JP4433111B2 - Method for producing stretched deoxygenated multilayer body - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a deoxygenated multilayer body having a deoxygenating function. The deoxygenated multilayer body is used for a deoxygenated body or a deoxygenated container having an action of preventing oxidation of various products that are easily affected by the influence of oxygen, such as foods, pharmaceuticals, and metal products.
[0002]
[Prior art]
For the purpose of preventing oxidation of various products that are easily affected by the influence of oxygen, such as foods, pharmaceuticals, and metal products, oxygen scavengers that remove oxygen have been used. The form that was initially developed as the oxygen scavenger and is still widely used is one in which a granular or powdered oxygen scavenging component is packed in a sachet. On the other hand, a film or sheet is considered as a safe oxygen absorber that is easier to handle, has a wide range of applications, and has no problems such as accidental eating.
[0003]
In order to obtain a deoxidized body in the form of a film or a sheet, a method is known in which a thermoplastic resin is used as a matrix component and is combined with a granular or powdered deoxygenated component to fix the deoxygenated component. The single layer film or sheet of the composite covers this single layer deoxygenation layer with another shielding layer or shielding package to prevent contact between the oxygen scavenging component and the contents, especially liquid. It is known. However, a deoxygenated film or sheet having a layer structure covered with such a shielding layer or the like has no problem of elution of deoxygenated components, but has a problem that deoxygenation performance is remarkably low.
[0004]
On the other hand, as shown in JP-A-9-234811 and JP-A-10-264279, the deoxygenated layer is made porous by stretching to increase the oxygen transmission rate, and the upper surface is protected by a shielding layer. By adopting a multilayer structure, a deoxygenated film or sheet having an improved deoxygenation rate and free of deoxygenated components can be produced. As a method for producing this multilayer structure, a general multilayer film and sheet production method such as coextrusion and extrusion lamination can be applied. However, a method of forming a multilayer structure at one time by coextrusion and then stretching as a subsequent process. It has been known.
[0005]
[Problems to be solved]
However, when the present inventors examined in detail, when producing a multilayer film or sheet by such coextrusion, the problem that breakage often occurs before the film or sheet is stretched to a sufficient magnification in the stretching process. I encountered it.
[0006]
[Means for Solving the Problems]
As a result of various investigations on the stretching conditions, the inventors found that the pressure of the cooling roll at the time of co-extrusion is a certain pressure or less, and that the variation can be solved if the thickness variation is within a certain range, The present invention has been completed. That is, in the method for producing a deoxygenated film or sheet of the present invention, the oxygen-permeable resin layer is disposed on at least one side of the resin layer containing the deoxygenated composition, and single-sided absorption is performed on the other side of the deoxygenated layer. In the case of double-sided absorption, in a deoxygenated multilayer body in which the same oxygen-permeable resin layer is arranged as the other surface in the case of double-sided absorption, at least two layers of deoxygenation layer and oxygen-permeable resin layer are laminated by coextrusion After that, in the production method in which the deoxidized layer is continuously made porous by stretching, the nip line pressure of the cooling roll during coextrusion is set to 200 N / cm or less.
[0007]
The nip line pressure referred to in the present invention is a value obtained by dividing the load applied to the entire width of the nip roll by the nip roll width. From the air pressure in operation, the cylinder diameter used and the width of the nip roll, it can be calculated by the following formula.
Nip wire pressure (N / cm) = Air pressure (N / cm ² ) x Cylinder cross-sectional area (cm ² ) ÷ Nip roll width (cm)
This can be converted into area pressure by accurate measurement of the contact area.
Moreover, it is preferable that 90% or more of thickness distribution after lamination | stacking by coextrusion enter into less than +/- 20% from thickness average value.
[0008]
As the oxygen scavenging composition used for the oxygen scavenging layer, known oxygen scavengers or oxygen scavenger compositions can be used, among them, iron powder, aluminum powder, metal powder such as silicon powder, inorganic salts such as ferrous salt, Deoxygenating agent composition mainly composed of ascorbic acid and its salts, alcohols or phenols such as catechol, gallic acid, glycerin, etc., unsaturated hydrocarbons such as butadiene, and unsaturated fatty acids such as tall oil and soybean oil. Things are preferred. If these deoxygenation components are in solid form, they can be used as a porous agent that becomes the starting point of pore formation when making a porous structure by stretching the deoxidation layer. Can be used as a porous agent. The particle size of the oxygen scavenger is not particularly limited as long as the maximum particle size is less than the thickness of the oxygen scavenging layer described later, but the oxidation rate and other layers are not damaged (layers) Finer particles are desirable in that they are not exposed to the surface, and the maximum particle size is preferably 200 [μm] or less, more preferably 100 [μm] or less. The amount of the oxygen scavenging composition in the oxygen scavenging layer is preferably 10 to 60 wt%, more preferably 30 to 55 wt%.
[0009]
Moreover, you may add the porosification auxiliary | assistant which assists porosity other than a deoxidation component to a deoxidation layer. The porous auxiliary agent is not particularly limited as long as it is an inorganic filler that is insoluble or hardly soluble in water. In particular, it is preferable to use an inorganic filler having a Mohs hardness of 3 or more, more preferably a hardness of 5 to 13 because the efficiency of the porous formation is high. Examples thereof include silica, alumina, diatomaceous earth, titania, barium sulfate and the like, and it is most preferable to use pulverized silica and α-alumina from the viewpoints of hardness, handling, and cost.
[0010]
Specific examples of the thermoplastic resin used in the oxygen scavenging layer include homopolymers and copolymers of olefins such as ethylene, propylene, 1-butene and 4-methyl-1-pentene, and ethylene-vinyl acetate. There are copolymers, polybutadiene, polyisoprene, styrene-butadiene copolymers and their hydrogenated products, various silicon resins, and the like, and these modified products, grafts, and mixtures may also be used. The thickness of the oxygen scavenging layer is determined by the amount of oxygen scavenger and the oxygen permeability coefficient of the resin. Generally, a thickness of about 5 to 50 [μm] is preferable.
[0011]
In the present invention, the thermoplastic resin constituting the oxygen-permeable resin layer for sending oxygen to the deoxidized layer has an oxygen permeability coefficient of 1 × 10 ⁻¹³ [cm ³ · cm / cm ² · sec · Pa] or more, preferably A thermoplastic resin of 1 × 10 ⁻¹² [cm ³ · cm / cm ² · sec · Pa] or more is selected. The maximum value of the thickness of the oxygen permeable resin layer is determined by the required performance of the object to be deoxidized expressed by the oxygen permeability and the oxygen permeability coefficient of the resin. However, if it can be stably manufactured so as not to cause pinholes and it is certain that pinholes and tears will not occur even in contact with the contents during normal use, it is as thin as possible from the maximum value. In general, the thickness is preferably about 5 to 50 [μm].
[0012]
The resin constituting the oxygen permeable resin layer may be not only a polymer polymerized from a single monomer species, but also various copolymers and a mixture of resins. Nonpolar or low polarity polymers are preferred. Furthermore, as long as the oxygen permeability of the entire oxygen permeable resin layer satisfies the above range, the oxygen permeable resin layer itself may be composed of a plurality of layers. In addition, it is preferable to use the same resin as the matrix component resin of the adjacent layer for the oxygen permeable resin layer. When different resins are used, they are compatible to the extent that they can be heat-sealed. The thermoplastic resin is preferable. Of course, an inorganic substance or an organic substance may be added for various purposes such as concealing or coloring the oxygen permeable resin layer or improving heat sealability when used as a package.
[0013]
For example, a plurality of oxygen permeable resin layers may be formed, and a pigment or an inorganic filler may be blended in the oxygen permeable resin layer on the deoxygenation layer side for the purpose of concealing deoxygenation components. By adding a pore forming auxiliary agent together with the masking agent to the masking layer, the masking layer becomes porous at the time of stretching, and oxygen permeation can be improved. The porous auxiliary agent can be considered in the same way as the deoxygenated layer, but in this case, since the concealing layer is located between the oxygen permeable resin layer and the deoxygenated layer, the particle size of the filler is the oxygen permeable resin. It is preferable to make it as small as possible so as not to penetrate the layer.
[0014]
As the resin used for the oxygen permeable resin layer and the concealing layer, the thermoplastic resin described above as the resin for the oxygen scavenger layer can be used. Preferably, it is the same kind of resin as the oxygen permeable resin layer.
[0015]
A low oxygen permeable barrier layer can be laminated on one side of the deoxidation layer. Materials constituting the barrier layer include polyesters such as polyethylene terephthalate, polyamides such as nylon 6, nylon 66 and nylon MXD6, chlorine-containing resins such as polyvinyl chloride and polyvinylidene chloride, and ethylene-vinyl alcohol copolymers. There are generally known resins such as low oxygen-permeable resins, laminated resins thereof; metal foils such as aluminum or metal vapor-deposited resins; inorganic compound vapor-deposited resins such as silicon oxide. When laminating the barrier layer and the deoxygenated layer, a thermoplastic resin compatible with the thermoplastic resin constituting the deoxygenated layer, preferably the same type of thermoplastic resin as the thermoplastic resin constituting the deoxygenated layer is used. Through the buffer layer.
[0016]
In the case where the deoxidation layer is bonded or fused to the oxygen permeable resin layer, a buffer layer or a fusion layer that enhances the adhesive force can be added between the layers as necessary. In this case, it is preferable to use the same resin as the resin used for the matrix component of the oxygen removal layer or a resin compatible with the resin. For example, a buffer layer made of the same resin as that used for the matrix component of the deoxygenation layer or a resin compatible with the resin is previously laminated on the outside of the deoxygenation layer. Can be glued or fused together.
[0017]
As materials constituting each layer, it is possible to maintain the high deoxygenation rate of the deoxygenated multilayer body and the prevention of elution of deoxygenated components. It is possible to add. Examples of the additives include pigments and dyes for coloring or hiding, stabilizing components for preventing oxidation and decomposition, antistatic components, moisture absorbing components, deodorizing components, plasticizing components, flame retardant components, etc. Is mentioned. Similarly, various layers such as a print layer, an easy-open layer, and an easy-release layer can be added as long as the performance as a deoxygenated film and sheet is not adversely affected.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
In the lamination of each layer before stretching constituting the present invention, a T-die coextrusion method is used. However, there is no particular limitation on this method, and the resin constituting each layer supplied from an individual extruder is a T-die discharge. What is necessary is just to laminate | stack and discharge by predetermined thickness and width from an exit. However, it is preferable that the thickness of the discharge port of the T die is as uniform as possible at this time, and it is important to make the thickness of the deoxidized multilayer body uniform by adjusting the opening of the discharge port of the T die. . After the nip with the cooling roll, it is necessary that the variation in thickness is within ± 20% of the predetermined thickness at any position.
[0019]
At this time, the thickness can be adjusted to an appropriate range by increasing the nip pressure of the cooling roll. However, when this is done, the molecular orientation becomes larger in the portion thicker or thinner than the surrounding at the time of ejection, and only that portion is stretched. Property will fall and sufficient draw ratio will not be obtained. Therefore, it is necessary to make the nip pressure of the cooling roll as low as possible to make the thickness uniform. Specifically, the nip line pressure of the cooling roll is 200 N / cm or less, preferably 120 N / cm or less. The lower limit of the nip line pressure of the cooling roll is 10 N / cm or more, preferably 20 N / cm or more. In addition, there is no restriction | limiting in particular about the apparatus which takes up an extrusion film or a sheet | seat, What is necessary is just to be used as a general manufacturing apparatus.
[0020]
In stretching, as is generally known, any method of uniaxial stretching, biaxial simultaneous stretching, and biaxial sequential stretching may be used. At this time, since the oxygen-permeable resin layer and the layer containing the poorly water-soluble inorganic filler are continuously porous so as to give high oxygen permeability, and at the same time, the oxygen-permeable resin layer needs to be thinned without breaking, the stretching temperature Is preferably below the melting temperature of the resin of the oxygen-permeable resin layer, and the draw ratio is 2 to 20 times.
[0021]
When adding a low oxygen-permeable barrier layer later, the deoxygenated layer and the oxygen-permeable layer are laminated and stretched in advance, and then the layer is subjected to conventional methods such as thermal lamination, dry lamination, and extrusion coating. It can be glued or fused to the final multilayer structure. When laminating a low oxygen-permeable resin as a barrier layer, it can be stretched after being previously laminated on the side where the oxygen-permeable layer of the deoxidized layer is not laminated. In this case, the thermoplastic resin compatible with the thermoplastic resin constituting the deoxidized layer in a molten state, preferably the barrier layer via the same kind of thermoplastic resin as the thermoplastic resin constituting the deoxygenated layer, A deoxygenated layer can be joined.
[0022]
The deoxygenated multilayer body in the production method of the present invention is a deoxygenated packaging material in which one side can absorb oxygen when one side is a low-oxygen permeable barrier layer. It is used in various forms for some and all of packaging containers. For example, as an oxygen-permeable resin that can be heat-sealed in order from one side, a continuous porous deoxygenated layer containing a deoxygenated composition, and a single-side absorption type deoxygenated film or sheet composed of a barrier layer that prevents oxygen permeation used. In addition, the oxygen-permeable resin layer, the continuous porous deoxygenated layer containing the deoxygenated composition, and the oxygen-permeable resin layer are used as a double-sided absorption deoxygenated film or sheet in order from one surface.
The packaged contents can be not only solid but also liquid or a mixture of solid and liquid. When both surfaces are oxygen permeable, they can be used in the same manner as a sachet-shaped oxygen absorber.
[0023]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example and a comparative example, this invention is not limited by this.
[0024]
Example 1
Deoxygenated composition coated by spraying an aqueous solution containing 2 parts by weight of calcium chloride to 100 parts by weight of iron powder with a maximum particle size of about 50μm and drying by heating, crushed silica as a poorly water-soluble inorganic filler (Ryu Co., Ltd.) 30mm diameter twin screw extruder after dry blending Mori, CRYSTALITE VX-S2, average particle size 5μm, maximum particle size 20μm) and polypropylene (Mitsubishi Chemical Corporation, FW3E, melt flow rate 7.0g / 10min) Kneading, extrusion from a strand die, cooling, and cutting with a pelletizer to obtain deoxidized resin pellets. The composition of the oxygen scavenging resin is 50 wt% oxygen scavenging composition, 10 wt% pulverized silica, and 40 wt% polypropylene.
[0025]
Ground silica as a poorly water-soluble inorganic filler (manufactured by Tatsumori, CRYSTALITE VX-S2, average particle size 5 μm, maximum particle size 20 μm), titanium oxide (manufactured by Sakai Chemical Industry Co., Ltd., SR-1) , Primary particle size 0.25 μm) and polypropylene (Mitsubishi Chemical Corporation, FW3E, melt flow rate 7.0 g / 10 min) after dry blending, kneading with a 30 mm diameter twin screw extruder, extruding from a strand die, cooling, Cutting with a pelletizer gave white resin pellets. The composition of the white resin is 50% by weight of pulverized silica, 10% by weight of titanium oxide, and 40% by weight of polypropylene.
[0026]
Weight ratio 1: 1 mixture of polypropylene (FW3E) and ethylene-hydrogenated butadiene copolymer (manufactured by JSR Corporation, DYNARON 6200P) as oxygen permeable resin layer, white resin as decontamination layer, deoxygenated A total of four layers of the deoxygenated resin as a layer and polypropylene (manufactured by Mitsubishi Chemical Corporation, FW3E) as a buffer layer were laminated so as to be arranged in this order by a co-extruder having a T die width of 500 mm. The nip pressure was 100 N / cm and the total thickness was 500 ± 50 μm. When the distribution of the thickness of the laminated body after lamination by coextrusion was measured, 95% was within ± 20% from the average value of the thickness.
[0027]
When this laminate was stretched 6 times with a uniaxial stretching machine, it could be stretched without breaking. Aluminum foil is used as a barrier layer for the buffer layer of the laminate stretched 6 times by using a urethane adhesive (a mixture of A-515, Takeda Pharmaceutical Co., Ltd., and a curing agent A-50 in a weight ratio of 10: 1). Bonding was performed by dry lamination to obtain a deoxidized multilayer film. The composition of the obtained deoxygenated multilayer film was oxygen permeable resin layer 20 μm / hiding layer 40 μm / deoxygenated layer 50 μm / buffer layer 10 μm / barrier layer 20 μm.
[0028]
Cooked rice was filled in a cup made of polyethylene terephthalate / ethylene-vinyl alcohol copolymer / polypropylene, and the resulting deoxygenated multilayer film was heat-sealed as a top seal film to prepare a packaging container. The change with time in the oxygen concentration at 25 ° C. was traced by a gas chromatograph (Shimadzu Corporation, GC-14B), and the deoxygenation rate was determined by the time until the oxygen concentration reached 0.1 vol% (deoxygenation time). The deoxygenation time was 20 hours. The flavor of cooked rice was well preserved after 2 weeks.
[0029]
Example 2
A deoxygenated composition coated with an aqueous solution containing 2 parts by weight of calcium chloride sprayed on 100 parts by weight of iron powder having a maximum particle size of about 50 μm and dried by heating, and linear low density polyethylene (Mitsui Chemicals, Inc.) Manufactured, SP2040, melt flow rate 4.0g / 10min), dry blended, kneaded with a 30mm diameter twin screw extruder, extruded from a strand die, cooled and cut with a pelletizer to obtain pellets of a deoxidizing resin composition It was. The composition of the deoxidizing resin composition is 50% by weight of the deoxidizing composition and 50% by weight of linear low density polyethylene.
[0030]
The same linear low density polyethylene as the deoxygenated layer is used as the heat seal layer, polymethylpentene resin (manufactured by Mitsui Chemicals, DX845), and titanium oxide (SR-1) for concealment in a weight ratio of 70. : 20:10 was mixed, and pellets were produced in the same manner as the deoxygenated layer. The pellets and deoxidized pellets were laminated by coextrusion in the same manner as in Example 1 to obtain a laminate comprising two layers. The nip pressure of the cooling roll was 75 N / cm, and the total thickness was 200 ± 30 μm. When the distribution of the thickness of the laminated body after lamination by coextrusion was measured, 95% was within ± 20% from the average value of the thickness.
[0031]
When this laminate was stretched 5 times with a uniaxial stretching machine, it could be stretched without breaking. Dry laminate the aluminum foil as a barrier layer on the buffer layer of this 5 times stretched film using urethane adhesive (A-515, Takeda Pharmaceutical Co., Ltd., 10: 1 mixture with curing agent A-50). To obtain a deoxidized multilayer film. The structure of the obtained deoxygenated multilayer film was oxygen permeable resin layer 30 μm / deoxygenated layer 50 μm / barrier layer 20 μm.
[0032]
A predetermined amount of air and bread were put in a bag having a deoxidized multilayer film on both sides so that the air amount was 1 cc per 1 cm ² of the deoxidized film, and heat sealed. When stored at 25 ° C. and the oxygen concentration was measured in the same manner as in Example 1, the deoxygenation time was 18 hours. The flavor of bread was well preserved after 2 weeks.
[0033]
Example 3
A deoxygenation layer and oxygen permeable layer pellets similar to those in Example 2 were prepared, and an oxygen permeable layer, a deoxygenation layer, and an oxygen permeable layer were laminated in this order to obtain a deoxygenation multilayer body composed of three layers. The nip pressure of the cooling roll was 150 N / cm, and the total thickness was 250 ± 30 μm. When the distribution of the thickness of the laminated body after lamination by coextrusion was measured, 95% was within ± 20% from the average value of the thickness. When the film was stretched 5 times in the same manner as in Example 1, the film could be stretched without breaking and a deoxidized multilayer body was obtained.
Put the deoxygenated multilayer film obtained on one side, a gas barrier transparent film made of polyethylene terephthalate / ethylene-vinyl alcohol copolymer / polyethylene on a side of 10 cm × 15 cm bag, put 50 g boiled beans and air 150 cc, Heat sealed. The deoxygenation time was 20 hours. The flavor of boiled beans was well preserved after 2 weeks.
[0034]
Comparative Example 1
The configuration of the deoxidized multilayer was the same as in Example 1, and the nip pressure during coextrusion was 250 N / cm, and the total thickness was 500 ± 30 μm. When stretched in the same manner as in Example 1, it was broken at a stretch ratio of 4 times.
[0035]
Comparative Example 2
The configuration of the deoxidized multilayer was the same as in Example 2, and the nip pressure during coextrusion was 250 N / cm, and the total thickness was 200 ± 20 μm. When stretched in the same manner as in Example 1, it was broken at a stretch ratio of 3 times.
[0036]
【The invention's effect】
The method for producing a deoxygenated multilayer body of the present invention makes it possible to stretch a laminate containing a deoxygenated composition at a high draw ratio, thereby making the deoxygenated layer porous and increasing the oxygen permeation rate. A deoxygenated multilayer body with improved speed and no elution of deoxygenated components is produced industrially.

Claims (4)

In the production of a deoxygenated multilayer body comprising a deoxygenated layer comprising a continuous porous resin blended with a deoxygenated composition and an oxygen permeable resin layer comprising an oxygen permeable resin on one surface thereof, the deoxygenated composition A thermoplastic resin and an oxygen permeable thermoplastic resin blended with each other are laminated by coextrusion with a nip line pressure of a cooling roll of 200 N / cm or less, and then stretched to continuously make the deoxygenated layer porous. A method for producing a deoxygenated multilayer body. In the production of a deoxygenated multilayer body comprising a deoxygenated layer composed of a continuous porous resin blended with a deoxygenated composition and an oxygen permeable resin layer composed of an oxygen permeable resin on both sides of the deoxygenated layer, The sheet constituting the sheet and the sheet constituting the oxygen permeable resin layer disposed on both sides thereof are laminated by coextrusion with the nip line pressure of the cooling roll being 200 N / cm or less, and then stretched to continuously make the deoxygenated layer porous. A method for producing a deoxidized multilayer body. The method for producing a deoxygenated multilayer body according to claim 1 or 2, wherein the thickness distribution after lamination by coextrusion is 90% or more within ± 20% of the average thickness value. 2. The method for producing a deoxygenated multilayer body according to claim 1, wherein a low oxygen-permeable resin as a barrier layer is previously laminated on a side of the deoxygenated layer where the oxygen-permeable layer is not laminated, and then stretched.