JP7619033B2 - Liquid-repellent structure and packaging material - Google Patents

Description

This disclosure relates to a liquid-repellent structure and a packaging material having this liquid-repellent structure on the side that comes into contact with an article.

Various forms of water-repellent structures are known. For example, Patent Document 1 discloses a water-repellent structure in which a fine particle layer in which scale-like inorganic fine particles are fixed by a binder resin and a water-repellent film layer covering the surface of the fine particle layer are provided on the surface of a substrate. Patent Document 2 discloses a single-layer water-repellent heat seal film containing a thermoplastic resin and hydrophobic particles. Patent Document 3 discloses that in a water-repellent laminate for a lid material comprising a substrate and a thermal adhesive layer on the substrate, the thermal adhesive layer contains a thermoplastic resin, water-repellent fine particles, and bead particles having an average particle size larger than that of the water-repellent fine particles.

JP 2017-132055 A JP 2017-155183 A International Publication No. 2017/204258

In the inventions described in Patent Documents 1 to 3, water repellency is evaluated based on the contact angle with a water droplet. In the inventions described in Patent Documents 2 and 3, yogurt repellency (adhesion of yogurt) is also evaluated. However, the inventions described in these documents do not consider liquid repellency against viscous liquids containing oil (e.g. curry, mayonnaise).

The present disclosure aims to provide a liquid-repellent structure that has excellent liquid repellency against water, as well as against oil or viscous liquids containing oil. The present disclosure also aims to provide a packaging material that has the above-mentioned liquid-repellent structure on the side that comes into contact with an article.

That is, the present invention relates to a liquid-repellent structure having a base layer and a liquid-repellent layer laminated in this order on a surface to be imparted with liquid repellency,
The underlayer contains a first filler,
the liquid-repellent layer contains a fluorine-containing resin and a second filler,
the gloss of the surface of the liquid-repellent layer at a measurement angle of 60 degrees is within a range of 1.5 to 5.0 GU;
the second filler is a spherical filler,
The liquid repellent layer further contains a scale-like filler,
The first filler has an average primary particle size in the range of 5 to 30 μm;
The average primary particle size of the second filler is within a range of 10 to 100 nm;
The liquid repellent structure is characterized in that the average primary particle diameter of the scale-like filler is within the range of 4 to 6 μm .

Next, the invention described in claim 2 is the liquid-repellent structure described in claim 1, characterized in that the weight of the scaly filler divided by the weight of the spherical filler is within the range of 0.05 to 0.30 .

Next, a third aspect of the present invention is the liquid repellent structure according to the first or second aspect, characterized in that the first filler is larger than the second filler .

Next, a fourth aspect of the present invention is a packaging material having the liquid repellent structure according to any one of the first to third aspects on a side that comes into contact with an article .

Glossiness is a concept related to unevenness at the wavelength level of visible light. As will be seen from the examples and comparative examples described below, when this glossiness is within the range of 1.5 to 5.0 GU, it not only exhibits excellent liquid repellency against water, but also against viscous liquids that contain oil (e.g. mayonnaise).

FIG. 1 is a cross-sectional view showing a typical example of a liquid repellent structure according to the present invention.

Specific examples of the present disclosure will now be described with reference to the accompanying drawings. Figure 1 shows a specific example of a liquid repellent structure 10 according to the present invention.

As can be seen from this figure, the liquid-repellent structure 10 comprises a substrate 1 having a surface to be treated (the surface to which liquid repellency is to be imparted), and a base layer 2 and a liquid-repellent layer 3 formed in sequence on the surface to be treated.

The glossiness of the surface of this liquid-repellent layer 3 at a measurement angle of 60 degrees must be within the range of 1.5 to 5.0 GU. As will be seen from the examples and comparative examples described later, when the glossiness is either greater or less than this range, the liquid repellency is poor. In particular, the property of repelling viscous liquids containing oil, such as mayonnaise, and preventing their adhesion (peelability) is poor. In contrast, when the glossiness is within this range, the layer exhibits excellent liquid repellency against water and oil, and also exhibits excellent liquid repellency against viscous liquids containing oil (such as mayonnaise).

The gloss level varies depending on the composition and coating amount of the undercoat layer 2 and the liquid-repellent layer 3, so the gloss level of the liquid-repellent layer 3 surface can be kept within the above range by appropriately controlling the composition and coating amount of each of these layers. Therefore, each layer, including the substrate 1, will be described in order.

(Substrate)
The substrate 1 is not particularly limited as long as it has a surface to be imparted with liquid repellency and serves as a support, and may be, for example, a film (thickness: about 10 to 200 μm) or a plate (thickness: about 1 to 10 mm). Examples of film-shaped substrates include paper, resin film, metal foil, etc. By using the inner surface of a film packaging material made of these materials as the treated surface and sequentially forming the undercoat layer 2 and the liquid repellent layer 3 on this, a packaging bag to which the contents do not easily adhere can be obtained. Examples of plate-shaped substrates include paper, resin, metal, glass, etc.

In addition, by forming a base layer 2 and a liquid-repellent layer 3 on the inner surface of a container molded from these materials, a container to which the contents do not easily adhere can be obtained.

Examples of the paper include fine paper, special fine paper, coated paper, art paper, cast coated paper, imitation paper, craft paper, etc. Examples of the resin include polyolefin, acid-modified polyolefin, polyester (e.g., polyethylene terephthalate (PET)), polyethylene (PE),
Examples of the material include polypropylene (PP), polyamide (PA), polyvinyl chloride (PVC), cellulose acetate, cellophane resin, etc. Examples of the metal include aluminum, nickel, etc.

(Base layer 2)
The underlayer 2 is a layer disposed between the substrate 1 and the liquid-repellent layer 3, and is formed so as to cover a part or the whole of the treated surface of the substrate 1. By interposing the underlayer between the substrate 1 and the liquid-repellent layer 3, it is possible to increase the adhesion between the substrate 1 and the liquid-repellent layer 3. Furthermore, by providing the underlayer 2, it is possible to further improve the liquid repellency of the liquid-repellent structure.

The base layer 2 contains at least a thermoplastic resin 2R.

Thermoplastic resin 2R is not particularly limited, and examples thereof include low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-α-olefin copolymer, homo, block, or random polypropylene, propylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, etc. For example, an ethylene-α-olefin copolymer can be said to be a block copolymer or random copolymer of propylene and α-olefin. Examples of the α-olefin component include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene, etc.

Thermoplastic resin 2R may be a modified polyolefin modified with a specific acid. The modified polyolefin is obtained by graft-modifying a polyolefin with an unsaturated carboxylic acid derivative component derived from, for example, an unsaturated carboxylic acid, an acid anhydride of an unsaturated carboxylic acid, or an ester of an unsaturated carboxylic acid. In addition, modified polyolefins such as hydroxyl-modified polyolefins and acrylic-modified polyolefins can also be used as the polyolefin. Examples of modified polyolefin resins include Auroren manufactured by Nippon Paper Industries Co., Ltd., ZAIXXEN manufactured by Sumitomo Seika Chemicals Co., Ltd., UNISTOLE manufactured by Mitsui Chemicals, Inc., and ARROWBASE manufactured by Unitika Ltd.

As shown in FIG. 1, the underlayer 2 must contain a first filler 2F. It is desirable that this first filler 2F is larger than the second filler 3Fβ contained in the liquid-repellent layer 3, which will be described later. When the underlayer 2 contains the first filler 2F having such a large particle diameter, the surface of the underlayer 2 is unevenly formed based on this first filler 2F, and the liquid-repellent layer 3 is provided along the unevenness of the surface of the underlayer 2. This makes it possible to make the unevenness of the surface of the liquid-repellent layer 3 large and complex, thereby reducing its glossiness and increasing the liquid repellency. It is desirable that the average primary particle diameter of the first filler 2F is within the range of 5 to 30 μm.

For example, the following commercially available products can be used as the first filler 2F. An example of a commercially available silica filler is Sunsphere manufactured by AGC Si-Tech Co., Ltd. An example of a commercially available silicone filler is Silicone Powder KMP manufactured by Shin-Etsu Silicone Co., Ltd. An example of a commercially available acrylic resin filler is Ganz Pearl manufactured by Aica Kogyo Co., Ltd. and Art Pearl (crosslinked acrylic beads) manufactured by Negami Chemical Industry Co., Ltd. An example of a commercially available urethane resin filler is Art Pearl (crosslinked urethane beads) manufactured by Negami Chemical Industry Co., Ltd. An example of a commercially available polyethylene filler is Flow Beads manufactured by Sumitomo Seika Chemicals Co., Ltd.

The undercoat layer 2 may contain other additives as necessary. Examples of other additives include flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers, and tackifiers.

The undercoat layer 2 can be formed by preparing a coating liquid containing a thermoplastic resin 2R, a first filler 2F and other additives that are added as necessary, and a solvent, applying the coating liquid onto the substrate 1 to form a coating film, and drying the coating film.

That is, first, a coating liquid containing the first filler 2F, the thermoplastic resin 2R, a solvent, and additives as necessary is prepared. Examples of the solvent include water, alcohol, and organic solvents. The thermoplastic resin may be in the form of an emulsion dispersed in water, alcohol, or the like. Such an emulsion may be prepared by a method of emulsifying a polymer produced by a polymerization reaction of the corresponding monomer, or may be prepared by emulsion polymerization of the corresponding monomer.

The obtained coating liquid is applied onto the substrate 1. Any known method can be used as the coating method without any particular restrictions, including immersion (dipping) method, and methods using a spray, coater, printer, brush, etc. In addition, the types of coaters and printers used in these methods and their coating methods include gravure coaters such as direct gravure method, reverse gravure method, kiss reverse gravure method, and offset gravure method, reverse roll coaters, microgravure coaters, coaters combined with chamber doctor, air knife coaters, dip coaters, bar coaters, comma coaters, die coaters, etc.

The coating film formed on the substrate 1 is dried and cured by heating. This allows the undercoat layer 2 to be formed on the substrate 1.

The coating amount of the undercoat layer 2 may be within the range of 1.0 to 10.0 g/ ^m2 . As will be seen from Examples 8 and 9 described later, the glossiness at a measurement angle of 60 degrees of the surface of the liquid-repellent layer 3 varies depending on the coating amount of the undercoat layer 2, so it is desirable to select an optimal coating amount within the range of 1.0 to 10.0 g/ ^m2 .

(Liquid-repellent layer)
The liquid-repellent layer 3 is a layer having liquid repellency, and is formed so as to cover the surface of the undercoat layer 2. Liquid repellency is a concept that includes both water repellency and oil repellency, and specifically, it is a property of repelling liquid or oily materials in a liquid, semi-solid, or gel state. Examples of water-based or oily materials include water, oil, mayonnaise, yogurt, curry, fresh cream, jelly, pudding, syrup, porridge, soup, and other foods, detergents such as hand soap and shampoo, medicines, cosmetics, and chemicals. In the liquid-repellent structure 10, the liquid-repellent layer 3 forms the innermost layer or the outermost layer so as to be in direct contact with these.

This liquid-repellent layer 3 contains a binder resin 3R and a filler 3F dispersed in the binder resin 3R. In addition, other additives may be included as necessary within a range that does not impair the liquid-repellent function. In this example, the filler 3F is composed of a scale-like third filler 3Fα and a spherical second filler 3Fβ that is smaller than the third filler 3Fα. By blending such spherical second filler 3Fβ into the liquid-repellent layer 3, a fine and complex uneven structure can be formed on the surface of the liquid-repellent layer 3. In addition, by blending scale-like third filler 3Fα in addition to the spherical second filler 3Fβ, a fine and even more complex uneven structure can be formed on the surface of the liquid-repellent layer 3. In this way, complex unevenness is formed on the surface of the liquid-repellent layer 3, which comes into contact with and supports contents such as oil or liquids containing oil, thereby further enhancing its liquid repellency.

In addition, when the liquid-repellent layer 3 contains the scaly second filler 3Fα in addition to the spherical third filler 3Fβ, if the weight of the scaly filler 3Fα is small, it is necessary to increase the amount of liquid-repellent layer 3 applied to cover the base layer 2, and the coarse unevenness formed by the scaly filler 3Fα will be buried, making it difficult to form a fine and complex uneven structure. To avoid this, and to cover the base layer 2 with a small amount of application and form a fine and complex uneven structure on its surface, it is desirable that the value obtained by dividing the weight of the scaly filler 3Fα by the weight of the spherical filler be within the range of 0.05 to 0.30.

Next, the binder resin 3R contains at least a fluorine-containing resin. The binder resin 3R may further contain one or both of a thermoplastic resin and a crosslinking agent. When the binder resin 3R contains a crosslinking agent, the binder resin 3R in the liquid-repellent layer 3 may have a crosslinked structure in which the fluorine-containing resin and the thermoplastic resin are crosslinked via the crosslinking agent.

The fluorine-containing resin is not particularly limited, and resins having structures such as perfluoroalkyl, perfluoroalkenyl, and perfluoropolyether can be used as appropriate. From the viewpoint of further improving the liquid repellency of the liquid repellent layer 3, it is preferable that the fluorine-containing resin contains a fluorine-acrylic copolymer. The fluorine-acrylic copolymer is a copolymer consisting of a fluorine-containing monomer and an acrylic monomer. The fluorine-acrylic copolymer may be a block copolymer or a random copolymer. By using the fluorine-acrylic copolymer, the weather resistance, water resistance, chemical resistance, and film-forming properties of the liquid repellent layer 3 can also be improved.

The fluorine content in the fluorine-containing resin is, for example, 30 to 60 mass %, and may be 40 to 50 mass %. The fluorine content refers to the ratio of the mass of fluorine atoms to the total mass of the atoms constituting the fluorine-containing resin.

As the fluorine-containing resin, commercially available fluorine-based paints can be used. Examples of commercially available fluorine-based paints include Asahi Guard manufactured by Asahi Glass Co., Ltd., SF Coat manufactured by AGC Seimi Chemical Co., Ltd., Futergent manufactured by Neos Co., Ltd., Fluorolink manufactured by Solvay, Unidyne manufactured by Daikin Industries, Ltd., H-3539 series manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and Modiper F series manufactured by NOF Corporation.

From the viewpoint of further improving the liquid repellency against liquids containing surfactants and having high viscosity (e.g., hand soap, body soap, shampoo, and rinse), the fluorine-containing resin may not contain structural units derived from pyrrolidone or its derivatives (pyrrolidones). Examples of pyrrolidones include N-vinyl-2-pyrrolidone, N-vinyl-3-methyl-2-pyrrolidone, N-vinyl-5-methyl-2-pyrrolidone, and N-vinyl-3,3-dimethyl-2-pyrrolidone. Examples of fluorine-containing resins that do not contain structural units derived from pyrrolidones include Asahi Guard AG-E060, AG-E070, and AG-E090 manufactured by Asahi Glass Co., Ltd., and Unidyne TG-8111 manufactured by Daikin Industries, Ltd.

There are no particular limitations on the thermoplastic resin, and for example, the resin used as the thermoplastic resin 2R of the undercoat layer 2 can be used. For example, low-density polyethylene, etc.

The melting point of the thermoplastic resin is, for example, 50 to 135°C. By having a melting point of 135°C or less, the fluorine-containing resin is easily bled out onto the surface of the liquid-repellent layer 3. By having the fluorine-containing resin bleed out onto the surface, the surface free energy can be reduced, and this allows the surface of the liquid-repellent layer 3 to exhibit excellent liquid repellency. Note that, although there is a method of drying at high temperatures to promote the bleeding out of the fluorine-containing resin, if the melting point of the thermoplastic resin is too high, a correspondingly high temperature is required, which may cause problems such as deformation of the substrate 1. On the other hand, by having a melting point of 50°C or more, a certain degree of crystallinity is ensured, and thus the occurrence of blocking due to softening is suppressed. From this viewpoint, the melting point of the thermoplastic resin is preferably 60 to 120°C.
°C is more preferable.

As the thermoplastic resin, it is also possible to use modified polyolefins modified with a specific acid. The modified polyolefins are obtained by graft-modifying polyolefins with unsaturated carboxylic acid derivative components derived from, for example, unsaturated carboxylic acids, acid anhydrides of unsaturated carboxylic acids, esters of unsaturated carboxylic acids, etc. In addition, modified polyolefins such as hydroxyl-modified polyolefins and acrylic-modified polyolefins can also be used as the polyolefin. Examples of modified polyolefin resins include Auroren manufactured by Nippon Paper Industries Co., Ltd., Zaixen manufactured by Sumitomo Seika Chemicals Co., Ltd., Unistall manufactured by Mitsui Chemicals, Inc., and Arrowbase manufactured by Unitika Ltd.

The modified polyolefin is also preferred from the viewpoint that it easily reacts with a crosslinking agent to form a crosslinked structure because functional groups have been introduced into it. Examples of the functional groups include carboxyl groups, hydroxyl groups, (meth)acryloyl groups, and amino groups. By using modified polyolefins having these functional groups together with a crosslinking agent described below, a crosslinked structure consisting of a thermoplastic resin, a fluorine-containing resin, and a crosslinking agent is formed in the liquid-repellent layer 3, and the liquid-repellent layer 3 can be given better durability.

The crosslinking agent preferably has a functional group that reacts with the fluorine-containing resin. Examples of such crosslinking agents include crosslinking agents having functional groups such as aziridine groups, isocyanate groups, carbodiimide groups, and amino groups. Examples of commercially available crosslinking agents include Chemitite manufactured by Nippon Shokubai Co., Ltd., Takenate manufactured by Mitsui Chemicals, Inc., Carbodilite manufactured by Nisshinbo Chemical Inc., Meikanate manufactured by Meisei Chemical Industry Co., Ltd., and Cymel manufactured by Cytec Industries, Inc.

In addition, fluorine-containing resins are generally used as aqueous dispersions in which they are dispersed in water. Therefore, many fluorine-containing resins have hydrophilic groups such as hydroxyl groups and amino groups to enhance their affinity with water. By using a crosslinking agent having functional groups that react with the fluorine-containing resin, these functional groups of the fluorine-containing resin react with the functional groups of the crosslinking agent to form a crosslinked structure in the liquid-repellent layer 3. In addition, these functional groups of the fluorine-containing resin are reduced by reacting with the crosslinking agent, so that the functional groups remaining in the liquid-repellent layer 3 are reduced. Therefore, even if the liquid-repellent layer 3 is in contact with a liquid for a long period of time, the decrease in liquid repellency can be suppressed, and excellent liquid repellency can be maintained for a long period of time. In addition, when the fluorine-containing resin is used as a dispersion in which it is dispersed in a solvent other than water, the fluorine-containing resin may have a structure (e.g., a hydrocarbon chain, etc.) to enhance its affinity with the solvent used.

The content of thermoplastic resin in binder resin 3R (based on the mass of binder resin 3R) is, for example, 5 to 90 mass%, and may be 10 to 50 mass% or 20 to 30 mass%. If the content of thermoplastic resin in binder resin 5b is 5 mass% or more, it is possible to sufficiently prevent the second filler 3Fα from falling off from the liquid-repellent layer 3, while if it is 90 mass% or less, it is possible to sufficiently ensure the content of fluorine-containing resin and crosslinking agent, and the liquid-repellent layer 3 is likely to exhibit excellent liquid repellency and durability.

Next, examples of materials constituting the scaly third filler 3Fα include silica, mica, aluminum oxide, talc, titanium oxide, calcium carbonate, barium sulfate, zinc oxide, smectite, and zeolite. An example of a commercially available product of scaly silica is Sunlovely manufactured by AGC Si-Tech Co., Ltd. An example of a commercially available product of scaly mica is Repco Mica manufactured by Repco Co., Ltd. An example of a commercially available product of scaly aluminum oxide is Serashure manufactured by Kawai Lime Industry Co., Ltd. The third filler 3Fα may not have been subjected to a hydrophobic or liquid-repellent treatment, or may have been subjected to such a hydrophobic or liquid-repellent treatment.

As shown in the figure, the scale-like third filler 3Fα may form an aggregate inside the liquid-repellent layer 3. These fillers 3Fα and their aggregates form unevenness on the surface of the liquid-repellent layer 3. The aggregate is composed of the third filler 3Fα and the binder resin 3R that covers it.

The average primary particle size of the scaly third filler 3Fα is preferably 0.1 to 6 μm, and may be 0.1 to 4 μm or 4 to 6 μm. When the average primary particle size of the third filler 3Fα is 0.1 μm or more, aggregates are easily formed, while when the average primary particle size is 6 μm or less, the liquid repellency resulting from the complex and fine shape of the third filler 3Fα is fully expressed.

The weight of the third filler 3Fα contained in the liquid-repellent layer 3 is preferably in the range of 0.01 to 2.5 g/m ^2. It may be 0.01 to 1.5 g/m ² , or may be 0.01 to 0.6 g/m ^2. If the weight of the third filler 3Fα is less than 0.01 g/m ² , the filler 3Fα is embedded in the binder resin 3R and cannot be given a complex scale-like uneven shape, so liquid repellency is not obtained. If the weight exceeds 2.5 g/m ² , the coarse unevenness formed by the underlayer 2 is embedded, and liquid repellency is not obtained. On the other hand, if the weight of the filler 3Fα is in the range of 0.01 to 2.5 g/m ² , appropriate unevenness is formed on the surface of the liquid-repellent layer 3, and liquid repellency can be obtained.

Examples of materials constituting the spherical second filler 3Fβ include silica, silicone, acrylic resin, urethane resin, talc, mica, titanium oxide, calcium carbonate, barium sulfate, zinc oxide, smectite, zeolite, and aluminum oxide. For example, the following commercially available products can be used as the filler 3Fβ. That is, an example of the silica filler is AEROSIL50 manufactured by Nippon Aerosil Co., Ltd. The average primary particle size of the second filler 3Fβ is desirably 10 to 100 nm.

The average particle size of these fillers 2F, 3Fα, and 3Fβ refers to the average value obtained by measuring the major and minor axis lengths of any 10 fillers in the field of view of the SEM or TEM and dividing the sum by 2.

The method for forming the liquid-repellent layer 3 is the same as the method for forming the underlayer 2. That is, the liquid-repellent layer 3 can be formed by preparing a coating liquid containing a binder resin 3R, a filler 3F and other additives, and a solvent, applying the coating liquid onto the underlayer 2 to form a coating film, and drying the coating film. The solvent used in the coating liquid, the method for applying the coating liquid, and the method for drying the coating film are the same as those for forming the underlayer 2.

The coating amount of the liquid-repellent layer 3 thus formed may be within the range of 0.5 to 10.0 g/ ^m2 . The glossiness of the surface of the liquid-repellent layer 3 at a measurement angle of 60 degrees varies depending on the coating amount of the liquid-repellent layer 3, and as will be seen from the examples and comparative examples described below, the glossiness of the surface of the liquid-repellent layer 3 at a measurement angle of 60 degrees tends to decrease as the coating amount of the liquid-repellent layer 3 increases. For example, when the composition and coating amount of the undercoat layer 2 are specific values and the composition of the liquid-repellent layer 3 is specific (Examples 1 to 7, Comparative Examples 1 to 3), and when the coating amount of the liquid-repellent layer 3 is more than 1.8 g/ ^m2 (Comparative Examples 1 to 3), the glossiness is less than 1.5 GU, and the peelability against a viscous liquid material (mayonnaise) containing oil is significantly inferior. In contrast, when the coating amount of the liquid-repellent layer 3 is in the range of 0.5 to 1.8 g/ ^m2 , the gloss level is in the range of 1.5 to 5.0 GU, and the peelability against viscous liquids containing oil (mayonnaise) is also excellent.

On the other hand, as can be seen from Examples 8 to 28, when the composition and coating amount of the undercoat layer 2, or the composition of the liquid-repellent layer 3, are different from those of Examples 1 to 7, by setting the coating amount of the liquid-repellent layer 3 to a coating amount other than the range of 0.5 to 1.8 g/ ^m2, it is possible to make the gloss level fall within the range of 1.5 to 5.0 GU, and to exhibit excellent peelability against a viscous liquid material containing oil (mayonnaise).

In this way, the glossiness and liquid repellency vary depending not only on the amount of liquid repellent layer 3 applied, but also on the composition of base layer 2, the amount applied, and the composition of liquid repellent layer 3. Therefore, the glossiness can be controlled by controlling the amount of liquid repellent layer 3 applied depending on the composition of base layer 2, the amount applied, and the composition of liquid repellent layer 3.

<Packaging materials>
The packaging material according to the present embodiment has a liquid-repellent structure 10 on the side that comes into contact with an article. The packaging material according to the present embodiment can be applied to articles containing moisture (e.g., water, beverages, yogurt) and articles containing oil (e.g., curry and fresh cream), and can also be applied to an article that is one type selected from the group consisting of hand soap, body soap, shampoo, and conditioner. Specific embodiments of the packaging material include retort pouches for curry or pasta sauce, containers and lids for yogurt or pudding, containers for toiletries such as hand soap, shampoo, conditioner, or refill pouches for these, tubes for toothpaste or medicines, etc.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

The following materials were prepared to fabricate the liquid-repellent structures of the examples and comparative examples.

First, a polyethylene terephthalate film (manufactured by Unitika Ltd., thickness 38 μm) was used as the substrate 1.

The following resins were prepared as thermoplastic resin 2R. All of them are acid-modified polyethylene resins. The following abbreviations are also used in this specification.

Arrowbase SB5230N (manufactured by Unitika Ltd.) ...Abbreviation: Resin a
The following three types of fillers were prepared as the first filler 2F. Abbreviations used in this specification are also shown below.

Flow Beads CL-2080 (manufactured by Sumitomo Seika Chemicals Co., Ltd.) - abbreviation: F2-a
Sunsphere NP100 (AGC Si-Tech Co., Ltd.) Abbreviation: F2-b
AEROSIL90G (manufactured by Nippon Aerosil Co., Ltd.)...Abbreviation: F2-c
As the binder resin 3R, a fluorine-containing resin and an acrylic resin were prepared.

The fluorine-containing resins are as follows. The abbreviations used in this specification are also shown.

Asahiguard AG-E060 (manufactured by Asahi Glass Co., Ltd.) - abbreviation: Fluorine resin a
Next, the following filler was prepared as the second spherical filler 3Fβ. Abbreviations used in this specification are also shown.

AEROSIL50 (manufactured by Nippon Aerosil Co., Ltd.)...Abbreviation: 3Fβ-a
The third scale-like filler 3Fα was Sunlovely manufactured by AGC Si-Tech Co., Ltd. In this specification, it is abbreviated as "3Fα-a".

And 2-propanol was used as the solvent.

<Preparation of Liquid-Repellent Structure>
(Examples 1 to 28, Comparative Examples 1 to 10)
Each component was added to a solvent so that the mass ratio (solid content) of each component in the undercoat layer 2 was as shown in Table 1. This was thoroughly stirred to prepare a coating solution for forming an undercoat layer, which was then applied to a PET film as a substrate by reverse gravure and dried in an oven to form a undercoat layer on the substrate. The coating speed was 30 m/min and the oven temperature was 100°C.

Next, each component was added to the solvent so that the mass ratio (solid content) of each component in the liquid-repellent layer 3 was as shown in Table 1. This was thoroughly stirred to prepare a coating liquid for forming the liquid-repellent layer, which was then applied onto the underlayer 2 by reverse gravure and dried in an oven to form a liquid-repellent layer on the underlayer 2. The coating speed was 30 m/min and the oven temperature was 100°C.

<Measurement of Glossiness>
Each liquid repellent structure was placed flat on a piece of black drawing paper with the liquid repellent layer facing up, and the glossiness was measured at an angle of 60° using a BYK surface gloss meter (Micro-Tri-Gloss).

<Evaluation of Liquid-Repellent Structure>
The liquid repellent structure was evaluated from the following viewpoints.

(Liquid repellency evaluation)
The liquid-repellent structure was placed flat with the liquid-repellent layer side facing up, and 2 μL of the following liquid was dropped onto the liquid-repellent layer using a dropper. The liquid-repellent structure was then stood vertically and left as is for 30 seconds, and the state of the dropped liquid was visually observed. The liquid repellency was evaluated based on the observation results and on the following evaluation criteria. An evaluation result of 2 or more is acceptable for practical use, but 3 or more is preferable.

[Liquid used]
Pure water salad oil: Nissin salad oil (Nissin Oillio).
Hand soap: Kurashi More Medicinal Hand Soap (Japanese Soap).

[Evaluation Criteria]
1: The liquid remained on the liquid-repellent layer and did not move, or the liquid soaked into the liquid-repellent layer.
2: The liquid ran down from the liquid-repellent layer, but left a linear trace.
3: The liquid ran down from the liquid-repellent layer, but dotted traces remained.
4: The liquid ran down from the liquid-repellent layer, leaving no trace.
5: The droplets became round and rolled off the water-repellent layer, or peeled off.

(Removability evaluation)
The peelability evaluation for viscous food was performed by the following method. A polypropylene (PP) film was laid flat, and 2 g of the following viscous food was taken with a medicine spoon and dropped onto the PP film. The liquid-repellent structure was placed so that the surface on the liquid-repellent layer side faced the PP film, and it was pressed against the viscous food with a load of 50 g/25 ^cm2 and left as it was for 10 seconds. Thereafter, the liquid-repellent structure was peeled off, and the adhesion state of the viscous food to the contact surface of the liquid-repellent layer that had been in contact with the viscous food was visually observed. The adhesion was evaluated based on the observation results based on the following evaluation criteria. If the evaluation result is 2 or more, there is no problem in practical use, but 3 or more is preferable.

[Viscous food used]
Mayonnaise: Kewpie Mayonnaise (Kewpie Corporation).

[Evaluation Criteria]
1: Viscous food was found to adhere to 70% or more of the contact surface.
2: Viscous food was found to adhere to 30% or more but less than 70% of the contact surface.
3: Viscous food was found to adhere to 10% or more but less than 30% of the contact surface.
4: Sticky food was found to adhere to less than 10% of the contact surface.
5: No sticky food was found to adhere to the contact surface.

The results are shown in Table 2.

<Considerations>
In Examples 1 to 7 and Comparative Examples 1 to 3, the composition and coating amount of the undercoat layer 2 and the composition of the liquid-repellent layer 3 are constant, and the coating amount of the liquid-repellent layer 3 is changed. As can be seen from the results of Examples 1 to 7 and Comparative Examples 1 to 3, the glossiness decreases monotonically as the coating amount of the liquid-repellent layer 3 increases. However, the lower the glossiness, that is, the greater the coating amount of the liquid-repellent layer 3, the better the liquid-repellent properties are against these four types of samples, including the liquid-repellent properties against hand soap and the releasability against mayonnaise. That is, the liquid-repellent properties against the four types of samples, pure water, salad oil, hand soap, and mayonnaise, are excellent in Examples 1 to 7, in which the coating amount of the liquid-repellent layer 3 is 0.50 to 1.76 g/m ² and the glossiness is in the range of 1.6 to 5.0 GU, while Comparative Examples 1 to 3, in which the coating amount of the liquid-repellent layer 3 is greater and the glossiness is higher, are inferior in the liquid-repellent properties against hand soap and the releasability against mayonnaise.

However, as can be seen from Examples 8 to 28, when the composition and coating amount of the undercoat layer 2, or the composition of the liquid-repellent layer 3, differs from those of Examples 1 to 7, the glossiness may be within the range of 1.5 to 5.0 GU even if the coating amount of the liquid-repellent layer 3 differs from that of Examples 1 to 7. And regardless of the coating amount of the liquid-repellent layer 3, as long as the glossiness is within the range of 1.5 to 5.0 GU, the liquid repellency is excellent for the four types of samples mentioned above.

For example, Example 17 uses silica particles having an average primary particle diameter of 10 μm as the first filler 2F contained in the undercoat layer 2. In this example, the coating amount of the liquid-repellent layer 3 is 2.05 g/ ^m2 , but the gloss is 1.8 GU, and the liquid repellency is excellent against the four types of samples described above.

For example, Comparative Example 7 with a gloss level of 5.3 GU and Comparative Example 8 with a gloss level of 5.5 GU only exhibit poor liquid repellency against hand soap and mayonnaise. On the other hand, Example 18 with a gloss level of 4.8 GU exhibits high liquid repellency against the four types of samples mentioned above.

From these results, it can be seen that the appropriate parameter related to liquid repellency is not the amount of coating of the liquid repellent layer 3, but rather the glossiness. By referring to Examples 8 to 28 in addition to Examples 1 to 7, it can be seen that if the glossiness is within the range of 1.5 to 5.0 GU, the material will have excellent liquid repellency against the four types of samples mentioned above, and will also exhibit excellent liquid repellency against viscous liquids containing oil (e.g. mayonnaise).

In addition, Example 10 is an example in which the liquid-repellent layer 3 contains the scaly third filler F3α but does not contain the spherical second filler F3β. When comparing this Example 10 with Examples 4 and 5, which contain the spherical second filler F3β and have the same coating amount, the glossiness of Examples 4 and 5, which contain the spherical second filler F3β, is lower than that of Example 10, which does not contain it. Therefore, it can be understood that by blending the spherical second filler F3β, a fine and complex uneven structure can be formed on the surface of the liquid-repellent layer 3. And, due to such unevenness on the surface of the liquid-repellent layer 3, Examples 4 and 5 exhibit excellent liquid repellency. It can be understood that the liquid repellency against salad oil and the peelability against mayonnaise are particularly excellent.

Moreover, Example 12 is an example in which the liquid repellent layer 3 contains the spherical second filler F3β but does not contain the scaly third filler F3α. When Example 12 is compared with Examples 4 and 5, which contain the scaly third filler F3α and have the same application amount, Example 12 has the same gloss as Examples 4 and 5, which contain the scaly third filler F3α, but the liquid repellency is different.
For this reason, it can be said that by blending the scaly third filler F3α in addition to the spherical second filler F3β, it is possible to form a finer and more complicated uneven structure on the surface of the liquid-repellent layer 3. And, due to such unevenness on the surface of the liquid-repellent layer 3, Examples 4 and 5 exhibit excellent liquid repellency.
The invention as originally claimed is set forth below.
[1]
A liquid-repellent structure formed by sequentially laminating a base layer and a liquid-repellent layer on a surface to which liquid repellency is to be imparted,
The underlayer contains a first filler,
the liquid-repellent layer contains a fluorine-containing resin and a second filler,
A liquid-repellent structure, characterized in that the gloss of the surface of the liquid-repellent layer at a measurement angle of 60 degrees is within the range of 1.5 to 5.0 GU.
[2]
2. The liquid repellent structure according to item 1, wherein the second filler is a spherical filler.
[3]
3. The liquid-repellent structure according to item 2, wherein the liquid-repellent layer further contains a scale-like filler.
[4]
4. The liquid repellent structure according to item 3, wherein a value obtained by dividing the weight of the scaly filler by the weight of the spherical filler is within a range of 0.05 to 0.30.
[5]
5. The liquid repellent structure according to any one of items 1 to 4, wherein the first filler is larger than the second filler.
[6]
Item 6. A packaging material having the liquid repellent structure according to any one of Items 1 to 5 on a side that comes into contact with an article.

10: Liquid-repellent structure 1: Substrate 2: Underlayer 2R: Thermoplastic resin 2F: First filler 3: Liquid-repellent layer 3R: Binder resin 3F: Filler 3Fα: Second filler 3Fβ: Third filler

Claims (4)

A liquid-repellent structure formed by sequentially laminating a base layer and a liquid-repellent layer on a surface to which liquid repellency is to be imparted,
The underlayer contains a first filler,
the liquid-repellent layer contains a fluorine-containing resin and a second filler,
the gloss of the surface of the liquid-repellent layer at a measurement angle of 60 degrees is within a range of 1.5 to 5.0 GU;
the second filler is a spherical filler,
The liquid repellent layer further contains a scale-like filler,
The first filler has an average primary particle size in the range of 5 to 30 μm;
The average primary particle size of the second filler is within a range of 10 to 100 nm;
The liquid repellent structure is characterized in that the average primary particle diameter of the scale-like filler is within the range of 4 to 6 μm . 2. The liquid repellent structure according to claim 1 , wherein a value obtained by dividing the weight of the scaly filler by the weight of the spherical filler is within a range of 0.05 to 0.30. 3. The liquid repellent structure according to claim 1, wherein the first filler is larger than the second filler. A packaging material having the liquid repellent structure according to any one of claims 1 to 3 on a side that comes into contact with an article.

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