Polyethylene resin composition and method for producing the polyethylene resin composition

Abstract

The objective is to provide a polyethylene resin composition containing so-called ultra-high molecular weight polyethylene with high intrinsic viscosity and polyethylene with lower intrinsic viscosity than said polyethylene, which yields a molded article with excellent mechanical strength and surface smoothness, and a method for producing said polyethylene resin composition. [Solution] A polyethylene resin composition comprising 5 to 30 parts by mass of polyethylene (A) satisfying specific requirement (a-1), 5 to 30 parts by mass of polyethylene (B) satisfying specific requirement (b-1), and 40 to 90 parts by mass of polyethylene (C) satisfying specific requirements (c-1) and (c-2) (provided that the total amount of polyethylene (A), polyethylene (B), and polyethylene (C) is 100 parts by mass), and having a specific intrinsic viscosity.

Description

[Technical Field]

[0001] The present invention relates to a polyethylene resin composition and a method for producing the composition. [Background technology]

[0002] So-called ultra-high molecular weight polyethylene, which has a very high intrinsic viscosity, exhibits weaker intermolecular cohesive forces, a symmetrical molecular structure, and high crystallinity compared to general-purpose resins like ordinary polyethylene. This results in excellent sliding properties, as well as superior impact resistance, abrasion resistance, and tensile strength, making it suitable for a wide range of applications. However, due to its high molecular weight, ultra-high molecular weight polyethylene is difficult to mold, and it is often challenging to directly utilize the molding methods employed for general-purpose polyethylene.

[0003] Therefore, various methods have been proposed to improve the moldability of ultra-high molecular weight polyethylene without impairing its excellent properties, such as blending ultra-high molecular weight polyethylene with polyethylene with low intrinsic viscosity.

[0004] For example, Patent Document 1 discloses a polyolefin composition for injection molding comprising 15-40% by weight of an ultra-high molecular weight polyolefin with an intrinsic viscosity of 10-40 dl / g and 85-60% by weight of a low molecular weight or high molecular weight polyolefin with an intrinsic viscosity of 0.1-5 dl / g. This composition has the advantage of being able to be injection molded despite containing an ultra-high molecular weight polyolefin, and furthermore, the molded product obtained by injection molding is excellent in that it has the excellent sliding properties and wear resistance of an ultra-high molecular weight polyolefin.

[0005] Patent Document 2 discloses a composition obtained by blending a specific polyolefin resin composition with a polyethylene resin composition containing more than 35% by weight and up to 90% by weight of ultra-high molecular weight polyethylene having an intrinsic viscosity of 10 to 40 dl / g and 10% by weight or more and less than 65% by weight of low molecular weight to high molecular weight polyethylene having an intrinsic viscosity of 0.1 to 5 dl / g. From this composition, a molded article excellent in the balance of wear resistance, appearance, and moldability can be obtained.

[0006] Patent Document 3 discloses a polyethylene resin composition satisfying specific conditions, which contains 5 to 35 parts by mass of ultra-high molecular weight polyethylene (A) having an intrinsic viscosity measured in a decalin solvent at 135°C of 33 to 50 dl / g and 95 to 65 parts by mass of low molecular weight to high molecular weight polyethylene (B) having an intrinsic viscosity measured in a decalin solvent at 135°C of 0.1 to 5.0 dl / g and a density in a specific range. From this composition, a polyethylene resin composition having a high melt fluidity that facilitates molding and wear resistance under high load conditions in good balance can be obtained.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] Excellent molded articles can be obtained from the polyethylene resin compositions disclosed in the patent documents. However, there was room for improvement in the mechanical strength and surface smoothness of the obtained molded articles.

[0009] The present invention aims to provide a polyethylene resin composition containing a so-called ultra-high molecular weight polyethylene having a high intrinsic viscosity and a polyethylene having an intrinsic viscosity lower than that of the polyethylene, and capable of obtaining a molded body excellent in mechanical strength and surface smoothness, and a method for producing the polyethylene resin composition.

Means for Solving the Problems

[0010] As a result of the research by the present inventors, it has been found that according to the following configuration examples, the above problems can be solved. The configuration examples of the present invention are as follows. In this specification, "A to B" indicating a numerical range means A or more and B or less.

[0011] [1] 5 to 30 parts by mass of polyethylene (A) satisfying the following requirement (a-1), 5 to 30 parts by mass of polyethylene (B) satisfying the following requirement (b-1), 40 to 90 parts by mass of polyethylene (C) satisfying the following requirements (c-1) and (c-2), (where the total amount of polyethylene (A), polyethylene (B) and polyethylene (C) is 100 parts by mass), A polyethylene resin composition having an intrinsic viscosity [η] measured in a decalin solvent at 135 °C of 2.0 to 15 dl / g. (a-1) The intrinsic viscosity [η] measured in a decalin solvent at 135 °C A is 8 to 40 dl / g; (b-1) The intrinsic viscosity [η] measured in a decalin solvent at 135 °C B is 1.5 dl / g or more and less than 8 dl / g; (c-1) The intrinsic viscosity [η] measured in a decalin solvent at 135 °C C is 0.1 dl / g or more and less than 1.5 dl / g; (c-2) The density is 950 to 985 kg / m 3 is.

[0012] [2] The polyethylene resin composition according to [1], wherein the melt flow rate (MFR) measured at 190°C and a 10 kg load in accordance with ASTM D1238E is 0.1 to 30 g / 10 min.

[0013] [3] A molded article comprising the polyethylene resin composition described in [1] or [2].

[0014] [4] Intrinsic viscosity measured in decalin solvent at 135°C [η] A A process for producing polyethylene (A) with a concentration of 8-40 dl / g, Intrinsic viscosity [η] measured in decalin solvent at 135°C B A process for producing polyethylene (B) having a concentration of 1.5 dl / g or more and less than 8 dl / g, Intrinsic viscosity [η] measured in decalin solvent at 135°C C A process for producing polyethylene (C) having a concentration of 0.1 dl / g or more and less than 1.5 dl / g, By a multi-stage polymerization method including at least three steps, A method for producing a polyethylene resin composition, wherein the polyethylene resin composition has an intrinsic viscosity [η] measured in a decalin solvent at 135°C in the range of 2.0 to 15 dl / g. [Effects of the Invention]

[0015] The present invention provides a polyethylene resin composition comprising so-called ultra-high molecular weight polyethylene with high intrinsic viscosity and polyethylene with lower intrinsic viscosity than said polyethylene, which yields molded articles with excellent mechanical strength and surface smoothness. [Modes for carrying out the invention]

[0016] Polyethylene resin composition The polyethylene resin composition according to the present invention comprises polyethylene (A) having a high intrinsic viscosity within a specific range, and two specific types of polyethylene (B) and polyethylene (C) having a lower intrinsic viscosity than polyethylene (A).

[0017] The intrinsic viscosity [η] of the above polyethylene resin composition, measured in decalin solvent at 135°C, is 2.0 to 15 dl / g. If the intrinsic viscosity [η] is less than 2.0 dl / g, the resulting molded article tends to have poor mechanical strength. On the other hand, if the intrinsic viscosity [η] exceeds 15 dl / g, the fluidity of the molten resin tends to decrease, leading to poor moldability and consequently, a loss of surface smoothness in the resulting molded article. Because the above polyethylene resin composition has such an intrinsic viscosity, the molded article obtained from this polyethylene resin composition has excellent surface smoothness and excellent mechanical strength.

[0018] From the viewpoint of obtaining a molded article with superior surface smoothness and superior mechanical strength, the intrinsic viscosity [η] of the polyethylene resin composition measured in decalin solvent at 135°C is preferably 2.0 to 10 dl / g, more preferably 3.0 to 8.0 dl / g, even more preferably 4.0 to 7.0 dl / g, and particularly preferably 4.0 to 6.0 dl / g.

[0019] The above polyethylene resin composition has a melt flow rate (hereinafter also referred to as "MFR") measured at 190°C and a 10 kg load in accordance with the measurement method of ASTM D1238E, which is preferably 0.1 to 30 g / 10 min, more preferably 0.2 to 20 g / 10 min, even more preferably 0.5 to 10 g / 10 min, and particularly preferably 1 to 5 g / 10 min. When the MFR of the polyethylene resin composition is within the above range, it has good moldability, and the resulting molded article has superior surface smoothness and superior mechanical strength.

[0020] In the polyethylene resin composition described above, the content of polyethylene (A) is 5 to 30 parts by mass, preferably 8 to 27 parts by mass, more preferably 10 to 24 parts by mass, even more preferably 12 to 20 parts by mass, and particularly preferably 12 to 18 parts by mass, based on a total of 100 parts by mass of polyethylene (A), polyethylene (B), and polyethylene (C). In the above polyethylene resin composition, the content of polyethylene (B) with respect to 100 parts by mass in total of polyethylene (A), polyethylene (B) and polyethylene (C) is 5 to 30 parts by mass, preferably 8 to 27 parts by mass, more preferably 10 to 24 parts by mass, still more preferably 12 to 20 parts by mass, and particularly preferably 12 to 18 parts by mass. In the above polyethylene resin composition, the content of polyethylene (C) with respect to 100 parts by mass in total of polyethylene (A), polyethylene (B) and polyethylene (C) is 40 to 90 parts by mass, preferably 46 to 84 parts by mass, more preferably 52 to 80 parts by mass, still more preferably 60 to 76 parts by mass, and particularly preferably 64 to 76 parts by mass. When the contents of polyethylene (A), polyethylene (B) and polyethylene (C) are within the above ranges, the compatibility of each component of the polyethylene resin composition obtained in the present invention is enhanced, and the molded body obtained from the composition is excellent in mechanical strength and surface smoothness.

[0021] The monomers serving as raw materials for the specific polyethylene (A), specific polyethylene (B), and specific polyethylene (C) contained in the polyethylene resin composition according to the present invention may use only biomass-derived raw materials, only fossil fuel-derived raw materials, or both biomass-derived raw materials and fossil fuel-derived raw materials. The biomass-derived raw material is a raw material made from any (renewable) natural raw material and its residue, such as plant-derived or animal-derived, including fungi, yeast, algae and bacteria. For example, as carbon 14 C isotope is contained at a ratio of about 1×10 -12 And a raw material having a biomass carbon concentration (unit: pMC) of about 100 pMC measured in accordance with ASTM D6866. The biomass-derived raw material (e.g., monomers such as ethylene and α-olefin) can be obtained by, for example, a conventionally known method. Polyethylene (A), polyethylene (B), and polyethylene (C) may be (co)polymers containing biomass-derived raw materials as long as the production conditions such as the polymerization catalyst, polymerization process, and polymerization temperature are the same.14 1 × 10¹¹ C isotopes -12 ~10 -14 Aside from the proportion of biomass-derived materials present, the molecular structure is equivalent to that of a (co)polymer made from fossil fuel-derived raw materials. Therefore, it is considered that the performance of a (co)polymer containing biomass-derived raw materials is the same as that of a (co)polymer made from fossil fuel-derived raw materials.

[0022] <Polyethylene (A)> Polyethylene (A) is a type of polyethylene classified as a so-called ultra-high molecular weight polyethylene with high intrinsic viscosity. Polyethylene (A) satisfies the following requirement (a-1).

[0023] [Requirement (a-1)] Polyethylene (A) has an intrinsic viscosity [η] measured in decalin solvent at 135°C. A The intrinsic viscosity [η] is 8-40 dl / g. A The concentration is preferably 10-37 dl / g, more preferably 15-35 dl / g, even more preferably 20-32 dl / g, and particularly preferably 25-32 dl / g.

[0024] The intrinsic viscosity [η] of polyethylene (A) measured in decalin solvent at 135°C. A When the value is above the aforementioned lower limit, the resulting polyethylene resin composition tends to have good mechanical strength. Also, the intrinsic viscosity [η] of polyethylene (A) measured in decalin solvent at 135°C A As long as the above-mentioned upper limit is below this value, the resulting polyethylene resin composition exhibits excellent melt-flow properties and excellent surface smoothness.

[0025] Polyethylene (A) may be a homopolymer of ethylene, or a copolymer of ethylene and α-olefin. When polyethylene (A) is a copolymer of ethylene and α-olefin, examples of α-olefins include linear or branched α-olefins having 3 to 20 carbon atoms, specifically propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 3,4-dimethyl-1-pentene, 4-methyl-1-hexene, 3-ethyl-1-pentene, 3-ethyl-4-methyl-1-pentene, 3,4-dimethyl-1-hexene, 4-methyl-1-heptene, 3,4-dimethyl-1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene.

[0026] Polyethylene (A) is preferably a homopolymer of ethylene, or a copolymer of ethylene and the above-mentioned α-olefin, wherein the copolymer is mainly composed of ethylene, and more preferably a homopolymer of ethylene. Here, the main component refers to the component with the highest content ratio (mol%) among the constituent units contained in the polymer. Polyethylene (A) may be used alone or in combination of two or more types.

[0027] <Polyethylene (B)> Polyethylene (B) has a lower intrinsic viscosity than polyethylene (A) and is classified as a low molecular weight or high molecular weight polyethylene. Polyethylene (B) satisfies the following requirement (b-1).

[0028] [Requirement (b-1)] Intrinsic viscosity [η] of polyethylene (B) measured in decalin solvent at 135°C. B The intrinsic viscosity [η] is 1.5 dl / g or more and less than 8 dl / g. B The amount is preferably 1.5 to 7.5 dl / g, more preferably 1.7 to 6.0 dl / g, even more preferably 2.0 to 4.0 dl / g, and particularly preferably 2.0 to 3.0 dl / g. Intrinsic viscosity [η] of polyethylene (B) measured in decalin solvent at 135°C. B Because the viscosity is within the aforementioned range, polyethylene (A) with a higher intrinsic viscosity and polyethylene (C) with a lower intrinsic viscosity become easier to mix, improving the compatibility of each component of the resulting polyethylene resin composition. As a result, the molded article obtained from the polyethylene resin composition has excellent mechanical strength and excellent surface smoothness.

[0029] From the standpoint of superior mechanical strength and superior surface smoothness of the resulting molded article, polyethylene (B) is preferably further satisfied with the following requirement (b-2). [Requirement (b-2)] Polyethylene (B) has a density of 950-985 kg / m³. 3 Preferably 960-980 kg / m 3 More preferably 960-975 kg / m 3 And more preferably 965-975 kg / m 3 That is the case. By using polyethylene (B) with a density within the above range, polyethylene (A) with a higher intrinsic viscosity and polyethylene (C) with a lower intrinsic viscosity become easier to mix, improving the compatibility of each component of the resulting polyethylene resin composition. This results in a molded article with superior mechanical strength and surface smoothness.

[0030] Polyethylene (B) may be a homopolymer of ethylene, or a copolymer of ethylene and α-olefin. When polyethylene (B) is a copolymer of ethylene and α-olefin, examples of α-olefins include linear or branched α-olefins having 3 to 20 carbon atoms, specifically propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 3,4-dimethyl-1-pentene, 4-methyl-1-hexene, 3-ethyl-1-pentene, 3-ethyl-4-methyl-1-pentene, 3,4-dimethyl-1-hexene, 4-methyl-1-heptene, 3,4-dimethyl-1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. Of these, propylene and 1-butene are preferred because they offer superior mechanical strength and surface smoothness in the resulting molded articles.

[0031] Furthermore, it is more preferable that the copolymer of ethylene and α-olefin contains 90 mol% or more of constituent units derived from ethylene, and even more preferable that it contains 95 mol% or more of constituent units derived from ethylene. Also, it is more preferable that the copolymer of ethylene and α-olefin contains 10 mol% or less of constituent units derived from α-olefin, and even more preferable that it contains 5 mol% or less of constituent units derived from α-olefin. When polyethylene (B) is a copolymer of ethylene and α-olefin, a higher amount of constituent units derived from ethylene is preferable.

[0032] Polyethylene (B) is preferably a homopolymer of ethylene. Polyethylene (B) may be used alone or in combination of two or more types.

[0033] <Polyethylene (C)> Polyethylene (C) has a lower intrinsic viscosity than polyethylene (A) and polyethylene (B), and is classified as a low molecular weight or high molecular weight polyethylene. Polyethylene (C) satisfies the following requirements (c-1) and (c-2).

[0034] [Requirement (c-1)] The intrinsic viscosity [η] of polyethylene (C) measured in decalin solvent at 135°C. C The intrinsic viscosity [η] is 0.1 dl / g or more and less than 1.5 dl / g. C The amount is preferably 0.4 to 1.4 dl / g, more preferably 0.6 to 1.3 dl / g, even more preferably 0.8 to 1.2 dl / g, and particularly preferably 0.9 to 1.1 dl / g.

[0035] The intrinsic viscosity [η] of polyethylene (C) measured in decalin solvent at 135°C. C When the value is above the aforementioned lower limit, the resulting polyethylene resin composition tends to have good mechanical strength. Also, the intrinsic viscosity [η] of polyethylene (C) measured in decalin solvent at 135°C C As the value is below the upper limit, the resulting polyethylene resin composition exhibits excellent melt-flow properties, and the molded article obtained using the polyethylene resin composition exhibits excellent surface smoothness.

[0036] [Requirement (c-2)] Polyethylene (C) has a density of 950-985 kg / m³. 3 The density is preferably 960-980 kg / m³. 3 More preferably 960-975 kg / m 3 More preferably 965-975 kg / m 3 That is the case. By using polyethylene (C) with a density within the above range, each polymer component in the polyethylene resin composition becomes easier to mix, the compatibility of each component in the resulting polyethylene resin composition is improved, and the molded article obtained from that polyethylene resin composition has superior mechanical strength and superior surface smoothness.

[0037] Polyethylene (C) may be a homopolymer of ethylene, or a copolymer of ethylene and α-olefin. When polyethylene (C) is a copolymer of ethylene and α-olefin, examples of α-olefins include linear or branched α-olefins having 3 to 20 carbon atoms, specifically propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 3,4-dimethyl-1-pentene, 4-methyl-1-hexene, 3-ethyl-1-pentene, 3-ethyl-4-methyl-1-pentene, 3,4-dimethyl-1-hexene, 4-methyl-1-heptene, 3,4-dimethyl-1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. Of these, propylene and 1-butene are preferred because they offer superior mechanical strength and surface smoothness in the resulting molded articles.

[0038] Furthermore, it is more preferable that the copolymer of ethylene and α-olefin contains 90 mol% or more of constituent units derived from ethylene, and even more preferable that it contains 95 mol% or more of constituent units derived from ethylene. Also, it is more preferable that the copolymer of ethylene and α-olefin contains 10 mol% or less of constituent units derived from α-olefin, and even more preferable that it contains 5 mol% or less of constituent units derived from α-olefin. When polyethylene (C) is a copolymer of ethylene and α-olefin, a higher amount of constituent units derived from ethylene is preferable.

[0039] Polyethylene (C) is preferably a homopolymer of ethylene. Polyethylene (C) may be used alone or in combination of two or more types.

[0040] <Other ingredients> The polyethylene resin composition may contain other thermoplastic resins such as polyolefin resins (however, different from polyethylene(A), polyethylene(B), and polyethylene(C)) or resin additives (for example, stabilizers such as heat-resistant stabilizers and weather-resistant stabilizers, crosslinking agents, crosslinking aids, antistatic agents, slip agents, antiblocking agents, antifogging agents, lubricants, dyes, pigments, fillers, mineral oil-based softeners, petroleum resins, waxes, etc.) as long as the objectives of the present invention are not impaired. If the aforementioned other components are included, the total amount of the aforementioned other components in the polyethylene resin composition is usually 5% by mass or less, preferably 2% by mass or less, and more preferably 1% by mass or less. In other words, the total mass of polyethylene (A), polyethylene (B), and polyethylene (C) in the polyethylene resin composition is usually 95% by mass or more, preferably 98% by mass or more, and more preferably 99% by mass or more.

[0041] <Method for producing polyethylene resin composition> The method for producing the polyethylene resin composition is not particularly limited as long as it is a method that can contain polyethylene (A), polyethylene (B), and polyethylene (C) in predetermined proportions, but preferred methods include the following methods (M-1) to (M-2).

[0042] Method (M-1): A method for producing polyethylene (A), polyethylene (B), and polyethylene (C) by first producing each in the presence of an olefin polymerization catalyst, and then blending these polyethylene (A), polyethylene (B), and polyethylene (C) to satisfy the conditions that the polyethylene resin composition should meet, such as the intrinsic viscosity [η] measured in decalin solvent at 135°C.

[0043] Method (M-2): In the presence of an olefin polymerization catalyst, the first step is to produce one type of polyethylene selected from the group consisting of polyethylene (A), polyethylene (B), and polyethylene (C); The second step involves producing one of the two types of polyethylene other than those produced in the first step; and A method of production by a multi-stage polymerization method, comprising at least three steps, including a third step of producing one remaining type of polyethylene other than those produced in the first and second steps. In method (M-2), the second step is carried out in the presence of polyethylene produced in the first step, and the third step is carried out in the presence of polyethylene produced in both the first and second steps. Furthermore, the polymerization conditions for the first, second, and third steps are selected to satisfy the conditions that the polyethylene resin composition should meet, such as the intrinsic viscosity [η] measured in decalin solvent at 135°C. A specific example of the above method (M-2) is the following method (M-2-1). Method (M-2-1): A first step involves producing polyethylene (A) in the presence of an olefin polymerization catalyst; The second step is to produce polyethylene (B); and A method for producing polyethylene(C) by a multi-stage polymerization method, comprising at least three steps, including a third step of producing polyethylene(C). In the above method (M-2-1), the second step is carried out in the presence of polyethylene (A) produced in the first step, and the third step is carried out in the presence of polyethylene (A) produced in the first step and polyethylene (B) produced in the second step. Furthermore, the polymerization conditions for the first, second, and third steps are selected to satisfy the conditions that the polyethylene resin composition should meet, such as the intrinsic viscosity [η] measured in decalin solvent at 135°C.

[0044] Polyethylene (A), polyethylene (B), and polyethylene (C) can be produced, for example, by polymerizing an ethylene-containing monomer in the presence of a known olefin polymerization catalyst described in WO2008 / 013144 and WO2010 / 074073, under polymerization conditions (temperature 70°C to 85°C, polymerization time 45 to 300 minutes) such that the resin composition (X) has the desired physical properties.

[0045] Of methods (M-1) and (M-2), method (M-2) using a multi-stage polymerization method is more preferred. When a multi-stage polymerization method is used, polyethylene (A), polyethylene (B), and polyethylene (C) contained in the polyethylene resin composition become compatible, improving dispersibility, and the molded article obtained from the polyethylene composition has excellent mechanical strength and excellent surface smoothness. Furthermore, among the methods (M-2), when using method (M-2-1), polyethylene is produced in order of decreasing intrinsic viscosity, so polyethylene (A), polyethylene (B), and polyethylene (C) contained in the polyethylene resin composition become more compatible, dispersibility is improved, and the molded article obtained from the polyethylene composition has superior mechanical strength and surface smoothness. Moreover, when this composition is produced using method (M-2-1), by adding a chain transfer agent that causes a chain transfer reaction and increasing the polymerization temperature in the second and third steps, the molecular weight of polyethylene (polyethylene (B)) obtained in the second step can be adjusted to be lower than the molecular weight of polyethylene (polyethylene (A)) obtained in the first step, and the molecular weight of polyethylene (polyethylene (C)) obtained in the third step can be adjusted to be lower than the molecular weight of polyethylene (polyethylene (B)) obtained in the second step, making it preferable in terms of superior production efficiency.

[0046] In this process, the olefins used for polymerization, such as ethylene, can be any of the various olefins listed in the sections on polyethylene (A), polyethylene (B), and polyethylene (C) without limitation.

[0047] Molded body From the above polyethylene resin composition, molded articles containing the polyethylene resin composition in various shapes such as containers, trays, sheets, rods, and films can be produced by conventionally known molding methods, specifically, for example, injection molding, shape extrusion molding, pipe molding, tube molding, injection blow molding, direct blow molding, T-die sheet or film molding, inflation film molding, and press molding. Furthermore, by the molding method described above, it is possible to coat various articles, such as different types of articles, and produce molded articles containing a polyethylene resin composition in which at least a portion of the surface of the various articles is coated with the polyethylene resin composition.

[0048] The molded articles obtained by the above molding method can be widely used in conventional polyethylene applications, but are particularly abrasion resistant, and are used in applications where this is required, such as coatings for metals such as steel pipes, electric wires, and automobile slide rails; reels of various rubbers such as pressure-resistant rubber hoses, automobile door gaskets, cleanroom door gaskets, automobile glass run channels, and automobile weatherstrips; conveyor guide covers for various transport equipment, sliding materials for the sliding surfaces of multifunction printers, elevator rail guides, various guide rails for vending machines and product shelves, PC mouse bottoms and mouse pads, hopper linings, sliding tapes, and various protective liner materials.

[0049] The coefficient of dynamic friction of a molded article containing the polyethylene resin composition of the present invention (measurement conditions: mating material: S45C, speed: 30 m / min, distance: 3 km, load: 15 kg, measurement ambient temperature: 23 °C) is preferably 0.1 to 0.3, more preferably 0.15 to 0.25. When the coefficient of dynamic friction of the molded article is within the above range, it is expected that wear and heat generation due to friction will be suppressed, and noise during sliding will be reduced.

[0050] When a molded article containing the polyethylene resin composition of the present invention is subjected to a high-load abrasion test (test conditions: mating material: S45C, speed: 30 m / min, sliding distance: 3 km, load: 15 kg, measurement ambient temperature: 23 °C), the specific wear amount is preferably 300 × 10⁻¹⁴. -3 mm 3 / kg·km or less, more preferably 200×10 -3 mm 3 / kg·km or less, more preferably 100×10 -3 mm 3 The specific wear rate should be less than or equal to / kg·km. A lower specific wear rate is preferable, but the lower limit is usually 50 × 10 -3 mm 3It is approximately / kg·km. When the specific wear amount obtained by the wear test under the above conditions is within the above range, it is preferable because the wear resistance is sufficient in the usage environment of the molded article containing the polyethylene resin composition.

[0051] The Izod impact strength of a molded article containing the polyethylene resin composition of the present invention, according to ASTM D256 (test specimen: 30cm × 30cm × 2mmt with notch (angle: 45°, R = 0.25mm ± 0.05mm)), is preferably 200 J / m or more, more preferably 250 J / m or more, and even more preferably 300 J / m or more. A higher Izod impact strength is preferable, but the upper limit is usually around 1000 J / m. An Izod impact strength within the above range is preferable because it results in excellent mechanical strength of the molded article containing the polyethylene resin composition.

[0052] The surface roughness (arithmetic mean roughness (Ra)) of the molded article containing the polyethylene resin composition of the present invention is preferably 3.0 μm or less, more preferably 2.0 μm or less. A lower surface roughness is preferable, but the lower limit is usually around 0.1 μm. A surface roughness within the above range is preferable because it provides excellent surface smoothness to the molded article containing the polyethylene resin composition. [Examples]

[0053] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. Note that the following polymerization steps may be performed multiple times to obtain the necessary amount of polymer and composition for evaluation.

[0054] [Measurement conditions, etc.] The measurement conditions for each physical property are as follows:

[0055] [Intrinsic viscosity [η]] The intrinsic viscosity of the various polymers and resin compositions obtained in the examples and comparative examples was measured at 135°C in decalin solvent.

[0056] 〔density〕 The density of polyethylene (C) was measured in accordance with ASTM D1505.

[0057] [MFR] The MFR of the compositions obtained in the examples or comparative examples was measured under a 10 kg load in accordance with ASTM D1238E. The measurement temperature was 190°C.

[0058] [Coefficient of dynamic friction and specific wear of molded body] A test specimen measuring 30cm x 30cm x 2mm thick was fabricated by injection molding. The measurements were taken using a Suzuki friction and wear tester in accordance with JIS K 7218 "Test Method for Sliding and Abrasion of Plastics". The test conditions were: mating material: S45C, speed: 30 m / min, distance: 3 km, load: 15 kg, and ambient temperature: 23 °C.

[0059] [Measurement of impact strength (Izod impact test)] Strip-shaped test pieces measuring 12 mm x 60 mm x 2 mm thick were fabricated by injection molding. After notching (angle: 45°, radius: 0.25mm ± 0.05mm), an Izod impact test was performed in accordance with ASTM D256 to measure the impact strength.

[0060] [Surface roughness of molded product] Ram extruded articles were manufactured from the compositions obtained in the examples or comparative examples by the method described later. The arithmetic mean roughness (Ra) of the surface of the obtained articles was determined by a method in accordance with JIS B 0601.

[0061] [Example 1] [Preparation of solid titanium catalyst component [D1]] 95.2 g of anhydrous magnesium chloride, 398.1 g of decane, and 306 g of 2-ethylhexyl alcohol were placed in a reaction vessel and heated at 140°C for 6 hours. After the solution in the reaction vessel was cooled to 50°C, 17.6 g of ethyl benzoate was added, and the mixture was stirred at 130°C for 1 hour to obtain a homogeneous solution. The homogeneous solution obtained in this way was cooled to room temperature. Then, the entire 50 ml of the homogeneous solution was added dropwise to 200 ml of titanium tetrachloride, which was kept at 0°C, over 60 minutes with stirring to form a mixture. After the dropwise addition was complete, the resulting mixture was kept at 0°C for 1 hour. The temperature of the mixture was then raised to 20°C over 1 hour, and then to 80°C over 30 minutes. When the temperature of the mixture reached 78°C, 2.35 g of ethyl benzoate was added to the mixture, and the reaction was carried out for 2 hours while maintaining the temperature at 80°C. After the 2-hour reaction was complete, the solid portion was collected by thermal filtration, and this solid portion was resuspended in 200 ml of titanium tetrachloride. A second heating reaction was then carried out at 90°C for 2 hours. After the second heating reaction was complete, the solid portion was again collected by thermal filtration, washed with 90°C decane until no free titanium compounds were detected in the washings, and then thoroughly washed with hexane at room temperature. The solid titanium catalyst components prepared by the above procedure were stored as a decance slurry, and a portion of it was dried in order to investigate the catalyst composition. The composition of the dried solid titanium catalyst component [D1] was 3.1% by mass of titanium, 18% by mass of magnesium, 60% by mass of chlorine, 15.4% by mass of ethyl benzoate, and 1.5% by mass of 2-ethylhexyl alcohol residues.

[0062] [Manufacturing of polyethylene resin compositions] In a 1-liter polymer chamber that had been thoroughly purged with nitrogen, 500 ml of purified decane was charged at room temperature. At a temperature of 48°C, 0.5 mmol of triisobutylaluminum and solid titanium catalyst component [D1] (0.01 mmol in terms of titanium atoms) were added. Next, ethylene was fed into the polymer chamber until the pressure reached a gauge pressure of 0.6 MPaG, and the first stage of ethylene polymerization was carried out at a temperature of 53°C. When 25 liters of ethylene had been fed, the ethylene feed was stopped, the temperature was rapidly cooled to 45°C, and then depressurization and nitrogen purging were performed. Polyethylene (A1) was obtained by performing the first stage of ethylene polymerization under the above conditions. Next, 260 milliliters of hydrogen were fed into the polymerizer, and then ethylene was fed in until the pressure inside the polymerizer reached a gauge pressure of 0.28 MPaG. The second stage of ethylene polymerization was carried out at a temperature of 82.5°C. The ethylene feeding was stopped when 25 liters of ethylene had been fed in, the temperature was rapidly cooled to 40°C, and then depressurization and purging were performed. Polyethylene (B1) was obtained by carrying out the second stage of ethylene polymerization under these conditions. Next, hydrogen was fed into the polymerizer until the pressure reached 0.40 MPaG gauge pressure, and then ethylene was fed in until the pressure reached 0.60 MPaG gauge pressure. The third stage of ethylene polymerization was carried out at a temperature of 85°C. The ethylene feed was stopped when 100 liters of ethylene had been fed, the temperature was rapidly cooled to 40°C, and then depressurization and purging were performed. Polyethylene (C1) was obtained by carrying out the third stage of ethylene polymerization under these conditions. The slurry containing the generated solid was filtered and dried under reduced pressure overnight at 80°C. The resulting polyethylene resin composition weighed 177 g and had an intrinsic viscosity [η] of 5.0 dl / g.

[0063] [Analysis of each component in polyethylene resin composition] • Polyethylene (A1) content and intrinsic viscosity [η] A Polyethylene (A2) was produced by separately carrying out only the first stage of polymerization, which was performed during the production of the polyethylene resin composition, under the same conditions as during the production of the polyethylene resin composition. The yield of the obtained polyethylene was 26.6 g. Since polyethylene (A1) and polyethylene (A2) are presumed to be the same polymer, the content of polyethylene (A1) in the polyethylene resin composition (yield 177 g) was calculated to be 15.0 mass%. Furthermore, the intrinsic viscosity of polyethylene (A2) was measured to be 30.0 dl / g, and therefore the intrinsic viscosity [η] of polyethylene (A1) contained in the polyethylene resin composition was calculated to be 30.0 dl / g. A This was set to 30.0 dl / g.

[0064] • Polyethylene (B1) content and physical properties Polyethylene (B2) was produced by omitting the first and third stages of polymerization during the production of the polyethylene resin composition, and performing only the second stage of polymerization separately under the same conditions as during the production of the polyethylene resin composition. The yield of polyethylene was 26.1 g. Since polyethylene (B1) and polyethylene (B2) are presumed to be the same polymer, the polyethylene (B1) content in the polyethylene resin composition (yield 177 g) was calculated to be 14.8 mass%. Furthermore, the intrinsic viscosity and density of polyethylene (B2) were measured, and the intrinsic viscosity was 2.45 dl / g, and the density was 971 kg / m³. 3 That was the case. Next, the molecular weight distribution of polyethylene (B2) was measured by gel permeation chromatography (GPC), and compared with the results of GPC molecular weight distribution measurements for the polyethylene resin composition obtained by the above three-step polymerization. The chromatogram showed that the peak position and shape matched those of the component (polyethylene (B1)) with molecular weights between the ultra-high molecular weight and low molecular weight components contained in the polyethylene resin composition. Based on these results, the physical properties of polyethylene (B1) were considered to be the same as those of polyethylene (B2). That is, the intrinsic viscosity [η] of polyethylene (B1) B Assuming a concentration of 2.45 dl / g, the density is 971 kg / m³. 3 That's what I decided.

[0065] • Polyethylene (C1) content and physical properties Polyethylene (C2) was produced by omitting the first and second stages of polymerization during the production of the polyethylene resin composition, and performing only the third stage of polymerization separately under the same conditions as during the production of the polyethylene resin composition. The intrinsic viscosity of polyethylene (C2) was 1.0 dl / g, and the density was 971 kg / m³. 3 That was the case. Next, the molecular weight distribution of polyethylene (C2) was measured by gel permeation chromatography (GPC), and compared with the results of the GPC molecular weight distribution measurement for the polyethylene resin composition obtained by the above three-step polymerization. The chromatogram matched that of the lowest molecular weight component (polyethylene (C1)) contained in the polyethylene resin composition. Based on this result, the physical properties of polyethylene (C1) were considered to be the same as those of polyethylene (C2). That is, the intrinsic viscosity [η] of polyethylene (C1) C Assuming a concentration of 1.0 dl / g, the density is 971 kg / m³. 3 That's what I decided.

[0066] [Granulation of polyethylene resin composition] The polyethylene resin composition obtained above was dry-blended with a known antioxidant, heat stabilizer, and hydrochloric acid absorbent commonly used in polyolefins. The total amount of these antioxidants, heat stabilizers, and hydrochloric acid absorbents blended was approximately 0.42% by mass, with the dry-blended composition being 100% by mass. The dry-blended composition was melt-kneaded using a twin-screw extruder (Technovel Co., Ltd., φ=15mm, L / D=30, cylinder temperature: 230℃), and then granulated into pellets. The MFR was measured using the obtained pellets. The results are shown in Table 1.

[0067] [Lamb extrusion molding] A capillary rheometer (Capillograph 1D, manufactured by Toyo Seiki Seisakusho) equipped with a slit die (1 mm x 6 mm) had its furnace (inner diameter 10 mm) heated to 230°C. A polyethylene resin composition was extruded at a piston speed of 75 mm / min, and the extruded polyethylene resin composition was water-cooled to obtain a molded body. Subsequently, the arithmetic mean roughness (Ra) of the surface of the obtained molded body was determined. The results are shown in Table 1.

[0068] [Comparative Example 1] After the first stage of polymerization in Example 1, the third stage of polymerization was carried out as the second stage. The polyethylene resin composition was produced under the same conditions as in Example 1, except that the amount of ethylene feed was changed from 25 liters to 21 liters in the first stage of polymerization, and from 100 liters to 119 liters in the second stage of polymerization. Then, each physical property was measured. The analysis results and the results of the physical property measurements are shown in Table 1.

[0069] [Comparative Example 2] A polyethylene resin composition was produced under the same conditions as in Comparative Example 1, except that the amount of ethylene fed in the first stage of polymerization was changed from 21 liters to 33.6 liters, and the amount of ethylene fed in the second stage of polymerization was changed from 119 liters to 106.4 liters. Then, each physical property was measured. The analysis results and the results of the physical property measurements are shown in Table 1.

[0070] [Table 1]

Claims

1. 5 to 30 parts by mass of polyethylene (A) that meet the following requirement (a-1), 5 to 30 parts by mass of polyethylene (B) that meet the following requirement (b-1), 40 to 90 parts by mass of polyethylene (C) that meet the following requirements (c-1) and (c-2), (However, the total amount of polyethylene (A), polyethylene (B), and polyethylene (C) shall be 100 parts by mass), A polyethylene resin composition having an intrinsic viscosity [η] of 2.0 to 15 dl / g as measured in decalin solvent at 135°C. (a-1) Intrinsic viscosity [η] measured in decalin solvent at 135°C A The concentration is 8-40 dl / g; (b-1) Intrinsic viscosity [η] measured in decalin solvent at 135°C B The concentration is 1.5 dl / g or more and less than 8 dl / g; (c-1) Intrinsic viscosity [η] measured in decalin solvent at 135°C C The concentration is 0.1 dl / g or more and less than 1.5 dl / g; (c-2) Density of 950-985 kg / m³ 3 That is the case.

2. The polyethylene resin composition according to claim 1, wherein the melt flow rate (MFR), measured at 190°C and a 10 kg load in accordance with ASTM D1238E, is 0.1 to 30 g / 10 min.

3. A molded article comprising the polyethylene resin composition according to claim 1 or 2.

4. Intrinsic viscosity [η] measured in decalin solvent at 135°C A A process for producing polyethylene (A) having a concentration of 8 to 40 dl / g, Intrinsic viscosity [η] measured in decalin solvent at 135°C B A process for producing polyethylene (B) having a concentration of 1.5 dl / g or more and less than 8 dl / g, Intrinsic viscosity [η] measured in decalin solvent at 135°C C A process for producing polyethylene (C) having a concentration of 0.1 dl / g or more and less than 1.5 dl / g, By a multi-stage polymerization method including at least three steps, A method for producing a polyethylene resin composition, wherein the polyethylene resin composition has an intrinsic viscosity [η] measured in a decalin solvent at 135°C in the range of 2.0 to 15 dl / g.

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