Sealing material composition for metal lids and metal lid having a coating film made therefrom.

Abstract

To provide a sealing material composition which is usable for winding and fixing an aluminum-made lid and a can containing limonene-containing food as a content, and can exhibit excellent sealing performance over a long period of time.SOLUTION: A sealing material composition for a metal lid contains at least a rubber component, a filler and an antioxidant, wherein the rubber component contains acrylonitrile butadiene rubber as a main component and does not contain styrenic rubber, and does not contain a rosin-based resin, and a film swelling ratio is 28% or less, which is calculated by the following expression: film swelling ratio (%)=[(M2 / 625)-1]×100, from an average value M (mm) of diameters in two directions perpendicular to each other of a film when a dry film with a thickness of 0.25 mm and a diameter of 25 mm, made of the sealing material composition, is immersed in d-limonene at 38°C for 72 hours.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a sealing material composition for a metal lid and a metal lid provided with a sealing material composed of this sealing material composition. More specifically, the present invention relates to a sealing material composition for a metal lid that can form a sealing material whose sealing performance is not impaired even for contents containing a high concentration of limonene.

Background Art

[0002] In a metal can used for canned food applications, after filling the contents, a metal lid coated with a winding sealing material is double-wound at one open end of the can to seal it. This winding sealing material is required to have a sealing performance that can ensure the sealing property of the container over a long period of time as well as the winding property during winding. As a sealing material having such performance, a sealing material composition based on a styrene-based elastomer such as styrene-butadiene rubber (SBR) or carboxylated styrene-butadiene rubber (CSBR) is widely used. For example, in the container sealant composition described in Patent Document 1 below, in addition to the above SBR, it is described that tackifiers such as rosin resins and fillers can be blended.

[0003] For carbonated beverages and alcoholic beverages filled in canned foods, d-limonene (hereinafter simply referred to as limonene) is widely used to impart flavors such as fruit flavors, and it has also been proposed to contain a high concentration of limonene to obtain a more favorable flavor (Patent Document 2). In addition, there are products containing limonene as an active ingredient for removing dirt in household detergents and the like. Such limonene is a terpene hydrocarbon and has the property of dissolving styrene-based compositions and rosin resins with similar structures. Therefore, for example, a sealing material composition based on SBR will interact with the contents when used for the lid of a can containing contents with a high concentration of limonene.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Patent No. 6116584 [Patent Document 2] Japanese Patent Publication No. 2018-99089 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] When filling cans with contents containing high concentrations of limonene, sealing them, and storing them, if an SBR-based sealing material composition is used for the lid, problems arise during the double-sealing process where the metal lid is joined to the can, or during subsequent storage of the canned goods. The film swells due to the action of the contents, causing it to protrude from the gap in the double-sealing, resulting in a poor appearance and detachment onto the contents. Furthermore, if rosin-based resin is added to the sealing material composition as a softening agent to impart flexibility and tackiness to the coating, the rosin-based resin may dissolve in the contents, splatter onto the outside of the can, and after the contents that have adhered to the can dry, the rosin-based resin will precipitate, causing stickiness on the outside of the can and impairing the product's value.

[0006] Sealing material compositions based on acrylonitrile butadiene rubber (NBR), rather than SBR, are also known. However, conventional lid sealing material compositions are generally used in steel cans containing industrial lubricants and the like, after being mixed with rosin-based resins to provide flexibility and tackiness, making them unsuitable for use as sealing material for metal cans containing food and beverages with high concentrations of limonene. Furthermore, when a composition blending NBR with SBR was used as a measure to impart flexibility to the coating, the swelling of the coating was suppressed compared to when SBR was used as the base material. At first glance, there seemed to be no problem with the appearance defects or detachment of the coating into the contents due to the coating protruding from the gap in the double seam. However, upon collection and observation of the contents, it was found that minute fragments of the coating had detached, indicating foreign matter contamination.

[0007] Therefore, the object of the present invention is to provide a sealing material composition that can exhibit excellent sealing performance over a long period of time without causing problems such as overflow due to swelling upon contact with contents containing a high concentration of limonene, precipitation of components dissolved in the contents, or generation of tiny fragments detached from the coating. [Means for solving the problem]

[0008] According to the present invention, the present invention contains at least a rubber component, a filler, and an anti-aging agent, wherein the rubber component is mainly composed of acrylonitrile butadiene rubber and does not contain styrene-based rubber, nor does it contain rosin-based resin. Beverage storage A sealing material composition for metal lids, The aforementioned sealing material composition does not contain a vulcanizing agent (crosslinking agent) and a vulcanization accelerator. A sealing material composition is provided, characterized in that the film swelling rate, calculated according to the following formula (1) from the average value M (mm) of the diameters of two orthogonal directions of the film when a dry film with a thickness of 0.25 mm and a diameter of 25 mm made of the sealing material composition is immersed in d-limonene (38°C) for 72 hours, is 28% or less. Film swelling rate (%)=[(M 2 / 625)-1]×100 ···(1)

[0009] In the sealing material composition of the present invention, 1. When the dry film has a thickness of 0.2 to 0.4 mm, the tensile strength in a tensile test (according to JIS K 6251) must be in the range of 0.4 to 6 MPa. 2. The rubber component is composed of one or more types of acrylonitrile butadiene rubber. 3. The filler is contained in an amount of 4 to 80 parts by weight per 100 parts by weight of the rubber component (solids). 4. The filler is an aluminum-based filler. This is preferable.

[0010] The present invention also provides a metal lid having a coating made of the above-mentioned sealing material composition. In the present invention, it is preferable that the metal lid is a double-sealed lid in which the coating film is formed on the outer edge that forms the crimped portion. [Effects of the Invention]

[0011] The coating made from the sealing material composition of the present invention, when applied to a metal lid of a can containing contents with a high concentration of limonene and subjected to double seam sealing, does not swell and overflow, and exhibits excellent sealing performance over a long period of time. Furthermore, despite using NBR and not using a softening agent, it possesses flexibility that ensures seamability and sealing performance. This is evident from the results of the examples described later. In other words, the dried film made from the sealing material composition of the present invention has tensile strength that makes it applicable to sealing aluminum cans and can lids, which are made of a softer material than steel and are widely used in beverage cans and the like. Furthermore, even when such a dried film is immersed in d-limonene, the swelling rate of the dried film is reduced, demonstrating that it can exhibit excellent sealing performance. [Modes for carrying out the invention]

[0012] As mentioned above, the sealing materials used in beverage cans and the like generally consisted of SBR-based sealing material compositions due to their crimping properties and sealing performance. However, when such sealing materials are used to store contents containing high concentrations of limonene, the SBR, which is the main component of the sealing material, and the rosin-based resin, which is a softening agent, dissolve in the limonene, and the sealing material components swell and fall out inside the container, potentially leading to contamination by foreign matter. An important feature of the present invention is that, as a sealing material composition that can handle contents containing such high concentrations of limonene, it does not contain SBR and rosin-based resins that dissolve in limonene, and instead has NBR as the main rubber component, and contains at least a filler and an anti-aging agent.

[0013] (Rubber component) In the sealing material composition of the present invention, NBR is used as the main rubber component. In the present invention, it is preferable to use NBR having an acrylonitrile content in the range of 25 to 35% by weight, particularly 25 to 30% by weight. That is, as mentioned above, a sealing material with NBR as the main component forms a hard film, but by having the acrylonitrile content within the above range, it is possible to impart appropriate flexibility to the sealing material. If the acrylonitrile content is less than the above range, the sealing performance and durability may decrease compared to when it is within the above range, and if the acrylonitrile content is more than the above range, the flexibility required for a sealing material may decrease compared to when it is within the above range. Hydrogenated or carboxylated NBR can also be used, which allows for adjustment of the hardness and other properties of the resulting film.

[0014] In this invention, NBR is used as the rubber component, but other than styrene-containing rubbers such as SBR and CSBR that are soluble in limonene, natural rubber, and isoprene rubber, known latex rubber components such as butadiene rubber, which have been conventionally used as sealing materials, may be blended in a range that does not impair the properties of NBR latex.

[0015] (Filler) In the sealing material composition of the present invention, a filler is added to impart physical properties such as resistance to contents and plasticity to the formed film, as well as to improve application workability and drying properties. As fillers, conventionally known fillers can be used, such as aluminum-based fillers like aluminum oxide, alumina white, alumina sulfate, aluminum hydroxide, and aluminum nitride; siliceous fillers like colloidal silica, anhydrous silicic acid, hydrated silicic acid, and synthetic silicates; talc, dolomite, barium sulfate, magnesium carbonate, magnesium silicate, magnesium oxide, calcium sulfate, fly ash, pumice powder, glass powder, asbestos, diatomaceous earth, bentonite, mica, or organic powders and hollow particles made from these. In the present invention, in particular, from the viewpoint of maintaining the flexibility of the sealing material and having low rubber reinforcing properties, aluminum-based fillers can be preferably used, and among them, aluminum hydroxide can be preferably used. The filler is preferably added in an amount of 4 to 80 parts by weight, particularly 8 to 72 parts by weight, based on 100 parts by weight of the rubber component.

[0016] (Antioxidant) In the sealing material composition of the present invention, an antioxidant is added to improve the durability of the sealing material. As the antioxidant, conventionally known antioxidants such as 2,2 - methylene - bis - [6 - (1 - methylcyclohexyl - p - cresol)], di - β - naphthyl - p - phenylenediamine, 4,4'-butylidenebis(6 - tert - butyl - m - cresol), 2,2'-methylenebis(6 - tert - butyl - 4 - ethylphenol), 2,2'-methylenebis(4 - methyl - 6 - tert - butylphenol), 4,4'-thiobis(6 - tert - butyl - m - cresol), hindered phenol - based reducing substances, vitamin E - based reducing substances, etc. can be used. In the present invention, in particular, from the viewpoint of stain resistance, 2,2 - methylene - bis - [6 - (1 - methylcyclohexyl - p - cresol)] can be preferably used. The antioxidant is preferably added in an amount of 0.5 to 8 parts by weight based on 100 parts by weight of the rubber component.

[0017] (Other components) In the sealing material composition of the present invention, in addition to the above essential components, under the condition of being a component that does not dissolve in limonene, a viscosity modifier, a dispersant, a pigment, etc., and if it is an application where the influence on taste and fragrance and the elution amount are not problematic, a vulcanizing agent, a vulcanization accelerator, and a vulcanization accelerator co - agent can also be blended as necessary. Examples of viscosity modifiers include methylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, alginates (sodium, zinc), polyvinyl alcohol, sodium polyacrylate, and guar gum, karaya gum, tragacanth gum, etc., which can be blended in an amount of 0.5 to 10 parts by weight per 100 parts by weight of the rubber component. Examples of dispersants include fatty acids such as oleic acid, stearic acid, palmitic acid, lauric acid, and myristic acid; or organic sulfonic acids such as alkylallyl sulfonic acid, sulfonates of dibasic fatty acid esters, and sulfonic acids of aliphatic amides; sodium salts, potassium salts, or ammonium salts of the above acids; or polyoxyalkylene derivatives, which can be blended in an amount of 0.5 to 5 parts by weight per 100 parts by weight of the rubber component.

[0018] Vulcanizing agents (crosslinking agents) and vulcanization accelerators should not be used when used on can lids for beverages, but they can be used, for example, on aerosol cans for household detergents, etc., from the standpoint of chemical resistance. Examples of vulcanizing agents include sulfur, sulfur-containing compounds, organic oxides, metal oxides, organic polyvalent amines, and modified phenolic resins. When used, they can be blended in an amount of 3 parts by weight or less per 100 parts by weight of the rubber component. Examples of vulcanization accelerators include thiram-based, dithioate-based, and quinsert-based agents, while examples of vulcanization accelerator aids include zinc oxide and fatty acids. When used, they can be blended in an amount of 3 parts by weight or less per 100 parts by weight of the rubber component. Examples of pigments include carbon black, titanium dioxide, and red iron oxide, which can be blended in an amount of 0.5 to 30 parts by weight per 100 parts by weight of rubber component.

[0019] In the sealing material composition of the present invention, an aqueous dispersion sealing material composition can be prepared by adjusting the viscosity, solid content, etc., by blending the above-mentioned NBR latex with additives such as the above-mentioned filler, and by adding aqueous ammonia to stabilize the dispersion so that the pH becomes 9 to 11.

[0020] (Sealing material) The sealing material composition of the present invention can be used by directly applying the aqueous dispersion prepared as described above to a metal lid material or the like, and a sealing material can be formed by heating it with hot air at a temperature that does not cause bumping to evaporate the water. The dried film of a sealing material made from the sealing material composition of the present invention has the following properties (details of the measurement method will be described later in the examples). In other words, as shown in formula (1) above, when the above-mentioned 0.25 mm thick dried film is immersed in limonene (38°C) for 3 days, the rate of increase in the projected area of ​​the planar portion due to swelling of the dried film is within the range of 28% or less. Therefore, even when used in metal cans and can lids that contain contents containing high concentrations of limonene, there is no overflow due to swelling upon contact with the contents, resulting in no defects in appearance or detachment into the contents. This effectively prevents foreign matter from contaminating the contents, and the sealant can maintain its sealing performance over a long period of time, exhibiting excellent durability. Furthermore, the above-mentioned dried film preferably has a tensile strength (tensile strength) of 0.4 to 6 MPa, particularly in the range of 0.4 to 5.6 MPa, in a tensile test (in accordance with JIS K 6251) of a dried film with a thickness of 0.2 to 0.4 mm. Having a tensile strength (tensile strength) within this range allows the sealing material to possess the required crimping properties and flexibility.

[0021] (Metal lid) The sealing material composition of the present invention can be suitably used for metal container lids, caps, mounting cups used in aerosol containers, or ends of container bodies such as the bottom of a three-piece container, which are crimped together. As metal materials to which the sealing material composition of the present invention can be applied, conventionally known metal materials for metal containers, such as various surface-treated steel sheets and light metal sheets such as aluminum, can be used. As surface-treated steel sheets, cold-rolled steel sheets can be annealed, then further rolled as needed, and subjected to one or more surface treatments such as zinc plating, tin plating, nickel plating, electrolytic chromic acid treatment, and chromic acid treatment. Aluminum-coated steel sheets that have been aluminum-plated or aluminum-rolled can also be used. As light metal sheets, in addition to so-called pure aluminum sheets, aluminum alloy sheets can also be used. These metal materials may have a resin coating made of polyester resin or the like, or a coating made of epoxy paint or the like. Because the sealing material composition of the present invention has excellent flexibility, it is a material that is weaker and softer than steel, and can be suitably used in the crimping portion of lids applied to aluminum alloy cans, which are widely used for beverage applications.

[0022] The sealing material composition of the present invention can be particularly suitable for use in double-sealed metal lids that are attached to the open end of a can by double-sealing. Preferably, a coating made of the sealing material composition of the present invention is formed on the outer peripheral edge of the metal lid, which forms the sealed portion, with a thickness of 10 to 40 μm in the case of an aluminum beverage can. [Examples]

[0023] (Examples 1-10) The NBR latex and filler shown in Table 1, and 2,2-methylene-bis-[6-(1-methylcyclohexyl-p-cresol)] as an antioxidant were used in parts by weight per 100 parts by weight of the rubber component (solids) in the latex shown in Table 1. To these components, methylcellulose was added in an aqueous dispersion with a pH of 9.5. This was done by adding methylcellulose in an amount of 3 parts by weight per 100 parts by weight of rubber components (solids) as a viscosity modifier, and ammonium oleate in an amount of 0.25 parts by weight per 100 parts by weight of rubber components (solids) as a dispersant. The obtained sealing material composition was used for evaluations described later. The evaluation results are shown in Table 1.

[0024] (Comparative Examples 1-6) The NBR and / or SBR latex and filler shown in Table 2, and 2,2-methylene-bis-[6-(1-methylcyclohexyl-p-cresol)] as an antioxidant were used in parts by weight per 100 parts by weight of the rubber component (solids) in the latex shown in Table 2. In Comparative Examples 5 and 6, a rosin-based resin was used in parts by weight per 100 parts by weight of the rubber component (solids) shown in Table 2. To these components, methylcellulose was added in an aqueous dispersion with a pH of 9.5. This was done by adding methylcellulose in an amount of 3 parts by weight per 100 parts by weight of rubber components (solids) as a viscosity modifier, and ammonium oleate in an amount of 0.25 parts by weight per 100 parts by weight of rubber components (solids) as a dispersant. The obtained sealing material compositions were used for evaluations described later. The evaluation results are shown in Table 2.

[0025] In Tables 1 and 2, NBR (medium nitrile) refers to NBR with an acrylonitrile content (weight%) of 25 or more and less than 31, NBR (medium-high nitrile) refers to NBR with an acrylonitrile content (weight%) of 31 or more and less than 36, and NBR (low nitrile) refers to NBR with an acrylonitrile content (weight%) of less than 25. The symbols used for each evaluation result in Tables 1 and 2 have the following meanings. ○: No phenomena were observed; the condition is good. △: The phenomenon is observed, but it does not pose a practical problem. ×: The phenomenon is observed and it is not suitable for practical use.

[0026] (Evaluation method) 1. Sealing material coating properties 1.1. Film swelling rate • A sealing material film was prepared to have a film thickness of 0.25 mm after drying, and a circular die with a diameter of 25 mm was used to punch out test specimens. • 100 ml of d-limonene was placed in a glass container, and one of the circular cut-out films described above was added. The container was sealed tightly and stored at 38°C for 3 days before the film was removed. The film swelling rate was calculated from the average value M (mm) of the diameter measured in two perpendicular directions of the extracted film, according to equation (1) above.

[0027] 1.2. Tensile strength of the coating The sealing material film, prepared to have a film thickness of 0.2 to 0.4 mm after drying, was punched out into JIS K 6251 dumbbell-shaped type 2, and marked with gauge lines at 20 mm intervals to create test specimens. • The material was subjected to a tensile test at a speed of 200 mm / min, and the tensile strength (MPa) was calculated.

[0028] 2. Performance evaluation of sealing materials 2.1. Blister formation during drying of coating on metal lids A sealant was applied to the outer circumference of a 204 diameter aluminum alloy lid made of 5000 series aluminum alloy with a plate thickness of 0.27 mm, and it was dried in a hot air electric oven at 90°C for 10 minutes. • If no blisters are observed in the sealant film after drying (evaluation symbol ○), or if blisters are present but the lid material is not exposed through the sealant layer (evaluation symbol △), it was determined that there are no practical problems. • In cases where blistering has occurred and the lid material is exposed (evaluation symbol ×), it was determined that the product is unsuitable for practical use from the perspective of maintaining long-term airtightness.

[0029] 2.2. Excess of sealant from double crimping gap A 204 diameter aluminum alloy lid made of 0.27 mm thick 5000 series aluminum alloy was coated with a sealant around its outer circumference, and then dried in a hot air electric oven at 90°C for 10 minutes to produce a 204 diameter aluminum alloy lid with the sealant applied. The following two types of contents were filled into a 211mm diameter, 350-gram, two-piece beverage can (compliant with JIS Z 1571) made of aluminum alloy, which had been necked in to fit this lid, and immediately joined by double crimping. The above-mentioned two-piece beverage can made of aluminum alloy is made of 3104 series aluminum alloy, with the thickness of the can's sidewall metal being 0.11 mm at its thinnest point and 0.17 mm at the flange portion. (1) 345.8 mL of carbonated spirit with an alcohol content of 7, cooled to 5°C, was placed in a can, and 4.2 mL of limonene was added. (Limonene is approximately 10 g / L). (2) 332.5 mL of carbonated spirit with an alcohol content of 9%, cooled to 5°C, was placed in a can, and 17.5 mL of limonene was added. (Limonene is approximately 42 g / L). • A sterilization treatment using a 55°C hot water shower for 10 minutes was performed. Cans filled with the two types of contents described above were stored at 37°C for 3 months with the lid facing upwards and tilted at a 20° angle. After that, the cans were cut at the neck-in section, and the gap between the lid and the can body was visually observed on the inside of the can. • If any excess sealant was found to be protruding, the product was deemed unsuitable for practical use.

[0030] 2.3. Contents after double crimping: Suspension of minute fragments detached from the coating. The same procedure was followed up to the hot water shower sterilization described in section 2.2 above. Canned goods filled with the two types of contents described above were stored at 37°C for 3 days with the lid facing upwards and tilted at a 20° angle. After that, a hole was made in the lid and the contents were filtered by suction using 5C filter paper. If solid matter remained on the filter paper, or if the can was cut at the neck-in part and the inside of the can was inspected and solid matter was found adhering to the inner surface of the can and lid, it was determined that the product was not suitable for practical use.

[0031] 2.4. Sticky exterior of can after double sealing. The same procedure was followed up to the hot water shower sterilization described in section 2.2 above. • After drying, lightly rub the area directly below the double seam on the outside of the can (the area where contents tend to adhere during the double seam process) with your finger. If you feel any stickiness, it is determined that the can is not suitable for practical use.

[0032] 2.5. Coating peeling off during double-sealing after heating the lid at 85°C for 20 days. A 204 diameter aluminum alloy lid made of 0.27 mm thick 5000 series aluminum alloy was coated with a sealant around its outer circumference and dried in a hot air electric oven at 90°C for 10 minutes to create a 204 diameter aluminum alloy lid with the sealant applied. Prior to applying the double seam seal, the aluminum alloy lid, which had the above-mentioned sealant applied, was heated in a hot-air electric oven at 85°C for 20 days. Then, without filling it with contents, it was double-sealed onto the aforementioned 211mm diameter, 350-gram two-piece aluminum alloy beverage can. • If the can was cut at the neck-in portion and any detached sealant material was found on the inside or outside of the can, it was determined that the can was unsuitable for practical use.

[0033] 2.6. Aluminum alloy cans: Dimensional abnormalities due to double crimping process When the contents were filled according to the two conditions in 2.2 above, if the body hooks in the double-sealed cross section were well extended (evaluation symbol ○), or if the body hooks were bent but buckling did not occur in the side wall of the can shell (evaluation symbol △), it was determined that there were no practical problems.

[0034] 2.7. Leakage from aluminum alloy cans The same procedure was followed up to the hot water shower sterilization described in section 2.2 above. The canned goods were stored at 37°C for 3 months with the SOT lid facing upwards and tilted at a 20° angle. After that, the contents were visually inspected for leakage from the seam and the internal pressure of the can was checked after returning to room temperature. If no leakage was detected as described above, and the internal pressure of the canned goods remained at 95% or more of the initial internal pressure measured at room temperature before storage at 37°C, it was determined that there was no practical problem.

[0035] 2.8. Steel cans with abnormal dimensions due to double crimping process This product was created by welding an open-top tinplate can with a thickness of 0.18 mm, conforming to a 202 mm diameter, 190-gram three-piece beverage can (JIS Z 1571). The openings at both ends were made with a diameter of 200 mm. The sealant was applied to the outer circumference of a 200 mm diameter aluminum alloy lid made of 0.3 mm thick 5000 series aluminum alloy, and the lid was dried in a hot-air electric oven at 90°C for 10 minutes before being joined to the can with a double crimp. • 179 mL of 9% alcohol carbonated spirits, cooled to 5°C, was placed in the above-mentioned open-top can, and then 11 mL of limonene was added. (Limonene is approximately 49 g / L). Immediately, another 200mm diameter aluminum alloy lid, coated with the same sealant as described above, was joined to the lid using a double crimping technique. • If the body hooks extend well in the double-sealed cross-section of the two lids (evaluation symbol ○), it was determined that there are no practical problems.

[0036] 2.9. Steel Can Leakage The canned goods prepared according to the procedure in 2.8 above were stored at 37°C for 3 months with the aluminum lid, which was sealed on the side where the contents were placed, facing upwards at a 20° angle. After storage, the contents were visually inspected for leakage from the sealed area, and the internal pressure of the cans was checked after returning to room temperature. If no leakage was detected as described above, and the internal pressure of the canned goods remained at 95% or more of the initial internal pressure measured at room temperature before storage at 37°C, it was determined that there was no practical problem.

[0037] [Table 1]

[0038] [Table 2] [Industrial applicability]

[0039] The sealing material composition of the present invention has excellent limonene resistance even to contents containing limonene at a concentration of approximately 4.2 g / L, and also possesses flexibility and durability. Therefore, it is particularly suitable for use as a sealing material for the lids of aluminum cans filled with limonene-containing beverages.

Claims

1. A sealing material composition for metal lids for beverage containers, comprising at least a rubber component, a filler, and an anti-aging agent, wherein the rubber component is mainly composed of acrylonitrile butadiene rubber and does not contain styrene-based rubber, and does not contain rosin-based resin, The aforementioned sealing material composition does not contain a vulcanizing agent (crosslinking agent) and a vulcanization accelerator. A sealing material composition characterized in that the film swelling rate, calculated according to the following formula from the average value M (mm) of the diameters of two orthogonal directions of the film when a dry film with a thickness of 0.25 mm and a diameter of 25 mm made of the sealing material composition is immersed in d-limonene (38°C) for 72 hours, is 28% or less. Film swelling rate (%) = [(M)] ２ / 625)-1]×100

2. The sealing material composition according to claim 1, wherein the tensile strength in a tensile test (in accordance with JIS K 6251) when the dried film has a thickness of 0.2 to 0.4 mm is in the range of 0.4 to 6 MPa.

3. The sealing material composition according to claim 1 or 2, wherein the rubber component is composed of one or more types of acrylonitrile butadiene rubber.

4. The sealing material composition according to any one of claims 1 to 3, wherein the filler is contained in an amount of 4 to 80 parts by weight per 100 parts by weight of the rubber component (solids).

5. The sealing material composition according to any one of claims 1 to 4, wherein the filler is an aluminum-based filler.

6. A metal lid characterized by having a coating film made of the sealing material composition according to any one of claims 1 to 5.

7. The metal lid according to claim 6, wherein the coating film is formed on the outer edge that forms the crimping portion, and is a metal lid for double crimping.

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