Multilayer structure container having inner and outer surfaces made of olefin resin

Abstract

To provide a multilayer structure container suitable for forming an oily liquid layer on the inner surface of the container without forming a lubricant-free olefin resin layer.SOLUTION: In the multilayer structure container 10 whose inner surface and outer surface are formed of olefin resin layers 1, 3 and which has a lubricant blocking intermediate layer 5, a lubricant absorbing resin layer 7 exists between the inner surface olefin resin layer 1 and the lubricant blocking intermediate layer 5. All of the inner layer 1 (olefin-based resin layer), the outer layer 3 (olefin-based resin layer), and the lubricant-absorbing resin layer 7 contain a solid lubricant having a melting point of 60 °C or higher, the total mass of the lubricant present on the inner surface side of the lubricant-blocking intermediate layer 5 is in the range of 0.0001% to 0.0100% with respect to the mass of the resin forming the inner surface side of the lubricant-blocking intermediate layer, and the lubricant coverage rate Φ inner in the inner layer 1 and the lubricant coverage rate Φ outer in the outer layer 3 satisfy the condition of Φ inner <Φ outer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multi-layered container whose inner and outer surfaces are made of an olefin-based resin, and more specifically to a type of multi-layered container in which, prior to filling with the contents, an oily liquid that exhibits lubricity toward the contents is applied to form a liquid layer. [Background technology]

[0002] Plastics are widely used for various purposes because they are easy to mold and can be easily formed into various shapes, etc. In particular, bottle-shaped or tube-shaped olefin resin containers, the inner surface of which is made of an olefin resin such as low-density polyethylene, are suitably used as containers for storing viscous slurry or paste-like contents such as ketchup, from the viewpoint of ease of squeezing out the contents.

[0003] Furthermore, in the case of bottles or tubes containing viscous contents, the bottles are often stored in an inverted state in order to quickly discharge the contents or to use up the contents completely without leaving any residue inside the bottle or tube. Therefore, it is desirable for the viscous contents to quickly fall off the bottle when it is turned upside down without adhering to the inner wall of the bottle and remaining there.

[0004] As a bottle that satisfies such requirements, for example, Patent Document 1 proposes a bottle with a multi-layer structure in which the innermost layer is made of an olefin resin with an MFR (melt flow rate) of 10 g / 10 min or more. The innermost layer of this multi-layered bottle has excellent wettability for oily contents. As a result, when the bottle is turned upside down or tilted, oily contents such as mayonnaise fall while spreading along the surface of the innermost layer, and can be discharged cleanly without remaining on the inner wall surface of the bottle (the surface of the innermost layer).

[0005] Furthermore, for bottles for viscous non-oily contents such as ketchup in which vegetable fibers are dispersed in water, Patent Document 2 or Patent Document 3 proposes a polyolefin resin bottle in which saturated or unsaturated aliphatic amide is blended as a lubricant in the innermost layer.

[0006] The above-mentioned Patent Documents 1 to 3 all relate to plastic containers in which the slipperiness of the contents is improved by varying the chemical composition of the thermoplastic resin composition that forms the inner surface of the container. Although a certain degree of improvement in slipperiness has been achieved, the types of thermoplastic resins and additives used are limited, so there is a limit to how much improvement in slipperiness can be achieved, and no dramatic improvement has been achieved.

[0007] Recently, a technology has been developed in which the inner surface of a container is made of a resin (e.g., an olefin resin) that has liquid permeability, and a layer of an oily liquid that exhibits lubricity to the container contents is formed on the inner surface of the container, thereby increasing the slipperiness of the container contents and enabling the contents to be quickly discharged (see Patent Document 4).This technology is currently attracting widespread attention because it dramatically improves slipperiness compared to technologies that use lubricants to improve the slipperiness of the container contents.

[0008] Incidentally, in order to form a layer of an oily liquid on the inner surface of a container, a method of spraying the oily liquid after molding the container is generally adopted. A method is also known in which the oily liquid is blended with the resin (e.g., olefin resin) that forms the inner surface of the container, and a layer of the oily liquid is formed on the inner surface of the container by bleeding after molding the container, but this method has the problem that it is difficult to control the amount and distribution of the oily liquid formed on the inner surface of the container, and therefore spraying is adopted in practical applications.

[0009] Furthermore, containers containing viscous contents, such as mayonnaise-like foods and ketchup, often have their inner and outer surfaces formed from olefin-based resins. Such containers made of olefin-based resins are highly flexible and can squeeze out the contents by pressing the container, making them suitable for containing viscous contents. However, in such containers made of olefin-based resins, in order to uniformly form the aforementioned oily liquid layer on the inner surface of the container, it was necessary to remove the lubricant from the inner surface of the container. This is because if a lubricant is present in the olefin-based resin forming the inner surface of the container, the oily liquid will be repelled by the lubricant, which will have a negative effect on the formation of the oily liquid layer. On the other hand, it is desirable to blend a lubricant into the olefin resin forming the outer surface of the container in order to improve the transportability of the container. By blending a lubricant, the lubricant bleeds onto the outer surface of the container, which effectively prevents the containers from sticking together or from adhering to a transport material (e.g., a belt) during the container transport process. In particular, when filling a container with contents, container transportability is an important function that determines productivity, and for multi-layer containers made of olefin resins, the addition of a lubricant to the olefin resin forming the outer surface of the container is essential.

[0010] From the above perspective, Patent Document 5 provides a multi-layer container in which the inner and outer surfaces of the container are formed from olefin-based resin layers, an intermediate layer between the outer and inner surface layers is provided with a lubricant-blocking layer (e.g., a layer of a resin with a glass transition point (Tg) of 35°C or higher) that blocks the migration of lubricant, and a layer containing lubricant is present outside the intermediate layer (lubricant-blocking layer), but the olefin-based resin inner layer that forms the inner surface is a lubricant-free layer. In this multi-layer container, the olefin-based resin inner layer is a lubricant-free layer, and since no lubricant is present, the oily liquid is not repelled, and a uniform layer of oily liquid can be formed on the inner surface of the container. As a result, by forming a layer of oily liquid on the inner surface of this container by, for example, spray application, and then filling it with viscous contents, it can be used as a container with excellent dischargeability of viscous contents. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-284066 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-222291 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-214914 [Patent Document 4] Patent No. 5971337 [Patent Document 5] Japanese Patent Application Laid-Open No. 2010-189052 Summary of the Invention [Problem to be solved by the invention]

[0012] However, it has been found that forming a lubricant-free inner surface of a container poses significant productivity problems. During container molding, the lubricant blended into the olefin-based resin flows in a molten state through a heated extruder and die head along with the olefin-based resin. The lubricant coats the metal surfaces of the extruder and die head, enhancing the resin's fluidity and providing so-called service lubrication. This also plays a role in reducing the extruder torque and reducing deterioration of the resin due to shear heating. Specifically, in multilayer extrusion molding, in which multiple molten resin layers are extruded from the die head in the form of a parison, sheet, or film, blending a lubricant into the olefin-based resin inner and outer layers of the container enhances the slip between the molten resin and the metal. However, when an olefin-based resin without a lubricant is extruded into the inner layer from an extruder, the smooth flow of the olefin-based resin is impeded, resulting in problems such as increased extruder torque, reduced productivity, and a decrease in the surface smoothness of the product.

[0013] Therefore, an object of the present invention is to provide a multi-layered container suitable for forming a layer of an oily liquid on the inner surface of the container without forming a lubricant-free olefin-based resin layer. [Means for solving the problem]

[0014] According to the present invention, there is provided a multilayer container having inner and outer surfaces formed of olefin-based resin layers and having a lubricant-blocking intermediate layer, a lubricant-absorbing resin layer is present between the inner olefin-based resin layer and the lubricant-blocking intermediate layer, each of the inner surface olefin-based resin layer, the outer surface olefin-based resin layer, and the lubricant-absorbing resin layer contains a solid lubricant having a melting point of 60°C or higher; the total mass of the lubricant present on the inner surface side of the lubricant-blocking intermediate layer is in the range of 0.0001 to 0.0100% based on the mass of the resin forming the inner surface side of the lubricant-blocking intermediate layer, The lubricant coverage rate Φinner of the inner surface olefin-based resin layer and the lubricant coverage rate Φouter of the outer surface olefin-based resin layer are expressed by the following formula (1): Φinner<Φouter (1) Here, the lubricant coverage ratios Φinner and Φouter are determined by measuring the water contact angle, respectively, as follows: The following formula (a): Φ=(cosθ-cosθresin) / (cosθs-cosθresin) (a) During the ceremony, Φ is Φinner or Φouter, θ is the water contact angle on the surface of the inner olefin resin layer when Φ is Φinner. When Φ is Φouter, the water contact angle on the surface of the outer olefin resin layer is can be, When Φ is Φinner, θresin forms the inner surface olefin resin layer. This is the water contact angle of the olefin resin alone, and when Φ is Φouter, it is the water contact angle of the outer surface is the water contact angle of the olefin-based resin alone forming the olefin-based resin layer, θs is the water contact angle of the lubricant alone; is a value calculated by The present invention provides a multilayer container characterized by satisfying the condition expressed by the following formula:

[0015] In the multilayer container of the present invention, the following aspects are preferably adopted. (1) The lubricant is an aliphatic amide. (2) The olefin resin is low-density polyethylene. (3) The lubricant-blocking intermediate layer contains a high glass transition resin having a glass transition temperature of 35° C. or higher. (4) The high glass transition resin is an ethylene-vinyl alcohol copolymer resin. (5) The thickness of the lubricant-absorbing resin layer is 500% or more of the thickness of the inner olefin-based resin layer. (6) The lubricant-absorbing resin layer is a regrind layer. (7) The regrind layer contains a polar polymer. (8) The lubricant coverage ratio Φinner is maintained at less than 0.55, and the lubricant coverage ratio Φouter is maintained at greater than 0.8. (9) The total mass of lubricants contained in the entire multilayer container is in the range of 0.0010 to 0.0135% of the total mass of the multilayer container, and the total mass of lubricants present on the inner side of the lubricant-blocking intermediate layer is in the range of 0.0005 to 0.0070% of the total mass of the multilayer container. (10) The lubricant-absorbent resin layer is adjacent to the inner surface olefin-based resin layer. (11) The multi-layered container is filled with the contents after an oily liquid that exhibits lubricity to the contents to be contained is sprayed onto the inner surface to form a liquid layer. (12) The oily liquid is an edible oil, a fatty acid triglyceride, a fluorine-based surfactant, or a silicone oil. (13) It must be a direct-blow container. [Effects of the Invention]

[0016] The multilayer container of the present invention has a basic structure in which the inner and outer surfaces of the container are formed from an olefin resin, a lubricant-blocking intermediate layer is formed between an inner surface layer (inner layer) and an outer surface layer (outer layer) of the olefin resin, and a lubricant-absorbing resin layer is further present between the inner surface olefin resin layer and the lubricant-blocking intermediate layer.In other words, in addition to this basic structure, a configuration is adopted in which a solid lubricant having a melting point of 60°C or higher is contained in both the layers located inside the lubricant-blocking intermediate layer (e.g., the inner surface layer and lubricant-absorbing resin layer) and the outer layer (e.g., the outer surface layer). By using such a lubricant, the multilayer container of the present invention can be formed without using an olefin resin containing no lubricant, and problems such as molding defects can be effectively prevented.

[0017] In the present invention, the lubricant is a solid lubricant with a melting point of 60°C or higher, not a liquid lubricant such as liquid paraffin. In the present invention, such a solid lubricant is incorporated into the outer olefin-based resin layer, which is isolated from the inner surface of the container by a lubricant-blocking intermediate layer. Therefore, the solid lubricant incorporated into the outer olefin-based resin layer selectively bleeds toward the outer surface, providing a constant lubricant coverage Φouter. This allows the multilayered container of the present invention to effectively prevent adhesion between containers and between the container and a conveying material (e.g., a belt) during the container conveyance process. When a liquid lubricant such as liquid paraffin is used, the effect of such a lubricant is not realized.

[0018] Furthermore, in the present invention, the total mass of the lubricant present on the inner side of the lubricant-blocking intermediate layer is in the range of 0.0001 to 0.0100% per mass of the resin forming the inner side of the lubricant-blocking intermediate layer, and the lubricant coverage Φinner on the inner surface of the container is controlled to be lower than the lubricant coverage Φouter on the outer surface of the container. That is, because an appropriate amount of lubricant is present on the inner side of the container, such that it does not exceed the lubricant coverage Φouter on the outer surface of the container, smooth flow of the olefin-based resin is maintained during container production, and the liquid repellency against oily liquids due to the lubricant coating on the inner surface of the container is controlled to be low without causing a decrease in productivity. As a result, a stable liquid layer of oily liquid can be formed on the inner surface of the container by spray application, etc., and the lubrication provided by the oily liquid can be utilized to effectively use the container as a container with excellent dischargeability for viscous contents.

[0019] As described above, the multilayer container of the present invention has various advantages, the greatest of which is that it is possible to use only olefin resins of a grade having a fixed lubricant content. In other words, it is possible to obtain a multilayer container with the above-mentioned characteristics by adjusting the layer thickness without using multiple olefin resins with different lubricant contents, and this is extremely useful industrially in terms of cost reduction, etc. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram showing the basic layer structure of a multilayer container of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] As shown in Fig. 1, the multilayer container of the present invention is generally designated 10 and has an inner surface olefin-based resin layer 1 (sometimes referred to as the inner layer) and an outer surface olefin-based resin layer 3 (sometimes referred to as the outer layer), with a lubricant-blocking intermediate layer 5 (hereinafter sometimes referred to as the lubricant-blocking layer) between these olefin-based resin layers 1 and 3, and further, a lubricant-absorbing resin layer 7 provided between the lubricant-blocking layer 5 and the inner surface olefin-based resin layer 1. In this basic structure, a lubricant is present in each of the inner surface olefin-based resin layer 1 (inner layer), outer surface olefin-based resin layer 3 (outer layer), and lubricant-absorbing resin layer 7.

[0022] That is, in the present invention, by blending the lubricant as described above, the lubricant is distributed on the inner and outer surfaces of the container, and the container is coated with the lubricant. However, the layer structure described above controls the bleeding of the lubricant onto the inner and outer surfaces, and by utilizing this, the lubricant coverage rate Φinner on the inner surface of the container and the lubricant coverage rate Φouter on the outer surface of the container are adjusted to satisfy certain conditions.

[0023] More specifically, this multilayer container 10 has a lubricant-blocking layer 5 as an intermediate layer. The lubricant does not pass through this lubricant-blocking layer 5. Therefore, the lubricant present in the outer olefin resin layer 3 does not migrate to the inner surface of the container 10, but only bleeds onto the outer surface of the container 10 (the surface of the outer olefin resin layer 3). Therefore, the lubricant coverage Φouter of the outer surface of the container is maintained at a constant value or above.

[0024] Meanwhile, a lubricant-absorbing resin layer 7 is provided between the lubricant-blocking layer 5 and the inner-surface olefin-based resin layer 1. That is, the lubricant-absorbing resin layer 7 is a layer that exhibits lubricant migration. Therefore, when molding the container 10, if a concentration distribution is set such that the amount of lubricant in the inner-surface olefin-based resin layer 1 (inner layer) is greater than the amount of lubricant in the lubricant-absorbing resin layer 7, the lubricant in the inner-surface olefin-based resin layer 1 (inner layer) will migrate from its surface toward the lubricant-absorbing resin layer 7, and this migration of the lubricant will be blocked by the lubricant-blocking layer 5, so it will not migrate toward the outer-surface olefin-based resin layer 3. In this way, the lubricant coverage rate Φinner on the inner surface of the container is maintained below a certain value and is kept in a range lower than the lubricant coverage rate Φouter on the outer surface of the container, which is the principle of the present invention.

[0025] Based on the above principle, the various materials and layers used in forming the multilayered container 10 of the present invention will be described.

[0026] Lubricants; The lubricant used in the present invention is a solid lubricant having a melting point of 60° C. or higher, particularly 65° C. or higher, that is, a lubricant that is solid at least at room temperature. As briefly mentioned above, the reason for using such a solid lubricant is to effectively prevent the problem of the lubricant adhering to the conveyor belt of the container or to other containers, which would otherwise occur if the lubricant were to be distributed in large amounts on the outer surface of the container due to bleeding, and to maximize the slipperiness and non-adhesive properties of the lubricant.

[0027] Examples of such solid lubricants include conventionally known lubricants, such as the following: (a) Natural or synthetic paraffin, microwax, polyethylene wax, chlorinated Hydrocarbon-based materials such as polyethylene wax. (b) Fatty acid-based compounds such as stearic acid and lauric acid. (c) Stearic acid amide, palmitic acid amide, oleic acid amide, erucic acid amide aliphatic amides such as methylene bisstearamide and ethylene bisstearamide thing. (d) Fatty acid esters such as stearyl stearate. (e) Hydrogenated oils such as hydrogenated castor oil. (e) Natural waxes such as carnauba wax. (g) Metallic soaps such as zinc stearate and calcium stearate.

[0028] In the present invention, the lubricants exemplified above can be used alone or in combination of two or more. In the present invention, aliphatic amides are preferred because they have particularly good bleeding properties, prevent blocking of the container conveyor belt or between containers, and reduce resistance during melt extrusion. Among these, unsaturated aliphatic amides such as oleic acid amide and erucic acid amide are most susceptible to bleeding and are therefore most suitable for the present invention.

[0029] an inner surface olefin-based resin layer 1 (inner layer) and an outer surface olefin-based resin layer 3 (outer layer); In the present invention, the olefin-based resin constituting the inner layer 1 and outer layer 3 of the multilayer container 10 is not particularly limited, and examples thereof include low-density polyethylene, linear low-density polyethylene, medium- or high-density polyethylene, polypropylene, poly-1-butene, and poly-4-methyl-1-pentene. Of course, random or block copolymers of α-olefins such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene may also be used. Furthermore, the cyclic olefin copolymer disclosed in JP-A-2007-284066 can be blended with the olefin-based resin constituting the inner or outer surface.

[0030] In the present invention, the olefin resins preferably used are polyethylene and polypropylene, with polyethylene being the most suitable. In particular, in order to impart squeezability to the container so that the contents of the container can be removed by squeezing, polyethylene having a density of 0.925 g / cm is preferred. 3 The following low-density polyethylenes and linear low-density polyethylenes are preferably used to form the inner layer 1 and the outer layer 3. From the viewpoint of extrusion moldability, it is preferable that the MFR (190°C) is 10 g / 10 min or less. In particular, such low-density polyethylenes and linear low-density polyethylenes are highly amorphous and exhibit high wettability with respect to oily liquids, making them ideal for forming a uniform layer of oily liquid on the inner surface of the container after molding.

[0031] In the present invention, the inner and outer surfaces of the multilayer container 10 are formed using the above-mentioned olefin-based resin mixed with a lubricant. The amount of lubricant to be blended into the olefin-based resin forming the inner surface can be reduced and the amount of lubricant to be blended into the olefin-based resin forming the outer surface can be increased to satisfy the condition (Φinner<Φouter) described below, but in the present invention, the above condition can be satisfied by using olefin-based resins of the same grade with the same lubricant content. For example, in the present invention, the inner and outer surfaces can be formed using an olefin-based resin with a lubricant content of 0.001% to 0.100% by mass, which reliably prevents the disadvantages of reduced productivity due to increased torque in the olefin-based resin extruder during molding and reduced surface smoothness of the product, and at the same time, the lubricant coverage rate Φouter on the outer surface can be maintained at a certain value or higher.

[0032] In the present invention, the thickness of the inner layer 1 (inner surface olefin-based resin layer) and the outer layer 3 (outer surface olefin-based resin layer) is such that the properties required of each layer (squeezability, oily liquid retention, strength, etc.) are satisfied. For example, although it varies depending on the capacity of the multilayer structure container 10, the inner layer 1 usually has a thickness of 10 to 200 μm, and the outer layer 3 has a thickness of 50 to 400 μm.

[0033] Lubricant barrier layer 5; In the present invention, in order to function as the lubricant barrier layer 5, the density of the lubricant barrier layer 5 is 1.00 g / cm 3Furthermore, it is necessary for the intermediate layer to be formed from a resin having a glass transition temperature (Tg) of 35°C or higher. In other words, a layer formed from such a resin is dense, which reliably prevents lubricant migration and effectively inhibits the migration of the lubricant present in the outer olefin-based resin layer (outside the lubricant-blocking layer 5) toward the inner layer. This maintains the amount of lubricant present in the outer olefin-based resin layer 3 within a certain range, thereby maintaining the lubricant coverage Φouter on the outer surface of the container at a certain value or higher. At the same time, bleeding of the lubricant present on the inner side of the lubricant-blocking layer 5 toward the outer surface is prevented, thereby maintaining the amount of lubricant present on the inner side of the lubricant-blocking layer 5 within a certain range. For example, if the intermediate layer is formed from a resin with a density or glass transition temperature (Tg) lower than the above ranges, the intermediate layer will be loose and will not function as a lubricant-blocking layer 5. The lubricant-blocking layer 5 may contain a lubricant as long as its density and glass transition temperature (Tg) are within the above ranges. After the container is formed, the lubricant-blocking layer 5 becomes glassy and is frozen at temperatures below the glass transition point, so the lubricant contained in the lubricant-blocking layer 5 is unlikely to migrate from the lubricant-blocking layer 5 and does not affect the inner or outer surfaces.

[0034] The resin forming the lubricant barrier layer 5 is not particularly limited as long as its density and glass transition temperature (Tg) are both within the above-mentioned ranges, and any moldable thermoplastic resin can be used. However, gas barrier resins with a glass transition temperature (Tg) of 35°C or higher, such as ethylene-vinyl alcohol copolymers (saponified ethylene-vinyl acetate copolymers), aliphatic polyamides, aromatic polyamides, cyclic olefin polymers, and cyclic olefin copolymers, are generally preferred, with ethylene-vinyl alcohol copolymers being the most suitable. That is, the use of a gas barrier resin can impart oxygen barrier properties to the intermediate layer in addition to lubricant barrier properties. Ethylene-vinyl alcohol copolymers, in particular, exhibit particularly excellent oxygen barrier properties, which effectively inhibit oxidative degradation of oily contents due to oxygen permeation, thereby maintaining excellent sliding properties and ensuring excellent contents shelf life. Furthermore, gas barrier resins such as ethylene-vinyl alcohol copolymers (saponified ethylene-vinyl acetate copolymers), aliphatic polyamides, and aromatic polyamides, which have a glass transition point (Tg) of 35°C or higher, are highly polar polymers, and therefore when a highly polar lubricant (aliphatic amides, fatty acids, aliphatic esters, aliphatic alcohols) is used, the attractive interaction between the polar polymer and the lubricant can be utilized, making them suitable for the lubricant blocking layer 5.

[0035] As the ethylene-vinyl alcohol copolymer, generally, a saponified copolymer obtained by saponifying an ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol%, particularly 25 to 50 mol%, to a degree of saponification of 96 mol% or more, particularly 99 mol% or more, is suitable. Among these, copolymers having a glass transition temperature (Tg) within the aforementioned range are selectively used.

[0036] The thickness of the lubricant-blocking layer 5 is generally preferably in the range of 1 to 50 μm, and particularly preferably in the range of 9 to 40 μm. If the thickness is too thin, the lubricant-blocking property will be reduced, and it may be difficult to effectively prevent the migration of the lubricant. If the thickness is too thick, no further improvement in the lubricant-blocking property will be obtained, and instead the thickness of the container wall will become thicker than necessary, or there will be inconveniences such as increased costs.

[0037] Furthermore, when forming the lubricant-blocking layer 5 using the gas barrier resin described above, it is preferable to provide an adhesive layer to improve adhesion between the inner and outer layers 1 and 3 and prevent delamination. This allows the lubricant-blocking layer 5 to be firmly adhered and fixed to the inner and outer layers 1 and 3. The adhesive resins used to form such adhesive layers are known per se. Examples include resins containing carbonyl groups (>C=O) in the main chain or side chain in an amount of 1 to 100 meq / 100 g of resin, particularly 10 to 100 meq / 100 g of resin. Specific examples of adhesive resins include olefin resins graft-modified with carboxylic acids such as maleic acid, itaconic acid, and fumaric acid, or their anhydrides, amides, and esters; ethylene-acrylic acid copolymers; ionically cross-linked olefin copolymers; and ethylene-vinyl acetate copolymers. The thickness of such adhesive layers (adhesive resin layers) may be sufficient to provide the appropriate adhesive strength, generally 0.5 to 20 μm, preferably 1 to 8 μm. Incidentally, such an adhesive layer (adhesive resin layer) also functions as a lubricant blocking layer if it satisfies the above-mentioned conditions of density and glass transition point.

[0038] Lubricant-absorbing resin layer 7; In the present invention, the lubricant-absorbing resin layer 7 is a layer in which the resin itself exhibits lubricant migration properties, and for example, 3or a layer formed from a resin having a glass transition point (Tg) of less than 35° C. That is, by providing such a lubricant-absorbing resin layer 7 between the lubricant-blocking layer 5 and the inner surface olefin-based resin layer 1, the lubricant present in the inner surface olefin-based resin layer 1 is transferred into the lubricant-absorbing resin layer 7, thereby maintaining the lubricant coverage Φinner of the inner surface of the container (surface of the inner surface olefin-based resin layer 1) at a certain value or less, and satisfying the condition Φinner<Φouter.

[0039] Although various resins can be used for forming the lubricant-absorbent resin layer 7 as long as their density or glass transition point falls within the above-mentioned range, it is preferable to form the lubricant-absorbent resin layer 7 by regrind, which includes waste materials such as burrs generated during the molding of this multilayer container, because this can be bonded and fixed to the inner surface olefin-based resin layer 1 without using an adhesive resin and there is no need to use an olefin-based resin of a grade with a different lubricant content from the olefin-based resin that forms the inner and outer surfaces. That is, this regrind (the resin component that forms the lubricant-absorbent resin layer 7) contains virgin olefin-based resin that is used to form the inner and outer layers 1 and 3, in order to avoid deterioration in moldability and physical properties due to the use of waste materials. In particular, the lubricant-absorbent resin layer 7 preferably contains a gas barrier resin such as an ethylene-vinyl alcohol copolymer (saponified ethylene-vinyl acetate copolymer) with a glass transition temperature (Tg) of 35°C or higher, an aliphatic polyamide, or an aromatic polyamide. This is because, as mentioned above, the attractive interaction between the polar polymer and the lubricant can be utilized to enhance lubricant absorption. The content of the polar polymer in the lubricant-absorbent resin layer 7 is 0.01 to 10%, preferably 0.1 to 5%, particularly preferably 0.2 to 3%, and especially preferably 0.5 to 3%, based on the total mass of the lubricant-absorbent resin layer 7. Furthermore, when transparency is required to check the remaining amount of contents, the content of the gas barrier resin is preferably 0.5 to 3%.

[0040] The thickness of the lubricant-absorbent resin layer 7 is set to satisfy the lubricant coverage (Φinner, Φouter) of the inner and outer surfaces, which will be described later, depending on the amount of lubricant contained in the lubricant-absorbent resin layer 7. In the present invention, the lubricant in the inner layer 1 (inner olefin-based resin layer) is migrated to the lubricant-absorbent resin layer 7 using a concentration gradient, thereby suppressing the lubricant coverage (Φinner) of the inner layer 1 to a certain value or less, and the migrated lubricant is retained in the lubricant-absorbent resin layer 7 due to the presence of the lubricant-blocking layer 5. For this reason, the thickness of the lubricant-absorbent resin layer 7 is generally preferably 500% or more, particularly 800% or more, and particularly 1000% or more of the thickness of the inner layer 1. If the thickness of the lubricant-absorbent resin layer 7 is thin relative to the thickness of the inner layer 1 (inner olefin-based resin layer), the lubricant concentration distribution will disappear shortly after molding, making it difficult to maintain the lubricant coverage (Φinner) of the inner layer 1 low.

[0041] Lubricant coverage on the inner and outer surfaces (Φinner, Φouter); The multilayer structure container 10 of the present invention having the basic layer structure described above has a lubricant coverage rate Φinner in the inner layer 1 (inner surface olefin-based resin layer) and a lubricant coverage rate Φouter in the outer layer 3 (outer surface olefin-based resin layer) that satisfy the condition expressed by the following formula (1). Φinner<Φouter (1) Here, the lubricant coverage ratios Φinner and Φouter are determined by measuring the water contact angle, respectively, as follows: The following formula (a): Φ=(cosθ-cosθresin) / (cosθs-cosθresin) (a) During the ceremony, Φ is Φinner or Φouter, θ is the water contact angle on the surface of the inner olefin resin layer when Φ is Φinner. When Φ is Φouter, the water contact angle on the surface of the outer olefin resin layer is can be, When Φ is Φinner, θresin forms inner layer 1 (inner olefin resin layer). The water contact angle of the olefin resin alone is Φouter. 3 (Outer olefin resin layer) antennae, θs is the water contact angle of the lubricant alone; It is calculated as follows.

[0042] It is well known that the water contact angle indicates the surface coverage of a substance (in this case, a lubricant) distributed on a surface, and is described, for example, in WO 2014 / 188883. That is, when the water contact angle θ on the inner or outer surface of the multilayer structure 10 is the same as the water contact angle θs of water on the lubricant alone, the coverage Φ on the inner or outer surface is 1.0, which means that the entire inner or outer surface is covered with the lubricant.

[0043] As can be seen from the above formula (1), in the present invention, the lubricant coverage Φinner on the surface of the inner olefin resin layer 1 (i.e., the inner surface of the container 10) is kept lower than the lubricant coverage Φouter on the surface of the outer olefin resin layer 3 (i.e., the outer surface of the container 10). That is, in the present invention, the distribution of the lubricant on the inner surface of the multilayer structure container 10 is kept low, making it possible to form a layer of lubricating liquid, which will be described later, evenly.

[0044] In the above formula (a), the water contact angle represented by θresin is a value determined by the olefin resin forming the inner layer 1 or the outer layer 3, but this water contact angle is almost constant regardless of its melt flow rate (MFR) or density, as long as the olefin resin has a molecular weight sufficient to form a film. Therefore, as will be used in the examples described later, the water contact angle (102.6 degrees) measured under specified conditions (e.g., 23°C, 50% RH) for low-density polyethylene (LDPE) containing no lubricant can be used as θresin.

[0045] In the present invention, in order to effectively avoid the inconvenience of liquid repellency against the lubricating liquid due to the lubricant distribution, the lower this lubricant coverage Φinner is, the better, and it is preferable that it is set to less than 0.55, particularly 0.50 or less, provided that it is lower than the lubricant coverage Φouter on the outer surface.

[0046] Furthermore, it is desirable that the lubricant coverage rate Φouter on the outer surface be as close to 1.00 as possible in order to prevent the containers 10 from sticking together or the container 10 from adhering to the conveying material (e.g., a belt), and it is preferable that it be set to, for example, greater than 0.80.

[0047] Furthermore, in the present invention, as can be seen from a comparison of the results of Experimental Examples 1 to 10 and Experimental Examples 13 to 19 described below, the total mass of lubricant present on the inner side of the lubricant-blocking intermediate layer (lubricant-blocking layer 5) must be in the range of 0.0001 to 0.0100% (i.e., the average lubricant concentration on the inner side) per mass of the resin forming the inner side of the lubricant-blocking intermediate layer. If this condition is not met, the amount of lubricant present on the inner side of the container will be too high, resulting in reduced wettability (oil wettability) with respect to the lubricating liquid (Experimental Examples 13 to 19).

[0048] In order to set the lubricant coverage ratios (Φinner, Φouter) of the inner and outer surfaces so as to satisfy the above-mentioned conditions, the thicknesses of the inner olefin resin layer 1, outer olefin resin layer 3, and lubricant-absorbing resin layer 7 are adjusted according to the amount of lubricant contained in the olefin resin or lubricant-absorbing resin (e.g., regrind) used to form each layer.

[0049] In the present invention, since lubricant is present in both the inner and outer layers 1 and 3 (olefin resin layers) and the lubricant-absorbent resin layer 7, when the conditions required for the above-mentioned lubricant coverage (Φinner, Φouter) are satisfied, the total mass of lubricant contained in the entire multilayer container 10 is in the range of 0.0010 to 0.0135% per total mass of the container 10. Furthermore, the total mass of lubricant present in the layers (layers 1 and 7) on the inner side of the lubricant-blocking intermediate layer (lubricant-blocking layer 5) is in the range of 0.0005 to 0.0070%, particularly 0.0008 to 0.0065%, and particularly 0.0010 to 0.0060% per total mass of the multilayer container 10.

[0050] Furthermore, the average lubricant concentration inside the lubricant-blocking intermediate layer is, as mentioned above, in the range of 0.0001 to 0.0100% by mass, and is particularly preferably 0.0005 to 0.0090% by mass, and even more preferably 0.0010 to 0.0080% by mass. In other words, by designing the layers so that the concentration of lubricant present inside the lubricant-blocking layer 5 is lower than that in the outer layer 3 (olefin-based resin layer), the bleeding of the lubricant after molding can satisfy the requirements for the lubricant coverage (Φinner, Φouter). The average lubricant concentration in the resin inside the lubricant-blocking layer 5 can be determined, for example, by measuring the mass of the multilayer container, then using this multilayer container to extract the inside of the container with a solvent (e.g., heptane extraction), and measuring the amount of lubricant contained by quantifying the evaporation residue after evaporating the extraction solvent using liquid chromatography using a known method, and then from the layer ratio determined from the layer structure measurement and the density of the constituent resin of each layer determined from mapping measurement using a known infrared microscope, etc.

[0051] In addition, the total mass of lubricant contained in the entire multilayer structure container can be determined, for example, by measuring the amount of lubricant contained using the above-mentioned solvent extraction and liquid chromatography on the inner and outer surfaces of the container.

[0052] 1, only the outer layer 3 (olefin-based resin layer) is provided outside the lubricant-blocking layer 5. However, as long as the conditions required for the lubricant coverage (Φinner, Φouter) described above are satisfied, a lubricant-migratory resin layer, such as a regrind layer, can be provided between the lubricant-blocking layer 5 and the outer layer 3. In this case, however, the amount of lubricant contained in the lubricant-migratory resin layer provided therebetween and its thickness should be set so that the lubricant coverage Φouter for the outer layer 3 does not decrease excessively due to bleeding. For example, if a regrind layer is provided between the lubricant-blocking layer 5 and the outer olefin-based resin layer 3, its thickness should preferably be 50 μm or less.

[0053] In the multilayer container 10 of the present invention, the optimum layer configuration from the inner surface to the outer surface is as follows: Here, OL is an olefin resin layer, RG is a regrind layer (corresponding to a lubricant-absorbing resin layer), AD is an adhesive layer, EVOH is an ethylene-vinyl alcohol copolymer resin layer (corresponding to a lubricant-blocking layer), and EVOH-B is a blend layer of ethylene-vinyl alcohol copolymer and olefin resin (corresponding to a lubricant-blocking layer, matrix is ​​ethylene-vinyl alcohol copolymer), and it is preferable that the lubricant-absorbing resin layer be adjacent to the OL layer on the inner surface. (inside) OL / RG / AD / EVOH / AD / OL (outside) (Inside) OL / RG / EVOH-B / OL (Outside)

[0054] Manufacturing of multi-layered container 10; The multilayer container 10 as described above is used as a direct blow container suitable for discharging viscous contents. Such containers are produced by preparing the resins that form each layer in an extruder, extruding the resins to form a pipe-shaped parison, pinching off one end of the parison, and then subjecting it to blow molding as is. In the present invention, a lubricant is blended in each of the olefin-based resins used, thereby effectively avoiding problems such as clogging of the flow paths of the olefin-based resin.

[0055] Such a multilayered container 10 is sprayed with an oily liquid that exhibits lubricity for the contents to be contained on the inner surface to form a liquid layer, and then filled with the contents before use.

[0056] The oily liquid is a non-volatile liquid with a low vapor pressure under atmospheric pressure, for example, a high-boiling liquid with a boiling point of 200°C or higher, and various types can be used, but in particular, from the viewpoint of imparting water repellency and slipperiness to water and hydrophilic substances containing water, fluorosurfactants, silicone oils, fatty acid triglycerides, various edible oils, etc. are preferably used. Examples of edible oils include soybean oil, rapeseed oil, olive oil, rice bran oil, corn oil, safflower oil, sesame oil, palm oil, castor oil, avocado oil, coconut oil, almond oil, walnut oil, hazelnut oil, and salad oil.

[0057] In the present invention, a liquid layer of the above-mentioned oily liquid can be uniformly formed, for example, at a concentration of 0.1 to 50 g / m 2 This allows a liquid layer of a certain amount to be uniformly distributed on the inner surface of the container 10, and allows viscous contents to be quickly discharged. For example, the container is suitable for storing contents such as ketchup, various sauces, honey, mayonnaise, mustard, jam, chocolate syrup, emulsion, various dressings, spicy seasonings such as mustard and wasabi, and liquid detergent. [Example]

[0058] The invention is illustrated in the following examples. The methods for measuring various characteristics and physical properties used in the following examples and the resins used to mold the multilayer containers are as follows:

[0059] 1. Measurement of lubricant coverage A 10 mm x 50 mm test piece was cut from the body of a 150 ml multilayer container prepared by the method described below. The test piece was fixed with either the inner or outer surface facing up, and 2 μL of pure water was placed on the test piece using a solid-liquid interface analysis system, DropMaster 700 (Kyowa Interface Science Co., Ltd.), at 23°C and 50% RH. The water contact angle θ was measured using the obtained water contact angle, and the lubricant coverage Φ on the multilayer structure surface was calculated using the following formula (a): Φ=(cosθ-cosθresin) / (cosθs-cosθresin) (a) During the ceremony, Φ is Φinner or Φouter, θ is the water contact angle on the surface of the inner olefin resin layer when Φ is Φinner. When Φ is Φouter, the water contact angle on the surface of the outer olefin resin layer is can be, When Φ is Φinner, θresin forms inner layer 1 (inner olefin resin layer). The water contact angle of the olefin resin alone is Φouter. 3 (Outer olefin resin layer) antennae, θs is the water contact angle of the lubricant alone.

[0060] In addition, in determining the lubricant coverage Φ, the following water contact angle values ​​were used as the values ​​of θresin and θs. θresin:102.6° (Values ​​for lubricant-free low-density polyethylene B (MFR=0.3) alone) θs:83.7° (Values ​​on oleic acid amide (solid))

[0061] The multilayer containers used were stored at 22°C and 60% RH for 16 days after molding. Prior research confirmed that the surface condition of the lubricant (oleic acid amide) was stabilized after 16 days from molding.

[0062] 2. Measuring the layer structure of multi-layered containers The layer structure at each position was confirmed by observing the structure at 0°, 90°, 180°, and 270° angles relative to the horizontal cross section of the body of a multilayered container molded using the method described below, 50 mm from the bottom. The average value in the four directions was taken as the thickness of each layer of the multilayered container.

[0063] 3. Evaluation of oil wettability of multilayered containers The inner surface of a multilayer container formed by the method described below was spray-coated with canola oil using a commercially available airbrush. The containers after coating were visually inspected, and those in which the canola oil was wetted and spread were marked with an ◯, and those in which the canola oil was repelled were marked with an ×.

[0064] <Resin for forming inner layer 1 and outer layer 3> Low-density polyethylene A (LDPE-A) Density 0.921g / cm 3 , MFR = 0.42 (g / 10 min, 190 °C) Contains 0.03% oleic acid amide as a lubricant

[0065] <Resin for forming lubricant-absorbing resin layer> Low-density polyethylene A (LDPE-A) Density 0.921g / cm 3 , MFR = 0.42 (g / 10 min, 190 °C) Contains 0.03% oleic acid amide as a lubricant Low-density polyethylene B (LDPE-B) Density 0.922g / cm 3 , MFR = 0.3 (g / 10 min, 190 °C) Contains no lubricant

[0066] <Resin for forming the lubricant blocking layer> Ethylene-vinyl alcohol copolymer (EVOH) Density 1.21g / cm 3 Tg = 63℃

[0067] <Resin for forming adhesive layer> Maleic anhydride modified polyethylene Density 0.920g / cm 3 Contains no lubricant

[0068] <Experimental Examples 1-19> Low-density polyethylene A (LDPE-A) was supplied to a 40mm extruder as the resin for forming the inner and outer layers, maleic anhydride-modified polyethylene was supplied to a 30mm extruder A as the resin for forming the adhesive layer, ethylene-vinyl alcohol copolymer was supplied to a 30mm extruder B as the resin for forming the lubricant barrier layer, and a mixture of low-density polyethylene A and low-density polyethylene B was supplied to a 50mm extruder as the resin for forming the lubricant-absorbing resin layer.The molten parison was extruded through a multilayer die head at a temperature of 210°C, and direct blow molding was carried out using a known method at a mold temperature of 20°C to produce a four-type, six-layer multilayer container with a capacity of approximately 150ml. Here, the rotation speed of each extruder and the mixing ratio of low-density polyethylene A and low-density polyethylene B used as the resins for forming the lubricant-absorbent resin layer were changed, and the concentration of oleic acid amide supplied to the lubricant-absorbent resin layer was adjusted. The body thickness and layer composition ratio of the obtained multilayered containers are shown in Table 1. All multilayered containers have a layer composition, from the inside out, of inner layer / lubricant-absorbent resin layer / adhesive layer / lubricant-blocking layer / adhesive layer / outer layer. The amount of oleic acid amide blended in each experimental example of the resin for forming the lubricant-absorbent resin layer was as follows: Experimental Examples 1 to 3: 0%, Experimental Examples 4 to 6: 0.003%, Experimental Examples 7 to 9: 0.006%, Experimental Examples 10 to 12: 0.009%, Experimental Examples 13 to 14: 0.012%, Experimental Example 15: 0.015%, Experimental Example 16: 0.018%, Experimental Example 17: 0.021%, Experimental Examples 18 to 19: 0.03%.

[0069] Using the manufactured containers, the layer composition of the multilayered containers described above was measured, the lubricant coverage rate was measured, and the oil wettability of the multilayered containers was evaluated. The average lubricant concentration and mass ratio in the resin (inner layer / lubricant-absorbent resin layer / adhesive layer) that forms the inner surface side of the lubricant-blocking intermediate layer was also determined. The results are summarized in Table 1. The containers of Experimental Examples 1 to 19 used lubricant-containing low-density polyethylene as the resin for forming the inner and outer layers, and it was confirmed visually and tactilely that the containers had high surface smoothness on both the inner and outer surfaces. It was also confirmed that no blocking occurred when the containers were brought into contact with each other, and that the outer surfaces had high slipperiness.

[0070] [Table 1]

[0071] In Table 1, A indicates the thickness ratio, and B to D indicate the amount of lubricant present in the multilayered container, and each has the following meaning. A: Thickness of lubricant-absorbing resin layer / thickness of inner layer (%) B: Average lubricant concentration (mass%) in the resin on the inner surface of the lubricant present inside the lubricant barrier layer C: Mass ratio (mass%) of lubricant contained in the entire multilayer container per multilayer container D: Mass percentage (mass%) of lubricant present inside the lubricant barrier layer per multilayer container [Explanation of symbols]

[0072] 1: Inner olefin resin layer 3: Outer olefin resin layer 5: Lubricant-blocking intermediate layer (lubricant-blocking layer) 7: Lubricant-absorbing resin layer 10:Multilayer structure container

Claims

1. A multi-layered container having inner and outer surfaces formed of olefin-based resin layers and having a lubricant-blocking intermediate layer, a lubricant-absorbing resin layer is present between the inner olefin-based resin layer and the lubricant-blocking intermediate layer, each of the inner surface olefin-based resin layer, the outer surface olefin-based resin layer, and the lubricant-absorbing resin layer contains a solid lubricant having a melting point of 60°C or higher; the total mass of the lubricant present on the inner surface side of the lubricant-blocking intermediate layer is in the range of 0.0001 to 0.0100% based on the mass of the resin forming the inner surface side of the lubricant-blocking intermediate layer, The lubricant coverage ratio Φinner of the inner surface olefin-based resin layer and the lubricant coverage ratio Φouter of the outer surface olefin-based resin layer are expressed by the following formula (1): Φinner<Φouter (1) Here, the lubricant coverage ratios Φinner and Φouter are calculated by measuring the water contact angle and are expressed by the following formula (a): Φ=(cosθ−cosθresin) / (cosθs−cosθresin) (a) During the ceremony, Φ is Φinner or Φouter, θ is the water contact angle on the surface of the inner olefin resin layer when Φ is Φinner. When Φ is Φouter, the water contact angle on the surface of the outer olefin resin layer is can be, When Φ is Φinner, θresin forms the inner surface olefin resin layer. This is the water contact angle of the olefin resin alone, and when Φ is Φouter, it is the water contact angle of the outer surface is the water contact angle of the olefin-based resin alone forming the olefin-based resin layer, θs is the water contact angle of the lubricant alone; is a value calculated by A multilayer container characterized by satisfying the conditions expressed by the following formula:

2. 2. The multi-layer container according to claim 1, wherein the lubricant is an aliphatic amide.

3. 2. The multilayer container according to claim 1, wherein the olefin resin is low-density polyethylene.

4. 2. The multi-layer container according to claim 1, wherein the lubricant-barrier intermediate layer comprises a high glass transition resin having a glass transition temperature of 35°C or higher.

5. 5. The multilayer container according to claim 4, wherein the high glass transition resin is an ethylene-vinyl alcohol copolymer resin.

6. 2. The multilayer container according to claim 1, wherein the lubricant-absorbent resin layer has a thickness that is 500% or more of the thickness of the inner olefin-based resin layer.

7. 7. The multi-layer container according to claim 6, wherein the lubricant-absorbent resin layer is a regrind layer.

8. 8. The multi-layer container according to claim 7, wherein said regrind layer contains a polar polymer.

9. 2. The multi-layer container according to claim 1, wherein the lubricant coverage ratio Φinner is maintained at less than 0.55, and the lubricant coverage ratio Φouter is maintained at greater than 0.

8.

10. A multilayer container as described in claim 1, wherein the total mass of lubricant contained in the entire multilayer container is in the range of 0.0010 to 0.0135% per total mass of the multilayer container, and the total mass of lubricant present on the inner side of the lubricant-blocking intermediate layer is in the range of 0.0005 to 0.0070% per total mass of the multilayer container.

11. 2. The multi-layer container according to claim 1, wherein the lubricant-absorbent resin layer is adjacent to the inner surface olefin-based resin layer.

12. 2. The multi-layered container according to claim 1, wherein the multi-layered container is filled with the contents after an oily liquid exhibiting lubricity to the contents to be contained is sprayed onto the inner surface to form a liquid layer.

13. 13. The multilayer container according to claim 12, wherein the oily liquid is an edible oil, a fatty acid triglyceride, a fluorine-based surfactant, or a silicone oil.

14. The multilayer container according to any one of claims 1 to 13, which is a direct-blow container.

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