JP7601983B2 - Styrenic thermoplastic elastomer composition and food bottle valve body - Google Patents

Description

The present invention relates to a styrene-based thermoplastic elastomer composition suitable for food bottle valve bodies, and to food bottle valve bodies molded from the composition.

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.

JP 2012-106800 A

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 often used to mold thermoplastic resins. Another problem is that the rubber used in rubber valve bodies cannot be recycled.

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.

Furthermore, because the valve of a food bottle comes into contact with liquid seasonings and other foods, it must be made of a material that will not allow the chemicals contained in the valve to leach out and contaminate the food. A leach test is used to check for the leach-out of chemicals. Heptane is used as the solvent for the leach-out test when the food stored in the food bottle is oil or fatty food.

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.

The present invention has been made in consideration of the above points, and aims to provide a styrene-based thermoplastic elastomer composition that can be injection molded into a food bottle valve body, and that satisfies all of the requirements for low hardness to ensure the necessary sealing properties for the food bottle valve body, heptane resistance to ensure safety, and recyclability of the valve body, and a food bottle valve body molded from the composition.

The first aspect relates to a styrenic thermoplastic elastomer composition 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, and containing no plasticizer.

A second aspect relates to a valve body of a food bottle molded from the styrene-based thermoplastic elastomer composition according to the first aspect .

The styrene-based thermoplastic elastomer composition according to the first aspect can be used to injection-mold valve bodies for food bottles, and can satisfy all of the requirements for low hardness to ensure the necessary sealing properties for the valve bodies of food bottles, heptane resistance to ensure safety, and recyclability of the valve bodies.

According to the second aspect , 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.

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. 2 is a cross-sectional view of the valve body and the valve body support body in the food bottle of FIG. 1. [0023] FIG. 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.

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

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 being able to exhibit 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.

The olefin block copolymer is a block copolymer containing soft and hard segments, with each block being connected. Examples of the soft segment include ethylene, a copolymer of ethylene and diene, or a partially crosslinked version of these. Examples of the hard segment include propylene, etc. 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.

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

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 reducing the hardness of thermoplastic resins and increasing their flexibility, and examples of such plasticizers include paraffin oil and naphthenic oil.

The styrene-based thermoplastic elastomer composition of the present invention may contain other additives. Examples of additives include colorants, processing aids, and fillers.

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) based on JIS K 7210 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. If the MFR is too small, the fluidity will be poor, and moldability in injection molding and the like using molten resin will be poor.

The method for producing the styrene-based thermoplastic elastomer composition of the present invention is not particularly limited, but 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, etc.

In addition, the styrene-based thermoplastic elastomer composition of the present invention is pelletized by a pelletizer and used to mold a molded article.

The method for molding the molded article from the styrene-based thermoplastic elastomer composition of the present invention 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.

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%), more preferably less than ±10% (-10% to +10%).

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 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.

The molded article made from the styrene-based thermoplastic elastomer composition of the present invention has a 40°C compression set according to JIS K 6262 of less than 70%, more preferably less than 60%, and even more preferably 0 to 60%. If the compression set of the molded article is too large, the rebound during compression will be poor, and the sealing ability as a valve body for food bottles will decrease.

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 has 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.

The bottle body 20 is a double container made up 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 outer tube 31. The air flow path 25 is connected to 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.

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 being 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 fix the position.

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

The outer lid 49 is connected to a portion of the outer periphery of the top surface 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.

The valve body 50 is circular with a roughly 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 portion of the outer periphery of the first valve 51.

The first valve 51 is "cone-shaped" and recessed downwards under normal conditions (when the bottle 10 is not in use), with holes 53 formed at multiple locations on the periphery. The outer side of the central portion of the first valve 51 is placed on the support portion 61 of the valve body support 60, and under normal conditions (when the bottle 10 is not in use), the holes 53 on the periphery of the first valve 51 are in close contact with the edge of the support portion 61 of the valve body support 60, thereby closing the holes 53.

The second valve 52 is formed in 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 outside air from entering. 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.

The method of using the bottle 10 will now be described. When using the bottle 10 (to dispense 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, blocking the lower end of the air inlet 44.

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 content storage section 22 inside the inner tube 21. The pressurization of the food content storage section 22 pushes the center portion of the first valve 51, which blocks the opening surrounded by the support portion 61 of the valve body support portion 60, upward. As a result, the first valve 51 expands upward to state 51a, the hole 53 on the periphery of the first valve 51 opens away from the surface of the valve body support portion 60, and the food contents in the food content storage section 22 are supplied to the outside through the food contents supply port 43 of the lid body 40 through the hole 53 on the periphery of the first valve 51.

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 deforms 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.

At the same time, the inner tube 21 of the bottle body 20 expands, attempting to return to the state it was in before the bottle 10 was used. This reduces the pressure in the food content storage section 22, and the first valve 51 returns to the lower position it was in before the bottle 10 was used, 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, blocking the hole 53.

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.

Each of the Examples and Comparative Examples having the compositions 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, manufactured 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/ ^cm3
Olefin block copolymer: Product name: INFUSE 9807, manufactured by Dow Chemical, MFR = 15 g/10 min (ASTM 1238, 190°C/2.16 kg)
Styrene-ethylene-butylene copolymer: Product name: Kraton G1651, manufactured by Kraton Polymer Japan Co., Ltd. Plasticizer: Paraffin-based oil, Product name: Diana Process Oil PW-380, manufactured by Idemitsu Kosan Co., Ltd.

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, and an overall judgment (overall evaluation) was made based on the judgments for all measurement items.

The heptane resistance was measured by preparing a molded body of 100 mm×100 mm×thickness 2 mm by injection molding from the styrene-based thermoplastic elastomer composition of each Example and Comparative Examples 2 to 5, cutting a sample of φ20 mm×thickness 2 mm from the molded body, and measuring the heptane resistance according to the above-mentioned method for measuring the heptane resistance. 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 ±1% or more but less than ±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.

For the measurement of hardness, three molded bodies each measuring 100 mm × 100 mm × 2 mm thick were prepared by injection molding from the styrene-based thermoplastic elastomer compositions of each Example and Comparative Examples 2 to 5, and the A hardness of each was measured based on JIS K 6253. In Comparative Example 1, a molded body was prepared by press molding after adding a vulcanizing agent, and in Comparative Examples 6 to 8, molded bodies were prepared 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 "A", if it was between 50 and less than 60, it was marked as "O", and if it was 60 or more, it was marked as "X".

The 40°C compression set was measured by preparing a sheet by injection molding a plurality of molded articles each having a diameter of 13 mm and a thickness of 2 mm from the styrene-based thermoplastic elastomer composition of each Example and Comparative Examples 2 to 5, and measuring the 40°C compression set according to JIS K 6262. In Comparative Example 1, a molded article was prepared by press molding after adding a vulcanizing agent, and in 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 follows: if the measurement result of the 40° C. compression set was less than 60%, it was marked as "A", if it was 60 to less than 70%, it was marked as "O", and if it was 70% or more, it was marked as "X".

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) was judged as follows: when the measured melt flow rate (MFR) was 10 g/10 min or more, it was marked as "◎", when it was 5 g/10 min to less than 10 g/10 min, it was marked as "◯", and when it was less than 5 g/10 min , it was marked as "×".

The overall judgment was "◎" when all measurement items were judged as "◎", "〇" when all measurement items were judged as "〇" or above (i.e., ○ or ◎) and at least one measurement item was judged as "〇", and "×" when at least one measurement item was judged as "×".

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

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 of Example 1 were that the heptane resistance was 0.2%, rated as "◎", the hardness was 42, rated as "◎", the 40°C compression set was 68%, rated as "◯", the melt flow rate was 7 g/10 min , rated as "◯", and the overall rated as "◯". Example 1 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 is rated as "◯", so that the safety and sealability are good, and molding such as injection molding performed by melting the resin composition is possible, and it is recyclable.

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

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 of Example 2 were: heptane resistance was 0.3%, rated as "◎", hardness was 43, rated as "◎", 40°C compression set was 55%, rated as "◎", melt flow rate was 10 g/10 min , rated as "◎", and the overall rated as "◎". Example 2 has good heptane resistance, low hardness, and small permanent set, so the functionality of the molded product is good, and furthermore, the melt flow rate is rated as "◎", so the safety and sealability are good, and molding such as injection molding performed by melting the resin composition is possible, and it is recyclable.

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

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 of Example 3 were: heptane resistance was 0.5%, rated as "◎", hardness was 44, rated as "◎", 40°C compression set was 54%, rated as "◎", melt flow rate was 13 g/10 min , rated as "◎", and the overall rated as "◎". Example 3 has good heptane resistance, low hardness, and small permanent set, so the functionality of the molded product is good, and furthermore, the melt flow rate is rated as "◎", so the safety and sealability are good, and molding such as injection molding performed by melting the resin composition is possible, and it is recyclable.

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

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 of Example 4 were as follows: heptane resistance was 1.3%, rated as "good", hardness was 44, rated as "good", 40°C compression set was 53%, rated as "good", melt flow rate was 14 g/10 min , rated as "good", and the overall rated as "good". Example 4 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 is rated as "good", so that the safety and sealability are good, and molding such as injection molding performed by melting the resin composition is possible, and it is recyclable.

Comparative Example 1 is an example made only of silicone rubber.
The results of each measurement item of Comparative Example 1 are as follows: heptane resistance was 0.1%, rated as "◎", hardness was 40, rated as "◎", 40°C compression set was 10%, rated as "◎", melt flow rate was not rubbery (-), rated as "×", and 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 performed by melting the resin composition was impossible, and it was not recyclable.

Comparative Example 2 is an example consisting of a styrene-ethylene copolymer alone.
The results of each measurement item of Comparative Example 2 were: heptane resistance was 0.1%, rated as "A", hardness was 50, rated as "◯", 40°C compression set was 90%, rated as "X", melt flow rate was 2 g/10 min , rated as "X", and the overall rated as "X". Comparative Example 2 had good heptane resistance and low hardness, but the permanent set was large, so the functionality of the molded product was poor, and the melt flow rate was rated as "X", making it difficult to perform molding such as injection molding by melting the resin composition.

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

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%, rated "x", hardness was 44, rated "◎", 40°C compression set was 50%, rated "◎", melt flow rate was 15 g/10 min , rated "◎", and the overall rated "x". Comparative Example 4 was rated "◎" for the other measurement items except for the heptane resistance, which was rated "x", but the heptane resistance was low, and therefore the safety for food was poor.

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 measurement items of Comparative Example 5 were that the heptane resistance was 20.5%, rated "x", the hardness was 40, rated "◎", the 40°C compression set was 60%, rated "◯", the melt flow rate was 17 g/10 min , rated "◎", and the overall rated "x". In Comparative Example 5, the other measurement items were rated "◯" or higher except for the heptane resistance, which was rated "x", but the heptane resistance was low, and therefore the safety for food was poor.

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 "◎", the melt flow rate was 20 g/10 min , rated as "◎", and the overall rated as "x". Comparative Example 6 is inferior in safety for food products because the heptane resistance and hardness are rated as "x", and the hardness is high, so the sealability is inferior.

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 and was judged as "x", the hardness was 35 and was judged as "◎", the 40°C compression set was 20% and was judged as "◎", the melt flow rate was 40g/ 10min and was judged as "◎", and the overall judgment was "x". Comparative Example 7 had an increased amount of paraffin oil as a plasticizer compared to Comparative Example 6, so the hardness was further reduced and the hardness was judged as "◎", but the heptane resistance was judged as "x", so the safety for food was poor.

Comparative Example 8 is an example in which the amount of paraffin-based 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 "◎", the melt flow rate was 50 g/10 min , rated as "◎", and the overall rated as "x". Comparative Example 8 had an increased amount of paraffin oil as a plasticizer compared to Comparative Examples 6 and 7, so the hardness was further reduced and rated as "◎", but the heptane resistance was rated as "x", so the safety for food was poor.

In this way, the styrene-based thermoplastic elastomer composition of the present invention is injection moldable and can satisfy all of the following requirements for the valve body of a food bottle: low hardness to ensure the sealing performance required for the valve body of a food bottle, heptane resistance to ensure safety, and recyclability. Furthermore, the valve body of a food bottle molded from the styrene-based thermoplastic elastomer composition of the present invention can satisfy all of the following requirements for the valve body of a food bottle: low hardness to ensure the sealing performance required for the valve body of a food bottle, heptane resistance to ensure safety, and recyclability.

REFERENCE SIGNS LIST 10 Food bottle 20 Bottle body 21 Inner cylinder 22 Food content storage section 31 Outer cylinder 43 Food content supply port 44 Outside air intake port 49 Outer lid 50 Valve body 51 First valve 52 Second valve

Claims (2)

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. A food bottle valve body molded from 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 containing no plasticizer.