JPS6235888B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing crowns and caps with bottle mouth sealing liners having a foamed sponge sealing surface.

Cork discs have been used for many years as crowns and cap liners for the purpose of sealing bottle mouths, but around 10 years ago, a new crown liner made use of the excellent elasticity of polyvinyl chloride resin appeared in the industry. , so-called resin liners became popular. However, later on, the safety of the plasticizer dioctyl phthalate and residual monomers in polyvinyl chloride resin became a major issue, and efforts were made in various fields to develop safer plastic liners to replace polyvinyl chloride resin. It was done. As a result, a liner using polyethylene resin and its copolymer resin was born, which is tasteless and odorless and is the safest resin for food packaging materials.

However, although polyethylene and copolymer resins have been highly evaluated as the safest resins from a sanitary standpoint, as mentioned above, polyvinyl chloride resins do not have the elasticity that is particularly required as a material property for crowns and cap liners. Various attempts have been made to improve polyethylene liners to ensure the sealing of bottle mouths, but they still have many drawbacks.

As an example, as shown in Fig. 1, a crown and cap with a liner, a so-called crown with a molded liner, are produced by supplying a predetermined amount of molten polyethylene resin into the crown and cap 1, and providing a predetermined seal liner 2 through a molding punch. And the cap was hot,
This molded liner crown exhibits extremely excellent sealing performance for normal and undamaged bottle caps that meet the standards, but it can be used against bottle cap defects such as cracks, cracks, hair cracks, and defects using polypropylene. Due to the lack of elasticity of the resin, it has poor adaptability, and a gap is created between the bottle mouth contact portion 4 and a reliable seal cannot be obtained. Furthermore, in order to ensure quality based on the premise of using molded liners, bottle opening dimensions and appearance inspection standards have become more stringent than necessary during the bottle making process, and bottle openings that occur during repeated use can be prevented. As a result, the frequency of reuse is reduced, which requires unnecessary labor and expense, and has the drawback of producing excessive quality and high costs.

To compensate for this drawback, a crown with a foamed polyethylene liner is made by foaming a polyethylene resin into a sheet, punching out a disk shape of a predetermined size from the foamed polyethylene sheet, and attaching it to the crown and the inner surface of the cap via an adhesive. However, it had major drawbacks in terms of manufacturing cost and quality assurance. In other words, the process requires multiple steps such as sheet manufacturing, punching, packaging, shipping, transportation, and crown and cap inner mounting to produce the crown and cap liner, and the manufacturing cost for each process must be considered. This resulted in a significant increase in cost, and the material yield due to the punching process was poor, making the cost even higher. In addition, because the punched liners are packed, packed, transported, or stacked in stock in an unprepared state, the surface of the liner may be dented, deformed, or wrinkled due to deformation, which can be critical to sealing the bottle mouth. Defects that cause serious problems may occur, or
This was a major drawback in terms of quality assurance, such as the liner falling off during the process.

In addition, thermoplastic resin and foaming agent are extruded using an extruder at a temperature higher than the decomposition temperature of the foaming agent, and a fixed amount of the foamed resin is supplied into the crown and cap, which is then molded with a cooled punch and sealed at the bottle mouth. The part is made of foam,
There was a crown with a liner made of non-foamed material in the center, but since this crown with a liner presses the foamed resin with a molding punch, the foamed state tends to be compressed and turn into a solid. The drawback was that a foamed liner could not be obtained. Furthermore, although this method can be expected to have a certain effect on resins with extremely good elasticity such as polyvinyl chloride resin, it is not effective on resins with extremely poor elasticity such as polyethylene resin. It was not possible to create a crown and cap with a liner that had excellent sealing properties.

The present invention eliminates these drawbacks and provides an ideal crown and cap with a foamed polyethylene liner.

That is, in the present invention, in order to obtain a foamed polyethylene liner having a uniform low or medium density, a blowing agent is first mixed into a polyethylene straight polymer or a polyethylene copolymer resin. Next, while melting the mixed resin at a temperature below the decomposition temperature of the foam material and extruding it with an extruder, a predetermined amount is supplied to the crown and the inner surface 1 of the cap through a cooled molding punch as shown in Fig. 2. Mold into shape 6a. At this point, the blowing agent is of course not decomposed, and the molten polyethylene resin 5 containing the blowing agent flows uniformly onto the crown and the inner surface 1 of the cap by the forming punch, forming the desired shape 6a. Next, the crown with the liner and the cap 1 are heated to a temperature higher than the decomposition temperature of the foaming agent contained in the liner. At this point, the resin softens, and at the same time, the gas generated by the decomposition of the blowing agent forms a closed cell sponge liner 6b as shown in FIG. In this case, the amount of foaming agent, heating temperature, and time are not particularly limited, but by adjusting these, a foamed liner with a uniform density and a desired height, width, hardness, etc. can be obtained.

However, if this is done, the central part will partially foam and the appearance will not be good, the shape of the thick foamed part of the outer seal part will become uneven due to the bubbles on the surface becoming rough, and the shape of the outer seal part will become foamed. The heated expanded polyethylene liner is used to prevent problems such as unstable sealing properties due to changes in conditions, and to ensure that the seal liner shape is a constant size and stable liner. Emboss the foamed polyethylene liner with a molding punch that has been cooled again.The foamed liner 6 is shaped into the desired shape as shown in Figure 4.
get c.

According to this method, a foamed polyethylene liner in the desired shape can be obtained by stamping the foamed liner with a cold molding punch while it is still warm, suppressing the foaming and preventing deformation, resulting in stable sealing performance. can get.

Next, examples will be shown.

First, polyethylene resin (Cocalone EH-
30) For 100 parts by weight, foaming agent (UNIFORM AZ
-H) 0.5 parts by weight and 1.0 parts by weight of liquid polybutadiene resin are mixed and sufficiently dispersed, and then extruded at a temperature of 150°C, at which temperature the blowing agent does not decompose.
Next, 0.25 g of this extruded molten resin is supplied to the crown and the inner surface of the cap, and molded into the desired liner shape using a cooled liner molding punch. After this, 20 minutes in an infrared heated oven on a propane gas burner.
When heated for seconds, the bottle mouth seal will foam sufficiently.
The crown and cap have a foamed polyethylene liner with almost no foaming in the central part of the crown and cap. In this case, the specific gravity of the bottle mouth seal part of the foamed polyethylene liner can be adjusted to 0.3 to 0.9 g/cm ³ by adjusting the amount of foaming agent, heating temperature, and time.
Select the desired specific gravity within the range. While the foamed liner is still warm, half of the crown and cap with a foamed polyethylene liner is pressed into a desired shape using a cooled liner molding punch to obtain a crown and cap with a foamed polyethylene liner.

The thus obtained crowns and caps with foamed polyethylene liners and the embossed crowns and caps with foamed polyethylene liners were tested for leakage (24 pieces each with the former as A and the latter as B).
After heating the volume of carbonated water at 65°C/Hr, and measuring the internal pressure of the bottle with the liner crown and cap sealed, the number of leaks was 3/24 for A and 0/24 for B. .

As described above, the foamed polyethylene liner of the present invention was also tested with ethylene α-olefin copolymer, ethylene vinyl acetate copolymer, or blend polymers thereof, and similar good effects were obtained.

As described above, according to the present invention, the lack of elasticity, which was the biggest drawback in the past, has been solved, and the bottle opening can be reliably sealed, and the conventional crown and cap with a solid polyethylene liner have sufficient sealing performance. It exhibits excellent sealing properties even for bottle opening defects (broken bottle opening, non-flat opening, etc.), and has excellent effects such as being able to always obtain a liner with a stable seal shape.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional molded liner crown in use. FIG. 2 is a sectional view of the liner-equipped crown and cap of the present invention before foaming. FIG. 3 is a sectional view of the crown and cap with a foamed polyethylene liner of the present invention in a foamed state. FIG. 4 is a cross-sectional view of a crown and cap with a foamed polyethylene liner after re-embossing the liner of the present invention. 1... Crown and cap, 6a... Liner,
6b...Liner, 6c...Liner.

Claims (1)

[Claims] 1. A blowing agent is mixed with a polyethylene straight polymer or copolymer such as polyethylene resin, ethylene vinyl acetate copolymer, ethylene acrylic acid copolymer, ethylene α-olefin copolymer, etc., and the above blowing agent is melted at a temperature below the decomposition temperature of the blowing agent. The containing resin is extruded by an extruder, a predetermined amount is supplied to the inner surface of the crown and the cap, and after molding into the desired liner shape through a cooled molding punch, the crown and the cap are heated to a temperature higher than the decomposition temperature of the blowing agent. A method for producing a crown and a cap with a foamed polyethylene liner, in which the foamed polyethylene liner is formed into a foamed polyethylene liner, and then the foamed polyethylene liner is embossed with a molding punch that has been cooled again to obtain a foamed liner in a desired shape.