JP4842884B2 - Rust prevention sheet, method for producing the same, and rust prevention container using the sheet - Google Patents

Description

  The present invention relates to a rust preventive sheet for packaging metal products that require rust prevention, a method for producing the same, and a rust preventive container using the sheet.

  In order to protect metal products from rust and discoloration, so-called “rust-proof packaging” has been carried out. As this rust-proof packaging, metal products have been soaked in rust-proof oil and the excess oil has been wiped off. A method of packaging this with a packaging material such as polyethylene has been adopted. However, this method has a problem in that it requires a lot of labor and time in each process, such as rust preventive oil application / residue wiping work at the time of packaging and degreasing / cleaning work at the time of opening the package.

  Therefore, in recent years, various types of metal product packaging films incorporating a vaporizable rust preventive have been developed (see, for example, Patent Document 1), and a method for directly packaging metal products with such films has been widely used. It has come to be.

  Here, `` vaporizable rust preventive agent '' is a chemical (compound) that vaporizes slowly at room temperature, the gas is adsorbed on the metal surface, forms an invisible rust preventive film, and prevents metal rust. For example, benzotriazole is an example.

In this way, if a resin film (rust preventive film) kneaded with a vaporizable rust preventive agent is used, there is no need to apply rust preventive oil to metal products, and the rust preventive work is completed simply by carrying out the packaging work. And rust-proof packaging can be performed very efficiently.
JP-A-10-86966

  However, the vaporizable rust preventive agent is easily affected by heat. For example, in the case of benzotriazole, which is a typical vaporizable rust preventive agent, the sublimation point is 200 ° C., and it thermally decomposes at about 260 ° C. Therefore, when such a vaporizable rust preventive agent is kneaded into a resin film, it is difficult to apply a resin having a high extrusion temperature such as a polypropylene resin in consideration of the extrusion temperature of the resin in the film production process. .

  This point will be described in detail. Since the extrusion processing temperature of the polypropylene resin is usually around 240 ° C., when a vaporizing rust preventive such as benzotriazole is kneaded into the polypropylene resin and the film is extruded, it is added at the time of molding. Even if the vaporizable rust preventive agent is gasified by heat and the vaporizable rust preventive agent in the resin disappears or does not disappear, the additive concentration becomes non-uniform and it is not suitable as an industrial product requiring homogeneity. It will be something. In addition, there is a problem that the environment at the manufacturing site is deteriorated due to fuming and a strange odor caused by the gasified vaporizable rust inhibitor.

  Therefore, not all thermoplastic resins can be applied as the base resin of the anticorrosive film, but are substantially limited to those having a relatively low melting point such as ethylene-vinyl acetate and low density polyethylene. For this reason, the obtained rust preventive film has poor heat resistance.

  Further, when a metal product requiring rust-proof packaging is a heavy object having a complicated shape, a plastic molded container such as a tray or a cup is used for transporting and handling the product. Here, if a vaporizable rust inhibitor can be kneaded into this molded container, the rust prevention of the metal product can be performed more efficiently, but as mentioned above, the resin that can incorporate the vaporizable rust inhibitor is However, it has been limited to resins having a relatively low melting point and poor moldability, such as ethylene-vinyl acetate and low density polyethylene. For this reason, the plastic rust prevention container which knead | mixed the vaporizable rust preventive agent has not yet been implement | achieved.

  Therefore, the main problem of the present invention is to provide a rust-proof sheet having high heat resistance and excellent thermoformability as well as excellent rust-proof performance, a method for producing the same, and a rust-proof container using the sheet. is there.

The invention described in claim 1 is a pair of an intermediate layer (12) made of a polypropylene resin to which a vaporizable rust preventive agent is added, and a polypropylene resin and laminated on both surfaces of the intermediate layer (12). the surface layer (14) (16) and de-configured, formed around the surface layer (14) at least one of (16) (16) sodium nitrite (18) was added Rutotomoni, sodium nitrite (18) The rust preventive sheet (10) is characterized in that the fine cavities (20) formed are connected to form micropores (22) connecting the intermediate layer (12) and the surface side of the surface layer (16). '' is there.

In the rust preventive sheet (10) of the present invention, since sodium nitrite (18) is added to at least one surface layer (16), the rust of the metal (especially iron) disposed in the vicinity of the layer (16). Can be prevented. In addition, although the rust prevention mechanism of sodium nitrite (18) is not clear, the function of lowering the humidity of the surrounding atmosphere by its hygroscopic action and corrosive gases in the atmosphere (for example, HCl, H ₂ S, SO _2, etc.) ) Neutralization.

  Also, when sodium nitrite (18) is added to the surface layer (16), the water absorbed in the sodium nitrite (18) expands as water vapor due to the heat applied during sheet molding, and sodium nitrite (18 ) Around the surface of the intermediate layer (12) and the rust preventive sheet (10) by connecting the adjacent fine cavities (20) to each other. 22) will be formed. For this reason, the vaporizable rust preventive agent added to the intermediate layer (12) can be gradually released from the sheet surface on the side to which sodium nitrite (18) is added, and the metal disposed in the vicinity of the surface also by this. Rust of (especially non-ferrous metals) can be prevented.

  Thus, in the rust preventive sheet (10) of the present invention, the synergistic action of sodium nitrite (18) and the vaporizable rust preventive agent can exert an excellent rust preventive effect on a wide variety of metals. it can.

  In addition, the rust preventive sheet (10) of the present invention has excellent moldability because the base materials constituting the intermediate layer (12) and the surface layers (14) and (16) are all made of polypropylene resin.

  The invention described in claim 2 is the rust preventive sheet (10) according to claim 1, wherein “the thickness of the surface layer (16) to which sodium nitrite (18) is added is 10 μm or more and 100 μm or less. In this way, the vaporizable rust inhibitor added to the intermediate layer (12) can be effectively and gradually released from the surface of the sheet (10).

  Here, when the thickness of the surface layer (16) to which sodium nitrite (18) is added is less than 10 μm, not only the formation of the surface layer (16) becomes difficult, but also the surface layer (16) The added sodium nitrite (18) is peeled off and dropped off, and it becomes difficult to seal the vaporizable rust preventive agent gasified during the production of the sheet, which will be described later, in the sheet (10). Conversely, when the thickness of the surface layer (16) to which sodium nitrite (18) has been added is greater than 100 μm, the gasified vaporizable rust prevention during the separation and removal of the sodium nitrite (18) and sheet production Although the agent does not diffuse, the vaporizable rust inhibitor added to the intermediate layer (12) cannot be sufficiently diffused from the sheet surface.

  The invention described in claim 3 relates to a method for producing the rust preventive sheet (10) according to claim 1 or 2, wherein “the front and back surfaces of the polypropylene resin layer to which a vaporizable rust preventive agent has been added is at least one sub-surface. It is co-extruded so as to be sandwiched between polypropylene resins to which sodium nitrate (18) has been added, and then immediately cooled ”.

  When a polypropylene resin is used as the base material of the rust preventive sheet (10) and is extruded, the extrusion processing temperature is about 240 ° C. If it does so, a part of vaporization rust preventive agent added to polypropylene resin will sublimate, and will become a gas body.

  However, in the present invention, both the front and back surfaces of the polypropylene resin to which the vaporizable rust preventive agent is added are co-extruded so as to be sandwiched by the polypropylene resin to which sodium nitrite (18) is added at least one side, so that it is gasified. It is possible to prevent the vaporizable rust inhibitor from diffusing into the surrounding atmosphere. Since the coextruded resin is immediately cooled, the gasified vaporizable rust inhibitor can be immediately solidified and fixed in the sheet.

  Therefore, almost all of the vaporizable rust inhibitor added to the polypropylene resin can contribute to the rust prevention of metal products, and prevent deterioration of the production site environment caused by the gasified vaporizable rust inhibitor. Can do.

  The invention described in claim 4 is “a rust-proof container for containing a metal product formed by thermoforming the rust-proof sheet according to claim 1 or 2, wherein the surface layer has sodium nitrite (18) added thereto. (16) is a rust-proof container characterized in that it is formed so as to form a metal product housing surface.

  As described above, the rust preventive sheet (10) of the present invention uses a polypropylene resin as a base material, and therefore has excellent moldability. Therefore, the rust-proof container obtained by thermoforming such a sheet (10) has excellent container characteristics such as light weight and stress cracking resistance, and also has excellent rust-proof characteristics.

  According to invention of Claim 1 or 2, since sodium nitrite is added to at least one surface layer, the rust of the metal arrange | positioned in the vicinity of the said layer can be prevented. In addition, by adding sodium nitrite to the surface layer, micropores connecting the intermediate layer and the surface side of the rust preventive sheet are formed, so the vaporizable rust inhibitor added to the intermediate layer is added to the sublayer. Slow release can be performed from the sheet surface on the side to which sodium nitrate has been added. As a result, the synergistic action of sodium nitrite and the vaporizable rust inhibitor can exert an excellent rust preventive effect on a wide variety of metals.

  According to the invention described in claim 3, since both sides of the polypropylene resin layer to which the vaporizable rust preventive agent is added are co-extruded so as to be sandwiched by the polypropylene resin to which sodium nitrite is added to at least one, The gasified vaporizable rust inhibitor can be prevented from diffusing into the surrounding atmosphere, and the co-extruded resin is immediately cooled, so the gasified vaporizable rust inhibitor is immediately solidified. And can be fixed in the sheet.

  According to invention of Claim 4, the rust prevention container excellent in the container characteristic and the rust prevention property can be obtained.

  Hereinafter, the present invention will be described in detail according to illustrated embodiments. FIG. 1 is a partially enlarged schematic view showing an example of the rust preventive sheet (10) of the present invention. As shown in this figure, the rust preventive sheet (10) of this example is composed of an intermediate layer (12) and surface layers (14) and (16) laminated on the surface of the intermediate layer (12). A three-layer sheet.

  The intermediate layer (12) is a layer formed by adding a vaporizable rust inhibitor to a polypropylene resin. Examples of the polypropylene resin constituting the intermediate layer (12) include a propylene homopolymer, a propylene-α-olefin random copolymer, a propylene-α-olefin block copolymer, and the like. Examples of the α-olefin include α-olefins having 2 or 4 to 10 carbon atoms such as ethylene, 1-butene, 1-pentene, 1-hexene and 1-octene. Since this polypropylene resin has the lightest specific gravity among plastics, the resulting sheet (10) is excellent in lightness.

  A vaporizable rust preventive agent is a chemical (compound) that slowly vaporizes at room temperature, the gas is adsorbed on the metal surface, and forms an invisible rust preventive film to prevent metal rust. , Benzotriazole, dicyclohexylammonium nitrite (Dican), dicyclohexylammonium salicylate, monoethanolamine benzoate, dicyclohexylammonium benzoate, diisopropylammonium benzoate, dicyclohexylammonium cyclohexanecarboxylate, cyclohexylamine cyclohexanecarboxylate, dicyclohexylammonium acrylate and cyclohexylamine acrylate Is mentioned.

  The addition ratio of the vaporizable rust inhibitor in the intermediate layer (12) is preferably in the range of 0.5 to 10 parts by weight with respect to 100 parts by weight of the polypropylene resin. When the addition ratio of the vaporizable rust preventive agent is less than 0.5 parts by weight, the addition effect of the vaporizable rust preventive agent, that is, the rust preventive effect by the vaporizable rust preventive agent is not recognized. When the addition ratio of the rusting agent is more than 10 parts by weight, the effect of adding the vaporizable rustproofing agent is sufficiently exerted, but per unit area of the resin surface that becomes the intermediate layer (12) during sheet molding described later. As a result of increasing the amount of gasifying vaporizable rust inhibitor, the physical properties of the sheet will deteriorate, such as the interlayer strength between the intermediate layer (12) and the surface layer (14) (16) will decrease. is there. In addition, if the thickness of the intermediate layer is increased (thickened), the addition ratio of the vaporizable rust inhibitor can be reduced.

  The intermediate layer (12) configured as described above is provided with an antioxidant, an antistatic material, a neutralizing material, a lubricant, a core material, a filler, an ultraviolet absorber, a flame retardant, and a surface active as necessary. Various additives such as materials may be added. Moreover, you may make it blend another thermoplastic resin in the range which does not interfere with this invention.

  The surface layers (14) and (16) are layers made of the same polypropylene resin as the intermediate layer (12). Among these layers, sodium nitrite (18) is added to one layer (16).

  The polypropylene resin constituting the surface layers (14) and (16) is, for example, a propylene homopolymer, a propylene-α-olefin random copolymer, a propylene-α, as in the intermediate layer (12) described above. -An olefin block copolymer etc. are mentioned. Examples of the α-olefin include α-olefins having 2 or 4 to 10 carbon atoms such as ethylene, 1-butene, 1-pentene, 1-hexene and 1-octene.

  Sodium nitrite (18) is a rust preventive agent mainly exhibiting a rust preventive effect on iron, and is a powder having a particle size of approximately 1 to 10 μm. When this sodium nitrite (18) is added to the polypropylene resin constituting the surface layer (16), the water absorbed in the sodium nitrite (18) expands as water vapor due to the heat applied during sheet molding. In addition, a fine cavity (20) is formed around the sodium nitrite (18), and the adjacent fine cavities (20) are connected to each other so that the intermediate layer (12) and the surface side of the rust preventive sheet (10) A fine hole (22) connecting the two is formed. By forming such fine pores (22), the vaporizable rust inhibitor added to the intermediate layer (12) can be gradually released from the surface of the sheet (10).

  Here, the addition ratio of sodium nitrite (18) added to the surface layer (16) is preferably in the range of 3 to 15% by weight with respect to the total weight of the material constituting the surface layer (16), More preferably, it is in the range of 5 to 10% by weight. When the addition ratio of sodium nitrite (18) is less than 3% by weight, the addition effect of sodium nitrite (18), that is, the rust prevention effect by sodium nitrite (18) is not recognized. When the addition ratio of sodium (18) is more than 15% by weight, the effect of adding sodium nitrite (18) is sufficiently exerted, but sodium nitrite (18) is hygroscopic, so the manufactured sheet This is because sodium nitrite (18) bleeds during storage and foaming occurs when the obtained sheet is thermoformed.

  Further, the thickness of the surface layer (16) to which sodium nitrite (18) is added is preferably 10 μm or more and 100 μm or less, more preferably 20 μm or more and 60 μm or less. When the thickness of the surface layer (16) to which sodium nitrite (18) is added is less than 10 μm, not only the formation of the surface layer (16) becomes difficult, but also the sub-layer added to the surface layer (16). As sodium nitrate (18) peels off and drops more, it becomes difficult to seal the vaporizable rust preventive agent gasified during sheet manufacturing, which will be described later, into the sheet (10), and conversely, sodium nitrite (18) When the thickness of the surface layer (16) with the addition of is larger than 100 μm, the nitrile (18) does not peel off or drop off and the gasified vaporizable rust inhibitor does not diffuse during sheet production. This is because the vaporizable rust inhibitor added to the layer (12) cannot sufficiently diffuse from the sheet surface.

  In this example, sodium nitrite (18) was added to only one surface layer (16). However, as shown in FIG. 2, sodium nitrite ( You may make it laminate | stack the surface layer (16) which added 18).

  In addition, the surface layer (14) (16) may include an antioxidant, an antistatic material, a neutralizing material, a lubricant, a core material, a filler, an ultraviolet absorber, a flame retardant, and a surfactant as necessary. These various additives may be added, or other thermoplastic resins may be blended within the range not hindering the present invention. Here, when a polymer type antistatic material (for example, Pelestat (registered trademark) 300 manufactured by Sanyo Chemical Industries, Ltd.) is further added to the surface layer (16) to which sodium nitrite (18) is added, the surface layer (16 ) Can be remarkably improved in antistatic performance. This is considered to be due to a synergistic action of the sodium nitrite (18) absorbing moisture and increasing the amount of water retained on the sheet surface and the antistatic action of the polymer antistatic material.

  The thickness of the rust preventive sheet (10) configured as described above can be appropriately set according to the intended use. For example, when the rust preventive sheet (10) of this example is used as a packaging film or bag, the thickness is preferably in the range of approximately 30 μm to 100 μm, and is used as a molding material for a thermoformed container. Is preferably in the range of about 500 μm to several mm.

  Next, the manufacturing method of the antirust sheet (10) of this example will be described. First, a predetermined amount of a vaporizable rust preventive agent is dry blended with the polypropylene resin as the intermediate layer (12), and the mixture is put into an extruder (not shown) and melted and kneaded. Then, the melted and kneaded resin is extruded into a strand shape, cooled, and then cut into a predetermined size to adjust the compound for the intermediate layer (12). In addition, sodium nitrite (18) is dry-blended with the polypropylene resin used as the surface layer (16), and the mixture is introduced into an extruder (not shown) and melted and kneaded. Then, the melted and kneaded resin is extruded into a strand shape, cooled, and then cut into a predetermined size to adjust the compound for the surface layer (16). By preparing such a compound, the dispersibility of the vaporizable rust preventive agent and sodium nitrite (18) in the polypropylene resin can be improved, and the occurrence of poor appearance and the like can be prevented.

  If there is no problem with the dispersibility of the vaporizable rust inhibitor and sodium nitrite (18) in the polypropylene resin, such a compound is not adjusted and the resin pellet and the vaporizable rust preventive agent or After dry blending with sodium nitrate (18), it may be put directly into the sheet molding machine.

  Subsequently, the compound prepared as described above was put into a melt extrusion molding machine (sheet molding machine; not shown) in which a T-die, an inflation die or the like was mounted and three-layer coextrusion was possible, and an intermediate layer ( The both sides of the molten resin layer 12) are extruded into a sheet so as to be sandwiched between the molten resins 14 and 16 which are the surface layers 14 and 16.

  Here, when a polypropylene resin is used as the base material of the rust preventive sheet (10) and this is extruded, the extrusion processing temperature is about 240 ° C. If it does so, a part of vaporization rust preventive agent added to polypropylene resin will sublimate, and will become a gas body. However, in the production method of the rust preventive sheet (10) of this example, both sides of the polypropylene resin to which the vaporizable rust preventive agent is added are sandwiched between the polypropylene resin to which sodium nitrite (18) is added at least one side. Since the coextrusion is performed, the gasified vaporizable rust preventive agent can be confined in the molten polypropylene resin, and the gas body can be prevented from diffusing into the surrounding atmosphere. Moreover, since it is not necessary to extremely lower the extrusion processing temperature in consideration of gasification of the vaporizable rust inhibitor, the rust preventive sheet (10) can be produced while maintaining high productivity.

  Then, the resin extruded into a sheet shape is immediately quenched using a cooling means such as a cooling roll to complete the rust preventive sheet (10) of this example.

  Thus, by immediately cooling the coextruded resin, the gasified vaporizable rust inhibitor can be immediately solidified and fixed in the sheet (10). Therefore, almost all of the vaporizable rust preventive agent added to the polypropylene resin can contribute to the rust prevention of the metal product, and also prevents the deterioration of the manufacturing site environment caused by the gasified vaporizable rust preventive agent. be able to.

  In addition, in the manufacturing method of the above-mentioned rust prevention film (10), you may make it add post processes, such as an extending process, as needed. For example, when the rust preventive sheet (10) of this example is used as a packaging film or bag, the strength and the like can be improved by applying the obtained sheet (10) to a stretching process and stretching.

  When manufacturing a rust-proof container for storing metal products using the rust-proof sheet (10) manufactured by the method as described above, a thermoforming method such as vacuum forming or pressure forming is used for mass productivity and homogeneity. In terms of surface. When producing a rust-proof container by such a method, it is preferable that the surface layer (16) to which sodium nitrite (18) has been added is formed so as to constitute a metal product housing surface. By doing so, it is possible to more effectively exert a rust prevention effect on the metal product accommodated in the container.

  According to the rust preventive sheet (10) of this example, since sodium nitrite (18) is added to at least one surface layer (16), a metal (particularly iron) arranged in the vicinity of the layer (18). ) Can prevent rust. Also, when sodium nitrite (18) is added to the surface layer (16), the water absorbed in the sodium nitrite (18) expands as water vapor due to the heat applied during sheet molding, and sodium nitrite (18 ) Is formed around the microcavity (20) and the micropores connecting the intermediate layer (12) and the surface side of the anticorrosion sheet (10) by connecting the adjacent microcavities (20) to each other. (22) is formed. For this reason, the vaporizable rust preventive agent added to the intermediate layer (12) can be gradually released from the sheet surface on the side to which sodium nitrite (18) is added, and a metal (particularly non-ferrous) arranged in the vicinity of the surface. Rust of metal) can be prevented. Thus, in the rust preventive sheet (10) of the present invention, the synergistic action of sodium nitrite (18) and the vaporizable rust preventive agent can exert an excellent rust preventive effect on a wide variety of metals. it can.

  Further, the rust preventive sheet (10) of the present example has excellent moldability because the base material constituting the intermediate layer (12) and the surface layers (14) and (16) are all made of polypropylene resin. It will be a thing. Therefore, a rust-proof container obtained by thermoforming such a sheet (10) has excellent container characteristics such as light weight and stress cracking resistance, and also has excellent rust-proof characteristics.

  Hereinafter, although an Example is given and the antirust sheet | seat of this invention is demonstrated concretely, this invention is not limited to this Example.

Manufacture of rust preventive sheet 6 parts vaporizable rust preventive (metal guard M type manufactured by DAUBERT CROMWELL USA) for 100 parts by weight of polypropylene resin (Sumitomo Nobrene FH1016 manufactured by Sumitomo Chemical Co., Ltd.) In addition to preparing a weight part addition, as a raw material constituting both surface layers, polypropylene resin (Sumitomo Chemical Co., Ltd. Sumitomo Nobrene FH1016) 90% by weight and polyethylene resin (Sumitomo Chemical Co., Ltd. Sumikasen F101-1) ) A 10% by weight mixture was prepared.

  Then, sodium nitrite (manufactured by Nissan Chemical Industries, Ltd.) was added to one of the raw materials constituting the surface layer so that sodium nitrite was 6% by weight with respect to 94% by weight of the raw material resin.

  Subsequently, the above raw materials are set in a three-layer coextrusion melt extrusion molding machine (sheet molding machine) equipped with a T-die, under the conditions of extrusion temperature (cylinder temperature) 240 ° C. and resin temperature 240 ° C. It was melt-extruded to obtain a molten sheet material in which surface layers were laminated on both surfaces of the intermediate layer. And this was immediately quenched with a cooling roll set at 90 ° C. to obtain a rust-proof sheet having a three-layer structure with a thickness of 600 μm in which a surface layer with a thickness of 100 μm was laminated on both surfaces of an intermediate layer with a thickness of 400 μm. .

Manufacture of anti-corrosion container The above anti-corrosion sheet is vacuum formed so that the surface layer to which sodium nitrite is added forms the storage surface of the metal product, and a round dish-shaped anti-corrosion container with an inner diameter of 100 mm and a depth of 15 mm is manufactured did. For comparison, a molded container having a thickness of 600 μm made of only a polypropylene resin (Sumitomo Chemical Co., Ltd., Sumitomo Nobrene FH1016) was also produced.

Confirmation of rust prevention effect A 1.2 mm x 300 mm x 500 mm steel plate (JIS G 3141) is prepared as a test piece, and each of a rust prevention container formed by using a rust prevention sheet and a molded container made of only a polypropylene resin. In addition, each container was packaged with a normal polyethylene film (that is, a rust inhibitor not added) to prepare a sample.

  Then, this sample was allowed to stand for 14 days under a test environment condition of a high-temperature and high-humidity atmosphere having a temperature of 50 ° C. and a relative humidity of 100%, and the presence or absence of rust and discoloration of the test piece was evaluated.

  As a result, in the rust-proof container formed using the rust-proof sheet, no rust or discoloration was observed on the placed test piece. On the other hand, in a molded container made of only a polypropylene resin, rust and discoloration occurred particularly on the contact surface of the placed test piece with the molded container.

It is the partial expansion schematic which shows the antirust sheet | seat of one Example in this invention. It is the partial expansion schematic which shows the antirust sheet | seat of the other Example in this invention.

Explanation of symbols

(10)… Rust prevention sheet
(12)… Middle layer
(14)… Surface layer (no sodium nitrite)
(16)… Surface layer (with sodium nitrite)
(18)… Sodium nitrite
(20)… Cavity
(22)… Micropore

Claims (4)

An intermediate layer made of a polypropylene resin to which a vaporizable rust preventive agent is added, and a pair of surface layers made of a polypropylene resin and laminated on both front and back surfaces of the intermediate layer,
At least one in addition sodium nitrite in the surface layer Rutotomoni, is said intermediate layer and fine pore connecting the surface side of the surface layer leads is formed fine voids around the sodium nitrite is formed Rust-proof sheet characterized by   The rust preventive sheet according to claim 1, wherein the thickness of the surface layer to which sodium nitrite is added is 10 µm or more and 100 µm or less. The front and back surfaces of the volatile corrosion inhibitor polypropylene resin layer obtained by adding, after coextruded so as to sandwich a polypropylene resin sodium nitrite is added in at least one, according to claim 1 or immediately, characterized in that cooling 2. A method for producing a rust preventive sheet according to 2 . A rust-proof container for housing a metal product formed by thermoforming the rust-proof sheet according to claim 1 or 2,
A rust-proof container, wherein a surface layer to which sodium nitrite is added is formed so as to form a receiving surface for metal products.

Images