JP2010241986A - Method of producing thermoplastic resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a thermoplastic resin composition enabling incorporation of a large amount of plant fiber and having sufficient fluidity when used for injection molding, or the like. <P>SOLUTION: The thermoplastic resin composition contains a thermoplastic resin (a polypropylene-based resin, particularly such as combination use of the polypropylene-based resin and an acid-modified polypropylene-based resin) and pulverized fibers formed by pulverizing plant fiber (kenaf fiber or the like), wherein the pulverized fiber is contained by 50-95 mass% per total of the resin and the fibers, and is provided with a cutting step of: cutting the plant fiber into a prescribed length to form cut fiber (the length of the fiber is preferably ≤20 mm); a pulverizing step of: pulverizing the cut fiber into the pulverized fiber (the length is preferably 0.5-6 mm and average fiber diameter is 10-60 μm); and a mixing step of: melting and kneading the thermoplastic resin with the pulverized fiber. The pulverized fiber is preferably made into pellets to be mixed with the thermoplastic resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a thermoplastic resin composition. More specifically, the present invention relates to a method for producing a thermoplastic resin composition which can contain a large amount of plant fiber in a thermoplastic resin and has sufficient fluidity when used for injection molding or the like.

  In recent years, plant materials such as kenaf that grow quickly and have a large amount of carbon dioxide absorption have attracted attention from the viewpoints of carbon dioxide emission reduction and carbon dioxide fixation, and are expected to be used for composite materials mixed with resin. Yes. A mixer such as a kneader, super mixer, Henschel mixer, etc. is used to mix the kenaf and the resin, but it is particularly difficult to mix a large amount of plant material into the resin. Requires time and labor, such as repeated charging and mixing in several degrees. Moreover, it is not easy to mold by a method such as injection molding using a composite material in which kenaf or the like is mixed. This is considered to be because it is difficult to impart sufficient fluidity to the composite material so that it can be molded with the same apparatus and conditions as those of conventional resins (see, for example, Patent Documents 1 and 2). ). Furthermore, since it is not easy to uniformly disperse and mix a large amount of plant material in a thermoplastic resin, the plant material is pelletized in advance, the specific gravity difference with the resin is reduced, and the plant material and the resin are mutually It is known that a uniformly dispersed composite material is used, and a molded body is manufactured using this composite material (see, for example, Patent Document 3).

JP-A-2005-105245 JP 2000-219812 A JP 2008-93956 A

  In Patent Document 1, the most precise injection molding can be performed when kenaf fibers are contained in polylactic acid. However, when the content of kenaf fibers exceeds 50% by mass, the fibers are not uniformly dispersed in the resin, and molding is performed. It is explained that problems such as clogging of the resin composition occur in the machine. Moreover, in patent document 2, when not mixing rosin and a plasticizer with resin, but only a plant fiber is mix | blended, a plant fiber is hard to disperse | distribute uniformly and the affinity between resin and a plant fiber is also not good. Therefore, it is described that the molded article is inferior in strength and the like, the quality is not uniform, and the practicality is poor. As described above, Patent Documents 1 and 2 describe that when a large amount of plant material exceeding 50% by mass is contained, it is difficult to obtain a molded product having no problem in terms of practicality by injection molding or the like. Has been. Furthermore, in the manufacturing method described in Patent Document 3, the plant material and the resin can be uniformly dispersed, but this is disadvantageous in terms of cost.

  The present invention has been made in view of the above-described conventional situation, and a thermoplastic resin can contain a large amount of plant fiber and has sufficient fluidity when used for injection molding or the like. It aims at providing the manufacturing method of a plastic resin composition.

The present invention is as follows.
1. Thermoplastic resin and pulverized fiber obtained by pulverizing vegetable fiber, and when the total of the thermoplastic resin and pulverized fiber is 100% by mass, the pulverized fiber is 50 to 95% by mass. A method for producing a resin composition, the cutting step of cutting the plant fiber into a predetermined length of cutting fiber, the step of pulverizing the cutting fiber into the pulverized fiber of a predetermined size, and the heat And a mixing step of kneading and mixing the plastic resin and the pulverized fiber. A method for producing a thermoplastic resin composition, comprising:
2. 1. The fiber length of the cut fiber is 25 mm or less. The manufacturing method of the thermoplastic resin composition as described in any one of.
3. 2. The average fiber length of the pulverized fiber is 0.5 to 6 mm, and the average fiber diameter is 10 to 60 μm. The manufacturing method of the thermoplastic resin composition as described in any one of.
4). The plant fiber is a kenaf fiber. To 3. The manufacturing method of the thermoplastic resin composition of any one of these.
5). The thermoplastic resin is a polypropylene resin or an acid-modified polypropylene resin. To 4. The manufacturing method of the thermoplastic resin composition of any one of them.
6). The acid-modified polypropylene resin is 1 to 30% by mass when the total of the polypropylene resin and the acid-modified polypropylene resin is 100% by mass. The manufacturing method of the thermoplastic resin composition as described in any one of.
7). The crushed fiber is pressed and pelletized, and then mixed with the thermoplastic resin. To 6. The manufacturing method of the thermoplastic resin composition of any one of these.
8). The mixing device used for the kneading and mixing includes a mixing chamber in which the mixing is performed and a mixing blade disposed in the mixing chamber, and the heat that is heated and melted by rotation of the mixing blade in the mixing chamber. The plastic resin and the pulverized fiber are kneaded and mixed. To 7. The manufacturing method of the thermoplastic resin composition of any one of these.

According to the method for producing a thermoplastic resin composition of the present invention, a pulverized fiber in which plant fibers are sufficiently defibrated is used, and both the fiber length and the fiber diameter are small and not bulky. These pulverized fibers can be easily contained, and when molded by a method such as injection molding, a thermoplastic resin composition having sufficient fluidity can be obtained. Therefore, a thermoplastic resin molded article having excellent bending strength, bending elastic modulus and the like, which is preferable from the viewpoint of practicality, can be formed.
In addition, when the fiber length of the cut fiber is 25 mm or less, it is easy to obtain a pulverized fiber that is sufficiently defibrated in the pulverization process, has a small fiber length and a small fiber diameter, and is not bulky. Sometimes, a thermoplastic resin composition having more sufficient fluidity can be obtained, and a thermoplastic resin molded article having excellent mechanical properties can be formed.
Furthermore, when the average fiber length of the pulverized fiber is 0.5 to 6 mm and the average fiber diameter is 10 to 60 μm, it is easy to contain a large amount in the thermoplastic resin, and at the time of molding such as injection molding In particular, a thermoplastic resin composition having sufficient fluidity can be obtained, and a thermoplastic resin molded article having excellent mechanical properties can be formed.
In addition, when the plant fiber is a kenaf fiber, it is an annual plant with an extremely high growth rate, and by using kenaf having excellent carbon dioxide absorption, the amount of carbon dioxide in the atmosphere can be reduced, and plant resources can be obtained. Can contribute to the effective use of
Furthermore, when the thermoplastic resin is a polypropylene resin or an acid-modified polypropylene resin, a thermoplastic resin composition having higher fluidity can be obtained, and a thermoplastic resin molding having excellent mechanical properties can be obtained. The body can be shaped.
In addition, when the total of the polypropylene resin and the acid-modified polypropylene resin is 100% by mass, when the acid-modified polypropylene resin is 1 to 30% by mass, there is an effect by using the acid-modified resin in combination. A thermoplastic resin composition that is sufficiently produced and has particularly high fluidity can be obtained, and a thermoplastic resin molded article having excellent mechanical properties can be formed.
Furthermore, when the pulverized fiber is pressed and pelletized and then mixed with the thermoplastic resin, more plant fibers can be added, and more thermoplastic resin composition can be produced proportionally. it can.
Further, the mixing device used for kneading and mixing includes a mixing chamber in which mixing is performed and a mixing blade disposed in the mixing chamber, and a thermoplastic resin heated and melted by rotation of the mixing blade in the mixing chamber; When the pulverized fiber is kneaded and mixed, it can be efficiently mixed in a short time without requiring external heating, and the cost can be reduced.

It is a part of system used for manufacture of a thermoplastic resin composition, Comprising: It is typical explanatory drawing when a cutting device, a crushing device, and a pelletizing device are arranged. It is typical explanatory drawing of the cross section seen from the front of a cutting device. It is typical explanatory drawing of the cross section seen from the side of the cutting device. It is typical explanatory drawing which looked at the rotary blade of the crushing device, and its circumference from the front. It is typical explanatory drawing which looked at the fixed blade of the crushing device, and its circumference from the front. It is typical sectional drawing of an example of a mixing apparatus. It is a typical side view of an example of the mixing blade | wing arrange | positioned at the mixing apparatus. It is a typical perspective view of the principal part of an example of a roller disc die type pelletizer.

Hereinafter, the present invention will be described in detail with reference to the drawings.
1. Production method of thermoplastic resin composition The thermoplastic resin composition contains a pulverized fiber obtained by pulverizing a thermoplastic resin and a vegetable fiber, and when the total of the thermoplastic resin and the pulverized fiber is 100% by mass, A cutting process in which the pulverized fiber is 50 to 95% by mass and the plant fiber is cut into a predetermined length, a pulverizing process in which the cut fiber is pulverized into a predetermined size, and a thermoplastic resin. And a mixing step of kneading and mixing the pulverized fibers.

[1] Material (1) Thermoplastic Resin The “thermoplastic resin” is a resin mixed with pulverized fibers in the mixing step. This thermoplastic resin is not particularly limited, and various thermoplastic resins can be used. Examples of the thermoplastic resin include polyolefin, polyester resin, polystyrene, acrylic resin, polyamide, polycarbonate, polyacetal, and ABS resin. Further, as the thermoplastic resin, polylactic acid, polycaprolactone, polybutylene succinate, and the like can be used. Among these, polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymer are preferable, and polypropylene, ethylene-propylene copolymer, and particularly ethylene-propylene block copolymer are more preferable. Only one thermoplastic resin may be used, or two or more thermoplastic resins may be used in combination.

  In particular, when a polyolefin is used as the thermoplastic resin, it is preferable to use an acid-modified polyolefin in combination. By using the acid-modified polyolefin, the mechanical properties of the thermoplastic resin molded article molded using the thermoplastic resin composition can be improved. As the base resin of the acid-modified polyolefin, the above-mentioned various polyolefins can be used. Furthermore, the non-modified polyolefin contained in the thermoplastic resin composition and the base resin used for acid modification are preferably the same type of resin. Further, in the case of the same type of resin, it is more preferable that the difference in average molecular weight, density, etc. of each resin is small, and in the case of a copolymer, the difference in the proportion of each monomer unit is more small. preferable.

  The method for introducing an acid group into the acid-modified polyolefin is not particularly limited, but it can be introduced by so-called graft polymerization, which is usually carried out by reacting a polyolefin-containing compound with an acid group. The compound having an acid group is not particularly limited, and examples thereof include maleic anhydride, itaconic anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, maleic acid, itaconic acid, fumaric acid, acrylic acid and methacrylic acid. These may be used alone or in combination of two or more. Of these, acid anhydrides are often used, and maleic anhydride and itaconic anhydride are often used.

The amount of acid groups introduced in the acid-modified polyolefin is not particularly limited, but is preferably an amount introduced so that the acid value is 5 or more. When the introduction amount is such that the acid value of the acid-modified polyolefin is 5 or more, the mechanical properties of the thermoplastic resin molded article can be sufficiently improved without adding a large amount of the acid-modified polyolefin. The acid value is more preferably 10 to 80, particularly 15 to 70, and further preferably 20 to 60.
The acid value can be measured according to JIS K0070.

Furthermore, the average molecular weight of the acid-modified polyolefin is not particularly limited, but the weight average molecular weight is preferably 10,000 to 200,000. That is, it is preferably a relatively low molecular weight acid-modified polyolefin. By using such an acid-modified polyolefin, it is possible to sufficiently improve the fluidity of the thermoplastic resin composition and to mold a thermoplastic resin molded article having excellent mechanical properties. The weight average molecular weight is 15,000 to 150,000, particularly 25,000 to 120,000, and more preferably 35,000 to 100,000.
The weight average molecular weight can be measured by gel permeation chromatography.

  As the thermoplastic resin, it is more preferable to use a polypropylene and / or an ethylene-propylene copolymer, particularly an ethylene-propylene block copolymer, and a resin obtained by acid-modifying these in combination. In this case, when the whole thermoplastic resin is 100 mass%, it is preferable that acid-modified resin is 1-30 mass%. If the blending amount is within this range, the mechanical properties of the thermoplastic resin molded body can be improved, and the fluidity of the thermoplastic resin composition during molding such as injection molding can be dramatically improved. . The compounding amount of the acid-modified resin is 1 to 25% by mass, particularly 1 to 20% by mass, and more preferably 1.5 to 10% by mass.

(2) Plant fiber The “plant fiber” is a plant-derived material. This plant fiber includes kenaf, jute hemp, manila hemp, sisal hemp, husk, cocoon, cocoon, banana, pineapple, coconut, corn, sugar cane, bagasse, palm, papyrus, cocoon, esparto, sabugrass, wheat, rice, bamboo, Examples include plant fibers possessed by various plants such as conifers (cedar, birch, etc.), hardwoods, and cotton. This plant fiber may be used alone or in combination of two or more. Among these, Kenaf's fiber is an annual plant that grows very fast, has excellent carbon dioxide absorption, and can contribute to reducing the amount of carbon dioxide in the atmosphere and effectively using forest resources. Is preferred. Moreover, the site | part used among plants is not specifically limited, Any site | parts which comprise plants, such as a non-wood part, a wood part, a leaf part, a stem part, and a root part, may be sufficient. Furthermore, only a specific part may be used and two or more different parts may be used in combination.

  Kenaf is a fast-growing annual plant with a woody stem and is a plant classified as a mallow. Examples of the kenaf include hibiscus cannabinus and hibiscus sabdariffa in scientific names, as well as red hemp, cuba kenaf, western hemp, taykenaf, mesta, bimli, ambari and bombay, etc. in common names. When using the fiber which kenaf has as a plant fiber, the outer-layer part called a bast which has a tough fiber can be used.

  The fiber length and fiber diameter of the plant fiber are not particularly limited, but the ratio (L / t) of the fiber length (L) to the fiber diameter (t) is preferably 5 to 20000. Moreover, the fiber length of a vegetable fiber is 1.0-300 mm normally, and a fiber diameter is 10-1000 micrometers normally. This fiber length is a value measured on a measuring scale by stretching one plant fiber straight without stretching in the same manner as in the direct method in JIS L1015. On the other hand, a fiber diameter is the value which measured the fiber diameter in the center part of the length direction of a fiber using the optical microscope about the vegetable fiber which measured fiber length.

  Furthermore, the average fiber length and the average fiber diameter of the plant fiber are not particularly limited, but the average fiber length is preferably 25 mm or less. By using plant fibers having an average fiber length of 25 mm or less (usually 1.0 mm or more), a cut fiber having a predetermined length can be easily obtained. This average fiber length was measured for a total of 200 fibers by taking out single fibers at random by a direct method in accordance with JIS L1015, stretching them straight without stretching, and measuring the fiber length on a measuring scale. Average value. The average fiber diameter is preferably 100 μm or less (usually 10 μm or more). If the average fiber diameter of the plant fiber is 100 μm or less, the chopped fiber obtained by cutting the plant fiber can be easily pulverized into a predetermined size (predetermined length and predetermined diameter). This average fiber diameter is an average value measured for a total of 200 fibers by taking out single fibers at random and measuring the fiber diameter at the center in the length direction of the fibers using an optical microscope.

  The thermoplastic resin composition can also contain a non-fibrous plant material. For example, when kenaf fibers are used as plant fibers, a core material portion called a core occupying about 60% by volume of the entire kenaf can be contained as a non-fibrous plant material. When plant fibers and non-fibrous plant materials are used in combination, the total amount of these is 100% by mass. In general, it is preferably 1% by mass or more. If the non-fibrous plant material is 10% by mass or less, a thermoplastic resin composition having sufficient fluidity can be obtained, and the mechanical properties of the thermoplastic resin molded article can be improved.

  The thermoplastic resin composition can contain other components excluding the thermoplastic resin and the pulverized fiber. Other components are not particularly limited, but include other additives such as antioxidants, ultraviolet absorbers, antistatic agents, flame retardants, antibacterial agents, and coloring agents in addition to the non-fibrous plant materials described above. It is done. Each of these additives may be used alone or in combination of two or more. Although the process of mix | blending these other components is not specifically limited, Usually, it mix | blends and contains in a mixing process.

[2] Process The manufacturing method of the thermoplastic resin composition of the present invention includes a cutting process using a cutting device 30 (see FIGS. 2 and 3 for details) to cut vegetable fibers into cut fibers, and a pulverizing device 40 (for details). A pulverization step of pulverizing cut fibers into pulverized fibers according to FIGS. 4 and 5, and mixing by kneading and mixing the pulverized fibers and thermoplastic resin with a mixing device 1 (see FIGS. 6 and 7 for details) A process. The pulverized fiber may be mixed with the thermoplastic resin as it is, but is made into a fiber pellet having a predetermined shape and size by a pelletizer 50 (see FIG. 8 for details), and this fiber pellet is thermoplastic. You may mix with resin.

  In the cutting step and the pulverizing step, it is preferable that the cutting device 30 and the pulverizing device 40 are arranged side by side, continuously cut, and pulverized as shown in FIG. That is, the cutting device 30 and the pulverizing device 40 are arranged at predetermined positions of the gantry 60, and the cut fibers cut by the cutting device 30 are transported through the duct 71 and introduced into the cyclone 81, and the rotary valve 811. Is opened and put into a pulverizing apparatus 40, and pulverized into a pulverized fiber. This pulverized fiber may be kneaded and mixed with the thermoplastic resin as it is, or may be pelletized and then kneaded and mixed with the thermoplastic resin. In the case of pelletization, as shown in FIG. 1, the pulverized fiber can be conveyed through the duct 72 and charged into the cyclone 82, and the rotary valve 821 can be opened and charged into the pelletizer 50 for pelletization. Thus, it is preferable to carry out pelletization continuously with cutting and pulverization.

(1) Cutting process The above-mentioned "cutting process" is a process of cutting a plant fiber into a cut fiber having a predetermined length.
The fiber length of the “cut fiber” is not particularly limited as long as the cut fiber can be pulverized into a pulverized fiber of a predetermined size, but is preferably 25 mm or less, 20 mm or less, particularly 15 mm or less. Further, it is more preferably 10 mm or less (usually 1.0 mm or more). If the fiber length of the cut fiber is 25 mm or less, the pulverized fiber having a predetermined size can be easily obtained in the pulverization step. Further, the average fiber diameter of the cut fiber is not particularly limited, but by cutting the plant fiber having the fiber diameter, the average fiber diameter of the cut fiber is usually 50 to 100 μm, particularly 70 to 90 μm. it can.
In addition, the fiber length of the cut fiber can be measured by the same method as in the case of the fiber length of the plant fiber. This fiber length can be adjusted with the dimension of the opening part of the screen with which the cutting device to be used is equipped. Further, the total amount of the cut fibers is preferably 25 mm or less, but fibers having a fiber length exceeding 25 mm may be contained in an amount of 10% or less, particularly 5% or less. This ratio is 10% or less, particularly 5% or less, of the fibers having a fiber length of more than 25 mm when the fiber length is measured for 200 fibers by the method for measuring the average fiber length of the plant fibers. Can be confirmed. Furthermore, the average fiber diameter of the cut fiber can be measured by the same method as that for the fiber length of the plant fiber.

The apparatus used in a cutting process is not specifically limited, What is necessary is just to be able to cut a plant fiber efficiently to predetermined length, for example, the cutting apparatus described in FIG.
The cutting device 30 includes a rotating blade 32 that is concentrically attached to a shaft 31 and is fixed, and a fixed blade 33 that is disposed so as to face the rotating blade 32, and is a plant introduced from a hopper 34. The fibers move to the fixed blades 33 while being pressed by the rotary blades 32, where the rotary blades 32 and the fixed blades 33 are engaged, and the plant fibers are cut. The rotary blade 32 and the fixed blade 33 are fixed so that the respective blade edge surfaces form an angle of, for example, 1 to 5 °, particularly 2 to 4 ° in the length direction. As a result, the plant fiber is not pressed and pulverized, but is efficiently cut particularly in the length direction, so that a cut fiber having a predetermined length can be obtained. In addition, the cut fiber passes through the mesh of the screen S disposed at least on the lower side of the casing, falls down, and is collected.

  Furthermore, in this cutting device 30, the some fixed blade 33 which adjoins in the rotation direction of the rotary blade 32 is arrange | positioned, and the vegetable fiber which was not cut | judged between the previous fixed blade 33 and the rotary blade 32, Cutting is performed between the fixed blade 33 and the rotary blade 32. Therefore, the vegetable fiber that has not been cut at the position of the fixed blade 33 stays in the casing and does not rotate again, so that it is possible to obtain a more uniform cut fiber having no great difference in fiber length. Further, since the rotary plate 36 that rotates together with the shaft 31 and the rotary blade 32 is provided flush with the side plate 35 of the casing, the cut fiber enters and is rubbed between the shaft 31 and the rotary blade 32. There is nothing. Further, a gap is provided between the side plate 35 and the rotating plate 36, and the cutting fibers around the boundary between the side plate 35 and the rotating plate 36 are discharged from the gap to the outside. It does not fit or stay and deteriorate.

(2) Pulverization step The “pulverization step” is a step of pulverizing the cut fibers to obtain pulverized fibers having a predetermined size, that is, a predetermined average fiber length and average fiber diameter.
The average fiber length of the “pulverized fiber” may be a thermoplastic resin composition capable of efficiently mixing the pulverized fiber and the thermoplastic resin and having sufficient fluidity during molding such as injection molding. Although it may be a predetermined average length, it is preferably 0.5 to 6 mm, more preferably 0.5 to 4 mm, particularly preferably 0.5 to 2 mm, and further preferably 0.5 to 1.5 mm. Moreover, the average fiber diameter of the pulverized fiber may be a predetermined average diameter that exhibits the above-described effects, but is preferably 10 to 60 μm, more preferably 20 to 60 μm, and particularly preferably 30 to 55 μm. preferable. If the average fiber length of the pulverized fiber is 0.5 to 6 mm and the average fiber diameter is 10 to 60 μm, the above-described effects are sufficiently exhibited.
The average fiber length and average fiber diameter of the pulverized fiber can be measured by the same method as in the case of the average fiber length and average fiber diameter of the plant fiber. This average fiber length can be adjusted by the size of the opening of the screen provided in the pulverizer to be used.

  Moreover, content of a grinding | pulverization fiber is 50-95 mass% when the sum total of a thermoplastic resin and a grinding | pulverization fiber is 100 mass%. This content is usually the same as the blending amount of the pulverized fiber blended into the thermoplastic resin during the production of the composition. That is, when the total amount of each of the thermoplastic resin and the pulverized fiber is 100% by mass, the amount of the pulverized fiber is 50 to 95% by mass. The content (blending amount) of the pulverized fiber is preferably 50 to 90% by mass, particularly preferably 50 to 80% by mass, 50 to 70% by mass, particularly 50 to 65% by mass, and further 50 to 60% by mass. It is more preferable.

  The apparatus used in the pulverization step is not particularly limited as long as the cut fiber can be efficiently pulverized into a predetermined size. As such an apparatus, it is possible to use a crushing apparatus that applies an impact to the cut fiber and can crush the cut fiber not only in the length direction but also in the radial direction. Thus, in the pulverization step, the cut fiber is also pulverized in the radial direction, that is, fibrillated, and by using the pulverized fiber thus fibrillated, mixing with the thermoplastic resin is performed. A thermoplastic resin composition that becomes easier and has sufficient fluidity in injection molding or the like can be obtained.

As described above, as a pulverizer capable of sufficiently pulverizing in the radial direction, that is, defibration, for example, a pulverizer having a fixed plate and a rotating plate described in FIGS. it can.
This crusher includes a fixed plate 41 as shown in FIG. 4 and a rotating plate 42 as shown in FIG. 5 that is disposed to face the fixed plate 41 and rotates in the circumferential direction.
On the inner surface of the fixed plate 41, a plurality of outer peripheral projections 411 are provided on the outer peripheral side and spaced apart in the circumferential direction (the outer peripheral projections 411 are usually provided at equal intervals in the circumferential direction). In the case of FIG. 4, four outer peripheral protrusions 411 are provided at intervals of 90 °.) On the inner peripheral side, a plurality of inner peripheral protrusions 412 are erected in the circumferential direction. (The inner peripheral projections 412 are also usually provided at regular intervals in the circumferential direction, and in the case of FIG. 4, four inner peripheral projections 412 are provided at intervals of 90 °.)

  In addition, the outer peripheral side protruding portion 411 and the inner peripheral side protruding portion 412 are usually provided at equal intervals in the circumferential direction, but the outer peripheral side protruding portion 411 and the inner peripheral side protruding portion 412 are also equally spaced from each other in the circumferential direction. Is preferably provided. The fixing plate 41 shown in FIG. 4 has such a structure, and the outer peripheral projections 411 and the inner peripheral projections 412 are provided at intervals of 45 ° in the circumferential direction. Further, the heights of the plurality of outer peripheral projections 411 may be the same or different, but are usually the same height, and the heights of the plurality of inner peripheral projections 412 may be the same or different. Usually, it is the same height. Also, the heights of the outer peripheral side protruding portion 411 and the inner peripheral side protruding portion 412 may be the same or different, and if they are different, either may be high, but usually the outer peripheral side protruding portion as shown in FIG. The side protrusion 411 is higher than the inner peripheral protrusion 412.

  On the other hand, a plurality of protrusions 421 are also provided on the inner surface of the rotating plate 42 so as to be spaced apart from each other in the circumferential direction (the protrusions 421 are usually provided at equal intervals in the circumferential direction. Sixteen protrusions 421 are provided at equal intervals in the circumferential direction.) Further, the positional relationship in the radial direction between the protruding portion 421 and the outer peripheral side protruding portion 411 and the inner peripheral side protruding portion 412 erected on the inner surface of the fixing plate 41 is not particularly limited. 411 and the inner peripheral side protruding portion 412 are arranged so that the protruding portion 421 is positioned (in the case of the fixed plate 41 and the rotating plate 42 in FIG. , Each protrusion is in the positional relationship as described above.) The pulverized fiber passes through the mesh of the screen S disposed at least on the lower side of the casing and falls downward to be collected.

  The cross-sectional shape of each of the outer peripheral side protruding portion 411, the inner peripheral side protruding portion 412 and the protruding portion 421 is not particularly limited, and may be any of a polygonal shape, a circular shape, an elliptical shape, etc. In particular, a rectangle having a long side in the circumferential direction is preferable. In order to further improve the pulverization efficiency, grooves and / or recesses and the like can be provided on the side surfaces and / or the top surfaces of the outer peripheral protrusions 411, the inner peripheral protrusions 412 and the protrusions 421. In particular, it is preferable to provide a groove 4211 in the height direction on the outer peripheral side surface and the inner peripheral side surface of the protrusion 421 provided on the inner surface of the rotating plate 42, so that the crushing efficiency, particularly the solution can be improved. The fiber efficiency can be further improved.

(3) Mixing Step The “mixing step” is a step of kneading and mixing the thermoplastic resin and the pulverized fiber.
In this mixing step, an extrusion type kneading and mixing apparatus excluding a mixer is used. Although this mixing apparatus is not specifically limited, What is necessary is just to be able to mix a lot of grinding | pulverization fibers with a thermoplastic resin, For example, the mixing apparatus described in FIG. 6, 7 can be used. When this specific mixing apparatus is used, a thermoplastic resin composition having higher fluidity can be more easily produced.

  This mixing apparatus [hereinafter, FIG. 6 (FIG. 6 refers to FIG. 1 of the pamphlet of International Publication No. 04/076044 obtained from the Patent Electronic Library of the JPO) and FIG. 7 (FIG. 7 shows the patent electronic library of the JPO. As the reference] (refer to FIG. 2 of the acquired International Publication No. 04/076044 pamphlet), the mixing device 1 described in the International Publication No. 04/076044 pamphlet is preferable. That is, the mixing apparatus 1 includes a material supply chamber 13, a mixing chamber 3 connected to the material supply chamber 13, and a rotary shaft 5 that is rotatably provided through the material supply chamber 13 and the mixing chamber 3. A screw blade 12 disposed on the rotary shaft 5 in the material supply chamber 13 and for conveying the mixed material of the thermoplastic resin and the pulverized fiber supplied to the material supply chamber 13 to the mixing chamber 3, and a mixing chamber The mixing device is preferably provided with mixing blades 10a to 10f that are disposed on the rotary shaft 5 in 3 and mix mixed materials.

  Using the mixing device 1, the thermoplastic resin and the pulverized fiber are put into the material supply chamber 13, conveyed to the mixing chamber 3 by the screw blade 12, and the mixing blades 10a to 10f are rotated, so that the thermoplastic resin and the pulverization are obtained. Both fibers are pressed toward the inner wall of the mixing chamber 3, hit the inner wall, and pushed forward in the rotation direction of the mixing blades 10 a to 10 f, and the thermoplastic resin softens in a short time by the heat generated by the collision between the materials. And then melted, kneaded and mixed with the ground fiber. The mixture (thermoplastic resin composition) thus produced is imparted with excellent fluidity capable of injection molding, for example.

  The mixing blades 10a to 10f are opposed to the axial direction at a position spaced apart by a constant angle in the circumferential direction of the rotating shaft 5 and are attached to the rotating shaft 5 at an attachment angle such that the opposing interval becomes narrow in the rotating direction. It is arranged and is constituted by at least two mixing blades (10a to 10f). The angle of attachment of the mixing blades 10a to 10f with respect to the rotating shaft 5 is preferably the same from the root portion of the mixing blades 10a to 10f attached to the rotating shaft 5 to the distal end portion in the radial direction. The planar shape of the mixing blades 10a to 10f is preferably rectangular. Furthermore, it is more preferable that the mixing chamber 3 includes a mixing chamber cooling means that can circulate a cooling medium around the constituent walls. By setting it as such a structure, it can suppress that a mixing chamber heats up too much, and can prevent or at least suppress the thermal deterioration of a thermoplastic resin.

  Various conditions in the mixing step are not particularly limited. For example, the temperature during mixing is preferably controlled to 200 ° C. or less, particularly 150 ° C. or less, and further 120 ° C. or less, and the temperature of the outer wall surface of the mixing chamber is 50 ° C. As described above, it is particularly preferable to control the temperature at 60 ° C. or higher, and further 80 ° C. or higher. The time for reaching this temperature is preferably within 10 minutes, particularly within 5 minutes. By reaching the predetermined temperature in a short time, moisture can be rapidly evaporated and mixed, and deterioration of the thermoplastic resin can be suppressed more effectively. Furthermore, it is preferable that the time for maintaining the temperature range is within 15 minutes, particularly within 10 minutes. Moreover, it is preferable to control this temperature by the rotational speed of the mixing blade of the mixing apparatus. More specifically, it is preferable to control the peripheral speed at the tip of the mixing blade to be 5 to 50 m / sec. By controlling the peripheral speed within this range, the thermoplastic resin can be efficiently softened and mixed with the pulverized fiber more uniformly while being melted.

  Furthermore, the end point of this mixing is not particularly limited, but can be determined by a change in torque applied to the rotating shaft. That is, it is preferable to measure the torque applied to the rotating shaft and stop mixing after the torque reaches the maximum value. Thereby, a thermoplastic resin and a ground fiber can fully be disperse | distributed mutually. Further, it is more preferable to stop the mixing after the torque reaches the maximum value and starts to decrease. Furthermore, it is particularly preferable to stop the mixing when the torque is in the range of 40% or more, particularly 50 to 80% with respect to the maximum torque. As a result, the thermoplastic resin and the pulverized fiber can be sufficiently dispersed to each other, and the mixture (thermoplastic resin composition) can be taken out from the mixing chamber at a temperature of 160 ° C. or more, and the thermoplastic resin is mixed into the mixing chamber. It can prevent more reliably that the resin composition adheres and remains.

(4) Pelletization process (a) Pelletization of thermoplastic resin composition The manufacturing method of the thermoplastic resin composition of this invention may be equipped with the other process except a cutting process, a grinding | pulverization process, and a mixing process. As this other process, the process of pelletizing the thermoplastic resin composition manufactured by the mixing process is mentioned. This is because the thermoplastic resin composition produced by the method of the present invention can then be subjected to molding such as injection molding, but at this time, molding is performed because the thermoplastic resin composition is pelletized. This is because it is easy and preferable.

  The pelletizing method is not particularly limited. For example, an apparatus in which a mixing apparatus and a pelletizing apparatus capable of pelletizing before the produced thermoplastic resin composition is removed from heat is used. The case is preferable because it can be pelletized continuously with mixing. In addition, when a pelletizing device is not provided, the bulk thermoplastic resin composition discharged from the mixing device is usually crushed by a crusher to form a granular material, and then melted by an extruder or the like. It can be kneaded and extruded to be pelletized. Further, it can be pelletized without reheating.

  The massive thermoplastic resin composition discharged from the mixing device is preferably heated and pelletized without heating. In this way, by pressing and solidifying without pelletizing, for example, the bulk thermoplastic resin composition is crushed by a crusher into a granular material, and the granular material is pelletized by an ordinary method such as an extruder. As compared with the case where the thermoplastic resin composition is used, the thermal history of the thermoplastic resin composition can be reduced, and the mechanical properties of the thermoplastic resin molded article molded using this thermoplastic resin composition can be further improved. it can.

  Any apparatus and means may be used in the step of pressing and solidifying without heating, and it is particularly preferable to use pelletization by various compression molding methods. Examples of the compression molding method include a roller molding method and an extruder molding method. Among these, the roller-type molding method is a method using a roller-type molding machine, and the mixture is pressed into the die by a roller that rotates in contact with the die, and then extruded from the die and pelletized. Examples of the roller type molding machine include a disk die type (roller disk die type molding machine) and a ring die type (roller ring die type molding machine), which have different die shapes. On the other hand, the extruder type molding method is a method using an extruder type molding machine, in which the mixture is pressed into a die by rotation of a screw auger, and then extruded from the die to be pelletized. Of these compression molding methods, a roller disk die molding method with high compression efficiency is more preferable.

Furthermore, in this method, it is particularly preferable to pelletize by using the following specific roller disk die-type molding machine [Pelletizer 50 (see FIG. 8 describing the main part)]. That is, a disk die 51 having a plurality of through holes 511 and a press roller 52 that rolls on the disk die 51 and pushes an uncompressed material (a mixture of thermoplastic resin and pulverized fibers) into the through holes 511. It is particularly preferable to use a roller disk die molding machine that includes a main rotating shaft 53 that drives the press roller 52. In this molding machine, the disk die 51 has a main rotation shaft insertion hole 512 that penetrates in the same direction as the through hole 511, and the main rotation shaft 53 is inserted through the main rotation shaft insertion hole 512 and the main rotation shaft 53. And a press roller fixing shaft 54 provided perpendicularly to the main body. The press roller 52 is rotatably supported by the press roller fixed shaft 54 and rolls on the disk die 51 as the main rotary shaft 53 rotates.
In this roller disk die type molding machine, in addition to the above configuration, it is more preferable that the surface of the press roller 52 is provided with irregularities 521. Further, it is more preferable that a cutting blade 55 that is rotated in accordance with the rotation of the main rotating shaft 53 is provided.

  In the roller disk die type molding machine, for example, in FIG. 8, the mixture charged from above the main rotating shaft 53 is caught by the unevenness 521 provided in the press roller 52 and pushed into the through hole 511, and The string-like mixture is extruded. This string-like mixture is cut into an appropriate length by a rotating cutting blade 55 to be pelletized, and dropped downward and collected. The shape and dimensions of the pelletized thermoplastic resin composition are not particularly limited, but are preferably columnar shapes such as a columnar shape. Furthermore, the maximum dimension is preferably 1 mm or more (usually 20 mm or less), more preferably 1 to 10 mm, and particularly preferably 2 to 7 mm.

(B) Pelletization of pulverized fiber In the method for producing a thermoplastic resin composition of the present invention, the pulverized fiber may be pelletized before mixing with the thermoplastic resin. The pelletizing apparatus used in the pelletizing step of the pulverized fiber is not particularly limited, but the roller disk die molding machine can be used in the same manner as the pelletizing step of the thermoplastic resin composition. By providing the pelletizing step of the pulverized fiber in this way, the difference in bulk density between the pulverized fiber and the thermoplastic resin can be reduced, workability is improved, and uneven distribution of the material during mixing can be suppressed. It is possible to obtain a thermoplastic resin composition in which the pulverized fiber and the thermoplastic resin are more uniformly dispersed, and the mechanical strength of the thermoplastic resin molded body can be further improved.

2. Production method of thermoplastic resin molded body The thermoplastic resin composition (pelletized thermoplastic resin composition) produced by the method of the present invention is produced by various molding methods such as injection molding, extrusion molding, compression molding, and the like. It can be set as a thermoplastic resin molding. This thermoplastic resin composition has excellent fluidity even though it contains a large amount of plant fiber (ground fiber), so it can also be used for injection molding that requires particularly sufficient fluidity. . If the thermoplastic resin composition is pelletized at the time of this injection molding, the measurement time, the injection time, etc. can be shortened. As a result, the molding cycle can be shortened and the molding efficiency can be improved. Moreover, the apparatus and molding conditions used for various moldings such as injection molding are not particularly limited, and may be appropriately selected and set depending on the type of thermoplastic resin, the shape of the thermoplastic resin molded body, the use, and the like.

  The shape and dimensions of the thermoplastic resin molded body are not particularly limited, and the use is not particularly limited. Examples of the molded body include interior materials, exterior materials, and structural materials such as automobiles, railway vehicles, ships, and airplanes. Among these, automotive materials include interior materials, instrument panels, exterior materials, etc., specifically, door base materials, package trays, pillar garnishes, switch bases, quarter panels, armrest core materials, door trims. Seat structural materials, seat backboards, ceiling materials, console boxes, dashboards, instrument panels, deck trims, bumpers, spoilers, cowlings and the like. Furthermore, examples of other uses other than automobiles include interior materials such as buildings and furniture, exterior materials, and structural materials. For example, a door cover material for a building, a door structure material, a cover material for various furniture such as a desk, a chair, a shelf, and a bag, a structural material, and the like. Still other examples include packaging bodies, containers such as trays, protective members, partition members, and the like.

Hereinafter, the present invention will be described specifically by way of examples.
[1] Production of thermoplastic resin composition Example 1
(1) Production of pulverized fiber Kenaf fiber (produced in Indonesia, rope shape) is cut with a cutting device (model “RC250”, manufactured by Yoshiko Co., Ltd.), and passed through a screen having an opening with a diameter of 10 mm as cutting fiber. It was collected. The cut fibers were continuously put into a pulverizer (manufactured by Hadano Sangyo Co., Ltd., model “Makino DD-2”), pulverized, passed through a screen having an opening with a diameter of 2 mm, and recovered as pulverized fibers. 200 pulverized fibers were observed with an optical microscope, the length and diameter of each fiber were measured, and the average fiber length and average fiber diameter were calculated by dividing the cumulative length and cumulative diameter by the number. The results are listed in Table 1.
In addition, the diameter of each fiber is a diameter of the center part of a length direction.

(2) Production of thermoplastic resin composition 360 g of the pulverized fiber prepared in (1) above, 225 g of polypropylene (manufactured by Nippon Polypro Co., Ltd., trade name “Novatech NBC03HR”), and acid-modified polypropylene (trade name, manufactured by Mitsubishi Chemical Corporation) “Modic P908”, maleic anhydride-modified polypropylene (15 g) (the mass ratio of pulverized fiber, polypropylene, and acid-modified polypropylene is as shown in Table 1), and the mixing apparatus 1 (WO 2004-076044) shown in FIG. Was then transferred to the mixing chamber 3 having a capacity of 5 liters, and the mixing blades (10a to 10f in FIG. 7) were rotated at 1750 rpm, kneaded and mixed. Then, the load (torque) applied to the mixing blades increased, reached the maximum value, stopped mixing after 6 seconds, and the mixture (the thermoplastic resin composition before pelletization) was discharged from the mixing apparatus 1. .

(3) Pelletization The massive thermoplastic resin composition produced in the above (2) is crushed to about 5 mm by a crusher (manufactured by Horai Co., Ltd., “Z10-420”). A die-shaped molding machine (manufactured by Kikukawa Iron Works, type “KP280”, using a die with a through-hole diameter of 4.2 mm and a thickness of 25 mm) is fed at a feeder frequency of 20 Hz, and a cylindrical shape with a diameter of about 4 mm and a length of about 5 mm. The pellets were then dried in an oven at 100 ° C. for 24 hours to obtain thermoplastic resin composition pellets.

Example 2
A thermoplastic resin composition was produced and pelletized in the same manner as in Example 1 except that a cutting apparatus having a screen with an opening diameter of 6 mm was used.
Example 3
A thermoplastic resin composition was produced and pelletized in the same manner as in Example 1 except that a cutting device having a screen with an opening having a diameter of 2 mm was used.
Example 4
The pulverized fiber is put into a roller disk die molding machine [manufactured by Kikukawa Iron Works, type “KP280”, die having a through-hole diameter of 6.2 mm and a thickness of 28 mm] at a feeder frequency of 40 Hz. A thermoplastic resin composition was produced and pelletized in the same manner as in Example 1 except that the pellets were formed into columnar pellets having a length of about 10 mm, and then kneaded and mixed with the thermoplastic resin.
Example 5
A thermoplastic resin composition was produced and pelletized in the same manner as in Example 1 except that the pulverized fiber, polypropylene, and acid-modified polypropylene were used in the mass ratio shown in Table 1.

Comparative Example 1
A thermoplastic resin composition was produced and pelletized in the same manner as in Example 1 except that the kenaf fiber was cut and not pulverized, and the cut fiber was kneaded and mixed with the thermoplastic resin.
Comparative Example 2
A thermoplastic resin composition was produced and pelletized in the same manner as in Comparative Example 1 except that the cut fibers, polypropylene, and acid-modified polypropylene were used in the mass ratio shown in Table 1.
As described above, the mass ratio between the pulverized fiber and the thermoplastic resin in Examples 1 to 5 and Comparative Examples 1 and 2, the opening diameter of the screen, the presence or absence of pelletization of the pulverized fiber, and the pulverized fiber (cut fiber in the comparative example) Table 1 shows the average fiber length and the average fiber diameter.
In Table 1, “PP” is an abbreviation for polypropylene, and “acid-modified PP” is an abbreviation for acid-modified polypropylene.

[2] Characteristic evaluation of thermoplastic resin composition The pellets of the thermoplastic resin compositions of Examples 1 to 5 and Comparative Examples 1 and 2 obtained in [1] were dried in an oven at 100 ° C for 5 hours. Then, injection molding was performed with an injection molding machine (Sumitomo Heavy Industries, Ltd., model “SE100DU”) under conditions of a cylinder temperature of 190 ° C. and a mold temperature of 40 ° C., and a test piece having a length of 80 mm, a width of 10 mm, and a thickness of 4 mm. Then, a bending test was performed in accordance with JIS K7171, and bending strength and bending elastic modulus were calculated. In addition, injection molding was similarly performed using a bar flow mold, and the flow length was evaluated. These results are also shown in Table 1.

  According to the results in Table 1, in Examples 1 to 4, in which predetermined amounts of kenaf pulverized fiber, polypropylene, and acid-modified polypropylene were blended in predetermined amounts, the opening diameter of the screen of the cutting device, and pulverized fiber pellets Regardless of the presence or absence of crystallization, it can be seen that it has sufficient bending properties and excellent fluidity with the bar flow length as an index. It can also be seen that Example 3 in which the fiber diameter of the pulverized fiber is larger than the other examples similarly has sufficient bending characteristics and fluidity. Furthermore, in Example 5, in which the blending amount of kenaf pulverized fiber is smaller than in other examples, the bending characteristics are slightly lowered, but the fluidity is more excellent, and the thermoplastic resin composition can be sufficiently put into practical use. On the other hand, Comparative Example 1 in which only kenaf fiber was cut and not pulverized was compared with Examples 1 to 4, and Comparative Example 2 was more flexible than Example 5, but the fluidity was sufficient. It turns out that is inferior.

  The method for producing a thermoplastic composition of the present invention can be used in a wide range of applications such as automobile-related fields and construction-related fields, and is used for interior materials, exterior materials, and structural materials for automobiles, railway vehicles, ships, airplanes, and the like. In particular, it can be suitably used in the field of automobile-related products such as automotive interior materials, automotive instrument panels, and automotive exterior materials.

  DESCRIPTION OF SYMBOLS 1; Stirrer, 3; Mixing chamber, 5; Rotating shaft, 10 and 10a-10f; Mixing blade, 12; Spiral blade, 13; Material supply chamber, 30; Cutting device, 31; Shaft, 32; 33; fixed blade, 40; pulverizer, 41; fixed plate, 411; outer peripheral projection, 412; inner peripheral projection, 42; rotating plate, 421; projection, 50; pelletizer [roller disk die type molding machine (Pelletization part)], 51; Disc die, 511; Through hole, 512; Main rotation shaft insertion hole, 52; Press roller, 521; Concavity and convexity, 53; Main rotation shaft, 54; Press roller fixed shaft, 55; Cutting blade.

Claims (8)

Thermoplastic resin and pulverized fiber obtained by pulverizing vegetable fiber, and when the total of the thermoplastic resin and pulverized fiber is 100% by mass, the pulverized fiber is 50 to 95% by mass. A method for producing a resin composition, comprising:
A cutting step of cutting the plant fiber into a predetermined length of cutting fiber, a pulverizing step of pulverizing the cutting fiber into the pulverized fiber of a predetermined size, and kneading the thermoplastic resin and the pulverized fiber. And a mixing step of mixing. A method for producing a thermoplastic resin composition.   The method for producing a thermoplastic resin composition according to claim 1, wherein the cut fiber has a fiber length of 25 mm or less.   The method for producing a thermoplastic resin composition according to claim 2, wherein an average fiber length of the pulverized fibers is 0.5 to 6 mm, and an average fiber diameter is 10 to 60 µm.   The method for producing a thermoplastic resin composition according to any one of claims 1 to 3, wherein the plant fiber is a kenaf fiber.   The method for producing a thermoplastic resin composition according to any one of claims 1 to 4, wherein the thermoplastic resin is a polypropylene resin and an acid-modified polypropylene resin.   The production of the thermoplastic resin composition according to claim 5, wherein the acid-modified polypropylene resin is 1 to 30% by mass when the total of the polypropylene resin and the acid-modified polypropylene resin is 100% by mass. Method.   The method for producing a thermoplastic resin composition according to any one of claims 1 to 6, wherein the pulverized fiber is pressed and pelletized, and then mixed with the thermoplastic resin. The mixing device used for the kneading and mixing includes a mixing chamber in which the mixing is performed and a mixing blade disposed in the mixing chamber,
The heat according to any one of claims 1 to 7, wherein the thermoplastic resin that has been heated and melted by rotation of the mixing blade and the pulverized fiber are kneaded and mixed in the mixing chamber. A method for producing a plastic resin composition.

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