JPH0471788B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a container lid with a heat-resistant liner, and more particularly to a container lid with a liner that improves the tendency for the opening torque to decrease when a package consisting of a container and a lid is heat-treated or stored in a hot state. Liners made of thermoplastic resins such as polyethylene are widely used as sealing liners or gaskets for container lids because they can be thermoformed, have excellent hygiene and flavor retention, and have appropriate cushioning properties. However, it is recognized that it still has drawbacks for certain applications as container lids. That is, in a package formed by sealingly engaging a container lid with a thermoplastic resin liner with a container opening such as a pin, it is assumed that the opening torque is maintained at a certain level that is satisfactory during this engagement. However, if the container is subjected to heat treatment such as heat sterilization after being bottled, or if it is sold while being stored hot in a vending machine, etc., the opening torque of the container becomes excessively small, which may result in poor sealing. There is often a tendency for the container lid to loosen due to unintentional rotation or the like, resulting in leakage of contents or outside oxygen. The cause of this is thought to be that while thermoplastic resins can be easily thermoformed into any liner shape, they tend to flow easily when heated, resulting in the aforementioned reduction in opening torque. It will be done. Furthermore, in container lids equipped with olefin resin liners such as polyethylene, the liners are attacked by heat and content vapor during the heat treatment and hot storage described above, resulting in so-called environmental stress cracking. However, there is also the problem that physical properties such as drop impact resistance are significantly reduced. Therefore, an object of the present invention is to maintain the opening torque of the container lid at a constant level without significantly decreasing even when a package consisting of a container and a lid is subjected to heat treatment after being sealed or stored at a high temperature. held at the level,
It is an object of the present invention to provide a container lid with a heat-resistant liner that provides excellent sealing reliability as a result. Another object of the present invention is to provide a new liner that has excellent cushioning properties, sealing reliability, environmental stress cracking resistance, and impact resistance, and that these properties do not change even with thermal history after sealing. Provide a container with a lid. According to the present invention, in the container lid with a liner,
The liner material is a heat-resistant material characterized in that it is made of a blend containing a hydrogenated block copolymer of an alkenyl aromatic hydrocarbon and a conjugated diene and a polyolefin in a weight ratio of 10:90 to 80:20. A container lid with a plastic liner is provided. In FIG. 1, which shows the container lid of the present invention together with the container mouth, the container lid shell 1 includes a disk-shaped top plate portion 2 formed from a painted metal plate and a cylindrical-shaped top plate portion 2 that hangs down from the periphery of the top plate portion. It consists of a skirt part 3. Inside the container lid shell 1, a disc-shaped liner 4 made of a specific resin or resin composition, which will be described in detail below, is provided on the underside of the top plate 2 via an adhesive layer 5. . The periphery of the liner 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.
In the skirt portion 3 of the container lid, adjacent to the lower edge,
A pilf-proof mechanism consisting of perforations 10, which is known per se, may be provided. An important feature of the present invention is that the liner 4 contains the aforementioned hydrogenated product of the block copolymer of alkenyl aromatic hydrocarbon and conjugated diene and polyolefin in a weight ratio of 10:90 to 80:20. It consists in forming from a blend. As already mentioned, low-density polyethylene can be thermoformed into liners at relatively low temperatures and has excellent liner properties such as cushioning properties. It has been observed that when the bottle mouth is capped, the initial opening torque is generally maintained at a high level of 20 to 40 kg/cm. However, when this sealed package is subjected to heat treatment at 80° C. for 30 minutes, it is recognized that the opening torque decreases to an extremely low level of 3 kg/cm or less. Furthermore, this heat treatment causes environmental stress cracking of the liner and a significant decrease in impact resistance. According to the present invention, the thermoplastic resin for liner formation contains a hydrogenated product of a block copolymer of an alkenyl aromatic hydrocarbon and a conjugated diene and a polyolefin in a weight ratio of 10:90 to 80:20. By selecting a blend, even when the liner after sealing is subjected to the heat treatment described above, the opening torque can be adjusted to the desired level from the standpoint of sealing performance and ease of opening.
The liner can always be maintained within the range of 15 kg/cm to 15 kg/cm, and the liner can have excellent environmental stress cracking resistance and impact resistance regardless of heat treatment. The hydrogenated block copolymer used in the present invention is
Styrene-butadiene rubber (SBR) is thermoplastic and can be easily thermoformed into any liner shape by extrusion molding, injection molding, etc.
This hydrogenated block copolymer is clearly distinguishable from thermoplastic styrene rubbers in that the double bonds in the conjugated diene units incorporated into the polymer chain are hydrogenated and saturated. -Butadiene-
It is distinguished from styrene block copolymer (S-B-S) and styrene-isoprene-styrene block copolymer (P-I-S). Not only S-B-S block copolymer and S-
The liner material made of I-S block copolymer is
Even if the liner has excellent elastic properties under untreated conditions, after undergoing high-temperature thermal history, the unsealing torque tends to decrease as a result of excessive stress relaxation. The alkenyl aromatic hydrocarbon unit of the hydrogenated block copolymer used in the present invention has the following formula: In the formula, R ₁ is a hydrogen atom or a lower alkyl group, and R ₂ is a hydrogen atom or a lower alkyl group. Mention may be made, in particular, of monomers of the formula In the formula, R ₃ is a hydrogen atom or a lower alkyl group, and examples thereof include monomers represented by the following, particularly those consisting of butadiene and isobrene. Polymerization block of alkenyl aromatic hydrocarbons (A)
is preferably in the range of 2 to 33% by weight of the total block copolymer from the viewpoint of rubber-like elastic properties and thermoformability.
It is desirable that the degree of hydrogenation is 70% or more, particularly 90% or more, in order to suppress the decrease in opening torque after heat treatment to a low level. Polymerization block of alkenyl aromatic hydrocarbons (A)
has an average molecular weight of 4,000 to 115,000, while the conjugated diene polymerization block (B) preferably has an average molecular weight of 20,000 to 450,000 in view of the elastic properties and hygienic properties required for the liner. The bonding type of both polymer blocks is most preferably ABA type, but B-A-B type or A-B-A type is most preferable.
-B type can also be used. Hydrogenated block copolymers are, for example,
As described in JP-A-6636, etc., it is easily produced by hydrogenating a block copolymer of an alkenyl aromatic hydrocarbon and a conjugated diene in the presence of a hydrogenation catalyst such as Raney nickel. Examples of the polyolefin used in the present invention include low-, medium-, or high-density polyethylene, crystalline polypropylene, crystalline ethylene-propylene copolymer, ethylene-propylene-butene-1 copolymer, and ionically crosslinked olefin copolymer ( ionomer), ethylene-vinyl acetate copolymer, or a combination of two or more thereof. The liner resin used in the present invention can be blended with known compounding materials according to known formulations. For example, in order to adjust the opening torque to a level that makes it easy to open, fatty acids, derivatives such as amides thereof, and lubricants such as various waxes are added, and titanium dioxide, etc. are added to color the liner or to impart opacity. White pigments such as carbon black, red pigment, tartrazine lake, and other coloring pigments can be blended, and calcium carbonate, calcium carbonate, etc. can be added to adjust the physical properties.
Fillers such as talc, clay, and barium sulfate can be added. In addition, an anti-blocking agent such as silica may be added to prevent blocking, and an antioxidant such as phenols having external effects may be added to prevent thermal deterioration during liner processing or sterilization. In the present invention, the aforementioned hydrogenated block copolymer () and polyolefin () are used as a liner material in the form of a mixture, that is, a blend, and the blending ratio with them is: = 10:90 by weight. Use within the range of ~80:20. In particular, it is desirable to use the weight ratio of:=20:8 to 60:40. Within the above range, by blending the hydrogenated block copolymer with the polyolefin, the excellent spirit of the polyolefin can be maintained, while the decrease in opening torque due to thermal history can be significantly suppressed.
Furthermore, it is possible to significantly improve the tendency for environmental stress-sucking and the deterioration of sealing performance due to impact. In other words, if the blending ratio of the hydrogenated block copolymer is less than the above range (:=10:90), there is a strong tendency for the opening torque to decrease due to thermal history, and furthermore, cracks occur in the environmental stress cracking test (ESC). This increases the tendency for liquid leakage due to impact tests and reduces sealing reliability. Furthermore, when the blending ratio of the hydrogenated block copolymer exceeds the above range (:=80:20), the opening torque tends to increase and is maintained at a high level, while the ease of opening tends to decrease. Furthermore, although results show that even if cracks occur in ESC, they occur very little, liquid leakage does occur in impact tests. Compared to the case where it is within the above range, sealing reliability, easy opening, impact resistance,
Poor overall evaluation of hygiene, flavor retention, etc. In addition, it is disadvantageous in terms of economy as the raw material prices are high. The resin or resin composition described above can be formed into a liner 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 liner on the spot. This molding method is advantageous in that it is possible to form a thick-walled portion with a raised wall that is desirable from the viewpoint of sealing performance around the liner that engages with the container opening. Of course, instead of melt extruding the resin composition directly into a container lid shell, the composition may be formed into a disc or other shaped preform.
The preform may be filled into a container lid shell, heated, and then formed into a liner. Alternatively, the resin composition described above can be formed into a seal by melt extrusion or roll molding, the sheet can be punched out into disk shapes, and the disks can be applied one by one into the container lid shell as a liner. In this case, the liner molding sheet may be made of a single layer of the resin or resin composition of the present invention, or may be a laminate in which the surface to be engaged with the container opening is made of at least a layer of the resin composition of the present invention. It can be a body. Such a laminate is produced by dry laminating, for example, a substrate such as paper, aluminum foil, a foam sheet, a polyester film such as Mylar, and a layer made of an olefin resin composition.
It can be manufactured by bonding by extrusion coating, coextrusion, or other means. The metal material constituting the container lid shell may be, for example, a light metal plate such as aluminum or a tin-plated steel plate.
They may consist of coated steel sheets, such as electrolytically chromated steel sheets (tain-free steel), and these metal materials may themselves be coated with well-known protective paints, such as epoxy-phenol type paints. can. The coating metal plate can be easily formed into a shell by drawing, deep drawing, drawing, ironing, press forming, or the like. 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. 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-on caps, pilfer-proof caps, lage caps, press-on/swist-off caps, and twist-off caps. The container lid can be fastened or sealed to the container neck.
Roll-on (threaded by threaded roller),
This can be done by press-on, screw-on, etc. The invention is illustrated by the following example. Example 1 Epoxy resin was applied to an aluminum plate with a thickness of 0.24 mm.
70 parts by weight, 10 parts by weight of urea resin, and polyethylene oxide
An adhesive paint consisting of 20 parts by weight and an organic solvent was roll coated and then heated at 200°C for 10 minutes to prepare a coated board. Next, the cap shell is press-molded so that the painted surface is on the inside. The obtained cap shell is heated to approximately 150℃ using a high-frequency heating device, and
Extrude resins with various compositions shown in the table from an extruder, and introduce the molten resin into the inside of the cap shell with a rotating blade,
A cap with a liner was immediately extruded. The weight of the liner resin at this time was 0.30g, and the shape of the molded liner and cap shell was
It is shown in Fig. 3 and Fig. 3. Carbonated beverages (gas pressure
2.5VOL) 100 c.c. and sealed with the various caps mentioned above that have been manufactured for about one week. Then 20 at 80℃
After immersing in hot water for 1 minute, immersing in 50℃ for 10 minutes, and leaving to cool indoors. 24 hours after cooling the filling process,
After being stored upright for one month under the conditions of 20℃-40%RH,
The opening torque of the cap was measured for each sample using a torque meter. Immediate torque means after filling
Torque value measured 10 minutes after heat treatment at 80℃ for 20 minutes and cooling at 50℃. Also, environmental stress cracking test (ESC) is a test using a sample prepared under the same conditions as the cap torque measurement sample described above.
After being left in a constant temperature room at 50°C for one month, the number of cracks in the cap liner was checked. In the impact performance test, using a sample prepared under the same conditions as those for cap torque measurement described above, the bottle was placed vertically on the floor from a height of 1 m with the cap facing downward, and the inside of the bottle was measured. The number of bottles of solution leaked was confirmed. The results are shown in Table 1. As a result, the cap performance of the liner material made of the hydrogenated block copolymer and polyolefin blended in a certain ratio was excellent. Furthermore, even if SBS, natural rubber, SIS, butyl rubber, etc. which are not hydrogenated block copolymers were ideally blended, the performance of the cap was not as excellent as in the case of hydrogenated block copolymers.

[Table] Example 2 A cap made in the same manner as in Example 1 was placed in a glass container with a full capacity of 145 c.c., which had a bottle opening to which 80 cc.
Fill with 130 c.c. of boiling water at ℃ and seal with various caps that have been aged for about a week since manufacture. Thereafter, it was immersed in hot water at 85°C for 30 minutes, cooled at 50°C for 10 minutes, and allowed to cool naturally indoors. One day later, 20℃－40%RH
After each sample was stored upright for one month under the following conditions, the opening torque values of the caps were measured using a torque meter. Further, the methods of environmental stress cracking test (ESC) and impact performance test were conducted in accordance with Example 1. The results are shown in Table 2. As a result, it was found that the performance as a cap is inferior if the ratio of the hydrogenated block copolymer is too high or too low compared to the polyolefin. As polyolefin,
HDPE, PP, and EVA all showed similar trends in performance.

【table】 [Brief explanation of the drawing]

FIG. 1 is a diagram showing the container lid of the present invention together with the container opening, FIG. 2 is a diagram showing the shape of the liner of the liner-equipped cap formed in Example 1, and FIG.
FIG. 4, which is a diagram showing the shape of the cap shell of the liner-equipped cap formed in Example 1, is a sectional view showing a part of the container opening into which the cap of FIG. 3 is attached. Reference number 1 is the container lid shell, 2 is the top plate, 3 is the skirt, 4 is the liner, 5 is the adhesive layer, 6 is the container, 7 is the circumferential opening, 8 and 9 are screws, 10 is the sewing machine Show your eyes.

Claims (1)

[Scope of Claims] 1. In the container lid with a liner, the liner material contains a hydrogenated product of a block copolymer of an alkenyl aromatic hydrocarbon and a conjugated diene and a polyolefin in a weight ratio of 10:90 to 80:20. A container lid with a heat-resistant liner, characterized in that it is made of a blend containing. 2. The hydrogenated block copolymer contains 2 to 33% by weight of alkenyl aromatic hydrocarbon polymer blocks, and 70% or more of the conjugated diene units in the conjugated diene polymer blocks are hydrogenated. A container lid according to claim 1.