JP2010275400A - Method for manufacturing thermoplastic resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a thermoplastic resin composition which can be made to contain a great deal of plant fibers and has a sufficient fluidity when used for injection molding or the like. <P>SOLUTION: This method for manufacturing a thermoplastic resin composition which contains a thermoplastic resin (a polypropylene-based resin, especially a combined use of a polypropylene-based resin and an acid-modified polypropylene-based resin), and a plant fiber (kenaf fiber or the like), in which if the sum total is 100 mass%, the plant fiber is 50-95 mass%, comprises a cutting process of cutting a raw material fiber, a mixing process of kneading and mixing the thermoplastic resin and the cut fibers, with the cut fibers passing through a screen having an opening of 0.5-2 mm in the cutting device and being of a straight form. <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 difference in bulk density from the resin is reduced, and the plant material and the resin are mixed. It is known that a composite material is uniformly dispersed with each other, and a molded body is manufactured using the composite material (see, for example, Patent Document 3).

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

  In Patent Document 1, when the biodegradable resin containing kenaf fibers is polylactic acid, the most accurate injection molding can be performed. However, when the content of kenaf fibers exceeds 50% by mass, the fibers are uniformly formed in the resin. It is described that problems such as clogging of the resin composition in the molding machine occur without being dispersed. 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 the number of steps increases, which 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. A method for producing a thermoplastic resin composition comprising a thermoplastic resin and plant fibers, wherein the total amount of the thermoplastic resin and the plant fibers is 100% by mass, and the plant fibers are 50 to 95% by mass. A cutting step of cutting raw material fibers into cutting fibers, and a mixing step of kneading and mixing the thermoplastic resin and the cutting fibers, wherein the cutting fibers have openings in a cutting device A method for producing a thermoplastic resin composition, which passes through a screen of 0.5 to 2 mm and is straight.
2. The raw material fibers are kenaf fibers. The manufacturing method of the thermoplastic resin composition as described in any one of.
3. The thermoplastic resin is a polypropylene resin or an acid-modified polypropylene resin. Or 2. The manufacturing method of the thermoplastic resin composition as described in any one of.
4). 2. 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.
5). The said 1. provided with the grinding | pulverization process which grind | pulverizes the resin fiber mixture obtained in the said mixing process to make a grinding | pulverization mixture. To 4. The manufacturing method of the thermoplastic resin composition of any one of these.
6). 4. A pelletizing step of pressing and solidifying the pulverized mixture to form a pellet. The manufacturing method of the thermoplastic resin composition as described in any one of.
7). 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. 1. The plastic resin and the cut fiber are kneaded and mixed. To 6. 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, since the fiber length of the cut fiber obtained by cutting the raw fiber is short, straight and not bulky, 50 to 95% by mass of a large amount of plant fiber is contained. The thermoplastic resin composition can be easily contained and has sufficient fluidity when molded by a method such as injection molding. Therefore, when this thermoplastic resin composition is used, a thermoplastic resin molded body (hereinafter abbreviated as “molded body”) that has an excellent flexural modulus and the like is preferable from the viewpoint of practicality. it can.
In addition, when the raw fiber is kenaf fiber, it is an annual plant with a very 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 molded article having excellent mechanical properties can be obtained. be able to.
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 molded article having excellent mechanical properties can be obtained.
Furthermore, when a pulverization step is performed by pulverizing the resin fiber mixture obtained in the mixing step, the pulverized mixture can be used as it is or as a pellet as a raw material for injection molding, etc. It is easier to handle than a lump-shaped resin fiber mixture, and a molded product can be easily produced.
In addition, when a pelletizing step is performed in which the pulverized mixture is pressed and pelletized, it can be pelletized without heating, so that the thermal degradation of the thermoplastic resin is suppressed, and the pellet is easy to handle and injection molding. It can be supplied more easily and more uniformly to a machine or the like, and the mechanical properties of the molded body can be further improved.
Furthermore, 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 by the rotation of the mixing blade and melted in the mixing chamber; When the cut 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 typical explanatory drawing of the cross section which looked at the cutting apparatus from the front. It is typical explanatory drawing of the cross section which saw the cutting device from the side. It is explanatory drawing based on the electronic data which observed the straight cut fiber with the microscope and image | photographed. It is explanatory drawing based on the electronic data which observed the cut | disconnected fiber which has a bending part with a microscope, and image | photographed. 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] Method for producing thermoplastic resin composition The thermoplastic resin composition contains a thermoplastic resin and a vegetable fiber, and the total amount of the thermoplastic resin and the vegetable fiber is 100% by mass. It is -95 mass%, can be manufactured by a method comprising a cutting step of cutting a raw fiber into a cut fiber, and a mixing step of kneading and mixing the thermoplastic resin and the cut fiber, and the cut fiber Passes through a screen having a mesh opening of 0.5 to 2 mm and has a straight shape.

(1) Raw material (a) Thermoplastic resin The "thermoplastic resin" is a resin mixed with the cut fiber 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. Two or more thermoplastic resins may be used in combination, but only one type is often used.

  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 fluidity of the thermoplastic resin composition can be further improved, and the mechanical properties of a molded article formed using this thermoplastic resin composition can be further 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 a 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. If the introduction amount is such that the acid value of the acid-modified polyolefin is 5 or more, the mechanical properties of the 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, the fluidity of the thermoplastic resin composition can be sufficiently improved, and a molded article having excellent mechanical properties can be obtained. 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.

  Moreover, when using together acid-modified polyolefin, when the whole thermoplastic resin is 100 mass%, it is preferable that acid-modified polyolefin is 1-30 mass%, 1-25 mass%, especially 1-20 mass%. Furthermore, it is more preferable that it is 1.5-10 mass%. If the blending amount of the acid-modified polyolefin is 1 to 30% by mass, the fluidity of the thermoplastic resin composition at the time of molding such as injection molding can be dramatically improved and the mechanical properties of the molded body are improved. Can be made. Furthermore, as the thermoplastic resin, it is more preferable to use a polypropylene resin, for example, polypropylene and / or an ethylene-propylene copolymer, particularly an ethylene-propylene block copolymer, and a resin obtained by acid-modifying these in combination. Thereby, the fluidity of the thermoplastic resin composition at the time of molding such as injection molding and the mechanical properties of the molded body can be sufficiently improved.

(B) Raw material fiber The "raw material fiber" is a fiber derived from a plant. This raw fiber includes kenaf, jute hemp, manila hemp, sisal hemp, husk, cocoon, cocoon, banana, pineapple, coconut, corn, sugar cane, bagasse, palm, papyrus, cocoon, esparto, sabaigrass, wheat, rice, bamboo, Examples thereof include fibers of various plants such as conifers (cedars, firewood, etc.), hardwoods, and cotton. This raw material fiber may use only 1 type and may use 2 or more types together. 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 raw material fiber, the outer layer part called a bast which has a tough fiber can be used.

  The fiber length and fiber diameter of the raw 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. The fiber length of the raw fiber is usually 10 to 300 mm, and the fiber diameter is usually 10 to 100 μm. This fiber length is a value measured on a measuring scale by stretching one raw fiber straight without stretching in the same manner as 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 fiber length direction using the optical microscope about the raw material fiber which measured fiber length.

  Furthermore, the average fiber length and average fiber diameter of the raw fiber are not particularly limited, but the average fiber length is preferably 100 mm or less (usually 20 mm or more). By using raw material fibers having an average fiber length of 100 mm or less, 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 15 μm or more). 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 contain other components excluding the thermoplastic resin and plant fibers. Other components are not particularly limited, and examples thereof include various additives such as antioxidants, ultraviolet absorbers, antistatic agents, flame retardants, antibacterial agents, and coloring agents. 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 in which raw fibers are cut with a cutting device to make a cut fiber, and the cut fiber and the thermoplastic resin are kneaded with a mixing device, A mixing step of mixing. Moreover, since the resin fiber mixture obtained in the mixing step is in a lump shape, it is preferably pulverized in the pulverizing step and used as a pulverized mixture. Further, this pulverized mixture may be used as it is as a raw material of a molded body, but it may be formed into pellets having a predetermined shape and size by a pelletizing apparatus, and this pellet may be used as a raw material of the molded body.

(A) Cutting process The above-mentioned "cutting process" is a process of cutting a raw fiber into a cut fiber having a predetermined length.
The apparatus used in the cutting step is not particularly limited as long as the raw material fibers can be efficiently cut into a predetermined length. As this cutting device, for example, the cutting device described in FIGS.

  The cutting device 30 described in FIGS. 1 and 2 includes a rotating tooth 32 that is concentrically attached and fixed to a shaft 31, and a fixed tooth 33 that is disposed to face the rotating tooth 32. The raw material fibers input from the hopper 34 move to the fixed teeth 33 while being pressed by the rotating teeth 32, where the rotating teeth 32 and the fixed teeth 33 are engaged, and the raw material fibers are cut. The rotating teeth 32 and the fixed teeth 33 are fixed so that their respective tip surfaces slightly form, for example, an angle of 1 to 5 °, particularly 2 to 4 ° in the length direction. Thereby, the raw material fibers are not pressed and pulverized, but are particularly efficiently cut in the length direction to obtain a cut fiber having a predetermined length. 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, a plurality of fixed teeth 33 adjacent to each other in the rotation direction of the rotary teeth 32 are disposed, and the raw fibers that have not been cut between the previous fixed teeth 33 and the rotary teeth 32, Cutting is performed between the rear fixed tooth 33 and the rotating tooth 32. Therefore, the raw fiber that has not been cut at the position of the fixed tooth 33 stays in the casing, does not rotate again, and can be made into a more uniform cut fiber with no great difference in fiber length. In addition, since the rotating plate 36 that rotates together with the shaft 31 and the rotating teeth 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 rotating teeth 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.

  The “cut fiber” passes through a screen having a mesh opening of 0.5 to 2 mm and has a straight shape. If the cut fiber passes through a screen having a mesh size of 0.5 to 2 mm, it can be easily kneaded with the thermoplastic resin in the mixing step, and can be mixed more uniformly. The fiber length of the cut fiber that has passed through a screen having a mesh opening of 0.5 to 2 mm can be 0.1 to 3 mm, particularly 0.5 to 2 mm. The screen opening is preferably smaller than 0.5 to 1.5 mm, particularly 0.5 to 1 mm, so that a cut fiber having a shorter fiber length can be obtained, and heat having superior fluidity can be obtained. A plastic resin composition can be produced. Further, the fiber diameter of the cut fiber is not particularly limited, but the fiber diameter of the cut fiber can be usually 10 to 100 μm, particularly 50 to 90 μm by cutting the raw fiber having the fiber diameter. The fiber length and fiber diameter of this cut fiber can be measured by the same method as in the case of the fiber length and fiber diameter of the raw fiber.

  Furthermore, since the cut fiber is straight, the difference in bulk density from the thermoplastic resin used in the form of pellets or powder is small, kneading is easy, and a larger amount of cut fiber is mixed more uniformly. Can do. The term “straight” means that the cut fiber does not have a bent portion bent at an angle of 90 ° or less (see FIG. 3), and the bent portion bent at an angle of 90 ° or less is at one place. If so, it is not straight (see FIG. 4). In addition, the straightness can be confirmed by the fact that the cut fibers having a bent portion in the field of view are not observed when the cut fibers are observed in a bright field with an optical microscope at a magnification of 50 times. Furthermore, since the plant material generally has a large bulk density, the amount that can be charged into the mixing device at a time is limited, and the production efficiency is not high, but the plant material passes through a screen having an aperture of 0.5 to 2 mm and has a bent portion. If it is a straight cut fiber that does not have, the amount of input can be increased, and the thermoplastic resin composition can be produced more efficiently.

Further, the cut fiber may be kneaded and mixed with a thermoplastic resin in a mixing step without being pelletized in advance, or may be pelletized in advance, and the pellet may be kneaded and mixed with the thermoplastic resin. Since the cut fiber has a sufficiently short fiber length and is straight, it can be sufficiently mixed with the thermoplastic resin as it is, and by using it without pelletization, it can be used more than when pelletized. It can be set as the thermoplastic resin composition which has the outstanding fluidity | liquidity.
In addition, when pelletizing a cut fiber, the method is not particularly limited, and can be carried out in the same manner as pelletizing a thermoplastic resin composition described later, and similarly, using a roller disk die molding machine. Is particularly preferred.

(B) Mixing Step The “mixing step” is a step of kneading and mixing the thermoplastic resin and the cut 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 cutting fibers with a thermoplastic resin, for example, the mixing apparatus described in FIG. 5, 6 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 [FIG. 5 (FIG. 5 refers to FIG. 1 of the pamphlet of International Publication No. 04/076044 obtained from the Patent Electronic Library of the JPO)] and FIG. 6 (FIG. 6 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 cut 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 cutting fiber are put into the material supply chamber 13, conveyed to the mixing chamber 3 by the screw blades 12, and the mixing blades 10a to 10f are rotated, so that the thermoplastic resin and the cutting material are cut. 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 cut fibers. 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 melted and more uniformly mixed with the cut fiber.

  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, the thermoplastic resin and the cut fiber can be sufficiently dispersed and mixed with each other. 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 cut fiber can be more sufficiently dispersed from each other, and the mixture (thermoplastic resin composition) can be taken out from the mixing chamber at a temperature of 160 ° C. or more. It can prevent more reliably that the resin composition adheres and remains.

  The “vegetable fiber” (a fiber contained in a thermoplastic resin composition obtained by kneading and mixing a cut fiber with a thermoplastic resin, and kneaded and mixed with the thermoplastic resin. Is a different form of fiber, and if it is provided with a pulverization step and a pelletizing step, the content of the fiber becomes a different form in these steps). When it is 100 mass%, it is 50-95 mass%. This content is usually the same as the blending amount of the cut fiber blended into the thermoplastic resin during the production of the thermoplastic resin composition. That is, when the total amount of each of the thermoplastic resin and the cut fiber is 100% by mass, the amount of the cut fiber is 50 to 95% by mass. The plant fiber content (blending fiber content) is preferably 55 to 65% by mass. If the content of the plant fiber (the blended amount of the cut fiber) is 50 to 95% by mass, the molded article has excellent bending elastic modulus and the like, and is preferable from the viewpoint of practicality.

(C) Crushing step When the crushing step is provided, the crushing apparatus is not particularly limited as long as the massive resin fiber mixture can be efficiently crushed. As such an apparatus, a pulverizing apparatus generally used for pulverizing a resin composition can be used. For example, a Z series grinder with high grinding efficiency manufactured by Horai Co., Ltd. can be used. Further, the shape and particle size of the particles of the pulverized mixture are not particularly limited, and operations such as sizing can be used as a raw material for the molded body without particularly requiring operations. The particle diameter (maximum dimension) is preferably 1 to 10 mm, particularly preferably 3 to 8 mm. If the particle diameter is 1 to 10 mm, it is easy to handle and can be easily supplied to a molding machine such as an injection molding machine.

(D) Pelletizing step When the pelletizing step is provided, the pulverized mixture produced and pulverized in the mixing step is supplied to a pelletizing apparatus to be pelletized. 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 apparatus used for this pelletization is not particularly limited as long as the pulverized mixture can be efficiently pelletized. As such an apparatus, a pelletizing apparatus generally used for pelletizing a resin composition can be used. Further, the pulverized mixture can be supplied to an extruder or the like, melted and kneaded, and extruded to be pelletized.

  Further, the pulverized mixture is preferably heated and pelletized without heating. Thus, without heating, by pressing and solidifying into pellets, for example, when the pulverized mixture is supplied to an extruder or the like, melted and kneaded, and extruded to be pelletized, the thermal history of the pulverized mixture is reduced. It can reduce, and the mechanical characteristic of the molded object shape | molded using this grinding | pulverization mixture can be improved more.

  Any apparatus and means may be used in the step of pressing and solidifying into pellets without heating, but pelletization by various compression molding methods is particularly preferable. 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. Among these compression molding methods, a method using a roller disk die type molding machine with high compression efficiency is more preferable.

Moreover, it is especially preferable to use the following specific roller disk die type | molding machine (refer FIG. 7 which described the principal part) for pelletization. That is, a disk die 41 having a plurality of through holes 411, a press roller 42 that rolls on the disk die 41 and pushes a non-compressed material (crushed mixture) into the through holes 411, and drives the press roller 42. It is particularly preferable to use a roller disk die molding machine 40 that includes a main rotating shaft 43 that performs the above operation. In this molding machine, the disk die 41 has a main rotation shaft insertion hole 412 that penetrates in the same direction as the through hole 411, and the main rotation shaft 43 is inserted through the main rotation shaft insertion hole 412 and the main rotation shaft 43. And a press roller fixing shaft 44 provided perpendicularly to the shaft. Further, the press roller 42 is rotatably supported by the press roller fixed shaft 44 and rolls on the disk die 41 as the main rotation shaft 43 rotates.
In this roller disk die type molding machine 40, in addition to the above-described configuration, it is more preferable that unevenness 421 is provided on the surface of the press roller. It is more preferable that a cutting blade 45 that rotates as the main rotating shaft 43 rotates is provided.

  In the roller disk die type molding machine 40, for example, in FIG. 7, the pulverized mixture charged from above the main rotating shaft 43 is caught by the unevenness 421 provided in the press roller 42 and pushed into the through hole 411, and the back surface of the disk die 41 A string-like pulverized mixture is extruded from the side. This string-like pulverized mixture is cut into an appropriate length by a rotating cutting blade 45 to be pelletized, and dropped downward and collected. Moreover, although the shape and dimension of a pellet are not specifically limited, It is preferable that they are columnar shapes, such as a column 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.

[2] Method for Producing Molded Body Thermoplastic resin composition produced by the method of the present invention (Since it is difficult to use as a lump after mixing, it is usually pulverized, pulverized, and pelletized for use. .) Can be formed into a molded body by various molding methods such as injection molding, extrusion molding, and compression molding. This thermoplastic resin composition has excellent fluidity even though it contains a large amount of plant fiber, and can therefore be used for injection molding that requires particularly sufficient fluidity. Further, if the thermoplastic resin composition is pelletized at the time of injection molding, the metering time and the injection time can be shortened, and as a result, the molding cycle can be shortened and the molding efficiency can be improved. . Furthermore, 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 molded body, the use, and the like.

  The shape and dimensions of the molded body are not particularly limited, and the use thereof 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 the above-described 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 cut fiber Kenaf fiber (made in Indonesia, rope shape), which is a raw material fiber, is cut with a cutting device (model “RC250”, manufactured by Yoshiko Co., Ltd.), passed through a screen with a mesh opening of 2 mm, and the fiber length It collect | recovered as a 1-2 mm cutting fiber. This cut fiber did not have a bent part and was straight.

(2) Production of thermoplastic resin composition 360 g of the cut 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) “P908”, maleic anhydride-modified polypropylene) 15 g [cut fiber, polypropylene and acid-modified polypropylene in a mass proportion (the total amount is 100% by mass) is 60% by mass of cut fiber and 37.5% by mass of polypropylene. The acid-modified polypropylene is 2.5% by mass. Are fed into the material supply chamber 13 of the mixing device 1 in FIG. 5 (the device described in WO 2004-076044), then transferred to the mixing chamber 3 having a capacity of 5 liters, and the mixing blade (10a in FIG. 6). -10 f) at a rotational speed of 1750 rpm, kneaded and mixed. Then, the load (torque) applied to the mixing blade increases, reaches the maximum value, stops mixing after the elapse of 4 seconds, and removes the mixture (the thermoplastic resin composition before pulverization and pelletization) from the mixing device 1. It was discharged.

(3) Pulverization and pelletization The massive thermoplastic resin composition produced in (2) above is pulverized to a maximum size of about 5 mm by a pulverizer (Holai, type “Z10-420”), and then pulverized product Is introduced into a roller disk die molding machine (manufactured by Kikukawa Iron Works, type “KP280”, die having a through-hole diameter of 4.2 mm and a thickness of 25 mm) at a feeder frequency of 20 Hz, a diameter of about 4 mm, and a length of about A 5 mm cylindrical pellet was formed, and then the pellet was dried in an oven at 100 ° C. for 24 hours to obtain a pellet of a thermoplastic resin composition.

Example 2
A thermoplastic resin composition was produced and pelletized in the same manner as in Example 1 except that a cutting device equipped with a screen having an opening of 1 mm was used. The fiber length of the cut fiber was 0.5 to 1 mm. This cut fiber did not have a bent part and was straight.
Example 3
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 a mesh opening of 0.5 mm was used. The fiber length of the cut fiber was 0.2 to 0.5 mm. This cut fiber did not have a bent part and was straight.

Example 4
The cut fiber obtained in Example 1 is put into a roller disk die type 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 a cylindrical pellet having a diameter of about 6 mm and a length of about 10 mm was previously prepared, and then kneaded and mixed with the thermoplastic resin. did.
Example 5
A thermoplastic resin composition was produced and pelletized in the same manner as in Example 1 except that the cut fiber obtained in Example 2 was pelletized in the same manner as in Example 4.
Example 6
A thermoplastic resin composition was produced and pelletized in the same manner as in Example 1 except that the cut fiber obtained in Example 3 was pelletized in the same manner as in Example 4.

Comparative Example 1
Instead of a cutting machine (made by Yoshiko Co., Ltd., model “RC250”), a raw material fiber is pulverized using a crusher (made by Horai Co., Ltd., model “Z10-420”), and passed through a screen with a mesh opening of 6 mm. , Recovered as pulverized fiber (fiber length is 4 to 6 mm, has a bent portion and is not straight), and tried to produce a thermoplastic resin composition in the same manner as in Example 1, Since the bulk was large, kneading and mixing could not be performed, and a thermoplastic resin composition could not be produced.
Comparative Example 2
A thermoplastic resin composition was produced and pelletized in the same manner as in Example 1 except that the pulverized fiber obtained in the same manner as in Comparative Example 1 was pelletized in the same manner as in Example 4.
As mentioned above, the opening of the screen which the cutting apparatus (pulverization apparatus) used for manufacture of the cutting fiber (pulverized fiber) in Examples 1-6 and Comparative Examples 1-2 has, the form of the cut fiber, and the presence or absence of pelletization of the cut fiber Table 1 shows the time from when the torque value reaches the peak until the torque is discharged (except for Comparative Example 1).

[2] Characteristic Evaluation of Thermoplastic Resin Composition The pellets of the thermoplastic resin compositions of Examples 1 to 6 and Comparative Example 2 obtained in [1] above were dried in an oven at 100 ° C. for 5 hours, and then Using an injection molding machine (model “SE100DU” manufactured by Sumitomo Heavy Industries, Ltd.), injection molding was performed under conditions of a cylinder temperature of 190 ° C. and a mold temperature of 40 ° C. to produce a test piece having a length of 110 mm, a width of 10 mm, and a thickness of 4 mm. Then, a bending test was carried out in accordance with ISO 178 to determine the flexural modulus. Further, injection molding was similarly performed using a bar flow mold, and the flow length (bar flow length) was evaluated. These results are also shown in Table 1.

  According to the results in Table 1, in Examples 1 to 6 in which a predetermined amount of a straight cut fiber, polypropylene, and acid-modified polypropylene was passed through a screen having a predetermined mesh size, the screen eyes Regardless of the opening, that is, regardless of the fiber length of the cut fiber, it has sufficient bending characteristics and has excellent fluidity with the bar flow length as an index. In addition, in Example 3 in which the screen opening is smaller than those in Examples 1 and 2, that is, the fiber length of the cut fiber is smaller, it can be seen that the bar flow length is longer and the fluidity is better. . Further, when Examples 1 to 3 using the cut fibers as they are and Examples 4 to 6 using the cut fibers pelletized, the bending characteristics are equivalent, but the fluidity is the same as that of the cut fibers. The used Examples 1-3 are more excellent. On the other hand, in Comparative Example 2 in which the pulverized fiber of Comparative Example 1 was used as pellets, it was found that although the thermoplastic resin composition could be produced, the fluidity was greatly reduced.

  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, 32; Teeth, 40; Roller disk die molding machine, 41; Disk die, 411; Through hole, 412; Main rotation shaft insertion hole, 42; Press roller, 421; Concavity and convexity, 43; Main rotation shaft, 44; Shaft 45; blade for cutting.

Claims (7)

A method for producing a thermoplastic resin composition comprising a thermoplastic resin and plant fibers, wherein the total amount of the thermoplastic resin and the plant fibers is 100% by mass, and the plant fibers are 50 to 95% by mass. There,
A cutting step of cutting raw material fibers into cutting fibers, and a mixing step of kneading and mixing the thermoplastic resin and the cutting fibers,
The method for producing a thermoplastic resin composition, wherein the cut fiber passes through a screen having a mesh opening of 0.5 to 2 mm and is straight.   The method for producing a thermoplastic resin composition according to claim 1, wherein the raw fiber is a kenaf fiber.   The method for producing a thermoplastic resin composition according to claim 1 or 2, wherein the thermoplastic resin is a polypropylene resin and an acid-modified polypropylene resin.   The production of the thermoplastic resin composition according to claim 3, wherein the total amount of the polypropylene resin and the acid-modified polypropylene resin is 100% by mass, and the acid-modified polypropylene resin is 1 to 30% by mass. Method.   The manufacturing method of the thermoplastic resin composition of any one of Claims 1 thru | or 4 provided with the grinding | pulverization process which grind | pulverizes the resin fiber mixture obtained in the said mixing process to make a grinding | pulverization mixture.   The method for producing a thermoplastic resin composition according to claim 5, further comprising a pelletizing step of pressing and solidifying the pulverized mixture. 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 6, wherein the thermoplastic resin heated and melted by rotation of the mixing blade and the cut fiber are kneaded and mixed in the mixing chamber. A method for producing a plastic resin composition.

Images