JPS6152057B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a plastic cap with excellent pressure-resistant sealing properties, and more specifically, the present invention relates to a plastic cap with excellent pressure-resistant sealing properties. The present invention relates to plastic caps that provide a combination of retention and anti-return properties. (Prior art) Plastic caps can be easily mass-produced by plastic injection molding, and the cap material also has elastic properties necessary for sealing, so they are widely used as sealing lids for containers such as bottles. It is used. However, the top surface of the mouth of a container such as a bottle is most susceptible to damage compared to other parts of the bottle, and plastics that form a seal between the top surface and the top of the bottle mouth are the most susceptible to damage compared to other parts of the bottle.
Caps tend to have poor sealing even if there are slight defects such as chips or cracks on the top surface of the bottle mouth. Furthermore, in the case of plastic caps that are sealed with the inner surface of the bottle mouth, there is a large variation in the inner diameter of the bottle mouth, so the probability of sealing failure is very high. As a solution to this problem, US Patent No.
FIG. 11 of the specification 3815771 shows that an inclined seal portion is provided at the inner corner connection between the top plate and the skirt of the cap, and this inclined seal portion is engaged with the outer edge of the container mouth. . (Problems to be Solved by the Invention) The cap that engages the above-mentioned slanted seal portion with the outer edge of the container mouth can provide a good seal regardless of defects such as chips and cracks on the upper surface of the container mouth. However, it is recognized that when a container is filled with a content having an autogenous pressure such as a carbonated beverage and subjected to heat treatment such as heat sterilization, or when it is allowed to age after that, a so-called return phenomenon occurs. This return phenomenon refers to a phenomenon in which the cap turns in the opposite direction to the fastening direction, that is, in the opening direction, due to the heat treatment or aging, resulting in a decrease in opening torque and a decrease in sealing performance. This return phenomenon occurs when the plastic, which has been compressed and deformed due to engagement with the outer edge of the container opening, attempts to elastically recover to its original state at the inclined seal portion of the cap that engages with the outer edge of the container mouth, and this elastic recovery force causes the cap to open. It is recognized that this is due to the fact that the valve is rotated in this direction, thereby acting to weaken the opening torque. (Means for Solving the Problems) The present inventors have proposed that in this type of plastic cap, the slanted seal portion and the outer surface of the bottle mouth be designed to reduce compressive stress to the plastic constituting the seal portion as much as possible. We have arrived at the idea that it is effective to prevent the above-mentioned return phenomenon by bringing the two into close contact with each other over as wide an area as possible while minimizing the amount of damage. Based on this idea, in the present invention, in order to prevent the above-mentioned return phenomenon in this kind of plastic cap, the taper angle of the inclined seal portion with respect to the skirt is in the range of 5 to 35 degrees, and the inclined seal The cross-sectional shape of the section is tapered with an S-shaped radius at both ends. (Function) As mentioned above, setting the taper angle θ of the inclined seal portion to the skirt at a relatively small angle of 5 to 35 degrees is effective when the taper angle is larger than the above range when compared with a constant fastening torque. This makes it possible to increase the engagement dimension in the axial direction between the inclined seal portion and the outer surface of the container mouth.
Furthermore, since the compressive stress on the inclined seal portion is T sin θ when the fastening torque is T, by reducing θ, it is possible to reduce the compressive stress on the plastic seal portion. In other words, fastening is performed in a state where shear stress is greater than compressive stress. As mentioned above, the cross-sectional shape of the inclined seal part is
The tapered shape with S-shape radius on both ends prevents the plastic seal from shearing and deforming when it engages with the container opening, as shown in Figure 3-B.
In other words, the plastic protrudes from the rounded portions at both ends 6
a, 6b, thereby making it possible to further increase the area of close contact between the outer surface of the container mouth and the sealing part.
In particular, in an internal pressure container, buckling of the top plate portion occurs, but the protruding portion 6a on the outer surface of the container mouth has a large sealing effect. According to the present invention, as described above, by increasing the area of close engagement between the inclined seal portion and the outer surface of the container mouth and reducing the compressive stress of the seal portion,
It is possible to prevent the return phenomenon after heat treatment and after that due to the passage of time, and it is possible to maintain the necessary opening torque and prevent leakage. (Operations and Effects of the Invention) The plastic cap of the present invention effectively prevents the return phenomenon caused by heat treatment or the passage of time thereafter, so excellent pressure resistance and long-lasting sealing performance can be obtained, and the plastic cap meets the pressure resistance based on JIS S-9017. It was confirmed that the container passed the test, in which the container was filled with gas (carbon dioxide) three times the internal volume of the container and heat-treated at 65° C. for one hour. (Example) In FIG. 1, a plastic cap 1 of the present invention is composed of a top plate part 2 integrally formed of plastic and a skirt 3 hanging down from the periphery of the top plate part. a fastening mechanism known per se, allowing engagement with the container;
For example, a screw 4 is provided. In the plastic cap 1 of the present invention, an inclined seal portion 6 whose diameter gradually decreases toward the top plate 2 is formed inside the inner connecting corner 5 between the top plate 2 and the skirt 3. In FIG. 2, which shows an enlarged view of this inclined seal portion 6, this seal portion 6 is
It has a tapered shape with rounded parts in an S-shape at both ends, with a maximum diameter part (Pmax) at the lower S-shaped end and a minimum diameter part (Pmin) at the upper S-shaped end. In the present invention, the taper angle (θ) is 5 to 5.
It is clear by referring to Table 1, which will be described later, that by setting the angle in the range of 35°, it is possible to prevent the return phenomenon and prevent leakage after heat treatment. Figures 3-A and 3-3 show the plastic cap 1 of the present invention covered with the neck 7 of the bottle.
In Figure B, when the screw 4 of the cap 1 is engaged with the screw 8 of the bottle opening 7 and the cap 1 is rotated to be fastened, the inclined seal portion 6 of the cap 1 and the bottle opening 7 are engaged. However, since the taper angle is small, the engagement dimension in the axial direction between the inclined seal portion 6 and the outer surface 9 of the bottle mouth can be increased. Moreover, in the range of θ=5 to 35°, engagement between the two is performed under a state where the shear stress is greater than the compressive pressure applied to the inclined seal portion. Further, due to the shear deformation of the plastic, protruding parts 6a and 6b are formed in the rounded part, which acts to enlarge the area of close contact between the inclined seal part 6 and the outer surface 9 of the bottle mouth. In this way, by increasing the contact area between the two and reducing the compressive stress, return is prevented, and a large opening torque is ensured in approximately proportion to the contact area between the two. Generally speaking, the maximum diameter (R _nax ) of the inclined seal portion 6 is 0.1 to 6.0 greater than the outer diameter (R _B ) of the bottle mouth.
mm, especially 0.2 to 4.0 mm larger, while the minimum diameter (R _nio ) of the inclined seal portion 6 has a smaller dimension of 0.1 to 4.0 mm, especially 0.5 to 2.0 mm smaller than the outer diameter of the bottle mouth (R _B ). This is desirable. In the present invention, various thermoplastic resins and thermosetting resins can be used as the plastic constituting the cap. Preferred are melt moldable thermoplastics, especially low, medium to high density polyethylene, polypropylene, ethylene-propylene copolymers, ionomers, poly(4-methylpentene)
1st class olefin resin; polystyrene, styrene-butadiene block copolymer, acrylonitrile-butadiene-styrene resin (ABS resin); vinyl chloride resin; acrylic resin; nylons; polyester; polycarbonate; etc., and further phenol-formaldehyde Molding thermosetting resins such as resins, urea resins, melamine resins, epoxy resins, polyurethane resins, and unsaturated polyester resins can also be used. These resins may be blended with one or more of fillers, reinforcing agents, colorants, mold release agents, heat stabilizers, antioxidants, lubricants, ultraviolet absorbers, etc. according to known formulations. I can do it. These resins can be easily molded into a cap by injection molding using a mold having a cavity corresponding to the shape of the cap described above. In the plastic cap of the present invention, the above-described inclined seal portion 6 is formed on the top plate 2 and the skirt 3.
It may be integrally formed of the same material as the plastic forming the top plate 2 and the skirt 3.
It may be made of a different material from the plastic from which it is made. For example, if the aforementioned plastic is an elastic olefin resin such as polyethylene or polypropylene, the inclined seal portion 6 can be integrally formed with the same material as the other parts. On the other hand, if the plastic forming the top plate 2 and skirt 3 is a harder thermoplastic resin, such as polystyrene, ABG resin, or thermosetting resin, only the inclined seal portion 6 may be made of low-density polyethylene, polypropylene, etc. It may be formed separately. FIG. 4 shows an example in which the inclined seal portion 6 is formed separately. Such plastic caps can be manufactured using the so-called two-stage molding (two-color molding) method, or by forming a slanted seal portion 6 separately molded as a liner.
It can be manufactured by inserting the cap into the cap body and adhering the two if necessary. Returning again to FIGS. 1 and 2, on the inside of the top plate 2 of the plastic cap of the present invention there is a rib 11 for engaging with the inner surface 10 of the bottle mouth 7.
may be provided as desired. The plastic cap of the present invention is capable of many modifications without departing from the spirit of the invention. For example, any mechanism other than a screw may be used to engage the container mouth 7 and the cap 1. For example, in FIGS. 5 and 6, an engagement protrusion (undercut) 12 is formed at the lower end of the skirt of the cap 1, and this protrusion 12
By engaging the jaws 13 provided on the outer surface of the bottle spout 7, the cap 1 is covered with the bottle spout 7 with an appropriate fastening force. In the case of FIG. 5, in order to facilitate opening of the cap 1, an opening tab 14 is provided at the lower end of the skirt portion 3, and a sub-score 16 extending from the skirt portion and tab 14 to a score 15 is provided. The package can be opened easily by breaking the caps 16 and 15, or in the case of FIG. 6, it can be opened with a bottle opener or the like. In addition, in FIG.
It can also be integrally molded via. Example 1 The taper of the seal part of the resin cap that touches the corner of the mouth of a 28 m/m pressure-resistant bottle (inner capacity 120 ml) is set at an angle of inclination θ of 5 degrees with respect to the side wall of the mouth of the bottle, as shown in Fig. 2. ，10゜，20゜，30゜，40゜，
Performance tests were conducted on resin caps integrally molded at 50° and 60°. The resin material used was high-density polyethylene (density 0.958, MFR 1.5), which was molded into a resin cap with an outer diameter of 30 m/m. In addition, as a comparative sample (conventional example), U.S. Patent No.
A prototype cap (inclined at an angle of 45 degrees) shown in FIG. 11 of the specification of No. 3815771 was manufactured and used as a test sample. The test was conducted in accordance with the sustained pressure test of JIS S 9017 ``Crown'', and the test cap was capped with dilute sulfuric acid and baking soda to bring the internal pressure to 3 vol. The torque for tightening the cap at this time was 20 kgf-cm. This at 60℃
After soaking in hot water for 1 hour, gas leakage during this time and changes in internal pressure after being left at room temperature for 24 hours after this heat treatment were measured using a volume gauge, and the number of leaks was determined. In addition, in order to examine the loosening of the cap after treatment, the opening torque and return angle were measured after the cap was left at room temperature for one day. The results are shown in Table 1.

[Table] Example 2 As shown in Fig. 4, the seal part and the fastening part (shell part) 5 were made of different materials (here, the seal part was made of low-density polyethylene (density 0.918, MI4.0)), and the fastening part was made of a different material. It was molded using high-density polyethylene (such as the aforementioned polystyrene), and the same test as in Example 1 was conducted.The molding was of the same type as in Example 1.The results are shown in Table 2. .

【table】 [Brief explanation of the drawing]

FIG. 1 is a partial sectional view of the plastic cap of the present invention, and FIG. 2 is a partial sectional view of the plastic cap of the invention.
Enlarged view of the cap part, Figure 3-A and Figure 3
- Figure B is a view showing the plastic cap of the present invention covering the neck of a bottle, Figure 4 is a partially enlarged sectional view showing an example in which the slanted seal portion is formed separately, and Figure 5. , 6 and 7 are sectional views for explaining various aspects of the present invention, in which reference numeral 1 is a plastic cap, 2 is a top plate, 3 is a skirt, 4 is a screw, and 5 is a plastic cap. 6 is an inclined seal portion, 7 is a bottle mouth, 8 is a screw, 9 is an outer surface of the bottle mouth, 10 is an inner surface of the bottle mouth, 11 is a rib, 12 is an engagement protrusion (undercut), and 13 is a chin part, 14 is tab, 15 is score, 16 is sub score, 17 is pilfer
The proof rings 18 each indicate a bridge portion.

Claims (1)

[Claims] 1 Consisting of a top plate and a skirt that hangs down from the periphery of the top plate, integrally molded of plastic, with a mechanism for fastening to the container provided on the inner peripheral surface of the skirt, and a container opening at the inner corner connection between the top plate and the skirt. In a plastic cap provided with an inclined seal portion that engages with the outer edge of the plastic cap, the tapered angle of the inclined seal portion with respect to the skirt is in the range of 5 to 35 degrees, and the cross-sectional shape of the inclined seal portion is rounded at both ends. A plastic cap characterized by a tapered part with an S-shape.