Resin composition and molded article

Abstract

A resin composition according to the present invention contains a thermoplastic resin, basic magnesium sulfate, and a carbodiimide-based compound.

Description

Resin composition and molded article

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

[0002] Biodegradable resin compositions are required to have a good balance between rigidity and impact strength, similar to conventional petroleum-derived resin compositions, and a method has been proposed for improving the rigidity of resin compositions by mixing an inorganic filler into an aliphatic polyester resin (see, for example, Patent Document 1).

[0003] It is also known that adding basic magnesium sulfate whiskers to polypropylene can provide a higher reinforcing effect than when talc or glass fiber is used. The application of basic magnesium sulfate whiskers to polyamide resins has also been proposed (see, for example, Patent Document 2). It is described that by replacing glass fiber as a reinforcing material with basic magnesium sulfate whiskers, molded articles with excellent surface smoothness were obtained.

[0004] JP 2021-167403 A JP 7-126522 A

[0005] When producing a molded article from a thermoplastic resin composition, raw materials are melt-kneaded using a twin-screw extrusion kneader or the like. Since the resin composition is extruded from the die nozzle of the kneader to form a strand, the strand is required to have high stability. Furthermore, in order to reduce the weight of the molded article, it is also desirable for the resin composition to have a low specific gravity. A resin composition that has excellent strand stability during melt-kneading, a low specific gravity, and can produce a molded article with high rigidity has not yet been obtained.

[0006] Therefore, an object of the present invention is to provide a resin composition which has excellent strand stability during melt-kneading, has a low specific gravity, and can give a molded article with high rigidity, and to provide a molded article with high rigidity.

[0007] The resin composition according to the present invention contains a thermoplastic resin, basic magnesium sulfate, and a carbodiimide compound.

[0008] The molded article according to the present invention is a molded product of the above-mentioned resin composition.

[0009] According to the present invention, it is possible to provide a resin composition which has excellent strand stability during melt-kneading, has a low specific gravity, and is capable of giving a molded article with high rigidity, and to provide a molded article with high rigidity.

[0010] As a result of extensive research, the present inventors have found that a resin composition obtained by blending a thermoplastic resin with a carbodiimide compound together with basic magnesium sulfate has excellent strand stability during melt-kneading and a low specific gravity, and that the use of such a resin composition allows for the production of molded articles with high rigidity, thereby completing the present invention. Hereinafter, embodiments of the present invention will be described in detail.

[0011] <Thermoplastic Resin> Examples of thermoplastic resins include polyamide resins; thermoplastic polyester resins such as polyethylene terephthalate resin, polytrimethylene terephthalate resin, and polybutylene terephthalate resin; polycarbonate resins; styrene-based resins; polyolefin resins such as polyethylene resin, polypropylene resin, and cyclic cycloolefin resin; polyacetal resins; polyimide resins; polyetherimide resins; polyurethane resins; polyphenylene ether resins; polyphenylene sulfide resins; polysulfone resins; polymethacrylate resins, etc. Polyamide resins are preferred as the thermoplastic resin in the present invention because of their excellent balance between mechanical properties and heat resistance.

[0012] The polyamide resin is not particularly limited, and examples thereof include polyhexamethylene adipamide (polyamide 66), polycaproamide (polyamide 6), polytetramethylene adipamide (polyamide 46), polyundecamethylene adipamide (polyamide 116), polymetaxylylene adipamide (polyamide MXD6), polyparaxylylene adipamide (polyamide PXD6), polyxylylene sebacamide (polyamide XD10), polytetramethylene sebacamide (polyamide 410), polyhexamethylene sebacamide (polyamide 610), polydecamethylene adipamide (polyamide 106), polydecamethylene sebacamide (polyamide 1010), polyhexamethylene dodecamide (polyamide 612), polydecamethylene dodecamide (polyamide 1012), and polyhexamethylene isophthalate. amide (polyamide 6I), polytetramethylene terephthalamide (polyamide 4T), polypentamethylene terephthalamide (polyamide 5T), poly-2-methylpentamethylene terephthalamide (polyamide M-5T), polyhexamethylene terephthalamide (polyamide 6T), polyhexamethylene hexahydroterephthalamide (polyamide 6T(H)), polynonamethylene terephthalamide (polyamide 9T), polydecamethylene terephthalamide (polyamide 10T), polyundecamethylene terephthalamide (polyamide 11T), polydodecamethylene terephthalamide (polyamide 12T), polylauryllactam (polyamide 12), poly-11-aminoundecanoic acid (polyamide 11), and copolymers containing these structural units.

[0013] The polyamide resin may be used alone or in combination of two or more. Among them, polyhexamethylene adipamide (polyamide 66), polycaproamide (polyamide 6), polymetaxylylene adipamide (polyamide MXD6), and polyhexamethylene terephthalamide (polyamide 6T) are preferred, with polyhexamethylene adipamide (polyamide 66) being particularly preferred.

[0014] In the resin composition of the present invention, the content of the thermoplastic resin is preferably 40 to 95 parts by mass, more preferably 50 to 80 parts by mass, when the total content of the thermoplastic resin and the basic magnesium sulfate described below is 100 parts by mass.

[0015] <Basic magnesium sulfate> Examples of basic magnesium sulfate include a compound represented by the following chemical formula (1): MgSO ４ 5Mg(OH) ２ ・3H ２ O (1) The compound represented by the above chemical formula (1) can be obtained by hydrothermal synthesis using, as raw materials, an alkaline substance such as sodium hydroxide, magnesium hydroxide, magnesium oxide, or calcium hydroxide, and magnesium sulfate.

[0016] Alternatively, a compound represented by the following chemical formula (2) can be used: MgSO ４ 5Mg(OH) ２ (2) The compound represented by the above chemical formula (2) can be called anhydrous MOS. Such a compound can be synthesized, for example, by hydrothermal synthesis.

[0017] The shape of the basic magnesium sulfate is not particularly limited, and basic magnesium sulfate of any shape, such as fibrous or fan-shaped, can be used. For example, in the case of fibrous basic magnesium sulfate, the average fiber length is generally in the range of 2 to 100 μm, preferably 5 to 50 μm, and the average fiber diameter is generally in the range of 0.1 to 2.0 μm, preferably 0.1 to 1.0 μm. The average aspect ratio (average fiber length / average fiber diameter) of basic magnesium sulfate is generally 2 or more, preferably 3 to 1000, more preferably 3 to 100, and particularly preferably 5 to 50. The average fiber length and average fiber diameter of basic magnesium sulfate can be calculated from the number-average values ​​of the fiber length and fiber diameter measured by image analysis of enlarged images taken with a scanning electron microscope (SEM).

[0018] The content of the basic magnesium sulfate is preferably 5 to 60 parts by mass, and more preferably 20 to 50 parts by mass, relative to 100 parts by mass of the total of the thermoplastic resin and the basic magnesium sulfate. By changing the content of the basic magnesium sulfate, it is possible to obtain a thermoplastic resin composition from which a molded article having a high flexural modulus can be produced.

[0019] <Carbodiimide Compound> Various carbodiimide compounds can be used, and are not particularly limited as long as they have one or more carbodiimide groups in the molecule. Examples of carbodiimide compounds include aliphatic monocarbodiimides, aliphatic polycarbodiimides, alicyclic monocarbodiimides, alicyclic polycarbodiimides, aromatic monocarbodiimides, and aromatic polycarbodiimides. Furthermore, the carbodiimide compounds may have various heterocycles or various functional groups in the molecule.

[0020] The method for producing a carbodiimide compound is not particularly limited, and many methods can be used, such as a method using an isocyanate compound as a raw material. As the carbodiimide compound, both a carbodiimide compound having an isocyanate group in the molecule and a carbodiimide compound not having an isocyanate group in the molecule can be used without distinction.

[0021] Examples of the carbodiimide skeleton of the carbodiimide compound include N,N'-di-o-triylcarbodiimide, N,N'-dioctyldecylcarbodiimide, N,N'-di-2,6-dimethylphenylcarbodiimide, N-triyl-N'-cyclohexylcarbodiimide, N-triyl-N'-phenylcarbodiimide, N,N'-di-p-nitrophenylcarbodiimide, N,N'-di-p-hydroxyphenylcarbodiimide, and N,N'-di- Examples of carbodiimide skeletons include many carbodiimide skeletons such as cyclohexylcarbodiimide, N,N'-di-cyclohexylcarbodiimide, N,N'-di-p-triylcarbodiimide, p-phenylene-bis-di-o-triylcarbodiimide, 4,4'-dicyclohexylmethanecarbodiimide, tetramethylxylylenecarbodiimide, N,N'-dimethylphenylcarbodiimide, and N,N'-di-2,6-diisopropylphenylcarbodiimide.

[0022] Many specific examples of carbodiimide compounds can be mentioned. Specifically, for example, alicyclic monocarbodiimides include dicyclohexylcarbodiimide. Alicyclic polycarbodiimides include polycarbodiimides derived from 4,4'-dicyclohexylmethane diisocyanate. Aromatic monocarbodiimides include N,N'-diphenylcarbodiimide and N,N'-di-2,6-diisopropylphenylcarbodiimide. Aromatic polycarbodiimides include polycarbodiimides derived from phenylene-p-diisocyanate and polycarbodiimides derived from 1,3,5-triisopropyl-phenylene-2,4-diisocyanate. The above carbodiimide compounds can be used alone or in combination of two or more.

[0023] In polycarbodiimide, both ends of the molecule or any part of the molecule may have a functional group such as an isocyanate group, or the molecular chain may be branched, or the molecular structure may be different from that of other parts.

[0024] The content of the carbodiimide compound is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, based on 100 parts by mass of the total of the thermoplastic resin and the basic magnesium sulfate.

[0025] The resin composition of the present invention may contain other components as long as the effects of the present invention are not impaired. For example, when magnesium stearate is added, a molded product having a superior flexural modulus can be obtained.

[0026] The resin composition of the present invention can be produced by mixing the components and then melt-kneading them. For example, the thermally decomposable resin, fibrous basic magnesium sulfate, and carbodiimide compound are first mixed together. Mixing can be performed using a tumbler, blender, Henschel mixer, or the like.

[0027] During mixing, the remaining components can be added to the thermoplastic resin in any order. Adding the fibrous basic magnesium sulfate and the carbodiimide compound simultaneously is advantageous in terms of cost reduction due to process simplification. Adding the carbodiimide compound to the thermoplastic resin and then adding the fibrous basic magnesium sulfate increases the remaining fiber length of the fibrous basic magnesium sulfate after kneading, resulting in a higher reinforcing effect. The resin composition of the present invention is obtained by melt-kneading the resulting mixture at 250 to 290°C using a twin-screw extrusion kneader or the like.

[0028] That is, the method for producing a resin composition of the present invention is a method having either of the following steps (1) or (2): (1) a simultaneous addition step of simultaneously adding a carbodiimide compound together with basic magnesium sulfate to a thermoplastic resin, or (2) a sequential addition step of adding a carbodiimide compound to a thermoplastic resin and then adding basic magnesium sulfate.

[0029] The resin composition of the present invention can be molded to produce various molded articles. For molding the resin composition, for example, a rolling molding machine (such as a calendar molding machine), a vacuum molding machine, an extrusion molding machine, an injection molding machine, a blow molding machine, a press molding machine, etc. can be used.

[0030] As described above, the resin composition of the present invention contains basic magnesium sulfate and a carbodiimide compound, and therefore, molded articles with excellent rigidity can be obtained. The resin composition of the present invention can adjust the flexural modulus by adjusting the content of basic magnesium sulfate, and therefore, molded articles for various uses can be obtained.

[0031] For example, the molded article of the present invention can be suitably used in a wide range of applications such as automobiles, etc. Specific examples of applications include peripheral parts for automobile engines.

[0032] Specific examples of the present invention will be shown below, but the present invention is not limited to these.

[0033] The raw materials used are summarized below. <Thermoplastic resin> A1: Polyamide 66 E2000 manufactured by Unitika Ltd. A2: Polyamide 6 1013B manufactured by UBE Ltd.

[0034] <Basic magnesium sulfate> B1: Fibrous basic magnesium sulfate MOS-Hige A-1, manufactured by Ube Material Industries, Ltd., average fiber length 15 μm, average fiber diameter 0.5 μm B2: Anhydrous MOS157 Anhydrous MOS157 is a fibrous material represented by the above chemical formula (2) having an average fiber length of 12 μm and an average fiber diameter of 0.5 μm, and was synthesized by the following method. Specifically, first, magnesium sulfate heptahydrate was dissolved in water to prepare 3 liters of a 3.0 mol / L magnesium sulfate aqueous solution. 70 g of magnesium hydroxide was added to this and dispersed well. The mixture was then placed in an autoclave and reacted at a temperature of 170°C and a pressure of 0.65 MPa for 20 hours to obtain 2MgSO ４ Mg(OH) ２ ・2H ２ After the reaction, 2MgSO ４ Mg(OH) ２ ・2H ２ The slurry was cooled to 100°C. 3 liters of an aqueous magnesium sulfate solution with a concentration of 1.5 mol / L and a temperature of 20°C was added, and the mixture was rapidly diluted to 40°C and cooled, and reacted for 6 hours to obtain a fibrous material. After the reaction, the product was collected by filtration, washed with water, and chemically analyzed, revealing that the product contained MgSO ４ 5Mg(OH) ２ ・7H２ This fibrous MgSO ４ 5Mg(OH) ２ ・7H ２ O was heat-treated at 300 °C for 2 hours. Chemical analysis of the obtained material revealed that MgSO ４ 5Mg(OH) ２ The rational formula was shown as follows.

[0035] <Glass fiber> B': Glass chopped strand ECS03-631K, manufactured by Central Glass Fiber Co., Ltd. <Carbodiimide compound> C: Carbodilite HMV-15CA, manufactured by Nisshinbo Chemical Co., Ltd.

[0036] Example 1 First, 80 parts by mass of polyamide 66 (A1), 20 parts by mass of MOS-HIGE A-1 (B1), and 1 part by mass of carbodiimide compound (C) were mixed together. The resulting mixture was melt-kneaded at 280°C using a twin-screw melt-kneading extruder (L / D=25, manufactured by Toyo Seiki Seisaku-sho, Ltd., Labo Plastomill) to obtain a resin composition of Example 1.

[0037] Example 2 A resin composition of Example 2 was obtained in the same manner as in Example 1, except that 70 parts by mass of polyamide 66 (A1), 30 parts by mass of MOS-HIGE A-1 (B1), and 1 part by mass of carbodiimide compound (C) were used.

[0038] Example 3 A resin composition of Example 3 was obtained in the same manner as in Example 1, except that 60 parts by mass of polyamide 66 (A1), 40 parts by mass of MOS-HIGE A-1 (B1), and 3 parts by mass of the carbodiimide compound (C) were used.

[0039] Example 4 A resin composition of Example 4 was obtained in the same manner as in Example 1, except that 90 parts by mass of polyamide 66 (A1), 10 parts by mass of anhydrous MOS157 (B2), and 3 parts by mass of the carbodiimide compound (C) were used.

[0040] Example 5 A resin composition of Example 5 was obtained in the same manner as in Example 1, except that 80 parts by mass of polyamide 66 (A1), 20 parts by mass of anhydrous MOS157 (B2), and 5 parts by mass of the carbodiimide compound (C) were used.

[0041] Example 6 60 parts by mass of polyamide 6 (A2), 40 parts by mass of MOS-HIGE A-1 (B1), and 1 part by mass of carbodiimide compound (C) were mixed together. The resulting mixture was melt-kneaded at 260°C using a twin-screw melt-kneading extruder (L / D=25, manufactured by Toyo Seiki Seisaku-sho, Ltd., Labo Plastomill) to obtain a resin composition of Example 6.

[0042] Example 7 A resin composition of Example 7 was obtained in the same manner as in Example 6, except that 50 parts by mass of polyamide 6 (A2), 50 parts by mass of MOS-HIGE A-1 (B1), and 1 part by mass of carbodiimide compound (C) were used.

[0043] Comparative Example 1 A resin composition of Comparative Example 1 was obtained in the same manner as in Example 1, except that the carbodiimide compound (C) was not added.

[0044] Comparative Example 2 A resin composition of Comparative Example 2 was obtained in the same manner as in Example 2, except that the carbodiimide compound (C) was not added.

[0045] Comparative Example 3 A resin composition of Comparative Example 3 was obtained in the same manner as in Example 3, except that the carbodiimide compound (C) was not added.

[0046] Comparative Example 4 A resin composition of Comparative Example 4 was obtained in the same manner as in Example 4, except that the carbodiimide compound (C) was not added.

[0047] Comparative Example 5 A resin composition of Comparative Example 5 was obtained in the same manner as in Example 5, except that the carbodiimide compound (C) was not added.

[0048] Comparative Example 6 A resin composition of Comparative Example 6 was obtained in the same manner as in Comparative Example 5, except that 50 parts by mass of polyamide 66 (A1) and 50 parts by weight of glass fiber (B') were used.

[0049] Comparative Example 7 A resin composition of Comparative Example 7 was obtained in the same manner as in Example 6, except that the carbodiimide compound (C) was not added.

[0050] Comparative Example 8 A resin composition of Comparative Example 8 was obtained in the same manner as in Example 7, except that the carbodiimide compound (C) was not added.

[0051] Comparative Example 9 A resin composition of Comparative Example 9 was obtained in the same manner as in Comparative Example 6, except that polyamide 66 (A1) was changed to polyamide 6 (A2).

[0052] Table 1 below summarizes the formulations of the resin compositions of the examples and comparative examples.

[0053]

[0054] As shown in Table 1 above, the resin compositions of the examples contain a carbodiimide compound (C) in addition to basic magnesium sulfate (B).

[0055] The strand stability and specific gravity during melt-kneading were determined for the resin compositions of the Examples and Comparative Examples. Furthermore, test pieces were prepared using each resin composition to examine the flexural modulus.

[0056] <Strand stability during melt-kneading> The degree of strand breakage during melt-kneading was visually observed and evaluated according to the following criteria: ◯: No strand breakage ×: Strand breakage If there are breaks in the strands, productivity is reduced, making practical application difficult.

[0057] <Specific Gravity> The specific gravity of the resin composition was measured by the following method. Specifically, it was measured by the underwater displacement method in accordance with JIS K7112 using an electronic hydrometer (MDS-300, Alpha Mirage Co., Ltd.). The specific gravity is preferably 1.5 or less, and more preferably 1.4 or less.

[0058] <Preparation of Test Pieces> Each resin composition was molded using a small electric injection molding machine (C.Mobile 0813, manufactured by Shinko Selvic Co., Ltd.) to obtain strip test pieces (length 80 mm, width 10 mm, thickness 4 mm) for evaluating mechanical properties.

[0059] <Flexural modulus> A three-point bending test was performed using a universal mechanical testing machine (AGS-X, manufactured by Shimadzu Corporation) according to a method conforming to JIS K7171. The flexural modulus was evaluated from the obtained load-deflection curve. The measurement temperature was 23°C.

[0060] The flexural modulus of the molded articles produced using each resin composition is shown in Table 2 below, along with the strand stability and specific gravity of each resin composition.

[0061]

[0062] The resin compositions of the examples contain a carbodiimide compound in addition to basic magnesium sulfate, which provides excellent strand stability and a low specific gravity. By using these resin compositions, molded articles having a flexural modulus of 4.0 GPa or more can be produced.

[0063] The resin compositions of the comparative examples do not contain a carbodiimide compound, and therefore cannot achieve the objective. Comparative Examples 1 to 5, 7, and 8 show that even when basic magnesium sulfate alone is contained, molded articles with low strand stability and excellent rigidity cannot be obtained. Comparative Examples 6 and 9 also show that when glass fiber is contained instead of basic magnesium sulfate, a resin composition with a low specific gravity cannot be obtained.

Claims

1. A resin composition containing a thermoplastic resin, basic magnesium sulfate, and a carbodiimide compound.

2. The resin composition according to claim 1, wherein the carbodiimide compound is selected from the group consisting of aliphatic monocarbodiimides, aliphatic polycarbodiimides, alicyclic monocarbodiimides, alicyclic polycarbodiimides, aromatic monocarbodiimides, and aromatic polycarbodiimides.

3. The resin composition according to claim 1 or 2, wherein the basic magnesium sulfate is represented by the following chemical formula (1) or (2): MgSO ４ 5Mg(OH) ２ ・3H ２ O (1) MgSO ４ 5Mg(OH) ２ (2) 4. The resin composition according to claim 3, wherein the basic magnesium sulfate has an average fiber length in the range of 2 to 100 μm and an average fiber diameter in the range of 0.1 to 2.0 μm.

5. The resin composition according to claim 1 or 2, wherein the thermoplastic resin is a polyamide resin.

6. The resin composition according to claim 5, wherein the polyamide resin is polyamide 66 or polyamide 6.

7. The resin composition according to claim 6, wherein the mass ratio of said polyamide resin to said basic magnesium sulfate is 40:60 to 95:

5.

8. A resin composition according to claim 7, wherein the content of the carbodiimide compound is 0.5 to 10 parts by mass when the total of the polyamide resin and the basic magnesium sulfate is 100 parts by mass.

9. A molded article made from the resin composition of claim 1 or 2.