JPH0573459B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing an oxygen absorber used to prevent and preserve foods from spoilage and deterioration. (Prior Art) Conventionally, the vacuum bag method, refrigeration method, and gas replacement method have been used to preserve foods such as vegetables and fish in order to prevent the growth of mold and rot. However, these methods have disadvantages in that they require expensive equipment and require considerable skill to implement. As a solution to this problem, various oxygen scavengers have been proposed and put into practical use that apply the principle that iron powder reacts with and fixes oxygen in the air in the presence of moisture. In particular, Japanese Patent Publication No. 56-33980 discloses that a metal powder is coated with a metal halide, the amount of metal halide coated is 0.001 to 5 parts per 100 parts of the metal powder, and the water content is 1 part of the total weight. % or less and metal powder are mixed with a metal halide solution, coated with the metal halide, and then dried until the water content is 1% by weight or less. Furthermore, JP-A No. 60-20986 proposes an oxygen scavenger in which iron powder having a 150 mesh passing amount of 50% by weight or more is uniformly mixed with electrolyte fine powder having a 150 mesh passing amount of 50% by weight or more. ing. However, these conventional oxygen scavengers have the following problems. Japanese Patent Publication No. 56-33980 is characterized in that the metal surface is coated with a metal halide. Therefore, it is necessary to dissolve the metal halide in a liquid such as water or alcohol and treat the metal powder with this solution. In other words, it requires a complicated operation of mixing the solution and metal powder and then drying them. Drying in this case requires rapid drying under vacuum or reduced pressure to prevent oxidation of the metal powder, which requires large equipment and therefore makes the product expensive. Furthermore, since the metal halide is used in the form of a solution, problems such as disposal of waste liquid arise, making this method unsatisfactory. On the other hand, the oxygen scavenger disclosed in JP-A No. 60-20986 does not require solution preparation and drying steps as in the former JP-A-56-33980, but it is There is. Before mixing, it is necessary to adjust the amount passing through the 150 mesh to 50% by weight or more for both, and there is a drawback that a sieving process is required. Furthermore, iron powder and electrolyte powder have a certain particle size range, and in order to obtain one that passes through 150 meshes at a rate of 50% by weight or more,
If only sieving is used, the balance will be lost and coarse particles will need to be crushed. Further, JP-A-60-129137 discloses obtaining an iron/electrolyte mixture in which iron powder and fine electrolyte powder are adhesively bonded. However, simply mixing the iron powder and the metal halide does not necessarily have a close positional relationship, which poses a problem in the reliability of the product. (Problems to be Solved by the Invention) The present invention solves the problem of producing an oxygen absorber using conventional techniques, which requires expensive equipment, difficult to prepare raw materials, or requires wastewater treatment. This is a method for producing an oxygen absorber that solves the above problems. (Means for solving the problem) When iron and metal halide aqueous solutions coexist,
It is well known that iron corrodes more rapidly than when exposed to a normal environment, that is, oxidation progresses. This is because the metal halide ionizes and facilitates the movement of electrons associated with oxidation. It is also known that even when metal halides are in a dry state, most of them have deliquescent properties, so they deliquesce when exposed to moisture in the air, and oxidation progresses in the same way. This is also mechanically as described above. In order to produce an oxygen scavenger with stable performance using iron and metal halide, it is necessary to mix appropriate amounts of iron powder and metal halide in a uniformly and intimately mixed state, preferably firmly attached to the metal surface. It is necessary to attach it to the However, if this were to be in a coated state, expensive equipment and complicated operations would be required as described above. Furthermore, simple mixing requires detailed conditions for the raw materials, making it impossible to obtain a stable product. According to experiments conducted by the present inventors, oxygen scavengers obtained from iron powder and halogenated metal powder have problems with seepage and stickiness, but this problem can be solved by using metal powder containing graphite. It has been resolved. Here, the metal powder containing graphite refers to a metal powder containing 2% or more of carbon and in which most of the carbon is present as graphite, and a metal powder generated during machining of the same metal. Hereinafter, they will be collectively referred to as metal powder in this specification. Further, according to the present invention, the metal powder and the metal halide are combined, and a cylindrical rod or a spherical ball is put into a crusher, preferably a crushing cylinder having an amplitude, and the metal powder and the metal halide are simultaneously crushed. It was found that the state of existence of metal halides can be obtained. That is, by simultaneously crushing, the brittle metal halide is preferentially crushed, becoming finer than the metal powder, and an activated interface is generated. Also, by crushing metal powder,
At the same time as an active interface is generated, an inert layer such as an oxide layer is removed from the surface by a grinding action, and a new active interface is generated. As a result, compared to metal halides, a stronger bond can be obtained on the surface of the coarse metal powder due to the particle size difference between the two and the action of a new active interface generated by the grinding action of the balls or rods. Further, due to close microscopic contact at the active interface, a strong bonding force can be obtained even when the difference in particle size between the metal halide and the metal powder is small. Furthermore, by applying vibration, the raw materials are dispersed at the same time as crushing and uniform mixing is performed, so segregation of halide metals does not occur and halogen metal-treated iron powder with uniform and stable oxygen scavenging ability can be obtained. We found out. (Function) The present invention is based on these findings, and according to the present invention, the disadvantages of equipment investment and complicated processes required for the production of conventional oxygen scavengers are eliminated, and stable performance can be easily achieved. It becomes possible to produce oxygen scavengers with FIG. 1 shows the manufacturing process of the oxygen scavenger according to the present invention. The particle size of the metal powder used in the present invention may be coarse or fine, and by appropriately setting crushing conditions, an oxygen scavenger having a desired particle size can be produced. Therefore, it can be said that there are almost no requirements regarding metal powder. Especially when used at relative humidity of 70% or higher or when using metal halides that are highly deliquescent,
Problems arise when fine particles generated by the hydroxylation reaction of the iron powder contained therein and/or a deliquescent solution of the metal halide seep into the packaging material surrounding the oxygen scavenger. Since the present invention uses cast iron powder or dry powder containing graphite as the metal powder, oozing is reduced, and the cast iron powder treated with halogenated metal is not sticky and is easy to handle. This is thought to be because the graphite in the cast iron powder plays the role of a moisture regulator and a metal halide retainer. The metal halides used in conjunction with the above metal components include, for example, alkali metal halides such as NaCl, KCl, NaBr, and KBr, NaCl, CaCl,
Alkaline earth metal halides such as CaBr ₂ , MgBr ₂ , and BaBr ₂ , as well as AgCl, ZnCl, AlCl ₃ ,
SnCl, MnCl, _FeCl3 , _CoCl2 , _NiCl2 , _ZnBr2 ,
Examples include halides of various metals such as SnBr ₂ , CuBr, and FeBr ₂ . In actual use, a single substance or a mixture of these may be appropriately selected and used. Of course, the metal halide may be in the form of powder, granules, or lumps. It can be said that the form is not particularly important in the present invention. In the present invention, the amount of metal halide used is not particularly limited based on the results shown in Figure 2, but it ranges from 0.01 to 100 parts by weight in terms of anhydride per 100 parts by weight of the metal powder component.
The amount is 10 parts by weight, preferably 0.5 to 5 parts by weight. If the amount of metal halide used is too small, such as 0.01 parts by weight or less, the effect will not be sufficient and the time required for the oxygen scavenger to rise will become longer. On the other hand, if the amount is too large (10 parts by weight or more), it is of course not economical, but it also generates hydrogen gas and causes the content to ooze out due to deliquescence of the metal halide. Therefore, in the case of the present invention, the amount of metal halide used is 0.5~
It is preferable that the amount is in the range of 5 parts by weight. The oxygen scavenger of the present invention is produced as follows. The metal powder and metal halide are first dried to reduce the moisture content to 1% or less. This drying process is usually carried out using commercially available metal powder or metal halide, and can be omitted if there are no problems with storage and handling before use. almost 1 water
% or less. Even when drying, special equipment such as vacuum drying is not required. Thereafter, the materials are weighed to a predetermined weight ratio and inserted into a crusher to be crushed and mixed. The crusher in this case is preferably a crusher with a crushing medium such as balls or rods. This is because an inactive layer such as an oxide layer on the surface can be removed by the grinding action. Metal halide treated metal powder after crushing is
Just take it out and use it, no post-processing such as drying is required. Therefore, unlike other methods for producing oxygen absorbers, the present invention is extremely simple to produce. In addition, compared to simple mixing methods or aqueous solution treatment methods, the oxygen scavenger obtained in this way has a similar effect on the surface of new highly active metal powders produced by crushing. The metal halide adheres to form a very strong bond, and even when these metal halide-treated metal powders are packaged and used as an oxygen scavenger, the metal halide does not fall off and has stable oxygen scavenging performance. The oxygen scavenger produced according to the present invention does not contain moisture and is therefore stable in an atmosphere with low humidity without causing a deoxidizing reaction. However, when moisture increases, the metal halide on the metal surface deliquesces. , reacts with atmospheric oxygen with an increased reaction rate. Therefore, by sealing the oxygen absorber according to the present invention together with a moisture-containing food in a non-breathable packaging material, the oxygen concentration in the packaging material decreases over time and eventually reaches zero. Example 1 Raw material 1 using cast iron powder and dry powder as metal powder and adding 1% NaCl as metal halide
I prepared Kg. This raw material was crushed and mixed for 60 minutes at an amplitude of 5 mm by inserting three SC rods with a diameter of 30 mm and a length of 210 mm into a vibrating mill with a container capacity of 3.59 mm. In order to compare with the oxygen scavenger produced in this way, 2ml of 10% NaCl was added to 20g of reduced iron powder and pure iron powder.
A conventional metal halide iron powder was prepared by mixing with an aqueous solution and vacuum drying at a temperature of about 100°C. An oxygen scavenger was prepared by sealing 5 g of these treated powders in a 35 x 45 mm paper bag laminated with a perforated polyethylene film. This was sealed in an airtight container with a capacity of 100 c.c., with the relative humidity controlled to be 90% or more and 50% or less. Thereafter, the oxygen concentration within the container was measured over time. The measurement temperature was adjusted to 20±1°C. The results are shown in Table 1. From this, the oxygen scavenger according to the present invention has a relative humidity of 90
% or more, the oxygen concentration in the container became 0% within 25 hours at the longest, showing better performance than the comparative materials. Further, at a relative humidity of 50% or less, the maximum amount of oxygen absorbed after time is approximately 3%, which is approximately 14% of the total capacity. It can be seen from this that there is almost no reaction at low humidity, indicating that it has the required performance as an oxygen scavenger. In particular, in the method of the present invention, stickiness was reduced compared to the comparative example, and the problem of dirt seeping out was resolved. Example 2 As a comparative example, reduced iron powder was used as a dull powder of cast iron material equivalent to FC ₂₀ , and a metal halide was added to it as a metal halide.
1% NaCl was added. The frequency of 1Kg of this raw material
Three rods of SC material with a diameter of 30 mm and a length of 210 mm were charged into a vibrating mill of 1200 cpm, amplitude of 5 mm, and container capacity of 3.59 mm. In the case of reduced iron, it was crushed and mixed for 60 minutes, and in the case of Dalai powder, it was crushed and mixed for 60 minutes and 120 minutes. An oxygen scavenger was prepared by sealing 5 g of this halogenated metal-treated iron powder in a paper bag laminated with a 35 x 45 mm perforated polyethylene film. This capacity is
It was sealed in a 100 c.c. airtight container with the relative humidity controlled to be 90% or higher. The measurement temperature was maintained at 20±1°C. Table 2 shows the results of measuring the oxygen concentration in this container over time. Table 3 shows the particle size of reduced iron and powdered powder before crushing. Although the particle size of reduced iron powder is coarser than that of reduced powder, the performance of the produced oxygen scavenger is close to that of reduced iron powder. It was hot. Furthermore, this metal halide treated powder was smooth and non-sticky and easy to handle. This is thought to be because the graphite in cast iron plays the role of holding halide metal powder and regulating moisture. In this way, by optimizing the crushing conditions even for coarse metal powder, the deoxidizing performance was improved. Example 3 As in Example 1, three types of metal powders, reduced iron powder, pure iron powder, and cast iron powder, were prepared and used as metal halides.
NaCl and _CaCl2 were added at 0.1, 0.5, 1, 5, and 10%. This was done in the same vibrating mill as in Example 1 for 60 minutes, 90 minutes,
Metal halide treated iron powder was produced by changing the crushing and mixing time to 120 minutes and 200 minutes. An oxygen absorber was prepared by enclosing 5 g of this iron powder in a paper bag laminated with a perforated polyethylene film having internal dimensions of 45 x 35 mm. As in Example 1, store this at a relative humidity of 90% or higher in a container with a capacity of 100cc.
Changes in oxygen content over time were measured at a temperature of 1°C. Table 4 shows the change in oxygen concentration in this container over time and the time when the oxygen concentration reaches 0%. As a result, it was found that using NaCl as the metal halide had better oxygen absorption ability than using CaCl ₂ . The influence of NaCl concentration is 0.1%
If it is reduced to 0.5~, the performance will deteriorate significantly.
At 10%, there is not much difference in performance between them. In addition, with 10% NaCl, oozing was observed on the wrapping paper with oxygen scavengers using reduced iron powder and pure iron powder, but not with cast iron powder. This is considered to be due to the same reason as stated in Example 2, and is a characteristic of cast iron powder. From this, the appropriate concentration of NaCl is 0.5 to 5%, taking into account the problem of seepage, performance, and economic aspects.
is preferred. Also, looking at the performance change when changing the crushing time with NaCl addition concentration at 1%, we can see that the crushing time was
Performance was improved by increasing the time up to 120 minutes. Even if the crushing time was increased further, no significant improvement effect was observed. This is thought to be because the longer crushing time promoted the generation of new active interfaces for both the iron powder and the metal halide, resulting in efficient production of the composite.

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[Table] (Effects of the Invention) The oxygen scavenger produced by the present invention has excellent oxygen absorption ability compared to conventional methods, is easy to produce, and has stable performance. In addition, by using metal powder containing graphite and adjusting the crushing conditions with metal halide, it is an oxygen scavenger that has performance equivalent to or better than iron powder that does not contain graphite, and it oozes out.
To obtain an oxygen absorber with reduced stickiness.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing in blocks the manufacturing process of the oxygen scavenger according to the present invention, and FIG. 2 is a chart showing the relationship between the amount of salt added, the time to reach zero oxygen concentration, and the rise time at the start of deoxidation.

Claims (1)

[Claims] 1. A metal powder containing graphite with a moisture content of 1% or less and a metal halide are charged into a crusher together with a crushing medium and simultaneously crushed and mixed to generate a crushed surface on the metal powder and metal halide. , the said crushing
A method for producing an oxygen scavenger, characterized in that a combination of finely pulverized metal powder and metal halide is obtained by using vibration at the time of mixing.