DE1782737C3 - Use of thermoplastic polymers for the production of seals for container closures - Google Patents

Description

For closing containers, which are usually made of glass, plastic, metal or a layered material are made, with a container closure is a seal between the pouring rim of the container and the closure is required to seal against the contents of the container. Serves in most cases the seal also creates a hermetic seal and thus protects the contents of the container against contamination by germs of all kinds.

The invention relates to the use of a compliant thermoplastic material which is a (Contains olefin polymers as a sealant for the manufacture of seals for container closures. wherein the compliant thermoplastic material according to the invention consists essentially of

a) a copolymer of a <\ - monoolefin mil Vinyl acetate. Acrylic acid or an acrylic acid ester.

b) a mixture of the copolymer a) with Rubber or

c) a mixture of polyethylene with polyisobutylene and / or butyl rubber and / or the copolymer a) and / or chlorosulfonated polyethylene
consists

Seals produced in a manner according to the invention have a better one over a long period of time Sealing capacity as seals that are exclusively Made of polyethylene or polyvinyl chloride ίο are how the values for maintaining the Show pressure inside containers, which are provided with closures, the seals contain.

Seals, which are an ethylene-vinyl acetate copolymer contain, have the further advantage that they are better than polyethylene on the epoxy paints that are normally used to paint crown caps. To prove this Property was made from a molded seal

half pulled out with a crown cap. The free edge of the gasket was in the top bracket a tensile strength measuring device clamped while the crown cap is fastened in the lower clamp whereupon the force required to tear the parts apart was determined. Polyethylene seals did not stick, so that the force was zero, while that was an ethylene-vinyl acetate copolymer containing or consisting of seals required a measurable force. For one out of one 2: 2: 1 mixture of polyethylene, butyl rubber and an ethylene-vinyl acetate copolymer The force of the seal was 1.6 to 1.8 kg.

Those made from polyethylene and butyl rubber Seals are also superior to those made of polyethylene alone in the "instant pressure test" which the closure caps are placed on bottles, the contents of which are under pressure, and then the maintenance of the pressure is measured on the closure of the bottles. Continue to show the seals have a greater resistance to mechanical effects, such as shows, when bottles are dropped, those with closures with seals according to the invention are provided. Furthermore, the sealing effect is better with bad glass, e.g. B. for bottles with a scratched or chipped edge.

The seals made of polyethylene and butyl rubber preferably contain approximately the same Amounts by weight of the two ingredients, but other ratios may also be used, e.g. B. 60% Polyethylene with 40% butyl rubber or 70% polyethylene with 30% butyl rubber. A special one preferred mass consists of 10 to 81% polyethylene, 15 to 50% butyl rubber and 4 to 40% of one Ethylene-vinyl acetate copolymer, in each case expressed as percent by weight.

From a mixture of polyethylene and polyisobutylene or from a mixture of polyethylene and Seals made from chlorosulfonated polyethylene

f> o generally have properties similar to those Containing polyethylene and butyl rubber, and those of any ethylene-acrylic acid or acrylic acid ester copolymer or a mixture of the same with polyethylene, gaskets generally have similar properties to the gaskets, which consists of an ethylene-vinyl acetate copolymer or a mixture of the same with polyethylene exist.

The polyethylene used is preferably a low density polyethylene. The ethylene-vinyl acetate copolymer normally contains 5 to 50, preferably 12 to 40 percent by weight vinyl acetate

The invention is applicable to the production of seals for the most varied types of closures, z. B. for crown corks of the normal type or with a short apron, pilfer-proof closures, closures with pull tab, plastic closures, rolled-on lids or flanged lids. Some of the Sealing compounds are particularly valuable for rolled-on closures and for pilfer-proof closures.

The compounds used for the seals can have the various components in any one Contain relationship that is related to the desired propriety shafts for the sealant is in line; such relationships can be determined by simple Identify attempts.

- Fillers, pigments, dyes, lubricants, blowing agents, cork particles, synthetic resins, rust inhibitors and other conventional additives can be added to the various thermoplastic materials as needed to achieve specific effects in each case. It shows up in the presence of a blowing agent in general, that the thin, disk-shaped protective layer of the seal does not or only slightly expands while the raised circular sealing ring adopts the typical cell structure. Both the Blowing agents as well as the other additives can be conventional. Typical suitable pigments are for example titanium dioxide and carbon black, while azo compounds known as blowing agents, e.g. B. azobiscarbonamide, can be used. For example, the fillers can be chalk (and other Calcium carbonate forms). Barytes and clays and the lubricants are silicones and waxes. Suitable Resins are rosin, resinates, and terpene resins. Sodium benzoate, for example, is used as a rust preventive in question which z. B. in amounts of 1 to 3 percent by weight, based on the sealant, can be added.

The following examples, in which all details in Parts, percentages or relative proportions are by weight unless otherwise specified.

example 1

50 parts of ethylene-vinyl acetate copolymer with a vinyl acetate content of 32 to 34%, a melt index of 22 to 28 and a density of 0.95 and 50 parts of a low density polyethylene with a melt flow index of 7.0 and a specific gravity of 0.918 were mixed 10 minutes on a two roll mill at 140 ⁰ C for one another, removed and the mixture as a sheet and with the help of a hot forn. was deformed at 150 ° C under a pressure of 210 kg / cm ² into a sheet 0.14 cm thick.

Slices of 11.1mm were cut from the sheet and inserted into the center of crown corks treated internally with a vinyl varnish and had been preheated on a hot plate with a surface temperature of about 100 ⁰ C. The crown caps with the sealing washers were then heated for 25 seconds on a heating plate, the surface temperature of which was 230 ^° C., so that the sealing compound became semi-liquid. The panes were then shaped into seals using a non-heated molding tool. Glass bottles packed with 3 parts by volume and 5 parts by volume of carbonic acid were stored for 1 month at 38 ° C. and then examined. There was no pressure drop.

Example 2

A mixture of equal parts of low density polyethylene according to Example 1 and butyl rubber with a content of double bonds (calculated as

/ '
C = C) ^of OJ mole percent and a Mooney

Viscosity of 70.0 was established at 140 ° C on a two roll mill. The mixture was removed from the roller frame in web form and processed in a hydraulic press at 150 ° C. under a pressure of 210 kg / cm ² to form a web 0.14 cm thick. Discs with a diameter of 26.2 mm were cut out of the material and placed in conventional crown corks with the application of heat and pressure. The compound produced seals with excellent sealing properties, as demonstrated when bottles were closed with carbonated water.

Example 3

A mixture of equal parts of a polyisobutylene with an average molecular weight due to viscosity between 117,000 and 135,000 the low density polyethylene of Example 1 (melt flow index 7.0 and specific gravity 0.918) was prepared as described in Example 2. Slices were cut from the mass and, as in Example 2 placed in lacquered crown caps. Similar leak tests as described in Example 2 were carried out and again gave excellent values for the sealing properties.

Example 4

Example 1 was repeated, but the sealing washers in conventional crown corks with a Epoxy paint applied using a solvent-based adhesive. Testing similar to those of Example 1 again showed excellent sealing properties.

Example 5

A mixture of 50 parts of the polyethylene of Example 1 and 50 parts of an ethylene-acrylate-copolymer having a melt index of 7.0 and a specific gravity of 0.931 was prepared at 130 ⁰ C on a two roll mill. After 10 minutes of mixing, the mixture was removed in the form of a web and pressed in a hydraulic press at a temperature of 140 ⁰ C under a pressure of 210 kg / cm ² into a sheet of 0.14 cm thickness. Discs were made from this web and placed in crown corks as described in Example 2; the elongation properties corresponded perfectly to those found for the gasket of Example 2.

Example 6

A mixture of 50 parts of the low density polyethylene of Example 1, 50 parts of the butyl rubber of Example 2 and 25 parts of the ethylene-vinyl acetate copolymer of Example 1 was prepared, too

processed into a web and cut into slices, whereupon the discs were placed in crown corks and cold-formed, as in each case in Example 1 described. The coating weight was 180 mg. The excellent sealing properties were shown in that the closed containers suffered no weight loss after 3 months of storage had.

Example 7

There were seals made of a mixture of polyethylene with butyl rubber with seals Compared to polyethylene alone.

Seals made of a 1: 1 mixture of the low density polyethylene of Example 1 and the butyl rubber ι s of Example 2 and seals made of the same polyethylene alone were molded into crown corks, which were then used to close steel bottles. The steel bottles were connected to a pressure source at room temperature. The pressure in the bottles was increased to 2.8 kg / cm ² and this pressure was maintained for 5 minutes. The pressure was then increased in stages by 0.7 kg / cm ² each time and kept constant for 1 minute in between. The seals failed at the following pressures at which compressed air escaped from the containers:

mens that was present in gaseous form when the bottles were opened.

Polyethylene C, 8 kg / cm ²

Mixture of polyethylene and

Butyl rubber> 12.6 kg / cm ²

The maximum pressure of the compressed air source was 12.6 kg / cm ² , so that the value given for the mixture according to the invention is only a minimum value.

Example 8

Seals made from a mixture of polyethylene with butyl rubber or from a mixture of polyethylene with butyl rubber and an ethylene-vinyl acetate copolymer were made with seals made of polyethylene alone as well as seals made of plasticized Compared polyvinyl chloride alone.

The following experiment served to ensure the pressure tightness over a long period of time at 38 ° C investigate.

Glass bottles were filled with an amount of hydrochloric acid sufficient to withstand the addition of one Excess sodium bicarbonate in a gelatin capsule is five times the volume of the bottle in carbon dioxide to release. After throwing the capsules into the bottles, they were immediately sealed with crown corks locked. The closed bottles were then pasteurized for 30 minutes at 68 ° C, whereupon the bottles were subjected to a shock test. The shock test consisted of two crates of bottles filled with bottles and then put a bottle crate upside down on top of the other would. The two boxes were then put together six times from a height of 15 to 25 cm onto one Dropped concrete floor. The bottles were now partly lying horizontally, partly vertically stored upright at 38 ° C. After the time indicated below had elapsed, the bottles were heated to 16 ° C cooled, whereupon the carbon dioxide pressure in the bottles was measured. In the following table is the measured pressure as a multiple of the bottle volume type of seal

1 3 6

Month month »* months

Polyvinyl chloride at 4.29

Plasticizers

Polyethylene 4.67

Mixture of polyethylene 5.14
with butyl rubber (1: 1)
Mixture of polyethylene 5.2!
with butyl rubber and
the ethylene-vinyl acetate copolymer des
Example 1 (2: 2: 1)

4.21

4.03
5.09

5.16

4.45

4.07
4.86

4.95

In a further experiment carried out, JO bottles, each containing 4.5 volumes of carbon dioxide contained, stored horizontally at 40 ° C and periodically checked for liquid leakage. None of the bottles whose seals are made of one 1: 1 mixture of polyethylene with butyl rubber or from a 2: 2: 1 mixture of polyethylene with butyl rubber and the Äthyle.i-vinyl acetate copolymer of example 1 passed, showed a leak after 2 weeks, while 5 to 6 bottles, whose seals were made of polyvinyl chloride with a plastic cutter, a leak after just 3 days showed; after 2 weeks, all 10 comparison bottles were no longer tight.

Example 9

3s Seals were made from a mixture of Polyethylene with an ethylene-vinyl acetate copolymer or a mixture of polyethylene with Butyl rubber and an ethylene-vinyl acetate copolymer with seals made of polyethylene alone and

made of a plasticized polyvinyl chloride compared with each other.

The pressure test was carried out as described in Example 7, the seals from a) a 1: 1 mixture of ethylene-vinyl acetate copolymer of Example 1 and the same polyethylene and b) consisted of the same polyethylene alone. the Seals failed at the following pressures:

Polyethylene 9.8 kg / cm ²

Ethylene vinyl acetate mixed poly

merisat-polyethylene mixture <12.6 kg / cm ²

Mixture of polyethylene with

Butyl rubber and the ethylene

Vinyl acetate copolymer des
Example 1 (2: 2: 1)> 12.6 kg / cm ²

60 In a similar compression test at 68 ⁰ C instead of room temperature, the following results were obtained:

Polyethylene 11.2 kg / cm ²

Polyvinyl chloride mass Π, 2 kg / cm ²

Ethylene vinyl acetate mixed poly

merisate-polyethylene mixture 12.4 kg / cm ²

Mixture of polyethylene with
Butyl rubber and the ethylene-vinyl acetate copolymer des
Example 1 (2: 2: 1)> 12.6 kg / cm ²

The results clearly show that a mixture of ethylene-vinyl acetate copolymer with polyethylene polyethylene alone and plasticized polyvinyl chloride as a sealing compound for container closures is superior.

Example 10

A web of the Äthylcn-vinyl acetate copolymer of Example 1 was molded at 15O ⁰ C under a pressure of 210 kg / cm ² into a sheet of 0.14 cm thickness, were prepared from the sealing liners as in Example. 1 These clear inlays were placed in lithographed, vinyl resin coated crown caps. The finished crown caps were tested as in Example 1 and showed excellent sealing properties.

Example Π

A web of ethylene-vinyl acetate copolymer with a melt index of 1.5, a specific gravity of 0.937 and a vinyl acetate content of 18% was at 150 ° C under a pressure of 210 kg / cm ² in a hydraulic press to a web of 0, 14 cm thick processed.

Disks with a diameter of 30 mm were cut from the web and placed in pilfer-proof closures with a diameter of 31.5 mm. The closures were placed on a hot plate with a surface temperature of 120 ° C for 1 minute placed so that the seal adhered to the softened paint of the Pilfer-Proof closure. The closures with the seal adhering to it were cooled and with the help of the "roll-on process" halfway with water filled bottles applied. The bottles were then kept for 3 months at room temperature and stored at 38 ° C and showed no weight loss thereafter, proving that the seal was good.

Similar tests were performed on bottles containing corn oil, olive oil, motor oil, nut oil, fruit juices, vinegar, 95% alcohol, detergent solution, bleach solution, and a 2,4-dichloroxylenol solution. The sealing material was practically not attacked at all ^{after storage at 38 ° C. for 2 months.}

Example 12

It was a web of a mixture of equal parts of the ethylene-vinyl acetate copolymer of the Example 11 and the ethylene-vinyl acetate copolymer of Example 1 prepared for mixing The procedure used and compression of the mass corresponded exactly to that described in Example 2.

Disks made from this mass were placed in crown caps with epoxy paint using of a solvent-based adhesive. The sealing properties were similar to those in Example 11 was tested and a similarly good seal was observed

The solvent-based adhesive was made as follows:

50 parts of the ethylene-vinyl acetate copolymer of Example 1 and 50 parts of a hydrogenated resin acid

The s were mixed together while hot in an internal mixer, and after cooling, the mixture became dissolved in toluene so that a 30% solution was obtained. This solution was in a crown cap introduced, allowed to dry partially and yielded a

ίο Adhesion to the seal once the layer is sufficient was sticky.

Example 13

A web of the copolymer of ethylene and an acrylic acid ester according to Example 11 was produced by pressing granules from the mass at a temperature of 150 ° C. under a pressure of 210 kg / cm ² to form a web 0.14 cm thick. Discs with a diameter of 26.7 mm were cut from the web and, as described above, placed in crown caps using the solvent-based adhesive of Example 12, which were then used to close bottles. The sealing properties were comparable to those of Example 2.

Example 14

A mixture of 50 parts of a chlorosulfonated polyethylene with a chlorine content of 29% and a sulfur content of 1.25% and 50 parts of the low density polyethylene of Example 1 was prepared at 150 ° C on a two-roll mill by mixing for 8 minutes, whereupon the The mixture was removed and pressed in a hydraulic press at a temperature of 150 ° C. under a pressure of 210 kg / cm ² to form a web 0.14 cm thick.

A.US the track were disks with a diameter cut out of 26.7 mm and placed in standard crown corks with epoxy coating, the Solvent-based adhesive described in Example 12 was used. The closures thus obtained were placed on bottles containing carbonated drinks; it turned out to be very good Sealing properties observed

Example 15

Seals were made from a mixture of equal parts by weight of the ethylene-vinyl acetate copolymer from Example 1 and the butyl rubber from Example 2 other applications can be used. The bottles closed with a stopper with these seals withstood internal pressures of more than 12.6 kg / cm ² .

Claims (6)

Patent claims: 1. Use of a compliant thermoplastic material containing an α-olefin polymer, as a sealing compound for the production of seals for container closures, characterized in that, that the resilient thermoplastic material consists essentially of a) a copolymer of a «monoolefin with vinyl acetate, acrylic acid or a Acrylic acid ester, b) a mixture of the copolymer a) with butyl rubber or c) a mixture of polyethylene with polyisobutylene and / or butyl rubber and / or the Copolymer a) and / or chlorosulfonated polyethylene consists. 2. Use according to claim 1, characterized in that the resilient thermoplastic Material essentially made of a copolymer of ethylene with vinyl acetate, acrylic acid or an acrylic acid ester or a mixture of such a copolymer with polyethylene and optionally also butyl rubber. 3. Use according to claim 2, characterized in that the resilient thermoplastic Material consists essentially of a mass, which SO to 81 weight percent polyethylene, 15 to 50 percent by weight of butyl rubber and 4 to 40 percent by weight of an ethylene-vinyl acetate copolymer contains. 4. Use according to claim ? or 3. characterized in that the copolymer of ethylene and vinyl acetate contains 5 to 50, preferably 10 to 40 percent by weight of vinyl acetate. 5. Use according to claim 1, characterized in that the resilient thermoplastic Material consists essentially of a mixture of polyethylene with butyl rubber. 6. Use according to claim 1 to 5, characterized in that a mixture is used, which contains low density polyethylene.