off at the interface between the filler layer and the paper substrate, and the silicone-based release agent layer is separated from the paper substrate together with the filler layer, making it easier to separate the release paper into the paper substrate and the silicone-based release agent layer.

[0062] By going through the above steps, the release paper according to this embodiment is separated into the paper substrate and the silicone-based release agent layer. The separated release paper can be recycled.

[0063] The present invention is not limited to the above-described embodiment, and may include modifications and improvements within the scope of the present invention. EXAMPLES

[0064] Examples will be described below, but the present invention is not limited to these examples in any way.

[0065] The following raw materials were prepared as materials for producing the release papers of the Examples and Comparative Examples.

[0066] (Paper base material) "P-1": Clay-coated glassine paper (manufactured by Lintec Corporation, basis weight 80 g / m 2 , glassine paper with a pigment-coated layer on one side) "P-2": Glassine paper (glassine made by Lintec Corporation, basis weight 73g / m 2 ) "P-3": High-quality paper (manufactured by Nippon Paper Industries Co., Ltd., "WM Seal 64.0G", basis weight 64g / m 2 )

[0067] (Sealing layer) "PES-1": Polyester resin (manufactured by GOO Chemical Industry Co., Ltd., "Pluscoat Z-730", acid value 40-60mgKOH / g, glass transition temperature Tg 46℃) "PES-2": Polyester resin (manufactured by Takamatsu Oil Co., Ltd., "PES Resin A-684G", acid value 20-30mgKOH / g, glass transition temperature Tg50℃) "StAc-1": Styrene-acrylic resin (acid value less than 5 mg KOH / g, glass transition temperature Tg 23°C)

[0068] (Release agent layer) "Si-1": A release agent composition prepared by adding 1.5 parts by mass of a platinum catalyst (manufactured by Dow Toray Industries, Inc., "DOWSIL SRX 212 Catalyst") to 100 parts by mass of a solventless addition curing type silicone release agent (manufactured by Dow Toray Industries, Inc., "DOWSIL LTC 1057 L", solid content concentration 100 mass%).

[0069] <Example 1> Polyester resin (PES-1) was applied to one side of the paper base material (P-1) at a coating weight of 2 g / m2 (solid content equivalent). 2After coating with an applicator so that the thickness became 1.0 g / m, the sheet was dried at 120° C. for 1 minute to form a sealing layer, and a sealed paper was obtained. Next, the release agent composition (Si-1) was applied to the surface of the sealing layer of the sealed paper in such a manner that the coating amount of the release agent layer after drying was 1.0 g / m 2 The solution was then dried at 150° C. for 30 seconds to harden the layer, forming a release agent layer. In this manner, the release paper of Example 1 was obtained, in which the paper substrate, the filling layer, and the silicone-based release agent layer were laminated in this order.

[0070] <Examples 2 to 4> According to Table 1, release papers of each example were obtained in the same manner as in Example 1, except that at least one of the conditions of the type of paper base material and the coating amount of the polyester resin used in the filling layer was changed.

[0071] <Comparative Example 1> In accordance with Table 1, a release paper of Comparative Example 1 was obtained in the same manner as in Example 1, except that no filling layer was provided.

[0072] <Comparative Examples 2 to 6> The release papers of each comparative example were obtained in the same manner as in Example 1, except that at least one of the conditions of the type of paper substrate, the type of resin used in the filling layer, and the coating amount of polyester resin was changed according to Table 1.

[0073] <Air permeability resistance> In each example, before providing a release agent layer, the air resistance was measured from the filling layer side of the paper base material provided with the filling layer by the Oken type testing machine method according to JIS P 8117: 2009. However, in Comparative Example 1, since no filling layer was provided, the air resistance of the paper base material was measured.

[0074] <Magic Barrier Properties> In each example, a line was drawn on the filling layer of the paper substrate provided with the filling layer using a commercially available oil-based marker ink (Teranishi Chemical Industry Co., Ltd.: product name: Magic Ink Extra Thick MGD-T2 Red) before providing a release agent layer. Strike-through to the side of the paper substrate not provided with the filling layer, which is the opposite side to the coating, was visually confirmed and evaluated according to the following three-level evaluation criteria. The results are shown in Table 1. However, for Comparative Example 1, since no filling layer was provided, the magic barrier property of the paper substrate was evaluated according to the same procedure as above. Evaluation criteria: "A": No bleed-through of oil-based marker ink is observed. "B": Permanent marker ink bleed-through was observed. "F": More bleed-through of oil-based marker ink was observed than in "B" above.

[0075] <Evaluation of hardening of release agent layer> For the release paper obtained in each example, the surface of the release agent layer was rubbed with a finger 10 times, and the presence or absence of cloudiness (smear) and peeling off of the release agent layer (rub-off) was visually confirmed, and the hardening property of the release agent layer was evaluated according to the following evaluation criteria. The results are shown in Table 1. Evaluation criteria: "A": Neither smear nor rub-off was observed. "F": At least one of smear and rub-off was observed.

[0076] <Separability evaluation> The release paper obtained in each example was cut to a size of 50 mm x 50 mm to prepare a sample for evaluating separability. The entire surface (release surface) of the release agent layer in the sample for evaluating separability was printed with a black ultraviolet-curable ink to provide a black solid-printed area. The black solid-printed area was then irradiated with ultraviolet light to harden it. The sample for evaluating separability provided with the hardened black solid-printed area was placed in 1 liter of 1.5% by mass sodium hydroxide aqueous solution (pH 13.6) heated to 60°C, and stirred at a rotation speed of 1400 rpm using a stirrer (High Power Stirrer HPS-100, manufactured by AS ONE Corporation). The stirring time was until the release agent layer and the paper substrate were separated. When it was difficult to separate the release agent layer and the paper substrate, the stirring time was set to a maximum of 30 minutes. The results of evaluation according to the following evaluation criteria are shown in Table 1. Evaluation criteria: "A": No pulp fibers were found adhering to the coating of the black solid printed area after stirring. "F": Pulp fibers are found adhering to the coating of the black solid printed area after stirring.

[0077] <Peeling force evaluation> The peel strength was measured according to the 180° peel adhesion test specified in JIS Z0237:2022. First, an acrylic adhesive (manufactured by Toyochem Co., Ltd., "Olivine (registered trademark) BPS 8170") was coated to a thickness of 40 μm on the surface (release surface) of the release paper obtained in each example to form an adhesive layer. Then, a synthetic paper (manufactured by Yupo Corporation, "Yupo SGS80") having a thickness of 80 μm was attached to the adhesive layer. Then, a 2 kg roller was moved back and forth once to prepare an adhesive body. After leaving this adhesive body under conditions of a temperature of 23° C. and a relative humidity of 50% for one day, the peel strength was measured at a peel speed of 0.3 m / min by a test method in which the synthetic paper and the adhesive layer were peeled off at 180° from the release paper. However, for Comparative Example 6, the curability evaluation of the release agent layer was F, and it was confirmed that curing inhibition occurred in the release agent layer, so the peel strength was not measured.

[0078] [Table 1]

[0079] Figures 3(A), 3(B), and 3(C) are images of the filling layer in the paper substrate on which the filling layer was provided, observed by an electron microscope before providing a release agent layer. Figure 3(A) is an electron microscope image of Example 1, Figure 3(B) is an electron microscope image of Example 4, and Figure 3(C) is an electron microscope image of Comparative Example 3. As shown in Figures 3(A), 3(B), and 3(C), it can be seen that Example 1 and Example 4 have a higher filling effect than Comparative Example 3.

[0080] Figures 4(A), 4(B), and 4(C) are images of the coating of the cured black solid print portion observed under an electron microscope after stirring the separation evaluation sample having the cured black solid print portion. Figure 4(A) is an electron microscope image of Example 1, Figure 4(B) is an electron microscope image of Example 4, and Figure 4(C) is an electron microscope image of Comparative Example 3. As shown in Figures 4(A), 4(B), and 4(C), it can be seen that there is no adhesion of fibers to the coating of the cured black solid print portion in Examples 1 and 4, compared to Comparative Example 3.

[0081] As a result of observing electron microscope images, it is considered that the release paper of each example, which has a high sealing effect for the sealing layer provided by the polyester resin having a specific acid value, is difficult for the silicone-based release agent to penetrate into the paper substrate.On the other hand, it is considered that the release paper of each comparative example, which has an insufficient sealing effect, is easy for the silicone-based release agent to penetrate into the paper substrate.Therefore, it is considered that the release paper of each example has a sealing layer with a sufficient sealing effect, and thus can be separated into the paper substrate and the release agent layer.

[0082] Furthermore, it can be seen that the release papers of the examples are provided with a sealing layer made of a polyester resin having a specific acid value, which makes it possible to separate the paper base material from the release agent layer, and also does not inhibit the curing of the silicone-based release agent.

[0083] In addition, (1) the surface of the paper substrate used to prepare the release paper of Example 1 on which the filler layer was to be provided, and (2) the surface of the paper substrate on which the filler layer was provided after the release agent layer was separated by the same method as in the above separation test, of the release paper of Example 1 prepared using the paper substrate, were analyzed by infrared spectroscopy (IR). As a result, the paper substrate of (2) above did not show any silicone-derived peaks or polyester-derived peaks, as with the paper substrate of (1) above. From this, it was confirmed that the release paper of Example 1 was separated between the paper substrate and the filler layer by the above separation test.

[0084] From the above results, it can be seen that the release papers of each Example are more easily separated into the paper substrate and the release agent layer than the release papers of each Comparative Example, and that the release papers of each Example suppress inhibition of the curing of the silicone-based release agent when forming the silicone-based release agent layer. [Explanation of symbols]

[0085] 10...paper substrate, 11...first paper substrate surface, 12...second paper substrate surface, 20...filler layer, 21...first filler layer surface, 22...second filler layer surface, 30...release agent layer, 31...first release agent layer surface, 32...second release agent layer surface, 100...release paper, 200...sealed paper.

Claims

1. A paper substrate; A filling layer provided on at least one surface of the paper base material and containing a polyester resin having an acid value of 35 mgKOH / g or more; a release agent layer provided on a surface of the filling layer opposite to the paper substrate side and containing a silicone-based release agent; Equipped with In the paper base material provided with the filling layer, the air permeability resistance measured from the filling layer side before providing the release agent layer according to the Oken type testing machine method in accordance with JIS P 8117:2009 is 10,000 seconds or more. Release paper.

2. The release paper according to claim 1, The paper substrate comprises glassine paper. Release paper.

3. The release paper according to claim 2, The paper base material comprises the glassine paper and a pigment coating layer provided on the glassine paper. Release paper.

4. The release paper according to any one of claims 1 to 3, The amount of the polyester resin applied is 1 g / m in terms of solid content. ２ That's all. Release paper.

5. The release paper according to any one of claims 1 to 3, When a pressure-sensitive adhesive layer is provided on the release agent layer, the release strength of the release agent layer to the pressure-sensitive adhesive layer is 300 mN / 50 mm or less. Release paper.

6. The release paper according to any one of claims 1 to 3, The silicone-based release agent is a solvent-free silicone-based release agent. Release paper.

7. A method for separating the release paper according to any one of claims 1 to 3, comprising the steps of: providing the release paper; separating the release paper into the paper substrate and the release agent layer in an alkaline solution; having How to separate the release paper.

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