Release sheet

Abstract

Providing release sheets to prevent deterioration of the quality of goods. [Solution] A release sheet 10 is formed by laminating a paper base material 11, a sealing layer 12, a resin layer 13, and a release layer 14 in this order, and has an oxygen permeability of 500 cc / (m²). 2 A release sheet 10 having an oxygen permeability of 500 cc / (m³) or less, after being pulled with a force of 500 N / m in the MD direction of the release sheet 10. 2 It is preferable that it be less than or equal to (day·atm).

Description

[Technical Field]

[0001] This invention relates to a release sheet. [Background technology]

[0002] Sheets obtained by heat-pressure molding a composite material (prepreg) containing fibers and resin are also called fiber-reinforced resin sheets, and have advantages such as higher mechanical strength compared to resin sheets that do not contain fibers. When manufacturing prepregs, a release sheet called process paper is usually used as a support material to facilitate the manufacturing, transportation, and storage of the prepregs.

[0003] Prepregs are manufactured, for example, as follows: A thermosetting resin, such as epoxy resin, is first coated onto the process paper as a matrix resin, and then cooled to form a semi-cured resin layer. Two of these resin-layered process papers are prepared, with the resin-layered surfaces facing each other, and reinforcing fibers, such as carbon fibers, are sandwiched between them. In this state, the process paper is heated to the extent that the thermosetting resin does not completely harden, and the reinforcing fibers are impregnated with the thermosetting resin to obtain a prepreg. The resulting prepreg is cooled and then wound onto the process paper in close contact with it. The prepreg wound together with the process paper (hereinafter also referred to as the "winding of prepreg") is transported and stored either as is or cut into sheets, and the process paper is removed immediately before molding.

[0004] Process paper is prone to dimensional changes because it dehydrates and shrinks when heated, and expands when it absorbs moisture during cooling, prepreg transport, and storage. Large dimensional changes can lead to delamination between the prepreg and the process paper. Furthermore, if the process paper shrinks during heat treatment, the surface of the prepreg in contact with the process paper may deteriorate, potentially leading to a decrease in quality. Therefore, dimensional stability is required for process paper. Patent Document 1 discloses a process paper in which a release layer is provided on a base paper under specific conditions and then curl correction is performed under specific conditions to reduce the dimensional change rate. Patent Document 2 discloses a process paper in which a polyvinyl alcohol that has been subjected to a water resistance treatment with a water resistance agent is coated or impregnated on a base paper mainly composed of wood pulp.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In recent years, high-speed curing prepregs using anaerobic matrix resins have been proposed. However, in the case of the process paper described in Patent Documents 1 and 2, when a prepreg using an anaerobic matrix resin is stored in a state where it is adhered to the process paper, the prepreg may deteriorate. An object of the present invention is to provide a release sheet that prevents quality deterioration of an article.

Means for Solving the Problems

[0007] As a result of intensive studies by the present inventors, it has been found that since the release sheet such as a conventional process paper has a high oxygen permeability, articles such as prepregs deteriorate due to the influence of oxygen that has permeated through the release sheet. In particular, when an article contains an anaerobic component, it is likely to deteriorate under the influence of oxygen. Therefore, the inventors have found that by making the release sheet have a specific laminated structure and regulating the oxygen permeability, it is possible to prevent quality deterioration of the article, and thus the present invention has been completed.

[0008] The present invention has the following aspects. [1] A release sheet comprising a paper substrate, a sealing layer, a resin layer and a release layer laminated in this order, Oxygen permeability of 500 cc / (m³) 2 The release sheet is less than or equal to (day·atm). [2] The oxygen permeability after pulling the release sheet in the MD direction with a force of 500 N / m is 500 cc / (m 2 The release sheet described in [1] above, wherein the value is less than or equal to (day·atm). [3] The release sheet according to [1] or [2], wherein the release sheet has a tensile modulus of 7 GPa or more in the MD direction. [4] The release sheet according to any one of [1] to [3], wherein the sealing layer is a clay coat layer or a laminate layer. [5] The release sheet according to any one of [1] to [4], wherein the resin layer contains a water-suspended polymer compound. [Effects of the Invention]

[0009] According to the present invention, a release sheet can be provided that prevents deterioration of the quality of articles. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view showing an example of the release sheet of the present invention. [Modes for carrying out the invention]

[0011] Hereinafter, one embodiment of the release sheet according to the present invention will be described in detail with reference to Figure 1 as appropriate. In this invention, "MD" means machine direction. The MD direction of the release sheet is the same as the MD direction of the paper substrate. The MD direction of the paper substrate is the direction of movement when the paper substrate is made in the paper machine, i.e., the papermaking direction, and is also called the longitudinal direction or flow direction. The orientation direction of the fibers in the paper substrate can be considered as the MD. "Packaging" refers to protecting or preserving goods in order to maintain their quality and condition during transportation and storage, as well as improving their handling and convenience.

[0012] Furthermore, in this specification, a numerical range represented by "~" means a numerical range that includes the numbers before and after "~" as the lower and upper limits, respectively. The numerical ranges of content, various physical properties, and characteristic values ​​disclosed herein can be modified by arbitrarily combining their lower and upper limits to create new numerical ranges. In addition, the drawings used in the following description may be enlarged for convenience to make their features easier to understand, and the dimensional ratios of each component may differ from those in reality. The materials, dimensions, etc. exemplified in the following description are examples only, and the release sheets according to the present invention are not limited to these examples. They can be modified as appropriate without departing from the spirit of the present invention.

[0013] [Release sheet] Figure 1 shows an example of the release sheet of the present invention. The release sheet 10 in this embodiment is a laminate in which a paper base material 11, a sealing layer 12, a resin layer 13, and a release layer 14 are laminated in this order. In this invention, the sealing layer 12 is also referred to as the "first resin layer," the resin layer 13 as the "second resin layer," and the release layer 14 as the "third resin layer."

[0014] <Paper base material> The paper substrate 11 is preferably composed mainly of pulp, and in particular, from the viewpoint of recycling, it is preferable that it be composed mainly of plant-derived pulp. Here, "primarily composed of pulp" means that the pulp content is 70% by mass or more of the total mass of the paper substrate 11. The pulp content is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and may be 100% by mass.

[0015] The paper substrate 11 may be any commonly used paper, for example, a paper substrate mainly composed of wood pulp. Specific examples of the paper substrate 11 include bleached kraft paper, unbleached kraft paper, bleached fine paper, unbleached fine paper, cardboard, liner paper, coated paper, bleached glossy paper, unbleached glossy paper, glassine paper, and graphane paper. Among these, fine paper, bleached glossy paper, unbleached glossy paper, and kraft paper are preferred, with fine paper being more preferred, from the viewpoint of high dimensional stability, ease of obtaining high strength, and good uniformity of the base material.

[0016] Examples of wood pulp include hardwood pulp such as bleached hardwood kraft pulp (LBKP) and bleached hardwood sulfite pulp (LBSP); and softwood pulp such as bleached softwood kraft pulp (NBKP) and bleached softwood sulfite pulp (NBSP). Examples of non-wood pulps include cotton pulp, hemp pulp, kenaf pulp, and bamboo pulp. Pulp may be used alone or in combination of two or more types.

[0017] Among these, wood pulp is preferred, hardwood pulp is more preferred because its fibers are short and flexible, and it can impart appropriate softness to the paper base material 11, and softwood pulp is even more preferred because its fibers are long and strong, and it can impart strength to the paper base material 11. The hardwood pulp content is preferably 50% by mass or more, more preferably 70% by mass or more, and may also be 100% by mass, relative to the total mass of the pulp. The softwood pulp content is preferably 10% by mass or more, more preferably 20% by mass or more, and may also be 100% by mass, relative to the total mass of the pulp.

[0018] Hardwood pulp and softwood pulp may be used in combination. When using both hardwood pulp and softwood pulp, it is preferable that the hardwood pulp content is 2 to 98% by mass and the softwood pulp content is 2 to 98% by mass relative to the total mass of pulp; more preferably, the hardwood pulp content is 30 to 95% by mass and the softwood pulp content is 5 to 70% by mass; and even more preferably, the hardwood pulp content is 50 to 90% by mass and the softwood pulp content is 10 to 50% by mass.

[0019] The pulp may be dry pulp or wet pulp, but wet pulp is preferred from the viewpoint of increasing the tensile modulus of the paper substrate 11. Here, dry pulp refers to pulp whose moisture content has been adjusted to 3-10% by mass through drying. On the other hand, wet pulp refers to pulp whose moisture content has been adjusted to 40-60% by mass through drying. The moisture content of the pulp is measured according to JIS P 8127:2010.

[0020] The Canadian standard filtration capacity (hereinafter also referred to as "disintegration-freeness") of pulp is preferably 200-600 cc (synonymous with 200-600 mL; the same applies hereinafter), more preferably 250-500 cc, even more preferably 300-450 cc, and still more preferably 300-400 cc. If the disintegration-freeness of the pulp is above the lower limit, the strength of the paper substrate 11 tends to be higher. If the disintegration-freeness of the pulp is below the upper limit, the oxygen permeability can be maintained well even after a tensile test is performed on the release sheet 10. In particular, if the disintegration-freeness is 450 cc or less, the oxygen permeability after pulling the release sheet 10 with a force of 500 N / m is 500 cc / (m 2 It tends to fall below (day·atm). The disintegration-freeness of pulp is measured by the following method. Specifically, the disintegrated pulp obtained by disintegrating the paper substrate 11 in accordance with JIS P 8220:2012 using a standard disintegrator is measured for its water filtration rate in accordance with JIS P 8121-2:2012 using a Canadian standard water filtration rate tester, and this water filtration rate is defined as the disintegration-freeness of the pulp. Disintegration freeness can be adjusted by the degree of pulp beating.

[0021] The basis weight of the paper substrate 11 is 10-500 g / m². 2 Preferably, 20-300 g / m² 2 More preferably, 30-200 g / m 2 This is even more preferable. If the basis weight of the paper substrate 11 is above the lower limit, good strength is more likely to be obtained. If the basis weight of the paper substrate 11 is below the upper limit, appropriate flexibility is obtained, which improves packaging properties. The basis weight of the paper substrate 11 is a value measured in accordance with JIS P 8124:2011.

[0022] The thickness of the paper substrate 11 is preferably 15 to 600 μm, more preferably 25 to 350 μm, and even more preferably 23 to 250 μm. If the thickness of the paper substrate 11 is above the lower limit, good strength is more likely to be obtained. If the thickness of the paper substrate 11 is below the upper limit, appropriate flexibility is obtained, which improves packaging properties. The thickness of the paper substrate 11 is a value measured in accordance with JIS P 8118:2014.

[0023] The paper substrate 11 may contain internal additives as needed, as long as they do not impair the effects of the present invention. Specific examples of internal additives include fibers other than pulp fibers (e.g., synthetic fibers such as rayon fibers and nylon fibers), sizing agents, fillers, paper strength enhancers, wet paper strength enhancers, yield enhancers, pH adjusters, water drainage enhancers, water resistance enhancers, softeners, antistatic agents, defoamers, slime control agents, dyes, pigments, and the like. Oral additives may be used individually or in combination of two or more.

[0024] <Sealing layer> The sealing layer 12 is a layer provided between the paper substrate 11 and the resin layer 13. The release sheet 10 includes a sealing layer 12 between the paper substrate 11 and the resin layer 13, which seals the paper substrate 11 and smooths it, allowing for the formation of a flatter resin layer 13. As a result, the gas barrier properties (mainly oxygen barrier properties) are improved, and the oxygen permeability of the release sheet 10 is 500 cc / (m²). 2 It tends to be less than (day·atm).

[0025] The sealing layer 12 is not particularly limited as long as it has a sealing effect, but examples include a clay court layer and a laminate layer.

[0026] The clay coat layer preferably contains an inorganic pigment and a binder. Examples of inorganic pigments include kaolin, talc, mica, calcium carbonate, titanium dioxide, satin white, and aluminum hydroxide. Inorganic pigments may be used individually or in combination of two or more types.

[0027] The average particle size of the inorganic pigment is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less, from the viewpoint of forming a uniform and smooth resin layer 13 on the clay coat layer and of finely scattering the inorganic pigment within the clay coat layer. There is no particular lower limit to the average particle size of the inorganic pigment, but for example, the average particle size of the inorganic pigment is preferably 0.05 μm or more, and more preferably 0.10 μm or more. The average particle size of inorganic pigments is measured using a laser diffraction particle size distribution analyzer in accordance with JIS Z 8825:2022, and refers to the particle size that accounts for 50% of the cumulative particle size distribution (d50: median diameter).

[0028] The inorganic pigment content in the clay coat layer is preferably 20 to 98% by mass, more preferably 50 to 90% by mass, and even more preferably 70 to 85% by mass, relative to the total mass of the clay coat layer. If the inorganic pigment content is above the lower limit, high smoothness is more easily obtained. If the inorganic pigment content is below the upper limit, cracking is less likely to occur under bending stress.

[0029] Examples of binders include styrene-(meth)acrylic resins, ethylene-(meth)acrylic resins, styrene-butadiene resins, (meth)acrylic resins, casein, starch, and polyvinyl alcohol. Among these, styrene-(meth)acrylic resins are preferred because they can reduce manufacturing costs, and ethylene-(meth)acrylic resins are preferred because they provide high film-forming properties. The binder may be used alone, or two or more types may be used in combination.

[0030] Here, styrene-(meth)acrylic resin is a copolymer of styrene and at least one monomer selected from (meth)acrylic acid and (meth)acrylic acid esters. Styrene-acrylic resin is preferred as the styrene-(meth)acrylic resin, and styrene-acrylic acid copolymer or styrene-acrylic acid ester copolymer is more preferred. The same applies to ethylene-(meth)acrylic resins. (Meth)acrylic resins are homopolymers or copolymers of one or more monomers selected from (meth)acrylic acid and (meth)acrylic acid esters. As the (meth)acrylic acid ester, alkyl esters of (meth)acrylic acid having 1 to 12 carbon atoms are preferred.

[0031] The binder content in the clay coat layer is preferably 2 to 80% by mass, more preferably 10 to 50% by mass, and even more preferably 15 to 30% by mass, relative to the total mass of the clay coat layer. If the binder content is above the lower limit, the surface strength tends to be higher. If the binder content is below the upper limit, when the release sheet 10 is used, for example, as process paper for the manufacture of prepregs, and the prepregs are wound together with the process paper, blocking and the like are less likely to occur.

[0032] Furthermore, the total content of inorganic pigments and binders is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, most preferably 95% by mass or more, and may also be 100% by mass.

[0033] Furthermore, the clay coat layer may contain optional components in addition to inorganic pigments and binders. Specific examples of optional components include dispersants, defoamers, lubricants, and preservatives. The optional components may be used individually or in combination of two or more.

[0034] The laminate layer preferably contains a thermoplastic resin. The thermoplastic resin is not particularly limited as long as it can be laminated, but examples include polyolefin resins such as polyethylene resin and polypropylene resin; vinylidene chloride copolymers; copolymers of ethylene with acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, or vinyl acetate, etc.; polylactic acid resin; and polybutylene succinate resin. Among these, polyethylene resin is preferred in terms of processability and other factors. Thermoplastic resins may be used individually or in combination of two or more types.

[0035] Examples of polyethylene resins include low-density polyethylene resin, medium-density polyethylene resin, high-density polyethylene resin, and linear low-density polyethylene resin.

[0036] The content of thermoplastic resin in the laminate layer is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, most preferably 95% by mass or more, and may also be 100% by mass.

[0037] Furthermore, the laminate layer may contain optional components in addition to the thermoplastic resin. Specific examples of optional components include inorganic pigments such as titanium dioxide, lubricants, and antistatic agents. The optional components may be used individually or in combination of two or more.

[0038] The thickness of the sealing layer 12 is preferably 3 to 80 μm, more preferably 5 to 50 μm, and even more preferably 7 to 30 μm. If the thickness of the sealing layer 12 is above the lower limit, high smoothness is more easily obtained. If the thickness of the sealing layer 12 is below the upper limit, good flexibility can be maintained. In particular, when the sealing layer 12 is a clay coat layer, the thickness of the clay coat layer is preferably 3 to 50 μm, more preferably 3.5 to 30 μm, and even more preferably 4 to 20 μm. If the sealing layer 12 is a laminate layer, the thickness of the laminate layer is preferably 3 to 80 μm, more preferably 5 to 50 μm, and even more preferably 7 to 30 μm. The thickness of the sealing layer 12 is a value measured in accordance with JIS K 7130:1999.

[0039] <Resin layer> The resin layer 13 is a layer provided between the sealing layer 12 and the release layer 14. The release sheet 10 has a resin layer 13 between the sealing layer 12 and the release layer 14, which improves the adhesion between the sealing layer 12 and the release layer 14, enhances the gas barrier properties (mainly oxygen barrier properties), and the oxygen permeability of the release sheet 10 is 500 cc / (m²). 2 It tends to be less than (day·atm).

[0040] The resin layer 13 preferably contains a water-suspendable polymer compound. The inclusion of a water-suspendable polymer compound in the resin layer 13 further improves its oxygen barrier properties. "Aqueous suspension" refers to a state in which resin particles are uniformly dispersed in water. Furthermore, a high-molecular-weight compound refers to a compound with a weight-average molecular weight of 10,000 or more. The weight-average molecular weight is measured by gel permeation chromatography (GPC) and is a value equivalent to standard polystyrene.

[0041] The water-suspended polymer compound is not particularly limited, but examples include alkyd resins; (meth)acrylic (co)polymers, styrene-(meth)acrylic resins; olefin-unsaturated carboxylic acid copolymers such as ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers; vinyl alcohol resins such as polyvinyl alcohol and ethylene vinyl alcohol copolymers (ethylene-modified polyvinyl alcohol); cellulose resins; polyurethane resins; and polyester resins. Among these, vinyl alcohol resins, polyurethane resins, and polyester resins are preferred, and from the viewpoint of further improving oxygen barrier properties, polyvinyl alcohol and polyurethane resins are more preferred, and polyurethane resins are even more preferred. The water-suspended polymer compound may be used alone or in combination of two or more types.

[0042] Polyurethane resins can be produced by known manufacturing methods. For example, polyurethane resins can be obtained by the reaction of a polyisocyanate compound (e.g., a diisocyanate compound) with a polyhydroxy acid (e.g., a dihydroxy acid). Alternatively, they can be obtained by the reaction of the above-mentioned polyisocyanate compound and polyhydroxy acid with at least one of a polyol compound (e.g., polyester polyol, polyether polyol) and a chain extender.

[0043] The polyurethane resin preferably contains at least one of the constituent units derived from metaxylylene diisocyanate and the constituent units derived from hydrogenated metaxylylene diisocyanate. The constituent units derived from metaxylylene diisocyanate refer to monomer units obtained by the reaction of metaxylylene diisocyanate in the urethane resin. A monomer unit refers to the form obtained by the reaction of monomer substances in a polymer.

[0044] When the polyurethane resin contains at least one of the structural units derived from metaxylylene diisocyanate and the structural units derived from hydrogenated metaxylylene diisocyanate, the total content of the structural units derived from metaxylylene diisocyanate and the structural units derived from hydrogenated metaxylylene diisocyanate with respect to the total amount of the structural units derived from polyisocyanate is preferably 50 to 95 mol%, more preferably 60 to 90 mol%. Such a polyurethane resin exhibits high cohesive force due to hydrogen bonds and the stacking effect between xylylene groups, and thus has excellent gas barrier properties. The above content is 1 It can be identified using known analytical methods such as H-NMR.

[0045] The polyurethane resin may have a hydroxy group. The hydroxyl value of the polyurethane resin is preferably 50 to 1000 mgKOH / g, more preferably 100 to 800 mgKOH / g, and even more preferably 150 to 600 mgKOH / g. If the hydroxyl value of the polyurethane resin is within the above range, the oxygen barrier property is further improved. The measurement of the hydroxyl value is carried out in accordance with JIS K 0070:1992, and when 1 g of the sample is acetylated, the mg number of potassium hydroxide required to neutralize the acetic acid bound to the hydroxyl group is measured.

[0046] The oxygen permeability of the polyurethane resin when formed into a sheet with a thickness of 25 μm (hereinafter also referred to as "polyurethane sheet") is 100 cc / (m 2 ·day·atm) or less (synonymous with 100 mL / (m 2 ·day·atm) or less. The same applies hereinafter.) is preferable, 50 cc / (m 2 ·day·atm) or less is more preferable, 25 cc / (m 2 ·day·atm) or less is even more preferable, 10 cc / (m 2 ·day·atm) or less is particularly preferable, and 5 cc / (m 2It is most preferable that the oxygen permeability of the polyurethane sheet is less than or equal to (day·atm). There is no particular limit to the lower limit of the oxygen permeability of the polyurethane sheet; for example, the oxygen permeability of the polyurethane sheet is 0 cc / (m 2 It may also be (day·atm). If the oxygen permeability of the polyurethane sheet is less than or equal to the above upper limit, the oxygen permeability of the release sheet 10 is 500 cc / (m 2 It tends to be less than (day·atm). The oxygen permeability of polyurethane sheets is measured using an oxygen permeability measuring device in accordance with JIS K 7126-2:2006, under conditions of 23°C and 50% RH humidity.

[0047] Commercially available polyurethane resins may be used, such as the "Takelac W" series, "Takelac WPB" series, and "Takelac WS" series manufactured by Mitsui Chemicals, Inc., and "HPU W-003" manufactured by Dainichi Seika Kogyo Co., Ltd.

[0048] The content of the water-suspended polymer compound in the resin layer 13 is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, most preferably 95% by mass or more, and may also be 100% by mass.

[0049] Furthermore, the resin layer 13 may contain optional components in addition to the water-suspendable polymer compound. Specific examples of optional components include crosslinking agents, defoaming agents, surfactants, and antistatic agents. The optional components may be used individually or in combination of two or more.

[0050] The thickness of the resin layer 13 is preferably 0.1 to 20 μm, more preferably 0.2 to 15 μm, and even more preferably 0.3 to 10 μm. If the thickness of the resin layer 13 is above the lower limit, the desired barrier properties are more easily obtained. If the thickness of the resin layer 13 is below the upper limit, cracks and the like are less likely to occur in the resin layer 13 under bending stress. The thickness of the resin layer 13 is a value measured in accordance with JIS K 7130:1999.

[0051] <Release layer> The release layer 14 is located on the outermost surface of the release sheet 10 and is the layer that comes into contact with the article when the article is packaged using the release sheet 10. The release layer 14 preferably contains a release agent. Examples of release agents include silicone compounds, fluorine compounds, long-chain alkyl group-containing compounds, and polypropylene resins. Among these, silicone compounds are preferred because they allow for easy control of the release force. The release agent may be used alone or in combination of two or more types.

[0052] Silicone compounds used include solvent-diluted silicones, which are diluted with organic solvents such as toluene or hexane, and solvent-free silicones with a solid content concentration of 100% by mass. Among these, solvent-free silicones are preferred from the viewpoint of environmental protection. Examples of solvent-free silicones include thermosetting silicone compounds such as addition-curing silicone compounds and condensation-curing silicone compounds; electron beam-curing silicone compounds; and ultraviolet-curing silicone compounds such as radical-curing silicone compounds, cationic-curing silicone compounds, and mercapto-curing silicone compounds. Among these, addition-curing silicone-based release agents are preferred because they are more cost-effective and can be sufficiently crosslinked at temperatures below 200°C.

[0053] The release agent content in the release layer 14 is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, most preferably 95% by mass or more, and may also be 100% by mass.

[0054] Furthermore, the release layer 14 may contain optional components in addition to the release agent. Specific examples of optional components include crosslinking agents, catalysts, and release control agents. The optional components may be used individually or in combination of two or more.

[0055] The thickness of the release layer 14 is preferably 0.1 to 10 μm, more preferably 0.2 to 8 μm, and even more preferably 0.3 to 5 μm. If the thickness of the release layer 14 is above the lower limit, the variation in peeling force will be reduced. In addition, while stability tends to increase as the thickness of the release layer 14 increases, if it is too thick, the effect of improving stability plateaus and only increases costs. The thickness of the release layer 14 is measured in accordance with JIS K 7130:1999.

[0056] <Physical properties> The oxygen permeability of release sheet 10 is 500 cc / (m²). 2 (day·atm) or less, 400cc / (m 2 Preferably less than 200cc / (m) 2 (day·atm) or less is more preferable, 100cc / (m 2 A value of less than or equal to (day·atm) is even more preferable. The lower limit of the oxygen permeability of the release sheet 10 is not particularly limited; for example, the oxygen permeability of the release sheet 10 is 0 cc / (m 2 It may also be (day·atm). If the oxygen permeability of the release sheet 10 is below the above upper limit, it has excellent oxygen barrier properties. Therefore, even if an item is packaged using the release sheet 10, oxygen does not easily permeate, so the effect of oxygen on the item is reduced, and deterioration of the item's quality can be prevented. The oxygen permeability of the release sheet 10 is measured using an oxygen permeability measuring device in accordance with JIS K 7126-2:2006, under conditions of a temperature of 23°C and a humidity of 50%RH. The oxygen permeability of the release sheet 10 can be controlled, for example, by the type and content of the resin components that make up the resin layer 13, specifically the water-suspended polymer compound.

[0057] Furthermore, the oxygen permeability after pulling the release sheet 10 in the MD direction with a force of 500 N / m (hereinafter also referred to as "after the tensile test") was 500 cc / (m 2Preferably less than 400cc / (m) 2 (day·atm) or less is preferable, 200cc / (m 2 (day·atm) or less is even more preferable, 100cc / (m 2 A value of less than or equal to (day·atm) is particularly preferred. The lower limit of the oxygen permeability of the release sheet 10 after the tensile test is not particularly limited; for example, the oxygen permeability of the release sheet 10 after the tensile test is 0 cc / (m 2 It may also be (day·atm). If the oxygen permeability of the release sheet 10 after the tensile test is below the above upper limit, the oxygen barrier properties can be maintained well even when tension is applied to the release sheet 10. The tensile test will be conducted in accordance with JIS P 8113:2006, under conditions of 23°C and 50% RH humidity.

[0058] The tensile modulus of the release sheet 10 in the MD direction is preferably 7 GPa or higher, more preferably 8 GPa or higher, and preferably 30 GPa or lower. If the tensile modulus of the release sheet 10 in the MD direction is above the lower limit, the elongation in the MD direction will not increase significantly even when tension is applied to the release sheet 10, the rupture of the resin layer 13 can be suppressed, and the oxygen permeability, especially the oxygen permeability after the tensile test, can be maintained well. If the tensile modulus of the release sheet 10 in the MD direction is below the upper limit, the mechanical balance with the article can be easily achieved when packaging the article, and the occurrence of curl can be suppressed. The tensile modulus of the release sheet 10 is a value measured in accordance with JIS P 8113:2006.

[0059] The thickness of the release sheet 10 is preferably 20 to 700 μm, more preferably 25 to 500 μm, and even more preferably 30 to 300 μm. If the thickness of the release sheet 10 is above the lower limit, the release sheet 10 is more likely to be formed uniformly, and the oxygen permeability is easier to control. If the thickness of the release sheet 10 is below the upper limit, cracks and the like are less likely to occur in the resin layer 13 under bending stress. The thickness of the release sheet 10 is a value measured in accordance with JIS K 7130:1999.

[0060] <Manufacturing method> The release sheet 10 can be manufactured, for example, as follows. First, a clay coat layer composition is applied to one surface of the paper substrate 11 and dried to form a clay coat layer as a sealing layer 12 on the paper substrate 11. Next, a resin layer composition is applied on the clay coat layer and dried to form a resin layer 13 on the clay coat layer. Then, a release layer composition is applied on the resin layer 13 and dried as necessary to form a release layer 14 on the resin layer 13 to obtain a release sheet 10.

[0061] As a method for coating the clay coat layer and the resin layer 13, generally known coating apparatus can be used. Examples of coating apparatus include blade coaters, air knife coaters, roll coaters, reverse roll coaters, bar coaters, curtain coaters, slot die coaters, gravure coaters, champlex coaters, brush coaters, slide bead coaters, two-roll or rod metering type size press coaters, pound size press coaters, bill rod metering size press coaters, short dwell coaters, gate roll coaters, and nip coaters using a calender.

[0062] Furthermore, after each layer has been formed, or at any stage after a particular layer has been formed, a smoothing process using a supercalender or the like may be applied.

[0063] The clay coat layer composition includes, for example, the inorganic pigment, binder, and solvent described above. Examples of solvents include water; alcohol-based solvents such as ethanol, methanol, and isopropanol. Of these, water is preferred. The solvent may be used alone or in combination of two or more. The solid content concentration of the clay coat layer composition is preferably 20 to 95% by mass, more preferably 30 to 90% by mass, and even more preferably 40 to 80% by mass. The solid content concentration is the total content of components other than the solvent. The coating amount of the clay coat layer composition is 1 to 50 g / m² in terms of solid content. 2 Preferably, 3-30 g / m 2 More preferably, 5-20 g / m 2 That is even more preferable.

[0064] The resin layer composition includes, for example, the above-mentioned aqueous suspension polymer compound and a solvent. Examples of solvents include those previously exemplified in the description of the composition for the clay coat layer. A single solvent may be used, or two or more solvents may be used in combination. The composition for the resin layer may be a dispersion or an emulsion. The solid content concentration of the resin layer composition is preferably 3 to 80% by mass, more preferably 4 to 60% by mass, and even more preferably 5 to 40% by mass. The coating amount of the resin layer composition is 0.1 to 30 g / m² in terms of solid content. 2 Preferably, 0.3 to 20 g / m 2 More preferably, 0.5-10 g / m 2 That is even more preferable.

[0065] The release layer composition includes, for example, the release agent described above. The release layer composition may contain a solvent as needed, or may not contain a solvent at all. In this specification, a release layer composition that is substantially free of solvents is also referred to as a "solvent-free release layer composition," and a release layer composition that contains a solvent is also referred to as a "solvent-type release layer composition." The resin contained in the resin layer 13 is less likely to swell when the release layer composition is applied, and from an environmental protection standpoint, the release layer composition is preferably solvent-free, and more preferably solvent-free silicone. Here, "substantially absent" means that solvents are not actively incorporated into the release layer composition, excluding those unintentionally present.

[0066] If the release layer composition contains a solvent, the solvent may be one of the solvents exemplified earlier in the description of the clay coat layer composition. The solvent may be used alone or two or more may be used in combination. If the release layer composition contains a solvent, the solid content concentration of the release layer composition is preferably 3 to 80% by mass, more preferably 4 to 50% by mass, and even more preferably 5 to 40% by mass. The coating amount of the release layer composition is 0.05 to 20 g / m² in terms of solid content. 2 Preferably, 0.1 to 10 g / m 2 More preferably, 0.2-8 g / m 2 That is even more preferable.

[0067] If the sealing layer 12 is a laminate layer, the resin that forms the laminate layer (for example, the thermoplastic resin mentioned above) can be laminated onto one surface of the paper substrate 11 to form the laminate layer on the paper substrate 11. The lamination method is not particularly limited, but examples include extrusion lamination and film lamination. Among these, extrusion lamination is preferred. Examples of extrusion lamination include the melt extrusion lamination method using various extrusion molding machines such as T-dies. The conditions for the melt extrusion lamination method are not particularly limited, but for example, when polyethylene resin is used as the thermoplastic resin, it is preferable that the resin temperature directly below the die of the extruder be 200 to 400°C. If the resin temperature is above the lower limit, film breakage of the resin can be suppressed. If the resin temperature is below the upper limit, thermal degradation of the polyethylene resin can be suppressed. Furthermore, the laminated surface of the paper substrate 11 may be coated with an adhesive, treated with ozone, or subjected to corona discharge treatment to improve adhesion with the laminate layer.

[0068] <Effects and Effects> The release sheet of this embodiment described above comprises the paper substrate, sealing layer, resin layer, and release layer, and has an oxygen permeability of 500 cc / (m²). 2Since it is less than or equal to (day·atm), it has excellent oxygen barrier properties. Therefore, even when goods are packaged using a release sheet, oxygen does not easily permeate, so the effects of oxygen on the goods are minimized, preventing deterioration of the goods' quality and enabling long-term storage of goods. In particular, the oxygen permeability of the release sheet after the tensile test was 500 cc / (m²). 2 If the temperature is below (day·atm), or if the tensile modulus of elasticity in the MD direction of the release sheet is 7 GPa or higher, the oxygen barrier properties can be well maintained even when tension is applied to the release sheet. Therefore, it can be suitably used in applications where tension is applied, such as as process paper used in the manufacture of prepregs and adhesive sheets.

[0069] <Application> The release sheet of this embodiment is suitable as a packaging material used for packaging articles. Specific examples of packaging materials include process paper; individual packaging paper for foods such as caramel, candy, chocolate, and gum; and collective packaging paper for bundling individual packages. Among these, the release sheet of this embodiment is more suitable as process paper, even more suitable as process paper used in the manufacture of prepregs and adhesive tapes, and particularly suitable as process paper used in the manufacture of prepregs using anaerobic matrix resins. Furthermore, when the release sheet of this embodiment is used, for example, as process paper for the manufacture of prepregs, the prepregs are wound in close contact with the process paper as described above, and are transported and stored as a prepreg winding or sheet, with the process paper removed immediately before molding. In the present invention, these prepreg windings and sheet-like materials are considered "packaging." Furthermore, when the release sheet of this embodiment is used, for example, as individual packaging paper for food products, the food products wrapped in the release sheet are considered to be "packaged goods."

[0070] <Other Embodiments> The release sheet of the present invention is not limited to those described above. For example, the paper substrate 11, sealing layer 12, resin layer 13, and release layer 14 of the release sheet 10 shown in Figure 1 are each single-layer structures, but one or more of these layers may be laminated structures of two or more layers. Furthermore, an anchor coat layer may be provided between the resin layer 13 and the release layer 14, if necessary. Furthermore, although the release sheet 10 shown in Figure 1 has a sealing layer 12, a resin layer 13, and a release layer 14 laminated in this order only on one surface of the paper substrate 11, the sealing layer 12, resin layer 13, and release layer 14 may also be laminated in this order on the other surface of the paper substrate 11. In addition, a printability layer may be provided on the other surface of the paper substrate 11 as needed. The printability layer is provided on the other surface of the paper substrate 11 to enable proper printing of various types of prints and printer markings. [Examples]

[0071] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Embodiments of the present invention can be modified in various ways without changing the essence of the invention.

[0072] [Measurement and Evaluation] <Measurement of Tensile Modulus> The tensile modulus of the release sheet in the MD direction was measured in accordance with JIS P 8113:2006.

[0073] <Measurement of oxygen permeability> Without applying tension to the release sheet, the oxygen permeability of the release sheet was measured using an oxygen permeability measuring device (MOCON Corporation, product name "OX-TRAN2 / 20") in accordance with JIS K 7126-2:2006, under conditions of 23°C and 50% RH humidity. This value was defined as the "oxygen permeability before tensile testing."

[0074] To simulate the manufacturing process of prepregs and adhesive sheets, a tensile test was conducted by pulling the release sheet in the MD direction with a force of 500 N / m. The tensile test was performed in accordance with JIS P 8113:2006, under conditions of 23°C and 50% RH. For the release sheets after the tensile test, the oxygen permeability of the release sheets was measured using an oxygen permeability measuring device (MOCON Corporation, product name "OX-TRAN2 / 20") in accordance with JIS K 7126-2:2006, under conditions of 23°C and 50% RH humidity. This value was defined as the "oxygen permeability after the tensile test."

[0075] [Example 1] A clay coat layer composition with a solid content of 40% by mass was prepared by mixing 200 parts by mass (80 parts by mass in terms of solid content) of a dispersion of kaolin (manufactured by IMERYS, trade name "Contour Xtreme", average particle size d50: 0.26 μm) as an inorganic pigment dispersed in water to a solid content concentration of 40% by mass, with 50 parts by mass (20 parts by mass in terms of solid content) of an aqueous emulsion of styrene-acrylic resin (manufactured by BASF, trade name "JONCRYL HSL-9012", solid content concentration: 40% by mass) as a binder. High-quality paper base material (bleached hardwood kraft pulp (LBKP) blend ratio: 100% by mass, disintegration-freeness: 350cc, basis weight: 80g / m²) 2 On one surface of the paper, the clay coat layer composition is applied using a Meyer bar, dried at 120°C for 1 minute, and a clay coat layer (coating amount: 12g / m²) is applied as a sealing layer on the fine paper. 2 A layer with a thickness of 4.6 μm was formed. Next, a polyurethane resin dispersion (manufactured by Mitsui Chemicals, Inc., product name "Takelac WPB-341", solid content concentration: 30% by mass) is applied to the clay coat layer using a Meyer bar, dried at 120°C for 1 minute, and then a resin layer (coating amount: 2g / m²) is applied to the clay coat layer. 2 A sheet (2 μm thick) was formed. The oxygen permeability when the polyurethane resin dispersion was molded into a 25 μm thick sheet (polyurethane sheet) was 2 cc / (m²) at a temperature of 23°C and a humidity of 50% RH. 2 It was ·day·atm). Next, silicone (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KNS-305", solvent-free addition-curing silicone compound) is applied to the resin layer using a Meyer bar, dried at 120°C for 1 minute, and a release layer (coating amount: 1 g / m²) is applied to the resin layer.2 A release sheet was obtained by forming a sheet with a thickness of 1 μm. The tensile modulus and oxygen permeability of the obtained release sheets were measured. The results are shown in Table 1.

[0076] [Example 2] Polyvinyl alcohol (manufactured by Kuraray Co., Ltd., product name "Exceval RS-2117", solid content concentration: 8% by mass) is applied to the clay coat layer using a Meyer bar, dried at 120°C for 1 minute, and then a resin layer (coating amount: 2g / m²) is applied to the clay coat layer. 2 A release sheet was obtained in the same manner as in Example 1, except that a sheet with a thickness of 2 μm was formed. The tensile modulus and oxygen permeability of the obtained release sheets were measured. The results are shown in Table 1.

[0077] [Example 3] In forming the sealing layer, a clay coat layer (coating amount: 12g / m²) is applied to one side of the high-quality paper. 2 A release sheet was obtained in the same manner as in Example 1, except that instead of forming a 4.6 μm thick layer, a 15 μm thick polyethylene resin layer (PE resin layer) was formed by a melt extrusion lamination method. The tensile modulus and oxygen permeability of the obtained release sheets were measured. The results are shown in Table 1.

[0078] [Example 4] As a paper base material, high-quality paper (coniferous bleached kraft pulp (NBKP) blend ratio: 50% by mass, hardwood bleached kraft pulp (LBKP) blend ratio: 50% by mass, disintegration-freeness: 300cc, basis weight: 80g / m²) 2 A release sheet was obtained in the same manner as in Example 1, except that ) was used. The tensile modulus and oxygen permeability of the obtained release sheets were measured. The results are shown in Table 1.

[0079] [Example 5] As a paper base material, high-quality paper (bleached hardwood kraft pulp (LBKP) blend ratio: 100% by mass, disintegration-freeness: 480cc, basis weight: 80g / m²) 2 A release sheet was obtained in the same manner as in Example 1, except that ) was used. The tensile modulus and oxygen permeability of the obtained release sheets were measured. The results are shown in Table 1.

[0080] [Comparative Example 1] As a paper base material, high-quality paper (bleached hardwood kraft pulp (LBKP) blend ratio: 100% by mass, disintegration-freeness: 480cc, basis weight: 80g / m²) 2 On one surface of the paper, a polyurethane resin dispersion (manufactured by Mitsui Chemicals, Inc., product name "Takelac WPB-341", solid content concentration: 30% by mass) is applied using a Meyer bar, and dried at 120°C for 1 minute to create a resin layer on the fine paper (coating amount: 2g / m²). 2 A sheet (2 μm thick) was formed. The oxygen permeability when the polyurethane resin dispersion was molded into a 25 μm thick sheet (polyurethane sheet) was 2 cc / (m²) at a temperature of 23°C and a humidity of 50% RH. 2 It was ·day·atm). Next, silicone (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KNS-305", solvent-free addition-curing silicone compound) is applied to the resin layer using a Meyer bar, dried at 120°C for 1 minute, and a release layer (coating amount: 1 g / m²) is applied to the resin layer. 2 A release sheet was obtained by forming a sheet with a thickness of 1 μm. The tensile modulus and oxygen permeability of the obtained release sheets were measured. The results are shown in Table 1.

[0081] [Comparative Example 2] A clay coat layer composition with a solid content of 40% by mass was prepared in the same manner as in Example 1. High-quality paper base material (bleached hardwood kraft pulp (LBKP) blend ratio: 100% by mass, disintegration-freeness: 480cc, basis weight: 80g / m²) 2 On one surface of the paper, the clay coat layer composition is applied using a Meyer bar, dried at 120°C for 1 minute, and a clay coat layer (coating amount: 12g / m²) is applied as a sealing layer on the fine paper. 2 A layer with a thickness of 4.6 μm was formed. Next, silicone (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KNS-305", solvent-free addition-curing silicone compound) is applied to the clay coat layer using a Meyer bar, dried at 120°C for 1 minute, and a release layer (coating amount: 1g / m²) is applied to the resin layer. 2 A release sheet was obtained by forming a sheet with a thickness of 1 μm. The tensile modulus and oxygen permeability of the obtained release sheets were measured. The results are shown in Table 1.

[0082] [Table 1]

[0083] As is clear from the results in Table 1, the release sheets obtained in each example had high oxygen permeability and excellent oxygen barrier properties. Therefore, even when articles are packaged using the release sheets of the present invention, the effects of oxygen on the articles are minimized, and deterioration of the quality of the articles can be prevented. In particular, the release sheets obtained in Examples 1 to 4 showed high tensile modulus and oxygen permeability after tensile testing. On the other hand, the release sheets obtained in Comparative Examples 1 and 2 had low oxygen permeability. [Industrial applicability]

[0084] The release sheet of the present invention can prevent deterioration of the quality of articles, enables long-term storage of articles, and is useful as process paper used in the manufacture of prepregs and adhesive tapes, as well as as individual packaging paper for food products. [Explanation of Symbols]

[0085] 10 Release sheets 11 Paper base material 12. Sealing layer 13 Resin layer 14 Release layer

Claims

1. A release sheet comprising a paper substrate, a sealing layer, a resin layer, and a release layer laminated in this order, Oxygen permeability of 500 cc / (m ２ Release sheet with a value of less than 2 days / atm.

2. The oxygen permeability of the aforementioned release sheet after being pulled with a force of 500 N / m in the MD direction is 500 cc / m ２ The release sheet according to claim 1, wherein the temperature is less than or equal to (day atm).

3. The release sheet according to claim 1 or 2, wherein the tensile modulus of elasticity in the MD direction of the release sheet is 7 GPa or more.

4. The release sheet according to claim 1 or 2, wherein the sealing layer is a clay coat layer or a laminate layer.

5. The release sheet according to claim 1 or 2, wherein the resin layer contains a water-suspended polymer compound.

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