Polyamide resin and polyamide resin composition

Abstract

To provide a polyamide resin and a polyamide resin composition in which deterioration in physical properties is suppressed while reducing greenhouse effect gas.SOLUTION: A recycled polyamide resin is pelletized by melting an end material in a manufacturing process or a working process or a used waste material once, and satisfies the following features: 1) a content of a pellet having a black point of 0.75 mm2 or more of 20 pieces / kg or less; 2) a moisture percentage of 0.75% or less; 3) a content of a metal-containing pellet of 10 g / kg or less; 4) a content of a discolored pellet of 50 g / kg or less; and 5) a content of a foamed pellet of 100 g / kg or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In recent years, various environmental measures have been implemented to realize a sustainable society. Since resins such as plastics emit carbon dioxide when burned, it is expected that the carbon neutral movement will further increase social demand to avoid burning resins. In particular, polyamide 66 (PA66) has a relatively high greenhouse gas (GHG) emission rate per kilogram of resin, so it is urgent to respond to the circular economy (CE). For this reason, while the replacement of resins with bio-derived resources and other materials is progressing, recycling to avoid burning parts that cannot be replaced is also progressing.

[0003] For example, Patent Document 1 discloses a method for recycling plastic waste materials that contain a plastic mixture made up of multiple types of plastics. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-130885 A Summary of the Invention [Problem to be solved by the invention]

[0005] Recycling is expected to reduce GHG emissions, but physical properties are significantly reduced and vary.

[0006] The present invention has been made in consideration of the above circumstances, and provides a polyamide resin and a polyamide resin composition that utilize process by-products and post-consumer waste materials, thereby reducing GHG emissions while suppressing deterioration of physical properties. [Means for solving the problem]

[0007] That is, the present invention includes the following aspects. [1] A recycled polyamide resin made by melting and pelletizing scraps from manufacturing or processing processes or used waste materials, and which meets the following characteristics: 1) 0.75 mm 2 The content of pellets with black spots or more is 20 pellets / kg or less; 2) Moisture content is 0.75% or less; 3) The content of metal-containing pellets is 10g / kg or less; 4) The content of discolored pellets is 50g / kg or less; and 5) The foam pellet content is 100g / kg or less. [2] A polyamide resin, in which the mass ratio of the recycled polyamide resin according to [1] to a virgin polyamide resin (recycled polyamide resin:virgin polyamide resin) is 1:99 to 100:0. [3] A polyamide resin composition comprising the polyamide resin according to [2] and an additive. [4] The polyamide resin according to [2] or the polyamide resin composition according to [3], for use in automobiles or industrial applications. Effect of the Invention

[0008] According to the above aspect, it is possible to provide a polyamide resin and a polyamide resin composition which reduce GHG emissions while suppressing deterioration in physical properties. [Brief description of the drawings]

[0009] [Figure 1] The flow diagram for producing recycled polyamide resin is shown below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment for carrying out the present invention (hereinafter, simply referred to as "the present embodiment") will be described in detail. The present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0011] In this specification, the term "polyamide" refers to a polymer having an amide (-NHCO-) ​​group in the main chain.

[0012] <Recycled polyamide resin> The recycled polyamide resin of the present embodiment is made by melting and pelletizing leftover materials from manufacturing or processing processes, or used waste materials.

[0013] The recycling method includes a melt-kneading step, and a pelletizing step of pelletizing the molten material after the melt-kneading step to obtain recycled pellets.

[0014] As an apparatus for carrying out the melt kneading, a known apparatus, for example, a melt kneader such as a single screw or twin screw extruder, a Banbury mixer, or a mixing roll, is preferably used.

[0015] The melt-kneading temperature is preferably a temperature higher by about 1° C. or more and 100° C. or less than the melting point of the polyamide resin, and more preferably a temperature higher by about 10° C. or more and 50° C. or less. The shear rate in the mixer is 100 sec -1 The average residence time during kneading is preferably about 0.5 to 5 minutes. During this melting process, a step of removing foreign matter by passing the melt through a metal mesh may be included.

[0016] In the pelletizing process, the molten material after the melt-kneading process is pelletized to obtain pellets of the recycled product. Specifically, the molten material is cooled and cut into pellets of a desired size using a known device such as a pelletizer or a cutter.

[0017] Examples of the polyamide resin include (Aa) polyamide obtained by ring-opening polymerization of lactam, (Ab) polyamide obtained by self-condensation of ω-aminocarboxylic acid, (Ac) polyamide obtained by condensing diamine and dicarboxylic acid, and copolymers thereof, etc. The polyamide resin may be used alone or in combination of two or more kinds.

[0018] (Aa) Lactams used in the production of polyamides include, but are not limited to, pyrrolidone, caprolactam, undecalactam, dodecalactam, and the like. The ω-aminocarboxylic acid used in the production of the polyamide (Ab) is not limited to the following, but examples thereof include ω-amino fatty acids which are ring-opening compounds of the above-mentioned lactams with water. Furthermore, two or more kinds of the lactam or ω-aminocarboxylic acid may be used in combination and condensed.

[0019] (Ac) Diamines (monomers) used in the production of polyamides include, but are not limited to, linear aliphatic diamines, branched aliphatic diamines, alicyclic diamines, aromatic diamines, and the like. Examples of linear aliphatic diamines include, but are not limited to, hexamethylenediamine and pentamethylenediamine. Examples of branched aliphatic diamines include, but are not limited to, 2-methylpentanediamine and 2-ethylhexamethylenediamine. Examples of alicyclic diamines include, but are not limited to, cyclohexanediamine, cyclopentanediamine, and cyclooctanediamine. Examples of aromatic diamines include, but are not limited to, p-phenylenediamine and m-phenylenediamine. (Ac) Dicarboxylic acids (monomers) used in the production of polyamides include, but are not limited to, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, aromatic dicarboxylic acids, and the like. Examples of the aliphatic dicarboxylic acid include, but are not limited to, adipic acid, pimelic acid, and sebacic acid. The alicyclic dicarboxylic acid is not limited to the following, but may be, for example, cyclohexanedicarboxylic acid. Examples of aromatic dicarboxylic acids include, but are not limited to, phthalic acid and isophthalic acid. The diamines and dicarboxylic acids as the monomers mentioned above may be condensed either alone or in combination of two or more kinds.

[0020] Specific examples of polyamide resins include polyamide 4 (poly-α-pyrrolidone), polyamide 6 (polycaproamide), polyamide 11 (polyundecane amide), polyamide 12 (polydodecanamide), polyamide 46 (polytetramethylene adipamide), polyamide 56 (polypentamethylene adipamide), polyamide 66 (polyhexamethylene adipamide), polyamide 610 (polyhexamethylene sebacamide), polyamide 612 (polyhexamethylene dodecamide), polyamide 6I (polyhexamethylene isophthalamide), polyamide 6T (polyhexamethylene terephthalamide), polyamide 9T (polynonamethylene terephthalamide), and copolymer polyamides containing these as constituent components. Among these, the polyamide resin is preferably polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 6I, polyamide 66 / 6, or polyamide 66 / 6I.

[0021] The ends of the polyamide resin may be capped with a known end-capping agent. Such an end-capping agent can also be added as a molecular weight regulator when producing a polyamide resin from the above dicarboxylic acid, the above diamine, and, if necessary, at least one of the above lactam and the above aminocarboxylic acid.

[0022] Examples of the terminal blocking agent include, but are not limited to, monocarboxylic acid, monoamine, acid anhydride, monoisocyanate, monoacid halide, monoester, monoalcohol, etc. Examples of the acid anhydride include, but are not limited to, phthalic anhydride, etc. These terminal blocking agents may be used alone or in combination of two or more. Among these, the terminal blocking agent is preferably a monocarboxylic acid or a monoamine. By blocking the terminals of the polyamide resin with the terminal blocking agent, the thermal stability tends to be superior.

[0023] The monocarboxylic acid that can be used as the terminal blocking agent may be any one that is reactive with amino groups that may be present at the terminals of the polyamide resin. Specific examples of the monocarboxylic acid include, but are not limited to, aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, and aromatic monocarboxylic acids. Examples of aliphatic monocarboxylic acids include, but are not limited to, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecylic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, and isobutyric acid. Examples of alicyclic monocarboxylic acids include, but are not limited to, cyclohexane carboxylic acid. Examples of aromatic monocarboxylic acids include, but are not limited to, benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid. These monocarboxylic acids may be used alone or in combination of two or more kinds.

[0024] The monoamine usable as the terminal blocking agent may be any monoamine that is reactive with a carboxy group that may be present at the terminal of the polyamide resin, and specific examples of the monoamine include, but are not limited to, aliphatic monoamines, alicyclic monoamines, and aromatic monoamines. Examples of the aliphatic amine include, but are not limited to, methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine. Examples of alicyclic amines include, but are not limited to, cyclohexylamine, dicyclohexylamine, and the like. Examples of aromatic amines include, but are not limited to, aniline, toluidine, diphenylamine, naphthylamine, and the like. These monoamines may be used alone or in combination of two or more kinds.

[0025] Polyamide resins end-capped with an end-capping agent tend to have better heat resistance, fluidity, toughness, low water absorbency and rigidity.

[0026] <Black dot> Black spots are carbonized resins that are produced by heating and adhere to the production line, and can be removed, for example, by using a metal mesh in the melt-kneading process during recycling or by using a black spot sorter. To check whether these methods have effectively removed black spots, it is effective to take samples and check visually.

[0027] <Moisture percentage> The moisture content can be measured, for example, by a Karl Fischer moisture meter (manufactured by Mitsubishi Chemical Corporation, CA-200 / VA-200). The moisture content can be adjusted by using a dryer or the like.

[0028] <Metal> Metals can be removed, for example, by using a metal mesh or a metal separator during the melt-kneading process during recycling. It is effective to check whether metals have been effectively removed by sampling and manually sorting with a magnet.

[0029] <Discoloration> Discoloration can be removed, for example, by using a metal mesh or black spot separator in the melt-kneading process during recycling. It is effective to check whether discoloration has been effectively removed by sampling and visually inspecting the sample.

[0030] <Foaming> Foaming occurs when voids form inside the pellets, and visual inspection is effective. It can be adjusted by controlling the moisture content and degassing of the raw materials during the melt-kneading process during regeneration.

[0031] <Virgin product> In this embodiment, the virgin product means a compound or composition prepared from raw material monomers, and does not include recycled products.

[0032] <Additives> Examples of additives include, but are not limited to, heat stabilizers, lubricants, catalysts, colorants (dyes, pigments), flow modifiers, molecular weight regulators, antioxidants, compatibilizers, oligomers, polymers, and the like.

[0033] The method for preparing a polyamide resin composition by adding recycled polyamide resin, virgin polyamide resin, additives, etc. is preferably compounding by melt kneading.

[0034] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples. EXAMPLES

[0035] Scraps from the polyamide polymerization process (such as defective products generated during pelletization) were collected, melt-kneaded, and pelletized to obtain recycled polyamide resin. Virgin products, fillers, etc. were added to the recycled polyamide resin, and compounded by melt-kneading to obtain a polyamide resin composition. Some of these are shown in the examples in Table 1.

[0036] <Components> [(A) Virgin polyamide resin] A-1: Polyamide 66

[0037] [(B) Recycled polyamide resin] B-1: Recycled polyamide 66 B-2: Regenerated polyamide 66 (0.75mm 2 (40 pellets / kg) with black spots or more B-3: Regenerated polyamide 66 (moisture content: 2.0%) B-4: Recycled polyamide 66 (metal-containing pellets 30g / kg) B-5: Recycled polyamide 66 (discolored pellets 100g / kg) B-6: Recycled polyamide 66 (foam pellets 200g / kg)

[0038] [(C) Additives] C-1: Maleic anhydride grafted ethylene-butene copolymer (Mitsui Chemicals, Tafmer MD715) C-2: Ethylene-butene copolymer (Mitsui Chemicals, Tafmer (trademark) DF605) C-3: Polyethylene-polystyrene graft copolymer (NOF Corporation, MODIPER-A1100) C-4: Polyolefin-polyamide polymer (Arkema, APOLHYA LP91) C-5: Polyethyleneimine (manufactured by BASF, Lupasol FG) C-6: Antioxidant (BASF, Irganox 1098) C-7: Nigrosine dye (Orient Chemical Co., Ltd., TH807) C-8: Carbon black (primary particle size 27 nm) C-9: Adipic acid (Wako Pure Chemical Industries, Ltd., adipic acid) C-10: Calcium stearate (manufactured by Nippon Oil & Fats Co., Ltd., calcium stearate) C-11: Sodium aluminate (Wako Pure Chemical Industries, Ltd., sodium aluminate) C-12: Mixture of copper iodide and potassium iodide (both copper iodide and potassium iodide are manufactured by Wako Pure Chemical Industries, Ltd.) 1 part by mass of copper iodide is mixed with 10 parts by mass of potassium iodide. C-13: Nigrosine (Orient Chemical Co., Ltd., Nubian Black TN-870) C-14: Copper iodide (Wako Pure Chemical Industries, Ltd., copper iodide) C-15: Potassium iodide (Wako Pure Chemical Industries, Ltd., Potassium iodide) C-16: Zinc sulfide (SACHTLEBEN, Sactris HD)

[0039] [(D) Filler] D-1: Glass fiber (Nippon Electric Glass Co., Ltd., ECS 03T-275H) D-2: Glass fiber (manufactured by Kyoseki Group Co., Ltd., E7CS-10-568H) D-3: Polyurethane resin (Dainippon Ink Co., Ltd., Bondic 1050) calculated as solid content The mixture was diluted with water to 2% by mass, 8% by mass of ethylene maleic anhydride copolymer (manufactured by Wako Pure Chemical Industries, Ltd.), 0.6% by mass of γ-aminopropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBE-903), and 0.1% by mass of lubricant (manufactured by Kato Yoko Co., Ltd., carnauba wax), and the total mass was adjusted to 100% by mass to obtain a glass fiber sizing agent. This glass fiber sizing agent was attached to melt-spun glass fibers having a number average fiber diameter of 10 μm. That is, the glass fiber sizing agent was applied to the glass fibers in the middle of being wound on a rotating drum using an applicator installed at a predetermined position. Next, this was dried to obtain a roving of glass fiber bundles (glass roving) surface-treated with the glass fiber sizing agent. At that time, the glass fibers were bundled into a bundle of 1,000 fibers. The amount of the glass fiber sizing agent attached was 0.6% by mass. This was cut to a length of 3 mm and used as glass chopped strands.

[0040] <Production method of (A) virgin polyamide resin and (B) recycled polyamide resin> [Raw materials] The (A) virgin polyamide resin and (B) recycled polyamide resin used in the examples and comparative examples were produced using the following (a) and (b) as appropriate. ((a) Dicarboxylic acid) a-1: Adipic acid (ADA) (manufactured by Wako Pure Chemical Industries, Ltd.) ((b) Diamine) b-1: 1,6-diaminohexane (hexamethylenediamine) (C6DA) (Tokyo Chemical Industry Co., Ltd.)

[0041] [Synthesis Example 1] Synthesis of virgin polyamide resin A-1 (polyamide 66) The polymerization reaction of polyamide was carried out by the "thermal melt polymerization method" as follows. First, 1500 g of an equimolar salt of adipic acid and hexamethylenediamine was dissolved in 1500 g of distilled water to prepare a 50% by mass equimolar homogeneous aqueous solution of the raw material monomers. This aqueous solution was placed in an autoclave with an internal volume of 5.4 L and purged with nitrogen. While stirring at a temperature of 110°C to 150°C, the solution was concentrated by gradually releasing steam until the solution concentration reached 70% by mass. The internal temperature was then raised to 220°C. At this time, the autoclave was pressurized to 1.8 MPa. The reaction was continued for 1 hour while gradually releasing steam to maintain the pressure at 1.8 MPa until the internal temperature reached 245°C. Next, the pressure was reduced over 1 hour, and then the inside of the autoclave was kept under a reduced pressure of 650 torr for 10 minutes using a vacuum device, at which time the final internal temperature of the polymerization was 265°C. Thereafter, the mixture was pressurized with nitrogen and formed into a strand from the lower spinneret (nozzle), water-cooled, cut, and discharged in the form of pellets, which were then dried at 100° C. in a nitrogen atmosphere for 12 hours to obtain virgin polyamide resin A-1. The virgin polyamide resin A-1 (polyamide 66) thus obtained had a weight average molecular weight (Mw) of 35,000 and a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 2.

[0042] [Synthesis Example 2] Synthesis of recycled polyamide resin B-1 (polyamide 66) According to the flow diagram shown in FIG. 1, virgin products were first produced. Next, non-standard products were collected, and after adjusting the moisture content, melt-kneading was performed using a twin-screw extruder (ZSK-26MC, manufactured by Coperion). That is, non-standard polyamide 66 products were dried at 100°C under a nitrogen atmosphere for 12 hours, and after adjusting the moisture content, melt-kneading was performed. The twin-screw extruder had a feed port in the first barrel from the upstream side of the extruder, and the temperature from the feed port to the die was set to the melting point Tm2+20°C of each polyamide, the screw rotation speed was set to 250 rpm, and the discharge rate was set to 25 kg / h. During this melt-kneading, black spots, metal, and foreign matter that may lead to discoloration were removed through a metal mesh (mesh number: 200), and the product was cooled in a strand shape, pelletized, and dried at 100°C under a nitrogen atmosphere for 12 hours to obtain a recycled polyamide resin. In addition, since the non-standard products used as the raw material for recycled polyamide resin vary widely in the amount of foreign matter that can cause black spots, metal, and discoloration, if necessary, the recycled polyamide resin produced can be passed through a black spot sorter or metal foreign matter removal device to remove black spots, metal, and discolored pellets.

[0043] [Synthesis Example 3] Recycled polyamide resin B-2 (Polyamide 66, 0.75 mm 2 Synthesis of pellets with black spots (40 pellets / kg) Recycled polyamide resin B-2 was obtained under the same conditions as in Synthesis Example 2 above, except that the metal mesh used during melt kneading was 100 mesh.

[0044] [Synthesis Example 4] Synthesis of recycled polyamide resin B-3 (polyamide 66, moisture content: 2.0%) Regenerated polyamide resin B-3 was obtained under the same conditions as in Synthesis Example 2 above, except that the strand immersion length during cooling in the strand form during pelletizing was 1.5 times that of the pellets, and drying under a nitrogen atmosphere was not performed.

[0045] [Synthesis Example 5] Synthesis of recycled polyamide resin B-4 (polyamide 66, metal-containing pellets 30g / kg) Recycled polyamide resin B-4 was obtained under the same conditions as in Synthesis Example 2 above, except that the metal mesh used during melt kneading was 50 mesh.

[0046] [Synthesis Example 6] Synthesis of recycled polyamide resin B-5 (polyamide 66, discolored pellets 100g / kg) Recycled polyamide resin B-5 was obtained under the same conditions as in Synthesis Example 2 above, except that no metal mesh was used during melt kneading and the strand immersion length during cooling in the strand form during pelletizing was 0.5 times that of the synthetic example 2.

[0047] [Synthesis Example 7] Synthesis of recycled polyamide resin B-6 (polyamide 66, foam pellets 200g / kg) Recycled polyamide resin B-6 was obtained under the same conditions as in Synthesis Example 2 above, except that the non-standard polyamide 66 used as the raw material in the melt-kneading was not dried at 100°C for 12 hours under a nitrogen atmosphere.

[0048] <Method of producing polyamide resin composition> [Examples 1 to 6 and Comparative Examples 1 to 11] Each polyamide resin composition was produced by the following method using the above (A) virgin polyamide resin, (B) recycled polyamide resin, (C) additive, and (D) filler in the types and proportions shown in Table 1 below. A twin-screw extruder (ZSK-26MC, manufactured by Coperion) was used as a manufacturing device for the polyamide resin composition. The twin-screw extruder had an upstream supply port in the first barrel from the upstream side of the extruder, a downstream first supply port in the sixth barrel, and a downstream second supply port in the ninth barrel. In addition, in the twin-screw extruder, the temperature from the upstream supply port to the die was set to the melting point Tm2+20°C of each polyamide, the screw rotation speed was set to 250 rpm, and the discharge rate was set to 25 kg / h.

[0049] As a specific manufacturing method using the above manufacturing apparatus, (A) virgin polyamide resin, (B) recycled polyamide resin, and (C) additives are premixed and then fed from the upstream feed port of a twin-screw extruder, (D) filler is fed from the downstream first feed port of the twin-screw extruder, and the molten mixture extruded from the die head is cooled in a strand shape and pelletized to obtain pellets of each polyamide composition. The obtained pellets of the polyamide composition are dried in a nitrogen stream to reduce the moisture content in the polyamide composition to 500 ppm or less.

[0050] <Physical properties and evaluation> First, the pellets of the resin compositions obtained in the Examples and Comparative Examples were dried in a nitrogen stream to reduce the moisture content in the resin compositions to 500 ppm or less. Next, the pellets of each resin composition with the adjusted moisture content were used to measure various physical properties and perform various evaluations using the following methods.

[0051] [Extrudability during production of polyamide resin composition] When melt-kneading was performed to obtain a polyamide resin composition, extrudability was evaluated. The evaluation criteria were as follows. A: Extrusion is possible without any problems. C: Water droplets accumulate in the raw material feeder, which can cause poor feeding.

[0052] [Tensile strength] Using an injection molding machine (PS-40E: manufactured by Nissei Plastics Co., Ltd.), each sample was molded into a multipurpose test piece type A in accordance with ISO 3167. The specific molding conditions were set as follows: injection + pressure holding time 25 seconds, cooling time 15 seconds, mold temperature 80°C, and molten resin temperature at the polyamide's high-temperature melting peak temperature (Tm2) + 20°C. Using the obtained molded multipurpose test piece A, a tensile test was carried out at a temperature of 23° C. in accordance with ISO 527 to measure the tensile yield stress, which was taken as the tensile strength. For the test at 80°C, a tensile test was carried out in a high temperature environment of 80°C.

[0053] [Tensile strength after heat aging] The multipurpose test piece A was thermally aged in a hot air circulating oven at 230°C for 250 hours. After cooling at 23°C for 24 hours or more, a tensile test was carried out at a temperature of 23°C in accordance with ISO 527 to measure the tensile yield stress, which was taken as the tensile strength.

[0054] [Spiral Flow (SFD)] The polyamide resin composition was injection molded under the following conditions to evaluate the flowability. (Measurement conditions) Injection molding machine: "NEX-50IV" manufactured by Nissei Plastics Co., Ltd., mold clamping force 50KN Measurement mold: Spiral mold with inner groove width (cavity width) of 10 mm and thickness of 2 mm Mold temperature: 80℃ Cylinder temperature setting: 280℃ Injection pressure: 60MPa (injection speed is set to maximum and controlled by pressure) Ejection time: 10 seconds Cooling time: 5 seconds Metering speed: 150 rpm Back pressure: 1MPa

[0055] [Sliding characteristics] (Wear coefficient, wear depth) A reciprocating friction and wear tester (Toyo Seimitsu Co., Ltd., AFT-15MS type) and a SUS304 test piece (ball with a diameter of 5 mm) as the counter material were used to conduct a sliding test at a linear velocity of 50 mm / sec, a reciprocating distance of 20 mm, a temperature of 23°C, and a humidity of 50%. In addition, a friction coefficient test was conducted with a load of 4 kg and 10,000 reciprocations. In addition, the maximum wear depth of the wear marks on the samples after the sliding test was measured using a surface roughness meter (manufactured by Toyo Seimitsu Co., Ltd., 575A-30).

[0056] As evaluation samples, each sample was molded into a multipurpose test piece type A using an injection molding machine NEX-50IV (manufactured by Nissei Plastics Co., Ltd.) in accordance with ISO 3167. The specific molding conditions were set as follows: injection + pressure holding time 25 seconds, cooling time 15 seconds, mold temperature 80°C, molten resin temperature polyamide high temperature melting peak temperature (Tm2) + 20°C, and injection speed 5 mm / s.

[0057] [Color tone] The color tone of the polyamide resin composition was visually observed and judged. The evaluation was made as follows. A: There is no variation in color tone and the quality is stable. C: The color tone is inconsistent and the quality is unstable.

[0058] [Transportation efficiency] The polyamide resin composition was packaged in a 25 kg bag, and the transportation efficiency was evaluated. The evaluation was made as follows. A: We can package 25kg without any problems and there are no problems with transportation efficiency. C: The bulk density of the pellets is low, making it impossible to package them in 25 kg packages, which adversely affects transportation efficiency.

[0059] [Environmental load (GHG emissions)] GHG emissions were estimated from the usage rate of recycled polyamide resin, and the degree of reduction in environmental impact was evaluated as follows. A: It is made from recycled materials, which reduces the environmental impact. B: Although recycled materials are used, there are problems with strength, extrusion properties, color tone, transportation efficiency, etc., and these areas result in waste, which places a burden on the environment. C: Not made from recycled materials, and made from materials with a high environmental impact.

[0060] [Table 1-1]

[0061] [Table 1-2] [Industrial Applicability]

[0062] The polyamide resin composition according to the present invention has excellent mechanical properties and can be suitably used as a molding material for various parts for automobiles, electrical and electronic applications, industrial materials, industrial materials, and daily necessities and household goods.

Claims

1. A recycled polyamide resin made by melting and pelletizing scraps from manufacturing or processing processes or used waste materials, and which meets the following characteristics: 1) 0.75 mm ２ The content of pellets having black spots or more is 20 pellets / kg or less; 2) The moisture content is 0.75% or less; 3) The content of metal-containing pellets is 10 g / kg or less; 4) The content of discolored pellets is 50 g / kg or less; and 5) The foam pellet content is 100 g / kg or less.

2. A polyamide resin, in which the mass ratio of the recycled polyamide resin according to claim 1 to a virgin polyamide resin (recycled polyamide resin:virgin polyamide resin) is 1:99 to 100:

0.

3. A polyamide resin composition comprising the polyamide resin according to claim 2 and an additive.

4. 4. The polyamide resin according to claim 2 or the polyamide resin composition according to claim 3, wherein the polyamide resin composition is used as an automotive material or an industrial material.

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