Styrenic thermoplastic elastomer composition and food bottle valve body

Abstract

To provide a styrene-based thermoplastic elastomer composition which is capable of injection molding a valve body of a food bottle and satisfies all following factors: low hardness for securing a sealing property required for the valve element of the food bottle; heptane resistance for securing safety; and ability for recycling, and to provide a molded article thereof.SOLUTION: There is provided a styrene-based thermoplastic elastomer composition comprising a styrene-ethylene copolymer and an olefin block copolymer, where the blending amount of the olefin block copolymer is 20 to 85 pts. wt. based on 100 pts. wt. of the styrene-ethylene copolymer and the composition contains no plasticizers. There is also provided a valve body of a food bottle molded from the styrene-based thermoplastic elastomer composition.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a styrene-based thermoplastic elastomer composition suitable for use as a valve body for a food bottle, and to a valve body for a food bottle molded from the composition. [Background technology]

[0002] Conventionally, food bottles such as soy sauce bottles and delaminated bottles are provided with a valve body (check valve) for sealing the inlet. The valve body of food bottles is made of rubber such as EPDM rubber or silicone rubber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-106800 A Summary of the Invention [Problem to be solved by the invention]

[0004] Rubber valve bodies are molded by press molding. Press molding has the problem that it is less easy to work with than injection molding, which is widely used for molding thermoplastic resins. In addition, the rubber used in rubber valve bodies cannot be recycled.

[0005] In order to solve the above problems with rubber valve bodies for food bottles, there is a demand for thermoplastic elastomers that can be injection molded into valve bodies and that are recyclable. However, conventional injection-moldable thermoplastic elastomers are required to have a low hardness in order to ensure the necessary sealing performance for the valves of food bottles.

[0006] Furthermore, since the valve of a food bottle comes into contact with food such as liquid seasonings, it must be made of a material that does not allow the chemicals contained in the valve to leach out and contaminate the food. A leach test is used to check the leach out of chemicals. Heptane is used as a solvent for the leach test when the food contained in the food bottle is oil or fatty food.

[0007] However, among conventional thermoplastic elastomers used in injection molding, there were none that satisfied both the low hardness required for the sealing properties of the valve body and the heptane resistance required for safety. In addition, when a conventional thermoplastic elastomer with high heptane resistance is added with a large amount of plasticizer to reduce the hardness, the heptane resistance decreases. On the other hand, a conventional thermoplastic elastomer with low hardness and good sealing properties has low heptane resistance.

[0008] The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to provide a styrene-based thermoplastic elastomer composition that can be injection-molded into a valve body for a food bottle, and that satisfies all of the requirements for a low hardness to ensure the sealing performance required for the valve body of a food bottle, heptane resistance to ensure safety, and recyclability of the valve body, and a valve body for a food bottle molded from the composition. [Means for solving the problem]

[0009] First aspect The styrene-based thermoplastic elastomer composition comprises a styrene-ethylene copolymer and an olefin block copolymer, the amount of the olefin block copolymer being 20 to 85 parts by weight per 100 parts by weight of the styrene-ethylene copolymer, and does not contain a plasticizer.

[0010] Second Aspect teeth, First aspect The present invention relates to a valve body of a food bottle molded from the styrenic thermoplastic elastomer composition described in 1. Effect of the Invention

[0011] First aspect The styrene-based thermoplastic elastomer composition according to the present invention can be used to injection-mold the valve bodies of food bottles, and can satisfy all of the requirements for the valve bodies of food bottles, including low hardness to ensure the sealing properties required for the valve bodies of food bottles, heptane resistance to ensure safety, and recyclability of the valve bodies.

[0012] Second Aspect According to the invention, the valve body of the molded food bottle can satisfy all of the requirements for the valve body, namely, low hardness for ensuring the necessary sealing performance, heptane resistance for ensuring safety, and recyclability of the valve body. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view of the upper portion of a food bottle equipped with a valve body molded from the styrene-based thermoplastic elastomer of the present invention. [Diagram 2] 2 is a cross-sectional view of a valve body and a valve body support body in the food bottle of FIG. 1. [Diagram 3] 1 is a table showing the blends, physical properties, physical property evaluations, and overall evaluations of examples and comparative examples of styrene-based thermoplastic elastomers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The styrene-based thermoplastic elastomer composition of the present invention comprises a styrene-ethylene copolymer and an olefin block copolymer, and does not contain a plasticizer.

[0015] The styrene-ethylene copolymer is a block copolymer having a hard segment made of polystyrene and a soft segment mainly made of polyethylene (which may contain a styrene-ethylene copolymer). The styrene-ethylene copolymer may be either a random copolymer or a graft copolymer. From the viewpoint of exhibiting flexibility without containing a plasticizer, the styrene content of the styrene-ethylene copolymer is 10 to 40% by weight, more preferably 15 to 35% by weight. Furthermore, from the viewpoint of moldability, the melt flow rate (MFR) is 0.3 to 30 g / 10 min, more preferably 1 to 20 g / 10 min.

[0016] The olefin block copolymer is a block copolymer containing a soft segment and a hard segment, and each block is connected. The soft segment may be ethylene, a copolymer of ethylene and a diene, or a partially crosslinked one of these. The hard segment may be propylene or the like. The olefin block copolymer is not limited to one type, and may be used in combination of two or more types. The olefin block copolymer has a melt flow rate (MFR) of 5 to 30 g / 10 min, more preferably 10 to 20 g / 10 min, from the viewpoint of improving the compression properties of the molded article.

[0017] The blending amount of the olefin block copolymer is preferably 20 to 85 parts by weight, more preferably 25 to 82 parts by weight, per 100 parts by weight of the styrene-ethylene copolymer. If the blending amount of the olefin block copolymer is too small, the flowability is poor, making molding such as injection molding difficult, and the compression characteristics of the molded product are also poor. On the other hand, if the blending amount of the olefin block copolymer is too large, the heptane resistance is poor.

[0018] The styrene-based thermoplastic elastomer composition of the present invention does not contain a plasticizer. By not containing a plasticizer, it is possible to increase the heptane resistance. Plasticizers are generally used for the purpose of decreasing the hardness of thermoplastic resins to increase their flexibility, and examples of such plasticizers include paraffin oil and naphthene oil.

[0019] The styrene-based thermoplastic elastomer composition of the present invention may contain other additives, such as colorants, processing aids, and fillers.

[0020] The styrene-based thermoplastic elastomer composition of the present invention preferably has an MFR (melt flow rate) value (value at 230°C and 2.16 kgf) of 5 g / 10 min or more, more preferably 10 g / 10 min or more, and even more preferably 10 g / 10 min to 40 g / 10 min, based on JIS K 7210. If the MFR is too small, the fluidity is poor, and moldability in injection molding and the like using a molten resin is poor.

[0021] The method for producing the styrene-based thermoplastic elastomer composition of the present invention is not particularly limited, and examples thereof include a method of melt kneading using a screw extruder such as a single screw extruder or a twin screw extruder, a Banbury mixer, a mixing roll, or the like.

[0022] The styrene-based thermoplastic elastomer composition of the present invention is pelletized by a pelletizer and used for molding a molded article.

[0023] The method for molding the styrene-based thermoplastic elastomer composition of the present invention into a molded article can be a known molding method such as extrusion molding or injection molding, which is used as a molding method for plastics. In particular, injection molding using a mold is a suitable molding method. For extrusion molding or injection molding, pellets formed from the styrene-based thermoplastic elastomer composition are used.

[0024] The molded article made from the styrenic thermoplastic elastomer composition of the present invention has good heptane resistance (chemical resistance). The heptane resistance is measured by measuring the weight of a sample of φ20 mm × thickness 2 mm cut from the molded product, immersing it in a heptane solution for 60 minutes, measuring the weight of the sample removed after immersion, and measuring the rate of weight change after immersion relative to the weight before immersion. The rate of weight change of the molded product molded from the styrene-based thermoplastic elastomer composition of the present invention is less than ±2% (-2% to +2%), and more preferably less than ±10% (-10% to +10%).

[0025] The molded article made from the styrene-based thermoplastic elastomer composition of the present invention has a hardness (A hardness) after 15 seconds based on JIS K 6253 of less than 60, more preferably less than 50, and even more preferably from 40 to less than 50. If the hardness of the molded article is too high, it will lack flexibility and will have poor sealing properties as a valve body for a food bottle.

[0026] Furthermore, the molded article made from the styrene-based thermoplastic elastomer composition of the present invention has a 40°C compression set of less than 70%, more preferably less than 60%, and even more preferably 0 to 60%, based on JIS K 6262. If the compression set of the molded article is too large, the rebound during compression is poor, and the sealing ability as a valve body for a food bottle is reduced.

[0027] Next, an example of a food bottle equipped with a valve body formed by injection molding from the styrene-based thermoplastic elastomer composition of the present invention will be described. The food bottle 10 shown in FIG. 1 comprises a bottle body 20, a lid body 40, an outer lid 49, a valve body 50, a valve body support 60, etc., and contains food contents, such as liquid seasoning.

[0028] The bottle body 20 is made of a double container made of a flexible and elastically deformable inner tube 21 and outer tube 31, and has an air flow path 25 between the inner tube 21 and the outer tube 31. The air flow path 25 communicates with the upper part of the cylindrical side part 45 of the lid body 40 located above. The inside of the inner tube 21 is a storage section 22 for the food contents.

[0029] A valve body support 60 is placed on the upper end of the bottle body 20. The valve body support 60 is generally cylindrical, with the inner periphery of the upper end forming an annular support part 61, and the central part surrounded by the support part 61 is open. Meanwhile, the lower end of the valve body support 60 is placed on the upper end of the bottle body 20 and is fitted into the upper end of the bottle body 20 to be fixed in position.

[0030] The lid body 40 has a dome-shaped upper portion 47 extending from the upper end of a cylindrical side portion 45 through a top surface portion 46, and a food content supply port 43 is formed at the apex of the dome-shaped upper portion 47. In addition, an outside air intake port 44 communicating with the air flow path 25 between the inner cylinder 21 and the outer cylinder 31 is formed in the top surface portion 46.

[0031] The outer lid 49 is connected to a part of the outer peripheral edge of the top surface portion 46 of the lid body 40 via a hinge 41. The outer lid 49 covers the lid body 40 when the bottle 10 is not in use, and is separated from the upper portion 47 of the lid body 40 when the bottle 10 is in use.

[0032] The valve body 50 has a circular shape with a generally M-shaped cross section, and is fitted onto the valve body support 60. The valve body 50 has a first valve 51 formed in the center, and a second valve 52 formed on a part of the outer periphery of the first valve 51.

[0033] The first valve 51 is formed in a "mortar shape" that is recessed downward under normal conditions (when the bottle 10 is not in use), and has holes 53 formed in multiple places on its periphery. The outer side of the central portion of the first valve 51 is placed on the support part 61 of the valve body support body 60, and under normal conditions (when the bottle 10 is not in use), the holes 53 on the periphery of the first valve 51 come into close contact with the edge of the support part 61 of the valve body support body 60, thereby closing the holes 53.

[0034] The second valve 52 is formed at a position where it can come into contact with the lower end of the air inlet 44 of the lid body 40, and by coming into contact with the lower end of the air inlet 44 of the lid body 40, it closes the lower end of the air inlet 44 and prevents the inflow of outside air. The lower surface of the second valve 52 is located above the air flow path 25 between the inner tube 21 and the outer tube 31 of the bottle body 20.

[0035] A method of using the bottle 10 will now be described. When using the bottle 10 (to expel the food contents), the outer tube 31 of the bottle body 20 is pushed from the outside. This pushes the air in the air flow path 25 between the outer tube 31 and the inner tube 21 upward, and the second valve 52 located above the air flow path 25 is pushed upward. This causes the second valve 52 to abut against the lower end of the air inlet 44 of the lid body 40, and the lower end of the air inlet 44 is closed.

[0036] At the same time, the inner tube 21 of the bottle body 20 is pushed inward by the air in the air flow path 25, thereby pressurizing the food contents storage section 22 inside the inner tube 21. The pressurization of the food contents storage section 22 pushes the center portion of the first valve 51, which closes the opening portion surrounded by the support portion 61 of the valve body support portion 60, upward. As a result, the first valve 51 bulges upward to the state 51a, the hole 53 on the periphery of the first valve 51 opens away from the surface of the valve body support member 60, and the food contents in the food contents storage section 22 are supplied to the outside from the food contents supply port 43 of the lid body 40 through the hole 53 on the periphery of the first valve 51.

[0037] On the other hand, when the use of the bottle 10 is finished, the pressure on the outer cylinder 31 of the bottle body 20 is stopped. As a result, a restoring force acts on the outer cylinder 31 of the bottle body 20 to return it to the state before the bottle 10 was used, the pressure inside the air flow path 25 between the inner cylinder 21 and the outer cylinder 31 is reduced, and the second valve 52 located above the air flow path 25 is deformed downward. As the second valve 52 is deformed downward, the lower end of the air flow path 25 is opened, outside air flows into the air flow path 25 from the outside air intake port 44, and the outer cylinder 31 is returned to the state before the bottle 10 was used.

[0038] At the same time, the inner tube 21 of the bottle body 20 expands, attempting to return to the state it was in before use of the bottle 10. This reduces the pressure in the food content storage section 22, causes the first valve 51 to return to the lower position it was in before use of the bottle 10, and the hole 53 on the periphery of the first valve 51 comes into close contact with the surface of the valve body support section 60 to close the hole 53.

[0039] The food bottle and its valve body are not limited to those shown in Figs. 1 and 2, and any structure usable as a food bottle and its valve body may be used. Furthermore, the method for manufacturing the valve body of the food bottle is not limited to injection molding, and other molding methods using molten resin may be used. EXAMPLES

[0040] Each of the examples and comparative examples having the composition shown in Figure 3 will be described below. The materials used in each of the examples and comparative examples will be described below. Silicone rubber: Product name: KE-941-U, made by Shin-Etsu Silicone Styrene-ethylene copolymer: Product name; SE Polymer SX006, manufactured by Denka Co., Ltd., styrene content = 25 mass%, MFR = 6.4 g / 10 min (200 °C, load 5 kg (JIS K7210)), density: 0.98 g / cm 3 Olefin block copolymer: Product name; INFUSE9807, manufactured by Dow Chemical, MFR=15g / 10min (ASTM 1238, 190℃ / 2.16kg) Styrene-ethylene-butylene copolymer: Product name: Kraton G1651, manufactured by Kraton Polymer Japan Co., Ltd. Plasticizer: Paraffin oil, Product name: Diana Process Oil PW-380, manufactured by Idemitsu Kosan Co., Ltd.

[0041] For each example and comparative example, the heptane resistance, hardness, 40°C compression set, and melt flow rate (MFR) were measured, and a judgment (evaluation) was made for each measurement item. Furthermore, an overall judgment (overall evaluation) was made based on the judgments for all measurement items.

[0042] The heptane resistance was measured by preparing a molded body of 100 mm×100 mm×thickness 2 mm from the styrene-based thermoplastic elastomer composition of each Example and Comparative Examples 2 to 5 by injection molding, cutting a sample of φ20 mm×thickness 2 mm from the molded body, and measuring the heptane resistance according to the above-mentioned measuring method for the sample. Note that, for Comparative Example 1, a molded body was prepared by press molding after adding a vulcanizing agent, and for Comparative Examples 6 to 8, molded bodies were prepared by injection molding, and samples formed from these molded bodies were used to measure the heptane resistance. Heptane resistance was judged as "◎" when the measurement result of the weight change rate was within ±1% (-1% to +1%), "〇" when it was between ±1% and ±2% (-2% to -1% or +1% to +2%), and "×" when it was ±2% or more (-2% or less or +2% or more) or when it dissolved.

[0043] The hardness was measured by injection molding three molded bodies each measuring 100 mm×100 mm×2 mm thick, which were stacked, from the styrene-based thermoplastic elastomer compositions of each Example and Comparative Examples 2 to 5, and measuring the A hardness of each of the molded bodies according to JIS K 6253. In Comparative Example 1, a molded body was produced by press molding after adding a vulcanizing agent, and in Comparative Examples 6 to 8, molded bodies were produced by injection molding, and samples formed from these molded bodies were used to measure the hardness. The hardness was judged as follows: if the hardness measurement result was less than 50, it was marked as "◎", if it was between 50 and 60, it was marked as "◯", and if it was 60 or more, it was marked as "X".

[0044] The 40°C compression set was measured by preparing a sheet by injection molding a plurality of molded articles of φ13 × thickness 2 mm from the styrene-based thermoplastic elastomer compositions of each Example and Comparative Examples 2 to 5, and measuring the compression set at 40°C according to JIS K 6262. Note that, for Comparative Example 1, a molded article was prepared by press molding after adding a vulcanizing agent, and for Comparative Examples 6 to 8, a molded article was prepared by injection molding, and samples formed from these molded articles were used to measure the 40°C compression set. The 40°C compression set was judged as "A" when the measurement result of the 40°C compression set was less than 60%, "O" when it was 60 to less than 70%, and "X" when it was 70% or more.

[0045] The melt flow rate (MFR) of each of the styrene-based thermoplastic elastomer compositions of Examples and Comparative Examples 2 to 8 was measured in accordance with JIS K 7210. The melt flow rate (MFR) is judged when the measured MFR is 10g / 10m in In the above cases, "◎" 5g / 10m in ~10g / 10m in "〇" if less than 5g / 10m in If it was less than this, it was marked as “×”.

[0046] The overall judgment was given as follows: when all measurement items were judged as "◎", the overall judgment was given as "◎", when all measurement items were judged as "O" or above (i.e., O or ◎) and at least one measurement item was judged as "O", the overall judgment was given as "O", and when at least one measurement item was judged as "X".

[0047] In Example 1, 100 parts by weight of a styrene-ethylene copolymer and 25 parts by weight of an olefin block copolymer were blended and melt-kneaded in an extruder at a temperature of 220° C. and a screw rotation speed of 400 rpm to prepare a styrene-based thermoplastic elastomer composition.

[0048] Example 1 is an example consisting of 100 parts by weight of a styrene-ethylene copolymer and 25 parts by weight of an olefin block copolymer. The results of each measurement item in Example 1 were as follows: heptane resistance was 0.2%, judged as "◎", hardness was 42, judged as "◎", 40°C compression set was 68%, judged as "◯", and melt flow rate was 7g / 10m in, and the overall evaluation was "good." Example 1 has good heptane resistance, low hardness, and small permanent deformation, so that the functionality of the molded product is good, and furthermore, the melt flow rate was evaluated as "good," so that the safety and sealability are good, and molding such as injection molding, which is performed by melting the resin composition, is possible, and the product is recyclable.

[0049] Example 2 is similar to Example 1 except that the olefin block copolymer in the Example 1 formulation was increased to 42.9 parts by weight.

[0050] Example 2 is an example consisting of 100 parts by weight of a styrene-ethylene copolymer and 42.9 parts by weight of an olefin block copolymer. The results of each measurement item in Example 2 were as follows: heptane resistance was 0.3%, judged as "◎", hardness was 43, judged as "◎", 40°C compression set was 55%, judged as "◎", and melt flow rate was 10g / 10m in , and the overall rating was "◎". Example 2 has good heptane resistance, low hardness, and small permanent set, so that the functionality of the molded product is good, and furthermore, the melt flow rate was rated "◎", so that the safety and sealability are good, and molding such as injection molding, which is performed by melting the resin composition, is possible, and the product is recyclable.

[0051] Example 3 is similar to Example 1 except that the olefin block copolymer in the Example 1 formulation was increased to 66.7 parts by weight.

[0052] Example 3 is an example consisting of 100 parts by weight of a styrene-ethylene copolymer and 66.7 parts by weight of an olefin block copolymer. The results of each measurement item in Example 3 were as follows: heptane resistance was 0.5%, judged as "◎", hardness was 44, judged as "◎", 40°C compression set was 54%, judged as "◎", and melt flow rate was 13g / 10m in, and the overall evaluation was "A". Example 3 has good heptane resistance, low hardness, and small permanent set, so that the functionality of the molded product is good, and furthermore, the melt flow rate was evaluated as "A", so that the safety and sealability are good, and molding such as injection molding, which is performed by melting the resin composition, is possible, and the product is recyclable.

[0053] Example 4 is similar to Example 1 except that the olefin block copolymer in the Example 1 formulation was increased to 81.8 parts by weight.

[0054] Example 4 is an example consisting of 100 parts by weight of a styrene-ethylene copolymer and 81.8 parts by weight of an olefin block copolymer. The results of each measurement item in Example 4 were as follows: heptane resistance was 1.3%, judged as "good", hardness was 44, judged as "good", 40°C compression set was 53%, judged as "good", and melt flow rate was 14g / 10m in The evaluation results were "◎", and the overall evaluation was "◯". Example 4 has good heptane resistance, low hardness, and small permanent deformation, so that the functionality of the molded product is good, and furthermore, the evaluation result of the melt flow rate was "◎", so that the safety and sealability are good, and molding such as injection molding, which is performed by melting the resin composition, is possible, and the product is recyclable.

[0055] Comparative Example 1 is an example made only of silicone rubber. The results of each measurement item of Comparative Example 1 were that the heptane resistance was 0.1%, rated as "◎", the hardness was 40, rated as "◎", the 40°C compression set was 10%, rated as "◎", the melt flow rate was not rubbery (-), rated as "×", and the overall rated as "×". Comparative Example 1 had good heptane resistance, low hardness, and small permanent set, so the functionality of the molded body was good, but since the melt flow rate was rated as "×", molding such as injection molding, which is performed by melting the resin composition, was impossible, and it was not recyclable.

[0056] Comparative Example 2 is an example consisting of a styrene-ethylene copolymer only. The results of each measurement item of Comparative Example 2 were as follows: heptane resistance was 0.1%, judged as "◎", hardness was 50, judged as "◯", 40°C compression set was 90%, judged as "×", and melt flow rate was 2g / 10m in In Comparative Example 2, the heptane resistance was good and the hardness was low, but the functionality of the molded product was poor due to the large permanent set, and the melt flow rate was also judged as "x", making it difficult to perform molding such as injection molding in which the resin composition is melted.

[0057] Comparative Example 3 is an example similar to Example 1, except that it contains 100 parts by weight of a styrene-ethylene copolymer and 10 parts by weight of an olefin block copolymer, which is less than the range of the present invention. The results of each measurement item of Comparative Example 3 were as follows: heptane resistance was 0.2%, judged as "◎", hardness was 43, judged as "◎", 40°C compression set was 88%, judged as "×", and melt flow rate was 3g / 10m in In Comparative Example 3, the heptane resistance was good and the hardness was low, but the functionality of the molded product was poor due to the large permanent set, and the melt flow rate was also judged as "x", making it difficult to perform molding such as injection molding in which the resin composition is melted.

[0058] Comparative Example 4 is an example which consists of only 100 parts by weight of a styrene-ethylene copolymer and 100 parts by weight of an olefin block copolymer which is greater than the range of the present invention, and is otherwise the same as Example 1. The results of each measurement item of Comparative Example 4 were as follows: heptane resistance was 5.7%, judged as "x", hardness was 44, judged as "◎", 40°C compression set was 50%, judged as "◎", and melt flow rate was 15g / 10m inIn Comparative Example 4, the heptane resistance was judged as "x", and the other measurement items were judged as "◎", but the heptane resistance was low, so the safety for food was poor.

[0059] Comparative Example 5 is an example similar to Example 1, except that 30 parts by weight of paraffin-based oil was added to the formulation of Example 1 as a plasticizer, which is not added in the present invention. The results of the measurements of the items in Comparative Example 5 were that the heptane resistance was 20.5%, judged as "x", the hardness was 40, judged as "◎", the 40°C compression set was 60%, judged as "◯", and the melt flow rate was 17 g / 10 m in In Comparative Example 5, the heptane resistance was judged as "x", and the other measurement items were judged as "good" or better, but the heptane resistance was low, so the safety for food was poor.

[0060] Comparative Example 6 is an example comprising 100 parts by weight of a styrene-ethylene-butylene copolymer, which is not used in the present invention, and 30 parts by weight of paraffinic oil as a plasticizer. The results of each measurement item of Comparative Example 6 were that the heptane resistance was not dissolved, rated as "x", the hardness was 55, rated as "x", the 40°C compression set was 20%, rated as "◎", and the melt flow rate was 20g / 10m in , and the overall evaluation was "×." Comparative Example 6 was evaluated as "×" for heptane resistance and hardness, and therefore was poor in safety for food, and had poor sealing properties due to its high hardness.

[0061] Comparative Example 7 is an example in which the amount of paraffin-based oil used as a plasticizer in Comparative Example 6 was increased to 50 parts by weight. The results of each measurement item of Comparative Example 7 were that the heptane resistance was not dissolved, rated as "x", the hardness was 35, rated as "◎", the 40°C compression set was 20%, rated as "◎", and the melt flow rate was 40g / 10m inIn Comparative Example 7, the amount of paraffin oil used as a plasticizer was increased from that in Comparative Example 6, so that the hardness was further reduced and the hardness was judged as "◎", but the heptane resistance was judged as "×", so that the safety for food use was poor.

[0062] Comparative Example 8 is an example in which the amount of paraffin oil used as a plasticizer in Comparative Example 6 was increased to 100 parts by weight. The results of each measurement item of Comparative Example 8 were that the heptane resistance was not dissolved, rated as "x", the hardness was 15, rated as "◎", the 40°C compression set was 30%, rated as "◎", and the melt flow rate was 50 g / 10 m in In Comparative Example 8, the amount of paraffin oil used as a plasticizer was increased more than in Comparative Examples 6 and 7, so the hardness was further reduced and the hardness was judged as "◎", but the heptane resistance was judged as "×", so the safety for food use was poor.

[0063] Thus, the styrene-based thermoplastic elastomer composition of the present invention is injection moldable and can satisfy all of the requirements for a valve body of a food bottle, namely, low hardness for ensuring sealing performance, heptane resistance for ensuring safety, and recyclability. Also, a valve body of a food bottle molded from the styrene-based thermoplastic elastomer composition of the present invention can satisfy all of the requirements for a valve body of a food bottle, namely, low hardness for ensuring sealing performance, heptane resistance for ensuring safety, and recyclability. [Explanation of symbols]

[0064] 10 Food Bottles 20 Bottle body 21 Inner cylinder 22 Food content storage section 31 Outer cylinder 43 Food content supply port 44 Fresh air intake 49 Outer lid 50 Valve body 51 First Valve 52 Second Valve

Claims

1. A styrene-ethylene copolymer and an olefin block copolymer, The styrene-ethylene copolymer has a melt flow rate of 1 to 20 g / 10 min at 200° C. under a load of 5 kg according to JIS K 7210; The olefin block copolymer has a melt flow rate of 10 to 20 g / 10 min at 190° C. and a load of 2.16 kg according to ASTM 1238; The amount of the olefin block copolymer is 20 to 85 parts by weight based on 100 parts by weight of the styrene-ethylene copolymer, Contains no plasticizers A styrene-based thermoplastic elastomer composition having a melt flow rate of 5 to 40 g / 10 min at 230° C. under a load of 2.16 kg according to JIS K 7210.

2. A valve body for a food bottle molded from a styrene-based thermoplastic elastomer composition containing no plasticizer, the valve body comprising a styrene-ethylene copolymer and an olefin block copolymer, the amount of the olefin block copolymer being 20 to 85 parts by weight per 100 parts by weight of the styrene-ethylene copolymer.

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