Tamper-evident band for a screw cap

Abstract

A screw cap 50 containing a TE tape 3, wherein the screw cap 50 is characterized by a biomass level of carbon components (according to ASTM D6866-11) of not less than 50 mass% and less than 94 mass%, or is constituted by polyethylene having a weight average molecular weight of 200,000 or more and a molecular weight distribution of 12 or more.

Description

Technical Field

[0001] This invention relates to a screw cap with a tamper-evident (TE) strip, which serves as an indicator that the container has been opened. More specifically, this invention relates to a screw cap from which the TE strip is removed when the cap is opened. Background Technology

[0002] Screw caps with a TE strip indicating whether the container has been opened are widely used for purposes such as ensuring the quality of the contents and preventing unauthorized access. This type of cap works as follows: when the cap is rotated and unscrewed, the bridge connecting the cap body and the TE strip breaks, causing the TE strip to be removed from the cap body. This indicates that the cap has been opened. Furthermore, a cap with the TE strip removed can be reattached to the container opening to reseal it.

[0003] The aforementioned screw caps with TE strips are typically made from olefin resins through compression molding or injection molding. Common examples of olefin resins include polyethylene and polypropylene. In particular, polyethylene caps are commonly used for polyethylene terephthalate (PET) containers because polyethylene is slightly more flexible than polypropylene and ensures a high seal at the opening of PET containers.

[0004] Meanwhile, in recent years, the release of carbon dioxide has become a serious environmental problem. In this context, the use of plant-derived olefin resins (such as biopolyethylene and biopolypropylene) is desirable. Plant-derived olefin resins are produced from plants that absorb atmospheric CO2, using either ethylene or propylene as raw materials. Therefore, compared to petroleum-derived resins, plant-derived olefin resins contribute to carbon neutrality and are highly effective in mitigating global warming.

[0005] Also in the field of caps, Patent Document 1 proposes a hinged cap (elbow-type cap) made of plant-derived olefin resin. Furthermore, Patent Document 2 proposes a two-piece screw cap with a plant-derived filler on the inner surface of its top plate.

[0006] Existing technical documents:

[0007] Patent documents:

[0008] Patent Document 1: JP-A-2013-184727

[0009] Patent Document 2: JP-A-2020-142835 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] Plant-derived olefin resins have relatively high molecular weights because the monomers ethylene or propylene are produced from plant-derived ethanol or propanol. Therefore, for the purpose of adjusting physical properties, plant-derived olefin resins are sold as blends with fossil fuel-derived olefin resins. In other words, the biomass levels of commercially available plant-derived olefin resins vary from low to high.

[0012] Higher biomass levels are desirable for various applications. However, the inventors have found that in caps with polyethylene TE tape, higher biomass levels make the bridge connecting the TE tape and the cap more difficult to break immediately. For example, when the biomass level is above 50% by mass, the bridge is stretched, increasing the so-called breakage angle. This often leads to problems such as the cap not being easily removed from the container opening, or the cap opening while the TE tape is still attached because the bridge portion is not broken. Caps with TE tape attached that are removed from the container opening are no longer suitable for tamper-evident opening. Therefore, using polyethylene with high biomass levels in caps with TE tape may require a change in the bridge design.

[0013] In view of the above, the object of the present invention is to provide a screw cap with a TE strip that effectively overcomes the problem of bridge breakage even when it is made of polyethylene with a high biomass level.

[0014] Solution for solving the problem

[0015] The present invention provides a screw cap with a TE strip comprising polyethylene having a biomass level (ASTM D6866-11) of 50% by mass and less than 94% by mass, a weight average molecular weight of 200,000 or more, and a molecular weight distribution of 12 or more.

[0016] Screw cap applicable to the present invention:

[0017] (1) The melt flow rate (MFR: 190℃) of polyethylene is greater than 1 g / 10 min and less than 20 g / 10 min;

[0018] (2) The density of polyethylene is 930 kg / m³. 3 The above; and

[0019] (3) The TE band includes a flap piece as a locking mechanism.

[0020] The effects of the invention

[0021] The polyethylene used in the TE strip of the cap of this invention has an extremely high biomass level of 50 to 90% by mass, and the weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) are adjusted within a specific range. Therefore, despite the high content of plant-derived polyethylene, the cap effectively overcomes the problem of the bridge connecting the TE strip and the cap body being prone to breakage.

[0022] For example, as shown in the following embodiments, the biomass levels of caps made of polyethylene with Mw and Mw / Mn falling outside the scope defined in this invention are 0% by mass (Comparative Example 1), 31% by mass (Comparative Example 3), and 50% by mass (Comparative Example 2), respectively, and the bridge breakage angle increases with the biomass level. In the cap with a biomass level of 50% by mass, the breakage angle is 299 degrees (this means that in order to unscrew the cap at the opening of the sealed container, the cap needs to be rotated approximately 300 degrees before the bridge breaks).

[0023] On the other hand, in the cap of the present invention (Example 1) made of polyethylene with Mw and Mw / Mn within the range specified in the present invention, although the biomass level was 51% by mass, the bridge fracture angle was 288 degrees, which is about 10 degrees smaller than the fracture angle in Comparative Example 3, resulting in immediate bridge fracture. Therefore, even though the cap of the present invention with TE tape is made of polyethylene with a high biomass level, the cap can be easily unscrewed, allowing the TE tape to effectively function as a quality assurance material and be suitable for resealing containers. Therefore, the present invention can effectively contribute to carbon neutrality. Attached Figure Description

[0024] [ Figure 1 [: A partial cross-sectional side view of the screw cap of the present invention.] Detailed Implementation

[0025] <Basic Structure of the Cover>

[0026] Reference Figure 1 The screw cap with a TE strip of the present invention, usually indicated by reference numeral 50, includes a cap body 1 and a TE strip (tamper-evident strip) 3.

[0027] The cover 1 includes a top plate portion 5 and a skirt portion (cylindrical sidewall) 7 extending vertically downward from the periphery of the top plate portion 5.

[0028] The top plate portion 5 includes, on its inner surface, an inner ring 9 formed away from the skirt portion 7 and extending downward with a slightly outwardly convex shape, a short outer ring 11 formed between the inner ring 9 and the skirt portion 7, and a small protrusion 13 disposed in the circumferential direction between the inner ring 9 and the outer ring 11.

[0029] The skirt 7 includes internal threads 17 on its inner surface. The internal threads 17, designed to engage with external threads provided at the opening of the container (not shown), are typically partially notched to form a path 17a in the height direction. When cleaning the inside of the cap, cleaning fluid is allowed to flow downwards through path 17a without remaining in the cap.

[0030] A non-slip knurling 19 is formed on the outer surface of the skirt 7, making the cap 50 (cap body 1) easy to rotate. The knurling 19 has a notch 19a at its upper end. The notch 19a serves as a mark so that when the cap 50 is securely screwed onto the mouth of the container, the cap 50 is tightened to a constant degree. More specifically, when the cap 50 is installed on the mouth of the container and engaged with the internal thread 17, the position of the notch 19a indicates whether the cap has been sufficiently tightened.

[0031] When the cap 50 (cap body 1) is fully tightened and securely fixed to the opening of the container (not shown), the opening is positioned such that the inner portion of the upper end of the opening is tightly fitted to the outer surface of the inner ring 9, while the outer corner of the upper end of the opening abuts against the outer ring 11. Therefore, the cap 50 is securely fixed to the opening of the container without gaps, thus sealing the opening. Furthermore, the upper surface of the container opening abuts against the small protrusion 13, resulting in improved sealing.

[0032] The TE band 3 used with the cover 1 of the above form is a form known per se. The TE band 3 is connected to the lower end of the skirt 7 of the cover 1 by a breakable bridge 21, and includes a plurality of upwardly oriented flaps 23 spaced apart in the circumferential direction on its inner surface to serve as locking members.

[0033] More specifically, when the cap 50 is screwed securely onto the mouth of the container, the internal thread 17 is tightened, and the flap 23, which opens from the inner surface of the TE belt 3, closes to face the inner surface of the TE belt 3, allowing the flap 23 to pass over the jaw formed on the mouth of the container. Once the flap 23 has passed the jaw, it reopens due to its elasticity. This is the state in which the cap 50 is installed at the mouth of the container.

[0034] When the lid 50 (lid body 1) in the above-described state rotates in the opening direction, the internal thread 17 gradually unscrews. As the lid body 1 unscrews, it moves upward along the opening of the container. However, because the tip of the flap 23 abuts against the lower surface of the container's jaw and locks in place, the upward movement of the TE band 3 is restricted. Therefore, as the lid body 1 continues to rotate in the opening direction, stress concentrates on the bridge 21, causing it to break. The angle formed from the time when the lid body 1 begins to rotate in the opening direction until the bridge 21 breaks is called the fracture angle.

[0035] As can be understood from the above description, in the cap 50, which has been rotated in the opening direction until the cap 1 is removed from the opening of the container, the bridge 21 breaks, causing the TE strap 3 to separate from the cap 1 and remain on the opening side of the container. Judging from the fact that the TE strap 3 has separated from the cap 1, a typical consumer can recognize that the cap 50 (cap 1) has been opened. This is the working principle of the screw cap 50 with TE strap of the present invention.

[0036] In the above embodiment, the wing 23 is disposed on the inner surface of the TE band 3 as a locking means for the jaw of the container. Optionally, such a locking means may be in the form of a hook-shaped protrusion such as an undercut. However, in order to maximize the advantages of the present invention, the wing 23 is most suitable as the locking means because the problem of bridge breakage due to increased biomass levels tends to be solved more significantly by the TE band 3 having the wing 23.

[0037] <Material for the Lid>

[0038] The screw cap with the above structure is made of polyethylene by molding means such as compression molding or injection molding.

[0039] The polyethylene used here includes not only homopolymers of ethylene, but also copolymers of ethylene and small amounts of α-olefins (e.g., having about 3 to 7 carbon atoms).

[0040] The polyethylene used in this invention comprises so-called bio-polyethylene. Bio-polyethylene is obtained from plants that absorb carbon dioxide and grow. For example, ethanol (called bioethanol) produced by fermenting the residue obtained after sugarcane juice extraction is used as a raw material. The bioethanol is dehydrated to form ethylene, which is then polymerized to produce bio-polyethylene. Compared to common polyethylene derived from fossil fuels (referred to herein as petroleum-based polyethylene), bio-polyethylene produces zero carbon dioxide emissions in total, thus significantly contributing to carbon neutrality. In other words, using polyethylene containing a large amount of bio-ethylene is more conducive to reducing greenhouse gas (carbon dioxide) emissions.

[0041] At the same time, bio-based polyethylene contains radioactive carbon, which is not found in petroleum-based polyethylene. 14 C. Therefore 14 Measuring C concentration reveals the concentration of bio-polyethylene content (i.e., biomass level) in commercially available polyethylene. The method for determining the biomass level is specified in ASTM D6866-11, as described in the examples below.

[0042] From a carbon neutrality perspective, the biomass level of the carbon component in the polyethylene used to form the cap of this invention is 50% by mass or more. Polyethylene with a biomass level of less than 50% by mass does not significantly contribute to carbon neutrality. Polyethylene with extremely high biomass levels (e.g., 94% by mass or more) is unsatisfactory in terms of cost if used for production (because bio-polyethylene is expensive and is usually sold as a blend with petroleum-based polyethylene).

[0043] However, when polyethylene with a biomass level of 50% or more is used in the formation of the cap 50 described above, a bridge breakage problem occurs. More specifically, when the cap 50, installed at the mouth of the container, is rotated open, the bridge 21 is stretched and barely breaks, resulting in a breakage angle of the bridge 21 greater than the necessary breakage angle. This trend becomes more likely as the bio-polyethylene content (i.e., biomass level) increases. Therefore, the bridge 21 may remain partially unbroken, allowing the cap 1 to unscrew from the mouth of the container, where the bridge 21 is partially connected to the TE band 3.

[0044] To address the bridge fracture problem, it is necessary in this invention to adjust the biomass level of polyethylene to be 50% by mass or more and less than 94% by mass, so that it has:

[0045] Weight-average molecular weight (Mw) in the range above 200,000, especially above 250,000; and

[0046] Molecular weight distribution Mw / Mn in the range of 12 and above, especially in the range of 14 and above.

[0047] The reason why polyethylene with higher biomass levels is more likely to cause bridge breakage remains to be determined. Considering that the bio-polyethylene produced is at a level with relatively high molecular weight or a narrow molecular weight distribution, it is speculated that higher biomass levels disrupt the balance of physical properties, thus making them more prone to bridge breakage. Therefore, the polyethylene used in this invention was adjusted by using commercially available petroleum-based polyethylene to achieve a biomass level of 50% by mass or more and further to have a weight-average molecular weight Mw and a molecular weight distribution Mw / Mn within the aforementioned range. As a result, the cap 50 with TE band 3 overcomes the bridge breakage problem even when made of polyethylene with a high biomass level.

[0048] The physical properties of the polyethylene to be formed can be adjusted by blending petroleum-based polyethylene (or polyethylene containing biomass) with the following parameters: biomass content (biomass level), Mw, and Mw / Mn, to ensure that the biomass level is not less than 50% by mass and that Mw or Mw / Mn is within a predetermined range.

[0049] When adjusting the physical properties, preferably, when the cap 50 is formed by compression molding or injection molding, the melt flow rate (MFR: 190°C) of polyethylene is in the range of, for example, 1 g / 10 min or more and less than 20 g / 10 min. Furthermore, in order to impart a suitable opening torque to the cap 50, the density of polyethylene is preferably 930 kg / m³. 3 The above is preferred, with 940 kg / m³ being more ideal. 3 .

[0050] The superior effects of the present invention will be described through the following embodiments.

[0051] Example:

[0052] <The Formation of the Cover>

[0053] The cap is formed by compression molding. Various types of resin granules, used as raw materials, are dry-mixed in a mixer and fed into an extruder. The molding temperature is 170°C, and the molding speed is 800 pieces / min.

[0054] <Preparation of Evaluation Samples>

[0055] A polyethylene terephthalate container with a neck of nominal diameter of 28 mm was filled with 500 mL of water, and the container cap was installed to the neck with a torque of 180 N·cm. The container was then sterilized at 75°C for 30 seconds and then sterilized at 30°C for 30 seconds.

[0056] <Lid opening torque evaluation>

[0057] The prepared evaluation sample container is rotated in the opening direction until the cap is removed from the neck of the container. The initial torque (i.e., the maximum torque required to begin rotating the container cap) of five evaluation samples is measured at this point, and the average value is determined as the opening torque. When the opening torque falls within the range of 100 to 150 N·cm, the cap is evaluated as "○". When the opening torque falls outside this range, the cap is evaluated as "×".

[0058] <Evaluation of the Fragment Angle of the Covered Bridge>

[0059] The prepared evaluation sample container was rotated in the opening direction until the cap was removed from the neck of the container. The rotation angle of the container cap was measured for five evaluation samples from the time the cap began to rotate until the bridge began to break, and the average value was determined as the bridge breakage angle. When the bridge breakage angle was less than 290°, the cap was evaluated as "○". When the breakage angle was not less than 290°, the cap was evaluated as "×" because the TE band may not have separated properly.

[0060] <Molecular Weight Evaluation>

[0061] The cap was cut into pieces with scissors and dissolved in o-dichlorobenzene, then hot-filtered through a 0.5 μm pore size filter. The filtrate was used as an evaluation sample.

[0062] For molecular weight measurement, a device, PL-GPC220, manufactured by Agilent Technologies Japan, Ltd., was used.

[0063] Two Plgel Olexis columns manufactured by Agilent Technologies Japan, Ltd. and one protective column were used together.

[0064] At 145 °C, o-dichlorobenzene at a concentration of 0.1 wt / vol% was used as the eluent, and the analysis was performed at a flow rate of 1.0 mL / min.

[0065] Detection was performed using a refractive index detector (RI).

[0066] The number-average molecular weight (Mn), weight-average molecular weight (Mw), and polydispersity (Mw / Mn) are evaluated based on the measured molecular weight distribution.

[0067] <Melt Flow Rate (MFR) Evaluation>

[0068] A melt indexer F-F01 manufactured by Toyo Seiki Seisaku-sho, Ltd. was used.

[0069] Cut the lid into pieces with scissors to use as raw material. Multiply the mass M obtained after the 5-minute test by two to obtain the MFR value. In Comparative Example 4, multiply the mass M after the 2-minute test by five to obtain the MFR value.

[0070] MFR (g / min) = M × 2

[0071] MFR (g / min) = M × 5

[0072] <Biomass Level Assessment>

[0073] According to ASTM D6866-21, carbon isotopes 14 C is measured using method B and is used to evaluate biomass levels. 14 Carbon is constantly produced and exists in the atmosphere in a certain proportion, but it is also found in petroleum or plants. 14 C decreases over time. Considering... 14 C has a half-life of 5730 years, and oil stored underground for millions of years does not contain C. 14 C.

[0074] Measurement of carbon in the sample 14 C concentration and standard modern carbon14 pMC (modern carbon percentage; δ) of C concentration ratio 13 C-corrected), as the biomass level of the cover (%). The biomass used as raw material should be manufactured in 2015.

[0075] The cap was cut into pieces with scissors and then burned to produce carbon dioxide. The carbon dioxide was purified in a vacuum line and then reduced with hydrogen in the presence of an iron catalyst to form graphite, which was used as the sample for measurement. Oxalic acid, provided by the National Institute of Standards and Technology (NIST), was used as the standard sample for measurement.

[0076] The device used is a specialized one manufactured by NEC Corporation. 14 C-AMS machine.

[0077] <Density Measurement>

[0078] The dry density meter AccuPyc, manufactured by SHIMADZU CORPORATION, was used.

[0079] Ten measurements were performed using a 10-cc measuring cell at 23°C. The average of the ten measurements was used. The cap was cut into pieces with scissors and placed into the cell for measurement.

[0080] <Example 1>

[0081] The cap is made from a combination of commercially available petroleum-derived HDPE resin and plant-derived HDPE resin. The resulting cap has the composition of biomass level, molecular weight, molecular weight distribution, and physical properties as shown in Table 1.

[0082] <Comparative Example 1>

[0083] The cap is made solely from commercially available petroleum-derived HDPE resin. The cap exhibits the biomass level, molecular weight, molecular weight distribution, and physical properties shown in Table 1.

[0084] <Comparative Example 2>

[0085] The cap is made from a combination of commercially available petroleum-derived HDPE resin and plant-derived HDPE resin, different from that of Example 1. The cap has the biomass level, molecular weight, molecular weight distribution, and physical properties shown in Table 1.

[0086] <Comparative Example 3>

[0087] The cap is made from commercially available petroleum-derived HDPE resin and plant-derived HDPE resin, in a combination different from that of Comparative Example 2, unlike Example 1. The cap has the biomass level, molecular weight, molecular weight distribution, and physical properties shown in Table 1.

[0088] <Comparative Example 4>

[0089] The cap is made from commercially available plant-derived HDPE resin. The cap has the biomass level, molecular weight, molecular weight distribution, and physical properties shown in Table 1.

[0090]

[0091] Explanation of reference numerals in the attached figures

[0092] 1: Cover

[0093] 3: TE tape

[0094] 5: Top plate section

[0095] 7: Skirt

[0096] 9: Inner ring

[0097] 11: Outer ring

[0098] 13: Small protrusions

[0099] 17: Internal thread

[0100] 19: Knurling

[0101] 21: Bridge

[0102] 23: Wing

Claims

1. A spin cap having a tamper-evident band, comprising a polyethylene having a biomass level of a carbon component of 50 mass% or more and less than 94 mass%, a weight average molecular weight of 200,000 or more, and a molecular weight distribution of 12 or more, wherein, The method of determining the level of biomass is specified in ASTM D6866-11, the polyethylene comprising bio-polyethylene.

2. A spin cap with tamper-evident band according to claim 1, wherein the polyethylene has a melt flow rate, MFR: 190°C, of 1 g / 10 min or more and less than 20 g / 10 min.

3. A spin-on cap having a tamper-evident band according to claim 1, wherein the polyethylene has a density of 930 kg / m 3 Above.

4. A spin cap with tamper-evident band according to claim 1, wherein the tamper-evident band comprises a flap as a locking means.

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