DE3247328A1 - INSERTLESS VACUUM SEAL FROM PLASTIC - Google Patents

Description

Patent Attorneys · · * European «Patent Attorneys Munich Stuttgart

20 "December 1982

ANCHOR HOCKING CORPORATION
109 North Broad Street
Lancaster, Ohio 43130 /V.-St.A.

Our sign A 1899

Linerless vacuum seal made of plastic

The invention relates to improved closures in the form of lids or caps include, for closing containers · made of glass, plastic or other materials, in particular a sprayed "molded or otherwise shaped plastic closure cap, the closure means sealing ribs or rafts, which as an integral part the cap are molded or cast on ",

Plastic closures with closure ribs or rafts Currently used to close containers on various types of packaging »One such The closure is screwed onto the threaded neck of the container and forms a seal when press its ribs or fins against the surface of the container or the rim of the container opening. Such closures are usually referred to as linerless closures »

Bestiinnite packaging requires a closure that is included in the sealed container maintains a vacuum to preserve the packaged product. Although the above described Ordinary type of plastic closures hold a vacuum up to a certain percentage of closed Holds packs is the percentage of packs where the seal does not hold the vacuum sustains, in many cases unacceptably high.

Plastic caps with locking ribs or fins are usually integrally molded from polyolefins, often of the polypropylene type. The lock rafts are Compared to other materials like plastisol ~ seals that are normally used to seal containers are used, relatively rigid. The polyolefin closure fins thus lacks the softness to get one

surface to achieve intimate connection with the top of the container, as is necessary to maintain a vacuum, especially during handling of the packs. Although container _m made it prescribed tolerances, they have perfect surfaces because of associated with their production process problems not always.

Another difficulty with the materials used to manufacture linerless plastic closures is that it is very difficult for other substances to adhere firmly to the polyolefin surfaces.

The way proposed according to the invention to achieve veron

A better seal is a softer one Material such as wax, hot melt, epoxy resin, To apply plastisol or soft plastic to the sealing ribs or fins of the sealing cap. For example paraffin wax and plastisol were examined,

and both improved the ability of the closure to maintain a vacuum. When using This plastisol is applied as a liquid to the closure fins and then heated to the liquid

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] To melt or gel the plastisol into a solid. The liquid plastisol can be applied to the fins by means of a stationary nozzle while the closure is being rotated. As described below, has proved to be useful on the ribs or fins of the plastisol a thickness from 25.4 to 508 /.

The invention is therefore based on the object of the sealing ability Linerless plastic caps, in particular for maintaining a vacuum in sealed packages to create a molded plastic cap that does is suitable for achieving a satisfactory percentage of perfectly sealed vacuum packs, the Sealing and closing are carried out on automatic closing devices at extremely high speeds can.

Another object of the invention is to create an improved linerless closure "made of plastic.

The invention is also to provide a molded linerless closure made of plastic, in which the sealing members of the cap with a relatively are provided with a thin coating of sealing material.

Finally, the object of the invention is to create a molded plastic linerless closure with a melted or gelled and relatively thin sealing coating on the closure fins or other sealing members.

Further subjects of the invention emerge from those described below and used by way of example Embodiments in conjunction with the drawing and the patent claims ι thereby result in various advantages, not expressly referred to in d "<e

will become apparent to those skilled in the art in practicing the invention.

For the purposes of illustration and description, preferred embodiments of the invention have been selected, which are shown in the drawing.

Fig. 1 is a partially sectioned side elevation of one preferred embodiment of the closure cap;

Fig. 2

and 3 are enlarged partial sections through different embodiments of the closure cap according to the invention and
Container;

._ cap and the closed by it

Fig. 4

and Fig. 5 are enlarged partial sections of various embodiments the closure cap according to the invention;

Fig. 6 shows schematically in side elevation a preferred method of applying the soft sealant Coating on the sealing members of the closure,

The closure cap 1 according to the invention has a cover 2 and a jacket 3 adapted to this with threads 4 for engagement in a thread of the to be closed

Container on. The outer surface of the jacket 3 can 30th

be knurled or other holding or grip means 5 for screwing and unscrewing the cap 1 on the or of the container 6. The cover 2, the jacket 3 and the threads 4 form together with sealing means a unitary or one-piece, molded closure cap for the container, which is based on conventional cap injection molding or molding devices is produced.

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Ί There are a number of suitable means of sealing and Closing of containers which are an integral part of the closures and which are usually in the form of Have fins or ribs or rings which extend downwardly from the underside of the closure cap. Sealing and closing means of this general type are described, for example, in US Pat. No. 3,815,771. This and other prior US patents describe protruding ribs or fins that are considered integral Part of the closure cap molded or cast on and arranged so that they are with the brim, cooperate with the bent edge of the container. The fins or ribs work with the brim of the container together and thus create the actual, sealing closure for the contents of the closed container.

As shown, the closure fins 7 are arranged at an angle, both with respect to the closure cap cover 2 as well as with respect to the container rim 8, so that they adapt to the adjacent container rim 8 and take a sealing, locking position,

The improvement according to the invention comprises the application of a thin film 9 of a softer sealant Material on the fins 7. Suitable sealing films include easy-to-apply films such as waxes, hot dip - compounds, epoxy resins, plastisols and other soft plastic materials that are used as a thin film on the fins 7 can be applied.

Films made from these materials have been studied and these thin layers have been found to be the sealants Improve properties of molded closures and, in particular, the ability of the closures to create a vacuum in the closures To maintain sealed containers, increase.

When using a plastisol, this is applied to the closure fins 7 sprayed or otherwise on

] distributed and then heated and fused or gelled to form a continuous, elastic sealing film on the fins. Plastisol films of 25.4 to 508 µm in thickness have been studied and found to be effective in providing the improved sealing effect.

The fused or gelled plastisol generally takes the form of the plastic closure fins

IQ and is in the lock not only by his own adhesive properties, but also through the resulting between the film 9 and the closure fins 7 physical lock held. Although packs made with in the manner described above coated fins were sealed, exposed to elevated temperatures, such as those exposed to resulting from the use of steam in the vacuum-forming sealing system, no clear i

If a molded or molded polyolefin closure is exposed to sufficient heat, it can shrink or melt. In order to avoid this, the melting or gelling of the liquid plastisol must be used heat applied to a solid be relatively mild. Tests have shown that certain copolymer dispersion resins, which have been developed for melting at relatively low temperatures, for this Application are particularly well suited. Temperatures from

"r-

149 to 166 C and times of 3 to 4 minutes successfully applied.

Butyl benzyl phthalate (BBP) plasticizers have been found to significantly reduce the heating period required.

A preferred plastisol composition, the vinyl chloride copolymers and other plastisol components and which melts or at low temperatures gelled is the following:

Approach (phr)

resin 100 1OO 100 Plasticizer (dioctyl phthalate
or butyl benzyl phthalate) 60 100 100 Stabilizer (Ferro 7O7X) 2 1 2 Pigment (Horsehead A-410) - 2 2 Lubricant (Crodamide OR) 5 5 5 Lubricant (Crodamide ER) - 7th Resin used supplier description Vinyl chloride homopolymer Hooker
Tenneco FPC-605
1759 Vinyl chloride vinyl acetate
Copolymer Hooker
Stauffer
Stauffer
Diamond
Shamrock
Tenneco FPC-6338
SCC-40
SCC-52
PVC-7401
0565 Vinyl chloride-vinyl ester- B
Copolymer • F. Goodrich Geon 138

The group of the six copolymer resins listed above has stood out over the homopolymer resins as turned out to be superior because they require less heat of fusion or gelation. In particular the copolymer * Develop resins SCC-40, PVC-7401, Geon 138 and FPC-6338 physical properties with a much lower heat requirement than the FPC-605 or Tenneco 1759 homopolymer

Resins. In addition, the copolymer resins achieve a higher maximum Tensile strength than the homopolymer resins as shown in the following table:

Resin Maximum Tensile Strength

(N / m ² )

PVC-7401 7136000

Geon 138 6860000

FPC-6338 6688000

SGC-40 6619000

SCC-52 6481000

0565 5860000

1759 5412000

FPC-605 5205000

These values not only show that copolymer resins such as SCC-40, Geon 138, PVC-7401 and FPC-6338 are physical Develop properties under milder heat conditions than the homopolymer resins, but they also show that they have a higher inherent strength than homopolymer resins like FPC-605 and Tenneco 1759.

It has been found that copolymer resins such as SCC-40,

therefore Geon 138 and PVC-7401 'are extraordinary for this application are well suited.

The ability of this composition to fuse relatively low temperatures protects the housing of the molded plastic cap from damage during the Coating, the melting or gelation stage.

Fig. 2 shows a coating according to the invention in one middle thickness range, the coating material 9 filling the space between the two closure fins 7. In In this case, the coating provides the sealing connection between the closure 1 and the container

Figure 3 shows a similar closure on a container 6, in which, however, a coating 10 of lesser thickness is turned and in which the coating more the outer shape

] who accept closure-7. Nevertheless, with such coatings with a thickness which is close to the lower limit of the thickness range, an improved, vacuum-sealing ability is achieved.

Figure 4 shows the use of a coating of the above described type on a closure cap 11 with other you titlitte In, the three closure fins 12 different Length and which have a smaller angle with the ■ jÖ cover 13 of the closure 11 form. This plating acts in a similar way and creates the improved sealing properties.

Fig. S shows another Äüsführungsbeispiel in which the closure 14 cooperates in a sealing manner with a container 19, and. in which a coating 16 provides a seal forms between the inclined fins 15 and the bent edge 18 of the container 19.

Fig. 6 shows a preferred method of application these * coatings in a specific, controlled layer thickness. The caps are in rotating shots one typical caulking machine attached. A spray nozzle that is in one for directing a coating spray is held on the sealing members suitable position, one works for the application of the desired Coating thickness for a sufficient time. After applying of the coating, the cap is used if a plastisol or other material requiring curing is used has been placed in a suitable heating device for hardening or for the gelation step.

As a result, the additional preferred soft cover creates an improved, liner-free closure cap with vacuum-sealing properties. The caps are manufactured in the currently usual manner , the coating steps being carried out in addition.

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Various changes in shape, structure and mutual Assignment of the parts described can take place without leaving the spirit and scope of the invention and without, to sacrifice any of their benefits.

Claims (11)

Claims 1. Molded cap with one-piece molded on Closure means for sealing a container, characterized in that the surfaces the closure means are covered with a relatively thin coating of a material, which is softer than the material from which the molded closure is made = 2. Closure cap according to claim 1, 'characterized in that that it has one or more raft-like closure members which provide the means for the interaction with the container and the coating applied to the surfaces of the closure means. 3 »Closure cap according to claim 1 or 2, characterized * that the coating has a thickness of about 25 _f 4 to 508 / µm» 4 «Closure cap according to one of claims 1 to 3, characterized in that the coating consists of a Wax, a hot dip, an epoxy resin or a Plastis.ol consists " 5. Closure cap according to claim 4, characterized in that that the coating consists of a plastisol. 6. Closure cap according to claim .5? characterized in that the plastisol resin is a PVC homopolymer. 7. Closure cap according to claim 5, characterized in that the plastisol resin is a copolymer of the
Vinyl chloride is. 8. Closure cap according to claim 7, characterized in that the plastisol resin is a vinyl acetate-vinyl chloride copolymer is. 9. Closure cap according to claim 7, characterized in that the copolymer of the SCC-40, Geon 138, PVC-7401 and FPC-6338 existing group is selected. 10. Closure cap according to claim 7, characterized in that the coating has a composition
those from the following group of approaches, respectively
in parts by weight, is selected Approach (Phr) 12 3 25 ■ " Resin (vinyl chloride Copolymer) 100 100 Ί00 Plasticizer (dioctyl-> phthalate or butylbenzyl phthalate) Stabilizer (Ferro 7O7X) 3Q pigment (Horsehead A-410) Lubricant (Crodamide OR) Lubricant (Crodamide ER) 11. Closure cap according to claim 7, characterized in that the plasticizer and butyl benzyl phthalate Resin is a vinyl chloride copolymer " 60 100 100 2 1 2 _ 2 2 5 5 5 " _ » 7th