Coating composition and coated paper

Abstract

To provide a coating composition that enables the formation of a coating layer with water repellency, suitability for bag fabrication (crack prevention and flexibility), and slipperiness.SOLUTION: A coating composition contains a resin, a water repellent, a urea compound, and an aqueous medium, wherein the resin contains a resin neutralized by a volatile basic compound and a resin neutralized by a nonvolatile basic compound, and the content of the water repellent is 1-28 mass% based on the total solid of the coating composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a coating composition and to coated paper. [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 ingredients, vinyl chloride resin, a plasticizer, calcium carbonate powder, a foaming agent, a foaming aid, and a moisture absorbent, and that uses fatty acid-treated urea or a urea-based compound as the foaming aid. [Prior art documents] [Patent documents]

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

[0006] The use of a coating agent containing such a resin and a urea-based compound on paper materials for paper bags is being considered.

[0007] Paper bags are primarily used as shopping bags, and are required to be water-repellent so that the products inside do not get wet even in rainy weather.

[0008] When making a paper bag, the paper material is folded to make the bag. Therefore, the coating agent applied to the paper needs to have the property of not causing cracks in the coating film even when the paper is folded. Furthermore, if the coating applied to the paper material is too hard, the folded part may open up, making it impossible to make a bag, so the coating film must also be flexible.

[0009] Furthermore, paper bags are made using a bag-making machine, and from the standpoint of production efficiency and yield, the coating agent is required to have the property of imparting slipperiness.

[0010] Conventional coating agents have not been able to form a coating film that combines water repellency, bag-making suitability (crack suppression, flexibility), and slipperiness, leaving room for further improvement. [Means for solving the problem]

[0011] The present invention is a coating composition containing a resin, a water repellent, a urea-based compound, and an aqueous medium, wherein the resin contains a resin neutralized with a volatile basic compound and a resin neutralized with a non-volatile basic compound, and the water repellent is contained in an amount of 1 to 28 mass % of the total solid content of the coating composition.

[0012] In the coating composition of the present invention, the content of the resin is preferably 20 to 50 mass % in terms of solid content relative to the total mass of the coating composition. The mass ratio of the resin neutralized with the volatile basic compound to the resin neutralized with the non-volatile basic compound in terms of solid content is preferably 7:1 to 1:1. The urea compound is preferably urea. The content of the urea compound is preferably 0.5 to 20% by mass relative to the total mass of the coating composition. The present invention also relates to a coated paper having a coating film of the above coating composition on a paper substrate. [Effects of the Invention]

[0013] The present invention can provide a coating composition that can form a coating film that combines water repellency, bag-making suitability (resistance to cracking, flexibility), and slip properties. DETAILED DESCRIPTION OF THE INVENTION

[0014] <Coating composition> The present invention is a coating composition containing a resin, a water repellent, a urea-based compound, and an aqueous medium, wherein the resin contains a resin neutralized with a volatile basic compound and a resin neutralized with a non-volatile basic compound, and the water repellent is contained in an amount of 1 to 28 mass % of the total solid content of the coating composition.

[0015] The coating composition of the present invention can impart water repellency to the coating film of the coating composition by combining a water repellent with a resin neutralized with a volatile basic compound. Furthermore, the combination of a water repellent with a resin neutralized with a non-volatile basic compound can impart slipperiness to the coating film of the coating composition. Furthermore, the use of a urea-based compound can impart bag-making suitability (resistance to cracking, flexibility) to the coating film of the coating composition while maintaining good water repellency and slipperiness. However, the present invention should not be construed as being limited to the above mechanism.

[0016] (resin) The coating composition of the present invention contains a resin.

[0017] The resin contains a resin neutralized with a volatile basic compound and a resin neutralized with a non-volatile basic compound. Hereinafter, the resin neutralized with the volatile basic compound and the resin neutralized with the non-volatile basic compound will be referred to simply as "resin."

[0018] 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, 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.).

[0019] Examples of the styrene-acrylic resin include polymers obtained by combining the following styrene-based monomers and acrylic-based monomers.

[0020] 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.

[0021] Examples of the acrylic monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (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, 2-benzoyloxyethyl (meth)acrylate, (meth)acrylonitrile, 2-hydroxyethyl (meth)acrylate, (meth)acrylic acid, and maleic acid. It should be noted that (meth)acrylate means acrylate and / or methacrylate, and (meth)acrylic acid means acrylic acid and / or methacrylic acid.

[0022] 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.

[0023] The styrene-acrylic resin may contain the following monomers as needed. 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;

[0024] The method for preparing a polymer of the above monomer is not particularly limited, and polymerization may be carried out by a known method. Also, known polymerization initiators, chain transfer agents, polymerization inhibitors, and the like can be used.

[0025] The styrene-acrylic resins may be used alone or in combination of two or more.

[0026] The 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 30 to 100 mg / KOH. In this specification, the term "acid value" refers to a theoretical acid value obtained by arithmetically calculating the number of milligrams of potassium hydroxide theoretically required to neutralize 1 g of the unneutralized resin. The acid value refers to the value before neutralization with a volatile basic compound or a non-volatile basic compound.

[0027] The resin preferably has a glass transition temperature (Tg) of 10°C or lower, more preferably 5°C or lower, and even more preferably 0°C or lower. By having the glass transition temperature (Tg) within the above range, compatibility with the water repellent agent described below can be suitably imparted. In this specification, the term "glass transition temperature" preferably refers to the theoretical glass transition temperature calculated by the following Wood's formula. 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's monomers 1, 2, 3...n. However, the glass transition temperature in Wood's equation is expressed in absolute temperature.) The glass transition temperature refers to the value before neutralization with a volatile basic compound or a non-volatile basic compound.

[0028] Examples of the volatile basic compound include ammonia, triethylamine, N,N-dimethylethanolamine, and monoethanolamine. Among these, ammonia is preferred from the viewpoint of suitably imparting water repellency. As used herein, "volatile" means that which evaporates when exposed to standard ambient air at 25°C and 1 atmosphere pressure.

[0029] Examples of non-volatile basic compounds include sodium hydroxide, potassium hydroxide, and polyamine compounds. In this specification, "non-volatile" means something that does not meet the requirements of "volatile" above.

[0030] The resin neutralized with the volatile basic compound and the resin neutralized with the non-volatile basic compound may be the same resin neutralized or different resins neutralized.

[0031] The method for neutralizing the resin is not particularly limited, and any known method can be used. For example, the above-mentioned volatile basic compound or non-volatile basic compound may be added to a resin having an acid value within the above range.

[0032] The content of the resin is preferably 20 to 50% 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 suitably impart water repellency, bag-making suitability (restraint of cracking, flexibility), and slipperiness. The content of the resin is more preferably 25 to 45 mass % in terms of solid content relative to the total mass of the coating composition.

[0033] The mass ratio in solid content between the resin neutralized with the volatile basic compound and the resin neutralized with the non-volatile basic compound is preferably 7:1 to 1:1. The above mass ratio makes it possible to suitably impart water repellency. The mass ratio of the resin neutralized with the volatile basic compound to the resin neutralized with the non-volatile basic compound in terms of solid content is more preferably 6:1 to 4:3.

[0034] (Water repellent) The coating composition of the present invention contains a water repellent.

[0035] Examples of the water repellent agent include rosin, solid paraffin, paraffin wax, polyethylene wax, polypropylene wax, Fischer-Tropsch wax, carnauba wax, and microcrystalline wax. The water repellents may be used alone or in combination of two or more.

[0036] Among the above water repellents, rosin and solid paraffin are preferred from the viewpoints of environmental friendliness and slip properties. The content of these water repellents is preferably 80 to 99% by mass relative to the total amount of the water repellents.

[0037] The water repellent preferably contains wax in order to provide the coating film with excellent abrasion resistance. Excellent abrasion resistance can further improve production efficiency and yield during bag production. As the wax, polyethylene wax and Fischer-Tropsch wax are more preferred. The content of the wax is preferably 0.1 to 10% by mass relative to the total amount of the water repellent.

[0038] It should be noted that fluorine-based water repellents are not preferred from an environmental standpoint, and silicone-based water repellents are not preferred from the standpoint of slipperiness. Therefore, it is preferable that the material does not contain a fluorine-based water repellent or a silicone-based water repellent.

[0039] Commercially available water repellents include, for example, OX-657, Celestial 40R, Celestial 80S (manufactured by Lion Specialty Chemicals), TH-44 (manufactured by Nicca Chemical Co., Ltd.), and Neolux (manufactured by Takamatsu Oil Co., Ltd.).

[0040] The water repellent agent is contained in an amount of 1 to 28 mass % based on the total solid content of the coating composition. By including the water repellent agent in the above range, bag-making suitability (flexibility) and slipperiness can be imparted. The water repellent agent is preferably contained in an amount of 6 to 22 mass % of the total solid content of the coating composition.

[0041] (Urea compounds) The coating composition of the present invention contains a urea-based compound.

[0042] Examples of the urea 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.

[0043] As the urea-based compound, urea is preferred from the viewpoint of suitably imparting bag-making suitability (flexibility).

[0044] The content of the urea compound is preferably 0.5 to 10% by mass, more preferably 1 to 9% by mass, based on the total mass of the coating composition, from the viewpoint of suitably imparting bag-making suitability (flexibility).

[0045] (aqueous medium) The coating composition of the present invention contains an aqueous medium.

[0046] Examples of the aqueous medium include water, alcohols such as methanol and ethanol, and amide compounds such as pyrrolidone. The aqueous medium may contain components other than the solid content, such as the resin (emulsion) and water repellent agent.

[0047] The content of the aqueous medium is not particularly limited, but is, for example, 20 to 80% by mass relative to the total mass of the coating composition.

[0048] (Inorganic fine particles) The coating composition of the present invention preferably contains inorganic fine particles from the viewpoint of providing suitable lubricity.

[0049] Examples of the inorganic fine particles include silica, alumina, titanium dioxide, and calcium carbonate. The inorganic fine particles may be used alone or in combination of two or more kinds.

[0050] The average particle size of the inorganic fine particles is preferably about 1 to 10 μm. The above-mentioned average particle size refers to a physical property value measured and calculated using a dynamic light scattering particle size distribution measuring device.

[0051] The content of the inorganic fine particles is preferably 0.01 to 1% by mass relative to the total mass of the coating composition.

[0052] (additives) The coating composition of the present invention may contain curing agents, plasticizers, wetting agents, surfactants, adhesion aids, antifoaming agents, antistatic agents, trapping agents, antiblocking agents, preservatives, and the like. These additives can be appropriately selected from known additives.

[0053] (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.

[0054] (Properties of Coating Composition) The coating composition of the present invention can form a coating film having excellent water repellency. In this specification, water repellency is measured by the following method.

[0055] The coating composition of the present invention is applied to unbleached FS Daioh Atlas paper (basis weight 120 g) using a hand proofer (200 L / inch) to obtain coated paper. Using the above coated paper, the water repellency is evaluated according to the method in accordance with JAPAN TAPPI Paper Pulp Test Method No. 68:2000. At room temperature, coated paper is tilted at a 45° angle, and a droplet of ion-exchanged water is dropped from 10 mm above the coated paper. The state of the water droplet after passing over the coated paper is checked to determine the water repellency level (R0 to R10). A material having a water repellency of R8 or higher is judged to have excellent water repellency. The water repellency is preferably R9 or more, and most preferably R10.

[0056] The coating composition of the present invention can form a coating film with excellent slip properties. In this specification, the slipperiness is evaluated by the following method.

[0057] Coated paper is prepared in the same manner as in the water-repellent method described above. The sliding angle of the surface of the coated paper coated with the coating composition is measured using a sliding angle tester manufactured by Toyo Seiki Seisakusho. A sliding angle of more than 15 degrees is considered to have excellent sliding properties.

[0058] The coating composition of the present invention is preferably capable of forming a coating film having excellent abrasion resistance. In this specification, the abrasion resistance is evaluated by the following method.

[0059] Coated paper is prepared in the same manner as in the water-repellent method described above. The surface of the coated paper to which the coating composition is applied is subjected to a Gakushin-type rub fastness test under the following conditions to evaluate the rub fastness. If the paper is free of stains, it is judged to have excellent abrasion resistance. (Measurement conditions) Load: 200g Number of times: 100 This paper: Kanakin

[0060] The coating composition of the present invention can form a coating film that is excellent in bag-making suitability (resistance to cracking, flexibility).

[0061] In this specification, the bag-making suitability (restraint of cracking) is evaluated by the following method. One part by mass (1 g) of the coating composition is poured into a circular container with a radius of 16 mm and dried for 24 hours to form a coating film. The coating film is folded in half and the fold is visually inspected for cracks. Products with no cracks at the folds are judged to be excellent in bag-making suitability (crack prevention).

[0062] In this specification, the bag-making suitability (flexibility) is evaluated by the following method. One part by mass (1 g) of the coating composition is poured into a circular container with a radius of 16 mm and dried for 24 hours to form a coating film. The coating film is folded in half, a 50g weight is placed on it, and it is visually checked whether the fold can be restored. Products that do not return to their original creases and remain folded are judged to have excellent suitability for bag making (flexibility).

[0063] The coating composition of the present invention has the above physical properties and can therefore be suitably used as a coating composition for paper bags.

[0064] <Coated paper> The coated paper of the present invention comprises a coating of the coating composition of the present invention on a paper substrate.

[0065] The paper substrate is not particularly limited as long as it is a paper substrate that can be used for paper bags, and for example, bleached or unbleached kraft paper, pure white roll paper, and fine paper can be used.

[0066] The method for applying the coating composition of the present invention to the paper substrate is not particularly limited, and application may be performed by a conventionally known general-purpose printing method such as gravure printing, flexographic printing, rotary letterpress printing, silk screen printing, or offset printing, or a coating method using a conventionally known general-purpose coater such as a bar coater, comma coater, or spray coater. The thickness of the coating film to be formed is preferably in the range of, for example, 0.5 to 10 μm.

[0067] The present specification discloses the following:

[0068] The present disclosure (1) is a coating composition containing a resin, a water repellent, a urea-based compound, and an aqueous medium, wherein the resin contains a resin neutralized with a volatile basic compound and a resin neutralized with a non-volatile basic compound, and the water repellent is contained in an amount of 1 to 28 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 content of the resin is 20 to 50 mass % in terms of solid content relative to the total mass of the coating composition. The present disclosure (3) is the coating composition according to the present disclosure (1) or (2), in which the mass ratio of the resin neutralized with the volatile basic compound to the resin neutralized with the non-volatile basic compound in solid content is 7:1 to 1:1. The present disclosure (4) is the coating composition according to any one of the present disclosures (1) to (3), wherein the urea-based compound is urea. The present disclosure (5) is the coating composition according to any one of the present disclosures (1) to (4), wherein the content of the urea compound is 0.5 to 20 mass % relative to the total mass of the coating composition. The present disclosure (6) is coated paper having a coating film of the coating composition according to any one of the present disclosures (1) to (5) on a paper substrate. [Example]

[0069] 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."

[0070] The materials used in the examples and comparative examples are as follows.

[0071] <Resin> (Resin neutralized with a volatile basic compound) Resin 1 (solid content 50%, styrene acrylic resin, acid value 59 mg KOH / g, glass transition temperature -4°C, ammonia neutralization) (Resin neutralized with a non-volatile basic compound) Resin 2 (solid content 56%, styrene acrylic resin, acid value 62 mg KOH / g, glass transition temperature -11°C, neutralized with sodium hydroxide) <Water repellent> OX-657 (product name "OX-657", solid paraffin, rosin, and nonionic surfactant, solids content 29%, manufactured by Lion Specialty Chemicals) (wax) Emaster 1309 (product name "Emaster 1309", Fischer-Tropsch wax / polyethylene wax, solids content 40%, manufactured by Nippon Seiro Co., Ltd.) <Urea compounds> urea <Aqueous medium> purified water <Other> Antifoaming agent (silicone-based antifoaming agent) Silica (amorphous silica, average particle size 6.8 μm)

[0072] (Preparation of Coating Composition) The materials were mixed and stirred using a stirrer according to the formulation shown in Table 1 to prepare coating compositions according to the examples and comparative examples.

[0073] <Water repellency> The prepared coating composition was applied to unbleached FS Daioh Atlas paper (basis weight 120 g) using a hand proofer (200 L / inch) to obtain coated paper. The water repellency of the coated paper was evaluated according to the method of JAPAN TAPPI Paper Pulp Test Method No. 68:2000. At room temperature, the coated paper was tilted at a 45° angle, and a droplet of ion-exchanged water was dropped from 10 mm above the coated paper. The state of the water droplet after passing over the coated paper was checked to determine the water repellency level R0 to R10. The results are shown in Table 1. Tests with a rating of R8 or higher were considered to be acceptable.

[0074] <Slipperiness> Coated paper was prepared in the same manner as in the evaluation of water repellency. The sliding angle of the coated surface of the coated paper was measured using a sliding angle tester manufactured by Toyo Seiki Seisaku-sha, and evaluated according to the following criteria. The results are shown in Table 1. Items rated "Good" were considered to be acceptable. (Evaluation criteria) ○: The sliding angle is more than 15 degrees. ×: Sliding angle is 15 degrees or less.

[0075] <Abrasion resistance> Coated paper was prepared in the same manner as in the evaluation of water repellency. The coated surface of the coated paper was subjected to a Gakushin-type rub fastness test under the following conditions and evaluated according to the following criteria. The results are shown in Table 1. Items rated "Good" were considered to pass. (Measurement conditions) Load: 200g Number of times: 100 This paper: Kanakin (Evaluation criteria) ○: The paper is not dirty △: Part of the paper is dirty ×: The entire paper is stained

[0076] <Bag making suitability (cracks)> One part by mass (1 g) of the prepared coating composition was poured into a circular container with a radius of 16 mm and dried for 24 hours to prepare a coating film. The prepared coating film was folded in half, and the fold was visually inspected for cracks and evaluated according to the following criteria. The results are shown in Table 1. A rating of "Good" was deemed to be acceptable. (Evaluation criteria) ○: No cracks were observed at the fold. ×: Cracks were observed at the fold.

[0077] <Bag making suitability (flexibility)> One part by mass (1 g) of the prepared coating composition was poured into a circular container with a radius of 16 mm and dried for 24 hours to prepare a coating film. The prepared coating film was folded in half, a 50 g weight was placed on top, and the restoration of the crease was visually confirmed and evaluated according to the following criteria. The results are shown in Table 1. A rating of "Good" was deemed to be acceptable. (Evaluation criteria) ○: The crease did not return to its original shape and remained folded. ×: The crease has returned to its original state

[0078] [Table 1]

[0079] From the coating compositions of the examples, it was confirmed that a coating film that combines water repellency, bag-making suitability (crack suppression, flexibility), and slip properties can be formed by containing a resin, a water repellent, a urea-based compound, and an aqueous medium, and the resin contains both a resin neutralized with a volatile basic compound and a resin neutralized with a non-volatile basic compound, and by setting the content of the water repellent within a specific range. [Industrial Applicability]

[0080] It is possible to provide a coating composition that can form a coating film that combines water repellency, bag-making suitability (resistance to cracking, flexibility), and slip properties.

Claims

1. A coating composition comprising a resin, a water repellent, a urea-based compound, and an aqueous medium, The resin includes a resin neutralized with a volatile basic compound and a resin neutralized with a non-volatile basic compound, The water repellent is contained in an amount of 1 to 28% by mass based on the total solid content of the coating composition. Coating composition.

2. The coating composition according to claim 1, wherein the content of the resin is 20 to 50 mass % in terms of solid content based on the total mass of the coating composition.

3. 3. The coating composition according to claim 1, wherein a mass ratio of the resin neutralized with the volatile basic compound to the resin neutralized with the non-volatile basic compound is 7:1 to 1:1 in solid content.

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

5. 2. The coating composition according to claim 1, wherein the content of the urea compound is 0.5 to 20% by mass based on the total mass of the coating composition.

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

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