Styrene-based thermoplastic elastomer composition and valve body for food bottle

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 styrenic thermoplastic elastomer composition suitable for a valve body of a food bottle and a valve body of a food bottle molded from the composition.

Background Art

[0002] Conventionally, food bottles such as soy sauce bottles and delami bottles are provided with a valve body (check valve) for sealing at the injection port. As materials for the valve body of food bottles, rubbers such as EPDM rubber and silicone rubber are used.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The molding of the rubber valve body is performed by press molding. Press molding has a problem of inferior workability compared to injection molding, which is frequently used for molding thermoplastic resins. In addition, there is also a problem that the rubber of the rubber valve body cannot be recycled.

[0005] In order to solve the above problems in the rubber valve body of food bottles, a thermoplastic elastomer that can be injection molded and recycled is required. However, conventional thermoplastic elastomers that can be injection molded require a low hardness to ensure the sealing performance required for the valve body of food bottles.

[0006] Furthermore, since the valve body of the food bottle comes into contact with foods such as liquid seasonings, it is necessary to be made of a material that does not contaminate the food by eluting chemical substances or the like contained in the valve body. There is an elution test as a test for confirming the elution of chemical substances or the like. As the solvent used in the elution test, when the food contained in the food bottle is an oil or fatty food, heptane is used.

[0007] However, among the conventional thermoplastic elastomers used for injection molding, there is none that satisfies both the low hardness required for the sealing property of the valve body and the heptane resistance for safety. In addition, for conventional thermoplastic elastomers with high heptane resistance, when a large amount of plasticizer is added to lower the hardness, the heptane resistance tends to decrease. On the other hand, conventional low-hardness thermoplastic elastomers with good sealing properties had low heptane resistance.

[0008] The present invention has been made in view of the above points, and an object thereof is to provide a styrenic thermoplastic elastomer composition that can be injection-molded into the valve body of a food bottle and satisfies all of the low hardness for ensuring the sealing property required for the valve body of the food bottle, the heptane resistance for ensuring safety, and the recyclability of the valve body, and a valve body of a food bottle molded from the composition.

Means for Solving the Problems

[0009] Aspect of the first invention It relates to a styrenic thermoplastic elastomer composition comprising a styrene-ethylene copolymer and an olefin block copolymer, wherein the blending amount of the olefin block copolymer is 20 to 85 parts by weight with respect to 100 parts by weight of the styrene-ethylene copolymer, and does not contain a plasticizer.

[0010] The aspect of the second invention pertains to the aspect of the first invention It relates to a valve body of a food bottle molded from the styrenic thermoplastic elastomer composition described in.

Effects of the Invention

[0011] Aspect of the first inventionThe styrenic thermoplastic elastomer composition according to [relevant content] can be injection-molded into the valve body of a food bottle, and can satisfy all of the low hardness for ensuring the sealing property required for the valve body of the food bottle, the heptane resistance for ensuring safety, and the recyclability of the valve body.

[0012] Aspect of the second invention According to [relevant content], the valve body of the formed food bottle can satisfy all of the low hardness for ensuring the sealing property required for the valve body, the heptane resistance for ensuring safety, and the recyclability of the valve body.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0014] The styrenic thermoplastic elastomer composition in the present invention is composed of 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 having polyethylene as a main component (which may include 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 is 10 to 40% by weight, more preferably 15 to 35% by weight. Further, 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 is used.

[0016] The olefin block copolymer is a block copolymer containing a soft segment and a hard segment, and each block is connected. Examples of the soft segment include ethylene, a copolymer of ethylene and diene, or those having partial crosslinking thereof. Examples of the hard segment include propylene and the like. The olefin block copolymer is not limited to one type, and two or more types may be mixed and used. From the viewpoint of improving the compression characteristics of the molded article, 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 is used.

[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, based on 100 parts by weight of the styrene-ethylene copolymer. If the blending amount of the olefin block copolymer is too small, the fluidity becomes poor and molding such as injection molding becomes difficult, and the compression characteristics of the molded article also deteriorate. On the other hand, if the blending amount of the olefin block copolymer is too large, the heptane resistance deteriorates.

[0018] The styrenic thermoplastic elastomer composition of the present invention does not contain a plasticizer. By not containing a plasticizer, the heptane resistance can be enhanced. Plasticizers are generally used for the purpose of reducing the hardness of thermoplastic resins and increasing flexibility, and examples thereof include paraffin oil and naphthene oil.

[0019] In addition, other additives may be blended in the styrenic thermoplastic elastomer composition of the present invention. Examples of the additives include colorants, processing aids, fillers, and the like.

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

[0021] The method for producing the styrenic 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, etc.

[0022] Further, the styrenic thermoplastic elastomer composition of the present invention is pelletized by a pelletizer and used for molding a molded body.

[0023] As the method for molding a molded body from the styrenic thermoplastic elastomer composition of the present invention, known molding methods such as extrusion molding and injection molding used as plastic molding methods can be used. In particular, injection molding using a mold is a suitable molding method. In addition, for extrusion molding and injection molding, pellets formed from the styrenic thermoplastic elastomer composition are used.

[0024] The molded body molded from the styrenic thermoplastic elastomer composition of the present invention has good heptane resistance (chemical resistance). For the measurement of heptane resistance, for a sample of φ20 mm × thickness 2 mm cut from the molded body, after measuring the weight, it is immersed in a heptane solution for 60 minutes, the weight of the sample taken out after immersion is measured, and the weight change rate after immersion with respect to the weight before immersion is measured. The molded body molded from the styrenic thermoplastic elastomer composition of the present invention has a weight change rate of less than ±2% (-2% to +2%), and more preferably less than ±10% (-10% to +10%).

[0025] The molded article formed from the styrenic 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 the sealing property will deteriorate when used as a valve body for a food bottle.

[0026] Further, the molded article formed from the styrenic thermoplastic elastomer composition of the present invention has a compression set at 40 °C based on JIS K 6262 of less than 70%, more preferably less than 60%, and even more preferably from 0 to 60%. If the compression set of the molded article is too large, the resilience during compression will deteriorate and the sealing property as a valve body for a food bottle will decrease.

[0027] Next, an example of a food bottle with a valve body molded by injection molding from the styrenic thermoplastic elastomer composition of the present invention is shown. 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 houses food contents such as liquid seasonings.

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

[0029] A valve body support 60 is placed on the upper end of the bottle body 20. The valve body support 60 has a substantially cylindrical shape, and the inner circumference of the upper end is an annular support part 61, and the central part surrounded by the support part 61 is open. On the other hand, the lower end of the valve body support 60 is placed on the upper end of the bottle body 20 and is fitted and position-fixed to the upper end of the bottle body 20.

[0030] The lid body 40 has a dome-shaped upper part 47 formed from the upper end of a cylindrical side part 45 via a top surface part 46, and a supply port 43 for food contents is formed at the top of the dome-shaped upper part 47. Further, an outside air suction port 44 that communicates with the air flow path 25 between the inner cylinder 21 and the outer cylinder 31 is formed in the top surface part 46.

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

[0032] The valve body 50 has a substantially M-shaped cross-section and is circular in shape, and is covered by a valve body support 60. The valve body 50 has a first valve 51 formed at the central part, and a second valve 52 is formed at a part of the outer periphery of the first valve 51.

[0033] The first valve 51 is in the shape of a "mortar shape" that is recessed downward during normal times (when the bottle 10 is not in use), and holes 53 are formed at a plurality of locations on the periphery. The outer side of the central part of the first valve 51 is placed on the support part 61 of the valve body support 60, and during normal times (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 part 61 of the valve body support 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 can block the lower end of the air inlet 44 and prevent the inflow of outside air. The lower surface of the second valve 52 is located above the air flow path 25 between the inner cylinder 21 and the outer cylinder 31 of the bottle body 20.

[0035] A method of using the bottle 10 will be described. When using the bottle 10 (discharging food contents), the outer cylinder 31 of the bottle body 20 is pushed from the outside. Thereby, the air in the air flow path 25 between the outer cylinder 31 and the inner cylinder 21 is pushed upward, and the second valve 52 located above the air flow path 25 is pushed upward. Thereby, the second valve 52 comes into contact with the lower end of the air inlet 44 of the lid body 40, and the lower end of the air inlet 44 is blocked.

[0036] At the same time, the inner cylinder 21 of the bottle body 20 is pushed inward by the air in the air flow path 25, whereby the storage portion 22 of the food content inside the inner cylinder 21 is pressurized. Due to the pressurization of the storage portion 22 of the food content, the central portion of the first valve 51 that closes the opening portion surrounded by the support portion 61 of the valve body support portion 60 is pushed upward. As a result, the first valve 51 bulges upward to a state of 51a, and the holes 53 at the periphery of the first valve 51 open away from the surface of the valve body support 60, and the food content in the storage portion 22 of the food content is supplied out through the holes 53 at the periphery of the first valve 51 from the food content supply port 43 of the lid body 40.

[0037] On the other hand, when the use of the bottle 10 is finished, the pressing of the outer cylinder 31 of the bottle body 20 is stopped. As a result, a restoring force that tries to return the outer cylinder 31 of the bottle body 20 to the state before use of the bottle 10 acts, the inside of the air flow path 25 between the inner cylinder 21 and the outer cylinder 31 is depressurized, and the second valve 52 located above the air flow path 25 deforms downward. When 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 inlet 44, and the outer cylinder 31 returns to the state before use of the bottle 10.

[0038] At the same time, the inner cylinder 21 of the bottle body 20 bulges and tries to return to the state before use of the bottle 10. As a result, the pressure in the storage portion 22 of the food content decreases, the first valve 51 returns to the lower position before use of the bottle 10, and the holes 53 at the periphery of the first valve 51 come into close contact with the surface of the valve body support portion 60 to close the holes 53.

[0039] Note that the food bottle and its valve body are not limited to those shown in FIGS. 1 and 2, and any structure that can be used as the food bottle and its valve body may be sufficient. Also, the manufacturing method of the valve body of the food bottle is not limited to injection molding, and other molding methods using molten resin may be used.

Example

[0040] Each example and each comparative example having the composition shown in FIG. 3 will be described. The materials used in each example or each comparative example are shown 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% by 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 = 15 g / 10 min (ASTM 1238, 190 °C / 2.16 kg) Styrene-ethylene-butylene copolymer: Product name; Clarion G1651, manufactured by Clarion 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 each comparative example, heptane resistance, hardness, 40 °C compression set, and melt flow rate (MFR) were measured, and a determination (evaluation) was made for each measurement item. Furthermore, a comprehensive determination (comprehensive evaluation) was made based on the determinations of all measurement items.

[0042] For the measurement of heptane resistance, a molded body of 100 mm × 100 mm × thickness 2 mm was produced by injection molding from the styrene-based thermoplastic elastomer compositions of each example and Comparative Examples 2 to 5. A sample of φ20 mm × thickness 2 mm was cut from the molded body, and the measurement of heptane resistance was carried out on the sample according to the above-described measurement method for heptane resistance. For Comparative Example 1, after adding a vulcanizing agent, a molded body was produced by press molding. For Comparative Examples 6 to 8, a molded body was produced by injection molding, and the measurement of heptane resistance was carried out using samples formed from those molded bodies. The determination of heptane resistance was rated as "◎" when the measurement result of the weight change rate was within ±1% (-1% to +1%), "〇" when it was ±1% or more and less than ±2% (-2% to -1% or +1% to +2%), and "×" when it was ±2% or more (less than -2% or +2% or more) or when it dissolved.

[0043] The hardness was measured by stacking three 100 mm × 100 mm × 2 mm thick molded bodies made by injection molding from the styrene-based thermoplastic elastomer compositions of each example and Comparative Examples 2 to 5, and measuring the A hardness based on JIS K 6253. For Comparative Example 1, after adding a vulcanizing agent, a molded body was produced by press molding. For Comparative Examples 6 to 8, molded bodies were produced by injection molding, and the hardness was measured using samples formed from those molded bodies. The hardness determination was rated as "◎" when the measurement result of the hardness was less than 50, "〇" when it was 50 to less than 60, and "×" when it was 60 or more.

[0044] The measurement of the 40°C compression set was carried out based on JIS K 6262 by producing a sheet by stacking a plurality of φ13 × 2 mm thick molded bodies made by injection molding from the styrene-based thermoplastic elastomer compositions of each example and Comparative Examples 2 to 5. For Comparative Example 1, after adding a vulcanizing agent, a molded body was produced by press molding. For Comparative Examples 6 to 8, molded bodies were produced by injection molding, and the 40°C compression set was measured using samples formed from those molded bodies. The determination of the 40°C compression set was rated as "◎" when the measurement result of the 40°C compression set was less than 60%, "〇" when it was 60 to less than 70%, and "×" when it was 70% or more.

[0045] The measurement of the melt flow rate (MFR) was carried out based on JIS K 7210 for the styrene-based thermoplastic elastomer compositions of each example and Comparative Examples 2 to 8. The determination of the melt flow rate (MFR) was rated as "◎" when the measurement result of the melt flow rate (MFR) was 10 g / 10 min or more, "〇" when it was 5 g / 10 min ~10 g / 10min When it is less than, it is marked as "〇", 5g / 10 min When it is less than, it is marked as "×".

[0046] For the comprehensive judgment, when the judgment of all measurement items is "◎", the comprehensive judgment is "◎"; when the judgment of all measurement items is "〇" or more (that is, ○ or ◎), and the judgment of at least one measurement item is "〇", the comprehensive judgment is "〇"; when the judgment of at least one measurement item is "×", the comprehensive judgment is "×".

[0047] Example 1 was prepared by blending 100 parts by weight of a styrene-ethylene copolymer and 25 parts by weight of an olefin block copolymer, and melt-kneading at a temperature of 220 °C and a screw rotation speed of 400 rpm using an extruder to produce a styrenic 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 are as follows: the measurement result of heptane resistance is 0.2%, and the judgment is "◎"; the measurement result of hardness is 42, and the judgment is "◎"; the measurement result of compression set at 40 °C is 68%, and the judgment is "〇"; the measurement result of melt flow rate is 7g / 10 min , and the judgment is "〇", and the comprehensive judgment is "〇". Example 1 has good heptane resistance, low hardness, and small permanent strain, so the functionality of the molded body is good. Moreover, since the judgment of the melt flow rate is "〇", the safety and sealing properties are good, and molding such as injection molding performed by melting the resin composition is possible, and it is recyclable.

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

[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 show that the measurement result of heptane resistance is 0.3%, the judgment is "◎", the measurement result of hardness is 43, the judgment is "◎", the measurement result of 40 °C compression set is 55%, the judgment is "◎", and the measurement result of melt flow rate is 10 g / 10 min , the judgment is "◎", and the comprehensive judgment is "◎". In Example 2, due to the good heptane resistance, low hardness, and small permanent distortion, the functionality of the molded body is good. Furthermore, since the judgment of the melt flow rate is "◎", the safety and sealing properties are good, and molding such as injection molding performed by melting the resin composition is possible, and it is recyclable.

[0051] Example 3 is the same as Example 1 except that the amount of the olefin block copolymer is increased to 66.7 parts by weight in the formulation of Example 1.

[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 show that the measurement result of heptane resistance is 0.5%, the judgment is "◎", the measurement result of hardness is 44, the judgment is "◎", the measurement result of 40 °C compression set is 54%, the judgment is "◎", and the measurement result of melt flow rate is 13 g / 10 min , the judgment is "◎", and the comprehensive judgment is "◎". In Example 3, due to the good heptane resistance, low hardness, and small permanent distortion, the functionality of the molded body is good. Furthermore, since the judgment of the melt flow rate is "◎", the safety and sealing properties are good, and molding such as injection molding performed by melting the resin composition is possible, and it is recyclable.

[0053] Example 4 is the same as Example 1 except that the amount of the olefin block copolymer is increased to 81.8 parts by weight in the formulation of Example 1.

[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 show that the measurement result of heptane resistance is 1.3%, and the judgment is "〇"; the measurement result of hardness is 44, and the judgment is "◎"; the measurement result of 40°C compression set is 53%, and the judgment is "◎"; the measurement result of melt flow rate is 14 g / 10 min , and the judgment is "◎", and the comprehensive judgment is "〇". In Example 4, due to its good heptane resistance, low hardness, and small permanent distortion, the functionality of the molded body is good. Moreover, since the judgment of the melt flow rate is "◎", its safety and sealing performance are good, and it can be molded by injection molding or the like that melts the resin composition, and it is recyclable.

[0055] Comparative Example 1 is an example consisting only of silicone rubber. The results of each measurement item in Comparative Example 1 show that the measurement result of heptane resistance is 0.1%, and the judgment is "◎"; the measurement result of hardness is 40, and the judgment is "◎"; the measurement result of 40°C compression set is 10%, and the judgment is "◎"; since there is no melt flow rate measurement result for rubber (-), the judgment is "×", and the comprehensive judgment is "×". In Comparative Example 1, due to its good heptane resistance, low hardness, and small permanent distortion, the functionality of the molded body was good. However, since the judgment of the melt flow rate is "×", molding by injection molding or the like that melts the resin composition is impossible, and it is not recyclable.

[0056] Comparative Example 2 is an example consisting only of a styrene-ethylene copolymer. The results of each measurement item in Comparative Example 2 show that the measurement result of heptane resistance is 0.1%, and the judgment is "◎"; the measurement result of hardness is 50, and the judgment is "〇"; the measurement result of 40°C compression set is 90%, and the judgment is "×"; the measurement result of melt flow rate is 2 g / 10 min , and the judgment is "×", and the comprehensive judgment is "×". In Comparative Example 2, although it has good heptane resistance and low hardness, due to its large permanent distortion, the functionality of the molded body is inferior. Moreover, since the judgment of the melt flow rate is "×", molding by injection molding or the like that melts the resin composition is difficult.

[0057] Comparative Example 3 consists of 100 parts by weight of a styrene-ethylene copolymer and 10 parts by weight of an olefin block copolymer, which is less than the scope of the present invention. Otherwise, it is the same as Example 1. The results of each measurement item in Comparative Example 3 are as follows: the measurement result of heptane resistance is 0.2%, and the judgment is "◎"; the measurement result of hardness is 43, and the judgment is "◎"; the measurement result of 40°C compression set is 88%, and the judgment is "×"; the measurement result of melt flow rate is 3 g / 10 min and the judgment is "×", and the comprehensive judgment is "×". In Comparative Example 3, although the heptane resistance was good and the hardness was low, the permanent distortion was large, resulting in inferior functionality of the molded body. In addition, since the judgment of the melt flow rate was "×", it was difficult to perform molding such as injection molding by melting the resin composition.

[0058] Comparative Example 4 consists of only 100 parts by weight of a styrene-ethylene copolymer and 100 parts by weight of an olefin block copolymer, which is more than the scope of the present invention. Otherwise, it is the same as Example 1. The results of each measurement item in Comparative Example 4 are as follows: the measurement result of heptane resistance is 5.7%, and the judgment is "×"; the measurement result of hardness is 44, and the judgment is "◎"; the measurement result of 40°C compression set is 50%, and the judgment is "◎"; the measurement result of melt flow rate is 15 g / 10 min and the judgment is "◎", and the comprehensive judgment is "×". In Comparative Example 4, except that the judgment of heptane resistance was "×", the judgments of other measurement items were "◎". However, due to the low heptane resistance, it is inferior in safety for food.

[0059] Comparative Example 5 is the same as Example 1, except that 30 parts by weight of paraffin oil is added as a plasticizer that is not added in the present invention to the formulation of Example 1. The results of the measurement items in Comparative Example 5 are as follows: the measurement result of heptane resistance is 20.5%, and the judgment is "×"; the measurement result of hardness is 40, and the judgment is "◎"; the measurement result of 40°C compression set is 60%, and the judgment is "〇"; the measurement result of melt flow rate is 17 g / 10 minThe determination was "◎", but the comprehensive determination was "×". In Comparative Example 5, except that the determination of heptane resistance was "×", the determinations of other measurement items were "〇" or higher. However, since the heptane resistance was low, it was inferior in safety for food.

[0060] Comparative Example 6 is an example consisting of 100 parts by weight of a styrene-ethylene-butylene copolymer not used in the present invention and 30 parts by weight of a paraffinic oil as a plasticizer. Regarding the results of each measurement item in Comparative Example 6, since the measurement result of heptane resistance was dissolved, the determination was "×". The measurement result of hardness was 55, and the determination was "×". The measurement result of 40 °C compression set was 20%, and the determination was "◎". The measurement result of melt flow rate was 20 g / 10 min The determination was "◎", but the comprehensive determination was "×". In Comparative Example 6, since the determinations of heptane resistance and hardness were "×", it was inferior in safety for food, and since the hardness was high, it was inferior in sealing property.

[0061] Comparative Example 7 is an example in which the amount of the paraffinic oil as a plasticizer in Comparative Example 6 was increased to 50 parts by weight. Regarding the results of each measurement item in Comparative Example 7, since the measurement result of heptane resistance was dissolved, the determination was "×". The measurement result of hardness was 35, and the determination was "◎". The measurement result of 40 °C compression set was 20%, and the determination was "◎". The measurement result of melt flow rate was 40 g / 10 min The determination was "◎", but the comprehensive determination was "×". In Comparative Example 7, since the amount of the paraffinic oil as a plasticizer was increased compared to Comparative Example 6, the hardness became even lower and the determination of hardness became "◎". However, since the determination of heptane resistance was "×", it was inferior in safety for food.

[0062] Comparative Example 8 is an example in which the amount of the paraffinic oil as a plasticizer in Comparative Example 6 was increased to 100 parts by weight. Regarding the results of each measurement item in Comparative Example 8, since the measurement result of heptane resistance was dissolved, the determination was "×". The measurement result of hardness was 15, and the determination was "◎". The measurement result of 40 °C compression set was 30%, and the determination was "◎". The measurement result of melt flow rate was 50 g / 10min It is judged as "◎", and the comprehensive judgment is "×". In Comparative Example 8, since the amount of paraffinic oil as a plasticizer was increased compared to Comparative Examples 6 and 7, the hardness became even lower and the hardness judgment became "◎", but since the heptane resistance judgment was "×", it is inferior in safety for food.

[0063] Thus, the styrenic thermoplastic elastomer composition of the present invention can be injection-molded and satisfies all of the low hardness for ensuring the sealing property required for the valve body of a food bottle, the heptane resistance for ensuring safety, and recyclability. Further, the valve body of a food bottle molded from the styrenic thermoplastic elastomer composition of the present invention can satisfy all of the low hardness for ensuring the sealing property required for the valve body of a food bottle, the heptane resistance for ensuring safety, and recyclability.

Explanation of Signs

[0064] 10 Food bottle 20 Bottle body 21 Inner cylinder 22 Storage part for food contents 31 Outer cylinder 43 Supply port for food contents 44 Outside air intake port 49 Outer lid 50 Valve body 51 First valve 52 Second valve

Claims

1. A sealing material formed from a styrene-ethylene copolymer and an olefin block copolymer, wherein the blending amount of the olefin block copolymer is 20 to 85 parts by weight based on 100 parts by weight of the styrene-ethylene copolymer, and which is a sealing material formed from a styrene-based thermoplastic elastomer composition not containing a plasticizer, and wherein the hardness (A hardness) after 15 seconds based on JIS K 6253 is less than 60.

2. The sealing material according to claim 1, wherein the styrene-based thermoplastic elastomer composition satisfies any one of the following conditions. 1) The melt flow rate of the styrene-ethylene copolymer is 1 to 20 g / 10 min. 2) The melt flow rate of the olefin block copolymer is 10 to 20 g / 10 min. 3) The melt flow rate of the styrenic thermoplastic elastomer composition is 5 to 40 g / 10 min.

Images