Oil-resistant coating composition and laminate

Abstract

The present invention provides an oil-resistant coating composition that does not contain fluorine components, thereby reducing environmental impact, and that can impart excellent oil resistance and breathability to paper substrates. [Solution] An oil-resistant coating composition containing a plant-derived biowax emulsion, a styrene-acrylic emulsion, and an aqueous medium, wherein the plant-derived biowax emulsion contains a structure derived from a fatty acid ester with 9 to 24 carbon atoms, and does not contain a fluorine component.

Description

[Technical Field]

[0001] This invention relates to an oil-resistant coating composition and a laminate. [Background technology]

[0002] Oil-resistant paper is widely used as packaging paper, packaging containers, or paper liners for food trays and other paper products for cooked foods such as fast food, fried foods, and baked foods that contain a lot of oil and moisture, as well as for foods that contain a lot of fat, such as chocolate. Oil-resistant paper requires both oil resistance and breathability. For example, packaging paper for hamburgers and hot snacks requires both oil resistance (to prevent oil from passing through) and breathability (to allow water vapor to pass through).

[0003] Conventionally, oil-resistant paper containing fluororesin has been used to provide oil resistance while maintaining breathability. For example, oil-resistant paper is known in which a fluororesin-containing coated paper is applied to the surface of paper or cardboard, or oil-resistant paper in which fluororesin is contained between (within) the paper layers (see, for example, Patent Document 1).

[0004] However, oil-resistant paper made with fluororesin may generate organic fluorine compounds during high-temperature processing such as cooking or incineration. Furthermore, among these organofluorine compounds, perfluorooctanesulfonic acid and perfluorooctanoic acid are persistent and highly bioaccumulative, leading to widespread presence in environmental water and wildlife, raising concerns about adverse health and environmental impacts.

[0005] To address these problems, oil-resistant paper using non-fluorine resins has been proposed. Furthermore, from the perspective of reducing environmental impact, oil-resistant paper made from naturally derived materials has also been proposed.

[0006] For example, Patent Document 2 describes applying at least one coating layer containing starch and / or polyvinyl alcohol and fatty acids to at least one side of a substrate at a density of 0.5 to 20 g / m². 2An oil-resistant sheet-like material characterized by having a feature is disclosed. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2017-036343 [Patent Document 2] Japanese Patent Publication No. 2006-219786 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] In recent years, there has been a demand for oil-resistant coating compositions that can provide sufficient oil resistance and breathability to paper substrates while being more environmentally friendly. Conventional oil-resistant coating compositions still had room for further improvement in terms of reducing environmental impact and providing oil resistance and breathability to paper substrates.

[0009] Therefore, the present invention aims to provide an oil-resistant coating composition that does not contain fluorine components, reduces environmental impact, and can impart excellent oil resistance and breathability to paper substrates. [Means for solving the problem]

[0010] The inventors have discovered that an oil-resistant coating composition containing a plant-derived biowax emulsion, a styrene-acrylic emulsion, and an aqueous medium, and free of fluorine components, can solve all of the above-mentioned problems, and have completed the present invention.

[0011] In other words, the present invention is an oil-resistant coating composition containing a plant-derived biowax emulsion, a styrene-acrylic emulsion, and an aqueous medium, wherein the plant-derived biowax emulsion contains a structure derived from a fatty acid ester with 9 to 24 carbon atoms and does not contain a fluorine component.

[0012] In the oil-resistant coating composition of the present invention, the solid content ratio of the plant-derived biowax emulsion to the styrene-acrylic emulsion (plant-derived biowax emulsion / styrene-acrylic emulsion) is preferably 25 / 75 to 75 / 25. Furthermore, the above-mentioned plant-derived biowax emulsion preferably has a softening point of 60°C to 90°C. Furthermore, the styrene-acrylic emulsion described above preferably has a glass transition temperature of -15°C or higher and 30°C or lower. Furthermore, the above-mentioned styrene-acrylic emulsion preferably has an acid value of 30 mg KOH / g or more and 90 mg KOH / g or less. The present invention also relates to a laminate comprising a coating film of the oil-resistant coating composition of the present invention on a paper substrate. [Effects of the Invention]

[0013] The present invention provides an oil-resistant coating composition that does not contain fluorine components, reduces environmental impact, and can impart excellent oil resistance and breathability to paper substrates. [Modes for carrying out the invention]

[0014] <Oil-resistant coating composition> The oil-resistant coating composition of the present invention contains a plant-derived biowax emulsion, a styrene-acrylic emulsion, and an aqueous medium. The plant-derived biowax emulsion contains a structure derived from a fatty acid ester with 9 to 24 carbon atoms and does not contain a fluorine component.

[0015] The oil-resistant coating composition of the present invention is obtained by blending a styrene-acrylic emulsion with excellent oil resistance and a bio-wax emulsion with excellent air permeability, whereby portions with excellent air permeability appear in various parts of the coating film. In addition, since the bio-wax emulsion also has a certain level of oil resistance, the oil resistance is not significantly impaired even in a state where air permeability is exhibited. Therefore, the oil-resistant coating composition of the present invention can reduce environmental load, and can impart excellent oil resistance and air permeability to a paper substrate. However, the mechanism is not limited to the above description.

[0016] (Plant-derived bio-wax emulsion) The oil-resistant coating composition of the present invention contains a plant-derived bio-wax emulsion.

[0017] The plant-derived bio-wax emulsion contains a structure derived from a fatty acid ester having 9 to 24 carbon atoms.

[0018] Examples of the aforementioned fatty acid ester include methyl esters and ethyl esters of saturated fatty acids such as lauric acid, palmitic acid, stearic acid, behenic acid, and hydroxystearic acid, or unsaturated fatty acids such as oleic acid and erucic acid. From the viewpoint of oil resistance, the aforementioned fatty acid ester more preferably has 14 to 20 carbon atoms, and examples thereof include methyl esters and ethyl esters of palmitic acid and stearic acid.

[0019] From the viewpoint of heat resistance, the plant-derived bio-wax emulsion preferably has a softening point of 60°C or higher, more preferably 70°C or higher. In addition, the softening point is preferably 90°C or lower. In the present specification, the softening point refers to a value measured in accordance with JIS K 5601-2-2:1999 "Testing methods for paint components - Part 2: Component analysis in solvent-soluble matter - Section 2: Softening point (Ring and Ball method)".

[0020] The above-mentioned plant-derived biowax emulsion may contain known surfactants as needed.

[0021] From the viewpoint of reducing environmental impact and imparting oil resistance to paper substrates, the above-mentioned plant-derived biowax emulsion is preferably present in an amount of 7% by mass or more, and more preferably 9% by mass or more, relative to the total solid content of the oil-resistant coating composition of the present invention. It is preferably present in an amount of 25% by mass or less, and more preferably 21% by mass or less, relative to the total solid content of the oil-resistant coating composition of the present invention. In this specification, "solids" refers to the components excluding volatile components such as water and solvents.

[0022] (Styrene-acrylic emulsion) The oil-resistant coating composition of the present invention contains a styrene-acrylic emulsion.

[0023] The styrene-acrylic emulsion described above is a copolymer of a styrene monomer and an acrylic monomer.

[0024] Examples of the styrene monomers mentioned above include styrene, α-methylstyrene, p-methoxystyrene, p-hydroxystyrene, and p-acetoxystyrene.

[0025] Examples of the above-mentioned acrylic monomers include (meth)acrylic acid; alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate; amino group-containing (meth)acrylates such as dimethylaminoethyl (meth)acrylate; and glycidyl group-containing (meth)acrylates such as glycidyl (meth)acrylate. In this specification, "(meth)acrylic acid" means acrylic acid and / or methacrylic acid, and "(meth)acrylate" means acrylate and / or methacrylate.

[0026] The styrene-acrylic emulsion mentioned above may be manufactured by a known method or may be a commercially available product. The above-mentioned styrene-acrylic emulsion is preferably obtained by copolymerizing a styrene monomer and, if necessary, an alkyl ester of (meth)acrylic acid using a water-soluble acrylic resin as a polymer emulsifier, and is capable of forming a film at room temperature.

[0027] In the above-mentioned styrene-acrylic emulsion, if a basic compound is used, examples of such basic compounds include ammonia and organic amines. Specifically, examples of the above-mentioned organic amines include alkylamines such as diethylamine, triethylamine, and ethylenediamine, and alkanolamines such as monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine, and triethanolamine.

[0028] The above styrene-acrylic emulsion preferably has an acid value of 30 mg KOH / g or more, more preferably 40 mg KOH / g or more. Furthermore, it is preferably 90 mg KOH / g or less, more preferably 80 mg KOH / g or less, even more preferably 70 mg KOH / g or less, and particularly preferably 60 mg KOH / g or less. In this specification, the acid value is the theoretical acid value obtained by arithmetically calculating the number of milligrams of potassium hydroxide theoretically required to neutralize 1 g of resin. When using commercially available products, the values ​​in the catalog may be referred to.

[0029] The above styrene-acrylic emulsion preferably has a glass transition temperature of -15°C or higher, more preferably -10°C or higher, even more preferably -5°C or higher, and particularly preferably 0°C or higher. Furthermore, it is preferable that the glass transition temperature be 30°C or lower, more preferably 25°C or lower, even more preferably 20°C or lower, and particularly preferably 15°C or lower. In this specification, the glass transition temperature is a value measured using a PerkinElmer Pyris1 DSC in accordance with JIS K7121:2012 (Method for measuring the transition temperature of plastics), under conditions of a heating rate of 20°C / min and a nitrogen gas flow rate of 20 ml / min. When using commercially available products, the values ​​in the catalog may be referred to.

[0030] Examples of commercially available styrene-acrylic emulsions include Saibinol EK-63 and EK-61 (both manufactured by Saiden Chemical Co., Ltd.), and Hyros X TE5205 (manufactured by Seikoh PMC Co., Ltd.).

[0031] The solid content ratio of the plant-derived biowax emulsion to the styrene-acrylic emulsion (plant-derived biowax emulsion / styrene-acrylic emulsion) is preferably 25 / 75 to 70 / 30, from the viewpoint of reducing environmental impact and imparting oil resistance and breathability to the paper substrate. The above solid content ratio is more preferably 30 / 70 to 70 / 30, even more preferably 40 / 60 to 70 / 30, and particularly preferably 45 / 55 to 70 / 30.

[0032] (aqueous medium) The oil-resistant coating composition of the present invention contains an aqueous medium.

[0033] Examples of the aqueous medium mentioned above include water and water containing a water-soluble organic solvent. The above-mentioned water-soluble organic solvent can be appropriately selected from alcohols, ethers, aprotic polar solvents, etc. In particular, water is preferred and can be suitably used to adjust the amount of oil-resistant agent applied and to adjust its viscosity.

[0034] The content of the aqueous medium is not particularly limited and can be adjusted as appropriate depending on the amount applied, viscosity, etc., of the oil-resistant coating composition.

[0035] (Fluorine component) The oil-resistant coating composition of the present invention does not contain any fluorine components. Therefore, adverse effects on health or the environment can be mitigated.

[0036] (others) The oil-resistant coating composition of the present invention may contain additives.

[0037] Examples of the above-mentioned additives include defoaming agents, surface tension modifiers, dispersants, and colorants. These can be selected from publicly available sources as appropriate.

[0038] The content of the above additives may be adjusted as needed, but for example, it is 0.1 to 3.0% by mass relative to the total mass of the oil-resistant coating composition of the present invention.

[0039] (Method for manufacturing an oil-resistant coating composition) The method for producing the oil-resistant coating composition of the present invention is not particularly limited, and the above-mentioned materials may be mixed and dispersed by known methods. For example, the above-mentioned materials can be mixed and dispersed using media such as paint shakers, ball mills, attritors, basket mills, sand mills, sand grinders, dyno mills, disperser mats, SC mills, spike mills, and agitator mills, or by using ultrasonic homogenizers, high-pressure homogenizers, nanomizers, dissolvers, dispersers, and high-speed impeller dispersers.

[0040] (Physical properties of oil-resistant coating compositions) The oil-resistant coating composition of the present invention can reduce environmental impact.

[0041] The oil-resistant coating composition of the present invention has a biomass component ratio of 25% to 70%. While a higher biomass component ratio is preferable, from the viewpoint of oil resistance and air permeability, it is preferably 40% or more, and more preferably 65% ​​or less. Here, the biomass component ratio refers to the proportion of biomass-derived components contained in the oil-resistant coating composition, and is expressed by the following formula. Biomass component ratio (%) = (Mass of biomass-derived components / Mass of solids in the oil-resistant coating composition) × 100

[0042] <Laminate> The laminate of the present invention comprises a coating film of the oil-resistant coating composition of the present invention on a paper substrate.

[0043] (Paper base material) Examples of the paper substrates mentioned above include chemical pulps such as bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), bleached hardwood sulfite pulp (LBSP), and bleached softwood sulfite pulp (NBSP); unbleached, semi-bleached, or bleached pulps such as stone gland pulp (GP), pressure stone gland pulp (PGW), refiner gland pulp (RGP), chemigland pulp (CGP), thermomechanical pulp (TMP), and chemothermetic pulp (CTMP); sulfite pulp; and recycled paper pulp.

[0044] (Application method for oil-resistant coating compositions) As a method for applying the oil-resistant coating composition of the present invention onto the paper substrate, flexographic printing, gravure printing, and a coater are preferred from the viewpoint of ensuring a sufficient amount of the oil-resistant coating composition is applied.

[0045] The recommended application amount of the oil-resistant coating composition of the present invention is 2 g / m² by dry weight, from the viewpoint of suitably exhibiting oil resistance, air permeability, and printability. 2 It is preferable that the above conditions are met.

[0046] (Physical properties of laminates) The laminate of the present invention exhibits excellent oil resistance.

[0047] Specifically, the oil resistance mentioned above is defined as an oil resistance (Kit) of 3 or higher, as measured by the following measurement method. The above oil resistance (Kit) is preferably 4 or higher, and more preferably 5 or higher. The above oil resistance measurement method is the kit method of JAPAN TAPPI Paper and Pulp Test Method No. 41:2000. The laminate used in the above test is a paper substrate with a pure white basis weight of 30 g / m². 2 Using the above oil-resistant coating composition, the oil-resistant coating composition is coated with a bar coater at a rate of 4.0 (dry) (g / m²). 2 The coating is applied using the specified amount and dried for 30 seconds in a dryer set to 120°C to form a coating film.

[0048] The laminate of the present invention has excellent air permeability.

[0049] Specifically, the above air permeability is defined as an Oken-type air permeability of 5000 seconds or less, measured according to JAPAN TAPPI Paper Pulp Test Method No. 5-2:2000. The above air permeability is preferably 4000 seconds or less, and more preferably 2500 seconds or less.

[0050] The laminate used in the above test is a paper substrate with a pure white basis weight of 30 g / m². 2 Using the above oil-resistant coating composition, the oil-resistant coating composition is coated with a bar coater at a rate of 4.0 (dry) (g / m²). 2 Apply the coating using the specified amount, and dry it in a hot air dryer set to 120°C for 30 seconds to form a coating film.

[0051] The laminate of the present invention preferably exhibits excellent water resistance.

[0052] The above water resistance is based on a paper substrate with a pure white basis weight of 30 g / m². 2 Using the above oil-resistant coating composition, the oil-resistant coating composition is coated with a bar coater at a rate of 4.0 (dry) (g / m²). 2 Apply the coating using the specified amount, and dry it in a hot air dryer set to 120°C for 30 seconds to form a coating film. After dropping water onto the above coating, the penetration of the water is visually observed after 5 minutes. If no penetration is observed, it is evaluated as having sufficient water resistance.

[0053] This specification discloses the following:

[0054] The present disclosure (1) is an oil-resistant coating composition comprising a plant-derived biowax emulsion, a styrene-acrylic emulsion, and an aqueous medium, wherein the plant-derived biowax emulsion contains a structure derived from a fatty acid ester with 9 to 24 carbon atoms and does not contain a fluorine component. Disclosure (2) is an oil-resistant coating composition according to Disclosure (1), wherein the solid content ratio of the plant-derived biowax emulsion to the styrene-acrylic emulsion (plant-derived biowax emulsion / styrene-acrylic emulsion) is 25 / 75 to 75 / 25. Disclosure (3) is an oil-resistant coating composition according to Disclosure (1) or (2), wherein the above-mentioned plant-derived biowax emulsion has a softening point of 60°C or higher and 90°C or lower. Disclosure (4) is an oil-resistant coating composition according to any one of Disclosures (1) to (3), wherein the styrene-acrylic emulsion has a glass transition temperature of -15°C or higher and 30°C or lower. Disclosure (5) is an oil-resistant coating composition according to any one of Disclosures (1) to (4), wherein the styrene-acrylic emulsion has an acid value of 30 mg KOH / g or more and 90 mg KOH / g or less. Disclosure (6) is a laminate comprising a coating film of an oil-resistant coating composition described in any of Disclosures (1) to (5) on a paper substrate. [Examples]

[0055] 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 "mass%" and "parts" means "parts by mass".

[0056] The following materials were prepared for the oil-resistant coating composition. (Plant-derived biowax emulsion) Plant-derived bio-wax emulsion (bio-wax emulsion containing a structure derived from a hydrogenated palm oil product, solid content 33 mass%) (Styrene-acrylic emulsion) Styrene-acrylic emulsion 1 (Saibinol EK-63, manufactured by Saiden Chemical Industry Co., Ltd., solid content 38.5 mass%, glass transition temperature 3°C, acid value 58 mgKOH / g) Styrene-acrylic emulsion 2 (Saibinol EK-61, manufactured by Saiden Chemical Industry Co., Ltd., solid content 40.0 mass%, glass transition temperature 24°C, acid value 87 mgKOH / g) Styrene-acrylic emulsion 3 (Hiros-X TE-5205, manufactured by Seiko PMC Corporation, solid content 46.5 mass%, glass transition temperature -12°C, acid value 53 mgKOH / g) The glass transition temperature and the acid value refer to the numerical values in the catalog. (Aqueous medium) Water

[0057] (Examples 1 to 7, Comparative Examples 1 to 4) Various materials were charged into a container at the blending amounts (mass%) shown in Table 1, stirred using a disper to uniformly mix and dissolve, and then filtered through a mesh to produce an oil-resistant coating composition. The "solid content ratio" shown in Table 1 is a value calculated as the solid content ratio (plant-derived bio-wax emulsion / styrene-acrylic emulsion).

[0058] [Table 1]

[0059] <Biomass component ratio> The biomass component ratio of the oil-resistant coating composition was calculated by the following formula. Biomass component ratio (%) = (mass of biomass-derived components / mass of solid content of the oil-resistant coating composition) × 100

[0060] <Oil resistance> As a paper substrate, pure white base weight 30 g / m 2Using this material, the oil-resistant coating composition was coated with a bar coater at a rate of 4.0 (dry) (g / m²). 2 The coating was applied using the specified amount and dried for 30 seconds in a hair dryer set to 120°C to form a coating film. The evaluation was conducted using the kit method of JAPAN TAPPI Paper and Pulp Testing Method No. 41:2000, according to the following criteria. "◎" and "〇" were judged as passing grades. (Evaluation Criteria) ◎: The Kit value was 4 or higher. ○: The Kit value was greater than 3 and less than 4. ×: The Kit value was less than 3.

[0061] <Air permeability> Paper base material: pure white, basis weight 30g / m² 2 Using this material, the oil-resistant coating composition was coated with a bar coater at a rate of 4.0 (dry) (g / m²). 2 The coating was applied using the specified amount and dried for 30 seconds in a hot air dryer set to 120°C to form a coating film. The air permeability was measured according to the JAPAN TAPPI Paper and Pulp Testing Method No. 5-2:2000, and evaluated according to the following criteria. "◎" and "〇" were judged as passing grades. ◎: The time was 2500 seconds or less. 〇: The time was between 2500 seconds and 5000 seconds. ×: It was 5000 seconds or more.

[0062] <Water resistance> Paper base material: pure white, basis weight 30g / m² 2 Using this material, the oil-resistant coating composition was coated with a bar coater at a rate of 4.0 (dry) (g / m²). 2 The coating was applied using the specified amount and dried for 30 seconds in a hot air dryer set to 120°C to form a coating film. After dropping water onto the above coating, the water penetration was visually observed after 5 minutes and evaluated according to the following criteria. "◎" and "〇" were judged as passing. ◎: No staining occurred. ○: There was staining. ×: There was a leak on the back.

[0063] [Table 2]

[0064] Tables 1 and 2 show that the examples did not contain fluorine components, thus reducing environmental impact, and were able to impart excellent oil resistance and breathability to paper substrates. [Industrial applicability]

[0065] The present invention provides an oil-resistant coating composition that does not contain fluorine components, reduces environmental impact, and can impart excellent oil resistance and breathability to paper substrates.

Claims

1. It contains a plant-derived biowax emulsion, a styrene-acrylic emulsion, and an aqueous medium. The aforementioned plant-derived biowax emulsion contains a structure derived from a fatty acid ester having 9 to 24 carbon atoms. An oil-resistant coating composition that does not contain fluorine components.

2. The oil-resistant coating composition according to claim 1, wherein the solid content ratio of the plant-derived biowax emulsion to the styrene-acrylic emulsion (plant-derived biowax emulsion / styrene-acrylic emulsion) is 25 / 75 to 75 / 25.

3. The oil-resistant coating composition according to claim 1 or 2, wherein the plant-derived biowax emulsion has a softening point of 60°C or higher and 90°C or lower.

4. The oil-resistant coating composition according to claim 1 or 2, wherein the styrene-acrylic emulsion has a glass transition temperature of -15°C or higher and 30°C or lower.

5. The oil-resistant coating composition according to claim 1 or 2, wherein the styrene-acrylic emulsion has an acid value of 30 mg KOH / g or more and 90 mg KOH / g or less.

6. A laminate comprising a coating film of the oil-resistant coating composition described in claim 1 or 2 on a paper substrate.

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