Resin composition, molded body, and method for producing molded body

Abstract

A resin composition comprising a polypropylene-based resin (A) and a polyethylene-based resin (B), and having a sea-island structure in which the polypropylene-based resin (A) forms a sea phase and the polyethylene-based resin (B) forms an island phase.

Description

Resin composition, molded article, and method for producing molded article

[0001] The present disclosure relates to a resin composition, a molded article produced using the resin composition, and a method for producing a molded article.

[0002] Polyolefin-based resins are inexpensive, lightweight, and excellent in mechanical properties and weather resistance, and are used as large containers such as ink storage containers and containers. Examples of their molding methods include blow molding, injection molding, vacuum molding, extrusion molding, foam molding, and the like.

[0003] However, molding defects often occur in various molding methods. It is known that molding defects depend on the fluidity and melt tension of the molten resin. Among them, in blow molding, a high melt tension is required to suppress drawdown during parison formation, and high fluidity is required when passing through the parison forming core of the blow molding apparatus or when transferring the surface to the mold.

[0004] In Patent Document 1, a resin composition in which the melt flow rate (MFR) of a polypropylene-based resin and a polyethylene-based resin has a specific ratio value to suppress drawdown is disclosed.

[0005] Japanese Unexamined Patent Application Publication No. 2015-196711

[0006] However, in the resin composition described in Patent Document 1, while the melt tension contributing to the suppression of drawdown is improved, the fluidity decreases, and molding defects may occur.

[0007] Therefore, the present disclosure aims to provide a resin composition having excellent moldability capable of achieving both melt tension and fluidity.

[0008] According to one aspect of the present disclosure, there is provided a resin composition containing a polypropylene-based resin (A) and a polyethylene-based resin (B), having a sea-island structure in which the polypropylene-based resin (A) forms a sea phase and the polyethylene-based resin (B) forms an island phase, and having a melt tension of 1.0 cN or more measured at a temperature of 200°C.

[0009] In another aspect of this disclosure, a resin composition is provided that contains a polypropylene resin (A) and a polyethylene resin (B), wherein the melt flow rate of the polypropylene resin (A) measured under conditions of a temperature of 230°C and a load of 2.16 kgf is MFR(A) (g / 10 min.), and the melt flow rate of the polyethylene resin (B) measured under conditions of a temperature of 190°C and a load of 2.16 kgf is MFR(B) (g / 10 min.), and the value of MFR(A) / MFR(B) is 500 or more and less than 5000.

[0010] In another aspect of this disclosure, a resin composition is provided that contains a polypropylene resin (A) and a polyethylene resin (B), wherein when the weight-average molecular weight of the polypropylene resin (A) is Mw(A) and the weight-average molecular weight of the polyethylene resin (B) is Mw(B), the value of Mw(B) / Mw(A) is 3.0 or more and less than 50.

[0011] In another aspect of this disclosure, a method for manufacturing a molded article by extrusion blow molding a resin composition is provided, wherein the resin composition contains a polypropylene resin (A) and a polyethylene resin (B), and the manufacturing method has a sea-island structure in which the polypropylene resin (A) forms a sea phase and the polyethylene resin (B) forms an island phase.

[0012] According to this disclosure, it is possible to provide a resin composition with excellent moldability that can achieve both melt tension and fluidity.

[0013] This is a schematic diagram showing an enlarged portion of the cross-section of the resin composition. This is a perspective view of the molded body. This is a cross-sectional view of the molded body shown in Figure 2A, including the A-A axis. This is a bottom view showing the bottom of the molded body.

[0014] In general, there is a trade-off relationship between melt tension and fluidity in polyolefin resin compositions. Therefore, in the resin composition described in Patent Document 1, while the melt tension was improved to suppress drawdown, it is thought that fluidity may have decreased. If the fluidity of the resin composition is low, it may be difficult for the resin composition to pass through the parison forming core of the blow molding apparatus, or when molding using a mold with a complex shape, the surface shape of the mold may not be sufficiently transferred. For these reasons, it is thought that molding defects may occur in the resin composition described in Patent Document 1.

[0015] The inventors of this application have conducted extensive research on polyolefin resin compositions that can achieve both melt tension and fluidity, and as a result, have arrived at this disclosure.

[0016] In other words, the resin composition according to this embodiment contains a polypropylene resin (A) and a polyethylene resin (B). Furthermore, it has a sea-island structure in which the polypropylene resin (A) forms the sea phase and the polyethylene resin (B) forms the island phase. In addition, the resin composition according to this embodiment has a melt tension of 1.0 cN or more, as measured at a temperature of 200°C.

[0017] Embodiments of this disclosure will be described below. However, the embodiments described below are each one embodiment of the disclosure and are not limited thereto. In this specification, room temperature refers to 25°C.

[0018] [First Embodiment] The melt flow rate of the polypropylene resin (A) is set to MFR(A) (g / 10 min.), and the melt flow rate of the polyethylene resin (B) is set to MFR(B) (g / 10 min.). In this embodiment, MFR(A) is greater than MFR(B) (MFR(A) > MFR(B)), and the value of MFR(A) / MFR(B) may be 500 or more and may be less than 5000.

[0019] If the MFR(A) / MFR(B) value is 500 or higher, the polypropylene resin (A) and the polyethylene resin (B) are not compatible with each other, and interfacial interaction can be suppressed. As a result, a sea-island structure is formed in which the polypropylene resin (A) is the sea phase and the polyethylene resin (B) is the island phase, which can suppress a decrease in the fluidity of the resin composition.

[0020] Furthermore, if the MFR(A) / MFR(B) value is less than 5000, aggregation of the polyethylene resin (B) constituting the island phase is suppressed within the polypropylene resin (A) constituting the sea phase of the sea-island structure, improving the dispersibility of the polyethylene resin (B). This improves transferability during molding and effectively suppresses molding defects such as uneven wall thickness of the molded product due to drawdown. It is more preferable that the MFR(A) / MFR(B) value is 750 or more and / or less than 3000.

[0021] Melt flow rate (MFR) is an index representing the fluidity of thermoplastic resins during melting, and is a value measured by the outflow rate of the resin extruded at a constant temperature and pressure. In this specification, the MFR is measured in accordance with JIS K7210, under a load of 2.16 kgf, with only the temperature varied depending on the material. For polyethylene resin (B), fluidity at the lower temperature end of 190°C is important.

[0022] Specifically, MFR(A) (g / 10 min.) is the melt flow rate measured for polypropylene resin (A) under conditions of a temperature of 230°C and a load of 2.16 kgf. MFR(B) (g / 10 min.) is the melt flow rate measured for polyethylene resin (B) under conditions of a temperature of 190°C and a load of 2.16 kgf.

[0023] The MFR of the resin composition according to this embodiment, measured under conditions of a temperature of 200°C and a load of 2.16 kgf, is preferably 1.0 g / 10 min. or higher, and also preferably 20 g / 10 min. or lower. If the MFR is 1.0 g / 10 min. or higher, sufficient fluidity can be obtained when passing through the parison forming core of the blow molding apparatus and when transferring the surface of the mold. Furthermore, if the MFR is 20 g / 10 min. or lower, the decrease in drawdown can be suppressed. Therefore, the MFR of the resin composition may be 20 g / 10 min. or higher and 50 g / 10 min. or lower. Furthermore, it is more preferable that the MFR is 1.0 g / 10 min. or higher and / or 10 g / 10 min. or lower. The MFR of the resin composition may also be 5.0 g / 10 min. or lower.

[0024] The melt tension of the resin composition according to this embodiment, as measured at a temperature of 200°C, is preferably 1.0 cN or more, more preferably 4.0 cN or more, and also preferably 20 cN or less. If the melt tension is 1.0 cN or more, it is suitable for blow molding, and if it is 4.0 cN or more, a stable parison can be formed in blow molding. Furthermore, if it is 20 cN or less, it can be stably inflated when air is blown in. Therefore, the melt tension of the resin composition can be between 4.0 cN and 20 cN. Furthermore, the melt tension of the resin composition is more preferably 4.0 cN or more and / or 15 cN or less.

[0025] The melt tension is the value measured under the following conditions: Piston descent speed: 0.222 mm / sec Winding speed: 0.444 mm / sec Nozzle L / D: 12.5 Nozzle diameter φ: 2.0 mm Pulley gap: 0.6 mm Die-pulley distance: 105 mm Measurement temperature: 200°C Inlet angle: 180°

[0026] The melt tension can be determined by measuring the tension generated when the molten resin is wound onto a pulley using equipment such as a capillary rheometer.

[0027] In this embodiment, the total content of polypropylene resin (A) and polyethylene resin (B) in the resin composition is preferably 55 parts by mass or more, based on 100 parts by mass of the total amount of the resin composition. If the total content of polypropylene resin (A) and polyethylene resin (B) is 55 parts by mass or more, the effects of this embodiment can be obtained to a high degree.

[0028] The polypropylene resin (A) and polyethylene resin (B) used in the resin composition according to this embodiment do not need to contain virgin material and may contain recycled resin material collected and recycled by home appliance manufacturers, printer manufacturers, and recycling companies. Furthermore, the polypropylene resin (A) and polyethylene resin (B) may also contain biomass plastics derived from natural materials or raw materials produced by microorganisms. Alternatively, recycled resin material may be kneaded with virgin material of the same type to create a resin material with an arbitrary recycling ratio, which can then be used as the polypropylene resin (A) and polyethylene resin (B). Among recycled resin materials, polyethylene-based recycled materials are abundant and can be preferably used as the polypropylene resin (A). In this case, in the resin composition according to this embodiment, it is preferable from the viewpoint of promoting the use of recycled materials that the content of polypropylene resin (A) is greater than the content of polyethylene resin (B).

[0029] While recycled materials may contain resins not intended for recycling during the collection process, such resin materials are also usable. Resins that may be mixed in include polystyrene-based resins, including high-impact polystyrene (HIPS), ABS resin, polyester resins such as polyethylene terephthalate (PET), polycarbonate resins and alloys with the aforementioned resins, polyacetal resins, polyphenylene ether resins, acrylic resins, polyamide resins, polylactic acid, polyvinyl chloride resins, fluororesins, and silicone resins, but are not particularly limited. Using these biomass plastics and recycled materials is preferable from the viewpoint of reducing environmental impact.

[0030] Furthermore, the content of halogen-containing compounds in the resin composition is preferably 1% by mass or less of the total resin composition, and it is even more preferable that they are not included at all.

[0031] The following describes in more detail each element related to the resin composition according to this embodiment.

[0032] • Polypropylene resin (A) In this embodiment, the polypropylene resin (A) is a resin that contains 50 mol% or more of structural units derived from propylene relative to the total structural units constituting the resin.

[0033] Examples of polypropylene resins (A) include homopolypropylene (homoPP), ethylene-propylene random copolymer (random copolymer PP), a mixture of ethylene-propylene-diene copolymer rubber (EPDM) and ethylene-propylene copolymer (block copolymer PP), and copolymers of unsaturated olefins having 2 to 8 carbon atoms, such as ethylene and butene, and propylene. Polypropylene resins (A) may also be mixtures thereof.

[0034] In this embodiment, MFR(A) is preferably 20 g / 10 min. or more, and also preferably 50 g / 10 min. or less. If MFR(A) is 20 g / 10 min. or more, the fluidity of the resin composition can be improved when passing through the parison forming core of the blow molding apparatus and when transferring the surface of the mold. If MFR(A) is 50 g / 10 min. or less, the decrease in melt tension can be effectively suppressed, and blow molding can be avoided. MFR(A) is more preferably 25 g / 10 min. or more. MFR(A) is also preferably 45 g / 10 min. or less, and more preferably 35 g / 10 min. or less. MFR(A) may be 24 g / 10 min. or more and / or 32 g / 10 min. or less.

[0035] The content of polypropylene resin (A) in the resin composition is preferably 50 parts by mass or more, based on 100 parts by mass of the total amount of the resin composition. When the content of polypropylene resin (A) is 50 parts by mass or more, based on 100 parts by mass of the total amount of the resin composition, the polypropylene resin (A) is formed as the sea phase of a sea-island structure, resulting in high fluidity and high melt tension of the resin composition. Furthermore, a good balance between chemical and mechanical properties is obtained. The content of polypropylene resin (A) in the resin composition is more preferably 60 parts by mass or more, based on 100 parts by mass of the total amount of the resin composition.

[0036] • Polyethylene resin (B) In this embodiment, polyethylene resin (B) is a resin that contains 50 mol% or more of structural units derived from polyethylene with respect to the total amount of structural units constituting the resin.

[0037] Examples of polyethylene resins (B) include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene (VLDPE), and ultra-high molecular weight polyethylene (UHMWPE). Polyethylene resins (B) may also be mixtures thereof.

[0038] The density of polyethylene resin (B) at room temperature is 0.90 g / cm³. ３ Preferably, it should be 0.98 g / cm³ or more. ３ The following is also preferable. High-density polyethylene (HDPE) can be preferably used as the polyethylene resin (B) having such density. By using high-density polyethylene (HDPE) as the polyethylene resin (B), a good balance between higher melt tension and impact resistance can be obtained. Therefore, the density of the polyethylene resin (B) at room temperature is 0.90 g / cm³. ３ 0.98g / cm or more ３ The following are possible:

[0039] In this embodiment, MFR(B) may be 0.005 g / 10 min. or more, but is preferably 0.01 g / 10 min. or more, and is also preferably 0.1 g / 10 min. or less. If MFR(B) is 0.005 g / 10 min. or more, fluidity can be improved when passing through the parison forming core of the blow molding apparatus and when transferring the surface of the mold. Also, if MFR(B) is 0.1 g / 10 min. or less, the decrease in melt tension can be suppressed, and drawdown can be effectively suppressed. Therefore, MFR(B) may be 0.005 g / 10 min. or more and 0.1 g / 10 min. or less. MFR(B) is more preferably 0.01 g / 10 min. or more and / or 0.05 g / 10 min. or less.

[0040] The content of polyethylene resin (B) in the resin composition is preferably 5 parts by mass or more and less than 50 parts by mass, based on 100 parts by mass of the total amount of the resin composition. If the content of polyethylene resin (B) is 5 parts by mass or more, based on 100 parts by mass of the total amount of the resin composition, sufficient melt tension to suppress drawdown can be obtained. Furthermore, if the content of polyethylene resin (B) is less than 50 parts by mass, based on 100 parts by mass of the total amount of the resin composition, sufficient fluidity can be obtained when passing through the parison forming core of the blow molding apparatus and when transferring the surface of the mold. More preferably, the content of polyethylene resin (B) in the resin composition is 10 parts by mass or more and less than 40 parts by mass, based on 100 parts by mass of the total amount of the resin composition. The content of polyethylene resin (B) in the resin composition may be greater than the content of polyester resin in the resin composition (including zero). Similarly, the content of polyethylene resin (B) in the resin composition may be greater than the content of polycarbonate resin, polyacetal resin, polyphenylene ether resin, acrylic resin, polyamide resin, polylactic acid, polyvinyl chloride resin, fluororesin, silicone resin, etc. (including zero).

[0041] - Additive (C) The resin composition according to this embodiment preferably further contains an additive (C) that forms a fibril structure (fine thread-like structure).

[0042] The fibril structure is generally a fine fibrous structure composed of fibrils having a length of several μm to several mm and a diameter of several nm to several μm. By containing an additive (C) that forms a fibril structure in addition to the polypropylene-based resin (A) and the polyethylene-based resin (B), the resin composition can achieve a higher level of compatibility between fluidity and melt tension. In addition, the additive (C) also contributes to the improvement of impact resistance.

[0043] FIG. 1 shows a schematic diagram in which a part of the cross-section of the resin composition is enlarged.

[0044] As shown in FIG. 1, the resin composition according to the present embodiment has a sea-island structure composed of a polypropylene-based resin (A) 1 that forms a sea phase and a polyethylene-based resin (B) 2 that forms an island phase. The diameter of the island phase (equivalent spherical diameter and / or equivalent circular diameter) of the polyethylene-based resin (B) 2 is such that more than half is 3 μm or more and 300 μm or less, and in particular, there can be many island phases of 50 μm or more and 150 μm or less. Therefore, the representative value (at least any one of the average value (average diameter), median diameter (median value, 50% diameter, D50), and mode diameter (most frequent value)) of the diameter of the island phase of the polyethylene-based resin (B) 2 can be 10 μm or more and 200 μm or less. Further, the representative value of the diameter of the island phase of the polyethylene-based resin (B) 2 can be 50 μm or more and 150 μm or less. That is, at least any one of the average diameter, median diameter, and mode diameter of the island phase of the polyethylene-based resin (B) 2 can be 10 μm or more and 200 μm or less.

[0045] Also, the 10% diameter (D10) can be 3 μm or more, and the 90% diameter (D90) can be 300 μm or less. By including an additive (C) that forms a fibril structure in the resin composition, the resin composition can have a fibril structure 3 formed so as to bridge the polyethylene-based resins (B) in the sea-island structure. At this time, when the fibril structure 3 is oriented along the flow direction of the resin composition, the apparent particle size of the polyethylene-based resin (B) 2 that forms the island phase increases. As a result, it is possible to suppress a decrease in fluidity while improving melt tension.

[0046] The structure shown in FIG. 1 can be observed from resin pellets made of the resin composition according to this embodiment, molded articles and containers composed of the resin composition according to this embodiment, and the like. For example, by observing a cross-section along the resin flow direction of the molded article with a scanning electron microscope or the like, the structure shown in FIG. 1 can be observed.

[0047] Examples of the additive (C) that forms the fibril structure include thermoplastic resin agents such as polytetrafluoroethylene (PTFE), inorganic fibers such as glass fibers, carbon fibers, and carbon nanotubes, plant fibers such as wood flour, pulp, and cellulose nanofibers (fine pulverized pulp), and synthetic fibers such as polyester fibers and polyamide fibers. These additives (C) may be used singly or in combination of two or more.

[0048] Among them, the additive (C) preferably contains polytetrafluoroethylene (PTFE). Since polytetrafluoroethylene (PTFE) has high crystallinity and low intermolecular force, it has the property of fibrillating with a slight stress. Therefore, when polytetrafluoroethylene (PTFE) is blended with the polypropylene-based resin (A) and the polyethylene-based resin (B), a fine fibril structure can be formed in the matrix to improve the melt tension.

[0049] The average diameter of the fibrils forming the fibril structure is preferably 1 nm or more and / or less than 1 μm. If the average diameter of the fibrils is 1 nm or more, the melt tension can be improved, and if it is less than 1 μm, the decrease in fluidity can be suppressed. Therefore, the average diameter of the fibrils forming the fibril structure can be 1 nm or more and less than 1 μm.

[0050] Further, the surface of the additive (C) may be treated with various surface treatment agents such as silane coupling agents, titanium coupling agents, organic fatty acids, alcohols, amines, waxes, and silicone resins.

[0051] The content of additive (C) in the resin composition is preferably 1 part by mass or more and less than 10 parts by mass, based on 100 parts by mass of the total amount of the resin composition. If the above content of additive (C) is 1 part by mass or more, sufficient melt tension to suppress drawdown can be obtained. Furthermore, if the above content of additive (C) is less than 10 parts by mass, a decrease in fluidity and appearance defects due to entanglement (aggregation) of fibril structures can be suppressed. More preferably, the content of additive (C) in the resin composition is 1 part by mass or more and less than 7 parts by mass, based on 100 parts by mass of the total amount of the resin composition.

[0052] Other components: The resin composition according to this embodiment may appropriately contain antioxidants, flame retardants, ultraviolet absorbers, neutralizing agents, nucleating agents, light stabilizers, antistatic agents, lubricants, antiblocking agents, odor adsorbents, antibacterial agents, pigments, colorants, inorganic and organic fillers, and other additives for synthetic resins.

[0053] Examples of antioxidants include phenolic antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.

[0054] Examples of flame retardants include organophosphorus compounds.

[0055] Examples of UV absorbers include those containing material components such as ethylhexyl methoxymate and t-butyl methoxydibenzoylmethane.

[0056] Examples of nucleating agents include metal salts of carboxylic acids, dibenzyl sorbitol derivatives, alkali metal phosphate salts, and talc.

[0057] Examples of light stabilizers include hindered amine-based light stabilizers.

[0058] Antimicrobial agents include organic (aldehyde, phenol, pyrithione) and inorganic (metals such as silver, copper, and zinc) types.

[0059] Examples of pigments include titanium dioxide, carbon, zinc oxide, and calcium carbonate.

[0060] Examples of neutralizing agents, lubricants, antiblocking agents, and colorants include salts of fatty acids with metals other than sodium and potassium (metal soaps).

[0061] Inorganic fillers used to improve mechanical properties include metal oxides, metal hydroxides, carbonates, sulfates, silicate compounds, glass-based fillers, silicate compounds, metal powders and metal fibers, carbon fibers, and carbon nanotubes. These inorganic fillers may also have their surfaces treated with various surface treatment agents such as silane coupling agents, titanium coupling agents, organic fatty acids, alcohols, and amines, as well as waxes and silicone resins.

[0062] Furthermore, the resin composition according to this embodiment may contain elastic components such as rubber or elastomer to improve impact strength.

[0063] Next, we will describe molded articles and the like manufactured using the resin composition according to this embodiment.

[0064] The molded article according to this embodiment is a molded article composed of the resin composition described above. The molded article according to this embodiment will be described below with reference to the drawings. In the drawings, the same reference numerals are used for similar or corresponding elements, and their descriptions may be omitted or simplified.

[0065] Figures 2A to 2C are schematic diagrams showing one embodiment of the molded body according to this embodiment. Figure 2A is a perspective view of the molded body, Figure 2B is a cross-sectional view of the molded body shown in Figure 2A including the A-A axis, and Figure 2C is a bottom view showing the bottom of the molded body. The direction along the A-A axis of the molded body is referred to as the axial direction.

[0066] The molded body 100 shown in Figures 2A to 2C is, for example, a blow-molded body. As shown in Figures 2A and 2B, the blow-molded body 100 has an opening 104, a body portion 103 connected to the opening 104 and having a space 102 communicating with the opening, and a bottom portion 105 connected to the body portion 103. The opening 104 and the body portion 103 are aligned in the axial direction, the body portion 103 and the bottom portion 105 are aligned in the axial direction, and the opening 104 and the bottom portion 105 are aligned in the axial direction. The axial direction is from the opening 104 to the bottom portion 105. In addition, at least one of the body portion 103 and the bottom portion 105 of the molded body 100 has a parting line 106. The parting line 106 may be formed to surround the perimeter of the molded body by being continuous from the opening 104 to the body portion 103 and further to the bottom portion 105. Of the parting lines 106, the parting line 106 at the bottom 105 may be a pinch line off. In this specification, a pinch line off is considered a type of parting line. This pinch line off is characteristic of extruded blow molded articles formed by extruded blow molding.

[0067] The molded body 100 shown in Figures 2A to 2C is an example in which the molded body consists only of a resin layer 101 containing the resin composition according to this embodiment, but the molded body according to this embodiment is not limited to this. For example, the molded body according to this embodiment may be a multilayer resin molded body having two or more resin layers, in which case one or more of the two or more resin layers are composed of the resin composition according to this embodiment.

[0068] The thickness of the resin layer 101 is not particularly limited as long as it provides sufficient strength as a molded body. In the molded body 100, the average hollow area of ​​the opening 104 is smaller than the average hollow area of ​​the body portion 103. In particular, it is preferable that the average hollow area of ​​the opening 104 is 25% or less of the average hollow area of ​​the body portion 103. Here, the hollow area of ​​the opening 104 and the hollow area of ​​the body portion 103 refer to the area of ​​the hollow space 102 surrounded by the opening 104 or the body portion 103 in a direction perpendicular to the axial direction in which the opening 104 and the body portion 103 are aligned.

[0069] When the resin composition according to this embodiment contained in the molded body 100 contains additive (C), the fibril structure formed by additive (C) is oriented along the flow direction of the resin composition when the molded body 100 is molded. For example, in the resin composition in the molded body 100, at least a portion of the fibril structure may be oriented along the axial direction. For example, it may be oriented in the same plane as a straight line parallel to the axial direction in which the opening 104 and the body portion 103 are aligned. Typically, in the body portion 103, at least a portion of the fibril structure is oriented along the direction from the opening 104 to the bottom portion 105 (axial direction). In Figure 1, the vertical extension of the fibril structure 3 represents the orientation of the fibril structure 3.

[0070] The molded article according to this embodiment can be obtained by molding it using the resin composition according to this embodiment and various molding methods used for thermoplastic resins. The molding method is not particularly limited, and various known molding methods can be applied depending on the application, the shape and size of the molded article, and the desired shape accuracy. Examples include blow molding, injection molding, extrusion molding, and compression molding. Among these, blow molding is preferred.

[0071] Blow molding can be classified into extrusion blow molding and injection blow molding. In extrusion blow molding, resin that has been plasticized by heating is extruded and a cylindrical parison (hot parison) is formed by a die. Without allowing it to solidify by cooling, it is directly placed into a blow molding die and air is blown in to shape it according to the shape of the blow molding die. For this reason, extrusion blow molding can also be called direct blow molding. To form the bottom 105 of the molded body 100, the parison is sandwiched between two blow molding dies and the resin is joined. The burr formed on the bottom 105 at this time is the pinch line. In injection blow molding, resin that has been plasticized by heating is molded into a bottomed parison, a preform (cold parison), in an injection molding die. This is reheated in a blow molding die, stretched into the blow molding die with a stretching rod, and shaped by blowing in air. Parting lines originating from the injection molding die and parting lines originating from the blow molding die are formed on the preform and the body 103 of the blow molded body. Furthermore, the shape of the cavity in the blow molding die is not limited to a cylinder. Also, by forming the bottom portion 105 with a single piece, it is possible to prevent the formation of a parting line on the bottom portion 105.

[0072] In injection blow molding, the molten resin can be held in the injection mold, but in extrusion blow molding, the hot parison extruded from the die maintains its shape (cylindrical) by the tension of the molten resin itself. Therefore, when performing extrusion blow molding, it is desirable for the resin composition to have high melt tension. On the other hand, in order to obtain good blowability and surface transferability, it is also desirable for the molten resin to have high fluidity, so the melt flow rate (MFR), which is an indicator of fluidity, is set to a suitable level. However, conventional resin compositions have not been able to adequately balance melt tension and melt flow rate, and the two have remained in a trade-off relationship. With the resin composition of this embodiment, it is possible to achieve a high level of both melt tension and melt flow rate. Therefore, the resin composition of this embodiment is particularly suitable for extrusion blow molding.

[0073] In other words, a method for manufacturing a molded article according to one embodiment of the present disclosure is a method for manufacturing a molded article by extrusion blow molding a resin composition. Here, the resin composition contains a polypropylene resin (A) and a polyethylene resin (B), and the manufacturing method has a sea-island structure in which the polypropylene resin (A) forms the sea phase and the polyethylene resin (B) forms the island phase.

[0074] Furthermore, the molded body according to this embodiment is preferably a blow-molded body, and has applications such as liquid storage containers like ink tank bottles. The blow-molded body of this embodiment may be a single-layer blow-molded body or a multi-layer blow-molded body. The multi-layer blow-molded body may be a two-layer blow-molded body or a blow-molded body with three or more layers. Among these, a two-layer blow-molded body is preferred. Also, when a resin composition other than that of this embodiment is used for the inner or outer layer, the constituent material is not particularly limited and may be any resin or resin composition that can be blow-molded. The multi-layer blow-molded body may have a barrier layer or an adhesive layer. Note that multi-layer blow molding can be combined with either the extrusion blow molding or injection blow molding described above.

[0075] The type and content of resins constituting the molded body, as well as its physical properties such as MFR, can be determined by mechanically cutting and separating the molded body as appropriate, and then applying a combination of known separation and analytical techniques. The specific methods and means are not particularly limited.

[0076] For a simpler method, a solvent extraction apparatus can be used to separate each type of resin by dissolving them in different solvents. For example, hexane can be used to separate polypropylene resin (A), and toluene can be used to separate polyethylene resin (B).

[0077] Next, by controlling the temperature and utilizing the difference in solubility, various resins can be extracted by separating them in a solvent. This allows for the separation and analysis of each component from a molded article consisting of a resin composition containing polypropylene resin (A) and polyethylene resin (B).

[0078] ・Container The container according to this embodiment is a container made of the resin composition according to this embodiment that is capable of holding contents such as liquid. The container according to this embodiment may be one embodiment of the molded body according to this embodiment. That is, the container according to this embodiment may be, for example, the molded body 100 shown in Figures 2A to 2C, and may further include a lid configured to be able to close the opening 104. The lid may be able to be opened and closed using, for example, a spiral-shaped uneven structure provided near the opening 104. The container according to this embodiment may further include a nozzle that constitutes at least a part of the opening 104 of the container.

[0079] The container according to this embodiment can be used as a liquid storage container. That is, the liquid holder according to this embodiment comprises a container according to this embodiment that is capable of holding (or storing) a liquid, and the liquid held (or stored) in the container. The liquid may be, for example, pharmaceuticals, agricultural chemicals, food, beverages, fuels, detergents, and inks. The ink may be, for example, ink for inkjet printers.

[0080] In particular, the container according to this embodiment can be suitably used as an ink tank mounted in an inkjet printer. That is, the ink tank is a container according to this embodiment that is capable of holding (or storing) liquid, and is filled with ink as a liquid. The ink tank according to this embodiment can be configured to be mounted, for example, in an inkjet printer having an inkjet head. In this case, the ink tank may have an opening for supplying ink to the inkjet, in addition to the opening for filling with ink.

[0081] Furthermore, the inkjet printer according to this embodiment is characterized by being equipped with a container according to this embodiment. The container equipped in the inkjet printer may be an ink cartridge that the user installs into the main unit, or an ink tank that is pre-installed in the inkjet printer main unit. Alternatively, the container equipped in the inkjet printer may be a container that already holds ink (e.g., an ink cartridge), or an empty container (e.g., an ink tank).

[0082] If the container provided by the inkjet printer is an empty container (first container; for example, an ink tank), the user can fill, inject, or replenish the first container with ink held in another container (second container; for example, an ink bottle). To do this, the ink that has been dispensed from the opening of the second container to the outside of the second container can be poured back into the first container through its opening. In this way, the user may cause the inkjet printer to hold ink in the first container.

[0083] The container according to this embodiment can be used as an ink cartridge, ink tank, or ink bottle as a container for an inkjet printer. For example, when using the container according to this embodiment, which has nozzles forming at least a part of its opening, as an ink bottle, the inkjet printer can be configured so that the nozzles can be fitted into the inkjet printer body.

[0084] Empty ink cartridges and ink bottles can be recycled.

[0085] • Resin pellets The resin composition according to this embodiment can be mixed and pelletized, for example, as follows, to produce resin pellets made from the resin composition according to this embodiment.

[0086] First, predetermined materials constituting the resin composition are heated, melted, and kneaded. For heating, melting, and kneading, a kneader, roll, twin-screw kneader, etc., preheated to 150-230°C can be used. Among these, a twin-screw kneader is preferred from the viewpoint of easy uniform dispersion and continuous productivity. Next, the kneaded strand-like resin composition is cut with a pelletizer to obtain resin pellets suitable for molding. The resin pellets are fed into the hopper of a molding machine and melted (plasticized) in a cylinder. The molten resin obtained by melting the resin pellets can be molded in a mold to produce a molded body.

[0087] <Examples> Next, this embodiment will be described in more detail with reference to examples and comparative examples, but this embodiment is not limited to the following examples.

[0088] The materials used in this embodiment are as follows: • Polypropylene resin (A) A-1: ​​Block copolymer polypropylene "M50GRAY" manufactured by Panasonic Industrial Marketing & Sales Co., Ltd., MFR(A) 28g / 10min. A-2: Propylene homopolymer "Novatec (product name) SA04M (model number)" manufactured by Nippon Polypropylene Co., Ltd., MFR(A) 40g / 10min. A-3: Block copolymer polypropylene "Prime Polypropylene (registered trademark) E701G (model number)" (B) MFR(A) 0.5g / 10min. A-4: Recycled polypropylene "MAYPRENE PP (product name) MW666 (model number)" manufactured by Metro Wealth Polymer Sdn. Bhd., MFR(A) 0.9g / 10min. A-5: Propylene homopolymer "Novatec (product name) SA06GA (model number)" manufactured by Nippon Polypropylene Co., Ltd., MFR (A) 60 g / 10 min. • Polyethylene resin (B) B-1: Polyethylene "KEIYO Polyethylene (product name) B5500 (model number)" manufactured by Keiyo Polyethylene Co., Ltd., MFR (B) 0.03 g / 10 min. B-2: Recycled polyethylene "F101-N" manufactured by Asahi Koyu, MFR (B) 0.01 g / 10 min. B-3: Polyethylene "KEIYO Polyethylene (product name) FX503 (model number)" manufactured by Keiyo Polyethylene Co., Ltd., MFR (B) 0.05 g / 10 min. • Additive (C) C-1: Resin modifier "Metablen A-3000" manufactured by Mitsubishi Chemical Corporation

[0089] <Method for manufacturing resin pellets> Polypropylene resin (A), polyethylene resin (B), and additive (C) were each fed into a twin-screw extruder "PCM30 (product name) manufactured by Ikegai Co., Ltd." using separate weight feeders to achieve the desired mass ratio. The materials were melted and kneaded under conditions of a cylinder temperature of 190°C and a screw rotation speed of 200 rpm to produce strands. After cooling the strands in a water bath, resin pellets were obtained by cutting them with a pelletizer.

[0090] <Method of Manufacturing Molded Body> The obtained resin pellets were extruded and blow-molded (direct blow-molded) using an extrusion blow molding machine (direct blow molding machine). First, the resin pellets were fed into the extruder installed in the extrusion blow molding machine to form a cylindrical ring-shaped parison. At this time, the resin temperature of the extruder was set to 200°C. Next, the parison was sandwiched in a mold, and blow air was injected to obtain a molded body with an outer shape that matched the cavity shape. A parting line was formed on the body of the molded body, and a pinch line was formed on the bottom.

[0091] Table 1 shows the composition and MFR(A) / MFR(B) values ​​of the molded articles for each example and comparative example.

[0092] <Evaluation Method> The above molding process and the resulting molded product were evaluated from the perspective of moldability using the following indicators.

[0093] • Extrudeability: Extrudeability was evaluated according to the following criteria: A: Good resin extrusion in the extruder B: Slightly poor resin extrusion in the extruder (pulsation occurs) C: Poor resin extrusion in the extruder (torque overload)

[0094] - Blow moldability: Blow moldability was evaluated according to the following criteria: A: Moldable C: Not moldable (problem with drawdown)

[0095] - Surface properties of the molded product The surface properties of the molded product were evaluated according to the following criteria. The surface condition was observed visually, and products with die lines or gas stains were classified as having a poor appearance. A: Good C: Poor appearance

[0096] The evaluation results are shown in Table 2.

[0097] As shown in Table 2, in Examples 1 to 4, the MFR(A) / MFR(B) ratio of the resin composition constituting the molded article was within the range of 500 or more and less than 5000, which allowed for a balance between fluidity and melt tension, resulting in excellent extrudeability, blow moldability, and surface properties.

[0098] On the other hand, the molded article according to Comparative Example 1, which consisted only of polypropylene resin (A) having low fluidity and high melt tension, achieved high melt tension but lacked fluidity. Furthermore, the molded articles according to Comparative Examples 2 and 3, where MFR(A) / MFR(B) was outside the range defined in this embodiment, could not achieve both fluidity and melt tension. Therefore, the molded articles according to Comparative Examples 1 to 3 could not obtain results that satisfied all of the requirements for extrudeability, blow moldability, and surface properties.

[0099] [Second Embodiment] The differences between the second embodiment and the first embodiment will be explained, and the common components will not be described.

[0100] In the resin composition according to this embodiment, when the weight-average molecular weight of the polypropylene resin (A) is Mw(A) and the weight-average molecular weight of the polyethylene resin (B) is Mw(B), the value of Mw(B) / Mw(A) may be 3.0 or more and may be less than 50.

[0101] When the Mw(B) / Mw(A) value is between 3.0 and less than 50, a sea-island structure is formed in which the polypropylene resin (A) forms the sea phase and the polyethylene resin (B) forms the island phase. This suppresses a decrease in the fluidity of the resin composition, improves transferability during molding, and effectively suppresses molding defects such as uneven wall thickness of the molded product due to drawdown.

[0102] Furthermore, Mw(A) and Mw(B) can be measured using gel permeation chromatography (GPC).

[0103] In this embodiment, the weight-average molecular weight Mw(A) of the polypropylene resin (A) is preferably 200,000 or more, and also preferably 400,000 or less. If Mw(A) is 200,000 or more, a high melt tension can be obtained as a resin composition, and drawdown can be effectively suppressed. Furthermore, if Mw(A) is 400,000 or less, the fluidity can be improved when passing through the parison forming core of the blow molding apparatus and when transferring the surface of the mold. Therefore, the weight-average molecular weight Mw(A) of the polypropylene resin (A) can be between 200,000 and 400,000.

[0104] Furthermore, in this embodiment, the weight-average molecular weight Mw(B) of the polypropylene resin (B) is preferably 750,000 or more, and also preferably 10,000,000 or less. If Mw(B) is 750,000 or more, a high melt tension can be obtained as a resin composition, and drawdown can be effectively suppressed. Also, if Mw(B) is 10,000,000 or less, the fluidity of the resin composition can be improved when passing through the parison forming core of the blow molding apparatus and when transferring the surface of the mold. Therefore, the weight-average molecular weight Mw(B) of the polypropylene resin (B) can be between 750,000 and 10,000,000.

[0105] Molded articles and containers containing the resin composition according to this embodiment are the same as those of the first embodiment, except that the resin composition used is replaced with that of this embodiment. Furthermore, in the manufacture of molded articles and containers, the resin composition according to the first embodiment and the resin composition according to this embodiment can be used in combination. Alternatively, the resin composition may correspond to either the resin composition according to the first embodiment or the resin composition according to this embodiment.

[0106] Furthermore, when measuring the weight-average molecular weight of each resin material contained in a molded article or the like manufactured using the resin composition according to this embodiment, the resins can be separated and extracted in the same manner as described in the first embodiment, and then measured by GPC.

[0107] <Examples> Next, this embodiment will be described in more detail with reference to examples and comparative examples, but this embodiment is not limited to the following examples. The manufacturing method and evaluation method are the same as in the above-described examples, so only the differences will be noted.

[0108] The materials used in this embodiment are as follows: • Polypropylene resin (A) A-6: Block copolymer polypropylene, weight-average molecular weight Mw(A) 280,000 A-7: Block copolymer polypropylene, weight-average molecular weight Mw(A) 830,000 A-8: Block copolymer polypropylene, weight-average molecular weight Mw(A) 160,000 • Polyethylene resin (B) B-4: Polyethylene, weight-average molecular weight Mw(B) 900,000 B-5: Polyethylene, weight-average molecular weight Mw(B) 7,000,000 B-6: Polyethylene, weight-average molecular weight Mw(B) 10,000,000 • Additive (C) C-1: Resin modifier "Metablen A-3000" manufactured by Mitsubishi Chemical Corporation

[0109] Using the materials shown in Table 3, molded articles according to Examples 5 and 6, and Comparative Examples 4 and 5 were manufactured and evaluated in the same manner as described in the examples for the first embodiment. The evaluation results are shown in Table 4.

[0110]

[0111]

[0112] As shown in Table 4, in Examples 5 and 6, the Mw(B) / Mw(A) ratio being in the range of 3.0 or more and less than 50 allowed for both high fluidity and high melt tension, resulting in excellent extrudeability, blow moldability, and surface properties.

[0113] On the other hand, in Comparative Examples 1 and 2, Mw(B) / Mw(A) was outside the above range, and it was not possible to achieve both high fluidity and high melt tension simultaneously, resulting in a failure to obtain results that satisfied all aspects of extrudeability, blow moldability, and surface properties.

[0114] The embodiments described above can be modified as appropriate without departing from the technical concept.

[0115] For example, multiple embodiments can be combined. Furthermore, some elements of at least one embodiment can be deleted or replaced.

[0116] Furthermore, new matters may be added to at least one embodiment. The disclosures of this specification include not only those explicitly stated herein, but also all matters that can be understood from this specification and the accompanying drawings.

[0117] Furthermore, the disclosures in this specification include the complements of the individual concepts described herein. That is, if this specification contains a statement such as "A is greater than B," then even if it omits a statement such as "A is not greater than B," it can be said that this specification discloses "A is not greater than B." This is because the statement "A is greater than B" presupposes that the case where "A is not greater than B" is being considered.

[0118] The technologies described herein may contribute to the realization of a sustainable society, such as a decarbonized / circular economy.

[0119] This disclosure is not limited to the embodiments described above, and various modifications and alterations are possible without departing from the spirit and scope of this disclosure. Accordingly, the following claims are attached to make the scope of this disclosure public.

[0120] This application claims priority based on Japanese Patent Application No. 2024-193974, filed on November 5, 2024, and all of its contents are incorporated herein by reference.

[0121] 1: Polypropylene resin (A) 2: Polyethylene resin (B) 3: Fibril structure 100: Molded body 101: Resin layer 102: Space 103: Body 104: Opening 105: Bottom 106: Parting line

Claims

1. A resin composition containing a polypropylene resin (A) and a polyethylene resin (B), wherein the polypropylene resin (A) forms a sea phase and the polyethylene resin (B) forms an island phase, having a sea-island structure, a melt tension of 1.0 cN or more measured at a temperature of 200°C, and a melt flow rate of 1.0 g / 10 min. or more measured under conditions of 200°C and a load of 2.16 kgf.

2. A resin composition containing a polypropylene resin (A) and a polyethylene resin (B), wherein the MFR(A) / MFR(B) value is 500 or more and less than 5000, when the melt flow rate of the polypropylene resin (A) is measured under conditions of a temperature of 230°C and a load of 2.16 kgf, and the melt flow rate of the polyethylene resin (B) is measured under conditions of a temperature of 190°C and a load of 2.16 kgf, and the MFR(A) / MFR(B) value is 500 or more and less than 5000.

3. The resin composition according to claim 2, wherein the MFR(A) (g / 10 min.) is 20 g / 10 min. or more and 50 g / 10 min. or less.

4. The resin composition according to claim 2 or 3, wherein the MFR(B) is 0.005 g / 10 min. or more and 0.1 g / 10 min. or less.

5. A resin composition containing a polypropylene resin (A) and a polyethylene resin (B), wherein when the weight-average molecular weight of the polypropylene resin (A) is Mw(A) and the weight-average molecular weight of the polyethylene resin (B) is Mw(B), the value of Mw(B) / Mw(A) is 3.0 or more and less than 50.

6. The resin composition according to claim 5, wherein the weight-average molecular weight Mw(A) of the polypropylene resin (A) is 200,000 or more and 400,000 or less.

7. The resin composition according to claim 5 or 6, wherein the weight-average molecular weight Mw(B) of the polyethylene resin (B) is 750,000 or more and 10,000,000 or less.

8. The resin composition according to any one of claims 2 to 7, wherein the melt flow rate measured under conditions of a temperature of 200°C and a load of 2.16 kgf is 1.0 g / 10 min. or more.

9. The resin composition according to any one of claims 1 to 8, wherein the melt flow rate measured under conditions of a temperature of 200°C and a load of 2.16 kgf is 20 g / 10 min. or less.

10. The resin composition according to any one of claims 1 to 9, wherein the total content of the polypropylene resin (A) and the polyethylene resin (B) is 55 parts by mass or more, based on 100 parts by mass of the total amount of the resin composition.

11. The resin composition according to any one of claims 1 to 10, wherein the content of the polypropylene resin (A) is greater than the content of the polyethylene resin (B).

12. The resin composition according to any one of claims 1 to 11, wherein the content of the polypropylene resin (A) is 50 parts by mass or more, based on 100 parts by mass of the total amount of the resin composition.

13. The resin composition according to any one of claims 1 to 12, wherein the content of the polyethylene resin (B) is 5 parts by mass or more and less than 50 parts by mass, based on 100 parts by mass of the total amount of the resin composition.

14. The resin composition according to any one of claims 1 to 13, further comprising an additive (C) that forms a fibril structure.

15. The resin composition according to claim 14, wherein the additive (C) contains polytetrafluoroethylene.

16. The resin composition according to claim 14 or 15, wherein the diameter of the fibrils forming the fibril structure is 1 nm or more and less than 1 μm.

17. The resin composition according to any one of claims 14 to 16, wherein the content of additive (C) is 1 part by mass or more and less than 10 parts by mass, based on 100 parts by mass of the total amount of the resin composition.

18. The density of the polyethylene resin (B) at room temperature is 0.90 g / cm³. ３ 0.98g / cm or more ３ The resin composition according to any one of claims 1 to 17, which is as follows:

19. The resin composition according to any one of claims 1 to 18, wherein the melt tension measured at a temperature of 200°C is 4.0 cN or more and 20 cN or less.

20. A molded article comprising a resin composition according to any one of claims 1 to 19, wherein at least one of the average diameter, median diameter, and mode diameter of the island phase is 10 μm or more and 200 μm or less.

21. A multilayer resin molded article having two or more resin layers, wherein one or more of the resin layers are composed of the resin composition described in any one of claims 1 to 19.

22. A molded article comprising a resin composition according to any one of claims 1 to 19, wherein the molded article is a blow-molded article.

23. A molded article comprising a resin composition according to any one of claims 1 to 19, the molded article having an opening having an opening, a body portion having a space inside that communicates with the opening and connected to the opening, and a bottom portion connected to the body portion, wherein at least one of the body portion and the bottom portion has a parting line.

24. A molded article comprising a resin composition according to any one of claims 14 to 17, the molded article having an opening, a body portion having a space inside that communicates with the opening and connected to the opening, and a bottom portion connected to the body portion, wherein in the body portion, at least a portion of the fibril structure is oriented in a direction toward the bottom portion from the opening.

25. A container capable of holding a liquid, comprising a resin composition according to any one of claims 1 to 19.

26. The container according to claim 25, further comprising a lid having an opening, a body portion having a space inside that communicates with the opening and connected to the opening, and a bottom portion connected to the body portion, wherein the lid is configured to be able to close the opening.

27. The container according to claim 26, further comprising a nozzle that constitutes at least a portion of the opening.

28. A liquid holder comprising the container described in claim 25 and a liquid held in the container.

29. The liquid holder according to claim 28, wherein the liquid is ink.

30. The liquid holder according to claim 29, wherein the ink is ink for an inkjet printer.

31. An inkjet printer comprising the container according to any one of claims 25 to 27.

32. Resin pellets comprising the resin composition according to any one of claims 1 to 19.

33. A method for manufacturing a molded article, comprising molding a molten resin obtained by melting the resin pellets described in claim 32 using a mold.

34. A method for manufacturing a molded article by extrusion blow molding a resin composition, wherein the resin composition contains a polypropylene resin (A) and a polyethylene resin (B), and the manufacturing method has a sea-island structure in which the polypropylene resin (A) forms a sea phase and the polyethylene resin (B) forms an island phase.

35. The manufacturing method according to claim 34, further comprising an additive (C) that forms a fibril structure in the resin composition.

Images