JP2009114509A - Rust preventive film and rust prevention method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rust preventive film used for sealing materials and products comprising silver, copper or their alloys and protecting the same from corrosion and discoloration particularly caused by sulfur-containing gas, in which the rust preventive components have high safety and the rust preventive components also have excellent effect, thus their amounts to be added can be suppressed, and therefore, transparency is high, and to provide a rust prevention method using the rust preventive film. <P>SOLUTION: As for the rust preventive film, active zinc oxide powder, basic zinc carbonate powder or their mixture are dispersed in a thermoplastic resin. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rust preventive film used for protecting a metal material and a rust preventive method using the rust preventive film.

  Silver, copper and their alloys are widely used as materials themselves and plating materials for ornaments, musical instruments, electrical circuit conductors and the like because of their unique color and electrical characteristics. However, a drawback of these metals is that they are easily discolored in the atmosphere, and discoloration and corrosion are particularly severe in the presence of a gas containing sulfur. If the color changes, the commercial value of the decorative article or musical instrument is significantly impaired, and if the conductor of the electronic circuit is corroded, it may develop into a fatal defect such as disconnection due to an increase in contact resistance.

  Thus, various techniques for avoiding the problems of corrosion and discoloration as described above have been studied.

  For example, Patent Documents 1 to 4 describe a technique for forming a film by removing a solvent after applying a solution of a specific compound such as an imidazole derivative to a metal surface as a rust prevention method for silver or the like. Patent Documents 5 and 6 describe a technique for suppressing discoloration by coating the surface of a metal layer with an acrylic resin containing polyurethane resin, zinc oxide, or the like.

  However, the technique of forming a resin film or the like on the metal surface has a problem that even if the shielding effect against the corrosive gas is good, soldering becomes difficult and electronic components cannot be mounted. In such a case, the film may be peeled off, but a resin film having high adhesion cannot be easily peeled off. Therefore, the field of application of the technology is limited.

  On the other hand, a technique for suppressing corrosion and discoloration by adding a corrosive gas adsorbing component to a sheet and hermetically packaging the metal with the sheet instead of forming a resin film on the metal surface has been developed. For example, Patent Document 7 discloses an adsorbent sheet in which a synthetic rubber latex is used as a binder and activated carbon is adhered to a nonwoven fabric. Patent Document 8 discloses a protective sheet in which activated carbon powder, copper sulfate, and a binder are coated or impregnated on paperboard. Edible paperboard is described.

  However, the adsorptive sheet of Patent Document 7 is insufficient in adsorbing performance of a reducing sulfur compound such as hydrogen sulfide, and is not satisfactory as a rust preventive means such as silver.

  Moreover, although the copper sulfate etc. which are illustrated as an anticorrosive component in patent document 8 exhibit excellent absorption performance with respect to hydrogen sulfide gas etc. in order to fully ionize a metal in a water-containing state, its toxicity is strong, Use and emission are restricted by the “Law Concerning Determination of Emissions of Specified Chemical Substances to the Environment and Promotion of Improvement of Management” (hereinafter referred to as “The PRTR Law”). Also, impregnation or application of these copper sulfates will not only cause the rust-proof paper and rust-proof film to become acidic and deteriorate, but also metal products and metal parts will come into direct contact with the acid-proof rust-proof paper and rust-proof film. In contrast, corrosion deterioration is accelerated.

  In addition, as disclosed in Patent Document 9, the present inventors have developed a metal rust-preventing composition containing a complex salt of a chelating agent (EDTA-Zn-2Na) and capable of capturing sulfur-containing gas. Patent application. The composition may be kneaded into a resin, formed into a film, and packaged with a metal product or the like.

However, if the composite salt showing neutrality when dissolved in water is applied to a rust-proof paper, a good effect can be obtained, but when applied to a rust-proof film made of a resin, about 12 wt% Since the crystal water of the composite salt is vaporized at the temperature at the time of film formation, a hole is formed in the film and continuous molding becomes impossible. Therefore, the composite salt is dried in advance at 120 ° C. or more to make an anhydride. There is a need. As a result, the manufacturing cost increases. Further, since zinc salts of ethylenediaminetetraacetic acid are water-soluble zinc salts, their use and discharge are restricted by the chemical conversion method.
Japanese Patent Publication No. 60-1314 Japanese Patent Publication No. 60-29707 Japanese Patent Publication No. 60-21982 Japanese Patent Publication No. 60-25504 JP 2002-256454 A JP 2006-124819 A Japanese Examined Patent Publication No. 46-210027 JP-A-63-99399 JP 2007-23372 A

  As described above, a technique for hermetically packaging with a film containing a rust-preventive component has been known in order to suppress corrosion and discoloration of metals such as silver, copper, and alloys thereof having excellent appearance. However, some of the conventional rust preventive components do not have a sufficient rust preventive effect against sulfur-containing gas which is the largest cause of corrosion and discoloration of these metals. As a result, in order to exert the effect, a large amount of rust-preventive ingredients must be added to the film, so the transparency of the film is lowered, and the product inside cannot be confirmed unless it is opened. It was. Moreover, although the component with a high adsorption effect with respect to sulfur-containing gas is known, the safety | security is not enough and it receives the restriction | limiting by a chemical tube method, or the use as a rust prevention component was not recognized at all. .

  Therefore, the problem to be solved by the present invention is a rust-proof film used for sealing materials and products containing silver, copper, and alloys thereof, and particularly for protecting them from corrosion and discoloration caused by sulfur-containing gas. An object of the present invention is to provide a highly transparent rust component because the safety of the rust component is high and the effect of the rust preventive component is excellent, so that the amount added can be suppressed. Another object of the present invention is to provide a rust prevention method using the rust prevention film.

  In order to solve the above-described problems, the present inventors have conducted extensive research on components that are particularly excellent in rust prevention effect. As a result, it was previously known that zinc oxide has the ability to adsorb sulfur-containing gases, and since certain zinc compounds are extremely excellent in rust prevention effects, the amount added can be reduced by using them as rust prevention components. The present invention was completed by finding that a highly transparent anticorrosive film was obtained.

  The rust preventive film of the present invention is characterized in that active zinc oxide powder, basic zinc carbonate powder, or a mixture thereof is dispersed in a thermoplastic resin.

  As said rust prevention film, what is content of the active zinc oxide powder in a film is 0.1 mass% or more and 2.0 mass% or less; And content of basic zinc carbonate powder is 0.05 mass % Or more and 5.0% by mass or less is preferable.

  The rust prevention method of the present invention is characterized in that a metal corroded or discolored by a sulfur-containing gas is hermetically packaged by the rust prevention film.

  Even if it is a material or product containing a metal that is easily corroded or discolored by a sulfur-containing gas, such as silver, copper, and alloys thereof, the corrosion and the like can be remarkably suppressed by sealing the rust-proof film of the present invention. Can do. The anticorrosive film of the present invention is excellent in transparency despite having an excellent anticorrosive effect, so that the inside can be confirmed even if the product or the like is sealed and packaged. Therefore, the present invention is extremely useful industrially as it is possible to store a silver product or the like excellent in appearance while suppressing discoloration and the like, and the inside can be confirmed without opening.

The rust preventive film of the present invention is characterized in that active zinc oxide powder, basic zinc carbonate powder, or a mixture thereof is dispersed in a thermoplastic resin. If a material or product containing silver or the like is hermetically packaged with the anticorrosive film of the present invention, the metal material or the like can be particularly protected from sulfur-containing gas, and its corrosion and discoloration can be suppressed. Moreover, since the rust-proof film of this invention has high transparency, even if it seal-wraps, an internal product etc. can be confirmed. As the sulfur-containing gases cause corrosion and discoloration of the silver or the like, can be mentioned hydrogen sulfide, ammonium sulfide, mercaptans, the SO _x and the like. These are slightly present in the atmosphere, and corrode or discolor silver and the like.

  Conventionally, it has been known that zinc oxide has the ability to adsorb sulfur-containing gas, but its effect is not always sufficient, and it is necessary to add a large amount when dispersed in a resin film and used as a rust-proof film Therefore, the transparency of the film had to be sacrificed. On the other hand, the active zinc oxide powder according to the present invention is extremely excellent in the rust prevention effect, so that the addition amount to the rust prevention film can be reduced while exhibiting the rust prevention effect, so the transparency of the film can be reduced. Can be secured.

  The active zinc oxide used in the present invention is also called active zinc white or transparent zinc white, and is particularly active because it has a large specific surface area and a mixture of zinc oxide and basic zinc carbonate, and contains sulfur. It can react with gas efficiently and be immobilized by adsorption.

Common zinc oxide is produced mainly by the French method, which oxidizes zinc vapor at high temperature in air, or the American method, which oxidizes zinc vapor generated by reducing zinc ore with coke, and its specific surface area is usually 1-5 m. It is about ² / g. Active zinc oxide, on the other hand, uses a wet method of drying a precipitate of zinc hydroxide obtained mainly from a solution of zinc chloride, zinc sulfate or zinc nitrate and an alkali metal hydroxide, or a basic zinc carbonate. It is manufactured by drying, and its specific surface area is about 30 to 90 m ² / g.

  In addition, what is necessary is just to refer to the specific surface area in this invention, if there is a catalog value of each powder and particle | grains, but when there is no catalog value, it should just measure it. For example, it may be measured by the BET method using a specific surface area pore distribution measuring device manufactured by Beckman Coulter.

  Active zinc oxide is commercially available, but its zinc oxide content is approximately 90%, which is nearly 10% lower than the zinc oxide content of 99.5% or more of general commercial zinc oxide products. The reason is considered that basic zinc carbonate, zinc carbonate, zinc hydroxide and the like are mixed in addition to zinc oxide by the above-described production method. For example, if zinc oxide is 60% and basic zinc carbonate is 40%, the calculated value of the zinc oxide content is 88.7%.

  As content in the film of the active zinc oxide powder of this invention, 0.1 to 2.0 mass% is preferable. Since the active zinc oxide powder is extremely excellent in the ability to adsorb sulfur-containing gas, if the content is 0.1% by mass or more, corrosion or discoloration of silver or the like can be more reliably suppressed. Moreover, if the said content is 2.0 mass% or less, the transparency of a rust prevention film can be ensured more reliably. As the said content, 0.2 to 1.5 mass% is more preferable.

The basic zinc carbonate used in the present invention is a mixture of zinc carbonate and zinc hydroxide, and a typical chemical composition formula is 2ZnCO ₃ .3Zn (OH) ₂ .H ₂ O.

For basic zinc carbonate, carbon dioxide gas is generally blown into a zinc oxide slurry, or ammonia and ammonium carbonate are reacted with zinc metal to form a solution, and then the resulting precipitate is dried by blowing water vapor. It is manufactured by. The zinc oxide content of commercially available basic zinc carbonate is 72%, which is close to 71.8%, which is the theoretical value of the zinc oxide content of 2ZnCO ₃ .3Zn (OH) ₂ .H ₂ O.

General zinc oxide has a solubility in water of 0.0003 to 0.0005% and hardly dissolves. On the other hand, the aqueous solubility of zinc carbonate is 0.0206%, and the aqueous solubility of zinc hydroxide is 0.0012%. Therefore, the aqueous solubility of basic zinc carbonate is higher than that of general zinc oxide. If water solubility is high, it will be dissolved by water vapor that permeates the film, so that zinc ions will increase, and it will be easy to react with the permeated sulfur-containing gas. On the other hand, if it is this degree of water solubility, it will not be restricted by the chemical tube method. The specific surface area of the basic zinc carbonate is large compared to 1 to 5 m ² / g of zinc oxide 24m ² / g approximately and generally.

  As content in the film of the basic zinc carbonate powder of this invention, 0.05 mass% or more and 5.0 mass% or less are preferable. Since the adsorbability of the basic zinc carbonate powder with respect to the sulfur-containing gas is particularly excellent, corrosion and discoloration of silver or the like can be more reliably suppressed when the content is 0.05% by mass or more. Moreover, since transparency of basic zinc carbonate is high, if the said content is 5.0 mass% or less, the transparency of a rust-proof film can be ensured more reliably. The content is more preferably 0.1% by mass or more and 4.0% by mass or less.

  Among the above-mentioned active zinc oxide powder and basic zinc carbonate powder, the basic zinc carbonate powder is particularly excellent in adsorption capacity for sulfur-containing gas. In addition, transparency is high. Therefore, as the rust preventive film according to the present invention, a film in which basic zinc carbonate powder is dispersed in a thermoplastic resin is particularly suitable.

  The rust preventive film of the present invention is characterized in that active zinc oxide powder or the like is dispersed in a thermoplastic resin. The manufacturing method may follow the manufacturing method of a general resin film.

  For example, the thermoplastic resin may be dissolved in a suitable organic solvent, and then an active zinc oxide powder or the like may be added and dispersed well, and then formed into a film by a spin coating method or the like. However, since active zinc oxide powder and the like may agglomerate in an organic solvent, it is preferable to use a thermoplastic resin and active zinc oxide powder or the like by using a device such as a Banbury mixer, a mixing roll kneader, or a twin-screw kneading extruder. After mixing, a method of forming a film by an inflation method or an extrusion method is preferable.

  The type of thermoplastic resin used as a raw material is not particularly limited. For example, polyolefin resins such as low density polyethylene, medium density polyethylene, high density polyethylene, and polypropylene; polystyrene resin; acrylonitrile resin; butadiene / styrene resin; polyethylene terephthalate and polybutylene terephthalate And polyester resins such as nylon 6, nylon 12 and amorphous nylon; copolymer resins such as ethylene / vinyl acetate and acrylic acid esters; and ionomer resins. These thermoplastic resins may be used alone or in combination of two or more. Among these, polyolefin resin is preferable, and polyethylene is preferable because it is inexpensive.

  The thickness of the rust preventive film of the present invention is not particularly limited, but if it is too thick, the handleability and transparency may be lowered, and if it is too thin, the rust preventive effect may not be sufficiently exerted or may be easily broken. There is. Therefore, the thickness of the rust preventive film is preferably about 30 μm or more and about 200 μm or less.

  The rust preventive film of the present invention is used for sealing and packaging metal materials and products containing silver, copper, and alloys thereof after forming into a bag shape. Since it is not used as a film laminated on the surface of these metal materials or the like, it does not hinder soldering or the like. It is also possible to remove the air inside and vacuum wrap it, but if it contains sulfur-containing gas contained in the air, it can be adsorbed sufficiently. be able to.

  The method of making the rust-proof film into a bag or sealing may be in accordance with a conventional method. For example, according to the inflation method, the rust-proof film of the present invention is obtained in a cylindrical shape, so that the cylindrical film is cut according to the size of the metal material or the like to be packaged, and then one end is closed. The other end may be closed after the metal material is inserted. How to close the end depends mainly on the type of thermoplastic resin. For example, if it can be heat-sealed, it may be heat-sealed, or an appropriate adhesive may be used.

  Since the rust preventive film of the present invention is particularly excellent in the effect of adsorbing sulfur-containing gas, it can protect internal metal materials and the like from sulfur-containing gas contained in the atmosphere, and can suppress corrosion and discoloration. Examples of metals to be protected, that is, metals that corrode or discolor due to sulfur-containing gas, include silver, copper, silver alloys, and copper alloys.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.

Production Example After blending low density polyethylene resin powder (manufactured by Sumitomo Seika Co., Ltd., trade name “Flocene G401-N”) and active zinc oxide powder or basic zinc carbonate powder in the proportions shown in Table 1, and stirring well A film having a thickness of 100 μm was prepared by an inflation method at 150 to 160 ° C. The physical properties of each compound used are as follows.
Active zinc oxide: manufactured by Hakusui Tech Co., Ltd., specific surface area: 39.5 m ² / g
Basic zinc carbonate: manufactured by Kanto Chemical Co., Ltd., special grade reagent, chemical formula: 2ZnCO ₃ .3Zn (OH) ₂ .H ₂ O, specific surface area: 23.7 m ² / g

For comparison, a film made of only a polyethylene resin and a film using normal zinc oxide powder in the blending amounts shown in Table 2 were also prepared. The physical properties of the used zinc oxide powder are as follows.
Zinc oxide powder: manufactured by Kanto Chemical Co., Inc., special grade reagent, specific surface area: 2.3 m ² / g

Test Example 1 Measurement of Haze (Haze Value) Using a color difference turbidimeter (COH-300A, manufactured by Nippon Denshoku Industries Co., Ltd.), haze (H%) according to JIS K 7105 (“Testing method for optical properties of plastics”) Were measured and the transparency of the films was compared. More specifically, after performing zero alignment with light shielding in the above color difference turbidimeter and standard alignment with a transparent cell, three films cut into 50 mm × 50 mm were prepared, fixed in the standard cell, and measured. .

  Rust prevention film No. Table 3 shows the results of 1 to 7 as the average value of 3 cases, The results of 8-12 are similarly shown in Table 4. Moreover, the external appearance by macroscopic observation is also shown.

Test Example 2 Rust Prevention Test A silver plate having a width of 40 mm, a length of 60 mm and a thickness of 0.5 mm was polished into a mirror surface using “Pical Metal Polishing” manufactured by Nippon Abrasive Industry. The silver plate was degreased and washed with a sodium metasilicate aqueous solution and then sufficiently washed with water, and then immersed in a silver discoloration remover “Kirescreen AG” (pH 1.0) manufactured by Kirest Co., Ltd. for 30 seconds. Next, after sufficiently washing with water to make a test piece without water repelling, it was washed with methanol and acetone and then dried. The obtained silver plate test piece was heat-sealed and packaged with each rust-proof film obtained in the above production example.

  As schematically shown in FIG. 1, a test piece suspension frame 1 is installed inside a glass desiccator having an internal volume of 4 liters, and silver plate test pieces 2 heat-sealed and sealed with each rust-proof film are suspended at the same time. The desiccator was sealed. Then, 20 g of ammonium sulfide solution (yellow solution, sulfur content = 6 to 7.5%) as the sulfide solution 5 and deionized water for cleaning the glass tube are then removed from the glass tube 3 for charging the sulfide. After 10 ml was charged to the lower part of the desiccator, the glass tube 3 and the glass tube 4 for gas detection tube insertion were closed. Gently shake the desiccator every 30 minutes to stir the internal space layer, and after 1 hour and 4 hours, insert a hydrogen sulfide gas detector tube (product number “No. 4H” manufactured by Gastec) from the glass tube 4 Then, the ammonium sulfide concentration (ppm) was measured. The measured ammonium sulfide concentration was 1200 ppm after 1 hour and 700 ppm after 4 hours. All the test pieces were taken out from the desiccator for 4 hours, and the discoloration state of the silver plate was confirmed with the naked eye, and the superiority or inferiority of the anticorrosion performance was evaluated according to the following criteria. That is, 1: No color change, 2: Light color change, 3: Light brown color change, 4: Color change to dark brown, 5: Color change from dark brown to blue purple, the smaller the score, the smaller the rust prevention effect Of high. Rust prevention film No. The results of 1 to 7 are shown in Table 3, and the rust prevention film No. The results of 8 to 12 are shown as “Evaluation: 1” in Table 4.

Test Example 3 Rust Prevention Test Similar to Test Example 2 above, a silver plate test piece heat sealed and packaged with each rust prevention film was prepared, and it was sealed after being suspended on the test piece suspension frame 1 inside the glass desiccator. did. A desiccator containing 0.5 g of an ammonium sulfide solution (colorless solution, sulfur content = 0.6 to 1.0%) as a sulfide solution 5 and 10 ml of deionized water for washing the glass tube from the glass tube 3 for sulfide charging. Then, the glass tube 3 and the glass tube 4 for gas detection tube insertion were closed. Gently shake the desiccator to stir the internal space layer, and after 4 hours and 1, 2, 3, and 4 days later, the hydrogen sulfide gas detector tube (manufactured by Gastec, The product number “No. 4LL”) was inserted and the ammonium sulfide concentration (ppm) was measured. The measured ammonium sulfide concentration was 7.5 ppm after 4 hours, 3.0 ppm after 1 day, 2.0 ppm after 2 days, 1.5 ppm after 3 days, and 1.0 ppm after 4 days. In addition, the silver plate was visually observed from the outside of the desiccator, and the number of days when the grayish black point discoloration occurred was confirmed to evaluate the superiority or inferiority of the anticorrosion performance. That is, the larger the number of days, the higher the rust prevention effect. Rust prevention film No. The results of 1 to 7 are shown in Table 3, and the rust preventive film No. The results of 8 to 12 are shown in Table 4 as “Evaluation: 2”.

  As is apparent from Table 4, a rust preventive film No. 1 comprising only a polyethylene resin and containing no zinc oxide or the like. The haze value of 8 was as low as 9.1% and was visually transparent. However, according to the rust prevention test in the presence of ammonium sulfide, the rust prevention effect was quite insufficient. Specifically, in Test Example 2, the inner silver plate turned dark brown, and in Test Example 3, point discoloration was confirmed on the first day from the start of the test.

  Also, a general anticorrosion film No. using zinc oxide. In Nos. 9-12, No. 4 having a particularly high zinc oxide concentration. Although the film of No. 9 shows an antirust effect, The haze values of films 9 to 11 were 25% or more, the appearance was white, and the transparency was low. On the other hand, no. Although the film No. 12 has satisfactory transparency, it has a rust prevention performance of No. 12. It was as low as 8 films.

  On the other hand, as shown in Table 3, a rust preventive film No. 1 containing at least one active zinc oxide or basic zinc carbonate as a rust preventive component. Nos. 1 to 7 were high in transparency and excellent in rust prevention effect. More specifically, the haze values of these films are all less than 21% and have transparency. No. In the films of 3 and 7, since the content of the rust preventive component according to the present invention is small, the rust preventive effect is slightly inferior. The anticorrosive effect of the films 1, 2, 4 to 6 is sufficient in practical use. Furthermore, from this result, it became clear that the rust-proof film containing basic zinc carbonate has the highest transparency and high rust-proof effect.

It is a conceptual diagram which shows the apparatus used by the rust prevention test.

Explanation of symbols

  1: Test piece suspension frame, 2: Silver plate test piece sealed in heat-sealing with a rust preventive film, 3: Glass tube for charging sulfide, 4: Glass tube for charging gas detection tube, 5: Sulfide solution

Claims (4)

  An anticorrosive film, wherein active zinc oxide powder, basic zinc carbonate powder, or a mixture thereof is dispersed in a thermoplastic resin.   The rust preventive film according to claim 1, wherein the content of the active zinc oxide powder in the film is 0.1% by mass or more and 2.0% by mass or less.   The rust preventive film according to claim 1, wherein the content of the basic zinc carbonate powder in the film is 0.05% by mass or more and 5.0% by mass or less.   A rust-preventing method, wherein a metal corroded or discolored by a sulfur-containing gas is hermetically packaged with the rust-proof film according to any one of claims 1 to 3.

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