Coating composition and laminate

Abstract

To provide a coating composition which enables formation of a coating film that is excellent in water repellency, ink top coating suitability and adhesion, and can suppress water absorption.SOLUTION: A coating composition contains a resin, a water-repellent agent, and an urea-based compound, where 10 to 60 mass% of the urea-based compound is contained in the total solid content of the coating composition.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to coating compositions and laminates. [Background technology]

[0002] Conventionally, coating agents containing a resin and a urea-based compound have been used.

[0003] For example, Patent Document 1 discloses a heat-sealable coating material containing egg white protein, a plasticizer, and an aqueous medium, and discloses the use of urea as the plasticizer.

[0004] Furthermore, for example, Patent Document 2 discloses a vinyl chloride plastisol-based undercoat composition that contains, as essential components, vinyl chloride resin, a plasticizer, calcium carbonate powder, a foaming agent, a foaming assistant, and a moisture absorbent, and is characterized in that fatty acid-treated urea or a urea-based compound is used as the foaming assistant. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-222915 A [Patent Document 2] Japanese Patent Application Publication No. 11-001658 Summary of the Invention [Problem to be solved by the invention]

[0006] Cardboard cases used for storing fresh produce such as cabbage are made of cardboard that has been coated to make it water-repellent.

[0007] In recent years, there has been a demand for coatings that, in addition to water repellency, have excellent adhesion to overprinting inks (hereinafter also referred to as overprinting suitability for inks) and adhesion between the paper substrate and the coating film of a coating agent (coating composition) (hereinafter also referred to as adhesion), and that can suppress water absorption.

[0008] The coating materials described in Patent Documents 1 and 2 did not provide a coating film that was excellent in water repellency, suitability for overprinting with ink, and adhesion, and that could also suppress water absorption, leaving room for further improvement. [Means for solving the problem]

[0009] The present invention is a coating composition containing a resin, a water repellent, and a urea-based compound, and the urea-based compound is contained in an amount of 10 to 60 mass % of the total solid content of the coating composition.

[0010] In the coating composition of the present invention, the urea compound is preferably urea. The water repellent preferably contains a paraffin-based compound. The urea compound is preferably contained in an amount of 20 mass % or more based on the total solid content of the coating composition. The water repellent is preferably contained in an amount of 20 to 50 mass % based on the total solid content of the coating composition. The present invention also relates to a laminate comprising a coating film of the above-mentioned coating composition on a paper substrate. Effect of the Invention

[0011] The present invention can provide a coating composition that is excellent in water repellency, suitability for overprinting with ink, and adhesion, and is capable of forming a coating film that can suppress water absorption. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <Coating Composition> The coating composition of the present invention contains a resin, a water repellent, and a urea compound, and the urea compound is contained in an amount of 10 to 60 mass % of the total solid content of the coating composition.

[0013] The coating composition of the present invention contains a specific amount of a urea compound, which exerts a salting-out effect, making it difficult for the ink printed on the coating film of the coating composition to penetrate into the paper substrate, which is believed to impart suitability for overprinting of the ink and adhesiveness to the coating film. In addition, it is believed that the urea compound produces the so-called "lotus effect," imparting water repellency to the coating film while forming a coating film that is less prone to water absorption. However, the present invention should not be construed as being limited to the above mechanism.

[0014] (resin) The coating composition of the present invention contains a resin.

[0015] The resin may be a resin neutralized with a basic compound.

[0016] Examples of the resin include urethane resin, polyester resin, acrylic resin, vinyl acetate resin, vinyl chloride resin, styrene-acrylic resin, and styrene-butadiene copolymer. The above resins may be used alone or in combination of two or more kinds, and may be in the form of an emulsion. Among these, styrene-acrylic resins are preferred from the viewpoint of various resistance properties of the coating film (water resistance, abrasion resistance, etc.).

[0017] The styrene-acrylic resin may be a polymer obtained by combining the following styrene-based monomer and acrylic-based monomer.

[0018] Examples of the styrene-based monomer include styrene, α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, and p-phenylstyrene.

[0019] Examples of the acrylic monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, iso-propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-amyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, dimethyl phosphate ethyl (meth)acrylate, diethyl phosphate ethyl (meth)acrylate, dibutyl phosphate ethyl (meth)acrylate, and 2-benzoyloxyethyl (meth)acrylate, (meth)acrylonitrile, 2-hydroxyethyl (meth)acrylate, (meth)acrylic acid, and maleic acid. Incidentally, (meth)acrylate means acrylate and / or methacrylate, and (meth)acrylic acid means acrylic acid and / or methacrylic acid.

[0020] The styrene-acrylic resin may contain a reaction product of maleic anhydride and a monoalcohol. Examples of the monoalcohol include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, pentanol, hexanol, decanol, alkyl carbitols such as ethyl carbitol, and alkyl cellosolves such as ethyl cellosolve.

[0021] The styrene-acrylic resin may contain the following monomers as necessary. Vinyl ether monomers such as vinyl methyl ether and vinyl isobutyl ether; Vinyl ketone monomers such as vinyl methyl ketone, vinyl ethyl ketone, and vinyl isopropenyl ketone; Olefins such as ethylene, propylene, and butadiene;

[0022] The method for preparing the polymer of the above monomer is not particularly limited, and the polymerization may be carried out by a known method. Furthermore, known polymerization initiators, chain transfer agents, polymerization inhibitors, and the like can also be used.

[0023] The above styrene-acrylic resins may be used alone or in combination of two or more kinds.

[0024] The above resin preferably has an acid value of 30 to 300 mg / KOH. When the acid value is within the above range, the storage stability of the coating composition can be improved. The acid value is more preferably 50 to 100 mg / KOH. 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.

[0025] The above resin preferably has a glass transition temperature (Tg) of 50° C. or lower, more preferably 30° C. or lower. When the glass transition temperature (Tg) is within the above range, compatibility with the water repellent agent described below can be favorably imparted. 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 n represents 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 means the value before neutralization with a basic compound described below.

[0026] Examples of the basic compound include ammonia, triethylamine, N,N-dimethylethanolamine, monoethanolamine, sodium hydroxide, potassium hydroxide, and polyamine compounds.

[0027] The method for neutralizing the resin 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.

[0028] The content of the resin is preferably 1 to 20% by mass in terms of solid content relative to the total mass of the coating composition. By ensuring that the content of the resin is within the above range, it is possible to form a coating film which can provide suitable water repellency and suitably inhibit water absorption. The content of the resin is more preferably 5 to 15% by mass in terms of solid content relative to the total mass of the coating composition.

[0029] (Water repellent) The coating composition of the present invention contains a water repellent.

[0030] Examples of the water repellent include paraffin compounds, rosin, polypropylene wax, Fischer-Tropsch wax, carnauba wax, and microcrystalline wax. The water repellents may be used alone or in combination of two or more kinds.

[0031] Among the above water repellents, paraffin-based compounds are preferred from the viewpoint of water repellency. The content of these water repellents is preferably 80 to 99% by mass based on the total amount of the water repellents.

[0032] The paraffinic compound is, for example, a compound having the molecular formula: CH3-(CH2) n Examples of the wax include paraffin wax and polyethylene wax, which are represented by the formula -CH3 (n=a positive number of 16 to 40, preferably 20 to 30).

[0033] From the viewpoint of water repellency, the water repellent agent preferably has a melting point of 50°C to 130°C, and more preferably 50°C to 80°C. The melting point can be measured in accordance with JIS K 2235:2022.

[0034] In addition, fluorine-based water repellents are not preferred from the viewpoint of the environment, silicone-based water repellents are not preferred from the viewpoint of slipperiness, and both fluorine-based and silicone-based water repellents are not preferred from the viewpoint of overprinting suitability of ink. Therefore, it is preferable that the ink does not contain a fluorine-based water repellent or a silicone-based water repellent.

[0035] An example of a commercially available water repellent agent is RP-907N (product name "Bertol RP-907N", paraffin-based compound, melting point 59°C, solid content 50%, manufactured by Kindai Chemical Industry Co., Ltd.).

[0036] The water repellent agent is contained in an amount of 10 to 50% by mass based on the total solid content of the coating composition. By including the water repellent in the above range, water repellency can be suitably imparted. The water repellent is contained in an amount of preferably 15 to 45% by mass, and more preferably 20 to 45% by mass, based on the total solid content of the coating composition.

[0037] (Urea-based compounds) The coating composition of the present invention contains a urea-based compound.

[0038] The urea compound is contained in an amount of 10 to 60% by mass based on the total solid content of the coating composition. By containing the urea compound in the above range, it is possible to form a coating film that is excellent in water repellency, suitability for overprinting with ink, and adhesion, and that can suppress water absorption. The urea compound is contained in an amount of preferably 20 mass % or more, more preferably 30 mass % or more, and even more preferably 40 mass % or more, of the total solid content of the coating composition.

[0039] Examples of the urea-based compounds include urea, dimethylacetylurea, benzenesulfonylurea, trimethylurea, tetraethylurea, tetramethylurea, triphenylurea, tetraphenylurea, methylurea, and hydantoin. The above urea compounds may be used alone or in combination of two or more kinds.

[0040] As the urea-based compound, urea is preferred from the viewpoint of the overprinting suitability of the ink.

[0041] (aqueous medium) The coating composition of the present invention may contain an aqueous medium.

[0042] Examples of the aqueous medium include water, alcohols such as methanol and ethanol, and amide compounds such as pyrrolidone. The aqueous medium may contain the above-mentioned resin (emulsion), water repellent, and other components other than the solid content.

[0043] The content of the aqueous medium is not particularly limited as long as it is within a range in which the urea compound can be dissolved, and is, for example, 20 to 80% by mass relative to the total mass of the coating composition.

[0044] (Additives) The coating composition of the present invention may contain lubricants, hardeners, plasticizers, wetting agents, surfactants, adhesion aids, defoamers, antistatic agents, trapping agents, antiblocking agents, preservatives, and the like. These additives can be appropriately selected from known additives.

[0045] (Method of producing coating composition) The method for producing the coating composition of the present invention is not particularly limited, and for example, the above materials may be mixed by stirring using a known method.

[0046] (Properties of Coating Composition) The coating composition of the present invention can form a coating film having excellent water repellency. In this specification, the water repellency is measured by the following method.

[0047] The coating composition of the present invention is applied to FS Daio Atlas unbleached (basis weight 120 g, paper substrate) using a mere bar (0.10 mm), and then ironed with a 180° C. iron for 5 seconds to obtain a laminate. The laminate is used to evaluate water repellency according to the JAPAN TAPPI Paper Pulp Test Method No. 68:2000. At room temperature, the laminate is tilted at an angle of 45° and a droplet of ion-exchanged water is dropped from 10 mm above the laminate. The state of the laminate after the droplet has passed over it is observed to determine the water repellency R0 to R10. A water repellency level of R9 or higher is considered to be excellent in water repellency. The water repellency is most preferably R10.

[0048] The coating composition of the present invention can form a coating film that can suppress water absorption. In this specification, the property of suppressing water absorption is evaluated by the following method using water absorbency.

[0049] A laminate is prepared in the same manner as in the water repellency method described above. The water absorbency of the coated surface of the laminate is measured in accordance with JIS P 8140:1998 under conditions of a temperature of 23° C. and a Cobb value (Cobb120) after a contact time of 120 seconds. If the water absorption rate is 20 or less, it is evaluated that water absorption can be suppressed. The water absorbency is preferably 19 or less, more preferably 18 or less, and even more preferably 17 or less.

[0050] The coating composition of the present invention can form a coating film having excellent adhesion. In this specification, adhesion is evaluated by the following method.

[0051] A laminate is prepared in the same manner as in the water repellency method described above. A cellophane tape (product name: Cellotape (registered trademark), manufactured by Nichiban Co., Ltd.) is applied to the surface of the laminate on which the coating film is formed, and the condition is visually confirmed when it is quickly peeled off. If the paper substrate is completely torn and adheres to the surface on which the coating is formed, the adhesion is rated as excellent.

[0052] The coating composition of the present invention can form a coating film that is excellent in suitability for overprinting of ink. In this specification, the overprinting suitability of an ink is evaluated by the following method.

[0053] A laminate is prepared in the same manner as in the water repellency method described above. On the surface of the laminate on which the coating film is formed, FK-FM DCB-312 indigo SSS-1 (ink composition, manufactured by Sakata Inx Corporation, diluted 50% with water) is applied using a 200-line hand proofer. Cellophane tape (product name: Cellotape (registered trademark), manufactured by Nichiban Co., Ltd.) is applied to the coated surface of the ink composition, and the adhesion of the coating film of the ink composition when it is quickly peeled off is visually confirmed. If the paper base material is completely torn and adheres to the surface on which the coating film (the coating composition and the coating film of the ink composition formed on the coating film) is formed, the paper base material is evaluated as having excellent overprinting suitability for the ink.

[0054] <Laminate> The laminate of the present invention comprises a coating of the coating composition of the present invention on a paper substrate.

[0055] The paper base material may be, for example, a liner base paper obtained by appropriately mixing two or more kinds of chemical pulp, mechanical pulp, recycled paper pulp, and the like. Furthermore, a base paper having a multi-layer structure formed by combining two or more pulp layers can also be used. Also, a corrugated board using the above-mentioned liner base paper can be used.

[0056] The method for applying the coating composition of the present invention to the paper substrate is not particularly limited, and any known printing or coating method can be used. For example, printing methods such as gravure printing, offset printing, flexographic printing, screen printing, and inkjet printing, and coating methods such as air knife coater, blade coater, bar coater, gravure coater, roll coater, roll knife coater, curtain coater, die coater, knife coater, screen coater, Mayer bar coater, kiss coater, air doctor coater, rod coater, squeeze coater, reverse roll coater, transfer roll coater, spray coater, and slot orifice coater can be used.

[0057] The coating amount of the coating composition of the present invention is 0.1 to 10 g / m in terms of solid content. 2 From the viewpoint of favorably imparting coating film resistance, the solid content is preferably 0.1 to 5 g / m 2 It is more preferable to set the above.

[0058] The present specification discloses the following:

[0059] The present disclosure (1) is a coating composition containing a resin, a water repellent, and a urea-based compound, the urea-based compound being contained in an amount of 10 to 60 mass% of the total solid content of the coating composition. The present disclosure (2) is the coating composition according to the present disclosure (1), wherein the urea-based compound is urea. The present disclosure (3) is the coating composition according to the present disclosure (1) or (2), wherein the water repellent contains a paraffin-based compound. The present disclosure (4) is the coating composition according to any one of the present disclosures (1) to (3), in which the urea compound is contained in an amount of 20 mass % or more based on the total solid content of the coating composition. The present disclosure (5) is the coating composition according to any one of the present disclosures (1) to (4), in which the water repellent is contained in an amount of 20 to 50 mass % based on the total solid content of the coating composition. The present disclosure (6) is a laminate comprising a coating film of the coating composition according to any one of the present disclosures (1) to (5) on a paper substrate. 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] <Resin> Resin 1 (product name: "Saibinol EK-61", solid content 40% by mass, styrene acrylic emulsion, acid value 87 mg KOH / g, glass transition temperature 24°C, alkali neutralized, manufactured by Saiden Chemical Industries, Ltd.) Resin 2 (product name "Joncryl PDX-7357", solid content 50 mass%, styrene acrylic emulsion, acid value 59 mg KOH / g, glass transition temperature -4°C, neutralizing alkali is ammonia, manufactured by BASF) <Water repellent> RP-907N (product name: "Bertol RP-907N", paraffin-based compound, melting point 59°C, solid content 50% by mass, manufactured by Kindai Chemical Industry Co., Ltd.) <Urea compounds> urea <Other> Defoamer (mineral oil-based defoamer) purified water

[0063] (Preparation of Coating Composition) The materials were mixed and stirred using a stirrer in the proportions shown in Table 1 to prepare coating compositions according to the examples and comparative examples.

[0064] <Water repellency> The prepared coating composition was applied to unbleached FS Daio Atlas (basis weight 120 g) using a mere bar (0.10 mm), and a laminate was obtained by applying an iron at 180° C. for 5 seconds. The laminate was used to evaluate water repellency in accordance with JAPAN TAPPI Paper Pulp Test Method No. 68:2000. At room temperature, the laminate was tilted at 45° and a droplet of ion-exchanged water was dropped from 10 mm above the laminate. The state of the laminate after the water droplet had passed over it was checked to determine the water repellency R0 to R10. The results are shown in Table 1. Test pieces that achieved R9 or higher were considered to have passed the test.

[0065] <Water absorption> A laminate was prepared in the same manner as in the evaluation of water repellency. The water absorbency of the coated surface of the laminate was measured in accordance with JIS P 8140:1998 under conditions of a temperature of 23° C. and a Cobb value (Cobb120) after a contact time of 120 seconds. The results are shown in Table 1. Note that samples with a water absorbency of 20 or less were judged to be acceptable.

[0066] <Adhesiveness> A laminate was prepared in the same manner as in the evaluation of water repellency. Cellophane tape (product name: Cellotape (registered trademark), manufactured by Nichiban Co., Ltd.) was applied to the surface of the laminate on which the coating film was formed, and the condition when it was quickly peeled off was visually observed and evaluated according to the following criteria. The results are shown in Table 1. Items rated as "good" were judged to pass. (Evaluation Criteria) ○: The paper base material is completely torn and adheres to the surface on which the coating film is formed. △: Part of the paper base is torn and the paper base is attached to the surface on which the coating film is formed. ×: Only the coating film formed is peeled off, and the paper base material is not torn.

[0067] <Ink overprinting suitability> A laminate was prepared in the same manner as in the water repellency test. On the surface of the laminate on which the coating film was formed, FK-FM DCB-312 indigo SSS-1 (ink composition, manufactured by Sakata Inx Corporation, diluted 50% with water) was applied using a 200-line hand proofer. Cellophane tape (product name: Cellotape (registered trademark), manufactured by Nichiban Co., Ltd.) was applied to the coated surface of the ink composition, and the adhesion of the coating film of the ink composition when it was quickly peeled off was visually observed and evaluated according to the following criteria. The results are shown in Table 1. Incidentally, a rating of "◯" was judged to be acceptable. (Evaluation Criteria) ○: The paper base material is completely torn, and the paper base material is attached to the surface on which the coating film (the coating film of the coating composition and the ink composition formed thereon) is formed. △: Part of the paper base is torn and the paper base is attached to the surface on which the coating film is formed. ×: Peeling occurred at the interface between the ink composition film and the coating composition film, and the paper base material was not torn.

[0068] [Table 1]

[0069] It was confirmed that the coating compositions of the examples were capable of forming coating films that were excellent in water repellency, suitability for overprinting with ink, and adhesion, and that could suppress water absorption. In addition, in Comparative Example 5, the urea compound precipitated from the coating composition, and each evaluation could not be performed. [Industrial Applicability]

[0070] It is possible to provide a coating composition that is excellent in water repellency, suitability for overprinting with ink, and adhesion, and is capable of forming a coating film that can suppress water absorption.

Claims

1. A coating composition comprising a resin, a water repellent, and a urea-based compound, The urea compound is contained in an amount of 10 to 60% by mass based on the total solid content of the coating composition. Coating composition.

2. The coating composition according to claim 1 , wherein the urea-based compound is urea.

3. The coating composition according to claim 1 or 2, wherein the water repellent agent comprises a paraffin-based compound.

4. 3. The coating composition according to claim 1, wherein the urea compound is contained in an amount of 20 mass % or more based on the total solid content of the coating composition.

5. 3. The coating composition according to claim 1, wherein the water repellent is contained in an amount of 20 to 50% by mass based on the total solid content of the coating composition.

6. A laminate comprising a coating of the coating composition according to claim 1 or 2 on a paper substrate.

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