Injection molded article made of a propylene-based polymer composition

Abstract

The purpose of the present invention is to obtain an injection molded article made of a propylene-based polymer composition that has high transparency, high stiffness and high impact strength, in other words, that is well-balanced in transparency, impact strength and stiffness. The present invention pertains to an injection molded article made of a propylene-based polymer composition, said propylene-based polymer composition comprising 60-90 mass% of propylene-based polymer (A) satisfying the following requirements (a-i) and (a-ii) and 10-40 mass% of ethylene / α-olefin copolymer (B) satisfying the following requirements (b-i) and (b-ii) [provided that the total amount of (A) and (B) is regarded as 100 mass%].　Requirement (a-i): The melt flow rate, which is measured at a temperature of 230°C under a load of 2.16 kg in accordance with JIS K6921, is in the range of 1-50 g / 10 min.　Requirement (a-ii): The content of α-olefin(s) other than propylene determined by infrared spectroscopy is 1 mass% or less (including 0).　Requirement (b-i): The melt flow rate, which is measured at a temperature of 190°C under a load of 2.16 kg in accordance with JIS K6921, is in the range of 0.1-15 g / 10 min.　Requirement (b-ii): The density measured in accordance with JIS K6922 is in the range of 900-920 kg / m3.

Description

Technical Field

[0001] The present invention relates to an injection molded article made of a propylene-based polymer composition having good transparency, rigidity, and excellent impact strength.

Background Art

[0002] Polyolefins (olefin-based polymers) represented by polyethylene and polypropylene have attracted more attention in the efforts of various industries to achieve the 3R (Reduce, Reuse, Recycle) for forming a recycling-based society because they have low production energy, are lightweight, and have excellent recyclability. Polyolefins are used in various fields such as daily necessities, kitchenware, household appliances, machine parts, electrical parts, and automotive parts.

[0003] Among olefin-based polymers, polypropylene is excellent in transparency, rigidity, and heat resistance, but is inferior in cold resistance and impact resistance compared to polyethylene. Therefore, many methods for improving the impact resistance of polypropylene have been proposed.

[0004] As a method for improving the impact strength without impairing the transparency and rigidity of polypropylene, a propylene resin composition comprising a propylene block copolymer and an ethylene-α-olefin copolymer having a density in the range of 900 to 919 kg / m 3 has been proposed (Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to obtain an injection molded article made of a propylene-based polymer composition having good transparency, rigidity, and excellent impact strength, in other words, excellent balance of transparency, impact strength, and rigidity.

Means for Solving the Problems

[0007] The present invention relates to the following [1] to [8]. [1] An injection molded article made of a propylene-based polymer composition containing 60 to 90% by mass of a propylene-based polymer (A) satisfying the following requirements (a-i) and (a-ii), and 10 to 40% by mass of an ethylene-α-olefin copolymer (B) satisfying the following requirements (b-i) and (b-ii) [provided that the total amount of (A) and (B) is 100% by mass]. Requirement (a-i): The melt flow rate measured at a temperature of 230 ° C and a load of 2.16 kg in accordance with JIS K6921 is in the range of 1 to 50 g / 10 min.

[0008] Requirement (a-ii): The content of α-olefin other than propylene determined by infrared spectroscopy is 1% by mass or less (including 0). Requirement (b-i): The melt flow rate measured at a temperature of 190 ° C and a load of 2.16 kg in accordance with JIS K6921 is in the range of 0.1 to 15 g / 10 min.

[0009] Requirement (b-ii): The density measured in accordance with JIS K6922 is in the range of 900 to 920 kg / m 3 range. [2] The injection molded article according to item [1], wherein the propylene-based polymer (A) is a propylene homopolymer.

[0010] [3] The injection molded article according to item [1], wherein the α-olefin of the ethylene-α-olefin copolymer (B) is 1-hexene.

[0011] [4] The injection molded article according to item [1], wherein the melt flow rate of the requirement (b-i) is in the range of 1 to 5 g / 10 minutes.

[0012] [5] The injection molded article according to item [1], wherein the density of the requirement (b-ii) is in the range of 903 to 915 kg / m 3 .

[0013] [6] The injection molded article according to item [1], wherein the content of the structural unit derived from ethylene in the ethylene·α-olefin copolymer (B) is in the range of 83 to 93 mol%.

[0014] [7] The injection molded article according to item [1], wherein the propylene-based polymer composition does not contain a nucleating agent.

[0015] [8] The injection molded article according to item [1], wherein the injection molded article is any one of a food container, a beverage container, a container, and a daily necessity.

Advantages of the Invention

[0016] The injection molded article of the present invention has good transparency and rigidity and excellent impact strength, and thus can be suitably used for food containers, beverage containers, containers, daily necessities, etc.

Modes for Carrying Out the Invention

[0017] <Propylene-based polymer (A)> The propylene-based polymer (A), which is one of the components contained in the propylene-based polymer composition (hereinafter sometimes abbreviated as "composition") for forming the injection molded article (hereinafter sometimes abbreviated as "molded article") of the present invention, is a propylene polymer that satisfies the following requirements (a-i) and (a-ii).

[0018] Requirement (a-i) The melt flow rate (MFR) measured at a temperature of 230°C and a load of 2.16 kg in accordance with JIS K6921 230) is in the range of 1 to 50 g / 10 min, preferably 1 to 30 g / 10 min.

[0019] MFR 230 The propylene-based polymer (A) satisfying the above range has good compatibility with the ethylene-α-olefin copolymer (B) according to the present invention below. MFR 230 If it exceeds the above range, the impact strength of the obtained molded body may be low. If it does not meet the above range, the back pressure during injection molding of the obtained composition may be high, making injection molding difficult.

[0020] The propylene-based polymer composition containing the propylene-based polymer (A) satisfying the above range has good injection moldability, and the obtained molded body has good mechanical properties and good transparency. Requirement (a-ii) The content of α-olefin other than propylene determined by infrared spectroscopy is 1% by mass or less (including 0), preferably 0.5% by mass or less (including 0), and more preferably a homopolymer of propylene.

[0021] When a homopolymer of propylene is used as the propylene-based polymer (A) according to the present invention, it is preferable because the heat resistance of the obtained molded body is more excellent. The α-olefin other than the above propylene is at least one α-olefin selected from ethylene and α-olefins having 4 to 8 carbon atoms.

[0022] The propylene-based polymer composition containing the propylene-based polymer (A) satisfying the above range has good injection moldability, and the obtained molded body has good mechanical properties and good transparency. The propylene-based polymer (A) according to the present invention can be obtained by various known production methods. Specifically, when the propylene-based polymer (A) contains only propylene, it can be obtained by homopolymerizing propylene or copolymerizing it with an α-olefin of 1% by mass or less in the presence of a known olefin polymerization catalyst. Specific examples of the olefin polymerization catalyst include titanium-based catalysts and metallocene-based catalysts. In particular, titanium-based catalysts are preferred.

[0023] <Ethylene·α-olefin copolymer (B)> The ethylene·α-olefin copolymer (B), which is one of the components contained in the propylene-based polymer composition for forming the injection molded article (hereinafter sometimes abbreviated as "molded article") of the present invention, is an ethylene·α-olefin copolymer that satisfies the following requirements (b-i) and (b-ii).

[0024] Requirement (b-i) The melt flow rate (MFR 190 ) measured in accordance with JIS K6921 at a temperature of 190 °C and a load of 2.16 kg is in the range of 0.1 to 15 g / 10 min, preferably 1 to 10 g / 10 min, and more preferably 1 to 5 g / 10 min.

[0025] The ethylene·α-olefin copolymer (B) that satisfies the above range has good compatibility with the propylene-based polymer (A) according to the present invention. In particular, when the ethylene·α-olefin copolymer (B) having an MFR 190 in the range of 1 to 5 g / 10 min is used, the impact resistance of the obtained molded article becomes better.

[0026] MFR 190 If it exceeds the above range, the impact strength of the obtained molded article may be low. If it does not meet the above range, the back pressure during injection molding of the obtained composition may be high, making injection molding difficult.

[0027] The propylene-based polymer composition containing the ethylene·α-olefin copolymer (B) that satisfies the above range has good injection moldability, and the obtained molded article has good mechanical properties and good transparency.

[0028] Requirement (b-ii) The density measured in accordance with JIS K6922 is in the range of 900 to 920 kg / m 3 , preferably 903 to 915 kg / m 3 .

[0029] The molded article obtained from the propylene-based polymer composition containing the ethylene·α-olefin copolymer (B) satisfying the above range far exceeds the impact strength of the molded article obtained from the propylene-based polymer (A) alone, is excellent in impact strength, hardly reduces transparency and rigidity, and is excellent in the balance of transparency, impact strength, and rigidity.

[0030] The ethylene·α-olefin copolymer (B) according to the present invention is a copolymer mainly composed of structural units derived from ethylene. The α-olefin is preferably at least one α-olefin selected from the group consisting of α-olefins having 3 to 8 carbon atoms, more preferably at least one α-olefin selected from the group consisting of propylene, 1-butene, 1-hexene, and 1-octene. Among them, 1-hexene is particularly preferred.

[0031] The ethylene·α-olefin copolymer (B) according to the present invention usually has a content of structural units derived from ethylene in the range of 83 to 93 mol%, preferably 86 to 90 mol%.

[0032] 《Propylene-based Polymer Composition》 The propylene-based polymer composition for forming the injection molded article (hereinafter sometimes abbreviated as "molded article") of the present invention contains 60 to 90% by mass, preferably 70 to 90% by mass, more preferably 70 to 80% by mass of the above propylene-based polymer (A), and 10 to 40% by mass, preferably 10 to 30% by mass, more preferably 10 to 20% by mass of the above ethylene·α-olefin copolymer (B) [however, the total amount of (A) and (B) is 100% by mass].

[0033] The propylene-based polymer composition according to the present invention usually has an MFR 230 in the range of 1 to 50 g / 10 min, preferably 3 to 30 g / 10 min, more preferably 5 to 20 g / 10 min. In addition to the above-mentioned propylene-based polymer (A) and ethylene-α-olefin copolymer (B), the propylene-based polymer composition according to the present invention may contain, within a range not impairing the object of the present invention, neutralizing agents, antioxidants, heat stabilizers, weathering agents, lubricants, ultraviolet absorbers, antistatic agents, antiblocking agents, antifogging agents, dispersants, flame retardants, antibacterial agents, fluorescent brighteners, crosslinking agents, crosslinking aids, and other additives; components exemplified by colorants such as dyes and pigments (hereinafter referred to as "other components").

[0034] The propylene-based polymer composition according to the present invention preferably does not contain a nucleating agent (nucleating agent). An injection molded article made of a composition containing a nucleating agent increases both transparency and rigidity at the same time. Therefore, for applications that require flexibility, it is easier to optimize the balance of transparency, impact strength, and rigidity without adding it.

[0035] An injection molded article made of the propylene-based polymer composition according to the present invention greatly exceeds the impact strength of a molded article obtained from the propylene-based polymer (A) alone, is excellent in impact strength, does not significantly reduce transparency and rigidity, and is excellent in the balance of transparency, impact strength, and rigidity.

[0036] <Manufacturing method of propylene-based polymer composition> The propylene-based polymer composition according to the present invention is obtained by dry blending the above-mentioned propylene-based polymer (A) and ethylene-α-olefin copolymer (B), mixing them with a Henschel mixer, Banbury mixer, etc., or after mixing, melt kneading them with a single screw extruder, twin screw extruder, high-speed twin screw extruder, etc.

[0037] <Injection molded article> The injection molded article of the present invention is a molded article obtained by injection molding the propylene-based polymer composition according to the present invention.

[0038] 《Manufacturing method of injection molded article》 The injection-molded article of the present invention can be produced by using a known injection molding machine, heating and melting the propylene-based polymer composition according to the present invention, injecting and pouring it into a mold, cooling and solidifying it, and then taking it out of the mold.

[0039] More specifically, the propylene-based polymer composition is put into the hopper of an injection molding machine, fed into a cylinder heated to approximately 200°C to 250°C, kneaded and plasticized to be in a molten state. This is injected from the nozzle at high pressure and high speed (maximum pressure 700 to 1500 kg / cm 3 ) into a mold closed by a mold clamping mechanism that is temperature-controlled to 5 to 50°C, preferably 10 to 40°C, with cooling water or warm water, etc. By cooling the propylene-based polymer composition injected from the mold to cool and solidify it, opening the mold with the mold clamping mechanism, and obtaining the injection-molded article.

[0040] Also, as injection stretch blow molding, for example, the propylene-based polymer composition is put into the hopper of an injection molding machine, the resin is fed into a cylinder heated to approximately 200°C to 250°C, kneaded and plasticized to be in a molten state. This is injection-molded from the nozzle at high pressure and high speed (maximum pressure 700 to 1500 kg / cm 3 ) into a mold closed by a mold clamping mechanism that is temperature-controlled to 5 to 80°C, preferably 10 to 60°C, with cooling water or warm water, etc., cooled there for 1.0 to 3.0 seconds to form a preform, then immediately opening the mold and stretching and orienting it in the longitudinal direction using a stretching rod, and further stretching and orienting it in the transverse direction by blow molding to obtain the injection-molded article.

[0041] 《Applications of the injection-molded article》 The injection-molded article of the present invention includes food containers, beverage containers, containers, daily necessities, etc. More specifically, it can be widely used as food containers for solids such as jelly, pudding, and yogurt (dessert cups), containers for pharmaceuticals, and containers for industrial liquids.

[0042] As for the dessert cup, it is preferable that the thickness of the container body part (the thinnest part) is in the range of 0.3 to 2.0 mm. Even when thinned in this way, the propylene-based resin composition of the present invention has sufficient impact strength and does not break during the manufacturing process to generate fragments.

[0043] The injection molded article of the present invention also has a good balance of impact resistance, transparency, and rigidity in these products.

Examples

[0044] Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not limited to these examples. Each polymer etc. used in the examples and comparative examples are shown below. (1) Propylene-based polymer (A) As the propylene-based polymer (A), the following propylene-based polymers were used. (1-1) Propylene-based polymer (A-1) MFR 230 = 15 g / 10 minutes of a propylene homopolymer, trade name Prime Polypro J106MG manufactured by Prime Polymer Co., Ltd. was used. (2) Ethylene·α-olefin copolymer (B) As the ethylene·α-olefin copolymer (B), the following ethylene·α-olefin copolymers were used. (2-1) Ethylene·1-hexene copolymer (B-1) MFR 190 = 3.8 g / 10 minutes, density = 903 kg / m 3 of the ethylene·1-hexene copolymer (B-1): trade name Evolue SP0540 manufactured by Prime Polymer Co., Ltd. was used. (2-2) Ethylene·1-hexene copolymer (B-2) MFR 190 = 3.8 g / 10 minutes, density = 918 kg / m 3 of the ethylene·1-hexene copolymer (B-2): trade name Evolue SP2040 manufactured by Prime Polymer Co., Ltd. was used. (2-3) Ethylene·1-hexene copolymer (B-3) MFR 190 = 1 g / 10 min, density = 915 kg / m 3 of ethylene-1-hexene copolymer (B-3): manufactured by Prime Polymer Co., Ltd., trade name Evolue SP0510 was used. (2-4) Ethylene-1-hexene copolymer (B-4) MFR 190 = 2 g / 10 min, density = 913 kg / m 3 of ethylene-1-hexene copolymer (B-4): manufactured by Prime Polymer Co., Ltd., trade name Evolue SP1520 was used. (2-5) Ethylene-1-hexene copolymer (B-5) MFR 190 = 10 g / 10 min, density = 911 kg / m 3 of ethylene-1-hexene copolymer (B-5): manufactured by Prime Polymer Co., Ltd., trade name Evolue SP1071C was used. (3) Ethylene-α-olefin copolymer (C) As the ethylene-α-olefin copolymer, the following ethylene-α-olefin copolymers were used. (3-1) Ethylene-α-olefin copolymer (C-1) MFR 190 = 1.5 g / 10 min, density = 862 kg / m 3 of ethylene-propylene copolymer (C-1): manufactured by ExxonMobil, trade name VISTAMAXX 6102FL was used. (3-2) Ethylene-α-olefin copolymer (C-2) MFR 190 = 4 g / 10 min, density = 879 kg / m 3 of ethylene-propylene copolymer (C-2): manufactured by ExxonMobil, trade name VISTAMAXX 3980FL was used.

[0045] The physical properties of the injection molded articles obtained in the examples and comparative examples were measured by the following methods. (1) Transparency Regarding the central part of the injection molded article, haze was measured in accordance with JIS K7136. Note that the total haze is the sum of the internal haze and the external haze. (2) High-rate surface impact test (High-rate impact) Using an injection molded article composed of a flat plate of 200 mm × 200 mm × 2.0 mm, a test piece for measurement was placed on a support base with a hole of 40 mm φ inner diameter, fixed using a sample holder of 76 mm φ inner diameter, and then the test piece was struck with a striker of 12.7 mm φ diameter having a hemispherical impact surface at an impact velocity of 1 m / sec, and the puncture energy (J) was determined according to JIS K7211-2. The average value of the puncture energy of each of the 4 test pieces for measurement was taken as the surface impact strength (high-rate impact). (3) Rigidity The tensile elastic modulus of the dumbbell test piece was measured in accordance with JIS K7161 and K7162-1.

[0046] [Example 1] An injection molding machine (FANUC ROBOSHOT α100C manufactured by FANUC Corporation) was used to prepare an injection molded article for high-rate surface impact test and measurement of transparency (haze) composed of a flat plate of 200 mm × 200 mm × 2.0 mm, and an injection molded article composed of a tensile elastic modulus test piece (dumbbell test piece conforming to JIS K7161 and K7162-1) under the conditions of a molten resin temperature of 200 °C, a mold temperature of 40 °C, an average injection speed of 35 mm / sec, a holding pressure time of 10 seconds, and a total cycle time of 45 seconds, by mixing 90 mass% of the above propylene-based polymer (A-1) and 10 mass% of the above ethylene·1-hexene copolymer (B-1).

[0047] Using the obtained injection molded article, the physical properties were measured by the method described above. The results are shown in Table 1. [Examples 2 to 11] An injection molded article was prepared in the same manner as in Example 1, except that the propylene-based polymer composition described in Table 1, which is the above propylene-based polymer (A-1) and the above ethylene·1-hexene copolymer (B-1), etc., was used instead of the propylene-based polymer composition used in Example 1.

[0048] Using the obtained injection molded article, the physical properties were measured by the method described above. The results are shown in Table 1. [Comparative Example 1] An injection molded article was produced in the same manner as in Example 1, except that the propylene-based polymer (A-1) was used alone instead of the propylene-based polymer composition used in Example 1.

[0049] Using the obtained injection molded article, the physical properties were measured by the method described above. The results are shown in Table 2. [Comparative Examples 2 to 8] An injection molded article was produced in the same manner as in Example 1, except that a propylene-based polymer composition of the above propylene-based polymer (A-1) and the above ethylene·α-olefin copolymer (C-1), etc., described in Table 2 was used instead of the propylene-based polymer composition used in Example 1.

[0050] Using the obtained injection molded article, the physical properties were measured by the method described above. The results are shown in Table 2.

[0051] [Table 1]

[0052] [Table 2] As shown in Tables 1 and 2, the injection molded articles obtained in Examples 1 to 11 have improved haze compared to the injection molded article made of the propylene-based polymer (A) alone obtained in Comparative Example 1. Also, the impact strength at 23°C, the impact strength at 0°C, and the impact strength at -20°C are improved.

[0053] On the other hand, the injection molded articles made of the propylene-based polymer compositions containing the ethylene·α-olefin copolymer with a density of 862 kg / m 3 obtained in Comparative Examples 2 to 5 have deteriorated haze and no improvement in the impact strength at -20°C.

[0054] Also, the injection molded articles obtained in Comparative Examples 6 to 8 with a density of 879 kg / m 3The injection molded article made of a propylene-based polymer composition containing the ethylene·α-olefin copolymer has no deterioration in haze, but there is no improvement in the impact strength at 0°C and the impact strength at -20°C.

Claims

1. 60 to 90% by mass of a propylene-based polymer (A) satisfying the following requirements (a-i) and (a-ii), and an ethylene / α-olefin copolymer (B) satisfying the following requirements (b-i), (b-ii) and (b-iii) (however, excluding an ethylene-based polymer component containing an ethylene-based polymer (B1) which simultaneously satisfies the following requirements (b1) to (b4) and is a copolymer of ethylene and at least one α-olefin having 4 to 10 carbon atoms).) is 10 to 40% by mass [however, the total amount of (A) and (B) is 100% by mass.], does not contain a nucleating agent, and has a melt flow rate (MFR 230 ) measured at a temperature of 230 °C and a load of 2.16 kg in accordance with JIS K6921 in the range of 5 to 50 g / 10 min; an injection molded article made of a propylene-based polymer composition Requirement (a-i): The melt flow rate measured at a temperature of 230°C and a load of 2.16 kg in accordance with JIS K6921 is in the range of 1 to 50 g / 10 min. Requirement (a-ii): The content of α-olefins other than propylene determined by infrared spectroscopy is 1 mass% or less (including 0). Requirement (b-i): The melt flow rate measured at a temperature of 190°C and a load of 2.16 kg in accordance with JIS K6921 is in the range of 0.1 to 15 g / 10 min. Requirement (b-ii): The density measured in accordance with JIS K6922 is in the range of 900 to 920 kg / m 3 ³. Requirement (b-iii): The content of the structural unit derived from ethylene is 93 mol% or less. (b1) The melt flow rate (MFR, 190°C, 2.16 kg load) obtained in accordance with ASTM D1238-89 is 0.1 g / 10 min or more and 10 g / 10 min or less. (b2) The density is 875 kg / m 3 or more and 945 kg / m 3 or less. (b3) 13 The sum [(Me + Et)( / 1000C)] of the number of methyl branches [Me( / 1000C)] and the number of ethyl branches [Et( / 1000C)] per 1000 carbon atoms measured by C-NMR is 1.80 or less. The ratio of the intrinsic viscosity [[η]] (dl / g) measured in decalin at 135°C to the 0.776th power of the weight-average molecular weight (Mw 0.776 ) measured by the GPC-viscosity detector method (GPC-VISCO) ([η] / Mw 0.776 ) is 0.90×10 -4 or more and 1.65×10 -4 or less.

2. The injection molded article according to Claim 1, wherein the propylene-based polymer (A) is a propylene homopolymer.

3. The injection molded article according to Claim 1, wherein the α-olefin of the ethylene / α-olefin copolymer (B) is 1-hexene.

4. The injection molded article according to Claim 1, wherein the melt flow rate of Requirement (b-i) is in the range of 1 to 5 g / 10 min.

5. The density of the above requirement (b-ii) is in the range of 903 to 915 kg / m 3 The injection molded article according to claim 1, wherein the density is in the range of 903 to 915 kg / m

6. The injection molded article according to Claim 1, wherein the content of the structural unit derived from ethylene of the ethylene / α-olefin copolymer (B) is in the range of 83 to 93 mol%.

7. The injection molded article according to Claim 1, wherein the injection molded article is any one of a food container, a beverage container, a container, and a daily necessity.

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