Laminate and method for manufacturing a laminate

Abstract

To provide a laminate which is excellent in shape retention property.SOLUTION: A laminate 100 includes a paper base material 10, a first resin layer 20 which is provided on one surface 11 of the paper base material and contains a first biodegradable resin, and a second resin layer 30 which is provided on a surface opposite to the paper base material 10 side of the first resin layer and contains a second biodegradable resin, wherein the first biodegradable resin is a biodegradable resin other than cellulose acetate, and the second biodegradable resin is the cellulose acetate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminate. [Background Art]

[0002] In recent years, biodegradable resins have been studied to reduce the environmental impact associated with the disposal of plastic waste. Biodegradable resins have the property of being ultimately decomposed into carbon dioxide and water by the action of microorganisms, and circulated into the natural world. Paper products have attracted attention because they are degradable after disposal, and laminated materials in which paper and a biodegradable resin are laminated have been proposed.

[0003] For example, Patent Document 1 discloses a laminated packaging material in which a paper layer is used as a base material, and at least two layers, i.e., an aliphatic / aromatic copolyester resin layer having good adhesion to paper on one surface of the paper layer and a seal layer, are laminated by a coextrusion method with the aliphatic / aromatic copolyester resin layer positioned on the paper layer side. The aliphatic / aromatic copolyester resin layer is a biodegradable copolyester resin layer composed of three components: terephthalic acid, adipic acid, and 1,4-butanediol. The seal layer is formed of a biodegradable resin made of polylactic acid, polybutylene succinate, or a starch / polycaprolactone mixture, or a blend resin obtained by kneading 50 to 90% by weight of a biodegradable resin made of polylactic acid, polybutylene succinate, or a starch / polycaprolactone mixture with 10 to 50% by weight of the aforementioned aliphatic / aromatic copolyester resin. [Prior Art Document] [Patent Document]

[0004] [Patent Document 1] Japanese Patent Laid-Open No. 2004-098321 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] Laminates made of biodegradable resins may be embossed, for example, to give the surface of the laminate an uneven pattern or to impart a desired function. However, the laminated packaging material described in Patent Document 1 does not consider embossing, nor does it consider the shape retention when embossed.

[0006] Generally, biodegradable resins tend to have low heat resistance. For example, if an embossed product (hereinafter, an embossed product made by laminating a paper substrate and a biodegradable resin) is produced and then exposed to a high-temperature environment, there is a concern that the uneven shape created by the embossing process may not be maintained and may return to its original state to some extent.

[0007] The object of the present invention is to provide a laminate in which a biodegradable resin is laminated on a paper substrate, which exhibits excellent shape retention even when the laminate is left in a high-temperature environment after being embossed. [Means for solving the problem]

[0008] [1] Paper substrate and A first resin layer containing a first biodegradable resin is provided on one side of the paper substrate, A second resin layer containing a second biodegradable resin is provided on the side of the first resin layer opposite to the paper substrate side, Equipped with, The first biodegradable resin is a biodegradable resin other than cellulose acetate, The second biodegradable resin is cellulose acetate. Laminated structure.

[0009] [2] In the laminate described in [1], The thickness of the second resin layer is 2 μm or more and 20 μm or less. Laminated structure.

[0010] The laminate according to [3] [1] or [2], wherein the acetylation degree of the cellulose acetate is 50% or more and 62% or less, laminate.

[0011] [4] The laminate according to any one of [1] to [3], wherein the total degree of acetyl group substitution of the cellulose acetate is 2.3 or more and 2.6 or less, laminate.

[0012] [5] The laminate according to any one of [1] to [4], wherein the second resin layer is a resin layer formed by coating a coating liquid in which the cellulose acetate is dissolved in an organic solvent, laminate.

[0013] [6] The laminate according to any one of [1] to [5], wherein the first biodegradable resin is at least one biodegradable resin selected from the group consisting of polylactic acid, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, polyethylene terephthalate succinate, polyglycolic acid, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), laminate.

[0014] [7] The laminate according to any one of [1] to [6], wherein the thickness of the first resin layer is 20 µm or more and 300 µm or less, laminate. Effects of the Invention

[0015] According to one aspect of the present invention, in a laminate in which a biodegradable resin is laminated on a paper base material, a laminate excellent in shape retention can be provided even when the embossed laminate is left to stand in a high-temperature environment. Brief Description of Drawings

[0016] [Figure 1]It is a schematic cross-sectional view schematically illustrating an example of the laminate according to the present embodiment. MODE FOR CARRYING OUT THE INVENTION

[0017] Hereinafter, a preferred embodiment of the laminate which is an example of the present invention will be described.

[0018] <Laminate> The laminate according to the present embodiment comprises: a paper base material; a first resin layer including a first biodegradable resin provided on one surface of the paper base material; and a second resin layer including a second biodegradable resin provided on a surface of the first resin layer opposite to the paper base material side. The first biodegradable resin is a biodegradable resin other than cellulose acetate, and the second biodegradable resin is the cellulose acetate.

[0019] With the above configuration, the laminate according to the present embodiment can achieve the characteristic that a laminate excellent in shape retention can be obtained even when the embossed laminate is left in a high-temperature environment. Although the reason is not clear, it is presumed that the above-described shape retention is obtained because cellulose acetate has higher heat resistance than biodegradable resins other than cellulose acetate.

[0020] The laminate according to this embodiment will be described with reference to the drawings. The laminate 100 shown in Figure 1 comprises a paper substrate 10, a first resin layer 20 provided on one side of the paper substrate 10 (the first main surface 11 of the paper substrate 10), and a second resin layer 30 provided on the side of the first resin layer 20 opposite to the paper substrate 10 (the main surface 21 of the first resin layer 20). The paper substrate 10, the first resin layer 20, and the second resin layer 30 are sequentially laminated in this order from the paper substrate 10 toward the second resin layer 30. The second main surface 13 of the paper substrate 10 is not provided with the first resin layer 20 or the second resin layer 30, and the second main surface 13 of the paper substrate 10 is exposed. The first resin layer 20 contains a first biodegradable resin, and the first biodegradable resin is a biodegradable resin other than cellulose acetate. The second resin layer 30 contains a second biodegradable resin, which is cellulose acetate. When embossing is applied to the laminate 100, for example, an embossed uneven shape is given to the main surface 31 of the second resin layer 30. Here, the main surface refers to the largest surface of the paper substrate, the first resin layer, or the second resin layer, and represents the surface facing the thickness direction (i.e., the lamination direction of each layer).

[0021] An example of a laminate according to this embodiment has been described above with reference to Figure 1, but the laminate according to this embodiment is not limited thereto. The laminate according to this embodiment can take various forms as long as it has the above configuration.

[0022] (Paper base material) The paper substrate is not particularly limited as long as it can support the first resin layer described later. Examples of paper substrates include kraft paper, glassine paper, uncoated paper (e.g., fine paper, medium-quality paper, and tissue paper), and coated paper (e.g., art paper, clay-coated paper, and cast-coated paper).

[0023] In this specification, coated paper comprises a base paper mainly composed of pulp fibers and a pigment coating layer provided on the base paper. The base paper is obtained, for example, by a known method, with the desired additives added to a base paper mainly composed of pulp fibers. The pigment coating layer is provided on the base paper by a known method. The pigment coating layer may have a single-layer structure or a multi-layer structure. The pigment coating layer contains, for example, 2 to 50 parts by mass of an adhesive, such as an aqueous resin, per 100 parts by mass of one or more pigments, such as calcium carbonate, kaolin, clay, talc, satin white, titanium dioxide, and plastic pigments.

[0024] The basis weight of the paper substrate is not particularly limited; for example, 30 g / m² 2 Preferably, it is 40 g / m 2 It is more preferable that the above is true. The basis weight of the paper substrate is, for example, 300 g / m². 2 Preferably, it is 200 g / m². 2 The following is more preferable: The thickness of the paper substrate is not particularly limited, but is preferably 5 μm or more, and more preferably 10 μm or more. The thickness of the paper substrate is preferably 300 μm or less, and more preferably 200 μm or less.

[0025] When the paper substrate is coated paper, the thickness of the base paper is preferably 50 μm or more, and more preferably 100 μm or more. The thickness of the base paper is preferably 250 μm or less, and more preferably 200 μm or less. The thickness of the pigment coating layer is preferably 5 μm or more, and more preferably 10 μm or more. The thickness of the pigment coating layer is preferably 40 μm or less, and more preferably 30 μm or less.

[0026] (First resin layer) The first resin layer is not particularly limited in type, as long as it contains a biodegradable resin other than cellulose acetate. The biodegradable resin other than cellulose acetate is preferably at least one biodegradable resin selected from the group consisting of polylactic acid, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, polyethylene terephthalate succinate, polyglycolic acid, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). Among these, the biodegradable resin other than cellulose acetate is more preferably one or more of polylactic acid, polybutylene succinate, polybutylene succinate adipate, and polybutylene adipate terephthalate, and even more preferably one or more of polybutylene succinate adipate and polybutylene adipate terephthalate.

[0027] The thickness of the first resin layer is not particularly limited, but from the viewpoint of film formation, it is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 40 μm or more. The thickness of the first resin layer is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 150 μm or less. Note that if the thickness of the first resin layer is 300 μm or less, for example, the occurrence of curl is easily suppressed.

[0028] The first resin layer may contain, in addition to the first biodegradable resin, other components such as additives as needed. Examples of additives include crystallization nucleating agents, plasticizers, hydrolysis inhibitors, antioxidants, ultraviolet absorbers, colorants, and fillers. These additives may be used individually or in combination of two or more.

[0029] (Second resin layer) The second resin layer contains cellulose acetate as the second biodegradable resin. Alternatively, the second resin layer may contain only cellulose acetate as the second biodegradable resin.

[0030] The thickness of the second resin layer is not particularly limited. From the viewpoint of superior shape retention when the embossed laminate is left in a high-temperature environment, the thickness of the second resin layer is preferably 2 μm or more, more preferably 3 μm or more, and even more preferably 4 μm or more. The thickness of the second resin layer is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. Note that if the thickness of the second resin layer is 20 μm or less, for example, the occurrence of curl is more easily suppressed.

[0031] From the viewpoint of easily obtaining biodegradability, it is preferable that the degree of acetic acid of cellulose acetate be 50% or higher. The degree of acetic acid of cellulose acetate may be 52% or higher, 53% or higher, or 54% or higher. From the viewpoint of easily obtaining biodegradability, it is preferable that the degree of acetic acid of cellulose acetate be 62% or lower.

[0032] The degree of acetic acidity of cellulose acetate can be measured in accordance with the measurement method for the degree of acetic acidity of ASTM D-817-91 (Test method for cellulose acetate, etc.).

[0033] The total degree of acetyl group substitution in cellulose acetate is preferably 2.3 or higher, and more preferably 2.4 or higher, from the viewpoint of easily obtaining biodegradability. The total degree of acetyl group substitution in cellulose acetate is preferably 2.6 or lower, and more preferably 2.5 or lower, from the viewpoint of easily obtaining biodegradability.

[0034] The total degree of acetyl group substitution in cellulose acetate can be determined by converting the degree of acetic acidization of cellulose acetate using the following formula (F1). DS=162.14×AV / (6005.2-AV×42.037)...(F1) In formula (F1), DS represents the total degree of acetyl group substitution, and AV represents the degree of acetic acid (%).

[0035] Furthermore, it is preferable that the cellulose acetate has a 6% viscosity (viscosity when diluted to 6%) at 25±1℃ of 50 mPa·s or more and 200 mPa·s or less. The 6% viscosity can be measured, for example, by dissolving 3 g of the dry sample in 39.9 g of a 95% acetone aqueous solution to a solution with a concentration of 6 wt / vol% (mass / volume%) using an Ostwald viscometer.

[0036] Cellulose acetate preferably has a melting point of 230°C or higher and 300°C or lower. The melting point of cellulose acetate can be measured, for example, in accordance with the method specified in JIS K7121:1987.

[0037] The viscosity of a solution containing cellulose acetate, such as the coating solution for the second resin layer-forming composition described later, can be measured, for example, in accordance with the method specified in JIS K7117-1:1999.

[0038] The second resin layer may be (i) a resin layer formed by melt extrusion of cellulose acetate, or (ii) a resin layer coated with a coating solution in which cellulose acetate is dissolved in an organic solvent. From the viewpoint of ease of formation of the second resin layer and adhesion to the paper substrate, it is preferable that the second resin layer is a resin layer coated with a coating solution in which cellulose acetate is dissolved in an organic solvent (the coating solution of the composition for forming the second resin layer).

[0039] In addition to the second biodegradable resin, the second resin layer may also contain other components, such as additives (e.g., plasticizers), as necessary, to the extent that they do not impair the effects of this embodiment.

[0040] (Method of manufacturing a laminate) The method for manufacturing the laminate according to this embodiment is not particularly limited. An example of a preferred method for manufacturing the laminate according to this embodiment is a method comprising the steps of: preparing a paper substrate; providing a first resin layer containing a first biodegradable resin on one side of the paper substrate; and providing a second resin layer containing a second biodegradable resin on the side of the first resin layer opposite to the paper substrate side, wherein the first biodegradable resin is a biodegradable resin other than cellulose acetate, and the second biodegradable resin is cellulose acetate.

[0041] The process of preparing the paper substrate is simply to prepare the paper substrate as described above.

[0042] The step of providing the first resin layer is not particularly limited, as long as the first resin layer containing the biodegradable resin described above can be provided on one side of the paper substrate. Examples of methods for providing the first resin layer on the paper substrate include (1) providing it by a method such as melt extrusion, and (2) obtaining a resin film of the first biodegradable resin by a casting method, and then providing it on the paper substrate via an adhesive, a primer, or both. In the step of providing the first resin layer, various surface treatments such as heating or corona discharge treatment may be applied to the surface of the paper substrate where the first resin layer is to be provided in order to improve adhesion with the paper substrate.

[0043] The step of providing the second resin layer is not particularly limited, as long as the second resin layer containing cellulose acetate can be provided on the side of the first resin layer provided on the paper substrate that is opposite to the paper substrate side. A method for providing the second resin layer on the first resin layer is, for example, to coat the first resin with a coating solution of a second resin layer forming composition, which is obtained by dissolving a second resin layer forming material containing cellulose acetate as a second biodegradable resin in an organic solvent. After coating the first resin with the coating solution of the second resin layer forming composition, the second resin layer is formed by drying. In the step of providing the second resin layer, various surface treatments such as heating or corona discharge treatment may be applied to the surface of the first resin layer to improve adhesion with the first resin layer.

[0044] The organic solvent used to dissolve cellulose acetate is not particularly limited and includes, for example, ketones (acetone, cyclohexanone, and methyl ethyl ketone (MEK), etc.), ethers (diethyl ether, ethylene glycol monomethyl ether, and propylene glycol monomethyl ether, etc.), amides (dimethylformamide, etc.), and esters (ethyl acetate, butyl acetate, etc.). These organic solvents may be used individually or in combination of two or more. Among these organic solvents, it is preferable to use at least one selected from the group consisting of ethyl methyl ketone, dimethylformamide, and cyclohexanone, from the viewpoint of ease of dissolving cellulose acetate.

[0045] The viscosity of the coating solution for the second resin layer forming composition at 25°C is preferably 20 mPa·s or more and 2000 mPa·s or less. If the viscosity is within this range, it becomes easier to form the second resin layer using the coating solution. This viscosity can be measured, for example, in accordance with the method specified in JIS K7117-1:1999. The non-volatile content concentration in the coating solution for the second resin layer forming composition is not particularly limited, as long as the viscosity at 25°C can be adjusted to within the above range.

[0046] Methods for coating the second resin layer-forming composition onto the first resin layer include, for example, bar coating, knife coating, roll knife coating, roll coating, blade coating, die coating, curtain coating, and gravure coating. The amount of coating solution of the second resin layer-forming composition is preferably such that the thickness of the second resin layer after drying is in the range of 2 μm or more and 20 μm or less. When the second resin layer is made only of cellulose acetate, the amount of coating solution of the second resin layer-forming composition is not particularly limited, for example, 3 g / m². 2 More than 30g / m 2 The following are some examples:

[0047] By completing the above steps, a laminate according to this embodiment can be obtained.

[0048] In order to impart functionality to the laminate according to this embodiment, the laminate obtained in the above process can be embossed by an embossing process. Embossing is performed, for example, by pressing the laminate by sandwiching it between an embossing roll having an uneven shape and a pressure roll. When embossing the laminate according to this embodiment, it is preferable to sandwich the laminate between the embossing roll and the pressure roll so that the second resin layer side of the laminate faces the embossing roll side. In this case, the uneven shape of the embossing roll is brought into contact with the second resin layer provided on the laminate, and the uneven shape is transferred to the second resin layer.

[0049] The processing conditions for embossing are not particularly limited. For example, the following conditions may be considered: The heating temperature for embossing is preferably 100°C or higher and 200°C or lower, and more preferably 120°C or higher and 180°C or lower. The pressure for embossing is preferably 1 MPa or higher and 50 MPa or lower, and more preferably 5 MPa or higher and 30 MPa or lower. The heating time for embossing is preferably 1 second or higher and 2 minutes or lower, and more preferably 5 seconds or higher and 1 minute or lower.

[0050] (Applications of laminates) The laminate according to this embodiment exhibits excellent shape retention, as the embossed shape is easily maintained even when the embossed laminate is left in a high-temperature environment (for example, 60°C or higher and 140°C or lower). Therefore, the laminate of this embodiment can be applied to applications where decorative properties are added by embossing, and to applications where a desired function is added. Specifically, the laminate of this embodiment is useful for applications such as microwaveable food containers.

[0051] The present invention is not limited to the embodiments described above. The present invention may include modifications and improvements to the extent that they can achieve the objectives of the present invention. [Examples]

[0052] Examples are described below, but the present invention is not limited to these examples.

[0053] The following raw materials were prepared to produce the laminates of each example and each comparative example.

[0054] (Paper base material) P-1: High-quality paper (manufactured by Nippon Paper Industries, npi high-quality paper, basis weight 64g / m²) 2 )

[0055] (First biodegradable resin) PBS-1: Polybutylene succinate (manufactured by Mitsubishi Chemical Corporation, FORZEAS DM9B01) PBS-2: Polybutylene succinate (manufactured by Mitsubishi Chemical Corporation, FORZEAS ZM9B02) PBAT-1: Polybutylene adipate terephthalate (BASF, Ecoflex C1200)

[0056] (Second biodegradable resin) CA-1: Cellulose acetate with a degree of 55% acetate (total acetyl group substitution degree 2.4) (manufactured by Daicel Corporation, L-20)

[0057] <Example 1> Polybutylene succinate (PBS-1) was used as the first biodegradable resin. PBS-1 was heated and melted at 190°C, and the molten PBS-1 was extruded from a T-die onto the surface of fine paper (P-1) to form a first resin layer with a thickness of 100 μm on one side of the fine paper. Next, a coating solution of a second resin layer-forming composition (viscosity of 1200 mPa·s at 25°C), prepared by dissolving cellulose acetate (CA-1) in methyl ethyl ketone, was coated onto the surface of this first resin layer using an applicator. After drying at 120°C for 1 minute, a second resin layer with a thickness of 5 μm was formed, obtaining the laminate of Example 1.

[0058] <Example 2> The laminate of Example 2 was obtained in the same manner as in Example 1, except that the first biodegradable resin was changed according to Table 1.

[0059] <Example 3> The laminate of Example 3 was obtained in the same manner as in Example 1, except that the first biodegradable resin was changed according to Table 1.

[0060] <Comparative Example 1> A laminate of Comparative Example 1 was obtained in the same manner as in Example 1, except that a second resin layer was not provided.

[0061] <Comparative Example 2> A laminate of Comparative Example 2 was obtained in the same manner as in Example 3, except that a second resin layer was not provided.

[0062] [Evaluation of shape retention] The resin layers of the laminates obtained in each of the above examples (the first and second resin layers in each example, and the first resin layer in the comparative example) were sequentially stacked with the uneven surface of the embossed material (material: stainless steel, arithmetic mean surface roughness Ra: 5.0 μm, dimensions: 100 mm × 100 mm, thickness: 3 mm). Using a hot press, the materials were heated and compressed and cooled under the conditions of a heating temperature of 130°C, a pressing pressure of 10 MPa, a heating time of 10 seconds, and a cooling time (left at room temperature) of 2 minutes to perform embossing.

[0063] Embossed laminates, obtained by embossing a laminate, were subjected to heat treatment by being placed in a constant temperature bath at 140°C for 5 minutes. The shape retention of the embossed laminates before and after heat treatment was confirmed by visual inspection of the changes in appearance according to the following evaluation criteria.

[0064] (Evaluation Criteria) A: No change F: Disappearance of uneven shape

[0065] Furthermore, the shape retention of the embossed laminate was evaluated by measuring the arithmetic mean surface roughness Ra of the embossed surface of both the embossed laminate before and after the heat treatment. The arithmetic mean surface roughness Ra was measured using a contact surface roughness meter (SV3000S4, manufactured by Mitutoyo Corporation) in accordance with JIS B0601:2001.

[0066] [Table 1]

[0067] Based on the above results, it can be seen that the laminates of each example, which are provided with a second resin layer containing a second biodegradable resin, cellulose acetate, exhibit superior shape retention compared to the laminates of each comparative example, which are not provided with the second resin layer, even when left in a high-temperature environment after embossing. [Explanation of Symbols]

[0068] 10...Paper substrate, 11...First main surface (first main surface of the paper substrate), 13...Second main surface (second main surface of the paper substrate), 20...First resin layer, 21...Main surface (main surface of the first resin layer 20), 30...Second resin layer, 31...Main surface (main surface of the second resin layer 30), 100...Laminate.

Claims

1. Paper substrate and A first resin layer containing a first biodegradable resin is provided on one side of the paper substrate, A second resin layer containing a second biodegradable resin is provided on the side of the first resin layer opposite to the paper substrate side, Equipped with, The first biodegradable resin is a biodegradable resin other than cellulose acetate, The second biodegradable resin includes only the cellulose acetate. Laminated structure.

2. In the laminate according to claim 1, The thickness of the second resin layer is 2 μm or more and 20 μm or less. Laminated structure.

3. In the laminate according to claim 1 or claim 2, The degree of acetic acidization of the cellulose acetate is 50% or more and 62% or less. Laminated structure.

4. In the laminate according to claim 1 or claim 2, The total degree of acetyl group substitution of the cellulose acetate is 2.3 or more and 2.6 or less. Laminated structure.

5. In the laminate according to claim 1 or claim 2, The first biodegradable resin is at least one biodegradable resin selected from the group consisting of polylactic acid, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, polyethylene terephthalate succinate, polyglycolic acid, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). Laminated structure.

6. In the laminate according to claim 1 or claim 2, The thickness of the first resin layer is 20 μm or more and 300 μm or less. Laminated structure.

7. In the method for manufacturing a laminate according to claim 1 or claim 2, The process includes a step of providing a second resin layer, which is formed by coating the aforementioned cellulose acetate with a coating solution in which the cellulose acetate is dissolved in an organic solvent. A method for manufacturing laminates.

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