JPH03270927A - Production of plastic container and plastic container - Google Patents

Abstract

PURPOSE: To permit a cover to be repeatedly press-fitted and removed by applying a second polymer material softer than a first polymer material to a cover ring and a cover sealing zone formed by the first polymer material. CONSTITUTION: A cover ring 16 and a cover 14 of a plastic container are formed of a first polymer material which is tolerant to a solvent of a solvent-based liquid product while sealing zones 34, 36 are respectively formed at the cover ring and the cover so as to be sealed state respectively when both are press- fitted. A second polymer material softer than the first polymer material is applied to this sealing zone. The second polymer material produces an annular thin sealing layer 38 in the sealing zone, thereby permitting the cover to be repeatedly press-fitted and removed in use.

Description

Detailed Description of the Invention A0 Object of the Invention (1) Industrial Application Field The present invention relates to a method for manufacturing plastic containers, particularly wide-mouthed plastic containers for solution-type liquid products such as glossy paints, varnishes, and inks. . The invention also relates to plastic containers produced by such a method, and also to the plastic containers themselves.

(2) Prior Art Plastic containers for water-based paints have become commonplace and have become an important substitute for the long-used metal paint cans.

However, various problems have been encountered in providing plastic containers for gloss paints, varnishes, inks, etc., as such containers have unforeseen drawbacks, particularly with respect to airtightness.

Polypropylene (PP) and polyethylene (HDPE)
Most of the above problems could not have been foreseen due to the success of plastic containers for water-based paints molded by. It has been found that the above materials, namely polypropylene and polyethylene, are not suitable for use in conjunction with the solvents contained in glossy paints, and polyethylene terephthalate (PE)
It has been found that other plastic materials are suitable for the above purpose, such as plastic formulations based on T).

For example, a polyester plastic material sold by DuPont under the trade name 5elar-P-T can be used.

Indeed, it is reasonable to expect that a lid ring molded from a solvent-resistant plastic material and a cooperating press-fit lid would provide an adequate hermetic seal for the above purpose.

In fact, many plastic products with tight tolerances are well available on the market, and therefore there are no serious problems with the sealing properties of plastic containers, especially considering the elasticity of these materials and the advanced technology for shaping them. It seemed like there wasn't.

Nevertheless, experience has shown that this is not the case; at the time of filing of the present application there were no plastic containers for gloss paints on the market, and that publications earlier proposed new and improved sealing tank bottoms. The absence of this indicates that the above-mentioned problems exist.

Of course, most problems of this kind can be solved at expense by laboratory and workshop techniques, including precision manufacturing methods, reduced tolerances to the lowest possible extent, and very strict quality control. be able to. However, these measures are not acceptable where the product necessarily has to compete with widely available and easily manufactured metal products. The general direction is to improve seal designs that are incorporated into container lid rings and/or the lid itself. The advantage of such a solution is that no matter how complex the seal design is, it can be manufactured in large quantities by molding, given the relative ease and speed of molding the product from a single uniformly supplied plastic material. If it is suitable for this purpose, the unit price on a high capacity basis may be relatively low.

(3) Problems to be solved by the invention According to the research of the present inventor, the conventional solutions to the above problems are as follows:
We consider that the dual requirements of maintaining adequate sealing levels while mass producing with normal manufacturing tolerances to avoid the formation of a skin layer of glossy paint over a relatively short period of time are probably not met. be.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a plastic container and a plastic container itself which are improved in view of the above-mentioned or general problems.

B1 Structure of the Invention (1) Means for Solving the Problems In order to remotely achieve the above object, the present invention provides a wide-mouthed plastic container for solution-type liquid products such as paint, which has a press-fit type lid. A manufacturing method, comprising the steps of: molding a lid ring of a plastic container to give the shape of a wide mouth; molding a lid that fits into the wide mouth; the lid ring and lid are formed using a solution. The lid ring and lid are molded of a first polymeric material that is resistant to the solvents of the liquid product and have cooperating sealing zones for sealing together when the lid is press-fitted to the lid ring. a second polymeric material or a composite material, which is different from the first polymeric material and softer under the processing conditions, in the sealing zone; The material is applied in liquid or semi-liquid form to the sealing zone to form a thin annular sealing layer which adheres to the first polymeric material and between the sealing portions of the lid and lid ring in the sealing zone. The present invention is characterized by providing a method for manufacturing a plastic container, which provides a sealing structure and allows repeated press-fitting and removal of the lid during use.

(2) Effect According to the above feature, the above-mentioned sealing problem can be largely eliminated, or at least substantially reduced, by adding a simple step to the conventional manufacturing process. The inherent simplicity and ease of production of plastic molded elements is ensured by not requiring significant improvements in manufacturing tolerances and by avoiding imposing undue complexity on the sealing structure. Furthermore, the above-mentioned sealing problem can also be solved at the same time with a small additional cost which is completely acceptable.

In fact, if prior proposals allow for the extra cost associated with sophisticated seal structures and/or precision manufacturing techniques, grinding operations, etc., there may be no extra cost in the present invention.

In an embodiment, the plastic container, including the lid ring and the lid itself, is conventionally molded from a plastic material that is resistant to the solvents contained in gloss paints. This first primary polymeric material is a much harder material than the PP or HDPE mentioned above. Also, this is a very difficult material to mold to fit. However, in actual cases, shrinkage and/or
Alternatively, distortions may be found to be acceptable considering the subsequent application of a second polymeric material or composite material, softer than PP or HDPE and different from said first polymer, to the sealing location.

The production of large volume molded articles incorporating two different polymeric materials was previously thought to be completely unacceptable in view of the complex production techniques involved. However, this problem is solved at an acceptable cost by simply providing a second polymeric or composite material at the sealing location, which is normally not in direct contact with the liquid itself within the container.

(3) Examples Examples of the present invention will be described below with reference to the accompanying drawings.

As shown in the drawings, the plastic container 10 is comprised of a cylindrical body 12 and a lid 14 that engages a lid ring 16 welded to the body 12.

All of these components are molded from a PH7 or similar first polymeric material that is resistant to solvents used in gloss paints, printing inks, varnishes, and the like.

The plastic container 10 is published in International Application Publication No. W○8B1(1).
□ is described in detail in Publication No. 5015, the entire disclosure of which is incorporated herein by reference.

The container 10 has a removable lid locking or latching means 18 for protection against tampering by children and the like.
is a removable latching means 1 which is a part of 114.
The sealing means 20 provided at a position apart from 11
4 and has a substantially cylindrical skirt 22 having an annular rib 24 having a substantially wedge-shaped cross section, and the rib 24 can be engaged with an annular seal flange 26 formed on the lid ring 16. . The ribs 24 face radially outward and the sealing flanges 26 face radially inward.

These members are sized to cooperate as shown in FIG. 1 prior to sealing engagement. Figure 2 shows the rib 2 after the lid 14 is pressed downward and into a sealed and secured state.
4 and a seal flange 26. FIG.

When the lid 14 is removed, the uppermost edge of the open top container 10 becomes the edge 28 of the lid ring 16.

The latching state of the removable latching means 18 shown in FIG.
6 is obtained by mutual cooperation of parallel horizontal latching surfaces 30 and 32 formed in each case.

As shown in FIG. 1, lid rings 16 and 114 have sealing zones 34 and 36, respectively, which cooperate with each other to form a seal when the lid is press-fitted to the position shown in FIG.

The lid 14 and lid ring 16 are manufactured using known manufacturing techniques. After the plastic material is removed from the mold,
It is cooled, with the natural shrinkage and distortion that accompanies such cooling. Thereafter, such a uniformly constituted article of PET plastic material is at this stage coated with a second polymeric material softer than said first polymeric material to form a thin annular sealing layer 38 affixed to the lid 14. Apply polymeric or composite materials. The sealing layer 38 is attached to the lid 14 and the lid ring 16.
provides a cooperating seal structure between the seal zones 34 and 36 of the lid 14 and allows repeated press-fitting and removal of the lid 14.

The sealing layer 38 is formed by continuously applying a liquid or semi-liquid polymeric or composite material around the annular sealing zone of the lid 14 while rotating the lid.

Preferred composite materials for the sealing layer include water-based rubber composite materials in which water acts as a curing inhibitor.

After being applied to the lid, it hardens as water evaporates.

Alternatively, hot melt polyethylene composites may be used. We believe that it is also possible to develop other suitable composite materials. For example, suitable polymers can be used, including natural and artificial elastomers, as well as their composites, including fillers and additives, in which This includes composite materials made from polymers conventionally used to mold plastic containers, as well as other composite sealing materials. The nature of the composite material selected for a given application will depend on the solvent in the liquid stored in the container.

As clearly shown in FIG. 1, the sealing layer 38 is
The sealing zone 34 of the lid ring 16 is applied at the precise location on the lid 14 that it engages in the condition shown in FIG.

After the liquid or semi-liquid sealing composite is applied, it is dried or cured, and the product is then immediately processed. The sealing composite material may be applied immediately after molding, which facilitates rapid curing and drying due to the relatively high temperature of the molded plastic component.

In use, the sealing layer 38 has a much lower hardness than the material of the rest of the plastic container 10, which provides an effective airtight seal when the lid 14 is in the position shown in FIG. Normal manufacturing tolerances due to shrinkage and distortion in tc-shaped plastic components are compensated for by the inherent visibility and elasticity of the sealing layer. Since the sealing layer is applied in a single additional manufacturing step that is simple and quick, its cost is relatively low.

Interestingly, in the embodiments described above, a second, softer, polymeric or composite material shaped sealing layer 3 is used.
8 eliminates the sealing problems inherent in molded PET constructions. Because the manufacturing technique used is relatively simple, this additional step also reduces the cost of increasing manufacturing tolerances and product defects by using two polymer materials instead of traditional one polymer material manufacturing. Since the rate increase can be avoided, it is possible to accept the offer.

This embodiment can be easily applied by using different shapes for the container lid and lid ring. The materials of the lid and lid ring may be different from those mentioned above; suitable plastic materials resistant to solvents used in glossy paints, varnishes, printing inks, etc. are generally PP or HDP.
It has a substantially higher hardness than E. Any of these polymers may be used and still obtain the benefits of the present invention. In practice, polypropylene and high density polypropylene can be sealed very easily using molded seal components, but similar sealing effects may be obtained.

Among other materials suitable for the body of the plastic container to which the present invention can be applied are polyamides.

Of course, the shape of the lid and lid ring may be any desired to accommodate the sealing layer; for example, the lid may be provided with a small step at the sealing zone.

The sealing zone may be arranged in an annular, generally groove-shaped area in cross-section and received by a clipping action on a cooperating annular portion on the lid ring.

Further, the annular seal layer may be formed so that the thickness decreases from the center toward at least one annular edge of the seal layer when viewed in cross section.

Furthermore, the sealing layer may also feature a further annular portion for receiving the annular portion of the lid ring.

Additionally, the polymeric or composite material may be applied to the plastic container and then allowed to cure gradually.

C1 Effects of the Invention As described above, according to the present invention, a second polymer material, which is softer under processing conditions than the first polymer material, is added to the sealing zone.
applying a polymeric material or composite material,
A second polymeric material is applied in liquid or semi-liquid form to the sealing zone to form a thin annular sealing layer, which adheres to the first polymeric material and covers the sealing zone of the lid and lid ring. This provides a sealing structure between the sealing parts of the lid and allows repeated press-fitting and removal of the lid during use, so the hardness of the sealing layer is lower than that of other parts, which provides an effective and airtight sealing effect. In addition, manufacturing tolerances due to shrinkage and distortion in the molded plastic components are compensated for by the inherent flexibility and resiliency of the sealing layer. Furthermore, the sealing layer is applied in a single additional manufacturing step, which is simple and quick;
Its cost is low.

[Brief explanation of drawings]

Figure 1 is an enlarged vertical cross-sectional view of the main parts of the lid and lid ring of a plastic paint container with the lid not pushed into the sealing and locking position, and Figure 2 is an enlarged longitudinal cross-sectional view of the main parts of the lid and the lid ring when the lid is not pushed into the sealing and locking position. FIG. 2 is a diagram similar to FIG.

Claims (15)

[Claims] (1) A method for manufacturing a plastic container with a press-fit type lid and a wide mouth for solution-based liquid products such as paint, the lid ring of the plastic container being molded to form a wide mouth. molding a lid that fits over the wide mouth; the lid ring and lid being molded from a first polymeric material that is resistant to solvents of solution-based liquid products; The lid ring and the lid are each formed with a cooperating sealing zone for sealing each other when the lid is press-fitted to the lid ring, wherein the sealing zone includes the first polymeric material and the lid. is different and includes applying a second polymeric material or composite material that is softer under processing conditions, said second polymeric material being applied to said sealing zone in liquid or semi-liquid form to form an annular thin layer. forming a sealing layer, the sealing layer adhering to the first polymeric material and providing a sealing structure between the sealing portions in the sealing zone of the lid and lid ring;
A method for manufacturing a plastic container, which allows repeated press-fitting and removal of a lid during use. (2) A press fit, in which a liquid or semi-liquid second soft polymeric material or composite material is applied to the sealing zone of the plastic container and/or lid to form an annular sealing layer. A method of manufacturing a plastic container with a lid of the same type. (3) A method according to paragraph (1) or (2), characterized in that the second polymeric material or composite material is applied to the sealing zone of the lid of the plastic container. (4) The sealing zone is arranged in an annular region having a generally groove-shaped cross section and receives a cooperating annular portion provided on the lid ring by a clipping action. Method. (5) Any one of items (1) to (4), wherein the annular seal layer is formed so that the thickness decreases from the center toward at least one annular edge of the seal layer when viewed in cross section. Method described in Crab. (6) The method according to item (4), characterized in that the sealing layer is formed with another annular portion for receiving the annular portion of the lid ring. (7) The method according to any one of items (1) to (6), wherein the polymeric material or composite material is gradually hardened after being applied to the plastic container. (8) A plastic container having a lid manufactured by the method according to any one of items (1) to (7). (9) A plastic container having a lid ring manufactured by the method according to any one of items (1) to (7). (10) A wide-mouth plastic container for solution-based liquid products such as paints, comprising a lid and a lid ring, the lid being press-fittable to the lid ring; The lid and lid ring are each formed with cooperating sealing zones for press-fitting the lid onto the lid ring and sealing each other, while being resistant to the solvents of solution-based liquid products. A thin annular sealing layer of a second polymeric or composite material applied to the sealing zone is attached to the lid or lid ring to create a seal structure between the sealing portions of the lid and lid ring in the sealing zone. 1. A plastic container, characterized in that the lid is press-fitted and removed repeatedly during use. (11) A plastic container having a press-fit lid, wherein the lid or a lid ring cooperating therewith is provided with a sealing layer, and the sealing layer is made of a second polymeric material or composite material that is softer than the plastic container. A plastic container made from materials. (12) The plastic container according to item (10) or (11), wherein the second polymer material or composite material is applied to a sealing zone of the plastic container. (13) The sealing zone is arranged in an annular zone having a substantially groove-shaped cross section and receives a cooperating annular portion provided on the lid ring by a clipping action. plastic container. (14) Item (11) characterized in that the annular seal layer is formed so that the thickness becomes thinner from the center toward at least one annular edge of the seal layer when viewed in cross section.
- The plastic container according to any one of (13). (15) The plastic container according to item (13), wherein the sealing layer is provided with another annular portion for receiving the annular portion of the lid ring.