JPH01318957A - Oxygen sensor, its molding and laminate having oxygen sensor function - Google Patents

Abstract

PURPOSE:To identify through which pinhole oxygen is intruded by constituting an oxygen sensor with bivalent manganese and ionomer wherein the complex ions of organic amine are cations. CONSTITUTION:A macromolecular compound has an acidic functional group such as a carboxylic acid group or sulfonic acid group as a side chain or an end group that is bonded to the main chain of hydrophobic hydrocarbon. Said macromolecular compound is partially or completely neutralized with complex ions of bivalent manganese and organic ions. This material is used as ionomer. In this way, an oxygen sensor is constituted. Said ionomer has the following property: the color is changed by the adsorption and desorption of oxygen. Therefore, it can identified through which pinhole the oxygen is intruded.

Description

Detailed Description of the Invention The present invention relates to an oxygen sensor made of an ionomer whose cation is a complex ion of divalent manganese and an organic amine, and a molded product having an oxygen sensor function obtained by molding the ionomer. The present invention relates to an oxygen barrier laminate having body and oxygen sensor functions.

In the field of food packaging, bottles and packaging bags are made of transparent materials that do not allow oxygen to pass through, such as glass and gas barrier polymer compounds such as polyvinylidene chloride, in order to prevent food from spoiling due to oxygen. It is widely practiced to prevent oxygen from entering the container by packaging food in containers, creating a vacuum inside the container, replacing the container with nitrogen gas to block oxygen, and then removing oxygen by putting an oxygen absorber inside the container. . For these packages, there is a need for an oxygen sensor that can easily identify from the outside when oxygen has entered the inside of the packaging container or package.

In addition, packaging that blocks oxygen is similarly used to store industrial chemicals and the like that are likely to react with oxygen, and in this case as well, there is a need for a method that can detect the ingress of oxygen.

For this purpose, a powder containing a dye that changes color when exposed to oxygen is placed in a pouch and packaged with the food to detect the ingress of oxygen.

For example, it has been proposed that compounds having an oxazine skeleton in their molecules have different color tones in the presence and absence of oxygen to be used as oxygen detection agents. (Japanese Unexamined Patent Publication No. 56-65072) However, the dyes used as oxygen sensors for this purpose may contaminate food. In addition, in these above-mentioned applications, it is important not only to detect the presence of oxygen, but also to detect the path of oxygen entry.
An oxygen sensor with such a function is desired.

For example, in food packaging films, oxygen often enters through pinholes in packaging bags, and there is hope for a sensor that can detect which pinholes oxygen has entered. However, it is difficult to detect even the entry route using dye-based oxygen sensors.

. In view of this situation, the inventors of the present invention determined that a polymer compound having an oxygen sensor function would not be likely to be mixed into foods, etc., and should be located in a position and shape that would allow the route of oxygen intrusion to be known. As a result of intense research aimed at searching for polymer compounds with oxygen sensing ability, we discovered that ionomer resins with specific complex ions as cations selectively adsorb oxygen and change color. , we have completed the present invention. Furthermore, it has been found that by laminating the ionomer resin of the present invention with an oxygen barrier polymer, an oxygen barrier laminate having an oxygen sensor function can be obtained.

As a polymer compound-based oxygen adsorbing/desorbing agent, a dispersion liquid in which hydrophobic polymer particles in which face-to-face divorphyrin metal plaques are embedded is dispersed in an aqueous medium is known. (Tokuko Showa 63-5
011) L/Kashi In such an oxygen sensor,
In order to embed the metal complex in a polymer compound, operations such as dissolving it in a solvent, separating it, and drying it are necessary.In addition, in this invention, the polymer compound is used as an aqueous dispersion, and it cannot be used as a molding material at all. Not suggested. In contrast, the present invention has an oxygen sensor function itself and has the feature that it can be molded into any shape and used.

That is, the present invention provides an oxygen sensor made of an ionomer whose cation is a complex ion of divalent manganese and an organic amine, a molded article having an oxygen sensor function obtained by molding the ionomer, and an oxygen barrier property having an oxygen sensor function. Regarding a laminate.

The ionomer used in the present invention is a polymer compound having an acidic functional group such as a carboxylic acid group or a sulfonic acid group as a side chain and/or terminal group on a hydrophobic hydrocarbon main chain, or a complex of divalent manganese and an organic amine. ions that are partially or completely neutralized in cattle. In a partially neutralized product of the above complex ion, as long as the above complex ion exists, the acidic functional groups that are not neutralized by the complex ion can be partially or completely neutralized by other metal ions, ammonium ions, etc. It may be neutralized.

As the base acidic polymer compound, an olefin and an unsaturated carboxylic acid, and if necessary, a copolymer with other unsaturated monomers, a sulfonated olefin polymer, etc. are used. Copolymers here include random copolymers, block copolymers, alternating copolymers, graft copolymers, 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 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 polymers, particularly ethylene-unsaturated carboxylic acid copolymers and ethylene-unsaturated carboxylic acid ester-unsaturated carboxylic acid copolymers, are preferred from the viewpoint of thermoformability into films and the like.

These ethylene copolymers preferably have an ethylene content of 70 to 99 mol%, particularly 90 to 99 mol%.

The ionomer cation is divalent manganese (hereinafter referred to as
A button ion of Mn(II) or Mn-) and an organic amine is used. Ionomers containing this complex ion as a cation have the unique property of changing color when adsorbing and desorbing oxygen, and it was discovered that they could be used as oxygen sensors. Ionomers whose cation is divalent manganese alone, which does not form complex ions with organic amines, change color in the presence of oxygen, but the rate of change is very slow and the extent of the change is small.

In addition to manganese, metal cations that form complex ions with organic amines include zinc (■), cobal (n), nickel (■), and copper (■), but these complex ions The ionomer with cation as a cation did not exhibit the property of selectively adsorbing and desorbing oxygen and causing discoloration.

As the organic amine that forms a complex ion with divalent manganese, a polyamine having two or more primary amino groups per molecule is suitable. In other words, an ionomer whose cation is a complex ion of a polyamine having two or more primary amino groups per molecule and divalent manganese is a polyamine having a secondary or tertiary amino group, or a primary monoamine having two or more molecules. Compared to ionomers whose cations are complex ions with cancer,
It is suitable as the oxygen sensor of the present invention because it is relatively stable against heat and there is little risk of it decomposing during thermoforming or that the amine is vaporized and desorbed from the ionomer.

Preferred organic amines include 1.3bisaminocyclohexane, metaxylene diamine, hexamethylene diamine, and tetraethylenepentamine. 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 type of base polymer, but is preferably about 0.1 to 10% by weight.

The amount of amine in the ionomer is 0.05 to 1 mole of acidic functional groups (including neutralized ones).
It is preferable to set it to about 3.0 mol.

The ionomer of the present invention whose cation is a complex ion of manganese and an organic amine can be used alone, but
It can also be used in combination with other cation-containing ionomers or other thermoplastic polymer compounds as long as they do not affect the color change reaction caused by oxygen.

The ionomer of the present invention is produced by a method similar to the method for producing the ionomer carried out in -M. A method for producing an ionomer is usually divided into a synthesis step of an acidic polymer compound and a subsequent ionomerization (neutralization) step. Synthesis of an acidic polymer compound, for example, in the case of ethylene-methacrylic acid copolymer, is 1000 to 3000 Kg/c.
A radical polymerization method using an organic peroxide as an initiator is used under reaction conditions of 150 to 250°C.For polyolefin-acrylic acid graft copolymers, 1
It is obtained by kneading a polyolefin, an acrylic acid monomer, and an organic peroxide at a temperature of 00 to 300°C. Sulfonic acid polymers such as sulfonated polystyrene are synthesized by sulfonating polystyrene in oleum.

The ionomerization (neutralization) step is carried out 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. It will be done. Water and molar acids produced as by-products of the reaction are removed by degassing or the like. As the mixing device, a screw extruder, a Banbury mixer, a roll mixer, etc. can be used, but an extruder is preferred from the viewpoint of ease of operation. In the ionomer process, two components, an organic acid salt of divalent manganese and an organic amine, can be reacted with an acidic polymer compound in the same process, or either one can be reacted with a polymer compound first to form a complex ion. It is possible. As the ionomerization step, a method can also be used in which a divalent manganese salt and an organic amine are reacted in a state in which an acidic polymer compound is dissolved in an organic solvent, and then the solvent is removed to obtain an ionomer.

The oxygen sensor of the present invention can also be used in the form of pellet or powder, which is the form in which the ionomer is manufactured, and even in this case, unlike oxygen sensors such as dyes, it has the advantage of not coloring or contaminating packaging materials and contents. has.

However, the ionomer having an oxygen sensor function of the present invention is a polymer that can be easily molded, and its characteristics can be utilized more effectively by molding it into various molded bodies. In particular, a sheet or film-like molded article has the feature that it can also detect the entry route of oxygen as a planar oxygen sensor with a wide area. When using the molded product, the melt flow rate (190
It is preferable to use one with a load of 0.1 to 1000 g (710 minutes at 12160 °C) for about 710 minutes.

As the method for molding the ionomer of the present invention, a general molding method for ordinary thermoplastic polymer compounds can be applied as is. That is, films can be formed by extrusion using a screw extruder, bottles by extrusion blow molding, molded bodies of various shapes by injection molding, sheets and films by hot press molding, sheets by roll molding, and the like.

These molded bodies can be molded not only using the ionomer alone, but also as a composite body with various thermoplastic polymer compounds. In particular, the multilayer body obtained by laminating the oxygen barrier polymer and the ionomer of the present invention is a package containing a planar oxygen sensor layer, and pinholes occur in a part of the package that is difficult to pass oxygen. Even if oxygen enters, the path of oxygen entry can be detected by the discoloration of the package at the entry area. In other words, an oxygen barrier laminate having a function of detecting an oxygen entry route can be obtained by combining a film or a hollow body.

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

The laminate can be manufactured by any conventional laminate manufacturing method such as coextrusion, hot melt pressing, extrusion lamination, or dry lamination. Further, in order to compensate for the drawbacks such as low moisture resistance of the oxygen barrier polymer, polyolefin or the like can be further laminated.

Compared to conventional oxygen sensors that utilize changes in electrical conductivity, the oxygen sensor of the present invention can easily and selectively detect oxygen by changing its color without using any special equipment. Can be detected. Therefore, in applications such as food packaging, it is possible to easily check the ingress of oxygen into the packaged product at the distribution stage or at the consumer.

Furthermore, since the oxygen sensor of the present invention is a polymer compound,
Unlike oxygen sensor dyes, which similarly detect the ingress of oxygen by changing color due to oxygen adsorption, they have the advantage of not contaminating packages.

Furthermore, the ionomer oxygen sensor of the present invention is a thermoplastic resin and can be easily molded into films, sheets, and various other molded bodies, and the resulting oxygen sensor molded body is in a form capable of detecting the path of oxygen entry. It can be used in A laminate made by laminating an ionomer and an oxygen barrier polymer, especially a laminated film, is an oxygen barrier film with an oxygen sensor function, and only the damaged parts of the oxygen barrier layer change color, allowing the path of oxygen entry to be detected. Therefore, it is extremely useful as a packaging bag for products that dislike oxygen.

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

The present invention will be explained below with reference to Examples.

A single-screw extruder (screw diameter 65
mm, L/D=33) and ethylene methacrylic acid copolymer (methacrylic acid content 15% by weight, MFR60dg/m1
n) pellets and manganese acetate (n) and ethylene methacrylic acid copolymer (methacrylic acid content 10% by weight, M
FR500d g/m 1 n) was melt-mixed in advance at a mixing ratio of 45 wt% and 55 wt% and pelletized, and the resin temperature of the extruder was set to 2200 ml.
An ionomer was synthesized by extrusion as C. The acetic acid generated during neutralization is removed by vacuum from the vent hole in the middle of the extruder, and the ionomer containing divalent manganese as a cation, which does not contain any reaction by-products, is taken out from the extruder in the form of a molten strand, and then mixed with water. After cooling, it was cut with a cutter to obtain a pellet-shaped ionomer.

The ionization degree (neutralization degree) of the ionomer was adjusted by changing the ratio of ethylene methacrylic acid copolymer and manganese acetate added to the extruder, and the ionization degree was 60% and 40%.
, and 20% manganese(n) ionomer were obtained.

The ionomer was a clear, very pale yellowish polymer.

The obtained pellet of manganese (n) ionomer is again fed from the same feed port of the extruder, and an organic amine (1,3 bisaminocyclohexane) is injected into the extruder using a high-pressure pump from the middle of the extruder. An ionomer containing a complex ion of (II) and an organic amine as a cation was synthesized. The product was taken in the form of a molten strand from the extruder, and the strand was cooled with water and then cut with a cutter to obtain a pellet of i1 ion ionomer. is 300T
ORR was maintained, but no gas was observed coming from the vent. The ionomer was transparent with a slight reddish tinge. The amount of organic amine added was controlled by the amount injected into the extruder from an injection pump.

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

BAC; bisaminomethylschifftetrahexaneonomer flume! The obtained ionomer sample was heated to 100 kg/a using a polyester film as a release film using a hot press method.
m'' and 140 to 180° C. for 4 to 8 minutes, and then a water-cooled press at 100 kg/cm” and 20° C. for 5 minutes to obtain a pressed film with a thickness of 0.5 mm. Immediately after the press film was created, it was a transparent thin red film.

-1 to 6 and 1 to 3 Ionomer pellets taken out from the extruder (approximately 3 m
The state of coloring due to oxygen in the m-diameter cylindrical shape was observed. The results are shown in Table 2.

Margin Table 2 Below The above example shows that the Mn (II)-1,3BAC complex ion ionomer changes color when it comes into contact with oxygen.

Next, in Example 5, 60% Mn++-10 that changed color to black-purple
．． 3. 30mm of wt% BAC ionomer pellets
Extrude using a screw extruder (L/D=32) at 40 revolutions per hour at a resin temperature of 200°C, and re-extrude with a residence time in the extruder of about 3 minutes.

The ionomer strands that came out of the extruder returned to their pale brown, transparent appearance before the discoloration.

Table 1: A 0.6 mm thick film of NO19 Mn (II) complex ion ionomer was heated at 180°C, 100 kg/
cm" under heating conditions for 6 minutes to obtain a pale cream-colored transparent film. When the polyester release film was removed from this film and left in contact with air at room temperature for one week, the film turned reddish-purple. The color changed to translucent.This discolored film was heated at 20°C to 0.4°C in the air.
The temperature was raised at a temperature increase rate of 10 minutes, and changes in the visible light spectrum were measured in the range of 30 to 140°C. Next, the sample heated to 140°C was quickly cooled to 30°C, and the sample was heated to 30°C.
The visible light spectra were measured at °C and compared with that of the sample heated at 30'C before cooling.

Both the sample before heating and the sample heated to 70°C are reddish-purple translucent, and the visible light spectrum is 469 nm.
It has an absorption maximum peak at m, and the entire visible region (400-80
0 nm) showed high absorption. The visible light spectrum at 300C is shown in FIG. Also temperature and 469n
Figure 2 shows the relationship between absorbance at m. Heating temperature is 8
When the temperature exceeded 0°C, the color of the film became lighter and the absorption peak at 469 nm began to decrease.

Samples heated at 100'C or higher had high transparency, and the film showed significant fading. The sample heated at 140°C became pale yellow and transparent, the same color as the ionomer immediately after synthesis. The visible light spectrum of the sample immediately after heating to 140°C and cooling to 30°C was almost the same as the visible light spectrum at 140°C, and was pale yellow and transparent.

The results of Example 7 show that oxygen adsorbed on the ionomer at room temperature is desorbed at elevated temperatures, thereby causing the ionomer to discolor, ie, the discoloration of the oxygen sensor of the present invention is reversible.

``1 retsu''.

Table I No. 9 Mn laminated with polyester film
” - Peel the polyester film from a 0.6 mm thick film of BAC1M ionomer and leave it at room temperature (2
It was brought into contact with four types of gases: oxygen, nitrogen, and water vapor at 3°C), and the change in absorbance at 490 nm over time was measured. The results are shown in FIG.

As a result, the absorbance at 490 nm increased rapidly in oxygen, and there was almost no change in absorbance in other gases. This shows that the ionomer of the present invention selectively adsorbs oxygen and changes color.

Low-density polyethylene 15μm Maleic anhydride-modified low-density polyethylene 10μm Gas barrier nylon (manufactured by DuPont, registered trademark “°°Sealer” PA) ・20μm
60%Mn (n) -10,3wt%BAC iono? -15 μm Na ion ionomer (registered trademark manufactured by Mitsui-DuPont Polychemical Company °゛Himirampa 1601
) 5 of 40μI
A laminated film consisting of layers was created using a coextrusion method.

Two of the resulting transparent films were folded with the Na ion ionomer on the inside, stacked on top of each other, the inside was evacuated, and the periphery was heat-sealed to create an oxygen barrier laminate film. This laminated film was stored in air for one week under the following conditions, and changes in color were observed.

[Brief explanation of the drawing]

FIG. 1 shows the visible light spectrum at 30°C of the oxygen sensor film of the present invention 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 sensor of the present invention, which has been discolored by oxygen, is heated. FIG. 3 shows the change in absorbance over time at 490 nm when the oxygen sensor of the present invention is brought into contact with various gases. - 2 layer GL length (nm1 30 40 506070 80 90 too 1
10 120130 warm ('C)

Claims (1)

[Claims] An oxygen sensor made of an ionomer whose cation is a complex ion of mono- and divalent manganese and an organic amine. A molded article having an oxygen sensor function obtained by molding an ionomer whose cation is a complex ion of divalent manganese and an organic amine. 3. The molded article having an oxygen sensor function according to claim 2, wherein the molded article is in the form of a film or a sheet. 4. An oxygen barrier laminate having an oxygen sensor function, which is formed by laminating an ionomer whose cation is a complex ion of divalent manganese and an organic amine and an oxygen barrier polymer.