JP5781778B2 - Multi-layer water vapor barrier sheet - Google Patents

Description

The present invention relates to a water vapor barrier sheet using a multilayer structure.

Generally, vapor deposition or lamination of an inorganic substance is used for a film or sheet having a water vapor barrier property. However, in the vapor deposition of inorganic substances, the number of water vapor barrier layers cannot be increased, so that the water vapor barrier property due to pinholes may deteriorate. Furthermore, in the method of laminating aluminum foil or the like, there is a problem that a large-scale manufacturing apparatus or the like is required for laminating and the manufacturing process becomes complicated.

Patent Document 1 proposes a laminated film having excellent barrier properties against oxygen gas and water vapor and pinhole resistance due to a laminated structure of polyamide resin and polyester resin. However, it is difficult to develop a sufficient water vapor barrier property only with a resin component, and in order to realize a high water vapor barrier property, it is necessary to use an inorganic substance.

On the other hand, as a method for imparting barrier properties other than vapor deposition and lamination, there are thermoplastic resins (nanocomposites) in which layered compounds represented by layered silicates are uniformly dispersed. These layered compounds have oxygen and water vapor barrier properties. Improvements in mechanical strength and mechanical strength are expected, and application to films or sheets has been studied. That is, when forming a sheet or the like, the above-described barrier property is improved by orienting these layered compounds with respect to the surface of the sheet. However, simply by forming a film or sheet, the plane orientation of the layered compound is small, so that a large amount of the layered compound needs to be added in order to obtain a sufficient water vapor barrier property. However, when the amount of addition increases, the flexibility of the sheet decreases. Therefore, it has not been possible to obtain a film or sheet having a sufficient water vapor barrier property and a practically sufficient flexibility.

On the other hand, techniques for stretching a sheet or film have been proposed as means for orienting layered compounds (Patent Documents 2 and 3). However, the orientation of the layered compound can be increased by such a method when the amount of the layered compound added is as small as 15% by mass or less, and therefore a gap is generated between the layered compounds when stretched. There was a limit to the effect of improving the water vapor barrier property.

JP 2004-114337 A JP 2010-155455 A JP 2010-131810 A

An object of the present invention is to provide a sheet having a high water vapor barrier property, having no problems such as pinholes, and having a practically sufficient flexibility.

As a result of intensive studies, the present inventors have achieved the above-mentioned problem with a multilayer sheet in which layers containing a scale-like inorganic substance at a specific ratio and layers composed of a thermoplastic resin are alternately laminated in 9 layers or more. It has been found that this can be done, and has led to the present invention. That is, the present invention
Even-numbered layers (A layers) and odd-numbered layers (B layers) are alternately laminated, and the total number of layers is composed of odd-numbered layers of nine or more, and the A layer is the following (1) to (2 And the B layer is a thermoplastic resin multilayer sheet made of the thermoplastic resin B.
(1) The A layer is composed of a mixture of 70 to 20% by mass of the thermoplastic resin A and 30 to 80% by mass of the scaly inorganic substance.
(2) The total thickness of the plurality of A layers is 5% or more and less than 50% with respect to the total thickness of the sheet.
As the thermoplastic resin A, any one or more selected from polyolefin resins, polyester resins, polystyrene resins, ABS resins, polycarbonate resins, ethylene-vinyl alcohol copolymer resins, and polyvinylidene chloride resins. A mixture is preferred. Furthermore, it is more preferable that the thermoplastic resin A is a polyolefin resin. The thermoplastic resin B is preferably one or a mixture of two or more selected from polyolefin resins, polyester resins, polystyrene resins, ABS resins, polycarbonate resins, and polyvinylidene chloride resins. . The scaly inorganic substance added to the A layer is preferably scaly with an aspect ratio of 5 or more.

According to the present invention, a multilayer sheet having a high water vapor barrier property, no problems such as pinholes, and practically sufficient flexibility can be obtained.

In the multilayer structure of the present invention, it is possible to have both a high water vapor barrier property and flexibility as a sheet by adopting a structure in which the inorganic high filling layer A and the thermoplastic resin layer B are alternately laminated. That is, the inorganic highly filled layer A is responsible for the expression of water vapor barrier properties, and the thermoplastic resin layer B is responsible for the expression of flexibility as a sheet.

The number of layers of the multilayer sheet is composed of an odd number of layers of 9 or more, preferably 9 or more and less than 50. If it is less than 9 layers, the effect of laminating the water vapor barrier property, for example, the effect of imparting pinhole resistance by the water vapor barrier layer lamination, etc. cannot be obtained, and sufficient water vapor barrier property cannot be exhibited. Also, if the number of layers becomes too large, there may be a problem in forming a sheet, and the thickness per layer is further reduced. As a result, the thermoplastic resin layer B is thinned to maintain the flexibility as a sheet. Since this is not possible, it is common to use a structure with less than 50 layers. When the total number of layers is an even number layer, one outermost layer is the inorganic high-filling layer B, and when the sheet is bent, cracks are easily generated starting from the inorganic high-filling layer B. On the other hand, as a sheet It is difficult to obtain flexibility.

Although the total thickness of the said multilayer sheet is not specifically limited, The range of 100-1000 micrometers is common. In the present invention, the average thickness per layer of the A layer and the B layer can be measured by cutting out a section of the multilayer sheet and observing under a microscope with a smooth end face so that the layer configuration can be determined. Thickness measurement can measure the thickness of each layer of the total number of layers, and can determine the average thickness per one layer of A layer and B layer. The thickness per layer of the A layer and the B layer can be individually adjusted according to the required characteristics. In addition, the thickness per layer in the A layer or the B layer is generally the same. Therefore, the total thickness of the A layer and the B layer is obtained by multiplying the average thickness per layer for each layer by the number of layers. be able to.

As the thermoplastic resin A and the thermoplastic resin B used in the present invention, a general thermoplastic resin can be used. For example, there are polyolefin resin, polyester resin, polystyrene (PS) resin, ABS resin, polycarbonate resin, ethylene-vinyl alcohol copolymer resin, and polyvinylidene chloride resin. A blend of other resins can also be used.

Examples of the polyolefin resin in the present invention include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene-based resin, homopolymers of aliphatic olefin compounds such as poly-1-butene resin, and copolymers of these It is a coalescence. Examples of the copolymer include an ethylene-propylene copolymer resin, an ethylene-1-butene copolymer, and an ethylene-methylpentene copolymer resin. The polypropylene resin includes a polyolefin copolymer containing at least 50 mol% of a polypropylene homopolymer and a propylene unit.

As the polyester resin, in addition to a polyester resin obtained from an aromatic and aliphatic polyfunctional carboxylic acid and a polyfunctional glycol, a hydroxycarboxylic acid polyester resin can also be used. Examples of the former include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene adipate, polybutylene adipate, and other copolymers thereof. Examples of the copolymer include polyester resins copolymerized with polyalkylene glycol, polycaprolactone, and the like. Examples of the latter include polylactic acid, polyglycolic acid and polycaprolactone. The former and latter copolymers can also be used.

Examples of polystyrene (PS) resins include PS resins and rubber-modified styrene resins (rubber-g-styrene resins or impact-resistant styrene resins). Examples of the aromatic vinyl monomer for forming the PS resin include styrene, alkyl-substituted styrene (for example, vinyl toluene, vinyl xylene, p-ethyl styrene, p-isopropyl styrene, butyl styrene, pt- Butyl styrene, etc.), halogen-substituted styrene (eg, chlorostyrene, bromostyrene, etc.), α-alkyl-substituted styrene (eg, α-methylstyrene, etc.) substituted with an alkyl group at the α-position, and the like. These aromatic vinyl monomers can be used alone or in combination of two or more. Of these monomers, styrene, vinyltoluene, α-methylstyrene, etc., particularly styrene is usually used.

The polycarbonate-based resin is derived from a dihydroxy compound, and is preferably an aromatic dihydroxy compound. In particular, an aromatic dihydroxy compound (bisphenol) in which two aromatic dihydroxy compounds are bonded through a certain bonding group. preferable. Those produced by a known production method can be used, and the production method is not limited to those, and commercially available resins can be used.

The ethylene-vinyl alcohol copolymer resin is a saponified ethylene-vinyl acetate copolymer, and known ones can be used. A higher saponification degree of vinyl acetate is preferable because gas barrier properties and water vapor barrier properties are improved.

Among the above resins, the thermoplastic resin A used for the layer A that is highly filled with an inorganic substance is preferably a polyolefin resin, and more preferably, from the viewpoint that a high water vapor barrier property can be easily obtained while ensuring flexibility. Is a polypropylene resin. Further, the thermoplastic resin A of the A layer and the thermoplastic resin B of the B layer are not necessarily limited to the same type of resin. However, when different types of resins are used, the adhesion between the layers is naturally sufficient. It is necessary to select a combination of resins.

The “scale-like inorganic substance” referred to in the present invention is an inorganic substance having an aspect ratio and a flat plate shape. Examples of the scale-like inorganic substance used in the present invention include inorganic substances such as mica, talc, montmorillonite, smectite, and bennite, and are not particularly limited. A scale-like inorganic substance with improved dispersibility can be used.

The shape of the scale-like inorganic substance is not particularly limited, and those having an aspect ratio of 5 to 5000, preferably 10 to 1000 can be used. When the aspect ratio is less than 5, the anisotropy of the scale-like inorganic substance is insufficient, and the orientation of the scale-like inorganic substance due to shear stress or the like at the time of forming a sheet cannot be expected, so that it is difficult to express the water vapor barrier property. On the other hand, if it exceeds 5000, the scale-like inorganic substance becomes too large, gaps are generated between the scale-like inorganic substances, and a dense arrangement cannot be expected, making it difficult to exhibit water vapor barrier properties. The average length of the major axis of the scale-like inorganic substance is 0.01 to 200 μm, preferably 0.05 to 100 μm, particularly preferably 0.1 to 50 μm.

30-80 mass% of the addition amount of the scale-like inorganic substance with respect to the thermoplastic resin A in said inorganic high filling layer A is preferable. When the addition amount of the flaky inorganic substance is less than 30% by mass, the addition amount of the flaky inorganic substance is small with respect to the thermoplastic resin, and a gap is generated between the flaky inorganic substances, so that the water vapor barrier effect cannot be obtained. On the other hand, when the added amount of the scale-like inorganic substance exceeds 80% by mass, the amount of the thermoplastic resin in the inorganic high-filled layer A is reduced, and the flexibility as a sheet cannot be obtained, for example, a crack is generated when it is bent.

The total thickness of the inorganic high-fill layer A is 5% or more and less than 50%. If it is less than 5%, the thickness of the inorganic highly filled layer A is too thin, and sufficient water vapor barrier properties cannot be exhibited. Moreover, if it is 50% or more, the inorganic high filling layer A increases with respect to the thermoplastic resin layer B, and the flexibility as a sheet cannot be maintained.

A method for producing the multilayer sheet of the present invention will be described. Basically, a resin forming a multilayer structure is supplied to an extruder, melted and kneaded, supplied to a feed block and laminated, and a multilayer sheet is extruded. For example, as described in Japanese Patent Application Laid-Open No. 2007-307893, resin is supplied from two extruders, and molten resin from each flow path is mixed with a multi-manifold type feed block that is a known laminating apparatus and a square. By using a mixer or using only comb-type feed blocks, it can be multi-layered to 9 layers or more. The square mixer is a known cylinder having a joining section that divides a polymer flow path into two with a square cross-sectional area and further joins the branched polymers so that they are stacked again in the thickness direction. Is the body.

The method for manufacturing a multilayer sheet having an odd-numbered layer structure according to the present invention includes a method in which a multilayer structure is formed by the above-described method, and then one layer is further laminated on one side of the multilayer sheet using a multi-layer die for two layers. .

<Evaluation method of sheet characteristics>
The following characteristics were evaluated for the sheets formed in each Example , Experimental Example and Comparative Example.
(Average thickness of one layer of layer A and layer B)
The average thickness per layer of the A layer and the B layer is obtained by cutting out a multilayer sheet section, smoothing the end face so that the layer configuration can be judged, and then using a laser microscope (KEYENCE: VK-8510). Observation was made and the thickness was measured. Thickness measurement measured the thickness of each layer of all the layers, and calculated | required the average thickness per 1 layer of A layer and B layer. Furthermore, it implemented 5 times in the sheet | seat width direction, and made the average value the average thickness per layer of a multilayer sheet.
(Water vapor barrier property)
Measurement was performed using a water vapor transmission meter (Lyssy: L80-5000) under the conditions of 40 ° C. and 90% RH. The obtained result was converted to a value at a thickness of 100 μm as a water vapor transmission rate (g / m 2 · dAy). Conversion to a value at 100 μm thickness is
It calculated | required as 100 micrometer conversion value = measured value x100 / film thickness.
In the multilayer sheet of the example of the present invention, the water vapor barrier property was never lost by the pinhole because the A layer had a multilayer configuration of at least 4 layers.
(Sheet flexibility)
The mandrel test described in JIS K5600 was conducted to confirm the flexibility as a sheet. A sample was cut into 150 × 50 pieces and bent along a mandrel. Sheet flexibility was evaluated based on the diameter of the mandrel when cracks occurred when bent.
If a sheet is wound around a φ5mm mandrel and no cracks (whitening) occur, ○, if a φ5mm mandrel is cracked, a sheet is wound around a φ8mm mandrel, and if there is no crack, Δ, a sheet is placed on the φ8mm mandrel. If winding cracks occurred, the flexibility of the sheet was evaluated in three stages.

(Example 1)
A twin-screw extruder having a diameter of 30 mm, comprising 52% by mass of polypropylene resin (manufactured by SUN-ALLOMER: PL400A) and 48% by mass of mica (manufactured by Yamaguchi Mica: 21P5 (330) average particle size: 22 μm, aspect ratio 70) as layer A Melt-kneaded and pelletized with a single-screw extruder of φ40 mm (mica addition amount 48 mass%), and polypropylene resin (manufactured by SUN-ALLOMER: PL400A) as a B layer is a single-screw extruder of φ40 mm After melt-kneading and laminating and laminating these molten resins using a feed block, a B layer is laminated on the outermost layer on the A layer side using a multi-layer die for two layers, and the temperature is adjusted to 60 ° C. A 17-layer sheet was formed by cooling and solidifying with The average total thickness of the obtained sheets was 172 μm (average thickness of each layer determined by calculation: A layer: 8 μm, B layer: 12 μm).

(Examples 2 and 3, Comparative Examples 3 and 4)
A multilayer sheet was formed in the same manner as in Example 1 except that the amount of mica added to the A layer was changed in the range of 10 to 90% by mass as described in Table 1 or Table 2, respectively.
(Examples 4 and 5)
Example 1 except that the thickness ratio of the A layer and the B layer was adjusted so that the ratio of the total thickness of the A layer to the total thickness of the multilayer sheet was 45% and 9% as shown in Table 1, respectively. Similarly, a multilayer sheet was formed.
(Examples 6 and 7)
Except for adjusting the thickness of each layer as shown in Table 1 so that the total number of layers is 33 and 11 respectively, and the ratio of the total thickness of the A layer to the total thickness of the multilayer sheet is 39% and 37%. In the same manner as in Example 1, a multilayer sheet was formed. In addition, the total thickness of the obtained multilayer sheet was 199 μm and 224 μm, respectively.
( Experimental Example 1 and Comparative Example 7)
Except for using HIPS resin (Toyo Styrene Co., Ltd .: H850) to which 48% by mass and 10% by mass of mica were added as the A layer, and using ABS resin (Electric Chemical Co., Ltd .: SE-10) as the B layer, respectively. A multilayer sheet was formed in the same manner as in Example 1.

(Comparative Example 1)
Polypropylene resin (manufactured by SUN-ALLOMER: PL400A) is melt-kneaded with a short-shaft extruder with a diameter of 65 mm, formed into a sheet using a T-die, and cooled and solidified with a roll adjusted to 60 ° C. to produce a polypropylene single-layer sheet. Filmed.
(Comparative Example 2)
Melting and kneading 74% by mass of polypropylene resin (manufactured by SUN-ALLOMER: PL400A) and 26% by mass of mica (manufactured by Yamaguchi Mica: 21P5 (330) average particle size: 22 μm, aspect ratio 70) in a twin screw extruder of φ30 mm The pelletized material was melt-kneaded with a 65 mm short shaft extruder, formed into a sheet using a T-die, and cooled and solidified with a roll adjusted to 60 ° C. to form a single-layer sheet. (Mica addition amount 26% by mass)
(Comparative Example 5)
The thickness ratio of the A layer and the B layer was adjusted as shown in Table 2 so that the ratio of the total thickness of the A layer to the total thickness of the multilayer sheet was 2.8%, so that the total thickness of the multilayer sheet was 359 μm. Except for the above, a multilayer sheet was formed in the same manner as in Example 1.
(Comparative Example 6)
The thickness ratio of the A layer and the B layer was adjusted as shown in Table 2 so that the ratio of the total thickness of the A layer to the total thickness of the multilayer sheet was 67%. A film was formed.

The evaluation results of each example , experimental example and comparative example are summarized in Tables 1 and 2.

Claims (2)

Even-numbered layers (A layers) and odd-numbered layers (B layers) are alternately laminated, and the total number of layers is composed of odd-numbered layers of 11 or more and 33 or less. A thermoplastic resin multilayer sheet having all the requirements of () to (2), wherein the B layer is made of a polyolefin resin .
(1) The A layer is composed of a mixture of 70 to 20% by mass of a polyolefin resin and 30 to 80% by mass of a scaly inorganic substance.
(2) The total thickness of the plurality of A layers is 5% or more and less than 50% with respect to the total thickness of the sheet. The thermoplastic resin multilayer sheet according to claim 1, wherein the scaly inorganic substance has a scaly shape having an aspect ratio of 5 or more.