Process for producing olefin-based thermoplastic elastomer composition

Abstract

To provide a method for producing an olefin-based thermoplastic elastomer, by which the generation of a gel material in a molded product is suppressed and the molded product has excellent appearance even when the extrusion amount of a twin-screw extruder is increased and the number of revolutions of a screw is increased.SOLUTION: A dynamic crosslinking step of dynamically crosslinking a polyolefin resin and a rubber component by a twin-screw extruder, wherein the twin-screw extruder has at least one rotor segment, a ratio of a cylinder-rotor clearance to a cylinder bore is 0.02 or more and 0.1 or less, the cylinder-rotor clearance being a clearance between an apex of a rotor in the rotor segment and a cylinder inner wall of the twin-screw extruder, and a ratio of a rotor-rotor clearance to the cylinder bore is 0.010 or more and 0.1 or less, the rotor-rotor clearance being a clearance between a pair of rotors in the rotor segment, the dynamic crosslinking step is performed in the rotor segment.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing an olefinic thermoplastic elastomer composition. [Background technology]

[0002] Olefin-based thermoplastic elastomers are lightweight and recyclable, and are used as energy- and resource-saving thermoplastic elastomers in automobile parts and industrial machinery parts, etc. Dynamically crosslinked rubber elastomers (TPV) are also widely used to impart properties such as tensile strength.

[0003] In molded articles made from olefin-based thermoplastic elastomers by molding methods such as sheet molding and profile extrusion, the appearance of the molded article is important, and poor appearance due to gel-like microscopic protrusions significantly reduces the value of the product. For example, in automotive skin materials, which are one of the uses for molded articles made from olefin-based thermoplastic elastomers, such poor appearance is undesirable to customers. Furthermore, when molded articles made from olefin-based thermoplastic elastomers are used as glass run channels, such poor appearance impairs the sliding properties of the molded article, accelerates wear of the molded article, and reduces long-term performance.

[0004] Therefore, as a method for producing an olefin-based thermoplastic elastomer that improves the above-mentioned poor appearance, the production methods disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2003-71829 and 2002-210732 have been studied. Japanese Patent Application Laid-Open No. 2003-71829 describes a production method using a twin-screw kneading extruder to disperse and knead raw material polymers under reactive conditions to produce a modified polymer, in which the shear rate at the tip of the screws of the twin-screw kneading extruder is changed to carry out the modification process, and one or more grooves are provided intermittently or continuously in the axial direction in two arc sections in the cross section perpendicular to the axis of the cylinder inner bore of the dispersion section and / or kneading section.

[0005] Japanese Patent Application Laid-Open No. 2002-210732 describes a method for producing an olefin-based thermoplastic elastomer composition comprising a polyolefin resin and a crosslinked rubber by dynamically crosslinking the composition using a twin-screw extruder, in which a screw having at least one kneading segment (α) is used, and the clearance between the apex of the kneading segment (α) (here, the apex refers to the point or portion farthest from the center of gravity of the cross section) and the inner wall of the cylinder of the extruder is 1 / 60 or more and 1 / 10 or less of the screw diameter. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-71829 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-210732 Summary of the Invention [Problem to be solved by the invention]

[0007] In the manufacturing method described in JP 2003-71829 A, grooves are provided in the cylinder, and rubber may remain in the grooves during long-term operation, damaging the appearance of the molded article. Also, in the manufacturing method described in JP 2002-210732 A, increasing the extrusion rate of the twin-screw extruder and increasing the screw rotation speed may increase the number of gelled substances in the molded article. The present invention aims to provide a method for producing an olefin-based thermoplastic elastomer, which can suppress the generation of gel matter in a molded product and produce a molded product with excellent appearance, even when the extrusion rate of a twin-screw extruder is increased and the screw rotation speed is increased when producing a thermoplastic elastomer composition. [Means for solving the problem]

[0008] The present invention has, for example, the following aspects. [1] a dynamic crosslinking step of dynamically crosslinking a polyolefin resin and a rubber component using a twin-screw extruder, The twin-screw extruder has at least one rotor segment; the ratio of a cylinder-rotor clearance, which is a clearance between an apex of the rotor in the rotor segment and an inner wall of the cylinder of the twin-screw extruder, to a cylinder bore diameter is 0.02 or more and 0.1 or less; the ratio of a rotor-to-rotor clearance, which is a clearance between a pair of rotors in the rotor segment, to a cylinder bore is 0.010 or more and 0.1 or less; The dynamic crosslinking step is carried out in the rotor segment. A method for producing an olefin-based thermoplastic elastomer composition.

[0009] [2] The dynamic crosslinking step is carried out on the rotor segment located most upstream among the rotor segments, The extrusion rate (Z) (kg / h) of the twin-screw extruder, the cylinder diameter (X) (mm), and the segment length (Y) (mm) of the rotor segment on the most upstream side are expressed as Z / X 3 ×Y>0.10 [1] A method for producing the olefin-based thermoplastic elastomer composition according to the present invention.

[0010] [3] The dynamic crosslinking step is carried out on the rotor segment located most upstream among the rotor segments, The twin-screw extruder has a kneading segment downstream of the most upstream rotor segment, The maximum shear rate (A) between the cylinder and the kneading disc in the kneading segment (s -1 ) and the rotor residence time (T) (s) in the most upstream rotor segment is 2 / T 3 <3.0×10 6 fulfill, A method for producing the olefin-based thermoplastic elastomer composition according to [1] or [2].

[0011] [4] supplying a cross-linking agent upstream of the most upstream rotor segment among the rotor segments; A method for producing the olefin-based thermoplastic elastomer composition according to any one of [1] to [3].

[0012] [5] the olefin-based thermoplastic elastomer composition contains 10 to 60 parts by mass of the polyolefin resin and 40 to 90 parts by mass of the crosslinked rubber component relative to 100 parts by mass in total of the polyolefin resin and the crosslinked rubber component obtained by crosslinking the rubber component, A method for producing the olefin-based thermoplastic elastomer composition according to any one of [1] to [4]. [Effects of the Invention]

[0013] The present invention can provide a method for producing an olefin-based thermoplastic elastomer, which can suppress the generation of gel matter in a molded product and produce a molded product with excellent appearance, even when the extrusion rate of a twin-screw extruder is increased and the screw rotation speed is increased when producing a thermoplastic elastomer composition. [Brief explanation of the drawings]

[0014] [Figure 1] Fig. 1 is a cross-sectional view taken perpendicular to the screw axis direction of a rotor segment having a rotor with three apexes. Fig. 1 also shows the inner wall of the cylinder. [Figure 2] Figure 2 is a view of a rotor segment having three apexes, each of which has a section twisted in the opposite direction to the screw rotation direction along the screw axis and a section twisted continuously in the same direction as the screw rotation direction, viewed from a direction perpendicular to the screw axis. Figure 2 also shows the inner wall of the cylinder. [Figure 3]Figure 3 is a schematic diagram of a kneading segment. (FK) is a schematic diagram of a forward (forward) kneading segment, (BK) is a schematic diagram of a return (reverse) kneading segment, and (CK) is a schematic diagram of a neutral (orthogonal) kneading segment. The flow direction of the polyolefin resin is from the front to the back of the page. [Figure 4] FIG. 4 is a diagram showing the screw configuration of the twin-screw extruder used in Examples 1 and 2, Examples 5, 7 and 8, and Comparative Examples 1 to 3. [Figure 5] FIG. 5 is a diagram showing the screw configuration of the twin-screw extruder used in Examples 3 and 4. [Figure 6] FIG. 6 is a diagram showing the screw configuration of the twin-screw extruder used in Example 6. DETAILED DESCRIPTION OF THE INVENTION

[0015] The method for producing an olefin-based thermoplastic elastomer of the present invention includes a dynamic crosslinking step of dynamically crosslinking a polyolefin resin and a rubber component using a twin-screw extruder. In the method for producing an olefin-based thermoplastic elastomer, the twin-screw extruder has at least one rotor segment, and the ratio of the cylinder-rotor clearance, which is the clearance between the apex of the rotor in the rotor segment and the inner wall of the cylinder of the twin-screw extruder, to the cylinder diameter is 0.02 to 0.1, and the ratio of the rotor-rotor clearance, which is the clearance between a pair of rotors in the rotor segment, to the cylinder diameter is 0.010 to 0.1, and the dynamic crosslinking step is carried out in the rotor segment.

[0016] [Polyolefin resin] The polyolefin resin is, for example, a polymer of an olefin such as an α-olefin, a cyclic olefin, a non-conjugated polyene, or an aromatic olefin, and includes a polymer having an α-olefin as the main component. A polymer having an α-olefin as the main component means that the content of structural units derived from an α-olefin is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more, relative to 100 mol% of all structural units derived from polymerizable monomers.

[0017] The content of each structural unit in the polyolefin resin was measured using an ECP500 nuclear magnetic resonance spectrometer manufactured by JEOL Ltd., using a mixed solvent of orthodichlorobenzene / deuterated benzene (80 / 20% by volume), a sample concentration of 55 mg / 0.6 mL, a measurement temperature of 120°C, and observation nuclei of 13 C (125 MHz), sequence: single pulse proton decoupling, pulse width: 4.7 μs (45° pulse), repetition time: 5.5 s, number of accumulations: 10,000 or more, chemical shift reference value: 27.50 ppm 13 It can be calculated by measuring the C-NMR spectrum.

[0018] Examples of the α-olefin include α-olefins having 2 to 20 carbon atoms. The α-olefin is preferably an α-olefin having 2 to 10 carbon atoms, and more preferably an α-olefin having 2 to 8 carbon atoms. Examples of the α-olefin include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 3-methyl-1-butene, and 4-methyl-1-pentene. One type of α-olefin may be used, or two or more types may be used.

[0019] Examples of polyolefin resins include polyethylene, polypropylene, poly-4-methyl-1-pentene, and polybutene.

[0020] Examples of the polyethylene include high-density polyethylene, medium-density polyethylene, high-pressure low-density polyethylene, linear low-density polyethylene, and copolymers of ethylene and an α-olefin other than ethylene. The content of structural units derived from ethylene in the polyethylene is preferably 50 to 100 mol%, more preferably 70 to 100 mol%, and even more preferably 90 to 100 mol%, relative to 100 mol% of all structural units derived from polymerizable monomers. The melt flow rate (MFR) of the polyethylene (ASTM D1238, 190°C, load 2.16 kg) is preferably in the range of 0.01 to 100 g / 10 min, more preferably 0.05 to 50 g / 10 min, still more preferably 0.5 to 40 g / 10 min, and particularly preferably 1 to 30 g / 10 min.

[0021] Examples of the polypropylene include propylene homopolymers and copolymers of propylene and α-olefins other than propylene. The content of propylene-derived structural units in the polypropylene is preferably 50 to 100 mol%, more preferably 70 to 100 mol%, and even more preferably 90 to 100 mol%, relative to 100 mol% of all structural units derived from polymerizable monomers. The MFR (ASTM D1238, 230°C, load 2.16 kg) of the polypropylene is preferably in the range of 0.01 to 100 g / 10 min, more preferably 0.05 to 50 g / 10 min, still more preferably 0.5 to 40 g / 10 min, and particularly preferably 1 to 30 g / 10 min.

[0022] The polyolefin resin plays a role in improving the flowability and heat resistance of the olefin-based thermoplastic elastomer composition. The polyolefin resins may be used alone or in combination of two or more. The polyolefin resin is preferably polyethylene and / or polypropylene, more preferably polyethylene and polypropylene. The polymerization mode of the polyolefin resin may be either random or block, as long as a resinous product can be obtained.

[0023] [Rubber component] Examples of the rubber component include ethylene-α-olefin-non-conjugated polyene copolymer rubber, ethylene-α-olefin copolymer rubber, isoprene rubber and hydrogenated products thereof, butadiene rubber and hydrogenated products thereof, styrene-butadiene rubber and hydrogenated products thereof, styrene-isoprene rubber and hydrogenated products thereof, chloroprene rubber, butyl rubber, halogenated butyl rubber, polyisobutylene rubber, acrylonitrile-butadiene rubber, chlorinated polyethylene rubber, fluororubber, silicone rubber, polysulfide rubber, and urethane rubber.

[0024] The α-olefin in the ethylene-α-olefin copolymer rubber and the ethylene-α-olefin-non-conjugated polyene copolymer rubber is preferably an α-olefin having a carbon number of 3 to 10. Examples of the α-olefin having a carbon number of 3 to 10 include propylene, 1-butene, 1-pentene, and 4-methyl-1-pentene.

[0025] Examples of the non-conjugated polyenes include cyclic dienes such as dicyclopentadiene, cyclooctadiene, methylenenorbornene (e.g., 5-methylene-2-norbornene), ethylidenenorbornene (e.g., 5-ethylidene-2-norbornene), methyltetrahydroindene, 5-vinyl-2-norbornene, 5-isopropylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2-norbornene, and norbornadiene; 1,4-hexadiene, 3-methyl-1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 4,5-dimethyl-1,4-hexadiene, 6-methyl Acyclic dienes such as 1,6-octadiene, 7-methyl-1,6-octadiene, 6-ethyl-1,6-octadiene, 6-propyl-1,6-octadiene, 6-butyl-1,6-octadiene, 6-methyl-1,6-nonadiene, 7-methyl-1,6-nonadiene, 6-ethyl-1,6-nonadiene, 7-ethyl-1,6-nonadiene, 6-methyl-1,6-decadiene, 7-methyl-1,6-decadiene, 6-methyl-1,6-undecadiene, and 7-methyl-1,6-octadiene; and trienes such as 2,3-diisopropylidene-5-norbornene and 2-ethylidene-3-isopropylidene-5-norbornene.

[0026] The rubber component is preferably an ethylene-α-olefin-non-conjugated polyene copolymer rubber or an ethylene-α-olefin copolymer rubber, more preferably an ethylene-α-olefin-non-conjugated polyene copolymer rubber, and even more preferably an ethylene-propylene-non-conjugated polyene copolymer rubber. When the rubber component is an ethylene-α-olefin-non-conjugated polyene copolymer rubber or an ethylene-α-olefin copolymer rubber, the resulting molded article can achieve both rubber elasticity at low temperatures and moldability.

[0027] In the ethylene-α-olefin-non-conjugated polyene copolymer rubber, the molar ratio of the content of structural units derived from ethylene to the content of structural units derived from α-olefin (content of structural units derived from ethylene / content of structural units derived from α-olefin) is preferably in the range of 30 / 70 to 90 / 10, more preferably 50 / 50 to 80 / 20. The content of structural units derived from α-olefin in the ethylene-α-olefin-non-conjugated polyene copolymer rubber is 13 It can be calculated by measuring the C-NMR spectrum.

[0028] The Mooney viscosity at 125°C of the ethylene-α-olefin-non-conjugated polyene copolymer rubber [ML(1+4)125°C] is preferably in the range of 15 to 250, more preferably 20 to 200, still more preferably 25 to 150, and particularly preferably 30 to 100. When the Mooney viscosity of the ethylene-α-olefin-non-conjugated polyene copolymer rubber is in the above range, the thermoplastic elastomer composition has excellent fluidity and dispersibility in the dynamic crosslinking step. The Mooney viscosity at 125° C. [ML(1+4)125° C.] can be measured in accordance with JIS K6300 using a Mooney viscometer "SMV-202" (manufactured by Shimadzu Corporation).

[0029] The amount of the polyolefin resin to be fed is preferably 10 to 60 parts by mass, more preferably 20 to 57 parts by mass, and even more preferably 25 to 55 parts by mass, per 100 parts by mass of the total of the polyolefin resin and the rubber component. The amount of the rubber component supplied is preferably 40 to 90 parts by mass, more preferably 43 to 80 parts by mass, and even more preferably 45 to 75 parts by mass, per 100 parts by mass of the total of the polyolefin resin and the rubber component. When the amounts of the polyolefin resin and the rubber component fed are within the above ranges, the olefin-based thermoplastic elastomer composition obtained is excellent in flexibility, rubber elasticity, heat resistance and moldability.

[0030] [Other ingredients] The olefin-based thermoplastic elastomer composition may contain components other than the polyolefin resin and the rubber component (hereinafter also referred to as "other components") within the scope of the present invention. Examples of the other components include additives such as softeners, inorganic fillers, crosslinking agents, heat stabilizers, antioxidants, weather stabilizers, antistatic agents, and lubricants.

[0031] As the softener, the softener that is usually used for rubber can be used.As the softener, for example, petroleum-based softener such as process oil, lubricating oil, paraffin oil, liquid paraffin, petroleum asphalt and Vaseline; coal tar such as coal tar and coal tar pitch; fatty oil such as castor oil, linseed oil, rapeseed oil, soybean oil and coconut oil; tall oil; wax such as beeswax, carnauba wax and lanolin; fatty acid or metal salt such as ricinoleic acid, palmitic acid, stearic acid, barium stearate, calcium stearate and zinc laurate; synthetic polymer material such as terpene resin, petroleum resin, coumarone-indene resin and atactic polypropylene; ester-based softener such as dioctyl phthalate, dioctyl adipate and dioctyl sebacate; microcrystalline wax, sub(factice), liquid polybutadiene, modified liquid polybutadiene, liquid thiocol and hydrocarbon-based synthetic lubricating oil.

[0032] The amount of the softener supplied is preferably 150 parts by mass or less, more preferably 2 to 100 parts by mass, and even more preferably 5 to 80 parts by mass, per 100 parts by mass of the total of the polyolefin resin and the rubber component. When the amount of the softener supplied is within the above range, the olefin-based thermoplastic elastomer composition has excellent flowability, and deterioration in the mechanical properties of the molded product can be suppressed. The softening agent may be supplied when the olefin-based thermoplastic elastomer composition is produced, or may be supplied as an oil-extending component in an oil-extended product in which the rubber component or the crosslinking agent is oil-extended.

[0033] Examples of the inorganic filler include calcium carbonate, calcium silicate, clay, kaolin, talc, silica, diatomaceous earth, mica powder, asbestos, alumina, barium sulfate, aluminum sulfate, calcium sulfate, basic magnesium carbonate, molybdenum disulfide, graphite, glass fiber, glass spheres, shirasu balloons, basic magnesium sulfate whiskers, calcium titanate whiskers, and aluminum borate whiskers.

[0034] From the viewpoint of the rubber elasticity and molding processability of the olefin-based thermoplastic elastomer composition, the amount of the inorganic filler supplied is preferably 100 parts by mass or less, more preferably 2 to 50 parts by mass, per 100 parts by mass of the polyolefin resin and the rubber component combined.

[0035] Examples of the crosslinking agent include organic peroxides, phenolic resins, sulfur, hydrosilicone compounds, amino resins, quinones or their derivatives, amine compounds, azo compounds, epoxy compounds, and isocyanates. Among these crosslinking agents, organic peroxides are preferred.

[0036] Examples of the organic peroxides include dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl peroxybenzoate, tert-butylperoxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, and tert-butylcumyl peroxide.

[0037] From the viewpoints of odor resistance and scorch stability, the organic peroxide is preferably 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3, or 1,3-bis(tert-butylperoxyisopropyl)benzene, and more preferably 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3.

[0038] The amount of the organic peroxide supplied is preferably 0.02 to 3 parts by mass, more preferably 0.05 to 1 part by mass, per 100 parts by mass of the polyolefin resin and the rubber component combined, from the viewpoints of the heat resistance, tensile properties, elastic recovery, rebound resilience, and moldability of the olefin-based thermoplastic elastomer composition.

[0039] When the organic peroxide is used, a crosslinking aid may be used. By using the crosslinking aid, a uniform and gentle crosslinking reaction can be expected. Examples of the crosslinking aid include sulfur, p-quinonedioxime, p,p'-dibenzoylquinonedioxime, N-methyl-N-4-dinitrosoaniline, nitrosobenzene, diphenylguanidine, trimethylolpropane, N,N'-m-phenylenebismaleimide, divinylbenzene, and triallyl cyanurate. Further examples of the crosslinking aid include polyfunctional methacrylate monomers such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and allyl methacrylate, as well as polyfunctional vinyl monomers such as vinyl butyrate and vinyl stearate.

[0040] The crosslinking aid is preferably divinylbenzene, which is easy to handle, has excellent compatibility with the polyolefin resin and rubber components such as ethylene-α-olefin-non-conjugated polyene copolymer rubber, and also functions as a dispersant for organic peroxides, resulting in a uniform crosslinking effect upon heat treatment and an olefin-based thermoplastic elastomer composition with a good balance between fluidity and physical properties.

[0041] The amount of the crosslinking aid to be supplied is preferably 2 parts by mass or less, and more preferably 0.2 to 1 part by mass, per 100 parts by mass of the total of the polyolefin resin and the rubber component.

[0042] [Method for producing olefin-based thermoplastic elastomer composition] The method for producing an olefin-based thermoplastic elastomer composition according to the present invention includes a dynamic crosslinking step of dynamically crosslinking a polyolefin resin and a rubber component using the twin-screw extruder.

[0043] <Twin-screw extruder> The twin-screw extruder used in the dynamic crosslinking step may have two screws rotating in the same direction or in different directions, and may have two screws that are fully or partially intermeshed or not intermeshed. The twin-screw extruder preferably has two screws that are fully or partially intermeshed and have two screws that are fully or partially intermeshed. The ratio of the effective screw length to the cylinder diameter in the twin-screw extruder (effective screw length / cylinder diameter, so-called L / D ratio) is preferably 25 to 70, more preferably 30 to 70, and even more preferably 40 to 70. In the twin-screw extruder, the side to which raw materials are supplied is sometimes referred to as the upstream side, and the side to which the olefin-based thermoplastic elastomer composition is discharged is sometimes referred to as the downstream side.

[0044] The twin-screw extruder usually has a plurality of segments, such as a rotor segment and a kneading segment. The twin-screw extruder used in the present invention has at least one rotor segment. The rotor segment is a segment having a rotor. When multiple rotors are arranged continuously without any intervening segments, the region having all the continuously arranged rotors is considered to be one rotor segment.

[0045] The rotor has multiple apexes in a cross section perpendicular to the screw axis, and the apexes are twisted along the screw axis. A rotor with apexes that are twisted continuously in the opposite direction to the screw rotation direction is called a forward rotor (FRO), and a rotor with apexes that are twisted less than 90 degrees in the same direction as the screw rotation direction is called a reverse rotor (BRO).

[0046] The rotor may have an apex portion that is continuously twisted along the screw axial direction in the opposite direction to the screw rotation direction, and an apex portion that is continuously twisted along the screw axial direction. The apex portion refers to a point or portion on the outer edge of the rotor that is located farthest from the center of the screw axial direction in a cross section perpendicular to the screw axial direction.

[0047] In the rotor segment, the ratio of the cylinder-rotor clearance to the cylinder bore is 0.02 or more and 0.1 or less, preferably 0.03 or more and 0.08 or less, and more preferably 0.04 or more and 0.07 or less. The cylinder diameter refers to the diameter of the inner wall of the cylinder in a twin-screw extruder. The cylinder-rotor clearance is the clearance between the apex of the rotor in the rotor segment and the inner wall of the cylinder of the twin-screw extruder, and refers to the minimum gap distance between the inner wall of the cylinder of the twin-screw extruder and the outer edge of the rotor in a cross section perpendicular to the screw axis direction.

[0048] When the ratio of the cylinder-rotor clearance to the cylinder diameter is within the above range, the polyolefin resin and rubber component have excellent dispersibility at low temperatures, thereby suppressing the generation of gel in molded articles obtained from the olefin-based thermoplastic elastomer composition and resulting in molded articles with excellent appearance.

[0049] In the rotor segment, the ratio of the rotor-to-rotor clearance to the cylinder bore is 0.010 or more and 0.1 or less, preferably 0.010 or more and 0.08 or less, more preferably 0.010 or more and 0.06 or less, even more preferably 0.010 or more and 0.04 or less, and particularly preferably 0.012 or more and 0.03 or less. The rotor-to-rotor clearance is the clearance between a pair of rotors in the rotor segment, and refers to the minimum gap distance between the outer edges of a pair of rotors in a cross section perpendicular to the screw axial direction.

[0050] When the ratio of the rotor-to-rotor clearance to the cylinder bore is within the above range, even if the extrusion rate is increased and the screw rotation speed is increased, the generation of gel in the molded product obtained from the olefin-based thermoplastic elastomer composition is suppressed, and the appearance of the molded product is excellent.

[0051] Methods for adjusting the ratio of rotor-to-rotor clearance to cylinder diameter include, for example, adjusting the inter-axial distance of the screw shafts of a twin-screw extruder, and adjusting the ratio of the rotor's major axis to its minor axis (major axis / minor axis). In a cross section perpendicular to the screw axis direction, the major axis of the rotor is defined as twice the maximum distance between the center of the screw axis and the outer edge of the rotor, and the minor axis of the rotor is defined as twice the minimum distance between the center of the screw axis and the outer edge of the rotor. The ratio of the rotor's major axis to its minor axis (major axis / minor axis) is preferably 1.1 or more and 1.5 or less, and more preferably 1.2 or more and 1.4 or less.

[0052] The kneading segment is a segment having kneading discs. When a plurality of kneading discs are arranged consecutively without any intervening segments, the region having all the consecutively arranged kneading discs is regarded as one kneading segment. The kneading disc is a so-called two-lobe type kneading disc.

[0053] The kneading segment usually has a plurality of kneading discs, and has a structure in which adjacent kneading discs are twisted discontinuously in the thickness direction of the kneading discs. The twisting direction may be the same as or different from the rotation direction of the screw. Adjacent kneading discs twisted by less than 90 degrees in the direction opposite to the rotation direction from the upstream side to the downstream side are sometimes called forward (forward) kneading segments (FK), those twisted by less than 90 degrees in the same direction as the rotation direction are sometimes called return (reverse) kneading segments (BK), and those twisted by 90 degrees are sometimes called neutral (orthogonal) kneading segments (CK).

[0054] In the kneading segment, the ratio of the clearance between the cylinder and the kneading disc to the cylinder bore is preferably 0.001 or more and 0.05 or less, more preferably 0.003 or more and 0.03 or less, and even more preferably 0.004 or more and 0.01 or less. The clearance between the cylinder and the kneading disc refers to the minimum gap distance between the inner wall surface of the cylinder of the twin-screw extruder and the outer edge of the kneading disc in a cross section perpendicular to the screw axial direction.

[0055] When the ratio of the clearance between the cylinder and the kneading disc to the cylinder diameter is within the above range, even if the extrusion rate is increased and the screw rotation speed is increased, the generation of gel in the molded product obtained from the olefin-based thermoplastic elastomer composition is suppressed, and the appearance of the molded product is excellent.

[0056] <Dynamic crosslinking process> The dynamic crosslinking refers to melt-kneading the polyolefin resin and the rubber component in the presence of a crosslinking agent to crosslink at least a portion of the rubber component. The dynamic crosslinking step is usually carried out after kneading the polyolefin resin, the rubber component, and other components that are added as needed. The other components may be fed using a feeder different from that used for the polyolefin resin and the rubber component, or may be fed using the same feeder. The rubber component may be oil-extended with a softener or the like. The crosslinking agent may be oil-extended with a softener or the like.

[0057] The dynamic crosslinking step is carried out in the rotor segment. When the twin-screw extruder has a plurality of rotor segments, the dynamic crosslinking step may be carried out in one rotor segment or in a plurality of rotor segments. The dynamic crosslinking step may be carried out in any rotor segment, and may also be carried out in a segment other than the rotor segment. In other words, carrying out the dynamic crosslinking step in the rotor segment also includes carrying out the dynamic crosslinking step in the rotor segment and a segment other than the rotor segment. An example of a segment other than the rotor segment is a kneading segment.

[0058] When the twin-screw extruder has a plurality of rotor segments, the dynamic crosslinking step is preferably carried out in the rotor segment located most upstream among the rotor segments.

[0059] The dynamic crosslinking step is preferably carried out in an atmosphere of an inert gas such as nitrogen or carbon dioxide gas, etc. The temperature of the rotor segment in the dynamic crosslinking step is preferably 300°C or lower, more preferably 50 to 250°C, and even more preferably 100 to 235°C.

[0060] When the dynamic crosslinking step is performed in the rotor segment on the most upstream side among the rotor segments, the extrusion rate (Z) (kg / h) of the twin-screw extruder, the cylinder diameter (X) (mm), and the segment length (Y) (mm) of the rotor segment on the most upstream side are set to Z / X 3 It is preferable that Z / X satisfy ×Y>0.10. 3 It is more preferable that Z / X be greater than 0.15. 3 x Y is a measure of the time that the material resides in the most upstream rotor segment.

[0061] When the cylinder diameter is 47 mm, the extrusion rate (Z) is preferably 100 to 300 kg / h, more preferably 130 to 280 kg / h, and even more preferably 150 to 260 kg / h. When the cylinder diameter is different, the preferred range of the extrusion rate (Z) varies in proportion to the cube of the cylinder diameter. The segment length (Y) of the most upstream rotor segment is defined as the distance between a perpendicular line from the upstream end of the most upstream rotor of the rotors constituting the rotor segment to the center line of the screw shaft, and a perpendicular line from the downstream end of the most downstream rotor of the rotors constituting the rotor segment to the center line of the screw shaft.

[0062] When the cylinder diameter is 47 mm, the segment length (Y) of the rotor segment on the most upstream side is preferably 70 to 250 mm, more preferably 80 to 240 mm, and even more preferably 90 to 230 mm. When the cylinder diameter is different, the preferred range of the segment length (Y) of the rotor segment on the most upstream side varies in proportion to the cylinder diameter. Z / X 3 When ×Y is within the above range, even if the extrusion rate is increased and the screw rotation speed is increased, the generation of gel matter in the molded article obtained from the olefin-based thermoplastic elastomer composition is suppressed, and the appearance of the molded article is excellent.

[0063] When the dynamic crosslinking step is carried out in the most upstream rotor segment among the rotor segments, the twin-screw extruder preferably has a kneading segment downstream of the most upstream rotor segment, which is preferably a feed kneading segment (FK) or a neutral kneading segment (CK). When the ratio of rotor-to-rotor clearance to cylinder diameter is within the above range and the twin-screw extruder has a kneading segment downstream of the most upstream rotor segment, dispersion and distribution of the rubber component are promoted, so that even if the extrusion rate and screw rotation speed are increased, the generation of gel in the molded product obtained from the olefin-based thermoplastic elastomer composition is suppressed, and the molded product has an excellent appearance and a smooth surface.

[0064] The maximum shear rate (A) between the cylinder and the kneading disc in the kneading segment (s -1 ) and the rotor residence time (T) (s) in the most upstream rotor segment are preferably 2 / T 3 <3.0×10 6 , more preferably A 2 / T 3 <2.8×10 6 , more preferably A 2 / T 3 <2.6×10 6 Satisfy. A 2 / T 3 is usually 1.0 x 10 4 It's super. A 2 is an index of the heat generated in the kneading segment, and T 3 is an index of the degree of melting of the polyolefin resin. 2 / T 3 is an index of the likelihood of gel formation. A 2 / T 3The fact that A is in the above range means that the polyolefin resin is sufficiently melted in the most upstream rotor segment, and then heated in the kneading segment. Therefore, when the screw configuration is the same, especially when the screw configuration and the ratio of the rotor-to-rotor clearance to the cylinder diameter are the same, A 2 / T 3 When the viscosity is within the above range, gel formation is particularly unlikely.

[0065] The maximum shear rate (A) (s -1 ) can be calculated using the formula A = (X × π × S) / U / 60, where X is the cylinder diameter of the twin-screw extruder (mm), S is the screw rotation speed per minute (rpm), and U is the clearance between the cylinder and the kneading disc (mm). The screw rotation speed is preferably 370 to 700 rpm, more preferably 390 to 670 rpm, and even more preferably 410 to 650 rpm. The maximum shear rate (A) is preferably 2000 to 4500 s -1 , more preferably 2200 to 4300 s -1 , more preferably 2400 to 4000 s -1 is.

[0066] The rotor residence time (T) (s) represents the time during which the raw material resides in the rotor segment at the most upstream side, and is expressed as the cross-sectional area (CA) of the cylinder (mm 2 ), cross-sectional area of ​​rotor (ca) (mm 2 ), the segment length (Y) of the rotor segment (mm), the extrusion rate (Z) (kg / h), and the density (d) of the olefin-based thermoplastic elastomer composition (kg / m 3 ) and use (CA-ca×2)×Y×d / Z / 3.6×10 6 It can be calculated as follows. Methods for adjusting the rotor residence time (T) include, for example, adjusting the segment length (Y) of the rotor segment, adjusting the major and minor diameters of the rotor, and adjusting the distance between the screw shafts of a twin-screw extruder. The residence time (T) in the rotor is preferably 1.00 to 6.00 s, more preferably 1.50 to 5.00 s, and even more preferably 2.00 to 4.50 s.

[0067] A 2 / T 3 When the extrusion rate is within the above range, even if the extrusion rate and screw rotation speed are increased, the generation of gel in the molded article obtained from the olefin-based thermoplastic elastomer composition is suppressed, and the appearance of the molded article is excellent.

[0068] When the dynamic crosslinking step is performed in the most upstream rotor segment among the rotor segments, it is preferable to supply the crosslinking agent upstream of the most upstream rotor segment. Supplying the crosslinking agent upstream of the most upstream rotor segment is safe and allows the crosslinking agent to be uniformly dispersed.

[0069] [Olefin-based thermoplastic elastomer composition] The olefin-based thermoplastic elastomer composition contains preferably 10 to 60 parts by mass, more preferably 20 to 57 parts by mass, and even more preferably 30 to 55 parts by mass of the polyolefin resin, and preferably 40 to 90 parts by mass, more preferably 43 to 80 parts by mass, and even more preferably 45 to 70 parts by mass of the crosslinked rubber component, relative to 100 parts by mass in total of the polyolefin resin and the crosslinked rubber component obtained by crosslinking the rubber component. When the contents of the polyolefin resin and the crosslinked rubber component are within the above ranges, the olefin-based thermoplastic elastomer composition is excellent in flexibility, rubber elasticity, heat resistance and moldability. [Example]

[0070] [Example 1] The twin-screw extruder used was a fully intermeshing twin-screw extruder (same rotation direction, cylinder diameter: 47 mm, number of cylinder blocks: 20). The cylinder blocks were designated C1, C2, C3, . . ., C18, C19, and C20 from the upstream side of the extruder. The set temperatures were C1 / C2 / C3 / C4 / C5 / C6 / C7 / C8 / C9 / C10 / C11 / C12 / C13 / C14 / C15 / C16 / C17 / C18 / C19 / C20 / die = water cooling / 30°C / 30°C / 30°C / 30°C / 30°C / 50°C / 110°C / 110°C / 110°C / 185°C / 215°C / 230°C / 230°C / 230°C / 230°C / 230°C / 230°C / 230°C / 230°C. The screw configuration is shown in Figure 4.

[0071] A propylene-ethylene block copolymer (MFR (230°C, load 2.16 kg): 27 g / 10 min), a high-pressure low-density polyethylene (MFR (190°C, load 2.16 kg): 2 g / 10 min), and a non-oil-extended ethylene-propylene-non-conjugated polyene copolymer rubber (Mooney viscosity [ML(1+4)125°C]: 61) were fed into the twin-screw extruder C1 using feeders at a mass ratio of propylene-ethylene block copolymer / high-pressure low-density polyethylene / non-oil-extended ethylene-propylene-non-conjugated polyene copolymer rubber = 25 / 25 / 50. The throughput of the extruder was 168 kg / h.

[0072] Organic peroxide (2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3) was diluted to 30% by mass with paraffinic process oil and further mixed with a cross-linking coagent (divinylbenzene). This was then added from C1 so that the amount of organic peroxide was 0.2 parts by mass per 100 parts by mass of the total of propylene-ethylene block copolymer, high-pressure low-density polyethylene, and non-oil-extended ethylene-propylene-non-conjugated polyene copolymer rubber. Furthermore, to adjust the hardness of the olefin-based thermoplastic elastomer composition, 15 parts by mass of oil was added from C14 for a total of 100 parts by mass of the propylene-ethylene block copolymer, high-pressure low-density polyethylene, and non-oil-extended ethylene-propylene-non-conjugated polyene copolymer rubber. Under the above conditions, kneading and dynamic crosslinking were carried out using a twin-screw extruder to produce pellets of the olefin-based thermoplastic elastomer composition.

[0073] [Examples 2, 5, 7 and 8, and Comparative Examples 1 to 3] Pellets of thermoplastic elastomer compositions were produced in the same manner as in Example 1, except that the extrusion rate, screw rotation speed, and rotor-to-rotor clearance were changed as shown in Table 1.

[0074] [Examples 3 to 4] Pellets of a thermoplastic elastomer composition were produced in the same manner as in Example 1, except that the extrusion rate, screw rotation speed, and rotor segment length were changed as shown in Table 1, and the screw configuration was changed as shown in Figure 5.

[0075] [Example 6] Pellets of a thermoplastic elastomer composition were produced in the same manner as in Example 1, except that the screw rotation speed was changed as shown in Table 1 and the screw configuration was changed as shown in FIG.

[0076] The segment length (Y) and residence time (T) of the rotor segments listed in Table 1 represent the segment length and residence time of the rotor segment furthest upstream among the rotor segments. In the rotor segment, the rotors were arranged in the order FRO, BRO from the upstream side of the twin-screw extruder. The clearance between the cylinder and the kneading disc and the maximum shear rate (A) between the cylinder and the kneading disc of the kneading segment listed in Table 1 are the clearance and the maximum shear rate in the kneading segment located downstream of the most upstream rotor segment without any other segments in between.

[0077] [Production and evaluation of molded products] <Number of gels> Using the pellets of the thermoplastic elastomer compositions produced in Examples 1 to 8 and Comparative Examples 1 to 3, pressed sheets measuring 100 mm x 100 mm x 0.5 mm thick were produced by press molding at 190° C. The pressed sheets were placed on a glass plate, and while illuminating them from below, gel particles measuring 0.3 mm x 0.1 mm or larger were carefully examined and counted using a graduated magnifying glass.

[0078] <Extruded skin> Using the pellets of the thermoplastic elastomer compositions produced in Examples 1 to 8 and Comparative Examples 1 to 3, sheets measuring 25 cm wide and 0.5 mm thick were produced using a T-die in a single-screw extruder with a diameter of 50 mm. The sheets were then lightly stroked with a finger to evaluate the smoothness of their surfaces. Sheets with a smooth surface were rated A, sheets with a slightly rough surface were rated B, and sheets with a rough surface were rated C.

[0079] <Overall Judgment> Those with 10 or fewer gel particles and an extrusion surface rating of A were rated A, and those with 10 or fewer gel particles and an extrusion surface rating of B were rated B. Those with more than 10 gel particles or an extrusion surface rating of C were rated C.

[0080] [Table 1]

[0081] We confirmed that the number of gel particles can be reduced by increasing the ratio of the rotor-rotor clearance to the cylinder diameter. Furthermore, comparing Comparative Examples 1 and 2, we found that when the ratio of the rotor-rotor clearance to the cylinder diameter is small, lowering the screw rotation speed can reduce the number of gel particles, but this results in poor extrusion texture. Therefore, by setting the ratio of the rotor-rotor clearance to the cylinder diameter to between 0.010 and 0.1, the number of gel particles can be reduced even if the extrusion rate and screw rotation speed are increased. [Explanation of symbols]

[0082] 1 Cylinder inner wall 2 rotors 3 Twin-screw extruder shafts p Rotor-to-rotor clearance q Cylinder-rotor clearance r Screw rotation direction s Resin flow direction a1 The part that is twisted continuously in the opposite direction to the screw rotation direction a2 The part that is twisted continuously in the same direction as the screw rotation direction F feed (progressive) kneading segment C Neutral (orthogonal) kneading segment R rotor segment

Claims

1. a dynamic crosslinking step of dynamically crosslinking a polyolefin resin and a rubber component using a twin-screw extruder, The twin-screw extruder has at least one rotor segment; a ratio of a cylinder-rotor clearance, which is a clearance between an apex of a rotor in the rotor segment and an inner wall of a cylinder of the twin-screw extruder, to a cylinder bore diameter is 0.02 or more and 0.1 or less; a ratio of a rotor-to-rotor clearance, which is a clearance between a pair of rotors in the rotor segment, to a cylinder bore diameter is 0.010 or more and 0.1 or less; The dynamic crosslinking step is carried out in the rotor segment. A method for producing an olefin-based thermoplastic elastomer composition.

2. The dynamic crosslinking step is carried out on the rotor segment located most upstream among the rotor segments, The extrusion rate (Z) (kg / h) of the twin-screw extruder, the cylinder diameter (X) (mm), and the segment length (Y) (mm) of the rotor segment on the most upstream side are expressed as Z / X 3 × Y>0.10 is satisfied. A method for producing the olefin-based thermoplastic elastomer composition according to claim 1.

3. The dynamic crosslinking step is carried out on the rotor segment located most upstream among the rotor segments, The twin-screw extruder has a kneading segment downstream of the most upstream rotor segment, The maximum shear rate (A) (s -1 ) and the rotor residence time (T) (s) in the most upstream rotor segment is 2 / T 3 <3.0 × 10 6 fulfill, A method for producing the olefin-based thermoplastic elastomer composition according to claim 1.

4. supplying a cross-linking agent upstream of the most upstream rotor segment among the rotor segments; A method for producing the olefin-based thermoplastic elastomer composition according to claim 1.

5. the olefin-based thermoplastic elastomer composition contains 10 to 60 parts by mass of the polyolefin resin and 40 to 90 parts by mass of the crosslinked rubber component relative to 100 parts by mass in total of the polyolefin resin and the crosslinked rubber component obtained by crosslinking the rubber component; A method for producing the olefin-based thermoplastic elastomer composition according to claim 1.

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