Method for producing polyolefin resin composition, recycled carbon fiber reinforced resin molded body, recycled carbon fiber reinforced resin pellet, and method for producing recycled carbon fiber reinforced resin molded body

Abstract

To provide a polyolefin resin composition capable of obtaining a molding excellent in quality using recycled carbon fibers; a recycled carbon fiber reinforcement resin molding; a method for manufacturing a recycled carbon fiber reinforcement resin pellet; and a method for manufacturing the recycled carbon fiber reinforcement resin molding.SOLUTION: A polyolefin resin composition includes a polyolefin resin, recycled carbon fibers and an imine modified polyolefin resin; a recycled carbon fiber reinforcement resin molding consists of the polyolefin resin composition; a method for manufacturing a recycled carbon fiber reinforcement resin pellet comprises kneading the recycled carbon fibers with the polyolefin resin and the imine modified polyolefin resin by a kneading extruder and extruding the mixture from the kneading extruder to form a pellet; and a method for manufacturing a molding includes manufacturing the molding by any of injection molding, extrusion molding and blow molding using the recycled carbon fiber reinforcement resin pellet.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a polyolefin resin composition containing recycled carbon fiber, a recycled carbon fiber-reinforced resin molded body, a method for producing recycled carbon fiber-reinforced resin pellets, and a method for producing a recycled carbon fiber-reinforced resin molded body.

Background Art

[0002] Carbon fiber-reinforced resin molded bodies are used in various fields because they are lightweight and have high rigidity. For example, carbon fiber-reinforced resin molded bodies are used in parts of automobiles and aircraft, and housings of portable devices such as notebook personal computers.

[0003] As the amount of carbon fiber-reinforced resin molded bodies used increases, the amount of waste carbon fiber-reinforced resin molded bodies after use also increases, and their reuse is required. As one method of reusing carbon fiber-reinforced resin molded bodies, a method of obtaining recycled carbon fiber from waste carbon fiber-reinforced resin molded bodies has been proposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, a recycled carbon fiber-reinforced resin molded body using recycled carbon fiber has a problem that its physical properties are inferior to those of a carbon fiber-reinforced resin molded body using virgin (unused) carbon fiber.

[0006] The present invention has been made in view of the above points, and an object thereof is to provide a polyolefin resin composition capable of obtaining a molded article of good quality using recycled carbon fibers, a recycled carbon fiber-reinforced resin molded article, a method for producing recycled carbon fiber-reinforced resin pellets, and a method for producing a recycled carbon fiber-reinforced resin molded article.

Means for Solving the Problems

[0007] First aspect relates to a polyolefin resin composition containing a polyolefin resin, recycled carbon fibers, and an imine-modified polyolefin resin.

[0008] Second aspect is First aspect wherein the imine-modified polyolefin resin is 10 to 50% by weight of the recycled carbon fibers.

[0009] Third aspect is First aspect or Second aspect wherein the recycled carbon fibers are 5 to 40 parts by weight with respect to 100 parts by weight of the polyolefin resin.

[0010] Fourth aspect is First aspect from Third aspect any one and wherein the recycled carbon fibers are chopped recycled carbon fibers that have been cut, or milled recycled carbon fibers that have been pulverized.

[0011] Fifth aspect is First aspect from Fourth aspect any one and wherein the recycled carbon fibers are pyrolysis products of waste carbon fiber-reinforced resins.

[0012] Sixth aspect is First aspect from Fifth aspect any one and relates to a recycled carbon fiber-reinforced resin molded article made of the polyolefin resin composition described in any one of

[0013] Seventh aspect It relates to a method for producing recycled carbon fiber reinforced resin pellets, characterized in that recycled carbon fibers are kneaded in a kneading extruder together with a polyolefin resin and an imine-modified polyolefin resin, and the kneaded product is extruded from the kneading extruder to form pellets.

[0014] Eighth aspect It relates to a method for producing a recycled carbon fiber reinforced resin molded body, characterized in that a molded body is obtained by injection molding, extrusion molding, or blow molding using the recycled carbon fiber reinforced resin pellets obtained from a polyolefin resin composition containing a polyolefin resin, recycled carbon fibers, and an imine-modified polyolefin resin.

Advantages of the Invention

[0015] The polyolefin resin composition obtained by the present invention is composed of a polyolefin resin, recycled carbon fibers, and an imine-modified polyolefin resin. Therefore, despite using recycled carbon fibers, a molded body of good quality can be obtained.

Brief Description of the Drawings

[0016]

Figure 1

Embodiments for Carrying Out the Invention

[0017] Hereinafter, the polyolefin resin composition, the method for producing the recycled carbon fiber reinforced resin molded body, the method for producing the recycled carbon fiber reinforced resin pellets, and the method for producing the recycled carbon fiber reinforced resin molded body in the present invention will be described. The polyolefin resin composition of the present invention is composed of a polyolefin resin, recycled carbon fibers, and an imine-modified polyolefin resin. Examples of polyolefin resins include polypropylene resin, low-density polyethylene (LDPE), high-density polyethylene (HDPE), ethylene-vinyl acetate copolymer resin, ethylene-propylene copolymer, ethylene-butene copolymer, copolymers of ethylene with acrylic acid esters such as methyl, ethyl, propyl or butyl, or chlorinated products thereof, or mixtures thereof, and further mixtures thereof with isotactic polypropylene or atactic polypropylene. Particularly preferred polyolefin resins are polypropylene and polyethylene.

[0018] The recycled carbon fiber is preferably a pyrolyzate obtained by heat-treating waste carbon fiber-reinforced resin. The waste carbon fiber-reinforced resin is waste of a carbon fiber-reinforced resin (CFRP) molded body composed of carbon fiber and resin. Further, the heat treatment for obtaining recycled carbon fiber from the waste carbon fiber-reinforced resin is a treatment of heating the waste carbon fiber-reinforced resin to convert the resin into a carbide and then oxidatively decomposing the carbide to obtain carbon fiber (recycled carbon fiber), which is a known treatment technique.

[0019] The recycled carbon fiber may be either chopped recycled carbon fiber (preferably 1 to 15 mm in length) or milled recycled carbon fiber that has been ground. Chopped recycled carbon fiber results in a lower coefficient of linear expansion and less stretchability of the molded body compared to milled recycled carbon fiber. On the other hand, milled recycled carbon fiber results in a better appearance (smoothness) of the molded body compared to chopped recycled carbon fiber.

[0020] The blending amount of the recycled carbon fiber is preferably 5 to 40 parts by weight, more preferably 5 to 10 parts by weight, based on 100 parts by weight of the polyolefin resin. If the blending amount of the recycled carbon fiber is too small, the rigidity of the molded body will be low, and conversely, if it is too large, the moldability of the molded body will deteriorate. Also, virgin carbon fiber may be used in combination with the recycled carbon fiber.

[0021] The imine-modified polyolefin resin is obtained by subjecting a polyimide compound containing a large number of imino groups to graft treatment on a polyolefin in the presence of a radical generator. Examples of the polyolefin that forms the basis of the polyimide compound include polyethylene, polypropylene, poly-1-butene, polyisobutylene, and the like.

[0022] By blending the imine-modified polyolefin resin into the polyolefin resin composition, the value of the limiting rate of melt tension during melt extrusion of the polyolefin resin composition increases, and the appearance of the molded article (smoothness of the molded article surface) can be improved. The limiting rate of melt tension is the maximum speed at break due to increased-speed take-up during melt extrusion of the resin and is measured based on JIS K7199. The larger the value of the limiting rate of melt tension, the less likely it is for the melt to rupture, and thus the surface smoothness of the resulting molded article becomes better. The blending amount of the imine-modified polyolefin resin is preferably 10 to 50% by weight of the recycled carbon fiber. If the blending amount of the imine-modified polyolefin resin is too small, the smoothness and impact strength of the molded article will deteriorate.

[0023] The polyolefin resin composition of the present invention is made into recycled carbon fiber-reinforced resin pellets and used for the production of recycled carbon fiber-reinforced resin molded articles. The production of the recycled carbon fiber-reinforced resin pellets is carried out by kneading recycled carbon fibers together with a polyolefin resin and an imine-modified polyolefin resin in a kneading extruder, extruding the kneaded product in a strand shape, passing it through a water cooling tank for cooling and hardening, and cutting it with a pelletizer to form pellets. Note that the pelletization of the resin is a known method.

[0024] The production of the recycled carbon fiber-reinforced resin molded article using the polyolefin resin composition of the present invention is carried out by any of injection molding, extrusion molding, and blow molding, and a molding method corresponding to the use of the molded article is adopted.

[0025] In injection molding, the recycled carbon fiber reinforced resin pellets are fed into an injection molding machine and melted, and the molten resin is injected into the cavity of a mold to form a recycled carbon fiber reinforced resin molded body having the cavity shape, and then taken out of the mold.

[0026] In extrusion molding, the recycled carbon fiber reinforced resin pellets are fed into an extruder and melted, and the molten resin is extruded from a die to form a recycled carbon fiber reinforced resin molded body in the form of a long product having the die shape.

[0027] In blow molding, the recycled carbon fiber reinforced resin pellets are fed into an extruder and melted, a tubular parison is extruded from a head, the parison is sandwiched in a blow mold, and in this state, a gas is blown into the parison to expand it to the shape of the inner surface of the mold, thereby forming a hollow recycled carbon fiber reinforced resin molded body, and then taken out of the mold.

[0028] Note that blow molding may also be a method in which instead of a tubular parison, two sheet-like parisons formed by extruding into a sheet shape are sandwiched by a blow mold, and a gas is blown between the two sheet-like parisons to expand it to the shape of the inner surface of the mold.

Examples

[0029] The polyolefin resin compositions of each example and each comparative example having the formulation shown in FIG. 1 were melt-kneaded with a kneading extruder (product name: KTX-30, manufactured by Kobe Steel, Ltd.), extruded into strands having a diameter of 3 mm and cooled in water, and cut into lengths of 3 to 4 mm with a pelletizer (product name: Strand Cutter, manufactured by Tanaka Co., Ltd.) to produce the pellets of each example and each comparative example. The melt-kneading conditions were a barrel and die temperature of 200°C, a screw rotation speed of 400 rpm, and a discharge rate of 20 kg / h.

[0030] The raw materials used are shown below. · Polyethylene: High-density polyethylene (HDPE), product name; High-Zex 5000H, manufactured by Prime Polymer Co., Ltd. · Recycled carbon fiber (chopped): Recycled carbon fiber with a fiber length of 10 mm or less, consisting of the pyrolysis product of waste carbon fiber reinforced resin, product name; Chopped recycled CF fiber, manufactured by Carbon Fiber Recycling Industry Co., Ltd. Manufactured by · Recycled carbon fiber (mild): Recycled carbon fiber with an average diameter of 25 μm, consisting of the pyrolysis product of waste carbon fiber reinforced resin, product name; Mild recycled CF fiber, manufactured by Carbon Fiber Recycling Industry Co., Ltd. · Imine-modified polyolefin resin: Product name: Admer (registered trademark) IP, manufactured by Mitsui Chemicals, Inc. · Acid-modified polyolefin resin: Maleic acid-modified polyolefin, product name; Yumex, manufactured by Sanyo Chemical Industries, Ltd.

[0031] The pellets of each example and each comparative example were put into an extrusion molding machine (product name: GS90, manufactured by Ikegai Corporation), and a tubular molded body with an outer diameter of 30 mm and an inner diameter of 25 mm was manufactured by extrusion molding. The molding conditions were a die temperature of 200 °C, a screw rotation speed of 30 rpm, and a take-up speed of 2.0 m / min.

[0032] For each example and each comparative example, the Charpy impact strength (with notch) was measured as a mechanical property, and the melt tension limiting speed and the linear expansion coefficient (20 °C → 60 °C) were measured as molding evaluations.

[0033] The Charpy impact strength (with notch) was measured by putting the pellets of each example and each comparative example into a thermoplastic injection molding machine, creating a notched test piece sample defined in JIS K7111, and measuring the sample based on JIS K7111.

[0034] The melt tension limiting speed was measured based on JIS K7199. The measurement conditions were a temperature of 200 °C and an extrusion speed of 10 m / min. The melt tension limiting speed is the take-up speed at the time of breakage due to speed increase take-up during the melt extrusion of the resin. The larger the value of the limiting speed, the less likely it is for the molten resin to break, so the appearance of the molded body (surface smoothness) becomes better. When the measurement result of the melt tension limit speed is less than 9 m / min, the appearance (surface smoothness) evaluation is "×"; when it is less than 9 to 12 m / min, it is "△"; when it is less than 12 to 18 m / min, it is "〇"; when it is 18 m / min or more, it is "◎".

[0035] The method for measuring the linear expansion coefficient is as follows: After storing a 1000 mm long sample in a constant temperature bath at 20°C for 8 hours, measure the length Lc of the sample. Next, after storing it in a constant temperature bath at 60°C for 8 hours, measure the length Lh of the sample, and use the values to calculate the linear expansion coefficient (unit: / °C) according to the formula linear expansion coefficient = (Lh - Lc) / [Lc(60 - 20)].

[0036] Example 1 is an example of a polyolefin resin composition composed of 100 parts by weight of polyethylene, 10 parts by weight of recycled carbon fiber (chopped), and 1 part by weight of imine-modified polyolefin resin. The molded body of Example 1 has a Charpy impact strength (with notch) of 10.1 KJ / m 2 , a melt tension limit speed of 12.7 m / min, an appearance (smoothness) of "〇", and a linear expansion coefficient (20°C → 60°C) of 5.2×10 -5 / °C. It had sufficient impact resistance (the Charpy impact strength was sufficiently large), good appearance smoothness, and a sufficiently small linear expansion coefficient.

[0037] Example 2 is an example in which the imine-modified polyolefin resin in Example 1 was increased to 3 parts by weight, and the others were the same as in Example 1. The molded body of Example 2 has a Charpy impact strength (with notch) of 16.9 KJ / m 2 , a melt tension limit speed of 17.1 m / min, an appearance (smoothness) of "〇", and a linear expansion coefficient (20°C → 60°C) of 2.7×10 -5 / °C. It had a greater impact resistance than Example 1, good appearance smoothness, and a small linear expansion coefficient.

[0038] Example 3 is an example in which the imine-modified polyolefin resin in Example 1 was increased to 5 parts by weight, and the others were the same as in Example 1. The molded body of Example 3 had a Charpy impact strength (with notch) of 16.1 KJ / m 2 , a melt tension limit speed of 16.8 m / min, an appearance (smoothness) of "〇", and a linear expansion coefficient (20°C → 60°C) of 3.4×10 -5 / °C. It had a greater impact strength, better appearance smoothness, and a smaller linear expansion coefficient than Example 1.

[0039] Example 4 is an example in which 10 parts by weight of recycled carbon fiber (milled) is blended instead of 10 parts by weight of recycled carbon fiber (chopped) in Example 2, and the rest is the same as in Example 2. The molded body of Example 4 had a Charpy impact strength (with notch) of 21.7 KJ / m 2 , a melt tension limit speed of 18.6 m / min, an appearance (smoothness) of "◎", and a linear expansion coefficient (20°C → 60°C) of 8.5×10 -5 / °C. As a result of blending recycled carbon fiber (milled) instead of recycled carbon fiber (chopped) in Example 4, the impact strength was greater and the appearance smoothness was better than in Example 2, but the linear expansion coefficient was larger than in Example 2.

[0040] Comparative Example 1 is an example of a polyolefin resin composition consisting of 100 parts by weight of polyethylene and 10 parts by weight of recycled carbon fiber (chopped), and does not contain an imine-modified polyolefin resin. It differs from Example 1 only in that it does not contain an imine-modified polyolefin resin. The molded body of Comparative Example 1 had a Charpy impact strength (with notch) of 7.8 KJ / m 2 , a melt tension limit speed of 8.6 m / min, an appearance (smoothness) of "×", and a linear expansion coefficient (20°C → 60°C) of 6.1×10 -5 / °C. Since Comparative Example 1 does not contain an imine-modified polyolefin resin, compared with Example 1 containing an imine-modified polyolefin resin, the impact strength was smaller (the value of the Charpy impact strength was smaller), the appearance smoothness was poor, and the linear expansion coefficient was larger.

[0041] Comparative Example 2 is an example of a polyolefin resin composition comprising 100 parts by weight of polyethylene, 10 parts by weight of recycled carbon fiber (chopped), and 3 parts by weight of an acid-modified polyolefin resin, and is an example containing 3 parts by weight of an acid-modified polyolefin resin instead of 3 parts by weight of the imine-modified polyolefin resin in Example 2. The molded article of Comparative Example 2 had a Charpy impact strength (with notch) of 10.3 KJ / m 2 , a melt tension limiting rate of 11.6 m / min, an appearance (smoothness) of "Δ", and a linear expansion coefficient (20°C → 60°C) of 5.6×10 -5 / °C. Since Comparative Example 2 contains 3 parts by weight of an acid-modified polyolefin resin, it was slightly improved in all of the impact resistance, appearance smoothness, and linear expansion coefficient compared to Comparative Example 1 that does not contain an acid-modified polyolefin resin and an imine-modified polyolefin resin. However, compared to Example 2 containing 3 parts by weight of an imine-modified polyolefin resin, it was inferior in all of the impact resistance, appearance smoothness, and linear expansion coefficient.

[0042] Comparative Example 3 is an example of a polyolefin resin composition comprising 100 parts by weight of polyethylene, 10 parts by weight of recycled carbon fiber (chopped), and 5 parts by weight of an acid-modified polyolefin resin, and is an example containing 5 parts by weight of an acid-modified polyolefin resin instead of 5 parts by weight of the imine-modified polyolefin resin in Example 3. The molded article of Comparative Example 3 had a Charpy impact strength (with notch) of 10.7 KJ / m 2 , a melt tension limiting rate of 11.3 m / min, an appearance (smoothness) of "Δ", and a linear expansion coefficient (20°C → 60°C) of 6.2×10 -5 / °C. In Comparative Example 3, the amount of the acid-modified polyolefin resin was increased from 3 parts by weight in Comparative Example 2 to 5 parts by weight. However, there was almost no change compared to Comparative Example 2 in all of the impact resistance, appearance smoothness, and linear expansion coefficient. Compared to Example 3 containing 5 parts by weight of an imine-modified polyolefin resin, it was inferior in all of the impact resistance, appearance smoothness, and linear expansion coefficient.

[0043] Thus, the polyolefin resin composition, the method for producing a recycled carbon fiber reinforced resin molded body, the method for producing recycled carbon fiber reinforced resin pellets, and the method for producing a recycled carbon fiber reinforced resin molded body of the present invention can obtain a recycled carbon fiber reinforced resin molded body with good quality.

Claims

1. A polyolefin resin composition comprising a polyolefin resin, recycled carbon fibers, and an imine-modified polyolefin resin, satisfying the following (D) and at least one of (A) to (C). (A) The Charpy impact strength (with notch) based on JIS K7111 is 10.1 KJ / m ２ or more. (B) The melt tension limiting rate based on JIS K7199 is 12 m / min or more at a temperature of 200 °C and an extrusion rate of 10 m / min. (C) The linear expansion coefficient under the following condition (i) is 8.5×10 －５ / °C or less. (i) After storing a sample with a length of 1000 mm in a constant temperature bath at 20 °C for 8 hours, measuring the length Lc of the sample, and then storing it in a constant temperature bath at 60 °C for 8 hours, measuring the length Lh of the sample, and using the values to calculate the linear expansion coefficient (unit: / °C) by the formula linear expansion coefficient = (Lh - Lc) / [Lc(60 - 20)]. (D) The polyolefin resin is at least one selected from the group consisting of low-density polyethylene (LDPE), high-density polyethylene (HDPE), ethylene-vinyl acetate copolymer resin, ethylene-propylene copolymer, ethylene-butene copolymer, copolymer of ethylene and each acrylic acid ester of methyl, ethyl, propyl or butyl, chlorinated low-density polyethylene (LDPE), chlorinated high-density polyethylene (HDPE), chlorinated ethylene-vinyl acetate copolymer resin, chlorinated ethylene-propylene copolymer, chlorinated ethylene-butene copolymer, chlorinated copolymer of ethylene and each acrylic acid ester of methyl, ethyl, propyl or butyl; mixtures of the compounds listed above; and mixtures of the compounds listed above and isotactic polypropylene or atactic polypropylene, and the recycled carbon fibers are 5 to 10 parts by weight based on 100 parts by weight of the polyolefin resin.

2. The polyolefin resin composition according to Claim 1, satisfying all of (A) to (D) above.

3. A recycled carbon fiber reinforced resin molded article comprising the polyolefin resin composition according to claim 1 or claim 2.

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