JPS6035252B2 - Manufacturing method for easy-open container lid gasket - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an easily-openable container lid gasket, and more specifically, the present invention relates to a method for manufacturing an easily-openable container lid gasket, and more specifically, by controlling the transfer of a thickening agent to the surface of an olefin resin gasket within an effective range, the openingability is improved. The present invention relates to a method for manufacturing a container lid gasket that provides an optimal combination of sealing performance.

Olefin resins such as low-density polyethylene have a combination of moderate cushioning properties and excellent hygiene properties, and have come to be widely used as sealing gaskets for container lids.

However, it has been found that various troubles occur when an olefin resin gasket is applied to a container lid. In other words, if a container lid equipped with an olefin resin gasket is fastened to the mouth of the container and stored for a long period of time, the opening torque of the container lid will increase significantly over time, making it difficult for the purchaser of the container to open the lid by hand. They are often difficult to open. In order to reduce the opening torque of the container lid, it is possible to incorporate a lubricant into the olefin resin that makes up the gasket, but the lubricant added to the olefin resin may migrate to the gasket surface.
If the pressure is too high, there will be a drawback that the torque at the initial stage of sealing the container lid will be excessively small.

In other words, if the torque at the initial stage of sealing the threaded container lid is too small, a sealing failure may occur at the initial stage of tightening, or the container lid may become loose due to rotation during post-processing or transportation of the sealed container. This will result in leakage of contents and outside air oxygen. The present inventors have incorporated a certain amount of normally solid lubricant into an olefin-based resin for gasket formation, molded it into a gasket, and heated the gasket at a temperature within a certain range with respect to the melting points of the olefin-based resin and the lubricant. It has been found that heat treatment can prevent the lubricant from migrating to the gasket surface without reducing the initial sealing torque excessively, thereby suppressing the tendency for the unsealing torque to increase over time.

That is, an object of the present invention is to provide a container lid equipped with an olefin resin gasket that has an excellent combination of sealing properties and easy-to-open properties.

Another object of the present invention is to ensure sufficient torque to ensure sealing performance at the initial stage of sealing the container lid, and to suppress abnormal increases in opening torque even when the sealed container is stored for a long period of time. To provide a container lid equipped with an olefin resin gasket that can be easily opened.

According to the present invention, an olefin resin composition containing a lubricant that is solid at room temperature in an amount of 0.001 to 1% by weight per olefin resin is formed into a gasket inside or outside the container lid, and the gasket is formed into a gasket. is lower than the melting point of the olefin resin and the lubricant, and 400% lower than the melting point of the lubricant.
Provided is a method for manufacturing an easy-open container diamond gasket, which is characterized by heat treatment at a temperature higher than zero.

In FIG. 1 showing the container lid of the present invention together with the container opening,
This container lid shell 1 consists of a disk-shaped top plate part 2 formed from a painted metal plate and a cylindrical skirt part 3 hanging down from the periphery of the top slope part. Inside the container lid shell 1,
A disk-shaped gasket 4 made of an olefin resin composition is provided on the lower side of the top plate portion 2 with an adhesive layer 5 interposed therebetween. The periphery of the gasket 4 engages with the circumferential opening 7 of the container 6 to form a sealing structure, and the skirt 3 of the container lid shell 1 has an opening for engaging with a screw 8 of the container neck. and a screw 9 for resealing. The skirt 3 of the container lid may be provided with a pilfer-proof mechanism, which consists of perforations 10, which are known per se, running close to the lower edge. An important feature of the present invention is that the gasket 4 contains 0.001 to 10% by weight (% is based on weight unless otherwise specified), preferably 0.05 to 5% by weight based on the olefin resin.
%, most preferably from 0.1 to 3% by weight of a thickening agent that is solid at room temperature, and the gasket after molding is formed by adjusting the melting point of the olefin resin (To°C) and the melting point of the lubricant (To°C). TL.○) and the melting point of the lubricant (TL℃
) is heat-treated at a temperature 40°C lower than That is,
If the amount of glue is less than the above range, it will be difficult to transfer a sufficient amount of glue to the surface of the olefin resin gasket to prevent the opening torque from increasing over time; If is larger than the above range, the initial sealing torque may become too small and sufficient sealing reliability may not be obtained.

In this case, it should be noted that if the normally solid solvent is blended with the olefin resin in the above-mentioned ratio and simply molded into a gasket, the opening torque will increase over time, as shown in the example below. This means that it cannot be effectively resolved.

In contrast, according to the present invention, by subjecting an olefin resin gasket containing such an amount of solid paste to heat treatment at the above-mentioned temperature, the increase in opening torque over time can be effectively eliminated. You get it.

That is, in the present invention, in a gasket containing an olefin resin and a solid lubricant, even when any of these components is in a molten state, the lubricant does not effectively migrate to the surface of the gasket, and the solid lubricant does not transfer to the gasket surface. It is novel that the transfer of lubricant occurs most effectively at a temperature just below the melting point of the solid lubricant, and that the transfer of the lubricant is sufficient to suppress the above-mentioned increase in opening torque over time up to a temperature 40 degrees lower than that. It is based on knowledge.

Therefore, in the present invention, the reason why the increase in unsealing torque over time is suppressed is presumed to be as follows.

In other words, one of the reasons why the opening torque increases over time may be that the coefficient of friction between the olefin resin gasket and the bottle opening increases over time; The biggest factor seems to be that the sugar content in the contents solidifies during this time to form a so-called sugar cement, and this sugar cement increases the opening torque of the container lid. In contrast, in the present invention, the lubricant that migrates to the gasket surface through the heat treatment described above provides a lubricating or peelable interface, as well as an easily broken and weakened interface, between the sugar cement and the gasket. It seems to be. In the present invention, polyolefins such as low-, medium-, or high-density polyethylene, isotactic polypropylene, crystalline ethylene-propylene copolymers, or blends thereof are preferably used as the olefin resin.

The most preferred olefinic resin is a crystalline ethylene copolymer containing the aforementioned polyethylene and other olefins such as propylene and butene-1 in an amount of 1 to 5 mol %, with the remainder being ethylene. This olefin resin may contain an ethylenically unsaturated monomer other than olefin in an amount of 0.5 to 55 mol%, such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, etc. , ionically crosslinked ethylene copolymers (ionomers), etc. may also be used for the purposes of the present invention. The molecular weight of the olefin resin may be within a range that allows film formation, and in particular, those having a melt index (MI) within the range of 0.01 to 100 are used. It is important that the lubricant used in the present invention is normally solid from the viewpoint of ease of opening and sealing.

Suitable examples of such lubricants are as follows. 1 Fatty acids, aliphatic alcohols Higher fatty acids Fatty acids obtained from animal or vegetable oils and hydrogenated fatty acids with 12 to 22 carbon atoms Hydroxystearic acid Direct mirror aliphatic monohydric alcohols Animal or vegetable oils Or those with a carbon number of 1 or more obtained by reducing these fatty acid esters or decomposing and distilling natural waxes, tridecyl alcohol with 2 polyglycols polyethylene glycols with a molecular weight of 200 to 9,500 polypropylene glycols with a molecular weight of 1000 or more polyoxypropylene -Polyoxyethylene-floc polymer with a molecular weight of 1,900 to 9,000 3 Amide, amine higher fatty acid amide oleyl/glumitoamide stearyl erucamide 2 stearomide ethyl stearate ethylethobis fatty acid amide NN' oleoyl stearyl ethylenediamine NN' bis (2hydroxyethyl)alkyl (C,2-C,8)
Amide NN′ bis(hydroxyethyl) lauroamide N Distearate ester of oleic fatty acid jetanolamine di(hydroxyethyl) diethylenetriamine monoacetate reacted with N alkyl (C,6-C,8) trimethylenediamine 4 Monovalent, polyhydric acid ester Fatty acid esters of alcohols n-butyl stearate Hydrogenated rosin methyl esters Dibutyl sebatate <n-butyl> Dioctyl sebacate <2-ethylhexyl and n-octyl> Glycerin fatty acid esters Glyceryl Lactostearyl Pentaerythritol Stearic acid Esthe/Pentalythritol Tetrastearate Sorbitan fatty acid ester Polyethylene glycol fatty acid ester Polyethylene glycol monostearate Polyethylene glycol dilaurate Polyethylene glycol monooleate Polyethylene glycol dioleate Polyethylene glycol Chassis fatty acid ester Polyethylene glycol Tall fat rib Acid ester Kentadiol Montanic acid ester 1,3 Butanediol Montanic acid ester Dethylene glycol Stearic acid ester Propylene glycol Fatty acid ester 5 Triglycerides, waxes Hydrogenated edible oils Cottonseed oil and other edible oils 12-hydroxystearic acid Glycerin ester Hydrogenated fish oil Beef tallow / Glycerin wax Montan wax Power Lunaba wax Beeswax Wood wax Monohydric aliphatic alcohol and aliphatic saturated acid Estenol <Example:
Hardened whale oil lauryl stearate, stearyl stearate > lanolin 6 Salts of higher fatty acids with alkali metals, alkaline earth metals, zinc and aluminum (metal soap) 7 Other propylene glycol alginate.

The lubricant used in the present invention lowers the melting point of the olefin resin to
(℃) When the melting point of the lubricant is TL (℃), the formula To+4
0ZTLZTo-80 Especially T.

120 and TL and T. It is desirable for heat treatment to have a melting point that satisfies -60.

Moreover, this lubricant has the formula 42ISP in relation to the type of olefin resin used.

-SPo≧0.5 In the formula, SPo is the solubility parameter of the olefin resin (SolsukegawatyParameter)
It is desirable that the SPL has a solubility parameter defined by , which indicates the solubility parameter of the lubricant, and by using a lubricant that satisfies this condition, the desired combination of openability and sealability can be more easily achieved.

In the present invention, it is preferable to use an amide of a higher fatty acid, particularly a fatty acid amide having 16 to 22 carbon atoms, as the lubricant.

These have the advantage of being excellent in the above-mentioned effect as a lubricant for olefinic resins, and also in retaining flavor (F1avour) for the contents of the container.

In addition to the above-mentioned essential components, arbitrary auxiliary components can be blended into the olefin resin composition used in the present invention.

For example, this composition contains a low-crystalline or non-crystalline ethylene copolymer or a conjugated polymer to control the amount of silk transfer and further improve the cushioning properties of the gasket. Alternatively, they can be blended in combination.

As the low crystallinity or non-crystalline ethylene copolymer, a copolymer of ethylene and other olefins with a degree of crystallinity of less than 10% may be used. Suitable examples of olefins other than ethylene are propylene, butene-1, etc., and the copolymer can further contain non-conjugated genes such as 1,4-hexadiene, ethylidenenorbornene, etc. Suitable examples of ethylene-based copolymers are copolymers containing 95 to 40 mol% ethylene, 5 to 60 mol% propylene or putene-1, or even 1 to 5 mol% non-conjugated diene. , especially ethylene-propylene copolymer/rubber and ethylene-propylene-gene terpolymer/rubber. The molecular weight of these copolymers is usually 50
00 to 200,000 heat 10,000 to 100,000
It is preferable that it be in the range of 0. Examples of the conjugated diene polymer used as the lubricity sustaining agent include homopolymers of conjugated diene and copolymers of conjugated diene and other ethylenically unsaturated monomers.

Examples of the conjugated diene include dienes of the formula RIF CH---C--CH--CH2, where RI represents a hydrogen atom, a halogen atom, or an alkyl group having 4 or less carbon atoms, especially butadiene, isoprene, chloroprene, etc. can be mentioned.

Examples of ethylenically unsaturated monomers include vinyl aromatic monomers such as styrene, vinyltoluene, and Q-methylstyrene;
Ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic anhydride, crotonic acid, citraconic anhydride, or their esters, amides, hydroxyalkyl esters, amino Acrylic monomers such as alkyl esters;
Vinyl ester monomers such as vinyl acetate, vinyl formate, and vinyl propionate; Ethylenically unsaturated nitriles such as acrylonitrile and methacrylonitrile; Vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; vinyl chloride, vinylidene chloride 1 of vinyl halides such as
Mention may be made of species or combinations of two or more species. It is also desirable for this conjugated diene polymer to contain at least 1% by weight, particularly preferably 2% by weight, of conjugated diene units, from the viewpoint of the above-mentioned lubricity sustainability.

Suitable examples of conjugated gene polymers are cis-1,4-polybutadiene, polyisoph. Ren, styrene-butadiene copolymer/rubber, nitrile-butadiene copolymer/rubber,
Natural or synthetic rubbers such as polychloroprene, thermoplastic butadiene copolymers, and thermoplastic resins. It is a ren copolymer. Suitable thermoplastic butadiene or isoprene copolymers are styrene-butadiene (or isoprene) floc copolymers containing from 15 to 4% by weight of butadiene or isoprene units, or styrene-butadiene (or isoprene)-styrene floc copolymer. The molecular weight of these conjugated polymers is generally desirably in the range of 10,000 to 1,000,000.

The aforementioned low crystallinity or non-crystalline ethylene copolymer is
It can be blended in an amount of 5 to 70% based on the base olefin resin, and the conjugated gene-containing polymer can be blended in an amount of 1 to 15% based on the base olefin resin. In addition, to color the gasket or give it opacity, white pigments such as titanium dioxide, coloring pigments such as carbon black, red iron oxide, and tartrazine lake, and fillers such as calcium carbonate, talc, clay, and barium sulfate are used. can be blended.

In addition, anti-blocking agents such as silica can be added to prevent flocking, and antioxidants such as externally harmful phenols can be added to prevent thermal deterioration during gasket processing or sterilization. . The above-mentioned olefin resin composition can be formed into a gasket by any method.

For example, after melting and kneading each of the above-mentioned components, a certain amount is extruded into the inside of a container lid shell, and this resin composition is embossed while cooling, so that it can be molded into a gasket on the spot. This molding method is advantageous in that it is possible to form a thick portion with a raised wall that is desirable in terms of sealing performance around the gasket that engages with the container opening. Of course, instead of melting the olefin resin composition directly into the container lid shell, the composition can be formed into a disk or other shaped preform, and the preform can be placed into the container lid shell. After filling and heating them, they may be formed into a gasket. Alternatively, the olefin resin composition of the present invention may be formed into a sheet by melt extrusion or roll molding, the sheet may be punched out into discs, and the discs may be used as gaskets to be applied one by one into the container lid shell. I can do it. In this case, even if the gasket forming sheet is made of a single layer of the olefin resin composition mentioned above,
Alternatively, the surface to be engaged with the container mouth may be a laminate comprising at least a layer of the olefin resin composition. Such laminates are produced by combining a substrate such as paper, aluminum foil, foam sheet, polyester film such as Mylar, and a layer made of an olefin resin composition using dry lamination, extrusion coating method, English extrusion method, etc. It can be manufactured by bonding by means. The metal material constituting the container lid shell can be, for example, a light metal plate such as aluminum or a coated steel plate such as a tin-plated steel plate or an electrolytic chromic acid treated steel plate (tin-free steel). The material can be coated with a protective coating that is known per se, such as an epoxyphenolic coating.

The forming of painted metal plates into shells involves drawing, deep drawing,
This can be easily done by means such as drawing and ironing or press molding.

The liner can be easily adhered to the container lid shell through an adhesive paint layer containing, for example, oxidized polyethylene or acid-modified olefin resin. In the present invention, the container lid shell may of course be made of plastic.

Heat treatment of the gasket can be easily performed by heating the gasket to a temperature within the above-mentioned range.

For heating, any means such as induction heating, infrared heating, hot air stove, steam heating, heating stamper, direct flame heating, etc. can be used. Heating time varies depending on the temperature, but
The time is determined such that effective lubricant transfer is achieved with the combination of resin and lubricant, generally from 10 minutes to 4 hours, and particularly from 10 minutes to 1 hour. It is most desirable to heat-treat the gasket with the gasket assembled into the container lid, but in the method of applying a gasket cut-out disc to the container lid, heat treatment is performed in the state of a gasket-forming sheet or in the state of the cut-out disc. The heat treatment may be performed outside the container lid. The present invention is applicable to any container lid in which the container lid is opened by relative rotation between the lid and the container, such as screw caps, pilfer-blue caps, lug caps, press-on/twist-off caps, twist crowns, etc. The container lid can be fastened or sealed to the container neck by roll-on (threaded by threaded rollers), press-on, screw-on, or the like. The invention is illustrated by the following example.

Example 1 7 parts by weight of vinyl chloride-vinyl acetate copolymer and 25 parts by weight of bisphenol A type epoxy resin were applied as a rust-preventive undercoat lacquer to an aluminum plate (manufactured by Sumitomo Light Metal Industries Ltd.) with a thickness of 0.24.
After roll coating a paint consisting of 5 parts by weight of amino resin and an organic solvent, heating was performed for 10 minutes at 19,000 °C.

A primer composition consisting of 70 parts by weight of eboxy resin, 1 part by weight of urea resin, 2 parts by weight of maleic acid-modified polyethylene, and an organic solvent was roll-coated onto this rust-preventing undercoat lacquer layer as an adhesive paint. ,1
Heating was performed for 0 minutes to create a coated board. Further, a vinyl-phenol paint was roll coated onto an aluminum plate for use as a polyvinyl chloride liner and heated for 19,000 to 1 minute.

Furthermore, for the polypropylene liner, maleic acid-modified polypropylene was used instead of modified polyethylene. Next, this coated plate was formed into a cap shell (38 legs in diameter, 18 sides in height) (commonly known as a 38 rib pp cap) so that the coated surface was the inner surface. The obtained cap shell was heated to 19,000 ℃ using a high-frequency heating device, various resins listed in Table 1 were extruded from an extruder, and the molten resin particles (0.4 mm) cut with a rotary blade were heated to the inner center of the cap shell. , and immediately pressed with a press mold to form a liner shape, thereby producing various liner-equipped caps.

In addition, 0.1 PHR or more of oleic acid amide was added as a solvent to the various resins shown in Table 1.

Each of the molded caps was placed in a 70q0 hot air oven and subjected to hot air treatment for 2 hours. Performance tests were conducted on various caps in comparison with caps that were not heat treated, and the results shown in Table 2 were obtained. The full opening torque value of the cap that promoted the bleeding of the solvent by the hot air treatment showed a better full opening torque value compared to the case without the hot air treatment. The test method is as follows. Test (1) Measurement of the amount of lubricant bleeding on the surface of the cap gasket The surface of the gasket pressed by the press die was quickly wiped with a cloth soaked in ethyl ether, then the gasket was dried, and the results were measured before and after wiping with the cloth. The difference in gasket weight was taken as the amount of lubricant bleed.

The value of the bleed amount of the glue was expressed in milligrams per woman of gasket 10. Test {2} Cap opening torque test A wing with a capacity of 1,000 tons was heated with concentrated sulfuric acid (98%) 40
．． Add 950 ml of diluted sulfuric acid made by diluting 5 ml of sulfuric acid to 7.5 ml of water, then put 10 ml of sodium hydrogen carbonate into the bottle, taking care not to touch the solution, and seal the sample cap completely. Completely dissolve the sodium bicarbonate.

The cap is left at room temperature for one week or one month, and the opening torque value of the cap is measured using a torque meter. In addition, a 10% sugar solution was applied to the weir mouth in advance, a test cap was placed in the same manner, and the torque value was measured one month later.
Table 1 (Note) The numbers in parentheses indicate the weight ratio of the composition.

PP: Polypropylene (MI=25 density 0.91) EV
A: Ethylene-vinyl acetate copolymer (vinyl acetate 19%
, MI = 2.5) PVC: European polyvinyl chloride consisting of 10 parts by weight of polyvinyl chloride, 6 parts of plasticizer (DOP) and 2 parts of heat stabilizer LDPE: Polyethylene (density 0.921 MI = 2.7
) PIB: Polyisobutylene rubber (Vistanetx L
IM-100, manufactured by Esso Chemical) EP: Ethylene propylene copolymer (propylene 26%, MI = 2.6) SIS
: Styrene-isoph.

Thin styrene flock copolymer (Califlex TR
-1107 manufactured by Shell Chemical) SBS: Styrene-butadiene-styrene flock copolymer (Califlex TR-1102 manufactured by Shell Chemical) PE: Polyester elastomer (Belprene P7 eaves,
Toyobo) EVA: Ethylene-vinyl acetate copolymer (
Vinyl acetate 60%, M1=40) PB: 1,2-polybutadiene (RB-820, manufactured by Nippon Rubber) HDPE: High density polyethylene (density 0.960, MI=4.0) Test results Table 2 Shit 1 ) Table 2 Shit 2) *60↑ means 60+...and it was impossible to measure.

Example 2 The shame of the sample ship listed in Table 1 of Example 1. 9 resin composition, namely LDPE (90) and SIS (
Various solvents having different melting points were added to the composition of 10) based on Table 3, and caps were molded in the same manner as in Example 1, followed by hot air treatment for 2 hours at different temperatures.

As a fourth result, when the hot air treatment temperature is higher than the melting point of the lubricant or when the hot air treatment is performed at a temperature considerably lower than the melting point, there is no difference in performance as a cap compared to no hot air treatment. No treatment effect was observed. Third
Note that the base resin LDPE to which this latent agent was added had a melting point of 110°C.

Table 4 Example 3 Sample M. listed in Table 1 of Example 1. 4 LDPE
Paraffin wax, polyethylene wax, etc. having different melting points were added to the caps, and caps were molded in the same manner as in Example 1, followed by hot air treatment for 2 hours at different temperatures.

As a result, as shown in Table 6, the SP value of the lubricant and the SP value of LDPE were determined.
In cases where the difference in values was small, no heat treatment effect was confirmed.
Table 5 Table 6

[Brief explanation of drawings]

FIG. 1 is a diagram showing the container lid of the present invention together with the container opening, in which reference numeral 1 is the container lid shell, 2 is the top plate, 3 is the skirt, 4 is the gasket, 5 is the adhesive layer, 6 is a container,
Reference numeral 7 indicates a circumferential opening, 8 indicates a thread on the neck of the container, 9 indicates a thread for opening and resealing, and 10 indicates a perforation. Figure 1

Claims (1)

[Scope of Claims] 1. An olefin resin composition containing 0.001 to 10% by weight of a lubricant that is solid at room temperature based on the olefin resin is formed into a gasket inside or outside the container lid, and the gasket is formed into a gasket. A method for producing an easily openable container lid gasket, characterized in that the gasket is heat-treated at a temperature lower than the melting point of the olefin resin and the lubricant and higher than a temperature 40° C. lower than the melting point of the solvent. 2 When the melting point of the olefin resin is T_O (℃) and the melting point of the lubricant is T_L (℃), the lubricant is T_O+40≧T_L
The method according to claim 1, characterized in that the melting point satisfies ≧T_O-80. 3. The lubricant has a solubility parameter that satisfies the formula 4≧|SP_O−SP_L|≧0.5, where SP_O represents the solubility parameter of the olefinic resin and SP_L represents the solubility parameter of the lubricant, respectively. The method described in Scope 1.