Cellophane laminate

Abstract

The objective is to obtain a cellophane laminate that has moisture resistance, heat sealability, and dimensional stability at high temperatures and humidity, without the need for anchor coat layers or adhesive layers. [Solution] A cellophane laminate is used, in which a moisture-resistant layer having heat-sealing properties with a thickness of 1.0 to 4.0 μm is provided on both surfaces of a base layer made of cellophane, and this moisture-resistant layer is made of one or more types of resins selected from olefin resins, aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, graft polymers of these resins, and modified versions of these resins.

Description

[Technical Field]

[0001] This invention relates to a cellophane laminate. [Background technology]

[0002] Currently, with the issue of marine pollution caused by microplastics and other materials attracting global attention, marine biodegradable cellophane made from wood pulp and other materials is being looked to as an alternative to petroleum-based plastic films. However, because cellophane is hygroscopic, using it as is can lead to problems such as wrinkling and expansion due to changes in ambient humidity. Furthermore, since cellophane does not have heat-sealing properties, it needs to be combined with a heat-sealing material when used as packaging.

[0003] As a countermeasure, a method is known in which moisture resistance and heat sealability are imparted to cellophane by laminating a layer made of a vinyl chloride-vinyl acetate copolymer (Patent Document 1). In addition, it is known that the hygroscopicity of cellophane can be suppressed by laminating an ionomer resin onto cellophane via an anchor coat layer (Patent Document 2).

[0004] Furthermore, a method is known for imparting moisture resistance and heat-sealability to cellophane by laminating a layer made of ethylene-methacrylic acid copolymer to cellophane via an anchor coat layer (Patent Document 3). Moreover, a method is known for imparting moisture resistance to cellophane by laminating a layer made of polyamide resin, nitrated cotton resin, or polyvinylidene chloride resin via an adhesive layer (Patent Document 4). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2009-154527 [Patent Document 2] Patent No. 2648578 [Patent Document 3] Japanese Patent Publication No. 2004-074665 [Patent Document 4] Japanese Patent Publication No. 2020-140164 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, when cellophane is laminated with layers made of vinyl chloride-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ionomer resin, polyamide resin, nitrated cotton resin, polyvinylidene chloride resin, etc., it has excellent moisture resistance, but its effect in suppressing wrinkles and shrinkage caused by changes in ambient humidity is not entirely sufficient. Furthermore, while laminating cellophane with petroleum-based plastic films such as olefin films can provide heat-sealing properties, it necessitates a thicker heat-sealing layer, which may lead to problems with biodegradability and recyclability. Furthermore, when laminating a resin layer onto cellophane, it is often necessary to add an anchor coat layer or adhesive layer to improve adhesion between the two, which can increase materials, costs, and processing steps.

[0007] Therefore, the objective of this invention is to obtain a cellophane laminate that has heat-sealing properties and dimensional stability at high temperature and humidity, i.e., moisture resistance, without the need for an anchor coat layer or adhesive layer. [Means for solving the problem]

[0008] This invention solves the aforementioned problems by providing a predetermined moisture-resistant layer on a base layer made of cellophane, and its gist is found in the following [1] to [4].

[0009] [1] A cellophane laminate comprising a base layer made of cellophane with a heat-sealable moisture-resistant layer having a thickness of 1.0 to 4.0 μm on both surfaces. [2] The heat-sealable moisture-resistant layer is a layer made of one or more resins selected from olefin resins, aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, graft polymers of these resins, and modified versions of these resins, as described in [1]. [3] The amount of the moisture-resistant layer is such that the solid content per surface of the base layer is 1.0 to 4.0 g / m² 2 The cellophane laminate described in [1] or [2]. [4] A coating solution containing one or more resins selected from olefin resins, aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, graft polymers of these resins, and modified versions of these resins is applied to both surfaces of a cellophane substrate layer in a solid content of 1.0 to 4.0 g / m². 2 A method for manufacturing cellophane laminates, in which a moisture-resistant layer with heat-sealing properties and a thickness of 1.0 to 4.0 μm is formed by coating and drying. [Effects of the Invention]

[0010] The cellophane laminate according to this invention includes a moisture-resistant layer made of a heat-sealable resin. Therefore, even without an anchor coat layer or adhesive layer, the adhesion between the cellophane base layer and the moisture-resistant layer can be improved, and heat-sealability can be provided. Furthermore, by improving moisture resistance, dimensional changes due to humidity changes are suppressed, thus preventing the occurrence of wrinkles and shrinkage. Furthermore, since the thickness of the moisture-resistant layer is kept within a predetermined range, there is no risk of impairing the biodegradability of the cellophane. [Brief explanation of the drawing]

[0011] [Figure 1] Cross-sectional view showing an example of a cellophane laminate according to this invention. [Modes for carrying out the invention]

[0012] The present invention will be described below. As shown in FIG. 1, the invention of the present application is an invention related to a cellophane laminate 11 provided with moisture-resistant layers 13 of a predetermined thickness on both surfaces of a base material layer 12.

[0013] <Cellophane laminate> The base material layer 12 constituting the cellophane laminate 11 according to this invention is made of cellophane having biodegradability.

[0014] The moisture-resistant layer 13 constituting the cellophane laminate 11 according to this invention is a layer that imparts heat-sealability and moisture resistance to the cellophane laminate 11. The material constituting this moisture-resistant layer is not particularly limited as long as it can exhibit heat-sealability and moisture resistance when used as the cellophane laminate 11. Examples of such materials include hydrocarbon-based resins, graft polymers or modified products of such resins, etc. Examples of this hydrocarbon-based resin include olefin-based resins, aliphatic hydrocarbon-based resins, alicyclic hydrocarbon-based resins, etc. When these resins are used, heat-sealability can be imparted to the cellophane laminate 11, and sufficient moisture resistance can be imparted, thereby improving dimensional stability at high temperature and high humidity.

[0015] The olefin-based resin is a homopolymer having olefin as a monomer unit, or a copolymer having olefin as a main monomer and copolymerized with other olefins or other types of monomers. Examples of this olefin-based resin include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butane copolymer, propylene-butane copolymer, etc.

[0016] In addition, examples of the aliphatic hydrocarbon-based resin include petroleum resins and terpene-based resins, etc. Further, examples of the alicyclic hydrocarbon-based resin include cyclic olefin-based polymers and norbornene-based polymers, etc.

[0017] Furthermore, the graft polymer is obtained by graft polymerization using the hydrocarbon resin, and examples include ethylene-propylene resin or propylene resin grafted with styrene, etc. Moreover, the modified product is a resin obtained by modifying the hydrocarbon resin with a modifying agent, and examples of modifying agents include polar monomers such as maleic acid, (meth)acrylic acid, (meth)acrylic acid ester, (meth)acrylamide, and halogen gases such as chlorine and bromine.

[0018] Furthermore, the resin constituting the moisture-resistant layer 13 may consist of only one of the following: polyolefin, aliphatic hydrocarbon resin, alicyclic hydrocarbon resin, graft polymers of these resins, or modified versions of these resins. Alternatively, a mixture of multiple resins may be used.

[0019] The thickness of the moisture-resistant layer 13 laminated on the base layer 12 is preferably 1.0 μm or more per surface, preferably 1.2 μm or more, particularly preferably 1.5 μm or more, and even more preferably 2.0 μm or more. It is also preferably 4.0 μm or less, preferably 3.5 μm or less, and even more preferably 3.0 μm or less. If it is thicker than 4.0 μm, it may impair the biodegradability of the cellophane laminate according to this invention, or if the moisture-resistant layer is formed by coating, it may reduce drying efficiency and hinder productivity. On the other hand, if it is thinner than 1.0 μm, it tends to be difficult to obtain sufficient moisture resistance and heat sealability, and therefore, dimensional stability under high temperature and high humidity conditions may not be sufficiently obtained. Also, if it is 1.0 μm or more and less than 1.5 μm, heat sealability can be obtained, but depending on the usage, it may be difficult to say that the heat sealability is sufficient. In contrast, if it is 1.5 μm or more, sufficient heat sealability can be obtained more reliably.

[0020] This moisture-resistant layer 13 can be formed by containing the resin constituting the moisture-resistant layer 13, dissolving this in a solvent, applying the resulting coating solution to both surfaces of the base material layer 12, and drying. The solvent is not particularly limited as long as it does not react with the resin constituting the moisture-resistant layer 13, can dissolve this resin, and can be volatilized at room temperature or by heating. Such a solvent may be a solvent having a boiling point of 150°C or lower, preferably 120°C or lower. For example, alkyl derivatives such as cyclohexane and its methylated and ethylated forms, acetate esters such as ethyl acetate and propyl acetate, lower alcohols such as propanol and butanol, ketones such as dimethyl ketone, diethyl ketone, and methyl ethyl ketone, alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether, and toluene. The propyl group and butyl group mentioned above include various isomers such as n-propyl group, isopropyl group, n-butyl group, s-butyl group, isobutyl group, and t-butyl group. These solvents may be used alone or in combination of two or more. The resin concentration of this coating solution is not particularly limited, but it is preferably 15% by mass or more and 35% by mass or less because it can sufficiently ensure the fluidity of the coating solution and does not require a long drying time.

[0021] The amount of the moisture-resistant layer 13 laminated on the base material layer 12 is the dry mass per unit area indicated by the solid content (hereinafter simply referred to as "solid content"), and any amount that satisfies the thickness of the moisture-resistant layer 13 may be used. Specifically, 1.0 g / m 2 or more is good, 1.2 g / m 2 or more is preferable, 1.5 g / m <{ 2 or more is particularly preferable, 2.0 g / m 2 or more is more preferable. Also, 4.0 g / m 2 or less is good, 3.5 g / m 2 or less is preferable, 3.0 g / m 2 or less is more preferable. 4.0 g / m 2If the amount is too high, it may impair the biodegradability of the cellophane laminate according to this invention, or, when a moisture-resistant layer is formed by coating, it may reduce drying efficiency and hinder productivity. On the other hand, 1.0 g / m 2 Using less than 1.0 g / m tends to make it difficult to obtain sufficient moisture resistance and heat sealability, and therefore may result in insufficient dimensional stability under high temperature and high humidity conditions. 2 The above and 1.5g / m 2 If the amount is less than 1.5 g / m², heat sealing properties may be achieved, but depending on the application, the heat sealing properties may not be considered sufficient. In contrast, 1.5 g / m² 2 As a result, sufficient heat sealing performance can be more reliably achieved.

[0022] <Method for manufacturing cellophane laminates> The cellophane laminate 11 according to this invention can be manufactured by the following method. First, one or more resins selected from the hydrocarbon resins, specifically olefin resins, aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, graft polymers of these resins, and modified versions of these resins, are dissolved in the solvent to prepare a coating solution having a resin concentration within the range described above. Next, a coating liquid with a solid content within the specified range is applied to both surfaces of the cellophane base layer 12. Then, it is dried to vaporize or volatilize the solvent in the coating liquid. This forms a moisture-resistant layer with a thickness within the specified range, and a cellophane laminate can be obtained. At this time, it is better to apply the same amount of coating in two steps rather than in a single-layer coating where a large amount is applied at once. Two-layer coating, where the coating is applied in layers, can sometimes result in higher drying efficiency, and is preferable in terms of productivity if the equipment allows for it.

[0023] The aforementioned coating methods include methods using coaters such as bar coaters, gravure coaters, roll coaters, and die coaters, as well as methods such as application by brush, dipping, and spraying. As mentioned above, since the aforementioned hydrocarbon resin is applied to form a moisture-resistant layer, the adhesion with the cellophane base layer is improved, and the use of anchor coats or adhesives is usually unnecessary. However, they may be used if even higher adhesion is required. In addition, if printing or other processing is required, a layer of printing or other processing can be provided between the cellophane base layer and the heat-resistant layer, as long as it does not impair adhesion.

[0024] <Physical properties of cellophane laminates> The heat seal strength of the cellophane laminate according to this invention is preferably 0.4 N / 15 mm or higher, and more preferably 0.8 N / 15 mm or higher. If it is lower than 0.4 N / 15 mm, it becomes difficult to achieve sufficient heat sealability. By setting it to 0.4 N / 15 mm or higher, heat sealability can be achieved. However, depending on the application, the heat sealability may not always be sufficient. In contrast, if it is 0.8 N / 15 mm or higher, more reliable heat sealability can be obtained. The heat seal strength is first measured by heat-sealing the outer and inner surfaces of the resulting cellophane laminate under conditions of 120°C, 0.2 MPa pressure, and 1 second of bonding time. Then, the heat seal strength is measured using the 180° peel test specified in JIS Z1707 and expressed in units of N / 15mm width. This allows for the measurement of the heat seal strength.

[0025] Furthermore, the dimensional stability of the cellophane laminate according to this invention under high temperature and high humidity conditions is preferably 99% or more, and more preferably 99.1% or more, based on the dimensional change rate calculated from the measured values ​​shown below. Also, it is preferable that it be 101% or less, and more preferably 100.5% or less. (99% or more and 101% or less) If present, it can prevent dimensional changes during storage, suppress wrinkles, peeling or tearing of heat-sealed areas, and reduce the likelihood of appearance defects when used as packaging material. To assess dimensional stability, when measuring MD, a 160mm MD x 30mm TD test specimen is cut from the cellophane laminate. When measuring TD, a 30mm MD x 160mm TD test specimen is cut from the cellophane laminate. The dimensions are measured immediately after conditioning at 23°C x 50%RH for one day, and then measured again after storage at 40°C x 90%RH for five days. The dimensional change rate can then be calculated. Note that MD refers to the flow direction of the rolled cellophane laminate or cellophane, i.e., the direction in which it is pulled from the roll, and TD direction refers to the direction perpendicular to the MD direction. [Examples]

[0026] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples. First, the raw materials and evaluation methods used in this example or comparative example are shown.

[0027] <Ingredients> [Base material layer] • Cellophane…Manufactured by Rengo Co., Ltd.: PT#300 [Moisture-resistant layer] • Resin A: Manufactured by Osaka Printing Ink Manufacturing Co., Ltd.: EXP31020, a resin solution containing 15-25% by mass of polyolefin resin, 40-50% by mass of methylcyclohexane, 5-15% by mass of methyl ethyl ketone, 1-10% by mass of isopropyl alcohol, and 5-15% by mass of propylene glycol monomethyl ether. • Resin B…Manufactured by Osaka Printing Ink Manufacturing Co., Ltd.: TA-O, a resin solution containing 15-25% by mass of polyolefin resin, 50-60% by mass of methylcyclohexane, 1-5% by mass of methyl ethyl ketone, 1-10% by mass of isopropyl alcohol, and 1-10% by mass of propylene glycol monomethyl ether. • Resin C…Manufactured by Sakata Inx Co., Ltd.: New PPL RE-7, chlorinated polyolefin resin Resin solution containing 15-20% by mass of fat, 60-70% by mass of toluene, 10-20% by mass of methyl ethyl ketone, and 1-5% by mass of isopropyl alcohol. • Solvent (for resins A and B): A mixed solvent consisting of 65-75% by mass of methylcyclohexane, 15-25% by mass of n-propyl acetate, and 5-15% by mass of isopropyl alcohol. • Solvent (for resin C): A mixed solvent consisting of 50-60% by mass of toluene, 40-50% by mass of ethyl acetate, and 10-20% by mass of isopropyl alcohol.

[0028] <Evaluation Method> (1) Thickness measurement The thickness of the cellophane laminate was measured using a micrometer (manufactured by Mitutoyo Corporation). The thickness of the moisture-resistant layer was calculated by subtracting the thickness of the base cellophane from the thickness of the cellophane laminate. (2) Measurement of heat seal strength The outer and inner surfaces of the resulting cellophane laminate are heat-sealed under conditions of 120°C, 0.2 MPa pressure, and a sealing time of 1 second. The heat seal strength is then measured using the 180° peel test according to JIS Z1707 and expressed in units of N / 15mm width.

[0029] (3) Evaluation of dimensional stability (measurement of dimensional change rate under high temperature and high humidity conditions) For MD measurement, a 160mm MD x 30mm TD test specimen is cut from the cellophane laminate. For TD measurement, a 30mm MD x 160mm TD test specimen is cut from the cellophane laminate. The dimensions are measured immediately after conditioning at 23°C x 50%RH for one day (referred to as "dimensions at the start of the test"). Then, the dimensions are measured after storing the specimens in an atmosphere of 40°C x 90%RH for five days (referred to as "dimensions after 5 days of storage"). This method is called the "method." Measure the dimensional change rate using the following formula. Dimensional change rate = (Dimensions after 5 days of storage) / (Dimensions at the start of the test) × 100

[0030] (4) Storage test Basis weight 270g / m 2A paperboard box measuring 10 cm (length) x 10 cm (width) x 20 cm (height) was made using white cardboard (manufactured by Rengo Co., Ltd.: CRC270). This box was then covered with the resulting cellophane laminate, and the side and end edges were heat-sealed using a hot plate heated to 160°C to create an overlap-wrapped paperboard box. The overlap-wrapped paperboard box was then left to stand for 7 days in an atmosphere of 40°C x 90% RH. The changes in appearance, i.e., the deformation of the paperboard box and the degree of wrinkling on the surface of the cellophane laminate, were visually evaluated according to the following criteria. ○: No deformation of the paperboard box was observed, and no wrinkles were found on the surface of the cellophane laminate. △: Minor deformation of the paper packaging box was observed. Or, minor wrinkles were observed on the surface of the cellophane laminate. ×: Deformation of the cardboard box was observed. Or, wrinkles were observed on the surface of the cellophane laminate.

[0031] (Examples 1-9, Comparative Example 2) A solvent was mixed with resins A to C, and the concentration of the resin components was adjusted to 25-35% by mass to obtain a coating solution. A coating liquid containing the resin shown in Table 1 was applied to one side of the cellophane constituting the base layer using a desktop automatic test coater (Matsuo Sangyo Co., Ltd.: K303 Multi Coater) equipped with a wire bar, in the amount of coating shown in Table 1, and dried at 80°C for 30 seconds. In Examples 4 and 5, a second layer of the coating liquid containing the resin shown in Table 1 was applied on the dried coated surface in the same manner, in the amount of coating shown in Table 1, and dried under the same conditions. After drying, a coating liquid containing the resin shown in Table 1 was applied to the other side of the cellophane in the same manner to the amount of coating shown in Table 1, and dried under the same conditions to obtain a cellophane laminate with moisture-resistant layers coated on both sides of the base layer. In Examples 4 and 5, a second layer of coating liquid containing the resin shown in Table 1 was applied on the dried coated surface in the same manner to the amount of coating shown in Table 1, and dried under the same conditions. The aforementioned evaluation was performed using the obtained cellophane laminate. The results are shown in Table 1.

[0032] (Comparative Examples 1 and 3) Comparative Example 1 was cellophane with no coating, and Comparative Example 3 was commercially available moisture-proof cellophane (vinyl chloride / vinyl acetate type: manufactured by Futamura Chemical Co., Ltd.: G-3#300, hereinafter referred to as "G-3"). The aforementioned evaluation was performed using these cellophane samples. The results are shown in Table 1.

[0033] [Table 1] [Explanation of Symbols]

[0034] 11 Cellophane laminate 12 Base material layer 13. Moisture-resistant layer

Claims

1. This is a cellophane laminate in which a moisture-resistant layer with heat-sealing properties and a thickness of 1.0 to 4.0 μm is provided on both surfaces of a base layer made of cellophane. The heat-sealable moisture-resistant layer is a layer made of one or more resins selected from homopolymers using olefins as monomer units and copolymers in which olefins are the main monomer and other olefins are copolymerized. A cellophane laminate in which the dimensional change rate after storage in an atmosphere of 40°C x 90% RH for 5 days is between 99% and 101% compared to the dimensions immediately after conditioning at 23°C x 50% RH for 1 day.

2. The amount of the moisture-resistant layer is such that the solid content per surface of the base layer is 1.0 to 4.0 g / m². ２ The cellophane laminate according to claim 1.

3. A coating solution containing one or more resins selected from homopolymers with olefins as monomer units and copolymers in which olefins are the main monomer and other olefins is copolymerized, is applied to both surfaces of a cellophane substrate layer at a solid content of 1.0 to 4.0 g / m². ２ By coating and drying, a moisture-resistant layer with heat-sealing properties and a thickness of 1.0 to 4.0 μm is formed. A method for manufacturing a cellophane laminate, wherein the dimensional change rate after storage in a 40°C x 90% RH atmosphere for 5 days, compared to the dimensions immediately after conditioning at 23°C x 50% RH for 1 day, is between 99% and 101%.

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