JPH0782001B2 - Oxygen indicator, its molded body and laminate having oxygen detection function - Google Patents

Description

TECHNICAL FIELD The present invention has an oxygen indicator comprising an ionomer having a complex ion of divalent manganese and an organic amine as a cation, and an oxygen detection function obtained by molding the ionomer. The present invention relates to a molded product and an oxygen barrier laminate having an oxygen detection function.

2. Description of the Related Art In the field of food packaging, in order to prevent food spoilage by oxygen, transparent materials that do not allow oxygen to pass through, such as glass and polyvinylidene chloride gas barrier polymer compound bottles and packaging bags, It is widely practiced to prevent the invasion of oxygen by, for example, packaging and evacuating the inside or replacing it with nitrogen gas to block oxygen, and further inserting an oxygen scavenger into the container to remove oxygen. In these packages, there is a demand for an oxygen indicator that can be easily identified from the outside when oxygen enters the inside of the packaging container or package.

Also, when storing industrial chemicals that easily react with oxygen, packaging is similarly performed to block oxygen, and in this case as well, there is a demand for a method that can similarly detect the ingress of oxygen.

For this purpose, it has been practiced to detect the invasion of oxygen by putting powder or the like containing a dye that changes color when it comes into contact with oxygen into a pouch and packaging it with food.

For example, it has been proposed to use a compound having an oxazine skeleton in its molecule as an oxygen detection agent by utilizing the property of having different color tones in the presence and absence of oxygen. (JP-A-56-65072) Problems to be Solved by the Invention However, dyes and the like used as oxygen indicators for such a purpose may contaminate foods. Further, in these above-mentioned applications, it is important not only to detect the presence of oxygen but also to detect the entry route of oxygen, and an oxygen indicator having such a function is desired. For example, in a packaging film for food, oxygen often enters through a pinhole of a packaging bag, and an indicator that can detect from which part of the pinhole the oxygen enters is expected. However, it is difficult to detect even the entry route with an oxygen indicator such as a dye.

Means for Solving the Problems In view of such a situation, the inventor of the present invention has no fear of mixing into a food or the like as long as it is a polymer compound having an oxygen detection function, and knows an oxygen entry route. Focusing on the fact that it can be used in such a position and shape, as a result of intensive research aimed at searching for a polymer compound having an oxygen detection ability, as a result, an ionomer resin having a specific complex ion as a cation selectively adsorbs oxygen. It was found that the color changed, and the present invention was completed. Further, it was also found that by laminating the ionomer resin of the present invention with an oxygen barrier polymer, an oxygen barrier laminate having an oxygen detection function can be obtained.

As a polymer compound-based oxygen adsorbing / desorbing agent, a dispersion liquid in which hydrophobic polymer particles in which a facing diporphyrin metal complex is embedded is dispersed in an aqueous medium is known. (Japanese Examined Sho 63-501
1) But in such an oxygen indicator,
In order to embed the metal complex in the polymer compound, operations such as dissolution in a solvent, separation, and drying are necessary. Further, in the present invention, the polymer compound is used as an aqueous dispersion and is never used as a molding material. Not suggested. On the other hand, the present invention has a feature that it has an oxygen detection function and can be molded into an arbitrary shape for use.

That is, the present invention relates to an oxygen indicator comprising an ionomer having a complex ion of divalent manganese and an organic amine as a cation, a molded product having an oxygen sensing function obtained by molding the ionomer into a film or a sheet, and oxygen sensing. The present invention relates to an oxygen barrier laminate having a function.

The ionomer used in the present invention is a complex compound of a divalent manganese and an organic amine in which a polymer compound having a hydrophobic hydrocarbon main chain as a side chain and / or an end group with an acidic functional group such as a carboxylic acid group or a sulfonic acid group. It is partially or completely neutralized with ions. In the partially neutralized product of the complex ion, as long as the complex ion is present,
An acidic functional group which is not neutralized with a complex ion may be partially or completely neutralized with another metal ion or ammonium ion.

As the acidic polymer compound serving as a base, a copolymer of an olefin and an unsaturated carboxylic acid, and if necessary, another unsaturated monomer, a sulfonated olefin polymer, and the like are used. Here, the copolymer is a random copolymer, a block copolymer, an alternating copolymer, a graft copolymer, etc.
Either can be used.

More specifically, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester- (meth)
Acrylic acid copolymer, ethylene-maleic anhydride copolymer, ethylene-maleic anhydride-vinyl acetate copolymer,
Examples thereof include ethylene-maleic acid monoester copolymer, ethylene-maleic acid monoester- (meth) acrylic acid ester copolymer, styrene-methacrylic acid copolymer, sulfonated polyethylene and sulfonated polystyrene. Among these, ethylene-based polymers, particularly ethylene-unsaturated carboxylic acid copolymers and ethylene-unsaturated carboxylic acid ester-unsaturated carboxylic acid copolymers, are preferable from the viewpoint of thermoformability into films and the like.
Further, as these ethylene-based copolymers, those having an ethylene content of 70 to 99 mol%, particularly 90 to 99 mol% are preferable.

As the cation of the ionomer, divalent manganese (hereinafter,
A complex ion of Mn (II) or Mn ⁺⁺ ) and an organic amine is used. It was found that the ionomer having this complex ion as a cation has a unique property that the color changes due to adsorption and desorption of oxygen, and can be used as an oxygen indicator. An ionomer having divalent manganese alone as a cation that does not form a complex ion with an organic amine discolors in the presence of oxygen, but its rate is very slow and the discoloration degree is small.

In addition to manganese, zinc (II), cobalt (II), nickel (II), copper (II), etc. are known as metal cations that form complex ions with organic amines. The ionomer used as a cation did not show the property of selectively adsorbing and desorbing oxygen and changing its color.

As the organic amine that forms a complex ion with divalent manganese, a polyamine having two or more primary amino groups in one molecule is preferable. That is, an ionomer having a cation that is a complex ion of a polyamine having two or more primary amino groups in one molecule and divalent manganese is a polyamine having a secondary or tertiary amino group, a primary monoamine and a divalent manganese. Compared to ionomers whose complex ion with is a cation,
It is relatively stable to heat and is suitable as the oxygen indicator of the present invention because it is less likely to be decomposed during thermoforming and amine is vaporized and desorbed from the ionomer. Preferred organic amines include 1,3 bisaminocyclohexane, metaxylene diamine, hexamethylene diamine and tetraethylene pentamine. It is also possible to use a mixture of two or more of these organic amines.

The manganese concentration in the ionomer varies depending on the kind of the base polymer, but is preferably about 0.1 to 10% by weight.

The amount of amino in the ionomer is 0.05 to 3.0 with respect to 1 mol of the acidic functional group (including neutralized one).
It is preferably about molar.

The ionomer having a complex ion of manganese and an organic amine of the present invention as a cation can also be used alone,
An ionomer having another cation or another thermoplastic polymer compound may be used as a mixture as long as it does not affect the discoloration reaction by oxygen.

The ionomer of the present invention is produced by a method similar to the generally practiced method for producing an ionomer. The method for producing an ionomer is usually divided into a step of synthesizing an acidic polymer compound and a subsequent step of ionizing (neutralizing) the ionomer. In the case of ethylene-methacrylic acid copolymer, for example, the acidic polymer compound is synthesized by a radical polymerization method using an organic peroxide as an initiator under the reaction conditions of 1000 to 3000 Kg / cm ² and 150 to 250 ° C. . The polyolefin-acrylic acid graft copolymer can be obtained by kneading the polyolefin, the acrylic acid monomer and the organic peracid compound under a temperature condition of 100 to 300 ° C. in an extruder or the like. Sulfonic acid polymers such as sulfonated polystyrene are synthesized by subjecting polystyrene to sulfonation in a fuming sulfuric acid bath.

The ionomerization (neutralization) step is performed by adding and mixing a desired amount of an organic acid salt of divalent manganese such as manganese acetate and an organic amine to an acidic polymer compound under a temperature condition of 100 to 300 ° C. and reacting them. . Water and organic acids by-produced by the reaction are removed by degassing treatment or the like. As a kneading device, a screw extruder, a Banbury mixer, a roll mixer or the like can be used, but an extruder is preferable from the viewpoint of easy operation. In the ionomer process, two components of an organic acid salt of divalent manganese and an organic amine may be reacted with an acidic polymer compound in the same process, or one of them may be reacted with the polymer compound first to form a complex ion. It is possible. In the ionomerization step, besides this, a method of reacting a divalent manganese salt and an organic amine in a state where an acidic polymer compound is dissolved in an organic solvent and then removing the solvent to obtain an ionomer can be used.

The oxygen indicator of the present invention can also be used as it is in the form of pellets or powder, which is the shape at the time of manufacturing an ionomer, and even in this case, unlike oxygen indicators such as dyes, there is an advantage that the packaging material and contents are not colored and contaminated. Have.

However, the ionomer having an oxygen detection function of the present invention is a polymer that can be easily molded, and its characteristics can be utilized more effectively by molding and using it in various molded products. In particular, a sheet- or film-shaped molded product has a feature that it can detect the entry path of oxygen as a planar oxygen indicator having a wide area. When used as a molded product, the melt flow rate (190
It is preferable to use one having a temperature of 2160 g and a temperature of 0.1 to 1000 g / 10 minutes.

As the method for molding the ionomer of the present invention, a general molding method for an ordinary thermoplastic polymer compound can be applied as it is. That is, a film formed by extrusion molding using a screw extruder, a bottle formed by extrusion blow molding, a molded body of various shapes formed by injection molding, a sheet formed by hot press molding, a film, a sheet formed by roll forming, and the like can be formed.

These moldings can be molded as a composite with various thermoplastic polymer compounds in addition to using the ionomer alone. In particular, the multilayer body obtained by laminating the oxygen barrier polymer and the ionomer of the present invention is a packaging body containing a planar oxygen indicator layer, and a pinhole is generated in a part of the packaging body that is difficult to pass oxygen, Even when oxygen enters, the oxygen entry route can be detected by the color change of the package at the entry part. That is, an oxygen barrier laminate having a function of detecting the entry path of oxygen can be obtained as a film or sheet.

As the oxygen barrier polymer, ethylene-vinyl alcohol copolymer, polyvinylidene chloride, nylon, polyester and the like can be used.

For the production of the laminated body, a usual method for producing the laminated body such as coextrusion, hot melt press, extrusion lamination, and dry lamination can be applied. Further, for the purpose of compensating for defects such as low moisture resistance of the oxygen barrier polymer, polyolefin or the like can be further laminated.

EFFECTS OF THE INVENTION The oxygen indicator of the present invention can detect oxygen easily and selectively by color change, without using a special device, as compared with the conventional oxygen indicators utilizing changes in electrical conductivity. You can Therefore, in food packaging applications and the like, it is possible to easily check the ingress of oxygen into the inside of the package at the distribution stage or at the consumer.

Further, since the oxygen indicator of the present invention is a high molecular compound, it has an advantage that it does not contaminate the package unlike the oxygen indicator dye which similarly detects the invasion of oxygen by the change in color due to the adsorption of oxygen. There is.

Furthermore, the ionomer oxygen sensor of the present invention is a thermoplastic resin and can be easily molded into a molded product such as a film or a sheet, and the obtained oxygen indicator molded product is in a form capable of detecting an oxygen entry path. Can be used. A laminate formed by laminating an ionomer and an oxygen barrier polymer, especially a laminated film is an oxygen barrier film having an oxygen detection function, and only the damaged part of the oxygen barrier layer is discolored, and the entry route of oxygen can be detected. Therefore, it is extremely useful as a packaging bag for products that dislike oxygen.

It should be noted that the oxygen indicator whose color has changed due to contact with oxygen can be returned to the state before color change by keeping it at a high temperature for a certain period of time, and can be used repeatedly.

The present invention will be described below with reference to examples.

Ionomer synthesis Single screw extruder with one vent (screw diameter 65m
m, L / D = 33) pellets of ethylene methacrylic acid copolymer (methacrylic acid content 15% by weight, MFR 60 dg / min) and ethylene methacrylic acid copolymer with manganese (II) acetate (methacrylic acid content 10% by weight, MFR500dg / min) was melt-mixed at a mixing ratio of 45 wt% and 55 wt% in advance and pelletized, and the resin temperature of the extruder was set to 220 ° C. to extrude the ionomer. The acetic acid generated by the neutralization reaction is degassed and removed from the vent port in the middle of the extruder by vacuum, and the ionomer containing divalent manganese, which does not contain reaction by-products as cations, is taken out from the extruder in the form of a molten strand, and then water is used. After cooling, it was cut with a cutter to obtain a pelletized ionomer.

The ionization degree (neutralization degree) of the ionomer is adjusted by changing the ratio of ethylene methacrylic acid copolymer and manganese acetate added to the extruder, and the ionization degree of 60%, 40%, and 20% manganese (II) ionomer is adjusted. Got The ionomer was a transparent, very pale yellowish polymer.

The obtained manganese (II) ionomer pellets were supplied again from the same extruder feed port, and an organic amine (1,3 bisaminocyclohexane) was injected into the extruder from the middle of the extruder using a high-pressure pump. Ionomer with complex ion of (II) and organic amine as cation was synthesized. The product is taken out as a molten strand from the extruder,
After the strand was cooled with water, it was cut with a cutter to obtain a complex ion ionomer pellet. Resin temperature in the extruder is 200 ℃
And the vent port of the extruder was kept at 300 Torr, but no gas generated from the vent port was observed. The ionomer was transparent and light reddish. The addition amount of the organic amine was controlled by the injection amount from the injection pump to the extruder.

The manganese (II) ionomer and manganese (II) -1,3 bisaminomethylcyclohexane complex ion ionomer shown in Table 1 were obtained by the above-mentioned method.

BAC; Bisaminomethylcyclohexane Preparation of ionomer film The obtained ionomer sample was treated with a polyester film as a release film by a hot pressing method at 100 kg / cm ² , 140
Pressurized at ~ 180 ℃ for 4 ~ 8 minutes, then 100kg with water-cooled press
A pressure film having a thickness of 0.5 mm was obtained by applying pressure at 20 ° C./cm ² for 5 minutes. The pressed film was a thin red transparent film immediately after preparation.

Examples 1-6 and Comparative Examples 1-3 Ionomer pellets (about 3 mm) removed from the extruder.
The state of coloring due to oxygen (in the form of a circular cylinder) was observed. The results are shown in Table 2.

The above examples show that Mn (II) -1,3BAC complex ion ionomers change color upon contact with oxygen.

Next, in Example 5, the color changed to black purple 60% Mn ⁺⁺ -10.3.wt% B
AC ionomer pellets were reextruded using a 30 mm single-screw extruder (L / D = 32) at a resin temperature of 200 ° C. with a screw extrusion of 40 rpm and a residence time in the extruder of about 3 minutes. The ionomer strands from the extruder returned to a light brown transparent appearance before discoloration.

Example 7 0.6 mm of Mn (II) complex ion ionomer No. 9 in Table 1
A thick film was prepared under heating conditions of 180 ° C. and 100 kg / cm ^{2 for} 6 minutes to obtain a light cream transparent film. When the polyester release film was removed from this film and it was left in contact with air at room temperature for one week, the film turned red-purple and became semitransparent. This discolored film in the air
The temperature was raised from 20 ° C. at a heating rate of 0.4 ° C./min, and changes in the visible light spectrum were measured in the range of 30 to 140 ° C. Then 140
Quickly cool samples heated to 30 ° C to 30 ° C
Visible spectrum was measured at ° C and compared with that of the heated sample at 30 ° C before cooling.

Both the sample before heating and the sample heated up to 70 ℃ were translucent reddish purple, the visible light spectrum had an absorption maximum peak at 469 nm, and showed high absorption even in the entire visible region (400 to 800 nm). First visible spectrum at 30 ℃
Shown in the figure. The relationship between temperature and absorbance at 469 nm is shown in FIG. When the heating temperature exceeded 80 ° C, the color of the film became light and the absorption peak at 469 nm started to decrease. Samples heated at 100 ° C or higher had high transparency, and the fading of the film was remarkable. The sample heated at 140 ° C. became transparent in light yellow color, which was the same as the color immediately after the synthesis of the ionomer. The visible light spectrum of the sample immediately after heating at 140 ° C. and cooling to 30 ° C. was almost the same as the visible light spectrum at 140 ° C., and it was light yellow and transparent.

The results of Example 7 indicate that oxygen adsorbed to the ionomer at room temperature desorbs at high temperature, causing the ionomer to fade. That is, it shows that the discoloration of the oxygen indicator of the present invention is reversible.

Example 8 A polyester film was peeled off from a 0.6 mm thick film of Mn ⁺⁺ -BAC complex ion ionomer of Table 1 No. 9 laminated with a polyester film, and oxygen, nitrogen, and water vapor were added at room temperature (23 ° C.). The mixture was brought into contact with a seed gas, and the change with time of the absorbance at 490 nm was measured. The results are shown in FIG.

As a result, the absorbance at 490 nm increased sharply in oxygen, and there was almost no change in the absorbance with color increase or other gases. From this, it is understood that the ionomer of the present invention selectively adsorbs oxygen and changes color.

Example 9 Low-density polyethylene 15 μm Maleic anhydride-modified low-density polyethylene 10 μm Gas Biary nylon (registered trademark “Sealer” PA manufactured by Dyupon Co., Ltd.) 20 μm 60% Mn (II) -10.3 wt% BAC ionomer 15 μm Na ion ionomer (Mitsui -Registered trademark "Himilan" 1601) manufactured by Deupon Polychemical Co., Ltd. A laminated film consisting of 5 layers of 40 μm was prepared by a coextrusion method.

The obtained transparent film was folded with the Na ion ionomer inside, and two sheets were stacked, the inside was evacuated, and the periphery was heat-sealed to prepare an oxygen barrier laminated film. This laminated film was stored in the air for 1 week under the following conditions, and the change in color was observed.

[Brief description of drawings]

FIG. 1 shows the visible light spectrum at 30 ° C. of the oxygen indicator film of the present invention which was brought into contact with air at 20 ° C. FIG. 2 shows the relationship between the temperature and the absorbance at 469 nm when the oxygen indicator of the present invention which is discolored by oxygen is heated. FIG. 3 shows changes with time in the absorbance at 490 nm when the oxygen indicator of the present invention was brought into contact with various gases.

Claims (3)

[Claims] 1. An oxygen indicator comprising an ionomer having a complex ion of divalent manganese and an organic amine as a cation. 2. A molded article having an oxygen detection function, which is obtained by molding an ionomer having a complex ion of divalent manganese and an organic amine as a cation in a film shape or a sheet shape. 3. An oxygen barrier laminate having an oxygen detection function, which is formed by laminating an ionomer having a complex ion of divalent manganese and an organic amine as a cation and an oxygen barrier polymer.