JPH04268085A - Method for preserving oxidizable powder - Google Patents

Abstract

PURPOSE:To provide the method for preserving the oxidizable powder which is simple and can be surely preserved over a long period of time by removing the oxygen, moisture or acidic material in a container and suppressing the oxidation and property change of the powder during preservation of the oxidizable powder to be used for sintering, magnetic materials, solders, heat resistant blank materials, etc. CONSTITUTION:The oxidizable powder is hermetically sealed into the container having a gas barrier property together with a package formed by packaging the compsn. consisting of an unsatd, fatty acid compd. and/or chain hydrocarbon polymer having an unsatd. group, catalyst, basic material, and adsorptive material in an air permeable packaging material. The oxidation and property change of the oxidizable powder are suppressed and the improvement in the strength of the molding formed by molding and sintering, the increase of its magnetic density and the prevention of the degradation in the electrical insulating characteristic are attained, by which the period of preserving the oxidizable powder is prolonged.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preservation method for transporting or storing oxidizable powder and its preservation form. In addition, in the specification of the present invention, "an unsaturated fatty acid compound and/or a chain hydrocarbon polymer having an unsaturated group" is sometimes referred to as "base ingredient such as an unsaturated fatty acid compound." In addition, "a package formed by packaging a composition containing an unsaturated fatty acid compound and/or a chain hydrocarbon polymer having an unsaturated group in a breathable packaging material" is simply referred to as a "package" or "
It is sometimes referred to as "packaging body of the present invention".

0002

[Prior Art] Metal powders made of copper powder, silver powder, iron powder, rare earth metals, lead, tin, and their alloys (hereinafter simply referred to as metal powder) are mainly used in sintered parts of machines and electronic parts, magnetic materials,
Used as a raw material for solder, conductive paste, etc. Carbon powder is also sintered and used for magnetic materials and heat-resistant parts. These powders are easily oxidized when exposed to the air, causing problems such as a decrease in the strength of sintered parts, a decrease in magnetic density, and a decrease in solder adhesion and insulation properties. Therefore, in order to prevent these powders from oxidizing, there is a method of replacing the air in the container with an inert gas such as nitrogen or argon (hereinafter referred to as the gas replacement method).
There are methods such as sealing with desiccant, immersing in animal and vegetable oil or silicone oil, etc.

0003

[Problems to be Solved by the Invention] However, in the gas replacement method, it is difficult to drive out oxygen and moisture between powder particles and completely replace them with inert gas, and it is difficult to completely replace oxygen and moisture between powder particles, and oxygen that permeates through the packaging material. It has the problem that moisture reduces its shelf life. Methods using desiccants have the problem that moisture permeates through the packaging material and reduces storage stability, and highly active powders are oxidized even in the absence of moisture.

[0004] The method of dipping in animal and vegetable oil or silicone oil does not provide strength when pressed, shaped and sintered, so the animal and vegetable oil must be washed with a solvent, and the use of a large amount of solvent may be harmful to the working environment. and has a negative impact on the natural environment. Organic halogen solvents used in this cleaning, ie, fluorocarbon compounds such as trichlorofluoromethane, trihaloethane, trihalomethane, etc., destroy the environment, so it is desired to reduce their use.

[0005] As described above, conventional methods for preserving oxidizable powders have limitations in their shelf life, and some highly active powders cannot be preserved. When producing oxidizable powders, where storage stability is an issue, the products must be made to order because they are difficult to preserve, and producers must have excessive equipment and personnel. Users also need to strictly adhere to delivery deadlines, usage times, etc. This unnecessarily complicates the process and other administrative procedures, leading to an unnecessary increase in costs.

[0006] It is an object of the present invention to develop a technique for simply and reliably preserving oxidizable powder by solving the problems of the conventional preservation methods.

[0007]

[Means for Solving the Problems] The present inventors conducted a number of studies in view of the above problems, and found that a chain hydrocarbon polymer having an unsaturated aliphatic compound and/or an unsaturated group and a catalyst material By sealing the oxidizable powder in a gas barrier container together with a rust preventive package made by packaging a composition consisting of a basic substance and an adsorbent in a breathable packaging material, it is possible to prevent oxygen in the container. Completely remove moisture and acidic substances,
They discovered that oxidation of powder can be suppressed and completed the present invention.

That is, the present invention provides a package formed by packaging a composition containing an unsaturated fatty acid compound and/or a chain hydrocarbon polymer having an unsaturated group in a gas-barrier container. The present invention relates to a method and form of preservation of oxidizable powder, which is characterized by sealing the oxidizable powder.

The oxidizable powder to be preserved in the present invention is oxidized by oxygen, and its oxygen absorption rate is 0.01ml.O2/g.Month.
There is no particular limitation as long as it is the above. Preferably, the oxidizable powder to be stored has a particle size of 5 mm or less and is made of metal powder, carbon powder, etc.

[0010] In the present invention, the composition containing an unsaturated fatty acid compound and/or a chain hydrocarbon polymer having an unsaturated group contains, in addition to a main ingredient such as an unsaturated fatty acid compound, a desiccant,
It is a composition containing one or more of an adsorbent, a basic substance, and a catalyst.

The unsaturated fatty acid compound and/or chain hydrocarbon polymer having an unsaturated group used in this composition are the main agents that absorb oxygen in the storage container. Further, the catalyst is something that accelerates the oxygen absorption rate of the main ingredient such as an unsaturated fatty acid compound, and examples thereof include a transition metal compound and a radical initiator.

[0012] The unsaturated fatty acid compounds used here are those having 10 or more carbon atoms and one or more double bonds between carbon atoms, that is, unsaturated fatty acids, unsaturated fatty acid esters, and unsaturated fatty acid salts. It is. Examples of unsaturated fatty acid compounds include unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid, arachidonic acid, parinaric acid, dimer acid, ricinoleic acid or ricinoleic acid, and esters of these unsaturated fatty acids and esters thereof. oils and fats, metal salts of the above-mentioned unsaturated fatty acids, etc.

[0013] The chain hydrocarbon polymer having an unsaturated group is one having 10 or more carbon atoms and one or more double bonds between carbon atoms, and derivatives thereof. As a substituent of the derivative, for example, a hydroxyl group, a formyl group, etc. may be present. Examples of chain hydrocarbon polymers having unsaturated groups include polymers of butadiene, isoprene, piperylene, and 1,3-pentadiene.

The base agent such as an unsaturated fatty acid compound does not necessarily have to be a pure substance, and may be a mixture of two or more of unsaturated fatty acids and salts thereof, hydrocarbon polymers having unsaturated groups, and derivatives thereof. . Preferably, a transition metal salt of an unsaturated fatty acid, a mixture of a transition metal salt of an unsaturated fatty acid and an unsaturated fatty acid, or a mixture thereof further contains a hydrocarbon polymer having an unsaturated group.

[0015] In the composition of the present invention, the basic substance is one that absorbs acidic substances that diffuse through the storage container and acidic substances that are generated in the reaction between the main ingredient such as an unsaturated fatty acid compound and oxygen. Although there is no particular limitation as long as the object is achieved, preferred examples include oxides, hydroxides, carbonates, organic acid salts, and organic amines of alkali metals or alkaline earth metals.

[0016] An adsorbent is an adsorbent that supports a main agent such as an unsaturated fatty acid compound to increase the contact area with oxygen and increase the oxygen absorption rate, while also supporting one or both of acidic substances and water.
There is no particular limitation as long as it can absorb more than seeds, and if it achieves this purpose, it is preferably paper made of natural pulp, synthetic pulp, synthetic paper, silica gel, activated carbon, etc.
Examples include zeolite and activated clay.

The ratio of each component in the composition is not particularly limited, but the catalyst is 0.01 to 10 parts by weight, and the basic substance is 1 to 1000 parts by weight to 100 parts by weight of the main ingredient such as an unsaturated fatty acid compound. It is preferable that the amount of adsorbent is 10 to 1000 parts by weight. The shape of the composition is not particularly limited, but examples include granules, tablets, and sheets.

[0018] The composition has an oxygen permeation rate of 1000ml/m2.
・Wrap with air-permeable packaging material of ATM Day or higher to form a package. The structure and material of this breathable packaging material are not particularly limited, but specifically, it may be a film or sheet,
Furthermore, a film is laminated onto a base material of paper or nonwoven fabric. This breathable packaging material is filled with a composition, and the periphery of the packaging material is adhered by a method such as heat sealing to form a package.

The package thus packaged has an oxygen permeability of 1000 ml/m2・atm・Day or more, a moisture permeability of 1 g/m2・Day or more, and a dust particle size of 0.3 μm or more when air is passed through. Collection efficiency is 50
It may be packaged in air-permeable packaging material with a permeability of % or more. The shape and form of this package are not particularly limited. For example, pouch-shaped
Examples include those in sheet form and blister packaging.

[0020] The gas barrier container according to the present invention has an oxygen permeation rate of 10 ml/day per 100 ml volume.
It is preferably 5 ml/Day or less, and the moisture permeability is 10 g/Day or less, preferably 5 g/Da.
y or less, and its shape, material, etc. are not limited. Examples include containers made of synthetic resin and metal. Preferably, metal cans made of iron, tinplate, stainless steel, or aluminum, cases made of synthetic resins such as polyethylene, polypropylene, nylon, polyester, vinyl chloride, polystyrene, polycarbonate, vinyl chloride, vinylidene chloride, aluminum foil, vapor-deposited aluminum, vapor-deposited oxidation Examples include bags made of a composite film obtained by laminating several materials such as silicon, nylon, polyethylene, polypropylene, polyester, etc., and sealed by means such as heat sealing. Additionally, antistatic agents may be added to the materials of these containers. Furthermore, in order to improve the gas barrier properties of the metal can/synthetic resin case, a gasket can be inserted between the main body and the lid.

[0021] The form in which the package of the present invention is sealed in a container together with the oxidizable powder and stored is not particularly limited;
Preferably, the method (1) is to provide a storage section for the package in a container and load it, or the oxidizable powder is packaged in a synthetic resin film such as polyethylene or polypropylene through which moisture and oxygen permeate, and the outside and/or Examples include method (2) in which the package is placed inside and loaded into a container. Particularly preferred is method (2) in which the powder is less trapped in the sealing portion and the airtightness of the container is easily maintained.

A mode of sealing the oxidizable powder together with the package in a container according to the present invention will be explained with reference to the drawings. Note that the embodiment shown in this figure is an example of the present invention, and does not limit the present invention in any way. FIG. 1 shows an example of an embodiment before loading oxidizable powder into a gas barrier container. In FIG. 1, when oxidizable powder is loaded from the upper opening of the inner bag, the powder becomes dust and flies up. but,
Since the upper opening of the inner bag protrudes from the outer container, dust does not scatter to the sealed portion of the outer container. FIG. 2 shows an example of an embodiment in which an inner bag is loaded with oxidizable powder and a package, and this is placed in a gas barrier container. Figure 3 shows the oxidizable powder wrapped in the inner bag and the package.
An example of an embodiment is shown in which the packaging body is sealed in a gas barrier container. Since there is no dust attached to the sealing part of the outer container, the sealing is complete and airtightness and strength can be maintained.

[0023] When this oxidizable powder is sealed in a container together with the package, the air inside the container may be replaced with an inert gas such as nitrogen or argon. Furthermore, the pressure inside the container may be reduced.

[0024]

[Example] Example 1 1 g of soybean oil fatty acid iron, 0.2 g of slaked lime, and 1.0 g of powdered activated carbon.
5g was mixed with a cutter mixer and left to stand at 25°C for 10 minutes to form a lump. This mass was crushed to obtain a granular composition. 2.7g of this composition and 2.5g of silica gel
g were weighed separately and filled into a pouch (size, 5 x 7.5 cm) of breathable packaging material (paper/perforated polyethylene), and the periphery of the pouch was heat-sealed to produce a package. This package was placed in a polyvinylidene chloride coated stretched nylon/polyethylene (KON/PE) bag (size, 15 x 24 cm) along with 250 ml of air containing various gases.
It was enclosed in. This bag was stored in an atmosphere of 35° C. and 80% RH, and changes in the concentration of each gas over time were measured. The results are shown in Table 1.

Comparative Example 1 A desiccant package was manufactured using 2.5 g of silica gel and the same packaging material as in Example 1. Changes in the concentration of each gas in the bag over time were measured in the same manner as in Example 1, except that a desiccant package was used instead of the package in Example 1. Table 1 shows the results.
Shown below.

[0026]

[Table 1]

Examples 2 to 7 1 kg or 0.2 kg of various oxidizable powders were placed in a KON/PE bag with a polyethylene film 40 micron (size 150 x 330 mm) bag inside together with the package produced in Example 1. Place the bag (size 170 x 300 mm) into the inner bag of a double bag on the outside, tie the opening of the inner polyethylene film bag with a rubber band, and then put it inside the KON/PE bag on the outside. Then, the opening of the outer bag was heat-sealed and sealed. This oxidizable powder was sealed and stored in an atmosphere of 25°C/RH50% for one day.
After confirming that the oxygen concentration in the bag was 0.01% or less, the oxidizable powders stored in Examples 2 to 7 were stored for 3 months in an atmosphere of 35°C/95% RH. The weight loss due to hydrogen reduction and the oxygen concentration inside the bag were measured. The results are listed in Table 2.

Comparative Example 2 Copper powder was hermetically packaged in the same manner as in Example 2, except that the desiccant package produced in Comparative Example 1 was used instead of the package in Example 2. This was stored in the same manner as in Example 2, and the weight loss due to hydrogen reduction and the oxygen concentration in the bag were measured in the same manner as in Example 2. The results are listed in Table 2.

Comparative Example 3 Sealed packaging was carried out in the same manner as in Comparative Example 2, except that when sealing the KON/PE bag in Comparative Example 2, the air inside the bag was replaced with nitrogen gas until the oxygen concentration reached 0.7%. The bag was stored, and the weight loss due to hydrogen reduction and the oxygen concentration in the bag were measured in the same manner as in Example 2. The results are listed in Table 2.

Comparative Example 4 In Example 2, the oxidizable powder was stored in the same manner as in Example 2, except that the package produced in Example 1 was not used. The oxygen concentration inside the bag was measured. The results are listed in Table 2.

[0031]

[Table 2] Note 1): ml/g・Month Note 2): Method for measuring oxygen absorption rate of oxidizable powder Powder 5
0g into an aluminum foil composite film bag (200 x 300mm)
) with 200 ml of air and stored at 25 degrees Celsius for one month. After storage, the oxygen concentration in the bag was analyzed, and the oxygen absorption rate was determined from the following formula. (20.6 - oxygen concentration after storage) x (0.01) x (2
00) ÷ 50 = Oxygen absorption amount after 1 month [ml/g・Mo
nth] Note 3): Hydrogen Reduction Weight Loss The amount of weight loss after 5 g of the sample was allowed to stand in a hydrogen gas (1000° C.) atmosphere for 4 hours was defined as the hydrogen reduction weight loss. This weight loss is primarily due to oxygen. Note 4): Weight is 0
．． 2Kg, other powder weight is 1Kg

Examples 8 to 13 After adding 0.7% zinc stearate to the oxidizable powders stored in Examples 2 to 7, 10 g of zinc stearate was added to a 5 mm diameter square.
It was then pressed and molded under a 5 t load. This molded product is heated to 1000℃ for copper powder and silver powder, 1150℃ for iron powder, and 1200℃ for carbon powder for 30 minutes using a mixed gas with a nitrogen/hydrogen ratio of 1/3. It was heated and sintered. The density and (longitudinal) tensile strength of this sintered product were measured. The results are listed in Table 3.

Comparative Examples 5 to 7 The oxidizable powders stored in Comparative Examples 2 to 4 were used in Examples 8 to 9.
After molding and sintering in the same manner as above, the density and (longitudinal) tensile strength of the sintered product were measured. The results are also listed in Table 3.

[0034]

[Table 3]

[0035]

Effects of the Invention: The preservation method of the present invention absorbs moisture and oxygen inside the container, and further absorbs moisture, oxygen, or acid gas penetrating from the atmosphere outside the container, and completely removes the oxidizable powder. We have completed a preservation method that was not possible with conventional technology, such as suppressing oxidation and deterioration of the body, improving the strength of molded and sintered products, and preventing a decrease in magnetic density. This storage method is simple and extends the storage period of the oxidizable powder.
Producers can now supply products with stable quality, and they also have the advantage of being able to change from made-to-order production to planned production, and can be shipped overseas by ship.

[0036]

[Brief explanation of the drawing]

FIG. 1: External view FIG. 1 shows an example of an embodiment before oxidizable powder is loaded into a gas barrier container.

FIG. 2: Cutaway view FIG. 2 shows an example of an embodiment in which an inner bag is loaded with oxidizable powder and a package, and this is placed in a gas barrier container.

FIG. 3 is a cross-sectional view. FIG. 3 shows an embodiment in which the oxidizable powder wrapped in the inner bag and the package are sealed together with the package in a gas barrier container.

[Explanation of symbols]

The numbers in each figure indicate the following. 1 Inner bag 2 Outer container (bag or molded container) 3 Oxidizable powder 4 Inner bag sealing part (sealed with heat seal or stopper) 5 Packaging body 6 Outer container sealed part (sealed with heat seal or sealing device) do.)

Claims (1)

[Claims] Claim 1: A package formed by packaging a composition containing an unsaturated fatty acid compound and/or a chain hydrocarbon polymer having an unsaturated group in an air-permeable packaging material, and a gas barrier container containing an oxidizable material. A method for preserving oxidizable powder and its preservation form, characterized by sealing the powder.