resin composition

Abstract

The present invention aims to provide a resin composition that can give a molded article that is excellent in bending rigidity and impact resistance and further suppressed in discoloration, and a molded article that can be obtained from the resin composition. [Solution] A resin composition containing a resin component and bleached kraft pulp fiber, wherein the resin component contains a polyamide with a melting point above 200°C and a resin with a melting point lower than that of the polyamide, and the resin composition has an endothermic value of 2mJ / mg or more between 100°C and 200°C as determined by differential scanning calorimetry at a heating rate of 10°C / min.

Description

[Technical Field]

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

[0002] Fiber-reinforced plastic molded products made from nonwoven fabrics containing reinforcing fibers such as carbon fiber and glass fiber (also called sheets for fiber-reinforced plastic molded products) are already used in a variety of fields, including sports and leisure goods, aircraft materials, electronic device components, etc. Thermosetting resins and thermoplastic resins are used as the matrix resins in fiber-reinforced plastic molded products, but in recent years, development of fiber-reinforced plastic molded products using thermoplastic resins has been progressing.

[0003] Carbon fiber, glass fiber, aramid fiber, etc. are used as reinforcing fibers. Such reinforcing fibers serve to increase the strength of fiber-reinforced plastic molded bodies. When such molded products are to be disposed of, they are usually buried or incinerated. However, molded products using such reinforcing fibers have low biodegradability after being buried, and there are problems with the load on incinerators and other equipment when they are incinerated.

[0004] For this reason, the use of pulp fibers as reinforcing fibers has been proposed in recent years. For example, Patent Document 1 proposes kneading lignocellulose fibers with a molten thermoplastic resin to obtain a mixed composition used as a fiber-reinforced resin material, and then producing a molded article from the mixed composition. Furthermore, Patent Document 2 proposes producing a molded article from a resin composition containing a polyolefin resin, a polyamide resin, and cellulose nanofibers. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-77910 [Patent Document 2] Japanese Patent Publication No. 2023-11541 Summary of the Invention [Problem to be solved by the invention]

[0006] The molded articles disclosed in Patent Documents 1 and 2 use pulp fibers as reinforcing fibers, and therefore have excellent mechanical properties and good biodegradability, and can reduce the environmental load when incinerated, etc. However, molded articles obtained from the mixed composition disclosed in Patent Document 1 and the resin composition disclosed in Patent Document 2 have a high degree of coloration, which limits their applications.

[0007] An object of the present invention is to provide a resin composition that can give a molded article that is excellent in bending rigidity and impact resistance and further suppressed in discoloration, and a molded article that can be obtained from the resin composition. [Means for solving the problem]

[0008] The present inventors discovered that a resin composition obtained by kneading bleached kraft pulp fibers, a polyamide having a melting point of over 200°C, and a resin having a melting point lower than that of the polyamide, and which has an endothermic amount equal to or greater than a specific value within a specific temperature range, produces a molded article having excellent bending rigidity and impact resistance, and furthermore, exhibits suppressed discoloration, leading to the completion of the present invention.

[0009] That is, the present invention provides the following: <1> ~ <7> Regarding. <1> A resin composition containing a resin component and bleached kraft pulp fibers, the resin component contains a polyamide having a melting point of more than 200°C and a resin having a melting point lower than that of the polyamide, A resin composition having an endothermic value of 2 mJ / mg or more between 100°C and 200°C as determined by differential scanning calorimetry at a heating rate of 10°C / min. <2> The resin having a melting point lower than that of polyamide includes polyolefin. <1> The resin composition according to claim 1. <3> The resin having a melting point lower than that of polyamide includes polypropylene and polyethylene. <1> or <2> The resin composition according to claim 1. <4> The content of the polyamide in the resin component is 80% by mass or more. <1> ~ <3> The resin composition according to any one of the above. <5> The content of the bleached kraft pulp fiber is 5% by mass or more and 70% by mass or less, <1> ~ <4> The resin composition according to any one of the above. <6> <1> ~ <5> 1. A molded article obtained by molding the resin composition according to any one of 1 to 8. <7> A method for producing a resin composition, comprising a step of kneading a polyamide having a melting point of more than 200°C with a nonwoven fabric containing bleached kraft pulp fibers and a resin having a melting point lower than that of the polyamide, A method for producing a resin composition, wherein the endothermic heat of the resin composition between 100°C and 200°C is 2 mJ / mg or more. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a resin composition that can give a molded article that has excellent bending rigidity and impact resistance and further has suppressed coloration, and a molded article obtained from the resin composition. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing the web forming apparatus used in the examples. [Figure 2] FIG. 2 shows the endothermic heat measurement results of the resin composition produced in Example 1 using a differential scanning calorimeter (DSC). DETAILED DESCRIPTION OF THE INVENTION

[0012] [Resin composition] The resin composition of this embodiment contains a resin component and bleached kraft pulp fibers, the resin component containing a polyamide having a melting point of over 200°C and a resin having a melting point lower than that of the polyamide, and the heat absorption between 100°C and 200°C is 2 mJ / mg or more. The resin composition of this embodiment provides a molded article that has excellent bending rigidity and impact resistance and is furthermore suppressed in coloration. The detailed reasons why the above effects are obtained are unknown, but some of the reasons are thought to be as follows. It is believed that the pulp fibers dispersed in the resin composition give the molded article obtained from the resin composition of this embodiment excellent bending rigidity and impact resistance. Polyamides with melting points exceeding 200°C have excellent rigidity, and pulp fibers are added to these polyamides to further improve impact resistance and rigidity. However, because polyamides have high melting points, there is a problem in that the pulp fibers become discolored due to heat generated during kneading. The resin composition of this embodiment contains a resin component comprising a polyamide with a melting point exceeding 200°C and a resin with a melting point lower than that of the polyamide. Resins with melting points lower than those of polyamides with melting points exceeding 200°C melt at a lower temperature range than polyamides with melting points exceeding 200°C, absorbing heat during the process. Therefore, when a resin composition is prepared by kneading a resin component with bleached kraft pulp fibers, shear heating within the kneaded product itself is suppressed compared to when a polyamide with a melting point exceeding 200°C is melted and kneaded at a lower temperature, which is thought to be one of the reasons why discoloration of the resin composition can be suppressed. Furthermore, when the resin composition is heated during production, the resin with a lower melting point than the polyamide with a melting point of over 200°C melts first and adheres to the pulp, preventing contact between the polyamide with a melting point of over 200°C and the pulp fibers, thereby inhibiting the reaction between the amide bond of the polyamide and the sugar in the pulp fibers. Furthermore, the resin composition contains a resin with a lower melting point than the polyamide, and the heat absorption capacity between 100°C and 200°C is 2 mJ / mg or more, which fully demonstrates the above-mentioned effect, and this is thought to be a factor in preventing discoloration of the molded product. The present invention will be described in detail below.

[0013] [Resin component] The resin composition of the present embodiment contains a resin component, and the resin component contains a polyamide having a melting point of more than 200° C. and a resin having a melting point lower than that of the polyamide.

[0014] <Polyamide with a melting point above 200°C> Examples of polyamide resins (hereinafter simply referred to as "polyamides") having a melting point of over 200°C include nylon 6 and nylon 66, and nylon 6 is preferred from the viewpoints of improving the bending rigidity and impact resistance of molded articles and suppressing coloration. The melting point of the polyamide resin is greater than 200°C, preferably 210°C or higher, more preferably 220°C or higher, from the viewpoints of ease of molding, improving the bending rigidity and impact resistance of molded articles, and suppressing discoloration, and is preferably 300°C or lower, more preferably 270°C or lower. The melting point of the polyamide is measured by the method described in the Examples.

[0015] <Resins with a lower melting point than polyamides with a melting point of over 200°C> Examples of resins having a melting point lower than that of polyamide include polyolefins and modified polyolefins, with polyolefins being preferred, from the viewpoints of improving the bending rigidity and impact resistance of molded articles and suppressing discoloration. When the resin component contains multiple polyamides with melting points higher than 200°C, the term "resin having a melting point lower than that of polyamide" refers to a resin having a melting point lower than that of the polyamide with the lowest melting point among the multiple polyamides with melting points higher than 200°C. The melting point of the resin having a lower melting point than polyamide is preferably 200°C or lower, more preferably 190°C or lower, even more preferably 180°C or lower, from the viewpoints of ease of molding, improving the bending rigidity and impact resistance of the molded product, and suppressing discoloration, and is preferably 80°C or higher, more preferably 90°C or higher, even more preferably 100°C or higher.

[0016] Examples of polyolefins include polyethylene, polypropylene, and ethylene-propylene copolymers, with polyethylene and polypropylene being preferred, and a combination of polyethylene and polypropylene being more preferred. In addition, in modified polyolefins, examples of methods for modifying polyolefins include acid modification and chlorination, and among these, acid modification is preferred from the viewpoint of improving affinity with bleached kraft pulp fibers. The acid-modifying component used for the acid modification of the acid-modified polyolefin is preferably an unsaturated carboxylic acid component. Examples of the unsaturated carboxylic acid component include components derived from unsaturated carboxylic acids and their acid anhydrides. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, and crotonic acid. Among these, the unsaturated carboxylic acid component is preferably at least one selected from acrylic acid, methacrylic acid, maleic acid, and maleic anhydride, and more preferably at least one selected from maleic acid and maleic anhydride. Polyolefins modified with at least one of maleic acid and maleic anhydride are also called maleic acid-modified polyolefins. The acid-modified polyolefin is preferably a maleic acid-modified polyolefin, more preferably a maleic acid-modified polyethylene or a maleic acid-modified polypropylene. The acid-modified polyolefin may be at least partially acid-modified. The resins having a melting point lower than that of polyamide may be used alone or in combination of two or more.

[0017] The content of the resin component in the resin composition is preferably 30% by mass or more, more preferably 45% by mass or more, and even more preferably 60% by mass or more from the viewpoints of productivity and ease of production, and is preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 93% by mass or less from the viewpoints of improving the bending rigidity and impact resistance of the molded article.

[0018] The content of polyamide in the resin component is preferably 65% ​​by mass or more, more preferably 70% by mass or more, even more preferably 75% by mass or more, and even more preferably 80% by mass or more, from the viewpoint of improving the bending rigidity and impact resistance of the molded article, and is preferably 99% by mass or less, more preferably 97% by mass or less, from the viewpoint of productivity and ease of production.

[0019] The content of the resin having a melting point lower than that of polyamide in the resin component is preferably 1% by mass or more, more preferably 3% by mass or more, from the viewpoint of improving the bending rigidity and impact resistance of the molded article, and is preferably 30% by mass or less, more preferably 25% by mass or less, from the viewpoint of productivity and ease of production.

[0020] From the viewpoint of improving the bending rigidity and impact resistance of the molded article, the total content of polyamide and resin having a melting point lower than that of polyamide in the resin component is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, and is 100% by mass or less, and even more preferably 100% by mass.

[0021] [Bleached Kraft Pulp Fiber] Bleached kraft pulp fibers are obtained by bleaching kraft pulp (bleached product) made by using caustic soda and sodium sulfide during wood chip cooking, and from the viewpoints of improving the bending rigidity and impact resistance of molded articles and suppressing discoloration, softwood bleached kraft pulp (NBKP) fibers and hardwood bleached kraft pulp (LBKP) fibers are preferred, with NBKP fibers being more preferred. In particular, softwood kraft pulp (NBKP) fibers with long fiber length are preferred from the viewpoint of further improving the bending rigidity and impact resistance of molded articles obtained from resin compositions. The bleached kraft pulp fibers may be used alone or in combination of two or more types.

[0022] The average fiber length of bleached kraft pulp fibers is preferably 0.1 mm or more, more preferably 0.5 mm or more, even more preferably 1 mm or more, even more preferably 1.5 mm or more, and even more preferably 2 mm or more, from the viewpoint of improving the bending rigidity and impact resistance of molded products and the ease of manufacturing nonwoven fabrics described below, and is preferably 50 mm or less, more preferably 10 mm or less, even more preferably 5 mm or less, and even more preferably 2.5 mm or less. The average fiber length of the bleached kraft pulp fibers is measured by the method described in the Examples.

[0023] The average fiber width of the bleached kraft pulp fibers is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, still more preferably 15 μm or more, from the viewpoint of improving the bending rigidity and impact resistance of the molded product and the ease of manufacturing the nonwoven fabric, and is preferably 150 μm or less, more preferably 100 μm or less, even more preferably 80 μm or less, and still more preferably 50 μm or less. The average fiber width of bleached kraft pulp fibers is measured by the method described in the Examples.

[0024] When the nonwoven fabric is formed via an airlaid process, the bleached kraft pulp fibers can be in the form of, for example, defibrated dry pulp.

[0025] The bleached kraft pulp fibers are preferably unbeaten pulp fibers from the viewpoint of improving impact resistance. In order for a molded body to exhibit impact resistance, the bleached kraft pulp fibers must be properly pulled out of the resin when an impact is applied, and for this purpose, it is preferable to use unbeaten pulp with a low fine fiber ratio. Furthermore, from the viewpoint of improving impact resistance, the fine fiber ratio of the bleached kraft pulp fibers is preferably 50% or less, more preferably 30% or less, and even more preferably 20% or less, with no particular lower limit. The fine fiber ratio of bleached kraft pulp fibers is measured by the method described in the Examples. The fine fiber ratio means the percentage (%) of the number of cellulose fibers (pulp fibers) with a length of 0.1 mm or less out of the total number of measured cellulose fibers (pulp fibers) (100 x "number of cellulose fibers with a length of 0.1 mm or less" / "number of all cellulose fibers").

[0026] The content of bleached kraft pulp fiber in the resin composition is preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more, from the viewpoint of improving the bending rigidity and impact resistance of the molded product, and is preferably 70% by mass or less, more preferably 55% by mass or less, and even more preferably 40% by mass or less, from the viewpoint of productivity and ease of production.

[0027] [Other ingredients] When the resin components in the resin composition of this embodiment are polyamide and polyolefin, the resin composition may contain other components in addition to the bleached kraft pulp fibers, polyamide, and polyolefin described above. Examples of other components include resins other than polyamide and polyolefin, and elastomers. In this specification, the term "elastomer" refers to a polymer compound that exhibits elastic deformation. That is, it is defined as a polymer compound that has the property of instantly deforming in response to the application of an external force and quickly recovering its original shape when the external force is removed. Examples of resins that can be used other than polyamides and polyolefins include various starches, casein, sodium alginate, hydroxyethyl cellulose, carboxymethyl cellulose, acrylic resins, styrene-(meth)acrylic acid ester copolymer resins, urethane resins, polyvinyl alcohol (PVA) resins, cellulose derivatives, sodium polyacrylate, polyacrylamide, polyvinylpyrrolidone, acrylamide-acrylic acid ester-methacrylic acid ester copolymers, styrene-maleic anhydride copolymer alkali salts, isobutylene-maleic anhydride copolymer alkali salts, polyvinyl acetate resins, vinyl chloride-vinyl acetate copolymers, and ethylene-vinyl acetate copolymers.

[0028] Examples of the elastomer include various elastomers described in paragraphs 0043 to 0065 of WO2020 / 080328.

[0029] The resin composition may further contain fillers, papermaking chemicals, and fatty acid metal salts. Examples of fillers include mineral pigments such as kaolin, calcined kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, talc, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, white carbon, bentonite, zeolite, sericite, and smectite, as well as organic pigments such as azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, and isoindolinone pigments. Examples of papermaking chemicals include paper strength agents, retention aids, drainage aids, dyes, fluorescent whitening agents, pH adjusters, antifoaming agents, pitch control agents, and slime control agents. Examples of dry strength agents include polyacrylamides. Wet strength agents can also be used in combination, such as polyamide resins, melamine-formaldehyde resins, urea-formaldehyde resins, polyamide-polyamine-epichlorohydrin resins, and polyethyleneimine resins.

[0030] The fatty acid metal salt is preferably a metal salt of an aliphatic carboxylic acid, and the aliphatic carboxylic acid is preferably a saturated aliphatic carboxylic acid or an unsaturated aliphatic carboxylic acid having from 12 to 24 carbon atoms, and specific examples include lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, heneicosylic acid, behenic acid, lignoceric acid, cerotic acid, montanic acid, melissic acid, myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, and elaidic acid. Examples of metal elements that form metal salts include Group 1 elements (alkali metals) such as sodium and potassium; Group 2 elements (alkaline earth metals) such as calcium, magnesium, and barium; and Group 3 elements such as zinc and aluminum, with calcium, magnesium, zinc, and aluminum being preferred. Examples of fatty acid metal salts include magnesium stearate, calcium stearate, zinc stearate, barium stearate, aluminum stearate, lithium stearate, zinc laurate, and barium laurate. Among these, from the viewpoint of improving the bending rigidity and impact resistance of a molded article, calcium stearate, magnesium stearate, zinc stearate, aluminum stearate, calcium oleate, magnesium oleate, zinc oleate, aluminum oleate, zinc laurate, or calcium laurate is preferred, and calcium stearate is more preferred.

[0031] The content of other components in the resin composition is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and even more preferably 1% by mass or less, and is 0% by mass or more.

[0032] The resin composition of the present embodiment may be in any shape such as pellets, rods, cylinders, sheets, or films, but is preferably in pellet form.

[0033] [Characteristics of Resin Composition] <Amount of heat absorbed> The resin composition of the present embodiment has an endothermic value between 100°C and 200°C, as determined by differential scanning calorimetry at a heating rate of 10°C / min, of 2 mJ / mg or more, preferably 2.5 mJ / mg or more, from the viewpoint of improving the bending rigidity and impact resistance of the molded article and suppressing discoloration. From the viewpoint of ease of production, the endothermic value is preferably 25 mJ / mg or less, more preferably 20 mJ / mg or less, and even more preferably 15 mJ / mg or less. The heat absorption amount between 100°C and 200°C can be adjusted by the type of resin with a lower melting point than polyamide, the content of polyamide and resin with a lower melting point than polyamide in the resin composition, etc. For example, by using a large amount of polyolefin, which shows an endothermic peak between 100°C and 200°C in differential scanning calorimetry at a heating rate of 10°C / min, as a resin with a lower melting point than polyamide, the heat absorption amount of the resin composition between 100°C and 200°C can be increased. The resin composition of the present embodiment has an endothermic value between 200°C and 250°C, as determined by differential scanning calorimetry at a heating rate of 10°C / min, of preferably 20 mJ / mg or more, more preferably 25 mJ / mg or more, and even more preferably 30 mJ / mg or more, from the viewpoint of improving the bending rigidity and impact resistance of the molded article and from the viewpoint of suppressing discoloration. From the viewpoint of ease of production, the endothermic value is preferably 75 mJ / mg or less, more preferably 70 mJ / mg or less, and even more preferably 65 mJ / mg or less. The endothermic amount between 200°C and 250°C can be adjusted by adjusting the content of polyamide and resin with a melting point lower than that of polyamide in the resin composition. For example, by using a large amount of polyamide, the endothermic amount of the resin composition between 200°C and 250°C can be increased. The polyamide preferably exhibits an endothermic peak between 200°C and 250°C in differential scanning calorimetry at a heating rate of 10°C / min. The endothermic amount of the resin composition of the present embodiment is measured by the method described in the examples.

[0034] [Molded body] The molded article of this embodiment is a molded article molded from the above-mentioned resin composition. The resin composition can be processed into any shape according to the shape and molding method of the target molded article.

[0035] [Characteristics of Molded Product] (Thickness) The thickness of the molded body is not particularly limited, but is preferably 0.5 mm or more, more preferably 1 mm or more, even more preferably 2 mm or more, and is preferably 200 mm or less, more preferably 100 mm or less, even more preferably 50 mm or less, even more preferably 20 mm or less, and even more preferably 10 mm or less. By making the thickness of the molded article 2 mm or more, it can be suitably used in applications requiring impact resistance, and therefore the thickness of the molded article is preferably 2 mm or more.

[0036] (density) In this embodiment, the density of the molded body is preferably 1.06 g / cm 3 More preferably, 1.11 g / cm 3 More preferably, 1.16 g / cm 3 and preferably 1.39 g / cm 3 or less, more preferably 1.34 g / cm 3 or less, more preferably 1.29 g / cm 3 The following is the result. The density of the molded body is calculated by the method described in the Examples.

[0037] (flexural modulus) The molded article of this embodiment has a flexural modulus of preferably 2.5 GPa or more, more preferably 3.0 GPa or more, even more preferably 3.3 GPa or more, and still more preferably 3.5 GPa or more, measured in accordance with JIS K 7171: 2016. The upper limit is not particularly limited, but from the viewpoint of ease of production, it is preferably 10 GPa or less.

[0038] (Charpy impact strength) The molded article of this embodiment preferably has high Charpy impact strength, and the Charpy impact strength of a molded article having a thickness of 4 mm is preferably 1.0 kJ / m 2 More preferably, 1.5 kJ / m 2 More preferably, 2.0 kJ / m 2 More preferably, 2.5 kJ / m 2The upper limit is not particularly limited, but from the viewpoint of ease of production, it is preferably 20 kJ / m 2 Less than or equal to 10 kJ / m 2 Less than 7 kJ / m, more preferably 2 The following is the result. The larger the Charpy impact strength value, the better the impact resistance. The Charpy impact strength is measured in accordance with JIS K 7111-1:2012, and more specifically, by the method described in the examples.

[0039] (chromaticity) The molded article of the present embodiment preferably has a small chromaticity, preferably not more than 14, more preferably not more than 13, and even more preferably not more than 12. The lower limit is not particularly limited, but from the viewpoint of ease of production, it is, for example, not less than 4. The color is measured by the method described in the examples.

[0040] [Method of producing resin composition] The method for producing the resin composition of this embodiment includes a step of kneading a polyamide having a melting point of more than 200°C with a nonwoven fabric containing bleached kraft pulp and a resin having a melting point lower than that of the polyamide, and the endothermic heat of the resin composition between 100°C and 200°C is 2 mJ / mg or more. The method for producing the resin composition of this embodiment is preferably a production method including, for example, the following steps 1 to 3. Process 1: A fiber assembly manufacturing process in which a fiber assembly containing bleached kraft pulp fiber and a resin with a melting point lower than polyamide (melting point over 200°C) is manufactured by dry papermaking. Step 2: Compressing the fiber assembly to produce nonwoven fabric. Step 3: A step of melt-kneading the nonwoven fabric and the polyamide having a melting point of over 200°C to produce a pellet-shaped resin composition. Each step will be described below.

[0041] <Process 1> Step 1 is a fiber assembly manufacturing step in which a fiber assembly containing bleached kraft pulp fibers and a resin having a melting point lower than that of polyamide is manufactured by dry papermaking. The resin composition of this embodiment is preferably produced by dry-laid papermaking of a cellulose fiber aggregate containing bleached kraft pulp fibers and a resin having a melting point lower than that of polyamide, followed by a process of compressing the cellulose fiber aggregate to produce a nonwoven fabric. That is, it is preferable that at least a resin having a melting point lower than that of polyamide is blended with the cellulose fiber aggregate. Note that, in the production of the resin composition, further resins or elastomers may be added.

[0042] In this embodiment, the resin having a melting point lower than that of polyamide to be contained in the fiber assembly can be in the form of any of fibers, powder, granules, and pellets. Among these, from the viewpoint of ease of papermaking in step 1 described below and the dispersibility of cellulose fibers in the resin composition and molded body, the resin having a melting point lower than that of polyamide to be contained in the fiber assembly is preferably in the form of fibers or powder, and more preferably fibers. In other words, the resin having a melting point lower than that of polyamide to be contained in the fiber assembly preferably includes resin fibers or resin powder, more preferably includes resin fibers, and even more preferably includes resin fibers.

[0043] From the viewpoint of improving the bending rigidity and impact resistance of the molded article, the content of resin having a lower melting point than polyamide in the fiber assembly is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less. When two or more resins having a melting point lower than that of polyamide are used, the above content means the total content of the resins having a melting point lower than that of polyamide.

[0044] When the resin having a melting point lower than that of polyamide is in the form of powder, granules, or pellets, the particle size thereof is not particularly limited.

[0045] In step 1, a fiber aggregate is produced by dry papermaking using bleached kraft pulp fibers and a resin with a lower melting point than polyamide. In the explanation of step 1, polyolefin fibers are used as the resin with a lower melting point than polyamide. When a resin other than polyolefin fibers is used as the resin with a lower melting point than polyamide, the resin should be read as the resin used in place of polyolefin fibers, and the rest of the explanation remains the same. Step 1 preferably includes a step of mixing bleached kraft pulp fibers and polyolefin fibers in air and depositing the mixture. That is, the fiber assembly of this embodiment is preferably a drylaid nonwoven fabric.

[0046] When producing a fiber aggregate using a dry papermaking method, it is preferable to use an airlaid method. The airlaid method is a method in which an airflow containing raw fibers, such as bleached kraft pulp fibers and polyolefin fibers that have been defibrated in the air and uniformly mixed in the airflow, is discharged onto a mesh-like endless belt equipped with a suction box below to form an airlaid web. That is, the airlaid method includes a step of mixing bleached kraft pulp fibers and polyolefin fibers in the air and depositing them. In the airlaid method, the above operation may be repeated multiple times as necessary.

[0047] The web formed by the above method is made into a sheet by the fiber bonding process described below. Examples of the fiber bonding process include a needle punching method in which needles are passed perpendicularly to the web surface to entangle bleached kraft pulp fibers or polyolefin fibers to form a sheet. This bonding process is preferably used in combination with a carding web formation method. The fiber bonding process can also be performed using a thermal bonding process, in which a heat-fusible adhesive incorporated into the dry-laid web is heated to fuse the raw fibers together, a chemical bonding process, in which an adhesive is applied to the resulting dry-laid web to bond the raw fibers, or a multi-bond process, in which the thermal bonding and chemical bonding processes are combined.

[0048] In the thermal bonding method, it is preferable to heat at a temperature at least 20° C. higher than the melting point of the heat-fusible adhesive. Examples of the heat treatment include hot air treatment and hot-air treatment followed by low-pressure heat and pressure treatment.

[0049] When the thermal bond method or the multi-bond method is employed, it is preferable to use a particulate or fibrous heat-fusible adhesive, which may be the polyolefin fiber or binder component described above. As the particulate heat-fusible adhesive, heat-fusible resin particles such as polyethylene, polypropylene, polyester low-melting polyethylene terephthalate, low-melting polyamide, low-melting polylactic acid, polybutylene succinate, etc. are used. Fibrous heat-bonding adhesives that can be used include polyesters such as maleic acid-modified polyethylene (MAPE), low-melting point polyethylene terephthalate, low-melting point polylactic acid, polybutylene succinate (PBS), polyethylene terephthalate (PET), low-melting point polyamide, acrylic resin, and polyvinyl acetate (PVAc) resin. Furthermore, as a fibrous heat-fusible adhesive, a heat-fusible composite synthetic fiber with a sheath-core structure, which is obtained by combining two types of resin with different melting points and in which only the surface of the fiber melts, can also be preferably used. Heat-fusible composite synthetic fibers with a sheath-core structure have a core made of a resin with a high melting point surrounded by a sheath made of a resin with a low melting point. Specific examples include those that combine two types of resin with different melting points (PET / PET composite fiber, PE / PET composite fiber, MAPE (maleic anhydride-modified polyethylene) / PP composite fiber, PP / PET composite fiber, PE / PP composite fiber, and PVAc (polyvinyl acetate) / PET composite fiber).

[0050] When chemical bonding is used to bond the fibers, the binder component described above may be added to bond the fibers together. The binder component may be in various forms, such as fiber, powder, granules, solution, or emulsion, and two or more types may be used in combination.

[0051] In the fiber aggregate produced by the above-mentioned dry papermaking method, the fibers constituting the fiber aggregate are three-dimensionally oriented randomly in the longitudinal, transverse and thickness directions.

[0052] In the manufacturing process of the fiber assembly, any sheet that does not impair moldability may be laminated on the fiber assembly to manufacture a laminated sheet. For example, the optional sheet can be laminated on the surface of the fiber assembly or between sheets when laminating the fiber assembly. The optional sheet to be laminated can be a tissue or a nonwoven fabric. These optional sheets are laminated for the purpose of improving the productivity of the fiber assembly in the manufacturing process.

[0053] <Process 2> Step 2 is a nonwoven fabric production step in which the fiber assembly obtained in step 1 is compressed to produce a nonwoven fabric. By compressing the fiber assembly obtained in step 1, a sheet-like nonwoven fabric is obtained. The compression may be carried out simultaneously with the heat treatment or after the heat treatment.

[0054] Compression of the fiber assembly can be achieved by applying pressure to the fiber assembly using a roll press. Heating may be performed simultaneously during the roll press process, resulting in a heat-pressure treatment. The roll press process uses metal rolls or resin rolls to apply pressure, allowing the density of the resulting nonwoven fabric to be controlled as desired. Specifically, a nonwoven fabric with any desired density can be obtained by setting any number of rolls, any temperature, and any clearance for the roll press process, and heating and pressurizing the sheet. The fiber assembly may be compressed to the desired density by passing through multiple rolls.

[0055] The fiber assembly can also be compressed by pressure treatment using a heat press or a supercalender. When compressing the fiber aggregate to produce a nonwoven fabric, a plurality of nonwoven fabrics may be appropriately laminated and compressed depending on the desired thickness of the cellulose fiber-containing sheet.

[0056] In this embodiment, the nonwoven fabric preferably has a T / Y ratio of 0.5 to 1.5, where T is the tensile strength in a first direction and Y is the tensile strength in a second direction perpendicular to the first direction. By setting the T / Y ratio to 0.5 to 1.5, the fibers constituting the nonwoven fabric are mixed extremely uniformly, which is preferable because it allows for a molded article to be obtained that is excellent in impact resistance as well as bending rigidity. T / Y is preferably 0.60 or more, more preferably 0.70 or more, even more preferably 0.80 or more, still more preferably 0.85 or more, and is preferably 1.40 or less, more preferably 1.30 or less, even more preferably 1.20 or less, and still more preferably 1.15 or less. The first direction of a nonwoven fabric is any one direction in the planar direction of the nonwoven fabric. However, if the fibers contained in the nonwoven fabric are oriented in any direction in the planar direction, that orientation direction is referred to as the first direction. Furthermore, if the flow direction in the manufacturing process of the fiber assembly by dry papermaking is known, that flow direction is referred to as the first direction. If the flow direction in the manufacturing process of the fiber assembly is known, the flow direction in the manufacturing process is referred to as the first direction (MD direction), and the flow direction in the resulting fiber assembly and nonwoven fabric is sometimes referred to as the T-mesh. The second direction of the fiber assembly is a direction in the planar direction of the fiber assembly, and is a direction perpendicular to the first direction. When the flow direction in the manufacturing process of the fiber assembly is known, the direction perpendicular to the flow direction in the manufacturing process is called the second direction (CD direction), and the second direction in the obtained fiber assembly and nonwoven fabric is sometimes called the Y direction. The tensile strength of the nonwoven fabric in the first and second directions is measured in accordance with JIS P 8113: 2006. The tensile strength in each direction is measured using a 15±0.1 mm x 180±1 mm strip at a speed of 20±5 mm / min using a Tensilon tensile tester manufactured by A&D Co., Ltd.

[0057] In this embodiment, the nonwoven fabric is a sheet-shaped fabric obtained by mixing at least bleached kraft pulp fibers and a resin (preferably polyolefin fibers) with a melting point lower than that of polyamide, followed by dry papermaking. The sheet is obtained by pressing the cotton-like fiber aggregate after dry papermaking, and may have various bulk specific gravities (densities). The bulk density of the nonwoven fabric is preferably 0.10 g / mL or more, more preferably 0.15 g / mL or more, and is preferably 0.60 g / mL or less, more preferably 0.50 g / mL or less, and even more preferably 0.40 g / mL or less, from the viewpoints of ease of compression in step 2, ease of subsequent melt-kneading, ease of cutting when cutting for feeding to a melt-kneader, and the like. The bulk density of the nonwoven fabric is measured by the method described in the examples.

[0058] <Process 3> Step 3 is a pellet-shaped resin composition production step in which the nonwoven fabric and polyamide are melt-kneaded to produce a pellet-shaped resin composition (hereinafter also simply referred to as "pellets"). The polyamide is preferably in the form of pellets from the viewpoint of ease of feeding into the melt kneader. Furthermore, from the viewpoint of facilitating feeding into the melt kneader before melt kneading, it is preferable to cut, crush, etc. the nonwoven fabric before feeding into the melt kneader. The cutting machine is not particularly limited, and examples thereof include a shredder. The size of the material after cutting, crushing, etc. is not particularly limited as long as it can be fed into a mixer.

[0059] There are no particular limitations on the method for producing the pelletized resin composition, and it is sufficient to supply the nonwoven fabric and polyamide and melt-knead them. Examples of the apparatus used for melt-kneading include a single-screw extruder, a twin-screw extruder, a kneader, a Banbury mixer, a mixing roll mill, an open roll mill, and a glass mixer. After the nonwoven fabric is fed and melt-kneaded, (1) A method of extruding the resin composition in the form of strands, followed by cooling and solidifying the strands to obtain a pellet-shaped resin composition; (2) A method in which the molten kneaded product is cooled and solidified as is or after being stretched into a sheet, and then crushed in a crusher to obtain a pellet-shaped resin composition; (3) A method in which the resin composition is extruded into a rod or cylinder and cooled to obtain a pellet-shaped resin composition. (4) A method in which a cellulose fiber-containing resin is extruded through a T-die to obtain a sheet or film of the resin, and then the resin is cut or crushed to obtain a pellet-shaped resin composition; or (5) A method in which the molten kneaded product immediately after extrusion is cut with a rotary blade in air or water to obtain cellulose fiber-containing resin pellets. Examples include:

[0060] The size of the pellets obtained in step 3 is not particularly limited, but is preferably 1 to 10 mm from the viewpoint of ease of feeding into an injection molding machine.

[0061] The melt-kneading temperature (barrel setting temperature) is not particularly limited, but the temperature of the melt-kneaded product (the temperature of the actually obtained kneaded product, the resin temperature) is preferably at least 5°C higher than the melting point of the polyamide, more preferably at least 12°C higher, and even more preferably at least 20°C higher.From the viewpoint of preventing degradation of the cellulose fiber, it is preferably at most 70°C higher than the melting point of the polyamide, more preferably at most 60°C higher, and even more preferably at most 50°C higher. The temperature of the melt-kneaded product becomes higher than the melt-kneading temperature (barrel set temperature) due to shear heat generated during melt-kneading. That is, it varies depending on various conditions during melt-kneading, such as the melt-kneading temperature (barrel set temperature), discharge speed, rotation speed, and screw design of the melt-kneader. In the case of the method described in the examples, the temperature of the melt-kneaded product becomes higher by about 20 to 40°C than the melt-kneading temperature (barrel set temperature), so the melt-kneading temperature (barrel set temperature) becomes lower by about 20 to 40°C than the preferred temperature of the melt-kneaded product.

[0062] Various conditions during melt-kneading, such as the discharge speed and rotation speed, may be adjusted according to known methods.

[0063] In step 3, a resin component such as an elastomer may be further blended together with the nonwoven fabric and melt-kneaded.

[0064] [Method of manufacturing molded body] The method for producing a molded article of this embodiment is a step of molding the resin composition of this embodiment. Various molding methods are used in the molding process, including, for example, injection molding (e.g., injection compression molding (press injection, hot flow stamping molding, gas injection compression molding), gas injection molding, and ultra-high speed injection molding), various extrusion moldings (cold runner method or hot runner method), compression (press) molding, insert molding, in-mold coating molding, insulating mold molding, rapid heating and cooling mold molding, and various profile extrusion moldings (e.g., two-color molding and sandwich molding). For example, various extrusion moldings are suitable for forming sheets, films, fibers, etc. Inflation, calendaring, casting, etc. can also be used to form sheets or films. Furthermore, a specific stretching operation may be performed. Hollow molded articles can also be formed by rotational molding or blow molding, etc. In addition, a plurality of molding steps may be combined, or a plurality of steps may be simultaneously performed as a single step. For example, the resin composition may be formed into a sheet and then subjected to heat press molding to obtain a molded article, or the resin composition may be formed into a sheet and then subjected to supercalendering to obtain a molded article. Furthermore, after forming into a sheet, the resin composition may be molded by vacuum forming, pressure forming, or the like. Among these, injection molding is a preferred example.

[0065] When the molding step is an injection molding step, the injection molding step involves, for example, using a known injection molding machine to heat and melt the resin composition, and then injecting the molten mixture into a mold to perform molding. Examples of known injection molding machines include screw injection molding machines, screw pre-plasticizing injection molding machines, plunger pre-plasticizing injection molding machines, plunger injection molding machines, etc. Examples of drive systems include hydraulic, electric, and hydraulic-electric hybrid systems.

[0066] As for the temperature conditions for injection molding, the cylinder temperature of the injection molding machine is preferably set to a temperature 0 to 100° C. higher than the flow initiation temperature of the polyamide. The temperature of the mold may be appropriately selected in consideration of the cooling rate of the resin and productivity, and is preferably set within the range of room temperature (for example, 23°C) to 120°C. Other injection conditions such as the screw rotation speed, back pressure, injection speed, pressure holding, and pressure holding time may be adjusted as appropriate.

[0067] The resin composition of the present embodiment may contain other resins such as elastomers by adding other resins, for example, elastomers, and melt-kneading them during molding. In the process of producing a molded article, other resins, various additives, masterbatches containing various additives, etc. may be added in addition to the resin composition during injection molding. The additives include those typically used in resin compositions, such as stabilizers, ultraviolet absorbers, plasticizers, flame retardants, flame retardant assistants, antistatic agents, surfactants, colorants, lubricants, and mold release agents. Examples of stabilizers include hindered phenols, hydroquinone, phosphites, and substituted versions thereof. Examples of ultraviolet absorbers include resorcinol, salicylate, benzotriazole, and benzophenone. Colorants include materials including dyes such as nitrosine, and pigments such as cadmium sulfide, phthalocyanine, and carbon black. Examples of lubricants include fatty acids such as stearic acid and montanic acid, their amides, their esters, their half esters with polyhydric alcohols, stearyl alcohol, stearamide, polyethylene wax, and paraffin wax.

[0068] (Application) Molded articles formed from the resin composition of the present embodiment are preferably used for electrical and electronic equipment, office automation equipment, home appliances, civil engineering and construction, automobile and aircraft parts, structural parts and housings, containers (for example, food containers, drug packaging containers, cosmetic packaging containers, and medical device packaging containers), furniture, daily necessities, medical tools, and the like. Among these, it is suitable for applications requiring impact resistance, such as civil engineering and construction, automobile or aircraft parts, structural parts, and housings. [Example]

[0069] The features of the present invention will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0070] Example 1 <Preparation of fiber assembly> The NBKP fiber was defibrated using a swirling jet airflow defibrator to obtain defibrated dry pulp. The processing air speed in the defibrator was 45 m / min, and turbulence was achieved using baffles installed inside the device. The average fiber length of the obtained defibrated dry pulp was 2.38 mm, the average fiber width was 34.3 μm, and the fine fiber ratio was 11.4%.

[0071] Next, the obtained defibrated dry pulp was uniformly mixed with polypropylene fiber (melting point 160°C, fineness 6.6 dtex, fiber length 5 mm, fiber diameter 30 μm, also called PP fiber) and polyethylene / polypropylene composite core-sheath fiber (core melting point 160°C, sheath melting point 110°C, fineness 1.7 dtex, fiber length 5 mm, fiber diameter 15 μm, also called PE / PP composite fiber (PE / PP (mass ratio) = 1 / 1)) in a ratio (mass ratio) of 70 / 15 / 15 using an air flow to obtain a fiber mixture.

[0072] Next, an airlaid web was formed from the fiber mixture using the web forming apparatus 1 shown in FIG. 1. Specifically, a first carrier sheet 41 was fed by a first carrier sheet supplying means 40 onto a permeable endless belt 20 that was attached to a conveyor 10 and running. In Example 1, tissue (basis weight 14 g / m) was used as the first carrier sheet 41. 2 The "basis weight" was measured in accordance with "Paper and paperboard - Method of measuring basis weight" described in JIS P 8124:2011.

[0073] While the permeable endless belt 20 was being sucked by the suction box 60, the fiber mixture was dropped and deposited on the first carrier sheet 41 together with the air flow from the fiber mixture supply means 30, to obtain a cotton-like fiber aggregate. At this time, the basis weight (set basis weight) of the airlaid web portion was 400 g / m 2 The fiber mixture was supplied so that

[0074] Next, a second carrier sheet 51 was laminated on the cotton-like fiber aggregate on the first carrier sheet 41 by a second carrier sheet supplying means 50, to obtain an air-laid web-containing laminated sheet. In Example 1, tissue (basis weight 14 g / m) was used as the second carrier sheet 51. 2 That is, in Example 1, the same sheet was used for first carrier sheet 41 and second carrier sheet 51.

[0075] <Production of dense fiber assembly sheets (nonwoven fabrics)> The obtained air-laid web-containing laminated sheet was passed through a box-type dryer with a hot air circulation conveyor oven system, and subjected to hot air treatment at a temperature of 140°C. After that, the density was adjusted by roll press treatment so that the bulk specific gravity was 0.3 g / mL, and a nonwoven fabric containing bleached kraft pulp fiber and a resin with a melting point lower than that of polyamide was obtained with a basis weight of 394.8 g / m. 2 The dense fiber assembly sheet had a T / Y ratio of 0.90, a bulk density of 0.28 g / mL, and a thickness of 1.41 mm. The dense fiber assembly sheet was shredded with a shredder (AFS100M, manufactured by Iris Ohyama Co., Ltd.) to obtain press-cut chips of approximately 4 mm x 13 mm.

[0076] <Production of Resin Composition and Molded Article of the Present Embodiment> Press-cut chips and polyamide pellets (Amilan CM1017, nylon 6, Toray Industries, Inc., melting point 225°C) were fed into a twin-screw extruder (Parker Corporation, HK-25D (41D)) at 1.0 kg / hour and 6.0 kg / hour, respectively, and melt-kneaded at a kneading temperature of 230°C. The screw used for kneading was divided into seven parts, with a kneading part consisting of six parts being used in only the fifth part counting from the raw material inlet side, and all other parts being feed screws, for a weak kneading configuration. The kneading part closest to the outlet was an L-type, and all others were R-type. After melt-kneading, the mixture was air-cooled to obtain the resin composition of this embodiment as pellets. The pellets were used to injection mold a Type A1 multipurpose test piece as specified in JIS K 7139:2009 at a molding temperature of 220°C and an injection speed of 10 mm / sec, to obtain a cellulose fiber-containing molded body having a thickness of 4 mm as the molded body of this embodiment.

[0077] Example 2 In Example 1 <Preparation of resin composition and molded body of this embodiment>, a cellulose fiber-containing molded body having a thickness of 4 mm was obtained as a molded body of this embodiment in the same manner as in Example 1, except that press-cut chips and polyamide pellets (Amilan CM1017, Toray Industries, Inc.) were supplied at 3.0 kg / hour and 4.0 kg / hour, respectively, to obtain pellets.

[0078] (Comparative Example 1) An NBKP sheet with a fiber width of 28.54 μm and a fiber length of 1.494 mm was shredded using a shredder (AFS100M, manufactured by Iris Ohyama Co., Ltd.) to obtain pulp cut chips of approximately 4 mm × 13 mm. A cellulose fiber-containing molded body with a thickness of 4 mm was obtained in the same manner as in Example 1, except that in <Production of Resin Composition and Molded Body of the Present Embodiment>, the pulp cut chips and polyamide pellets (Amilan CM1017, Toray Industries, Inc.) were supplied at 2.1 kg / hour and 4.9 kg / hour, respectively, to obtain pellets.

[0079] (Comparative Example 2) In Example 1 <Preparation of the resin composition and molded body of the present embodiment>, a molded body having a thickness of 4 mm was obtained in the same manner as in Example 1, except that only polyamide pellets (Amilan CM1017, Toray Industries, Inc.) were supplied at 7.0 kg / hour to obtain the pellets.

[0080] (Comparative Example 3) In Example 1 <Preparation of the resin composition and molded body of this embodiment>, a cellulose fiber-containing molded body having a thickness of 4 mm was obtained in the same manner as in Example 1, except that pulp cutting chips and polyamide pellets (Amilan CM1017, Toray Industries, Inc.) were supplied at 0.7 kg / hour and 6.3 kg / hour, respectively, to obtain pellets.

[0081] [Measurement and evaluation method] (Method for measuring fiber length and diameter of polyolefin fibers) Twenty randomly selected polyolefin fibers were observed under an optical microscope, and the fiber length and fiber diameter were measured.

[0082] (Method for measuring average fiber length, average fiber diameter, and fine fiber ratio of cellulose fibers (bleached kraft pulp fibers)) The average fiber length and average fiber diameter of cellulose fibers (pulp fibers) were measured using a fiber image analyzer (Valmet FS5, manufactured by Valmet Ltd.) in accordance with ISO 16065-2. The percentage of the number of all measured cellulose fibers (pulp fibers) and the number of cellulose fibers (pulp fibers) with a length of 0.1 mm or less (100 × number of cellulose fibers (pulp fibers) with a length of 0.1 mm or less / number of all cellulose fibers (pulp fibers)) was used as the fine fiber ratio (%).

[0083] (Method for measuring the melting point of resin) Five mg of resin fibers or resin pellets were cut out and the melting point of the resin was measured using a Perkin-Elmer Diamond DSC under a nitrogen atmosphere by heating from 30°C to 280°C at a rate of 20°C / min.

[0084] (Method for measuring bulk density of fiber assembly) The bulk density of the bulky fiber assembly sheet and dense fiber assembly sheet was calculated by measuring the thickness and mass of a 50 mm square sheet after 24 hours at 23°C and 50% RH. The thickness of the sheet was measured using a digital thickness gauge (DG-127, manufactured by Ozaki Seisakusho Co., Ltd.).

[0085] (T / Y measurement method) The flow direction of the resulting fiber aggregate in the manufacturing process (the running direction of the conveyor 10) was defined as the first direction, and the direction perpendicular to the first direction was defined as the second direction. The tensile strength (unit: N / m) was measured according to JIS P 8113:2006. The tensile strength in each direction was calculated by dividing the tensile strength by the thickness of the test piece (unit: MPa). A Tensilon manufactured by A&D Co., Ltd. was used as a tensile tester, and measurements were taken on 15 mm x 180 mm strips at a speed of 20 mm / min.

[0086] (Method for measuring endothermic heat) The endothermic amount of the resulting resin composition was measured by the following method, and the results are shown in Table 1. A 5 mg pellet (resin composition) was cut out and the endotherm was measured using a differential scanning calorimeter (DSC). Using a Hitachi High-Tech NEXTA DSC600, the temperature was raised from 30°C to 270°C at 10°C / min under a nitrogen atmosphere. After reaching 270°C, the temperature was held for 3 minutes. The temperature was then lowered from 270°C to 30°C at 10°C / min. After reaching 30°C, the temperature was held for 3 minutes. The endotherm and peak temperature during the second heating were measured. The sum of the endotherms between 100°C and 200°C and between 200°C and 250°C were calculated. In Examples 1 and 2, an endotherm derived from polyethylene was observed at 120° C. to 130° C., an endotherm derived from polypropylene at 155° C. to 165° C., and two endotherms derived from polyamide at 210° C. to 220° C. The measurement results of Example 1 by DSC are shown in FIG.

[0087] The density, flexural modulus, impact resistance, and color of the obtained molded article were calculated or measured by the following methods. The results are shown in Table 1.

[0088] (Method for calculating density of compact) The obtained molded body was cut into strip-shaped test pieces with a length of 80 mm and a width of 10 mm. The thickness of the strip-shaped test pieces was measured using a constant pressure thickness measuring device (manufactured by Teclock Corporation, model number PG-02J), and the volume of the strip-shaped test pieces was calculated. Furthermore, the density was calculated by measuring the mass of the strip-shaped test pieces.

[0089] (Method for measuring the flexural modulus of molded products) The obtained molded article was cut into a rectangular test piece of 80 mm length x 10 mm width, and a three-point bending test was carried out in accordance with JIS K 7171: 2016. The obtained bending modulus was evaluated such that the larger the value, the better the rigidity against bending.

[0090] (Method for measuring impact resistance of molded products) The obtained molded products were cut into rectangular test pieces measuring 80 mm in length and 10 mm in width, and notched Charpy impact tests (impact direction: edgewise) were carried out in accordance with JIS K 7111-1: 2012. The higher the Charpy impact strength value, the better the impact resistance and the stronger the impact resistance.

[0091] (Method of measuring chromaticity) The obtained molded product was cut into strip-shaped test pieces measuring 20 mm in length and 10 mm in width, and b* was measured using a Colour Cute i manufactured by Suga Test Instruments Co., Ltd., with a D65 light source and reflected light at a 2-degree field of view. A larger b* value indicated more yellow or brown coloration, and a smaller b* value indicated less coloration.

[0092] [Table 1]

[0093] As shown in Examples 1 and 2, the molded articles produced using the resin compositions of the present invention were excellent in flexural modulus and impact resistance, and were suppressed in coloration. On the other hand, as shown in Comparative Examples 1 and 3, when no resin with a melting point lower than that of polyamide was contained, the flexural modulus was similar to that of Example 2, which contained a resin with a melting point lower than that of polyamide, but the impact resistance was inferior and the coloring was significant. Furthermore, as shown in Comparative Example 2, when the kraft pulp fiber and the resin having a melting point lower than that of polyamide were not contained, the flexural modulus and impact resistance were poor. [Explanation of symbols]

[0094] 1. Web forming device 10 Conveyor 11 Roller 20 Breathable endless belt 30 Fiber mixture supply means 40 First carrier sheet supply means 41 First Career Sheet 50 Second carrier sheet supply means 51 Second Career Sheet 60 Suction Box A Airlaid Web

Claims

1. A resin composition containing a resin component and bleached kraft pulp fibers, the resin component contains a polyamide having a melting point of more than 200°C and a resin having a melting point lower than that of the polyamide, A resin composition having an endothermic value of 2 mJ / mg or more between 100°C and 200°C as determined by differential scanning calorimetry at a heating rate of 10°C / min.

2. The resin composition according to claim 1 , wherein the resin having a melting point lower than that of polyamide comprises a polyolefin.

3. The resin composition according to claim 1 or 2, wherein the resin having a melting point lower than that of polyamide comprises polypropylene and polyethylene.

4. The resin composition according to claim 1 or 2, wherein the content of the polyamide in the resin component is 80 mass % or more.

5. The resin composition according to claim 1 or 2, wherein the content of the bleached kraft pulp fiber is 5% by mass or more and 70% by mass or less.

6. A molded article obtained by molding the resin composition according to claim 1 or 2.

7. A method for producing a resin composition, comprising a step of kneading a polyamide having a melting point of more than 200°C with a nonwoven fabric containing bleached kraft pulp fibers and a resin having a melting point lower than that of the polyamide, A method for producing a resin composition, wherein the endothermic amount of the resin composition between 100°C and 200°C is 2 mJ / mg or more.

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