Thermoplastic resin composition

Abstract

To provide a thermoplastic resin composition which is excellent in flexibility in a temperature range between low temperature and normal temperature, and is small in temperature dependency of the flexibility.SOLUTION: A thermoplastic resin composition contains an elastomer and a thermoplastic resin, wherein a heat quantity of the thermoplastic resin composition in a crystallization heating peak of a DSC curve of the thermoplastic resin composition obtained by a differential scanning calorimetric measurement method (DSC method) is within the range of 0.2 J to 50 J per 1 g of the thermoplastic resin composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic resin composition that has excellent flexibility in a temperature range from low temperature to room temperature and exhibits little temperature dependency of flexibility. [Background technology]

[0002] As demand for lightweight automobiles increases, efforts are underway to reduce the weight of conventional rubber hoses by replacing rubber with highly barrier-resistant resins and thinning their walls. In particular, the refrigerant transport hoses currently used in automobile air conditioners are primarily made of rubber, and replacing this primary material with highly barrier-resistant resins would enable weight reduction. Furthermore, the manufacturing process for such rubber hoses typically involves first kneading raw rubber materials, fillers, softeners, and the like in an internal mixer such as a Banbury mixer or pressure kneader, then adding crosslinking agents and crosslinking accelerators using an open roll or similar device. The resulting unvulcanized composition is then processed into pellets or other shapes, molded into a hose using an injection molding machine or extrusion molding machine, and then vulcanized. However, this manufacturing process is problematic in that it requires significant effort for the kneading and vulcanization processes and generates significant CO2 emissions.

[0003] For example, Patent Document 1 discloses a thermoplastic resin composition for refrigerant transport piping, which comprises a matrix containing a thermoplastic resin and domains containing rubber dispersed in the matrix, wherein the thermoplastic resin has a melting point of 150°C or higher, the rubber is a butyl-based rubber or an olefin-based rubber, the matrix contains a viscosity stabilizer, the thermoplastic resin composition contains at least one selected from the group consisting of a phenylenediamine-based antioxidant, a quinoline-based antioxidant, and a trihydric alcohol having a triazine skeleton, and a processing aid, and at least a portion of the rubber is crosslinked. This thermoplastic resin composition has high barrier properties, flexibility, and good extrusion processability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-105284 Summary of the Invention [Problem to be solved by the invention]

[0005] The thermoplastic resin composition described in Patent Document 1 has high barrier properties, flexibility, and good extrusion processability, but there is a demand for a thermoplastic resin composition that has excellent flexibility in a temperature range from low temperature (e.g., 0°C) to room temperature (25°C) and that has little temperature dependency of flexibility in this temperature range. Therefore, an object of the present invention is to provide a thermoplastic resin composition that has excellent flexibility in a temperature range from low temperature to room temperature and that has little temperature dependency of flexibility in this temperature range. [Means for solving the problem]

[0006] The present inventors focused on the relationship between the degree of crystallinity (%) of the thermoplastic resin in a thermoplastic resin composition containing an elastomer and a thermoplastic resin and flexibility, and discovered that when the calorific value of the thermoplastic resin composition at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition obtained by differential scanning calorimetry (DSC) is within the range of 0.2 to 50 joules (J) per 1 g of the thermoplastic resin composition, the thermoplastic resin composition has excellent flexibility in a temperature range from low temperature to room temperature and the temperature dependency of flexibility in this temperature range is small, thereby completing the present invention.

[0007] That is, the present invention is a thermoplastic resin composition containing an elastomer and a thermoplastic resin, characterized in that the heat generation amount of the thermoplastic resin composition at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition obtained by differential scanning calorimetry (DSC) is within the range of 0.2 J to 50 J per 1 g of the thermoplastic resin composition.

[0008] Specifically, the present invention includes the following embodiments [1] to [5]. [1] A thermoplastic resin composition comprising an elastomer and a thermoplastic resin, wherein the heat generation amount of the thermoplastic resin composition at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition obtained by differential scanning calorimetry (DSC) is within the range of 0.2 J to 50 J per 1 g of the thermoplastic resin composition. [2] The thermoplastic resin composition according to embodiment 1, wherein the heat generation amount of the thermoplastic resin composition at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition is within the range of 1 J to 91 J per 1 g of the thermoplastic resin. [3] The thermoplastic resin composition according to embodiment 1, comprising 30 to 115 parts by mass of a thermoplastic resin per 100 parts by mass of an elastomer. [4] The thermoplastic resin composition according to embodiment 1, wherein the thermoplastic resin composition has an islands-in-a-sea structure in which domains containing the elastomer exist in a matrix containing a thermoplastic resin. [5] The thermoplastic resin composition according to embodiment 1, wherein the elastomer comprises at least one selected from the group consisting of butyl rubber, halogenated butyl rubber, isobutylene-paramethylstyrene copolymer rubber, halogenated isobutylene-paramethylstyrene copolymer rubber, and styrene-isobutylene-styrene block copolymer. [Effects of the Invention]

[0009] The thermoplastic resin composition of the present invention has high flexibility even in a temperature range from low temperature (0°C) to room temperature (25°C), and the temperature dependency of the flexibility is low. Therefore, by molding the thermoplastic resin composition of the present invention, it is possible to provide a molded article that exhibits excellent flexibility even in a temperature range from low temperature (0°C) to room temperature (25°C), and has low temperature dependency of the flexibility in this temperature range, and therefore has excellent vibration damping properties even in a temperature range from low temperature (0°C) to room temperature (25°C), and has low temperature dependency of the vibration damping properties. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 shows the crystallization exothermic peaks in the DSC curves of the thermoplastic resin of Comparative Example 1 and the thermoplastic resin composition of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] The thermoplastic resin composition of the present invention contains an elastomer and a thermoplastic resin, and the calorific value of the thermoplastic resin composition at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition obtained by the DSC method is in the range of 0.2 J to 50 J per gram of the thermoplastic resin composition. The calorific value of the thermoplastic resin composition per gram of the thermoplastic resin at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition reflects the crystallinity (%) of the thermoplastic resin in the thermoplastic resin composition. The greater the calorific value of the thermoplastic resin composition at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition, the greater the amount of crystals of the thermoplastic resin per gram of thermoplastic resin in the thermoplastic resin composition, i.e., the higher the crystallinity (%) of the thermoplastic resin. Therefore, the greater the calorific value of the thermoplastic resin composition at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition, the higher the crystallinity (%) of the thermoplastic resin, which improves gas barrier properties but reduces flexibility. Therefore, from the viewpoint of a balance between high flexibility in the temperature range from low temperature (0°C) to room temperature (25°C), low temperature dependency of flexibility in this temperature range, and gas barrier properties, the calorific value of the thermoplastic resin composition at the exothermic crystallization peak in the DSC curve of the thermoplastic resin composition is preferably in the range of 5 J to 50 J per 1 g, and more preferably in the range of 5 J to 45 J per 1 g. If the calorific value of the thermoplastic resin composition at the exothermic crystallization peak in the DSC curve of the thermoplastic resin composition exceeds 50 J per 1 g, the flexibility will be low and the temperature dependency of the flexibility in the temperature range from low temperature to room temperature will be high.

[0012] The calorific value of a thermoplastic resin composition at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition refers to the calorific value measured in accordance with JIS K7121-1987. Specifically, in a nitrogen atmosphere, a 10 mg sample of the thermoplastic resin composition is heated from 25°C at a heating rate of 10°C / min to a temperature approximately 30°C higher than the end of the melting (endothermic) peak to obtain a heating curve. The sample is then held at that temperature for 10 minutes, and then cooled at a cooling rate of 10°C / min to a temperature approximately 50°C lower than the end of the crystallization exothermic peak to obtain a heating curve. Next, the integrated value of the area of ​​the crystallization exothermic peak is calculated and converted to the calorific value per gram of the thermoplastic resin composition.

[0013] The elastomer is not particularly limited, but is preferably one having a polyisobutylene skeleton. When the thermoplastic resin composition contains an elastomer having a polyisobutylene skeleton, the flexibility and water vapor barrier properties of the resin composition are improved. The polyisobutylene skeleton is a chemical structure formed by polymerizing multiple isobutylenes, i.e., -[-CH2-C(CH3)2-] n - (where n is an integer of 2 or greater).

[0014] The elastomer having a polyisobutylene skeleton is not limited as long as it has a polyisobutylene skeleton, but is preferably butyl rubber (IIR), halogenated butyl rubber, isobutylene-paramethylstyrene copolymer rubber, halogenated isobutylene-paramethylstyrene copolymer rubber, or styrene-isobutylene-styrene block copolymer (SIBS), and more preferably butyl rubber or halogenated butyl rubber. Butyl rubber refers to an isobutylene-isoprene copolymer obtained by copolymerizing isobutylene with a small amount of isoprene. Halogenated butyl rubber is more preferably brominated butyl rubber or chlorinated butyl rubber, and even more preferably brominated butyl rubber.

[0015] In the thermoplastic resin composition of the present invention, the elastomer having a polyisobutylene skeleton is preferably dynamically crosslinked. Dynamic crosslinking improves the durability of molded articles obtained by molding the thermoplastic resin composition.

[0016] In the thermoplastic resin composition of the present invention, the thermoplastic resin is not particularly limited, but preferably contains at least one selected from the group consisting of polyolefins, polyamides, polyesters, polyvinyl alcohols, and polyketones. Examples of polyolefins include polyethylene, cross-linked polyethylene, copolymers of ethylene and α-olefins, polypropylene, copolymers of cross-linked polypropylene and other α-olefins, and the like. Examples of polyamides include nylon 6, nylon 66, nylon 11, nylon 12, nylon 610, nylon 6 / 66 copolymer, nylon 6 / 12 copolymer, nylon 46, nylon 6T, nylon 9T, and nylon MXD6. Examples of polyester include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate. Examples of polyvinyl alcohol include polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and modified ethylene-vinyl alcohol copolymer. The polyketones include ketone-ethylene copolymers, ketone-ethylene-propylene terpolymers, and the like. The thermoplastic resin is particularly preferably polyolefin, and the polyolefin is preferably low-melting polypropylene (PP) having a melting point of 100°C or higher but lower than 150°C. From the viewpoints of ease of production of the thermoplastic resin composition, processability into molded articles, reduction of CO2 emissions during processing, and improvement of melt adhesion to other materials, a low-melting-point resin with a melting point of 100°C or higher but lower than 150°C is preferred as the thermoplastic resin.

[0017] Furthermore, the thermoplastic resin preferably has a calorific value of 1 J to 91 J per gram of thermoplastic resin at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition, more preferably 1 J to 90 J per gram of thermoplastic resin. The temperature at the top of the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition is preferably 200°C or lower. The calorific value of the thermoplastic resin composition at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition reflects the degree of crystallinity (%) of the thermoplastic resin. The higher the calorific value of the thermoplastic resin composition at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition, the higher the degree of crystallinity (%) of the thermoplastic resin. The higher the crystallinity (%) of the thermoplastic resin in the thermoplastic resin composition, the higher the gas barrier property but the lower the flexibility. Therefore, from the viewpoint of a balance between high flexibility in the temperature range from low temperature (0°C) to room temperature (25°C), low temperature dependency of flexibility in this temperature range, and gas barrier properties, the calorific value of the thermoplastic resin composition at the exothermic crystallization peak in the DSC curve of the thermoplastic resin composition is preferably in the range of 30 J to 90 J per 1 g of thermoplastic resin, and more preferably 35 J to 90 J. If the calorific value of the thermoplastic resin composition at the exothermic crystallization peak in the DSC curve of the thermoplastic resin composition exceeds 91 J per 1 g of thermoplastic resin, the flexibility will be low and the temperature dependency of flexibility in the temperature range from low temperature to room temperature will be high.

[0018] The calorific value per 1 g of thermoplastic resin of the thermoplastic resin composition at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition can be determined by dividing the calorific value of the thermoplastic resin composition measured in accordance with JIS K7121-1987 as described above by the content of the thermoplastic resin, which can be determined as follows.

[0019] The thermoplastic resin composition of the present invention preferably contains 30 to 115 parts by mass of the thermoplastic resin per 100 parts by mass of the elastomer, and more preferably 30 to 95 parts by mass of the thermoplastic resin per 100 parts by mass of the elastomer. By including the elastomer and the thermoplastic resin in the thermoplastic resin composition in this ratio, the effect of reducing the amount of heat generated by crystallization per gram of the thermoplastic resin in the thermoplastic resin composition compared to the amount of heat generated by crystallization per gram of the thermoplastic resin alone is enhanced. The ratio of the elastomer to the thermoplastic resin in the thermoplastic resin composition can be determined, for example, by dissolving the thermoplastic resin composition in a solvent that dissolves only the thermoplastic resin, and then measuring the weights before and after dissolution to calculate the weight ratio of the elastomer to the thermoplastic resin.

[0020] The thermoplastic resin composition of the present invention preferably has a sea-island structure in which domains containing an elastomer are present in a matrix containing a thermoplastic resin. In other words, the thermoplastic resin composition of the present invention is preferably a polymer alloy having a phase structure in which the matrix containing a thermoplastic resin is a sea phase and the domains containing an elastomer are island phases. By having such a sea-island structure, the thermoplastic resin composition can possess both the thermoplasticity of a thermoplastic resin and the flexibility of an elastomer.

[0021] The thermoplastic resin composition of the present invention is preferably alloyed as described above, so that the amount of heat generated by crystallization per 1 g of thermoplastic resin in the thermoplastic resin composition is reduced compared to the amount of heat generated by crystallization per 1 g of the thermoplastic resin alone (see Figure 1). In other words, alloying reduces the crystallinity (%) of the thermoplastic resin in the thermoplastic resin composition compared to the crystallinity (%) of the thermoplastic resin alone. Therefore, the thermoplastic resin composition exhibits high flexibility in a temperature range from low to room temperature, and the temperature dependency of flexibility is suppressed.

[0022] The flexibility of the thermoplastic resin composition of the present invention can be evaluated by measuring the tensile stress at 10% elongation, i.e., the 10% modulus (M10@25°C), at a temperature of 25°C and a tensile speed of 500 mm / min, according to the measurement method specified in JIS K6251, "Vulcanized rubber and thermoplastic rubber - Determination of tensile properties." The storage modulus E' (E'@0°C), measured using a viscoelasticity spectrometer, is measured at a frequency of 20 Hz, an initial strain of 2%, a dynamic strain of ±0.1%, and a temperature of 0°C, according to JIS K6394. The 10% modulus at 25°C (M10@25°C) is an index of flexibility at room temperature (25°C), and a smaller M10@25°C value indicates better flexibility. Furthermore, the smaller the storage modulus E', the higher the stress relaxation property and the easier it is to follow deformation. Therefore, molded articles obtained by molding the thermoplastic resin composition of the present invention can exhibit excellent vibration damping properties at low temperatures (0°C). The temperature dependence of the flexibility of a thermoplastic resin composition in a temperature range from low temperature (0 ° C) to room temperature (25 ° C) can be evaluated by the absolute value of the difference between the index "M10 index @ 25 ° C" when the value of M10 @ 25 ° C of the thermoplastic resin composition is set to 100, and the index "E' index @ 0 ° C" when the value of E' @ 0 ° C of the thermoplastic resin composition is set to 100. The reason why the temperature dependence of the flexibility of a thermoplastic resin composition in a temperature range from low temperature (0 ° C) to room temperature (25 ° C) is evaluated by the absolute value of the difference between the "M10 index @ 25 ° C" and the "E' index @ 0 ° C" is that the flexibility of a thermoplastic resin composition correlates with the M10 index at 25 ° C and the E' index at 0 ° C.

[0023] The thermoplastic resin composition of the present invention can be produced, for example, by melt-kneading a thermoplastic resin and an elastomer in the presence of a crosslinking agent at a temperature equal to or higher than the melting point of the thermoplastic resin. By melt-kneading in the presence of a crosslinking agent, the elastomer can be dynamically crosslinked. By dynamic crosslinking, the dispersed phase (elastomer phase) can be stabilized (or fixed) in the continuous phase (thermoplastic resin phase) in the thermoplastic resin composition.

[0024] When blending the thermoplastic resin and the elastomer, general compounding agents for general resins or rubbers, such as fillers, reinforcing agents, processing aids, compatibilizers, stabilizers, antioxidants, and antiaging agents, may be added as needed to improve properties such as reinforcement, processability, dispersibility, heat resistance, and antioxidant properties, provided that the effects of the present invention are not impaired. Furthermore, before blending the thermoplastic resin and the elastomer to produce the thermoplastic resin composition of the present invention, general compounding agents for general resins or rubbers, such as fillers, reinforcing agents, processing aids, compatibilizers, stabilizers, antioxidants, and antiaging agents, may be added in advance to one or more of the thermoplastic resin and the elastomer, as needed, to improve properties such as reinforcement, processability, dispersibility, heat resistance, and antioxidant properties, provided that the effects of the present invention are not impaired.

[0025] As a specific example, the thermoplastic resin composition of the present invention can be produced by a method including the following steps (1) to (4): (1) adding a viscosity stabilizer to a thermoplastic resin and kneading the mixture; (2) adding an elastomer to the kneaded mixture obtained in step (1) and kneading the mixture; (3) adding a crosslinking agent to the kneaded product obtained in step (2) as needed; and (4) If necessary, a step of crosslinking at least a part of the rubber in the kneaded product containing the crosslinking agent obtained in the step (3).

[0026] The thermoplastic resin composition of the present invention can be produced by melt-kneading the above-mentioned essential components and optional additives using a kneading extruder commonly used in the production of thermoplastic resin compositions, such as a kneader, Banbury mixer, single-screw kneading extruder, or twin-screw kneading extruder. Melt-kneading is preferably carried out using a twin-screw kneading extruder due to its high productivity. Kneading conditions can be varied depending on the types and amounts of the essential components and optional additives used. The lower limit of the melt-kneading temperature should be at least equal to or higher than the melting point of the thermoplastic resin, and is preferably at least about 10°C higher than the melting point. The melt-kneading temperature is typically about 130°C to about 250°C. The melt-kneading time is typically about 3 to about 5 minutes.

[0027] The thermoplastic resin composition melt-kneaded as described above is then extruded in a molten state from a die attached to the discharge port of a twin-screw kneading extruder into a shape such as a film or a tube, or is extruded into a strand and once pelletized using a resin pelletizer, and the resulting pellets can then be molded into a desired shape such as a film, sheet, or tube depending on the application by a conventional resin molding method such as inflation molding, calendar molding, or extrusion molding. [Example]

[0028] The present invention will be described in more detail with reference to the following examples and comparative examples, but the scope of the present invention is not limited to these examples.

[0029] Comparative Example 1 Pelletized polypropylene (Novatec (registered trademark) PP MG03BD manufactured by Japan Polypropylene Corporation) (referred to as "thermoplastic resin 1" in Table 1 below) was molded into a sheet with an average thickness of 1.0 mm using a 40 mmφ single-screw extruder equipped with a 550 mm wide T-die (manufactured by Plagiken Co., Ltd.). The cylinder and die of this extruder were set to a temperature 10°C higher than the melting point of the polypropylene, the cooling roll temperature was set to 50°C, and the take-up speed was set to 3 m / min. For the obtained thermoplastic resin sheet, the amount of heat generated at the crystallization exothermic peak was determined by the DSC method for the raw material polypropylene, and the tensile properties and dynamic viscoelasticity were also determined, as described below.

[0030] (A) Heat generation at the crystallization exothermic peak by DSC method Using a differential scanning calorimeter (DSC823e manufactured by METTLER TOLEDO), the calorific value at the crystallization exothermic peak of the raw material thermoplastic resin (polypropylene) was measured in accordance with JIS K 7121-1987. Specifically, the measurement was performed as follows. First, a 10 mg sample of thermoplastic resin was heated under a nitrogen atmosphere from 25°C at a heating rate of 10°C / min to a temperature approximately 30°C higher than the end of the melting (endothermic) peak, to obtain a heating curve. The sample was then held at that temperature for 10 minutes, and then cooled at a cooling rate of 10°C / min to a temperature approximately 50°C lower than the end of the crystallization exothermic peak, to obtain a heating curve. The integrated value of the area of ​​the crystallization exothermic peak was then calculated and converted into the calorific value per gram of thermoplastic resin. The crystallization exothermic peak of the thermoplastic resin of Comparative Example 1 is shown in Figure 1, along with the crystallization exothermic peak of the thermoplastic resin composition of Example 1 below.

[0031] (B) Tensile properties The thermoplastic resin sheet obtained as described above was punched into a JIS No. 3 dumbbell shape and subjected to a tensile test at a temperature of 25°C and a tensile speed of 500 mm / min in accordance with the measurement method specified in JIS K6251 "Vulcanized rubber and thermoplastic rubber - Determination of tensile properties." The tensile stress at 10% elongation, i.e., the 10% modulus M10, was determined from the resulting stress-strain curve. The 10% modulus at 25°C (M10@25°C) is an index of flexibility at room temperature (25°C), and a smaller M10@25°C value indicates better flexibility.

[0032] (C) Dynamic viscoelasticity The dynamic viscoelasticity of the thermoplastic resin sheet obtained as described above was measured in accordance with JIS K6394 using a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisakusho, Ltd.) under conditions of a frequency of 20 Hz, an initial strain of 2%, a dynamic strain of ±0.1%, and a temperature of 0°C, and the storage modulus E' was calculated.

[0033] Comparative Example 2 A thermoplastic resin sheet was obtained in the same manner as in Comparative Example 1, except that the polypropylene was replaced with Novatec (registered trademark) PP BC10HRF manufactured by Japan Polypropylene Corporation (referred to as "thermoplastic resin 2" in Table 1 below). For the obtained thermoplastic resin sheet, the calorific value at the crystallization exothermic peak was determined in the same manner as in Comparative Example 1, and the tensile properties and dynamic viscoelasticity were also determined.

[0034] Examples 1 to 6 and Comparative Example 3 (1) Raw materials for thermoplastic resin compositions (A) Elastomer: Elastomer 1: Brominated butyl rubber (Br-IIR) (Exxon™ Bromobutyl 2255, ExxonMobil Chemical Company) Elastomer 2: Styrene-isobutylene-styrene block copolymer (SIBS) (SIBSTAR® 102T manufactured by Kaneka Corporation) (B) Thermoplastic resin Thermoplastic resin 1: Polypropylene (Novatec (registered trademark) PP, grade MG03BD, manufactured by Japan Polypropylene Corporation) Thermoplastic resin 2: Polypropylene (Novatec (registered trademark) PP, grade BC10HRF, manufactured by Japan Polypropylene Corporation) (C) Additives Rubber crosslinking agent: Zinc oxide (Zinc oxide type 3 manufactured by Seido Chemical Industry Co., Ltd.) Processing aid: calcium stearate (calcium stearate SC-PG manufactured by Sakai Chemical Industry Co., Ltd.)

[0035] (2) Preparation of thermoplastic resin composition The raw materials were fed into a twin-screw kneading extruder (manufactured by The Japan Steel Works, Ltd.) in the blending ratios shown in Table 1 below, and kneaded for 3 minutes at 235° C. The kneaded product was continuously extruded from the twin-screw kneading extruder in the form of a strand, cooled with water, and then cut with a cutter to obtain a thermoplastic resin composition in the form of pellets.

[0036] (3) Evaluation of thermoplastic resin composition properties The pelletized thermoplastic resin composition obtained as described above was molded into a sheet with an average thickness of 1.0 mm using a 40 mm diameter single-screw extruder equipped with a 550 mm wide T-die (manufactured by Plagiken Co., Ltd.). The temperature of the cylinder and die of this extruder was set to the melting point of the polymer component with the highest melting point in the sample composition + 10°C, the cooling roll temperature was set to 50°C, and the take-up speed was set to 3 m / min. For the obtained thermoplastic resin composition sheet, the calorific value at the crystallization exothermic peak was determined as described below, and the tensile properties and dynamic viscoelasticity were also determined, and the temperature dependence of flexibility from room temperature (25°C) to low temperature (0°C) was evaluated.

[0037] (A) Heat generation at the crystallization exothermic peak by DSC method The calorific value of the thermoplastic resin composition at the crystallization exothermic peak of the thermoplastic resin composition was measured using a differential scanning calorimeter (DSC823e manufactured by METTLER TOLEDO) in accordance with JIS K 7121-1987, as in Comparative Example 1. Specifically, the measurement was performed as follows. First, under a nitrogen atmosphere, a 10 mg sample of the thermoplastic resin composition was heated from 25°C at a heating rate of 10°C / min to a temperature approximately 30°C higher than the end of the melting (endothermic) peak, to obtain a heating curve. Next, the sample was held at that temperature for 10 minutes, and then cooled at a cooling rate of 10°C / min to a temperature approximately 50°C lower than the end of the crystallization exothermic peak, to obtain a heating curve. Next, the integrated value of the area of ​​the crystallization exothermic peak was calculated and converted into the amount of heat generated per 1 g of the thermoplastic resin composition.

[0038] (B) Tensile properties The thermoplastic resin composition sheet obtained as described above was punched into a JIS No. 3 dumbbell shape and subjected to a tensile test at a temperature of 25°C and a tensile speed of 500 mm / min in accordance with the measurement method specified in JIS K6251 "Vulcanized rubber and thermoplastic rubber - Determination of tensile properties." The tensile stress at 10% elongation, i.e., the 10% modulus (M10@25°C), was determined from the resulting stress-strain curve. The M10@25°C of the thermoplastic resin composition was then expressed as an index ("M10 index@25°C"), where the M10@25°C value of the raw material thermoplastic resin alone is set to 100. The smaller the M10 index@25°C, the better the flexibility.

[0039] (C) Dynamic viscoelasticity The dynamic viscoelasticity of the sheet of thermoplastic resin composition obtained as described above was measured in the same manner as in Comparative Example 1, and the storage modulus E' at 0°C (E'@0°C) was determined. Next, this E' value of the thermoplastic resin composition was expressed as an index "E' index@0°C" when the E' value of the raw material thermoplastic resin alone was set to 100. A smaller E' index@0°C indicates higher stress relaxation properties and more excellent vibration damping properties.

[0040] (D) Temperature dependence of flexibility in the temperature range from low to room temperature The absolute value of the difference between the M10 index @ 25°C and the E' index @ 0°C obtained as described above was calculated and used as an index representing the temperature dependence of flexibility in the temperature range from low temperature (0°C) to room temperature (25°C). In Table 1 below, the M10 index @ 25°C is "A" and the E' index @ 0°C is "B", and the absolute value of the difference between A and B is represented as |AB|.

[0041] [Table 1]

[0042] From the evaluation results of Examples 1 to 6 and Comparative Examples 1 to 3 shown in Table 1, it can be seen that the greater the calorific value, i.e., the higher the degree of crystallinity, the greater the absolute value |AB| of the difference between A and B, i.e., the greater the change in physical properties. In other words, compared to Comparative Examples 1 to 3, the thermoplastic resin compositions of Examples 1 to 6 have a lower degree of crystallinity, and therefore are excellent in flexibility in the temperature range from low temperature to room temperature, and the temperature dependency of flexibility is low.

[0043] The present invention further includes the following embodiments. [Embodiment 1] A thermoplastic resin composition comprising an elastomer and a thermoplastic resin, wherein the heat generation amount of the thermoplastic resin composition at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition obtained by differential scanning calorimetry (DSC) is within the range of 0.2 J to 50 J per 1 g of the thermoplastic resin composition. [Embodiment 2] The thermoplastic resin composition according to embodiment 1, wherein the heat generation amount of the thermoplastic resin composition at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition is within the range of 1 J to 91 J per 1 g of thermoplastic resin. [Embodiment 3] The thermoplastic resin composition according to embodiment 1 or 2, comprising 30 to 115 parts by mass of a thermoplastic resin per 100 parts by mass of an elastomer. [Embodiment 4] A thermoplastic resin composition according to any one of embodiments 1 to 3, wherein the thermoplastic resin composition has an island-sea structure in which domains containing the elastomer exist in a matrix containing a thermoplastic resin. [Embodiment 5] A thermoplastic resin composition according to any one of embodiments 1 to 4, wherein the elastomer comprises at least one selected from the group consisting of butyl rubber, halogenated butyl rubber, isobutylene-paramethylstyrene copolymer rubber, halogenated isobutylene-paramethylstyrene copolymer rubber, and styrene-isobutylene-styrene block copolymer. [Industrial Applicability]

[0044] The thermoplastic resin composition of the present invention has high flexibility in a temperature range from low temperature to room temperature and low temperature dependency of flexibility in a temperature range from low temperature to room temperature. Therefore, the composition is useful in applications where such properties are required, and can be particularly suitably used for hoses for transporting refrigerants.

Claims

1. A thermoplastic resin composition comprising an elastomer and a thermoplastic resin, wherein the heat release value of the thermoplastic resin composition at a crystallization exothermic peak in a DSC curve of the thermoplastic resin composition obtained by differential scanning calorimetry (DSC) is within a range of 0.2 J to 50 J per 1 g of the thermoplastic resin composition.

2. The thermoplastic resin composition according to claim 1, wherein the heat generation amount of the thermoplastic resin composition at the crystallization exothermic peak in the DSC curve of the thermoplastic resin composition is in the range of 1 J to 91 J per 1 g of the thermoplastic resin.

3. The thermoplastic resin composition according to claim 1, comprising 30 to 115 parts by mass of the thermoplastic resin per 100 parts by mass of the elastomer.

4. The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin composition has an island-in-a-sea structure in which domains containing the elastomer exist in a matrix containing the thermoplastic resin.

5. 2. The thermoplastic resin composition according to claim 1, wherein the elastomer comprises at least one selected from the group consisting of butyl rubber, halogenated butyl rubber, isobutylene-paramethylstyrene copolymer rubber, halogenated isobutylene-paramethylstyrene copolymer rubber, and styrene-isobutylene-styrene block copolymer.

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