JP7515317B2 - Thermoplastic resin composition and molded article made thereof - Google Patents

Description

The present invention aims to provide a thermoplastic resin composition having excellent transparency, toughness, and heat resistance, and a molded article made from the same.

Hydrogenated aromatic vinyl polymers have excellent transparency and heat resistance, and are therefore expected to be used as materials for medical equipment, optical components, and electric and electronic components.
For example, Patent Document 1 proposes the use of a resin composition in optical disk applications, in which a hydrogenated aromatic vinyl polymer is blended with a hydrogenated aromatic vinyl/conjugated diene block copolymer.

Japanese Patent Application Laid-Open No. 4-288360

However, according to the present inventors' investigations, the resin composition proposed in Patent Document 1 has insufficient toughness, and it is difficult to use it as a material for medical devices, optical components, electric/electronic components, etc. It has been found that in order to use it in these applications, it is necessary to improve the toughness while maintaining the transparency and heat resistance. It has also been found that further improvement in heat resistance is necessary depending on the application.
The present invention has been made in view of the above problems. That is, an object of the present invention is to provide a thermoplastic resin composition and a molded article having excellent transparency, toughness and heat resistance.

As a result of intensive research, the present inventors have found that by using a hydrogenated aromatic vinyl polymer and a specific styrene-based elastomer, a thermoplastic resin composition excellent in transparency, toughness and heat resistance can be obtained, and that this can be suitably used as a material for medical devices, optical parts, electric/electronic parts, etc., and have completed the present invention.
That is, the present invention has the following features.

[1] A thermoplastic resin composition containing a hydrogenated aromatic vinyl polymer (A) and a styrene-based elastomer (B).
[2] The thermoplastic resin composition according to [1], wherein the hydrogenated aromatic vinyl polymer (A) is hydrogenated polystyrene.
[3] The thermoplastic resin composition according to [1] or [2], containing 5 to 200 parts by mass of a styrene-based elastomer (B) per 100 parts by mass of the hydrogenated aromatic vinyl polymer (A).
[4] The thermoplastic resin composition according to any one of [1] to [3], wherein the hydrogenated aromatic vinyl polymer (A) has a hydrogenation level of 90% or more.

[5] The thermoplastic resin composition according to any one of [1] to [4], wherein the styrene-based elastomer (B) comprises a hydrogenated block copolymer which is a hydrogenated product of a block copolymer containing at least one type of aromatic vinyl monomer unit and at least one type of conjugated diene monomer unit, and the hydrogenated block copolymer has an aromatic vinyl polymer block unit composed of the aromatic vinyl monomer unit, and a hydrogenated conjugated diene polymer block unit which is a hydrogenated product of a polymer block composed of the conjugated diene monomer unit.
[6] The thermoplastic resin composition according to [5], wherein the content of aromatic vinyl polymer block units in the styrene-based elastomer (B) is 25 to 35 mass%.

[7] The thermoplastic resin composition according to any one of [1] to [6], wherein the weight average molecular weight of the styrene-based elastomer (B) is 10,000 to 100,000.
[8] A molded article made of the thermoplastic resin composition according to any one of [1] to [7].
[9] The molded article according to [8], which is a medical device, an optical component, or an electric/electronic component.
[10] The molded article according to [9], wherein the medical device is a syringe.
[11] The molded article according to [9], wherein the optical component is a lens.

The thermoplastic resin composition and molded article containing the hydrogenated aromatic vinyl polymer and styrene-based elastomer according to the present invention have excellent transparency, toughness, and heat resistance, and can be suitably used as materials for medical equipment, optical parts, electrical and electronic parts, etc.

The present invention will be described in detail below. However, the following description is an example of an embodiment of the present invention, and the present invention is not limited to the contents of the following description as long as it does not exceed the gist of the present invention. The present invention can be modified and implemented as desired without departing from the gist of the present invention.
In the following description, when "~" is used with a numerical value or physical property value enclosed therein, the values before and after the "~" are included.

The present invention relates to a thermoplastic resin composition containing a hydrogenated aromatic vinyl polymer (A) and a styrene-based elastomer (B).

<Hydrogenated aromatic vinyl polymer (A)>
The hydrogenated aromatic vinyl polymer (A) of the present invention is a hydrogenated aromatic vinyl polymer.
The hydrogenated aromatic vinyl polymer of the present invention is produced by hydrogenating an aromatic vinyl polymer such as polystyrene, a styrene/α-methylstyrene copolymer, a styrene/vinylnaphthalene copolymer, etc. Among these, hydrogenated polystyrene, which is a hydrogenated product of polystyrene, is preferred.

The aromatic vinyl monomer used as the raw material for the aromatic vinyl polymer is a monomer represented by the general formula (1).

In general formula (1), R is hydrogen or an alkyl group.
The alkyl group may be a mono- or poly-substituted alkyl group with functional groups such as halo, nitro, amino, hydroxy, cyano, carbonyl, and carboxyl groups, and preferably has 1 to 6 carbon atoms.
Of these, R is preferably hydrogen.

In general formula (1), Ar is a phenyl group, a halophenyl group, an alkylphenyl group, an alkylhalophenyl group, a naphthyl group, a pyridinyl group, or an anthracenyl group.
Of these, Ar is preferably a phenyl group or an alkylphenyl group, more preferably a phenyl group.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, vinyltoluene (including all isomers, particularly p-vinyltoluene), ethylstyrene, propylstyrene, butylstyrene, vinylbiphenyl, vinylnaphthalene, vinylanthracene (all isomers), and mixtures thereof, with styrene being preferred.

The lower limit of the weight average molecular weight (Mw) of the hydrogenated aromatic vinyl polymer (A) is preferably 100,000 or more, and the upper limit of Mw is preferably 400,000 or less, more preferably 300,000 or less, and even more preferably 200,000 or less.
When Mw is equal to or greater than the lower limit, the mechanical strength does not decrease, and when Mw is equal to or less than the upper limit, the moldability does not deteriorate.

Here, the Mw of the hydrogenated aromatic vinyl polymer (A) is a value calculated in terms of polystyrene measured by GPC under the following conditions.
・Equipment: Tosoh Corporation "GPC HLC-832GPC/HT"
Column: Showa Denko K.K. "AD806M/S" x 3 (The columns were calibrated using Tosoh monodisperse polystyrene (A500, A2500, F1, F2, F4, F10, F20, F40, F288, each 0.5 mg/mL solution), and the elution volume and the logarithm of the molecular weight were approximated by a cubic equation.)
Detector: MIRAN "1A Infrared Spectrophotometer" (measurement wavelength: 3.42 μm)
Solvent: o-dichlorobenzene Temperature: 135°C
Flow rate: 1.0 mL/min Injection volume: 200 μL
Concentration: 20 mg/10 mL

The hydrogenation level of the hydrogenated aromatic vinyl polymer (A) is preferably 90% or more, more preferably 95% or more, and even more preferably 97% or more.
The hydrogenation level of the hydrogenated aromatic vinyl polymer refers to the proportion of the aromatic vinyl polymer that is saturated by hydrogenation. Such a high level of hydrogenation is preferred for heat resistance and transparency.
The hydrogenation level of the aromatic vinyl polymer is determined using proton NMR.

The melt flow rate (MFR) of the hydrogenated aromatic vinyl polymer (A) of the present invention is preferably 0.1 g/10 min or more, more preferably 0.2 g/10 min or more, from the viewpoint of the molding method and the appearance of the molded product, and is preferably 200 g/10 min or less, more preferably 100 g/10 min or less, and even more preferably 50 g/10 min or less, from the viewpoint of the material strength.
The MFR was measured in accordance with ISO R1133 at a measurement temperature of 230° C. and a measurement load of 2.16 kg.
The hydrogenated aromatic vinyl polymer (A) may be used alone or in combination of two or more types differing in monomer unit composition, physical properties, etc.

<Styrene-based elastomer (B)>
The styrene-based elastomer (B) of the present invention is a copolymer containing at least one aromatic vinyl monomer unit and at least one conjugated diene monomer unit, and among these copolymers, a block copolymer containing both of the above units and a hydrogenated block copolymer which is a hydrogenated product of this block copolymer are preferred.
This block copolymer is a styrene-based block copolymer having an aromatic vinyl polymer block unit composed of at least one aromatic vinyl monomer unit, and a conjugated diene polymer block unit composed of at least one conjugated diene monomer unit.

The hydrogenated block copolymer is a styrene-based hydrogenated block copolymer (hereinafter, sometimes simply referred to as "styrene-based hydrogenated block copolymer") having hydrogenated conjugated diene polymer block units, which are hydrogenated polymer blocks composed of the conjugated diene monomer units, and aromatic vinyl polymer block units composed of the aromatic vinyl monomer units. Most of the conjugated diene polymer block units in this styrene-based hydrogenated block copolymer are hydrogenated, while the aromatic vinyl polymer block units are not hydrogenated.

The relationship between the two block units of the styrene-based block copolymer or the hydrogenated styrene-based block copolymer can be represented by the following formula (2) or formula (3).
S-(D-S)m ... (2)
(S-D) n ... (3)
(In the formula, S represents a polymer block composed of aromatic vinyl monomer units, D represents a polymer block composed of conjugated diene monomer units and/or a hydrogenated polymer block composed of conjugated diene monomer units, and m and n represent integers of 1 to 5.)

The styrene-based elastomer (B) is more preferably the above-mentioned hydrogenated styrene-based block copolymer.
The styrene-based block copolymer and the hydrogenated styrene-based block copolymer may be linear, branched and/or radial.

As the aromatic vinyl monomer used as the raw material for the styrene-based block copolymer, styrene or a styrene derivative such as α-methylstyrene is preferred. As the conjugated diene monomer used as the raw material for the styrene-based block copolymer, butadiene and/or isoprene is preferred, and butadiene is more preferred.

As the styrene-based block copolymer, styrene/butadiene copolymer rubber and styrene/isoprene copolymer rubber are particularly preferred, and as the styrene-based hydrogenated block copolymer, styrene/butadiene copolymer rubber and styrene/isoprene copolymer rubber in which the polybutadiene block unit and the polyisoprene block unit are hydrogenated (hydrogenated) are particularly preferred.

When the block copolymer represented by the formula (2) and/or formula (3) is a styrene-based hydrogenated block copolymer and the polymer block D is composed only of a hydrogenated polybutadiene block unit, it is preferable for the 1,2-addition structure in the microstructure of the polymer block D to be 20 to 70 mass % in order to maintain the properties as an elastomer after hydrogenation.

The above m and n are preferably large in terms of lowering the order-disorder transition temperature, but are preferably small in terms of ease of production and cost.
As the styrene-based block copolymer, a styrene-based block copolymer or a hydrogenated styrene-based block copolymer represented by formula (2) is preferred because of its excellent rubber elasticity, a styrene-based block copolymer or a hydrogenated styrene-based block copolymer represented by formula (2) in which m is 3 or less is more preferred, and a styrene-based block copolymer or a hydrogenated styrene-based block copolymer represented by formula (2) in which m is 2 or less is even more preferred.

The proportion of the "polymer block S" in the styrene-based block copolymer or hydrogenated styrene-based block copolymer represented by the above formula (2) and/or formula (3) is preferably high from the viewpoint of the rigidity of the styrene-based elastomer, and is preferably low from the viewpoints of flexibility and resistance to bleeding out.

The proportion of the "S polymer block" in the styrene-based elastomer (B), i.e., the styrene-based block copolymer or hydrogenated styrene-based block copolymer, is preferably 25% by mass or more, more preferably 26% by mass or more, and even more preferably 27% by mass or more. Also, it is preferably 35% by mass or less, more preferably 34% by mass or less, and even more preferably 33% by mass or less. By satisfying this range, it is possible to obtain a thermoplastic resin composition of the present invention that has excellent transparency.

The weight average molecular weight (Mw) of the styrene-based elastomer (B) is preferably large from the viewpoint of mechanical strength, but is preferably small from the viewpoints of transparency, molded appearance and flowability, and heat shrinkage resistance due to low molded distortion.
The Mw of the styrene-based elastomer (B) is preferably 10,000 or more, more preferably 30,000 or more, and is preferably 100,000 or less, more preferably 80,000 or less, even more preferably 70,000 or less, and particularly preferably 65,000 or less.

Here, the Mw of the styrene-based elastomer (B) is a polystyrene-equivalent value measured by GPC under the following conditions.
Equipment: "150CALC/GPC" manufactured by Nihon Millipore Co., Ltd.
Column: Showa Denko K.K. "AD80M/S" x 3 Detector: FOXBORO Infrared Spectrophotometer "MIRANIA"
Wavelength: 3.42 μm
Solvent: o-dichlorobenzene Temperature: 140°C
Flow rate: 1.0 mL/min Injection volume: 200 μL
Concentration: 20 mg/10 mL
・0.2% by mass of 2,6-di-t-butyl-p-phenol was added as an antioxidant.

Commercially available products of the styrene-based hydrogenated block copolymer include "Typol (registered trademark)" manufactured by TSRC, "Kraton (registered trademark) G" manufactured by Kraton Polymers, "Septon (registered trademark)" manufactured by Kuraray Co., Ltd., and "Tuftec (registered trademark)" manufactured by Asahi Kasei Corporation.

The styrene-based elastomer (B) may be used alone or in combination of two or more types.

<Production of styrene-based elastomer>
The styrene elastomer (B), that is, the styrene block copolymer and the hydrogenated styrene block copolymer, may be produced by any method as long as the above-mentioned structure and physical properties can be obtained.
First, the styrene-based block copolymer can be produced by block copolymerization using a known method, for example, the method described in JP-B-40-23798, in which block polymerization is carried out in an inert solvent using a lithium catalyst or the like.

Next, the hydrogenated styrene-based block copolymer can be produced by hydrogenating the styrene-based block copolymer obtained by the above-mentioned method by a known method, for example, in an inert solvent in the presence of a hydrogenation catalyst by the methods described in JP-B-42-8704, JP-B-43-6636, JP-A-59-133203, and JP-A-60-79005.
In this hydrogenation treatment, from the viewpoint of thermal stability, it is preferable that 50% or more, and more preferably 80% or more of the conjugated diene polymer block units are hydrogenated.

<Thermoplastic resin composition>
The thermoplastic resin composition of the present invention contains the above-mentioned hydrogenated aromatic vinyl polymer (A) and a styrene-based elastomer (B).
The thermoplastic resin composition preferably contains 5 to 200 parts by mass of the styrene-based elastomer (B) based on 100 parts by mass of the hydrogenated aromatic vinyl polymer (A).

The content of the styrene-based elastomer (B) is more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, based on 100 parts by mass of the hydrogenated aromatic vinyl polymer (A), and is more preferably 150 parts by mass or less, and even more preferably 125 parts by mass or less.
When the content of the styrene-based elastomer (B) is within the above range, the transparency, toughness, and heat resistance are good.

The haze of the thermoplastic resin composition is an index of transparency and is preferably 30% or less, more preferably 20% or less, and even more preferably 10% or less. The smaller the value, the more excellent the transparency.
The thermoplastic resin composition preferably has a flexural modulus of 100 to 3,000 MPa, more preferably 200 to 2,800 MPa, and further preferably 300 to 2,500 MPa.
Within the above range, toughness and the rigidity required for the molded article can be obtained.

The shrinkage rate of the thermoplastic resin composition when sterilized in an autoclave at 121° C. for 15 minutes is an index of heat resistance and is preferably 2% or less, more preferably 1% or less, and even more preferably 0.8% or less. The smaller the value, the better the heat resistance.
Furthermore, cracks occurring during autoclave sterilization of the thermoplastic resin composition at 121° C. for 15 minutes are an index of toughness, and it is preferable that no cracks occur.

<Other ingredients>
The thermoplastic resin composition of the present invention may contain, as other components, compounding agents that are commonly used in resin compositions, within the range that does not impair the effects of the present invention.
Examples of such additives include heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, crystal nucleating agents, rust inhibitors, inorganic fillers, foaming agents, and pigments.
Among these, it is preferable to contain an antioxidant, particularly a phenol-based, sulfur-based or phosphorus-based antioxidant, in an amount of 0.01 to 2 parts by mass per 100 parts by mass of the thermoplastic resin composition.

Furthermore, resin components and elastomer components other than the styrene-based elastomer (B) may be contained within the range that does not impair the effects of the present invention.
Examples of such resin components include polyethylene resins, polypropylene resins, ethylene/α-olefin copolymer resins, propylene/α-olefin copolymer resins, ethylene/vinyl acetate copolymer resins, ethylene/acrylic acid ester copolymer resins, ethylene/(meth)acrylic acid copolymer resins, polystyrene-based resins, polyvinyl chloride-based resins, polyester-based resins, polyamide-based resins, ethylene/vinyl alcohol copolymers, acrylic resins, and petroleum resins.

Examples of elastomer components include olefin-based elastomers, polyester-based elastomers, urethane-based elastomers, acrylic-based elastomers, and nylon-based elastomers.

The other components may be added to the hydrogenated aromatic vinyl polymer (A) and the styrene-based elastomer (B) by a kneading method commonly used for melt-kneading of thermoplastic resins, or may be dissolved in an organic solvent together with the hydrogenated aromatic vinyl polymer (A) and mixed.
The content of other resin components and elastomer components is preferably 50% by mass or less, and more preferably 30% by mass or less, of the total components.

<Method of producing thermoplastic resin composition>
The thermoplastic resin composition of the present invention can be produced by kneading the hydrogenated aromatic vinyl polymer (A), the styrene-based elastomer (B), and, if necessary, the other components in a conventional manner using a conventional extruder, Banbury mixer, roll, Brabender Plastograph, kneader-Brabender or the like.
Among these production methods, it is preferable to use an extruder, in particular a twin-screw extruder.
When the thermoplastic resin composition of the present invention is produced by kneading it in an extruder or the like, it is melt-kneaded in a heated state usually at 220 to 320°C, preferably 250 to 300°C.

<Molded body and its manufacturing method>
The thermoplastic resin composition of the present invention can be molded to obtain various molded articles.
Examples of the molding method include various molding methods such as ordinary injection molding, gas injection molding, injection compression molding, and short shot foam molding.
The thermoplastic resin composition of the present invention is preferably injection molded into a molded article, and the molding conditions for injection molding are as follows.
The molding temperature is 250 to 320°C, preferably 270 to 300°C.
The injection pressure is from 5 to 100 MPa, preferably from 10 to 80 MPa.
The mold temperature is 0 to 100°C, preferably 30 to 95°C, and more preferably 70 to 95°C.

<Applications>
Since the thermoplastic resin composition and molded article of the present invention have the above-mentioned properties, they can be suitably used for medical devices such as syringes, caps, and cases; optical parts such as lenses; and electric and electronic parts such as cases.

The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples as long as it does not exceed the gist of the invention. The values of various production conditions and evaluation results in the following examples are meant as preferred upper or lower limit values in the embodiment of the present invention, and the preferred range may be a range defined by a combination of the above-mentioned upper or lower limit values and the values of the following examples or values of the examples.
In the following description, "parts" means "parts by mass" and "%" means "% by mass".

[Physical Properties]
<Hydrogenation Level of Hydrogenated Aromatic Vinyl Polymer (A)>
[Measurement by proton NMR]
- Apparatus: JASCO Corporation "400YH spectrometer"
Solvent: deuterated chloroform Concentration: 0.045 g/1.0 mL
Measurement: ¹ H-NMR
Resonance frequency: 400MHz
・Number of times: 8
Measurement temperature: 18.5°C
Hydrogenation level of hydrogenated aromatic vinyl polymer (A): integral value reduction rate of 6.8 to 7.5 ppm

<Melt flow rate (MFR)>
The measurement was carried out in accordance with ISO R1133 under the following conditions.
・Equipment: "Melt Indexer" manufactured by Toyo Seiki Seisakusho Co., Ltd.
Temperature: 230°C
Orifice diameter: 2 mm
Load capacity: 2.16kg

<Haze>
Using a plunger-type injection molding machine (an attached injection molding machine to a small kneader Xplore MC15 manufactured by Xplore Instruments), test pieces with a thickness of 2 mm, a width of 30 mm, and a length of 80 mm were molded at an injection pressure of 3.5 bar, a cylinder temperature of 290°C, and a mold temperature of 90°C, and the haze, which is an index of transparency, was measured in accordance with ISO 14782.

<Flexural modulus>
Using a plunger-type injection molding machine (an injection molding machine attached to a small kneader Xplore MC15 manufactured by Xplore Instruments), test pieces having a thickness of 4 mm, a width of 10 mm, and a length of 80 mm were molded at an injection pressure of 3.5 bar, a cylinder temperature of 290°C, and a mold temperature of 90°C.
Using this test piece, the flexural modulus, which is an index of rigidity, was measured in accordance with ISO178 at a span of 64 mm and a bending speed of 2 mm/min.

<Autoclave sterilization, shrinkage rate, presence or absence of cracks>
Using a plunger-type injection molding machine (an attached injection molding machine to a small kneader Xplore MC15 manufactured by Xplore Instruments), a test piece having a thickness of 2 mm, a width of 30 mm, and a length of 80 mm was molded at an injection pressure of 3.5 bar, a cylinder temperature of 290°C, and a mold temperature of 90°C. The test piece was autoclaved for 15 minutes at 121°C using a high-pressure steam sterilizer (high-pressure steam sterilizer model CLS-32S manufactured by Alp), and the shrinkage rate was measured from the change in the lengthwise dimension of the test piece. The presence or absence of cracks was also visually confirmed.

[material]
<Hydrogenated aromatic vinyl polymer (A-1)>
Polystyrene (HH-102 manufactured by Mitsubishi Monsite Chemicals) was dissolved in tetrahydrofuran, 5% Pd/C was added as a catalyst, and hydrogenation reaction was carried out at a temperature of 170°C and a hydrogen pressure of 100 kg/ ^cm2 for 6 hours to obtain hydrogenated polystyrene with the following physical properties.
Hydrogenated polystyrene Density (ASTM D792): 0.94 g/ ^cm3
MFR (230°C, 2.16 kg): 0.3 g/10 min Hydrogenation level of hydrogenated aromatic vinyl polymer: 99.9% or more Mw: 160,000

<Styrene-based elastomer (B-1)>
Kraton Polymers, Inc. Kraton (registered trademark) G1652MU
Hydrogenated styrene/butadiene/styrene block copolymer Aromatic vinyl polymer block unit: 30%
・Butadiene hydrogenation level: 99% or more ・Mw: 69,000

<Styrene-based elastomer (B-2)>
Kraton Polymers, Inc. Kraton (registered trademark) MD1653
Hydrogenated styrene/butadiene/styrene block copolymer Aromatic vinyl polymer block unit: 30%
・Butadiene hydrogenation level: 99% or more ・Mw: 60,000

Example 1
100 parts of hydrogenated aromatic vinyl polymer (A-1), 43 parts of styrene-based elastomer (B-1), and 0.05 parts of Irganox 1010 manufactured by BASF and 0.05 parts of Irgafos 168 manufactured by BASF as antioxidants were added, and the mixture was melt-kneaded for 1 minute at a temperature of 290°C and a screw rotation speed of 100 rpm using a plunger-type injection molding machine (an injection molding machine attached to a small kneader Xplore MC15 manufactured by Xplore Instruments), and molded into a test piece having a thickness of 2 mm, a width of 30 mm, and a length of 80 mm and a test piece having a thickness of 4 mm, a width of 10 mm, and a length of 80 mm at an injection pressure of 3.5 bar, a cylinder temperature of 290°C, and a mold temperature of 90°C.
The evaluation results of various physical properties are shown in Table 1.

<Examples 2 to 4, Comparative Example 1>
Components (A) and (B) were blended as shown in Table 1, and test pieces of the thermoplastic resin composition were molded in the same manner as in Example 1. The evaluation results of various physical properties are shown in Table 1.

From Table 1, it can be seen that Examples 1 to 4 corresponding to the present invention have excellent transparency, have small shrinkage rates during autoclave sterilization and excellent heat resistance, and furthermore, do not generate cracks during autoclave sterilization and have excellent toughness.
In contrast, Comparative Example 1, which did not contain the styrene-based elastomer (B), had excellent transparency, but showed slightly large shrinkage during autoclave sterilization, poor heat resistance, high rigidity, and cracks that occurred during autoclave sterilization, resulting in poor toughness.

The thermoplastic resin composition and molded article of the present invention have excellent transparency, toughness, and heat resistance, and are extremely useful as materials for medical equipment, optical components, electrical and electronic components, etc.

Claims (6)

The present invention relates to a composition comprising a hydrogenated aromatic vinyl polymer (A) and a styrene-based elastomer (B),
the styrene-based elastomer (B) is a hydrogenated block copolymer which is a hydrogenated product of a block copolymer containing at least one aromatic vinyl monomer unit and at least one conjugated diene monomer unit,
the hydrogenated block copolymer has an aromatic vinyl polymer block unit composed of the aromatic vinyl monomer unit, and a hydrogenated conjugated diene polymer block unit which is a hydrogenated product of a polymer block composed of the conjugated diene monomer unit,
The medical device comprises a thermoplastic resin composition in which the content of aromatic vinyl polymer block units in the styrene-based elastomer (B) is 25 to 35 mass % . The medical device according to claim 1, wherein the hydrogenated aromatic vinyl polymer (A) is hydrogenated polystyrene. The medical device according to claim 1 or 2, which contains 5 to 200 parts by mass of a styrene-based elastomer (B) per 100 parts by mass of the hydrogenated aromatic vinyl polymer (A). The medical device according to any one of claims 1 to 3, wherein the hydrogenated aromatic vinyl polymer (A) has a hydrogenation level of 90% or more. The medical device according to any one of claims 1 to 4 , wherein the styrene-based elastomer (B) has a weight average molecular weight of 10,000 to 100,000. The medical device according to any one of claims 1 to 5 , which is a syringe.