Coating agent

Abstract

To provide a coating agent that exhibits excellent permeability and dryability for a paper substrate, and forms a coating film with excellent releasability (both immediately after formation and with aging).SOLUTION: A coating agent contains a silicone compound, wherein the silicone compound has a viscosity of 1100 mPa s or more at 25°C when mixed at a mass ratio of 1:1 with a silicone oil whose viscosity is 145 to 155 mPa s at 25°C.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a coating agent. [Background technology]

[0002] Release paper is used for product labels and the like.

[0003] Such release paper is well known to have a structure containing a paper base material, an anchor coat layer, and a release layer in this order.

[0004] For example, Patent Document 1 discloses a coating composition comprising a base paper, a filling layer and a release layer on the base paper in this order, the filling layer containing a water-soluble resin and an acetylene glycol compound, and the release layer containing a solventless silicone resin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-245426 A Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, as the movement towards SDGs has accelerated worldwide, there has been an increasing demand from users to reduce the amount of release paper waste and recycle it.

[0007] However, because release paper is a composite material, it is difficult to separate the individual materials, making it difficult to recycle.

[0008] The release paper described in Patent Document 1 also has insufficient releasability (immediately after production and over time) of each material (each layer), and has problems with recycling.

[0009] Furthermore, the release paper described in Patent Document 1 has room for further improvement in terms of the permeability of the release agent forming the release layer into the paper base material and the drying property of the release agent.

[0010] Therefore, an object of the present invention is to provide a coating agent which has excellent permeability and drying properties for paper substrates, and which produces a coating film with excellent releasability (immediately after preparation and over time). [Means for solving the problem]

[0011] The present invention is a coating agent that contains a silicone compound, and when mixed in a mass ratio of 1:1 with a silicone oil having a viscosity of 145 to 155 mPa·s at 25°C, the silicone compound has a viscosity of 1100 mPa·s or more at 25°C.

[0012] In the coating agent of the present invention, the silicone compound preferably has a viscosity at 25°C of 1300 mPa·s or more when mixed in a mass ratio of 1:1 with a silicone oil having a viscosity at 25°C of 145 to 155 mPa·s. Moreover, the coating agent of the present invention is applied onto a coating film of an anchor coating agent, and the anchor coating agent preferably contains a resin emulsion having a glass transition temperature of -10°C or lower. The resin is preferably at least one selected from the group consisting of acrylic resins, styrene-acrylic resins, styrene-maleic acid resins, styrene-butadiene resins, acrylonitrile resins, and polyurethane resins. The resin is preferably at least one selected from the group consisting of styrene-acrylic resins and acrylonitrile resins. Effect of the Invention

[0013] The present invention can provide a coating agent that has excellent permeability and drying properties for paper substrates, and also provides a coating film with excellent releasability (immediately after preparation and over time). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] <Coating agent> The coating agent of the present invention contains a silicone compound, which has a viscosity of 1100 mPa·s or more at 25°C when mixed in a mass ratio of 1:1 with a silicone oil having a viscosity of 145 to 155 mPa·s at 25°C.

[0015] The coating agent of the present invention has excellent releasability because it contains a silicone component. In addition, by compounding the silicone component with silica, etc., the viscosity is high and the particle size is large compared to the silicone component alone, which suppresses the penetration into the substrate or anchor coat layer, so that the releasability does not decrease even after coating. However, the present invention should not be construed as being limited to the above mechanism.

[0016] (Silicone compound) The coating agent of the present invention contains a silicone compound.

[0017] Examples of the silicone compound include a mixture of polydimethylsiloxane and silica, a mixture of modified silicone oil and silica, and a mixture of polydimethylsiloxane, modified silicone oil and silica.

[0018] The silicone compound has a viscosity of 1100 mPa·s or more at 25°C when mixed in a mass ratio of 1:1 with a silicone oil having a viscosity of 145 to 155 mPa·s at 25°C. By ensuring that the viscosity is within the above range, the composition has excellent permeability into the paper substrate and excellent drying properties, and the coating film has excellent releasability (immediately after preparation and over time). The silicone compound, when mixed in a 1:1 mass ratio with a silicone oil having a viscosity of 145 to 155 mPa·s at 25°C, preferably has a viscosity at 25°C of 1300 mPa·s or more, more preferably 1350 mPa·s or more, even more preferably 1400 mPa·s or more, and particularly preferably 1450 mPa·s or more.

[0019] In this specification, the term "viscosity" refers to a viscosity measured using a Brookfield viscometer (manufactured by Tokyo Keiki Co., Ltd.) at 25°C and 10 rpm.

[0020] Examples of commercially available products that satisfy the above silicone compound viscosity include Shin-Etsu Silicone KS-6P (manufactured by Shin-Etsu Silicone Co., Ltd.) and Shin-Etsu Silicone KS-505 (manufactured by Shin-Etsu Silicone Co., Ltd.).

[0021] An example of the silicone oil having a viscosity of 145 to 155 mPa·s at 25° C. is Shin-Etsu Silicone KS-511 (viscosity of 152 mPa·s at 25° C., manufactured by Shin-Etsu Silicone Co., Ltd.).

[0022] The content of the silicone compound is preferably 50 to 90 mass %, and more preferably 60 to 80 mass %, of the total solid content of the coating agent. By setting the content of the silicone compound within the above range, it is possible to provide favorable permeability and drying properties for the paper substrate, as well as favorable releasability (immediately after preparation and over time) to the coating film.

[0023] (Resin component) The coating agent of the present invention may contain a resin component.

[0024] Examples of the resin component include styrene-maleic acid resins, acrylic resins, styrene-acrylic resins, styrene-butadiene resins, acrylonitrile resins, and polyurethane resins. The above resin components may be used alone or in combination of two or more kinds. Among these, styrene-maleic acid resins are preferred from the viewpoint of dispersion stability of the silicone compound.

[0025] From the viewpoint of dispersion stability of the silicone compound, the above resin component preferably has an acid value of 50 to 300 mgKOH / g, and more preferably 150 to 250 mgKOH / g. In this specification, the term "acid value" refers to a theoretical acid value calculated arithmetically from the number of milligrams of potassium hydroxide theoretically required to neutralize 1 g of the unneutralized resin. The acid value mentioned above means the value before neutralization with a basic compound described below.

[0026] The resin component may be a resin neutralized with a basic compound.

[0027] Examples of the basic compound include ammonia, triethylamine, N,N-dimethylethanolamine, monoethanolamine, sodium hydroxide, potassium hydroxide, and polyamine compounds.

[0028] The method for neutralizing the resin component is not particularly limited, and any known method can be used. For example, the above-mentioned basic compound may be added to a resin having an acid value in the above range.

[0029] The above resin component preferably has a glass transition temperature (Tg) of 0 to 150°C, and more preferably 50 to 100°C, from the viewpoint of various resistance properties of the coating layer. In this specification, the "glass transition temperature" may be measured using a thermal analysis device such as a differential scanning calorimeter (DSC), but when the following Wood's equation is applicable, it is preferable to refer to the theoretical glass transition temperature calculated by the following Wood's equation. Wood's formula: 1 / Tg=W1 / Tg1+W2 / Tg2+W3 / Tg3+········+W n / Tg n (In the formula, Tg is the theoretical glass transition temperature of the resin; Tg1 to Tg n are the glass transition temperatures of the homopolymers of the monomers 1, 2, 3, n that make up the resin copolymer; W1~W nrepresents the polymerization fraction of each of the resin monomers 1, 2, 3...n. However, the glass transition temperature in Wood's equation is an absolute temperature.) The above glass transition temperature refers to the value before neutralization with the basic compound.

[0030] From the viewpoint of various resistances of the coating layer, the content of the resin component is preferably 10 to 50 mass % (solid content) of the total solid content of the coating agent, and more preferably 20 to 40 mass % (solid content).

[0031] (solvent) The coating agent of the present invention may contain a solvent.

[0032] Examples of the solvent include alcohol compounds such as methanol, ethanol, isopropyl alcohol, normal propyl alcohol, isobutyl alcohol, normal butyl alcohol, tertiary butyl alcohol, and 2-ethylhexanol; ketone compounds such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, diisobutyl ketone, cyclohexanone, methylcyclohexanone, and diacetone alcohol; ketone compounds such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, methoxybutyl acetate, amyl acetate, normal propyl acetate, isopropyl acetate, methyl lactate, ethyl lactate, and butyl lactate; benzene, toluene, xylene, normal hexane, isohexane, cyclohexane, methylcyclohexane, ethylcyclohexane, isooctane, normal decahexane, and the like. Examples of the organic solvent include hydrocarbon compounds such as diethyl ether, tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, diisopropyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, 3-methoxy-3-methyl-1-butanol, ethylene glycol monotertiary butyl ether, propylene glycol monomethyl ether propionate, 3-methoxybutanol, diethylene glycol dimethyl ether, anisole, and 4-methylanisole; nitrogen-containing compounds such as acetonitrile, N,N-dimethylformamide, and N,N-dimethylacetamide; and water.

[0033] The content of the solvent is preferably 10 to 90% by mass based on the total mass of the coating agent.

[0034] (others) The coating agent of the present invention may contain additives such as viscosity modifiers, adhesion improvers, antifoamers, plasticizers, water-resistant agents, preservatives, antioxidants, penetrating agents, surfactants, fillers, starch and derivatives thereof, and latex, as necessary. The content of the additives is, for example, 0.01 to 5% by mass relative to the total mass of the coating agent.

[0035] (Method of applying coating agent) The method for applying the coating agent of the present invention is not particularly limited, and any known method can be appropriately selected and used. For example, a bar coater, a hand proofer, a direct gravure coater, an offset gravure coater, an air knife coater, a multi-stage roll coater, a spin coater, a dip coater, a kneader coater, a curtain coater, a blade coater, and the like can be mentioned.

[0036] The drying method after coating is not particularly limited, and any known method such as hot air heating, gas heater heating, or infrared heater heating can be appropriately selected and used.

[0037] <Anchor coating agent> The coating agent of the present invention is preferably applied onto a coating film of an anchor coating agent. The anchor coating agent will be described in detail below.

[0038] (resin) The anchor coating agent preferably contains a resin emulsion having a glass transition temperature of -10°C or lower. By containing a resin emulsion having a glass transition temperature of -10°C or lower, it is possible to impart favorable film-forming properties. The anchor coating agent more preferably contains a resin emulsion having a glass transition temperature of -20°C or lower.

[0039] From the viewpoint of suppressing the penetration of the coating agent, the resin is preferably one or more selected from acrylic resins, styrene-acrylic resins, styrene-maleic acid resins, styrene-butadiene resins, acrylonitrile resins, and polyurethane resins. Among them, it is more preferable to use one or more resins selected from styrene-acrylic resins and acrylonitrile resins.

[0040] When an acrylonitrile resin is used as the resin, the acrylonitrile content is preferably 20% or more, and more preferably 25% or more, from the viewpoint of the filling effect.

[0041] From the viewpoint of suppressing penetration of the coating agent, the content of the above resin is preferably 30 to 100 mass %, and more preferably 40 to 100 mass %, in terms of solid content relative to the total mass of the anchor coating agent.

[0042] (dispersion medium) The anchor coating agent contains a dispersion medium.

[0043] The dispersion medium is not particularly limited as long as it can disperse the resin. For example, the solvents exemplified above can be used as the dispersion medium.

[0044] (others) The above anchor coating agent may contain additives such as a leveling agent, an antifoaming agent, an antiseptic, a pH adjuster, and a film-forming agent, if necessary. The content of the additives is, for example, 0.01 to 5% by mass relative to the total mass of the anchor coating agent.

[0045] (How to apply anchor coat agent) The method for applying the anchor coating agent is not particularly limited, and may be appropriately selected from the methods described above for applying the coating agent of the present invention.

[0046] As for the drying method after application, any of the methods described for the coating agent of the present invention may be appropriately selected.

[0047] <Properties of coating agent> The coating agent of the present invention has excellent permeability into paper substrates.

[0048] The permeability into the paper substrate can be measured and evaluated by the following method.

[0049] An anchor coat agent is applied onto a paper substrate (product name "OK Prince Joujin", manufactured by Oji Materia, basis weight 52.3 g) using a hand proofer (165 line) to form an anchor coat layer. Thereafter, a coating agent is applied onto the above anchor coat layer using a hand proofer (165 line), and dried with a dryer at 60° C. to form a coating layer, thereby producing a laminate.

[0050] An adhesive tape (product name "31B", manufactured by Nitto Denko Corporation) is attached to the surface of the paper substrate opposite to the surface on which the anchor coat layer is formed, and 24 hours later, a peel test is performed according to JIS Z 0237 using a tensile tester (device name "Strograph M-50", manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a tensile speed of 300 mm / min and 180° peeling.

[0051] If the peel strength is 2000 mN / 50 mm or more, it can be determined that the permeability is excellent. If the peel strength is 4000 mN / 50 mm or more, it can be determined that the permeability is extremely excellent.

[0052] The coating agent of the present invention has excellent drying properties.

[0053] A laminate is prepared in the same manner as in the above-mentioned method for evaluating permeability. Immediately after preparing the laminate, aluminum foil is placed on the surface of the coating layer and pressed down with a rubber roller. Thereafter, the aluminum foil is peeled off and the contact surface of the aluminum foil with the coating layer is visually inspected.

[0054] When no removal of the coating layer from the aluminum foil was observed, it can be determined that the coating has excellent drying properties.

[0055] The coating agent of the present invention provides a coating film with excellent releasability (immediately after preparation and over time).

[0056] A laminate is prepared in the same manner as in the above-mentioned method for evaluating permeability. An adhesive tape (product name "31B", manufactured by Nitto Denko Corporation) is attached to the surface on which the coating layer is formed, and after 24 hours and two weeks, a peel test is performed according to JIS Z 0237 using a tensile tester (device name "Strograph M-50", manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a tensile speed of 300 mm / min and 180° peeling to measure the peel strength.

[0057] If the peel strength after 24 hours and after 2 weeks is less than 650 mN / 50 mm, it can be determined that the releasability (immediately after preparation and over time) is excellent. The peel strength after 24 hours and after 2 weeks is preferably 600 mN / 50 mm or less, more preferably 450 mN / 50 mm or less, even more preferably 350 mN / 50 mm or less, even more preferably 250 mN / 50 mm or less, particularly preferably 150 mN / 50 mm or less, and most preferably 100 mN / 50 mm or less.

[0058] The present specification discloses the following:

[0059] The present disclosure (1) is a coating agent containing a silicone compound, the silicone compound having a viscosity of 1100 mPa·s or more at 25°C when mixed in a mass ratio of 1:1 with a silicone oil having a viscosity of 145 to 155 mPa·s at 25°C. The present disclosure (2) is the coating agent according to the present disclosure (1), wherein the silicone compound has a viscosity of 1,300 mPa s or more at 25°C when mixed in a mass ratio of 1:1 with a silicone oil having a viscosity of 145 to 155 mPa s at 25°C. The present disclosure (3) is a coating agent according to the present disclosure (1) or (2), which is applied onto a coating film of an anchor coating agent, and the anchor coating agent contains a resin emulsion having a glass transition temperature of −10° C. or lower. The present disclosure (4) is the coating agent according to the present disclosure (3), wherein the resin is one or more selected from an acrylic resin, a styrene-acrylic resin, a styrene-maleic acid resin, a styrene-butadiene resin, an acrylonitrile resin, and a polyurethane resin. The present disclosure (5) is the coating agent according to the present disclosure (4), in which the resin is at least one selected from a styrene-acrylic resin and an acrylonitrile resin. EXAMPLES

[0060] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass."

[0061] The materials used in the examples and comparative examples are as follows.

[0062] <Silicone compound> KS-6P (product name "Shin-Etsu Silicone KS-6P", viscosity at 25°C when mixed with KS-511 below in a 1:1 (mass ratio) is 1473 mPa s, manufactured by Shin-Etsu Silicone Co., Ltd.) KS-505 (product name "Shin-Etsu Silicone KS-505", viscosity at 25°C when mixed with KS-511 below in a 1:1 (mass ratio) is 1359 mPa s, manufactured by Shin-Etsu Silicone Co., Ltd.) KS-2T (product name "Shin-Etsu Silicone KS-2T", viscosity at 25°C when mixed with KS-511 below in a 1:1 (mass ratio) is 1086 mPa s, manufactured by Shin-Etsu Silicone Co., Ltd.) The viscosity was measured using a Brookfield viscometer (Tokyo Keiki Co., Ltd.) at 25° C. and 10 rpm.

[0063] <Silicone oil> KS-511 (product name "Shin-Etsu Silicone KS-511", viscosity at 25°C 152 mPa·s, manufactured by Shin-Etsu Silicone Co., Ltd.)

[0064] <Resin components (for coating agents)> (Resin varnish 1) Purified water was added to a styrene-maleic acid resin (acid value 220 mgKOH / g, glass transition temperature 87° C.), heated and stirred, and neutralized with ammonia to a solid content of 16 mass % and pH of 8.0 to prepare resin varnish 1.

[0065] <Solvent> Water (purified water)

[0066] (Preparation of coating agent) The components shown in Table 1 were mixed and stirred using a high-speed mixer to produce a coating agent.

[0067] [Table 1]

[0068] <Resin emulsion (for anchor coating)> Resin emulsion 1 (product name "Cyatex NA-106", acrylonitrile-butadiene rubber emulsion, glass transition temperature -35°C, acrylonitrile content 25-30%, solid content 50% by mass, manufactured by Nippon A&L Co., Ltd.) Resin emulsion 2 (product name "AE610H", acrylonitrile-acrylic acid ester copolymer, glass transition temperature -56°C, solid content 45% by mass, manufactured by E-Tech Co., Ltd.) Resin emulsion 3 (product name "AE200A", styrene-acrylic resin, glass transition temperature -44°C, solid content 51% by mass, manufactured by E-Tech Co., Ltd.) Resin emulsion 4 (product name "AE831A", acrylonitrile-acrylic acid ester copolymer, glass transition temperature -22°C, solid content 46% by mass, manufactured by E-Tech Co., Ltd.)

[0069] (Resin Emulsion 5) An aqueous solution of an ammonia-neutralized alkali-soluble resin (containing 30.4 parts by mass of acrylic acid, 8.5 parts by mass of styrene, and 61.1 parts by mass of α-methylstyrene as monomer components when the total solid content is taken as 100 parts by mass) was prepared as a polymer emulsifier. Next, 75.5 parts by mass of a monomer mixture (containing 20.0 parts by mass of styrene, 45.5 parts by mass of 2-ethylhexyl acrylate, and 10.0 parts by mass of methyl methacrylate) was added to 24.5 parts by mass of the solid content of the above polymer emulsifier, and emulsion polymerization was performed by a conventional method to obtain resin emulsion 5 (glass transition temperature 3°C, solid content 38.5% by mass).

[0070] (Resin Emulsion 6) An aqueous solution of an alkali-soluble resin (containing 25.0 parts by mass of acrylic acid, 15.0 parts by mass of methyl methacrylate, 10.0 parts by mass of butyl methacrylate, 25.0 parts by mass of styrene, and 25.0 parts by mass of α-methylstyrene when the total solid content is taken as 100 parts by mass) neutralized with ammonia and sodium hydroxide was prepared as a polymer emulsifier. Next, 70 parts by mass of a monomer mixture (containing 43.0 parts by mass of methyl methacrylate and 57.0 parts by mass of 2-ethylhexyl acrylate) was added to 30 parts by mass of the solid content of the above polymer emulsifier, and emulsion polymerization was performed by a conventional method to obtain resin emulsion 6 (glass transition temperature -4°C, solid content 46.0% by mass).

[0071] (Preparation of anchor coating agent) The components shown in Table 2 were mixed and stirred using a high-speed mixer to produce an anchor coating agent.

[0072] [Table 2]

[0073] <Preparation of Laminate> An anchor coat agent was applied onto a paper substrate (product name "OK Prince Joujin", manufactured by Oji Materia, basis weight 52.3 g) using a hand proofer (165 line) to form an anchor coat layer. Thereafter, a coating agent was applied onto the above anchor coat layer using a hand proofer (165 line) and dried with a dryer at 60° C. to form a coating layer, thereby producing a laminate.

[0074] <Permeability> An adhesive tape (product name "31B", manufactured by Nitto Denko Corporation) was applied to the surface of the laminate opposite to the surface on which the anchor coat layer was formed, and 24 hours later, a peel test was performed according to JIS Z 0237 using a tensile tester (device name "Strograph M-50", manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a tensile speed of 300 mm / min and 180° peeling, and the results were evaluated according to the following criteria. "◎" and "◯" were judged to be acceptable. The results are shown in Table 3. (Evaluation Criteria) ◎: Peel strength was 4000mN / 50mm or more ○: Peel strength was 2000mN / 50mm or more and less than 4000mN / 50mm ×: Peel strength was less than 2000 mN / 50 mm

[0075] <Drying> Immediately after preparing the laminate, aluminum foil is placed on the surface of the coating layer and pressed down with a rubber roller. Thereafter, the aluminum foil was peeled off, and the contact surface of the aluminum foil with the coating layer was visually inspected and evaluated according to the following criteria. "Good" was judged to be acceptable. The results are shown in Table 3. (Evaluation Criteria) ○: No removal of the coating layer from the aluminum foil was observed. ×: Removal of the coating layer from the aluminum foil was observed.

[0076] <Releasability (immediately after preparation and over time)> An adhesive tape (product name "31B", manufactured by Nitto Denko Corporation) was attached to the surface of the prepared laminate on which the coating layer was formed, and after 24 hours and two weeks, a peel test was performed according to JIS Z 0237 using a tensile tester (device name "Strograph M-50", manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a tensile speed of 300 mm / min and 180° peeling to measure the peel strength. The results are shown in Table 3. If the peel strength after 24 hours and after 2 weeks was less than 650 mN / 50 mm, the releasability (immediately after preparation and over time) was determined to be excellent.

[0077] [Table 3]

[0078] It was confirmed that the coating agents of the examples had excellent permeability into paper substrates and drying properties, and that the coating films had excellent releasability (immediately after preparation and over time). [Industrial Applicability]

[0079] It is possible to provide a coating agent that has excellent permeability and drying properties for paper substrates, and also produces a coating film that has excellent releasability (immediately after preparation and over time).

Claims

1. Contains a silicone compound, The silicone compound is a coating agent having a viscosity of 1100 mPa·s or more at 25° C. when mixed in a mass ratio of 1:1 with a silicone oil having a viscosity of 145 to 155 mPa·s at 25° C.

2. 2. The coating agent according to claim 1, wherein the silicone compound has a viscosity of 1,300 mPa·s or more at 25° C. when mixed in a mass ratio of 1:1 with a silicone oil having a viscosity of 145 to 155 mPa·s at 25° C.

3. It is applied on top of the anchor coating agent. The anchor coating agent contains a resin emulsion having a glass transition temperature of -10°C or lower. The coating agent according to claim 1 or 2.

4. 4. The coating agent according to claim 3, wherein the resin is at least one selected from the group consisting of acrylic resins, styrene-acrylic resins, styrene-maleic acid resins, styrene-butadiene resins, acrylonitrile resins, and polyurethane resins.

5. 5. The coating agent according to claim 4, wherein the resin is at least one selected from the group consisting of styrene-acrylic resins and acrylonitrile resins.

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