JP6251556B2 - Sealing compound for can lid - Google Patents

Description

  The present invention relates to a sealing compound for a can lid that is applied to a can lid of a metal can for beverages or foods and used as a sealing material for a double winding portion.

  A sealing compound having rubber-like elasticity is used as a sealing material that fills a gap slightly generated between a can barrel flange portion and a can lid curl portion in a double tightening portion of a metal can for beverages or food.

  The main components essential as a raw material for the sealing compound are rubber, resin, and filler. The sealing compound includes a solvent type in which rubber, resin, and filler are dissolved or dispersed in an aliphatic organic solvent, and a solvent type. There are two types of water-soluble types suspended and dispersed in water (Patent Documents 1 and 2).

  Among the main components, rubber is the base material, and the resin is the main purpose of tacking the can lid, which is a metal material. The filler is the main purpose of increasing the weight and adjusting the physical properties. Agents, thickeners, antibacterial agents, vulcanizing agents, vulcanization accelerators, emulsion stabilizers and the like are also used as appropriate. Note that the aliphatic organic solvent is required to have a quick drying property at room temperature or low temperature, and isohexane, cyclohexane, or the like is used.

  The sealing compound is applied to a compound channel provided in a groove shape on the outer periphery of the can lid, and an organic solvent or water solvent is evaporated and dried to form an elastic film, which is used as a sealing material.

  The viscosity of the sealing compound (solution viscosity) requires lining workability that can be applied to the compound channel around the outer periphery of the can lid at high speed without contaminating the can lid and the working environment. The sealing compound is filled in an extremely narrow gap of the double tightening portion and has a function of completely blocking the inner surface and the outer surface of the can to prevent the passage of gas and bacteria. For this purpose, it is necessary to have properties such as appropriate tackiness, elasticity, strength, hardness and heat resistance of the dried film.

  Among these, the adhesiveness has a certain degree of adhesiveness to the can lid, which is a metal material, and it is necessary that the sealing material does not move (does not flow) due to a pressure difference between the inside and outside of the can generated during the sterilization treatment of the can.

  As for the elasticity, strength, and hardness of the dry film, it is necessary for the sealing compound to escape properly by compression during double winding, and to fill the gap, but the sealing compound is too hard, the resilience is too strong, or the viscosity is If it is inferior, good winding cannot be obtained and the sealing performance is lowered. Further, even if the sealing compound is too soft, the impact resilience is too weak, or the viscosity is too strong, the sealing performance cannot be secured.

  Regarding heat resistance, canned foods are often treated at high temperatures, and if the heat resistance of the sealing compound is inferior, the sealing compound is pushed out from the double tightening part due to high temperature sterilization heat and the internal pressure of the can generated by squeeze out phenomenon This is not preferable in terms of appearance and sealing performance.

  However, the packer can be streamlined on the can-making side, such as by reducing the thickness of the metal substrate and mini-seam of the double-winding part, shortening the sterilization time (increasing the sterilization temperature) and increasing the speed of tightening In recent years, the required performance for sealing compounds has become more demanding due to the rationalization of the side.

  Under such circumstances, among conventional general-purpose sealing compounds, a solvent type using an organic solvent has caused a problem in terms of heat resistance. That is, in the solvent type, a rubber having a relatively low molecular weight (low Mooney viscosity) has been used from the viewpoint of solubility and dispersibility of the solvent in an organic solvent and lining workability, but a rubber having a low molecular weight. In the above situation, it becomes difficult to ensure the heat resistance of the sealing material.

  As measures against these problems, an organic peroxide polymerization initiator (alkyl peroxyester, etc.) is blended to improve the film strength of the sealant, and after sealing the sealing compound on the can lid, heat treatment is performed to rubber. A method for improving the heat resistance by polymerizing the polymer is proposed (Patent Document 1), and the heat resistance is improved by adding a vulcanization aid (such as zinc oxide) and a vulcanization accelerator (such as thiuram). A method has been used.

JP 2008-308594 A JP 2005-290326 A

  However, in the technique of Patent Document 1 using an organic peroxide, the polymerization reaction of rubber is advanced by using a heat treatment in a can lid manufacturing process or a can manufacturing process, thereby increasing the molecular weight. However, there is a concern that the quality may vary due to differences in polymerization depending on the environment and conditions during production.

  In addition, in the technology for improving heat resistance using a vulcanization auxiliary (such as zinc oxide) and a vulcanization accelerator, some users feel resistance in food hygiene safety because heavy metals are used.

  The present invention has been made in view of the circumstances as described above, the lining workability and the sealing performance are good, the heat resistance is excellent, and the quality does not vary depending on the environment and conditions during production. The object is to provide a sealing compound for can lids that is excellent in food hygiene.

  Although it has been clear from the past that heat resistance is improved by using a rubber having a high molecular weight (a rubber having a high Mooney viscosity), it cannot be used because the rubber does not dissolve in the organic solvent as the molecular weight of the rubber increases. . However, as a result of intensive studies, the present inventors have found that even a rubber having a high molecular weight can be dissolved in an organic solvent as a solvent by blending a higher fatty acid, thereby solving the above-mentioned problems. The present invention has been completed.

That is, the sealing compound for can lids of the present invention contains a rubber, a resin, and a filler as essential components, and in a sealing compound for can lids in which these are dissolved or dispersed in an aliphatic organic solvent, the Mooney viscosity of the rubber (ML _{1 + 4} , 100 ° C.) is 65 to 150 and contains higher fatty acids.

  In this can lid sealing compound, the higher fatty acid preferably has 12 or more carbon atoms, and the content of the higher fatty acid is preferably 0.5 to 3.0 parts by mass with respect to 100 parts by mass of the rubber.

  In the sealing compound for can lids, the resin is at least one selected from rosin resin, terpene resin, and petroleum resin, and the resin content is 10 to 100 parts by mass with respect to 100 parts by mass of rubber. Preferably there is.

  In the sealing compound for can lids, the filler is at least one selected from siliceous filler, clay, and talc, and the content of the filler is 10 to 100 parts by mass with respect to 100 parts by mass of rubber. It is preferable that

  According to the sealing compound for can lids of the present invention, the lining workability and the sealing performance are good, the heat resistance is excellent, the quality does not vary depending on the environment and conditions during production, and the food hygiene is also excellent. ing.

  The present invention is described in detail below.

The rubber used for the sealing compound for can lids of the present invention has a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 65 to 150, preferably 68 to 130.

In the present invention, Mooney viscosity (ML _{1 + 4} , 100 ° C.) can be measured in accordance with JIS K6300, using an L rotor under conditions of preheating 1 minute, rotor operating time 4 minutes, and temperature 100 ° C. . The Mooney viscosity can be adjusted by the monomer composition, the kind and amount of the molecular weight regulator, the polymerization temperature, the polymerization conversion rate, and the like.

  If the Mooney viscosity is too small, it will be difficult to ensure the heat resistance that has been required in recent years as the performance of the sealing compound. On the other hand, if the Mooney viscosity is too high, sealing properties, solubility in organic solvents, lining workability, and the like deteriorate.

  Examples of the rubber used in the sealing compound for can lids of the present invention include styrene-butadiene rubber (SBR), butadiene rubber (BR), natural rubber, synthetic natural rubber (IR), nitrile rubber (NBR), propylene- Butadiene rubber (PBR), nitrile isoprene rubber (NIR), chloroprene rubber (CR), butyl rubber (IIR), ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), acrylic rubber (ACM, ANM), fluorine Rubber, urethane rubber, silicone rubber or the like can be used. These may be used alone or in combination of two or more. Moreover, these can be used as aqueous latex, for example.

  Among these, styrene-butadiene rubber is preferable, and styrene-butadiene rubber having a styrene content of 20 to 50% by mass is preferable. Emulsion polymerization SBR latex can be generally divided into two types, cold rubber and hot rubber, depending on the emulsion polymerization temperature, but hot rubber (hot type) is used from the standpoint of reducing adverse effects of canned contents on flavor. It is preferable.

  Examples of the resin used in the sealing compound for can lids of the present invention include rosin resins such as rosin, hydrogenated rosin, rosin ester, hydrogenated rosin ester, polymerized rosin, polymerized rosin ester, α-pinene, β- Terpenic resins such as pinene and dipentene, petroleum resins such as aliphatic hydrocarbon resins (including those produced by hydrogenation), phenol formaldehyde resins, phenol resins modified with natural resins such as rosin and terpenes, xylene Examples include formaldehyde resins and modified resins thereof. These may be used alone or in combination of two or more. Among these, rosin resin, terpene resin, and petroleum resin are preferable.

  10-100 mass parts is preferable with respect to 100 mass parts of rubber | gum, and, as for content of resin in the sealing compound for can lids of this invention, 20-30 mass parts is more preferable. Within this range, moderate tackiness can be imparted and a balance with other physical properties required for a can lid sealing compound can be maintained.

  Examples of the filler used in the sealing compound for can lids of the present invention include siliceous fillers such as colloidal silica, anhydrous silicic acid, hydrous silicic acid, and synthetic silicate, and clay (calcined clay, silane-modified clay). , Talc, heavy calcium carbonate, light calcium carbonate, activated calcium carbonate, barium sulfate and the like. These may be used alone or in combination of two or more. Among these, siliceous fillers, clay and talc are preferable. Although the particle size of a filler is not specifically limited, For example, the thing of 0.3-30 micrometers can be used.

  10-100 mass parts is preferable with respect to 100 mass parts of rubber | gum, and, as for content of the filler in the sealing compound for can lids of this invention, 15-40 mass parts is more preferable. Within this range, the rheological properties of the sealing compound can be improved, the hardness of the dry film can be adjusted to an appropriate range, and the cost can be reduced by increasing the amount.

  In addition to the above essential components, higher fatty acids are blended in the sealing compound for can lids of the present invention. By blending higher fatty acids, rubber with a large molecular weight with a Mooney viscosity of 65 or more can be dissolved well in organic solvents such as isohexane and cyclohexane, and can be used as a base rubber for sealing compounds. Heat resistance can be improved.

  The higher fatty acid used in the sealing compound for can lids of the present invention preferably has 12 or more carbon atoms, more preferably 12 to 18 carbon atoms. When the carbon number of the higher fatty acid is within this range, a rubber having a Mooney viscosity of 65 or more and a large molecular weight can be dissolved well in an organic solvent. Of these higher fatty acids, stearic acid and palmitic acid are preferred.

  The content of the higher fatty acid in the sealing compound for can lids of the present invention is preferably 0.5 to 3.0 parts by mass with respect to 100 parts by mass of rubber. Within this range, a rubber having a Mooney viscosity of 65 or higher and a large molecular weight can be dissolved particularly well in an organic solvent.

  The sealing compound for can lids of the present invention can be blended with other components other than the above-mentioned main components within a range not impairing the effects of the present invention. Examples of such other components include colorants, anti-aging agents, thickeners, and antibacterial agents. 10 mass parts or less are preferable with respect to 100 mass parts of rubber | gum, and, as for the compounding quantity of these other components, 2-9 mass parts is more preferable. For example, another component can be 5-9 mass parts containing 4-7 mass parts of titanium oxide of a coloring agent with respect to 100 mass parts of rubber | gum.

  The sealing compound for can lids of the present invention can be prepared according to a conventional method. For example, in the case of the solvent type sealing compound of the present invention, various components blended in the sealing compound for can lids are kneaded using a pressure kneader, made into a sheet, and then cut and dissolved or dispersed in an organic solvent. Can be prepared. In the case of an aqueous type sealing compound, various components to be blended in the can lid sealing compound are appropriately prepared as an aqueous dispersion or an aqueous solution, and blended so as to have a predetermined ratio.

  As the organic solvent, volatile aliphatic organic solvents such as toluene, n-hexane, cyclohexane, methyl ethyl ketone and the like can be used. These may be used alone or in combination of two or more.

  Although content of the organic solvent in the sealing compound for can lids of this invention is not specifically limited, 100-230 mass parts is preferable with respect to 100 mass parts of solid content. Within this range, the lining workability is good and the applied sealing compound can be quickly dried at room temperature or low temperature.

  Next, the manufacturing process of the can using the sealing compound for can lids of this invention is demonstrated.

  In manufacturing canned foods, for example, after filling the can body with the contents, the can lid is put on, and then double-tightening is performed between the can body flange portion and the can lid curl portion to perform sealing. After tightening the can lid, heat treatment is appropriately performed according to the contents and the like, and sterilization treatment such as retort sterilization is performed. In this case, the sealing compound for can lid of the present invention is preliminarily provided in the compound channel provided in a groove shape on the outer periphery of the can lid by a nozzle lining in advance in order to completely seal the double winding portion of the can body and the can lid. Is applied. This sealing compound for can lids is completely double-clamped and fills a slight gap between the can barrel flange portion and the can lid curl portion to complete sealing of the can.

  When the sealing compound for can lids of the present invention is applied to the compound channel on the outer periphery of the can lid, for example, it can be performed by a known nozzle lining method. The applied sealing compound is quickly dried at room temperature or low temperature, for example, to form a sealing material layer.

  The sealing compound for can lids of the present invention is intended for metal cans for beverages and foods. For example, tin cans are tin plated tin cans and tin-free steels with electrode chromic acid treatment on the steel plate surface. It can be applied to steel cans such as cans (TFS), aluminum cans such as beer cans and carbonated beverage cans. Moreover, it can be used as a sealing material for the canopy and can body of a three-piece can, as a sealing material for the ground and can body, and can also be used as a sealing material for a canopy and can body of a two-piece can.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. In addition, the compounding quantity shown in Table 1 represents a mass part.
<Example 1>
As rubber, 100 parts by mass of Ashland's hot type SBR 1009 (Mooney viscosity 70, styrene content 23.5%), as resin, alicyclic saturated hydrocarbon resin (hydrogenated petroleum resin) manufactured by Arakawa Chemical Industries, Ltd. 25 parts by mass of Alcon P and 20 parts by mass of polymerized rosin ester K manufactured by the same company, 20 parts by mass of Silica L manufactured by Nippon Silica Co., Ltd., 5 parts by mass of clay ASP manufactured by BASF, and New Japan Rika as higher fatty acids ( Co., Ltd. Stearic acid 300S 1 part by mass, as a colorant, Sakai Chemical Industry Co., Ltd. titanium oxide S 6.5 parts by mass, and as an anti-aging agent, 1 part by mass of Kawaguchi Chemical Industry Co., Ltd. Antage W , Which is dissolved or dispersed in 360 parts by mass of a mixed solvent of 85% by mass of isohexane and 15% by mass of cyclohexane. It was de.
<Example 2>
In Example 1, the compounding amount of the higher fatty acid (stearic acid) was changed to 0.6 parts by mass. Otherwise, a sealing compound of the sample was obtained in the same manner as in Example 1.
<Example 3>
A sample was obtained in the same manner as in Example 1 except that the amount of the higher fatty acid (stearic acid) was changed to 2.5 parts by mass in Example 1.
<Example 4>
In Example 1, 30% by mass of the rubber 1009 was changed to Ashland's hot type SBR having a high Mooney viscosity, and a sealing compound was obtained in the same manner as in Example 1 except that.
<Comparative Example 1>
A sealing compound of the sample was obtained in the same manner as in Example 1 except that the higher fatty acid (stearic acid) was not blended in Example 1.
<Comparative example 2>
In Example 1, the total amount of rubber 1009 was changed to Ashland's hot type 1006 (Mooney viscosity 49, styrene content 23.5%) having a low Mooney viscosity, and the sealing compound of the sample was otherwise the same as in Example 1. Got.
<Comparative Example 3>
In Example 1, the total amount of rubber 1009 was changed to Ashland's hot type 1011AE (Mooney viscosity 54, styrene content 23.5%) having a low Mooney viscosity. Otherwise, the sealing compound of the sample was the same as in Example 1. Got.
<Comparative Example 4>
In Example 1, the total amount of rubber 1009 was changed to Ashland's hot type 1011AE with a low Mooney viscosity, and 4 parts by mass of a polymerization accelerator (peroxide such as dicumyl peroxide) instead of higher fatty acid (stearic acid) Otherwise, a sealing compound of the sample was obtained in the same manner as in Example 1.
<Comparative Example 5>
In Example 1, the total amount of rubber 1009 was changed to Ashland's hot type 1011AE having a low Mooney viscosity, and instead of higher fatty acid (stearic acid), 2 parts by mass of a vulcanization aid (zinc oxide) and a vulcanization accelerator were used. 1 part by mass of TRA (thiuram-based) was added, and a sealing compound of the sample was obtained in the same manner as in Example 1 except that.

The following evaluation was performed about the sample of the Example and the comparative example.
[Compound dissolved state]
The compound dissolution state was evaluated according to the following criteria.
○: Good without particles.
Δ: There are some particles.
X: There are particles. Gelation.
[Lining workability]
Using a Nordson pumping unit, a compound was applied from a nozzle to a φ200 diameter aluminum can lid so that the film volume was 53 mm ^3, and lining workability was evaluated according to the following criteria. In addition, the lining workability | operativity was confirmed by performing the continuous lining of 100 lid | covers using the compound which passed 1 week or more after manufacture.
○: After setting to the prescribed coating amount, no adjustment was made, and continuous lining was possible within ± 10% of the coating amount, and no cover contamination such as protrusion of the compound occurred.
Δ: After setting to the prescribed coating amount, without adjustment, the coating amount exceeded ± 10%, and continuous lining was possible within ± 20%, and no cover contamination such as protrusion of the compound occurred.
X: After setting to a prescribed coating amount, continuous lining was impossible within ± 20% of the coating amount without adjustment.
[Sealing]
Apply a sealing compound to a φ200 diameter lid, air dry and season for 3 days, fill the lid with 90 ° C hot water at 90 ° C, wrap and tighten and then sterilize at 125 ° C for 30 minutes. A sample of 100 cans was prepared by cooling. After dropping an iron block with a weight of 500 g from a height of 10 cm to the tightening part of the side seam of the obtained can, deformed, and stored at room temperature for 1 month, the number of leaking cans was examined by measuring the degree of vacuum. The sealability was evaluated according to the criteria shown in.
○: 5 cans leaked out of 100 cans.
Δ: 6 to 20 cans leaked out of 100 cans.
X: Leaked 21 or more out of 100 cans.
[Heat resistance (squeeze out)]
Apply sealing compound to φ200 diameter lid, air dry and season for 3 days. Fill the lid with 90 ° C hot water at 90 ° C, wrap and tighten, then sterilize at 125 ° C for 30 minutes, cool The number of squeeze-out cans to the outside of the rear sealing compound was counted, and the heat resistance was evaluated according to the following criteria (n = 100 cans).
○: 5 cans out of 100 cans.
Δ: 6 to 15 cans squeeze out of 100 cans.
X: 16 or more cans out of 100 cans.

 The evaluation results are shown in Table 1.

Claims (4)

In a sealing compound for can lids containing styrene-butadiene rubber (SBR) , a resin, and a filler as essential components, which are dissolved or dispersed in an aliphatic organic solvent,
A sealing compound for can lids having a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of styrene-butadiene rubber (SBR) of 65 to 150 and containing a higher fatty acid.   The sealing compound for can lids of Claim 1 whose carbon number of a higher fatty acid is 12 or more, and content of a higher fatty acid is 0.5-3.0 mass parts with respect to 100 mass parts of rubber | gum.   The resin is at least one selected from a rosin resin, a terpene resin, and a petroleum resin, and the resin content is 10 to 100 parts by mass with respect to 100 parts by mass of the rubber. Sealing compound for can lids. The filler is at least one selected from siliceous filler, clay, and talc, and the content of the filler is 10 to 100 parts by mass with respect to 100 parts by mass of the rubber. The sealing compound for can lids as described in any one.