Oil-resistant paper

Abstract

To provide oil-resistant paper which has both excellent oil resistance and moisture permeability, and is also excellent in oil resistance when folded and cracked.SOLUTION: Oil-resistant paper of the invention comprises base paper, and an oil-resistant agent and a resin impregnated in the vicinity of at least one surface of the base paper, wherein the base paper has a beating degree of 20°SR or more and 50°SR or less, and a sizing degree of 0 seconds or more and less than 10 seconds, the oil-resistant agent is a long-chain aliphatic compound, and the resin is at least one polyurethane selected from polyether-based polyurethane, polyester-based polyurethane, and polycarbonate-based polyurethane.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to greaseproof paper. [Background technology]

[0002] Greaseproof paper is widely used as packaging paper and packaging containers for cooked foods such as fast food, fried foods, and baked foods that contain a lot of oil and moisture, and foods that contain a lot of fats and oils such as chocolate, or as paper coverings for food trays, etc.

[0003] Generally, fluororesin-based oil-resistant agents are widely used as oil-resistant agents that impart oil resistance to paper, and for example, grease-resistant paper in which an oil-resistant layer is formed by coating a fluororesin-based oil-resistant agent on the surface of a paper substrate, and grease-resistant paper in which a fluororesin-based oil-resistant agent is internally added to a paper substrate are known. However, grease-resistant paper using fluororesin-based oil-resistant agents is considered to be environmentally hazardous due to perfluoro compounds and the like generated during combustion, and grease-resistant paper that does not contain fluororesin-based oil-resistant agents is in demand.

[0004] On the other hand, moisture permeability is required for packaging papers and packaging containers from the viewpoint of food flavor, storage stability, etc. For example, Patent Document 1 discloses an greaseproof paper having excellent oil resistance and breathability, which is obtained by coating a base paper with a water-based greaseproofing agent containing an olefin resin, a urethane resin, and paraffin wax. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2022-188338 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, even if the material has oil resistance and moisture permeability, there is a problem that oil leaks out from the folds when the material is processed into packaging and containers. The present invention has been made in consideration of the above circumstances, and has an object to provide an oil-resistant paper that has excellent oil resistance and moisture permeability while also having excellent cracking and oil resistance. [Means for solving the problem]

[0007] The present invention provides an greaseproof paper comprising a base paper and an oil-proofing agent and a resin impregnated near at least one surface of the base paper, wherein the base paper has a beating degree of 20°SR or more and 50°SR or less and a sizing degree of 0 seconds or more and less than 10 seconds, the oil-proofing agent is a long-chain aliphatic compound, and the resin is at least one type of polyurethane selected from polyether-based polyurethanes, polyester-based polyurethanes, and polycarbonate-based polyurethanes.

[0008] The long-chain aliphatic compound is preferably a reaction product between an alkylamine having an alkyl group having 8 to 24 carbon atoms and a polycarboxylic acid having a hydroxy group.

[0009] The sizing degree of the base paper is preferably from 0 seconds to 10 seconds.

[0010] It is preferable that the oil-resistant agent and resin are also impregnated into the vicinity of the other surface of the base paper.

[0011] The air resistance is preferably 500 seconds or less.

[0012] The content of polyurethane relative to the total amount of the long-chain aliphatic compound and polyurethane is preferably 15% by mass or more and 90% by mass or less. Effect of the Invention

[0013] According to the present invention, it is possible to obtain greaseproof paper that has excellent oil resistance and moisture permeability while also having excellent fold crack resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] [Oil-resistant paper] The grease-resistant paper in this embodiment comprises a base paper and an oil-resistant agent and a resin impregnated near at least one surface of the base paper, the base paper having a beating degree of 20°SR or more and 50°SR or less and a sizing degree of 0 seconds or more and less than 10 seconds, the oil-resistant agent is a long-chain aliphatic compound, and the resin is at least one type of polyurethane selected from polyether-based polyurethanes, polyester-based polyurethanes, and polycarbonate-based polyurethanes. The thickness of the greaseproof paper of this embodiment is preferably 20 μm to 150 μm, more preferably 35 μm to 100 μm. When the thickness of the greaseproof paper is within the above range, it has sufficient strength, oil resistance (normal state), and cracking oil resistance to be used as a base material for food packaging, etc. In this specification, oil resistance in a flat state is simply referred to as "oil resistance" or "oil resistance (normal)", and oil resistance on the inside (valley fold) in an open state after being creased or folded is referred to as "fold crack oil resistance" or "oil resistance (fold crack)".

[0015] The air resistance of the greaseproof paper is preferably 500 seconds or less, more preferably 300 seconds or less, and even more preferably 100 seconds or less. By having the air resistance in the above range, the greaseproof paper has appropriate moisture permeability that can be compatible with oil resistance. Each component will be described below.

[0016] <Base paper> The base paper has a beating degree of 20° SR or more and 50° SR or less, and a sizing degree of 0 seconds or more and less than 10 seconds. By having a base paper beating degree of 20°SR or more, the base paper has sufficient strength when used as a base material for food packaging, etc. Also, by having a base paper beating degree of 50°SR or less, the paper can be impregnated with a coating liquid containing an oil-resistant agent to the inside, making it easy to develop oil resistance. Furthermore, appropriate moisture permeability can be ensured. The base paper beating degree is preferably 25°SR or more and 45°SR or less. The degree of beating of the base paper is the value determined by the Schopper-Riegler method based on JIS P 8121-1:2012.

[0017] The sizing degree of the base paper is 0 seconds or more and less than 10 seconds. By having the sizing degree of the base paper be 0 seconds or more and less than 10 seconds, it is easy to impregnate the base paper with a coating liquid containing an oil-proofing agent, and it is easy to develop oil resistance. The sizing degree of the base paper is preferably 0 seconds or more and 5 seconds or less. The sizing degree 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, and the like. The sizing degree of the base paper is a value measured by the Stockigt method based on JIS P 8122:2004.

[0018] The base paper used for the grease-resistant paper of this embodiment preferably contains chemical pulp such as bleached hardwood kraft pulp (LBKP (L material)), bleached softwood kraft pulp (NBKP (N material)), bleached hardwood sulfite pulp (LBSP), or bleached softwood sulfite pulp (NBSP).

[0019] The base paper may contain wood pulp other than bleached hardwood kraft pulp / bleached softwood kraft pulp or non-wood pulp within the scope of the invention. In addition, the base paper may contain conventional additives, such as paper strength agents (starch, polyacrylamide, polyamidoamine epichlorohydrin, etc.), retention aids, drainage aids, aluminum sulfate, pH adjusters, defoamers, pitch control agents, slime control agents, etc., selected appropriately as necessary within the scope of the invention.

[0020] The thickness of the base paper is preferably 20 μm or more and 150 μm or less. The lower limit of the thickness of the base paper 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 thickness of the base paper is more preferably 80 μm or less, even more preferably 70 μm or less, and even more preferably 60 μm or less.

[0021] In addition, if the base paper in this embodiment contains a sizing agent, it will be prevented from incorporating the coating liquid described below into the base paper, making it difficult to exhibit fold-crack oil resistance, so it is more preferable that the base paper does not contain a sizing agent, such as an alkyl ketene dimer-based, alkenyl succinic anhydride-based, higher fatty acid-based, petroleum resin-based, or rosin-based sizing agent.

[0022] <Coating fluid> The greaseproof paper of this embodiment comprises an oil-proofing agent and a resin impregnated in the vicinity of at least one surface of the base paper. The oil-proofing agent and the resin are impregnated by applying a coating liquid containing the oil-proofing agent and the resin to at least one surface of the base paper. By applying a coating liquid containing an oil-proofing agent and a resin to the base paper, the base paper is impregnated with the oil-proofing agent and the resin near at least one side thereof, thereby exhibiting oil resistance. It is also preferable that the base paper is also impregnated with the oil-proofing agent and the resin near the other side thereof, and furthermore, the base paper may be impregnated throughout its entire depth direction. By impregnating the paper throughout its entire depth direction, both oil resistance in normal condition and fold crack oil resistance are easily exhibited.

[0023] The coating liquid preferably has a solid content concentration of 10% by mass or more and 50% by mass or less.

[0024] Examples of the method for applying the coating liquid include a method of applying the coating liquid to the surface of the base paper using a coater such as a bar coater, a die coater, a gravure coater, a roll coater, a blade coater, an air knife coater, a size press coater, etc. A size press coater is preferred because it is compatible with high papermaking speeds and can stably apply a desired amount of coating liquid. The coating liquid will be described in detail below.

[0025] (oil resistant agent) The oil-resistant agent is a long-chain aliphatic compound. As the long-chain aliphatic compound, a polycarboxylic acid having an alkyl group with 8 to 24 carbon atoms is preferable, and more specifically, a reaction product between an alkylamine having an alkyl group with 8 to 24 carbon atoms and a polycarboxylic acid having a hydroxyl group can be mentioned. Specific examples of the polycarboxylic acid having a hydroxyl group include, but are not limited to, 2-hydroxybutanedioic acid (malic acid), 2,3-dihydroxybutanedioic acid (tartaric acid), 2-hydroxy-1,2,3-propanetricarboxylic acid (citric acid), 1-hydroxypropane-1,2,3-tricarboxylic acid (isocitric acid), and the like. More specifically, examples include the product name "Sizepine CA-956" (manufactured by Arakawa Chemical Industries, Ltd.), which is a reaction product of an alkylamine having an alkyl group having 8 to 24 carbon atoms and a polycarboxylic acid having a hydroxyl group. The oil-resistant agent preferably does not contain paraffin wax. In this embodiment, the amount of oil-resistant agent applied is 0.2 g / m2 on one side of the base paper. 2 More than 2g / m 2 It is preferable that:

[0026] (resin) The resin is at least one type of polyurethane selected from polyether-based polyurethane, polyester-based polyurethane, and polycarbonate-based polyurethane. More specifically, examples of such products include those sold under the trade names "HYDRAN WLS-201", "HYDRAN WLS-230", "HYDRAN WLS-102", "HYDRAN HW-311", and "HYDRAN WLS-210" (manufactured by DIC Corporation).

[0027] The content of polyurethane in the coating liquid relative to the total amount of the long-chain aliphatic compound and polyurethane is preferably 15% by mass or more and 90% by mass or less. By having the content of polyurethane in the coating liquid relative to the total amount of the long-chain aliphatic compound and polyurethane within the above range, oil resistance (normal state) and oil resistance (cracks at break) are easily exhibited. The content of polyurethane in the coating liquid relative to the total amount of the long-chain aliphatic compound and polyurethane is more preferably 25% by mass or more and 80% by mass or less, and even more preferably 35% by mass or more and 70% by mass or less.

[0028] The grease-resistant paper of this embodiment is oil-resistant and moisture-permeable, and also has excellent oil-resistance when folded and cracked, so even if it is processed into a three-dimensional shape, the container will not become oily or will not leak oil. Therefore, it is suitable as packaging paper and packaging containers, or food trays, for cooked foods such as fast food, fried foods, and baked foods that contain a lot of oil and moisture, and foods that contain a lot of fats and oils, such as chocolate. EXAMPLES

[0029] The present invention will be described below with reference to examples. The present invention is not limited to these examples. In addition, % and parts are by mass % and parts by mass unless otherwise specified.

[0030] The sizing degree of the base paper, the composition of the coating liquid, and the coating amount used in the examples and comparative examples are shown in Table 1. The details in Table 1 are as follows. Note that the parts by mass of the oil-proofing agent and resin in Table 1 are the masses of the non-volatile components. Also, in the examples and comparative examples, the coating liquid is impregnated into both sides of the base paper, but is shown in terms of "dry coating amount on one side".

[0031] <Base paper> Base paper 1: Base paper was prepared using pulp with a beating degree of 20°SR to 50°SR (Canadian standard freeness of 250 to 600 ml) without adding any internal sizing agent. The sizing degree of base paper 1 was 0 seconds. Base paper 2: Using pulp with a beating degree of 20°SR to 50°SR (Canadian standard freeness 250 to 600 ml), about 5% of an internal rosin sizing agent (product name "Sizepine E-50", manufactured by Arakawa Chemical Industries Co., Ltd.) was mixed with about 2% of aluminum sulfate relative to the (dry) pulp to prepare base paper 2. The sizing degree of base paper 2 was 20 seconds.

[0032] <Coating fluid> (oil resistant agent) A1: Long-chain aliphatic compound (product name "Sizepain CA-956", manufactured by Arakawa Chemical Industries, Ltd.) A2: Paraffin wax (product name "SPW-116H", manufactured by Arakawa Chemical Industries, Ltd.) (resin) B1: Polyether-based polyurethane resin (product names "HYDRAN WLS-102" and "HYDRAN WLS-230", manufactured by DIC Corporation) B2: Polyester-based polyurethane resin (product name "Hydran HW-311", manufactured by DIC Corporation) B3: Polycarbonate-based polyurethane resin (product name "Hydran WLS-210", manufactured by DIC Corporation) B4: Hydroxy polyurethane resin (product name "HPU-W011A", manufactured by Dainichiseika Chemicals Mfg. Co., Ltd.) B5: Starch (product name "DYNACOTE-68NB", manufactured by GSL JAPAN Co., Ltd.) B6: Olefin resin (product name "Chemipearl (registered trademark) S-120", manufactured by Mitsui Chemicals, Inc.)

[0033] [Example 1] A coating liquid was prepared using the raw materials and compositions shown in Table 1, and diluted appropriately with water. Next, both sides of the base paper 1 were impregnated with the coating liquid shown in Table 1 using Hishiracopy (product name ONE STEP PROCESSOR S-III, manufactured by Mitsubishi Paper Mills, Ltd.), a tabletop impregnation device that imitates the size press process of a papermaking machine. Finally, the paper was dried at 120°C for 2 minutes to obtain a grease-resistant paper sample.

[0034] [Examples 2 to 6, Comparative Examples 1 to 8] Grease-resistant paper samples were prepared in the same manner as in Example 1, except that the base paper, the composition of the coating liquid, and the coating amount were as shown in Table 1.

[0035] [evaluation] The grease-resistant paper samples prepared in the above Examples and Comparative Examples were evaluated as follows. The evaluation results are shown in Table 1.

[0036] (Oil resistance: normal) A drop of Nisshin Canola Oil (Nissin Oillio Group, Ltd.) was placed on the prepared grease-resistant paper sample, and after 30 minutes the oil was wiped off and visually inspected. 〇: No oil stains △: Oil stains, but no bleed-through ×: Oil stains and bleed-through

[0037] (Oil resistance: cracking) The prepared greaseproof paper sample was folded once with a 1 kg roller while applying a load, and then the folded part was opened and folded again with the roller to create a cross. After that, a drop of Nissin Canola Oil was dropped on the inside of the folded part (the valley side), and after 30 minutes the oil was wiped off and the sample was visually inspected. 〇: No oil stains △: Oil stains, but no bleed-through ×: Oil stains and bleed-through

[0038] (Air resistance) Air permeability resistance was measured according to the air permeability test method / Oken method (JIS P8117:2009).

[0039] [Table 1]

[0040] As shown in Table 1, in the examples in which a long-chain aliphatic compound was impregnated with a polyether-based polyurethane resin, a polyester-based polyurethane resin, or a polycarbonate-based polyurethane resin, good results were obtained in terms of oil resistance in both the normal state and cracking, and the moisture permeability was also good. On the other hand, Comparative Example 1, which contained only a long-chain aliphatic compound, was inferior in oil resistance to fracture. Comparative Example 2, which contained only a polyether-based polyurethane resin, was poor in both oil resistance and crack resistance. Comparative Example 3, which contained a long-chain aliphatic compound and a polyether-based polyurethane resin but had a sizing degree of 20 seconds, was inferior in all evaluations. Comparative Example 4, which contained a long-chain aliphatic compound and a hydroxy polyurethane resin, was poor in both oil resistance and crack resistance. Comparative Examples 5 and 6, which contained a long-chain aliphatic compound but used starch and an olefin resin as the resin, were inferior in all evaluations. Comparative Example 7, which contained a long-chain aliphatic compound and paraffin wax but no resin, was poor in oil resistance and crack resistance. Comparative Example 8, which contained a polyether polyurethane resin but used paraffin wax as an oil-resistant agent, was poor in both oil resistance and crack resistance.

Claims

1. The sheet comprises a base paper and an oil-resistant agent and a resin 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 a sizing degree of 0 seconds or more and less than 10 seconds, The oil-resistant agent is a long-chain aliphatic compound, The greaseproof paper, wherein the resin is at least one type of polyurethane selected from the group consisting of polyether-based polyurethane, polyester-based polyurethane, and polycarbonate-based polyurethane.

2. 2. The greaseproof paper according to claim 1, wherein the long-chain aliphatic compound is a reaction product of an alkylamine having an alkyl group having 8 to 24 carbon atoms and a polycarboxylic acid having a hydroxyl group.

3. 2. The greaseproof paper according to claim 1, wherein the sizing degree of the base paper is from 0 seconds to 10 seconds.

4. 2. The greaseproof paper according to claim 1, wherein the base paper is further impregnated in the vicinity of the other surface thereof with the greaseproofing agent and the resin.

5. 2. The greaseproof paper according to claim 1, which has an air resistance of 500 seconds or less.

6. 2. The greaseproof paper according to claim 1, wherein the content of the polyurethane relative to the total amount of the long-chain aliphatic compound and the polyurethane is 15% by mass or more and 90% by mass or less.

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