Transparent material manufacturing method and water-repellent agent for cellulose-based material

Abstract

To provide a method for manufacturing a transparent material excellent in water repellency.SOLUTION: A method for manufacturing a transparent material according to one aspect of the present disclosure is a method for manufacturing a transparent material which has water repellency and whose haze is 30% or less. The transparent material is obtained by forming a coating film by applying a solution including a water-repellent component to a surface of a cellulose-based material, followed by drying the coating film.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a transparent material and a water repellent for cellulose-based materials.

Background Art

[0002] In order to address the apparent problem of marine plastic pollution and to build a sustainable society, attempts are being actively made to replace materials derived from fossil resources with natural materials and achieve carbon neutrality. Cellulose, the world's largest biomass, is one of the most promising candidates for such natural materials.

[0003] As a molded article containing cellulose, Patent Document 1 discloses a cellulose-based molded article having a specific thickness and haze. Such a cellulose-based molded article or cellophane, which is a film made of cellulose, is highly expected to replace packaging materials, which are the most common uses of disposable plastics.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, packaging materials are required to have high water repellency. Cellophane and the cellulose-based molded article disclosed in Patent Document 1 have room for improvement in terms of water repellency.

[0006] The inventors of the present invention considered imparting water repellency to cellophane and the cellulose-based molded article disclosed in Patent Document 1. As methods for imparting water repellency, reactions of a cellulose-based molded article with a silane compound or an isocyanate compound, impregnation of a cellulose-based molded article with a fluorine-based water repellent, and imparting a fractal structure to the surface of a cellulose-based molded article can be considered. However, when water repellency is imparted to a cellulose-based molded article by such a technique, the transparency decreases.

[0007] The present disclosure provides a method for producing a transparent material having excellent water repellency. Further, the present disclosure provides a water repellent for a cellulose-based material capable of obtaining a transparent material having excellent water repellency.

Means for Solving the Problems

[0008] One aspect of the present disclosure relates to the following method for producing a transparent material and a water repellent for a cellulose-based material. [1] A method for producing a transparent material having water repellency and a haze of 30% or less, A method for producing a transparent material, which comprises applying a solution containing a water-repellent component to the surface of a cellulose-based material to form a coating film, and drying the coating film to obtain a transparent material. [2] The production method according to [1], wherein the water-repellent component contains a fatty acid metal salt. [3] The production method according to [2], wherein the fatty acid constituting the fatty acid metal salt has 16 to 20 carbon atoms. [4] The production method according to [1], wherein the water-repellent component contains aluminum distearate. [5] The production method according to any one of [1] to [4], wherein the solution contains a hydrocarbon solvent and an alcohol having 1 to 5 carbon atoms. [6] The production method according to [5], wherein the amount of the alcohol having 1 to 5 carbon atoms with respect to 100 parts by mass of the hydrocarbon solvent is 0.25 to 20 parts by mass. [7] The production method according to any one of [1] to [6], wherein the solution contains ethanol and cyclohexane. [8] The production method according to any one of [1] to [7], wherein the cellulose-based material contains cellulose, methyl cellulose, and hydroxypropyl methyl cellulose. [9] The production method according to any one of [1] to [8], wherein the content of the water-repellent component in the solution is 2.5% by mass or less based on the total amount of the solution.

[10] The production method according to any one of [1] to [9], wherein the thickness of the dried coating film is 10 μm or less.

[11] A water-repellent agent for a cellulose-based material, comprising a fatty acid metal salt, a hydrocarbon-based solvent, and an alcohol having 1 to 5 carbon atoms. [Advantages of the Invention]

[0009] According to the present disclosure, a method for producing a transparent material having excellent water repellency is provided. Further, according to the present disclosure, a water-repellent agent for a cellulose-based material capable of obtaining a transparent material having excellent water repellency is provided. [Modes for Carrying Out the Invention]

[0010] Hereinafter, a plurality of embodiments of the present disclosure will be described in detail. The present invention is not limited to the embodiments described below. In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value of a numerical range at a certain step may be replaced with the upper limit value or the lower limit value of a numerical range at another step. In the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.

[0011] In this specification, that a material has water repellency means that the contact angle with respect to water is 90° or more on at least a part of the surface of the material. In this specification, a transparent material means a material having a haze of 30% or less.

[0012] [Method for Producing Transparent Material] Hereinafter, a method for producing a transparent material according to an embodiment will be described. The method for producing a transparent material according to this embodiment is to apply a solution containing a water-repellent component to the surface of a cellulose-based material to form a coating film, and dry the coating film to obtain a transparent material having water repellency. By drying the coating film containing the water-repellent component, the water-repellent component adheres to the surface of the cellulose-based material and water repellency is exhibited.

[0013] <Solution containing a water-repellent component> Examples of the water-repellent component include fatty acid metal salts and fatty acids. The water-repellent component is preferably a fatty acid metal salt. Thereby, the water-repellency and transparency of the transparent material tend to be further improved. The fatty acid metal salt is composed of a metal ion and a fatty acid.

[0014] The fatty acid and the number of carbon atoms of the fatty acid constituting the fatty acid metal salt are preferably 12 to 24, more preferably 14 to 20, still more preferably 16 to 20, and particularly preferably 16 to 18. Thereby, the water-repellency and transparency of the transparent material tend to be further improved.

[0015] Specific examples of the fatty acid and the fatty acid constituting the fatty acid metal salt include, for example, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, and lignoceric acid.

[0016] The number of fatty acids coordinated to the metal ion may be one, but is preferably two or more.

[0017] Examples of the metal ion include aluminum ion, magnesium ion, and calcium ion.

[0018] The water-repellent component is preferably aluminum distearate. Thereby, the water-repellency and transparency of the transparent material tend to be further improved.

[0019] The water-repellent component may be used alone or in combination of two or more, but is preferably used alone. Thereby, the transparency of the transparent material tends to be further improved.

[0020] The content of the water-repellent component in the solution may be 1% by mass or more, 1.5% by mass or more, or 2% by mass or more, and may be 4% by mass or less, 3.5% by mass or less, 3.0% by mass or less, or 2.5% by mass or less based on the total amount of the solution.

[0021] The solution contains a solvent. Examples of the solvent include hydrocarbon solvents and alcohols. The solvent is preferably a mixture of a hydrocarbon solvent and an alcohol having 1 to 5 carbon atoms. Thereby, the viscosity of the solution is reduced and the formation of irregularities on the surface of the transparent material is suppressed. As a result, the transparency of the transparent material tends to be further improved.

[0022] When the solvent is a mixture of a hydrocarbon solvent and an alcohol having 1 to 5 carbon atoms, the amount of the alcohol having 1 to 5 carbon atoms relative to 100 parts by mass of the hydrocarbon solvent is preferably 0.03 parts by mass or more, more preferably 0.2 parts by mass or more, still more preferably 0.25 parts by mass or more, and particularly preferably 0.3 parts by mass or more. The amount of the alcohol having 1 to 5 carbon atoms relative to 100 parts by mass of the hydrocarbon solvent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 4 parts by mass or less, and particularly preferably 0.5 parts by mass or less. Within the above numerical range, the transparency of the transparent material tends to be further improved. The amount of the alcohol having 1 to 5 carbon atoms relative to 100 parts by mass of the hydrocarbon solvent may be 0.25 to 20 parts by mass, 0.03 to 15 parts by mass, 0.2 to 4 parts by mass, 0.25 to 0.5 parts by mass, or 0.3 to 0.5 parts by mass.

[0023] Examples of the hydrocarbon solvent include alkanes and aromatic hydrocarbons. The alkane may be linear or cyclic. The number of carbon atoms of the hydrocarbon solvent is preferably 4 to 9, more preferably 5 to 8, and still more preferably 6 to 7. Thereby, the viscosity of the solution is reduced and the formation of irregularities on the surface of the transparent material tends to be suppressed.

[0024] Examples of hydrocarbon solvents include pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, icosane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, cyclododecane, cyclotridecane, cyclotetradecane, cyclopentadecane, cyclohexadecane, cycloheptadecane, cyclooctadecane, cyclononadecane, and cyclicosane. The hydrocarbon solvent is preferably cyclohexane. This tends to further improve the transparency of the transparent material.

[0025] The number of carbon atoms of the alcohol is preferably 1 to 5. This tends to further improve the transparency of the transparent material.

[0026] Examples of alcohols include methanol, ethanol, propanol, butanol, and pentanol. The alcohol is preferably ethanol. This tends to further improve the transparency of the transparent material.

[0027] The solvent is preferably a mixture of ethanol and cyclohexane. This reduces the viscosity of the solution and suppresses the formation of irregularities on the surface of the transparent material. As a result, the transparency of the transparent material tends to be further improved.

[0028] The content of the solvent in the solution may be 97.5% by mass or more, 98% by mass or more, or 98.5% by mass or more, and may be 97% by mass or less, 96.5% by mass or less, or 96% by mass or less, based on the total amount of the solution.

[0029] The solution containing a water-repellent component preferably contains a fatty acid metal salt, a hydrocarbon solvent, and an alcohol having 1 to 5 carbon atoms. By using this solution, it is possible to easily impart water repellency to a cellulose-based material while maintaining transparency without subjecting the cellulose-based material to chemical reactions or coatings made of petroleum-derived plastics and without using an adhesive.

[0030] The method of applying the solution containing a water-repellent component is not particularly limited, and examples thereof include a method of applying it with a cotton swab, a spray, or an applicator.

[0031] Examples of the method of drying the coating film include natural drying and oven drying.

[0032] The temperature for drying the coating film may be, for example, 25 to 150°C.

[0033] The time for drying the coating film may be, for example, 1 to 180 minutes.

[0034] [Cellulose-based material] The cellulose-based material contains a cellulose-based compound. Examples of such cellulose-based compounds include methyl cellulose and hydroxypropyl methyl cellulose (HPMC). Known methyl cellulose and hydroxypropyl methyl cellulose can be appropriately used. Examples of commercially available methyl cellulose include "Metlose MCE-4000 for Food Additives" manufactured by Shin-Etsu Chemical Co., Ltd. Examples of commercially available hydroxypropyl methyl cellulose include "Metlose SFE-4000 for Food Additives" manufactured by Shin-Etsu Chemical Co., Ltd.

[0035] The degree of substitution in the cellulose-based compound may be 45% or more, 60% or more, 65% or less, or 63% or less. In the present specification, the degree of substitution in a water-soluble cellulose-based compound means the ratio of the introduced substituents to the total amount of hydroxyl groups and introduced substituents contained in the cellulose-based compound.

[0036] The weight average molecular weight of the cellulose-based compound is not particularly limited, but is, for example, from 10,000 to 200,000. In the present specification, the weight average molecular weight means the weight average molecular weight determined by conversion to standard polystyrene by the GPC method.

[0037] The content of the cellulose-based compound in the cellulose-based material may be, for example, 95% by mass or more, or 100% by mass.

[0038] The haze of the cellulose-based material may be 30% or less, 20% or less, 15% or less, 10% or less, or 5% or less. The haze means a value measured by a haze meter in the thickness direction of the cellulose-based material.

[0039] The thickness of the cellulose-based material may be, for example, 0.1 mm or more, 1 mm or more, or 10 mm or more, and may be 0.1 mm or less, 0.05 mm or less, or 0.01 mm or less.

[0040] The shape of the cellulose-based material may be film-like or plate-like.

[0041] The cellulose-based material may be a molded body obtained by the following Method 1 or Method 2.

[0042] <Method 1> Method 1 includes the following steps (A1) to (C1). (A1) A step of obtaining a hydrogel by repeating a series of steps from step (b) to step (c) until the content of the cellulose-based compound in the object to be treated becomes 10% by mass or more, including the following steps (a), (b), and (c) (B1) A step of heating the molded body of the hydrogel while applying a pressing force (C1) A step of obtaining a cellulose-based molded body having a cellulose-based compound content of 95% by mass or more through the heat treatment in step (B1) (a) A step of preparing an object to be treated containing a water-soluble cellulose-based compound and water (b) A step of separating water from the object to be treated by heating the object to be treated (c) Step of cooling the object to be treated with increased cellulose compound content after the treatment in step (b)

[0043] <Method 2> Method 2 includes the following steps. (A2) Step of obtaining a cellulose-containing solution by dissolving cellulose in an aqueous lithium bromide solution under temperature conditions of 100 °C or higher (B2) Step of obtaining a molded body from the cellulose-containing solution (C2) Step of removing lithium bromide from the molded body by washing the molded body (D2) Step of heating the molded body after lithium bromide removal under a pressing force (E2) Step of obtaining a cellulose-based molded body with a cellulose content of 95% by mass or more after the heat treatment in step (D2)

[0044] The cellulose-based material may be cellophane, which is a film made of cellulose.

[0045] [Transparent material] The content of the water-repellent component in the transparent material may be 1% by mass or less, or 0.5% by mass or less based on the total amount of the transparent material.

[0046] The content of the cellulose-based compound in the transparent material is preferably 90% by mass or more, more preferably 95% by mass or less, still more preferably 99% by mass or more, and particularly preferably 99.5% by mass or more based on the total amount of the transparent material. Thereby, the transparent material tends to be excellent in environmental suitability.

[0047] The thickness of the dried product (water-repellent layer) of the coating film of the solution containing the water-repellent component is preferably 10 μm or less. Thereby, the transparent material tends to be more excellent in transparency. The thickness of the water-repellent layer may be, for example, 0.1 μm or more.

[0048] The cellulose-based compound contained in the transparent material may be the same as the cellulose-based material. The haze, thickness, and shape of the transparent material may be the same as those of the cellulose-based material.

[0049] Examples of the uses of the transparent material include packaging materials, packing materials, and structural materials.

[0050] [Water repellent for cellulose-based materials] The water repellent for cellulose-based materials according to this embodiment contains a fatty acid metal salt, a hydrocarbon-based solvent, and an alcohol having 1 to 5 carbon atoms. As the fatty acid metal salt, hydrocarbon-based solvent, and alcohol having 1 to 5 carbon atoms, those exemplified in the solution according to the above embodiment can be used. The content of each component may be within the range exemplified in the solution according to the above embodiment.

Examples

[0051] Hereinafter, the present disclosure will be described more specifically based on examples, but the present disclosure is not limited to the following examples.

[0052] (Example 1) Lithium bromide was dissolved in distilled water to prepare an aqueous lithium bromide solution in which 60% by mass of lithium bromide was dissolved. Cellulose (manufactured by Asahi Kasei Corporation, trade name: “Bencot”) was dissolved in the prepared aqueous lithium bromide solution so that the concentration of cellulose became 2% by mass. Further, a cellulose-containing liquid was prepared by heating and stirring the aqueous lithium bromide solution at 120 °C or higher. 140 g of the cellulose-containing liquid was poured into a heat-resistant container (12 cm in length × 12 cm in width × 10 cm in height), and allowed to cool at 25 °C to obtain a cellulose gel. The cellulose gel was washed by immersing it in distilled water to remove the contained lithium bromide. Next, drying was performed while applying a pressing force of 30 g / cm 2 to the cellulose gel from which lithium bromide had been removed. As a result, a cellulose molded body (thickness: 0.4 mm) was obtained as the cellulose-based material. The cellulose content of the cellulose-based material was 100% by mass. The cellulose-based material was dense without cracks and had a density of 1.3 g / cm 3It was. For the cellulose-based material, haze measurement and contact angle measurement were performed. As a result, the haze was 26.7% and the contact angle was 60.9°.

[0053] Next, 0.4 g of aluminum distearate was mixed with 20 g of cyclohexane, and the mixture was further stirred while heating to 65°C to prepare a gel-like aluminum distearate-cyclohexane solution. By adding 0.079 g (0.1 mL) of ethanol to this aluminum distearate-cyclohexane solution and stirring, an aluminum distearate-cyclohexane solution containing a trace amount of ethanol was prepared and used as a coating solution. This coating solution was applied to the surface of the cellulose-based material using a cotton swab to obtain a coating film. The ethanol and cyclohexane contained in the coating film were volatilized and dried. Thereby, a water-repellent transparent material was obtained. The content of aluminum distearate was 0.3% by mass based on the total amount of the transparent material. For the transparent material, haze measurement and contact angle measurement were performed. As a result, the haze was 17.7% and the contact angle was 93.5°.

[0054] (Example 2) Powdery methyl cellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: "Metrose MCE-4000 for food additives") as a water-soluble cellulose-based compound was dissolved in distilled water to prepare a treated product in which 2% by mass of methyl cellulose was dissolved. Next, 250 g of the obtained treated product was poured into a heat-resistant container (12 cm in length × 12 cm in width × 10 cm in height). By heating the heat-resistant container containing the treated product in an oven at 110°C for 3 hours, the treated product was phase-separated into a methyl cellulose gel and separated water. Then, the separated water was discharged from the heat-resistant container. The methyl cellulose gel was allowed to cool at room temperature until it reached room temperature. Next, the methyl cellulose gel was cooled in a refrigerator at an internal temperature of 4°C for 1 hour to obtain a treated product containing methyl cellulose and water. By performing this heat-induced water separation and cooling treatment 7 times, a hydrogel containing methyl cellulose (8 cm in length × 8 cm in width × 0.25 cm in thickness) was obtained. Next, with respect to the hydrogel containing methyl cellulose, 30 g / cm 2Drying was carried out while applying a pressing force. As a result, a methyl cellulose molded body (original thickness 0.5 mm) was obtained as a cellulose-based material. The cellulose content of the cellulose-based material was 100% by mass. The cellulose-based material was dense without cracks and fractures, and the density was 1.3 g / cm 3 It was. For the cellulose-based material, haze measurement and contact angle measurement were carried out by the method described later. As a result, the haze was 5.4% and the contact angle was 77.5°.

[0055] Next, the cellulose-based material was subjected to water-repellent treatment with a coating liquid in the same manner as in Example 1 to obtain a transparent material. The content of aluminum distearate was 0.3% by mass based on the total amount of the transparent material. For the transparent material, haze measurement and contact angle measurement were carried out by the method described later. As a result, the haze was 5.9% and the contact angle was 95.8°.

[0056] (Example 3) A hydrogel containing hydroxypropylmethylcellulose was obtained in the same manner as in Example 2, except that hydroxypropylmethylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: "Metrose SFE-4000 for food additives"), a water-soluble cellulose-based compound, was used. Drying was carried out while applying a pressing force of 30 g / cm 2 As a result, a hydroxypropylmethylcellulose molded body (thickness 0.5 mm) was obtained as a cellulose-based material. The cellulose content of the cellulose-based material was 100% by mass. The cellulose-based material was dense without cracks and fractures, and the density was 1.3 g / cm 3 It was. For the cellulose-based material, haze measurement and contact angle measurement were carried out by the method described later. As a result, the haze was 15% and the contact angle was 80°.

[0057] Next, a water-repellent treatment was performed on the cellulose-based material with a coating liquid in the same manner as in Example 1 to obtain a transparent material. The content of aluminum distearate was 0.3% by mass based on the total amount of the transparent material. For the transparent material, haze measurement and contact angle measurement were performed by the methods described below. As a result, the haze was 15% and the contact angle was 94°.

[0058] (Example 4) As the cellulose-based material, a water-repellent treatment was performed in the same manner as in Example 1 except that cellophane (a transparent thin film made of cellulose, manufactured by Hayco Co., Ltd., trade name "rolled cellophane") was used instead of the cellulose molded body to obtain a transparent material. The content of aluminum distearate was 0.3% by mass based on the total amount of the transparent material. Haze measurement and contact angle measurement were performed on the cellophane before and after the water-repellent treatment. As a result, in the cellophane before the water-repellent treatment, the haze was 2.8% and the contact angle was 28.9°. In the cellophane after the water-repellent treatment, the haze was 3.8% and the contact angle was 107.2°.

[0059] [Measurement of Haze] For the measurement, a spectrophotometer V-750 (device name, manufactured by JASCO Corporation) equipped with an integrating sphere unit ISV-922 (device name, manufactured by JASCO Corporation) was used.

[0060] [Measurement of Contact Angle with Water] For the measurement, SImage Auto 100 (device name, manufactured by Excimer Co., Ltd.) was used. A 3.6 μL water droplet was dropped onto the surface of the cellulose-based material of each example and the surface of the transparent material subjected to the water-repellent treatment, and the contact angle 20 seconds after the dropping was measured.

Claims

1. A method for manufacturing a transparent material having water repellency and a haze of 30% or less, comprising applying a solution containing a water-repellent component to the surface of a cellulose-based material to form a coating film, and drying the coating film to obtain a transparent material.

2. The manufacturing method according to Claim 1, wherein the water-repellent component contains a fatty acid metal salt.

3. The manufacturing method according to Claim 2, wherein the fatty acid constituting the fatty acid metal salt has 16 to 20 carbon atoms.

4. The manufacturing method according to Claim 1, wherein the water-repellent component contains aluminum distearate.

5. The manufacturing method according to Claim 1, wherein the solution contains a hydrocarbon solvent and an alcohol having 1 to 5 carbon atoms.

6. The manufacturing method according to Claim 5, wherein the amount of the alcohol having 1 to 5 carbon atoms relative to 100 parts by mass of the hydrocarbon solvent is 0.25 to 0.5 parts by mass.

7. The manufacturing method according to Claim 1, wherein the solution contains ethanol and cyclohexane.

8. The manufacturing method according to Claim 1, wherein the cellulose-based material contains cellulose, methylcellulose, and hydroxypropylmethylcellulose.

9. The manufacturing method according to Claim 1, wherein the content of the water-repellent component in the solution is 2.5% by mass or less based on the total amount of the solution.

10. The manufacturing method according to Claim 1, wherein the thickness of the dried coating film is 10 μm or less.

11. A water-repellent agent for a cellulose-based material, containing a fatty acid metal salt, a hydrocarbon solvent, and an alcohol having 1 to 5 carbon atoms.