Pellet manufacturing method

Abstract

To provide a resin material for injection molding, which is made by blending polylactic acid resin with a wood flour, and which produces molded products with high tensile strength and good flowability within a mold.SOLUTION: A granular pellet used in injection molding have a base material of polylactic acid resin mixed with wood grains with a particle size not exceeding 50 μm. As shown in Fig. 9(e), even if the wood grains 25 are retained in a tunnel gate 92, a state immediately changes to Fig. 9(d), and a pressure fluctuation is corrected. As a result, a flowability in a mold is improved.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to granular pellet technology for injection molding. [Background technology]

[0002] It is known that waste plastic flows into the ocean, breaks down into micron-sized particles, and causes harm to fish and other marine life. If the waste plastic is biodegradable, it will not harm marine life. Therefore, it is desirable to replace plastics with biodegradable plastics.

[0003] However, biodegradable plastics are more expensive than other ordinary plastics. As a countermeasure, it is known to reduce costs by mixing waste wood such as sawdust into biodegradable plastics to increase the volume, and devices for this purpose have been proposed (see, for example, Patent Document 1 (Figure 1)).

[0004] The technology of Patent Document 1 will be described with reference to FIG. As shown in Fig. 11, wood flour 102 and polylactic acid resin 103 are put into a hopper 101 and stirred with a stirring blade 104. The stirred mixture 105 is extruded while being kneaded in a molding machine 106 to obtain a molded product. The grain size of the wood flour 102 is 300 μm or more (Patent Document 1, paragraph 0025).

[0005] However, the technology of Patent Document 1 has the following drawbacks. First, the molded article produced by the technique of Patent Document 1 has low tensile strength. Secondly, the resin material has poor fluidity inside the mold.

[0006] As the uses of molded products become more diverse, there is a demand for improved tensile strength. Furthermore, in molds used for injection molding small or ultra-small molded products, the gate diameter is inevitably small. While the polylactic acid resin 103 becomes close to a liquid through kneading, the wood flour 102 remains solid. When the gate diameter becomes small, the wood flour 102 can hinder fluidization, and measures to prevent this are required.

[0007] Therefore, there is a demand for a resin material for injection molding that is made by blending wood flour with polylactic acid resin, and that provides molded products with high tensile strength and good fluidity within the mold. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 5321254 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention aims to provide a resin material for injection molding, which is made by blending wood flour with polylactic acid resin, and which produces molded products with high tensile strength and good fluidity within the mold. [Means for solving the problem]

[0012] The invention according to claim 1 is a pellet manufacturing method for manufacturing pellets for injection molding in which a base material is a polylactic acid resin and wood grains having a particle size not exceeding 50 μm are mixed into the base material, A step of preparing wood chips, a grinder, polylactic acid resin granules, a two-type blending mechanism, and a pellet manufacturing device; A step of feeding the wood chips into the crusher and crushing them in the crusher to obtain wood grains having a particle size of 50 μm or less; A step of feeding the wood grains and the polylactic acid resin grains into the two-type blending mechanism and obtaining blended grains in the two-type blending mechanism; a step of feeding the blended grains into the pellet manufacturing apparatus, kneading and extruding the blended grains in the pellet manufacturing apparatus, and cutting the resulting strands to obtain pellets; The two-kind blending mechanism includes a measure, a first pipe extending horizontally from the measure, a first spiral coil rotatably housed in the first pipe and feeding the polylactic acid resin particles to the measure, a first motor rotating the first spiral coil, a second pipe extending horizontally from the measure, and a second motor rotatably housed in the second pipe and feeding the polylactic acid resin particles to the measure. grain a second spiral coil that sends the liquid to the container, and a second motor that rotates the second spiral coil, In the step of obtaining the blended granules, the polylactic acid resin granules and the wood grain The method is characterized in that the ingredients are only blended without being mixed. In addition, pellet means a small ball or a small grain in Japanese.

[0013] The invention according to claim 2 is a pellet manufacturing method for manufacturing pellets for injection molding in which a base material is a polylactic acid resin and wood grains having a particle size not exceeding 30 μm are mixed into the base material, A step of preparing wood chips, a grinder, a classification screen, polylactic acid resin granules, a two-type blending mechanism, and a pellet manufacturing device; A step of feeding the wood pieces into the crusher and crushing them in the crusher to obtain wood grains; A step of classifying the obtained wood grains using the classification net to obtain wood fine grains with a particle size of 30 μm or less; A step of feeding the wood granules and the polylactic acid resin granules into the two-type blending mechanism and obtaining blended granules in the two-type blending mechanism; a step of feeding the blended grains into the pellet manufacturing apparatus, kneading and extruding the blended grains in the pellet manufacturing apparatus, and cutting the resulting strands to obtain pellets; The two-kind blending mechanism includes a measure, a first pipe extending horizontally from the measure, a first spiral coil rotatably housed in the first pipe and feeding the polylactic acid resin particles to the measure, a first motor rotating the first spiral coil, a second pipe extending horizontally from the measure, and a second motor rotatably housed in the second pipe and feeding the polylactic acid resin particles to the measure. grain a second spiral coil that sends the liquid to the container, and a second motor that rotates the second spiral coil, In the step of obtaining the blended granules, the polylactic acid resin granules and the wood fine particles are mixed. grainThe method is characterized in that the ingredients are only blended without being mixed. [Effects of the Invention]

[0014] In the invention according to claim 1, the granular pellets are fed into an injector, where they are kneaded and plasticized. The plasticization causes the polylactic acid resin to become fluid, but the wood grains remain solid. The diameter of the gate inside the mold varies, but the minimum diameter of the tunnel gate is said to be about 0.50 mm. With conventional technology, wood powder is 300 μm (0.30 mm), so it is difficult for it to pass through a 0.50 mm tunnel gate. In contrast, the wood grains of the present invention are 50 μm (0.05 mm) in diameter, which is significantly smaller than the minimum diameter (0.50 mm) of the tunnel gate, so the resin material passes through the 0.50 mm tunnel gate without delay.

[0015] Furthermore, as will be explained in more detail later, wood grains of 50 μm are expected to produce a structure with approximately 1.4 times the tensile strength of wood powder of 300 μm. Therefore, according to claim 1, a resin material (pellets for injection molding) is provided that provides a molded product with high tensile strength and good fluidity within a mold.

[0016] In the invention according to claim 2, the wood grains have a diameter of 30 μm (0.03 mm), which is significantly smaller than the minimum diameter (0.50 mm) of the tunnel gate, so the resin material passes through the 0.50 mm tunnel gate more smoothly.

[0017] Furthermore, as will be explained in more detail later, 30 μm wood grains can be expected to produce a structure with approximately 1.5 times the tensile strength compared to 300 μm wood powder. Therefore, according to claim 2, a resin material (pellets for injection molding) is provided that produces a molded product with high tensile strength and has good fluidity within a mold.

[0018] In addition, Claim 1 The invention is a pellet manufacturing method in which pellets are manufactured using a pulverizer, a two-component blending mechanism, and a pellet manufacturing device. The pulverizer, the two-component blending mechanism, and the pellet manufacturing device are relatively simple in structure and inexpensive, making it possible to manufacture pellets for injection molding at a relatively low cost. Furthermore, the first helical coil and the second helical coil are obtained by processing a steel wire into a helical coil, and are therefore significantly cheaper than a screw. By adopting the first spiral coil and the second spiral coil, the manufacturing cost of the dual blending mechanism can be reduced.

[0019] Also, Claim 2 The invention is a pellet manufacturing method in which pellets are manufactured using a pulverizer, a classification net, a two-type blending mechanism, and a pellet manufacturing device. The pulverizer, the two-component blending mechanism, and the pellet manufacturing device are relatively simple in structure and inexpensive, and the classification screen is also extremely inexpensive, making it possible to manufacture pellets for injection molding at a relatively low cost. In addition, the first helical coil and the second helical coil are obtained by processing a steel wire into a helical coil, and are therefore significantly cheaper than a screw. By adopting the first spiral coil and the second spiral coil, the manufacturing cost of the dual blending mechanism can be reduced. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram illustrating the principle of a pulverizer used in the present invention. [Figure 2] FIG. 1 is a diagram illustrating the principle of a classification net. [Figure 3] (a) is a plan view of the two-type mixing mechanism, (b) is a cross-sectional view taken along line bb in (a), and (c) is a cross-sectional view taken along line cc in (a). [Figure 4] FIG. 2 is a plan view of the pellet manufacturing apparatus. [Figure 5] FIG. [Figure 6] 1(a) to 1(c) are diagrams illustrating the principle of a tunnel gate. [Figure 7] 1 is a graph showing the correlation between grain size and tensile strength of wood grains. [Figure 8] 1 is a graph showing the correlation between the blending ratio of wood grains and tensile strength. [Figure 9] (a) is a graph showing the relationship between grain size of wood grains and pressure fluctuation, and (b) to (e) are diagrams explaining the principle of fluidity. [Figure 10]FIG. 1 is a flow diagram illustrating a pellet production method of the present invention. [Figure 11] FIG. 1 is a diagram illustrating a conventional technique. DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment of the present invention will be described below with reference to the accompanying drawings. [Example]

[0022] [Crusher] As shown in Figure 1, the crusher 10 consists of legs 12 that rest on a floor 11, a main chamber 13 that is supported by these legs 12, a crushing blade 14 that is built into this main chamber 13, a motor 15 that rotates this crushing blade 14 at high speed, a conical cylinder 16 that extends upward from the main chamber 13, a vertical cylinder 17 that extends upward from this conical cylinder 16, and a sub-chamber 18 that surrounds the conical cylinder 16. The conical cylinder 16 has a plurality of holes 19 formed therein that connect the main chamber 13 and the sub-chamber 18, and the sub-chamber 18 is provided with an outlet 21.

[0023] The crushing blade 14 is rotated at a speed of 1,000 to 20,000 revolutions per minute (16.7 to 333 revolutions per second). When wood chips 23 are fed into vertical tube 17, they are crushed by crushing blades 14. While remaining in main chamber 13, the crushed wood chips are repeatedly crushed by crushing blades 14 and the centrifugal force caused by rotation, becoming wood grains 25 with a particle size of 50 μm or less. These wood grains 25 are carried by tornado-shaped swirling flow 26 up to sub-chamber 18 and then discharged from outlet 21. As a result of the above, wood grains 25 having a grain size of 50 μm or less are obtained.

[0024] [Classification network] The wood grains 25 obtained by the crusher 10 of FIG. 1 are used when further classification is required. 2, the classification net 28 is, for example, a wire net having mesh that allows particles of 30 μm or less to pass through and blocks particles of more than 30 μm. The wire net is moved back and forth in a fine motion.

[0025] When wood grains 25 are dropped onto the classification net 28 from above, wood grains 25 with a particle size exceeding 30 μm remain on the net and are discharged as shown by the arrow (1). The material that passes through the classification net 28 and falls becomes fine wood particles 29 of 30 μm or less.

[0026] [Two types of combination mechanism] As shown in Figure 3(a), the two-type blending mechanism 30 consists of a measure 31, a first tube 32 extending horizontally from the measure 31, a first spiral coil 33 rotatably stored in the first tube 32, a first motor 34 that rotates the first spiral coil 33, a first hopper 35 provided midway along the first tube 32, a second tube 36 extending horizontally from the measure 31, a second spiral coil 37 rotatably stored in the second tube 36, a second motor 38 that rotates the second spiral coil 37, and a second hopper 39 provided midway along the second tube 36.

[0027] As shown in Figure 3(b), polylactic acid resin granules 40 fed into the first hopper 35 drop into the first pipe 32, are transported by the first spiral coil 33, and reach the measure 31. The rotation speed of the first spiral coil 33 is controlled by the first motor 34, and the amount of polylactic acid resin granules 40 fed (mixed amount) is controlled.

[0028] Preferably, the tip of the first tube 32 protrudes from the wall of the measure 31, and protrudes to the center of the measure 31. This allows the polylactic acid resin particles 40 to reach the drop opening without adhering to the wall of the measure 31. At this time, the measure 31 does not perform a blending function but prevents the polylactic acid resin particles 40 from scattering.

[0029] As shown in Figure 3(c), the wood particles 25 or fine wood particles 29 fed into the second hopper 39 fall into the second pipe 36, are transported by the second spiral coil 37, and reach the basin 31. The rotation speed of the second spiral coil 37 is controlled by the second motor 38, and the amount of wood particles 25 or fine wood particles 29 sent (mixed amount) is controlled.

[0030] Preferably, the tip of the second pipe 36 protrudes from the wall of the box 31, protruding to near the center of the box 31. This allows the wood particles 25 or fine wood particles 29 to reach the drop opening without adhering to the wall of the box 31. At this time, the box 31 does not perform a blending function but prevents the wood particles 25 or fine wood particles 29 from scattering.

[0031] The first helical coil 33 may be a screw with a helical blade attached to a shaft. However, since the first helical coil 33 is obtained by processing a steel wire into a helical coil shape, it is significantly cheaper than a screw. The same applies to the second helical coil 37. By employing the first spiral coil 33 and the second spiral coil 37, the manufacturing cost of the two-kind blending mechanism 30 can be reduced.

[0032] As a result of the above, a blended granule (FIG. 4, reference numeral 63) is obtained in which an appropriate amount of polylactic acid resin granules 40 is blended with an appropriate amount of wood granules 25 or wood fine granules 29.

[0033] [Pellet manufacturing equipment] As shown in Figure 4, the pellet manufacturing apparatus 50 comprises a first screw 51, a second screw 52 arranged alongside the first screw 51, a barrel 53 that rotatably houses the first screw 51 and the second screw 52, ​​a heater 54 that surrounds the barrel 53, a drop block 55 that is arranged at one end of the barrel 53, a converter 56 and a drive motor 57 that rotate the first screw 51 and the second screw 52, ​​a die 58 that is arranged at the other end of the barrel 53, a strand cooling conveyor 61 that is arranged outside the die 58 and in series with the barrel 53, and a stride cutter 62 that is arranged at the outlet of the strand cooling conveyor 61.

[0034] The converter 56 is a device that distributes the power of the drive motor 57 to the rotational force of the first screw 51 and the rotational force of the second screw 52. The converter 56 can rotate the first screw 51 and the second screw 52 at the same speed in the same direction. By changing the internal structure of the converter 56, it is also possible to rotate the second screw 52 in the opposite direction to the first screw 51. Therefore, the rotational directions of the first screw 51 and the second screw 52 can be set as desired.

[0035] The bucket 31 is bolted to the drop hole block 55. That is, the two-kind blending mechanism 30 is mounted on the pellet manufacturing apparatus 50. By mounting it, it is no longer necessary to place the two-kind blending mechanism 30 on the floor, and the blended granules 63 immediately after blending can be fed into the barrel 53, thereby suppressing deterioration of the blended granules 63 over time.

[0036] If deterioration over time is acceptable, the two-kind blending mechanism 30 may be located away from the pellet manufacturing apparatus 50. In this case, the blended granules 63 are transported in a bag or bucket from the two-kind blending mechanism 30 to the pellet manufacturing apparatus 50. Since the blended granules 63 can be prepared and stored, there is an advantage in that the flexibility of production is increased.

[0037] The particle size of the polylactic acid resin particles 40 fed into the first hopper 35 is, for example, 3.0 mm. The grain size of the wood grains 25 fed into the second hopper 39 is, for example, 50 μmm or less. Alternatively, the grain size of the fine wood grains 29 fed into the second hopper 39 is, for example, 30 μmm or less.

[0038] The ratio of the mixture in the portion of the measure 31 is, for example, polylactic acid resin particles 40:wood particles 25 (or fine wood particles 29)=70-99% by mass:30-1.0% by mass.

[0039] The blended granules 63 are kneaded by the rotation of the first screw 51 and the second screw 52, ​​melted by the heat of the heater 54, and discharged from the die 58 in the form of thin rod-like strands 64. The strand 64 is cooled and solidified while being conveyed by the strand cooling conveyor 61, and is cut by a stride cutter 62 into pellets 66 for injection molding. The particle size of the pellets 66 for injection molding is, for example, 2.0 to 3.0 mm.

[0040] [Injection molding equipment] As shown in FIG. 5, the injection molding apparatus 70 comprises a bed 71, an injection mechanism 72 mounted on the bed 71, and a mold clamping mechanism 82. In the mold clamping mechanism 82, a mold 83 is clamped by a fixed platen 84, a movable platen 85, and a toggle mechanism 86. The mold 83 is made up of, for example, a fixed mold 87 and a movable mold 88.

[0041] In the injection mechanism 72, pellets 66 for injection molding are fed into a heating barrel 74 via a hopper 73. The fed pellets 66 for injection molding are kneaded by the rotation of a screw 75 contained in the heating barrel 74 and the heat from the heating barrel 74, and become plasticized.

[0042] The injection mechanism 72 is moved horizontally so that the nozzle 89 at the tip of the heating barrel 74 comes into contact with a sprue provided on the fixed platen 84 (or fixed mold 87). The plasticized injection molding pellets 66 (hereinafter referred to as molten resin material) accumulate on the nozzle 89 side inside the heating barrel 74. As the amount of accumulated material increases, the screw 75 retreats. When the retreat distance reaches a predetermined value, the screw 75 is advanced at high speed. As the screw 75 advances, the molten resin material is injected into the mold 83.

[0043] The internal state of the mold 83 and the subsequent operations will be explained with reference to FIG. 6(a), inside the mold 83, the molten resin material 94 flows in the order of runner 91 → tunnel gate 92 → product cavity 93, and the molten resin material 94 fills the runner 91, tunnel gate 92, and product cavity 93. In this state, the molten resin material 94 is cooled. After cooling is complete, the movable mold 88 is separated from the fixed mold 87.

[0044] 6(b), the solidified product portion 96, gate portion 97, and runner portion 98 remain on the movable mold 88. In this state, the ejector pin 99 is advanced.

[0045] 6(c), the product part 96 is released from the movable mold 88 by the ejector pin 99. A gate mark 97a remains in this product part 96, but the gate mark 97a is small. A molded product is obtained by finishing the product part 96, including the gate mark 97a.

[0046] In the direct gate method, the product portion 96 is separated from the movable mold 88 with the gate portion 97 connected to it. A process of cutting the gate portion 97 from the product portion 96 with a gate cutter (gate cutting process) is essential.

[0047] In contrast, the tunnel gate method has the advantage that the gate portion 97 is cut in the product ejection process as explained in Figures 6(b) and 6(c), so the gate cutting process using a gate cutter is not required.

[0048] On the other hand, in order to cut the gate portion 97 in the product ejection process, it is necessary to reduce the gate diameter at the tip of the tunnel gate 92 in Fig. 6(a). The minimum diameter of the gate is, for example, 0.50 mm.

[0049] (experiment) As described above, the object of the present invention is to provide a resin material for injection molding, which is made by mixing wood flour with polylactic acid resin, and which produces molded products with high tensile strength and good fluidity within the mold. To this end, test specimens were prepared using a pellet manufacturing apparatus (Fig. 4, reference numeral 50) and an injection molding apparatus (Fig. 5, reference numeral 70), and the tensile strength of the test specimens was examined. The mold (Fig. 5, reference numeral 93) was replaced with a mold that could produce test specimens.

[0050] (material) Polylactic acid resin granules: FY201 manufactured by HighChem Wood chips: Larch

[0051] (wood grain) Wood grain: For comparison, three types of grains were prepared: 300 μm, 212 μm, and 2 μm.

[0052] (composition ratio) The blend ratio was 90% by mass of polylactic acid resin granules and 10% by mass of wood grains.

[0053] (Test piece) Test specimen: Dumbbell tensile test specimen Number of test specimens: Five test specimens were prepared in consideration of the reliability of the measurements.

[0054] (Test equipment) Testing equipment: Shimadzu AG-IS 250KN precision universal testing machine

[0055] The tensile strengths obtained as described above are shown in Table 1.

[0056] [Table 1]

[0057] The average tensile strengths shown in Table 1 are plotted in Figure 7. As shown in Figure 7, the smaller the grain size of the wood, the greater the tensile strength. The particle size of 300 μm in Comparative Example 1 corresponds to that of Patent Document 1 described in the prior art. One of the objectives of the present invention is to increase the tensile strength compared to conventional methods, and the degree of increase (expected value) is set to 1.5 times. If the horizontal axis shows 30 μm or less, 1.5 times the tensile strength is achieved. Even if the particle size is 50 μm or less, the tensile strength is almost achieved. Therefore, it was confirmed that the grain size of wood grains should be 50 μm or less, and even better if it is 30 μm or less.

[0058] (Additional experiment) Next, additional experiments were conducted on the compounding ratio.

[0059] (composition ratio) The composition was 80% by mass of polylactic acid resin granules and 20% by mass of wood grains.

[0060] (wood grain) ·Wood grain: 2μm

[0061] The other conditions were the same as those in the experiment described above. The results are shown in Table 2.

[0062] [Table 2]

[0063] The average tensile strengths shown in Table 2 are plotted in Figure 8. Example 1 and Comparative Example 1 are also included in FIG. 8 for comparison. According to FIG. 8, the higher the proportion of wood grains, the lower the tensile strength.

[0064] Although this is an estimated value, when the proportion of wood grains is 40 mass %, it becomes 0.95 times that of Comparative Example 1, and the object of the present invention cannot be achieved. If the proportion of wood grains is 30 mass %, the tensile strength is 1.16 times that of Comparative Example 1, which is somewhat unsatisfactory, but an improvement in tensile strength is expected. Therefore, the blending ratio of wood grains is preferably 30% by mass or less, and even better if it is 20% by mass or less, and if it is 10% by mass or less, a further increase in tensile strength can be expected.

[0065] (Liquidity considerations) The minimum diameter of the tunnel gate was 0.50 mm, that is, 500 μm, and the wood grain content was 10 mass %, and the pressure (internal pressure) at the time of injection from the nozzle 89 shown in FIG. 5 was investigated. As a result, the tendency shown in Figure 9(a) was confirmed.

[0066] FIG. 9(a) is a graph in which the horizontal axis indicates the grain size (μm) of wood grains and the vertical axis indicates pressure fluctuations. As shown in Figure 9(a), when the grain size exceeds 50 μm, the pressure fluctuation increases. On the other hand, when the grain size is 50 μm or less, the pressure fluctuation is small.

[0067] The reason for the pressure fluctuations is estimated from Figures 9(b) to (e). As shown in Figure 9(b), a 150µm grain 25 is about 1 / 3 of the minimum diameter of the gate (500µm), and is smaller than the minimum diameter of the gate, so it flows as shown by the arrow (←). At this time, the pressure becomes a predetermined pressure.

[0068] As shown in Figure 9(c), even if the grains are 150 μm in size, when several grains 25 solidify, they block the gate and the pressure rises sharply. After a short time, the block collapses. That is, the states of FIG. 9(b) and FIG. 9(c) are repeated, and the pressure fluctuation becomes larger.

[0069] As shown in Figure 9(d), a 50 μm grain 25 is 1 / 10 of the minimum diameter of the gate (500 μm), and is much smaller than the minimum diameter of the gate, so it flows as shown by the arrow (←). At this time, the pressure becomes a predetermined pressure. Although the frequency of occurrence is very low, if a large number of 50 μm wood grains 25 clump together, they will block the gate in Figure 9(e). However, these clumps will quickly collapse and return to Figure 9(d). As a result, the pressure fluctuations will become smaller.

[0070] From the above, it was confirmed that even with a tunnel gate, if the grain size of the wood grains is 50 μm or less, preferably 30 μm or less, a stable flow as shown in Figure 9(d) can be maintained and fluidity can be increased.

[0071] From the above findings, the following pellet manufacturing method is derived. In step number (hereinafter referred to as ST) 01 in Figure 10, a piece of wood and crushing A machine, a classification net, polylactic acid resin granules, a two-type blending mechanism, and a pellet manufacturing device are prepared. In ST02, crushing Put the wood chips into the machine, crushing This crushing This results in wood grains of 1 to 50 μm (i.e., 50 μm or less).

[0072] In ST03, it is determined whether or not to classify. If classification is not required, ST01 can be used to omit the preparation of a classification net. Also, crushing If wood fines of 40 μm or less (or 30 μm or less) can be obtained by increasing the rotation speed of the crushing blade (FIG. 1, reference numeral 14) in the mill, the classification step can be omitted.

[0073] If classification is necessary, classification is carried out using a classification mesh in ST04. By this classification, wood fine particles of 1 to 30 μm (i.e., 30 μm or less) are obtained. In ST05, wood particles (or fine wood particles) and polylactic acid resin particles are fed into the two-component blending mechanism and blended. As a result, blended particles are obtained. In ST06, the compounded particles are fed into a pellet manufacturing device, kneaded, extruded, and the resulting strands are cut, resulting in pellets for injection molding.

[0074] In addition, as explained in the embodiment crushing The machine 10, the two-kind blending mechanism 30, and the pellet manufacturing device 50 are merely examples, and the structure and principle may be changed.

[0075] Although the injection molding pellets according to the present invention are suitable for tunnel gates, they may also be used for injection into molds with other gates, such as direct gates, side gates, and pin gates. [Industrial Applicability]

[0076] The present invention is suitable for injection molding pellets made of polylactic acid resin and wood grains (or wood fines). [Explanation of symbols]

[0077] 10… crushing machine, 23... wood chips, 25... wood grains, 29... wood fine grains, 30... two-type blending mechanism, 40... polylactic acid resin grains, 50... pellet manufacturing device, 63... blended grains , 64…Strand , 66... ​​Pellets for injection molding.

Claims

1. A pellet manufacturing method for manufacturing injection molding pellets in which a base material is a polylactic acid resin and wood grains having a particle size not exceeding 50 μm are mixed into the base material, the method comprising: A step of preparing wood chips, a grinder, polylactic acid resin granules, a two-type blending mechanism, and a pellet manufacturing device; A step of feeding the wood chips into the crusher and crushing them in the crusher to obtain wood grains having a particle size of 50 μm or less; A step of feeding the wood grains and the polylactic acid resin grains into the two-type blending mechanism and obtaining blended grains in the two-type blending mechanism; a step of feeding the blended grains into the pellet manufacturing apparatus, kneading and extruding the blended grains in the pellet manufacturing apparatus, and cutting the resulting strands to obtain pellets; The two-kind blending mechanism includes a measure, a first pipe extending horizontally from the measure, a first spiral coil rotatably housed in the first pipe and sending the polylactic acid resin granules to the measure, a first motor for rotating the first spiral coil, a second pipe extending horizontally from the measure, a second spiral coil rotatably housed in the second pipe and sending the wood grains to the measure, and a second motor for rotating the second spiral coil; A pellet manufacturing method characterized in that in the step of obtaining the blended granules, the polylactic acid resin granules and the wood granules are only blended without being mixed.

2. A pellet manufacturing method for manufacturing injection molding pellets in which a base material is a polylactic acid resin and wood grains having a particle size not exceeding 30 μm are mixed into the base material, the method comprising: A step of preparing wood chips, a grinder, a classification screen, polylactic acid resin granules, a two-type blending mechanism, and a pellet manufacturing device; A step of feeding the wood pieces into the crusher and crushing them in the crusher to obtain wood grains; A step of classifying the obtained wood grains using the classification mesh to obtain wood fine grains with a particle size of 30 μm or less; A step of feeding the wood granules and the polylactic acid resin granules into the two-type blending mechanism and obtaining blended granules in the two-type blending mechanism; a step of feeding the blended grains into the pellet manufacturing apparatus, kneading and extruding the blended grains in the pellet manufacturing apparatus, and cutting the resulting strands to obtain pellets; The two-kind blending mechanism includes a measure, a first pipe extending horizontally from the measure, a first spiral coil rotatably housed in the first pipe and sending the polylactic acid resin granules to the measure, a first motor for rotating the first spiral coil, a second pipe extending horizontally from the measure, a second spiral coil rotatably housed in the second pipe and sending the wood granules to the measure, and a second motor for rotating the second spiral coil; A pellet manufacturing method characterized in that in the step of obtaining the blended granules, the polylactic acid resin granules and the wood fine granules are only blended without being mixed.

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