Polypropylene composition for screw caps

Abstract

To provide a resin material suitable for molding a screw cap with a TE band, which has excellent impact resistance, is easy to open, and exhibits high sealing force.SOLUTION: There is provided a polypropylene composition for screw caps, comprising impact polypropylene having a structure in which polypropylene is used as a matrix and elastomer components are dispersed in the polypropylene, containing the elastomer component in an amount of 10 mass% or more and less than 20 mass% based on the material, in which Charpy impact strength is in a range of 8.9 kJ / m2 or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a polypropylene composition used for molding a screw cap, and more particularly, to a polypropylene composition used for molding a screw cap provided with a tamper-evident band (hereinafter sometimes referred to as a TE band) having functions for preventing unauthorized use and ensuring quality, and further relates to a screw cap molded from the composition.

Background Art

[0002] Screw caps are molded by molding means such as compression molding and injection molding, and polyethylene and polypropylene are generally used as molding materials. Among them, caps molded from polypropylene have high heat resistance, pressure resistance, and rigidity.

[0003] By the way, in a screw cap, a TE band is often provided at the lower end of the cap body via a breakable bridge in order to provide an unauthorized use prevention function and a quality assurance function. When the screw cap attached to the container mouth is turned (opened) and removed from the container mouth, the TE band is separated from the cap removed from the container mouth due to the breakage of the bridge during opening. That is, since the TE band is separated from the cap, the general consumer can recognize the fact that the cap has been opened. By making the general consumer recognize the opening history of the cap in this way, unauthorized use such as replacement of the container contents can be prevented, and further, the quality assurance function of the contents is also shown.

[0004] Such TE band-type screw caps require not only mechanical properties such as impact resistance and strength, but also performance characteristics such as ease of opening and resistance to bridge breakage. As a resin material suitable for molding caps that possess these performance characteristics, Patent Document 1 proposes a compression molding resin composition comprising a propylene-based resin and a nucleating agent, wherein the propylene-based resin is a reaction blend resin of a polypropylene homopolymer and an ethylene-propylene polymer.

[0005] The compression molding resin composition described in Patent Document 1 is what is known as impact polypropylene (impact PP) or block polypropylene (block PP), and it is capable of molding caps with good openability and bridge breakage. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2014-91781 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, regarding caps formed by impact PP, while the ease of opening the cap (bridge breakage) has been considered, the actual airtightness required of the cap has hardly been studied.

[0008] In other words, with a screw cap with a TE band, the cap attached to the container opening is rotated in the opening direction to initiate screw engagement. Subsequently, when the engaging projection of the TE band contacts the underside of the jaw of the container opening, stress is applied to the bridge connecting the TE band. Further rotation in the opening direction causes the bridge to break, and continued rotation in the opening direction removes the cap from the container opening, detaching the TE band from the cap.

[0009] Therefore, if the torque required to break the bridge (2nd torque) is small, the bridge will break easily, resulting in good opening performance. However, the torque required to initiate opening to release the screw engagement with the container opening (1st torque) has not been evaluated for impact-resistant PP caps. For example, in Patent Document 1, a sample piece of a certain shape is formed, an incision is made in this sample piece, and the bridge breakage is evaluated by the elongation at the incision (bridge portion) when pulled at a certain tensile speed, and the ease of opening is determined. In other words, the airtightness required of the cap is related to the above-mentioned 1st torque, and the larger the 1st torque, the better the airtightness. However, since the bridge breakage (ease of opening) is determined without forming the cap, it is not possible to determine the airtightness from Patent Document 1.

[0010] Therefore, the object of the present invention is to provide a resin material suitable for molding screw caps with TE bands that have excellent impact resistance, are easy to open, and exhibit high sealing power. Another object of the present invention is to provide a screw cap with a TE band molded from the above resin material. [Means for solving the problem]

[0011] According to the present invention, A screw cap comprising a cap body formed from a top plate and a cylindrical side wall descending from the periphery of the top plate, and a tamper-evident band connected to the cylindrical side wall by a plurality of breakable bridges, wherein the inner surface of the cylindrical side wall is provided with threads that engage with the outer surface of the container mouth, and the inner surface of the tamper-evident band is provided with an engaging member that can engage with the lower surface of the jaw formed on the container mouth, wherein the cap body and the tamper-evident band, including the bridges, are integrally molded from a polypropylene composition for screw caps, and the polypropylene composition for screw caps is Impact polypropylene has a structure in which polypropylene is used as a matrix and elastomer components are dispersed within the polypropylene. The aforementioned polypropylene The composition contains the elastomer component in an amount of 10% by mass or more and less than 20% by mass, Charpy impact strength is 8.9 kJ / m 2 Within the above range Furthermore, the MFR at 230℃ is 5g / 10min or more and less than 15g / 10min. A screw cap characterized by Pu It will be provided.

[0012] In the polypropylene composition of the present invention, (1) The number average molecular weight Mn of the polypropylene is in the range of 60,000 or less, and the molecular weight distribution Mw / Mn is in the range of 3.0 to 6.5. (2) The weight-average molecular weight Mw of the elastomer component is in the range of 400,000 or more. 、 This is preferable. [Effects of the Invention]

[0014] The polypropylene composition for screw caps of the present invention is made of impact PP and contains elastomer components, resulting in high impact strength, for example, a Charpy impact strength of 8.9 kJ / m². 2 That concludes the explanation. Moreover, since this Impact PP has an elastomer content of 10% by mass or more and less than 20% by mass per unit of material, when a screw cap with a TE band is formed, the second torque of the cap can be reduced without changing the design of the conventional bridge shape, and the bridge breaks well, resulting in excellent openability.

[0015] Furthermore, TE band screw caps molded from polypropylene compositions in which the number-average molecular weight Mn of polypropylene is 60,000 or less and the molecular weight distribution Mw / Mn is adjusted to the range of 3.0 to 6.5 exhibit the property that the 2nd torque is lower than the 1st torque. As a result, they exhibit good bridge breakage, excellent opening performance, and good sealing force.

[0016] Thus, the polypropylene composition of the present invention exhibits excellent performance when applied to the molding of screw caps with TE bands. [Brief explanation of the drawing]

[0017] [Figure 1] A half-cross-sectional side view of a screw cap with a TE band, molded from the polypropylene composition of the present invention. [Figure 2] A cross-sectional view showing the container opening to which the screw cap in Figure 1 is attached. [Figure 3] A curve showing the change in opening torque measured for a screw cap with a TE band molded from the polypropylene composition of Example 1.

Best Mode for Carrying Out the Invention

[0018] <Form of Screw Cap with TE Band> Referring to FIG. 1, the screw cap 1 formed from the polypropylene composition of the present invention can be suitably used, although not limited thereto, in the case of a so-called hot pack filling method in which the contents are heated to about 80 to 95° C. and filled into a container, and is formed from a cap body 3 and a TE band (tamper-evident band) 5.

[0019] The cap body 3 includes a top plate portion 7 and a cylindrical side wall 9 descending from the periphery of the top plate portion 7, and the TE band 5 is connected to the lower end of the cylindrical side wall 9 by a breakable bridge 11. A plurality of bridges 11 are provided at intervals in the circumferential direction. That is, the screw cap 1 in such a form is injection-molded or compression-molded using the polypropylene composition of the present invention, and the cap body 3 and the TE band 5 are integrally connected via the bridge 11.

[0020] Referring to FIG. 2 together with FIG. 1, the form of the container mouth portion to which the above-described screw cap 1 is attached will be described. On the outer surface of this mouth portion 50, a screw thread 51 for cap engagement is formed. Below the screw thread 51, a jaw portion (bead) 53 having a slightly larger diameter than the screw thread 51 is formed, and at the lowermost portion, a support ring 55 is formed for conveying the container and fixing various jigs. A container provided with such a container mouth portion 50 is formed by blow molding, extrusion molding, etc. using various thermoplastic resins. Generally, it is formed from an olefin resin such as polyethylene or polypropylene, or a polyester resin typified by polyethylene terephthalate.

[0021] In the screw cap 1 attached to the container mouth portion 50 as described above, a screw thread 13 that engages with the screw thread 51 provided on the outer surface of the container mouth portion 50 is provided on the inner surface of the cylindrical side wall 9 of the cap body 3. In other words, when the cap body 3 is placed over the container opening 50 and rotated in the closing direction, the screw engagement between the threads 13 and 51 progresses, the cap body 3 descends along the outer surface of the container opening 50, and the TE band 5 connected to the lower end of the cylindrical side wall 9 goes over the jaw portion 53.

[0022] On the other hand, an inner ring 15 for sealing is formed on the inner surface of the top plate portion 7 of the cap body 3. This inner ring 15 extends downward from the inner surface of the top plate portion 7, and its outer circumferential surface extends radially outward with respect to the central axis A of the screw cap 1, and then extends radially inward with respect to the central axis A. Therefore, there is a bend B (seal point) on the outer circumferential surface of the inner ring 15 where the direction of inclination is reversed. In other words, the inner ring 15 has a shape that bulges slightly outward, and when the cap body 3 is rotated in the closing direction and lowered, the bent portion B on the outer surface of the inner ring 15 firmly adheres to the inner surface of the container opening 50, thereby ensuring that the container is sealed.

[0023] Outside the inner ring 15, an outer ring 17 is formed, which is shorter than the extended length of the inner ring 15 and approximately one-third the extended length of the inner ring 15. The inner circumferential surface of the outer ring 17 extends linearly, inclined radially inward toward the central axis A, and then extends in a roughly arc shape, inclined radially outward toward the central axis A. The outer circumferential surface of the outer ring 17 extends linearly, inclined radially inward toward the central axis A. Furthermore, a circumferential projection 19 is provided between the outer ring 17 and the inner ring 15. The amount of protrusion of the circumferential projection 19 is considerably smaller than the extension length of the inner ring 15 and the outer ring 17. The inner ring 15 and the outer ring 17 have relatively large flexibility, bending radially inward and outward, but the circumferential projection 19 has virtually no flexibility. Specifically, as the cap body 3 (cylindrical side wall 9) is rotated in the closing direction, the upper portion of the container opening 50 enters and is sandwiched in the space between the inner ring 15 and the outer ring 17. The bent portion B on the outer surface of the inner ring 15 comes into close contact with the inner surface of the container opening 50, the inner surface of the outer ring 17 comes into close contact with the upper outer surface of the container opening 50, and the circumferential projection 19 comes into contact with the upper end surface of the container opening 50. Thus, the outer ring 17 and the circumferential projection 19 reinforce the sealing performance achieved by the inner ring 15. For details of the sealing mechanism appropriately adopted in such a so-called hot pack filling method, please refer to, for example, the already published Japanese Patent Application Publication No. 2002-173157.

[0024] Furthermore, an engaging member 21 is provided on the inner circumferential surface of the TE band 5 connected to the cap body 3 (cylindrical side wall 9). In the embodiment shown in Figure 1, the engaging member 21 is composed of a plurality of flap pieces 21, for example, eight, which are spaced apart in the circumferential direction. Each of the flap pieces 21 protrudes upward and inclined radially inward from its base edge connected to the inner circumferential surface of the TE band 5. In other words, as the cap body 3 (cylindrical side wall 9) is rotated and lowered in the closing direction, the flap piece 21 of the TE band 5 moves over the jaw portion 53, and when the sealing by the inner ring 15, outer ring 17 and circumferential small projection 19 is completed (the state in which the cap is closed), the flap piece 21 of the TE band 5 is located below the jaw portion 53. In the illustrated embodiment, the engaging member 21 is made up of a flap piece 21, but it can also be made up of other suitable shapes of protruding pieces, ridges or projections instead of the flap piece 21.

[0025] After the cap is closed in this manner, when the cap body 3 (cylindrical side wall 9) is rotated in the opening direction, the screw engagement between the threads 13 and 51 is released, and the cap body 3 rises along the outer surface of the container opening 50. As a result, the engaging member 21 of the TE band 5 engages with the lower surface of the jaw portion 53, and the upward movement of the TE band 5 is restricted. Therefore, if the rotation of the cap body 3 (cylindrical side wall 9) in the opening direction continues, stress concentrates on the bridge 11, causing the bridge 11 to break. In other words, the TE band 5 is separated from the cap body 3. In this way, when the cap body 3 is removed from the container opening 50, the TE band 5 is separated from the cap body 3, allowing the opening history of the cap body 3 to be recognized. This prevents tampering and other misuse, and furthermore, it also provides a quality assurance function for the contents of the container.

[0026] <Polypropylene composition> The polypropylene composition of the present invention is called impact polypropylene (impact PP), and is sometimes called block PP. That is, this impact PP has a structure in which polypropylene is used as a matrix and elastomer components are dispersed within the polypropylene.

[0027] In this type of impact-resistant polypropylene, the matrix is ​​either homopolypropylene or random polypropylene (polypropylene copolymerized with a small amount of ethylene). However, because elastomer components are dispersed within this polypropylene matrix, impact resistance is enhanced, for example, with a Charpy impact strength of 8.9 kJ / m². 2 The above points are particularly within the range of 8.9 to 10.0. This effectively prevents damage to the molded screw cap due to drops from heights or collisions with other parts. Furthermore, the Charpy impact strength is measured according to JIS K7111-1 / 1eA, as shown in the examples described later.

[0028] Examples of the elastomer components mentioned above include ethylene-propylene copolymer (EPR), styrene-butadiene copolymer (SBR), and ethylene-propylene-butene copolymer (EPBR), but EPR is particularly preferred in terms of improving impact strength. In such EPR, the ratio of ethylene to propylene, E / P, is usually in the range of 30 / 70 to 40 / 60 mass%.

[0029] In the present invention, the elastomer content is in the range of 10% by mass or more and less than 20% by mass, particularly in the range of 10 to 15% by mass, per matrix material. This allows for the development of appropriate rubber-like properties without compromising rigidity, and improves impact resistance while ensuring bridging of the molded cap. For example, if the elastomer content is low, the rubber-like properties will decrease, resulting in impaired impact resistance, and for example, the Charpy impact strength will be 8.9 kJ / m². 2 It falls below that level. Also, if the elastomer content is too high, the rigidity is impaired, and for example, the screw cap 1 molded from this polypropylene composition becomes easily deformed, the bridge breakage is poor, the bridge 11 becomes difficult to break, the 1st torque when opening is reduced, and the sealing force is also reduced.

[0030] Furthermore, the elastomer content mentioned above can be measured as the xylene-soluble portion by extraction with boiling xylene. Therefore, the polypropylene, which is the matrix component in Impact PP, becomes the xylene-insoluble portion.

[0031] Furthermore, the weight-average molecular weight Mw (measured in polystyrene equivalent by GPC) of the elastomer component (i.e., the xylene-soluble portion) is usually preferably in the range of 400,000 or more, and particularly in the range of 500,000 to 800,000. If this weight-average molecular weight Mw is low, the properties as an elastomer are less likely to be reflected, and impact strength and other properties tend to decrease. Also, if the weight-average molecular weight Mw of the elastomer component is excessively high, the moldability may become unsatisfactory.

[0032] Furthermore, the molecular weight characteristics of the polypropylene (xylene-insoluble portion) in the impact PP described above can also be calculated in polystyrene equivalent using GPC. However, in the present invention, it is preferable that the number-average molecular weight Mn of the xylene-insoluble portion is 60,000 or less, particularly in the range of 20,000 to 40,000, and that the molecular weight distribution Mw / Mn is in the range of 3.0 to 6.5, particularly in the range of 5.0 to 6.0. That is, by having such molecular weight characteristics in the matrix polypropylene, good cap moldability can be ensured, and at the same time, when the torque when opening the molded cap is measured, a torque curve like the one shown in Figure 3 is obtained.

[0033] Specifically, Figure 3 is a curve obtained by plotting the opening torque for the TE band-equipped screw cap of Example 1, described later, against the opening angle. It shows a unique tendency in that the 1st torque at the start of opening is greater than the 2nd torque at which bridge breakage occurs. In other words, the TE band-equipped screw cap molded from the Impact PP of the present invention exhibits appropriate rigidity, resulting in good bridge breakage. However, it shows a tendency in that the 1st torque at the start of opening is higher than the torque that breaks the bridge (2nd torque). This means that by molding the TE band-equipped screw cap using the Impact PP of the present invention, it is possible to reduce the 2nd torque for cap bridge breakage, thereby ensuring good bridge breakage, while simultaneously increasing the 1st torque related to sealing, thereby ensuring high sealing force. In the present invention, the reason why a torque curve like that shown in Figure 3 appears has not been elucidated, but the inventors speculate that one of the factors is that the polypropylene matrix exhibits a sharp molecular weight distribution, and a quantitative balance with the elastic elastomer component is maintained, resulting in very little variation in rigidity and elasticity.

[0034] Therefore, when forming a screw cap 1 with a TE band using the polypropylene composition (Impact PP) of the present invention, the number and thickness of the bridges 11, as well as the width of each bridge 11, are set so that the bridges break smoothly when opening the cap, and the 1st torque is increased so that the seal is not easily compromised.

[0035] Furthermore, in the present invention, the impact PP described above may also contain a nucleating agent in an amount that does not impair the impact resistance improvement effect of the elastomer component, for example, an amount of less than 1% by mass per material. By incorporating such a nucleating agent, crystallinity is exhibited, and for example, in the cooling curve at 10°C / min measured by DSC, a crystallization peak appears above 120°C, thereby improving heat resistance and effectively suppressing thermal deformation during heating.

[0036] The nucleating agents mentioned above are not limited to these, but typical examples include organic compounds such as sorbitol compounds, metal salts of carboxylic acids, and aromatic phosphate esters, as well as inorganic compounds such as silica, talc, and mica.

[0037] Furthermore, from the viewpoint of moldability for forming caps, the MFR of the impact PP described above is preferably in the range of 7 to 15 g / 10 min at 230°C or higher.

[0038] Furthermore, the impact PP used in molding the screw cap of the present invention is produced by polymerizing propylene in the presence of a predetermined elastomer. During this process, various physical properties can be adjusted by setting the amounts of various monomers, the type of catalyst, the reaction temperature, and the reaction time within an appropriate range. Since impact PP with various physical properties is commercially available from various manufacturers, by blending appropriate ones and adjusting the amount of elastomer, the type of elastomer, and various molecular weights, an impact PP used in the present invention, i.e., a polypropylene composition for producing a screw cap with a TE band, can be obtained. By using such impact PP, the number, width, and thickness of the bridges 11 can be adjusted according to the size of the cap to obtain a screw cap with a TE band that has good bridge breakage and high sealing force. [Examples]

[0039] The excellent effects of the present invention will be explained in the following examples. Various molding and measurement processes were carried out using the following methods.

[0040] <Forming of test specimens> A test specimen of type A1 (10 mm wide, 4 mm thick) conforming to JIS K 7139 was prepared by injection molding. Injection molding was performed according to JIS K 6922-2, with a mold temperature of 40 ± 1°C, a resin temperature of 200 ± 3°C, a cycle time of 60 ± 3 seconds, and an average injection speed of molten resin of 195 ± 10 mm / s.

[0041] <Cap molding> The caps were manufactured by compression molding. The material was prepared by a dry-blending method, where multiple types of resin pellets were mixed in a blender and then fed into an extruder. At a molding temperature of 170°C and a molding speed of approximately 800 pieces / minute, caps with the shape shown in Figure 1 were compression-molded. The molded caps were for containers with a nominal diameter neck of 28 mm.

[0042] <Meltflow Rate (MFR) Evaluation> The MFR was evaluated using test specimens fabricated by the injection molding method described above. The evaluation was conducted in accordance with JIS K 6921-2 and 7210-1, at a temperature of 230°C and a load of 2.17 kg. The apparatus used was a MELT INDEXER F-F01 manufactured by Toyo Seiki.

[0043] <Separation of xylene-soluble and xylene-insoluble parts> The PP cap was refluxed and dissolved in p-xylene (140-145°C), then cooled to room temperature, and solid-liquid separation was performed. The separated liquid component was concentrated by vacuum distillation, precipitated with methanol, and the precipitate was removed by filtration. It was dried at 70°C under reduced pressure to obtain the xylene-soluble portion. The solid component from the solid-liquid separation was used as the xylene-insoluble portion.

[0044] <Evaluation of xylene-soluble content> The mass w of the xylene-soluble portion extracted as described above was measured and taken as the total mass W of the cap used in the experiment. The EPR content E of the soluble portion was then calculated using the following formula. E(%) = 100 × w / w

[0045] <Molecular weight evaluation> The cap product was cut into small pieces with scissors and dissolved in o-dichlorobenzene. The solution was filtered using a 0.5 μm pore size filter under heat to obtain the measurement sample. The instrument used was an Agilent Technologies PL-GPC220. Two Agilent PLgel Olexis columns were used, with a separate guard column. The eluent was o-dichlorobenzene at 145°C, with a concentration of 0.1 wt / vol% and a flow rate of 1.0 mL / min. A differential refractometer (RI) was used as the detector. Evaluation was performed using polystyrene standard samples.

[0046] <Charpy impact strength of test specimens> Using the test specimens produced by the aforementioned injection molding method, a Charpy impact test was conducted in accordance with JIS K 7111-1. The notches were machined after forming. The equipment used was the Toyo Seiki IT impact testing machine and A-4 notching tool.

[0047] <Evaluation of cap opening torque> • Integration into bottles A polyethylene terephthalate container with a nominal diameter neck of 28 mm was filled with 500 mL of 87°C hot water, and the cap, which was manufactured by the aforementioned compression molding method, was attached to the neck by applying a tightening torque of 260 N·cm. Then, the container was tilted on its side for 30 seconds and then returned to an upright position. A 76°C hot water shower was applied for 3.5 minutes, followed by a 50°C hot water shower for 4.2 minutes, then a 40°C hot water shower for 4.0 minutes, and finally a 30°C hot water shower for 5.9 minutes. After that, the container was stored in a constant temperature room at 23°C for 7 days, and then the opening torque evaluation described later was performed.

[0048] • Evaluation of opening torque The evaluation container, which incorporated the bottle and cap, was rotated in the opening direction, causing it to detach from the neck of the container. The initial torque at this time (i.e., the maximum torque required to initiate the rotation of the container lid) was defined as the 1st torque, and the second torque (i.e., the maximum torque required to break the bridge) was defined as the 2nd torque. Measurements were taken for 15 evaluation samples, and the average value was used as the evaluation value.

[0049] <Example 1> Three types of commercially available PP resin were combined to create test pieces and caps, which were then evaluated. The physical properties are shown in Table 1. Figure 3 shows the change in opening torque.

[0050] <Comparative Example 1> Test specimens and caps were prepared and evaluated using one type of commercially available PP resin. The physical properties are shown in Table 1.

[0051] <Comparative Example 2> Using a different resin than that used in Comparative Example 1, a commercially available PP resin (Type 1) was used to prepare test specimens and caps for evaluation. The physical properties are shown in Table 1.

[0052] Furthermore, we marked items with a circle (○) if the 2nd torque was lower than the 1st torque, and items with a cross (×) if it was not. Furthermore, in the above examples and comparative examples, those that demonstrated excellent opening and sealing properties were given an overall rating of ○, while those that did not demonstrated excellent opening and sealing properties were given an overall rating of ×.

[0053] [Table 1] [Explanation of symbols]

[0054] 1: TE band with screw cap 3: Cap body 5: TE Band 7:Top plate part 9: Cylindrical side wall 11: Bridge 13: Spiral 15: Inner Ring 17: Outer ring 19: Circumferential process 21: Engaging member 50: Container mouth 51: Spiral 53: Jaw 55: Support Ring

Claims

1. A cap body formed from a top plate and a cylindrical side wall descending from the periphery of the top plate, and a tamper-evident band connected to the cylindrical side wall by a plurality of breakable bridges, In a screw cap, the inner surface of the cylindrical side wall is provided with a screw that engages with the outer surface of the container opening, and the inner surface of the tamper-evident band is provided with an engaging member that can engage with the lower surface of the jaw formed on the container opening, The cap body and tamper-evident band, including the bridge, are integrally molded from a polypropylene composition for screw caps. The aforementioned polypropylene composition for screw caps includes impact polypropylene having a structure in which polypropylene is used as a matrix and an elastomer component is dispersed within the polypropylene. The polypropylene composition contains the elastomer component in an amount of 10% by mass or more and less than 20% by mass. Charpy impact strength is 8.9 kJ / m ２ It is within the above range, A screw cap characterized by having an MFR of 5 g / 10 min or more and less than 15 g / 10 min at 230°C.

2. The screw cap according to claim 1, wherein the number average molecular weight Mn of the polypropylene is in the range of 60,000 or less, and the molecular weight distribution Mw / Mn is in the range of 3.0 to 6.

5.

3. The screw cap according to claim 2, wherein the weight-average molecular weight Mw of the elastomer component is in the range of 400,000 or more.

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