Resin composition and molded article

Abstract

The present invention provides a resin composition that enables stable molding and allows for the production of molded products that achieve both good mechanical strength and rigidity. [Solution] The resin composition comprises an acid-modified polyolefin resin, a thermoplastic resin other than the acid-modified polyolefin resin, an inorganic powder, and lignocellulose fibers. The mass ratio of the thermoplastic resin to the inorganic powder is 10:90 to 60:40, the content of the lignocellulose fibers is 1.0% by mass or more and 10.0% by mass or less relative to the resin composition, and the content of the acid-modified polyolefin resin is 1.0% by mass or more and 5.0% by mass or less relative to the resin composition.

Description

Technical Field

[0001] The present invention relates to a resin composition and a molded article.

Background Art

[0002] Thermoplastic resins such as polyolefin resins are widely used as molding materials. From the viewpoint of improving various functions of molded articles, it has been considered to fill thermoplastic resins with inorganic powders such as calcium carbonate powder (see, for example, Patent Document 1).

[0003] In addition, in a resin composition filled with an inorganic powder as described above, in order to enhance the compatibility between the inorganic powder and the thermoplastic resin, it has also been considered to add a compatibilizer such as an acid-modified polyolefin resin (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, according to the studies by the present inventors, a resin composition containing an inorganic powder such as calcium carbonate powder has a problem that the mechanical strength (tensile strength and flexural strength) of a molded article is likely to decrease as compared with a resin composition not containing the inorganic powder.

[0006] In contrast, while the mechanical strength of molded products can be improved by adding compatibilizers such as acid-modified polyolefin resins, sufficient improvement has been difficult to achieve. Furthermore, it has become clear that the rigidity of molded products decreases with the addition of compatibilizers. Therefore, there is a need to obtain molded products that achieve both good mechanical strength and rigidity while enabling stable molding.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a resin composition and a molded article containing the resin composition that can be reliably molded and can produce a molded article that has both good mechanical strength and rigidity. [Means for solving the problem]

[0008] The present invention relates to the following resin compositions and molded articles. [1] A resin composition comprising an acid-modified polyolefin resin, a thermoplastic resin other than the acid-modified polyolefin resin, an inorganic powder, and lignocellulose fibers, wherein the mass ratio of the thermoplastic resin to the inorganic powder is 10:90 to 60:40, the content of the lignocellulose fibers is 1.0% by mass or more and 10.0% by mass or less relative to the resin composition, and the content of the acid-modified polyolefin resin is 1.0% by mass or more and 5.0% by mass or less relative to the resin composition. [2] The resin composition according to [1], wherein the thermoplastic resin comprises a polyolefin resin. [3] The resin composition according to [2], wherein the polyolefin resin comprises a polypropylene resin. [4] The resin composition according to [3], wherein the polypropylene resin comprises block polypropylene. [5] The resin composition according to any one of [1] to [4], wherein the mass ratio of the thermoplastic resin to the inorganic powder is 10:90 to 50:50. [6] The resin composition according to any one of [1] to [5], wherein the inorganic powder comprises calcium carbonate powder. [7] The resin composition according to any one of [1] to [6], wherein the lignocellulose fiber is a hemp fiber. [8] The resin composition according to any one of [1] to [7], wherein the acid value of the acid-modified polyolefin resin according to JIS K 0070:1992 is 20 mg KOH / g or more and 60 mg KOH / g or less. A molded article comprising the resin composition described in any of [9][1] to [8]. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a resin composition that enables stable molding and can produce molded articles that have both good mechanical strength and rigidity, as well as a molded article containing the resin composition. [Brief explanation of the drawing]

[0010] [Figure 1] Figures 1A to 1D are SEM images of the fracture surfaces of the dumbbell pieces prepared in the example. [Modes for carrying out the invention]

[0011] Through diligent research, the inventors discovered that by further incorporating lignocellulose fibers and acid-modified polyolefin resin into a resin composition containing thermoplastic resin and inorganic powder, both the mechanical strength (flexural strength and tensile strength) and rigidity (flexural modulus) of the molded product can be increased, even when the inorganic powder is highly packed. In particular, it was found that the mechanical strength was higher than that of thermoplastic resin alone, despite the inclusion of inorganic powder.

[0012] The reason for this is not clear, but it can be inferred as follows: By incorporating acid-modified polyolefin resins, the compatibility between inorganic powders and resins is improved, thereby increasing the mechanical strength of the molded product, but the rigidity of the molded product tends to decrease. In contrast, by further incorporating lignocellulose fibers, it is possible to increase the rigidity of the molded product while maintaining its mechanical strength. This is presumed to be because lignocellulose fibers, compared to ordinary cellulose fibers, contain more lignin and hemicellulose, resulting in higher strength of the fibers themselves, and also because they interact more readily with acid-modified polyolefin resins and inorganic powders. Furthermore, acid-modified polyolefin resins can make inorganic powders and thermoplastic resins compatible, as well as lignocellulose fibers compatible with thermoplastic resins. As a result, the thermoplastic resin, inorganic powders, and lignocellulose fibers are uniformly compatible via the acid-modified polyolefin resin, making it possible to obtain molded articles with high mechanical strength and high rigidity.

[0013] Lignocellulose fibers are prone to generating gases due to lignin and discoloration due to the heat generated during molding. Therefore, cellulose fibers are usually used after being treated to remove lignin and other substances. In contrast, according to the inventors' research, by using inorganic powder in combination with lignocellulose fibers, the inorganic powder can adsorb lignin and its decomposition products generated from the lignocellulose fibers during molding. This makes it possible to reduce gas generation during molding and discoloration caused by lignin.

[0014] One embodiment of the present invention will be described in detail below. However, the present invention is not limited to this embodiment. Furthermore, in this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower limit and upper limit.

[0015] 1.Resin composition The resin composition includes a thermoplastic resin, an inorganic powder, lignocellulose fibers, and an acid-modified polyolefin resin.

[0016] The ratio of the mass of the inorganic powder to the total mass of the thermoplastic resin and the inorganic powder is 40% by mass or more and 90% by mass or less, preferably 50% by mass or more and 90% by mass or less. When the ratio of the mass of the inorganic powder is 40% by mass or more, the rigidity of the molded product can be increased. When the ratio of the mass of the inorganic powder is 90% by mass or less, the molding processability of the resin composition can be increased. Hereinafter, each component will be described.

[0017] 1-1. Thermoplastic resin The thermoplastic resin is a thermoplastic resin other than an acid-modified polyolefin-based resin, and its type is not particularly limited. As the thermoplastic resin, for example, polyolefin-based resins, poly(meth)acrylic acid esters, polyvinyl acetate, polyacrylonitrile, polystyrene, ABS resins, polycarbonates, polyamides, polyvinyl alcohol, petroleum hydrocarbon resins, coumarone-indene resins and other thermoplastic resins; styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-butadiene-ethylene copolymers, styrene-isoprene-ethylene copolymers, acrylonitrile-butadiene copolymers, fluorine-based elastomers and other elastomers can be used. Among these, polyolefin-based resins are preferred from the viewpoints of mechanical strength and molding processability.

[0018] That is, the thermoplastic resin preferably contains a polyolefin-based resin. Specifically, the amount of the polyolefin-based resin in the thermoplastic resin is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The thermoplastic resin may contain only one kind of polyolefin-based resin or two or more kinds.

[0019] Polyolefin resins are resins with constituent units derived from olefins as the main component. The polyolefin resin may be a homopolymer of a single type of olefin, a copolymer of two or more types of olefins, or a copolymer of one or more olefins and one or more other monomers (monomers other than olefins). In addition, the amount of the constituent units derived from olefins in the polyolefin resin is preferably 50% by mass or more, more preferably 75% by mass or more, still more preferably 85% by mass or more, and particularly preferably 90% by mass or more.

[0020] Examples of olefins include ethylene and α-olefins having 3 to 10 carbon atoms. Specific examples thereof include ethylene, propylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1-heptene, 4-methylpentene-1, 3-methyl-1-hexene, and 1-octene. The polyolefin resin may contain only one type of the constituent units derived therefrom, or may contain two or more types.

[0021] Examples of other monomers include diene monomers such as 1,4-hexadiene, 1,6-octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, dicyclopentadiene (DCPD), ethylidene norbornene (ENB), norbornadiene, and 5-vinyl-2-norbornene; (meth)acrylates such as methyl (meth)acrylate. The polyolefin resin may contain only one type of the constituent units derived therefrom, or may contain two or more types.

[0022] Among them, the polyolefin resin preferably contains a polypropylene resin.

[0023] Polypropylene resins are resins containing 50% by mass or more of propylene-derived structural units. The amount of propylene-derived structural units in the polypropylene resin is preferably 75% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more. Examples of polypropylene resins include homopolypropylene, random polypropylene, and block polypropylene.

[0024] Homopolypropylene is a homopolymer of propylene.

[0025] Random polypropylene is a random copolymer of propylene and other monomers. Examples of other monomers include ethylene, α-olefins with 4 or more carbon atoms, tetrafluoroethylene, vinyl acetate, etc., with ethylene being preferred.

[0026] Block polypropylene is a block copolymer of propylene and the other monomers mentioned above, or a composition in which a propylene copolymer is dispersed in homopolypropylene. Preferably, block polypropylene is a composition in which ethylene propylene copolymer (ethylene propylene rubber, EPR) is dispersed in homopolypropylene. Block polypropylene may have island phases of polyethylene dispersed in a sea phase of homopolypropylene, and further have a phase of EPR surrounding the polyethylene island phases. By using such block polypropylene, it is possible to make it less likely to reduce the mechanical strength of molded articles, even with resin compositions containing inorganic powders or lignocellulose fibers. Such block polypropylene can be obtained by first obtaining homopolypropylene by polymerization of propylene gas, and then copolymerizing EPR in the presence of ethylene gas in the subsequent step.

[0027] The melt mass flow rate (MFR) of the polypropylene resin, measured by the method described in JIS K 7210-1:2014 (ISO 1133-1:2011) under conditions of a temperature of 230°C and a load of 2.16 kg, is preferably, for example, 10 g / 10 min to 120 g / 10 min, and more preferably 30 g / 10 min to 100 g / 10 min. When the resin composition contains lignocellulose fibers and acid-modified polyolefin resins, it tends to thicken easily during molding, resulting in poor fluidity. In contrast, if the MFR of the polypropylene resin is 10 g / 10 min or higher, even such a resin composition can have improved fluidity during molding and improved moldability. If the MFR of the polypropylene resin is 120 g / 10 min or lower, the molding stability of the resin composition can be further improved.

[0028] The polypropylene resin may be virgin resin, recycled resin, or a mixture thereof.

[0029] The content of thermoplastic resin in the resin composition is not particularly limited as long as the mass of inorganic powder relative to the total mass of thermoplastic resin and inorganic powder satisfies the above range. Preferably, the content of thermoplastic resin in the resin composition is 5% by mass or more and 58% by mass or less, and more preferably 10% by mass or more and 46% by mass or less, based on the total mass of the resin composition. If the content of thermoplastic resin is above the lower limit, the proportion of inorganic powder will not become too high, thereby improving moldability and making it less likely to reduce the mechanical strength of the molded product. If the content of thermoplastic resin is below the upper limit, the proportion of inorganic powder will not become too low, thereby improving the rigidity of the molded product.

[0030] 1-2.Inorganic powder Inorganic powders are powders of inorganic substances. Examples of inorganic substances include carbonates, sulfates, silicates, phosphates, borates, oxides, or hydrates of calcium, magnesium, aluminum, titanium, zinc, silicon, barium, molybdenum, sodium, and potassium. Examples of inorganic substances also include inorganic carbon compounds.

[0031] Specific examples of inorganic substances include calcium carbonate, magnesium carbonate, zinc oxide, titanium dioxide, silica, alumina, clay (e.g., talc and kaolin), aluminum hydroxide, magnesium hydroxide, aluminum silicate, magnesium silicate, calcium silicate, aluminum sulfate, magnesium sulfate, calcium sulfate, magnesium phosphate, barium sulfate, silica sand, carbon black, zeolite, molybdenum, diatomaceous earth, sericite, shirasu, calcium sulfite, sodium sulfate, potassium titanate, bentonite, wollastonite, dolomite, and graphite. These may be synthetic or derived from natural minerals. The inorganic powder may consist of only one type or two or more types.

[0032] Preferred examples of inorganic powders include calcium carbonate, magnesium carbonate, dolomite, zinc oxide, titanium oxide, silica, alumina, clay, talc, kaolin, aluminum hydroxide, and magnesium hydroxide powders, with calcium carbonate powder being particularly preferred.

[0033] The calcium carbonate powder may be so-called light calcium carbonate powder, prepared by a synthetic method, or so-called heavy calcium carbonate powder, obtained by mechanically crushing and classifying natural raw materials such as limestone, which are mainly composed of CaCO3. The light calcium carbonate powder may also be powder made from raw materials such as concrete sludge, steel slag, carbide slag, waste concrete, coal ash, biomass ash, incinerator ash, waste gypsum, or alkaline wastewater. In particular, using light calcium carbonate powder can further reduce the environmental burden. It also tends to have a larger surface area (oil absorption capacity) compared to heavy calcium carbonate powder. Therefore, light calcium carbonate powder readily adsorbs lignin released from lignocellulose fibers during molding, further reducing gas generation and discoloration caused by this.

[0034] The amount of oil absorbed by calcium carbonate powder is not particularly limited, but can be, for example, 10 ml / 100g or more and 60 ml / 100g or less, preferably 30 ml / 100g or more and 55 ml / 100g or less. The amount of oil absorbed can be measured using DOP in accordance with JIS K 5101-13-1:2004.

[0035] The shape of the inorganic powder is not particularly limited and may be particulate, flake, granular, or fibrous. In the case of particulate powder, it may be spherical, as is generally the case with synthesis methods, or it may be irregularly shaped, as is the case with natural minerals that have been collected and crushed.

[0036] Inorganic powders may be surface-modified or unmodified. Examples of surface modification methods for inorganic powders include physical modification methods such as plasma treatment, and chemical modification methods using coupling agents or surfactants. Examples of coupling agents that can be used in chemical modification methods include silane coupling agents and titanium coupling agents. Any type of surfactant can be used, including anionic, cationic, nonionic, and amphoteric surfactants, and examples include higher fatty acids, higher fatty acid esters, higher fatty acid amides, and higher fatty acid salts.

[0037] The 50% particle size (median diameter D50) in the volume-based particle size distribution of inorganic powder is not particularly limited, but is preferably 0.7 μm or more and 10.0 μm or less, and more preferably 1.0 μm or more and 8.0 μm or less. When the median diameter D50 of the inorganic powder is 10.0 μm or less, the inorganic powder is less likely to fall off the molded product. When the average particle size of the inorganic powder is 0.7 μm or more, it is easier to adjust the viscosity to a desired range when kneading with thermoplastic resin. The median diameter D50 can be measured using a laser diffraction particle size distribution analyzer.

[0038] The inorganic powder content in the resin composition is not particularly limited, as long as the mass of the inorganic powder relative to the total mass of the thermoplastic resin and inorganic powder satisfies the above range. For example, the inorganic powder content in the resin composition is preferably 20% to 88% by mass, and more preferably 30% to 82% by mass, based on the total mass of the resin composition. If the inorganic powder content is above the lower limit, the rigidity of the molded article can be further increased. If the inorganic powder content is below the upper limit, the moldability of the resin composition and the mechanical strength of the molded article can be further increased.

[0039] 1-3. Lignocellulose fibers Lignocellulose fibers are fibers that primarily consist of cellulose and lignin. In addition to cellulose and lignin, lignocellulose fibers may also contain other components such as hemicellulose and pectin.

[0040] The amount of lignin in the lignocellulose fiber is, for example, 5% by mass or more, preferably 8% by mass or more and 30% by mass or less. The amount of hemicellulose in the lignocellulose fiber may be the same as described above.

[0041] Specific examples of such lignocellulose fibers include fibers extracted from the basts of hemp plants such as kenaf, flax, ramie, cannabis, and jute; fibers extracted from the stems or leaf veins of hemp plants such as Manila hemp and sisal hemp; and wood fibers. Furthermore, lignocellulose fibers can be plant fibers that have not been intentionally treated to remove lignin, hemicellulose, etc. Among these, hemp fibers are preferred because they have a particularly high strength due to their high proportion of crystalline, high-strength cellulose (over 60%), which is higher than the 30-50% found in wood fibers, and hemp fibers are even more preferred.

[0042] The aspect ratio (length / diameter) of the lignocellulose fibers is not particularly limited, but is preferably between 20 and 300. Setting the aspect ratio of the lignocellulose fibers to 20 or higher increases the number of bonding points due to entanglement between fibers, thereby increasing the mechanical strength of the molded product. Setting the aspect ratio of the lignocellulose fibers to 300 or lower increases the fluidity of the resin composition during molding. The length of the lignocellulose fibers is not particularly limited, but can be, for example, 10 mm or more, preferably 10 to 200 mm. The aspect ratio can be determined, for example, by measuring the aspect ratio of any 50 lignocellulose fibers in an SEM image of the recovered lignocellulose fibers after removing the resin components from the resin composition with a solvent, and taking the average value.

[0043] The lignocellulose fiber content in the resin composition is 1.0% by mass or more and 10.0% by mass or less based on the total mass of the resin composition. A lignocellulose fiber content of 1.0% by mass or more can further increase the rigidity (flexural modulus) of the molded product. A lignocellulose fiber content of 10.0% by mass or less can further suppress the fluidity and gas generation of the resin composition during molding. Preferably, the lignocellulose fiber content in the resin composition is 1.5% by mass or more and 8.0% by mass or less based on the total mass of the resin composition, and more preferably 2.0% by mass or more and 5.0% by mass or less.

[0044] 1-4. Acid-modified polyolefin resins Acid-modified polyolefin resins are obtained by acid-modifying polyolefin resins. The polyolefin resin before acid modification is the same as the polyolefin resin described above. In particular, acid-modified polyolefin resins preferably contain acid-modified polyethylene resins or acid-modified polypropylene resins, and more preferably contain acid-modified polypropylene resins. The polypropylene resin before acid modification is the same as the polypropylene resin described above, and is preferably a propylene homopolymer (homopolypropylene).

[0045] The acids used for acid modification can be mono- or polycarboxylic acids, such as maleic acid, fumaric acid, succinic acid, phthalic acid and their anhydrides, as well as citric acid. Among these, maleic acid or its anhydride is preferred.

[0046] The acid value of the acid-modified polyolefin resin is not particularly limited, but it is preferably 20 mg KOH / g or more and 60 mg KOH / g or less, and more preferably 50 mg KOH / g or more and 60 mg KOH / g or less. When the acid value of the acid-modified polyolefin resin is 20 mg KOH / g or more, the interaction between the lignocellulose fibers or inorganic powder and the resin is made easier, so the mechanical strength of the molded product can be increased. When the acid value of the acid-modified polyolefin resin is 60 mg KOH / g or less, the decrease in fluidity due to excessive interaction between the thermoplastic resin, lignocellulose fibers and inorganic powder can be suppressed. The acid value of the acid-modified polyolefin resin can be measured according to JIS K 0070:1992.

[0047] The melting point of acid-modified polyolefin resins is not particularly limited, but from the viewpoint of good mechanical properties of the resin composition, it is preferable that it be, for example, 140°C to 190°C, preferably 150°C to 180°C.

[0048] The melting point is defined as the peak top temperature of the endothermic peak that appears when the temperature is increased from 23°C at a heating rate of 10°C / min using a differential scanning calorimetry (DSC). If two or more endothermic peaks appear, the peak top temperature of the highest-temperature endothermic peak is defined. The enthalpy of this endothermic peak is preferably 10 J / g or higher, and more preferably 20 J / g or higher.

[0049] The weight-average molecular weight of the acid-modified polyolefin resin is not particularly limited, but is preferably between 10,000 and 150,000, and more preferably between 30,000 and 100,000. When the weight-average molecular weight of the acid-modified polyolefin resin is 150,000 or less, the acid-modified polyolefin resin disperses more easily, thus increasing the mechanical strength of the molded product. When the weight-average molecular weight of the acid-modified polyolefin resin is 10,000 or more, the acid-modified polyolefin resin is less likely to bleed out from the molded product. The weight-average molecular weight of the acid-modified polyolefin resin can be measured in polystyrene equivalent by gel permeation chromatography.

[0050] The content of acid-modified polyolefin resin in the resin composition is 1.0% by mass or more and 5.0% by mass or less based on the total mass of the resin composition. When the content of acid-modified polyolefin resin is 1.0% by mass or more, it is possible to make the lignocellulose fibers or inorganic powder and the thermoplastic resin more compatible, and the mechanical strength of the molded product can be further increased. When the content of acid-modified polyolefin resin is 5.0% by mass or less, the lignocellulose fibers or inorganic powder and the thermoplastic resin do not interact excessively, so the fluidity of the resin composition during molding can be further increased. Preferably, the content of acid-modified polyolefin resin in the resin composition is 1.2% by mass or more and 4.0% by mass or less based on the total mass of the resin composition, and more preferably 1.5% by mass or more and 3.0% by mass or less.

[0051] 1-5. Other ingredients The resin composition may further contain components other than those mentioned above, as long as they do not impair the effects of the present invention. Examples of components other than those mentioned above include polyethylene wax, paraffin oil, lubricants, plasticizers, colorants, antioxidants, flame retardants, foaming agents, and flow regulators.

[0052] (Polyethylene-based wax) The resin composition may further contain a polyethylene-based wax. The polyethylene-based wax may be any wax mainly composed of polyethylene, and may contain more than 50% by mass of polyethylene, but it is preferable that it contains 80% by mass or more of polyethylene, and more preferably 90% by mass or more.

[0053] The melting point of polyethylene-based wax is not particularly limited, but it is preferably between 70°C and 150°C, and more preferably between 80°C and 130°C. A melting point within this range of polyethylene-based wax can further enhance the fluidity of the resin composition. The melting point is measured in accordance with JIS K 7121:2012.

[0054] Polyethylene-based waxes can be commercially available products, including the POLYWAX series from NuCera Solutions, the Hiwax series and Excellex series from Mitsui Chemicals, the Sunwax series from Sanyo Chemical Industries, and Q-112 from Qingdao Sinoplas Hi-New Materia.

[0055] The polyethylene-based wax content in the resin composition is preferably 0.01% to 0.9% by mass, and more preferably 0.1% to 0.7% by mass, relative to the total mass of the resin composition. When the amount of polyethylene-based wax is 0.01% by mass or more, the fluidity of the resin composition can be further increased. On the other hand, when the polyethylene-based wax content is 0.9% by mass or less, bleed-out from the molded product can be further suppressed.

[0056] (Paraffin oil) The paraffin oil is not particularly limited as long as it is liquid at 23°C, and any known paraffin oil can be used. The paraffin oil is, for example, a linear or branched hydrocarbon with 14 to 30 carbon atoms, but it may also contain some cyclic hydrocarbons (naphthenes) or aromatic hydrocarbons.

[0057] The paraffin oil content in the resin composition is preferably 0.01% by mass or more and 0.9% by mass or less, and more preferably 0.1% by mass or more and 0.7% by mass or less, relative to the total mass of the resin composition. When the paraffin oil content is 0.01% by mass or more, the fluidity of the resin composition can be further increased. On the other hand, when the paraffin oil content is 0.9% by mass or less, bleed-out from the molded product can be further suppressed.

[0058] (Lubricant) Examples of lubricants include fatty acids such as stearic acid, hydroxystearic acid, complex stearic acid, and oleic acid; aliphatic alcohols; aliphatic amides such as stearamide, oxystearamide, oleylamide, erucylamide, ricinolamide, behenamide, methylolamide, methylenebisstearoamide, methylenebisstearobehenamide, bisamic acid of higher fatty acids, and complex amides; aliphatic esters such as n-butyl stearate, methyl hydroxystearate, polyhydric alcohol fatty acid esters, saturated fatty acid esters, and ester waxes; and fatty acid metal soaps such as zinc stearate and magnesium stearate.

[0059] The lubricant content in the resin composition is preferably 0.5% by mass or less, and more preferably 0.1% by mass or less, relative to the total mass of the resin composition. The inclusion of a lubricant in the resin composition can further enhance the fluidity of the resin composition during molding. On the other hand, the inclusion of a lubricant in the resin composition makes it difficult to obtain the effect of improving the mechanical strength and rigidity of the molded product by including lignocellulose fibers or acid-modified polyolefin resins. Therefore, from the viewpoint of improving the mechanical strength and rigidity of the molded product, it is preferable to have as little lubricant content as possible, and preferably to have substantially no lubricant.

[0060] (Plasticizer) Examples of plasticizers include, for example, triethyl citrate, acetyl triethyl citrate, dibutyl phthalate, diaryl phthalate, dimethyl phthalate, diethyl phthalate, dioctyl phthalate, di(2-ethylhexyl) phthalate, di-2-methoxyethyl phthalate, dibutyl tartrate, o-benzoyl benzoate, diacetin, and epoxidized soybean oil. The resin composition may contain one of these individually or two or more.

[0061] (Colorants) The colorant may be any known organic pigment, inorganic pigment, or dye. Specific examples of colorants include organic pigments such as azo, anthraquinone, phthalocyanine, quinacridone, isoindolinone, diosadin, perinone, quinophthalone, and perylene pigments, as well as inorganic pigments such as ultramarine, titanium dioxide, titanium yellow, iron oxide (red iron oxide), chromium oxide, zinc oxide, and carbon black. The resin composition may contain one of these individually or two or more.

[0062] (Antioxidant) Examples of antioxidants include phosphorus-based antioxidants, phenol-based antioxidants, and pentaerythritol-based antioxidants. The resin composition may contain one or more of these. Phosphorus-based antioxidant stabilizers, more specifically phosphorus-based phosphate esters and phosphoric acid esters, are preferably used. Examples of phosphorus-based phosphate esters include, for example, triphenyl phosphite, trisnonylphenyl phosphite, tris(2,4-di-t-butylphenyl) phosphite, and other triesters, diesters, and monoesters of phosphorus-based phosphates.

[0063] Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris(nonylphenyl) phosphate, and 2-ethylphenyldiphenyl phosphate.

[0064] Examples of phenolic antioxidants include α-tocopherol, butylhydroxytoluene, cinapyl alcohol, vitamin E, n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-t-butyl-6-(3'-t-butyl-5'-methyl-2'-hydroxybenzyl)-4-methylphenyl acrylate, 2,6-di-t-butyl-4-(N,N-dimethylaminomethyl)phenol, 3,5-di-t-butyl-4-hydroxybenzylphosphonate diethyl ester, and tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxymethyl]methane.

[0065] (Flame retardant) The flame retardant is not particularly limited, but for example, halogenated flame retardants or non-phosphorus halogenated flame retardants such as phosphorus-based flame retardants or metal hydrates can be used. The resin composition may contain one of these alone or two or more of them.

[0066] Examples of halogenated flame retardants include halogenated bisphenol compounds such as halogenated bisphenylalkanes, halogenated bisphenyl ethers, halogenated bisphenyl thioethers, and halogenated bisphenylsulfones, as well as bisphenol-bis(alkyl ether) compounds such as brominated bisphenol A, brominated bisphenol S, chlorinated bisphenol A, and chlorinated bisphenol S. Examples of phosphorus-based flame retardants include aluminum tris(diethylphosphinate), bisphenol A bis(diphenyl phosphate), triarylisopropyl phosphate, cresyl di2,6-xylenyl phosphate, and aromatic condensed phosphate esters. Examples of metal hydrates include aluminum trihydrate, magnesium dihydrate, or combinations thereof.

[0067] Furthermore, the above-mentioned flame retardants may be combined with flame retardant additives. Examples of flame retardant additives include antimony oxides such as antimony trioxide and antimony pentoxide, and other known flame retardant additives.

[0068] (Foaming agent) The blowing agent is not particularly limited as long as it is a compound capable of generating bubbles when mixed with or injected under pressure into a composition that is in a molten state in a melting and mixing machine. Examples of blowing agents include those that change phase from solid to gas to generate bubbles, those that change phase from liquid to gas to generate bubbles, or the gas itself.

[0069] Examples of blowing agents include aliphatic hydrocarbons such as propane, butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane; halogenated hydrocarbons such as chlorodifluoromethane, difluoromethane, trifluoromethane, trichlorofluoromethane, dichloromethane, dichlorodifluoromethane, chloromethane, chloroethane, dichlorotrifluoroethane, dichloropentafluoroethane, tetrafluoroethane, difluoroethane, pentafluoroethane, trifluoroethane, dichlorotetrafluoroethane, trichlorotrifluoroethane, tetrachlorodifluoroethane, and perfluorocyclobutane; inorganic gases such as carbon dioxide, nitrogen, and air; and water.

[0070] The foaming agent may contain the active ingredient of the foaming agent together with the carrier resin. Examples of carrier resins include crystalline olefin resins such as crystalline propylene. Examples of active ingredients include bicarbonates. Of these, bicarbonates are preferred. Preferably, the foaming agent concentrate contains crystalline polypropylene resin as the carrier resin and bicarbonates as a thermal decomposition type foaming agent.

[0071] (Flow modifier) Known fluidity modifiers can also be used. Examples of fluidity modifiers include peroxides such as dialkyl peroxides, for example, 1,4-bis[(t-butylperoxy)isopropyl]benzene.

[0072] (Antistatic agent) Examples of antistatic agents include fatty acid diethanolamides such as lauryl diethanolamide and stearyl diethanolamide; and hydroxyl group-containing compounds, including alcoholamine compounds. Alcoholamines, such as monoethanolamine, diethanolamine, and triethanolamine, are particularly preferred. Two or more antistatic agents can also be used in combination. These antistatic agents may be supported on calcium silicate or calcium carbonate. Furthermore, a range of 8 to 22 carbon atoms in the acyl group of fatty acid diethanolamides is preferred from the viewpoint of exhibiting sufficient antistatic effect.

[0073] The total amount of other components in the resin composition (excluding polyethylene-based wax, paraffin oil, and lubricant) is not particularly limited, but can be, for example, 2% by mass or less of the total mass of the resin composition.

[0074] 2. Method for producing resin compositions The resin composition can be manufactured by mixing the above-mentioned thermoplastic resin, inorganic powder, lignocellulose fiber, acid-modified polyolefin resin, and other components as needed.

[0075] The mixing method is not particularly limited, but may be, for example, by melt kneading. All components may be mixed before melt kneading, or some components may be melt kneaded first and the remaining components may be kneaded afterward. In addition, inorganic powders and lignocellulose fibers may be used in the form of a masterbatch. The apparatus for performing melt kneading is not particularly limited, and general extruders, kneaders, Banbury mixers, etc., can be used. In particular, from the viewpoint of obtaining a resin composition with a uniform composition, kneading with a twin-screw kneader is preferable.

[0076] 3. Molded articles and methods for manufacturing the same By molding the resin composition described above, a molded article containing the resin composition can be obtained.

[0077] The molding method is not particularly limited and may be any of the following: inflation molding, extrusion molding, injection molding, foam injection molding, injection compression molding, blow molding, press molding, calendering, vacuum forming, etc.

[0078] The shape of the molded product is not particularly limited, and it can be used in films, sheets, containers (such as food containers), daily necessities, automotive parts, electrical and electronic components, home appliances, toys, and various consumables. In particular, molded products containing the above resin composition have high mechanical strength and rigidity, making them suitable for applications such as automotive parts and home appliances. [Examples]

[0079] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0080] 1. Preparation of materials The following materials were used in the following examples and comparative examples.

[0081] 1-1.Thermoplastic resin • bPP: Block polypropylene (recycled product, MFR: 70g / 10min, melting point 163℃) • hPP: Homopolypropylene (manufactured by Prime Polymer, MFR: 45g / 10min) The above-mentioned MFR is a value measured at 230°C and under a 2.16 kg load, in accordance with JIS K 7210-1:2014 (ISO 1133-1:2011).

[0082] 1-2.Inorganic powder F-1: Light calcium carbonate powder (calcium carbonate powder made from steel slag, median diameter D50: 5.8 μm, oil absorption: 43 ml / 100 g) • F-2: Light calcium carbonate powder (calcium carbonate powder made from carbide slag, median diameter D50: 6.5 μm) F-3: Heavy calcium carbonate powder (manufactured by Takehara Chemical Co., Ltd., Sunlight SL-1500, median diameter D50: 4.0 μm, oil absorption capacity: 21 ml / 100 g) • F-4: Talc powder (median diameter D50: 6μm) The median diameter D50 mentioned above was measured using a laser diffraction particle size distribution analyzer.

[0083] 1-3. Plant Fibers • Lignocellulose fiber: Masterbatch (Hartland's Narutre 50, 50% hemp fiber by mass, 46% bPP by mass, 4% PE wax by mass, aspect ratio of hemp fiber: tens to hundreds)

[0084] 1-4. Acid-modified polyolefin resins • M-1: Manufactured by Sanyo Chemical Industries, Ltd., U-1010 (acid-modified polypropylene, acid value 52 mg KOH / g, weight-average molecular weight 30,000, softening point 145°C) • M-2: Manufactured by Sanyo Chemical Industries, Ltd., U-1001 (acid-modified polypropylene, acid value 26 mg KOH / g, weight-average molecular weight 45,000, softening point 153°C) • M-3: MG-250P (acid-modified polypropylene, acid value 28 mg KOH / g, weight-average molecular weight 58,000), manufactured by Riken Vitamin Co., Ltd. The weight-average molecular weight mentioned above is a value measured in polystyrene equivalent by gel permeation chromatography (GPC). The acid value is a value measured according to JIS K 0070:1992.

[0085] 1-5. Others • Zinc stearate (manufactured by NOF Corporation, a metallic soap)

[0086] 2. Preparation of resin composition and production of molded articles 2-1. Preparation of resin compositions 1 to 26 Each component shown in Tables 1 to 3 was mixed in the mass ratios shown in the same tables and fed into a Parker HK-25D co-rotating twin-screw compounding extruder (φ25mm, L / D=41). The mixture was melt-kneaded at a cylinder temperature of 215°C and a rotation speed of 50 rpm for approximately 8 to 15 minutes, after which it was extruded into strands. After the extruded resin composition was cooled, it was pulverized to obtain pulverized resin composition.

[0087] 2-2. Evaluation The tensile properties, bending properties, impact resistance, and moldability of the obtained resin composition were evaluated by the following methods.

[0088] 2-2-1. Tensile properties The resulting pulverized resin composition was fed into an injection molding machine to produce dumbbell-shaped (Type 1A) test specimens according to JIS K 7161-2:2014. Using this test specimen, the tensile strength was measured in accordance with JIS K 7161-2:2014 under conditions of 23°C and 50% RH using an Autograph AG-100kNXplus (Shimadzu Corporation). The elongation rate was 5 mm / min.

[0089] 2-2-2. Bending properties The pulverized resin composition obtained was fed into an injection molding machine to produce test specimens conforming to JIS K 7171:2016, with a length of 80 mm, a width of 10 mm, and a thickness of 4 mm. Using this test specimen, the bending strength and bending modulus were measured at a speed of 2 mm / min using an Autograph AG-100kNXplus (Shimadzu Corporation) under conditions of 23°C and 50%RH, in accordance with JIS K 7171:2016.

[0090] 2-2-3. Impact resistance The pulverized resin composition obtained was fed into an injection molding machine to produce test specimens conforming to JIS K 7171:2016, with a length of 80 mm, a width of 10 mm, and a thickness of 4 mm. Using this test specimen, an impact resistance test was conducted in accordance with ISO 179 / 1eA.

[0091] 2-2-4.Moldability The MFR of the resin composition was measured according to K7210:2014 and evaluated according to the following criteria. A: No gas generation, and MFR is 15g / 10min or higher. B: No gas generation, and MFR is between 10g / 10min and 15g / 10min. C: No gas generation, and MFR is 5g / 10min or more but less than 10g / 10min. D: Gas generation occurs, or viscosity increases beyond a certain level. We determined that moldability was more stable if the result was C or higher.

[0092] 2-2-5. SEM Observation The fracture surface of a dumbbell piece made of resin composition 1, when broken in half, was observed using a scanning electron microscope (SEM) at 15kV and a magnification of 100 to 1000x.

[0093] The evaluation results for resin compositions 1-8 are shown in Table 1, the evaluation results for resin compositions 9-18 are shown in Table 2, and the evaluation results for resin compositions 19-26 are shown in Table 3. Figures 1A-1D are SEM images of the fracture surface of a dumbbell piece of resin composition 1. Figure 1A is a photograph of the fracture surface of the dumbbell piece observed at 100x magnification, and Figures 1B-1D are photographs of multiple locations observed at 1000x magnification. In the tables, "-" indicates that measurement was not performed.

[0094] [Table 1]

[0095] [Table 2]

[0096] [Table 3]

[0097] As shown in Table 3, resin compositions 19-20, which contain inorganic powder but do not contain either acid-modified polyolefin resin or lignocellulose fibers, exhibit low flexural and tensile strength. Furthermore, resin composition 22, which contains inorganic powder and acid-modified polyolefin resin but does not contain lignocellulose fibers, exhibits low flexural modulus and poor rigidity. Additionally, resin composition 21, which contains inorganic powder and lignocellulose fibers but does not contain acid-modified polyolefin resin, still exhibits low flexural and tensile strength. Furthermore, it was found that resin composition 25, which contains a large amount of lignocellulose fibers, generates gas during molding and exhibits poor moldability. Additionally, it was found that resin composition 26, which contains a large amount of acid-modified polyolefin resin, exhibits low fluidity during molding and poor moldability.

[0098] In contrast, as shown in Tables 1 and 2, resin compositions 1 to 18, which contain inorganic powder and acid-modified polyolefin resin and lignocellulose fibers, yield molded articles with high bending strength, tensile strength, and rigidity while maintaining moldability.

[0099] Furthermore, as shown in Figures 1A to 1D, holes where fibers have been removed are observed on the fracture surface, and it can be seen that fibers are attached around the holes. In other words, it can be seen that the fracture does not occur at the interface between the resin and the fibers, but rather between the fibers themselves. From this, it can be inferred that by including an acid-modified polyolefin resin in addition to hemp fibers, a strong interaction (covalent bond) is formed between the resin and the fibers, contributing to the improvement of tensile strength and flexural strength.

[0100] In particular, it can be seen that the higher the acid value of the acid-modified polyolefin resin, the more significantly the tensile strength and flexural strength improve (comparison of resin compositions 2, 13, and 14).

[0101] Furthermore, it can be seen that moldability and impact resistance are further improved when the thermoplastic resin is block polypropylene (comparison of resin compositions 1 and 18).

[0102] Furthermore, visual inspection of the molded products for resin compositions 1 and 15-17 revealed that those using F-1 (light calcium carbonate) as the inorganic powder produced less gas and discoloration during molding than those using F-3 (heavy calcium carbonate) or F-4 (talc). This is thought to be because lignin generated from hemp fibers during molding was adsorbed more readily by the light calcium carbonate, which has a larger surface area.

[0103] Furthermore, generally speaking, the higher the rigidity of a molded product, the lower its impact resistance (Charpy impact strength) tends to be. In contrast, it can be seen that by incorporating lignocellulose fibers and acid-modified polyolefin resin in the presence of inorganic powder, impact resistance can be maintained well even when rigidity is increased (comparison of resin compositions 1, 2, 19, and 20).

[0104] Furthermore, while the inclusion of a lubricant improves moldability, the absence of a lubricant significantly improves flexural modulus, tensile strength, and bending strength (for example, comparing resin compositions 1 and 4, and resin compositions 2 and 6). [Industrial applicability]

[0105] According to the resin composition of the present invention, it is possible to obtain molded articles that enable stable molding and achieve both good mechanical strength and rigidity.

Claims

1. A resin composition, The material comprises an acid-modified polyolefin resin, a thermoplastic resin other than the acid-modified polyolefin resin, an inorganic powder, and lignocellulose fibers. The mass ratio of the thermoplastic resin to the inorganic powder is 10:90 to 60:

40. The lignocellulose fiber content is 1.0% by mass or more and 10.0% by mass or less relative to the resin composition. The content of the acid-modified polyolefin resin is 1.0% by mass or more and 5.0% by mass or less relative to the resin composition. Resin composition.

2. The thermoplastic resin includes a polyolefin resin. The resin composition according to claim 1.

3. The aforementioned polyolefin resin includes a polypropylene resin. The resin composition according to claim 2.

4. The aforementioned polypropylene resin includes block polypropylene, The resin composition according to claim 3.

5. The mass ratio of the thermoplastic resin to the inorganic powder is 10:90 to 50:

50. The resin composition according to claim 1.

6. The inorganic powder includes calcium carbonate powder. The resin composition according to claim 1.

7. The lignocellulose fiber includes hemp fiber. The resin composition according to claim 1.

8. The acid value of the acid-modified polyolefin resin according to JIS K 0070:1992 is 20 mg KOH / g or more and 60 mg KOH / g or less. The resin composition according to claim 1.

9. A resin composition comprising any one of claims 1 to 8, Molded products.

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