Oil-resistant paper

Abstract

To provide oil-resistant paper that is heat-resistant, oil-resistant, and breathable. [Solution] The present invention comprises a base paper and an oil-resistant agent impregnated near at least one surface of the base paper, wherein the base paper has a beaten degree of 20°SR or more and 50°SR or less, and the oil-resistant agent is a silicone-modified polyester oil-resistant paper.

Description

[Technical Field]

[0001] This invention relates to oil-resistant paper. [Background technology]

[0002] Oil-resistant paper is widely used as packaging paper and containers for cooked foods such as fast food, fried foods, and baked foods that contain a lot of oil and moisture, as well as for foods containing a lot of fat such as chocolate, and as paper liners such as food trays.

[0003] Generally, fluororesin-based oil repellents are commonly used to impart oil resistance to paper. For example, oil-resistant paper is known in which an oil-resistant layer is formed by coating the surface of the paper substrate with a fluororesin-based oil repellent, or oil-resistant paper in which a fluororesin-based oil repellent is internally added to the paper substrate. However, oil-resistant paper using fluororesin-based oil repellents has been criticized for its environmental impact due to perfluoro compounds and other substances generated during combustion, and there is a demand for oil-resistant paper that does not contain fluororesin-based oil repellents.

[0004] Patent Document 1 discloses an oil-resistant paper made from a non-fluorine-based material that achieves both high oil resistance and high breathability, comprising starch, styrene-acrylic resin, and wax.

[0005] Patent Document 2 describes an oil-resistant paper having an oil-resistant layer containing an oil-resistant agent on at least one side of a paper substrate, wherein the oil-resistant layer contains a polyester resin with a glass transition temperature of 50°C to 80°C as the oil-resistant agent, and the amount of oil-resistant agent applied is 1.5 to 5.0 g / m² in terms of solid content per side of the paper substrate. 2 An oil-resistant paper is disclosed.

[0006] Patent Document 3 discloses an oil-resistant paper obtained by coating a base paper with a water-based oil-resistant agent containing an olefin resin, a urethane resin, and paraffin wax. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2013-237941 [Patent Document 2] Japanese Patent Publication No. 2024-005691 [Patent Document 3] Japanese Patent Publication No. 2022-188338 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, while the technology described in the above-mentioned patent document discloses oil-resistant paper that has oil resistance in an environment of 50°C, it does not achieve heat resistance or oil resistance at temperatures above 50°C. This invention has been made in view of the above circumstances, and aims to provide oil-resistant paper having heat resistance, oil resistance, and moisture permeability. [Means for solving the problem]

[0009] The present invention has the following configuration. [1] The oil-resistant paper comprises a base paper and an oil-resistant agent impregnated near at least one surface of the base paper, wherein the base paper has a beaten degree of 20°SR or more and 50°SR or less, and the oil-resistant agent is a silicone-modified polyester. [2] The oil-resistant paper described in [1] above, wherein the softening point of the oil-resistant agent is 90° or higher. [3] The oil-resistant paper described in [2] above, wherein the glass transition temperature of the oil-resistant agent is 10°C or higher and 90°C or lower. [4] The oil-resistant paper according to [1] above, wherein a binder resin is further impregnated near at least one surface of the base paper, the binder resin being at least one of starch, polyvinyl alcohol, dextrin, and water-soluble polyester. [5] The oil-resistant paper described in [4] above, wherein the oil-resistant agent and binder resin are further impregnated near the other side of the base paper. [Effects of the Invention]

[0010] According to the present invention, an oil-resistant paper having heat resistance, oil resistance, and moisture permeability can be obtained.

Mode for Carrying Out the Invention

[0011] [Oil-resistant paper] The oil-resistant paper of the present invention comprises a base paper and an oil-resistant agent impregnated in the vicinity of at least one surface of the base paper. The base paper has a beating degree of 20°SR or more and 50°SR or less, and the oil-resistant agent is a silicone-modified polyester. Hereinafter, each component of the oil-resistant paper will be described.

[0012] (Base paper) The base paper has a beating degree of 20°SR or more and 50°SR or less. When the beating degree of the base paper is within the above range, it has sufficient strength when used as a base material for food packaging or the like. Further, since the beating degree of the base paper is 50°SR or less, the coating liquid containing the oil-resistant agent can be impregnated into the paper interior, so that it is easy to exhibit oil resistance. Furthermore, appropriate moisture permeability can be ensured. The beating degree of the base paper is preferably 25°SR or more and 45°SR or less. The beating degree of the base paper is a value determined by the Shopper-Riegler method based on JIS P 8121-1:2012.

[0013] -Air permeability resistance- The air permeability resistance of the oil-resistant paper is preferably 500 seconds or less, more preferably 300 seconds or less, and still more preferably 100 seconds or less. When the air permeability resistance is within the above range, the oil-resistant paper has appropriate moisture permeability that can be compatible with oil resistance. The air permeability resistance can be measured by a measuring method according to the air permeability test method / King Research method (JIS P8117:2009). Hereinafter, each component will be described.

[0014] -Sizing degree- The sizing degree of the base paper is preferably 0 seconds or more and less than 10 seconds. When the sizing degree of the base paper is within the above range, it is easy to impregnate the base paper with the coating liquid containing the oil-resistant agent, and it is easy to exhibit oil resistance. The sizing degree of the base paper is more preferably 0 seconds or more and 5 seconds or less. The sizing of the base paper can be adjusted, for example, by the type of pulp, the content or type of sizing agent, the degree of beating, etc. The size degree of the base paper shall be the value measured by the Stechhit method in accordance with JIS P 8122:2004.

[0015] The base paper used in the oil-resistant paper of this embodiment preferably contains bleached hardwood kraft pulp (LBKP (L material)), bleached softwood kraft pulp (NBKP (N material)), bleached hardwood sulfite pulp (LBSP), bleached softwood sulfite pulp (NBSP), and other chemical pulps.

[0016] The base paper may contain wood pulp other than bleached hardwood kraft pulp / bleached softwood kraft pulp, or non-wood pulp, to the extent that the effects of the invention are not impaired. In addition, the base paper may contain conventional additives, such as paper strength enhancers (starch, polyacrylamide, polyamidoamine epichlorohydrin, etc.), yield enhancers, water drainage enhancers, aluminum sulfate, pH adjusters, defoamers, pitch control agents, slime control agents, etc., as needed, to the extent that the effects of the invention are not impaired.

[0017] The thickness of the base paper is preferably 20 μm or more and 150 μm or less. The lower limit of the base paper thickness is more preferably 25 μm or more, even more preferably 30 μm or more, and even more preferably 35 μm or more. The upper limit of the base paper thickness is more preferably 80 μm or less, even more preferably 70 μm or less, and even more preferably 60 μm or less.

[0018] In this embodiment, if the base paper contains a sizing agent, it will be difficult for the coating liquid described later to be incorporated into the base paper, making it difficult for oil resistance to be achieved. Therefore, it is more preferable that the base paper substantially does not contain sizing agents, such as alkyl ketene dimer-based, alkenyl succinic anhydride-based, higher fatty acid-based, petroleum resin-based, or rosin-based sizing agents. Here, "substantially absent" means that the content in the oil resistant agent is 3% by mass or less, and moreover, 1% by mass or less.

[0019] (Oil resistant agent) The oil-resistant agent used in the oil-resistant paper of the present invention is a silicone-modified polyester. Furthermore, the silicone-modified polyester preferably has a softening point of 90° or higher. Specifically, examples of silicone-modified polyester include reaction products of an alcohol component containing a dihydric or higher alcohol, a carboxylic acid component containing one or more selected from aromatic dicarboxylic acids and aliphatic dicarboxylic acids, and a modified silicone having at least one functional group selected from amino groups, hydroxyl groups, carboxyl groups, and epoxy groups. Silicone is an organosilicon polymer and has high water repellency, but when an oil component such as silicone oil is applied to the base paper, it penetrates into the paper but does not exhibit sufficient water repellency. Therefore, by coating a paper substrate with a silicone-modified polyester in which a water-repellent modified silicone is attached to the side chains, one or both ends of the polyester resin, it is possible to achieve both affinity to paper and high oil resistance. The silicone-modified polyester resin used in this embodiment is preferably a water-dispersible emulsion because it is easy to handle. The dispersion medium of the emulsion is preferably water, but a dispersion medium other than water may be added to the water as long as it does not hinder dispersibility.

[0020] - Softening point of oil-resistant agents - The softening point of the oil resistant agent is preferably 90°C or higher, more preferably 100°C or higher, and even more preferably 120°C or higher, and similarly, preferably 165°C or lower, more preferably 155°C or lower, and even more preferably 150°C or lower. Specifically, it is measured by the method described below.

[0021] <Method for measuring the softening point of oil-resistant agents> Using a flow tester, a 1g sample is heated at a heating rate of 6°C / min while a load of 1.96 MPa is applied by a plunger, and the sample is extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. Next, the amount of plunger descent of the flow tester is plotted against temperature, and the temperature at which half of the sample has flowed out is defined as the softening point.

[0022] -Glass transition point of the oil-resistant agent The glass transition point of the oil-resistant agent is preferably 10 °C or higher, preferably 15 °C or higher, more preferably 20 °C or higher, and even more preferably 30 °C or higher. The upper limit is preferably 90 °C or lower, more preferably 80 °C or lower, and even more preferably 50 °C or lower. The lower the glass transition point, the easier it is for the oil-resistant agent to penetrate into the base paper and the easier it is to exhibit oil resistance. The glass transition point is measured using a differential scanning calorimeter, and specifically, it is measured by the method described below.

[0023] <Method for measuring the glass transition point of the oil-resistant agent> Using a differential scanning calorimeter, weigh 0.01 - 0.02 g of the sample into an aluminum pan, heat it up to 200 °C, cool it from that temperature to 0 °C at a cooling rate of 10 °C / min to prepare a measurement sample. Next, heat it up at a heating rate of 10 °C / min and measure the heat quantity. Among the observed endothermic peaks, the peak temperature with the largest peak area is taken as the maximum peak temperature of the endotherm. The temperature at the intersection of the extension line of the baseline below the maximum peak temperature of the endotherm and the tangent line indicating the maximum slope from the rising part of the peak to the peak apex is taken as the glass transition point.

[0024] The coating amount of the oil-resistant agent in this embodiment is such that the dry coating amount per side of the base paper is 0.2 g / m 2 or more and 10 g / m 2 or less, preferably 0.2 g / m 2 or more and 6 g / m 2 or less is more preferable. More specifically, when impregnating with the binder resin described later, the coating amount of the oil-resistant agent is preferably 0.2 g / m 2 or more and 3 g / m 2 or less, preferably 0.3 g / m 2 or more and 2 g / m 2 or less is more preferable. When not impregnating with the binder resin, the coating amount of the oil-resistant agent is preferably 3 g / m 2 or more and 10 g / m 2 or less, preferably 4 g / m 2 or more and 6 g / m 2The following are preferable.

[0025] (Binder resin) In addition to an oil-resistant agent, a binder resin may also be impregnated near at least one side of the base paper. The binder resin is preferably at least one selected from starch, polyvinyl alcohol, dextrin, water-soluble polyester, polyacrylamide, acrylate, styrene-acrylic polymer, and polyamide-polyamine-epichlorohydrin resin, with starch and dextrin being more preferred.

[0026] When the total mass of the oil resistant agent and binder resin in the coating liquid is taken as 100, the oil resistant agent content is preferably 5% by mass or more, and more preferably 10% by mass or more. Furthermore, the upper limit of the oil resistant agent content is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. By keeping the oil resistant agent content within the above range, it is possible to achieve both heat resistance, oil resistance, and moisture permeability. The oil-resistant paper of the present invention, by further including a binder resin in the oil-resistant agent, provides heat and oil resistance while further reducing the amount of oil-resistant agent required for application. Since the surface tension of oil is around 30 mN / m, the lower the surface free energy of the surface impregnated with the oil-resistant agent in the oil-resistant paper of the present invention, the more easily it repels oil. The surface free energy of the surface impregnated with the oil-resistant agent in the oil-resistant paper of the present invention is 30 mJ / m 2 It is less than 30 mJ / m³. 2 If the value exceeds this, the oil resistance is poor. The surface free energy is 25 mJ / m 2 It is more preferable that it be less than 10 mJ / m³. The lower limit of the surface free energy is 10 mJ / m³. 2 That's all.

[0027] [Method for manufacturing oil-resistant paper] The oil-resistant paper of the present invention can be manufactured by coating a base paper with a coating solution containing an oil-resistant agent and an optional binder resin, and then drying it. By coating the base paper with the coating solution, the oil-resistant agent and the optional binder resin are impregnated near at least one surface of the base paper, resulting in oil resistance. It is also preferable that the oil-resistant agent and the optional binder resin are impregnated near the other surface of the base paper, and may even be impregnated throughout the entire depth direction of the base paper. By impregnating the entire depth direction of the paper, heat resistance and oil resistance at temperatures above 100°C can be more reliably obtained.

[0028] The solid content concentration of the coating solution is preferably 10% by mass or more and 50% by mass or less, from the viewpoint of ensuring impregnation, oil resistance, etc. Additives may be added to the coating solution containing an oil resistant agent as needed. Examples of such additives include dispersants, defoamers, thickeners, water-resistant agents, plasticizers, fluorescent whitening agents, coloring pigments, coloring dyes, reducing agents, ultraviolet absorbers, antioxidants, fragrances, or deodorizers.

[0029] Methods for applying the coating solution include applying it to the surface of the base paper using a coating machine such as a bar coater, die coater, gravure coater, roll coater, blade coater, air knife coater, or sizing press coater. A sizing press coater is preferred because it can handle high papermaking speeds and can stably apply the desired amount of coating solution. Drying methods include heating the surface of the coating liquid on the paper substrate by applying hot air, heating the surface of the coating liquid on the paper substrate by bringing a heater close to it, heating the surface of the paper substrate opposite to the surface coated with the coating liquid by bringing a heater into contact with it, and heating by steam curing using high-temperature steam at normal or high pressure. One or more drying methods may be used. From the viewpoint of improving water repellency, the drying temperature is preferably 30°C or higher, more preferably 40°C or higher, even more preferably 50°C or higher, even more preferably 70°C or higher, and even more preferably 90°C or higher. From the viewpoint of suppressing deformation of the base paper due to heat and reducing energy, the drying temperature is preferably 200°C or lower, more preferably 150°C or lower, and even more preferably 130°C or lower. By setting the drying temperature to a temperature above the softening point of the oil resistant agent, the emulsion particles of the oil resistant agent melt thoroughly and form a film, thereby providing excellent oil resistance. [Examples]

[0030] The present invention will be described below with reference to examples. The present invention is not limited in any way to these examples. Unless otherwise specified, % and parts represent mass % and parts by mass.

[0031] Table 1 shows the paper size, coating solution composition, and application amount used in the examples and comparative examples. Details in Table 1 are as follows. Note that the mass parts of oil resistant agents and resins in Table 1 refer to the mass of non-volatile components. Also, in the examples and comparative examples, the coating solution is impregnated on both sides of the base paper, but the figures are shown converted to "dry coating amount on one side".

[0032] [Sample preparation] <Base paper> Pulp with a beating degree of 20°SR to 50°SR (Canadian standard filtration rate of 250 to 600 ml) was used.

[0033] <Coating liquid> The following oil-resistant agents and binder resins were used to prepare the coating solution. (Oil resistant agent) A1: Silicone-modified polyester resin with a softening point of 125°C (product code "LKE-07", manufactured by Kao Corporation) A2: Silicone-modified polyester resin with a softening point of 150°C (product number "LKE-09", manufactured by Kao Corporation) A3: Silicone-modified polyester resin with a softening point of 158°C (product number "LKE-15", manufactured by Kao Corporation) A4: Silicone-modified polyester resin with a softening point of 118°C (product number "LKE-23", manufactured by Kao Corporation) A5: Silicone-modified polyester resin with a softening point of 109°C (product number "LKE-24", manufactured by Kao Corporation) A6: A polyester resin with a softening point of 100°C and long-chain alkyl groups as hydrophobic groups (product code "LKE-01", manufactured by Kao Corporation) A7: A polyester resin with a softening point of 65°C and having long-chain alkyl groups as hydrophobic groups (product code "LKE-04", manufactured by Kao Corporation) A8: A polyester resin with a softening point of 98°C and long-chain alkyl groups as hydrophobic groups (product code "LKE-13", manufactured by Kao Corporation) (Binder resin) B1: Dextrin (product code "Sandec #300", manufactured by Sanwa Starch Industry Co., Ltd.) B2: Starch (product code "Dynacoat 68NB", manufactured by SWI Japan) B3: PVA (Product code "25-88 KL", manufactured by Kuraray Co., Ltd.)

[0034] <Sample Preparation> As the impregnation device, we used a tabletop impregnation device called a Hishiracopy, which mimics the size pressing process of a paper machine. Then, the paper substrate containing the processing solution was placed between filter paper and placed in a hot press machine, where it was pressed and dried at a drying temperature of 120°C for 3 minutes. After drying, the filter paper was removed to obtain oil-resistant paper (sample).

[0035] [Examples 2-10, Comparative Examples 1-4] Oil-resistant paper samples were prepared in the same manner as in Example 1, except that the composition of the base paper and coating solution, and the amount of coating applied, were as shown in Table 1.

[0036] [evaluation] The oil-resistant paper samples prepared in the above examples and comparative examples were evaluated as follows. The evaluation results are shown in Table 1.

[0037] (Oil resistance: normal temperature) One drop of Nisshin Canola Oil (Nisshin Oillio Group, Ltd.) was placed on the prepared oil-resistant paper sample, and after 30 minutes, the oil was wiped off and visually inspected. ○: No oil stains △: Oil stain present ×: Oil seeped through to the back.

[0038] (Oil resistance: 70℃, 100℃) One drop of Nissin canola oil was placed on the prepared oil-resistant paper sample, and it was placed in a hot air oven at 70°C and 100°C respectively for 15 minutes. After that, the oil was wiped off and the sample was visually inspected. ○: No oil stains △: Oil stain present ×: Oil seeped through to the back.

[0039] (Air permeability resistance) The air permeability resistance was measured according to the air permeability test method / Wang Gan method (JIS P8117:2009).

[0040] (Surface free energy of the surface) The surface free energy (γtotal) was determined using water, diiodomethane, and bromonaphthalene, all of which have known contact angles, as probe solutions. The contact angles of each probe solution were measured using a contact angle meter, and the resulting contact angles were then calculated according to the Kitazaki-Hata method (see Kitazaki, Yasuaki et al., Journal of the Adhesion Society of Japan, Vol. 8, No. 3, 1972, pp. 131-141). A contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name "Fully Automatic Contact Angle Meter DM-701") was used.

[0041] [Table 1]

[0042] As shown in Table 1, the examples using silicone-modified polyester as an oil resistant agent exhibited good oil resistance and air permeability resistance at room temperature, 70°C, and 100°C.

Claims

1. It comprises a base paper and an oil-resistant agent impregnated near at least one surface of the base paper, The aforementioned base paper has a beaten degree of 20°SR or more and 50°SR or less. Oil-resistant paper in which the oil-resistant agent is silicone-modified polyester.

2. The oil-resistant paper according to claim 1, wherein the softening point of the oil-resistant agent is 90° or higher.

3. The oil-resistant paper according to claim 2, wherein the glass transition temperature of the oil-resistant agent is 10°C or more and 90°C or less.

4. A binder resin is further impregnated near at least one surface of the aforementioned base paper. The oil-resistant paper according to claim 1, wherein the binder resin is at least one of starch, polyvinyl alcohol, dextrin, and water-soluble polyester.

5. The oil-resistant paper according to claim 4, wherein the oil-resistant agent and the binder resin are further impregnated near the other surface of the base paper.

Images