Inorganic powder-filled resin compositions and molded articles

Abstract

This invention provides an inorganic powder-filled resin composition capable of manufacturing molded articles with good mechanical properties, flexibility, excellent processability, and a good surface appearance, as well as molded articles composed of such a resin composition. The inorganic powder-filled resin composition contains a thermoplastic resin and inorganic powder in a mass ratio of 50:50 to 10:90, characterized in that the thermoplastic resin comprises a propylene homopolymer and a propylene block copolymer, wherein the content of the propylene block copolymer is 10 to 30 parts by mass relative to 100 parts by mass of the propylene homopolymer. Furthermore, it may contain maleic anhydride-modified polypropylene in an amount of 0.5 to 3.0 parts by mass.

Description

Technical Field

[0001] This invention relates to inorganic powder-filled resin compositions and molded articles. More specifically, this invention relates to resin compositions that, despite being highly filled with inorganic powder in a thermoplastic resin, still possess good mechanical properties and flexibility, and also exhibit excellent molding processability and a good surface appearance, as well as molded articles made from such resin compositions. Background Technology

[0002] Thermoplastic resins have long been widely used, alongside paper derived from forest resources, as materials for various molded products, food packaging, and general consumer goods in both industrial and household applications. However, with environmental protection becoming an increasingly important international issue, the reduction of thermoplastic resin and paper consumption has been extensively discussed, alongside the pursuit of making these materials non-toxic, recyclable, and incinerable. Based on this, a novel approach has been proposed: thermoplastic resin compositions containing inorganic powders, primarily calcium carbonate, are highly filled into the thermoplastic resin, and this approach has already been put into practical use (see, for example, Patent Document 1).

[0003] However, resin compositions heavily filled with inorganic powder are generally less flexible and more brittle compared to conventional thermoplastic resins without inorganic powder. Therefore, molded products from such heavily filled resin compositions often suffer from insufficient mechanical properties such as elongation and tensile strength during stretching, leading to breakage during use. Furthermore, resin compositions heavily filled with inorganic powder also present challenges in molding and processing, particularly in injection molding, resulting in low production efficiency and the formation of undesirable appearances such as flow marks (tiger stripes) on molded products. These problems are especially prevalent in recycled products, particularly those containing inks used as paper substitutes.

[0004] As a means of improving the mechanical properties and moldability of resin compositions, techniques for mixing modified polymers and elastomer components are known. For example, Patent Documents 2 and 3 disclose resin compositions containing modified polyolefins, ethylene vinyl acetate copolymers, etc., together with thermoplastic resins such as polypropylene and fillers. Patent Document 4 describes a polypropylene resin, an elastomer having polar functional groups, and a polypropylene resin composition containing fillers.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-10931

[0008] Patent Document 2: Japanese Patent Application Publication No. 2010-106270

[0009] Patent Document 3: Japanese Patent Application Publication No. 2019-178265

[0010] Patent Document 4: Japanese Patent Application Publication No. 2019-99807 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] It is believed that the modified polymers or copolymers mixed in the resin composition form chemical bonds with the fillers, thereby improving mechanical properties by strengthening the interface. Therefore, polymers with polar groups are mostly used as such polymers, and maleic anhydride-modified polypropylene is also exemplified in the aforementioned Patent Documents 2-4. However, even when such polymers containing polar groups are mixed in highly filled resin compositions, mechanical properties and moldability are not necessarily improved. As shown in the examples and comparative examples described later, when the mixed polymers are not appropriate, the highly filled resin composition may sometimes become brittle or develop molding defects such as tiger stripes. The same applies to elastomer components; if the types of elastomers are not carefully selected, the mechanical properties of the resin composition will not be sufficiently improved.

[0013] The present invention was made in view of the above facts and the object of the invention is to provide an inorganic powder-filled resin composition capable of manufacturing molded articles with good mechanical properties, good flexibility, excellent processability and good surface appearance, and a molded article made of the resin composition.

[0014] Solution for solving the problem

[0015] To address the aforementioned issues, the inventors conducted in-depth research and discovered that in a highly filled resin composition, the thermoplastic resin component comprises propylene homopolymer and propylene block copolymer. If the content of the propylene block copolymer is between 10 and 30 parts by mass relative to 100 parts by mass of the propylene homopolymer, a thermoplastic resin composition with softness and good mechanical properties can be obtained. Furthermore, if the resin composition also contains maleic anhydride-modified polypropylene, molded articles with excellent moldability and good surface appearance can be obtained, thereby achieving the present invention.

[0016] The present invention is an inorganic powder-filled resin composition containing thermoplastic resin and inorganic powder in a mass ratio of 50:50 to 10:90. The thermoplastic resin comprises propylene homopolymer and propylene block copolymer, wherein the content of the propylene block copolymer is more than 10 parts by mass and less than 30 parts by mass relative to 100 parts by mass of the propylene homopolymer.

[0017] In one embodiment of the inorganic powder-filled resin composition according to the present invention, the inorganic powder-filled resin composition further contains maleic anhydride-modified polypropylene in an amount of 0.5 to 3.0 parts by mass relative to 100 parts by mass of the thermoplastic resin relative to the total mass of the inorganic powder-filled resin composition.

[0018] In one embodiment of the inorganic powder-filled resin composition according to the present invention, an inorganic powder-filled resin composition is shown, wherein the maleic anhydride-modified polypropylene has a mass-average molecular weight of 25,000 to 35,000 and a grafting amount of 3.0% to 4.9% by mass.

[0019] In one embodiment of the inorganic powder-filled resin composition according to the present invention, an inorganic powder-filled resin composition in which the inorganic powder is heavy calcium carbonate is shown.

[0020] In one embodiment of the inorganic powder-filled resin composition according to the present invention, the heavy calcium carbonate is shown as an inorganic powder-filled resin composition containing heavy calcium carbonate particles with an average particle size of 0.7 μm to 6.0 μm as determined by the air permeation method according to JIS M-8511.

[0021] The present invention, which addresses the above-mentioned problems, is also a molded article composed of the above-mentioned inorganic powder-filled resin composition.

[0022] In one embodiment of the molded article involved in this invention, the molded article is an injection-molded article.

[0023] Invention Effects

[0024] According to the present invention, an inorganic powder-filled resin composition capable of manufacturing molded articles with good mechanical properties, high flexibility, excellent processability, and good surface appearance is provided, as well as molded articles composed of such resin compositions. The inorganic powder-filled resin composition of the present invention exhibits particularly excellent flexibility and high impact strength, and also has the advantage of not easily causing undesirable appearances such as tiger stripes in the molded articles. Attached Figure Description

[0025] Figure 1 Photographs illustrating the flexibility test method in the embodiments, and showing test examples of inorganic powder-filled resin composition molded articles according to Embodiment 2 of the present invention. Detailed Implementation

[0026] The present invention will now be described in detail based on its embodiments.

[0027] Inorganic Powder Filled Resin Composition

[0028] The inorganic powder-filled resin composition of the present invention contains a thermoplastic resin and an inorganic powder in a mass ratio of 50:50 to 10:90. The thermoplastic resin comprises a propylene homopolymer and a propylene block copolymer, wherein the content of the propylene block copolymer is 10 to 30 parts by mass relative to 100 parts by mass of the propylene homopolymer. Hereinafter, each component constituting the inorganic powder-filled resin composition (hereinafter sometimes simply referred to as the "resin composition") of the present invention will be described in detail.

[0029] <Propylene homopolymer>

[0030] Propylene homopolymer (hereinafter sometimes simply referred to as "PP") is essentially a polymer formed by polymerizing only propylene, exhibiting excellent rigidity and heat resistance. A wide variety of commercially available products are available, including, for example, WINTEC (registered trademark) and Novatec (registered trademark) from Nippon Polypro Co., Ltd., NOBLEN (registered trademark) from Sumitomo Chemical Co., Ltd., Prime Polypro (registered trademark) from Prime Polymer Co., Ltd., TORAYCA (registered trademark) from Toray Industries, Inc., SABIC (registered trademark) PP from SABIC Cetrochemicals, and SUN-ALLOMER (registered trademark) from SunAllomer Co., Ltd., etc. However, this invention is not limited to these and may contain any type of PP. Multiple types of PP may also be used in combination.

[0031] Propylene homopolymers can be classified into isotactic PP, syndiotactic PP, atactic PP, and hemiisotactic PP based on their stereoregularity. The resin composition of the present invention may contain any one of these, or a combination of them. Furthermore, the homopolymer may contain trace components generated as byproducts during polymerization or have a branched structure. There are no particular limitations on its molecular weight. However, in the present invention, PP with a mass average molecular weight of 50,000 to 500,000, particularly 100,000 to 400,000, is preferably used as the PP. Generally, higher molecular weight results in superior mechanical properties such as strength, while lower molecular weight results in superior moldability. PP with a mass average molecular weight of 50,000 to 200,000 and PP with a mass average molecular weight of 200,000 to 500,000 can also be used in combination. By using PP with different molecular weights, moldability can be improved and defects in the appearance of the molded articles can be reduced.

[0032] <Propylene block copolymer>

[0033] Propylene block copolymers are copolymers composed of continuous blocks of propylene monomers and continuous blocks of other monomeric components. Here, there are no particular limitations on the monomeric components copolymerized with propylene, and the block copolymer is not limited to a binary system, but can also be a ternary system, quaternary system, etc. There are also no particular limitations on the copolymerization ratio of each monomer, the length of each block, the overall molecular weight, etc. However, in this invention, block copolymers composed of propylene and other α-olefins are preferred. If it is a block copolymer of propylene and α-olefins, due to its excellent compatibility with propylene homopolymers, the resin composition of this invention exhibits further improved mechanical properties and moldability.

[0034] Block copolymers of propylene and α-olefins are well known, and various commercially available varieties exist. Examples include Novatec (registered trademark) of Polypro Corporation of Japan, PrimePolypro (registered trademark) of Prime Polymer Co., Ltd., Umex (registered trademark) of Sanyo Chemical Industry Co., Ltd., and SUN-ALLOMER (registered trademark) of SunAllomer Co., Ltd., but this invention is not limited to these, and may contain any propylene block copolymer. Two or more block copolymers may also be used together. There are no particular limitations on the comonomers used with propylene; for example, it may be one or more monomer components selected from ethylene and α-olefins having 4 to 10 carbon atoms. Examples include ethylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1-heptene, 3-methyl-1-hexene, 1-octene, etc., but this invention is not limited to these. The preferred copolymers are those with ethylene, 1-butene, isobutene, 1-hexene, and / or 1-octene, especially with ethylene. The copolymerization ratio and molecular weight are not particularly limited, but copolymers derived from α-olefins as comonomers are preferably used at 5% by mass or more, more preferably 7% by mass or more, and especially preferably 8% by mass or more. Furthermore, copolymers with 35% by mass or less, more preferably 25% by mass or less, further preferably 20% by mass or less, and especially preferably 18% by mass or less are preferred. These block copolymers are flexible and have excellent compatibility with propylene homopolymers, thus exhibiting particularly excellent mechanical properties and moldability when mixed in the inorganic powder-filled resin composition of the present invention.

[0035] Block copolymers of propylene and α-olefins may also contain structural units derived from dienes, carboxylic acid (ester) modified olefins, etc. Examples of dienes include 1,4-hexadiene, 1,6-octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, dicyclopentadiene (DCPD), ethylene norbornene (ENB), norbornadiene, and 5-vinyl-2-norbornene; examples of carboxylic acid (ester) modified olefins include carboxyl-containing olefins, but are not limited thereto. Copolymers containing structural units derived from these third components, for example, 0.1–10% by mass, particularly 0.5–8% by mass, and of which 1–5% by mass, sometimes exhibit different melting behavior and compatibility than the block copolymers without the third component. The physical properties and processability of the inorganic powder-filled resin compositions of the present invention can be controlled according to their mixing. Structural units derived from dienes can also serve as crosslinking sites, thus allowing the processability of the block copolymers to be partially crosslinked by mixing them with crosslinking agents such as peroxides and other components. Furthermore, by using the block copolymers with functional groups such as carboxylic acid groups, the miscibility with inorganic powders is sometimes improved, and the physical properties and formability are enhanced.

[0036] The properties of the aforementioned propylene block copolymers encompass various aspects, including, for example, a weight-average molecular weight range of 20,000–5,000,000, typically 50,000–1,000,000, and particularly around 70,000–400,000; and a density of 0.84–0.92 g / cm³. 3 Typical values ​​are 0.85–0.91 g / cm³. 3 The range is approximately 0.5% to 40%, typically 5% to 25%; the melt flow rate (MFR at 230°C, 2.16 kg according to ASTM D1238) is approximately 0.1% to 90 g / 10 min, typically 0.5% to 30 g / 10 min; the melting temperature is approximately 120% to 180°C, typically 150% to 170°C, especially 160% to 165°C, but not limited thereto. The present invention may use propylene-α-olefin copolymers of any properties.

[0037] However, in this invention, the propylene block copolymer is preferably a propylene-ethylene block copolymer composed of propylene blocks and ethylene-propylene copolymer blocks. More preferably, a block copolymer using propylene-derived structural units of 80% or more by mass and ethylene-derived structural units of 20% or less by mass is used; particularly, a block copolymer using propylene-derived structural units of 82-92% by mass and ethylene-derived structural units of 8-18% by mass; wherein, a block copolymer using propylene-derived structural units of 84-90% by mass and ethylene-derived structural units of 10-16% by mass is used. Such a polymer can be manufactured, for example, by polymerizing propylene alone and then copolymerizing ethylene. Generally, in propylene-ethylene block copolymers, a so-called island structure of phase dispersion of ethylene-propylene copolymer blocks is found in the continuous phase of the dedicated propylene polymerization. Ethylene-propylene copolymers are generally soft, thus giving the inorganic powder-filled resin composition flexibility. Moreover, the continuous phase and the propylene homopolymer have almost the same composition, resulting in excellent compatibility. Therefore, separation does not occur in the inorganic powder-filled resin composition of this invention, thereby providing good mechanical properties and moldability.

[0038] The inorganic powder-filled resin composition of the present invention contains propylene block copolymers in an amount of 10 to 30 parts by mass, preferably 15 to 28 parts by mass, and more preferably 20 to 25 parts by mass, relative to 100 parts by mass of the propylene homopolymer. When the content of the propylene block copolymers is 10 parts by mass or more, the inorganic powder-filled resin composition of the present invention exhibits excellent mechanical properties, such as high flexibility, impact strength, and particularly excellent tensile properties. Furthermore, when the content is 30 parts by mass or less, excellent rigidity, heat resistance, and moldability are maintained. To achieve these excellent properties, the content of the propylene block copolymers is also based on 100% of the total mass of the inorganic powder-filled resin composition of the present invention, preferably 1 to 11.5% by mass, further 3 to 11% by mass, and particularly 5 to 10% by mass.

[0039] <Maleic anhydride modified polypropylene>

[0040] The inorganic powder-filled resin composition of the present invention may further contain maleic anhydride-modified polypropylene as a thermoplastic resin component. By containing maleic anhydride-modified polypropylene, the moldability, especially the injection molding properties, of the inorganic powder-filled resin composition of the present invention are improved, and defects such as tiger stripes on the molded articles can be reduced.

[0041] There is no particular limitation on the weight-average molecular weight of maleic anhydride-modified polypropylene, but it is preferably between 25,000 and 35,000, and more particularly between 28,000 and 32,000. If the weight-average molecular weight is within the above range, it separates from the thermoplastic resin without adversely affecting the physical properties of the resin composition, thus more reliably improving moldability and reducing adverse effects such as tiger stripes. There is also no particular limitation on the grafting amount (modification rate) of maleic anhydride, for example, it can be grafted up to about 6.0% by mass. However, for the same reasons as with the weight-average molecular weight, the grafting amount of maleic anhydride in maleic anhydride-modified polypropylene is preferably between 3.0% and 4.9% by mass, and more particularly preferably between 3.5% and 4.8% by mass. When the grafting amount of maleic anhydride becomes about 5% by mass or more, the physical properties of the resin composition, such as flexibility, may sometimes decrease. Such maleic anhydride-modified polypropylene can be obtained, for example, by reacting the desired polypropylene with the desired amount of maleic anhydride in the presence of peroxides or the like. However, a wide variety of commercially available products are available, and preferred varieties can be selected for use.

[0042] The content of maleic anhydride-modified polypropylene in the inorganic powder-filled resin composition of the present invention can be 0.5 parts by weight or more and 3.0 parts by weight or less, more preferably 0.7 parts by weight or more and 2.0 parts by weight or less, and particularly preferably 0.8 parts by weight or more and 1.5 parts by weight or less, relative to 100 parts by weight of the total inorganic powder-filled resin composition. If the content of maleic anhydride-modified polypropylene is 0.5 parts by weight or more, adverse conditions such as tiger stripes can be significantly reduced. Furthermore, if it is 3.0 parts by weight or less, the risk of separation from the aforementioned thermoplastic resin can be avoided, and good mechanical properties can be maintained.

[0043] In the inorganic powder-filled resin composition of the present invention, the thermoplastic resin is configured to contain the aforementioned propylene homopolymer and propylene block copolymer, and maleic anhydride-modified polypropylene as desired, but may also contain other resin components. Examples include thermoplastic resins such as poly(meth)acrylate, polyvinyl acetate, polyacrylonitrile, polystyrene, ABS resin, polycarbonate, polyamide, polyvinyl alcohol, petroleum hydrocarbon resin, and benzofuran-indene resin; and elastomers such as styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-butadiene-ethylene copolymer, styrene-isoprene-ethylene copolymer, acrylonitrile-butadiene copolymer, and fluorinated elastomers. By mixing these resin components, the components in the inorganic powder-filled resin composition are sometimes more uniformly dispersed, and the physical properties and processability are improved.

[0044] However, in the inorganic powder-filled resin composition of the present invention, from the viewpoint of the compatibility of various resin components, the thermoplastic resin component is preferably 90% by mass or more, more preferably 97% by mass or more, and particularly preferably substantially composed of the aforementioned propylene homopolymer and propylene block copolymer, or of the aforementioned propylene homopolymer, propylene block copolymer, and maleic anhydride-modified polypropylene. If the inorganic powder-filled resin composition substantially does not contain any resin components other than these, a portion of the resin components will hardly separate, and a decrease in mechanical properties and moldability can be prevented. The inorganic powder-filled resin composition of the present invention preferably contains, relative to the total mass, 9 to 45% by mass, particularly 15 to 40% by mass, particularly 20 to 38% by mass of propylene homopolymer, 1 to 11.5% by mass, particularly 3 to 11% by mass of propylene block copolymer, 0% by mass or 0.5 to 3.0% by mass, particularly 0.7 to 2.0% by mass of maleic anhydride-modified polypropylene, and 90 to 50% by mass, particularly 80 to 52% by mass of the inorganic powder described later.

[0045] <Inorganic Powder>

[0046] The inorganic powder-filled resin composition of the present invention contains the aforementioned thermoplastic resin and inorganic powder. The inorganic powder is not particularly limited; examples include powdered substances such as carbonates, sulfates, silicates, phosphates, borates, oxides, or hydrates of calcium, magnesium, aluminum, titanium, iron, zinc, etc. Specifically, examples include calcium carbonate, magnesium carbonate, zinc oxide, titanium oxide, silicon dioxide, aluminum oxide, talc, kaolin, etc., 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, silash, calcium sulfite, sodium sulfate, potassium titanate, bentonite, wollastonite, dolomite, graphite, etc. These can be synthetic or derived from natural minerals, and can be contained individually or in combination of two or more types.

[0047] Furthermore, the shape of the inorganic powder is not particularly limited; it can be any shape, such as particle, flake, granule, or fibrous. In addition, as a particle, it can be a spherical particle obtained by general synthesis or an irregularly shaped particle obtained by crushing collected natural minerals.

[0048] The preferred inorganic powders are calcium carbonate, magnesium carbonate, zinc oxide, titanium dioxide, silicon dioxide, aluminum oxide, talc, clay such as kaolin, aluminum hydroxide, magnesium hydroxide, etc., and especially those containing calcium carbonate. Furthermore, the calcium carbonate can be any of the following: a substance prepared by synthesis, so-called light calcium carbonate, or so-called heavy calcium carbonate obtained by mechanically crushing and classifying natural raw materials with limestone or other CaCO3 as the main component; or a combination of these substances.

[0049] However, in this invention, it is preferable to use inorganic powder containing heavy calcium carbonate. Here, heavy calcium carbonate is obtained by mechanically crushing and processing natural limestone, etc., and is clearly distinguished from synthetic calcium carbonate produced by chemical precipitation reactions, etc. Furthermore, there are dry and wet crushing methods, but the dry method is preferred.

[0050] For example, unlike light calcium carbonate produced by synthesis, heavy calcium carbonate particles are characterized by surface amorphization and a large specific surface area due to the fact that particle formation occurs through a pulverization process. Because of this amorphization and large specific surface area, heavy calcium carbonate particles, when compounded in thermoplastic resins, have more contact interfaces than the thermoplastic resin, which is effective for uniform dispersion.

[0051] Although not specifically defined, the specific surface area of ​​heavy calcium carbonate particles is also affected by their average particle size, but a value of 3,000 cm⁻¹ is desirable. 2 / g or more 35,000cm 2 The specific surface area is approximately / g or less. The specific surface area referred to here is obtained by the air permeation method. When the specific surface area is within this range, there is a tendency to suppress the decrease in the processability of the obtained molded product.

[0052] Furthermore, the amorphous nature of the heavy calcium carbonate particles can be represented by the low degree of sphericity of the particle shape. Although not particularly limited, specifically, the roundness is 0.50 to 0.95, more preferably 0.55 to 0.93, and even more preferably 0.60 to 0.90. When the roundness of the heavy calcium carbonate particles is within this range, the strength and processability of the molded article are also appropriate. Furthermore, here, roundness is expressed as (projected area of ​​the particle) / (area of ​​a circle having the same circumference as the projected perimeter of the particle). The method for measuring roundness is not particularly limited; for example, the projected area and projected perimeter of the particle can be measured by microscopic photographs, or commercially available image analysis software can be used.

[0053] Furthermore, to improve the dispersibility or reactivity of inorganic powders, the surface can be modified using common methods. Examples of surface modification methods include physical methods such as plasma treatment, and chemical surface treatment methods using coupling agents or surfactants. Examples of coupling agents include silane coupling agents and titanium coupling agents. Surfactants can be anionic, cationic, nonionic, or amphoteric, and examples include higher fatty acids, higher fatty acid esters, higher fatty acid amides, and higher fatty acid salts. Conversely, the surface may also contain inorganic powders that have not undergone surface treatment.

[0054] The inorganic powder, such as heavy calcium carbonate particles, is not particularly limited, but its average particle size is preferably 0.5 μm to 9.0 μm, more preferably 0.7 μm to 6.0 μm, even more preferably 1.0 μm to 4.0 μm, and especially preferably 1.2 μm to 3.0 μm. Furthermore, the average particle size of the inorganic powder described in this specification refers to a value calculated from the measurement results of the specific surface area determined according to the air permeation method of JIS M-8511. For example, the specific surface area measuring device SS-100 manufactured by Shimadzu Corporation is preferably used as the measuring instrument. When the average particle size is greater than 9.0 μm, for example, in the case of forming a sheet-like molded article, although it also depends on the layer thickness of the molded article, the inorganic powder may protrude from the surface of the molded article, potentially causing powder shedding or damage to surface properties and mechanical strength. It is particularly preferable that the particle size distribution does not contain particles with a particle size of 45 μm or larger. On the other hand, when the particles become too fine, the viscosity may increase significantly when mixed with the resin, making it difficult to manufacture the molded article. Such problems can be prevented by making the average particle size of the inorganic powder 0.5 μm or more, further 0.7 μm or more and 6.0 μm or less, and especially 1.0 μm or more and 3.0 μm or less.

[0055] As described above, in this invention, calcium carbonate is preferably used as the inorganic powder. It is desirable that this calcium carbonate may also contain a first calcium carbonate with an average particle size of 0.5 μm or more and less than 2.0 μm, particularly 0.7 μm or more and less than 2.0 μm, as determined by the air permeation method of JIS M-8511, and a second calcium carbonate with an average particle size of 2.0 μm or more and less than 9.0 μm, particularly 2.0 μm or more and less than 6.0 μm, as determined by the air permeation method of JIS M-8511. This improves the surface properties, printability, adhesion, and other physical properties of the molded article. Furthermore, the unevenness of the calcium carbonate is suppressed, resulting in molded articles with good appearance and mechanical properties such as elongation at break, and also reducing the shedding of calcium carbonate from the resin composition molded article. Although not specifically limited, when the average particle size of the first calcium carbonate is set as 'a' and the average particle size of the second calcium carbonate is set as 'b', it is desirable that the a / b ratio be approximately 0.85 or less, more preferably 0.10 to 0.70, and even more preferably around 0.10 to 0.50. This is because by using substances with such a clearly defined difference in average particle size, particularly superior effects can be expected. Furthermore, the coefficient of variation (Cv) of the particle size (μm) distribution of the first and second calcium carbonates is desirable to be around 0.01 to 0.10, and particularly desirable to be around 0.03 to 0.08. If the deviation in particle size defined by the coefficient of variation (Cv) is at this level, it is considered that each powder group can provide a more complementary effect. The mass ratio of the first calcium carbonate to the second calcium carbonate is preferably 90:10 to 98:2, and particularly around 92:8 to 95:5. Three or more groups of calcium carbonates with different average particle size distributions can also be used. Furthermore, both the first calcium carbonate and the second calcium carbonate are preferably surface-treated heavy calcium carbonate.

[0056] The inorganic powder-filled resin composition of the present invention contains the aforementioned thermoplastic resin and inorganic powder in a mass ratio of 50:50 to 10:90. This is because when the content of inorganic powder is low, it is difficult to obtain the physical properties of the resin composition, such as texture and strength; when it is excessive, mixing and molding become difficult, and the flexibility becomes insufficient. The ratio of the total mass of thermoplastic resin to inorganic powder to the total mass of inorganic powder is preferably 52% by mass or more, more preferably 55% by mass or more. The upper limit of this ratio is preferably 80% by mass or less, more preferably 75% by mass or less, and particularly preferably 70% by mass or less. When considering that the flexibility of the inorganic powder-filled resin composition may be greatly affected by the propylene block copolymer, the mass ratio of propylene block copolymer to inorganic powder can be specified together with the above-mentioned mass ratio. By setting the mass ratio of the propylene block copolymer to the inorganic powder to, for example, 3:97 to 25:75, further to 5:95 to 20:80, and in the range of 10:90 to 18:82, a resin composition with a particularly excellent balance between softness and strength can be prepared.

[0057] <Other Additives>

[0058] Other additives may be mixed as adjuvants as needed in the inorganic powder-filled resin composition according to the present invention. Other additives may include, for example, colorants, lubricants, coupling agents, flow modifiers (flow regulators), crosslinking agents, dispersants, antioxidants, UV absorbers, flame retardants, stabilizers, antistatic agents, foaming agents, plasticizers, etc. These additives may be used alone or in combination of two or more. Furthermore, these additives may be mixed during the mixing process described later, or they may be pre-mixed in the raw material components before the mixing process. In the inorganic powder-filled resin composition according to the present invention, the amount of these other additives added is not particularly limited as long as it does not impair the desired physical properties and processability. However, for example, when the total mass of the inorganic powder-filled resin composition is 100%, it is desirable to mix these other additives at a ratio of about 0 to 10% by mass, particularly about 0.04 to 5% by mass, and at a ratio of less than 10% by mass in the total mass of the other additives.

[0059] The following are examples of what we consider important, but we are not limited to them.

[0060] Examples of plasticizers include triethyl citrate, acetyl triethyl citrate, dibutyl phthalate, diaryl phthalate, dimethyl phthalate, diethyl phthalate, di-2-methoxyethyl phthalate, dibutyl tartrate, benzoylbenzoate, glyceryl diacetate, and epoxidized soybean oil. These plasticizers are typically mixed in at a concentration of about a few percent by weight relative to the thermoplastic resin, but the amount is not limited to this range; approximately 20 to 50 parts by weight of epoxidized soybean oil may also be mixed depending on the purpose of the molded article. However, in the inorganic powder-filled resin composition of the present invention, the mixing amount relative to 100 parts by weight of the thermoplastic resin is preferably about 0.5 to 10 parts by weight, and more particularly about 1 to 5 parts by weight.

[0061] As a coloring agent, any known organic or inorganic pigment or dye can be used. Specifically, examples include organic pigments such as azo, anthraquinone, phthalocyanine, quinacridone, isoindolinone, dioxazine, pyrene, quinophthalone yellow, and perylene pigments, as well as inorganic pigments such as ultramarine, titanium dioxide, titanium yellow, iron oxide (red iron), chromium oxide, zinc oxide, and carbon black.

[0062] Examples of lubricants include fatty acid-based lubricants such as stearic acid, hydroxystearic acid, complex stearic acid, and oleic acid; aliphatic alcohol-based lubricants; aliphatic amide-based lubricants such as stearamide, oxystearamide, oleamide, erucyl amide, castor oil amide, behenamide, hydroxymethyl amide, methylene bis-stearamide, methylene bis-stearic acid, and complex amides of higher fatty acids; aliphatic ester-based lubricants such as n-butyl stearate, methyl hydroxystearate, polyol fatty acid esters, saturated fatty acid esters, and ester waxes; and fatty acid metal soap-based lubricants, such as zinc stearate.

[0063] As antioxidants, phosphorus-based antioxidants, phenolic antioxidants, and pentaerythritol-based antioxidants can be used. Phosphorus-based antioxidants are preferred, and more specifically, phosphorus-based antioxidant stabilizers such as phosphites and phosphates. Examples of phosphites include triphenyl phosphite, trinonylphenyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, and other triesters, diesters, and monoesters of phosphites.

[0064] Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tri(nonyl) phosphate, and 2-ethylphenyl diphenyl phosphate. These phosphorus-based antioxidants can be used alone or in combination of two or more.

[0065] Examples of phenolic antioxidants include α-tocopherol, butylated hydroxytoluene, sinapoxetine, vitamin E, n-octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2-tert-butyl-6-(3'-tert-butyl-5'-methyl-2'-hydroxybenzyl)-4-methylphenyl acrylate, 2,6-di-tert-butyl-4-(N,N-dimethylaminomethyl)phenol, diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, and tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxymethyl]methane, which can be used alone or in combination of two or more.

[0066] There are no particular limitations on its use as a flame retardant, but halogenated flame retardants, phosphorus-based flame retardants, and non-phosphorus halogenated flame retardants such as metal hydrates can be used, for example. Specific examples of halogenated flame retardants include halodiphenylalkanes, halodiphenyl ethers, halodiphenyl sulfides, halodiphenyl sulfones, halobisphenol compounds, bromobisphenol A, bromobisphenol S, chlorobisphenol A, chlorobisphenol S, and bisphenol-bis(alkyl ether) compounds. Examples of phosphorus-based flame retardants include tris(diethylphosphine)aluminum, bisphenol A bis(diphenyl phosphate), isopropyl compounds, cresyldi-2,6-xylenyl phosphate, and aromatic condensed phosphates. Examples of metal hydrates include aluminum trihydrate, magnesium dihydroxide, or combinations thereof. These can be used alone or in combination of two or more. They also act as flame retardant additives, further enhancing the flame retardant effect. Furthermore, it can also be used in combination with antimony oxides such as antimony trioxide and antimony pentoxide, as well as zinc oxide, iron oxide, aluminum oxide, molybdenum oxide, titanium oxide, calcium oxide, and magnesium oxide as flame retardant additives.

[0067] Foaming agents are inorganic powders used as raw materials to fill resin compositions, which are mixed or pressed into a melt mixer to become molten. They are substances that change from a solid phase to a gas, from a liquid phase to a gas, or are gases themselves. They are primarily used to control the foaming ratio (foaming density) of foamed sheets. Foaming agents that are liquid at room temperature change phase to gas due to the resin temperature and dissolve in the molten resin, while substances that are gaseous at room temperature dissolve in the molten resin in an un-phase-changed state. When the molten resin is extruded from an extruder to form sheets, the foaming agent dispersed and dissolved in the molten resin expands inside the sheet due to the release of pressure, forming multiple fine, independent bubbles within the sheet to obtain the foamed sheet. Foaming agents also act as plasticizers, primarily reducing the melt viscosity of the raw resin composition and lowering the temperature required to plasticize the raw resin composition.

[0068] Examples of foaming agents include aliphatic hydrocarbons such as propane, butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane; halogenated hydrocarbons such as difluoromethane, difluoromethane, trifluoromethane, trichlorofluoromethane, dichloromethane, dichlorofluoromethane, 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.

[0069] The foaming agent can be further preferably a substance containing an effective component of the foaming agent in a carrier resin. Examples of carrier resins include crystalline olefin resins. Among these, crystalline polypropylene resin is preferred. Furthermore, examples of effective components include bicarbonates. Among these, bicarbonates are preferred. A foaming agent concentrate containing crystalline polypropylene resin as the carrier resin and bicarbonate as a thermally decomposable foaming agent is preferred.

[0070] In the molding process, the content of the foaming agent can be appropriately set according to the amount of propylene homopolymer, propylene block copolymer and inorganic powder, and preferably in the range of 0.04 to 5.00% by mass relative to the total mass of the inorganic powder-filled resin composition.

[0071] Various conventional flow modifiers can be used as flow modifiers. Examples include peroxides such as dialkyl peroxides and 1,4-bis[(tert-butylperoxy)isopropyl]benzene, but these are not limited to. Depending on the type of thermoplastic resin used, these peroxides can also function as crosslinking agents. In particular, when the aforementioned propylene block copolymer has structural units derived from diene, a portion of the copolymer is crosslinked under the action of the aforementioned peroxides, which can help control the physical properties and processability of the resin composition. There is no particular limitation on the amount of peroxide added, but it is preferably in the range of about 0.04 to 2.00% by mass, and particularly preferably about 0.05 to 0.50% by mass, relative to the total mass of the inorganic powder-filled resin composition.

[0072] Method for manufacturing inorganic powder-filled resin compositions

[0073] The method for manufacturing the inorganic powder-filled resin composition of the present invention can use conventional methods and can be appropriately set according to the molding method (extrusion molding, injection molding, vacuum molding, etc.). For example, the propylene homopolymer, propylene block copolymer, and maleic anhydride-modified polypropylene and inorganic powder as arbitrary components can be mixed and melted before being fed from the hopper into the molding machine, or the propylene homopolymer, propylene block copolymer, and maleic anhydride-modified polypropylene and inorganic powder as arbitrary components can be mixed and melted while integrally molding with the molding machine. It is preferable to perform melt mixing to uniformly disperse the components while applying high shear stress. Various mixing devices such as general extruders, kneaders, and Banbury mixers can be used as mixing devices, but for example, a twin-shaft mixer is preferred.

[0074] In the manufacturing method of this invention, the mixing order of the propylene homopolymer, propylene block copolymer, maleic anhydride-modified polypropylene (as an optional component), and inorganic powder is not particularly limited. For example, three to four of these components can be mixed simultaneously, or the thermoplastic resin mixture and inorganic powder can be mixed after the propylene homopolymer and propylene block copolymer have been temporarily mixed. Alternatively, the propylene homopolymer and propylene block copolymer can be mixed separately with the inorganic powder, and then the two thermoplastic resins can be mixed after their melt viscosities are made consistent. Alternatively, the propylene homopolymer and inorganic powder can be temporarily mixed with maleic anhydride-modified polypropylene, and then the propylene block copolymer can be mixed. Propylene block copolymers generally tend to be soft and have low melt viscosity, so the method of mixing last, as in the latter case, is more advantageous in making the components in the inorganic powder-filled resin composition more homogeneously dispersed. This method can also be flexibly applied to the effective utilization of recycled materials from the market and factory scraps. Compositions made by highly filling inorganic powder into thermoplastic resins, as described above, have been put into practical use and are used in the general market. Especially in manufacturing plants, the end products of these compositions are sometimes stored in a batch-by-batch managed manner. The inorganic powder-filled resin compositions of the present invention can also be manufactured by further compounding a specified amount of propylene block copolymer with maleic anhydride-modified polypropylene in these recycled materials and scraps as desired.

[0075] In the manufacturing method of the inorganic powder-filled resin composition of the present invention, the inorganic powder-filled resin composition may be in the form of particles or not. However, when it is in the form of particles, the shape of the particles is not particularly limited. For example, cylindrical, spherical, ellipsoidal and other particles may also be formed.

[0076] The size of the particles can be appropriately set according to their shape, but for example, in the case of spherical particles, the diameter can be 1 to 10 mm. In the case of ellipsoidal particles, they can be elliptical with an aspect ratio of 0.1 to 1.0 and a length of 1 to 10 mm. In the case of cylindrical particles, the diameter and length can both be within the range of 1 to 10 mm. Their shape can be formed relative to the particles after the mixing process described later. The shape of the particles can be formed using conventional methods.

[0077] Molded Products

[0078] The molded articles involved in this invention are molded articles composed of the above-mentioned inorganic substance powder-filled resin composition.

[0079] The shape of the molded articles involved in this invention is not particularly limited, and they can be of various shapes. However, they can be molded into various molded articles such as sheets, especially paper, paper substitutes, brushes, shoehorns and other daily necessities, frames for remote controls, telephones and other items, food containers and other container bodies. Due to their excellent flexibility, the molded articles of this invention are suitable as frames, sheets, daily necessities and other items that apply force during assembly and use.

[0080] The wall thickness of the molded article involved in this invention is not particularly limited. Depending on the shape of the molded article, it can be of various wall thicknesses, ranging from thin to thick. However, for example, a molded article with a wall thickness of 40 μm to 40 mm, more preferably 50 μm to 30 mm, is shown. If the wall thickness is within this range, there are no problems with moldability and processability, and a molded article that does not produce deviations, is homogeneous, and is free of defects can be formed.

[0081] Especially when the molded product is in sheet form, a wall thickness of 50 μm to 1,000 μm is preferred, and a wall thickness of 50 μm to 400 μm is even more preferred. Sheets with wall thicknesses within this range can be appropriately used to replace paper or synthetic paper used for general printing / information and packaging purposes.

[0082] Manufacturing Methods for Molded Articles

[0083] As for the manufacturing method of the molded article of the present invention, there are no particular limitations as long as it can be molded into the desired shape, and it can be molded by any conventionally known method such as extrusion molding, injection molding, vacuum molding, blow molding, and calender molding. Injection molding is particularly preferred. Furthermore, the inorganic powder-filled resin composition involved in the present invention also contains a foaming agent. When obtaining a molded article in the form of a foam, as long as it can be molded into the desired shape, the molding method for the foam can also use any conventionally known liquid-phase foaming method, such as injection foaming, extrusion foaming, or foam blow molding, or solid-phase foaming method, such as bead foaming, batch foaming, stamping foaming, or atmospheric pressure secondary foaming. In a thermoplastic composition containing the aforementioned crystalline polypropylene as a carrier resin and bicarbonate as a thermally decomposable foaming agent, injection foaming and extrusion foaming methods are desirable.

[0084] <Manufacturing Method of Injection Molded Articles>

[0085] Because the inorganic powder-filled resin composition of the present invention also exhibits excellent moldability as described above, it can be injection molded into articles of various shapes. The present invention also includes molded articles of the aforementioned inorganic powder-filled resin composition, particularly injection-molded articles. Such molded articles of the present invention have the advantages of being free from undesirable appearances such as tiger stripes, and possessing excellent mechanical properties, primarily softness. This effect has also been observed in some of the raw materials of the inorganic powder-filled resin composition from recycled products from the market and factories; therefore, the molded articles of the present invention exhibit good properties even when recycled. The inorganic powder-filled resin composition of the present invention also possesses excellent softness, and is not prone to cracking or chipping even under stress, making it suitable for molding processes that include the process of fitting multiple parts together after molding them into mating surfaces. For example, after separately injection molding the handle and other parts (body part) of a brush, safety razor, or the frame of a remote control, telephone, etc., external force can be applied to fit them together, thereby producing the desired product.

[0086] Furthermore, the molding temperature for injection molding, extrusion molding, etc., varies to some extent depending on the molding method and the type of thermoplastic resin used, so it cannot be generalized. However, for example, as long as the temperature is 180 to 260°C, more preferably 190 to 230°C, the inorganic powder-filled resin composition involved in this invention has good drawdown properties and ductility, and the composition can be molded into a specified shape without local modification.

[0087] <Sheet Manufacturing Method>

[0088] In the case of the molded article being a sheet material, the manufacturing method is not particularly limited as long as it is a method of forming a sheet material. The conventionally known molding methods described above can be used. However, if the smoothness of the sheet surface is taken into special consideration, it is preferable to use an extrusion molding method to produce the sheet material.

[0089] The molding process can be a direct method that involves continuous mixing and molding into sheet form, such as using a biaxial extrusion molding machine with a T-die.

[0090] Furthermore, when formed into a sheet shape, it can be extended uniaxially, biaxially, or even multiaxially (such as tubular extension) during or after forming. In the case of biaxial extension, it can be biaxially extended sequentially or simultaneously.

[0091] When the formed sheet is stretched (e.g., longitudinally and / or transversely), tiny voids are created within the sheet. These tiny voids contribute to the sheet's good whiteness.

[0092]

Example

[0093] The present invention will now be described in more detail based on embodiments. Furthermore, these embodiments are provided to facilitate understanding of the concepts and scope of the invention disclosed in this specification and set forth in the appended claims, and are merely illustrative of specific methods and implementations; the invention is not limited by these embodiments.

[0094] [Example 1, Comparative Examples 1-3]

[0095] Various inorganic powder-filled resin compositions were prepared using the following raw materials, molded into test pieces, and subjected to physical property tests.

[0096] • Homopolymer: Propylene homopolymer manufactured by Polypro Corporation, Japan (MFR: 0.5g / 10min)

[0097] • Copolymer: Propylene block copolymer (J709QG, melting point: 160~165℃) manufactured by Prime Polymer Co., Ltd.

[0098] • Calcium carbonate: Heavy calcium carbonate manufactured by Bikita Powder Chemical Industry Co., Ltd. (surface treated, average particle size 2.20 μm as measured by JIS M-8511 air permeation method)

[0099] • Elastomer: Hydrogenated styrene-based thermoplastic elastomer manufactured by Asahi Kasei Corporation (Tuftec (registered trademark) H1221)

[0100] • Modified PP-1: Maleic anhydride modified polypropylene (Umex 1010) manufactured by Sanyo Chemical Industries, Ltd.

[0101] By feeding 40 parts by weight of the above-mentioned propylene homopolymer and 60 parts by weight of heavy calcium carbonate powder into a co-rotating twin-screw compounding extruder HK-25D manufactured by Parker Corporation, The first granules were produced by extruding filaments (L / D = 41) at a cylinder temperature of 190–200°C, followed by cooling and cutting. Next, 90 parts by weight of these granules and 10 parts by weight of the aforementioned propylene block copolymer were extruded under the same conditions using the aforementioned biaxial compounding extruder to produce the second granules. These second granules were then fed into an injection molding machine to form dumbbell-shaped test pieces, etc. (Example 1).

[0102] Under the same conditions as described above, resin compositions without propylene block copolymers (Comparative Example 1), resin compositions containing hydrogenated styrene-based thermoplastic elastomers instead of propylene block copolymers (Comparative Example 2), and resin compositions containing maleic anhydride-modified polypropylene (Comparative Example 3) were prepared, and test pieces were molded. The composition of each resin composition is shown in Table 1 described below.

[0103] The test specimens prepared in the manner described above were evaluated for tensile properties, Charpy impact strength, and flexibility using the following test methods. The results are shown in Table 1 below.

[0104] (Tensive properties)

[0105] Based on JIS K 7161-2:2014, the tensile modulus of elasticity and elongation at break were determined using an Autograph AG-100kN X plus electronic universal testing machine (Shimadzu Corporation) at 23°C and 50% RH. The elongation rate was 10 mm / min.

[0106] (Charpy impact strength)

[0107] The 80mm × 10mm test pieces were tested according to ISO 179 / 1eA. Some samples were not tested.

[0108] (Flexibility test)

[0109] The above test pieces are as follows Figure 1 Bend it by hand and evaluate its flexibility according to the following criteria.

[0110] •◎: The test piece was bent 10 times until it reached about 160°, but it did not break.

[0111] •〇: Unless the test piece is bent 2 to 3 times until it reaches about 160°, it will not break.

[0112] •△: When the test piece is bent at about 120° or more, it breaks on the first try.

[0113] ×: When the test piece is bent at about 90 to 120 degrees, it breaks on the first try.

[0114] Table 1

[0115] [Table 1 Composition and Evaluation Results of Each Sample]

[0116]

[0117] * Unit: parts by weight # Values ​​in parentheses: Mass percentage relative to homopolymer (%)

[0118] 1) Unit: MPa 2) unit:%

[0119] 3) Charpy impact strength, unit: kJ / m 2

[0120] According to the present invention, the inorganic powder-filled resin composition of Example 1, which contains a specified amount of propylene homopolymer and propylene block copolymer as a thermoplastic resin, exhibits higher values ​​for elastic modulus, elongation at break, and Charpy impact strength compared to the resin composition of Comparative Example 1, which does not contain propylene block copolymer, and its mechanical properties are improved. Its flexibility is also extremely good. On the other hand, the resin composition of Comparative Example 2, due to the presence of a styrene-based elastomer, shows a significant improvement in elongation at break and flexibility, but its elastic modulus is about half the value in Example 1. The resin composition of Comparative Example 3, due to the addition of maleic anhydride-modified polypropylene, has an increased elastic modulus, but compared to the resin composition of Comparative Example 1, its elongation at break and Charpy impact strength are lower. Its flexibility is also slightly improved.

[0121] According to the present invention, a balanced improvement in both mechanical strength and flexibility has been demonstrated for the first time through the use of propylene block copolymers.

[0122] [Examples 2-3]

[0123] By varying the composition of the inorganic powder-filled resin composition and performing the same procedures as in Example 1, samples with various compositions were prepared and their properties evaluated. Furthermore, the appearance of the test pieces was observed, and the moldability was evaluated based on the presence or absence of tiger stripes (flow marks in a striped pattern). The composition of each sample and the evaluation results are presented together with the results from Example 1, etc., in Table 2.

[0124] Table 2

[0125] [Table 2 Composition and Evaluation Results of Each Sample]

[0126]

[0127] * Unit: mass % # Values ​​in parentheses: Mass percentage relative to homopolymer (%)

[0128] 1) Unit: MPa 2) unit:%

[0129] 3) Charpy impact strength, unit: kJ / m 2

[0130] The inorganic powder-filled resin compositions of Examples 2 and 3 contain maleic anhydride-modified polypropylene, propylene homopolymer, and propylene block copolymer as thermoplastic resin components, resulting in molded articles with not only good mechanical properties and excellent flexibility but also a good appearance without tiger stripes. In particular, the inorganic powder-filled resin composition of Example 2, with a propylene block copolymer content of 9% by mass, showed satisfactory results in terms of elongation at break and flexibility, as well as high values ​​for elastic modulus and Charpy impact strength. Figure 1 This is a photograph of the test piece from Example 2 when bent at approximately 160°. The inorganic powder-filled resin composition of the present invention does not break even after repeated bending and exhibits excellent flexibility. Furthermore, it is shown that even the test piece from Comparative Example 3 containing maleic anhydride-modified polypropylene exhibits tiger stripes. To improve moldability and reduce appearance defects, it is necessary to contain not only maleic anhydride-modified polypropylene but also propylene block copolymer.

[0131] [Examples 4-8]

[0132] By changing the type of maleic anhydride-modified polypropylene, test pieces were prepared in the same manner as in Example 2, and the moldability was evaluated based on the presence or absence of tiger stripes (flow marks in a striped pattern). The types of maleic anhydride-modified polypropylene used and the appearance evaluation results of each sample are shown in Table 3.

[0133] Table 3

[0134] [Table 3: Types and Evaluation Results of Maleic Anhydride Modified Polypropylene]

[0135]

[0136] ※Modified PP-2: Sanyo Chemical's Umex1001

[0137] Modified PP-3: BYK Chemicals SCONA TPPP 9012

[0138] Modified PP-4: BYK Chemicals SCONA TPPP 9012

[0139] Modified PP-5: Nouryon Chemicals manufactures Kayabrid002PP

[0140] Modified PP-6: BYK Chemicals SCONA TPPP 10213

[0141] #Compared to Example 2, the values ​​of flexibility / elongation at break decreased.

[0142] If the maleic anhydride-modified polypropylene has a maleic acid modification rate of 3.0% to 4.9% by mass, tiger stripes are almost completely unobservable, and it is clear that the moldability of the inorganic powder-filled resin composition is improved. Furthermore, it was clarified that the moldability of maleic anhydride-modified polypropylene with a modification rate (grafting amount) of 5.0% or higher is not improved, and may also be accompanied by a decrease in the physical properties of the inorganic powder-filled resin composition.

[0143] Based on the above, even in resin compositions with high levels of inorganic powder, it is clear that as long as the thermoplastic resin component contains propylene homopolymer and propylene block copolymer, and the content of the propylene block copolymer is between 10 and 30 parts by mass relative to 100 parts by mass of propylene homopolymer, it is soft and exhibits good mechanical properties. It has been found that as long as the resin composition further contains maleic anhydride-modified polypropylene, especially the same modified polypropylene with a modification rate of 3.0 to 4.9% by mass, molded articles with good surface appearance can be obtained.

Claims

1. An inorganic powder-filled resin composition, comprising thermoplastic resin and inorganic powder in a mass ratio of 50:50 to 10:90, characterized in that, The thermoplastic resin comprises a propylene homopolymer and a propylene block copolymer, wherein the content of the propylene block copolymer is between 10 and 30 parts by weight relative to 100 parts by weight of the propylene homopolymer. The thermoplastic resin further contains maleic anhydride-modified polypropylene in an amount of 0.5 to 3.0 parts by mass relative to 100 parts by mass of the inorganic powder-filled resin composition, with a grafting amount of 3.0% to 4.9% by mass.

2. The inorganic powder-filled resin composition according to claim 1, characterized in that, The maleic anhydride-modified polypropylene has a mass-average molecular weight of 25,000 to 35,000.

3. The inorganic powder-filled resin composition according to claim 1 or 2, characterized in that, The inorganic powder is heavy calcium carbonate.

4. The inorganic powder-filled resin composition according to claim 3, characterized in that, The heavy calcium carbonate refers to heavy calcium carbonate particles with an average particle size of 0.7 μm to 6.0 μm as determined by the air permeation method according to JIS M-8511.

5. A molded article, characterized in that, It is composed of an inorganic powder-filled resin composition according to any one of claims 1 to 4.

6. The molded article according to claim 5, characterized in that, The molded product is an injection molded product.

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